Influence of Aggregate Gradation and Binder Type on Bond Slippage Failures in Stone Matrix Asphalt under the Coupled Effect of Temperature and Moisture

The performance of stone matrix asphalt (SMA) is strongly influenced by the stone-on-stone contact (SoSc) of coarse aggregate and the properties of the asphalt binder. This interfacial contact is key to the stability of the aggregate skeleton and is affected by factors such as aggregate gradation, binder properties, temperature, and moisture. This study examines SMA performance across various aggregate gradations (coarse, mid, fine), binder types [unmodified viscosity grades VG30 and VG40, and polymer-modified binder (PMB)], and conditioning states (dry and wet) at different temperatures (25°C, 40°C, and 60°C). The basic characteristics of the SMA mixes were evaluated using SoSc and binder stripping tests, whereas mechanical properties were assessed through Cantabro abrasion loss, tensile strength ratio, and aggregate bond slippage tests. The slippage tests measured slip failure using parameters such as slip load (Ps), slip modulus (SM), and slip energy index (SEI). Additionally, statistical and correlation analysis was conducted to explore the relationship between a mixture of mechanical characteristics with material physical properties. Notably, SMA mixes with PMB and fine aggregate gradation demonstrated higher resistance to bond slippage and greater aggregate mixture stability compared to mixes with VG40 and VG30 binders given all tested temperatures and moisture conditions.