Analysis of deformation behavior and microscopic characteristics of asphalt mixture based on interface contact-slip test

To analyze the slip deformation behavior of asphalt mixture, an interface contact-slip tester of asphalt mixture was developed in this investigation. Four evaluation indicators, including the maximum slip shear stress tau(sl), the slip shear strain epsilon(S), the slip failure modulusE(S) and the interface slip energy index E-T, were proposed. According to the correlation and sensitivity analysis, the optimum evaluation indicator was determined. By analyzing the variation coefficient of test results, the key experiment parameters were recommended. The gray binarization method of MATLAB software was adopted to process the slip failure surface of specimen, and the bonding ratio B-n was calculated to analyze the effect of asphalt bonding on strength formation. Based on the deformation curve, the slip deformation behavior of asphalt mixture and the influence factors were analyzed from the microscopic perspective. Results obtained indicated that the optimum test conditions are the loading head of 28.5 mm, the diameter of the support ring of 80 mm, and the loading rate of 5 mm/min. The tau(sl) was selected as the evaluation indicator of slip deformation behavior due to the best correlation with RD, good stability and sensitivity. The bonding effect of asphalt binder is greater than particle contact effect for suspended-dense asphalt mixture. The slip deformation of asphalt mixture can be divided into five stages, including densification, elastic deformation, viscoelastic deformation, initial cracking and plasticity slip deformation. The contact from coarse aggregates and bonding from asphalt binder can enhance the slip deformation resistibility. While the interference of fine particles and the lubrication of asphalt can accelerate the slip deformation of asphalt mixture. (C) 2020 Elsevier Ltd. All rights reserved.