1. CONCRETE TECHNOLOGY

2. CONTENTS Unit-I: Cements & Admixtures Unit-II: Aggregates
Unit-III: Fresh Concrete
Unit-IV: Hardened Concrete
Unit-V: Testing of Hardened Concrete
Unit-VI: Elasticity, Creep & Shrinkage
Unit-VII: Mix Design
Unit-VIII: Special Concretes

3. Unit-I: CEMENTS & ADMIXTURES
Learning Objectives and Lecture Plan :
Topic
No. Of Hours
Introduction to binding materials, manufacture of Portland cement 01
Chemical composition of Portland cement
Hydration and strength development
Physical properties and tests
Grades of cement
Admixtures –mineral admixtures and their effects on properties of concrete
Chemical admixtures and their effects on properties of concrete
Review, Tutorial & Assignment

4. INTRODUCTION
Concrete is the most widely used man-made construction material in the world.
It is obtained by mixing cementitious materials, water and aggregates in required proportions.
The mixture when placed in forms and allowed to cure, hardens into a rock-like mass known as concrete.
The hardening is caused by chemical reaction between water and cement.

5. 1.Introduction to binding materials
Ingredients of Concrete:
Cement
Aggregates
Fine
Coarse
Water
Admixture

6. CEMENT
Cement is a fine, soft, powdery-type substance. It is made from a mixture of elements that are found in natural materials such as limestone, clay, sand and/or shale. When cement is mixed with water, it can bind sand and gravel into a hard, solid mass called concrete.
Cement mixed with water, sand and gravel, forms concrete. Cement mixed with water and sand, forms cement plaster. Cement mixed with water, lime and sand, forms mortar.
Cement powder is very, very fine. One kilo (2.2 lbs) contains over 300 billion grains, although we haven't actually counted them to see if that is completely accurate! The powder is so fine it will pass through a sieve capable of holding water.

7. Cement is a material having adhesive and cohesive properties capable of binding mineral fragments into a compact mass.
OPC – Ordinary Portland cement
Name Portland due to resemblance of colour and quality of the set cement to Portland stone, a limestone quarried in a place ‘Dorset’ in UK
OPC – Ordinary Portland cement obtained by intimate mixing of mainly
Calcarious material – lime stone or chalk
Argillaceous material – clay/shale
Silicious material – Silica
Burning at C results in 3-25 mm clinkers
Clinkers finely grounded to get OP Cement

9. Oxides % Used
CaO %
SiO %
Al2O3 3-6%
Fe2O3 1-4%
MgO %

10. COMPOUNDS OF CEMENT S.No Name of Compound Oxide composi-tion Abb.
Approx %age 1
Tri calcium Silicate
3CaO. SiO2
C3S
39-50% 2
Di calcium Silicate
2CaO.SiO2
C2S
20-45% 3
Tri calcium Aluminate
3CaO.Al2O3
C3A
8-12% 4
Tetra calcium Alumino ferrite
4CaO.Al2O3Fe2O3
C4AF
6-10%

11. Function Oxide composition
C3S
Mainly responsible for early strength (1 to 7 days)
C2S
Mainly responsible for later strength (7 days & beyond)
C3A
C3A gives flash set in absence of gypsum
C4AF
It hydrates rapidly but its contribution to strength is uncertain and generally very low.

18. Different types of cement
OPC
Rapid hardening
Sulphate resistant-C3A, C4AF Controlled
Blast furnace slag –ggbfs(20-65% added) In Rly allowed in PSC works upto 50 % only
Quick setting- reduce gypsum content
Air entraining
Expansive – sulphoaluminate (8-20% added)
High alumina cement

19. TESTING OF CEMENT
Field testing – for quick appreciation
Laboratory testing – for confirmed quality

20. FIELD TESTING
Date of manufacture –
Because aging reduces the strength
Open the bags – No lumps should be present (Mean no setting)
Thrust your hand into the cement - There should be cool feeling (means no heat of hydration no setting)
Pinch of cement between fingers-It should give smooth feeling (means no setting).

21. Period of storage %age of 28-days strength
Fresh %
3 months %
6months %
12months %
24 months %

22. FIELD TESTING Contd ..
Handful of cement thrown on water -It should float initially before finally settling
Take 100 gm of cement, make stiff paste, prepare cake with sharp edges, put on glass plate and Immerse in water
Shape shouldn’t be disturbed
It should set and attain strength.

