1. UNIT-I
INTRODUCTION TO RCC

2. Topics Covered in this unit are
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Description of topic
No. of Hrs.
Introduction to RCC 1
Constituents of concrete , grades of concrete 2
Recommendations of I.S. 456 – 2000
Assumptions in elastic theory &Derivation
of Stress block parameters
Problems on finding Moment of resistance, stresses in concrete and steel and design of singly reinforced Rectangular beams
Tutorial on singly reinforced beams
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3. After completion of this unit, student will be able to
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LEARNING OBJECTIVES
After completion of this unit, student will be able to
Identify the various materials used in concrete
List the various grades of concrete
Acquaintance with the Codal provisions of IS 456 – 2000
List the salient features of elastic theory and assumptions in it
Design a Singly reinforced Rectangular Section
using working stress method

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9. Concrete is everywhere!!
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Concrete is everywhere!!
Roads, sidewalks, houses, bridges, skyscrapers, pipes, dams, canals, missile silos, and nuclear waste containment
The word concrete comes from the Latin word "concretus" (meaning compact or condensed),

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12. When was concrete first made? 500 BC
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When was concrete first made? 500 BC
What is the purpose of cement in concrete? It acts as a primary binder to join the aggregate into a solid mass.
What role does water play in producing concrete? Water is required for the cement to hydrate and solidify.
Why does concrete harden? The chemical process called cement hydration produces crystals that interlock and bind together.

13. Is concrete stronger in compression, tension, or the same in either?
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Why does concrete set (harden) slowly? It takes time for the hydrated cement crystals to form
Is concrete stronger in compression, tension, or the same in either?
It is stronger in compression.
How long can concrete last (in years)? 50,000

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Concrete is strong in Compression but weak in tension, thus adding reinforcement increases the strength in tension

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Concrete is reinforced to give it extra tensile strength; without reinforcement, many concrete buildings would not have been possible.

16. Concrete Reinforcing “Place reinforcing steel where the
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Concrete Reinforcing
Concrete - No Useful Tensile Strength
Reinforcing Steel - Tensile Strength
Similar Coefficient of thermal expansion
Chemical Compatibility
Adhesion Of Concrete To Steel
Theory of Steel Location
“Place reinforcing steel where the
concrete is in tension”

17. Reinforced concrete can be classified as precast or cast-in-situ
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Reinforced concrete can encompass many types of structures and components, including slabs,beams,columns,foundations,frames
and more.
Reinforced concrete can be classified as precast or cast-in-situ

18. Concrete Properties Versatile Pliable when mixed Strong & Durable
Does not Rust or Rot
Does Not Need a Coating
Resists Fire
It can be molded to just about any shape.

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20. APPLICATIONS OF CONCRETE Past, Present, and Future
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APPLICATIONS OF CONCRETE
Past, Present, and Future
roads
sidewalks
houses
bricks/blocks
bridges
walls
beams
foundations
floors
sewer pipes
water mains
computer chip backing **
canals
missile silos
containment of nuclear waste
dams
churches
automobile brake lining **
caskets
monuments
solidification of hazardous wastes
tombs
indoor furniture
garden ornaments
swimming pools
airport runways
sailing boats
canoes
barges
subways
tunnels
parking garages
patio bricks
holding tanks
cement "overshoes"
sculptures

21. flower pots & planters
chimneys
mantels
ballast
bath tubs
grave vaults
bank vaults
basements
lamp posts
telephone poles
electric light poles
Frisbees
headstones
steps
fence posts
business/credit cards **
fertilizer
bone replacement **
insulating tiles/bricks
corn silos
park benches
parking stones
roof tiles
water troughs
water tanks
curb & gutters
nuclear reactor containment structures
artificial rocks
office buildings
parking lots
railroad ties
airports
monorails
picnic tables
swimming pools
break waters
wharves & piers
bird baths
barbecue pits
stadium seats
fountains
lunar bases **
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22. Concrete Rocklike Material Ingredients Portland Cement
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Concrete
Rocklike Material
Ingredients
Portland Cement
Course Aggregate
Fine Aggregate
Water
Admixtures (optional)

