ASTM C109/C109M-23

Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 50 mm [2 in.] Cube Specimens)

SIGNIFICANCE AND USE
4.1 This test method provides a means of determining the compressive strength of hydraulic cement and other mortars and results may be used to determine compliance with specifications. Further, this test method is referenced by numerous other specifications and test methods. Caution must be exercised in using the results of this test method to predict the strength of concretes.
SCOPE
1.1 This test method covers determination of the compressive strength of hydraulic cement mortars, using 50 mm [2 in.] cube specimens.  
Note 1: Test Method C349 provides an alternative procedure for this determination (not to be used for acceptance tests).  
1.2 This test method covers the application of the test using either SI or inch-pound units. The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the inch-pound units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.  
1.3 Values in SI units shall be obtained by measurement in SI units or by appropriate conversion, using the Rules for Conversion and Rounding given in IEEE/ASTM SI-10, of measurements made in other units.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. (Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure.2)  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Dec-2023
• ICS: 91.100.10 - Cement. Gypsum. Lime. Mortar
• Technical Committee: C01 - Cement
• Drafting Committee: C01.27 - Strength

Relations

• Replaces: ASTM C109/C109M-21 - Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50 mm] Cube Specimens)
• Effective Date: 15-Dec-2023
• Refers: ASTM C989/C989M-24 - Standard Specification for Slag Cement for Use in Concrete and Mortars
• Effective Date: 01-Feb-2024
• Refers: ASTM C670-24a - Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
• Effective Date: 01-Feb-2024
• Refers: ASTM C670-24 - Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM C670-15 - Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
• Effective Date: 15-Jun-2015
• Referred By: ASTM C1073-18(2023) - Standard Test Method for Hydraulic Activity of Slag Cement by Reaction with Alkali
• Effective Date: 15-Dec-2023
• Referred By: ASTM C87/C87M-23 - Standard Test Method for Effect of Organic Impurities in Fine Aggregate on Strength of Mortar
• Effective Date: 15-Dec-2023
• Referred By: ASTM C928/C928M-20a - Standard Specification for Packaged, Dry, Rapid-Hardening Cementitious Materials for Concrete Repairs
• Effective Date: 15-Dec-2023
• Referred By: ASTM C1247-20 - Standard Test Method for Durability of Sealants Exposed to Continuous Immersion in Liquids
• Effective Date: 15-Dec-2023
• Referred By: ASTM D4796-17(2022) - Standard Test Method for Bond Strength of Thermoplastic Pavement Marking Materials
• Effective Date: 15-Dec-2023
• Referred By: ASTM C387/C387M-23 - Standard Specification for Packaged, Dry, Combined Materials for Concrete and High Strength Mortar
• Effective Date: 15-Dec-2023
• Referred By: ASTM A1081/A1081M-21 - Standard Test Method for Evaluating Bond of Seven-Wire Steel Prestressing Strand
• Effective Date: 15-Dec-2023
• Referred By: ASTM F2678-16(2021) - Standard Practice for Preparing Panel Underlayments, Thick Poured Gypsum Concrete Underlayments, Thick Poured Lightweight Cellular Concrete Underlayments, and Concrete Subfloors with Underlayment Patching Compounds to Receive Resilient Flooring
• Effective Date: 15-Dec-2023
• Referred By: ASTM C563-20 - Standard Guide for Approximation of Optimum SO<inf>3</inf> in Hydraulic Cement
• Effective Date: 15-Dec-2023
• Referred By: ASTM D5860-95(2022) - Standard Test Method for Evaluation of the Effect of Water Repellent Treatments on Freeze-Thaw Resistance of Hydraulic Cement Mortar Specimens
• Effective Date: 15-Dec-2023

Overview

ASTM C109/C109M-23 is the internationally recognized standard test method for determining the compressive strength of hydraulic cement mortars using 50 mm [2 in.] cube specimens. Published by ASTM International, this standard provides essential guidance for laboratories, construction materials manufacturers, and quality control professionals to evaluate and ensure the performance of hydraulic cement mortars. The test results are critical for compliance with a wide range of cement and mortar specifications and are referenced by numerous other standards.

Key Topics

• Compressive Strength Measurement: Establishes standardized procedures for preparing, curing, and testing 50 mm [2 in.] mortar cubes to determine their compressive strength.
• Applicability of Test Results: Results are used to determine specification compliance for hydraulic cements and mortars, but should not be directly used to predict the compressive strength of concrete.
• Dual Units: The standard allows testing and reporting in both SI and inch-pound units. Measurements must be consistent within each batch to ensure compliance.
• Specimen Preparation: Details requirements for materials, mixing, molding, and curing of mortar cubes to ensure repeatable and reliable results.
• Testing Procedure: Specifies apparatus calibration, load application, speed, and measurement techniques for accurate compressive strength determination.
• Precision and Reporting: Outlines procedures to calculate, average, and report test results, as well as the handling of faulty specimens and retests.
• Safety and Compliance: Emphasizes workplace safety due to the caustic nature of fresh hydraulic cement mixtures and adherence to international standardization and regulatory principles.

Applications

The ASTM C109/C109M-23 test method is widely used in the construction and materials industry for:

• Quality Control: Verifying batch-to-batch consistency in hydraulic cements and mortars at production facilities and job sites.
• Specification Compliance: Demonstrating that a product meets the mechanical performance requirements set by relevant building codes, regulations, and project specifications.
• Research and Development: Supporting the development of new cements, blended cements, pozzolans, or slag-based materials by providing a repeatable metric of compressive strength.
• Reference Testing: Serving as a standard reference method for evaluating alternative or new testing procedures.
• Regulatory Approval: Facilitating product acceptance by agencies such as the U.S. Department of Defense, showcasing pedigree in official procurement and infrastructure projects.

