Yearbook: 2005-2006

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TheINSTITUTE OF CONCRETE TECHNOLOGY

4 Meadows Business Park, Blackwater, Camberley, Surrey GU17 9AB

Tel/Fax: 01276 37831Email: ict@ictech.org Website: www.ictech.org

THE ICTThe Institute of Concrete Technologywas formed in 1972 from theAssociation of Concrete Technologists.Full membership is open to all thosewho have obtained the Diploma inAdvanced Concrete Technology. TheInstitute is internationally recognisedand the Diploma has world-wideacceptance as the leading qualificationin concrete technology. The Institutesets high educational standards andrequires its members to abide by a Codeof Professional Conduct, thus enhancingthe profession of concrete technology.The Institute is a Professional Affiliatebody of the UK Engineering Council.

AIMSThe Institute aims to promote concretetechnology as a recognised engineeringdiscipline and to consolidate theprofessional status of practisingconcrete technologists.

PROFESSIONAL ACTIVITIESIt is the Institute's policy to stimulateresearch and encourage the publicationof findings and to promotecommunication between academic andcommercial organisations. The ICTAnnual Convention includes a TechnicalSymposium on a subject of topicalinterest and these symposia are wellattended both by members and non-members. Many other technicalmeetings are held. The Institute isrepresented on a number of committeesformulating National and InternationalStandards and dealing with policymatters at the highest level. TheInstitute is also actively involved in theeducation and training of personnel inthe concrete industry and thoseentering the profession of concretetechnologist.

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ICT RELATED INSTITUTIONS & ORGANISATIONS

ASSOCIATION OFCONSULTING ENGINEERSAlliance House12 Caxton StreetLondon SW1H 0QLTel: 020 7222 6557www.acenet.co.uk

ASSOCIATION OF INDUSTRIALFLOORING CONTRACTORS33 Oxford StreetLeamington SpaCV32 4RATel: 01926 833 633www.acifc.org.uk

ASSOCIATION OF LIGHTWEIGHTAGGREGATE MANUFACTURERSWellington StRipleyDerbyshire DE5 3DZTel: 01773 746111

BRE (BUILDING RESEARCHESTABLISHMENT) LTDBucknalls LaneGarstonWatford WD25 9XXTel: 01923 664000www.bre.co.uk

BRITISH BOARD OF AGRÉMENTP.O.Box 195Bucknalls LaneGarstonWatfordHerts WD25 9BATel: 01923 665300www.bbacerts.co.uk

BRITISH CEMENT ASSOCIATION4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608700www.bca.org.uk

BRITISH PRECASTCONCRETE FEDERATION60 Charles StreetLeicester LE1 1FBTel: 0116 253 6161www.britishprecast.org.uk

BSI STANDARDSBritish Standards House389 Chiswick High RoadLondon W4 4ALTel: 020 8996 9000www.bsi.org.uk

BRITPAVEBritish In-Situ ConcretePaving Association4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 33160www.britpave.org.uk

CEMENT ADMIXTURES ASSOCIATION38a Tilehouse Green LaneKnowleWest MidlandsB93 9EYTel: 01564 776362

CEMENTITIOUS SLAG MAKERS ASSOCIATIONCroudace HouseGoldstone RoadCaterhamSurrey CR3 6XQTel: 01883 331071www.ukcsma.co.uk

CONCRETE ADVISORY SERVICE4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk

CONCRETE BRIDGE DEVELOPMENT GROUP4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 33777www.cbdg.org.uk

CONCRETE INFORMATION LTD4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608770www.concrete-info.com

CONCRETE REPAIR ASSOCIATIONAssociation House99 West StFarnhamSurrey GU9 7ENTel: 01252 739145www.cra.org.uk

THE CONCRETE CENTRE4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 606800www.concretecentre.com

THE CONCRETE SOCIETY4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk

CONSTRUCT4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 38444www.construct.org.uk

CIRIAConstruction Industry Research& Information Association

6 Storey’s GateWestminsterLondon SW1P 3AUTel: 020 7222 8891www.ciria.org.uk

CORROSION PREVENTION ASSOCIATIONAssociation House99 West StFarnhamSurrey GU9 7ENTel: 01252 739145www.corrosionprevention.org.uk

INSTITUTE OF CORROSIONCorrosion HouseVimy CourtLeighton BuzzardBeds LU7 1FG Tel: 01525 851771www.icorr.org

INSTITUTE OF MATERIALSMINERALS & MINING1 Carlton House TerraceLondon SW1Y 5DBTel: 020 7451 7300www.materials.org.uk

INSTITUTION OF CIVIL ENGINEERSOne Great George StreetLondon SW1P 3AATel: 020 7222 7722www.ice.org.uk

INSTITUTION OF HIGHWAYS& TRANSPORTATION6 Endsleigh StreetLondon WC1H 0DZTel: 020 7387 2525www.iht.org

INSTITUTION OFROYAL ENGINEERSBrompton BarracksChathamKent ME4 4UGTel: 01634 842669

INSTITUTION OFSTRUCTURAL ENGINEERS11 Upper Belgrave StreetLondon SW1X 8BHTel: 020 7235 4535www.istructe.org.uk

INTERPAVEConcrete Block Paving Association60 Charles StreetLeicester LE1 1FBTel: 0116 253 6161www.paving.org.uk

MORTAR INDUSTRY ASSOCIATION38-44 Gillingham StreetLondon SW1V IHUTel: 020 7963 8000www.mortar.org.uk

QSRMCQuality Scheme for ReadyMixed Concrete1 Mount Mews High Street, HamptonMiddlesex TW12 2SHTel: 020 8941 0273www.qsrmc.co.uk

QUARRY PRODUCTS ASSOCIATION38-44 Gillingham StreetLondon SW1V IHUTel: 020 7963 8000www.qpa.org

RIBARoyal Institute of British Architects66 Portland PlaceLondon W1B 1ADTel: 020 7580 5533www.architecture.com

SOCIETY OF CHEMICAL INDUSTRY14/15 Belgrave SquareLondon SW1X 8PSTel: 020 7598 1500www.sci.mond.org

UNITED KINGDOM ACCREDITATION SERVICE21-47 High StreetFelthamMiddlesex TW13 4UNTel: 020 8917 8400www.ukas.org.uk

UNITED KINGDOM CAST STONE ASSOCIATION4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608771www.ukcsa.co.uk

UNITED KINGDOM QUALITY ASH ASSOCIATIONRegent HouseBath AvenueWolverhamptonWV1 4EGTel: 01902 576 586www.ukqaa.org.uk

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Published by:THE INSTITUTE OF

CONCRETE TECHNOLOGY4 Meadows Business Park,

Blackwater, Camberley, Surrey GU17 9AB

Tel/Fax: 01276 37831Email: ict@ictech.org

Website: www.ictech.org

ICT YEARBOOK 2005-2006

EDITORIAL COMMITTEE

Professor Peter C. Hewlett (Chairman)BRITISH BOARD OF AGRÉMENT LTD

& UNIVERSITY OF DUNDEE

Peter C. OldhamCHRISTEYNS UK LTD

Dr. Bill PriceLAFARGE CEMENT UK

Graham TaylorINSTITUTE OF CONCRETE TECHNOLOGY

Laurence E. PerkisINITIAL CONTACTS

Rights reserved. No part of this publication maybe reproduced or transmitted in any formwithout the prior written consent of the

publisher. The comments expressed in thispublication are those of the Author and not

necessarily those of the ICT.

ISSN 1366 - 4824£50.00

Engineering CouncilProfessional Affiliate

Covers ICT 2005 20/8/2005 11:59 am Page 2

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Yearbook: 2005-2006

CONCRETE TECHNOLOGYINSTITUTE OF

The

CONTENTS PAGE

PRESIDENT’S PERSPECTIVE 5By Rob GaimsterPresident, INSTITUTE OF CONCRETE TECHNOLOGY

THE INSTITUTE 6

COUNCIL, OFFICERS AND COMMITTEES 7

FACE TO FACE 9 - 11A personal interview with incoming president Bryan Marsh

MILESTONES IN THE HISTORY OF CONCRETE TECHNOLOGY: 13 - 18A LOOK AT THE HISTORY OF PRECAST CONCRETE:By Martin Clarke

ANNUAL CONVENTION SYMPOSIUM: 19 - 84PAPERS PRESENTED 2005

ADVANCED CONCRETE TECHNOLOGY DIPLOMA: 85 - 87SUMMARIES OF PROJECT REPORTS 2004

RELATED INSTITUTIONS & ORGANISATIONS 89

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55

PRESIDENT’S PERSPECTIVE

It is once again my pleasure to welcome you to

the Institute’s Yearbook, and I trust you find

the contents interesting and informative. Whilst we

are still effectively a small-in-size institute, the

contents show that the scope of our members’ and

associates’ operations is indeed quite wide and

deep.

The year just gone has been, as with the

previous years, one of change in the various

industrial, education and research sectors which

use concrete technology and technologists. The

continuing process of takeovers, mergers and

consolidation can be unsettling for personal and

professional aspects but I am pleased to hear that

for the vast majority of our members working life

continues as normal. What were areas of

pessimism have now turned to optimism as the use

of concrete materials and products continue to

increase, which brings with it areas of growth for

technology and innovations in the design and use

of concrete. For example, it is particularly pleasing

that the new Highways Agency Policy Interim

Advice Note 60/05 confirms concrete as its material

of choice for motorway and trunk road safety

barriers because whole life costing indicates

superior performance in terms of economy and

safety. Well done to all who were involved in

illustrating one of the many benefits of concrete as

a material. We should, of course, be celebrating

concrete as a fabulous construction material, which

helps to shape both the old world and the new.

The theme of the 2005 Symposium was Concrete

for a New World and speakers who are eminent in

their field gave talks on developments in concrete

technologies both at home and abroad. The

Convention was a resounding success, with a high

attendance and support from those who showed

their wares, to whom thanks are due. Many thanks

are also due to Ian Ferguson and the Events

Committee, with unstinting assistance from

Graham Taylor, both for the Convention and other

technical meetings through the year. Ian’s

additional role of Associate Members’ co-ordinator,

illustrates the time that ICT members of all

categories get involved in making the Institute

work for all members. Our Honorary Treasurer,

John Gibbs, unfortunately had to resign the post

due to re-locating to Kenya, and we wish him well

in his new location, with many thanks to John for

his endeavours and also to Bill Wild for taking the

reins again.

The educational side of the Institute continues

apace, it is pleasing to see that the web-based

course in Advanced Concrete Technology is going

well.

I sometimes perceive a slight change in the

public perception of concrete, which has been

often not good but does seem to be improving,

from both an engineering and an aesthetic

viewpoint. Sustainability of resources is also a

positive point, with the image of grey walls and

despoliation of the countryside being counter-

balanced by pleasing and decorative concrete

finishes and the re-use of a valuable construction

material. We, as an Institute and an industry, need

to maintain our efforts to raise the profile of

concrete; the papers presented at the Symposium

assist in this.

The editorial board under Professor Peter

Hewlett have, once again, produced another

excellent document which I hope you will enjoy.

ROB GAIMSTERPRESIDENTINSTITUTE OF CONCRETE TECHNOLOGY

6

INTRODUCTIONThe Institute of Concrete Technology was

formed in 1972. Full membership is open to allthose who have obtained the Diploma inAdvanced Concrete Technology. The Institute isinternationally recognised and the Diploma hasworld-wide acceptance as the leading qualificationin concrete technology. The Institute sets higheducational standards and requires its members toabide by a Code of Professional Conduct, thusenhancing the profession of concrete technology.The Institute is a Professional Affiliate body of theUK Engineering Council.

MEMBERSHIP STRUCTUREA guide on ‘Routes to Membership’ has been

published and contains full details on thequalifications required for entry to each grade ofmembership, which are summarised below:

A FELLOW shall have been a CorporateMember of the Institute for at least 10 years, havea minimum of 15 years appropriate experience,including CPD records from the date ofintroduction, and be at least 40 years old.

A MEMBER (Corporate) shall hold theDiploma in Advanced Concrete Technology andwill have a minimum of 5 years appropriateexperience (including CPD). This will have beendemonstrated in a written ‘Technical andManagerial/Supervisory Experience Report’. Analternative route exists for those not holding theACT Diploma but is deliberately more onerous. A Member shall be at least 25 years old.

AN ASSOCIATE shall hold the City and GuildsCGLI 6290 Certificate in Concrete Technology andConstruction (General Principles and PracticalApplications) and have a minimum of 3 yearsappropriate experience demonstrated in a writtenreport. An appropriate university degree exempts aGraduate member from the requirement to holdCGLI 6290 qualifications. Those who have passedthe written papers of the ACT course but have yetto complete their Diploma may also becomeAssociate members. All candidates for Associatemembership will be invited to nominate acorporate member to act as SuperintendingTechnologist. There is no minimum age limit in thisgrade.

A TECHNICIAN holding the CGLI 5800Certificate in Concrete Practice must also submit awritten report demonstrating 12 monthsexperience in a technician role in the concreteindustry. An alternative route exists for those whocan demonstrate a minimum of 3 yearsappropriate experience in a technician role. Allcandidates for Technician membership will beinvited to nominate a corporate member to act asSuperintending Technologist. There is no minimumage limit in this grade.

A GRADUATE shall hold a relevant universitydegree containing a significant concretetechnology component. All candidates forGraduate membership will be invited to nominatea corporate member to act as SuperintendingTechnologist. There is no minimum age limit in thisgrade.

The STUDENT grade is intended to suit twotypes of applicant.

i) The school leaver working in the concreteindustry working towards the Techniciangrade of membership.

ii) The undergraduate working towards anappropriate university degree containing asignificant concrete technology component.

All candidates for Student membership will beinvited to nominate a corporate member to act asSuperintending Technologist. There is no minimumage limit in this grade. There is a limit of 4 years inthis grade.

Candidates are not obliged to attend anycourse (including the ACT course) prior to sittingan examination at any level.

Academic qualifications and relevant experiencecan be gained in any order for any grade ofmembership.

Corporate members will need to be competentin the science of concrete technology and havesuch commercial, legal and financial awareness asis deemed necessary to discharge their duties inaccordance with the Institute’s Code ofProfessional Conduct.

Continuing Professional Development (CPD) iscommon to most professions to keep theirmembers up to date. All members exceptstudents, are obliged to spend a minimum of 25hours per annum on CPD; approximately 75% ontechnical development and 25% on personaldevelopment. The Institute’s guide on ‘ContinuingProfessional Development’ includes a record sheetfor use by members. This is included in theMembership Handbook. Annual random checksare conducted in addition to inspection at times ofapplication for upgraded membership.

ACT DIPLOMAThe Institute is the examining body for the

Diploma in Advanced Concrete Technology. A residential course is run in South Africa. A newpart-residential/part home-based course isexpected to run in Singapore. The worldwide web-based course is run from the UK, starting inSeptember of alternate years. Further details ofthis course can be found on the website:www.actcourse.com and the ICT office has details of the others.

THE INSTITUTE

7

EXAMINATIONSCOMMITTEE

COUNCILADMISSIONS AND

MEMBERSHIPCOMMITTEE

FINANCECOMMITTEE

MARKETINGCOMMITTEE

EVENTSCOMMITTEE

COUNCIL, OFFICERS AND COMMITTEES - SUMMER 2005

R. RYLEChairman

G. TaylorSecretary

Dr. P.L.J. Domone

R. Gaimster

J. Lay

Dr. J.B. Newman

Dr. R.G.D. Rankine (corresponding)

Dr. R.P. West

J.D. Wootten

W. WILDChairman

C.D. Nessfield

R. Gaimster

A.M. HARTLEYChairman

D.G. King(corresponding)

Dr. B.J. Magee

R.J. Majek

P.L. Mallory

C.D. Nessfield

M.S. Norton

B.F. Perry

G.Taylor

R. GAIMSTERPresident

Dr. B.K. MarshVice President

C.D. NessfieldHon Secretary

W. WildHon Treasurer

M.D. Connell

I.F. Ferguson

A.M. Hartley

P.L. Mallory

R.J. Mangabhai

P.C. Oldham

B.F. Perry

Dr. R.G.D. Rankine (corresponding)

K.C. Sutherland

M.D. CONNELLChairman

G. TaylorSecretary

Dr. W.F. Price

J.D. Wootten

I.F. FERGUSONChairman

G. TaylorSecretary

R.G. Boult

P.M. Latham

P.L. Mallory

P.C. Oldham

B.C. Patel

G. Prior(corresponding)

SCOTTISH CLUBCOMMITTEE

R.C. BROWNChairman

G. PriorSecretary

L.R. BakerTreasurer

J.G. Bell

K.W. Head

B.J. O’Shea

J. Wilson

EXECUTIVE OFFICER

G. TAYLOR

TECHNICAL ANDEDUCATIONCOMMITTEE

Dr. B.K. MARSHChairman

J.V. TaylorSecretary

L.K. Abbey

R.A. Binns

M.W. Burton

Dr. A.J. Dowson

R.J. Greenfield

R. Hutton

J. Lay

C.B. Richards

A.T. Wilson

8

9

Q: I suppose that the obvious firstquestion is to ask what first stimulated yourinterest in concrete?

A: My Mother maintains that "concrete" wasthe second word I uttered (after "motorbike”,that was). In truth, I initially developed aninterest in construction through helping my fatherwho was a builder, and despite his advice not togo “on the buildings” I started to study civilengineering. The growing interest in concrete wasa gradual process during my days as a civilengineering undergraduate that took me awayfrom my planned career in contracting and intoconcrete research. The first sparks were struck inconcrete technology lectures and lab classes, myinterest then smouldered through a final yearproject and burst into flames when I took a 12month research contract in concrete technologyfollowing graduation.

Q: You spent many years as head ofConcrete Technology at BRE before moving toyour present position with Arup. What wouldyou describe as your most fulfillingachievements during this period?

A: A very tricky question. Odd as it mayseem, and although it was a highly enjoyable andrewarding time in my career, nothing really standsout above the rest. A predictable answer, I know,but honest!

I was more of a generalist than a specialist, sothat I never got involved in many of the ‘glamour’projects being carried out at BRE, such as work onASR and sulfates (or should that be sulphates?)my work was more in a supporting role than‘centre stage’.

Q: When you moved from BRE to Arup,what were the main differences in the typeof work you were undertaking?

A: Probably the biggest difference was that Iwas now facing questions that were being askedbecause an Arup engineer needed to know theanswer rather than because it would be good toknow the answer or "to further knowledge", aswas more the case at BRE. Deadlines tend to bea lot shorter, answers need to be more definite(no longer can the largest section of a report bethe self-perpetuating "need for further research")but much more varied. One project that standsout was an urgent request to sort out potentialproblems with ASR on a job in Siberia whereconstruction had already started. Indeed, I thinkit's fair to say that since I joined Arup I've usedjust about every part of the ACT syllabus - andsome bits that aren't yet included (such as ice-abrasion).

Q: There is a widespread perception thatthe level of technical expertise in theconcrete industry is falling; do you have anyviews on this?

A: Personally, I find it difficult to find a datumagainst which to make a valid comparison. I havebeen fortunate to work alongside some peoplewith very high levels of technical expertise but Ialso deal with people who I feel "really shouldknow better". The technical specialists do nowseem to be concentrated in a few companiesrather than spread throughout the industry. Ofcourse, there are still a lot of very good peopleout there but whether there are enough - I don'tknow.

Q: On a related topic, how does the useof concrete in the UK, and the application ofnew technology, differ from that in othercountries?

A: I really don’t have enough overseasexperience to make an informed comment, except

FACE TO FACEWITH INCOMING PRESIDENT BRYAN MARSH

Incoming ICT President Dr. Bryan Marsh is a member ofthe materials advisory team within Arup MaterialsConsulting, which provides advice to all parts of the OveArup Partnership and external clients, worldwide, on theuse of materials in construction processes. He dealsparticularly with concrete technology and materials. He isalso involved with UK and European standards forconcrete, particularly with respect to durability. Prior tojoining Arup, he was Head of the Concrete TechnologySection at the Building Research Establishment for overten years.

10

to note that the approach to the adoption of newideas varies in different countries. It’s too easy totrot out that old line that British engineers arevery conservative and I don’t wish to fall into thattrap.

Q: What do you think the most significantnew developments in concrete technologyhave been in the last 5-10 years and whatfuture developments do you anticipate?

A: Gosh, these questions are difficult! For amaterial that's been around, in some form orother, since ancient times, it never ceases toamaze me that we keep coming up with newthings at all. I think new developments will begradual advances rather than major revolutions.Admixture development continues to impress meand I hope it may long continue. Thedevelopment of self-compacting concrete and therecent introduction of shrinkage reducingadmixtures are testament to this process.Developments I would like to see would be thosethat improve sustainability by allowing the use ofalternative aggregates and less environmentallydamaging cements, possibly also with a moreattractive colour! Concrete that retains itsworkability, gains strength instantly when inplace, gives off no heat, doesn't shrink and hasuniform appearance would do for a start. Inert tocarbon dioxide, sulfates and acids, impervious tochlorides, unaffected by frost and totallyrecyclable would do for a follow up. As a songsays “it’s too much to expect but it’s not toomuch to ask!”.

Q: : Given that concrete is probably themost widely used construction material onearth, do you think that it is studied insufficient depth by students of engineeringand do you feel that there is a need forspecific qualifications in concrete technologyand its application?

A: Not only is concrete the most widely usedconstruction material, I read recently that it's thesecond most used material after water - though Iwould have thought "earth" would have come inthere somewhere...

No, I don’t think it is given enough time inmost undergraduate engineering courses and,yes, I think there is a need for specificqualifications in concrete technology butrecognising that this will always be a nichemarket, so to speak. Everyone involved inconcrete needs to know something of the basicsbut we don’t all need to be concretetechnologists. Concrete technologists can,

however, bring it all together and all goodspecialist firms should have one (or more).

Q: You are heavily involved in thedevelopment of new standards for concreteand concrete construction as well as theimplementation of these new standards(both British and European) in practice. Whatis your view on recent developments instandardisation?

A: When concrete was sand, gravel, OPC andwater (dirt, burnt dirt and water as some of mynon-concrete colleagues would have it) standardscould be, and were, fairly simple. Increasingstrength improved just about everything else – sowhen the going got tough, the grade simply gotupped. But times have changed, concrete needsto be much more closely tailored to the job it isbeing asked to do. And, of course, we have hadsome failures in the past so we need standardsthat will help protect us from such things in thefuture. It is the interfaces that need to be keptsimple and perhaps we are failing somewhat inthat area. By interfaces I mean the places wheredesign meets specification and wherespecification meets supply. Suppliers understandconcrete intimately as regards materials,production and economics - most designers don’t.But they know what properties they require of theconcrete whereas the suppliers might not. Weneed our standards to be based on a reasonablelevel of understanding on the part of each personin the chain.

Despite some involvement in the creation of EN206-1 and BS 8500, I still feel that theintroduction of these new standards almostcoincidentally with BRE Special Digest 1 suddenlymade life very complicated, at least for a while.Concrete specification by EN 206-1 is simple inprinciple but, unfortunately, based on a systemthat didn’t readily translate to the way, in the UK,we trade between cover to reinforcement andconcrete quality. New standards obviously have tobe technically justified, but they also need to bereadily understandable by the people who usethem, not just by standards writers. Betterguidance for practitioners would be valuable andcertainly reduce the degree of uncertainty in somequarters about what the standard actually means.

Q: : What inspired you to join the ICT(and have you ever regretted it)?

A: On joining BRE after an academic researchbackground I convinced them to let me sign upfor the ACT course to broaden my knowledge; atthat stage I must admit I’d never heard of the ICT.

11

On getting the diploma I joined the ICT toestablish my identity as a concrete technologistand not just as a civil engineer. Perhaps the onlytime I have regretted it (or might yet) was beingtalked into standing for President!

Q: As the incoming President of the ICT,how can you help to strengthen the ICT‘brand image’ in a period of continuingchange in the concrete industry and how doyou see the future for the ICT?

A: Our last two presidents, in particular, havedone a marvellous job in strengthening ICT, itsimage and what it offers to members. I'm strictlya technical chap, not a "marketeer" or a “leaderof men”, so I aim to concentrate on maintainingtechnical excellence. I would like to see ICT attaina raised awareness within the industry as thebody representing the professional practitioners ofa technically-based discipline. I believe we canonly do that by demonstrating that MICT andFICT mean we really know what we’re talkingabout. I would also like all our AMICT memberswho really know what they’re talking about(hopefully most of them) to demonstrate that bymoving up to MICT.

Our future is perhaps a little uncertain. Wehave been losing members faster than we havebeen gaining them and currently over 40% of ourmembers are associates. That is not healthy. Thebalance between corporate and associatemembers needs to change. I would like to thinkthat the ultimate objective of all associates wouldbe to eventually gain full corporate membershipstatus. If we continue the way we are, we riskbecoming a club instead of a professional body.

Q: I do not think we can conclude thisinterview without at least a passingreference to your well-known interest inmotorcycling. I believe you have eventravelled to New Zealand in search of theultimate biking experience. What is it aboutmotorcycling that has inspired such passionfor this form of transport?

