CO2 sequestration by high initial strength Portland cement pastes

Too high moisture content prevents CO2 from penetrating into the inner part of samples, compromising CO2 diffusion and overall carbonation effect.

“It is believed that too high moisture content prevents CO 2 from penetrating into the inner part of samples [31,87,91,94,95], therefore compromising CO 2 diffusion and overall carbonation effect.”

Most previous studies suggested an optimal relative humidity between 50% and 70% for gas-solid carbonation of RCA at ambient temperature.

“Because carbonation reactions hardly take place at low moisture content, most previous studies suggested an optimal RH ranging between 50% and 70% for gas-solid carbonation at ambient temperature [19,86,93,94].”

Carbonation curing of fresh cement-based composites at fluid state appears to be less effective due to the blocked diffusion of CO2 by liquid.

“Generally, the carbonation curing of fresh cement-based composites at fluid state appears to be less effective [20,57,94], due to the blocked diffusion of CO 2 by liquid.”

From the hydration accelerating period of cement paste onwards, with substantial production of calcium hydroxide and C-S-H, cement-based composites become ready for carbonation.

“From the hydration accelerating period of cement paste onwards, with substantial production of calcium hydroxide and C-S-H taking place, the cement-based composites become ready for carbonation [94].”