Journal of Minerals & Materials Characterization & Engineering, Vol. 10, No.15, pp.1449-1455, 2011
jmmce.org Printed in the USA. All rights reserved
1449
Effect of Varying Corn Cob and Rice Husk Ashes on
Properties of Moulding Sand
Sunday Aribo
Department of Metallurgical and Materials Engineering
Federal University of Technology, PMB 704, Akure, Nigeria
Corresponding Author: [e-mail]
ABSTRACT
The use of rice husk and corn cob ashes as aggregates for foundry moulding sand has been
studied. 5-12.5 weight percent of rice husk and corn cob ashes were added to the sand mixture
and the sand properties determined. A mixture of equal proportion of rice husk and corn cob
ashes was also used. In each case, four weight percent water and clay were added to the sand
mixture. Some of the properties of the sand tested are: permeability, green compression strength,
dry compression strength, green shear strength, dry shear strength, moisture content and
permeability. The results showed that the green compression strength, green shear strength,
moisture content and permeability decrease with increase in the additives (rice husk ash, corn
cob ash, and (50% rice husk and 50% corn cob ashes). While dry compression strength and dry
shear strength increase with increase in weight percent of the additives.
Key words: moulding sand, rice husk, corn cob, ashes, sand properties.
1. INTRODUCTION
The urgent need to develop the foundry industries in Nigeria in order to meet the technological
development of the country has led to so much interest in the characterization of the locally
available materials.
Silica sand is an extremely good material for making casting moulds because it has the ability to
withstand the temperature of the molten metal. It can absorb and transmit heat, and has sufficient
permeability to allow gasses generated during casting to pass between the particles without
causing casting defects. Foundry sand is made within strict particle size distribution to tailor the
properties of the materials to the intended casting process [1].
There are many deposits of silica sand for foundry application scattered all over Nigeria.
Investigation shows that silica sand are abundant in Ogun, Ondo and Lagos states of the western

1450 Sunday Aribo Vol.10, No.15
region of Nigeria but most of the castings made using these sands have one form of defect or the
other [2].
Rice husk and corn cob are waste by products of agricultural processing industries. These
materials constitute ecological problem and the need has arisen to reuse these materials for
economically viable ventures. The disposal of the rice husk and the corn cob present a serious
ecological problem to the processing industries [3]. Therefore the development of suitable
scientific and economic method of recycling of rice husk and corn cob is very pressing and
important. Research has shown that rice husk and corn cob materials have high silica contents.
The ashes from these agricultural wastes are also of high binding properties [4]. In addition,
since the pulverized form of these materials have very fine grain sizes; they can therefore act as
good blend to the coarse sized silica sand. Also it is expected that some of these materials will
burn off at a very high temperature given rise to better permeability of the moulding sand. The
outcome of this research will help foundry shops and research institutes to solve the problem
associated with coarse sand grain. Better casting with better surface finished are expected to be
made by blending this fine grains corn cob and rice husk ashes with silica sand. The use of these
agricultural waste products will also help the environmentalist in solving the pollution problem
associated with the disposal of these materials.
2. MATERIALS AND METHOD
The materials that were used in this research are: silica sand (sourced from Epe, Lagos State,
Nigeria; Rice husk and corn cob were sourced from Adaja village in Ondo State, Nigeria. The
equipment that were used in this research are, moisture tester, permeability machine, universal
sand strength testing machine, heat treatment furnace, oven and mixer. The corn cob and rice
husk were burnt in open atmosphere and the black ashes were packed into crucible and heated in
an air tight furnace for 6 hours at 1000
o
C to obtain a white coloured ash.
The particle size distribution of the silica sand, corn cob ash and rice husk ash were determined
using the American Foundry Society (AFS) specifications.100 g of each sample was taken and
pour into the topmost screen. The sample was shaken for 15 minutes by a vibrator set at 3 hertz.
The grains retained on each sieve and the bottom pan were removed and weighed.
For the determination of moulding sand properties, known weight of the silica sand and varying
weight percent of rice husk and corn cob ashes ( 5 , 7.5, 10 and 12.5 weight percent
respectively) were used . In each case 4 percent weight of water and bentonite were added and
the mixture thoroughly mixed with an electricity driven mixer.
For permeability, 150 g of the sample each was weighed and transferred to a specimen sleeve
with the base already plugged in the socket. The sample was rammed three times using George
Fisher Rammer. The sample was then removed from the sleeve and placed on an electric
permeter in an inverted form. The permeter was then switched on and the allowed to settle down.
It was then adjusted to zero by the control knob. The lever was then moved to check the position
and then the value read off.

