HD 35-04 Provisions for the Use of Secondary and Recycled Materials (Nov 2004)

November 2004

DESIGN MANUAL FOR ROADS AND BRIDGES

VOLUME 7 PAVEMENT DESIGN ANDMAINTENANCE

SECTION 1 PREAMBLE

PART 2

HD 35/04

CONSERVATION AND THE USE OFSECONDARY AND RECYCLEDMATERIALS

SUMMARY

This part, previously called ‘Technical Information’,gives advice on the conservation and use of reclaimedmaterials in road construction and maintenance. Thisrevised version has been updated and now includesadditional materials and the latest advice.

INSTRUCTIONS FOR USE

1. Remove Contents pages for Volume 7 and insertnew Contents pages for Volume 7, datedNovember 2004.

2. Remove HD 35/95 from Volume 7, Section 1which is superseded by this Standard and archiveas appropriate.

3. Insert HD 35/04 into Volume 7, Section 1.

4. Please archive this sheet as appropriate.

Note: A quarterly index with a full set of VolumeContents Pages is available separately from TheStationery Office Ltd.

HD 35/04

Conservation and the Use ofSecondary and Recyclced

Materials

Summary: This part, previously called ‘Technical Information’, gives advice on theconservation and use of reclaimed materials in road construction andmaintenance. This revised version has been updated and now includesadditional materials and the latest advice.


THE HIGHWAYS AGENCY

SCOTTISH EXECUTIVE

WELSH ASSEMBLY GOVERNMENTLLYWODRAETH CYNULLIAD CYMRU

THE DEPARTMENT FOR REGIONAL DEVELOPMENTNORTHERN IRELAND

Volume 7 Section 1Part 2 HD 35/04

November 2004

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Registration of Amendments


November 2004

REGISTRATION OF AMENDMENTS

Amend Page No Signature & Date of Amend Page No Signature & Date ofNo incorporation of No incorporation of

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Registration of Amendments

VOLUME 7 PAVEMENT DESIGN ANDMAINTENANCE

SECTION 1 PREAMBLE

PART 2

HD 35/04

CONSERVATION AND THE USE OFSECONDARY AND RECYCLEDMATERIALS

Contents

Chapter

1. Introduction

2. Provisions for the Use of Secondary andRecycled Materials

3. References

4. Enquiries


November 2004


November 2004 1/1

Chapter 1Introduction

1. INTRODUCTION

General

1.1 This part contains general items of a technicalnature that have relevance to the construction andmaintenance of all types of pavement. Advice is givenon the conservation and use of secondary and recycledmaterials in road construction and maintenance.Specific or general provision for the use of recycled andsecondary materials within the Specification(MCHW 1) does not automatically infer environmentalsuitability, and although the increased use of recycledand secondary materials can have a significant positiveimpact on the environment via reductions in landfilling,quarrying and transportation of aggregates, it isimportant to assess the acceptable application of thesematerials in line with current environmental guidelines.

Scope

1.2 This part gives guidance to design organisationson conservation techniques and the use of secondaryand recycled materials that are currently permitted inthe Specification (MCHW 1) and in the earthworks,drainage and pavement construction parts of the DesignManual for Roads and Bridges (DMRB 4.1, 4.2 and 7).

Implementation

1.3 This part may be used forthwith on all schemesfor construction, improvement and maintenance oftrunk roads including motorways being prepared,provided that in the opinion of the OverseeingOrganisation, this would not result in significantadditional expense or delay in progress. Designorganisations should confirm its application toparticular schemes with the Overseeing Organisation.For use in Northern Ireland, this part will be applicableto those roads designated by the OverseeingOrganisation.


Chapter 2Provisions for the Use of Secondary and Recycled Materials

SE OF SECONDARY AND
2. PROVISIONS FOR THE URECYCLED MATERIALS
General

2.1 The attention of those responsible for the design,specification, construction and maintenance of roads isdrawn to the opportunities to conserve and re-usematerials arising from roadworks, as well as thepotential uses for secondary or recycled materials fromother sources that may be proposed when cost effective.

2.2 It is Government policy to encourageconservation and facilitate the use of reclaimed andmarginal materials wherever possible, in order to obtainenvironmental benefits and reduce the pressure onnatural reserves of primary aggregates. The LandfillTax and Aggregate Levy are seen as powerful driverstowards sustainable construction with the main aimsbeing the increased use of secondary and recycledmaterials in construction, a reduction in constructionwaste going to landfill, and a reduction in primaryaggregates output per unit of construction value.

