Abstract:This paper investigates laboratory test methods for resilient modulus of foamed asphalt mixes. By comparing test results from different laboratory test methods, the effects of various stress states are identified. The indirect tensile resilient modulus test and the free-free resonant column test were found to yield stress states irrelevant to pavement structures, and to greatly overestimate resilient modulus. Triaxial resilient modulus test results showed that the role of foamed asphalt treatment is to transform the material behavior from that of typical unbound granular materials to that of partially asphalt-bound materials. Flexural beam tests indicated that when subjected to tension, the resilient modulus of soaked foamed asphalt mixes can be very low. Since triaxial and flexural beam tests each characterize one of the two most important stress states relevant to pavement design, test results from these two methods need to be combined to be used in design.