Study On Polyethylene Fiber Reinforced Sulphoaluminate Cement Composite And Its Repairing Concrete

With the rapid development of coastal areas of china,a large number of coastal buildings have been built.However,due to the harsh environment of coastal projects,seawater contains a large amount of aggressive ions,which will lead to the reduction of concrete strength and corrosion of steel inside concrete,this puts higher requirements on the concrete reinforcement material in the coastal environment.Engineering cement-based composite(ECC)is a newly developed cement-based material for concrete reinforcement,which has high toughness,high strength and high ductility.At present,ECC is mainly based on Portland cement,and there is no sulphoaluminate-based ECC in the research of coastal concrete.Therefore,the sulphoaluminate cement-based ECC materials prepared in this paper are fits the above requirements.This study makes full use of the sulphoaluminate cement itself's good durability and early-strength performance and make use of modern composite material theory and modern technology to innovatively combine sulphoaluminate cement with high-performance fiber to prepared a sulphoaluminate cement-based fast reinforcement material for coastal concrete named SAC-ECC.The experiment determined the compounding ratio of the materials by orthogonal experiment,and analyzed the mechanical property,reinforcement property and durability about SAC-ECC.The results are as follows: The optimum fiber volume of SAC-ECC is 0.75%,the ratio of cement aggregate ratios is 0.5,and the amount of water reducing agent is 1.5%.The flexural strength of SAC-ECC can reach up to 21.9MPa and its toughness and ductility are significantly improved.The material has obvious strain hardening characteristics,and the material failure morphology exhibits obvious characteristics of multi-slit cracking.The polyethylene fiber is well preserved and uniform distribution in the cement matrix,so mechanical properties of fiber can be fully utilized.SAC-ECC has good bonding property with concrete,and it has close bond with concrete interface without defects.The material is applied to concrete girders and concrete beam for reinforcement.,the test results show that the flexural strength of concrete after reinforcement can be increased by up to 111.9%,and the compressive strength can be increased by up to 26.3%.The anti-chloride corrosion resistance of SAC-ECC materials was studied by NC-ER and fast chloride ion migration.The mechanism of anti-chloride adsorption of SAC-ECC materials was studied by microscopic analysis,nitrogen adsorption and isothermal adsorption.The results show that SAC-ECC has good resistance to chloride ion penetration,and its hydration products can react with chloride ions to improve the ability of materials.Moreover,the pore structure of SAC-ECC material is obviously improved,and the harmful pore volume is reduced.The chloride ion diffusion coefficient is reduced by nearly 30% compared with ordinary Portland cement mortar,which indicates that the SAC-ECC reinforcing material prepared in this study has good resistance to chloride ion corrosion.Therefore,SAC-ECC can not only realize the three functions of mechanical properties reinforcement,physical protection and chemical protection of coastal concrete,but also can be applied to the rapid repair of construction engineering.