INFLUENCE OF SILICA FUME ON THE PRODUCTION PROCESS AND PROPERTIES OF POROUS GLASS COMPOSITE

The article is devoted to the development of the composition and production of a porous glass composite for thermal insulation purposes using a single-stage technology with a reduced NaOH content at temperatures not exceeding 850 °C. Silica-containing natural (tripoli) and technogenic (silica fume) raw materials were used for the synthesis of glass composite. The composition of the charge based on tripoli and silica fume is proposed, which ensures the production of a porous glass composite using energy-saving technology. A mixture of tripoli and silica fume activated with sodium hydroxide is an alternative to the traditional method of producing foam glass materials. The high dispersion of raw materials, the amorphous-crystalline structure of tripoli and the amorphous structure of silica fume ensure a high reactivity of the charge. The novelty of the study lies in reducing the amount of alkali to 10.5% and obtaining a material with increased mechanical strength (up to 4 MPa). It is established that the increased mechanical strength of the material is due to the dissolution of residual quartz and crystallization of cristobalite, as well as the production of a homogeneous fine-porous structure of a porous glass composite with an average pore size of 0.6+ 0.2 mm. Addition of SiO2 to the charge in the form of silica fume in an amount from 10 to 50 wt.% reduces the foaming temperature from 860 to 820 °C and increases the strength of the material from 1.5 MPa (without silica fume) to 4 MPa (30 wt.% of silica fume). The resulting porous glass composite differs from traditional foam glass type heat insulators in increased strength and is considered as a thermal insulation and structural material. The article is of great practical importance, as it solves two problems. On the one hand, the expansion of the raw material base for the production of porous materials with the involvement of waste. On the other hand, the expansion of the scope of application by increasing the strength of the material.