A: Passion for motorcycles? What? Me?Although I suppose a stable of five Triumphsdating from 1913 to 2000, and having riddenover 400,000 miles in about 20 countries couldbe interpreted that way. I won’t claim it’s thewind in my hair and flies in my teeth type ofexperience, or the adrenalin rush of outrageousspeed (certainly not on my 1913 or 1930 bikesanyway!), or being at one – man & machine. Ialways say it’s a passing phase – but it’s been 32years and hasn’t passed yet!

Bryan, many thanks for sharing your thoughtswith us. I found our conversation interesting andinformative. I certainly wish you well in yourPresidency and in your ongoing career. Manythanks.

12

13

IntroductionThe precast concrete producers are arguably

approaching a golden age of tertiary development

built on a combination of improving materials

technology, new generations of production and

handling equipment, added value product

options, excellent sustainability credentials and

coincident market requirements. It is an exciting

time to be in the industry with change and

improvement the watchwords. The sector

accounts for about 28% of cement used in the

UK but with better control of cement content

these days it accounts for around a third of

concrete produced by volume. The overall

turnover of the sector is now over £2 billion with

around 850 factories of all sizes. Four million

tonnes of cementitious products are consumed

annually along with over 35 million tonnes of

aggregates. Precast has indeed become a

significant part of the overall construction market

in the UK, as well as across the globe. Used to

solve practical engineering problems, improve

construction programme times, reduce costs,

improve safety or enhance the appearance of a

building or structure, precast concrete is now

thoroughly integrated into the construction

process.

At its simplest precast concrete is any

manufactured concrete element or structure, large

or small, that is cast in one place and used in

another. Sizes start with paving blocks of around

0.0004 m2, progress through the common precast

products seen on building sites everywhere, past

civil engineering structures such as bridge

sections, right up to the massive storage and

ballast sections of oil extraction platforms. These

can contain over 200,000 m3 of concrete, and

may have to travel many hundreds of miles from

the manufacturing site to the point of use. This

makes the precast concrete production range

cover around 10 orders of magnitude in size, a

truly awesome variation in scale.

Precast concrete has provided some of the

most ingenious developments in manufacturing

and construction, and this history highlights some

of the more unusual parts that it has played.

Early production of precastconcrete

History is vague about precisely where the

earliest recorded examples of precast concrete can

be found; to discover items of precast concrete in

forms that we would recognise, we have to look

at around the time of the development of

Portland Cement. When Joseph Aspdin came to

patent his ‘Portland’ Cement in 1824, he had

already seen concrete manufactured from earlier,

poorer quality cements. Statues made from

various types of ‘cement’ and aggregates were

starting to appear, ranging from Williams

Champion’s ‘Neptune’ in about 1750 to Aspdin’s

own son James’ commission in around 1850 of

‘The Prophet Samuel in Infancy’. Whilst there is

some debate regarding the exact movement of

these statutes, some of these early works were

moved from casting to their site of erection, and

can therefore be regarded as ‘precast’.

As engineers and builders grew to appreciate

the potential for repetition in manufacture with

Portland cement, the 1850s started to see sales of

A LOOK AT THE HISTORY OF PRECAST CONCRETE.By Martin Clarke, Chief Executive, British Precast

The technology of cement based materials has been developing since the firstconcrete mix was produced. Much of this technology was further improved withtime but much was forgotten (sometimes to be later ‘reinvented’). Somedevelopments have been accidental, such as the discovery of the benefits of airentrainment, some have been the result of foresight and endeavour, or commercialgain, whilst others have been born of necessity such as those for military andstructural reasons.

This series of articles - "Milestones in the history of concrete technology" - hasincluded diverse papers on advances in concrete technology for military and sportingconstruction, and different cement types. Given the increasing emphasis on off-siteconstruction, the paper below is particularly timely.

MILESTONES IN THE HISTORY OF CONCRETE TECHNOLOGY

14

concrete products, mostly in the way of floor

beams and large building blocks, and a range of

ornate garden landscape products. There was

particular interest recently when Castle House in

Bridgwater was nominated for the BBC

Restoration award. The “Concrete Castle” was

built as a showhouse for Board & Co in 1851

featuring their concrete product ranges both

functional and decorative, a forerunner of this

year’s Hanson House at Offsite2005.

Other examples of precasting using ‘Roman’

cement (previously patented in 1796, and named

from the belief that the secrets of the cement that

the Romans had used had been duplicated to

create it) includes the first all-concrete house, in

which a number of elements were precast – not

least of which were the concrete gnomes placed

in the gardens. Built for John Bazley White, who

was a manufacturer of Roman cement from the

Swanscombe area in Kent, it was completed in

1835, although precisely how much of the all-

concrete structure was precast is not known.

Another concrete house built in Gravesend in

1850 by William Aspdin to demonstrate the uses

of Portland cement featured ornate precast

elements that formed a garden balustrade (see

Figure 1), which can still be seen today.

By 1848, even accidental production of precast

concrete was put to good use. Joseph Aspdin’s

elder son, William, had set up a cement works in

Northfleet, and was shipping barrels of cement

far and wide. A ship loaded with cement barrels

from his works sailed down the River Thames and

ran aground at Sheerness. The locals are

rumoured to have leapt to the aid of the stricken

ship, rescuing the barrels in the mistaken belief

that they contained brandy. By the time the

barrels had been recovered and opened, the

contents had set, and the townsfolk had to

decide what to do with them. With their original

intentions in mind, no doubt, they elected to

build a public house from them! The ‘Ship on

Shore’, or ‘Grotto’ as it was sometimes known,

was the result, with the original barrels still clearly

on display in the remaining sections.

Mass productionAround the 1850s, real examples of precast

manufacturing start to appear with the formation

of Adolph Kroher’s ‘Staudacher-Cementfabrik’

concrete tile manufacturing business in Southern

Bavaria by 1858 [1]. Examples of tiles made by

Kroher before forming his manufacturing

company date back at least to 1848,

manufactured from locally occurring naturally

cementitious materials.

Kroher’s early tiles were predominantly

diamond-shaped, a property which they shared

with Roman stone slates used in Britain some

1500 years before. He soon designed wooden

‘forme’ to make concrete pantiles and ridgetiles,

as well as flat, interlocked tiles. Kroher also made

a device to form his tiles that allowed one person

to make between 120 and 160 tiles a day, all

perfectly shaped. Without knowing it, Kroher had

invented the modern concrete tile manufacturing

business.

As Portland cement became readily available,

reliable and of sufficient quality, precasters started

to benefit from the improved performance that

the use of factory controlled conditions could

provide, although very few recognised the full

benefits at the time. With the Victorian passion

for engineering and technological innovation,

many advances in production techniques came

about. Perhaps one of the least known of its time

was the Fielding and Platt hydraulic press; the first

hydraulic press in the UK, and possibly the world,

which was was manufactured in 1890. Powered

by water to rotate its sophisticated triple mould

rotating table, the press developed 500 tons of

force translated into 2 tons per square inch of

product-pressing mechanism. The second press

was manufactured three months later. It was

transferred to the Adamant Stone and Paving

Company of Aberdeen in 1897, where it then

continued production for a further 73 years

before its retirement – a truly magnificent

performance.

From 1904 to 1907 a precast facility was set

up at Calstock on the banks of the Tamar by local

contractor John Lang. The aim was a new railway

viaduct to connect the industrial and agricultural

riches of the area with the main rail network at

Plymouth. The magnificent result continues to

carry rail traffic across the river every hour. TheFigure 1: Precast elements in WilliamAspdin’s garden balustrade.

quality of the large precast blocks, which

controversially replaced the usual granite on cost

grounds, was and is superb and rightly Calstock

Viaduct won a Concrete Society Mature Structure

award in 2004. (see Figure 2)

As the twentieth century eased its way through

political turmoil and the First World War, the

manufacture of precast concrete became well

established. The benefits of controlled

manufacturing conditions, mechanisation, regular

skilled labour and the sourcing of raw materials of

consistent quality meant that precast concrete

was being made to the highest standards possible

at the time.

Roofing tiles from the 1930s can be seen in

Figure 3, on top of an all-concrete house. Figure

4 shows coloured precast concrete for the Carrera

Building in Mornington Crescent, London;

yellows, reds, greens, browns and blacks all

featured. The production of polished precast

Figure 2: Calstock Viaduct

Figure 3: ‘Defiance’ roofing tiles. Figure 4: The Carrera Building in London

15

partition panes shown in Figure 5 were cast in the

1920s with marble aggregate. Figure 6 shows a

precast London police box of 1930 and

pipemaking at Mono Concrete’s plant around that

time is shown in Figure 7. At this time,

manufacturers were getting organised and the era

of the ‘Product Association’ was arriving.

Early trade associations Although British Precast (formally the British

Precast Concrete Federation) can trace its history

back to 1918, there are signs that the American

industry was well ahead in terms of being an

organised ‘body’. In 1926, the distinguished

Brigadier-General A.C. Critchley, C.M.G., D.S.O.,

and Vice President of the British Portland Cement

Association, wrote with passion to

the Editor of Concrete for the

Builder & Concrete Products[2],

asking for support for ‘a body

similar to the Concrete Products

Association of America’. Citing the

improvements to product quality

and the dissemination of

knowledge amongst its members,

it is doubtful that the message hit

home until the next sentence;

‘official figures show that last year

alone no fewer than 500,000,000

concrete articles of all descriptions

were made and sold in that country’. The Editor

not only printed the request, but also dedicated

his entire editorial page to supporting the plea,

and to wishing the Association all success.

From skyscrapers to ships Whilst the Americans stole a march on trade

associations, the British had already tried what

would later become an American trademark – the

skyscraper. In 1879, Andrew Peterson started

work on building a folly in form of the 66 m tall

Sway Tower in Hampshire. On completion, in

1885, it was the tallest concrete building in the

world and was built with precast concrete steps,

cornices and window mouldings, although the

main structure was in situ concrete. It showed

remarkable foresight and engineering faith in

both in situ and precast materials.

The first world war also brought about a

shortage of steel and the shipbuilders of Britain

turned to concrete. In 1919[3], the SS Armistice,

the first self-propelled concrete ship to be built in

Britain, was launched; another example of the

Figure 5: Partition panels

Figure 6: Precast London police box Figure 7: Pipemaking in the 1930s

16

extremes to which the use of precasting was

starting to be considered. Many canal and sea-

going barges were also constructed all over

Britain during the First World War, some of which

are still afloat. Again, however, the British lagged

behind the Americans who, although not as short

of steel as Britain, had already launched the SS

Palo Alto on 19 May 1918. At 434 feet and 6,144

tons, the Palo Alto carried 1.3 millions gallons of

oil, on top of a steam engine for propulsion. The

vessel remained in service until the depression and

in 1930 was deliberately sunk at the end of a pier

in Seacliff, California, USA, for use as an

amusement centre, and to protect the pier from

the worst of the weather. She remains there to

this day, and despite cracking her hull during the

first year of resting on the seabed, is largely still

intact.

Civil and wartime usesIn the 1920s the British precast industry really

started to develop, alongside the development of

steel reinforcement. Pipes, culverts and storage

tanks were to the fore, the manufacture of

concrete roof tiles was adopted from Germany,

and the building block was introduced for mass

housing. The Second World War also saw the first

production of railway sleepers, although full-scale

production only really got going after the war had

ended.

Wartime seemed to encourage the

adventurous side of precasting, from the

ambitious plan in 1918 to float 16 concrete

towers out into the English channel for German

submarine interception (two were built before the

war came to an end), to the innovative Mulberry

harbour pontoons, each 61 metres long and 18

metres wide and deep. A total of 200 of these

huge structures were floated across the English

Channel in one night, to form the

harbour wall and play a vital role in

the D-Day landings.

Technical and aestheticdevelopments

In it’s infancy by WWII, prestressing

was just starting to become

established as a viable technique, and

during the early part of the war a

number of prestressed concrete

bridge beams were manufactured and

stored for emergency use. Several

bridges were built from these beams

but, for security reasons, the exact

locations were not released.

As precast concrete technology developed, so

did the functional processes that work around it

in manufacturing, production control and design.

Today, modern automated systems control

increasingly sophisticated factory systems; in fact

the most advanced hollowcore flooring factory in

the world has been opened by Bison at

Swadlincote, Derbyshire in 2005.

Precast concrete has been tooled, textured and

stained for aesthetic purposes; coloured and

textured concretes allowed architects to express

themselves more freely and to help develop the

potential of what, during the 1960s, became a

material that was hated in some quarters for its

bland, grey appearance.

Block paving – 30 years ofdevelopment

During the 1970s, concrete block paving was

introduced into the UK; a delayed introduction of

a well-established product from Europe. The

industry has never looked back. Modern block

paving can be found in a wide variety of colours,

textures, shapes and laying patterns. It can be

designed to take the heaviest of industrial loads,

or provide the lightest touch to a domestic

installation. It can also be adapted to absorb

traffic fumes, or as permeable paving to provide

sustainable drainage through the surface to the

underlying strata. In addition the paving surface is

repairable and the elements are recyclable. Made

with decorative, recycled or artificial aggregates,

and a range of cementitious and colour

combinations, block paving typifies the way that

precast concrete has been able to develop in the

past century and a half.

Two modern examples of precast concrete are

shown in Figures 8 and 9.

Figure 8: H&H Celcon Aircrete production

17

18

The futureWith innovation, technological advances and

an eye for opportunity, the precast industry

continues to progress worldwide. Modern

manufacturing in the UK needs to take account of

health, safety and environmental issues, together

with the many layers of legislation both from the

UK and Europe, which affect both working

practices and business methods. Additionally,

modern precast manufacturers have to get along

with all their stakeholders, from shareholders to

the next-door neighbour, from the workforce to

the local environment. British Precast reflects

these new challenges in its Best Practice Awards

schemes (see www.britishprecast.org/awards.) The

entries for these awards clearly track how the

industry is moving forward. Productivity is being

boosted by the strides in equipment design and

outputs, materials technology is improving quality

and consistency, robotics are making the

workplace safer, tagging is improving customer

service and inventory control efficiency and the

potential for integrated 4D design detailing and

production programmes is massive. A similar

retrospective in 20 years time will undoubtedly

record a time of much progress and improvement.

References

1 Charles Dobson. The History of theConcrete Roofing Tile’ B.T. Batsford Ltd,1959.

2 Concrete for the Builder & ConcreteProducts Yearbook 1926-1927, ConcretePublications Ltd, 1927.

3 Concrete Through the Ages, British CementAssociation, 1999.

Figure 9: Arsenal Football Club’s new stadium under construction

19

ANNUAL CONVENTION SYMPOSIUM: PAPERS PRESENTED 2005

PAPERS: AUTHORS:

A major part of the ICT Annual Convention is the Technical Symposium, where guestspeakers who are eminent in their field present papers on their specialist subjects.Each year papers are linked by a theme. The title of the 2005 Symposium was:

CONCRETE FOR A NEW WORLD Symposium Chairman: Ian Cox, BSc, MSc, CEng, FIStructE, MICE, MIHT, MInstSMM, FCIM. The Concrete Centre

Edited versions of the papers are given in the following pages. Some papers vary in writtenstyle notwithstanding limited editing.

KEYNOTE ADDRESS Dr. John MilesMEETING THE CHALLENGES FREng, CEng, FIMechE, BSc(Hons), PhDOF THE NEW WORLD Arup Group

THAMESLINK 2000 CTRL Jasen GauldENABLING WORKS MICT

CEMEX - RMC Materials Ltd

THE TECHNICAL PERFORMANCE OF STEEL Ann Lambrechts AND POLYMER-BASED FIBRE CONCRETE MSCE

nv Bekaert sa., Belgium

MARINE CONCRETE EXPERIENCE IN THE Peter de VriesNETHERLANDS - WHAT HAS BEEN LEARNED? FICT

ENCI B.V., HeidelbergcementgroupNetherlands

THE ROLE OF PRECAST CONCRETE Peter Kelly IN STADIA BSc, CEng, MIStructE

and Nick Webb Bison Concrete Ltd

RECENT ADVANCES IN THE UNDERSTANDING Larry RobertsOF CEMENT/ADMIXTURE INTERACTIONS BSc, MSc

W R Grace & Co., USA

THE GREAT MAN-MADE RIVER PROJECT, LIBYA Andy RogersMICTPrice Brothers (UK) Ltd

DUCTAL®: ULTRA-HIGH PERFORMANCE Dr. Mouloud BehloulCONCRETE TECHNOLOGY FOR A WIDE RANGE Lafarge Group, FranceOF APPLICATIONS

ADVANCED CONCRETE TECHNOLOGY FOR A Dr. Mario CorradiCOMPLEX BRIDGE SYSTEM WITH LOW Degussa Construction ENVIRONMENTAL IMPACT Chemicals Europe, Italy

HIGH-PERFORMANCE MICROSILICA CONCRETE Kshemendra NathFOR THE BANDRA-WORLI SEA-LINK, MUMBAI BTech, MICT

Elkem India Private Ltd

20

21

Dr John Miles is a Member of

the Arup Group Board and has

been Chairman of their Global

Consulting Sector since April

2004, following spells as

Chairman of the firm’s Business

Investment Executive and Chairman of the firm’s

Corporate Services Division. The Consulting

Business offers clients a service that is

complementary to Arup’s more conventional lines

of business, thus ensuring that the firm remains

unique in its ability to perceive need; create

solutions and deliver results.

John Miles had previously accumulated 20

years of professional experience in the area of

design for high performance structures. This

included mechanical and civil engineering

structural design for buildings, and the

structural/mechanical design of road vehicles and

rail systems under extreme loadings such as crash,

blast, impact and seismic shock. Subsequently,

his experience developed into the areas of design

for manufacture and, in particular, off-site

fabrication for the housing sector.

He is a fellow of the Royal Academy of

Engineering and has served terms as a

commissioner for CABE (Commission for

Architecture in the Built Environment) and a

Director of the UK Housing Forum. He is author

of numerous technical and business publications

and he is a Visiting Professor of Design Principles

at Warwick University.

ABSTRACTThis paper examines the market share, both

current and potential, for concrete. It illustrates,

using a case study, the feasibility of building

houses with factory produced systems and lists

the reasons, including sustainability, why this

should be so. In the current scene, the

government’s aim to increase the housing stock

by using Modern Methods of Construction is

outlined and the requirement to change the

approach to design, construction and delivery is

noted.

KEYWORDSSustainability, Environment, Business

challenges, Factory-produced, Housing, Added

value, Whole building delivery, Modern Methods

of Construction (MMC).

MEETING THE CHALLENGE OF THE NEW WORLD

Dr. John Miles FREng, CEng, FIMechE, BSc(Hons), PhD

Arup Group

Figure 1: Cementitious Product v New Construction Output

22

INTRODUCTIONConcrete is a marvellous material. It is cheap

and plentiful. It is robust and well understood. It

is easily formed into complex shapes. It can be

used to create buildings which are almost

unlimited in their form and, with care, it can be

pushed to some extraordinary extremes.

Concrete coil springs and canopies as thin as

fabric membranes come to mind.

Yet, with all these successes and track-record,

the place of concrete in a strong UK construction

market is under threat. As a fraction of total

construction output, cementitious product market

share is declining (Figure 1). On top of this,

environmentalists and the sustainability lobby are

raising ever stronger voices resisting the

despoilment of the countryside and the depletion

of natural resources that accompany aggregate

extraction. And the same voices are raised

against the high levels of energy consumption

associated with the production of cement.

Against a backdrop of reducing market share

and increasing environmental opposition, where

does the concrete industry go from here?

This question is not so much a question of

technology, it is more a question of business

requirement. In order to answer the question,

the concrete fraternity needs a root-and-branch

evaluation of the business challenges facing the

developers and constructors who procure and

deliver completed buildings. From this must be

constructed a re-statement of the competitive

advantages of concrete in distinct and business-

like terms.

A CASE STUDYAn example of this sort of root-and-branch

business thinking can be found in the

housebuilding industry. The issue, from a

business perspective, is to build better quality

housing in the UK at lower costs than current

practices can deliver. An examination of

conventional processes sets the targets for build

price and finished quality. Build cost, it turns out,

is very low (much lower than the norm for

commercial construction); build quality is patchy

(at best). Meeting the second target wil be easier

than meeting the first!

An independent study[1] concluded that

concrete would be an ideal material on which to

base the development of an advanced, factory-

based, production system for modern housing in

Britain. A factory, with low capital intensity of

equipment, was designed. Practical trials and

tests were conducted to demonstrate the

technical performance of concrete within this

application environment. And a prototype house

was built to demonstrate that conventional

appearances could be delivered from factory-

based systems (Figure 2). (This is an important

customer-satisfaction issue).

Concrete was chosen as the base-material for

the product for a variety of very simple reasons:

• It is a low-cost, robust, material that needs

minimal maintenance

• Its characteristics and behaviour are well

understood

• It can be used for low, medium and high-rise

configurations with minimal adaptation

• It has excellent fire-resistance

• It can be produced with a very high surface

quality, (thus removing the cost of plastering)

• It has good sustainability characteristics.

The last point deserves some elaboration, since

current opinion often raises questions in this area.

There are clear disadvantages from a sustainability

point-of-view in terms of embodied energy

(cement) and despoilment/resource deprivation

(aggregate). There are, however, some positive

aspects which can outweigh these headline

disadvantages:

• Embodied Energy is not significantly worse

than competitor products (brick and block;

steel; etc)

Figure 2: Concrete-based ‘Meteor System’ developed for UK Housing Market

23

• Embodied CO2 likewise

• High mass gives good acoustic insulation

• High mass, when combined with good

insulation, gives good thermal and energy-

in-use characteristics

• Robust material has good ‘wear’

characteristics and therefore low

maintenance cost (for social housing)

• Near-net-shape material has minimal

wastage during production.

These excellent baseline characteristics,

however, are not enough on their own. The key

to the business case for this product was to

maximise the ‘value added’ in the factory

environment, and minimise the labour hours

required to complete the house on site. By doing

this, the capital value of the factory could be

amortised more effectively and the error-prone,

site-based, processes of plumbing, cabling and

finishing be fundamentally changed for the

better. As a consequence, quality could be

improved and costs reduced simultaneously.

This coupling of economic advantage and

improved product performance neatly illustrates

the concept of ‘Whole Building Delivery’.

Essential to this idea is an appreciation that the

cost of the structure is only one element in the

total cost of delivering a house. Indeed, the

combined cost of the services, fittings and

finishes far exceeds the cost of the ‘brick and

block’. These value-adding items must be dealt

with in the factory if concrete-based off-site

systems are to become cost-effective when

compared to conventional processes.

THE CURRENT SCENEAt the time of writing, the Government

continues to promote its desire for the

Construction Industry (and particularly the

housebuilding sector) to change its traditional

approach and embrace Modern Methods of

Construction (MMC). In the face of a clear need

to increase the rate of housebuilding at a national

level, MMC is seen as a panacea for the need to

build better houses faster at no extra cost (or,

indeed, at even lower cost). How can the

concrete fraternity respond to this pressure?

Unfortunately, at present, there is no precise

definition of MMC. However, recognising that

the impetus for this new approach stems directly

from a desire to build more product with less

available skilled labour on site, the key issue

could be interpreted as a requirement to increase

the productivity of those remaining site-based

operatives. From this, a working definition of

MMC might be proposed which goes along the

following lines:

“Modern Methods of Construction are those

which reduce significantly the labour hours

required on site to complete any building when

compared to the current industry norm. Such

methods must also be inherently sustainable and

must produce buildings of high quality”.

If a definition along these lines becomes

adopted, what response will be offered? Will we

see a return to the ‘70s style of precast concrete

panel systems for housing (Figure 3) or will the

industry offer more than that?

Observation of previous cycles of off-site

manufacture lead to the conclusion that none of

them created lasting change in the industry. The

prefabs of the late ‘40s and the precast systems

of the ‘70s fell into disuse once the hand of

government was removed. The reason for this

was very simple: those factory-based systems

were more costly (not less costly) than

conventional methods of construction. Thus,

when left to free-market forces, the new systems

died and conventional methods

returned to domination.

If the current round of enthusiasm for

MMC is to endow lasting change, the

economic equation must be squared.

Modern Methods must not only

produce better houses; they must

produce more cost effective houses.

This can only be achieved by

considering the delivery of the whole

building from the outset, rather than

considering it as a collection of isolated

components which are brought

together on site. And this argument

extends beyond housebuilding to theFigure 3: Will we see a return to 70s’ style panelsystems?

24

wider horizons of the construction industry at

large. In short, the industry’s response to the

Government’s challenge of MMC must be to

produce new products that address ‘Whole

Building Delivery’ not ‘Part Building Delivery’.

This requires a sea-change of approach.

CONCLUSIONSConcrete is an ideal material from which to

develop new construction systems that will meet

the Government’s demand for MMC. However,

these systems are more likely to be successful if

they are based on the concept of ‘Whole Building

Delivery’ than if they are simple extensions of

low-value, structural component type products.

‘Whole Building Delivery’ recognises that the

majority of ‘value’ in any building lies in the

services, fittings and finishes which are integral to

the finished product. Successful Modern

Methods of Construction must therefore

integrate the installation of these value-adding

components with the production of the basic

(concrete) structure.

To do this successfully requires a radically

different approach to design, construction, and

delivery. Holistic design must be employed which

recognises, from the outset, the integrated

requirements of structure, services, fittings, and

finishes. And multi-skilled production techniques

must be deployed in the production environment

which enable these elements to be installed

simultaneously and without error. Quite likely

(but not necessarily) such production facilities will

be off-site.

