Standard Method of Test for

Making and Curing Concrete

Test Specimens in the Field

AASHTO Designation: T 23-181

Technical Section: 3b, Fresh Concrete
Release: Group 1 (April)
ASTM Designation: C31-15a

American Association of State Highway and Transportation Officials

444 North Capitol Street N.W., Suite 249
Washington, D.C. 20001

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS Not for Resale,2018-12-20 07:30:27 UTC
 Standard Method of Test for

Making and Curing Concrete

Test Specimens in the Field

AASHTO Designation: T 23-181

Technical Section: 3b, Fresh Concrete
Release: Group 1 (April)
ASTM Designation: C31-15a

1. SCOPE
1.1. This method covers procedures for making and curing cylinder and beam specimens from
representative samples of fresh concrete for a construction project.

1.2. The concrete used to make the molded specimens shall be sampled after all on-site adjustments
have been made to the mixture proportions, including the addition of mix water and admixtures.
This practice is not satisfactory for making specimens from concrete not having measurable slump
or requiring other sizes or shapes of specimens.

1.3. The values stated in SI units or inch-pound units are to be regarded separately as standard. 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.

1.4. 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.
Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to
exposed skin and tissue upon prolonged exposure.

1.5. The text of this standard references notes that provide explanatory material. These notes shall not
be considered as requirements of the standard.

2. REFERENCED DOCUMENTS
2.1. AASHTO Standards:
 M 195, Lightweight Aggregates for Structural Concrete
 M 201, Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the
Testing of Hydraulic Cements and Concretes
 M 205M/M 205, Molds for Forming Concrete Test Cylinders Vertically
 R 60, Sampling Freshly Mixed Concrete
 T 119M/T 119, Slump of Hydraulic Cement Concrete
 T 121M/T 121, Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete

TS-3b
--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`--- T 23-1 AASHTO
Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC
  T 152, Air Content of Freshly Mixed Concrete by the Pressure Method
 T 196M/T 196, Air Content of Freshly Mixed Concrete by the Volumetric Method
 T 197M/T 197, Time of Setting of Concrete Mixtures by Penetration Resistance
 T 231, Capping Cylindrical Concrete Specimens
 T 309, Temperature of Freshly Mixed Portland Cement Concrete

2.2. ASTM Standard:

 C125, Standard Terminology Relating to Concrete and Concrete Aggregates

2.3. ACI Standard:

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---
 ACI 309R, Guide for Consolidation of Concrete

3. TERMINOLOGY
3.1. For definitions of terms used in this practice, refer to ASTM C125.

4. SIGNIFICANCE AND USE

4.1. This method provides standardized requirements for making, curing, protecting, and transporting
concrete test specimens under field conditions.

4.2. If the specimens are made and standard cured, as stipulated herein, the resulting strength test
data where the specimens are tested are able to be used for the following purposes:

4.2.1. Acceptance testing for specified strength;

4.2.2. Checking the adequacy of mixture proportions for strength;

4.2.3. Quality control.

4.3. If the specimens are made and field cured, as stipulated herein, the resulting strength test data
when the specimens are tested are able to be used for the following purposes:

4.3.1. Determination of whether a structure is capable of being put in service;

4.3.2. Comparison with test results of standard cured specimens or with test results from various in-place
test methods;

4.3.3. Adequacy of curing and protection of concrete in the structure; or

4.3.4. Form or shoring removal time requirements.

5. APPARATUS
5.1. Molds, General—Molds for specimens or fastenings thereto in contact with the concrete shall be
made of steel, cast iron, or other nonabsorbent material, nonreactive with concrete containing
portland or other hydraulic cements. Molds shall hold their dimensions and shape under conditions
of use. Molds shall be watertight during use as judged by their ability to hold water poured into
them. Provisions for tests of watertightness are given in M 205M/M 205. A suitable sealant, such
as heavy grease, modeling clay, or microcrystalline wax shall be used where necessary to prevent
leakage through the joints. Positive means shall be provided to hold base plates firmly to the

TS-3b T 23-2 AASHTO

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC
 molds. Reusable molds shall be lightly coated with mineral oil or a suitable nonreactive form
release material before use.

