IMPROVING THE REFRACTORY PROPERTIES OF ALKALERI CLAY USING RICE HUSK ASH AS ADDITIVE FOR FERROUS CASTING

Refractory materials are non-metallic materials with high melting point, inert to chemical corrosion and maintain their structural properties at high temperature. This research evaluated the physical properties such as bulk density, apparent porosity, linear shrinkage, cold compressive strength, thermal shock resistance, loss on ignition and refractoriness of Alkaleri clay with rice husk ash (RHA) admixture using design expert 7.1.6 Central Composite Design (CCD). The physico-chemical properties of Alkaleri clay and rice husk ash ( RHA ) from Rafin zurfi, Yelwa in Bauchi State was characterized using Energy Dispersive X-ray Fluorescence Spectrometry (ED-XRFS), the result show that Alkaleri clay has 33.3wt% of aluminum oxide (Al2O3) and 46.35wt% of silicate oxide (SiO2), hence the clay belongs to alumino-silicate clay while the RHA has 74.2wt% of silicate oxide  and 8.52wt% of potassium oxide (K2O) that is responsible for its pozzolanic effect, 2.0% of magnesium oxide (MgO) and 4.09% of calcium oxide (CaO) that is responsible for its  increase in bonding strength with the clay. From the optimization results, desirability of 0.617 suggested an optimum refractory property at 88.75g of Alkaleri clay and 14.22g of RHA. The refractory properties corresponding to this desirability is apparent porosity of 22.3536%, cold crushing strength (CCS) of 2.0838kN/cm2, firing shrinkage of 3.214%, bulk density of 1.92084g/cm3, loss on ignition (L.O.I) of 9.3099%, thermal shock resistance of 14.7424 cycles and refractoriness of 1595.99OC. These results fall within ASTM standard of refractory material for ferrous casting.