lecture-02_materials_1

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Lecture-02

Materials By: Prof Dr. Qaisar Ali Civil Engineering Department UET Peshawar drqaisarali@nwfpuet.edu.pk mumarbsc@yahoo.com

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

1

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Topics Addressed  Concrete 

Components



Admixtures



Properties



Factors Affecting Strength of Concrete



High Strength Concrete

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

2

1

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Topics Addressed 

Durability of Concrete



Concrete Subjected to High Temperatures

 Reinforcing Steel 

Types



Properties

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

3

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Topics Addressed  ACI Code Provisions for Concrete and Steel 

Chapter 3 : Materials



Chapter 4 : Durability of Concrete



Chapter 5 : Concrete Quality, Mixing and Placing

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

4

2

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Concrete  A composite material composed of: 

Paste (Portland Cement + water)



Aggregates (generally sand and gravel)

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

5

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Concrete Components  Paste 

Cementitious materials 

Portland cement



Pozzolans (fly ash, silica fume, ground granulated blast furnace slag)



Water

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

6

3

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Concrete Components  Aggregates 



Coarse 

Gravel



Crushed stone

Fine 

Sand

Coarse Aggregates Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

7

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Concrete Components  Percentage Composition 

Paste: 25% - 40%



Cement: 7% - 15%



Water: 14% - 21%



Air: 4% - 8%



Aggregates: 60% - 75%

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

8

4

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Admixtures  Definition 

A material other than cement, water and aggregates, that is used as an ingredient of concrete and is added to the batch immediately before or during mixing.

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

9

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Admixtures  Uses Admixtures are used to: 

reduce the cost of concrete construction.



achieve certain properties in concrete more effectively than by other means.



maintain the quality of concrete during the stages of mixing, transporting, placing, and curing in adverse weather conditions.

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

10

5

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Admixtures  Types 

As per ACI Committee 212, admixtures have been classified into following groups: 

Air-entraining Admixtures: causes the development of a system of microscopic air bubbles in concrete, mortar, or cement paste during mixing. Air-entrained concrete should be used wherever water saturated concrete may be exposed to freezing and thawing. Air entrainment also improves the workability of concrete.

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

11

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Admixtures  Types 

Accelerating Admixtures: causes an increase in the rate of hydration of the hydraulic cement and thus shortens the time of setting, increases the rate of strength development, or both.



Water Reducing and Set-Controlling Admixtures: Reduce the water requirements of a concrete mixture for a given slump, modify the time of setting, or both.

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

12

6

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Admixtures  Types 

Admixtures for Flowing Concrete: Flowing Concrete is concrete that is characterized as having a slump greater than 190 mm (7-1/2 in.) while maintaining a cohesive nature.



Miscellaneous 

Freeze Resistant, Pigments, Bonding, Grouting etc. (Refer ACI 212 for details and more types of miscellaneous admixtures)



Brief Visit of ACI 212

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

13

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Compressive Strength 

The uniaxial compressive strength is measured by a compression test of a standard test cylinder. This test is used to monitor the concrete strength for quality control or acceptance purposes.



The specified compressive strength is measured by compression tests on 6 by 12 inches cylinders, tested after 28 days of moist curing (testing methods: ASTM Standards C31 and C39).

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

14

7

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Compressive Strength 

Load

Stress Strain Curve

Stress

Typical concrete stress strain curves in compression

Strain Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

15

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Tensile Strength 

Varies between 8% and 15% of the compressive strength.



The type of test that is used to determine the tensile strength has a strong effect on the value that is obtained.



Two types of tests are widely used: 

Modulus of Rupture (Flexural Test)



Split Cylinder Test

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

16

8

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Tensile Strength 

Modulus of Rupture (Flexural Test)

b h

fr = Prof. Dr. Qaisar Ali

6M bh2

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

17

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Tensile Strength 

Modulus of Rupture (Flexural Test) 

ASTM C 78 – Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)



ASTM C 293 – Standard Test Method for Flexural Strength of Concrete (Using Simple Beam With Center-Point Loading)

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

18

9

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Tensile Strength 

Split Cylinder Test

P

d 

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

19

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Tensile Strength 

Split Cylinder Test Tension

Prof. Dr. Qaisar Ali

Compression

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

20

10

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Tensile Strength 

Split Cylinder Test

P

d 

fct = Prof. Dr. Qaisar Ali

2P d

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

21

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Tensile Strength 

Split Cylinder Test 

ASTM C 496 – Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

22

11

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Relationship Between Compressive and Tensile Strengths 

Tensile strength increases with an increase in compressive strength



Ratio of tensile strength to compressive strength decreases as the compression strength increases



Tensile strength  fc

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

23

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Relationship Between Compressive and Tensile Strengths 