Related Standards

This test method is closely connected to several other ASTM and international standards, ensuring a harmonized approach to cement and mortar testing:

• ASTM C91/C91M - Specification for Masonry Cement
• ASTM C114 - Test Methods for Chemical Analysis of Hydraulic Cement
• ASTM C150/C150M - Specification for Portland Cement
• ASTM C230/C230M - Specification for Flow Table for Use in Tests of Hydraulic Cement
• ASTM C305 - Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars
• ASTM C349 - Alternative Test Method for Compressive Strength Using Prism Portions (not for acceptance tests)
• ASTM C511 - Specification for Curing Facilities
• ASTM C595/C595M - Specification for Blended Hydraulic Cements
• ASTM C618 - Specification for Pozzolan for Use in Concrete
• ASTM C1328/C1328M - Specification for Plastic (Stucco) Cement
• ASTM C1329/C1329M - Specification for Mortar Cement
• ASTM C1437 - Flow of Hydraulic Cement Mortar
• IEEE/ASTM SI-10 - Use of SI Units

Practical Value

Following ASTM C109/C109M-23 provides organizations with a scientifically validated, globally accepted framework for determining the compressive strength of hydraulic cement mortars. Adherence ensures test result comparability worldwide, supports compliance with diverse project and legal requirements, and underpins dependable performance for crucial construction materials. Using standardized testing methods such as ASTM C109/C109M-23 is essential for producing high-quality, resilient, and durable concrete structures.

