This document discusses the properties of fresh and hardened concrete. It covers topics like preparation of concrete including batching, mixing, transporting, placing, compacting, and curing. For mixing, it describes different types of mixers like pan, drum, tilting, and continuous mixers. It also discusses various methods of transporting, compacting, and curing concrete, including water curing, membrane curing, steam curing, and others. The overall document provides an overview of the different stages and properties involved in the production and strengthening of concrete.

1. CONCRETE
TECHNOLOGY
MODULE 2
PROPERTIES OF CONCRETE
Ref.: M.S. Shetty

2. MODULE 2
2
PROPERTIES
OFFRESH
CONCRETE
1
PREPARATION
OFCONCRETE
3
PROPERTIES OF
HARDENED
CONCRETE
2

3. 1.
Preparation of Concrete
3

4. Stages in Preparation of Concrete
1.BATCHING 2.MIXING 3.TRANSPORTING
4.PLACING 5.COMPACTING 6.CURING
7.FINISHING
4

5. 1. BATCHINGOF CONCRETE
5
Measurement of materials required for making concrete is called
BATCHING.
VOLUMEBATCHING
◎ Measurement is based on volumeof materials.
◎ Cement is always measured by weight.
◎ 1bagof cement=35litres
◎ Knowing volume of cement, other materials are
measured on gaugeboxesof various volumes.
◎ Not so effective as measuring material in volume
can be erroneous.

6. WEIGHBATCHING
6
◎ Measurement is based on weightof materials.
◎ Accurate method and hence used in all important concreting works.
◎ Weigh batchers (mechanical and electronic) or other types of weighing
equipment are used to measure weight of materials.

7. 2. MIXING OF CONCRETE
7
The measured quantities are mixed thoroughly to form a uniform
paste.
Mixingisdonetoensure that:
◎ Various particles are distributed evenly
◎ Concrete has required consistency
◎ Concrete has uniform colour and homogeneity
◎ Cement is spread uniformly over fine and coarse aggregate particles ensuring
good bond

8. HANDM
IXING
8
◎ Done on impervious floor and used for small unimportant works.
◎ Measured quantity of cement and fine aggregates are spread out in and mixed by
turning over and over.
◎ The sand – cement mixture is then spread out and measured quantity of coarse
aggregate is laid over it as different layers.
◎ The mixture is then mixed thoroughly using a spade or shovel.
◎ Water is poured into a small pond created at middle of mixture and then then
mixed to obtain concrete of uniform consistency.

9. MACHINEM
IXING
◎ Mixing of concrete using machines is efficient and economic for large concrete
works.
TYPE
OF
MIXERS
BATCH MIXERS
PAN TYPE
DRUM TYPE
TILTING TYPE
NON-TILTING TYPE
REVERSING TYPE
FORCEDACTION
TYPE
CONTINUOUS
MIXERS
Produce mixes batch by
batch in time intervals.
Produce mixes continuously
9
without any stoppage in
between

10. PAN TYPE/ PADDLE TYPE
10
◎ Pan type mixers consists of a
circular pan in which concrete is
mixed.
◎ The mixing is done by blades
which are arranged in star shape
inside the pan.
TILTING DRUM TYPE
◎ Drum type mixers mix concrete
ingredients in a drum which is
actually in a double conical frustum
shape.
◎ Tilting drum mixer means the drum
will discharge concrete by tilting
downwards.

11. NON-TILTING DRUM TYPE
◎ Non-tilting drum mixers are not
allowed to tilt and the drum
rotates about its horizontalaxis.
◎ A chute is arranged in inclined
position which receives the mix
from drum and discharges it out.
REVERSING DRUM TYPE
◎ Similar to non-tilting type mixers,
but in this case reversal of
rotation takes place for different
action.
◎ The rotation of drum takes place in
one direction for mixing and in
opposite direction for discharging.
11

12. CONTINUOUS MIXERS
12

13. 3. TRANSPORTINGOF CONCRETE
In this stage the mixed concrete has to be moved to the location
where it has to be placed without losing its homogeneity.
Methods fortransportingconcrete
WHEEL
BARROW,
HANDCART
MORTARPAN
CRANE,
BUCKETAND
ROPEW
AY
DUMPER
TRUCKS
BELT
CONVEYORS
CHUTE
SKIPAND
HOIST
TRANSIT
MIXER
PUMPAND
PIPELINE
HELICOPTER
13

