Sustainable utilization of industrial furnace slags as CO2-reactive materials for construction

The incorporation of industrial by-product such as ground granulated blast furnace slag (GGBS) and ladle furnace slag (LFS) in cement-based materials has gained attention as a sustainable approach to reduce carbon emissions, as well as transforming them into valuable resources. However, their effectiveness in early-strength development and performance under accelerated carbonation remain underexplored. This study investigates the influence of GGBS and LFS on the early-age mechanical properties and carbonation behaviour of blended cement mortars exposed to accelerated CO 2 curing (ACC). Mortar samples with up to 50 % replacement of cement by GGBS or LFS were prepared and subjected to both standard curing and ACC. Compressive strength tests are conducted to evaluate hardened performances. The hydration and carbonation behaviour of the samples are analysed through X-ray diffraction, thermogravimetric analysis, and microstructural characterisation. Results indicate that GGBS can replace cement up to 50 % while maintaining early strength through C-S-H formation. In contrast, LFS is effective only up to 10 %, as excess replacement leads to weaker C-A-H formation. Under ACC, GGBS-blended cement undergoes greater carbonation, while LFS-blended cement shows lower carbonation potential due to pre-existing CaCO 3 and stable C-A-H phases. These findings demonstrate the potential of ACC to improve performance in GGBS-based green cement, whereas its benefit in LFS systems is limited by its inherent mineralogical stability. This highlights the importance of tailoring ACC parameters to slag composition is crucial for maximising performance and supporting the transition toward more sustainable and low-carbon construction technologies.