concrete technology fresh concrete

1. Student Enrollment no:
Patel Meet D. 151100106051
Patel Nirav B. 151100106059
Patel Sweeteeben S. 151100106062
Prajapati Dharmendra G. 151100106069

2. GUIDE BY: KRUTIKA CHAUHAN MAM
NILESH PARMAAR SIR
FRESH CONCRETE

3. • INTRODUCTION
• WORKABILITY
• FACTOR AFFECTING WORKABILITY
• MEASUREMENT OF WORKABILITY
• SEGREGATION
• BLEEDING
• ADMIXTURES USED TO IMPROVE WORKABILITY
• PRODUCTION OF CONCRETE
CONTENT

4.  The potential strength and durability of concrete of a given mix proportion
is very dependent on the degree of its compaction.
 It is vital, therefore, that the consistency of the mix be such that the
concrete can be transported, placed, and finished sufficiently early enough
to attain the expected strength and durability.
SIGNIFICANCE
 The first 48 hours are very important for the performance of the concrete
structure.
It controls the long-term behavior, influence ,Ec (elastic modulus), creep,
and durability.
INTRODUCTION

5. WORKABILITY
 Definition
 The property of fresh concrete which is indicated by the amount of
useful internal work required to fully compact the concrete without
bleeding or segregation in the finished product.
 Workability is one of the physical parameters of concrete which affects
the strength and durability as well as the cost of labor and appearance
of the finished product.
 Concrete is said to be workable when it is easily placed and
compacted homogeneously i.e without bleeding or Segregation.
Unworkable concrete needs more work or effort to be compacted in
place, also honeycombs &/or pockets may also be visible in finished
concrete.

6. Factors affecting workability
 Water content in the concrete mix
 Amount of cement & its Properties
 Aggregate Grading (Size Distribution)
 Nature of Aggregate Particles (Shape, Surface Texture, Porosity etc.)
 Temperature of the concrete mix
 Humidity of the environment
 Mode of compaction
 Method of placement of concrete
 Method of transmission of concrete.

7. MEASUREMENT OF WORKABILITY
 WORKABILITY OF CONCRETE IS A COMPOSITE PROPERTY.
 NUMEROUS EMPRICAL TESTS ARE VARIABLE FOR MEASURING THE
WORKABILITY OF FRESH CONCRETYE,BUT NONE OF THEM IS WHOLLY
SATISFACTORY.
 EACH TEST MEASURES ONLY A PARTICULAR ASPECT OF IT.
 THRE IS REALLY NO UNIQUE MEHOD WHICH MEASURES THE WORKABILITY
OF COCRETE TO BRING OUT ITS FULL MEANING.
 THE FOLLOWING TESTS ARE COMMONLY USED TO MEASURE WORKABILITY:
1) SLUMP TEST
2) COMPACTING FACTOR TEST
3) FLOW TEST
4) VEE BEE CONSISTOMETER TEST
5) KELLY BALL TEST.

8. 1) SLUMP TEST
 Definition
 A slump test is a method used to determine the consistency of concrete.
 The consistency, or stiffness, indicates how much water has been used in
the mix.
 The stiffness of the concrete mix should be matched to the requirements
for the finished product quality.
 Slump is a measurement of concrete’s workability, or fluidity.
 It’s an indirect measurement of concrete consistency or stiffness.
 Principle
The slump test result is a measure of the behavior of a compacted inverted
cone of concrete under the action of gravity. It measures the consistency or
the wetness of concrete.

9.  Apparatus
 Slump cone : frustum of a cone, 300 mm (12 in) of height. The base is
200 mm (8in) in diameter and it has a smaller opening at the top of
100 mm,
 Scale for measurement,
 Temping rod(steel) 15mm diameter, 60cm length.

10.  Procedure
 The base is placed on a smooth surface and the container is filled with
concrete in three layers, whose workability is to be tested .
 Each layer is temped 25 times with a standard 16 mm (5/8 in) diameter
steel rod, rounded at the end.
 When the mold is completely filled with concrete, the top surface is
struck off (leveled with mold top opening) by means of screening and
rolling motion of the temping rod.
 The mold must be firmly held against its base during the entire
operation so that it could not move due to the pouring of concrete and
this can be done by means of handles or foot – rests brazed to the
mold.