2.3 Suitable materials may be those reclaimed fromroads during reconstruction, from residues of industrialprocesses including mining, and from the demolition ofother construction projects. Such materials may providegood value for money, particularly if their use involvesless haulage. Where existing road foundations are ingood condition, conservation of the pavement structureby strengthening with an overlay or inlay and wideningwhere necessary, can also be an effective strategy forreducing the demand for primary aggregates.

2.4 The Joint Circular from the DoE (20/87), DoT(3/87) and Welsh Office (36/87) entitled ‘Use of WasteMaterial for Road Fill’ sets out administrativeprocedures to ensure that information about future roadschemes and their likely fill requirements are given tolocal Planning Authorities at the earliest possible stage.The circular states that, while it will be for tenderers tochoose their sources of fill on a commercial basis, theacceptability of sites for borrow pits is a matter for theland use planning system. It recommends that PlanningAuthorities should therefore treat planning applicationsfor borrow pits in the same way as applications forother mineral developments, taking into account theavailability of suitable material. In Scotland theNational Planning Policy Guideline NPPG4, Land forMineral Working, issued by the Scottish OfficeEnvironment Department, gives guidance to planning

November 2004

authorities on the recycling and re-use of constructionwaste and materials in waste tips where this isenvironmentally acceptable.

2.5 The Specification for Highway Works(MCHW 1) permits a wide range of reclaimed materialssuch as road planings, crushed concrete and mineralby-products such as slags, furnace bottom ash (FBA)and the like, to be used in place of primary aggregate.But where the Specification (MCHW 1) refers toindividual materials, this may be taken to imply thatother materials not specified by name might beinherently unsuitable in some way even if conformingto the appropriate standard. One aim of this advice noteis to highlight the existing provisions made in theSpecification (MCHW 1) for the reuse and recycling ofreclaimed materials and to encourage their widestapplication.

2.6 The variability of recycled and secondarymaterials may require more frequent test regimes toenable their re-use at high level within the roadpavement construction. Recycling of road planingsrequires considerable processing and control proceduresto ensure standards are maintained. Thus it may provemore efficient and cost effective to re-use such arisingslower down in the pavement or in the foundations, oralternatively to limit replacement levels in higher layersto percentages which will minimise additional testing.Similarly, the re-use of old pavement quality concrete,after crushing and grading, as recycled concreteaggregate for the lower layer of the monolithic slab oras a continuously reinforced concrete base (CRCR)slab, is likely to prove efficient and cost effective.

2.7 The conservation of existing pavements and theuse of secondary and recycled materials helps to reducethe impact on the environment by reducing theextraction of primary aggregates and at the same timereduces the amount of waste being generated.Environmental benefits can also arise from theconsequent reduction of construction traffic on localroads. Any additional costs of sorting and processing ofsecondary or recycled materials may be offset byreduced energy requirements compared with theextraction and transportation of primary aggregates.There may also be a reduction in the amount of freshbitumen required when recycling bituminous boundmaterials.

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Application Pipe Embank- Capping Unbound Hydraulically Bitumen PQand Bedding ment and Mixtures Bound Bound Concrete

Series Fill for Mixtures LayersSub-base for Sub-base

and Base

Material 500 600 600 800 800 900 1000

Blast furnace Slag

Burnt Colliery Spoil x x x

China Clay Sand/Stent

Coal Fly Ash/PulverisedFuel Ash (CFA/PFA) x

Foundry Sand

Furnace Bottom Ash(FBA) x x x

Incinerator BottomAsh Aggregate (IBAA)

Phosphoric Slag

Recycled Aggregate

Recycled Asphalt

Recycled Concrete

Recycled Glass x

Slate Aggregate

Spent Oil Shale/Blaise x x x

Steel Slag x

Unburnt Colliery Spoil x x x x x

KEY:

Specific (permitted as a constituent if the material complies with the Specification (MCHW 1)) orGeneral Provision (permitted as a constituent if the material complies with the Specification (MCHW 1)requirements but not named within the Specification (MCHW 1)).

x Not permitted.

IMPORTANT NOTES:

1. Table 2.1 is for guidance only and reference must be made to the accompanying text and the Specification (MCHW 1).Materials indicated as complying with the Specification (MCHW 1) for a particular application may not necessarilycomply with all the requirements of the series listed, only particular clauses. For example in the 600 series, UnburntColliery Spoil can satisfy the Specification (MCHW 1) as a general fill, but is excluded as a selected fill; and in Series1000 recycled or secondary materials are not permitted within the running surface of PQ concrete. Reference should alsobe made to the Specification (MCHW 1) for any maximum constituent percentages of specific recycled or secondaryaggregates. For example in the 1000 Series, the maximum by mass constituent of Recycled Asphalt is given under thelimits for ‘other material’ (Table 10/2) within the Specification (MCHW 1).

