ASTM C1698-09
(Test Method)Standard Test Method for Autogenous Strain of Cement Paste and Mortar
Standard Test Method for Autogenous Strain of Cement Paste and Mortar
SIGNIFICANCE AND USE
Autogenous strain is the self-created bulk strain of cement paste, mortar, or concrete during hardening at constant temperature. In conventional concrete, autogenous shrinkage strain is generally negligible, but in concrete with low water-cementitious materials ratio (w/cm) or with silica fume it may be considerable (1). Restraint of the autogenous strain by aggregates or adjoining structural members may result in formation of micro and macro cracks that impair strength, durability and aesthetics. Cracks may also be a problem with regard to hygienic cleaning of surfaces.
An accurate measurement of the autogenous strain of cementitious mixtures with low w/cm is important for evaluating the risk of early-age cracking of concrete structures. Measurements of autogenous strain have been carried out using either volumetric or linear methods. Both methods may show evidence of significant artifacts (1); therefore, results of the two methods may disagree considerably if not carried out properly.
A sealed, flexible corrugated mold system (2) combines the advantages of linear and volumetric measurement of autogenous strain, while avoiding most of their disadvantages. The mold effectively prevents moisture loss and minimizes restraint to volume change during hardening. Moreover, results obtained with the corrugated mold system agree with those from the volumetric method, once some artifacts, in particular water absorption through the membrane used to contain the test specimen, have been eliminated in the latter (3,4). The corrugated mold system is easier to use and shows better repeatability than the volumetric technique (3,4). Measurements with the corrugated mold system are in good agreement with unrestrained length change measurements obtained using Test Method C157/C157M with sealed specimens (5); however, Test Method C157/C157M does not allow measurement of the shrinkage occurring before 24 h (5).
This test method can be used to evaluate the effects of cementitious m...
SCOPE
1.1 This test method measures the bulk strain of a sealed cement paste or mortar specimen, including those containing admixtures, various supplementary cementitious materials (SCM), and other fine materials, at constant temperature and not subjected to external forces, from the time of final setting until a specified age. This strain is known as autogenous strain. Autogenous strain is most significant in concrete with low water-cementitious materials ratio (w/cm) (See Note 1).
Note 1—A low water-cementitious materials ratio (w/cm) can be considered to be a water to cement ratio of 0.40 or lower for this test.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure. )
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C1698 − 09
StandardTest Method for
Autogenous Strain of Cement Paste and Mortar
This standard is issued under the fixed designation C1698; 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.
1. Scope C305 Practice for Mechanical Mixing of Hydraulic Cement
Pastes and Mortars of Plastic Consistency
1.1 This test method measures the bulk strain of a sealed
C403/C403M Test Method for Time of Setting of Concrete
cement paste or mortar specimen, including those containing
Mixtures by Penetration Resistance
admixtures, various supplementary cementitious materials
C1005 Specification for Reference Masses and Devices for
(SCM), and other fine materials, at constant temperature and
Determining Mass and Volume for Use in the Physical
not subjected to external forces, from the time of final setting
Testing of Hydraulic Cements
untilaspecifiedage.Thisstrainisknownas autogenous strain.
2.2 API Specification
Autogenous strain is most significant in concrete with low
RP 10B-2/ISO 10426-2 Recommended Practice for Testing
water-cementitious materials ratio (w/cm) (See Note 1).
NOTE 1—A low water-cementitious materials ratio (w/cm) can be Well Cements
considered to be a water to cement ratio of 0.40 or lower for this test.
3. Terminology
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3.1 Definitions:
standard.
3.1.1 For definitions of terms used in this test method, refer
to Terminologies C125 and C219.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 autogenous strain, n—the bulk strain of a sealed
priate safety and health practices and determine the applica-
specimen of a cementitious mixture, not subjected to external
bility of regulatory limitations prior to use. (Warning—Fresh
forcesandunderconstanttemperature,measuredfromthetime
hydraulic cementitious mixtures are caustic and may cause
offinalsettinguntilaspecifiedage;negativestraincorresponds
chemical burns to skin and tissue upon prolonged exposure. )
to shrinkage and positive strain corresponds to expansion.
