aashto . fhwa - napa - shrp - tai - trb · approximate conversions to si units approximate...

Report on the 1990

AASHTO . FHWA - NAPA - SHRP - TAI - TRB

APPROXIMATE CONVERSIONS TO SI UNITS APPROXIMATE CONVERSIONS FROM SI UNITS 111

symbol When You Know Multiply By To Find Symbol Symbol When You Know Multiply By To Find

in

;mi

inchesfeetyardsmiles

LENGTH25.40.3050 . 9 1 41.61

millimetres m mmetres mmetres m

ki lometres k m

AREAir+

sac

mi2

square inches 645.2. millimetres squared mm2square feet 0 . 0 9 3 metres squared mzsquare yards 0 . 6 3 6 metres squared dacres 0 . 4 0 5 hectares hasquare miles 2 . 5 9 kilometres squared kn?

floz fluid ouncesgal gallonsIt’ cubic feet

yd3 cubic yards

VOLUME2 9 . 5 73 . 7 6 50 . 0 2 60 . 7 6 5

milliliiesliiresmetres cubedmetres cubed

mLLm3ma

NOTE: Volumes greater than 1000 L shall be shown in m3.

MASS02 ounces 2 6 . 3 5 grams 9lb pounds 0 . 4 5 4 kilograms kgT short tons (2000 lb) 0 . 9 0 7 megagrams MS

“F

TEMPERATURE (exact)Fahrenheit 5( F-32)/9 Cekiustemperature temperature

“C

l SI is the symbol for the International System of Measurement

m

k”,

m2ha

kn?

AREAmillimetres squared 0 . 0 0 1 6 square inches in2me&es squared 1 0 . 7 6 4 square feet whectares 2 . 4 7 acres a ckilometres squared 0 . 3 8 6 square miles mi2

. VOLUMEmL milliliires 0 . 0 3 4 fluid ounces fl 02L liies 0 . 2 6 4 galkxts gal

m3 metres cubed 3 5 . 3 1 5 cubic feet Pm3 metres cubed 1.308 cubic yards W

9

x

“C

gramskilogramsmegagrams

MASS0 . 0 3 52 . 2 0 51 . 1 0 2

ounces 02poundsshort tons (2000 lb) F

TEMPERATURE (exact)Cekius 1X+32 Fahrenheittemperature temperature

OF 3 2 96.6 ;:2- 4 0 0 40 60 120 160 200r’;‘,“,‘~~:~,‘~,~l,,:‘;‘,‘,“,’

-G-20 0 20

37?60 60 ‘g

“F

milliietresmetresmetreskilometres

LENGTH0 . 0 3 93 . 2 81 .OQ0.621

inches i nfeet ftyards ydmiles mi

(Revised April 1989) III

EUROPEAN ASPHALT STUDY TOUR

1990

SPONSORING ORGANIZATIONS

American Association of State Highway and Transportation Offtcials

Federal Highway Administration

National Asphalt Pavement Association

Strategic Highway Research Program

The Asphalt Institute

Transportation Research Board

ACKNOWLEDGEMENT

The sponsors and members of the European Asphalt Study Tour teamwould like to express our appreciation and thanks to all the people

in the countries visited who contributed to making the trip the successthat it was. We would also like to extend a special debt of gratitude to two

individuals from the Federal Highway Administration--Mr. Richard F. Weingroffand Mrs. Deborah L. Stroessner--for their efforts in editing and rewritingsections of the report prepared by members of the tour group, and for the

proofreading, graphic design, and page layout work performed.

This report is published by :American Association of State Highway and Transportation Officials,444 North Capitol Street, NW., Suite 225, Washington, D.C. 20001

Permission to reproduce material contained within the report is hearby granted,June 1991.

i i

TABLE OF CONTENTS

I. INTRODUCTION by Federal Highway Administrator Thomas D. Larson l-6

II. TOUR PARTICIPANTS . . . . . . . . . . . . . . . . . . . . . 7-10

III. AN OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . 11-26

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Table 1 - Demographics . . . . . . . . . . . . . . . . . . . . . 14Table 2 - Highway Factors . . . . . . . . . . . . . . . . . . . 14Table 3 - Taxation Effort . . . . . . . . . . . . . . . . . . . . 15Stronger Emphasis on Durability . . . . . . . . . . . . . . . . 1 6Structural, Not Visual, Factors Trigger Rehabilitation . . . . . . . 1 7Stronger Emphasis on Noise Reduction and Skid Resistance . . . . 1 7Asphalt Modification . . . . . . . . . . . . . . . . . . . . . . 1 8Innovative Special-Purpose Mix Designs and Advanced

Mix-Design Systems . . . . . . . . . . . . . . . . . . . . . 1 9Scale, Diversity, and Efficiency . . . . . . . . . . . . . . . . . 2 0Performance-Enhancing Contracting Procedures . . . . . . . . . 2 1Environmental Concerns . . . . . . . . . . . . . . . . . . . . 2 1Stronger Research Emphasis . . . . . . . . . . . . . . . . . . 2 2Pending Market Changes . . . . . . . . . . . . . . . . . . . . 2 2Industry/Government Relationships and Industrial Structure . . . . 2 3

Public/Private Cooperation . . . . . . . . . . . . . . . . 2 3Concentrated Industry Structure . . . . . . . . . . . . . 2 4

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .24

IV. TRIP SUMMARIES . . . . . . . . . . . . . . . . . . . . . . 27-64

o Sweden . . . . . . . . . . . . . . . . . . . . . . . . . . . .29o Denmark . . . . . . . . . . . . . . . . . . . . . . . . . . .35o Germany . . . . . . . . . . . . . . . . . . . . . . . . . . .390 Italy . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45o France . . . . . . . . . . . . . . . . . . . . . . . . . . . .51o United Kingdom . . . . . . . . . . . . . . . . . . . . . . .57

s e .

111

V. INNOVATIVE ASPHALT TECHNOLOGY . . . . ; . . . . . . 65-98

o Possible Uses of European Technology in the United States . . . . . 6 7o Stone Mastic Asphalt . . . . . . . . . . . . . . . . . . . . . .69

General Description . . . . . . . . . . . . . . . . . . . 6 9Stone Mastic Asphalt in Germany . . . . . . . . . . . . . 72Stone Mastic Asphalt in Sweden . . . . . . . . . . . . . 7 5Stone Mastic Asphalt in Denmark . . . . . . . . . . . . . 8 1

o Porous Asphalt . . . . . . . . . . . . . . . . . . . . . . . . 8 2General Description . . . . . . . . . . . . . . . . . . . 8 2Porous Asphalt in Sweden . . . . . . . . . . . . . . . . 8 3Porous Asphalt in Germany . . . . . . . . . . . . . . . . 8 6Porous Asphalt in France . . . . . . . . . . . . . . . . 8 7

o Modified Asphalts and Asphalt Aggregate Mixtures . . . . . . . . 9 0General Remarks . . . . . . . . . . . . . . . . . . . . 9 0Stone Mastic Asphalt and Porous Asphalt . . . . . . . . . 9 0Very Thin Asphalt Concrete (France) . . . . . . . . . . . 9 0Paver-Laid Chip Seal (France) . . . . . . . . . . . . . . 9 1Gussasphalt (Germany) . . . . . . . . . . . . . . . . . 9 2Hot-Rolled Asphalt and Bitumen

Macadam (United Kingdom) . . . . . . . . . . . . . 9 4o Other Special Purpose Mixtures . . . . . . . . . . . . . . . . . 9 6o Mixture Design Techniques and Test Apparatus . . . . . . . . . . 9 7

Novel Mixture Design Techniques . . . . . . . . . . . . 9 7Novel Test Apparatus . . . . . . . . . . . . . . . . . . 1 0 0References . . . . . . . . . . . . . . . . . . . . . . . 103

VI. APPLICATION of FINDINGS . . . . . . . . . . . . . . . . . . 105-112

o Asphalt Pavement Mixtures . . . . . . . . . . . . . . . . . . 1 0 7o Laboratory Equipment . . . . . . . . . . . . . . . . . . . . . 1 0 90 Innovative Contracting Practices . . . . . . . . . . . . . . . . 1 1 0o Research ........................... 110

VII. ACRONYMS, DEFINITIONS and TECHNICAL TERMS . . . . . 113-116

APPENDIX: Technical Project Data . . . . . . . . . . . . . . . . . 117-184

A metric conversion table has been provided on the inside front cover for yourconvenience. A list of commonly used acronyms and technical terms has also beenprovided to assist you. It can be found on page 115.

iv

INTRODUCTION

INTRODUCTION

3

b yThomas D. Larson

Federal Highway Administrator

For the average motorist, one question about highways is of top priority: is the pavementsmooth? Dating back to the 1970's the answer to that question has, unfortunately, oftenbeen “no.”

The reasons for the problem are many. Some involve political decisions, such as how muchfunding is available for pavement maintenance. But to a large extent, the issues are tech-nical. How can we make our predictions about pavement use more reliable? What is thebest design? What surface is most durable for current traffic loadings? How can we bestrecycle old pavements? Just to cite a few.

In addition to the usual research and knowledge gained from experience, we have launchedseveral major efforts to find the answers. The best known and the most promising is theStrategic Highway Research Program (SHRP). The need for new or improved pavementtechnologies was one of the driving forces behind the SHRP’s development and most of itswork is directed toward these technologies. The result of the SHRP’s efforts should berecommendations for both the industry and the State highway agencies for improving thedurability and longevity of the Nation’s pavements.

One element of pavement research has, however, been missing--until now. That element isresearch into how other countries build and maintain their pavements. This is not an idlequestion. During my years of teaching at Penn State, I had the opportunity to work withengineers from the United Kingdom and Sweden, and I learned many new and innovativetechniques to deal with common highway problems. I also learned that we can gain a greatdeal through joint efforts with our counterparts in other countries who have advanced thestate-of-the-art in roads and bridges.

Since being appointed Federal Highway Administrator, I have gained increased respectfor the European highway community’s knowledge and understanding of pavements. Thisrenewed respect is a result of my own observations of European highways in the past2 years, as well as conversations with European experts who have visited the United Statesto learn how we solve common problems. Although the purpose of their visit in manycases is to gain knowledge about SHRP and the Federal-aid highway program, they oftencomment on the poor condition of pavements in the United States and contrast them withtheir own experience in Europe.

European Asphalt Study Tour 1990

4

The National Asphalt Pavement Association (NAPA) provided the impetus for the 1990European Asphalt Study Tour (EAST). John Gray, President of the NAPA, asked me topromote a closer relationship between government and industry asphalt experts and toexpand the concept to include European experts. He proposed an “on-the-ground” pilotprogram to review and evaluate foreign pavements and asphalt technology.

I agreed, as did the American Association of State Highway and Transportation Officials(AASHTO), and we decided to arrange a study tour of Europe. The objective was toexchange ideas and experience with highway agencies and the construction industry inEurope on design, production, and placement of asphalt pavements. We were particularlyinterested in the design of asphalt wearing courses, the use of asphalt modifiers and thebenefits they offer to improve the durability of asphalt pavements, as well as recycling--bothhot and cold. In addition, we were interested in contracting practices that would be inno-vative in the United States and cooperative public/private activities, not only in design andfinancing, but in research into new materials,‘methods, and machines. Most important, wewanted not only to discuss these and other subjects, but to see European technology at work.

Working together, the AASHTO, the NAPA, and the Federal Highway Administration(FHWA) selected a 21-member study group that included six AASHTO and eight industryrepresentatives, as well as the Chairman of the Transportation Research Board, thePresident of The Asphalt Institute, and two SHRP officials. I asked Deputy FederalHighway Administrator Gene McCormick to represent the FHWA.

Through cooperation with six government and industry representatives in Europe, wearranged a 14-day study tour of six countries: Denmark, France, Germany, Italy, Sweden,and the United Kingdom. It began on September 7, 1990, with a flight from Dulles Airportto Goteborg, Sweden, and ended on September 22 with weary study tour participantsarriving at Dulles after a flight from London. Whatever else the tour may have been, it wasan exhausting experience for all concerned.

If the participants began with any chauvinistic ideas about the superiority of United Statestechnology, they quickly realized we have a lot to learn from Europe about asphaltpavements and about pavement philosophy in general. European pavements ;are, better thanours and it’s no accident. The Europeans invest more in research, development, anddeployment of new pavement technology. They build their pavement foundations better.They use innovative--for us--surfaces, such as Stone Mastic Asphalt (SMA), and mix inadditives to a greater extent and with better results than we do. Government and industryhave a closer relationship--probably closer than would ever be possible in the UnitedStates--that encourages innovation and quality. And, the Europeans maintain theirpavements to get the maximum life out of them.


5

Upon return to the United States, the participants developed the plan for this report. Itdescribes the mission of the tour, and provides an overview, as well as a description of theactivities observed in each country; summarizes the findings not only for asphalt technologybut for innovative contracting practices and innovative construction equipment; andprovides a plan for applying these findings in the United States.

The implementation plan may be the most important part of the report, because we do notsee the 1990 EAST as the culmination of our efforts. It’s just the start. The FHWA willwork with the NAPA, the AASHTO, the SHRP, and other industry and State officials tobegin incorporating what we have learned into everyday practice.

The success of the study tour is the result of a lot of hard working people. Dick Morgan ofthe NAPA, Frank Francois of the AASHTO, and Doug Bernard of the FHWA deservespecial thanks for making the arrangements. At times, the tour--trying to get 21 peopleacross Europe in 14 days--was something like doing a jigsaw puzzle, but amazingly, they fitall the pieces together and the picture proved to be perfect.

In the end, though, the success of the study tour depended on the willingness of Europeanhighway and industry officials to share their ideas and their technology. Tour participantsfound their European counterparts not only willing but eager to do so. This was especiallyappreciated because the tight schedule imposed restrictions on the European hosts, too.Nevertheless, the schedules were adhered to in every case, and with good cheer. In everycountry, team members made many new friends.

For too long, we have seen international technology transfer as a one-way street, with theUnited States showing other countries how to build better highways. Today, we can nolonger afford such an attitude. Our transportation network is our greatest economic asset. Ifwe do not give it our best--and Europe’s best--we will undermine our own success.Internationally, our ability to compete in the world markets is dependent on our ability todemonstrate our expertise. We are, today, a world leader in highway technology, but thatreputation will slip, along with our competitiveness, if we do not expand our technologysharing, in both directions, with the international community.

Some of the European technologies seen, such as SMA and some mix design testingequipment, will be displayed at AASHTO’s ‘Technology Transfer Fair,“ in conjunction withthat organization’s annual meeting in Milwaukee, Wisconsin. The “Fair” is scheduled forOctober 12 and 13, 1991, and booths will be staffed by specialists, who can discuss thetechnologies displayed and answer questions.


TOUR PARTICIPANTS

9

TOUR PARTICIPANTS

American Association of State Highway and Transportation Offkials

Mr. Thomas H. Espy, Jr., Chief Engineer, Alabama Highway DepartmentMr. Byron C. Blaschke, State Engineer-Director,Texas State Department of

Highways and Public TransportationMr. James D. Quin, Chief Engineer, Mississippi State Highway DepartmentMr. Bernard B. Hurst, Director, Ohio Department of TransportationMr. Francis B. Francois, Executive Director, AASHTOMr. Dwight Bower, Deputy Director, Colorado Department of Highways

Federal Highway Administration

Mr. Gene McCormick, Deputy AdministratorMr. Edwin Wood, Regional AdministratorMr. Douglas A. Bernard, Chief, Demonstration Projects DivisionMr. Robert A. Ford, Chief, International Cooperation Division

National Asphalt Pavement Association

Mr. Lloyd 0. Thompson, President, Border States Paving, Inc.Mr. Ned W. Bechthold, President, Payne & Dolan, Inc.Mr. G. W. “Bill” Jones, President/Chief Executive Officer, APAC, Inc.Mr. Roger L. Yarbrough, President, University Asphalt CompanyMr. Robert M. Thompson, President, Thompson-McCully CompanyMr. Fred M. Fehsenfeld, Chairman of the Board, Contractors United, Inc.Mr. Richard D. Morgan, Vice President, National Asphalt Pavement Assoc.

Strategic Highway Research Program

Mr. Damien J. Kulash, DirectorMr. Edward T. Harrigan, Asphalt Program Manager

The Asphalt Institute

Mr. Gerald S. Triplett, President, The Asphalt Institute

Transportation Research Board

Mr. Wayne Muri, Transportation Research Board Chairman, andChief Engineer, Missouri Highway and Transportation Department


OVERVIEW

13

THEl990EUROPEANASPHALTSTUDYTOUR

ANOVERVIEWIn mid-September 1990, a team of pave-ment specialists from the United Statesparticipated in a 2-week tour of sixEuropean nations. The team includedrepresentatives from the AASHTO, theFHWA, the NAPA, the SHRP, TAI,and the TRB. The full European AsphaltStudy Tour (EAST) team visited, inorder, Sweden, Denmark, Germany,France, and the United Kingdom, whilea subcommittee drawn from theAASHTO and the FHWA participantsvisited Italy.

The six nations have much in commonwith the United States. All are indus-trialized, have extensive highway androad systems, and rely increasingly onmotor vehicles for moving people andfreight. While the six nations havemature railroad networks that move largenumbers of passengers and considerablefreight, the number of motor vehicles andthe use of trucks to move goods havegrown constantly. All the nations visitedhave modern, capable highway agenciesand a mature construction industry.Some also have extensive highwayresearch facilities.

The emerging European EconomicCommunity of the 1990’s will cause tar-iff and trade barriers to decline amongthe nations, leading to a confederationthat--to some extent--will resemble theUnited States, but without our strongnational government. The comingtogether of the nations is affecting

highways, as it is many other aspects oflife in Europe. For example, a highwaysystem is emerging that is comparable inmany ways to the Interstate System in theUnited States. The European motorwaynetwork totals some 40,000 km (about25,000 miles), including approximately13,500 km (8,400 miles) of toll roads. Itwill be capable of moving goods by truckfrom Norway in the north to Italy in theSouth, and from Eastern Europe to theAtlantic ports.

Despite these similarities, the six nationsdiffer from the United States and fromeach other in many ways. The tablesfound on the following two pages illus-trate some of the differences in demo-graphics, including density of population(table 1); the number of vehicles perperson and on an area basis as well as thedensity of the road system (table 2); andthe overall approach to government fin-ance (table 3). In addition, while all thenations visited are Western industrialdemocracies, each country has a morecentralized government than does theUnited States . The Federal-State part-nership that has been essential to thesuccess of the Federal-aid highway pro-gram in the United States has nocounterpart in Europe.

The 1990 EAST visited asphalt mixingplants, contracting firms, governmentagencies, laboratories, and materialsuppliers, and inspected scores of pave-ments and ongoing paving projects in


1 4

Table 1 d

NATIONAL STATISTICAL COMPARISONSDEMOGRAPHICS

Nation W Population Pop. Density Percent Urban(millions) @erson/sq km) (percent)

(1990) (1986) (1985)

U.S. 248.0 25.7 7 4Sweden 8.2 18.6 8 6Denmark 5.2 118.8 8 6W. Germany 60.7 245.6 8 6Italy 57.4 190.0 6 7France 55.4 101.3 7 3U.K. 55.8 231.9 9 2

Auto Expenseas % of

Pers. Spndg.(1980-85)

62

Table 2 aJ

NATIONAL STATISTICAL COMPARISONSHIGHWAY FACTORS

Nation ti Vehicles(millions)

(1987)

Pers. Per Veh.(tot./per car)

Veh. Density Hwy. Density(veh./sq km) wss km)

(1987) (1987)

U.S. 179.04 1.411.8 14.5 0.67Sweden 3.63 2.312.5 7.6 0.4Denmark 1.88 2.713.2 nla n/aW. Germany 30.11 2.012.1 113.9 1.98Italy 24.72 2.312.5 77.5 1.01France 24.85 2.212.5 40.0 1.46U.K. 23.02 2.512.8 74.1 1.53


Table 3 d

15

NATIONAL STATISTICAL COMPARISONSTAXATION EFFORT

Nation W Tot. Tax Receiptsas % of GNP

(1985)

Road Taxes as % of % of User FeesTotal Receipts Used for Roads

U.S. 29.2 4.7 1 0 0Sweden 50.5 6.3 34Denmark 49.2 6.2 31W. Germany 37.8 3.7 64Italy 34.7 n/a d aFrance 45.6 15.0 n/aU.K. 38.1 11.5 23

&Tables 1,2, and 3 are drawn from a variety of sources, including the World Bank, theInternational Road Federation, The World Almaw, the Organization for Economic. .Cooperation and Development, and MVMA Motor Vehr& Facts and Frmrres , 8 9.Statistics compiled prior to the unification of Germany.

b/The nations are listed in the order visitied, with the United States added as the firstcountry, for comparison purposes.

five of the countries visited--Sweden,Denmark, Germany, France, and theUnited Kingdom. The subcommitteethat visited Italy inspected a mixing plant,a paving project, as well as roadway fac-ilities, and met with officials of govern-ment agencies and Societa Autostrade, aconcessionaire with responsibility for alarge portion of Italy’s toll motorways.While some local roads were observedfirst hand, the tour concentrated pri-marily on major highways and motor-ways comparable to the Interstate System .and similar high-volume highways in theUnited States.

The highway systems observed duringthe study tour are similar to theirUnited States counterparts in someways, but different in others. Amongthe similarities:

o All six countries have Interstate-typemotorways. Like their United Statescounterparts, the motorways typicallymake up a small percentage of thenation’s overall road network but carrylarge shares of its highway traffic(approximately 25 percent).


1 6

Heavy motor truck traffic is concentra-ted on these routes, often representing20 percent or more of all vehicles.

Road professionals in every countrycomplained of inadequate road-invest-ment levels.

The observations reported here are im-pressions based on the study tour’s sitevisits, dozens of interviews, and manyhundreds of miles of highway travel bymotor coach. The impressions, however,are just that: subjective comments basedon the people met and the things seen.

A few impressions will help put thetechnologies, procurement procedures,and organizational roles into context. Byfar the study team’s most striking obser-vation was that the pavements on Euro-pean motorways and trunk routes are insuperior condition. The extreme formsof distress that are evident in many partsof the United States--rutting, raveling,cracking, and potholes--were, simply,rarely seen. Even pavements that werebeing rehabilitated or resurfaced were infairly good condition by United Statesstandards.

This observation is ‘true even thoughmotor truck usage in Europe is around20 percent of the total traffic, with vol-umes growing on many highways, andEuropean axle weights substantially ex-ceed those allowed in the United States.Germany, for example, allows an 11.5metric ton axle loading, or about 25,400pounds, while France allows a 13 metricton axle loading, or about 31,200 pounds.These weights may also be carried in Eu-rope on “super singles”--a tire confignra-tion that concentrates much of the weightof the vehicle in a fairly narrow path.

Aside from superior pavement condi-tions, the European highways are gener-ally not more advanced than comparableUnited States highways. For example,many routes were congested and oppos-ing lanes of traffic generally ran closetogether. The alignment of lesser routes,particularly in the United Kingdom, wasnot always suited to modern traffic needs.

The superior pavement condition ofEuropean motorways appears to stemfrom, or be related to, several differencesbetween United States and Europeanapproaches:

STRONGER EMPHASIS ON DURABILITY

Most of the countries visited use a40-year analysis period for the design oftheir motorway pavements, as opposed tothe 20-year design period used in theUnited States. In the 40-year analysis,European highway officials consider theinitial pavement design and various reha-bilitation strategies, as well as the antici-pated life and cost of the design and the

strategies. In the United Kingdom, a40-year life-cycle cost analysis is requiredfor all pavement designs.

Most of the countries emphasize buildinga sound subgrade and base rather thantrying to solve subgrade problems in thepavement design process. Structurallysound design practices are generally usedeven when they impose significant con-


1 7

struction costs through excavation andreplacement of subgrade material or in-corporation of active drainage systems.The most striking instance of this was inGermany, where one official stated that,“We no longer design roads; we havedone that. Now, we simply look at a tableand select the appropriate pavementdesign.”

German pavement design practices arepredicated on the fact that the subgradeis structurally sound and adequatelydrained. Over-design of pavement struc-tures is not needed as a way of compensat-ing for inadequacies in the subgrade. Theeconomic implications of high durabilitywere not challenged. On the contrary,the German representative noted that,“Whether or not it is more economical totolerate some frost heaves is a debate weshould not start.”

The German approach to sound designstands out as exceptional, even amongEuropean practices. However, all the

countries visited aim for longer design-life than in the United States and appearmore willing to increase initial costs toavoid problems later. Strong, well-drained bases and subbases are the normthroughout the countries visited, ratherthan the exception.

Five of the six countries have prohibitedthe use of studded snow tires. The excep-tion is Sweden, where studded tires are amajor source of rutting. Relatively shortlives for wearing courses in Sweden areinevitable because of the damage fromstudded tires. One unusual aspect of theresulting accelerated replacement ofwearing courses is that the pavementstructure is continually restored or evenimproved. When resurfacing takes place,the underlying structure is still sound andrelatively new. This structural predict-ability has helped to make some innova-tive forms of contracting for surfacecourses work effectively (namely, func-tional contracts and guarantees).

STRUCTURAL, NOT VISUAL, FACTORS TRIGGER REHABILITATION

Pavement-management practices in the evident, it is too late to correct structuralcountries visited appear to be driven problems. Societa Autostrade in Italy, formore by structural condition, and less by example, virtually ignores visual distressvisual condition, than is the case in the on its 3,000 km of motorways in favor ofUnited States. Systems for monitoring twice-yearly total pavement surveys withpavement condition and for programming condition-measuring devices that exam-rehabilitation projects rely primarily on ine skid resistance, bearing capacity,deflectograph or falling-weight deflection rutting and surface texture, profile, andmeasurements. Some European officials other cross-slope geometricalnoted that by the time visual distress is characteristics.

STRONGER EMPHASIS ON NOISE REDUCTION AND SKID RESISTANCE

Great emphasis is placed on skid are serious concerns in the United Statesresistance and pavement noise reduction as well, they play a much more prominentin all the countries visited. While these role in determining when and how


18

resurfacing work is done in Europe.Open-graded friction courses, under suchnames as drain asphalt and porous asphalt(PA), are advocated in several countrieslargely because of favorable noise andskid properties. Some of the concernsraised about the durability of earlier ver-sions of these mixes appear to have beenresolved by the use of modified binders.However, long-term performance infor-mation on durability is not fully available.

Because of concern about noise, thepublic in Europe appears to be involvedin riding surface design decisions to a fargreater extent than is common in theUnited States. The type of riding surface

used is itself a subject of direct publicparticipation--in at least some countries,the noise properties of different ridingsurfaces are matters of public knowledge.An agency’s choice of treatment may beinfluenced by popular demand.

As in the United States, noise barriers arecommon, although their extent and thenumber of design variations are greateralong European motorways. This fact,coupled with the European public’sinvolvement in decisions on ridingsurface, may be good indicators of wherethe United States is headed as trafficincreases and as our own public concernsabout highway noise continue to grow.

ASPHALT MODIFICATION

European officials described many typesof asphalt modification. They includemineral and cellulous fibers for SMA andthe use of carbon black, EVA, SBS, poly-ethylene, and ground rubber in other mixdesigns, as well as the addition of secretor proprietary materials whose nature isunclear (e.g., an ingredient identified tothe study tour only as “dope” was used inone contractor’s modified mixtures).

The use of these modifiers appears tobe widespread, judging from the numberof references and the time devoted tothem by the European hosts. On theother hand, the fact that they knew inadvance of the study group’s desire to seeand discuss “cutting-edge” technologyundoubtedly encouraged a strong focuson modification, even though it may notbe common practice. Some commentsfrom contractors and officials suggestedthat modified binders still represent asmall, special-purpose nitch in the overallpavement market.


Regardless of the extent, several nationsclearly have drawn up high-performancestandards or contracting approaches thatpermit and, in fact, encourage contractorsto use a range of modified binders andinnovative mix designs. Of the nationsvisited, France appears to make the larg-est and most sophisticated use of addi-tives and modifiers, and French contrac-tors have developed several patentedpavement materials. In Italy, to citeanother example, Societa Autostrade ismaking extensive use of proprietarymodified mixes and processes.

It should be noted that compared with theUnited States, the nations visited oftenhave fewer stable sources of asphalt. InSweden and Denmark, for example,Venezuela is essentially the only sourceof asphalt. The European nations findthat developing specifications based onthe known characteristics of this asphalt iseasier than if they had multiple sources.

19

INNOVATIVE SPECIAL-PURPOSE MIX DESIGNS ANDADVANCED MIX-DESIGN SYSTEMS

Mix designs similar to the conventional,continuous-graded designs employed inthe United States are used for much ofthe construction, rehabilitation, andmaintenance of European motorways andtrunk roads. All the countries visited,however, also use special-purpose mixdesigns, particularly in surface courses, toenhance the resistance of high-volumepavements to rutting, skidding, and, to alesser degree, fatigue and thermalcracking.

Examples of such mix designs are SMAin Sweden, Denmark and Germany; hotrolled asphalt (HRA) and penetrationmacadam in the United Kingdom;gussasphalt in Germany; and special thinand very thin asphalt overlays in France.To achieve superior performance, thesemix designs tend to feature gap-gradedaggregate blends and modified or low-penetration grade binders, sometimeswith the addition of fibers, as in the caseof SMA. Several of these designs areintended to control rutting and otherdistress for as long as 10 to 12 years underheavy volumes of truck traffic and, inSweden, SMA is used to combat thedeterioration stemming from the use ofstudded tires.

The use of “large-stone” mixes, with topaggregate sizes of 40 mm (1.5 inch ormore), to resist rutting does not appear tobe prevalent in Europe. Surface coursesgenerally employ a top aggregate size offrom 11 to 16 mm (about .5 to .75 inches).Many European mix designs also appearfar richer in binder content than conven-tional wisdom in the United States would

dictate for rut-resistant surfaces. How-ever, the different aggregate gradings andthe modifiers and filled mastics generallyappear to prevent rutting, flushing, andbleeding. None of these conditions wereobserved on anything approaching thescale they are found in the United States.

Mix design systems in Europe are sirni-larly varied, as illustrated by these exam-ples from three of the countries studied:

o Germany: Mix designs in the usualsense of the term are not done. Rather,mix designs for the surface and basecourses on motorway projects are sel-ected from a series of standard designsthat have been developed throughexperience for various classes of trafficvolume.

o France: The national laboratory, theCentral Laboratory of Bridges and‘Roads (Laboratoire Central des Pontset Chaussees--LCPC), developed themix design system that is used today.This system incorporates both gyratoryand rolling-wheel compactors, withsophisticated wheel-tracking and directtension equipment used to determine therutting, stripping, and load-related fatiguecharacteristics of trial mixes.

o United Kingdom: The Marshall designmethod is used by some county author-ities (which correspond to the statehighway administrations in the UnitedStates), but others rely on standard“recipe” designs with a history of goodservice.


