The Technology of Foam-Glass Building Materials for Heat-Insulating Purposes Using Amorphous-Silica Rocks
Abstract
Amorphous-silica rocks are valuable sources of SiO2 and contain alumina, alkali, and alkaline earth oxides, reducing costs and raw material needs. This study investigates glassed amorphous-silica rocks for foam-glass building materials. Using X-ray phase and electron microscopy, the glassed opoks from the Turkestan-Urangai deposit in Kazakhstan were analyzed to determine their chemical and mineral composition as well as structural properties. Key thermal properties and reactivity patterns of amorphous-silica raw materials were identified. The firing temperature of opok-based charges is lower than that of quartz sand due to the weaker bonding energy of ≡Si-O-Si≡ and a higher proportion of ≡Si-OH bonds in opoks, facilitating layered structure formation at reduced temperatures. The temperature-time regime for foaming opoks materials was experimentally established, and technological factors lowering heat treatment temperatures were identified. Silicate formation processes and the phase composition and structure of foam glass were studied. Parameters for producing foam glass directly from natural silica were determined, and the resulting material’s physical and technical properties were evaluated. Thermodynamic modeling of silicate formation, based on the principle of maximum entropy, demonstrated energy-efficient technology for heat-insulating foam glass.