5.2. Cylinder—Molds for casting concrete test specimens shall conform to the requirements of
M 205M/M 205.

5.3. Beam Molds—Beam molds shall be of the shape and dimensions required to produce the
specimens stipulated in Section 6.2. The inside surfaces of the molds shall be smooth. The sides,
bottom, and ends shall be at right angles to each other and shall be straight and true and free of
warpage. Maximum variation from the nominal cross section shall not exceed 3.2 mm (1/8 in.) for
molds with depth or breadth of 152 mm (6 in.) or more, or 1.6 mm (1/16 in.) for molds of smaller
depth or breadth. Except for flexure specimens, molds shall not vary from the nominal length by
more than 1.6 mm (1/16 in.). Flexure molds shall not be shorter than 1.6 mm (1/16 in.) of the
required length (greater lengths are allowed).

5.4. Tamping Rods—A round, smooth, straight, steel rod with a diameter conforming to the
requirements in Table 1. The length of the tamping rod shall be at least 100 mm (4 in.) greater
than the depth of the mold in which rodding is being performed, but not greater than 600 mm

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---
(24 in.) in overall length (see Note 1). The rod shall have the tamping end or both ends rounded to
a hemispherical tip of the same diameter as the rod.
Note 1—A rod length of 400 mm (16 in.) to 600 mm (24 in.) meets the requirements of the
following: T 119M/T 119, T 121M/T 121, T 152, and T 196M/T 196.

Table 1—Tamping Rod Requirements

Rod Dimensionsa
Diameter of Cylinder or Width of Diameter, Length of Rod,
Beam, mm (in.) mm (in.) mm (in.)
<150 (6) 10 (3/8) 300 (12)
150 (6) 16 (5/8) 500 (20)
225 (9) 16 (5/8) 650 (26)
a
Rod tolerances length ±100 mm (4 in.) and diameter ±2 mm (1/16 in.).

5.5. Vibrators—Internal vibrators shall be used. The vibrator frequency shall be at least 9000
vibrations per minute (150 Hz) while the vibrator is operating in the concrete. The diameter of a
round vibrator shall be no more than one fourth of the diameter of the cylinder mold or one fourth
the width of the beam mold. Other shaped vibrators shall have a perimeter equivalent to the
circumference of an appropriate round vibrator. The combined length of the vibrator shaft and
vibrating element shall exceed the depth of the section being vibrated by at least 75 mm (3 in.).
The vibrator frequency shall be checked periodically.
Note 2—For information on size and frequency of various vibrators and a method to periodically
check vibrator frequency, see ACI 309R.

5.6. Mallet—A mallet with a rubber or rawhide head weighing 0.57 ± 0.23 kg (1.25 ± 0.50 lb) shall
be used.

5.7. Placement Tools—Of a size large enough so that each amount of concrete obtained from the
sampling receptacle is representative and small enough so that concrete is not spilled during the
placement of the mold. For placing concrete in a cylinder mold, the acceptable tool is a scoop. For
placing concrete in a beam mold, either a shovel or scoop is permitted.

5.8. Finishing Tools—Handheld float or a trowel.

TS-3b T 23-3 AASHTO

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC
 5.9. Slump Apparatus—The apparatus for measurement of slump shall conform to the requirements
of T 119M/T 119.

5.10. Sampling Receptacle—The receptacle shall be a suitable heavy gauge metal pan, wheelbarrow, or
flat, clean, nonabsorbent mixing board of sufficient capacity to allow easy remixing of the entire
sample with a shovel or trowel.

5.11. Air Content Apparatus—The apparatus for measuring air content shall conform to the
requirements of T 196M/T 196 or T 152.

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---
5.12. Temperature Measuring Devices—The temperature measuring devices shall conform to the
applicable requirements of T 309M/T 309.

