2025
ACL
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M.Mesnage, R.Omnee, J.Colin, H.Ramezani, J.Jeong, E.Raymundo-Piñero, 'Porous biochar for improving the CO2 uptake capacities and kinetics of concrete', Cement and Concrete Composites 157 105932 (2025) doi:10.1016/j.cemconcomp.2025.105932
Carbonation is a natural process in concrete where atmospheric CO2 diffuses into the pores of the material and
reacts with cement hydrates to form calcium carbonate. Although this process can help to sequester atmospheric
CO2 and mitigate rising levels in urban areas, it slows down over time, resulting in low CO2 uptake over the
service life of concrete. This study proposes a sustainable method to improve carbonation kinetics and CO2
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 CO2 adsorption, mesopores and
macropores, as well as oxygen-rich surface groups. These properties allow the biochar to efficiently adsorb CO2
and retain water. The biochar particles embedded in the cement matrix act as reservoirs for water and CO2,
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 CO2
through the composite, allowing deeper carbonation. The interaction between biochar and cement matrix enhances
CO2 diffusion and promotes calcium carbonate formation both within the biochar and at the biocharcement
interface, further improving CO2 uptake. The study demonstrates that the incorporation of porous biochar
into cement materials significantly increases their potential for CO2 capture, offering a promising approach
to sustainable construction and carbon sequestration.
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