1.
KAS-2012 1
CONCRETE HANDLING IN THE
FIELD
By K.Shah
B.E.(Civil Engg) NIT Rourkela,India
M.Sc. (Environment), University of Leeds, UK
Ex-GM(Civil & Environment) – MNC
Currently Guest faculty-College of Technology &
Engineering

2.
KAS-2012 2
Stages of producing concrete.
(1) Batching
(2) Mixing
(3) Transportation
(4) Placing
(5) Compacting
(6) Curing
(7) Finishing

3.
KAS-2012 3
(1) Batching
(a) Volume batching
(b) weight Baching

4.
KAS-2012 4
Volume batching
 Volume batching is not good method
 Moist sand in loose condition weights less
than the same volume of dry sand.
 Practiced for small work.
 For quality work ,weigh batching is
practiced.

5.
KAS-2012 5
VOLUME BATCH
Gauge box
 Various gauge boxes of different volumes are
used.
Length Width Depth Volume
33.3 cm 30 cm 20 cm 20 liters
33.3 cm 30 cm 25 cm 25 liters
Grade Cement- kg Sand -lts Coarse
Aggregate
lts
1:11/2:3 (M
200)
50 35 70
1:2:4 (M
150)
50 70 140
1:3:6 (M100) 50 105 210

6.
KAS-2012 6
Weigh Batch Machine

7.
KAS-2012 7
Weigh batching
 Weigh batching is correct method
 Facilitates accuracy, flexibility & simplicity
Different batching machine are available :
(a) manual machines & (b) Automatic machines
Manual machine :
 Has two buckets
 Buckets mounted on common spindle about which they rotate.
 One is loaded while other is discharged in mixer.
 Spring loaded dials indicate the weight.

8.
KAS-2012 8
Automatic weigh batch
 For large works
 Over head hopper and discharges into
mixer.
 Useful in ready mix concrete plant
 Recorders for weight
 Calibration is required from time to time.

9.
KAS-2012 9
(2) MIXING
Mixing of cement,sand aggregates should
ensure that:
 The mass is homogeneous
 Uniform in color
 consistent

10.
KAS-2012 10
MIXING METHODS :
(1) Hand mixing
(2) Machine mixing

11.
KAS-2012 11
Hand mixing
 Practiced for small scale work (small
house, repairing of house etc)
 10 % extra cement is added to
compensate inferior concrete produced by
this method.
 Spread fine & coarse aggregate in
alternate layer
 Spread cement over it
 Mix with shovel till uniform color is
achieved

12.
KAS-2012 12
Machine mixing
 Medium & large scale work use machine
mixing
 Mixing is efficient, economical & produce
quality concrete.
Type of mixer:
(a) Batch mixer : batch by batch with time
interval
(b) Continuous mixer: continuously mixed &
discharged (in dam construction)

13.
KAS-2012 13
CONCRETE MIXER
(1) Pan type
(2) drum Type:
(a) tilting
(b) Non –tilting
(c) Reversing

14.
KAS-2012 14
PAN MIXER

15.
KAS-2012 15
PAN MIXER
A forced movement pan mixer has blades
that are fixed to an assembly that agitates
the concrete throughout the pan as the
vertical shaft rotates.

16.
KAS-2012 16
DRUM MIXER
 As per IS: 1791-1985 mixers are
designated by number which shows
capacity (liters) of batch:
a) Tilting : 85 T, 100T, 140 T, 200T
b) Non tilting : 200 NT,280 NT, 375 NT, 500
NT, 1000 R
c) Reversing : 200 R, 280 R, 375 R,500 R,
1000 R
T= Tilting, NT =non tilting, R=Reversing

17.
KAS-2012 17
TILTING MIXER

18.
KAS-2012 18
TILTING MIXER
 Internal blades lift and tumble the
ingredients onto itself.
Two primary types exist:
 horizontal (one end has and opening for
charging and a different end for
discharging)
 single drum (materials are charged and
discharged through a single opening).

19.
KAS-2012 19
NON TILTING MIXER

20.
KAS-2012 20
NON TILTING MIXER
 Single drum rotating about a horizontal
axis.
 Fixed blades work the concrete towards
the discharge end of the mixer, in order to
provide a rapid rate of discharge.

21.
KAS-2012 21
REVERSING MIXER

22.
KAS-2012 22
REVERSING MIXER
 The entire drum rotates around its axis as
materials are loaded through a charge chute at
one end of the drum and exit through a
discharge chute at the opposite end of the drum.
 Mixing blades are mounted on the inside surface
of the drum and as the drum rotates the blades
mix by lifting and dropping the materials during
each rotation.
 Once the materials are sufficiently mixed the
rotation of the drum is reversed and the blade
arrangement pushes the concrete through to the
discharge end of the mixer.

