May 2007 DESIGN MANUAL FOR ROADS AND BRIDGES VOLUME 2 HIGHWAY STRUCTURES: DESIGN (SUBSTRUCTURES AND SPECIAL STRUCTURES) MATERIALS SECTION 3 MATERIALS AND COMPONENTS PART 9 BA 92/07 THE USE OF RECYCLED CONCRETE AGGREGATE IN STRUCTURAL CONCRETE SUMMARY This Advice Note provides information on the use of recycled concrete aggregate (RCA) as a replacement for coarse natural aggregate in structural grade concrete. INSTRUCTIONS FOR USE 1. Remove Contents pages from Volume 2 and insert new Contents pages dated May 2007. 2. Insert the new Advice Note BA 92/07 into Volume 2, Section 3. 3. Please archive this sheet as appropriate. Note: A quarterly index with a full set of Volume Contents Pages is available separately from The Stationery Office Ltd.
THE USE OF RECYCLED CONCRETEAGGREGATE IN STRUCTURALCONCRETE
SUMMARY
This Advice Note provides information on the use ofrecycled concrete aggregate (RCA) as a replacement forcoarse natural aggregate in structural grade concrete.
INSTRUCTIONS FOR USE
1. Remove Contents pages from Volume 2 andinsert new Contents pages dated May 2007.
2. Insert the new Advice Note BA 92/07 intoVolume 2, Section 3.
3. Please archive this sheet as appropriate.
Note: A quarterly index with a full set of VolumeContents Pages is available separately from TheStationery Office Ltd.
BA 92/07Volume 2, Section 3,Part 9
The Use of Recycled ConcreteAggregate in Structural Concrete
Summary: This Advice Note provides information on the use of recycled concreteaggregate (RCA) as a replacement for coarse natural aggregate in structuralgrade concrete.
DESIGN MANUAL FOR ROADS AND BRIDGES
THE HIGHWAYS AGENCY
TRANSPORT SCOTLAND
WELSH ASSEMBLY GOVERNMENTLLYWODRAETH CYNULLIAD CYMRU
THE DEPARTMENT FOR REGIONAL DEVELOPMENTNORTHERN IRELAND
Volume 2 Section 3Part 9 BA 92/07
May 2007
REGISTRATION OF AMENDMENTS
Amend Page No Signature & Date of Amend Page No Signature & Date ofNo incorporation of No incorporation of
amendments amendments
Registration of Amendments
Volume 2 Section 3Part 9 BA 92/07
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THE USE OF RECYCLED CONCRETEAGGREGATE IN STRUCTURALCONCRETE
Contents
Chapter
1. Introduction
2. Supply, Specification and Properties of RecycledAggregates
3. Design of Concrete Mixes Incorporating RCA
4. Properties of RCA Concrete
5. Compatibility Issues
6. Design Issues
7. Specification
8. In Service Issues
9. Limitations
10. References
11. Enquiries
Appendix A Test Requirements for Acceptance ofRCA
Appendix B Procedure for Trial Mixes Using RCA
Appendix C Calculation of Chloride Class andAssessment of ASR Susceptibility for aConcrete Mix Design IncorporatingRCA
DESIGN MANUAL FOR ROADS AND BRIDGES
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Volume 2 Section 3Part 9 BA 92/07
Chapter 1Introduction
1. INTRODUCTION
Scope
1.1 This Advice Note provides information on theuse of recycled concrete aggregate (RCA) as areplacement for coarse natural aggregate in structuralgrade concrete. It deals specifically with sourced andtracked high quality material comprising mainlycrushed concrete with low levels of impurities –equivalent to RCA (II) in BRE Digest 433 – RecycledAggregates (BRE 1998). Designers, Contractors andconcrete suppliers are encouraged to consider the use ofRCA.
1.2 The effects of RCA on concrete properties aredescribed. Specific guidance is given on thespecification and testing of RCA, and on concrete mixdesign to achieve particular concrete strengths.
1.3 Guidance is also given on the types ofconstruction and structure for which the use RCA isappropriate and also where, for the time being it shouldnot be considered.
1.4 The Advice Note is intended to supplement otherdesign guides and standards for the specification anduse of aggregates in structural grade concrete,particularly the Specification for Highway Works(MCHW Volume 1) and the related Notes for Guidance(MCHW Volume 2), BS EN 206-1 Concrete – Part 1:‘Specification, performance, production andconformity’, and the complementary British StandardsBS 8500-1: 2006 ‘Method of specifying and guidancefor the specifier’ and BS 8500-2 ‘Specification forconstituent materials and concrete’.
Development of the Advice Note
1.5 The Advice Note is based on work undertaken atBRE and subsequent research carried out at TRL onengineering and durability aspects relevant to the use ofRCA in structural concrete (Calder and Roberts, 2005).This work was funded by the Highways Agency (HA).The RMC Community Fund provided additionalfunding to assess the susceptibility of a range of RCA toalkali silica reaction (ASR) (Calder and Mckenzie,2005).
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1.6 There are still areas where the effects of RCA onconcrete properties are uncertain. These are noted in thetext. Further research and experience will be neededbefore these issues can be resolved.
Benefits and Limitations of the Use of RCA inStructural Concrete
1.7 The principles of sustainable developmentrequire the prudent use of natural resources andmaximum use of recycling of construction waste. Inkeeping with this approach, the UK Government isactively encouraging the use of recycled aggregate as analternative to primary aggregate. Along with thepotential for direct cost savings associated with using awaste material, there are additional economic benefitsassociated with incentives to use recycled material anddisincentives to use natural aggregates providedthrough land fill tax credits.
1.8 There will however be increased costs in otherareas. Recycled aggregates will require extra treatmentto remove contaminants, along with a testing regime toensure adequate and consistent quality. Dedicatedprocessing, testing, storage and handling facilities willbe needed at ready mixed concrete plants. Additionaladministration will be needed to deal with the logisticsof combining recycled aggregate with naturalaggregate, and maintaining suitable records. Materialsalso need to be carefully tracked from source to end-use. There are also issues to resolve to ensurecompliance with waste management regulations.
1.9 From a sustainability point of view the idealsource of recycled aggregate would be a generalmaterial available from aggregate suppliers in the sameway as for natural aggregate. It would come from mixedsources but meet a general specification ensuringappropriate quality. However considering the widepotential range of source materials it would be anonerous task for aggregate suppliers to achieve aconsistent product.
