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Yearbook: 2004-2005

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TheINSTITUTE OF CONCRETE TECHNOLOGY

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

Tel/Fax: 01276 37831Email: [email protected] 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.

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.concreterepair.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 ASSOCIATION156 Buckingham Palace RoadLondon SW1W 9TRTel: 020 7730 8194www.mortar.org.uk

QSRMCQuality Scheme for ReadyMixed Concrete3 High StreetHamptonMiddlesex TW12 2SQTel: 020 8941 0273www.qsrmc.co.uk

QUARRY PRODUCTS ASSOCIATION156 Buckingham Palace RoadLondon SW1W 9TRTel: 020 7730 8194www.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

97

Published by:THE INSTITUTE OF

CONCRETE TECHNOLOGY4, Meadows Business Park

Blackwater Camberley Surrey GU17 9AB

Tel/Fax: 01276 37831Email: [email protected]

Website: www.ictech.org

ICT YEARBOOK 2004-2005

EDITORIAL COMMITTEE

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

& UNIVERSITY OF DUNDEE

Peter C. OldhamCHRISTEYNS UK LIMITED

Dr. Philip J. NixonBUILDING RESEARCH ESTABLISHMENT

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.

Engineering CouncilProfessional Affiliate

3

Yearbook: 2004-2005


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 Ray Ryle 9 - 11

MILESTONES IN THE HISTORY OF CONCRETE TECHNOLOGY: 13 - 19THE HISTORY OF THE USE OF CONCRETE ADMIXTURES:By Nick Jowett

ANNUAL CONVENTION SYMPOSIUM: 21 - 100PAPERS PRESENTED 2004

ICT MEMBERSHIP DIRECTORY 101 - 113

RELATED INSTITUTIONS & ORGANISATIONS 115

55

PRESIDENT’S PERSPECTIVE

It is with pleasure that I introduce you to the2004-2005 Yearbook. Once again, Professor

Peter Hewlett and his editorial team have delivereda vibrant document, which I commend to you.

At the time of writing, late summer, the earlyspring days when we attended our AGM andannual convention (March 22nd and 23rd) seemlike only yesterday. Whilst the whole range ofspeakers at the symposium gave interesting andinformative talks, I was especially pleased to attendand listen to Professor Nick Buenfeld’s Sir FrederickLea Memorial Lecture - real food for thought, anda good insight into another concept of some of thecharacteristics of concrete as a material.

The technology and business environments inwhich our members operate remain dynamic, witha mix of challenges and opportunities. Industryconsolidation continues at a steady pace, as doesthe need to investigate and assess new materialsand processes. The Concrete Centre was launchedin September 2003 with its aim to provide a newfocus for excellence in concrete, which will enableinterested stakeholders to realise this fantasticmaterial’s full potential. I wish chief executive, IanCox and his team well in their endeavours.

The year has also seen the introduction of awhole raft of new, European standards replacingfamiliar British standards. They have introduced anew level of complexity for specifiers andproducers in several sectors of the concrete andassociated materials industries.

Whilst the new standards have not always beenwarmly welcomed, however, some see a positiveside to the changes, and, as a colleague andMember wrote in one concrete industry magazinearticle “over time, real benefits will be derived fromthe new Standards, such as improvements in thesustainability of concrete”. I am sure that thoseresponsible for the implementation of the newstandards affecting concrete and its specification,production, monitoring and use will all have aneffect on the resultant structure, unit or productand the end result will be to improve the publicperception of the material. The role of the concretetechnologist therefore remains central to the publicimage of concrete. This has not always been agood image, but one which seems to be graduallyimproving with time.

The demise of many of the earlier standardsgoes unnoticed; however one standard which hada major effect on concrete materials quality, andwas one of the first to be replaced by a Europeanstandard, should celebrate a centenary in 2004.British Standard Specification No. 12 (for Portlandcements) was first published in 1904 - the fruits ofthe then Engineering Standards Committee. Thisstandard became a world standard for cement,being copied, adopted and adapted by numerous

countries over many years. I do not know if themembers of the originating committee of fivecement producers, eight public authorities, fourcontractors, three consulting engineers, onearchitect and one chemist knew the position thisstandard would adopt in world cement production,but I suspect they knew the importance of theirlabours.

The work carried out by many of thecommittees of the ICT, often unnoticed andunrecognised (except by Council!), helps to ensurethat the Institute is able to react to, and benefitfrom, changes in the industrial climate. Survival asa species dictates that we must change or head fora world of Darwinian demise, sophisticated butdrowning in a sea of obscurity. I think it was HaroldWilson who said, “He who rejects change is thearchitect of decay”. So, many thanks to thoseinvolved in the planning and promulgating of theweb-based ACT course, which I hope and expectmany will benefit from. This is following in thefootsteps of the ICT ‘who we are’ CD produced bythe marketing committee and giving a good insightinto the careers and positions of some of ourtypical members.

The professional recognition of MICT by theEngineering Council is the result of work by ourimmediate past president, Dr Bill Price, and I wouldextend a recognition and thanks for this to Bill.Some of our members will be able to achievechartered status through this initiative. Manythanks also to members of other committees,without whose work no institute could function.

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.Residential courses are run in Ireland and SouthAfrica. A new part-residential/part home-basedcourse is run in Singapore. The worldwide web-based course is run from the UK, starting inSeptember of each year. Further details of thiscourse can be found on the website:www.actcourse.com and the ICT office has details of the others.

THE INSTITUTE

7

EXAMINATIONSCOMMITTEE

COUNCILTECHNICAL AND

EDUCATIONCOMMITTEE

FINANCECOMMITTEE

ADMISSIONS ANDMEMBERSHIPCOMMITTEE

SCOTTISH CLUBCOMMITTEE

EVENTSCOMMITTEE

MARKETINGCOMMITTEE

COUNCIL, OFFICERS AND COMMITTEES

R. RYLEChairman

G. TaylorSecretary

Dr. Ban Seng Choo

Dr. P.L.J. Domone

R. Gaimster

J. Lay

Dr. J.B. Newman

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

J.D. Wootten

J.C. GIBBSChairman

C.D. Nessfield

R. Gaimster

W. Wild

J. WILSONChairman

J.C. GibbsSecretary & Treasurer

L.R. Baker

R.C. Brown

H.T. Cowan

K.W. Head

G. Prior

R.A. Wilson

R. GAIMSTERPresident

Dr. B.K. MarshVice President

C.D. NessfieldHon Secretary

J.C. GibbsHon Treasurer

M.D. Connell

I.F. Ferguson

M.G. Grantham

R.E.T. Hall

P.C. Oldham

B.F. Perry

A.R. Price

Dr. W.F. Price

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

W. Wild

Dr. B.K. MARSHChairman

J.V. TaylorSecretary

L.K. Abbey

R.A. Binns

M.W. Burton

R. Hutton

J. Lay

C.B. Richards

A.T. Wilson

A.M. HARTLEYChairman

D.G. King(corresponding)

R.J. Majek

P.L. Mallory

C.D. Nessfield

M.S. Norton

B.F. Perry

G.Taylor

M.D. CONNELLChairman

G. TaylorSecretary

Dr. W.F. Price

J.D. Wootten

P.M. LATHAMChairman

G. TaylorSecretary

R.G. Boult

I.A Callander

I.F. Ferguson

P.L. Mallory

P.C. Oldham

B.C. Patel

G. Prior(corresponding)

EXECUTIVE OFFICER

G. TAYLOR

9

Q: How would you describe yourselfpersonally and professionally?

A: I can’t pretend that I had a serious careerplan that led me into the construction industry. Ileft school with 6 O levels, determined to dosomething involving chemistry. There were tworeasons, firstly it was my strongest subject and Ienjoyed it and secondly my careers advisor hadadvised me “no chance, your maths aren’t strongenough”. A job was found for me and I started tostudy chemistry on a day release scheme. Afterabout 2 years I discovered cars and girls and studystopped. After much sowing of wild oats I metmy wife, Joan; she decided that a change ofdirection was in order.

Q: What sort of age were you when thatchange occurred?

A: I was in my early twenties and still nocareer plan, no real ambitions. Looking back Isuppose my wife saw something in me that Ididn’t; I guess I’ve got her to thank. Just beforewe married I applied for a job in the chemistrylabs of Tunnel Cement and my life in theconstruction industry had begun.

Q: Did you at this point have anytechnical qualifications?

A: Not really, I had made a start at studyingchemistry but with the encouragement of my newboss and my wife I started again.

Q: Professionally, how would youdescribe yourself, a fair manager,technically profound or technicallyenthusiastic, harsh?

A: I think that I was fair, I certainly tried to be.I guess that there are some people who workedfor me who would describe me as harsh; difficultdecisions were necessary sometimes. The

recipients of such decisions usually saw only oneside of the story. I don’t think I would describemyself as technically profound but I was certainlyan enthusiast. In the early days in my job I metpeople who had been in the business muchlonger than me, some had a rather jaundicedview of materials such as admixtures and the like.I always tried to keep an open mind. If goodquality, high precision lab work proved that amaterial worked in concrete I was happy topresent the information and the case to mybosses. In the early days I did this withadmixtures, pfa and slag.

Q: By nature you are an opportunist - Idon’t mean that in a negative way - but youcan see opportunity, when all the facts maynot always be there. Very often there are tengood reasons for not doing something andonly one good reason for doing it. You implyyou have to believe in that level of self-belief. If you had to write a list of yourachievements, things you had changed, whatwould you put on your list?

A: I was responsible for the work of theTechnical Centre of RMC. That involved theCentral Laboratories, Technical Training, theTechnical Management Development Scheme andother bits and pieces. The job of Central Lab wasto carry out investigations and provide data thatcould be used by colleagues to improve theproduct. We were also expected to develop newproducts on the basis of perceived need. Inaddition we had to look at the impact of newtests on the business. This became important aswe became more involved in helping to writeEuropean Standards for materials. We were alsoinvolved in research associated with industryproblems such as alkali silica reaction (ASR) andthaumasite formation. So, I guess that the data

FACE TO FACEA personal interview with Ray Ryle

Ray Ryle retired some five years ago from the RMCGroup but his legacy and enthusiasm, well known inthe industry, remain. His contribution to the ICT andconcrete on a wider front have been exemplary. Evennow he retains the chairmanship of the ICT'sExamination Committee.

This brief interview with Peter Hewlett gives aninsight into the man and his contribution.

10

we provided helped to change our approach tomix proportioning, assisted in the introduction ofpfa and slag and in the increased use ofadmixtures. We provided data which helped us toprepare for some of the more exotic Europeantests and our work on topics such as ASR andthaumasite helped us to formulate policies to dealwith these and other problems. The results ofsuch research were usually provided toorganisations such as BRE Ltd (Building ResearchEstablishment).

Q: What about admixtures?A: In the early days the use of admixtures was

not very common. The ones that were availableworked in some localities but not in others. Atthat time there were about 20 to 30 differentcements in use across the UK. A fairly large scaleinvestigation helped us to select appropriateadmixtures for the right combinations. The use ofadmixtures increased slowly but nowadays theiruse is much more common, in fact I believe thatRMC now make their own.

Q: Did you go looking for ideas or didyou wait for ideas to come to you?

A: When I worked for RMC I didn’t havemuch time to go looking for ideas; there werealways things to do, problems to be solved;looking for ideas took a bit of a back seat, I guessI considered that we were problem solvers.

Q: How would you describe your career?A: I joined RMC in 1964 and retired in 1999,

35 years with RMC, all spent on the technical sideof the business. When I started I worked for JoeDewar, he was a great teacher, a great boss. I didall of the testing in those days, all hands-on stuff.When I retired I was directing the work of theTechnical Centre. I reckon that I had the best jobin the world. I looked forward to going to work.Not too bad for a guy who started out without agame-plan. I was fortunate to work for and withsome great people, a number of them had asignificant influence on my career. I shall beforever thankful to them.

Q: Do you think that concrete and acareer in concrete have a future?

A: Of course concrete has a future, it alwayswill have. It will change to meet new demands,new fashions, new circumstances, new materialsbut it will always be there. In the future I thinkthat it will be a more technically demandingproduct too, so in a way I’ve answered the secondpart of your question. If it’s more technically

demanding there will be a need for well trainedtechnologists too. Change is inevitable. I spent35 years in the business, not long in the grandscheme of things maybe but during that timethere have been major changes. From the point ofview of cement production, if we go back 15years there has been a reduction in the volumeproduced, perhaps an over provision, we haveseen a large number of plant closures. When Ijoined RMC there were something like 30 cementworks in the UK. By comparison there are only ahandful now, interestingly only one of thecompanies is now British owned, Rugby. Theothers are parts of French or Germanmultinationals. Who in the sixties would havepredicted that companies like Blue Circle wouldhave been swallowed up by a French company? Iguess that there are still a large number ofconcrete plants though, there were about 1000plants in total when I retired. The emergence ofthe Concrete Centre is an interestingdevelopment. Over a period of about 4 to 5 yearsit has obviously got to demonstrate its worth andmy understanding of the benchmark of success isthe additional tonnage of cement that is going tobe produced as a result of the existence of theCentre. I believe that they are putting the figureat about 1 million tonnes. That is about an 8%increase on current production. I guess that theemergence of a Concrete Centre that can pulltogether the disparate players in the game hasalways been an aspiration of the Concrete Society.However, the Concrete Society is a membershipdriven organisation so you have a band ofinterests, all with their differing enthusiasms andpreferences as opposed to being manufacturerand commercially benefit driven – very differentmotives. There is a need for both.

Q: Do you have any hobbies?A: Not really, I took up golf very late and even

though I enjoy it I’m not very good at it. I playtwice a week, once with my wife and once with aneighbour. I usually manage to beat both of thembut I struggle to go round in less than 95 strokes.Like many other retirees I also took up genealogy.I’ve researched my family tree back to 1750. Iliked to think of myself as a Welshman but I’monly second generation Welsh. My ancestors areall Cheshire folk. One was the first Bishop ofLiverpool and his son was Bishop of Winchesterand Dean of Westminster. Another ancestor wasSir Martin Ryle, Astronomer Royal and winner ofthe Nobel Prize for Physics in 1974-5. So, I havesomething of a pedigree buried in the genessomewhere.

11

Q: Are you a family man?A: Yes, I’ve got three children and nine

grandchildren. The children are making a successof their lives and the grandchildren are bright. Thetwo eldest have been classified as amongst thetop 5% in the country in recent exams. One ofthe others has just been accepted into one ofReading’s premier schools and one is somethingof a sportsman, recently coming first in a county-wide event. Yes I’m a proud family man.

Q: What would you say you failed at? A: Well some people have aspirations for

acquiring lots of money or being good at sport.Much to my father’s disappointment I was neververy interested in sport so I guess that I failed himin a way. If he was alive today he would beastonished at my current interest in golf butwould undoubtedly be highly critical of my game.I could have done better at some of the projectswe undertook at work, one in particular comes tomind and I guess that I could have tried a bitharder for some of the people that worked forme. However, in the wider university of life, Ithink I have made a mark.

Q: How do you see the future of the ICT?A: I don’t see the Institute ever being large in

terms of its membership, we seem to have stuckat about 600-800 members; having said that, themembership is a rather elite band and I wouldn’tlike to think that that level would be downgradedin any way. Increasing the number of grades ofmembership should help to increase membershipnumbers but it will be necessary to “advertise”the Institute and the benefits of membership to aswide an audience as possible. I’m sure that thenew President will have things like this in mind ashe commences his presidency. From time to timewe have considered the possibility of joiningforces with other like-minded organisations. Youand I explored the possibilities of the ICT and theConcrete Society working more closely together.We made a start at cooperating but didn’t getvery far. There did not appear to be enoughcommitment on either side. On reflection, andwith the advantage of hindsight, I’m not too surethat it was such a good idea anyway.

Q: Do you think that our industry valuesqualification?

A: I’ve been retired now for 5 years so I canonly comment on the past and I can only speakfrom the RMC point of view. They certainly didthen, thanks to guys like Bev Brown it was almostimpossible to move from Supervisory level to

Management level unless you had the ACTDiploma or could achieve it within a short time.Joe Dewar instituted a scheme that logged all ofthe qualifications of all of the members of theTechnical Department. Directors and GeneralManagers used the report to assess candidates forjobs. So, the answer to your question is yes, RMCdoes.

Q: Are you a good judge of people?A: I used to flatter myself that I was. Many

people who worked for me, at one time oranother, people that I had taken on, are now infairly senior positions in RMC, some in technicalpositions and some in commercial jobs. TheTechnical Management Development Scheme forwhich I was responsible took in graduates, manyof these are now in senior positions in RMC. Itwould be wrong to pretend that there weren’tfailures; of course there were, but on the whole Ithink I was reasonably successful.

Q: Professionally, looking back would youhave done anything differently?

A: Yes, I would have joined RMC earlier.

Q: Having retired is there anything youmiss?

A: Yes I miss the people. I worked with somefantastic people and met other equally nicepeople in the course of my job. Indeed being herewith you today chatting about the business makesme realise just how much I miss the people.

Q: Have you settled into retirement well?A: Undoubtedly.

Q: A contented man?A: Yes very contented.

Q: A further question, and this is for theworld at large. Have your jokes improved?The way you used to tell a joke, a hesitancythat creates a ripple of joyful apprehensionbecause nobody thinks you are going tofinish it, is it contrived?

A: No, I am just hopeless at jokes. We havevisitors coming to dinner tonight and I’ve beenwarned, please don’t tell any jokes.

Q: Do you have any final comments?A: Yes, I am both optimistic and grateful.

