Moisture susceptibility of chemically treated quartzite aggregates in hot mix asphalt

Abstract

Quartzite aggregates are widely available siliceous aggregates that are weak in adhesion with asphalt binder. This study focused on improving the moisture susceptibility of hot mix asphalt (HMA) using chemical treatments to quartzite aggregates. Hydrated lime (HL), nano-organosilane additive (NOS), and two silane coupling agents (SCA) were used to treat aggregates. Moisture susceptibility was investigated using different tests such as retained stability, indirect tensile strength (ITS), and fracture energy. Scanning electron microscope (SEM) analysis was conducted to identify surface modifications and the treatment mechanisms, it was observed that HL treatment forms the rough surface over the aggregate by precipitating CaCO3, on the other hand, SCA treatments make perfect hydrophobic nano-layer over the surface of the aggregates. After the boil test, Coating retention was quantified with image processing, and coating retention was increased to greater than 95 percent compared to control mixes (i.e. 40–45 percent). The tensile strength ratio (TSR) of HMA with treated aggregates was increased by 20–25 percent to control mixes. HL and SCA-1 showed better TSR and fracture energy ratio (FER). Based upon the study results, it was concluded that chemical treatment methods can able to reduce the moisture induce damage of HMA with quartzite aggregates.