1.10 At the moment it is likely that recycled aggregatewill be obtained from two main supply streams, eitherpreconsumer waste from concrete production (precastor ready-mix concrete plants) or from demolitionprojects such as disused airfield structures, concreteframed or clad buildings. Potential sources need to beable to provide sufficient quantity and consistent
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Chapter 1Introduction
quality and usually be fairly close to the site where theconcrete is to be used to ensure that the economics areviable. Preconsumer waste is likely to be of moreconsistent quality. Procedures are required to ensurethat the source material is of appropriate quality. Wherethe source is a demolished structure, information willbe needed prior to the start of the supply on the historyof the structure along with inspection and testing toensure that it is fit for purpose. This is in addition to theroutine testing to ensure consistent quality once therecycled material is in use.
1.11 Whilst the use of recycled aggregate has areasonable track record in low grade applications (eg assub base in road construction), its use in structuralgrade concrete is a relatively new area, though somenotable structural projects have been completed. Hencethe usage of RCA is not advised for use in particularlysensitive or critical structural elements or structures,until it has a longer track record.
1.12 It is acknowledged that the sources of suitableconsistent high quality materials to produce RCA maybe limited at present. Similarly there are few plants ableto handle and process such materials. Combined withthe often limited quantities of concrete involved inbridge construction and the logistics, this may precludethe option of using RCA on economic grounds on manyprojects. However it is expected that this situation willchange and improve over time. Hence this Advice Noteprovides the opportunity to consider RCA as a partialreplacement for natural resources on larger projectswhere significant volumes of structural concrete are tobe used.
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Chapter 2Supply, Specification and Properties of Recycled Aggregates
N AND PROPERTIES OFES
2. SUPPLY, SPECIFICATIORECYCLED AGGREGAT
Types of recycled aggregate
2.1 Recycled aggregate (RA) is defined in BS 8500-1(2006) as the generic term for aggregate resulting fromthe reprocessing of inorganic material previously usedin construction. In addition to significant quantities ofnatural aggregates, recycled aggregates are likely tocontain impurities such as wood, metal, asphalt andplastic; these need to be controlled to acceptable levelsdependant on the proposed use of the recycledaggregate. Where the composition of the recycledaggregate is principally crushed concrete, the materialis defined in BS 8500-1 (2006) as RCA. BRE (1998)subdivided recycled aggregates into three classes,dependent on the brick content (BRE Digest 433):
RCA (I) defines the lowest quality material. It couldhave relatively low strength and high levels ofimpurities. It might contain up to 100% brick or blockmasonry, or could comprise mainly concrete but withhigh levels of impurities.
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Table 1 Acc
Contaminant BS 8500% by mass
Masonry < 5%a
Lightweight material < 1000kg/m3 c < 0.5%b
Asphalt < 5%d
Other impurities (eg. glass, < 1%plastic and metals)
Other foreign material Included in othe
Wood Not quoted but 0.1% as per EN
Total < 11.5%
a Limit may be increased to < 10% for exposed cob Limit set to < 0.1% for exposed concrete.c ‘Floating stony’ materials only.d Limit set to < 0.5% for exposed concrete.
RCA (II) defines a relatively high quality materialcomprising mainly crushed concrete with up to 10%brick by weight but low levels of impurities, less than1.5% by weight (wood, asphalt, glass, plastics, andmetals). In some cases it could contain an appreciableamount of natural aggregate.
RCA (III) defines a mixed material with up to 50%brick and high levels of impurities.
This Advice Note refers only to RCA (II) type material,and materials conforming to RCA(I) and (III) are notpermitted.
BS 8500-2: 2006 also has a description of RCA whichdefines the quality and impurities in RCA in a slightlydifferent way to BRE (1998). This is also acceptable.However asphalt impurities should be excluded from allconcrete that is exposed, and the limit is set to < 0.5%accordingly. In such circumstances the limit of masonryimpurities may be increased to <9.5% by mass, andlightweight material (floating stony materials only) lessthan 1000 kg/m3 should also be < 0.1% as allowed inBS EN 12620 ‘Aggregates for concrete’.
eptable RCA Quality
BRE Digest 433RCA (II)
<10%
Included in other foreign material
Included in other foreign material
Included in other foreign material
r impurities < 1%
should be less than < 0.5% 12620
< 11.5%
ncrete when asphalt limit reduced to < 0.5%.
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Chapter 2Supply, Specification and Properties of Recycled Aggregates
Sources and Production of RCA
2.2 RCA can be obtained from a variety of sourcessuch as waste material from prefabricating yards,general demolition waste or demolition of individualstructures. Aggregate is prepared using conventionalaggregate plant with additional features to remove someof the contaminants; for example, magnetic separatorsto remove steel. Preparation methods influence theproperties of the resulting RCA so it is important toestablish a procedure to characterise the RCA andensure fitness for purpose.
Quality Control
2.3 There are potential problems with ensuring anadequate supply of RCA of consistent quality. RCA canrange from essentially new, uncontaminated concrete ofknown specification and history to unknown material ofuncertain history. Even RCA from a single source islikely to be variable dependant on the environmentalconditions that different parts of a structure may haveexperienced during its life. The use of mixed supplysources exacerbates such problems. It is, therefore,essential that a quality control scheme is set up tocontrol the supply and provide an audit trail of materialused so that any problems potentially associated withthe use of RCA can be traced back to the sourceconcrete used in the preparation of RCA. Mention hasalready been made of the differences betweenpreconsumer waste as opposed to other sources of RCA(clause 1.10).
2.4 The design of a scheme would depend on thelikely variability in source material and would have tobe tailored to the likely causes of variability. Forexample waste material from a prefabrication yardwould be less variable than demolition waste from aspecific structure.
2.5 A general approach to quality control in recycledaggregate production has been prepared (BRE 2000). AQuality Protocol (2004) was prepared as part of theWaste and Resources Action Programme (WRAP) toprovide a uniform control process for producers so thatthey can reasonably state and demonstrate that theirproduct has been fully recovered and is no longer awaste. The protocol covers factory production control,product descriptions, specification, acceptance criteriaand testing. Although the WRAP Quality Protocol wasintended primarily for recycling of materials inassociation with road pavement construction (refer toMCHW – SHW clause 710), nevertheless the principlesshould be adopted where RCA is to be considered for
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use in structural concrete. The concrete itself shouldalso be supplied in accordance with a ProductCertification Scheme for ready-mixed concrete asdetailed in Appendix B of MCHW Volume 1Specification for Highway Works.
