Study On Bonding Mechanism Between Polypropylene Crude Fiber And Cement Matrix Under Sulfate Erosion

In hydraulic engineering,the building structure gradually develops towards large volume and large span.Due to inherent defects such as low tensile strength,poor toughness and easy cracking,it is difficult for traditional cement-based composite to meet the application requirements of certain projects or reduce the economic efficiency of the project.Therefore,researchers add fibers to improve the performance of cement-based composites to meet the engineering needs.In fiber cement-based composites,fiber and matrix are bonded together through interfacial transition zone.When the fiber cement-based composites bear the load,the matrix transfers the load to the fiber through the interface transition zone,thereby playing the role of fiber reinforcement and toughness.Therefore,the interfacial bonding between the two materials is particularly important,which plays a decisive role in the performance of fiber cement-based composites.However,due to the different clastic modulus of fiber and matrix,the interfacial bonding performance has always been the focus and difficulty in scientific research.Therefore,it is necessary to study the influence of various factors on the interfacial bonding performance of fiber cement-based composites.At the same time,the interfacial bonding performance of fiber cement-based composites will be corroded and destroyed by various factors during the service process.Especially under the attack of sulfate,the interfacial bonding performance between the fiber and matrix will be seriously damaged.Therefore,it is necessary to study the degradation law and degradation mechanism of the interfacial bonding performance between fiber and matrix under sulfate erosion.At the same time,it also provides a meso-basis for the study of durability of fiber cement matrix composites against sulfate attack.In this paper,the interfacial bonding performance between polypropy.ene crude fiber and cement matrix is taken as the object,the experimental and theoretical research methods are adopted.Fiber pull-out test,sulfate erosion test and dry-wet cycle test were mainly carried out to explore the interface bonding mechanism between polypropylene crude fiber and cement matrix.The main contents and results of this research are as follows:(1)Through basic fiber pull-out tests,the influence of curing age(12 hours,18 hours,1 day,2 days,4 days,7 days,14 days and 28 days),loading rate(1,3,6,10,15 and 30mm/min),fiber burial depth(10,20,30,40,50 and 60mm),and fly ash content(10%,20%and 30%)on the interfacial bonding performance of fiber cement matrix composites were investigated.The research results show that with the increase of curing age,loading rate and fiber depth,the interfacial bonding performance between the fiber and the matrix have been enhanced.The interfacial bonding performance between the fiber and the matrix showed a trend of first strengthening and then weakening with the increase of fly ash content.When the fly ash content is 20%,the enhancement effect on the interfacial bonding performance is the best.(2)Through sulfate erosion test and dry-wet cycle erosion test,the durability of interfacial bonding performance of fiber cement-based composites was studied.In order to explore the degradation law of interfacial bonding performance under different concentrations of sodium sulfate(0%,5%,10%and 15%)erosion.The research results show that the erosion rate and degree of the interfacial bonding performance between the fiber and the matrix increased significantly with the increase of the sodium sulfate concentration.(3)By changing the amount of fly ash(0%,10%,20%and 30%),it reveals the influence of different fly ash content on the sulfate erosion resistance of the interface bonding performance between the fiber and the matrix.The research results show that with the increase of the fly ash content,the sulfate resistance durability of the interfacial bonding performance between the fiber and the matrix increases first and then decreases.When fly ash content is 20%,the interfacial bonding performance between the fiber and the matrix has the best sulfate corrosion resistance durability.