Manufacture of Concrete by various processes

Process of Manufacture of Concrete
• It
It is
is interesting
interesting to
to note
note that
that the
the ingredients
ingredients of
of good
good concrete
concrete
and
and bad
bad concrete
concrete are
are the
the same.
same.
• If
If meticulous
meticulous care
care is
is not
not exercised,
exercised, and
and good
good rules
rules are
are not
not
observed,
observed, the
the resultant
resultant concrete
concrete is
is going
going to
to be
be of
of bad
bad quality.
quality.
• With
With the
the same
same material
material if
if intense
intense care
care is
is taken
taken to
to exercise
exercise
control
control at
at every
every stage,
stage, it
it will
will result
result in
in good
good concrete.
concrete.

Good
Good C
Concrete
oncrete and
and B
Bad
ad C
Concrete
oncrete Quality
Quality

• The
The various stages
various stages of
of manufacture
manufacture of
of concrete
concrete are:
are:
• (a) Batching
(a) Batching
• (b) Mixing
(b) Mixing
• (c) Transporting
(c) Transporting
• (d)
(d) Placing
Placing
• (e)
(e) Compacting
Compacting
• (f
(f )
) Curing
Curing
• (g)
(g) Finishing.
Finishing.

Batching
Batching
Volume
Volume Batching:
Batching:
• Volume
Volume batching
batching is
is not
not a
a good
good method
method for
for proportioning
proportioning the
the
material
material because
because of
of the
the difficulty
difficulty it
it offers
offers to
to measure
measure
granular
granular material
material in
in terms
terms of
of volume.
volume.
•Volume
Volume of
of moist
moist sand
sand in
in a
a loose
loose condition
condition weighs
weighs much
much less
less
than
than the
the same
same volume
volume of
of dry
dry compacted
compacted sand.
sand.
•The
The effect
effect of
of bulking
bulking should
should be
be consider
consider for
for moist
moist fine
fine
aggregate.
aggregate.
•For
For unimportant
unimportant concrete
concrete or
or for
for any
any small
small job
job,
, concrete
concrete may
may
be
be batched
batched by
by volume.
volume.

Batching : Volume Batching
• Volume batching:
Volume batching:
volume 35 litres(35x25x40)cm

Batching
Batching
Weigh
Weigh Batching:
Batching:
•Weigh
Weigh batching
batching is
is the
the correct
correct method
method of
of measuring
measuring the
the materials.
materials.
•Use
Use of
of weight
weight system
system in
in batching,
batching, facilitates
facilitates,
, accuracy,
accuracy,
flexibility
flexibility and
and simplicity
simplicity.
.
•Large
Large weigh
weigh batching
batching plants
plants have
have automatic
automatic weighing
weighing equipment.
equipment.
•On
On large
large work
work sites,
sites, the
the weigh
weigh bucket
bucket type
type of
of weighing
weighing
equipment's
equipment's are
are used.
used.

Batching : Weigh Batching
Batching : Weigh Batching

Mixing
Mixing
• Thorough
Thorough mixing
mixing of
of the
the materials
materials
production
production of
of uniform
uniform concrete.
concrete.
• The
The mixing
mixing should
should ensure
ensure that
that
is
is essential
essentialf
for
or the
the
T
The
he mass
mass becomes
becomes
homogeneous, uniform in colour
homogeneous, uniform in colour and consistency.
and consistency.
•There are two methods adopted for mixing
There are two methods adopted for mixing
concrete:
concrete:
(i)
(i) Hand mixing (ii )Machine mixing
Hand mixing (ii )Machine mixing

Mixing: Hand mixing
Mixing: Hand mixing
• Hand
Hand mixing
mixing is
is practised
practised for
for small
small scale
scale unimportant
unimportant
concrete
concrete works.
works.
• As
As the
the mixing
mixing cannot
cannot be
be thorough
thorough and
and efficient
efficient,
, it
it is
is
desirable
desirable to
to add
add 10
10 per
per cent
cent more
more cement
cement to
to cater
cater for
for the
the
inferior
inferior concrete
concrete produced
produced by
by this
this method.
method.
• Hand
Hand mixing
mixing should
should be
be done
done over
over an
an impervious
impervious
concrete
concrete or
or brick
brick floor
floor of
of sufficiently
sufficiently large
large size
size to
to take
take
one
one bag
bag of
of cement.
cement.
• Spread
Spread out
out the
the measured
measured quantity
quantity of
of coarse
coarse aggregate
aggregate
and
and fine
fine aggregate
aggregate in
in alternate
alternate layers.
layers.

Mixing: Hand mixing
Mixing: Hand mixing
• Pour
Pour the
the cement
cement on
on the
the top
top of
of it,
it,
and
and mix
mix them
them dry
dry by
by shovel,
shovel,
turning
turning the
the mixture
mixture over
over and
and
over
over again
again until
until uniformity
uniformity of
of colour
colour
is
is achieved.
achieved.
• Water
Water is
is taken
taken in
in a
a water-can
water-can
fitted
fitted with
with a
a rose-head
rose-head and
and
sprinkled
sprinkled over
over the
the mixture
mixture and
and
simultaneously
simultaneously turned
turned over.
over.
• This
This operation
operation is
is continued
continued till
till
such
such time
time a
a good
good uniform
uniform,
,
homogeneous
homogeneous concrete
concrete is
is obtained.
obtained.

