volume 7 pavement design and maintenance section 2

August 2001

DESIGN MANUAL FOR ROADS AND BRIDGES

VOLUME 7 PAVEMENT DESIGN ANDMAINTENANCE

SECTION 2 PAVEMENT DESIGN ANDCONSTRUCTION

PART 3

HD 26/01

PAVEMENT DESIGN

SUMMARY

This revision to HD 26 provides updated informationon the materials and thicknesses for new pavementconstruction. The revision includes a design chart forperformance-related fully flexible design.

INSTRUCTIONS FOR USE

This is a revised Standard to be incorporated in theManual.

1. This document supersedes HD 26/94, which isnow withdrawn.

2. Remove HD 26/94, which is superseded byHD 26/01, and archive as appropriate.

3. Insert HD 26/01 into Volume 7, Section 2,Part 3.

4. Archive this sheet as appropriate.

Note: A quarterly index with a full set of VolumeContents Pages is available separately from TheStationery Office Ltd.

HD 26/01

Pavement Design

Summary: This revision to HD 26 provides updated information on the materials andthicknesses for new pavement construction. The revision includes a designchart for performance-related fully flexible design.


THE HIGHWAYS AGENCY

SCOTTISH EXECUTIVE DEVELOPMENT DEPARTMENT

THE NATIONAL ASSEMBLY FOR WALESCYNULLIAD CENEDLAETHOL CYMRU

THE DEPARTMENT FOR REGIONAL DEVELOPMENTNORTHERN IRELAND

Volume 7 Section 2Part 3 HD 26/01

August 2001

REGISTRATION OF AMENDMENTS

Amend Page No Signature & Date of Amend Page No Signature & Date ofNo incorporation of No incorporation of

amendments amendments

Registration of Amendments


August 2001

REGISTRATION OF AMENDMENTS

Amend Page No Signature & Date of Amend Page No Signature & Date ofNo incorporation of No incorporation of

amendments amendments

Registration of Amendments

VOLUME 7 PAVEMENT DESIGN ANDMAINTENANCE

SECTION 2 PAVEMENT DESIGN ANDCONSTRUCTION

PART 3

HD 26/01

PAVEMENT DESIGN

Contents

Chapter

1. Introduction

2. Standard Designs

3. Materials

4. Alternative Design Procedures

5. References

6. Enquiries


August 2001


Chapter 1Introduction

1. INTRODUCTION

General

1.1 This part details various combinations ofmaterials and thicknesses which may be considered forpavement construction, whether new build or fullreconstruction. The design guidance is also useful whendeveloping recommendations for partial reconstructionor strengthening overlays, if used in connection withthe investigation techniques described in HD 30(DMRB 7.3.3). It does not include the estimation ofdesign traffic (see HD 24, DMRB 7.2.1), nor does itcover the design of pavement foundations (see HD 25,DMRB 7.2.2). Additional information on surfacing andsurfacing materials is given in HD36 (DMRB 7.5.1).

1.2 The naming of the various pavement layers willbe subject to change over the next few years to reflectEuropean harmonisation:

Wearing Course will become Surface CourseBasecourse will become Binder CourseRoadbase will become Base

The naming used in this Part has been amended toreflect this change although changes to theSpecification and to British Standards will take longerto implement. In addition, all bituminous materials arenow covered by the generic description ‘asphalt’.

1.3 Chapter 2 sets down the philosophy behind theStandard Designs and summarises the alternatives in theform of charts. Chapter 3 provides additionalinformation on material behaviour to assist the designer,and Chapter 4 introduces analytical procedures whichmay be used by the designer to produce AlternativeDesigns.

Implementation

1.4 This Part shall be used forthwith on all schemesfor the construction, improvement and maintenance oftrunk roads including motorways currently beingprepared, provided that, in the opinion of theOverseeing Organisation this would not result insignificant additional expense or delay. Designorganisations should confirm its application toparticular schemes with the Overseeing Organisation.

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utual Recognition

5 The construction and maintenance of highwayvements will normally be carried out under contractscorporating the Overseeing Organisation’secification for Highway Works (MCHW1). In suchses products conforming to equivalent standards andecifications of other States of the European Economicrea and tests undertaken in the other States will beceptable in accordance with the terms of the 104 and5 Series of Clauses of that Specification. Anyntract not containing these Clauses must containitable clauses of mutual recognition having the samefect regarding which advice should be sought.

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Chapter 2Standard Designs

2. STANDARD DESIGNS

DESIGN PHILISOPHY

2.1 The designs given in this Part are based onLR1132 (1984), for flexible and flexible compositeconstruction, and RR87 (1987), for rigid and rigidcomposite construction, but amended and updated totake account of later research on new pavementmaterials and observed performance.

Flexible Pavements

2.2 LR1132 was based on observations andmeasurements of full-scale road experiments over a20 year period, supplemented by structural analysis torationalise and extend the data. The analysis used theelastic stiffness modulus of the various pavement andfoundation layers, to calculate the strains developedwithin the structure. The strains could be related to lifefor the type of ‘determinate’ pavement structures whichthen existed.

2.3 Monitoring the performance of heavilytrafficked roads has indicated that deterioration, in theform of cracking or deformation, is far more likely to befound in the surfacing rather than deeper in thestructure for the thicker pavements which are moretypical today. Therefore a well constructed flexiblepavement, built above a threshold strength, will have avery long structural life - provided that distress, seen ascracks and ruts at the surface, is treated before it beginsto affect the structural integrity of the road. Furtherbackground information is available in TRL Report 250(1997).

2.4 Full scale road trials have also been carried outusing high stiffness macadams - High Modulus Base(HMB) - manufactured to a standard composition fordense bitumen macadam (DBM) but using a binder of35pen (HMB35). The trials demonstrated that thematerial behaved in a similar way to conventional basemacadams, provided that the appropriate mixing,laying, and compaction temperatures were maintained.HMB35 has a high stiffness, and therefore offers betterload spreading capabilities than either DBM, or HeavyDuty Macadam (HDM), so it is possible to achieve thesame life with a thinner base. After allowance has beenmade for increases in production costs, savings can beachieved compared to conventional DBM.

