Self-formed mullite containing refractory barium silicate cements and their castable applications

Six batches consisting of different percentages of barite, kaolin and calcined alumina were sintered at 1500-1600degreesC for 3 h to produce self-formed mullite containing barium silicate cements. The compositions of the cement mixes were investigated using X-ray diffraction. Physicomechanical, sintering and refractory properties were tested according to standard specifications. Each of the mixes, composed mainly of varying proportions of mullite and dibarium silicate minerals, showed different behaviour. The best compromise between cementing, sintering and refractory properties was provided by the mix prepared from 60 wt-% barite, 25 wt-% kaolin and 15 wt-% calcined alumina, consisting of about 54 wt-% dibarium silicate and 33 wt-% mullite. Self-formed mullite containing castable prepared from 15 wt-% of a fine powder of the chosen mix as the cement and 85 wt-% of graded aggregate of the same mix showed good volume stability, high mechanical properties, high thermal shock resistance as well as high loadbearing capacity.