Enhancing cement-based materials hydration and carbonation efficiency with pre-carbonated lime mud

Lime mud (LM) is a highly alkaline solid waste generated during the papermaking process, and its direct application in cement-based materials can result in insufficient material properties. Pre-carbonation can reduce the alkalinity of LM and improve its ability as a supplementary cementitious material. This study explored the potential of pre-carbonated lime mud (CLM) to partially replace Portland cement under normal and carbonation curing. It was found that CLM absorbed some CO₂ and reduced a small amount of alkalinity after pre-carbonation treatment. Under normal curing conditions, LM can promote the hydration reaction at an early age but inhibit subsequent cement hydration due to its alkalinity. In contrast, CLM significantly alleviated the negative impacts of directly incorporating LM into Portland cement. Under carbonation curing conditions, a significant improvement in the compressive strength of cement-based materials containing LM and CLM was observed. The alkaline properties and nucleation effects of CLM and LM enhanced CO₂ sequestration efficiency. Especially after 14 days of carbonation curing, the sample with CLM exhibited higher CO₂ uptake and better mechanical properties than the sample with LM. This study provides a new solution to improve the resource utilization of LM and mitigates the negative impacts of LM on cement-based materials.