Keywords: ASTM C109, compressive strength, hydraulic cement mortar, cement testing, mortar strength, 50 mm cube, construction materials, quality control, cement specifications.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C109/C109M − 23
Standard Test Method for
Compressive Strength of Hydraulic Cement Mortars (Using
50 mm [2 in.] Cube Specimens)
This standard is issued under the fixed designation C109/C109M; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers determination of the compres-
C91/C91M Specification for Masonry Cement
sive strength of hydraulic cement mortars, using 50 mm [2 in.]
cube specimens. C114 Test Methods for Chemical Analysis of Hydraulic
Cement
NOTE 1—Test Method C349 provides an alternative procedure for this
C150/C150M Specification for Portland Cement
determination (not to be used for acceptance tests).
C230/C230M Specification for Flow Table for Use in Tests
1.2 This test method covers the application of the test using
of Hydraulic Cement
either SI or inch-pound units. The values stated in either SI
C305 Practice for Mechanical Mixing of Hydraulic Cement
units or inch-pound units are to be regarded separately as
Pastes and Mortars of Plastic Consistency
standard. Within the text, the inch-pound units are shown in
C349 Test Method for Compressive Strength of Hydraulic-
brackets. The values stated in each system may not be exact
Cement Mortars (Using Portions of Prisms Broken in
equivalents; therefore, each system shall be used independently
Flexure)
of the other. Combining values from the two systems may
C511 Specification for Mixing Rooms, Moist Cabinets,
result in nonconformance with the standard.
Moist Rooms, and Water Storage Tanks Used in the
1.3 Values in SI units shall be obtained by measurement in Testing of Hydraulic Cements and Concretes
SI units or by appropriate conversion, using the Rules for
C595/C595M Specification for Blended Hydraulic Cements
Conversion and Rounding given in IEEE/ASTM SI-10, of C618 Specification for Coal Ash and Raw or Calcined
measurements made in other units.
Natural Pozzolan for Use in Concrete
C670 Practice for Preparing Precision and Bias Statements
1.4 This standard does not purport to address all of the
for Test Methods for Construction Materials
safety concerns, if any, associated with its use. It is the
C778 Specification for Standard Sand
responsibility of the user of this standard to establish appro-
C989/C989M Specification for Slag Cement for Use in
priate safety, health, and environmental practices and deter-
Concrete and Mortars
mine the applicability of regulatory limitations prior to use.
C1005 Specification for Reference Masses and Devices for
(Warning—Fresh hydraulic cementitious mixtures are caustic
Determining Mass and Volume for Use in Physical Testing
and may cause chemical burns to skin and tissue upon
of Hydraulic Cements
prolonged exposure. )
C1157/C1157M Performance Specification for Hydraulic
1.5 This international standard was developed in accor-
Cement
dance with internationally recognized principles on standard-
C1328/C1328M Specification for Plastic (Stucco) Cement
ization established in the Decision on Principles for the
C1329/C1329M Specification for Mortar Cement
Development of International Standards, Guides and Recom-
C1437 Test Method for Flow of Hydraulic Cement Mortar
mendations issued by the World Trade Organization Technical
E4 Practices for Force Calibration and Verification of Test-
Barriers to Trade (TBT) Committee.
ing Machines
2.2 IEEE/ASTM Standard:
IEEE/ASTM SI-10 Standard for Use of the International
This test method is under the jurisdiction of ASTM Committee C01 on Cement
System of Units (SI): The Modern Metric System
and is the direct responsibility of Subcommittee C01.27 on Strength.
Current edition approved Dec. 15, 2023. Published February 2024. Originally
approved in 1934. Last previous edition approved in 2021 as C109/C109M – 21. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
DOI: 10.1520/C0109_C0109M-23. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
See the section on Safety, Manual of Cement Testing, Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on
Standards, Vol 04.01. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C109/C109M − 23
3. Summary of Test Method prevent spreading or warping. The interior faces of the molds
shall be plane surfaces and shall conform to the tolerances of
3.1 The mortar used consists of 1 part cement and 2.75 parts
Table 1.
of sand proportioned by mass. Portland, air-entraining
5.3.1 Cube molds shall be checked for conformance to the
portland, portland-limestone, or air-entraining portland-
design and dimensional requirements of this test method at
limestone cements are mixed at a specified water content.
least every 2 ⁄2 years.
Water content for other cements is that sufficient to obtain a
flow of 110 6 5 in 25 drops of the flow table. The 50 mm
5.4 Mixer, Bowl, and Paddle, an electrically driven me-
[2 in.] test cubes are compacted by tamping in two layers. The chanical mixer of the type equipped with paddle and mixing
cubes are cured one day in the molds and stripped and
bowl, as specified in Practice C305.
immersed in lime water until tested.
5.5 Flow Table and Flow Mold, conforming to the require-
ments of Specification C230/C230M.
4. Significance and Use
5.6 Tamper, a nonabsorptive, nonabrasive, nonbrittle mate-
4.1 This test method provides a means of determining the
rial such as a rubber compound having a Shore A durometer
compressive strength of hydraulic cement and other mortars
hardness of 80 6 10 or seasoned oak wood rendered nonab-
and results may be used to determine compliance with speci-
sorptive by immersion for 15 min in paraffin at approximately
fications. Further, this test method is referenced by numerous
200 °C [392 °F], shall have a cross section of 13 mm 6 1.6 mm
other specifications and test methods. Caution must be exer-
by 25 mm 61.6 mm [0.5 in. 6 0.06 in. by 1 in. 6 0.06 in.] and
cised in using the results of this test method to predict the
a length of 120 mm to 150 mm [5 in. to 6 in.]. The tamping
strength of concretes.
face shall be flat and at right angles to the length of the tamper.
5.6.1 Tampers shall be checked for conformance to the
5. Apparatus
design and dimensional requirements of this test method at
5.1 Weights and Weighing Devices, shall conform to the
least every six months.
requirements of Specification C1005. The weighing device
NOTE 2—Each day that the tamper is used a visual inspection should
shall be evaluated for precision and accuracy at a total load of
confirm that the end is flat and at a right angle to the long axis of the
2000 g.
tamper. Rounded or peeling tampers should not be allowed for use.
5.2 Glass Graduates, of suitable capacities (preferably large
5.7 Trowel, having a steel blade 100 mm to 150 mm [4 in. to
enough to measure the mixing water in a single operation) to
6 in.] in length, with straight edges.
deliver the indicated volume at 20 °C [68 ºF]. The permissible
variation shall be 62 mL. These graduates shall be subdivided 5.8 Moist Cabinet or Room, conforming to the require-
ments of Specification C511.
to at least 5 mL, except that the graduation lines may be
omitted for the lowest 10 mL for a 250 mL graduate and for the
5.9 Testing Machine, either the hydraulic or the screw type,
lowest 25 mL of a 500 mL graduate. The main graduation lines
with sufficient opening between the upper bearing surface and
shall be circles and shall be numbered. The least graduations
