The use of warm-mix asphalt (WMA) has increased substantially in recent years. Given the significant differences to hot-mix asphalt (HMA) practice and fears of a moratorium on the use of the technology if unexplained problems occur, the California Department of Transportation decided to follow a more conservative approach, by designing and implementing a phased comprehensive study. Phase 1 investigated rutting behavior of three different WMA technologies against an HMA in an accelerated loading test with associated laboratory testing assessing rutting and fatigue performance and moisture sensitivity. Phase 2 investigated the effects of the three WMA technologies on moisture sensitivity in an accelerated loading test. Phase 3 is investigating the use of seven different WMA technologies in rubberized asphalt in the same testing program. This paper provides an overview of the California WMA study as well as the results of the first two phases. (a) For the covering entry of this conference, please see ITRD abstract no. E220164.
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