23. LABORATORY TESTING Fineness Test Setting Time Test Strength Test
Soundness Test
Heat of Hydration Test
Chemical Composition Test

24. LABORATORY TEST -i
Fineness of cement by dry sieving (IS – 4031 – 1968)
100 gm cement taken
Hand sieving for 15 minutes on 90  IS sieve
Residue on sieve weighed
For OPC limit of residue = 10%
PPC,HSOPC, SGC residue = 5%
More fineness increases only the early strength not the ultimate strength.

25. LABORATORY TEST -i Contd ..
Fineness of cement by Air Permeability Method

26. constant value of h1/h2. Specific surface Sw is calculated from the following formula:
where, ξ = Porosity, i.e., A= Area of the cement bed L= Length (cm) of the cement bed d = Density of cement, and C= Flowmeter constant

27. LABORATORY TEST -ii
Standard consistency test (IS : )
Apparatus used : Vicat’s Apparatus
Measured cement & water taken to make paste.
Mould filled within 3-5 minutes from adding of water at room temperature (270 C + 2 c)
Mould kept in position so that Vicat plunger touching paste
Plunger released quickly & reading on scale noted
Water adjusted such that penetration is 5-7 mm from bottom of mould
This water content (% by wt. Of cement) is called STANDARD CONSISTENCY ‘P’

30. INITIAL SETTING TIME (IS : 4031)
Time required from addition of water to time the paste starts loosing its plasticity
Procedure : Apparatus : Vicat’s apparatus
Cement paste of 0.85 P made. Time noted
Vicat’s needle lowered to touch the paste in mould
Needle released quickly, Initially it may touch the bottom of mould
Time noted when needle stops 5 mm mm above bottom of mould
This time is called ‘Initial Setting Time.’

31. FINAL SETTING TIME (IS : 4031)
Time required from addition of water to time the paste completely looses its plasticity
Procedure : Same as above except needle attachment is changed. Initially when needle lowered – There are two impressions one of needle and other of circular cutting edge
Final setting time – when the circular cutting edge fails to make an impression.

33. SOUNDNESS (IS : 4031)
This test is correlated to ‘expansibility of cement during setting.’
Apparatus : Le-Chatelier apparatus
Step 1 :
Paste of 0.78 P consistency prepared
Paste filled up in mould
Glass plates placed at bottom and top
Assembly kept in water at 270C – 320C for 24 Hours.
After 24 hours distance ‘X’ between pointers recorded

34. 30 mm dia, 30 mm. Ht, 165 mm length brass split cylinder with pointer

35. Step 2 :
Again submerged in water & water brought to boiling point in about 30 minutes ( i.e. controlled heating done)
Kept in boiling water for 3 hrs
Distance between pointers ‘Y’ recorded
Expansion = Y-X
It should be max 10 mm for all cements except special grade cement SGC i.e. Gr. 53 for which it should be 5 mm).

36. STRENGTH (IS: 4031)
Material for each cube is mixed separately.
Cement 200 gms + Sand 600 gms and
Water =
mixed for 3 – 4 minutes & filled in mould (7.06 cm cube)
& kept on standard vibrating table for compaction.
kept in mould for 24 hrs at 270C + 20C & further cured at 90% relative humidity
cubes tested at 1, 3, 7, 28 days for different cements. Average of 3 cubes taken as compressive strength.

38. QUALITY CONTROL IN CEMENT
Obtain test certificate from company
Every bag should carry these markings
Ref. to IS : specification
Wt. of bag in Kg or other method
Week/year of packing i.e. 33/2002
Type of cement
Record of daily variation in cement strength as tested in plant
Good plants will not hesitate in providing

39. PROPERTIES REQUIRED OF DIFFERENT CEMENTS

57. Unit-II: AGGREGATES Learning Objectives and Lecture Plan : Topic
No. Of Hours
classification of aggregates, shape & texture of aggregates. 01
Strength and mechanical properties of aggregates.
Specific gravity, Bulk density, porosity and absorption of aggregates.
Moisture content & bulking of sand , deleterious substances in aggregates.
Soundness of aggregates - Alkali aggregate reaction.
Thermal properties.
Sieve analysis and fineness modulus.
Grading zones of fine aggregate, grading of coarse aggregate.
Grading curves, gap graded aggregate and size of aggregate.

