Effect of mullite formation on properties of refractory castables

In order to study the effect of the mullite bond phase on the physico-mecha nical and refractory properties of the refractory castables, four castable samples were prepared castable 1 contained 15 wt.% calcium aluminate cement (80% alumina) and 85 wt.% well graded tabular alumina. The other three sam ples (2, 3, 4) contained 10, 5 and 2% cement and 5, 10 and 13% of an alimin a/silica mixture (in the ratio 2.33:1, the molecular ratio of mullite). The ir composition was investigated after firing at different firing temperatur es using X-ray diffractin analysis. The physico-mechanical and refractory p roperties of such castables were determined according to standard specifica tions. Castable 4 that contained only 2 wt.% cement with 13 wt.% alumina/si lica mixture and 85 wt.% well graded tabular alumina aggregate exhibited ou tstanding physico-mechanical and refractory properties after firing at 1500 degreesC due to the presence of mullite in the bond phase with very little CaO. This enables their use in various refractory applications such as in steel, aluminium, copper, glass, cement, chemical and ceramic production. ( C) 2001 Elsevier Science Ltd and Techna S.r.l. All rights reserved.