ASTM C1550-02
(Test Method)Standard Test Method for Flexural Toughness of Fiber Reinforced Concrete (Using Centrally Loaded Round Panel)
Standard Test Method for Flexural Toughness of Fiber Reinforced Concrete (Using Centrally Loaded Round Panel)
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1.1 This test method covers the determination of flexural toughness of fiber-reinforced concrete expressed as energy absorption in the post-crack range using a round panel supported on three symmetrically arranged pivots and subjected to a central point load. The performance of specimens tested by this method is quantified in terms of the energy absorbed between the onset of loading and selected values of central deflection.
1.2 This test method provides for the scaling of results whenever specimens do not comply with the target thickness and diameter, as long as dimensions do not fall outside of give limits.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C 1550 – 02
Standard Test Method for
Flexural Toughness of Fiber Reinforced Concrete (Using
Centrally Loaded Round Panel)
This standard is issued under the fixed designation C 1550; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope that excludes extraneous deformations of the load train and
local crushing of the panel at the point of load application and
1.1 This test method covers the determination of flexural
points of support.
toughness of fiber-reinforced concrete expressed as energy
3.2.2 compliance—a measure of the tendency of a structure
absorption in the post-crack range using a round panel sup-
to deflect under load, found as the inverse of stiffness or
ported on three symmetrically arranged pivots and subjected to
deflection divided by the corresponding load.
a central point load. The performance of specimens tested by
3.2.3 load train—those parts of a testing machine that
this method is quantified in terms of the energy absorbed
experience load and undergo straining during a mechanical
between the onset of loading and selected values of central
test, including the actuator, frame, support fixtures, load cell,
deflection.
and specimen.
1.2 This test method provides for the scaling of results
3.2.4 toughness—the energy absorbed by the specimen
whenever specimens do not comply with the target thickness
equivalent to the area under the load-deflection curve between
and diameter, as long as dimensions do not fall outside of given
the onset of loading and a specified central deflection.
limits.
1.3 The values stated in SI units are to be regarded as the
4. Summary of Test Method
standard.
4.1 Molded round panels of cast fiber-reinforced concrete or
1.4 This standard does not purport to address all of the
fiber-reinforced shotcrete are subjected to a central point load
safety concerns, if any, associated with its use. It is the
while supported on three symmetrically arranged pivots. The
responsibility of the user of this standard to establish appro-
load is applied through a hemispherical-ended steel piston
priate safety and health practices and determine the applica-
advanced at a prescribed rate of displacement. Load and
bility of regulatory limitations prior to use.
deflection are recorded simultaneously up to a specified central
2. Referenced Documents deflection. The energy absorbed by the panel up to a specified
central deflection is representative of the flexural toughness of
2.1 ASTM Standards:
the fiber-reinforced concrete panel.
C 125 Terminology Relating to Concrete and Concrete
Aggregates
5. Significance and Use
C 670 Practice for Preparing Precision and Bias Statements
2 5.1 The post-crack behavior of plate-like fiber-reinforced
for Test Methods for Construction Materials
concrete structural members is well represented by a centrally
3. Terminology loaded round panel test specimen that is simply supported on
three pivots symmetrically arranged around its circumference.
3.1 Definitions—For definitions of terms used in this test
Such a test panel experiences bi-axial bending in response to a
method, refer to Terminology C 125.
central point load and exhibits a mode of failure related to the
3.2 Definitions of Terms Specific to This Standard:
in situ behavior of structures such as concrete slabs-on-grade,
3.2.1 central deflection—the net deflection at the center of
shotcrete tunnel linings, and shotcrete embankment stabiliza-
the panel measured relative to a plane defined by the three
tion linings. The post-crack performance of round panels
pivots used to support the panel; this is a conditioned deflection
subject to a central point load can be represented by the energy
absorbed by the panel up to a specified central deflection. In
This test method is under the jurisdiction of ASTM Committee C09 on this test method, the energy absorbed up to a specified central
Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee
deflection is taken to represent the ability of a fiber-reinforced
C09.42 on Fiber-Reinforced Concrete.
concrete to redistribute stress following cracking.
