DEVELOPMENT OF A FRACTURE MECHANICS-BASED ASPHALT BINDER TEST METHOD FOR LOW TEMPERATURE PERFORMANCE PREDICTION

Abstract

This Innovations Deserving Exploratory Analysis (IDEA) project developed of an improved low-temperature asphalt binder specification method. The report examines the effectiveness and/or deficiencies of current Performance Graded Asphalt Cement specification testing to predict low-temperature performance. It documents the development of a new and apparently more accurate specification approach that avoids the problems of current methods. The ability of various binder properties to predict transverse stress cracking in the field is assessed from a total of 17 pavement trial sections constructed in northern Ontario. The properties considered include those obtained from the bending beam rheometer and direct tension test as well as those from a more fundamental fracture mechanics-based test method. The results indicate that the currently used grading procedure does a reasonable yet not perfect job at predicting the ranking for most sections within each site but a poor job at the prediction of the onset of cracking. Physical aging of the binder is indicated as a likely cause for early distress. Other deficiencies in current specification testing, such as inadequate chemical aging in the pressure aging vessel and the absence of true fracture mechanics-based failure tests in both the brittle and ductile states, are evaluated and recommendations are provided to address most problems. The method as developed in this project was able to predict the onset of low-temperature cracking with much improved accuracy for five northern Ontario trial sections that showed early distress.