Chapter 11
Steel Reinforcement Tests
Standard Test Procedures
CHAPTER 11
STEEL REINFORCEMENT TESTS
11.1
General Requirements
11.1.1
Introduction
Reinforcing bars are used in reinforced concrete and are one of the main parts of
R.C.C. structure. For that reason, quality of plain and deformed bars should be
checked specially for yield, ultimate strength and elongation (ductility). The most
important test is the tensile strength test. But sometimes bending test is also done.
Tension test provides information on the strength and ductility of materials under
uniaxial tensile stresses. This information may be useful in comparisons of materials,
alloy development, quality control and design under certain circumstances. Bend test is
also a method for evaluating ductility but it cannot be considered as a quantitative
means of predicting service performance in bending operations. The severity of the
bend test is primarily a function of the angle of bend and inside diameter to which the
specimen is bent and of the cross-section of the specimen.
Plain round, hot rolled, mild steel bars are commonly used as reinforcement in concrete
in Bangladesh. Reinforcing bars with various surface protrusions are also used.
Reinforcing steel used in road structures must have yield and ultimate tensile strength
as specified later.
This chapter covers the dimensions of reinforcing bars, tensile strength and bending
procedure.
11.1.2
Terminology
11.1.2.1 Definitions
(1) Deformed bar. Steel bar with protrusions; a bar that is intended for use as
reinforcement in reinforced concrete construction.
(2) Discontinuous yielding. A hesitation or fluctuation of force observed at the onset
of plastic deformation due to localized yielding. (The stress-strain curve need not
appear to be discontinuous.)
(3) Lower yield strength. The minimum stress recorded during discontinuous
yielding, ignoring transient effects.
(4) Upper yield strength. The first stress maximum (stress at first zero slope)
associated with discontinuous yielding.
(5) Yield point elongation. The strain (expressed in percent) separating the stressstrain curves first point of zero slope from the point of transition from discontinuous
yielding to uniform strain hardening.
11.1.3
Dimensions of reinforcing bar
The steel bars should be made straight and ends should be plain surface perpendicular
to the longitudinal axis before measuring weight and length. Length should be sufficient
(provided it does not exceed the capacity of balance) for rods of large diameter for
better result. The length of the properly prepared sample to be measured in mm. The
weight (W) to be taken in gm. Then the average diameter of the bar can be found as:
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Chapter 11
Steel Reinforcement Tests
Standard Test Procedures
Average bar diameter (mm) = 12.736 x
W
L
Actual diameters of many bars available in the market are less than their stated
diameters. Care must therefore be exercised in procuring steel from local markets.
Standard diameters and other physical properties of standard plain round bars are
given in Table 11.1.1.
Table 11.1.1 Dimensions of Standard Reinforcing Bars
Nominal
Diameter
mm
(in)
6
(1/4)
10
mm
6.350
(in)
(0.250)
Cross Sectional
Area
mm2
(in2)
32.26
(0.05)
Perimeter
mm
20.07
(in)
(0.79)
Mass / UnitLength
kg/m
(1b/ft)
0.248 (0.167)
9.525
(0.375)
70.79
(0.11)
29.97
(1.18)
0.560
(0.376)
1
12.700
(0.500)
129.03
(0.20)
39.88
(1.57)
0.994
(0.668)
5
15.875
(0.625)
200.00
(0.31)
49.78
(1.96)
1.552
(1.043)
3
19.050
(0.750)
283.87
(0.44)
59.94
(2.36)
2.235
(1.502)
22
7
( /8)
22.225
(0.875)
387.10
(0.60)
69.85
(2.75)
3.042
(2.044)
25
(1)
25.400
(1.000)
509.68
(0.79)
79.76
(3.14)
3.973
(2.670)
29
1
(1 /3)
28.575
(1.128)
645.16
(1.00)
89.92
(3.54)
5.059
(3.400)
32
1
32.260
(1.270)
819.35
(1.27)
101.35
(3.99)
6.403
(4.303)
12
16
19
11.1.4
(3/8)
Actual Diameter
( /2)
( /8)
( /4)
(1 /4)
Requirements of deformed bar
Deformed bars are of many sizes. From size no. 10 to size no. 55 in metric units are
given in Table 11.1.2 and from size no. 3 to size no. 18 in FPS units are given in Table
11.1.3.
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Chapter 11
Steel Reinforcement Tests
Table 11.1.2
Standard Test Procedures
Deformed Bar Designation Numbers, Nominal Masses, Nominal
Dimensions and Deformation Requirements as per ASTM A 615-M
(Metric Units)
Nominal Dimension
Mass
Diameter
CrossSectional
Area
kg/m
mm
mm2
Deformation Requirement, mm
Max. Gap
Bar
(chord of
Designatio
12.5% of
n No.
Max. Av. Min. Av.