58. FINE AGG
Which passes through 4.75 mm IS sieve
(5-10% oversize permitted by IS : )
Coarse Agg : Which are retained on 4.75 mm IS : sieve
(5-20% passing the sieve are permitted )

59. AGGREGATES
Occupy 70 – 75 % of total volume of concrete
Though earlier viewed as inert material, it is no more considered so now
Physical, chemical & thermal properties of aggregates do influence the performance of concrete

60. SOURCES OF AGGREGATES
Igneous rocks : Hard, tough & dense. Granite,Basalt
Sedimentary rocks : Lime stone make good aggregate.
Metamorphic rocks : Slate, gneiss,marble, make good aggregate.
(Acquired properties equally important apart from source)

61. Properties of Aggregate & Influence on Concrete Properties
1 Sp. Gr
Strength
2 Porosity
Absorption
3 Texture
Bond Grip
4 Shape
Water Demand(Strength)
5 Gradation
Water Demand,Cohesion, Bleeding,Segregation
6 Max Agg Size
7 Chemical Stability
Durability
8 Deleterious Materials

62. PHYSICAL PROPERTIES OF AGGREGATE
Shape (IS : 383 – 1970)
It affects – workability &
– cement requirement
Angularity No. = * /G
When voids are 33 % =0.67G
Angularity No.= rounded agg.
Max. Angularity No. =11 when voids=44%
i.e =0.56G

63. PHYSICAL PROPERTIES OF AGG contd
Texture
It defines the surface of aggregates
Smooth – Requires less cement
– Permits denser packing
– Permits better workability
Rough – High bond strength in tension.
Requires less cement

64. Max Aggregate Size should be as large as possible to reduce water demand. But
Limitation:
Mini dimension of section 4*MAS
Mini cover MAS+5mm
Clear distance between Reinforcement  MAS+5mm

65. PHYSICAL PROPERTIES ..ii
ABSORPTION
Bone dry aggregates absorbs certain amount of water. It affects
Workability
W/C ratio
Durability
Porosity affects durability as it is harmful under conditions of alternate freezing and thawing.
(But the rate and amount of absorption is significant only up to final setting time.)

66. Aggregate dryness Bone Dry- When internal pores are all dry.
Air Dry- When some of the pores are dry.
Saturated Surface Dry (SSD)- When all the pores are filled.
Saturated-When all the pores are filled & if water is also sticking on surface

68. PHYSICAL PROPERTIES ..iii
BULK DENSITY & SPECIFIC GRAVITY
Bulk density in loose state is directly proportional to sp. Gravity of aggregate and angularity
Bulk density = wt. of agg. in cylinder
volume of cylinder.
Sp. Gravity for rock should be 2.6 to 2.8

69. AGG. CRUSHING VALUE (ACV)
Agg. passing 12.5 mm & retained over 10 mm IS sieve taken for test.
Agg dried in oven at C for 3-4 hrs.
Filled up to 10 cm in 3 layers in cylinder by 25 stroke of tamping rod (wt. Of sample = A)
Surface is levelled & then crushing load of 40 T applied in 10 minutes
Sieved on 2.36 mm IS sieve
Fraction passing the sieve = B
ACV = B/A x 100
ACV < 30% for roads and pavements
< 45% for other structures.

71. AGG IMPACT VALUE (IS : 2386- Pt. IV – 1963)
Same procedure as ACV test upto applying loading
Here 15 blows of hammer (interval not less than 1 sec)
Sieved through 2.36 mm IS sieve
Fraction passing through sieve = B
AIV =
AIV < 30% for road & pavements
< 45% for other works.

73. Aggregate Impact Value Apparatus

74. AGG ABRASION VALUE
Machine : Los Angeles
Grading of Aggregate – given in table
Abrasive charge & wt. of sample – in table
‘Wt A’ of cleaned and over dried sample taken
Machine rev/min
No. of revolution
= (for A, B, C & D samples)
= (for E, F & G )
(cont.)

