Monitoring the pozzolanic effect of coal fly ash in mortars by EIS

Coal Fly Ash (CFA) is a pozzolanic material widely used to replace ordinary Portland cement (OPC) in mortars and concretes. The main purpose of this replacement is to improve the durability of these materials in a sustainable way from an environmental and economical perspective. In this research, the corrosion process of steel embedded in mortar with 6% of CFA was tested under complete immersion in sodium sulfate solution. The corrosion process was followed by monitoring of open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The addition of CFA led to a 30% increase in mortar resistivity and extended the time for corrosion initiation by approximately 25%, while the corrosion rate decreased by 20%. These improvements highlight the effectiveness of CFA in enhancing the durability of cementitious materials, offering a sustainable and economically viable solution.