Analysis of Low-Temperature Rheological and Mechanical Properties of Steel Slag Asphalt Mixture Based on Direct Tensile Test

Abstract

Due to the high resource requirements for specimen preparation and testing equipment, the direct tensile test method is seldom used to study the cracking behavior of asphalt mixture at low temperatures. In this study, three asphalt mixtures were prepared in which all of the basalt or part of the basalt and basalt aggregate was replaced by steel slag. Through the direct tensile creep test and direct tensile relaxation tests including the measurement of creep rate, cumulative strain change rate, and relaxation time, the variation law of rheological properties of low-temperature steel slag asphalt mixture was analyzed and the variation law of viscoelastic properties was explored. Meanwhile, based on the traditional viscoelastic constitutive model, the creep compliance and relaxation modulus were fitted. The mechanical response of the transformation from creep compliance to relaxation modulus of steel slag asphalt mixture was analyzed by a numerical method. The results show that, with the decrease of temperature, the creep rate εs and cumulative strain change rate of the three asphalt mixtures gradually decline, and the relaxation time gradually increases. In particular, when the temperature was reduced from −20°C to −30°C, the cumulative strain change rate of all three asphalt mixtures reached the minimum, which was less than 10%. Moreover, none of them relax to 75% σ0 within 3,600 s at −30°C. The mixture specimens with steel slag replacing all basalt exhibited the best low-temperature deformation adaptation performance under different temperature conditions. Mixture specimens with basalt as aggregate have the worst low-temperature deformation adaptation performance. The relaxation modulus obtained by the measurement of creep compliance is similar to that obtained by testing, and the relaxation modulus calculated through the direct tensile test is more accurate.