Preliminary study of the effect of carbonation curing on geopolymers

Estudo preliminar do efeito da cura por carbonatação em geopolímeros

Abstract

Carbonation curing differs from weathering carbonation since it is performed intentionally at the early ages of cement hydration. This cure involves applying different levels of CO₂ (5% to 99%) to concrete for a short period of time, usually followed by conventional hydration. The objective of this article was to evaluate the carbonation curing in metakaolin-based geopolymer concretes, activated with NaOH and Na₂SiO₃, and compare them with Portland cement (PC) concrete. The following tests were applied: determination of pH, carbonation depth, water absorption by immersion, void index, and compressive strength. The results showed that after the carbonation curing, the geopolymer concrete had compressive strength and carbonation depth equivalent to the concrete with PC, but with a lower absorbed CO₂ content. Although this type of cement absorbs less CO₂ but is more sensitive to carbonation. The effect on the void ratio was not remarkable. Furthermore, the alkalinity of concretes can be partially recovered after subsequent curing by water immersion.

Keywords:
carbonation curing; geopolymer; metakaolin; carbon dioxide