11.  Immediately after filling is completed and the concrete is leveled,
the cone is slowly and carefully lifted vertically, an unsupported
concrete will now slump.
 The decrease in the height of the center of the slumped concrete is
called slump.
 The slump is measured by placing the cone just besides the slump
concrete and the temping rod is placed over the cone so that it
should also come over the area of slumped concrete.
 The decrease in height of concrete to that of mould is noted with
scale. (usually measured to the nearest 5 mm (1/4 in).

12.  Types Of Slump
The slumped concrete takes various shapes, and according to the profile
of slumped concrete, the slump is termed as;
o Collapse Slump
o Shear Slump
o True Slump

13.  Collapse Slump
In a collapse slump the concrete collapses completely.
 A collapse slump will generally mean that the mix is too wet
or that it is a high workability mix, for which slump test is not
appropriate.
 Shear Slump
In a shear slump the top portion of the concrete shears off and
slips sideways. OR
If one-half of the cone slides down an inclined plane, the slump is
said to be a shear slump.
 If a shear or collapse slump is achieved, a fresh sample should
be taken and the test is repeated.
 If the shear slump persists, as may the case with harsh mixes,
this is an indication of lack of cohesion of the mix.

14. • True Slump
 In a true slump the concrete simply subsides, keeping more or
less to shape.
 This is the only slump which is used in various tests.
 Mixes of stiff consistence have a Zero slump, so that in the
rather dry range no variation can be detected between mixes of
different workability.
 However , in a lean mix with a tendency to harshness, a true
slump can easily change to the shear slump type or even to
collapse, and widely different values of slump can be obtained
in different samples from the same mix; thus, the slump test is
unreliable for lean mixes.

15.  Uses
 The slump test is used to ensure uniformity for different batches
similar concrete under field conditions and to ascertain the effects
of plasticizers on their introduction.
 This test is very useful on site as a check on the day-to-day or
hour- to-hour variation in the materials being fed into the mixer.
An increase in slump may mean, for instance, that the moisture
content of aggregate has unexpectedly increases.
 Other cause would be a change in the grading of the aggregate,
such as a deficiency of sand.
 Too high or too low a slump gives immediate warning and
the mixer operator to remedy the situation.
 This application of slump test as well as its simplicity, is responsible
for its widespread use.

16. Degree of
workability
Slump (mm)
Compacting
Factor
Use for which concrete is suitable
Very low 0 - 25 0.78
Very dry mixes; used in road
making. Roads vibrated by power
operated machines
Low 25 - 50 0.85
Low workability mixes; used for
foundations with light
reinforcement. Roads vibrated by
hand operated Machines
Medium 50 - 100 0.92
Medium workability mixes;
manually compacted flat slabs
using crushed aggregates.
reinforced concrete manually
compacted and heavily
sections with vibrations
High 100 - 175 0.95
High workability concrete; for
sections with congested
reinforcement. Not normally
suitable for vibration
• SUGGESTED RANGES OF WORKABILITY OF CONCRETE

17. 2) Compacting Factor Test
 Introduction
 These tests were developed in the UK by Glanville ( 1947 ) and it
is measure the degree of compaction For the standard amount of
work and thus offer a direct and reasonably reliable assessment
of the workability Of concrete.
 The test require measurement of the weight of the partially and
fully compacted concrete and the ratio the partially compacted
weight to the fully compacted weight, which is always less than
one, is known as compacted factor.
 For the normal range of concrete the compacting factor lies
between 0.8 - 0.92.

18.  Apparatus
 Trowels
 Hand Scoop (15.2 cm long)
 Rod of steel or other suitable material
(1.6 cm diameter, 61 cm long rounded at one end ).
 Balance.

19.  Procedure
 Ensure the apparatus and associated equipment are clean before
test and free from hardened concrete and superfluous water.
 Weigh the bottom cylinder to nearest 10gm , put it back on the
stand and cover it up with a pair of floats.
 Gently fill the upper hopper with the sampled concrete to the level
of the rim with use of a scoop.
 Immediately open the trap door of the upper hopper and allow the
sampled concrete to fall into the middle hopper .
 Remove the floats on top of the bottom cylinder and open the trap
door of the middle hopper allowing the sampled concrete to fall
the bottom cylinder.
 Remove the surplus concrete above the top of the bottom cylinder
by holding a float in each hand and move towards each other to
off the concrete across the top of cylinder.

