Understanding concrete

1. Seminar by : Arivusudar NagarajanSeminar by : Arivusudar Nagarajan

2. 2
CEMENT REPLACEMENT
MATERIALS
FLY ASH
 It is finely divided residue resulting from the combustion
of powdered coal and transported by the flue gases and
collected by electrostatic precipitator ( Thermal Power
plants)
 Mostly used pozzolonic material
 Reference IS-3812
Contd…

3. 3
 Savings in cement
 Reducing heat of hydration
 Reducing water demand
 Spherical shape and smooth surface of flyash helps to
reduce the inter-particle friction and thus facilitates
mobility.
 Reduce Bleeding and drying shrinkage.
 Fly ash particles plasticize cement paste and improves
flowability and rheology of the mix.
 Contributes to strength
Contd…
ADVANTAGES OF FLY ASH

4. 4
CEMENT
+ C-S-H Gel + Ca(OH)2
WATER
FLYASH C-S-H Gel
SECONDARY HYDRATION OF FLY
ASH

5. 5
PETROGRAPHIC VIEW OF FLY ASH

6. 6

7. 7
FLYASH-PARTICLE PACKING
EFFECT
FLYASH

8. 8
Cement Flyash
BALL BEARING EFFECT

9. 9
Trapped Water
DISPERSION OF CEMENT
PARTICLES WITH FLY ASH

10. 10
 By-product from steel Industries.
 Specific surface of about 400-600 m2
/kg
 Higher cement replacement levels upto 70%
 Glass content 85% (Min)
 Blended with cement
 Secondary hydration
Slag (GGBS)

11. 11
 Reduces water demand
 Water can be reduced based on slag content and fineness
of slag
 Reduces bleeding
 Water retention
 Improves workability
 Increases Pumpability
Effect of GGBS on Fresh Concrete

12. 12
 Reduces heat of hydration
 Improves the pore structure
 Reduces permeability
 Improves resistance to corrosion of reinforcement
 Increased resistance to chemical attack
 Higher ultimate strength
 Saving cement in concrete mix
Effect of GGBS on Hardened
Concrete

13. 13
 Condensed Silica Fume is a by product of ferro-Silicon
alloy industry and it is the dust which is collected from
furnace exhaust system
 Fineness of silica fume is @ 15000 m2
/kg as against 280 to
290 m2
/kg of Cement
 Contributes significantly to compressive strength due to
micro-filler effect and excellent pozzolanic properties
 Leads to increase in density and reduction of permeability
in concrete
 It’s use is must for manufacturing of concrete above M50
Contd…
SILICA FUME (Micro Silica)

14. 14
SILICA FUME

15. 15
Admixtures are materials mostly chemicals that are added in small
quantities during the preparation of concrete to impart certain specific
properties to it.
The requirements may be
 Improving the workability of concrete during placing
 Retarding or accelerating setting
 Improving the impermeability and water tightness of the cast
concrete.
 Imparting corrosion inhibition etc
 Entraining air in concrete
Chemical Admixtures

16. 16
Compatibility test by
Marsh Cone Apparatus

17. 17
DEFLOCCULATION OF CEMENT
PARTICLES

18. 18
DISPERSION OF MECHANISM

19. Dispersion Mechanism
 Electro static repulsion
 Steric Hindrance
19

20. 20
EFFECT OF SUPER PLASTICISER
ON WORKABILITY

21. 21
SLUMP : Collapse

22. 22
EFFECT OF SUPER PLASTICISER
ON WORKABILITY

23. 23
PUMPABLE CONCRETE

24. 1. Air entrainers :
TYPES OF ADMIXTURES
They entrain air in the form of micro air bubbles which
helps in improving the durability of concrete in freezing
environment, sulphate and alkali attack.
2. Water reducers
To reduce the water-cement ratio and yet retain
workability. It is possible to reduce water upto 12%.
The only precaution is that it should be mixed thoroughly

25. 3. Accelerating admixtures :
To accelerate setting of cement in
cold environment or where early setting is desired.
It assists in early removal of form work
4. Retarding admixtures :
To delay the setting time of concrete, for RMC supplied
to far off sites.
Prolongs setting time, giving higher strength at later
stages, also results in reduction in micro cracks.

