Synergistic Effect of Ladle Furnace Slag and Biomass Bottom Ash in Alkali‐Activated Binders

ABSTRACT In this study, the co‐activation of ladle furnace slag (LFS) with biomass bottom ash (BBA) is proposed as an effective approach to enhance the mechanical performance and microstructural development of alkali‐activated binders. Blends containing different LFS/BBA ratios were activated using a potassium‐based alkaline solution. Mechanical properties were evaluated up to 90 days. The evolution of reaction products and microstructure was investigated by x‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results indicate that increasing the BBA content significantly improves the mechanical response, reaching maximum compressive and flexural strength values of 11.1 and 2.9 MPa, respectively, for binders containing 75 wt% BBA. This enhancement is associated with a higher availability of amorphous silica from the BBA, which acts as a chemical buffer that mitigates the potential expansion issues related to the free CaO and MgO present in the LFS. The synergistic interaction between these residues promotes the formation of a stable hybrid (K,C)‐A‐S‐H gel and a more refined pore structure. These findings demonstrate that the co‐activation of LFS with BBA is a viable and sustainable route for producing alkali‐activated binders, contributing to the high‐value recycling of metallurgical and biomass residues within a circular economy framework.