Properties of Sintered Brick Containing Lignite Bottom Ash Substitutions

Abstract

This study examined the feasibility of utilizing lignite bottom ash as a partial substitute for ball clay in an insulating brick composition. Lignite bottom ash is a waste byproduct that is high in alumina and silicates and is therefore a candidate material for replacing aluminosilicate minerals such as clay. The lignite bottom ash powder was obtained from the Mae Moh power plant, Thailand. Small brick specimens were produced by die pressing a mixture of lignite bottom ash, ball clay and aluminum hydroxide. The composition of the mixture contained a fixed amount of aluminum hydroxide, while the lignite bottom ash replaced from 30 to 70% of the ball clay. The pressed samples were sintered at 1300 oC for 1 hour in air. The density, porosity, strength and thermal properties of the samples were measured. A microstructural analysis of the sintered brick was also performed. It was found that the porosity of the samples increased from 35 to 45% with increased lignite bottom ash content. The modulus of rupture and the thermal conductivity of the bricks were reduced with increased lignite bottom ash content, likely due to the increased amount of porosity. Dilatometric analysis found that the thermal expansion increased with increased amounts of lignite bottom ash, possibly as a result of an increased amount of glassy phase. Despite the high thermal expansion coefficient at high temperature, the feasibility of using lignite bottom ash in the insulating brick composition was demonstrated.