Strain Response Regularity and Viscoplastic Model of Asphalt Binder and Asphalt Mastic Based on Repeated Creep and Recovery Test

Abstract

As a viscoelastic material, asphalt mixture mainly derives its viscoelastic properties from the asphalt binder. This research aims to comparatively evaluate the strain response regularity of asphalt binder and asphalt mastic through repeated creep and recovery (RCR) test indices. The influences of the asphalt binders, filler volume fraction and filler type on the strain response indices: deformation recovery rate (R) and non-recoverable creep compliance (Jnr) were analyzed according to the RCR test results of the mastics. The viscoplastic (VP) model for characterizing asphalt binder and asphalt mastic behavior was described. The parameters of the model were determined in the prepeak region of the loading, under different stress levels. Simultaneously, the prediction accuracy of the developed VP model was verified, and the applicability of the model was analyzed. The filler volume fraction has the most significant effect on the strain response of the mastic. The R value decreases but the Jnr value increases with the filler volume fractions. The average non-recoverable percent Jnr value decreases with the aging degree increasing. Compared with the unaged (OR) mastics, the Jnr values after rolling thin film oven test (RTFOT) and pressure aging vessel (PAV) decreases by more than 20% and 88%. The improved strain hardening VP model can better simulate the viscoplastic strain response of the asphalt binder and mastic in the RCR test, and the prediction accuracy was greatly improved. The prediction accuracy slightly decreased with creep time increasing. Further research shows that the improved strain hardening VP model is also applicable to the calculation of viscoplastic strains in the RCR test of the asphalt binder and the mastic after RTFOT aging and PAV aging. The improved VP model increases from 5% to 92% off the reference line to within 3%.