The first because concrete has a bright future andsecondly because I have been fortunate inmeeting with and working with good people. Ialso judge the business to be in good hands.

13

IntroductionConcrete admixtures are used today to modify

many properties of cement-based materials and to

correct some of the mechanisms of cement

hydration products. Ranges of chemicals are used

to speed up or slow down hydration; include or

exclude air; retain or inhibit water; reduce

shrinkage or cause expansion; make concrete

harder, stronger or, in some circumstances, such

as foam, weaker. They are used to increase

durability and decrease costs. Some processes,

such as self-compacting concrete, vibrated semi-

dry concrete products and ready-to-use mortar

systems, would be difficult or impossible without

specific admixtures.

The history of the development and use of

admixtures is a long one. This paper charts its

history from possible use of blood and urine,

through animal fats/stearates and lignins to the

latest generation of polycarboxylate ethers. The

scope of this paper does not include specific or

detailed chemistry or the properties or

performance of concrete admixtures.

First reported usage ofadmixtures

It has been reported that the Romans used

animal blood and urine to improve the properties

of the concrete used in their structures, many of

which, or at least the remains of them, still stand

around many parts of the countries bordering the

Mediterranean Sea. The author has tried to

determine the source of this information, but

there seems to be no recorded usage in classical

literature. Most information on Roman building

technology comes from Marcus Vitruvius Pollio

(90-26 BC), who, in de Architectura libri decem,

or Ten Books of Architecture, left a considerable

amount of information on the materials which

were being used in Roman construction at the

time: types of clays for brick making, various

sands for mixing with lime for mortars, the effects

of the nature of the stone to be burnt to produce

lime and the use of pozzolanic material in the mix

design. “If pit sand be used, three parts of sand

are mixed with one of lime. If river or sea sand be

made use of, two parts of sand are given to one

of lime, which will be found a proper proportion.

If to river or sea sand, potsherds ground and

passed through a sieve, in the proportion of one

third part, be added, the mortar will be better for

use” [3].

In addition to the use of ground potsherds, or

clay pottery, as mix improvers, pozzolanic

materials from volcanic deposits around Baiae and

Vesuvius are documented by Vitruvius, as are

properties of different types of stone for building,

together with information on properties of trees

for timber but he makes no mention of the use of

animal blood, urine or milk.

The legacy and longevity of Roman buildings

are well known. Examples, the more famous ones

such as the Parthenon, and lesser known but just

as interesting from a construction viewpoint such

as the Greek Theatre at Taormina in Sicily, rebuilt

by the Romans in several phases (Figure 1) can

still be studied.

Another possible source of the ‘factoid’ or

repeated information on the use of early

admixtures is another Roman building historian,

HISTORY OF THE USE OF CONCRETE ADMIXTURES.By Nick Jowett, Technical Manager, Oscrete Admixtures Division of Christeyns UK Ltd

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 some 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. The paper below outlines the history of arange of materials - admixtures - which have sometimes had a mixed press but todayare often an integral part of concrete and mortar mix designs.

MILESTONES IN THE HISTORY OF CONCRETE TECHNOLOGY

14

Caius Plinius Secundus, or Pliny the Elder (23-79

AD), in Book 36, Stone, of Natural History [2]. Pliny

gives a general mix design of 1 part lime to 4

parts sand, but he also makes no mention of the

use of animal products to improve the mix.

A latter-day source is an American paper in

1955 by Blanks and Kennedy, who report the use

of milk, blood and lard in ancient times [3]. The

origin of their information has not been

determined.

Balagopal Prabhu [4] reports that ancient

indigenous buildings in Kerala, a state in south

west India, were constructed using laterite blocks

bonded with a mortar of shell lime improved with

vegetable juices: time period is not given.

Presumably the fatty acids were used to provide

some plasticity to the harsh mortar resulting from

the use of broken and flaky shells.

The addition of sheep˙s wool oil, lanolin,

derived from the wool processing industry, to

waterproof lime renders and increase the weather

resistance, and lime washes to reduce rain

washing has been practiced in British buildings for

a number of centuries although the first use has

not been recorded.

The birth of Portland cement, following work

by Aspdin, Johnson and others in the 19th

Century, lead to the material being used in an

ever growing number of ways and situations. It

also became clear that the concrete produced,

whilst excellent for most aspects of constructions,

did have some properties that could be improved.

Technological advances in concrete, and the

properties of hydration, shrinkage, rheology, air

and water porosity, together with improvements

in construction methods, were made easier by the

addition of chemical admixtures.

Figure 1: A typical Roman mass concrete and clay brick masonry construction fromthe time of Vitruvius, the Teatro Greco (Greek Theatre) at Taormina, Sicily. It is oftenclaimed that for such constructions animal blood and milk were used to plasticise thelime concrete and mortar mixes.

Figure 2. Water repellents, to reducethe absorbancy and porosity ofcement-based building materials, arewidely used to improve quality andmaintain appearance. This example ofquality modern housing, in traditionalstyle, has such admixtures in the spilt-stone masonry blocks and cast stonewindow sills and lintels. Manyconcrete roof tiles also containadmixtures to increase strength andporosity and masonry mortars includeair entrainers/plasticisers and probablyset retarder. The concrete foundationsand floor slab concretes often containplasticiser or superplasticiser.

15

Water Repellents andPermeability Reducers

An early improvement was to reduce the

permeability, preventing the passage of water by

blocking the pores in the cement paste. The first

proprietary admixtures, metallic stearates sold as

‘waterproofers’ e.g. Pudlo and Novoid, appeared

towards the end of the 19th century, being sold

to builders for waterproofing walls, basements,

municipal swimming pools and sewerage works[5].

It is likely that the performances of some of the

admixtures were variable, partly because the

mechanism of permeability was not fully

understood and partly because the Portland

cements themselves were variable, especially

before 1904, when the publication of BS 12 lead

to the standardisation of some of the properties.

Whereas most of the early admixtures

disappeared from the market, Pudlo is still

commercially available and in use, Novoid

remained in use as a concrete waterproofer until

the 1930s and is today used as an insulator for

high voltage electricity cables - still apparently

similar to the original material, a blend of vinsol

resin and castor oil.

By the 1970s the mechanism of the

hydrophobic effect of materials such as stearic,

caprylic, capric and oleic acids, and salts of

stearate such as aluminium and calcium, was

fairly well understood and commercial water-

repelling admixtures such as Medusa found some

use, although on a limited scale. Greater use was

made, with an increased understanding of the

difference between those which acted simply by

blocking pores and those which reacted with

cement hydration products, with the advent of

hydraulically pressed semi-dry concretes for bricks,

block paving and decorative products in the

1970s. The control of efflorescence became an

important issue, combined with a new breed of

plasticisers or compaction aids for very low

workability mixes.

Accelerators Early Portland cements were rather more

coarsely ground than those of today, with a

concomitant slower rate of strength development.

It was found that the addition of calcium chloride

had the effect of increasing the early age

hardening: its first reported use in concrete is in

Germany in 1873, and a patent on such use was

issued in England in 1885[6]. A comprehensive

evaluation of the effects of this material was

carried out in the 1920s in America by Abrams[7].

A similar investigation in Sweden in 1938 by

Forsen[8] lead to an increased level of

understanding of the material. During this period

the use of calcium chloride - and knowledge of

the possible deleterious side effects - was not

uncommon in Britain, both in precast and in situ

work. In 1930 Grundy, Lecturer in Building at

Bournemouth Municipal College, wrote that the

use of CaCl2 at up to 2% would lower the

freezing point of water and give fresh concrete

some protection against frost but warned about

possible steel corrosion and increased

efflorescence[9].

Calcium chloride, generally complying with a

chemical specification which pre-dated any

general admixture standard, BS 3587:1963,

continued in general use, in the precast industry,

as a strength accelerator to permit earlier

stripping of moulds, and in in situ work, as a

‘frostproofer’ into the 1970s. This was despite

knowledge of the corrosion potential at doses

higher than recommended, and warnings of the

problems associated with misuse from

investigations and reports such as Bauml in

1959[10]. Whereas much use at normal dosages

was quite successful, and went and stays

unreported, some over-enthusiastic use and high

dosages caused some well publicised problems

with steel corrosion, allied with an increase in

drying shrinkage. The effect was that in the

concrete specification of the 1970s, BS CP

110:Part 1:1972, calcium chloride was banned

from use in concrete containing reinforcing steel.

This lead to the effective banning of almost all

admixture usage by many specifying and

approving authorities and set the development of

associated technology back by a considerable

amount. This ban was seen by many as blocking

development. In 1980 Diamond wrote that “the

complete prohibition of chloride from concrete

would be a technological over-reaction”[11]. This

prohibition was to have a significant effect on

accelerator usage, as accelerators were “divided

into two categories - CaCl2 which has the lion’˙s

share of the market, and everything else.“

It is unfortunate that the use of CaCl2 can give

rise to unwanted side effects: other, ‘safe’,

materials which have been developed and used as

accelerators have not been found to be as

effective. Calcium formate, aluminium chloride,

potassium carbonate and sodium nitrite have

been used but generally with limited efficiency

and sometimes uneconomical costs: the

performance of triethanolamine is not linear to

dosage and its use is still generally limited to

adjusting the characteristics of formulations.

Experience of the use of efficient

superplasticisers and the use of reduced water

additions has resulted in such materials being

used to accelerate strength, and many concrete

producers now use superplasticisers as effective

accelerators.

Air Entrainers The construction of engineered roads and

pavements in Europe began with the Romans.

Whereas many were of stone, Vitruvius records

the use of lime/pozzolan mortars for bedding and

jointing clay tiles, recommending that ‘at the

approach of winter every year it should be

saturated with the dregs of oil, which will prevent

the frost affecting it’ [1].

In the early decades of the 20th century

concrete was becoming more widely used for the

construction of roads and pavements. Apart from

improvements in design, necessitated by the

increase in traffic and vehicle weight, it was found

that stretches of some roads in the northern USA

had withstood the effects of repeated cycles of

freeze-thaw and the application of de-icing salts

better than others. One of the major cement

manufacturers, the Universal Atlas Cement

Company, working with the New York State

Department of Public Works, recognised that

materials which had been used to help disperse

cement grains during grinding were having the

beneficial effect of increasing durability by the

incorporation of minute air bubbles dispersed

throughout the mix.[12] At this time chemical

manufacturing company Dewey and Almy had

been supplying beef tallow derivatives and wood

resins as grinding aids and, following the

investigations, began producing and supplying air

entraining agents, based on the above materials,

as concrete admixtures. Further field investigations

included the construction of trial lengths of air

entrained concrete roads. T. C. Powers concluded

that the mechanism of the minute air bubbles had

a significant effect in allowing the expansion of

ice crystals which would otherwise disrupt

capillaries [13]. Powers also did many further and

more detailed investigations into durability and air

entrainment.

The most widely used materials for

commercially available air entrainers were based

on abietic and pimeric acids, produced from wood

resins extracted from pine stumps and neutralised

with caustic soda: the resulting Vinsol resin

became universally used. Concrete benefits were

found to include improvements in workability,

cohesion and reduction of bleed water. British

use of the materials followed the American

experiences, although at a much slower rate, and

proprietary materials such as Airen and A.E.1

started to be used in pavements and roads. It was

stated by Murdock and Blackledge that air

entrainers were not used to the same extent in

Britain probably because of the customary use of

lower water contents than in the USA [14].

The use of air entrained concrete has increased

steadily since the 1950s, as the significant

benefits in durability, finish and appearance at

minimal cost, allied to the commercial advantages

of increased mix volume, are readily perceived.

With the reported and expected reduction in

availability of the raw materials to produce Vinsol

resin, synthetic alternatives were developed by

admixture manufacturers. The use of alkyl

sulphates, olein sulphonates and amido betaines

is now widespread, and whilst Vinsol resin-based

air entrainers are still produced, the volumes of

the synthetic alternatives continue to increase.

The synthetic materials offer some improvement

in size distribution, spacing and stability over the

naturally occurring, processed material.

Plasticisers and SuperplasticisersThe use of plasticisers, or water reducing

agents, to minimise the amount of mix water for

concrete workability began fairly simultaneously in

the early 1930s in Great Britain, Germany and the

USA. The American use of waste sulphite liquor in

1932 to increase mix fluidity and the granting to

EW Scripture, Jr., of an American patent for this is

reported by Mielenz [15]. Meanwhile a German

industrialist, K.Winkler, was granted, in 1932,

British and German patents [16] for water soluble

salts of hydroxylated carboxylic acids used to

achieve reductions in water requirement and

increase in strength. Use of such material appears

to have been readily accepted in the USA, helped

by government sponsored investigations lead by

Bryant Mather [17] and others, but adoption of the

technology was much slower in Britain, being

slow to increase pre-war and through the 1950s

and 1960s. The problems associated with the

misuse of calcium chloride referred to earlier

undoubtedly helped retard this progress. Papers

presented at international symposia on cements

and admixture usage held in Brussels in 1967 [18]

and Tokyo in 1968 [19] helped increase general

awareness of technological benefits and

advantages of admixtures to concrete as a

material.

1717

Rixom reported that in 1975 the proportion of

concrete containing admixtures in the UK was

12%, compared to 60% in Germany, 70% in the

USA, and 80% in Australia and Japan [20]. As it can

be presumed that much of this 12% is admixtures

which are specified to fulfil a particular function

e.g. air entrainment, waterproofing and

accelerating, it is apparent that little use was

being made of plasticisers or water reducers at

this time. The calcium/sodium lignosulphonates

and hydroxylated carboxylic acids which were in

use, giving a water reduction of 5 to 15%, had

limited effectiveness. Whereas precast concrete

product manufacturers, with a limited number of

mix designs and a smaller number of mixing

operatives, were able to make use of this, ready

mixed concrete producers, with a much higher

number of mix designs, mixing operatives and

needing approval for each supply contract, were

less able to do so.

Although growth of usage during this period

was slow, the admixtures themselves were

undergoing some improvement as chemically

oriented admixture manufacturers increased

product consistency with raw material selection,

manufacturing processes and product quality

control. Industrial training courses, such as those

held by the Cement and Concrete Association,

and greater experience gained by contractors and

client authorities lead to a small but increasing

rise in general acceptance of water reducing

agents for both quality improvement and mix cost

benefits. This growth was helped by the

development of properly designed admixture

dispensing systems and equipment such as the

Aliva MK1 which replaced earlier adaptations of

liquid measuring devices and hand-measuring

systems such as the measuring cylinder and the

milk bottle.

Advances in admixture research and

technology in the late 1960s and the need for

higher levels of water reduction and workability

without increased segregation and retardation

resulted in the almost simultaneous development

and launch of the ‘superplasticiser’ or high range

water reducer. Based partly on work carried out in

America in the 1930s by GR Tucker, who patented

a compound produced by condensing

formaldehyde with naphthalene sulphonic acid

and neutralising the condensate to form water-

soluble salts which gave good reductions in water

content [21] but with improvements to the

performance and tolerance of varying doses, the

Kao Soap Company, Japan, started to market a

superplasticiser in Britain for which a British

patent had been granted in 1972 [22] under the

name ‘Mighty 150’. Development in Germany

resulted in SKW Trostberg promoting admixtures

with a similar performance, based on sulphonated

melamine condensate, Melment L10.

These new materials permitted the production

of concrete with water reductions of 20-25%,

very high strength or very high workability (200

mm slump, or 510-620 mm flow value) and

‘flowing concrete’ began to show some major

advantages in construction. In 1978 an

international symposium was held in Canada at

which a number of papers were presented

discussing the performance, benefits and

potential of these new materials; British

production of flowing concrete was reported by

Hewlett as being 130,000-140,000 m3 at this

period [23].

One property which needed addressing and

improving was slump loss of high workability

concrete. Edmeades and Hewlett suggested that

the addition of heptonate retarder to the

formulation was effective in maintaining flow for

most situations [24]. Adjustments and

improvements to superplasticising admixture

formulations continued as properties such as

stability, effect on cement setting time and

strength development were modified.

Admixtures based on the naphthalene

sulphonate formaldehyde condensate (NSFC) and

melamine sulphonate formaldehyde condensate

(MSFC) were offered by British and other

admixture suppliers to the construction industry

and concrete product manufacturers. As with the

earlier generation of plasticisers, precast concrete

product manufacturers were more keen to realise

and adopt the benefits of the high water

reduction, lower water/cement ratios and high

flow values than the ready mixed concrete

industry, who had to re-sell the benefits to

contractors and specifiers. Hence flowing or high

workability concrete production maintained a

fairly small percentage of concrete output

through the 1980s and into the mid 1990s.

New Generation Superplasticisers(Hyperplasticisers)

The limitations of the NSFC and MSFC

superplasticisers were examined by admixture

manufacturers, with the intention of producing

materials which would be able to impart full

fluidity to a concrete mix without the unwanted

side effects of segregation, premature workability

18 18

loss and strength retardation. It was also

considered that the development of such

admixtures could be used to produce very high

strength concrete, in excess of 100 MPa.

To enable these characteristics - a high

workability with very efficient cement and fines

dispersion but without segregation - a new

generation of superplasticisers, based on

polycarboxylate ethers, was developed. Initially

advocated by Professor Okamura at Tokyo

University in 1989. Early successes in Japan, using

polycarboxylates combined with beta-1,3- Glucan

for viscosity, to produce self-compacting concrete

(SCC), were subsequently reported by workers

such as T Shindoh and Y Matsuoka [25] , Tanaka et

al [26] and others. Polysaccharide based viscosity

agents such as Welan, Xanthan and Guar gums

were compared to assess optimal effects on

viscosity [27]. After several major constructions

utilising the new technology were successfully

completed in Japan, concrete industry researchers

in Sweden were some of the earliest to appreciate

the potential of SCC, to be immediately followed

by British researchers.

