混凝土减缩剂抗裂性能研究

Investigation on crack resistance of shrinkage reducing admixture for concrete

为推广应用混凝土减缩剂,通过测定掺减缩剂砂浆的干燥收缩、圆环开裂性能和掺减缩剂的混凝土平板抗裂性能,评价了JG-SRA混凝土减缩剂的抗裂性能,并通过测定掺减缩剂的模拟水泥石孔溶液的表面张力,分析了减缩剂的作用机理。结果表明,JG-SRA的砂浆减缩率大于35%,圆环开裂时间比基准砂浆推迟34 h,混凝土裂缝控制率大于50%。减缩剂通过降低水泥石孔溶液表面张力,提高内部相对湿度,减少水分蒸发,有效地提高了混凝土体积稳定性。

In order to apply shrinkage reducing admixture for concrete, crack reslstauce of JG-SRA type shrinkage reducing admixture was evaluated by testing dry shrinkage and ring experiment of mortar with JG- SRA, and concrete plate experiment. Mechanism of shrinkage reducing admixture was analyzed by surface tension measurement of modeling pore solution of cement paste. Experimental results indicate that more than 35% dry shrinkage of mortar with JG-SRA is reduced, and crack time of mortar ring is delayed for 34 hours compared to basic mortar. No less than 50% crack can be controlled by use of JG-SRA in concrete. Lower surface tension of pore solution of cement paste containing shrinkage reducing admixture results in higher internal relative humidity,less water evaporation, and volume stability of concrete may be efficiently enhanced.