Vol.10, No.15 Effect of Varying Corn Cob 1451
The Green Compression Strength (GCS) and the Green Shear Strength (GSS) were determined
immediately after ramming, while the Dry Compression Strength (DCS) and Dry Shear
Strengths (DSS) were determined after baking the rammed piece. In each case 150 g of the
prepared moulding sand was weighed and properly rammed. For the compression strengths the
sample was placed between two parallel plates of a compressible jig, while for the shear
strengths the sample was placed between the parallel plates of the shear jig. The entire jig
systems are detachable accessories of the main universal sand testing machine. The samples and
the jigs were then placed on the universal sand testing machine in such a manner that the
movable jaws clamped the sample to fracture in a slow but continuous movement without shock.
Table 1: The Particle Size Analysis of Epe Silica Sand
Mesh
Dimension(µm)
Mass of Sand
on Meshes(g)
A
Multiplier
B
Result
Obtained
AXB
Cumulative
Retained
Sand
1400 0.2 6 1.2 1.2
1000 2.8 9 25.2 26.4
710 1.6 15 16.6 43
500 9.8 25 245 288
355 34.2 35 1197 1485
250 27.0 45 1215 2700
180 14.5 60 870 3570
125 5.1 81 413.1 3983.1
90 3.2 118 377.6 4360.7
63 1.2 164 196.8 4557.5
Pan 0.2 275 55 4612.5
Total 99.8 4612.5
Grain Finess Index (GFI) = 4612.5/99.8 = 46.21

1452 Sunday Aribo Vol.10, No.15
Table 2: The Particle Size Analysis Corn Cob Ash
Grain Finess Index (GFI) = 9380.41/99.9 = 93.90
Table 3: The Particle Size Analysis Rice Husk Ash
Grain Finess Index (GFI) = 9224/99.85= 92.38
Mesh
Dimension(µm)
Mass of Corn Cob
Ash Meshes(g)
A
Multiplier
B
Result
Obtained
AXB
Cumulative
Retained
Corn Cob
Ash
1400 0.005 6 0.03 0.03
1000 0.07 9 0.63 0.66
710 2.00 15 30.00 30.66
500 3.25 25 81.25 111.91
355 7.01 35 245.35 357.26
250 10.05 45 452.25 809.51
180 14.68 60 880.80 1690.31
125 19.40 81 1571.40 3261.71
90 26.60 118 3138.8 6400.51
63 14.85 164 2435.4 8835.91
Pan 1.98 275 544.50 9380.41
Total 99.90 9380.41
Mesh
Dimension(µm)
Mass of Rice
Husk Ash on
Meshes(g)
A
Multiplier
B
Result
Obtained
AXB
Cumulative
Retained
Rice Husk
Ash
1400 ------- 6 0.00 0.00
1000 0.10 9 0.9 0.90
710 1.96 15 29.40 30.30
500 3.50 25 87.50 117.80
355 6.80 35 238 355.80
250 12.05 45 542.25 898.05
180 11.65 60 699 1597.05
125 22.70 81 1838.7 3435.75
90 24.50 118 2891 6326.75
63 15.00 164 2460 8786.75
Pan 1.59 275 437.25 9224
Total 99.85 9224

Vol.10, No.15 Effect of Varying Corn Cob 1453
3. RESULTS AND DISCUSSION
0
20
40
60
80
100
120
140
160
180
57.510 12.5
% Rice Husk
S and P roperties
green compression(kN/M²)
permeability(vol/mins)
dry compresion strength(kN/M²)
green shear strength(kN/M²)
dry shear strength(KN/M²)
M oisture(%)
Figure 1: Variation of Sand properties with % of Rice Husk Ash.
0
20
40
60
80
100
120
140
160
57.510 12.5
% Corn Cob
Sand Properties
green compression(kN/M²)
permeability(V ol/mins)
dry compression strength(kN/M²)
green shear strength(KN/M²)
dry shear strength(KN/M²)
M oisture(%)
Figure 2: Variation of Sand properties with % Corn Cob Ash.

