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Presentation on Bricks 1 1.1 INTRODUCTION This report deals with entire study of construction material, bricks, which is made from clay and are also known as clay products. One of the oldest building material bricks continues to be a most popular and leading construction material because of being cheap, durable and easy to handle and work with. In primitive ages sun dried clay bricks were used. Egyptians were probably the first to use the burnt clay bricks. By heating thee clay products to about its constituents fuse and because of the affected chemical changes, the product becomes hard, brittle and a strong and stable clay product most suitable as a primary building unit for construction. Clay bricks are used for building-up exterior and interior walls, partitions, piers, footings and other load bearing structures. The density of bricks range between 2.5 to 2.8 g/cm 3 depending upon the clay composition. Bricks are generally resistant to alkalis, acids, and chemical and are excellent fire resistant building materials. The modulus of elasticity of brick range between 5-30 × 10 3 N/mm 3 . A brick is regular in shape and of size that can be conveniently handled with one hand. Bricks may be makes of burnt clay or mixture of sand and lime, or flyash lime and sand, or of Portland cement concrete. Clay bricks are commonly used since these are economical and easily available. Size of a standard bricks (also known as modulur bricks) should be 19 × 9 × 9 cm and 19 × 9 × 4 cm. when placed in masonry the 19 × 9 × 9 cm brick with mortar becomes 20 × 10 × 10 cm. Burning of moulded clay products make them sufficiently strong for use as construction material. Though tiles, refectory bricks, earth wares and stones wares serve different construction purpose, brick is the most commonly used building material. It is light, easily available, uniform in shape and size, and relatively cheaper except in hilly areas. Bricks are easily moulded from plastic clays, also known as brick clay or brick earth.

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  • Presentation on Bricks

    1

    1.1 INTRODUCTION

    This report deals with entire study of construction material, bricks, which is made from clay and

    are also known as clay products. One of the oldest building material bricks continues to be a most popular

    and leading construction material because of being cheap, durable and easy to handle and work with. In

    primitive ages sun dried clay bricks were used. Egyptians were probably the first to use the burnt clay

    bricks. By heating thee clay products to about its constituents fuse and because of the affected

    chemical changes, the product becomes hard, brittle and a strong and stable clay product most suitable as

    a primary building unit for construction. Clay bricks are used for building-up exterior and interior walls,

    partitions, piers, footings and other load bearing structures. The density of bricks range between 2.5 to 2.8

    g/cm3

    depending upon the clay composition. Bricks are generally resistant to alkalis, acids, and chemical

    and are excellent fire resistant building materials. The modulus of elasticity of brick range between 5-30

    103 N/mm

    3.

    A brick is regular in shape and of size that can be conveniently handled with one hand. Bricks

    may be makes of burnt clay or mixture of sand and lime, or flyash lime and sand, or of Portland cement

    concrete. Clay bricks are commonly used since these are economical and easily available.

    Size of a standard bricks (also known as modulur bricks) should be 19 9 9 cm and 19 9 4

    cm. when placed in masonry the 19 9 9 cm brick with mortar becomes 20 10 10 cm.

    Burning of moulded clay products make them sufficiently strong for use as construction material.

    Though tiles, refectory bricks, earth wares and stones wares serve different construction purpose, brick is

    the most commonly used building material. It is light, easily available, uniform in shape and size, and

    relatively cheaper except in hilly areas. Bricks are easily moulded from plastic clays, also known as brick

    clay or brick earth.

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    1.2 SOURCES AND QUALITIES OF BRICK EARTH

    1.2.1 Sources of brick earth

    Brick earth is derived by the disintegration of igneous rocks. Potash feldspars, orthoclase or

    microcline (K2O: Al2 O3 6SiO2) is mainly responsible for yielding clay mineral in the earth. This mineral

    decomposes to yields kaolinite, a silicate of alumina which on hydration gives a clay deposit Al2 O3

    2H2O known as kaolin.

