ISO 1920-6:2019

INTERNATIONAL ISO
STANDARD 1920-6
Second edition
2019-10
Testing of concrete —
Part 6:
Sampling, preparing and testing of
concrete cores
Essais du béton —
Partie 6: Échantillonnage, préparation et essais sur des carottes de
béton
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Apparatus . 1
5 Taking of cores . 2
5.1 Age of concrete . 2
5.2 Location . 2
5.3 Drilling . 3
5.4 Number of cores. 3
5.5 Diameter of cores . 3
5.6 Length of cores . 3
5.7 Length-to-diameter (l/d) ratio . 4
5.8 Marking and identification . 4
5.9 Reinforcement . 4
6 Examination . 4
6.1 Visual inspection . 4
6.2 Measurements and calculations of drilled core specimens . 4
7 Preparation of cores . 4
7.1 General . 4
8 Compression test . 5
8.1 Storage . 5
8.2 Testing . 5
9 Test results . 5
10 Test report . 5
Annex A (informative) Example of a test report of core strength . 7
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
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electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
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.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and
prestressed concrete, Subcommittee SC 1, Test methods for concrete.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
This second edition cancels and replaces the first edition (ISO 1920-6:2004), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— requirements of compressive testing machine have been included and defined;
— Clause 5 has been redrafted;
— accuracy requirements at the time of measuring core diameter, core length have been redefined;
— tolerances of the prepared test specimen have been redefined;
— the curing of test specimens under tropical climate has been included and defined.
A list of all parts in the ISO 1920 series can be found on the ISO website.
iv © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 1920-6:2019(E)
Testing of concrete —
Part 6:
Sampling, preparing and testing of concrete cores
1 Scope
This document specifies a method for taking cores from hardened concrete, their examination,
preparation for testing and determination of compressive strength.
This document does not give guidance on the decision to drill cores or on the locations for drilling and
does not provide procedures for interpreting the core strength results.
It is recommended that before coring, full agreement should be reached by all parties on the need for
core testing and how the results should be interpreted.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1920-4, Testing of concrete — Part 4: Strength of hardened concrete
ISO 1920-5, Testing of concrete — Part 5: Density and water penetration depth
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
core strength
compressive strength of the cored specimen, as determined by the test defined in this document
4 Apparatus
4.1 Core drill, capable of extracting cores from the hardened concrete to the dimensions specified in
5.3 with the tolerances specified in Clause 7.
4.2 Compression testing machine
4.2.1 The test shall be carried out using a compression-testing machine which shall be robust, related
to the size of specimen and capable of providing rate of loading with minimum desired specifications the
place of testing.
4.2.1.1 Accuracy of the test machine shall be such that the percentage error for the loads within
proposed range of use of the machine and shall not exceed ±1,0 % of the indicated load.
4.2.1.2 The compression testing machine shall be provided with a control system. The control system
can be operated either by manual or automatic means. If the machine is not equipped with automatic
application of force, a pacer shall be fitted to enable the operator to maintain the specified rate. The
pacer shall indicate a rate within ±5,0 % of the specified rate.
4.2.1.3 Machine platens and auxiliary platens shall have a hardness value at least 550 HV (Vickers
Hardness).
4.2.1.4 The thickness of the auxiliary platens shall be at least 23 mm with roughness value, Ra, for the
surface texture of the contact faces of the auxiliary platen shall be in the range 0,4 µm to 3,2 µm.
4.2.2 The test machine shall be in calibration at the time of test. The calibration shall be carried out at
least once per year.
4.3 Balance or scale, capable of determining the mass of the core, as tested, to within an accuracy of
0,1 % of the mass.
4.4 Callipers and/or rules, capable of measuring the dimensions of the core and the steel
reinforcement to a tolerance of ±0,01 mm.
4.5 Gauge, capable of establishing that the relevant flatness of the specimen is within the requirements
of Clause 7.
4.6 Squares and gauges, capable of establishing that the perpendicularity and parallelism of
specimens and moulds are within the requirements of Clause 7.
5 Taking of cores
5.1 Age of concrete
Core to be tested for strength shall not be removed from the structure until the concrete has become
hard enough to permit its removal without disturbing the bond between the mortar and the coarse
aggregate. As a general guideline, concrete with specified or characteristics compressive strength up
to 25 MPa, such concrete can be at least 14 days old before the cores are taken. For higher grades, cores
may be taken at an earlier age.
5.2 Location
Possible structural implications resulting from taking a core shall be considered prior to drilling and
the location where the cores are to be taken specified.
Cores shall preferably be taken at points not near to joints or edges of the concrete element to avoid as
far as possible any reinforcement.
2 © ISO 2019 – All rights reserved

Cores shall be taken preferably from the middle part of the member leaving top and bottom parts where
variation can be greater. While taking cores vertically from top, like from slab or from foundation top,
the test length of core shall not contain concrete from the top 15 % to 20 % depth as top part of the core
can contain non-uniform distribution of aggregates (maximum up to 60 mm). In case of cores which are
not across full depth of member, about 10 % to 15 % portion of the bottom side of core may be trimmed
off as the portion near to the broken end can contain some micro cracks/fractures.
Locations where there can be micro cracks due to tension shall be avoided and cores shall preferably be
taken from compression zone.
5.3 Drilling
Unless otherwise specified, the cores shall be d
...