20.  Wipe clean the outside of cylinder of concrete and weigh to
nearest 10gm.
 Subtract the weight of empty cylinder from the weight of
cylinder plus concrete to obtain the weight of partially
compacted concrete.
 Remove the concrete from the cylinder and refill with sampled
concrete in layers.
 Compact each layer thoroughly with the standard Compacting
Bar to achieve full compaction.
 Float off the surplus concrete to top of cylinder and wipe it clean.
 Weigh the cylinder to nearest 10gm and subtract the weight of
empty cylinder from the weight of cylinder plus concrete to
obtain the weight of fully compacted concrete.
 The Compacting Factor Is Under :

21. Workability Slump (mm) C.F Uses
Very Low 0 - 25 0.78 Roads - Pavements
Low 25 - 50 0.85 Foundations Concrete
Medium 25 - 100 0.92 Reinforced Concrete
High 100 - 175 0.95 Reinforced Concrete (High
Reinforcement)

22. 3) Flow test
 Definition
The flow table test or flow test is a method to determine the
consistence of fresh concrete.
 Application When fresh concrete is delivered to a site by a truck
mixer it is sometimes necessary to check its consistence before
pouring it into formwork.
 If the consistence is not correct, the concrete will not have the
desired qualities once it has set, particularly the desired
strength. If the concrete is too pasty, it may result in cavities
within the concrete which leads to corrosion of the rebar,
eventually leading to the formation of cracks (as the rebar
expands as it corrodes) which will accelerate the whole process,
rather like insufficient concrete cover. Cavities will also lower the
stress the concrete is able to support.

23.  Equipment
 Flow table with a grip and a hinge, 70 cm x 70 cm.
 Abrams cone, open at the top and at the bottom - 30 cm high,
cm top diameter, 25 cm base diameter
 Water bucket and broom for wetting the flow table.
 Tamping rod, 60 cm height
 Scale for measurement

24.  Conducting
 The flow table is wetted.
 The cone is placed on the flow table and filled with fresh
concrete in two layers, each layer 25 times tamp with tamping
rod.
 The cone is lifted, allowing the concrete to flow.
 The flow table is then lifted up several centimeters and then
dropped, causing the concrete flow a little bit further.
 After this the diameter of the concrete is measured in a 6
different direction and take the average.

25. Percent of Flow 0 – 20 % 20 – 60 % 60 – 100 % 100 – 120 % 120 – 150 %
Consistency Dry Stiff Plastic Wet Sloppy

26. 4) Vee Bee Consistometer Test
 Definition
 It is based on measuring the time (Called VEBE time) needed to
transfer the shape of a concrete mix from a frustum cone to a
cylinder (these shapes are standardized by the apparatus of this
test), by vibrating and compacting the mix. The more VEBE time
needed the less workable the mix is. This method is very useful for
stiff mixes.
 Apparatus
 Cylindrical container with diameter = 240 mm, and height = 200
mm
 Mold: the same mold used in the slump test.
 Disc : A transparent horizontal disc attached to a rod which slides
vertically
 Vibrating Table : 380*260 mm, supported by four rubber shock
absorbers
 Tamping Rod
 Stop watch.

27.  Procedure
 Slump test as described earlier is performed, placing the slump cone
inside the sheet metal cylindrical pot of the consist meter.
 The glass disc attached to the swivel arm is turn and place on the top of
the concrete in the pot.
 The electrical vibrator is then switched on and simultaneously a stop
watch started.
 The vibration is continued till such time as the conical shape of the
concrete disappears and the concrete assume a cylindrical shape.
 This can be judge by observing the glass disc from the top
of transparency.
 Immediately when the concrete fully assume a cylindrical shape, the stop
watch is switched off.
 The time required for the shape of concrete to change from slump cone
shape to cylindrical shape in second is known as Vibe Degree.
 This method is very suitable for very dry concrete whose slump value
cannot be measure by slump test, but the vibration is too vigorous for
concrete with slump greater than about 50m.