2. There is no Specific or General Provision for the use of recycled glass as an aggregate in PQ concrete or HydraulicallyBound Mixtures due to the potential for deleterious alkali-silica reaction (ASR). However, its use may be permitted bythe Overseeing Organisation if sufficient provisions to minimise the risk of deleterious ASR are included in the mixturedesign.

3. There is no Specific or General Provision for the use of steel slag as an aggregate in PQ concrete or HydraulicallyBound Mixtures due to the potential for volume instability. However, its use may be permitted by the OverseeingOrganisation if sufficient assurance of volume stability is provided.

Table 2.1: Specification for Highway Works (MCHW 1):Application of Secondary And Recycled Aggregates

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The Provision for Secondary and RecycledMaterials Within the Specification for HighwayWorks (MCHW 1)

2.8 Table 2.1 illustrates that all the secondary andrecycled materials listed can be suitable in one form oranother for inclusion in drainage work or earthworks orfoundations or pavements, providing always that theycomply with the requirements of the Specification(MCHW 1). For definitions of terminology used in thissection refer to the Glossary of Terms (paragraph 2.37).

Health and Safety

2.9 Although Table 2.1 indicates that all thesecondary and recycled materials listed are permitted bythe Specification (MCHW 1), consideration must begiven to aspects of health and safety. Of particularconcern is dust arising from materials, which may affectboth workers and others, as well as reducing visibilityand hence safety. Leachate from reclaimed materialsshould be assessed from a health and safety point ofview, and appropriate protective equipment used andwashing facilities provided.

Series 500 Drainage

2.10 Recycled coarse aggregate and recycled concreteaggregate are specified by name. Maximum watersoluble sulphate levels may restrict the use of some ofthe secondary and recycled materials listed in Table 2.1.Other uses of secondary and recycled materials includerecycled tyres as drainage materials in the form ofbonded crumb rubber.

Series 600 Earthworks

2.11 The Specification (MCHW 1) permits a verywide range of bulk fill materials under the headings‘general granular fill’ and ‘general cohesive fill’.Unacceptable materials are listed and include materialshaving hazardous chemical or physical properties.Thus, the possibility of leachate from any material mustbe addressed.

Blast Furnace Slag can comply as selected granularfill and is specified by name, but this would be awasteful re-use of a premium material. Slag isspecifically excluded from granular fill overlyingburied steel structures.

Burnt Colliery Spoil can comply as bulk or selectedgranular fill and is specified by name for manyapplications.

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November 2004

hina Clay Sand and Stent, being natural aggregates,n both comply as bulk and selected granular fills.

oal Fly Ash/Pulverised Fuel Ash is specified byme as PFA in both general cohesive fill containingt more than 20% FBA, and as conditioned ash inlected cohesive fill to structures and for reinforcedrth.

urnace Bottom Ash (FBA) can comply as bulk filld as selected granular fill that is to be stabilised withment. However, it is not a named selected granular

ll since it would generally fail the strengthquirement.

oundry Sands can comply as a bulk fill and as alected granular fill.

cinerator Bottom Ash Aggregate (IBAA) canmply as bulk fill and as a selected granular fill.

hosphoric Slag can comply both as a bulk fill and asselected fill. However, as with blast furnace slag, thee of this premium material for granular fill would beasteful.

ecycled Aggregate, as crushed demolition debris, canmply as bulk fill provided it does not containacceptable materials as defined in this series.

ecycled Asphalt can comply as bulk fill, although thisould in general be a wasteful re-use of a premiumaterial. Accurate measurement of the moisture content bituminous planings can be difficult and should beven specific consideration.

ecycled Concrete can comply as a selected granularll and is specified by name as crushed concrete undernumber of applications.

ecycled Glass could comply as a bulk fill and selectedanular fill but would be unlikely to be used in thesercumstances.

ecycled Rubber in the form of shredded tyres or tyreles could potentially be used as a lightweight bulk fill back fill to structures. Rubber is not named in theecification (MCHW 1) and advice should be sought

om specialists, and the Overseeing Organisationnsulted with regard to its use. Of note is any potentialr pyrolysis or combustion of these materials.

ate Aggregate is a natural aggregate and can comply both bulk and selected granular fill.

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Spent Oil Shale/Blaise can comply as bulk fill but isnot permitted as selected granular fill.