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.5 Generally for “long life” indeterminate flexibleavements designed to carry traffic for at least 40 years,t is not necessary to increase the pavement thicknesseyond that required for 80msa. Nevertheless, “longife” designs are not recommended to be thinner than00mm, in order to help avoid structural rutting and toetard the progression of cracks from the surface downhrough the asphalt layers.

lexible Composite Pavements

.6 “Long life” indeterminate designs are alsoresented for flexible composite pavements, for trafficrom 20 to 200msa. The thickness of the cementedower base is reduced as the CBM strength increases,ut all CBMs of strength equal to or greater thanBM1A, 2A and 3 must have induced cracks. As aonsequence, the thickness of the asphalt overlay forndeterminate designs has been reduced to 190mm.

igid and Rigid Composite Pavements

.7 RR87 was largely empirical, based on theerformance of full scale experimental roads. Thereas less performance data for Continuously Reinforcedoncrete Pavements (CRCP) and designs wereeveloped from jointed reinforced concrete (JRC). Forigid composite structures, an allowance was made forhe structural contribution and thermal insulationffected by the asphalt surfacing.

.8 Use of CRCP with a Thin Wearing Courseystem (TWCS) can provide a “long life” with all thedvantages offered by the noise reducing properties ofhe surfacing. Such pavements are ideally suited to thepplication of further asphalt overlays at stages duringhe future pavement life.

.9 Developments in maintenance techniques, suchs “crack and seat”, have shown that some types ofigid pavement can now be effectively incorporated into pavement strengthened with an overlay. Futureevelopments, such as concrete inlays (currently underrial) may require consideration of lower design liveshan the traditional 40 years as part of an overalllanned maintenance strategy for a section of highway.

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Pavement Deterioration

2.10 There are four main phases of structuraldeterioration for a flexible pavement that is not definedas indeterminate (See Annex 3 of HD 29 DMRB 7.3.2).

1) When a new or strengthened pavement isreaching equilibrium with a steady improvementin load spreading ability.

2) When load spreading ability is fairly stable, andthe rate of structural deterioration may bepredicted with some confidence.

3) When structural deterioration becomes lesspredictable. Pavements entering this phase shouldbe monitored and investigated to determine what,if any, maintenance is appropriate to ensure thatthe next phase is not reached; hence this phase istermed the “investigatory” phase. (The term“critical” is no longer used). Residual life is thetime period before a pavement is expected toenter its investigatory phase.

4) When the pavement deteriorates to a “failure”condition from which it can be strengthened onlyby total reconstruction. It is important to realisehowever that such pavements may not needreconstruction immediately, but will probablyhave several years of useful life, beforeincreasing routine maintenance costs trigger theneed for reconstruction.

2.11 More detailed information on pavementdeterioration mechanisms for all pavement types isgiven in HD 30/99 (DMRB 7.3.3.2), and the “failure”criteria for rigid pavements are described in RR87.

Whole Life Cost

2.12 A Whole Life Cost assessment of a pavementconsiders both Works Costs (New construction;Maintenance; Residual Value) and User Costs (Trafficdelay; Accidents at Roadworks; Skidding Accidents;Fuel Consumption/Tyre Wear; Residual Allowance).

2.13 A minimum whole life cost for a new pavementis generally achieved when a design life ofapproximately 40 years is assumed. For this reason, thestandard design life for all types of pavement, withappropriate maintenance, is 40 years. An importantfactor is the degree to which future maintenance islikely to cause disruption.

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.14 For roads surfaced with asphalt, surfaceeatment would be expected to be required at about 10ear intervals. The period until surface treatment isequired will also vary depending on the site’sequirement for skidding resistance.

.15 CRCP can be considered as part of a stagedonstruction, because it can be strengthened with anverlay of asphalt or concrete (with asphalt surfacing inngland) at a later date. The implications for additionalading on underbridges, clearance at overbridges, and

roblems at wide-flange steel beams should beonsidered.

.16 It is often more economical to continue CRCPonstruction over buried structures rather than to ende pavement on each side of the structure which would

ecessitate the use of anchorages or movement joints.

ESIGN IMPLEMENTATION

avement Type

2.17 Options for permitted surfacings are set outin HD 36 (DMRB 7.5.1) and further details givenin HD 37 and HD 38 (DMRB 7.5). Four types ofpavement are generally considered as follows:

a) Flexible; where the surface course, bindercourse and base materials are bound with bitumen.Permitted binder course and base materials are asfollows:

- Dense Bitumen Macadam (DBM)- DBM with 50 penetration bitumen

(DBM50)- Heavy Duty Macadam (HDM)- High Modulus Base with 35pen bitumen

(HMB35), except in Scotland where aDeparture from Standard shall beobtained from the OverseeingOrganisation.

- Stone Mastic Asphalt (SMA), for use asbinder course only, except in Scotlandwhere a Departure from Standard shallbe obtained from the OverseeingOrganisation.

- Hot Rolled Asphalt (HRA), which shallonly be used in England and Wales withthe approval of the OverseeingOrganisation.

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Details of composition, manufacture and laying aregiven in the Specification (MCHW1) Series 900and in British Standards.

b) Flexible Composite; where the surfacecourse and upper base materials are bound withbitumen on a lower base of cement bound material(CBM). Various strength CBMs are permitted (seeFigure 2.3 and MCHW1 Series 1000). For alldesigns the CBM layers (of strength equal orgreater than CBM1A, 2A and 3) have transversecracks induced.

Lower base materials comprising other hydraulic/pozzolanic binders which achieve adequateflexural strength and stiffness modulus, may alsobe considered by the Overseeing Organisation.These materials typically have lower early agestrength than CBMs but may provide a more costeffective pavement structure, especially if used asa combined sub-base/lower base layer. Thepotentially large range of material combinations,and difficulty in predicting future performance,means that no standard design charts can beprepared at present.

c) Rigid; comprising concrete slabs in thefollowing categories:

- Unreinforced Concrete (URC)- Jointed Reinforced Concrete (JRC)- Continuously Reinforced Concrete

Pavement (CRCP)

In England, rigid concrete construction of anytype is not a permitted option for trunk roadsunless it has an asphalt surfacing, see HD 36(DMRB 7.5.1).

d) Rigid Composite; CRCR with an asphaltoverlay or surfacing of at least 100mm. A groundbeam anchorage is required at terminations ofevery CRCR.

For all rigid and rigid composite pavementalternatives the concrete slab shall be PavementQuality Concrete (PQC), manufactured, laid andcured in accordance with the Specification(MCHW1) Series 1000.

