Quantification of Coarse Aggregate Shape and Its Effect on Engineering Properties of Hot-Mix Asphalt Mixtures

This paper is aimed at quantifying coarse aggregate shape in an efficient manner and relating aggregate characteristics to mix properties. Digital image analysis was used to evaluate aggregate characteristics such as elongation, flatness, and other shape indices. The following particle shapes were selected for this study: cubical, rod, disk, and blade. Data showed that the morphological characteristics of coarse aggregate correlated well with the results of other indirect tests such as the particle index. Cubical particles possessed the best rutting resistance over the other shapes. Flaky and/or elongated aggregate in a mixture resulted in a lower resistance to shear deformation. The morphological characteristics of coarse aggregates found from image analysis were in good agreement with the engineering properties of hot-mix asphalt (HMA) mixtures. This paper presents a precise method to evaluate the aggregate characteristics in an HMA mix and demonstrates their effects on pavement performance.