Mean f ct = 6.4fc



For deflections (Eq. 9-10): 



fr = 7.5fc

For strength (ACI 11.4.3.1): 

Prof. Dr. Qaisar Ali

fr = 6fc

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

24

12

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Time Dependent Volume Changes 

Shrinkage



Creep



Thermal expansion

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

25

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Shrinkage 

Shortening of concrete during hardening and drying under constant temperature 

Moisture diffuses out of the concrete



Exterior shrinks more than the interior



Tensile stresses in the outer layer of concrete

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

26

13

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Shrinkage

Shrinkage Strain

Time Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

27

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Shrinkage 



When not adequately controlled, can cause: 

Unsightly or harmful cracks



Large and harmful stresses



Partial loss of initial prestress

Reinforcement restrains the development of shrinkage.

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

28

14

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Creep Load removed

Strain

Load applied Elastic recovery Creep strain

Elastic strain

Creep recovery

Permanent Deformation

Time Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

29

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Creep: Creep strains can lead to: 

Increase in deflections with time



Redistribution of stresses



Decrease in prestressing forces

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

30

15

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Thermal Expansion or Contraction 

Expansion or contraction due to change in temperature 

Coefficient of Thermal Expansion or Contraction 

Prof. Dr. Qaisar Ali

Affected by: 

Composition of the concrete



Moisture content of the concrete



Age of the concrete

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

31

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Thermal Expansion 

Coefficient of Thermal Expansion or Contraction 



Normal weight concrete 

Siliceous aggregate: 5 to 7 x 10-6 strain/F



Limestone/calcareous aggregate: 3.5 to 7 x 10-6 strain/F

Lightweight concrete 



Prof. Dr. Qaisar Ali

3.6 to 6.2 x 10-6 strain/F

For calculation purposes, a value of 5.5 x 10-6 strain/F is satisfactory

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

32

16

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Factors Affecting Concrete Strength 

In addition to mixing, conveying, placing and compaction, the strength of concrete primarily depends on:



Water Cement Ratio:

Decrease in water cement ratio increases the

strength. 

Aggregate Cement Ratio:

Decrease in aggregate cement ratio

increases the strength up to a value of around 2.0. Further decrease may cause decrease in strength.

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

33

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Factors Affecting Concrete Strength 

Aggregate:

The concrete strength is affected by the aggregate strength,

its surface texture, its grading and to lesser extent, by the maximum size of the aggregate. 

Curing: Prolonged

Prof. Dr. Qaisar Ali

moist curing leads to the highest concrete strength

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

34

17

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Rate of Strength Gain 

ACI Committee 209 [3-21] has proposed the following equation to represent the rate of strength gain for concrete made from Type 1 cement and moist-cured at 70°F.

f ’c(t) = f ’c(28) {t/(4 + 0.85t)} 

Prof. Dr. Qaisar Ali

Where f ’c(t) = is the compressive strength at age t in days.

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

35

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Properties of Concrete  Rate of Strength Gain and Cement Types 

Figure shows the effect of type of cement on strength gain of concrete (moist cured; w/c = 0.49).

I = Normal II = Modified III = High early strength IV = Low heat V = Sulfate resisting

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

36

18

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

High Strength Concrete  Introduction 

Concretes with strengths in excess of 6000 psi are referred to as high strength concrete.



The resulting concrete has a low void ratio.



Only the amount of water needed to hydrate the cement in the mix is provided.

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

37

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

High Strength Concrete  Shrinkage and Creep 

Shrinkage of concrete is approximately proportional to the percentage of water by volume in the concrete. Highstrength concrete has a higher paste content, but the paste has a lower water cement ratio. As a result, the shrinkage of high-strength concrete is about the same as that of normal concrete.



Test data suggest that the creep coefficient for high strength concrete is considerably less than that for normal concrete.

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

38

19

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

High Strength Concrete  UET Lab Results for Producing High Strength Concrete 

Mix design results for 6000 and 8000 psi concrete.

Table-A

Trial Test

Proportion

No. of cylinders

Date of preparation

Date of Testing

Slump (in)

Avg. Strength (psi)

6000 psi

(1:1:2) w/c (0.36)

6

25/6/2010

22/7/2010

2.5

6100

8000 psi

(1:0.8:1.5) w/c (0.31)

6

28/6/2010

25/7/2010

2

8000



Admixture used: Sikament 520BA

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

39

Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

Durability of Concrete  Three most common durability problems in concrete are: 

Corrosion of steel in concrete.



Breakdown of the structure of concrete due to freezing and thawing.



Breakdown of the structure of concrete due to chemical action.

Prof. Dr. Qaisar Ali

CE 5115 Advance Design of Reinforced Concrete Structures

Fall 2011

40

20