Surface-Modified Nanoclays for Enhancing Resistance to Moisture Damage in Hot Mix Asphalt

Abstract

Previous research indicated that nanomaterials have potential in improving pavement properties, particularly moisture resistance. This study evaluated the effectiveness of nanoclays in enhancing the resistance of Hot Mix Asphalt (HMA) to moisture damage and compared its performance to standard modifiers. Asphalt binder modified using four additives was tested using a Dynamic Shear Rheometer (DSR) before and after being aged in a Rolling Thin Film Oven (RTFO): two surface-modified nanoclays and two liquid anti-stripping chemicals (HP+ and LOF 6500). The DSR and RTFO tests showed that the two nanoclays had a stiffening effect on the binder, while both liquid antistripping agents had the opposite effect, decreasing both the elastic and complex modulus of the binder. After RTFO aging, similar trends were observed, except the binder had become much stiffer in all cases. HMA designed employing the Superpave mix design procedure was tested for moisture sensitivity in accordance with AASHTO T-283. The dry tensile strength for the two nanoclays and LOF 6500 modified mixes were higher than the control mix. However, all modified mixes resulted in wet tensile strengths that were higher than the control. The tensile strength ratios for all modified mixes were also higher than the control and exceeded the Superpave mix design method minimum of 0.80. Evaluation of these additives in the field would further benefit asphalt pavement research.