ABSTRACT

This study involves empirical evaluation of Ohiya clay to determine the optimal framework of composing it with other materials into standard ceramic tiles to enable effective industrial scale harnessing of this stranded natural resource in Abia State of Nigeria. Chemical composition of this clay deposit was analyzed using Atomic Absorption Spectrophotometer while two levels central composite response surface design/models were applied in quantifying the effects of varying matrix of this clay and additives on the properties of tiles produced from it. Desirability function analysis was used to determine the optimal tile formulation. Apparent porosity, linear shrinkage, bulk density, water absorption rate and modulus of rupture constitute the tile properties (responses) investigated. Results revealed percentage content of silica, alumina, hematite, calcium oxide, magnesium oxide, sodium oxide, potassium oxide, loss on ignition and alumina-silica ratio of Ohiya clay as 49.02 %, 30.16 %, 1.15 %, 0.32 %, 1.98 %, 0.28 %, 1.57 %, 13.20 % and 0.615% respectively. This confirmed that Ohiya clay meets Grimshaw’s specifications for ceramics applications. Response surface analysis showed that the main effects of the clay and additives influence the tile properties significantly with quadratic and interaction effects. It also revealed 50wt% of clay, 21.39wt% of talc, 3wt% of pyrophyllite, 25wt% of feldspar and 6.01wt% of quartz as the optimal proportions of the constituents for standard ceramics tile production. This optimal tile formulation yields quality tiles with 52.69 kg/cm³ of modulus of rupture, 7.99 % of linear shrinkage, 2.067 g/cm³ of bulk density, 4.97 % of apparent porosity and 2.5 % of water absorption rate which conforms to ISO specifications.The cost of producing 0.0929m² of floor tile based on this optimal design variables is one thousand five hundred and twenty-nine naira (₦1,529). This amounts to 4.64% savings when compared to prevailing market price of one thousand six hundred naira (₦1,600). Hence, adoption of the developed empirical models and optimal tile formulation developed in this study for producing standard ceramic tiles from Ohiya clay is recommended.