Effect of warm mix additives and hydrated lime on viscosity and bonding–debonding behaviour of RET and PPA modified asphalt binder with aggregates

Higher energy requirement for asphaltic layer construction with asphalt binder containing reactive elastomeric terpolymer (RET) and poly phosphoric acid (PPA) can be addressed to a greater extent with the addition of warm mix asphalt (WMA) additives. However, moisture damage related problem is one of the concerns with such addition, which further aggravates with an increase in ageing level. The addition of lime may help in addressing moisture damage related problems in such cases. Previous research works show that based on the interaction between asphalt binder and particular WMA additive, the viscosity may undesirably increase also. So far, the influence of different WMA additives (wax, chemical surfactant (CS) and water-based (WB)) on the workability related properties of asphalt binder containing RET and PPA is not understood. It is also not clear if such warm mix additives with/without lime can help in improving long-term bonding with different aggregate types or not. Therefore, this research work aimed at identifying the appropriate WMA additive (with/without lime) which can help in (a) addressing the workability related problem and (b) improving long-term bonding with different aggregate types. To achieve this, different types of WMA additives (with/without lime) were added to RET and PPA modified binder. Viscosity-based measurement and chemical analysis using Fourier transform infrared spectroscopy were performed to understand workability and underlying chemical changes. Results indicated that although wax and CS-based warm mix additives can help in reducing energy demand, the addition of WB warm mix additive will have a negative impact from the workability perspective. Likewise, dynamic contact angle for different binder combinations was measured to evaluate the surface free energy components, which further helped to examine the long-term bonding with different aggregate types. Among different WMA additive types, the use of wax-based WMA additive was found to be most effective in improving compatibility with different aggregate types. Also, irrespective of the binder combination, the addition of lime improved the long-term bonding with considered aggregate types.