SIST EN 12390-19:2023
(Main)Testing of hardened concrete - Determination of electrical resistivity
Testing of hardened concrete - Determination of electrical resistivity
This document describes a method for determining the electrical resistivity of concrete in water saturated conditions. Two methods of measuring the resistivity are standardized: the volumetric method (see 3.1.3), which is the reference method, and the surface method (see 3.1.4).
NOTE The volumetric method is applicable to cast specimens or cores, while the surface method is suitable for use on cast specimens, cores and on construction site, but not all these applications are covered in this document.
The method can be applied to the normal range of concretes covered by current standards. It does not cover the concretes made with porous aggregates or having metallic components.
The use of resistivity to assess the potential for corrosion of reinforcement in existing structures is not specified in this document.
The use of resistivity to assess cores taken from an existing structure, which need pre-condition on water saturation, is not directly specified in this document.
Prüfung von Festbeton - Teil 19: Bestimmung des elektrischen Widerstands
In diesem Dokument wird ein Verfahren zur Bestimmung des spezifischen elektrischen Widerstandes von Beton in wassergesättigtem Zustand beschrieben. Es werden zwei Verfahren zur Messung des spezifischen Widerstandes genormt: das Volumenverfahren (siehe 3.1.3), bei dem es sich um das Referenzverfahren handelt, und das Oberflächenverfahren (siehe 3.1.4).
ANMERKUNG Das Volumenverfahren ist auf gegossene Probekörper oder Bohrkerne anwendbar, während sich das Oberflächenverfahren für die Anwendung auf gegossene Probekörper, Bohrkerne und Ortbetone eignet, es werden jedoch nicht alle diese Anwendungen in diesem Dokument behandelt.
Das Verfahren kann auf die übliche Bandbreite der von den aktuellen Normen abgedeckten Betone angewendet werden. Es gilt nicht für Betone, die unter Verwendung porenhaltiger Zuschläge hergestellt wurden oder die metallische Bestandteile enthalten.
Die Verwendung des spezifischen Widerstandes zur Beurteilung des Korrosionspotentials von Bewehrungen in bestehenden Tragwerken wird in diesem Dokument nicht festgelegt.
Die Verwendung des spezifischen Widerstandes zur Beurteilung von aus bestehenden Tragwerken entnommenen Bohrkernen, bei denen eine Vorbehandlung zur Erzielung der Wassersättigung notwendig ist, wird in diesem Dokument nicht direkt festgelegt.
Essais pour béton durci - Détermination de la résistivité électrique
Le présent document décrit une méthode permettant de déterminer la résistivité électrique du béton dans des conditions de saturation en eau. Deux méthodes de mesure de la résistivité sont normalisées : la méthode volumique (voir 3.1.3), qui est la méthode de référence, et la méthode de surface (voir 3.1.4).
NOTE La méthode volumique est applicable aux échantillons coulés ou aux carottes, tandis que la méthode de surface est adaptée aux échantillons coulés, aux carottes et aux sites de construction ; toutefois, toutes ces applications ne sont pas couvertes dans le présent document.
La méthode peut être appliquée à la gamme normale de bétons couverte par les normes actuelles. Elle ne couvre pas les bétons à base de granulats poreux ou comportant des composants métalliques.
L’utilisation de la résistivité pour évaluer le potentiel de corrosion de l’armature sur des structures existantes n’est pas spécifiée dans le présent document.
Le recours à la résistivité pour évaluer des carottes prélevées sur une structure existante, nécessitant une condition préalables de saturation en eau, n’est pas directement spécifié dans le présent document.
Preskušanje strjenega betona - 19. del: Ugotavljanje električne upornosti
Ta dokument opisuje metodo za ugotavljanje električne upornosti betona v pogojih, nasičenih z vodo. Za merjenje upornosti sta standardizirani dve metodi: volumetrična metoda (glej točko 3.1.3), ki je referenčna metoda, in površinska metoda (glej točko 3.1.4).
OPOMBA: Volumetrična metoda se uporablja za ulite vzorce ali jedra, medtem ko je površinska metoda primerna za uporabo na ulitih vzorcih, jedrih in na gradbišču, vendar ta dokument ne zajema vseh teh vrst uporabe.
