不同外加剂对混凝土抗裂性能的影响

Influence of different admixture on crack resistance of the concrete

采用改进的平板试验法研究了减水剂、减缩剂、膨胀剂对混凝抗裂性能的影响。试验结果表明掺入萘系减水剂,混凝土的初始裂缝推迟,但单位开裂面积和最大裂缝宽度都要大于未添加减水剂的混凝土;减缩剂能推迟裂缝出现时间,减小混凝开裂面积及最大裂缝宽度;在早期养护不充分的情况下,膨胀剂使初始开裂时间有所提前,单位开裂面积增大,但是适量的膨胀剂能减小最大裂缝宽度;同时掺入膨胀剂和减缩剂,其抗裂效果较单掺入膨胀剂并没有大幅的提升,较单掺入减缩剂的混凝土反而有所降低。

Studied on the influence of water reducing admixture, shrinkage reducing admixture and expansion admixture on crack resis- tance of the concrete through the improved slab test.The experimental results shows that the water reducing admixture will increase initial cracking time, unit crack area and the maximum crack width of the concrete;the shrinkage reducing admixture will decrease initial crack- ing time, unit crack area and the maximum crack width;under the condition of insufficient early curing, the expansion admixture can make the initial cracking time advance, the crack area increased, but the proper amount of expansion admixture can reduce the maximum crack width.The effect of the crack resistance of the concrete which mixed with expansion admixture and shrinkage-reducing admixture at the same time, did not significantly improved compared with the concrete with only expansion admixture, however even worse than the con- crete with only shrinkage reducing admixture.