The sintering of barley straw ash was significantly depressed with addition of calcite powder. CaO was
again observed as the major crystalline phase from the sintered mixture of calcite and barley straw ash. It
indicates presence of surplus CaO that did not react with the barley straw ash. The unreacted CaO will
dilute the barley straw ash without further sintering, which was confirmed by observation of a rather loose
structure of ash residues even after sintered at 1000 °C. The calcite may provide basic calcium oxide for
reaction with silica and incorporates into the low melting temperature potassium silicate.[16] This was
confirmed by identification of more calcium silicates in the sintered barley straw ash-calcite mixture