Grade of bricks | testing of bricks | types of bond

 Grade of bricks | testing of bricks | types of bond

Grade of Bricks :- ( 15 10776:1992) 

Grade 10 

1. The compressive strength of brick shall be 10 MPa (100 kg/cm²).
2. Water absorption capacity shall not exceed 12-15%.
3. The presence of Efflorescence (presence of alkali and salt) should be NIL.
4. The permissible tolerance in size is ±3%

 
Grade 7.5

1. The compressive strength of the brick is 7.5MPa.
2. Water absorption shall not exceed 20%.
3. The presence of Efflorescence shall be Slight. 
4. The permissible Tolerance in sire is ±8%

 Grade 5.

1. The compressive strength shall not be less than 5 MPa (50kg/cm²). 
2. Water absorption shall not exceed 22%
3. The presence of Efflorescence should be slight. 
4. The maximum permissible tolerance in shape and sire is ± 8 %

Important Notes

1.The compressive strength of 1st class brick. is about 10 MPa. (100kg/cm² and water absorption. shall not exceed  20%.
2. The compressive strength of A-Grade brick is in the range of 7.5-14 MPa.
3.The compressive strength of AA Grade brick is >14MPa.
4.The compressive strength of brick used in Building construction shall not be less than 5.5MPa and water absorbtion shall not exceed \ 20% The brick should not break after falling from a height of 1m. 
6.The average of five test results of compressive strength is taken as the compressive strength of brick. 
7.The No. of bricks used to test the size of brick Shall be 20.
8.The actual size of Modular brick Shall be 190 mm x 90 mm x 90 mm.
9.The nominal size of a Modular brick shall consist of a thickness of Mortar (10mm)
 200 mm x 100 mm x 100mm. 
10. In India, the size of traditional brick is 9" x 4" x 3"

 

Testing of Bricks :

 

Crushing Test :

It is performed on the brick to find the compressive strength of the brick where the average of five test results conducted on five specimens of brick is adopted.The brick is dipped in water for 24 hours at a temperature of 27 ±2 °C. The Brick is taken out from the water and the excess water is wiped off.

Testing-of-Bricks-using-Concrete-Crushing-Machine

 

The frog of the brick is filled in cement morlar. (1:3 proportion) and it is allowed to be hardened under moist curing. The Brick specimen is kept under the testing machine where the compressive load applied is  14 MPa Per minute, and it is continued till the Brick gets crushed. The total compressive load applied at the time of crushing divided by the surface area! the brick is called as the compressive ea of strength.
 
According to 15 1077: 1992, the cushing value is dependent on the grade of Brick.
 
a) Grade 10 -10 MPa 

b) Grade 7.5-7.SMPa

c) Grade 5 5MPa

d) Grade 3.5-3.5MPa.
 

 Water absorption test

 
There are two types of water absorption test. 

a) cold water absorption test. 

b) Five hour Boiling water test.
 

 Cold water absorption test :

 
The brick specimen is dried in oven of temperature 110 ±5°C. brick is found . The mass of dried.The same brick is immersed in water having temperature 27±2°C for a duration of 24 hours. (Minimum 16 hrs).The brick is taken out from the water and excess water is removed off. The total mass of brick is determined 
 
 Five hour Boiling Water absorption Test : 

 The brick is dried in an oven having a temperature 110 ± 5°c for 24 hours, and it's mass is determined. The same brick is immersed in water and water is boiled slowly. The brick is kept inside the boiling water for a duration of 5 hours.  After 5 hours the brick is taken out and it is cooled.
 
Test for the presence of alkali and salt
 (Efflorescence) :
 
The brick is immersed in water and after 24 hours it is taken out from the water bath and it is dried in normal condition. After complete drying, the surface of the brick is noticed properly find the presence of White deposit called Efflorescence. 

If the White deposit is nil then there is no efflorescence. (Grade 10).  If while deposit covers 10% of the surface then it is called slight efflorescence. (Grade 7.5& 5). If while deposit covers 10 to 50% of surface, then it is known as Moderate Efflorescence (Grade 3.5). If a white deposit is more than 50%.of surface the area then it is known as high efflorescence which is not permitted.
 
Test for Hardness :
 
The hardness of the brick is determined by scratching the brick surface by nail of fingers. for good quality brick, there shall be no scratching on the surface.
 
Test for Soundness

To determine the soundness of the brick, two bricks are struck each other and if they produce metallic ringing then the brick will be of high quality.
 
Test for structure:
 

The brick is broken and the internal part is observed. It should be homogeneous, free from holes and free from pebbles.
 
Bonds in brick Work:
 

 Bond is the interlacement of bricks formed when they are laid immediately below or above them. It is the method of arranging the bricks in Courses so that individual units are tied together and the vertical joints of the successive courser donot lie in the same vertical line.It shall not be vertically continuous.
 
Types of Bond:
 
1. Stretches Bond. (Partition Wall ) No wad Bearing)
2. Header Bond.
3. English Bond.
4. Flemish Bond.
5. Garden Wall Bond.
6. Dutch Bond.
7. English Cross Bond.
8.Raking Band
9. Zig-zag Bond.
10. Facing Bond.

 English Bond:
 
This is the most commonly used band for wall thicknesses (>20cm).This bond is considered to be the Strongest Bond. The bond consists of alternate courses of headers and stretchers. In this bond, the vertical joints of the header courses come over each other. Similarly the vertical joints of the stretcher courses also come over each other.
 
Flemish Bond:
 
In this type of Bond each course comprise of an Alternate header and stretcher. Every alternate coarse start with a header at the corner and queen closure is placed next to the quine header in alternate courses to develop the lap. 

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