Long-term Performance Of Coral Concrete Reinforced With CFRP Bars Under The Action Of Ocean Tide

In the process of island construction,concrete as the most basic building material,the amount of concrete is huge,if the conventional aggregate is used to prepare concrete,it will greatly increase the engineering cost.The preparation of coral concrete with coral aggregate around offshore islands and reefs can effectively solve the problem of engineering cost.In the South China Sea island and reef project,the main cause of durability failure of coral concrete structure is the cracking,spalling,collapse and steel bar corrosion caused by chloride invasion.In recent years,more and more studies have shown that fiber reinforced plastic bars(Fiber Reinforced Polymer Rebar,FRP bars)have good mechanical properties and good corrosion resistance in a variety of civil engineering environments,which provides a new method to solve the problem of steel bar corrosion in coastal concrete structures.Similarly,FRP bars also have a good application prospect in solving the durability failure of coral concrete structures caused by steel bar corrosion.However,in the marine environment with high heat and high salt for a long time,the performance of coral concrete reinforced with FRP bars will also be greatly affected.Based on this,the chloride-dry-wet cycle test is designed to simulate the ocean tide,and the physical and mechanical properties of coral concrete and CFRP bars are studied respectively.At the same time,the bond properties of CFRP bars and coral concrete under the action of ocean tides are studied,and the bond slip model of CFRP reinforced coral concrete considering damage is proposed.Finally,the bond finite element analysis of CFRP reinforced coral concrete is carried out by using ABAQUS.It mainly includes the following five aspects:(1)The deterioration behavior of the physical and mechanical properties of coral concrete caused by ocean tide is found out.The chlorate-dry-wet cycle test is carried out with 3.5% Na Cl solution to simulate seawater,and the physical and mechanical properties of coral concrete and ordinary concrete are studied respectively.The mass and dynamic elastic modulus of coral concrete and ordinary concrete are tested by non-destructive testing method,and the law of variation with dry-wet cycle time is obtained.With the increase of dry-wet cycle,the mass and dynamic elastic modulus of both increase at first and then decrease.(2)The influence of ocean tide on the mechanical properties of CFRP bars is explored.Through the dry-wet cycle test of chloride salt to simulate the action of ocean tide,the property evolution of CFRP bars under the action of ocean tide is studied,the effect of different dry-wet cycle time on the tensile strength of CFRP bars is analyzed,and the deterioration of CFRP bars is observed by scanning electron microscope.The results show that the chloride-dry-wet cycle has little effect on the tensile strength of CFRP.(3)The evolution law of bond performance of CFRP reinforced coral concrete under the action of ocean tide is revealed.Through the chloride-dry-wet cycle test to simulate the action of ocean tide,the central pull-out test of coral concrete with CFRP bars is carried out,the change of bond properties of coral concrete reinforced with CFRP bars under the action of ocean tides is explored,and the change mechanism of bond properties was revealed.The results show that with the increase of the number of dry-wet cycles,the ultimate bond strength between coral concrete with CFRP bars increases at first and then decreases.At the same time,increasing the bond length will lead to the decrease of the ultimate bond strength.(4)The interface damage model of coral concrete reinforced with CFRP bars under the action of ocean tide is established.Combined with the damage mechanics method,the deterioration of the interfacial bond performance between CFRP bars and coral concrete under the action of ocean tide is analyzed,the interface damage model of coral concrete reinforced with CFRP bars under the action of ocean tide is established,and the bond-slip constitutive model considering damage is obtained.(5)The correctness of the bond-slip constitutive model is verified by ABAQUS finite element analysis.By defining material properties and selecting element types,the pull-out test model of CFRP reinforced coral concrete is established.Combined with the bond-slip constitutive relation considering damage,the pull-out specimens with different dry-wet cycle time are analyzed by adding nonlinear spring element,and the test results are compared with the simulation results.The simulation results are in good agreement with the experimental results.