Effect of Mixing Time and Temperature on the Homogeneity of Asphalt Mixtures Containing Reclaimed Asphalt Pavement Material

Abstract

Laboratory-produced reclaimed asphalt pavement (RAP) material, new aggregate, and tinted new binder were mixed (RAP proportion: 40%) with 12 different combinations of mixing temperatures and times, based on which circular specimens of various thicknesses were fabricated and then subjected to multi-direction indirect tensile stiffness modulus (ITSM) testing and color image analysis. Statistical calculations including average value, coefficient of variation, standard deviation, and range were carried out to investigate the effects of different mixing conditions on the homogeneity of asphalt mixtures containing RAP. The results show that the deterioration of homogeneity of asphalt mixtures containing RAP was mainly caused by the asynchronous breaking of clusters. The mixing temperature was decisive in determining the resistance of clusters to breaking, and for mixing conditions chosen in this study, the resistance increases with the increase of mixing temperature. Short mixing time might lead to a phenomenon of “momentary homogeneity,” in which clusters were not broken and the blending degree between aged and new binder was low.