Suitability of alkali activated ggbs/fly ash concrete for chloride environments

This study investigates chloride ingress into alkali-activated slag/fly ash (AA-S/F) concretes with various ratios of slag to fly ash (80/20, 60/40,40/60 and 20/80). Alkaline activators were a mixture of sodium hydroxide and sodium silicate to obtain between 6-8% sodium hydroxide (NaOH) concentration by weight of cementitious material. The Si0₂/Na₂0 ratios (silica modulus, Ms) of mixtures were 0.45, 1.0 and 1.25. Tests applied included typical fresh and hardened properties, air content, slump, compressive strength, bulk resistivity and non-steady state chloride migration. The results show that while attractive engineering properties can be achieved, the chloride ingress in the AA-S/F concretes studied here with > 20% fly ash is moderate to high and this may make them unsuitable for use in reinforced concrete in chloride environments.