Choosing the right soil or clay for Compressed Earth Blocks (C.E.Bs) is crucial for the strength, durability, and overall quality of the blocks. Here are key guidelines to follow when selecting and preparing soil or clay for C.E.B production:
- Soil Composition: Ideal soil for C.E.Bs typically contains a mix of sand, silt, and clay. The recommended composition is usually about 40-70% sand and 30-60% clay. The presence of too much clay can cause excessive shrinkage and cracking, while too much sand can lead to weak blocks.
- Perform a Soil Test: Conduct a simple soil test to determine the composition of your soil. This can be done through a jar test, where soil is mixed with water in a transparent jar, shaken, and then left to settle. The layers of sand, silt, and clay will separate over time, giving you an idea of the soil composition.
- Check for Organic Matter: Soil used for C.E.B should be free from organic matter such as leaves, roots, or compost. Organic material decomposes over time, which can compromise the structural integrity of the blocks.
- Stabilizers if Needed: Depending on the soil composition, a stabilizer such as cement or lime might be necessary to enhance the block’s strength and durability, particularly in wetter climates. The proportion of stabilizer typically ranges from 5% to 10% of the soil volume.
- Moisture Content: The soil should have the right amount of moisture before compression. It should be moist enough to hold together when compressed, but not so wet that it oozes water. A general test is to squeeze a handful of soil and observe if it forms a stable ball without leaving moisture on your hand.
- Uniformity: Ensure the soil is well mixed and uniform in texture before pressing. This consistency is crucial for producing blocks with uniform strength and size.
- Clay Quality: If the soil is too sandy, adding clay can improve its binding properties. However, ensure the clay is of good quality, free from stones and organic material.
- Avoid Expansive Clay: Some clays expand when wet and shrink when dry, causing instability. Avoid soils with high amounts of expansive clays like montmorillonite.
- Testing and Adjusting: It’s often necessary to experiment with different soil mixtures and stabilization methods. Make test blocks with various mixtures and test them for strength and durability after drying.
- Consult Local Expertise: In areas where C.E.B construction is common, local experts or soil scientists can provide valuable advice on soil selection and block making techniques.
Remember, the success of C.E.B construction largely depends on the quality of the blocks, which in turn relies on the quality of the soil used. Taking the time to properly select and test your soil will pay off in the long run.
Tips for Soil Selection
Haven noted the ratios that help in producing the block; let us look at other helpful tips. The rule is that you should determine the plasticity index to be certain that the soil would be suitable for block production.
The first point is that the soil or clay must be free of organic materials. It must also contain sufficient clay to bind the block. Third, the soil should not contain harmful quantities of salt.
As a rule, you need to ensure that the soil with high clay and silt content (usually above 35-40%) should be blended with sandy soil.
As we said, except for organic soil (black soil), any other soil can be used. If the soil contains little or no sand, you can add sand. The ratio is 5 earth buckets+5 sand buckets+1cement bucket.
The organic mateials can be not used.