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2.18 Except where the pavement design is theresponsibility of the contractor, designs shall becarried out for several options. These shall coverthe range of base types (flexible/rigid/composite)permitted by the Overseeing Organisation, exceptwhere there are technical or environmental reasonswhy only one pavement type is suitable. Advice onsurfacing types permitted by each OverseeingOrganisation is available in HD 36 (DMRB 7.5.1).

esign Life

2.19 A pavement should preferably be designedfor the predicted traffic over 40 years. For mosttrunk roads where design traffic is heavy inrelation to the capacity of the layout, and in allcases where whole life costing is taken intoaccount, 40 year designs shall be included aspermitted options. 20 year designs may beappropriate for less heavily trafficked schemes orfor major maintenance where other site constraintsapply. The design traffic in msa shall be obtainedfrom HD 24 (DMRB 7.2.1), Figs 2.1 and 2.2 forthe 20 year designs and Figs 2.3 and 2.4 for the40 year designs.

esign Charts

2.20 Figures 2.1 - 2.5 give the pavement materialthicknesses appropriate to the various base typesfor a Standard Foundation. The total boundthickness shall be rounded up to the nearest 10mmin each case. They assume a granular Type 1 sub-base for flexible and flexible compositepavements, but CBMs or stabilised materials maybe substituted provided it can be demonstrated thattheir performance is not inferior to Type 1. Whereit can be demonstrated that the performance of thefoundation is better than the Standard (refer toHD 25, DMRB 7.2.2) and can be expected toremain so for the design life of the pavement, thenthe Overseeing Organisation may consider reducedpavement thicknesses. Advice on procedures forassessing revised thicknesses can be found inChapter 4 of this Part and HD 30 (DMRB 7.3.3).These procedures can also be applied in theassessment of the additional thickness of boundmaterials which is necessary where the foundationis below the Standard.

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Flexible Construction

2.21 For fully flexible pavements two designcharts are given (Figures 2.1 and 2.2). Thepreferred chart is Figure 2.1, which providesthicknesses based on Grades of Base ranked interms of their characteristic stiffness. (Therequirements for these Performance-specifiedGrades are given in the Specification (MCHW 1)Series 900, Clauses 929 and 944; also the Notesfor Guidance (MCHW 2) Clause NG 944). Forschemes where the additional materials testingrequired for the Performance-specified Grades isnot justified, Figure 2.2 may be used inconjunction with the Specification (MCHW 1),Clause 929 and the appropriate recipe-basedmaterial specifications.

2.22 A number of surface course, binder course andbase materials are now available. The total thickness fora fully flexible pavement depends on the base type. ADBM base is the least stiff material, and so requires thethickest construction. The stiffness of asphalt materialthen increases from DBM50, through HDM, toHMB35. As the stiffness increases, a reduced thicknessof material will provide the same structuralequivalence.

Flexible Composite Construction

2.23 Similarly, for flexible composite pavements, arange of strengths for CBM materials are permittedwith thinner construction resulting from strongermaterial. For a given strength, better performance isexpected for those CBM’s made with coarse aggregatethat has a lower coefficient of thermal expansion. Forindeterminate designs in the range 20-200msa thedesign thicknesses are uniform for a given materialcombination.

2.24 Individual construction widths of CBMroadbase shall not exceed 4.75m. This minimisesthe risk of longitudinal cracking induced bycombined stresses in a flexible compositepavement designed with indeterminate life(ie design life exceeds 20msa). HighwayConstruction Details (MCHW3) gives typical jointlayouts. Flexible composite roads with determinatelife (ie thinner construction) are more likely to

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deteriorate by general cracking; consequentlyrestricting the individual laid width will notnecessarily lead to improved performance.

Rigid and Rigid Composite Construction

2.25 For jointed concrete pavements, load inducedstresses at slab corners and edges are greater than in theslab centre, necessitating dowel bars to distribute loadsbetween slabs. Joint associated distress occursprincipally when dowels do not function properly. Theuse of a tied shoulder or 1m edge strip ensures that theuntied edge is remote from the wheelpaths, with aconsequent reduction in stress. This load distributionoccurs whether or not a longitudinal construction jointor wet-formed joint is included adjacent to the edge lineas permitted by Highway Construction Details(MCHW3).

2.26 Figures 2.4 and 2.5 assume the presence of aminimum 1m edge strip or tied hardshoulderadjacent to the most heavily trafficked lane. Urbanroads, and any other roads that do not have a 1medge strip or a tied hardshoulder adjacent to theleft hand lane will require thicker slabs. Theadditional thickness required is given in Figure 2.6.Heavy trafficking of right hand lanes andhardshoulders during future maintenance will be ofrelatively short duration and need not beconsidered in design.

2.27 Edge treatments and other construction drawingsare given in the Highway Construction Details(MCHW3). For further advice on edge of pavementdrainage, refer to HA 39 (DMRB 4.2.1).

2.28 For CRCP and CRCR the depth of reinforcementin the slab has been chosen to reduce the risk ofcorrosion caused by salts penetrating the cracks.Transverse reinforcement is required for ease andconsistency of construction. Transverse bars may beincorporated into the support arrangement for thereinforcement, so long as the required quantities andposition of steel is maintained. (See Notes to Figure2.5).

2.29 Longitudinal steel in CRCP or CRCR may bewelded or spliced on site and positioned so that frontloading of concrete to a slipform paver is possible,provided the bars are guided into the correct position inthe slab through gates in the paver.

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2.30 To ensure that forces are not transmitted tostructures and adjacent forms of pavementconstruction by the expansion of the slab, eitherthe ends of the CRCP and CRCR shall berestrained by a ground beam anchorage, or (forCRCP only) movement shall be accommodatedwithin a wide flange steel beam. Both types usetransition slabs, as shown in the HighwayConstruction Details (MCHW3).

2.31 Ground beam anchors shall not be used forCRCP where the subgrade strength is poor,especially on high embankments whereconsolidation may be insufficient to restrainmovement of the beam downstands.

2.32 CRCP or CRCR options shall be consideredwhere the design traffic loading exceeds 30msa. Itis recommended that they should also be includedfor less heavily trafficked schemes where theadvantages of lower maintenance throughout thedesign life may be worthwhile. Proposals fordesigns above 400msa will be considered by theOverseeing Organisations under the normalDepartures procedure.

Ground Subject to Movement

2.33 Flexible composite and URC construction aresuitable in normal applications except wheredifferential movement, subsidence or appreciablesettlement is expected. This includes areas where minesare currently worked, or may be worked in the future.Flexible and JRC construction are suitable in allapplications, except where large differential movementsor large settlements caused by compressible ground, orconsiderable subsidence caused by mining are expected.CRCP and CRCR constructions are suitable in allapplications. They may be particularly suitable wherelarge differential movements are expected because theycan withstand significant strains while remainingsubstantially intact.

