聚丙烯纤维对混凝土早期收缩影响的试验研究

Experimental study on effects of polypropylene fiber on early-age shrinkage in concrete

研究在同水灰比的试验条件下,聚丙烯纤维掺量对混凝土早期收缩和流动性等的影响。试验结果表明:聚丙烯纤维能在一定范围内降低混凝土的早期收缩,纤维的减缩效果随掺量的增加而增加;减缩率与掺量不呈线性关系,当纤维掺量达到一定时减缩率增加不明显。由于聚丙烯纤维的掺入会明显降低新拌混凝土的坍落度,在确定聚丙烯纤维的最佳掺量时应综合考虑减缩效果和坍落度损失、经济等因素,聚丙烯纤维的掺量宜选在0.9kg/m 3左右,即体积掺量在0.1%左右。

The effects of early-age shrinkage and workability of concrete were investigated by adding the different additions of polypropylene fibers in the same water-cement ratio condition.The results indicate that polypropylene fibers can reduce the degree of early-age shrinkage of concrete within limits.With the addition of polypropylene fibers increasing,the degree of shrinkage of concrete increases.However,the change of the degree of shrinkage of concrete becomes slowly with the excess addition of polypropylene fibers.At the same time the addition of polypropylene fibers bringing an obvious slump loss to fresh concrete, so many factors must be considered such as the effect of shrinkage and slump of concrete and the cost of concrete to determine the best addition of polypropylene fibers.ln this experiment,the best addition of polypropylene fibers is 0.9kg/m^3 or 0.1% （volume ratio）.