Processes of foaming and formation of the structure of porous glass ceramics from siliceous rocks
Porous glass-ceramic materials are used in the construction and repair of industrial and civil facilities. They are produced from rocks and industrial waste. The article establishes the influence of the chemical and mineralogical composition of the charge for the production of porous glass ceramics from siliceous (zeolite-containing) rocks and corrective additives (Mg(OH)2, MgCO3, Al2O3) on the processes occurring during its heating. The charge was obtained by joint grinding in a planetary ball mill of siliceous rocks, soda ash and corrective additives. The influence of the charge composition on the processes occurring during its heating has been established by methods of thermal analysis (TA), X-ray phase analysis (XRD), etc. Calcite in the composition of siliceous rocks has a significant effect on the foaming process of the charge. The temperature range of foaming is reduced, and the intensity increases. The additives used have a greater influence on the crystallization process of glass ceramics. As a result, anorthoclase, wollastonite, wollastonite-combeite and diopside glass ceramics were developed. Samples of porous glass ceramics have an apparent density from 154.6 kg/m3 to 298.4 kg/m3, compressive strength from 0.84 MPa to 3.31 MPa, bending strength from 0.57 MPa to 1.52 MPa, maximum operating temperature from 840 °C to 870 °C. According to many physico-mechanical and thermophysical properties, the materials obtained are superior to foam glass and other analogues. They can be used as a thermal insulation material in civil and industrial construction.