For this scenario to become a reality, a massive

challenge is presented in the areas of education

and training. The next generation of designers,

fabricators and constructors must have an innate

appreciation of Whole Building Delivery (or

‘Embodied Value’). With its emphasis on

qualifications and accreditation, this is a particular

challenge for the ICT.

How, exactly, will the ICT respond?

REFERENCE1. Opportunity of a Lifetime - Ingenia :

Issue 17, Oct/Nov 2003

2525

Jasen Gauld is the London Area

Technical Manager for CEMEX

UK Operations, formerly

known as RMC Materials

Limited. He joined RMC in the

close of 1988 and was

assigned a managerial role in London in 1996. In

his role the need to investigate and assess new

materials and processes is vital to remaining

dynamic to the challenges and opportunities of

the London business.

ABSTRACTThe customer base seeks concrete solutions to

meet given applications. This paper considers an

exclusive project from the perspective of the

concrete supplier and illustrates that concrete

solutions continue to have their rightful place

within our industry. Furthermore, it illustrates the

importance of a meaningful resource within the

structure of the concrete supplier to deliver and

secure completion with specialised concreting

materials. Survival within our sector is not based

upon volume alone, but requires the ability to

redefine the properties of our product to an

acceptable order of confidence. Such demands

can be met and secure concrete’s central place as

a malleable heavy building material.

KEYWORDSConcrete solution, Equivalent flexural strength,

Customer, Validation process, Constructability.

INTRODUCTIONHigh velocity trains enter the United Kingdom

from the continent through the Channel Tunnel

and currently arrive at Waterloo Station, London.

To maximise the benefits of high-speed travel,

extensive programmes to develop existing

facilities and install new track are ongoing,

together with an ever-developing vision of

outsourcing such facilities beyond Waterloo

Station. A review of the existing facility at

Clerkenwell Tunnels 2 and 3 (i.e. local to Kings

Cross Station) required that the existing track slab

be upgraded, without raising the height of the

track slab or undermining the existing

foundation. The existing track slab was

instrumental to the integrity of the foundation.

A novel thin concrete overlay was required to

meet the requirements of the specification. The

suitability of this innovative product would have a

significant bearing on the project’s success or

failure.

The main contractor was Balfour Beatty Rail

Projects and at the time the concrete supplier was

RMC South East.

DESCRIPTION OF THE PROJECTThe project required the application of

experience and concrete technology in the

preparation of an innovative concreting material.

The purpose of the material was to enable the

client to run trains on time once the blockade

window had closed and to upgrade the existing

facility in readiness for the forthcoming high

velocity trains from the continent.

The main works took place from late

December 2003 to early January 2004 during the

blockade of the Clerkenwell Tunnels 2 and 3.

The planned placement of the new material was

to take place during the period 28th to 30th

December 2003.

The tunnel blockade allowed for removal of

the existing track and the removal / trimming of

the existing concrete surface, prior to placing a

new concrete overlay to the existing slab. The

new concrete was anchored to the existing slab

by galvanised steel shear studs and was

reinforced with steel mesh and steel fibres.

The new material was delivered to the point of

placement by pump over a linear pipeline

distance greater than 100 metres. The material

would be placed in both tunnels simultaneously

and would require an adequate supply of

concrete to service both pumps.

From an early age a large volume of the new

material would face vigorous demands in situ and

be laid to a thickness as low as 80 millimetres.

Initial in situ performance was required to allow

the uninterrupted passage of the equipment for

construction of the track. At 7 days a greater

THAMESLINK 2000 CTRL ENABLING WORKS

Jasen Gauld MICT

CEMEX - RMC Materials Ltd

Disclaimer: The views and opinions expressed in this paper are those of the author and not neccessarily those ofCEMEX UK Operations and/or RMC Materials Ltd.

2626

performance was required to allow for the

passage of trains through the tunnel and at 28

days an even greater performance to meet the

durability design criteria.

PRIMARY REQUIREMENTS OF THE SPECIFICATION

The structural performance level as derived

from BS 8500 Table A.3 was ‘high’ requiring the

material to fulfil a long service life solution in

excess of 100 years.

The in situ concrete was to achieve

compressive strength values (as determined from

150 mm concrete test cubes) of 6.0 N/mm2 at 24

hours, 40.0 N/mm2 at 7 days and 50.0 N/mm2 at

28 days. These values are further complimented

with an in situ equivalent flexural strength

(fctm,eq300) requirement (as determined from

150 mm x 150 mm x 500 mm concrete test

beams) of 4.5 N/mm2 to JSCE SF4. Inevitably this

would mean that all test samples were cured

adjacent to the slab.

The material was to be pumped without

segregation or blockage at a rate suitable for the

construction process from the point of delivery to

the placement location.

The concrete supplier proposed both the

required workability / consistence and the

method by which to measure it. The consistence

of the concrete had to be such that the concrete

was suitable for the conditions of handling and

placing so that after compaction it surrounded all

reinforcement and completely filled the form.

The resulting concrete surface had to be

smooth and free from honeycombing. The

material, in conjunction with finishing activities,

had to be flat with no exposed steel fibres or

aggregate particles.

The maximum nominal aggregate size was 14

mm, however the overall grading of the materials

produced a concrete of the specified quality that

would work readily into position without

segregation or exhibiting a depth of bleed water

in excess of 0.2% of the height of the pour.

The minimum cement content was 360 kg/m3

and the maximum cement content was 450

kg/m3. The maximum free water / cement ratio

was 0.45.

The concrete design had to reflect a material

of low shrinkage characteristics. The concrete

included a shrinkage reducing or compensating

admixture and had a minimum drying shrinkage

of 0.03% at 28 days when assessed primarily

against ASTM C157.

Resistance to alkali silica reaction was to be

achieved through following the minimising

precautions within BS 8500:2 Section 5.2[1].

The concrete was to be of normal weight (i.e.

2000 – 2600 kg/m3). The maximum chloride class

of the concrete was Cl 0,20. The total acid

soluble sulphate content of the design could not

exceed 4.0% by weight of cementitious material.

WHAT IS EQUIVALENT FLEXURAL STRENGTH OF 4.5N/mm2

(fctm,eq300) AND ITS IMPACT ON THE DESIGN ?

The Equivalent Flexural Strength (fctm,eq300) is a

post crack flexural strength to a deflection of 1.5

mm and is attained through the inclusion of steel

fibres. A definition of fctm,eq300 is outlined in

Figure 1[2].

2727

An example of a bending test on a prismatic

sample is outlined in Figure 2 and relates to a

laboratory specimen incorporating the selected

fibre type and quantity.

An equivalent flexural strength of 4.5 N/mm2

(fctm,eq300) is a demanding requirement especially

given the likely in situ curing condition of the test

beams and the early age of compliance (i.e. 7

days). In such instances the selection of the

appropriate fibre is critical together with the

ability to harness the active involvement of the

fibre manufacturer over an extensive validation

program prior to implementation.

The author was aware of a fibre type that had

achieved values greater than 4.5 N/mm2, however

the test specimens were prepared under

laboratory conditions and tested at a later age

than 7 days. At certain dosages this fibre had

commendably provided good post crack

performance and a sustainable loading capacity

through a deflection term. Subsequent Re1.5 (i.e.

[equivalent flexural strength / modulus of

rupture]100) values reassuringly offered a high

percentage in comparison with other known

fibres. In principle, providing the performance

could be validated with the local design

constituents and account for the reduced initial

performance due to a lowered maturity (i.e. a

maturity associated with site curing and tested at

7 days), then a solution to this part of the

specification was feasible. Nevertheless, the

design would be required to accommodate a

good length, high performance cold drawn wire

fibre of a sizeable aspect ratio and allow for the

presence of over 225,000 of these fibres per

cubic metre.

SPECIFICATION LEADS

Validation processThe specification insisted on an extensive

validation process. This was undertaken to secure

customer satisfaction and ensure that

performance was achievable, prior to the

incorporation of the concrete into the final

works. Initial testing to determine the optimum

quantities of the constituents to satisfy the

requirements for the fresh and hardened

properties was required. In addition to the initial

testing, the concrete supplier was to undertake

trials to demonstrate constructability, the

suitability of the mix and compatibility with the

intended construction methods. In order to

satisfy these requirements full-scale site trials

formed part of the specification. The trials would

involve the approved/proposed materials, plant

and equipment and the typical reinforcement

configuration to be used in the final works.

The concrete supplier submitted details of the

initial testing against a detailed sampling regime

Figure 2: Prismatic sample beingprepared for testing

Figure 1: Load/deflection diagram for steel wire fibre reinforcement concrete

2828

especially in relation to compressive and

equivalent flexural strength. Each successful trial

required 75 cubic metres of the proposed

material to be batched and placed on two

occasions prior to commencing final works.

Silica fumeThe specification allowed for the use of a

slurried silica fume. The body utilised by the

main contractor in preparing the specification

were enthusiastic about the incorporation of this

material within the design.

The merits of silica fume from a durability

perspective are notable and in this instance

would serve to assist in meeting certain physical

criteria of the specification and reduce the ingress

of chloride ions. By extension, the use of silica

fume from a concrete rheology perspective also

aids cohesion and enhances the slickness of the

cementitious fraction which enabled greater

control over pumping especially in the context of

the number of fibres involved.

In certain countries where many of the

aggregates are alkali silica reactive and where the

available CEM I has a high alkali content, it is

reported[3]. that the use of silica fume at 5.0 to

7.5% by mass of cement has been effective in

preventing cracking caused by alkali silica

reaction. Conversely it is also reported that some

research has suggested that the replacement of

only 5% by mass of high alkali cement by silica

fume can result in increased expansion of the

concrete by alkali silica reaction. The design in

question did not incorporate high reactivity

aggregate types or high alkali cement, however

the paradoxical practice of increasing the level of

certain proportions beyond the so-called

pessimum level serves to minimise expansion to

insignificant levels. BRE Information Paper IP1/02

as referred to in BS 8500-2 5.2.7 states that

where a silica fume with greater than 85%

amorphous SiO2 is administered at a minimum of

8% silica fume by mass as a percentage of the

total binders, the damaging effects of alkali silica

reaction are considered to be minimised.

Curing / concrete warmingThe specification required that the concrete

surface immediately benefited from proven curing

techniques and by implication the effects of

curing would have an impact on early age

performance values. The specification allowed

for the concrete to be warmed and/or insulated

during the curing period. The main contractor

responded favourably to this lead and

implemented proven curing techniques and the

practice of trying to insulate against heat loss at

the end of each tunnel, thereby enabling the in

situ material to benefit from a temperature

greater than ambient.

London Weather CentreThe main contractor instigated a review of the

weather conditions at the proposed construction

period over the previous decade. It was found

that the London Weather Centre regularly record

temperatures from Clerkenwell Street throughout

the year. The past 10 years of data for the

proposed date of construction was made

available for consideration. It was found that it

was remarkably cold in 1996/97 and 2001/02,

but the mean hourly air temperature for the

proposed construction period over the past 10

years was 5.5˚C.

Balfour Beatty Rail ProjectsLimited

The main contractor was Balfour Beatty Rail

Projects Limited. Whilst the primary requirements

of the specification were demanding they were

made easier through a collaborative lead. This

does not mean that the specification was

changed or undermined but rather a strong

management structure existed within Balfour

Beatty Rail Projects Limited. As a result the

concrete supplier was invited to a number of

open meetings/project management forums and

furnished with regular updates on progress made.

An extensive part of the work was to identify the

makeup of the processes that would enable

successful completion, which involved

establishing and cataloguing the risk and to

formalise contingency plans where possible.

Immense emphasis was placed on both the

laboratory and site trials to the extent that a

proven performance was required prior to

implementation. The learning points from the

site trials were fairly assessed and best practices

identified. The main contractor wanted to

understand the product and capture the resource

of the concrete supplier in the promotion and

validation of the concrete solution.

Within establishing the processes to ensure

completion an array of items were considered

and as an example included such things as

secondary supply source; the verification of

material from that source; training of concrete

supplier operatives in new product; preparation

for cold weather/winter concreting; preparatory

operations on the plant; material resourcing and

stocking; resources for concrete validation and

training of technical operatives with new test

methods; assigning specialist test house to test

the prismatic specimens and to establish channels

for promptly reporting results at the required

interval to mention a few.

A common goal that existed was that there

was going to be nothing new to learn at the time

of placing the material into the final works as

such learning points would be derived and acted

on at the trial stage.

28th – 30th December 2003Upon reflection the events of the above dates

passed off fairly smoothly. The concrete was

produced, pumped, placed, finished and

compacted within the allotted time frame as

illustrated in Figures 3, 4, 5 and 6.

The tunnel was opened on time some 7 days

later and the trains were running over the

material without restriction. Compliance was

achieved at the given intervals of the

specification.

CONCLUSIONSCustomers are vital to the heavy building

materials sector and the ability to provide and

promote concrete solutions is essential.

To deliver effective and efficient concrete

solutions on time you have to be innovative and

follow the collaborative lead of customers who

share similar values.

A process of effective planning and

preparation close to the work face is essential

both to verify performance and secure an

acceptable order of confidence.

The ability to desensitise the concrete solution

to readily enable production, placement,

compaction and finishing is instrumental in

achieving success, yet possessing the balance to

maintain the required performance is a fine art.

2929

Figure 3: The concrete solution beingreceived at two pumps simultaneously

Figure 4: Concrete being lowered intothe Clerkenwell Tunnels by pump

Figure 5: The concrete solution beingpumped and placed in situ

Figure 6: The finished surface afterreceiving a spray of curing compound

3030

REFERENCES

1. BS 8500 – Part 1 & 2 2002 Method ofSpecifying and Guidance for the Specifiers& Specification for Constituent Materialsand Concrete.

2. Balfour Beatty Rail Projects Limited concretespecification for Thameslink 2000 – CTRLBlockade Enabling Works ClerkenwellTunnels 2 & 3 Crossovers – Trackslab.

3. BRE Information Paper IP1/02 Minimisingthe Risk of Alkali Silica Reaction: AlternativeMethods. Working Party into AlternativeMethods to Minimise ASR.

ACKNOWLEDGMENTSThe author would like to acknowledge the

assistance of Johan Vermeeren of Bekaert for his

assistance in the verification of the design at

Bekaert laboratories in Zwevegen, Belgium.

31

Ann Lambrechts graduated in

1991 as a civil engineer at the

University of Leuven. She

joined the company Bekaert

and worked consecutively as

Manager Product

Development, Quality Engineer and Product

Manager. She is a member of several CEN

commissions dealing with fibres and fibre

concrete and is secretary of the FIB Taskgroup

8.3, responsible for the creation of design rules

for fibre concrete.

ABSTRACTThis paper discusses various material

characteristics of steel and polymer fibres, with

the translation into applications such as sprayed

concrete linings and flooring.

KEYWORDSMacro synthetic fibre, Steel fibre, Sprayed

concrete, Flooring

INTRODUCTIONSteel fibre reinforced concrete (SFRC) was

introduced into the European market in the

second half of the 1970s. No standards, nor

recommendations, were available at that time

which was a major obstacle for the acceptance of

this new technology. SFRC has been applied since

then in many different construction applications,

such as in tunnel linings, mining, floors on grade,

floors on piles, prefabricated elements, etc. In

the beginning, steel fibres were used as substitute

for secondary reinforcement or for crack control

in less critical constructions parts. Nowadays,

steel fibres are widely used as the main and

unique reinforcement for industrial floor slabs

and prefabricated concrete products. Steel fibres

are also considered for structural purposes,

helping to guarantee the construction’s ability

and durability in:

- foundation piles reinforcement

- reinforcement of slabs on piles

- full replacement of the standard reinforcing

cage for tunnel segments

- reinforcement of concrete basements and

slab foundations

- steel fibres as shear reinforcement in

prestressed construction elements.

This evolution into structural applications was

mainly the result of the progress in SFRC

technology, as well as the research done at

different universities and technical institutes in

order to understand and quantify the material

properties. In the early nineties, recommendations

for design rules for steel fibre reinforced concrete

started to be developed. From October 2003,

Rilem TC 162-TDF committee’s recommendations

for design rules are available for steel fibre

reinforced concrete.

Around the start of the millennium, suppliers

of micro synthetic fibres started to offer macro

synthetic fibres. Micro synthetic fibres are typically

6 to 12 mm long and have a diameter of 16 to

35 micron, and are widely used to reduce plastic

shrinkage cracks, as well as to reduce concrete

spalling during a fire. As Young’s Modulus of a

polyolefine is typically around 3000 to 5000 MPa,

it is generally understood that the reinforcing

effect of these fibres is gone after a couple of

hours of hardening of the concrete, as hardened

concrete typically shows a Young’s Modulus of

around 30 000 MPa. Macro synthetic fibres

typically have dimensions equal to steel fibres,

with lengths varying from 15 to 60 mm, and

diameters from 0.4 to 1.5 mm. Macro synthetic

fibres are to be considered as a relatively new

construction material, but are often marketed as

being equal to steel fibres. But is this really true?

MATERIAL PROPERTIES OF STEELAND POLYMER FIBRES

Young‘s Modulus of the fibresThe reinforcing ability of a fibre depends on

the anchorage of the fibre into the concrete, the

tensile strength and the Young’s Modulus.

The Young’s Modulus of concrete is typically

30 000 MPa, of steel fibre typically 210 000 MPa,

and of polyolefine fibre typically 3000 to 5000

MPa.

31

THE TECHNICAL PERFORMANCE OF STEEL

AND POLYMER-BASED FIBRE CONCRETE

Ann N. Lambrechts MSCE

N.V. Bekaert S.A., Belgium

32

For well anchored fibres, and equal solicitation

of the fibre, the elongation of the polymer fibre,

and the corresponding crack width in concrete,

might be considerably higher compared to steel

fibres. This might have an impact on the

durability of the concrete, especially in

combination with traditional reinforcement.

Tensile strength of the fibresThe tensile strength of steel wire is typically

1000 - 2000 MPa, compared to 300 - 600 MPa

for macro synthetic fibres.

Specific density of the fibresThe specific density of steel fibres is typically

7850 kg/m3, compared to 910 kg/m3 for polymer

fibres, and 1000 kg/m3 for water. Polymer fibres

are light, which is favourable for health and

safety, but they are lighter than water: the

polymer fibres actually float on water, with

potential risks for fibres at the surface in flooring

applications.

Fire resistance of the fibresPolypropylene fibres typically melt at

temperatures around 160°C. Therefore micro

polypropylene fibres are proven to be suitable for

improving fire resistance. The exact reason is not

yet fully understood, but it is generally accepted

that the fine micro fibres start to melt in extreme

fire conditions, thereby leaving small channels

through which the pressurised vapour can

escape. Consequently less damage, less spalling,

of the concrete is to be expected.

Macro synthetic fibres melt at the same

temperature, but are not fine enough to provide

the concrete under fire with the necessary

network of channels. Moreover, since the fibres

melt, they are less suitable in those buildings

where the reinforcing effect of the fibres is

important.

Resistance against oxidationPolymer fibres don’t rust, even if the fibres are

sticking out at the surface. Bright steel fibres can

show some staining if the fibres are at the

surface, but they never cause spalling of the

concrete. If, for aesthetical reasons, staining is

not allowed, as in some prefabricated structures,

galvanised steel fibres can be used.

Mixability of the fibresSome macro synthetic fibres tend to fibrillate

during mixing. This fibrillation process goes on in

the truck mixer, until all fibres are completely

destroyed. Quality degradation during mixing

does not occur with steel fibres.

PROPERTIES OF STEEL ANDMACRO SYNTHETIC FIBRE CONCRETE

Fibre concrete is well known for its ductility.

The effect of fibres is a combination of

reinforcement and networking. Steel fibres in

particular mainly change the behaviour of the

concrete: they transform a brittle concrete into a

ductile material which is able to withstand fairly

large deformations without loosing bearing

capacity. Ductility means load redistribution and a

higher bearing capacity of the structure with the

mechanical properties of the basic concrete

material unchanged.

Reinforcing effect measured in beam tests

In general, most macro synthetic fibres

perform rather moderately in a bending test. The

pure reinforcing effect is rather poor due to the

low Young’s Modulus and the rather low tensile

strength. As can be seen from the curves in

Figures 1 and 2, most macro synthetic fibres start

working at much larger crack widths than steel

fibres; steel fibres with anchorage, depending on

fibre type, typically work optimally at crack

widths of 0.5 to 1 mm, whereas macro synthetic

fibres work optimally after 3 mm of crack width

Figure 1: typical load / deflection curvefor 1% by volume of macro syntheticfibres

33

Creep of steel fibre and macrosynthetic fibre concrete

There is little information available as to the

creep of concrete reinforced with macro synthetic

fibres. The few papers that are available[3, 4] must

be treated with care because the conclusions are

sometimes based on a limited amount of test

specimens, the creep tests are executed on

different size test specimens, and different test

procedures, as no standard test procedure is

available, and some creep tests are executed only

over three months. The conclusion from those

papers is that the creep coefficient is, depending

on the type of the macro polymer fibres, of the

order of 1 to 20 times the creep coefficient for

steel fibre concrete.

In order to investigate the difference in creep

behaviour between steel fibre and macro

synthetic fibre reinforced concrete, N.V. Bekaert

has set up a test program to compare the creep

of both materials.

Beams have been produced at the Bekaert

laboratory using the following mix design:

427 kg/m3 Cement CEM I 42.5R

854 kg/m3 Sand 0/5

854 kg/m3 Broken limestone 4/7

w/c = 0,50

Macro synthetic fibres type1 and type 2 have

been added at a dosage of 4.55 kg/m3 (0.5 by

vol%).

Dramix“ RC-65/35-BN steel fibres have been

dosed at 20 kg/m3.

The beams have been pre-cracked: the beams

have been loaded in a displacement-controlled

way, as prescribed by most standards on steel

fibre concrete. At a deflection of 5 mm, the load

has been removed. The residual load at that

moment can be read from the load deflection

curve. (Figure 3)

The beams are now ready to be subjected to

the creep test. 50% of the residual load is

applied to the pre-cracked specimens. The load is

applied in a four-point bending configuration.

The deflection is measured, and shown on the Y-

axis in Figure 4. in hundredths of a millimetre.

As can seen from Figure 4, the polypropylene

fibres tend to creep 7 to 20 times more than the

steel fibres after 1 year. Moreover, the creep of

the macro synthetic fibre is not finished yet: the

creep curve for the macro synthetic fibre is not

yet stabilised. Therefore at present, the creep

tests are still going on, as considerably higher

creep can still be expected for the macro

synthetic fibres.

These deformations, of course, induce wider

cracks.

Figure 2: Typical load / deflection curvefor 0.5% of steel fibres with hookedends

Figure 3: Set-up of creep test

34

Design rules for steel and macrosynthetic fibres

Since October, 2003, Rilem TC 162-TDF

design guidelines have been available for steel

fibre concrete. No such guidelines are yet

available for macro synthetic fibre concrete.

Quality control of steel versusmacro synthetic fibre concrete

As part of the quality production control,

wash-out tests are quite common in order to

check the dosage of fibres in fresh concrete. This

is always time consuming, but a lot easier when

the fibres can be removed using a magnet, as is

the case for steel fibres.

FIBRE CONCRETE PROPERTIES TRANSLATED INTO FLOORING APPLICATIONS

It is generally accepted that a toughness ratio

(Re3) of minimum 30% is required of the fibre

concrete in order to be able to increase the load

bearing capacity of the fibre concrete floor in

bending. This can generally not be reached by

dosages lower than 4 kg/m3 for most macro

synthetic fibre types. Mixing a quantity as much

as 4 kg/m3 (0.4% by vol) requires special

attention. Moreover, there is the intrinsic

tendency of the fibre to float on top of the

concrete, which does not make it easier to power

float the surface.

It can be expected that an accidental shrinkage

or bending crack might result in a relatively wide

crack due to the low Young’s Modulus of the

polymer fibre, and that the crack might even

open further due to the expected creep.

FIBRE CONCRETE PROPERTIESTRANSLATED INTO SOIL SUPPORTING APPLICATIONS SUCH AS SPRAYED CONCRETE LININGS IN MINES

Immediately after the excavation of a tunnel,

the rock material is regarded as elastic. A short

time after excavation, the stress situation will

change and, if the rock is weak enough, a

crushed zone will develop around the tunnel

opening (plastic zone).

If some support is established, the Pi of Figure

5 represents the support pressure against the rock

surface. When designing the rock support

necessary to limit and stop deformation, the

ground reaction curve and the support curves are

used. Considering stable rock, as shown by the

dashed line 1 in Figure 5, the load decreases

when deformation is allowed to take place. No

support would be required here. For less stable or

fractured rock, as shown by the full line 2 in

Figure 5, the load increases again, due to the

weight of the broken plastic zone in the roof. In

this case support is needed, and should be

established before the plastic zone loses

cohesion.

Figure 4: Creep (deflection in 1/100 mm) with time (days)

35

The ability to sustain loads whilst undergoing

significant deflections needs to be an intrinsic

property of the chosen support system. The

presence of steel fibres in a concrete matrix, with

the potential to bridge and apply tension across

any cracks that form, has the ability to change an

inherently brittle material into a ductile one.

