'.

Guidance notes and model specification clauses

Report of a Working Party

October 1987

,ForewordThe Guidance Notes aimed at minimising the risk of Alkali-Silica Reaction (ASR) werefirst published in 1983 and tilled a vacuum in a subject that continues to cause concernto engineers and contractors alike.

Since publication the \X'orking Party has remained in touch with developments on thissubject through its subsequent affiliation to The Concrete Society. During this period itbecame apparent that in addition to the need to keep abreast of developments there wasa widespread need tor guidance towards writing specifications on the subject. Thesecond edition of the Guidance Notes published in 1985 was a direct result of thisdemand and was prepared as a consultation document. The resultant comments havemade a valuable contribution to the preparation of the present edition.

In revising the Guidance Notes, the Working Party has been very conscious of the factthat the subject is continuing to develop. This is reflected in changes which have beenmade to the advice given in this edition. In order to arrive at an acceptable resolution ofthe conflicting demands of safety, economy and best use of available materials, furtherresearch will be required which may lead in turn to new ways of approaching ASR

The intervening years since the first publication have confirmed the limitedgeographical extent to which the general problem exists throughout the country and itsserious threat to the durabilitv of concrete. Furthermore, there are indications that thephenomenon is not unrelated to other forces affecting the durability of concrete. Thefact remains however that when compared with the amount of concrete constructionundertaken, damage by ASR affects only a small proportion. Nevertheless, when it doesoccur the cost of remedial work can in some cases be very high.

It has been recognised during the preparation of this report that recommendations forminimising the risk of ASR vary from country to country around the world, according tolocal circumstances. The model specification clauses and the guidance given arespecifically for the United Kingdom (which includes the Isle of Man, the ChannelIslands and Northern Ireland). Advice given in this document may therefore not bereadily applicable in other countries such as the Repub!ic of Ireland, where it isunderstood British Standards and other UK publications are used frequently as a basisof specifications.

\X'hilst this work represents current advice, it is inevitable that as research andexperience develops modifications may need to be made from time to time. TheWorking Party will arrange to publish any significant amendments to the advice at thefirst opportunity and in due course incorporate any changes in a subsequent reprint ofthe guidance notes. As before it is hoped that this document will provide a valuablebackground to the problem confronting engineers and contractors alike and assist ineliminating this defect. I am particularly grateful to the dedication and professionalismof those members of the Working Party for their contributions towards this work.

M R HAWKINS

Chairman of the Working Party

Addition to ForewordThe Societ y's Working Party is aware that conflicting advice exi~ts o~ a~kalilevels in binders (see section 5) and has set up a separate mult1dlsc~plmedTechnical Sub-Committee to examine this subject in greater detail.When available this sub-committee's findings and any recommendationswill be pu blished.25 Norcmbcr 1987

I

Members of the Working Party (1984 to 1986)

,\1 R Hawkins, CEng, FICE, FIStructE, MRTPI, FIHT, CountyEngineer and Planning Officer, Devon (Chairman)I3Sc(Eng), DCT, CEng, !\lICE, Department ofTransport (replaced by D B Storrar, Department ofTransport)BSc, CPhys, MInstP, xucr, Rl\lC TechnicalServices LimitedBSc, PhD, CC hem, i\1RSC, Consultant ChemistBSc, CEng, MICE, ACGI, MICT, Blue CircleIndustries PLCBSc(Eng), CEng, MICE, MITD, FGS, FICT,British Readv Mixed Concrete AssociationBSc, DIe, CEng, FlCE, FlStructE, ,\ lSocIS (France),Consultant Engineer representing the Institution ofStructural EngineersBSc(Eng), DIe, CEng, MIStructE, Central ElectricityGenerating BoardMSc, CPhys, MlnstP, Cement and ConcreteAssociation (Secretary)MSc, PhD, Civil and Marine Limited (replacingLJ Huss, Frodingham Cement Company Limited)BSc, CEng, ,\:HCE, Frodingham Cement CompanyLimited (replaced by 0 0 Higgins, Civil and MarineLimited)BSc, PhD, DIC, ARCS, Building ResearchEstablish men tAMCT, CEng, FlCE, FIPHE NorthumbrianWater AuthoritvGroup Technic·al Controller, Arney RoadstoneCorporation LimitedBSc(Eng), OIC, CEng, MICE, Cement and ConcreteAssociationBSc, PhD, CEng, MIMM, MIGeol, FGS, ,\lessrsSandbergBSc, CEng, MICE, Department of Transport(replacing R Adarn, Department of Transport)BSc, CEng, MICE, FlHT, Devon County CouncilBSc, PhD, CEng, MICE, FIAgrE, Mott, Hay andAnderson

R Adarn,

B V Brown,

F G Buttler,A T Corish,

J 0 Dewar,

D K Ooran,

I P Gillson,

W A Gutteridge,

DD Higgins,

L J Huss,

P J Nixon,

W B Norgrove,

P O'Connell,

o Palmer,

I Sirns,

DB Storrar,

NO Waine,J G M Wood,

iCONTENTS

Page

PART 1. GUIDANCE NOTES 7

INTRODUCTION 7

2 ALKALI-SILICA REACTION 7

3 MINIMISING THE RISK OF ASR 83.1 Moisture from the environment 83.2 Alkalis 8

3.2.1 General recommendations for reducing alkalis 83.2.2 Use of low alkali cement 83.2.3 Limiting the reactive alkali content of concrete 9

3.3 Selecting aggregates 9

4 LEVEL OF PRECAUTIONS 9

4.1 Risks and consequences 94.2 General concrete construction 94.3 Particularly vulnerable construction 9

5 ALKALI CONTENT OF CEMENTITIOUS MATERIAL 95.1 Portland cement 95.2 Ground granulated blastfurnace slag and pulverised fuel ash 105.3 Portland blastfurnace cement, low heat cement and pulverized

fuel ash cement 105.4 Microsilica 10

6 AGGREGATES 10

6.1 Reactive minerals 106.2 Tests for reactive aggregates 116.3 Assessment of aggregates 11

6.3.1 Initial consideration 116.3.2 Aggregate unlikely to be reactive 116.3.3 Artificial aggregates 126.3.4 Aggregates containing Chert and Flint 126.3.5 Aggregate combinations 12

7 OTHER POSSIBLE FACTORS 127.1 Alkali migration 137.2 Alkalis other than from cernentitious materials 137.3 Precautions against alkali migration and alkalis other than

from cernentitious materials 137.4 Variations in cement content or source of cement 13

8 EFFECT OF PRECAUTIONS ON CONCRETE PROPERTIES 13

8.1 General durability 138.2 Other concrete properties 13

9 CONCRETE MIX DESIGN 149.1 Using cement containing less than 0.60/< reactive alkali 14

9.1.1 Certified maximum acid soluble alkali level 149.1.2 500/< ground granulated blastfurnace slag 14

9.2 Limiting the reactive alkali content to 3 kg/rrr' of concrete 149.2.1 Limiting the Portland cement content of the concrete

(Tables 2 & 3) 149.2.2 Use of 25';; or more ggbfs or pfa 14

5

10 CALCULATING THE REACTIVE ALKALI CONTENTOF THE CONCRETE 1710.1 Factory-made cements 1710.2 Site combinations of Portland cement with either ggbfs or pfa 1710.3 Factory-made cements in conjunction with aggregates

containing chlorides 1710.4 Site combinations of Portland cement with either ggbfs or pfa

in conjunction with aggregates containing chlorides 17

11 A PROCEDURE FOR DETERMINING PRECAUTIONSAGAINST DAMAGE FROM ASR 1711.1 Application of the Guidance Notes 1711.2 Assessing the degree of risk and likely consequences 1811.3 Summary of Precautions 1811.4 Where no specification requirements may be necessary 1811.5 Particularlv vulnerable structures 1811.6 Further co~siderations 1811.7 Flow chart 20

PART 2. DESCRIPTION OF MODELSPECIFICATION CLAUSES

12 INTRODUCTION TO THE MODEL SPECIFICATIONCLAUSES 20

13 BASIS FOR THE USE OF THE MODEL SPECIFICATIONCLAUSES 20

14 MATTERS COVERED BY THE MODEL SPECIFICATIONCLAUSES 21

PART 3. MODEL SPECIFICATION CLAUSES FORMINIMISING THE RISK OF THE ALKALI-SILICAREACTION IN CONCRETE15 PRECAUTIONS AGAINST ALKALI-SILICA REACTION (ASR)

IN CONCRETE

16 CEMENTITIOUS MATERIALS (HYDRAULIC BINDERS):DEFINITIONS AND GENERAL CLAUSES

17 MINIMISING THE RISK BY USING PORTLAND CEMENTCONTAINING LESS THAN 0.6% REACTIVE ALKALI

18 MINIMISING THE RISK BY LIMITING THE REACTIVEALKALI CONTENT OF THE CONCRETE TO 3.0 kg/m!

19 MINIMISING THE RISK BY USING SELECTEDAGGREGATES

20 WATER

21 ADMIXTURES AND PIGMENTS

Appendix 1Appendix 2

Chemistry of the alkali-silica reactionWorked examples to illustraterecommendationsGuidance for the assessment ofrock types not included inTable 4 (19.2 (a) of PART 3)British Standards and other publicationsmentioned in the textBibliographyDefinitions

Appendix 3

Appendix 4

Appendix 5Appendix 6

20

22

22

22

23

24~'.',

26<~

]26 'I

j27

:1:1

27 IJ"I

28 jq

30

313233

PART 1. GUIDANCE NOTESA summary appears in Section 111 INTRODUCTIONThe Guidance Notes are based on the best information available at the present time.They give only the basic essential information on the circumstances under whichdamage caused by Alkali-Silica Reaction could occur and how to avoid or minimise suchdamage in new concrete construction. Further reading will be necessary for a greaterunderstanding of the subject and a bibliography is given in Appendix 5 which alsocontains a list of other committees concerned with ASR.

,\lore is now known of the problem and the means by which the risks can be reducedthan was the case in 1983 when the first edition was published. This revised editionincorporates the new knowledge and moreover puts forward Model Clauses whichEngineers might find helpful in the preparation of specifications designed to minimisethe risk of ASR.

Several significant changes to the recommendations have been made since 1983. Theseinclude extra precautions which recognise the important relationship between sodiumchloride and the development of ASR, and the contribution made to the reactive alkalisin concrete by ground granulated blastfurnace slag (ggbfs) and pulverized-fuel ash (pfa).There is in addition a relaxation, as it is now considered that aggregates containing morethan sixty percent chert or flint are unlikely to cause damage.