2.6 To standardise and document the qualityprocedures in a specific case a Quality Plan should beprepared. The complexity of any such plan woulddepend on the nature of the construction project and thesource of the recycled material but should incorporatethe following sections:
Definition of Product
2.7 This would describe the product and intended usein a similar manner to that used for normal aggregate eg4/20 coarse aggregate for use in structural concrete
Specification of Product
2.8 The specification requirements of the productshould be referenced; this could be an externalspecification or a specific section of the Quality Plan
Background Information
2.9 This would describe the source of the RCA andgive details of the specification of the source concretewherever possible. Where the source concrete comesfrom a demolished structure, some history of thestructure should be provided along with the reasons fordemolition. In particular problems such as chloridecontamination, carbonation or ASR should be recorded.
2.10 Evaluation of such background information couldwell influence whether specific potential sources ofRCA would be likely to be acceptable. However it mustbe accepted that information on some of these aspectsmay not be available.
Acceptance Criteria for Source Concrete
2.11 Acceptance criteria should be established toensure that the source concrete to be recycled meets allstatutory and regulatory requirements. The criteriashould specify the types and proportions/levels ofmaterials that are acceptable, and the methods used toestablish acceptance. If necessary testing may berequired. In the first instance these criteria would beapplied to determine whether a potential source issuitable to supply RCA. Thereafter they would be usedto ensure consistent quality.
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Chapter 2Supply, Specification and Properties of Recycled Aggregates
2.12 Acceptance would normally be based on visualinspection of each delivery from the source to theprocessing plant, supplemented by testing whereappropriate. Inspection and testing should beundertaken and managed by personnel trained with therequisite skills. Particular importance should be givento the presence of hazardous waste (eg asbestos), whichshould always be rejected. Some other potentialcontaminants are domestic waste, chemical waste, oil,felt, mastic, asphalt, metal, wood, glass, and plastic.There should be strict adherence to the definition ofRCA (II) in BRE Digest 433, in terms of acceptance. Arecord giving supply details and test results should bekept for each delivery. Where appropriate the deliveryrecords should be cross referenced with the sourcematerial including reference to any particular problems(eg chloride contamination or ASR in specificelements).
Production Method
2.13 A method statement should be prepared detailingthe process by which the RCA is produced. Productionmethods can influence RCA properties (refer 2.16). Themethod statement should include details of the qualitycontrol regimes, testing, processing, and subsequentstorage conditions of the RCA, prior to use in concrete.
Testing Regime for Recycled Aggregate
2.14 A testing regime shall be established with detailsof the tests to be carried out, acceptance criteria andfrequency – this would depend on anticipatedvariability in properties of the RCA. It should takeaccount of significant changes in the source of materials– either a different source or from different structuralelements within the existing source location, and withdifferent levels of contamination.
Sampling should be carried out in accordance withBS EN 932-1 (1997).
Appendix A gives a list of test requirements, acceptancecriteria and typical test frequencies.
Record Management
2.15 A system of recording the information generatedon incoming materials, production data and test resultsshould be established. This should also includeprovision for notification of non-conformities.
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Properties of RCA
2.16 Particles of RCA consist of natural aggregatepartially coated with mortar or cement paste. Theamount of surrounding mortar will vary depending onthe method by which the RCA was produced; forexample, an increasing number of cycles in a ballcrusher can reduce the amount of mortar present.However there are other more efficient processingmethods available, but the aim should still be to removeas much of the mortar as possible. The mortar, which islighter and more porous than natural aggregate, affectsthe physical properties of the recycled material notablywith respect to water absorption and density. This hasimplications for concrete mix design and concreteproperties such as elastic modulus, shrinkage, creep andpermeability. Moreover, the increased alkali contentresulting from the mortar, and the presence of unknownaggregate types in the parent concrete of the RCA mightincrease the risk of ASR. The parent concrete could alsohave additional contaminants such as high chloridelevels, carbonated material or ASR reaction products. Infact such features might be the reason for the concreteto have been recycled in the first place.
2.17 The differences in the properties of RCAcompared with natural aggregate require specialconsideration in relation to concrete mix design andexpected structural performance. It is crucial that theRCA is characterised by specific test procedures, andwhere possible from knowledge of the parent concretemix design and subsequent history. Required testprocedures are given in Appendix A.
Specification for the Use of RCA in StructuralConcrete
2.18 The specification in the published 1700 series ofthe SHW (2004) requires that the concrete should be adesigned concrete compliant with the requirements ofBS EN 206-1 (2000) and BS 8500-1 (2006). The basicand additional requirements are given in clauses 4.3.2and 4.3.3 of BS 8500-1 (2006) respectively. Althoughthe use of RCA and RA is not expressly permitted in thepublished specification, this Advice Note allows theopportunity to utilise RCA within specific limitationsand for particular applications.
2.19 Draft Specification clauses and Notes forGuidance have also been developed (refer clause 7.1)and are applicable to concretes in which a proportion ofthe natural aggregate has been replaced with RCA.There are additional requirements for the RCA asdetailed below.
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Chapter 2Supply, Specification and Properties of Recycled Aggregates
2.20 RCA must comply with BS EN 12620 (2002).There are several additional requirements for RCAgiven in BS 8500-2 (2006) and RILEMRecommendation TC121-DRG (1994). Before any RCAis proposed for the replacement of the coarse naturalaggregate in structural concrete, the tests detailed inAppendix A, Table A1 must be carried out and thevalues obtained must meet the acceptance criteria. OnceRCA from a particular source has been accepted assuitable, additional tests to determine the chloride ion,sodium and potassium oxide concentrations as detailedin Appendix A, Table A2 must be carried out. Thisinformation is required for checking the designedconcretes for chloride and alkali contents.
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Chapter 3Design of Concrete Mixes Incorporating RCA
MIXES
3. DESIGN OF CONCRETEINCORPORATING RCA
Procedure
3.1 This procedure refers to designs where aproportion of the natural coarse aggregate is replacedwith RCA. Due to excessive adverse effects on waterdemand and increased levels of contamination, the useof RCA as a replacement for fine aggregate (< 4mm) isnot permitted at present.
