Chloride-initiated corrosion in alkali activated reinforced concrete

The use of ordinary Portland cement (PC) as the principal binder in concrete brings with it significant environmental challenges through the consumption of fossil fuels and emission of carbon dioxide (CO2) during cement production. Concrete specimens made with an alkali activated cementitious material (AACM) produced from an alternative binder and conventional Portland cement concrete were exposed to corrosion inducing environments for 1750 days to monitor their relative durability. AACM concrete shows higher corrosion potential Ecorr and corrosion current densities Icorr than PC concrete due to a reducing environment around the steel surface in AACM concrete, caused by high sulfide concentration in the pore solution. Corrosion resistance of the AACM concretes increases with increasing molarity of the alkali activator, at a constant liquid to binder ratio. The threshold Cl−/OH− value for pitting corrosion initiation in the AACM concrete is between 2.1 and 2.8 compared with 1.08 for the control PC concrete. The AACM concrete evaluated in this study showed greater resistance to chloride induced corrosion than the PC concrete.