Investigate the adhesion behavior and mechanisms of salty ice on bitumen surface based on the ice heterogeneous nucleation kinetics and quasi-liquid layer theory

Abstract

Understanding the freezing and adhesion properties of de-icing salt solutions is crucial for optimizing de-icing strategies in infrastructure and minimizing damage to the environment and road materials from de-icing salts. This work employed a customized ice-adhesion testing system to investigate the evolution of ice-adhesion strength (IAS) of NaCl and NaCH₃COO salts on bitumen surfaces under different concentrations and temperatures. The icing phase transition process and thermodynamic properties of the salt solution were analyzed using multi-channel temperature setting and differential scanning calorimetry (DSC). Moreover, the adhesive mechanisms of salty ice were elucidated based on heterogeneous nucleation kinetics and quasi-liquid layer (QLL) theory. The results show that even a 0.5 wt% salt solution can lower the IAS to approximately 40–50 % of the value observed with pure water. The concentration of salt solution required to achieve adhesive failure is temperature-dependent. Additionally, the latent heat of fusion (h_f) of NaCl solutions at concentrations from 0.5 to 2.5 wt% sequentially decreased by 45.3 J/g, 63.1 J/g, 79.9 J/g, 90.0 J/g, and 117.6 J/g compared to pure water. The freezing temperature (T_F) of 2.5 wt% NaCH₃COO and NaCl solutions dropped by 1.3 °C and 1.6 °C, respectively. Based on the ice nucleation kinetics, lowering the T_F and h_f leads to an increase in the nucleation energy barrier (ΔG*), with IAS showing a logarithmic correlation with ΔG*. Furthermore, the QLL transitions from droplets to a thin film as salinity increases, further reducing the contact area and IAS. This work offers novel insights into the freezing progress and adhesion mechanisms of salty ice, aiming to reduce maintenance costs and environmental damage from de-icing salts.