23. CONSTITUENT MATERIALS AND PROPERTIES (
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CONSTITUENT MATERIALS AND PROPERTIES (
Types of cement (CSA)
- Standard Portland cement - Used for general purposes; air entrained
(50% C3S; 24% C2S; 11%C3A; 8% C4AF; 72% passing 45 μm sieve)
- Modified Portland cement - Used when sulphate resistance and/or generation of moderate heat of hydration are required; air entrained (42%
C3S; 33% C2S; 5% C3A; 13% C4AF; 72% passing 45 μm sieve)
- High early strength Portland cement - Used for early strength and cold weather operations; air entrained (60% C3S; 13% C2S; 9% C3A; 8% C4AF; ….)
- Low heat Portland cement - Used where low heat of hydration is
required; air entrained (26% C3S; 50% C2S; 5% C3A; 12% C4AF; …….)
- High sulphate-resistant concrete - Used where sulphate concentration is very high; also used for marine and sewer structures; air entrained (40% C3S; 40 % C2S; 3.5 % C3A; 9% C4AF; 72% passing 45 μm sieve)

24. Di-calcium silicate (C2S) - 2CaO.SiO2 (15-40%)
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Constituents of cement: 75% is composed of calcium silicates; rest is made up of Al2O3, Fe2O3 and CaSO4
Di-calcium silicate (C2S) - 2CaO.SiO2 (15-40%)
Tri-calcium silicate (C3S) - 3CaO.SiO2 (35-65%)
Tri-calcium aluminate (C3A) - 3CaO.Al2O3 (0-15%)
Tetra-calcium alumino-ferrite (C4AF) -
4CaO.Al2O3..Fe2O3 (6 -20%)
Calcium sulphate (CaSO4) (2%)

25. CONSTITUENT MATERIALS AND PROPERTIES
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CONSTITUENT MATERIALS AND PROPERTIES
Setting, Hydration and Hardening
- When cement is mixed with sufficient water, it loses its plasticity and slowly forms into a hard rock-type material; this whole process is called setting.
- Initial set: Initially the paste loses its fluidity and within a few hours a noticeable hardening occurs - Measured by Vicat’s apparatus
- Final set: Further to building up of hydration products is the commencement of hardening process that is responsible for strength of concrete - Measured by Vicat’s apparatus
- Gypsum retards the setting process
- Hot water used in mixing will accelerate the setting process
- During hydration process the following actions occur:

26. CONSTITUENT MATERIALS AND PROPERTIES
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CONSTITUENT MATERIALS AND PROPERTIES
2(3CaO.SiO2) + 6H2O = 3CaO.2SiO2.3H2O + 3Ca(OH)2
(Tricalcium silicate) (Tobermerite gel)
2(2CaO.SiO2) + 4H2O = 3CaO.2SiO2.3H2O+Ca(OH)2
(Dicalcium silicate) (Tobermerite gel)
3CaO.Al2O3 + 12H2O + Ca(OH)2 = 3CaO. Al2O3. Ca(OH)2.12H2O
(Tricalcium aluminate) (Tetra-calcium aluminate hydrate)
4CaO.Al2O3..Fe2O3 + 10H2O + 2Ca(OH)2 = 6CaO. Al2O3. Fe2O3.12H2O
(Tetra-calcium alumino-ferrite) (Calcium alumino-ferrite hydrate)
3CaO.Al2O3+10H2O+ CaSO4.2H2O = 3CaO.Al2O3.CaSO4.12H2O
(Tricalcium aluminate) (Calcium sulphoaluminate hydrate)
- C3S hardens rapidly: responsible for early strength
- C2S hardens slowly and responsible for strength gain beyond one week
- Heat of hydration: Hydration is always accompanied by release of heat
- C3A liberates the most heat
- C2S liberates the least

27. CONSTITUENT MATERIALS AND PROPERTIES
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CONSTITUENT MATERIALS AND PROPERTIES
Properties of Aggregates, Water and Admixtures
- Aggregates make up up 59-75% of concrete volume; paste constitutes 25-40% of concrete volume. Volume of cement occupies 25-45% of the paste and water makes up to 55-75%. It also contains air, which varies from 2-8% by volume
- Strength of concrete is dependent on the strength of aggregate particles and the strength of hardened paste

