ISO 23945-3

• Abstract:

  This document specifies the test methods for measurement and determination of the compressive strength of sprayed concrete at different age, from young hardened to long term hardened sprayed concrete. Initial and early compressive strength development of sprayed concrete up to 24h are measured using indirect methods, namely needle penetration and pin driving methods. Both methods correlate the impact of the compressive strength on the penetration of a needle. The test methods could be applied to measure compressive strength of sprayed concrete in the range of 0.5MPa to 100MPa. The specimens of hardened sprayed concrete are extracted from either an in situ element or a test panel.

• Status: Not Published
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: ISO/TC 71/SC 1 - Test methods for concrete
• Drafting Committee: ISO/TC 71/SC 1 - Test methods for concrete
• Current Stage: 6000 - International Standard under publication
• Start Date: 10-Sep-2026
• Completion Date: 19-Sep-2026

Overview

ISO 23945-3: Test Methods for Sprayed Concrete - Part 3: Measurement of Compressive Strength outlines standardized procedures for determining the compressive strength of sprayed concrete. Developed by ISO, this international standard is essential for ensuring reliable quality control and structural integrity in projects that utilize sprayed concrete (also known as shotcrete). The document covers test methods for sprayed concrete at various stages, from early age to fully hardened, supporting a range of practical applications in construction and civil engineering.

Key Topics

• Scope of Application
  • Measurement and determination of compressive strength of sprayed concrete at different ages.
  • Applicable to sprayed concrete with compressive strength ranging from 0.5 MPa to 100 MPa.
  • Suitable for both in situ elements and test panels.
• Test Methods
  • Needle Penetration Method: Used for measuring early strength (up to 24 hours) using a calibrated penetrometer to determine resistance force as a proxy for compressive strength.
  • Pin Driving Method: Used for slightly more mature concrete, where depth of a driven pin (using a controlled energy device) is measured to estimate compressive strength.
• Result Interpretation
  • Both indirect methods rely on calibration curves provided by equipment manufacturers.
  • Mean values from multiple measurements are used for accurate results.
  • Standardized reporting requirements enhance traceability and repeatability.

Applications

ISO 23945-3 is a critical reference for:

• Ground Support in Tunneling and Mining: Provides rapid assessment of sprayed concrete strength essential for safety.
• Structural Repairs and Retrofitting: Enables quality verification of shotcrete applications in rehabilitation projects.
• New Construction: Assures compliance with strength requirements in sprayed concrete elements for buildings, infrastructure, and civil works.
• Quality Control: Allows construction teams and laboratories to validate the performance of sprayed concrete before, during, and after application.
• Testing in Diverse Environments: Suitable for standard, tropical, and subtropical conditions, supporting global adoption.

Related Standards

For comprehensive testing and understanding of sprayed concrete, the following standards are relevant:

• ISO 23945-2: Test methods for sprayed concrete - Sampling fresh and hardened concrete.
• ISO 1920-3: Testing of concrete - Making and curing test specimens.
• ISO 1920-4: Testing of concrete - Strength of hardened concrete.
• EN 12390-3: Testing hardened concrete - Compressive strength of test specimens.
• ASTM C803/C803M: Penetration resistance of hardened concrete.

Practical Value

• International Consistency: Defines clear procedures and reporting, supporting international construction projects and trade.
• Efficiency and Safety: Early assessment of compressive strength enables timely decision-making and improved site safety, particularly important for sprayed concrete’s rapid-set applications.
• Adaptability: Methods support testing directly on structures or using test panels, minimizing disruption and maximizing relevance to real-world conditions.
• Comprehensive Guidelines: Test methods include preparation, apparatus requirements, procedures, result calculations, and reporting-facilitating accurate, repeatable results.

By following ISO 23945-3, construction professionals, engineers, and quality controllers can ensure that the sprayed concrete meets required strength standards, supporting durable, safe, and compliant built environments.

