Ammonium bicarbonate-activated steel slag as a multifunctional cementitious material with enhanced electromagnetic wave absorption
摘要
Steel slag is a major industrial byproduct with limited applications due to its low reactivity and poor volumetric stability. To enable its high-value utilization, this study proposes a novel activation strategy using ammonium bicarbonate (NH₄HCO₃) to enhance the activity index and stability of steel slag, facilitating its use in multifunctional, environmentally friendly building materials with electromagnetic wave absorption capabilities. The hydration behavior, microstructural evolution, and multifunctional performance of the activated slag were systematically investigated. Results reveal that the addition of 10 wt% NH₄HCO₃ significantly enhances volumetric stability and mechanical performance by consuming a substantial amount of free CaO and Ca(OH)₂, promoting the formation of calcium silicate hydrate (C–S–H), and accelerating f-CaO carbonation through CO₂ released during decomposition. When 30 wt% of the activated slag is incorporated into cement, the activity index reaches 92%, while the 28-day curing volumetric expansion is markedly reduced from 2 to 1 mm. Furthermore, EM characterization reveals that the material containing 10 wt% activator exhibits a minimum reflection loss of − 45 dB at a matching thickness of 2.3 cm—an improvement of 30.4% over untreated slag. Thus, this work provides a new technological pathway for developing advanced construction materials that integrate mechanical robustness, electromagnetic shielding, and environmental sustainability, enabling the high-value utilization of metallurgical solid waste.