Comparing and correlating various laboratory rutting performance tests

Abstract

The loading magnitude, loading frequency, contact area, confinement condition and sample size vary for different laboratory rutting performance tests. Hence, it is necessary to compare how several rutting performance tests evaluate same mixtures under similar testing conditions. This research compared Cooper wheel tracking test (CWTT), Asphalt pavement analyzer test (APA), and Repeated load axial test (RLAT). Thirty wearing course and eight base course mixtures were tested according to standard procedures at the temperature condition of 50°C. In order to compare relative performance of the selected tests, time required to achieve an absolute rut depth of 1 mm, was used. It was concluded that APA test took the maximum time to attain 1 mm rut depth, as compared to CWTT and RLAT. This conclusion was further endorsed by relatively more significant linear correlations (in terms of R²) developed between asphalt mixture design parameters i.e. stability, optimum binder contents, voids in mineral aggregates, voids filled with asphalt and theoretical maximum specific gravity versus APA output parameter of rut depth; as compared to the correlations developed for CWTT and RLAT output parameters. Quadratic function correlation was ultimately developed between the output parameters of CWTT, APA and RLAT; and it was found that the most significant correlation existed between CWTT rut depth vs. RLAT strain/cycle as translated by R².