Mechanism Of Improving Chlorine And Sulfate Corrosion Resistance Of Reinforced Concrete By Hydrotalcite

In accordance with the needs of national construction and development and the urgent vision of achieving ’ Carbon neutralization ’ and ’ Carbon Peaking ’,it is urgent to make significant changes in the green,healthy,and sustainable development of reinforced concrete building materials.As an important part of the western development,the construction of infrastructure in Inner Mongolia is facing the problems of coupling dry-wet cycle erosion of high concentration chlorine salt and sulfate and reducing structural durability.As a new anti-corrosion and anti-rust additive for reinforced concrete,hydrotalcite can significantly improve the durability of reinforced concrete and provide solutions and theoretical basis for structural durability in Inner Mongolia.In this thesis,the material composition of undisturbed hydrotalcite(LDHs)and calcined hydrotalcite(CLDHs)was analyzed by XRD to clarify their spatial layered structure.The experiment determined that the maximum adsorption capacity of chloride ion of LDHs and CLDHs in aqueous solution was 24.72mg/g and 122.25mg/g respectively.Among them,the adsorption of chloride ion by CLDHs was more in line with Langmuir adsorption model,belonging to single and stable chemical adsorption,and the maximum adsorption capacity decreased in alkaline solution and coupled salt solution.One percent CLDHs can increase the p H of salt solution from 7 to 11.21 and that of alkaline solution from 12.39 to 12.98.The addition of 1% CLDHs to the simulated pore solution can reduce the corrosion current density by more than 80% and play an obvious anti-corrosion effect on the steel sheet.By adding hydrotalcite to the concrete matrix,it is found that CLDHs has the greatest effect on the physical properties of concrete,reduces the cement setting time by about8% ～ 14%,and improves the hydration heat release rate and hydration heat release of cement.And CLDHs can improve the 28 d compressive strength of concrete by 6%,optimize the pore structure and improve the chloride ion binding rate of the system.The corrosion condition is simulated by wet-dry cycling of coupled salt.The electrochemical test results of reinforced concrete inner reinforcement after using hydrotalcite are compared and analyzed,the rust resistance efficiency is higher than 80%..It is found that CLDHs can significantly improve the corrosion state of reinforcement.By analyzing the microstructures of reinforced concrete after 30 and 90 times of wet and dry cycle erosion of coupled salts,it is found that CLDHs can significantly reduce the proportion of corrosion on the surface of reinforcement and the number of harmful products such as needle alunite in concrete.During the test,it is also found that sulfate decreases the corrosion degree of steel bar before and after 30 cycles and increases the corrosion degree of steel bar before and after 90 cycles.Comparing the free chloride ion content and total chloride ion content in each corrosion state of rebar,the result shows that the free chloride ion content can more accurately correspond to the possible corrosion state of rebar.The addition of calcined CLDHs into concrete can significantly improve the resistance to chloride and sulfate attack of concrete,which is of great significance and effect to improve the durability of new structures in Inner Mongolia Salt Lake region.However,attention should be paid to the influence on ease of use.