On Inhibitive Effect Of Inhibitors On Corrosion Of Rebars Induced By Carbonation

Damage of construction induced by corrosion of steel embedded in concrete due to carbonation is familiar and serious. But in the previous research, there was a little work on influence of inhibitors on corrosion of steel embedded in carbonated concrete. In this paper, it was mainly investigated for corrosion of rebar embedded in carbonated mortar and inhibitive effect inhibitors (such as organic inhibitors OA and OB, NaNOi). Investigation included effect of cement type (ordinary Portland cement and sulphoaluminate cement) and mineral admixtures (fly ash and granulated blast furnace slag) on corrosion embedded in carbonated mortar.COi of heavy concentration was used in order to make reinforced mortars carbonated fully in a short time. Corrosion behavior was investigated by electrochemical methods. Application of potential corrosion and potentiodynamic linear polarization response in carbonated mortar samples was studied and discussed. In the experiments, it was established that reinforced samples were immersed for 4 hours before polarized in order to furthest reduce the influence of IR drop and improve the precision.In the paper, corrosion of rebar in following three conditions was mainly investigated:1. Corrosion behavior at different temperature: Corrosion rates were inspected in carbonated samples made of OPC with organic or NaNO2 inhibitors, cured at ordinary temperature, 40℃ or 50 ℃. Tests showed: organic inhibitors have a good inhibitive effects in OPC samples, and higher temperature, worst inhibitive effect. NaNO2 still has a good inhibitive effect, at 40℃ or 50 ℃.2. Corrosion behavior of steel embedded in carbonated mortars cured in combine regime of immersion in solution with 3% NaCl (by %wt) and standard curing room after cured in 20℃, above 90%RH for 112 days. Tests showed: Corrosion rate is high without inhibitors, high dosage of organic inhibitors has good beneficial effect. However, inhibitive effect of NaNO2 decreased after a period of time.3. Corrosion behavior of steel bar embedded in mortar with Cl- .When carbonated samples was cured in standard curing room, corrosion rate of steel was high without inhibitors. Organic inhibitors has a poor inhibitive effect, NaNO2 withabove 2% dosage has a good inhibitive effect in a period of time.In the experiments' results, organic inhibitor has a lower inhibitive efficiency in reinforced specimens made of sulphoaluminate cement (SAC) than made of ordinary Portland cement (OPC), however NaNO2 has a good inhibitive effect in SAC. Corrosion rate of rebar embedded in carbonated OPC specimens mixed with FA or SL increase. Higher dosage of FA or SL, higher corrosion rate.Besides, macro-cell corrosion made with carbonated specimen and non-carbonated specimen cured in 60℃ vapor in sealed trunk or in solution with 3% NaCl(by %wt) was also investigated by LPR. Corrosion rate was measured by LPR. Meaning of experimental data by LPR was discussed in macro-cell samples.