14. MORTARPAN
◎ Conventional method
◎ Concrete carried in small quantities
◎ Greater loss of water
WHEELBARROW
◎ Useful for carrying to longer
distance in ground.
◎ Chances of segregation due to
vibration.
◎ Can be reduced by pneumatic
wheels and a wooden plank road.
14

15. CRANE, BUCKET&ROPEWAY
◎ For transporting concrete above ground level.
◎ Crane can be used for transporting concrete vertically, horizontally or inclined
and useful for highriseconstruction.
◎ Ropeway buckets are more suitable for concrete work in the valley, dam site,
pier in the river and over some obstruction,etc.
15

16. DUMPERTRUCKS
◎ For large concrete works at ground
level.
◎ Ordinary open steel body tipping
lorries can be used.
◎ There are chances of segregation.
BELTCONVEYORS
◎ Used for a small horizontal distance
(5m – 10 m).
◎ Steep slope causes segregation.
◎ Long exposure of concrete leads to
loss of water.
◎ Not of very efficient application in
concrete construction. 16

17. CHUTE
◎ Slope of chute 1 vertical to 2.5
horizontal.
◎ Layout is such a way that it controls
segregation and separation.
◎ Not a perfect method but useful
when the labour cant reach the
place of concrete due to less space
like trenches.
SKIPANDHOIST
◎ Used for transporting concrete
vertically up in high rise building.
◎ At ground level, skip is directly fed
by the mixer and at the discharging
point, it discharges automatically
or manually.
17

18. TRANSITM
IXER
◎ Used in readymixconcrete plants.
◎ Transit mixer is mounted on the
truck.
◎ Concrete is continuously agitated
in the truck with 2 to 6 revolutions
per minute.
◎ A small pump is fitted on a truck
mixer for discharge of concrete.
PUMPSANDPIPELINE
◎ Pumping of concrete is universally
accepted and more reliable
method of concrete transportation
and placing.
◎ For the suction and delivery of
concrete, a piston is provided.
◎ Blockage is the common problem.
Hence, only pumpable concrete
can be used.
18

19. 4. PLACINGOF CONCRETE
19

20. 5. COMPACTINGOF CONCRETE
It is the method adopted for expelling the entrapped air in the
concrete.
Methods of
Compaction
Hand
Compaction
Rodding Ramming T
amping
Compaction
By Vibration
Formwork
Vibrator
Platform
Vibrator
Surface
Vibrator
Vibratory
Rollers
Compaction
By Pressure
And Jolting
Compaction
By Spinning
20

21. Manual Compaction
RODDING
◎ Poking concrete
with a steel rod.
◎ Used for lesser
important works.
RAMMING
◎ Compacting using a
rammer.
◎ Usually used for
PPC.
TAMPING
◎ Beating up the top
surface with wooden
cross beam of
section 10cmx10cm.
21

22. Compaction by Vibrators
NEEDLEVIBRATORS
◎ Also known as Internal Vibrators
or Immersion Vibrators.
◎ Commonly used for the large works
whose surfaces are flat, i.e., floor
slab, roof slab, etc.
FORMVIBRATORS
◎ Also known as External Vibrators
or Shutter Vibrators.
◎ Vibration is given to formwork by a
machine attached to formwork.
◎ Useful for columns, vertical walls,
etc. were reinforcement cage is
more.
22

23. Compaction by Vibrators
TABLEVIBRATORS
◎ This formwork is clamped to the
steel platform which is mounted
ontheflexible spring.
◎ The platformis vibrated by means
of a motor or a rotating mass.
◎ Useful for small precast
components and in laboratories.
PLATFORMVIBRATORS
◎ A kind of table vibrator which is
largein size.
◎ Platform vibrator is used in the
manufacturing of large precast
sections like electric poles,
railway sleepers, etc.
23

24. Compaction by Vibrators
SURFACEVIBRATORS
◎ Also known as screed vibrators.
◎ These are vibrators mounted on
platforms or concrete screeds.
◎ Generally used to compact and
finish the thin concrete members
like floor slabs, roof slabs, road
surfaces, etc.
VIBRATORYROLLERS
◎ Nowadays dry and lean concrete
are compacted by using the
vibratory roller.
◎ Heavy roller which vibrates while
rolling is used for compaction.
◎ The compacted concrete is known
as roller compacted concrete.
24

