Combined Chemical and Physical Activation of Blast‐Furnace Slag Using Lime Kiln Dust: Mechanisms and Performance Enhancement

Utilizing industrial by‐products as supplementary cementitious materials is an effective strategy for improving the sustainability of the construction industry. This study investigates a waste‐to‐waste approach in which lime kiln dust (LKD)—a fine particulate by‐product of lime calcination—is employed as a multifunctional activator to enhance the reactivity of ground granulated blast‐furnace slag (GGBS) in blended cement systems. GGBS–cement composites containing 0–7 wt.% LKD (replacing the corresponding proportion of the initial GGBS mass) were prepared by dry premixing, and their mechanical performance and hydration‐associated microstructural evolution were systematically examined. The 5 wt.% LKD mixture exhibited the highest 7 days activity index of 77.95%, whereas the 3 wt.% mixture exhibited the highest 28 days activity index of 99.62% and provided the best overall balance between early‐ and later‐age performance. The X‐ray diffraction, thermogravimetric and derivative thermogravimetric, Fourier‐transform infrared, and SEM observations are consistent with combined chemical and physical contributions from LKD. Chemically, CaO/Ca(OH) 2 in LKD may provide alkalinity that promotes the latent hydraulic reaction of slag, whereas CaCO 3 may participate in the formation of AFm‐type carboaluminate hydrates (Hc/Mc). Physically, fine LKD particles may act as microfillers and nucleation sites, consistent with the denser microstructure observed in the examined regions. Overall, the enhanced mechanical performance is consistent with concurrent chemical activation and LKD‐induced physical modification. These findings highlight LKD as a low‐cost and effective activator for GGBS and indicate potential environmental benefits associated with lower Portland‐cement demand and the coordinated utilization of the steel‐industry by‐products GGBS and LKD.