Engineered Ceramic Composites from Electrolytic Manganese Residue and Fly Ash: Fabrication Optimization and Additive Modification Mechanisms

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The sustainable valorization of electrolytic manganese residue (EMR) and fly ash (FA) presents critical environmental challenges. This study systematically investigates the performance optimization of EMR-FA ceramic composites through the coordinated regulation of raw material ratios, sintering temperatures, and additive effects. While the composite with 85 g FA exhibits the highest mechanical strength, lowest porosity, and minimal water absorption, the formulation consisting of 45 wt% EMR, 40 wt% FA, and 15 wt% kaolin is identified as a balanced composition that achieves an effective compromise between mechanical performance and solid waste utilization efficiency. Sintering temperature studies revealed temperature-dependent property enhancement, with controlled sintering at 1150 °C preventing the over-firing phenomena observed at 1200 °C while promoting phase evolution. XRD-SEM analyses confirmed accelerated anorthite formation and the morphological transformations of FA spherical particles under thermal activation. Additive engineering demonstrated that 8 wt% CaO addition enhanced structural densification through hydrogrossular crystallization, whereas Na2SiO3 induced sodium-rich calcium silicate phases that suppressed anorthite development. Contrastingly, ZrO2 facilitated zircon nucleation, while TiO2 enabled progressive performance enhancement through amorphous phase modification. This work establishes fundamental phase–structure–property relationships and provides actionable engineering parameters for sustainable ceramic production from industrial solid wastes.