The advent of polycarboxylate ether

(sometimes termed comb polymer)

superplasticisers saw a surge in interest in the

possibilities of SCC and the beneficial effects of

the elimination of vibration for health and safety

reasons. Some construction contractors also saw

merit in handling, placing and finishing such

concrete. This safer and more environmentally

acceptable aspect also allowed precast companies

to produce structural and decorative elements

without using internal or external vibration, such

as vibrating table lines, to eliminate air voids. The

highly effective and efficient dispersal of the

cement particles by polycarboxylates and the

potential for much greater water reductions - up

to 40% whilst maintaining workability - than the

earlier MSFC and NSFC superplasticisers, gave rise

to some significant changes to concrete mix

design and handling. Significant cement content

reductions, for economy, together with much

faster strength development, gave advantages in

precast concrete factories.

The availability of polycarboxylate chemistry to

admixture producers allows true chemical

engineering of the organic molecule to take

place. Various modifications can be made,

including lengthening and shortening of the

polymer backbone, an increase or decrease in

both the number and length of grafted side-

chains and modifications to the degree of steric

charge produced. These changes give rise to

benefits in the way in which the resultant

concrete mixes are handles and used, and

properties of the finished product or structure.

AcknowledgementsAssistance and contributions are gratefully

acknowledged from the following persons: David Ball, Zak Barrett, Professor Peter Hewlett,Les Hodgkinson, Sandra Jackson.

References

1. Marcus Vitruvius Pollius. de Architectura libridecem. (Ten Books of Architecture). Trans.W Thayer, electronic publication.

2. Pliny the Elder. Natural History. Book 36,Stone. Loeb Classics Edition, HarvardUniversity Press.

3. Blanks, Robert F and Kennedy, Henry L. TheTechnology of Cement and Concrete, Vol 1,Concrete Materials, John Wiley and Sons,New York, 1955.

Figure 3. Special superplasticisers anddispersion aids improve the productionrate of semi-dry concrete productssuch as block paving and allow qualityto be maximised. Appearance ismaintained by controlling andminimising the occurrence of saltsforming efflorescence.

1919

4. Balagobal T S Prabhu. Kerala Architecture.Essays on the Cultural Formation of Kerala.Ed. Cherian, PJ. Electronic publication.

5. Treatise on Reinforced Concrete. Pub.Cassells, London, 1913.

6. Skalny, J and Maycock, JN. ‘Mechanisms ofAcceleration of Calcium Chloride: AReview’. Journal of Testing and Evaluation.Vol. 3, July 1975.

7. Abrams, Duff A. ‘Calcium Chloride as anAdmixture in Concrete’. Proceedings,American Society for Testing and Materials,Vol. 24, 1924.

8. Forsen, L. ‘The Chemistry of Retarders andAccelerators’. Proceedings, 2nd InternationalSymposium on the Chemistry of Cement(Stockholm, 1938).

9. RFB Grundy. ‘Builders Materials’. Longmans,Green and Co, London, 1930.

10. Bauml, A. ‘The Effect of ConcreteAdmixtures on the Corrosion of SteelReinforcement in Concrete’. Zement-Kalk-Gips. Vol 7. 1959.

11. Diamond, S. ‘Accelerating Admixtures’Proceedings of the International Congresson Admixtures. London, April 1980.

12. US Department of Transportation, FederalHighway Administration, Air-Entrainment.Materials Group. Information Paper. 2004

13. TC Powers. Portland Cement AssociationBulletin, No. 90, Chicago, 1958.

14. LJ Murdock and GF Blackledge. ConcreteMaterials and Practice. Fourth Edition. Pub.Edward Arnold, London. 1968.

15. RC Mielenz. ‘History of ChemicalAdmixtures for Concrete’. ConcreteInternational, April 1984, pp 40-53.

16. Winkler K. British Patent No. 379,320,1932, and German Patent dated May1932.Â

17. B. Mather. ‘Effects of a Proprietary ChemicalAdmixture on the Properties of Concrete’.Technical Memorandum No. 6-390. USArmy Engineer Waterways ExperimentStation, Vicksburg, 1961.

18. International Symposium on Admixtures forMortar and Concrete. Brussels, 1967.

19. 5th International Symposium on theChemistry of Cement. Tokyo, 1968.

20. MR Rixom. Chemical Admixtures forConcrete. Pub. E & FN Spon Ltd, London1978.

21. RG Tucker. US Patent No. 2,141,569. 1938.

22. British Patent 1286798. Kao Soap Company.

23. PC Hewlett. Experiences in the use ofSuperplasticizers in England.Superplasticizers in Concrete Symposium.Ottowa, Canada. May 1978.

24. RM Edmeades and PC Hewlett.Superplasticised concrete-high workabilityretention. Proceedings of the InternationalCongress on Admixtures. London, 16-17April 1980.

25. T Shindoh and Y Matsuoka. Development ofCombination-Type Self-CompactingConcrete and Evaluation Test Methods.Journal of Advanced Concrete Technology,Vol 1, April 2003.

26. Y. Tanaka, S Matsuo, A Ohta, and M Ueda.A New Admixture for High-PerformanceConcrete.

27. N Sakata, K Maruyama and M Minami. Basic Properties of Welan Gum on Self-Consolidating Concrete. ProductionMethods and Workability of Concrete. Pub. E & FN Spon, London, 1996.

21

ANNUAL CONVENTION SYMPOSIUM: PAPERS PRESENTED 2004

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 2004 Symposium was:

CONCRETE STRUCTURES - get it right or put it right Chairman: Professor John Bungey MSc, PhD, DIC, CEng, FICE, MIStructE, FInstNDT

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

APPLYING LESSONS FROM CARDINGTON Dr. Richard MossTO ST GEORGE WHARF BSc(Hons), PhD, DIC, CEng, MICE, MIStructE

BRE Ltd

CANARY WHARF - Mr. Mike WetherillCONTROL OF CONCRETE QUALITY BA, IEng, AMICE, FIQA, FICT

Canary Wharf Contractors LimitedMr. Rey EmeryHanson PremixMr. Ian HudsonSandberg LLP

A CONCRETE DOCTOR’S CASEBOOK Mr. Deryk Simpson– THE WORK OF THE CONCRETE BSc(Hons), CEng, MICE, FCSADVISORY SERVICE The Concrete Advisory Service

WHERE ARE WE GOING WITH Mr. Michael Grantham TESTING OF STRUCTURES? BA, EurChem, CChem, FRSC, IEng, MIQA, MICT

MG Associates Construction Consultancy Ltd

AN OVERVIEW OF CURRENT Mr. Bob BerryREPAIR SYSTEMS Concrete Repair Association

COATINGS AND THEIR BENEFITS Dr. Shaun HurleyBSc, PhD, MRSC Taylor Woodrow

A CONSULTING ENGINEER’S VIEW Professor Peter RoberyOF REPAIRS BSc, PhD, CEng, MICE, MICT, MCS

FaberMaunsell

Professor Nick BuenfeldPhD, MSc, BSc, DIC, CEng, MICE, MICTImperial College. London

THE SEVENTH SIR FREDERICK LEAMEMORIAL LECTURE

ADVANCES IN PREDICTINGTHE DETERIORATION OFREINFORCED CONCRETE

2323

Nick Buenfeld is Professor of

Concrete Structures at Imperial

College London. He

established and heads the

Concrete Durability Group, a

multi-disciplinary group of

scientists and engineers aiming to advance

understanding of deterioration processes and so

develop more effective methods of design,

assessment and repair of concrete structures. He

has authored/co-authored around 140

publications in refereed journals and conference

proceedings and has been a member of many

technical committees producing guidance

documents for industry. He undertakes

consultancy assignments linked to his research

interests, providing durability guidance to the

designers and constructors of major projects.

ABSTRACTDemands for enhanced technical

performance, safety, economics and

environmental protection create a need to be

able to determine, at the design stage or in-

service, with an acceptable degree of confidence,

the projected service life of concrete structures.

This requires models of reinforced concrete

deterioration. This paper presents a view of the

current state of the art, presenting examples of

the main model types to highlight generic

advances and to indicate the main challenges to

future progress.

KEYWORDSConcrete structures, Reinforced concrete,

Durability, Deterioration, Service life, Prediction,

Modelling, Reinforcement corrosion, Chlorides,

Carbonation.

INTRODUCTIONMost of the world’s built environment is

formed from concrete and concrete is the most

heavily consumed material after water, way ahead

of other construction materials. Close to one

cubic metre per person on the planet is placed

each year. The use of concrete is increasing and

this is expected to continue[1].

The constituents of concrete are widely

available, it is easy to make, strong and stiff in

compression, flexible in form and scale and of

low cost. These strengths make it unique and

irreplaceable for many structural applications.

The very large majority of concrete structures

have adequately fulfilled their purpose, but

concrete is a sensitive material. For example, it is

sensitive to minor constituents and poor

workmanship, it is weak in tension and

susceptible to cracking. The fact that concrete is

a complex porous chemical material, usually

reinforced with steel and exposed to a wide

range of environments, results in reinforced

concrete being vulnerable to a larger number of

deterioration mechanisms than most other

construction materials.

The consequences to society of premature

deterioration are enormous. First, deterioration

may compromise safety. Deterioration has

occasionally caused concrete structures to

collapse. For example, the top deck of Piper’s

Row car park, a 30 year old multi-storey structure

in Wolverhampton, collapsed early one March

morning[2]. If this had occurred a few hours later

there would almost certainly have been fatalities.

The main cause was weakening of the concrete

due to frost action. Less dramatic failures may

still represent a serious safety hazard. For

example, fragments of concrete cover spalling, as

a result of reinforcement corrosion, from a multi-

storey building on to pedestrians below. Second

are the financial consequences of premature

deterioration. In developed economies around

50% of construction spending is on maintenance

and repair, a large proportion of this on concrete

structures. In both the UK and US around 5% of

GDP is spent on maintenance and repair, as

opposed to around 3% on defence. We must

not forget lost productivity, which for roads in the

UK is estimated to be up to ten times the cost of

the work done. Third are the environmental

consequences. If structures have to be replaced

early we are unnecessarily consuming raw

materials and producing CO2 and construction

waste. Finally, premature deterioration has a

negative influence on our quality of life through

THE 7th SIR FREDERICK LEA MEMORIAL LECTURE

ADVANCES IN PREDICTING THE DETERIORATION

OF REINFORCED CONCRETE

Professor Nick Buenfeld PhD, MSc, BSc, DIC, CEng, MICE, MICT

Imperial College, London

2424

the unattractive appearance of deteriorating

concrete, the inconvenience of loss of use and

the disturbance caused by repair or replacement.

Concrete is thermodynamically unstable and

deteriorates in most environments. The

challenge is to ensure that the rate of

deterioration is not so rapid as to give problems

within the required service life.

THE NEED FOR SERVICE LIFE PREDICTION

In most new projects, durability is “taken care

of” by selecting materials, mix proportions

(notably water/cement and binder content), cover

depth and curing regime compliant with code of

practice requirements for a particular exposure

environment. The code of practice requirements

are generally based on a specific life. The new

British Standard, BS8500, which complements the

European Standard for concrete (BS EN 206-1

2000), is more flexible than most in that while it

is primarily based on 50 years, for a limited

number of scenarios it extends to 100 years.

Design code recommendations are generally

based on previous code clauses, tightened where

case studies have shown problems.

Unfortunately there are many practical situations

that are not covered by existing codes. First, they

do not cover some important classes of structure.

For example tunnels, which, as will be seen later,

are often exposed to an unusually aggressive

environment. Second, longer lives than those

adopted by the codes are generally required for

structures such as important public buildings,

churches, major bridges and nuclear waste

storage facilities. Third, current codes of practice

do not take account of additional protective

measures such as special admixtures (for example,

integral waterproofing admixtures and corrosion

inhibitors), surface coatings or cathodic

protection. The fact that codes are developed

based on experience of successful performance

acts as a barrier to the adoption of new materials

that may be superior to those in common use.

Demands for enhanced technical performance,

safety, economics and environmental protection

create a pressing need to be able to determine, at

the design stage and with an acceptable degree

of confidence, the projected service life of any

important concrete structure such as a major

bridge or tunnel, or a nuclear waste containment

facility[3]. Such a predictive capability would also

provide a more rational basis for developing

future codes of practice. There is also a need to

predict the residual life of existing structures, with

and without the benefits of different life-

enhancing treatments.

A UK highway bridge is required to remain

serviceable for 120 years, a new cathedral often

400 or 500 years and the required life of a

radioactive waste storage facility could be

measured in millennia. However, the history of

reinforced concrete is barely 100 years long and

during this time cement chemistry has changed

and mineral additions and chemical admixtures

have been introduced and become commonplace.

Consequently, we are generally required to

predict way beyond our experience (Fig. 1).

This fact is often emphasised on high profile

projects where the architect or consulting

Figure 1: Required lives and experience of concrete materials and structures.

2525

Table 1: Deterioration mechanisms encountered according to structure type(modified from [3]).

engineer would like to use the latest materials

that have been shown to enhance short-term

performance, despite the project requiring an

unusually long service life.

This paper presents a view of the current state

of the art of predicting the deterioration of

concrete structures. A single paper on this wide-

ranging subject cannot be comprehensive. The

aim is to present examples of the main model

types to highlight generic advances and to

indicate the main challenges to future progress.

DETERIORATION MECHANISMSThe are at least 10 different deterioration

mechanisms that may affect concrete structures;

the main ones and the types of concrete structure

commonly affected are presented in Table 1. The

mechanisms that frequently control service life are

indicated by darker shading. It is convenient that

it is generally found that there is only one

controlling deterioration mechanism as this

reduces the need for multi-mechanism models.

Clearly, many of the mechanisms indicated as

relevant in Table 1 can be discounted where the

aggressive agent involved is not part of the

exposure environment. For example chloride-

induced reinforcement corrosion is indicated as a

critical mechanism for tunnels and bridges, but if

sea-water and chloride-based de-icing salts are

not present (and chlorides were not present at

detrimental levels in the original constituent

materials), then chloride-induced corrosion can be

discounted. Similarly, frost action and sulfate

exposure may not be issues. Alkali-aggregate

reaction is indicated as a common problem but,

of course, can be avoided through appropriate

material selection.

With the exception of abrasion, all of these

deterioration mechanisms involve transport of

ions, gas or water. All except abrasion and frost

action also involve chemical reactions between

the penetrating species and constituents of the

concrete. All of them involve microstructural

changes leading to degradation of the physical

properties of the concrete. The fact that each

deterioration mechanism involves several different

contributory processes results in accelerated

testing being of very limited value in service life

prediction. Generally measures to accelerate one

process do not accelerate the other processes

involved to the same extent such that the overall

mechanism is distorted in relation to natural

exposure. For example, laboratory experiments to

accelerate sulfate attack have generally been

undertaken at elevated temperatures, but it is

now recognised that this eliminates the possibility

of the thaumasite form of sulfate attack[4].

There are too many deterioration mechanisms

to consider them all in any detail in this paper.

The fact that several similar processes are involved

in most of the deterioration mechanisms justifies

taking one or two deterioration mechanisms as

examples to highlight the issues that are relevant

more generally. Reinforcement corrosion,

induced by either chloride penetration or

carbonation, is the most widespread and costly

2626

deterioration mechanism and is selected for more

detailed consideration. End of service life due to

corrosion-induced deterioration may be defined

by depassivation, cracking, spalling or structural

failure. This paper focuses on predicting

deterioration and does not dwell on failure

criteria. For new structures, the objective of

durability design is usually to ensure that the time

to depassivation (t1) is no less than the required

life and so prediction of t1 is the target of the

examples presented here.

TYPES OF MODELIt is instructive to divide models for predicting

the deterioration of concrete into the categories

of empirical, semi-empirical and mechanistic so

that differences in approach can be highlighted.

An empirical model makes predictions based on

previously observed relationships between

concrete composition and exposure conditions

and the consequent degree of deterioration of

concrete, without consideration of the processes

involved. In contrast, in a mechanistic model,

individual transport processes and chemical

reactions are mathematically modelled and their

individual effects combined. Semi-empirical

models lie in between empirical and mechanistic

models. They generally take the form of an

equation in which the degree of deterioration is

related to a quasi-transport coefficient (largely

dependent on the concrete properties)

representing the combined effects of individual

transport processes and chemical reactions,

exposure time and possibly one or more

constants accounting for the influence of the

exposure environment.

EMPIRICAL MODELS

GeneralAn empirical model makes predictions based

on previously observed relationships between

concrete composition and exposure conditions

and the deterioration of concrete, without

invoking an understanding of the scientific

reasons for the relationships. Most models of this

type have been based on curve fitting to the

results of a single exposure trial in which a range

of concretes have been exposed in a particular

environment and performance (most commonly

carbonation depth or chloride profile) has been

monitored. Because individual studies are almost

always undertaken at a single geographical

location, it has rarely been possible to quantify

adequately the effects of environmental

parameters. This might be possible if data from

different studies from around the world could be

combined, but the variables and their values in

different studies have rarely been the same,

rendering conventional methods of data analysis

of limited value.

A large amount of data concerning the effects

of concrete composition and exposure

environment on carbonation depth, chloride

profile and, to a lesser extent, indicators of some

of the other deterioration processes, is being

generated by condition surveys of concrete

structures. This type of data is particularly

valuable because it incorporates the effects of

some aspects of real construction that may affect

durability, but that are difficult to reproduce in

the laboratory such as slip-forming and heat of

hydration effects in thick elements.

