A new blister test to measure bond strength of asphaltic materials

Approximately 60% of the U.S. annual national transportation budget is spent on pavement maintenance. One of the most common pavement maintenance treatments is crack sealing. Sealing pavement cracks significantly extends pavement service life, provided that an appropriate sealant is selected and properly installed. However, adhesion loss often leads to premature sealant failures. The adhesion quality and field performance of bituminous crack sealant cannot be predicted because the current test method (ASTM D6690) is empirical and only provides a qualitative measure of bond strength. Hence, there is a great need for test methods based on bituminous sealant rheology, which can better predict field performance. This paper presents the development of a pressure-loaded blister test and apparatus to measure the adhesion of asphaltic materials, and bituminous crack sealant in particular. The blister test provides two fundamental parameters of the tested material, the interfacial fracture energy, which is related to the adhesion strength, and the modulus. In this test, a fluid is injected at a constant rate at the interface between the substrate (aggregate or a standard material) and the adhesive (crack sealant) to create a blister. The fluid pressure and blister height are measured as a function of time. Using these two quantities and utilizing the classical plate and fracture mechanics principle, the interfacial fracture energy is calculated.