Clay for brick making is prepared differently in a rural environment – manually in small brick yards – and near towns and urban areas mostly in large-scale factories employing heavy duty machinery and equipment. Since modern clay works, quite often cannot satisfy the demand for brick and tiles, rural brick makers are increasingly playing an important role as suppliers and thus, are confronted with the demand for good quality fired clay products.Brick makers are faced with the challenges of producing bricks of satisfactory quality efficiently, economically and sustain-ably and with particular regards to mitigating environmental damage.TESTING PRINCIPLE There are three ways for checking the quality of soil.
Before sending the soil to the laboratory the first is to test the soil sample using simple field tests that require no special equipment’s. These tests are quite satisfactory but occasionally the results of these field tests can be quite misleading if the person have no experience in brick making.
The second method is to check the soil in the laboratory for suitability in brick making. The results of the tests are usually quite accurate and can be very informative if they are interpreted well.
The last and the most important (usually ignored by all) is to simulate the laboratory conditions into pilot plant scale. Most of the soil testing units do not perform this step due to paucity of the required facilities. However pilot trials are extremely necessary to have a feel of the production process and to actually feel the product expected during the actual production process.
Soil to be tested is ground to a fine powder, mixed with sufficient quantity of water and kneaded into a plastic mass of required consistency. Balls of about 8 cm diameter are then moulded with hands and allowed to dry in the sun.
If the dry balls show deformation in shape and crumble easily on pressing the excessive sand content in the soil is indicated. If however, the sand content is deficient then the balls shall develop surface cracks on drying.
A second field test is performed by moulding bricks of standard sizes from well kneaded soil of plastic consistency which is capable of being rolled in threads of 3 mm in diameter. The edges and corners of such bricks should be sharp. These bricks are left to dry for four days in the sun and examined for shrinkage cracks.
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