# To determine the Compressive strength of bricks

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

Compression testing machine

Fig: Compression Testing Machine

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

Sampling
Remove unevenness observed the bed faces to provide two smooth parallel faces by grinding .Immerse in water at room temperature for 24 hours .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
(I) Place the specimen with flat face s horizontal and mortar filled face facing upwards between plates of the testing machine.

(II) Apply load axially at a uniform rate of 14 N/mm(square) per minute till failure occurs and note maximum load at failure.

(III) The load at failure is maximum load at which the specimen fails to produce any further increase in the indicator reading on the testing machine.

Calculation :

Compressive Strength = Maximum load at failure / Average Area of Bed face.

The average of result shall be reported.

##### Range Calculation

Maximum compressive strength =

Contact area =

The range to be selected is …………………

Result

Average compressive strength of the given bricks =…………..

##### IS SPECIFICATIONS

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

 Class Designation Average compressive strength Not less than   () Less than   () 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