Nominal
Perimeter)
10
0.785
11.3
100
7.9
0.45
4.4
15
1.570
16.0
200
11.2
0.72
6.3
20
2.355
19.5
300
13.6
0.98
7.7
25
3.925
25.2
500
17.6
1.26
9.9
30
5.495
29.9
700
20.9
1.48
11.7
35
7.850
35.7
1000
25.0
1.79
14.0
45
11.775
43.7
1500
30.6
2.20
17.2
55
19.625
56.4
2500
39.4
2.55
22.2
Note.
• The nominal dimensions of a deformed bar are equivalent to those of a
plain round bar having the same mass per meter as the deformed bar.
• Bar designation numbers approximate the number of millimetres of the
nominal diameter of the bar.
Table 11.1.3
Bar
Designat
ion No.
3
4
5
6
7
8
9
10
11
14
18
Note.
Deformed Bar Designation Numbers, Nominal Masses, Nominal
Dimensions and Deformation Requirements as per ASTM A 615-M
(FPS Units)
Nominal Dimension
Nominal Diamet
CrossMass
er
Sectional
Area
1b/ft
in2
in
0.376
0.375
0.11
0.668
0.500
0.20
1.043
0.625
0.31
1.502
0.750
0.44
2.044
0.875
0.60
2.670
1.000
0.79
3.400
1.128
1.00
4.303
1.270
1.27
5.313
1.410
1.56
7.650
1.693
2.25
13.600
2.257
4.00
Deformation Requirement, mm
Max. Gap (Chord
Spacing Height of
12.5% of Nominal
Max.
Min. Av.
Perimeter)
Av.
0.262
0.015
0.143
0.350
0.020
0.191
0.437
0.028
0.239
0.525
0.038
0.286
0.612
0.044
0.334
0.700
0.050
0.383
0.790
0.056
0.431
0.889
0.064
0.487
0.987
0.071
0.540
1.185
0.085
0648
1.580
0.102
0864
• The nominal dimensions of a deformed bar are equivalent to those of a
plain round bar having the same weight per foot as the deformed bar.
• Bar numbers are based on the number of eighths of an inch included in
the nominal diameter of the bar.
11.1.4.1 Requirements for deformation
(1)
Deformations shall be spaced along the bar at substantially uniform distances.
The deformations on opposite sides of the bar shall be similar in size and shape.
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Chapter 11
Steel Reinforcement Tests
(2)
(3)
(4)
(5)
Standard Test Procedures
The deformations shall be placed with respect to the axis of the bar so that the
included angle is not less than 450. Where the line of deformations forms an
included angle with the axis of the bar of from 450 to 700 inclusive, the
deformations shall alternately reverse in direction on each side, or those on one
side shall be reversed in direction from those on the opposite side. Where the line
of deformation is over 700, a reversal in direction is not required.
The average spacing or distance between deformations on each side of the bar
shall not exceed seven tenths of the nominal diameter of the bar.
The overall length of deformations shall be such that the gap between the ends of
the deformations on opposite side of the bar shall not exceed 12.5% of the
nominal perimeter of the bar. Where the ends terminate in a longitudinal rib, the
width of the longitudinal rib shall be considered the gap. Where more than two
longitudinal ribs are involved, the total width of all longitudinal ribs shall not
exceed 25% of the nominal perimeter of the bar. Furthermore, the summation of
gaps shall not exceed 25% of the nominal perimeter of the bar. The nominal
perimeter of the bar shall be 3.14 times the nominal diameter.
The spacing, height, and gap of deformations shall conform to the requirements
prescribed in Table 11.1.2 and 11.1.3.
11.1.4.2 Measurement of deformations
(1)
(2)
(3)
The average spacing of deformations shall be determined by dividing a measured
length of the bar specimen by the number of individual deformations and
fractional parts of deformations on any one side of the bar specimen. A measured
length of the bar specimen shall be considered the distance from a point on a
deformation to a corresponding point on any other deformation on the same side
of the bar. Spacing measurements shall not be made over a bar area containing
bar making symbols involving letters or numbers.
The average height of deformations shall be determined from measurements
made on not less than two typical deformations. Determinations shall be based
on three measurements per deformation, one at the centre of the overall length
and the other two at the quarter points of the overall length.
Insufficient height, insufficient circumferential coverage, or excessive spacing of
deformations shall not constitute cause for rejection unless it has been clearly
established by determinations on each lot tested that typical deformation height,
gap or spacing do not conform to the minimum requirements prescribed in
Section 11.1.4.1. No rejection may be made on the basis of measurements if
fewer than ten adjacent deformations on each side of the bar are measured.
Note.
11.1.5
A lot is defined as all the bars of one bar number and pattern and pattern
of deformation contained in an individual shipping release or shipping
order.
Tensile requirements
(1)
(2)
The material, as represented by the test specimens, shall conform to the
requirements for tensile properties prescribed in Table 11.1.4 (metric) and in
Table 11.1.5 (FPS).
The percentage of elongation shall be as prescribed in Table 11.1.4
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Chapter 11
Steel Reinforcement Tests
Table 11.1.4
Standard Test Procedures
Tensile requirements as per ASTM A 615-M (Metric Units)
Parameter
Tensile Strength (minimum), Mpa
Yield Strength (minimum), Mpa
Requirements
Grade 300
Grade 400
500
600
300
400
Elongation (minimum) in 200 mm
gauge, %, for the bar size of:
#10
11
#15
12
#20
#25
#30
#35
#45
#55
Note. Grade 300 bars are furnished only in sizes 10 through 20.
