Chemical Treatment of Quartzite Aggregates and Its Effect on Moisture Susceptibility of Asphalt Mix

Abstract

Quartzite aggregates have poor adhesion with asphalt binder due to the higher silica content present in the mineral composition. Apart from conventional asphalt mixture testing methods, the surface free energy (SFE)-based adhesion evaluation method is most widely used in recent times to predict compatibility between aggregate and asphalt binder and moisture susceptibility in asphalt mixtures. This study tried to improve quartzite aggregates’ adhesion properties by modifying the aggregates’ surface with a nano-organosilicon (NOS), and two silane coupling agents (SCA) were used in modifying the aggregates’ surface. Results showed that surface modifications by chemical treatments reduced the aggregate’s SFE by increasing the aggregate nonpolar components to make a better bond with asphalt binder, which is also a non-polar material. From tensile strength ratio (TSR) results, it is found that the asphalt mixtures prepared with surface-modified aggregates showed better resistance to moisture damage with a 12%–15% increase in TSR. SFE indices like adhesion energy and energy ratio (ER) also showed significant improvement in adhesion between aggregates and asphalt binder, even in the presence of moisture. The ER values were above acceptable limits after surface treatments and showed a 100% increase compared with control mixes. SCA-1 and SCA-2 treatments effectively improved moisture damage in hot-mix asphalt with quartzite aggregates. One-way ANOVA was used to predict the effect of treatment methods and aggregate types on conventional TSR values and advanced SFE indices. The statistical results proved significant improvements in TSR and ER after the treatment of aggregates, but aggregate types do not make significant changes.