How do macro synthetic fibres compare

towards steel fibres in linings? With respect to

the hardened shotcrete, steel fibre reinforced

shotcrete is, typically, better at providing higher

post-crack residual load carrying capacity than

high volume synthetic fibre reinforced shotcretes

at low deformations when crack widths are

narrow. Hence steel fibre reinforced sprayed

concrete with a sufficient dosage of performant

fibres is generally preferred in permanent mine

works where a durable structure with near-

watertight conditions and narrow crack widths is

needed, e.g. underground hoist rooms, crusher

stations, electrical and pump rooms.

On the other hand, high volume macro

synthetic fibre reinforced shotcretes may display

good ductile behaviour at what is considered

larger deformations. As such, its use could be

considered in applications where larger ground

deformations, and hence wider cracks developing

in the shotcrete, are to be expected and are

allowed, such as temporary mining openings.

But, the support system has to withstand

continuously the ground pressure, particularly in

mining operations where the loading conditions

may even change frequently when mining is

going on. Creep becomes an issue. There is very

little information as to the creep of concrete

reinforced with macro synthetic fibres, or on the

ageing effect of these synthetic fibres in an

alkaline concrete matrix. As can be seen from

Figure 6, steel fibre reinforced shotcrete (SFRS)

has a minor creep behaviour keeping the extra

deformation under loading to a minimum while

sprayed concrete reinforced with synthetic fibres

shows a large increase in the deformation, which

finally may result in the collapse of the structure.

CONCLUSIONSteel fibre concrete/shotcrete has proved, over

the years, to be a reliable construction material.

After 30 years of experience, the first Rilem

design guidelines for steel fibre concrete were

edited in October, 2003.

New fibre concretes, such as macro synthetic

fibre concrete, are not yet fully understood, but

gain attention. Creep data, shear resistance, crack

control, durability, design methods, etc. are

lacking at the moment for macro synthetic fibre

concrete, but the experience will be gained.

REFERENCES

1. Rilem TC162-TDF: “Test and designmethods for teel fibre reinforced concrete”,TC Membership, Chairlady L. Vandewalle,Materials and Structures, Vol 36, October2003, p560-567

2. M. Vandewalle, The evolution of theinternational projects in the development ofsteel fibre reinforced concrete, presented atconference in Bergamot, Sept. 2004

3. J. MacKay, and J.F. Trottier, Post-crackbehavior of steel and synthetic FRC underflexural loading, Shotcrete: MoreEngineering Developments – Bernard (ed.),2004 Taylor and Francis Group, London,ISBN 04 1535 898 1

4. Bernard E.S. Creep of cracked fibrereinforced shotcrete panels in Shotcrete:More Engineering Developments – Bernard(ed.), 2004, Taylor and Francis Group,London, ISBN 04 1535 898 1

Figure 5: Support pressure after atunnel is excavated

Figure 6: Creep effect on the support of a lining

36

37

Peter de Vries is employed as a

technical service manager for

ENCI B.V. in the Netherlands.

ENCI is a sub-division of the

HEIDELBERGCEMENTGroup. As

a technical service manager

Peter is responsible for the technical support of

clients of ENCI. He acts as a freelance teacher for

the Dutch Concrete Society on topics such as

concrete technology, durability of concrete

structures and execution of concrete works.

He works on several standards committees for

concrete technology. Recently he has been working

on the introduction of EN 206 and the drawing up

of the Dutch national annex to EN 206.

ABSTRACTThe present design approach with respect to

durability of concrete structures is based on a

reasonable understanding of the main

degradation processes for (reinforced) concrete.

Concrete in a marine environment is exposed to

all kinds of harmful effects. This paper will give a

survey of the Dutch experience with concrete in

the marine environment and the very important

role of blastfurnace slag cement in relation to

durability.

KEYWORDSDurability, Marine environment, Sulfate attack,

Alkali silica reaction (ASR), Corrosion, Chloride

penetration, Heat development, Early age thermal

shrinkage, Ground granulated blastfurnace slag

(GGBS), DuraCrete.

INTRODUCTIONDue to the high construction costs and the

social importance, the durability demands for

large infrastructures becomes more and more

important.

A research project of the European Community

with the name DuraCrete has developed the

existing reliability and performance based

structural design method by introducing the

modelling of degradation and environmental

actions.

Performing probabilistic calculations show,

however, that the outcome is largely influenced

by the accuracy of the input parameters. I will

certainly not refuse the DuraCrete approach

because I think it is a good way to get more

understanding of degradation processes. The

DuraCrete approach, however, is not ready yet to

be used in our daily routine.

The present design approach with respect to

durability of concrete structures is based on a

reasonable understanding of the main

degradation processes for concrete,

reinforcement and prestressed steel. The design,

however, is not explicitly formulated as a service

life. It is based on deem-to-satisfy rules and the

assumption that if these rules are met, the

structure will achieve an acceptable long but

unspecified life.

This paper is about the Dutch experience with

concrete in the marine environment in the past

hundred years and what we have learned of the

behaviour of concrete in this environment.

Major data concerning thedevelopment of cement

1824 Is the year in which Joseph Aspdin

gained the patent on the development of

Portland cement; a very important moment in the

concrete industry.

But it was Isaac Charles Johnson, supervisor of

John Bazley, White & Sons in Swanscombe, who

improved the process of making clinker by using

unusually strong heat until the raw material was

nearly vitrified.

In 1853 a German blastfurnace operator

started water granulation of the molten slag. The

granules could easily be transported and

deposited which was an advantage over the air

cooling applied up till then. It was Emil Lange

who, in 1862, discovered the latent hydraulic

properties of the water granulated blastfurnace

slag. Initially the slag was activated by lime. Later

on Portland cement was used as an activator.

In 1888 the first blastfurnace cement works

was opened in Germany. Already from the

beginning blastfurnace slag cement was used for

concrete exposed to harsh conditions.

MARINE CONCRETE EXPERIENCE IN THE NETHERLANDS

-WHAT HAS BEEN LEARNED?

Peter de Vries, FICT

ENCI B.V. HEIDELBERGCEMENTGROUP, NETHERLANDS

38

In 1917 the Minister of Public Affairs in

Pruisen (Germany) declared, based on extensive

research by the Material Testing Institute in Berlin,

that blastfurnace cement had an equivalent

performance in concrete compared to ordinary

Portland cement.

This is a major statement for concrete in the

marine environment.

In 1912 the first Dutch Standard for reinforced

concrete was published (GBV 1912). Any

description on concrete technology is very poor.

Cement should be an industrially produced

cement but without any additions of slag. The

cement producer must have a reliable reputation.

The source of sand and gravel should be the river.

The code gives a standardized prescribed

concrete. To get a certain guarantee for a good

quality of concrete the amount of cement is

based on kilograms. The amount of water

depends on the preferred workability for mixing

and placing the concrete.

EXAMPLES OF CONCRETE STRUCTURES IN THE MARINE ENVIRONMENT

Concrete to protect dunes anddams

According to the GBV 1912, a lot a concrete

has been used for the protection of dunes, dams

and dykes by a combination of concrete slabs and

beams.

Although the addition of slag was prohibited,

it was well know in those days that the

combination of Portland cement and a pozzolanic

material such as trass gives the concrete good

resistance against the deterioration of seawater.

Trass is a volcanic rock with its origin in the Eifel

mountains in Germany.

Probably due to the poor way of placing the

concrete, most of this type of protection has

disappeared. It turned out not to be durable

enough and the concrete, no longer protecting

the dunes and dykes, has been replaced by basalt

rock.

Locks near IJmuidenOne of first major projects in marine

conditions is the construction of the locks in

IJmuiden. In 1876, the Kleine Sluis, or small lock,

was opened at IJmuiden concurrently with the

Noordzeekanaal, the connection between

Amsterdam and the North Sea. It soon became

apparent that its 120 by 18 metres was too small

and in 1896 the Groote Sluis or Middensluis (225

by 25 m) was brought into use. The rapid

increase in both the number and the size of

vessels led to the construction of a third lock. The

largest ocean liners had to be able to reach the

Dutch capital with ease. The work started in 1921

and was completed in 1930. At that time the

Noordersluis (400 m by 50 m and 15 m deep)

was consequently regarded as a monument of

national strength. For a full fifty years the lock

was the largest in the world.

1824 – Joseph Aspdin, chemical compositionfor Portland cement

1844 – Johnson, optimising burning clinkerprocess

1888 – Germany, opening of first blastfurnacecement works

1917 – Germany: blastfurnace cement has anequal performance to Portland cement

Table 1: Major Dates

Figure 1: Concrete to protect dunes and dams

Figure 2: Noordersluisunder construction

39

The two smaller locks had been constructed

before we had any Standard on reinforced

concrete and no specification on concrete had

been available. It is most likely that the cement

used for this concrete was only ordinary Portland

cement. After a service life of more than ninety

years it was necessary to demolish the

construction and to rebuild the two small locks

completely.

Before the year 1994 we thought that the

problem of alkali silica reaction was only a

problem in foreign countries and the diagnosis

was that those locks had only suffered from

sulfate attack. But ASR was also recognized in the

construction.

At the time the Noordersluis was built the

second version of the Dutch Standard on

reinforced concrete was available (GBV 1918).

And also in this Standard the use of cement with

blastfurnace slag was not permitted.

But, for the construction of the big Lock the

engineers decided to deviate from this Standard.

A normal mix design at that time was a 1:2:3

volume by volume for cement, sand and gravel.

The experts, however, had the opinion that a

composition like this was too permeable for such

an important structure. They also realised that

increasing the cement content was not

favourable because of thermal shrinkage in the

massive construction. The engineers decided to

use blastfurncace slag cement for the massive

walls of the biggest ship lock at that time in

world.

This decision was also based on the

development in Germany and an extensive testing

programme executed by Dyckerhoff.

Many trial mixes were made, very well

documented, and over 10,000 cubes were

tested; tests on strength, water absorption, heat

development and durability in seawater.

Several mixes were developed and, depending

the part of the construction, a choice was made

between Portland cement in combination with

trass as a pozzolanic binder and for blastfurnace

slag cement.

The slag content of the blastfurnace slag

cement was approximately 45- 50 %.

The cement content varied between 380 and

450 kg /m3.

Typically, the amount of mixing water is not

well documented. The role of the water/cement

ratio seemed to be unknown.

The workability of the mixture, or in other

words the way that the concrete was transported

placed and compacted, determined the water

content.

During several years now the big lock goes

through a thorough maintenance project.

Particularly concerning the lock heads,

concrete elements suffering from ASR have been

removed.

The service buildings and the gate chambers

are renovated. But the lock chamber walls are in

perfect shape after 75 years of service life.

Even a close look at the concrete tells that

there are no signs of corrosion or chemical attack

going on. We expect this structure to perform

well over the next coming decades.

Locks and sluices in Afsluitdijk Between 1927 and 1932 The State

Department of Roads and Waterways,

Rijkswaterstaat, constructed the thirty kilometre

long Afsluitdijk in the north area of the

Netherlands between Noord Holland and

Friesland. By building this dyke, protection against

flooding of a large area in the centre of Holland

has been guaranteed

Constituents Typical Mix Designs

Lock head Chamber walls and floors

Litres Ratio (v/v) Litres Ratio (v/v)

Portland Cement (CEM I) 225 1

Trass (pozzolanic) 56 1/4

Blastfurnace Cement (CEM III) -- -- 240 1 1/8

Fine sand 193 0,85 193 0,9

Coarse sand 387 1,7 387 1,8

Gravel 700 3,1 700 3,3

Water ?? ?? ?? ??

Table 2: Typical mix designs

40

The Afsluitdijk contains a system of concrete

sluices that allows the Ijsselmeer to discharge

water into the sea twice a day at low water. To

spread the discharge stream over a sufficient

width, two sluice complexes were built into the

dyke. They have been described as the lungs of

the IJsselmeer: the Stevinsluizen at Den Oever

and the Lorentzsluizen at Kornwerderzand.

Rising more than seven metres above the road

deck, the twelve towers per block of five sluices

dictate to a large degree the silhouette of the

complexes.

For the free passage of fishing boats and cargo

ships several locks were build on both sides near

Den Oever and Kornwerderzand.

From a certain distance the whole construction

and concrete looks all right.

Looking at it closely, it is evident that the

concrete structure suffers from sulfate attack and

alkali silica reaction. The State Department

decided in 1993 to implement an extensive

maintenance programme during the next five

years. Total costs around 20 million Euro.

At some spots the concrete had to be removed

for over 400 mm.

The constructive safety of the total structure is

not in danger. And the aim of the repair method

is to decrease the possibility of further damage.

After completion of the renovation, the locks

and sluices remain subject to routine inspection

and yearly maintenance.

HaukesschutsluisIn this same period many more locks were

built. A good example is the Haukesschutsluis.

As mentioned before, until only fifteen years

ago, alkali-silica-reaction was not known to be

present in our constructions. We thought that

sulfate attack was the major cause of

deterioration of concrete structures. Petrographic

examination on cores taken from several locks

showed that alkali silica gel was present most of

the time. Drilling of the cores was difficult

because of delamination of the concrete.

It is surprising to see that the damage to the

concrete above water level is more severe than

below. The explanation for this is that the

damage might be a combination of ASR and

frost attack. Due to the high water/cement ratio

and/or bad compaction, the concrete of many

locks is not frost-resistant.

As a result of the survey, recommendations

were made for maintenance and repair.

It was found that the constructive safety of the

Haukesschutsluis was no longer guaranteed.

The many delaminations and regular spalling

of concrete forms a danger for passing ships.

Also, the combination of low water in the lock

chamber and a high level of groundwater is a risk

for the stability of the lock chamber walls.

It has been decided not to repair this lock but

to build a new one.

Figure 3: Haukesschutsluis

41

In 1930 a successive version of the Standard

on reinforced concrete (GBV 1930) was

published.

Not surprisingly that blastfurnace slag cement

was permitted now. But only when customer and

contractor have agreed upon it.

That means that the acceptance of

blastfurnace cement was not unconditional.

For the Haukesschutsluis, and a few other

locks and sluices this Standard is too late. The

cement type normally used was Portland cement

from Germany or a combination of Portland

cement and trass, a pozzolanic rock.

The production of blastfurnace slag cement in

the Netherlands did not start until 1931.

Concrete blocks to protect jettiesA good example of a very simple manner of

using concrete for protection is the use of big

concrete blocks for the protection of the jetties of

the harbour in IJmuiden and also other locations.

Those blocks form an open structure to break

the energy of the waves during stormy weather.

The choice of an open structure was made

more than seventy years ago.

The massive blocks had to be produced in a

short period of time. In the early days, to speed

up production, an ordinary Portland cement was

used. The contractor was able to use the

formwork daily but not realizing that doing so he

introduced several technological problems that

reduced the durability dramatically.

The hydration will increase the temperature of

the concrete and in massive concrete

constructions in particular. When this temperature

is constant over the cross-section no problem will

occur. But changes in the temperature profile

across the section can cause one part of the

section to restrain the movement of another part

of the same section. For example, if the

formwork is removed while the concrete is still

hot, the rapid cooling and contraction of the

surface zone is restrained by the hot interior and

the surface cracks. These cracks can penetrate

significantly, but, because of the position of the

restraint, cannot be continuous through the

section. As the core cools, the cracks tend to

close up. Because of the higher temperature the

core continues to contract more than the surface

zones and its contraction becomes restrained by

the surface zone. This results in compressive

Figure 4: Internal restraint causes thermal cracks

42

stresses in the surface zones and tensile stresses

in the core. (see Figure 4)

The evidence that internal cracks occur as a

result of tensile stresses in the core can been seen

in practice. The small cracks will be saturated

continuously with water that will expand during

times of frost. Beside that, the massive blocks are

exposed to the mechanical impact of the waves

year after year.

What happened is that the originally cubic

blocks end up as nearly rounded blocks initiated

by the internal cracks. At the same time we see a

deposit of ettringite that is not surprising in this

marine environment.

These days the blocks are produced

conforming to a precise prescribed standard:

cement type: CEM III/B 42,5 N LH HS,

environmental Class: XA3,

aggregate: combination of gravel, sand

and magnetite.

To reduce the temperature gradient across the

section, the temperature difference between the

core and the surface shall not exceed the 25ºC.

The AtlantikwallA completely different type of coastal defence

appeared in the dunes more than sixty years ago.

And the enemy was not exactly the seawater.

Since the second world war the Germans left us a

few souvenirs. Not only in Holland but

throughout Europe; The Altlantikwall. The

Atlantikwall consisted of a number of strong-

points and these consisted of bunkers that were

present in all kind of sizes and different functions.

For example: gun emplacements, hospitals,

ammunition storage, housing, radar bunkers, etc.

The major goal was to protect men and material

from enemy attacks.

The thickness of the walls varied from 300 mm

for small shelters to 7 metres for those which had

to resist an attack from submarine missiles. To

speed up the construction of the bunkers,

Germans standardized those bunkers: the amount

of concrete, amount of steel, ventilation system,

electrical system, etc.

Whilst transport was available, German

cement of good quality was used in the

construction of the Atlantic Wall, but as the war

progressed supplies were increasingly drawn from

occupied countries. That happened in Holland as

well. From old reports we can read that the

Dutch Cement Industry was also forced to deliver

cement to the Germans. The cement plant in

IJmuiden is only within a stone’s throw away from

the bunkers near Wijk aan Zee. Therefore these

bunkers have been constructed using

blastfurnace slag cement.

A brief inspection, just a few weeks ago,

revealed that the concrete looks safe and sound

and that these bunkers will stay there for decades

and decades. In the meantime the Dutch

Government has declared that these souvenirs are

now part of our national inheritance.

At a few places you can find some corrosion

of the reinforcement. But this corrosion is only

due to a total lack of concrete cover as a result of

inadequate execution.

The DELTA-ProjectIn February 1953 the North Sea struck

mercilessly. Large areas of the islands in the south

west of the Netherlands were swallowed. Around

eight percent of the total territory of the

Netherlands was under water. More than 1800

people drowned. Around 1000 km of dykes

turned out to be too low and had to be raised.

Figure 5: Protection of jetty by concreteblocks

Figure 6: Bunker as a part of theAtlantikwall

43

The government decided to close the tidal in-

and outlets by heavy dams. To do so the coastline

was cut down by 700 km. The Delta project was

born.

With the start of the construction of the

Haringvliet sluice complex in 1958 the south west

of the Netherlands became the biggest civil

engineering site we had ever seen. And concrete

was a major building material.

The requirements for the concrete were based

on the expert opinion of that time.

For the large infrastructures the requirements

with respect to durability were in general more

stringent than the codes. The concrete cover was

raised to 70 mm, the water/cement ratio was

restricted to 0,45 and blastfurnace slag cement

was used as a binder.

The information about the service life to

achieve was, to a large extent, empirical. No

method had been specified to prove this service

life. Since the concrete codes are only based on

deem–to–satisfy rules for durability.

For the Eastern Scheldt Barrier, designed and

build in the early eighties, the durability

requirements were for the first time expressed in

terms of time. A service life of 200 years had

been required. For the concrete cover this was

not feasible. A mean service life of about 85 year

has therefore been accepted. Already during the

design provisions have been made for

maintenance in the future.

The storm surge barrier across the Eastern

Scheldt is, with a length of 2800 m, the most

impressive part of the Delta works.

In order to affect the natural tidal range as

little as possible the barrier contains 62 openings

that can be closed by steel sliding doors when

there is an increased risk of flooding. During

normal weather conditions the sliding doors are

fixed in a raised position. Only during periods of

severe storm the barrier will close by lowering the

steel sliding doors. The complete barrier

comprises 65 monolithic piers. The concrete piers

are considered to be the backbone of the storm

surge barrier transferring the forces exerted by a

storm to the foundations.

Each pier was cast in several phases. The

concrete composition of each phase contained

350 kg per cubic metre of CEM III/B and the

target water/cement ratio was 0,45. The concrete

was actively cooled with cooling tubes. From the

construction records we get the information that

cooling started 6 hours after casting had started

and continued for almost the next four days. The

maximum registered temperature was 36 degrees

Celsius. The concrete cover to the reinforcement

should be from 70 up to 100 mm.

CONCRETE IN THE MARINE ENVIRONMENT

After discussing several concrete structures in a

marine environment it is time to gather our

experience.

Concrete in a marine environment is exposed

to several parameters that will influence the

service life of the structure. Sulfates, alkalis and

chlorides all have their own destructive quality.

Concrete structures in a marine environment are

usually massive and that means that we have to

be aware of early thermal cracking. At this

moment concrete technology has a simple

Figure 7: The flood of February 1953

Figure 7: Eastern Scheldt storm surgebarrier

44

solution for these potential problems:

blastfurnace slag cement as binder. (see Table 3)

Dutch civil engineers use CEM III/B when the

concrete construction is exposed to chlorides and

sulfates. No other cement type will be accepted.

Only from recent experience are we aware that

also in the Netherlands ASR might be a problem.

Not only some locks and sluices suffered from

ASR, several bridges were suspect as well. That

means that technical instructions to prevent ASR

had to be developed.

In 1994 the first CUR Recommendation

appeared and since then this document has

evaluated a few times. The latest version

describes exhaustively the testing of the

aggregate itself.

We must realize that this is a complex

procedure.

More easy are the rules for the concrete

composition depending on the environment of

the construction, the type of cement in particular;

use CEM III/B.

The technical motivation about the prevention

of ASR has been explained by Prof. dr. Jan Beijen

in his publication “Blast Furnace Slag Cement for

Durable Marine Structures [1] : Concrete in a wet

environment and the possibility of de-icing salts,

seawater or in environmental class XA shall be

made with a cement type II – Portland fly-ash

cement or with blast furnace slag cement CEM

III/B or CEM III/C.

Without giving an order of importance, the

following factors contribute to the favourable

behaviour of blast furnace slag cement in

concrete:

• in general the alkalinity of the pore water is

less

• there is not very much free lime available:

free lime is regarded by some experts as

essential for alkali-silica expansion

• the interfacial zone between aggregate and

matrix is very small and none or only a little

amount of free lime is present

• the mobility of the ions is much reduced.

Therefore the building-up rate of stresses is

decreased. Brodersen in 1982 already

showed the relation between the slag

content and the diffusion coefficient for

sodium ions. (see Figure 9).

CALCULATION OF SERVICE LIFE TIME

In the specifications for new concrete

structures it has become more and more

accepted that the designer should demonstrate

that a concrete structure will have reliable

performance during a defined service life.

To guarantee a target service life of let’s say

one hundred years we have to calculate on an

average service lifetime of 400 – 600 years.

The methodology for performance-based

service life design of concrete structures has been

developed in a European BRITE EuRam research

Deterioration of concrete Protection of concrete Solution

sulfate attack cement type HS:

- low C3A; CEM III/B

- > 65% slag;

low permeability

alkali silica reaction cement type LA CEM III/B

low permeability

corrosion of reinforcement low permeability CEM III/B

cracks caused by early cement type LH CEM III/B

thermal shrinkage

Table 3: Deterioration of concrete and the rational solution

Figure 9: Relationship between diffusioncoefficient and slag content

45

project called “Probabilistic Performance based

Durability Design of Concrete Structures, in short

“DuraCrete”.

The results have been formulated in a set of

service life design equations. These equations are

based on mathematical models of degradation

and environmental influences on materials,

combined with probabilistic calculations of the

performance of the structure.

The most advanced model, however, is the

model describing chloride-induced corrosion,

more than models for other types of degradation.

A CUR research committee, Durability of

Marine Concrete Structures (DuMaCon) is

working on an extensive research program to

collect data and to validate the service life model

developed in the DuraCrete program.

The Haringvliet Sluice Complex is chosen as

one of the structures in this research program. [2]

For example, the piers of the Haringvliet sluice

complex have been investigated thoroughly in the

course of this examination. The main objective in

this investigation was to examine the influence of

the height on the exposure of the concrete that is

one of the parameters in the DuraCrete

approach. Therefore, three locations have been

chosen on the same pier at different heights.

On site, each test area of about 1 m2 of

concrete surface was investigated in depth to

collect the following data:

• Visual examination and description of test

area

• Determination of rebar position and depth

• Determination of carbonation depth

• Measurement of concrete resistivity by

Wenner

• Measurement of rebar potential

• Measurement of corrosion current.

Also from each test area various core samples

have been taken for further investigation in the

laboratory to collect data on:

- Chloride profiles

- Microscopy

- Tensile splitting strength

- Rapid chloride migration (RCM)

- Compressive strength

- Electrical resistivity (TEM).

Chloride profiles have been determined up to

a depth of 60 mm. Then, using those chloride

profiles, diffusion coefficients can be determined,

assuming that Fick’s second law applies and that

the surface chloride content and the diffusion

coefficient are constant.

When analysing the data it is found that the

chloride ingress in the tidal zone is much greater

than in the other test areas. Chloride content

levels are expected to be the highest in this test

area. This test area has also been chosen to

perform probabilistic calculations according to the

DuraCrete approach.

The starting point for calculations is the

assumption that the service life time has finished

when the critical chloride content to start

corrosion has reached the reinforcement.

The probability of initiation of corrosion of 3%

(reliability index b = 1,8) is reached on a time

scale of 100 to 200 years depending on which

model of DuraCrete is used for the calculations.

As far as can be judged now, after 40 years of

exposure, these model calculation results are

supported by visual and electrochemical

observations.

