ASTM C1018-97

Standard Test Method for Flexural Toughness and First-Crack Strength of Fiber-Reinforced Concrete (Using Beam With Third-Point Loading) (Withdrawn 2006)

SCOPE
1.1 This test method evaluates the flexural performance of toughness parameters derived from fiber-reinforced concrete in terms of areas under the load-deflection curve obtained by testing a simply supported beam under third-point loading.  Note 1-Toughness determined in terms of areas under the load-deflection curve is an indication of the energy absorption capability of the particular test specimen, and, consequently, its magnitude depends directly on the geometrical characteristics of the test specimen and the loading system.
1.2 This test method provides for the determination of a number of ratios called toughness indices that identify the pattern of material behavior up to the selected deflection criteria. These indices are determined by dividing the area under the load-deflection curve up to a specified deflection criterion, by the area up to the deflection at which first crack is deemed to have occurred. Residual strength factors that represent the average post-crack load retained over a specific deflection interval as a percentage of the load at first crack are derived from these indices.  Note 2-Index values may be increased by preferential alignment of fibers parallel to the longitudinal axis of the beam caused by fiber contact with the mold surfaces or by external vibration. However, index values appear to be independent of geometrical specimen and testing variables, such as span length, which do not directly affect fiber alignment.
1.3 This test method provides for the determination of the first-crack flexural strength using the load corresponding to the point on the load-deflection curve defined in 3.1.1 as first crack, and the formula for modulus of rupture given in Test Method C78.  
1.4 Values of flexural toughness and first-crack flexural strength stated in inch-pound units are to be regarded as the standard. Values of toughness indices and residual strength factors are independent of the system of units used to measure load and deflection.
1.5 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.
WITHDRAWN RATIONALE
This test method evaluates the flexural performance of toughness parameters derived from fiber-reinforced concrete in terms of areas under the load-deflection curve obtained by testing a simply supported beam under third-point loading.
Formerly under the jurisdiction of Committee C09 on Concrete and Concrete Aggregates, this test method was withdrawn in May 2006 due to lack of interest and support for its continued use.

General Information

• Status: Withdrawn
• Publication Date: 09-Dec-1997
• Withdrawal Date: 14-May-2006
• ICS: 91.100.30 - Concrete and concrete products
• ICS: 91.100.40 - Products in fibre-reinforced cement
• Technical Committee: C09 - Concrete and Concrete Aggregates
• Drafting Committee: C09.42 - Fiber-Reinforced Concrete

Relations

• Referred By: ASTM C1140/C1140M-11(2019) - Standard Practice for Preparing and Testing Specimens from Shotcrete Test Panels
• Effective Date: 10-Dec-1997

