Water Absorption Test on Bricks

Water Absorption Test on Bricks

Water absorption test on bricks is conducted to determine the durability property of bricks such as degree of burning, quality and behaviour of bricks in weathering. A brick with water absorption of less than 7% provides better resistance to damage by freezing. The degree of compactness of bricks can be obtained by water absorption test, as water is absorbed by pores in bricks. The water absorption by bricks increases with the increase in pores. So, the bricks, which have water absorption less than 3 per cent can be called as vitrified. This test provides the percentage of water absorption of bricks and the procedure of the same is discussed below.

Apparatus

A sensitive balance capable of weighing within 0.1% of the mass of the specimen and ventilated oven

Specimen

Three numbers of whole bricks from samples collected for testing should be taken.

Procedure of Water Absorption Test

1. Dry the specimen in a ventilated oven at a temperature of 105 °C to 115°C till it attains substantially constant mass.
2. Cool the specimen to room temperature and obtain its weight (M1) specimen too warm to touch shall not be used for this purpose.
3. Immerse completely dried specimen in clean water at a temperature of 27+2°C for 24 hours.
4. Remove the specimen and wipe out any traces of water with a damp cloth and weigh the specimen after it has been removed from water (M2).

Calculation of Water Absorption of Bricks

Water absorption, % by mass, after 24 hours immersion in cold water is given by the formula,

                                                                    

The average result shall be reported.

Result

Water absorption of the given bricks = ………….%

Water Absorption Values for Bricks

When tested as above, the average water absorption shall not be more than 20% by weight up to class 12.5 and 15% by weight for the higher class.

Compressive Strength Test on Bricks

Compressive Strength Test on Bricks

Compressive strength test on bricks is carried out to determine the load-carrying capacity of bricks under compression with the help of a compression testing machine. Bricks are generally used for the construction of load-bearing masonry walls, columns and footings. These load-bearing masonry structures experience mostly the compressive loads. Thus, it is important to know the compressive strength of bricks to check for its suitability for construction.

Apparatus

Compression testing machine, the compression a plate of which shall have ball seating in the form of a portion of a sphere centre of which coincides with the centre of the plate.

 specimens

Three numbers of whole bricks from a sample collected should be taken. The dimensions should be measured to the nearest 1mm.

Sampling of Bricks

Remove unevenness observed the bed faces of bricks to provide two smooth parallel faces by grinding. Immerse the bricks in the water at room temperature for 24 hours, then remove the specimen and drain out any surplus moisture at room temperature.

Fill the frog and all voids in the bed faces flush with cement mortar (1 cement, 1 clean coarse sand of grade 3mm and down). Store it under the damp jute bags for 24 hours filled by immersion in clean water for 3 days. Remove and wipe out any traces of moisture.

Procedure of Compressive Strength Test on Bricks

1. Place the specimen with flat face s horizontal and mortar filled face facing upwards between plates of the testing machine.
2. Apply load axially at a uniform rate of 14 N/mm² (140 kg/cm²) per minute till failure occurs and notes maximum load at failure.
3. The load at failure is the maximum load at which the specimen fails to produce any further increase in the indicator reading on the testing machine.

Calculation

Compressive Strength of Bricks = Maximum Load at Failure (N)/Average area of bed face (mm²)

The average result shall be reported.

Range Calculation

Maximum compressive strength =

Contact area =

Maximum expected load =

The range to be selected is …………………

Result

Average compressive strength of the given bricks =………….. N/mm²

 

Specifications of Bricks

Speciation of Common Clay Building Bricks

Dimensions: The standard size of clay bricks shall be as follows

Length (mm)	Width (mm)	Height (mm)
190	90	90
190	90	40

Classification of Bricks based on Compressive Strength

The common burnt clay shall be classified on the basis of average compressive strength as given in table.

Bricks Class Designation	Average compressive strength of Bricks
	Not less then (N/mm2)	Less than (N/mm2)
350	35	40
300	30	35
250	25	30
200	20	25
175	17.5	20
150	15	17.5
125	12.5	15
100	10	12.5
75	7.5	10
50	5	7.5
35	3.5	5

laboratory test of bricks

Test to Justify Brick Quality

To know the quality of bricks following 7 tests can be performed. In these tests, some are performed in the laboratory and the rest are on the field.

1.   Compressive strength test

2.   Water Absorption test

3.   Efflorescence test

4.   Hardness test

5.   Size, Shape and Color  test

6.   Soundness test

7.   Structure test

1. Compressive strength test: This test is done to know the compressive strength of brick. It is also called crushing strength of brick. Generally, 5 specimens of bricks are taken to the laboratory for testing and tested one by one. In this test, a brick specimen is put on crushing machine and applied pressure till it breaks. The ultimate pressure at which brick is crushed is taken into account. All five brick specimens are tested one by one and the average result is taken as brick's compressive/crushing strength.

2. Water Absorption test: In this test, bricks are weighed in dry condition and let them immersed in fresh water for 24 hours. After 24 hours of immersion, those are taken out from the water and wipe out with a cloth. Then brick is weighed in wet condition. The difference between weights is the water absorbed by brick. The percentage of water absorption is then calculated.

**The less water absorbed by brick the greater it's quality. Good quality brick doesn't absorb more than 20% water of its own weight.

3. Efflorescence test: The presence of alkalies in bricks is harmful and they form a grey or white layer on the brick surface by absorbing moisture. To find out the presence of alkalis in bricks this test is performed. In this test, a brick is immersed in freshwater for 24 hours and then it's taken out from the water and allowed to dry in shade.

If the whitish layer is not visible on the surface it proofs that absence of alkalis in brick. If the whitish layer visible about 10% of the brick surface then the presence of alkalis is in an acceptable range. If that is about 50% of the surface then it is moderate. If the alkalis' presence is over 50% then the brick is severely affected by alkalies

4. Hardness test: In this test, a scratch is made on a brick surface with a hard thing. If that doesn't leave any impression on brick then that is good quality brick.

5. Size, shape and colour test: In this test randomly collected 20 bricks are staked along lengthwise, widthwise and heightwise and then those are measured to know the variation of sizes as per standard. Bricks are closely viewed to check if its edges are sharp and straight and uniform in shape. A good quality brick should have bright and uniform colour throughout.

6. Soundness test: In this test two bricks are held by both hands and stuck with one another. If the bricks give clear metallic ringing sound and don't break then those are good quality bricks.

7. Structure test: In this test, a brick is broken or a broken brick is collected and closely observed. If there are any flaws, cracks or holes present on that broken face then that isn't good quality brick.