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Preparation of lightweight ceramsite utilizing weathered metamorphic sandstone and fly ash: Optimization of roasting regime and formation mechanism
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DOI：10.1016/j.cemconcomp.2026.106650.png)
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Abstract
En 中文
Weathered metamorphic sandstone (MS) is considered a specific type of solid waste produced during aggregate mining. The feasibility of utilizing MS and fly ash (FA) as raw materials for the preparation of lightweight ceramsite was investigated in this study. The effects of roasting temperature, raw material ratio, and SiC dosage on the properties of ceramsite were systematically investigated. Under the optimal preparation conditions (MS:FA = 90:10, SiC dosage = 3 wt.%, and roasting at 1200 °C for 30 min), the ceramsite achieved a high compressive strength of 3.81 MPa, an expansion rate of 513%, a 1-h water absorption of 1.1%, and an apparent density of 0.76 g/cm3. The thermal conductivity of the as-synthesized ceramsite reached 0.28 W/(m·K). TG/DTG-DSC, XRD, and SEM analyses show that the formation of an amorphous glassy phase during high-temperature roasting contributed to the mechanical strength of the ceramsite. The formation mechanism within the MS-FA-SiC system was further clarified: liquid phase viscosity and anorthite precipitation were synergistically controlled by roasting temperature and Ca/Si ratio (0.14), while the stepwise release of bound water from MS/FA and CO2 generated by SiC oxidation exerted a synergistic foaming effect. Distinct advantages of the as-prepared ceramsite over traditional ceramsite were exhibited. This work provides a novel green technical route for the high-value utilization of MS, updates the foaming theory of high-silicon solid waste-based ceramsite, and provides important references for related studies.
Keywords:
weathered metamorphic sandstone
fly ash
lightweight ceramsite
roasting temperature
formation mechanism
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