Metodo je mogoče uporabiti za običajne vrste betona, ki jih pokrivajo veljavni standardi. Ne velja za tiste vrste betona, ki so narejene s poroznimi agregati ali s kovinskimi komponentami.
Dokument ne obravnava uporabe upornosti za oceno možnosti korozije armature v obstoječih strukturah.
Dokument neposredno ne določa uporabe upornosti za oceno jeder, vzetih iz obstoječe strukture, ki zahtevajo vnaprejšnjo pripravo za nasičenost z vodo.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 12390-19:2023
01-junij-2023
Preskušanje strjenega betona - 19. del: Ugotavljanje električne upornosti
Testing of hardened concrete - Determination of electrical resistivity
Prüfung von Festbeton - Teil 19: Bestimmung des elektrischen Widerstands
Essais pour béton durci - Détermination de la résistivité électrique
Ta slovenski standard je istoveten z: EN 12390-19:2023
ICS:
91.100.30 Beton in betonski izdelki Concrete and concrete
products
SIST EN 12390-19:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 12390-19:2023
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SIST EN 12390-19:2023
EN 12390-19
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2023
EUROPÄISCHE NORM
ICS 91.100.30
English Version
Testing of hardened concrete - Determination of electrical
resistivity
Essais pour béton durci - Détermination de la Prüfung von Festbeton - Teil 19: Bestimmung des
résistivité électrique elektrischen Widerstands
This European Standard was approved by CEN on 9 January 2023.
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. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists 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.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12390-19:2023 E
worldwide for CEN national Members.
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SIST EN 12390-19:2023
EN 12390-19:2023 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and symbols . 5
3.1 Terms and definitions . 5
3.2 Symbols . 7
4 Principle . 7
5 Apparatus . 8
5.1 Resistivity meter . 8
5.2 Data logger . 9
5.3 Electrodes . 9
5.4 Sponges . 9
5.5 Wetting liquid at the sponge/concrete interface . 10
6 Preparation of test specimens . 10
6.1 Minimum number of specimens/readings to obtain a test result for a concrete . 10
6.2 Test specimen preparation. 11
7 Test procedure volumetric method (reference method) . 11
7.1 Determination of the volumetric resistance . 11
7.2 Two-electrode arrangement . 13
8 Test procedure surface method . 13
8.1 Measurements . 13
8.2 Calculation of resistivity . 15
8.2.1 General . 15
8.2.2 Volumetric method . 15
8.2.3 Surface method . 15
9 Test report . 16
10 Precision . 17
Annex A (informative) Determination of the precision of the equipment . 18
Bibliography . 19
2
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SIST EN 12390-19:2023
EN 12390-19:2023 (E)
European foreword
This document (EN 12390-19:2023) has been prepared by Technical Committee CEN/TC 104 “Concrete
and related products”, Subcommittee SC1 “Concrete - Specification, performance, production and
conformity”, the secretariat of which is held by SN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2023, and conflicting national standards shall be
withdrawn at the latest by August 2023.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
A list of all parts in the EN 12390 series can be found on the CEN website.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: 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 the United
Kingdom.
3
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SIST EN 12390-19:2023
EN 12390-19:2023 (E)
Introduction
This test method is one of a series concerned with testing hardened concrete.
This document is based on current national standards and in particular the Spanish standard UNE
PNE 83988 Part 1 and Part 2.
Resistivity is a property that quantifies how strongly a given material opposes the flow of electric current.
3
Resistivity is the electrical resistance of a unit volume (e.g. 1 m ) of a concrete. It is the inverse of
conductivity, and it is obtained from the ratio between the voltage drop and the current (Ohm’s law).
The resistivity of a water-saturated concrete is mainly a function of the pore size distribution and the
connectivity/tortuosity of the pore system. It also depends on the pore solution composition, which is
strongly affected by the cement type, additions, w/c ratio, aggregate type and the degree of hydration of
the cement.
Resistivity is also dependent on temperature and for quality control testing, the temperature of the
concrete specimens should be held within a defined range for comparable results.
The document is applied to water saturated concretes because the resistivity is affected by the degree of
water saturation. A reduction in the moisture content increases the resistivity. Loss of continuity of the
pore system by drying can have more impact on the resistivity value than a change in the volume of
capillary porosity because drying can produce changes of more than one order of magnitude while a
change in capillary porosity can be reflected in changes of two or three times.