2 0

SCALE, DIVERSITY, AND EFFICIENCY

In most of the countries visited, a fewlarge companies appear to receive(through bid or negotiation) a large maj-ority of contracting jobs on motorwaysand major national routes. At the sametime, asphalt paving contractors clearlyhave to supply quality materials meet-ing the numerous, diverse specificationsof agencies at different levels of govern-ments. Asphalt plant owners frequentlynoted the large number of different mixdesigns--generally over 100--program-med into their batch-plant control rooms.The inefficiency of an excessive numberof mixes was broadly recognized. In fact,it is part of the reason that the Germannational government decided to adopt amanageable number of standard pave-ment designs, and why the United King-dom’s standard-setting groups areconcentrating on a small number of“preferred designs.”

Production rates in the asphalt plantsvisited were typically one-half to one-third the productivity of their UnitedStates counterparts. Likewise, unit costsof paving materials and constructed pave-ments ran two or more times the corres-ponding costs in the United States.

Comparing cost or production rates inEurope and the United States, however,requires caution. The EAST participantsrecognized the difficulty of interpretingEuropean economic conditions in theUnited States context, due to differentmaterials prices, hauling distances, taxsystems, labor conditions and rates,

design differences, scale economics, andother factors. Amidst so many economicfactors, each of which differs from itsUnited States counterpart, isolating theextra cost attributable to some individualperformance-enhancing feature is notpossible.

In short, where higher quality was evidentin Europe, study tour participants couldnot gauge cost-effectiveness with anyaccuracy. The large disparity in finalcost means that when United States offi-cials or pavement experts examine a high-performance European technology, theyshould carefully evaluate likely cost-effec-tiveness, as well as quality, in possibledomestic applications. Improvements inquality do come at a price, but while thequality is evident, the value, in relation tocost, remains to be determined.

What was clear to study tour partici-pants was that the European nationsvisited have looked at the cost-benefitequation for building high performancepavements on well engineered subgradesand bases--and have found such pave-ments to be in their national interest.The commitment to quality is obvious,and the Europeans have been willing topay the cost. This commitment is some-thing that Federal and State highwayofficials in the United States shouldcarefully consider if this country intendsto offer a highway system competitivewith that of the European EconomicCommunity in the 1990’s.


2 1

PERFORMANCE-ENHANCING CONTRACTING PROCEDURES

One of the most striking features of theEuropean paving practice is the ability ofEuropean countries to stimulate contrac-tor innovations and apply them within acompetitive process. These innovationsinclude the use of modifiers and additiveswithin asphalt-binders, the use of high-quality aggregates, and new mix designs.While components of some innovativeEuropean mix systems are of a proprie-tary nature, public agencies are able toobtain them by competitive proceduresthat do not require particular proprietarymaterials or processes. Each country hasits own approach, but these proceduresgenerally had two features that differfrom the current process of competitivebidding in the United States:

o Specifications were broader than mostof the method specifications used in theUnited States, allowing contractorsgreater latitude to select effectivematerials and designs; and

0 Contracts require contractors to offerguarantees or warranties that extend1 to 5 years after the work is completed.

The first feature gives the contractorgreater responsibility in selecting aneffective approach. The second holds thecontractor accountable for that choice.

Together, they apparently provide aworking arrangement for tapping theexperience and ingenuity of the contrac-tor while maintaining sufficient controlto ensure public funds are spent effec-tively. Contractors appear to accept theguarantee or warranty requirement, atleast in part because of the existence ofgood quality pavement designs that, inmany cases, they had a role in formula-ting. The study tour participants believethat in the absence of high quality pave-ment designs trusted by the contractors,European contractors would opposeguarantees and warranties.

The countries visited do not generally useperformance-based specifications, whichgauge the quality of the finished product.They also do not use end-product speci-fications, which pin down key character-istics of the final product. Rather, theEuropean procedures reviewed duringthe study tour generally depend uponguarantees and latitude within methodspecifications to build a contracting envi-ronment that encourages contractors touse advance technologies to enhance per-formance. In addition, Sweden has exper-imented with projects using completelyfunctional (design/build/maintain) speci-fications, with some apparent success.

ENVIRONMENTAL CONCERNS

Public concern about the environmental Because of the generally dense popula-aspects of highway construction in gen- tion and the proximity of plants to proj-era1 and asphalt paving in particular were ects, the European countries appear toclearly evident wherever the study tour rely on permanent plants, with portablewent in Europe. Concerns covered topics units that can be relocated being theranging from location of asphalt plants to exception. The choice of location forhow the roads are constructed. permanent plants is a sensitive local land-


2 2

use issue. As a result, totally enclosedplants were seen in Germany and theUnited Kingdom, and landscapingrequirements appeared to be extensive insome cases. Common practice is for anasphalt plant to serve several contractors.Some plants were independently owned,while others were owned by groups ofcontractors.

Generally, study tour participants foundthat at the paving site, environmentalregulations for laying asphalt pavementsdid not appear to be any stricter thanthose in the United States. Indeed,blue-smoke emissions from gussasphaltpaving (which requires higher

temperatures than normal asphalt con-crete) were tolerated in Germany, aswere noticeable emissions from in-placerecycling. When members of the studytour inspected an asphalt recycling ma-chine in Italy, they found thick depositson the exhaust stack, apparently left byplant emissions and particulates.

The study tour also observed the safetyenvironment for construction workers.Some innovative work zone traffic man-agement concepts were observed, espe-cially in Sweden. Overall, however, safetyin work zones is apparently not generallyemphasized to the same extent as in theUnited States.

STRONGER RESEARCH EMPHASIS

Tour participants found that the emphasisplaced on highway and asphalt research,by both contractors and central govern-ments, is much stronger in Europe thanin the United States. Denmark, France,Germany, Sweden, and the United Ring-dom have large centralized research fac-ilities and capabilities, including full-scalepavement testing devices and test tracks(France and the United Kingdom),wheel-tracking tests for rutting, acceler-ated wheel-wearing devices for evalu-ating surface treatments (Sweden andGermany), rolling compactors for prepar-ing large test specimens, and extensivelaboratory capabilities. In four of these

countries, laboratories were larger (instaff and budget) than the FHWA’sTurner-Fair-bank Highway ResearchCenter, even though the population ofthe countries is only 4 to 25 percent thatof the United States.

Research and development by privatecontractors is not only common, but muchgreater than in the United States. This isreflected in the diverse array of speciali-zed paving mixtures and equipment thatcontractors have developed so they cancompete in European markets outsidetheir own country.

PENDING MARKET CHANGES

The planned adoption of uniform agencies are already required to solicitstandards throughout the European bids from the entire European EconomicEconomic Community after 1992 has Community, not just from the countrystimulated public officials, contractors, where the project is located. To date,and research laboratories to examine cross-national awards do not appeartheir own approaches and to prepare for cornmon on paving work, although somebroader competition. On large-scale jobs, contracts for bridge projects and other


2 3

specialized work have been awarded tocontractors from other countries. Asstandards become more uniform, con-tractors and materials suppliers areexpected to be able to compete inbroader markets. Large contracting firmsalready appear to be exploring theprospect of international expansion.

Officials of the centralized researchlaboratories likewise recognize thatchanges planned for the post-1992 erawill affect the need for, and suitability of,some current activities. The European

national laboratories recently formed theForum of European National HighwayResearch Laboratories, an internationalassociation that is helping to reconciletheir activities in the face of thosechanges. Development of the SHRP’sbinder and mixture specifications, whichare likely to be released in 1992, is beingwatched with considerable Europeaninterest because parts of the SHRP’sbattery of performance-orientedspecifications and tests could find useswithin the new system of standards.

INDUSTRY/GOVERNMENT RELATIONSHIPS AND INDUSTRIAL STRUCTURE

The study tour participants found that thebusiness climate in the European pavingindustry differs significantly from that inthe United States in two main respects:public/private cooperation and concen-trated industry structure.

Public/Private Cooueration

Government and industry in Europecooperate to obtain high quality, eventhough costs may be higher. Industryplays a much more active role in research,product development, and new producttesting than in the United States. Thenational governments cooperate withindustry by helping to develop or approvestandardized tests, by arranging fieldtrials of new industry products, and bysetting specifications that ensure ade-quate performance but permit sufficientlatitude to embrace innovative industryproducts.

The method used to select contractorsalso affects quality. For example:

The United Kingdom: On at least someprojects, only qualified companies sel-ected by agency officials are allowed tobid. In addition, various lane-rentalapproaches are used at the national andcounty (state) levels so the duration oflane closure is factored directly into thecost comparison.

Sweden: Only a few large, well-qualified companies appeared able tooffer the necessary assurances underthe performance-guarantee system usedthere.

Germany: A combined system of costand quality-related factors is used toselect the most acceptable contractor,namely the one with the best combina-tion of quality and cost.

Each of these contractual approaches hadsubtleties that varied from country tocountry and even from project to project,but each system differs from UnitedStates practices in several ways:


24

In Europe, much greater emphasis andlatitude are given, within competitivecontracting procedures, to encouragingand hence achieving quality products;

Government and industry work coop-eratively to develop improved products;

And, government officials in Europehave a much stronger ability than theircounterparts in the United States to limitcompetition to well-qualified contractors,and to consider their performance onprojects in the past and the quality of thatwork in the final selection process.

Concentrated Industrv Structure

In Europe, the paving industry is moreconcentrated within a small number oflarge firms than is the case in the UnitedStates, even after the smaller scale ofEuropean countries is taken into account.Further, the contractors are often linkedthrough overlapping ownership of shares,ownership of common suppliers, or otherfinancial ties. In Italy, the nationalgovernment may even own substantialstock in the contractor. Because of these

links, the European contracting industryis even more concentrated than thelimited number of firms would imply.

The concentrated industrial structurehelps explain how some features of theclose industry/government association can work. For example, larger “up front”investments in research and develop-ment make more sense in this structure,as does industry’s acceptance of thegovernment’s strong role in qualifyingand choosing high-quality contractors.

Moreover, government authorities havea large influence on the managementof each company. Perhaps the mostpronounced cases of this are the Frenchand Italian tollway concessions, whichare operated much like a utility in theUnited States. They appear to generateneither excess profits nor potential losses.As in the United States, though, conces-sionaires or toll agencies can generategreater-than-minimum costs for provid-ing and maintaining their motorways,which the governments in Europe areapparently willing to pay for in recog-nition of the obviously high-qualityhighways they receive.

SUMMARY

Based on 2 weeks of discussions withprivate contractors and many governmentofficials, as well as detailed observationof pavements, plants, and laboratories,EAST participants formed severalgeneral impressions:

substantially above United States limitsand truck traffic that often accounts for20 percent of highway usage.

o Greater durability is engineered intopavement structures in Europe, withmore emphasis on providing well-

o European motorways are in much better drained, structurally sound subgrades.condition than equivalent roads in theUnited States, despite axle weight limits


2 5

o Rehabilitation is typically triggered bystructural measures, not by the appear-

search laboratories. European hot-mixcontractors also do more research than

ance of visible distress. their United States counterparts.

o Concerns about noise reduction and 0skid resistance dominate the timing andselection of surface treatments to a fargreater extent than in the United States.

o European countries appear to be mak-ing more use of modified binders, com-monly proprietary, than is the case in 0the United States.

o Innovative mix designs are applied onthe wearing courses of heavily travelledroutes. The designs often use gap-gradedmixes and modified or low-penetration 0binders (between 40-60 percent).

o The scale and diversity of hot-mix prod-ucts, together with numerous economicfeatures of the European environment,result in unit costs for hot-mix productsthat appear to be substantially above theirUnited States counterparts. 0

o European countries have developedcontracting approaches that encouragecontractors to innovate and enhancethe quality and performance of theirproducts.

0

o Environmental controls on Europeanpaving projects appear to be no greaterthan in the United States and are perhapslooser, while zoning controls of asphaltplants in at least some countries appearmuch stricter.

o European governments are much moreactive than governmental agencies in theUnited States in supporting highway re-

Research results tend to be more aggres-sively marketed in Europe, particularly inFrance where the LCPC sometimesmarkets directly, or licenses manufac-turers to market, its proprietary inven-tions.

The coming of standards in 1992 thatwill apply to the entire EuropeanEconomic Community is a dominantgeneral concern of contractors andgovernments alike.

One response to the need for thedevelopment of European EconomicCommunity standards may be the adoption of European performance specifications, which could be more easily adaptedby each European nation to its own highway system procedures and practices.

European governments and the privatesector work more closely than is true inthe United States. At least part of thereason for the presence of higher qual-ity highways in Europe can be traced tothis cooperation.

The concentration of Europe’s highwayindustry into a few companies, oftenwith overlapping ownership and some-times with a degree of ownership bygovernment, provides for an improvedclimate of cooperation, but at the costof the intense competitive environmentthat exists in the United States andprovides the countries with lower costhighways.


TRIP SUMMARIES

3 1

SWEDENItems with the Highest Potential forImplementation in the United States:

o Stone Mastic Asphalt

o Drainage asphalt (also known as PA)

o Contract administration procedures, in-cluding warranties and functional con-tracts

ITINERARY

The Swedish tour consisted of a Sundayafternoon seminar with government andindustry officials, as well as tours ofprojects, both active and completed, andan asphalt plant.

SUMMARY

The Sunday afternoon seminar featuredpresentations on several subjects:

1 . Heavy duty asphalt pavements (SMAand PA).

2. Government and industry perspectiveson the Swedish experience with SMAand PA.

3 . The Swedish experience in functionalcontracts and the use of guarantees.

Unlike the other countries visited,Sweden faces the problem of extensiveuse of studded tires, which cause rutting.In the northern region, 90 to 95 percentof all vehicles use studded tires. In the

Goteborg area, reported use was 50 per-cent. Swedish authorities have concludedthat designing conventional asphalt con-crete mixes with good shear resistance aswell as satisfactory durability and resist-ance to cracking is difficult, if not impos-sible. In Sweden, the answer is SMA.

The three main characteristics of an SMAmix are:

1 .

2 .

3.

The coarse particles must form a stoneskeleton with firm contact between theparticles.

The glue between and the coating ofthe coarse particles should consist of avoid-less mastic.

The mastic must be stabilized so it doesnot drain off the coarse particles duringstorage, hauling, and laying.

Mastic, as used in this context, means theasphalt cement, fine aggregate (less than2 mm), and filler.

Stone Mastic Asphalt is a gap-gradedmix using high-quality crushed aggregatewith a maximum size of 16 mm. Approxi-mately 80 percent of the aggregate islarger than 2 mm, with 65 to 70 percentlarger than 8 mm. By weight, the bindercontent ranges between 6.6 and 7 percentof the total mix. The main additives usedto stabilize the mastic seem to be eithercellulose or mineral fibers. The fiberslook like rock wool and are reported tobe approximately 1.5 mm long. In short,


3 2

the SMA mix basically consists of twoparts: a rather single-sized coarseaggregate and the mastic.

Porous asphalt, sometimes called drain-age asphalt, is also receiving considerableattention in Sweden. This mix, whichseems to be similar to our open-gradedfriction courses and some plant mix seals,has excellent noise reduction and skidresistance properties. It has not, how-ever, shown sufficient durability inSweden. In the view of Swedish author-ities, this mix can be improved by usingfibers or modified asphalt binders. Theyalso emphasized that the existing surfacemust be sealed prior to laying PA.

Field reviews of projects completed andunderway generally confirmed what waspresented in the seminar. City streetssurfaced with SMA and subjected toheavy truck traffic and abuse from stud-ded tires seemed to hold up well. A heav-ily traveled PA city street had a rut depthof approximately 25 mm after 6 years.The pores in the mix appeared to beclogged with debris, and this blockagetends to destroy the strong skid resistanceof the mix.

The two active projects reviewed involvedSMA construction. The contractor foreach project used different SMA mixes,as was evident from their appearance.Compaction was achieved with steel-wheeled rollers. As a general rule,pneumatic-tire rollers are not used onsurface courses in Europe. The typicalSMA overlay in Sweden is between 30and 40 mm thick. Both active projectshave thicknesses of approximately 30 mm.

The price difference between SMA andthe standard asphalt concrete mix wasdifficult to tie down. Comments indica-ted, however, that SMA is somewherebetween 10 and 12 percent more expen-sive. The cost of PA is somewherebetween the two. Top quality aggregate isused in all the mixes, even if the materialmust be imported at significant cost. InMay 1990, 40 Nordic asphalt technolo-gists compared different asphalt mixeswith standard hot mix asphalt (HMA).The table on the facing page shows theresults.

One Swedish expert offered the opinionthat SMA and PA will dominate thesurface market in Europe for the fore-seeable future. Nobody argued with hisconclusion.

Cooperation between the private andpublic sectors in Sweden seemed verygood. In general, Sweden operates undera quality assurance process and requires2- to 3-year warranties on asphalt pave-ments. Neither government nor industryhas any problems with the warranty con-cept. The required surety of up to 5 per-cent of the contract price is released aftersatisfactory completion of the warranty.

In the early 1980’s, Sweden tried twoprojects with completely functional(design/build/maintain) specifications,including a maximum tolerated rut depth,smoothness, and friction. No defectswere allowed and warranties of 5 yearswere required. These projects were suc-cessful, but have not yet resulted in fur-ther functional contracts. Swedish offi-cials are tentatively planning more, butbelieve functional contracts have onlylimited application.


PROPERTY

Shear resistanceAbrasion resistanceDurabilityLoad distributionCracking resistanceSkid resistanceWater sprayReflectionNoise reductionPublic recognition

NG COMPARED WITH HOT-MIX ASPHAIJTHot-Rolled* SMA Porous AsphaltAsphalt-(-) + + + +

+ + + (-)+ +(+) + + -(-)

(-) (-) -(-)+ +(+) +(+) (-)

0 + +(+)0 0 + + ++ + +(+)

0 + + ++ + + + + +

* The hot-rolled asphalt is the British surface mix.

0 Means equal to the asphaltic concrete+ Means better than asphaltic concrete

+ + Means much better+ + + Means very much better

- Means worse-- Means much worse

--- Means very much worseItems in ( ) indicate a half mark

The large contractors--but not smallcontractors--seem to favor this type ofcontract, but have some concerns. Theywould like the government to set lessdemanding specifications. One majorcontractor stated that functional con-tracts provide an opportunity to empha-size and measure the real quality of thework. The current system, as the largecontractors see it, often measures theexactness of theoretical recipes, ratherthan quality. They also believe currenttest methods are often unreliable andunrepeatable, a view that contractors inthe United States have expressed abouttests in this country.

Two large multinational contractors doabout 85 percent of the asphalt pavementbusiness in Sweden. Each has tradenames for several of its products.Whether or not patent rights or propri-etary rights were involved with any of themix designs or mix processes was notclear. Swedish specifications are report-edly open enough that anyone can com-pete, although the market dominance bythe two major contractors makes marketentry for other contractors difficult.

The two large contractors own and oper-ate the asphalt plant visited in Sweden.As in the rest of Europe, this plant and


3 4

others in Sweden are not geared to highproduction. The one visited couldreportedly produce about 240 metric tonsper hour. The plant was equipped with aconveyor that introduces fibers into themix for SMA. The fibers are eithercellulose or mineral, depending on whichcontractor’s mix is being produced. Tomake it easier to introduce cellulosefibers into the mix, pellets can be madeconsisting of 50 percent bitumen and 50percent fiber. The bitumen and fiber canbe hauled in bulk and introduced into themix directly. The other fibers areintroduced into the ix in bags.

CONCLUSIONS

Stone Mastic Asphalt has the potential toassist United States highway agencies insolving some of the problems we havehad with HMA surfaces, at least in thenorthern tier of States. The effect thatthe higher temperatures in the South andSouthwest would have on this mix needsfurther evaluation. The Swedish experi-ence suggests several factors that willhave to be kept in mind in deciding howSMA might be used in this country. Itmust be placed on a sound pavementstructure. It requires premium aggre-gates. In addition, SMA is sensitive tovariations in mix proportioning, so tightercontrols in mixing and placement arenecessary.


DENMARK

3 7

Items with the Highest Potential forImplementation in the United States:

o Use of additives

o Contract administration procedures,including warranties

o Bridge deck protection

ITINERARY

The Study Tour stayed in Denmark lessthan 1 day. The stay included a visit tothe offices and laboratory of the DanishAsphalt Pavement Association, a reviewof a paving project at the CopenhagenAirport, a briefing by officials of theDanish Road Directorate, and a review ofcompleted projects.

SUMMARY

The paving project at the CopenhagenAirport consisted of paving a taxiway.The project was particularly well run.Two pavers operating side-by-side elim-inated any appearance of a longitudinaljoint in the wide mat. Seven rollers op-erated behind the paver in a relativelyconfined space. Carbon black was usedas an additive in the mix (12-15 percent).According to contractor personnel, thecarbon black makes the mix extremelydifficult to compact. According to theconsultant, however, the difficulty is jus-tified because the carbon black improvestemperature susceptibility and resistance

to aging. The contractor also reportedlyused lime and cellulose fibers in the mix.This project required an S-year warranty.

According to Road Directorate officials,Denmark is experiencing some problemswith rutting. The country does not permitstudded tires, so the rutting that does oc-cur is caused by traffic--namely increasedcommercial vehicles and higher tire pres-sures. Pavements that have been in placefor some time have, in recent years,started to rut. The Road Directorate isusing SMA-type surfaces to try to over-come this problem. Gap-graded HMAwith pre-coated chips rolled in has alsobeen widely used. However, SMAseems to hold the most promise fora rut-resistant surface course.

Denmark requires a 5-year warranty onhighway pavements covering smoothness,durability, and skid-resistance. The con-tractors select the mix design within theRoad Directorate’s guidelines. The struc-tural design was the responsibility of theRoad Directorate, not the contractor. Thecontractor is responsible for routine test-ing, with periodic checks by the RoadDirectorate. Of the contract price, 5 per-cent is withheld during the warrantyperiod.

Denmark seems to do more recyclingthan the other European countries, main-ly for environmental reasons althougheconomic benefits result, too. The coun-try’s road contractors reportedly recycleabout 200 ,000 tons of HMA per year.


3 8

Danish road officials emphasize bridgedeck protection and claim considerablesuccess with the process used. All bridgedecks, whether concrete or steel, arecovered by a protective system of fourbituminous layers ranging from a mem-brane seal to a chip seal wearing course.

The Danish Asphalt Pavement Associa-tion’s laboratory is well-equipped andappears to be used mainly for testingmixes and mix design. The tests basicallygive contractors a level of comfort withtheir designs--an important factorbecause of the warranty requirement onall major highway projects.

A Danish contractor demonstrated inno-vative equipment for applying edgelinepavement strips. The process is marketedas “Spotflex.” A machine applies dotsapproximately 3 mm high but can be anywidth desired. The marking material con-sists of a two component acrylic resinused as a binder, glass beads, titaniumdioxide, and filling substances. They are

laid on the road at a distance commen-surate with the height of the dots, givingthe driver the impression of an unbrokenline. Because of the height of the dots,incidental light from headlights isreflected toward the driver, therebyenhancing visibility, while the raised dotscreate a noise that alerts the driver whenthe vehicle is leaving the roadway.

CONCLUSIONS

The problems Denmark is experiencingwith its asphalt surfaces are similar tothose in the United States, though not asextensive. As in other countries, SMAshows great promise as a solution. TheRoad Directorate is participating in theStrategic Highway Research Program, soperhaps mutual solutions can be found.

Contract administration features,including the warranty provisions, shouldbe further studied for potential use in theUnited States.


GERMANY

4 1

Items With the Highest Potential forImplementation in the United States:

o Splitmastixasphalt (SMA)

o Drainage asphalt

o Contract administration procedures

ITINERARY

The German leg of the study consisted ofmeetings with government and industrypersonnel, a tour of the Federal HighwayResearch Center (BundesanstaltfurStrassenwesen--BAST) near Bonn, visitsto construction sites where activitiesranged from laying HMA base to thinoverlays and projects to fill ruts. Person-nel from all three levels of government(city, state and federal) were involved atone time or another in the meetings andon-site reviews.

SUMMARY

The review in Germany concentrated onthe Autobahns and major arterial routes.The Autobahns are the main arteries ofcommerce in the German transportationsystem carrying approximately 30 percentof the traffic. Although trucks compriseabout 20 percent of the total, study tourparticipants observed a much higherpercentage of trucks on some sections.

The Autobahns generally have 1940’sgeometry. Because of environmentalconcerns, German road officials havefound that improving the Autobahns to

United States freeway standards isextremely difficult. Motorway pavementstructures are designed for a 40-year life,as opposed to the 20 years often used inthe United States. Surface conditions aregenerally excellent, but some rutting andcracking was observed on a few sections.In general, the Autobahn network is amature system with many miles underrehabilitation, much the same as ourInterstate system.

Most major highways have a bituminoussurface (71 percent of the Autobahns and99 percent of federal highways). Themain types of bituminous surface areGussasphalt, SMA, and HMA. TheGermans consider Gussasphalt to betheir most durable surface, followed bySMA and HMA.

Gussasphalt is a poured mastic mix withchips rolled into the mixture. It requiresspecial equipment, as well as quite a bitof hand work, and is placed at approxi-mately 425’ F. German officials useGussasphalt on sections of the Autobahnwith the highest traffic volumes and onbridge decks.. The expected service life is12-18 years and it costs about 90 percentmore than HMA.

Germany is given credit for inventingSMA, which is used as a surface coarse onnormal traffic sections of the Autobahnand on other major federal highways withhigh traffic counts. The maximum aggre-gate size used for SMA in Germany wassmaller than in Sweden. In some cases,a maximum size of 8 mm is used, but11 mm is typical. The grading curve also


4 2

seems to be a little flatter than in Sweden.Asphalt cement content is relatively high(7 percent, plus or minus) and fibers areused as a stabilizer for the mastic. Sand issometimes added to the surface toincrease initial skid resistance. Expectedservice life is 10-15 years.Splittmastixasphalt, as SMA is known inGermany, costs 20 to 30 percent morethan HMA. Hot-mix asphalt is used as asurface course on other Federal, state andcounty highways. The expected servicelife is 8-12 years.

Porous asphalt is not yet in general use inGermany. Because, however, of a strongemphasis on noise abatement, PA maybecome more common. German roadofficials see it as having strong potentialfor reducing noise as well as increasingsafety. They are looking not only toreduce the noise caused by theinteraction of tire and pavement, but todampen traffic noise created from allsources.

The Germans underlay the PA surfacewith a sealing membrane to eliminatewater intrusion into the structure. Across-section of one such project alsoshowed an underdrain system in theexisting pavement structure to take awaythe water. This surface is limited to highvelocity traffic areas because debris tendsto fill up the voids. Porous asphalt isabout as expensive as Gussasphalt,probably because of the requirement forthe membrane sealer and drainage.

A patented slurry seal process known asRalumac is being used with some successas a rut filler and thin overlay. The majoradvantage is that it will adhere to PCCand is quick setting. Traffic can be placed


on it within a half-hour after it is laid.Several States in the United States areusing this product.

The Germans no longer do individualstructural designs for pavement projects.Typical structural sections have beendeveloped for asphalt and PCC pave-ments on the basis of traffic volume andclassification. Mix designs are selectedthe same way. These structural sectionsand designs are based on experience andthe Germans are not interested in anyother approach. Because the Germansdo not tolerate frost or moisture prob-lems in the underlying layers, they do nothave to try designing the upper courses tocompensate for inadequacies in thesubgrade or subbase. They can base theirdesign practices on the fact that thesubgrade is structurally sound andadequately drained.

Specifications seem to reflect a combin-ation of method and end result. Thecontractor does the mix design withinlimits shown in the government’s recipesfor different mixes. The contractor alsodoes the quality control, but the govern-ment does the quality assurance, eitherwith its own staff or, most often, throughprivate labs. Of the countries visited, theGerman government appears to exercisethe most oversight of contractoroperations.

Study tour participants observed majorreconstruction on older sections of theAutobahn, but most work involved cor-recting such surface problems as ruttingand skid resistance. The German pave-ment engineering philosophy is to fix theproblem before it occurs. As a result,much of the work was on pavements that

4 3

would be considered in good condition inthe United States. The Germans alsobelieve in fixing only the existing prob-lem. If one lane is deformed or is losingskid resistance, the Germans will mill offand resurface only that lane. Often, twodifferent mixes can be observed inadjoining lanes because one wasrehabilitated and the other was not.

Contracts are awarded to what theGermans termed “the most acceptablebidder.” Time did not permit the studytour participants to collect enoughinformation to determine how theselection process works. In most cases,the contract reportedly is awarded to thelowest bidder, but technical elements arealso considered. While bid documentsmay specify the type of pavement (asphaltor PCC), the contractor can propose analternate type. This process appears to bemore like value engineering thanalternate bidding.

For reconstruction projects, how thebidders propose to use recycled asphaltpavements (RAP) is another technicalfactor considered in the award. Thecontractor is required to recyclematerials, to the highest level possible, onthe project. For example, a contractorwho demonstrated he could use 50percent RAP in the binder course wouldbe favored over a contractor who plannedto use the RAP as subbase material or fill.No RAP is permitted in the surfacecourse. Study tour participants could notdetermine how often technical factorsoverride cost considerations in awardingcontracts. Several large contractors seemto dominate the market, a situation thatalso exists in the other countries visited.

A 4-year warranty is required on highwaycontracts. On most projects, an amountequal to 3 percent of the bid price isretained during the warranty period.Whether this is a cash retainage or can bebonded was not clear. The contractor isresponsible for any defects that occurduring the 4-year period. In essence, heis responsible for maintaining the pave-ment while the warranty period is ineffect.

The sophisticated asphalt plant nearHamburg was completely enclosed exceptfor its 15 cold storage bins and its aggre-gate stockpiles. The plant has two dryerdrums, although it still uses a batch mixer.One drum preheats the RAP, while theother heats virgin material. Exhaust gasfrom the virgin drum, which has a burner,goes through the other drum to preheatthe RAP. The plant is fully automatedand reportedly capable of producing 160different mixes. It routinely produces,however, only about 20. German asphaltplants are not geared to high production,ranging from 160-250 tons per hour.Shared ownership of a plant by two ormore contractors is reportedly fairlycommon.

As in the other European countries,Germany has a large centralized researchfacility. The BAST employs about 350people--more than twice the number atthe FHWA’s Turner-Fairbank HighwayResearch Center. The lab includes afull-scale pavement testing device, wheeltracking tests for rutting, and acceleratedwheel wearing devices for evaluatingtire-pavement interaction. Germany hasmade a much stronger commitment thanthe United States to research as a majorpart of the problem-solving process.


4 4

The Germans are dedicated to protect-ing bridge decks and assuring good ride-ability. The noise levels of traffic onbridges is also an important consider-ation. Bridge deck protective systemsseem quite expensive, but they areeffective. The systems generally consistof an epoxy resin on top of the surface tobe protected, followed by an asphalt sealwith a gussasphalt surface.

