Admixture for rapid setting

摘要

The purpose is to provide an admixture for rapid setting with which it is possible to impart an adequate flash-setting property for practical use at low temperature without lowering the ability to actualize early strength and with far less lowering of the flash-setting property than in the past even when applied in a low-temperature environment such as below 10℃ in addition to imparting characteristics such as a rapid-setting property, improved medium- and long-term strength and long-term stability in a hardened state to a cement composition. The present invention relates to an admixture containing (A) 100 parts by mass of calcium aluminate, (B) 10-40 parts by mass of aluminum sulfate, and (C) 7.5-75 parts by mass of one or more selected from alkali metal sulfates and alkaline earth metal sulfates wherein the admixture for rapid setting is characterized by the (B) aluminum sulfate containing 0.03-3.5 mass% of alkali metal-containing substances in terms of alkali metal oxides.