the lower bearing surface of the machine to permit the use of
shall extend at least one seventh of the way around, and
verifying apparatus. The load applied to the test specimen shall
intermediate graduations shall extend at least one fifth of the
be indicated with an accuracy of 61.0 %. If the load applied by
way around.
the compression machine is registered on a dial, the dial shall
5.3 Specimen Molds, for the 50 mm [2 in.] cube specimens be provided with a graduated scale that can be read to at least
shall be tight fitting. The molds shall have not more than three
the nearest 0.1 % of the full scale load (Note 3). The dial shall
cube compartments and shall be separable into not more than be readable within 1 % of the indicated load at any given load
two parts. The parts of the molds when assembled shall be level within the loading range. In no case shall the loading
positively held together. The molds shall be made of hard metal range of a dial be considered to include loads below the value
not attacked by the cement mortar. For new molds the that is 100 times the smallest change of load that can be read
Rockwell hardness number of the metal shall be not less than on the scale. The scale shall be provided with a graduation line
55 HRB. The sides of the molds shall be sufficiently rigid to equal to zero and so numbered. The dial pointer shall be of
TABLE 1 Permissible Variations of Specimen Molds
50 mm Cube Molds 2 in. Cube Molds
Parameter
New In Use New In Use
Planeness of sides <0.025 mm <0.05 mm <0.001 in. <0.002 in.
Distance between opposite sides 50 mm ± 0.13 mm 50 mm ± 0.50 mm 2 in. ± 0.005 in. 2 in. ± 0.02 in.
Height of each compartment 50 mm + 0.25 mm to − 50 mm + 0.25 mm to − 2 in. + 0.01 in. to − 2 in. + 0.01 in. to −
0.13 mm 0.38 mm 0.005 in. 0.015 in.
A
Angle between adjacent faces 90° ± 0.5° 90° ± 0.5° 90° ± 0.5° 90° ± 0.5°
A
Measured at points slightly removed from the intersection. Measured separately for each compartment between all the interior faces and the adjacent face and between
interior faces and top and bottom planes of the mold.
C109/C109M − 23
sufficient length to reach the graduation marks; the width of the surfaces shall not depart from plane surfaces by more than
end of the pointer shall not exceed the clear distance between 0.013 mm [0.0005 in.] when the blocks are new and shall be
the smallest graduations. Each dial shall be equipped with a maintained within a permissible variation of 0.025 mm
zero adjustment that is easily accessible from the outside of the [0.001 in.].
dial case, and with a suitable device that at all times until reset, 5.9.3.1 Compression machine bearing blocks shall be
will indicate to within 1 % accuracy the maximum load applied checked for planeness in accordance with this test method at
to the specimen. least annually using a straightedge and feeler stock and shall be
refinished if found to be out of tolerance.
5.9.1 If the testing machine load is indicated in digital form,
NOTE 4—The diagonal of a 50 mm [2 in.] cube is 70.7 mm [2.83 in.].
the numerical display must be large enough to be easily read.
The numerical increment must be equal to or less than 0.10 %
6. Materials
of the full scale load of a given loading range. In no case shall
the verified loading range include loads less than the minimum 6.1 Graded Standard Sand:
numerical increment multiplied by 100. The accuracy of the 6.1.1 The sand (Note 5) used for making test specimens
indicated load must be within 1.0 % for any value displayed shall be natural silica sand conforming to the requirements for
within the verified loading range. Provision must be made for graded standard sand in Specification C778.
adjusting to indicate true zero at zero load. There shall be
NOTE 5—Segregation of Graded Sand—The graded standard sand
provided a maximum load indicator that at all times until reset
should be handled in such a manner as to prevent segregation, since
will indicate within 1 % system accuracy the maximum load
variations in the grading of the sand cause variations in the consistency of
the mortar. In emptying bins or sacks, care should be exercised to prevent
applied to the specimen.
the formation of mounds of sand or craters in the sand, down the slopes
5.9.2 Compression machines shall be verified in accordance
of which the coarser particles will roll. Bins should be of sufficient size to
with Practices E4 at least annually to determine if indicated
permit these precautions. Devices for drawing the sand from bins by
loads, with and without the maximum load indicator (when so
gravity should not be used.
equipped), are accurate to 61.0 %.
7. Temperature and Humidity
NOTE 3—As close as can be read is considered 0.5 mm [0.02 in.] along
the arc described by the end of the pointer. Also, one half of the scale 7.1 Temperature—The temperature of the air in the vicinity
interval is about as close as can reasonably be read when the spacing on
of the mixing slab, the dry materials, molds, base plates, and
the load indicating mechanism is between 1 mm [0.04 in.] and 1.6 mm
mixing bowl, shall be maintained between 23.0 °C 6 3.0 °C
[0.06 in.]. When the spacing is between 1.6 mm [0.06 in.] and 3.2 mm
[73.5 °F 6 5.5 °F]. The temperature of the mixing water, moist
[0.13 in.], one third of the scale interval can be read with reasonable
closet or moist room, and water in the storage tank shall be set
certainty. When the spacing is 3.2 mm [0.13] or more, one fourth of the
scale interval can be read with reasonable certainty. at 23 °C 6 2 °C [73.5 °F 6 3.5 °F].
5.9.3 The upper bearing assembly shall be a spherically
7.2 Humidity—The relative humidity of the laboratory shall
seated, hardened metal block firmly attached at the center of be not less than 50 %. The moist closet or moist room shall
the upper head of the machine. The center of the sphere shall
conform to the requirements of Specification C511.
coincide with the surface of the bearing face within a tolerance
of 65 % of the radius of the sphere. Unless otherwise specified 8. Test Specimens
by the manufacturer, the spherical portion of the bearing block
8.1 Make two or three specimens from a batch of mortar for
and the seat that holds this portion shall be cleaned and
each period of test or test age.
lubricated with a petroleum type oil such as motor oil at least
every six months. The block shall be closely held in its
9. Preparation of Specimen Molds
spherical seat, but shall be free to tilt in any direction. A
9.1 Apply a thin coating of release agent to the interior faces
hardened metal bearing block shall be used beneath the
of the mold and non-absorptive base plates. Apply oils and
specimen to minimize wear of the lower platen of the machine.
greases using an impregnated cloth or other suitable means.
To facilitate accurate centering of the test specimen in the
Wipe the mold faces and the base plate with a cloth as
compression machine, one of the two surfaces of the bearing
necessary to remove any excess release agent and to achieve a
blocks shall have a diameter or diagonal of between 70.7 mm
thin, even coating on the interior surfaces. When using an
[2.83 in.] (see Note 4) and 73.7 mm [2.9 in.]. When the upper
aerosol lubricant, spray the release agent directly onto the mold
block bearing surface meets this requirement, the lower block
faces and base plate from a distance of 150 mm to 200 mm
bearing surface shall be greater than 70.7 mm [2.83 in.]. When
[6 in. to 8 in.] to achieve complete coverage. After spraying,
the lower block bearing surface meets this requirement, the
