Performance of WMA additives under freeze–thaw action

Warm mix asphalt (WMA) is an energy-saving and environmental-friendly technology with a broad prospect for application in highway construction. When compared with hot mix asphalt (HMA), WMA reduces the mixing and compaction temperatures (by 25–30°C) and hence reduction in energy consumption and emissions of harmful gases while maintaining the workability of HMA. In this study, three different additives, namely, Sasobit (organic wax additive), Evotherm (emulsion-based chemical additive) and Zycotherm (anti-stripping chemical additive) were evaluated for their laboratory performance under repeated weathering actions. HMA and WMA laboratory samples for Marshall stability, indirect tensile strength and tensile strength ratio were cast and subjected to 0, 2, 4, 6 and 8 freeze and thaw cycles (F&T cycles) in numbers and then tested. A comparative study was performed among HMA and three WMA mixes (control and weathered), that is, Sasobit-WMA (S-WMA), Evotherm-WMA (E-WMA) and Zycotherm-WMA (Z-WMA) to analyse the trend of variation in strength and properties with varying F&T cycles. Aggregate coating and compactibility were also analysed.