28. Properties of Aggregates
compressive strength: Should be higher than concrete strength of MPa
Voids: Represent the amount of air space between the aggregate particles - Course aggregates contain 30-50% of voids and fine aggregate 35-40%
Moisture content represents the amount of water in aggregates: absorbed and surface moisture - Course aggregates contain very little absorbed water while fine aggregates contain 3-5% of absorbed water and 4-5% surface moisture
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29. UNIT-I
Properties of Water
Any drinkable water can be used for concrete making - Water containing more than 2000 ppm of dissolved salts should be tested for its effect on concrete
- Chloride ions not more than 1000 ppm - Sulphate ions not more than 3000 ppm
- Bicarbonate ions not more than 400 ppm
The water should satisfy the requirements of Section 5.4 of IS:
“Water used for mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials or other substances that may be deleterious to concrete and steel”.

30. Admixtures
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Admixture are materials that are added to plastic concrete to change one or more properties of fresh or hardened concrete.
To fresh concrete: Added to influence its workability, setting times and heat of hydration
To hardened concrete : Added to influence the concrete’s durability and strength
Types: Chemical admixtures and mineral admixtures
Chemical: Accelerators, retarders, water-reducing and air-entraining
Mineral : Strength and durability

31. The common chemical admixtures are as follows.
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The common chemical admixtures are as follows.
1) Air-entraining admixtures
2) Water reducing admixtures
3) Set retarding admixtures
4) Set accelerating admixtures
5) Water reducing and set retarding admixtures
6) Water reducing and set accelerating admixtures.

32. The common mineral admixtures are as follows.
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The common mineral admixtures are as follows.
1) Fly ash
2) Ground granulated blast-furnace slag
3) Silica fumes
4) Rice husk ash
5) Metakoline
These are cementitious and pozzolanic materials.

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Fly ash: By-product of coal from electrical power plants - Finer than cement - Consists of complex compounds of silica, ferric oxide and alumina - Increases the strength of concrete and decreases the heat of hydration - Reduces alkali aggregate reaction.
Silica fume: By-product of electric arc furnaces - Size less than 0.1μm - Consists of non-crystalline silica - Increases the compressive strength by 40-60%

34. Properties of Hardened Concrete The concrete in prestressed applications has to be of good quality. It requires the following attributes. 1) High strength with low water-to-cement ratio 2) Durability with low permeability, minimum cement content and proper mixing, compaction and curing 3) Minimum shrinkage and creep by limiting the cement content.
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1) Strength of concrete 2) Stiffness of concrete 3) Durability of concrete 4) High performance concrete 5) Allowable stresses in concrete.

36. Strength of Concrete
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The following sections describe the properties with reference to IS: The strength of concrete is required to calculate the strength of the members. For prestressed concrete applications, high strength concrete is required for the following reasons.
1) To sustain the high stresses at anchorage regions.
2) To have higher resistance in compression, tension, shear and bond.
3) To have higher stiffness for reduced deflection.
4) To have reduced shrinkage cracks

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Compressive Strength
The compressive strength of concrete is given in terms of the characteristic compressive strength of 150 mm size cubes tested at 28 days (fck). The characteristic strength is defined as the strength of the concrete below which not more than 5% of the test results are expected to fall. This concept assumes a normal distribution of the strengths of the samples of concrete.

38. UNIT-I
Idealized distribution of the values of compressive strength for a sizeable number of test cubes
The horizontal axis represents the values of compressive strength. The vertical axis represents the number of test samples for a particular compressive strength. (frequency)

39. Idealized normal distribution of concrete strength
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Idealized normal distribution of concrete strength

40. UNIT-I
The average of the values of compressive strength (mean strength) is represented as f cm.
The characteristic strength (fck) is the value in the x-axis below which 5% of the total area under the curve falls.
The value of fck is lower than fcm by 1.65σ, where σ is the standard deviation of the normal distribution.

