ISO 1920-8:2009 download free.Testing of concrete — Part 8: Determination of drying shrinkage of concrete for samples prepared in the field or in the laboratory.
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 s 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.
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 x 100 mm x 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.
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.
6.2 Test specimens
6.2.1 General
At least three specimens shall be prepared from each sample of concrete.
6.2.2 Size and shape of standard test specimens
The test specimen shall be a prism of 75 mm × 75 mm and approximately 280 mm long, or a prism of 100 mm × 100 mm and approximately 400 mm long. A stainless steel gauge stud (5.3) shall be cast into each end of the specimen. The gauge studs shall be cast so that their principal axes coincide with the principal axis of the test specimen and shall extend into the specimen approximately 15 mm for specimens having dimensions of 75 mm × 75 mm × 280 mm and approximately 20 mm for specimens having dimensions of 100 mm × 100 mm × 400 mm.
6.2.3 Identification of specimens
Each specimen shall be identified by the mould marking or by other means that will not adversely affect the concrete. Scratch markings shall not be used.
The use of permanent markings on the external face of the mould (5.2) is recommended.
7 Procedure
7.1 Measurement of consistence and temperature of concrete
a) Measure slump and, if required, other determination of the consistence of the concrete. In accordance with ISO 1920-2, and record it.
b) Measure and record the temperature of the concrete at the time of moulding.
7.2 Preparation and filling of the moulds
a) Prepare the specimens as required in ISO 1920-3:2004, 6.2.
— reading of length comparator for specimen;
14) drying shrinkage for each specimen and the average for each set, at each required drying period, to the nearest 5 microstrain;
15) such other information contained in the records as may be requested;
16) any deviation from the standard method;
17) a declaration from the person technically responsible for the test that the testing was carried out in accordance with ISO 1920-8, except as noted in 9 b) 16).
10 Precision for laboratory-prepared specimens
For a set of three specimens moulded in the laboratory from the same sample of concrete cured under identical conditons and with a nominal aggregate size (see ISO 6274) not greater than 20 mm. the repeatability expressed as a percentage of the mean of the set of three specimens is 8 % at the 95 % probability level.
Precision data are not available for field-moulded specimens or specimens prepared in a laboratory other than the measuring laboratory. (This statement on repeatability is based on limited Australian data and may be amended when more data are collected.)