The diversified types of bricks available in market might confuse you while deciding what type of brick would be suitable for your building type. Knowing about classification of bricks would make this decision making an easy step for you while planning for your house construction.
Each set of brick classification is a result of predominant consensus on specific requirements including physical properties and appearance features. But wait a minute; you must not get confused between types of bricks and classification of bricks. There is a very narrow gap between two subjects but actually these are two different topics. But you don’t worry as this article would cover both the subjects.
When we say types of bricks we are actually talking about various kinds and categories of bricks based on its method of production, composition, shape as well as finish quality. Classification of bricks is specific in accordance to standards.
A widely accepted and predominant standard throughout the world is that of ASTM (American Society for Testing and Materials). All the model buildings in the United States refer ASTM standards for bricks. In similar to that of ASTM, Canadian Standards Association (CSA) has also prepared codes for fired Masonry Bricks made from clay or shale.
The cheap and local availability of bricks, strength, durability, reliability and insulation properties have made bricks as one of the most popular building unit that is extensively used. The hilly area where required quality of clay is not found in abundance, stone is used as its replacement which is a natural material.
Bricks are blocks of tampered clay moulded to suitable shapes and sizes while it is still in plastic condition, dried in the sun and burnt as desired so as to make them more strong, hard and durable.
But in comparison to bricks, stone is heavier to lift and cost too much to dress in required shapes but as bricks are readily formed in molds so they are already in standard size and shape.
The use of stones is encouraged in water retaining structures as it is less porous where as in case of bricks water proofing treatment needs to be done. Stones are durable enough to withstand attack of weather but bricks need plastering or pointing for the protection needs.
Literally there is hundreds of different classification of bricks and in the planning phase of your construction project you would also get confused on what type would suite your needs and demands of the project.
[ctt template=”2″ link=”bbedT” via=”yes” ]So whether you need brick for facing of your building or for vehicular paving or for sewer and manhole you need to be specific and must not intermix.[/ctt]
Major Classification of Bricks
There are literally thousands of different bricks, but they can be broken down into a handful of basic types. The vast majority are made from clay and are kiln-fired.
In the past unburnt bricks were used for temporary and cheap natured buildings for saving cost and time. They were developed in moulds and were dried with the help of sun heat.
Unburnt bricks are also termed as Kacha Bricks in India and Pakistan. Unburnt bricks should never be used for load bearing structures and should never be exposed to heavy rain and severe temperatures. Unburnt bricks are sometimes referred as sun-dried bricks and are found application some 6000 years ago.
Now a days only burnt bricks are used that are either made of clay or shale formed in standard shape and size with the help of standard moulds. After extrusion it is dried and fired in kilns which are then stored after coating or glazing if needed.
Based on procedure of moulding, extrusion and degree of burning; burnt bricks are further classified in to four classes with three standard classes.
First Class Bricks
As the name suggests, it is the highest quality brick free from all defects and flaws. First Class bricks are in standard size of 19 x 9 x 9 cm. The source of clay decided for production of first class brick should be free from all saline deposit. The first class bricks should be of uniform color i.e. yellow or red and are well burnt. They must have sharp edges with uniform and smooth faces.
When the two first class bricks are struck together it should give a sharp metallic ringing sound and when broken apart must show uniform compact texture. The fractured surface should not show fissures and bubbles or lumps of lime.
Such brick when scratched with finger nails it leave no mark. The compressive strength of the first class brick should not be less than 140 kg/cm2. Such types of brick do not absorb more than 15% of their weight of water when kept immersed for 24 hours. They may have no / slight presence of efflorescence and are free from modules of free lime. These bricks when dropped on hard ground from height must not break.
First class bricks are very costly and are only used for face work of structures and need not be plastered and only pointing is sufficient. They are also used in flooring as well as reinforced brick work.
Second Class Bricks
Like first class bricks, second class bricks are also hard and well burnt but may have somewhat irregular in shape or size and may have slight irregularities in surface. Other qualities are the same as those of first class. Its compressive strength should not be less than 70 kg/cm2 and absorption value should not be greater than 22 percent when soaked for 24 hours in water.
Second class bricks when used for exterior work required plastering and are very useful for interior works but are not suitable for flooring.