41. What is grade of concrete?
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What is grade of concrete?
Grade of concrete refers to the strength of concrete after a period of 28 days, i.e. M20 grade refers to strength of concrete after 28 days as 200kg / cm square or
20 N/mm2 or 20 MPa
Concrete cubes measuring 150mm x 150mm x 150mm are cast at regular intervals and the same cubes are tested to find out crushing strength on 7th and 28th day. The strength of the cube, which is the representative sample of the concrete, will indicate strength of concrete,

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M 20 refers to grade of concrete wherein M refers to mix viz aggregate, sand,cement..and
20 refers to the "characteristic" compressive strength in N/mm2 of a 15 cm cube casted out of that concrete...

43. GRADES OF CONCRETE
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The grades of concrete are explained in Table 1 of the Code.
The minimum grades of concrete for prestressed applications are as follows.
• 30 MPa for post-tensioned members
• 40 MPa for pre-tensioned members.
The maximum grade of concrete is ? MPa.
The increase in strength with age as given in IS: , is not observed in present day concrete that gains substantial strength in 28 days. Hence, the age factor given in Clause should not be used. It has been removed from IS:

44. Design of concrete Mix Nominal mix concrete Design mix concrete
The proportions of cement,sand,coarse aggregate for a design strength can be adopted or rationally designed

45. Nominal mix
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A concrete mix in which the proportions are adopted by volume is referred to as Nominal mix
Design Mix
A concrete mix in which the proportions are adopted to achieve desired strength is referred to as Design mix

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Tensile Strength
The tensile strength of concrete can be expressed as follows.
1) Flexural tensile strength: It is measured by testing beams under 2 point loading (also called 4 point loading including the reactions).
2) Splitting tensile strength: It is measured by testing cylinders under diametral compression
3) Direct tensile strength: It is measured by testing rectangular specimens under direct tension.

47. fcr = flexural tensile strength in N/mm2
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In absence of test results, the Code recommends to use an estimate of the flexural tensile strength from the compressive strength by the following equation.
fcr = flexural tensile strength in N/mm2
fck = characteristic compressive strength of cubes in N/mm2.

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Stiffness of Concrete
The stiffness of concrete is required to estimate the deflection of members. The stiffness is given by the modulus of elasticity.
For a non-linear stress (fc) versus strain (εc) behaviour of concrete the modulus can be initial, tangential or secant modulus.
The modulus of elasticity for short term loading (neglecting the effect of creep) is given by the following equation.

49. Durability of Concrete
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Durability of Concrete
The durability of concrete is of vital importance regarding the life cycle cost of a structure. The life cycle cost includes not only the initial cost of the materials and labour, but also the cost of maintenance and repair.

50. high performance concrete
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high performance concrete
Some special types of high performance concrete are as follows.
1) High strength concrete
2) High workability concrete
3) Self-compacting concrete
4) Reactive powder concrete
5) High volume fly ash concrete
6) Fibre reinforced concrete

51. DESIGN PHILOSOPHIES THE WORKING STRESS METHOD
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DESIGN PHILOSOPHIES
THE WORKING STRESS METHOD
THE ULTIMATE LOAD METHOD or LOAD FACTOR METHOD
THE LIMIT STATE METHOD

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53. The method is designated as working stress method as the loads for the design of structures are the service loads or the working loads. The failure of the structure will occur at a much higher load. The ratio of the failure loads to the working loads is the factor of safety.

54. Assumptions in working stress method
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Assumptions in working stress method
A section which is plane before remain plane after bending.
Bond between steel and concrete is perfect within elastic limit of steel
The tensile strength of concrete is ignored
Concrete is elastic,i.e the stress in concrete varies linearly from zero at the neutral axis to a minimum at the extreme fibre

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The modular ratio,m has the value(280/3σcbc) where σcbc is the permissible compressive stress in bending
In N/mm2 or MPa
Permissible stresses are prescribed by building code to provide suitable factors of safety to allow for uncertainities in estimation of working loads and variation in properties of materials.
FS=3 for concrete
=1.78 for steel as per IS:456

56. Working stress can be expressed as μ R >L
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Working stress can be expressed as
μ R >L
μ =inverse of factor of safety which is less than unity
R= resistance of the structural elements
L= working loads on the structural elements

57. Drawbacks of working stress method
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Drawbacks of working stress method
Concrete is not elastic. The inelastic behaviour of concrete starts right from very low stresses. The actual stress distribution in a concrete section cannot be described by a triangular stress diagram.
Since factor of safety is on the stresses under working loads, there is no way to account for different degrees of uncertainty associated with different types of loads. With elastic theory it is impossible to determine the actual factor of safety with respect to loads.
It is difficult to account for shrinkage and creep effects by using the working stress method.