Laybys and Hardstandings

2.34 To resist the problems caused by oil and dieselspillage, laybys and hardstandings shall be surfacedwith either:

i) Concrete, see Specification (MCHW1) Series1000;

August 2001

ii) Block paving, see Specification (MCHW1)Series 1100;

iii) A deformation resistant surfacing made with aproprietary fuel resistant binder.

Alternative Designs

2.35 If any pavement design other than thosegiven in this section is to be considered, approvalto proceed is required from the OverseeingOrganisation at the preliminary design stage.Submissions seeking approval for alternativedesigns shall include a justification for the choiceof non-standard materials and/or thicknesses,supporting calculations and an indication of anyadditional specification requirements or testingregime which may be necessary for theirvalidation. Analytical pavement design procedures(see Chapter 4) may be used in support of any suchalternative proposal.

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(mm

Characteristic Stiffnesses (GPa)Grade 1 = 1.0Grade 3 = 3.0

Grade 4.5 = 4.5

Grade 1

Grade 3

Grade 4.5

Example

Roadbase Material

BaseMaterial

Characteristic Stiffness (GPa)Grade 1 = 1.0Grade 3 = 3.0

Grade 4.5 = 4.5

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DBM50

DBM/HRA

HDM

HMB35

Roadbase Material

Example

Design Traffic in Left Hand Lane (millions of standard axles)

Figure 2.1: Design Thickness for Flexible Pavements:Performance-specified Grades of Base

Design Traffic Left Hand Lane (millions of standard axles)

Figure 2.2: Design Thickness for Flexible Pavements:Recipe-based Specifications of Base

BaseMaterial

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Notes on Figures 2.1 and 2.2:

1. Surface course shall consist of one of thepermitted materials presented in Tables 2.2E, 2.2S,2.2NI or 2.2W (as appropriate) in HD 36 (DMRB7.5.1). For further details refer to HD 37 andHD 38 (DMRB 7.5).

2. For HRA surfacing where permitted, refer toeither:

Clause 943 of the Specification (MCHW1),or to:

Clause 911, with reference to BS594: Part 1:Annex B: Table B1 for stability and flow valuesrelated to traffic loading.

For Scotland, design values are given in theOverseeing Organisation’s special requirements inClause NG911S.SO (MCHW2).

In Northern Ireland recipe mixes to BS594: Part 1may be used where considered appropriate by theOverseeing Organisation.

3. If 50mm of Porous Asphalt (PA) surfacing isto be used, it shall be modified with a polymer orfibre additive. Its contribution to the materialdesign thickness is only 20mm. A 60mm densebinder course, compacted to meet the maximum airvoids requirement in the Specification (MCHW1)Series 900, is required beneath PA surfacing.

4. A binder course, or upper base layer,compacted to meet the maximum air voidsrequirements in the Specification (MCHW1)Series 900 is required beneath the surface course.It shall be of any permitted material (subject toNote 6) and be at least 50mm thick, except forSMA binder course which should be a minimum of30mm thick.

5. Figures 2.1 and 2.2 assume a maximumthickness of 50mm for HRA. Although otherpermitted materials may have lower stiffness thanHRA it is assumed that the additional roadbaserequired to make up for the thinner surfacingadequately compensates in overall load spreadingability.

E

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2.

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6. Figure 2.1 assumes that the binder courseachieves the same minimum stiffnesscharacteristics as the base; Figure 2.2 assumes thatthe binder course is the same material as the base.However any permitted material may be used aslong as the overall pavement thickness is adjustedto give equivalent load spreading ability. (Refer toChapter 4 of this Part for guidance).

7. DBM and HMB 35 base (and binder course)shall contain 100 and 35 penetration grade binderrespectively. HRA, DBM50 and HDM base (andbinder course) shall contain 50 penetration gradebinder.

8. Where traffic exceeds 80msa, binder courseand base materials shall contain crushed rock, orslag coarse aggregate, unless local experienceexists of the successful use of gravel.

xamples

Using Performance-specified Grades of Base(Figure 2.1)

Design Traffic 200msa

Binder course/Base options, assuming 30mm ofThin Wearing Course System (TWCS):

a) 30mm TWCS50mm Grade 4.5 binder course230mm Grade 4.5 base

b) 30mm TWCS50mm Grade 3 binder course250mm Grade 3 base

Using Recipe-based Specifications for Base(Figure 2.2)

Design Traffic 30msaAssuming HDM base as an example:-

Design Thickness 280mm(275mm rounded up to nearest 10mm)

Surfacing options permitted for each scheme willvary but some examples are given below:

30mm TWCS + 60mm HDM binder course +190mm HDM base

45mm HRA surface course (where permitted)*235mm HDM base

or 50mm HRA surface course can be used

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hickn

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mm

)

0

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Design Traffic in Left Hand Lane(millions of standard axles)

Des

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hickn

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mm

)

Design Thickness ofAsphalt Layers

Design Thicknessof Lower Base

CBM 3 G

CBM 3 GCBM 3 RCBM 4 G

CBM 4 RCBM 5 G

CBM 3 RCBM 4 GCBM 5 R

ongranular orCBM 1 or 2Sub-base,

but only onCBM 2above80msa

onCBM 1A

or CBM 2ASub-base,

but only onCBM 2A

above80msa

LOW

ER B

ASE

TY

PES

Example

Example

Example

Example

Determ inate Inde term ina te (long-life)

R = Roadbase having a coefficient of thermal expansion less than 10 x 10-6 per °C, containing crushed rockaggregate.

G = Roadbase containing gravel aggregate or Roadbase that has a coefficient of thermal expansion morethan 10 x 10-6 per °C, containing crushed rock aggregate.

Figure 2.3: Design Thicknesses for Flexible Composite Pavements

Determinate Indeterminate (long-life)

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Notes on Figure 2.3

1. Notes 1-4 and 7-8 for Figures 2.1 and 2.2shall apply to Figure 2.3.

2. The thickness of asphalt layers in Figure 2.3is applicable to all permitted binder coursebase materials.

3. In Scotland, the minimum thickness of CBM3 or 4 shall be 175mm.

4. Where a cement bound sub-base is used, itmust be checked to ensure that nolongitudinal cracks are present before thelower base is laid.

5. All CBM 1A, 2A, 3 or stronger sub-basesand bases shall have cracks induced,normally at 3m centres, in accordance withthe Specification (MCHW1) Clause 1047.Cracks induced in the base shall beapproximately aligned with the inducedcracks in the sub-base (±100mm).