    For the preparation of bricks, clay or other suitable earth is molded to the desired shape after

    subjecting it to several processes. After drying, it should not shrink and no crack should develop. The clay

    used for brick making consist mainly of silica and alumina mixed in such a proportion that the lcay

    becomes plastics when water is added to it. It also consists of small proportions of lime, iron, manganese,

    sulphur, etc. the proportions of various ingredients are as follows in the table shown below.

    Sl.no. Ingridents Proportions Functions

    1 Silica 50-60% Adds durability, prevents shrinkage and warping.

    2 Alumina 20-30% Absorbs water and renders the clay plastics.

    3 Lime 10% Reduces shrinkage, lowers the fusion point and

    helps in binding of clay and silica.

    4 Magnesia

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    3. They are free from flaws, cracks and stones.

    4. These should have uniform texture.

    5. No impression should be left on the bricks when a scratch is made by a finger nail.

    6. The fractured surface of the bricks should not show lumps of lime.

    7. A metallic or ringing sound should come when two bricks are struck against each other.

    8. Water absorption should be 12-15% of its dry weight when immersed in cold water for 24 hours.

    9. The crushing strength of the bricks should not be less than 10 N/mm2.

    Uses: First class bricks are recommended for pointing, exposed face work in masonry structures,

    flooring and reinforcement brick work.

    Second class bricks: are supposed to have the same requirements as the first class ones except that

    1. Small cracks and distortions are permitted.

    2. A little higher water absorption of about 16-20% of its dry weight is allowed.

    3. The crushing strength should not be less than 7.0 N/mm2.

    Uses: second class bricks are recommended for all important or unimportant hidden masonry wroks

    and centering of reinforced brick and reinforced cement concrete (RCC) structures.

    Third class bricks: are underburnt. They are soft and light coloured producing a dull sound when

    struck against each other. Water absorption is about 25 per cent of dry weight.

    Uses: it is used for building temporary structures.

    Fourth class bricks: are over burnt and badly distorted in shape and size and are brittle in nature.

    Uses: The ballast of such bricks is used for foundation and floors in lime concrete and road metal.

    1.3.1 On the basis of strength

    The Bureau of Indian Standard (BIS) has classified the bricks on the basis of compressive

    strength and is as given in table below:

    Sl. no Class Average compressive strength not less than (N/mm2)

    1 35 35.0

    2 30 30.0

    3 25 25.0

    4 20 20.0

    5 17.5 17.5

    6 15 15.0

    7 12.5 12.5

    8 10 10.0

    9 7.5 7.5

    10 5 5.0

    11 3.5 3.5

    classification of bricks based on compressive strength (IS:10700)

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    1.3.2 On the basis of uses

    Common bricks: is a general multi-purpose unit manufactured economically without special

    reference to appearance. These may vary greatly in strength and durability and are used for

    filling, backing and in walls where appearance is of no consequence.

    Facing bricks: are made primarily with a view to have good appearance, either of colour or

    texture or both. These are durable under severe exposure and are used in fronts of building walls

    for which a pleasing appearance is desired.

    Engineering bricks: are strong, impermeable, smooth, table moulded, hard and conform to

    defined limits of water absorption and strength. These are used for all loas bearing structures.

    1.3.3 On the basis of finish

    Sand-faced bricks: has textured surface manufactured by sprinkling sand on the inner surfaces

    of the mould.

    Rustic bricks: has mechanically textured finish, varying in pattern.

    1.3.4 On the basis of manufacture

    Hand-made: these bricks are hand moulded.

    Machine made: depending upon mechanical arrangement, bricks are known as wire-cut bricks-

    bricks cut from clay extruded in a column and cut off into sizes by wires; pressed-bricks- when

    bricks are manufactured from stiff plastic or semi-dry clay and pressed into moulds; moulded

    bricks-when bricks are moulded by mechanics imitating hand mixing.

    1.3.5 On the basis of burning

    Pale bricks: are under burnt bricks obtained from outer portion of the kiln.

    Body bricks: are well burnt bricks occupying central portion of kiln.

    Arch bricks: are over burnt also known as clinker bricks obtained from inner portions of the kiln.

    1.3.6 On the basis of types

    Solid: small holes not exceeding 25 per cent of the volume of the bricks are permitted;

    alternatively, frogs not exceeding 20 per cent of the total volume are permitted.

