减缩剂和PVA纤维对超轻水泥复合材料收缩开裂行为的影响

Effect of Shrinkage Reduce Admixture and PVA Fiber on Shrinkage Cracking Behaviors of Ultra Lightweight Cement Composite

研究了减缩剂和聚乙烯醇(PVA)纤维对超轻水泥复合材料(ULCC)收缩开裂行为的影响,测试了ULCC的基本力学性能、四点弯曲性能、自由收缩以及圆环约束条件下的开裂行为.结果表明:减缩剂可以明显降低ULCC的自由收缩,纤维对ULCC的自由收缩基本没有影响;由于纤维对裂纹的抑制作用,掺入PVA纤维可以比减缩剂更有效地控制ULCC的裂缝宽度,推迟首次开裂时间,其中以掺入6%减缩剂和长度12 mm细PVA纤维的效果最佳;弯曲试验中小挠度下的残余弯曲强度与纤维增强ULCC的早期最大裂缝宽度之间存在相关性.

The effects of shrinkage reduction admixture and PVA fiber on the shrinkage and cracking behavior of ultra-light cement composites were studied.The series properties of materials were tested,such as basic mechanical properties,four-point bending properties,free shrinkage,and cracking behavior under ring constraints.The results show that shrinkage reduction admixture can reduce free shrinkage significanly,but the fiber has no effect on the free shrinkage basically.However,due to the inhibitory effect of fiber on cracks,PVA fiber can control crack width and delay the first cracking time more effectively than shrinkage reduction admixture.The inclusion of 6%shrinkage reduction admixture and micro PVA fiber with a length of 12 mm is the most effective way to control the crack width and delay the first cracking time.And studies show that there is a correlation between the residual flexural strength at small deflections in the bending test and the maximum crack width of the fiber-reinforced ULCC at early age.