The increasing requirements for environmental protection make the development of energy-efficient technologies for building materials urgent, combining a number of stages in the production of materials into one technological redistribution using more efficient methods of their heat treatment. The article discusses the possibility of obtaining gypsum products from two-water gypsum stone, bypassing the production of gypsum binder, using microwave heating as the most effective and convenient of the existing heating methods, which does not require direct connection of external electrodes to the internal electrodes of the mold, to which the material can burn. rendering the electrodes unusable. Due to the combination of the processes of binder production (dehydration of ground gypsum dihydrate with the elimination of 1.5 water molecules) and the finished product (the reaction of semi-aqueous gypsum with water to form a monolith of gypsum dihydrate) in one apparatus, the total production time of the product is greatly reduced, starting from the extraction of quarries.
Results are provided for a study of the possibilities of preparing corundum heat insulation objects based on hydrophobized crude unground alumina; its content may reach 80%. The saving obtained is due to shortening the service life, use of crude alumina without grinding, including drying of the unfinished product, trimming and grinding of objects, and a reduction in raw material consumption for producing 1 m 3 of objects.Analysis of the production of corundum heat insulation materials shows that their preparation technology is difficult, energy consuming, and in the majority of cases it is far from the optimum. Materials are prepared from finely ground commercial grade alumina. A mix is poured into molds and unfinished product drying lasts two days. After drying an object is trimmed and ground, and the waste comprises up to 40%. Due to the high material content of objects (average density 1300 kg/m 3 ), considerable waste, a requirement for fine grinding of alumina, and prolonged drying this technology is considered to be inefficient under market conditions. Therefore, creation of an efficient and economic composition for corundum lightweight materials with prescribed properties by rational technology with simultaneous intensification of production is an important and urgent task.The actual method is introduction into a mix of microporous filler, within which it is possible to use crude unground commercial grade alumina, consisting of porous aggregates of spherolitic structure. The vibration ground alumina and microporous filler are considered as a single binder of uniform chemical composition with low shrinkage on firing.The essence of the method for preparing modified corundum heat insulation material includes the following. The binder (ground alumina) and hydrophobized microporous filler (unground commercial grade alumina) are mixed with foamed polystyrene and mixed with an aqueous solution. The casting mix obtained is poured into a closed perforated mold and heated electrically. Above 80°C there is final foaming of the polystyrene granules; an excess pressure up to 0.4 -0.5 MPa is created in the mold. Under the action of this pressure there is removal of physically bonded moisture, and this promotes compaction of the mix. After removing from the mold on to a tray the unfinished product is dried and sent for firing.In this work the possibility is evaluated of changing the physicochemical properties of the surface layers consisting of porous spherolites of the filler, in order to prevent moisture absorption during preparation, shipment and charging into a mold of the alumina-polystyrene. For this different water-repellent substances are used of the hydrophobic and hydrophobizing types, not containing any subsidiary products, which reduce corundum refractoriness.Analysis of the effect of adding both forms on the capacity for changing the physicochemical properties of the surface layers of alumina particles showed that a hydrophobizing substance, containing coarse asymmetrically arranged polar molecules, is capab...
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