23.
KAS-2012 23
Sequence of charging drum
 First half quantity of coarse aggregate is
placed in skip
 Over it half quantity of sand
 On that full quantity of cement
 Over it balance quantity of coarse & fine
aggregates is place.
 This prevents spillage of cement in air
while discharging in drum

24.
KAS-2012 24
 25 % Water is placed in drum and then
mix from skip is discharged in the drum
 This prevents sticking of cement on blades
 75 water is immediately poured after
placing mix material (cement sand etc) in
drum.

25.
KAS-2012 25
Mixing time
 In small machine, mixing time varies
between 1-2 minutes
 In Ready Mix Cement mixer – 15-30
seconds
 RPM of drum : 15-20
 Compressive strength of concrete
increases with increase in mixing time but
after 2 minutes increase in compressive
strength is not significant.

26.
KAS-2012 26
 If concrete is not used after mixing it may
set
 But when concrete is agitated on time to
time in drum setting time rule does not
follow.

27.
KAS-2012 27
Retempering of concrete :
 Some time concrete from RMC plant is not
delivered to site due to traffic congestion
 Concrete becomes stiff and becomes
unworkable
 Site engineers can reject the concrete if
delay is more
 If it can be of used then small volume of
water is added and again agitated in the
drum. This is called RETEMPERING OF
CONCRETE.

28.
KAS-2012 28
MANUFACTURING OF
CONCRETE
 With same material if care is not taken,
resulting concrete will be bad concrete
 What are good rules to make good quality
concrete.

29.
KAS-2012 29
TRANSPORTATION OF CONCRETE
Precaution in concrete transportation:
 Homogeneity of conc. Mass is maintained
 Movement of hand trolly or truck on rough
road surface makes vibrations
 This results in deposition of heavy
aggregates at bottom of truck
 Water & cement slurry comes on top.

30.
KAS-2012 30
METHODS OF TRANSPORTATION
1. Mortar Pan
2. Wheel barrow
3. Truck Mixer & dumpers
4. Crane, Bucket & rope way
5. Belt conveyors
6. Chutes
7. Skip & hoist
8. Transit Mixer
9. Pump & pipeline
10. Helicopter

31.
KAS-2012 31
MORTAR PAN
 Common method in India
 More labour required
 Segregation of concrete is less
 Greater surface area of concrete is
exposed to sun, concrete dries.

32.
KAS-2012 32
WHEEL BARROW
 When transportation of concrete is at
ground level.
 Movement of wheel on rough road
surface, segregates concrete.
 Some wheel barrows have pneumatic
wheel to reduce vibration

33.
KAS-2012 33
CRANE
 Used for transporting concrete above
ground level.
 For high rise buildings.
 Cranes are fast
 Can move horizontally & vertically
 Concrete in skip discharge from bottom
 In bucket concrete is discharged by tilting.

34.
KAS-2012 34
BUCKET & ROPEWAY
Use for construction in:
 Valley
 Bridge pier in river
 Dam
Advantage:
Concrete is not exposed to sun or air & no
loss of water.

35.
KAS-2012 35
Truck Mixer & dumpers
 Used for large concrete works.
 Can travel any part of site.
 Dumpers - 2-3 M3 Capacity
 Trucks – 4 M3 Capacity
 Bottom surface of truck is kept wet
 Top of truck is covered to prevent
evaporation

36.
KAS-2012 36
BELT CONVEYORS
 Limited use in construction
Advantages:
 Can transport large volume
 Very quick
 Can go where access is limited
Disadvantages :
 On steep slope concrete segregates.
 Exposed to sun for long time.

37.
KAS-2012 37
CHUTE
 For transporting from ground level to lower
level. (basement etc).
 Used where labour can not reach due to
less space in trench etc.
 Made of metal
 Slope should not be < 1 vertical : 2.5
horizontal.

38.
KAS-2012 38
SKIP & HOIST
 Labour can go upto 3rd or 4th floors.
 So skip is used for transport vertically up
(in multistory building).
 Skip travels on vertical rail.
 Skip can discharge manually or
automatically.

39.
KAS-2012 39
TRANSIT MIXER

40.
KAS-2012 40
TRANSIT MIXER
 Used for long distance travel in RMC plant.
 Concrete is continuously agitated in truck drum
(2 – 6 rpm).
 Also transported mix in dry condition and water
is added on reaching the destination.
 Wet Mix in truck must reach site in 1- 1.5 hours.
 Pumps are also fitted on truck mixer to
discharge concrete.

