This study examined the influence of a hydrogen-containing atmosphere on cement-bonded refractory castables. Four series of tests were conducted using different materials, including fireclay, high-alumina bricks with SiC, and sol-gel bonded phases such as mullite and anorthite. Each test series consisted of three samples, which were subjected to aging in a tube furnace at temperatures of 1100 °C and 1500 °C and holding times of 24 and 72 hours, respectively. The temperature of 1100 °C represents the upper temperature limit of a direct reduction plant, while the temperature of 1500 °C represents a temperature range in which corrosion is accelerated. An optical examination of the samples revealed a change in colour, indicative of the formation of oxygen vacancies. At 1100 °C, there were only minor changes, with no significant loss of mass or change in porosity. At 1500 °C, however, a greater loss of mass was observed, particularly at the gas inlet, as well as an increase in porosity. The chemical composition of thretee high-alumina material undergoes a transformation, with the loss of SiO2, MgO, and alkalis. Depending on the temperature and holding time, non-oxide agglomerates, primarily composed of iron and phosphorus, form on the surface of the samples. Similarly, agglomeration occurs in the castable with a high alumina content and SiC. In contrast to the other test series, however, these agglomerates do not consist of iron and phosphorus, but of iron and silicon.