Effects of Firing Conditions on the Properties of Calcareous Clay Roofing Tiles

The effects of firing conditions on the microstructure and physical properties of clay roofing tiles are studied. This research presents the effects of oxidizing and reducing atmosphere on Kanjiža clay material with carbonate content up to 22% by weight and the characterization of the final products. The firing was done both in the laboratory and under industrial conditions. The Fe2+/Fetotal ratio played a decisive role in the sintering process under a reducing atmosphere. The formed glassy phase, with the presence of Fe2+, attacked the earth-alkali oxides after the carbonate decomposition and more effectively filled smaller pores. The obtained results justified the benefits of the reducing firing atmosphere with 5% CO, lower porosity, higher frost resistance values, and changed microstructural characteristics