Unfortunately it is extremely unusual to find

several structures having all key variables except

one set at the same level, enabling the effect of

the variable to be quantified. Furthermore, with

relatively old structures it is rare to have

comprehensive information concerning the

concrete mix constituents, proportions and curing

regime, again limiting the useful information that

can be extracted using conventional methods.

An advance in this area has been the use of

neural networks to combine multi-variable data

from different sources and to analyse it to enable

the effects of individual variables to be quantified

and predictions for new scenarios to be made[5].

This is equivalent to finding the best-fit surface to

data in multi-dimensional space, as defined by

the known variables and the parameters to be

predicted. Neural network models are the most

sophisticated and powerful empirical models

available and are therefore highlighted here.

Neural NetworksA neural network (NN) consists of a number of

neurons (processing units) grouped together in

layers and connected to form a net-like structure

(Fig. 2). Neurons in an input layer describe the

influencing factors, i.e. concrete constituents and

environmental parameters. An output layer gives

the response (e.g. carbonation depth or chloride

content) to a set of inputs. In addition, there is

usually at least one hidden layer. Neurons receive

the output signal from many other neurons. A

neuron calculates its own output by determining

the weighted sum of its inputs, generating an

activation level and passing this through a

2727

transfer function. Two neurons communicate via

a connection, and the strength of the connection

between two neurons is its weight.

NNs are trained by presenting a series of

records, i.e. inputs and the corresponding desired

output. The most popular learning method is by

example and repetition; the NN is presented with

a set of records and each time an input is

presented the NN predicts an output. This is

compared with the correct output and, if it is

incorrect, the NN adjusts the weights. This

training process is repeated until

the discrepancy is minimised.

The NN is then tested to assess

its precision in predicting for

cases not previously seen by the

NN and, if adequately accurate,

the NN can then be used to

make predictions.

Neural NetworkModelling ofCarbonationThe high pH of concrete

protecting embedded steel from

corrosion is neutralised by

atmospheric carbon dioxide. This

carbonation process may be

envisaged as a front gradually

penetrating the concrete, and life prediction

involves predicting the time for this carbonation

front to reach the reinforcement, enabling

corrosion to occur. The carbonation front is

usually measured by spraying a fractured section

through the concrete with phenolphthalein, a pH

indicator.

A literature search located 88 papers (listed in

[6]) reporting around 7000 carbonation depth

measurements and corresponding key variable

input values. NNs were formulated based on

Figure 2: Structure of neural network to predictcarbonation.

Table 2: Inputs to carbonation depth neural network model[6].

2828

training with data from 68 of the papers and

testing was done using the data from the other

20. They were developed using the back-

propagation algorithm, delta learning rule and

sigmoid ((1+e-x)-1) transfer functions using

NeuralWorks Professional II/PLUS. The optimum

NN used 39 inputs, as detailed in Table 2, and

involved data from a few accelerated

programmes in addition to data from natural

exposure trials and surveys of structures. There

were 2 hidden layers of 39 and 19 neurons

respectively. The average error (absolute

error/measured value) in predicting the test data

was 27.5% and the error was smaller for the

more critical cases where the carbonation depth

was large. Predictions for real structures were as

accurate as for naturally exposed specimens.

Much of the error is associated with the local

variability of concrete, with the carbonated area

tested not being truly representative. Another

source of error is the influence of variables that

are rarely reported, but which have some effect,

such as formwork surface, mould oil and micro-

environment.

The NN was used to predict the effects of

concrete and environmental variables on

carbonation. Relatively well-established

relationships were replicated, such as the effects

of time, sheltering from the rain and w/c (Fig. 3)

and mineral additions (Fig. 4). The NN was then

used to predict the less well-understood effects of

other variables, particularly those not varied in a

single study, such as geographical location (Fig.

4). The input values for Figs 3 and 4 are listed in

Table 2.

Figure 4: Predicted effects of mineral additions and geographical location.

Figure 3: Predicted effects of time, exposure environment and w/c.

2929

General Conclusions Regardingthe Application of NeuralNetworks to Service LifePrediction

The most time-consuming aspect of NN

development is collecting and collating input

data. It is generally best to include as inputs all

factors that could possibly influence the output,

only omitting variables when data are limited.

Defining inputs to describe the concrete

constituents and their proportions is usually

straightforward. Characterising the exposure

environment is generally more difficult because

environmental parameters fluctuate on a daily

and seasonal basis. It is recommended that

during NN development the effect on NN

accuracy of different ways of characterising

exposure environment is investigated.

Transforming important variables and

incorporating them as alternative or additional

variables (e.g. including both time and root time)

is often beneficial; this takes advantage of prior

understanding of processes.

With noisy data, prolonged training does not

necessarily lead to better performance, as the NN

begins to learn the noise, and this impairs its

ability to generalise. It is therefore important to

monitor NNs during training to determine when

to stop. The importance of thorough testing of

NNs cannot be overemphasised and, where

possible, a completely independent set (i.e. one

obtained from different workers/laboratories)

should be used.

It is wise to limit predictions to input values

within the ranges used in training. When

assessing the effect of an input, it is usual to hold

all other inputs at a constant value. This may be

misleading; dependent inputs should also be

varied. For example, varying the C3S content of a

cement should be accompanied by corresponding

changes in other phases. For this reason it is

unwise to use concrete properties (e.g.

compressive strength), in addition to concrete mix

parameters, as inputs.

Service life predictions generally need to be

made to periods of at least 50 years, yet relevant

training data rarely extend this far. This is a

problem for all empirical models. The best

approach is to use the NN to produce a plot of

deterioration (e.g. carbonation depth) vs. time,

within the time range of the training data, and

then to fit a function to allow extrapolation to

longer times. To use the NN for design requires

the application of a safety factor to take into

account the uncertainty in prediction. In the case

of carbonation, the preferred approach applies a

safety factor directly to the predicted carbonation

depth. Fig. 5 shows the effect of a safety factor

of 1.5 with a fixed increment of 5 mm for

predicted carbonation depths of less than 10 mm;

this would be safe for 96.5% of predictions.

NNs allow existing design code durability

clauses to be checked and new ones to be

developed, incorporating data from a wide range

of sources that would not normally be

comparable, in a dispassionate way. Ideally

databases relating to the deterioration of

concrete structures and associated NNs would be

established and maintained to aid in future code

development and service life prediction of specific

structures. However, it is not clear how this could

be funded.

For more detail on the application of neural

networks to predicting concrete deterioration see[5].

Figure 5: Predicted vs. measured carbonation depth for test data, showing line touse in design.

30

SEMI-EMPIRICAL MODELS

GeneralSemi-empirical models lie between empirical

and mechanistic models. They generally take the

form of an equation in which the degree of

deterioration is related to a quasi-transport

coefficient (largely dependent on the concrete

properties) representing the combined effects of

individual transport processes and chemical

reactions, exposure time and possibly one or

more constants accounting for the influence of

the exposure environment.

The most simple, yet still useful, of the semi-

empirical models is one representing

carbonation[7]:

X = kt0.5

where:

X = carbonation depth at time t

k = a constant related to concrete quality

and environment conditions (temperature

and humidity).

Models of this type are very useful for

estimating the residual life of existing structures.

The current carbonation depth range and age can

be used to calculate k and hence to predict the

time for carbonation to reach the reinforcement.

Fick’s 2nd Law Modelling ofChloride Penetration

To date, the most widely used service life

model of any type has been the error function

solution of Fick’s 2nd Law applied to predicting

chloride penetration into concrete[8]:

( (Eq. 1)

where:

C(x,t) = chloride content at depth x and time t

Ci = initial chloride content

Cs = surface chloride content

t = exposure time

x = depth

erfc = error function

Da = apparent diffusion coefficient

Fick’s 2nd Law describes the diffusion of an

unreactive species held at a fixed concentration

into a semi-infinite medium. If chloride did not

react with concrete, then this would be a

mechanistic model for thick OPC concrete

elements submerged at shallow depth in sea-

water. However a large fraction of chloride

entering concrete is chemically bound by cement

paste constituents, with only a small proportion

remaining free to diffuse; at low chloride

contents most of the chloride present is bound,

with the bound proportion decreasing with

increasing chloride content (Fig. 6).

Furthermore, in most situations where

chloride-induced corrosion is a problem, ion

diffusion is not the only transport process

responsible for chloride penetration; as discussed

in Mechanistic models, transport processes such

as water absorption (during wetting and drying

cycles), pressure induced flow and wick action

may also be involved. There is no reason why

Fick’s 2nd Law should apply to these processes.

Nevertheless, measured chloride profiles generally

decrease with depth from the exposed surface in

a shape consistent with the profiles expected for

pure diffusion based on Fick’s 2nd Law.

Consequently, Eq. 1 can be used to fit a curve to

the profiles by appropriate selection of the two

fitting variables, Cs and Da.

The most common application of this model is

to extrapolate from the chloride profile (i.e. Cx vs.

x) measured after a relatively short period of

exposure, to predict t1. In the case of residual

service life prediction, chloride profiles produced

from a condition survey would be used. In the

case of a new structure, chloride profiles

measured in specimens of similar concrete after a

period of immersion in a chloride solution would

be used.

In theory, Da is the only unknown in Eq. 1 and

can be calculated by measuring Cs, Ci and Cx at a

single value of x. However, direct measurement

of Cs is unreliable as Cs is the chloride content in

the concrete right at the exposed surface and if

Figure 6: Chloride binding curves for OPCat different w/c values.

4)-(+=),(

aisi

tD

xerfcCCCtxC

31

the depth increment were small enough to

represent the surface it would not be

representative of the concrete. Furthermore, Cs

may vary with time, for example it may reduce if

the surface is washed by rain. The usual

approach, therefore, is to fit a curve to the

chloride profile with Cs and Da as the

independent variables (Fig. 7).

In the case of residual service life prediction,

these values of Cs and Da can then be used to

predict the time (t1) when the chloride content at

x=cover depth reaches the chloride threshold level

for corrosion, most commonly taken as 0.4%

chloride by weight of cement[9], as shown by the

predicted profile in Fig. 7. In the case of a new

structure, the calculated value of Da is generally

used, but if the concrete is exposed to a different

concentration solution in the test (generally a

higher concentration to accelerate the short-term

test) than in practice, a more appropriate value of

Cs should be chosen.

As concrete ages in a wet environment, further

hydration results in a tightening of the pore

structure and an increasing resistance to

ionic/molecular penetration. This manifests itself

in a reduction in Da. This effect is particularly

important for concrete containing PFA and GGBS.

The most widely available chloride penetration

model of this kind is Life-365, produced under

the auspices of American Concrete Institute

Committee 365. Life-365 uses the following

relationship to account for a Da reducing with

time:

where :

Da(t)= apparent diffusion coefficient

Dref = apparent diffusion coefficient at

reference time tref

m = 0.2 + 0.4(%PFA/50), where PFA ≤ 50%

= 0.2 + 0.4(%GGBS/70), where GGBS ≤

70%

= constant after 30 years.

m is prevented from reducing beyond 30 years

because of lack of data concerning performance

over this duration. In the absence of PFA and

GGBS, Da is predicted to reduce to 30% of its 28

day value by 30 years. If 50% PFA or 70% GGBS

are used, then Da is predicted to reduce to

around 2.8% of its 28 day value by 30 years.

Probabilistic ApproachConcrete properties and environmental

conditions are stochastic variables and the

chloride penetration model described above will

predict mean behaviour, for example, in the case

of predicting t1, the time until half of the steel is

corroding. However, it can be argued that this is

an over-estimation of service life and that the

time to, say, 1% or 5% of the steel corroding is

of far more practical value to designers of new

structures. To accomplish this requires a

probabilistic approach in which Cs, Da, m, cover

depth and chloride threshold level are

represented by statistical distributions, rather than

by unique values. Fig. 8 illustrates the approach.

Life-365 does not offer this capability, but this

approach has been adopted by a number of

Figure 7: Measured, fitted and predicted chloride profiles.

mrefrefa ttDtD )(=)(

)

32

groups working on service life prediction, the

most notable work being that by the EC funded

Duracrete Project[10].

MECHANISTIC MODELS

GeneralAll deterioration mechanisms can be broken

down into a number of distinct processes, most

commonly different transport processes and

chemical reactions. A mechanistic model

mathematically models these individual

contributory processes and then combines their

effects.

This can be approached at the scale of the

cement paste microstructure, modelling the

movement of individual species through tortuous

pores. However, this is hugely challenging due to

the multi-scale nature of the problem, and the

physical and chemical complexity of cement

paste. This approach is considered further in

Microstructural models. The more simple

approach is to use continuum mechanics where

pores and solid are treated as a single phase.

This is explored in the next section.

Continuum Mechanics ModelsContinuum mechanics models use, as inputs,

bulk properties of the concrete that are usually

controlled by both the porosity and the solid

phases. Where possible, models should be

formulated so that the bulk properties are easily

measured. If one of the individual processes

contributing to a particular deterioration

mechanism dominates, it may be possible to

formulate a continuum mechanics model to

obtain an analytical solution, i.e. a relatively

simple model involving substitution of values into

an equation to make a prediction, but this is

rarely the case. Usually it is necessary, or easier,

to formulate a numerical solution.

Numerical solutions, most commonly using

finite difference or finite element methods,

generally involve dividing the concrete into a

large number of discrete elements; in uniaxial

penetration problems this is generally a series of

laminae, each parallel to the exposed concrete

surface. Initial boundary conditions are set on

each side of the concrete and physical properties

(e.g. transport coefficients) and chemical

properties are attributed to each element. The

equations governing behaviour are then solved

for each element for a small step forward in time;

the resulting values are used in the next time

increment.

Continuum mechanics modellingof chloride penetration

Ion diffusion is never the only mechanism

contributing to chloride transport. As discussed

earlier, chloride binding will always occur and will

slow penetration. In most environments, other

transport processes will also contribute to, or

influence, chloride penetration. For example, in

Figure 8: Probabilistic modelling of initiation of chloride-induced corrosion.

33

the case of a concrete-lined tunnel submerged in

chloride-contaminated groundwater (illustrated in

Fig. 9), water will be forced into the concrete due

to the hydrostatic head (pressure-induced flow).

It the inside of the tunnel is below 100% RH, as

is the case for most metro tunnels, the concrete

will dry (by water vapour diffusion) on the inside

face and this will allow absorption of water at the

outside face; the combined process is termed

wick action. If water collects at the bottom of

the inside of the tunnel, which is often the case

for segmentally lined tunnels exposed to water

pressure, the water may splash against higher

sections of the concrete, for example each time a

train passes, resulting in absorption of water on

the inside face. Carbonation of the inside face of

the concrete will reduce the binding capacity of

the concrete and modify the pore structure

increasing or decreasing transport coefficients

according to the type of cement used.

Fig. 10 shows four chloride profiles in a 200mm

thick concrete element exposed to sea-water on

one face, predicted by a finite difference model of

chloride transport[11]. Common inputs for all of the

predicted chloride profiles in Fig. 10 are:

- sea-water Cl conc.: 20 g/l

- concrete density: 2400 kg/m3

- binder content: 400 kg/m3

- accessible porosity: 12%

- initial chloride content: 0%

- water permeability: 10-13 m/s

- element thickness; 200 mm

- exposure period: 50 years.

The other inputs required, which were varied

to produce the profiles in Fig. 10, are presented

in Table 3.

Figure 9: Tunnel environment and associated transport processes.

Figure 10: Numerically predicted chlorideprofiles (from [11]).

Profile Diffusion coefficient (m2/s) Binding Head(m)

1 10-12 No 0

2 10-12 Yes 0

3 10-12 to 10-13 over the first 5 years Yes 0

4 10-12 to 10-13 over the first 5 years Yes 10

Table 3 : Input variables for chloride profiles presented in Figure 10.

34

Each successive profile involves one more

process than the profile before in order to show

the impact of each process and to demonstrate

the flexibility and power of the approach. Profile

1 in Fig. 10 is the predicted profile due to ion

diffusion alone and therefore is a hypothetical

case because it does not include the effects of

chloride binding. Ion diffusion is modelled by

Fick’s 1st Law (flux through an element is

proportional to the concentration gradient across

it).

Profile 2 has identical input variables to Profile

1, except that chloride binding is included.

Chloride binding is represented by a binding

curve typical of OPC[11]. Currently there is no

reliable mechanistic model of chloride binding,

because the chemistry is unresolved. However,

there is a neural network model based on

measurements reported in 21 papers that will

predict the binding curve for a particular cement

paste/mortar according to 18 different input

variables[12]. This is a good example how different

types of model may be used in combination. It

can be seen that binding dramatically reduces the

depth of penetration, but results in higher

chloride contents in the penetrated zone. In this

model chloride binding is assumed to occur

instantaneously in relation to the long exposure

period. In models of electrochemical removal of

chloride, time dependence may be introduced[13].

Because the finite difference method involves

stepping forward in time in small increments,

properties of the concrete may be varied with

time. Profile 3 is the result of an order of

magnitude linear reduction in diffusion coefficient

over the first 5 years of sea-water exposure, all

other inputs being the same as for Profile 2.

Additionally, concrete properties may be varied

with depth, to take account of the

effects of curing, natural surface

layer formation[14] or to predict the

protective effect of a surface

treatment[15].

As the depth of sea-water

increases, the contribution of

pressure-induced flow becomes

important. Pressure-induced flow is

modelled by Darcy’s Law (flux is

proportional to the hydrostatic head

and inversely proportional to the

element thickness). It is assumed

that chloride ions diffuse in the pore

water as it is pushed, en masse,

though the concrete pores; this

assumption in discussed in more detail later.