In this document a 4-electrode arrangement is recommended as it avoids the voltage drop produced by
the concrete/electrode interfacial resistance. This interfacial resistance can appear when using only two
electrodes placed on parallel faces of the specimen, electrodes which apply the current and measure the
voltage at the same geometrical point. If two electrodes are used, calibration is recommended with the 4
electrodes arrangement described in this document.
The measured resistivity is also affected by the electrical frequency of testing ([1], [2], [3], [4]) and so the
measured resistivity could be increased by reducing the electrical frequency. In addition, for the same
electrical frequency, the measured resistivity is dependent on the specific pattern of the electrical field
across the specimen. Notwithstanding these differences, where the electrical resistivity is determined in
the same conditions, in a frequency range where the electrode polarization phenomena are independent
of its variation, changes in resistivity reflect changes occurring in the concrete.
An electrically conductive or porous aggregate also influences the magnitude of concrete resistivity. This
should be considered when establishing threshold values as it prevents a comparison of resistivity values
between concretes if the aggregates show a difference of half an order of magnitude (higher or lower) of
resistivity. The same effect of decreasing the measured resistivity is produced when metallic or electricity
conducting fibres or particles, are present.
4
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SIST EN 12390-19:2023
EN 12390-19:2023 (E)
1 Scope
This document describes two methods for measuring the electrical resistivity of concrete in water
saturated conditions: the volumetric method (see 3.1.3), which is the reference method, and the surface
method (see 3.1.4). The document gives the procedure to calibrate the surface method by means of the
reference-volumetric method. Both methods give the same resistivity result, provided the provisions of
) for equivalence between them) are followed.
the present document (using the Form Factor (F
f
NOTE The volumetric method is applicable to cast specimens or cores, while the surface method is suitable for
use on cast specimens, cores and on construction sites, but not all of these applications are covered in this document.
The method can be applied to the normal range of concretes covered by current standards. It does not
cover concretes containing metallic components or made with porous aggregates.
The use of resistivity to assess the potential for corrosion of reinforcement in existing structures is not
specified in this document.
The use of resistivity to test cores taken from an existing structure, which require pre-conditioning by
water saturation, is not covered in this document.
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 12390-2, Testing hardened concrete - Part 2: Making and curing specimens for strength tests
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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/ui
3.1.1
electrical resistance
R
e
voltage drop divided by current (in Ohm)
U
R = (1)
e
I
where
U is the difference in voltage drop before and after the application of the current between the
voltage electrode; and
I is current circulating through the current electrodes
5
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SIST EN 12390-19:2023
EN 12390-19:2023 (E)
3.1.2
resistivity of a concrete
ρ
material parameter independent of the geometry of the specimen which indicates the resistance of the
material to the circulation of an electrical current (in Ohm⋅ m)
ρ RA× / l
(2)
e
Note 1 to entry: It is the proportionality constant between electrical resistance and geometry of the specimen.
Assuming a regular geometry of a cube the resistivity is equal to the electrical resistance multiplied by the cross-
section area (A) and divided by the width of the cube (l).
Note 2 to entry: Some commercial equipment expresses the resistivity in alternative units, e.g. kOhm⋅cm. The
conversion between Ohm⋅m and kOhm⋅cm is: 1 Ohm⋅m = 0,1 kOhm⋅cm.
3.1.3
volumetric resistivity
ρ
v
resistivity when the electrodes for applying the current are placed on the top and bottom of a cylindrical,
cubic or prismatic specimen and cover all these top and bottom surfaces
Cross− sectional area
(3)
ρ= RR×=F ×
ve gve
Distance between voltage electrodes
Note 1 to entry: Its value results from multiplying the measured resistance R by the volumetric geometrical factor
e
F . The volumetric resistivity is taken as the reference value for the resistivity of a concrete.
gv
Note 2 to entry: The volumetric geometrical factor F is equal to the relation A/l in Formula (2). The voltage
gv
electrodes are the clamps as shown in Figure 2.
3.1.4
surface resistivity-infinite medium
ρ
s,inf
resistivity value obtained when four equally spaced electrodes of cylindrical shape are placed on the
specimen surface
ρπ= RR×F = ××2 × d
(4)
s,inf e gs e
Note 1 to entry: Its value results from multiplying the measured resistance by the surface geometrical factor F ,
gs
which is equal to 2π multiplied by the distance (d) between each of the four equally spaced electrodes.
