Effect of chalk thermal treatment mode on its strength
Vadim A. Lipin, Saint-Petersburg State University of Industrial Technologies and Design, Saint-Petersburg, Russia;
Daniil A. Trufanov, LLC AMC «Explorer», Belgorod region, Old Oskol, Russia.
Natural chalk is characterized by a fine-grained structure. The processing of chalk in conditions traditional for calcium carbonate baking is accompanied by its almost destruction and the formation of a huge amount of dust. The paper presents strength characteristics of chalk and chalky stone baking obtained with different temperature-time conditions of heating the raw material to a temperature of 450-600 C. The uniaxial compression method was used to determine the strength depending on variable factors.
Based on the experimental data, a model was constructed that determines the dependence of chalk strength on time and heating temperature. In the temperature range of 450-600 C, the strength of chalk stone increases with increasing temperature and decreases with the increasing heating rate. In the process of isothermal heating, several factors will immediately affect the strength of a chalky stone: the formation and growth of calcite crystals, the evaporation of water, and the agglomeration of calcite grains. With an increase in the heating temperature from 450 to 600 C, the average size of the crystals significantly increases and crystals with an estimated size of more than 4 microns are detected. An increase in the size of crystals is associated with an increase in their growth rate. The agglomeration of grains occurs at a temperature of 600 C.
Keywords: chalk; baking; calcium oxide; tensile strength; lime.
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Scientifiс periodical «Zapiski Gornogo Instituta / Journal of Mining Institute» has been published since 1907 as a periodical scientific and scientific-educational edition in Saint-Petersburg Mining University. The periodicity of publishing is 6 volumes per year.