Effects of deicing agents on asphalt–aggregate interfacial adhesion and moisture stability: insights from surface free energy theory

To elucidate how different deicing agents degrade interfacial interactions in asphalt pavements, 90# base asphalt and SBS-modified asphalt with limestone and basalt aggregates were immersed in 25 wt% solutions of six deicing agents (NaCl, NaNO2, KAc, CaAc2, MgAc2, and urea). Surface free energy (SFE) parameters before and after immersion were obtained via contact angle measurements, and the cohesion work of asphalt plus the adhesion work, stripping work, and energy ratio (ER) of asphalt–aggregate systems were calculated. Results showed that deicing agents markedly reduced the total SFE of both asphalt and aggregates, with NaCl exhibiting the strongest effect and MgAc2 the weakest. Under identical erosion conditions, SBS-modified asphalt retained higher cohesion than base asphalt, and alkaline limestone exhibited stronger interfacial adhesion with asphalt than basalt. MgAc2 caused the smallest reduction in adhesion work, the lowest stripping work, and the highest ER, indicating the best-preserved interfacial bonding and moisture resistance. In contrast, NaCl and urea significantly weakened interfacial adhesion, increased stripping work, and reduced ER values, elevating the risk of moisture damage. These findings provide a theoretical basis for selecting low-corrosive deicing agents and designing erosion-resistant asphalt mixtures.