laboratory test of bricks

Test to Justify Brick Quality

To know the quality of bricks following 7 tests can be performed. In these tests, some are performed in the laboratory and the rest are on the field.

1.   Compressive strength test

2.   Water Absorption test

3.   Efflorescence test

4.   Hardness test

5.   Size, Shape and Color  test

6.   Soundness test

7.   Structure test

1. 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 the 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 the average result is taken as brick's compressive/crushing strength.

2. 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 the water and wipe out with a 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 it's quality. Good quality brick doesn't absorb more than 20% water of its own weight.

3. Efflorescence test: The presence of alkalies in bricks is harmful and they form a grey or white layer on the 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 freshwater for 24 hours and then it's taken out from the water and allowed to dry in shade.

If the whitish layer is not visible on the surface it proofs that absence of alkalis in brick. If the whitish layer visible about 10% of the brick surface then the presence of alkalis is in an acceptable range. If that is about 50% of the surface then it is moderate. If the alkalis' presence is over 50% then the brick is severely affected by alkalies

4. Hardness test: In this test, a scratch is made on a brick surface with a hard thing. If that doesn't leave any impression on brick then that is good quality brick.

5. Size, shape and colour 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 colour throughout.

6. Soundness test: In this test two bricks are held by both hands and stuck with one another. If the bricks give clear metallic ringing sound and don't break then those are good quality bricks.

7. Structure test: In this test, a brick is broken or a broken brick is collected and closely observed. If there are any flaws, cracks or holes present on that broken face then that isn't good quality brick.