3.2 The starting point is a mix containing naturalaggregates only. This may be a well established mixdesign in use at a mixing plant or it may be aspecifically designed mix. In the latter case, it isnecessary to check the consistency and strength bycarrying out trial mixes. In order to limit the risk ofdamaging ASR, experience has shown that it can becontrolled by limiting the alkali content of the concreteand that this is practically achieved by using blends ofPortland cement (CEMI) with either ggbs, pfa or flyash. The use of low alkali content water reducing agentsshould also be considered. The aim is to produce a mixin which a proportion of the natural aggregate isreplaced with RCA. The requirement for a particularapplication is to design the RCA mix with the samecharacteristic strength and consistence as the originalmix containing natural aggregates. Dhir et al. (2001)proposed a method for achieving this.
3.3 The basis of Dhir’s method is to reduce thewater/cement ratio and coarse and fine aggregatecontents to take account of the different properties ofthe RCA. Dhir et al. (2001) designed concrete mixesusing natural aggregates with design strengths of50N/mm2, 60N/mm2 and 70N/mm2. Further mixes werethen designed with 30%, 50% and 100% of the coarsenatural aggregates replaced with RCA for each designstrength. The coarse and fine aggregate contents werealso reduced to achieve the required mixes. The results,reproduced from the report by Dhir et al. (2001), aregiven in Figure 1 and can be used as the basis of thedesign method to adjust the water/cement ratio andcoarse and fine aggregate contents to achieve therequired properties. Experience at TRL has shown thatthe water demand increases with increase in RCAcontent. It is advisable to select two or three differentwater/cement ratios and carry out trial mixes to achievethe required consistency for each. The 28 day strengthfor each water/cement ratio will be determined and the
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mix that gives the required strength selected. Theprocedure proposed for the trial mixes is given inAppendix B.
3.4 Table 2 gives an example of the method forC40/50 concretes though it should be noted that theyare not completely compliant with BS 8500. Mix Acontained 100% natural aggregate and for Mix B, 60%of the coarse aggregate was replaced with RCA whichwas crushed concrete from a precast yard in Derby. Inthis case the required strength of the RCA mix wasachieved by reducing the water/cement ratio of the100% natural aggregate mix by 0.01 and the coarse andfine aggregate contents by 22 kg/m3 and 13 kg/m3
respectively. Note that water content and the amount ofwater reducing agent was also increased to maintain theconsistency of the mix. The mean 28 day compressivestrengths of Mixes A and B were 58.5 N/mm2 and62.0 N/mm2 respectively. These strengths were in therange normally acceptable for C50 concrete.
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Chapter 3Design of Concrete Mixes Incorporating RCA
Figure 1 Mix Proportions for Mixes with Design Strength of 50 N/mm2 to 70 N/mm2
(Water Content Fixed at 165 kg/m3)(Reproduced from report by Dhir et al. (2001): Resolving Applications Issues with the Use of Recycled
Concrete Aggregate)
Table 2 Mix designs
Item Mix A Mix B100% natural 60% of natural coarse
Chapter 3Design of Concrete Mixes Incorporating RCA
Requirements for the Designed Concrete
3.5 Clause 1704 of the SHW (2004) gives the generalrequirements for the concrete. It is necessary to checkthat the designed concretes containing RCA complywith these requirements.
3.6 The total chloride content of the concrete iscalculated by summing the chloride content of each ofthe constituents and expressing the result as apercentage of the cement content inclusive of ggbs andfly ash when these are used as cement. It isrecommended that the acid soluble method ofmeasuring the chloride content of concrete given inBS 1881-124 (1988) should be used for thedetermination of the chloride content of the RCA. Thechloride content of the admixtures can be taken as thecertified value supplied by the manufacturer or bytesting in accordance with BS EN 480-10 (1997). Itshould be noted that BS 1881-124 (1988) is to bereplaced by a BS EN document, currently prEN 1744-5,which utilises a very similar test method.
3.7 It is also necessary to check that there is minimalrisk of damage as a result of alkali silica reaction.Amendment 1 to BS 8500-2 (2002) Clause 5.2.6,published in October 2003, requires that the following 4conditions are met:
1) The aggregate other than the RCA is not classedas highly or extremely reactive (see BRE Digest330 (2004)).
2) The guaranteed alkali limit of any ggbs is notmore than 1.0% Na20 eq and the guaranteedalkali limit of any fly ash or pfa is not more than5.0 % Na20 eq.
3) Where used, the pfa conforms to BS 3892-1(1997) and the fly ash conforms to BS EN 450(2005) and has a loss on ignition of not more than7%.
4) The calculated total alkali content does notexceed:
3.5 kg/m3 Na20 eq where the declared mean alkalicontent of a cement or the CEMI component of acombination is not greater than 0.75%;
3.0 kg/m3 Na20 eq where the declared mean alkalicontent of a cement or the CEMI component of acombination is 0.76% or greater.
3.8be
1)
2)
3)
4)
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Guidance for each of these conditions is givenlow:
BRE Digest 330 (2004) considers that crushedgreywacke, greywacke-type sandstones ormudstones, or combinations containing morethan 10% of these are highly reactive.
All other aggregates can be considered to be oflow or normal reactivity.
If the alkali limits of the additions (cementreplacement) are not guaranteed by the supplier,it will be necessary to determine these bymeasuring the sodium and potassium oxidecontents in accordance with the methodsdescribed in BS EN 196-2 (1995). The % Na2Oeq is equal to (%Na20 + 0.658%K20).
Conformity with BS EN 450-1 (2005) requiresthe loss of ignition test to be carried out inaccordance with BS EN 196-2 (2005) with anignition time of one hour.
The total alkali content expressed as the Na2O eqof the mix is calculated as the sum of the alkalicontents of each of the constituents andcompared with the values given:
(i) The alkali content of the cement isdetermined from the sodium and potassiumoxides and is equal to (%Na20 +0.658%K20). No account needs to be takenof the alkali in the ggbs or pfa if used at orabove the minimum recommendedproportions (BRE Digest 330-2 (2004)).
(ii) The alkali contributed by the salts in thenatural aggregates are calculated from themeasured chloride ion concentration andexpressed as the equivalent sodium oxide% Na2O eq = 0.76 x Cl- . BRE Digest330-1 (2004).
(iii) The alkali contribution from RCA shall beeither:
a) 0.20 kg Na20 eq per 100 kg of RCA;or
b) where the composition of the RCAis known (eg surplus precast units;fresh concrete returned to a plant,allowed to harden and then crushed),the alkali content calculated for theoriginal concrete.
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Alternatively, the sodium and potassiumoxides of the RCA can be determined bythe method described in BS 1881-124(1988) and these values are used tocalculate the %Na2Oeq in the RCA(%Na2O + 0.658%K2O). However itshould be noted that this method has atendency to overestimate available alkalis,and BS 1881-124 (1988) does permitalternative methods.
