Study on the influence of cooling rate on the freeze-thaw deterioration characteristics of salt-contaminated earthen site

The coupled effects of freeze-thaw cycles and salt are key drivers of deterioration in earthen heritage site. This study investigates the influence of cooling rate on deterioration by conducting simulated freeze-thaw cycles on salt-contaminated earth specimens. Macro- and micro-deterioration characteristics, along with salt crystallization behavior, were analyzed to elucidate the mechanism by which cooling rates induce pore damage through water-salt phase transformation. Results indicate that NaCl causes more severe damage than Na₂SO₄ during freeze-thaw cycles, with the extent of deterioration increasing at slower cooling rates. Salt and earth particles coagulate into aggregates, increasing surface strength, an effect is more pronounced at slower cooling rates. Additionally, cooling rates affect the distribution and crystal growth of salts, with slower rates forming larger and more complete crystals. These findings enhance understanding of the deterioration process and provide valuable insights for conservation strategies to mitigate freeze-thaw and salt-induced damage in earthen sites.