Evaluating bonding-debonding properties and moisture susceptibility of chemical-based warm mix asphalt binder and mixes

The construction of asphalt mixes has recently used a variety of warm mix asphalt (WMA) to encourage a cleaner atmosphere and improved working conditions. Due to lower construction temperature during WMA construction, there could be improper or less heating of aggregates, and aggregate may contain some moisture. The existence of moisture may influence the bonding between aggregate and asphalt binder, which may affect the moisture susceptibility of the asphalt mix. Therefore, there is a need to understand the bonding-debonding properties and moisture susceptibility of asphalt binders and mixes at the materials selection stage. The present study uses surface free energy (SFE) and indirect tensile strength (ITS) to evaluate bonding-debonding properties and moisture susceptibility of WMA binders and mixes. A Static Contact Angle (SCA) analyser was used in the lab to measure the SFE components of unmodified (VG30), polymer modified (PMB40), and crumb rubber modified (CRMB60) asphalt binders. Further, the asphalt binders were modified using chemical based (CB) WMA. The ITS test was performed to understand the moisture susceptibility of asphalt mixes. Notably, the bonding-debonding properties of asphalt binder and asphalt mixes will change with time. To address the same, the present study considered the evaluation of mixes in short-term aged (STA) and long-term aged (LTA) conditions to simulate the field conditions. CB-modified the asphalt binder, which showed encouraging results with increased work of adhesion and energy ratio (ER), indicating a stronger bond between the asphalt binder and basaltic aggregate. The PMB40 + CB asphalt binder exhibited the lowest work of adhesion in wet conditions and a higher ER, suggesting the highest resistance to moisture damage. The tensile strength ratio (TSR) results also showed that adding the CB additive increased the TSR values in both short STA and LTA samples, and all samples except the VG30 sample met the minimum requirement of 80% TSR.