6. TESTING REQUIREMENTS
6.1. Cylindrical Specimens—Compressive or splitting tensile strength specimens shall be cylinders
cast and allowed to set in an upright position. The number and size of cylinders cast shall be as
directed by the specifier of the tests. In addition, the length shall be twice the diameter, and the
cylinder diameter shall be at least three times the nominal maximum size of the coarse aggregate.
When the nominal maximum size of the coarse aggregate exceeds 50 mm (2 in.), the concrete
sample shall be treated by wet sieving through a 50-mm (2-in.) sieve as described in R 60. For
acceptance testing for specified compressive strength, cylinders shall be 152 by 300 mm (6 by
12 in.) or 100 by 200 mm (4 by 8 in.) (Note 3).
Note 3—When molds in SI units are required and not available, equivalent inch-pound unit size
molds should be permitted.

6.2. Beam Specimens—Flexural strength specimens shall be beams of concrete cast and hardened with
long axes horizontal. The length shall be at least 50 mm (2 in.) greater than three times the depth
as tested. The ratio of width to depth as molded shall not exceed 1.5.

6.2.1. The minimum cross-sectional dimension of the beam shall be as stated in Table 2. Unless
otherwise specified by the specifier of the tests, the standard beam shall be 152 by 152 mm (6 by
6 in.) in cross section.

Table 2—Minimum Cross-Sectional Dimensions of Beams

Nominal Maximum Aggregate Size (NMAS) Minimum Cross-Sectional Dimension
≤25 mm (≤1 in.) 100 by 100 mm (4 by 4 in.)
25 mm (1 in.) <NMAS ≤50 mm (2 in.) 152 by 152 mm (6 by 6 in.)

6.2.2. When the nominal maximum size of the coarse aggregate exceeds 50 mm (2 in.), the concrete
sample shall be treated by wet sieving through a 50-mm (2-in.) sieve as described in R 60.

6.2.3. The specifier of tests shall specify the specimen size and the number of specimens to be tested to
obtain an average test result (Note 4 and Note 5). The same specimen size shall be used when
comparing results and for mixture qualification and acceptance testing.
Note 4—The modulus of rupture can be determined using different specimen sizes. However,
measured modulus of rupture generally increases as specimen size decreases. 2,3 The strength ratio
for beams of different sizes depends primarily on the maximum size of aggregate. 4 Experimental
data obtained in two different studies have shown that for maximum aggregate size between 19.0
and 25.0 mm (3/4 and 1 in.), the ratio between the modulus of rupture determined with a 152 by
152 mm (6 by 6 in.) and a 100 by 100 mm (4 by 4 in.) may vary from 0.90 to 1.072 for maximum
aggregate size between 9.5 and 37.5 mm (3/8 and 11/2 in.), the ratio between the modulus of rupture

TS-3b T 23-4 AASHTO

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC
 determined with a 152 by 152 mm (6 by 6 in.) and a 115 by 115 mm (4.5 by 4.5 in.) may vary
from 0.86 to 1.00.3
Note 5—It has been shown that the variability of individual tests results increases as the
specimen size decreases.2,3

7. SAMPLING CONCRETE
7.1. The samples used to fabricate test specimens under this standard shall be obtained in accordance
with R 60 unless an alternative procedure has been approved.

7.2. Record the identification of the sample with respect to the location of the concrete represented and
the time of casting.

8. SLUMP, AIR CONTENT, AND TEMPERATURE

8.1. Slump—Measure and record the slump of each batch of concrete, from which specimens are made,
immediately after remixing in the receptacle as required in T 119M/T 119.

8.2. Air Content—Determine and record the air content in accordance with either T 152 or
T 196M/T 196. The concrete used in performing the air content test shall not be used in fabricating
test specimens.

8.3. Temperature—Determine and record the temperature in accordance with T 309.

Note 6—Some specifications may require the measurement of the unit weight of concrete.
The volume of concrete produced per batch may be desired on some projects. Also, additional
information on the air content measurements may be desired. Test Method T 121M/T 121 is used
to measure the unit weight, yield, and gravimetric air content of freshly mixed concrete.

