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 device 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 of 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.