Some ceramic properties of clays from central Cambodia

In this study, the natural clay deposits from central Cambodia (Kampong Chhnang and Kandal) were collected and investigated for their physical, chemical, mineralogical, thermal, and firing characteristics to evaluate their potential suitability as raw materials in various ceramic applications. Physical properties were identified by particle size distribution, specific surface area, consistency limits, total organic content, and cation exchange capacity (CEC). Chemical, mineralogical, and thermal properties were carried out by XRF, XRD, and TG/DTA techniques, respectively. To evaluate their ceramic behaviours, the samples were fired at temperatures from 800 to 1200 °C. Firing characteristics were determined by bulk density, linear firing shrinkage, water absorption, and flexural strength. A Malaysian clay (BBC), which is a common raw material in ceramic tiles manufacturing, was used as reference sample. Results show that the main oxides in the samples were SiO2, Al2O3, and Fe2O3, whereas the other oxides were present only in small quantities. The amount of Fe2O3 in Cambodian clays ranged from 5 to 11 wt.%, whereas Fe2O3 in BBC clay is about 2 wt.%. Illite, chlorite-vermiculite, kaolinite, and quartz were present as dominant mineral phases and the minor phases of albite and calcite also appeared in the samples. From the results of the fired properties, a significant development of densification of ceramic behaviour could be noticed at firing temperatures above 1000 °C. Analyses of chemical and mineralogical composition along with the mechanical properties of Cambodian clays demonstrated that they are most appropriate to be used as raw materials for the production of structural ceramics.

Research Highlights
► Clay deposits from central Cambodia were investigated on their ceramic behaviours.
► Cambodian clays presented high iron content (5 to 11 wt.%) with high plasticity.
► Major peaks assigned to quartz, kaolinite, illite and vermiculite-chlorite.
► High densification of ceramic was noticed at the firing temperature above 1000 °C.
► Clays C1 and C4 were most suitable for structural ceramics compared to C2 and C3.