Assessment of in-situ compressive strength in structures and precast concrete components

(1) This document:
- gives methods and procedures for the estimation of the in situ compressive strength and characteristic in situ compressive strength of concrete in structures and precast concrete components using direct methods (core testing) and indirect methods, e.g. ultra-sonic pulse velocity, rebound number;
NOTE    To align with the design standard EN 1992-1-1, where the compressive strength is based on 2:1 cylinders, the in situ compressive strength is based in 2:1 cores of diameter ≥ 75 mm.
- provides principles and guidance for establishing the relationships between test results from indirect test methods and the in situ compressive strength;
- provides procedures and guidance for assessing the conformity with the compressive strength class of concrete supplied to structures under construction where standard tests indicate doubt or where the quality of execution is in doubt.
(2) This document provides requirements for determining the in situ strength at test locations and the characteristic strength of test regions, but how this information is to be applied needs to be considered in the light of the specific situation and engineering judgement applied to the specific case.
(3) This document does not include the assessment of the quality of concrete for properties other than compressive strength, e.g. durability-related properties.
(4) This document is not for the assessment of conformity of concrete compressive strength in accordance with EN 206 or EN 13369, except as indicated in EN 206:2013+A1:2016, 5.5.1.2 or 8.4.
(5) This document does not cover the procedures or criteria for the routine conformity control of precast concrete components using either direct or indirect measurements of the in situ strength.
(3) This document does not include the assessment of the quality of concrete for properties other than compressive strength, e.g. durability-related properties.
(4)   This document is not for the assessment of conformity of concrete compressive strength in accordance with EN 206 or EN 13369, except as indicated in EN 206:2013+A1:2016, 5.5.1.2 or 8.4.
(5)   This document does not cover the procedures or criteria for the routine conformity control of precast concrete components using either direct or indirect measurements of the in-situ strength.

Bewertung der Druckfestigkeit von Beton in Bauwerken und in Bauwerksteilen

(1) Dieses Dokument:
- enthält Verfahren und Vorgehensweisen für die Abschätzung der Druckfestigkeit von Bauwerksbeton und der charakteristischen Druckfestigkeit des Betons in Bauwerken und Bauwerksteilen nach direkten Verfahren (Bohrkernprüfung) und indirekten Verfahren, z. B. Ultraschallgeschwindigkeit, Rückprallzahl;
ANMERKUNG   In Anpassung an die Bemessungsnorm EN 1992 1 1, in der die Druckfestigkeit auf Zylindern im Verhältnis von 2:1 basiert, basiert die Druckfestigkeit von Bauwerksbeton auf 2:1-Bohrkernen mit einem Durch-messer ≥ 75 mm.
- enthält Grundsätze und Anleitungen zum Aufstellen der Beziehung zwischen den Prüfergebnissen indirekter Prüfverfahren und der Druckfestigkeit von Bauwerksbeton;
- stellt Verfahrensweisen und Anleitungen für die Bewertung der Übereinstimmung mit der Druckfestig¬keitsklasse von Beton bereit, der in im Bau befindliche Bauwerke eingebracht wurde, für den Fall, dass Standardprüfungen Zweifel hervorrufen oder die Ausführungsqualität in Zweifel steht.
(2) Das vorliegende Dokument legt Anforderungen an die Bestimmung der Druckfestigkeit von Bauwerksbeton an Messstellen und der charakteristischen Festigkeit von Prüfbereichen fest, wie diese Angaben jedoch anzuwenden sind, ist unter Berücksichtigung der konkreten Situation und nach ingenieurtechnischer Beurteilung zu betrachten.
(3) Das vorliegende Dokument umfasst nicht die Bewertung der Betonqualität in Bezug auf andere Eigenschaften als die Druckfestigkeit, wie z. B. auf dauerhaftigkeitsbezogene Eigenschaften.
(4) Dieses Dokument dient nicht der Bewertung der Übereinstimmung der Betondruckfestigkeit nach EN 206 oder EN 13369, es sei denn, dies ist nach EN 206:2013+A1:2016, 5.5.1.2 oder 8.4, angegeben.
(5) Das vorliegende Dokument deckt weder die Verfahrensweisen noch die Kriterien für die routinemäßige Konformitätskontrolle von Betonfertigteilen mit Hilfe entweder direkter oder indirekter Messungen der Festigkeit des Bauwerksbetons ab.