International
Standard
First edition
Test methods for sprayed
concrete —
Part 3:
Measurement of compressive
strength
PROOF/ÉPREUVE
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
PROOF/ÉPREUVE
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Needle penetration method . 1
4.1 General .1
4.2 Principle .1
4.3 Specimens .2
4.4 Apparatus .2
4.4.1 Penetrometer .2
4.4.2 Needle .2
4.5 Procedures .2
4.6 Expression of results . .2
4.7 Test report .2
5 Pin driving method . 3
5.1 General .3
5.2 Principles .3
5.3 Specimens .3
5.4 Apparatus .3
5.4.1 Pin driving equipment . .3
5.4.2 Spring-actuated driver .4
5.4.3 Pin .4
5.4.4 Measuring Instrument .4
5.5 Sampling .4
5.6 Procedures .6
5.7 Expression of results .6
5.8 Test report .6
5.9 Precision . . .7
6 Determination of compressive strength by specimens . 7
6.1 General .7
6.2 Principle .7
6.3 Specimens .7
6.4 Expression of results . .7
6.5 Precision . . .8
6.6 Test report .9
Annex A (informative) Example of calibration curves for needle penetrometer .10
Annex B (informative) Example of calibration curves for pin driving method .11
Bibliography .12
PROOF/ÉPREUVE
iii
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.
The procedures used to develop this document and those intended for its further maintenance are 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and pre-
stressed concrete, Subcommittee SC 1, Test methods for concrete.
A list of all parts in the ISO 23945 series can be found on the ISO website.
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.
PROOF/ÉPREUVE
iv
Introduction
Sprayed concrete is widely used for the stabilization of structures in a very short time and for concrete
applications without using moulds. In addition to being ideal for ground support in tunnelling and mining,
sprayed concrete is also used in repairs, restoration, new constructions and many other fields.
The requirements for properties, test methods, standards and specifications for the spray forming process
of concrete are different from those of cast forming concrete. This document is intended to provide a
normative test method for sprayed concrete.
This document is applied under various climatic and geographical conditions, various levels of protection
and under different established regional traditions and experiences. Consequently, this document includes
conditions for tests covering standard, tropical and subtropical region environments.
This document is intended for use with other parts of the ISO 23945 series which provide requirements
associated with the level of quality specified and the methods to be employed for the execution of sprayed
concrete.
PROOF/ÉPREUVE
v
International Standard ISO 23945-3:2026(en)
Test methods for sprayed concrete —
Part 3:
Measurement of compressive strength
1 Scope
This document specifies the test methods for measurement and determination of the compressive strength
of sprayed concrete at different age, from young hardened to long term hardened sprayed concrete. The test
methods could be applied to measure compressive strength of sprayed concrete in the range of 0,2 MPa to
100 MPa. The specimens of hardened sprayed concrete are extracted from either an in-situ element or a test
panel.
This document does not purport to address all of the safety concerns, if any, associated with its use.
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 23945-2, Test Methods for Sprayed Concrete —Part 2: Sampling fresh and hardened concrete
ISO 1920-3, Testing of concrete — Part 3: Making and curing test specimens
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Needle penetration method
4.1 General
This part specifies the method from which an estimate of the in-situ compressive strength of young hardened
sprayed concrete can be made in the range of 0,2 MPa to 1,5 MPa.
4.2 Principle
Needle penetration method is used to measure the force required to push a needle of specified dimensions
to penetrate into the sprayed concrete to a depth of 15 mm +/- 2 mm. A penetrometer indicates the resisting
force, through compression of a calibrated spring from which an estimated compressive strength can be
derived from a calibration curve provided by the producer of the test equipment.
PROOF/ÉPREUVE
