Gradation and Moisture Effects on Resilient Moduli of Aggregate Bases

Resilient modulus (M R ) which properly characterizes the load-deformation response of pavement materials under traffic loading, is evaluated. The M R values due to three different gradations and three different moisture contents were investigated for the Richard Spur and the Sawyer aggregates, which are commonly used in Oklahoma as the subbase or base materials of roadway pavements. The three gradations were finer limit, median, and coarser limit, as specified by the Oklahoma Department of Transportation for Type A aggregate. The three moisture contents selected are optimum moisture content (OMC), 2 percent below OMC, and 2 percent above OMC. To investigate the variability of the test results, six duplicate M R tests under identical conditions were performed for each case by using the AASHTO T294-94 method. Furthermore, the material properties, K1 and K2, which are required input in the AASHTO pavement design equation, were evaluated for the M R values obtained. Finally, multiple linear regression models for predicting the M R values of the two aggregates were established.