(iv) The contribution of alkali from theadditions will be calculated from thecertified acid soluble value supplied by themanufacturer or tested in accordance withBS EN 480-12 (1998).
3.9 A worked example of the calculation of chlorideand alkali contents of mix design B given earlier isshown in Appendix C.
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Chapter 4Properties of RCA Concrete
NCRETE
4. PROPERTIES OF RCA CO
General
4.1 The approach to mix design described earlier wasaimed at producing a concrete with a particularcharacteristic strength. As the level of replacement ofnatural aggregate with RCA increases, the changes fromthe starting concrete mix based on natural aggregatebecome more pronounced. This can lead to changes inphysical properties of the concrete and potential effectson durability. Areas where there are likely to bedifferences compared with similar strength concretesmade with natural aggregates are given below:
Effect on Physical Properties
4.2 Density is reduced. The degree of reductionincreases as the proportion of RCA increases. As anexample for 100% RCA replacement in concrete mixesof blended CEMI/fly ash and CEMI/ggbs C40/50concrete, the density is reduced by up to 5% (Calderand Roberts, 2005).
4.3 Modulus of elasticity is reduced. Measurementsof dynamic modulus after 28 days for C40/50 concretesincorporating blended CEMI/fly ash and CEMI/ggbswith various RCA replacement levels gave reductionsof about 4% with 20% RCA replacement, about 13%with 60% RCA replacement; and 20% with 100% RCA(Calder and Roberts, 2005).
4.4 BS 5400-4 (1990) states that concrete made fromsome aggregates may have a modulus ‘substantially’outside the normal range. These are permitted providedthe modulus used to check load/deflections aremeasured values and not values based on cube strength(as is often used for normal concrete), as therelationship between cube strength and modulus may bedifferent.
4.5 Shrinkage is increased. Increasing levels of RCAlead to increased shrinkage. Drying shrinkagemeasurements carried out by TRL after six months onC40/50 concretes incorporating blended CEMI/ggbswith varying levels of RCA gave a shrinkage increaseof about 11% for 20% RCA replacement but increasedto 50% for 60% replacement and 90% for 100%replacement.( Calder and Roberts, 2005). It has beenproposed that the maximum cement content permittedfor structural concrete should be reduced from550kg/m3 to 450kg/m3 when RCA is used, as the
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hardened cement paste attached to the aggregatecontributes to creep and shrinkage. However, Calderand Roberts (2005) showed that the shrinkage of CEMI/ggbs mixes with cement contents of less than 450kg/m3
were similar to the equivalent CEMI/flyash mixeswhich had cement contents up to 615kg/m3. Based onthese results it would appear that to limit the cementcontent of mixes that contain RCA may beconservative, although there may be a problem withcreep. Further work is required to investigate this.
4.6 BS 5400-4 (2000) gives some guidance onshrinkage for normal concrete but states that ‘the typeof aggregate may seriously affect the magnitude ofshrinkage and creep’. Advice is given on how to makeallowances for the restraining effect of thereinforcement.
4.7 Permeability is increased which could result inmore rapid ingress of contaminants.
4.8 There are possible effects on other concreteproperties: creep – particularly in relation toprestressing, coefficient of thermal expansion, tensilestrength, and bond strength. These require furtherevaluation before advice can be given on likely effects.Until such research has been undertaken and evaluated,the use of RCA in prestressed or post-tensionedconcrete is not permitted unless a fully justified aspectnot covered by standards submission (departuresprocedures) is agreed. The departure is to include bothdesign and specification requirements. The limit forreplacement in such cases is 20% of coarse aggregate.
4.9 The effects outlined above need to be taken intoaccount in the design of concrete structures where RCAis used. As there is only limited information availableon the degree of such effects, it would be prudent toadopt a conservative approach to the use of RCA incritical structures or elements (refer section 9).
Effect on Durability
4.10 Alkali silica reaction needs greaterconsideration where RCA is used. The mortarsurrounding the aggregate particles will increase alkalilevels and there is the possibility that the sourceconcrete for the RCA included reactive aggregates,although the risk of expansion would be reducedbecause of the higher porosity of RCA. If the
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Chapter 4Properties of RCA Concrete
specification for the original source concrete is knownthen the aggregate reactivity could be assessed but thiswill not always be the case. There is also the possibilitythat partial replacement of natural aggregates with RCAcould result in pessimum proportions – theconcentration of reactive aggregates where the reactionis maximised. Until recently a very conservativeapproach was taken by considering all RCA as highlyreactive. This restriction was relaxed in an amendmentto BS 8500-2 (2002) Clause 5.2.6 in October 2003 sothat RCA can be classed as having normal reactivity forconcrete mix design provided some other conditions aremet (see Appendix C). However if it is known thatactive ASR or significant quantities of ASR werepresent in a source structure this would preclude its useas a source of RCA. Moreover if there is any reason tobelieve that there might be reactive aggregates in theRCA, a petrograhical examination should be carriedout.
4.11 Freeze thaw resistance is generally similar incomparison with natural aggregate concrete, providedthat compliant and consistent quality controlled RCAhas been used.
4.12 Corrosion resistance depends on the reaction ofRCA concrete to carbonation, chloride ingress and therate of corrosion once initiated.
4.13 As RCA concrete is more permeable than naturalaggregate concrete carbonation may proceed morerapidly but will depend on the moisture content.However the increased alkalinity conferred by RCAmay mitigate any effects. Ongoing research at TRL hasshown no significant increase in the rate of carbonationafter 12 months accelerated testing (Calder and Roberts,2005).
4.14 The increased permeability may also increase therate of chloride ingress and could lead to highercorrosion rates. However the increased alkali contentcould assist in raising the threshold chloride levelwhich triggers corrosion. Research is underway at TRLto investigate the relative corrosion resistance of RCAand natural aggregate concrete but no conclusions canbe drawn at the time of writing.
4.15 Current practice is to apply a hydrophobic pore-lining impregnant such as silane to at risk structuralconcrete to limit ingress of moisture and associatedchlorides. This requirement should also apply toconcrete containing RCA.
4.16 Sulfate attack can result in expansive disruptionof concrete. In some cases sulfate contamination could
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e present in RCA (eg from plaster). It is important thathis is taken into account in choosing source materialor RCA. Resistance to external sources of sulfateould be similar to natural aggregate concrete. Testing
or acid soluble sulfates must be included in thepecification for RCA – the limit being < 1% asequired in BS 8500-2.
