Alkalinity and Cl-/Oh- affecting reinforcement corrosion in alkali activated concrete

The paper reports the effect of hydroxyl ion (OH) and chloride (Cl) concentrations of pore fluid on reinforcement corrosion in AAC under long term chloride exposure. The OH and Cl are influenced by the activator molarity. AAC has much higher OH than the control Portland cement (PC) concrete at early ages of chloride exposure and the corresponding Cl/OH ratios are lower for AAC. However, under long term chloride exposure, the Cl/OH ratios of AAC start exceeding the PC concrete due to the superior chloride binding capacity of Portland cement. The critical threshold Cl/OH ratio for corrosion initiation in AAC is between 2 and 3.28, whereas it is < 1 for PC concrete. The steel reinforcement in AAC remains free from chloride induced corrosion for a longer period and up to higher Cl-/OH- ratios than PC concrete due to the presence of elemental Sulphur (sulfides) on the steel surface in AAC.