Investigation of two Warm Mix Asphalt additives

In order to address pertinent issues in relation to the use of Warm Mix Asphalt (WMA) in pavement construction, it is imperative to understand the effects that such additives have on rheological and failure properties in service. In this study, two commercial WMA additives, a proprietary siloxane-based compound and an oxidized polyethylene wax, were added to a soft Roofing Asphalt Flux (RAF), a soft Recycled Engine Oil Bottom (REOB) tainted binder, and a somewhat harder binder containing 20% oxidized asphalt derived from Recycled Asphalt Pavement (RAP). Binders were aged according to standard Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV) protocols. Selected compositions were subjected to a period of extended PAV aging for 40 h. Standard and advanced rheological and failure tests were used to predict the performance of these binders in service. Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests according to Superpave™ protocols were done to determine performance grades. Extended BBR (EBBR) and Double-Edge-Notched Tension (DENT) tests were done to provide further insights into durability and strain tolerance, properties of utmost importance to assure long term pavement performance. The findings of this study show that the addition of the oxidized polyethylene wax WMA additive to REOB and/or RAP tainted systems can provide binders that are unstable and likely prone to premature and excessive low temperature failure in service. In contrast, the siloxane-based WMA additive appears to be a better choice to avoid premature low temperature and fatigue cracking distress.