Soil Based Blocks
Most of the soils could be satisfactorily stabilised through the addition of lime or cement. It is therefore essential to analyse the properties of the soil by a laboratory testing to determine the optimum quantity of stabilisers to be added to impart the desired properties to the block. Soil containing 0-10% gravel, 40-75% sand, 15-25% silt, and 8-25% clay is appropriate for making blocks. It should not contain more than 0.5% of organic matter and the pH value should be less than 7. Soil based blocks is cheap and could be used along with advantage in the construction of low cost houses.
These blocks are manufactured from the mixture of appropriate soil and a stabilizer (cement, gypsum or lime or a combination) thoroughly mixed, preferably within a mechanical mixer at appropriate moisture content and then pressed within moulds. The blocks are cured for 14 days through gently sprinkling water. Cement (5% through weight) is commonly recommended for non-cohesive soils along with low clay content although a combination of cement and lime (2.5% through weight of each) could be used if the clay content is higher. The nominal sizes of the blocks are 20 × 10 × 10 cm, 20 × 10 × 5 cm and 30 × 20 × 10 cm. The density of the block is about 20 kN/m3 and the compressive strength of the sequence of 2 to 3 N/mm2. Water absorption of the block should be less than 20%.