Study On Properties Of Alumino-silicate Castables For Burnt Stove Door

The paper aimed at increasing service life of bricks for burnt stove door in domestic. On the base of analyzing three kinds of castables with excellent properties for burnt stove door, clay based, semi-silica based and clay-fused silica castables were researched. By using flint clay and alabaster as starting materials, the effect of aluminate cement and silica fume addition on properties of clay based and semi-silica based castables were researched. By adding fused silica particle, changing different cements and match of cement and silica fume, using XRD, SEM, coefficient of thermal expansion determinator and aperture distribution determinator, the influence of fused silica addition on normally physical and chemical properties and thermal shock resistance of castables were systematically studied. Also the mechanism of fused silica improving thermal shock resistance of clay castables and crystallization of fused silica were analyzed and discussed. Industrial test was proceeded at the burnt stove. The results show that:When the addition of silica fume was 2%, the addition of aluminate cement was more than 10% or the addition of aluminate cement was 15%, the addition of silica fume was less than 1%, the properties of clay based and semi-silica based castables could meet the need of bricks for burnt stove door.When fused silica was added to clay castables, the addition of calcium cement was 5% and fume silica was 3%, the castables had most excellent compound properties. The strength of castables did not meet the need of bricks for burnt stove door when calcium cement was replaced by aluminate cement.After further studies, the results showed that: strength, bulk density and apparent porosity approximately reduced with the increase of fused silica addition. Thermal shock resistance was approximately improved with fused silica addition increasing. The main reasons were: thermal-expansion coefficient of castables reduced with fused silica added which has low thermal-expansion coefficient, many micro cracks and pores also formed simultaneously in castables when they were subjected to thermal shock because of the difference in thermal-expansion coefficient of fused silica and matrix. Besides of reduction in the thermal-expansion coefficient and increase in toughness, fused silica particle was not prone to crystallization in the condition that the bricks for burnt stove door was using, so thermal shock resistance was approximately improved with fused silica addition increasing.Three kinds of castables were compared: clay-fused silica castables had most excellent properties, clay based castables took the second place and the properties of semi-silica based castables was the worst, however, the production cost sequentially reduced.On the base of the research in the lab and considering the ration of properties to production cost, clay-fused silica and clay based castables were used for industrial test at one of 7.63m burnt stove. The abnormality did not appear at the stage of dring stove.