Strain response and creep behavior of asphalt mixture based on multi-damage fractional visco-elasto-plastic constitutive model

Abstract

This study aims to accurately represent the strain response and cumulative strain of asphalt mixture by constitutive model and to further investigate its creep behavior. For this, dynamic loading tests of asphalt mixture were conducted under different temperature and stress conditions, and the investigation into the strain response variations showed that different mechanical properties of asphalt mixture have different evolutionary processes. Then, the fractional visco-elasto-plastic constitutive model was constructed to express the strain response under intermittent haversine loading. Furthermore, by analyzing the evolutions of the different mechanical properties, the multi-damage fractional visco-elasto-plastic constitutive model was developed by introducing multiple relative damage variables to reflect different mechanical properties. Subsequently, analytical solutions for strain response and cumulative strain were derived, and a methodology for identifying model parameters was proposed. The results demonstrated that effectiveness of model application was excellent: fitting correlation coefficients averaged above 0.997 for cumulative strain curves under 15 test conditions; fitting correlation coefficients for tens of thousands of strain response were mostly clustered above 0.98. Creep behavior of asphalt mixture expressed by MD-FVEP model was the dynamic evolution where viscous strain decreased and viscoplastic strain increased. The steady-state creep stage resulted from dynamic equilibrium between viscous strain gradually decreasing and viscoplastic strain gradually increasing. Evolutions of viscous and viscoplastic relative damage variables showed clear environmental correlations.