9. MOLDING SPECIMENS
9.1. Place of Molding—Mold specimens promptly on a level, rigid, horizontal surface, free from
vibration and other disturbances, at a place as near as practicable to the location where they are to
be stored.

9.2. Casting Cylinders—Select the proper tamping rod from Section 5.4 and Table 1 or the proper
vibrator from Section 5.5. Determine the method of consolidation from Table 3, unless another
method is specified. If the method of consolidation is rodding, determine molding requirements
from Table 4. If the method of consolidation is vibration, determine molding requirements from

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---
Table 5. Select a scoop of the size described in Section 5.7. While placing the concrete in the
mold, move the scoop around the perimeter of the mold opening to ensure an even distribution of
the concrete with minimal segregation. Each layer of concrete shall be consolidated as required. In
placing the final layer, add the amount of concrete that will fill the mold after consolidation.

9.2.1. Self-Consolidating Concrete—Cast specimens as described in Section 9.2 without layers or

consolidation.

Table 3—Method of Consolidation Requirements

Slump, mm (in.) Method of Consolidation
≥25 mm (≥1 in.) Rodding or vibration
≤25 mm (≤1 in.) Vibration

TS-3b T 23-5 AASHTO

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC
 9.3. Number of Casting Beams—Select the proper tamping rod from Section 5.4 and Table 1 or the
proper vibrator from Section 5.5. Determine the method of consolidation from Table 3, unless
another method is specified. If the method of consolidation is rodding, determine molding
requirements from Table 4. If the method of consolidation is vibration, determine molding
requirements from Table 5. Determine the number of roddings per layer, one for each 14 cm2
(2 in.2) of the top surface area of the beam. Select a placement tool as described in Section 5.7.
Using the scoop or shovel, place the concrete in the mold to the height required for each layer.
Place the concrete so that it is uniformly distributed within each layer with minimal segregation.
Each layer shall be consolidated as required. In placing the final layer, add an amount of concrete
that will fill the mold after consolidation.

Table 4—Molding Requirements by Rodding

Number of Layers of
Specimen Approximately Number of Roddings per

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---
Type and Size Equal Depth Layer
Cylinders:
Diameter, mm (in.)
100 (4) 2 25
150 (6) 3 25
225 (9) 4 50
Beams:
Width, mm (in.)
100 (4) to 200 (8) 2 See Section 9.4.1
Over 200 (8) 3 or more equal depths, See Section 9.4.1
each not to exceed
150 mm (6 in.)

Table 5—Molding Requirements by Vibration

Specimen Number of Vibrator Approximate Depth of
Type and Size Number of Layers Insertions per Layer Layer, mm (in.)
Cylinders:
Diameter, mm (in.)
100 (4) 2 1 One-half depth of specimen
150 (6) 2 2 One-half depth of specimen
225 (9) 2 4 One-half depth of specimen
Beams:
Width, mm (in.)
100 (4) to 200 (8) 1 See Section 9.4.2.2 Depth of specimen 200 (8)
as near as practicable
Over 200 (8) 2 or more See Section 9.4.2.2 Depth of specimen 200 (8)
as near as practicable

9.4. Consolidation—The methods of consolidation for this practice are rodding or internal vibration.

9.4.1. Rodding—Place the concrete in the mold, in the required number of layers of approximately equal
volume. Rod each layer uniformly over the cross section with the rounded end of the rod using the
number of roddings specified in Table 4. Rod the bottom layer throughout its depth. In rodding
this layer, use care not to damage the bottom of the mold. For each upper layer, allow the rod to
penetrate through the layer being rodded and into the layer below approximately 25 mm (1 in.).
After each layer is rodded, tap the outsides of the mold lightly 10 to 15 times with the mallet, to
close any holes left by rodding and to release any large air bubbles that may have been trapped.
Use an open hand to tap light-gauge single-use molds that are susceptible to damage if tapped with
a mallet. After tapping, spade each layer of the concrete along the sides and ends of beam molds
with a trowel or other suitable tool. Underfilled molds shall be adjusted with representative

TS-3b T 23-6 AASHTO

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC
 concrete during consolidation of the top layer. Overfilled molds shall have excess concrete
removed.

