Preparation and Properties of Quartz-Anorthite Ceramics Synthesized Using Desert Sand and Coal Fly Ash

Low-cost desert sand and coal fly ash were used to synthesize high-quality quartz-anorthite composite ceramics. The effects of the addition of fly ash on the densification of green bodies, phase transformation, microstructure, and mechanical and thermal properties were investigated. The results showed that the densification of green bodies occurred when they were sintered from 1,100 degrees C-1,200 degrees C, and the phase transformation of anorthite mainly occurred in fly ash from 846.9 degrees C to 982.7 degrees C. Temperatures of densification and anorthite transformation increased with increased addition of fly ash. At 1,100 degrees C, beta-cristobalite formed in desert sand and remained at room temperature; the content increased with increased sintering temperature. The quartz-anorthite ceramics were composed of alpha-quartz, beta-cristobalite, anorthite, and amorphous phase. Anorthite was formed by the solid-state reaction of quartz, mullite, and other phases in the desert sand and fly ash and was promoted by liquid-phase sintering at higher temperatures. The highest bending strength of 115.6 MPa and highest hardness of 668.3 Vickers hardness (HV) were produced for samples with 40% by weight fly ash sintered at 1,100 degrees C. Samples with 100% by weight added fly ash had the lowest mean thermal expansion coefficient (5.1 x 10(-6).K-1), the highest linear shrinkage (24.2%), and the highest bulk density (2.5 g/cm(3)) when sintered at 1,200 degrees C. The samples with 0%-60%, 80%, and 100% by weight added fly ash exhibited a low water absorption of 0.8%-1.8% when sintered at 1,100 degrees C, 1,150 degrees C, and 1,200 degrees C, respectively. This technique can be feasibly used to fabricate civil engineering materials such as decorative ceramics, roof tiles, wall bricks, and insulation and filling materials. DOI: 10.1061/JMCEE7.MTENG-14712. (c) 2023 American Society of Civil Engineers.

Automated summary

Low-cost desert sand and coal fly ash were used to synthesize high-quality quartz-anorthite composite ceramics. The addition of fly ash affected the densification, phase transformation, microstructure, and mechanical and thermal properties of the ceramics. The results showed that anorthite was formed by the solid-state reaction of quartz, mullite, and other phases in the desert sand and fly ash, promoted by liquid-phase sintering at higher temperatures. The technique has potential applications in civil engineering materials.