As per norms, five bricks are taken at random and their dimensions are measured accurately to 1 mm. They are immersed in water at 25–29°C for a period of 24 hours. After that they are taken out, and excess moisture is allowed to drain. If the bricks have frogs they are filled with C.M 1:3. They are again kept under a jute bag for another 24 hours. They are again immersed in clean water for three days.
Just at the time of testing they are taken out, one at a time, from the water and wiped dry. The horizontal and mortar-filled surface is placed facing upwards with three thin plywood sheets on a brick-testing machine.
Load is applied on the brick at a rate of 140 kg/cm2 per minute till the failure of the brick. An average of five test values of bricks is reported. While computing the average value, any single value obtained as compressive strength which is higher than the upper value of the class of the bricks tested should be taken only as the upper limit of the class. Test values less than 20% of the average should be rejected. Also the average value should not be less than the specified value of the class of the brick.
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