Study On The Mechanical Properties Of Toughing Tailings PVA Reinforced Cementitious Composites

Toughing tailings PVA fiber reinforced cementitious composites is a kind of composite material in which mining abandoned tailings replace fine aggregate and the fly ash replaces cementitious material partly, by using the technology called ECC. Meanwhile, it saves natural sand,reduces cementitious consumption, and protects the environment. To prepare it, use a large replacement rate amounting to the proportion of 50% tailings sand and 54% fly ash, on the basis of the preliminary work. Through the experimental on the mechanical properties of cubic compression,sheet stretch, sheet bending, double shear and impact toughness, the composite basic static and dynamic mechanical properties are obtained with the reference to methods home and abroad, the interaction between fiber and frame and the toughening mechanism are analyzed, and the influence of fiber content and water-binder ratio on toughening effect are discussed. Moreover, three-point bending tests and the deflection damage are carried out. The main work and achievements of this paper are as follows:(1) Through theoretical analysis and experimental study, the mixture ratio and feasible preparation procedures are determined, and the fiber, cement, aggregate and additives as raw materials are selected properly. Thus, the dispersion is solved effectively in cement frame. It turns out that the mixture ratio and the preparation process are feasible.(2) To study toughing tailings PVA fiber reinforced cementitious composites, the basic static mechanical test is implemented, and the strength and toughness index about compression, stretch,bending and anti-shearing is achieved, as well as the deformation characteristics in the process of all kinds of tests. In different tests, the composite materials show good strength, ductility and toughness.What’s more, in the tensile and bending tests, the phenomenon of false strain hardening proves obvious, and it turns out multi-cracking under the tension stress. What’s more, the characteristics above are presented typical in the ductile deformation. Therefore, All of above turn out that the composite materials has a strong energy absorption capacity.(3) Applying the test of the dropping hammer impacting plate and scanning electron microscope to study the micro characteristics of impacting toughness and damage, the antiimpacting mechanism and ratio of key parameters are confirmed through the combination of macro and micro methods. Experiments in the scanning electron microscope show that PVA fiber in the tailings of the PVA fiber cementitious composite is of balanced distribution, fiber distribution in state and space is reasonable, and fiber and cement frame are in a good bonded condition.Impacting test shows two damage forms, that is, fiber pulled-out and fiber breakage, which is reasonable.(4) From the point of view of the bilinear model, introducing the deflection as the dependent variable damage model and carrying on the three point bending test, the damage of the toughing tailings PVA fiber reinforced cementitious composites is analyzed, the effect on which the waterbinder ratio has is discussed. The sample confirms that variable values of crack and instability damage prove small under different water-binder ratio and the damage state was not improved despite buckling deflection increased with the increase of water-binder ratio.(5) Based on the fracture morphology of the specimen, the bridging and the function of energy transfer of the fiber in the cracking frame are analyzed, the fiber transmits the releasing stress of the cracking substrate to not cracking parts surrounding, and the anti-cracking and toughening mechanism of fiber is studied. The mechanical properties and the interaction of the fiber content and the water-binder ratio are discussed in the experiment.