Evaluation of Workability and Mechanical Properties of Stone Matrix Asphalt Mixtures Made With and Without Stabilizing Additives

Abstract

Stone matrix asphalt (SMA) is a gap-graded mixture which is the combination of higher concentration of coarse aggregate and binder mortar. The coarse aggregate skeleton provides the mixture with stone-on-stone contact, giving it strength, while the high binder content mortar adds durability. The mortar is typically composed of fine aggregate, mineral filler, binder, and a stabilizing additive. A stabilizing additive such as cellulose fibers, mineral fibers, or polymers is added to SMA mixtures to prevent draindown of the mastics. In addition, it has the potential of reinforcing and improving the tensile strength of SMA mixtures. This paper presents the findings of performance of SMA mixtures with and without stabilizing additive. Superpave mix design, draindown, fatigue, rutting, workability, and moisture-induced damage properties of the SMA mixtures was evaluated. Three types of stabilizing additives (B, S, and V), one nominal maximum aggregate size (NMAS) 13.0 mm, and an unmodified asphalt binder (VG-30) were used in the study. Results indicate that the addition of stabilizing additive controls binder draindown and mix design properties of SMA mixtures satisfies the IRC SP 79 requirements. Resistance to rutting, fatigue, and moisture-induced damage of SMA with stabilizing additives were higher than SMA mixture without stabilizing additive. Further, SMA mixture without stabilizing additive takes less energy for densification compared with SMA mixture with stabilizing additives.