A study on compressive strength and corrosion behaviour of reinforcing steel in chloride contaminated fly ash based geopolymer concrete

This paper investigates the effect of alkali concentration on compressive strength and corrosion behaviour of reinforcing steel in chloride contaminated geopolymer concrete (GPC) mixes. In this work, fly ash based GPC mixes were prepared with different concentrations of NaOH solution i.e. 8 M and 10 M. Chloride was admixed to GPC mixes at the time of preparation in the form of sodium chloride. Sodium chloride concentrations used were 0%, 1.5% and 3% by mass of geopolymer solids content. Cube specimens and prismatic reinforced concrete specimens were prepared from GPC mixes for determining 7-days compressive strength and corrosion parameters respectively. Potential measurement and corrosion current density by linear polarization resistance (LPR) measurement were carried out on prismatic reinforced concrete specimens at different testing ages. From the results, it is observed that the compressive strength of GPC specimens increased with increase in molarity of NaOH solution. The potential values of steel reinforcement in chloride contaminated GPC specimens were more negative than -270 mV (SCE) for both molarity of NaOH solution, indicating greater probability of occurrence of steel reinforcement corrosion. Further, the corrosion current density of steel reinforcement increased with increase in admixed sodium chloride concentration for both concentrations of NaOH solution. There was an increase in corrosion current density with increase in molarity of NaOH solution i.e. from 8 M to 10 M at all testing ages till 180 days.