Mixing: Hand mixing
Mixing: Hand mixing

Mixing: Machine Mixing
• Mixing
Mixing of
of concrete
concrete is
is almost
almost invariably
invariably carried
carried out
out by
by
machine
machine,
, for
for reinforced
reinforced concrete
concrete work
work and
and for
for medium
medium or
or
large
large scale
scale mass
mass concrete
concrete work.
work.
• Machine
Machine mixing
mixing is
is not
not only
only efficient,
efficient, but
but also
also economical,
economical,
when
when the
the quantity
quantity of
of concrete
concrete to
to be
be produced
produced is
is large.
large.
• They
They can
can be
be classified
classified as
as batch-mixers
batch-mixers and
and continuous
continuous mixers.
mixers.
• Batch
Batch mixers
mixers produce
produce concrete,
concrete, batch
batch by
by batch
batch with
with time
time
interval,
interval, whereas
whereas continuous
continuous mixers
mixers produce
produce concrete
concrete
continuously
continuously without
without stoppage
stoppage till
till such
such time
time the
the plant
plant is
is
working.
working.

• In
In normal
normal concrete
concrete work,
work, it
it is
is the
the batch
batch mixers
mixers that
that are
are
used.
used.
Batch
Batch mixer
mixer may
may be
be of
of pan
pan type
type or
or drum
drum type.
type.
• The
The drum
drum type
type may
may be
be further
further classified
classified as
as tilting,
tilting, non-tilting,
non-tilting,
reversing
reversing or
or forced
forced action
action type.
type.
• As
As per
per I.S.
I.S. 1791–1985,
1791–1985, concrete
concrete mixers
mixers are
are designated
designated by
by a
a
number
number representing
representing its
its nominal
nominal mixed
mixed batch
batch capacity
capacity in
in litres.
litres.
The
The following
following are
are the
the standardized
standardized sizes
sizes of
of three
three types:
types:
• a. Tilting:
a. Tilting: 85
85 T,
T, 100
100 T,
T, 140
140 T,
T, 200
200 T
T
• b.
b. Non-Tilting:
Non-Tilting: 200
200 NT,
NT, 280
280 NT,
NT, 375
375 NT,
NT, 500
500 NT,
NT, 1000
1000 NT
NT
• c.
c. Reversing:
Reversing: 200
200 R,
R, 280
280 R,
R, 375
375 R,
R, 500
500 R
R and
and 1000
1000 R
R

Transporting : Mortar Pan
Transporting : Mortar Pan
• Use
Use of
of mortar
mortar pan
pan for
for transporation
transporation of
of concrete
concrete is
is
one
one of
of the
the common
common methods
methods adopted
adopted in
in this
this country.
country.
• In
In this
this case,
case, concrete
concrete is
is carried
carried in
in small
small quantities.
quantities.
• While
While this
this method
method nullifies
nullifies the
the segregation
segregation to
to
some
some extent,
extent, particularly
particularly in
in thick
thick members
members
Greater
Greater loss
loss of
of water,
water, particularly,
particularly, in
in hot
hot weather
weather
concreting
concreting

Transporting : Wheel Barrow
• Wheel
Wheel barrows
barrows are
are normally
normally used
used for
for
transporting
transporting concrete
concrete to
to be
be placed
placed at
at
ground
ground level.
level.
• This
This method
method is
is employed
employed for
for hauling
hauling
concrete
concrete for
for comparatively
comparatively longer
longer distance
distance
as
as in
in the
the case
case of
of concrete
concrete road
road construction.
construction.
• If
If concrete
concrete is
is conveyed
conveyed by
by wheel
wheel barrow
barrow
over
over a
a long
long distance,
distance, on
on rough
rough ground,
ground, it
it is
is
likely
likely that
that the
the concrete
concrete gets
gets segregated
segregated due
due to
to
vibration.
vibration.

Transporting : Crane, Bucket and Rope way
• A
A crane
crane and
and bucket
bucket is
is one
one of
of the
the right
right equipment
equipment for
for
transporting
concrete above
above ground
ground level.
level.
• Crane
Crane can
can handle
handle concrete
concrete in
in high
high rise
rise construction
construction
projects
projects and
and are
are becoming
becoming a
a familiar
familiar sites
sites in
in big
big cities.
cities.
• Cranes
Cranes are
are fast
fast and
and versatile
versatile to
to move
move concrete
concrete
horizontally
horizontally as
as well
well as
as vertically
vertically along
along the
the boom
boom and
and
allows
allows the
the placement
placement of
of concrete
concrete at
at the
the exact
exact point.
point.
• Cranes
Cranes carry
carry skips
skips or
or buckets
buckets containing
containing concrete.
concrete.
Skips
Skips have
have discharge
discharge door
door at
at the
the bottom
bottom,
, whereas
whereas
buckets
buckets are
are tilted
tilted for
for emptying.
emptying.
• For
For a
a medium
medium scale
scale job
job the
the bucket
bucket capacity
capacity may
may be
be 0.5
0.5
m
m3
3
.
.

