FEASIBILITY OF DEVELOPING SMA MIXTURES WITH ALTERNATIVE AGGREGATES

Abstract: Missouri specifies traprock as the primary coarse aggregate for Stone Matrix Asphalt (SMA) mixtures. However, its source is confined to the southeastern part of the state. Hence, this study aimed to identify locally available, cost-effective, and durable crushed coarse aggregates as alternatives to traprock for SMA mixtures. Multiple well-distributed aggregates in Missouri were collected and evaluated, including traprock (control), chat, gravels, steel slag, limestone, and dolomite. Aggregate screening and durability evaluations were first conducted to identify candidate aggregates meeting Missouri Department of Transportation (MoDOT) specification requirements. SMA mixtures were then designed with these aggregates in accordance with MoDOT current practices and specifications. Performance verification included Hamburg Wheel Tracking rutting test (HWTT) and IDEAL-CT cracking test to finalize the mix designs. Adjustments to binder content were applied if the volumetric optimum designs failed to meet performance requirements. The testing results indicated the feasibility of use alterantive aggregates for SMA mixtures. The SMA mixes with traprock and gravel could satisfy both volumetric and performance thresholds. Limestone and dolomite needed to be blended with chat as coarse aggregates in SMA mixes to pass volumetric limits. For SMA mixtures with steel slag, the binder contents from the volumetric designs had to be increased to meet the cracking resistance requirements.