The Effect of Loading Pulse Related Parameters on the Resilient Modulus of Asphalt Mixes using Viscoelastic Theory

Resilient modulus of asphalt concrete is one of the key input parameters in design of flexible pavements using mechanistic-empirical methods. Resilient modulus of asphalt mixes in laboratory is usually measured by applying a haversine pulse with a constant duration which could not be an actual simulation of stress pulse in field. In this paper، the effect of various parameters of loading pulse consisting of the shape، duration; the ratio of the pulse duration to rest period as well as the number of pre-conditioning cycles on the resilient modulus of asphalt concretes was investigated. For this purpose، complex modulus of four different asphalt mixes were utilized and after validating results of numerical method based on viscoelastic theory، resilient modulus of these mixes was computed under different conditions. Results of this research showed that the shape and duration of loading pulse affects the resilient modulus of asphalt concrete، significantly and these parameters should be considered in analysis and design of flexible pavements. In addition، the ratio of the loading duration to rest period must be equal to 9 or greater values to achieve the minimum accuracy of 3% in measurement of resilient modulus. In this paper، two models with high generalization ability have been presented to predict the resilient modulus of asphalt mixture with respect to loading duration and temperature. By taking advantage of these models، it is possible to carry out a limited number of resilient modulus tests and calibrate the model for the desired asphalt mix and then the resilient modulus of asphalt mix can be predicted in any temperature and loading frequency، accurately. It was also observed that there is a good relation between the resilient modulus under haversine pulse and resilient modulus under square pulse and after calibration of model in basis of limited number of experimental tests and known resilient modulus under Haversine pulse، the resilient modulus under square pulse can be predicted، accurately.