    Perforated: small holes may exceed 25 per cent of the total volume of the bricks.

    Hollow: the total of holes, which need not be small, may exceed 25 percent of the volume of

    bricks.

    Cellular: holes closed at one end exceed 20 per cent of the volume.

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    1.4 GENERAL CHARACTERISTICS OF GOOD BRICKS

    The essential requirement for building bricks are sufficient strength in crushing, regularity in size,

    a proper suction rate, and a pleasing appearance when exposed to view.

    Size and shape: The bricks should have uniform size and plane, rectangular surface with parallel

    sides and sharp straight edges.

    Colour: The bricks should have a uniform deep red or cheery colour as indicative of uniformity

    in chemical composition and thoroughness in the burning of the bricks.

    Texture and Compactness: The surface should not be too smooth to cause slipping of mortar.

    The brick should have precompact and uniform texture. A fractured surface should not show

    fissures, holes grits or lumps of lime.

    Hardness and Soundness: The bricks should be so hard that when scratched by a finger nail no

    impression is made. When two bricks are struck together, a metallic sound should be produces.

    Water absorption: should not exceed 20 per cent of its dry weight when kept immersed in water

    for 24 hours.

    Crushing strength: should not be less than 10 N/mm2.

    Brick earth: Should be free from stones, kankars, organic matters, saltpeter, etc.

    1.5 DEFECTS OF CLAY BRICKS

    Over-burning of bricks: Bricks should be burned at temperature at which incipient,

    complete and viscous vitrification occur. However, if the bricks are over burnt, a soft

    molten mass is produced and the bricks lose their shape. Such bricks are not used for

    construction works.

    Under-burning bricks: When bricks are not burnt to cause complete vitrification, the

    clay is not softened because of insufficient heat and the pores are not closed. This results

    in higher degree of water absorption and less compressive strength. Such bricks are not

    recommended for construction works.

    Bloating: this defect observed as spongy swollen mass over the surface of burned bricks

    is caused due to the presence of excess carbonaceous matter and sulphur in brick-clay.

    Black core: When brick-clay contains bituminous matter or carbon and they are not

    completely removed by oxidation, the brick results in black core mainly because of

    improper burning.

    Chuffs: The deformation of the shape of bricks caused by the rain water falling on hot

    bricks is known as chuffs.

    Spots: Iron sulphide, if present in the bricks clay, results in dark surface spots on the

    bricks surface. Such bricks though not harmful are unsuitable for exposed masonry work.

    Blisters: Broken blisters are generally caused on the surface of sewer pipes and drain

    tiles due to air imprisoned during their moulding.

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    1.6 MANUFACTURE OF BRICKS

    1.6.1 Additives

    Additives are generally added to improve the certain qualities of bricks. And its of various types,

    some gives strength, some helps to control the drying property, etc some of the examples are mentioned

    below.

    1. Fly ash.

    It helps towards the strength of the bricks due to its silicate constituent. Fly ash is available as a

    waste from thermal power plants.

    2. Sandy loam.

    This additive helps in controlling the drying property of the highly plastic soil mass containing

    expanding group of clay minerals.

    3. Basalt stone dust.

    Its layer of cottony soil obtained from the covering of the basalt stone. It helps us to properly

    shape the bricks.

    1.7 PREPARATION OF BRICK EARTH

    Its consist of the following steps,

    Unsoiling

    Its the removal of top soil as top soil generally contains stones, roots, etc. about 20 cm of top soil

    is removed.

    Digging

    After removal of top soil, the additives are spreaded over the surface. Soil mass then is manually

    excavated, puddled and watered.

    Weathering

    Then the soil which undergone digging is heaped on a level ground in layer of 60 to 120 cm so

    for the weathering to occur for the maintenance of uniformity.

    Blending

    Then the weathered soil is mixed with the calcareous soil so to modify its composition. Then

    water is also added and the whole composition is uniformly mixed with spade.

    Tempering

    Its done if required, its done to maintain the uniformity. Its done in a pug mill and process is

    called pugging.

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    Moulding

    Its the shaping and sizing of brick into required dimension. Moulding is of four types, hand, and

    machine moulding.

