Significance Analysis Of Critical Chloride Ion Concentration And Incipient Rust Parameters Of Steel Bars In Light Aggregate Concrete Under Chloride Environment

Porous aggregate makes the internal ion transport and diffusion behavior of lightweight aggregate concrete different from that of ordinary concrete,but the corrosion resistance of the lightweight aggregate concrete structure is always controversial due to the influence of a strong interface,especially in a chlorine-salt environment.In this paper,the critical chloride ion concentration of reinforcement corrosion in light aggregate concrete under a chlorine salt environment is systematically studied,the critical chloride ion concentration of reinforcement corrosion in light aggregate concrete is analyzed,the similarities and differences between light aggregate concrete and ordinary concrete are analyzed,and corresponding suggestions are put forward to provide theoretical reference for the engineering application of this kind of concrete.The main contents include:1.Test the critical concentration of chloride ions in lightweight aggregate concrete.Under the natural dry-wet cycle,the samples were monitored in real-time by the half-cell potential method,linear polarization method,and AC impedance spectroscopy to analyze the undulating trend of steel bars,and to study the change rule of critical chloride ion concentration under different aggregate stages,admixtures and different water-cement ratios.The results show that increasing the aggregate order can increase the critical chloride ion concentration of reinforcement corrosion.With the increase of wollastonite content,the concentration of OH-in concrete is greatly reduced,and the critical chloride ion concentration is decreased.With the increase of water cement ratio,the critical chloride ion concentration of steel corrosion decreases.2.Analysis of corrosion microstructure of reinforcement in lightweight aggregate concrete.The pore structure parameters of concrete under different water-cement ratios were analyzed,and the relationship between pore structure parameters and critical chloride ion concentration was established.The X-ray diffraction test and the scanning electron microscope test on the surface of lightweight aggregate concrete at microscopic scale were completed.The results show that with the increase of water-cement ratio,the porosity of reinforced concrete interface increases and the critical chloride ion concentration decreases.With the increase of wollastonite content,Ca（OH）₂ decreases in the concrete pore solution,and a small Friedel salt ratio is generated.Meanwhile,the structure of the surface layer is loose.3.Significance analysis of influencing factors of lightweight aggregate concrete.The database of critical chloride ion concentration in common concrete was established,and the significant analysis of critical chloride ion concentration parameters was completed.The results show that the water-cement ratio,p H value,and mineral admixture have the most significant influence on the critical chloride ion concentration,and the three factors that have the greatest influence on the critical chloride ion concentration of reinforcement corrosion in lightweight aggregate concrete are consistent with those in ordinary concrete.The data show that the increase in the water-cement ratio not only increases the porosity of concrete but also increases the oxygen content and water content,which accelerates the corrosion rate of reinforcement and reduces the critical chloride ion concentration.A high p H value can promote the formation of steel bar passivation film and inhibit the damage of Cl-to the passivation film.With the increase in p H value,the critical chloride ion concentration shows an upward trend.Mineral admixtures reduce pore solution p H value and chloride binding ability,and the decrease in p H value is more obvious than the increase in chloride ion binding ability,so the critical chloride ion concentration decreases.Through the research of this paper,the change law of the critical chloride ion concentration value of steel corrosion under different factors was revealed,the undulating characteristics of the steel bar of light aggregate concrete under the natural dry-wet circulation mechanism were defined,and the influence degree of various variables of light aggregate concrete on the critical chloride ion was analyzed,which has important theoretical significance for promoting the engineering application of light aggregate concrete.