28. 5) Kelly Ball Test
 Definition
Another method used in the field and laboratory to measure the
consistency of concrete is the ball penetration test (ASTM C360)
which is also known as the Kelly ball test.
 Procedure
 It is performed by measuring the penetration, in inches, of a 6-
in. diameter steel cylinder with a hemi spherically shaped
bottom , weighing 30 lbs.

29.  Advantages
 One of the advantages of the ball penetration test can be
performed on the concrete in a hopper, buggy, wheelbarrow, or
other suitable container.
 Another advantage of this method is its simplicity and the rapidity
with which the consistency of the concrete can be determined.
 It is also not dependent on a procedure of filling and rodding a
container like the slump test.

30. SEGREGATION
 Definition
 Segregation is when the coarse and fine aggregate, and cement
paste, become separated. Segregation may happen when the
concrete is mixed, transported, placed or compacted
• Segregation makes the concrete
 Weaker,
 Less durable,
 And will leave a poor surface finish

31.  Basic types of segregation
 Coarse segregation : Occurs when gradation is shifted to include
much coarse aggregate and not enough fine aggregate. Coarse
segregation is characterized by low asphalt content, low density,
air voids, rough surface texture, and accelerated rutting and fatigue
failure. Typically, coarse segregation is considered the most
prevalent and damaging type of segregation; thus segregation
research has typically focused on coarse segregation. The term
“segregation” by itself is usually taken to mean “coarse segregation.”
 Fine segregation : Occurs when gradation is shifted to include too
much fine aggregate and not enough course aggregate. High
asphalt content, low density, smooth surface texture, accelerated
rutting, and better fatigue performance characterize fine

32.  To Avoid Segregation
 Check the concrete is not 'too wet' or 'too dry'.
 Make sure the concrete is properly mixed. It is important that the
concrete is mixed at the correct speed in a transit mixer for at least
two minutes immediately prior to discharge.
 The concrete should be placed as soon as possible.
 When transporting the mix, load carefully.
 Always pour new concrete into the face of concrete already in
 When compacting with a poker vibrator be sure to use it carefully.

33.  To Avoid Segregation
 If placing concrete straight from a truck, pour vertically and never let
the concrete fall more than one-and-a-half meters.

34. BLEEDING

35. • Definition
Bleeding is the form of segregation in which some of the water from the
concrete comes out to the surface of the concrete , being of the lowest
specific gravity among all the ingredients of concrete . It is sometime
referred as water gain . It causes formation of aporous , weak and non-
durable concrete layer at the top of the concrete.
The main causes of bleeding are:
1) Highly wet mix
2) Badly proportioned mix
3) Insufficiently mixed concrete.
Bleeding is due to rise of water in the mix to the surface because of the
inability of the solid particles in the mix to hold all the mixing water
during the setting of the particles under the3 effect of compaction.

36. • Remedies of bleeding:
1) using rich mixes.
2) Using finer cement .
3) Proper proportioning the mx.
4) Uniform and sufficient mixing of concrete.
5) Use of finely divided pozzolanic materials create a longer path for the
water to traverse and reduced bleeding.
6) Use of air entraining agent is also effective in reducing the bleeding.

37. • Test for bleeding of concrete:
 In this test the relative quantity of mixing water that bleed from a sample of
freshly mixed concrete is determined.
 For this test a cylindrical container of approximately 0.01 m^3 capacity , having
internal diameter of 250 mm and inside height 280 mm is used.
 A freshly mixed concrete sample is filled in the container in 5 equal layers ,
each of about 50 mm thickness of a total depth of 250 mm . each layer is
tamped by giving 25 strokes using tamping rod of 16 mm diameter and 600
mm long with bullet end. The top surface of concrete is made smooth is a
calculated.
 The container is kept on a level surface free from vibration at a temperature of
27+ or 2 degree Celsius.it is covered with a lid . water accumulated at the top
surface of concrete is drawn by means of pipette at 10 minutes internal for the
first 40 minutes and at 30 minutes interval subsequently till bleeding stop . the
quantity of water collected is measured by measuring cylinder.
 Percentage of bleeding water = total quantity of bleeding water / total quantity
of water in the sample of concrete * 100.

