Evaluating Performance of PPA-and-Elvaloy-Modified Binder Containing WMA Additives and Lime Using MSCR and LAS Tests

Abstract

Modification of asphalt binder with Elvaloy (Elv) and polyphosphoric acid (PPA) has been reported to have better performance. However, such modification may increase mixing and compaction temperatures of asphalt binder. Furthermore, the positive effect of PPA may get neutralized with the addition of lime, which can lead to inferior performance of asphalt binders. Recently, different types of warm mix additives (WMA) are being introduced to reduce production and construction temperatures of asphalt binder. However, the effects of WMA additives with and without lime on various rheological response of PPA + Elv modified asphalt binder is not well understood so far. Therefore, the present study was undertaken to evaluate the rutting and fatigue performance of PPA + Elv modified asphalt binder (referred as Control binder) containing three WMA additives (water, chemical, and wax-based) with and without lime. The multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests were conducted to capture the rutting and fatigue performance of asphalt binders, respectively. The results show that rutting and fatigue performance of Control asphalt binder decreased with the addition of chemical and water-based WMA additives. The performance of Control asphalt binder further deteriorated when these WMA additives (chemical and water) were used with lime. Interestingly, the addition of wax showed higher rutting resistance and similar fatigue life as that of Control asphalt binder. The addition of lime with wax additive showed improved rutting resistance and reduced fatigue life compared with Control asphalt binder. Regardless of the type of WMA additives, the addition of lime decreased the fatigue life of Control asphalt binder. The adverse effect of lime was prominent when used with wax compared with water and chemical-based WMA additives. Furthermore, the addition of WMA additives increased the stress sensitivity of Control asphalt binder. The stress sensitivity of asphalt binder further increased when wax and chemical-based WMA additives were used with lime. However, use of water-based WMA additive and lime reduced the stress sensitivity of Control asphalt binder. Overall, it can be concluded that the performance of Elv + PPA modified asphalt binder depends largely on the type of WMA additives and their combination with lime.