Effects of particle distribution of matrix on microstructure and slag resistance of lightweight Al 2 O 3 –MgO castables

Abstract For lightweight castables containing microporous aggregates, the compacted matrix component is a key factor in determining their useable lifespan, and this matrix is influenced by both the particle packing and sintering process. In this study, the grain grading of lightweight Al 2 O 3 –MgO castable matrices was adjusted to create a particle size distribution that close to the Andreassen model with q -values of 0.25, 0.28, 0.31, and 0.34. After sintering at 1500 °C for 3 h, the microstructures and slag resistances of lightweight Al 2 O 3 –MgO castables with different particle packing arrangements were compared and discussed. The results show that a q -value no higher than 0.31 was needed to ensure formation of a denser matrix. For the smallest q -value that was studied (0.25), the resulting matrix had a large grain size (5–12 µm) and a relatively small average pore size ( D 50 =2.10 µm), which favours the formation of Ca (Al, Fe, Mn) 12 O 19 layer distributed within the matrix. This resulted in the highest resistance to slag corrosion observed ( I c =7.93%), whereas the cracks existing between the matrix and the aggregates due to a large volume shrinkage decreased the slag penetration resistance ( I p =45.9%). The microstructure of the matrix with a q -value of 0.28 was uniform and compacted, which reached an acceptable compromise between resistance to slag corrosion ( I c =22.4%) and resistance to slag penetration ( I p =11.5%).