ISO 1920-9:2009 download free.Testing of concrete Part 9 : Determination of creep of concrete cylinders in compression.
This part of ISO 1920 specifies a method for determining the creep of standard concrete test cylinders subjected to a sustained longitudinal compressive load.
NOTE The conditions for curing and storage (see 6.1) can be varied to suit different requirements, e.g. early pre-stress, The time of loading (see 6.2) can also be varied to give an indication of other properties. These variations, however, will not conform to the requirements for a creep test as specified in this part or iso 1920 and it is necessary that any deviation from the standard procedure be recorded in the test report.
2 Normative references
The following referenced documents are essential for the application of ISO 1920-9. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1920-3:2004, Testing of concrete — Part 3: Making and curing test specimens
ISO 1920-4:2005, Testing of concrete — Part 4: Strength of hardened concrete
ISO 1920-8:2009, Testing of concrete — Part 8: Oetermination of drying shrinkage of concrete for samples
prepared in the field or in the laboratory
3 Principle
The creep of the concrete is obtained by determining the total combined creep and drying shrinkage of the loaded specimens and subtracting from this value the drying shrinkage of the unloaded specimens, all specimens being stored in the same environmental conditions. This part of ISO 1920 details the fixed environmental conditions for carrying out the test, which allows comparison with previously tested specimens and specimens tested in other laboratories.
4 Apparatus
4.1 Loading frame, capable of applying and maintaining the required load on the specimen or group of specimens for the duration of the test. The means of maintaining the load may be either a spring or system of springs: alternatively, a hydraulic ram or capsule may be used.
Means shall be provided for measuring the load to the nearest 2 % of the total applied load. Suitable means of measuring the load are by
a) a permanently installed hydraulic load cell with calibrated pressure gauge,
b) a calibrated hydraulic jack with pressure gauge, or
c) a calibrated load cell inserted in the frame at the time of loading or when the load is adjusted.
All end plates of the loading frame shall be sufficiently rigid to ensure uniform loading of the cylinders. At one end of the specimen or group of specimens a suitable spherical seating device shall be provided between the specimens and the end plates, Bearing surfaces of any plates in contact with the loaded specimens shall not depart from a plane by more than 0,05 mm.
In any loading frame, a group of specimens may be stacked for simultaneous loading.
4.2 Strain-measuring device, which meets the following requirements.
a) A suitable apparatus shall be provided for the measurement of longitudinal strain in each specimen to the nearest 10 microstrain. The apparatus may be attached or portable. In all cases, reference gauge points shall be positively attached to the specimen. Gauges relying on friction contact shall not be used.
b) Deformations shall be measured on gauge lines spaced uniformly around the periphery of the specimen. The gauge reference points shall be evenly spaced at about the mid-height of the specimen. The number of gauge lines shall be not less than two for control specimens and not less than three for loaded specimens.
c) The effective gauge length shall be not less than three times the maximum aggregate size and not greater than
1) 260 mm for large specimens without end plates, and 160mm for small specimens without end plates, and
2) 150 mm for large specimens having attached end plates, and 100 mm for small specimens having attached end plates.
NOTE 1 A ‘small specimen made of concrete is one having the maximum nominal size of the aggregate not greater than 25 mm, while a large specimen made of concrete is one having the maximum nominal size of the
For each test condition, not less than nine cylinders of the same size shall be made from a given batch of concrete. Of these cylinders, a minimum of
a) three shall be tested for compressive strength,
b) three shall be loaded and observed for deformation, and
c) three shall remain unloaded for use as controls for deformations from causes other than loads.
5.3 End preparation
Specimens that are perpendicular to the axis within ± 0,5 may be capped or used against end plates. Specimens beyond this tolerance shall be sawn and re-checked for conformity prior to capping or use with end plates.
The ends of specimens shall meet the plainness requirements of ISO 1920-4.
IMPORTANT — The alignment of the axes of the individual specimens is critical and the end preparation necessary to achieve this alignment is likewise critical. Great care must be exercised in achieving the plainness and perpendicularity within the tolerances specified. The requirements for plainness and perpendicularity may be met by capping with Portland cement mortar or sulfur, by lapping, or at the time of casting by fitting the ends with steel bearing plates normal to the axis of the specimen. The necessary axiality may also be achieved by bonding the specimens together with a thin layer of epoxy resin using a suitable jig.
5.4 Fixing gauge points
Gauge points shall be cast-in or fixed to the creep and control specimens prior to testing.
Where gauge points are to be attached to the surface of specimens, this should be done in sufficient time to allow checking of their stability prior to the time of loading.
l) gauge length:
m) magnitude of any preload;
n) applied stress and strain readings if not one-third of the compressive strength:
o) specific creep (creep strain per megapascal) at designated ages up to 1 year for each specimen and average value:
p) creep rate, F(K);
q) creep coefficient:
r) any other information contained in the records that could be requested;
s) any deviations from the standard method;
t) a declaration from the person technically responsible for the test that the testing was carried out in accordance with this part of ISO 1920, except as noted in s) above.
Where available, the following additional information may be recorded:
u) mix description (specified slump, specified compressive strength or nominal mix proportions);
v) water/cement ratio;
w) cement type and strength class;
x) coarse and fine aggregate-type and source;
y) maximum size of aggregate:
z) admixtures — type, brand and quantity.
9 Precision
No reproducibility and repeatability data are available for the test method described in this part of ISO 1920.