Asphalt Mix Cracking State of the Art: Materials, Design, and Testing

Abstract

Mix testing that can properly characterize cracking of asphalt pavements is one of the most relevant present day issues for the industry. The 91st Annual Meeting (AM) of the Association of Asphalt Paving Technologists (AAPT) provides evidence to this effect as, in the assessment of the authors, cracking was far and away the meeting’s prevailing theme. The 91st AAPT AM began with a Leading Edge Workshop (LEW) that focused exclusively on cracking and associated test methods, and a key factor in most of the remaining content presented at the meeting was cracking. This paper stemmed from the 91st AM LEW in response to cracking’s perceived prevalence in the minds of so many AAPT members. The primary objective of this paper is to provide the state of the art in asphalt mix cracking from the perspective of the authors and to use this perspective to explain what has been accomplished in the cracking arena and what needs to be accomplished. First, a historical perspective beginning in the mid-1950s and ending in present day is presented that is generally divided into pre and post Superpave mix design. With this historical perspective as a reference, emphasis is shifted to the AM and LEW as they pertained to cracking. A set of prevailing themes was established and used as a segue into discussion of cracking test methods (first what has been accomplished and then what needs to be accomplished). Six areas were identified by the authors where advancement needs to be made with regard to mitigation of cracking: 1) closing the gap between the state of the art and the state of practice; 2) evaluating rapid mix test methods usable during production; 3) emphasizing education; 4) improving reliance on accelerated pavement testing; 5) improving cracking models; and 6) performing large test programs where parallel testing occurs on comparable mixes by way of several test methods.