Évaluation de la résistance à la compression sur site des structures et des éléments préfabriqués en béton

(1)   Le présent document :
   fournit des méthodes et des procédures permettant d’estimer la résistance à la compression sur site et la résistance caractéristique à la compression sur site du béton dans les structures et les éléments préfabriqués en béton, à l’aide de méthodes directes (essais sur carottes) et de méthodes indirectes, par exemple vitesse de propagation du son, indice de rebondissement ;
NOTE   Afin de s’aligner sur la norme de calcul EN 1992 1 1, où la résistance à la compression est basée sur des cylindres 2:1, la résistance à la compression sur site est basée sur des carottes 2:1 d’un diamètre ≥ 75 mm.
   donne des principes et des recommandations pour l’établissement des relations entre les résultats de méthodes d’essai indirectes et la résistance à la compression sur site ;
   fournit des procédures et des recommandations pour l’évaluation de la conformité à la classe de résistance à la compression d’un béton fourni à des structures en construction lorsque les essais normalisés indiquent un doute ou en cas de doute sur la qualité de l’exécution.
(2)   Le présent document spécifie des exigences relatives à la détermination de la résistance sur site au niveau d’aires d’essai et de la résistance caractéristique de zones d’essai, mais la manière dont ces informations doivent être utilisées doit être considérée à la lumière de la situation spécifique et d’une expertise technique appliquée au cas particulier.
(3)   Le présent document n’inclut pas l’évaluation de la qualité du béton pour des propriétés autres que la résistance à la compression, par exemple les propriétés liées à la durabilité.
(4)   Le présent document ne traite pas de l’évaluation de la conformité de la résistance à la compression du béton selon l’EN 206 ou l’EN 13369, sauf pour les points évoqués dans l’EN 206:2013+A1:2016, 5.5.1.2 ou 8.4.
(5)   Le présent document ne traite pas des procédures ou critères pour le contrôle courant de la conformité des éléments préfabriqués en béton par des mesurages directs ou indirects de la résistance sur site.

Ocenjevanje in-situ tlačne trdnosti betona v konstrukcijah in v montažnih betonskih elementih

Ta evropski standard:
– podaja metode in postopke za ocenjevanje tlačne trdnosti in-situ ter značilne in-situ tlačne trdnosti betona v konstrukcijah in montažnih betonskih elementih z uporabo neposrednih metod (preskušanje jedra) ter posrednih metod, npr. hitrost ultrazvočnega impulza, sklerometrični indeks;
– podaja načela in smernice za določitev razmerja med rezultati preskusov iz posrednih preskusnih metod ter in-situ tlačno trdnostjo;
– ponuja postopke in smernice za in-situ oceno razreda tlačne trdnosti betona, kadar obstaja dvom glede trdnosti betona, ki je bil pred kratkim uporabljen v konstrukciji, ali montažnega betonskega elementa.
Ta evropski standard ne zajema:
– ocene na osnovi jeder s premerom manj kot 50 mm, mikro jeder;
– ocene drugih lastnosti betona razen tlačne trdnosti, npr. lastnosti, povezane z vzdržljivostjo;
– posebnih določb za lahke vrste betona;
– uporabe izvlečnega preskušanja;
– (v postopkih točke 8) določb za manj kot 8 jeder brez posrednega preskušanja;
– uporabe primerjalnega preskušanja (za pojasnilo glej nadaljnja navodila CEN/TR za uporabo standarda EN 13791:2016 in ozadje določb [1]).
(2) Ta evropski standard se ne uporablja za ocenjevanje skladnosti tlačne trdnosti betona v skladu s standardom EN 206 ali EN 13369, razen kot je navedeno v točkah 5.5.1.2 ali 8.4 standarda EN 206:2013.
(3) Ta evropski standard ne zajema postopkov ali meril za rutinski nadzor skladnosti montažnih betonskih elementov z uporabo neposrednih ali posrednih meritev trdnosti in-situ.

