Laboratory Tests and Raw Material Tests before Clay Brick Making

 

Laboratory tests

If bricks have to satisfy an official standard, they will probably have to be tested in a laboratory. These tests will need to be repeated periodically to maintain quality control. Tests normally specify the sizes for bricks and the acceptable compressive strength - how much weight they can bear before crushing. For certain uses, such as damp-proof courses, water absorption or suction rate may also be specified.

Raw material tests

The quality of brick which can be made at a particular site is largely predetermined by the type of soil available. There are some simple soil tests which don't need very special equipment. In the sedimentation jar test, a sample of soil is dissolved in a transparent jar of water. When the soil settles you can get an idea of the fractions of clay, fine and coarse sand that are present. Another test is the linear shrinkage test. A sample column of wetted and mixed soil is pressed into a mould and allowed to dry. The shrinkage indicates how much clay there is in the soil and whether problems can be expected when drying bricks. Soil test are useful indicators, but you really only find out whether good bricks can be made by firing samples. Before investing in a full size kiln, however, it is possible to fire cubes or eggs of soil either in a laboratory kiln or a simple field oven.

Conclusion

These guidelines will help field-workers judge the quality of bricks. Furthermore, if the information presented is used as a basis by those working with brickmakers, it will go some way to establishing an agreed approach to assessing the technical problems they face and proposing appropriate solutions. That is, solutions which make the best use of available resources: are affordable, manageable, cost effective, and ultimately successful.