9.4.2. Vibration—Maintain a uniform time period for duration of vibration for the particular kind of
concrete, vibrator, and specimen mold involved. The duration of vibration required will depend
upon the workability of the concrete and the effectiveness of the vibrator. Usually, sufficient
vibration has been applied as soon as the surface of the concrete has become relatively smooth and
large air bubbles cease to break through the top surface. Continue vibration only long enough to
achieve proper consolidation of the concrete. (See Note 7.) Fill the molds and vibrate in the
required number of approximately equal layers. Place all the concrete for each layer in the mold
before starting vibration of that layer. Compacting the specimen, insert the vibrator slowly and do
not allow it to rest on the bottom or sides of the mold. Slowly withdraw the vibrator so that no
large air pockets are left in the specimen. When placing the final layer, avoid overfilling by more
than 6 mm (1/4 in.).
Note 7—Generally, no more than 5 s of vibration should be required for each insertion to
adequately consolidate concrete with a slump greater than 75 mm (3 in.). Longer times may be
required for lower slump concrete, but the vibration time should rarely have to exceed 10 s per
insertion.

9.4.2.1. Cylinders—The number of insertions of a vibrator per layer is given in Table 5. When more than
one insertion per layer is required, distribute the insertion uniformly within each layer. Allow the
vibration to penetrate through the layer being vibrated, and into the layer below, approximately
25 mm (1 in.). After each layer is vibrated, tap the outsides of the mold 10 to 15 times with the
mallet, to close holes left by vibrating and to release entrapped air voids. Use an open hand to tap
single-use metal molds that are susceptible to damage if tapped with a mallet.

9.4.2.2. Beam—Insert the vibrator at intervals not exceeding 150 mm (6 in.) along the center line of the
long dimension of the specimen. For specimens wider than 6 in., use alternating insertions along
two lines. Allow the shaft of the vibrator to penetrate into the bottom layer approximately 25 mm
(1 in.). After each layer is vibrated, tap the outsides of the mold sharply 10 to 15 times with the
mallet, to close any holes left by vibrating and to release entrapped air voids.

9.5. Finishing—Perform all finishing with the minimum manipulation necessary to produce a flat,
even surface that is level with the rim or edge of the mold and that has no depressions or
projections larger than 3.2 mm (1/8 in.).

9.5.1. Cylinders—After consolidation, finish the top surfaces by striking them off with the tamping rod
where the consistency of the concrete permits or with a handheld float or trowel. If desired, cap
the top surface of freshly made cylinders with a thin layer of stiff portland cement paste that is
permitted to harden and cure with the specimen. See section on Capping Materials of T 231.

9.5.2. Beams—After consolidation of the concrete, use a handheld float or trowel to strike off the top
surface to the required tolerance to produce a flat, even surface.

9.6. Identification—Mark the specimens to positively identify them and the concrete they represent.
Use a method that will not alter the top surface of the concrete. Do not mark the removable caps.
Upon removal of the molds, mark the test specimens to retain their identities.

10. CURING
10.1. Standard Curing—Standard curing is the curing method used when the specimens are made and
cured for the purposes stated in Section 4.2.

TS-3b T 23-7 AASHTO

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC
 10.1.1. Storage—If specimens cannot be molded at the place where they will receive initial curing,
immediately after finishing, move the specimens to an initial curing place for storage. The
supporting surface on which specimens are stored shall be level to within 20 mm/m (1/4 in./ft). If
cylinders in the single-use molds are moved, lift and support the cylinders from the bottom of the
molds with a large trowel or similar device. If the top surface is marred during movement to place
of initial storage, immediately refinish.