General Information

Status
Published
Publication Date
20-Aug-2019
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
21-Aug-2019
Completion Date
21-Aug-2019

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SLOVENSKI STANDARD
SIST EN 13791:2019
01-oktober-2019
Nadomešča:
SIST EN 13791:2007
Ocenjevanje in-situ tlačne trdnosti betona v konstrukcijah in v montažnih
betonskih elementih
Assessment of in-situ compressive strength in structures and precast concrete
components
Bewertung der Druckfestigkeit von Beton in Bauwerken oder in Bauwerksteilen

Évaluation de la résistance à la compression sur site des structures et des éléments

préfabriqués en béton
Ta slovenski standard je istoveten z: EN 13791:2019
ICS:
91.080.40 Betonske konstrukcije Concrete structures
91.100.30 Beton in betonski izdelki Concrete and concrete
products
SIST EN 13791:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 13791:2019
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SIST EN 13791:2019
EN 13791
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2019
EUROPÄISCHE NORM
ICS 91.080.40 Supersedes EN 13791:2007
English Version
Assessment of in-situ compressive strength in structures
and precast concrete components

Évaluation de la résistance à la compression sur site Bewertung der Druckfestigkeit von Beton in

des structures et des éléments préfabriqués en béton Bauwerken oder in Bauwerksteilen

This European Standard was approved by CEN on 7 July 2019.

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, Turkey 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

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 13791:2019 E

worldwide for CEN national Members.
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SIST EN 13791:2019
EN 13791:2018 (E)
Contents Page

European foreword ...................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 7

2 Normative references .................................................................................................................................... 7

3 Terms, definitions, symbols and abbreviations .................................................................................. 8

3.1 Terms and definitions ................................................................................................................................... 8

3.2 Symbols and abbreviations ....................................................................................................................... 10

4 Investigation objective and test parameters ...................................................................................... 12

5 Test regions, test locations and number of tests ............................................................................... 15

5.1 Test regions ..................................................................................................................................................... 15

5.2 Test locations ................................................................................................................................................. 15

6 Core testing and the determination of the in situ compressive strength ................................. 17

7 Initial evaluation of the data set .............................................................................................................. 18

7.1 Evaluation of the test region to determine if it represents a single concrete strength class18

7.2 Assessment of individual test results within a test region ............................................................ 19

8 Estimation of compressive strength for structural assessment of an existing structure ... 21

8.1 Based only on core test data ..................................................................................................................... 21

8.2 Based on a combination of indirect test data and core test data ................................................. 22

8.3 Use of indirect testing with at least three core test data ................................................................ 24

9 Assessment of compressive strength class of concrete in case of doubt .................................. 25

9.1 General.............................................................................................................................................................. 25

9.2 Use of core test data ..................................................................................................................................... 26

9.3 Indirect testing plus selected core test data ....................................................................................... 27

9.4 Screening test using a general or specific relationship with an indirect test procedure ... 28

9.5 Procedure where the producer has declared non-conformity of compressive strength ... 29

Annex A (informative) Guidance on undertaking an investigation ......................................................... 30

Annex B (informative) Example of a generic relationship between rebound number and

compressive strength class ....................................................................................................................... 38

Bibliography ................................................................................................................................................................. 41

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SIST EN 13791:2019
EN 13791:2019 (E)
European foreword

This document (EN 13791:2019) has been prepared by Technical Committee CEN/TC 104 “Concrete

and related products”, 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 February 2020, and conflicting national standards

shall be withdrawn at the latest by February 2020.

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.

This document supersedes EN 13791:2007.
The main changes compared to EN 13791:2007 are:

a) the standard is fully revised but for continuity the methodological approaches and scope is retained

as well as much of the previous layout;

b) the primary focus is on the determination of the characteristic in situ compressive strength for

application with EN 1990 and EN 1992-1-1;

c) more comprehensive guidance is provided on applying the procedures, particularly with respect to

defining a test result, a measurement, volume of concrete, test location, small test region and test

region;

d) requirements to set out the purpose of the investigation, procedures to be adopted, test methods,

test locations and test regions to be defined prior to commencing the testing, are included;

e) Clause 8, "Estimation of compressive strength for structural assessment of an existing structure",

covers the previous requirements for assessment of characteristic in situ compressive strength by

either testing cores or indirect methods;

f) Clause 9, "Assessment of compressive strength class of concrete in case of doubt", covers previous

requirements for the assessment where conformity of concrete based on standard tests is in doubt;

g) approaches A and B in EN 13791:2007 are no longer valid;
h) EN 13791 is aligned with the requirements of EN 206.

