Adhesion of aggregate-binder systems

Abstract

Adhesion is a difficult, but important phenomenon which needs to be addressed in the field of pavement engineering. A strong adhesion between the constituents of pavement and between the layers of the pavement is an indication of its durability. Many modern materials like rubber, fibre, epoxy binder, adhesion promoter etc., are used as a replacement or addition to the conventional bitumen and aggregate materials in pavement construction. The introduction of these materials thus require a better understanding of their adhesive properties, which influences to a great extent, the pavement performance. Since there are no standard tests available to quantify adhesion in pavement engineering, the study aims at developing a framework of easily implementable test procedure that can be used for the assessment of the adhesive bond between the different materials used in pavement construction. This was achieved by performing direct tension test on different types of aggregate-binder systems. As the presence of moisture is a known factor that affects adhesion, in turn affecting performance of the pavement, the study also concentrated towards this aspect. Three types of aggregates (porphyry, diorite and sandstone), in combination with four different binders (bitumen pen70/100, SBS polymer modified bitumen, polyurethane based binder and epoxy based binder) and two adhesion promoters (Type a and b, with variation in curing time) were tested in this study. They were subjected to low and high temperature and strain rates and the effect of moisture on these materials were also investigated. It was found from this study that the direct tension test was easily implementable, which could help the contractors and researchers in quantifying the adhesion between the various aggregate-binder systems.