Examples

1. Design Traffic 13msaAsphalt Layers: Total = 140mm

Some surfacing options:

a) 45mm HRA surface course (where permitted)95mm DBM base

b) 15mm TWCS30mm SMA binder course95mm HDM base

c) 30mm TWCS110mm DBM 50 binder course/base

Some lower base options:

a) 220mm CBM 3G on granular, CBM 1 orCBM 2 sub-base

b) 200mm CBM 3R on granular, CBM 1 orCBM 2 sub-base

c) 200mm CBM 3G on CBM 1A or CBM 2Asub-base

d) 200mm CBM 4G on granular, CBM 1 orCBM 2 sub-base

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e) 150mm CBM 5R on granular, CBM 1 orCBM 2 sub-base

Design Traffic 120msa.

me options:

a) 15mm TWCS50mm DBM binder course125mm HDM base200mm CBM 3G (pre-cracked)on CBM2A sub-base (pre-cracked)

b) 30mm TWCS30mm SMA binder course130mm HDM base150mm CBM 5R (pre-cracked)on CBM 2 sub-base

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0

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m

Example

0 - URC500600 JRC700800

LongitudinalReinforcement

(mm2/m)

Maximum TransverseJoint Spacing (m) for

5 00 mm2/m Longitud inalRein forcement

20

22

24 25

(max)

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m

Example

CRCP with no surfacingor with a Thin WearingCourse System (min 30mm)

CRCR with 100mmAsphalt Surfacing


Figure 2.4: Design Thickness for Rigid Jointed Pavements


Figure 2.4: Design Thickness for Continuously Reinforced Concrete Pavements (CRCP) andContinuously Reinforced Concrete Roadbase (CRCR)

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Notes on Figure 2.4

1. Maximum transverse joint spacings for URCpavements:

a) For slab thickness up to 230mm- 4m for contraction joints

b) For slab thickness 230mm and over- 5m for contraction joints

2. The maximum transverse joint spacings forJRC pavements shall be 25m except forslabs having 500mm²/m reinforcement,where the maximum joint spacing shall beread from the insert to Figure 2.4.

3. For JRC pavements, intermediate values ofslab thickness, longitudinal reinforcementarea, and maximum transverse joint spacing,may be interpolated. The minimumlongitudinal reinforcement permitted is500mm²/m.

4. If limestone coarse aggregate is usedthroughout the depth of the slab, transversejoint spacings may be increased by 20%.

5. For details of permissible concrete surfacingrefer to HD 36 and HD 38 (DMRB 7.5.1 and7.5.3).

Example

Design Traffic 130msaPavement Type JRCReinforcement 500mm²/m

Design Thickness 260mmTransverse Joint Spacing

25m (non limestone coarse aggregate)or 30m (limestone coarse aggregate)

(Note: Unsuitable in England since JRC would requirean asphalt surface, which would lead to reflectioncracking and subsequent maintenance of surfacing).

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Notes on Figure 2.5:

1. Notes 1, 2, 4, 7-8 for Figures 2.1 and 2.2shall apply to Figure 2.5.

2. Two options for CRCP are available:

a) CRCP with no surfacing - not a permittedoption in England

b) CRCP with minimum 30mm of ThinWearing Course System.

3. If PA surface course is used over CRCR, itshall be over a dense binder course inaccordance with Clause 929 of theSpecification (MCHW1) and either:

i) 50mm thick over 90mm of binder course,or:

ii) 50mm thick over 60mm of binder coursebut with the CRCR slab thicknessincreased by 10mm.

4. PA surface course shall be modified with apolymer or fibre additive.

5. Longitudinal reinforcement in CRCPwithout surfacing, or with a minimum of30mm Thin Wearing Course System, shallbe 0.6% of the concrete slab cross-sectionalarea, comprising 16mm diameter deformedsteel bars. Transverse reinforcement shall be12mm diameter deformed bars at 600mmspacings.

6. Longitudinal reinforcement in CRCR with aminimum of 100mm asphalt surface courseand binder course shall be 0.4% of theconcrete slab cross-sectional area,comprising 12mm diameter deformed bars.

7. For CRCP, a ground beam anchorage orwide-flange steel beam shall be provided atthe ends of all pavements and anydiscontinuities.

8. A ground beam anchorage is required at thetermination or at any discontinuity of aCRCR.

2/11



9. Exposed Aggregate Concrete Surfacing(EACS) shall only be used with the approvalof the Overseeing Organisation. For optionsand details refer to HD 36 and HD 38(DMRB 7.5.3.1 and 3).

Example

Tied hardshoulder or 1m edge strip.Design Traffic 170msa

Some options:

a) 30mm TWCS220mm CRCP

b) 45mm HRA surface course (where permitted)55mm DBM binder course210mm CRCR

c) 15mm TWCS85mm DBM binder course210mm CRCR

Note: For b) above, use of a Performance basedsurfacing to Clause 943 is recommended.

Figure 2.6: Additional Concrete Slab Thicknessfor Pavements without 1m Edge

Strip or Tied Hardshoulder

Slab Design Thickness (mm)

Add

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August 20012/12


Chapter 3Materials

3. MATERIALS

BITUMEN BOUND MATERIALS

3.1 Most asphalt binder course and base materialsare characterised by an aggregate skeleton, where theindividual particles are mechanically interlocked, boundwith penetration grade bitumen in the range 35-100pen.The aggregate skeleton provides deformation resistance(provided that in-situ air voids are typically in the range2-6%), as well as contributing to stiffness. Clause 929of the Specification (MCHW1) provides guidance. Thebinder content should be sufficient to provide thickenough binder films on the aggregate to create fatigueresistance and achieve durability. Generally the lowerpenetration binders are used to obtain increasedstiffness.

Premature Rutting

3.2 Early age deformation (rutting) in surface andbinder course layers may be initiated by slow movingcommercial vehicles (eg in a contraflow), especially onuphill lengths and when pavement temperatures arehigh, relatively soon after the materials have been laid(eg during major maintenance). Such situations shouldtherefore be avoided. Where HRA (if permitted) isused, Clause 943 of the Specification (MCHW1) andNotes for Guidance (MCHW 2) provide guidance onperformance requirements. For SMA binder courseperformance requirements, see Clause 937 and NG 937(MCHW 1 & 2).

Bond

3.3 The designs given in this Part are based on thestructural requirements for the pavement layers. Theyimplicitly assume that full bond is achieved betweenlayers (unless specifically required otherwise, such asbetween a jointed concrete slab and underlying sub-base). This bond may take some time to develop, and isone of the reasons why deflection measurements takenat early age can be higher than expected. For ‘lean’base materials, particularly where low penetrationbinder is used, it may be prudent to specify use of abond coat to ensure satisfactory whole life performance.