wipe the surface with a cloth as necessary to remove any
diameter or diagonal of upper block bearing surface shall be
excess aerosol lubricant. The residue coating should be just
between 70.7 mm and 79.4 mm [2.83 in. and 3.13 in.]. When
sufficient to allow a distinct finger print to remain following
the lower block is the only block with a diameter or diagonal
light finger pressure (Note 6).
between 70.7 mm and 73.7 mm [2.83 in. and 2.9 in.], the lower
block shall be used to center the test specimen. In that case, the 9.2 Seal the surfaces where the halves of the mold join by
lower block shall be centered with respect to the upper bearing applying a coating of light cup grease such as petrolatum. The
block and held in position by suitable means. The bearing amount should be sufficient to extrude slightly when the two
block surfaces intended for contact with the specimen shall halves are tightened together. Remove any excess grease with
have a Rockwell harness number not less than 60 HRC. These a cloth.
C109/C109M − 23
9.3 Seal molds to their base plates with a watertight sealant. 10.3.2 For portland, portland-limestone, air-entraining
Use microcrystalline wax or a mixture of three parts paraffin portland, or air-entraining portland-limestone cements, record
wax to five parts rosin by mass. Paraffin wax is permitted as a the flow.
sealant with molds that clamp to the base plate. Liquefy the
10.3.3 In the case of cements other than portland, portland-
wax by heating it to a temperature of between 110 °C and
limestone, air-entraining portland, or air-entraining portland-
120 °C [230 °F and 248 °F]. Effect a watertight seal by
limestone cements, make trial mortars with varying percent-
applying the liquefied sealant at the outside contact lines
ages of water until the specified flow is obtained. Make each
between the mold and its base plate (Note 7).
trial with fresh mortar. Record the water content used to
achieve the specified flow as weight percent of cement.
9.4 Optionally, a watertight sealant of petroleum jelly is
10.3.4 Immediately following completion of the flow test,
permitted for clamped molds. Apply a small amount of
return the mortar from the flow table to the mixing bowl.
petroleum jelly to the entire surface of the face of the mold that
Quickly scrape the bowl sides and transfer into the batch the
will be contacting the base plate. Clamp the mold to the base
mortar that may have collected on the side of the bowl and then
plate and wipe any excess sealant from the interior of the mold
remix the entire batch 15 s at medium speed. Upon completion
and base plate.
of mixing, the mixing paddle shall be shaken to remove excess
NOTE 6—Because aerosol lubricants evaporate, molds should be
checked for a sufficient coating of lubricant immediately prior to use. If an
mortar into the mixing bowl.
extended period of time has elapsed since treatment, retreatment may be
10.3.5 When a duplicate batch is to be made immediately
necessary.
for additional specimens, the flow test may be omitted and the
NOTE 7—Watertight Molds—The mixture of paraffin wax and rosin
mortar allowed to stand in the mixing bowl 90 s without
specified for sealing the joints between molds and base plates may be
found difficult to remove when molds are being cleaned. Use of straight
covering. During the last 15 s of this interval, quickly scrape
paraffin wax is permissible if a watertight joint is secured, but due to the
the bowl sides and transfer into the batch the mortar that may
low strength of paraffin wax it should be used only when the mold is not
have collected on the side of the bowl. Then remix for 15 s at
held to the base plate by the paraffin wax alone. When securing clamped
medium speed.
molds with paraffin wax, an improved seal can be obtained by slightly
warming the mold and base plate prior to applying the wax. Molds so
10.4 Molding Test Specimens:
treated should be allowed to return to room temperature before use.
10.4.1 Complete the consolidation of the mortar in the
molds either by hand tamping or by a qualified alternative
10. Specimen Preparation Procedure
method. Alternative methods include but are not limited to the
10.1 Composition of Mortars:
use of a vibrating table or mechanical devices.
10.1.1 Materials for the standard mortar shall be cement,
10.4.2 Hand Tamping—Start molding the specimens within
graded standard sand, and water. The quantities of materials to
a total elapsed time of not more than 2 min and 30 s after
be mixed at one time in the batch of mortar for making six,
completion of the original mixing of the mortar batch. Place a
nine, and twelve test specimens shall be in accordance with
layer of mortar about 25 mm [1 in.] (approximately one half of
Table 2. Use specified water content for all portland, portland-
the depth of the mold) in all of the cube compartments. Tamp
limestone, air-entraining portland, or air-entraining portland-
the mortar in each cube compartment 32 times in about 10 s in
limestone cements. The amount of mixing water for other
four rounds, each round to be at right angles to the other and
cements shall be such as to produce a flow of 110 6 5 as
consisting of eight adjoining strokes over the surface of the
determined in accordance with 10.3.
specimen, as illustrated in Fig. 1. The tamping pressure shall be
NOTE 8—The water-to-portland-cement and water-to-portland-
just sufficient to ensure uniform filling of the molds. The
limestone-cement ratio used in Table 2 is 0.485 by mass. For air-
four rounds of tamping (32 strokes) of the mortar shall be
entraining cements, the water-to-portland-cement or water-to-portland-
completed in one cube before going to the next. When the
limestone-cement ratio is 0.460 by mass. The sand-to-cement ratio is 2.75.
tamping of the first layer in all of the cube compartments is
10.2 Preparation of Mortar:
completed, fill the compartments with the remaining mortar
10.2.1 Mechanically mix in accordance with the procedure
and then tamp as specified for the first layer. During tamping of
given in Practice C305.
the second layer, bring in the mortar forced out onto the tops of
10.3 Determination of Flow: the molds after each round of tamping by means of the gloved
10.3.1 Determine flow in accordance with procedure given fingers and the tamper upon completion of each round and
in Test Method C1437. before starting the next round of tamping. On completion of the
TABLE 2 Standard Test Mortar Proportions
Number of Specimens
Material
6 9 12
Cement, g 500 740 1060
Sand, g 1375 2035 2915
Water, mL
Portland or portland-limestone cements 242 359 514
Air-entraining portland or air-entraining portland-limestone cements 230 340 488
Other cements (to flow of 110 ± 5) . . . . . . . . .
C109/C109M − 23
10.4.4.1 In one day, prepare replicate six-cube or nine-cube
batches using one of the cements and cast a minimum of 36
cubes. Complete one round of tests on each cement on different
days. Store and test all specimens as prescribed in the sections
below. Test all cubes at the age of seven days.
10.4.4.2 Tabulate the compressive strength data and com-
plete the mathematical analyses as instructed in Annex A1.
10.4.5 Requalification of Alternate Compaction Method:
10.4.5.1 Requalification of the method shall be required if
any of the following occur:
(1) Evidence that the method may not be providing d
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C109/C109M − 21 C109/C109M − 23
Standard Test Method for
Compressive Strength of Hydraulic Cement Mortars (Using
