Warm Mix Asphalt - Aapaq.org

Interstates 55 and 57 in Missouri170,000 tons of Warm MixFigure 8GPCChromatogramsof the binders -Polymer Peak Detail6.004.002.000.00>.. -2.00·4.00-6.00·8.00Decreasing molecular weight Ileft peak: polymerMrxa119JOCMueat 1ar cMlx at lSr cOrigIna l binder30Right peak: bitumen0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00oMat Density vs. Surface Temperature & Roller Passes94.0 ~ 5 vibratory passes2 BrNk Down rollfl'Sclose 10 each other92.0is} 90.02 Break Down rollers, gin tandem behindpaver 6 passesvibratory + 1 statkISWater is greenerSince 2005, Colas Inc. has been evaluating technically,environmentally and economically all warm mixtechnologies available: organic waxes, chemical surfactantsand the different foam technologies. Colas SolutionsTechnical Center coordinated this methodical laboratoryand field research jointly with operations, equipment,environmental and laboratory personnel.This factual evaluation evidenced that Warm Mixtechnologies have benefits in terms of mix performance,energy savings and emissions reduction; however foamedasphalt technologies stood out in terms of practicality,cost-effectiveness and low carbon footprint:no additive is greener than water. This led Colas companiesto strategically invest in foam technologies, resultingin an exponential growth of warm mix tonnage:last year 18.5% of Colas US bituminous mixeswere foamed produced; in 2011 the share is projectedto be 27.9% (see Figure 10).Figure 9Mat Densityvs. Temperature& Rollers Passes~ 88.086.084.0160 140 120AverageTemperature (0C)• HMA B 1/82 Vibr. t:=.. WMA Tandem 81182 Vib. 1:::100 8030.0% 27.9%25.0%20.0% 18.5%15.0%10.0%5.5%5.0% 3.6%0.0% 0.4".0.1%0.0%2007 2008 2009 2010 2011PWUSA • CANADAFigure 10Evolution of EcoMat (COLAS Inc. WMA trade Mark) in share of totalCOLAS US production~;3Photo 8Temperature Check(279°F - 137°C)behind the ScreedPhoto 9Density controlduring compactionThis was particularly criticalbecause these 19mm high traffic designs(PG76-22, 125 gyrations) placed in 2-inare usually not the easiest to compact.Pavers & Rollers Type: Cedar Rapids Paverwith Material Transfer Vehicle; 2 CAT CB634vibratory rollers; DD IR Finish Roller.Foamed asphalt mix refers to a bituminous mixturein which 1 % to 2% of water injected into the hot bitumen,results in spontaneous foaming and temporaryalteration of the physical properties of the binder;when foam dissipates the original properties of bitumenare regained.By foaming the bitumen temporarily:1. Expands its volume, facilitating the coatingof the cooler aggregates,2. Increases mixture workability at lower temperaturethanks to Foam's Shear Thinning qualities.Shear thinning means that viscosity decreases as shear rateincreases; it occurs in substances such as shaving creamand is crucial to its use: the cream stays put in your handbut glides smoothly on your skin under the bladeof the razor. Similarly foamed asphalt Shear Thinningproperties help maintaining a thick film of binderwithout risks of draindown when stored in the siloor when hauled in a truck, but increase its workabilityunder the shear of the screed and the compactive effortof the rollers.lIB europea"roads revIew 1 B • Spring 2011 • RGRA