Volume 19, Issue 1 (January 1991)
Evaluation of Variability in Resilient Modulus Test Results (ASTM D 4123)
Samples of asphalt mixture were evaluated in the laboratory under various conditions to evaluate the repeatability of the resilient modulus test and the effect of stress on the measured resilient modulus. Some samples were prepared in the laboratory, others were obtained from in-place pavements that had been subjected to traffic. The independent variables included stress, test temperature, and maximum aggregate size.
Tests were repeated a number of times, and the data were analyzed by Statistical Analysis System (SAS) to investigate their repeatability. This study quantified the repeatability of the ASTM D 4123 resilient modulus test as a function of stiffness. The repeatability of ASTM D 4123 is low. A significant increase in the number of samples or number of measurements is required to improve the repeatability. Tests conducted at different stresses showed the resilient modulus to be stress sensitive. This indicated that stress should be specified in the test procedure. A correction factor was established for stresses differing from the recommended stress (15% of tensile strength) for test temperatures of 25 and 40°C.