Transporting : Crane, Bucket and Rope
Transporting : Crane, Bucket and Rope
way
way

Transporting : Truck Mixer and Dumpers
• For
For large
large concrete
concrete works
works particularly
particularly for
for concrete
concrete to
to
be
be placed
placed at
at ground
ground level
level,
, trucks
trucks and
and dumpers
dumpers or
or
ordinary
ordinary open
open steel-body
steel-body tipping
tipping lorries
lorries can
can be
be used.
used.
• As
As they
they can
can travel
travel to
to any
any part
part of
of the
the work,
work, they
they have
have
much
much advantage
advantage over
over the
the jubilee
jubilee wagons
wagons,
, which
which
require
require rail
rail tracks.
tracks.
• Dumpers
Dumpers are
are of
of usually
usually 2
2 to
to 3
3 cubic
cubic metre
metre capacity,
capacity,
whereas
whereas the
the capacity
capacity of
of truck
truck may
may be
be 4
4 cubic
cubic metre
metre or
or
more.
more.

Transporting :Belt Conveyors
• Belt
Belt conveyors
conveyors have
have very
very limited
limited applications
applications in
in
concrete
concrete construction.
construction.
• The
The principal
principal objection
objection is
is the
the tendency
tendency of
of the
the concrete
concrete
to
to segregate
segregate on
on steep
steep inclines,
inclines, at
at transfer
transfer points
points or
or
change
change of
of direction,
direction, and
and at
at the
the points
points where
where the
the belt
belt
passes
passes over
over the
the rollers.
rollers.
• Conveyors
Conveyors can
can place
place large
large volumes
volumes of
of concrete
concrete
quickly
quickly where
where access
access is
is limited.
limited.

Transporting :Chute
Transporting :Chute
• Chutes
Chutes are
are generally
generally provided
provided for
for transporting
transporting
concrete
concrete from
from ground
ground level
level to
to a
a lower
lower level.
level.
• The
The sections
sections of
of chute
chute should
should be
be made
made of
of or
or lined
lined with
with
metal
metal and
and all
all runs
runs shall
shall have
have approximately
approximately the
the same
same
slope,
slope, not
not flatter
flatter than
than 1
1 vertical
vertical to
to 2
2 1/2
1/2
horizontal.
horizontal.
• The
The lay-out
lay-out is
is made
made in
in such
such a
a way
way that
that the
the concrete
concrete
will
will slide
slide evenly
evenly in
in a
a compact
compact mass
mass without
without any
any
separation
separation or
or segregation.
segregation.

Transporting : Chute
Transporting : Chute

Transporting :Skip and Hoist
Transporting :Skip and Hoist
• This
This is
is one
one of
of the
the widely
widely
adopted
adopted methods
methods for
for
transporting
concrete vertically
vertically
up
up for
for multi-storey
multi-storey building
building
construction.
construction.
• At
At the
the ground
ground level,
level, mixer
mixer
directly
directly feeds
feeds the
the skip
skip and
and the
the
skip
skip travels
travels up
up over
over rails
rails upto
upto
the
the level
level where
where concrete
concrete is
is
required.
required.
• At
At that
that point,
point, the
the skip
skip
discharges
discharges the
the concrete
concrete
automatically
automatically or
or on
on manual
manual
operation.
operation.

Transporting :Transit Mixer
Transporting :Transit Mixer
• Transit
Transit mixer
mixer is
is one
one of
of the
the most
most popular
popular equipments
equipments
for
for transporting
concrete over
over a
a long
long distance
distance particularly
particularly in
in
Ready
Ready Mixed
Mixed Concrete
Concrete plant
plant (RMC).
(RMC).
• In
In India,
India, today
today (2000
(2000 AD)
AD) there
there are
are about
about 35
35 RMC
RMC plants
plants and
and
a
a number
number of
of central
central batching
batching plants
plants are
are working
working.
. They
They
are
are truck
truck mounted
mounted having
having a
a capacity
capacity of
of 4
4 to
to 7
7 m
m3
3.
.
• In
In one,
one, mixed
mixed concrete
concrete is
is transported
transported to
to the
the site
site by
by
keeping
keeping it
it agitated
agitated all
all along
along at
at a
a speed
speed varying
varying between
between 2
2 to
to 6
6
revolutions
revolutions per
per minute.
minute.
• In
In the
the other
other category,
category, the
the concrete
concrete is
is batched
batched at
at the
the
central
central batching
batching plant
plant and
and mixing
mixing is
is done
done in
in the
the truck
truck
mixer
mixer either
either in transit or immediately prior to discharging the
in transit or immediately prior to discharging the
concrete at site.
concrete at site.

Transporting :Pumps and Pipeline
Transporting :Pumps and Pipeline
• Pumping
Pumping of
of concrete
concrete is
is universally
universally accepted
accepted as
as one
one of
of the
the
main
main methods
methods of
of concrete
concrete transportation
transportation and
and placing.
placing.
• Adoption
Adoption of
of pumping
pumping is
is increasing
increasing throughout
throughout the
the world
world as
as
pumps
pumps become
become more
more reliable
reliable and
and also
also the
the concrete
concrete mixes
mixes that
that
enable
enable the
the concrete
concrete to
to be
be pumped
pumped are
are also
also better
better understood.
understood.
• The
The first
first patent
patent for
for a
a concrete
concrete pump
pump was
was taken
taken in
in USA
USA in
in
the
the year
year 1913
1913.
.
• By
By about
about 1930
1930 several
several countries
countries developed
developed and
and manufactured
manufactured
concrete
concrete pump
pump with
with sliding
sliding plate
plate valves.
valves.
• The
The modern
modern concrete
concrete pump
pump is
is a
a sophisticated,
sophisticated, reliable
reliable and
and
robust
robust machine.
machine.

