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0HBRC Journal (2012) 8, 1-7
Housing and Building National Research Center HBRC Journal
http://ees.elsevier.com/hbrcj
Use of cement in concrete according to European standard EN 206-1
Christoph Müller *
Head of the Concrete Technology Department of the Research Institute of the Cement Industry, Düsseldorf, Germany Received 12 July 2011; accepted 5 August 2011
Abstract The manufacture of cements with several main constituents (blended cements) is of particular importance with regard to reducing climatically relevant CO2 emissions in the cement industry. A wide variety of common cement products exists in the different EU Member States. They match local manufacturing conditions, throughout meeting particular climatic or other local conditions, including building practices. In general, all cements conforming to European Cement Standard EN 197-1 are suitable for the manufacture of concrete according to European Concrete Standard EN 206-1. Depending on the area of application, however, differences related to the cement type may possibly have to be taken into account to ensure the durability of the concretes manufactured with these cements. These regulations were laid down in National Application Documents (NADs) to EN 206-1 dependent upon the exposure classes that a structural element is assigned to. This paper deals with the overall concept of EN 206-1 with regard to concrete durability. It gives an overview of the cement types used in Europe and the areas of application of cements conforming to EN 197-1 in concrete conforming to EN 206-1 and various national annexes. The option of combining several main constituents makes blended cements particularly well suited for combining the advantages of individual main constituents, and thus for developing these cements into even more robust systems. This process requires an integrated assessment of all requirements to be met by cements during manufacture and application. From a technical perspective these include the strength formation potential as well as good workability of the concrete and, in particular, the durability of the concrete made from these cements. The effects that the main constituents have with regard to properties relevant to durability can be utilized in particular in cements
KEYWORDS
Blended cements;
Cement;
Concrete;
Durability;
Carbonation;
Chloride migration;
Freeze-thaw-resistance
* Research Institute of the Cement Industry, Tannenstrasse 2, Duesseldorf 40476, Germany. Tel.: +49 211 4578 372; fax: +49 211 4578 219.
E-mail address: christoph.mueller@vdz-online.de.
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made from a combination of limestone/blastfurnace slag or limestone/fly ash as main constituents. This is demonstrated using the parameters of density, carbonation, resistance to chloride penetration, resistance to freeze-thaw and resistance to freeze-thaw with de-icing salt.
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Introduction
The European concrete standard EN 206-1 was internationally adopted in 2000 as a non-harmonised EN-standard. EN 206-1 therefore has the status of a framework document, which needs national specifications. A task force of CEN/TC 104/ SC1 "Concrete" elaborated a synopsis of the National Application Documents (NADs) to European concrete standard EN 206-1. The synopsis highlighted that further harmonisation, especially with regard to specifications relevant to durability, is virtually impossible. The summaries make evident, for example, that internal components are not subject to any restrictions regarding either the maximum water/cement ratio (hereinafter w/c ratio) or the minimum cement content in some countries. Although the vast majority of NADs specifies values, their levels vary widely in some cases. Many countries call for minimum compressive strength of concrete, while five countries have not specified any requirements at all.
The exposure class most frequently defined for interior components is XC1, while some countries assigned classes X0 or XC3, respectively. A combination of exposure classes XC4 and XF1 is assigned to external components in several countries. Specifications for minimum compressive strength either range between C25/30 and C32/40 or do not exist. A maximum w/c ratio of 0.60-0.50 is indicated. The minimum cement content ranges between 150 and 320 kg/m3, the most frequently used value is 300 kg/m3. The discrepancies regarding cement application are considerable in some cases as well. In addition to the traditional differences in market conditions and construction practice this also reflects the philosophies underlying the imposition of rules.
Following the basic principles of the European concrete standard EN 206-1 are introduced. Moreover, this paper gives an overview of the cement types used in Europe and the areas of application of cements conforming to EN 197-1 in concrete conforming to EN 206-1 and various national annexes. The technical performance of cements with several main constituents (blended cements) is demonstrated using the parameters of density, carbonation, resistance to chloride penetration, resistance to freeze-thaw and resistance to freeze-thaw with de-icing salt.
