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close this book Sustainable Energy News. - No. 15 November 1996
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Compressed! Earth Blocks for North & South

By Willem OsKam, Holland

New Mobile Compressing

Machine Developed

The new model of a mobile machine to compress earth blocks raised high interest at the Habitat Conference in June. In October, the Minister of Housing of South Africa and the Habitat UN Commission of Low-Cost Housing visited the exhibited machine in the main square of Amsterdam. It is being considered as a tool to implement the building plan of 1 million low-cost houses over the next 5 years in South Africa.

The first prototype of the mobile, light manufacturing mechanism was constructed by OSKAM in 1982 in Holland. In 1996, a newly developed, much more cheaper and more reliable machine produced high quality compressed earth blocks for 24 houses in Denmark.

100-200 Times Less Energy

It uses 100-200 times less energy than producing bricks and concrete. The machine makes 200 blocks on one liter diesel fuel. The capacity of one machine is 2,400 blocks per day, enough for a low-cost family house. Because of the high (5-6 N/mm2) bearing capacity of the earth block walls, the building methods can be kept very simple. A simple roof construction can be fitted directly on the walls.

Cool in Summer

Its ability to regulate humidity is one of the strongest points of the material. It gives indoor corn fort and in tropical regions, air-conditioning is not necessary. Earth blocks are equally bad conductors and insulators. The houses feel cool in the summer and warm in the winter. The walls hold the temperature steady for long periods of time.

Produced on Building Site

Clay and earth are commonly available materials. The producer of the blocks can communicate directly with the builder, because the blocks are produced on the building site.

This method of building can establish the link between people's needs and their capacities in many other ways than the mere financial. The cost of the building process can also be kept within the local means.

Building Process

The fertile topsoil is removed and the subsoil, in most places containing clay, that is necessary to the binding, is spread out and dried in the sun. Then it is collected and stored in a dry place. The soil has to be tested for its binding capacity, and in some cases mixing of different clays is necessary for a good binding. The machinery for processing blocks in a continual process can be operated by three persons.

Pulverizing, mixing, and pressing takes place at the same time. In one end, the raw earth is taken into the pulveriser. From here it is fed into a mixer, where eventually sand and fine gravel are added, depending on the composition of the earth (Generally the clay content is less than 20% A small amount of water is added and then the earth is pressed into uniform blocks at a rate of 5 blocks per minute. After drying for 14 days, the blocks can be used for building.

Worldwide Solution

The immense housing shortage of the over-populated part of the world causes social unrest and health problems. The earth blocks building technique is an ancient one that yields other economic and social benefits along with new low-cost housing. The earth blocks technology raises hopes of a worldwide solution to humanity's basic need for housing because it is:

· Iow in cost,

· minimal in its use of energy,

· decentralized production is done on the building site,

· a way to decrease unemployment by creating self-employment, and

· method that uses locally available material, eliminating import.

More informatiion: OSKAM V/F, Opperddit 66, 2941, AL Lekkerkerk Holland