4.3 Specimens
The thickness of the sprayed concrete layer shall be not less than 100 mm for testing.
The specimens for test shall be prepared according to ISO 23945-2.
No special test specimen is required for test of in-situ structures. The testing procedure can be used for
measurements at any location without advance preparation.
4.4 Apparatus
4.4.1 Penetrometer
The penetrometer shall be capable of driving the needle into the surface and recording the force required to
an accuracy of 10 N. The penetrometer shall be provided with a certified calibration curve, able to correlate
readings to estimated compressive strength. An example of calibration curves is shown in Annex A.
4.4.2 Needle
The needle shall be with a diameter of 3 mm ± 0,1 mm and a tip with a taper angle of 60° ± 5°, the needle
length shall be more than 15 mm.
4.5 Procedures
4.5.1 Record time and place of completion of spraying and start of testing.
4.5.2 Ensure the force indicator is set to zero.
4.5.3 Apply the device perpendicularly to the surface of the sprayed concrete layer and steadily push in
the needle to a depth of 15 mm in a single continuous movement. If this is prevented, for instance because of
a large aggregate particle or reinforcement, then discontinue the test and repeat in an adjacent location.
4.5.4 Read the resistance force from the scale, record the value on the protocol form and return indicator
to original position.
4.5.5 Clean the needle if necessary.
4.5.6 Repeat the test ten times as quickly as possible (and within 1 min for strengths below 0,5 MPa) in an
area representative of the sprayed region.
4.5.7 Record the time at which the testing is finished (on protocol form).
4.6 Expression of results
Calculate the mean resistance force from the 10 measurements.
The estimated compressive strength is derived from the man
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ISO/DISPRF 23945-3:2026(en)
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ISO/TC 71/SC 1/WG 7
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Secretariat: SII
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Date: 2026-04-16.08-12
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Test methods for sprayed concrete —
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Part 3: .
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Measurement of compressive strength .
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PROOF
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St l D fi iti
ISO #####-#:####(X/PRF 23945-3:2026(en)
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, Formatted: Indent: Left: 0 cm, Right: 0 cm, Space
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO Before: 0 pt, No page break before, Adjust space
at the address below or ISO’s member body in the country of the requester. between Latin and Asian text, Adjust space between
Asian text and numbers
ISO copyright office
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CP 401 • Ch. de Blandonnet 8
Header distance from edge: 1.27 cm, Footer distance
CH-1214 Vernier, Geneva
from edge: 0.5 cm
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
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ii © ISO #### 2026 – All rights reserved
ii
ISO/DISPRF 23945-3:2026(en)
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Contents
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Foreword . v
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Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Needle penetration method . 1
4.1 General . 1
4.2 Principle . 2
4.3 Specimens . 2
4.4 Apparatus . 2
4.5 Procedures . 2
4.6 Expression of results . 2
4.7 Test report . 3
5 Pin driving method . 3
5.1 General . 3
5.2 Principles . 3
5.3 Specimens . 3
5.4 Apparatus . 4
5.5 Sampling . 4
5.6 Procedures . 6
5.7 Expression of results . 6
5.8 Test report . 6
5.9 Precision . 7
6 Determination of compressive strength by specimens . 7
6.1 General . 7
6.2 Principle . 7
6.3 Specimens . 7
6.4 Expression of results . 8
6.5 Precision . 8
6.6 Test report . 9
Annex A (informative) Example of calibration curves for needle penetrometer . 11
Annex B (informative) Example of calibration curves for pin driving method . 13
Bibliography . 15