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, Turkey and the

United Kingdom.
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SIST EN 13791:2019
EN 13791:2018 (E)
Introduction

(1) This document covers two applications of in situ strength assessments. These are:

— to estimate in situ characteristic compressive strength of a test region and/or in situ strength at

specific locations;

— assessment of compressive strength class of concrete supplied to a structure under construction

where there is doubt about the compressive strength based on results of standard tests or doubt

about the quality of execution.

(2) Both applications have a number of common steps as shown in Table 1, but the assessment methods

differ. The reason for this difference is that with the estimation of the in situ strength (Clause 8) there is

no presumption as to what this should be and the uncertainty associated with the number of data are

taken into account when estimating the value. The in situ strength determined in accordance with

Clause 8 is a value based on testing a finished structure or element, as referred to by EN 1992-1-1:2004,

A.2.3.

NOTE Information may be available on the original quality of the supplied concrete, but the in situ strength

may have changed over time.

(3) Most of the procedures in Clause 9 apply where there is verification that the concrete supplied is in

accordance with the producer's declaration of performance for compressive strength but test results

from samples taken on site indicate non-conformity, and where this difference cannot be resolved by

other means. As the procedures given in CEN standards for the verification of the declaration of

performance are regarded as being reliable, the assumption is that the concrete conforms to the

specified characteristic strength and the applied statistical tests check the validity of this hypothesis.

Where a Clause 9 assessment indicates non-conformity of compressive strength then the 9.5 procedure

should be adopted by the producer and other involved parties.

(4) The Clause 8 and Clause 9 procedures have different approaches that may lead to significantly

different outcomes.

(5) Unless indicated otherwise, the provisions given in this document apply to concrete structures

made from normal-weight, lightweight or heavyweight concrete.

(6) This document only covers the use of a single relationship between an indirect test method (UPV or

rebound hammer) and compressive strength. The combined use of both UPV and rebound hammer

techniques with core strength is a useful technique, but the procedures are not detailed in this

document.

(7) This document was developed with the expectation that it will be used with EN 1992-1-1. If it is

used in conjunction with other design standards, some of the factors may need modification. In

addition, this document uses the EN 1992-1-1:2004, 3.1.6, recommended value of 1,0 for the factor α

and EN 1992-1-1:2004, A.2.3, recommended value of 0,85 for the factor η. Where national provisions

adopt different values for these coefficients then adjustments to the appropriate formula within this

Standard may be required.

(8) Techniques outside the range of those specified in this document may be given in provisions valid in

the place of use. For example, these include:
— combining two indirect test methods with core testing;
— use of cores of diameter less than 50 mm;
— use of pull-out testing;
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SIST EN 13791:2019
EN 13791:2019 (E)
— a screening test conforming to the principles specified in 9.4;

— in the Clause 8 procedures, provisions for less than 8 cores without indirect testing;

— assessing the strength gradient across a section after a fire;

— in the Clause 9 procedures, comparing an element where the concrete quality is in doubt with a

similar element containing conforming concrete.

In addition, provisions valid in the place of use may give requirements for other aspects not specified in

this document. For example, these include:

— relationship between 2:1 and 1:1 core compressive strengths if a value other than 0,82 is justified

on the basis of test data for the local materials;

— relationship between in situ compressive strength and core length to diameter ratio for values

other than 2:1 or 1:1;

— relationship between in situ compressive strength for lightweight concretes and core length to

diameter ratio;
— adjustment to core strength for cores containing transverse reinforcement;

— relationship between core strength and the strength of a cast cylinder of equal diameter and length;

— factors when the assessment is other than with EN 1992-1-1 or EN 1990;

— factor η given in A.2.3 of EN 1992-1-1:2004 where the national provisions use a value different to

the recommended value of 0,85;
— in 8.3 different criteria for structural assessment;

— in 9.2 and 9.3 different criteria where the criteria for compressive strength in

EN 206:2013+A1:2016, B.3.1, were not used for the assessment of a number of loads delivered to a

construction site;

— guidance on appropriate actions where the producer of the concrete has declared non-conformity

or where the concrete has been proven to be non-conforming.
(9) Guidance on undertaking an investigation is given in Annex A.