Note 2 to entry: This is the electrical resistivity known as Wenner method for a quasi-infinite medium.
3.1.5
surface resistivity-finite medium
ρ
s
resistivity when four equally spaced electrodes are placed aligned on the specimen surface and the
obtained value is multiplied by a form factor, F that depends on the geometry and size of the specimen
f
and is required to equal the volumetric resistivity to the surface resistivity
ρρ= ×F= ρ
(5)
s s,inf f v
6
=
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SIST EN 12390-19:2023
EN 12390-19:2023 (E)
3.1.6
volumetric geometrical factor
F
gv
in the volumetric method, relationship between the measured electrical resistance and the resistivity
Note 1 to entry: This factor is the cross-sectional area of the test specimen (A) divided by the distance between
voltage electrodes (d):
Cross− sectional area
(6)
F =
gv
Distance between voltage electrodes
3.1.7
surface geometrical factor
F
gs
in an infinite medium using the four equally aligned electrodes arrangement, this factor is 2π times the
distance, d between the electrodes (see Formula (4))
F2=⋅π⋅ d
(7)
gs
3.1.8
form factor
F
f
in the surface method, factor that equals the volumetric resistivity and the surface resistivity as indicated
by Formula (8)
ρ
s
F= (8)
f
ρ
s,inf
3.2 Symbols
For the purposes of this document, the following symbols apply:
2
A
In the volumetric method, the cross-sectional area of the test specimen [m ]
d In the volumetric method, the distance between the voltage electrodes (see Figure 2); in the
surface method, the centreline to centreline distance between each of the four electrodes (see
Figure 3) [m]
I Current flowing in the concrete specimen introduced by the outer pair of current electrodes [A]
U Difference in potential drop before and after the application of the current between the inner
pair of voltage electrodes [V]
4 Principle
In the volumetric method (Formulae (1) and (3)), the electrical resistance of a concrete cylinder, prism
or cube is measured by passing a current of known magnitude (I) through the whole volume of the water-
saturated specimen and measuring the resulting voltage drop (U) over the central part of the specimen.
This procedure of placing the voltage electrodes in the central part of the specimen avoids the possible
nonlinear ohmic-drop at the concrete/electrode interface.
In the surface method (Formulae (4) and (5)), the determination of concrete resistivity is by means of the
application of a current between the two outer electrodes and the measurement of the difference in
voltage drop between the two inner electrodes located in between and aligned with the outer two
7
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SIST EN 12390-19:2023
EN 12390-19:2023 (E)
electrodes. All the four electrodes are placed on the surface of the cylinder, prism or cube. The
measurement provides the concrete electrical resistance (R ) with that arrangement of electrodes.
e
Knowing the distance between electrodes and the dimensions of the specimen, the surface geometrical
and form factors are applied to calculate the resistivity. Then, the surface resistivity is obtained by
multiplying the 4-electrode resistivity by the form factor (see Formula (5) and Table 2 where the form
factor is given as a function of the geometry of the specimen). Thanks to this form factor, the same
resistivity value is obtained between the surface method and the volumetric (reference) method.
5 Apparatus
5.1 Resistivity meter
Resistivity meter or convenient voltage sources and multi-meters for measuring the voltage drop and
current between the electrodes shall be used. If the equipment applies alternating current (AC) its
frequency should be between 40 Hz and 10 000 Hz. If a direct current (DC) is applied, the measurement
should be as short as possible and equipment should show/record results at least every second. The
measurement is taken between 2 s and 5 s when a stable enough value is measured. Figure 1 shows an
example of arrangement of hand-made resistivimeter based on a battery and two multimeters, in addition
to the four points probe.
The resistivity meter shall be calibrated before each set of measurements or with the frequency deduced
from its use. This calibration can be made through the measurement of good quality electrical resistors
or a “dummy cell” of known resistance, as provided by some manufacturers. The resistors should be at
least of 103, 104 and 105 ohms, in order to cover the range of possible values in the concrete. For the
calibration, the measurement is made as a “two-electrode” system, provided that the resistors have only
two terminals, by plugging one current and voltage terminal to one connection of the resistor and the
other current and voltage terminals to the other side of the resistor. The offset with respect to the value
of the resistor should be taken into account when measuring on concrete by correcting the values by that
offset. The “dummy cells” provided by the manufacturer are made to directly insert the resitivimeter
terminals.