Steel Slags are excluded (except where mentionedbelow) due to the possible presence of free lime (CaO)and/or free magnesia and the consequent risk ofexpansion when hydration occurs. Weathering of steelslag over several months allows these hydrationreactions to occur and produces a more stable material.Weathered Steel Slag (as specified in Series 800) maybe permissible if adequately controlled to minimise riskof particle disintegration or expansion.

Unburnt Colliery Spoil can comply as bulk fill but isexcluded from selected granular fill.

Series 600 Capping

2.12 Table 2.1 shows that all secondary and recycledmaterials except steel slag (except where mentionedbelow) and unburnt colliery shale can meet theSpecification (MCHW 1) as capping on their own or aspart of a combination, as either unbound selectedgranular fill or bound with cement and/or other binders.Weathered steel slags can comply as selected granularfill. Selected conditioned PFA for stabilisation withcement to form capping is specified as a separate class.Accurate measurement of the moisture content ofasphalt planings, and the determination of optimummoisture content, can be difficult and should be givenspecific consideration.

Series 800 Unbound Mixtures for Subbases

2.13 Recycled concrete, asphalt (up to 50% by massas a constituent of recycled aggregate) and aggregate,blast furnace slag, and non-plastic shale (burnt collieryspoil and spent oil shale) can all comply with theSpecification (MCHW 1) and are named. Specificprovision is given for a sub-base comprised of asphaltplanings. Steel slag, well weathered and conforming tothe requirements of BS 4987-1 is also specified. Chinaclay Stent and slate aggregate are quarried rocks andcan comply when processed. Foundry sand, glass,IBAA (up to 15% by mass) and China clay sand canalso comply as components within the Specification(MCHW 1). Higher proportions of IBAA may beacceptable within unbound sub-bases followingadditional testing.

Series 800 Hydraulically Bound Mixtures forSubbase and Base

2.14 Slag Bound Material (SBM), bound withGranulated Blast Furnace Slag (GBS), and using

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recycled coarse and/or concrete aggregate is namedwithin the Specification (MCHW 1). All the secondaryand recycled materials in Table 2.1 can meet theSpecification (MCHW 1) as the coarse aggregate orwithin blends for SBM. Alternative binders include FlyAshes (including PFA) to form Fly Ash Bound Mixtures(FABM), Flue gas desulphurised Gypsum and CementKiln Dust (CKD). The potential risk of expansivechemical reactions exists with the incorporation ofgypsum into a bound material and should be givenspecific consideration.

2.15 Cementitious binders in this series can include anumber of alternatives to Portland cement with wellestablished properties. These include Portland Fly AshCement, Portland Slag Cement and variouscombinations including GGBS and PFA. Wherecrushed concrete aggregate is used (within recycledconcrete/aggregate), it should only be sourced fromidentified structures with a known history. Appropriateadditional testing is required under the Specification(MCHW 1) to detect substances and chemicals harmfulto the durability of concrete.

2.16 All reclaimed materials listed in Table 2.1 can beused for Cement Bound Granular Mixtures (CBGM)formally called Cement Bound Materials (CBM) if theycomply with the Specification (MCHW 1). CementBound Granular Mixtures are now included in Series800 of the specification (MCHW 1) together with allother Hydraulically Bound Mixtures.

2.17 Any of the reclaimed materials listed in Table 2.1to comply with the requirements for Cement BoundGranular materials may require washing or processing.Strength requirements for the various Grades of CementBound Granular Mixtures are established on a scheme-specific basis.

2.18 Recycled aggregate, recycled concrete,Phosphoric slag, crushed air-cooled blast furnace slagand PFA are all capable of complying with theSpecification (MCHW 1). Stent and slate aggregate,crushed and graded, both have the potential to complywith the Specification (MCHW 1) being naturalaggregates. The maximum by mass percentage forrecycled asphalt is given under the limits for ‘othermaterials’ within the Specification (MCHW 1). Chinaclay sand, IBAA and foundry sand are also potentiallysuitable as fine aggregate. There are no Specific orGeneral Provisions for the use of steel slag or recycledglass as an aggregate. However, their use may bepermitted by the Overseeing Organisation.

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Series 900 Bitumen Bound Layers

2.19 Industrial By-products. Blast furnace slag, steelslag (well weathered), China clay sand and slateaggregate can meet the Specification (MCHW 1) andare named. Recycled glass, IBAA, foundry sand, PFA,recycled concrete and phosphoric slag can comply ascomponents of recycled aggregates within bitumenbound layers.

