Study on the early volume stability of cement-based materials during CO₂ curing

In this study, the impact of carbonation curing regime and fly ash dosage on the volume stability of concrete was investigated. The shrinkage of cement pastes specimens incorporating 0–30 % fly ash after 2–24 h pre-conditioning and 4–24 h carbonation curing was experimentally determined. Carbonation curing can lead to a maximum increase of 39.4 % on dry shrinkage of cement paste compared to the standard-cured ones. Prolonged carbonation curing can also enlarge the average and critical pore sizes by 123.4 % and 697.8 %, respectively. The water penetration of prolonged carbonation-cured cement mortar was increased by 56.1 %, consequently. However, appropriate carbonation curing increased compressive strength and sequestered CO₂ effectively. The addition of an appropriate dosage of low-calcium fly ash can mitigate the adverse impact of carbonation curing on the volume stability of cement paste.