2. Referenced Documents
4. Summary of Test Method
2.1 ASTM Standards:
4.1 Aspecimen of freshly mixed paste or mortar is prepared
C125 Terminology Relating to Concrete and Concrete Ag-
using a corrugated mold that offers little resistance to length
gregates
changeofthespecimen.Themoldissealedtopreventmoisture
C157/C157M Test Method for Length Change of Hardened
loss and the specimen is stored at constant temperature.
Hydraulic-Cement Mortar and Concrete
Starting at the time of final setting, the length of the specimen
C191 TestMethodsforTimeofSettingofHydraulicCement
is measured using a dilatometer. The change in length is
by Vicat Needle
recorded at regular time intervals until the designated age. The
C192/C192M Practice for Making and Curing Concrete Test
change in length and original length of the specimen are used
Specimens in the Laboratory
to compute the autogenous strain.
C219 Terminology Relating to Hydraulic Cement
5. Significance and Use
This test method is under the jurisdiction of ASTM Committee C09 on 5.1 Autogenous strain is the self-created bulk strain of
Concrete and ConcreteAggregates and is the direct responsibility of Subcommittee
cement paste, mortar, or concrete during hardening at constant
C09.68 on Volume Change.
temperature. In conventional concrete, autogenous shrinkage
Current edition approved Oct. 1, 2009. Published November 2009. DOI:
strain is generally negligible, but in concrete with low water-
10.1520/C1698-09.
Section on Safety Precautions, Manual of Aggregate and Concrete Testing,
cementitious materials ratio (w/cm) or with silica fume it may
Annual Book of ASTM Standards, Vol 04.02.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from American Petroleum Institute (API), 1220 L. St., NW,
the ASTM website. Washington, DC 20005-4070, http://www.api.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1698 − 09
be considerable (1). Restraint of the autogenous strain by 5.5 The autogenous shrinkage strain of mortar specimens
aggregates or adjoining structural members may result in will be less than that of paste specimens for the same w/cm.
formation of micro and macro cracks that impair strength, The autogenous shrinkage strain of concrete will be less than
durability and aesthetics. Cracks may also be a problem with that of mortar for the same w/cm. The nominal maximum
regard to hygienic cleaning of surfaces. aggregate size for mortar used in this test method is 4.75 mm.
5.2 An accurate measurement of the autogenous strain of
6. Apparatus
cementitious mixtures with low w/cm is important for evalu-
6.1 The apparatus to measure autogenous strain is com-
ating the risk of early-age cracking of concrete structures.
posed of a corrugated mold with two end plugs, a dilatometer
Measurementsofautogenousstrainhavebeencarriedoutusing
bench, a length measuring gauge, and a reference bar (see Fig.
either volumetric or linear methods. Both methods may show
1).
evidence of significant artifacts (1); therefore, results of the
two methods may disagree considerably if not carried out
6.2 Molds—The molds consist of corrugated plastic tubes,
properly.
having a length of 420 6 5 mm and an outer diameter of 29 6
0.5 mm (see Note 2). The plastic tubes are made of 0.5 6
5.3 Asealed, flexible corrugated mold system (2) combines
0.2-mm thick low-density polyethylene (PE) and have
the advantages of linear and volumetric measurement of
triangular-shaped corrugations in order to minimize restraint in
autogenous strain, while avoiding most of their disadvantages.
the longitudinal direction (see Fig. 2). The distance between
The mold effectively prevents moisture loss and minimizes
corrugations is 5.8 6 0.2 mm. The mold is tightly closed with
restraint to volume change during hardening. Moreover, results
two tapered end plugs having a length of 19 6 0.5 mm. The
obtained with the corrugated mold system agree with those
diameter of the plastic end plugs tapers from 21 6 0.1 mm to
from the volumetric method, once some artifacts, in particular
22.4 6 0.1 mm (see Fig. 3).
