A New CO2 Sequestration Process via Concrete Products Production

This paper investigates the possibility of using concrete building products to absorb carbon dioxide during their production and develop high early strength at the same time. Type 10 and Type 30 Portland cements were examined by their abilities to serve as CO₂ absorbents when exposed to carbon dioxide with 100% and 25% concentrations, the former simulating the recovered CO₂ and the latter representing the as-captured flue gas without processing. The reaction took place in a chamber under 0.5 MPa pressure, at ambient temperature and in a duration of two hours. CO₂ uptake was quantified by the direct mass gain and by infrared based carbon analyzer. The performance of carbonated concrete was evaluated by MOR and compressive strength. It was found that the CO₂ concentration played a critical role in CO₂ uptake. Two-hour carbonation using 100%, CO₂ enabled the Portland cement to consume up to 16%, of carbon dioxide, gain a strength equivalent to 2-month conventional curing and have an all-solid section in a 14 mm thickness. Carbonation with 25%, CO₂ enabled a maximum 9.7% mass gain with lower strength and a partially solid section. Without reinforcing steels, carbonated concrete products can have better strength and durability due to the depletion of calcium hydroxide, and can be fabricated faster than the conventional steam curing. If the process can be shown technically and commercially viable, concrete building products will become more environmental friendly and shall contribute directly to the reduction in global greenhouse gas emission.