Transporting :Concrete Pumps
• In
In the
the past
past a
a simple
simple two-stroke
two-stroke mechanical
mechanical pump
pump consisted
consisted
of
of a
a receiving
receiving hopper
hopper,
, an
an inlet
inlet and
and an
an outlet
outlet valve,
valve, a
a piston
piston
and
and a
a cylinder.
cylinder.
• The
The pump
pump was
was powered
powered by
by a
a diesel
diesel engine.
engine.
• The
The pumping
pumping action
action starts
starts with
with the
the suction
suction stroke
stroke drawing
drawing
concrete
concrete into
into the
the cylinder
cylinder as
as the
the piston
piston moves
moves backwards.
backwards.
• During
During this
this operation
operation the
the outlet
outlet value
value is
is closed.
closed. On
On the
the
forward
forward stroke,
stroke, the
the inlet
inlet valve
valve closes
closes and
and the
the outlet
outlet valve
valve
opens
opens to
to allow
allow concrete
concrete to
to be
be pushed
pushed into
into the
the delivery
delivery pipe.
pipe.

• The
The modern
modern concrete
concrete pump
pump still
still operates
operates on
on the
the
same
same principles
principles but
but with
with lot
lot of
of improvements
improvements and
and refinements
refinements
in
in the
the whole
whole operations.
operations.
• In
In this
this concrete
concrete placed
placed in
in a
a collecting
collecting hopper
hopper is
is fed
fed by
by
rotating
rotating blades
blades into
into a
a flexible
flexible pipe
pipe connected
connected to
to the
the
pumping
pumping chamber
chamber,
, which
which is
is under
under a
a vacuum
vacuum of
of about
about 600
600 mm
mm
of
of mercury.
mercury.
• The
The vacuum
vacuum ensures
ensures that,
that, except
except when
when being
being squeezed
squeezed
by
by roller,
roller, the
the pipe
pipe shape
shape remains
remains cylindrical
cylindrical and
and thus
thus
permits
permits a
a continuous
continuous flow
flow of
of concrete.
concrete.
• Two
Two rotating
rotating rollers
rollers progressively
progressively squeeze
squeeze the
the flexible
flexible
pipes
pipes and
and thus
thus move
move the
the concrete
concrete into
into the
the delivery
delivery pipe.
pipe.

Transporting :Pipelines and couplings
• It
It is
is equally
equally important
important to
to have
have correct
correct diameter
diameter of
of
pipeline
pipeline with
with adequate
adequate wall
wall thickness
thickness for
for a
a given
given
operating
operating pressure
pressure and
and well
well designed
designed coupling
coupling system
system for
for
trouble
trouble free
free operation.
operation.
• A
A poor
poor pipeline
pipeline can
can easily
easily cause
cause blockages
blockages arising
arising from
from
leakage
leakage of
of grout.
grout. Pushing
Pushing of
of abrasive
abrasive material
material at
at high
high
pressure,
pressure, through
through pipeline
pipeline inevitably
inevitably creates
creates a
a great
great deal
deal of
of
wear.
wear.
• Continuous
Continuous handling,
handling, frequent
frequent securing
securing and
and releasing
releasing
of
of couplings
couplings creates
creates wear
wear at
at joints..
joints..

• Generally
Generally almost
almost all
all
concrete
concrete is
is conveyed
conveyed
125
125 mm
mm pipeline.
pipeline.
pumped
pumped
through
through
• General
General rule
rule is
is that
that the
the pipe
pipe
diameter
diameter should
should be
be between
between 3
3
to
to 4
4 times
times the
the largest
largest size
size of
of
aggregate.
aggregate.
• Concrete
Concrete has
has been
been
pumped
pumped to
to
A
A height
height horizontal
horizontal
2000
2000 m.
m.
over
over 400
400 m
m and
and a
a
distance
distance of
of over
over

Pumpable Concrete
Pumpable Concrete
• A
A concrete
concrete which
which can
can be
be pushed
pushed through
through a
a pipeline
pipeline is
is called
called
a
a pumpable
pumpable concrete
concrete.
.
• It
It is
is made
made in
in such
such a
a manner
manner that
that its
its friction
friction at
at the
the inner
inner
wall
wall of
of the
the pipeline
pipeline does
does not
not become
become very
very high
high and
and that
that
it
it does
does not
not wedge
wedge while
while flowing
flowing through
through the
the pipeline.
pipeline.
• Pumpable
Pumpable concrete
concrete emerging
emerging from
from a
a pipeline
pipeline flows
flows in
in the
the
form
form of
of a
a plug
plug which
which is
is separated
separated from
from the
the pipe
pipe wall
wall
by
by a
a thin
thin lubricating
lubricating layer
layer consisting
consisting of
of cement
cement paste.
paste.
• For
For continuous
continuous plug
plug movement,
movement, the
the pressure
pressure generated
generated by
by
the
the flow
flow resistance
resistance must
must not
not be
be greater
greater than
than the
the pump
pump
pressure
pressure rating.
rating.

