Corrosion behaviour of carbon steel reinforcement in simulated concrete pore solutions: Influence of a bio-additive

摘要

Reinforcing steel bars in concrete are usually in a passive state, due to the formation of a protective oxide layer that remains stable in the high alkaline surrounding pore solution. However, carbonation and contamination with chloride and sulphate induce passive film breakdown and pitting corrosion. To prevent such damages, corrosion inhibitors can be added to fresh concrete as admixtures. The aim of this work was to study the influence of a bio-admixture (BA) on the electrochemical behaviour of C15 carbon steel, in concrete pore solutions with different composition at pH =13. For that purpose, electrochemical measurements were performed in various electrolytes representative of concrete pore solutions (CPS) extracted from different fresh concrete mixtures with or without the adjunction of 10 % (v/v) of BA. At E_(corr) in the absence of BA, the corrosion rate and the polarisation resistance, R_p, were shown to depend on the CPS composition, mainly on the sulphate concentration. Consequently, pH is not the only determining parameter for predicting the electrochemical behaviour of steel in concrete environments. In the presence of BA, no corrosion inhibition effect could be observed in the presence of low sulphate concentration at pH 13. On the contrary, in the presence of higher sulphate concentration a corrosion inhibition effect was clearly observed with a lowering of the corrosion rate by an order of magnitude when BA was added into the solution.