10.1.2. Initial Curing—Immediately after molding and finishing, the specimens shall be stored for a
period up to 48 h in a temperature range from 16 to 27°C (60 to 80°F) in an environment
preventing moisture loss from the specimens. For concrete mixtures with a specified strength of
40 MPa (6000 psi) or greater, the initial curing temperature shall be between 20 and 26°C (68 and
78°F). Various procedures are capable of being used during the initial curing period to maintain
the specified moisture and temperature conditions. An appropriate procedure or combination of
procedures shall be used (Note 8). Shield all specimens from direct sunlight and, if used, radiant
heating devices. The storage temperature shall be controlled by the use of heating and cooling
devices, as necessary. Record the temperature using a maximum-minimum thermometer.
Note 8—A satisfactory moisture environment can be created during the initial curing of the
specimens by one or more of the following procedures: (1) immediately immerse molded
specimens with plastic lids in water saturated with calcium hydroxide; (2) store in properly
constructed wood boxes or structures; (3) place in damp sand pits; (4) cover with removable
plastic lids; (5) place inside plastic bags; or (6) cover with plastic sheets or nonabsorbent plates if
provisions are made to avoid drying and damp burlap is used inside the enclosure, but the burlap is
prevented from contacting the concrete surfaces.

Note 9—A satisfactory temperature environment can be controlled during the initial curing of the
specimens by one or more of the following procedures: (1) use of ventilation, (2) use of ice,
(3) use of thermostatically controlled heating or cooling devices, or (4) use of heating methods
such as stoves or lightbulbs. Other suitable methods may be used if the requirements limiting
specimen storage temperature and moisture loss are met. For concrete mixtures with a specified
strength of 40 MPa (6000 psi) or greater, heat generated during the early ages may raise the
temperature above the required storage temperature. When specimens are to be immersed in water
saturated with calcium hydroxide, specimens in molds that expand when immersed in water
should not be used. Early-age strength test results may be lower when stored at 16°C (60°F) and
higher when stored at 27°C (80°F). On the other hand, at later ages, test results may be lower for
higher initial storage temperatures.

10.1.3. Final Curing:

10.1.3.1. Cylinders—On completion of initial curing and within 30 min after removing the molds, cure

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---
specimens with free water maintained on their surfaces at all times at a temperature of 23 ± 2°C
(73.5 ± 3.5°F) using water storage tanks or moist rooms complying with the requirements of
Specification M 201, except when capping with sulfur mortar capping compound and immediately
before testing. When capping with sulfur mortar capping compounds, the ends of the cylinder
shall be dry enough to preclude the formation of steam or foam pockets under or in the cap larger
than 6 mm (1/4 in.) as described in T 231. For a period not to exceed 3 h immediately prior to test,
standard curing temperature is not required, provided free moisture is maintained on the cylinders
and ambient temperature is between 20 to 30°C (68 to 80°F).

10.1.3.2. Beams—Beams are to be cured the same as cylinders (see Section 10.1.3.1), except that they shall
be stored in water saturated with calcium hydroxide at 23 ± 2°C (73.5 ± 3.5°F) at least 20 h prior
to testing. Drying of the surfaces of the beam shall be prevented between removal from water
storage and completion of testing (Note 10).
Note 10—Relatively small amounts of surface drying of flexural specimens can induce tensile
stresses in the extreme fibers that will markedly reduce the indicated flexural strength.

TS-3b T 23-8 AASHTO

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC
 10.2. Field Curing—Field curing is the curing method used for the specimens made for the purposes
stated in Section 4.3.

10.2.1. Cylinders—Store cylinders in or on the structure as near to the point of deposit of the concrete
represented as possible. Protect all surfaces of the cylinders from the elements in as near as
possible the same way as the formed work. Provide the cylinders with the same temperature and
moisture environment as the structural work. Test the specimens in the moisture condition
resulting from the specified curing treatment. To meet these conditions, specimens made for the
purpose of determining when a structure is capable of being put in service shall be removed from
the molds at the time of removal of form work.

