A Review on the Performance of Additives in Warm Mix Asphalt

Road construction involves emission of CO₂, greenhouse gases, and ultimately leads to global warming. India is one of the major contributors to the CO₂ emissions and is in the process to reduce it by 35% in the coming 15 years. Roads in India are paved with conventional hot mix asphalt (HMA) technique, which involves heating at elevated temperature (approximately 150-170°C). HMA production needs a large amount of energy and the release of CO₂ emission is also high. Therefore, an attempt should be made to develop and adopt alternative technologies for road construction and maintenance to reduce the consumption of fuel, heating temperature, aggregates, and binder. Warm mix asphalt (WMA) is a modern technology to discourse this issue, which reduces the energy requirement and the CO₂ emission. It reduces the heating temperature by 25-35% compared to HMA. In return, WMA reduces the CO₂ emission by 30% and saves valuable energy for sustainable development. WMA tends to provide a complete aggregate coating, high workability, and compaction at a lower temperature. The temperature reduction of WMA is achieved by decreasing the asphalt viscosity by adding some additives. In general, these warm mix additives are classified into two groups, namely water foaming and organic, based on the manufacturing process. The main aim of this review paper is to the elucidated overview of different technologies used in the manufacturing of WMA, to evaluate the performance of different additives, which are best suitable for the Indian conditions, and a detailed description with cost analysis and life-cycle analysis.