2.20 Reclaimed Materials. Reclaimed bituminousmaterials can be used for hot mix recycling in theproduction of bituminous base, binder course andsurface course; up to 10% of reclaimed bituminousmaterial being permitted without a requirement fortrials. The maximum content of reclaimed materials isrestricted to 10% for hot rolled asphalt surface courseand 50% in other layers. It should be noted that not allroad planings are suitable for hot mix recycling as olderlayers may contain tar. For further advice, refer toHD 31 DMRB 7.4.1.

2.21 In-situ Recycling. ‘Repave’ is a process thatconserves existing structurally sound pavements,restoring the surface by bonding a thin overlay or inlayto the pre-heated, scarified and reprofiled existing roadsurface. The ‘Remix’ process is an adaptation of the‘Repave’ system where the machine is fitted with asmall mixing unit. Material from the scarified surface isaugured into the pug mill mixer where it is blendedwith hot freshly mixed new material. The recycled mixis placed evenly on the heated surface to form thereplacement surface course which must conform to theappropriate standard.

2.22 Cold deep recycling of bitumen bound pavementsis covered within the Specification (MCHW 1) and formore detailed information refer to HD 31 (DMRB7.4.1). The primary aggregate source is from coldpulverisation of part, or all, of the existing roadstructure, with foamed bitumen or bitumen emulsionused as the primary binding agent. Trials are required todemonstrate that the existing pavement materials arecapable of being recycled to form the primary aggregatecomponent of cold recycled bitumen bound materialand to achieve the requirements of the Specification(MCHW 1).

Series 1000 PQ Concrete and Cold Recycled CementBound Material

2.23 PQ Concrete. Recycled concrete, crushed air-cooled blast furnace slag and PFA are capable ofcomplying with the Specification (MCHW 1), butexcluding exposed aggregate surfacing. The maximum

November 2004

by mass percentage for recycled asphalt is given underthe limits for ‘other materials’ for recycled concreteaggregate within the Specification (MCHW 1). Stentand slate aggregate, crushed and graded, both have thepotential to comply with the Specification (MCHW 1)being natural aggregates. IBAA, phosphoric slag andrecycled aggregate also have the potential to complywith the Specification (MCHW1). China clay sand, andfoundry sand are also potentially suitable as fineaggregate. There are no Specific or General Provisionsfor the use of steel slag or recycled glass as anaggregate. However, their use may be permitted by theOverseeing Organisation.

2.24 Cold Deep Recycling using a Cement Binder.Existing pavement layers can be recycled to form thefoundation or main structural layer of a new roadpavement. Hydraulic binder is used as the stabilisingagent with the pulverised material recycled for theaggregate. End product performance tests of therecycled cement bound material are required to judgethe expected performance of the recycled stabilisedmaterial against the performance of standard CBGMbase materials as detailed in the Specification(MCHW 1).

Conservation of Existing Pavements

2.25 Numerous opportunities exist for conservation,when maintaining or improving existing roads. By farthe most efficient approach is to conserve soundpavement layers or to stabilise and strengthen unsoundlayers, thus making the best use of materials by leavingthem in place. This will require careful attention to thetiming of maintenance, and decisions will be influencedby the type of road and the residual life of thepavement. For further advice refer to HD 30 (DMRB7.3.3). Traffic management alternatives and likelytraffic delay costs must be taken into account, to ensurethe most cost effective solution overall and inaccordance with good practice.

Concrete Pavements

2.26 Surface Restoration. Where concrete surfacesare still permitted, the skidding resistance of concretesurfaces that have polished, but are otherwise soundafter minor repair, can be restored by transversegrooving or by overlaying with an asphalt surfacing.For further advice refer to HD 32 (DMRB 7.4.2) andHD 38 (DMRB 7.5.3).

2.27 Strengthening. Using crack and seat techniques,concrete pavements can be conserved as the lower base

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in flexible composite construction or as the subbase fora new pavement. Continuously reinforced concretepavements (CRCP) can be converted to become thebase (CRCR) with a strengthening flexible overlay.Jointed concrete pavements can be converted tofunction as a lower base with a strengthening flexibleoverlay of adequate thickness to inhibit the formation ofreflection cracks over joints. For further advice refer toHD 30 (DMRB 7.3.3). Concrete pavements which arestructurally sound can be strengthened by thin bondedconcrete or thick unbonded concrete overlays, using‘fast track’ concrete paving techniques where necessary,in accordance with HD 27 (DMRB 7.2.4).

