Development of a wireless field tack coat tester to evaluate in-situ tack coat performance

Abstract

Tack coats are the asphalt cements applied between pavement lifts to provide adequate bond between the two surfaces. The adhesive bond between the two layers helps the pavement system to behave as a monolithic structure and improves the structural integrity. The absence, inadequacy, or failure of this bond result in a significant reduction in the shear strength resistance of the pavement structure and make the system more vulnerable to many distress types, such as cracking, rutting, and potholes. In this study, a wireless field tack coat testing system, the Oregon Field Tack Coat Tester (OFTCT), was developed to predict the long-term performance of tack coat bonds based on the results of tests conducted during construction. The OFTCT device was further used to evaluate the impact of pavement surface cleanliness before tack coat application on bond strength. In order to reduce the tack coat’s curing time and control temperature during testing, an adjustable heat gun, and environmental chamber were developed. Results of the analysis showed that the correlation between OFTCT and laboratory shear test results is statistically significant (R2 = 0.52) and OFTCT can be effectively used to predict the long-term performance of tack coat bonds. It was also determined that the OFTCT can be successfully utilised in the field as a test to quantify the cleanliness of the pavement surfaces before tack coat application.