Deterioration of concrete freezing-thawing in different salts solution

The frost resistance of concrete subjected to 3.5% NaCl solution, 5%, 7%, and 10% Na₂SO₄ solution and seawater were investigated by quick freeze-thaw test. There were two criteria, the relative dynamic modulus of elasticity (RDME) and the mass of scaling, for evaluating the frost resistance of concrete. The results showed that scaling was the main characteristic of deterioration when concrete subjected to freeze-thaw cycles in 3.5% NaCl solution and seawater, whereas RDME had little change. When freezing and thawing in Na₂SO₄ solution, concrete failed because of internal damage and surfaces of lower strength concrete specimens appeared local swelling and scaling before failure. Concentration of Na₂SO₄ solution had influence on frost resistance of concrete: deterioration of concrete in 5% or 7% Na₂SO₄ solution was severe but slower when the concentration reached to 10%. Entraining air into concrete was the best method to improve the durability of concrete subjected to freeze-thaw cycles in all solutions.