The incidence of damage diagnosed as being caused by ASR in the United Kingdom I isvery small when compared with the total amount of concrete construction carried out.Between the first reported occurrence in 1976 and publication of the first edition of theGuidance Notes in 1983, about fiftv cases were identified. The recorded instances havenow (1986) risen to over one huri"dred although these are not distributed uniformlythrough all forms of construction. The frequency with which ASR occurs appears atpresent to be greater in certain regions, for example the Midlands and the South West,than in others, The increasing transportation over long distances of both materials andconcrete products means that the potential for damage from ASR will not be restrictedto particular regions.

The effects of ASR in different structures range from extensive areas of cracks severalmillimetres wide which are still growing after fifteen years to slight map crackingshowing little or no change after more than twenty years. The most serious cases haverequired major strengthening or replacement works, while the slight cases need onlyextra care in moisture protection and long-term monitoring as the reaction continues.

These Guidance Notes are based on conditions, practices and materials known to havebeen used in the United Kingdom at the time of drafting. They will not necessarilyapply in other countries.

( .

2 ALKALI-SILICA REACTIONThree types of reaction, namely the alkali-silica, alkali-silicate and alkali-carbonatereactions, can occur between aggregates and the alkali hydroxides of sodium andpotassium which are produced by the hydration of cement (See Appendix 1.). TheseGuidance Notes deal on lv with alkali-silica reaction, ASR, as the other reactions arerare. However some instances involving a possible alkali-silicate reaction in coarseaggregate have been reported recently in the UK Little is known about this reaction andit is not clear to what extent the advice given in this document applies to such cases.

Damage from ASR can occur when the hydroxyl ions present in the pore solution of aconcrete react with certain forms of silica in the aggregate to form a gel which absorbssome of the pore fluid, swells and exerts a pressure which can crack the concrete.

ASR causes damage only if all the following three factors are present:

(i) sufficient moisture - see Section 3.1

(ii) a sufficiently high alkalinity - see Section 3.2

(iii) a critical amount of reactive silica in the aggregate - see Section 6.

, In the context and lhrou~holllthis document the phrase 'L'niled Kingdom' refers to GreatBritain, :-:onhcrn Ireland. the Chunnel Islands andthe Isle of .\tan,

7

If anyone of these factors is absent, then damage from ASR will not occur and noprecautions need be taken.The recommendations given in these Guidance Notes tor minimising the risk of damagefrom ASR in new concrete construction are based on ensuring that at least one of thefactors (i), (ii), or (iii) above, is absent.

In the small number of instances where ASR has been diagnosed and is continuing tocause distress in a structure, there are at present no methods which can be reliablyrecommended tor either preventing further damage or carrying out effective and lastingrepairs. However, limiting the access of moisture to an affected structure may retard therate of deterioration.

3 MINIMISING THE RISK OF ASR3.1 Moisture from the environmentDamage from ASR can occur only when the concrete is damp. Only when the internalrelative humidity is reduced after curing to below 757< can the cracking from ASR beprevented. However, once the reaction has occurred and sufficient gel has formed, anyincrease in the humidity can lead to rapid expansion.

Where the concrete can be consistent lv maintained with an internal equilibrium relativehumidity ofless than 75~;;,other precautions will be unnecessary. This can be the case indry, well-ventilated parts of buildings but not in foundations, even if waterproofed, norwill it apply to cladding and external beams or members where condensation can occur.Special care will be required when concrete is exposed to warm, humid conditions, e.g.swimming pools.

As a guide, structures and structural elements which have been identified as sufferingfrom ASR in the United Kingdom include: foundations in a range of ground conditions;water-retaining structures; exposed concrete frames and panels of buildings; concretemembers protected from the rain under bridges; bridge columns, beams and parapets;and internal members subject to either condensation or high humidity.

3.2 Alkalis3.2.1 General recommendations for reducing alkalisDamage to concrete due to ASR is unlikely to occur if the amount of reactive alkali(DI6)' is limited by adopting one of the methods described below (not given in anyorder of preference) which refer to the reactive alkali content (DI5) of the cementitiousmaterial (D8). If alkalis in excess of'O.Zkg/rn' of concrete come from other sources they.must be taken into account.

Reference should be made to BS 1957:1953 for guidance on the presentation ofnumerical values.

3.2.2 Use of low alkali cement (See Model Specification Clause 17)Using

(a) cementitious material (D8) (see Section 5.1) with a reactive alkali content(DI7) 01'0.67< or less, in accordance with Sections 9.1.1 and 9.1.2;

(b) a combination (DlO) of ordinary Portland cement to BS 12 witha minimum of50';{ ggbfs (D4) to BS 6699 in accordance with 9.1.2;

(c) low heat Portland-blastfurnace cement to BS 4246;

(d) Portland-blastfurnace cement to BS 146 containing a minimum 01'50,/; ggbfs.

In these instances the maximum acid soluble content (DB) of the combination ofcement and the gghls must no! exceed 1.1'.;. The 1.1',; limit is consistent with UK andContinental experience.

3.2.3 Limiting the reactive alkali content 'If the concrete(See Model Specification Clause 15.)

Using(a) a Portland pulverized-fuel ash cement to BS 6588;

a combination of ordinary Portland cement to BS 12 with pulverized-fuel ash(pfa) (D5) to ~~~3~'-'~ ~l:,_' 1,

a Portland-blastfurnace cement to BS 146;a combination of ordinary Port' 'ld cement to BS 12 with ggbfs toBS 6699.

The target mean (D26) pfa or ggbfs content of the cementitious material should be atleast 25',1; by mass and the reactive alkali content of the concrete should be 3.0 kg/m' orless calculated in accordance with Section 10.(b) Limiting the reactive alkali content of the concrete (DI6) to 3.0 kg/m' or less, in

accordance with Sections 9.2.

3.3 Selecting Aggregates

3.3.1 An alternative method of taking precautions is to make sure that the aggregateis not reactive by following the recommendations given in Section 6.

4 LEVEL OF PRECAUTIONS4.1 Risks and consequences

The advice given in these Guidance Notes is aimed at ensuring that the risk of damagefrom ASR in concrete is minimised. The Engineer has to decide not only the likelihoodof damage occurring, but also the risks and economic consequences of such damage.When these are considered to be acceptable, specific precautions against ASR need notbe taken.

4.2 General concrete construction

In general, concrete construction is not particularly vulnerable to damage from ASR. Ifprecautions are considered necessary because of a moist environment (see Section 3.1),any of the methods described in Sections 3.2 and 3.3 should prove an adequate safeguard.

4.3 Particularly vulnerable construction

Construction in this category includes:

Concrete frequently saturated or in areas of high humidity, such as highway structures,multi-storey car parks, water retaining structures and buried concrete.

Analysis of affected concrete in this vulnerable category has indicated that method3.2.3(b) which limits the alkali in the concrete to the nominal 3.0 kg/m' defined in ModelClause 18.1 may not in itself produce a sufficient margin of safety against damage. 3

4.3.1 The methods described in Sections 3.2.2( a), (b) and 3.2.3( a) are believed to givesufficient safeguards for particularly vulnerable forms of construction.

5 ALKALI CONTENTS OF CEMENTITIOUS MATERIALS5.1 Portland cement

Portland cements which comply with the requirements given in BS 12 contain alkalisderived from the raw materials. The level of alkalis inherent in these is the dominant

It should be noted in relation to hi~hway structures that in the oth Edition ofthe Specification for Hi~h\\'aY \\'orks; August 1986 the DepartmentotTransport employs a method otculculating reactive alkalis in concrete which makes an allowance in respect ofcement alkali vuriabilirv. Thisetlcctivctv provides a lower reactive alkali limit in concrete that' tbc nominal 3,0 kgm' calculated in accordance with Sections 3,2.3 (h)and l),2,

9

int1uence on the ultimate level of alkalis in the Portland cement. Whilst themanufacturing process can also influence, it is of less importance than that due to theraw materials. The alkali content of these BS 12 Portland cements is measured assodium oxideand potassium oxidet Na.O and K!O) and is expressed as the sodium oxideequivalent (012).The annual average alkali levels of cements manufactured in the UK which conformwith the requirements ofBS 12 now range from 0.4'7,to 1.07.,expressed as sodium oxideequivalent. The national average, weighted for production tonnage, is currentlyaround 0.65';;. -The precision of the analytical method is such that reporting single results to the nearestO.OYi; is not justified, and values reported by competent laboratories could differ byO.OY;;sodium oxide equivalent. Further information is given in the Concrete SocietyTechnical Report No 29 'Changes in Portland cement properties and their effect onconcrete'.Cement manufacturers will on request, supply the certified average acid soluble alkalilevels (022) at the time of delivery and will advise on future alkali levels on request.They will also supply a sulphate-resisting Portland cement (srpc) to BS4027 (D7) with acertified maximum acid soluble alkali content (025) of 0.67. sodium oxide equivalentprovided that this certification is requested at the time of ordering. If this certification isnot obtained srpc will not necessarily have an acid soluble alkali content below 0.67..Some variation in acid soluble alkali level is inevitable in the production of cement andthis may occasionally amount to ±O.15/; about the certified average. The limit placedon the alkali content of concrete recommended in Section 9.2 includes anallowance for this variation.

5.2 Ground granulated blastfurnace slag to BS 6699 and pulverised-fuelash to BS 3892: Part 1

Both ggbfs and pfa can have comparatively high levels of total alkali. Most of this alkaliis combined in the glassy structure of these materials and is released relatively slowly asthe ggbfsor pfa hydrate in the concrete. Alkalis derived from this source do not appear tobe available to promote the alkali-silica reaction in the same manner as those derivedfrom Portland cement, but the inhibiting mechanism is not fully understood. A smallproportion of the alkalis will however contribute to the alkalinity of the pore solution inthe early stages of hydration and should be included in any calculation relating to thereactive alkali content of the concrete (016).

5.3 Portland-blastfurnace cement to BS 146, Low heat Portland-blastfurnace cement to BS 4246, Portland pulverized-fuel ash cementto BS 6588

For these factory made cements (027) the manufacturers will on request certify theaverage acid soluble alkali levels. Where either ggbfs or pfa is combined with ordinaryPortland cement on site it will be necessary to include the reactive alkali content ofeither the ggbfs or the pfa in calculating the reactive content of the concrete.Note:The procedure for measuring the reactive alkali in both ggbfs and pfa incorporates theextraction method for sand given in BS 812 Part-l: 1976 and the test method for cementgiven in Clause 16 AMO 4260 BS 4550 Part 2 except that the multiplier will be thatgiven in Clause 16.11 (b) of the Model Specification. Further information about thereactive alkali levels of these materials may be obtained from the manufacturers.

