ইটের রাসায়নিক উপাদানসমুহ (Constituents of Brick)
A good brick -clay should be such a mature of pure clay and sand that when prepared with water, it can easily be molded and dried without cracking or warping
Silica = 55%
Alumina = 30%
Iron oxide =8%
Magnesia =5%
Lime =1%
Organic matters =1%
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Total =100%
*Classification of Bricks: The following is the classification of bricks by P.W.D in our country.
1.First class Bricks:These first class bricks are table moulded and of uniform shape and they are burnt in kilns. The surfaces and edges of the bricks are sharp, square, smooth and straight. They comply with all the qualities of good bricks. These bricks are used for important work of permanent nature.
এই প্রথম বর্গ ইটগুলি টেবিলের গঠন এবং অভিন্ন আকৃতির এবং তারা ভাণ্ডারে পোড়া হয়। ইটগুলির পৃষ্ঠতলের এবং প্রান্ত ধারালো, বর্গাকার, মসৃণ এবং সোজা। তারা ভাল ইটের সব গুণাবলী মেনে চলুন। এই ইট স্থায়ী প্রকৃতির গুরুত্বপূর্ণ কাজ জন্য ব্যবহৃত হয়।
2.Second class of Bricks:The second class bricks are ground moulded and they are burnt in kilns. The surface of the second class bricks is slightly rough and shape is also slightly regular. These bricks may have hair cracks and their edges may not be sharp and uniform. These bricks are commonly used at places where brickwork is to be provided with a coat of plaster.
দ্বিতীয় শ্রেণীর ইটগুলি মাটি দিয়ে ঢেকে রাখা হয় এবং ভাণ্ডারে পুড়িয়ে দেওয়া হয়। দ্বিতীয় শ্রেণীর ইটের পৃষ্ঠ সামান্য রুক্ষ এবং আকৃতিটি সামান্য নিয়মিতও। এই ইট চুল ফাটল থাকতে পারে এবং তাদের প্রান্ত ধারালো এবং অভিন্ন হতে পারে না। এই ইষ্টকগুলি সাধারণত এমন জায়গাগুলিতে ব্যবহৃত হয় যেখানে ব্রোকারের প্লাস্টারের একটি কোট দেওয়া হয়।
3.Third class Bricks:These bricks are ground-moulded and they are burnt in clamps. These bricks are not very hard and they have rough surfaces with irregular and blunt edges. These bricks give dull sound when they are struck together. They are used for unimportant works, temporary structures and at places where rainfall is not heavy
এই ইট স্থল-ছাঁচযুক্ত এবং তারা clamps মধ্যে পোড়া হয়। এই ইটগুলি খুব কঠিন নয় এবং তাদের অনিয়মিত এবং কদর্য প্রান্তগুলি সঙ্গে রুক্ষ পৃষ্ঠতল আছে। এই ইটগুলি যখন একসঙ্গে আঘাত করা হয় তখন নিস্তেজ শব্দটি শুকিয়ে যায়। তারা অসমর্থত কাজ, অস্থায়ী কাঠামোর জন্য এবং বৃষ্টিপাত ভারী নয় এমন স্থানে ব্যবহার করা হয়
4.First class Bats:
5.Second class Bats:
6.Picked jhama Bricks:
7.jhama Bricks
8.jhama Bats:
The Bricks
Dimensions or Size of Bricks
The bricks are prepared in various sizes. The custom in the locality is the governing factor for deciding the dimensions or size of bricks. Such bricks which are not standardized are known as the traditional bricks.
If bricks are large, it is difficult to burn them properly and they become too heavy to be placed with a single hand. On the other hand, if bricks are small. more quantity of mortar is required.
For India, a brick of standard size 190 mm x 90 mm x 90 mm is recommended by the BIS. With mortar thickness, the size of such a brick becomes 200 mm x 100 mm x 100 mm and it is known as the nominal size of the modular brick. Thus the nominal size of brick includes the mortar thickness.
It is found that the weight of 1 cu.m of brick earth is about 18 kN. Hence the average weight of a brick will be about 30 to 35 N.
Hence these are the dimensions or size of bricks.
Classification of Bricks
The classification of bricks is as follows:
(i) unburnt or sun-dried bricks; and
(ii) burnt bricks.
The unburnt or sun-dried bricks are those bricks which are dried with the help of heat that is received from sun after the process of moulding. The unburnt bricks can only be used in the construction of simple temporary and cheap structures. Unburnt bricks should not be used at places exposed to heavy rains.
The bricks used in construction works are burnt bricks and they are classified into the following four categories:
(1) First class bricks
(2) Second class bricks
(3) Third class bricks
(4) Fourth class bricks.
(1) First class bricks:
These first class bricks are table moulded and of uniform shape and they are burnt in kilns. The surfaces and edges of the bricks are sharp, square, smooth and straight. They comply with all the qualities of good bricks. These bricks are used for important work of permanent nature.
(2) Second class bricks:
The second class bricks are ground moulded and they are burnt in kilns. The surface of the second class bricks is slightly rough and shape is also slightly regular. These bricks may have hair cracks and their edges may not be sharp and uniform. These bricks are commonly used at places where brickwork is to be provided with a coat of plaster.
