Development of a pull-off test to measure the bond strength of bituminous emulsions

Abstract

It is now generally recognized that good adhesion between different layers of an asphalt pavement is of great importance for its lifetime. Poor interfacial bond strength leads to a higher probability of cracking, early fatigue failure, delamination, etc. Many factors have an impact on the bond strength between layers. Despite all these factors, it is important that the performance of tack coats can be evaluated independently of the asphalt complex for the purpose of comparison, optimization and selection of these products. Consequently, the development of a reproducible quantitative test method to characterize the bond strength of a bituminous tack coat is crucial. This paper describes the development and validation of a pull-off test on a bituminous tack coat film. In a first step, the test device, the breaking and curing conditions and the pull-off test conditions were optimized to ensure that failure occurs within the film and not at the interface between the film and the contacting plates of the test device. In a second step, a validation of the pull-off device and procedure was conducted by comparing the results of the pull-off tests for different emulsions with direct tensile tests carried out on multi-layer asphalt samples in which the same tack coats were applied. This paper is an overview of BRRC’s work in this field.