5.4 Microsilica (also known as condensed silica fume)j\ ticrosilica or condensed silica fume (csf) is a generic name for a range ofby-products ofthe silicon and ferro-silicon smelting industry. Some have been used with apparentsuccess in the control ofASR elsewhere in the world (e.g. Iceland). However, experienceof microsilica is at present very limited in the UK and no recommendation can yet beoffered for its use in minimising the risk of ASR.

6 AGGREGATES6.1 Reactive mineralsThe reactive constituents in the cases of ASR so far identified in the UK arcmicrocrystalline and cl}'plOcr~:s.tallinesilica and chalcedony found in flints and cherts,

10

and possibly also strained quartz in some quartzites. In many of these cases the reactiveconstituents have been found in the fine aggregate when this has been combined with anon-reactive coarse aggregate, but in some cases reaction has occurred in the coarseaggregate.

ASR has occurred in Jersey as a result of the presence of opaline silica as a minorconstituent in the crushed igneous rock coarse aggregate. No such cases of ASR havebeen found elsewhere in the UK and there is no record of any significant quantity ofopaline silica being found in land based or sea dredged aggregates currently used forconcrete on the UK mainland. Sources of aggregate known to contain opaline materialshould not be used even when the alkali content of either cementitious material or theconcrete is being controlled.

6.2 Tests for reactive aggregatesThere are at present no British Standard tests for the alkali-reactivity of aggregates,although a BSI Working Group is currently evaluating a range of test methods and aprocedure for petrographical examination of aggregates is being considered forinclusion in BS 812.

Two tests commonly used in other countries were developed in the United States. Theyare ASTM C289-81 (Chemical Method) and ASTM C227-81 (Mortar-bar Method).However, these tests do not appear to be a practical basis for the specification ofUKconcrete materials.

The ASTM Chemical Method will usually classify aggregates containing chert or flint,and sometimes quartzite, as being 'deleterious' or 'potentially deleterious'. This iswidely regarded as being unduly pessimistic, especially since the method does not assessthe effects of varying the combination of coarse and fine aggregates. Because a largeproportion of British fine aggregates contain chert, flint or quartzite, source by sourcetesting by this method will not provide useful information.

The ASTM Mortar-bar Method has been considered internationally to be the mostreliable test presently available, bur to date no UK aggregates in known use have beenshown to be deleterious by this test under the standard conditions, including aggregatesof the types involved in reported cases of ASR. This indicates that UK aggregates cannotbe effectively classified by this method.

Preliminary indications suggest that expansion tests on concrete prism specimens mightbe more appropriate for UK aggregates and a test method using concrete specimens isbeing developed by the BSI Working Group. In due course, it may become possible toinclude a concrete prism test for aggregates in the Model Specification Clauses.

6.3 Assessment of aggregates6.3.1 Initial considerationsGiven the present difficulties with the application of test methods, extensive testing ofan aggregate is not appropriate in the majority of cases. However, consideration of thecomposition may enable a decision to be made as to whether an aggregate is unlikely tobe reactive, or contains constituents which are sometimes found to be reactive.Assessment of aggregates should take place as soon as practicable and preferably beforeContract letting.

In many cases, a rudimentary consideration of aggregate composition will suffice, butoccasionally a more detailed assessment of the aggregate, including petrographicanalysis, may be considered.

6.3.2 Aggregate unlikely to be reactiveAt present, it is considered that aggregates consisting wholly of the rock and mineraltypes listed in Table 1 (using the petrological terms listed in BS 812: Part 102: 1984, plustwo common mineral types) would be classified in the UK as 'unlikely to be reactive'.'Wholly' in this context means:

(a) the fine and coarse aggregate each consist of at least 9S7r of the rock or mineraltypes listed in Table 1.

(b) the aggregate source does not contain any detectable opal or sufficientpotentially reactive silica to cause damage from the alkali silica reaction. Formsof silica such as Ilint or chert (which may occur in limestones) or chalcedony(which may occur in igneous or other rocks) should not be present in sufficientquantity to cause damage from ASR. No cases of ASR in the UK have beencaused by such contamination of crushed rock aggregates. Experience to date

11

from cases of ASR involving sands ami gravels indicates that up ro a maximumof S'Ic by mass of flint, chert or chalcedony taken together in the combinedaggregate can be tolerated. The engineer may consider setting a specific limitless than S'lr for a particular project but the variability of natural materials andthe accuracy of the method of assessment should be taken into account.

Rocks and minerals unlikely to be reactiveTable 1.

AndesiteBasaltChalk'DioriteDoleriteDolomite

Feldspar"GabbroGneissGraniteLimestoneMarble

MicrograniteQuartz!' -'SchistSlateSyeniteTrachyteTuff

Notes on Table 1:

1. Chalk is included in the list since it may occasionally be a minor constituent of concrete aggregates.2. Feldspar and quartz are not rock types but are discrete mineral grains occurring principally in fine

aggregates.3. ~ot highly-strained quartz and not quartzite.

Some further guidance for the assessment of aggregate samples containing rock typesnot included in Table 1 is provided in Appendix 3. It should be recognised that allnatural aggregate sources may be expected to exhibit variations in both composition andproperties as extraction proceeds.

A high proportion ofUK aggregates contain flint and/or quartzite materials and usuallyit will not be economicallv feasible or desirable to avoid their use. However, in thesecases there is a risk that th~ aggregate will be susceptible to ASR when the other factors,sufficient moisture and alkalis are present.

6.3.3 Artificial aggregatesLimited information is currently available for the assessment of artificial aggregates andspecialist advice should be obtained. However, at present it seems that air-cooledblastfurnace slag, expanded clay or shale or slate and sintered pfa aggregates maybeconsidered to be non-reactive in UK conditions.

6.3.4 Aggregates containing Chert and FlintOne feature of ASR is that damaging expansion occurs when a critical proportion (or'pessirnum') of the reactive silica is present in the concrete. In many cases, expansionwill be either lower or non-existent when the proportion is significantly different ineither direction from this critical amount. Knowledge of pessimum proportions in UKaggregates is not yet complete. However, few cases of significant damage due to ASRhave been recorded in regions of the UK where the sources of both fine and coarseaggregate contain a high proportion offlint or chert. It is currently considered that acombination offine and coarse aggregate which contains more than 60'k by mass offlintor chert is unlikely to cause damage due to ASR.

6.3.5 Aggregate combinationsIt should be recognised that, even where an aggregate has proved in practice to be non-expansive when used as both fine and coarse material in the same mix, it might causedamaging expansion when either fraction is used in conjunction with a different, non- --reactive aggregate. This might arise if~ by so combining the aggregates, the criticalproportion of reactive material were approached.

7 OTHER POSSIBLE FACTORSWhen assessing whether carnage due to ASR could occur, there may be other factorswhich need considering.

12

7.1 Alkali migrationThe passage of moisture through concrete can cause alkalis to migrate and createtemporary or permanent concentrations of these in some regions of the concrete. Oneexample of where this can occur is in foundation blocks where the tops are exposed,allowing water to evaporate from the surface. Opinions vary on whether, or by howmuch, alkali migration can cause or increase damage due to ASR.

7.2 Alkalis other than from cementitious materialsNo significant amounts of reactive alkali will be derived either from potable water or(chlorides excepted) from natural aggregates in the UK

Where there is a possibility that sodium chloride will be incorporated in the mix, e.g.from salt in aggregates or from seawater used for mixing, the alkali contributed to theconcrete by the sodium chloride should be included in the calculation of the totalreactive alkali content of the concrete if the reactive alkali.level is being controlled. Evenwhen low alkali cements, with a maximum acid soluble alkali content of 0.67< are used,account should be taken of reactive alkalis from other sources when these exceed 0.2kg/m' (see 3.2.1). If, however, the aggregate can be regarded as non-reactive no accountneed be taken of the sodium chloride for the purpose of minimising ASR.

There are no admixtures known to prevent damage due to ASR. It is also necessary totake into account the reactive alkali content of anv admixture used.

Alkali salts may be absorbed by hardened concrete in contact with seawater, somegroundwaters a-nd other materials such as de-icing salts. Whilst opinions vary on theextent to which such external sources of alkalis can cause or increase damage due toASR, these factors should not be ignored.

7.3 Precautions against alkali migration and alkalis other than fromcementitious materials

Not enough is known about the effects of alkali migration or external alkalis to enablerecommendations to be made on what additional precautions against damage from ASRmay be necessary, if any. Where considered essential, it may be wise to ensure that sucheff~cts cannot cause damage, This may be done by tanking or otherwise protecting theconcrete, by making sure the aggregates are non-reactive, or by compensating for theadditional alkali by reducing the recommended maximum alkali contents of theconcrete or cernentitious material.

7.4 Variations in source of materialsThe cernentitious content of the mix may differ from that given in the specification ordetermined by trial mixes. Normal fluctuations about the assumed figure are notthought to be large, but action should be taken to avoid large variations, alterations inthe alkali content, or changes in the sources of materials which might lead to theconcrete or cernentitious material alkali content limit being significantly exceeded.

8 EFFECT OF PRECAUTIONS ON CONCRETE PROPERTIESWhen deciding what precautions to take, if any, to avoid damage from ASR, the overallperformance of the concrete must be kept in mind.

8.1 General durabilityASR is only one phenomenon which could affect the life of the concrete. For themajority of structures, action to reduce the risk of ASR should not detract from theimportance of considering the concrete's resistance to weathering and other potentiallydestructive agencies, and the ability of the concrete to protect reinforcement and otherembedded metal. It is essential that adjustments which may be made to the mix in orderto avoid ASR should never lead to the use or materials, cement contents or water/cement ratios which will be inadequate to ensure general durability.

8.2 Other concrete propertiesIn selecting materials or mix proportions to avoid damage due to ASR, considerationshould be gi\'t~n to the etlcct or these on other desired properties or the concrete,

13

including colour, workability, early and later strengths, heat evolution, shrinkage andcreep. The cost, availability and convenience of using alternative materials, mixes orconstruction methods also will he important considerations.

