Impact of laboratory mixing procedure on the properties of reclaimed asphalt pavement mixtures

Reclaimed asphalt (RA) mixtures have been extensively studied over the last decade, but there is no common procedure for producing high RA mixtures in the laboratory. This study evaluates the effect of asphalt mixing parameters, including rejuvenator incorporation method, mixing temperature, mixing time, and mixer equipment on properties of high RA content mixtures. The asphalt mixtures containing 60% RA material were evaluated using the indirect tensile strength test and the stiffness modulus test. In parallel, a stage extraction method was developed to obtain four layers of bitumen from loose mixtures and then further analyzing them using the dynamic shear rheometer and the Fourier transform infrared spectroscopy. The results identified mixing and heating temperature as an important parameter that must be carefully controlled to avoid excessive aging of the binder. It was also found that laboratory mixer equipment could affect the degree of blending and hence should be taken into account for comparing mixtures. Based on this study, a mixing procedure is recommended for producing high RA mixtures using the rejuvenator in the laboratory. (C) 2020 The Authors. Published by Elsevier Ltd.