Sulfates in Portland cement: characteristics and influence on concrete

• 作 者: QIANJueshi;MAYing;YANGSha;HUANGYongbo;
• 机 构: College of Materials Science and Engineering, Chongqing University, Chongqing 400045, China
• 出 处: The 14th International Congress on the Chemistry of Cement (
• 发表日期: 2015年期

　　Sulfates in Portland cement mainly come from clinker, including alkali sulfates, anhydrite, sulfates present in silicates and aluminates, and from added gypsum and its dehydration products.The content and dissolution property of sulfates associated with their impacts on concrete properties are discussed.Alkali sulfates, with a quick release, have great influence on early properties of concrete, including the setting, the early strength development and the compatibility with superplasticizers.Anhydrite rarely exists in clinker;but, the amount of it would highly increase with using fly ash and CFBC ash in cement, and much attention should be paid.Sulfate in belite presents in a minor amount in cement, but it may release at later ages and favor the later strength development and durability of concrete.A possibility is also proposed that in belite-rich cement, the sulfate in belite may pose a risk of causing DEF-induced expansion with experiencing an elevated temperature.