Third Class Bricks
Third class bricks as name suggests are slightly under burnt bricks having somewhat soft edges but are generally of uniform reddish yellow color. These bricks when struck together produce dull or thud sound while compressive strength is slightly higher than above types of bricks. Third class bricks when used may suffer from intensive efflorescence. It should not absorb water more than 25 % of its own dry weight when kept immersed in water for 24 hours. The texture surface is not uniform and it may show lot of pebbles on freshly fractured surface of the brick.
These bricks are mostly used for temporary construction that is not subjected to heavy loads.
Fourth Class Bricks – Over burnt Bricks – Jhama Bricks
The bricks are actually irregular in shape and are dark in color due to over burning. Mostly the bricks placed near the fire in the kiln are produced as over burnt bricks which get fused and loose their shape. These are also termed as over burnt bricks or Jhama Bricks. Their compressive strength is more than 150 kg/cm2 with low porosity and absorption.
Being high compressive strength over burnt bricks is used in foundations of structures or as aggregates in concrete. They also find application as road metal or for construction of inferior structures.
Classification of Bricks according to ISI (Indian Standard Institute)
As per IS 1077-1976 common burnt clay bricks are classified on the basis of their average compressive strength. Each class of brick is further classified into two sub-classes A and B based on tolerances and shapes e.g. brick of classification 100 is further sub-divided as 100A and 100B and so on. Bricks of sub-class A shall have smooth faces, sharp edges and corners and uniformity in color whereas bricks of sub-class B may be slightly distorted or may have slightly rounded edges subject to the condition that these distortions do not cause any difficulty in laying of uniform courses.
|Class Designation||Average Compressive Strength|
|Not less than (kg/cm2)||Less than (kg/cm2)|
Classification of Bricks according to Constituent Raw Material
Mostly and widely the bricks are made of clay but sometimes they are also made with lime-sand or concrete depending on the requirement of the project and keeping in mind the economic parameters.
Clay bricks are mainly produced with the help of alumina, silica, lime, iron oxide and magnesia.
Sand – Lime Bricks
Sand – lime bricks are manufactures by sand and lime, sometimes pigments are also added of suitable color.
Concrete bricks are manufactured from a mixture of Portland cement and aggregate for use in brick masonry. Typical aggregate include sand, gravel, crushed stone and blast furnace slag. Mix proportion varies from 1:2:4 to 1:8:16 according to the required bearing capacity. These bricks are often made hollow for economical purposes and to reduce the weight of the brick. The dimensions of the brick are 40x20x6-35 cm.
Concrete bricks are widely used for construction purposes especially in area where soils are not suitable for manufacture of clay bricks and may be used in the construction of bricks panels for light weight structures and multistory formed structures.
The using of concrete bricks save time and effort as brick are light in weight and are large in size. These bricks give good bonding with plastering materials used in their construction. These bricks have accurate size and shape. They are produced with various bearing capacity according to the cement content used in their production. The weight of bricks can be controlled by varying the size of openings.
Special Classification of Bricks
Some types of bricks are especially manufactured for a purpose or a location these are described below :-
Facing bricks are intended for use in both structural and nonstructural masonry, including veneer, where appearance is a requirement.
Hollow brick are used as either building or facing brick but have a greater void area. Most hollow brick are used as facing brick in anchored veneer. Hollow brick with very large cores are used in reinforced brickwork and contain steel reinforcement and grout.
Building bricks are intended for use in both structural and nonstructural brickwork where appearance is not a requirement. Building bricks are typically used as a backing material.
Thin veneer brick have normal face dimensions but a reduced thickness. They are used in adhered veneer applications.
Paving bricks are intended for use as the wearing surface on clay paving systems. As such they are subject to pedestrian and light or heavy vehicular traffic.
Glazed brick have a ceramic glaze finish fused to the brick body. The glaze can be applied before or after the firing of the brick body. These brick may be used as structural or facing components in masonry.
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The selection of brick types is a very tricky job and you must know about the classification of bricks and the various types so that you can select what is suitable and feasible for your project. I hope that I have covered all the types here but anyhow if I have missed something you can mention in the comments.
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