#6 proposed guide spec for wma mixes


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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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#6 proposed guide spec for wma mixes

  1. 1. 1
  2. 2. 2Warm Mix Asphalt Warm Mix Asphalt (WMA) refers to asphalt mixtures producedat temperatures approximately 30°F (17°C) or more belowthose typically used in production of HMA. Temperaturereductions may be achieved through approved additivesand/or water injection systems. A common spec requirementis a maximum mixing temperature of 275 F. All specification requirements for HMA shall apply to WMAexcept as noted herein. The mixture shall be produced with a WMA technology fromthe approved list and in accordance with the WMA technologyprovider’s guidelines for dosage rate, plant mixingtemperature, and laboratory compaction temperature.
  3. 3. 3Warm Mix Asphalt An approved HMA mix design may be used for the WMAprovided that:a. The asphalt absorption of the HMA mix design is lessthan 2.0%, andb. An initial field trial of the WMA produced with the plantdesignated for the mix design meets all asphalt mixturespecifications. If either a or b are not met, then the WMA shall be designed inaccordance with the procedures and criteria in NCHRP Report691. The WMA mix design submitted by the contractor shall includethe name of the WMA technology, dosage rate, plant mixingtemperature, and laboratory compaction temperature.
  4. 4. 4Warm Mix Asphalt The antistrip-additive may be eliminated from the WMAmixture provided that:a. The WMA additive contains active antistrippingcomponents as certified by the WMA technologyprovider.b. The WMA mixture without an additional antistrippingagent meets the standard HMA moisture damage testcriteria.
  5. 5. 5Warm Mix Asphalt Plant operations for WMA production The burner shall be properly tuned to operate at the WMAmix temperature such that the fuel is entirely consumed inthe combustion zone of the drier. Production shallimmediately cease if evidence of uncombusted fuel isdetected in the produced asphalt mixture or in thebaghouse. The plant discharge temperature of the WMA shall bewithin 20°F of the temperature designated on the WMAmix design. During plant start up or at project transitionpoints, the mix temperature may be above the designatedWMA mix temperature, but no greater than 340°F.
  6. 6. 6Warm Mix Asphalt Plant operations for WMA production The addition of WMA additives, including water, shall becontrolled by a calibrated metering system interlocked withthe plant’s controls. Chemical additives may be added at the asphalt terminal atthe dosage rate recommended by the WMA technologyprovider. The dosage rate and additive name shall beprinted on the Bill of Lading for the asphalt binder.
  7. 7. 7Any Questions???