(10) Further guidance and background information on this revision of EN 13791 and worked examples

of the calculations are given in CEN/TR 17086 [1].
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SIST EN 13791:2019
EN 13791:2018 (E)
Table 1 — Guidance on relevant clauses
Action Clause
Objective of the investigation Clause 4, A.1
Selection of test methods A.3, A.4
Selection of assessment method: A.2
for determination of in situ strength based on:
— core test data; 8.1
— indirect testing calibrated against test specimens; 8.2
— core and indirect testing. 8.3
or, for assessment of compressive strength where production control data
show conformity and identity testing data indicate non-conformity based on:
— core test data; 9.2
— indirect testing and selected core testing; 9.3
— screening test. 9.4
Procedure where the producer has declared non-conformity of compressive
9.5
strength
Selection of test regions and test locations 5.1, 5.2, A.4
Determination of in situ strength from core test data Clause 6
Evaluation of data set to see if it comprises a single concrete 7.1
Evaluation of data set to see if it includes outliers 7.2
Assessment and use of the data A.4, A.5, A.6
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SIST EN 13791:2019
EN 13791:2019 (E)
1 Scope
(1) This document:

— gives methods and procedures for the estimation of the in situ compressive strength and

characteristic in situ compressive strength of concrete in structures and precast concrete

components using direct methods (core testing) and indirect methods, e.g. ultra-sonic pulse

velocity, rebound number;

NOTE To align with the design standard EN 1992-1-1, where the compressive strength is based on 2:1

cylinders, the in situ compressive strength is based in 2:1 cores of diameter ≥ 75 mm.

— provides principles and guidance for establishing the relationships between test results from

indirect test methods and the in situ compressive strength;

— provides procedures and guidance for assessing the conformity with the compressive strength class

of concrete supplied to structures under construction where standard tests indicate doubt or

where the quality of execution is in doubt.

(2) This document provides requirements for determining the in situ strength at test locations and the

characteristic strength of test regions, but how this information is to be applied needs to be considered

in the light of the specific situation and engineering judgement applied to the specific case.

(3) This document does not include the assessment of the quality of concrete for properties other than

compressive strength, e.g. durability-related properties.

(4) This document is not for the assessment of conformity of concrete compressive strength in

accordance with EN 206 or EN 13369, except as indicated in EN 206:2013+A1:2016, 5.5.1.2 or 8.4.

(5) This document does not cover the procedures or criteria for the routine conformity control of

precast concrete components using either direct or indirect measurements of the in situ strength.

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 206:2013+A1:2016, Concrete — Specification, performance, production and conformity

EN 1990:2002, Eurocode — Basis of structural design

EN 1992-1-1:2004, Eurocode 2: Design of concrete structures — Part 1-1: General rules and rules for

buildings
EN 12350-1, Testing fresh concrete — Part 1: Sampling

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

EN 12504-1, Testing concrete in structures — Part 1: Cored specimens — Taking, examining and testing

in compression

EN 12504-2, Testing concrete in structures — Part 2: Non-destructive testing — Determination of

rebound number
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SIST EN 13791:2019
EN 13791:2018 (E)

EN 12504-4, Testing concrete — Part 4: Determination of ultrasonic pulse velocity

EN 13369:2018, Common rules for precast concrete products
EN 13670, Execution of concrete structures
3 Terms, definitions, symbols and abbreviations
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 http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

NOTE Abbreviations related to expressions of compressive strength and their meaning are given in 3.2.