CONCLUSIONS

For the United States, SMA has strongpotential. While a 40 mm overlay seemsto be standard in Germany, thinneroverlays with SMA are used, as are asmaller maximum size course aggregate.Gussasphalt, by contrast, does not havestrong potential for use in the UnitedStates. Factors working against the use of

Gussasphalt are its cost, specialequipment requirements, and highlaydown temperature, which posespotential air pollution problems.

Prudent use of fibers and polymers canenhance a mix, but cannot compensatefor poor mix design or poor materials. InGermany, as in the other countriesvisited, premium crushed aggregate isused where premium mixes are required.Hauling aggregate several hundred milesor importing it from other countries is therule rather than the exception.

Again, as in the other countries, qualitycontrol by the private and public sectorsin Germany appears excellent. Warrantyrequirements are partly responsible.Another major reason is the fact that eachcontractor has more responsibility thancontractors in the United States for mixdesign, production, and laydownoperations.

Warranty provisions should be givencloser review to see if they would beapplicable in the United States.Similarly, the provisions in the biddocuments allowing the contractor tosubmit alternate solutions should beexamined.


ITALYItems With Highest Potential forImplementation in the United States:

System of concessionaires to buildmotorways

Contracting procedures

Use of modifiers and additives

Pavement management system

ITINERARY

A subcommittee of AASHTO andFHWA study tour participants visitedItaly for one evening and a full day. Thegroup toured several installations, includ-ing the headquarters of the NationalRoad Board (Azienda NazionaleAutonoma delle Strada--ANAS), anasphalt plant using the Novophalt processand a section of motorway where themodified asphalt was being laid, and arestaurant concession operated byFerretti at the FZaminia Est HighwayService Area north of Rome. During avisit to the Societa Autostrade Laboratoryat Fiano Romano, the subcommitteelearned about Italian highway engineer-ing and asphalt technology, as well as theprocess and equipment used to managepavements on the motorways thecompany controls.

SUMMARY

The ownership, management, andoperation of the Italian highway system isquite different from what we are familiar

with in the United States, and may seemcomplicated by comparison. FollowingWorld War II, the Italian governmentestablished a new national highwayagency to reconstruct the nation’s war-damaged highways. That agency evolvedinto today’s ANAS, which operates au-tonomously, with the Italian Minister ofPublic Works serving as Chairman. TheANAS is responsible for overall highwayplanning in Italy and works to bring high-ways to both wealthy and poor areas.

In the early years after World War II,Italy concentrated on repairing itsdamaged highways and bridges. In themid-1950’s, development of a majormotorway network began. The Italiangovernment, short on resources, decidedthat the best way to build the motorwayswas to grant concessions to private com-panies. They would design and build tollmotorways and operate them for 30 years,before turning them over to the govern-ment. In addition to providing a mech-anism for using private capital, thisarrangement had the advantage of allow-ing the concessionaires to avoid the bid-ding procedures normally used by ANASfor letting construction contracts. Theconcessionaires, being wholly responsiblefor the motorways under their control,are free to negotiate contracts as privatebusinesses.

Today, ANAS is directly responsible forsome 50,000 km of state highways androads, including about 1,000 km of toll-free motorways. The agency also super-vises the network of concessionaires andmay make capital contributions toward


48

concession toll roads. It does so when aconcessionaire is constructing a motorwayin a depressed area where toll revenuesmay not be sufficient. In all, 27 conces-sionaires manage 6,000 km of Italy’s 7,000km of existing or planned motorways.

Societa Autostrade, which received thefirst concession for a motorway in 1958,controls some 3,000 km of the motorwaynetwork. The company is part of a corp-orate structure that goes back to the post-war period when capital was short and thecountry needed to reestablish its privateindustrial activity. One method used toovercome these problems was creation oflarge private companies funded mainlywith public money. The giant Institutefor Industrial Reconstruction, known asthe IRI Group, is one of these companies.It includes many subsidiary corporationsin a variety of fields. Within the IRIGroup is the IRI-INTALSTAT Group,which includes Societa Autostrade.

Another IRI-INTALSTAT Groupcompany, PAVIMENTAL S.P.A., is thecontractor for construction and mainten-ance of motorways under concession toIRI-INTALSTAT. Similarly, the group’sBONIFICA is a civil engineering consult-ing company that works for Societa Auto-stmde. This is a greatly simplified descrip-tion of a complex array of relationshipsdeveloped over several decades. In ess-ence, though, Societa Autostrti differsfrom United States toll authorities in itsability to negotiate contracts for work bywhat are, in effect, related companieswith overlapping ownership and direc-tors--and with no apparent use ofcompetitive bidding.

In several ways, Societa Autostade issimilar to toll authorities in the UnitedStates. The company has a largeengineering staff and a well-equippedlaboratory in which development wasobserved to be underway on several newideas in pavement technology. Tollsgenerate a healthy revenue, with ANASobserving that typically, the Italian con-cession companies have maintenancefunds available that are “five/six foldhigher than” funds available to ANAS.Italy, like toll authorities in the UnitedStates, uses concessions for the operationof restaurants and other service facilitieson its toll roads; the one visited by thesubcommittee was excellent. Accordingto Societa Autostrade officials, nearly25 percent of the company’s operatingrevenues are generated by the servicefacilities or the leasing of excess land atinterchanges.

In Italy today, the highway and roadsystem carries 85.4 percent of all passen-gers and 61.5 percent of all goods move-ments. Highway traffic growth has beenhigh in recent years, with Societa Auto-strade reporting a 45.4 percent increaseon its motorways between 1984 and 1989(47 percent for passengers, 40 percent forgoods). In 1989 alone, the company sawa 7.6 percent increase (7.2 percent forpassengers, 9.1 percent for goods).

Societa Autostrade’s concessions wererecently extended and now run to 2018.Since the concession started in 1958, theextension means the company will beresponsible for some motorways forabout 60 years. This realization, and thedesire to reduce maintenance costs andthereby increase net revenue from tolls,caused Societa Autostrade to establish a


49

comprehensive pavement management Deep repaving is done with base coursesystem. It includes a twice-yearly struc- polymer-modified asphalt mixes, some-tural examination of all 3,000 km of its times at night. The old asphalt mix ismotorways. The company reported that cold-milled and recycled in place. Thenits system has resulted in an overall cost a non-woven fabric is placed, followed byreduction of around 30 percent because the laying of a polymer-modified asphaltof a more intelligent use of maintenance base course and asphalt mix binder andactivities. wearing courses.

The Societa Autostrade pavementmanagement system tries to reduce allfactors to numbers, which are thencompared with pavement performancecurves to design specific maintenanceactivities. The analysis devices have beenphased in over the years, and now includea SCRIM skid resistance truck (1982), afalling weight deflectometer (1983), anARAN truck for measuring profile andgeometric characteristics (1985), an APLdevice for measuring the longitudinalprofile (1988), and a newer truck, knownas SUMMS, for measuring skid resistanceand texture. The machines take measure-ments at different intervals and operate atdifferent speeds, as follows: ARAN, 20 mand 60 km/h; APL, 25 cm and 72 km/h;and SUMMS, 10 m and 60 km/h. Thefalling weight deflectometer stops for 10measurements every km, with one minuteper measurement.

Societa Autostrade has placed pavementmaintenance activities in six categories:reinforcing, surface dressing, milling andrepaving, deep repaving, recycling inplace and at plant, and poly-functionalcomposite pavement. The company isincreasingly using open-graded bitumi-nous mixes, both to reduce rolling noiseand hydroplaning, and does considerablerecycling.

Poly-functional composite pavementsare just being introduced. They are beingconsidered for future reconstruction ofall motorways. One has been placed onthe Fiano-S. Cesareo connector. It com-prises a continuously reinforced concretepavement (CRCP) course laid on agraded aggregate base and covered withan open graded drainage course ofasphalt concrete. The CRCP providesresistance to fatigue, while the wearingcourse is considered as a renewablesurface that has high skid resistance andreduces water spray and rolling noise.

The subcommittee visited an asphaltplant that produces a modified asphalt bythe Novophalt process. It blends usedpolyethylene scraps, in this case fromground electrical insulation, into theasphalt cement. While costs increasesubstantially with the Novophalt process,the pavement reportedly might last morethan twice as long.

At the same plant, the subcommitteeexamined two asphalt recycling pavementtrains owned by PAVIMENTAL. Theexhaust of one train was coated withasphalt, indicating a possible problemwith substantial operating emissions.Another machine is being modified foroperation in the Soviet Union.


5 0

The subcommittee was told about Italianasphalt practice, which includes exten-sive use of such modifiers as polyethyleneand rubber (the fact that the rubber wasnot from tires was emphasized). Theaggregates used in Italy are usually eitherbasalt or limestone. In a basaltic basecourse, asphalt content will typically beabout 4.5 percent. The second coursemay use limestone, with about 5.2 per-cent asphalt and 3-4 percent voids. Thetypical wearing course has aggregate inthe 10-15 mm range, with an asphalt con-tent of about 6 percent and 2-3 percentvoids. However, for drainage or PA wear-ing courses, aggregates average around18 mm, with an asphalt content of about8 percent and 22 percent voids.

CONCLUSIONS

The Italians have amply demonstratedthat toll authorities can construct andmaintain a modern motorway system,although the specific institutionalarrangements used in Italy seem uniqueto that nation’s situation. Sociefa Aufo-sfrade’s pavement management processand some of its highway engineeringdevelopments, such as its proposed useof composite pavement, are worth furtherstudy.


5 3

FRANCEItems with the Highest Potential forImplementation in the United States:

o Patented additives and polymer-modified binders

o Contract Administration Procedures

o Well-equipped laboratories, bothgovernment and private

o Thin overlays and surface treatments

ITINERARY

In France, the study group’s travel wasmostly by air and rail, rather than bymotor vehicle as in the other countries.The trip included a tour of the CentralLaboratory of Bridges and Roads(Laboratoire Central des Ponts etChausees--LCPC), the main laboratoryof the Ministry of Public Works inNantes. Most government-sponsoredcivil engineering research and develop-ment occurs in the laboratory. The 2-daytour was rounded out by tours of activeand completed projects in the vicinity ofNantes and Lyon as well as visits to con-tractor facilities and laboratories. Thework underway generally consisted of thinoverlays and slurry seals.

SUMMARY

France has approximately 7,000 kilome-ters of motorways comparable to ourInterstate System. Most are toll facilitiesdesigned, built, and operated by conces-sionaires (about 6,000 kilometers). Of

the eight concessionaires involved, sevenare quasi-public entities (public-privatepartnerships) and one is fully private. Athree-person commission representingthe Ministries of Transport, Finance, andDevelopment selects the concessionaires,whose contracts are for 35 years and canbe renegotiated. A 5year warranty isrequired. The concessionaire sets tollrates, with the approval of the FinanceMinister.

France uses more polymer-modifiedasphalt than the United States and prob-ably uses more than any other countryin Europe. In fact, France reportedlyuses more than half the polymer sold inEurope. Approximately 7 percent ofall asphalt mixes used in France arepolymer-modified, but the polymers areused only in the surface course. Thecomparable figure for polymer-modifiedasphalt in the United States is 2-3 per-cent. Polymer-modified binders costabout twice as much as standard asphaltcement and on average, the mix isapproximately 20 percent moreexpensive.

More patented or proprietary mixes,additives, and processes appeared to bein use in France than in the other coun-tries visited or in the United States. Eachlarge contractor the study group met withhad several. In some cases, the productswere developed by government-industrycooperative ventures. Some of the prod-ucts are marketed and used in the UnitedStates.


5 4

Overall, in fact, the French systemencourages innovation by giving con-tractors the opportunity to use theirown technology in pavement design andconstruction. For example, specificationsusually identify desired end-results.While many patented additives and pro-cesses can be used in the six basic mixesdescribed below, contractors may proposeother solutions--and the contractingagency often accepts them. The proposerof an innovative solution, however, mustbe able”to demonstrate to the owner’ssatisfaction that the desired results canbe achieved. This public-private cooper-ative approach seems to result in superiorproducts and superior pavements.

The study tour members observed aparticularly unique patented operationused to produce a stress absorbing mem-brane (SAM). The operation consists of amodified binder strengthened by contin-uous synthetic organic threads spreadover the binder and covered by chips.The unusual feature was that the binderand the threads were distributed by thecontractor’s patented machine. Largereels were mounted on the back of thismachine and the threads were dispersedover the binder in a single operation. Aconventional spreader following the otherpiece of equipment distributed the chips.The result seemed to be similar to fabricsembedded in a sprayed binder. It’s obvi-ously an expensive operation but the con-tractor claimed it was successful. Othercontractors reported that they had theirown less expensive version of a SAM thatdid not include the threads.

The government specifies six basic classesof hot-mix for use in France:

1 . Conventional hot-mix road base--Thismix, which is 120 to 180 mm thick, isplaced in a single lift. Maximum sizeaggregate is 20 mm and all aggregateis crushed. It contains approximately4.2 percent asphalt, which has either40/50 penetration or 60/70 penetration.

A variation of this x-nix is high modulusroad base, which contains 6 percentasphalt with a lo/20 penetration and apolyethylene additive. The French claima 25-40 percent thickness reduction forthe same structural effect with the highmodulus mix.

2. Conventional HMAconcrete--This isused in new construction and for over-lays. Thickness is 60-80 mm while themaximum size of aggregate is 14 mm forthe thicker lift and 10 mm if the lift is60 mm. Only crushed aggregate is used.It is continuous-graded, with 30-35 per-cent passing the 2 mm sieve. Asphaltcontent is 5.7 percent of 40/50 penetra-tion or 60/70 penetration with 5 percentplus or minus voids.

3. Thin asphalt concrete--This mix is usedfor overlays of approximately 40 mm.It’s a gap-graded mix with a maximumaggregate size of 10 mm using 100 per-cent crushed aggregate. Asphalt contentis 5.7 to 6 percent using a 40/50 penetra-tion or 60/70 penetration. The Frenchclaim excellent rut resistance and skidresistance with this mix.

4. Very thin asphalt concrete--This mix,which is used for overlays of approxi-mately 25 mm, is similar to the thinasphalt concrete just described. Thedifferences are that the binder is modi-


5 5

5 .

fied with polyrners, rubber, or fibers andthe asphalt cement content can go upto 7 percent, depending on the modifierused. In addition, a heavy tack ofpolymer modified emulsion is used.

Porous asphalt--This mix is similar tothe open-graded friction course usedin the United States and the PA anddrainage asphalt used in other Europeancountries. It’s a gap-graded mix with amaximum aggregate size of 14 mm and a22 percent void content. The thicknessis 40 mm or less. In most cases, a modi-fied binder of polymer, rubber, or fibersis used.

6. Paver laid chip seal--The LCPC and aprivate contractor developed this rel-atively new product. It’s approximately15 mm thick. The binder layer is apolymer-modified emulsion and the chipsare between 6 and 10 mm, pre-coated hotwith sand and asphalt. This mix, which isused only on pavements that are notdeformed, is intended to improve surfacecharacteristics. A special paver was alsodeveloped to lay this material.

is similar in concept to the FIIWA’s ALF(Accelerated Loading Facility). Theloading wheels of LCPC’s facility rotatein a circular pattern from a fixed centerpoint at a speed of 70 km/hr, adjustedfrom 8 to 18 metric tons, with eithersingle- or dual-wheel configuration.Laboratory officials reported that a20-year load for a typical major highwaycould be achieves in about 2 months. Thefacility has three separate tracks thatallow for continuous testing while newstructural sections are constructed.

Another unique feature of the LCPCcomplex was the equipment testing area.Part of it is dedicated to testing suchequipment as pavers and finishing mach-ines for speed, vibration, accuracy ofcontrol, etc. Another part of the facilitytests mixers for speed of production andmeasuring accuracy. A unique featurewas an attempt to use electronic screen-ing with an optical readout to check grad-ation. If such a feature became opera-tional, it would‘significantly improveplant operation by permitting accurateand consistent batching.

France does not use SMA, which has pro-duced excellent results in other Europeancountries. The chief concern is reported-ly the difficulty of achieving the desiredmicro-texture for skid resistance.

The LCPC laboratory at Names is theflagship of the public works laboratoriesnetwork, which includes an additional 17regional laboratories. In all, the networkemploys about 2,700 people. The LCPCalone employs about 580 people, of which200 are engineers. The lab includes afull-scale accelerated testing facility that

Some of the equipment used in mixdesign and verification was of a type notgenerally seen in the United States. Thegyratory compactor, the pneumatic-tirecompactor, the rolling wheel rut tester,and the fatigue equipment were particu-larly impressive. The LCPC developedmuch of the equipment, which privateconcerns manufacture and distributeunder exclusive licenses.

Laboratories operated by the major con-tractors are also well equipped, generallywith the LCPC-designed equipment.One result is that the contractors are


highly confident when testing their mixesbecause the government will use the samemodel of equipment and the same tests.Agreements on test procedures to beused to predict performance of propri-etary products were worked out afterprivate/public sector discussions over2 years.

As in the other countries visited, severallarge contractors dominate the market.Contracts are generally awarded bycompetitive bid except for motorwayconstruction. As mentioned previously,motorway construction contracts requirea 5-year warranty, but on other highways,the warranty is for 1 year.

All bridge decks were sealed with asphaltmaterial for protection and to improverideability. Several patented processesfor this purpose would be worth lookinginto for use in the United States.

Another similarity with the other coun-tries visited was the fact that hot-mixmanufacturing facilities are not geared tohigh production. Because of the sophisti-cated surface mixes used, the facilities arcdesigned more for quality and uniformity.Shared ownership of plants by two ormore contractors is reportedly fairlycommon.

The emphasis in France is on preventivemaintenance. The government promotesinnovative solutions. In addition, the gov-

ernment requires top quality aggregateand sophisticated surface mixes. Recycl-ing occurs, but the recycled asphalt pro-duct is never used in the surface courses.

CONCLUSIONS

The United States should try the Frenchapproach to mix design and the equip-ment used as tools to verify the designs inthe laboratory. French testing simulatesthe real-world performance of the pro-ducts. Several of these concepts andsome of the equipment are being evalu-ated by the SHRP. The private sectoraccepts the results because of the exten-sive public/private dialogue and theevaluation of testing approaches beforeadoption.

France is far advanced in the use ofpolymers and modified binders. Thesemixes are used judiciously and, seem-ingly, successfully. An in-depth study ofthe French experience should be under-taken for possible application in theUnited States.

The cooperation between industry andgovernment in France fosters innovation.The institutional relationships are differ-ent from those in the United States, butsome techniques could be borrowed foruse in this country to promote closergovernment-industry cooperation. Theresult would be a higher quality product.

..::.

. . . . .:.:.:.,. . . . . . . . .. . . . . . . .xc.:.:

0

,.:::: jj j j.. . . .A.

. ..: j. . . .. . . .

M

5 9

UNITED KINGDOMItems With the Highest Potential forImplementation in the United States:

o Heavy Duty Asphalt Bases

The study tour participants reviewedwork on the Motorway system, includingmajor reconstruction on the M-l motor-way and new construction for an exten-sion of the M-40. The extension was the

o Pavement Management Equipment only major construction on new locationthat was observed during the European

o Contract Administrations Procedures(Lane Rental)

o University Highway Research Program

trip. In Europe, as in the United States,construction on new location is rarebecause of environmental concerns andthe high cost of right-of-way acquisition.

ITINERARY

The itinerary in the United Kingdom(U.K.) consisted of a tour of the labor-atory at the University of Nottingham; areview of active construction projects,where activities ranged from placingHMA lower base course to surfacing withHRA; a discussion with government andindustry officials at the TransportationRoad Research Laboratory (TRRL); atour of the TRRL facilities; and a visit toa completely enclosed production facility.

SUMMARY

In the U.K., the federal Department ofTransport is responsible for approxi-mately 4 percent of total road mileage.This 4 percent, which consists of 1,600miles of Motorway (equivalent to theInterstate System) and 5,000 miles oftrunk highways, carries approximately30 percent of all traffic. Approximately90 percent of all roads are surfaced withasphalt.

On the M-l, the existing structure con-tains 340 mm of asphalt on a limestonesubbase. The structure has 200 mm ofmacadam base, 60 mm of HRA basecourse, 40 mm of HRA wearing course,and an overlay of 40 mm of HRA, whichwas put down in the early 1980’s. Thereconstruction project varied fromcomplete replacement of the full-depthasphalt pavement structure in the outerlane, where truck traffic is heavy, tomilling and replacement of the upperbase and/or wearing course on the otherlanes.

The new structural section consists ofapproximately 380 mm full-depth asphaltconstruction over the same limestonesubbase--40 mm of HRA wearing course,215 mm of upper road base, and 125 mmof lower road base. This design is thepreferred pavement structure for high-volume motorways in the U.K. It is basedon a 40-year design, with planned surfacereplacement in 20 years.

The unique feature of this section is thatthe highest strength lift is the lower roadbase. It is a gap-graded mix with a


6 0

maximum size aggregate of 40 mm andan asphalt content of 5.7 percent--50 penasphalt cement was used and 60 percentof the aggregate was larger than 2 mm.The base is designed for stone-on-stonebearing with no specified density require-ment. It has high tensile strength and isfatigue-resistant and waterproof.

The upper road base is a dense-gradedbituminous macadam. The maximum sizeaggregate is 40 mm with approximately3.7 percent of 50 pen asphalt cement.

The surface or wearing course was aHRA gap-graded mix with a maximumaggregate size of 14 mm and 7.9 percentof 50 pen asphalt cement. This course isunique because pre-coated chips arerolled into the surface to enhance skidresistance and improve drainage. Thechipping operation is labor intensive, withthree laborers following the spreader tomake sure chips are evenly distributed. Itis similar to the so-called sprinkle mixthat was tried briefly in the United Statesseveral years ago. United Kingdom offi-cials, who claim the chips do stay imbed-ded and are not a hazard to windshields,are satisfied with this HRA surfacecourse.

On the M-40 new construction project,the structural section varied slightly in thethickness of the base course layers butfollowed the same principles.

The HMA manufacturing facilities in theU.K. seemed geared more toward pro-duction than those in the other countriesvisited. On the M-l and M-40 projects,the contractor was laying about 5,000metric tons per day from three plants.

The plant visited, which was not invol-ved in either project, included 13 aggre-gate storage bins and 28 cold feed bins.It was unique because it was completelyenclosed, having been built in an existingbuilding (50 by 240 meters) to satisfy theconcerns of the surrounding community.While the plant looked neat from theoutside, the interior was noisy and dusty.It has a capacity of 600 tons per hour andis expected to produce 650,000 tons thisyear. The owner of the plant hauls aggre-gate in from his own quarries on trainsthat he also owns. He has several otherplants in the area, all of which are drummixers, in contrast to what was observedin the other countries visited.

Incidentally, this company regularly shipsgranite aggregate to Houston, Texas, at areasonable price of $6 to $8 per ton. Thecost can be kept relatively low becausethe aggregate is used as ballast whenships hauling grain to Europe return toHouston for a new load.

Additives are not used extensively in theU.K. as yet. Only one, natural rubber, isfound in the specifications. Officials areresearching such other additives as poly-mers and manganese and are trying todevelop a functional specification. Now,when additives are specified, it is by tradename and, as in the United States, U.K.officials do not favor this method. Theuse of polymers is reportedly increasing,but EAST participants did not learn ifpolymers were in any of the mixes theyobserved.

The mixes are basically recipe mixesexcept that surface mixes are reportedlydesigned. As was observed in Germanyand France, a large number of mixes are


6 1

in use throughout the country. Only a fewbasic mix designs are used, but the manyspecifying agencies (all levels of Govern-ment) add their own twists to the recipes.The plant visited by the EAST partici-pants reportedly produced 158 types ofmixes last year.

New specifications are being developedto identify a small number of “preferredmixes” for various applications in thehope of reducing the large number ofmixes in use today. Generally, currentspecifications are of the method type. Inthe revised version, U.K. officials arestriving more for end-result or end-product specifications. One factor moti-vating U.K. officials to revise the specifi-cations is a concern about what willhappen when EC 92 comes about andeach country has different specificationsand testing procedures. They believe thatall the countries of Europe should movetowards comrnon end-result specifica-tions and common testing procedures.

Warranties, per se, are not required inthe UK; however, the contractor mustmaintain the project for 1 year, afterwhich any needed corrections are madeand it is given final acceptance. Duringthat time, 1.5 percent of the contract costis retained.

Officials in the UK would like to move tothe quality assurance/quality control (QA/QC) concept. The contractors seem tofavor it but are leery of the third-partyconcept being advanced by some advisorsand consultants. Under this concept, anindependent third party would have thefinal say-so over the quality of the work.The third party might be an engineeringsociety or a consultant (not retained by

either party). The contractors’ concernsare that this system would create anotherlevel of oversight, with resultant addedpaperwork, and that the specificationsand test procedures are not preciseenough to impose such a system.

In the U.K., a “lane rental” contract isused on sensitive projects where theproject must be re-opened at the earliestpossible time. This type of contracting isbeing used on 25 to 30 projects a year.Three types of lane rental contracts havebeen used:

1 . The contractor’s bid includes the costof the work and the time he needs tocomplete it. The bid with the shortestcompletion time becomes the base. Thegovernment adds whatever the pre-determined daily incentive is to the otherbids proposing longer times. The lowbidder is then selected on the basis of costto do the work plus time to complete it.On the M-l reconstruction project, forexample, the incentive/disincentive was25,000 pounds sterling per day, thehighest amount allowed by the Depart-ment of Transport. If the contractorcompletes the work in advance of thetotal days he specified, that amount ishis daily bonus. If he goes beyond thespecified time, he is penalized a likeamount.

2. The contractor pays a pre-determineddaily rate for the site. The quicker hegets in and out, the less his rental pay-ment is.


6 2

3 . In a true lane rental arrangement, thecontractor pays a daily rate for the closetlanes. This, again, is a pre-determinedamount. Obviously, the fewer days thelanes are closed, the less he pays.

The first option, which has been adoptedas standard, is a variation on the incen-tive/disincentive clauses used in someStates in the United States. The varia-tion--sometimes referred to as A + B typecontracting--has been tried in severalStates as well. The lane rental concept orincentive/disincentive concept is onlypractical if a large degree of certaintyexists on the scope of work. If severalstructures are involved or if completiondepends on completion of an adjoiningsection by another contractor, the con-cept is not used. Officials stated that achange order on a lane rental project isessentially a blank check. The other twotypes of lane rental contracting are nolonger used in the U.K.

On a large project, the government uses arequest-for-proposal (RFP) process toselect a contractor. An advertisement ispublished inviting solicitations of interest.The responses are short-listed, normallyto six contractors but the number canrange from as low as four to as high asseven. The selected contractors areinvited to submit detailed proposals(bids). The contractor who submits atechnically acceptable proposal with thelowest cost will be awarded the contract.Naturally, if the project involves a lanerental contract, the time and cost to dothe work will determine which contractoris selected.

As in the other countries visited, severalil contractors dominate the market. None

of the contractors who met with theEAST participants expressed discomfortwith the RFP process and all supportedthe lane rental contract approach.

Some of the contractors’ concerns,however, are similar to those heard in theUnited States. They claim the processinvolves too much paperwork and toomuch bureaucracy. Further, problemsoften occur in getting decisions on a proj-ect. To solve this problem, the contrac-tors would like an experienced projectengineer on the project, full-time, withdecisionmaking authority. According tosome contractors, contract lettings andfunding involve too many peaks andvalleys. Moreover, contractors would likemore control over the work, preferablyusing the QA/QC system, and recom-mend the U.K. consider adopting the useof warranties, as in the other countries ofEurope. Government officials are look-ing into it, but they are just not ready togo into warranties now. In this area, as inothers, concerns exist because of EC 92.The other countries in Europe requiresome type of warranty and give contrac-tors more control over projects.

The pavement research group at theUniversity of Nottingham has been inexistence since 1954 and handles researchas well as technology transfer. Officialsand staff members see bridging the gapbetween research and development workand practical technology as one of theirmain missions. They have received fund-ing from industry (oil companies, contrac-tors, suppliers, and consulting engineers),U.K. government agencies, and UnitedStates agencies (the Army, Air Force,


6 3

SHRP, NAPA, and NCHRP). They areaffiliated with a private consultant andcontracting firm with offices on-site. Theprivate contractor plays a major role intechnology transfer. Current majoractivities include asphalt mix design,reinforced haul roads, asphaltmodification, pavement foundations, andstructural evaluation.

The lab has a pavement test facility that isabout 5 meters long and can test a pave-ment that is 1.5 meters deep. The testpavement is loaded by a wheel with aloading capacity of 1 ton. It applies asingle-direction load with a realistic dis-tribution of transverse variation in theactual wheel path. Other smaller scalewheel-tracking devices for fatigue testsare also in use. The staff has done somework on correlating field performancewith the various laboratory tests but can-not fully validate the results. They areworking on this. Validation is, of course,a common problem for virtually any lab inthe world. If the pavement researchgroup can overcome the problem, it willbe a major step forward.

The TRRL is the flagship facility for roadresearch in the U.K. It is involved inresearch in all three elements of the high-way system (the highway, the vehicle, andthe driver). The equipment used forpavement management at TRRL was ofparticular note. While the equipmentitself may not be unique, what was uniquewas the fact that it is used in the decision-making process. Certain readings onpavement condition act as a “trigger” toinitiate improvements.

The machine to measure deflection is,in essence, a mobile Benkelman Beam.The equipment consists of a truck withBenkelman Beams, which are mountedon opposite sides of the vehicle in front ofthe rear wheels, and equipment inside thevehicle for recording and analyzing data.The measurement cycle includes loweringthe beams, rolling the vehicle forwardwhile measuring the deflection, andthen lifting the beams. In the U.K., 17machines of this type are in use and theMotorway system is measured every3 years.

A standard, trailer-mounted FallingWeight Deflectometer (FWD) is used formore detailed analyses of the pavement.Personnel of TRRL are experimentingwith ground radar to determine pavementcondition and they think this approachlooks promising. Some work of this typeis also underway in the United States.

A high-speed road monitor is used foroverall condition survey work. It useslasers as the detection system. The firstversion, a trailer, is in routine use. Thenewest version is self-contained andincorporates television survey equipmentsimilar to that used by SHRP. Thisdevice can measure rutting, cross-slope,grade, curvature, and microtexture. It isused more on the rural and lower-ordersystems because it can be operated athigh speeds and generally gives sufficientinformation rapidly to determine ifimprovement is needed.

A considerable amount of human factorsresearch has been done at a TRRL testtrack. The diverse subjects coveredinclude the noise impacts on occupants of


6 4

a house adjacent to a roadway, the accept-ability of a driverless bus, and the effectof alcohol and drugs on the driver.

CONCLUSIONS

The public/private partnership is not aspronounced in the U.K. as in the othercountries visited, except in the researcharea. Particularly noteworthy was thepublic/private partnership at the Univ-ersity of Nottingham. It appears to be anefficient, effective approach to problemsolving and to basic research. More ofthis type of partnership may be on thehorizon in the United States if the con-cept of University Research Centers takeshold. Some barriers will have to comedown and some effort will be required forthis concept to be accepted in the UnitedStates, but experience in the U.K. sug-gests it can work.

