Characterization of Permanent Deformation of Asphalt Mixtures Based on Shear Properties

Abstract

A permanent deformation model was developed in this study on the basis of shear properties of asphalt mixtures, such as cohesion and friction angle. Two types of laboratory tests—triaxial compressive strength test and repeated load permanent deformation test—for three types of asphalt mixtures with various volumetric properties were performed to correlate the shear properties with rutting performance. A rational approach was proposed to determine flow number (FN) more accurately with the Hoerl model and roughness penalty method. It was observed from the test results that the FN was not accurate enough to differentiate the rutting characteristics of asphalt mixtures. Unlike the FN, the shear stress to strength ratio accurately identified the mixture rutting performance. Because the same value of the shear stress to strength ratio produced the same level of permanent strain regardless of mixture type, the ratio could be used as the rutting criterion for a performance-based mix design. A permanent deformation model was established on the basis of the shear stress to strength ratio. The proposed model is able to successfully predict the permanent deformation of the various mixtures without changing the model coefficients and could predict the permanent deformation all the way up to failure, including the tertiary flow.