INNOVATIVE EARTH-FRIENDLY BUILDING PRODUCTS
INNOVATIVE EARTH-FRIENDLY BUILDING PRODUCTS |
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| Preparing the Soil Proper soil preparation is paramount to successful block making. Most soils, when reasonably free from organic matter, will make good compressed earth blocks and tiles. Best results are obtained by first screening the soil through 1/8 inch or 1/4 inch wire mesh to remove any pebbles, rocks, chunks of compacted soil, roots and so on. The 1/8 inch mesh tends to produce a finer product, though the 1/4 inch size as shown below performs almost as well.
The soil MUST have some amount of clay; it is the binder which holds the block together when compressed. If the clay content is excessive (generally no more than about 20%), sand must be added. Portland cement and/or lime can be added to the soil to increase strength and resistance to erosion, but this will increase the curing time. When using Portland cement in the soil, getting the formula right is critical; too little cement produces a block that will crumble when handled, while too much cement greatly increases the cost with no additional benefit. The amount of moisture in the soil is also critical; a too-wet or too-dry mixture weakens the block; experimentation is required to determine the proper amount of moisture, but be assured that it takes surprisingly little to produce a strong and solid block. To demonstrate just how critical the moisture content is, we will first make a block with an excessive amount of water in the soil. After screening the soil and adding just a bit too much water, our soil clumps into little balls as shown below.
The mould box is filled, but with an insufficient amount of soil -- the corners need to be filled in and it all needs to be tamped down.
With the corners filled in and the contents of the mould box tamped down, we're ready to compress it into a block.
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