SIST-TP CEN/TR 16639:2015
(Main)Use of k-value concept, equivalent concrete performance concept and equivalent performance of combinations concept
Use of k-value concept, equivalent concrete performance concept and equivalent performance of combinations concept
This Technical Report provides more detailed information on the k-value concept principles of the equivalent concrete performance concept (ECPC) and the equivalent performance of combinations concept (EPCC) in accordance to prEN 206:2012, 5.2.5.
k-Wert-Ansatz, Prinzipien des Konzepts der gleichwertigen Betonleistungsfähigkeit und Konzept der gleichwertigen Leistungsfähigkeit von Kombinationen aus Zement und Zusatzstoff
Utilisation du concept de coefficient k, concept d’équivalence de performance et concept d’équivalence de performance en combinaison
Uporaba koncepta k-vrednosti, koncepta enakovrednega obnašanja betona in koncepta enakovrednega obnašanja kombinacij
To tehnično poročilo zagotavlja bolj podrobne informacije o načelih koncepta k-vrednosti, konceptu enakovrednega obnašanja betona (ECPC) in konceptu enakovrednega obnašanja kombinacij (EPCC) v skladu s standardom prEN 206:2012, 5.2.5.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 16639:2015
01-april-2015
Uporaba koncepta k-vrednosti, koncepta enakovrednega obnašanja betona in
koncepta enakovrednega obnašanja kombinacij
Use of k-value concept, equivalent concrete performance concept and equivalent
performance of combinations concept
k-Wert-Ansatz, Prinzipien des Konzepts der gleichwertigen Betonleistungsfähigkeit und
Konzept der gleichwertigen Leistungsfähigkeit von Kombinationen aus Zement und
Zusatzstoff
Utilisation du concept de coefficient k, concept d’équivalence de performance et concept
d’équivalence de performance en combinaison
Ta slovenski standard je istoveten z: CEN/TR 16639:2014
ICS:
91.100.30 Beton in betonski izdelki Concrete and concrete
products
SIST-TP CEN/TR 16639:2015 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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TECHNICAL REPORT
CEN/TR 16639
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
March 2014
ICS 91.100.30
English Version
Use of k-value concept, equivalent concrete performance
concept and equivalent performance of combinations concept
Utilisation du concept de coefficient k, concept k-Wert-Ansatz, Prinzipien des Konzepts der gleichwertigen
d'équivalence de performance et concept d'équivalence de Betonleistungsfähigkeit und Konzept der gleichwertigen
performance en combinaison Leistungsfähigkeit von Kombinationen aus Zement und
Zusatzstoff
This Technical Report was approved by CEN on 26 November 2013. It has been drawn up by the Technical Committee CEN/TC 104.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, 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: Avenue Marnix 17, B-1000 Brussels
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16639:2014 E
worldwide for CEN national Members.
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Contents Page
Foreword .3
0 Introduction .4
0.1 General .4
0.2 Task Group 5 .4
0.3 k-value concept .4
0.4 ECPC and EPCC.4
1 Scope .5
2 k-value concept .6
2.1 k-values in EN 206:2013 .6
2.2 Use of k-values in the member states .6
2.3 Procedure for using the k-value concept .7
2.3.1 Principle of the k-value concept .7
2.3.2 Method of calculation .8
2.3.3 Example for determination of k . 10
2.3.4 Further recommendations for the application of the k-value . 12
2.3.5 Example for establishing a general concept using the k-value concept . 12
2.4 Application of k-value concept by the users . 14
2.4.1 General . 14
2.4.2 Example for concrete mix design applying the k-value concept . 14
3 Equivalent concrete performance concept (ECPC) . 15
3.1 General . 15
3.2 Dutch Method . 15
3.2.1 Definitions . 15
3.2.2 Procedure and criteria for assessment of durability aspects . 17
3.2.3 Test methods . 22
3.2.4 Quality assurance . 23
3.3 Recommendations for the application of ECPC . 24
3.4 Additional information to the use of the Dutch method . 25
4 Equivalent performance of combinations concept . 26
4.1 General . 26
4.2 UK method . 27
4.3 Irish method . 28
4.4 Portuguese method . 29
4.5 Recommendation for application of EPCC . 30
4.6 Additional information the UK method . 30
4.6.1 Annexes from BS 8500-2 relating to conformity control of combinations . 30
4.6.2 How this works when specifying concrete to BS 8500 . 35
4.7 Additional information to the Irish method . 39
4.8 Additional information to the Portuguese method . 41
Annex A (informative) Replies to the k -value questionnaire of CEN/TC 104/SC 1/TG 5 . 47
A.1 General questionnaire . 47
A.2 Addition to answer of Finland . 57
Bibliography . 60
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Foreword
This document (CEN/TR 16639:2014) has been prepared by Technical Committee CEN/TC 104 “Concrete
and related products”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
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0 Introduction
0.1 General
This report outlines the current understanding of the use and application of three concepts used within
EN 206:2013 for Type II additions to concrete. These are the k-value concept, the Equivalent Concrete
Performance Concept (ECPC) and Equivalent Performance of Combinations Concept (EPCC).
