Chloride Permeability and Deterioration Mechanism of Pavement Concrete Under Load–Temperature Coupling

The permeability of concrete pavement is the primary property in a durability system, and it is an important characteristic of concrete to prevent the invasion of water, gas and ions from the external environment and to resist the occurrence of various distresses, such as freeze–thaw damage and steel corrosion. To systematically investigate the effects of traffic load, ambient temperature and their coupling effects on the permeability of pavement concrete, the rapid chloride migration (RCM) method was used to determine the chloride diffusion coefficient, and then permeability models under a single field and coupling field were established. Finally, the microstructures were examined by scanning electron microscopy, and the deterioration mechanism for chloride permeability was analysed. The results show that under a single field with load or temperature, the chloride diffusion coefficient increases with the extension of the action time. As the load level increases, the compression process shortens, and the deterioration time advances. Load and freeze–thaw cycle coupling conditions have the most significant effect on concrete permeability. The dynamic fatigue load factor Kσ, the temperature factor KT, and the coupling field factor Kσ+T were introduced to correct the permeability models. High load stress and temperature expansion and contraction stress generated inside the concrete cause the energy to accumulate rapidly at the crack tip, causing the cracks to rapidly expand and interconnect with each other, which accelerates the deterioration of concrete durability.