Short history of the European concrete standard EN 206-1
The decisive impetus for standardization activities at European level was provided by the goal of lifting trade barriers that is enshrined in the EU Construction Products Directive. The lifting of trade barriers presupposes that the construction products in circulation on the European single market meet uniform requirements that have been laid down in technical specifications, i.e. harmonised European standards or uniform technical approvals. In the late 70's the EU Commission set about commissioning the elaboration of Eurocodes for the design and execution of structures which were to be appropriate for Europe-wide application. The provisions made in the technical product specifications must ensure that the requirements for the safe design and execution of structures are met. In parallel to that process, the Technical Committees of CEN elaborated harmonised product standards and Eurocodes. While the design standards have not all yet been finally adopted, most of the product standards are now available. As regards concrete technology, the work on harmonised European regulations commenced in the mid-70s with the establishment of a ''Code of good practice for ready-mixed concrete'' by ERMCO, the European organisation of ready-mixed concrete manufacturers (Table 1).
While CEN/TC 94 ''Ready-mixed concrete'' took this document as a basis for developing draft standard prEN 199 ''Ready-mixed concrete - production and delivery'', CEN/ TC 104 ''Concrete and associated products'' elaborated the draft for EN 206 ''Concrete; properties, production, processing and quality control''. Neither standard could muster a weighted majority from the CEN member states in the mid-80s. The combination of both standard parts after due consideration of all technical oppositions resulted in the creation of an acceptable paper that was submitted as European prestan-dard ENV 206 in 1990. Until 1997, CEN/TC 104, which originated from the merging of Technical Committees TC 94 and TC 104, discussed numerous questions that had arisen in conjunction with the application of the prestandard. This resulted in the compilation of the draft standard prEN 206 ''Concrete; specification performance, production and conformity'', which was officially adopted as a non-harmonized European
Table 1 Development of the European Concrete Standard EN 206-1.
Year Regulation
Mid-70s 1979 1981 1982 1984 1989/90 1990 2000 ERMCO "Code of good practice for ready-mixed concrete'' Establishment of CEN/TC 94 "Ready-mixed concrete'' Establishment of CEN/TC 104 "Concrete and associated products'' prEN 199 "Ready-mixed concrete-production and delivery'' prEN 206 "Concrete; properties, production, processing and quality attestation" ENV 206 "Concrete; properties, production, processing and quality attestation" Merging of CEN/TC 94 and CEN/TC 104 EN 206-1 "Concrete part 1; specification, properties, production, and conformity" Not adopted Adopted
EN ... Standards for precast concrete products
Concrete structure
EN 1992
(EC 2) Design of concrete structures
EN 12350 Testing fresh concrete
EN 12390 Testing hardened concrete
EN 13791 Assessment ■ of concrete strength in structures EN 12504 Testing concrete in structures
EN 206-1 Concrete
ENV 13670-1
Execution of concrete structures
EN 197 Cement EN 450 Fly ash EN 13263 Silica fume EN 934-2 Admixtures for concrete EN 12620 Aggregates for concrete EN 13055-1 Light-weight aggregates EN 1008 Mixing water for concrete EN 12878 Pigments
Fig. 1 Relationship between En 206-1 and other standards.
standard in spring 2000 following further consultations and amendments. Application of this European concrete standard EN 206-1 in European member states required the elaboration of national application rules. The total set of European standards in concrete construction takes into consideration the interfaces between design and construction, concrete composition and manufacture, as well as the execution of concrete structures (Fig. 1).
Basic principles of the European concrete standard EN 206-1
The European standardisation concept in concrete construction takes the current status of construction and execution technology into account and aims to realise two main goals in particular:
• The interfaces between design and construction, concrete composition and manufacture, as well as the execution of concrete structures are to be identified and bridged by the specifications in the standard.
• The durability of the concrete structures subject to different kinds of exposure is to be verified systematically in planning and execution.
The basic elements of the concrete standard are given in Fig. 2. EN 206-1 specifies requirements for:
• The constituent materials of concrete.
