Compressive Strength of Bricks (All Types) Test Procedure and IS code

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Update: November 19, 2021

          Hi friends, you are welcomed in the Civil Allied Gyan. In this article I have explained about compressive strength of bricks.

By the help of this blog you can easily test the compressive strength of bricks. So please continue to the end & keep your love and support on me.

  • IS: 3495 (Part-1): 1992

a). Solid brick – Solid bricks have no holes, cavities or depressions.

b). Cellular brick – Cellular bricks have no holes, but may have frogs or cavities not exceeding 20% of the gross volume of the brick.

c). Perforated brick – Perforated bricks have holes not exceeding 25% of the gross volume of the brick. The area of any one hole shall not exceed 10% of the gross area of the brick.

d). Frogged brick – Frogged bricks shall have depressions in one bed. Frog size should not exceed 130mm×50 mm×10 mm.

  • Compression testing machine
  • The compression plate of which shall have a ball seating in the form of portion of a sphere the center of which coincides with the center of the plate, shall be used.
Compression Testing Machine

Preparation of Specimens:-
  1. Take twelve bricks randomly from sample.
  2. You can take halved bricks and use half of each whole brick for determining the compressive strength.
  3. The overall dimension of each bedding face shall be measured to the nearest of 1.3 mm and the area of the face having smaller area shall be taken as the area of the bricks for testing the compressive strength.

  1. Immerse the bricks in water at room temperature for 24 hours.
  2. Remove the specimens and allow to dry at room temperature for about 5 minutes.
  3. Then fill the frogs with cement-sand mortar with a ratio of 1:11/2. (Sand should be clean and well graded and passing through 3.35 mm sieve).
  4. Trowel the mortar off flush with surface of the bricks.
  5. After filling the frogs, store the bricks under the damp sacks for 24 hours and then immerse in water for 6 days before bricks are considered ready for testing.
  6. After seven days of filling the frogs, take out the specimens and wipe off the moisture with damp cloth.
  7. Then place the specimen with flat surface horizontally and the mortar filled face facing upwards between two plywood sheets of 3-ply, normally 3 to 4 mm thick and carefully centered between the plates of the compression testing machine.
  8. Then apply the load axially at a uniform rate of 14 N/mm² per minute, until failure. The failure shall be deemed to have occurred when no further increase in the load is registered with unchanged rate of moving head travel.
B)Solid bricks / bricks with a frog intended to be laid downwards / perforated bricks / cellular bricks
Immerse the brick in water for 6 days or saturate the brick by boiling as well as water absorption test.

(Heat the water to boiling point (100ยบC) in approximately 1 h. Boil theme for 5 hour continuously, and then quit it for cooling to room temperature by natural loss of heat for not less than 16 h or more than 19 h).
–: Then follow the row no. 7. and 8. of procedure.

Fill the cavities with capping compound or mortar mix and immerse in water for 6 days and then follow the row no. 7. and 8. of procedure.

No capping compound is used and holes remain empty. Immerse the brick in water for 6 days, take out and wipe off the moisture and then follow the row no. 7. and 8. of procedure.

Calculation of compressive strength:- Obtain the strength of each specimen by dividing the maximum load obtained during loading by the appropriate area of the bed face. Record the strength in N/mm² to the nearest 0.1 N/mm².

Calculate the average of the 12 compressive strengths and report it to the nearest 0.1 N/mm². See the equation given below.

For bricks with holes,
Net area of brick = Gross area of brick – area of holes.
Gross area = Length of brick × width of brick.


Where d is the diameter of the hole.

Note. When bricks are to be used as crushed aggregate, for in a blend as unfound material, the necessity to determine the compressive strength accurately as it is when the bricks are to be used in load-bearing walls, is not so critical.

REPORT:- Report the compressive strength in a data sheet to the nearest 0.1 N/mm².

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