Using design of mixture experiments to optimize triaxial ceramic tile compositions incorporating Cambodian clays

Two Cambodian clay deposits were used for the development of tile formulations using the statistical design of mixture experiments. The tile formulation also included addition of feldspar and silica sand and Malaysian industrial clay was used for comparison. The specimens were pressed (30 MPa) before firing (1170 °C) and then characterized for their linear firing shrinkage, water absorption and modulus of rupture. Regression models were calculated by relating the sintered properties with the compositions. The significance and adequacy of the models were confirmed by statistical analysis and experimental verification. It was found that Cambodian clays are suitable to be used as raw material in the ceramic tile industry and that the regression models can be used to select the optional compositions with respect to the standard ceramic tile specifications. The models were not tested with the lack-of-fit test as this is only a preliminary study to evaluate the properties of the fired ceramics.