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5. COMPATIBILITY ISSUES
5.1 In general RCA concrete would not be expectedto pose any difficulties in relation to the usual cementreplacements and admixtures that could be used inconcrete. However trial mixes should be used if there isany reason for concern. Additions (cementreplacements) such as fly ash and ggbs are compatiblewith RCA and generally would be adopted.
5.2 The use of porelining hydrophobic impregnants(eg Silane) are unaffected. Requirements are containedin BD 43 and are no different for concrete containingRCA.
Chapter 5Compatibility Issues
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6. DESIGN ISSUES
6.1 Design related issues have been identifiedthroughout this Advice Note and should be addressedby designers if RCA is to be selected (refer clause 9.1and 9.2).
6.2 If RCA is to be adopted it should be identified inthe Approval in Principle documentation for particularstructures and the associated specification will besubject to departure procedures in accordance withBD 2.
Chapter 6Design Issues
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7. SPECIFICATION
7.1 Alongside the research work at TRL, aSpecification and related Notes for Guidance for RCAhas been developed. It is proposed that this will not beformally published for the present as part of theMCHW, as they are likely to evolve and developthrough experience with RCA, but can be madeavailable by contact with Overseeing Organisations. Forthe time being any use of RCA and its specificationshould be considered as an aspect not fully covered bystandards and will require submission and approvalthrough the Overseeing Organisation’s departuresprocesses, as part of technical approval arrangementsand in compliance with BD 2. All such submissions willrequire fully detailed specifications together withproposals for quality control. Where levels ofreplacement are between 20% and 60% of naturalaggregate (refer clause 9 below), or is for pre-stressedor post-tensioned applications, the submission shouldalso include proposals for design considerations.
7.2 It is strongly recommended that trial mixes areundertaken when the use of RCA is proposed, includingthe construction of trial panels to check on finishes andmethods of placement. On occasion it may be necessaryfor such panels to be tested by coring to verify adequatecompaction, and integrity of concrete surroundingreinforcement.
Chapter 7Specification
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8. IN SERVICE ISSUES
8.1 Inspection of structures incorporating RCAshould be carried out in the same way as for structureswith natural aggregate. Special inspection and testingtechniques (eg half cell potential measurement,chlorides, resistivity) will not be affected and will havethe same assessment criteria.
8.2 Concrete repair procedures should not beaffected.
8.3 As-built records should be provided withdocumentation to identify the source, type and quantityof any RCA used in a structure, test results and thelocations where the materials have been used inaccordance with BD 62. Where required it should alsobe recorded in electronic structures managementinformation systems. This will assist in relating anydefects which might subsequently develop to thepresence of RCA in the structural concrete.
Chapter 8In Service Issues
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9. LIMITATIONS
Recommended Replacement Levels
9.1 Research and experience suggest thatreplacement of 20% of natural aggregate with RCA forreinforced concrete should have minimal effect onconcrete properties or design issues and no specialadditional measures need be undertaken. This limit hasbeen included in the specification clauses.
9.2 At increased replacement levels effects on someconcrete properties assume more importance and needcareful consideration during design. Based on currentexperience a maximum replacement level of 60% isrecommended. However for replacement levels between20% and 60% trial mixes are essential at an early stageand designers must consider design and structuralperformance implications. At these higher replacementlevels designers will require a justified aspect notcovered by standards via departures procedures,including details of any proposed changes in designparameters.
Types of Structure
9.3 The use of RCA in structural concrete is arelatively new application. Hence until a significanttrack record of performance is available, a cautiousapproach is being taken to its use in structural concrete.The type of RCA available will also be of relevance indeciding whether or not to use RCA in any particularapplication. A known high quality source such as wastefrom a pre-casting yard would pose fewer risks than,say, general demolition waste.
9.4 Based on the potentially higher drying shrinkage,RCA is not to be used in prestressed and post-tensionedconcrete applications above the 20% replacement limitand only then with an agreed departure from standard.It is also recommended that RCA is not used instructurally critical insitu concrete bridge elements,such as mid to long span bridge decks greater than 20metres. Where the concrete is buried or difficult toaccess for future inspection the maximum 20%replacement limit should be adopted. It is anticipatedthat the main initial uses will be in large exposed areasof less structurally critical concrete such as abutments,piers, retaining walls and foundations.
Chapter 9Limitations
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Chapter 10References
10. REFERENCES
British Standards Institution (1988). Testing concrete.Methods for analysis of hardened concrete.BS 1881-124. London: British Standards Institution.
British Standards Institution (1990). Steel, concreteand composite bridges. Code of practice for design ofconcrete bridges British Standard BS 5400-4. London:British Standards Institution.
British Standards Institution (2005). Cement.Composition, specifications and conformity criteria forcommon cements. BS EN 197-1. London: BritishStandards Institution.
British Standards Institution (2005). Methods oftesting cement. Chemical analysis of cement.BS EN 196-2. London: British Standards Institution.
British Standards Institution (2005). Fly ash forconcrete. Definitions, specification and conformitycriteria. British Standard BS EN 450-1. London: BritishStandards Institution.
British Standards Institution (1996). Specification forsulfate-resisting Portland cement British StandardBS 4027. London: British Standards Institution.
British Standards Institution (1997). Admixtures forconcrete, mortar and grout. Test methods.Determination of water soluble chloride content.BS EN 480-10 (1997). London: British StandardsInstitution.
British Standards Institution (1997). Tests for generalproperties of aggregates. Methods for sampling.BS EN 932-1. London: British Standards Institution.
British Standards Institution (1997). Pulverized-fuelash. Specification for pulverized-fuel ash for use withPortland cement. British Standard BS 3892-1. London:British Standards Institution.
British Standards Institution (1997). Tests forgeometrical properties of aggregates. Determination ofparticle size distribution. Sieving method. BritishStandard BS EN 933-1. London: British StandardsInstitution, London.
May 2007
British Standards Institution (1997). Tests forgeometrical properties of aggregates. Determination ofparticle shape. Flakiness index. British StandardBS EN 933-3. London: British Standards Institution,London.
British Standards Institution (1998). Admixtures forconcrete, mortar and grout. Test methods.Determination of the alkali content of admixtures.BS EN 480-12. London: British Standards Institution.