Practices in the U.K. seem similar to theUnited States in many ways. Theseinclude method specifications, contractadministration (except, of course, for theRFP process), pavement designs, the NIHsyndrome (Not Invented Here), andindustry objections to governmentoversight, red-tape, and paperwork.

A noticeable difference is that littlelitigation is involved in government/contractor disputes. They are usuallysettled administratively, as they are in theother countries visited. Often, in fact,when EAST participants asked aboutlawsuits, the government and industrypeople looked perplexed because theywere surprised to learn that in the UnitedStates, claims are commonly settled incourt, rather than administratively. Ingeneral, the adversarial relationship thatexists in the United States does not existEurope, so government and contractorsseem able to work things out much better.They are not litigious societies.

Large Scale Pavement testing devices areused in most of the countries visited, aswell as in other European countries.Calibrating these machines, one againstthe other, would admittedly be a majoreffort, but would seem to be worthwhile.If the machines were calibrated, researchin one country would have more credi-bility in the other countries. This sharingof research would help forge a strongerbond between the countries. It might alsorepresent a substantial savings in that thesame problem would not have to besolved over and over again across thecountry or state borders.


INNOVATIVE ASPHALT TECHNOLOGY

6 7

INNOVATIVE ASPHALT TECHNOLOGY

POSSIBLE USES OF EUROPEAN TECHNOLOGY IN THE UNITED STATES

Conventional, continuous-graded mixdesigns similar to those employed in theUnited States are used in Europe forconstruction, maintenance, and rehabili-tation. All the countries visited by theEAST, however, make extensive use ofspecial-purpose mixtures, particularly insurface courses, to enhance the perform-ance of high-volume pavements. Thesemixtures are designed to control ruttingand other distress under very heavy vol-umes of truck traffic. Many of these mix-tures rely on modifiers to help achievethe enhanced level of performanceneeded.

Much of the EAST’s time was spentexamining these novel, special-purposemix designs. Members inspected 27 fieldpavements incorporating the mixtures“on the ground” in Denmark, France,Germany, Sweden, and the United King-dom. They also examined the operationof hot-mix plants producing these mix-tures in Germany, France, Sweden, andthe United Kingdom. Further, they rodeover almost 1,200 miles of Interstate-typepavements in the company of personnelfrom road authorities, paving contractors,and material suppliers who provided ex-tensive commentary on the design, con-struction, maintenance, and performanceof pavements incorporating these special-purpose mixtures.

The EAST also visited research andoperations laboratories belonging tonational road authorities, contractor trade

groups, and individual paving contractorsand bitumen producers in each country.At these laboratories, the group discusseddesign features of the special-purposemixtures, pavement design parameters,and advanced test methods and labor-atory equipment for measuring the mech-anical properties of asphalt mixtures.

This chapter mainly reports on thespecial-purpose mixtures. It is basedprimarily on the observation of pave-ments, both in-service and under con-struction, incorporating them. A site visitreport (SVR) was prepared for eachobserved pavement feature. The SVR’sare presented in appendix A. In addition,the observations of the EAST memberswere employed in preparing this chapter,supplemented by substantial and invalu-able written and oral technical informa-tion provided by the relevant road auth-orities, paving contractors, and materialsuppliers.

In assessing the significance of the asphalttechnology discussed in the followingsections for the United States, the EASTmembers kept several factors in mind.First, European practice stresses regularmaintenance of asphalt pavements toslow or prevent distresses, particularlyrutting and fatigue and low-temperaturecracking, that result from climate or anincrease of traffic. Much of the mainten-ance and rehabilitation is carried out onpavements with little or no visibledistress. These activities, including


6 8

overlays and more substantial recon-struction, are performed on a schedule orare triggered by the results of periodicdeflectometer or other instrumentalmeasurements. This maintenance work isespecially useful because all the high-performance pavements observed appearto have been placed on foundations thatwere in very good condition.

Second, the climatic conditions in thefive countries are not as wide-rangingas those found in many regions of theUnited States. In particular, the highsummer temperatures prevalent in muchof the United States are uncommon inDenmark, Germany, Sweden, and theUnited Kingdom. Therefore, care mustbe taken in translating technology em-ployed in these regions to areas of theUnited States with markedly differentclimates.

Third, these special-purpose mixturesoften employ select materials. Hard,low-penetration grade bitumens’ areroutinely used. For the coarse aggregate,specifications often stipulate 100 percentcrushed stone or rock, which may betransported hundreds of miles acrossnational borders to obtain the correctpetrographic properties. Manufacturedsands and limestone fillers are generallyrequired. Such modifiers as crumb rubberand polymers are also frequently used.

Employment of these mixtures in theUnited States will probably require asimilar strict attention to materials quality.

Fourth, typical traffic volumes, vehiclemixes, truck weights, and tire pressuresare equal to or exceed those found in theUnited States. The special-purpose mix-tures were observed almost exclusively onheavily-trafficked routes comparable tothe United States Interstate and primaryhighways. Moreover, four-lane motor-ways are still common in Europe in situ-ations where practice in the United Stateswould dictate six- or eight-lane roadways.Thus, traffic demand on each lane ofthese special-purpose mixtures is com-parable to that generally experienced inthe United States.

Fifth, and last, European HMA pro-duction almost universally employs batchplants. The technology observed has beenused rarely, if at all, with drum mixers,which are common in the United States.As a result, transferring the technology toUnited States practice will require care-ful consideration of possible changesnecessitated by the differences in produc-tion methods. Typical European HMAproduction rates are much lower thanthose attained in routine United Statesoperations. This circumstance should alsobe weighed in evaluating the applicabilityof these technologies to United Statespractice.

1 In conformity with European practice, the term “bitumen” will be used herein in placeof the United States term, “asphalt cement.” In this context, the European term“asphalt,” as used in PA or SMA, generally denotes an asphalt aggregate mixture or theUnited States “asphalt concrete.”


69

STONE MASTIC ASPHALT

General Descritdion

In the opinion of the EAST members, thespecial-purpose mixture with the greatestpromise for use in the United States isSMA. It was developed in the 1960’s inGermany as an overlay especially resist-ant to studded tire damage. The termsplittmastrjcasphalt is used in the GermanSupplemental Technical Specifications andGuidelines on Asphalt Sulfate Courses(Zustzliche Technische Vertragsbedi ng-ungen und Richtlinien fur den l3au vonFahrbahndecken aus Asphalt, abbreviatedZTV bit-StB 84, published by Der Bun-desminister FGr Verkehr, 1990 revision).This term is variously translated as “stone-filled mastic” or “grit mastic asphalt.” (Inthe former East Germany, it was aptlytermed “skeleton asphalt”). Today, SMAis widely employed in Germany, the

Netherlands, and Scandinavia as anoverlay or surface course to resist load-induced rutting and studded-tire damage.

Select materials are usually employed inSMA construction. A hard, low-penetra-tion grade of bitumen is used. It is modi-fied by the addition of cellulose fibers,mineral rock wool or, less often, polymersto prevent drainage of the mortar off thecoarse aggregate during pavement con-struction. The coarse aggregate is typic-ally 100 percent crushed rock or stone.The sand fraction contains a large amountof manufactured crushed sand that maybe washed if it contains an unacceptableamount of fine particles.

To provide resistance to rutting andstudded tire damage, SMA relies on astone-on-stone skeleton. The point-

DENSE GRADED PAVEMENT STONE MASTIC ASPHALT


7 0

100

9 0

8 0

7 0

FIGURE 1

oUSHM4

-0.05 .l 1 10 15SIEVE SIZE, mm

to-point contact achieved in the stoneskeleton provides an internal frictionthroughout the overlay that resists load-induced shear. The stone skeleton is filledand held together with a mastic composedof the bitumen, the sand fraction, andaggregate fines. The mastic is bitumen-rich and voidless so it provides a durablesurface that is resistant to cracking. Thestone skeleton must accommodate themastic without disrupting the point-to-point contact of the coarse aggregateparticles (those retained on the 2 mmsieve) or the overlay will be susceptible todistress.

tions, but typical parameters have emer-ged. The coarse material (retained onthe 2 mm sieve) makes up 70 to 80 per-cent of the weight of the aggregate; thetop size of the coarse aggregate mayrange from 5 mm to 22 mm., but is typi-cally between 11 and 16 mm. Filler mat-erial (defined as passing the 0.09 mmsieve) accounts for another 8 to 13 per-cent of the weight. The sand fraction,comprising the material sized between0.09 and 2 mm, makes up only about 12to 17 percent of the aggregate’s weight.Figure 1 presents a typical 11.2 mm topsize SMA gradation in comparison with acontinuous, 3/8-in top size gradationrepresentative of HMA practice in theUnited States.

To achieve the stone-on-stone skeleton,an aggregate blend rich in coarse materialis used in SMA. Details of the SMA mixdesign vary somewhat from country tocountry, and from contractor to contrac-tor, as will be seen in the following sec-

The weight of the bitumen content ofSMA is usually within the range of 6.5 to7.5 percent by weight of the mixture. The


filler-to-bitumen ratio of SMA farexceeds the upper limit of 1.2 percentrecommended in the United States forconventional, continuously-gradedmixtures.

Cellulose or mineral fibers are widelyemployed to stabilize the binder-richSMA mixtures and prevent their sepa-ration during production and laydown.When cellulose fibers are employed asthe modifier, they are added at a rate ofabout 0.3 weight percent of the mixture2.Such modifiers as carbon black and poly-mers are allowed as stabilizing additives,but the EAST members did not observeexamples of their use.

or fiber content. For example, in Ger-many an &solute tolerance of 10 percentis allowed in the aggregate gradation (ifthe 8 to 11 mm fraction were specified at20 percent, the allowable range would be18 to 22 percent). For the filler, thetolerance is even stricter, &S percent.

Liljedahl (l990) gives an excellentdiscussion of the critical nature of SMAmixtures. Too much mastic will spreadthe coarse aggregate apart, leading to apavement that is susceptible to shear. Toolittle mastic will create an unacceptablyhigh air voids content, expose the bitu-men to accelerated aging and moisturedamage, and lead to a poorly-bound,distress-prone pavement.

The SMA is usually designed to have anair voids content of 3 percent. This targetvalue provides an air voids content of lessthan 6 percent in in-situ pavements, asrequired by European specifications.Field compaction is needed primarily toorient the aggregate exposed in the upperpart of the pavement; little additionaldensification occurs under the rollers.Because the mastic is not substantiallycompacted during construction, it mustbe rich in bitumen to obtain the essen-tially voidless character needed forsatisfactory durability.

The stone skeleton must accommodate allthe mastic while maintaining point-to-point contact. Therefore, little latitude ispermissible in the production control ofthe aggregate gradation, bitumen content,

In addition to its structural capabilities,an SMA pavement surface has a granulartexture characterized by large, roughdepressions. This surface offers good skidproperties over time. The skid resistanceof the SMA surface, however, may belessened during approximately the firstmonth of service until the initial thickbinder film on the surface wears off undertraffic, exposing the rough edges of thecoarse aggregate particles. Bitumen-coated crushed sand (sized between 1 and3 mm) is sometimes rolled into the hotSMA surface at a rate of 600 to 900 gramsper square meter to provide added skidresistance until the surface film of binderis removed.

2 Existing specifications usually allow the addition of cellulose fibers at concentrationsup to 1.5 percent of the weight of the mixture, but concentrations greater than 0.3 per-cent are rarely used.

7 1


72

Stone Mastic Asahalt in Germany

Design--The German specification forSMA is contained on pages 47 and 48 ofthe publication entitled SupplementaTechnical Specifcations and Guidelines onAsphalt Swjkce Courses. Three SMAcompositions are provided, differing inthe top size of the aggregates (5,8 or 11mm) and the grade of bitumen employed(penetration grades B65 or B80). Figure 2compares the aggregate gradation limitsfor the three SMA compositions.

100

90

80

70

60

50

40

30

20

10

n

FIGURE 2

-0.05 .l 1 10 15SIEVE SIZE, mm

a top size of 11 mm. However, SMAmixes used for surface course reha-bilitation generally employ a smallertop size (8 mm).

A bitumen content of 6.5 to 7.5 per-cent by weight of the mixture is spec-ified except for the 5 mm top sizeaggregate mixture, where 7 to 8 per-cent is recommended. All mixturesrequire a stabilizing additive, usuallycellulose fiber weighing about 0.3 per-cent of the mixture.

The recommended thickness of the SMA Because of lower cost, higher possibleoverlay varies with the top size of the mixing temperatures, and increased timeaggregates. When the top size is 11 mm, available for paving, cellulose fibers arethe thickness ranges from 25 to 50 mm. A preferred to polymers as a stabilizingthickness of 15 to 30 mm would be suit- additive. Fibers have proven to be aable when the top size is 5 mm. The SMA conservative, secure choice for the SMAoverlay thickness is determined by the stabilizing additive because they helpclass of roadway it is placed on. For the reduce the mix segregation that mayAutobahns and other heavy-duty motor- result from small changes in the bitumenways, the standard appears to be a 40 mm content during production. For example,overlay incorporating the SMA design for 0.3 percent cellulose fibers provides an


7 3

excellent margin of safety; under uconditions, as little as 0.1 percent mightbe adequate.

In theory, mix designs in the usual senseare not carried out in Germany for SMAor any other type of asphalt-aggregatemixture. Instead, the mix designs forthe surface and base courses on a particu-lar project are selected from a series ofstandard designs. These have been devel-oped through experience for differentclasses of traffic volume. This approachrequires careful selection of materials,tight control of the variables in the hot-mix production process and, generally,strict adherence to all requirements ofthe specification.

In practice, since the SMA specificationsdo allow some latitude in the details ofthe aggregate gradation and the bitumenand additive contents, the voids analysisprocedure in the Marshall mix designmethod is sometimes used to narrow thespecific job mix formula. For example,Marshall specimens are prepared at 50blows per side for several bitumen con-tents mixed with a selected aggregategradation at 135+5’C. The bitumen con-tent that yields a Marshall air voidscontent of 3 percent is selected as thetarget value for the job mix formula.

Alternatively, road authorities in theGerman state of Lower Saxony recom-mend beginning with a bitumen contentof 6.8 percent and checking to determineif the compacted mixture has an accept-able air voids content. In either case,further mechanical or engineering testrequirements, such as Marshall stability,

creep compliance, and resilient modulus,do not appear necessary for selection ofthe final SMA job mix formula.

Construction--Operationally, SMAconstruction in Germany does notpresent any unique difficulties comparedwith construction of conventional asphaltconcrete overlays. In fact, some roadauthorities consider SMA easier to layand compact than conventional mixes,especially in thin layers, and less sensitiveto poor quality construction practices.

The EAST members witnessed a pave-ment reconstruction project and a main-tenance overlay in Germany involving theuse of SMA, and also observed SMA pro-duction at a hot-mix plant. The recon-struction project was on the A-65 Auto-bahn near Neustadt an der Weinstrasse(appendix A, SVR g-13-90, #2).

Substantial rutting had developed in theright-hand (driving) lane of the originalpavement. No estimate of the averagedaily traffic (ADT) was given, but all theAutobahns observed carry heavy traffic.The average ADT for the Autobahnsystem is 39,000, with trucks comprising20 percent of the total; by law, trucks arelimited to the driving lane.

The lane had been milled to a depth of 38cm; reconstruction was in progress, withconventional asphalt and cement-treatedbase courses and an asphalt binder coursereplacing the milled-out material. TheEAST team observed asphalt base courseconstruction. Both lanes of the Autobahnwill be surfaced with a 40 mm SMA over-lay over an impermeable membrane.


74

The members of the EAST observedproduction of SMA for the reconstructionproject at a batch plant in Bitzfeld (SVR9-14-90, #4). Operations appearedgenerally consistent with United Statespractice except for the addition of thecellulose fiber as a stabilizing additivefor the SMA. The cellulose fibers, pack-aged in 1 kg polyethylene pressure-packs,were added by hand to the hopper carry-ing aggregate to the pug mill. The aggre-gate and fibers were dry mixed for 6 to10 seconds, after which the bitumen wasintroduced. The normal mixing time wasincreased by a few seconds to ensure sat-isfactory blending of the materials. (Thepolyethylene film used for the fiber pack-ages has a very low melting point andrapidly dissolves in the hot ingredients).

The maintenance project on Route 19near Schwbisch Hall (SVR 9-14-90, #5)involved placement of a 25 mm SMAoverlay on a heater-planed pavementsurface. The SMA mix had a nominalaggregate top size of 8 mm. Again, anestimate of the ADT was not given.Route 19 is a rural route; on average,roads of this class in Germany have anADT of about 3,000.

The existing pavement surface, whichshowed only random, minor distress, wasrecycled with a heater-planer unit. TheSMA overlay was immediately placedwith a conventional paver and compactedby two static, steel-wheeled rollers run-ning in tandem. (Vibratory compaction isnot recommended, at least after the firstrolling pass, since it has been shown todraw bitumen to the pavement surface;rubber-tired rollers are also not recom-mended). The SMA occasionally showedsome marking under the rollers. The

compacted SMA surface appeared richin bitumen. Stone chips were then rolledon for extra skid resistance.

Cost and Serviceability--In Germany,the bid price for an SMA overlay is gen-erally about 120 percent of that for con-ventional asphalt concrete overlay, term-ed asphaltbeton in the ZTV bit-StB 84.When a polymer is employed in place ofcellulose fiber as the stabilizing additive,the cost increases to 130 percent of con-ventional asphalt concrete. (Dependingon the mix design, the cost of hot mix atthe plant is $40 to $70 per ton inGermany; see SVR 9-12-90, #l).

A substantial service life is expected forthis increased cost. On normally-traffic-ked Autobahns and heavily-traffickedfederal highways (corresponding respec-tively to the United States Interstate andprimary systems), SMA overlays are thesurface course of choice. A normal ser-vice life of 10 to 15 years is expected. Bycontrast, asphaltbeton surface courses arerecommended for normally-traffickedfederal highways and lesser-traffickedlocal and regional road networks. Aservice life of 8 to 12 years is expected.All other things being equal, SMA isexpected to yield up to 25 percent longerservice than a conventional overlay.

In-Service Pavements--A good exampleof the use of an SMA surface course isdescribed in SVR 9-12-90, #2. It des-cribes a 6-year old SMA surface coursethe EAST team observed on the Barm-bekerstrasse in Hamburg. This urbanstreet has an ADT of 40,000, including6 percent truck traffic. The entire pave-ment structure is 740 mm or about29 inches thick and is built upon


frost-proof sand. The pavement did notshow any signs of distress. Hamburg roadauthority personnel indicated the typicalservice life for SMA in similarcircumstances is 10 years.

The EAST team also rode over an exten-sive SMA surface on the A-7 Autobahnabout 12 km north of Kassel in the stateof Hessen. This pavement was about2 years old; no distress of any significancewas visible at Autobahn speeds of 55 to60 miles per hour. The ride was smooth.

Stone Mastic Amhalt in Sweden

Design--The Swedish National RoadAdministration’s (SNRA) term for SMAis HA&S; the Swedish term for conven-tional, continuously-graded asphalt con-crete is HAM’. The Swedish nationalspecifications for SMA are contained inSNRA (Vgverket) publication 1988:42,.e Fr&&We- (Slitlager av HABS),December 1988.

7s

In Sweden, SMA was introduced in thelate 1960’s to reduce pavement damagecaused by studded tire use. Asbestosfibers were employed as the stabilizingadditive (as also was the case in Germanyat that time). Shortly, however, asbestoswas prohibited because of health, safety,and environmental concerns. A corres-ponding hiatus in the use of SMA occur-red until cellulose fibers were introducedin the early 1980’s.

The principal function of HABS overlaysin Sweden continues to be the reductionof studded tire damage. Swedish SMAdesign differs from the German design inseveral ways. First, nominal aggregate topsizes in Sweden are larger. Swedish grad-ations for SMA are based on top sizes of12 mm (HABS 12) and 16 mm (HABS16) compared with the German top sizesof 5,8 and 11 mm. (Swedish authoritiesare considering SMA designs based on a22 mm top size). The gradation limits forthe HABS 12 and 16 are shown in figures3 and 4. Laboratory studies by the SNRA

FIGURE 3

9 0

80

70

60

50

40

30

20

lo

1SIEVE SIZE, mm


76

FIGURE 4

9 0

80

70

othBS16

indicate that HABS 16 will yield as much fibers are less common. The SMAas a 40-percent reduction in studded tire specification also permits the use ofwear compared with HABS 12. powdered rubber and polymers.3

Second, the variety of stabilizing additivesemployed in Sweden is greater. Cellulosefibers are employed in loose form and inpreformed pellets composed of equalparts by weight of fibers and bitumen.The latter form is easier to handle inhot-mix production operations and lessdusty than the loose fibers. It would beessential for SMA production in drummixers. In addition, mineral fibers arewidely used, while fiberglass and plastic

1SIEVE SIZE, mm

Third, and last, SMA is marketed by atleast two major Swedish paving contrac-tors under proprietary trade names:Stabinor available from Skanska Entre-prenad AB and Vkzcotop from NCC ByggAB (Nordic Construction Company).Both products conform to the SNRAspecification, but differ in several waysthat will be discussed in the followingsections.

3 Field experiments are underway on the E-3 motorway in Goteborg to compare theperformance of an SMA overlay containing Styrene-Butadiene-Styrene (SBS)-modi-fied bitumen with an overlay using a conventional B85 bitumen. Apparently, cellulosefibers are used with both binders. After two winters, the two overlays exhibited littleapparent difference. The monitoring will continue for several more years.


77

In Sweden, recommended SMA overlaythicknesses range from 34 to 43 mm forHABS 12, and 38 to 47 mm for HABS 16.The SMA overlays are advised for allSwedish roads with an ADT over 15,000or where studded tire damage is the maincause of distress. In practice, this usuallymeans all roads with an ADT of 4,000 ormore, and particularly those in the south-ern part of the country where the trafficdensity is highest.

The Swedish specification advises a targetbitumen content of 6.3 percent for HABS16 and 6.6 percent for HABS 12; in bothcases, a bitumen of grade B 85 (85 pene-tration grade is recommended). The useof a stabilizing additive is ti required,but the contractor is given wide latitudeto employ additives if they are judged tobe warranted. The specification notes thatwhen additives are used, the bitumencontent may require adjustment abovethe suggested levels.

In addition to gradation requirements,the coarse aggregate must satisfy specifictest limits for abrasion resistance, flaki-ness index, impact crush strength, andproportion of crushed material.

The voids analysis procedure of theMarshall mix design method is employedto develop the job mix formula for SMAmixes. In practice, an initial target valuefor the bitumen content is obtained bymeasuring the void space in the coarseaggregate (retained on the 2 mm sieve).With this quantity, the allowable volumesof the mastic and the air voids in the com-pacted mix can be calculated for a rangeof bitumen contents. Then, the bitumencontent and the aggregate gradation areadjusted within the specified limits to

achieve a job mix formula with a Marshallair voids content of 3 percent. The speci-fication does not provide any require-ments for Marshall properties other thanthe air voids content.

Many Swedish contractor personnelstressed the importance of the 2 mm sievesize in judging the acceptability of theSMA design and in the field control ofthe hot-mix production. While the specifi-cation permits the amount of aggregatepassing 2 mm to vary between 16 and29 percent for HABS 16 mixes or 19 and30 percent for HABS 12 mixes (similar tothe German specification), the contractorpersonnel strongly advocated a morestringent requirement of no more than 20to 23 percent passing the 2 mm sieve.

Liljedahl (l990) demonstrates that allow-ing more than 23 percent of the aggregateto pass the 2 mm sieve (or, conversely,employing an aggregate gradation withless than 77 percent coarse aggregate)increases the mastic volume to a pointwhere the necessary stone-on-stone con-tact of the coarse aggregate and, conse-quently, the rutting resistance of the SMAare lost. Additionally, he shows that theabsolute necessity for stone-on-stonecontact in the SMA mix also requires thatthe largest stones make up the bulk of thecoarse aggregate. For example, for anHABS 16 mix, at least 70 percent of theaggregate should be in the 10 to 16 mmsizes.

Construction--The EAST team witnessedthe construction of two SMA overlays inSweden. They also visited a hot-mix plantnear Goteborg that routinely producesSMA mix.


7 8

Both SMA overlay projects were onEuropean Route E-6, a divided four-lane,limited-access motorway that runs north-south along the west coast of Sweden.The two projects were approximately55 miles apart on the portion of the E-6between Goteborg and Halmstad to thesouth. The ADT is about 13,000, withtruck traffic comprising about 25 percentof the total; in the winter months 65 to75 percent of the vehicles use studdedtires. Compacted overlay thickness wasspecified at 38 mm for a general HABS16 mix design.

The northerly project (SVR g-10-90, #5),near Varberg, was under construction bySkanska Entreprenad AB using itsStabinor SMA mixture. Inorphil mineralfibers were employed as the stabilizingadditive, introduced at a rate of 8 percentby weight of the binder (0.5 percent byweight of the mixture). An 85-penetra-tion grade bitumen (B85) was employed.Twenty percent of the stone (coarseaggregate) was described as “qualified’;that is, it meets the minimum require-ments established in Slitlager av HABSfor SMA coarse aggregate.4

The Stabinor gradation used in this proj-ect is shown in figure 5, where it is com-pared with that of Viacotop as well as therecommended gradation limits for a con-ventional United States dense-gradedasphalt concrete with a 16 mm (approxi-

mately 5/8-inch) top size. The gradationfalls outside the limits presented inSlitlager av HABS for HABS 16 at the8 mm sieve size and above. Based onLiljedahl’s analysis (1990), this might beconsidered a “critical” mix since the voidspace in the coarse aggregate could beinsufficient to accommodate the masticand achieve stone-on-stone contact.

The original pavement at this locationdid not show substantial distress; how-ever, photographs taken at the time ofthe visit show some studded tire wear inthe wheel paths. The SMA was placedover a thin (12 to 16 mm) leveling coursewith a conventional Dynapac paver ata temperature of 16O’C. Two steel-wheeled rollers followed close behindthe paver; vibration was not used. Thecontractor personnel indicated thatrolling is mainly intended to orient thestone skeleton in the overlay rather thanto compact the mat substantially. Rollingis permitted until the mat temperaturefalls to 75’C; the second roller in thetrain was equipped with an infraredpyrometer for this purpose.

The southerly project (SVR g-10-90, #7)was near Bastad. As with the northerlypavement near Varberg, the existingpavement surface on the southerly projectdid not exhibit exceptional distress. Theproject was under construction by NCCBygg AB using its trade named VYacotop

4 This implies that the quality requirement was waived by the road authority for theremainder of the stone. In Sweden, “qualified” stone intended for use in HABSoverlays is generally quartzite or porphyry that must often be obtained from remotesources. For this project, the cost of the qualified stone is estimated at 46 Swedishkronor per square meter or about $0.75/square foot of roadway.


FIGURE 5

innIUU

9 0

80

7 0

6 0

50

40

3 0

20

10

n

SMA mixture. Cellulose-bitumen pellets the Stabinor mix. The amount passing thewere used as the stabilizing additive. They 2 mm sieve, the dividing line between thewere added at a rate of 0.6 percent by coarse aggregate and the sand and fillerweight of the mix, yielding a cellulose fraction, is only 22 percent, comparedfiber content of 0.3 percent. The bitumen with 25 percent for the Stabinor (as noted(grade B85) content of the Viacotop earlier, many Swedish authorities preferHABS 16 was 6.7 percent by weight of the the lower figure at this sieve size). Thesemix. This was considerably higher than differences in gradation allow the Viaco-that used in Skanska Entreprenad AB’s top mix to accommodate the increasedVarberg project, even considering that bitumen content; in theory, this leads to0.3 percent is contributed by the cellulose lower compactive effort and increasedpellets. durability of the SMA.

The aggregate gradation (figure 5) in this The SMA was laid with a conventionalViacotop mix conforms more closely than paver and rolling was accomplished bythe Stabinor mix with the gradation limits two 10-ton rollers. Roller marks werepresented in Slitlager av HABS for a typi- much less pronounced than for thecal HABS 16 mix. In particular, 60 perent Stabinor mix. The compacted pavementof the aggregate is retained on the 12 mm surface appeared rich in binder, almostsieve, compared with only 30 percent for to the point of flushing, but the road auth-

79

1 10 20SIEVE SIZE, mm


80

ority and contractor personnel reportedthat Viacotop has good friction propertieswhen newly laid. Unlike the Germanpractice, no stone chips or sand wererolled on either project to provide extrainitial friction.

The batch plant in suburban Goteborgproduces SMA as well as conventionalHMA and porous asphalt mixes (SVRg-10-90, #4). No production was under-way at the time of the visit. Unlike theGerman hot-mix plant described in theprevious section, this plant has a mechan-ical system for dispersing both celluloseand mineral fibers into the pug mill.

This plant (of several in Sweden) is alsocapable of handling the cellulose pelletsmechanically. The pellets are deliveredin 700 kg sacks (1,543 pound). These arehoisted into a storage silo where an inter-nal knife cuts them open, depositing thepellets in the silo. The pellets fall by gra-vity through a pipe to the same scale usedto weigh filler. The weighed pellets areconveyed by a screw drive into the pugmill.

Cost and Serviceability--In Sweden, SMAhot mix (HABS) costs about 10 percentmore than continuously-graded, densehot mix (HABT in SNRA terminology)employed for overlays. The precisedifferential depends on the material usedas the stabilizing additive.

A 20-percent increase in service life(measured in ADT of vehicles with stud-ded tires) is a realistic expectation forSMA compared with dense-graded HMAoverlays. The favorable Swedish exper-ience has led to the use of SMA for most

overlays on motorways, primary routes,industrial streets, congested urban inter-sections and bridges with an ADT greaterthan about 5,000. NCC Bygg AB aloneplaced almost 300,000 tons in 1990 orabout 32 million square feet of overlay.

Personnel of the Goteborg city roadauthority indicated to the EAST teamthat SMA has become the overlay ofchoice in recent years for most of theirroad surfaces because of its enhancedresistance to rutting caused by increasedtraffic volumes and the action of stud-ded tires. In Goteborg, traffic volumesincreased dramatically year-by-year inthe 1980’s and typically 70 percent of thevehicles in the city use studded tiresduring the winter. Yet in the Tingstadtunnel, which EAST visited to see anin-service installation, city road authoritypersonnel indicated that SMA overlayshave experienced only 17 mm of ruttingafter 30 million vehicle passes comparedwith 25 to 30 mm for the previous HABTsurface after 25 million vehicle passes.

In-Service Pavements--The EAST teamobserved a variety of in-service SMApavements around Goteborg and on theE-6 motorway between Goteborg andHelsingborg.