• The properties of fresh and hardened concrete and their verification.
Fig. 2 European Standard EN 206-1 headwords and basic elements.
The limitations for concrete composition (for durability).
The specification of concrete.
The delivery of fresh concrete.
The production control procedures.
The conformity criteria and evaluation of conformity.
EN 206-1 discerns Designed concrete
Concrete for which the required properties and additional characteristics are specified to the producer who is responsible for providing a concrete conforming to the required properties and additional characteristics.
Prescribed concrete
Concrete for which the composition of the concrete and the constituent materials to be used are specified to the producer who is responsible for providing a concrete with the specified composition.
Standardized prescribed concrete
Prescribed concrete for which the composition is given in a standard valid in the place of use of the concrete.
The following definition of durability has gained wide acceptance and is also the basis of the European concrete standards: A structure is considered durable if it exhibits:
• The requested useful properties.
• Subject to the planned exposures.
• Throughout the projected service life.
• At appropriate maintenance costs.
All the parameters listed are already part of the planning concept of a structure. Planners and designers must establish the necessary working properties (strength, resistance to freezing and thawing, etc.), taking into consideration the planned exposures (stress, weather conditions, etc.). A design concept for durability is required to prevent the exposure ("attack") from causing an early and unplanned exhaustion of the working properties (the "resistance"). The "descriptive concept'' and the "performance concept'' are differentiated. The calculated forecast of the durability according to a performance concept is currently only possible for steel corrosion and involves enormous expenses. Therefore, the durability design is established according to the descriptive concept in the European concrete standard. It is based on class divisions for the exposures (exposure classes) and on associated measures, such as concrete composition, concrete cover of reinforcement and curing. A differentiation is made between the exposure classes XO (no attack), XC (carbonation), XD (de-icing salt), XS (chloride from sea water), XF (freezing and freeze-thaw with de-icing salt) and XA (chemical attack). As EN 206-1 is a non-harmonized European standard, it only contains recommendations for limiting values of concrete composition. The final requirements are given in National Application Documents (NADs).
By using examples, the classification into up to four levels is explained in further detail in the standard. The concrete technology measures to be taken refer mostly to the maximum w/c ratio, the minimum cement content, the minimum concrete strength class, application rules for concrete additions and,
in individual cases, by the limitation of usable cements, which must be maintained depending on the respective exposure class. Thus, this is the first time that a concrete standard has stated that planners and designers must take into account the stress by the exposure classes analogous to the stress by the outer loads.
Cement market and application regulations
A wide variety of common cement products exists in the different EU Member States. They match local manufacturing conditions, throughout meeting particular climatic or other local conditions, including building practices. The industry has identified and agreed upon 27 common cement products, which are standardized in the European cement standard EN 197-1. The standard defines these 27 common cement products and their constituents. It includes specifications on the proportions in which they are to be combined, as well as the mechanical, physical and chemical requirements for both the products and their constituents.
The products are divided into five groups, according to the content of constituents other than cement clinker. Since April 2002, all common cements have been CE-marked according to EN 197-2. Besides Portland cement CEM I all other cements are blended cements (comp. [1]). Ecological and economical reasons initiated a change in the development of different types of cement throughout Europe. CEM I cements are being increasingly replaced by CEM II cements which contain other main constituents in addition to clinker. Fig. 3 gives a survey of the European cement sales for the year 2005 according to CEMBUREAU statistics. Experience in the production and application of blended cements already exists as most of cements produced and/or used in Europe are blended cements (Fig. 3). In general, all cements conforming to EN 197-1 are suitable for the manufacture of concrete according to EN 206-1. Depending on the area of application, however, differences related to the cement type may possibly have to be taken into account to ensure the durability of the concretes manufactured with these cements. Therefore, in some cases these cements, which comply with EN 197-1, are excluded in parts of Europe from the use in certain exposure classes because of the lack of building experience within the scope of the respective national annexes to concrete standard EN 206-1 and because there have been no scientific investigations into the use of these cements (Table 2). The table provides an overview of the possible applications of cements complying with EN 197-1 for usual external components in building construction without appreciable external exposure to chlorides. The information was gathered from various sources [2,9,10]. The
CEM I CEM II CEM III CEM IV CEM V and others
Fig. 3 Domestic market share of cement in Cembureau countries in% (2005) - Source: Cembureau.