26. 5. Super plasticisers :
To make flowing concrete for concreting in
heavily reinforced sections, tremie concrete, for
pumping concrete.
(when added to normal concrete with 75mm slump
upto 250mm can be achieved)
6. High range water reducers :
PC based admixtures
Water reduction capacity of about 25-40%
High performance
Early strength and early setting

27. 7. Bonding agents :
To increase bond strength,
old and new concrete(in repair and rehabilitation works),
they are usually modified latex or polymer compounds
8. Corrosion inhibitors :
To inhibit corrosion

28.  Aggregate is the word used to describe any inert material .
 Usually rock derivative generally between 50mm down to 75 micron
used to produce concrete .
 It is divided into coarse aggregate and fine aggregate
 Those which are 4.75mm to 50mm are classified as coarse aggregates
 Those below 4.75mm to 75 micron as fine aggregates
 Except for mass concrete in dams etc. which may contain upto 150mm
size aggregate, the maximum size of aggregate is normally 20mm in
most cases
 But it may be 40mm for plain concrete or massive works.
28
AGGREGATES

29. 29
 Specific gravity: it should have good crushing strength
and density
 Surface texture: it should be smooth,slightly rough but
not honeycombed
 Particle shape : it should not be flaky or elongated.
 Porosity : it should have very low water absorption
 Should not be Reactive
PROPERTIES OF COARSE
AGGREGATES

30.  Water demand,
 Workability
 Cohesion of concrete in plastic state
 Strength,
 Density,
 Durability
 Porosity of hardened concrete
 Stability : it should be chemically inert.
 Impurities: it should be free from impurities (like silt,
clay)
 Compactness: it should be graded, as then only the
voids can be less.
30
PROPERTIES OF AGGREGATE
EFFECT

31.  Specific gravity implies the absolute weight per unit volume
of aggregates
 A low specific gravity may indicate
 high porosity
 poor durability
 low strength.
 Specific gravity of aggregates is used in arriving at mix
design
 Generally the specific gravity of good aggregates is greater
than 2.5 g/cm3
31
SPECIFIC GRAVITY

32.  Surface texture reveals how grainy or smooth the surface
of the aggregate is.
 It indicates bonding strength and porosity.
 Higher the smoothness of the particle, lesser is the
bonding between aggregate and cement matrix.
 rough textured aggregates develop higher bond strength
than smooth textured aggregates,
 This property is especially considered while producing
high strength concretes.
32
SURFACE TEXTURE

33. Particle shapes are classified as
 Irregular
 Rounded
 Flaky
 Angular
 Aggregates should be as much cubical as possible in
shape
33
PARTICLE SHAPE

34.  Grading of aggregates means particle size
distribution of the aggregates.
 Principle of grading is that smaller size particles
fill up the voids left in larger size particles.
34
GRADING

35. IS sieve
Designatio
n
Percentage passing for single size aggregate of nominal size by
weight
63 mm 40mm 20 mm 16 mm 12.5 mm 10 mm Remarks
80 mm 100 - - -
63 mm 85-100 100 - -
40 mm 0-30 85-100 100 -
20 mm 0-5 0-20 85-100 100
16 mm - - 85-100 100
12.5 mm - - - 85-100 100
10 mm 0-5 0-5 0-20 0-30 0-45 85-100
4.75 mm 0-5 0-5 0-10 0-20
2.26 mm - - - 0-5
35
GRADING OF COARSE
AGGREGATE

36.  Indian standards divides the sand into four zones
 zone-I to zone-IV based on the sieve analysis
 Sand falling in zone-I is coarse and that falling in
zone-IV is fine.
 Sand falling in zone IV shall not be used for
reinforced concrete work.
 Fineness modulus for sand : ranges from 2.2 to 3.2,
higher value indicates coarser grading
36
SAND

37. 37
IS sieve
designation
Percentage passing
Zone-I Zone-II Zone-III Zone-IV
10 mm 100 100 100 100
4.75 mm 90-100 90-100 90-100 90-100
2.36 mm 60-95 75-100 85-100 95-100
1.18 mm 36-70 55-90 75-100 90-100
600 microns 15-34 35-59 60-79 80-100
300 microns 5-20 8-30 12-40 15-50
150 microns 0-10 0-10 0-10 0-15
Remarks Very coarse Coarse Medium Fine
REQUIREMENT OF FINE
AGGREGATES

38.  Water helps in dispersing the cement evenly
 Quality of water for making concrete and for
curing
 Water should be free from salts, oils, acids,
alkalis, sugar and organic materials
 pH value shall not be less than 6
 Sea water is not suitable for making concrete
38
WATER

39. SL.
No.
Description Tested as per Permissible limit (max) mg/l
1 Organic IS-3025(part-18) 200
2 Inorganic IS-3025(part-18) 3000
3 Sulphates (as SO3)
Sulphates (as SO4)
IS-3025(part-24)
IS-3025(part-24)
400
500
4 Chlorides (as Cl) IS-3025(part-32) 2000 mg/l for concrete not
containing embedded steel
1000 mg/l for RCC work
5 Suspended matter IS-3025(part-17) 2000
39
PERMISSIBLE LIMITS FOR SOLIDS IN
WATER

