EN 12390-10:2026

• Abstract:

  This document specifies a method of determining the carbonation rate of a concrete, expressed in mm/√a.; This document establishes a procedure where a standardized climate-controlled chamber is used and where specimens are placed on a natural exposure site protected from direct rainfall. The standardized climate-controlled chamber procedure is the reference method.; These procedures are applicable for the initial testing of concrete, including that manufactured with slowly reacting binders, provided that the ages at which the carbonation depth is measured, the number of measurements required to calculate the carbonation rate, as well as the length of exposure to CO2, are appropriately selected, as described in this document.; These procedures are not applicable for factory production control.

• Status: Not Published
• Publication Date: 15-Dec-2026
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: CEN/TC 104 - Concrete ( performance, production, placing and compliance criteria )
• Drafting Committee: CEN/TC 104/SC 1 - Revision of ENV 206
• Current Stage: 5060 - Closure of Vote - Formal Approval
• Start Date: 22-Oct-2026
• Due Date: 03-Dec-2026
• Completion Date: 22-Oct-2026
• Ref Project: kSIST FprEN 12390-10:2026 - Testing hardened concrete - Part 10: Determination of the carbonation resistance of concrete at atmospheric levels of carbon dioxide

• Revises: EN 12390-10:2018 - Testing hardened concrete - Part 10: Determination of the carbonation resistance of concrete at atmospheric levels of carbon dioxide
• Effective Date: 18-Jan-2023

EN 12390-10:2026 is a CEN standard for testing hardened concrete. It specifies how to determine the carbonation rate of concrete at atmospheric levels of carbon dioxide, reported in mm/√a. The document is aimed at initial testing of concrete, including concrete made with slowly reacting binders, and it uses a standardized climate-controlled chamber as the reference method.

What does EN 12390-10:2026 specify?

EN 12390-10:2026 specifies a test method for measuring the carbonation resistance of concrete and for calculating the carbonation rate from carbonation depth measurements over time. The document covers both a standardized climate-controlled chamber procedure and an alternative natural exposure site procedure protected from direct rainfall.

The standard is organized into clauses 1 to 10 and two informative annexes.

Annex	What it covers
Annex A	Guidance on suitable climate controlled chambers
Annex B	Guidance on natural exposure sites

Clauses 4 to 10 cover the principle, reagents and apparatus, production of specimens, carbonation depth measurements, determination of the rate of carbonation, the test report, and precision. The scope excludes factory production control.

What are the key requirements of EN 12390-10:2026?

EN 12390-10:2026 sets out a controlled way to expose concrete specimens, measure the carbonation front, and turn those measurements into a carbonation rate. In practice, the value of the standard is that it gives comparable test results for mixture assessment, durability classification, and later use in carbonation models.

Exposure conditions and specimen preparation

Clause 4 requires specimens from the same batch of concrete, either pairs of beams or two cubes per test age. Beams are the reference specimens, and compressive strength specimens are also made from the same batch.

Clause 6 requires representative constituents and careful specimen production. For laboratory production, a minimum batch volume of 50 l is recommended, and mould release agents should be avoided or minimized because they can influence carbonation depth.

For the climate-controlled chamber procedure, Clause 6 requires standard curing, then exposure in a chamber controlled at 400 ppm carbon dioxide (CO2), 20 °C and 65 % relative humidity. The chamber must allow free air circulation around all test faces, and the CO2 level must be monitored and kept within the stated limits. This matters because the chamber method is the reference method and gives the most standardized comparison.

Natural exposure site procedure

Clause 6 also allows a natural exposure site, but the specimens must be protected from direct precipitation and placed so that air can move freely around them. The site must be monitored for temperature, relative humidity and CO2, and daily readings are required, or local meteorological data may be used when appropriate.

For this procedure, the specimens are held until they reach 50 % of the reference strength before exposure begins. That makes the starting condition more consistent when concrete strength development is still progressing. Annex B gives practical guidance for a sheltered outdoor arrangement, including a Stevenson Screen.

Carbonation depth measurement

Clause 7 requires the testing ages to be defined before the test starts, counted from the date the specimens are placed in the chamber or on the exposure site. The document recommends measurements after at least three months, six months and one year, and if the carbonation depth is still below 5 mm after one year, the test should be extended to two years.

