1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationFramework for a specification on the avoidance of a damaging Alkali-Silica Reaction (ASR) in concretePD CEN/TR 16349:2012National forewordThis Published Document is the UK implem
2、entation of CEN/TR 16349:2012.The UK participation in its preparation was entrusted to Technical CommitteeB/517, Concrete.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisions of acon
3、tract. Users are responsible for its correct application. The British Standards Institution 2012Published by BSI Standards Limited 2012ISBN 978 0 580 76676 3ICS 91.100.30Compliance with a British Standard cannot confer immunity fromlegal obligations.This Published Document was published under the au
4、thority of theStandards Policy and Strategy Committee on 30 June 2012.Amendments issued since publicationAmd. No. Date Text affectedPUBLISHED DOCUMENTPD CEN/TR 16349:2012TECHNICAL REPORT RAPPORT TECHNIQUE TECHNISCHER BERICHT CEN/TR 16349 April 2012 ICS 91.100.30 English Version Framework for a speci
5、fication on the avoidance of a damaging Alkali-Silica Reaction (ASR) in concrete Cadre dune spcification destine prvenir les dgradations causes au bton par lalcali-raction Anwendung von Qualittsregelkarten bei der Herstellung von Beton This Technical Report was approved by CEN on 14 February 2012. I
6、t 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherl
7、ands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2012 CEN All rights of exploit
8、ation in any form and by any means reserved worldwide for CEN national Members. Ref. No. CEN/TR 16349:2012: EPD CEN/TR 16349:2012CEN/TR 16349:2012 (E) 2 Contents Page Foreword 3Introduction .41 Scope 52 Alkali-Silica Reaction (ASR) .53 Elements of specifications .54 Characterisation of environment .
9、55 Precautionary measures appropriate to concrete 65.1 General remarks.65.2 Use of cement with a low effective alkali content 75.3 Use of slag, fly ash, silica fume or other pozzolana (in cement or as an addition) 75.4 Limiting the effective alkali content of the concrete 75.5 Verification of the su
10、itability of a concrete mix in a performance test 85.6 Use of a non-reactive aggregate combination 86 Summary .8Bibliography 9PD CEN/TR 16349:2012CEN/TR 16349:2012 (E) 3 Foreword This document (CEN/TR 16349:2012) has been prepared by Technical Committee CEN/TC 104 “Concrete and related products”, th
11、e 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. This Technical Report is partly based on the re
12、commendation of RILEM TC ACS (Part 1 of AAR-7) 6. PD CEN/TR 16349:2012CEN/TR 16349:2012 (E) 4 Introduction This Technical Report has been prepared by the Joint Working Group (JWG) on Alkali-Silica Reaction (ASR) that was set up by the chairmen of CEN/TC 51, CEN/TC 104 and CEN/TC 154 and composed of
13、representatives from CEN/TC 51, CEN/TC 104, CEN/TC 154 and RILEM TC ACS. The following is a list of the members of the JWG on ASR: Name Represents Michel Delort CEN/TC 51 Christer Ljungkrantz CEN/TC 51 Tom Harrison CEN/TC 104 Christoph Mller CEN/TC 104 Philip Nixon (until 2009) CEN/TC 154 Robert Gos
14、sling (from 2010) CEN/TC 154 Jean-Marc Vanbelle CEN/TC 154 Terje F. Ronning RILEM Ingmar Borchers (VDZ) Guest In CEN member countries, ASR has been recognised as a problem in concrete structures since the 1970s.Consequently, a number of countries have established provisions to avoid a damaging ASR.
