Utilization of cow-dung in brickmaking
Practical Action
Cow-Dung "Ziballa": The Best Additive to Brick Clays
Ziballa is an Arabic word meaning dung. It also means garbage, and garbage collectors in Egypt
are known there as "Zaballeen". Cow-dung imparts useful properties to the raw bricks when
mixed with brick clays. Dung has also many other uses (some are described above), especially
among cattle herders of southern Sudan(7).
Cow-dung improves the plasticity of clays and
acts as reinforcing agent reducing concentrated
cracks that can lead to breakage within the raw
bricks. Upon firing the dung fibres ignite, thus
assisting in even .firing of bricks and minimizing
the development of high temperature gradients
within the brick - a phenomenon which may lead
to firing cracks. When the fibres burn out they
leave cavities within the brick which reduce unit
weight and improve thermal characteristics.
Cavities on top and bottom surfaces of the bricks
increase the bond when bricks are laid in a
mortar bed.
Figure 2: Slop-moulding and drying of
bricks. Photo: Practical Action
The effect of four organic additives on Blue Nile clay was studied at the Building and Roads
Research Institute (BRRI) of Khartoum University. Four sets of raw brick samples were machine-
moulded. Half of each set was sun-dried and the other half dried in shade. Both halves were
fired to the same predetermined temperature. While the mode of drying had no appreciable
influence on properties, crushing strength varied greatly with the type of additive. The study
found out that mixing Blue Nile clay with Ziballa yielded the highest average strength value (170
- 180 kg/ cm2). Next to Ziballa came groundnut shells (120 - 135 kg / cm2) and saw dust (110 -
125 kg/ cm2). Garad seeds yielded the least value.
Dung %
Slop-moulded
Sand-moulded
Water
Strength Absorp-
tion
Density Strength
Water
Absorp-
tion
Density
4.8 45
25 1.37 61 24 1.45
13.0 20
30 1.22 43 28 1.39
20.0 17
33 1.22 92 29 1.31
25.9 13
31.0 23
34 1.15 18 33 1.21
31 1.19 16 34 1.20
35.5 15
35 1.15 25 25 1.31
39.4 17
35 1.12 23 33 1.07
42.9 30
31 1.27 26 31 1.21
46.0 80
36 1.13 22 32 1.19
Table (3): Effect of varying dung content on selected properties of slop- and sandmoulded bricks
Effects of Cow-Dung on Brick Properties
These findings are based on experiments undertaken by Practical Action in Kassala, eastern
Sudan to study the effect of cow-dung on brick clays and properties of fired red bricks. The
predominant type of soil in Kassala is "gurera" (see Table 2 for chemical composition).
For the study clay was taken from a depth of 0.5 - 1.5m, cutting vertically to ensure mixing
different layers. Dry dung collected from nearby farms was sieved using rabbit wire to eliminate
stalks and other coarse impurities like gravel. Ten sets of raw brick samples with dung contents
ranging from 5 - 47% by volume were moulded. Contents of each sample were thoroughly mixed
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