The carbonation depth is measured on freshly broken surfaces after applying an indicator solution. Phenolphthalein is the reference indicator, but the standard allows another indicator if it gives a clear colour change in the pH 8 to pH 11 range. The surface is measured at three points on each face, giving up to 12 measurements per specimen, and the mean is recorded.

Dense aggregates, pores and porous aggregates must be treated consistently when they interrupt the carbonation front. Clause 7 explains how to handle those cases so that the mean depth reflects the real front rather than local anomalies. At least three valid readings are required on each face, and the total number of valid readings should be at least 12.

Determination of carbonation rate

Clause 8 determines the carbonation rate from the mean carbonation depth and effective time. The standard uses the square root of time relationship, with a linear regression of average carbonation depth against square root of effective time in years. The slope of that line is the carbonation rate in mm/√a.

Clause 8 also allows a direct calculation at each test age using the stated relationship between average carbonation depth, the rate constant and the square root of time. In practice, this is the part of the standard that turns a series of depth readings into a single comparable rate value.

Reporting and precision

Clause 9 requires the test report to state the test method used, the exposure conditions, specimen details, test ages, carbonation depths, the number of measuring points, any displaced measurement points, excluded extreme values, the regression result and the average carbonation rate. Any deviation from the test conditions must also be reported.

Clause 10 gives precision estimates for chamber testing and natural exposure site testing. This matters when comparing laboratories or deciding how much confidence to place in small differences between results. The clause also notes that precision improves when the carbonation depth is greater than 4 mm and is lower when the depth is 1 mm or less.

What changed in EN 12390-10:2026 from the previous edition?

EN 12390-10:2026 supersedes EN 12390-10:2018. The foreword states one significant technical change: the scope has been updated to account for slowly reacting binders.

The introduction also states that the chamber carbon dioxide concentration is fixed at 400 ppm, which is 50 ppm higher than the previous version used.

Which standards are used with EN 12390-10:2026?

EN 12390-10:2026 names three normative references that support specimen preparation and strength testing.

Reference	What it contributes
EN 12390-1	Shape, dimensions and other requirements for specimens and moulds
EN 12390-2	Making and curing specimens for strength tests
EN 12390-3	Compressive strength of test specimens

The foreword also places this standard in the EN 12390 series, alongside other parts covering hardened concrete tests such as specimen preparation, compressive strength, density, water penetration, freeze-thaw scaling, chloride resistance, accelerated carbonation, modulus of elasticity, heat of hydration, shrinkage, creep and electrical resistivity.

What does the EN 12390-10:2026 document contain?

EN 12390-10:2026 contains the full test workflow for carbonation resistance testing, from apparatus and specimen preparation through to calculation and reporting. Clause 5 defines the indicator solution, measurement tools, chamber requirements, monitoring equipment and air circulation needs. Clause 6 gives the production and curing routes for chamber testing and natural exposure testing, and Clause 7 describes when to measure, how to break specimens, how to spray the indicator, and how to treat dense aggregates, pores and extreme values.

The document also includes guidance figures and examples. Annex A shows chamber arrangements, CO2 injection and monitoring, horizontal and vertical storage, and spacing of specimens. Annex B shows a sheltered natural exposure arrangement, including a Stevenson Screen and the intended airflow and drainage features. Clause 10 includes a precision table for repeatability and reproducibility, which is useful for laboratory comparisons, audits and interpretation of test variability.

SLOVENSKI STANDARD
oSIST prEN 12390-10:2025
01-december-2025
Preskušanje strjenega betona - 10. del: Določanje odpornosti betona proti
karbonatizaciji pri atmosferski koncentraciji ogljikovega dioksida
Testing hardened concrete - Part 10: Determination of the carbonation resistance of
concrete at atmospheric levels of carbon dioxide
Prüfung von Festbeton - Teil 10: Bestimmung des Karbonatisierungswiderstandes von
Beton bei atmosphärischer Konzentration von Kohlenstoffdioxid
Essais pour béton durci - Partie 10 : Détermination de la résistance à la carbonatation du
béton à des niveaux atmosphériques de dioxyde de carbone
Ta slovenski standard je istoveten z: prEN 12390-10
ICS:
91.100.30 Beton in betonski izdelki Concrete and concrete
products
oSIST prEN 12390-10:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 12390-10:2025
oSIST prEN 12390-10:2025
DRAFT
EUROPEAN STANDARD
prEN 12390-10
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 91.100.30 Will supersede EN 12390-10:2018
English Version
Testing hardened concrete - Part 10: Determination of the
carbonation resistance of concrete at atmospheric levels of
carbon dioxide
Essais pour béton durci - Partie 10 : Détermination de Prüfung von Festbeton - Teil 10: Bestimmung des
la résistance à la carbonatation du béton à des niveaux Karbonatisierungswiderstandes von Beton bei
atmosphériques de dioxyde de carbone atmosphärischer Konzentration von Kohlenstoffdioxid
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 104.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12390-10:2025 E
worldwide for CEN national Members.