40. FRESH CONCRETE
 Fresh concrete is a freshly mixed material which can
be moulded into any shape.
 Workability: is the ease with which fresh concrete
can be mixed, transported, placed and compacted
in the moulds or forms
 Apart from water-cement ratio the concrete has to
be compacted well to get the required strength
40
UNDERSTANDING CONCRETE

41. TESTS ON FRESH CONCRETE
 WORKABILITY
1. Slump Test
2. Compaction Factor Test
3. Flow Test.
 Yield Test

42. 42
 It is the science of the deformation and flow of
materials and is concerned with relationships
between stress, strain, rate of strain and time.
 The term Rheology deals with the materials
whose flow properties are more complicated
than those of fluids (liquids or gases)
RHEOLOGY OF CONCRETE

43. Factors affecting workability:
 Water content
 Mix proportions
 Size of aggregates
 Shape of aggregates
 Surface texture of aggregate
 Grading of aggregate
 Use of admixture
43

44. Segregation:
 Segregation can be defined as the separation of the
constituent materials of concrete.
Bleeding:
 Sometimes referred as water gain
 It’s a particular form of segregation due to
highly wet mix
 If water cement ratio is more than 0.7
 Badly proportioned and insufficiently mixed
concrete
44

45. BLEEDING
45
 While traversing from bottom to top
 Bleeding channels responsible for permeability
 It may be interrupted by aggregates (flaky)
 It may be interrupted by reinforcement
 Reduces bond between reinforcement,
aggregate and paste
 Remedy— re-vibration, delayed finishing

46. Cement – 3.15
Coarse aggregate – 2.70
Sand – 2.60
Water – 1.00
Fly ash – 2.15
Silica Fume - 2.20
46
SPECIFIC GRAVITY

47.  Compaction of concrete is the process
adopted for expelling the entrapped air from
the concrete.
 The entrapped air in the form of voids reduces
the strength of concrete.
 For every 1% of entrapped air, the strength of
concrete falls about 5% to 6%.
47
COMPACTION

48.  Hand compaction
 Tamping
 Ramming : generally permitted for
unreinforced foundation concrete
 RCC should never be rammed
 Compaction by vibration: common needle
vibrator dia is 25mm to 40mm
 External vibrators
 Surface vibrators
48
METHODS OF COMPACTION
Contd…

49.  When inserting a needle vibrator, allow it to
penetrate the bottom of the layer as quickly as
possible.
 If it is done slowly, the upper part of the
concrete will get compacted and prevent the
air in the bottom layer from escaping.
 The vibrator should be left in the concrete for
about 10 sec. and then withdrawn slowly. If it is
withdrawn fast, a hole will be left in the
concrete.
49
PRECAUTIONS
Contd…

50.  The vibrator should be inserted again at a
distance of not more than 50 cm from its last
position.
 The vibrator should not be allowed to touch
the face of the form work or the reinforcement
to prevent the reinforcement from losing bond
with concrete
 Do not stop the vibrator when the needle is in
the concrete.
 Do not over vibrate or under vibrate
50

51. 51
 The rate of levelling should not be less than
the rate placing of concrete
FINISHING OF CONCRETE

52. 52
 Effect ofWater-Cement ratio
 Effect of maximum size of aggregate on
strength
 Grades of concrete:
 Concrete in construction is specified by grade
like M20,M25 etc. Usually increments of five.
 M20 means the specified crushing strength is
20 N/mm2
STRENGTH OF CONCRETE

53. 53
CURING
 Why Curing ?
 To prevent loss of moisture from the Concrete due
to combined effect of hot sun and drying wind
 Creation of conditions for promotion of
uninterrupted and progressive hydration of
cement during the period immediately after
placing
 Curing does not mean only application of water
HARDENED CONCRETE

54. 54
1. WATER CURING
2. MEMBRANE CURING
3. APPLICATION OF HEAT (Steam Curing)
4. ACCELERATED CURING
CURING METHODS

55. 55
 Sampling Criteria
 CubeTesting
 Acceptance Criteria
 Non DestructiveTesting of Concrete
1. Rebound HammerTest
2. Ultra sonic pulse velocity testing
 CoreTest
COMPRESSIVE STRENGTH

56. 56
OTHER CONCRETES :
 High strength concrete
 High performance concrete
 Mass Concrete
 Light-weight concrete
 High-density concrete
 No-fines concrete
 Roller compacted concrete
 Ferrocement
 Self compacting concrete.

