Nano-clay and styrene-butadiene-styrene modified bitumen for improvement of rutting performance in asphalt mixtures containing steel slag aggregates

Abstract

Nanoparticles have exhibited a promising potential in enhancing the bituminous materials’ performance. As a cost-effective material, hot mix asphalt (HMA) has been employed in pavement structure for a long time. Their viscoelasticity however results in various modes of failure under different temperature profiles and loading stress. Rutting of asphalt pavements is considered as the most prominent distress factor under almost all climate conditions. Moreover, steel slag has been employed for improvement of asphalt mixture properties as it exhibits excellent physical features. In this content the aim of the present research is to analyze improving effects of nano clay and styrene-butadiene-styrene (SBS) on the rutting resistance of modified steel slag asphalt mixture (SSAM). Various tests were employed to investigate the asphalt binder properties and the rheological characteristics of modified bitumen among which penetration grade, softening point, ductility and dynamic shear rheometer (DSR) can be mentioned. Marshal Test was applied to examine the optimum bitumen content in conventional and modified asphalt mixture. The rutting resistance against was then evaluated through two tests: repeated load axial (RLA) test and wheel track test. The results indicated respective improvement of toughness and viscosity by an average of 25% and 101% upon addition of nano-polymer which enhanced the bitumen rheological characteristics while reducing the penetration grade. The asphalt rutting resistance and rutting depth exhibited some improvements as well.