Effect of addition of talc on the sintering characteristics of fly ash based ceramic tiles

The sintering characteristics of fly ash-talc mixtures having 0-100% talc (w/w) in the presence of 10% (w/w) sodium hexa meta phosphate (SHMP) have been studied. In the fly ash rich mixtures, the presence of needle shaped mullite and rhombohedral aluminum phosphate phases is responsible for providing impact strength to sintered tile bodies. On gradual addition of talc, the decrease in the concentration of sillimanite and increase in the concentration of sodium magnesium phosphate crystals is responsible for the observed improvement in the impact strength of tiles. With increase in talc content, initially the % water absorption decreases to reach a minimum for a fly ash-talc mix containing 60% (w/w talc) where after it again starts increasing. The apparent density of the tile samples increases with increasing talc content in the raw mix due to densification as well as higher density of talc as compared to fly ash.