Also the Eastern Scheldt Surge Barrier has

been observed and tested.[3] And from that

experience and calculations we can see that,

Figure 10: Haringvliet Sluice Complex

Figure 11: Example of measured chlorideprofiles

46

using the same DuraCrete-model, the time-to-

initiation of corrosion is very short and differs

from only several months up to 8 years. This

seems not to be realistic because the exposure

time is only 20 years now and the investigation

shows that the concrete structure is in a very

good condition. That means that the model does

not fit with reality.

Until the accuracy of the parameters as used in

the DuraCrete models is better understood, the

large differences will remain.

And that means that we do not have to worry

about our scientists, they have plenty of work to

do to optimise their models.

CONCLUSIONSIn the meantime I think that we have

demonstrated that concrete in a marine

environment needs the law of good common

concrete practice:

• make the right choice of cement type, i.e.

CEM III/B

• take care of sufficient cover

• take care of sufficient curing.

As simple as that; the results we have obtained

in the past are the guarantee for the future.

Concrete for a new world has been developed

in the past.

REFERENCES

1. BIJEN,J. Blast furnace Slag Cement forDurable Marine Structures,VNC/BetonPrisma, 1998 pp. 62.

2. DE ROOIJ, M.R. and POLDER,R.B.Investigation of the influence of marineexposure on concrete piers of theHaringvliet sluice complex, TNO Report2003-CI-R0122-2, 2004, pp.22.

3. DE ROOIJ, M.R. and POLDER,R.B.Investigation of the concrete structure ofthe Eastern Scheldt Barrier after 20 years ofexposure to marine environment, TNOReport 2002-CI-R2118-3, 2004, pp.48.

47

Peter Kelly is a chartered

structural engineer with over

30 years of experience in the

design of structures in all

materials. He is a member of

the Council and of various

Committees’ of the Institution of Structural

Engineers. A member of the Techical Committee

of the International Precast Hollowcore

Asssociation and he has been the Technical

Director for Bison Concrete Products for the last 8

years.

His principal material is concrete, where he has

been responsible for the design of offices

(including the BRE Eco building), hospitals, retail

buildings and associated car parking (Manchester

Trafford Centre) together with most of the recent

major stadia (Manchester Utd, Hull, Leicester City

and Wembley).

Nick Webb has been

Operations Engineer for Bison

Concrete Products at their

Lichfield factory for the last 10

years and has been responsible

for the technical and quality

management for all production, including major

stadia; for example, Millennium Stadium Cardiff,

Manchester Utd, Leicester City and Wembley. He

has also been responsible for the development

and implementation of self-compacting concrete

in the works.

ABSTRACTThis paper reviews the role of precast concrete

in modern sports stadia showing the compelling

reasons for its use. It concentrates on the

development that Bison Precast Concrete has

undertaken in recent years in design,

manufacture and erection of the components to

suit the needs of modern construction practise.

KEYWORDSStadia, Precast concrete, Quality, Design,

Terrace units, Vomitory units, Stairs, Off-site

production, Installation.

INTRODUCTIONIn order to meet the stringent programme

requirements in today’s modern stadia, speed of

construction is a major and critical requirement.

Precast concrete components contribute a major

part in achieving this objective. These

components include floors, terrace units,

vomitories, stairs and the supporting frames. This

paper covers the following important aspects of

the use of precast concrete in stadia:

• The benefits of precast concrete,

• The structural aspects of stadia design,

• The manufacture of precast components,

• The site application of precast.

THE COMPELLING REASONS FOR PRECAST CONCRETE

An analysis of the criteria for the use of

precast concrete highlights the compelling

reasons for the use of precast concrete in stadia.

These benefits are:

a) Off-site production

On-site activities are complicated by a great

many factors such as:

• bad weather

• overlapping trades and the logistical problem

of large quantities of materials and labour

within a relatively confined space

• it is much easier to cast a concrete

component on the factory floor than several

metres up in the air.

b) Control of quality

• All contractors and designers acknowledge

that the quality of components produced

under factory conditions is far superior to

those produced on site

• Bison were one of the first to introduce a

quality system into the manufacture of

precast products. The system is assessed by

BSI each year, from design through to

manufacture, at each of the company’s

locations.

THE ROLE OF PRECAST CONCRETE IN STADIA

Peter Kelly BSc, CEng, MIStructE and Nick Webb

Bison Concrete Products Ltd

48

c) Speed of erection

• The principal advantage of the use of precast

concrete is the speed of erection.

Programme is always a major consideration

for any project and this is even more so

where stadia clients require a rapid return on

investment

• The key feature of precasting is that the

superstructure work is progressing off-site

while the foundations are being constructed.

d) The provision of an immediate working

platform.

• The erection of a precast structure allows the

use of that floor or terrace area immediately.

Floors can be stood on and worked from

• The provision of precast stairs allows access

to the floors and terrace areas

• Following trades have easy access and a

reduction in the construction programme is

possible.

e) Minimum propping

• Most precast components are designed with

minimum or no propping and comparison

with in situ construction is obvious. In situ

construction, with large numbers of props

for formwork, is time consuming in erection

and stripping and is, at worst, impractical

due to high floor-to- ceiling heights.

f) Minimum wet trades

• Since the objective of precasting is to cast

the concrete off-site, it follows that there is

major reduction or the virtual elimination in

the volume of concrete to batched at the site

or delivered by other means. Precast walls as

a replacement for conventional masonry

avoid the need for large quantities of mortar,

bricklaying labour, plasterwork and again the

reduction is time.

THE STRUCTURAL ASPECTS OF STADIA DESIGN

The use of precast components in stadia

provides many structural design advantages

which are summarised below.

FloorsThe use of hollow core slabs with or without

structural topping provides significant advantages

to the contractor. They are extremely structurally

efficient and may be combined with the

steelwork to enable the steel to be designed

compositely. This can lead to significant

reductions in steel tonnages and site time due to

the reduction in the number of steel members.

For hollow core slabs the concrete strength is 55

N/mm2 together with 5 mm diameter prestressing

wire having a tensile strength of 1770 N/mm2.

Design allows for the final forces and for the

handling of the units during the early stages.

Hollow core slabs of 200 mm depth can provide

spans of 7 – 8 m for grandstand loadings.

Terrace UnitsThe design of terrace units requires careful

attention to ensure the maximum benefit for the

project. The main considerations are the seating

details, geometry of the unit and practical

reinforcement detailing.

The design of terrace units is based on a simple

reinforced concrete design with a minimum beam

section of 150 mm. The beam section is increased

Figure 1: General details of terrace unit

49

in width only to accommodate reinforcement.

The terrace units are designed to optimise the

concrete section/reinforcement relationship

together with maintaining the rigidity of the unit

for dynamic purposes. The general details are

given in Figure 1.

The detail at the seating stool is dictated by

practical reinforcement detailing. A minimum

seating of 165 mm is required but for large spans

this may need to be increased to cater for larger

anchorage bars. Where the depth of the unit is

restricted by the riser height then a downstand

below the tread is provided. As the rise of each

terrace alters as the ‘C’ values alter, the terrace

units were grouped together in a rise of 10 – 15

mm for practical purposes.

Vomitory UnitsVomitory units are the second unique type of

unit to be found in stadia and provide the access

and egress to the terrace areas from the

concourse and circulation areas. The vomitory

units consist of walls supporting the terrace units

and stairs. See figure 6. These are seated onto

the floors and steelwork at the concourse level.

Cast-in sockets together with stainless steel

fittings provide both for location of the walls and

support for the terrace units.

StairsThe total of number of stairs supplied may

account for 10% of the precast concrete for a

scheme. See figure 2. Stairs can be designed

utilising Bison’s standard mould system and the

appropriate geometry. The design allows for the

use of stair flights with angles supported by

intermediate landings. Finishes are required on

the landings to take up tolerances of

manufacture and site construction. The provision

of stairs allows immediate access to the various

levels making the need for scaffold access

redundant.

Support BeamsAlthough steel is generally used for beam

supports in stadia, concrete raker and support

beams can used. Connection of transverse beams

can be provided using the Bison BSF connector.

This is a simple yet extremely strong connection.

See figure 3 below.

THE MANUFACTURE OF PRECAST COMPONENTS

Terrace and associated unitsThe manufacture of the terrace and associated

units is undertaken utilising steel moulds. See

figure 4. The manufacture of these units utilises

Figure 2: General details of terrace unit

Figure 3: The BSF connectorFigure 4: Mould prior to placingconcrete

50

self compacting concrete and, together with

magnetic formers, allows for a high quality finish

to be obtained. The terrace units are

manufactured using Bison’s standard terrace

mould used on many of the stadia throughout

the country. The terrace units are cast with the

tread part vertical and the beam part horizontal.

This enables all faces of the terrace to be cast

against steel mould faces, except for the rear of

the beam which is a float finish. The units

provided have a fall to the front of 1:100 to

facilitate the removal of water. Handling of the

units is undertaken using standard Deha lifters for

handling in the factory and on the site.

The vomitory walls were cast in vertical steel

battery moulds. Components to allow fixing of

the walls to form a completed unit were cast-in

where required.

Stair manufacture was undertaken using

Bison’s standard stair moulds. The steps are

formed using adjustable formers with preset

treads and a set cut-back rake. The moulds allow

the manufacture of the stairs on their side

ensuring that, apart from one string and the end

of the unit, the cast faces are against the steel of

the mould. A view of a typical stair mould is

illustrated below. Handling of the units was

undertaken using standard Deha lifters for

handling in the factory and the site.

Hollow core flooring is manufactured by slip

forming, using the long-line method. The units

were manufactured with notched and prepared

ends to allow for composite action between the

slabs and the steelwork. The concrete is a dry mix

with a high level of vibration to allow the

formation of the slab.

Manufacture of all the components for the

project was subject to a quality assurance

scheme. Bison Concrete Products Limited were

one of the first to obtain a registration with BSI

for the manufacture of precast concrete. The

system covers the design and manufacture of all

precast components from estimate to delivery.

The system is regularly inspected internally and

externally to ensure compliance with the objects

of the scheme.

The site application of precastIt must be recognised that the expertise of the

installer in the erection of precast concrete is

paramount. The installation of any precast

concrete component requires that the installers

understand the procedures for a successful

installation. The installer must consider the

following:

• The management of the health and safety of

the operation

• The adequate training of the personnel

involved

• Design considerations

• The responsibilities of the general contractor

and the installation contractor

• The importance of the foreman’s role

Figure 5: Installation of terrace units

51

• On site storage of components

• The safe use of cranes etc

• Access to the site and to the working area

• Installation of the components and other site

work

• Protection of the workforce and third parties.

The successful installation of any project relies

entirely upon a well thought out plan of action

and the implementation of safe and correct

procedures to achieve that. The typical installation

of terrace units is shown in Figure 5.

The installation of the terrace units shows the

provision of neoprene pads at the bearing

position with further shims at the toe of the unit.

The initial unit installed sets the standard for the

subsequent units and therefore it is important

that the unit is correctly installed with the correct

level to avoid any back fall of the terrace units.

The units are subsequently sealed to prevent

water ingress.

Vomitory units are installed in a strict order -

walls and head beam, terrace units and finally the

stair unit. The walls are erected with lateral props.

The head wall is then fixed using a cast in bolt

connection. Stainless steel location angles are

provided at the floor level. The terrace units are

then fixed onto stainless steel angles on the sides

of the walls. The stairs are finally fixed seated on

the floor and onto the terrace unit along the

front of the vomitory unit. See Figure 6.

SUMMARYIn summary, the case for using precast

concrete is overwhelming. A well defined design

brief and carefully thought out details are

essential on a fastrack programme. Manufacture

to the right standard, on time requires planning,

manufacturing expertise and good quality

controls. Installation requires to be controlled by

experienced personnel working to a well thought

out erection plan.

Any project relies on the people involved and

therefore the choice of a contractor and his

design team is paramount.

Finally remember: keep it simple, and the

benefits of precast will contribute to a successful

and economic stadium.

Figure 6: Vomitory unit Installation

52

53

Lawrence R Roberts, over the

last 37 years, has been in

various research and technical

service positions with W. R.

Grace and Co., and is currently

Key Accounts Technical

Manager, with global responsibility. He has been

involved in admixture and cement additive

development and investigation, problem

resolution, and in some cases advised in cement

alteration for improved admixture response. He is

past chairman of ASTM subcommittees on

Admixtures and Cement Research, and

participates in many technical organizations

centred on cement and concrete. He holds

Bachelors and Masters degrees in Chemistry.

ABSTRACTThis paper discusses recent advances in our

understanding the interaction of admixtures with

cements. It focuses largely on the use of high

resolution isothermal calorimetry to investigate

the impact of admixtures on cement sulphate

consumption, and how the use of different

admixtures can affect the sulphate level needed

for proper admixture response. Several examples

are given and the employment of the calorimetric

technique explained.

KEYWORDSCalorimetry, Portland cement, Cement, Sulfate,

Sulphate, Isothermal, Hydration, Retardation,

Slump loss, Dispersion, Setting time, Silicate,

Aluminate, C3S, C3A, C4AF.

INTRODUCTIONIn recent years the performance possibilities of

concrete have been greatly widened by the

application of chemical admixtures. Degrees of

placeability, set control, strength development

and durability have been achieved which would

have been impossible without the employment of

admixtures. Nevertheless, there are continually

reported instances in which concrete has not

performed as desired, which can many time be

traced to undesirable interaction between the

admixture chemicals and the cementitious system

employed. No admixture can be expected to work

regardless of the cement composition, just as no

cement can be expected to work with all

admixtures, under all conditions. The key is to

understand the factors that influence the

interaction of admixtures with cements, and take

steps to avoid problems.

In 1995 the present author gave an overview

paper to the Institute of Concrete Technology,

summarizing a number of the principles and

procedures involved in understanding cement

admixture interactions. It is the intent of this

paper to present some of the new techniques

used in resolving such issues, and to discuss a

few recent examples, in the hope that the

information will be useful in avoiding some of

these problems, or at least in resolving them

more quickly. It is not the intent to be exhaustive

by any means, as the subject in its entirety is too

complex for the available space.

Chief among the techniques found useful is

high resolution isothermal calorimetry, which has

been made possible through recent improvements

in equipment sensitivity and convenience. This

allows tracking of the cement sulphate phase

consumption to a degree not previously possible,

without the effort of complex extraction and

chemical analysis, and allows us to demonstrate

that sulphate consumption can be much more

rapid that thought previously, especially in certain

highly dispersed systems.

Due to the author's location in the United

States, the majority of the cements conformed to

the ASTM standards not EN, and are therefore

unmodified Portland cements.

BACKGROUNDThe reader is referred to the previously

mentioned paper[1] and to several others [3-5] for

detailed background to the issue. We will briefly

summarize some key points. Proper setting and

strength development in cements depends on

having the right amount of cement sulphate to

control the aluminate phase reactions in the

cement. Figure 1 summarizes the situation.

RECENT ADVANCES IN UNDERSTANDING OF CEMENT

ADMIXTURE INTERACTIONS

Lawrence R. Roberts, BSc, MSc

W. R. Grace & Co., USA

54

Calcium aluminate compounds are capable of

reacting very quickly with water and in the

absence of sulphate can cause such a significant

exotherm that a cement paste patty can be seen

to steam within a few minutes. Sulphate is added

to control this, and the calcium sulphoaluminate

reaction products deposit on the aluminate

surface and slow down reactions. The required

amount of cement sulphate is influenced by the

factors shown. If the aluminate is not adequately

controlled, then rapid loss of slump and poor or

even non-existent strength gain may ensue, due

to the aluminate hydration products occluding

the surface of the calcium silicates and restricting

their access to water.

Factors Controlling AluminateActivity

The more active the aluminate phases are,

considering C3A and C4AF together, the more

sulphate will need to be supplied. C3A being

more reactive than C4AF, higher C3A cements

generally will require more sulphate. We will see

later that dispersion can affect this relationship.

The finer the cement, the more aluminate surface

area is available, and more sulphate is needed.

If dispersing admixtures are used, more

effective surface area becomes available, and

greater levels of sulphate may be needed. Figure

2 illustrates this effect of dispersants.

Alkali modification of the aluminate phase

occurs when there is not enough sulphate in the

clinkering process to keep the alkali in the alkali

sulphate form. The alkali modified C3A changes

crystal habit from cubic to orthorhombic,

increasing significantly in reactivity, requiring

more sulphate, faster.

Finally, supplementary cementitious materials

such as sub-bituminous coal fly ash or higher

aluminate slags can increase the available

aluminates, requiring higher sulphate availability.

Factors Controlling SulphateAvailability

The sulphate availability is first affected by the

amount added. It should be understood that the

amount found on a certificate of analysis reflects

the total sulphate, both present in the clinker and

added in milling. The clinker sulphate may be

readily available, if in the alkali sulphate phase, or

if alkalis are low, combined into the clinker

minerals, in which case much of the sulphate will

not be available during the early reactions critical

to slump loss and setting.

The hydration state of the sulphate is critical.

The most common form added to cement mills is

natural rock gypsum, although a number of

waste gypsums are increasingly being used. In

hot mills, gypsum dehydrates to plaster, which

dissolves faster than gypsum and thus is preferred

if a rapidly hydrating aluminate must be

controlled. In the case to too much plaster

formation, false set may occur as plaster reacts

Figure 1: Cement sulphate balanceprinciples

Figure 2: Effect of dispersants on sulphate demand

55

with mix water to re-form gypsum crystals, which

stiffen the mix. Usually however, the cement

aluminates react quickly enough to consume the

sulphate, and no false set occurs. In the case

where false set is a concern, or sometimes for

cost reasons, natural anhydrite may be used to

supplement the gypsum. This goes into solution

much more slowly and does not support false set.

Due to its slow dissolution, it may not be able to

control rapidly hydrating aluminates, but can be

ideal for slowly hydrating aluminates. A

complicating factor is that admixtures tend to

sorb out on anhydrite surfaces, further slowing its

dissolution. This can induce aluminate control

problems.

Finally, alkali sulphates, which form during

clinkering, can be a rapid source of sulphate

providing good aluminate control. As kiln fuels

change the alkali sulphate content can vary,

leading to potential variation in aluminate control

and admixture response.[6,7]

Figure 3, below, summarizes the overall

sulphate balance issues, without dealing with the

impact of admixtures. We will use the examples

to discuss the effect of admixtures.

Isothermal ConductionCalorimetry

The isothermal conduction calorimeter had

been used in cement research for more than half

a century. Lerch's ground -breaking work[4],

published in 1946, demonstrated its utility and

showed that calorimetry can define properly

sulphated cements. Researchers have used a

variety of equipment ever since, but most units

have suffered from electric and mechanical

problems, with resultant lack of productivity,

sensitivity and reproducibility. Sensitivity was a

special problem with low aluminate content

(sulphate resisting) cements, as the lower

reactivity of these cements gave poorer signal to

noise ratios. Recently, however equipment has

become available [8] which increases the

convenience and improves the precision of the

results. Figure 4 illustrates both the general form

of the output of isothermal calorimetry and the

particular sensitivity and reproducibility of the

equipment. Heat flow is graphed on the y axis

against time on the x axis, giving a fingerprint of

the hydration behaviour.

In this equipment cement paste may be mixed

either inside or outside the cell. Our experience is

that the higher energy of outside mixing is

needed to replicate the agitation of concrete

mixing. In at least one case, field concrete

problems were reproduced by outside mixing,

where companion tests (in another laboratory)

did not demonstrate the problem when the water

plus admixture was simply injected into the cell

containing the cement. When the other

laboratory repeated the work by outside mixing,

the problem was reproduced.

After initial mixing, a rapid exotherm occurs

which comprises both initial heat of wetting and

direct aluminate phase reaction with water. This

is shown by the initial descending curve. Then a

dormant period ensues, due to coverage of the

reacting cement grains largely by the reaction

products of the sulphate with the aluminate

phases. After a while the reaction of the calcium

silicates (C3S) begins, which is responsible for true

set and strength development. The area under

this curve is roughly proportional to the early

strength, as it reflects the heat output from the

reaction, and is thus a measure of the total

reaction. At some point during the hydration,

the sulphate used to react with the aluminates is

depleted by that reaction, and a second reaction

begins. There is some disagreement where this is

all conversion of the original reaction product, the

Figure 3: Overall sulphate balance

Figure 4: High Resolution IsothermalCalorimetry showing subtle sulphatedepletion peak and excellentreproducibility

56

trisulphate form known as AFt or more commonly

ettringite, to the monosulphate form designated

AFm, of if it is direct reaction of the aluminates

with water. For convenience then we simply

designate this the "sulphate depletion reaction".

It is characteristically less distinct, the greater the

iron content of the cement. It is in these cements

that the new calorimetry technology allows us to

see the depletion peak, whereas in earlier work

that was frequently not visible.

When this peak shows up, as it does here in

Figure 4, well after the silicate peak maximum,

cements generally have few response issues to

admixtures. However, when cements have less

sulphate and it is depleted earlier, as shown in

Figure 5, we may see problems when admixtures

are used which increase the demand for sulphate

further. We must emphasise that this cement by

itself is perfectly balanced and meets

specifications, but may not respond to admixtures

as well as one with more sulphate.

EXAMPLES

Example 1: Excessive admixturedose resulting in sensitivity tominor cement changes

In 2002 a bridge deck placement resulted in

concrete which did not set. This occurred despite

temperatures approaching 35ºC. On investigation

it was found that the concrete producer had

been using a combination of admixtures, both

plasticisers. One, a so-called "mid-range water

reducer" (MRWR) in U. S. parlance, had little

impact on set. The other, a conventional "water

reducer" or plasticiser, was a moderately strong

retarder.

The producer was experienced in using them

in combination, with the mid range water reducer

at a fixed dose, the other at variable dose to

adjust for temperature. On the day in question

reported slump loss at the site cause the producer

to increase the plasticiser dose, expecting to

lengthen set. Instead he got rapid slump loss, but

the concrete put in place with difficulty failed to

set and required removal. The doses in question

were approximately 550 ml/100 kg of the MRWR,

and 250 ml/100 kg of the plasticiser. The standard

dose of the plasticiser was 125 ml/100 kg.

Numerous samples of cement were received

and investigated both by calorimetry and

chemical analysis. It was found that the cement

had been reduced in sulphate content by

approximately 0.5% compared to recent

shipments which had worked well. Yet of all the

samples encountered, only the sample from that

day failed to set. See Figure 6. Note that the

problem cement sample had a much higher initial

exotherm, indicating higher aluminate reaction,

than did the other samples from the same plant,

or the two alternate cements. It then failed to

show any silicate reaction over the test interval.

This behaviour is characteristic of this kind of

problem - when the sulphate is too low is seems

frequently to act as a switch, and the hydration is

entirely shut off, not mere delayed a few hours.

On further investigation in to the chemistry of

the various samples, it was found that the sample

which failed to set normally had a soluble alkali

content of 0.54% as Na2O, whereas similar

samples which hydrated normally with the high

admixture doses had soluble alkali of 0.62 to

0.70 percent. No other significant differences

could be found.

It would appear then that the high admixture

doses, in combination with a reduced sulphate

level, put this cement in the very edge of

performance problems, so that a very small

difference in the rapidly available alkali sulphate

was enough to make a critical difference. This

was confirmed by the addition of extra sulphate,

in the form of plaster, to the isothermal

calorimeter mixes. As seen in Figure 7, this

addition eliminated the problems in setting

Figure 5: Early sulphate depletion peaks

Figure 6: Lack of set and strengthdevelopment with one cement sampleand 550 ml/100 kg of the MRWR, and250 ml/100 kg of plasticiser.

57

Example 2: Acceleration problemswith alkali-modified C3A

Our second example covers a cement which

was found to have variable response to non

chloride accelerators. In the extreme case, the

accelerators would cause several hours

retardation. We investigated the problem using

both isothermal calorimetry and quantitative x-ray

diffraction. The results showed that variations in

the degree of alkali modification of the cement

were causing the extremes of variation, and while

extra sulphate helped, the real solution was

control of the alkali content in the aluminate

phase of the cement.

Figure 7 summarizes the problem. This is most

extreme cement sample, and it can be seen that

while the cement hydrates normally by itself at

23ºC, giving a C3S peak maximum at about 8

hours, addition of the non chloride accelerator

causes numerous early hydration peaks of

unknown composition, followed by a delayed C3S

peak with a maximum at about 18 hours.

Addition of various levels of sulphate as plaster

improved the situation, but even at 1.14%, while

there was greater reaction as shown by the

increased area under the curve, there was no

acceleration of the C3S peak maximum. Note in

all these cases the very

high early aluminate

hydration peak.

Since sulphate addition

did not completely restore

performance, the cement

samples were further

investigated by

quantitative x-ray

diffraction. Alkali-modified

orthorhombic C3A shows

distinctly under x-ray

diffraction and we were

able to pick out three

cements at low, medium

and high levels of orthorhombic C3A. The cement

in Figure 7 was the highest level. We then tested

the early cement exotherm in duplicate, with the

results shown in Figure 8. Note that the time

scale in this chart is greatly expanded, with the

maximum time being 6 hour. The initial

exotherm is greater the greater is the proportion

of orthorhombic C3A.

Problems of this type typically relate to

variation in the sulphate level of the fuel used to

burn the clinker. When the fuel becomes low in

sulphate, alkali is forced into the aluminate

phase. In this case discussion with the technical

staff of the cement company resulted in more

predictable performance.

