If the water absorption capacity of a brick is more, its strength will be comparatively low. For first class bricks, the water absorption capacity should not be more than 20% by weight.
4. Efflorescence Test on Bricks
This test is performed to know the presence of of any alkaline matter in the bricks.
Take five bricks at random from the given sample.
Place each brick on end in a dish containing distilled water ensuring depth immersion at least 2.5cm.
Keep the dish in a ventilated room (temperature 20 deg to 30 deg C) till the whole of distilled water in the dish evaporates.
Again pore 2.5 cm depth of distilled water in the dish and keep it till whole of water gets evaporated.
Now examine the bricks for efflorescence as detailed below:
No perceptible deposit
Nil – efflorescence
10% are covered with deposit of salts
Slight – efflorescence
50% area covered with deposits of salts without any powdering or flaking surface
Moderate – efflorescence
50 % area covered with deposit of salts accompanied by flaking of surface
Heavy – efflorescence
Heavy deposits of salts accompanied by flaking of the surface
Serious – efflorescence
Terra Cotta made from a mixture of fine clay 60%, crushed pottery 20%, while sand 14% and powdered glass 6% with a quantity of desired colouring substance. It is baked earth of superior variety of clay.
Terra-cotta is used for architectural and ornamental parts of superior building as a substitute for stones. It is used as sound proof material and its hollow blocks prevent dampness in the structure.