“Aging and Restoration of Asphaltic Materials: Chemo-Physical Analysis Based on Experimental Multi-Scale Approach”

Advisor: Dr. Yong-Rak Kim

Asphalt binder is a highly heterogeneous organic material; thus, its aging and restoration phenomena are very complex. Since the effects of aging and restoration on behavior of asphaltic materials are considered chemo-physical and mechanical in multiple length scales, a multiscale experimental approach can provide some significant insights to the understanding of the complex phenomenon. This study aims to investigate the laboratory aging protocol and compare it with the field aging process as well as to examine the short and long-term effects of different restorators on the mechanical, rheological, and chemical characteristics of asphaltic materials. To meet the objectives of this study, a multiscale experimental method was proposed and conducted. Three different binders (i.e. two virgin and one field aged binder) and restorators, a blend of different source of aggregates, and reclaimed asphalt pavement were selected/used. Test results from binders aged showed that the mechanical/rheological properties and chemical analyses of the laboratory aged binders presented good correlations between aging indicators (e.g. carbonyl and colloidal index). It was also found that the long-term laboratory aging process has a limited ability to properly simulate long-term field aging. The kinetic analysis indicated that the chemical-transformation process due to binder laboratory aging was closely associated with diffusion, not a chemical reaction. Test results from binders restored due to additives showed that the addition of restorators improve viscoelastic properties and fatigue resistance while they diminish rutting resistance. However, the petroleum-based restorator might contribute to maintaining the performance of the binder after another round of long-term aging. The chemical analysis indicated that the tall oil restorator contained many hydrogen bond-forming functional groups (-OH), which may increase the moisture sensitivity of the mixture. Outcomes from this study are expected to help more sustainable and energy-efficient civil infrastructure engineering.