conducted an experimental study on expansion and destruction of concretes immersed in sulfate solution with different concentrations, and identified internal expansive forces generated by delayed ettringite formation (DEF) and gypsum as the main reason for expansion. With the aid of scanning electron microscopy (SEM) and X-ray diffraction (XRD), Chen et al. Based on the damage evolution in concretes subjected to sulfate attack, Shanahan and Zayed found that the changes of material expansion and compressive strength can be used to evaluate the concrete durability under corrosion attack. Moreover, the mix proportion of concretes is a key parameter for their resistance to damage. For example, Boyd and Mindess studied compressive and tensile strengths of several types of concretes and showed that, when concrete is exposed to a sulfate corrosive environment, the water-to-cement ratio should be taken into account for verification of its durability. Although much effort has been devoted to investigating sulfate attack in concretes, there is still a lack of full understanding on its physical mechanism because it is a complicated physicochemical destructive process. Corrosion damage in concretes is an important influential factor on the durability of concrete structures in a marine environment (e.g., ).
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