1454 Sunday Aribo Vol.10, No.15
0
20
40
60
80
100
120
140
160
180
57.510 12.5
%(50% Rice Husk+50% Corn Cob)
Sand Properties
green compression strength(kN/M²)
permeability(vo l/M ins)
dry compression Strength(KN/M²)
green shear strength(kN/M²)
dry shear strength (kN/M²)
M o isture(%)
Figure 3: Variation of Sand properties with % of (50% Rice Husk and 50% Corn cob) Ash.
From figures 1, 2 and 3 there is generally a decrease in the moisture content with increase in the
percentage of rice husk and corn cob ashes. The decrease in the moisture content is due to the
fact that more water is needed to blend the mixture with increase in the additives. The moisture
content decreases from 5.44% to 2.44% with the addition of 5-12.5% rice husk ash. It also
decreases from 2.6-1.49% for the same percentage of corn cob ash. For 50% rice husk and 50%
corn cob ashes, the moisture decreases from 2.2-1.76% with the same increases in the additive
from 5-12.5%. The decrease is an indication that the sand developed plasticity with the increases
in the percentage of the additive [5]. From Figures 1, 2 and, 3, the permeability of the sand
mixture also decreases with the increase in the percentage rice husk and corn cob ashes. This
can be explained from the fact that the grain sizes of the rice husk ash and corn cob ash are finer
than that of the silica sand. So, the finer grains of the additives block the pores between the sand
grains hence air is restricted from escaping [6]. However, the permeability still falls within the
acceptable limit.
From figures 1, 2 and 3, the green compression strength increases slightly (42.67 to
48.24KN/m
2
) with addition of rice husk ash from 5 to 12.5%. However, there is a marginal
increase for the corn cob ash up to a point where there is slight decrease. The trend for (rice husk
+ corn cob) ash is somehow different for the green compression strength decreases with addition
of the mixture of the ashes. However, the dry compression strength increases with increase in all
these additives. We also realized that the green shear strength follows the same trend with the
green compression strength. In all these the optimum dry shear strength is obtained with addition
12.5% of rice husk ash.

Vol.10, No.15 Effect of Varying Corn Cob 1455
4. CONCLUSION
1. The additives (rice husk and corn cob ashes) improve the dry strength of the moulding sand.
2. There is generally a decrease in the green strength of the moulding sand with increase
additives.
3. Though there is generally a decrease in the moisture content and permeability in all cases, the
values still fall within acceptable limits.
REFERENCES
[1] Plain P.L. (2000). Principle of Foundry Technology, McGraw –Hill publishing Limited,
New Delhi. Pp 100-125
[2] Aribo S., Folorunso D.O., Olaniran O., and Oladele I.O. (2009). Optimizing the Green
Compression Strength and Permeability of Green Sand Made from Epe Silica Sand
International Journal of Engineering , India .Vol.3, No 1,.Pp119-126.
[3] Oladeji, J.T. (2010). Fuel Characterization of Briquettes Produced from Corncob and Rice
Husk Resides. Pacific Journal of Science and Technology, 11(1):101-106.
[4] Mohamed A. Elsayed and Taher M. El Samni (2006). Physical and Chemical Properties of
Rice Husk Straw Ash and its Effects on Cement Paste Produced from Different Cement
Types. J. King Saud University, Volume 19, Eng Sci(1) Pp 21-30.
[5] AigedionV.S, Hassan S.B. Olajide S.O, Agunsoye O.J, Abdulrahaman A.S. Okafor G.E.
(2008).The Use of Rice Husk Ash as an Aggregate for Foundry Sand Mould Production,
Proceeding of the 25
th
NMS Conference, Nigeria.
[6] Roa P.N. (2001). Manufacturing Technology, Foundry, Forming, and Welding, Tata,
McGraw Hill, New Delhi India. Pp97-106.