58. Permissible stresses in concrete
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Permissible stresses in concrete

59. Permissible Stresses in Steel Reinforcement

60. UNIT-I
Reinforced concrete analysis is performed at a given section for either axial force and bending moment or transverse shear loads.  The axial force and bending moment analysis usually idealizes the stress-strain behavior of the concrete with a rectangular stress block to simplify the calculations

61. Singly Reinforced Rectangular section
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Singly Reinforced Rectangular section
Stress strain curve in working stress Design

62. x = kd = depth of the neutral axis, where k is a factor,
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x = kd = depth of the neutral axis, where k is a factor,
fcbc = actual stress of concrete in bending compression at the top fibre which should not exceed the respective permissible stress of concrete in bending compression σcbc,
fst = actual stress of steel at the level of centroid of steel which should not exceed the respective permissible stress of steel in tension σst,
jd = d(1-k/3) = lever arm i.e., the distance between lines of action of total compressive and tensile forces C and T , respectively.
the value of the stress at the level of centroid of steel of Fig. is fst /m due to the transformation of steel into equivalent concrete of area mAst.

63. Types of Problems Analysis of a section Design of a section
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Analysis of a section
Design of a section
Types of sections
Under reinforced section
Balanced section
Over reinforced section

64. Analysis Type of Problems
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Analysis Type of Problems
For the purpose of analysing a singly-reinforced beam where the working loads, area of steel, b and d of the cross section are given, the actual stresses of concrete at the top fibre and steel at the centroid of steel are to be determined in the following manner.
Step 1: To determine the depth of the neutral axis kd from Eq
Step 2: The beam is under-reinforced, balanced or over-reinforced, if k is less than, equal to or greater than kb, to be obtained from Eq
Step 3: The actual compressive stress of concrete fcbc and tensile stress of steel at the centroid of steel fst are determined in the following manner for the three cases of Step 2.

65. Case (i) When k < kb (under-reinforced section)
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Case (i) When k < kb (under-reinforced section)
From the moment equation, we have
M= Ast fst d(1 - k/3)
or fst =M /{Ast d(1 - k/3)} (13.24)
where M is obtained from the given load, Ast and d are given, and k is determined in Step 1.
Equating C = T, we have: (1/2) fcbc b(kd) = Ast fst
or fcbc = (2 Ast fst) / (b kd) (13.25)
where Ast, b and d are given and k and fst are determined in steps 1 and 2, respectively.
Case (ii) When k = kb (balanced section)
In the balanced section fcbc = σcbc and fst = σst.
Case (iii) When k > kb (over-reinforced section)
Such beams are not to be used as in this case fcbc shall reach σcbc while fst shall not reach σst. These sections are to be redesigned either by increasing the depth of the beam or by providing compression reinforcement. Beams with compression and tension reinforcement are known as doubly

66. Step 1. Selection of preliminary dimension b and D
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Step 1. Selection of preliminary dimension b and D
Step 2. Determination of d
Step 3. Determination of Ast
Step 4. Checking for the stresses

67. UNIT-I
The working stress model assumes a constant increase in compression strain form the neutral axis to the outer compression fiber and no concrete tension.
Only the rebar contributes to the moment tension. This is because the concrete is assumed to be fully cracked by the tensile stress

68. UNIT-I
Assignment-1
What is grading of concrete & grading of aggregate? Explain in detail the role of grading on properties of concrete.
Explain environmental exposure conditions as given in IS:
Explain under reinforced, over reinforced & balanced sections.
Explain durability requirements as per IS:
Explain how concrete is divided into different grades based on strength as per IS: