Using Hydrophobic Coating on Aggregate Surfaces to Reduce Moisture Damage in Asphalt Mixture

Abstract

One of the proposed techniques of reducing moisture damage in asphalt mixture is to utilize coating on the aggregate surface. In this study, two types of additives as an aggregate surface modification, two types of aggregates, limestone and granite, along with an asphalt binder of 6–7 are the materials used to make asphalt mixtures. The thermodynamic concepts with cyclic loading have been used to evaluate the effect of using these materials. The results obtained in the study indicate that the hydrophobic coating on the surface of the aggregate has caused the acidic and basic components of surface free energy to reduce and increase, respectively. The changes have caused an increase in the adhesion of the asphalt binder aggregate and the better wettability of asphalt binder over the aggregate. The results of calculations based on the thermodynamic concepts indicate that aggregate surface coating has caused the reduction of debonding energy of the system and the desire for stripping. The results of dynamic modulus ratio in wet to dry conditions indicate that the use of aggregate coating decreases moisture damage of modified mixtures. The combination of thermodynamic concepts and cyclic loading results also shows that the coating on the surface of aggregates has led to reduction in the rates of stripping of the asphalt binder aggregate.