77. AGG ABRASION VALUE (cont..)
After revolutions :
Material finer than 1.7 mm separated by sieving
Coarse portion washed & dried in oven at C
Weight of dried portion = B (retained)
Abrasion value =
AV < 30% for Pavement works
< 50% for other works

78. ABRASIVE CHARGE GRADING NO. OF BALLS WT. OF CHARGE A 12 5000 + 25 B 11 C 8 D 6 E F G
AV < 30% for pavements and AV< 50% for other works.

79. Weight in gm of Test sample for Grade
Sieve Size
Weight in gm of Test sample for Grade
Passing
Retained A B C D E F G mm - 80 63
2500 50 40
5000 25
1250 20
12.5 10
6.3
4.75
2.36

80. SPECIFIC GRAVITY
Specific Gravity is the ratio of Mass of solid ina a given volume of sample to mass of an equal volume of water at same temperature.
Specific Gravity = C
B-A
Apparent Specific Gravity = C
C-A
Water Absoption = 100(B-C) C
Sp. Gravity for rock should be 2.5 to 2.8

81. BULK DENSITY
Bulk density is Mass of material ina given volume (Kg / Lit)
Bulk density = Net wt. of agg. in Kg
Capacity of container in Lit.
% of Voids = (Gs – γ ) x 100 γ
Gs = Specific Gravity of Agg.
γ = Bulk Density in Kg / Lit.

82. IMPORTANCE OF GRADATION
Gradation affects
Workability
Finishing characteristics of fresh concrete
Void in the concrete
Strength of concrete
Good grading : It contains all standard fractions of aggregate in required proportions.

83. FINESS MODULUS (FM)
FM is an empirical factor obtained by adding cumulative % ages of agg. retained on each sieve and dividing by 100.
Larger the factor coarser the aggregate
Fine sand FM – 2.6
Medium sand FM – 2.9
Coarse sand FM – 3.2
FM more than 3.2 considered unsuitable for concrete

84. BULKING OF SAND It happens because of surface tension
Fine sand bulking can be as much as 38%
In volume batching it becomes more important.

85. Fineness Modulus Sieve Wt Retained (gm) Cumu. Wt (gms) Cumu. Wt %
4.75 mm 10 2
2.36 mm 50 60 12
1.18 mm
110 22
600  95
205 41
300 
175
380 76
150  85
465 93
Dust 35
500 -
246
Fineness
246/100 =
2.46

86. CLASSIFICATION OF FINE AGGREGATE
Is sieve designation
Percentage passing for
Grading zone I
Grading Zone II
Grading Zone III
Grading Zone IV
10 mm
100
4.75 MM
90-100
95-100
2.36MM
60-95
75-100
85-100
1.18 MM
30-70
55-90
600 micron
15-34
35-59
60-79
80-100
300 micron
5-20
8-30
12-40
15-50
150 micron
0-10
0.10
0-15

87. GRADING OF TEST SAMPLES

88. DELETERIOUS MATERIALS
Clay & Silt
Coal & lignite
Shale
Mica – max 2%
Material finer than 75 µ IS sieve
These interfere with the process of hydration and prevent bond between cement & aggregate
Every 1% mica reduces strength by 5-8 %

89. SALT CONTAMINATION
Sea dredged aggregates have problem of salt contamination
These shouldn’t be used for PSC works
If permission granted in spl. case, these should be washed &
i) Chloride content shouldn’t be more than 0.04% (by wt. of FA)
0.02%(by wt. of CA)
ii)Sulphate content shouldn’t be more than
0.4% (by total wt. of FA & CA )
(CBC C/S no.1)

90. IMPORTANCE OF GRADATION
Gradation affects
Workability
Finishing characteristics of fresh concrete
Void in the concrete
Strength of concrete
Good grading : It contains all standard fractions of aggregate in required proportions.