Within 5.2.5 of EN 206:2013 k-values are given for fly ash and silica fume and a recommended k-value for
GGBS as well as general principles for the ECPC and the EPCC concepts. It is also stated in EN 206:2013
that modifications to the rules of application of the k-value concept are permitted if ‘suitability is established’.
As stated within EN 206:2013 the establishment of suitability should result from provisions valid in the place of
use of the concrete. In order to further explain the three concepts and to give guidance to the regulation
writers and users of these concepts, this report provides background information and an overview of these
concepts and rules of application as used within Europe.
0.2 Task Group 5
CEN/TC 104/SC 1 created Task Group 5 (TG 5) “Use of Additions” and assigned them the task to update
EN 206-1:2000, 5.2.5 as part of the revision of EN 206-1. Because of the publication of product standard
EN 15167-1 for ground granulated blastfurnace slag (GGBS), TG 5 was also asked to include rules for GGBS.
CEN/TC 104/SC 1 passed various resolutions instructing TG 5 that it should implement the EPCC and ECPC
concepts and the existing k-value concept for use of additions at the concrete mixer.
The rules for the use of type II additions in concrete according to EN 206:2013 are given in 5.2.5 “Use of
additions”. For two additions, fly ash and silica fume, specific requirements for their use with k-values are
given. In this prescriptive k-value concept for concrete mix design, the defined rules are on the safe side and
cover all possible variations for the possible permutations of cement and addition. An alternative option is the
use of ECPC and EPCC concepts. Their principles are described in EN 206:2013, 5.2.5.3 and 5.2.5.4 while
examples for the assessment using these concepts are given in this CEN/TR. The rules for these performance
concepts should also be safe and lead to a more efficient use of additions.
0.3 k-value concept
With respect to the k-value concept in EN 206:2013, it was agreed that for fly ash and silica fume prescriptive
k-values and cement substitution rates will be given which are proven to be on the safe side. Although the
k-value concept for GGBS is included in some national regulations (see /2/) only a recommended value is
given in EN 206:2013 due to limited practical experience. In national provisions, however, modifications to the
rules of the k-value concept may be applied where their suitability has been established, e.g. higher k-values,
increased proportions of additions, other additions (including type I), combinations of additions and other
cements than those normally permitted. In this report the derivation of the prescriptive k-value approach is
explained. The report also describes how the k-value concept should be applied by users such as the
concrete producers.
0.4 ECPC and EPCC
The equivalent performance concepts, ECPC and EPCC, for the use of additions may be applied where
suitability has been established. In countries where ECPC and EPCC are applied, nearly always, GGBS as
addition to concrete is used under these concepts. This report describes how the ECPC and EPCC are
applied in some European countries.
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1 Scope
This Technical Report provides more detailed information on the k-value concept principles of the equivalent
concrete performance concept (ECPC) and the equivalent performance of combinations concept (EPCC) in
accordance to EN 206:2013, 5.2.5.
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2 k-value concept
2.1 k-values in EN 206:2013
The k-value concept has been established for a number of years in a number of countries and was therefore
implemented in EN 206-1 for fly ash and silica fume. In CEN/TC 104/SC 1 report N 278 (June 1996) the
background was given to the application of k-value concept with fly ash concrete [1]. Later this concept was
also applied for concretes containing silica fume and in some member states k-values for concretes with
ground granulated blastfurnace slag (GGBS) are given in national application documents.
In EN 206:2013 prescriptive k-values are given for fly ash and silica fume and a recommended one for GGBS.
These k-values allow the use of these additions in concrete throughout Europe with a restricted range of
cement types within the requirements of the standard without any further verification procedure, i.e. without
further testing except for the normal quality control for the concrete. In a prescriptive concept for concrete mix
designs, the defined rules shall be on the safe side and cover all possible combinations of materials and
variations for the given addition.
