Laboratory tests performed on bricks

January 19, 2019

Compressive Strength of bricks is the load bearing capacity before it ruptures, when subjected to compressive stress. Hard and well burnt bricks have more compressive strength than the porous bricks. The crushing strength is the important factor for bricks, because it decides the suitability of brick for different uses. The crushing strength of brick can be find out with the help of crushing testing machine. Brick is fixed to the crushing testing machine and then compressive force is applied to the brick during testing operation. The crushing strength of brick should be minimum 105 kg/cm2.

Water Absorption Test – It is the percentage of water absorbed by the dry brick ( oven dried and cooled) to its weight. A brick is taken and it’s weighed dry. It is then immersed in water for a period of 24 hours. Excess water is wiped off and It is weighed again, the difference in weight indicates the quantity of water absorbed by the brick. Bricks used in construction work should not absorb the water more than 20% of its dry weight. If any brick absorb the more water that means it will loose its crushing strength. As per IS codes the loading on brick specimen should be uniform in CTM at rate of 14N/mm2 per minute. The maximum percent of water absorption for 2nd class bricks in 24 hours is limited to 22%. And for third class brick it is 25%.

Efflorescence Test-If any brick absorb the water more than 20% of its dry weight, along its pores by capillary action and carries with it dissolved salts. The solution having white colour will evaporates from brick work and deposited on the surface. These white deposits of salts are called as efflorescence. This test of the brick is necessary because if salts are presence in abundant on the surface then it will damage the bricks as well as the masonry and will give ugly appearance to the building.