Adhesive properties of asphalts and aggregates in tropical climates

In Central and South America, pavement deterioration due to moisture is high. The deterioration is directly related to the compatibility between the asphalt and aggregates, as well as the cohesiveness of the asphalt matrix. The affinity between these materials affects how well the bond will behave in the presence of water, and therefore the susceptibility of the asphalt mixture to moisture in the long term. It is well accepted that traditional tests for assessing moisture damage are not necessarily representative of high moisture conditions, such as those present in Colombia and Costa Rica. Therefore, it is imperative that methods to quantify the actual moisture susceptibility of hot-mix asphalt be adopted and implemented in local specifications. In order to characterise the true adhesion properties of regional materials, both physicochemical and mechanical analysis has been implemented to determine the moisture susceptibility of different binder–aggregate combinations typically used in Costa Rica and Colombia. The effect of antistrip additives on the water resistance of such combinations was also evaluated. The asphalt bond strength test was applied to mechanically determine the adhesive and cohesive strength of the binder–aggregate pairs. In addition, the measurement of physicochemical properties such as surface free energies of aggregates and binders allowed the determination of work of adhesion, cohesion and debonding of asphalt from the aggregate surface in the presence of water. A correlation between the physicochemical and the mechanical properties was found for most of the cases.