Effect of aggregate morphologies and compaction methods on the skeleton structures in asphalt mixtures

Abstract

Aggregate skeleton is a significant factor that determines load transfer paths in asphalt concrete. This study prepared asphalt mixtures with different aggregate morphologies, gradations and compaction methods. Digital image processing technique was used to quantify aggregate skeleton structures including orientation, distribution and contact properties of aggregate. Indirect tensile strength and fatigue tests were conducted to explore the relationship between skeleton indexes with mechanical properties. The results show that gradation types have a significant impact on average contact number and internal structure index of asphalt mixtures. In a certain gradation and abrasion times, the average contact number of samples manufactured by roller compactor are larger than that of Marshall compactor samples. Moreover, the abrasion has a negative effect on average contact number as the loss of aggregate morphologies would adversely impact aggregate interlocking. The results of indirect tensile strength and fatigue test are basically consistent with the results of average contact number and internal structure index, which shows that the short-term and long-term mechanical properties of asphalt mixtures are directly affected by aggregate contact characteristics.