Example 3: Setting problemswith very low C3A cementassociated with dispersion

Our final example covers another case of

extended set. A large placement of concrete

containing both a polycarboxylate superplasticiser

and a corrosion inhibitor failed to set. The

cement, an ASTM Type V (highly sulphate

resisting) had a nominal 3% C3A content, but

quantitative x-ray diffraction indicated it was near

zero. Thus essentially all the aluminate in the

Figure 7: Normal set and strength development restored at550 ml/100 kg of the MRWR, and 250 ml/100 kg of plasticiser,0.5% SO3 as plaster added to mix water in all samples.

Figure 8: Lack of accelerationperformance of a non-chloride acceleratorin conjunction with a plasticiser, withimprovement by sulphate addition.

Figure 9: Initial exotherms of threecements at different levels of alkali-modified (orthorhombic) C3A

58

cement was in the C4AF or ferrite form. The

sulphate content was 1.8%, a normal amount for

such a low aluminate clinker, but analysis for the

gypsum phases indicated only 0.7% was present

as gypsum, plaster, anhydrite or syngenite. Thus

more than half of the sulphate was locked in the

cement clinker phases, and unavailable in the

early stages of hydration.

Figure 10 summarises the hydration behaviour.

This is a different representation of the

calorimetry output, with the left showing the

hydration to half an hour, the right showing the

hydration to 20 hours. The cement alone

hydrates normally, but the combination of the

polycarboxylate superplasticizer and corrosion

inhibitor in the mix water give a much larger

initial exotherm. Subsequent silicate reaction is

completely suppressed and the curve follows the

baseline out to 20 hours. Interestingly, when

both admixtures are delayed by one minute, the

initial exotherm is significantly reduced, and

normal silicate hydration is achieved.

Figure 11 shows the impact of adding

sulphate. The curves indicated as cement only

contain only the cement, while the others contain

the mixture of admixtures, added in the mix

water, and various levels of added sulphate as

plaster. These are 0, 0.13%, 0.5%, 0.75%, and

1%. When significant amounts of extra sulphate

are added, normal setting behaviour is restored,

even though the early exotherm is not reduced.

0.13% does not help, and 0.5% helps only

marginally. This indicates that the character of the

reaction products must be modified by the

sulphate.

Close inspection of the plain cement shows

the sulphate depletion to occur at about 7 hours,

confirmed by expanding the chart for multiple

replicates of the plain cement. See Figure 12. Yet

inspecting the admixtured sample's early peak

shows a slight inflection on the 0% sulphate

curve starting at about _ hour, while the addition

of only 0.13% SO3 moves this out to about 0.35

hours, confirming it is the sulphate depletion

Figure 10. Initial and 20 hour calorimeter curves of problem system showing positiveimpact of one minute delay in addition

Figure 11: Initial and 20 hour calorimeter curves of problem system with addedsulphate at various levels, showing change in sulphate depletion time andrestoration of silicate hydration

59

peak. 0.5% SO3, which is beginning to achieve

silicate hydration, moves the depletion peak to

about 0.6 hours. Thus close inspection of the

curves easily shows the progressive increase in

time to depletion by addition of sulphate.

So what is causing this problem and why do

either delaying the addition or adding sulphate

solve the problem? The answer is complex and

still somewhat conjectural, so we will deal with it

as bullet points for clarity:

• The cement is low on sulphate, with

depletion occurring before the peak of the

silicate reaction

• The cement has lots of ultrafines (10% less

than 1 micrometre) which will be rich in

ferrite phase.

• Without admixtures these will be clumped

together, and have insufficient surface to

coat all the silicate phases.

• On initital hydration these will release iron

hydroxides which will glue the clumps

together more strongly.

• Thus hydration is normal.

• When the admixtures are present in the mix

water, the ferrite particles are strongly

dispersed and coat the silicates. When the

iron hydroxides are released, they further

coat the silicates. The corrosion inhibitor

strengthens the hydroxide barrier, preventing

water from getting to the silicate

• When the admixtures are delayed, the

clumps which form are strongly enough

glued together that they don't disperse as

well, and the coating of the silicates in not

enough to prevent hydration.

• When extra sulphate is added, some of the

iron is found as the iron sulphates which are

not stabilized by the corrosion inhibitor, and

this the barrier can be attacked by the water

and the silicates hydrate normally.

Work too extensive to report in detail showed

these effects to be dosage sensitive to both

admixtures, and that the critical product to be

delayed is the polycarboxylate superplasticiser. It

is important to note that this work showed that

the ferrite phase of a very low C3A cement was

capable of consuming the sulphate in about 15

minutes. Thus care must be taken with these

kinds of cements when strong dispersion is

achieved through the powerful newer

polycarboxylate admixtures.

CONCLUSIONSHigh resolution isothermal calorimetry is the a

very effective tool for understanding the

behaviour of cement in the presence of

admixtures. It is simple to run and requires no

expensive chemical analysis to get useful data.

Sulphate control of aluminate phase hydration

frequently is key to effective admixture

performance.

Excessive admixture dosage can exacerbate

cement-admixture problems and should be

avoided. If higher doses of plasticiser or

superplasticiser seem to be needed, review of mix

components for their natural water demand is in

order as likely something has changed.

Reaction in the first few minutes can strongly

influence the hydration behaviour.

High levels of dispersion can influence the rate

of C4AF consumption strongly.

ACKNOWLEDGEMENTS

The author would like to express his

appreciation to his colleague Paul Sandberg, PhD,

who developed much of the data shown here,

and to W. R. Grace & Co. for permission to

publish.

FURTHER READING

1. ROBERTS, L. R., Dealing with Cement -Admixture Interactions, Institute ofConcrete Technology Yearbook 1995-1996

2. DODSON, V. H. and HAYDEN, T. D., AnotherLook at the Portland Cement/ChemicalAdmixture Incompatibility Problem, Cement,Concrete, and Aggregates, CCAGDP, Vol.11, No. 1, p. 52-56

Figure 12: Sulphate depletion peaks ofmultiple tests on the plain cement

60

3. SANDBERG, P. and ROBERTS, L., Studies ofCement-Admixture Interactions Related toAluminate Hydration Control by IsothermalCalorimetry, ACI Special Publication SP-217,2003, p. 529-542.

4. LERCH, W., The influence of gypsum on thehydration and properties of portlandcement pastes, Proceedings,1946, Vol. 46,of the American Society for TestingMaterials

5. JIANG, S., KIM, B.G. and AITCIN, P.-C.,Importance of Adequate Soluble AlkaliContent to Ensure Cement/SuperplasticizerCompatibility. Cement and ConcreteResearch, 1999, Vol. 29, p. 71-78.

6. POLLITT, H. W. W. and BROWN, A.W., Thedistribution of alkalies in portland cementclinker”, 1968, Proceedings of the 5th Int.Symp. On the Chemistry of Cement, Tokyo.

7. ODLER, I. And WONNEMANN, R., Effect ofAlkalies on Portland Cement Hydration, I.Alkali Oxides Incorporated into theCrystalline Lattice of Clinker Minerals,Cement and Concrete Research,1983, Vol.13, p. 477-482

8. WADSÖ, L., et al., The isothermal heatconduction calorimeter: a versatileinstrument for studying processes inphysics, chemistry and biology, 2001, J. Chem. Educ. 78 p. 1080-1086

61

Andy Rogers joined the

concrete industry in 1984 and

has moved from Area Technical

Supervisor in North Wales for

RMC to QA/QC Engineer for

major civils contracts in Qatar,

to Area Technical Manager in North Wales for

RMC covering Cheshire, Merseyside, Lancashire

and North Wales. He is currently working in Libya

as Contract Co-ordinator where he is in charge of

the assessment and review of contract quality and

works procedures, technical and materials

specifications.

ABSTRACTThis paper describes the production of 1900

km of large diameter prestressed concrete pipes

and their installation on the Great Man Made

River Project, to transport water from desert

aquifers to fertile coastal areas.

KEYWORDSConcrete pipes, Prestressing, Design, Sprayed

concrete, Plant, Admixtures, Superplasticisers.

INTRODUCTIONGlobal warming is a fact. Predictive modelling

indicates that arid regions will become drier and

that wetter regions will receive more rain; overall

precipitation will increase. For example, the flow

of the Yukon River in Canada is expected to

increase by over 40% but those of the Nile and

Mekong Rivers will diminish by over 20%.

Growing populations in the areas short of

water have compounded the problem as

discussed at the 3rd World Water Forum in March

2003 (see Appendix 1) where the global situation

was summarised as:

• 1.2 billion people in developing countries

lacked access to safe drinking water

• 2.4 billion people were without adequate

sanitation

• 4 million children were dying each year from

water-related diseases.

As reported in New Scientist articles “Running

on Empty” (21st August 2004 edition) and

“Asian Farmers Suck the Continent Dry” (28th

August 2004 edition) the short-term solution of

drilling local wells is depleting groundwater

stocks, which is unsurprising as an Olympic-sized

swimming pool would irrigate enough crops to

feed only one person for a year.

The anticipated widening gap between the

haves and the have-nots of water supplies

presents a problem that spans international

frontiers. The solutions are necessarily of similar

proportions.

The Great Man-made River Project (GMRP) in

Libya, North Africa, is a case study for the

problems associated with such an undertaking.

Geographical scaleThe pipelines planned are shown in Figure 1.

The project intends to tap underground

reservoirs of water, or aquifers, situated under the

north-east corner of the Sahara desert in Libya

and transport it to the coastal regions where the

soil is fertile and the population is concentrated.

Although the population of Libya is under 6

million, the land area of the country is over seven

times greater than that of the United Kingdom.

To put the scale of the project in perspective,

1900 kilometres of pipeline are required;

equivalent to laying a line from Scotland to

Northern Italy via Belgium, Holland, Germany,

France and Switzerland.

The water reserves are contained in four large

aquifers and two smaller ones in the north of the

country. The four larger ones (Murzug, Kufra,

Sarir and Hamad) are shown in Figure 2 and

THE GREAT MAN-MADE RIVER PROJECT, LIBYA

Andy Rogers, MICT

Price Brothers (UK) Ltd

Figure 1: Pipeline network

62

contain a volume of water estimated at over 120

billion cubic metres.

The flow rate anticipated once all the pipes are

in full production is greater than that of the River

Thames.

Construction scaleThe project has been split into three phases;

the cost of each is shown in Table 1.

The infrastructure items included in the

costs are

• Roads

• Power Stations

• Production Plants

• Wells and Pipelines

• Pumping Stations

• Reservoirs

• Distribution Lines

• Operation and Maintenance Facilities.

Although none of these items are of

extraordinary construction, the size of every facet

of the project throws up amazing statistics. For

example, the reservoirs’ capacities are shown

below:

The concrete required could construct a path

to the moon.

The prestressing wire needed could encircle

the earth over 280 times.

The transporters for the pipes would travel a

total distance that reaches the sun and back!!

The logistics are quite literally astronomical!

Why use prestressed concretecylinder pipe (PCCP)?

A comparison of the relative benefits of pipe

materials is given in Appendix 2. Alternative

materials to cement and aggregates were not

readily available in Libya; pipes other than

concrete would be imported as a finished article

resulting in little of the expenditure benefiting the

country.

Figure 2: Main aquifer locations

Main Contract Daily Water CostAward Date Production, m3 US $ Billion

Phase I 1983 2,000,000 5.53

Phase II 1990 2,500,000 8.05

Phase III 1999 1,680,000 6.00

TOTALS 8,180,000 19.58

Table 1: Project cost

Figure 3: Pipe being lifted into trench

Reservoir Capacity M m3

Ajdabiya Holding 4.0

Al Gardabiya 6.8

Omar Mukhtar 4.7

Al Khadra 24.0

63

Fabricating locally, where possible, gives a

boost to economies by providing employment

and a market for materials and services; there are

also opportunities created to expand the local

workforce skills base. Four m diameter pipes

were required for the volumes of water

envisaged; this diameter requires a high degree of

stiffness from the pipe wall.

Pipe design principles are detailed in the

American Water Works Association C304 (latest

edition is C304-99) “Design of Prestressed

Concrete Cylinder Pipe” and roughly follow the

considerations taken for arch spans. Thus, for

small diameters, steel and plastic piping give

adequate stiffness with reasonable economy. As

stiffness is a cubic function of thickness, the pipe

walls for large pipes are necessarily thick.

Concrete is a value-for-money bulk stiffness

provider and for an extended design life,

particularly where water exposure is concerned,

this is a construction material which improves

with age.

The design life also means that operation and

maintenance costs become more significant.

Figure 4 shows an extract from a report

performed by Wisconsin Municipal Engineers and

clearly demonstrates the value of PCCP in

accordance with AWWA C301 “Prestressed

Concrete Pressure Pipe, Steel Cylinder Type”.

Technically and economically, PCCP was the

choice for the Great Man Made River Project.

PCCP for the projectMain supply pipes are 7.52 m long with an

inside diameter of 4 m.

Each finished pipe weighs 75 tonnes using

approximately 26m3 of concrete and up to 18

kilometres of high-carbon steel prestressing wire.

A cross section of the pipe is shown in Figure 6.

Figure 4: Pipe operation and maintenance costs

Figure 5: Pipe profile

Figure 6: Pipe Cross Section

64

The concrete is used to encase a thin-walled

steel cylinder which provides the water-

tightness. The joints rings for the steel cylinder

are welded to give a spigot and bell at each

end (see Figure 8)

Resistance to tensile forces imposed on the

concrete caused by internal pressures, self-

weight and earth loads is provided by placing

the concrete in permanent compression by

wrapping the concrete core in steel wire at a

specified pitch and tension.

The remaining operations do not contribute

to the structural performance but provide

protection to the wire. These involve a thin

coating of bonded mortar followed by the

application of a waterproof membrane; the

preferred membrane for the project is coal-tar

epoxy resin. Each operation in itself is fairly simple

and can be represented schematically as shown in

Figure 7; however, the outputs required and the

size of each pipe once again required outsize

plant.

Plant OperationsOver 500,000 pipes were required at rates of

up to one per production line every 15 minutes;

five production lines were needed, each 2.5

kilometres long and one kilometre wide (see

Figure 9).

The manufacturing plants were designed and

constructed by Price Brothers and were

commissioned in 1986. They are still fully

operational.

Technical Difficulties withConcrete and Mortar

From sourcing of sufficient materials to the

magnified consequences of quality control

problems, the project scale presents several

challenges to a concrete technologist.

Brega plant benefits from a huge limestone

Figure 8: Bell and spigot joint

Figure 7: Schematic representation ofPCCP manufacturing process

Figure 9: Aerial photograph of Sarir PCCPmanufacturing plant

65

deposit. The view from ground level in Sarir (see

figure 10), however, gives no clue where to find

aggregates in the desert….

……. but a satellite picture tells a different

story (see Figure 11).

The ancient river courses were revealed which

then allowed the focussing of a ground-

penetrating radar (GPR) survey.

GPR is affected by moisture variations in the

ground. Desert conditions were perfect for a fast,

accurate survey.

The deposits proved to be in thin beds

requiring a highly mobile set-up. With a coarse

aggregate recovery rate expected at 5% - 7% the

raw material needed separating in situ to be

economical.

Four track-mounted, mobile screening units

were custom made (see Figure 12) and could be

remotely operated.

Bulldozers ramp up the desert from a depth of

approximately 2m and front loaders then feed the

mobile screening plant (see Figure 13). All

aggregate over 3mm discharges directly into 40

tonne dumpers.

The aggregate proved to be predominantly

rounded 3-10mm (using ASTM terminology,

which was the basis for the concrete

specification).

The specified characteristic cylinder

compressive strength of 42 MPa (equivalent to a

cube strength of 54 N/mm2) as defined in AWWA

C301 was achievable. Some pipe designs,

however, required 48 MPa concrete which was

unattainable without very high cement contents

(which caused excessive shrinkage, heat of

hydration and creep) due to the ceiling strength

associated with the round aggregate. The

solution lay in separately processing oversized

material and using the crushed aggregate to

improve bond strengths.

Efforts to improve strength without increasing

cement contents led to research into the

performance of new superplasticisers; modified

polycarboxylate ethers in lieu of melamine-based

admixtures (Melment products) showed

significant improvements in compressive strengths

at constant free water/cement ratio 0.35 (see

Figure 14).

Figure 10: Ground level view of Sarir

Figure 11: Satellite photograph

Figure 12: One of four mobileaggregate screening plants

Figure 13: Mobile screening plant inoperation

Figure 14: Admixtures - primary lab trials

66

Use of PFA was examined, particularly for its

effect on in situ strength at elevated temperature.

Later age strength gains shown by cylinders were

reflected in situ despite pipe storage conditions

which encouraged desiccation.

Variable C3A contents in cement supplies

coupled with inconsistent admixture addition and

mixing times gave variable bleed characteristics.

The lift rate of 7.5 m in 15 minutes with heavy

external vibration gave rise to extensive sand

streaking (see Figure 15). This sand streaking is

known to be reflected at the concrete/steel

cylinder interfaces although it is not visible. With

the removal of the cement by this scouring

passivation of the steel cylinder is not assured.

The pipes are not acceptable in this condition (see

Figure 16).

The avoidance of sand-streaking was achieved

through more robust mix design with increased

cohesion and lower slump but more importantly

by educating and training site personnel.

Although the inner and outer concrete pipe

walls were only 75 mm and 175 mm thick

respectively, in situ temperature rises were

significant. This was due to the inner pipe

annulus being sealed by the top and bottom

pallets to effectively provide insulation against

heat loss. This became a problem when

demoulding at night or in the cooler months.

The effects were mitigated by

• Depressing the initial concrete temperature

by using ice

• Use of mist curing

• Use of thermocouples to monitor in situ,

kiln and ambient temperatures

• Careful timing of kiln opening and

demoulding.

Occasionally, water spraying malfunctions

would give localised rapid cooling leading to

thermal cracking (see Figure 17).

Other developments researched and

implemented to improve the pipe manufacturing

process include incorporating styrene butadiene

latex in sprayed mortar to increase consolidation

and reduce absorption, and the pre-coating of

pre-stressing wire with sodium nitrite-based

corrosion inhibitor.

Many opportunities have been taken to

examine the wealth of information generated byFigure 16: No remedy for extensivesand-streaking

Figure 15: Sand-streaked pipes

Age Cylinder Core Core/Cylinder (%)

28-Days 60.5 MPa 53.7 MPa 88.8

56-Days 66.5 MPa 57.3 MPa 86.2

Figure 17: Thermal cracks cause bylocalised cooling water spray (Note thecalcium carbonate deposit caused by thereaction between water-bornecarbonates and the lime leached fromthe concrete).

67

such a large project. This information, in the

hands of experienced concrete technologists, has

led to constantly reducing reject rates, savings on

material costs and an improved final product.

It remains to be seen if or when more water

re-distribution schemes on the same scale as the

Great Man-Made River Project will be necessary. If

they are, it would make sense to take note of the

lessons learned in Libya.

ACKNOWLEDGEMENTS

The author would like to express his

appreciation to his colleague Paul Sandberg, PhD,

who developed much of the data shown here,

and to W. R. Grace & Co. for permission to

publish.

Acknowledgement is given to Ken McGinley,

Brown and Root North Africa, for many of the

facts and illustrations.

APPENDIX 1

Extract from India’s Address

Global:a) 1.2 billion people in developing countries

lacked access to safe drinking water.

b) 2.4 billion people are without adequate

sanitation.

c) 4 million children died each year from

water-related diseases.

National:a) In India, 125 million people lack access to

safe drinking water

b) In India, 700 million people lack access to

sanitation facilities & defecate in open.

c) In India, 1 million children lose their lives

to diarrhoea every year

d) India is one among the developing

countries facing serious drinking water

problems. It was reported that a major

freshwater crisis is gradually unfolding in

India as a result of inadequate water

management and environmental

degradation by human action.

1. Actionsa) “WASH Campaign” in South India is

launched by Centre for Community Health

Research

(CCHR). The objective is to raise

consciousness about sanitation and

hygiene, gain the commitment of political,

social and opinion leaders and ultimately,

bring about the structural and behavioural

changes that will provide a permanent

solution to this preventable international

crisis.

b) Rainwater Harvesting.

c) Water Quality Control (WQC) and Water

Quality Surveillance (WQS) programme.

2. CommitmentsIt is the duty of every body to work together,

in order to attain the goal. Global, National and

local stakeholders should co-operate with

participatory approach.

3. Recommendations1) Access,

2) Finance,

3) Participatory,

4) More concern to the “poorest of the

poor”.

68

PCCP56 years of use in the US and Canada, 32,000 km in service

Supplies 90 out of North America’s 100 largest metropolitan areas

200 million people in North America depend on PCCP

All pipelines supplied by Price Brothers since 1943 are still in service.

ADVANTAGES & DISADVANTAGES OF DIFFERENT MATERIALS FOR PIPE CONSTRUCTION

APPENDIX 2

Advantages

Ductile Iron

• Good corrosion resistancewhen coated

• High strength

Concrete

• Good corrosion resistance

• Widespread availability

• High strength

• Good load supporting capacity

Vitrified Clay

• Very resistant to acids and most chemicals

• Strong

Thermoplastics (PVC, PE, HDPE, ABS)

• Very lightweight

• Easy to install

• Economical

• Good corrosion resistance

• Smooth surface reduces friction losses

• Long pipe sections reduce infiltrationpotential

• Flexible

Thermosets (FRP)

• High strength

• Lightweight

• Corrosion resistant

Disadvantages

• Heavy

• Requires careful installation to avoid cracking

• Heavy

• Susceptible to attack by H2S and acids whenpipes are not coated

• Joints are susceptible to chemical attack

• Brittle (may crack); requires carefulinstallation

• Short length and numerous joints make itprone to infiltration and more costly to install

• Susceptible to chemical attack, particularly bysolvents

• Strength affected by sunlight (UV protection)

• Requires special bedding

• High material cost

• Brittle, requires careful installation

• High installation cost

6969

Dr. Mouloud Behloul is a

structural and materials

engineer and has been involved

since 1994 in the study and

engineering of ultra-high

performance fibre reinforced

concrete. He was Project Manager of several R&D

projects and Project Manager for the construction

of structures. Currently, he is Technical Director,

Ductal®. for the Lafarge Group, in Paris, France

. ABSTRACT

Ductal®, a new material technology developed

over the last decade, is a combination of superior

technical characteristics of strength, ductility and

durability, whilst providing high quality surface

aspect on mouldable products.

This technology offers flexural resistance

exceeding 40 MPa with ductility and compression

strength beyond 200 MPa. As a result of its

tensile strength and ductility it is possible to avoid

reinforcement bars in structural elements.

Ductal® covers a range of formulations that

can be adapted to meet specific demands of

different customer segments, enhancing the

usage value and contributing to the overall

construction performance, reducing labour

requirement, enhancing durability, lowering

maintenance need and increasing total life cycle.

Ductal®’s unique combination of superior

properties enables designers to create thinner

sections, longer spans and higher structures that

are lighter, innovative in geometry and form,

while providing superior durability and

impermeability against corrosion, abrasion and

impact.

A number of reference prototypes in Ductal®

already exist in different countries both in

structural and architectural segments. A number

of selected references such as the recent

footbridges, retrofitting elements and

architectural realisations will be illustrated in this

article. Currently there are many other innovative

applications of this material in projects at

different stages of development.

KEYWORDS:Ultrahigh performance concrete, Ductility, Self-

placing concrete, Applications, Ductal®.

INTRODUCTIONDuctal®, the outcome of the research over the

last 10 years in the area of concrete, is a new

construction material technology belonging to

the UHPFRC family, with very high durability,

compressive strength, flexural resistance with

ductility and aesthetics.

The Ductal® technology was developed by the

combined efforts of three companies, Lafarge,

the construction materials manufacturer,

Bouygues, contractor in civil and structural

engineering and Rhodia, chemical materials

manufacturer. With this joint effort through

intensive research and development, a material

product range was patented, industrialised and

commercialised [1].

There were more than 15 universities and 6

testing laboratories in different disciplines and

countries which participated in the important

research effort over several years.

In France, new recommendations for the

design of structures and elements made of

ultrahigh strength concretes reinforced with fibres

were issued in May 2002 [2]. These

recommendations were established by a BFUP

working group (Béton Fibré Ultra Performant)

coordinated by SETRA (Road and traffic

governmental agency) and with representatives

from the construction industry (contractors,

control agencies, suppliers, certification

authorities).

Through the development period, several

prototypes were manufactured, prior to extensive

use in various civil works, structural and

architectural applications.

Ductal® TECHNOLOGY: THE RESULT OF A DECADE OF RESEARCH

Ductal® refers to a simple concept, minimising

the number of defects such as micro-cracks and

pore spaces, that allow achievement of a greater

Ductal®: ULTRA-HIGH PERFORMANCE CONCRETE TECHNOLOGY

FOR A WIDE RANGE OF APPLICATIONS

Dr. Mouloud Behloul

Lafarge Group, France

7070

percentage of the potential ultimate load carrying

capacity defined by its components and provide

enhanced durability properties. To apply that

concept, a concrete was proportioned with

particle sizes ranging from a maximum of

approximately 600 µm, down to less than 0.1 µm

to obtain a very dense mixture which minimized

void spaces in the concrete.