sometimes substantial differences in the cement usage in the concrete standards of the different European states based on EN 206-1 can be seen very clearly. This reflects not only the traditionally different factors of the market and building practice but also different philosophies in setting regulations. For example, specifications are given in the German application standard DIN 1045-2 for the application of all 27 basic types of cement and also for a number of CEM II-M cements whereas other national annexes to EN 206-1 regulate the application of only a few types of cement that traditionally play a part in the particular national market.
Performance of different cements/cement types
General
From the technical point of view the requirements for developing a new cement do not only include the strength-forming potential and good workability but also, and in particular, the durability of the concrete produced from the cement. From the cement producer's point of view costs and possible environmental aspects naturally also play a part. From the technical point of view, CEM I, CEM II and CEM III cements sometimes have different properties and the concretes made using these cements exhibit different characteristics in laboratory trials and - depending on the property being examined - also in practice. No cement - not even Portland cement -represents the optimum solution in all applications. The option of combining several main constituents makes blended cements particularly well suited for combining the advantages of individual main constituents, and thus for developing these cements into even more robust systems. This means that in addition to the aspects of CO2 abatement and the conservation of resources these cements offer outstanding opportunities for optimizing properties that are relevant to applications - such as workability, strength development and durability.
Porosity/pore size distribution/density
Porosity and pore size distribution are of fundamental importance for practically all properties of cement-bonded building materials that are relevant to durability This is because, as a rule, harmful influences find their way into the building material through the pore system. The resistance of the concrete to penetration by harmful substances, i.e. the impermeability of the concrete, therefore plays a special role in its durability. Fig. 4 shows the influence of cements containing limestone (LL), fly ash (V), silica fume (D) and granulated blastfurnace slag (S) on the total porosity and the pore size distribution of cement paste compared to cement paste with Portland cement. The definition of a relationship between paste porosity and concrete durability requires a case by case assessment. Whereas higher amounts of limestone meal can lead to a higher porosity and especially to a higher amount of capillary pores >0.1 im, the use of blended cements containing silica fume or higher amounts of fly ash or granulated blastfurnace slag causes an increase of fine pores and a decrease of capillary pores resulting in a higher density of the concrete containing these blended cements. The combination of limestone and fly ash and/or limestone and granulated blastfurnace slag therefore results into cements for concrete with a high durability.
Table 2 Areas of application of cements conforming to EN 197-1 in concrete conforming to EN 206-1 and various national annexes -example: Exposed vertical surface of inland concrete with no significant levels of external chlorides [8].1)
Country Exposure class minfe max (w/c)«. min c CEM 1 CEM II CEM III CEM IV CEM V
S D P/Q V w T LL L M
A B A A B A B A B A B A B A B A B A B c A 3 A B
Austria XC1+XF1 - 0.55 300 X X X X X X X 9 X V
Belgium EE3 (XC4+XF1) C30/37 0.50 320 X X X X X X X X X X X X X X X X X X X X X
Czech Republic XC1 to XC4 orXFI C30/37 0.50 or 0.55 300 X X X X X X X X X X X X X X X X X X X X
Denmark (XC2, XC3, XC4, XF1, XA1) C25/30 0.55 150" w" (i> <i> (X)
Finland XC3 or XC4, XF1 C25/30 0.60 250 " X X (i> X X X 6} X
Germany XC4 + XF1 C25/30 0.60 280 X X X X X X X X o o X X X o o o <s> <s> X X o O (X) V (X)" (x i>
Ireland XC2 or XC4 + XF1 C30/37 if XC4 + XF1 0.55 320 X X X
Italy XC1 C25/30 0.60 300 X X X X X X X X X X X X X X X X X X X X X X X X X
XC2 + XF1 C32/40 0.50 320 X X X X X X X X X X X X X X X X X X X X X X X X X
Luxembourg XC4 * XF1 C25/30 0.60 280 X X X X X X X (5Î X X
Netherlands XC3 - 0.55 260 X X X X X X X X X
XC4 + XF1 - 0.50 300 X X X X X X X X X
Norway XC4 + XF1 0.60 250 X X X X X X
Portugal XC4 + XF11" C30/37 0.60 280 X X X X X X X X X X
0.55 300 X X X X X X X X X X X X X X X X X X $ « « «
Sweden XC4, XF1 0.55 300 x41 x4) X 4) X 4> X 4) <i> x3> X 3)
Switzerland XC4 t XF1 0.50 300 X X X X <ï> 13)
United Kingdom XC3/4 + XF1 C28/35 0.60 280 X X X X X X X X X X X X
allowed
j allowed with restrictions
not mentioned not allowed
Sources: [2 9,10]
1) Due to the complexity of the rational annexes, this compilation is not exhaustive and the accurate repetition of all specifications cannot be guaranteed.