92. Unit-III: FRESH CONCRETE
Learning Objectives and Lecture Plan :
Topic
No. Of Hours
Fresh concrete, properties, workability and factors affecting it 01
Workability –slump, compaction factor and consistency tests
Setting time, segregation & bleeding
Manufacture, mixing and compaction
Quality of water

93. FRESH CONCRETE
Fresh concrete or Plastic concrete is a Freshly mixed material which can be molded into any shape.
Performance of Hardened Concrete depends upon Fresh Concrete.
To achieve this Fresh Concrete should satisfy some requirements
Mixability
Stability or Cohesiveness
Flowability
Compactability
Finishability

94. WORKABILITY
IS: 6461 (Part-VII) – 1973 Defines workability as that property of freshly mixed concrete or mortar which determines the ease and homogeneity with which it can be mixed , placed, compacted and finished.
Factors Effecting
Water content
Mix Proportions
Size of Aggregates
Shape of Aggregates
Surface Texture of Aggregate
Grading of Aggregate
Use of Admixtures

95. Measurement of Workability:
Following are different empirical tests used to measure workability:
Slump Test
Compacting Factor Test
Vee-Bee Consistency Test
Flow Test

96. viii) This difference in height in mm is the slump of the concrete.
Slump Test :
Slump test is to determine the workability of fresh concrete as per IS: 1199 – The apparatus used for doing slump test are Slump cone and Tamping rod.
Test Procedure:
i) The internal surface of the mould is thoroughly cleaned and applied with a light coat of oil.
ii) The mould is placed on a smooth, horizontal, rigid and nonabsorbent surface.
iii) The mould is then filled in four layers with freshly mixed concrete, each approximately to one-fourth of the height of the mould.
iv) Each layer is tamped 25 times by the rounded end of the tamping rod (strokes are distributed evenly over the cross section).
v) After the top layer is rodded, the concrete is struck off the level with a trowel.
vi) The mould is removed from the concrete immediately by raising it slowly in the vertical direction.
vii) The difference in level between the height of the mould and that of the highest point of the subsided concrete is measured.
viii) This difference in height in mm is the slump of the concrete.

97. SLUMP CONE

98. Water Content

99. Compaction Factor Test
Compacting factor test is to determine the workability of fresh concrete as per IS: 1199 – The apparatus used is Compacting factor apparatus.
Test Procedure:
i) The sample of concrete is placed in the upper hopper up to the brim.
ii) The trap-door is opened so that the concrete falls into the lower hopper.
iii) The trap-door of the lower hopper is opened and the concrete is allowed to fall into the cylinder.
iv) The excess concrete remaining above the top level of the cylinder is then cut off with the help of plane blades.
v) The concrete in the cylinder is weighed. This is known as weight of partially compacted concrete.
vi) The cylinder is filled with a fresh sample of concrete and vibrated to obtain full compaction. The concrete in the cylinder is weighed again. This weight is known as the weight of fully compacted concrete. Compacting factor = (Weight of partially compacted concrete)/(Weight of fully compacted concrete)

100. COMPACTION FACTOR APPARATUS

101. Vee-Bee Consistency Test
To determine the workability of fresh concrete by using a Vee-Bee consistometer as per IS: 1199 – The apparatus used is Vee-Bee consistometer.
Test Procedure:
i) A conventional slump test is performed, placing the slump cone inside the cylindrical part of the consistometer.
ii) The glass disc attached to the swivel arm is turned and placed on the top of the concrete in the pot.
iii) The electrical vibrator is switched on and a stop-watch is started, simultaneously.
iv) Vibration is continued till the conical shape of the concrete disappears and the concrete assumes a cylindrical shape.
v) When the concrete fully assumes a cylindrical shape, the stop-watch is switched off immediately. The time is noted.The consistency of the concrete should be expressed in VB-degrees, which is equal to the time in seconds recorded above.

103. Segregation and Bleeding:
The choice of workability depends upon the type of compacting equipment available. The size of the section and concentration of reinforcement. An insufficient workability may result in incomplete compaction, thereby severely affecting the strength, durability and surface finish of concrete and may indeed prove to be uneconomical in the long run.
Segregation can be defined as separating out of the ingredients of concrete mix so that the mix is no longer in a homogeneous condition. Only a stable homogeneous mix can be fully compacted. Two types of segregation can occur:
The separating out of coarser particles in a dry mix, termed segregation, and
Separation of cement paste from the mix in the case of lean and wet mixes, termed bleeding.
Segregation can be minimized by:
Reducing height of drop of concrete
Not using vibration as a means of spreading a heap of concrete into a level mass over a large area, and
Reducing the continued vibration over a longer time, as the coarse aggregate tends to settle to the bottom and the scum rises to the surface.
Bleeding is due to rise of water in the mix to the surface because of inability of the solid particles in the mix to hold all the mixing water during the settling of the particles under the effect of compaction.