ISO 1920-8:2009
(Main)Testing of concrete — Part 8: Determination of drying shrinkage of concrete for samples prepared in the field or in the laboratory
Testing of concrete — Part 8: Determination of drying shrinkage of concrete for samples prepared in the field or in the laboratory
ISO 1920-8:2009 specifies a method for determining the length changes of concrete specimens due to drying in air, and the method of preparing and curing the concrete specimens to be tested.
Essais du béton — Partie 8: Détermination du retrait de séchage du béton d'échantillons préparés sur le terrain ou en laboratoire
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 1920-8
First edition
2009-04-01
Testing of concrete —
Part 8:
Determination of drying shrinkage of
concrete for samples prepared in the field
or in the laboratory
Essais du béton —
Partie 8: Détermination du retrait de séchage du béton d'échantillons
préparés sur le terrain ou en laboratoire
Reference number
ISO 1920-8:2009(E)
©
ISO 2009
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ISO 1920-8:2009(E)
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ISO 1920-8:2009(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle. 2
5 Apparatus . 2
6 Test samples and specimens . 7
6.1 Sampling. 7
6.2 Test specimens . 8
7 Procedure . 8
7.1 Measurement of consistence and temperature of concrete. 8
7.2 Preparation and filling of the moulds . 8
7.3 Compacting of concrete. 8
7.4 Curing of specimens . 9
7.5 Drying and measurement of specimens. 10
8 Calculation and expression of results. 12
9 Test report . 12
10 Precision for laboratory-prepared specimens. 14
Annex A (informative) A suitable horizontal length comparator. 15
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ISO 1920-8:2009(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 1920-8 was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and pre-
stressed concrete, Subcommittee SC 1, Test methods for concrete.
ISO 1920 consists of the following parts, under the general title Testing of concrete:
⎯ Part 1: Sampling of fresh concrete
⎯ Part 2: Properties of fresh concrete
⎯ Part 3: Making and curing test specimens
⎯ Part 4: Strength of hardened concrete
⎯ Part 5: Properties of hardened concrete other than strength
⎯ Part 6: Sampling, preparing and testing of concrete cores
⎯ Part 7: Non-destructive tests on hardened concrete
⎯ Part 8: Determination of drying shrinkage of concrete for samples prepared in the field or in the laboratory
⎯ Part 9: Determination of creep of concrete cylinders in compression
The following part is under preparation:
⎯ Part 10: Determination of static modulus of elasticity in compression
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INTERNATIONAL STANDARD ISO 1920-8:2009(E)
Testing of concrete —
Part 8:
Determination of drying shrinkage of concrete for samples
prepared in the field or in the laboratory
1 Scope
This part of ISO 1920 specifies a method for determining the length changes of concrete specimens due to
drying in air, and the method of preparing and curing the concrete specimens to be tested.
It is applicable for the testing of specimens prepared in the laboratory or in the field, in which the maximum
nominal size of aggregate in the concrete, in accordance with ISO 6274, does not exceed 25 mm.
The precision statement in Clause 10 does not apply to specimens that have had non-standard initial curing
(normally field-prepared specimens). In addition, this part of ISO 1920 requires that field-prepared specimens
be marked, recorded and reported as such.
NOTE 1 This test method is not always suitable for very low slump concrete (less than 20 mm), primarily due to the
difficulties in obtaining adequate compaction. Provided adequate compaction is obtained, the method is applicable.
NOTE 2 The method is specifically developed for measurement of drying shrinkage of concrete, but it is capable of
adaptation for measurement of length changes of specimens subjected to a variety of environmental conditions.
2 Normative references
The following referenced documents are essential for the application of this part of ISO 1920. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 1920-1, Testing of concrete — Part 1: Sampling of fresh concrete
ISO 1920-2, Testing of concrete — Part 2: Properties of fresh concrete
ISO 1920-3:2004, Testing of concrete — Part 3: Making and curing test specimens
ISO 6274, Concrete — Sieve analysis of aggregates
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
preparing laboratory
laboratory responsible for sampling of concrete, moulding of specimens, initial curing in moulds, demoulding,
initial moist curing and transport to measuring laboratory (if required)
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ISO 1920-8:2009(E)
3.2
measuring laboratory
laboratory responsible for completion of initial moist curing, storage in drying room and measurement of
specimens
NOTE In some instances, the preparing and measuring laboratories will be the same.
4 Principle
Specimens are cured and air dried for a specified time, and the change in length is measured.
5 Apparatus
5.1 Drying room, with suitably controlled temperature, humidity and air circulation, for storing specimens in
air and for measuring their length.