99.19.1.1

CONCRETE MIX DESIGNUsing a cement containing less than 0.6%reactive alkaliUse of cementitious material having a certified maximum acidsoluble alkali content of 0.6%

The use of Portland cement with an alkali content ofO.67ror less is accepted worldwideas a means of minimising the risk of damage due to ASR, providing that there is nosignificant addition of reactive alkali from other internal sources such as aggregates andadmixtures and external sources such as de-icing salt.When significant reactive alkalis are contributed from other sources to a mix usingcement having a certified maximum acid soluble alkali content ofO.67r, the averagereactive alkali content of the concrete should be calculated in accordance with 10.3and 10.4.If the reactive alkali content of a particular Portland cement is known and is above 0.67rthen the 0.67r limit can be achieved by replacing part of the Portland cement by therequisite amount of ggbfs or pfa providing that at least 257r of either is used.

9.1.2 Use of 50%or more ground granulated blastfurnace slag to BS 6699A combination which contains 507r or more ggbfs and ordinary UK Portland cement toBS 12, is considered equivalent to a Portland cement with 0.6% maximum acid solublealkali content (see Section 9.1.1), provided that the acid soluble alkali content of thecombination is less than 1.17r.

Low heat Portland-blastfurnace cement to BS 4246 and Portland-blastfurnace cementto BS 146 containing a minimum of 50% granulated slag will be similarly effective.

9.2 Limiting the reactive alkali content to 3.0kg/cubic metre of concrete9.2.1 Use of Portland cementThe calculated reactive alkali content of the concrete, calculated using the appropriateequation from Section 10, should be 3.0 kg/m! or less. The variation of±0.15% aboutthe certified average referred to in 5.1, will lead occasionally to alkali levels in theconcrete approaching 3.75 kg/rn '. An allowance for this variation has been included inthe recommendations given in this document. A worked example is given in Appendix 2.As an alternative to considering the concrete alkali content directly, it may be preferablewhen writing a specification to limit the alkali content to 3.0 kg/m' by placing a limit onthe Portland cement content of the concrete, calculated using the certified average acidsoluble alkali content of the Portland cement in accordance with Section 10.Maximum Portland cement contents are given in Table 2. Maximum concrete alkalicontents are given in Table 3.

9.2.2 Use of 25%or more ground granulated blastfurnace slag to BS 6699or pulverized-fuel ash to BS 3892:Part 1

A proportion of ordinary Portland cement can be replaced by 25%or more ggbfs or pfa,provided that the reactive alkali content of the concrete is not more than 3.0 kg/m"(calculated using the appropriate equation in Section 10).

14

·Table 2. Target Mean content of factory made Portland cement for use in concrete at nominal3.0 kg/m3 maximum alkali level

Where site blended composite cements incorporating either ggbfs or pfa are used this table does not apply. Anallowance for the reactive alkali content of the ggbfs or pfa or other material can be made using the appropriateequation in 4B, 4C or 4D in 10.

Reactive alkali content ofPortland Cement (D22) to (D25)

(1)0.500.550.600.650.700.750.800.850.900.951.00

Target Mean PortlandCement Content (kg/m')

(2)600545500460430400375350335315300

Notes on Table 2

1. The cement manufacturer will on request advise certified average acid soluble alkali levels which will not beexceeded without notice on a works by works basis.

2. Caution, see BS 8110 in relation to other aspects of durability particularly minimum cement content.

15

TABLE 3. Reactive alkali content of concrete using equation 4A in 10.1

Target Certified Average Reactive Alkali Content ('a') of the Portland Cement (7< Na20 Equivalent)MeanPortlandCementContent .55 .60 .65 .70 .75 .80 .85 .90 .95 1.00(Kg/m')

180 1.0 1.1 1.2 1.3 1.3 1.4 1.5 1.6 1.7 1.8190 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9200 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0210 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1220 1.2 1.3 1.4 1.5 1.7 1.8 1.9 2.0 2.1 2.2230 1.3 1.4 1.5 1.6 1.7 1.8 2.0 2.1 2.2 2.3240 1.3 1.4 1.6 1.7 1.8 1.9 2.0 2.2 2.3 2.4250 1.4 1.5 1.6 1.8 1.9 2.0 2.1 2.3 2.4 2.5260 1.4 1.6 1.7 1.8 2.0 2.1 2.2 2.3 2.5 2.6270 1.5 1.6 1.8 1.9 2.0 2.2 2.3 2.4 2.6 2.7280 1.5 1.7 1.8 2.0 2.1 2.2 2.4 2.5 2.7 2.8290 1.6 1.7 1.9 2.0 2.2 2.3 2.5 2.6 2.8 2.9300 1.7 1.8 2.0 2.1 2.3 2.4 2.6 2.7 2.9 3.0310 1.7 1.9 2.0 2.2 2.3 2.5 2.6 2.8 2.9 I 3.1320 1.8 1.9 2.1 2.2 2.4 2.6 2.7 2.9 3.0 3.2330 1.8 2.0 2.1 2.3 2.5 2.6 2.8 3.0 I 3.1 3.3340 1.9 2.0 2.2 2.4 2.6 2.7 2.9 I 3.1 3.2 3.4350 1.9 2.1 2.3 2.5 2.6 2.8 3.0 3.2 3.3 3.5360 2.0 2.2 2.3 2.5 2.7 2.9 3.1 3.2 3.4 3.6370 2.0 2.2 2.4 2.6 2.8 3.0 3.1 3.3 3.5 3.7380 2.1 2.3 2.5 2.7 2.9 3.0 3.2 3.4 3.6 3.8390 2.1 2.3 2.5 2.7 2.9 I 3.1 3.3 3.5 3.7 3.9400 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0410 2.3 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1420 2.3 2.5 2.7 2.9 3.2 3.4 3.6 3.8 4.0 4.2430 2.4 2.6 2.8 3.0 3.2 3.4 3.7 3.9 4.1 4.3440 2.4 2.6 2.9 3.1 3.3 3.5 3.7 4.0 4.2 4.4450 2.5 2.7 2.9 3.2 3.4 3.6 3.8 4.1 4.3 4.5460 2.5 2.8 3.0 3.2 3.5 3.7 3.9 4.1 4.4 4.6470 2.6 2.8 3.1 3.3 3.5 3.8 4.0 4.2 4.5 4.7480 2.6 2.9 3.1 3.4 3.6 3.8 4.1 4.3 4.6 4.8490 2.7 2.9 3.2 3.4 3.7 3.9 4.2 4.4 4.7 4.9500 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0510 2.8 3.1 3.3 3.6 3.8 4.1 4.3 4.6 4.8 5.1520 2.9 3.1 3.4 3.6 3.9 4.2 4.4 4.7 4.9 5.2530 2.9 3.2 3.4 3.7 4.0 4.2 4.5 4.8 5.0 5.3540 3.0 3.2 3.5 3.8 4.1 4.3 4.6 4.9 5.1 5.4550 3.0 3.3 3.6 3.9 4.1 4.4 4.7 5.0 5.2 5.5

~ote: TABLE 3 applies only to cements which are factory made and to concrete which does not contain alkali fromanv source other than the cement.

16

A,= C x a100

(4A)

10 REACTIVE ALKALI CONTENT OF CONCRETE10.1 Factory-made cementsFor factory made cements (027) the reactive alkali content of concrete is calculated from:

Where A

C= reactive alkali content of concrete (kg/m')

= target mean Portland cement content of concrete (kg/rrr')

= reactive alkali content (7<) of the cement (022) to (025).a

10.2 Site combinations of Portland cement with either ggbfs or pfaWhen cement to BS 12 is combined on site with either ggbfs or pfa the reactive alkalicontent of the concrete is calculated from:

A = (C x a) + (E x d) (4B)100

Where A, C and a are as defined above and

E = target mean content of either ggbfs or pfa in the concrete (kg/m')

d = average reactive alkali content (7c) of either the ggbfs or the pfa asprovided bv the manufacturers.

10.3 Factory-made cement in conjunction with aggregates containingchlorides

When factory made cement is used with aggregate containing salt the reactive alkalicontent of the concrete is calculated as:

A = (C x a) + 0.76((NF x MF) + (NC x MC)) (4C)100

Where A, C and a are as defined above.

The factor 0.76 is obtained from a consideration of the composition of sea water.

NF = chloride ion content of the fine aggregate expressed as a percentage bymass of dry aggregate and measured according to BS 812: Part 4: 1976(in draft as Part 117). See Specification Clause 18.2

NC = chloride ion content of the coarse aggregate expressed as a percentageby mass of dry aggregate and measured according to BS 812: Part4: 1976(in draft as Part 117)

MF = fine aggregate content (kg/m")

MC = coarse aggregate content (kg/m')

lOA Site combination of Portland cement with either ggbfs or pfa inconjunction with aggregates containing chlorides

When cement to BS 12 is combined on site with either ggbfs or pfa and used withaggregate containing salt the reactive alkali content of the concrete is calculated from:

A = (C x a) + (E x d) + 0.76((NF x MF) + (NC x MC)) (40)100

Where A, C, a, E, d, NF, MF, NC, and MC, are as defined above.

11 A PROCEDURE FOR DETERMINING PRECAUTIONSAGAINST DAMAGE FROM ASR

11.1 Application of the Guidance NotesThe recommendations have been prepared for use in the United Kingdom. Becausematerials and standards mav be different elsewhere, the Guidance Notes should not beused in other countries without very careful consideration (Section 1).

17

11.2 Assessingthe degree of risk and consequenceThe Engineer can assess the risk and consequence of damage from ASR to any structureat the design stage from a consideration of the following factors-(i) The importance of each element or the whole structure.

(ii) The cost of taking any particular precautions.

(iii) Materials which are likely to be used.

(iv) Likely cement contents required to achieve the specified concrete strengths.

If damage from ASR is likely to occur, the Specification should include clauses aimed atminimising the risk.

11.3 Summary of PrecautionsDamage from ASR is unlikely to occur if one or more of the following conditions obtains-

(i) The concrete will be in a dry environment (Section 3.1).

(ii) The alkali content of the cementitious material is 0.6'/; or less and alkalis fromother sources do not exceed 0.2 kg/m' of concrete (Section 3.2.2 (a) and (b)).

(iii) The mass of alkalis from all sources in the concrete mix is less than 3.0 kg/m'(Section 3.2.3 (a) and (b)).

(iv) The fine and coarse aggregates are both composed wholly of rock types whichare considered to be non-reactive (Sections 3.3.1 and 6).

(v) The combined fine and coarse aggregates contain more than 607<chert or flint(Section 6.3.4).

11.4 Where no specification requirements may be necessaryWhenever a clause is written into a specification which restricts the producer in hischoice of materials, or requires an additional guarantee, the result may be an additionalcost to the specifier and his client.

There will be many cases where, although there may be no guarantee, it is notconsidered necessary to introduce into the specification additional clauses to minimisethe risk of damage from ASR, either because the possibility of ASR is judged sufficientlyremote, or the additional expense is not warranted.