15、These provisions are currently set out in national guidance documents and specifications. Provisions vary in the different CEN member countries and depend on local experiences; some member countries have not yet found the need to set up specifications. The JWG was established to review the situation
16、 and to see whether it is possible to go further in providing pragmatic and unified economic European specifications for the avoidance of a damaging ASR in concrete. The JWG concluded that, unless there is any sound scientific explanation of a damaging ASR which can be used uniformly all over Europe
17、, it is premature to have harmonised classes for alkali-reactivity of aggregates and provisions for avoiding a damaging ASR on a European level. Additionally, safety margins are determined at national level and are related to the reliability at which a damaging ASR will not occur. Nevertheless, a fr
18、amework for the specification of the avoidance of a damaging ASR in concrete can be given. PD CEN/TR 16349:2012CEN/TR 16349:2012 (E) 5 1 Scope This Technical Report gives guidance for avoiding a damaging Alkali-Silica Reaction (ASR) in concrete. 2 Alkali-Silica Reaction (ASR) Alkali-Silica Reactions
19、 in concrete are a result of reaction between the alkaline pore solution in concrete and reactive mineral species (as reactive silica and silicates) in the aggregate. The reaction leads to the formation of a gel that can absorb water and exert an expansive force on the concrete. In certain condition
20、s, these reactions can lead to damaging expansions and cracking in the concrete. For such damaging expansion to occur, all of the following conditions must be present simultaneously: a critical amount of reactive mineral species; a sufficiently high alkali hydroxide concentration in the pore solutio
21、n; a sufficient supply of water. Effective specifications to avoid damage from the reaction are based on ensuring that at least one of these conditions is absent. NOTE Another type of reaction between reactive mineral species in the aggregates and the alkaline pore solution, which has been reported
22、(e.g. from Canada and China), is the alkali-carbonate reaction. As alkali-carbonate reaction has not been recognised as a significant problem in Europe, it is not covered by this Technical Report. 3 Elements of specifications In order to promote the sustainable use of locally available materials, it
23、 is important to tailor the precautions to the environment that the structure is exposed to as well as to local experience in building practice. Based on these principles, specifications for avoiding a damaging ASR in concrete are given within the following structure: a) characterisation of the envi
24、ronment (environmental category): 1) degree of saturation of the concrete with water; 2) alkali supply; 3) further aggravating factors. b) undertaking recommendations for precautionary measures appropriate to concrete, depending on the environmental category. 4 Characterisation of environment When a
25、ll the necessary compositional factors are present, the likelihood and extent of damaging alkali-silica reaction is dependent on the environment. Three levels of categorisation of environment are therefore appropriate: E1: the concrete is essentially protected from extraneous moisture; E2: the concr
26、ete is exposed to extraneous moisture; E3: the concrete is exposed to extraneous moisture and additionally to aggravating factors, such as de-icing agents, freezing and thawing (or wetting and drying in a marine environment) or fluctuating loads. PD CEN/TR 16349:2012CEN/TR 16349:2012 (E) 6 More deta
27、ils on the factors affecting the environmental categorisation are given in Table 1. Table 1 Environmental categories Environmental categories Description Exposure of the concrete a,b,cE1 Dry environment protected from extraneous moisture - Internal concrete within buildings in dry aservice condition
28、s E2 Exposed to extraneous moisture b- Internal concrete in buildings where humidity is high; e.g. laundries, tanks, swimming pools - Concrete exposed to moisture from the external atmosphere, to non-aggressive ground or immersed in plain water or permanently immersed in seawater c. E3 Exposed to ex
29、traneous moisture plus aggravating factors - Concrete exposed to de-icing salts - Concrete exposed to wetting and drying by seawater cor to salt spray - Concrete exposed to freezing and thawing whilst wet - Concrete subjected to prolonged elevated temperatures whilst wet - Concrete roads subject to
30、fluctuating loads aA dry environment corresponds to an ambient average relative humidity condition lower than 75 % (normally only found inside buildings) and no exposure to external moisture sources. bA risk of a damaging ASR may exist for concrete that is unlikely to dry significantly during its se
31、rviceable life, even in a dry environment. Corresponding concrete structural elements should be included in category E2 and their dimensions may be defined in national specifications. cConcrete constantly immersed in seawater does not suffer a higher risk of ASR than a similar element exposed to hum
32、id air, buried in the ground, or immersed in plain water, because the alkali concentration of sea water is lower than the alkali concentration of the pore solution of most concretes. 5 Precautionary measures appropriate to concrete 5.1 General remarks Depending on the environmental category, precaut
33、ionary measures have to be applied. The type of measure, as well as the limits and levels in a measure itself, shall be defined on a national level because they depend on the national safety margin, the experiences of building practices, and the geology and climate. Precautionary measures include: a
34、) no measures necessary; b) use of a non-reactive aggregate combination; c) limiting the alkalinity of the pore solution by: 1) the use of cement with a low effective alkali content; 2) the use of an adequate proportion of slag, fly ash, silica fume or other pozzolana (in cement or as an addition);
35、3) conforming to a numerical limit on the effective alkali content of the concrete; 4) verification of the suitability of a concrete mix in a performance test. PD CEN/TR 16349:2012CEN/TR 16349:2012 (E) 7 NOTE The appropriate precautionary measures for different environmental categories are found in
36、the provisions valid in the place of use. Examples are the proportion of the fly ash/ground granulated blastfurnace slag (ggbs) that is necessary to avoid a damaging ASR, or the limit on the effective alkali content of the concrete. Such examples differ between CEN member countries and depend on bot
37、h the reactivity of the aggregate combination and the national determined safety margin. 5.2 Use of cement with a low effective alkali content In the case of low-alkali Portland cements (CEM I), an upper limit of 0,60 mass % Na2O-equivalent is generally applied. The use of such low-alkali cements ha
38、s been found to be effective in some regions in preventing ASR damage. This measure may not be effective in the case of concretes with unusually high cement contents, concretes with significant alkalis from constituents other than the cement, if there are significant sources of extraneous alkali (e.