The room shall meet the following requirements.
a) Air shall be circulated through the room in a uniform manner, so that the specified conditions are
attained adjacent to all specimens under test.
b) The temperature in the drying room shall be maintained at (22 ± 2) °C.
c) The relative humidity in the drying room shall be maintained at (55 ± 5) % at all times.
d) The room shall be fitted with recording devices, capable of rapid response to changes in room
conditions, which will continuously record the temperature and the relative humidity.
The recording detectors shall be verified against a standardized Assmann hygrometer at intervals of time
that will assure compliance with the temperature and humidity requirements specified in 5.1, b) and c).
NOTE 1 A suitable rapid response device for recording temperature and humidity uses a combined detector with a
thin-film capacitor for humidity and a platinum resistance thermocouple for temperature measurement. Response
time for this type of detector is measured in seconds and is virtually instantaneous within the narrow range required
for this test method.
NOTE 2 Most thermo hygrographs are unsuitable for the purpose, as the response is too slow to detect the full
extent of fluctuations, particularly with the hair type of humidity detector.
e) The rate of air movement in the drying room shall be determined and controlled by sensors in order
to maintain the rate of evaporation at (12 ± 5) ml per 24 h. The evaporation rates shall be determined
by measuring the loss in weight of water in 400 ml low-form beakers of internal diameter
(78 ± 5) mm, initially containing approximately 375 g of water at a temperature of (20 ± 2) °C. The
weight of water in the beaker shall not fall below 325 g. Each beaker shall be placed midway
between test specimens on the storage racks with the water level at approximately the same height
as the top of the specimens.
Systematic checks shall be carried out on the sensors or on the evaporation rates by varying the location
of the beakers within the drying room at least monthly, or where conditions have changed. The results
shall be recorded.
f) The requirements for temperature, humidity and evaporation rate apply to each storage position.
Only positions that conform to these requirements shall be used for storage of test specimens.
g) The drying room shall be fitted with suitable racks for storing specimens. The racks shall permit free
circulation of air around specimens, except for necessary supports, and shall be so situated with
respect to the nearest wall or other obstruction that air circulation is not restricted in the intervening
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ISO 1920-8:2009(E)
space. The horizontal supports shall consist of non-absorptive members having a total bearing width
supporting the specimen of not more than 25 mm.
5.2 Moulds, made of non-absorbent material that does not react with cement paste and their internal
surfaces; shall have a smooth finish.
The moulds shall be substantial enough to hold their form without distortion and shall be substantially leak proof.
They shall meet the following requirements.
5.2.1 General
Each mould shall be provided with a base plate, two end plates and two side plates which are securely
fastened to the end plates, and two partially loose end plates which act as gauge stud holders. Each gauge
stud holder shall fit inside the end of the mould and shall locate and secure a gauge stud during the setting
period of the concrete. Each gauge stud holder shall be held in position against the end plate by a retaining
screw and shall be capable of release after compaction of the concrete. The opposite side plates shall be
parallel.
The dimensions of the mould shall be one of the following.
a) For specimens having dimensions of 75 mm × 75 mm × 280 mm (see 6.2.2)
⎯ the distance between the opposite side plates shall be (75 ± 1) mm, and
⎯ the inside height shall be (75 ± 1) mm;
b) For specimens having dimensions of 100 mm × 100 mm × 400 mm
⎯ the distance between the opposite side plates shall be (100 ± 1) mm, and
⎯ the inside height shall be (100 ± 1) mm.
5.2.2 Construction of the mould
The mould shall be aligned coaxially along the central axis of the mould.
a) For specimens having dimensions of 75 mm × 75 mm × 280 mm:
⎯ the distance between the inner ends of the two studs shall be (250 ± 0,5) mm;
⎯ the distance between the outer ends of the gauge studs shall be (295 ± 1) mm;
⎯ gauge studs shall protrude from the gauge stud holders to a distance of (15 ± 1) mm.
b) For specimens having dimensions of 100 mm × 100 mm × 400 mm:
⎯ the distance between the inner ends of the two studs shall be (360 ± 0,5) mm;
⎯ the distance between the outer ends of the gauge studs shall be (420 ± 1) mm;
⎯ gauge studs shall protrude from the gauge stud holders to a distance of (20 ± 1) mm.
A suitable form of construction of the moulds is shown in Figure 1.
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ISO 1920-8:2009(E)
5.3 Gauge studs, made of stainless steel and conforming to the dimensions shown in Figure 2.
The radius of the gauge stud end shall be such as to assure compliance to the precision requirements for
measuring length changes, as specified in 5.8.1.
Gauge studs for horizontal and vertical comparators shall not be interchanged.
5.4 Length gauge, for checking the nominal length between gauge studs (5.3).
The length gauge shall be made of metal, and the specifications shall be as follows.
a) For specimens having dimensions of 75 mm × 75 mm × 280 mm
⎯ the diameter of the length gauge shall be not less than 6 mm, and
⎯ the length of the length gauge shall be (250 ± 0,2) mm;
b) For specimens having dimensions of 100 mm × 100 mm × 400 mm
⎯ the diameter of the length gauge shall be not less than 10 mm, and
⎯ the length of the length gauge shall be (360 ± 0,2) mm.