2) Cements need testing
3) min filler: 375 kg/m3
4) Minimum strength class 42,5
5) min c = 270 kg/m3 for XG4
6) Cement not approved for XC4)
7) Only CEM ll/A-M (S-D; S-t: S-ll: D-T: D-LL: T-ll: S-P: S-V: D-P: D-V; P-V; P-t; P-ll; V-t; V-LL) and CEM ll/B-M (S-D: S-T: D-t; S-P: D-P: P-t; S-V; D-V P-V; V-T|
8) Only CEM MB (p) and valid only for trass according to din 51043. used as a main constituent up to a maximum content of 40 % (m/m)
9) Only CEM VIA (S-P) and CEM V/B (S-P) and valid only for trass according to DIN 51043
10) Only CEM ll/A-M (S-D: S-T; S-ll; S-V)
11) Assumption
12) Not less than 50 mass% clinker
13) Only CEM ll/A-M (O-LL)
Even the increased fineness of the clinker in filler-containing cement may positively influence the pore size distribution, compared to site blends of CEM I and filler.
Carbonation
Investigations [3,4] on a number of reinforced concrete and prestressed concrete structures made of concretes of various strength classes and different compositions have shown that there is no influence of the cement type on the carbonation behaviour for concrete elements in outdoor exposure, because CO2-diffusion and therewith carbonation depth decreases significantly with increasing moisture content. Inside structures can show a higher degree of carbonation.
However, due to the low moisture content of these elements there is no risk of corrosion. Fig. 5 shows the results from lab-
oratory scale tests concerning the carbonation behaviour of concretes with different cements. It depicts that the depth of carbonation of CEM II concretes lies within the range of CEM I and CEM III/A concretes (CEM III/A cements are permitted in countries with a long tradition in the use of blastfurnace slag (e.g. Germany, Netherlands, UK) without restrictions concerning corrosion induced by carbonation.). Thus, carbonation results for the other concretes with CEM II lie within an acceptable range.
Penetration of chlorides
As regards resistance to penetrating chlorides, practice shows that there are differences between concretes with different cements. The use of cements containing fly ash or granulated blastfurnace slag can increase the resistance of concrete to pe-
* 2.0 cn 2 o
« 1.5
£ 1.0 0.5 0.0
□ 35 % LL □25 % LL
□ CEM I ■40 % V
■ 15 %D
■ 50 % S
>0.1 (jm
Fig. 4 Influence of cements containing limestone (Ll), fly ash (V), silica fume (D) and ground granulated blastfurnace slag (S) on the total porosity and the pore size distribution of cement paste compared to cement paste with portland cement [2].
-□-CEM I -■-CEM Ill/A -O-20 % LL 20 % V -A-15%V, 15%LL
c = 260 kg/m3 w/c = 0.65
200 Age in days
Fig. 5 Depths of carbonation of concretes made with portland-composite cements and reference cements (Cem I, Cem III/A) as a function of test age and cement composition [6,7].
netrating chlorides due to a higher percentage of fine pores [5], i.e. the chloride migration coefficient of chloride ions decreases (cf. Fig. 6).
