The study on the working performance of the Fiber Reinforced Cement Mortar mixing by the Polyvinyl Alcohol Fiber and the Steel Fiber
Abstract: In order to study that the effects of different fibers on the working performance of fresh cement mortar under different water cement ratio and fiber content (volume fraction), the rheometer, mini-slump cone and V-funnel are used. The results show that the rheological property and the flow ability of the cement mortar are reinforced by the polyvinyl alcohol fiber and steel fiber. The yield stress and plastic viscosity of the two fibers reinforced the cement mortar mixtures decrease with the increase of water cement ratio, while the flow expansion and flow rate increase with the increase of the water cement ratio. When the content of the PVA fiber is 0.25%, it has little influence on the performance of the mixture. When the steel fiber content is less than 0.75%, it can promote the the flow ability of the fiber reinforced cement mortar. When the steel fiber content is increased to 100%, the flow of the mixture is reduced obviously. The flow expansion of fiber reinforced cement mortar mixture is negatively exponential with the yield stress and the flow ratio also negatively exponential with the plastic ratio. The correlation coefficients are is 0.808 and 0.730, respectively.
Keywords: polyvinyl alcohol fiber; Steel fiber; Cement mortar; Rheological property; The flow ability
The inherent high brittleness of cement-based composite material is the main reason for low tensile strength, poor cracking ability and low toughness. The introduction of the fiber with high tensile strength and high modulus of elasticity to enhance the strengthening and toughening is the effective method to improve the ultimate elongation and the crack control ability of the cement-based composite material (Zhenbo, 2015).
The research shows that a certain length ratio, high admixture and uniform dispersion are the necessary conditions for obtaining good fiber reinforcement (Zhang, 2017). When the fiber content is too high, however, the work performance of the new mix cement base composite material will decline rapidly. And also, the dispersion of fiber in its internal becoming poor. Eventually enhancement effect by the fiber is not obvious or even degradation (Zhang, 2016). Therefore, it is necessary to study the performance of fiber reinforced cement composite materials in the new mix, and the relationship between the fiber admixture and the long diameter ratio.
The rheological property as the evaluation of material is the index of flow and deformation capacity under the external shear index (Jin, 2016). This property can show the macro performance characterization of cement based material mixture from the size, morphology, the surface state of the composition materials and the group interaction between different materials (Bu, 2015). Also, this property can provide guidance for the mixture ratio designing and performance optimization of materials. On the new mix of fiber reinforced cement base composite materials, good rheological property can ensure that the mixture has good construction performance, proper yield stress and plastic viscosity. And this property can help the fiber in cement matrix disperse more evenly and remain stable. In addition, due to testing operation of the expansion of the flow and flow rate is simple, equipment is readily available, these tests are applied in much more engineering practices (Wongprachum, 2017). Therefore, if the parameters between the flow-ability and the rheological property are established, more accurate rheological parameters are obtained by using simple flow performance testing instruments.
In this paper, under different water cement ratio and fiber content, the rheological property and the flow-ability of the cement mortar reinforced by the polyvinyl alcohol fiber and steel fiber are studied (Etri, 2015). Also, the influence factors for the working pe