Production of Spherical Porous Ceramic from Waste Coal Fly Ash and Waste Glass for Construction Lightweight Aggregate

The use of solid waste materials as feedstock for lightweight aggregate (LWA) production is a potential waste management strategy. Creating value-added LWAs solely from solid waste enhances the sustainability of their production. This study investigated the potential of synergistic blends of waste coal fly ash (WCFA) and waste glass (WG) to produce spherical porous ceramics for construction LWA. The research focused on identifying optimal sintering conditions to produce WCFA/WG-based LWAs with desirable engineering properties. A rapid sintering method using a stationary tube furnace was employed to manufacture WG-WCFA-based LWA. Process conditions were selected with guidance from thermodynamic predictions of the slag content and the Krieger and Dougherty empirical model for the viscosity of the slag-solid suspension. From the prediction, ranges of experimental parameters were identified, including sintering temperatures from 950°C to 1,100°C for WG contents of 0–40 wt%. The physical and mechanical properties of LWA depend on the pore structure formation during sintering, which is governed by slag quantity, viscosity of the slag-solid suspension, availability of unburnt carbon, and neck growth of particles. The required slag content and viscosity of the slag-solid suspension for achieving the desirable properties of LWA based on WG and WCFA were determined to be in the range of 45%–60% slag content and 1×104–2×105 Pa·s viscosity.