3.4 Particular attention should be paid to specifyingand achieving good bond between a Thin WearingCourse System and the underlying flexible or rigidconstruction. This is because, under certain

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August 2001

ircumstances (eg braking vehicles), high shear stressesan be developed at these shallow interfaces.

.5 Since Thin Wearing Course Systems may have aigher void content (with larger individual air voids)an the more traditional Hot Rolled Asphalt, it isportant to ensure that the chosen binder course or

pper base layer can provide an effective barrier toater entering the lower pavement layers. Suchurability issues are particularly important where thease may be manufactured quite ‘lean’ in binder,erhaps in an attempt to provide high stiffness and rutesistance. For SMA binder course an air void contentf 2-6% is required for durability, and wheeltrackingmits are imposed, see the Specification (MCHW1)eries 900.

.6 When considering the costs and benefits of usingorous Asphalt (PA), it should be remembered that:

PA can be significantly more expensive;

PA has shorter life than other surfacings;

PA will cost more to repair;

Other sound reduction measures or surfacingsmay be more worthwhile in whole life cost terms;

Although spray may be reduced, evidencesuggests that there is no reduction in accidents.

.7 A decision on whether to use PA should be takennly after consideration of all relevant factors. Theverseeing Organisation may be consulted for advicen the suitability of using PA in particularircumstances. Further details on PA are contained inD 37 (DMRB 7.5.2).

AVEMENT QUALITY CONCRETE

.8 The stress generated in a concrete slab partlyepends on the stiffness ratio between the slab and itsnderlying support. To maximise the pavement life, alligid pavements are specified with a relatively stiffemented sub-base. This type of sub-base erodes lessan an unbound material and is less water susceptible

hould joint sealants fail.

3/1


Chapter 3Materials

3.9 Concrete is inherently strong in compression,but weak in tension. Repeated stressing will eventuallylead to crack initiation unless the stress is very low.Thicker slabs result in lower stresses being generatedunder the combined influence of vehicular andtemperature loading.

Jointed Pavements

3.10 Temperature and, to a lesser extent, moisturechanges cause shrinkage/expansion of the slab which, ifrestrained, induce stresses in the concrete. A separationmembrane is required between slab and sub-base forboth URC and JRC pavements, in order to reduce thisrestraint and thus inhibit the formation of mid baycracks. It also helps reduce loss of water from the freshconcrete.

3.11 Three different types of joints are used inconcrete pavements. They are contraction, expansionand warping joints, typical details of which areillustrated in Highway Construction Details (MCHW3).All three types permit warping movement.

3.12 Contraction joints enable the slab to shortenwhen its temperature falls and allow the slab to expandsubsequently by approximately the same amount.Expansion joints allow the slab to shorten and alsocater for the expansion movement that would naturallyoccur at temperatures higher than that of the concrete atthe time the slab was constructed. Transverse joints areeither expansion or contraction types. However,longitudinal joints are of the warping type only. Thesetie the slabs together, and can be thought of as acting as‘hinges’ in the slab.

3.13 The permitted spacing of transverse joints is afunction of slab thickness, aggregate type, and, for JRC,the quantity of reinforcement. Joint spacing reflects thecapacity of the slab to distribute strain rather than allowdamaging strain concentrations.

3.14 Limestone aggregate has a lower coefficient ofthermal expansion than other aggregate types, resultingin less expansion/contraction of the slab. Thereforegreater joint spacings can be used. The effectiveness ofreinforcement, as a distributor of strain, increases withthe amount used. Greater joint spacings can be usedwith larger areas of reinforcement, although this resultsin greater movement at each joint, necessitatingappropriate selection of sealants.

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3/2

ntinuously Reinforced Concrete (CRCP andCR)

5 CRCP/CRCR pavements develop a finensverse crack pattern soon after the concrete is laid.itially the crack spacing is about 3 or 4m. Furthercking is usual after the road has been in service for ae. The continuous longitudinal reinforcement holds cracks tightly closed, ensuring load transfer by

gregate interlock and minimising corrosion of thenforcement. The crack propagation in CRCP/CRCRvements is closely related to the proportion of steel, strength of the concrete and the aggregate used.

6 The separation membrane is omitted fromCP/CRCR construction in order to give a higherel of friction between the concrete slab and the sub-

se than for jointed slabs. The restraint provided by sub-base reduces the amount of movement at the

ds of the pavement and encourages the desired crackttern. The use of a layer of material under the CRCP/CR with uniform surface properties, such as may be

ovided by paver-laid wet-lean concrete or an asphaltterial, is recommended. The thickness of any dense

phalt material may be considered as part of the boundb-base.

7 Discontinuities in the slab should be avoidederever possible as they encourage the formation ofsely spaced cracks, with increased risk of spalling.llies and manholes should be located outside thein CRCP/CRCR slab for this reason. If this is notssible, the slab around the gullies and manholesould be heavily reinforced as shown in the Highwaynstruction Details (MCHW3).

8 Where a CRCP has an asphalt surface course,rface noise generation is reduced and waternetration (and the potential for reinforcementrrosion) is likely to be reduced. If the surfacing is0mm thick (or more) it also provides a degree ofrmal protection from rapid temperature changes for concrete base. If the 30mm minimum TWCS is

ed, the bond coat required to ensure good adhesiontween the CRCP and the TWCS shall comply with requirements of the Specification (MCHW1) Clause2 and any additional BBA HAPAS requirements for TWCS being used.

ack and Seat

3.19 Cracking and seating of URC pavements, priorto application of an asphalt overlay, can be a costeffective strengthening alternative to reconstruction, for

August 2001


Chapter 3Materials

concrete pavements near the end of their design life.Procedures for determining the thickness of the overlaycan be based on an analytical procedure as described inChapter 4 of this Part.

CEMENT AND OTHER HYDRAULIC/POZZOLANIC BOUND MATERIALS

Crack Inducement/Pre-cracking of CBM’s

3.20 Transverse cracks may occur in the surface offlexible composite pavements as a “reflection” of thenaturally occurring thermal stress cracks in the CBMbase, which typically occur at a natural spacing of10-30m. The introduction of cracks in the CBM base ata closer spacing will reduce the magnitude of thethermal movements at individual cracks, and hence thetensile stresses in the asphalt overlay. This minimisesthe size and severity of the surface crack, which reducesfuture maintenance costs and allows the pavement lifeto be extended.

