Experimental Study On Square Plate Method Of PVA Fiber Cement Composites

PVA fiber cement-based composite material refers to a new type of fine concrete formed by adding a certain volume of PVA fiber into conventional ordinary concrete.In PVA fiber cement matrix composites,compared with polypropylene fiber,flexible PVA fiber with high elastic modulus can improve the brittle failure of ordinary concrete.At the same time,it can improve the strength and bending toughness of ordinary concrete.The test pieces commonly used for the test methods of bending toughness are beam test pieces to measure,and the limitations of the beam size of the test pieces will affect the dispersion of PVA fibers in cement-based composite materials.The measurement results are more discrete.Therefore,the bending toughness test beam method can not truly reflect the ability of the two-way continuous plate structure in energy dissipation.In this paper,the combination of structural tests and theoretical analysis is used to study the compressive strength and bending toughness properties of cubic PVA fiber cement matrix composites.The main research work and results are as follows:(1)A cubic compressive strength test was conducted on PVA fiber cement-based composites to investigate the effect of PVA fiber incorporation on the cubic compressive strength of cement-based composites.The results show that the addition of PVA fiber can not only increase the cubic compressive strength of cement-based composites,but also improve the brittle failure of cement-based composites without fibers.The compressive strength of cube-bonded cement-based composites increases between 6% and 10%,and the most suitable volume content is 10%.(2)PVA fiber cement matrix composites were tested by the bending toughness square plate method to study the influence of PVA fiber incorporation on the bending toughness of cement-based composite materials.The results show that the toughening effect of PVA fiber on cement-based composites improves with the increase in volume content.PVA fiber can significantly increase the bending ultimate load and residual load value,but the impact of the initial crack load value of the opposite plate is not significant.When the volume content of PVA fiber exceeds 2.0%,the toughening effect of PVA fiber on cement-based composite materials is weakened,and the latter is particularly evident.The effect of reinforcing and toughening is best when PVA fiber volume content is 2.0%.(3)Based on the load-deflection curve of the specimen plate,the toughness of the specimen plate was evaluated by the energy method.The influence of the volume content of PVA fiber on the flexural toughness of the specimen plate was studied.The results of the study indicate that the three evaluation methods,energy-deflection evaluation,bending toughness index evaluation,and toughness evaluation based on energy absorption after cracking of the board,all reflect that the test piece board has a better toughening effect as the volume content of PVA fiber increases.And there is an optimal volume content of 2.0%.Among them,the toughness index is most sensitive to changes in the volume of PVA fibers.The toughness index of fiber cement-based composites with a volume content of PVA of 2.0% is about 40 times that of cement-based composites without PVA fibers,which reflects the influence of volume content of PVA fibers on bending toughness.