Many years of practical experience in various European countries show that concretes with blended cements and with appropriate concrete composition, processing and curing, reliably comply with the standard for freeze-thaw-resistance with and without de-icing salt. The freeze-thaw-resistance of concrete tested in the laboratory to a large extent depends on the type of test. Fig. 7 shows an example of the scaling of concretes using different CEM II cements which were determined according to the cube test (freeze-thaw test according to EN 12390-9). Cements that had complied with the assessment criterion of 610 mass% scaling after 100 freeze-thaw cycles have also stood the test of practice.
Fig. 8 shows the results from freeze-thaw tests with de-icing salt with the CDF method on concretes with different cements. For the evaluation of the results - if testing is required - a criterion for scaling of 1.5 kg/m2 after 28 freeze-thaw cycles is used, e.g. in Germany. This criterion corresponds to a scaling depth of approx. 0.6 mm. The concretes made with Portlandlimestone cement or Portland-fly ash cement do not show
Fig. 6 Chloride migration coefficients of concretes made with portland cement as well as limestone-, fly ash- and slag-containing CEM II cements [2,7,8] freeze-thaw-resistance with and without de-icing salt.
Fig. 7 Scaling of concretes (cube test, c = 300 kg/m3, w/ c = 0.60) made using various portland-composite cements and well proven cements Cem I - Cem III/A (grey shading) as a function of the number of freeze-thaw cycles and of the cement composition [2,6,7].
F 1.50
c 1.25
s co 0.75
CEM I -»-30%LL A 15 % V, 15 % LL -€>- 20 % V
Criterion for scaling
-A-4" io
0 7 14 21 28 Freeze-thaw cycles
Fig. 8 Scaling of air-entrained concretes (CDF test, c = 320 kg/ m3, w/c = 0.50) made using various portland-composite cements and CEM III as a function of the number of freeze-thaw cycles and of the cement composition [2,6,7].
any significantly different scaling behaviour from that of concrete made with Portland cement.
References
[1] Schneider, M.: European Specification of Cement. 1st International conference on cement, Cairo, EGYPT 2008.
[2] ECOserve NETWORK. CLUSTER 2: Production and Application of Blended Cements (<www.eco-serve.net/ uploads/0032_Cluster2_argumentation_paper_final.pdf>).
[3] Schröder, F., Smolczyk, H.-G., Grade, K., Vinkeloe, R., Roth, R., "Einfluß von Luftkohlensaure und Feuchtigkeit auf die Beschaffenheit des Betons als Korrosionsschutz für Stahleinlagen (Influence of CO2. and moisture on the consistency of concrete as resistance against corrosion of steel reinforcement)''. Deutscher Ausschuss für Stahlbeton No. 182 (1967) 142-182.
[4] R.F.M. Bakker, G. Roesink, Zum Einfluss der Carbonatisierung und der Feuchte auf die Korrosion der Bewehrung im Beton (Influence of carbonation and moisture on the corrosion of the reinforcement in concrete), Beton-Informationen 31 (3/4) (1991) 32-35.
[5] H.A. Brodersen, Transportvorgange verschiedener Ionen im Beton (Migration of various ions in concrete)'', BetonInformationen 23 (3) (1983) 36-38.
[6] Müller, C., Lang, E., "Durability of concrete made with Portland-limestone and Portland-composite cements CEM II/ M (S-LL)''. Concrete Technology Reports 2004-2006, pp. 2953.
[7] C. Müller, K. Severins, Durability of concretes made with cements containing fly ash, Cement International (5) (2007) 102109.
[8] C. Müller, Performance of Portland-composite cements, Cement International 4 (2) (2006) 112-119.
[9] Draft CEN Report CR: CEN TC 104/SC1 survey of national requirements used in conjunction with EN 206-1: 2000 (Document CEN/TC 104/SC1 N0482), 2006, not published.
[10] DIN 1045-2: Concrete, reinforced and prestressed concrete structures. Part 2: Concrete Specification, properties, production and conformity - Application rules for DIN EN 206-1.