oSIST prEN 12390-10:2025
prEN 12390-10:2025 (E)
Contents Page
European foreword . 3
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Principle . 6
5 Reagents and apparatus . 7
6 Production of specimens . 7
6.1 General . 7
6.2 Procedure when using climate controlled chamber . 8
6.3 Procedure when using a natural exposure site . 8
7 Carbonation depth measurements . 9
7.1 Testing age and generation of colour change . 9
7.2 Determination of the carbonation depth . 10
7.2.1 General . 10
7.2.2 Measuring the depth of carbonation . 10
7.2.3 Appreciation of dense aggregates . 10
7.2.4 Appreciation of pores and porous aggregates and extreme values . 10
8 Determination of the rate of carbonation . 10
9 Test report . 11
10 Precision . 12
Annex A (informative) Guidance on suitable climate controlled chambers . 14
Annex B (informative) Guidance on natural exposure sites . 18
Bibliography . 20

oSIST prEN 12390-10:2025
prEN 12390-10:2025 (E)
European foreword
This document (prEN 12390-10:2025) has been prepared by Technical Committee CEN/TC 104
“Concrete and related products”,”, the secretariat of which is held by SN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 12390-10:2018.
prEN 12390-10:2025 includes the following significant technical changes with respect to
EN 12390-10:2018:
— The scope has been updated in order to account for slowly reacting binders.
The EN 12390 series, under the general title Testing hardened concrete, consists of the following parts:
— Part 1: Shape, dimensions and other requirements for specimens and moulds
— Part 2: Making and curing specimens for strength tests
— Part 3: Compressive strength of test specimens
— Part 4: Compressive strength - Specification for testing machines
— Part 5: Flexural strength of test specimens
— Part 6: Tensile splitting strength of test specimens
— Part 7: Density of hardened concrete
— Part 8: Depth of penetration of water under pressure
— Part 9: Freeze–thaw resistance with de-icing salts - Scaling (Technical Specification)
— Part 10: Determination of the carbonation resistance of concrete at atmospheric levels of carbon
dioxide
— Part 11: Determination of the chloride resistance of concrete, unidirectional diffusion
— Pert 12: Determination of the carbonation resistance of concrete – Accelerated carbonation method
— Part 13: Determination of the secant modulus of elasticity in compression
— Part 14: Semi-adiabatic method for the determination of heat released by concrete during its
hardening process
— Part 15: Adiabatic method for the determination of heat released by concrete during its hardening
process
— Part 16: Determination of the shrinkage of concrete
— Part 17: Determination of creep of concrete in compression
oSIST prEN 12390-10:2025
prEN 12390-10:2025 (E)
— Part 18: Determination of the chloride migration coefficient
— Part 19: Determination of electrical resistivity
oSIST prEN 12390-10:2025
prEN 12390-10:2025 (E)
Introduction
In reinforced and prestressed concrete structures, a sufficient concrete cover protects conventional
steel reinforcement from corrosion and contributes to ensure that the intended working life is achieved.
Reinforcement corrosion induced by carbonation can play a significant role in a structure’s
serviceability and consequently carbonation resistance of concrete, in particular of the cover zone, is an
important property to be quantified.
This document describes a test method for the quantification of the carbonation rate of any freshly cast
concrete. This document quantifies concrete behaviour in the conditions of carbonation at natural
levels of carbon dioxide. For standardization purposes, the carbon dioxide concentration in the climate
controlled chamber is fixed at 400 ppm, which is an increase of 50 ppm over the value used in the
previous version of this document. However, atmospheric levels of carbon dioxide are not constant in
location or time, and in some urban and industrial areas, carbon dioxide concentration exceeds
400 ppm.
From a European perspective, it makes sense to have common test procedures and common assessment
procedures, but with various possible purposes.
One of the intended applications of this document is the comparison of concrete mixtures, and in
particular the assessment of the impact of a change of constituent, e.g. cement type, addition, or the
impact of a change in mix proportions, e.g. w/c ratio, cement content, fines content. Such a comparison,
is also carried out when assessing the durability performance, and more precisely the ‘equivalent
