Edition

Volume 103 Number 4 • APRIL 2013

Site-K Construction Zone

page 1

INSIDE

Serving Minnesota, North Dakota, South Dakota and Wisconsin Since 1902

Industry Newspage 7

Association Newspage 40

2013 Infrastructure Report Card

page 11

Also in this issue:

• 8 Point Check List for Hydraulic Excavators

• Tilt-Up Concrete – Trends and Developments

• Strengthen Internal Business Controls

NEW PAVEMENT TECHNOLOGIES TRIED IN TWIN CITIESStreets, alleyways and parking lots undergo trial applications of latest technologies designed to extend service life of pavements

S treets, alleyways and parking lots of all sizes in the Minneapolis-St. Paul area are undergoing trial ap-plications of the latest technologies

designed to extend the life of asphalt pave-ments.

Paving crews are installing warm mix as-phalt, biologically based pavement protective coatings, highly modified asphalt mixes and combinations of these technologies in differ-ent sections of Minnesota’s Twin Cities region, which forms the core of the 16th-largest met-ropolitan area in the United States and houses some 3.3 million residents.

In constant search for cost-efficient, longer-lived pavements, municipal officials approved the trial applications, all of which are the hand-iwork of Bituminous Roadways Inc. (BRI), a local paving contractor who has been operat-ing in the Twin Cities area for nearly seven de-cades. (See accompanying sidebar containing a list of some trial applications).

BRI works with asphalt suppliers, public works officials and other sources to learn about innovative technologies. When approved, the contractor incorporates new processes into its daily operations, and markets new techniques and materials to current and potential custom-ers.

One of the technologies is warm mix asphalt (WMA), introduced to America just a decade ago from Europe. The company invested in necessar y equipment and began producing

By Paul Fournier

In Bloomington, Bituminous Roadways Inc. installs highly modified asphalt overlay – one

of a number of new technologies being tested in Twin Cities area.

WMA in its own facility about 3 years ago, and has already produced and installed well over a million tons of WMA. All of the current trial applications involve WMA.

Warm Mix Benefits

According to the Federal Highway Adminis-tration (FHWA), the term Warm Mix Asphalt refers to a variety of new technologies that al-low producers of hot mix asphalt (HMA) to lower the temperature at which pavement mate-rial is mixed and placed on a road.

The agency notes that high production temperatures are traditionally needed to make the asphalt binder fluid and less sticky during mixing in order to completely coat aggregates and also have good workability during haul-ing , placement, and compaction. Various WMA technologies use water, water-bearing minerals, chemicals, waxes, organic additives or a com-bination of these materials that allow asphalt binder to remain fluid at lower temperatures during mixing while still completely coating the aggregates.

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Owners: Twin Cities Area Municipalities and Commercial Businesses Asphalt Producer/Contractor: Bituminous Roadways Inc.

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At BRI’s own facility, Kraton D0243 Polymer is blended with asphalt to make HiMA binder which is then mixed with aggregate using warm mix technolog y.

Left: A Volvo paver is employed by BRI to install a 1-1/2-inch overlay incorporating HiMA asphalt binder and AQUABlack warm mix technolog y.

In general, WMA is produced at 30 to 70 degrees Fahr-enheit lower than HMA during mixing , and the tempera-ture remains lower during trucking , placement, and com-paction. This results in significant savings in fuel costs. FHWA says this proven technolog y can reduce overall paving costs, extend paving seasons, improve asphalt compaction and allow asphalt mix to be hauled longer distances.

Perhaps most importantly from a worker standpoint, the use of WMA increases safety and improves working conditions by reducing exposure to hot materials and ac-companying odors.

BRI uses two warm mix technologies: AQUABlack So-lutions manufactured by MAXAM, and Evotherm Warm Mix Asphalt produced by MeadWestvaco.

AQUABlack Solutions is a water injection system that uses MicroBubble technolog y and pressures of 1,000 psi at the drum to produce foamed warm mix asphalt, while Evotherm is a chemical additive package that is typically added to the asphalt binder.

Bio-Based CoatingAnother innovative product being applied throughout

the area is Biorestor, listed by the U.S. Department of Agriculture as a BioPreferred product composed of 95 percent biobased material. BRI recently became Minne-sota's exclusive dealer for the product, which is a protec-tive polymer coating that is applied to new asphalt pave-ments – installed within the last 2 years – to retard oxidation from the elements.

Manufactured by BioBased Spray Systems LLC, Biore-stor cures in 20 to 30 minutes depending on weather con-ditions. It penetrates the pavement, making it more flex-ible, has little effect on pavement friction, and since it is clear, requires no re-application of pavement markings.