Pumpable Concrete
Pumpable Concrete
However if the concrete
However if the concrete
is too saturated at higher
is too saturated at higher
W/C ratio the concrete at
W/C ratio the concrete at
certain pump
certain pump pressures
pressures
may
may be
be such
such that
that water
water is
is
forced
forced out
out of
of the
the mix,
mix,
creating
creating an
an increase
increase in
in flow
flow
resistance
resistance and
and a
a possible
possible
blockage.
blockage.

Design Considerations for Pumpable
Design Considerations for Pumpable
Concrete
Concrete

Placing Concrete
Placing Concrete
• It
It is
is not
not enough
enough that
that a
a concrete
concrete mix
mix correctly Designed
correctly Designed
• batched,
batched, mixed
mixed and
and transported,
transported, it
it is
is of
of utmost
utmost
importance
importance that
that the
the concrete
concrete must
must be
be placed
placed in
in
systematic
systematic manner
manner to
to yield
yield optimum
optimum results.
results.
• Placing
Placing concrete
concrete within
within earth
earth mould.
mould. (example:
(example:
Foundation
Foundation concrete
concrete for
for a
a wall
wall or
or column).
column).
• Placing
Placing concrete
concrete within
within large
large earth
earth mould
mould or
or timber
timber
plank formwork.
plank formwork. (example:
(example: Road
Road slab
slab and
and Airfield
Airfield slab).
slab).
• Placing
Placing concrete
concrete in
in layers
layers within
within timber
timber or
or steel
steel
shutters.
shutters. (example:
(example: Mass
Mass concrete
concrete in
in dam
dam construction
construction or
or
construction
construction of
of concrete
concrete abutment
abutment or
or pier).
pier).

Placing Concrete
Placing Concrete
• Placing
Placing concrete
concrete within
within usual
usual from
from work.
work. (example:
(example:
Columns,
Columns, beams
beams and
and floors).
floors).
• Placing
Placing concrete
concrete under
under water.
water.

Placing Concrete
Placing Concrete
Placement with Conveyor Belt
Placement with Conveyor Belt
Concrete spread evenly
across the subgrade by the
paver before consolidation
and finishing

Placing
Placing and
and Finishing
Finishing Concrete
Concrete
Curb/Curb
Curb/Curb and
and
Gutter
Gutter
Concrete
Concrete deposited
deposited into
into
hopper
hopper of
of slip
slip form
form curb
curb and
and
gutter
gutter machine
machine which
which then
then
extrudes
extrudes the
the concrete
concrete into
into
the
the desired
desired shape
shape
Placing Concrete
Placing Concrete

Placing and Finishing Concrete
Concrete
Concrete Pump
Pump
Placing
Placing concrete
concrete by
by pump
pump
and
and placing
placing boom.
boom.
Placing Concrete
Placing Concrete

Compaction of Concrete
• Compaction
Compaction of
of concrete
concrete is
is the
the process
process adopted
adopted for
for
expelling
expelling the
the entrapped
entrapped air
air from
from the
the concrete.
concrete.
• In
In the
the process
process of
of mixing,
mixing, transporting
transporting and
and placing
placing of
of
concrete air
concrete air is
is likely
likely to
to get
get entrapped
entrapped in
in the
the concrete.
concrete.
• In
In other
other words,
words, stiff
stiff concrete
concrete mix
mix has
has high
high percentage
percentage
of
of entrapped
entrapped air
air and,
and, therefore
therefore ,
, would
would need
need higher
higher
compacting
compacting efforts
efforts than
than high
high workable
workable mixes.
mixes.
• In
In order
order to
to achieve
achieve full
full compaction
compaction and
and maximum
maximum density,
density,
with
with reasonable
reasonable compacting
compacting efforts
efforts available
available at
at site
site,
, it
it is
is
necessary
necessary to
to use
use a
a mix
mix with
with adequate
adequate workability.
workability.

• The
The following
following methods
methods are
are adopted
adopted for
for compacting
compacting the
the
concrete:
concrete:
• Hand
Hand Compaction
Compaction
• (i
(i )
) Rodding
Rodding (ii
(ii )
) Ramming
Ramming (iii
(iii )
) Tamping
Tamping
• Compaction
Compaction by
by Vibration
Vibration
• (i
(i )
) Internal
Internal vibrator
vibrator (Needle
(Needle vibrator)
vibrator)
• (ii
(ii )
) Formwork
Formwork vibrator
vibrator (External
(External vibrator)
vibrator)
• (iii
(iii )
) Table
Table vibrator
vibrator
• (iv
(iv )
) Platform
Platform vibrator
vibrator
• (v
(v )
) Surface
Surface vibrator
vibrator (Screed
(Screed vibrator)
vibrator)
• vi
vi )
) Vibratory
Vibratory Roller.
Roller.
• (c
(c )
) Compaction
Compaction by
by Pressure
Pressure and
and Jolting
Jolting
• (d)
(d) Compaction
Compaction by
by Spinning.
Spinning.