38. ADMIXTER USED TO IMPROVE WORKABILTY
• Mainly three types of admixture are used to improve workability
of concrete.
1) Air entraining agents :
Air entraining incorporate millions of minute spherical air bubbles,
which will act as flexible ball bearing and will modify the properties of
plastic concrete regrading workability , segregation and bleeding.
 Natural wood resins. Vinsol resin
 Animal and vegetable fats and oils,
 Water soluble soaps of resin acids.

39. 2) Water reducing agents:
The use of plasticizer reduces the water/cement ratio for the given
workability which naturally increase the strength of concrete
FOR E.G
 Calcium chloride
 Sodium lingo-sulponate.
3) Finely divided material:
 Benfinite clay
 Fly ash
 Fine silica
 Hydrated lime , talc etc.

40. PRODUCTION OF CONCRETE
The good quality concrete is a homogeneous mixture of cement , C.A. ,F.A. , water
and other admixtures . It is just a matter of mixing these ingredients to obtains
some kind of plastic mass, but it is a specific process which is based on some well
established principles and governs the properties of concrete in fresh as will as in
hardened state.
• Stages for production of concrete :
1) BATCHING
2) MIXING
3) TRANSPORTING
4) PLACING
5) COMPACTING
6) CURING
7) FINISHING

41. 1) BATCHING
Batching is the process of measuring concrete mix ingredients by either mass
or volume and introducing them into the mixer. To produce concrete of
uniform quality, the ingredients must be measured accurately for each batch.
There are two method of batching or aggregate:
1) Volume batching
2) Weight batching
1) Volume batching:
 This method is generally adopted for small jobs .
 Gauge boxes are used for measuring the fine and
coarse aggregate.
 The volume of gauge box is equal to the volume of one bag of cement.

42.  Gauge bow are also called as FARMAS
 They can be made of timbers or steel.
 They are made generally deep and narrow
 Bottomless gauge boxes are generally avoided.
 While filling the gauge boxes the material should be filled loosely , no
compaction is allowed.
2) Weigh Batching:-
 Batching by weight is more preferable
to volume batching ,as it is more accurate and leads to more uniform
proportioning.
 It does not have uncertainties associated with bulking

43. 2) MIXING
 The mixing should be ensured that the mass becomes homogeneous ,
uniform in colour and consistency .
Methods of Mixing :
1) Hands(using hand shovels)
2)Stationary Mixers
1) Hand Mixing:-
 Mixing by hands using ordinary tools like
hand shovels etc.
 This type of mixing is done for
 less output of concrete.

44. 2) Stationary mixer :-
Concrete is sometime mixed at jobsite in a stationary mixer having a size of 9
cubic meter.
These mixers may be of :
• Tilting type ,
• Non-Tilting type ,
Tilting type mixer:-
 It consist a conical drum which
rotates on an inclinable axis.
 It has only one opening.
 The drum charged directly and discharged
by tilting and reversing the drum.

45. Non tilting type mixer:-
 The mixing drum is cylindrical
in shape and revolves two –
horizontal axis.
 It has opening on both sides.
 The ingredients are charged
in from one opening.
 For discharging concrete chute
is introducing to other opening
by operating a lever.

46. 3) TRANSPORTING
1) Mortar Pan :
 Concrete is carried in small Quantities
2) Wheelbarrows and Buggies:
 The capacity of wheelbarrows varies
 from 70 to 80 litres .
 Suitable for concrete road construction where
concrete is deposited at or below mixer level.

47. 3) Belt Conveyors:
Conveying concrete horizontally
or higher/lower level.
4) Cranes and Buckets:
Used for Work above ground level ,
Buckets use with Cranes, cableways,
and helicopters.

48. 5) Pumps:
 Conveying concrete from
central discharge point to
formwork.
6) Transit Mixe:
Used for transporting the concrete
over long distance particularly in
RMC plant .

49. 4) PLACING OF CONCRETE
Th process of depositing concrete in its required position is termed as placing.
Concrete should be placed in systematic manner to get optimum results.
Precautions:-
 Placing concrete within earth mould:-
• Concrete is invariable as foundation bed below the walls and columns before
placing concrete.
• All loose earth must be removed.
• Roots of trees must be cut.
 Placing concrete in layers with in timber or steel shutter :-
• Dam construction
• Construction of concrete abutments
• Raft for a high rise building
• Size if vibrator.