2-in. or [50 mm]50 mm [2 in.] Cube Specimens)
This standard is issued under the fixed designation C109/C109M; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method covers determination of the compressive strength of hydraulic cement mortars, using 2-in. or [50 mm] 50 mm
[2 in.] cube specimens.
NOTE 1—Test Method C349 provides an alternative procedure for this determination (not to be used for acceptance tests).
1.2 This test method covers the application of the test using either inch-pound or SISI or inch-pound units. The values stated in
either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SIinch-pound units are shown in
brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of
the other. Combining values from the two systems may result in nonconformance with the standard.
1.3 Values in SI units shall be obtained by measurement in SI units or by appropriate conversion, using the Rules for Conversion
and Rounding given in IEEE/ASTM SI-10, of measurements made in other units.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. (Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns
to skin and tissue upon prolonged exposure. )
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C91/C91M Specification for Masonry Cement
C114 Test Methods for Chemical Analysis of Hydraulic Cement
C150/C150M Specification for Portland Cement
C230/C230M Specification for Flow Table for Use in Tests of Hydraulic Cement
C305 Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency
This test method is under the jurisdiction of ASTM Committee C01 on Cement and is the direct responsibility of Subcommittee C01.27 on Strength.
Current edition approved July 15, 2021Dec. 15, 2023. Published August 2021February 2024. Originally approved in 1934. Last previous edition approved in 20202021
as C109/C109M – 20b.C109/C109M – 21. DOI: 10.1520/C0109_C0109M-21.10.1520/C0109_C0109M-23.
See the section on Safety, Manual of Cement Testing, Annual Book of ASTM Standards, Vol 04.01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C109/C109M − 23
C349 Test Method for Compressive Strength of Hydraulic-Cement Mortars (Using Portions of Prisms Broken in Flexure)
C511 Specification for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic
Cements and Concretes
C595/C595M Specification for Blended Hydraulic Cements
C618 Specification for Coal Ash and Raw or Calcined Natural Pozzolan for Use in Concrete
C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
C778 Specification for Standard Sand
C989/C989M Specification for Slag Cement for Use in Concrete and Mortars
C1005 Specification for Reference Masses and Devices for Determining Mass and Volume for Use in Physical Testing of
Hydraulic Cements
C1157/C1157M Performance Specification for Hydraulic Cement
C1328/C1328M Specification for Plastic (Stucco) Cement
C1329/C1329M Specification for Mortar Cement
C1437 Test Method for Flow of Hydraulic Cement Mortar
E4 Practices for Force Calibration and Verification of Testing Machines
2.2 IEEE/ASTM Standard:
IEEE/ASTM SI-10 Standard for Use of the International System of Units (SI): The Modern Metric System
3. Summary of Test Method
3.1 The mortar used consists of 1 part cement and 2.75 parts of sand proportioned by mass. Portland, air-entraining portland,
portland-limestone, or air-entraining portland-limestone cements are mixed at a specified water content. Water content for other
cements is that sufficient to obtain a flow of 110 6 5 in 25 drops of the flow table. Two-inch or [50 mm] The 50 mm [2 in.] test
cubes are compacted by tamping in two layers. The cubes are cured one day in the molds and stripped and immersed in lime water
until tested.
4. Significance and Use
4.1 This test method provides a means of determining the compressive strength of hydraulic cement and other mortars and results
may be used to determine compliance with specifications. Further, this test method is referenced by numerous other specifications
and test methods. Caution must be exercised in using the results of this test method to predict the strength of concretes.
5. Apparatus
5.1 Weights and Weighing Devices, shall conform to the requirements of Specification C1005. The weighing device shall be
evaluated for precision and accuracy at a total load of 2000 g.
5.2 Glass Graduates, of suitable capacities (preferably large enough to measure the mixing water in a single operation) to deliver
the indicated volume at 20 °C. 20 °C [68 ºF]. The permissible variation shall be 62 mL. These graduates shall be subdivided to
at least 5 mL, except that the graduation lines may be omitted for the lowest 10 mL for a 250 mL graduate and for the lowest 25 mL
of a 500 mL graduate. The main graduation lines shall be circles and shall be numbered. The least graduations shall extend at least
one seventh of the way around, and intermediate graduations shall extend at least one fifth of the way around.
5.3 Specimen Molds, for the 2-in. or [50 mm] 50 mm [2 in.] cube specimens shall be tight fitting. The molds shall have not more
than three cube compartments and shall be separable into not more than two parts. The parts of the molds when assembled shall
be positively held together. The molds shall be made of hard metal not attacked by the cement mortar. For new molds the Rockwell
hardness number of the metal shall be not less than 55 HRB. The sides of the molds shall be sufficiently rigid to prevent spreading
or warping. The interior faces of the molds shall be plane surfaces and shall conform to the tolerances of Table 1.
5.3.1 Cube molds shall be checked for conformance to the design and dimensional requirements of this test method at least every
2½2 ⁄2 years.
5.4 Mixer, Bowl, and Paddle, an electrically driven mechanical mixer of the type equipped with paddle and mixing bowl, as
specified in Practice C305.
5.5 Flow Table and Flow Mold, conforming to the requirements of Specification C230/C230M.
C109/C109M − 23
TABLE 1 Permissible Variations of Specimen Molds
2-in. Cube Molds [50 mm] Cube
Parameter
50 mm Cube Molds 2 in. Cube Molds
Parameter
New In Use New In Use
Planeness of sides <0.001 in. <0.002 in [<0.025 mm] [<0.05 mm]
Planeness of sides <0.025 mm <0.05 mm <0.001 in. <0.002 in.
Distance between opposite sides 2 in. ± 0.005 2 in. ± 0.02 [50 mm ± 0.13 mm] [50 mm ± 0.50 mm]
Distance between opposite sides 50 mm ± 0.13 mm 50 mm ± 0.50 mm 2 in. ± 0.005 in. 2 in. ± 0.02 in.
Height of each compartment 2 in. + 0.01 in. to − 0.005 2 in. + 0.01 in. to − 0.015 [50 mm + 0.25 mm to − 0.13 mm] [50 mm + 0.25 mm to − 0.38 mm]
in. in.
Height of each compartment 50 mm + 0.25 mm to − 50 mm + 0.25 mm to − 2 in. + 0.01 in. to − 2 in. + 0.01 in. to −
0.13 mm 0.38 mm 0.005 in. 0.015 in.
A
Angle between adjacent faces 90 ± 0.5° 90 ± 0.5° 90 ± 0.5° 90 ± 0.5°
A
Angle between adjacent faces 90° ± 0.5° 90° ± 0.5° 90° ± 0.5° 90° ± 0.5°
A
Measured at points slightly removed from the intersection. Measured separately for each compartment between all the interior faces and the adjacent face and between
interior faces and top and bottom planes of the mold.
5.6 Tamper, a nonabsorptive, nonabrasive, nonbrittle material such as a rubber compound having a Shore A durometer hardness
of 80 6 10 or seasoned oak wood rendered nonabsorptive by immersion for 15 min in paraffin at approximately 392 °F or [200
°C], 200 °C [392 °F], shall have a cross section of 0.5 (60.06) by 1 in (60.06) [13 (61.6) by 25 (61.6) mm] and 13 mm 6 1.6
mm by 25 mm 61.6 mm [0.5 in. 6 0.06 in. by 1 in. 6 0.06 in.] and a length of 5 to 6 in. or [120 to 150 mm].120 mm to 150 mm
