Influence of Warm-Mix Additives and Reduced Aging on the Rheology of Asphalt Binders with Different Natural Wax Contents

Abstract

This paper presents the results of our study to investigate the influence of natural wax in asphalt binders, warm-mix asphalt (WMA) additives, and reduced short-term aging on viscosity, stiffness, susceptibility to permanent deformation, fracture resistance, and thermal cracking resistance of asphalt binders. We used two controls to differentiate between the influence of WMA additive and that of reduced aging on the rheology of asphalt binders. The asphalt binder used in a WMA undergoes reduced short-term aging and consequently has relatively reduced stiffness compared with the binder in a similar hot-mix asphalt (HMA). Results indicate that certain WMA additives compensate, whereas others aggravate the initial reduced stiffness of asphalt binders used in WMA. Short-term aged binders with high natural wax content demonstrated strong interactions with some of the WMA additives and increased susceptibility to permanent deformation. In most cases, pressure aging vessel (PAV) residues of binders with WMA additives had similar or lower fracture resistance compared with PAV residues of binders that were subjected to conventional short-term aging. Results from this study suggest that strategies—such as the use of recycled asphalt—to compensate for the initially reduced stiffness of binders in WMA mixtures must be carefully selected for each asphalt binder–WMA additive pair to avoid an adverse impact on the fatigue cracking performance of the mix.