waterabsorptionthroughthemembraneusedtocontainthetest
NOTE 2—The small diameter of the molds limits the temperature
specimen, have been eliminated in the latter (3,4). The corru-
differences that may arise during hydration of the cementitious materials.
gated mold system is easier to use and shows better repeatabil-
Typical maximum temperature increase in the center of the test specimen,
ity than the volumetric technique (3,4). Measurements with the
due to heat of hydration of cement paste or mortar has been determined to
corrugated mold system are in good agreement with unre-
be 2 °C. The maximum longitudinal restraint stress exerted by the molds
has been determined to be 0.001 MPa (6).
strained length change measurements obtained using Test
Method C157/C157M with sealed specimens (5); however,
6.3 Dilatometer Bench—The dilatometer bench consists of
Test Method C157/C157M does not allow measurement of the
three stainless steel rods with a diameter of 20 6 1.0 mm and
shrinkage occurring before 24 h (5).
two stainless steel end plates. Technical drawings of a suitable
dilatometer bench are shown in Fig. 4. During measurement,
5.4 This test method can be used to evaluate the effects of
the test specimen is positioned horizontally and is supported
cementitious materials, admixtures, and mixture proportions
longitudinally by the two upper rods.
on autogenous shrinkage strain of paste or mortar specimens.
6.4 Length Measuring Gauge—A gauge measures length
changes at one end of the specimen. The measuring range of
The boldface numbers in parentheses refer to a list of references at the end of
the gauge shall be at least 10 mm and the resolution shall be at
this standard.
NOTE 1—In the foreground a corrugated PE-mold with two specially shaped end plugs and a 425 mm reference bar. In the background the dilatometer
bench with a test specimen placed for length measurement. To the right a digital length gauge with remote control.
FIG. 1 A Suitable Dilatometer Bench with Accessories
C1698 − 09
FIG. 2 Corrugated Polyethylene Mold
NOTE 1—Plastic Tube Wall Thickness 0.5 6 0.2 mm.
FIG. 3 Outer Dimensions (mm) of Corrugated Low-Density Polyethylene Mold and End Plug
least 0.0025 mm, corresponding to a resolution of about 6 6.9 Tamping Rod for consolidation of the paste or mortar. It
µm/m for the calculated strain. shall be made of a rigid, non-absorptive material that does not
react with the cementitious mixture.The length of the rod shall
6.5 Reference Bar—Measurements in the dilatometer are
be at least 500 mm and the diameter shall be 6 6 1 mm. The
performed relative to the length of the reference bar.The bar is
ends may be flat or hemispherical.
made of Invar with a length of 425 6 0.5 mm and a diameter
of 20 6 1.0, tapering to 10 6 1.0 mm at both ends as shown
7. Procedure
inFig.5.Theactuallengthofthereferencebarshallbemarked
7.1 Number of Specimens—Three replicate specimens shall
permanently on the bar to the nearest 0.01 mm. Two plastic
be tested for each cement paste or mortar (see Note 3).
rings with an external diameter 30 6 0.5 mm are mounted on
7.1.1 Mixing—Mix cement pastes and mortars according to
the reference bar, as shown in Fig. 1.
Practice C305. Record the time when the cementitious mate-
6.6 Reference Masses and Devices for Determining Mass
rials are added to the water.
and Volume shall conform to the requirements of Specification
7.1.2 Mixing Apparatus
C1005.
7.1.2.1 Mortar Preparation—The mixer shall comply with
6.7 Support Tube used to support the corrugated mold the sequence in Practice C305.
during specimen fabrication. The support tube has a length of 7.1.2.2 Paste Preparation—A high shear blender, or simi-
400 6 5 mm and an inside diameter of 32 6 1 mm (see Fig. lar variable speed blender capable of maintaining a no-load
6).Thetubeisattachedtoabasethatcanbefixedtoavibrating speed of at least 15 000 r/min, with optional cooling device.A
table.
