1. Clay – a natural earth
To a clay mineralogist:
 is a layer silicate mineral (called phyllosilicate) or
other mineral which imparts plasticity and
hardens upon drying or firing (Guggenheim and
Martin, 1995)
 could be referred to as a particle size in a soil or
sediment of a diameter < 0.002 mm or 2 microns)
 composed of silica (SiO2), Alumina (Al2O3) and
water (H2O) plus appreciable concentrations of
oxides of iron, alkali and alkaline earth.

2. Clay - classification
 As smectite, vermiculite, kaolinite, illite, chlorite,
allophane, hematite, geothite, ferrihydrite, and
lepidocrocite.
 Ofinterest in this study is the kaolinites, which are
classified based on their physical properties, mode of
formation and resistance to high temperature.
 Further classifications in relation to high
temperature resistance are as:
refractories,
high melting clays and
low-melting clays.

3. Kaolinitic Clay Deposit in South-west Nigeria
An estimated reserve
of 3 billion tonnes of
good kaolinitic clay
has been identified in
many locations in
Nigeria (south-west)
ready for massive
development
and exploitation.
*
* South-West Nigeria

4. Purpose
 To improve the thermal and physical
properties of kaolinitic clay (south-
western Nigeria deposits) for industrial
application as insulators .

5. Approach
 Wood particles (sawdust)
 Clay samples were collected from Ibule, Ikeji-
Arakeji and Ikere-Ekiti deposits in Ondo, Osun and
Ekiti states respectively.
 Clay samples were crushed to 150 µm and
proportions needed for different analyses were
weighed.
 Classical chemical analysis (Wet Analysis
Technique) was used to determine the chemical
composition(Beeley,1990).

6. Approach –Physical properties
 Physical properties such as:
- bulk density,
- porosity,
- shrinkage,
- sintering temperature,
- spalling resistance,
- cold crushing and strength and
- thermal conductivity were determined
using standard methods of the American
Foundrymen’s Society (AFS, 1993).

7. Approach
 Ikere-Ekiti / Ikeji-Arakeji clay in ratios 50:50, 60:40 and
70:30 by mass.
 Each blend was soaked separately in a basin for 3days.
 Mixing and wet sieving was performed to remove
deleterious particles followed by sun drying, crushing,
grinding to fine particles to obtain 50 µm.
 Sawdust was mixed with the clay blends in varying
percentages of 5, 10, 20 and 30%.
 Cubical, cylindrical, spherical and rectangular shapes
were obtained from the blends and then thermo- physical
properties determined using AFS (1993) method.

8. Results – Characterization
 Ikere-Ekiti Clay was an Alumino-Silicate clay (fire-clays) which consists
essentially of Al2O3 and SiO2 associated with impurity oxides such as Fe2O3,
TiO2, MgO, Na2O and K2O of about 13%.
 The ratio of aluminium oxide to silicon oxide of Ikeji-Arakeji (19.67:48.24)
confirms the clay deposit as a bentonite-montmorillonite.
Chemical composition of selected samples
Chemical composition in wt %
Oxide Ikeji-Arakeji Ikere-Ekiti Fire- clay ((Omotoyinbo &
Oluwole, 2008)
Al2O3 19.67 30.82 23 -34
SiO2 48.24 47.14 48-60
Fe2O3 10.81 2.00 2-4
MgO 1.33 0.32
TiO2 1.51 0.50
CaO 0.55 0.25
Na2O 0.87 0.80
K2O 3.00 1.90
Ignition loss 9.74 7.98 7-11
Others 4.78 1.09
Total 100.00 100.00

9. Results and Discussion
Thermal and physical properties of selected clays and clay blends
Properties Ikeji- Ikere- Ikere- Ikere- Ikere- Fire clay
Arakeji Ekiti Ekiti/Ikeji Ekiti/Ikeji Ekiti/Ikeji accepted
-Arakeji -Arakeji -Arakeji standard
70/30 60/40 50/50 range
(Omotoyinbo &
Oluwole, 2008)
Bulk density 1.56 1.51 1.518 1.522 1.528 1.5-2.1
(g/cm 3)
Volume fraction 0.28 0.56 0.37 0.46 0.43 0.25-0.4
of open porosity
Shrinkage on 4 2 2.47 2.63 2.91 3-7
firing (%)
Thermal 0.64 0.14 0.342 0.392 0.529 0.1-0.5
conductivity
(W/mK)
Sintering 1200 1400 1430 1350 1300 1500-1750
temperature (oC)
Spalling 10 15 10 11 11 30+
resistance
(cycles)
Cold crushing 4870 3610 3880 4090 4510 5000+
strength (kN/m2)

10. Results and Discussion

11. Results and Discussion
500
450
400
CCS x 10 (Kn/m 2 )
350
300
250 70/30
200
60/40
150
50/50
100
50
0
0.37 0.39 0.43 0.48 0.57 0.61
Volume fraction of open porosity
Fig. 4 Effect of porosity on cold crushing strength of clay blends

12. Results and Discussion

13. Results and Discussion

14. Results and Discussion

15. Conclusion
Clay blends - low sintering temperature, spalling resistance and cold
crushing strength as compared to standard values of 1500 0C – 1700 0C;
30+ cycles and 5000+ kN/m2 respectively.
The effect of sawdust addition on Ikere Ekiti and Ikeji Arakeji clay
blends of 50:50, 60:40 and 70:30 showed that important properties such
as, bulk density, porosity, shrinkage and thermal conductivity, improved,
thus making the blends fit as fire clay.
However, the addition of sawdust has no effect on sintering temperature,
spalling resistance and cold crushing strength.
A 10 % sawdust addition to 70:30 Ikere Ekiti / Ikeji Arakeji clay blend,
makes the blend fit as a fire clay.