Current edition approved Sept. 10, 2002. Published October 2002.
Annual Book of ASTM Standards, Vol 04.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C1550–02
NOTE 1—The use of three pivoted point supports in the test configura-
6. Apparatus
tion results in determinate out-of-plane reactions prior to cracking,
6.1 Testing Machine—The testing machine shall be capable
however the support reactions are indeterminate after cracking due to the
of operating in a manner that produces a controlled and
unknown distribution of flexural resistance along each crack. There is also
constant rate of increase of deflection of the specimen without
a change in load resistance mechanism in the specimen as the test
the intervention of an operator. To avoid unstable behavior
proceeds, starting with predominantly flexural resistance and progressing
after cracking, the system stiffness of the testing machine
to tensile membrane action around the center as the imposed deflection is
increased. The energy absorbed up to a specified central deflection is
inclusive of load frame, load cell (if used), and support fixture
related to the toughness of the material but is specific to this specimen
shall exceed that of the specimen. The system stiffness of the
configuration because it is also determined by the support conditions and
testing machine can be determined in accordance with the
size of the specimen. Selection of the most appropriate central deflection
procedure described in Annex A1. A closed-loop testing
to specify depends on the intended application for the material. The energy
machine in which the measured deflection of the center of the
absorbed up to 5 mm central deflection is applicable to situations in which
specimen is used to automatically control the rate of increase of
the material is required to hold cracks tightly closed at low levels of
deflection of the loading device is acceptable. A testing
deformation. Examples include final linings in underground civil struc-
machine in which the displacement rate of the loading device
tures such as railway tunnels that may be required to remain water-tight.
The energy absorbed up to 40 mm is more applicable to situations in that
is constant is also acceptable provided the load train stiffness
the material is expected to suffer severe deformation in situ (for example,
exceeds the value listed above. Do not use a load-controlled
shotcrete linings in mine tunnels and temporary linings in swelling
test machine. The load-sensing device shall have a resolution
ground). Energy absorption up to intermediate values of central deflection
sufficient to record load to 6 50 N.
can be specified in situations requiring performance at intermediate levels
NOTE 3—Although it is commonly believed that closed-loop control
of deformation.
systems are capable of overcoming the disadvantages of a structurally
5.2 The motivation for use of a round panel with three
compliant testing machine, this will depend on the speed and sensitivity of
supports is based on the within-batch repeatability found in the feed-back loop and the mechanical response rate of the loading
3 4
apparatus. A more reliable configuration comprises a displacement-
laboratory and field experience. The consistency of the
controlled hydraulic actuator in a testing machine with high system
failure mode that arises through the use of three symmetrically
stiffness. Alternately, a stiff screw-driven machine in which the displace-
arranged support pivots results in low within-batch variability
ment of the cross-head is advanced at a constant rate is also acceptable.
in the energy absorbed by a set of panels up to a specified
This test method has been developed for use with displacement-controlled
central deflection. The use of round panels also eliminates the
machines so that the high cost of closed-loop machines can be avoided.
sawing that is required to prepare shotcrete beam specimens. Experience has indicated that the redistribution of stress that occurs in
fiber-reinforced concrete panels following cracking of the concrete matrix
5.3 The nominal dimensions of the panel are 75 mm in
generally results in stable post-crack behavior provided a testing machine
thickness and 800 mm in diameter. Thickness has been shown
complying with the requirements of this section is used.
to strongly influence panel performance in this test, while
6.2 Support Fixture—The fixture supporting the panel dur-
variations in diameter have been shown to exert a minor
ing testing shall consist of any configuration that includes three
influence on performance. Correction factors are provided to
symmetrically arranged pivot points on a pitch circle diameter
account for actual measured dimensions.
of 750 mm capable of supporting a load of 100 kN without
displacing in the radial direction by more than 0.5 mm relative
NOTE 2—The target dimensions of the panel specimen used in this test
are held constant regardless of the characteristics of aggregate and fibers
to the central axis. The three supports must be restrained
used in the concrete comprising the specimen. Post-crack performance
against radial or circumferential translation, and the pivots
may be influenced by size and boundary effects if large aggregate particles
shall not restrict rotation of the panel fragments after cracking.
