1. Reinforced Concrete Design
Lecture 2
Dr. Nader Okasha

2. Introduction
Topics
Reinforced concrete structures and concrete-producing materials
Concrete mixing
Mechanical properties of concrete
Steel reinforcement sizes and mechanical properties

3. Reinforced Concrete Structures and Concrete-Producing Materials

4. Concrete
Concrete is a mixture of cement, fine and coarse aggregates, and water. This mixture creates a formable paste that hardens into a rocklike mass.

9. Concrete Producing Materials
Portland Cement
Course Aggregates
Fine Aggregates
Water
Admixtures

10. Portland Cement Types of Cement Type I: General Purpose
Type II: Lower heat of hydration than Type I
Type III: High Early Strength
Higher heat of hydration
quicker strength (7 days vs. 28 days for Type I)

11. Types of Cement Type IV: Low Heat of Hydration
Gradually heats up, less distortion (massive structures).
Type V: Sulfate Resisting
For footings, basements, sewers, etc. exposed to soils with sulfates.

12. Aggregates
Coarse Aggregates
Fine Aggregates

13. Water

14. Admixtures Applications: Improve workability (superplasticizers)
Accelerate or retard setting and hardening
Aid in curing
Improve durability

15. Concrete Mixing

16. Concrete Mixing
In the design of concrete mixes, three principal requirements for concrete are of importance:
Quality
Workability
Economy

17. Concrete Mixing
Quality of concrete is measured by its strength and durability.
The compressive strength of concrete is mainly affected by the water/cement ratio, degree of compaction, age, and temperature.
Durability of concrete is the ability of the concrete to resist disintegration due to freezing and thawing and chemical attack.

18. Concrete Mixing
Workability of concrete may be defined as a composite characteristic indicative of the ease with which the mass of plastic material may be deposited in its final place without segregation during placement, and its ability to conform to fine forming detail.

19. Concrete Mixing Workability Workability is measured by the slump test
12”
slump
Layer 1: Fill 1/3 full. 25 stokes
Layer 2: Fill 2/3 full. 25 stokes
Layer 3: Fill full. 25 stokes
Lift cone and measure slump (typically 2-6 in.)

21. Concrete Mixing

22. Concrete Mixing
Economical takes into account effective use of materials, effective operation, and ease of handling. The cost of producing good quality concrete is an important consideration in the overall cost of the construction project.

23. Mechanical Properties of Concrete

24. Mechanical Concrete Properties
Compressive Strength,
Modulus of Elasticity, Ec
Maximum ‘Ultimate’ Strain
Tensile, Splitting and Rupture Strength, ft , fct , fr

25. Mechanical Concrete Properties
Compressive Strength,
Normally use 28-day strength for design strength
It is determined through testing standard cylinders 15 cm in diameter and 30 cm in length in uniaxial compression at 28 days (ASTM C470-93a)

26. Mechanical Concrete Properties

27. Mechanical Concrete Properties

28. Mechanical Concrete Properties
Modulus of Elasticity, Ec
Corresponds to secant modulus at 0.45
ACI (Sec ) for normal concrete:

29. Mechanical Concrete Properties
Maximum ‘ultimate’ strain
ACI Code: = 0.003
Used for flexural and axial compression
For normal strength concrete, ~ 0.002

30. Mechanical Concrete Properties
Typical Concrete Stress-Strain Curves in Compression

31. Mechanical Concrete Properties
Tensile Strength
Tensile strength ~ 8% to 15% of
Modulus of Rupture, fr
For deflection calculations, use:
Test:
ACI Eq. 9-10 P fr
unreinforced concrete beam

32. Mechanical Concrete Properties
Tensile Strength
Splitting Tensile Strength, fct
Split Cylinder Test P
Concrete Cylinder
Poisson’s
Effect

33. Creep
Creep is defined as the long-term deformation caused by the application of loads for long periods of time, usually years.
Creep strain occurs due to sustaining the same load with time.

34. Creep
The total deformation is divided into two parts; the first is called elastic deformation occurring right after the application of loads, and the second which is time dependent, is called creep

35. Shrinkage
Shrinkage of concrete is defined as the reduction in volume of concrete due to loss of moisture

36. Steel Reinforcement Sizes and Mechanical Properties

37. Steel Reinforcement
Bars are deformed to increase bonding with concrete

38. Steel Reinforcement Stress-strain diagrams fu fy Yield stress, fy
Ultimate stress, fy

39. Steel Reinforcement
Steel grades
MPa
ksi
276 40
414 60
552 80

40. Steel Reinforcement
Bar sizes