#1 wma background and overview
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#1 wma background and overview



Warm Mix Asphalt training documents provided by the National Center for Asphalt Technology (NCAT) for classes held June 26 & 27, 2013 in California, sponsored by the California Asphalt Pavement ...

Warm Mix Asphalt training documents provided by the National Center for Asphalt Technology (NCAT) for classes held June 26 & 27, 2013 in California, sponsored by the California Asphalt Pavement Association (CalAPA).



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#1 wma background and overview Presentation Transcript

  • 1. 1
  • 2. 2OverviewUse of WMA in the USAWMA CategoriesOpportunities & Challenges with WMA
  • 3. 3Warm Mix Asphalt WMA definitions asphalt mix produced with special technologies attemperatures 30 to 70°F lower than typical HMA Asphalt mix produced at temps below 275 F Lower temperatures result in… Less energy to produce asphalt mixes thus reduced cost Fewer emissions from asphalt plants Less fumes and odors for paving crew and neighbors Better workability at lower temperatures
  • 4. 42003
  • 5. 52012
  • 6. 6WMA Categories1. Organic Additives2. Chemical Additives3. Asphalt Foaming Technologiesa. Foaming additivesb. Water Injection Systems4. Combinations of above
  • 7. 7WMA Categories1. Organic Additives Sasobit (Sasol) SonneWarmix (Sonneborn) Rediset (Akzo Nobel) – also contains chemicaladditives Bitutech PER (Engineered Additives) LEADCAP (KICT-KUMHO Petrochemical) Thiopave (Shell)
  • 8. 8WMA Categories2. Chemical Additives (Surfactants) Evotherm (MeadWestvaco) Cecabase RT (Arkema Group) HyperTherm/QualiTherm (QPR) ECOBIT (All States Materials Group) Revix (Mathy)Typical dosage rates of 0.2 to 0.5% of the binderMany of the WMA Chemical Additives provideanti-stripping additive compounds
  • 9. 9WMA Categories3. Asphalt Foaming Technologiesa. Foaming Additives (Zeolites) Advera (PQ Corp.) Aspha-min (Eurovia)Foaming Additive rates are typically 0.25 to 0.30% byweight of mix
  • 10. 10WMA Categories3. Asphalt Foaming Technologiesb. Water Injection Systems Accu-Shear (Stansteel) AquaBlack (Maxam) AquaFoam Double Barrel Green (Astec) Eco-Foam II (AESCO/MADSEN) HGrant Warm Mix System (Herman Grant Co.) Meeker Warm Mix Terex WMA System Ultrafoam GX2 (Gencor)Most waterinjection foamingsystems add 1 to 2%water by weight ofbinder
  • 11. 11WMA Categories4. Combinations Rediset (Akzo Nobel) Low Emission Asphalt (McConnaughay) Combined foaming and chemical additives Mix production temperatures are typicallylower than other WMA processesWhat are the most popularWMA Technologies?
  • 12. 12Estimated WMA Production051015202530352009 2010 2011WMAUsage(%)StateOther Govt.Non-Govt.77.9%19.6%2.3% 0.2%Water-injection foamingChemical additiveFoaming additiveOrganic additive
  • 13. 13WMA in 2011 (NAPA)
  • 14. 14Economics of WMA Water-Injection systems cost $30k to$80k. Assuming $50k cost, 150,000 tons/yr.,5-year depreciation, then foamedWMA cost about 7ȼ/ton. If only 1/3 of production is WMA,then cost is 21ȼ/ton. Popular WMA additives are reported toincrease cost by $2 - $3/ton of mix.
  • 15. 15Energy Savings with WMA Fuel savings for WMA isproportional to the temperaturereduction. Most contractors report burnerfuel usage decrease of about 10to 15%. Savings will range from $0.10 to$0.80 depending on fuel typeand temperature decrease.
  • 16. 16Reduced Emissions with WMA Especially noticeable at load-out
  • 17. 17Better Work Environment
  • 18. 18Improved Compactability Compaction of asphaltmixtures to specifieddensity criteria is one of themost important aspects ofquality construction thataffects the long-termperformance of thepavement.
  • 19. 19Potential WMA Density Benefit Some contractors use WMA primarily for a densitybenefit. Data from NCHRP 9-47A indicates WMA test sectionshave only an average density 0.17% higher thancompanion HMA sections. In a typical PWL specification, even that smallimprovement can impact the density pay factor andtranslate to a benefit of up to $1 per ton.
  • 20. 20Overlaying a Crack Sealed Pavement Overlaying pavementswith joint/crack sealantcauses moisture trapped in& beneath sealant toexpand Expansion causes bumps inoverlay that do not rollout, results in poor rideand density WMA has been used tosolve this problem
  • 21. 21Better Workability? Most, but not all,contractors reportWMA improvesworkability Some also report finishto be better, especiallyjoints.
  • 22. 22Long Haul Distances Haul times with WMAfrom 1 to 3 hours reported Generally successful inachieving target density Crusting / lumps of mixreported on a few jobs Some contractors usenormal mix temperaturesso the WMA technology isjust a compaction aid
  • 23. 23Cold Weather Paving Several example projectsusing WMA to pave in nearfreezing temperatureshave been reported intrade literature. Use Multi-cool program toestimate time available forcompaction
  • 24. 24Plant Concerns with Initial use of WMA Lower production temperatures could lead to: Less efficient burner operation Incomplete drying of the virgin aggregates Condensation in the baghouse Increase amperage on motors24
  • 25. 25Lab Tests on WMA Nearly all WMA produced to date have used HMA mixdesigns Lower mix temperatures cause less asphalt adsorptionfor some aggregates that can change volumetricproperties. Lab tests for rutting and moisture damage potential forWMA commonly yield less favorable results comparedto HMA
  • 26. 26Combining WMA and RAP WMA technologies canimprove the ability toproperly coat aggregatesand RAP during production Improved workability Lower productiontemperatures will reduceplant aging of binderswhich may allow forincreased use of RAPwithout grade bumping26
  • 27. 27Summary of PotentialEconomic Benefits w/ WMA Energy savings Improved density? → higher pay Improved smoothness? → higher pay Increased RAP contents? Longer hauls/extended paving season Eliminate other mix additives? Liquid anti-strip agents Odor scavengers/masking agents Fibers for drain-down?
  • 28. 28Other Resources www.warmixasphalt.com NAPA (www.asphaltpavements.org) Warm Mix Asphalt: Best Practices, 3 rd Ed. (QIP-125) ncat.us all NCAT reports can be downloaded FHWA-NHI Webinar Special Mixture Design Considerations andMethods for Warm-Mix Asphalt Course Number FHWA-NHI 131137 Free, 2 hours