Impacts of Aggregate Morphological Characteristics on Asphalt-Mixture Performance During Mixing

Abstract

Abstract This paper presents an experimental approach to investigate the influence of aggregate morphological characteristics on rheological properties of asphalt mixtures during mixing. Three different types of natural aggregates (limestone, gneiss, and basalt) and three types of glass aggregates (sphere, cuboid, and triangular prism shapes) were selected in the analysis. Digital image processing was applied to quantify geometrical features of aggregate, such as sieving diameter, shape index, and angularity. A mixing rheometer was developed for testing the rheological property of mixture during mixing period. The correlation between aggregate geometrical features and mixing rheological property was analyzed. Results show that the rank of average shape index value is limestone 2>basalt>limestone 1>gneiss for different types of natural aggregates with the same size, whereas the rank of average angularity value is limestone 1>basalt>limestone 2>gneiss. It was found that during the mixing period, the effect of sieving diameter or shape index of aggregate on the K value (the slope of the rotate speed-torque diagram line) is linear, which means K value increases as sieving diameter or shape index increases. For analyzing the effects of aggregate geometrical features on the rheological property of asphalt mixture during mixing, the gray relational analysis method was applied. The results show that the rheological property of asphalt mixture during mixing stage is more sensitive to sieving diameter and shape index, but less sensitive to angularity of aggregate.