British Standards Institution (1998). Tests forgeometrical properties of aggregates. Determination ofshell content. Percentage of shells in coarseaggregates. British Standard BS EN 933-7. London:British Standards Institution, London.
British Standards Institution (1998). Tests formechanical and physical properties of aggregates.Methods for the determination of resistance tofragmentation. BS EN 1097-2 London: BritishStandards Institution.
British Standards Institution (2000). Concrete.Specification, performance, production and conformity.BS EN 206-1. London: British Standards Institution.
British Standards Institution (2000). Tests formechanical and physical properties of aggregates.Determination of particle density and water absorption.British Standard BS EN 1097-6. London: BritishStandards Institution.
British Standards Institution (2000). Testinghardened concrete. Density of hardened concrete.BS EN 12390-7. London: British Standards Institution.
British Standards Institution (2000). Testing freshconcrete. Slump test. British Standard BS EN 12350-2.London: British Standards Institution.
British Standards Institution (2002). Testinghardened concrete. Compressive strength of testspecimens. BS EN 12390-3. London: British StandardsInstitution.
British Standards Institution (2002). Tests for generalproperties of aggregates. Methods for sampling. BritishStandard BS 932-1. London: British StandardsInstitution.
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Chapter 10References
British Standards Institution (2006). Concrete.Complementary British Standard to BS EN 206-1.Method of specifying and guidance for the specifier.British Standard BS 8500-1. London: British StandardsInstitution.
British Standards Institution (2006). Concrete.Complementary British Standard to BS EN 206-1.Specification for constituent materials for concrete.British Standard BS 8500-2. London: British StandardsInstitution.
British Standards Institution (2002). Aggregates forconcrete. British Standard BS EN 12620. London:British Standards Institution.
British Standards Institution (2002). Testinghardened concrete. Compressive strength of testspecimens. BS EN 12390-3. London: British StandardsInstitution.
Building Research Establishment (1998). Recycledaggregates. BRE Digest 433. Garston: BuildingResearch Establishment Ltd.
Building Research Establishment (2004). Alkali-silica reaction in concrete. BRE Digest 330. Garston:Building Research Establishment Ltd.
Calder, AJJ and Roberts, CP (2005). The use ofrecycled aggregate in structural concrete. TRLPublished Project Report PRR036. Crowthorne, TRLLtd.
Calder, AJJ and Mckenzie, M (2005). Thesusceptibility of recycled concrete aggregate to alkalisilica reaction. TRL Published Project PPR037.Crowthorne, TRL Ltd.
CSS, Quarry Products Association, HighwaysAgency, DETR, BRE (2000). Quality control theproduction of recycled aggregates. Garston: BuildingResearch Establishment Ltd.
Dhir RK. MC Limbachiya and A Beggs (2001).Resolving application issues with the use of recycledconcrete aggregate. Confidential Report CTU/1601.Dundee: University of Dundee.
The Highways Agency, Quarry ProductsAssociation, WRAP. The quality protocol for theproduction of aggregates from inert waste.
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The Highways Agency, the Scottish OfficeDevelopment Department, the Welsh AssemblyGovernment (Y Llywodraeth Cynulliad Cymru) andthe Department of the Environment for NorthernIreland (2004). Manual of Contract Documents forHighway Works. Volume 1: Notes for Guidance on theSpecification for Highway Works. London: TheStationery Office, London.
The Highways Agency, the Scottish OfficeDevelopment Department, the Welsh AssemblyGovernment (Y Llywodraeth Cynulliad Cymru) andthe Department of the Environment for NorthernIreland (2004). Manual of Contract Documents forHighway Works. Volume 2: Notes for Guidance on theSpecification for Highway Works. London: TheStationery Office, London.
The Highways Agency, the Scottish OfficeDevelopment Department, the Welsh AssemblyGovernment (Y Llywodraeth Cynulliad Cymru) andthe Department of the Environment for NorthernIreland. BD 2 Technical Approval of HighwayStructures
The Highways Agency, the Scottish OfficeDevelopment Department, the Welsh AssemblyGovernment (Y Llywodraeth Cynulliad Cymru) andthe Department of the Environment for NorthernIreland. BD 62 As Built, Operational and MaintenanceRecords for Highway Structures.
The Highways Agency, the Scottish OfficeDevelopment Department, the Welsh AssemblyGovernment (Y Llywodraeth Cynulliad Cymru) andthe Department of the Environment for NorthernIreland. BD 43 The Impregnation of Reinforced andPrestressed Concrete Highway Structures usingHydrophobic Pore-Lining Impregnants.
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11. ENQUIRIES
All technical enquiries or comments on this Advice Note should be sent in writing as appropriate to:
Director of Trunk Roads: Infrastructure andProfessional ServicesTransport ScotlandTrunk Road Network Management8th Floor, Buchanan House58 Port Dundas Road A C McLAUGHLINGlasgow Director of Trunk Roads: InfrastructureG4 0HF and Professional Services
Chief Highway EngineerTransport WalesWelsh Assembly GovernmentCathays Parks M J A PARKERCardiff Chief Highway EngineerCF10 3NQ Transport Wales
Director of EngineeringThe Department for Regional DevelopmentRoads ServiceClarence Court10-18 Adelaide Street R J M CAIRNSBelfast BT2 8GB Director of Engineering
Chapter 11Enquiries
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APPENDIX A TEST REQUIREMENTS FORACCEPTANCE OF RCA
The tests listed in Table A.1 refer to basic properties ofthe aggregate. Tests listed in Table A.2 refer toadditional tests required principally for the design ofappropriate concrete mixes. However if chloride levelsare particularly high this could preclude a particularsource of RCA from consideration.
Table A.1 Schedule of Aggregate Tests
Property Test Method Standard Acceptance criteria
Grading Determination of particle BS EN 933-1 Sand content < 5%size distribution
Impurities Determination of shell BS EN 933-7a Brick/masonry < 5%content
Asphalt < 5%
Lightweight materialb < 0.5%
Other foreign materialc < 1%
Bulk density and Determination of particle BS EN 1097-6 Dry densityd > 2000kg/m3
water absorption density and water absorptionWater absorptiond < 10%
Particle shape Determination of particle BS EN 933-3 Flakiness index shall not exceed 35shape. Flakiness index
Strength Method for determination of BS EN 1097-2 LA coefficient shall be less than 40resistance to fragmentation
Sulfate content Method for analysis of BS 1881-124e < 1% by mass of samplehardened concrete
Notes
a The standard test is to determine the shell content of a sample of aggregate. To determine the content of eachof the impurities, the ‘name of each impurity’ was substituted for ‘shells’ in the standard. An alternative is touse the test in BS 8500-2 Annex B.
b Material with a density less than 1000kg/m3 but excluding ‘floating non-stony’ materials.
c eg: glass, plastics, metal.
d Can be declared where known or tested.