Flexible, Flexible Composite and Rigid CompositePavements

2.28 Surface Restoration. The skidding resistance offlexible surfaces that have polished, but are otherwisesound, can be restored by application of a bituminousoverlay or inlay, or by retexturing. Apart from theretexturing option, the systems all help to reseal thepavement against deterioration. For further informationrefer to HD 31 (DMRB 7.4.1) and HD 37 (DMRB7.5.2).

2.29 Strengthening. Flexible and Compositepavements can be strengthened by the application of abituminous overlay, with or without the removal of theexisting surfacing layers. Where reflective cracking hasoccurred, restoration of Composite pavements(particularly with respect to Rigid CompositePavements) can be undertaken by removal of the upperasphalt layers, with subsequent conversion of theconcrete layer, using crack and seat techniques, to givea sub-base in a flexible pavement. Depending on designconstraints and traffic flows, continuously reinforcedconcrete pavements (CRCP) or bases (CRCR) can alsobe used to overlay or as an inlay to flexible pavements.These are probably the best options where significantdifferential settlement of the existing road has occurredand is likely to continue. For further advice refer toHD 30 (DMRB 7.3.3) and HD 31 (DMRB 7.4.1).

2.30 Road Widening. Advice on the widening ofroads and motorways is given in HD 27 (DMRB 7.2.4),which stresses that the maximum use should be made ofexisting construction wherever possible. There is littlerestriction on the type of material to be laid alongsidean existing pavement providing it conforms to theSpecification (MCHW 1). There can be positiveadvantages in having dissimilar construction, forexample to increase load carrying capacity of the newlane yet match the thickness of the new pavement withthe existing to ensure subsurface drainage is not

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impeded. Where an existing pavement is to be partiallyor completely removed, the material arising can bere-cycled and re-used in or under the new construction,subject to compliance with the Specification(MCHW 1).

Protection of the Environment

2.31 Many reclaimed materials and industrialby-products that are available in sufficient quantities forroad construction cause no significant environmentalproblems. However, depending on their former usethese secondary and recycled materials may containvarying proportions of chemicals, such as organics andmetals. The potential for these chemicals to leach andmigrate, and their proximity to surface and groundwater, will affect their suitability for use. Mitigationmeasures at source or site, such as utilisation withinbound applications, can be employed to reduce anypotential risks.

2.32 The Environment Agency (EA) is responsible formaintaining the quality of surface and ground water inEngland and Wales. The Scottish EnvironmentProtection Agency (SEPA) is responsible for Scotland.The use of secondary and recycled materials shouldcomply with the relevant guidelines of the responsibleagency.

2.33 The handling, storage, processing and depositionof waste materials are subject to separate control by theWaste Management Regulations made under theEnvironmental Protection Act (EPA) 1990. These willapply to all surplus materials taken off site. Thecarriage and processing of waste will need to belicensed; however there will be a general exemptionfrom requirements for waste to be deposited at alicensed site, if instead it is to be incorporated into adevelopment which has planning consent. It ispresumed that such use of waste materials will beadequately controlled since they must be deposited inaccordance with the Specification (MCHW 1) for thedevelopment, including any special conditions requiredto prevent adverse effects on the environment.

2.34 The Waste Management Regulations permittemporary storage on site of restricted amounts of wastematerials approved for incorporation in the works, afterthe award of a contract, but prior to beginning work.Similarly, road planings may be stockpiled off site forreprocessing. Nevertheless, there are good reasons toutilise planings as they arise or as soon as possiblethereafter. Stockpiles can become quite difficult tobreak up if they are allowed to consolidate. On theother hand, if they become saturated with water, then

November 2004



compaction as fill or to form a capping layer may bedifficult and considerable amounts of energy are neededto drive off water if they are to be recycled to form anew base. There may also be concerns about thepossibility of both organic and mineral leachate if waterbegins to drain through a large stockpile. Certainmaterials are exempt from the regulations underspecific circumstances and consultation with the locallicensing officer should be undertaken to confirm siteand/or activity specific classifications. Exemptactivities are still required to be registered with the EAor SEPA.

2.35 Where reclaimed materials are being consideredfor use in landscaping and areas of planting, care shouldbe taken to ensure that they are compatible with theplants and trees to be grown. For further advice refer toHA 44 (DMRB 4.1.1).

Future Developments

2.36 It is expected that the quantities of materials thatcan be used will increase as the range of recycled andsecondary materials permitted in the Specification(MCHW 1) is extended. A number of research projectsare currently underway, including those on recycledplastic and non-ferrous slag from zinc production,which aim to develop suitable acceptance criteria toencourage the wider use of such materials when theyoffer best value for money. In addition, other materialssuch as quarry fines, recycled railway ballast andceramics may be considered by the OverseeingOrganisation on a site specific basis.

