Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
Concrete Subjected to High Temperatures Compressive
Strength
of
Concrete
at
High
Temperatures
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
41
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
Reinforcing Steels Types
Deformed Bar Reinforcement: ACI 3.5.3
Plain Reinforcement: ACI 3.5.4
Prestressing Steel: ACI 3.5.5
Structural Steel Shapes: ACI 3.5.6
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
42
21
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
Deformed Bar Reinforcement ASTM A 615, Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement. ASTM A 706, Specification for LowAlloy Steel Deformed and Plain Bars for Concrete Reinforcement. ASTM A 996, Specification for RailSteel
and
Axle-Steel
Deformed
Bars for Concrete Reinforcement.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
43
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
Deformed Bar Reinforcement
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
44
22
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
Deformed Bar Reinforcement Bar Designation
Area (in.2)
Weight (plf)
Diameter (in.)
No. 3
0.11
0.376
0.375
No. 4
0.20
0.668
0.500
No. 5
0.31
1.043
0.625
No. 6
0.44
1.502
0.750
No. 7
0.60
2.044
0.875
No. 8
0.79
2.670
1.000
No. 9
1.00
3.400
1.128
No. 10
1.27
4.303
1.270
No. 11
1.56
5.313
1.410
No. 14
2.25
7.650
1.693
No. 18
4.00
13.600
2.257
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
45
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
Deformed Bar Reinforcement
fs = fy fs = Esď Ľs
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
46
23
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
Deformed Bar Reinforcement Steel Minimum yield Ultimate Grade stress, f y (ksi) strength (ksi) 40
40
70
50
50
80
60
60
90
75
75
100
Prof. Dr. Qaisar Ali
Stress strain curves for reinforcement
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
47
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
Deformed Bar Reinforcement ď‚— Variation in Yield Strength ď‚— Distribution of mill test yield strength for grade 60 steel.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
48
24
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
Deformed Bar Reinforcement Strength of Reinforcing Steel at High temperatures Deformed reinforcement subjected to high temperatures in fires tends to lose its strength.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
49
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 3: Materials Tests of Materials
A complete record of tests of materials and of concrete shall be retained by the inspector for 2 years after completion of the project, and made available for inspection during the progress of the work.
Water
Water used in mixing concrete shall be clean and free from injurious amounts of oils, acids, alkalis, salts, organic materials, or other substances deleterious to concrete or reinforcement.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
50
25
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 3: Materials Steel Reinforcement
Reinforcement shall be deformed reinforcement, except that plain reinforcement shall be permitted for spirals or prestressing steel; and reinforcement consisting of structural steel, steel pipe, or steel tubing shall be permitted as specified in this code.
Visit of the Chapter
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
51
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 4: Durability of Concrete Sulfate exposures
Concrete to be exposed to sulfate-containing solutions or soils shall conform to requirements of Table 4.3.1 or shall be concrete made with a cement that provides sulfate resistance and that has a maximum water-cementitious materials ratio and minimum compressive strength from Table 4.3.1.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
52
26
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 4: Durability of Concrete Corrosion Protection
For corrosion protection of reinforcement in concrete, maximum water soluble chloride ion concentrations in hardened concrete at ages from 28 to 42 days contributed from
the
ingredients
including
water,
aggregates,
cementitious materials, and admixtures shall not exceed the limits of Table 4.4.1. When testing is performed to determine
water
soluble
chloride
ion
content,
test
procedures shall conform to ASTM C 1218.
Visit of the Chapter
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
53
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing
Average Strength of Concrete Produced in the Field
It is emphasized in this chapter that the average strength of concrete produced in the filed should always exceed the specified value of fc′ used in the structural design calculations.
