Analysis Of Bricks

Bricks

Bricks may be defined as the uniformly burnt rectangular unit having high compressive strength.

Standard size of brick

Constituents Of Brick

 (Formula-ASLOM)

1. Alumina:It provide plastic character to clay in wet condition.
• Alumina content: 20% to 30%
• Alumina excess: Brick will shrink more
• Alumina less: Difficulties in moulding of brick

2. Silica:It present in the free form or combined from with clay.
• Silica content: 50% to 60%
• Silica excess: Make brick brittle
• It prevent shrinkage, cracking, warping of brick

3. Lime:It is present in finally powdered form.
• Lime content: 5%
• It provide strength, durability to brick

4. Oxide Of Iron:A small quantity of iron help to fuse silica at comparatively lower temperature.
• Iron content: 5% to 6%
• It increase the durability and impermeability of brick

5. Magnesia:Magnesia present in clay with oxide of iron make the brick yellow.
• It present in small quantity: Decrease the shrinkage
• Excess quantity: Decay the brick

Classification Of Brick

These are the following classification of brick.

1. First Class Brick:These brick having first class quality. These are well burnt having smooth and even surface. The shape of brick is perfectly rectangular and reddish colour.
• These should not given any mark when stretched with fingernail.
• Water absorption should not exceed 20% and compressive strength more than 140kg/cm^2.
• The efflorescence should be nil.

2. Second Class Brick:It is slightly over burnt and not having the perfectly rectangular shape. These brick are hard enough and colour of brick is uniform.
• Water absorption not more than 22%.
• Compressive strength should not more than 70kg/cm^2.
• They can show slightly efflorescence.

3. Third Class Brick:These brick are not properly burnt. These brick may be under or over burnt. The shape and size of these brick are not uniform and colour is light red and yellow spot.
• Water absorption 23% and more.
• Compressive strength less than 70kg/cm^2.
• High or low efflorescence may be these.

4. Over Burnt Or Jamma Brick:These are over burnt with irregular shape and size. They may be twisted due to over burning.
• Water absorption very low.
• Compressive strength more than 150kg/cm^2.

Tests For Bricks 

These are the following tests for bricks:

1. Compressive strength Test

2. Water absorption test

3. Dimensions tolerance test

4. Effloresencence test

1.Compressive Strength Test:

The following are the steps to determine the compressive strength of bricks.

• Select some bricks randomly from a lot of prepared bricks. Let us take bricks.
• Immerse these bricks in water for 24 hours.
• Remove the bricks from water and allow these to drain for 5 minutes after that clean the surplus water.
• Fill the frogs with 1:1×1/2 cement,sand and mortar.
• The bricks are stored under damp jute bags for 24 hours so that mortar set properly.
• Then immerse these in clean water for seven days.
• The individual specimen is then placed between the plate compressive testing machine and load is applied gradually till the brick fails.
• The maximum load at which the specimen fails is noted and compressive strength of brick is determined as follows:                         compressive strength=load at failure/area of brick.
• All the five bricks taken are tested and arithmetic mean of these calculated to give the final result. 
• The bricks are classified into different categories on the basis of these results.

2. Water Absorption Test:

The steps of water absorption test is as follows:

• Take 5 bricks randomly from a lot of bricks.
• Place the bricks in a ventilation oven at 110°C to 115°C for 48 hours. Due to this a constant weight of bricks is obtained.
• Then allow the bricks to cool at room temperature.
• After cooling, the bricks are weighted individually. Let the weights is W1.
• Then these bricks are immersed completely in cleaning water at room temperature between 15°C to 30°C for 24 hours.
• After this the bricks are weighted again individually. Let the weights at the stage is W2.
• The water absorption percentage by weight is calculated as follows.                                       Water absorption=weight of absorption water/weight of dry brick ×100   (% by weight)                                                                    water absorption=W2-W1/W1×100
• The calculation in step seven is done for individual bricks and all the bricks are checked.
• The arithmetic mean of all the five bricks is calculated and the result is recorded water absorption percentage by weight should not exceed by 20% for first class bricks.

3. Dimensions Tolerance Test:

In this, the standard size of the brick is tested steps are as follows:

• Take 20 bricks randomly from a lot of bricks.
• Choose a flat levelled ground.
• Then arrange the bricks in the following manner such that the adjacent surfaces touch the other properly.                                Class A Bricks
• Length=368cm to 392cm 
• Width=174cm to 186cm
• Height=174cm to 186cm (If height of brick is 9cm)                                                                        Height=77cm to 83cm (If height of brick is 4cm)                                                                        Class B Bricks
• Length=350cm to 410cm
• Width=165cm to 195cm
• Height=165cm to 195cm (If height of brick is 9cm)                                                                        Height=74cm to 86cm (If height of brick is 4cm)

 4. Effloresencence Test:

White patches and salt deposit on the surface of brick masonry structure it is known as effloresencence.

It is due to the presence of soluble salt such as sulphate of sodium and potassium in brick.

• Take five bricks at randomly from the lot of bricks.
• Place them in a container and fill the container with water such that bricks are fully immersed under water.
• Keep this in a well ventilated warm room.
• The whole water will be lost due to the absorption & evaporation and bricks become dry after some days.
• Now, again add water to the containers as in step 2 and repeat step 3 & step 4.
• At the end of second drying observe the bricks for effloresencence.                                               

The percentage area to be covered by white and grey patches. If there is not any white or grey patches over the surface the it is noted as effloresencence is nil. The effloresencence is listed as

• Slightly: If the percentage area covered is up to 10%.
• Moderate: If the percentage area covered is between 10% to 50%.
• Heavy: If the percentage area covered is above 50%.

Properties Of Bricks

These are the following properties:

1. Size: The shape of the bricks is rectangular but the size may be different form place to place. As per IS code 1077-1970 the following two sizes are recommended in india.

2. Weight Of Brick:A standard single brick should have weight between 3kg to 3.5kg. The weight of brick depends upon the type of clay used and method of moulding of bricks.

3. Insulation:A dense, heavy and low porous brick have adequate insulation against heat, noise and cold.

Moulding Of Brick Units

The process of giving the required shape to the prepared brick earth is known as moulding of bricks.

Following are the two ways of moulding:

1. Hand moulding

2. Machine moulding

1. Hand Moulding: In hand moulding, bricks are moulded by hands i.e. manually. For hand moulding of bricks, skilled man power is required. It is done with the help of moulds.

These are the two types of hand moulding.

A) Ground Moulding: In ground moulding, first of all the ground to be used is prepared. The ground is levelled and cleaned. It is often made smooth my mud plastering.

B) Table Moulding: When moulding is done on a table, instead of ground is known as table moulding.

2. Machine Moulding: When moulding is done with the help of machine, it is known as machine moulding.