To know the quality of bricks following 7 tests can be performed. In these tests some are performed in laboratory and the rest are on field.
- Compressive strength test
- Water Absorption test
- Efflorescense test
- Hardness test
- Size, Shape and Color test
- Soundness test
- Structure test
Compressive strength test:
This test is done to know the compressive strength of brick. It is also called crushing strength of brick. Generally 5 specimens of bricks are taken to laboratory for testing and tested one by one. In this test a brick specimen is put on crushing machine and applied pressure till it breaks. The ultimate pressure at which brick is crushed is taken into account. All five brick specimens are tested one by one and average result is taken as brick’s compressive/crushing strength.
Water Absorption test:
In this test bricks are weighed in dry condition and let them immersed in fresh water for 24 hours. After 24 hours of immersion those are taken out from water and wipe out with cloth. Then brick is weighed in wet condition. The difference between weights is the water absorbed by brick. The percentage of water absorption is then calculated.
The less water absorbed by brick the greater its quality. Good quality brick doesn’t absorb more than 20% water of its own weight.
The presence of alkalies in bricks is harmful and they form a gray or white layer on brick surface by absorbing moisture. To find out the presence of alkalis in bricks this test is performed. In this test a brick is immersed in fresh water for 24 hours and then it’s taken out from water and allowed to dry in shade.
If the whitish layer is not visible on surface it proofs that absence of alkalis in brick. If the whitish layer visible about 10% of brick surface then the presence of alkalis is in acceptable range. If that is about 50% of surface then it is moderate. If the alkalis’s presence is over 50% then the brick is severely affected by alkalies
In this test a scratch is made on brick surface with a hard thing. If that doesn’t left any impression on brick then that is good quality brick.
Size, shape and color test:
In this test randomly collected 20 bricks are staked along lengthwise, widthwise and heightwise and then those are measured to know the variation of sizes as per standard. Bricks are closely viewed to check if its edges are sharp and straight and uniform in shape. A good quality brick should have bright and uniform color throughout.
In this test two bricks are held by both hands and struck with one another. If the bricks give clear metallic ringing sound and don’t break then those are good quality bricks.
In this test a brick is broken or a broken brick is collected and closely observed. If there are any flows, cracks or holes present on that broken face then that isn’t good quality brick.