For masonry works we usually use bricks or stone. Stone masonry was adopted before brick making was invented. Brick tiles, concrete blocks or precast concrete blocks are also used for masonry. Bricks and tiles are made by burning clay while stone is a natural material. Concrete blocks are made of stone, cement and sand. Properly executed masonry shall have a fairly long life.
Due to increased cost of bricks we now a days construct thinner walls utilising the intrinsic strength of the brick and masonry, supervision has therefore become more important.
Bricks
Lime
Bricks
Common Burnt Clay Bricks
They
shall be free from modules of free lime, visible cracks, flaws, warpage
and organic matter. They shall have a frog of size 100 mm x 40 mm x 10
to 20 mm deep in one face. Machine made bricks and brick tiles may not
have frogs.
Flyash Bricks
It
shall be sound, compact and uniform in shape and free from cracks etc.
having a frog like common clay bricks. Flyash shall confirm to grade 1
or Grade 2 of IS: 3812-1981.
Tile Bricks
The bricks of 4 cm height are usually moulded without frogs.
Brick Bats
Brick bats shall be obtained from well burnt bricks.
Sand
Clay and silt in the sand shall preferably be less than 5%.
Lime
Lime is most commonly used material
from olden days. There are afferent type of limes available for various
uses. Lime shall confirm to class C hydrated lime of IS 712-1984.
Quick Lime: It
should be received in the form of lumps and not powders. All over burnt
and under burnt lump and powders should be removed from the supply of
lime. It should then be converted to lime putty and used.
Hydrated Lime: It
should be in the form of dry powder. It should be received in water
proof bags or containers and used within 4 months of manufacture.
Storage: Lime should be stored in water proof stores.
Light
weight aggregate may also be used. Coarse aggregate should not contain
any deleterious material that could affect the strength or durability of
concrete or affect the reinforcement. Aggregates which are chemically
reactive with alkalies of cement should not be used. The percentage of
deleterious material by weight should be less than 5.
Stone
Fine Aggregate
Aggregate most of which passes through 4.75 mm IS Sieve, known as fine aggregate, is used in mortar. It can be sand, crushed stone, stone dust, fly ash or crushed brick or cinder commonly known as sushi. It should be clean, chemically inert, hard, durable, tree from organic impurities etc. The silt content in sand should be less than 8%, otherwise it should be washed. The grading of fine aggregate should be determined and checked with the specified grading. By mixing fine aggregate of the same type but of different grading we may get the specified grading.
Stone
The stone shall be of the type
specified such as granite, trap, lime stone, sand stone, quartzite etc,
and shall be obtained from approved quarries.
Generally
the length of stones.for stone masonry shall not exceed three times the
height and the breadth or base shall not be greater than three fourth
of the thickness of wall or not less than 15cm. The height of stone may
be upto 30 cm.
Each stone shall be hammer dressed on the face, the sides and the bed. This would enable stones to be laid closely.
Hydrated lime should be stored like cement.
Coarse Aggregate
Aggregates most of which is retained on 4.75 mm IS Sieve is known as coarse aggregate. It can be stone, gravel or brick and should'be obtained from approved sources only.
Coarse Aggregate
Aggregates most of which is retained on 4.75 mm IS Sieve is known as coarse aggregate. It can be stone, gravel or brick and should'be obtained from approved sources only.
a) Stone Aggregate
It
should consist of broken, crushed or uncrushed stones. It should be
hard, strong, dense, durable and clean. It should be hard, strong,
dense, durable and clean. It should be hard, strong, dense, durable and
clean. It should be free from veins, adherent coatings, alkali,
vegetable matter and other deleterious substances. It should be roughly
cubical in shape. Flaky and elongated pieces should be avoided. It
should conform to IS:383-1970.
b) Gravel
It
should consist of naturally occurring river bed (shingle) or pit
gravel-crushed, uncrushed or broken. It should be clean, sound and hard.
It should be free from flat particles or shale powdered clay, silt,
loam, adherent coatings and other deleterious substances. Pit gravels
should be properly washed. These should conform to IS 138 3- 1970.
c) Brick Aggregate
Brick
aggregate should be obtained by breaking well burnt or over burnt dense
bricks. They should be homogeneous in texture, roughly cubical in
shape, clean and free from unburnt clay, vegetable matters and other
deleterious substances. Sulphale content should be less than one per
cent. They should absorb less than 10% of their own mass of water when
used in cement concrete and less than 20% when used in lime concrete. It
should conform to IS 306-1986.
d) Grading
The
aggregate should conform to the specified grading. At work site
different aggregate may be mixed lo obtain the required grading. Nominal
size of brick aggregate should be 40 mm and conform to specified
grading.
Testing: Physical and chemical properties of lime should be tested as per IS 6932- 1973.
Fine Aggregate
Aggregate most of which passes through 4.75 mm IS Sieve, known as fine aggregate, is used in mortar. It can be sand, crushed stone, stone dust, fly ash or crushed brick or cinder commonly known as sushi. It should be clean, chemically inert, hard, durable, tree from organic impurities etc. The silt content in sand should be less than 8%, otherwise it should be washed. The grading of fine aggregate should be determined and checked with the specified grading. By mixing fine aggregate of the same type but of different grading we may get the specified grading.
Bulking
Fine
aggregates when fully saturated or dry has almost the same volume but
presence of water increases the volume. This is known as bulkage. At the
time of preparation of mortar or concrete the bulkage of most fine
aggregate need be accounted for so that correct quantity is used. The
moisture content of fine aggregate may be determined by any field
method. For guidance the following relation can be considered.
Broken Brick Fine Aggregate
Fine
aggregate from broken bricks, known as surkhl, should be made by
grinding well burnt, not over or under burnt, broken bricks as specified
in IS 3068-1986. It should not contain any harmful impurities like
salts, coal, mica, shale etc. as to adversely affect hardening,
strength, durability or appearance of the mortar.
Flyash
Flyash is produced during burning of pulverished coal in boilers. Flyash, used should conform to IS 38 12- 198 1. It should be free from impurities. It is generally used as a part replacement of fine aggregate in mortar.
Flyash
Flyash is produced during burning of pulverished coal in boilers. Flyash, used should conform to IS 38 12- 198 1. It should be free from impurities. It is generally used as a part replacement of fine aggregate in mortar.
Water
It
is importiant to ensure that water used for mixing and curing is free
from harmful quantities of alkalies, acids, oils, organic materials,
etc. Otherwise, the masonry may be affected in the long run. Generally
potable water is considered satisfactory for mixing and curing. The
value of water should be not less than 6. It is also important to ensure
that sulphite and chloride contents are less than 500 and 2000
mg./litre respectively. It should also be checked that curing water does
not produce any stain on the surface.
Sea water should not be used for mixing or curing.
Water
from each source should be tested before commencement and subsequently
after every three months till the completion of the work as the
properties of the underground water gets changed. Test of treated water
supplied by municipalities may be less frequent.
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