41.
KAS-2012 41
PUMPS & PIPELINE
 Most popular method
 Reliable & good quality pumps are used.
 Mostly operated by diesel.
 Concrete is placed in collecting hopper.
 Rotating blades in hopper pushes concrete
towards pipe.
 Vacume in hose pipe (600 mm Hg)
 Rotating rollers in pump chambers squeeze the
concrete in pipe and flow of concrete is started.
 Concrete is discharged from other end of hose
pipe.
 Concrete can be pumped upto 400 m height and
2000 m distance.

42.
KAS-2012 42
SECTION OF PUMP

43.
KAS-2012 43
PIPELINE
Pipeline should :
 Have correct diameter as per pump
pressure. (generally 125 mm)
 Have sufficient thickness
 Good couplings
 Poor pipeline can cause blockage.

44.
KAS-2012 44
PIPELINE
 Thumb rule : For 30 M3 /hr concrete and
200 m length, dia should be 100 mm.
 Length > 500 m then dia = 150 mm.
 Dia = 3 to 4 times the size of aggregate
 Leaky pipe & coupling result in escape of
water /air & finally block the concrete.
 Vertical pipe should good otherwise
difficult to change at height.
 Pump is kept at distance from building
about 15 % of vertical length.

45.
KAS-2012 45
PUMPABLE CONCRETE
 Concrete which can be pushed through a pipeline is
called pumpable concrete.
 Friction between pipe wall and concrete is less.
 Concrete flows in the form of plug which is separated
from pipe wall by a thin layer of lubricating cement paste.
 Flow resistant must be < pump pressure.
 If the concrete is more wet then water comes out of mix
which makes more resistance to flow.
 Stiff and also very wet concrete is not pumpable.

46.
KAS-2012 46
Design of pumpable concrete
 Concrete Mix is so designed that all material remain
together.
 Mix must make redial movement of grout to maintain
lubricating paste.
 Mix should be deformed at bends
 Cement & fine particles (0.25 mm size) are important for
good flow.
 350 to 400 Kg/ M3 of fine particles are necessary for
flow.
 Slump of pumpable concrete is above 75 mm.

47.
KAS-2012 47
PROBLEMS IN PUMPING
 Blockage in pipe
 Pipe should be cleaned after each day
operation
 Blockage can be cleaned by forward-
backward pumping.
 Tapping pipe with hammer
 Clean pipe with rod or sponge ball pushed
by compressed air.

48.
KAS-2012 48
PLACING CONCRETE
 Must be placed in systematic manner.
Can be placed with following methods:
 Within earth mould : Foundation
 In timber plank formwork : Road, airport
slab.
 Steel shuttering : Dam
 Under water

49.
KAS-2012 49
Concrete in Foundation
 In foundation, ground is made wet.
 Plastic sheet are laid between ground & slab
 Concrete is dumped not poured.
 No heap and dragging
 Placed in layers of 35 – 40 cm in mass concrete
 Avoid cold joints between 2 layers
 Surface of previous layer is cleaned with wire brush
 Sometime, cement slurry is placed on old surface
 Top of previous layer kept rough for good bond.

50.
KAS-2012 50
Concrete on Road, airport, floor slabs
 Placed in alternate bays (allow shrinkage)
with contraction joints :
contraction joints
Bays

51.
KAS-2012 51
Concrete in Beams & Column
 Reinforcement correctly placed.
 Correct cover required
 Joints of shuttering to be plugged.
 Mould releasing agent inside formwork

52.
KAS-2012 52
STRIPPING TIME
 Form work should not removed until good
strength has come.
Type of form work Time
Vertical wall, columns 16-24 hrs
Soffit of slab (Prop should be refixed immediately) 3 days
Soffit of beam (Prop should be refixed immediately) 7 days
Props to slab Span < 4.5 m 7 days
Props to slab Span > 4.5 m 14 days
Props of beam (Span < 6 m) 14 days
Props of beam (Span > 6 m) 21 days

53.
KAS-2012 53
UNDER WATER CONCRETE

54.
KAS-2012 54
UNDER WATER CONCRETE
 Tremie (means hopper) is used.
 Funnel on top
 Pipe of 200 mm size
 Pipe bottom is plugged
 Fill pipe with concrete
 Lift pipe or jerk to release the plug
 Keep bottom of pipe inside concrete