Glossary of Terms

2.37 The following terms are used in this Chapter:

BLAST FURNACE SLAG:A by-product from the production of iron, resultingfrom the fusion of fluxing stone (fluorspar) with coke,ash and the siliceous and aluminous residues remainingafter the reduction and separation of iron from the ore.Due to its potential variability and possible inclusion ofvolumetrically expansive components, ‘Old Bank’ slag,produced prior to modern high-level quality controlprocedures, may require additional processing prior touse. Various forms of solidified blast furnace slag areproduced dependent on the rate and technique used tocool the molten material. Granulated blast furnace slag(GBS) is formed by quenching the molten material withjets of water. This material is then processed to produceground granulated blast furnace slag (GGBS) for use asa hydraulic binder.

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November 2004

URNT COLLIERY SPOIL:lso known as burnt minestone. The residue following

gnition of coal mine spoil heaps which results in partialr complete combustion of coal particles in the spoil,eaving calcined rocks.

EMENT KILN DUST (CKD):y-product from the calcining of raw materials during

he production of Portland Cement. CKD is extractedrom gases generated within the cement kilns during theanufacturing process and comprises a light fine

rained particulate material. If chemically suitable,KD is generally re-used within the cement works. Theomposition of the CKD will be dependent on the kilnrocess employed and the degree of separation in theust collection system.

OAL FLY ASH (CFA):ulverised fuel ash or Coal fly ash is extracted bylectrostatic precipitation from the flue gases of modernoal-burning power stations and is similar in fineness toement. It can be used both as a binder in Fly Ashound Mixtures (FABM) and as an aggregate.

HINA CLAY SAND AND STENT:he by-products from the extraction of china clay fromecomposed granite, consisting largely of two distinctaterials: ‘Stent’, which is waste rock, and ‘Tip Sand’.hina Clay Tip Sand is defined as the washed materialroduced as a by-product during the extraction of Chinalay (Kaolin) from Kaolinitic granite, predominantlyomprising quartz with some mica, and is relativelyonsistent from within each source of production.

OUNDRY SANDS:y-product of the castings industry, typicallyomprising uniformly sized sands with variousdditives and metals associated with the specific castingrocess.

URNACE BOTTOM ASH (FBA):urnace bottom ash is the coarser fraction of ashroduced in coal burning power stations resulting fromhe fusion of PFA particles which fall to the bottom ofhe furnace. It varies in size from fine sand to coarseravel and has a porous structure.

BS AND GGBS:ee Blast Furnace Slag.

YPSUM:y-product of power stations burning lignite or sulphurontaminated coal. Gas scrubbers remove the gypsumrom flue gasses in the desulphurisation process.

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INCINERATOR BOTTOM ASH AGGREGATE(IBAA):IBAA is processed from the material discharged into theburning grate of Municipal Solid Waste (MSW)incinerators and comprises 80 to 90% of the total MSWash production. It is a heterogeneous material that maycontain varying proportions of glass, ceramics, brickand concrete in addition to clinker and ash.

NON-FERROUS SLAG:Non-ferrous slags include lead-zinc slag, tin slag andcopper slag, and are by-products produced during therecovery and processing of non-ferrous metal fromnatural ores. Slags of note for potential use assecondary aggregates are those associated with theproduction of phosphorous and zinc.

PFA:See Coal Fly Ash.

PHOSPHORIC SLAG:See non-ferrous slag.

QUARRY FINES:Processing of crushed rock for use as constructionaggregate consists of blasting, crushing, washing,screening and stockpiling operations. The production ofprimary aggregates can involve a number of processes,with quarry fines being the associatedby-product. The grading of the material is typicallyassociated with the parent rock and subsequentproduction process. Chemical and mineralogicalproperties are directly related to the parent rock.

RECYCLED AGGREGATE:An aggregate resulting from the processing of materialused in a construction process. Recycled Asphalt isnoted as an exception to the above and treated as aseparate material.

RECYCLED ASPHALT:Recycled asphalt can comprise millings, planings,return loads and offcuts from bituminous layer jointpreparation. Asphalt planings are defined as materialsderived from the layers of the pavement using a mobilemachine fitted with milling cutters. Granulated asphaltis defined as asphalt bound material recycled fromroads under reconstruction or surplus asphalt materialdestined for bound pavement layers, but unused, whichhas been granulated.