50.  Placing concrete with in usual form work:-
• Adopted for column,beam and floors rules that should be followed while
placing the concrete.
• Check the reinforcements are correctly tied and placed.
• Mould releasing agent should be applied.
 Placing concrete under water:-
• Concrete having cement content at least
450kg/m3 and a slump of
10 to 17.5cm can be
placed underwater.

51. 5) COMPACTION OF CONCRETE
 Compaction of concrete is process adopted for expelling the
entrapped air from the concrete
 In the process of mixing , transporting and placing of concrete air is
likely to get entrapped in the concrete .
 It has been found from the experimental studies that 1% air in the
concrete approximately reduces the strength by 6%.
 If we don’t expel this air, it will result into honeycombing and
reduced strength
• Different Methods Of Concrete Compaction:-
1) Hand Compaction
2) Compaction by Vibration:

52. 1) Hand Compaction:-
 Hand compaction is used for ordinary and unimportant structures.
Workability should be decided in such a way that the chances of
honeycombing should be minimum. The various methods of hand
compaction are as given below:
• Rodding:
 It is a method of poking with 2m
long, 16 mm dia. rod at sharp
corners and edges. The thickness
of layers for rodding should be
15 to 20 cm.

53. • Ramming:
 It is generally used for compaction
on ground in plain concrete. It is not
used either in RCC or on upper floors.
• Tamping:
 It is a method in which the top surface
is beaten by wooden cross beam of
cross section 10 cm x 10 cm.
 Both compaction and leveling are
achieved simultaneously.
 It is mainly used for roof slabs and road
pavements.

54. 2) Compaction by Vibration:-
 Vibration is imparted to the concrete by mechanical means.
 It causes temporary liquefaction so that air bubbles come on to the top and
expelled ultimately.
 Mechanical vibration can be of various types as given under.
• Internal Vibration:
 It is most commonly used technique of concrete vibration.
 Vibration is achieved due to eccentric weights attached to the shaft.
 The needle diameter varies from 20 mm to 75 mm and its length varies from 25
cm to 90 cm.
 the frequency range adopted is normally 3500 to 5000 rpm.

55. • Table Vibration:
 It is mainly used for laboratories where
concrete is put on the table.
• Platform Vibration:
 It is similar to table vibrators but these
are generally used on a very large scale.
• Surface Vibration:
 These are also called screed board
vibrators.
 The action is similar to that of tamping.

56. 6) CURING
 Curing can be defined as a procedure for insuring the hydration of the
Portland cement in newly-placed concrete.
 Curing is the process in which the concrete is protected from loss of
moisture and kept within a reasonable temperature range.
 The result of this process is increased strength and decreased
permeability.
 Curing is also a key player in mitigating cracks in the concrete, which
severely impacts durability.

57.  Method Of Curing:-
1) water curing:-
 It consist in the application of water directly to the concrete or by
means of wet coverings of earth, sand, dust, etc
• Immersion:
 The precast concrete items are normally immersed in curing tanks..
• Ponding:
 Pavement slabs, roof slab etc. are covered under water by
making small ponds
• Spraying :
 Vertical retaining wall or plastered surfaces or concrete columns
etc. are cured by spraying water.
• Wet covering:
 Wet gunny bags, hessian cloth, jute matting, straw etc., are wrapped
to vertical surface for keeping the concrete wet.

58. 2) Membrane curing:-
 In it, concrete is covered with membrane which effectively
seal off the evaporation of water from concrete.
 It is carried out at the interface of the ground and concrete
to prevent the absorption of water by the ground from the
concrete.
 Membrane curing maintains a satisfactory state of wetness
in the body of concrete to promote continuous hydration
when original water/cement ratio used is not less than 0.5.
3) Application of heat:-
 Subjecting the concrete to higher temperature and
 Maintaining the required wetness can be achieved by
subjecting the concrete to steam curing.

59. 7) FINISHING
 The finish can be strictly functional or decorative.
 Finishing makes concrete attractive and serviceable.
 The final texture, hardness and joint pattern on slabs, floors,
sidewalks, patios and driveways depend on the concrete's end use.

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