| 摘要 |
PROBLEM TO BE SOLVED: To obtain an additive for cement, capable of extremely improving a compression strength by a small amount addition thereof by using a vinyl alcoholic polymer containing a specific amount of a specified structural unit. SOLUTION: This additive for cement comprises a vinyl alcoholic polymer including 0.1-45 mol.% structural unit of formulas I and II [R<1> to R<5> are each H or a <=8C hydrocarbon group; A is a divalent hydrocarbon (containing N, O and S); X is carboxyl, sulfonic acid group, hydroxy group, amide or a quarternary ammonium group]. The polymerization degree thereof is preferably <=60 mPa.s expressed by the viscosity of an aqueous solution having 4 wt.% polymer concentration. The average saponification degree of the vinyl ester part of the polymer is preferably >=70 mol.%. The addition amount of the additive for the cement is preferably 0.01-10 pts.wt. based on 100 pts.wt. cement, though the amount is different according to the amount of the used aggregate and water, and the ratio of the water to the cement is preferably 0.1-2.0. |
