Research On Mechanical Behavior Of TRC With Sea Sand And Sea Water And Its Confined Concrete Columns

With the rapid development of my country's economy and coastal economic development zones,the demand for concrete for infrastructure construction in the South China Sea has been increasing year by year,and the phenomenon of "sand shortage" has appeared in some areas of my country.The process of producing concrete consumes a lot of natural resources such as river water and sand,which will have a huge adverse impact on the social environment.As we all know,there are steel bars in reinforced concrete structures,and the steel bars are prone to corrosion problems,especially in this marine environment,which is flooded with a large amount of chloride ions.These chloride ions will dissociate into the concrete by means of internal and external seepage.The passive film that protects the steel bar is destroyed on the surface,which promotes the corrosion of the steel bar.Therefore,there is an urgent need for a new type of concrete structure and components suitable for the environment of marine islands and reefs,which has attracted the attention of many scholars at home and abroad.The Textile Reinforced Concrete(TRC)is a new type of fiber-reinforced high-performance concrete composite material,which is mainly formed by using high-performance fiber mesh to strengthen the fine aggregate concrete matrix.Because its reinforcing rib is a non-corrosive non-metallic fiber mesh,the material has corrosion resistance requirements,adapts to marine high-salt and high-humidity environments,and has the advantages of thin wall,good compatibility,high temperature and fire resistance,and can improve its toughness.And durability.On this basis,considering replacing the matrix of TRC composite material with sea sand and sea water concrete,a new type of sea sand and sea water TRC prefabricated shell restrained concrete column structure was developed.This new constrained composite structural column has a certain vertical load-bearing capacity and deformation capacity;all materials are corrosion-resistant,can well adapt to the high-salt and high-humidity marine environment,and can be widely used in the development of infrastructure construction in the South China Sea;At the same time,local materials can be obtained,resources can be used continuously,and costs can be saved;TRC prefabricated shell can also be used as a template,eliminating the need for supporting template steps.However,domestic research on this new type of sea sand and seawater TRC prefabricated shell confined concrete columns is still relatively small.Therefore,it is necessary to carry out relevant researches on the mechanical performance of the confined concrete columns with the TRC precast shell of sea sand and sea water.This article is in the National Natural Science Foundation of China "Research on the Life Cycle Mechanical Properties of Fabric-reinforced Concrete Formwork and Composite Beams and Slabs(51478408)" and "Research on the Seismic Performance and Earthquake Damage Mechanism of RC Columns with Bending and Shear Failure Considering the History of Cyclic Load Action(51508154)" With the funding of the project,a study on the mechanical properties of the TRC sheet and its confined concrete columns in sea sand and seawater was carried out.The main research contents and conclusions are as follows:(1)Through the axial tension test and four-point bending test of 50 groups of sea sand and seawater TRC sheets under different working conditions,the effect of the number of fabric net layers,the water-cement ratio and the volume of chopped PVA fibers on the fiber net reinforced sea sand was discussed.The influence of seawater concrete sheet on axial tension and bending properties.By studying the cracking stress,cracking strain,tensile strength,ultimate strain and the number of cracks of the concrete thin plate axial tension specimen,the influence of each parameter on the stress-strain curve of the axial tension specimen is analyzed;Performance indicators such as cracking load,cracking deflection,ultimate load,ultimate deflection and displacement ductility coefficient of concrete sheet bending specimens are studied,and the influence of each parameter on the load-displacement curve of the bending specimens is analyzed.According to the comprehensive analysis of the test data,when the number of fabric net layers is 4 and the volume of chopped PVA fiber is 1%,the uniaxial tensile strength of the fiber net reinforced sea sand seawater concrete sheet reaches the maximum value of 5.38 MPa At this time,the corresponding ultimate strain is 13.57%;the ultimate load of the four-point bending specimen of the fiber-net-reinforced sea-sand seawater concrete sheet reaches the maximum value of4.76 k N,and the corresponding ultimate deflection is 6.40 mm.(2)Through the study of the vertical bonding performance of 20 different PVC pipes and TRC composite concrete columns,the number of notches,the number of notches,the number of implanted stainless steel screws,and the hollowing rate of the PVC plastic pipe and the outer wall were studied.The effect of wrapping fiber mesh fabric to enhance the bonding performance of the concrete column interface.The experiment conducted a comprehensive analysis of the ultimate load,ultimate displacement and ductility coefficient of the PVC plastic pipe and the outer wall wrapped fiber mesh fabric reinforced concrete column specimens.The PVC plastic pipe and the outer wall wrapped fiber mesh fabric reinforced concrete column specimens were studied.The influence of load-displacement curve changes.The results show that the interface treatment methods such as scoring,scoring and implanting stainless steel screws and hollowing rate on the surface of the PVC pipe can improve the interface bonding performance between the PVC pipe and the fiber mesh fabric-reinforced concrete to a certain extent.Through the comprehensive comparison and analysis of the above test data,it is concluded that when using 6notches and implanting 32 stainless steel screws(200PVC-R6Q32-C3),the interface bonding load between the PVC pipe and the TRC composite-coated concrete is optimal The bonding performance parameter,the maximum bonding load value of the interface is 173.53 k N.(3)Through the axial compression performance test of 20 precast TRC shell confined concrete columns,the effects of restraint type,distribution network ratio,specimen size,hoop ratio and core concrete strength grade on the axial compression performance of precast TRC shell confined concrete columns are discussed Impact.Through multi-angle comparative analysis of the cracking load,cracking deflection,ultimate load,ultimate displacement and ductility coefficient of the concrete column specimens,it is found that the distribution network ratio is the same,the specimen size is the same,the hoop ratio is the same,and the core concrete strength grade is the same The cracking load and peak load value of concrete columns confined by sea sand and seawater TRC confined by PVC pipes are significantly higher than those of concrete columns without PVC pipes.The specimens of concrete columns with PVC pipes are better than those without PVC pipes.The maximum increase in cracking load of the concrete column specimens is 13.69%,the maximum increase in ultimate load is 19.07%,and the maximum increase in ductility is 40.71%,indicating that the rigidity of the core concrete column constrained by PVC pipes has been significantly improved,and it also has a good Ductility.With the increase in the number of reinforcement layers wrapped with TRC fabric mesh on the outer surface of the PVC pipe,the ultimate load,ultimate displacement and ductility of the concrete column specimens have been significantly improved.With the increase of the distribution network rate,the maximum increase of the cracking load of the concrete column specimen is 65.24%,the maximum increase of the ultimate load is 60.17%,and the maximum increase of the ductility is 50%.Compared with the concrete column with two layers of fiber fabric net wrapped on the outer surface of the PVC pipe,the concrete column with a four-layer distribution network has higher compressive bearing capacity and better ductility.