10.2.2. Beams—As nearly as practicable, cure beams in the same manner as the concrete in the structure.
At the end of 48 ± 4 h after molding, take the molded specimens to the storage location and
remove from the molds. Store specimens representing pavements of slabs on grade by placing
them on the ground as molded, with their top surfaces up. Bank the sides and ends of the
specimens with earth or sand that shall be kept damp, leaving the top surfaces exposed to the
specified curing treatment. Store specimens representing structure concrete as near the point in the
structure they represent as possible, and afford them the same temperature protection and moisture
environment as the structure. At the end of the curing period, leave the specimens in place exposed
to the weather in the same manner as the structure. Remove all beam specimens from field storage
and store in water saturated with calcium hydroxide at 23 ± 2°C (73.5 ± 3.5°F) for 24 ± 4 h
immediately before time of testing to ensure uniform moisture condition from specimen to
specimen. Observe the precautions given in Section 10.1.3.2 to guard against drying between time
of removal from curing to testing.

10.3. Structural Lightweight Concrete Curing—Cure structural lightweight concrete cylinders in

accordance with M 195.

11. TRANSPORTATION OF SPECIMENS TO LABORATORY

11.1. Prior to transporting, cure and protect specimens as required in Section 10. Specimens shall not be
transported until at least 8 h after final set. (See Note 11.) During transporting, protect the
specimen with suitable cushioning material to prevent damage from jarring. During cold weather,
protect the specimens from freezing with suitable insulation material. Prevent moisture loss during
transportation by wrapping the specimens in plastic, wet burlap, by surrounding them with wet
sand or tight-fitting plastic caps on plastic molds. Transportation time shall not exceed 4 h.
Note 11—Setting time may be measured by T 197M/T 197.

12. REPORT
12.1. Report the following information to the laboratory that will test the specimens:

12.1.1. Identification number;

12.1.2. Location of concrete represented by the samples;

12.1.3. Date, time, and name of individual molding specimens;

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---

12.1.4. Slump, air content, and concrete temperature, test results and results of any other tests on the fresh
concrete, and any deviations from referenced standard test methods; and

12.1.5. Curing Method—For standard curing method, report the initial curing method with maximum and
minimum temperatures and final curing method. For field curing method, report the location

TS-3b T 23-9 AASHTO

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC
 where stored, manner of protection from the elements, temperature, and moisture environment,
and time of removal from molds.

13. KEYWORDS
13.1. Concrete cylinder specimens; concrete beam specimens; concrete field specimens.

1
T 23 conforms to ASTM C31-15a except that C31-15a includes requirements for certification of field technicians.
2
Tanesi, J, A. Ardani, and J. Leavitt. Reducing the Specimen Size of Concrete Flexural Strength Test (AASHTO
T 97) for Safety and Ease of Handling. In Transportation Research Record 2342. TRB, National Research Council,
Washington, DC, 2013, pp. 99–105.
3
Carrasquillo, P. M. and R. L. Carrasquillo. Improved Concrete Quality Control Procedures Using Third Point
Loading. Research Report 119-1F, Project 3-9-87-1119. Center for Transportation Research, The University of
Texas at Austin, November 1987.
4
Bazant, Z. and D. Novak. Proposal for Standard Test of Modulus of Rupture of Concrete with its Size Dependence.
In ACI Materials Journal, Vol. 98, No. 1, January–February 2001. American Concrete Institute, Farmington Hills,
MI, pp. 79–87.

--`,,,,,`,,,`,`,``,`,`,,-`-``,```,,,`---

TS-3b T 23-10 AASHTO

Copyright American Association of State Highway and Transportation Officials Order Number: W2132692
Provided by IHS Markit under license with AASHTO © 2018 by the American Association of State Highway and Transportation Officials.
Sold to:GULF TESTING SOLUTIONS LLC [232659100001] - INFO@GULFTESTINGLAB.COM,
No reproduction or networking permitted without license from IHS
All rights reserved. Duplication is a violation of applicable law.
Not for Resale,2018-12-20 07:30:27 UTC