NOTE 1 The use of D
...
SLOVENSKI STANDARD
oSIST prEN 12390-19:2021
01-december-2021
Preskušanje strjenega betona - 19. del: Ugotavljanje upornosti
Testing of hardened concrete - Part 19: Determination of resistivity
Prüfung von Festbeton - Teil 19: Bestimmung des elektrischen Widerstands
Essais pour béton durci - Partie 19 : Détermination de la résistivité électrique
Ta slovenski standard je istoveten z: prEN 12390-19
ICS:
91.100.30 Beton in betonski izdelki Concrete and concrete
products
oSIST prEN 12390-19:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN 12390-19:2021
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oSIST prEN 12390-19:2021
DRAFT
EUROPEAN STANDARD
prEN 12390-19
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2021
ICS 91.100.30
English Version
Testing of hardened concrete - Part 19: Determination of
resistivity
Prüfung von Festbeton - Teil 19: Bestimmung des
elektrischen Widerstands
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, Turkey 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
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12390-19:2021 E
worldwide for CEN national Members.
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oSIST prEN 12390-19:2021
prEN 12390-19:2021 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Principle . 7
5 Apparatus . 8
6 Preparation of test specimens . 9
7 Test procedure volumetric method (reference method) . 11
8 Test procedure surface method. 13
9 Test report . 16
10 Precision . 17
Annex A (informative) Determination of the precision of the equipment . 18
Bibliography . 19
2
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oSIST prEN 12390-19:2021
prEN 12390-19:2021 (E)
European foreword
This document (prEN 12390-19:2021) has been prepared by Technical Committee CEN/TC 104
“Concrete and related products”, Subcommittee SC1 “Concrete - Specification, performance, production
and conformity”, the secretariat of which is held by SN.
This document is currently submitted to the CEN Enquiry.
A list of all parts in the EN 12390 series can be found on the CEN website.
3
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oSIST prEN 12390-19:2021
prEN 12390-19:2021 (E)
Introduction
This test method is one of a series concerned with testing hardened concrete.
This document is based on current national standards and in particular the Spanish standard UNE
PNE 83988 Part 1 and Part 2.
Resistivity is a property that quantifies how strongly a given material opposes the flow of electric current.
3
Resistivity is the electrical resistance of a unit volume (e.g. 1 m ) of a concrete. It is the inverse of
conductivity, and it is obtained from the ratio between the voltage drop and the current (Ohm’s law).
The resistivity of a water-saturated concrete is mainly a function of the pore size distribution and the
connectivity/tortuosity of the pore system. It also depends on the pore solution composition, which is
strongly affected by the cement type, additions, w/c ratio, aggregate type and the degree of hydration of
the cement.
Resistivity is also dependent on temperature and for quality control testing, the temperature of the
concrete specimens should be held within a defined range for comparable results.
The standard is applied to water saturated concretes because the resistivity is affected by the degree of
water saturation. A reduction in the moisture content increases the resistivity. Loss of continuity of the
pore system by drying may have more impact on the resistivity value than a change in the volume of
capillary porosity because drying may produce changes of more than one order of magnitude while a
change in capillary porosity may be reflected in changes of two or three times.
In present standard a 4-electrode is recommended due to it avoids the frequency dependent voltage drop
produced by the concrete/electrode interfacial resistance. This interfacial resistance may appear when
using only two electrodes placed in the parallel faces of the specimen, electrodes which apply the current
and measure the voltage in the same geometrical point. If two electrodes are used, calibration is
recommended with the 4 electrodes arrangement described in present standard.
The measured resistivity is also affected by the electrical frequency of testing ([1], [2], [3], [4]) and so the
measured resistivity could be increased by reducing the electrical frequency. In addition, for the same
electrical frequency, the measured resistivity is depending on the specific pattern of the electrical field
across the specimen. Notwithstanding these differences, where the electrical resistivity is determined in
the same conditions, in a frequency range where the electrode polarization phenomena are independent
of its variation, changes in resistivity reflect changes occurring in the concrete.
If the aggregate is electrically conductive or porous also influences the magnitude of concrete resistivity.
