Dependence of the properties of concrete samples from fireclay concrete mix before and after heat treatment on the amount of alumina cement and refractory clay additive

During operation, refractory concretes are exposed to the complex effects of thermal shock, corrosion, mechanical shock and abrasion, and the resistance of these materials depends on such factors as chemical composition, microstructure and phase transformations that occur at high temperatures. Given this, the present study investigated the effect of the amount of alumina cement of the Gorkal­40 brand and the addition of refractory clay on the main properties of fireclay concrete before and after heat treatment. It was found that the introduction of an additive of 0.5 % clay into the concrete mixture containing 15 % Gorkal­40 cement provides samples with a set of high property indicators: apparent density 2.19 g/cm3; open porosity 20.3 %; cold crushing strength after 7 days of curing — 40.8 N/mm2, after firing at a temperature of 1350 ºС — 35.8 N/mm2. The pilot product in the form of burner stone from a concrete mix of optimal composition was made. After firing, the burner stone had no external defects (it was not melted, had no cracks or notches, and had a uniform yellow color). Properties of the satellite samples: cold crushing strength after 7 days of hardening — 41 N/mm2, after firing at a temperature of 1350 ºС — 38 N/mm2; open porosity and apparent density of the fired samples — 20.2 % and 2.18 g/cm3, respectively. Based on the research results, the technology of the fireclay concrete mix of the SSHBG brand, which is produced by the Institute according to technical specification TU U 23.2—00190503—445:2019, was improved.