Utilization of cow-dung in brickmaking
Practical Action
and enough water was added to give a
workable plasticity. Each sample set
consisted of 50 bricks, half of them slop-
moulded in a double metal mould, and
the other half sand-moulded in a single
compartment wooden mould. Both
moulds have the same dimensions (23 x
11 x 7 cm). All samples were-sun dried
(8) for three weeks, and fired in a clamp
kiln for four consecutive days(9). Capacity
of the kiln was completed to 14000(10)
bricks by loading 20 - 30% "normal"
bricks together with the samples. After
firing, 4 individual bricks from each
sample set were packed and sent for
testing strength, water absorption and
density. Green and fired dimensions were
also determined. Table (3) shows the
experimental results for the slop and
sandmoulded samples with the same
dung content.
Figure 3: Staking of bricks for clamp-firing. Photo:
Practical Action
Graphical Presentation of Data of Table (3)
Figures following below depict a graphical representation of dung content of bricks (by volume
percent) vs. strength, water absorption and density respectively. Each figure shows the relation
between percentage of dung and one of the three properties for two sets of samples. One set is
slop-moulded and the other is sandmoulded.
For all samples it was found, that irrespective of the manner of releasing bricks from moulds, an
increasing percentage of dung in the raw bricks decreases their strength and density. Water
absorption increases in the same way. Cow-dung has less density than clays and leaves voids
(pores) in fired bricks. Once a crack is occurring the pores ease the propagation of the crack
along the direction of load thus decreasing strength of the brick. The more pores there are in the
brick the higher the amount of water is needed to fill them, resulting in a higher water
absorption. Sand-moulding produces bricks of better qualities than slop-moulding. For the same
cow-dung content strength and density are found to be higher and water absorption lower. Clay
for sand-released bricks is more stiff compared to the more wet clay for water-released bricks.
The initial water content influences the number of pores in the fired brick. Slopmoulded bricks
also tend to have the higher shrinkage.
Energy and Other Costs
The main objective for the Practical Action intervention with bricks manufacturers in Kassala
was to lower energy cost below 50% of total production costs and to improve the quality of fired
bricks. Quality improvement has been achieved by training the producers to improve their
production techniques and use sand-moulding.
Improvements in energy terms can be illustrated in the case of one producer in Khor Shaigiyia, 8
km north of Kassala town. The producer, Abdel Hamid Ahmed Ali, produced bricks of poor
quality(11) before the Practical Action intervention.
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