Compressive Strength of Brick As Per IS Code

Compressive Strength of Brick - Compression Test on Bricks

Compressive strength of first class brick is 10 N/mm². It is the ability of a brick to resist the maximum vertical applied load by a CTM machine. The compression test is performed on bricks to check the quality of brick as well as class of bricks.

Compressive Strength of Various Bricks

The minimum compressive strength of various types of brick is given below.

Type of Brick	Min. Compressive Strength of Brick
First Class Brick	10 N/mm² or 100 kgf/cm²
Second Class Brick	7.5 N/mm² or 75 kgf/cm²
Third Class Brick	3.5 N/mm² or 35 kgf/cm²
Fourth Class or Un-Burned Brick	1.5 N/mm² or 15 kgf/cm²
Type-A Engineering Brick	125 N/mm²
Type-B Engineering Brick	75 N/mm²
Sand Lime Brick	10 N/mm² (Approx)

Compressive Strength of Brick As Per IS Code 3495 Part -1

The compressive strength of brick is determined as per IS:3495 (Part-1). The procedure is given below.

Indian Standard Used

• IS: 5454 - 1978 [Method for Sampling of Clay Bricks]
• IS: 3495 (Part 1) - 1992 [Method of Test of Burnt Clay Building Bricks]
• IS: 1077 - 1992 [Common Burnt Clay Building Bricks- Specification]

General Requirements

• The dimensions of the bricks shall be measured to the nearest 1 mm.
• All apparatus and testing equipment shall be calibrated at frequent intervals.
• The number of specimens for the test shall be selected as per IS: 5454 - 1978.

Apparatus and Materials Required

1. Compression Testing Machine [C.T.M.]
2. Measuring Tape [Least Count 1 mm]
3. Plywood or Plaster of Paris [3 mm Thick]
4. Trowel [To Mix the Mortar & Fill the Frog]
5. Grinder [To Make Smooth & Parallel Faces of Brick Beds]
6. Sand [Graded 3 mm and down]

Compressive Strength of Brick Formula

Compressive Strength (N/mm²)= [Maximum Peak Load (N)/ Average Area of Bed Faces (mm²)]

Note:- ''Peak Load'' is also known as ''Maximum Breaking Load' or ''Maximum Load at Failure''.

Preconditioning (Only For Solid Bricks)

Step-1: By grinding, Remove the unevenness observed in the bed faces (frog side and its opposite side) to provide two smooth and parallel faces.

Step-2: Measure the bed faces with measuring tape and note its average.

Step-3: Immerse the specimens in water at room temperature for 21 hours.

Step-4: Remove all the specimens and drain out any surplus moisture at room temperature. 

Step-5: Prepare cement mortar of ratio (1 Cement : 3 Sand of grade 3 mm and down).

Step-6: Fill the frog (where provided) and all voids in the bed faces flush with the cement mortar.

Step-7: Store the Sample under the damp jute bags for 24 hours.

Step-8: Immerse in clean water for 3 days.

Step-9: After then, bring out from water and wipe out any traces of moisture.

Test Procedure For Compressive Strength of Brick

Step-10: Place the specimen with flat faces horizontally, the mortar filled face upward.

Step-11: Place two 3-ply plywood sheets (each of 3 mm thick) and carefully centered between plates of the compression testing machine.

Step-12: Apply load axially at a uniform rate of 14 N/mm² (or 140 kg/cm²) per minute till failure occurs and note the maximum load at failure. The load at failure shall be the maximum load at which the specimen fails to produce any further increase in the indicator reading on the testing machine. Repeat the ''Step-10'' for rest specimens. 

Note:- In place of plywood sheets, plaster of Paris may be used to ensure a uniform surface for the application of load.

Test Result of Brick

Compressive strength of bricks after filling frog and immersing in water for 5 days in different stages is calculated as:

Compressive Strength of Brick (N/mm²) = [Maximum Peak Load (N)/ Average Area of Bed Faces (mm²)]

The brick test result is obtained as average test result of the sample and the result should be greater than or equal to the minimum compressive strength of particular brick.  

Compressive Strength of Brick Lab Report

Compressive strength of  brick lab report is the average of results obtained from each specimen, it shall be reported as:

Compressive Strength of Brick As Per IS:3495 (Part-1) is = ...... N/mm².

Requirements of Compressive Strength of Brick

As per IS: 1077 - 1992 [Common Burnt Clay Building Bricks- Specification], The brick test accordance with the procedure given in IS: 3495 (Part 1)- 1992, shall have a minimum average compressive strength given below separately for each and every classes of bricks.

The compressive strength of any individual brick tested shall not fall below the min. compressive strength specified for the corresponding class of brick. The lot shall be then checked for the next lower class of bricks.

Reasons Behind Compressive Strength of Brick Test

Compressive strength of brick is an important quality control "brick test" to ensure their suitability for the use in construction. The compressive strength of brick is also defined as the ability of a brick to withstand crushing or pressure exerted on it without crumbling or breaking. The main reasons behind conducting this brick test are following:

Comparing Different Types of Bricks:

When we perform the compression test on brick, we can compare its result (strength) to different types of bricks and also we can categories different classes of bricks like first class, second class and third class. The test result allows architects and engineers to choose the most appropriate type of brick for a particular construction project.

Ensuring Durability:

The compression test is a measure of brick's ability to withstand loads and pressure that may be vary during its lifetime. High compressive strength of brick ensures that the brick will be durable and can withstand heavy loads without crumbling or breaking.

Quality Control:

The compressive strength test is used as a "quality control" measure to ensure that bricks produced by manufacturers meet the required standards. The bricks with low compressive strength may not be suitable for use in construction and can lead to structural failure.

Design of Structures:

It is an important factor in the design of structures. Engineers use the compressive strength of bricks to determine the load-bearing capacity of walls and other structures. This ensures that the structures are safe and can withstand the expected loads.

Read More: Water Absorption Test of Brick As Per IS Code.

👉FAQs

What is the Minimum Compressive Strength of Brick?

The minimum compressive strength of brick is 10 N/mm² or approx 100 kgf/cm² for first class bricks.

Compressive Strength of First Class Brick?

The compressive strength of first class brick when it tested as per IS:3495 (Part-1) is 10 N/mm² or 100 kgf/cm².

What is the Compressive Strength of Engineering Bricks?

The compressive strength of Type-A Engineering Brick is Minimum 125 N/mm² and the compressive strength of Type-B Engineering Brick is Minimum 75 N/mm².

How Many Brick Samples are Taken For Compression Test?

Minimum 5 bricks are taken for the compressive strength (compression) test of brick as per IS:5454:1978 Table-2 for a lot of 2,001 to 10,000 bricks.

Standard Compressive Strength of Brick in N/mm2?

The standard compressive strength of brick is the minimum compressive strength of brick tested under ctm as per IS code book standard method. The standard compressive strength of brick in N/mm2 is given as 10 N/mm² for first class brick and 7.5 N/mm² for second class brick.

What is Compressive Strength of Brick Formula?

Compressive strength of brick formula is given as following:

Compressive Strength (N/mm²)= [Maximum Peak Load (N)/ Average Area of Bed Faces (mm²)]

Compressive Strength of Brick in psi?

Compressive strength of brick is 1450.38 psi for first class and 1087.79 psi for second class.

Compressive Strength of Brick in MPa?

Compressive strength of brick is 10 MPa for first class bricks and 7.5 MPa for second class bricks.