Effect of Aggregate Gradation and Morphology on Porous Asphalt Mixture Performance

Abstract

Previous studies have reported the effects of aggregate gradation and angularity on the pavement performance of hot asphalt mixtures, while little work has been done on the role of aggregate gradation and morphology related to porous asphalt (PA) mixture performance. The primary objective of this article was to evaluate the effects of aggregate gradation and morphology on the mechanical properties and volumetric characteristics of PA mixtures. Ten PA mixtures, prepared by regulating the percentages of aggregate passing 9.5-, 4.75-, 2.36-, and 1.18-mm sieves and using two types of aggregate sources, were compared by evaluating air voids, shear strength, Marshall stability, indirect tensile strength, and micromorphology. The analytic hierarchy process method was used to analyze the priority weights of various influencing factors on PA mixture performance. The results indicate that aggregate gradation had significant effects on the performance of the PA mixtures. There was an excellent linear relationship between the percentages of aggregate passing the 9.5-, 4.75-, and 2.36-mm sieves and the respective mixture air voids. Increasing the proportion of 4.75–9.5-mm aggregate particles in the PA mixes did not contribute to its moisture damage resistance. The percentage of 2.36–4.75-mm aggregate fractions was the most critical influencing factor for the PA mixtures’ mechanical properties and volumetric characteristics. Additionally, aggregate morphology does affect PA performance. The permanent deformation resistance and moisture resistance were notably improved as the aggregate sphericity value increased. Based on the test results, the mechanical properties and volumetric characteristics of PA mixtures can be optimized depending on engineering requirements by regulating the aggregate gradation and type.