A Ductal® research program was conducted

based on the following principles:

• enhancement of homogeneity by elimination

of coarse aggregate

• enhancement of density by optimization of

the granular mixture

• enhancement of the microstructure by post-

set heat-treatment

• enhancement of ductility by incorporating

adequate size fibres

• maintaining mixing and casting procedures

as close as possible to existing practice.

By applying the first three principles, it was

possible to define a concrete with very high

compressive strength, but with not enough

ductility compared to a conventional mortar. The

inclusion of adequate fibres improves drastically

the tensile strength and provides a substantial

level of ductility.

The various Ductal® formulations are all based

on an optimised composition combining

homogeneity and granular compacted density.

To enhance performances, especially

mechanical ones, the option of heat treatment

can be chosen. For each application according to

technical and economical challenges, the Ductal®

technology is adjusted to achieve the most

adapted product to the customer’s requirements.

As described above, Ductal® is an Ultra High

Performance Concrete reinforced with fibres.

These fibres can be made of steel (Ductal®-FM),

made of organic material (Ductal®-FO) or a

combination of both steel and organic material

(Ductal®-AF).

The fresh mix of all these ranges of materials

have very useful properties in term of fluidity and

self placing. Most of the standard industrial

batching facilities are able to mix Ductal® with

only minor adjustments.

The Ductal® matrix is very fine and dense and

shows outstanding capacity to replicate any kind

of surface textures. By using adequate pigments a

very wide range of colouring effects can be

achieved. Thanks to these properties, Ductal® is a

favoured material for architectural applications

where combining high mechanical properties with

outstanding aesthetics for a castable mineral-

based material.

In the case of lower mechanical requirement

the steel fibres can be replaced by fewer organic

fibres and heat treatment may not be required.

This range of material is named Ductal®-FO.

Mechanical Properties andAnalysis

Ductal®-FM, the first developed mix, is

designed for structural applications where high

bending and direct tensile strengths are required.

These mechanical properties are achieved by

using short steel fibres. A content of 2% by

volume of 13-15 mm length fibres with diameters

around 0.2 mm emerged as the best option out

of thousands of tests.

Figure 1 shows the bending behaviour of

Ductal®. It can be observed that it has an ultimate

bending strength which is over twice its first

crack stress and more than ten times the ultimate

stress of conventional mortar. Such very high

strength and consequent ductility allows the

design of structures without any secondary

passive reinforcement and no shear

reinforcement.

The ductile behaviour observed in the bending

test before the peak is characterised by multiple

cracking, without any localisation of a major

crack, as shown in Figure 2.

Figure 1: Ductal® behaviour in bending

71

Figure 2 (left) shows an image obtained by X-

ray scanning, where can be seen the high density

of fibres (2% volume) of a 40x40x40 mm cube

sawn from a Ductal® beam (courtesy of TOMO-

ADOUR). Figure 2 (right) shows multiple cracking

in the tensile zone as observed after bending

failure; it is noticeable that the crack widths are

so small that they cannot be seen by the naked

eye and the surface needs to be wetted with

alcohol to reveal the cracks; the appearance of

the single visible crack coincides with the peak

load (“localisation” process).

Creep & Shrinkage BehaviourCreep and shrinkage are probably the most

outstanding characteristics of Ductal®. Creep was

tested by ECN [3]. For normal concrete the so-

called creep coefficient can reach 3 to 4, for high-

performance concrete the creep coefficient is

reduced, but the delayed strain is already higher

than the elastic one. The creep coefficient of

Ductal® is less than 0.8 and, when a thermal

treatment is applied, the creep coefficient is as

low as 0.2 (Figure 3) [4]. When using prestressing

technology, the prestress losses are substantially

reduced.

This very surprising result has been analysed [5],

and this analysis will certainly impact our view on

the creep mechanisms and theory.

As the water to cement ratio is very low,

Ductal® does not exhibit any drying (no weight

loss can be measured) nor drying shrinkage. A

high autogenous shrinkage can be observed (300

to 400 microstrain) but when a heat treatment is

applied, this shrinkage is completed at the end of

the treatment and, when this treatment is over,

absolutely no residual shrinkage occurs (Figure 4).

Fire And High Temperature Fire resistance is one of the main issues for

developments in the building industry. For

material developments like any concrete, Ultra

High Performance Concretes are listed in the M0

class of products (non-inflammable) which slow

down the spread of fire. However, the very low

porosity of UHPCs induces greater internal

stresses. In these materials, the porosity is totally

enclosed, which prevents water vapour (steam)

from escaping. By increasing the pressure within

the material the spalling phenomenon occurs.

Spalling has been almost suppressed by using

adequate organic fibres. Above 150°C such fibres

begin to soften and melt, thereby providing

escape routes for trapped steam. This approach

was applied to a new Ductal®. As the matrix is

completely closed when compared to an HPC

matrix, very important work was performed in

order to up-grade Ductal® and to find the correct

mix, geometry of fibres and the dosage when

Figure 3: Ductal® basic creep [3]

Figure 4: Ductal® shrinkage: afterthermal treatment, no shrinkage isobserved [3]

Figure 2: 3-D image (left), multiple cracking (right)

72

keeping the target of ultra high strength, very

good workability and no spalling when subjected

to fire.

Different kinds of structures, loaded or

unloaded columns, loaded and unloaded beams,

were tested in France (CSTB) and Finland (VTT),

under ISO fire with success. Direct tensile

hot tests were also performed by the Politecnico

di Milano [6].

The mechanical properties of this new

Ductal® referred to as Ductal®-AF are similar to

Ductal®-FM.

DurabilityThe microstructure of Ductal® is completely

closed and prevents the intrusion of any

aggressive agent. Such characteristics give the

material an ultra-high durability performance.

Full characterisation of the durability properties

of the material were performed in different

laboratories - INSA Toulouse, LCPC, EDF/CEMETE,

ESPCI, Mines de Nancy, LERM - in which the

porosity distribution, gas permeability,

carbonation, chlorine diffusion, leaching and the

MNR microstructure characterisation tests were

made. Also the chemical stability of the material

was checked [7].

Freeze-thaw tests were performed on Ductal®

samples at CEA [8] and also at CEBTP. The tests

were performed for 300 cycles above the

normative 100 cycles without any degradation.

UHPFRCs materials stand up to chemical

conditions under which ordinary reinforced

concretes are rapidly and severely damaged.

Laboratory tests were performed by CSIC (Spain)

in which Ductal® was submitted to different

aggressive chemical compounds (calcium sulfate,

sodium sulfate, acetic acid, ammonium sulfide

and nitrate and also sea water and distilled

water). The results exhibit a very good resistance

to chemical attack [2].

Other severe operating condition tests were

performed at IFP in which Ductal® was submitted

to different gases (CO2, CH4, H2S), at high

temperature (120°C) and high pressure (7MPa)

showing again unexpected high resistance.

Ageing tests were also performed at CSTB in

which the self-sealing of Ductal® was

demonstrated [9].

APPLICATIONSThe ultra high performance of Ductal® opens

up applications in different domains requiring at

least :

• ultra high strength

• durability

• architectural aspects

Mechanical StrengthA material with such high ultimate

compressive and flexural-tensile strength offers

interesting opportunities in the field of

prestressed concrete. As might be expected, the

high flexural tension capacity also gives rise to

extremely high shear capacity. This allows

Ductal® to carry the shear loads in a structure

without providing auxiliary shear reinforcement.

The elimination of passive reinforcement

makes it possible to use thinner sections and a

wider variety of innovative and acceptable cross-

sectional shapes. The current structural precast

shapes used for prestressed beams in bridges and

buildings have been shaped for concretes with

much lower strength properties. Their dimensions

and design would not allow to take advantage of

very high performances of Ductal®. In order to

make the best use of the higher mechanical

properties, there are several opportunities to

introduce new shapes in prestressed beam

design. Through such re-design approach of the

elements the beam dead load can be reduced by

a factor of three.

Figure 5: Seonyu footbridge, Korea (left) and Sakata Mirai footbridge, Japan (right)

73

Among these kinds of applications we can list

the Shepherds Traffic Bridge erected in

Australia[10], 5 footbridges: Sherbrooke footbridge

in Canada, Seonyu footbridge in Korea (Figure 5)[11], Sermaises footbridge in France, Sakata Mirai

(Figure 5) and Akakura footbridges in Japan and

the canopies of the LRT station of Shawnessy

(Figure 6).

Durability Oriented Applications The durability of Ductal® is as important as the

mechanical strength. Combining strength and

durability, Ductal® can be an ideal solution for

structures in severe environments. Also the

durability of the material lowers maintenance

costs and makes the solution very competitive.

Ductal® was used in several durability/fire

resistance oriented applications like the beams

and girders (more than 2000) used for the

Cattenom power plant cooling tower in France,

the retained earth anchorages (more than 6000)

used in Réunion Island (Figure 7) and the Ductal®-

AF used for the construction of composite

columns in the Reina Sofia Museum in Madrid

(Spain).

Architectural ApplicationsThe use of a concrete-like material but with

almost unlimited possibilities of appearance,

texture and colour has excited architects by giving

them access to an unexpected new world of

shapes and volumes. Ductal® was used in several

architecturally oriented applications like the bus

shelters in Tucson (USA), flower pots in Rennes

(France), shower booths, sun shades (Fig. 8),

façade panels in Monaco and Kyoto clock tower

in Japan.

CONCLUSIONDuctal® is a new technology of ultra high

strength concretes that constitutes a

breakthrough in concrete mix design. This family

of products is characterised by a very dense

microstructure and very high compressive

strength achieving and possibly exceeding 200

MPa. Steel and organic fibres or a combination of

both are one of the major components of the

material, enhancing the bending strength,

ductility and fire resistance.

The three main categories of applications are:

- Mechanical strength: The very high

mechanical properties combined with prestressing

technology offer engineers and architects a lot of

opportunities to design elegant structures by

avoiding heavy steel reinforcement. Ductal®

technology gives access to very slender and

elegant structures like footbridges.

- Durability: the very dense microstructure of

the Ductal® matrix offers a material which resists

very aggressive environments and therefore opens

up a very wide range of applications.

Figure 6: Ductal®-FO canopies - LRTTrain Station, Shawnessy, Canada

Figure 7: Ductal®

retained earthanchors – La RéunionIsland

Figure 8: Architectural applications -examples

Flower pots, Rennes

Sun shades, La Doua university Lyon

74

- Architectural: a very wide range of textures

and colours effects are accessible to Ductal®.

Such properties provide architects with very high

potential of innovative design in all elements that

build up new architecture.

REFERENCES1. Orange, G.; Dugat, J.; Acker, P.; ‘A new

generation of UHP concrete: Ductal®.Damage resistance and micromechanicalanalysis’, Proc. of the 3d Internat. RILEMWorkshop, HPFRCC3. (1999), 101-111.

2. BFUP. AFGC, ‘Ultra High Performance Fibre-Reinforced Concretes, InterimRecommendations’, AFGC publication,France, (2002).

3. Loukili, A; Richard,P and Lamirault,J; ‘AStudy on Delayed Deformations of an UltraHigh Strength Cementitious Material’;Fourth CANMET/ACI/JCI Conference,Special Publication, American ConcreteInstitute SP-179. (1998) 929- 950.

4. Acker, P.; ‘Why does Ultrahigh-PerformanceConcrete (UHPC) exhibit such a LowShrinkage and such a Low Creep ?’;Proceedings of: Autogenous Deformationsof Concrete, ACI Fall Convention, Phoenix,USA (2002).

5. Acker, P.; ‘Swelling, shrinkage and creep: amechanical approach to cement hydration’;Concrete Science & Engineering, Vol. 37(2004) 11-17.

6. Behloul, M.; ‘Fire resistance of Ductal Ultrahigh Performance Concrete’; Proc. FIB 2002,Osaka, Japan. Vol. 2. (2002) 101-110.

7. Vernet, C.; ‘UHPC Microstructure andrelated Durability Performances - LaboratoryAssessment and Field Experience Examples’;PCI / FHWA 3rd International Symposium onHPC, Orlando, USA (2003).

8. ‘Conteneur haute intégrité à base de lianthydraulique tenue aux cycles gel/dégel’;Rapport scientifique 1997-CEA, Directiondu cycle du combustible- ISSN 0429-3460,(1997) 152-159.

9. Pimienta, P.; Chanvillard, G.; ‘Retention ofthe mechanical performances of Ductalspecimens kept in various aggressiveenvironments’; Fib Symposium, Avignon,France (2004).

10. B.Cavill and G.Chirgwin. ‘The worlds firstDuctal road bridge Sherpherds gully creekbridge, NSW’; 21st Biennial Conference ofthe Concrete Institute of Australia, Brisbane(2003).

11. Behloul,M.; Lee, KC.; ‘Ductal Seonyufootbridge’; Structural Concrete. 4 (4),(2003) 195-201.

12. Hartmann, J.; Graybeal, B.; Perry, V.;Durukal, A.; ‘Early Results of the FHWAUHPC Research Program’; InternationalConference on Advanced Materials forConstruction of Bridges, Buildings andOther Structures, Davos, Switzerland(2003).

13. Chuang, E.-Y.; Ulm, F.-J.; ‘Two-phasecomposite Model for high performancecementitious composites’; M.ASCE Journalof Engineering Mechanics, (2002)1314-1323.

Abbreviation Name ExplanationBFUP Béton Fibré Ultra Performant Ultra high performance fibre-

reinforced concreteSETRA Service d’Etudes Techniques French administration for roads and

des routes et autoroutes bridgesECN Ecole Centrale de Nantes Engineering school at Nantes, FranceCSTB Centre Scientifique et Technique Testing/approval organisation for

du Batîment building application (Private/Public), FranceVTT Vattion teknillinen tutkimuskeskus Technical Research Centre of FinlandINSA Institut National des Engineering school, France

Sciences AppliquéesLCPC Laboratoire Centrale des Ponts Government laboratory for roads and

et Chaussées bridges FranceEDF/CEMETE Electricité De France Testing laboratory of the electricity

distributor in FranceESPCI Ecole Spéciale de Physique et Physics and Chemistry university

Chimie Industrielles – Paris, France LERM Private testing laboratory, FranceCEA Commissariat de l’Energie Atomique Atomic Energy Agency. France.CEBTP Centre d’Essais pour le Batiment Private laboratory for civil engineering,

et les Travaux Publics FranceCSIC Spanish testing laboratory, Madrid, SpainIFP Institut Français du Petrol French Oil Institute

LIST OF ORGANISATIONS

75

Mario Corradi is a graduate in

Industrial Chemistry from Milan

University. He is the Senior Vice

President of Technology and

Development for Business Unit

Admixtures System Europe of

Degussa Construction Chemicals. He has more

than 30 years of experience in R&D and

technology management in construction

chemicals.

ABSTRACTThe Italian high speed rail network is a part of

the European Project for the reorganisation of the

rail transport system to link the countries of the

Union by 2010. The section between Milan and

Bologna has a length of 182 km and crosses

Lombardia and Emilia regions. In the province of

Modena there is a complex system of bridges that

cross the existing motorways, urban roads, the

Panaro and Secchia Rivers. The main contractor

for the 24,760 m bridges is the Modena Scarl

Consortium. The bridge network consist of 755

omega shaped precast beams of 24 to 31.5 m

span and 9 cast in situ beams of 136 m span.

This complex system required innovative

construction techniques and a special precast

factory was set up by the contractor Pizzarotti.

The prefabrication process starts with the

assembly of the reinforcement cages in 8

templates that are able to produce 2 cages per

day. The assembly is completed with the anchor

heads, ducts with the prestressing cables and are

then positioned on the casting beds.

The particular shape and the density

of the reinforcement required a

concrete with some specific

properties. Durability was another

requirement. Specific admixtures

were developed for this project and

their mechanism of action is

presented in this paper. Also, some

details on the design and

construction techniques adopted on

this project are presented. In spite

of the complexity of the works the

Project was completed ahead of the

scheduled date.

KEYWORDSRailways, Viaducts, Bridges, Precasting plant,

Prestressing, Reinforcement, Formwork, Concrete

mix, Superplasticisers, Monomers.

INTRODUCTIONThe Italian high speed rail network is a part of

the European Project for the reorganisation of the

rail transport system to link the countries of the

Union by 2010. The Italian link extends over 1400

km along the main routes from Turin to Venice

and from Milan to Sicily with links to the rest of

Europe (see Figure 1).

The Italian State Railway has appointed TAV

(Treno Alta Velocità) for the design and

construction of the 1100 km of the track and the

General Contractor is Cepav Uno. The guiding

principle for the design of this section was to

increase the capacity of the whole railway system

by integration with the existing network with the

maximum respect of the environment by the use

of advanced technology and high quality

standards

The section between Milan and Bologna has a

length of 182 km and crosses Lombardia and

Emilia regions. The railway track follows the

“Autostrada del Sole” motorway to Modena. In

the province of Modena the track deviates from

the motorway and there is a complex system of

bridges that cross the existing motorways, urban

roads, the Panaro and Secchia Rivers (see Figure 2).

ADVANCED CONCRETE TECHNOLOGY FOR A COMPLEX

BRIDGE SYSTEM WITH LOW ENVIRONMENTAL IMPACT

Dr. Mario Corradi

Degussa Construction Chemicals Europe, Italy

Figure 1: The European High Speed Train Network

76

The track will cross the territory of 42

communes. There are four types of construction

involved: embankments (63%), viaducts (34%),

trenches or cuts (2.7%) and tunnels (0.3%). The

main contractor for the 24,760 m bridges is the

Modena Scarl, a Consortium Pizzarotti,

Snamprogetti and Aquater .

THE MODENA VIADUCTS SYSTEM

The system of viaducts develops over a length

of 24,760 metres and consists of two types of

structures. The major part consists of omega-

shaped precast and prestressed beams produced

in a plant specially build for this project. The

location of the plant was selected so as to be

equidistant from the various viaducts to be

constructed. 755 beams were produced for a

total length of 23,538 metres of which 713

beams have a span of 31.50 metres, 28 beams of

29.00 metres and 14 beams of 24 metres. The

remaining 1223 metres were cast in situ as

continuous beams, 9 in number, having a span of

136 metres.

THE PRECAST CONCRETE PLANT

The reinforcement assemblyThe reinforcement cages are produced in a

147.5 x 74.4 m shed where there are 8 templates

for the assembly of the reinforcement. The head

of the formwork is already positioned and its

inclination is regulated as per the design. A

squad of 12 persons complete the assembly of

the reinforcement for one beam in 4 days. The

weight of the cage for the 31.50 m span beam is

about 33 tonnes. 10 cages are produced per

week. The assembly already has the prestress

ducts and the 20 cables already positioned. Each

cable has 12 tendons of 0.6”. The handling of

the reinforcement is carried out with the help of

4 gantry cranes, each of 12.5 tonne capacity. The

assembled cage is transported to the casting bed

by a special lifting and transport system. Figure 3

shows assembly of the reinforcement cages.

The concrete production plant The concrete production plant has two

terminals for discharging the concrete. At the first

point, used only in case of emergency, is the

traditional type where components are loaded

into the truck mixer for subsequent mixing and

transport. The second point has two forced action

pan mixer, each of 3.2 m3 capacity. These mixers

discharge the concrete into two agitating

containers of 7 m3 capacity. From these containers

the concrete is fed into two pumps for

transporting and distributing it to the forms.

Figure 4 shows the plant.

The concrete casting shed andformwork

The dimensions of the shed where the omega

shaped beams are cast are 37.20 m x 133.50 m.

There are 2 casting beds with 3 external

formworks each. Each bed is provided with an

internal form which moves on a rail track. The

Figure 3: The reinforcement assemblytemplate

Figure 2: Track section between Milan and Bologna

Figure 4: The concrete production plant

77

internal and the external forms are equipped with

fixed electric vibrators of 1.7 of kW and 2000 kg

centrifugal force with variable frequency. These

vibrators are operated in sequential zones. The

upper part of the pour is compacted with

electrical poker vibrators. Two gantry cranes of

12.5 tonne capacity are available for supporting

the production process. Each casting bed has an

independent compressed air plant and water

supply for cleaning out the concrete pump and

the hose. The pour for the standard 31.50 m

beam requires 276 m3 of concrete and the pour is

completed in four hours. After about 24 hours,

when the concrete has achieved a compressive

strength of 30 MPa, the internal formwork is

extracted and the forms at the two extremities of

the beam are removed. At this stage the beams

are partially prestressed to 35% of the design

value and transported to the stockyard. Two

beams are produced daily with a total of 10

beams per week. Figure 5 shows the set-up in the

casting shed.

In the stockyard the beams are placed on

columns where the bearings have been

positioned. There are 16 stations for this type of

operation. These bearings are then fixed to the

beam. When the concrete in the beam achieves a

compressive strength of 45 MPa, the final post-

tensioning of the cables is carried out. The cables

are then injected with a special grout made with

Flowcable, a specific admixture for these types of

applications.

THE CONCRETEThe concrete for the beams had some special

requirements. The characteristic compressive

strength (fck) was 45 MPa and the minimum

strength at 24 hours was 30 MPa for the

application of the initial post tensioning (35% of

the design value). The cement used was type

CEM I 52,5. A limestone filler, two types of sand

and three classes of coarse aggregates with a

maximum size of 32 mm were used. The

consistence class of the fresh concrete was S5

(slump > 220 mm). The mixture composition, per

cubic metre, is given in Table 1.

The superplasticiser used was specially

formulated for this project and is based on the

state of the art Total Performance Control

concept. The mechanism of action of the

superplasticiser is briefly illustrated here.

Superplasticiser PCE SKYSuperplasticiser PCE SKY is based on

innovative polycarboxylic ether polymers designed

according to a specific balance between electrical

charges, side chains, length of the main

backbone, new functional monomers and

molecule geometry. This nanotechnology is the

fruit of the experience built up over several

decades in the design of polymers in the nano-

metric scale and in the comprehension of the

phenomena occurring between superplasticisers

and the cement surface. In order to better

understand the novelty of these molecules, it is

worthwhile to summarise the mechanism of

action of the state of the art superplasticisers.

In general, traditional superplasticisers such as

beta naphthalene formaldehyde condensate,

which are formed by a backbone with negative

functional groups attached to it, act through a

mechanism of adsorption of the molecules onto

the cement particles. This creates an electrostatic

repulsive effect which results in the dispersion of

cement particles. However, because of the

hydration process, the molecules are subsequently

covered by the crystals of the hydration products

Figure 5: Positioning of the internalformwork

Cement CEM I 52,5 360 kg

Limestone filler 4.5% 85 kg

Sand 0-2 mm 7.5% 102 kg

Sand 0-8 mm 37% 702 kg

Gravel 8-12 mm 11% 209 kg

Coarse aggregate 15-22 mm 23% 436 kg

Coarse aggregate 22-32 mm 17% 322 kg

Water 137 l

PCE Superplasticiser 5.2 l

W/C 0.39

Table 1: The concrete mixturecomposition

78

thus causing a decrease of the repulsive effect

and loss of workability over time.

The polycarboxylate superplasticisers available

on the market nowadays are characterised not

only by the presence in their structure of electrical

charges but also of side chains. The side chains

improve not only the water reducing effect but,

especially the workability retention properties due

to their steric effect.

However, due to the intrinsic nature of their

chemical structure, an optimisation of the water

reduction capabilities leads to a worsening of the

workability retention and vice-versa.

Therefore, using this kind of technology, which

has been anyway the most effective one available

so far, is a compromise between water reduction

and workability retention obtained.

A complication in the mechanism of action of

the existing superplasticisers is the chemical

composition of cement that, in some cases,

prevents the complete exploitation of the

performance of the admixture. The cause of this

incompatibility can often be found in what

happens in the first minutes of the hydration

process. In the first few minutes the water reacts

with the aluminate phases of cement forming a

dense growth of crystals, or what can be

compared with a “lawn”, of ettringite, which can

have a thickness in the range of microns.

Depending on the kinetics of formation of

ettringite and the kinetics of adsorption of the

superplasticiser, which has dimensions in the

range of nano-metres, we can have two different

situations (Figure 6):

• The adsorption of the superplasticiser is

above the ettringite “lawn”. In this case

there is a good dispersing effect

• The adsorption of the superplasticisers is

below the ettringite “lawn”. In this case the

superplasticiser is being covered and,

therefore, cannot act any longer. In this

situation part of the superplasticiser may be

considered to be wasted.

Since the chemical composition of the cement

can considerably influence the kinetics of

formation of ettringite, it is clear that it can play

an important role in the compatibility between

the cement and the superplasticiser.

As previously mentioned, the usual tool to

control the rate of adsorption and workability

retention of a state of the art polycarboxylic

polymer is the ratio between the negative

charges and the side chains, which also affect the

water reduction capability.

The key aspect of the SKY molecules is the

presence of new functional monomers which

control the adsorption rate of the polymer

without having a side effect on the water

reduction. The hypothesis of the mechanism of

action is that these new monomers act as

“parachutes” slowing down the adsorption, and

thus controlling the workability retention; and not

wasting the polymer that could be adsorbed

under the ettringite “lawn” (Figure 7).

Figure 6: Adsorption of the superplasticiser

79

This allows the obtaining of an independent

control on the water reduction and on the

workability retention. These two properties are

opposing performances in the state of the art

superplasticisers technology.

But with the innovative superplasticisers it is

possible to minimise the sensitivity of the

polymers with respect to the chemical

composition of the various cements (Figure 8).

