Dual effect of fly ash on the corrosion resistance of lateral reinforcement and the stress-strain curve of confined concrete

Abstract

This paper investigates the dual effect of fly ash on the corrosion resistance of lateral reinforcement and stressstrain behavior of confined concrete in reinforced concrete (RC) columns. Twelve columns (150 mm by 150
mm cross-section and 600 mm in height), including four plain (Group 1) and eight RC columns (Groups 2 and
3) were cast with varying fly ash replacement proportions (0%, 10%, 20% and 40%) by weight of ordinary
Portland cement (OPC). Lateral reinforcements of Group 2 and 3 were subjected to induce corrosion by an anodic impressed voltage of 3V DC and 6V DC respectively for around 460 hours (19 days). All columns were
then tested, and the lateral reinforcement was retrieved to obtain the degree of corrosion. The test results show
that the corrosion resistance of the lateral reinforcement was improved significantly when fly ash was used to
replace OPC. The corrosion current density passing through lateral reinforcement reduced by more than 80%
when 40% of fly ash was used to replace OPC. Under accelerated corrosion, fly ash increases the confinement
effect of lateral reinforcement resulting in improvements to the peak stress, corresponding strain at peak stress
and ductility of confined concrete. The best improvement in the stress-strain response of confined concrete was
when fly ash was used to replace OPC at a proportion of less than 20%. The observed increases were around
10% for peak stress and 92% for strain at peak stress.