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The compressive strength of bricks is one of the most important properties that determines their quality and suitability for construction purposes. It is defined as the capacity of a brick to resist loads without cracking or deformation.

The compressive strength is calculated using the formula:

Compressive Strength (MPa) = Maximum Load (N) / Contact Area (mm²)

As per IS 1077:1992, bricks are classified based on their compressive strength:

• Class 10: Minimum compressive strength of 10 N/mm²
• Class 12.5: Minimum compressive strength of 12.5 N/mm²
• Class 15: Minimum compressive strength of 15 N/mm²
• Class 17.5: Minimum compressive strength of 17.5 N/mm²
• Class 20: Minimum compressive strength of 20 N/mm²

Standard brick dimensions in India are 230mm × 115mm × 75mm. The test is conducted on bricks that have been immersed in water for 24 hours to ensure uniform moisture content.

• Compression testing machine
• Vernier caliper
• Measuring scale
• Water tank

1. Select five representative bricks from the sample for testing.
2. Immerse the bricks in water at room temperature for 24 hours.
3. Remove the bricks from water and wipe out any traces of water with a damp cloth.
4. Measure the length and width of the bed face (the face to be in contact with mortar) to the nearest 1mm.
5. Place the brick in the compression testing machine with the bed face horizontal and the frog (if any) facing upward.
6. Apply the load uniformly at a rate of 14 N/mm² per minute until failure occurs.
7. Record the maximum load at which the brick fails.
8. Calculate the compressive strength for each brick.
9. Take the average of compressive strengths of all tested bricks as the compressive strength of the sample.

The average compressive strength of the tested brick samples was found to be 14.24 MPa.

As per IS 1077:1992, this brick sample falls under Class 12.5 category.

The compressive strength test conducted on the brick samples showed satisfactory results with an average strength of 14.24 MPa, meeting the requirements for Class 12.5 bricks as per IS standards.

• Ensure bricks are properly saturated before testing.
• Measure dimensions accurately to calculate the correct contact area.
• Apply load uniformly without any shock or impact.
• Ensure proper alignment of brick in the testing machine.
• Record the maximum load accurately at the point of failure.