Study Of Concrete Deterioration Process On Corrosion Behaviour Of Two Kinds Of Steel Rebar

Traditional structural materials will inevitably face severe corrosion problems in the application of the marine environment.And the lack of durability of large structures such as bridges and piers caused by rebar corrosion is particularly prominent in the construction of southeast coastal areas and offshore islands in China,seriously restricting the development of marine economy.Concrete provides the direct service environment for steel rebar,and its deterioration is the main cause for rebar corrosion.In the present study,based on the chemical composition of the deteriorating concrete pore fluid,the corrosion behaviour of HRB400 steel and 2304 duplex stainless steel rebar in simulated pore solutions of deteriorating concrete were studied through electrochemical test methods and XPS analysis techniques.It is expected to provide basic corrosion data for the prediction of service life of reinforced concrete buildings,and provide new ideas for the construction of island infrastructure.The passive film formation process of HRB400 steel rebar in curing stage of concrete and the depassivation behaviour of HRB400 steel during immersion in simulated pore solutions of deteriorating concrete were investigate.Results demonstrate that HRB400 steel rebar exhibits good corrosion resistance in simulated solution of curing concrete,and a stable passive film can be formed after 5 days of immersion.The XPS analysis shows that the passive film has a two-layer structure,a thin inner layer rich in Fe(?)products and the outer layer mainly composed of Fe(?)products.In inland areas,concrete acidification is the main reason for the depassivation of HRB400 steel rebar.And its corrosion process will be dramatically enhanced when the pH of concrete pore fluid drops to 9.In marine environment,the critical chloride threshold necessary for depassivation of HRB400 steel was highly dependent on pH value.The threshold expressed as the ratio of[Cl-]/[OH-]increased with pH,indicating that the inhibitory effect of OH-was stronger at high pH values.In addition,the carbonate and bicarbonate ions presented in the concrete pore fluid can also inhibit the depassivation of HRB400 rebars caused by chloride ingress.The study found that 2304 duplex stainless steel rebar had the feasibility of being applied in concrete preparation of seawater and marine sand.In the curing stage of concrete,2304 duplex stainless steel can withstand up to 2 M implanted chloride ions.In the deteriorating stage of concrete,when the pH of the pore liquid was not lower than 11,the pre-passivation film of the 2304 duplex stainless steel can maintain stability under the condition of chloride ions concentration up to 2 M.Until the pH value dropped to 9,the rebar will suffer corrosive attack by chloride due to the lack of OH-inhibition.The thesis proposed a new idea of service state evaluation and life prediction of reinforced concrete buildings,based on the corrosion behaviour of HRB400 steel rebar in deterioration concrete environment,combined with the changes of pore fluid near reinforced concrete interface with time under the influence of external environment.