Regeneration and Alternative Utilization of Spent Sand-Sodium Silicate Mixtures Structured via Sodium Silicate Dehydration
DOI:
https://doi.org/10.15407/steelcast2026.02.046Keywords:
Sand-sodium silicate mixtures, hydro-regeneration, water resistance, silicate bridges, dehydration, resource conservation, secondary raw materialsAbstract
Relevance. The relevance of this work is driven by the urgent need to mitigate the environmental impact of spent foundry molding sands and to develop high-efficiency, low-energy, and resource-saving reclamation technologies.
Results. It was established that the water resistance of sand-sodium silicate mixtures structured by dehydration exhibits an inversion-type dependence on the sodium silicate content and the duration of MW-structuring (microwave structuring). This behavior is attributed to the competitive processes between the formation and dehydration of silicate bridges (cuffs). It is shown that the structural degradation in water follows a diffusion-kinetic mechanism and is determined by temperature, water volume, and binder content. A generalized parameter ΘSMS, is proposed to synthesize the influence of composition and structuring regimes on the system's properties. It was found that strength, water resistance, and hydro-regeneration duration are described by monotonic exponential functions with asymptotic saturation relative to ΘSMS parameter. An analytical model for estimating the neutralizing agent consumption was developed with a margin of error within 10 %. The study demonstrates the feasibility of effective hydro-regeneration using limited water volumes and subsequent reuse of the mixture.
Scientific Novelty. For the first time, a generalized dimensionless parameter ΘSMS has been introduced. This parameter integrates the sodium silicate dosage and its degree of dehydration, defining the structural state and the complex of properties of sand-sodium silicate mixtures structured by dehydration. A unified correlation between strength, water resistance, and hydro-regeneration duration via the ΘSMS parameter was established and interpreted as a percolation-type transi- tion within the intergranular silicate framework.
Practical Significance. The findings allow for the optimization of MW-structuring and hydro-regeneration regimes for dehydration-structured sand-sodium silicate mixtures. This ensures a reduction in water, energy, and binder consumption while maintaining the required level of technological properties.
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