Developing a load-temperature master curve for the permanent deformation of asphalt mixtures by the power function model

Abstract

The multiple repeated load test, consisting of 189 test conditions from different combinations of three test temperatures, three confining stresses, three loading frequencies and seven vertical stresses, was developed to obtain the permanent deformation parameters. Three asphalt mixtures with different asphalt binder types were designed to conduct this multiple repeated load test. A linear fitting process was applied to each increment to obtain the slopes of cumulative strain growth. A multiple linear regression method was utilized to analyse the effects of different test conditions on the permanent deformation characteristics of asphalt mixtures. A power function model was proposed to establish the load-temperature master-curve of the slope versus reduced vertical stress. Results show that neat asphalt mixtures have the largest slope distribution, followed by PG 70–22 mixtures and PG 76–22 mixtures. Based on the multiple linear regression methods, higher vertical stress, higher temperature, lower confining stress, and lower loading frequency could increase the slope of permanent deformation growth from strongly to weakly. Fitting parameters α and β from the power function model could be utilized to rank the rutting resistance of different asphalt mixtures. The shifted parameters were divided into temperature part, confining stress part, loading frequency part and vertical stress part. The slope of cumulative strain growth under varying test conditions could be successfully shifted to a power function model, which could be used to predict the rutting resistance of asphalt mixtures under a broad range of test conditions.