Recovery of waste and side products of apatite-nepheline and eudialyte ores processing in manufacture of heat-insulating foam glassy-crystalline materials

Overburden and dressing tailings accumulated in the Murmansk region in impressive volumes represent serious challenges of both economic and ecological character. Maintenance of overburden dumps and dressing tailings involves considerable capital and material expenses. Therefore reprocessing of mining waste and manufacture of building materials, including heat-insulating foam-glass materials, is a promising trend. The work discusses the feasibility of recovering silica-containing waste and ore processing byproducts on the Kola Peninsula. Compositions and techniques for producing blocks and pellets from foam-glass crystalline materials have been developed. The effect of modifying agents on the foam-silicate materials' mechanical properties has been investigated. The production conditions for high-quality foam-silicate blocks have been identified. The foam silicates obtained under optimal conditions have featured a relatively low viscosity (0.3-0.5 g/cm³), high strength (up to 5 MPa) and heat conductivity (0.09-0.107 Wt/m·K). Methods of improving the operating characteristics of foam silicates based on structure perfecting have been proposed. It has been found that as a result of short-time baking of grainy samples the product has a grain strength of 5-6 MPa, density of 0.25-0.35 g/cm3 and a resistance to crushing in cylinder of 2.2-3 MPa, which is 2-3 times higher than that of a material subjected to one-stage thermal treatment. The water absorption of the material is 5-6 %, which is by a half lower compared to a one-stage treated material. The thermal conduction coefficient is 0.091-0.096 Wt/m·K. The obtained materials are recommended for use as heat-insulating surfacing and filling material for garrets, floors and roofs in construction and renovation of industrial and civic buildings.