| 摘要 |
PROBLEM TO BE SOLVED: To provide a modified gypsum used for cement-based injection materials and injection materials for prereceive construction method, control of the reactivity of anhydrous gypsum and obtained from natural anhydrous gypsum, which cannot be used so far, capable of using for cement admixture as cement injection materials or cement quick hardening materials. SOLUTION: The modified gypsum is obtained by coating fatty acids, which are shown as (RCOO)nX (R is a saturated or unsaturated hydrocarbon; (n) is 1 or 2; and X is hydrogen, an alkali metal, or an alkali earth metal) and one or more kinds of lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, behenic acid, oleic acid, or their salts. The cement admixture is composed of the modified gypsum and calcium aluminate and used for cement compositions.
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