Effectiveness of fly ash activation on the corrosion performance of steel embedded in concrete

The use of fly ash to replace a portion of cement has resulted in significant savings in the cost of cement production. Fly ash blended cement concretes require a longer curing time and their early strength is low when compared with ordinary Portland cement (OPC) concrete. By adopting various activation techniques such as physical, thermal and chemical methods, hydration of fly ash blended cement concrete was accelerated and thereby improved the corrosion resistance of concrete. Concrete specimens prepared with 10, 20, 30 and 40% of activated fly ash replacement were evaluated for their open-circuit potential measurements, weight loss measurements, impedance measurements, linear polarisation measurements, water absorption test, rapid chloride ion penetration test and scanning electron microscopy test and the results were compared with those for OPC concrete without fly ash. All the studies confirmed that, up to a critical level of 20–30% replacement, activated fly ash cement improved the corrosion resistance properties of concrete. It was also confirmed that the chemical activation of fly ash yielded better results than the other methods of activation investigated in the current study.