By Asitha Jayawardena
(Dept. of Civil Engineering, University of Moratuwa)
The French have landed...at Moratuwa University. Unfortunately not for baking bread but for a two-day workshop, 8 and 9 September 2000, on Earth Block Architecture conducted by the Faculties of Architecture and Engineering, Moratuwa University, together with the French Embassy.

Recently, use of earth block technology in building construction in Sri Lanka has created much interest and awareness among engineers and architects. Therefore, the workshop aimed to promote Moratuwa University as a ‘centre of reference’ for those who seek knowledge, training and expertise on Earth Block Technology.

There were three resource persons: Architect Satprem Maini from Auroville Building Centre / Earth Unit, India; Dr. Asoka Perera and Dr. (Mrs.) Chinta Jayasinghe, both from the Department of Civil Engineering, Moratuwa University.

The workshop set off, with the traditional lighting of the oil lamp.

Prof. Dayantha Wijesekera, Vice Chancellor, Moratuwa University, welcomed all. It is encouraging, he said, to see the two faculties jointly holding a workshop. Moreover, he looked forward to future collaboration with the French government in this field.

The representative of the French Ambassador revealed that Earth Architecture had existed for a long time but later on, for some time, it was forgotten; now however, with increased concern for the environment, it is on the rise again. Architecture is for people not for architects, she said. She ended her speech, stating this would be a new field of cooperation between France and Sri Lanka.

Prof. Lakshman Ratnayake, Dean, Faculty of Engineering, thanked his Architecture counterpart for the initiation of the workshop. Although earth blocks are not unfamiliar to Sri Lanka, he observed, mainly the underprivileged use them at present. He predicted that, with the progress in recent research work by Dr. Asoka Perera and Dr. (Mrs.) Chinta Jayasinghe, the earth block of improved quality would soon become popular among all the people.

A presentation on Diversity and Universality of earth Architecture by Architect Maini was followed by another, on Earth Construction Applications in Sri Lanka, by Dr. Perera.

Vote of thanks was by Prof. Lal Balasuriya, who was happy to see so many participants. It is important that representatives from various organisations are present so that the knowledge disseminated here can be applied in practice, he observed. There is no use in confining such valuable findings to the auditorium, he added. Thanking the French in English, he ended the inaugural session, opening the doors for a much more enchanting session: tea.

The first time I tasted French bread (or was it bread?). Whatever, it was, it was fantastic. I hoped, between munches, that the next field of co-operation between the two countries would be bread technology.

The following is a broad overview of Earth Architecture and construction. More detailed articles will appear in future.

Earth architecture and construction

Will mother earth remain pretty for long? No, if things are allowed to go on as they are today. For example, in various fields, over-exploitation of natural resources combined with careless management is leading towards her destruction. One such field is building construction.

Robert Lynd thinks that, when it comes to building construction, we should learn a lot from birds. There is nothing in which the birds differ more from man than the way in which they can build and yet leave a landscape as it was before. In other words, construct with minimum damage to the environment.

One way to achieve this is to use environmentally sound materials for construction. Such materials use natural resources but with much awareness and respect for both nature and people. They have the following characteristics:

> Their use does not exhaust natural resources.

> They require a little energy to be produced or processed.

> Their production or processing is possible with minimal pollution.

> They are locally available, and can be managed by the locals.

> They contribute to a sustainable development.

A leading environmentally sound material is the earth itself, or soil. All over the world, throughout the ages, people transformed this heavy, dark and formless material into a lighter building material for creation of their living spaces. No wonder buildings built from earth have a great past. The oldest such earth structure still standing is in Egypt, built 3300 years ago!

Compressed Earth Blocks (CEB)

Over the years twelve techniques of earth construction have been developed worldwide; one of them is the pressed technique. This can either be rammed earth (practised for centuries) or compressed earth blocks (developed more recently).

For production of CEBs, soil is slightly moistened, poured into a steel press (with or without stabiliser), and then compressed manually or mechanically.

Not every soil is suitable for earth construction, especially for CEBs. With some knowledge and experience, however, most soils can be used for producing CEBs. To achieve a good quality product, proper identification of soil properties is essential. For small projects, simple sensitive analyses which can be performed after a short training will be adequate; for large projects, however, specialist laboratories should be consulted. Under no circumstances, top soil or organic soils should be used.

In concrete the binder is cement. In soil the binder is silt and clay, which unfortunately are not stable under water. Therefore they should be stabilised to maintain some strength under wet conditions. Stabilisers can be fibres (natural or synthetic), cement, lime, bitumen, fly ash, resins, natural products (eg. straw, fur, blood, juice of plants, latex) or synthetic products. Besides water resistance, stabilisation promotes the compressive strength.

When the stabiliser is cement, its average percentage is around 5%. Cement stabilised blocks should be cured for four weeks, and then, after allowing them to dry, they can be used like common bricks but along with a soil-cement stabilised mortar.

Advantages and disadvantages

* Local material: Production of CEBs is ideally done at the site itself or a nearby area, resulting in savings in time and in costs of transport and fuel. As it is a local product, it can easily be adapted to various needs: technical, social or cultural.

* Technology: Only semi skilled labour is needed as the technology is simple. It can be transferred to villagers in a week if an efficient training centre is available.

* Bio-degradation: Suppose an old CEB building is abandoned and vegetation grows on it with a gradual collapse. The bio chemicals contained in the humus of the top soil will destroy the soil-cement mix in 10 to 20 years. Finally, CEBs will just mix with Mother Earth!

* Energy efficiency and pollution: Only a relatively small amount of stabiliser is needed, hence a little amount of energy. Moreover, firing is not needed, resulting in fuel savings and reduction of pollution.

* Structural performance: Well designed CEB houses around the world have withstood, with minimum maintenance, various external forces without damage for over half a century. However, CEB construction gives problems when it comes to long span, high rise or elongated buildings. Moreover, the technical performance of CEBs is lower than that of concrete.

* Employment: By adopting manual compression, employment can be generated for unskilled people, making them skilled and employed.

* Quality: Inadequate training, poor identification of soil properties, ignorance of basic principles of production, bad quality or unadapted production equipment, and understabilisation can lead to poor quality products.

* Management of resources: If resources are managed well, the results will be profitable; if unplanned, disastrous! For example, quarries should be planned to be used for water harvesting, waste water treatment, reservoirs, landscaping etc. Otherwise the pits will end up as garbage dumps.

* Production scale: CEB equipment is available from manual to motorized tools, ranging from village to semi-industry scale. To achieve the best results, selection of equipment is vital.

* Cost: Local production, semi-skilled labour, simple technology, less dependence on energy - all lead to cost savings. However, over stabilisation through fear or ignorance can increase the cost.

* Social acceptance: CEB technology is easily adaptable to various income groups. Its quality, regularity and style allow a wide range of buildings. However, when referring to compressed earth blocks (CEBs) terms such as "Stabilised mud block" should be avoided. Moreover, social acceptance may drop due to negative examples (resulting from bad workmanship, poor identification of soil etc.).

Note: Co-ordination work by Ms. Marie Helen Estave, Cultural Counsellor, Embassy of France, is gratefully acknowledged.