The Numerical Simulation Research Of Cathodic Protection In Reinforced Concrete Structures

For the marine reinforced concrete structures,the corrosion of steel rebar embedded in the RC structures induced by chloride ion contamination is the major reason for the deterioration.To prevent steel rebar from corrosion and lengthen the service lifetime of marine RC structures,much more impressed current cathodic protection systems have been applied to the marine RC structures.More and more researchers have adopted the numerical simulation method to design the ICCP?impressed current cathodic protection?systems and investigate the protective potential and current distribution in ICCP systems for marine RC structures under different environmental conditions with the development of the numerical simulation method.However,the cathodic protection models established for underwater RC structures are based on microcell corrosion mechanism.It is not sound for the research on the coupled macro-and microcell corrosion mechanism controlled cathodic protection systems of underwater RC structures now.And much more work should be done to explore the effect induced by different geometry parameters of RC structures for the cathodic protection potential and current distribution in coupled macro-and microcell corrosion systems.Therefore,the corresponding numerical simulation models of cathodic protection for two different underwater RC structures controlled by coupled macro-and microcell corrosion mechanism were established in this paper based on experimental and mechanism analysis.The effects induced by macrocell corrosion,state of initial corrosion of steel bar,crack and different structural parameters for the cathodic protection systems were investigated.Then the reliability of two numerical simulation models were discussed and the two models were applied to further explore the influence of other structural parameters for cathodic protection system.The main work is summarized as follows:?1?The research on the underwater three-layer RC structures shows that:through the analysis about the corrosion rules of the underwater three-layer RC structures,cathodic protection numerical simulation model based on oxygen concentration corrosion cell can well reflect the protective potential and current distribution in the underwater three-layer RC structures.The results of the research also show that the protective current tends to flow into the more positive steel rebar when relatively low cathodic protection current density is applied to control the corrosion of the RC structures which is controlled by coupled macro-and microcell corrosion.And the results also show that the system of the higher initial corrosion rate needs higher impressed current density to get complete protection and the current distribution of the system is more uneven.?2?The research on the underwater cracked RC structures shows that:through the analysis about the corrosion rules of the underwater cracked RC structures,protective potential distribution calculated by cathodic protection numerical simulation model which is based on chloride ion concentration distribution coincides well with the experimental prototypes.The presence of crack on the concrete cover makes the potential difference between the steel rebar in the crack zone and sound concrete zone,which changes the microcell corrosion mechanism into the coupled micro-and macro-cell corrosion process.The results of the research show that protective current tends to flow into the more positive steel rebar embedded in the sound concrete zone.To provide whole the steel rebar in the RC structure which is covering a crack of 0.5 mm width with complete cathodic protection,the impressed current density is increased to 60m A·m^-2.And higher impressed current density is needed with more cracks on the concrete cover and more current is required to control the microcell corrosion of the steel rebar in the cracked zone.