In the eastbound lanes of the Tingstadtunnel in Goteborg (SVR g-10-90, #l),a Stabinor (HABS 12) SMA overlay con-structed in 1985 was viewed at normaltraffic speeds. The ADT is 100,000 overthe six lanes of the tunnel. In addition toa mean rut depth of 17 mm, the pavementexhibited some rutting due to studdedtires, but not uniformly through thelength of the tunnel. Other types ofdistress were not visible. A 20-percent


81

increase in service life is projected for theSMA overlay compared with the con-ventional HABT used previously.

A S-year old VTacotop (MS 12) SMAoverlay was observed on a four-laneurban street in the Stlhandskegatandistrict of Goteborg (SVR g-10-90, #2).Measured rut depth was 10 mm with a30,000 ADT over four lanes. Little or nodistress of any kind was noted at normaltraffic speeds. This overlay had beenconstructed by the forces of the GoteborgStreet and Highway Department.

A l-year old SMA pavement on the E-6south of Varberg was inspected by theEAST team on foot (SVR g-10-90, #6).This overlay used an 18 mm top sizeaggregate; only local, unqualified stonewas used. The pavement surface was wetfrom an earlier rain shower, and showedan irregular drying pattern that empha-sized what appeared at first to be ravel-ling in areas away from the wheel paths.The United States contractors in theEAST, however, agreed that thecondition more likely arose from mixsegregation during construction than lossof aggregate during service. The wheelpaths appeared normal, perhapsreflecting movement of the mastic to thesurface under traffic. No other distresswas noted.

On the E-6 motorway south of Goteborg,the SMA surface (HABS 16, built in1988) had a smooth, almost flushedappearance. Aggregate was less apparenton the surface than on the sectiondescribed previously. No distress of anyconsequence was noted on the pavementsurface.

Further south on the E-6, an SMA over-lay (HABS 12) constructed in 1987 wasexamined. No rutting or cracking wasnoted, but some aggregate pop-outs wereapparent in the driving lane. The SNRApersonnel with the EAST indicated that a10- to 12-year service life was forecast,based on the little distress measured todate.

Stone Mastic AsDhalt in Denmark

The use of SMA is not as widespread inDenmark as it is in Germany and Sweden.The Danish Road Directorate indicatedthat a gap-graded asphalt concrete mixdesign, similar to the hot-rolled asphaltdescribed in a later section on the UnitedKingdom, is used extensively to preparerut-resistant surfaces on roadwayssubjected to heavy truck traffic.

However, the EAST team did see someinteresting examples of in-service SMApavements in Denmark. The most note-worthy is the modified SMA overlayinspected on the Helsingor (E-4) Motor-way (40,000 ADT, 5 percent trucks) thatruns north from Copenhagen (SVRg-11-90, #2). The SMA was the 40 mmwearing course of a 100 to 200 mmasphalt concrete overlay placed between1988 and 1990 on the original 30-year old,distressed PCC pavement. The PCC hadbeen either cracked and seated or com-pletely removed, depending on its state ofdeterioration.

The contractor, Superfos Dammann-Luxol a/s, selected an SMA wearingcourse because of its good durability andresistance to deformation. A bitumenmodified with both an SBS-type polymerand cellulose fibers was chosen as the


8 2

binder to obtain a highly flexible, crackresistant pavement surface. The modi-fied bitumen content was 6.9 percent byweight of the mix; SBS polymer com-prised 6 percent of the binder. Cellulosefibers, which comprised 0.25 percent ofthe mix, cost $0.65 per pound or about$3.25 per ton of hot mix. The aggregategradation generally falls within theSNRA’s limits for HABS 12 mixes.

The driving lane presented a slightlyflushed appearance in the wheel paths,but as noted for the E-6 motorway inSweden (SVR 9-10-90, #6), perhaps thisappearance signaled movement of themastic to the surface under the action of

traffic. By contrast, the passing lane hadan even appearance. The only distressnoted was slight rutting in the wheelpaths of the driving lane.

The EAST members also examined anSMA surface course on the E-4 motor-way on the way south from Copenhagento Rodby, just north of the Route 37interchange. This surface course was2 years old and had flushed in the wheelpaths of the driving lane. The Danishroad authority personnel indicatedthat the flushing had reduced the skidresistance appreciably. It is suspectedthat the binder content of the SMA mixwas too high.

POROUS ASPHALT

General Descriwtion

In general, PA may be considered theEuropean equivalent of the open-gradedasphalt friction courses (OGAFC) oropen friction courses (OFC) used in theUnited States. Both are intended toprovide a wearing course that rapidlydrains rainwater from the pavementsurface and reduces hydroplaning. Forcomparison, the original United Statesdesign method for OGAFC is given inSmith et al. (1974).

In Europe, PA is also used to reducetraffic noise where high-capacity road-ways are in populated areas. In contrastwith the United States, many Europeanmix designs for wearing courses have aharsh macrotexture that generates sub-stantial tire noise. Porous asphalt pro-vides a way of absorbing and dissipatingthis noise within the pavement surfaceand is favored for use even where

hydroplaning is not a significant concern.In addition, the French road authoritiesnote that the open texture of the PAhelps reduce reflected glare fromheadlights.

The EAST members observed PAwearing courses in France, Germany,and Sweden. France and Sweden havestandard specifications for PA mixes(discussed later) and use PA routinely.In Germany, PA appears to be treatedas an experimental feature, intendedmainly as a noise reducer, but is inincreasingly greater demand as publicconcern about traffic noise grows. (Inthe United Kingdom,porous macadamsurfacing has been examined, but has notyet been adopted by specifying agencies;consistently demonstrating a favorablecost-to-benefit ratio for its use has notbeen possible).


83

The main characteristic of PA mixes istheir high air void contents, in the rangeof 20 percent or more, which provide the“open” nature necessary for water drain-age and noise muffling. These air voidcontent values are obtained by using gap-graded aggregates or by reducing the pro-portion of fine aggregate and filler in thetotal continuous aggregate gradation toless than 20 percent of the weight; and, ineither case, by employing binder contentsin the range of 5 percent of the totalmixture’s weight.

Modified bitumens appear to be usedexclusively in PA mixes. The EAST teamsaw examples of binders modified withcellulose and mineral fibers, polymerssuch as SBS latex, and even reclaimed tirerubber. As with SMA, the PA binder ismodified to prevent its drainage duringmix production and transport, but themodification is also intended to increasethe durability of the mix when it isexposed in situ to air and water.

To be effective, PA surface courses mustbe linked with pavement drain systems.Germany and Sweden have constructionrequirements on the smoothness of thebase or binder course under the PAsurface as well as minimum transversecrossfall in the pavement to promotedrainage through the PA surface to thedrains.

All PA pavements experience a gradualdecrease in drainage and noise reductionas they become filled over time with air-and water-borne debris, anti-icing abra-sive, etc. This is particularly a problem inurban areas where low traffic speeds arenot effective in flushing debris forciblythrough the PA layer. None of the road

authorities appears to have an effectivemaintenance procedure to reverse thistrend so the useful service life of the PAis limited by how fast the air voids fill withdebris. Another facet of this problem isthat the open structure of PA pavementsrequires increased amounts of deicingchemicals and abrasive for effective snowand ice control, and the pavements aremore difficult to keep free of frost and ice.

In the United States, the use of OGAFChas been hampered by unfavorable exper-ience with the stripping and deteriora-tion of underlying pavement courses. Toaddress this problem, European practicerequires placement of an impermeablemembrane or seal layer directly under PAsurface courses to prevent the intrusion ofwater into the underlying pavementstructure.

Porous Asphalt in Sweden

Design, Cost and Serviceability--TheSNRA's term for PA is HABD, which isroughly translated as drainage asphaltconcrete. The Swedish national specifi-cations for PA are contained in SNRA(Vagverket) publication BYA 84, Techni-cal Specifications for Construction andGeneral Advice (Byggnadstekniskaforeskrifter och allmannna rad) , 1384edition, pages 30 through 35. Thespecifications for HABD 12 and HABD16 mixes are based on top aggregate sizesof 12 and 16 mm, respectively.

Figure 6 (found on the following page)compares the aggregate limits establishedfor HABD 16 with those for the SMA mixHABS 16. The two gradations overlapsubstantially above the 4 mm aggregatesize, but the proportion of fine aggregate


8 4

100

9 0

8 0

7 0

6 0

5 0

40

3 0

2 0

10

n

FIGURE 6

o HAl3Sl6

n HABD 16

-0.05 .l 1SIEVE SIZE, mm

and filler in the HABD 16 mix is substan-tially lower than that in the HABS 16 mix.Since the coarse aggregate (retained onthe 2 mm sieve) gradation is similar forthe two, the PA mix is expected to havethe same stone-on-stone skeleton andresultant performance characteristics asthe SMA.

aggregate quality requirements forHABD mixes are similar to thosediscussed above for HABS mixes.

The use of modifiers is not specificallyrequired by BYA 84 to prevent drainageof the binder from the PA mix duringmix production and transport. However,if stabilizing additives are not used, thePA mix must be maintained at 120 to135’C during construction to deterbinder drainage. The specification doesrequire the use of amine-type anti-stripagents to alleviate the damaging effects ofmoisture in the open structure of the PA

A target bitumen content of 5.2 percentby weight of the mix is specified for bothHABD 12 and 16, compared with 6.6 per-cent for Swedish SMA mixes. The SNRAnotes, however, that even 5.2 percent isa high binder content in relation to theaggregate grading curve. Thus, HABDmixes have adequate resistance to chang-es in the binder caused by exposure to air,water, deicing chemicals, etc., but theiroverall durability is not expected to be asgood as that of SMA. Bitumen grade and

10 25

The thickness of the PA surface layeralso is not specified. The PA coursemust be placed on an impermeable bitu-minous tack coat or membrane to pre-vent moisture damage to the underlyingpavement.


8 5

The SNRA indicated that the cost of PAis similar to that of SMA, but that thedurability of the PA is no better than thatof conventional HMA. Indeed, in manycases, PA is much less resistant to stud-ded tire damage than conventional HMA.. . .the use of PA must be justified on a.asls where the benefits of.mse redwiuuuuandr dra1na.eoutwelPh the increased cost .

Measurements on PA pavements inGoteborg in the early 1980’s indicatedthat the initial 4.8 dB(A) noise reductionfell to 0 dB(A) within 2 years of service.Similarly, the water drainage capacity ofthe pavements was found to decrease by50 percent within 3 years. Thesedecreases in serviceability were blamedon silting of the void spaces with debrisand studded tire damage. The Goteborgroad authority considers these levels ofperformance sufficient to justify PA usein certain instances.

Obviously, PA surfaces cannot be reha-bilitated simply by overlaying. The oldPA layer must be milled off, and thepavement must be recycled or sealedwith bitumen. The SNRA does not allow,under any circumstances, the encapsula-tion of an old HABD layer betweenother types of bituminous courses.

In-Service Pavements--The EAST mem-bers observed in-service PA pavements inthe Goteborg area and on the E-6 motor-way between Goteborg and Helsingborg.

On the westbound lanes of Brackevagen(Route 159) in Goteborg (SVR g-10-90,#3), a 43 mm-thick Drainor (HABD 16)PA overlay constructed in 1986 was view-ed at normal traffic speeds. Drainor is thetrade name for PA produced by theSkanska Entreprenad AB.

This PA mix contained 5.0 percent binderby weight of the mix; the binder was mod-ified with Inorphil mineral fibers at a rateof 0.8 percent by weight of the binder toprevent binder drainage during construc-tion.5 Of the coarse aggregate, 55 percentwas quartzite, a very hard mineral aggre-gate that does not crush during compac-tion and resists studded tire wear. The airvoids content of the compacted mix at thetime of construction was greater than15 percent.

Personnel of the city road authorityindicated that the measured mean rutdepth was between 6 and 7 mm; ADT is25,000 over the four lanes of the highway.The pavement was viewed at speed fromthe bus; little or no significant distresswas visible. The pavement surface, how-ever, appeared rough, with aggregateshowing.

5 Limited field experiments in Goteborg with PA mixes containing a binder modifiedwith both mineral fibers and 6 percent styrene-butadiene thermoplastic suggest thatpolymer modification increases the durability of the binder against wear andweathering.


86

In Goteborg, only HABD 16 mixes areused; the HABD 12 mixes were found tohave poor resistance to studded tire dam-age, lasting only about half as long as con-ventional HMA surface courses. The cityroad authority selects the use of new PAsurface courses primarily to reduce trafficnoise; in the city, water drainage is ofsecondary importance.

The EAST study team also drove over aPA surface course at the entrance to theTingstad tunnel in Goteborg (see SVR9-10-90). This surface course was placedin 1984 and has distinct ruts caused bystudded tire wear. The city road authoritypersonnel indicated that the rut depthwas about 25 mm.

In addition, several sections of PA sur-facing on the E-6 motorway betweenGoteborg and Helsingborg were exam-ined. One section of unknown age wascontiguous to an SMA surface course.After a moderate rainfall, much lesswater was visible on the PA than on theSMA surface. Another PA section(15,000 ADT) had been built in 1982 andrecycled in 1988. The recycled mix had acompacted air voids content of 12 per-cent, compared with 15 percent in theoriginal mix. No substantial degree ofdistress was noted.

Porous Asuhalt in Germanv

Germany does not yet have standardspecifications for PA (termedLarmmindemde Asphalt) in Germany.The German road authorities consider itan experimental feature, but are underincreasingly strong public pressure to useit to reduce traffic noise. As in Sweden,PA is employed to reduce traffic noise

and to prevent hydroplaning by drainingrainwater. Experimental pavements havealready yielded 6 to 7 years of satisfactoryperformance.

Larmmindernde Asphalt mix designs areavailable with both 8 and 11 mm nominalaggregate top sizes. Mixes are designedto have an air voids content in excess of20 percent. In practice, compactedLarmmindernde Asphalt pavements haveair voids contents ranging from 15 to25 percent. This percentage is achievedby using a very high proportion of coarseaggregate (retained on the 2 mm sieve),a low sand and mineral filler content, anda binder content of about 5 percent byweight of the mix.

The existing pavement is milled out, onelane at a time, to a depth of 70 mm. Anew 70 mm-thick asphalt binder course isplaced, followed by an impermeable sealcoat. The seal coat is prepared by apply-ing a polymer-modified cationic bitumenemulsion at a rate of 2 kg/m2 and dressingit with chippings applied at 8 to 10 kg/m2.

A 40 mm-thick Larmmindernde Asphaltsurface layer is then applied. This em-ploys an 11 mm top size coarse aggregate;85 percent of the aggregate is retainedon the 2 mm sieve. The mineral fillerpassing the 0.09 mm sieve represents anominal 5 percent of the total aggregate.The binder is a polymer-modified cat-ionic B65 bitumen emulsion containing0.5 percent (by weight of the mix)cellulose fibers.

German practice uses polymer-modifiedbitumens exclusively in LarmminderndeAsphalt; this is done to increase binder-


8 7

aggregate adhesion in the presence ofcopious amounts of air and water. Cell-ulose fibers are also added to the rnix toreduce binder drainage during construc-tion. Larmmindernde Asphalt surfacecourses are always placed over some kindof impervious membrane or seal layer toprotect the underlying pavement fromwater.

In Germany, the in-place cost of Larm-mindernde Asphalt is about 100 percentmore than a comparable HMA surfacecourse. Given the cost, it is primarily usedto reduce noise on highways with highvelocity traffic, usually in or near residen-tial areas. As in Sweden, filling of the voidstructure in the Larmmindernde Asphaltwith debris gradually reduces its effec-tiveness, and two to three times theamount of deicing chemicals is neededfor snow and ice control.

The EAST team saw several examples ofthis type of mix on the Autobahn system(SVR g-14-90, #‘s 1,2, and 3). On theA-S 1 Autobahn near Freiberg in Breis-gau, reconstruction was underway, includ-ing placement of a PA surface course onthe entire pavement, shoulders, and allbridge decks. This is a very high capacity,four-lane freeway that had experiencedsubstantial rutting; the current ADT is90,000, with trucks totalling 33 percent ofthe traffic. It is noteworthy that Larmmin-dernde Asphalt is considered a viableremedy for pavements where load-induced rutting has been a problem.

On another project, only binder courseconstruction was underway on the day ofthe visit (SVR g-14-90, #2) and theEAST members also observed a pave-ment section completed earlier in 1990

(SVR g-14-90, #3). The pavementsection that had been completed in 1990showed no apparent distress. The ride onthe Larmmindernde Asphalt pavementwas quiet, indicating its effectiveness, atleast when new, at absorbing tire noise.

Several sections of LarmminderndeAsphalt surface course were also viewedby the EAST members on the A-6 Auto-bahn east of Heilbronn (SVR g-14-90,#l). The dates of construction are notknown, but the team did not observe anyvisible distress and the ride was quiet.The Larmmindernde Asphalt mix designsused here were virtually the same as thatemployed in the A-81 construction dis-cussed earlier; however, both 8 and11 mm top size aggregate gradationswere employed.

Porous Asuhalt in France

Design, Application, and Cost--For pave-ment surface maintenance, PA is one ofseveral alternative strategies specified bythe French Transport Ministry (Mnisterede L’Equipement et du Logement desTransports et de la Mer) and its compon-ent agencies, particularly the Directorateof Roads (Direction des Routes), theCentral Laboratory of Bridges and Roads(Laboratoire Central des Ponts etChawsees or LCPC), and the Roads andHighways Engineering Department(Service D’Etudes Techniques desRoutes et Autoroutes or SETRA).

Porous asphalt is classified with the var-ious maintenance techniques that provideno structural effect; this classificationplaces it in the same category as very thinasphalt concrete (to be discussed in thenext chapter) and conventional chip seals.


88

It is employed to rehabilitate pavementsurfaces while providing significant noisereduction and reduced hydroplaning.

On the French toll motorway system, PAcomprises about 16 percent (22.4 millionft2) of the surface courses. It is also usedextensively on the national road system,comparable to the United States primary‘system. The toll motorways have ADT’sbetween 7,000 and 50,000, with 15 to20 percent trucks and maximum singleaxle loads of 13 metric tons.

General French requirements for PAmixes differ from Swedish and Germanrequirements in two important ways: 1) agap-graded aggregate blend is employedwith little or no aggregate sized between2 and 6 mm; and 2) the mineral filler con-tent (passing the 0.09 mm sieve) is verysmall, usually 1 to 1.5 percent of the totalaggregate.

Nominal aggregate top sizes of 10 and14 mm are used; the coarse fraction(2 mm) typically makes up 85 percent ofthe total aggregate. Air voids contents aredesigned at about 22 percent. Bindercompositions over a wide range areallowed, including pure bitumen, poly-mer-modified bitumen, rubber bitumen,and fiber-modified bitumen.

Major French paving contractors produceproprietary or trade named PA mixes tosatisfy the general French PA specifica-tion. These mixes feature modified bitu-mens to provide perceived benefits inperformance and durability. The EAST

team did not receive information on thecost of these PA mixes in-place comparedwith conventional HMA overlays. InFrance, however, polymer-modifiedbitumens cost about 100 percent morethan unmodified bitumen, and polyrner-modified HMA, as produced, about20 percent more than conventional HMA.

In-Service Pavements--Members of theEAST inspected three in-service PApavements around Nantes and Lyon.

A 25 mm-thick PA overlay on low-trafficvolume, two-lane RN 23 in suburbanNantes was constructed in July 1989(SVR 9-17-90, #2). The PA mix used wasPERMFLEX, a proprietary product of theFrench paving contractor COLAS S.A. Itemploys the modified binder COLFLEX253, an SBS6 latex-modified bitumen. Thebinder content of the mix is 5.2 percent;the SBS latex comprised 5 percent byweight of the binder. Aggregate top sizewas 10 mm. Nominal air voids contentwas 23 percent.

The underlying pavement was preparedby application of a tack coat of polymer-modified bitumen emulsion. The PAoverlay was placed with a conventionalpaver and compacted with steel-wheeledrollers. The overlay was placed thinnerthan usual to prevent frost build-up onthe pavement during the winter months.The pavement had an open appearance,but no distress was apparent.

6 SBS = styrene-butadiene-styrene block copolymer.


8 9

Another PERMFLEX overlay wasinspected on Boulevard Dolon in Nantes(SVR g-17-90, #3). This was also con-structed in July 1989. In this case, a two-layer pervious pavement was used: a20-mm PA overlay basically identical tothat employed on RN 23 over a 60 mmpervious bituminous macadam basecourse. This two-layer construction wasused to provide the pavement with thecapacity to store large volumes ofrainwater temporarily.

The pervious base course, which uses anunmodified 60/70 penetration grade bitu-men, has an aggregate top size of 14 mmand a binder content of 4.8 percent. Agap-graded aggregate was used, rich in 10to 14 mm sizes, but with little mineralfiller content. This heavily-traffickedurban route did not show any apparentdistress after 1 year in service.

The A47 toll motorway south of Givoisin suburban Lyon is a heavily-traffickedroute to the French Riviera. In the sum-mer, the traffic volume is on the orderof 160,000 ADT. The EAST membersinspected a 40 mm-thick PA overlayconstructed in July 1989 (SVR g-18-90,#l). The PA mix used was DRAINO-CHAPE FE, a proprietary product of theFrench contracting firm BEUGNETTechnical Management. It employs aproprietary bitumen-rubber binder,FLEXOCHAPE E, also produced byBEUGNET. Reclaimed tire rubbertreated with aromatic oil is used. Thebinder content of the PA mix is 6.6 per-cent. The reclaimed rubber content is

5 percent by weight of the binder. Thegap-graded aggregate has a top size of10 mm; 88 percent falls between 6 and10 mm. A hard, crushed porphyry rock isused for the coarse aggregate.

This type of overlay is also placed withconventional pavers and compactionequipment. The hot mix plant, however,must be equipped with a special unit forprecise production of the rubber-bitumenbinder.

Inspection of this DRAINOCHAPE FEpavement showed it to be in excellentcondition after 1 year of service. Thepavement surface appeared fresh, with-out any visible distress.

The EAST members were also showna 2-year old PA overlay on a steeply-sloped suburban street in the Lyon area.The overlay, which is approximately45 mm thick, was produced with a poly-mer-modified bitumen and a gap-gradedaggregate blend with a nominal 14 mmtop size. The air voids content was 20 per-cent. During the summer of 1990, the airtemperature had reached 40°C daily forseveral weeks and the pavement temp-erature 60°C. Remarkably, little or novisible distress was noted in the overlay.


9 0

MODIFIED ASPHALTS AND ASPHALT-AGGREGATE MIXTURES

Qneral Remarb

The use of modified binders andbitumen-aggregate mixtures appearsmuch more prevalent and routinelyaccepted in the European countriesvisited than in the United States.Although latex-modified asphalt cementand asphalt-rubber binder are used insubstantial quantities in several Americanstates, European practice seems toencompass larger volumes of material aswell as a wide range of modifiers.

The group’s impression was that the freeruse of modified materials arises fromseveral factors. First, the latitude given topaving contractors to design and producepavements that meet specified warrantyconditions, rather than the lowest firstcost, encourages more experimentationby the contractors in the use of novelmaterials and mix designs.

Second, major differences in contractingpractices permit much higher HMAprices in Europe than in the UnitedStates. As a result, the additional cost ofmodified materials is not as significant afactor in choosing the “best” system forthe job at hand.

Third, European HMA production,almost exclusively by batch plants, isgeared to relatively smaller daily volumesthan in the United States. The additionalplant units and production times for


modified materials do not exact the samepenalties in Europe as they would in theUnited States.

Last, the European paving contractorsappear to take the main responsibility forthe development and adoption ofmodified materials, and have a directeconomic stake in their successful use.The promotion of new products by thirdparties, as is prevalent in the UnitedStates, seems much less common inEurope.

stone Mastic AsDhalt and Porous Asphalt

The extensive use of a wide range ofbitumen modifiers in SMA and PA mixeshas been discussed in detail in sections IIand III. The production of both types ofmixes would appear to be difficult with-out modifiers. Moreover, the generallysuccessful performance of the smallsample of SMA and PA pavementsobserved by the EAST team suggests theadditional cost and production timeneeded for the modified mixes arejustified.

Verv Thin Asphalt Concrete (France1

Very thin asphalt concrete (VTAC) isanother of the alternative strategiesspecified for pavement surface mainten-ance by the French Transport Ministry.

9 1

In addition to providing enhanced skidproperties, VTAC is intended to seal andrenew existing pavement surfaces. It isconsidered a paver-laid alternative toslurry seals, and does not affect thepavement structurally.

was placed in 1988 using the MEDIFLEXproprietary mix produced by SCREGRoutes Group. Like COLRUG, MEDI-FLEXuses a binder modified with 5-per-cent SBS latex. This overlay also appear-ed in excellent condition; close examina-tion did not reveal any overt distress.

A VTAC overlay consists of a gap-gradedaggregate combined in most cases with amodified bitumen binder. The aggregatetop size is 10 mm; 83 percent of theaggregate is in the 6 to 10 mm range, with15 percent between 0.09 and 2 mm. Theremainder of the mixture is limestonefiller.

Paver-Laid Chir, Seal @rancel

Paver-laid chip seal is another mainten-ance strategy permitted under FrenchMinistry of Transport specifications. Thistechnique is not intended to provide anystructural effect, and its use is confined topavements that are not deformed.

A variety of modifiers are used, includingpolymers, rubber, and fibers. Dependingon the modifier selected, the binder con-tent can vary from 5.7 to 6.7 percent byweight of the mix. The air voids contentof VTAC is high, generally in the range of15 percent.

The East members inspected two exam-ples of VTAC treatments. The first wason route RD 68 between Ste-Lute andThouare (SVR g-17-90, #l). A 15 mmVTAC overlay had been placed on thistwo-lane secondary road in July 1990.

The overlay mix is trade namedCOLRUG, a proprietary product of theFrench paving contractor, COLAS S.A.COLRUG uses 5-percent SBS latex as thebitumen modifier. The overlay appearedfresh and in excellent condition; EASTmembers did not note any distress.

The second VTAC overlay was on routeN 165,30 km west of St. Nazaire; this is afour-lane, divided freeway carrying a hightraffic volume. The 10-mm thick overlay

The chip seal is constructed with a binderlayer of polymer-modified bitumen emul-sion. Hot precoated chips (6 to 10 mm)with a 17 to 1 blend of sand and bitumenare applied. A single, self-propelled unitsprays the binder layer and immediatelyapplies the chips. The chip seal is thensmoothed by a rubber-tired roller.

Three benefits are claimed for this paver-laid chip seal: 1) use of a modified binderand precoated chips virtually eliminatesloose chips and allows immediate open-ing to traffic; 2) noise levels are lowerthan for conventional chip seals; and 3) itis suitable for a variety of traffic volumes.

The members of the EAST inspected apaver-laid chip seal constructed in July1989 on route RN 171 near La Baule(SVR g-17-90, #7). This is a four-lanehighway with an ADT of 25,000. TheNOVACHIP chip seal system marketedby SCREG Routes Group was used in theconstruction. The binder layer was anemulsified, 60/70 penetration grade bitu-men modified with 5-percent Neofler (an


9 2

SBS latex). The binder was applied at arate of 0.95 kg/m*; the chips were placedat a rate of 25 to 30 kglm2.

The pavement had an open look, withoutany apparent distress except for someminor tearing along the centerline of thedriving lane. Considering the trafficvolume and loads, the group judged theperformance to be impressive.

Gussasuhalt (Germanv)

Design, Cost, and Serviceability--Theterm “Gussasphalt” is difficult to translateprecisely, but may be best approximatedas floated or pourable asphalt or bitumenmastic. In Germany, Gussasphalt is con-sidered a premium paving mix intendedfor surface and wearing courses bearingthe highest traffic volumes and highlychannelized truck traffic.

Gussasphalt is placed at 200 to 250°C(390 to 4809) with a special screedon a specially-prepared pavementsurface. It may also be poured frombuckets and “floated” with hand toolsin a manner similar to PCC. No com-paction is required; therefore, one m*of Gussasphalt surface course can belaid with the same quality as 1 million m*.The fresh Gussasphalt surface is dressedwith excess chippings at a rate of about15 kg/m*; these are rolled into the hotsurface with a heavy steel-wheeledroller. The German specification forGussasphalt is contained in the ZTV~ 84, pages 47,48,50 and 51.

Figure 7 compares the gradation limitsfor a German O/llS Gussasphalt mix withthose for the German O/llS SMA mix. Ascan be seen, the Gussasphalt aggregategradation is relatively rich in the middle

FIGURE 7

80 -

70 -

60 -

50 -

0 I, Ill t I I IllIll I I I Ilrrll0.05 .l 1 10 15

SIEVE SIZE, mm


9 3

fraction (0.09 to 2 mm) and mineral filler( 0.09 mm) content compared with SMA.In different terms, the coarse aggregatefraction (retained on the 2 mm sieve) istypically 55 percent for Gussasphaltcompared with 80 percent for SMA; themineral filler fraction is a maximum of30 percent for Gussasphalt comparedwith only 15 percent for SMA.

The bitumen content of Gussasphaltmixes may range from 6.5 to 8.5 percentby weight of the mix, depending on thetop size of the aggregate used and theresult of a specific permeability test. Alow-penetration grade of bitumen isrequired, typically B 25 (25 penetration)or B 45. Given the high bitumen contentcombined with the rich gradation, in-place air voids contents are close to0.0 percent. This is the essential charac-teristic of Gussasphalt; it prevents thepenetration of oxygen and the aging ofthe bitumen.

Pavement structures incorporatingGussasphalt surface courses must bemassively designed to distribute the loadstransferred through the Gussasphaltcourses; otherwise, pavement rutting mayeventually develop through deformationof the underlying courses. Well-designedGussasphalt pavements, however, areexpected to perform satisfactorily for15 years or more, and service lives of20 years or more do not appearuncommon.

This longevity does not come withoutcosts. Typically, the bid price of aGussasphalt overlay is almost 200 per-cent that of a conventional HMA overlay.Gussasphalt surfaces are much noisierthan either SMA or conventional HMA

surfaces. Most important, the hightemperatures required for Gussasphaltmixing and paving operations might leadto air quality concerns in the UnitedStates.

In-Service Pavements--The EASTteam closely inspected two in-serviceGussasphalt pavements, one in the cityof Hamburg (SVR g-12-90, #3) and theother in Lower Saxony (SVR g-12-90, #4).

The Gussasphalt pavement in Hamburgwas placed on the Behringstrasse in 1973.This four-lane city street has a 40,000ADT with 6 percent heavy trucks; it isone of several routes leading to and froma vehicular tunnel under the Elbe River.

The 40 mm thick Gussasphalt surfacecourse was placed over an 80 mm HMAbinder course and 400 mm of treated basematerial on a frost-proof sand subbase.The Gussasphalt overlay is in excellentcondition; only slight rutting was notedhere and there on the section of pave-ment inspected.

