Synthesis of a mineralizing agent for Portland cement from aluminum production waste

Abstract

Priority directions in innovative technologies of the construction materials industry are the expansion of the use of mineral and chemical additives in the production of cements, as well as alternative raw materials and fuels in production processes. During the production of aluminum at the enterprise JSC RUSAL Krasnoyarsk, the method of electrolytic reduction of aluminum oxide or alumina dissolved in a cryolite-based melt generates fluorocarbon-containing (FCC) waste, which currently accumulates more than 16,000 tons per year. Due to the increased year-round generation of waste with a high content of carbon, fluorine and aluminum, it is urgent to develop technologies that will effectively use them as a new mineralizer product for the production of Portland cement clinker - calcium fluoride. This paper describes the thermal method of waste processing FCC for receipt of the mineralizing agent (fluorite). The disadvantage of FCC as a raw material is an increased concentration of alkali metals, whose oxides negatively affect the process of hydration of clinker minerals, and lead to the formation of efflorescence on products. To reduce their content, the finished fluorite was washed with water. Calcium fluoride as a mineralizing agent in the production of Portland cement, reduces the clinkerization temperature, increases the content of alite, changes the stability, polymorphism and reactivity of phases. The resulting fluorite with a high mass concentration of 73.9% CaF2 makes it possible to reduce the clinker formation temperature, which increases the energy efficiency of obtaining Portland cement. The technological process for removing alkaline components from the product will reduce the likelihood of destructive processes in concrete caused by the aggressive action of reactive silica aggregates and freezing and thawing processes.