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< prev - next > Construction Earth construction KnO 100096_Mud as a Mortar (Printable PDF)
Mud as a mortar
Practical Action
are bigger than 5 to 8 mm. Mixing of materials in small batches is also important so that the
mortar mix can be used quickly and any significant setting of the stabiliser before the mortar
is used is then avoided. Stabilised mud joints are quite expensive so that there is always a
tendency to reduce their thickness. However, it generally becomes more difficult to sieve out
the oversize fraction in the soil the smaller the chosen maximum particle size in it. The
minimum thickness for the joint is 1cm but this renders the laying process difficult, so a
more realistic minimum effective joint thickness would be 1.5 cm.
If the stabiliser sets by reaction with water, Ordinary Portland cement for example, some
precautions have to be taken in order to avoid the applied mortar drying out too quickly. In
particular the elements to be laid have to be wetted before, but not immediately before,
applying the mortar, - otherwise the water is not absorbed by the element and remains as a
surface film which prevents good bond between the mortar and the element. In dry areas, it
would also be necessary to keep the wall wet for several days after construction to achieve a
high level of cure of the mortar, but this is generally very difficult to achieve, due to shortage
of water for example. If this is cannot be done then it is best to increase the proportion of
cement in the mortar so that the loss in quality would be compensated for. Pointing should be
done just after laying (that is when the mortar starts to set). Repointing is always a much
lengthier process and is really only applicable in the case of application of a protective
stabilised mortar finish to an unstabilised mortar core.
Reference and further Reading
Alternatives to Portland Cement Practical Action Technical Brief
Additives to Clay: Organic additives derived from Natural Sources, Practical Action
Technical Brief
Additives to Clay: Minerals and synthetic additives, Practical Action Technical Brief
Mud Plasters and Renders: An introduction Practical Action Technical Brief,
Clay as a binder Practical Action Technical Brief,
How to Make Stabilised Soil Blocks, Technical Brief by Practical Action Southern
*Earth construction, A comprehensive guide, CRATerre, Practical Action Publishing,
Building with Earth, CRATerre, Mud Village Society, Delhi, India, 1990
*Building with Earth, A handbook, 2nd Ed., J. Norton, Practical Action Publishing,
*Appropriate Building Materials, A Catalogue of Potential Solutions, R. Stulz, K.
Mukerji, Practical Action Publishing/SKAT, 1993
Soil Preparation Equipment (product information), by Kiran Mukerji et al, GTZ,
Eschborn, Germany, 1991
Earth Building Materials and Techniques, Select bibliography, CRATerre, GTZ,
Eschborn, Germany, 1991.
The basics of compressed earth blocks, CRATerre,GTZ, Eschborn, Germany, 1991
Stabilisers and Mortars (for stabilised soil blocks) product information, by Kiran
Mukerji, CRATerre, GTZ, 1994
Compressed Earth Blocks: Vol. 1,Manual of Production, Vince Rigassi, CRATerre-
EAG, GTZ, 1995
Earthen Architecture, Hands On Brief, Practical Action / TVE, Series 1,
Rammed Earth Structures Keable & Keable Practical Action Publishing 2011