CONCRETE ADDITIVE AND CONCRETE COMPOSITION FOR REINFORCING EARLY STRENGTH

摘要

A concrete additive for improving early strength of concrete composition is provided to be used as a binder for the concrete composition and to give improved initial strength to the concrete composition while not reducing flexibility thereof by comprising inorganic material containing SO3, K, Na and Si ions in specific molar ratios as well as gypsum source. The additive includes: 25-85wt.% of gypsum source; and 15-75wt.% of inorganic material containing SO3, K, Na and Si ions in molar ratios of 5 to 20 : 1 to 10 : 5 to 20 : 2 to 10. The gypsum source comprises 30-98% of gypsum anhydrite, 1-35% of gypsum hemihydrate and 1-35% of gypsum dihydrate. The additive is used to form the early strength concrete composition in a ratio of 0.2 to 5% relative to a binder. The binder further contains 5-70% of industrial byproduct selected from fly ash and furnace slag fine powder relative to total weight of the binder, as well as cement.