PRINCIPLES OF MIXING RATIO IN MAKING FIRECLAY BRICKS

Abstract

In making fireclay bricks by plastic process, we can calculate the total shrinkage, the apparent porocity, and the cold crushing strength of any mixing ratio, from contain properties of raw materials. The formulas are as follows:Cb=(Pg-1)/(Pc-Pg-1);Gb=1-CbWhere, Cb & Gb: clay's & grog's weight portions of the boundary batch mix.Ps & Pc: the packing volumes of the grog and the clay.V=Vg'.G+Pc.CWhere, V: packing volume of the batch.Vg': the surface coeff. of the grog.G&C: the clay & grog weights per unit batch.S=Sb+(Sc+Sb)C-k⋅Sc(C-Cb)G/G2bWhere, S: the total volume-shrinkage of the batch.Sb: the total volume-shrinkage of the boundary mixture≅0.1Sc: the total volume-shrinkage of the raw clay.k: the coeff. of shrinkage resistance between the clay and the grog≅0.40P(%)=100[1-{α+(1-α)G}/V(1-S)]Where, P: the apparent porocity of the brick.α: the apparent volume ratio of the raw clay to the fired.Y=a(Bc⋅C+Bg⋅G-P)2Where, Y: the cold crushing strength of the brick.a: the constant depending on refractoriness≅0.7 for SK 33.Bc: the sintering coeff. of the clay.Bg: the combination coeff. of the grog.The calculated values are well approximated to the observed values. The process is also applicable to the selection of raw materials.