The paper discusses the use of aluminum-magnesium spinel (previously synthesized or formed during use) in refractory concretes not only from the viewpoint of its high stability and scope for the formation of solid solutions with components of steel-melting slag and also of good thermophysical properties but also from the purposive reactive formation of structures with elevated high-temperature strength.Current trends in the refractory industry include the production and use of unformed refractories preferentially over block ones. The accelerated progress in unformed refractories in recent years has arisen particularly from elevated consumer demands for dry refractory mixtures for linings and concretes, including ones for use in pneumatic and vibrational emplacement. These dry refractory mixtures represent a qualitatively new stage in the progress of unshaped refractories, since their production and use most effectively incorporates user specifications for maximal simplicity in lining operations and also the scope for users to employ advanced technologies in combination with rigorous technical monitoring of the dispensing, grinding, and mixing operations with precision equipment. Dry refractory mixtures are prepared with optimal grain-size composition and they are balanced on material and phase compositions of the ingredients, amongst which there are uniformly distributed special additives in small or ultrasmall amounts, which serve to regulate the rheological and working properties.Steel melting is one of the largest users of dry refractory mixtures based on corundum. They traditionally employ alumina and high-alumina cements (denoted by CAC in the foreign literature), whose amounts are restricted to provide elevated refractory performance (the abbreviation for concretes with low contents of cement in LCC, and for ultralow it is ULCC). For similar reasons, use is made of cements in which the CaO content is restricted and whose phase compositions are represented in the main by calcium monoaluminates and dialuminates, such as Secar 71 and Secar 80 [1] or CA-270 [2].The corundum component is provided by a wide range of natural items (bauxite, andalusite, disthene-sillimanite concentrate) as well as especially prepared materials (sintered and electrically melted corundum, or bonite, which is a technical product based on calcium hexaaluminate, high-alumina firebrick, tabular corundum, and ultrafine and reactive aluminas, including ones containing aluminum-magnesium spinel) [2 -8]. The inclusion of silica in the concrete components increases the strength and thermal stability as a result of the synthesis of mullite in the concrete under the conditions of use, but it restricts the refractory performance. Silica can be used as an independent component in dry refractory mixtures, usually in the ultrafine state. In that situation, it regulates not only the phase composition of the concrete but also its rheological characteristics, since it provides higher mobility and flow than reactive alumina [3,6].Aluminum-magnesium spi...
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