Recent advances for CO2 mineralization in biochar-amended cementitious composites

Biochar, a carbonaceous material derived from organic waste, has recently been explored to mitigate the negative effects of accelerated carbon-di-oxide (CO2) curing (ACC) on concrete properties. This review categorizes the literature on biochar-amended cementitious composites and examines the key mechanisms governing CO2 mineralization. The influence of CO2 phases (gaseous and liquid) on mineralization during curing is discussed, focusing on how altering CO2 pressure and temperature can enhance the process. We explore the role of biochar's surface functional groups, aromaticity, porosity, and honeycomb structures in both carbonation and hydration. Additionally, the properties of the cementitious matrix—such as saturation degree, porosity, and ideal amorphous phases—are shown to improve carbonation. Despite these advancements, several gaps remain before biochar-amended composites can be adopted as conventional construction materials. These include the development of homogeneous biochar, standardization of ACC conditions, and the assessment of end-of-life leaching. The review highlights that strength gains of up to 71 % and CO2 uptake levels of up to 13 % are achievable in biochar-amended cementitious composites. Furthermore, the knowledge from other hydrocarbon-based materials in the petroleum industry is discussed to better understand the complex interactions of gas-air-solid flow during ACC.