Diffusion Study Using Fine-Aggregate Matrices Comprised of Reclaimed Asphalt Pavements and a Bio-Based Recycling Agent

Abstract

The use of reclaimed asphalt pavements (RAP) is an increasing trend nowadays due to environmental and economical appeal. The use of higher percentages of RAP might result on cracking issues associated with the performance of the aged binder. In order to enable the use of RAP, recycling agents of distinct natures have been used to enhance the performance of recycled asphalt mixtures. Diffusion of the recycling agent into the RAP binder is a complex phenomenon influenced by many variables such as temperature and time of exposure to heat. This paper aims to investigate the influence of the diffusion time and mixing temperature on the fatigue performance of fine-aggregate matrices (FAMs) because more studies at this scale are needed to broaden the knowledge on the diffusion process and to improve the techniques for mixture recycling. In this study, the diffusion process is evaluated by comparing the fatigue performance of FAM samples comprised of 40% RAP and bio-oil with a target air void of 5.0%±0.5%. The analyzed samples were produced under 10 different scenarios, varying the diffusion time (0, 40, 80, 120, and 160 min) and temperature (135°C and 160°C). Linear-viscoelastic properties and fatigue parameters of the FAMs were monitored by means of tests carried out in a DSR, and by applying the simplified viscoelastic continuum damage (S-VECD) theory. The best fatigue performance of the FAM mixtures was achieved for a diffusion time of 80 min at 135°C. The temperature of 160°C also presented the best performance for the diffusion of 80 min. Longer diffusion times did not improve the fatigue performance due to prolonged aging, and the impact of extended aging on the linear-viscoelastic properties showed that the higher the mixing temperature the greater the impact of aging on the material stiffness and damage evolution rate.