Evaluation of rutting potential of flexible pavement structures using energy-based pseudo variables

Abstract

Permanent deformation is a long-term irrecoverable depression accumulated in the wheel path when the flexible pavement is subjected to heavy loads at high temperature, which can be simulated using the vertically loaded wheel test (VLWT) in the laboratory. The objective of this study is to develop a new approach to analyze the vertically loaded wheel test results based on the elastic-viscoelastic correspondence principle. The energy-based pseudo variables are proposed to perform rutting evaluation of asphalt mixtures in the VLWT.Four types of styrene-butadienestyrene modified asphalt mixtures were prepared to conduct the undamaged compressive dynamic modulus test at different temperatures. Then the master curves of dynamic modulus for these mixtures were converted to get the relaxation modulus. The innovative VLWT for four types of two-layer structure with different asphalt mixture combinations were performed to investigate the rutting development. After that, a new mechanical-empirical rutting prediction model was introduced to predict the rutting development for each layer in the two-layer structure. The energy-based pseudo variables including pseudo strain, pseudo strain rate and dissipated pseudo strain energy (DPSE) were introduced to correlate with the rutting resistance.The results show that the developed mechanical-empirical rutting prediction model is proficient in capturing the rutting development of a two-layer structure of asphalt mixtures measured by a vertically loaded wheel tester. The rutting contributions of the top and bottom layers can be separated using this model. Compared with the total strain, the pseudo strain which removes the viscoelastic effect, is more accurate to evaluate the permanent deformation in a cyclic loading condition. The DPSE increases with the increase of loading cycles and rut depth. Two typical stages with an inflection point can be observed from the test results which indicate that the faster to reach the inflection point, the better rutting performance will be achieved.