25. Compaction by Pressure and Jolting
◎ Used in manufacture of hollow bricks, cavity blocks and
solid concrete blocks.
◎ Very dry concrete is vibrated, pressed andapplied jolts.
◎ The combined action of pressure, jolts and vibrations
compact to denser state.
Compaction by Spinning
◎ Concrete is compacted by spinning at very high speeds
over rollers.
◎ Compaction is due to the centrifugal action.
◎ Used in manufacture of concrete pipes.
25

26. 6. CURINGOF CONCRETE
Curing is the process of preventing the loss of moisture from
the concrete by maintaining a satisfactory temperature.
No curing
No
enough
water for
hydration
Concrete does
not achieve its
full strength
and cracks
may develop
26

27. Curingensures
Better water proofing
Elimination of shrinkage
Absorption of heat of hydration
27
Weathering and wear resistance
Gain of full strength of concrete
Effective hydration of all particles

28. Curing
Methods
Immersion
Ponding
Water Curing
Spraying
Membrane Curing
Wet covering
Steam Curing at Ordinary Pressure
Steam Curing at High Pressure
Application of Heat
Curing by IR radiation
Miscellaneous Methods
Electrical Curing
28

29. Water Curing
It is the most effective method of curing in which temperature is maintained
by applying water on concrete surface.
IMMERSION
◎ Members are immersed in curing
tanks
◎ Useful for precast members.
PONDING
◎ Curing by creating small ponds
over the surface.
◎ Usually used for slabs.
29

30. SPRAYING/FOGGING
◎ Members are cured by applying
water
◎ Useful for vertical walls, retaining
walls, etc.
WETCOVERING
◎ Curing by covering surface by wet
gunny bags, jute bags, jute, straw,
etc.
method for curing
◎ Suitable
columns.
30

31. Membrane Curing
Curing by limiting the escape of water from the surface by applying coating
on surfaces.
◎ Useful in water scarce areas
Membrane Covering
Water Proof Papers
Polythene or Polyester Film
Applying Sealing
Compounds
Rubber Compounds
Bituminous Compounds
Waxes
Varnishes
31

32. Curing by Application of Heat
The increase in temperature in presence of moisture increases hydration
and hence results in faster development of strength.
STEAMCURINGATORDINARYPRESSURE
Effective for prefabricated structural elements
Steam curing is done in enclosures made with tarpaulin or polyethylene
sheets
The elements are stacked and steam is applied continuously or
intermittently
The increase in temperature along with the presence of moisture
accelerate hydration
28 days’ strength for normally cured concrete can be achieved in 3 days by
steam curing
32

33. Being faster, steam curing method helps in faster constructions
STEAMCURINGATHIGHPRESSURE/AUTOCLAVING
Steam curing is done in high pressure chambers
The temperature of steam (<175°C) is higher than that used in
ordinary pressure curing (<100°C)
The super heated steam along with the pressure in chamber
accelerates the hydration
28 days’ strength for normally cured concrete can be achieved in
just a day or less than that
33

34. CURINGBYINFRAREDRADIATIONS Cured by passing infrared radiations to concrete
Radiation heats concrete and fastens hydrations
Operates at a temperature of 90°C & produces
more strength than that achieved by steam curing
Used for curing hollow concrete products
ELECTRICALCURING
Concrete is heated by passing alternating current
Current is passed through electrode plates
connected
Expensive and is only used in very cold climatic
conditions
34

35. Miscellaneous Methods of Curing
35
CalciumChloride
◎ Can absorb and retain moisture content
◎ Ifapplied as a surface coating, can prevent evaporation
◎ Can keepconcrete wetfor a long time to promote hydration
KeepingFormworks
◎ Beam and column formworks, whose joints if sealed by wax, etc. can hold
moisture
◎ Keeping these sealed formwork intact for sometime prevents evaporation and
helps hydration

36. 7. FINISHING OF CONCRETE SURFACE
FORMWORKFINISHES
◎ Concrete generally takes up
the shape of formwork
◎ Pleasing surface can be
obtained by adjusting and
assembling formwork
SURFACETREATMENTS
◎ Finishing the surfaces
based on the surface use
APPLIEDFINISHES
◎ The surface is cleaned
◎ Cement mortar of 1:3is applied
◎ Above mortar sand or pebble
rendering can be done
◎ Coloured finishes also can be
applied.
36