The ends of the bar shall be flat and perpendicular to its length.
5.5 Means of compaction, consisting of the following.
5.5.1 Tamping bar, compacting bar, straight, made of steel having a rectangular shape of approximately
25 mm × 10 mm, a length of approximately 600 mm and with a ramming face square with the axis.
5.5.2 Tamping rod, compacting rod of circular cross-section, straight, made of steel, having a diameter of
approximately 16 mm, a length of approximately 600 mm and with round ends.
5.5.3 External vibrator, table type with provision for clamping of the mould (5.2), capable of compacting
concrete in the moulds. Internal vibrators shall not be used.
NOTE A vibrating table with a nominal frequency of vibration of 50 Hz is usually suitable.
5.6 Mallet.
5.7 Balance, used to determine the mass of the concrete specimen and having an accuracy of at least
0,1 g.
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ISO 1920-8:2009(E)
Dimensions in millimetres
a) Double mould
b) Single mould
c) Selection of mould
Figure 1 — Details of a typical mould (continued)
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ISO 1920-8:2009(E)
d) Gauge stud holder e) End plate details
Key
1 gauge stud holder retaining screw
2 drill and tap with an M6 × 1-6g thread (to take baseplate screw)
3 drill and tap centrally with an M6 × 1-6g thread (to take gauge stud and spacer screw)
4 dowel pin ∅5 press fitted in end plate
a
The dimensions in Figure 1 refer to a mould suitable for casting specimens having dimensions of (75 × 75 × 280) mm.
The dimensions in parentheses refer to a mould suitable for casting specimens having dimensions of
(100 × 100 × 400) mm.
Figure 1 — Details of a typical mould
Dimensions in millimetres
a) Gauge stud for (75 × 75 × 280) mm specimen
b) Gauge stud for (100 × 100 × 400) mm specimen
Key
1 coarse knurl
2 thread M6 × 1-6g
3 buff tip to a polished finish
Figure 2 — Details for typical gauge studs
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ISO 1920-8:2009(E)
5.8 Length comparator, used for measuring changes in length.
5.8.1 General
The comparator shall be capable of measuring the length of specimens over a range of 290 mm to 300 mm
for specimens of (75 × 75 × 280) mm, and over a range of 415 mm to 425 mm for specimens of
(100 × 100 × 400) mm. The precision of the measurement shall be 0,001 mm.
It is recommended that, where a horizontal comparator is used, micrometers be of the digital read-out type.
Details of a suitable horizontal length comparator are provided in Annex A.
5.8.2 Reference bar
A specific reference bar made of a material characterized by an extremely low coefficient of thermal
expansion shall be used with each comparator.
a) For specimens having dimensions of 75 mm × 75 mm × 280 mm
⎯ the diameter of the reference bar shall be not less than 6 mm, and
⎯ the overall length of the reference bar shall be (295 ± 1,5) mm;
b) For specimens having dimensions of 100 mm × 100 mm × 400 mm
⎯ the diameter of the reference bar shall be not less than 10 mm, and
⎯ the overall length of the reference bar shall be (420 ± 1,5) mm.
Each end shall be reduced in diameter and the end 5 mm shall have approximately the same diameter and
have the same end radius as the projecting end of the gauge stud (5.3) being used in the specimen. Each end
of the reference bar shall be polished.
The central section of the reference bar shall be covered by a rubber tube, or equivalent, of length
approximately 100 mm and wall thickness of at least 3 mm to minimize the effect of temperature change
during handling. The reference bar shall be provided with a positioning mark and shall always be placed in the
comparator in the same orientation.
5.8.3 Check of precision
The precision of the length comparator and the performance of the operator shall be checked by recording the
difference in length between the reference bar and a typical specimen 20 times, replacing each in the
comparator for each reading. The standard deviation of these 20 length differences shall not exceed
0,002 mm. When a check of precision fails to meet this requirement, further checks shall be made with
another specimen or with another operator to ascertain whether the lack of precision is associated with the
comparator or with the operator.
The frequency of the checking shall confirm with the quality management programme of the laboratory.
6 Test samples and specimens
6.1 Sampling
Specimens may be prepared either in the laboratory or in the field. Particular care should be taken to ensure
that sampling and preparation are strictly in accordance with Clause 6, as these activities are crucial to the
accuracy and repeatability of the test. Full records should also be kept for inclusion in the report (see Clause 9
and Clause 10).
For concrete sampled in the field, the test sample shall be obtained in accordance with ISO 1920-1.
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ISO 1920-8:2009(E)
6.2 Test specimens
...
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