The Gussasphalt surface course in LowerSaxony was on the A-7 Autobahn north ofKassel. This four-lane facility has a maxi-mum seasonal ADT of 80,000, of which17 to 20 percent are trucks. The 40 mmGussasphalt surface course was placed inMay 1990 over an 80 mm HMA bindercourse and a 180 mm asphalt base course.The binder in the Gussasphalt was modi-fied with Trinidad Lake asphalt at a rateof 33 percent by weight of the binder orabout 2.2 percent by weight of themixture.


94

The pavement did not show any apparentdistress. The surface appeared rough, butthis is considered normal because of therolled-in chips. The wheel paths had asmoother overall appearance. Some areasappeared ravelled, but this may also berelated to the rolled-in chips.

The EAST team examined otherGussasphalt pavements briefly at loca-tions on the A-7 and A-61 Autobahns.These were 10 to 20 years old and were insatisfactory condition. In several cases,the Gussasphalt was rutted in the drivinglane; this was explained as a failure in theunderlying binder course. On the A-3Autobahn, the group observed a 10 yearold Gussasphalt overlay on a PCC pave-ment. Other than some transverse crack-ing, this pavement was also in satisfactorycondition.

Hot-Rolled Asuhalt and BitumenMacadam (United Kingdom1

Mixture Designs--For heavy duty serviceon motorways and other trunk routescarrying high traffic volumes and substan-tial truck traffic, the typical pavementstructure in the United Kingdom includesvarious types of hot-rolled asphalt andbitumen macadam.

Hot-rolled asphalt is the general term fora gap-graded mixture meeting BritishStandard BS594. The bitumen-fillermortar and the sand fraction providemechanical strength; the bitumen contentprovides cohesion. A hard, low penetra-tion grade bitumen is used as the binder.

Dense bitumen macadam (DBM) is ageneral term for a continuously-gradedmixture meeting United Kingdom

Department of Transport specificationCL.930. Nominal aggregate top sizes of1.5, 1.0, and 0.75 inches are specified.Compared with HRA, a DBM employs asofter bitumen and lower fines content. Itdepends markedly on mechanical inter-lock of the aggregate for strength andresistance to load-induced stresses.

A mixture designated 30%-HRA is usedfor wearing courses. The bitumen contentis about 8 percent; a 50 penetration bitu-men is used. Of the mineral aggregate,30 percent is crushed stone retained onthe #7 sieve; the top size aggregate isnominally 0.5 in. Another 55 percent issand and 10 percent is limestone mineralfiller (passing the #200 sieve). Design airvoids are about 4 percent. The mixture isdressed with precoated inch chips rolledinto the surface at a rate of 12 to 13 kg/m2to improve durability and skid resistance.30%-HRA is considered a functionalalternative to SMA with the bitumencontent providing the necessary cohesiveelement in the mix.

A mixture termed 60%-HRA is used forroad base layers. This mixture has a bitu-men content of about 5.6 percent and italso employs a 50 penetration-gradebitumen. Sixty percent of the mineralaggregate is crushed stone retained onthe #7 sieve; the nominal top sizeaggregate is in.

Dense bitumen macadam and its variantsare employed principally for road baseand subbase course. For example, heavyduty bitumen macadam (HDM) has acontinuously-graded aggregate with a topsize of 1.5 inches, but has a bitumen con-tent of 3.5 percent compared with 4.0 to4.5 percent for DBM. A DBM that uses a


95

50 penetration grade bitumen in place ofthe usual 100 to 200 penetration grade istermed DBM 50.

At smaller thicknesses than DBM, pave-ment layers of HDM and DBM 50 pro-vide equal service. All other things beingequal, relative thicknesses of 1.00,0.90,and 0.88 for DBM, DBM 50 and HDM,respectively, provide equal resistance totraffic loads.

Structural Design Incorporating HRAand DBM Mixes--A currently favoredpavement structure for heavy service onmotorways and trunk roads uses a 30%-HRA wearing course, an HBM upperroad base, and a 60%-HRA lower roadbase over a substantial combination ofbound and unbound subbase and sub-grade courses. This structure is designedto provide resistance to deformation inthe upper courses while simultaneouslyproviding resistance to tensile stresses inthe bottom layers.

Severe rutting of HRA wearing coursesdid not occur during the unusually hotsummer of 1990 when pavement temper-atures as high as 50°C (122’F) were com-mon throughout the United Kingdom,although this temperature is near the(ring and ball) softening point of thebitumens used.

Reconstruction of the southbound lanesof the M-l was prompted by deflectionmeasurements; the existing northboundlanes showed little apparent distress. Themotorway was constructed in 1969 andoverlaid in 1981 with a 40 mm HRAwearing course. Traffic volume is 60,650,including 25 percent trucks.

Major reconstruction was taking place inthe left-hand driving lane (#l of three)where 300 mm of the existing pavementwas milled out with a cold planer. Themilled-out material was replaced by fourpavement layers, including a 40 mm 30%-HRA wearing course, 215 mm of HDMupper road base, 125 mm of 60%-HRAlower road base, and 100 mm of DBMsubbase, for a total depth of 380 mm overthe existing 300 mm graded limestonesubgrade.

The EAST members witnessedconstruction of the upper road base onthe #l lane. Two conventional paverswith fixed screeds were in use; laydowntemperature was 160°C on a cold, windyand intermittently rainy day. Daily ton-nage was about 5,500, requiring 100 haultrucks to continuously supply hot-mix forthe pavers. The total reconstruction of9 km of six-lane pavement will cost about$8 million or about $34.25 per squareyard.

Construction--The EAST team observedconstruction of heavy duty pavements ontwo motorway projects in the UnitedKingdom: reconstruction of the M-lmotorway near junction 27 north ofNottingham (SVR g-20-90, #l) andconstruction of a new section of the M-40north of Oxford (SVR g-20-90, #2).

The M-40 extension is completely newconstruction. This six-lane facility willhave an initial pavement 510 mm in depthcomprised of a 40 mm 30%-HRA wear-ing course, a 195 mm HDM upper roadbase, a 125 mm 60%-HRA lower roadbase, and a 150 mm subbase prepared


9 6

from better quality crushed rock. Thisstructure is placed on a preparedsubgrade of 600 mm of crushed rock.

with a chip spreader at a rate of 12 to13 kg/m2 and rolled with three rollers toachieve firm anchoring.

The EAST team also observed construc-tion of an HRA wearing course on the #3outer passing lane. Laydown was with aconventional paver at 160 to 170’C. Aftercompaction of the HRA, the crew imme-diately applied 20 mm of precoated chips

The HRA wearing course mix was beingproduced on site, but road base mixeswere hauled almost 2 hours from aremote location to take advantage ofbetter quality aggregate. Up to 20,000tons of road base mix was being laid eachweek.

OTHER SPECIAL, PURPOSE MIXES

In Germany, an application of a Ralumac earlier reconstruction projects, but hadslurry seal was observed by the EAST presented problems with bitumenteam (SVR g-13-90, #l). This proprietary compatibility and separation. Further-system, which is used in the United more, the SBS and EVA-modifiedStates, employs a latex-modified, pavements failed under heavy, static tireemulsified bitumen. loads.

In Denmark, the EAST memberswitnessed taxiway reconstruction at theKastrup Airport, Copenhagen (SVRg-11-90, #l). The HMA binder coursethat was being laid was modified with acombination of Microfil carbon black,hydrated lime, and cellulose fibers. Thecarbon black was intended principally toflatten the temperature-viscosity response

of the binder; it also has been found toslow the aging of the bitumen duringhot-mix production.

Two other special-purpose overlaysystems based on SBS latex-modifiedbitumens were observed in France.BETOFLEX is a proprietary,deformation-resistant overlay for bridgedecks. A 1 year-old overlay was inspectedon the Anne de Bretagne Bridge inNantes (SVR g-17-90, #4).

Personnel of the Copenhagen AirportsAuthority noted that both SBS latex andEVA7 had been employed as modifiers in

Construction of a two-layer overlayspecially designed to prevent reflectivecracking was observed on route RN 165near Sautron (SVR g-17-90, #6). Boththe SAFLEX wearing course and theRUFLEX binder course use SBSlatex-modified bitumen.

7 EVA = Ethylene Vinyl Acetate.


9 7

MIXTURE DESIGN TECHNIQUES AND TEST APPARATUS

Novel Mixture Desbn Techniaues

Germany--As noted in the section onSMA in Germany (page 72), mix designsfor the surface and base courses on eachproject in Germany are selected from aseries of standard designs. These havebeen developed through experience fordifferent traffic volume classes. How-ever, the Marshall mix design method isused extensively for voids analysis and theselection of target bitumen contents.

This approach requires careful selectionof materials, tight control of all variablesin the hot-mix production process and,generally, a rigorous adherence to allrequirements of the specification. It alsodemands strict attention to pavementdrainage requirements and universalprovision of frost-proof foundations forall classes of pavement structures.

During construction, the contractor isrequired to conduct quality controlmeasures according to the specificationsfor the project. Furthermore, loose mixsamples are taken on behalf of the Stateroad authority from the hopper of thepaver and checked for satisfactory bitu-men content and aggregate gradation byan independent, fJlird-party laboratory.Cores are also taken from the new pave-ment to determine that requirements forcompaction, air voids content, and bondbetween layers have been met.

France--In France, the LCPC mix designsystem is universally employed by thecentral road authority and the pavingcontractors. Compactors and a battery ofsophisticated mechanical engineering testequipment are used to measure the per-formance characteristics of the trial mixes(resistance to rutting, fatigue cracking,and moisture sensitivity). The two typesof compactors in use are gyratory, whichis similar to equipment used by the U.S.Army Corps of Engineers, and rollingwheel. (Resistance to low-temperaturecracking is not specifically addressed).

General Procedures--The procedurevaries according to the knowledge avail-able on the mix to be used. If the mixhas been used with the same materialcomposition, the gyrator-y shear testingmachine is used for verification to assurethe mixture’s workability has not chang-ed. If one or two of the material com-ponents are new, verification is per-formed regarding workability using thegyratory shear testing machine; theDURIEZ test similar to the U.S.immersion-compression procedure, isused for compressive strength andresistance to immersion.

If the mix design employs materials ofunknown performance, a completebattery of tests is performed, includingverification of mixture workability bygyratory shear testing, compressivestrength and resistance to immersion inwater, wheel tracking test, and direct


9 8

tension test. On occasion, when anasphalt contractor develops a newproprietary mix, the complex modulusand fatigue tests are used instead of thedirect tension.

Initial screening of candidate mix designsis done by compaction with the gyrator-yshear testing machine to select a trial mixwithin the desired air voids content range.Empirical relationships have been devel-oped that correlate the laboratory airvoids content to that found in actual pave-ments. A rubber-tired, rolling wheelcompactor is then used to prepare plateor slab specimens from which cylindricaland trapezoidal beam specimens may becut for mechanical engineering testing.

The rutting, stripping and load-relatedfatigue characteristics of trial mixes aredetermined with sophisticated wheel-tracking and direct tension testing equip-ment. These results are compared with adatabase of similar measurements onfield pavement specimens to gauge thesuitability of the trial mix design.

Permanwt Deformation and MoistureSensitivity--For permanent deformation,a wheel-tracking test is used. It measuresthe rut created by the repeated passage ofa wheel over a prismatic asphalt concretesample. The French strongly believe thatthe laboratory simulation of the ruttingphenomenon must approach actual pave-ment stress conditions so the result ob-tained can provide one of the selectioncriteria for a mix design.

The equipment provides for testing twosamples simultaneously at a fixed temp-erature. To evaluate rutting sensitivity,

consideration is given not only to the rutdepth occurring after a certain number ofcycles at a specified void content at thejob site, but to the cross-section of therutted specimen and the sensitivity of thiscurve to a variation in air void content.The equipment also allows the specimento be conditioned by exposure to water sothat moisture sensitivity can be estimated.

Fatigue Cracking--Because tests forfatigue cracking characterization arecostly and time consuming, they arecarried out only for research. The firsttype of fatigue test is an imposed dis-placement alternating bend test. Fourtrapezoidal-shaped test samples may betested simultaneously. This test consistsof maintaining constant displacementamplitude and frequency for the free endof the test sample. During the test, con-tinuous reduction of the stiffness modulusfrom accumulated fatigue damage is re-corded. This is reflected in a reduction inthe force required to maintain constantdisplacement amplitude. The test is con-tinued until the initial force required toimpose displacement is reduced byone-half.

A trend has emerged in France towardshear fatigue testing. This test is also runat imposed strain amplitudes. The shearfatigue test provides results showing lessscatter than the bending fatigue test. Italso takes more effective account of thetypes of load to which thin surfacecourses and interlayers are subjected. Inconnection with current research, this testis being used in France to study thecapacity of asphalt concretes forself-repair during periods at rest and thelaws of damage accumulation.


99

A single-axle direct tensile load test hasbeen developed for comparing the fatigueresistance thickness design of asphaltconcretes, where the critical stress in thepavement layer concerned may be assimi-lated to a tensile load. Strain, the form ofwhich is parabolic over time, is applied.It is first applied in a minor strain field todefine the moduli dependent on time andtemperature. Then it is applied in amajor strain field to the point of ruptureto deduce a linearity loss. Definition of asimplified test procedure incorporatingseveral tests and carried out on a singlesample substantially reduces cost andmakes it possible to use the test in routinemix design.

United Kingdom--In the United King-dom, the Marshall design method is usedby some county road authorities whileothers rely on standard recipe designsthat have performed well. Historically,use of the Marshall design method beganbecause pavements constructed withrecipe mixes experienced severe ruttingduring the extremely hot sumrner of 1976.

This situation has led to a proliferation of“standard” rnix designs--more than 200variations, extant, that met the umbrellaspecification requirements for HRA andDBM discussed on page 94.

The University of Nottingham hasdeveloped a more performance-orienteddesign method that characterizes themechanical behavior of trial mixes usingrepeated load indirect tensile, uniaxialcreep, and repeated load axial tests. Com-paction of cylindrical trial specimensemploys a specially-adapted vibratoryhammer called a PRD or percentagerefusal density apparatus.

Test Specimen Fabrication andCompaction--Although roller compaction(rolling wheel device) simulates site com-paction equipment, this device is notconsidered suitable for the routine manu-facture of specimens necessary for awidely acceptable method of mix design.

The University of Nottingham has iden-tified a procedure that uses the PRD testapparatus to manufacture test specimens,make the use of large aggregate easier,and introduce a kneading compactiveeffort. The procedure involves a 6-inchdiameter split mold and a vibrating ham-mer. The PRD test is widely used in theUnited Kingdom to determine the degreeof compaction of materials laid on site.Therefore, this test apparatus wasadopted as the laboratory procedure.

By varying the time and the temperatureat which the specimen is compacted, arange of PRD’s for each mix formulationcan be obtained. Initially, three levels ofcompaction conditions are used toachieve 100,96 and 93 PRD.

Volumetric Analysis--The -volumetricproportions of the materials are impor-tant parameters that influence the mech-anical performance of mixes. Ranges forthese parameters are specified as part ofthe mix design process and as a prelim-inary step before mechanical testing.

The control variables used are: VMA,voids in the mineral aggregate;Vv, voidsin the mix; and VB, volume of asphalt inthe mix (similar to VFA in United Statespractice). For mixes compacted to 100PRD, the mix properties should be withinthe following limits to maintain satisfac-


1 0 0

tory fatigue strength: VMA, 13 to 18 per-cent; Vv, 3 to 8 percent; and VB, 8 per-cent or greater.

Mechanical Engineering Tests--Mixesthat meet the established volumetricproperty criteria are then subjected tomechanical engineering tests to estimatetheir probable performance in pave-ments. These tests require special equip-ment, which is necessary to assess endproduct performance of bituminousmixtures.

The equipment advocated for this pur-pose is the Nottingham Asphalt Tester,which is an all-in-one test apparatuscapable of performing indirect tensiletests, static load creep tests, repeated loadaxial tests, and fatigue tests. For design,two tests are used: the indirect tensile testto obtain elastic stiffness and the uncon-fined repeated load axial test to assessresistance to deformation.

The indirect tensile test is performed firstbecause it is non-destructive. Values ofelastic stiffness should not be less than2,000 MPa at 20°C. Generally, speci-mens with satisfactory volumetric pro-portions will have elastic stiffnesses inexcess of this value.

The unconfined repeated load axial testhas adopted the conditions of the staticcreep test (100 kPa load at 40°C appliedfor 1 hour), but the load is pulsed ontothe specimen at a frequency of 0.5 Hz.

The test is terminated at 3,600 cycles orearlier if specimen failure appearsirnminent. Precise interpretation ofresults from this test is not yet possible.The results, however, will clearly rankmaterials in order of their deformationresistance and engineering judgment willhelp in the decisionmaking process. Atthis stage, satisfactory mixes should notexhibit more than 1 percent strain at theend of the test.

Tests for fatigue strength are not recom-mended; this testing requires an excessivenumber of test specimens for reliableresults. The minimum VB of 8 percent isdesigned to avoid mixes that may be sus-ceptible to cracks. The fatigue strength ofthe optimum mix formulations may bechecked by using a prediction methodinvolving the softening point of the bind-er and the volume of binder in the mix(VB). This method is considered to be ofuse when the results are combined withpavement design calculations using themechanistic approach.

The final check is the durability of theselected mix. The indirect tensile test isperformed on a specimen at the optimummix formulation after immersing thespecimen in water for 24 hours at 25’C.If the elastic stiffness is within 70 percentof its pre-immersed original value, themix is satisfactory. If it fails this criterion,the binder content must be increased.

NOVEL TEST APPARATUS

Compaction Devices--As discussed in the compaction devices in European mix“General Remarks” found on page 90, the design and analysis systems. Ause of gyratory and rolling-wheel compaction device similar in size and


101

capabilities to the well-known U.S. ArmyCorps of Engineers device and termed aGyratory Shear Compacting Press isemployed in the LCPC design method.The device is commercially availablefrom the French manufacturer MAP, witha retail cost in France of 230,000 Ffr(about $43,000).

The LCPC method also requires the useof a rubber-tired rolling wheel compac-tor, termed a Plate Compactor. Thisdevice mounts single or dual 0.415 mdiameter by 0.109 m wide tires, and canachieve a loading pressure of 700,000 Pa.It requires the use of an 80 kg batch mixerand produces compacted slabs in 20 min-utes. Maximum slab size is 0.6 m long,0.4 m wide and 0.15 m high. Cylindricalspecimens are typically cored horizontallyfrom the slab, allowing specimen lengthsnear 0.6 m. This apparatus is also avail-able from MAP at a cost of about 250,000Ffr ($46,000).

In the United Kingdom, both the TRRLand the University of Nottingham haveone-of-a-kind rolling wheel compactiondevices that are used principally forresearch studies. These employ a partialsegment of steel wheel, similar to thoseemployed on steel-wheeled pavementrollers, to provide the compactive effortneeded for slab production. These are notpresently available from commercialsources.

The PRD test apparatus employed forlaboratory compaction in the Universityof Nottingham (or Brown-Ackroyd) MixDesign System is a cornmercially-avail-able vibratory hammer that produces6-inch diameter cylindrical mix specimensin split steel molds. This type of vibratory

hammer is used extensively by the high-way community in the United Kingdomfor soil tests, a fact that should facilitateits adoption in a laboratory mix designand field quality control system.

Compared with current practice in theUnited States, the gyrator-y and rollingwheel compaction devices discussed hererepresent substantial increases in equip-ment costs and complexity of operations.In particular, the rolling wheel compac-tors produce large, massive slab speci-mens; high-volume batch mixers areneeded to produce the HMA required,and forklift trucks are necessary to movethe specimens. Finally, the rolling wheelcompactors produce slabs from which theactual test specimens must be cored orsawn, depending on the test configura-tion.

Mechanical Engineering TestDevices--The LCPC design methoddiscussed on page 97 employs twoengineering test devices that are unknownin routine U.S. mix design practice.

The Pavement Rutting Tester is a wheeltracking device in which two rubber-tiredwheels are driven in back-and-forthmotion over a rectangular slab preparedin the laboratory or cut from a fieldpavement.

The dependence of the rut depth in thespecimen with material types, number ofloading cycles, tire pressure, wheel load,temperature, and moisture conditioningcan be determined. An extensive database is available to relate the measuredrut depths obtained in the test to thoseexpected in actual field pavements. This


1 0 2

apparatus is available commercially fromthe French manufacture MAP at a cost of250,000 Ffr ($46,000).

Wheel-tracking test devices of varioussizes and degrees of complexity are alsoused in the United Kingdom for researchstudies and to calibrate, for field perform-ance, the results of such other methods asstatic and dynamic creep tests. Thesedevices are not used directly in mix designand analysis systems. They generallyemploy pneumatic rubber-tired wheelslike the LCPC device, but in someinstances, steel wheels or hard rubber-tired wheels are used.

The LCPC method further incorporatesthe use of the Fatigue Bend Machine forBituminous Mixes. This machine carriesout fatigue tests on trapezoidal beamspecimens cut from laboratory-compact-ed slabs or actual pavements. The beam isloaded repeatedly at a nominal excita-tion frequency of 25 Hz. For various mat-erial combinations and temperatures, thedependence of the number of load cyclesto specimen failure or some predeter-mined reduction in stiffness modulus isdetermined. This method also is calibrat-ed to an extensive data base of Frenchpavement performance, but because of itscomplexity, is run only when completelynew or unfamiliar materials and mixdesigns are evaluated. Commercially, thisapparatus is available for about $50,000.

Similar devices are used in many researchlaboratories in the United States andEurope.

The Nottingham Asphalt Tester, whichwas discussed on page 99, combinesseveral test devices into one computer-controlled assembly. The apparatus iscapable of performing indirect tensiletests, static load creep tests, repeatedload axial tests, and fatigue tests. For theBrown-Ackroyd mixture design proce-dure, only two test procedures are rout-inely used: the indirect tensile test toobtain elastic stiffness and the uncon-fined repeated load axial test to assessresistance to deformation.

The functions contained in the Notting-ham Asphalt Tester are used extensivelyaround the world for research studies, buthave never before been integrated into acomplete design procedure in this way.Many of the individual pieces of testequipment, particularly the indirect ten-sile test device, are available in statehighway agency laboratories in theUnited States.

Agencies considering adoption of thisdesign procedure, but that do not haveany of the component apparatus avail-able, can obtain the complete AsphaltTester from commercial sources in theUnited Kingdom for approximately$140,000.


103

REFERENCES

Liljedahl, B., Heavy-Duty AsphaltPavements, in the Proceedings of a.Seminar, aminous Roads m h199Qs ,The Irish Branch of the Institute ofAsphalt Technology, Dublin, Ireland, 1November, 1990.

Smith, R.W., Rice, J.M. and Spelman,S.R., Design of Open-Graded AsphaltFriction Courses, FHWA Report No.FHWA-RD-74-2, Washington, D.C.January 1974.


APPLICATION OF FINDINGS

1 0 7

APPLICATION OF FINDINGSAs described throughout this report, theEAST’s mission of identifying potentiallypromising asphalt technologies and con-tract administration practices was consid-ered by all participants to be an over-whelming success. But identifying newtechnologies is not enough. The success-ful adaptation of those findings for poss-ible use in the United States will be thedetermining factor in measuring themission’s success.

in adapting the EAST’s findings for use inthe United States through carefullydesigned experimental plans.

After returning from Europe, members ofthe EAST met to consider, first, whichEuropean technologies should be focusedon initially and then to develop a plan forthe application of their findings. Afterconsidering all the possibilities, the studyteam identified four general areas andseveral specific areas:

While immediate implementation of thefindings is desired, caution must be exer-cised. The United States cannot just “hitthe ground running” with Europe’s meth-ods. For special reasons, these technolo-gies may work well in Europe and not aswell or as efficiently in the United States.Cultures are different. For example, onenoticeable fact in Europe is the limitedamount of litigation in the transportationindustry. In Europe, a close and exten-sive working relationship exists betweengovernment and private industry. Whilethis situation may be due partly to legisla-tion or regulation, it does exist and offersmore opportunities than in the UnitedStates for cooperative ventures in thedevelopment and implementation oftechnology. For these and other reasons,patience and persistence are paramount

Asphalt Pavement Mixtures:Stone Mastic AsphaltPorous asphaltModified Binders

Laboratory EquipmentMix Design EquipmentLaboratory CompactionRut Tester

Innovative Contracting PracticesLane RentalContractor Warranties/Guarantees

Research

The members then developed anexperimental plan for implementing theirfindings:

ASPHALT PAVEMENT MIXTURES

Stone Mastic AsDhalt tions has been assigned the lead in coor-dinating evaluation of this technology,

Stone Mastic Asphalt is a special purpose, adapting it to this country’s needs andrut resistant surface pavement mixture of construction characteristics, and imple-coarse aggregates held together by an menting it in the United States. Toasphalt-filler-stabilizer mastic. The accomplish these assignments, the OfficeFHWA’s Office of Technology Applica- prepared a work plan that describes a


108

series of field tests in five or more States;collection and refinement of existinginformation to include a followup Euro-pean trip; material, mix design, and con-struction evaluation; and a detailed studyof SMA’s mechanical and physicalproperties.

Existing reports and data on SMA havebeen reviewed and a Technology Syn-thesis on the subject has been released.The technical fact-finding visit focused onSMA in Germany and Sweden was com-pleted in late April. Inquiries during thevisit focused on mixture design andcontrols for material and construction.Samples of SMA materials planned forprojects in this country will be providedto European experts for evaluation.

A Technical Advisory Committee (TAC)has been established and information onthe technology distributed. Membershipin the TAC includes representatives fromseven States, FHWA, SHRP, NAPA, TheAsphalt Institute, and the National Cen-ter for Asphalt Technology (NCAT). Theseven States are Colorado, Georgia,Michigan, Missouri, Texas, Virginia, andWisconsin. A formal meeting of the TACwill be scheduled to coincide with theconstruction of an initial State fieldproject.

Proposals have been received for fieldprojects in Georgia and Michigan. Con-struction is scheduled for mid to latesummer. An additional project is beingplanned in Wisconsin, with several otherStates expressing interest in constructingSMA pavements, pending results of thepilot projects.

Material sources have been identified forthe Michigan pilot project. The State’sand the FHWA’s laboratories have begunpreliminary material and design investi-gations. Laboratory activity will alsoexamine the effectiveness and composi-tion of such SMA stabilizers as cellulose,mineral fibers, and various polymer/elastomer modifiers.

The NCAT has submitted a proposal toestablish SMA’s characteristics and eval-uate its sensitivity to changes in its com-ponents. This effort, lasting 3 months,will primarily concentrate on the materialbeing used in the Michigan pilot project.

Initial and periodic post constructionevaluations will be performed on theGeorgia and Michigan pilot projects.Data from additional field projects alongwith State, FHWA, and industry labora-tory research will be pooled and analyzedfor eventual national implementation ofSMA.

Porous Asphalt

European PA pavements are similar tothe open-graded friction courses used inthe United States. They provide a pave-ment surface that drains rainwater rapid-ly, thus reducing the incidence of hydro-planing. European PA also provides ameans of absorbing and dissipating noise.The use of modified asphalt cements(cellulose, mineral fibers, and polymers)in the European PA allows for increasedasphalt film thickness, thus reducingaging while enhancing durability.

Use of open-graded friction courses withmodified asphalts, similar to the Euro-pean PA, is being examined for possible


1 0 9

field evaluation and implementation.Projects are planned for the summer of1991 in several States using thismethodology.

cation. The guidelines will include uni-formity in the classification of modifiertypes, test methods for evaluating themodifiers, life-cycle cost effectiveness,methods of acceptance, and potential

Modified Asuhalt Binda specifications.

European practice routinely uses a widerange of modified asphalt cements inconstruction of roadway wearing surfaces.The Office of Technology Applications isexamining an approach and formulatingguidelines for a study on asphalt modifi-

Evaluation and implementation of thesemodifications will, in part, take placethrough our efforts in the areas of SMAand PA.

LABORATORY EQUIPMENT

Mix Desbn Eauiument ales, and equipment. These systems willthen be used in developing and testingmethodologies for mixture design in thiscountry.

Representatives from the FHWA, theColorado Department of Highways, andthe NAPA will jointly investigate the flex-ible pavement design testing technolo-gies used in Europe. They developed awork plan that addresses equipmentacquisition, installation, staffing, training,test and evaluation, and ultimateimplementation in this country.

Comuaction Devices

The FHWA will evaluate such Europeancompaction testing devices as the rollingwheel compactor and the British vibra-tory hammer. Data generated on thesedevices will be compared with existingUnited States compaction methodology(Marshall), gyrator-y compaction devices(Corps of Engineers and Texas), andmodified Marshall hammers.

The work plan focuses on mix design sys-tems from France and the United King-dom. The French system incorporatestwo types of compactor, namely gyrator-y(similar to equipmentused by the U.S.Corps of Engineers) and rolling wheel, aswell as a series of mechanical tests tomeasure trial-mix performance charac-teristics. The University of Nottinghamin the United Kingdom has developed anasphalt tester that is an all-in-one testapparatus capable of performing indirecttensile, static load, creep, repeated axialload, and fatigue tests. The evaluation ofthese two systems will include examina-tion of the various methodologies, ration-

Rut Tester

The French wheel tracking device will beevaluated and compared with current rutprediction methodologies, as evidencedin the current Asphalt Aggregate MixtureAnalysis System. Comparisons will alsobe made with the Georgia rut-test devicebeing evaluated in six States.


1 1 0

INNOVATIVE CONTRACTING PRACTICES

The TRB established Task Force A2T51in 1987 to address innovative contractingpractices. That task force was chargedwith soliciting, studying, and compilinginformation on the practices under whichthe United States and foreign agenciescontract for construction as they affectquality, progress, and costs; call attentionto practices that inhibit quality construc-tion and ways to counter them; and sug-gest ways for improving contracting pro-cesses with attendant quality improve-ment in construction. The members ofTask Force A2T51 plan to publish areport on innovative contracting practicesin 1991. The report will contain signifi-cant findings on bidding, materials,quality, and insurance/bonding.

mental Project 14 to address the call.Now that the project has been announc-ed, the FHWA is seeking--and stronglyencouraging--additional State DOTinterest.

A number of activities the members ofthe EAST observed in Europe are sup-portive of Task Force A2T5 l’s findings,including time/lane rental bidding, con-tractor responsibility factors (quality andperformance), design/build, performance-based specification and testing, alternatebids, regional testing/product evaluationcenters, and warranties/guarantees.

In 1989, Task Force A2T51 asked theFHWA to establish a mechanism forassisting State departments of transpor-tation (DOT) in evaluating and validatingsome of the Task Force’s early findings.The FHWA established Special Experi-

Moreover, the proposed SurfaceTransportation Assistance Act of 1991,which the President submitted to theCongress in February, contains provisionsdirectly related to one of the group’sfindings. The bill would, for the firsttime, allow State DOT’s to requestwarranties/guarantees from contractorson Federal-aid projects.