The k-value concept is a prescriptive concept. It is based on the comparison of the durability performance (or
strength as a proxy-criterion for durability where appropriate) of a reference concrete with cement “A” against
a test concrete in which part of cement “A” is replaced by an addition as function of the water/cement ratio and
the addition content. With the proof of durability indirectly the proof for the exposure classes is given.
The k-value concept permits type II additions to be taken into account:
— by replacing the term “water/cement ratio” with “water/(cement + k * addition) ratio” and;
— the amount of (cement + k * addition) shall not be less than the minimum cement content required for the
relevant exposure class.
When part of Cement “A” is replaced by an addition, the limiting values that have to be applied are those that
would apply for Cement “A”.
The rules of application of the k-value concept for fly ash conforming to EN 450-1, silica fume conforming to
EN 13263-1 and ground granulated blast furnace slag conforming to EN 15167-1 together with cements of
type CEM I and CEM II/A conforming to EN 197-1 are given in corresponding clauses in EN 206:2013.
Modifications to the rules of the k-value concept may be applied where their suitability has been established
(e.g. higher k-values, increased proportions of additions, other additions (including type I), combinations of
additions and other cements than permitted.
2.2 Use of k-values in the member states
The use of k-values for type II additions in concrete has developed differently across the European member
states over years. Within the revision work of EN 206:2013 member states experience was compiled with a
series of differing enquiries. In 2007 a “Survey of National requirements used in conjunction with EN 206-
1:2000” was published [2]. For the use of additions this enquiry was focused to the regulations for different
classes of LOI for fly ash, environmental compatibility and the use of k-values, especially for fly ash and silica
fume. Five countries responded on the use of k-values for GGBS.
In March 2007, CEN/TC 104/WG 15 presented the results of a survey on the “Use of GGBS as a type II
addition in concrete to EN 206-1”. Eight countries reported on the use of GGBS and it was found that GGBS is
used as type II addition under the ECPC, EPCC and the k-value principles. However, the amount used based
on the k-value concept is relatively limited and this experience is confined only to some Nordic countries [3].
Within the revision work of 5.2.5 “Use of additions” in EN 206:2013, TG 5 also prepared an enquiry on the use
of k-values for additions [4] focusing the experience with the different additions, the k-values and the
determination of these k-values. In total 12 countries answered to the enquiry. Three countries do not use the
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k-value concept as they are using existing performance concepts and one country does not use the k-value
concept for GGBS resulting in nine countries with regulations for using GGBS with the k-value concept. The
answers of the enquiry can be compiled as follows:
— The k-value was mostly established based on results of research work and experience.
— The compressive strength is mostly evaluated after 28 days on concrete samples (9 countries) or mortar
(1 country).
— Where the k-value was determined the relationship between the compressive strength and water/cement-
ratio of concrete samples was used.
— The type of cement and the maximum proportions of additions permitted vary widely in the National
regulations, from the use with CEM I only to the use with all cements where the additions are also used in
cement.
— Fly ash is used with more cement types than silica fume and GGBS using the k-value concept.
— k-values for fly ash vary from 0,2 to 0,8, those for silica fume from 1,0 to 2,0 and those for GGBS from 0,4
to 1,0.
— Where k-values had been determined the durability aspects had also been taken into account.
— Most of the countries have experience with k-value concept for fly ash and silica fume, only a few
countries use the k-value concept for GGBS.
The single answers to the TG 5 enquiry are given at the end of this report.
2.3 Procedure for using the k-value concept
2.3.1 Principle of the k-value concept
Type II additions contribute to concrete properties by various mechanisms. Their influence on concrete
properties depends on the characteristics of the individual material properties, on the age of concrete, on the
ambient conditions (temperature, humidity) and various other parameters. To take into account these effects
in the concrete mix design, the k-value method uses the relationship between the water/cement ratio and the
strength of concrete. The concept was introduced by Iain A. Smith for the first time in 1967 for the design of fly
ash concretes with fly ash amount up to 25 % [5] and has developed further on.
Based on the established concept of EN 206-1 and related Eurocodes the concrete mix design is based on
the 28 days strength of concrete. Consequently the standardised prescriptive k-value for a concrete addition is
related to this age. Nevertheless, when a k-value has to be defined, the durability of concretes shall be
considered for the relevant exposure classes.
In concretes containing type II additions, the term “water/cement ratio” is replaced with
“water/(cement + k · addition)” ratio. The factor k indicates the contribution of the addition in concrete
compositions reaching the same strength like the reference concretes without addition.
