FOUNDRY PROPERTIES OF UJAGBA CLAY AND AJAOKUTA RIVER NIGER SILICA SAND BONDED WITH BENTONITE

Abstract

The ceramic refractory was produced from Ujagba clay, Ajaokuta River Niger silica sand and Bentonite. The physical properties like coefficient of linear expansion, linear shrinkages, bulk density and porosity of the ceramic refractory produced were investigated. Varied volume percentages of clay, silica and fixed percentage of bentonite were thoroughly blended in a ball mill. The test samples that contain homogeneous mixture of raw materials were produced via uniaxial compaction. The compacted samples were subjected to firing (sintering) at 12000C held at the temperature for an hour to determine the coefficient of linear expansion and shrinkage. The physical properties like bulk density and porosity were also determined using the ASTM standard. The result obtained from linear thermal expansion revealed that the quartz (SiO2) chemical content in the mixture causes the blend to expand on heating to 1200οC. The shrinkage test carried out revealed that some minerals were burnt off as the temperature reaches 1200οC and a new phase of mullite developed and led to the shrinkage of the brick. The bulk density property is important in the transportation or handling of refractory materials and building houses. The bulk density which is close to the standard bulk density was chosen to be the good one in lining the crucible furnace. The result obtained from porosity test shows that most of the samples have high percentage porosity because of combustible materials in their composition which usually burn off on firing. The chemical analysis result shows that Ujagba clay is not suitable for fire clay production as their SiO2 content is below standard. Hence, the need for upgrading the silica content of the clay