    Drying

    Drying is the removal of moisture content of the bricks. Drying can also be done artificially,

    where artificial is also classified into two, hot floor drying and tunnel drying.

    Burning

    Its further of three sub stages 1. Dehydration (completely removal of water content heated to

    400-650 degree centigrade), 2.oxidation (removal of carbon content and ferrous iron converted to

    ferric oxide heated t 650-900 degree centigrade), 3. Vertification (to convert the final product into

    glass like substance, heated to 900-1250 degree Celsius).

    1.8 SPECIAL FORMS OF BRICKS AND THEIR USES

    Different forms of bricks:

    The different forms in which bricks are made for special purposes are almost innumerable.

    It would not be worthwhile, even if space were available, to describe them all; but a few of the principal

    varieties may be mentioned.

    Ordinary Bricks are of rectangular section, both longitudinally and transversely, and solid throughout.

    Purpose-made Bricks are those which are specially moulded to shapes suited for particular situations

    There are several advantages in having the bricks thus purpose-moulded: cutting is saved, and the surface-

    skin of the brick is left intact, which enables the brick to resist the weather far better than if the surface

    were removed by cutting.

    Note:

    Bricks are made in a wide range of shapes to suit the requirements.

    Avoid the burdensome process of cutting and rounding the rectangular bricks to the desired shape.

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    1. Bull Nosed Bricks: A brick moulded with a rounded angle is termed as a bullnose. It is used for a rounded quoin. A connection which is formed when a wall takes a turn is known as a

    quoin. . The centre of the curved portion is situated on the long centre-line of brick.

    A brick moulded with a double bullnose on end is known as a cownose.

    Uses: Bull nosed bricks are used to create soft and attractive curved edges to steps, sills, or in

    capping walls.

    2. Perforated Bricks: have cylindrical holes through their thickness, which makes them easier to burn (because the fire can penetrate them more thoroughly), and lighter to handle. Such bricks are

    often made from the denser and heavier clays. Drawbacks of using Perforated Brick is that they

    transmit sound readily.

    Uses: Perforated Bricks are used for constructing load bearing walls of low buildings, panel walls for

    multistoried buildings and for providing partition walls.

    3. Hollow Bricks: These are also known as the cellular or cavity bricks. Such bricks have wall

    thickness of about 20 mm to 25 mm. They are prepared from special homogeneous clay. They are

    light in weight about one-third the weight of the ordinary brick of the same size. These bricks can

    be laid almost about four times as fast as the ordinary bricks and thus the use of such bricks leads

    to speedy construction. They also reduce the transmission of heat, sound and damp.

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    Uses: They are used for the construction of non-load bearing walls, partition walls or panel walls to

    multistoried buildings.

    4. Circular Bricks: These bricks are used for constructing wells, towers etc.

    5. Paving Bricks: These types of bricks are prepared from clay containing higher percentage of iron. The excess iron vitrifies the bricks at a low temperature. Such bricks resist better the

    abrasive action of traffic. The paving bricks may be plain or chequered.

    Uses: These bricks are extensively used for garden walks, street pavements, stable floors, etc. These

    bricks also render the brick floor less slippery.

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    6. Cant bricks: A cant brick is type of brick manufactured with a slight taper on one brick face. Uses: used to soften the edges of windows and door openings.

    Single cant brick double cant brick

    7. Squint Bricks: are used to continue the line of brickwork around a 45 degree corner, such as that required for a bay window.

    Bay window

    The above different types of bricks are usually more costly than the ordinary bricks. But they grant safe,

    clean and quick construction. Hence, their cost is justified by their excellent performance in situations for

    which they are purposely prepared.

    1.9 TESTING OF BRICKS

    Bricks is one of the most important and basic unit for constructing a building. In fact, no structure can be

    built without them. Therefore, it is imperative to test them for their useful properties and also to ensure

    that consequent to their usage no undesirable effects are noticeable. Testing of bricks for strength,

    durability, efflorescence and dimensional tolerance are mandatory.