55.
KAS-2012 55
Underwater Concrete
 No compaction required as hydrostatic pr
of water compacts concrete.
 Concrete of 0.3 W/C ratio can be placed
with Tremie.
 Used for Pile or well foundation

56.
KAS-2012 56
SLIP FORM TECHNIQUE
 In this method, concrete is continuously placed, compacted & form work is
pulled up for next layer of concrete.
 Vertical slip form for Tall structure like silo, chimney
 Horizontal slip form paver machine (HSFP) for road construction.
 Concrete is dumped in front of HSFP machine by dumpers.
 Compaction by vibrator installed inside HSFP machines.
 Finishing of surface by HSF paver.
 Operation of road alignment, gradient, curve are controlled by
Computerized Laser Control system.
 Speed of construction is 1 mt /min.
 1 km of concrete road of 3.75 mt width is built in one day (16 hrs work).
 Mumbai-Pune Expressway was constructed by this machine.

57.
KAS-2012 57
VERTICAL SLIP FORM

58.
KAS-2012 58
HORIZONTAL SLIP FORM ROAD PAVER

59.
KAS-2012 59
COMPACTION OF CONCRETE
 Compaction is a process of expelling the entrapped air inside
concrete mass.
 During mixing, transporting & placing the concrete, air gets trapped
in concrete mass.
 If this air is not removed, concrete will not get strength.
 5 % of air voids reduces strength by 30 %
 10 % of air voids reduces strength by 50 %
 Durability of concrete is also reduces with air voids.
 Insufficient compaction increases permeability of concrete.
 Results in entry of aggressive chemicals in solution.
 Chemicals attack concrete & reinforcement and life of concrete is
reduced.

60.
KAS-2012 60
METHODS OF COMPACTION
1. Hand compaction
2. Compaction by vibration
3. Compaction by pressure &
jolting
4. Compaction by spinning

61.
KAS-2012 61
(2) COMPACTION BY VIBRATION
a) Internal Vibrator
b) Formwork Vibrator
c) Table Vibrator
d) Platform Vibrator
e) Surface Vibrator

62.
KAS-2012 62
(1) HAND COMPACTION
 Hand Rodding
Poking inside concrete with 1-2 mt long steel rod
 Ramming
Unreinforced foundation & ground floor work
 Tamping
Wooden beam is used to beat concrete (low
thickness slab, road slab)

63.
KAS-2012 63
COMPACTION BY VIBRATION
 In hand compaction w/c ratio is more so
we get less strength in concrete.
 In mechanical vibrator w/c can be kept low
so we get good strength.

64.
KAS-2012 64
INTERNAL VIBRATOR

65.
KAS-2012 65
(a) INTERNAL VIBRATOR
 Most common in use
 Called, Needle Vibrator or Immersion vibrator or
Poker vibrator.
 Consists : electrical/diesel power supply, Needle
and shaft.
 Frequency of vibrations can be 12000 cycles
vibration per minute.
 Needle diameter 20 to 75 mm
 Length 25 to 90 cm.
 Portable.

66.
KAS-2012 66
FORMWORK VIBRATOR
 Used for columns, walls, precast slab
 Vibrator is clamped to formwork
 Vibration is given to formwork
 Vibration is transferred from formwork to
concrete
 Useful in thin wall where reinforcement
obstruct the needle type vibrator.
 Efficiency is lower then needle vibrator

67.
KAS-2012 67
TABLE VIBRATOR
 Vibrator is clamped to table
 Used for concrete test cubes
 Cubes are kept on table to get vibrations
 Also used for small prefabricated slab

68.
KAS-2012 68
TABLE VIBRATOR

69.
KAS-2012 69
PLATFORM VIBRATOR
 Similar to table vibrator but of large size
 Used for long concrete electrical pole,
railway sleeper,prefabricated roofing
element

70.
KAS-2012 70
PLATEFORM VIBRATOR

71.
KAS-2012 71
SURFACE VIBRATOR
 Known as Screed Board Vibrator
 Used for thin roof slab where needle
vibrator can not be used
 Not effective if slab thickness is more then
15 cm.

72.
KAS-2012 72
SURFACE VIBRATOR

73.
KAS-2012 73
COMPACTION BY PRESSURE & JOLTING
 Used for hollow blocks, solid concrete
blocks
 Stiff concrete is vibrated, pressed & given
jolts
 Stiff concrete is compacted to get dense
form & good strength is achived.