durability’ with respect to carbonation, of a concrete, with unknown carbonation resistance or of a
concrete with one or more unfamiliar constituents. CEN/TR 16563 sets out basic principles to be
followed by 'equivalent durability' procedures.
In addition, this document provides parameters used in the classification of concrete on the basis of its
carbonation resistance.
Moreover, the rate of carbonation, as determined by the described test procedure, is used in some
models that estimate the start of reinforcement corrosion.
As this document provides test procedures, it only describes the production of standardized test
results; how these test results are used is not within the scope of this document.
oSIST prEN 12390-10:2025
prEN 12390-10:2025 (E)
1 Scope
This document specifies a method of determining the carbonation rate of a concrete, expressed in
mm/√a.
This document establishes a procedure where a standardized climate controlled chamber is used and
where specimens are placed on a natural exposure site protected from direct rainfall. The standardized
climate controlled chamber procedure is the reference method.
These procedures are applicable for the initial testing of concrete, including those manufactured with
slowly reacting binders, provided that the ages at which the carbonation depth is measured, the number
of measurements required to calculate the carbonation rate, as well as the length of exposure to CO , are
appropriately selected, as described in this document.
These procedures are not applicable for factory production control.
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.
EN 12390-1, Testing hardened concrete — Part 1: Shape, dimensions and other requirements for
specimens and moulds
EN 12390-2, Testing hardened concrete — Part 2: Making and curing specimens for strength tests
EN 12390-3, Testing hardened concrete — Part 3: Compressive strength of 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:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
4 Principle
Pairs of beams of concrete (or two cubes per test age) from the same batch of concrete are stored in a
climate controlled chamber as specified in 5.4 or on a natural exposure site as specified in 5.5. After
defined periods of exposure, an approximately 50 mm thick slice of the beam is broken off at each test
age and tested for its carbonation depth. If cubes are being used, they are broken in half and one half of
each cube is used to measure the carbonation depth, the other half being discarded.
The carbonation depth is measured at three locations on each face of each beam/cube giving a potential
total of 12 measurements per specimen and potentially 24 measurements for the two specimens. The
mean carbonation depth of all measurements is calculated. The remains of the beams are returned to
the climate controlled chamber for testing at other pre-defined ages. Using at least three sets of
measurements taken at 3 months, 6 months and 1 year, the rate of carbonation expressed as mm/√a is
determined.
oSIST prEN 12390-10:2025
prEN 12390-10:2025 (E)
5 Reagents and apparatus
5.1 A solution of 1 g of phenolphthalein powder dissolved in a solution of 70 ml ethanol and 30 ml of
deionized water. Phenolphthalein is the reference method but an alternative indicator giving a colour
change in the range pH 8 to pH 11 that gives a sufficiently clear colour change in concrete to
differentiate the neutralized zone may be used, e.g. thymolphthalein, flavonoids, curcumine, or
antocianines.
WARNING — Phenolphthalein is listed on the REACH candidate list of substances of very high concern
for authorization. Phenolphthalein powder should be handled with the greatest care using safety gloves
in a fume cupboard fitted with an extractor.
5.2 Where used, a fixing solution to permanently fix the colour change in the concrete specimen (see
7.1).
NOTE Suppliers of some indicator solutions also provide a fixing solution that permanently fixes the colour
change.
5.3 A magnifier and a gauge to measure the depth of carbonation perpendicular to the exposed
concrete surface which ensure a precision of the measurement of 0,5 mm.
5.4 A climate controlled chamber controlling the average over the test duration carbon dioxide
concentration at (0,040 ± 0,001) % by volume with no variation outside (0,040 ± 0,005) %, temperature
at (20 ± 2) °C and a relative humidity at (65 ± 2) % (see Annex A for details of a suitable chamber).
5.5 Alternatively to climate controlled chamber, a natural exposure site where specimens are
protected from direct precipitation such as rain, hail and snow (see Annex B for details of a suitable
