Asphalt Rubber Technology Information Center
Caltrans Experience with Asphalt-Rubber Concrete – An Overview and Future Direction
Van Kirk, Jack, P.E., Caltrans  
Key Words:
Dense graded asphalt
Caltrans has considerable experience with the use of rubber in dense graded asphalt concrete hot mix (DGAC).  This
experience began in 1978 and has continued to the present.  The experience to date has indicated that the most
effective use of rubber is in asphalt-rubber concrete (ARC).
On the early projects, Caltrans compared equal thickness of RAC to conventional DGAC.  The ARC has outperformed the
conventional mixes on these projects, but the question of cost-effectiveness is difficult to answer since most of the
projects are still in service.  In 1983, a project was constructed using reduced thickness RAC (as compared to the design
thickness for the conventional DGAC).  This project, which is still being evaluated, has shown that thinner sections of
ARC can outperform thicker sections of conventional DGAC.  But the question that remains is, what reduction in
thickness can be made and still provide the desired service (design) life.
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