Experimental Study On Properties Of PVA-Basalt Fiber Cementitious Composites

Fiber reinforcement has long been an important way and research hotspot for cementitious materials to achieve high performance.Single fiber reinforced cementitious composites are increasingly used in modern engineering,but the strengthening and toughening effect of single fiber on cement composites is limited.The blending of two or more different fiber materials into a certain base material in appropriate proportions can result in a new composite material with both the advantages of different fibers and synergistic effects,which can play a more enhanced performance than the original single fiber.In this thesis,the properties of cementitious composites blended with polyvinyl alcohol(PVA)fibers and basalt fibers were investigated.Through experimental studies,the improvement of flexural strength,compressive strength,flexural to compressive ratio,dry shrinkage properties and consistency of cementitious composites was firstly investigated when PVA fibers and basalt fibers were blended alone,and then the effect on physical and mechanical properties of cementitious composites was investigated when fibers were blended in different proportions at different total volume dosing.Based on the indoor test data,the mechanical properties of PVA/basalt fiber cement mortar were predicted by using BP neural network.The specific work is as follows.(1)The effect of single PVA fiber admixture on the properties of cementitious composites.The test results show that the strength,toughness and dry shrinkage resistance of cementitious composites are well enhanced within the fiber admixture range of 0.25%～0.50% when no significant deterioration of fluidity is ensured.(2)The effect of single-doped basalt fiber on the performance of cementitious composites.The test results show that the enhancement effect of basalt fibers on the physical and mechanical properties of mortar differs under different volume dosing.In general,the single dose of basalt fiber can significantly improve the flexural strength,compressive strength and dry shrinkage resistance of cement mortar,and the optimal fiber dose ranges from 0.25% to 0.50%.However,the improvement effect of basalt fiber on the compressive strength of mortar in the early stage is not significant.(3)The effect of mixed fibers on the performance of cementitious composites.When PVA fibers are mixed with basalt fibers,only when the two fibers are mixed in a suitable proportion can the composite material with better results than when a single fiber is mixed,and the increase in strength at a later stage is more obvious.The results of this test show that when the ratio of PVA fiber to basalt fiber volume doping ratio of2:3,the total fiber doping is 0.50%,the best performance in all aspects.(4)Based on the indoor test results,BP neural network was used to train samples and predict the flexural and compressive strengths of PVA/basalt fiber cement matrix composites.The results show that the errors between the obtained predicted values and the experimental values are small,and the prediction results are good and provide references for engineering practice.