3.1.1
core length factor

factor for converting the core test measurement or a core test result to the equivalent value of the same

diameter core with a length that is twice its diameter
3.1.2
indirect test

non-destructive test in accordance with either EN 12504-2 for rebound number or EN 12504-4 for

ultrasonic pulse velocity (UPV)
3.1.3
load
quantity of concrete transported in a vehicle comprising one or more batches
3.1.4
maturity

function of age and temperature such that for a given concrete, any batch with the same maturity has

the same compressive strength

Note 1 to entry: Maturity is often expressed as equivalent age in days at 20 °C. In accordance with EN 13670,

maturity calculations shall be based on an appropriate maturity function, proven for the type of cement or

combination of cement and addition in use.
3.1.5
rebound number

median of at least nine valid rebound hammer readings taken at one test location after adjusting where

necessary for the orientation of the rebound hammer
Note 1 to entry: The rebound number is expressed as a whole number.

Note 2 to entry: The procedure for determining the rebound number is specified in EN 12504-2.

3.1.6
screening test

indirect test procedure with a generic or specific relationship to compressive strength

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SIST EN 13791:2019
EN 13791:2019 (E)

Note 1 to entry: The established relationship may be used to indicate conformity to a specified compressive

strength class.
3.1.7
small test region

for structural assessment a small test region is one that is sufficiently small for the variations in the in-

situ compressive strength to be primarily due to the selected test locations and testing variability and

not due to variations in the quality of the concrete supplied
3.1.8
test location

limited area selected for measurements usually used to estimate one test result that is to be used in the

assessment of in-situ compressive strength
Note 1 to entry: See Clause 6 (9) and 8.1 (2) for the exception.
3.1.9
test region

one or several similar structural elements or precast concrete components known or assumed to be

made from concrete with the same constituents and the same compressive strength class or equivalent

to the defined volume associated with identity testing for compressive strength
Note 1 to entry: A test region contains test locations.
3.1.10
test result

arithmetic mean of the measurements or in the case of a rebound number the median of the

measurements taken at a test location

Note 1 to entry: A test result may comprise a single ≥ 75 mm diameter core or a single UPV measurement.

3.1.11
ultrasonic pulse velocity
UPV
speed at which an ultrasonic pulse passes through concrete

Note 1 to entry: The procedure for determining the UPV is specified in EN 12504-4.

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SIST EN 13791:2019
EN 13791:2018 (E)
3.2 Symbols and abbreviations
CLF core length factor
G critical value according to Grubbs’ test
k characteristic fractile factor [SOURCE: EN 1990:2002]
m number of valid indirect test results in test region under investigation
n number of core test results
p number of parameters of the correlation curve
s estimate of the overall standard deviation of in situ compressive strength
NOTE 1 See Formula (6) for the calculation of s.

s residual standard deviation, which is a measure of the spread of the core strength test data

around the fitted regression curve
NOTE 2 See Formula (8) for the calculation of s .

s standard deviation of all the estimated strength values, which is a measure of the spread of the

estimated core strengths around its mean value
NOTE 3 See Formula (7) for the calculation of s .
x indirect test value at test location "i" that is used for the correlation
i,cor

x indirect test value at test location "0" (where the in situ strength is required for structural

assessment purposes)
mean of the m indirect test values used for the correlation
NOTE 4 The abbreviations used for compressive strength are given in Table 2.
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SIST EN 13791:2019
EN 13791:2019 (E)
Table 2 — Abbreviations used for compressive strength
Abbreviation Description and explanation
Compressive strength determined from samples of concrete taken in accordance

f or f with EN 12350-1, made into cylinder or cube specimens and cured in accordance

c c,cube
with EN 12390-2 and tested in accordance with EN 12390-3.
Compressive strength of a core determined in accordance with EN 12504-1.
c,core
NOTE This is a generic abbreviation used to cover all length to diameter ratios.
Compressive strength of a core determined in accordance with EN 12504-1.
f or f
c,1:1core c,2:1core

NOTE Where the length to diameter ratio of the core is 1:1 the abbreviation fc,1:1core is

used and where the length to diameter ratio is 2:1, the abbreviation fc:2:1core is used.