Profile 4 includes the effects of 10 m head of sea-

water, all other inputs being the same as for

Profile 3.

The influence of temperature gradients and

cycles can be taken into account by defining the

temperature dependence of the transport

coefficients and chemical constants involved.

Complex boundary conditions, for example

varying head due to tidal effects, are not difficult

to implement. The numerical approach also

allows modelling in more than one dimension, for

example, biaxial penetration at a corner, joint or

crack. It should be noted that cracks and other

defects are often the cause of premature

deterioration, yet very few models, of any type,

take them into account.

As models become more complex, it gets

progressively more difficult to test whether the

predictions are realistic and accurate. Laboratory

measurements and predictions may be compared.

For example, Fig. 11 shows measured (individual

data points) and predicted (solid lines) chloride

profiles resulting from a combination of ion

diffusion, chloride binding and wick action

through 0.5 w/c, 50 mm thick, OPC mortar

specimens exposed to two different

concentrations of sodium chloride solution for 9

months[16]. The correlation between

measurements and predictions is (unusually) good

and it can be seen that the peak in the chloride

profiles, which occurs where water evaporates 11

or 12 mm from the downstream face of the

specimens, is replicated. Where possible, a

numerical model should be checked for all

relevant situations (normally simplified cases)

where an analytical model is available. For

example, in the case of wick action, see [17].

Figure 11: Measured and predicted chloride profilesprincipally due to wick action.

35

Ideally, for design purposes, mechanistic

models would be probabilistic, but the author is

not aware of any such models. There are several

possible reasons for this. First, effort is being

focussed on refining the basic (deterministic)

models. Second, there are insufficient data to

determine the statistical distributions of many of

the inputs. Third, there are few, if any, individual

researchers with the range of expertise necessary

to develop them.

The model described above models the

transport of water and chloride ions alone and

not the other ions present, either in the original

concrete pore solution or the exposure solution.

This approach results in the effect of membrane

potential[18] which may be important in some

situations, being overlooked. Different ions

diffuse into concrete at different rates and this

produces a localised charge imbalance, equating

to an electric field over the depth of ion

penetration, which has an influence on

subsequent ion diffusion[19]. This effect can be

reproduced by modelling the transport of all of

the ions present in appreciable concentration, i.e.

OH-, Ca2+, Na+, K+ and possibly SO4-, in addition

to Cl- [20]. However, the downside of doing this is

the very large number of model inputs required,

most of which need to be measured on the

concrete of interest.

Up to here, little has been said about the

coupling of processes, but this is a very important

issue and as more processes and ions are

involved, the associated errors are likely to

accumulate[21]. In the example presented in Fig.

10 it was implicitly assumed that pressure-

induced water flow and ion diffusion contribute

in the same relative proportions across all pores.

However, we know that the

capillary pores supporting

transport range in size over

several orders of magnitude

and, while it is expected that

ion diffusion will not be

greatly affected by pore size, it

is reasonable to expect

pressure-induced water flow

to predominate in the larger

pores. How best to

incorporate this dispersive

effect into a continuum

mechanics model is currently

being investigated at Imperial

College. This is a good

example of how the mechanistic

modelling approach tends to

highlights areas where more understanding is

required, thereby providing additional focus to

laboratory studies.

One method of reducing the number of

assumptions and measurements required to make

sensible life predictions for some exposure

situations is to simulate natural exposure in the

laboratory, monitor performance over an

extended period of time and to use a numerical

model to extrapolate to longer times. This

approach has been adopted to estimate the life

of concrete tunnel linings exposed to chloride

contaminated groundwater[22]. Opposite faces of

specimens of tunnel lining concrete were exposed

to the maximum hydrostatic head (30 m) of

groundwater and the minimum relative humidity

(35%) expected inside the tunnel and water

outflow and chloride accumulation were

monitored over a 3 year period (Fig. 12). Water

vapour diffusion, chloride binding and porosity

measurements were made on parallel specimens.

The measurements were used as inputs to a

numerical model of water and chloride transport

to extrapolate from the measured chloride

profiles to predict future chloride profiles.

Microstructural ModelsSome processes contributing to deterioration

mechanisms are not well-suited to continuum

mechanics modelling. For example, in the case of

the wick action, ions will concentrate in the

region where evaporation occurs within the

concrete section and then, if back-diffusion

cannot prevent the concentration of the

corresponding salts exceeding their solubility, salts

will precipitate. This will result in localised pore

blocking, reducing transport coefficients and

Figure 12: Laboratory based simulation of tunnelexposure.

36

subsequently, as pores are filled and expansive

stresses are generated, may produce micro-

cracking. To attempt to model this localised

behaviour using continuum mechanics involves

many speculative assumptions. For example, over

what depth should precipitation occur. If it

occurs at a point, the porosity will be filled and

expansive stresses generated instantly.

Conversely, if the distance is longer than in reality,

damage will be underestimated. The actual

behaviour will be partially controlled by the local

size and geometry of the pores. Ideally this

problem would be modelled at the scale of

capillary pores, i.e. with a resolution of less than

a micron.

Computer-based models of concrete

microstructure have been developed to give

measures of physical properties. At present these

models have a role in explaining experiments,

rather than in predicting long-term behaviour, but

their contribution in this area is likely to increase

in the future.

The most concerted and successful work in

this area has been undertaken by the US National

Institute of Standards[23]. The cement of interest

is dispersed in a low-viscosity epoxy and the

resulting specimen is polished, carbon coated,

then imaged (backscattered electron mode) and

analysed (x-ray mapping) to produce a detailed

image showing the distribution of the cement

phases. This image is then used as an input to a

2D hydration model. Cement hydration is

modelled, using cellular automaton type (CA)

rules, as three inter-related processes in which

pixels of material: 1) dissolve from the original

cement particle surfaces, 2) diffuse (random walk)

within the available pore space, and 3) react with

water and other dissolved or solid species to form

hydration products through aggregation. The

computer-generated microstructure that develops

when the model is executed to various degrees of

hydration is then used to compute physical

parameters such as capillary porosity and

conductivity.

CA rules could be developed to model the

degradation of cement paste microstructure. This

would be particularly appropriate for modelling

deterioration processes where the distribution of

cement phases is important as in the cases of

leaching and sulphate attack. The main

challenge is the multi-scale nature of the

problem. Behaviour at the sub-micron level has

to be modelled, to predict behaviour at the cm

level; if the structure of C-S-H, which is defined

at the nm level, is important, 7 orders of

magnitude of scale are involved. Furthermore,

current 2D models need to be replaced by more

representative 3D models. These factors demand

far greater computing power than will be

available in the near future.

CONCLUSIONS1. Demands for enhanced technical

performance, safety, economics and

environmental protection create a need to

be able to determine, at the design stage

or in-service, with an acceptable degree of

confidence, the projected service life of

concrete structures. This requires models

of reinforced concrete deterioration.

2. There are at least 10 different

deterioration mechanisms. Most of them

involve transport of ions, gas or water,

chemical reactions between the

penetrating species and constituents of

the concrete and microstructural changes

leading to degradation of the physical

properties of the concrete. Accelerated

testing is of very limited value in service

life prediction because measures to

accelerate one process do not generally

accelerate the other processes involved to

the same extent so that the overall

mechanism is distorted in relation to

natural exposure

3. Deterioration models can be conveniently

categorised as empirical, semi-empirical or

mechanistic according to the extent to

which the processes involved in

deterioration are explicitly modelled.

There are present and future roles for each

of these model categories.

4. Empirical models make predictions based

on previously observed relationships

between concrete composition and

exposure conditions and the consequent

degree of deterioration of concrete,

without consideration of the processes

involved. Their development requires

large quantities of relevant, long-term real

exposure data from natural exposure

studies or durability surveys of structures.

They can incorporate effects of scale, site

practice and real exposure that are difficult

to capture in a mechanistic model.

37

5. Semi-empirical models generally relate

deterioration to a quasi-transport

coefficient (largely dependent on the

concrete properties) representing the

combined effects of individual transport

processes and chemical reactions,

exposure time and possibly one or more

constants accounting for the influence of

the exposure environment. To date, these

have been the most widely used service

life models and are particularly appropriate

for incorporating a probabilistic approach

and for predicting the residual life of

existing structures.

6. Mechanistic models mathematically

represent individual transport processes

and chemical reactions, based on

measurable coefficients, and combine

their effects to make an overall prediction.

This necessitates, and may help to

develop, a detailed understanding of the

processes involved. Mechanistic models

offer the best hope of predicting long-

term performance in new situations, such

as the use of novel materials or exposure

to unusually hostile environments.

7. Service life prediction of concrete

structures is still in its infancy. There are

no standard models. There a very few

mechanistic models and none that

incorporate a probabilistic approach. Very

few models incorporate the effects of

cracks and other defects or combine the

effects of different deterioration

mechanisms. Clearly, there is still much

research to be done. Major challenges

include the chemical and physical

complexity of concrete and some of the

environments in which it is exposed, the

large spatial and temporal scale ranges

involved and the multi-disciplinary nature

of the subject.

REFERENCES

1 Nixon, P.J. "More sustainable construction:the role of concrete”, Proc. Int. Conf.Sustainable Concrete Construction, Dundee,Thomas Telford, 2002, 1-12.

2 New Civil Engineer, 4 July 2002.

3 Frohnsdorff, G., Buenfeld, N.R., Diamond,S., Hansson, C., Marchand, J., Myers, D.,Snyder, K., Sutter, L. and Taylor, P."Mathematical models and standards forprediction of concrete service life" Reportfrom Working Group 1, Anna Maria Island

2003 Workshop on Durability, 2004.

4 DETR, "Report of the Thaumasite ExpertGroup", 1999.

5 Buenfeld, N.R. and Hassanein, N.M., "Lifeprediction of concrete structures usingneural networks", Proc. Inst. Civ. Eng.,Struct. & Buildgs 128, 1998, 38-48.

6 Buenfeld, N.R., Hassanein, N.M. and Jones,A.J., "An artificial neural network forpredicting carbonation depth in concretestructures", Ch. 4 in "Artificial NeuralNetworks for Civil Engineers: AdvancedFeatures and Applications", Flood, I. andKartam, N. eds (American Society of CivilEngineers), 1998, 77-117.

7 BRE, "Carbonation of concrete and itseffects on durability", Digest 405, 1995,8pp.

8 Glass, G.K. and Buenfeld, N.R. “Chlorideinduced corrosion of steel in concrete”,Prog. Struct. Engg & Mats, 2, 2001, 448-458.

9 Glass, G.K. and Buenfeld, N.R., "Thepresentation of the chloride threshold levelfor corrosion of steel in concrete", Corr. Sci.39, 1997, 1001-1013.

10 Duracrete: www.duranetwork.com

11 Buenfeld, N.R.,"Measuring and modellingtransport phenomena in concrete for lifeprediction of structures", Ch. 5 in"Prediction of Concrete Durability",Glanville, J. & Neville, A.M. eds (E & FNSpon, London), 1997, 77-90.

12 Glass, G.K., Hassanein, N.M. and Buenfeld,N.R., "Neural network modelling of chloridebinding", Mag. Concr. Res. 49, 1997, 323-335.

13 Hassanein, A.M., Glass, G.K. and Buenfeld,N.R., "A mathematical model for theelectrochemical removal of chloride fromconcrete structures", Corrosion, 54, 1998,323-332.

14 Buenfeld N.R. & Newman J.B., "Thedevelopment and stability of surface layerson concrete exposed to seawater", Cem. &Concr. Res. 16, 1986, 721732.

15 Zhang, J.-Z., McLoughlin, I.M. andBuenfeld, N.R, "Modelling of chloridediffusion into surface treated concrete",Cem. & Concr. Comps 10, 1998, 253-261.

16 Buenfeld, N.R., Shurafa-Daoudi, M-T. andMcLoughlin, I.M., "Chloride transport dueto wick action in concrete" in "ChloridePenetration into Concrete" Nilsson, L.O. &Ollivier, J.P. eds (RILEM, Paris) 1997, 315-324.

38

17 Puyate, Y.T., Lawrence, C.J., Buenfeld, N.R.and McLoughlin, I.M., "Chloride transportmodels for wick action in concrete at largePeclet number", Physics of Fluids 10, 1998,566-575.

18 Zhang, J-Z. and Buenfeld, N.R., "Presenceand possible implications of a membranepotential in concrete exposed to chloridesolution", Cem. & Concr. Res. 27, 1997,853-859.

19 Buenfeld, N.R., Glass, G.K., Hassanein,A.M., and Zhang, J.-Z., "Chloride transportin concrete subjected to an electric field”,ASCE, J. Mats Civ. Eng. 10, 1998, 220-228.

20 Truc, O. “Prediction of chloride penetrationinto saturated concrete – Multi-speciesapproach”, PhD thesis, Chalmers Universityof Technology, 2000.

21 McLoughlin, I.M. "Modelling of chlorideand moisture transport in concrete”, PhDthesis, University of London, 1998.

22 Buenfeld, N.R. "Service life demonstrationbased on simulated exposure and numericalmodelling" in “Durability of Concrete”Malhotra, V.M. ed. (ACI SP-212) 2003, 1-10. (Proc. 6th Int. Conf. on Durability ofConcrete, 2003).

23 NIST, Electronic Monographhttp://ciks.cbt.nist.gov

39

Dr Richard Moss is a Senior

Consultant within the Centre

for Concrete Construction at

BRE, and now also works part-

time for Powell Tolner and

Associates. His area of

expertise is in the structural use of concrete and

he is a member of the British Standards Institute

committee dealing with this topic.

ABSTRACTThis paper gives details of a research project

aimed at applying innovations to the construction

of a series of multi-storey in situ concrete frame

structures at the St George Wharf development in

South London. The innovations to be applied

have largely emanated from the European

Concrete Building Project at Cardington, and

these have been summarised as a series of Best

Practice guides. The aims of the project are to

apply many of these ideas to an actual live

construction project and measure the benefits

that can be achieved under site conditions.

KEYWORDSConcrete, Flat slab, In situ, Innovation, Frame,

Construction

INTRODUCTIONThe European Concrete Building Project at

Cardington[1] has helped advance knowledge in

relation to in situ concrete frame construction

and the logical next step in getting that

knowledge and experience out into practice is to

apply many of the ideas to live construction

projects.

The principal objective of the St George Wharf

project was therefore to demonstrate the

practical benefits of adopting many of the

innovative features and techniques used in the

design and construction of the in situ concrete

building at Cardington. By demonstrating these

benefits under commercial conditions the other

principal objective was to further persuade the

wider industry of the quantifiable value to them

of taking up these innovations and approaches,

to improve their efficiency and profitability.

These benefits are in terms of increased

efficiency and profitability not just on this

particular phased project but also on other

projects in the future. The intended long-term

impact is the more widespread adoption of new

techniques and approaches, which will benefit

the wider industry. A further project is underway

intended to apply the ideas on a range of case

study projects.

DESCRIPTION OF THE PROJECTThe project involved applying innovations to a

live case study centring on the construction of a

series of flat slab frame structures in a large

residential and mixed use development to

demonstrate continuous improvement, and

establishing this as a demonstration project in its

own right.

The St George Wharf development in Vauxhall,

South London represented an ideal opportunity

for a number of reasons not least the nature of

the blocks being built in discrete stages and the

opportunities this provides for continuous

improvement. The development is very large

comprising 100,000 sq m of mixed-use

accommodation including 750 homes and is very

high profile occupying as it does 275 m of

frontage on the River Thames (Figure 1).

BRE worked directly with St George and their

engineers and contractors to develop and

implement possible solutions and improvements

tailored to the St George Wharf development.

This approach was followed so that the benefits,

though specific to a particular project, were more

clearly visible and measurable. The St George

DESIGN FOR BUILDABILITY

- APPLYING LESSONS FROM CARDINGTON TO ST GEORGE WHARF

Dr. Richard Moss, BSc(Hons), PhD, DIC, CEng, MICE, MIStructE

BRE Ltd

Figure 1: St George Wharf Development

40

Wharf development offered the advantage that it

is being taken forward in a series of repetitive

phases enabling benchmarking and measurement

of performance improvements, as a result of

implementing the proposed innovations.

The other principal advantage is that because

of the nature of St George themselves being a

developer/contractor, they effectively have control

over all phases of the project, enabling the

pushing through of new ideas and innovations

which would be more difficult in a more

conventional contractual arrangement.

The intention was that lessons learnt during

the construction of successive blocks would be

carried forward on to the next block so that a

process of continuous improvement could be

established. A team-based approach was

favoured working closely with the frame

contractor so that maximum benefit could be

achieved.

The St George Wharf development had already

been established as a demonstration project with

the Housing Forum. The concrete frame

construction aspects of this project were also

established as an M4I project in its own right.

A series of case histories have been prepared

summarising the experiences with each of the

innovations adopted during the construction. In

addition to an overview, these are:

• Early age concrete strength assessment

• Early age construction loading

• Reinforcement rationalisation and supply

• Slab deflections

• Special concretes.

Two background reports have also been

prepared summarising the work[2,3]. The work is

being taken forward in a follow-on project in

which further case study projects are being

identified. To date one such case study is up and

running at Newbury Central, a residential

development for Bellway Homes in East London.

The trade associations BCA, The Concrete

Centre and Construct, who were principal

partners for the original Cardington project, have

continued their involvement.

INNOVATIONS TRIALLED ATST GEORGE WHARF

The innovations trialled together with the

expected improvements and methods of

measurement are described below.

Electronic exchange of rebarinformation

The basic concept is the exchange of bending

schedules electronically all the way through the

supply chain. This has now become a commercial

reality with the availability of proprietary

products. Figure 2 illustrates a schedule

generated using SteelPac (www.SteelPac.co.uk)

which was the software chosen for the project.

