Compressive Strength and Efflorescence Tests for Bricks

The quality and durability of bricks is crucial for any construction project. Two essential tests that help in determining these properties are the Compressive Strength Test and the Efflorescence Test. This blog post provides a detailed guide on how to perform these tests, interpret the results, and ensure the quality of bricks used in construction.

Compressive Strength and Efflorescence Tests for Bricks

Compressive Strength Test

The compressive strength of bricks provides a basis for comparing the quality of bricks. However, it is of little value in determining the strength of a wall, as wall strength mainly depends on the strength of the mortar.

Procedure:

1. Sample Preparation:
• Take 5 brick samples.
• Immerse in water at room temperature for 24 hours.
• Frog and all voids in bed faces of bricks are filled flush with cement mortar (1:3).
2. Curing:
• Store the bricks under damp jute bags for 24 hours.
• Followed by immersion in clean water for 3 days.
3. Testing:
• Place the brick specimen with flat faces horizontal and mortar face facing upward between the plates of the compression testing machine.
• Load is then applied axially at a uniform rate of 14 N/mm² per minute until failure occurs, and the maximum load at failure is noted.

Calculation:

• Compressive Strength (N/mm²) = Maximum Load at Failure / Loaded Area of Brick

Results:

• Average of 5 results noted:

Type of Brick	Compressive Strength (N/mm²)
1st Class	10.5
2nd Class	7.5
Common Bricks	5.0
Sun Dried Bricks	2.5

Efflorescence Test

The aim of the efflorescence test is to check the presence of soluble salts in bricks.

Procedure:

1. Sample Preparation:
• Place the brick specimen in a glass dish containing water to a depth of 25 mm in a well-ventilated room at 20-30°C.
• After all the water is absorbed or evaporated, add water to a depth of 25 mm again.
• After the second evaporation, observe the bricks for white/grey deposits.

Categories of Efflorescence:

Category	Deposits of Efflorescence
Nil	Imperceptible (No patches)
Slight	<10% of exposed area of brick
Moderate	10-50% of exposed area of brick
Heavy	>50%, but deposits don’t powder or flake away
Serious	>50%, deposits are heavy with powdering or flaking

Notes:

• For 1st class bricks, efflorescence should not be more than moderate (10-50%).
• For higher class bricks, efflorescence should not be more than slight (<10%).

FAQs

Q1: What is the significance of the compressive strength test for bricks? A1: The compressive strength test helps in determining the quality of bricks by measuring their ability to withstand loads. It is crucial for ensuring the durability and stability of construction materials.

Q2: How is the compressive strength of bricks calculated? A2: The compressive strength is calculated by dividing the maximum load at failure by the loaded area of the brick.

Q3: What does the efflorescence test indicate? A3: The efflorescence test indicates the presence of soluble salts in bricks, which can cause white or grey deposits on the surface, affecting the appearance and durability of the bricks.

Q4: What are the acceptable levels of efflorescence for 1st class bricks? A4: For 1st class bricks, efflorescence should not be more than moderate, which means 10-50% of the exposed area of the brick.

Q5: Why is it important to perform both compressive strength and efflorescence tests on bricks? A5: Performing both tests ensures that the bricks used in construction are not only strong and durable but also free from harmful salts that can affect their longevity and appearance.

Conclusion

By following the procedures outlined for the compressive strength and efflorescence tests, you can ensure the quality and durability of bricks used in your construction projects. Regular testing and adherence to standards will help in achieving long-lasting and aesthetically pleasing structures.