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 =

Maximum expected load =

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