(3) Third class bricks:
These bricks are ground-moulded and they are burnt in clamps. These bricks are not very hard and they have rough surfaces with irregular and blunt edges. These bricks give dull sound when they are struck together. They are used for unimportant works, temporary structures and at places where rainfall is not heavy.
(4) Fourth class bricks:
These are overburnt bricks with irregular shape and dark colour. These bricks are used as aggregate for concrete in foundations, brick floors, surkhi, roads, etc. because of the fact that the overburnt bricks have a compact structure and hence they are sometimes found to be stronger than even the first class bricks. It is thus seen that the above classification of bricks is based on the of manufacturing or preparing bricks.
Test for Bricks
A brick is generally subjected to the following tests to find for the construction work,
(1) Absorption
(2) Crushing strength
(3) Hardness
(4) Presence of soluble salts
(5) Shape and size
(6) Soundness
(7) Structure
(1) Absorption:
A brick is taken and it is weighed dry. It is then immersed in water for a period of 16 hours. It is weighed again and the difference in weight indicates the amount of water absorbed by the brick. It should not in exceed 20 per cent of weight of dry brick.
(2) Compressive/Crushing strength of Bricks:
The crushing strength of a brick is found out by placing it in a compression testing machine. It is pressed till it breaks. As per BIS: 1077-1957, the minimum crushing or compressive strength of bricks is 3.50 N/mm2. The bricks with crushing strength of 7 to 14 N/mm2 are graded as A and those having above 14 N/mm2 are graded as AA.
(3) Hardness test on bricks:
In this test, a scratch is made on brick surface with the help of a finger nail. If no impression is left on the surface, the brick is r sufficiently hard.
(4) Presence of soluble salts:
The soluble salts, if present in cause efflorescence on the surface of bricks. For finding out the presence of soluble salts in a brick, it is immersed in water for 24 hours. It is then taken out and allowed to dry in shade. The absence of grey or white deposits on indicates absence of soluble salts.
If the white deposits cover about 10 per cent surface, the efflorescence is said to be slight and it is considered as moderate, when the white deposits cover about 50 per cent of surface. If grey or white deposits are found on more than 50 per cent of surface, the efflorescence becomes heavy and it is treated as serious, when such deposits are converted into powdery mass.
(5) Shape and size:
In this test, a brick is closely inspected. It should be of standard size and its shape should be truly rectangular with sharp edges. For this purpose, 20 bricks of standard size (190 mm x 90 mm x 90 mm) are selected at random and they are stacked lengthwise, along the width and along the height. For good quality bricks, the results should be within the following permissible limits.
(6) Soundness test on brick:
In this test, the two bricks are taken and they are struck with each other. The bricks should not break and a clear ringing sound should be produced.
(7) Structure of a brick:
A brick is broken and its structure is examined. It should be homogeneous, compact and free from any defects such as holes, lumps, etc.
Various forms of bricks ar found within the market which may be utilized in building construction. The bricks ar classified on the idea of producing method that vary from Unburnt or preserved bricks and Burnt bricks. Given below the elaborate lists of assorted forms of bricks :-
Unburnt bricks: Unburnt bricks or preserved bricks belong to the kinds that ar dehydrated through heat generated by the sun once the method of moulding is completed. These forms of bricks ar used for building the temporary and affordable structures. it's counseled that these forms of bricks ar unfit for the areas uncovered to deep rain.
Burnt Bricks: Burnt bricks ar fashioned when blazing the brick-mould within the drying kitchen appliance among the manufactory. These forms of bricks ar usually used for construction processes. Burnt Bricks ar sequestered into the subsequent four categories:
First class bricks: These bricks belong to table-moulded and contain customary form. The bricks ar parched in drying kitchen appliance. The facades and edges of the bricks ar sharp, square, flat and straight. These bricks maintain superior quality. The bricks ar crack free. The brick contains least crushing strength of seven N/mm2. this is often used for the development of superior work i.e. significant foundation and structures.
Second category brick: These bricks belong to ground-moulded and that they ar burnt in kilns. The facade of those bricks is uneven to some extent and form is additionally somewhat unequal. These bricks could contain fine hair cracks and small distortion. The edgings of those bricks ar sharp and consistent. These bricks ar usually applied within the areas wherever masonry is supported with a coat of plaster. The minimum crushing strength of second category brick ought to be seventy metric weight unit per sq cm
Third category bricks: These bricks belong to ground-moulded and ar moulded in drying ovens. These bricks don't seem to be therefore exhausting and embody rough surfaces with uneven and distorted edges. These bricks offeruninteresting sound if set conjointly. The bricks ar helpful for minor and temporary structures and at areas wherever rain is traditional. The bricks ar fashioned with light-weight color and ar relatively soft.
Fourth category bricks: These forms of bricks are called over-burnt bricks that contain uneven form and dark black or gray color. These bricks ar used as mixture for concrete in foundations, floors, roads, etc. as a result of the over-burnt bricks comprises a solid structure and then they're robust enough as compared to the primary category bricks. These forms of bricks ar usually utilized in substandard construction and as gravel for flooring. The bricks contain bulging surfaces. The compressive strength of this brick is extremely low.
The categorization may also be created on the idea of shapes to suit them for specific form of construction. bearthe subsequent link to grasp varied forms of bricks on the market in numerous shapes.
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