Influences of the joint action of sulfate erosion and cementitious capillary crystalline waterproofing materials on the hydration products and properties of cement-based materials: A review

Cementitious capillary crystalline waterproofing materials (CCCW) can improve the sulfate resistance of cement-based materials. This paper reviews the influence of the joint action of sulfate erosion and CCCW on the hydration products and properties of cement-based materials. It was found that the reaction process and products of sulfate erosion and CCCW with cement-based materials remain unchanged. However, due to the competition of sulfate and CCCW for Ca2+ in cement-based materials, the reaction products of both are reduced. Among them, the consumed Ca2+ by CCCW is originating from its active substances, which can react with Ca2+ from CaCO3 and CaSiO3, etc., to fill the pores of cement-based materials. The consumed Ca2+ by sulfate is stemming from the reaction between Ca2+ and SO42−, which can generate gypsum or ettringite and deteriorate the properties of cement-based materials. According to the thermodynamic principle and the influence of CCCW on Ca2+ content in cement-based materials under sulfate erosion, it was proved that the crystallization reaction of CCCW is dominant. Consequently, CCCW can improve the properties of cement-based materials under sulfate erosion. CCCW in clean water can heal 0.4–0.5 mm cracks in cement-based materials, while sulfate attack will reduce the healing degree of CCCW on cement-based materials. Under sulfate erosion, CCCW can heal 0.3 mm cracks in cement-based materials. •Influences of the joint action of sulfate erosion and CCCW on the properties of cement-based materials were summarized.•Influences of the joint action of sulfate erosion and CCCW on the hydration products were summarized.•The competition between sulfate erosion and CCCW for Ca2+ was summarized.•Influences of sulfate erosion on cement-based materials repaired by CCCW were summarized.