纤维增强自密实混凝土早龄期非自由收缩研究

通过坍落流动度、J环和U型管试验,评价了纤维混凝土拌和物的流动性能、粘度、钢筋间隙通过性能和抗离析性能,得到了满足工作性能和强度要求的纤维自密实混凝土.在此基础上深入研究了各种不同类型纤维(高耐碱玻璃纤维HARGF、改性聚丙烯纤维MPPF、混杂纤维CF)对自密实混凝土早龄期非自由收缩性能的影响.结果表明:通过阻止骨料沉降和水分上浮,减少泌水通道和泌水量,纤维可减缓混凝土中水分的蒸发速率,起到一定的保水作用;单掺HARGF或MPPF可以有效限制混凝土基体早龄期的塑性收缩和干缩,阻止收缩裂缝的产生和发展;CF限制混凝土基体早龄期收缩和裂缝展开的能力优于HARGF和MPPF,呈现出明显的正混杂效应.

Study on Early Age Restrained Shrinkage of Fiber Reinforced Self-compacting Concrete

Based on slump flow test,J-ring test and U-box test,the flowability,viscosity,passing ability and segregation resistance of the fresh concrete were analyzed,and a kind of fiber reinforced self-compacting concrete,which met workability and strength requirement,was obtained.Then,the effect of different types of fiber(high alkali-resistant glass fiber(HARGF),modified polypropylene fiber(MPPF) and hybrid fiber(CF)) on early shrinkage of self-compacting concrete was studied.The result indicates that:(1)by blocking aggregate settling and moisture floating,fiber can reduce number of capillary,slow down the evaporation,sequentially reduce the mass loss of fresh concrete;(2)both HARGF and MPPF can restrict plastic or dry shrinkage effectively,prevent the initiation and development of shrinkage crack;(3)the ability of CF resisted shrinkage and crack is better than that of HARGF and MPPF,which displays distinctly positive hybrid effect.