When the condition of equal strength is assumed, Formula (1) is fulfilled for a specific k-value.
ω w / c+⋅ka (1)
( )
o aa
When these parameters have been determined for equal strength, k can be calculated;
k=(w /ω −c )/ a (2)
a o a
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=
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or if normalized to the cement content c of the concrete with addition
a
k=(ω /ω −1)/(a / c ) (3)
a o a
where
ω is the water/cement ratio of reference concrete without addition;
o
w is the water content of the concrete with addition;
a
c is the cement content of the concrete with addition;
a
a is the addition content;
ω is the water/cement ratio of concrete with addition (w /c ).
a a a
In prescriptive concrete design methods using the k-value concept, the constant k reflects the maximum value,
which could be used to prove that the water/(cement + k · addition) ratio of the concrete does not exceed the
maximum water/cement ratio as defined for the respective exposure class. It does not give any information
about the effective performance of the used addition in the individual concrete mix.
When evaluating the results of different sets of concrete tests, various k-values could be determined as the
efficiency of a concrete addition is dependent on a number of parameters (e.g. quality and properties of
addition, amount of addition, cement type and properties, water/cement ratio, age, temperature, etc.). The
calculation of k-values indicating the efficiency of a concrete addition is usually performed by the comparison
of the water/cement ratio vs. compressive strength relationship for references concretes without addition and
concretes with addition. For determining the efficiency of an addition, all concretes of a data set calculating k
shall be made of the same cement.
2.3.2 Method of calculation
The method of calculating k-values is generally applicable to type II additions according to EN 206:2013. The
k-value concept is based on the comparison of the performance of a reference concrete with cement “A”
against a test concrete in which part of cement “A” is replaced by an addition as function of the water/cement
ratio and the addition content.
The method described in the following, is based on the Smith method developed for fly ash in 1967 [5]. The
basis for the calculation of k-value is based on the water/cement ratio vs. strength relationship of concretes
with the same content of addition. The determination should preferably not be done on the results of single
concretes mixes, but by a set of data. This allows a more precise determination of the water/cement ratio vs.
strength relationship. To arithmetically describe that relationship, different empirical formulae could be used.
Usually a linear relationship gives a good approximation of strength in restricted ranges of water/cement ratio
Compressive strength = a - b · water/cement ratio
But also other nonlinear approaches (e.g. Abrams law [6, 7], could be used [8, 9]. The values of the factor “k”
may also be given by technical feedback. E.g. in France, where the k-value concept is used for Type II and
some type I addition (limestone and siliceous filler), the values are derived from the Bolomey method [10] and
adjusted by experience.
Comparison of the different approaches shows that there might be slight differences in the calculated k-
values, but the level of the results is similar. The variances in the measured compressive strength results have
a much higher impact on the calculated values [11].
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Key
1 addition with content a
2 reference
Y strength
Figure 1 — Principle of k-value determination (shown for w / (c + a))
Strength vs. water/cement – relationship of reference concrete:
f= AB−⋅ω
o o oo
For a selected c/a ratio, the linear approximation can be assumed also for the correlation f versus w / (c + a)
a
as shown by the following formula:
f =A −B ⋅(w /(c+ a))
a a a
When a functional relationship between water/cement ratio and compressive strength based on test results
has been determined for reference concretes without addition and concretes with a defined addition/cement
ratio respectively both formulae are set to be equal;
ff=
o(reference) a(addition)
f = f ⇒ A − B ⋅ω = A − B ⋅ w /(c+ a) (4)
o a o o o a a a
ω w / c+⋅ka ⇒ w ω⋅ c+⋅ka (5)
( ) ( )
o a a o
A − B ⋅ω = A − B ⋅ω ⋅(c+ k⋅ a)/(c+ a) (5) substituted in (4)
o o o a a o
or A− B⋅ωωA− B⋅ ⋅ 1+⋅k ac/ /1+ ac/
( ) ( )
o oo a a o
This follows the principle that the parameter k has to be determined on the basis of equal strength. Now, using
Formula (3) and necessary arithmetic transformations, k can be determined. In this way of calculation, k will
not be a single value but will be a parameter in functional dependence of the water/cement ratio of the
reference concretes (ω ).
