Corrosion monitoring by open circuit potential in steel reinforcements embedded in cementitious composites with industrial wastes

Abstract

Corrosion is one of the main issues affecting service life of reinforced concrete structures. The Open Circuit Potential (OCP) technique is a non-destructive method used to survey and monitor this problem. This test can also be used in laboratory environment and provide valuable information supporting the selection process of supplementary materials for durable concretes. Although this qualitative technique is commonly used, there is still a lack of consensus on the suitability of specific procedures for experimental analysis, such as type of reference electrode and influence of accelerated aging procedures (adoption of wetting/drying cycles and level of immersion of specimens). Therefore, the present study aims to evaluate the method for prediction of early steel corrosion activity in the accelerated OCP tests. The paper is focused on testing eco-efficient cementitious composites containing industrial wastes, such as sugarcane bagasse ash sand (SBAS) and water treatment plant sludge (WTPS), in replacement of natural sand. The results showed that an adoption of combined wetting/drying cycles, together with a partial (rather than total) immersion of specimens in NaCl solution, leads to earlier appearance of corrosion. This allows to shorten the period of testing by almost 10 weeks. It is due to higher access to oxygen and higher concentration of free chlorides from the saline solution accumulated in a porous system. The type of reference electrode is of lesser importance. Moreover, incorporation of 30% SBAS and 3% WTPS results in higher protection for steel corrosion, confirming wide applicability of the OCP technique to any cementitious matrices with or without industrial wastes.

Keywords

• Steel corrosion
• Reinforced concrete
• Open Circuit Potential (OPC) technique
• Non-destructive method
• Water treatment plant sludge (WTPS)
• Sugarcane bagasse ash sand (SBAS)