Mechanical Properties and Carbonation Behavior of Hydrated Lime-Activated Systems: Recent Advances and Future Perspectives

This review examines recent advances in hydrated lime-activated systems using hydrated lime (HL) as the sole alkaline activator, with particular emphasis on the effects of reactive precursors and auxiliary materials on mechanical properties and carbonation behavior. Compared with conventional strong alkali activators, HL provides a milder alkaline environment and an additional Ca source, promoting precursor reactions and the formation of C–S–H, C–(A)–S–H, and other calcium-containing hydration products. Precursor characteristics, multicomponent mixture design, water-to-binder ratio, and curing conditions strongly influence reaction kinetics, strength development, hydration products, and microstructure. Carbonation is a key process that distinguishes hydrated lime-activated systems from conventional strong alkali-activated systems and plays an important role in their microstructural and mechanical development. It has a dual effect on material performance, as it can contribute to matrix densification but may also lead to the degradation of calcium-containing binding phases as carbonation progresses. Therefore, material composition and curing conditions should be considered together to balance mechanical performance and carbonation behavior. From a sustainability perspective, hydrated lime-activated systems show promise in by-product utilization, reduced use of conventional strong alkalis, substitution of OPC, and CO2 uptake through mineral carbonation. Further systematic studies are needed to evaluate these potential sustainability benefits.