Storage and Utilization of CO2 in Ready-mix Concrete Using CO2-loaded Aqueous Inorganic Solvent

By: Benjamin Asare

Recently, there has been significant attention focused on utilizing captured CO2 to produce valuable materials. An example is sequestering CO2 through mineral carbonation and converting it into a commercially valuable product (Jang et al., 2016. Constr Build Mater, vol. 127, pp. 762–773, Elsevier Ltd). A case in point is using CO2 as an input in concrete manufacturing process. Concrete is produced by combining cement, water, and various types of solid aggregates (such as sand and crushed rock or stone) in a mixing container. CO2 can be utilized and permanently sequestered in concrete through the formation of carbonates by the reaction of CO2 with minerals such as calcium oxide or magnesium oxide (Winnefeld et al., 2022. Curr Opin Green Sustain Chem, vol. 38:100672). This process typically takes place naturally in conventional concrete using atmospheric CO2 and at a slow rate. This is because the CO2 in the air can only penetrate the concrete at a rate of few millimeters per year (Alberici et al,. 2017. Ecofys UK, Ltd.). Current curing technologies such as using liquid CO2 and pressurized CO2 gas have all been explored to both accelerate the process and a greater extent of curing. These methods have had limited success.

To improve carbonation or curing of concrete and employ it as a pathway for CO2 utilization, an aqueous inorganic solvent (Sam Rhule, 2023. Faculty of Graduate Studies and Research, University of Regina, pp. 104) was used to absorb CO2 from flue gas emanating from cement production industry. Following the absorption of CO2, the resulting CO2-rich aqueous inorganic solvent was directly utilized in concrete making. During this study, two different types of concrete were produced to assess the feasibility of this approach. One of the concretes labelled conventional concrete was composed of regular sand, cement, rocks and water. The other type of concrete was produced by replacing the water in the conventional concrete with the CO2-loaded solvent. The concrete produced using the CO2-loaded solvent had a higher compressive strength and accelerated curing (i.e. shorter curing time) compared to the control mix or the conventional concrete. This finding suggests that the incorporation of the CO2-loaded solvent penetrated deeper and yield a significantly higher extent of curing and shortened curing time of the concrete.