Abstract: Sulfate attack is a pivotal factor affecting the durability of cement-based materials, which will not only shortens the service life of the materials, but may even threaten the safety of the structure. During the process of sulfate attack, erosive products, including ettringite, gypsum, and thaumasite are continuously formed, resulting in various forms of damage such as expansion, cracking, softening, and spalling of the material. Since the formation conditions of diverse erosion products as well as the erosion mechanisms of cement-based materials are significantly different, wherein the erosion mechanism is a crucial basis for guiding the prevention of sulfate attack in engineering practice. Therefore, the formation and stability conditions of diverse erosion products and the corresponding erosion mechanism have become the focus of this project. The ettringite form of sulfate attack is well studied and established in the existing researches. The ettringite is considered as the main erosion product formed under the high alkaline condition, and when it grows in micro pores, expansion even cracks will occur in materials. The corresponding expansion mechanisms include water swelling theory, crystallization pressure theory and solid-state reaction theory. In addition, the research on the prevention of ettringite form of sulfate attack indicated that the expansion caused by ettringite can be controlled effectively by reducing the contents of tricalcium aluminate in cement. In recent years, serious damage to concrete structures caused by the formation of thaumasite has been reported in many countries. Therefore, the thaumasite form of sulfate attack has aroused increasing attention. Currently, it is generally believed that the formation of thaumasite mainly leads to the mudification and decomposition of material, but the formation conditions are relatively complex and only happen in some harsh environments. Gypsum is another common corrosion product of cement-based materials formed by sulfate attack, and its formation impacts on the durability of cement-based materials as well. The studies demonstrate that the high concentration of the sulfate solution contri-butes to the better formation of gypsum, yet later find that the pH value of the solution remarkably affects the formation and stability of gypsum, while the solution temperature, ion species and immersion regime have a certain impact on the formation of gypsum as well. Due to the chemical composition of gypsum is relatively simple and does not contain aluminum phase, the utilization of a common anti-sulfate attack method does not effectively suppress the formation and deterioration of gypsum. The formation of gypsum is often accompanied by dissolution and decalcification of the hydration products, which leads to softening and detaching of the material, but there is still considerable controversy over the issue of gypsum expansion. In this paper, the influencing factors of the formation of gypsum in concrete under sulfate attack are reviewed, and its growth position and decalcification caused by gypsum are summarized. Finally, the expansion of gypsum is discussed as well.
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