Co-melting mechanism of foam ceramics prepared using blast furnace slag and multiple solid wastes

Current research on the preparation of foam ceramics predominantly centers on individual solid waste materials or simple mixed systems. There is a notable absence of systematic analysis regarding the synergetic reaction mechanisms of multiple complex solid wastes, as well as comprehensive studies on the material migration pathways in multi-component solid waste systems. To systematically investigate the sintering reaction mechanism for preparing foam ceramics using blast furnace slag in conjunction with multiple solid wastes, to this end, raw materials were divided into high- and low-melting-point solid waste mixtures, and a eutectic temperature range of 1160–1220 °C was determined through thermodynamic calculations and melting point experiments. Layered eutectic experiments were performed, and X-ray diffraction analysis, scanning electron microscopy, and other analysis methods were used to study the phase transition law and structural evolution characteristics of heterogeneous interfaces under temperature gradients. The results indicate that, at 1180 °C, eutectic zones of high- and low-melting-point solid waste mixtures form a stable structure with diopside as the main crystalline phase and uniformly distributed pore structures. The diffusion of Na⁺ in the low-melting point solid waste mixture can significantly reduce the liquid phase formation temperature of the CaO-SiO₂-Al₂O₃-MgO system, and the resulting silicate melt can continuously corrode the solid particles of the high-melting point solid waste mixture, promoting the synthesis of diopside and pyroxene phases in the eutectic zone. This “solid–liquid erosion” effect not only optimizes the matching relationship between melt viscosity and surface tension but also achieves precise control of the pore structure by regulating the ion migration rate. This study clarifies the synergistic preparation mechanism of foam ceramics from multicomponent solid waste in terms of multiphase interface reaction kinetics through layered eutectic experiments and material migration path research. This study presents a theoretical basis for developing new solid-waste-based lightweight high-strength ceramic materials.