SHCC (Strain hardening cement-based composites) is a type of ultra-high performance concrete (UHPC).Cracks were introduced into ordinary cement mortar and SHCC specimens by means of three-point bending test,and the cracking characteris tic and crack distribution were investigated.The results indicated that SHCC displayed higher bearing capacity and strain capacity than ordinary cement mortar,as the former's initial cracking load was about 1.5 times higher than the latter.The bridging effect of PVA fibers effectively delays crack initiation and propagation in SHCC,and causes the transform of lesser,wider cracks in ordinary mortar into much more and finer cracks in SHCC,which implies a multiple cracking characteristic.The crack width measured in SHCC specimens coincided well with normal distribution,and moreover,90％ of the cracks had ＜30 μm width.These micro-cracks were capable of autogenous self-healing under humid condition,as higher self-healing degree and self-healing rate were observed in water than those in humid air.%应变硬化水泥基复合材料(Strain hardening cement-based composites,SHCC)是超高性能水泥基材料的一种.通过三点弯曲加载试验,分别对普通砂浆和SHCC试件诱导开裂,对两种材料的开裂特性及其裂缝分布规律进行了研究.结果表明,SHCC材料试件与普通水泥砂浆试件相比具有更高的承载力和应变能力,初始开裂荷载约为普通砂浆试件的2.5倍.SHCC材料中的PVA纤维的桥接作用有效延迟了裂缝的产生与扩展,将普通砂浆试件中数量少而大的裂缝转化为多而细的微小裂缝,呈现多缝开裂特性,产生的裂缝宽度符合正态分布规律,且90％的微小裂缝小于30 μm.这些微小裂缝在潮湿环境中产生一定程度的自生愈合,在水中的愈合程度和速度均高于在潮湿空气中.
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