TRB WMA Webinar Review

Sep 14, 2011

Do you have questions regarding how to properly design and evaluate Evotherm mixes in the laboratory? The Transportation Research Board (TRB) recently released a proposed Appendix of AASHTO R 35 for evaluations of Warm Mix Asphalt (WMA) technologies in the laboratory. A webinar on the research was held last week.

This report, NCHRP 691, gives recommendations on how to evaluate all of the current WMA technologies.  Among the topics covered are the proper handling and introduction, in the cases of chemical additives, and the need for laboratory foaming equipment to evaluate foamed WMA. Dr. Brian Prowell with Advanced Materials Services, LLC pointed out that these laboratory foaming units can often cost as much or more than the production units.

The study concluded that volumetrics are not significantly different than those of standard Hot Mix Asphalt and separate WMA designs are not needed.  However, the report recommends preparing WMA samples in the laboratory and evaluating their performance properties.  The results also showed that RAP-containing WMA mixes do show blending of the RAP and virgin binder at WMA temperatures.  Additional testing parameters are also discussed.

To learn more about these and other topics related to WMA technologies, go to

Author: Tom Girardeau