A comprehensive review on CO₂ utilization in cement and concrete: From microstructural transformations to structural applications

The cement and concrete industry (CCI) are a dominant source of CO₂ emissions, contributing nearly 8 %. While traditional mitigation strategies focus on reducing emissions, CO₂ utilization presents a paradigm shift transforming CO₂ from an industrial by-product into a functional material component. This review provides a novel integrative perspective, evaluating carbonation curing, CO₂-reactive aggregates, and alternative binders in terms of physicochemical mechanisms, structural performance, and large-scale implementation potential. Carbonation curing has demonstrated the ability to accelerate hydration kinetics, enhance early-age strength, and refine pore structures while permanently sequestering CO₂. CO₂-modified aggregates, such as carbonated recycled concrete aggregates (RCA) and steel slag, not only reduce waste but also improve mechanical integrity. Emerging binders, including alkali-activated and magnesium-based cements, enable in-situ CO₂ mineralization, presenting a viable low-carbon alternative to Portland cement. These advancements contribute to increased durability, enhanced sulfate resistance, and superior microstructural stability. However, scaling up laboratory innovations to an industrial level remains a challenging task. High CO₂ capture costs, suboptimal carbonation kinetics, and the absence of regulatory frameworks hinder widespread implementation. This review highlights key knowledge gaps and suggests future research directions, including machine learning-driven mix optimization, automated carbonation control, and integrated life-cycle assessment. By shifting CO₂ from an environmental burden to a value-added resource, this study lays the foundation for next-generation carbon-neutral cementitious materials, advancing both sustainability and high-performance construction.