3. Results and discussion
3.1. Characteristics of raw materials
Results of chemical analyses of the raw materials are presented in Table 1. From the table, the result shows high silica content of all raw materials. Iron content of 8.83% in the clay was sufficient to develop a reddish color. The high K2O (3.5%) content in clay raw material is probably due to the relatively large amount of illite content.
Table 1. Chemical compositions (in wt%) of clay and rock dust.