Research On Anti-corrosion Protection Of Reinforced Concrete With Smart OH~--regulated Microcapsules

Reinforced concrete is one of the most widely used building materials today.In view of the development needs of China’s coastal strategy,the development of reinforced concrete infrastructure in the coastal environment is increasingly demanding.Under the coastal environment,however,the reinforced concrete structure is easily affected by the environment action,especially in the splash zone,where the concrete structure is easily susceptible to chloride ion ingression which then induced steel corrosion.Corrosion of the reinforcing steel in the concrete will cause cracking of the structure ahead of its design service life,greatly reducing the original designed service life and causing major losses to the national economy directly and indirectly.Aiming at the problem of corrosion of steel bars in special environments,pH-adjusted microcapsule technology provides a new type of solution for the durability of reinforced concrete structures,which is of great importance for the performance protection on structure during the service process and for extending the life of the structure in the coastal environment significance.Based on the environmental effects of the splash zone,the theory of steel corrosion,and polymer microcapsule preparation technology,an intelligent OH~-regulated microcapsule system is designed to enhance the corrosion resistance of steel bars in reinforced concrete structures in the coastal environment.In situ X-ray tomography imaging tracked the OH~-regulated microcapsule system’s corrosion protection process.Generally speaking,the onset of corrosion of steel bars is often related to the chloride ion concentration and OH~-concentration inside the concrete.The wet and dry cycle process in the coastal environment splash area not only accelerates the penetration of chloride ions,but also results in the loss of alkalinity and calcium phase,which makes the steel structure corrosion in the coastal environment often occur in the splash area.This paper proposed the intelligent OH~-adjusting microcapsule system with ethyl cellulose material(EC)as the microcapsule wall material and calcium oxide(Ca O)as the core material.It mainly adjusts the pH environment inside the reinforced concrete to ensure that the steel is passive.The stability of the film structure in a certain pH environment can delay the occurrence of steel bar corrosion or reduce the steel bar corrosion rate.The successfully prepared intelligent OH~-regulated microcapsules(Ca O/EC microcapsules)are firstly analyzed for basic performance,including basic indicators such as the microcapsule morphology,particle size range,and mechanical properties of the cement mixing process.The research results showed that the intelligent OH~-adjusting microcapsules have a micron-level rough surface,a moderate particle size,and still have good mechanical properties after being stirred and hydrated with concrete,meeting the basic requirements of concrete in this system.Secondly,the wet-dry cycle was used to simulate the effect of the coastal environment splash zone,and a new non-destructive X-ray computed tomography(X-rayμCT)technology was used to track and compare in situ the corrosion characteristics of steel bars in reinforced concrete structures with and without microcapsule system,and quantitatively analyze the corrosion inhibition effect of the steel bars in this system.The research indicates:(1)The intelligent OH~-regulated microcapsule system can delay the occurrence of corrosion of steel bars(rusting point);(2)The intelligent OH~-adjusting microcapsule system slows down the corrosion rate of steel bars through pH adjustment,thereby delaying the cracking(cracking point)of concrete,thereby showing effective protection of steel bar corrosion.(3)SEM research shows that under dry and wet cycling conditions,when Cl-erodes to concrete,the microcapsules will be triggered to rupture,and intelligent OH~-regulation can be achieved in the concrete by releasing CaO.(4)The realization effect of intelligent OH~-regulated microcapsule systems with different amounts is not consistent,and the protection effect of steel bar corrosion is not proportional to the amount of microcapsules incorporated.Excessive amount of microcapsules will introduce new concrete strength problems.