This test is performed to know the crushing strength which should not be less than the specified limit.
With horizontal flat faces, the specimen is arranged in the compression testing machine for testing.
At a speed of 14 N/mm2 per minute, the load applied till collapse.
The compression strength is calculated by dividing the maximum load at the failure by the area of brick.
3. Efflorescence test
This test is done to know the presence of alkaline matter in the brick.
They are kept in a 150mm dia glass dish containing 25mm depth of water at room temperature.
On the brick exterior, white or grey patches appear on drying.
Presence of efflorescence is classified as:
a. Nil
When no visual deposit of efflorescence
b.Slight
When the brick surface is covered with a thin deposit of salts not more than 10% of area, then it is termed as slight efflorescence.
c.Moderate
If the exposed area of brick is deposited salts between 10% to 15% of surface area, then it termed as the moderate Efflorescence.
d.Serious
Deposits are heavy and I the flakes or powder falling from the surface of the brick with heavy deposits of salts, then it is termed as serious Efflorescence.
e.Heavy
Efflorescence is greater than 50% of the exposed area of brick.
4. Warping test
Using a glass-surface or flat stool warping test is performed and measure the largest distance between the straightness edges of the brick surface.
This test is of two types:
a.Concave warpage
b.Convex warpage
Refractory bricks :
Without becoming soft or melting, the clay which can tolerate high temperature is termed as
refractory or fire clay.
This clay is burnt at a very temperature in a special kiln.
Fire clay has grater % of alumina.
These clays are capable of resisting of high temperature up to 1700 degree Celsius without softening.
Presence of a small percentage of lime and magnesia help to melt the clay particles at high temperature.
Uses:
Refractory brick is used in lining furnaces having acid slag, steel industries, coke oven and copper reverberatory furnaces.
Additives in the manufacture of Brick
The following are the additives used:
1.Fly ash
2.Sandy loam
3.Rice husk
4.Basalt stone dust.
1.Fly ash
From thermal power plants, this Fly ash waste material is available.
This includes mullite, amorphous glassy material, magnetite, hematite etc.
In clay bodies, these silicates help to improve strength on firing.
By adding Fly ash chock drying losses and shrinkage on drying can be reduced.
2.Sandy loam
Sandy loam is effective in controlling the drying behaviour of highly plastic soil which contain an expanding group of clay.
3.Rice husk ash
Carbon content should be <3 % to 5 %
In plastic soils which shows excessive shrinkage’s this rice husk ash is utilised.
4.Basalt stone dust
From blast stone crushing units basal stone dust is available as the waste product in extensive quantity.
This is utilised to improve the drying, shaping and firing performance of bricks.
How many bricks required for 3.7 m3 brickwork, size of brickwork 190mm x 90mm x 90mm?
Answer: Volume of one brick = 0.19m x 0.09m x 0.09m = 0.01539 Cum
For 1 m3 No. of bricks required =1/0.01539
= 649.77, approximately 650 bricks are required.
So, for 3.7 m3 Numbers required = 3.7 x 650 =2405.
So, for 3.7 m3 brickwork, approximately 2405 numbers are required.