Foreword . v
Introduction . vi
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1 Scope . 1
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2 Normative references . 1
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3 Terms and definitions . 1
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4 Needle penetration method . 1
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iii
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4.1 Scope . 1
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4.2 Principle . 1
4.3 Specimens . 2
4.4 Apparatus . 2
4.4.1 Penetrometer . 2
4.4.2 Needle . 2
4.4.3 Test protocol form . 2
4.5 Procedures . 2
4.6 Expression of results. 2
4.7 Test report . 2
5 Pin driving method . 3
5.1 Scope . 3
5.2 Principles . 3
5.3 Specimens . 3
5.4 Apparatus . 3
5.4.1 Pin driving equipment . 3
5.4.2 Spring-actuated driver . 3
5.4.3 Pin . 3
5.4.4 Measuring Instrument . 4
5.5 Sampling . 4
5.6 Procedures . 5
5.7 Expression of results. 5
5.8 Test report . 5
5.9 Precision . 5
6 Determination of compressive strength by specimens . 6
6.1 Scope . 6
6.2 Principle . 6
6.3 Specimens . 6
6.4 Expression of results. 6
6.5 Precision . 8
6.6 Test report . 8
Annex A (informative) Example of calibration curves for needle penetrometer . 10
Annex B (informative) Example of calibration curves for pin driving method . 11
Example of calibration curves for penetration pneumatic pin method
Annex C (informative) . 11
Bibliography . 12
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iv © ISO #### 2026 – All rights reserved
iv
ISO/DISPRF 23945-3:2026(en)
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Foreword
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ISO (the International Organization for Standardization) is a worldwide federation of national standards
Adjust space between Asian text and numbers
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.
The procedures used to develop this document and those intended for its further maintenance are 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/directiveswww.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 71, Concrete, reinforced concrete and pre-
stressed concrete, Subcommittee SC 1, Test methods for concrete.
A list of all parts in the ISO 23945 series can be found on the ISO website.
Formatted: English (United Kingdom)
Formatted: Font: Cambria
Any feedback or questions on this document should be directed to the user’s national standards body. A
Formatted: Adjust space between Latin and Asian text,
complete listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.
Adjust space between Asian text and numbers
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v
ISO #####-#:####(X/PRF 23945-3:2026(en)
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Introduction
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Sprayed concrete is widely used for the stabilization of structures in a very short time and for concrete
applications without using moulds. In addition to being ideal for ground support in tunnelling and mining,
sprayed concrete is also used in repairs, restoration, new constructions and many other fields.
The requirements for properties, test methods, standards and specifications for the spray forming process of
concrete are different from those of cast forming concrete. This document is intended to provide a normative
test method for sprayed concrete.
This document is applied under various climatic and geographical conditions, various levels of protection and
under different established regional traditions and experiences. Consequently, this document includes
conditions for tests covering standard, tropical and subtropical region environments.
Formatted: English (United Kingdom)
Formatted: English (United Kingdom)
This document is intended for use with other parts of the ISO 23945 series which provide requirements
Formatted: Default Paragraph Font
associated with the level of quality specified and the methods to be employed for the execution of sprayed
concrete.
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vi © ISO #### 2026 – All rights reserved
vi
DRAFT International Standard ISO/DIS 23945-3:2026(en)