39、g. concrete roads), or if the passage of moisture concentrates the alkalis in certain parts of the structure. Other cement types with low effective alkali content can be manufactured (for example cement types containing slag, fly ash or natural pozzolanas as a main constituent). The allowable alkali
40、 content depends on the percentage of slag, fly ash or natural pozzolanas, although there is no agreed value at European level. 5.3 Use of slag, fly ash, silica fume or other pozzolana (in cement or as an addition) The use of slag, fly ash, silica fume or other pozzolana (in cement or as an addition
41、) can be very effective in preventing ASR damage. Fly ashes conforming to EN 450-1, ground granulated blastfurnace slag (ggbs) conforming to EN 15167-1 and silica fume conforming to EN 13263-1 have been well-established as effective concrete additions. The effectiveness of cement types containing si
42、liceous fly ash, natural pozzolanas or granulated blastfurnace slag conforming to EN 197-1 is also well-established. Both provide effective protection against ASR damage, provided a sufficient proportion (as a proportion of the total cementitious material) is used. The proportion necessary depends o
43、n the reactivity of the aggregate combination and the properties of the granulated blastfurnace slag/fly ash/silica fume/natural pozzolana. The requirements naturally differ between CEN member countries. 5.4 Limiting the effective alkali content of the concrete The alkalinity of the pore solution is
44、 primarily dependent on the alkali content of the concrete mix. The effective application of limiting the effective alkali content of the concrete requires either the classification of all constituents used for a specific concrete mix with respect to their effective alkali content, or the quality as
45、sured declaration of the average alkali level of each constituent and a measure of its variability. All constituents may contribute alkalis, but usually the majority of effective alkalis come from the Portland cement clinker. When using, granulated blastfurnace slag, fly ash, silica fume or other po
46、zzolana, the contributions to the effective alkali content of the concrete depend on the proportion used and their reactivity. If concrete is exposed to de-icing salts, the contribution of the de-icing salts to the effective alkali content of the concrete shall be considered. NOTE 1 CEN/TC 154 is ta
47、sked with developing and publishing a test method for measuring the releasable alkalis from aggregates. NOTE 2 CEN/TC 51 is tasked with developing a procedure for determining the effective alkali content of cement and additions and a way of reporting this information to users. PD CEN/TR 16349:2012CE
48、N/TR 16349:2012 (E) 8 NOTE 3 EN 206 cannot contain limits on the effective alkali content of concrete, as this depends on the classification of the reactivity of the aggregate combination and the national safety margin. However, in a future revision of EN 206, it is expected that a common method for
49、 calculating and reporting the effective alkali content of concrete will be included. 5.5 Verification of the suitability of a concrete mix in a performance test Performance tests have been used in several CEN member countries for more than a decade. They are presently covered by national provisions. With the aim to propose for European standardisation a robust common procedure, RILEM technical Committee 219-ACS is tasked with reviewing and developing test methodologies for the reliable accelerated perfo
