Chapter 4 (d) hollow concrete block masonry

CONCRETE HOLLOW
BLOCKS
•Is a large rectangular brick used in construction.
• Portland cement and aggregate, usually sand
and fine gravel for high-density blocks.
BASIC INFORMATION
3

CEMENT CONCRETE MASONRY
•Cement concrete is widely used for the
construction purpose due to its various
advantages over the other building materials.
•Hollow concrete units are manufactured
from light weight aggregates. They may be used
for load bearing as well as non load bearing
walls.
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The concrete blocks are moulded in machine in
the various standard sizes , as follows ,
(1) Standard sizes hollow concrete blocks
39cm*19cm*30cm
(2) Hollow building tiles
39cm*19cm*20cm
(3) Hollow concrete blocks for partition
39cm*19cm*10cm
To ensure maximum economy in construction ,
the overall length and height of walls is so fixed
that the maximum use of full and half length
blocks is possible.

• The different types of concrete hollow block include:
CONCRETE HOLLOW BLOCK:-
a. Stretchers
b. Headers
c. Corner blocks
d. Jamb blocks
e. Beam or lintel
blocks
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Manufacturing of Hollow Concrete Blocks:
oThey are manufactured with mix of sand (40%) and coarse
aggregates(60%) of size 6 to 12mm.
oThe concrete mix 1: 6 (C:CA) cement to Combined
aggregate.
oUses hand mould or machine moulding.
oKept for 24 hrs undisturbed.
oCured for minimum 7 days.
oThe minimum strength prescribed is 4 N/mm2.
oThe block should have sharp edges and right angled
corners.
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MANUFACTURING OF CONCRETE
BLOCKS
•The ratio of cement of aggregate should not be
more than 1:6.
•The blocks should be taken out from the moulds
only when the concrete has set sufficiently.
•In order to obtain better finishing , the machine
casting is more preferred than hand casting.
•The blocks should be used only after 3 to 4 weeks
of taking out from tank.
•The compressive strength of blocks should not be
less than 30 kg/cm*cm. after 28 days curing.
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• The construction is started with two corners or
two ends of the wall. First, the construction of few
courses of blocks is done at both the ends and
then the string is stretched between two end
blocks and the blocks are laid in between. Before
laying the blocks the mortar is applied.
WALL CONSTRUCTION WITH
CONCRETE BLOCKS

WALL CONSTRUCTION WITH
CONCRETE BLOCKS
The various point should be followed during the
construction work :
• The concrete blocks used in masonry are dry.
•Blocks of successive courses should be laid in such a
way that the vertical joints are staggered.
• The joints should be uniform and 5 to 10 mm thick.
•Generally cement-lime-sand mortar of mix proportion
is used and it should not stronger than the concrete mix
used for concrete blocks.
•The blocks used for external walls should have
absorption less than 10%. For internal walls the
absorption should be less than 15%.
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ADVANTAGES OF HOLLOW CONCRETE
BLOCK MASONRY
•The concrete blocks are available in regular
and uniform size and less weight , the masonry
construction done very rapidly.
•As the blocks are light in weight they easy to
handle construction is speedy resulting in less
labour cost.
•It is possible to construct thin wall with
concrete blocks resulting in the increase of floor
area.
•As the blocks are hollow , there is saving of
material. 14

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•As the size of blocks is large , the number of
joints are less and hence there is saving of
mortar.
•The rough surface of concrete blocks makes
plastering easier.
•The hollow concrete blocks can safely
withstand against atmospheric action, it does not
required any plastering as required in brick
masonry.

Chapter 4 (d) hollow concrete block masonry

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Chapter 4 (d) hollow concrete block masonry