Examples of circumstances in which specification clauses may not be needed are:

(i) The element is not expected to be exposed to moisture.

(ii) The available sources of cementitious material are known to have certified lowaverage reactive alkali levels.

(iii) Either a ggbfs or pfa at normal replacement level is included in the concrete.

(iv) The Engineer is satisfied that the sources of aggregates have a long historylocally of satisfactory use in concrete.

Because none of the above examples carries any certainty of avoiding damage due toASR, more positive or quantitative advice cannot be given. The decision on whetherprecautions are necessary or not must be made by the specifier, taking intoconsideration the importance of the structure and how closely the expectedconstruction materials and methods come to satisfying the precautions recommended inSection 6.

11.5 Particularly vulnerable structuresSome concrete structures may be regarded as particularly vulnerable or susceptible todamage due to ASR and these may call for more stringent precautions. Examplesinclude water retaining structures and highway bridges. The Department of Transporthas taken note of this in preparing the 6th Edition of the Specification for HighwayWorks (Section 4.3).

11.6 Further considerationsWhen precautions are taken to avoid damage from ASR, it is important to ensure that.other properties of the concrete are not affected adversely. For example the durability ola structure should not be put at risk by using a mix design which controls the alkali levelbut which reduces the cernentitious material below an acceptable level.

18

IsENVIRONMENTjudged to be safeagainst ASR?

Is alkali contentofCEMENTITIOUSMATERIALS:<:0.6%?

Doescementitiousmaterial contain50% or moreGROUNDGRANULATEDBLASTFURNACESLAG?

Doescementitiousmaterial contain25% or more PFAor GGBFS and isthe alkali contentof the concrete:<:3.0kg/m3?

Is alkali contentof CONCRETE3.0 kg/ m3 or less?

AreAGGREGATESjudged to bepotentially safe?

See 3.2.2(a) See 3.2.2(b) See 3.2.3(a) See 3.2.3(b)

Allow for ALKALIS from other sources andALKALIS associated with CHLORIDES in aggregates

See 3.1 See 7.2, 7.3 See 6

NOEXTRA A.S.R.PRECAUTIONSNEEDED

Are the risks andeconomic consequencesof ASR acceptable?

See 4.2See 4 & 7

CONSIDER THE TECHNICAL AND ECONOMIC MERITS OF THESE OPTIONS

After curing Specify a Specify 50% or Specify 25% or Specify Specify anmaintain concrete CEMENT or more GROUND more PFA or CONCRETE with AGGREGATEat less than 75% CEMENTITIOUS GRANULATED GGBFS and an an alkali content combinationRH MATERIAL with BLASTFURNACE alkali content in of 3.0 kg/ m3 or judged to be

an alkali content SLAG the concrete of less potentially safe:<:0.6% 3.0 kg/ m3 or less

See 3.1 See 9.1.1, 9.1.2 & See 9.1.2 & 17.2, See 9.2.2 & 18 See 9.2.1 & 18 See 6.3.2, 6.3.3,17.1,17.4,17.5 17.3 6.3.4 & 19

Re-check otherDURABILITY requirements

of CONCRETE

Figure 1. Assessment of Risks and Precautions against ASR

19

11.7 Flow ChartFigure I summarises the process of assessing the risks and selecting the precautionswhich may be taken to minimise the risk of damage due to ASR in general concreteconstruction.

PART 2. DESCRIPTION F MODFL SPECIFICATION CLAUSES

12 INTRODUCTION TO THE MODELSPECIFICATION CLAUSES

12.1 These clauses have been drawn up as a way of implementing the GuidanceNotes and should not be used without reference to them. The clauses can beincorporated in either new or existing specifications. It is hoped that the appropriateclauses in Part 3 of this document will be accepted nationally and form the basis for newclauses in British Standards and other specifications.

12.2 The revised Guidance Notes in Part 1 and Model Clauses in Part 3 are writtenfor materials, conditions and practices currently found in the United Kingdom. They donot necessarily apply elsewhere as the materials and quality standards may be differentin other countries.

13 BASIS FOR THE USE OF THE MODEL SPECIFICATIONCLAUSES

13.1 The responsibility for drawing up a Specification rests with the Engineer, whowill consider the particular requirements of the Client. These requirements will includeinter alia minimising the risk of ASR and the achieving of adequate strength anddurability in the concrete.

13.2 If the Engineer concludes that it is necessary to take precautions to minimisethe risk of ASR he should consider the most cost-effective way of doing so whilstensuring that the other properties of the concrete are not affected adversely.

13.3 Variations in the type, price and availability of aggregates and cernentitiousmaterials throughout the UK will mean that the cost of minimising the risk of ASR willvary from region to region. Part 3 of this document includes clauses covering variousoptions so that the final choice can be based on local knowledge.

13.4 Particular care will be needed when specifying aggregates. Flint, chert andquartzite occur in a high proportion ofUK aggregates particularly in the fine material.They may be reactive and will remain so when they are used in conjunction with aninert coarse aggregate. It may not be economically feasible or desirable to avoid the useof such aggregates. Sources known to contain opaline silica should not be used evenwhen the alkali content of either the cementitious material or the concrete is beingcontrolled. This aspect is expanded in Section 6.

13.5 It rests with the Engineer to determine, through his selection from the ModelClauses, those options which are acceptable in each particular instance. However, itmust be recognised that any unnecessary restriction in the acceptable options orduplication of precautions may lead to an increase in cost.

13.6 After a COntract is let the time available for approval of concrete mixes is short.For this reason it is recommended that, if the specification includes clauses relating toASR, the instructions for tendering should require tenderers to disclose both themethod by which they intend meeting the ASR specification and the sources of allmaterials.

13.7 The numbering of Parts 1,2 and 3 is consecutive for ease of reference. Themodel clauses in Pan 3 will have to be selected, ordered and renumbered both to suit theapproach adopted by the Engineer in minimising the risk of ASR and to be consistentwith any document in which they are incorporated.

20

14 MATTERS COVERED BY THE MODEL SPECIFICATIONCLAUSES

14.1 The Model Clauses and Guidance Notes relate solely to the various ways inwhich materials can be selected to minimise the risk of the deleterious ASR and donot cover other phenomena, such as the alkali-carbonate reaction or the alkali-silicatereaction.

14.2 Although it is intended that the clauses should be capable ofincorporation intoany document, it is recognised that they may have to be adapted. For instance nomention is made of mix design, strength or methods of mixing and placing concrete.These will have to be covered by either a general specification or a reference to BS 5328.

14.3 It is recognised that specification clauses tor three options. which an engineermight consider in minimising the risk of ASR have not been included in thisdocument:

(a) the prevention of contact between the concrete and an external source ofmoisture. See Section 3.1 in Part 1.

(b) a satisfactory performance record for which the combination of cement andaggregates has a long history of satisfactory use in concrete and therefore ASRis judged to be sufficiently remote.

(c) the use of microsilica. See Section S.4.

These omissions must not be interpreted as an invalidation of these options, but it willbe for the Engineer to assess the risks involved and select appropriate specificationclauses.

14.4 The following are explanatory notes relating to the selection of aggregatematerials.

(a) Aggregates are obtained by the large-scale extraction of materials formed bygeological processes over long periods. As a result they may vary incomposition as extraction proceeds. As with other options, the best that can beachieved is to minimise the risk not to guarantee the avoidance of ASR.

In preparing the Specification for a particular Contract, the Engineer has threeoptions when he considers aggregates, which are>

1. Place no restrictions on the selection of aggregates (but see Section 13.4)and rely solely on the clauses for cementitious materials (See Clauses 17and 18).

2. Specify types of aggregate which minimise the risk regardless of thecementitious material used (See Clause 19).

3. Nominate specific sources offine and coarse aggregate.

It is advisable tor the Engineer to consider alternative ways in which the risk ofASR can be minimised and to provide for these in the specification. If, forexample, option 2 (given above) is included without the alternative option 1,tenderers might find that there are no acceptable aggregates available at arealistic cost and yet there is no other way of making concrete.

(b) Table 4 lists rocks and minerals which can be considered as non-reactive. Theycan be used in the UK to minimise the risk of damage due to ASR regardless ofalkali levels in the cementitious material and irrespective of environmentalconditions or exposure of the concrete to external sources of alkali . The rocktypes are taken from those listed in BS 812: Part 2: 1984. Methods ofpetrographical examination will be included in BS 812.

Appendix 3 gives advice on the classification of rock types together withinformation on the constituents of aggregates which may be potentially reactive.

(c) Great care is necessary when using fine and coarse aggregates from differentsources. Depending on the materials used, the effects can appear contradictory.For example, cases of ASR damage have been recorded where a non-reactivecoarse aggregate has been used with a fine aggregate containing flint/chert. Onthe other hand few cases of signiti cant damage due to ASR have been recordedin regions where the sources of both fine and coarse aggregate contain a high

21

proportion of .lint/chert, Based on experience to date and some laboratorywork, it is considered at present that a combination of aggregates which containmore than 60%by mass offlint/ chert may be regarded as unlikely to be reactiveand the Engineer should satisfy himself on this.

(d) If the Engineer is able to confirm from extensive and recorded data that certainsources of aggregate are satisfactory it may be possible tominimise the riskby nominating them. These sources may be either individual quarries orparticular sources and Clause 19.2(b) provides for this.

PART 3. MODEL SPECIFICATION CLAUSES FOR MINIMISINGTHE RISK OF ALKALI-SILICA REACTION IN CONCRETE

15 PRECAUTIONS AGAINST ALKALI-SILICA REACTION(ASR) IN CONCRETE

15.1 Concrete mixes for use in permanent works in the locations designated as .shall comply with one of the Clauses 15.2, 15.3, 15.4. The Contractor shall notify theEngineer of his proposals for complying with this requirement.

15.2 The cementitious material shall have a reactive alkali content not exceeding amaximum value of0.6%by mass when defined and tested in accordance with Clauses 16and 17.

OR

15.3 The total mass of reactive alkali in the concrete mix shall not exceed 3.0 kg/m'of concrete when defined, tested and calculated in accordance with Clauses 16 and 18.

OR

15.4 The aggregate shall be classed as non-reactive in accordance with the definitionin Clause 19.

16 CEMENTITIOUS MATERIAL(HYDRAULIC AND LATENT HYDRAULIC BINDERS):DEFINITIONS AND GENERAL CLAUSES

16.1 Cementitious materials shall comply with the relevant British Standardswhich are:-BS 12, BS 146, BS 1370, BS 3892:Part 1, BS 4027, BS 4246, BS 6588, BS 6699.

