Sharp changes in temperature lead to thermal stresses in the refractory material, and as a consequence, to the formation of micro and macro cracks, as well as to a decrease in its mechanical characteristics. In this work, the destruction of heat-resistant fireclay concrete of various classes: low-cement and medium-cement with the addition of quartz sand (added to the composition to increase the alkali resistance of concrete) and with the addition of metal fiber (to reduce cracking) have been investigated after exposure to thermal shocks. Two methods were used to determine the heat resistance of concrete, in which the destruction of the material was assessed using ultrasound: the “water-cooled slab” method and the one-sided heating-cooling method. Studies carried out using the one-sided heating-cooling method revealed the formation of macrocracks in the samples of low-cement concrete. This method also turned out to be more sensitive in assessing the destruction of concrete.