Hydraulic/Pozzolanic Binders

3.21 Use of secondary aggregates, combined withhydraulic or pozzolanic binders, for sub-base and lowerbase layers has become increasingly common, and canresult in environmental benefits. Due to the relativelyslow strength gain of such materials (compared to aCBM for example) they should be considered more likeunbound granular layers in the short term (constructionphase). Strength gain in the medium to long term (givenappropriate environmental conditions) results in astronger foundation for the upper pavement layers. Theslower strength gain (and reduced heat of hydration)may have additional benefits in reducing the magnitudeof initial thermal movements. This helps to increase thepavement life, or alternatively, in some circumstances areduced thickness for the upper pavement layers may bejustified. Chapter 5 lists a number of publications thatprovide guidance on suitable materials.

August 2001 3/3


Chapter 4Alternative Design Procedures

ROCEDURES
4. ALTERNATIVE DESIGN P
Analytical Pavement Design

4.1 The philosophy of analytical design is that thepavement should be treated in the same way as othercivil engineering structures, the procedure for whichmay be summarised as follows:

a) Specify the loading.

b) Estimate the size of components.

c) Consider the materials available.

d) Carry out a structural analysis using theoreticalprinciples.

e) Compare critical stresses, strains or deflectionswith allowable values.

f) Make adjustments to materials or geometry untila satisfactory design is achieved.

g) Consider the economic feasibility of the result.

4.2 Classical pavement design relies upon the use ofa simplified multi-layer linear elastic model of thepavement structure. Appropriate stiffness moduli arechosen for the various pavement layers, either on thebasis of known mixture properties or from laboratory orfield tests. A standard axle load (40kN wheel load) isthen applied, and the relevant critical strains or stressesare calculated.

4.3 The classical approach assumes two primarymodes of failure caused by trafficking of a pavement:

• Fatigue cracking at bottom of the base.

• Overstressing of the subgrade, resulting indeformation.

However, the designer should always use judgementand consider other modes of failure which might bemore critical for the particular pavement underconstruction. For example:

• Permanent deformation within the asphaltmaterials.

• Reflection cracking, for composite pavements.

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August 2001

Surface initiated cracking and other durabilityrelated issues.

.4 The design task is to proportion the pavementructure so that the critical levels of stress or strain willot be exceeded in the design life. To achieve this, theesigner needs information on the engineeringroperties of the materials, particularly:

Effective stiffness modulus, which governs loadspreading behaviour.

Deformation resistance, which governs ruttingbehaviour. (Asphalt materials only.)

Fatigue resistance, which governs crackingbehaviour.

.5 Relationships between pavement life and theseitical strains or stresses have been derived from ambination of laboratory testing and pavement

erformance monitoring. The references given inhapter 5 of this Part give further background.

.6 However it is still necessary for the designer toake appropriate judgements. For example two very

ifferent asphalt mixes, even if both nominally of theme type (eg HDM) could yield different lives,

epending on the aggregate structure and binderntent. Similarly, the permanent deformation

ehaviour of a sandy subgrade will differ from a clay,en if they have the same stiffness.

.7 It should be noted that a specific analyticalesign method has not been defined. The availableethods differ in their mathematical formulation andch method is generally internally consistent. It should

e appreciated that inadequate designs can result ifements from different methods are combinedappropriately.

lternative Pavement Designs

.8 The analytical approach provides a means ofstomising a pavement design to locally availableaterials, or construction methods (eg stabilisation).owever, it is essential that the material propertiessumed are actually achieved on site if the whole life

erformance of the pavement structure is to beachieved. It is also essential that due consideration is

4/1


Chapter 4Alternative Design Procedures

given to the overall durability of the pavement structure(ie the resistance of the materials to the deleteriouseffects of water, air, and other environmental factors).

4.9 Where used appropriately, the OverseeingOrganisations will accept the use of analyticalpavement design to justify alternatives. However,full supporting details must be submitted in orderfor a Departure from Standard to be authorised.

4.10 Where Alternative Pavement Designs can bereadily compared with the Standard Design chartsin this Part, it should be shown that the overallload spreading ability of the alternative pavement(in terms of critical strains, stresses and stiffnessmoduli) is equal to or greater than the standardobtained from HD 25 and Chapter 2 of this Part. Inaddition the expected serviceability (eg skiddingresistance) and maintainability should not beinferior to the Standard Design. Values for theengineering properties of all materials proposedshould be provided. Proposals should show arealistic balance between the strength of thefoundation and that of the pavement. Designthickness proposals shall make allowance forconstruction tolerances.

4.11 Values of elastic stiffness modulus for use inanalytical design shall be:

DBM 3,100 MPaDBM50 & HDM 5,600 MPaHMB 35 7,000 MPa

Design stiffness moduli used for pavement designare at the reference condition of 20oC and 5 Hz andshall not be confused with ITSM stiffness, whichis measured for compliance testing at the lowerfrequency of 2.5 Hz. Design stiffness moduli forfoundation layers shall not be confused withfoundation surface stiffness measured using theFWD or plate bearing tests.

4.12 In other cases, in order to assist with theevaluation of the alternative, the following shouldalso be supplied:

• Information on the analytical pavementdesign model adopted;

4.AthovCas

4/2

• Definition of pavement requirements interms of design traffic normally given inmillion standard axles (msa);

• Material properties assumed and howobtained (eg from site or laboratory testingor published data);

• Information on the failure mechanismsconsidered by the designers;

• Test procedures to be adopted on site toensure that the mean and minimumparameter values assumed in the design areachieved on site;

• Sensitivity analysis to identify theparameters that have most influence on life;

• Procedures to be adopted on site to reducethe variability of pavement construction, inparticular the most influential parametersidentified from the sensitivity analysis;

• Experience of long term performance ofsimilar pavements, both in the UK andoverseas;

• Comparisons with other published designs,especially from countries with similartrafficking levels, climatic conditions andmaterial properties to the UK.

13 It should be noted that the procedures laid out innnex B of HD 30/99 (DMRB 7.3.3) for determininge thickness of a continuously reinforced concreteerlay (based on RR87) can also be used to design a

RCP on a foundation stronger than the standardsumed in HD 25 (DMRB 7.2.2).

August 2001


Chapter 5References and Bibliography

OGRAPHY
5. REFERENCES AND BIBLI
References

1984

LR1132; Powell W D, Potter J F, Mayhew H C andNunn M E, “The Structural Design of BituminousRoads”, TRRL.

1987

RR87; Mayhew H C and Harding H M, “ThicknessDesign of Concrete Roads”, TRRL.

