Comprehensive research of clay of the Chap deposit

Abstract

A study was conducted on the physicochemical changes in the technological characteristics of clay raw materials from the “Chap” deposit in the Issyk-Kul Region during the firing process. The chemical and particle size distributions, plasticity, molding moisture content, air shrinkage, firing shrinkage, water absorption, bulk density, and strength index were determined for the mixtures. An increase in temperature was accompanied by intensified firing shrinkage, increased strength, and reduced water absorption. It was established that an increase in temperature is accompanied by an increase in firing shrinkage and strength, along with a simultaneous decrease in water absorption. Two compositions were used in this study: the first without any additives in the batch, and the second containing 97% clay and 3% charcoal. During the firing of clay minerals, metakaolinite forms, the formation of mullite-like phases begins, interparticle contacts develop, and liquid-phase sintering occurs under the action of alkali and alkaline earth oxides. The addition of charcoal reduced air shrinkage but, after burning out, created additional open porosity; therefore, density and strength remained lower, while water absorption was higher than the control values. The results obtained characterize the initial stage of sintering, additional tests are required to confirm the material’s suitability for refractory applications. Temperature-dependent curves for the studied parameters were plotted, and a comparison of the two compositions was performed.