RESEARCH

Research is another area where theEuropean practice may offer an oppor-tunity for enhancement of the U.S.industry/government/academic researchand development relationship. InEurope, government and industry haveextensive research facilities, and theresults are marketed aggressively. Insome countries, in fact, research andmarketing are joint ventures betweengovernment and industry.

The FHWA and the State DOT’s musttake a fresh look at the way research isconducted in the United States. The

research process must be realigned tostrengthen our competitiveness in inter-national markets. It must be adrninis-tered to strengthen and foster innovation,instead of deterring or stifling the questfor innovation, as is the case with somecurrent practices.

Contracting practices in the UnitedStates, in contrast with those in Europe,tend to discourage contractors fromoperating large-scale research facilities.One primary reason is size. Europeancountries generally work with a few largecontractors. Another reason is the oppor-


1 1 1

tunity in Europe to reward innovationthrough such contracting practices. asdesign/build and warranties/guarantees.Regardless of the differences, researchand development must be given as high apriority in the United States as it is inEurope if economic competitiveness inthe world market is to be maintained.

In addition, the United States needs morecooperative research between govern-ment and private sector laboratories.Such an arrangement could lead to lowerresearch and development costs by mini-mizing duplication of specialized scienti-fic expertise and expensive laboratoryfacilities and equipment. To this end,efforts are underway through AASHTO’s

Research Advisory Cormnittee to identifythe capabilities and facilities of theUnited States highway communitythrough an inventory of academic, gov-ernment, and industry resources. Thisinventory is the first step toward a nation-al consortium of highway research labora-tories similar to research laboratories inEurope. In addition, fostering a cooper-ative, collaborative environment amongindustry and government is important ifthe United States is to fully use the cap-abilities and results of the nationalresearch and development resourceswithout significant concerns aboutownership turf.


ACRONYMS, DEFINITIONS and TECHNICAL TERMS

115

ACRONYMS, DEFINITIONS and TECHNICAL TERMS

ACRONYMS DEFINITIONS/TECHNICAL TERMS

ANAS - Azienda Nazionale Autonomadelle Strada - the National Road Board,an asphalt plant (in Italy)

AASHTOAmerican Association of StateTransportation Officials444 North Capitol Street, NW., Suite 225Washington, D.C. 20001Phone (202) 624-5800

FHWAFederal Highway Administration400 Seventh Street, SW.Washington, D.C. 20590Phone: (202) 366-0660

NAPANational Asphalt Pavement AssociationNAPA Building, 5 100 Forbes BoulevardLanham, Maryland 20706-44 13Phone: (301) 73 l-4748

SHRPStrategic Highway Research Program818 Connecticut Avenue, NW., Suite 400Washington, D.C. 20006Phone: (202) 334-3774

TAIThe Asphalt InstituteResearch Asphalt DriveP.O. Box 14052Lexington, Kentucky 405 12-4052Phone: (606) 288-4960

TRBTransportation Research Board2101 Constitution Avenue, NW.Washington, D.C. 20037Phone: (202) 334-2989

BAST - Bundesanstalt fur Strassenwesen -the Federal Highway Research Center (inGermany)

DBM - Dense Bitumen Macadam

EVA - Ethylvinyl Acetate

HABS - Swedish term for SMA

HABT - Swedish term for conventional,continuously-graded asphalt concrete

HMA - Hot-Mix Asphalt

HRA - Hot Rolled Asphalt

LCPC - Laboratoire Central des Ponts etChaussees - the Central Laboratory ofBridges ad Roads (in France)

PA - Porous Asphalt

PCC - Portland Cement Concrete

SBS - Styrene-Butadiene-Styrene

SMA - Stone Mastic Asphalt

TRRL - Transportation Road ResearchLaboratory

European Asphalt Study Tour

APPENDIX A

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-10-90 #I

DESCRIPTION OF NOVEL PAVEMENT FEATURE:

STONE MASTIC ASPHALT (S&M): Tradename Stabinor produced by skanska AR.

LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):

Tingstad Tunnel (east side), Route E6, Gothenborg Sweden

DATE OF CONSTRUCTION I985 LENGTH (mi/km) # OF LANES 3 (east bound)

ACTUAL ADT % TRUCKS E A L SWHEN OPENED ACTUALCURRENT 1 0 0 , 0 0 0 (6 lanes) DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):

38 mm overlay of 80 stabinor 12 (80 kg/m’, I2 mm top size).

ASPHALT CONTENTm(% OF MIX) AIR VOIDS CONTENT a(%)

MODIFIER TYPE Mineral Fiber MODIFIER CONTENT 0.8(% OF BINDER)

AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):

TOP SIZE: 12mm; 50 % Quartzite typical gradation: 26% passing 2mm, 30 % passing 4mm, 50%passing 8mm, 10% filler passing 0.075mm (#200 sieve).

DISTRESS TYPE EXTENT OR FREOUENCYLOW MEDIUM HIGH

RUTTING 1 17mm

LONGITUDINAL CRACKING 1 X

TRANSVERSE CRACKING 1 X I

RAVELLING IX

ALLIGATOR CRACKING IXBLOCK CRACKING lx

POTHOLES lx I

NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:

High traffic volume precluded stopping bus to view pavement. However, rutting due to studded tires wasapparent in some areas, not in others. Pavement generally had a roughly-textured, overall appearance.No other distress of consequence apparent at speed of 50 to 70 km/hr.

(form continued on reverse side)/26 JUNE 90

DRAINAGE FACILITIES:

COMMERCIAL SOURCE (IF PROPRIETARY FEATURE):

Stabinor is the tradename for SMA produced by Skanska AB. Mineral filler, tradename Inorphil, is usedas modifier.

OTHER REMARKS:

POST-VISIT DEBRIEFING NOTES:

To date, SM.4 has taken 20 percent more traffic than the conventional HMA overlay previously usedwhich lasted 5 years before rehabilitation was necessary.

At 5 years service, HM had a rut depth of 25mm compared to 17 mm for SMA. A 20 percent increasein service life for SMA compared to HMA is projected.

APPLICABILITY TO U.S. PRACTICE:

High

COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:

Increased. Swedish authorities justify increased first cost by longer service life.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SVIDEOTAPE: NO- YES- CASSETTE #AUDIOTAPE: NO- YES- CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-10-90 #2


STONE MASTIC ASPHALT (SMA): Tradename Wacotop produced by the Swedish paving contractorNCC.


Stalhanskegatan., Gothenborg, Sweden

DATE OF CONSTRUCTION 198.5 LENGTH (mi/km) # OF LANES 2 (east bound)

ACTUAL ADT % TRUCKS E A L SWHEN OPENED ACTUALCURRENT 30,000 (4 lanes) DESIGNED


38 mm overlay of 80 viacotop 12 (80 kg/m’, 12 mm top size).

ASPHALT CONTENTm(% OF MIX) AIR VOIDS CONTENT a(%)

MODIFIER TYPE Cellulose fibers MODIFIER CONTENT 0.3(% OF MIX)


TOP SIZE: 12mm; 50 % Quartzite; typical gradation: 22% passing 2mm, 31 % passing 4mm, 38%passing 8mm, 10.5% filler passing 0.075mm (#200 sieve).

DISTRESS TYPE

RUTTING

LONGITUDINAL CRACKING

TRANSVERSE CRACKING

RAVELLING

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES

EXTENT OR FREOUENCYLOW MEDIUM HIGH

1 10mm

lx

IX I I Ilx I


High traffic volume precluded stopping bus to view pavement. Pavement viewed at speed showed little orno apparent distress.




Viacotop LY the tradename for SMA produced by NCC. Cellulose fiber is used as modifier.

OTHER REMARKS:

Paving was done by the Gothenborg Street and Highway Department.



High.


35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SV I D E O T A P E : NO-YES- CASSETTE #A U D I O T A P E : NO-YES- CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT D A T E 9 - 1 0 - 9 0 #3


Porous Asphalt (PA): Tradename Drainor produced by Skanska AB.


Brackevagen, Route 159, Gothenberg, Sweden

DATE OF CONSTRUCTION 1986 LENGTH (mi/km) # OF LANES 2 (westbound)

ACTUAL ADT % TRUCKS E A L SWHEN OPENED ACTUALCURRENT 25,000 (4 lanes) DESIGNED


43 mm overlay of 90 Drainor 16 (90 kg/m: 16 mm top size).

ASPHALT CONTENT ‘5.0 (% OF MIX) AIR VOIDS CONTENT >1.5 (%)I

MODIFIER TYPE Mineral Fiber MODIFIER CONTENT 0.8(% OF BINDER)

AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):TOP SIZE: 16mm; 55 % Quartzite; typical gradation: IO-15% passing 2mm, 20-24% passing 4mm, 36-42% passing 8mm, 60% passing 11.3mm, 4-6% filler passing 0.075mm (#200 sieve).

DISTRESS TYPE

RUTTING


TRANSVERSE CRACKING

RAVELLING

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES


1 6-7mm I

IX I

lx

IX I


Pavement uses 16mm maximum stone size to increase resistance to studded tires. Pavement has a rough-looking surface; lots of aggregate show. Pavement was viewed at speed from bus; little or no significantdistress was visible.

‘. Nominal(form continued on reverse side)/26 JUNE 90



Drainor is the tradename for porous asphalt produced by Skanska AB. Mineral filler (Inorphil) is used asmodifier.

OTHER REMARKS:


80 Drainor 12 showed inadequate resistance to studded tires. 90 Drainor 16 is about as resistant tostudded tires as conventional HMA.


Uncertain


In Sweden, PA costs about as much as SMA, but resists wear comparably to HMA. PA costs are justifiedon a case-by-case basis where noise reduction and water drainage are- required.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SVIDEOTAPE: NO- YES- CASSETTE #A U D I O T A P E : N O - YES- CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-10-90 #A

DESCRIPTIONOFNOVELTECHNOLOGY:

"Vikan" Asphalt Hot Mix Plant

LOCATION (couw~Y,Loc~~ G~VERNMENTUNIT,HIGHWAY#,MILEPOST):Near Gothenberg, Sweden

DETAILSOFOPERATION:

This is a 240 ton/hour batch plant employed to produce HMA, SMA and PA. The plant can handleboth cellulose and mineral jibers which are dispersed mechanically into the pugmill. Fibers may also beused in pelletized form with asphalt cement as the binder. It is not necessary to coat the fibers withasphalt cement in the pug mill.


OTHER REMARKS:



COSTS RELATIVE TO CURRENT U.S. PRACTICE:


REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT D A T E 9-12-90 #I

DESCRIPTION OF NOVEL TECHNOLOGY:

Hot mix plant - Permanent Batch Operation(Operated by Hamburg Asphalt Geschag)


Nordersted, Germany (Northern Suburb of Hamburg)

DETAILS OF OPERATION:

1.2 .3 .4.5.

6.

7.

8.

9.

Very compactly organized-operations are “enclosed” to a large degree.Employs 15 hot aggregate bins.Much of the process heat is supplied by recylced waste gases.Much high quality stone is imported from Norway.Has two drums for heating aggregate. In the first, virgin aggregate is heated and screened. Hot wastegases are directed to the second drum (at 300°C) to heat RAP to 120°C. Particulate matter from virginaggregate is trapped in heated RAP or in a baghouse filter when RAP is not being used in mixoperations.Aggregate is stored in hot bins at 180°C. The use of 16 hot bins allows mix designs to be variedrapidly. The plant is computer-controlled and can produce 160 different mix designs at present. Mixrecipes in computer can be altered only at central oftice; plant operators can only select among storeddesigns. Total hot bin storage is 360 tons; filler is stored in separate bin.RAP is used in base course mixes up to 50% (20% in Hamburg), and in surface course mixes up to15%. No RAP is used in SMA.Aggregate is heated and screened at night. Hot-mix is prepared in 2.5 ton batches. Production rate isabout 160 tons/hr. Yearly production is near 100,000 tons. Mix cost at plant varies from $40 to 70.Mixing time is 20-30 seconds per batch for virgin materials, 50 seconds for mixes with RAP content.Total hot mix storage capacity is 560 tons in eight storage silos.

10. A 60-80 pen grade asphalt cement is used. No rejuvenating agents are employed in recylced mixes.11. Plant operating tolerances are &OS-0.2% for asphalt content, +0.3% for aggregate gradation.12 . There is no strict control of the final asphalt properties in recycled mixes. However, stockpiles of RAP

are sampled every 300 tons to check gradation, asphalt content and ring-and-ball softening point ofthe binder, RAP stockpiles are blended to maintain an average R&B softening point of 70°C for therecovered asphalt cement.

13 . When SMA mixes are produced, cellulose fibers are added through the filler bin.14. Plant staff is 6 persons.


OTHER REMARKS:



COSTS RELATIVE TO CURRENT U.S. PRACTICE:


REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-IO-90 #L


SMA Under Construction (SKanska AB Stabinor)


European Route E-4 near Varberg, Sweden, KP 51500

DATE OF CONSTRUCTION 9-10-90 LENGTH-(mi/km) # OF LANES Divided 4-lane

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT 13,000 2 5 DESIGNED


2” (uncompacted) SMA overlay: 90 Stabinor 16, compacted to 38mm.

ASPHALT CONTENTq,L(% OF MIX) AIR VOIDS CONTENT 3-4(%)

MODIFIER TYPE Inorphil MODIFIER CONTENT &(% OF BINDER)


TOP SIZE: 16mm; 20% qualified stone (46 kr/m2); nominal gradation: 25010 passing 2mm, 28% passing4mm, 45% passing 8mm, 70% passing 12mm, 8% passing 0.075mm (#200 sieve).


RUTTING I

LONGITUDINAL CRACKING I

TRANSVERSE CRACKING I

RAVELLING I I

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES


New; construction in progress. Asphalt cement grade: B85.




Stabinor is the tradename for SMA produced by Skanska AB. Mineral filler, trade named Inorphil, isused as modifier.

OTHER REMARKS:


SMA was placed with conventional paver at 160°C. Compaction was accomplished with two steel-wheeledrollers. No vibration was employed. Rollers operated close behind the paver.

Rolling is intended to orient stone skeleton; little compaction of the mat is expected. SMA is placed overa thin, I2-16mm, leveling course.

The air temperature at construction was about 6o”F, sky partly cloudy and wind at about 10 to I5 mph.Rolling can continue until mat temperature falls to 75°C. Second roller is equipped with infraredthermometer.


High


35 mm PHOTOS: NO YES NEGATIVE #‘SVIDEOTAPE: NO- YES-AUDIOTAPE: NO- YES- CASSETTE #

REPORTER(S) :



SMA


European Route E-4 South of KP 51500 (see #5)

DATE OF CONSTRUCTION 1989 LENGTH (mi/km) # OF LANES Divided 4-lane

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT 13,000 2 5 DESIGNED


ASPHALT CONTENT-(% OF MIX) AIR VOIDS CONTENT -(%)

M O D I F I E R T Y P E MODIFIER CONTENT -(% OF BINDER)


Probably similar to datasheet #5 (9-10-90); however only local stone used; no qualified (select) materialimported Top size: 18mm.

DISTRESS TYPE EXTENT OR FREOUENCYLOW MEDIUM H T G H

RUTTING 1 None 1

LONGITUDINAL CRACKING 1 None

TRANSVERSE CRACKING 1 None IRAVELLING I x* IALLIGATOR CRACKING

BLOCK CRACKING

1 None

1 None

I I

IPOTHOLES

* SEGREGATION

1 None


Viewed northbound lanes. Pavement wet from earlier rain. Pavement showed irregular drying patterncaused by mix segregation. Pavement appeared very porous in randomly-spaced locations in betweenwheel paths. Wheel paths appeared normal, perhaps due to movement of mastic under traffic.




OTHER REMARKS:


Pavement distress appeared to be ravelling. However, U.S. contractors on team agreed that distressresulted from mix segregation during construction.




REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT D A T E 9 - 1 0 - 9 0 #L


SMA under construction (NCC Viacotop)


European Route E-6, just North of Bastad, Sweden

DATE OF CONSTRUCTION 9-10-90 LENGTH (mi/km) # OF LANES Divided 4-lane

ACTUAL ADT % TRUCKS EALsWHEN OPENED ACTUALCURRENT DESIGNED


38rnm thick (compacted) SMA overlay: 90 Viacotop 16.

ASPHALT CONTENT 6.7* (% OF MIX) AIR VOIDS CONTENT 3_(%)

MODIFIER TYPE Cellulose PelletsFibers * Includes 0.3% from fiber pelletsBinder)

MODIFIER CONTENT 0.3(% OF MIX) (0.6%+


Top size: 16mm; nominal gradation: 22% passing 2mm; 27% passing 4mm, 33% passing 8mm, 40%passing 12mm, 95% passing 16mm, 10% filler passing 0.075mm (#200 sieve).


RUTTING I I

LONGITUDINAL CRACKING 1

TRANSVERSE CRACKING I I I I

RAVELLING

ALLIGATOR CRACKING IBLOCK CRACKING

POTHOLES

* SEGREGATION


New; construction in progress. Asphalt cement grade: B85.




Viacotop is the tradename for SMA produced by NCC. This job employed pelletized cellulose fibers as amodifier.

OTHER REMARKS:


The binder content is considerably higher for this project than for the Stabinor project reported in #5 (9-10-90). However this mix is reported to hae good friction properties when newly laid.

Rolling was accomplished with two steel-wheeled rollers (10 metric tons each).

Pavement surface appeared rich in binder, almost to the point of flushing. However, the roller marks weremuch less pronounced than for the Stabinor mix. This mix appears much more stable.




REPORTER(S):



Runway and Taxiway Rehabilitation Projects at Copenhagen Airport: a) EVA - Modified AC overlay onPCC (Accuplast Seal) b) Open graded A/C filled with superplasticized PCC (Densiphalt); c) Microfil-Modified AC overlay; d) Recycled 40 year old AC pavement.


Klastrup Airport, Copenhagen, Denmark

DATE OF CONSTRUCTION 9-11-90 LENGTH (mi/km) # OF LANES Divided 4-lane

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT N/A DESIGNED N/A


c) Taxiway Reconstruction: Binder course and open-graded surface course. Binder course consists ofHMA. Modified with carbon black (Microfil), hydrated lime (1.5% of mix) and cellulose fibers (0.25%)

ASPHALT CONTENTn(% OF MIX)

MODIFIER TYPE Micro”$1BINDER)

AIR VOIDS CONTENT 4J%)

MODIFIER CONT& 15- (% OF


c) Top size: 20mm. Binder course employs conventional dense-graded aggregate.


RUTTING I


TRANSVERSE CRACKING

RAVELLING I

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES


a) EVA - Modified AC overlay: No visible distress. Another section developed rutting from heavy statictire loads.

(fom continued on reverse side)/26 JUNE. 90



Microfil is the tradename for a commercial carbon black product produced by Cabot Corporation.

OTHER REMARKS:

c) Microfil-Modified AC overlay: SBS rubber and EVA polymer have also been tried as modifiers, butthese present bitumen compatibility and separation problems. Also, SBS and EVA-modified pavementshave failed under heavy static tire loads.


c) Microfil-Modified AC Overlay:The carbon black is employed to flatten the temperature susceptibility response of the 60 pm PDA-refinedDanish bitumen. Carbon black apparently increases the compaction effort required to achieve satisfactorydensity The roller complement employed here was double that needed for unmodified HMA. Both steel-wheeled and pnuematic-tired rollers are used. The pneumatic-tired rollers are held off the pavement for24 hours; this finish rolling is designed to improve durability. Compaction was intended to achieve 298%of Marshall density at 4% air voids.

Microfil appears to slow aging of HMA during production. It also flattens the response of Marshallstability and flow to changes in binder content. It has been employed with bitumens up to 120 pen. Costin Denmark is about $1 per kg.


Uncertain.


Increased due to modifier cost and changes in construction practices.

35 mm PHOTOS: NO YES R O L L # NEGATIVE #‘SVIDEOTAPE: NO- YES CASSETTE #AUDIOTAPE: NO YES CASSETTE #

REPORTER(S) :



SBS - Modified SMA overlay on a cracked and seated, 32-year old PCC pavement.


Helsingor Motorway (European Route E4) North from Copenhagen, Denmark

. DATE OF CONSTRUCTION 1988-90 LENGTH-&@i/km) # OF LANES Divided 4-lane

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT 40,000 5 DESIGNED N/A


40 mm SMA over 60mm HMA binder course over either cracked and seated PCC slabs or 100 mm HMAbase course where poor PCC was replaced.

ASPHALT CONTENTm(% OF MIX) AIR VOIDS CONTENT -(%)

MODIFIER TYPE SBS/Cellulose Fibers SBS CONTENT 6 (% OF BINDER)FIBER CONTENT 0.25(% OF MIX)


82% crushed rock, 15% luxovit (burned flint, light stones), 2.75% filler, 0.25% fibers. Nominal gradation:22% passing 2mm; 28% passing 4mm, 53% passing 8mm, 93% passing 11.2mm, 100% passing 16mm,7.2% jiller passing 0.075mm (#200 sieve).


RUTTING 1 Slight I I I

LONGITUDINAL CRACKING 1 None I I I

TRANSVERSE CRACKING 1 None I I IRAVELLING 1 None

ALLIGATOR CRACKING 1 None I I I

BLOCK CRACKING 1 None I I IPOTHOLES 1 None I I I


Slight flushed appearance in wheel tracks of driving lane. Passing lane has very even appearance.




OTHER REMARKS:

Binder course is 50% recycled HMA.

Cellulose fibers cost 10 kr/kg ($0.65/lb).

SMA binder is modified with SBS to increase flexibility.



High.


First costs increased by addition of cellulose fibers and SBS.


REPORTER(S):



SMA Surface Course on a heavily trafjiced urban street.


Barmbekerstrasse, Hamburg, Germany

DATE OF CONSTRUCTION 1984 LENGTH-(mi/km) # OF LANES 4 (undivided)

ACTUAL ADT % TRUCKS EALsWHEN OPENED ACTUALCURRENT 40,000 6 DESIGNED


40 mm SMA over 40mm HMA binder course over 140mm asphalt base course over 520mm of treatedbase material on frost-proof sand. This pavement section is intended for intermediate traffic loads.

ASPHALT CONTENT-(% OF MIX) AIR VOIDS CONTENT -(%)

MODIFIER TYPE Cellulose Fibers MODIFIER CONTENT (% OF MIX)


Top size: 11mm.. 70 to 80% of aggregate is crushed material. Remainder consists of manufactured andnatural sands and filler. Nominal gradation: 90-100% passing 11.2mm, 50- 75% passing 8mm, 30-50%passing 5mm, 20-30% passing 2mm and 8-13% passing 0.09mm.


RUTTING 1 None


TRANSVERSE CRACKING 1 None

RAVELLING 1 None

ALLIGATOR CRACKING 1 None

BLOCK CRACKING

POTHOLES

1 None

1 None


As noted, no distress is apparent of a significant nature. Hamburg roads and streets agency personnelindicated that typical service life for SMA in these circumstances is 10 years.




OTHER REMARKS:



High.


In Germany, SMA costs about 20 percent more than conventional HMA.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SV I D E O T A P E : NO- YES- CASSETTE #A U D I O T A P E : NO- YES- CASSETTE #

REPORTER(S):

FH.WA/AASHTO/NAPA SITE VISIT REPORT D A T E 9 - 1 2 - 9 0 #3


Gussasphalt Surface Course on a heavily trafficed urban street.


Behringstrasse, Hamburg, Germany

DATE OF CONSTRUCTION 1973 LENGTH-(rni/km) # OF LANES 4 (undivided)

ACTUAL ADT % TRUCKS EALsWHEN OPENED 40,000 ACTUALCURRENT 40,000 6 DESIGNED


40 mm Gussasphalt over 80mm HMA binder course Er 160mm HMA over 400mm of treated basematerial on frost-proof sand. This pavement section is intended for the highest traffic loads.

ASPHALT CONTENT7-8 (% OF MIX) AIR VOIDS CONTENT &(%)

MODIFIER TYPE _ MODIFIER CONTENT (% OF MIX)


Top size: 12mm. Nominal gradation: 90 to 100% passing 11.2mm, 70-80% passing 8mm, 45-55%passing 2mm and 20-30% passing 0.09mm. Aggregate consists of crushed stone, manufactured or naturalsand and filler.


RUTTING 1 None to 1

LONGITUDINAL CRACmmne-w


RAVELLING 1 None

ALLIGATOR CRACKING 1 None

BLOCK CRACKING 1 None

POTHOLES 1 None


Excellent considering its long service life. Gussaphalt typically yields a service life of 1.5 years or morecompared to 12 years for SMA.




OTHER REMARKS:

Gussasphalt is a pourable HMA that is placed at ,TO@‘C (575°F) with a special screed. It can also bepoured from buckets and "floated" with hand tools similar to PCC. No compaction is required. It iscovered with excess chipping at a rate of 1.5 kg/m2 which are rolled in with a very heavy roller.



Low. Its use probably would be prohibited almost every where due to air pollution regulations. High.


In Germany, Gussaphalt costs almost two times as much as conventional HMA.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SVIDEOTAPE: NO YES- CASSETTE #AUDIOTAPE: NO- YES- CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT D A T E 9 - 1 2 - 9 0 #A


Gussasphalt Surface Course


Autobahn A-7, North of Kassel, Lower Saxony, Germany

DATE OF CONSTRUCTION 5-1990 LENGTH-(mi/km) # OF LANES 4 (divided)

ACTUAL ADT % TRUCKS EALSWHEN OPENED 50,000 17-20 ACTUALCURRENT 50,000 (mean) 17-20 DESIGNED

80,000 (maximum)


40 mm Gussasphalt Surface Course over 80mm HMA Binder course over 180mm asphalt base course.

ASPHALT CONTENTd(% OF MIX) AIR VOIDS CONTENT OJ%)

MODIFIER TYPE Trinidad Lake Asphalt MODIFIER CONTENT 2 (% OF MIX)


Top size: llmm. Nominal Gradation: 90 to 100% passing 11.2mm, 70-85% passing 8mm, 45-55%passing 2mm, and 2 0 - 3 0 % passing 0.09mm. Aggregate consists of crushed stone, manufactured andnatural sand, and mineral filler.


RUTTING 1 None I

LONGITUDINAL CRACI 1


RAVELLING

ALLIGATOR CRACKING

BLOCK CRACKING

1 None

1 None

1 None

POTHOLES 1 None


Surface appeared rough, but this is normal due to the rolled-in chippings. Wheel paths have a smootheroverall appearance. There were isolated paths that appeared to be ravelled, but may be related to therolled-in chippings.




OTHER REMARKS:

Gussasphalt is a pour-able HMA that is placed at 300°C (575°F) with a special screed. It can also bepoured from buckets and "floated" with hand tools in a manner similar to PCC. No compaction isrequired. It is covered with excess chipping at a rate of 15 kg/m’, these are rolled into the surface with avery heavy roller.



Low due to environmental problems.


In Germany, Gussaphalt costs almost two times as much as conventional HMA.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SVIDEOTAPE: NO YES CASSETTE #AUDIOTAPE: NO YES- CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT D A T E 9-13-90 #1


Ralumac Slurry Seal


Highway P38 westbound between Autobahn A-65 and Neustadt and der Weinstrasse, Rheinland - Pfalz,Germany.

DATE OF CONSTRUCTION 9-13-90 LENGTH-(mi/km) # OF LANESA

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT 12,500 DESIGNED


Ralumac slurry seal (Microsurfacing) applied at a nominal thickness of 8mm to fill existing ruts inpavement and provide a level surface.

ASPHALT CONTENTN/A (% OF MIX) AIR VOIDS CONTENT y/A (%)

MODIFIER TYPE Latex rubber/emulsifier MODIFIER CONTENT (% OF MIXi

AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):Top size: 5mm. 8mm top size has been used on east-bound lane surfaced earlier in day.


RUTTING 1 N/A

LONGITUDINAL CRACtimxx

TRANSVERSE CRACKING I WA

RAVELLING 1 N/A

ALLIGATOR CRACKING 1 N/A

BLOCK CRACKING 1 N/A

POTHOLES I N/A


The existing pavement had been deeply rutted. A first layer of Ralumac was applied to fill the ruts. Thena second complete layer 8mm thick was applied. Traffic was permitted onto surface also immediately;however, it typically takes several days for all the water in the emulsion to evaporate. Ralumac isconsidered to have more structural value than other slurry seals. A useable service life of 2-3 years isexpected for this Microsurfacing.




Ralumac is a proprietary product of Raschig AC, Ludwigshafen, Germany.

OTHER REMARKS:



This product is widely used in US.


35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SV I D E O T A P E : N O YES- CASSETTE #A U D I O T A P E : NO-YES CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-13-90 #A


Reconstruction of a rutted pavement with SMA surface course. (At time of visit, asphalt base course wasbeing laid).


Autobahn A-65 (Northbound), North of Neustadt an der Weinstrasse Interchange, near KP 117,100,Rheinland - Pfal., Germany.

DATE OF CONSTRUCTION 9-13-90 LENGTH-(n-d/km) # OF LANES 4 (divided)

ACTUAL ADT % TRUCKS EALsWHEN OPENED ACTUALCURRENT DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):Driving (Right-Hand) Lane: 35mm SMA over stress-absorbing membrane interlayer over 80 mm HMAbinder course over 100 mm asphalt base course over 200 mm cement-treated base.

ASPHALT CONTENT Z.5* (% OF MIX) AIR VOIDS CONTENT 3x(%)

MODIFIER TYPE Cellulose fibers* Nominal

MODIFIER CONTENT 0.3* (% OF MIX)

AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):Top size: 11 mm. TYPICAL GRADATION: 90-100% Passing 11.2mm, 50-75% passing 8mm, 30-50%passing 5mm, 20-30% passing 2mm and 8-13% filler passing 0/09mm. Crushed rock or stone composes75% of aggregate, natural and manufactured sand 15% and mineral filler 10%.


RUTTING I WA

LONGITUDINAL CRACr

TRANSVERSE CRACKING I N/A

RAVELLING I WA

ALLIGATOR CRACKING I WA

BLOCK CRACKING 1 N/A

POTHOLES 1 N/A

NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:Rutting had occurred in driving lane of original pavement. This lane was milled out to a depth of 38cmand reconstructed with the pavement section described above. SMA and SAM will extend across entirepavement width. This type of reconstruction was necessitated by the fact that substantial overlays would

have blocked the existing drainage system.




OTHER REMARKS:





REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT D A T E 9-14-90 #.J-.


Danasphalt (Porous Asphalt) overlay on pavement and shoulders


Autobahn A-6, east of Heilbronn, Baden - Wurttemberg, Germany.

DATE OF CONSTRUCTION _ LENGTH-(mi/km) # OF LANES-

ACTUAL ALIT % TRUCKS EALsWHEN OPENED ACTUALCURRENT DESIGNED


ASPHALT CONTENT5.0 (% OF MIX)Polymer-modified

MODIFIER TYPE emulsion and 0.5%cellulose fibers

AIR VOIDS CONTENT B( %) (Marshall Design)

MODIFIER CONTENT (% OF MIX)

AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):Top size: 8 and 11 mmin different sections. Nominal gradation: 85% retained on 2mm, 5% fillerpassing 0.09 mm. Binder is polymer-modified cationic emulsion of a B65 - grade bitumen. Cellulose fibersare added to reduce drainage during construction.