In addition to the basic mechanism for transfer of

the information between parties this can provide

added value in terms of intelligent call-off and

revision control.

If the additional functionality provided by such

proprietary systems is not considered

advantageous by the contractor, manually

generated schedules can still obviously be

produced and sent electronically and it is likely

that many organisations have developed their

own in-house spreadsheets for this purpose. The

spreadsheet available at www.structural-

engineering.fsnet.co.uk is believed to have the

advantage however in that it has been modified

to output a SteelPac file, which may then be

imported by rebar suppliers who have the

relevant EDI module.

Compatibility of electronic information supplied

and received by different parties in the supply

chain for reinforcement is important in improving

efficiency in this process. Although not fully

exploited on this project, electronic exchange of

rebar information has the potential for

considerable efficiencies in the overall rebar supply

chain by the removal of the need to re-key in the

information by different parties. As a result of the

project the frame contractor Stephensons are

more committed to it and are actively seeking to

take it forward on the next phase. Andersons,

who are the frame contractor on the Newbury

Central project, have also embraced it.

Use of National StructuralConcrete Specification (NSCS)

The intention of the National Structural

Concrete Specification is to have an agreed

common specification for the majority of building

structures. This is seen of particular value to the

contractor in knowing what is required of him at

tender stage. In the context of St George Wharf

the contractor already had a good understanding

of what is expected of him, so that the benefits

of adopting the NSCS were limited. Nevertheless

some useful feedback was obtained as a result of

applying the document.

41

Rationalisation of reinforcementThe basic concept of rationalising the

reinforcement is reducing unnecessary variation in

bar sizes and spacings, making the detailing,

scheduling, supply, call-off and fixing of the

reinforcement more straightforward. Although

material costs can be increased as a result this will

be more than offset by the savings in time and

labour costs.

In the context of St George the reinforcement

is now highly rationalised. However historical

information was available for a non-rationalised

solution on earlier phases against which

comparisons could be made. These indicate a

21% saving in total man-hours.

The placing of the main slab reinforcement is

invariably on the critical path for the construction

of the frame as a whole. Provided it is feasible to

bring forward the next pour date, savings in time

for the placing of the reinforcement will therefore

feed through directly into savings in the overall

programme.

At an early stage however it was decided that

the benefits of rationalisation at St George on the

blocks investigated would be focussed quite

narrowly as savings in overall construction costs

by the contractor.

Various options for rationalising the main

reinforcement were considered. Eventually the

favoured solution emerged as using stock length

rebar. The approach to rationalisation of the

rebar is likely in practice to vary from job to job,

so it may be difficult to generalise.

In practice it proved very difficult to extract

meaningful information to assess the level of

reinforcement rationalisation adopted. The types

of information identified as being suitable

measures were:

• Comparison of rebar weights, which with

information on costs per tonne could be

used to calculate material costs

• Comparison of fixing time, both actual

and man hours per unit area which

coupled with information on labour rates

and total areas could be used to assess

total costs and time.

Successful reinforcement rationalisation

involves optimisation of the reinforcement

content and economies in the man hours to fix it.

Very simple reinforcement layouts can be fixed

very quickly. Savings are being generated at

Newbury Central by adopting very uniform bar

arrangements and adopting one-way spanning

mats. The uniform bar arrangements are believed

to be resulting from a yield line approach to the

design of the slabs. The small cost premium in

terms of weight of steel can be more than

compensated for in time savings both in terms of

Figure 2: Schedule generated using SteelPac.

4242

man hours and overall programme time. For

example, the contractor at St George Wharf,

Stephenson, stated that the company typically

quotes total reinforcement costs 10-15% less if a

rationalised solution is adopted.

Another factor may be the skill level of the

operatives. Less skilled labour may be able to be

used if the reinforcement layout is very

straightforward.

Use of prefabricated punchingshear reinforcement

This is a specific form of reinforcement

rationalisation relating to the provision of

reinforcement to resist punching shear. The same

principles as for reinforcement rationalisation in

general apply, but the benefits can be much more

significant.

In the context of St George the primary

approach which has been adopted has been to

reduce the number of columns requiring

punching shear reinforcement and the amount of

punching shear reinforcement to be provided at

those where it is required. This has simply been

achieved by increasing the amount of main

hogging steel provided over columns. This has

the effect of increasing the allowable shear force

that may be carried by the concrete section but

may not be the most effective method. Site

diaries indicate that as a result of this the time

spent fixing punching shear reinforcement has

been very small.

The intention was to directly compare the

fixing time and costs of a number of proprietary

systems. One such proprietary system is

illustrated in Figure 3.

Two stud rail systems were actually used for

comparison with traditional links.

The Shearail system involves shear studs placed

on rectangular perimeters whereas the Studrail

system has the studs projecting radially from the

face of the column.

Both the Studrail and Shearail systems were

perceived as quicker to fix than traditional links

(about 4 times faster). For this particular project,

based on very limited data, stud rails arranged on

an orthogonal grid and fixed from the top

appeared to be the more cost-effective of these

two options. The contractor perceived

advantages in minimising clashes with main

reinforcement and the designer was more

comfortable with an arrangement involving more

shear reinforcement and resembling a more

conventional rectangular layout.

Depending on the amount of punching shear

reinforcement to be fixed it was concluded that

the practical time saving generated needed to be

sufficient to merit use of the systems (i.e. the

number of days by which the next pour date

could be brought forward). The overall value of

this saving to the programme as a whole should

be assessed as well as the direct balance between

reduction in man hours offset against the

additional materials cost of such systems. Other

factors to be considered are the lead-in times,

and approval both by the Permanent Works

designer and Building Control.

Accurate prediction ofdeflections

Prediction of deflections can be a specific

requirement to meet clients' requirements and

those of follow-on trades such as cladding and

internal finishes. At St George Wharf a

complicated fixing detail has had to be adopted

to accommodate movements in internal finishes

which it is suspected is unnecessary.

Measurement of the deflections actually

occurring have provided valuable data for

calibration of theoretical models. This will

provide justification for simpler and cheaper

architectural details on future blocks. Deflections

were typically measured before and after striking

and application of peak construction loads. Tests

were carried out to establish the creep and

shrinkage characteristics of the concrete.

Prediction of deflections in two-way spanning

systems is not straightforward and may not be

amenable to hand calculation. The components

of deflection and the times at which they occur

need to be considered in conjunction with the

limits associated with these components. In

general total deflections and deflections

subsequent to installation of cladding and

partitions need to be considered.

42

Figure 3: Proprietary punching shearreinforcement stud rail system.

434343

Early age construction loading can have a

significant impact on deflections as a result of

induced cracking. Appropriate modelling of

cracking behaviour is therefore essential if realistic

deflections are to be predicted. The sensitivity of

the predicted deflections to the assumptions

made, particularly the tensile strength of the

concrete, should be assessed and the likely error

bounds determined.

Past experience suggests error bounds typically

+0/-30% in the calculated deflection resulting

from conservatism in knowledge of material

properties.

Deflections were predicted at St George Wharf

using various methods based on finite element

analysis[3]. The predicted deflections from the

Imperial College non-linear finite element analysis

compared well with the measured deflections as

shown typically in Figure 4 and were significantly

greater than originally predicted neglecting

cracking.

Early age strength assessmentusing Lok tests

Reliable methods for the determination of

early age strength are a prerequisite

for being able to strike slabs at

early ages and can be useful for

other purposes (e.g. prestressing).

The intention at St George

Wharf was to investigate the

practical benefits of using LOK tests

(Figure 5) for determining the

strength at which the slabs can be

struck. Initially the carrying out of

LOK tests was run in parallel with

the making and testing of cubes, so

that confidence could be gained in

their use and comparison made

with cube test results. A particular

advantage of the LOK test is that

it is giving an indication of the actual strength of

the concrete within the structure.

The costs and convenience of carrying out LOK

tests was also compared with that of making and

testing cubes.

Work at Cardington coupled with the work

undertaken here, suggests that the LOK test itself

is reliable but other factors come into play once

the structure itself is being sampled. The

advantage of the LOK test is limited if time

permits other more established methods (i.e.

cubes) to be used.

It proved difficult in practice to derive a

meaningful correlation between air-cured cubes

and LOK tests. In general the cube strengths

derived from LOK test strength measurements

were less than those of corresponding air-cured

cubes which had hitherto been used as the basis

for striking (Figure 6). The work has highlighted

the natural variability of concrete strengths at

early ages and suggests caution should be

exercised in assessing strength based on limited

sampling whatever test method is used. More

confidence should however be able to be placed

on the LOK tests in the sense that the actual

concrete in the structure is being sampled.

Figure 4: Maximum deflections at StGeorge Wharf.

Figure 6: Comparison of concrete strengths derivedfrom LOK test results with air-cured cubes at StGeorge Wharf.

Figure 5: LOK test system.

44

Specification of 'superstriker'concrete

There may be advantages in specifying a

higher grade of concrete to enable required early

age strengths for striking to be achieved,

especially in cold conditions. The additional cost

associated with this should be weighed up

against the benefits that accrue if this option is

pursued.

Revised striking criteriaAs a result from the work at Cardington new

striking criteria have been proposed taking

serviceability criteria as those which are critical.

The opportunity was taken at St George Wharf to

assess the practical implications of the new

criteria in terms of promoting early striking and

the benefits which result from it in terms of

speeding up the floor cycle.

The expectation was that adoption of the new

criteria would allow striking at lower concrete

strengths than currently permitted. However this

was found to very much depend on the

assumptions made. Because the strengths

required using the existing criteria were arrived at

using fairly optimistic assumptions, it was not

considered prudent to revise these strengths.

The minimum strengths requiring to be

achieved were 22 N/mm2 for slab pours without

balconies and 25 N/mm2 with balconies based on

a characteristic cube strength at 28 days of 40

N/mm2.

The minimum age at which striking actually

took place was 3 days. The results of air-cured

cubes indicated that these minimum strengths

were exceeded when the slabs were struck.

New criteria for design ofbackpropping

Again as a result from the work at Cardington

improved understanding of the true distribution

of loads through backprops and supporting slabs

has been gained. This potentially can enable the

numbers of levels of backpropping and total

amount of backpropping to be reduced.

Experience from St George Wharf is that

typical site practice is to have quite high levels of

preload in backprops and as this is generally

beneficial there seems little reason to change this.

Such preloading will generally result in a more

even distribution of load between supporting

slabs as assumed by conventional approaches.

An Excel spreadsheet is now available with

Reference 4 that allows the influence of cracking

of the slabs and the effects of pre-load to be

taken account of in calculations for up to two

levels of backpropping. It should be recognised

however that the level of pre-load might prove

very difficult to control in practice, especially for

multiple floors of backpropping.

The issue of the design of the backpropping

will be most acute for situations where low

imposed loads are specified, such as in car parks

and residential developments because of the

limited spare capacity of the slabs. Marginal

exceedance of the design service load of the slabs

will not be a safety issue, but could have some

impact on serviceability performance. The

Permanent Works designer should therefore be

involved in any decisions to theoretically overload

slabs and should consider possible implications

for serviceability.

If the developer is closely involved in the

design and construction process as is the case

with St George, they can perhaps take a more

informed decision as to the relative merits of

accepting a higher design load to cater for the

construction load conditions.

Use of CRC JointCast The potential scope this material offers for

speeding up the construction of the vertical

elements and hence the overall programme was

investigated.

The construction of vertical bracing elements

such as cores and shear walls using in situ

concrete can be time-consuming and can limit

the reduction in floor cycle time which can be

achieved as a result of introducing other

innovations.

CRC JointCast showed potential to be used to

speed up the construction of vertical elements by

using precast components and to greatly reduce

the crane time required for this activity.

CRC JointCast is an ultra high strength

jointing material which may be used to create

monolithic construction using precast elements.

Use of self-compacting concreteSelf-compacting concrete offers potential

advantages in terms of reduced noise and

improved health and safety. Self-compacting

concrete is becoming more widely used

particularly for precast components. The

opportunity was taken to use it in limited areas at

St George Wharf to compare costs and the

quality of finish achieved, and the ease of

specifying and obtaining the material.

45

Both the contractor and the client found self-

compacting concrete (SCC) of a high quality and

easy to use and savings were made in manpower

and time. However, the unit cost per m3 for SCC

still made it more expensive than conventional

concrete overall.

The benefits in terms of improved quality of

surface finish were demonstrated, and the

reduction in making required good could

outweigh the cost premium. As a result its more

widespread use for vertical elements on future

phases is being actively pursued. The cost of self-

compacting concrete is believed to be reducing

generally making the economics of it use more

attractive.

1

2

Item to be measured

Electronicexchange ofrebarinformation

Use ofNationalStructuralConcreteSpecification

Benchmark

Anecdotalevidence onpreviousmistakes usinghand-writtenschedules.

Time and costof processinghand-writtenschedules bythe rebarsupplier

Time and costof producinghand- writtenschedules bythe detailerfrom rebardrawings

Currentmethods usedby thecontractor forhandling call-offs, deliveriesand invoices

Individualconsultantswriting theirownspecifications

Method ofMeasurement

Anecdotalevidence onreduction innumber ofmistakes

Cost and timecomparison bythe rebarsupplier

Cost and timecomparison bythe rebardetailer

Cost and timecomparison bythe contractor

Feedback onexperience ofuse bydesigner/contractor

Comments

Extraneouscircumstancesconcerningsupply ofreinforcementwas the mainreason whythis innovationwas not fullyimplemented

Understandingofrequirementsalready existsfrom work onearlier phases.Hence difficultto obtainobjectivemeasurementofimprovementobtained fromits use on thisproject

Actual ImprovementachievedNot fullyimplementedon this phase,but contractorconvinced ofits benefitswith firmproposals forimplementation on nextphase andmore generally.

Not Applicable

ExpectedImprovement

Significantsavings in timeon the part ofthe rebarsupplier

Some savingsin time on thepart of theframecontractor andthe maincontractor

Familiarisationwith thedocument

Table 1: Improvements in Concrete Frame Construction investigatedas part of St George Wharf Case Study.

46

3

4

5

Item to be measured

Rationalisa-tion of mainreinforcement

Use ofprefabricatedpunchingshearreinforcement

Shear ladders(prefabricatedon and offsite)

DEHA studrails

RSJ Cruciformsections

Accurateprediction ofdeflections

Benchmark

Information onman-hours andweights ofrebar per unitfloor area frominitial non-rationalisedphase

Framecontractor'stender pricinginformation for non-rationalised/rationalisedsolution

Directcomparisonwith use oftraditionalloose links

Data fromCardington

WYG predicteddeflections ascompared withcriteria set bySt George(20mm)


Directcomparisonbetweenrationalised/non-rationalisedby framecontractor

Out-turn coston steel fixingfrom framecontractor

No. of manhours percolumn headfrom framecontractor

Overall costsper columnhead fromframecontractor

Actualdeflectionsmeasuredcompared withpredicteddeflectionsusing simple/sophisticatedmodels

Comments

Extent ofrationalisationfound verydifficult toquantify inpractice

Actual ImprovementachievedBlocks B to D21%

Not Available

Up to 86%

Up to 32%moreexpensive, butno accounttaken of valueof time saved

Further datafor validatingmodels.Simplifiedguidance forpredictingdeflections.Need forcomplicateddeflectionhead detail tobe reassessed.

ExpectedImprovement

15% reductionin man hours

15% reductionin combinedsteel supplyand fixingcosts

Frommanufacturer'sliterature (upto 80% savingin man hours)

Frommanufacturer'sliterature (upto 50% inoverall cost)

Greaterpredictability of actualdeflectionsoccurringleading tosavings onfuture blocksonarchitecturaldetails toaccommodatedeflections (i.e.cladding/internal finishes)

Table 1 continued.

474747

6

7

8

Item to be measured

Early agestrengthassessmentusing LOKtests

Specificationof'superstriker'concrete toallow earlystrikingns

New criteriafor strikingand benefitstherefrom

Benchmark

Time and costassociated withmaking andtesting cubes

Historicalinformation onconcretestrengthdevelopmentandrelationship toenvironmentalconditions

Historicalapproachesbased on timeandenvironmentalconditions

Earlier phasesof the project(3-4 days)


Directcomparison ofcosts andavailability oftest resultsusing LOKtests asopposed tocubes

Accuracy andspread of testresults

Need forcorrelation

Cost/benefitanalysis ofspecifying ahigherstrengthconcrete topromote earlystriking

Comparison ofcriteria usedand limitationson age atwhich strikingcan beundertaken

Comments

Potential forearlier strikingexists if barrierposed byconstruction ofverticalelements canbe removed

Actual ImprovementachievedPotentialshown in termsof speed andconvenience

Costcomparablewith those ofcubes

Not proven onsite

Potential forthis, butfurther workrequired

Not requiredowing to timesat whichstriking wastargeted

Influence onrequiredstrengths forstriking limitedas existingcriteria basedon optimisticassumptions

ExpectedImprovement

Quickerconfirmationof slabstrength

Cheaper andless timeconsumingthan makingand testingcubes

Manufacturerscorrelation maybe relied upon

Cubes nolonger requiredfor early agestrengthassessment

Possiblegreaterflexibility andcertainty ofprogramme

Benefits tospeeding upfloor cyclewith/withoutlimitationposed byverticalelements

Increasedcertainty ofdeliveringexistingprogramme

Speeding up ofexistingprogramme

Table 1 continued.