or long fibers are used in the concrete. These influences are acknowledged
The support fixture must be configured so that the specimen
and accepted in this test method because issues of size effect and fiber
does not come into contact with any portion of the support
alignment arise in actual structures and no single test specimen can
fixture apart from the three pivots during a test. A photograph
suitably model structures of all sizes. Differences in post-crack behavior
of a suggested design is shown in Fig. 1. The contact between
exhibited in this test method can be expected relative to cast fiber-
the specimen and each pivot shall comprise a steel transfer
reinforced concrete members thicker than 100 mm. Because fiber align-
ment is pronounced in structures produced by shotcreting, and the
maximum aggregate size in shotcrete mixtures is typically 10 mm,
post-crack behavior in specimens tested by this method are more
representative of in situ behavior when they are produced by spraying
rather than casting concrete.
Bernard, E. S. “Correlations in the Behaviour of Fibre Reinforced Shotcrete
Beam and Panel Specimens,” Materials and Structures, RILEM, Vol 35, April 2002,
pp. 156-164.
Hanke, S. A., Collis, A., and Bernard, E. S., “The M5 Motorway: An Education
in Quality Assurance for Fibre Reinforced Shotcrete,” Shotcrete: Engineering
Developments, Bernard (ed.), Swets & Zeitlinger, Lisse, 2001, pp. 145-156.
Bernard, E. S. and Pircher, M., 2001, “The Influence of Thickness on
Performance of Fiber-Reinforced Concrete in a Round Determinate Panel Test,”
Cement, Concrete, and Aggregates, CCAGDP, Vol 23, No. 1, June 2001, pp. 27–33. FIG. 1 Photograph of a Suggested Support Fixture
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C1550–02
NOTE 4—All components of the load train in a test system experience
plate with plan dimensions of approximately 40 3 50 mm with
deformation when the specimen is placed under load. If the deflection of
a spherical seat of about 4 mm depth machined into one surface
the specimen is measured relative to the machine crosshead, then the
to accept a ball pivot (see Fig. 2). The distance between the
deformation of the load train is included as extraneous deformations in the
surface of the panel and the center of the pivot shall be 20 6
deflection record. Additional extraneous deformations may arise from
2 mm. The diameter of the pivot ball shall be 16 6 2 mm.
local crushing of concrete under the load point (especially debris on the
Grease is permitted to reduce friction in the seat of each pivot,
surface), or from crushing of any debris between the specimen and
but rollers or grease are not permitted to reduce friction
transfer plates. This second form of extraneous deformation usually results
between the transfer plates and specimen. in curvature in the initial portion of the load-deflection curve.
6.3 Deflection Measuring Equipment—Determine the cen-
NOTE 5—If the deflection of the center of the tensile surface of the
tral deflection of the specimen relative to the support points in specimen is measured directly with a transducer, an incomplete or
erroneous deflection record may occur if a crack opens at the point of
a manner that excludes extraneous deformations of the testing
measurement. It may be possible to alleviate this problem through the use
machine and support fixture. This is achieved by one of two
of a transducer with a probe approximately 20 mm wide. The probe should
methods. If the displacement of the tensile surface of the panel
not exceed this width because off-center cracks may induce exaggerated
at the center is measured relative to the pivot supports, then no
apparent deflections if they occur adjacent to a wide probe.
correction for extraneous deformations of the testing machine
6.4 Data Logging System—Record the deflection imposed
and support fixture need be made to the recorded deflections. If
on the panel and corresponding load resistance simultaneously
the movement of the loading piston relative to the crosshead of
at a rate sufficient to record deflection in increments of no more
the testing machine is used to measure deflection, the deflec-
than 0.05 mm if using a digital recording system. For a test up
tion record must be adjusted to discount extraneous deforma-
to a specified central deflection of 40 mm, record at least 800
tions. A method of adjusting the deflection record to account
for extraneous deformations is given in the calculation section. data points. Deflection increments for measurements beyond
Regardless of the method of deflection measurement selected, this point shall be increased to 0.20 mm. If an analog X-Y
use a displacement transducer with a resolution sufficient to plotter is used to
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