Mud as a mortar
Practical Action
done on two bricks or blocks mortared together with a layer of mortar on top. Several such
samples need to be made up to avoid the acceptance of rogue results and to enable
comparisons to be made. Observations of weathering and erosion of the samples can be
complemented by a number of other tests, which can be varied according to the desired
properties of the construction. Such tests can be started after one day of curing, but it would
be preferable to have a longer curing and drying period, especially if stabilizers are used.
Field tests which can be used include:
the force required to separate two bricks or blocks
abrasion resistance, using a metal brush
water resistance, using a watering can
cohesion, i.e. resistance to crushing of a mortar sample
shrinkage measurement.
Additional laboratory-based tests which can be used include:
wet and dry crushing strength
shear strength of small walls.
Figure 3: Test carried out on unstabilised and stabilised mortars to determine the optimum
soil/sand ratio. Photo: CRATerre/EAG
Using mud mortars
The use of ordinary mud mortars doesn't require any special precautions. However they
should not contain any particles larger than one third the thickness of the joints, and, to avoid
possible shrinkage problems subsequently, the prepared mix should be just workable enough
for smooth and easy laying of the building elements (bricks, blocks,. ..).
On the other
hand some
additional
operations are
necessary when
the mud mortar
is stabilised. To
get a good
homogenous
distribution of
the stabilizer in
the mixture, it
is necessary to
sieve out or
crush the lumps
in the soil that
Figure 4: Demonstration house in Jos, Nigeria, built with adobe laid in
mud mortar and plastered with mud mortar. Photo: CRATerre/EAG
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