Study On The Application Of Cement Based Composite Materials In Concrete Bridge Maintenance And Reinforcement

Cement-based composites showed significant multiple cracking feature and strain hardening behavior during forcing,with better mechanical properties and durability.It has been successfully applied to many practical projects.In this paper,the mix ratio,physical and mechanical properties and durability of cement matrix composites was research on.The research contents are as follows:Try to use a variety of fibers to replace the Japanese PVA fiber for cement matrix composites preparation.Select the optimal alternative fiber,adjust the mix of cement-based composite,the effects of water-cement ratio,cement-sand ratio and fly ash content on the physical and mechanical properties of ultra-high tenacity fiber cement-based composites were studied.The reasonable range of the cement-based composite material mix was put forward,the chloride ion permeation test was performed.PVA fiber and PP fiber improve the ductility of cement-based composites significantly.Carbon fiber and basalt fiber improve the breaking strength of cement base composite material is more significant.The ductility of the cement-based influenced by fiber content is more obvious,when the fiber content was less than critical volume,the ductility was improved with the increase of fiber content.When the fiber content was larger than critical volume,the fibers reunited,critical volume ratio related to fiber diameter size and composition.The content of each component has a suitable range,water-cement ratio was 0.36-0.42,mortar sand ratio was 0.3-0.35,the fiber content was 1.3%?2%Vol.With the increase of fiber content,the diffusion coefficient of chloride ion decreases,increases later.The minimum value of diffusion coefficient of chloride ion was at the fiber content was 1.4%.The effects of composite strength,fiber type,interface treatment(roughness)on bond strength of cement-based composites and concrete were studied.Single shaft tensile test showed that:Interface was brittle failure when it was pulled,the interface which was untreated was binding weakest,and then is the surface coarse concrete interface,the best is to use epoxy resin cement macadam processing interface.The shear test showed that,the interface was ductile failure when was sheared,untreated concrete interface was weakest,and then was the surface is coarse.the interface which was treated with epoxy resin cemented gravel was strongest.Beam tests show that,after added cement-based composites,the concrete surface appears small cracks.With the increased load,the surface of cement-based composites showed uniform cracking.Destruction process:cement-based composite was stripped from concrete,longitudinal tensile steel yield,finally,the compression zone concrete was destroyed.Concrete beams which bridge deck continuous material was toughness fiber cement-based composites.The maximum value of plastic strain was larger 11.53 times than bridge deck with concrete beams at initial fracture,the crack resistance of the bridge deck continuous structure was improved.The composite material can improve the cracking load of the test beam.Under the same load conditions,the crack-resistance of composite continuous deck structure was better.