    1. Dimension test (IS: 1077): While preparing the estimate standards sizes of the bricks are

    considered and the numbers of bricks to be used in the structure are estimated. If the dimensions

    of the bricks will have deviated more than the permitted, the estimated cost will inflate. Further,

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    more numbers of bricks-bats or plaster/mortar will be required to make up the standard

    dimensions specified on drawings for constructions. This may disturb the regular specified type

    of pattern (bond) and may impair the strength and consequently cracks may develop.

    For example, 20 pieces of bricks out of selected pieces are taken and laid flat as shown in the

    figure below. They are arranged height, length and width by changing the order every time and

    the measurements are taking for height, length and width respectively.

    2. Water absorption (IS: 3495, part II): Fractured surface of a burnt brick reveals a continuous

    network of voids. The existence of minutes pores confers marked capillary properties on bricks

    ceramics. In particular all bricks absorb water by capillary action. The percentage of water

    absorption is a very valuable indication of the degree of burning. Vitrification, in the true sense,

    corresponds to such a degree of compactness that the absorption of the bricks is not over 3 per

    cent after 48 hours of immersion. It has been reported that for absorption less than 5 per cent

    danger from frost negligible.

    Water absorption does not necessarily indicate the behavior of a bricks in weathering. Low

    absorption (

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    produces a weak bond. The rate at which a brick absorbs water, frequently called its suction rate,

    may be measured by immersing one face of the bricks in water. The one minute water uptake

    (initial rate of absorption) is taken as the suction rate. Bricks having a suction rate between 10 to

    35 g per brick per minute are preferred for their superior bonding properties. For long periods of

    immersion in this test, the total weight of water absorbed per unit area,

    Where, A is the water absorption coefficient

    And t is the time elapsed in the test.

    The standard methods of finding the absorption value of the brick are discussed below. If the

    absorption by volume is desired it can be obtained by multiplying the weight percentage by the

    apparent specific gravity.

    24 hours Immersion Cold Water Test: Dry bricks are put in an oven at a temperature of 150 to

    155C till these attain constant mass. The weight (W1) of the bricks is recorded after cooling them

    to room temperature. The bricks are then immersed in water at a temperature of 27 2C for 24

    hours. The specimens are then taken out of water and wiped with a damp cloth. Three minutes,

    thereafter it is weighed again and recorded as W2.

    The water absorption in % =

    The average water absorption shall not be more than 20 per cent by weight up to class 12.5 and

    15 per cent by weight for higher classes.

    Five Hours Boiling Water Test: The weight of the oven dried bricks (W1) is recorded as above.

    Then the specimen is immersed in the water and boiled for five hours, followed by cooling down

    to 27 2C by natural loss of heat within 16-19 hours. The specimen is taken out of water and

    wiped with a damp cloth and weight is recorded as W3.

    The water absorption in % =

    100

    3. Compressive strength Test (IS:3495 (Part II)): The crushing affords a basis for comparing the

    quality of bricks but is of little value in determining the strength of a masonry wall, since the latter

    depends primarily on the strength of mortar. Six bricks are taken for the compressive strength test

    although it may be found that an individual brick varies by 20% or more from the average, the

    permissible stresses allowed for load bearing walls take account of this, being based on an average

    strength if six bricks. It is, therefore, both unnecessary and uneconomical to insist that every brick is

    above certain strength. As a criterion of structural strength for brick, the transverse failure in a wall or

    pavement is likely to occur on account of improper bedment. For testing bricks for compressive

    strength from a sample the two bed faces of bricks are ground to provide smooth, even and parallel

    faces with frogs filled with hardened mortar. The bricks are then immersed in water at room

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    temperature for 24 hours. These are then taken out of water and surplus water on the surface is wiped

    off with cotton or a moist cloth. The frogs of bricks are flushed level with cement mortar and the

    brick is stored under damp jute bags for 24 hours followed by its immersion in water at room

    temperature for three days. The specimen is placed in the compression testing machine with flat faces

    horizontal and mortar filled face being upwards. Load is applied at a uniform rate of 14 N/m2 per

    minute till failure. The maximum load at failure divided by the average area of bed faces gives the

    compressive strength.

