- OSKAM V/F - C.E.B.M.

SUSTAINABLE BUILDING CONSTRUCTION USING CEB´S
Since the very earliest of times, earth has been used as a major building material and today we can find evidence of this fact over vast areas of our planet. The development of industrial building materials such as concrete and steel have to a large extent suppressed the use of unfired earth.
Today however, we witness a re-awaking of the use of this traditional building material, not only in developing countries, but also significantly in the developed western world. Earth, which has often been criticized for its susceptibility towards moisture and its lack of durability, has in its development form many advantages with its use for the construction of low-cost buildings. Using modern construction technology earth can be said to have the following advantages:
· Durable and adaptable.
· Easy and low cost acquisition.
· Stimulates the training and employment of manpower.
· Environmentally friendly and recyclable.
Present day use of earth as a building material ranges from the most straightforward construction techniques to more advanced industrial processes. Furthermore, recent research shows that the production and use of earth building blocks is in every way as reliable as the various modern alternatives. The idea of industrial production of CEB´s(Compressed earth blocks) was born some 25 years ago, where the first blocks were mechanically pressed. Today the use of earth blocks is no longer confined to use by local builders/craftsmen, but it is applicable on a far larger scale.

C.E.B.´S MAKE BIOLOGICAL CONSTRUCTION ECONOMICALLY VIABLE
Earth, the oldest of building materials on our planet, is still today the most commonly used.
It is also the most popular material amongst Europe's bio-ecological constructors on account of its physical attributes and ability to regulate moisture and temperature.
This in turn allows for heating/energy reductions of up to 30 % and in some cases even up to 80 %. Earth, that 'most living' of building materials, also influences the indoor climate- ventilation in a positive way. The technology behind the production of compressed earth blocks is based on a mechanical process. This ensures a high quality product regular in dimension and of durability consistent with high quality traditional brick building. Earth, as opposed to pure clay, is the raw material used in the production of earth blocks.
By earth, we mean a combination of clay (ca. 15 - 20 %) silt, sand and stones, other substances and oxygen. Generally speaking, this raw material can be found about 20 - 30 cm under the fertile topsoil. The earth soil often comes to the surface during the preparation of the foundation on building sites. On some sites it may be necessary to add clay, if earth is to be used for block manufacturing.
By making use of a specially developed transportable mechanical press, it is possible to produce compressed earth blocks from earth on the actual building site.
In the case of Denmark and the shorter distances involved, it will usually be more
practical to transport the earth blocks from a conveniently located production site
The energy required for this production process is 100 - 200 times less than is the case in the production of conventional bricks and concrete. One litre of diesel fuel is all that is required to produce 200 earth blocks, and with a rate of 5 - 6 blocks per minute.
A daily production of 2.400 - 3.000 blocks can be achieved.

PRODUCTION PROCEDURE FOR COMPRESSED EARTH BLOCKS
The fertile topsoil is removed from the site, and the earth soil is spread out on the surface and allowed to dry under the sun, before being moved to a dry storage place. At this stage the earth should be checked with regard to it's binding quality. In some cases, it may be desirable to supplement with other soil types in order to enhance this binding quality, to avoid shrinkage, or simply to increase the strength of the block. The raw earth must be of a homogeneous consistence before pressing, and to ensure this, the earth is passed through a specially designed pulverizer.

Depending on the composition of the earth, sand, fine gravel, or other soil types can be added in a mixing machine designed specially for this purpose. During this process, the mixer measures with great precision the required amounts of the various soil types while at the same time adding the precise volume of water to enable optimal pressing.

The actual pressing procedure is automatic and PLC controlled. The compressed earth blocks are left to dry out in a sheltered and well-ventilated place, and will be ready for use in about 1-2 weeks. This means in other words that the blocks are dried as opposed to fired. Furthermore, if the weather at the time of pressing is warm and dry, then the blocks may be put to use immediately.

This well planned manufacturing process whereby pulverizing, mixing and pressing are carried out continually means that four persons are sufficient to maintain production.
The first person ensures that the raw material, the dry stored earth is carried to the pulverizer by conveyer belt. The earth powder and other eventual additives such as sand or gravel are carried to the mixer on their own individual conveyer belt. The second person mans the mixer and supervises the dosage of the various constituents.
This final mixture is then transported via a mass dosering to the press, which on account of the dosering is able to press blocks of a highly homogenous nature. As the press emits
blocks in a continual stream, the third person places them on pallets while carrying out a visual control. Finely the fourth member of the team alternates between supplying the necessary raw materials and transporting the pallets with completed blocks to the dry storage area. It is essential that this manufacturing procedure is well organized, since the production capacity is dependent on a continuous supply of raw material.

