Refractory ceramics from clays of Mayouom and Mvan in Cameroon

Refractory ceramic bricks were prepared by mixing chamotte to sand-poor Mayouom and sandy Mvan clays, with 30 to 50 wt.% and 10 to 30 wt.% of chamotte, respectively. Samples were shaped by uniaxial pressing of wet granules and fired between 1200 and 1350 °C. They were characterized with the open porosity, the bulk density and the flexural strength. Results indicate that a minimum of 40 wt.% and a maximum of 20 wt.% of chamotte must be added to Mayouom and Mvan clays, respectively, to attain an open porosity in the range of 31 to 44% and a flexural strength of 2 to 4 MPa. Structures of fired bricks contain mullite, cristobalite and quartz crystals embedded into a porous and interconnected microcrystalline matrix. The average thermal dilatation coefficient varies from 4.9 to 8.7 10− 6 °C− 1 and from 9.4 to 11.7 10− 6 °C− 1 for Mayouom and Mvan materials, respectively. All materials undergo weak damages after strong thermal shocks and a long holding time at 1200 °C.