| 摘要 |
PURPOSE:To obtain the title improver of one-pack liq. type exhibiting long gel time and capable of providing a high strength, by adding a monovalent alkali metal and calcium carbonate to an alkali silicate. CONSTITUTION:An improver prepd. by adding a monovalent alkali metal hydroxide and calcium carbonate having a particle size of 20mum or less to M2O.nSiO2 (wherein M is a monovalent alkali metal). Although Na, K, Li or the like can be used as the alkali metal to be added, Na is most suitable. The added alkali metal ionizes the silicate to give an activated alkali silicate (or a salt of silicic acid). The SiO2 to Na2O molar ratio of the silicate is pref. 0.7-2.0, particularly pref. 0.7-1.5. When the molecular ratio exceeds 2.0, the reaction of the silicate with calcium carbonate is insufficient, which makes it difficult to prepare excellent crystals. When consideration is given to the dispersibility of calcium carbonate and the preparation of an improver capable of providing a higher strength than that provided by conventional improvers, the molar ratio is pref. lower than 1.5. |