6.8 Vibrating Table as described in Practice C192/C192M. Mixing devices described in API Specification RP 10B-2/ISO 10426-2.
C1698 − 09
NOTE 1—All dimensions are in mm (tolerance 6 0.5 %).
FIG. 4 Technical Drawing of the Dilatometer Bench Shown in Fig. 1
Top: Plan View. Bottom: Elevation View of End Plate
NOTE 1—All dimensions are in mm and tolerances given in the text.
FIG. 5 Technical Drawing of the Reference Bar Shown in Fig. 1
hand-held household mixer capable of mixing paste at not less cementitiousmixture,dropthemintothemold,andconsolidate
than 400 r/min or other mixers for paste or mortar preparation with the tamping rod. To ensure that the cast specimens have
are also permitted.
approximately the same length, do not stretch or compress the
NOTE 3—About 185 mL of cement paste or mortar are needed to fill
corrugated mold during filling. For fluid mixtures, the corru-
each corrugated mold. For a paste with a water-cement ratio of 0.4, this
gated mold shall be held only by the support tube during
corresponds to approximately 360 g of paste.
casting. For semi-fluid and stiff mixtures, manually maintain
7.2 Filling and Closing of Molds—Clamp the mounting
the initial length of the mold during compaction. Fill the mold
base of the support tube to a vibrating table. Measure the
to approximately 15 mm below the top end of the mold to
lengths of the plugs to be used for each specimen. Place a plug
allow room for the top end plug. Before mounting the top end
intooneendofthemold,andpositionthemold,withtheclosed
plug, gently compress the corrugated mold to bring the cement
end down, inside the support tube. If the cementitious mixture
paste or mortar in contact with the end plug. Mount the end
is pourable, slowly pour the mixture into the corrugated mold
plug during relief of the compression of the corrugated mold.
with the vibrating table turned on (see Fig. 7). For a semi-fluid
Use a screwing motion of the end plug to ease the mounting
mixture, fill the mold in four equal layers and compact each
operation.Immediatelyaftercasting,carefullywipethesurface
layer 5 times with the tamping rod before each subsequent
of the corrugated mold with a dry cloth to remove any cement
layer is cast. The rod shall just penetrate the underlying layer.
paste, mortar, or water.
For a stiff mixture, hand prepare rolled sections of the
C1698 − 09
NOTE 1—All dimensions are in mm. The base of the support tube allows clamping to a vibration table.
FIG. 6 Suitable Dimensions of the Support Tube That is Used During Filling of the Corrugated Molds
7.3 Measuring Room—To minimize the influence of tem-
perature variations, both the specimens and the dilatometer
shallbekeptinathermostaticallycontrolledroomorcabinetat
all times during the test. Maintain the surrounding air tempera-
ture at 23.0 6 1.0 °C, unless otherwise specified (see Note 4).
Do not store specimens in a water bath due to possible water
transport through the corrugated molds.
NOTE 4—The measurement can be performed at any temperature
specified by the user, provided that the temperature in the measuring room
or cabinet is maintained constant during the test with a tolerance of 6 1.0
°C.
7.4 Specimen Storage—After filling and sealing the molds,
store the specimens horizontally on a smooth surface, to avoid
any restraint to length change. Support specimens along their
entire length to avoid damage and to ensure they remain
straight (see Note 5). Maintain a separation of at least 30 mm
between specimens during the first day of measurement to
allow dispersion of their heats of hydration.
NOTE 5—Corrugated plastic sheets as shown in Fig. 8 or other suitable
materials can be used to support the molded specimens.
NOTE 1—An empty corrugated mold, closed at one end with an end
plug, is inserted into the support tube and positioned vertically on a
7.5 Time of First Measurement—Start
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.