合成粗聚丙烯纤维与水泥砂浆界面黏结力学性能

Interface mechanical bonding properties between coarse synthetic polypropylene fiber and cement mortar

纤维嵌入水泥基材料中的界面黏结力学性能对纤维增强混凝土材料的力学性能起着重要作用。单纤维拉拔试验可以较好地模拟纤维与水泥基体材料界面间的受力条件,因此考虑3种纤维直径(0.2 mm、0.6 mm、0.8 mm)、3种纤维埋置长度(10 mm、20 mm、30 mm)和3种纤维表面性状(压痕型、波浪型、光圆型)与3种水泥砂浆基体水胶比(0.66、0.51、0.41)影响因素,进行了单根粗聚丙烯纤维从水泥砂浆基体中的拔出试验,使用SEM观测了纤维被拔出后的形貌特征,通过ABAQUS有限元建立了纤维拔出过程的数值模型,以研究单根纤维与水泥基界面间的剪切应力。同时将试验结果和模拟结果进行了数值拟合,得到了各因素对界面黏结力学性能的影响规律:(1)水泥砂浆的最佳水胶比为0.41~0.49;(2)合成粗聚丙烯纤维埋置长度最佳为8~10 mm,最佳纤维直径在0.26~0.39 mm范围;(3)纤维表面性状为压痕型时,纤维在水泥基材料中的利用率较大,并且与水泥砂浆的界面黏结性能良好。

The interfacial bonding mechanical properties of fiber-embedded cement-based materials play an important role in the mechanical properties of fiber-reinforced concrete materials.The pull-out test of single fiber can better simulate the stress conditions between the fiber and the cement matrix material interface.Therefore,a pullout test of a single coarse polypropylene fiber from cement mortar matrix was carried out which considered three fiber diameters(0.2 mm,0.6 mm,0.8 mm),three fiber embedding lengths(10 mm,20 mm,30 mm),three fiber surface properties(indentation type,wave type,smooth type)and three kinds of cement mortar matrix water-binder ratio(0.66,0.51,0.41)influencing factors.The morphological characteristics of the fibers after being pulled out were observed by SEM,a numerical model of the fiber pull-out process was established by ABAQUS finite element to study the shear stress between a single fiber and the cement-based interface.At the same time,the experimental results and the simulation results were numerically fitted,and the influence rules of various factors on the interface bonding mechanical properties were obtained:(1)The optimum water-binder ratio of cement mortar is 0.41-0.49;(2)The embedded length of the synthetic crude polypropylene fiber is 8-10 mm,and the optimal fiber diameter is in the range of 0.26-0.39 mm;(3)When the fiber surface properties are indentation type,the utilization rate of fibers in cement-based materials is large,and the interface bonding performance with cement mortar is good.