RESILIENT MODULI OF AGGREGATE MATERIALS: VARIABILITY DUE TO TESTING PROCEDURE AND AGGREGATE TYPE

The variability of resilient modulus (RM) values is investigated for six aggregate materials that are commonly used in Oklahoma as subbases or bases. Six RM tests each under identical conditions for two aggregate types and three tests each for four aggregate types were performed according to the AASHTO T292-91I procedure to investigate the variability of the test results. All specimens were prepared at the same gradation that meets the Oklahoma Department of Transportation specifications for Type A materials. The effects of testing procedures on RM values were investigated for two selected aggregate types by conducting six tests each using the AASHTO T292-91I and T294-92I testing procedures. The variability of test data and consistency of the RM values are investigated within a statistical framework. The variability of RM values obtained ranges from 19 to 26% in terms of maximum coefficient of variation (MCOV). The results indicate that consistently higher RM values are obtained when using the T294-92I testing method than when using the T292-91I testing method, and the degree of increase depends on the type of aggregate. The variability of RM values due to testing procedure was found to be higher than that due to aggregate source. One aggregate type experienced a lower MCOV when using T294-92I than when using T292-91I, but the other aggregate type exhibited an opposite trend. Overall, the RM values range from 41.3 to 261.8 MPa, depending on bulk stress, material type, and testing method, and they are slightly lower than those reported in the literature.