EFFECTS OF WARM ASPHALT ADDITIVES ON ASPHALT BINDER AND MIXTURE PROPERTIES

With increasing concerns of global warming and increasing emissions, the asphalt industry is making a constant effort to lower its emissions by reducing the mixing and compaction temperatures of the asphalt mixture without affecting the properties of the mix. Several proprietary chemicals are available in the industry that can help reduce the mixing and compaction temperatures. A significant reduction of required heat can be achieved in most cases. While some studies have been conducted to evaluate the properties of warm mix asphalt; properties of binders and mixtures, in fresh and aged conditions, containing these chemicals have not been studied in great detail. This research presents the results of tests conducted to evaluate the properties of warm mix asphalt binders and mixtures, in fresh and aged conditions. This study was broadly classified into two; study of binder properties, where 3 binder sources were studied with and without Asphamin® and Sasobit® as the warm asphalt additives; and study of mixture properties, where two binder sources and two aggregate sources were studied with and without Asphamin® and Sasobit® as the warm asphalt additives. The results of the study indicated that the two warm asphalt additives affected the binder and mixture properties differently. It was observed that the addition of Sasobit® significantly reduced the viscosity of the binders at 135 °C and 120 °C, whereas, the addition of Asphamin® did not have any significant effect on the viscosity of the binders at 135 °C and 120 °C. However, both the additives improved the mid-temperature rheological properties of the binders namely creep response, creep recovery, and the complex modulus. Tests on binders aged in the laboratory and binders extracted from freshly mixed and aged mixtures indicated that the WMA binders extracted from WMA mixtures had significantly lower viscosities and G* / sin δ compared to binders extracted from HMA and binders aged in the RTFO at 163 °C, indicating that the lower mixing and compaction temperatures reduce the aging of the binders. When the mixture properties were compared, it was observed that Asphamin® reduced the MR values of the mixes, Sasobit® reduced the rut depths of the mixes, and both the additives improved the TSR of the mixes. When the laboratory aged mixtures were compared, either of the two warm asphalt additives did not have significantly different rutting depth, TSR or MR values compared to the control mixes