Use of digital images for fracture performance evaluation of asphalt mixtures

Abstract

To address the inadequate understanding of the effects of micro characteristics of aggregates on the anti-crack performance of asphalt mixtures, this study used digital image processing techniques and a semi-circular bending test to investigate the anti-crack performance from the perspectives of crack evolution and micro characteristics of aggregates. The results show that specimens with the same gradation but better anti-crack performance exhibit the following micro characteristics: a smaller angle between the coarse aggregate long axis and the horizontal direction, and better angularity and more uniform distribution of the coarse aggregate. Moreover, for specimens with different gradations, a single increase or reduction in the coarse aggregate content is not conducive to the anti-crack performance of the asphalt mixture. After the asphalt mixture undergoes cracking, the gradation with less coarse aggregate content has weaker resistance to continuous cracking, and increasing the coarse aggregate content can hinder crack development. When the raw materials and external factors are consistent, grading is the main factor influencing the fracture performance of the asphalt mixture, and the micro characteristics of the coarse aggregates significantly affect the mixture fracture performance only when the mixtures have the same gradation. These findings can provide a theoretical basis and valuable suggestions for pavement engineering in terms of improving the micro characteristics of aggregates and thus enhancing the anti-crack performance of asphalt mixtures.