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对3种不同水灰比(0.2,0.4,0.65)形成的聚乙烯醇(PVA)纤维增强水泥基材料,通过三点弯曲试验,结合表观裂缝形状和裂缝处PVA纤维形态,研究了水灰比对材料弯曲性能的影响;通过对断裂面处纤维表面、纤维嵌入端和纤维拉断或拔出端的SEM影像分析,从微观层面研究了水灰比对PVA纤维-基体界面显微结构的影响。弯曲试验结果表明:随着水灰比增加,跨中部位裂缝数量明显增加,裂缝处拔出的纤维数量增多而拉断的数量减少,材料的弯曲韧度和开裂强度到弯曲强度的增强幅度提高。界面显微结构表明:随着水灰比增加,基体结构由致密变疏松,界面粘结力减弱,桥接裂缝的PVA纤维状态由瞬间猝断转变为滑动拔出且表面有轻微刮削,纤维对材料增强增韧的效率显著提高。
Polyvinyl alcohol (PVA) fiber-reinforced cement-based materials with three different water-cement ratios (0.2,0.4,0.65) were investigated by three-point bending test combined with apparent crack shape and PVA fiber morphology at the crack. The effect of water-cement ratio on the microstructure of PVA fiber-matrix interface was studied from the microscopic level by SEM image analysis of fiber surface, fiber embedded end and fiber pull-out or pull-out end at the fracture surface. . The results of the bending test show that as the water-cement ratio increases, the number of cracks in the mid-span increases obviously, the number of fibers pulled out at the cracks increases and the number of break-off decreases, and the increase of the flexural strength and flexural strength of the material increases . The microstructure of the interface shows that with the increase of the water-cement ratio, the matrix structure is loosened by the densification and the interfacial adhesion is weakened. The state of the PVA fiber in the bridged crack changes from an instantaneous arrest to a sliding pull-out and the surface has a slight scraping. Enhance the efficiency of toughening significantly increased.