A Notched Disk Crack Propagation Test for Asphalt Concrete

Abstract

Mitigating cracking distress in asphalt concrete is a major challenge for road agencies around the world and assessment of fracture and crack propagation in asphalt concrete has proven an equally difficult task. Many of the current fracture mechanics based tests available to assess asphalt concrete are based on the assumption of elastic behavior and it is difficult to extend the analysis to assess fracture at intermediate pavement service temperatures. In addition, the difficulty of monitoring crack length and propagation has led to asphalt concrete related test methods that focus solely on fracture mechanics parameters with little regard for crack speed. The C* Line Integral test was identified as a promising test to evaluate crack propagation and obtain the fracture mechanics based, C* parameter that considers time-dependent creep behavior of the materials. The test is not well defined in previous literature and lacks a test procedure and detailed data analysis method. This paper describes test method development of a notched disk crack propagation test for asphalt concrete, the C* Fracture Test (CFT). Development included specimen geometry, test temperature variation study, and a refined data analysis procedure. Two distinct plant produced asphalt mixtures were also subjected to the crack propagation test and results indicated that the CFT was able to distinguish improved crack resistance potential of an asphalt-rubber mixture compared to an unmodified asphalt mixture. The asphalt-rubber mixture was more resistant to crack propagation than the unmodified mixture. Continuous monitoring of the field test sections is necessary to validate the laboratory findings.