Early-age strength of CO2 cured alkali-activated blast furnace slag pastes

Abstract

The effect of CO2 curing including pre-conditioning on alkali-activated slags, activated by different alkaline activators (NaOH, Na2SiO3, and KOH solution), is studied. While dry pre-conditioning before the CO2 curing increases the strengths of all mixtures, the effect of pre-conditioning time is dependent on the alkali activator used to produce samples. The CO3-bearing reaction product in samples also depends on the alkali activator. Gaylussite, pirssonite, hydrotalcite, and calcite are observed in the NaOH activator, and calcite, hydrotalcite, and C4AcH11 are detected in the NaOH and Na2SiO3 (9:1) mixture. The NaOH and Na2SiO3 (5:5) mixture yielded only calcite, and the KOH mixture produced calcite, hydrotalcite, and hydrocalumite. The most significant benefit of the CO2 curing, in terms of the strength gain, of the samples is confirmed by the NaOH and Na2SiO3 mixture (5:5).