The samples were taken from five randomly selected locations in Nigeria Namely: Okpella (Edo¹) and Ojirami (Edo²) in Edo; Ikere in Ekiti state; FUTA in Ondo state and Onibode in Ogun.

The collected samples were dried in open air, after which, the samples were manually crushed into thin particles using a mortar and pestle, and then levitated using the water extraction method. The clay samples were mixed with distilled water and thoroughly stirred and allowed to hydrate for several hours and latter decanted this process is repeated until purer clay is obtained. The samples were sun dried and subsequently dried in a laboratory oven at 110˚C for 24 hours. The resulting dried clay samples were pulverized and sieve with a digital octagon sieve shaker BS/ISO 3310 to an average particle size of 150 µm, and label as processed clay (PC), and sent for analysis.

The clay samples were mixed with sawdust in five (5) different ratios into homogenous paste using an electronic mill, with water as the binding agent. The resulting mixture (clay, sawdust and water) was form into 3 geo- metrical shapes; cylindrical, flat and cubes slabs; it was there after dried in an oven (temperature of 105˚C, humidity of 40%) for 24 hours. After drying, the samples were sintered in a muffle furnace. The firing involved pre-heating of the sample to 450˚C - 500˚C (to burn off the sawdust), followed by heating to the sintering temperature of 850˚C for six hours in the same muffle furnace.

X-Ray Diffraction Analysis the clay samples are shown in Figure 1, while the average crystal size and lattice structure parameter are shown in Table 1.

Mineralogical compositions as determined by X-ray diffraction in Figure 1, shows that kaolinite Al₂Si₂O₅(OH)₄, as the predominant mineral content in all samples Other mineral constituents detected include

free silica or quartz (SiO₂), illite {KAl₂ (Si₃,Al)O₁₀(OH)₂}, The major non-clay mineral constituent in these samples were quartz. The percentage composition of quartz ranges from 9% to 21%. Feldspar’s {(K,Na)AlSi₃O₈}, composition in sample d, was however lower than that of other clays used in the research. According to Brown et al. [6] feldspars are the most abundant mineral group found in Earth’s crust. Albite (NaAlSi₃O₈) anchors the two main feldspar compositional series: the alkali feldspars (Na,K) AlSi₃O₈ and the plagioclase series (Na,Ca)Al(Si,Al)Si₂O₈.

Generally, the XRD result revealed a high degree of crystalinity in all the samples. Careful investigation has reveals that all samples were composed essentially of SiO₂, Al₂O₃, and to very limited extent of K₂O and Fe₂O₃. Some other oxides were also present but in very negligible proportions. All the samples showed Kaolinite Al₂Si₂O₅(OH)₄ as the predominant mineral content with main reflections of silicon oxide and kaolinite.

The X-ray Fluorescence (XRF) results showed in Table 2 indicated that all the clays except Ekiti were siliceous in nature, having the highest number of silica present. Also the presence of Aluminum oxide of the order of between 34% - 45% makes them to fall under the class of Alumino-Silicate refractories [8] . These values are comparable to those obtained for residual and secondary clays from other parts of Nigeria. The presence of iron in the clay samples is clearly observed although in various amounts; this has been supported by various researchers as a rule rather than exception [9] -[11] .

The ratio of clay-sawdust are shown in Table 3, while Table 4 shows test result of Bulk density, linear shrinkage, water absorption and compressive strength of both raw and blended clay.

Water absorption and Liner shrinkage results shown in Figure 2; indicate that as the volume ratio of sawdust increases the water absorption of blended clay increases, this might be due to the porosity of the ceramic filter with the addition of sawdust which is hydrophilic in nature. Ondo clay has the highest water absorption followed by Ogun, while Edo² recorded the lowest water absorption rate.

Linear shrinkage shown in Figure 3 indicates that clay from Ogun has the lowest shrinkage, while Ekiti clay recorded has the highest shrinkage value.

Compressive strength result are shown in Figure 4, were it was seen to decrease linearly (R² = 0.8869) with increasing porosity caused by the addition of different volume ratio of sawdust. Clay samples from Edo² shows superior strength compare to other clay sample used for this research.

From Figure 5, it was observed that, the flow rate of the clays samples increase as sawdust volume fraction increase, with clay from Lagos having the highest flow rate. However clay from Ogun has the lowest flow rate of 0.087 liters per hour.