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

In this post we will discuss about the compressive strength of fly ash brick as per IS Code 3495 Part-1 along with test procedure, formula, lab test report and test result requirements. 

Compressive Strength of Fly Ash Bricks As Per IS Code 3495 Part-1

Compressive strength of fly ash brick is important to determine before use in the project to check the quality of brick. Since the fly ash brick is made by mixing sand, gypsum, lime in a ratio to make the fly-ash bricks, we cannot ensure the quality of bricks without putting it in the compression testing machine.

Table of Contents

Standard Procedure For Fly Ash Brick Compressive Strength

Standard procedure as per IS:3495 Part-1 for fly ash brick compressive strength is given below. Apply this procedure to find out the compressive strength of fly ash bricks.

Aim of the Test

The aim of this test is to determine the compressive strength of fly ash bricks by using laboratory equipment.

Indian Standard Used in Compressive Strength of Fly Ash Brick

The below Indian Standards are used to sampling, testing and comparing test result requirements of fly ash brick test.

• IS: 5454 - 1978 [Method for Sampling of Clay Bricks]
• IS: 3495 (Part 1) - 1992 [Method of Test of Burnt Clay Building Bricks]
• IS: 12894 - 2002 [Pulverize Fuel Ash-Lime Bricks- Specification]

General Requirements For Fly Ash Brick Compressive Strength Test

• 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 Required in Fly Ash Brick Test 

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 Fly Ash Brick Formula

Compressive Strength of Fly Ash Brick Formula is-

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'' 

Only For Solid Bricks

Preconditioning For Compressive Strength of Fly Ash Brick

Step-1: By grinding, Remove the unevenness observed in the bed faces of fly ash bricks (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.

Procedure For Fly Ash Brick Compressive Strength

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 kgf/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.

Fly Ash Brick Compressive Strength Test Result

Compressive strength of fly ash bricks after filling frog and immersing in water for 5 days in different stages is given below

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

Fly Ash Brick Test Report

The average of results obtained from each specimen shall be reported as

Compressive Strength of Fly Ash Brick (N/mm²)= ......

Requirements of Compressive Strength of Fly Ash Brick Test

As per IS: 12894 - 2002 [Pulverize Fuel Ash-Lime Bricks- Specification], The brick test accordance with the procedure given in IS:3495 (Part-1)- 1992, The min. average wet compressive strength of

pulverized fuel ash-lime bricks shall not be less than the one specified for each class in 4.1. The wet compressive strength of any individual brick shall not fall below the min. average wet compressive strength specified for the corresponding class of bricks by more than 20 percent.

Note: In case any of the test results of wet compressive strength exceed the upper limit for the class, the same shall be limited to the upper limit of the class for the purpose of averaging.

Read: Water Absorption of Fly Ash Brick.

Also Read: Manufacturing Process of Fly Ash Bricks.

👉FAQs:

What is Compressive Strength of First Class Fly Ash Brick?

The Minimum Compressive Strength of First Class Fly Ash Brick is 10 MPa or 10 N/mm² or 100 kg/cm².

Compressive Strength of Fly Ash Brick in N/mm2?

Compressive Strength of First Class Fly Ash Brick is 10 N/mm² when tested as per IS Code 3495 Part-1.

Compressive Strength of Fly Ash Brick in kg/cm2?

Compressive Strength of First Class Fly Ash Brick is 100 kgf/cm² when tested as per IS Code 3495 Part-1.

What is Compressive Strength of Second Class Fly Ash Brick?

The Minimum Compressive Strength of Second Class Fly Ash Brick is 7.5 MPa or 7.5 N/mm² or 75 kg/cm².

How to Increase the Strength of Fly Ash Brick?

There is a common method that manufacturers use to increase the strength of fly ash bricks. The Compressive Strength of Fly Ash Brick can be increased by using extra chemicals like cement with marble/stone dust.

Minimum Compressive Strength of Fly Ash Bricks?

The minimum compressive strength of first class fly ash brick is 10 N/mm² when tested as per IS Code 3495 Part-1.

What is the Compressive Strength of Fly Ash Bricks?

The compressive strength of fly ash brick is the maximum load per unit area resist by the fly ash brick under compression testing machine at a certain speed of loading. For first class fly ash brick, the minimum compressive strength is 10 N/mm².

Is A Fly-Ash Brick Load Bearing Brick?

No, fly-ash brick is not a load bearing brick. It is generally used in masonry work. Now a days it is widely used in government projects.

Is AAC Brick Stronger than Fly Ash Brick?

AAC brick is lighter in weight and strong in strength compare to fly ash brick or clay brick.
There is a problem with fly ash brick, it gets strength slowly-slowly.