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Test methods for sprayed concrete — —
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Part 3:
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Measurement of compressive strength
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1 Scope
between Asian text and numbers
This document specifies the test methods for measurement and determination of the compressive strength of
Formatted: Top: 1.4 cm, Bottom: 1 cm, Section start:
sprayed concrete at different age, from young hardened to long term hardened sprayed concrete. The test New page, Header distance from edge: 1.27 cm, Footer
methods could be applied to measure compressive strength of sprayed concrete in the range of 0,2 MPa to distance from edge: 0.5 cm
100 MPa. The specimens of hardened sprayed concrete are extracted from either an in-situ element or a test
Formatted: Font: (Asian) Japanese
panel.
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Adjust space between Asian text and numbers
This document does not purport to address all of the safety concerns, if any, associated with its use.
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2 Normative references
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The following documents are referred to in the text in such a way that some or all of their content constitutes
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requirements of this document. For dated references, only the edition cited applies. For undated references,
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the latest edition of the referenced document (including any amendments) applies.
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ISO 23945--2, Test Methods for Sprayed Concrete —Part 2: Sampling fresh and hardened concrete Adjust space between Asian text and numbers, Tab
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
ASTM C803/C803M, Standard Test Method for Penetration Resistance of Hardened Concrete
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ISO 1920-3, Testing of concrete — Part 3: Making and curing test specimens
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ISO 1920-4, Testing of concrete —Strength of hardened concrete Formatted: Default Paragraph Font, English (United
Kingdom)
EN 12390-3, Testing hardened concrete—Part 3: Compressive strength of test specimens
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3 Terms and definitions
Asian text, Adjust space between Asian text and
numbers, Tab stops: Not at 0.7 cm + 1.4 cm + 2.1 cm
No terms and definitions are listed in this document.
+ 2.8 cm + 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3
cm + 7 cm
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
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Adjust space between Asian text and numbers
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
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— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
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stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm +
4 Needle penetration method 3.5 cm + 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
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4.1 General
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This part specifies the method from which an estimate of the in-situ compressive strength of young hardened
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sprayed concrete can be made in the range of 0,2 MPa to 1,5 MPa.
...
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4.2 Principle
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Needle penetration method is used to measure the force required to push a needle of specified dimensions to
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penetrate into the sprayed concrete to a depth of 15 mm +/- 2 mm. A penetrometer indicates the resisting
stops: Not at 0.71 cm
force, through compression of a calibrated spring from which an estimated compressive strength can be
derived from a calibration curve provided by the producer of the test equipment. Formatted: English (United Kingdom)
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4.3 Specimens
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The thickness of the sprayed concrete layer shall be not less than 100 mm for testing.
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stops: Not at 0.71 cm
The specimens for test shall be prepared according to ISO 23945-2.
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No special test specimen is required for test of in-situ structures. The testing procedure can be used for
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measurements at any location without advance preparation.
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4.4 Apparatus
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4.4.1 Penetrometer
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The penetrometer shall be capable of driving the needle into the surface and recording the force required to
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an accuracy of 10 N. The penetrometer shall be provided with a certified calibration curve, able to correlate
readings to estimated compressive strength. An example of calibration curves is shown in Annex A.Annex A. Formatted
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4.4.2 Needle
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The needle shall be with a diameter of 3 mm ± 0,1 mm and a tip with a taper angle of 60° ± 5°, the needle length
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shall be more than 15 mm.
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4.5 Procedures Formatted
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4.5.1 4.5.1 Record time and place of completion of spraying and start of testing.
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4.5.2 4.5.2 Ensure the force indicator is set to zero.
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4.5.3 4.5.3 Apply the device perpendicularly to the surface of the sprayed concrete layer and steadily push
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in the needle to a depth of 15 mm in a single continuous movement. If this is prevented, for instance
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because of a large aggregate particle or reinforcement, then discontinue the test and repeat in an
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4.5.4 4.5.4 Read the resistance force from the scale, record the value on the protocol form and return
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indicator to original position.
4.5.5 4.5.5 Clean the needle if necessary.
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4.5.6 4.5.6 Repeat the test ten times as quickly as possible (and within 1 min for strengths below 0,5 MPa)
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in an area representative of the sprayed region.
4.5.7 4.5.7 Record the time at which the testing is finished (on protocol form).
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4.6 Expression of results Formatted
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Calculate the mean resistance force from the 10 measurements.
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The estimated compressive strength is derived from the manufacturer's calibration curve. Extrapolation is not
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permitted.
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2 © ISO #### 2026 – All rights reserved
ISO/DISPRF 23945-3:2026(en)
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4.7 Test report
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The test report shall include the following information:
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a) a) the identification of the test sample;
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b) b) the International Standard used (including its year of publication);
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c) c) the method used;
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d) d) type and serial number of the test equipment;
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e) e) the location where the test was performed;
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f) f) the date and time of test, age of specimen at time of test (if known);
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g) g) time of completing spraying and start and finish of testing, to the nearest minute;
h) h) ten measurements of resistance force and the mean value to nearest 10 N;
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i) i) the result (compressive strength);
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j) j) the ambient temperature and humidity;
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k) k) any deviations from the procedure; Formatted: English (United Kingdom)
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l) l) any unusual features observed;
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