Compaction of Concrete: Hand Compaction
• Hand
Hand compaction
compaction of
of concrete
concrete is
is adopted
adopted in
in case
case of
of unimportant
unimportant
concrete
concrete work
work of
of small
small magnitude.
magnitude.
• Rodding
Rodding is
is done
done continuously
continuously over
over the
the complete
complete area
area to
to
effectively
effectively pack
pack the
the concrete
concrete and
and drive
drive away
away entrapped
entrapped air.
air.
• Light
Light ramming
ramming can
can be
be permitted
permitted in
in unreinforced
unreinforced
foundation
foundation concrete
concrete or
or in
in ground
ground floor
floor construction.
construction.
• Tamping
Tamping is
is one
one of
of the
the usual
usual methods
methods adopted
adopted in
in
compacting
compacting roof
roof or
or floor
floor slab
slab or
or road
road pavements
pavements where
where
the
the thickness
thickness of
of concrete
concrete is
is comparatively
comparatively less
less and
and the
the
surface
surface to
to be
be finished
finished smooth
smooth and
and level.
level. Tamping
Tamping consists
consists of
of
beating
beating the
the top
top surface
surface by
by wooden
wooden cross
cross beam
beam

Compaction of Concrete: By Vibration
• Where
Where high
high strength
strength is
is required,
required, it
it is
is necessary
necessary that
that stiff
stiff
concrete, with
concrete, with low
low water/cement
water/cement ratio
ratio be
be used.
used. To
To compact
compact
such
such concrete,
concrete, mechanically
mechanically operated
operated vibratory
vibratory equipment,
equipment,
must
must be
be used.
used.
•A
A concrete
concrete with
with about
about 4
4 cm
cm slump
slump can
can be
be placed
placed
and
and compacted
compacted fully
fully in
in a
a closely
closely spaced
spaced reinforced
reinforced
concrete
concrete work,
work, whereas,
whereas, for
for hand
hand compaction,
compaction, much
much higher
higher
consistency
consistency say
say about
about 12
12 cm
cm slump
slump may
may be
be required.
required.
•The
The action
action of
of vibration
vibration is
is to
to set
set the
the particles
particles of
of fresh
fresh
concrete
concrete in
in motion,
motion, reducing
reducing the
the friction
friction between
between them
them and
and
affecting
affecting a
a temporary
temporary liquefaction
liquefaction of
of concrete
concrete which
which
enables
enables easy
easy settlement.
settlement.

• Internal
Internal Vibrator:
Vibrator: Of
Of all
all the
the vibrators,
vibrators, the
the internal
internal
vibrator
vibrator is
is most
most commonly
commonly used.
used. This
This is
is also
also called,
called, “Needle
“Needle
Vibrator”, or
Vibrator”, or “Poker Vibrator”.
“Poker Vibrator”. This
This essentially
essentially consists
consists
of
of a
a power
power unit,
unit, a
a flexible
flexible shaft
shaft and
and a
a needle.
needle.
• Formwork
Formwork Vibrator
Vibrator (External
(External Vibrator):
Vibrator): Formwork
Formwork
vibrators
vibrators are
are used
used for
for concreting
concreting columns,
columns, thin
thin walls
walls or
or in
in the
the
casting
casting of
of precast
precast units.
units. The
The machine
machine is
is clamped
clamped on
on to
to the
the
external
external wall
wall surface
surface of
of the
the formwork.
formwork.
• Table
Table Vibrator:
Vibrator: This
This is
is the
the special
special case
case of
of formwork
formwork
vibrator,
vibrator, where
where the
the vibrator
vibrator is
is clamped
clamped to
to the
the table.
table.
They
They are
are commonly
commonly used
used for
for vibrating
vibrating concrete
concrete cubes.
cubes.

• Platform
Platform Vibrator:
Vibrator: Platform
Platform vibrator
vibrator is
is nothing
nothing but
but a
a
table
table vibrator,
vibrator, but
but it
it is
is larger
larger in
in size.
size. This
This is
is used
used in
in the
the
manufacture
manufacture of
of large
large prefabricated
prefabricated concrete
concrete elements
elements such
such
as
as electric
electric poles,
poles, railway
railway sleepers,
sleepers, prefabricated
prefabricated roofing
roofing
elements
elements etc.
etc.
• Surface
Surface Vibrator:
Vibrator: Surface
Surface vibrators
vibrators are
are sometimes
sometimes knows
knows
as,
as, “Screed Board
“Screed Board Vibrators”.
Vibrators”. A
A small
small vibrator
vibrator placed
placed on
on
the
the screed
screed board
board gives
gives an
an effective
effective method
method of
of compacting
compacting
and
and leveling
leveling of
of thin
thin concrete
concrete members,
members, such
such as
as floor
floor
slabs,
slabs, roof
roof slabs
slabs and
and road
road surface.
surface.
• Vibratory
Vibratory Roller:
Roller: One
One of
of the
the recent
recent developments
developments of
of
compacting
compacting very
very dry
dry and
and lean
lean concrete
concrete is
is the
the use
use of
of Vibratory
Vibratory
Roller.
Roller. Such
Such concrete
concrete is
is known
known as
as Roller
Roller
Compacted
Compacted Concrete.
Concrete.