This fact should be taken into account when establishing threshold values. It prevents comparison of
resistivity values between concretes if the aggregates show difference of half an order of magnitude
(higher or lower) of resistivity. The same effect of decreasing the measured resistivity is produced when
metallic or electricity conducting fibres or particles, are present.
4
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oSIST prEN 12390-19:2021
prEN 12390-19:2021 (E)
1 Scope
This document describes a method for determining the electrical resistivity of concrete in water
saturated conditions. Two methods of measuring the resistivity are standardized: the volumetric method
(see 3.1.3), which is the reference method, and the surface method (see 3.1.4).
NOTE The volumetric method is applicable to cast specimens or cores, while the surface method is suitable for
use on cast specimens, cores and on construction site, but not all these applications are covered in this document.
The method can be applied to the normal range of concretes covered by current standards. It does not
cover the concretes made with porous aggregates or having metallic components.
The use of resistivity to assess the potential for corrosion of reinforcement in existing structures is not
specified in this document.
The use of resistivity to assess cores taken from an existing structure, which need pre-condition on water
saturation, is not directly specified in this document.
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 12390-2, Testing hardened concrete — Part 2: Making and curing specimens for strength tests
3 Terms and definitions
3.1 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:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1
electrical resistance
R
e
voltage drop divided by current (in Ohm)
U
R = (1)
e
I
where
U is the difference in voltage drop before and after the application of the current between the
voltage electrode; and
I is current circulating through the current electrodes
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3.1.2
resistivity of a concrete
ρ
material parameter independent of the geometry of the specimen which indicates the resistance of the
material to the circulation of an electrical current (in Ohm⋅ m)
ρ RA× /l (2)
e
Note 1 to entry: It is the proportionality constant between electrical resistance and geometry of the specimen.
Assuming a regular geometry of a cube the resistivity is equal to the electrical resistance multiplied by the cross
section area (A) an divided by the width of the cube (l).
Note 2 to entry: Some commercial equipment expresses the resistivity in alternative units, e.g. kOhm⋅cm. The
conversion between Ohm⋅m and kOhm⋅cm is: 1Ohm⋅m = 0,1 kOhm⋅cm.
3.1.3
volumetric resistivity
ρ
v
resistivity when the electrodes for applying the current are placed on the top and bottom of a cylindrical,
cubic or prismatic specimen and cover all these top and bottom surfaces
Cross sectionarea
ρ RF⋅⋅R (3)
ve gve
Distance between voltageelectrodes
Note 1 to entry: Its value results from multiplying the measured resistance R by the volumetric geometrical factor
e
F . The volumetric resistivity is taken as the reference value for the resistivity of a concrete.
gv
Note 2 to entry: The volumetric geometrical factor F is equal to the relation A/l in Formula (2). The voltage
gv
electrodes are the clamps as shown in Figure 2.
3.1.4
surface resistivity-infinite medium
ρ
s,inf
resistivity value obtained when four equally spaced electrodes of cylindrical shape are placed on the
specimen surface
ρ RF⋅ R⋅⋅2π⋅d (4)
s,inf e gs e
Note 1 to entry: Its value results from multiplying the measured resistance by the surface geometrical factor F ,
gs
which is equal to 2π multiplied by the distance (d) between every of the four equally spaced electrodes.
Note 2 to entry: This is the electrical resistivity known as Wenner method for a quasi-infinite medium.
3.1.5
surface resistivity-finite medium
ρ
s
resistivity when four equally spaced electrodes are placed aligned on the specimen surface and the
obtained value is multiplied by a form factor, F that depends on the geometry and size of the specimen
f
and is required to equal the volumetric resistivity to the surface resistivity
ρρ ⋅=F ρ (5)
s s,inf f v
6
=
==
==
=
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3.1.6
volumetric geometrical factor
F
gv
in the volumetric method, relationship between the measured electrical resistance and the resistivity
Note 1 to entry: This factor is the cross-sectional area of the test specimen (A) divided by the distance between
voltage electrodes (d):
Cross sectionarea
F = (6)
gv
Distance between voltageelectrodes
3.1.7
surface geometrical factor
F
gs
in an infinite medium using the four equally aligned electrodes arrangement, this factor is 2π times the
distance, d between the electrodes (see Formula (4))
(7)
Fd= 2⋅⋅π
gs
3.1.8
form factor
F
f
in the surface method, factor that equals the volumetric resistivity and the surface resistivity as indicated
by Formula (8)
ρ
s
F = (8)
f
ρ
s,inf
3.2 Symbols
For the purposes of this document, the following symbols apply:
2
A
In the volumetric method, the cross-sectional area of the test specimen [m ]
d In the volumetric method, the distance between the voltage electrodes (see Figure 2, distance
in inch); in the surface method, the centreline to centreline distance between each of the four
electrodes (see Figure 3) [m]
I Current flowing in concrete specimen introduced by the outer pair of current electrodes [A]
U Difference in potential drop before and after the application of the current between the inner
pair of voltage electrodes [V]
4 Principle
In the volumetric method (Formulae (1) and (3)), the electrical resistance of a concrete cylinder, prism
or cube is measured by passing a current of known magnitude (I) through the whole volume of the water-
saturated specimen and measuring the resulting voltage drop (U) over the central part of the specimen.
