The critical need to mitigate climate change has intensified research into carbon sequestration technologies, particularly within the construction sector, where concrete production contributes significantly to global CO 2 emissions. Foam concrete, due to its high porosity and lightweight structure, presents a promising medium for enhanced CO 2 uptake and permanent storage. This work introduces an integrated approach that combines biochar, CO 2 -entrained foam bubbles, and carbonation curing to enhance both carbon sequestration and mechanical performance in foam concrete. Biochar derived from biomass pyrolysis was incorporated at low dosages, enhancing both carbonation reactivity and strength through its high surface area and porosity. CO 2 foam bubbles served as localised reservoirs, facilitating early-age carbonation and mineralisation. The separate and combined effects of biochar and CO 2 foaming were systematically evaluated under carbonation curing at different ages, demonstrating that carbonation timing is a critical controlling factor, with carbonation applied at ≥ 14 days enabling sufficient strength development while maintaining effective CO 2 uptake. Biochar-modified mixes achieved up to 66% higher CO 2 uptake than controls, and the integration of CO 2 foams further boosted CaCO 3 mineralisation, reaching ∼41 kg/m 3 of stored CO 2 without compromising strength. Characterisation analyses confirmed the formation of calcium carbonate and the presence of carboaluminate phases, indicating multiple carbonation pathways not previously characterised in foamed concretes. Collectively, these findings indicate the potential of porous concrete to serve as a future scalable carbon sink, supporting the development of carbon-sequestering construction materials.
Siddika et al. (Mon,) studied this question.