The diametral resilient modulus test is a procedure by which theresilient or elastic modulus of asphalt mixes can be determined. The resilient modulus is used as a fundamental input parameter in the layer theory for flexible pavements design. In the 1986 "aashto guide for design of pavement structures", the basis for materials characterization is the elastic or resilient modulus. The diametral resilient modulus test uses the repeated-load indirect tensile strength. Astm d4123-82 recommends that the resilient modulus (m sub r) be measured by applying stresses with magnitudes in the range of 10 to 50% of the indirect tensile strength of the specimens. It has been observed that the measured m sub r value depends on the percentage of indirect tensile strength used. For example, the value of m sub r obtained by testing at a load of 10% indirect tensile strength will be different than that obtained by testing at a load of 30% indirect tensile strength. A comprehensive test program investigated the previousobservation. To ensure that the difference between the m sub r values measured under various loadings is not statistical, several identical specimens were cast and the m sub r value for a particular loading was found by averaging the results. Also, three different asphalt contents were used to see if the change in m sub r is affected by the percentage of asphalt in the mix. The results indicate that the m sub r value measured using astm d4123-82 depends on the percentageof indirect tensile strength used as the load for testing. Also, the difference in the m sub r value was found to be less for mixes with higher asphalt contents. This paper appears in transportation research record no. 1317, Asphalt mixtures: design, testing, and evaluation 1991.
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