48

9

10

11

Item to be measured

New criteriafor design ofbackpropping

Use of CRCJointcast

Use of self-compactingconcrete inlimited areas(e.g. verticalelements withcongestedsteel)

Benchmark

Currentassumptionsconcerningdistribution ofloads

Earlier phasesof the project

Time toconstruct insitu verticalelements suchas multiple liftcores

Existing costsof placedconcrete

Quality offinish achieved


Comparison ofbackproppingarrangementsand inparticularnumbers oflevels ofbackproppingrequired

Feasibilitystudy onadvantagesoffered

Possible use onupper floors asstresses lower

Increasedmaterial costspartially off-setby savings inlabour forcompaction

Ease ofspecificationandprocurement

Comparison ofquality offinish achieved

Comments

Effect ofpreload,althoughucontrolled,was to achievea fairly evendistributionwhich wastheoreticallyrequired

Actual ImprovementachievedJustification ofone level ofbackproppingstill difficult

Potentialbenefitidentified andbeing activelypursued fornext phase.Greatestsavings are incrane time.

Improvementin quality offinish clearlydemonstratedwith potentialfor savings incosts ofmaking goodto outweighmaterial costpremium

ExpectedImprovement

Reducedrequirementforbackproppingwithconsequentsavings inlabour andmaterials(50%)

Significantreduction infloor cycle timeif adopted

Reduced noise

ImprovedHealth andSafety

Possibleimprovedquality of finishand durability

Table 1 continued.

49

PERFORMANCE MONITORING

Site DiariesThe collection of information to form the basis

for assessing the success or otherwise of

adopting particular innovations was seen as a key

requirement. The key activities in relation to the

construction of the concrete frame superstructure

were identified and a proforma spreadsheet was

developed for recording key information.

For slab pour areas the key operations

identified were decking, placing of rebar,

concreting and striking. For individual columns

and sections of walls the key activities were

prefabrication and fitting of rebar cages,

completion of formwork, concreting and striking.

The form of the site diaries evolved during the

project. Initially data entry into the spreadsheet

was intended to be on a daily basis but in

practice this proved too time-consuming and the

data generated not that directly useful. The

method of data recording was then amended to

be on a Floor Level by Level basis, with the slab

pour floor areas and corresponding vertical

elements supporting that area of floor identified

on a corresponding floor plan.

An example of the proforma, which is

currently being developed to meet specific

requirements on other case study projects, is

given in Figure 7 below.

Figure 7: Site diary information.

50

What became clear from looking at the data

was the large number of man hours spent

constructing the vertical elements compared to

the horizontal elements, particularly taking into

account the smaller volumes of concrete involved.

This is a strong driver for the contractor to

consider alternative methods of forming the

vertical elements, for example by precasting. This

is even more significant for the upper floor levels

because of the reduced size of the floor plate.

The man hours recorded relate only to

observed and recorded activities and by definition

will therefore be an underestimate.

Prefabrication of the rebar for the vertical

elements has in some cases allowed the potential

for shortening of the floor cycle.

The contractor had enough equipment on site

for striking of the slabs not to be an issue.

However, earlier striking could have permitted use

of less falsework.

If sufficient resources and equipment were

available it would have been possible to speed up

the floor cycle considerably for any given floor by

constructing the vertical elements more as one

complete group per floor. However if this is done

by conventional means this might require the

provision of more vertical falsework and

formwork.

Differentiation was made in the spreadsheet

between time spent fixing main steel and

punching shear reinforcement so that these two

activities could be separated out. In practice this

proved difficult to do as the amount of time

spent fixing shear reinforcement was fairly

minimal.

The frame contractor Stephensons

independently calculated an average figure for

man hours per floor for the lower Floor Levels of

6057 but this includes all productive and non-

productive time.

Construction programmeA preliminary overall construction programme

was reviewed and it was observed that:

1. There is limited benefit in speeding up the

frame construction to beyond the speed at

which the cladding can be fixed afterwards

2. The benefit of speeding up the fixing of the

cladding is in turn limited by the speed at

which the internal trades and other items

can be completed.

Concrete for all the vertical elements was

skipped and that for the slabs pumped as far as

approximately Floor Level 20. It would appear

that the pour size for the lower slabs was largely

governed by the volume of concrete that could

comfortably be placed in a day - of the order of

150-200 m3, although the shape of the building

and the crane availability are other important

factors. To speed up the construction further two

of the pour areas (A1 and A3) on some of the

lower Levels (1-7) were combined, albeit that they

were on different floor Levels.

Information on the actual vs. intended

construction programmes has been used to

determine a measure of predictability at key

handover points. This is discussed further below

in the section dealing with Key Performance

Indicators.

The identified handover points were the

commencement of the precast cladding, and

completion of the lift shafts.

Identification of the key handover points is a

key factor in determining the optimum length of

the concrete frame construction programme and

has been flagged up as a key factor to be

considered on further case study projects now in

hand.

Key Performance Indicators (KPIs)A number of Key Performance Indicators were

developed in relation to the concrete frame

construction aspects. These included

measurements of productivity and construction

time. These two indicators in particular were

monitored throughout the life of the project with

the intention of gaining an overview of the

performance and to see if there are

improvements which have been detected at a

project level as a result of adopting the

innovations.

These two indicators need to be considered

together. One way of reducing overall

construction time for the frame is within limits to

have more resources. However dependent on

issues such as multi-skilling this may not be the

most efficient or cost-effective use of labour,

plant and materials. The importance placed on

construction time by the client will have a bearing

on the optimum solution for any specific project.

The influence of the data on which the

measures are calculated needs to be considered.

For example two sources of data on man hours

were used with widely differing results. It is

therefore important that a consistent approach is

taken to recording the data so as to identify

trends across projects.

51

Figure 8 presents productivity data which

might be considered as a benchmark based on

good site practice for the type of building

considered. Because of the lack of available

comparative data it is not possible to compare

with performance on previous blocks.

The construction time KPI illustrated in Figure

9 relates to the total elapsed time associated

with constructing each floor level and is expressed

in hours/m2. For comparison the overall average

time taken per m2 on this phase was 0.1 hours

which is the same as on the previous phase.

Since the construction time is expressed in

hours/m2, to maintain the same improvement in

rate of construction as the floor plate reduces

additional steps would need to be taken to reduce

the floor cycle. This has not been possible given

the constraints of constructing the vertical

Figure 8: Productivity KPI.

Figure 9: Construction time KPI.

52

elements in a traditional manner. The floor areas

used to calculate the KPIs are plotted in Figure 10.

CONCLUSIONS1. The work has led to an improved

understanding and clearer identification of

the issues and constraints and barriers to

change concerning flat slab construction.

2. For maximum benefit to be derived from

innovations geared towards speeding up the

frame construction process, fundamental

barriers and issues need to be addressed at

the outset. The single most important item

is considered to be overcoming the

restrictions imposed by the construction of

the vertical elements.

3. Key Performance Indicators have been

developed with benchmark values for

productivity and construction time set for

future projects.

4. The project has yielded useful further data

to extend the work and best practice

recommendations emerging from

Cardington.

5. Contractual arrangements should be

reviewed with the frame contractor

appointed at an earlier stage on individual

projects. For large repetitive projects,

partnering arrangements should be

encouraged which are devised to give

continuity of work for integrated design and

construction teams coupled with incentives

for continuous improvement between

phases.

6. The relevance and benefits of particular

innovations should be considered on a

project by project basis. Important issues to

be considered are the contractual basis on

which the project is taking place, and relative

changes over time in costs of plant, labour

and materials.

ACKNOWLEDGEMENTSThe author would like to acknowledge the

funding provided for the case study projects

referred to in this paper by the DTI under the

Partners in Innovation scheme.

REFERENCES

1. The European Concrete Building Project,The Structural Engineer, Vol.78, No.2 18January 2000.

2. Practical application of Best Practice inconcrete frame construction at St GeorgeWharf, by R M Moss. BRE Report BR462,2003.

3. Backprop forces and deflections in flatslabs: construction at St George Wharf by RVollum. BRE Report BR463, 2004.

4. Guide to flat slab formwork and falsework,by Eur Ing P.F. Pallett, Published by theConcrete Society on behalf of Construct.Ref. CS 140, 2003

Figure 10: Floor areas constructed on each level.

53

Mike Wetherill is Senior Quality

Manager for Canary Wharf

Contractors Limited. In this role

and because of his previous

experience with the concrete

industry, he was responsible for

setting up an integrated quality management

system for the concrete used in the development.

This paper was presented by Neil Spence of

Hanson Premix.

ABSTRACTCanary Wharf is a major development in East

London which required a range of concrete types

and grades. For these reasons and because of the

scale of development within a relatively short

programme, an on-site concrete production

facility was desirable. This also presented the

opportunity for an integrated approach to quality

management for the benefit of all parties.

KEYWORDSCanary Wharf, Concrete supply, Production

control, Quality management.

INTRODUCTIONThis paper describes the quality management

of concrete supplied and used in the Canary

Wharf Project over the period 1997 to date.

A number of parties were involved with, or

interested in, the management of concrete

quality. These included:

• Canary Wharf Contractors Limited (CWCL)

as the Project Manager

• The concrete producer, mainly Hanson

Premix

• The concrete contractors, mainly Byrne

Bros, P C Harrington and Laing O’Rourke

• The structural design consultants,

principally Arup, Yolles and Cantor Seinuk

• The Building Control Department of

London Borough of Tower Hamlets

• Independent test laboratories, including

Sandberg.

The paper has associated contributions from

Hanson relating to production control and from

Sandberg relating to compliance testing.

CANARY WHARF DEVELOPMENTCanary Wharf is situated on the Isle of Dogs in

East London. In 1987 a master building

agreement was signed between the developer,

Olympia & York, and the London Docklands

Development Corporation. Canary Wharf

Contractors Ltd (CWCL) was set up to carry out

the project management for design and

construction of all the buildings and

infrastructure.

The first phase of the development took place

between 1988 and 1992. Following a lull in the

construction programme, the second main phase

of development began in 1997.

CONCRETE SUPPLYDuring this second phase the project was

supplied from on-site dedicated concrete plants

to ensure continuity of supply, which would

otherwise be susceptible to traffic delays during

peak rush hours. A second important

consideration was to reduce the impact of the

construction work on the local roads and

environment. The majority of concrete materials

(aggregates and most of the cement) were

brought to the plants by barge.

The third consideration was quality. CWCL

required a production control process that was

effective and totally visible to all parties, to be

backed up by a thorough regime of compliance

testing. The records of the control tests and

compliance tests were made available to all

parties, in a form that highlighted any

deficiencies.

Hanson Premix set up and operated the on-site

plants. Unusually, they suggested that they would

carry out the compliance strength testing. CWCL

agreed that this would be acceptable provided

the cubes were crushed at an approved

independent laboratory, and several of the

contractors agreed to this arrangement.

Details of the concrete production and control

are given in the next paper, from Rey Emery of

Hanson Premix.

CANARY WHARF – CONTROL OF CONCRETE QUALITY

Mr. Mike Wetherill BA, I Eng, AMICE, FIQA, FICT

Canary Wharf Contractors Limited

54

THE NEED FOR COMPLIANCETESTING

CWCL required that a thorough regime of

compliance strength testing should be

implemented, to satisfy all parties including the

design consultants and the District Surveyor. As

mentioned earlier, CWCL agreed that Hanson

could offer to Contractors a service whereby

Hanson would arrange the compliance testing by

sampling and making cubes, to be tested in an

approved independent laboratory.

Details are presented in the paper on

compliance testing implementation by Ian

Hudson of Sandberg llp.

CONCLUSION - BENEFITS OF AN INTEGRATED SYSTEM

CWCL and the trade contractors have been

pleased with the success of this integrated

approach to the management of concrete quality.

The number of problems encountered was small,

while the amount of checking ensured the risk of

undiscovered inferior quality would be very low,

thus keeping costs and delays to a minimum and

creating an attitude of teamwork among all the

parties involved.

55

Over the past 36 years, Rey

Emery has been responsible for

the concrete for many major

projects, including Millennium

Dome, Lords Cricket Ground,

Wimbledon Tennis Club,

Medway Bridge, Docklands Light Railway, M25,

M3.

ABSTRACTThis paper discusses the quality control

systems put into place by Hanson Premix for the

supply of concrete to the Canary Wharf projects.

It covers the basic hardware and software

required for production control and records. The

software for tolerance checks, management of

data and actions arising together with the special

requirement for chloride content, water cement

ratio and E modulus.

KEYWORDSHardware and software batching tolerances,

Testing regime, Significant non-compliance

reporting systems and frequency, Special

requirements, Water cement ratio and chloride

content control and E modulus.

INTRODUCTION- Basic hardware and software for production

control and records

- Software for tolerance checks

- Management of data and action arising

- Special requirements for chloride, water

cement ratio and E modulus.

Basic Hardware and Software forProduction Control and Records

Steelfields SM80 – floating plant with twin pan

mixers together with a Steelfields Major 75,

single pan mixer based on land.

Both mixer operations were fitted out with

Alkon computers, which controlled all the

batching processes.

CCTV was used on both plants to monitor

loading operations.

All equipment was calibrated monthly.

On Site Technical Set UpSite Laboratory: crushing machine, curing

tanks, etc.

Had the ability to carry out all the normal

functions of a concrete laboratory.

Staffing Levels: Technical Manager, Senior

Technician and up to 6 Field Technicians

An intensive testing regime was initiated from

the very beginning. During the project over

60,000 cubes were taken, together with the

appropriate workability tests.

Due to the method and speed of construction

early-age cube results were frequently required:

12 hours – 18 hours – 3 days etc.

These results were used to establish stripping,

loading and jump-form movement times.

Software for Tolerance ChecksHanson Premix developed the software that

was compatible with the Alkon batch computer

software.

The tolerances were set asfollows:

Within tolerance

• Cement ± 2% or (- 10kg / +20kg)

whichever greater

• Total Aggregates ± 2% or (- 50kg/+80kg)

whichever greater

• Admixture ± 5 % or 10ml

whichever greater

Acceptable out of tolerance

• Cement PC – 2% to +10%. PFA – 2%

to + 20%

• Total Aggregates – 2% to +4%

• Admixtures – 5% to +20%

Significant non-compliance

• Cement - < - 2% & PC > + 10% PFA >

+20%

• Total Aggregate - < - 2% & > + 4% with no

corrective action > + 10%

• Admixtures - < - 5 % & > + 20%

The software developed enabled approximately

5000 batch records per week to be monitored.

CANARY WHARF – CONTROL OF CONCRETE QUALITY

Mr. Rey Emery

Hanson Premix

56

Any significant non-compliances were

identified and flagged up for action.

Any action deemed necessary to bring the load

back into tolerance was done strictly in

accordance with the quality plan specifically

written for the Canary Wharf Projects.

An apparent significant out of tolerance report

was submitted to CWCL.

Management of Data and ActionsArising

Loads which fell into the category of

‘acceptable out of tolerance’.

Batch details, together with the action taken

to bring the load back into tolerance, were

submitted to CWCL.

Summary of out of toleranceactions for batchers

PC over +2% up to +10% - Load can be

dispatched without adjustment

PFA over +2% up to +20% - Load can be

dispatched without adjustment

Aggregates over +2% up to +4% - Load can

be dispatched without adjustment

Sand over +4% up to +10% - 25kg/m3 of

Portland cement added before dispatch

Coarse Aggregate over +4% up to +10% -

50kg/m3 of sand and 50kg/m3 of Portland cement

added before dispatch

Any loads above these limits must not be

dispatched into works but disposed of elsewhere.

Typical Pour ReportThis type of information submitted to CWCL

for each pour.

Submission to Canary WharfContractors Ltd

• Chloride ion & calculated chloride content

• Workability report

• Gradings – All aggregates at all plants

• Flow retention for each load / plant / pour

• Significant out of tolerance report / all plants

/ all pours.

Special RequirementsBP 1 Slab: Chloride ingress was considered to

be a potential problem, and as a consequence

the specification for the concrete was modified.

The concrete was to have a maximum w/c

ratio of 0.40

The maximum chloride content to be 0.15%

It was also required that Hanson Premix were

able to demonstrate compliance with these limits

on every load dispatched.

A report was submitted to CWCL for each

pour.

Water/Cement RatioMoisture content tests were carried out on all

aggregates immediately prior to and during the

pour; Typically 6 – 10 samples of each aggregate

from each plant for a 200m3 pour.

The water/cement ratio was calculated on the

average of these results and recalculated on the

highest value.

These results were put into a spreadsheet

along with the actual weights batched, including

added water and the water/cement ratio was

calculated in accordance with BS 5328 Clause

3.14.1

Chloride ContentChloride ion tests were carried out, using a

calibrated Salcon meter, on all aggregates prior to

and during the pour.

A limit of 0.025% or lower was considered to

be safe. This giving an overall chloride content of

less than 0.15%

These results together with those given for the

cements were put into the previously mentioned

spreadsheet and submitted as a complete

document for the entire pour.

When using limestone coarse aggregate and

marine sand, chloride content was generally in

the region of 0.06% or lower. When using

marine coarse and fine aggregates the chloride

content was 0.10% or less.

Canary Wharf Projects Quality Plan

Supplementary to the Company Quality

Manual & Product Conformity Procedures.

Date Mix

Cement content Plant

Docket No Time batched

Flow at plant Time tested on site

Flow on site Loss of flow

Ambient temperature Subsequent cube

strengths

57

Detailed instructions to deal with batching &

workability out of tolerances.

Review of batch records & reporting of

significant out of tolerances.

Testing and reporting on strengths, gradings,

and chloride content, moisture contents and

calculation of water/cement ratios for a particular

mix as supplied.