Curing of Concrete
Curing of Concrete
• Concrete
Concrete derives
derives its
its strength
strength by
by the
the hydration
hydration of
of
cement
cement particles.
particles. The
The hydration
hydration of
of cement
cement is
is not
not a
a
momentary
momentary action
action but
but a
a process
process continuing
continuing for
for long
long
time.
time. The
The quantity
quantity of
of the
the product
product of
of hydration
hydration and
and
consequently
consequently the
the amount
amount of
of gel
gel formed
formed depends
depends upon
upon the
the
extent
extent of
of hydration.
hydration.
• Cement
Cement requires
requires a
a water/cement
water/cement ratio
ratio about
about 0.23
0.23
for
for hydration
hydration and
and a
a water/cement
water/cement ratio
ratio of
of 0.15
0.15 for
for filling
filling
the
the voids
voids in
in the
the gel
gel pores.
pores. In
In other
other words,
words, a
a water/cement
water/cement
ratio
ratio of
of about 0.38
about 0.38 would
would be
be required
required to
to hydrate
hydrate all
all the
the
particles
particles of
of cement
cement and
and also
also to
to occupy
occupy the
the space
space in
in the
the gel
gel
pores.
pores.

Curing of Concrete
Curing of Concrete
• Curing
Curing is
is the
the process
process of
of controlling
controlling the
the rate
rate and
and
extent
extent of
of moisture
moisture loss
loss from
from concrete
concrete during
during cement
cement
hydration
hydration
• Curing
Curing can
can also
also be
be described
described as
as keeping
keeping the
the concrete
concrete
moist
moist and
and warm
warm enough
enough so
so that
that the
the hydration
hydration of
of
cement
cement can
can continue.
continue.
• Curing
Curing methods
methods may
may be
be divided
divided broadly
broadly into
into four
four categories:
categories:
• (a)
(a) Water
Water curing
curing
• (b)
(b) Membrane
Membrane curing
curing
• (c)
(c) Application
Application of
of heat
heat
• (d)
(d) Miscellaneous
Miscellaneous

Curing of Concrete: Water curing
Curing of Concrete: Water curing
• This
This is
is
method
method
satisfie
satisfie
s
s
by far
by far the
the best
best
of
of curing
curing as
as it
it
all
all the
the
of
of
requirements
requirements curing
curing
,
,
namely,
namely,
hydration,
hydration,
promotion
promotion of
of
elimination
elimination of
of
• shrinkage and absorption
shrinkage and absorption
of
of the heat of hydration.
the heat of hydration.
• (a)
(a) Immersion
Immersion
• (b)
(b) Ponding
Ponding
(c)Spraying
(c)Spraying or
or
Fogging
Fogging
(d)
(d) Wet covering
Wet covering

Curing of Concrete
Curing of Concrete
Membrane
Membrane curing
curing is
is the
the most
most
practical
practical with
with today's
today's
Construction
Construction schedules.
schedules.
Water
Water curing
curing is
is when
when the
the
concrete
concrete is
is covered
covered with
with a
a
layer
layer of
of water
water for
for a
a period
period of
of
time
time and
and the
the evaporation
evaporation of
of
moisture
moisture is
is from
from the
the surface
surface
of
of the
the water.
water.

Curing of Concrete: Membrane Curing
• Sometimes,
Sometimes, concrete
concrete works
works are
are carried
carried out
out in
in places
places
where
where there
there is
is acute
acute shortage
shortage of
of water.
water.
• The
The quantity
quantity of
of water,
water, normally
normally mixed
mixed for
for making
making
concrete
concrete is
is more
more than
than sufficient
sufficient to
to hydrate
hydrate the
the cement
cement,
,
provided
provided this
this water
water is
is not
not allowed
allowed to
to go
go out
out from
from the
the body
body of
of
concrete.
concrete.
• Concrete
Concrete could
could be
be covered
covered with
with membrane
membrane which
which
effectively
effectively seal
seal off
off the
the evaporation
evaporation of
of water
water from
from concrete.
concrete.
will
• Curing
Curing compounds
compounds are
are liquids
liquids which
which are
are usually
usually
sprayed
sprayed directly
directly onto
onto concrete
concrete surfaces
surfaces and
and which
which then
then dry
dry to
to
form
form a
a relatively
relatively impermeable
impermeable membrane
membrane that
that retards
retards the
the
loss
loss of
of moisture
moisture from
from the
the concrete.
concrete.

Curing of Concrete: Application of heat
• When
When concrete
concrete is
is subjected
subjected to
to higher
higher temperature
temperature it
it
A
Accelerates
ccelerates the
the hydration
hydration process
process resulting
resulting in
in
development of strength.
development of strength.
faster
• Therefore,
Therefore, subjecting
subjecting the
the concrete
concrete to
to higher
higher temperature
temperature
and
and maintaining
maintaining the
the required
required wetness
wetness can
can be
be achieved
achieved by
by
subjecting
subjecting the
the concrete
concrete to
to steam
steam curing.
curing.
• The
The exposure
exposure of
of concrete
concrete to
to higher
higher temperature
temperature is
is done
done in
in
the
the following
following manner:
manner:
• (a)
(a) Steam
Steam curing
curing at
at ordinary
ordinary pressure.
pressure.
• (b)
(b) Steam
Steam curing
curing at
at high
high pressure.
pressure.
• (c)
(c) Curing
Curing by
by Infra-red
Infra-red radiation.
radiation.
• (d)
(d) Electrical
Electrical curing.
curing.

