中文摘要：

采用3点弯曲试验，结合宏观裂缝形态与PVA纤维桥接状态，研究了不同粉煤灰掺量下聚乙烯醇纤维水泥基材料（PVA—ECC）的弯曲性能；通过分析试件断裂面处纤维表面、纤维嵌入端和纤维拉断或拔出端的扫描电镜形貌，研究了不同粉煤灰掺量下PVA纤维-基体界面微观结构特征。结果表明：不同粉煤灰掺量下PVA纤维对水泥基材料的增强增韧效果不同，高掺量下增强增韧的效果显著；随粉煤灰掺量增加，基体结构特征更均匀，裂缝处PVA纤维的桥接应力和纤维-基体界面黏结力降低，桥接裂缝的PVA纤维状态由少量纤维短距离滑动拔出转变为大量纤维长距离滑动拔出，纤维桥接裂缝的效率提高，增强增韧的作用增加。

英文摘要：

Three-point bending test was implemented to evaluate effects of fly ash content on bending properties of polyvinyl alcohol （PVA） fiber reinforced cementitious composites（PVA-ECC） based on crack patterns and PVA fibers morphology in cracks,the mechanism of PVA fiber-reinforced and fiber toughening cementitious composites was analyzed.SEM micrographs of PVA fiber side surface,fibers＇ embedded and ruptured or pullouted ends in fracture surface were investigated to analysis PVA fiber-matrix interface microstructure.Test results find out that PVA fibers play a significantly role on strength and toughness.Moreover, the rate of improvement remarkably increases with more fly ash content.With increasing fly ash content, the eementious matrix characteristic become more uniform, the strength of PVA fibers bridging cracks and interface bonding ability become lower.Meanwhile, the PVA fibers morphology of bridging cracks changes from little PVA fiber short pullouted and slipped to larger number fibers long pullouted and slipped,which significantly improve the rate of fiber-reinforced and fiber toughening and increase bending strength and toughness.