BLOCK-LAYING PROCEDURE
The earth blocks are usually laid using an earth mortar prepared on site. The mortar consists of pulverized earth mixed with coarse sand and water. This earth mortar is also available in bags, in which case the mortar can be prepared simply by adding water to the mix in a mixer, or a stavmixer. Earth blocks should be kept dry during the laying procedure. The blocks should be pressed down into the moist mortar, as opposed to being knocked down whereby the earth mortar joints may become too thin. Furthermore, harsh use of a sharp trowel can cause additional damage to the blocks. The thickness of the joint can vary from 0,5 to 1,5 cm, and the mortar should be applied liberally so that it is pressed out of the joint. The excess mortar should be scraped off on completion of the first meter in height. In order to achieve a brushed sand effect this excess mortar can be removed with the use of a wet broom/brush in a circular motion.
If a clean brick finish is required, traditional earth mortar may be used.
Similarly, it is also possible to plaster with earth, and finally the blocks may be finished with a coat of mineral paint or Tierrafino earth colour finish.

THE BUILDING PLAN
When using earth blocks it is important that the architect should be aware of the earth blocks special characteristics. This means among other things, that the blocks should only experience down load bearing while tensile forces should be avoided. The foundation should be carried out using the appropriate method, while paying attention to the fact that earth blocks are heavier than traditional blocks. On no account should earth be exposed to the wet, so the roof-overhang protects the blocks at the top, while a moisture- resistant coating is applied up to 40 cm above ground level. A good plaster coating is applied to the walls to protect against splashing and erosion, and finally to avoid rising moisture a membrane should be laid between the foundation and the blocks. In this way, the building can be said to be protected from water, wearing hat and boots.
Where windows and doors are concerned, lintels may be used. On account on the earth blocks physical characteristics, this overlapping is completed wider than usual. A statistical calculation that achieves a bearing-capacity of 3 N/mm² should be used.
When building on wet sites earth-blocks stabilized with Bio-cement or Puzzolan-Trass- Kalkcement can be supplied providing for a more shock and waterproof product.
Walls may be constructed in different ways; they can either be built with solid single or double layer construction, or with two layers and insulation space. The insulation can consist of reed matting or cellulose (Various types of porous wood fibre). On account of the earth soils moisture regulating properties the use of a damp proof membrane in the wall should be avoided. Such a membrane can prevent the earth soil from effecting sufficient evaporation, thereby cancelling out its natural moisture regulating capacity and thus affecting the indoor climate in a negative way.
At the time of writing, experiments are under way using stabilized and ventilated outer walls with the hollow space filled with mussel-shells.
The pressed earth blocks properties regarding heat retention with slow radiation make them very suitable for both supporting and non-supporting heating-walls, and furthermore there is good potential for combining with passive solar energy.

ECONOMICAL ASPECTS
The soil used for the production of earth blocks is a soil with a certain clay content
which, in relation to the ceramic industry, is often considered unsuitable, or even as refuse, which in turn makes for an inexpensive raw material. The practical mechanization of the manufacturing process also means that the finished product is eminently comparable to other building materials. This picture however is not complete, since the manufacturing costs of traditional building materials do not take into account the cost to the environment for future generations. Some of the traditional materials therefore appear cheaper than they would be if one took into account this cost to future generations.
Since compressed earth-blocks are environmentally friendly, robust and biodegradable, they are able to withstand the most thorough scrutiny pertinent to the demands for sustainable and environmentally correct building today. The advantage to the indoor climate the raw product itself, and the natural sheen on the outer surface caused by the reflection of silica and crystal, gives the finished building an aesthetic quality, a depth of colour that further enhances the value of the product.

SOCIAL ASPECTS
If the raw materials are locally available, the advantages of the mechanical press are increased inasmuch as the saving of energy becomes a genuine factor, thereby increasing the possibilities of carrying out the entire process on site, which in turn increases the enthusiasm of the entrepreneur. In this case, the manufacturer of the earth blocks and the aforementioned entrepreneur are able to work closely together, exchanging experiences and adjusting the building procedure along the way.

OSKAM V/F (founded in 1973)
Oskam develops and manufactures a range of machines for the production of compressed earth blocks. Oskam has been involved in manufacture of earth block machinery since the prototypes development in Australia in 1984. Much experience has been gained during the last decade from the use of compressed earth blocks with various building complexes in Denmark. Oskam has also been involved in the production of earth blocks in Holland for many years. Oskam is therefore experienced and ready for any project involving the production on site of compressed earth blocks for serious building development. As well as his involvement in the manufacture of machinery for, and production of compressed earth blocks, Oskam also manufactures a range of ergonomical tools and machinery for use in developing countries.