o
(A − A )⋅(1+ a / c) 1 B ⋅(1+ a / c) 1
a o o
k= ⋅ + −1⋅
B ⋅ a / c ω B a / c
a o a
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= =
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where
ω water/cement ratio of reference concrete without addition
o
ω water/cement ratio of concrete with addition (w /c )
a a a
w 3
a water content of concrete with addition [kg/m ]
c 3
a cement content of concrete with addition [kg/m ]
a
3
content of addition [kg/m ]
f , f compressive strength of concretes [MPa]
0 a
A , A , B , B empirical coefficients of the linear relations between water-cement ratio and strength of the reference
0 a 0 a
concrete and the concrete with additions
2.3.3 Example for determination of k
For demonstrating the calculation of k, an example is used with concretes containing a fly ash content of 20 %
by mass (related to cement plus fly ash). Figure 2 shows the relationship between water/(cement + fly ash)
ratio and strength for the concretes with fly ash and the reference concretes without addition which have been
used for the calculation.
Key
1 0 % fly ash
2 20 % fly ash
X water / (cement + fly ash) ratio
Y compressive strength at 28 days [MPa]
Figure 2 — Example for strength vs. water / (cement + fly ash) relationship
f =91,64−95,20⋅ω
o o
f=101,8−124,6⋅water/ cement+flyash with fly ash/cement = 0,25 (20 % fly ash)
( )
f
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(101,8−91,64)⋅+(1 0,25) 1195,20⋅+(1 0,25)
k ⋅+ −⋅1
124,6⋅0,25 ω 124,6 0,25
o
⇒= k 0,408⋅1/ω−0,180
o
With this term, the k-value can be plotted as function of ω (see Figure 3).
o
For a given ω , k can be calculated, for example: ω = 0,50 k = 0,64
o o
ω = 0,60 k = 0,50
o
Key
1 20 % fly ash
Y k-value at 28 days
Figure 3 — k-value plotted as function of water/cement ratio ω of reference concrete
o
Control
Alternative 1
Select a compressive strength, e.g. 35 MPa
f= AB−⋅ωω= 35= 91,64−95,20⋅
o o o o o
⇒=ω (91,64−35)/95,20 0,595
o
f=A− B⋅+wc/ f=35=101,8−124,6⋅+wc/ f
( ) ( )
f ff
⇒ wc/(+ f) (101,8−35)/124,6 0,536
k=(ω /ω −1)/( f / c) with ω w/(c+ f)⋅+(1 fc/ ) (see box in Figure 1)
f o
f
11
=
= =
=
=
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k 0,536(1+0,25)/0,595−1 /0,25 0,504
[( ) ]
Alternative 2
Select a w/c ratio, e.g. ω = 0,50
o
k ω= 0,50= 0,408/0,50−=0,180 0,636
( )
o
f ω= 0,50= 91,64−95,20⋅=0,50 44,0MPa
( )
oo
f A− B⋅ω⋅ 1+⋅kf / c /1+ f / b
( ) ( )
f f fo
101,8−124,6⋅0,50⋅+1 0,636⋅0,25 / 1+0,25 44,0MPa
( ) ( )
NOTE The example origins from concretes with fly ash as addition therefore in the formulae the amount of fly ash is
represented by the symbol f.
2.3.4 Further recommendations for the application of the k-value
For the application of the k-value concept the following recommendations should be considered:
— k-values should be calculated only for water/cement ratios in the range investigated (no extrapolation).
— Beside cement and addition all other concrete components have an effect on the strength of concrete.
Therefore keep them constant.
— If a constant workability is preferred, where necessary use a water reducing admixture (plasticiser) to
ensure no excessive air is entrained.
— Ensure the variability in the determination of compressive strength is as low as possible because any
scattering is magnified in the calculation of the k-value.
2.3.5 Example for establishing a general concept using the k-value concept
As an example the principles of the procedure of introducing the k-value for fly ash in the 1990s is
demonstrated. The results of this approach were included in EN 206-1:2000.
The determination of the prescriptive k-value is performed in two steps. In the first step, k-values are
calculated from concrete tests according to the procedure and recommendation reported above. In the
concrete tests all relevant parameters (cement type, strength class, quality of addition, water/cement ratio,
etc.) should be considered to allow the definition of a generally applicable prescriptive k-value. Figure 4
demonstrates the range of calculated k-values resulting from concrete strength tests using various
combinations of different cements and a fly ash. The fly ash used for durability test as shown in Figures 5 and
6 is representative for a fly ash according to EN 450-1. It had been selected from pre-tests out of a range of
more than 30 fly ashes. As shown in Figure 4 a prescriptive k-value of 0,4 was derived taking i
...
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