According to Dusty Ordorff, BRI’s quality control/materials manager, the company has applied the product on industrial, commercial residential and retail pave-ments throughout the Twin Cities area.

Learning About HiMAThe latest innovative pavement product being placed

in the trial applications is an asphalt mix made with a highly polymer modified asphalt binder (HiMA).

“ We learned about HiMA mixes from an article pub-lished in Western Builder magazine which described a Minnesota DOT research mill-and-fill project involving the use of HiMA asphalt binder,” said Ordorff.

That article explains that although MnDOT has had success using 12.5 mm Superpave mix to reduce thermal cracking , which is caused by shrinkage of the pavement surface due to low temperatures, the agency needed a way to reduce reflection cracks that appear in wearing courses due to cracks in underlying material reflect-ing up to the surface. The article details application of HiMA overlay for a mill-and-fill operation on a section

A CAT 980H Loader fills cold feed bin at BRI’s Shakopee asphalt plant.

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BRI’s CAT AP1055E Paver lays down a 3-inch wear-ing course for new construction pavement in a Plym-

outh industrial-use parking lot.

of highway TH100. For the approximately 2-mile sin-gle-lane test, the agency substituted HiMA binder for its traditional Performance Grade 64-28 binder.

Superpave binders are designated with a high and low temperature grade, such as PG 64-28. For this binder, "64" is the high temperature grade and is the 7-day maximum pavement design temperature in de-grees centigrade that the binder must meet perfor-mance criteria . The low temperature grade, "-28," is the minimum pavement design temperature in degrees centigrade. Both high and low temperature grades are established in 6-de-gree increments.

The HiMA binder for the TH100 test was modified with 7.5 percent of Kraton D0243, a new SBS (styrene-butadiene-sty-rene) polymer developed and manufactured by Houston-based Kraton Performance Polymers Inc.

While modification of asphalt with polymer reduces pave-ment rutting , stripping and thermal cracking , and also boosts pavement resistance to traffic-induced stress, there is a practi-cal limit to the dosage. Conventional polymer increases binder viscosity as dosage exceeds three percent, making plant produc-tion more difficult and reducing workability for paving crews. But D0243 polymer retains the benefits of polymer modification without significantly increasing binder viscosity – even at dos-ages exceeding 7.5 percent.

About one-quarter of the section of TH100 involved a 1-1/2-inch mill-and-fill while the remainder consisted of 2-inch mill-and-fill – the usual thickness for the procedure. Both portions of the section incorporated HiMA binder and 25-percent RAP (recycled asphalt pavement).

A New Paving Tool“After reading about this, we thought HiMA might be anoth-

er paving tool we could offer our existing and potential custom-ers,” Ordorff said.

BRI contacted Kraton to learn more about the product, got the material approved by city engineers and set up equipment needed to make HiMA at one of their plants. The contractor created HiMA binder by blending D0243 polymer at 7.5 percent loading with neat (unmodified) PG 58-28 Asphalt Binder. Then they mixed HiMA binder with aggregate to produce warm mix asphalt.

Ordorff pointed out that they tried using HiMA with each of their warm mix technologies – AQUABlack and Evotherm – achieving success in both cases.

In 2012, BRI crews constructed a number of trial pavement sections using HiMA mix on various park-ing lots, alleyways and two streets in the Twin Cities area . All HiMA mixes and control section mixes ad-hered to MnDOT specifications.

Municipal officials will monitor the trial applica-tions of these new technologies over the next several years and compare them with control pavement sec-tions to determine their performance.

New HiMA Pavement Undergoing Trial Applications

Some of the HiMA projects included in the trial applications are :

• 11/2-inch mill and overlay on street project in the city of Bloomington. The control section is a 2-inch-thick mill and overlay made with PG 58-28 Binder.

• 6-inch mill and fill street project comprised of three lifts of 2-inch-thick MnDOT wearing course. The control sec-tion is a 6-inch total pavement reconstruction using PG 58-28 Binder.

• 3-inch wearing course for new construction pavement on an industrial-use parking lot in the city of Plymouth. The control section is 3-inch wearing course using a PG 64-34 Binder constructed by BRI the prior season.

• 3-inch lift of porous asphalt on an alley in the city of St. Paul near Hamline University.

• 11/2-inch partial mill and overlay of a parking lot in the city of Columbia Heights.

• 6 inches of wearing course mix comprised of 3- 2-inch lifts incorporating HiMA binder for a newly constructed park-ing lot in the city of Columbia Heights.

Photo shows completed mill and HiMA overlay at a parking lot in Robbinsdale.

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