Effect of curing conditions on the pore solution and carbonation resistance of alkali-activated fly ash and slag pastes

The effect of curing conditions (sealed and unsealed) on the pore solution composition and carbonation resistance of different binary alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) pastes is investigated in this study. The studied mixtures were with FA/GBFS ratios of 100:0, 70:30; 50:50, 30:70, 0:100. Ordinary Portland cement (OPC) and Cement III/B (70 wt% of GBFS and 30 wt% OPC) pastes with the same precursor content were also studied to provide a baseline for comparison. Accelerated carbonation conditions (1% (v/v) CO2, 60% RH for 500 days) were considered for evaluating the carbonation resistance of the pastes. The results show a substantial lower [Na+] in the pore solution of the unsealed cured samples compared to the sealed cured samples. it is also found that unsealed curing of the samples leads to a faster carbonation rate. Additionally, it is observed that the carbonation rate decreases with increasing GBFS content independent of the curing conditions. The potential risks with respect to carbonation of the pore solution are also identified and discussed.