Optimization of the structure and properties of foam-glass ceramics

The basic properties of foam-glass ceramics — a porous inorganic material are optimized in the study. This material is used for thermal insulation of various engineering structures: foundations of buildings, roads and railways, pipelines, etc. The main raw material components of the material are sodium hydroxide and opal-cristobalite rocks: diatomite, tripoli, opoka. The mixture of components is subjected to firing and foams with the formation of a porous structure with vitreous and crystalline phases. A significant impact of two different ways of preparing the batch on the basic properties of the material was studied and analyzed. In the first method, the batch was obtained as a suspension with a high water content, which was subjected to mechanical activation in a vibratory mill. In the second method, the batch was obtained by pushing a mixture of components through calibrated holes with the help of a screw auger. Thus, the batch was an extruded tough-plastic granular mass with lower water content. As a result, the formation of a heterogeneous structure of the samples and the presence of dense non-foamed inclusions, leading to an increased average density of the material were established in the first method. The extruded batch in the second method was foamed more evenly without stratification; thereby the average density of the samples was reduced.  An additional reduction in the average density of the samples by 17% due to the intensification of dissolution of silica during the autoclave treatment of extruded batch was observed. The extrusion method is recommended for the production of foam-glass ceramics in granular form, which contributes to the saving of expensive sodium hydroxide.