• A
A faster
faster attainment
attainment of
of strength
strength will
will contribute
contribute to
to many
many other
other
advantages
advantages mentioned
mentioned below.
below.
• (a
(a )
) Concrete
Concrete is
is vulnerable
vulnerable to
to damage
damage only
only for
for short
short time.
time.
• (b)
(b) Concrete
Concrete member
member can
can be
be handled
handled very
very quickly.
quickly.
• (d
(d )
) A
A smaller
smaller curing
curing tank
tank will
will be
be sufficient.
sufficient.
• (e)
(e) The
The work
work can
can be
be put
put on
on to
to service
service at
at a
a much
much early
early time,
time,
• (f)
(f) Pre-stressing
Pre-stressing bed
bed can
can be
be released
released early
early for
for further
further casting.
casting.
• (g)
(g) A
A fewer
fewer number
number of
of formwork
formwork will
will be
be sufficient
sufficient or
or alternatively
alternatively with
with
the
the given
given number
number of
of formwork
formwork more
more outturn
outturn will
will be
be achieved.
achieved.

Steam curing at ordinary pressure
Steam curing at ordinary pressure
• Application
Application of
of steam
steam curing
curing to
to in
in situ
situ construction
construction will
will be
be a
a
little
little difficult
difficult task.
task. However,
However, at
at some
some places
places it
it has
has been
been tried
tried
for
for in
in situ
situ construction
construction by
by forming
forming a
a steam
steam jacket
jacket with
with the
the help
help
of
of tarpaulin
tarpaulin or
or thick
thick polyethylene
polyethylene sheets.
sheets.

High Pressure Steam Curing
• The
The high
high pressure
pressure steam
steam curing
curing is
is something
something different
different
from
from ordinary
ordinary steam
steam curing,
curing, in
in that
that the
the curing
curing is
is carried
carried
out
out in
in a
a closed
closed chamber.
chamber.
• High
High pressure
pressure steam
steam cured
cured concrete
concrete develops
develops in
in one
one
day,
day, or
or less
less the
the strength
strength as
as much
much as
as the
the 28
28 days’ strength
days’ strength of
of
normally
normally cured
cured concrete
concrete.
. The
The strength
strength developed
developed does
does
not
not show
show retrogression.
retrogression.
• High
High pressure
pressure steam
steam cured
cured concrete
concrete exhibits
exhibits higher
higher
resistance
resistance to
to sulphate
sulphate attack,
attack, freezing
freezing and
and thawing
thawing action
action
and
and chemical
chemical action.
action. It
It also
also shows
shows less
less efflorescence.
efflorescence.

• High
High pressure
pressure steam
steam cured
cured concrete
concrete exhibits
exhibits lower
lower
drying
drying shrinkage,
shrinkage, and
and moisture
moisture movement.
movement.
• In
In high
high pressure
pressure steam
steam curing,
curing, concrete
concrete is
is subjected
subjected to
to
a
a maximum
maximum temperature
temperature of
of about
about 175°C
175°C which
which corresponds
corresponds
to
to a
a steam
steam pressure
pressure of
of about
about 8.5
8.5 kg/sq.cm.
kg/sq.cm.

Curing by Infra-red Radiation
• Curing
Curing of
of concrete
concrete by
by Infra-red
Infra-red Radiation
Radiation has
has been
been
practised
practised in
in very
very cold
cold climatic
climatic regions
regions in
in Russia.
Russia.
• It
It is
is claimed
claimed that
that much
much more
more rapid
rapid gain
gain of
of strength
strength
can
can be
be obtained
obtained than
than with
with steam
steam curing
curing and
and that
that
rapid
rapid initial
initial temperature
temperature does
does not
not cause
cause a
a decrease
decrease
in
in the
the ultimate
ultimate strength
strength as
as in
in the
the case
case of
of steam
steam curing
curing at
at
ordinary
ordinary pressure.
pressure.
• The
The system
system is
is very
very often
often adopted
adopted for
for the
the curing
curing of
of
hollow
hollow concrete
concrete products.
products. The
The normal
normal operative
operative temperature
temperature
is
is kept
kept at
at about
about 90°C.
90°C.

Electrical Curing
Electrical Curing
• Concrete
Concrete can
can be
be cured
cured electrically
electrically by
by passing
passing an
an
alternating
alternating current
current (Electrolysis
(Electrolysis trouble
trouble will
will be
be
encountered
encountered if
if direct
direct current
current is
is used)
used) through
through the
the
concrete
concrete itself
itself between
between two
two electrodes
electrodes either
either buried
buried in
in or
or
applied
applied to
to the
the surface
surface of
of the
the concrete.
concrete.
• Care
Care must
must be
be taken
taken to
to prevent
prevent the
the moisture
moisture from
from
going
going out
out leaving
leaving the
the concrete
concrete completely
completely dry.
dry.

Electrical Curing
Electrical Curing

Manufacture of Concrete by various processes

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