What is Compressive strength?
Compressive strength determines the load-carrying capacity of a material or an element. To understand clear, Let’s take an example of a boy weighs 12kg sitting on a small chair. The specific chair is made only for kids so that they can sit without any harm. Now say, an adult weighs 60kg sat on the chair, The chair is unable to carry the load of 60kg on it. Hence it will break. Same in the case of Building materials, there is a load-carrying capacity for any material upto an extent, once the limit is met the material starts failing.
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Compressive Strength of Bricks:
Compressive strength of bricks is the capacity of brick to resist or withstand under compression when tested on Compressive testing machine [CTM]. The Compressive strength of a material is determined by the ability of the material to resist failure in the form of cracks and fissure.
First Class Brick: The brick which has a compressive strength of 10N/mm2 is called as a First class brick
Second Class Brick: The brick with compressive strength of 7N/mm2 is called as a Second class brick
Building brick: The brick which we use for building has a compressive strength of 3.5N/mm2
Sundried Brick: The sun dried brick has a compressive strength of 1.5N/mm2 to 2.5N/mm2
HomeBuilding MaterialsCompressive Strength Test on Bricks and its importance
Compressive Strength Test on Bricks and its importance Krishna March 13, 2020 No Comments
The different types of tests conducted on bricks are already discussed in the article how to test the quality of brick on site. The Compressive strength test on bricks is done indoors in a lab and requires a specific apparatus to conduct the test.
Contents
What is Compressive strength?
Compressive Strength of Bricks:
Classification of Bricks based on Compressive Strength:
Compressive Strength test on Bricks:
Apparatus:
Precautions:
Procedure:
Observations :
Formula to calculate the Compressive strength:
References:
First of all,
What is Compressive strength?
Compressive strength determines the load-carrying capacity of a material or an element. To understand clear, Let’s take an example of a boy weighs 12kg sitting on a small chair. The specific chair is made only for kids so that they can sit without any harm. Now say, an adult weighs 60kg sat on the chair, The chair is unable to carry the load of 60kg on it. Hence it will break. Same in the case of Building materials, there is a load-carrying capacity for any material upto an extent, once the limit is met the material starts failing.
Compressive Strength of Bricks:
Compressive strength of bricks is the capacity of brick to resist or withstand under compression when tested on Compressive testing machine [CTM]. The Compressive strength of a material is determined by the ability of the material to resist failure in the form of cracks and fissure.
In this test, the compression force is applied on both the faces of brick and the maximum compression that brick can bear without cracking is observed and recorded.
Compressive strength test on bricks
Classification of Bricks based on Compressive Strength:
IS 1077-1992 bricks are classified into 11 different types based on Compressive strength of a brick
Below table tabulates the Compressive strength of Brick of different classes:
Bricks Class Designation
Average Compressive Strength not less than
(N/mm2)
(Kgf/cm2)
35
35
35
30
30.0
300
25
25.0
250
20
20.0
200
17.5
17.5
175
15
15.0
150
12.5
12.5
125
10
10.0
100
7.5
7.5
75
5
5.0
50
3.5
3.5
35
to remember the classification easily while selecting the right brick , the bricks are classified as
First Class Brick: The brick which has a compressive strength of 10N/mm2 is called as a First class brick
Second Class Brick: The brick with compressive strength of 7N/mm2 is called as a Second class brick
Building brick: The brick which we use for building has a compressive strength of 3.5N/mm2
Sundried Brick: The sun dried brick has a compressive strength of 1.5N/mm2 to 2.5N/mm2
Read: BrickWork Calculation | Types of Bricks | Bricks in Construction
Compressive Strength test on Bricks:
Apparatus:
Compressive testing machine [CTM], Three samples of bricks collected randomly from the brick pouch. Cement mortar of ratio 1:1 (1 Part of cement and 1 part of sand), Plywood sheets and trowel to fill the mortar in the brick frog is required.
Precautions:
The sampling of bricks should be done carefully and the dimensions of bricks should be measured near to 1mm and ensure the three bricks have the same and equal size.
Bricks without efflorescence are selected for the test.
Clean water is used
Three bricks are picked from the brick pouch and the unevenness on the brick faces are removed by grinding.
Immerse the brick samples in the water for 24 hours at the temperature of 23-degree centigrade.
Prepare the mortar by mixing the cement and sand at the ratio of 1:1.
Fill the frog with the mortar paste and allow to set the bricks in jute bags for the period of 24hrs
Also, check for the voids on the brick surface. If there any fill the voids by flushing the mortar on them.
Take out the bricks from bags and immerse them back in the water for 7 days to complete the hardening of mortar on brick.
Allow the bricks to dry, before placing it on the compressive testing machine
Place the specimen flat-wise on the base of CTM, with mortar filled face upwards between the two flat plywood sheets.
Plywood sheets are used to hold the brick in the correct position while testing.
Start the CTM and apply the load axially on the specimen at the rate of 14 N/mm2 (140 kg/cm2) per minute till the brick starts breaking
Repeat the same procedure with the leftover bricks
Note down the reading of each brick from CTM once the brick starts tearing.
Observations :.
Compressive Strength = Max load at which Specimen starts breaking (N) / Contact area (mm2).