arrangement). The site shall be equipped with instruments to measure relative humidity, temperature
and carbon dioxide concentration at least 4 times per day. If this is not possible, local meteorological
data can be used.
5.6 Apparatus for recording the relative humidity, which ensures a precision of the measurement
of ± 1,0 %, and the temperature with a precision of ± 0,5 °C.
5.7 Apparatus for recording CO concentration with a precision of ± 0,001 % by volume. If a climate
controlled chamber is being used, it shall be fitted with an audible/visual/electronic alarm to signify
breaching of limits.
5.8 Fan to provide a homogeneous CO concentration in the air. Type, dimensions and power of the
fan shall be adapted to the dimension of the chamber.
6 Production of specimens
6.1 General
Representative samples of the constituents, e.g. cement, aggregates, shall be used for making the test
specimens. Either a sample of concrete is taken from the concrete production plant or the concrete
mixes shall be produced using the laboratory’s standard procedures. The specimens for one test, which
include specimens for the carbonation test and compressive strength tests, shall be cast from a single
batch of concrete.
For laboratory production, a minimum batch volume of 50 l is recommended.
oSIST prEN 12390-10:2025
prEN 12390-10:2025 (E)
Each test shall comprise at least two prismatic beams each being at least 350 mm long and the other
dimensions at least three times the maximum aggregate size or two cubes per test age with a side
length of at least three times the maximum aggregate size. Beams are the reference specimens.
Avoid or minimize the use of mould release agents on the moulds as they may influence the carbonation
depth.
All compressive strength specimens, either cubes or cylinders, shall be made and cured in accordance
with EN 12390-1 and EN 12390-2 and tested in accordance with EN 12390-3.
6.2 Procedure when using climate controlled chamber
After moulding the test specimens, cover the exposed concrete surface with polythene or similar
impermeable sheeting to prevent drying. After (24 ± 2) h, the moulds shall be stripped and the test
specimens transferred without delay into the standard curing condition according to EN 12390-2. After
27 days of standard curing, the test specimens shall be exposed to laboratory air, T = (20 ± 2) °C,
RH = (65 ± 5) % for (16 ± 2) h and then they are placed in the climate controlled chamber.
NOTE 1 The reason for the 27 day wet curing is to allow cements to hydrate prior to carbonation testing as
further hydration is hindered by the carbonation test conditions.
NOTE 2 In climate controlled chambers that do not have the facility to reduce the relative humidity, if the test
specimens are placed immediately in the climate controlled chamber, the rate of carbonation decreases when the
relative humidity is too high and (temporarily) exceeds the limit. If the climate controlled chamber is fitted with
facilities to reduce the relative humidity (not the normal situation), the test specimens can be placed directly in
the climate controlled chamber.
The test specimens shall be positioned in the climate controlled chamber in a way that permits air to
circulate freely around all the four faces to be tested. This is either by horizontal storage or vertical
storage, but ensuring a 50 mm gap between adjacent specimens. The temperature shall be measured at
least once per day at a constant time.
The relative humidity and carbon dioxide concentration shall be measured and recorded at least once
every two hours. The average carbon dioxide concentration in the climate controlled chamber over the
duration of the test shall be (0,040 ± 0,001) % with no variation outside (0,040 ± 0,005) %.
6.3 Procedure when using a natural exposure site
For each concrete mix, cast at least two beams or at least six cubes for carbonation testing and at least 2
or if the strength development is not known, at least 5 compressive strength specimens from a single
batch of concrete. The test specimens shall be cast horizontally in accordance with EN 12390-2. After
finishing the test specimens, cover the exposed surface with polythene or similar impermeable sheeting
to prevent drying.
After (24 ± 2) h, the moulds shall be stripped and the carbonation test specimens transferred without
delay into close-fitting, sealed polythene bags or similar storage material and stored at (20 ± 2) °C until
they have reached 50 % of the reference strength. If the temperature range is from 15 °C to 25 °C, 50 %
of the reference strength
...