粗合成纤维活性粉末混凝土抗弯韧性试验

摘要

为研究不同粗合成纤维用量下活性粉末混凝土的抗弯韧性，采用四点弯曲试验对粗合成纤维用量分别为4．75，9．5，14．25，19 kg ・ m -3的纤维活性粉末混凝土试件进行了研究，同时与不掺入纤维的素活性粉末混凝土进行了对比分析。结果表明：不掺入纤维的素活性粉末混凝土弯拉试件发生脆性破坏，试件一裂即断，未得到荷载-挠度曲线的下降段；而粗合成纤维掺入后能够提高活性粉末混凝土的韧性，使弯拉试件转变为明显的延性破坏，荷载-挠度曲线都可得到稳定的下降段，同时曲线还出现了二次强化现象，有2个峰值；随着粗合成纤维掺量的增加，弯拉试件荷载-挠度曲线的下降段愈加平缓，韧性指数增大；粗合成纤维掺量（体积分数）为1．0％～2．0％时，剩余强度在抗折强度的85％以上，此时粗合成纤维对裂后基体具有较强的阻裂能力，能够大大提高弯拉试件开裂后的韧性。%In order to evaluate the flexural toughness of synthetic macro-fiber reinforced reactive powder concrete ,beam specimens were tested under four points flexural method .The contents of synthetic macro-fiber were 4 .75 ,9 .5 ,14 .25 ,19 kg ・ m - 3 ,respectively ,and plain reactive powder concrete specimens without fiber were analyzed in contrast .The results show that plain reactive powder concrete specimens without fiber are brittleness ,specimens breakdown when the crack is appeared ,and the descending branch of load-deflection curves cannot be collected . While the failure mode of specimens with synthetic macro-fiber is ductility and a steady descending branch of load-deflection curves is collected .At the same time ,the curves all have two peaks ,presenting the phenomenon of secondary reinforcement .This means that synthetic macro-fiber can improve the flexural toughness of reactive powder concrete .Descending branch of load-deflection curves is flatter and toughness index with the increasing of fiber content .The residual intensity is above 85% of flexural strength when the fiber content (volume fraction ) is 1 .0% -2 .0% , which indicates that synthetic macro-fiber has excellent crack resistance ,and can improve the ductility of bending-tension specimens after cracking .