Testing of the bricks and specifications as per the IS code standards

Bricks are generally used in the construction of walls. Generally depending upon the requirement of the strength brick classes are classified. Testing of the bricks is an important aspect before construction to check the quality. Depends upon the test results obtained from the observation the classification of bricks is made. In this article you will able to learn about different types of the tests used for the bricks and the specifications as per IS code standards.

The test methods of the bricks are obtained from IS 3495:1992 code specifications and common burnt clay building brick specifications are obtained from IS 1077:1992 code provisions.

Various testing of the bricks types

The major test methods of the bricks are classified as the following

1. Dimensional tolerances test
2. Water absorption test
3. Saturation coefficient test
4. Efflorescence test
5. Compressive strength test

Dimensional tolerances testing of bricks

The dimensional tolerances test for the bricks is carried out in two ways one is length wise tolerance and another one is width and height wise tolerance. For this experimental study minimum of 20 numbers of the modular size bricks are considered.

For the length wise tolerance 20 numbers of the bricks are laid on the flat surface in length wise direction and the length is measured from the starting brick to the ending brick. The measured length should not be greater than the 3800±80mm as per the length consideration.

For the width and height wise tolerance 20 numbers of the bricks are laid on the flat surface in width wise and height wise direction and the length is measured from the starting brick to the ending brick. The measured length should not be greater than the 1900±40mm as per the width and height wise direction considerations. We can measure this tolerance by considering height direction also by taking measurements from starting brick to ending brick in height direction.

The tolerance in the length wise direction is taken as 80mm and the tolerances in the width and height wise direction is taken as 40mm.

Water absorption testing of bricks

The water absorption test is conducted according to IS 1077 code for the modular bricks. Initially the weight of the brick is measured before soaking in the water. Now soak the brick in the water for 24 hours. After 24 hours of observation remove the brick from the water and clean the top surface with dry cloth. Now again measure the weight of the wet brick. The water absorption is calculated by using below expression.

Water absorption = (W1-W2)/W1

Here W1= weight of full brick,

W2 weight after soaking in water for 24 hours

Specifications

For the class up to 12.5 Class (2nd Class bricks) the water absorption value is taken as less than 20%.

For the class more than 12.5 Class (1st Class bricks) the water absorption value is taken as less than 15%.

Saturation coefficient testing of bricks

The saturation coefficient is the ratio of percentage of water absorbed by soaking the brick 24 hours in cold water (A) to the percentage of water absorbed by soaking the brick 5 hours in hot water (B).

Saturation coefficient = A/B

Where A= weight by soaking in cold water for 24 hours

B=weight by soaking in hot water for 5 hours

Specifications

For good freeze and thaw resistance the Saturation coefficient (SC) should be less than 1.

Efflorescence test of bricks

The efflorescence test is conducted to study the concentration of salts present on the brick. The test is carried out by immersing the brick in 25cm depth distilled water container and close it with the cap to avoid excess of evaporation. Allow the water to get absorbed and evaporated for the same brick to form salts.

Specifications

1. If no white patches are present then this will indicates that efflorescence is nil.
2. If not more that 10% white patches are present on the brick then this will indicates that efflorescence is slight.
3. If not more that 50% white patches are present on the brick then this will indicates that efflorescence is moderate.
4. Greater than 50% white patches are present on the brick then this will indicates that efflorescence is heavy.
5. High deposit of salts are present on the surface of brick with powdering and flaking of exposed surfaces this will indicates that efflorescence is serious.

Note:  For good bricks efflorescence is moderate up to class 12.5 class and slight for class greater than 12.5 class according to IS 1077 code specifications.

Compressive strength test of bricks

The compressive strength of the brick is determined by using compression testing machine (CTM). Initially remove all the unevenness from the brick surface then immerse the brick in the cold water for 24 hours. Now after 24 hours fill the frog with the help of the cement mortar using proportion of 1:3 ratio (1 indicates cement and 3 indicates fine aggregates). Now then dry it for 24 hours. Finally immerse the brick in the clean water for 3 days duration.

Now the final brick is removed from the clean water and remove moisture with the help of the dry cloth. And place it under the CTM, apply loading at the rate of 140kg/cm2/min. Record the maximum load (P) value from the testing machine.

The compressive strength of the brick is calculated by using below expression

Compressive strength = P/A

Where P= load in kN

A= Surface area of brick work

Depending upon the compressive strength value obtained from this experimental analysis the classification of brick is made namely class 1, class 2, class 3, class 4 etc.

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Conclusions of testing of the bricks and specifications

Well now the above explained concepts are related to complete testing methods of bricks used in the building constructions. The tests are related to dimensional tolerances test, water absorption test, saturation coefficient test, efflorescence test and compressive strength test. The test process is done according to IS 3495:1992 code standards and the specifications are considered from 1077:1992 code. Depending upon the strength values the bricks are classified in to Class 1, Class2, Class3, Class 4 etc.

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