[5 in. to 6 in.]. The tamping face shall be flat and at right angles to the length of the tamper.
5.6.1 Tampers shall be checked for conformance to the design and dimensional requirements of this test method at least every six
months.
NOTE 2—Each day that the tamper is used a visual inspection should confirm that the end is flat and at a right angle to the long axis of the tamper. Rounded
or peeling tampers should not be allowed for use.
5.7 Trowel, having a steel blade 4 to 6 in. [100 to 150 mm]100 mm to 150 mm [4 in. to 6 in.] in length, with straight edges.
5.8 Moist Cabinet or Room, conforming to the requirements of Specification C511.
5.9 Testing Machine, either the hydraulic or the screw type, with sufficient opening between the upper bearing surface and the
lower bearing surface of the machine to permit the use of verifying apparatus. The load applied to the test specimen shall be
indicated with an accuracy of 61.0 %. If the load applied by the compression machine is registered on a dial, the dial shall be
provided with a graduated scale that can be read to at least the nearest 0.1 % of the full scale load (Note 3). The dial shall be
readable within 1 % of the indicated load at any given load level within the loading range. In no case shall the loading range of
a dial be considered to include loads below the value that is 100 times the smallest change of load that can be read on the scale.
The scale shall be provided with a graduation line equal to zero and so numbered. The dial pointer shall be of sufficient length to
reach the graduation marks; the width of the end of the pointer shall not exceed the clear distance between the smallest graduations.
Each dial shall be equipped with a zero adjustment that is easily accessible from the outside of the dial case, and with a suitable
device that at all times until reset, will indicate to within 1 % accuracy the maximum load applied to the specimen.
5.9.1 If the testing machine load is indicated in digital form, the numerical display must be large enough to be easily read. The
numerical increment must be equal to or less than 0.10 % of the full scale load of a given loading range. In no case shall the verified
loading range include loads less than the minimum numerical increment multiplied by 100. The accuracy of the indicated load must
be within 1.0 % for any value displayed within the verified loading range. Provision must be made for adjusting to indicate true
zero at zero load. There shall be provided a maximum load indicator that at all times until reset will indicate within 1 % system
accuracy the maximum load applied to the specimen.
5.9.2 Compression machines shall be verified in accordance with Practices E4 at least annually to determine if indicated loads,
with and without the maximum load indicator (when so equipped), are accurate to 61.0 %.
NOTE 3—As close as can be read is considered ⁄50 in. or [0.5 mm] 0.5 mm [0.02 in.] along the arc described by the end of the pointer. Also, one half
of the scale interval is about as close as can reasonably be read when the spacing on the load indicating mechanism is between ⁄25 in. or [1 mm] 1 mm
C109/C109M − 23
1 1 1
[0.04 in.] and ⁄16 in. or [1.6 mm]. 1.6 mm [0.06 in.]. When the spacing is between ⁄16 in. or [1.6 mm] 1.6 mm [0.06 in.] and ⁄8 in. or [3.2 mm], 3.2 mm
[0.13 in.], one third of the scale interval can be read with reasonable certainty. When the spacing is ⁄8 in. or [3.2 mm] 3.2 mm [0.13] or more, one fourth
of the scale interval can be read with reasonable certainty.
5.9.3 The upper bearing assembly shall be a spherically seated, hardened metal block firmly attached at the center of the upper
head of the machine. The center of the sphere shall coincide with the surface of the bearing face within a tolerance of 65 % of
the radius of the sphere. Unless otherwise specified by the manufacturer, the spherical portion of the bearing block and the seat
that holds this portion shall be cleaned and lubricated with a petroleum type oil such as motor oil at least every six months. The
block shall be closely held in its spherical seat, but shall be free to tilt in any direction. A hardened metal bearing block shall be
used beneath the specimen to minimize wear of the lower platen of the machine. To facilitate accurate centering of the test
specimen in the compression machine, one of the two surfaces of the bearing blocks shall have a diameter or diagonal of between
2.83 in. [70.7 mm]70.7 mm [2.83 in.] (see Note 4) and 2.9 in. [73.7 mm].73.7 mm [2.9 in.]. When the upper block bearing surface
meets this requirement, the lower block bearing surface shall be greater than 2.83 in. [70.7 mm].70.7 mm [2.83 in.]. When the
lower block bearing surface meets this requirement, the diameter or diagonal of upper block bearing surface shall be between 2.83
and 370.7 mm and 79.4 ⁄8 in. [70.7 and 79.4 mm]. mm [2.83 in. and 3.13 in.]. When the lower block is the only block with a
diameter or diagonal between 2.83 and 2.9 in. [70.7 and 73.7 mm],70.7 mm and 73.7 mm [2.83 in. and 2.9 in.], the lower block
shall be used to center the test specimen. In that case, the lower block shall be centered with respect to the upper bearing block
and held in position by suitable means. The bearing block surfaces intended for contact with the specimen shall have a Rockwell
harness number not less than 60 HRC. These surfaces shall not depart from plane surfaces by more than 0.0005 in. [0.013
mm]0.013 mm [0.0005 in.] when the blocks are new and shall be maintained within a permissible variation of 0.001 in. or [0.025
mm].0.025 mm [0.001 in.].
5.9.3.1 Compression machine bearing blocks shall be checked for planeness in accordance with this test method at least annually
using a straightedge and feeler stock and shall be refinished if found to be out of tolerance.
NOTE 4—The diagonal of a 2 in. [50 mm] cube is 2.83 in. [70.7 mm].50 mm [2 in.] cube is 70.7 mm [2.83 in.].
6. Materials
6.1 Graded Standard Sand:
6.1.1 The sand (Note 5) used for making test specimens shall be natural silica sand conforming to the requirements for graded
standard sand in Specification C778.
NOTE 5—Segregation of Graded Sand—The graded standard sand should be handled in such a manner as to prevent segregation, since variations in the
grading of the sand cause variations in the consistency of the mortar. In emptying bins or sacks, care should be exercised to prevent the formation of
mounds of sand or craters in the sand, down the slopes of which the coarser particles will roll. Bins should be of sufficient size to permit these precautions.
Devices for drawing the sand from bins by gravity should not be used.
7. Temperature and Humidity
7.1 Temperature—The temperature of the air in the vicinity of the mixing slab, the dry materials, molds, base plates, and mixing
bowl, shall be maintained between 73.5 6 5.5 °F or [23.0 6 3.0 °C].23.0 °C 6 3.0 °C [73.5 °F 6 5.5 °F]. The temperature of
the mixing water, moist closet or moist room, and water in the storage tank shall be set at 73.5 6 3.5 °F or [23 6 2 °C].23 °C
6 2 °C [73.5 °F 6 3.5 °F].
7.2 Humidity—The relative humidity of the laboratory shall be not less than 50 %. The moist closet or moist room shall conform
to the requirements of Specification C511.
8. Test Specimens
8.1 Make two or three specimens from a batch of mortar for each period of test or test age.
9. Preparation of Specimen Molds
9.1 Apply a thin coating of release agent to the interior faces of the mold and non-absorptive base plates. Apply oils and greases
