Rutting Evaluation of Asphalt Mixtures Using Static, Dynamic, and Repeated Creep Load Tests

Abstract

Flow tests (flow number and flow time) are explicatory indices for the evaluation of the rutting potential of asphalt mixtures. This study investigates the rutting susceptibility of various asphalt mixtures subjected to static and dynamic creep tests. Four wearing course gradations were selected; and asphalt mixture’s specimens were fabricated using Superpave gyratory compactor. The flow tests were performed at a single effective temperature of 54.4 ${^{\circ }}\hbox {C}$ and a stress level of 300 kPa using asphalt mixture performance tester. Dynamic modulus (${\vert }{E}^{*}{\vert }$) test was conducted at different temperatures and frequency levels. The test results indicate that specimens of mixtures experienced tertiary flow state in the flow number (FN) test, but no specimen achieved tertiary flow state in the flow time (FT) test. Data smoothening technique was employed for removing the resonance from the raw test data. The performance of mixtures was compared using: (a) FN values; (b) number of cycles at which the 50,000 microstrains occurred; and (c) intercept obtained from regression analysis of total permanent strain. The observed accumulated axial strains at time of termination were used for comparison purpose of mixtures as tertiary phase was not achieved in FT tests. Three statistical models were developed of the different functional formulation—i.e. Cobb–Douglas, power and first-order multiple linear regression—using ${\vert }{E}^{*}{\vert }$, FN, and mix volumetric data. The laboratory results were used to rank the mixtures based on their resistance to rutting. The findings of the study are envisaged to facilitate the implementation of performance-based mechanistic-empirical pavement design approach.