16.2 The term alkali refers to the alkali metals sodium and potassium expressed astheir oxides. The reactive alkali content of Portland cements to BS 12, BS 4027 andBS 1370 shall be defined as the percentage by mass of equivalent sodium oxide (Na20)calculated from: .

% equivalent Na.O =%acid soluble Na20 +0.658x (%acidsolubleK20)

16.3 The method used in determining the acid soluble alkali content of the materialsto BS 12, BS 1370 and BS 4027 shall be in accordance with BS 4550: Part 2: 1970,Clause 16.2.

16.4 For the purpose of this specification the reactive alkali content of groundgranulated blastfurnace slag(ggbfs) shall be taken as the water soluble alkali determinedin accordance with Clause 16.11.

16.5 For the purpose of this specification the reactive alkali content of pulverizedfuel ash (pfa) shall be taken as the water soluble alkali determined in accordance withClans- 16.11.

16.6 The Contractor shall make available the certified average acid soluble alkalicontent of Portland cement to BS 12, BS 1370 or BS 4027 on a weekly basis.

22

16.7 The Contractor shall gi\-c immediate notice of any change which may increasethe certified average acid soluble lkali content above the level used in the mix design torthe concrete. A revised mix dcsiun for any concrete which would be affected by theincreased alkali content shall be submitted for approval with notification of the change.

16.8 The method of determining the amount of pfa in a cement to BS 6588 shall bein accordance with Appendix A of that standard.

16.9 The method of determining the amount ofggbfs in cement to BS 146 shall be inaccordance with BS 4550: Part 0000 (when available).

16.10 The Contractor shall certify to the Engineer the ratio by mass of ggbfs or pfa toPortland cement in the concrete.

16.11 The reactive alkali content of either ggbfs or pfa shall be the water soluble leveldetermined using:

(a) The extraction method tor sand given in BS 812: Part 4: 1976, namely:

Place a mass 01'500 g of the dry subsample of the pfa or ggbfs in a wide mouthscrew topped plastic bottle. Add 500 ml distilled water and allow to stand for 24hours with occasional shaking. Take a 5 ml aliquot of the supernatant liquid(filtered when necessary) by means of a pipette and transfer to a 500 mlvolumetric flask.

(b) The test method tor cement given in Clause 16; AMD 4260: BS 4550: Part 2,namely:

Using the specified reagents add 5 ml of nitric acid and SO ml aluminiumsolution and where necessary, sufficient of the calcium solution to bring theconcentration of calcium oxide in the diluted solution to approximately630 mg/l. Dilute to the mark with water and mix thoroughly. Follow theprocedure given in Clause 16.2.4.1 (of the document quoted above) from thesecond paragraph onwards.

The calculation will proceed as in 16.2.5 of the document quoted above exceptthat for the given conditions of extraction and dilution the alkali oxide= 0.01e.

(c) Clause 16.2 of this Model Specification to convert the data so obtained toequivalent Na,O.

17 MINIMISING THE RISK BY USING CEMENTITIOUSMATERIAL CONTAINING LESS THAN 0.6% REACTIVEALKALI

The requirements of Clause 15.2 will be met by anyone of Clauses 17.1,17.2,17.3,17.4or 17.5 provided that the contribution of alkalis from other sources does not exceed0.2 kg/m" (see Clauses 18.2 and 21.2). Where these alkalis exceed 0.2 kg/rrr' therequirements of Clause 18 shall apply.

17.1 The cementitious material shall be Portland cement complying with BS 4027and shall have additionally a certified maximum acid soluble alkali content notexceeding 0.6';;. -

The Contractor shall provide on request wceklv certificates which name the source ofthe cement and confirm compliance with the Specification.

OR

17.2 The cernentitious material shall be Portland-blasrfumace cement complyingwith BS 146 and containing a minimum 01'50';; by mass of'ggbfs or a low heat Portland-blastfurnacc ccm~1 complying with BS 4246. The cement shall have a maximum acidsoluble alkali content of 1.1 r/; measured in accordance with the method given inClause 16-3_

23

The Contractor shall provide certificates on request confirming compliance with theSpecification and stating:

(a) The proportion of ggbfs expressed as a percentage by mass of the totalcementitious material.

(b) The certified acid soluble alkali content of the cement.

(c) The certified average reactive alkali content of the ggbfs.

(d) The name of the works manufacturing the cement.

OR

17.3 The cemenutious material shall be a combination of Portland cementcomplying with BS 12 and a ggbfs complying with BS 6699 and shall contain aminimum of507, by mass of ggbfs. The combination of Portland cement and ggbfs shallhave a certified maximum acid soluble alkali content of 1. l/f measured in accordancewith the method given in Clause 16.3.

The Contractor shall provide certificates on request confirming compliance with theSpecification and stating:

(a) The proportion of ggbfs expressed as a percentage by mass of the rotalcernentitious material.

(b) The certified average acid soluble alkali contents of the cementitiousmaterial.

(c) The names of the works manufacturing the cement and the ggbfs.

OR

17.4 The cernentitious material shall be a Portland cement complying with BS 146,BS 4246 or BS 6588 and shall contain ggbfs or pfa so that the total reactive alkali contentof the cernentitious material does not exceed 0.67,. The target mean ggbfs or pfa contentof the cementitious material shall be at least 257, by mass. The Contractor shall providecertificates on request confirming compliance with the Specification and stating:

(a) The proportion of ggbfs or pfa expressed as a percentage by mass of the totalcementitious material.

(b) The reactive alkali contents of the cements and their components.

(c) The name of the works manufacturing the cement and that supplying the ggbfsor pfa.

OR

17.5 The cernennuous material shall be a combination of Portland cementcomplying with BS 12 and a ggbfs complying with BS 6699 or a pfa complying with BS3892: Part 1 and shall contain sufficient ggbfs or pfa so that the total reactive alkalicontent of the cementitious material does not exceed 0.67,. The target mean ggbfs or pfacontent of the cementitious material shall be at least 25% bv mass. The Contractor shallprovide certificates on request confirming compliance 'with the Specification andstating:

(a) The proportion of ggbfs or pfa expressed as a percentage by mass of the totalcementitious material.

(b) The reactive alkali content of the Portland cement and ggbfs or pfa.

(c) The names of the works manufacturing the Portland cement and thatsupplying the ggbfs or pfa.

18 MINIMISING THE RISK BY LIMITING THE REACTIVEALKALI CONTENT OF THE CONCRETE TO 3.0 kg/m.'

The requirements of Clause 15.3 will be met provided that Clauses 18.1,18.2 and 18.3are satisfied.

18.1 The reactive alkali content of the concrete contributed bv the Portland cement,ggbfs or pfa to the concrete shall be calculated from: .

24

(a Portland cement

A= Cxa100

where A

C

a

(b) ggbfs or pfa

B= Exd100

where B

Ed

reactive alkali content of the concrete to the nearest0.1 (kg/m")

target mean Portland cement content of the concrete(kg/rrr')

certified average acid soluble alkali content of thePortland cement ('If).

average reactive alkali content contributed by ggbfsor pfa (kg/rrr')

target mean ggbfs or pfa content of the concrete (kg/ rrr')

reactive alkali content of ggbfs or pfa (';{). (SeeClause 16.5)

18.2 W'here reactive alkalis in excess 01'0.2 kg/rrr' are contributed to the concretefrom sources other than the cementitious material the limit of 3.0 kg/m' from thecementitious material shall be reduced by the total amount so contributed.

The reactive alkali contributed by sodium chloride contamination of aggregates shall becalculated from:

H = 0.76 x ((NF x MF) + (NC x i\1C»100

where HThe factor 0.76 is obtained from a consideration of the composition of sea water.

NF

MF

NC

MC

equivalent alkali contribution made to the concreteby the sodium chloride (kg/rrr')

chloride ion content of the fine aggregate as apercentage by mass of dry aggregates and measuredaccording to BS 812: Part 4: 1976 (now in draft asPart 117)

fine aggregate content (kg/m')

chloride ion content of the coarse aggregate as apercentage by mass of dry aggregate and measuredaccording to BS 812: Part 4: 1976 (now in draft aspart 117)

coarse aggregate content (kg/rrr')

The chloride ion content of aggregate sources containing 0.01 'Ir of chloride ion by massor more shall be determined weekly in accordance with BS 812 or another approvedmethod. When the chloride ion level is less that 0.01'j, it shall be regarded as nil.

18.3 The Contractor shall provide certificates on request confirming compliancewith the Specification and stating:

(a) The target mean cementitious material content of the concrete.

(b) The names of the works manufacturing the cement, ggbfs and pfa.

(c) The proportion of ggbfs or pfa expressed as a percentage by mass of the totalcernenririous material.

(d) A weekly report of the cement alkali deterrninations in accordance withClause 16.6.

(e) The certified average acid soluble alkali content of the Portland cement.

(n A weekly report of either the reactive alkali determinations on ggbls and pia ora certified maximum value.

2S

Table 4

19 MINIMISING THE RISK BY USING SELECTEDAGGREGATES

19.1 Fine and coarse aggregate material shall comply with the requirements ofBS 882, BS 1047 or BS 3797.

19.2 The aggregate shall be classed as non reactive if the Engineer is satisfied thatthe source does not contain opaline silica and one of the following sub-clauses issatisfied.

(a) The fine and coarse aggregate each consist of at least 951; of one or more of therock types or artificial aggregates listed in Table 4 and provided that theEngineer is satisfied that the source does not contain a quantity offlint, chert orchalcedony that could cause damage from alkali-silica reaction. (See Section6.3.2 of the Notes for Guidance.)

MicrograniteAircooled blast-furnace slag

AndesiteBasaltDioriteDoleriteDolomite

Expanded clay/shale/slateFeldspar I

GabbroGneissGraniteLimestoneMarble

Quartz I ~

SchistSintered pfaSlateSveniteTrachyteTuff

~otes on Table 4:

1. Feldspar and quartz are not rock types but are discrete mineral grains occurring principally 10 fineaggregate.

2. Not highly strained quartz and not quartzite.

(b) Fine aggregate shall be obtained from the following source:

(Specify Source) .

Coarse aggregate shall be obtained from the following source:

(Specify Source) .(c) The proportion of chert and flint in the sources of aggregate is such that the

proportion of chert and flint in the total aggregate is greater than 60% by masswhen the fine and coarse fractions are combined. (See Section 6.3.4.)