57. 57
HIGH STRENGTH CONCRETE
 CONCRETE GRADE FROM M60 ONWARDS
REGARDED AS HIGH STRENGTH CONCRETE
 FOR HIGH STRENGTH CONCRETE DESIGN
STANDARDS GIVEN INTHE CODE IS-456-2000
MAY NOT BE APPLICABLE
 THEY HAVETO BE OBTAINED FROM SPECIFIED
LITERATURES OR BY EXPERIMENTAL RESULTS
SPECIAL CONCRETES

58. 58
POSSESSING
1. HIGHWORKABILITY
2. HIGH STRENGTH
3. HIGH DENSITY
4. HIGH DIMENSIONAL STABILITY
5. LOW PERMEABILITY
6. RESISTANCETO CHEMICAL ATTACK
HIGH PERFORMANCE CONCRETE

59. 59
NORMAL CONCRETE
 HEAVY SELFWEIGHT
(DENSITY 2200 to 2600 KG/M3
)
LIGHT WEIGHT CONCRETE
 DENSITY (300 to 1850 KG/M3
)
 LOWTHERMAL CONDUCTIVITY
LIGHT WEIGHT CONCRETE

60. 60
 DENSITY 3360TO 3840 KG/M3
EVEN 5280
KG/M3
USING IRON AS BOTH F.A. AND C.A
 DENSITY 50% HIGHERTHANTHE
CONVENTIONAL CONCRETE
 USED AS A SHIELDING MATERIAL FOR
PROTECTION FROM RADIATION
HIGH DENSITY CONCRETE

61. 61
 It is made by introducing air or gas into the
slurry composed of cement and finely
crushed sand by alluminium powder.
 Uniformly cellular structure is formed.
 Also called as gas concrete, foam concrete,
cellular concrete
AERATED CONCRETE

62. 62
 By Omitting fine aggregate fraction
 Made by cement, water and single sized coarse
aggregates
 Having large voids and hence light in weight
 Applications
 Temporary structures
 In external walls forThermal insulation
 Rough texture gives good base for plastering
 Free from dampness because of low capillary action
on account of large voids
NO-FINES CONCRETE

63. ROLLER COMPACTING CONCRETE
 Recent development particularly in the
field of Dam construction.
 Lean mix
 No slump concrete
 High volume fly ash to the extent of 60 to
65%
 Compacted by Rollers.
 Compressive strength of about 7 Mpa to
30 Mpa

64. FERRO CEMENT
 It is a relatively new material consisting of wire
meshes and cement morar.
 Thickness of elements is 2 to 3 cm
 Water –cement ratio 0.4 to 0.45
 Cement -sand ratio 1:2
 External cover to reinforcement is 2 to 3mm

65. APPLICATIONS OF FERROCEMNT
 FOR CASTING DOMESTIC OVER-HEAD
WATER TANKS
 FOR TANKS USED AS GRAIN SILOS IN
VILLAGES
 FOR CONTAINER USED AS GAS HOLDER
UNIT IN “GOBBAR GAS” PLANTS.
 IDEAL MATERIAL FOR BOAT BUILDING
 FOR MANHOLE COVER

66. SELF COMPACTING CONCRETE
 Self levelling concrete
 With Super plasticizer (Glenium )
 Fines
 Should not be vibrated
 Applications
Precast units.

67. MASS CONCRETE
 It’s is a concrete having considerable dimensions
that may get affected by thermal behavior of
Concrete. Ex-Concrete Dam
 Members with minimum cross sectional
dimension of a solid concrete member
approaches or exceeds 2 to 3 ft
 Cement contents above 364 kg/m3

68.  It is a latest development in the construction
industry
 Concrete is batched and mixed in a centralised
Plant and transported to the sites far-away
from the plant through Transit-Mixers and
placed through pumps to the required height
and distances.
68
RMC (READY MIX CONCRETE)

69. 69

RMC PLANT

70. 70
PLANT LAYOUTPLANT LAYOUT

71. 71
CONVEYOR BELT

72. 72
DOUBLE SHAFT MIXER

73. 73
BATCHING PLANTBATCHING PLANT

74. CONCRETE PUMPS
74

75. TRUCK MOUNTED BOOM PUMPS
75

76. RMC PLACEMENT THROUGH BOOM PUMPS
76

77. 77
RMC PLACEMENT THROUGH BOOM
PUMPS

78. ANY QUESTIONS ?
78

79. THANK YOU
79