Porous biochar for improving the CO2 uptake capacities and kinetics of concrete

Carbonation is a natural process in concrete where atmospheric CO 2 diffuses into the pores of the material and reacts with cement hydrates to form calcium carbonate . Although this process can help to sequester atmospheric CO 2 and mitigate rising levels in urban areas, it slows down over time, resulting in low CO 2 uptake over the service life of concrete. This study proposes a sustainable method to improve carbonation kinetics and CO 2 capture in cement materials by incorporating highly porous biochar. The biochar, derived from seaweed pyrolysis , has a highly developed surface area, including micropores optimised for CO 2 adsorption, mesopores and macropores , as well as oxygen-rich surface groups. These properties allow the biochar to efficiently adsorb CO 2 and retain water. The biochar particles embedded in the cement matrix act as reservoirs for water and CO 2 , influencing hydration and carbonation. The addition of biochar increases water retention in the composite, which promotes the formation of capillary pores and enhances the carbonation process . Experimental data and numerical simulations show that the adsorption of CO₂ in the micropores of biochar facilitates the flow of CO 2 through the composite, allowing deeper carbonation. The interaction between biochar and cement matrix enhances CO 2 diffusion and promotes calcium carbonate formation both within the biochar and at the biochar-cement interface, further improving CO 2 uptake. The study demonstrates that the incorporation of porous biochar into cement materials significantly increases their potential for CO 2 capture, offering a promising approach to sustainable construction and carbon sequestration .