“TAILOR MADE” BEAMSMany specialists and authorities are involved in

the planning and selection of the route that the

railway track has to take. They include

management of the transportation system,

electrical, mechanical and hydraulic engineers

(waterway crossings), specialists in environmental

studies and analysis of environmental impact,

Figure 7: Parachute effect of the monomers

Figure 8: Balancing performances of concrete with SKY polymer

80

acoustic engineers (for urban sites) and landscape

architects, just to list a few players in the decision

making. All this must fulfil many criteria related

to user comfort, speed of use, security of the

existing structures during construction,

harmonious integration into the surroundings.

The bridge engineer plays a central role in this

process. To overcome the diverse type of

obstacles such as, motorways, state highways and

urban roads and river crossing, encountered on

this route, two techniques of bridge construction

were selected for the cast in situ concrete. 9

viaducts of 136 m span and consisting of

sections 40 m, 50 m and 40 m between the

piers. These beams also have an omega shape

section and made up of sections of 53.10 m,

57.45 m and 25.4 m. The construction technique

adopted is such that the load distribution in the

structure is as if it was a monolithic hyper static

structure.

Figure 9 shows the construction phase of

beams cast with the traditional formworks and

Figure 10 shows the construction of beams with

self supporting formwork across the Secchia River.

CONCLUSIONSThe construction of the bridge network around

Modena posed major challenges which required

innovative solutions that took in consideration the

environmental impact. On its completion by the

end of 2005 it will link the south of Italy to the

rest of Europe through Bologna.

FURTHER READING

1. Impresa Pizzarotti & C., Sistema ViadottiModena: Le Travi ad Omega, InternalPublication, November 2004 (in Italian).

2 Corradi, M., Khurana, R., Magarotto, R.,Total Performance Control: An innovativetechnology for improving the performancesof fresh and hardened ready mixedconcrete, Proceedings of ERMCO Congress,Helsinki, June 2004.

Figure 9: Construction of Modena Westinter-crossing

Figure 10: Construction of the bridgeacross the Secchia River

81

Kshemendra Nath is currently

working with Elkem India

Private limited, part of the

Norway-based Elkem ASA, as

the Deputy Managing Director,

responsible for the Elkem

Materials business in India and the SAARC

countries. He is a civil engineering graduate with

more than 17 years of experience in the building

materials, construction and ready-mixed concrete

industry in India. He is also a corporate member

of the Institute of Concrete Technology. Prior to

joining Elkem, Kshemendra Nath worked as the

General Manager sales and marketing and also as

General Manager – Technical and Marketing of

RMC Readymix India Limited, part of the RMC

Group plc UK.

ABSTRACTThis paper discusses the use of high

performance microsilica concrete for the Bandra-

Worli sea link project in Mumbai. The sea-link

which is built over the Arabian sea is subject to

severe exposure and high ambient temperatures.

This necessitated the use of high performance

concrete in the structure with stringent concrete

specifications, particularly on its resistance to

chlorides and water penetration. The transporting

and placing of high performance concrete in the

sea was a challenging task. The success of the

sea-link is crucial, as there are a few more similar

projects in the pipeline in Mumbai including the

extension of this sea-link to south Mumbai and a

bigger 22 km long trans-harbour link project

connecting Mumbai and New Mumbai.

KEYWORDSHigh performance concrete, Microsilica,

Durability, Slump retention, Pile, Pile cap, Precast

box girder.

INTRODUCTIONThe Bandra-Worli Sea-Link is a prestigious

project that envisages the construction of 5.86

km long eight-lane freeway to be built across the

Arabian sea. The sea-link is expected to de-

congest traffic in Mumbai and reduce travel time

to south Mumbai. Most of the concrete specified

for this project is high strength, high

performance.

Distinctive features of this bridge are:

(a) Out of the 5.86 km length, the length of

the bridge portion is 4 km including a

500m long cable-stayed portion,

(b) Two independent four-lane, cable-stayed

bridges of 500 m length on a single pylon

of 126 metre height,

(c) Two independent four-lane, cable-stayed

bridges of 350 m length at the Worli end,

(d) The bridge is supported on friction piles.

The piles are drilled and concreted in the

sea bed, 8-10 m below water level,

(e) There are two curves on the sea-link, for

which different types of trapezoidal

segments (in plan) are necessary.

(f) The superstructure consists of precast,

prestressed box girders.

The segmental construction is made of high

performance concrete (HPC), M60 grade, with

Microsilica. The segments are post-tensioned

longitudinally. Each Segment will accommodate

four lanes of traffic and the maximum weight of

each will be about 140 tonnes. Total concrete

required is estimated at 200,000 m3, out of

which about 100,000 m3 of M 60 grade concrete

will be required for about 3050 precast segments.

The remaining concrete is for piles, pile caps,

piers and pier caps in the sea.

The sea-link will provide a faster and safer

north / south traffic corridor. It is expected that

this facility will cut down by approximately 45

minutes, the time taken to reach Worli from

Bandra, a suburb of Mumbai. In the second

phase, which is currently in the planning stage,

Worli will be connected with Nariman Point in the

central business district of Mumbai in the

southernmost part of the city.

HIGH PERFORMANCE CONCRETE

MaterialsOrdinary Portland Cement (OPC)

OPC 53 grade conforming to IS-12269 was

selected for use in concrete.

HIGH-PERFORMANCE MICROSILICA CONCRETE FOR THE

BANDRA-WORLI SEA-LINK, MUMBAI

Kshemendra Nath, BTech, MICT

Elkem India Private Limited

82

Microsilica

Elkem Microsilica in slurry form (50:50)

conforming to ASTM C - 1240, was used for the

high performance concrete. The slurry was

produced at site in two blender units having the

capacity to produce and store 2 tonnes of

Microsilica in slurry form and were installed near

the batching plant.

Fly ash

ASTM Class F fly ash conforming to the

requirement of ASTM C-618 from field 3 of the

thermal power station at Dahanu, 90 km from

Mumbai, was utilized after conducting the

necessary physical and chemical tests.

Aggregates

Crushed basalt rock of maximum size 20mm

was used as coarse aggregate. Fine aggregate

consisted of crushed sand manufactured from

basalt rock and river sand from the Ambica river.

Admixture

A sulphonated naphthalene formaldehyde-

based high-range water reducing admixture

conforming to ASTM C - 494 Type G was used.

Durability tests specified for the concrete

included a water penetrability test and a rapid

chloride penetration test. The specifications were:

• Concrete shall meet a permeability of less

than 25mm as determined by the DIN 1048

test

• Chloride penetrability when tested as per

AASHTO 227 shall be between 100 and

1000 coulombs.

Concrete ProductionConcrete was from two plants each producing

90 m3/hour; one for the precast yard, and one for

the in situ casting. Both plants were supplied with

silica fume in a slurry form, from two individual

mixer units at each plant. This enabled the rapid

and thorough dispersion of the silica fume

throughout the low w/c ratio mix.

The concrete produced for the in situ casting

had to be transported and placed within the sea

and thus required special arrangements. The

concrete, after mixing at batching plant, was

discharged through a conveyor into the transit

mixers mounted on barges, which then hauled it

to the placing point. The concrete, after arrival at

the placing point ,was taken in buckets, which

discharged into the concrete pumps located on

the jack-up platform. The concrete was finally

placed by means of a pump.

Figure1: Plant truck to skip

Figure 2: Skip to transit mixer on abarge

Figure 3: Barge to offshore piling rig

Figure 4: Barge skip to pour into pilingrig

83

Precast segments

About 100,000 m3 of concrete of grade M 60

meeting the specified durability parameters was

used in the casting of the precast box girders.

Typical compressive strength results obtained

are given below:

Pile Concrete

M-50 Grade Microsilica concrete was specified

for the in situ piling. Since the batching plant was

situated on shore and the average transportation

time amounted to 3 hours, the concrete was

designed to give a slump of 180 mm at 3 hours

after mixing. In the high ambient temperatures

prevailing in Mumbai, establishing the mix proved

to be really challenging.

Typical compressive strengths achieved were as

follows;

Continuos improvements were made to the

mix to arrive at the optimal costs and the current

mix design is reproduced in Table 1 below.

Pile Cap Concrete

As per the project specifications, the

characteristic strength of the concrete in the pile

cap is 60 MPa. The target mean strength has

been stipulated as 74 MPa.

Typical compressive strength results achieved

for the pile cap concrete are as below:

The pile cap was to be cast at a level of 2-4 m

below the mean sea level within the tidal

variation. Further, due to the large dimensions of

the pile cap, control of temperature of the

concrete and thermal gradients were essential to

prevent the development of thermal cracks. From

these considerations, the specifications required

that the maximum temperature of concrete

should be limited to 70ºC and the maximum

temperature difference between the core and the

surface should be limited to 20ºC.

Installing thermocouples at different locations

in the pile cap monitored the temperature of the

concrete. The maximum temperature observed

was 68ºC and the difference between the core

and surface of concrete was less than 20ºC.

MIX OPTIMIZATIONContinuous improvements and

monitoring of the performance of the concrete

have resulted in optimization of the mix. The

current mix proportions are shown in the table on

the following page.

CONCLUDING SUMMARYThe effective use of high performance

microsilica concrete is possible, economic and

practical in the Indian environment.

The success of the high performance concrete

application in the Bandra-Worli sea-link will

hopefully result in similar specifications for

important structures, especially those subjected to

aggressive environments. This will also lead to the

concept of life cycle cost gaining currency in India

and will encourage good construction practices

and better concrete structures to be built.

Figure 5: Artist’s view of Bandra-WorliSea-link when completed

Characteristic Strength M60

Target strength 74 MPa

Minimum Microsilica content 10% of

cement

Maximum W/c ratio 0.35

Compressive strength (20 hours) 22 MPa

Compressive strength (48 hours) 35 MPa

Slump (Initial) 200 mm

Slump (3 hours) 160 mm

Time Strength (MPa)

20 hours 26

1 day 30

48 hours 40

3 days 52

7 days 64

28 days 75

Time Strength (MPa)

3 days 33

7 days 48

28 days 64

Time Strength (MPa)

3 days 39

7 days 56

28 days 76

84

Material Mix quantities (kg/m3)

Grade of concrete M 50 M 60 M 60

Unit type Pile Precast Segment Pile Cap

Cement 364 420 300

Microsilica slurry 36 42 40

Flyash 0 0 196

Total binder content 400 462 536

20 mm aggregate 520 540 577

10 mm aggregate 450 460 500

River sand 470 440 423

Crusher dust 480 480 327

Free water 134 127 134

Admixture 3% 3.2% 2.50%

Water/binder ratio 0.34 0.27 0.25

Initial slump 220 200 220

Final slump 200 (3 Hrs) 190 (2 Hrs) 170 (4 Hrs)

Table 1: Current mix details

Limits are ourChallenge.

Our daily challenge is to push the limits to find unusual solutions. We do it by applying our innovation potential and our understanding

of the market. Using this combination, we get more out of concrete. We are constantly creating new and better properties for concrete, expanding

its field of application. That means added value for everyone in the project.

Degussa Construction Chemicals (UK),

Albany House, Swinton Hall Road, Swinton, Manchester M27 2DT

Tel: 0161 794 7411 Fax: 0161 727 8881

e-mail: mbtfeb@degussa.com www.degussa-cc.co.uk Adding Value to Concrete

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85

ADVANCED CONCRETE TECHNOLOGY DIPLOMA:

SUMMARIES OF PROJECT REPORTS 2004

The project reports are an integral and important part of the ACT Diploma.

The purpose of the projects is to show that the candidates can think about a topic or problem in alogical and disciplined way. The project normally spans some six months. Significant advances can bemade and several of the projects have evolved into research programmes in their own right.

Summaries of a selection of projects submitted during the 2003 - 2004 course are given in thefollowing pages.

PROJECT TITLE: AUTHOR:

THE EFFECTS OF RESTRICTED COVER AND CONGESTED REINFORCEMENT S. BrownON THE MOVEMENT AND DISTRIBUTION OF AGGREGATE

A PRACTICAL EVALUATION OF THE USE OF SELF-COMPACTING CONCRETE G.F.R. EvansIN POWER-FLOATED INDUSTRIAL FLOORS

A STUDY OF VARYING SOURCES OF PORTLAND CEMENTS WITH B. HiscockSUPERPLASTICISING ADMIXTURES

A full list of earlier ACT projects, dating back to 1971 when the individual project was introduced as arequirement for the Advanced Concrete Technology Diploma examination, was published in the 2000 - 2001edition of the ICT yearbook. A list of subsequent reports is obtainable from the ICT.

Copies of the reports (except those that are confidential) are held in the Concrete Information Ltd (CIL) Libraryand these can be made available on loan. Subscribers to the CIL’s information service, Concquest, may obtaincopies on loan, free of charge. Requests should be addressed to: Concrete Information Ltd, 4 Meadows BusinessPark, Blackwater, Camberley, Surrey GU17 9AB.

ICT members may address their requests to: The Executive Officer, Institute of Concrete Technology, 4 MeadowsBusiness Park, Blackwater, Camberley, Surrey GU17 9AB. Copies can then be obtained from CIL free of charge.

8686

SUMMARYThis project examines the use of self-

compacting concrete (SCC) for industrial flooringapplications.

It includes a general background to thedevelopment of SCC and describes in detail arange of tests for measuring the fresh properties(workability, bleed and settlement) of theconcrete. These are those recommended in theEFNARC specification.

The process of selecting constituent materialsfor SCC is examined in detail, with particularemphasis on aggregates.

Five SCC mix designs were used in aprogramme of trial mixes. These included mixesbased on both Portland cement and acombination of Portland cement and fly ash. Themixes were tested using a range of rheologicaltests and also for compressive strength. Followingthe trials a mix containing Portland cement alone,with a 28 day compressive strength of 30 N/mm2,was selected for use in large scale trial panels (1.5m x 1.0 m x 0.50 m). This was compared to aconventional concrete of similar cement content.

Following placing the panels were power-floated. Visual observation combined withexamination of cores cut through the panels wasused to assess the effects of the finishing process.

It was concluded that:

• SCC mix design for industrial flooringrequires careful attention to the finefractions of the aggregate and fillers. Theamount of additions (extenders) should beminimised

• the use of a light vibrating beam prior topower-floating was beneficial for SCC

• the application of the power-float to theSCC should be delayed slightly relative toconventional concrete

• the use of fog sprays or plastic coveringimmediately after placing the SCCimproves the finishability

• overall, correctly proportioned SCC can befinished to the same standard asconventional concrete

• the cost of the SCC used in the trials wasonly about 10% higher than theequivalent conventional concrete.

A PRACTICAL EVALUATION OF THE USEOF SELF-COMPACTING CONCRETE INPOWER-FLOATED INDUSTRIAL FLOORS

By: G.F.R. Evans

THE EFFECTS OF RESTRICTED COVERAND CONGESTED REINFORCEMENT ONTHE MOVEMENT AND DISTRIBUTION OFAGGREGATE

By: S. Brown

SUMMARYThis project deals with the effect of coarse

aggregate size on the homogeneity of concrete inthe cover zone and in areas of congestedreinforcement.

Laboratory work involved casting both smallbeams (500 x 225 x 300 mm deep) and largerreinforced concrete columns (225 x 225 x 2100 mmhigh) The maximum aggregate size in the concretevaried from 19.0 mm to 26.5 mm and the cover tothe reinforcement or spacing between bars variedwithin the range 13 mm to 35 mm. This providedspecimens where the ratio of the depth of cover (orbar spacing) to the maximum aggregate sizeranged from 0.75:1 to 1.0:1 to 1.25:1.

Cores were cut from the hardened concrete toexamine visually the distribution of the coarseaggregate around the reinforcing bars. Although nohoneycombing was observed, it was apparent thatat a cover to aggregate size ratio of 1.0 or less, theconcrete surrounding the reinforcing bar wascharacterised by a lack of coarse aggregate and apaste-rich matrix. This in turn could increase the riskof cracking and reduce the resistance of the coverconcrete to the ingress of aggressive agents such aschlorides.

When the aggregate grading was altered toinclude more of the smaller (intermediate) sizefractions, the concrete surrounding the reinforcingbars became more homogeneous and less rich inpaste.

The conclusions drawn from this study were:

• the depth of cover or minimum spacingbetween reinforcing bars should be greaterthan 1.0 x the maximum aggregate size anda ratio of 1.25:1 is preferred

• sufficient spacer blocks should be used toensure that the correct cover is maintained

• the overall aggregate grading shouldinclude sufficient proportions of theintermediate size fractions to enable theconcrete directly surrounding the reinforcingbars to be homogeneous and not containexcessive amounts of cement paste

• concrete workability should be increased insections with congested reinforcement.

8787

A STUDY OF VARYING SOURCES OFPORTLAND CEMENTS WITHSUPERPLASTICISING ADMIXTURES

By: B. Hiscock

SUMMARYThe use of superplasticisers is now part of

established good concreting practice. However,their performance can vary and this report isconcerned with the interaction of Portlandcements from different sources together withthree types of superplasticiser.

Six differing cements were used, chosen forcompositional and physical variation. The cementscomplied with BS EN 197-1:2000.

The three superplasticers were representativeof sulphonated naphthalene and melamineformaldehyde condensate types together with thenew polyacrylic carboxylate or ‘comb’ type ofadmixture.

Admixture dosages varied from 500 ml to1500 ml/100 kg cement using ten mixes, one ofwhich was the control. A standard mixingsequence was used throughout.

Variation in concrete performance wasmanifested in plastic density, itself reflecting airentrainment and/or improved compaction.

The finer the cement the higher thesuperplasticiser dose required to achieve a givenworkability.

The effect of high alkali content in reducingworkability, particularly for polysulphonatedsuperplasticisers has been previously recorded.However, in this work the correlation wastenuous. A similar trend was found for the effectof varying the C3A content. The expectedcorrelation of low C3A with increased admixtureeffectiveness was not generally observed.

It is recommended that, due to theinconsistency of admixture performance withcement properties, trial mixes should be used toestablish their effectiveness on a case by casebasis.

88

ICT RELATED INSTITUTIONS & ORGANISATIONS

ASSOCIATION OFCONSULTING ENGINEERSAlliance House12 Caxton StreetLondon SW1H 0QLTel: 020 7222 6557www.acenet.co.uk

ASSOCIATION OF INDUSTRIALFLOORING CONTRACTORS33 Oxford StreetLeamington SpaCV32 4RATel: 01926 833 633www.acifc.org.uk

ASSOCIATION OF LIGHTWEIGHTAGGREGATE MANUFACTURERSWellington StRipleyDerbyshire DE5 3DZTel: 01773 746111

BRE (BUILDING RESEARCHESTABLISHMENT) LTDBucknalls LaneGarstonWatford WD25 9XXTel: 01923 664000www.bre.co.uk

BRITISH BOARD OF AGRÉMENTP.O.Box 195Bucknalls LaneGarstonWatfordHerts WD25 9BATel: 01923 665300www.bbacerts.co.uk

BRITISH CEMENT ASSOCIATION4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608700www.bca.org.uk

BRITISH PRECASTCONCRETE FEDERATION60 Charles StreetLeicester LE1 1FBTel: 0116 253 6161www.britishprecast.org.uk

BSI STANDARDSBritish Standards House389 Chiswick High RoadLondon W4 4ALTel: 020 8996 9000www.bsi.org.uk

BRITPAVEBritish In-Situ ConcretePaving Association4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 33160www.britpave.org.uk

CEMENT ADMIXTURES ASSOCIATION38a Tilehouse Green LaneKnowleWest MidlandsB93 9EYTel: 01564 776362

CEMENTITIOUS SLAG MAKERS ASSOCIATIONCroudace HouseGoldstone RoadCaterhamSurrey CR3 6XQTel: 01883 331071www.ukcsma.co.uk

CONCRETE ADVISORY SERVICE4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk

CONCRETE BRIDGE DEVELOPMENT GROUP4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 33777www.cbdg.org.uk

CONCRETE INFORMATION LTD4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608770www.concrete-info.com

CONCRETE REPAIR ASSOCIATIONAssociation House99 West StFarnhamSurrey GU9 7ENTel: 01252 739145www.cra.org.uk

THE CONCRETE CENTRE4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 606800www.concretecentre.com

THE CONCRETE SOCIETY4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk

CONSTRUCT4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 38444www.construct.org.uk

CIRIAConstruction Industry Research& Information Association

6 Storey’s GateWestminsterLondon SW1P 3AUTel: 020 7222 8891www.ciria.org.uk

CORROSION PREVENTION ASSOCIATIONAssociation House99 West StFarnhamSurrey GU9 7ENTel: 01252 739145www.corrosionprevention.org.uk

INSTITUTE OF CORROSIONCorrosion HouseVimy CourtLeighton BuzzardBeds LU7 1FG Tel: 01525 851771www.icorr.org

INSTITUTE OF MATERIALSMINERALS & MINING1 Carlton House TerraceLondon SW1Y 5DBTel: 020 7451 7300www.materials.org.uk

INSTITUTION OF CIVIL ENGINEERSOne Great George StreetLondon SW1P 3AATel: 020 7222 7722www.ice.org.uk

INSTITUTION OF HIGHWAYS& TRANSPORTATION6 Endsleigh StreetLondon WC1H 0DZTel: 020 7387 2525www.iht.org

INSTITUTION OFROYAL ENGINEERSBrompton BarracksChathamKent ME4 4UGTel: 01634 842669

INSTITUTION OFSTRUCTURAL ENGINEERS11 Upper Belgrave StreetLondon SW1X 8BHTel: 020 7235 4535www.istructe.org.uk

INTERPAVEConcrete Block Paving Association60 Charles StreetLeicester LE1 1FBTel: 0116 253 6161www.paving.org.uk

MORTAR INDUSTRY ASSOCIATION38-44 Gillingham StreetLondon SW1V IHUTel: 020 7963 8000www.mortar.org.uk

QSRMCQuality Scheme for ReadyMixed Concrete1 Mount Mews High Street, HamptonMiddlesex TW12 2SHTel: 020 8941 0273www.qsrmc.co.uk

QUARRY PRODUCTS ASSOCIATION38-44 Gillingham StreetLondon SW1V IHUTel: 020 7963 8000www.qpa.org

RIBARoyal Institute of British Architects66 Portland PlaceLondon W1B 1ADTel: 020 7580 5533www.architecture.com

SOCIETY OF CHEMICAL INDUSTRY14/15 Belgrave SquareLondon SW1X 8PSTel: 020 7598 1500www.sci.mond.org

UNITED KINGDOM ACCREDITATION SERVICE21-47 High StreetFelthamMiddlesex TW13 4UNTel: 020 8917 8400www.ukas.org.uk

UNITED KINGDOM CAST STONE ASSOCIATION4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608771www.ukcsa.co.uk

UNITED KINGDOM QUALITY ASH ASSOCIATIONRegent HouseBath AvenueWolverhamptonWV1 4EGTel: 01902 576 586www.ukqaa.org.uk

89

Published by:THE INSTITUTE OF

CONCRETE TECHNOLOGY4 Meadows Business Park,

Blackwater, Camberley, Surrey GU17 9AB

Tel/Fax: 01276 37831Email: ict@ictech.org

Website: www.ictech.org

ICT YEARBOOK 2005-2006

EDITORIAL COMMITTEE

Professor Peter C. Hewlett (Chairman)BRITISH BOARD OF AGRÉMENT LTD

& UNIVERSITY OF DUNDEE

Peter C. OldhamCHRISTEYNS UK LTD

Dr. Bill PriceLAFARGE CEMENT UK

Graham TaylorINSTITUTE OF CONCRETE TECHNOLOGY

Laurence E. PerkisINITIAL CONTACTS

Rights reserved. No part of this publication maybe reproduced or transmitted in any formwithout the prior written consent of the

publisher. The comments expressed in thispublication are those of the Author and not

necessarily those of the ICT.

ISSN 1366 - 4824£50.00

Engineering CouncilProfessional Affiliate

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Yearbook: 2005-2006

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4 Meadows Business Park, Blackwater, Camberley, Surrey GU17 9AB

Tel/Fax: 01276 37831Email: ict@ictech.org Website: www.ictech.org

THE ICTThe Institute of Concrete Technologywas formed in 1972 from theAssociation of Concrete Technologists.Full membership is open to all thosewho have obtained the Diploma inAdvanced Concrete Technology. TheInstitute is internationally recognisedand the Diploma has world-wideacceptance as the leading qualificationin concrete technology. The Institutesets high educational standards andrequires its members to abide by a Codeof Professional Conduct, thus enhancingthe profession of concrete technology.The Institute is a Professional Affiliatebody of the UK Engineering Council.

AIMSThe Institute aims to promote concretetechnology as a recognised engineeringdiscipline and to consolidate theprofessional status of practisingconcrete technologists.

PROFESSIONAL ACTIVITIESIt is the Institute's policy to stimulateresearch and encourage the publicationof findings and to promotecommunication between academic andcommercial organisations. The ICTAnnual Convention includes a TechnicalSymposium on a subject of topicalinterest and these symposia are wellattended both by members and non-members. Many other technicalmeetings are held. The Institute isrepresented on a number of committeesformulating National and InternationalStandards and dealing with policymatters at the highest level. TheInstitute is also actively involved in theeducation and training of personnel inthe concrete industry and thoseentering the profession of concretetechnologist.

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