ASTM C348-97
(Test Method)Standard Test Method for Flexural Strength of Hydraulic-Cement Mortars
Standard Test Method for Flexural Strength of Hydraulic-Cement Mortars
SCOPE
1.1 This test method covers the determination of the flexural strength of hydraulic-cement mortars.
1.2 The values stated in SI units are to be regarded as the standard. The values shown in parentheses are for information only.
1.3 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.
General Information
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Standards Content (Sample)
Designation: C 348 – 97
Standard Test Method for
Flexural Strength of Hydraulic-Cement Mortars
This standard is issued under the fixed designation C348; 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 portland cements are mixed at specified water-cement ratios.
Water content of other cements is that sufficient to obtain a
1.1 Thistestmethodcoversthedeterminationoftheflexural
flowof110 65%with25dropsoftheflowtable.Testprisms,
strength of hydraulic-cement mortars.
40 by 40 by 160-mm are molded by tamping in two layers.
1.2 The values stated in SI units are to be regarded as the
Prisms are cured one day in the molds and stripped until tested
standard. The values shown in parentheses are for information
by center point loading.
only.
1.3 Values in SI units shall be obtained by measurement in
4. Significance and Use
SI units or by appropriate conversion, using the Rules for
4.1 This test method provides a means for determining the
Conversion and rounding given in Standard IEEE/ASTM SI
flexural strength of hydraulic cement mortars. Portions of the
10, of measurements made in other units.
mortar prisms tested in flexure according to this test method
1.4 This standard does not purport to address all of the
may be used for the determination of compressive strength in
safety concerns, if any, associated with its use. It is the
accordance with Test Method C349.
responsibility of the user of this standard to establish appro-
4.2 The values are determined from this test method for
priate safety and health practices and determine the applica-
research or reference purposes only and are not used for
bility of regulatory limitations prior to use.
determining compliance with specification requirements.
2. Referenced Documents
5. Apparatus
2.1 ASTM Standards:
5.1 Weights, Weighing Devices and Glass Graduates, shall
C109/C109M Test Method for Compressive Strength of
conform to the Apparatus Section of Test Method C109/
Hydraulic Cement Mortars (Using 2-in. or 50-mm Cube
2 C109M.
Specimens)
5.2 Mixer, Bowl and Paddle, an electrically driven me-
C230 Specification for Flow Table for Use in Tests of
chanical mixer of the type equipped with paddle and mixing
Hydraulic Cement
bowl, as specified in theApparatus Section of Practice C305.
C305 PracticeforMechanicalMixingofHydraulicCement
5.3 Flow Table and Flow Mold, shall conform to Specifica-
Pastes and Mortars of Plastic Consistency
tion C230.
C349 Test Method for Compressive Strength of Hydraulic
5.4 Specimen Molds—Molds for the 40 by 40 by 160-mm
Cement Mortars (Using Portions of Prisms Broken in
2 prism specimens shall be triple-gang molds and shall be so
Flexure)
designed that the specimens will be molded with their longi-
C670 Practice for Preparing Precision and Bias Statements
3 tudinal axes in a horizontal position. The molds shall be made
for Test Methods for Construction Materials
2 of a hard metal, not attacked by cement mortar, and with a
C778 Specification for Standard Sand
Rockwell hardness of not less than HRB 55. The parts of the
IEEE/ASTM SI 10 Standard for Use of the International
4 molds shall be matchmarked and, when assembled, shall be
System of Units (SI): The Modern Metric System
tight-fittingandpositivelyheldtogether.Thesidesofthemolds
3. Summary of Test Method shall be sufficiently rigid to prevent spreading or warping.The
interior faces of the molds shall be plane surfaces with a
3.1 The test mortar used consists of 1 part cement and 2.75
permissible variation, in any 50-mm line on a surface, of 0.03
parts of sand proportion by mass. Portland or air-entraining
mmfornewmoldsand0.05mmformoldsinuse.Thedistance
between opposite sides shall be 40 6 0.13 mm for new molds
This test method is under the jurisdiction ofASTM Committee C-1 on Cement
and 40 6 0.3 mm for molds in use. The height of the molds
and is the direct responsibility of Subcommittee C01.27 on Strength.
shall be 40 mm with permissible variations of+0.25 and−0.15
Current edition approved May 10, 1997. Published June 1998. Originally
mmfornewmolds,and+0.25and−0.40mmformoldsinuse.
published as C348–54 T. Last previous edition C348–95.