Appendix ATest Requirements for Acceptance of RCA
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Table A.2 Additional Tests for Chloride and Alkali Content
Property Test Method Standard
Chloride content Method for analysis of hardened concrete BS 1881-124*
Sodium oxide and potassium oxide Method for analysis of hardened concrete BS 1881-124 **
* It should be noted that BS 1881-124 (1988) is to be replaced by a BS EN document, currently prEN 1744-5,which utilises a very similar test method.
** Refer to clause 3.8 for further guidance.
Table A.3 Frequency of Testing*
Property Test Method Standard Frequency
Grading Determination of particle size distribution BS EN 933-1 1 per week
Impurities Determination of shell content BS EN 933-7a 1 per day**
Bulk density and Determination of particle density and BS EN 1097-6 1 per weekwater absorption water absorption
Particle shape Determination of particle shape. BS EN 933-3 1 per monthFlakiness index
Strength Method for determination of resistance BS EN 1097-2 1 per monthto fragmentation
Sulfate content Method for analysis of hardened concrete BS 1881-124 4 per year
Chloride content Method for analysis of hardened concrete BS 1881-124 4 per year
Sodium oxide and Method for analysis of hardened concrete BS 1881-124 4 per yearpotassium oxide
* The frequencies given are typical values. These may be adjusted to take account of the source of the RCA and thenature of the construction project. If there was reason to suspect changes in levels in particular parts of a structuresupplying the source concrete for the RCA, more frequent testing is required.
** Where successive test results are well below the limiting values the frequency may be reduced to one per weekcoupled with a daily inspection of the stockpile. If from an inspection an increase in the impurities content issuspected then further tests shall be made. For supplies from consistent sources like preconsumer waste thenfrequency of tests may be reduced to one per month, subject to satisfactory daily inspections.
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E FOR TRIAL MIXES
s
r
Appendix BProcedure for Trial Mixes Using RCA
APPENDIX B PROCEDURUSING RCA
The following procedure for carrying out the trial mixeis recommended:
The aggregate content of each fraction is specified asthe saturated surface dry (SSD) weight per cubic metre,wssd. The water absorption measured by the methodgiven in BS EN 1097-6 (2000) is denoted as wa.
All the aggregates should be stored in the laboratory foa few days prior to being used. A representative sampleof each aggregate is taken and the moisture content(mc) determined in accordance with BS EN 1097-5(1999).
For each fraction,
the weight of aggregate Wag is calculated as:
)(1)(1
wamcwW ssdag +
+=
and the excess water we is:
)(1)(
wa wa- mcww ssde +
=
These formulae are used to calculate the weight ofstock material of each aggregate size required and theadjustment needed to the total water in the mixture toaccount for the moisture in the aggregate prior tomixing. The total water to be added to the mixture wm isthen calculated as:
∑−= efm www
where wf is the specified free water content and is ∑wethe sum of the excess water in each fraction.
The aggregates and water (including the water reducingagent) are first batched and placed in the pan mixer.These are mixed for four minutes to allow theaggregates to become close to saturation. The cement isthen added and mixing continued for a further threeminutes.
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It is recommended that the slump is measured on themixed concrete in accordance with BS EN 12350-2(2000) and 100mm cubes are cast to determine thedensity (BS EN 12390-7 (2000) and compressivestrength (BS EN 12390-3 (2002)).
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ION OF CHLORIDE CLASSSMENT OF ASRILITY FOR A CONCRETEN
sit
.7
.3
-
-
-
-
.0
.0
Appendix CCalculation of Chloride Class and Assessment of ASR Susceptibility for a
Concrete Mix Design Incorporating RCA
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APPENDIX C CALCULATAND ASSESSUSCEPTIBMIX DESIG
This example shows the calculation of the chloride andalkali contents of a mix containing 60% RCAreplacement of coarse aggregate. This is mix B inclause 3. The calculated values are then used to give achloride class and to assess potential ASR reactivity.
Table C.1 Calculation of Ch
Item Chloride Sodium Potaion oxide ox
content content con(%) (%) (%
Cement 0.06 0.11 0
GGBS 0.08 0.31 0
WRA 0.00 -
Natural Sand 0.05 -marine
20-10mm 0.03 -
10-5mm 0.02 -
(RCA) 20-10mm 0.01 0.01 0
10-5mm 0.01 0.01 0
Total
Check on Chloride Content of Mix
The mass of chloride ions in each constituent issummed to give the total chloride content of the mix.This is expressed as the percentage by mass of cement(inclusive of the ggbs) to be 0.19%. The chloride ioncontent for this particular mix would be classed as Cl0,20 and would be permitted for concrete containingembedded metal. Note that this mix would not be
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INCORPORATING RCA
Calculation of chloride and alkali levels is shown inTable C1. The chloride ion and sodium and potassiumoxide contents of each of the constituents aredetermined by the appropriate test methods or fromcertified values from the manufacturers.
loride Ion and Alkali Contents
sium Sodium Mass of Mass of Mass ofde oxide each chloride alkalient eq constituent ion) (%) (kg/m3) (kg/m3) (kg/m3)
The mix design is checked against the four conditionsset out in amendment to Clause 5.2.6 to BS 8500-2(2002):
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Appendix CCalculation of Chloride Class and Assessment of ASR Susceptibility for aConcrete Mix Design Incorporating RCA
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1) The natural aggregate is a dredged flint graveland therefore is classed as normally reactive.
2) The alkali content of the ggbs is less than limit of1.0% Na20 eq.
3) This clause was not applicable as pfa is not usedfor this concrete.
4) The sodium oxide equivalents for the cement,ggbs and RCA are calculated from the sodiumand potassium oxide contents as (%Na20 +0.658%K20). The sodium oxide equivalent forthe natural marine aggregate is calculated as 0.76times the chloride ion concentration. Thecertified value supplied by the manufacturer isused for the WRA.
The calculated total alkali content of the mix(1.80kg/m3) is less than the limit of 3.0kg/m3
specified for a cement or a CEMI component of acombination which is not greater than 0.75%.
Points 1-4 above demonstrate that the risk of Mix Bdeveloping ASR is minimal.
