China's Refractories

Abstract: Lightweight alumina-silica castables were prepared using closed-cell perlite (2-4 mm), open-cell perlite (4-6 mm) and coal gangue ceramsites (2-5 mm) as aggregates, floating beads (0.3-0.5 mm), sinking beads (0.6-0.8 mm), silica micropowder, α-Al₂O₃ micropowder, zirconia and zircon micropowder as fines, and Secar 71 cement (calcium aluminate cement) as the binder. The effects of the coal gangue ceramsites addition (0, 6%, 12%, 18% and 24%, by mass) on the properties of the as-prepared lightweight alumina-silica castables were investigated. The results show that: (1) the addition of coal gangue ceramsites can reduce the sintering shrinkage of the specimens and help to improve the strength and thermal shock resistance; (2) the samples with the addition of coal gangue ceramsites can produce pores in the matrix of the sintered samples, which provides enough space for the growth of CA₆ complex solid solution and expands the irregular lamellar structure; (3) with the addition of coal gangue ceramsites increasing, the linear shrinkage of the samples heat treated at 1 000 or 1 200 ℃ firstly reduces and then increases, the bulk density increases and the apparent porosity decreases; the cold compression strength and the thermal shock resistance of the specimens heat treated at 1 200 ℃ firstly increase and then decrease. Thus, the optimal addition of coal gangue ceramsites is 18%.

Key words: alumina-silica castables, closed-cell perlite, coal gangue ceramsites, comprehensive performance