Table 11.1.5
Tensile requirements as per ASTM A 615-M (FPS Units)
Parameter
Tensile Strength (minimum), psi
Yield Strength (minimum), psi
Grade 40
70,000
40,000
Requirements
Grade 60
Grade 75
90,000
100,000
60,000
Elongation (minimum) in 8 inch
gauge, %, for the bar size of:
#3
11
9
#4, 5, 6
12
9
#7, 8
8
#9, 10
7
#11, 14, 18
7
Note. Grade 40 bars are furnished only in sizes 3 through 6.
Grade 75 bars are furnished only in sizes 11, 14 and 18.
11.1.6
9
9
8
7
7
7
-
75,000
6
Bending requirements
The bend-test specimen shall withstand being bent around a pin without cracking on
the outside of the bent portion. The requirements for degree of bending and sizes of
pins are prescribed in Table 11.1.6. (metric units) and in Table 11.1.7 (FPS units).
Table 11.1.6
Bend test requirements as per ASTM A 615-M (Metric Units)
Bar Size
Pin Diameter for Bend Test
Grade 300
Grade 400
3.5d
3.5d
5d
5d
5d
7d
9d
#10, 15
#20
#25
#30, 35
#45, 55 (900)
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Chapter 11
Steel Reinforcement Tests
Table 11.1.7
Standard Test Procedures
Bend test requirements as per ASTM A 615-M (FPS Units)
Bar Size
Note.
11.1.7
Pin Diameter for Bend Test
Grade 40
Grade 60
Grade 75
#3, 4, 5
3.5d
3.5d
#6
5d
5d
#7, 8
5d
#9, 10
7d
#11
7d
7d
#14, 18 (900)
9d
9d
Test bends 1800 unless noted otherwise.
‘d’ is the nominal diameter of the specimen.
Permissible variation in mass
The permissible variation shall not exceed 6% under nominal mass. Reinforcing bars
are evaluated on the basis of nominal mass. In no case shall the overpass of any bar
be the cause for rejection.
11.1.8
Finish
(1)
(2)
(3)
11.1.9
The bars shall be free of detrimental surface imperfections.
Rust, seams, surface irregularities, or mill scale shall not be cause for rejection,
provided the mass, dimensions, cross-sectional area, and tensile properties of a
hand wire brushed test specimen are not less than the requirements of this
specification.
Surface imperfections other than those specified above shall be considered
detrimental when specimens containing such imperfections fail to conform to
either tensile or bending requirements.
Test specimens
(a)
Tension test
1) For round reinforcing bars, full size test specimens should be used. The total
length of the specimen shall be at least equal to the gauge length plus the
length required for the full use of the grips employed. The test specimen must
be straight.
2) Orientation of test specimen for longitudinal test : The lengthwise axis of the
specimen should be parallel to the direction of the greatest extension of the
steel during rolling or forging. The stress applied to a longitudinal tension test
specimen is in the direction of greatest extension. The unit stress
determination shall be based on the nominal bar cross-sectional area.
(b)
Bend test
The bend test specimen shall be the full section of the bar as rolled.
11.1.10 Number of tests
(a)
(b)
For bar size no. 10 to 35, inclusive, one tension test and one bend test shall be
made of the largest size rolled from each batch. If however, material from one
batch differs by three or more designation numbers, one tension and one bend
test shall be made from both the highest and lowest designation number of the
deformed bars rolled.
For bar sizes nos. 45 and 55, one tension test and one bend test shall be made
of each size rolled from each batch.
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Chapter 11
Steel Reinforcement Tests
Standard Test Procedures
11.1.11 Retest
1)
2)
3)
4)
5)
If any tensile property of any tension test specimen is less than that specified,
and any part of the fracture is outside the middle third of the gage length as
indicated by scribe scratches marked on the specimen before testing, a retest
shall be allowed.
If the results of an original tension specimen fail to meet the minimum
requirements and are within 14 MPa of the required tensile strength, within 7 MPa
of the required yield point, or within two percentage units of the required
elongation, a retest shall be permitted on two random specimens for each original
tension specimen failure from the lot. If all results of these retest specimens meet
the specified requirements, the lot shall be accepted.
If a bend test fails for reasons other than mechanical reasons or flaws in the
specimen as described in 11.1.11(4) and 11.1.11(5) below, a retest shall be
permitted on two random specimens from the same lot. If the results of both test
specimens meet the specified requirements, the lot shall be accepted. The retest
shall be performed on test specimens that are at air temperature, but not less
than 16 0C.
If any test specimen fails because of mechanical reasons such as failure of
testing equipment or improper specimen preparation, it may be discarded and
another specimen taken.
If any test specimen develops flaws, it may be discarded and another specimen
of the same size bar from the same batch substituted.
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