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C 1018 – 97
Standard Test Method for
Flexural Toughness and First-Crack Strength of
Fiber-Reinforced Concrete (Using Beam With Third-Point
Loading)
This standard is issued under the fixed designation C1018; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method evaluates the flexural performance of
responsibility of the user of this standard to establish appro-
toughnessparametersderivedfromfiber-reinforcedconcretein
priate safety and health practices and determine the applica-
terms of areas under the load-deflection curve obtained by
bility of regulatory limitations prior to use.
testing a simply supported beam under third-point loading.
NOTE 1—Toughness determined in terms of areas under the load- 2. Referenced Documents
deflection curve is an indication of the energy absorption capability of the
2.1 ASTM Standards:
particular test specimen, and, consequently, its magnitude depends di-
C31 Practice for Making and Curing Concrete Test Speci-
rectly on the geometrical characteristics of the test specimen and the
mens in the Field
loading system.
C42 Test Method for Obtaining and Testing Drilled Cores
1.2 This test method provides for the determination of a
and Sawed Beams of Concrete
number of ratios called toughness indices that identify the
C78 Test Method for Flexural Strength of Concrete (Using
pattern of material behavior up to the selected deflection
Simple Beam with Third-Point Loading)
criteria. These indices are determined by dividing the area
C172 Practice for Sampling Freshly Mixed Concrete
under the load-deflection curve up to a specified deflection
C192 PracticeforMakingandCuringConcreteTestSpeci-
criterion, by the area up to the deflection at which first crack is
mens in the Laboratory
deemed to have occurred. Residual strength factors that repre-
C670 Practice for Preparing Precision and Bias Statements
sent the average post-crack load retained over a specific
for Test Methods for Construction Materials
deflection interval as a percentage of the load at first crack are
C823 Practice for Examination and Sampling of Hardened
derived from these indices.
Concrete in Constructions
NOTE 2—Index values may be increased by preferential alignment of
3. Terminology
fibers parallel to the longitudinal axis of the beam caused by fiber contact
with the mold surfaces or by external vibration. However, index values
3.1 Definitions of Terms Specific to This Standard:
appear to be independent of geometrical specimen and testing variables,
3.1.1 first crack—the point on the load-deflection curve at
such as span length, which do not directly affect fiber alignment.
which the form of the curve first becomes nonlinear (approxi-
1.3 This test method provides for the determination of the
mates the onset of cracking in the concrete matrix).
first-crackflexuralstrengthusingtheloadcorrespondingtothe
3.1.2 first-crack deflection—the deflection value on the
point on the load-deflection curve defined in 3.1.1 as first
load-deflection curve at first crack.
crack, and the formula for modulus of rupture given in Test
3.1.3 first-crack strength—thestressobtainedwhentheload
Method C78.
corresponding to first crack is inserted in the formula for
1.4 Values of flexural toughness and first-crack flexural
modulus of rupture given in Test Method C78.
strength stated in inch-pound units are to be regarded as the
3.1.4 first-crack toughness—the energy equivalent to the
standard. Values of toughness indices and residual strength
area under the load-deflection curve up to the first-crack
factors are independent of the system of units used to measure
deflection.
load and deflection.
3.1.5 toughness—the energy equivalent to the area under
the load-deflection curve up to a specified deflection.
3.1.6 toughness indices—the numbers obtained by dividing
1 theareauptoaspecifieddeflectionbytheareauptofirstcrack.
ThistestmethodisunderthejurisdictionofASTMCommitteeC-9onConcrete
andConcreteAggregatesandisthedirectresponsibilityofSubcommitteeC09.42on
Fiber-Reinforced Concrete.
Current edition approved Dec. 10, 1997. Published October 1998. Originally
published as C1018–84. Last previous edition C1018–94b. 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.
C 1018
NOTE 3—Values of 5.0, 10.0, and 20.0 for I , I , and I respectively,
toughness indices are of little practical significance since they
5 10 20
as defined below, correspond to linear elastic material behavior up to first
are directly dependent upon geometrical variables associated
crack and perfectly plastic behavior thereafter (see Appendix X1).
with the specimen and the loading arrangement.
3.1.6.1 toughness index I — the number obtained by divid-
NOTE 4—In applications where the energy absorption capability of a
ing the area up to a deflection of 3.0 times the first-crack
structuralconcreteelementisimportant,itmaybepossibletoobtainsome
deflection by the area up to first crack.
indication of its performance by testing a specimen equivalent to the
3.1.6.2 toughness index I — the number obtained by di-
10 element in terms of size, span, and mode of loading.
viding the area up to a deflection of 5.5 times the first-crack
5.3 In determining which toughness index is most appropri-
deflection by the area up to first crack.
ate as a measure of material performance for a specific
3.1.6.3 toughness index I — the number obtained by di-
application, the level of serviceability required in terms of
viding the area up to a deflection of 10.5 times the first-crack
cracking and deflection shall be considered, and an index
deflection by the area up to first crack.
appropriate to the service conditions shall be selected in
3.1.6.4 residual strength factor R —the number obtained
5,10
accordancewiththerationaledescribedin9.6andinAppendix
by calculating the value of 20 ( I − I ).
10 5
X1.
3.1.6.5 residualstrengthfactorR —thenumberobtained
10,20
5.4 Values of toughness indices, residual strength factors,
by calculating the value of 10 ( I − I ).
20 10
and first-crack strength may be used for comparing the
4. Summary of Test Method
performance of various fiber-reinforced concretes during the
mixture proportioning process or in research and development
4.1 Molded or sawn beams of fiber-reinforced concrete are
work. They may also be used to monitor concrete quality, to
tested in flexure using the third-point loading arrangement
verifycompliancewithconstructionspecifications,ortoevalu-
specified in Test Method C78. Load and beam deflection are
ate the quality of concrete already in service.
monitored either continuously by means of an X-Y plotter, or
incrementally by means of dial gages read at sufficiently
NOTE 5—Values of toughness index at different ages may not be
frequent intervals to ensure accurate reproduction of the
comparable.
load-deflection curve. A point termed first crack which corre-
5.5 Values of toughness indices, residual strength factors,
sponds approximately to the onset of cracking in the concrete
andfirst-crackstrengthobtainedusingthe14by4by4in.(350
matrixisidentifiedontheloaddeflectioncurve.Thefirst-crack
by 100 by 100 mm) preferred standard size of molded
load and deflection are used to determine the first-crack