RUTTING 1 None

LONGITUDINAL CRACamFe


I I

I

RAVELLING 1 None

ALLIGATOR CRACKING 1 None I IBLOCK CRACKING 1 None

POTHOLES 1 None I I I

NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:Viewed several sections of porous asphalt overlays intended to reduce hydroplaning and traffic noise.

(form continued on reverse side)/26 JUNE 9U



OTHER REMARKS:Porous asphalt surface courses on main lines are self-cleaning due to the action of high-speed traffic.


No standard mix design has been established yet for porous asphalt by the German road authorities.Riding surface is very quiet.


Uncertain. Use of impermeable seal layer under porous asphalt might eliminate some of the problemsexperienced in the U.S. with open-graded asphalt courses.

COSTS RELATIVE TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:In Germany, porous asphalt costs 100% more than conventional HMA.


REPORTER(S):



Surface course on reconstructed pavement, including bridge decks. Dranasphalt (Porous Asphalt).


Autobahn A-81, south of Heilbronn, Baden - Wurttemberg, Germany, near KP 561.0.

DATE OF CONSTRUCTION 9-14-90 LENGTH-(mi/km) # OF LANES-

ACTUAL ADT % TRUCKS EALsWHEN OPENED ACTUALCURRENT 90,000 3 3 DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):35mm Dranasphalt over 40mm (seal layer prepared with polymer-modified asphalt emulsion over existingpavement milled-out pavement.

ASPHALT CONTENT5.0 (% OF MIX)Polymer-modified

MODIFIER TYPE emulsion and 0.5%cellulose fibers

AIR VOIDS CONTENT ,Is( %) (Marshall Design)

MODIFIER CONTENT (% OF MIX)

AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):Top size: 11 mm. Nominal gradation: 8.5% retained on 2mm, 5% filler passing 0.09 mm. Binder ispolymer-modified cationic emulsion of a B65 - grade bitumen. Cellulose fibers are added to reducedrainage during construction.


RUTTING I I

LONGITUDINAL CRACmr-j

TRANSVERSE CRACKING

RAVELLING

ALLIGATOR CRACKING I

BLOCK CRACKING

POTHOLES

NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:Reconstruction of rutted pavement subjected to very high traffic volume and channelized truck traffic.



Box drains installed 40 mm into the binder course, extending through the seal layer to contact the porousasphalt.


OTHER REMARKS:Group witnessed construction of asphalt binder course. Three rollers follow closely upon paver. T w opneumatic-tired rollers provide breakdown, followed by a single steel-wheeled roller. Porous asphalt is alsocompacted with normal rollers without vibration.


No standard mix design has been established yet for porous asphalt by the German road authorities. Thisproject involves the reconstruction of an existing pavement structure. Existing pavement is milled out, onelane at a time, to a depth of 70mm. A new 70 mm polymer-modified asphalt emulsion seal layer and a35mm porous asphalt surface course. The seal layer is designed to prevent the intrusion of water into thepavement structure underlying the porous asphalt. The seal layer and the porous asphalt extend across thepavement and the shoulders; it consists of polymer-modified cationic asphalt emulsion, applied at 2 kg/m’,dressed with chippings applied at 8 to 10 kg/m2.



COSTS RELATIVE, TO CONVENTIONAL U.S. CONSTRUCTION PRACTICE:In Germany, porous asphalt costs 100% more than conventional HMA.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SVIDEOTAPE: NO- YES CASSETTE #AUDIOTAPE: NO- YES- CASSETTE #

REPORTER(S):



Dranasphalt (Porous Asphalt) Surface Course.


Autobahn A-81 northbound, near Freiberg in Breisgan, Baden - Wurttembetg, Germany, near KP 561.0.

DATE OF CONSTRUCTION 1990 LENGTH-(mi/km) # OF LANES 6 (divided)


BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):35mm Dranasphalt over 40mm seal layer over 70 mm asphalt binder course.

ASPHALT CONTENT5.0 (% OF MIX)Polymer-modified B65

AIR VOIDS CONTENT ZJ( %) (Marshall Design)

MODIFIER TYPE Bitumen in Cationic emulsion MODIFIER CONTENT (% OF MIX)cellulose fibers

AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):Top size: 11 mm. Nominal gradation: 85% retained on 2mm, 5% filler passing 0.09 mm. Binder ispolymer-modified B65 bitumen in cationic emulsion. Cellulose fibers are added to reduce drainage duringconstruction.


RUTTING 1 None

LONGITUDINAL CRACU!; I I


RAVELLING 1 None

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES

1 None

1 None

1 None

NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:No apparent distress. Pavement is very quiet.




OTHER REMARKS:


No standard mix design has been established yet for porous asphalt by the German road authorities,Impermeable seal layer is always applied under porous asphalt. The layer is nominally 40mm thick It iscomposed of a polymer-modified B65 bitumen cationic emulsion applied at 2 kg/m2 and dressed withstone chipping applied at 8 to IO kg/m2.


Uncertain Use of impermeable seal layer under porous asphalt might eliminate some of the problemsexperienced in the U.S. with open-graded asphalt courses.



REPORTER(S):



Dranasphalt (Porous Asphalt) Surface Course.


Autobahn A-81 northbound, near Freiberg in Breisgan, Baden - Wurttemberg, Germany, near KP 561.0.


ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT 90,000 33 DESIGNED


ASPHALT CONTENTA I R V O I D S C O N T E N T u(%) ( M a r s h a l l D e s i g n )5.0 (% OF MIX)Polymer-modified B65


AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):Top size: 11 mm. Nominal gradation: 85% retained on 2mm, 5% filler passing 0.09 mm. Binder ispolymer-modified B65 bitumen in cationic emulsion Cellulose fibers are added to reduce drainage duringconstruction

DISTRESS TYPE

RUTTING


1 None I

LONGITUDINAL CRACK?!; I I

TRANSVERSE CRACKING I None I IRAVELLING INone

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES

1 None

1 None

1 None I I





OTHER REMARKS:


No standard mix design has been established yet for porous asphalt by the German road authorities.Impermeable seal layer is always applied under porous asphalt. The layer is nominally 40mm thick. It iscomposed of a polymer-modified B65 bitumen cationic emulsion applied at 2 kg/m2 and dressed withstone chipping applied at 8 to 10 kg/m2.




35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SVIDEOTAPE: NO- YES- CASSETI’E #AUDIOTAPE: NO- YES- CASSETTE #

REPORTER(S):



Reconstruction of the MI motorway to strengthen pavement and extend its service life (originalconstruction: 1968).

LOCATION (COUNTRY, LOCAL GOVERNMENT UNIT, HIGHWAY #, MILEPOST):Motorway Ml southbound, near junction 27, north of Nottingham, Nottinghamshire, United Kingdom.




ASPHALT CONTENTu(% OF MIX) AIR VOIDS CONTENT B(%) (Marshall Design)Polymer-modified B65


AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):Top size: II mm. Nominal gradation: 85% retained on 2mm, 5% filler passing 0.09 mm. Binder ispolymer-modified B65 bitumen in cationic emulsion. Cellulose fibers are added to reduce drainage duringconstruction.


RUTTING 1 None

LONGITUDINAL CRACU-T


I

.I

RAVELLING INone I IALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES

1 None

1 None

1 None

I

I





OTHER REMARKS:


No standard mix design has been established yet for porous asphalt by the German road authorities.Impermeable seal layer is always applied under porous asphalt. The layer is nominally 40mm thick. It iscomposed of a polymer-modi’ed B65 bitumen cationic emulsion applied at 2 kg/in’ and dressed with

stone chipping applied at 8 to 10 kg/m2.




35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SV I D E O T A P E : NO- YES CASSETTE #A U D I O T A P E : NO- YES CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT D A T E 9 - 2 0 - 9 0 #I


Reconstruction of the Ml motorway to strengthen pavement and extend its service life (originalconstruction: 1968).


Motorway MI southbound, near junction 27, north of Nottingham, Nottinghamshire, United Kingdom.

DATE OF CONSTRUCTION 9-20-90 LENGTH 9--(mi/km) # OF LANES 6 (Divided)

ACTUAL ADT % TRUCKS EALsWHEN OPENED ACTUALCURRENT 60,650 25 DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):Maximum reconstruction taking place in inner (slow) lane; center and outer lanes are receiving lesserreconstruction. Inner lane pavement structure: 40mm hot-rolled asphalt (HRA) wearing course Er215mm heavy duty bitumen macadam upper road base over 125 mm HRA lower road base.

ASPHALT CONTENT_T_(% OF MIX) AIR VOIDS CONTENT _T_(%)

MODIFIER TYPE _2_

AGGREGATE DESCRIPTION*

DISTRESS TYPE

RUTTING


TRANSVERSE CRACKING

RAVELLING

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES

MODIFIER CONTENT “(% OF MIX)

(GRADATION, MATERIAL TYPES, etc.):


I I I I

1 I

I I I I

I

I I I I

NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:Original pavement in northbound lanes shows little apparent distress. Motorway was built in 1968 andoverlaid in 1981 with a 40 mm HRA wearing course. Decision to reconstruct was based upon deflectionmeasurements. It was noted that the condition of the northbound lanes would require less reconstructionthan witnessed for the southbound lanes.

* See reverse and attached sheet.(form continued on reverse side)/26 JUNE 90

DRAINAGE FACILITIES:Filter drains on verges (shoulders) and medians. These are being excavated and replaced with freshlimestone chippings.


None

OTHER REMARKS:1. Lanes milled out to required depths with a cold planer: 30mm on inner lane, 100mm on center

lane, none on outer lane.2 . The old laydown of upperoad base on inner lane. Pavers have fixed screeds. Two pavers lay about

5,500 tons of mix per day. Laydown accomplished at 160°C.(continued on attachment)

POST-VISIT DEBRIEFING NOTES: Details of Reconstruction:INNER (#1) LANE CENTER (#2) LANE OUTER (#3) LANE

_ _ _ - - - - I - - -T4omm 30%

Hot-rolledAsphalt

- - - - -40mm 30%

Hot-rolledAsphalt

.------

40MM 30%Hot-rolledAsphalt

WearingCourse(1 W-servicelife)- - - -Upper roadbase(resistsrutting)

- - -Lower roadbase(resiststensilestresses)- - - -Subgrade/Subbase

115mm + 100mmHeavy dutybitumen macadam

60mm 60%Hot-rolled

asphalt base course____________________--------

60mm 60% Hotrolled Asphaltbase course---------------

(ExistingSurface)

125mm 60%Hot-rolledAsphalt

EXISTING PAVEMENT STR UCTURE

-------------#100mm dense-graded Macadam over $200 to 300mm continuously gradedlimestone on a stiff marl.

APPLICABILITY TO U.S. PRACTICE:Uncertain. This pavement structure should be compared to usual U.S. designs for similar cirumstances, todetermine if equal or improved pavement service can be achieved at comparable costs.


Total project cost about $8,000,000 for reconstruction of 9 km (5.4 miles) of 6-lane pavement. This worksour roughly to an average of $34.25 per square yard.


REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #I


Ultrathin Asphalt Wearing Course.


R D 68 between Ste-lute and Thouare, Loire Atlantique, France

DATE OF CONSTRUCTION 7-90 LENGTH - -(mi/km) # OF LANES2

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT L o w DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):15 mm overlay laid with conventional paver.

ASPHALT CONTENTJ&(% OF MIX) AIR VOIDS CONTENT fi(%)

MODIFIER TYPE SBS Latex NOMINAL CONTENT J(% OF BINDER)


Top size: 10mm. Usual gap-gradation: 83% between 6 and 10mm, 15% between 0.09 and 2mm, 2%limestone filler passing 0.09mm

DISTRESS TYPE

RUTTING


TRANSVERSE CRACKING

RAVELLING

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES


1 None

1 None

1 None

1 None

1 None

1 None

1 None I

I

NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:Excellent, fresh-appearing overlay on secondary road,




This overlay is tradenamed COLRUG;it is marketed by the French contractor COLAS (S.A). It may beconsidered a proprietary formulation designed to satisfy the LCPC requirements for a very thin asphaltconcrete overlay.

OTHER REMARKS:The underlying pavement surface is prepared for COLRUG with a tack coat of polymer-modified asphaltemulsion. In this case, a COLAS proprietary product, EMULCOL, was used.

POST-VISIT DEBRIEFING NOTES:These very thin asphalt overlays are used as an alternative to slurry seals to provide surface maintenancewithout changing the structural capacity of the pavement.

APPLICABILITY TO U.S. PRACTICE:May provide alternative to slurry and chipseals. Systems such as COLRUG have the advantage of beinglaid with conventional pavers.


Comparable to slurry seals.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SVIDEOTAPE: NO YES- CASSETTE #AUDIOTAPE: NO- YES- CASSETTE #

REPORTER(S):



Very thin pervious asphalt wearing course.


RN 23, Le Chemin Nantais, Loire Atlantique, France

DATE OF CONSTRUCTION 7-89 LENGTH - -(mi/km) # OF LANES2

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT Low DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):25 mm porous asphalt overlay.

ASPHALT CONTENT_SLZ(% OF MIX) AIR VOIDS CONTENT a(%)

MODIFIER TYPE SBS Latex NOMINAL CONTENT s(% OF BINDER)


Top size: 10mm. Gap-gradation:passing 0.09mm.

DISTRESS TYPE

RUTTING


TRANSVERSE CRACKING

RAVELLING

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES

86.5% between 6 and 10mm, 12% between 0.09 and 2mm, 1.5% filler


1 None I

1 None

1 None

1 None

1 None

1 None

1 None

NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:Very open appearance; no visible distress.




This overlay is tradenamed PERMFLEX; it is marketed by the French contractor COLAS S.A. It isproprietary formulation designed to satisfy the LCPC requirements for a thin porous asphalt overlay.

OTHER REMARKS:The underlying surface was prepared by application of a tack coat of polymer-modified asphalt emulsion.In this case, a COLAS S.A. product EMULCOL, was used.

POST-VISIT DEBRIEFING NOTES:These thin porous overlays are used for surface maintenance; they provide no additional structuralcapacity. The usual thickness is 40mm; the overlay here is thinner than normal to prevent frost buildup inthe winter months.

The binder used in PERMFLEX is COLFLEX 253, a proprietary SBS latex-modified asphalt produced byCOLAS S.A.

This overlay is placed with a conventional paver.


May provide a possible alternative to slurry and chip seals.


Uncertain. In France, polymer-modified HMA costs 20% more than conventional HMA.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SV I D E O T A P E : NO-YES- CASSETT’E #A U D I O T A P E : NO-YES- CASSETTE #

REPORTER(S):

FH.WA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #5


FILAFLEX: A reinforced bituminous membrane, made in-situ.


Demonstrated on a parking area at a hot-mix plant west of Nantes, Loire Atlantique, France.

COMMERCIAL SOURCE (IF PROPRIETARY):

Filaflex is a patented process of SCREG Routes Group.

DETAILS OF OPERATION:

This is an in-situ manufacturing process to produce a stress absorbing membrane interlayer made up of afilm of polymer-modified asphalt binder strengthened by continuous polyester-fiber threads.

It is designed for maintenance of cracked asphalt and PCC pavements. It is intended as an impervious,crack-resistent base for asphalt wearing courses.

A single, large self-propelled machine sprays polymer-modifted asphalt emulsion or binder and immediatelyspreads chopped polyester threads on the binder. The binder is sprayed at 0.9 to 1.5 kg/m2 while thethreads are spread at 50 to 150 g/m2.

Spreader trucks follow the main unit within 2 minutes, spreading 4/6 or 6/10 granite chips at a rate of 4to 6 liters per m’


OTHER REMARKS:


1. The spreader truck tires pressed the chips into the polyester threads and the bituminous emulsionemployed for the demonstration.

2 . There was some pick-up of threads and emulsion on the truck tires.

3. The self-propelled binder/thread laydown unit costs about $600,000.

4 . Since 1988, about one million m2 of FILAFLEX has been successfully laid according to themanufacturer.


Uncertain.


Considered competitive in France to other maintenance treatments designed to control reflective cracking.


REPORTER(S):

FHJVA/AASHTO/NAPA SITE VISIT REPORT D A T E 9-17-90 #4


Deformation-resistant overlay for bridge decks.


Anne de Bretagne Bridge, Nantes, Loire Atlantique, France

DATE OF CONSTRUCTION 7-89 LENGTH - -(mi/km) # OF LANES&

ACTUAL ADT % TRUCKS E A L SWHEN OPENED A C T U A LCURRENT Heavy High DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):60mm BETOFLEX overlay on PCC bridge deck

ASPHALT CONTENTx(% OF MIX) AIR VOIDS CONTENT -(%)

MODIFIER TYPE SBS Latex NOMINAL CONTENT S(% OF BINDER)


Top size: 14mm. Coarse aggregate and sand form continuously - graded blend. Filler content (passing0.09mm) is 7.5% of total.


RUTTING 1 None

LONGITUDINAL CRACKING 1 None I

TRANSVERSE CRACKING 1 None I I I

RAVELLING 1 None I I IALLIGATOR CRACKING 1 None

BLOCK CRACKING

POTHOLES

1 None

1 None

NARRATIVE DESCRIPTION OF PAVEMENT CONDITION:No apparent distress.




Betoflex is a proprietary product of COLAS S.A.; it employs the COLFLEX 253 polymer-modified asphaltbinder produced by COLAS.

OTHER REMARKS:

BETOFLEX is a deformation-resistant HMA designed for very heavy traffic loads on deformable support.



Uncertain. Further investigations may be warranted.


Uncertain. In France, polymer-modified HMA costs 20% more than conventional HMA.


REPORTER(S):



M40 Motorway construction


Extension of the M40 motorway north from oxford, Oxfordshire


ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LPREDICTED DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):40mm hot-rolled asphalt wearing course over 195mm heavy duty bitumen macadam upper road base over125mm hot-rolled asphalt lower road base over 150mm better qualify crashed rock over 600mm crashedrock

ASPHALT CONTENTm(% OF MIX) AIR VOIDS CONTENT -J%)

MODIFIER TYPE _ MODIFIER CONTENT S(% OF BINDER)

AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.):*

Top size: 14mm. Nominal composition: 70% Crashed Stone (retained on #7 sieve). 27-28% sandpassing #7 sieve, retained on #200); and 2-3% limestone filler.

* For HRA wearing course

DISTRESS TYPE

RUTTING


TRANSVERSE CRACKING

RAVELLING

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES






OTHER REMARKS:


1. HRA wearing course employs 50 penetration grade asphalt cement.

2. HRA wearing course is batched on site. It is dressed with 20mm coated chippings applied at 12-13kg/m?.

3 . Wearing course is laid at 160-l 70°C.

4. Road base mixes are hauled from 2 hours distance in order to take advantage of the best qualityaggregate. About 20,000 tons of these mixes are laid each week Road base mixes were designedto purpose rather than batched to recipe. The upper road base was required to meet a refusaldensity criterion of 93%.



35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SVIDEOTAPE: NO- YES- CASSETTE #AUDIOTAPE: NO- YES CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9- 14-90 #L


SMA Overlay on heater-planed pavement surface.


Route 19, South of Schwabisch Hall, Baden- Wurttemberg, Germany

DATE OF CONSTRUCTION 9-14-90 LENGTH- -(mi/km) # OF LANES2

ACTUAL ADT % TRUCKS EALSWHEN OPENED A C T U A LCURRENT DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):25mm SMA overlay on heater-planed pavement.

ASPHALT CONTENTa(% OF MIX) AIR VOIDS CONTENT &.&(%)

MODIFIER TYPE Cellulose fibers MODIFIER CONTENT 0.3(% OF MIX)

AGGREGATE DESCRIPTION (GRADATION, MATERIAL TYPES, etc.): *

Top size: 8mm. Nominal gradation: 90 - 100% passing 8mm, 30 to 55% passing Smm, 20-30% passing2mm and 8-13% filler passing 0.09mm.


RUTTING

LONGITUDINAL CRACKING 1 I

TRANSVERSE CRACKING 1 IRAVELLING

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES

I I1 I I


Existing pavement showed some minor distress.




OTHER REMARKS:

This is considered an alternative to other possible overlay treatments.


Paving train consisted of a heater-planer, a paver serviced from the front by a dump mix truck, and twosteel- wheeled rollers.

The heater-planer heated the old pavement surface and planed it off to a predetermined depth. SMA wasimmediately placed and compacted. After rolling, surface of SMA looked very rich in binder so stonechippings were rolled on for extra friction. Mix occasionally showed some marking under the rollers.

Heater-planer technique is used only once due to large decrease in bitumen penetration. Nextrehabilitation (in 2-3 years) will involve scarification and removal of pavement surface.

APPLICABILITY TO U.S. PRACTICE:High.


In Germany, SMA costs 50% more than conventional HMA.


REPORTER(S):

FI-IWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #3


Porous Pavement for noise reduction and rain water flow.


Boulevard Dolon, Nantes, Loire Atlantique, France


ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):20rnm Pervious Asphalt Wearing Course over 60mm pervious bituminous Macadam base course.

ASPHALT CONTENT_T_(% OF MIX) AIR VOIDS CONTENT “(%)

MODIFIER TYPE _T . MODIFIER CONTENT “(% OF MIX)


DISTRESS TYPE

RUTTING


1 None


TRANSVERSE CRACKING 1 None ‘I

RAVELLING 1 None

ALLIGATOR CRACKING

BLOCK CRACKING

1 None

_I None

POTHOLES 1 None I I


The 80 mm thickness is greater than usual for pavements of this type to provide the capacity totemporarily store significant volumes of rainwater.

*

See reverse(form continued on reverse side)/26 JUNE 90



Permflex is a proprietary thin pervious asphalt produced by COLAS S.A. COLFLEX 253 is an SBS latex-modified asphalt binder produced by COLAS S.A.

Pervious pavement is designed to reduce traffic noise and control flow of rain water.

Both courses employ gap-graded aggregate.


Asphalt Content

Air Voids Content

Modifier Type

Modifier Content

AggregateGradation:

Coarse

Sand

Filler

Wearing course Base course---___ -T-- -----A-----

5.2% COLFLEX 253 4.8% 60/70 Bitumen-----_ -- -------------_ -~-

20% 20%

SBS Latex

5% Nominal

86.5% 6mm - 10 mm 84% 10mm - 14mm-----------_-----~ ------_---------------------

12% 0.09mm - 2mm 14.5% 0.09mm - 3mm

1.5% passing 0.09mm I 1.5% passing 0.09mm

APPLICABILITY TO U.S. PRACTICE:Uncertain, but may warrant investigation as alternative to open-graded friction courses and porouspavement.


Unknown. In France, polymer-modified HMA costs 20% more than conventional HMA.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SV I D E O T A P E : N O YES- CASSETTE #A U D I O T A P E : NO- YES- CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9- 17-90 #A


Construction of a special overlay to prevent reflective cracking.


RN 165, Sautron, Loire Atlantique, France

DATE OF CONSTRUCTION 9-17-90 LENGTH- -(mi/km) # OF LANES4

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT High DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):30mm special wearing course over a 15mm special, anti-reflective cracking binder course.

ASPHALT CONTENT_IC__(% OF MIX) AIR VOIDS CONTENT JL(%/o)

MODIFIER TYPE * MODIFIER CONTENT L(% OF MIX)



RUTTING


TRANSVERSE CRACKING

RAVELLING 1ALLIGATOR CRACKING

BLOCK CRACKING I I

POTHOLES 1 I


* See table on reverse




The binder course is a proprietary product of COLAS S.A. called SAFLEX. The wearing course is aproprietary COLAS S.A. product called RUFLEX.

OTHER REMARKS:

The wearing course uses a gap-graded aggregate. It contains no large aggregate (top size is about 3/8inch), but the modified binder is formulated to prevent rutting. Rolling with steel-wheeled rollers left noroller marks or evidence of significant compaction.


Wearing course Base course

Asphalt Content

Air Voids Content

Modifier Type

Modifier Content

AggregateGradation:

Coarse

Sand

Filler

5.6% COLFLEX 253 9.5% COLFLEX 253_-------~~~~----~~~~_______c____________----

-------------~~~-----~_----~~-------------_____________I_SBS LATEX SBS LATEX

_----------~~~~~----~~---~~~~-----------~~~-~--------5% Nominal 5% NOMINAL

46% 0 - 2mm65% 6mm - 10mm 35% 2 m m - 4mm

------__-------------------------------------- ---___35% 0 - 2mm 17% 0 - 3mm ROLLED SAND

~I~~~~-~~~~~~~~~~--~~~~~~~-~------------~---------2% Limestone



35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SV I D E O T A P E : NO- YES- CASSETTE #AUDIOTAPE: NO YES- CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-17-90 #J-


Chip seal constructed with modified asphalt emulsion and hot, pre-coated chips.


RN 171 Eastbound, near La Baule, Loire Atlantique, France.

DATE OF CONSTRUCTION 7-89 LENGTH3 (mi/km) # OF LANES4

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT 25,000 10 DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):Paver-laid chip seal. Binder layer of polymer-modified 60/70 penetration-grade asphalt emulsion appliedat 0.95 kg/m” chipss spread at a rate of 25 kg/m2.

ASPHALT CONTENT N/A (% OF MIX) AIR VOIDS CONTENT N/A (%)NOMINAL

MODIFIER TYPE Neoflex (SBS Latex) MODIFIER CONTENT S(% OF BINDER)


6mm to 1Omm chips precoated with 25 weight percent of hot sand-asphalt (5.5 % asphalt, 94.5% sand).


RUTTING 1 None


TRANSVERSE CRACKING

RAVELLING

1 None

1 None

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES

1 None

1 None

1 None

I

I


Pavement had an open look There was no apparent distress except for some minor tearing alone thecenterline of the driving lane. Considering the traffic volume and loads, the performance was judged asvery impressive.




The system employed for this project is tradenamed NOVACHIP, It is a proprietary product of SCREGRoutes Group and conforms to the general LCPC specifications for paver-laid chipseal.

OTHER REMARKS:


Paver-laid chip seals are intended for surface maintenance without structural effect. They seal the surfaceand increase skid resistance, but are substantially less noisy than conventional chip seals. It is claimedthat loose chips are virtually eliminated due to the precoating and use of modified binder.

NOVACHIP is laid with a purpose-built, self-propelled unit that sprays the binder, spreads the hot, pre-coated chips and smooths the chip seal. Additional rolling is accomplished by a rubber-tired roller and asteel-wheel roller acting in tondem. This system can be applied at a rate of 3500 m2/hr at forward speedsof 0.7 mph. The paver costs approximately $800,000; there are five in operation in France.

APPLICABILITY TO U.S. PRACTICE:May provide alternative maintenance treatment for high-volume interstate and primary routes. Somesimilarity to chip seals applied with modified asphalt binders in Texas and New Mexico.


Probably higher. Costs may be offset by improved performance.

35 mm PHOTOS: NO YES ROLL # NEGATIVE #‘SV I D E O T A P E : N O YES- CASSETTE #A U D I O T A P E : NO- YES- CASSETTE #

REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT DATE 9-l 7-90 #8


Very thin asphalt concrete overlay for surface maintenance.


N 165, 30 km West of St. Nazaire, France.

DATE OF CONSTRUCTION 1988 LENGTH - -(mi/km) # OF LANES&

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT High DESIGNED

BRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):1 Omm wearing course overlaid on existing pavement.

ASPHALT CONTENTL(% OF MIX)’ AIR VOIDS CONTENT fi(%)’

MODIFIER TYPE (SBS Latex,) MODIFIER CONTENT 5-(% OF MIX)’


Top size: 10mm. Usual gap-gradation: 83% between 6 and 10mm, 15% between 0.09 and 2%limestone filler passing 0.09mm.

DISTRESS TYPE

RUTTING


1 None


TRANSVERSE CRACKING 1 None I

RAVELLING 1 None

ALLIGATOR CRACKING

BLOCK CRACKING

1 None

1 None

POTHOLES 1 None

NARRATIVE DESCRIPTION

Excellent. No visible distress.

OF PAVEMENT CONDITION:

1 Nominal(form continued on reverse side)/26 JUNE 90



This overlay is tradenamed MEDIFLEX. It is a proprietary product of SCREG Routes Group,

OTHER REMARKS:


These very thin asphalt concrete overlays are employed as an alternative to slurry seals to provide surfacemaintenance without changing the structural capacity of the pavement.

They are laid with conventional pavers.


May provide an alternative to slurry and chipseals. They offer the advantage of being laid withconventional paving equipment.


In France, comparable to slurry seals.


REPORTER(S):

FHWA/AASHTO/NAPA SITE VISIT REPORT D A T E 9-I8-90 #I


Very thin Porous Asphalt Overlay


A47 Motorway South of Givois (Suburban Lyon), France.

DATE OF CONSTRUCTION 7-89 LENGTH--(mi/km) # OF LANES4

ACTUAL ADT % TRUCKS EALsWHEN OPENED A C T U A LCURRENT 80,000 winter DESIGNED

160,000 SummerBRIEF DESCRIPTION OF PAVEMENT STRUCTURE (# OF LAYERS, LAYER THICKNESSES,etc):40mm overlay on existing pavement surface.

ASPHALT CONTENTfi(% OF MIX) AIR VOIDS CONTENT x(%)

MODIFIER TYPE Reclaimed tire rubbertreated with aromaticoil and catalyst.

MODIFIER CONTENT 5-(% OF BINDER)’


Top size: 10mm. Gap-gradation: 88% between 6mm and 10mm, 11 % between 0.09 and 2mm, 1 %filler passing 0.09mm. Aggregate is exclusively crushed porphyry.

DISTRESS TYPE

RUTTING


TRANSVERSE CRACKING

RAVELLING

ALLIGATOR CRACKING

BLOCK CRACKING

POTHOLES


1 None

1None I

1 None I

1 N one

1 None

1None

1None


Appears fresh and in excellent condition. There is no apparent distress.


’ Nominal

DRAINAGE FACILITIES:Adequate drainage must be provided to allow water flow through and out of the pavement surface.


This project used a proprietary product DRAINOCHA PE marketed by BEUGNET Technicalmanagement. The asphalt-rubber binder is also a proprietary product, FLEXOCHAPE E, produced byB E U G N E T .

OTHER REMARKS:


This product is designed to meet the general LCPC specification for porous asphalt overlays.

The overlay is placed with a conventional paver.

APPLICABILITY TO U.S. PRACTICE:May provide a possible alternative to slurry and chip seals.


Uncertain. In France, modified HMA costs 20% more than conventional HMA.


REPORTER(S):

aashto . fhwa - napa - shrp - tai - trb · approximate conversions to si units approximate...

Documents