This procedure of placing the voltage electrodes in the central part of the specimen avoids the possible
nonlinear ohmic-drop at the concrete/electrode interface.
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In the surface method (Formulae (4) and (5)), the determination of concrete resistivity is by means of the
application of a current between the two outer electrodes and the measurement of the difference in
voltage drop between the two inner electrodes located in between and aligned with the outer two
electrodes. All the four electrodes are placed on the surface of the cylinder, prism or cube. The
measurement provides the concrete electrical resistance (R ) with that disposition of electrodes.
e
Knowing the distance between electrodes and the dimensions of the specimen, the surface geometrical
and form factors are applied to calculate the resistivity. Then, the surface resistivity is obtained by
multiplying the 4-electrode resistivity by the form factor (see Formula (5)).
5 Apparatus
5.1 Resistivity meter or convenient voltage sources and multi-meters for measuring the voltage drop
and current between the electrodes. If the equipment applies an AC (alternating current) its frequency
should be between 40 and 10 000 Hz. If a DC (direct current) is applied, the measurement should be as
short as possible and then, equipment shall be able to show/record results at least each second. The
measurement is taken between 2 s and 5 s when an enough stable value is measured. Figure 1 shows an
example of arrangement of hand-made resistivimeter based on a battery and two multimeters, in addition
to the four points probe.
NOTE 1 The use of DC current is only feasible if the measurement is lasting very short time, to avoid polarization
of the electrodes. In the DC measurements the typical minimum applied voltage is of ≥ 4,5 V.
NOTE 2 The conversion from the time domain (DC measurement) to the frequency domain (AC measurement)
is not straight forward, which prevents to calculate the equivalent frequency from the waiting time, unless the
amplitude of the AC signal or the voltage applied is known. The equivalence of DC resistivity values to the AC ones
is based in empiric correlations.
Key
1 Current
2 Voltage
3 Battery ≥4,5 V
4 Sponges
NOTE 3 The left-hand side figure shows a hand-made resistivimeter with two multimeters and one battery. The
central figure shows the probe with small sponges inserted in the bottom of the electrodes and fixed with an elastic
rubber. The right-hand side figure shows the connections.
Figure 1 — Hand-made resistivimeter
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5.2 Data logger for the simultaneous recording of voltage drop and current. It is optional but
recommended.
NOTE 4 Commercial equipment is available that fulfils the requirements in 5.1 and 5.2.
5.3 Electrodes of stainless steel or copper free for surface impurities (e.g. rust, other oxides). For the
volumetric method, they shall be a mesh or plain sheet with dimensions equal or larger in size/diameter
to that of the contact faces of the specimens, i.e. for a 150 mm diameter cylinder, the electrode shall have
a diameter of ≥ 150 mm. For the voltage drop measurement in the volumetric method, two stainless steel
clamps of around 1 cm wide or copper wires with a diameter of 1 mm to 2 mm shall be placed to ensure
good electrical contact with the concrete surface. If a 4-electrodes-type probe is to be used for measuring
the resistivity, the volumetric method requires 4 cables with the corresponding plugs to connect the 4
electrodes of the probe to the two current and two voltage electrodes.
For the surface method the four electrodes shall be round bars of diameter in the range 4 mm to 10 mm
made of stainless steel, carbon steel, copper or any other conducting metal free for surface impurities
(e.g. rust, other oxides) a
...
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