Compressive strength of a core taken at a test location within a structural element

or precast concrete component expressed in terms of the strength of a 2:1 core of

diameter ≥ 75 mm.
c,is

NOTE 1 If more than one core is taken at a test location, the test result is the mean of the

individual test measurements.

NOTE 2 This value is based on the in situ moisture condition and it is not adjusted to a

standard moisture condition.
Characteristic in situ compressive strength (expressed as the strength of a 2:1
core of diameter ≥ 75 mm), i.e. the in situ compressive strength below which 5 %
of test results are expected to fall if all the volume of concrete under
consideration had been cored and tested.
ck,is
NOTE 1 These values are not normalized to a standard moisture condition.

NOTE 2 The in situ volume of concrete under consideration is unlikely to be the same

volume used to determine the conformity of the fresh concrete in accordance with
EN 206. It is generally a smaller volume.
f Estimated in situ compressive strength at a specific test location.
c,is,est
Highest value of in situ compressive strength in a set of "n" test locations
(expressed as the strength of a 2:1 core of diameter ≥ 75 mm).
c,is,highest

NOTE If more than one core is taken at a test location, the core test values for each test

location are averaged and the "highest value" is the highest of these averaged
measurements.
Lowest value of in situ compressive strength in the set of "n" test locations
(expressed as the strength of a 2:1 core of diameter ≥ 75 mm).
c,is,lowest

NOTE If more than one core is taken at a test location, the core test values for each test

location are averaged and the "lowest value" is the lowest of these averaged
measurements.

Indirect test value converted to its equivalent in situ compressive strength using a

c,is,reg
regression equation.

Minimum characteristic strength of 2:1 cylindrical test specimens associated with

the specified compressive strength class.
ck,spec
NOTE For example f is 30 MPa for compressive strength class C30/37. See EN 206
ck,spec
for all strength classes.

Mean in situ compressive strength of a set of "i" test locations (expressed as the

c,m(i)is
strength of a 2:1 core of diameter ≥ 75 mm).
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SIST EN 13791:2019
EN 13791:2018 (E)
4 Investigation objective and test parameters

(1) Prior to commencing testing on site, the following shall be determined and documented:

a) objective of the investigation;
b) standards, test methods and assessment techniques to be applied;
NOTE 1 See A.3 and test method standards for limitations on test methods.
c) test region(s) and test locations;
d) number of measurements per test location;

e) if cores are being taken, the diameter and length of the cores to be taken from the surface;

NOTE 2 The specified diameter of the core refers to the finished core diameter and not the hole size.

f) where the cores are to be cut to obtain the trimmed length(s) for testing;
g) technique to be used to prepare the ends of the cores;

h) whether sampling and testing shall be undertaken by a laboratory that has accredited procedures

according to ISO/IEC 17025 [3];
i) method of reinstatement after cores have been taken;
j) any deviations from the procedures specified in this document.

(2) Figure 1 and Figure 2 are flowcharts to help select the appropriate techniques and clauses.

(3) Guidance on undertaking an investigation is provided in Annex A.
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SIST EN 13791:2019
EN 13791:2019 (E)

Figure 1 — Flowchart for the estimation of characteristic in situ compressive strength for the

test region and the in situ compressive strength at specific locations
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SIST EN 13791:2019
EN 13791:2018 (E)

Figure 2 — Flowchart for assessment of compressive strength class of supplied concrete in cases

of doubt
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SIST EN 13791:2019
EN 13791:2019 (E)
5 Test regions, test locations and number of tests
5.1 Test regions

(1) The test regions shall be defined. They may comprise a series of similar elements, one large element

or the defined volume associated with identity testing (on-site control) for compressive strength.

Different concretes with regard to mix design shall have separate test regions. Where the concrete

strengths are not known, engineering judgement shall be applied to group elements into test regions

and the test results checked to see whether they comprise more than one concrete.

NOTE 1 With existing structures it may not be known whether the concrete:
—was produced on or off-site;
—was supplied as a designed or prescribed concrete;
—came from different sources, at different times;
—has undergone variations in curing due to variable exposure.

For these reasons the in situ concrete may fall across a range of compressive strength classes.

(2) Concretes from different batching plants may be placed in the same t
...

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