ISO 1920-12:2015

INTERNATIONAL ISO
STANDARD 1920-12
First edition
2015-05-15
Testing of concrete —
Part 12:
Determination of the carbonation
resistance of concrete — Accelerated
carbonation method
Essais du béton —
Partie 12: Détermination de la résistance du béton à la carbonation
— Méthode de carbonation accélérée
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents and apparatus . 2
6 Preparation of specimens . 3
6.1 General . 3
6.2 Making, curing, and testing of prisms and cubes . 3
7 Carbonation depth measurements . 5
7.1 Exposure period and generation of colour change . 5
8 Determination of the carbonation depth . 5
8.1 General . 5
8.2 Measuring the depth of carbonation . 5
8.3 Appreciation of dense aggregates . 5
8.4 Appreciation of pores and porous aggregates and extreme values . 6
8.5 Expression of the results . 7
9 Test report . 7
10 Precision . 7
Annex A (informative) Guidance on suitable storage chambers . 8
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
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different types of ISO documents should be noted. This document was drafted in accordance with the
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 71, Concrete, reinforced concrete and pre-stressed
concrete, Subcommittee SC 1, Test methods for concrete.
ISO 1920 consists of the following parts, under the general title Testing of concrete:
— Part 1: Sampling of fresh concrete
— Part 2: Properties of fresh concrete
— Part 3: Making and curing test specimens
— Part 4: Strength of hardened concrete
— Part 5: Properties of hardened concrete other than strength
— Part 6: Sampling, preparing and testing of concrete cores
— Part 7: Non-destructive tests on hardened concrete
— Part 8: Determination of drying shrinkage of concrete for samples prepared in the field or in the laboratory
— Part 9: Determination of creep of concrete cylinders in compression
— Part 10: Determination of static modulus of elasticity in compression
— Part 11: Determination of the chloride resistance of concrete, unidirectional diffusion
— Part 12: Determination of the carbonation resistance of concrete — Accelerated carbonation method
iv © ISO 2015 – All rights reserved

Introduction
Ferrous steel reinforced concrete structures need to be durable to ensure that the intended service
life is achieved. The corrosion of reinforcement induced by carbonation can play a significant role in
the serviceability of a structure and consequently carbonation resistance of concrete is an important
property to measure. This International Standard sets out a test method that may be applied to cast test
specimens to assess the potential carbonation resistance properties of a concrete mix.
INTERNATIONAL STANDARD ISO 1920-12:2015(E)
Testing of concrete —
Part 12:
Determination of the carbonation resistance of concrete —
Accelerated carbonation method
1 Scope
This procedure is a method for evaluating the carbonation resistance of concrete using an accelerated
carbonation test. After a period of preconditioning, the test is carried out under controlled exposure
conditions using an increased level of carbon dioxide to which, the vertical sides of the specimen are exposed.
The test results are not designated to set performance requirements but to compare the carbonation
resistance of different concretes of the same strength class, which are used in the same environmental
conditions.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 1920-2, Testing of concrete — Part 2: Properties of fresh concrete
ISO 1920-3, Testing of concrete — Part 3: Making and curing test specimens
ISO 1920-4, Testing of concrete — Part 4: Strength of hardened concrete
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
depth of carbonation
depth as measured using a phenolphthalein solution sprayed on a freshly-split concrete surface
3.2
single point carbonation depth
depth of carbonation measured at a single point on a specimen, d
k,point
3.3
specimen face carbonation depth
mean depth of carbonation of a single exposed face of a single specimen, d
k,face
3.4
specimen carbonation depth
mean depth of carbonation of a single specimen, d
k,spec
3.5
mean carbonation depth
mean depth of carbonation of two specimens, d
k
4 Principle
Two concrete cubes are cast and cured for 28 d in accordance with ISO 1920-3 (see also changes to the
curing conditions in 6.2). The two concrete cubes are then conditioned in a laboratory air environment
for 14 d prior to sealing the top, bottom, and two opposite side faces. After sealing of all but two faces,
the cubes are placed in a storage chamber meeting the conditions specified in 5.4 and having a carbon
dioxide level of (3,0 ± 0,5) % for a period of 70 d. After 70 d of exposure, the cubes shall be split in half,
perpendicular to the exposed faces, and the depth of carbonation measured in accordance with the
procedure given in Clause 7.
The test under reference conditions takes therefore a minimum of 112 d, period that comprises a
minimum age of the specimen of 28 d prior to conditioning, a minimum conditioning period of 14 d,
and a minimum exposure to increased carbon dioxide levels of 70 d. In case where a higher range of
additions such as pozzolanic materials, slag, and others are used, extended curing and drying times are
allowed and the same should be reported.
If required, further cubic specimens may be casted and used for measurement of the depth of carbonation
at exposure periods other than 70 d. Each cubic specimens shall be used for testing at one period of
exposure only.
When the purpose of the test is to measure the depth of carbonation on the same specimen at more than
one exposure period, concrete prisms shall be used.
In this case, two prisms are cast and cured for 28 d in accordance with ISO 1920-3 (see also amendments
of the curing conditions in 6.2). The prisms are conditioned in a laboratory air environment for 14 d prior
to sealing the top, bottom, and two end faces. After sealing all but two longitudinal faces, the prisms are
placed in a storage chamber, meeting the conditions specified in 5.4 and having a carbon dioxide level of
(3,0 ± 0.5) % for the overall test period which should be 70 d. After each exposure period, a 50 mm slice
is broken from each prism and tested for carbonation depth. After splitting off a slice, the split end faces
of the prisms are sealed and the remainder of the prisms returned to the storage chamber.
The specimens, cubes, or prisms shall be positioned with their exposed faces in the vertical position.
The curing conditions may vary from one country to another in accordance with local provisions;
however, these conditions shall be recorded and reported.
5 Reagents and apparatus
5.1 Paraffin wax or equivalent, for sealing the non-exposed faces of test specimens.
5.2 A solution, made of 1 g of phenolphthalein powder dissolved in 100 ml solution composed of 70 ml
ethanol and 30 ml of deionised water.
5.3 A magnifier and a gauge, to measure the depth of carbonation perpendicular to the exposed
concrete surface with a precision of 0,5 mm.
5.4 A storage chamber with a carbon dioxide concentration at (3,0 ± 0,5) % by volume,
temperature at (22 ± 2) °C, and a relative humidity at (55 ± 5) %, see Annex A for details of a suitable
chamber. In hot climate locations, the conditions in the storage chamber may be temperature at (27 ± 2) °C
and relative humidity at (65 ± 5) %.
Experience has shown that if saturated surface-dry specimens are placed in the storage chamber shortly
after removal from water curing, the relative humidity could exceed that permitted. Also, in storage
chambers without active control of the carbon dioxide, the levels could drop below the permitted
tolerance as the carbonation process continues. It is therefore a recommendation of this test method
that the storage chamber has active control on carbon dioxide, relative humidity, and temperature.
2 © ISO 2015 – All rights reserved

Other carbon dioxide concentration levels, other humidity levels, and other temperature levels may be
used. However, this shall be recorded and reported.
NOTE Relative humidity levels may be maintained using methods at the discretion of the laboratory, for
example, active humidification/dehumidification or saturated salt solutions.
5.5 Apparatus, for recording the relative humidity with a precision of ±2,0 % and the temperature with
a precision of ±0,5 °C.
5.6 Apparatus, for recording CO concentration with a precision of ±0,1 %
...