California warm-mix asphalt study: an overview of research, pilot studies and implementation

The use of warm-mix asphalt (WMA) has increased substantially in recent years and considerable funding has been allocated to research on the topic. Some road authorities implemented its use based only on results from limited testing, while other states adopted a more conservative approach. 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 (Caltrans) 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 control in an accelerated loading test with associated laboratory testing assessing rutting and fatigue performance and moisture sensitivity. A number of controlled pilot studies, primarily focused on the use of WMA in open-graded friction courses, were also constructed during this phase. Phase 2 investigated the effects of the same three WMA technologies on moisture sensitivity in an accelerated loading test. Phase 3 investigated the use of seven different WMA technologies in rubberized asphalt following the same testing program used in Phase 1. An investigation into emissions reductions during paving was also undertaken in this phase. The findings from the research were used to prepare a WMA technology approval process, specification language, and a framework for statewide implementation that resulted in over one million tons of warm-mix asphalt being placed on state highways in the 2011 paving season. Although the use of warm-mix asphalt in a project must be reported in California, use statistics were not monitored in the 2012 and 2013 paving seasons given that the technology is now considered to be fully implemented.


  • English

Media Info

  • Pagination: 8p
  • Monograph Title: 11th Conference on Asphalt Pavements for Southern Africa: CAPSA15, 16-19 August 2015, Sun City, South Africa

Subject/Index Terms

Filing Info

  • Accession Number: 01597083
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ATRI
  • Created Date: Apr 22 2016 11:13AM