using an impregnated cloth or other suitable means. Wipe the mold faces and the base plate with a cloth as necessary to remove
any excess release agent and to achieve a thin, even coating on the interior surfaces. When using an aerosol lubricant, spray the
release agent directly onto the mold faces and base plate from a distance of 6 to 8 in. or [150 to 200 mm] to 150 mm to 200 mm
C109/C109M − 23
[6 in. to 8 in.] to achieve complete coverage. After spraying, wipe the surface with a cloth as necessary to remove any excess
aerosol lubricant. The residue coating should be just sufficient to allow a distinct finger print to remain following light finger
pressure (Note 6).
9.2 Seal the surfaces where the halves of the mold join by applying a coating of light cup grease such as petrolatum. The amount
should be sufficient to extrude slightly when the two halves are tightened together. Remove any excess grease with a cloth.
9.3 Seal molds to their base plates with a watertight sealant. Use microcrystalline wax or a mixture of three parts paraffin wax to
five parts rosin by mass. Paraffin wax is permitted as a sealant with molds that clamp to the base plate. Liquefy the wax by heating
it to a temperature of between 230 and 248 °F or [110 and 120 °C].110 °C and 120 °C [230 °F and 248 °F]. Effect a watertight
seal by applying the liquefied sealant at the outside contact lines between the mold and its base plate (Note 7).
9.4 Optionally, a watertight sealant of petroleum jelly is permitted for clamped molds. Apply a small amount of petroleum jelly
to the entire surface of the face of the mold that will be contacting the base plate. Clamp the mold to the base plate and wipe any
excess sealant from the interior of the mold and base plate.
NOTE 6—Because aerosol lubricants evaporate, molds should be checked for a sufficient coating of lubricant immediately prior to use. If an extended
period of time has elapsed since treatment, retreatment may be necessary.
NOTE 7—Watertight Molds—The mixture of paraffin wax and rosin specified for sealing the joints between molds and base plates may be found difficult
to remove when molds are being cleaned. Use of straight paraffin wax is permissible if a watertight joint is secured, but due to the low strength of paraffin
wax it should be used only when the mold is not held to the base plate by the paraffin wax alone. When securing clamped molds with paraffin wax, an
improved seal can be obtained by slightly warming the mold and base plate prior to applying the wax. Molds so treated should be allowed to return to
room temperature before use.
10. Specimen Preparation Procedure
10.1 Composition of Mortars:
10.1.1 Materials for the standard mortar shall be cement, graded standard sand, and water. The quantities of materials to be mixed
at one time in the batch of mortar for making six, nine, and twelve test specimens shall be in accordance with Table 2. Use specified
water content for all portland, portland-limestone, air-entraining portland, or air-entraining portland-limestone cements. The
amount of mixing water for other cements shall be such as to produce a flow of 110 6 5 as determined in accordance with 10.3.
NOTE 8—The water-to-portland-cement and water-to-portland-limestone-cement ratio used in Table 2 is 0.485 by mass. For air-entraining cements, the
water-to-portland-cement or water-toportland-limestone-cementwater-to-portland-limestone-cement ratio is 0.460 by mass. The sand-to-cement ratio is
2.75.
10.2 Preparation of Mortar:
10.2.1 Mechanically mix in accordance with the procedure given in Practice C305.
10.3 Determination of Flow:
10.3.1 Determine flow in accordance with procedure given in Test Method C1437.
10.3.2 For portland, portland-limestone, air-entraining portland, or air-entraining portland-limestone cements, record the flow.
10.3.3 In the case of cements other than portland, portland-limestone, air-entraining portland, or air-entraining portland-limestone
TABLE 2 Standard Test Mortar Proportions
Number of Specimens
Material
6 9 12
Cement, g 500 740 1060
Sand, g 1375 2035 2915
Water, mL
Portland or portland-limestone cements 242 359 514
Air-entraining portland or air-entraining portland-limestone cements 230 340 488
Other cements (to flow of 110 ± 5) . . . . . . . . .
C109/C109M − 23
cements, make trial mortars with varying percentages of water until the specified flow is obtained. Make each trial with fresh
mortar. Record the water content used to achieve the specified flow as weight percent of cement.
10.3.4 Immediately following completion of the flow test, return the mortar from the flow table to the mixing bowl. Quickly scrape
the bowl sides and transfer into the batch the mortar that may have collected on the side of the bowl and then remix the entire batch
15 s at medium speed. Upon completion of mixing, the mixing paddle shall be shaken to remove excess mortar into the mixing
bowl.
10.3.5 When a duplicate batch is to be made immediately for additional specimens, the flow test may be omitted and the mortar
allowed to stand in the mixing bowl 90 s without covering. During the last 15 s of this interval, quickly scrape the bowl sides and
transfer into the batch the mortar that may have collected on the side of the bowl. Then remix for 15 s at medium speed.
10.4 Molding Test Specimens:
10.4.1 Complete the consolidation of the mortar in the molds either by hand tamping or by a qualified alternative method.
Alternative methods include but are not limited to the use of a vibrating table or mechanical devices.
10.4.2 Hand Tamping—Start molding the specimens within a total elapsed time of not more than 2 min and 30 s after completion
of the original mixing of the mortar batch. Place a layer of mortar about 1 in. or [25 mm] 25 mm [1 in.] (approximately one half
of the depth of the mold) in all of the cube compartments. Tamp the mortar in each cube compartment 32 times in about 10 s in
four rounds, each round to be at right angles to the other and consisting of eight adjoining strokes over the surface of the specimen,
as illustrated in Fig. 1. The tamping pressure shall be just sufficient to ensure uniform filling of the molds. The four rounds of
tamping (32 strokes) of the mortar shall be completed in one cube before going to the next. When the tamping of the first layer
in all of the cube compartments is completed, fill the compartments with the remaining mortar and then tamp as specified for the
first layer. During tamping of the second layer, bring in the mortar forced out onto the tops of the molds after each round of tamping
by means of the gloved fingers and the tamper upon completion of each round and before starting the next round of tamping. On
completion of the tamping, the tops of all cubes should extend slightly above the tops of the molds. Bring in the mortar that has
been forced out onto the tops of the molds with a trowel and smooth off the cubes by drawing the flat side of the trowel (with the
leading edge slightly raised) once across the top of each cube at right angles to the length of the mold. Then, for the purpose of
leveling the mortar and making the mortar that protrudes above the top of the mold of more uniform thickness, draw the flat side
of the trowel (with the leading edge slightly raised) lightly once along the length of the mold. Cut off the mortar to a plane surface
flush with the top of the mold by drawing the straight edge of the trowel (held nearly perpendicular to the mold) with a saw
...