    Compressive strength (N/mm2)=

    The average of results shall be reported. The compressive strength of any individual brick tested

    in the sample should not fall below the minimum average compressive strength specified for the

    corresponding class of brick by more than 20 per cent.

    4. Warpage Test (IS:3495(Part IV)

    The warpage of brick is measured with flat steel or glass surface and measuring ruler graduated in 0.5 mm

    divisions or wedge of steel 601515 mm.

    Concave warpage

    the brick is placed on the surface to be measured such that it shows the greatest deviation from

    straightness. The greatest distance of brick from edge of straightness is measured by a ruler.

    Convex warpage

    the brick is placed on the plane surface with the convex surface in contact with the flat surface and the

    distances from the four corners to the flat surface is measured. The largest distance is reported as

    warpage.

    5. Efflorescence test (IS:3495 Part III)

    The ends of bricks are kept in a 150 mm diameter porcelain dish and immersed in 25 mm depth of water

    at room temperature. After all water is gone, either through absorption or evaporation it is again filled till

    25 mm and made to be absorbed or evaporated. Presence of efflorescence is classified as follows:

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    Nil When the deposit of efflorescence is imperceptible.

    Slight when deposit of efflorescence doesnt cover more than 10 % of the exposed area of the

    brick.

    Moderate when deposit of efflorescence is more than 10 % of the exposed area but less than

    50% .

    Heavy when deposits of efflorescence is more than 50 % but it doesnt flake away the surface

    of the brick.

    Serious when deposits are heavy and flake away the brick surface.

    1.10 ADVANTAGES AND LIMITATIONS OF BRICKS

    1.10.1 Advantages.

    Uniformity is size and shape. Therefore it can be easily laid in masonry.

    Unlike stone brick do not need dressing. Therefore there is reduction time and labor and

    moreover skilled labor is not needed.

    Cheaper than stone. Though same quantity of brick cost more than same quantity stone. More

    expenditure is consumed on processing of stone masonry, such as breaking of stone into smaller

    size and dressing.

    Smaller in size and lighter therefore less effort is required while building brick masonry.

    1.10.2 Disadvantage.

    Bricks are less durable than stone.

    Plastering is required.

    Alkalis & salts present in the brick earth have hygroscopic properties. They absorb moisture from

    the air and creating a damp and unhygienic condition

    1.11 MARKET SURVEY

    Code Description Units P/ling GP SJ

    MT0125 Bricks 2nd

    class 1000# 7250 8000 78333.33

    MT0126 Brick aggregate Cu.m 1066.21 1664.24 877.25

    MT0127 Graded brick aggregate cu.m 1251.60 1164.24 957.00

    MT0128 Interlocking cement earth bock

    (300mmx150mmx100mm)

    1000# 27300 32300 38300

    MT1029 Interlocking cement earth block

    (250mmx125mmx100mm)

    1000# 15700 18200 21300

    MT0130 concrete block bricks 1000# 11000 10500 1300

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    Bricks aggregate Graded brick aggregate

    interlocking cement block concrete brick blocks

    1.11.1 General Price of bricks in India

    Bricks-18000/lorry load.

    Mud bricks Rs.1.50-1.75 per piece (Price depends upon thickness and finishing)

    Mud bricks (light weight) Rs.2.50-2.75 per tons.

    Fly ash/Hallow bricks Rs.3.25 and more.

    Mud bricks and its house. Fly ash bricks

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    1.11.2 Advantages of fly ash bricks

    High compressive strength

    Lower water absorption

    Dimensional accuracy through uniform shape

    High strength to weight ratio

    No emission of greenhouse gases during production

    Zero efflorescence

    Consume less mortar in construction

    1.11.3 Prices of bricks in Jaigoan

    1st class- Rs.8-9 regular size.

    2nd class-Rs.6-7 regular size.

    They import from Assam, Guwati, Bihar and west Bengal. But most of the time they import from

    Assam and Guwati.

    From there, they deal to local contactors and especially to Bhutan as per their demand.

    While Bhutanese contactors are importing bricks from Jaigoan, Govt. of Bhutan charge a tax of

    5% on the total amount.