为研究聚丙烯纤维掺入量对不同养护龄期的水泥砂浆试件变形破坏规律的影响,对水泥砂浆试件进行单轴压缩实验,同时利用数字散斑相关方法(DSCM)、扫描电子显微镜(SEM)对试件侧向变形场、断口形貌进行细观观测.结果表明:试件养护龄期相同时,抗压强度随聚丙烯纤维掺量增加呈先增加后减小趋势,在设置的变量梯度范围内,纤维最优掺量为0.5%;掺入聚丙烯纤维的试件峰后表现出明显的塑性特征,峰后广义刚度系数变化量较大;试件侧向变形场演化过程分为四个阶段:均匀阶段、成核阶段、变形局部化阶段、破坏阶段;聚丙烯纤维与水泥砂浆的粘结强度弱于砂粒与水泥的粘结强度,含聚丙烯纤维的试件在破坏形态上表现出"裂而不断"的特点.提出了含聚丙烯纤维水泥砂浆的微观胶结接触模型,模型的力学关系较好的解释了聚丙烯纤维试件峰后塑性提高的特征.
In order to study the deformation damage law of cement mortar samples mixed by polypropylene fiber under different curing ages, uniaxial compression test was conducted for cement mortar samples.Lateral deformation field was observed by digital speckle correlation method, and fracture morphology was observed by scanning electron microscope.The results show that compressive strength increases first and then decreased with the increase of polypropylene fiber content at the same curing age.In the range of variable gradient, the optimum quantity of polypropylene fiber is 0.5%.In post-peak, the samples containing polypropylene fiber exhibited a obvious plastic characteristics and the generalized stiffness coefficient changed greatly.The evolution of lateral deformation field was divided into four stages, uniform stage, nucleation stage, deformation localization stage and failure stage.Bond strength of polypropylene fiber and cement mortar was weaker than that of sand and cement.The failure mode of polypropylene fiber samples exhibited fissure but continuous.The microscopic bond contact model put forward in this research can be used to explain the characteristics of plastic improvement of polypropylene fiber samples in post-peak.
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