Enhancing concrete sulfate resistance by adding NaCl

This study aimed to investigate the effects of adding NaCl on sulfate resistance of ordinary concrete. Concrete specimens were fabricated with 0.1%, 0.5%, and 1.0% NaCl (by weight of cement) and subjected to 10% Na2SO4 solution. The visual appearance of concrete was observed regularly. The compressive strength, ultrasonic velocity, and SO42- ion concentrations in concrete were also determined. Results indicated that incorporating NaCl in concrete can effectively inhibit the entry of external SO42- ions, consume the corrodible cement hydration products, and reduce corrosion product formation in concrete, thereby substantially enhancing the sulfate resistance of concrete. Under either full or partial immersion corrosion test, adding NaCl can reduce the compressive strength loss of concrete, lessen the development of concrete damaged layer thickness, and prevent the decline of concrete's relative dynamic modulus. The sulfate resistance of concrete is approximately linear with NaCl content, particularly for concrete under partial immersion sulfate attack condition.