Effects of Wax-Based, Chemical-Based, and Water-Based Warm-Mix Additives on Mechanical Performance of Asphalt Binders

Production of hot-mix asphalt (HMA) involves high mixing and compaction temperatures, which leads to the emission of greenhouse gases and high fuel consumption. Recently, various warm-mix asphalts (WMAs) have been used for production of asphalt mixes to promote a cleaner environment and better working conditions. Although selected WMA additives may be beneficial in reducing the mixing and compaction temperatures of a binder, they may also adversely affect rheological properties of asphalt binders and thus may discourage users from fully utilizing their potential. The current study evaluates effects of different types of WMA additives on mixing and compaction temperatures, rut resistance, and fatigue performance of an AC-30 binder. A control AC-30 was modified with three WMA [Fischer Tropsch (FT) wax based, water based (WB), and chemical surfactant based (CS)] additives in varying dosages. First, the effect of WMA additives on the viscosity of the AC-30 binder was measured, followed by the effect on mixing and compaction temperatures. Thereafter, rutting and fatigue performance of the AC-30 with and without different WMA additives was evaluated using multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS), respectively. Further, effects of WMA additives on Superpave high-temperature performance grade (PG) of AC-30 was also determined. The paper also discusses changes in chemical composition of AC-30 binder after addition of WMA additives, which was evaluated using the Fourier transform infrared spectroscopy (FTIR) technique. All three WMA additives (FT, WB, and CS) decreased mixing and compaction temperatures of AC-30, except the addition of 8% WB. Superpave high PG of AC-30 did not alter with the addition of WB and CS. Fatigue and rutting performances of AC-30 degraded after addition of WB and CS. The effect of FT was found to be promising not only in enhancing rutting and fatigue performances but also to bump the Superpave high PG of AC-30. Considering reductions in mixing and compaction temperatures and other rheological performances, the effective dosages of FT, WB, and CS for AC-30 binder were found to be 1, 4, and 1%, respectively.