Study On Cooperative Protection Performance Of CASC Under Load

In recent years,all countries that have marine resources and have some ability to develop them are stepping up the development of marine resources and are building various related facilities.Therefore,the use and research of concrete in the marine environment has become a top priority.However,traditional gravel aggregates and fresh water for mixing concrete are often lacking on offshore reefs.Then the cost of large-scale construction would be astronomical.Therefore,engineers use the coral reef rock mined on the island to produce coarse and fine aggregates through crushing and screening processes.And seawater is used to mix the concrete.At the same time,reinforced concrete structures in the marine environment are subjected to long-term immersion in seawater.The chloride ions in the seawater will penetrate the concrete protective layer to reach the surface of the reinforcement.Caused by the concrete inside the reinforcing steel corrosion of different degrees.Chlorine salt corrosion not only reduces the durability of the structure,but also reduces the safety of the structure.The chloride ion attack has a great impact on the service life of the structure and is one of the main causes of damage to concrete structures.The protection of reinforced concrete structures in the marine environment starts from two main aspects.On the one hand,it is to improve the durability of the concrete itself.On the other hand,additional anti-corrosion measures are taken.Among the various measures to prevent corrosion of reinforcing steel,the use of coating is not only easy to construct,but also has a very good effect.In this thesis,firstly,the diffusion of chloride ions in coral concrete under different loads and water-cement ratios is studied.The compressive strengths of three groups of coral concrete with different water-cement ratios were determined.The ultimate compressive strengths of different water-cement ratios were obtained.Continuous loads of 0%,10% and20% of the ultimate compressive strength were applied to concrete specimens with different water-cement ratios.The chloride ion diffusion coefficients were determined at different depths after passing 30 d,60d,90 d,120d and 180 d of seawater erosion.Meanwhile,the chloride ion diffusion coefficient of coral concrete was verified by combining with COMSOL software numerical simulation.The results show that with the increase of applied load,the internal pore space of coral concrete increases and the chloride ion transport rate is accelerated.With the increase of coral concrete water-cement ratio,the initial chloride ion solubility of coral concrete increases.The solubility gradient water formation with artificial sea decreases.The chloride ion transport rate decreases.The water-cement ratio decreases when the watercement ratio and the load act together.The strength of coral concrete increases.The value of diffusion coefficient is large in the initial period.It decreases faster in the later period.Using the numerical simulation method of COMSOL software,it is demonstrated that the model has good applicability and accuracy for chloride ion transport in coral concrete.The transport process of chloride ions in coral concrete is also better and clearly elucidated.Next,the surface coating of coral concrete and the coating of steel reinforcement under load are studied.Continuous loads of 0%,20% and 40% of their ultimate compressive strength were applied to the different coated coral concrete specimens.The chloride ion diffusion coefficients were determined at different depths after passing 30 d,60d,90 d,120d and 180 d of seawater erosion.The results show that the coral concrete surface coating is epoxy-rich zinc.The resistance to chloride ions increases when the thickness of the coating increases.Finally,the steel coating was used as the study object.Different coated steel bars were immersed in simulated pore solutions with chloride ion solubility ranging from 0.00 mol/L to0.30 mol/L.Electrochemical tests were performed to obtain the critical chloride ion solubility for different coatings and coating thicknesses.The results show that the surface coating of the steel is made of polyurethane.The resistance to chloride ions increases when the thickness of the coating increases.