This is based on probabilistic concepts, and is intended to ensure that adequate concrete strength will be developed in the structure.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
54
27
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Average Strength of Concrete Produced in the Field
Variation in Strength
Variations in the properties or proportions of constituents of concrete, as well as variations in transporting, placing, and compaction of the concrete, lead to variations in the strength of the finished concrete. In addition, discrepancies in the tests will lead to apparent differences in strength.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
55
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Average Strength of Concrete Produced in the Field
Variation in Strength
Figure shows the distribution of strengths in a sample of 176 concrete cylinder tests for the concrete having nominal strength of 3000 psi
Results of tests
Strength less than nominal = 9
Strength more than nominal = 167
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
56
28
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing ACI recommendations for achieving specified strength in the field
The ACI code recommends that selection of concrete proportions for achieving a specified concrete strength in the field shall be based on the required average compressive strength of concrete f cr′ and not on the specified strength.
ACI table 5.2.2.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
57
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Selection of Concrete Proportions
Proportions of materials for concrete shall be established to provide:
Workability and consistency to permit concrete to be worked readily into forms and around reinforcement under conditions of placement to be employed, without segregation or excessive bleeding;
Resistance to special exposures as required by Chapter 4 of ACI;
Prof. Dr. Qaisar Ali
Conformance with strength test requirements of ACI 5.6. CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
58
29
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Selection of Concrete Proportions
Recommendations for selecting
proportions for concrete
are given in detail in “Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete” (ACI 211.1).
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
59
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Sampling Frequency for Strength Tests
ACI R5.6.2.1: As a measure of quality control, the code recommends following criteria for collecting samples of concrete cylinders from a given class of concrete:
Once each day a given class is placed, nor less than
Once for each 150 yd3 of each class placed each day, nor less than
Once for each 5000 ft2 of slab or wall surface area placed each day.
In calculating surface area, only one side of the slab or wall should be considered.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
60
30
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Strength Test
A strength test shall be the average of the strengths of two cylinders made from the same sample of concrete and tested at 28 days or at test age designated for determination of fc′.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
61
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Criterion for Satisfactory Concrete Strength
ACI 5.6.3.3: Strength level of an individual class of concrete shall be considered satisfactory if both of the following requirements are met:
(a) Every arithmetic average of any three consecutive strength tests equals or exceeds fc′;
(b) No individual strength test (average of two cylinders) falls below fc′ by more than 500 psi when fc′ is 5000 psi or less; or by more than 0.10fc′ when fc′ is more than 5000 psi.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
62
31
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing The steps taken to increase the average level of test results:
It will depend on the particular circumstances, but could include one or more of the following:
An increase in cementitious materials content
Changes in mixture proportions
Reductions in or better control of levels of slump supplied
Closer control of air content
An improvement in the quality of the testing, including strict compliance with standard test procedures
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
63
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Investigation of Low Strength Test Results
If any strength test of laboratory-cured cylinders falls below specified value of fc′ by more than the values given in 5.6.3.3(b), steps shall be taken to assure that load-carrying capacity of the structure is not jeopardized.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
64
32
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Investigation of Low Strength Test Results
If the likelihood of low-strength concrete is confirmed and calculations
indicate
that
load-carrying
capacity
is
significantly reduced, tests of cores drilled from the area in question in accordance with “Method of Obtaining and Testing Drilled Cores and Sawed Beams of Concrete” (ASTM C 42) shall be permitted.
In such cases, three cores shall be taken for each strength test that falls below the values given in 5.6.3.3(b).
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
65
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Investigation of Low Strength Test Results
According to ACI 5.6.5.4, concrete in an area represented by core tests shall be considered structurally adequate if the average of three cores is equal to at least 85 percent of fc′ and if no single core is less than 75 percent of fc′.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
66
33
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
ACI Chapter 5: Concrete Quality, Mixing and Placing Investigation of Low Strength Test Results
If criteria of ACI 5.6.5.4 are not met and if the structural adequacy remains in doubt, the responsible authority shall be permitted to order a strength evaluation in accordance with Chapter 20 for the questionable portion of the structure, or take other appropriate action.
Visit ACI Chapter 5.
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
67
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
References Reinforced Concrete - Mechanics and Design (4th Ed.) by James MacGregor. ACI 318-02 PCA 2002
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
68
34
Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan
The End
Prof. Dr. Qaisar Ali
CE 5115 Advance Design of Reinforced Concrete Structures
Fall 2011
69
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