Study on the high-temperature resistance of tungsten tailings-based alkali-activated materials by pressure forming

Abstract

Alkali-activated materials (AAMs) were prepared using tungsten tailings via pressure molding and casting, and their high-temperature resistances were analyzed. Variations in their compressive strength, gel, and physical phase transformation, pore structure, and morphology at different temperatures were investigated and comparatively analyzed. Results showed that the compressive strength of both AAMs first increased and then decreased with increasing temperature. At 600°C, the pressure-molded AAM exhibited a considerably higher compressive strength (152.38 MPa) than the cast-molded AAM (42.05 MPa). Thermogravimetric–differential scanning calorimetry, XRD, and FTIR analyses showed that the pressure-molded AAM contained more gel phases than the cast-molded AAM at the same temperature. The gel phase further polymerized and decomposed at high temperatures (>800°C), forming nepheline and zeolite crystals. Mercury intrusion porosimetry and scanning electron microscopy results revealed that pressure molding increases the contact between the gel and unreacted materials, effectively reducing the porosity and densifying the AAM. The pressure-molded AAM had a considerably smaller pore diameter than the cast-molded AAM; thus, the former had considerably higher compressive strength. The porosity and pore size of the pressure-molded AAM gradually increased with the temperature, which polymerized the gel phase and eventually decomposed it; this increased its compressive strength first and then decreased.