specimen may not necessarily correspond with the perfor-
flexural strength and to establish end-point deflections for
manceoflargerorsmallermoldedspecimens,concreteinlarge
toughness calculations. Computations of toughness and tough-
structuralunits,orspecimenssawnfromsuchunits,becauseof
ness indices are based on areas under the load-deflection curve
differencesinthedegreeofpreferentialfiberalignmentparallel
uptothefirst-crackdeflectionanduptothespecifiedend-point
to the longitudinal axis of the specimen. For molded speci-
deflection.
mens, they tend to increase as the degree of preferential fiber
alignment increases.
5. Significance and Use
5.5.1 Preferential fiber alignment is likely to occur in
5.1 Thefirst-crackstrengthcharacterizesthebehaviorofthe
molded specimens when fibers in the vicinity of the mold
fiber-reinforced concrete up to the onset of cracking in the
surfaces tend to align in the plane of the surface, and is most
matrix, while the toughness indices characterize the toughness
pronounced in specimens of small cross-section containing
thereafter up to specified end-point deflections. Residual
long fibers.
strength factors, which are derived directly from toughness
5.5.2 In thin concrete sections, such as overlays and shot-
indices, characterize the level of strength retained after first
crete linings, fibers tend to align in the plane of the section, so
crack simply by expressing the average post-crack load over a
in-place performance is best evaluated using either molded or
specific deflection interval as a percentage of the load at first
sawn specimens of depth equal to the thickness of the section.
crack. The importance of each depends on the nature of the
Consequently, toughness indices, residual strength values, and
proposed application and the level of serviceability required in
first-crack strengths for thin sections may differ from those for
terms of cracking and deflection. Toughness and first-crack
standard molded specimens of nominally identical concrete.
strength are influenced in different ways by the amount and
5.5.3 External vibration promotes preferential alignment of
type of fiber in the concrete matrix. In some cases, fibers may
fibers parallel to the vibrating surface of the form or screeding
greatly increase the toughness, toughness indices, and residual
device used, while internal vibration does not have this effect.
strength factors determined by this test method while produc-
Consequently, toughness indices, residual strength values, and
ing a first-crack strength only slightly greater than the flexural
first-crack strengths for identical concrete specimens prepared
strengthoftheplainconcretematrix.Inothercases,fibersmay
using the two kinds of vibration may differ.
significantly increase the first-crack strength with only rela-
tively small increases in toughness, toughness indices, and 5.5.4 Preferential fiber alignment is negligible in mass
residual strength factors. concrete because the aligning effect of mold surfaces is absent
5.2 The toughness indices and residual strength factors and because internal vibration is often used, so toughness
determined by this test method reflect the post-crack behavior indices, residual strength values, and first-crack strengths for
of fiber-reinforced concrete under static flexural loading. The standard molded specimens may differ from those for sawn
absolute values of toughness determined to compute the specimens of nominally identical concrete.
C 1018
NOTE 6—The degree of preferential fiber alignment may be less for
fibers that are flexible enough to be bent by contact with aggregate
particles or mold surfaces than for fibers rigid enough to remain straight
during mixing and specimen preparation.
6. Apparatus
6.1 Testing Machine—The testing machine shall be capable
of operating in a manner which produces a controlled and
constant increase of deflection of the specimen. A testing
arrangementwherespecimennetmid-spandeflectionisusedto
control the rate of increase of deflection using a closed-loop,
servo-controlledtestingsystemshallbeused.Testingmachines
that use stroke displacement control or load control are not
suitable for establishing the post-crack portion of the load-
deflection curve. The loading and specimen support system
shall be capable of reproducing third-point loading on the
specimen without eccentricity or torque. The system specified
in Test Method C78 is suitable.
NOTE 7—Load-deflection curves produced from closed-loop testing
systems may show substantial toughness for non-fibrous concrete in the
post-crack deflection area up to a deflection of 5.5 times the first-crack
deflection. Values of toughness indices I and I and residual strength R
5,10, should be used with caution, as they may not accurately reflect the
contribution of fibers to post-crack toughness at these deflections.
6.2 Deflection-Measuring Equipment— Devices such as
electronic transducers or electronic deflection gages shall be
located in a manner that ensures accurate determination of the
net deflection at the mid-span exclusive of any effects due to
seating or twisting of the specimen on its supports. Two
FIG. 1 Arrangement Using 3 Transducers
alternativearrangementsformeasuringnetmid-spandeflection
have evolved. In the first arrangement three electronic trans-
ducers or similar digital devices mounted on a supporting
sively large load-deflection plots. With some plotting equipment it is
frame are positioned along the centerline of the top surface of
possible to use a relatively large scale up to the I criterion and switch to
the test specimen, one at the mid-span and one at each support
a smaller scale at higher deflections without interrupting the test. This
(Fig. 1). The average of the support deflections is electrically keepsthesizeoftheplotreasonablewithoutadverselyaffectingtheability
to accurately determine the area up to first crack and the areas up to the
subtracted from the mid-span deflection. The second arrange-
I and I deflection criteria. For test specimens that exhibit a very rapid
5 10
ment employs a rectangular jig which surrounds the specimen
decrease in load and increase in deflection immediately after first crack,
andisclampedtoitatthesupports(Fig.2).Twotransducersor
the shape of the portion of the load-deflection curve immediately
similar digital devices mounted on the jig at mid-span, one on
following first crack may be affected by the response rate of the data
each side, measure deflection through contact with appropriate
recording and plotting system.
brackets attached to the specimen. The average of the mea-
7. Sampling, Test Specimens, and Test Units
surements represents net mid-span deflection.
6.3 Data Compilation System—An X-Y plotter coupled
7.1 General Requirements—The nominal maximum size of
directly to electronic outputs of load and deflection is the
aggregate and cross-sectional dimensions of test specimens
simplest acceptable means of expediently and accurately ob-
shall be in accordance with Practice C31 or Practice C192
taining the relationship between load and net mid-span deflec-
when using molded specimens, or in accordance with T
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