Biochar in cementitious materials: linking feedstock and production to structure, performance, and carbon sequestration

The incorporation of biochar into cementitious systems has attracted growing attention as a strategy to enhance concrete performance while contributing to carbon sequestration and sustainability in construction materials. The structural characteristics of biochar evolve significantly depending on feedstock origin and production conditions, leading to considerable variability in its behaviour within cement matrices. This review critically examines how feedstock diversity and key production parameters, including pyrolysis temperature, activation, and post treatment, govern the structural and physicochemical properties of biochar, such as pore structure, surface area, functional groups, mineral composition, and morphology. These characteristics determine the functional roles of biochar in cement composites, influencing workability, hydration processes, strength development, thermal behaviour, and durability performance. Biochar derived from agricultural residues, woody biomass, and biosolids is comparatively evaluated to highlight how different feedstocks contribute to performance enhancement and carbon sequestration potential in cementitious materials. Despite these promising advantages, challenges remain in optimising biochar dosage, ensuring compatibility with cement hydration, and balancing mechanical performance with environmental benefits. Key knowledge gaps and future research directions are identified to guide the development of high performance and sustainable biochar based cementitious materials.