20 WATER20.1 Water for use in the manufacture of concrete shall be obtained from a publicutility undertaking supply and shall be of potable quality.

20.2 Where a potable mains supply is not available the contractor shall obtain"confirmation of the quality and reliability of the proposed source from the appropriatewater authority and shall thereafter seek approval lrorn the Engineer to use theproposed source.

20.3 Water other than from a public utility undertaking supply shall be sampled at afrequency to be determined by the Engineer and tested in accordance with the relevantprovisions ofBS 3148. The sodium oxide and potassium oxide content shall be declaredand expressed as equivalent Na~O and shall be taken into account when calculating thetotal reactive alkali content of the concrete mix.

26

21 ADMIXTURES AND PIGMENTS21.1 Admixtures ar.d pigments shall comply with the requirements ofBS 5()75 andBS 1014. The manufacturers declared equivalent acid soluble alkali content and thedosage rate of any admixture or pigment to be incorporated shall be included withdetails ofall concrete mixes submitted for approval.

21.2 The alkali content of admixtures shall be taken into account when determiningthe total equivalent alkali content of the concrete mix.

APPENDIX 1. CHEMISTRY OF THE ALKALI-SILICA REACTIONThe alkali metal ions in Portland cement clinker, although conventionally expressed astheir oxides Na~O and K~O, are often present as the neutral sulphates Na~SO~ andK~SO~ or as the mixed salt (Na,K)~SO~. In this form they are readily soluble. Othersmaller amounts are in solid solution in the cement minerals and are released as thecement hydrates.

When water is added to the ground cement clinker these alkali sulphates take part in acomplex series of reactions with the hydrating tricalcium aluminate and calciumhydroxide in which ettringite (calcium sulphoaluminate) is precipitated and the poresolution is enriched with sodium, potassium and hydroxide ions. It is now recognisedthat the pore solution in mortars and concretes contains almost entirely sodium,potassium and hvdroxide ions with very low concentrations of other ions such ascalcium, sulphate and chloride. The pH of the pore solution is in the range 13 to 14,depending on the alkali level of the cement. This compares with a pH of about 12.5 atnormal temperatures for a saturated calcium hydroxide solution containing no alkalimetal ions.

Sodium chloride may be introduced to concrete in several ways. For instance, as animpurity in some aggregates and in rare instances by the use ofseawater for mixing orfrom an ingress of de-icing salts. It is readily soluble in the pore water and reacts in ananalogous way with the tricalcium aluminates, calcium aluminoferrite and calciumhydroxide to form calcium chloroaluminate hydrate and raising the sodium ion andhydroxyl ion concentration in the pore solution. The extent to which this happensdepends upon the amount of chloride introduced and the tricalcium aluminate andcalcium aluminoferrite contents of the cement.

However, at levels of chloride up to that permitted by BS 8110 in reinforced concretecomplete conversion of sodium chloride to sodium hydroxide can be assumed. Thesereactions are summarised by expressing the combined amounts of sodium andpotassium in the clinker as Na~O equivalent, i.e. the amount of sodium plus themolecular equivalent of potassium, expressed as their oxides. This is a way ofrepresenting the amount of hydroxide ions that these alkali metal sulphates will producein solution.

The alkali-silica reaction is, therefore, essentially an attack by sodium or potassiumhydroxide solution on silica, producing an alkali silicate gel. The rate of this attack willdepend on the relative concentration of these hydroxides in the pore solution and it isonly at the upper end of the pH range that significant attack develops. The gel rapidlytakes up calcium, the most likely source being the portlandite (Ca(OH)~) produced bythe cement hydration reactions, so that the gels analysed in concrete are usually foundto contain calcium, sodium, potassium silicates and be ofa variable composition. Suchgels are capable of taking water into their structure and expanding. It is this expansiveforce which creates tensile stress within the concrete and can ultimately cause cracking.The severity of the expansive force varies both with the composition of the gel, in a waywhich is not fully understood, and with the total amount of gel present in the concrete.

The amount of gel also depends on the amount of available reactive silica and, therefore,up to a point an increase in the amount of reactive silica produces an increase inexpansion. Above a certain proportion of reactive silica to alkali, however, theconcentration of hvdroxide in solution is insufficient to maintain the same degree ofattack and the expansion decreases again. This is the reason tor the critical, or'pessirnurn', proportion of reactive aggregate.

27

APPE~DIX 2. WORKED EXAMPLES TO ILI,USTRATE THERECOMMENDATIONSAl.1 To meet the specified requirements for strength and durability, a target meanPortland cement content of 390 kg/rrr' is necessary. Non-reactive aggregate is notavailable and the concrete will be exposed to moisture, so precautions against ASR areconsidered necessary. The concrete is not considered to be particularly vulnerable (seeSection 4). The cement available locally has a certified average acid soluble alkalicontent (022) 01'0.8';'; Na~O equivalent and the manufacturer has declared that thiscertified mean (023) will be no higher than 0.97< until further notice.Referring to 10.1

a 0.9/;

390 kg/m'

390 x 0.9100

3.5 kg Na~O/m3

Al.2 This exceeds the recommended limit of3.0 kg Na~O/m3, so one of the followingprecautions must be used:

(a) moisture must be excluded,

(b) another source of factory made Portland cement must be used,

(c) the Portland cement must be partially replaced on site by ggbfs or pfa,(d) the aggregate must be changed to one known to be non-reactive.

Note: For either (b) or (c) the total reactive alkali content of any admixturemust be taken into account. \~'hen this exceeds 0.2 kg/rrr' the 3kg/rrr'{imitmust be observed.

Alkali content of concrete,C

A

Al.3 Alternative precautions against ASRAl.3.1 Excluding moistureIf an attempt is to be made to exclude moisture, reference should be made toSection 3.1.

Al.3.2 Changing the source of factory-made cementTo meet the 3.0 kg Na.Oz'm'Timitcn the alkali content of the concrete with an expectedmaximum Portland cement content of390 kg/m', the maximum assumed alkali contentof the Portland cement must be:

3.0 x 100 = 0.777c390

The certified average acid soluble alkali content of the alternative source of Portlandcement should therefore never be greater than 0.77.

Al.3.3 Using a site blended cementAlternatively it may be decided to use the original cement, but partially replaced by pfa.A replacement rate of30'7c is decided upon and it is found that the reactive alkali contentof the pfa is 0.17c.

In order to achieve the specified 28 day strength, trial mixes show that it is necessary toincrease the target mean cementitious material content to 430 kg/m'.

Reactive alkali content of concrete, A, due to Portland cement is

430 x 30'; x 0.1 = 0.13 kg/m'100

430 x 70'/; x 0.9 = 2.71 kg/rrr'100

Reactive alkali content of concrete, B, due to pfa is

Total = 2.84 kg/ru'

This meets the required limit on.o kg Na.Ozrn'.

28

Al.3.4 Concrete containing alkalis from other sources

These worked examples indic. le how the reactive alkalis contributed bv admixtures andby aggregates contaminated with sea salt should be calculated. .

Whilst the cement content of390 kg/rrr' is the same as that considered in the previousexample, the cement itselfhas a lower level of alkali. Typical values have been taken forthe chloride ion concentrations in the aggregates and the equivalent alkalis have beencalculated in accordance with Clause 18.2.

The alkali content of the admixture as determined will be that declared bv themanufacturer in accordance with Clause 21.1. Values are those typical of admixtureshaving a low alkali content and of superplasticizers having a high alkali content.

AlA Examples: concrete containing alkalis from other sources

AlA.! The mix design

Material

Portland cement

Coarse aggregates

Fine aggregates

Case A

Typical admixture

Mix proportions

390 kg/m'

1135 kg/m'

560 kg/rrr'

Alkalis

NazO equivalent 0.757<Chloride ion content 0.037<

Chloride ion content 0.057<

Manufacturer'srecommendeddosage.

Na.O equivalent 0.01 kgper 100 kg Portland cementwhen used at recommendeddosage

Case B

Superplasticizer as above. NazO equivalent 0.1 kgper 100 kg Portland Cement

AlA.2 Calculation of the reactive alkali content of the concrete

Case AAlkali content usingtypical admixture

Case BAlkali content using asuperp1asticizer

Portland cement

Coarse aggregate

Fine aggregate

Admixture

390 x 0.757<

1135 x 0.037< x 0.76

560 x 0.057< x 0.76

390 x 0.01100

2.93

0.260.21

0.04

390 x 0.757<

1135 x 0.03% x 0.76560 x 0.057< x 0.76

Superplasticizer390 x 0.1100

2.930.26

0.21

0.40

Reactive alkali contentof the concrete

3.44 3.80

AlA.3 Available options

In both Case A and in Case B the recommended limit of 3.0 kg/m! is exceeded.

The options available which will minimise the risk ofASR include those quoted in (a) to(d) (see A2.2).

the use of aggregates with lower chloride ion content

and in Case B the use of an alternative superplasticizer which has a lower equivalentalkali content.

Al.5 Changing to a non reactive aggregateIfa non-reactive aggregate is to be chosen (option (d) ofA2.2), guidance should be takenfrom Section 6.

29

APPENDIX 3. SOME GUIDANCE FOR THE ASSESSMENT OF ROCK TYPES NOTINCLUDED IN TABLE 4 (19.2(a) OF PART 3)

Rock type Definition Potentially alkali-reactivecomponents that maysometimes be present

Arkose Detrital sedimentary rockcontaining more than 2S/; feldspar

Coarse detrital rock containingangular fragments

Micro- or crypto-crystalline silica

Coarse detrital rock containingrounded fragments

Strictly, chert occurring inCretaceous chalk

Breccia

Chen

Conglomerate

Flint

Granulite Granular

GrevwackeMetamorphic rock

Detrital Sedimentary rockcontaining poorly sorted rockfragments and mineral grains

Sandstone with coarse, angular grains

Fine-grained, thermallymetamorphosed rock

Gritsrone

Hornfels

Quartz Discrete mineral grains verycommon in fine aggregates

(i) Sedimentary or ortho-quartzite

(ii) Metamorphic or rneta-quartzite

Quartzite

Rhyolite Fine-grained to glassy acidvolcanic rock

Sandstone Detrital sedimentary rock. Thegrains are most commonly quartz,but fragments or grains of almostany type of rock or mineral arepossible.

See Sandstone

See Sandstone

See Flint

See Sandstone

Chalcedonic silica and micro- orcrypto-crystalline quartz. Somevarieties may contain opaline silica.

