Roles of biochar in improving carbon mineralisation and sequestration in sustainable cement–based materials

Biochar (BC) can enhance the carbon sequestration capacity of cementitious composites, offering a promising strategy for reducing carbon emissions. This study reviews the effects of BC on the carbon sequestration capacity of biochar–cement composites (BCC) from a microstructural perspective. Firstly, the effects of biomass type, pyrolysis conditions, and activation methods on the physicochemical properties of BC are discussed. Then, the effects of various types of BC on the hydration and carbonation reactions of cementitious matrices are summarised through micro-characterisation techniques. Moreover, BC significantly affects fresh properties, mechanical properties, and durability of cement composites. Additionally, the mechanisms of carbon sequestration in BCC are analysed. Both physical and chemical methods can significantly modify the microstructure of BC, thereby enhancing its CO 2 adsorption capacity. With increasing CO 2 concentration, both the hydration and carbonation processes in cement composites are further enhanced. Finally, the carbon sequestration abilities and economic benefits of BCC are quantitatively summarised through related case studies. The effects of the physicochemical properties of BC on low-carbon cementitious composites are systematically analysed, demonstrating that BC with different properties exhibits significant variations in the carbon sequestration capacity of cementitious composites. Therefore, optimizing the physicochemical properties of BC represents an effective strategy for reducing the carbon emissions of cementitious composites.