Using stabilised mud
Applying traditional mud-based construction methods in modern urban contexts
We owe the early studies about mud architecture to CRATerre at Grenoble, France, the ASTRA group at Indian Institute of Science, Bangalore, Development Alternates at Delhi and Auroville at Pondicherry. The work at ASTRA during the 70s directly focused on how to apply the traditional mud-based construction methods for modern urban contexts. Very soon, they realised that mud cannot be used directly in its raw state. The process of stabilisation does the magic and the powdery soil becomes hard.
About this process, I tried to write on my own, but nothing came as good as what K.S. Jagadish, among the early researchers at ASTRA, IISc., wrote in his book ‘Building with stabilised mud’ (I.K. International Publishing, 2007). To quote him, “Since mud is the most widely distributed resource for building construction, it is useful to explore ways of ‘stabilising mud’ without employing energy-intensive techniques like brick burning. Stabilised mud may now be defined as mud which does not soften due to the action of water, by the use of a small quantity of a binding agent. Cement, lime, cement and lime, lime and pozzolona, bitumen and organic binders are some of the typical stabilisers which can be used.
Criterion:The performance of a soil-based building block depends to a large extent on its density
The performance of a soil-based building block depends to a considerable extent on its density. Low-density blocks are rather porous and will not have good strength. It is hence necessary to densify soil while making a stabilised block besides adding the stabiliser. For this purpose, the soil has to be subjected to adequate pressure at suitable moisture content. This process is known as ‘compaction’. The compaction can be done inside a machine mould to produce a standard-sized ‘mud block’. Alternately, the soil can be directly compacted in a wall using a moveable mould in what is known as ‘rammed earth’ construction.’
Though today in Bangalore, we build more with compressed blocks, the rammed earth practice pre-dates it as a vernacular method. In recent times, Bangalore-based Mrinmayee centre has improvised the ramming technology further, attempting to popularise it.
It’s a simple mechanism with two side plates anchored together within which soil is poured and a flat wide-based hammer is used to manually compress it. All the components are removed and re-fixed again for the next section of the wall.
Only one horizontal course up to 60 cm can be built in one day. As per the plan, the openings can be left for windows, grooves can be cut for electrical wiring or nails can be hit for hanging art works.
There of course are few precautions to be followed, but at the end, one can get a rammed earth house which is no less beautiful or strong compared to a conventional one. May be, the mud house could be better!