Highly-strained/ quartz

Mav be alkali-silicate reactive'.See Sandstone

See Sandstone

G lass I or devitrified glass.Highly-strained' and/ormicrocrystalline quartz. Phyllosilicates '

Highly-strained/ quartz

See SandstoneHighly-strained? quartz and/orhigh-energy quartzite grain boundaries

Glass I or devitrified glass.Tridymite. Cristobalite. Opalineor chalcedonic veination orvugh- fullings

Highly-strained quartz. Some types ofrock cement, notably opalinesilica, chalcedonic silica, andmicro-crystalline or crypto-crystallinequartz. Phyllosilicates'

Notes on Table:

1. Rocks containing more than S7r (by volume) glass, partially devitrified glass or devitrified glass should beclassified as potentially alkali-reactive.

2. If the average undulatory extinction angle obtained from at least 20 separate quartz grains (measured in thinsection under a petrological microscope) is more than 25 degrees the quartz should be classified as 'highly-strained'. Rocks containing more than 307. highly-strained quartz should be classified as potentially alkali-reactive.

3. Phyllosilicates are sheet silicate minerals, including the chlorite, vermiculite, mica and clay mineral groups.\X'ithin the UK a few cases of possible alkali silicate reaction have been reported in coarse aggregatescontaining greywacke and related rocks. The matrix in such rocks is verv finely divided and consists ofphyllosilicatcs, quartz and other minerals.

30

BS 12

BS 146

BS 812

BS 882

BS 1014

BS 1047

BS 1370

BS 1957

BS 3148

BS 3681

BS 3797

BS 3892

BS 4027

BS 4246

BS 4550

BS 5075

BS 5328

BS 6100

BS 6588

BS 6699

BS 8110

APPENDIX 4. BRITISH STANDARDS AND OTHERPUBLICATIONS MENTIONED IN THE TEXT

British Standards (Published by British Standards Institution)

Specification tor ordinary and rapid-hardening Portland cement. 1978.AMD 4259, May 1983.

Specification for Porrland-blastfurnace cement.Part 2: 1973. Metric units. Al\1O 2615, June 1978. AMD 4419, March 1984.

,\ lethods for sampling and testing c " nineral aggregates, sands and fillers.Part 1: 1974. Sampling, size, shape and classification. AMD 2069, August 1976.A.\1O 4572, July 1984.Part 2: 1975. Physical properties. AMD 4615, August 1984.Part 4: 1976. Chemical properties. AMD 4295, June 1983.A\\D 4617, August 1984.

Specification for aggregates from natural sources for concrete. 1983

Pigments for Portland cement and Portland cement products. 1975.

Specification for air-cooled blasrfurnace slag aggregate for use in construction. 1983.

Specification for low heat Portland cement. 1979. AMD 4416, March 1984.

Presentation of numerical values. 1953.

Methods of tests for water for making concrete (including notes on the suitability of thewater). 1980.

Methods for the sampling and testing of lightweight aggregates for concrete.Part 2: 1973 (1983). Metric units.

Specification for lightweight aggregates for concrete.Part 2: 1976. Metric units. AMD 3518, January 1981.

Pulverised fuel ash.Part 1: 1982. Specification for pulverized-fuel ash for use as a cementitious componentin structural concrete.

Specification for sulphate-resisting Portland cement. 1980. AMD 4418,March 1984.

Low heat Portland-blastfurnace cement.Part 2: 1974. Metric units.

Methods of testing cement.Part 2: 1970. Chemical tests. MiD 4260, May 1983. M1D 4373, September 1983.Pan 000.

Concrete admixtures.Pan 1: 1982.Specification for accelerating admixtures retarding admixtures ang water-reducingadmixtures. AMD 4183, February 1983.Pan 2: 1982. Specification for air-entrained admixtures.Pan 3: 1982. Specification for superplasticizing admixtures.

Methods for specifying concrete, including ready-mixed concrete. 1981.AMD 4862, 1985.

Building and Civil Engineering terms.Pan 6: Section 6.1: Binders. 1984

Section 6.3: Aggregates. 1984Section 6.4: Admixtures. 1986

Specification for Ponland pulverized-fuel ash cement. 1985.

Specification for ground granulated blastfurnace slag for use with Portland cement.

Structural use of concrete.Pan 1: 1985. Code of practice for design and construction.Concrete Society Technical Repon 29, 'Changes in Portland Cement properties andtheir effect on concrete'.

31

American Society for Testing and Materials. Tc:t for potential alkali reactivity ofcement-aggregate combinations (Mortar-bar method). 1982 Annual Book of ASTMStandards. Philadelphia. Part 14, pp.153-158, C227-81.American Society for Testing and Materials. Standard test method for potentialreactivity of aggregates (Chemical method). 1982 Annual Book of ASTM Standards.Philadelphia. Part 14, pp.198-205, C289-81.Department of Transport. Specification tor Highway Works Part 5 and Notes forGuidance, HJ\1S0 1986.

APPENDIX 5. SOURCES OF FURTHER INFORMATION(a) Bibliography1. BUILDING RESEARCH ESTABLISHMENT. Alkali aggregate reactions in

concrete. Garston 1982. 8 pp. Digest 258.2. CEMBUREAU. Alkali-Aggregate Reactivity in concrete. A state of the art

report, Paris, 1977, 155 pp.3. CEMBUREAU. Alkali-Aggregate (Alkali-Silica and Alkali-Silicate) Reactivity

in Concrete. Bibliography, Paris, 1977, 88 pp.4. ICELANDIC BUILDING RESEARCH INSTITUTE. (2nd International)

Symposium on Alkali-Aggregate Reaction, Preventative Measures. Reykjavik,Iceland, 1975, 270 pp.

S. CEMENT AND CONCRETE ASSOCIATION. Proceedings of a (3rd Inter-national) Symposium: The Effect of Alkalis on the Properties of Concrete.(Editor: A Poole.) London, 1976,374 pp.

6. PURDUE UNIVERSITY. Proceedings of 4th International Conference on theEffects of Alkalis in Cement and Concrete. Publication CE-MAT-I-78, Schoolof Civil Engineering. Purdue, USA, 1978, 376 pp.

7. NATIONAL BUILDING RESEARCH INSTITUTE OF THE C.S.I.RProceedings of the 5th International Conference on Alkali-Aggregate Reactionin Concrete. Cape Town, South Africa, 1981.

8. DANISH CONCRETE ASSOCIATION. Proceedings of 6th InternationalConference on Alkalis in Concrete, Research and Practice. Copenhagen,Denmark, 1983. 532 pp.

9. NATIONAL RESEARCH COUNCIL OF CANADA. Proceedings of7th International Conference on Alkali-Aggregate Reaction. Ottawa, Canada,1986. (To be published.)

10. INSTITUTION OF CIVIL ENGINEERS AND INSTITUTION OFSTRUCTURAL ENGINEERS. Standing Committee on Structural Safety.6th Report, London, 1985. 20 pp.

(b) Other Committees concerned with ASRBuilding Research Establishment Forum on ASRCement and Concrete Association Working Party on the diagnosis of ASRThe Institution of Structural Engineers ad hoc Committee. EngineeringAppraisal of Structures with ASRThe Institution of Structural Engineers and the Institution of Civil Engineers.Standing Committee on Structural Safety.

32

•t APPENDIX 6. DEFINITIONS

No Term Definition

ALKALI

Dll Alkali

D12 Sodium oxideequivalent

DB Acid soluble alkalicontent

D14 Water solublealkali content

REACTIVE ALKALI CONTENT

D15 Reactive alkali That part of the alkali expressed as sodium oxide equivalent which is considered tocontent contribute to the alkali silica reaction.

The sum of the reactive alkalis contributed to concrete by the cementitiousmaterial, aggregates, admixtures and water.

The acid soluble alkali content (See DB).

The acid soluble alkali content of the pc component (See DB) plus the watersoluble alkali content of either the ggbfs or the pfa (See DI4).

The water soluble alkali content (See DI4).

BI~DER

m Binder

D2 Hvdraulic binder

D3 Portland cement (pc)1)4 Ground granulated

blast-furnace slag~~hls

D.:' Pulverised-fuel ashiptJ

1)6 Ordinarv PortlandCement (opc)

1)7 Sulphate resistingPortland cement(srpc)

D8 Cementitiousmaterial

D9 Composite cement

DIO Combination

D16 of concrete

D17 of pc

Dl8 of compositecement

Dl9 of either ggbfs orpfa

D20 of an admixtureD21 of aggregates

.\ latcrial used Ior the purpose of holding solid particles together in a coherent mass.

Binder that acts and hardens by chemical interaction with water and is capable ofdoing so under water.

Active hydraulic binder based on ground Portland cement clinker.

Fine powder resulting from drying and grinding granulated blastfurnace slag.

Solid material extracted by electro-static and mechanical means from flue gases offurnaces fired with pulverized bituminous coal.

Portland cement complying with the requirements of BS 12 for ordinary Portlandcement.

Portland cement complying with the requirements ofBS 4027.

Hvdraulic binder.

Cement complying with the requirements ofBS 146, BS 4246 or BS 6588containing ope and either ggbfs or pfa.

Mixture of pc and either ggbfs or pfa where such mixing takes place with otheringredients in a concrete mixer.

Sodium oxide (Na~O) or Potassium oxide (K~O)

Na~O + 0.658 K~O.

Determination in accordance with BS 4550: Part 2: 1970, Clause 16.2, using nitricacid expressed as percent sodium oxide equivalent.

Determination in accordance with Clause 16.11 of this document.

The sodium oxide equivalent (See D12) of the admixture.

Throughout this document this refers only to alkalis arising from sodium chlorideand whose determination is in accordance with Clause 18.2.

CERTIFIED AVERAGE ALKALI CONTENT

\)22 Acid soluble of pc The average of the last 2S deterrninations carried out on daily samples prepared inaccordance with the requirements of Clause 3.5.1 of BSI Quality AssessmentSchedule 2420/47 Issue 3 and is considered to be the reactive alkali content ofthe pc.

The value of acid soluble alkali (DI3) which the cement manufacturers declare willnot he exceeded without prior notice

\)23 Acid soluble of pcwhich shall not beexceeded

33

..

D24 of compositecement

D25 Certified maximumacid soluble alkalicontent of pc

Target mean

The reactive alkali content of the composite cement.

The value of acid soluble alkali content which shall not be exceeded for anycement delivery.

The mean required by mix design of any constituent of concrete. The actual masswill vary from batch to batch, the values exhibiting a Normal Distribution.

A Portland cement or a composite cement (not made on site) which ismanufactured to the requirements of a specific British Standard and for which themanufacturer will provide certification of the reactive alkali content.

D26

027 Factory madecement

34