Shrinkage and carbonation of alkali-activated calcined clay-ground granulated blast furnace slag (GGBFS) concrete

Abstract

This research investigates the influence of alkaline concentration and calcium content on the shrinkage mechanisms, carbonation resistance and reinforcement corrosion of alkali-activated concrete system composed of calcined clay and ground granulated blast furnace slag (GGBFS). An increase in Na₂O% led to an improvement in the mechanical performance, pore structure refinement, reducing both accelerated and natural carbonation. However, the increase in alkaline concentration generated a greater shrinkage for mixtures with a higher proportion of GGBFS; the opposite was observed for mixtures with calcined clay as the dominant precursor. The results of 1-year of total shrinkage shows that the concrete containing high calcined clay and Na₂O contents demonstrated the best performance. Importantly, there was no evidence of reinforcement corrosion observed after the carbonation front had reached the steel-concrete interface following 2 % CO₂ accelerated carbonation exposure. This was attributed to the high pH values measured in the carbonated region of the alkali-activated concrete.