Laboratory and Field Evaluations of Foamed Warm-Mix Asphalt Projects

Warm-mix asphalt (WMA) is much like hot-mix asphalt (HMA), but it is produced at lower plant temperatures than conventional HMA. Key benefits of the reduced WMA production temperature include the reduction of fuel consumption and of emissions. Granite Construction performed two WMA paving demonstration projects from its Indio, California, facility in early 2008. Both projects were paved with WMA produced with the free water method (Astec Double Barrel Green). The objectives of these demonstrations were (a) to demonstrate that WMA with reclaimed asphalt pavement could be produced and placed at lower temperatures while yielding mix properties and field compaction similar to those of conventional HMA and (b) to construct field test sections so that WMA and HMA performance could be compared side by side. These objectives were accomplished by producing and placing the WMA and by completing an in-depth sampling and testing program to compare the WMA and HMA paved on similar test sections and produced with similar methods (the only exception was production temperatures). The initial field performance of the WMA and HMA has been similar, and the long-term performance will be monitored. The WMA demonstration objectives were achieved, with the WMA exhibiting mix properties and field compaction similar to those of the HMA, with slightly lower initial stiffness, as expected. The potential rutting concern with WMA has not been an issue in this arid Southern California climate, and the sections placed on the haul road into and out of the Indio plant have been exposed to significant truck traffic.