RECYCLED CERAMICS:IBAA processed from the MSW stream may contain acomponent of ceramics. The wide range of ceramicproducts is reflected within the variation of thematerials mechanical properties.

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ECYCLED GLASS:lass for subsequent recycling via crushing orranulation is typically separated at source, separated inecycling facilities, or collected from bottle banks. Therincipal raw materials are quartz sand and sodiumarbonate with varying proportions of otherompounds.

ECYCLED PLASTICS:lastics fall into two main categories, broadly defineds Thermoplastics, which can be reheated withoutignificant alterations to their structure, and Thermosetshich stiffen under application of heat. This

undamental division dictates applicable recyclingrocesses and subsequent possibilities for re-use.

ECYCLED RAILWAY BALLAST:ailway ballast is usually replaced due to inter-articulate attrition and filling of the aggregate voidsith fines. These fines can enter the railway ballast

rom a number of on-site sources, and treatmentrocesses such as screening and washing may beequired prior to subsequent re-use.

ECYCLED RUBBER:sed tyres comprise a combination of natural and

ynthetic rubber. They can either be recycled or used asecondary materials. Recycled products include crumbubber and granulate. Secondary uses include tyreales.

LATE AGGREGATE:he by-product of slate quarries primarily producing

oofing slates. The waste represents 70-90% of grossuarried volume.

PENT OIL SHALE:he residue of shale mined in the Lothian Region ofcotland after heating to drive off volatileydrocarbons. Similar in nature to burnt colliery shale.

TEEL SLAG:y-product of the manufacture of steel from pig iron.here are two types; basic oxygen slag (BOS) andlectric arc furnace (EAF) slag. EAF slag generally hasower free lime and magnesia contents than BOS as aesult of the manufacturing process, and is thus moreasily weathered.

NBURNT COLLIERY SPOIL:lso known as minestone, a by-product of coal mining.

t is derived from the rocks which lie above, below andometimes within the coal measures of Carboniferouseological age. These rocks comprise mainly siltstonesnd mudstones, and in some areas sandstones andimestones.

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Chapter 3References

3. REFERENCES

1. Design Manual for Roads and Bridges - TheStationery Office (TSO)

HA 44 (DMRB 4.1.1) ‘Earthworks: Design andContract Documents’ (includes amendment 1 April1995)

HD 27 (DMRB 7.2.4) ‘Pavement ConstructionMethods’

HD 31 (DMRB 7.4.1) ‘Maintenance of BituminousRoads’

HD 32 (DMRB 7.4.2) ‘Maintenance of ConcreteRoads’

HD 33 (DMRB 4.2.3) ‘Drainage: Surface and subsurface drainage systems for highways’

HD 38 (DMRB 7.5.1) ‘Concrete Surfacing andMaterials’ (includes amendment 1 dated Feb 1999)

HD 30 (DMRB 7.3.3) ‘Structural AssessmentProcedure’

HD 37 (DMRB 7.5.2) ‘Bituminous Surfacing Materialsand Techniques’

2. Manual of Contract Documents for HighwaysWorks - The Stationery Office (TSO)

Manual of Contract Documents for Highway Works,Volume 1 (MCHW 1): Specification for HighwayWorks.

3. British Standard Institution

BS4987 : ‘Coated macadam (Asphalt Concrete) forroads and other paved areas’; Part 1 : ‘Specification forconstituent materials and for mixtures’. BSI

November 2004

4. Others

1987

Use of waste material for road fill. DOE Circular 20/87,Department of Transport Circular 3/87, Welsh OfficeCircular 36/87; TSO

1990

Environmental Protection Act 1990; TSO

1994

Waste Management Licensing Regulations 1994. TSO

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November 2004 4/1

4. ENQUIRIES

All technical enquiries or comments on this Standard should be sent in writing as appropriate to:

Chief Highway EngineerThe Highways Agency123 Buckingham Palace RoadLondon G CLARKESW1W 9HA Chief Highway Engineer

Chief Road EngineerScottish ExecutiveVictoria QuayEdinburgh J HOWISONEH6 6QQ Chief Road Engineer

Chief Highway EngineerTransport DirectorateWelsh Assembly GovernmentLlywodraeth Cynulliad CymruCrown Buildings M J A PARKERCardiff Chief Highway EngineerCF10 3NQ Transport Directorate

Director of EngineeringThe Department for Regional DevelopmentRoads ServiceClarence Court10-18 Adelaide Street G W ALLISTERBelfast BT2 8GB Director of Engineering

Chapter 4Enquiries