74.
KAS-2012 74
VIBRATION BY SPINNING
 New method
 Used for concrete pipes
 Concrete when spun at high speed gets
compaction by centrifugal force

75.
KAS-2012 75
VIBRATORY ROLLER
 Road rollers has vibrating system
 Roller while moving on raod slab gives
vibrations
 Used for Lean concrete (M10) for road
base


76.
KAS-2012 76
ROLLER VIBRATOR

77.
KAS-2012 77
PRECAUTIONS IN VIBRATING CONCRETE
 Vibrator gets damaged if comes in contact
with hard object (Formwork, hard
concrete)
 Switch on when needle is inside fresh
concrete mass
 Should conform to IS 2505-1963
 Degree of compaction can be recognized
from rising air bubbles & formation of thin
film on top

78.
KAS-2012 78
HYDRATION OF CEMENT
 Cement is made by Cao, SiO2, Al2O3, Fe2O3, MgO, K2O,
SO3
 After burning in Kiln following products are made:
3Cao. SiO2 (C3S) - Tri calcium silicate
2Cao. SiO2(C2S) – Di cacium silicate
3Cao. Al2O3 (C3A) – Tri cacium aluminate
4Cao. Al2O3. Fe2O3(C3AF) -Tricalcium alumino ferrite.
On addition of water in cement reaction of C3S, C2S, C3A
& C3AF liberate heat. Heat is suside by addition of water.

79.
KAS-2012 79
CURING OF CONCRETE
 Curing is defined as “ making satisfactory moisture
content & favourable temperature” in concrete after
placing the concrete. So that hydration may continue
until the strength is developed.
 Curing is required immediately after placing concrete.
 During hydration, heat of hydration is released.

80.
KAS-2012 80
CURING OF CONCRETE
 Concrete delivers its strength by the hydration of cement
particles.
 Hydration is continuous & long time process.
 Rate of hydration is fast immediately after making the
concrete
 Theoretically 0.23 w/c ratio required for hydration
 0.15 w/c ratio required for filling the voids in gel.
 Total 0.38 w/c ratio is optimum
 In field condition, water evaporates & available water
quantity reduced for hydration
 Extra water is given by curing

81.
KAS-2012 81
METHODS OF CURING
a) Water curing
b) Membrane curing
c) Application of heat
d) Other methods

82.
KAS-2012 82
WATER CURING
a) Immersion : Slab is kept in water tank
b) Ponding: Roof slab is filled with water
c) Spraying : water spary on concrete wall is
d) Wet covering : Wet gunny bags on wall

83.
KAS-2012 83
MEMBRANE CURING
 Concrete surface is covered by plastic
membrane
 It is used where water availability is less.
 Plastic sheet reduces evaporation in
concrete
 Membrane is applied after 2 days of water
curing

84.
KAS-2012 84
APPLICATION OF HEAT
 Spraying of steam on concrete provides heat & moisture.
 Higher temperature accelerates hydration rate & strength
of concrete is attended
 Early strength of structure is obtained
 Steam application possible at precast factory only.
 Precast prestressed concrete girders of bridge are cured
with steam
 Fast construction of bridge

85.
KAS-2012 85
HIGH PRESSURE STEAM CURING
 Superheated steam at high pressure (8.5 kg/cm2) & high
temperature(175 deg C) is applied on concrete.
 This process is called “Autoclaving”
 28 days strength of concrete is achieved in one day
 Concrete becomes sulphate resistant
 Low shrinkage in concrete
 Used in production of Cellular concrete products(
Siporex, Celcrete)

86.
FINISHING OF CONCRETE
 Finishing is last operation of concrete making.
 Finishing of top surface is required in roads, airport
strip, home floor
Methods of Finishing:
a) Form work Finish
b) Surface Treatment
c) Applied Finishes
SHAH K.A. 86

87.
FORMWORK FINISH
 Concrete obeys the shape of formwork
 Grooves & lining on formwork plate gives
makes grooves & lining on concrete
 Prefabricated tiles can be made of any
design

88.
SURFACE TREATMENT
 Domestic floor should be smooth, wear resistant, crack
free.
 Mix should have good proportion without excess “Matrix”
 Exposed aggregate finish : Colored pebbles on top layer
of wall
 Bush Hammering : Electrically operated Brush with teeth
when applied on concrete removes top cement layer,
exposes aggregates and makes shining aggregates.
KAS-2012 88

89.
APPLIED FINISH
 Rough cast finish : mixture of cement, sand, round
gravel is applied on wall
 Non slip finish: Railway platform & walkway around
pool are given non slippery finish by mixing large size
sand particles in floor concrete.