CONTAMINANT CHARACTERISTICS OF WASTE FOUNDRY SAND: TOXICITY, MECHANICAL PROPERTIES AND USES

Residual molding sands from iron casting processes in Tepeapulco, Hidalgo, Mexico—accounting for 65–85% of total foundry waste—were characterized. Mineralogical phases were identified via X-ray diffraction (XRD), while chemical composition was determined using X-ray fluorescence (XRF), inductively coupled plasma (ICP), and atomic absorption spectroscopy (AAS), supported by particle size distribution analysis. Predominant phases included quartz (PDF [96-900-6304]), albite (PDF [96-900-0528]), and orthoclase (PDF [96-900-0312]); minor phases comprised montmorillonite and berlinite. Chemical composition was: 70.1% SiO2, 14.7% Al2O3, 4.4% Fe, 0.20% MnO, 4.30% MgO, 0.40% K2O, 0.6% CaO, 5.26% Na2O, and 0.2% TiO2. Corrosivity testing yielded a pH of 9.38, and reactivity tests showed no reactions with water or air. CN? and S²? ions were below detection limits, and flammability testing confirmed the absence of alcohols, classifying the material as non-toxic and non-flammable. Physical characterization included density, Atterberg limits, thixotropy, stickiness, plasticity, and color. Bricks were fabricated by combining residual sand with clay, vermiculite, and mining waste. The composites exhibited compressive strength of 3.024–16.883?MPa, water absorption of 8.90–18.41%, permeability of (1.64–2.23) × 10?³?cm³/s, and bulk density of 1050–1600?kg/m³. These findings highlight the material’s potential for reuse in construction applications, offering mechanical performance comparable to or exceeding commercial products, with the added benefit of being environmentally safe. Keywords: Residual Sand; Mining Waste; Construction Material; Water Absorption; Permeability; Compressive Strength