1988

BS4987; Parts 1 and 2 “Coated Macadam for Roads andOther Paved Areas”, BSI.

1989

HA 39 (DMRB 5.3) Edge of Pavement Details.

1992

BS594; Part 1, Hot rolled asphalt for roads and otherpaved areas, BSI.

1994

HD 27 (DMRB 7.2.4) Pavement Construction Methods.

HD 32 (DMRB 7.4.2) Maintenance of Concrete Roads.

1996

HD 24 (DMRB 7.2.1) Traffic Assessment.

1998

HA 39 (DMRB 5.3) Edge of Pavement Details.

Undated

Specification for Highway Works (MCHW1).

Highway Construction Details (MCHW3).

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August 2001

ibliography

ansport Research Laboratory

93

arswell, J and Gershkoff, D.R., “The Performance ofodified Dense Bitumen Macadam Roadbases,esearch Report 358.

94

unn, M.E. and Smith, T., “Evaluation of arformance Specification in Road Construction”,oject Report 55.

97

unn, M.E. and Smith, T., “Road Trials of Highodulus Base for Heavily Trafficked Roads”, Report1.

haddock, B.C.J. and Atkinson, V.M., “Stabilised Sub-ses in Road Foundations : Structural Assessment and

enefits”, Report 248.

unn, M.E., Brown, A., Weston D. and Nicholls, J.C.,he Design of Long-life Flexible Pavements for

eavily Trafficked Roads”, Report 250.

icholls, J.C., “Review of UK Porous Asphalt Trials”,eport 264.

lis, S.J., Megan, M.A and Wilde, L.A., “Construction Full-Scale Trials to Evaluate the Performance ofduced Cracked CBM Roadbases”, Report 289.

ewitt, A.P., Abbott, P.G. and Nelson, P.M.,lternative Textures for Concrete Roads : Results of

18 and A50 Trials”, Report 291.

icholls, J.C., “Road Trials of Stone Mastic Asphaltd other Thin Surfacings”, Report 314.

99

tkinson, V.M., Chaddock, B.C and Dawson, A.R.,nabling the Use of Secondary Aggregates and

Binders in Pavement Foundations”, Report 408.

5/1


Chapter 5References and Bibliography

2000

Weston D., Nunn M, Brown A. and Lawrence D.,“Development of a Performance Based Specificationfor High Performance Asphalt Pavement”, Report 456.

2001

Ellis S.J., Langdale P.C. and Carswell I., “Maintenanceof Concrete Pavements using Bituminous Overlays -a Design and Specification”, Report 437.

Others

1987

Brunton J.M., Brown S.F. and Pell P.S., “Developmentsto the Nottingham Analytical Design Method forAsphalt Pavements”, Proc 6th Int. Conf. StructuralDesign of Asphalt Pavements, Ann Arbor, Michigan,pp 366-377.

Freeme C.R., De Beer M. and Vilijoen A.W., “TheBehaviour and Mechanistic Design of AsphaltPavements”, Proc 6th Int Conf Structural Design ofAsphalt Pavements, Ann Arbor, Michigan, pp 333-343.

Monismith C.L., Finn F.N., Ahlborn G. and MarkevichN., “A General Analytically Based Approach to theDesign of Asphalt Concrete Pavements”, Proc 6th Int.Conf. Structural Design of Asphalt Pavements, AnnArbor, Michigan, pp 344-365.

1995

Elliott R.C. and Mercer J., “Assessment of IndustrialBy-Products for Bituminous Roadbases”, Joint SCI/IAT/IHT Symposium on “Waste and Industrial By-Products in Asphalt”, London, 26 October.

Dawson A.R., Elliott R.C. Rowe, G.M. and Williams J.,“Assessment of Suitability of Some Industrial By-Products for Use in Pavement Bases in the UnitedKingdom”, Transportation Research Record 1486,pp 114-123, Transportation Research Board,Washington.

1996

Thom N.H. and Shahid M.A., “Controlled Cracking inCement Bound Bases”, Journal of the Institution ofHighways and Transportation, pp 20-23, October.

1

RB1

1

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1

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APJT

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2

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5/2

997

ead J.M., “Practical Fatigue Characterisation ofituminous Paving Mixtures”, The Asphalt Yearbook997, Inst. of Asphalt Technology.

998

rown Prof S.F., “Developments in Pavementtructural Design and Maintenance”, Proc. of thenstitution of Civil Engineers - Transport, 129, Nov.,p 201-206.

l Hakim, B., Armitage, R.J. and Thom, N.H.,Pavement Assessment including Bonding Condition :ase Studies”, 5th International Conference on Bearingapacity of Roads and Airfields, Trondheim, 6-8 July.

uropean Co-operation in Science and TechnologyCOST) Action 333, “Development of New Bituminousavements Design Method - Final Report”.http://www.cordis.lu/cost-transport/home.html).

999

hompson I., Peaston C.H and Thom N.H., “Fibreeinforced Cement Bound Roadbase”, Asia-Pacificpeciality Conference on Fibre Reinforced Concrete,7-28 August, Singapore.

l Hakim Dr B., Jennison C.W. and Falls D., “Concreteavement Strengthening Using Crack and Seat”,ournal of the Institution of Highways andransportation, October.

alsh I.D., “The Evaluation and Use of Slag Boundub-base/Roadbase with Performance Related Tests”,roc. 3rd European Symposium on Performance andurability of Bituminous Materials and Hydraulictabilised Composites, Leeds, pp 327-242.

000

otter J.F., Dudgeon R.P. and Langdale P.C.,Implementation of Crack and Seat for Concreteavement Maintenance”, 4th International RILEMonference on Reflection Cracking, Ottowa.

August 2001


August 2001 6/1

6. ENQUIRIES

All technical enquiries or comments on this Standard should be sent in writing as appropriate to:

Chief Highway EngineerThe Highways AgencySt Christopher HouseSouthwark Street G CLARKELondon SE1 0TE Chief Highway Engineer

Chief Road EngineerScottish Executive Development DepartmentVictoria QuayEdinburgh J HOWISONEH6 6QQ Chief Road Engineer

Chief Highway EngineerThe National Assembly for WalesCynulliad Cenedlaethol CymruCrown BuildingsCathays Park J R REESCardiff CF10 3NQ Chief Highway Engineer

Director of EngineeringDepartment for Regional DevelopmentRoads ServiceClarence Court10-18 Adelaide Street G W ALLISTERBelfast BT2 8GB Director of Engineering

Chapter 6Enquiries

volume 7 pavement design and maintenance section 2

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