The inside length of the molds shall be 160 6 2.5 mm. The
Annual Book of ASTM Standards, Vol 04.01.
Annual Book of ASTM Standards, Vol 04.02.
angle between adjacent interior faces and top and bottom
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C348–97
50-mm (2-in.) cubes have a relatively small diameter lower bearing
planes of the mold shall be 90 6 0.5°, measured at points
surface directly centered below the upper spherically seated head, on
slightly removed from the intersections of the faces. The base
which close-fitting pedestals of appropriate heights are set for breaking
plateshallbeapproximately10mminthicknessandshallhave
50-mm cubes and 50-mm (2-in.) and 50 by 100-mm (2 by 4-in.) or 75 by
a plane surface 200 by 180 mm with a permissible variation in
150-mm (3 by 6-in.) cylinders. The base plate of the flexure testing
any 50-mm line on the surface of 0.03 mm.
apparatus shown in Fig. 3 is designed to rest on the low pedestal intended
5.5 Tamper—The tamper (see Fig. 1) shall be made of
for tests on 75 by 150-mm (3 by 6-in.).
nonabsorptive, nonabrasive material, such as a rubber com- NOTE 2—In the absence of self-centering arrangements on machines
withlargelowerbearingsurfaces,thecenterofthissurfacedirectlybelow
pound having a Shore A durometer hardness of 80 6 10 or
thecenteroftheuppersphericallyseatedheadshallbeaccuratelylocated.
seasoned oak wood rendered nonabsorptive by immersion for
Acircle or concentric circles of appropriate diameters shall be scribed on
15mininparaffinatapproximately200°C(392°F).Thefaceof
the lower bearing surface around this point. A cylindrical pedestal of
the tamper shall be 22 by 85 mm.
appropriate diameter and height shall be obtained. End faces of the
5.6 Tamper Guide—The tamper guide (see Fig. 2), shall be
pedestal must be plane and parallel and at 90° to the axis of the cylinder.
made of metal (such as brass of Rockwell hardness not less
The upper face shall have a diameter of 77.5 mm (3.05 in.).
thanHRB55)notattackedbythecementmortar.Itshalllieflat
6. Materials
onthemoldandshallnotprotrudeoveranyinterioredgeofthe
form more than 0.40 mm. The height of the guide shall be 25 6.1 Graded Standard Sand:
mm. 6.1.1 The sand used for making test specimens shall be
5.7 Trowel—The trowel shall have a steel blade 115 by 250 natural silica sand and conform to Specification C778.
mm (4.5 by 10 in.) in length, with straight edges.
7. Number of Specimens
5.8 Flexure Testing Device—The centerpoint loading
7.1 Three or more specimens shall be made for each period
method shall be used in making flexure tests on the prism
of test specified.
specimens. The device used shall be designed such that the
forcesappliedtothespecimenwillbeverticalonlyandapplied
8. Preparing Specimen Molds
without eccentricity. A device that accomplishes this purpose,
8.1 Prepare the specimen molds as prescribed in Test
for use in a compression testing machine, is shown in Fig. 3.
Method C109/C109M.
Apparatus for making flexure tests of mortar specimens shall
be designed to incorporate the following principles:
9. Procedure
5.8.1 The distance between supports and points of load
9.1 Proportioning, Consistency, and Mixing of Mortars—
application shall remain constant.
The proportioning, consistency, and mixing of the standard
5.8.2 Theloadshallbeappliednormaltotheloadedsurface
mortar shall be in accordance with the Procedure Section of
of the specimen and in such a manner as to avoid all
Test Method C109.
eccentricity of loading.
9.2 Determination of Flow—The flow shall be determined
5.8.3 The direction of the reactions should be parallel to the
in accordance with Test Method C109.
direction of the applied load at all times during the test.
9.3 Molding Test Specimens:
5.8.4 The load should be applied at a uniform rate and in a
9.3.1 Immediately following completion of the flow test,
manner to avoid shock.
return the mortar from the flow table to the mixing bowl.
5.9 Compression Testing Machine—The compression test-
Quickly scrape down into the batch the mortar that may have
ing machine used with the flexure testing device, as shown in
collected on the side of the bowl and then remix the entire
Fig. 3, shall be of the hydraulic type and conform to the
batch 15 s at medium speed. Upon completion of mixing, the
requirements prescribed in Test Me
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