Theory

Bricks are classified as I.S. 1977-1976 into  three grade. The minimum compressive strength is at the class A. Bricks equal to 350 kg/cm2. The minimum compressive strength of class ‘C’ should not be less than 350 kg/cm2. The compressive test of individual bricks shall not fall below the maximum requirement by more than 20 %.


Apparatus

1.      Compressive testing machine

2.    Bricks sample

3.    Scale


Application

Compressive strength is very important property of bricks as different types of bricks are used for different grade of work. It is essential to determine its compressive strength for given stock of brick.


Diagram

Compressive Testing Machine
Procedure

1.      Take a sample of brick and measure its dimension.

2.    With the help of dimensions calculate cross-sectional area of bricks.

3.   Place the sample of bricks between the jaws of compressive testing machine.

4.  Applied the load gradually on the brick till cracks are taking place in the brick.

5.   When cracks are observed on bricks stop the machine and measure applied load and note down it.

6.    Repeat the above procedure for three different types of machine.


Precautions

1.      There should not be any crack in the brick before testing.

2.    Apparatus of crack on the brick should be observed carefully.

3.    Reading should be taken without doing any mistake.


Observation table

Sr.no.
TYPE OF BRICKS
SIZE OF BRICKS
CROSS-SECTIONAL AREA OF BRICKS
LOAD APPLIED
COMPRESSIVE
STRENGTH
1
A
22x10x5.5
55 cm2
5000 kg
90.90 kg/ cm2
2
B
22x10x5.4
54.32 cm2
6000 kg
110.46 kg/ cm2
3
C
22.5x9.5x5.8
50.35 cm2
10000 kg
198.60 kg/ cm2


Calculation

a)    Compressive strength of brick (A)

P/A = 5000 / 55 = 90.96 kg/cm2

b)   Compressive strength of brick (B)

P/A = 6000 / 34.32 = 110.40 kg/cm2


c)    Compressive strength of brick (B)

P/A = 10000 / 50.35 = 198.60 kg/cm2



Result

Compressive strength of brick is

1)     ‘A’ is 90.90 kg/cm2

2)   ‘B’ is 110.40 kg/cm2

3)   ‘C’ is 198.60 kg/cm2