Technical DevelopmentsMuch of the concrete mix development is

attributable to the company adopting “Best

Practice” knowledge. Specific and valuable input

being provided from the experience gained from

supplying concrete to the Petronas Towers in

Kuala Lumpur.

High flow piling mixes utilizing superplasticiser

in lieu of normal water reducer when placing

concrete in polymer slurry rather than betonite.

Increased flow of Lytag concrete to target 650

mm flow and pumpable to 40 storeys plus.

Reduction in allowable chloride content in

basement rafts and slabs to 0.15%

Reduction in the w/c ratio in the deep rafts to

0.40 whilst not exceeding the maximum concrete

temperature of 65ºC

Grade C100 concrete pumpable to 40 storeys

plus.

As part of the ongoing development of Canary

Wharf Projects we were also required to develop

a mix with an E modulus of 45 GPa or greater.

This was successfully achieved by the careful

selection of aggregates and admixtures.

Results of these trials suggest that C100 or

C120 concrete, with the required minimum

modulus of elasticity, can be produced from a

suitable batching operation.

59

Ian Hudson, for the past 30

years, has been involved in the

testing and inspection of

concrete and concrete

structures. Joining Messrs

Sandberg in 1973 he was

immediately involved in the production of 1/4

million tunnel lining segments with the smallest

tolerance being ±0.004", before moving on to

the delights of site concreting control during the

building of the Heathrow Central Station for

London Underground. Between then and the

present, he has controlled the inspection and

testing of all forms of concrete production and

usage and has been involved in the investigation

of many concrete failure issues. Most recently, Ian

was seconded to Canary Wharf Contractors

Limited for 2 years to provide monitoring of the

concrete production and usage on the 15 major

building and retail contracts undertaken on this

prestigious development.

ABSTRACTThis paper discusses the further quality

controls employed at Canary Wharf during the

main concrete pouring period of June 2001 to

December 2002.

KEYWORDSSite Control, Site Sampling, Site Testing

INTRODUCTIONThe two previous papers have indicated the

systems that were put in place to ensure that the

concrete supplied to Canary Wharf was

acceptable to all of the interested parties.

However, the checking did not stop there.

Canary Wharf Contractors Limited (CWCL)

were aware that even with the best prevention

systems available, that when you are pouring

35,000 m3 of concrete per month, month after

month, that human and other unexpected errors

can still occur, no matter how efficiently the

quality systems that are in place are performing.

To make matters worse, Hanson offered some

183 different design mixes to the Contractors so

the scope for error in the acceptance of the

concrete was even greater. Therefore Canary

Wharf Contractors Limited insisted that the

quality assurance was backed up with practical

monitoring and quality control.

The contractors were naturally required to

control their concrete. As a minimum they were

required to have a technical based concrete

receiving system, undertaking the normal

concrete acceptance testing and inspection. This

included checking the concrete at the point of

delivery to ensure that the correct mixes had

been supplied, and that those mixes were within

the normal specification limits as required by BS

5328, which was of course the primary British

Standard applicable at the time.

This was normally accomplished through

workability testing using the British Standard BS

EN 12350-2: 2000 slump test for mixes with a

design workability of up to 125 mm slump and

the British Standard BS EN 12350-5: 2000 flow

test for mixes with higher workabilities. Site

sampling was of course undertaken to British

Standard BS EN 12350-1: 2000.

Normal contract cube testing was also

required, although the Contractors had the

opportunity to contract this element of the

control system to a suitably qualified sub-

contractor. In order to avoid the arguments that

normally ensue when cubes fail, where the

concrete producer questions the quality of the

site cube making, Hanson Premix were therefore

allowed to undertake this testing on behalf of

those contractors who wished to avail themselves

of the service. What! I hear you cry, allow the

poacher to turn gamekeeper? Well yes, given

that there were a few extra controls put in place

to ensure that the systems were followed

correctly.

The basic restrictions placed onthe testing were:

•That the site sampling and testing were

controlled in accordance with the current

relevant British standards and that the site

testing was UKAS accredited

•That the 28 day contract cubes were crushed

by a current competent UKAS accredited

laboratory

•That result certificates would be distributed

by the independent testing laboratory directly

to the contractor, Canary Wharf Contractors

COMPLIANCE TESTING IMPLEMENTATION AT CANARY WHARF

Mr. Ian Hudson

Sandberg LLP

60

Limited, the Structural Engineer for the

package concerned and The Local Authority’s

Building Control Department.

In addition, Canary Wharf Contractors Limited

required that the site batching plants and both

the concrete producer’s and the contractors’

testing and inspection operations would be

subject to inspection by their own and CWCL’s

staff.

It was my job to implement the above system

under Mike Wetherill’s watchful eye.

The current requirements for concrete are

generally getting more and more stringent (BS EN

206 and BS 8500 notwithstanding), as concrete

itself is being asked to perform to ever greater

extents, especially in terms of strength, finish and

resistance to various chemical environments.

As you have heard, in the BP1 Building at

Canary Wharf (the new Barclays Bank

Headquarters building) the concrete areas that

would be subject to traffic had stringent chloride

content levels set by the Client. These were

translated by Canary Wharf Contractors into a

requirement for the concrete to be supplied with

a maximum chloride content of < 0.15% by

weight of cement.

To put this into perspective, the normal BS EN

206-1: 2000 limits for chloride content are:

• Cl 0.10 or 0.10% by weight of cement for

concrete containing prestressing steel

reinforcement in class 1 conditions


concrete containing prestressing steel

reinforcement in class 2 conditions


concrete containing steel reinforcement or

other embedded metal in class 1 conditions


concrete containing steel reinforcement or

other embedded metal in class 2 conditions


concrete which does not contain steel

reinforcement other embedded metal with

the exception of corrosion resistant lifting

devices.

(The limits above are taken from BS EN 206-1:

2000, Table 10 - Maximum chloride content of

concrete).

By use of an aggregate testing probe, the

problem of the determination of the constituent

with the greatest chloride level variation - the

natural marine aggregates - was solved. The

remainder of the chloride level information was

provided by material certification and the

application of suitable statistical limits to ensure

that the maximum potential chloride levels of the

constituent materials was taken into

consideration when calculating the total chloride

contents.

The requirement for monitoring of the

batching operations was eased by the systems

that Hanson Premix had put in place and that

have been described by Rey Emery.

Indeed, without the computerised analysis of

the out of tolerance data, the job of checking up

to 5000 batch records per week would have

occupied virtually all my time. As it was, this task

was normally completed in a couple of hours per

week, allowing me to get out into the field and

check on some of the other activities being

undertaken by the concrete suppliers and the

Contractors. For, while Hanson Premix supplied

the lion’s share of the concrete to site, they were

not the sole supplier. Readymix Concrete and

some of the smaller London concrete suppliers

were contracted to provide concrete to some of

the schemes under construction.

Where the Contractor elected to utilise the

Hanson testing facility, Hanson also took

responsibility for site sampling to the specified

contract rate for the various grades of mix being

supplied. Of the 183 mixes referred to earlier,

grades ranged from C7.5 up to a normal highest

strength mix of C60 grade concrete. During this

period the C100 grade concrete referred to by

Rey was also developed and used on site.

Material variation in the aggregate supplied

probably accounted for more investigative time

than any other single variable.

Much of the raw materials were supplied in

bulk by barge and these offered the opportunity

to undertake visual inspection of the aggregates

prior to use in the batching plants. The marine

coarse aggregates used in concretes up to grade

C40 were reasonably consistent. However, once

the strength grade requirement exceeded C40,

limestone aggregate was utilised in the mixes and

this material was found to have a far greater

variability which at times required specific

sampling and testing in order to keep the quality

up to the required level.

A great deal of lightweight aggregate was

utilised in the development in the construction of

the composite metal deck floors of the buildings.

The raw Lytag material was sourced from Poland

and presented its own quality problems, the most

recurring of which was an accumulation of

61

hardened dust that built up in the bottom of the

delivery barges.

The reason for this was due to the fact that

the barges were also used to soak the Lytag in

order to bring the moisture content up to the

optimum 22%-24% required for the mixes being

produced. This moisture content assisted in

achieving the controlled high flow and therefore

allow the concrete to be pumped the required 48

floors in a single pump lift.

The barges proved to be an excellent soaking

container, but the action of soaking also had the

effect of washing down the finer dust that

accompanied the Lytag material. This then settled

in the barges and after a period the build up

would become critical and would then need to be

removed before the scale started to break up and

potentially be incorporated in the mixes.

The contractors that did not avail themselves

of the Hanson testing facility had to set up their

own site laboratories that also required

monitoring. The site laboratories were required to

sample the concrete and make the test cubes as

well as undertake initial curing of the cubes prior

to pick up by the nominated UKAS testing

laboratory.

In some instances, the fundamentals of site

laboratory work were found hard to grasp by the

laboratory technicians employed on the works.

Ensuring that cubes are correctly marked,

segregated and cured became another major

element in the normal quality monitoring regime

when 300 plus cubes of up to 6 different

concrete types were made during a site day..

Environmental considerations also played their

part in the concrete production and acceptance

testing. Hanson Premix supplied concrete using

heated water supplies during extreme cold

periods in order to maintain the required

minimum 5ºC temperature at the point of use.

Maximum temperatures are not so much of a

problem in the UK but maximum temperatures

also had to be monitored.

As with many site operations, the cry of “wet

it up” could occasionally be heard.

No adjustment to the concrete supplied by the

simple addition of water was allowed at the point

of use. A system was therefore put in place to

allow the contractors to return mixes to the plant

to be adjusted by the use of controlled quantities

of plasticiser, based upon the workability of the

mix. This system was controlled by the batching

plant and was required to be fully documented as

an adjustment to the concrete.

Successfully supplying something like 1.8

million tonnes of concrete over a 2 year period

can only be achieved through teamwork. The

Client , Contractor, Supplier system used at

Canary Wharf was, at the end of the day, A

TEAM EFFORT.

63

Deryk Simpson has worked for

the Concrete Advisory Service

since its inception in July 1987,

previously working for the

Cement and Concrete

Association. The first part of his

career was spent working for contractors and

consulting engineers on site and in design offices,

specialising in the design and construction of

reinforced concrete structures.

ABSTRACTThis paper outlines the author’s experiences in

giving impartial advice on concrete matters to the

construction industry for the past 18 years,

describing how many of the problems have

remained depressingly similar over the years. Also

how the use of the advice has evolved over

recent years, and how the construction industry

appears to have changed.

KEYWORDSAdvice, Disputes, Training, Experience, Skills,

Problems.

INTRODUCTION

Background HistoryThe construction industry has enjoyed a

regionally based advisory service in concrete,

staffed by experienced engineers, for about 40

years, and before that a centralised advisory

service. These advisory services were provided by

the Cement and Concrete Association (C&CA).

The C&CA, by means of its advisory service,

training and publications, had permeated the

construction industry so well that by the time the

author joined the construction industry in the

early 1970s concrete was the dominant

construction material. In the mid 1980s the

C&CA had five offices throughout the UK staffed

by experienced engineers. The author joined one

of these offices in late 1985 (as it turned out he

was the last regional staff member ever recruited

by the C&CA).

Then in 1987 the cement companies wanted

to downsize their payments to the C&CA and so

the C&CA was culled, losing the advisory service

and the training centre (the very things of most

use to the construction industry!). Due to the

efforts of some C&CA regional staff the Concrete

Society was persuaded to take on an, albeit

smaller, advisory service. So on 1st July 1987 the

Concrete Advisory Service (CAS) was formed and

staffed by a number of former C&CA engineers.

This was not to be a free service like that

provided by the C&CA, but one funded by

membership.

So in July 1987 a brave new world started for

a number of ex-C&CA staff. They were now in

the real world, they had to sell their services and

respond to commercial pressures, unlike in C&CA

days!

The aim of this paper is to give an overview of

the work of the CAS advisory engineers, how

that work has and has not changed since the

demise of the C&CA, and give some idea of the

types of problems dealt with by the advisory

engineers.

THE WORK OF THE ADVISORYENGINEERS AND HOW IT HAS CHANGED OVER TIME

Purely from a mechanistic approach, the work

of the Advisory Engineers can be summarised as

follows:

• Provide verbal and written advice in

response to phone calls, letters, faxes and

e-mails

• Undertake site visits and provide follow up

reports

• To promote the Concrete Society

• To write articles and contribute to

Concrete Society publications

• To liaise with the Concrete Society regions

and clubs

• To act as expert witnesses.

What are more interesting are the reasons

behind the first three of these.

When the CAS was established the

predominant reason it was contacted was for

straightforward advice on a design or

specification issue or more probably why a

particular defect or problem had occurred. As

A CONCRETE DOCTOR’S CASEBOOK

- THE WORK OF THE CONCRETE ADVISORY SERVICE

Mr. Deryk Simpson, BSc(Hons), CEng, MICE, FCS

The Concrete Advisory Service

64

time has progressed the major reason why the

CAS is contacted, particularly for the site visits,

has changed to that as acting as an informal,

impartial technical arbitration service, i.e. to try to

help in the solving of a dispute over matters

related to the design, specification, construction

or performance of a concrete or cement related

material. As the construction industry appears to

have become more and more combative in its

approach, the need for the parties to try to

resolve disputes seems to grow. Most of the site

visit reports now requested are because of some

form of dispute over a technical matter.

We now have a blame culture in the

construction industry and it is interesting to note

that many in the construction industry want

simple answers to complex problems, e.g. which

party is at fault! In reality construction is not like

that and most problems are due to a combination

of causes, e.g. workmanship, specification,

design, etc. and determining which party is to

blame is not always possible.

It is generally hoped that a site visit may help

to solve a dispute before it goes to litigation, as

deep down all in the construction industry know

that the only true winners of litigation are the

lawyers! Unfortunately in our increasingly litigious

society, litigation is resorted to far too quickly.

However, this also provides work for the CAS, as

advisory engineers do act as expert witnesses.

Unfortunately the CAS is usually contacted far

too late for the prevention of disputes. Instead of

waiting for the problem to occur and then asking

for help with solving a problem, the CAS would

much prefer to receive enquiries at the design

stage or pre-construction stage, so that costly

disputes and problems could be avoided.

The Need for Advice/HelpThe fundamental need for advice is the same

as it always was, in that seeking early advice

would prevent costly problems and disputes, and

would save the construction industry and its

clients huge sums of money every year. Why the

industry does not seek advice early enough is

often down to ignorance. The author’s view is

that the problem is that most people are actually

“ignorant of their own ignorance” and that

enquirers are the clever ones, in that they

recognise their need for help or advice.

The problem of the timely seeking of advice is

not going to get any better, probably worse, as

the construction industry looses skilled and

experienced personnel. The need for training has

never been greater.

Common Advisory Topicsand Change in Advisory Topics over Time

In introduction to this section a quote from

one of the now retired Advisory Engineers is

pertinent.

When the C&CA service closed down and the

CAS was started someone asked an engineer

“How are you now going to keep up-to-date

without the back-up of the C&CA organisation?”

The engineer replied, somewhat tongue-in-cheek,

“We will not need to, as we will be dealing for

the next 20 years with exactly the same problems

as we have been dealing with for the last 20

years”.

This could be taken as a cynical view, but in

many ways it has, unfortunately, been true. Many

of the problems experienced are not new and

have been well researched and documented, and

yet year on year the CAS sees the same problems

- like hardy perennials they blossom every year!

The overwhelming conclusions from this are that:

• The construction industry does not learn

from its mistakes

• There is little knowledge transfer from one

working generation to another

• No one appears to read or even know

about the existing guidance publications

issued by various bodies like the Concrete

Society, BRE, BCA, etc.

• Poor training of staff

• A poor level of even a basic understanding

of the behaviour of construction materials

by designers, specifiers, and contractors.

Although many issues are the same from year

to year (‘Hardy Perennials’) some new issues

(‘New Varieties’) do arise, partly as a result of

reducing construction timescales, economic

design options and changing construction

practices.

‘Hardy Perennial’ TopicsThe following is a list of some of the topics

which occur year on year on year (in no particular

rank order).

• Concrete floors and screeds -

- Design and specification

- Cracking

- Curling

- Debonding

- Joints

- Surface finish

65

• Renders

• External paving

- Design and specification

- Cracking

- Surface finish

- Durability

- Joints

• Formed finishes

- Achieving good finishes

- Blemishes and making good

- Cracking

• Poor cube results

• Interpretation of core results

• RC structural design and detailing

• Concrete specification

• General workmanship issues

• Mortars.

‘New Variety’ TopicsThe following are some topics that either have

become more prevalent in recent years or are

relatively new (again in no particular rank order):

• Cracking of suspended industrial ground

floor slabs (lack of published information

on this topic led to a CAS paper on this

topic)

• Cracking of composite decks (lack of

published information led to a CAS paper

on this topic)

• Tolerances of suspended floors, particularly

composite decks

• Floor flatness. (Probably partly as a result

of the Concrete Society Technical Report

on industrial floors [TR34])

• Floor moisture problems

• Problems with resin floors

• Problems with calcium sulfate-based

screeds

• Large area pour industrial floors’ defects

and problems

• Steel fibre floor problems and defects

• Concrete specification to BS 8500

• Internal architectural polished concrete

surfaces.

‘Dead Wood’ TopicsThere are some topics on which the number of

enquiries has significantly reduced over the last

few years, e.g.:

• Granolithic wearing screeds. Enquiries

have dropped almost to nothing, as these

are now little used

• Cement-sand levelling screeds. The

enquiries have dropped as screeds are

either eliminated or replaced by alternative

materials.

It can be seen that the CAS deals with a very

wide range of topics and these are not all

material related. Engineering knowledge and

experience is needed to deal with many of these

enquiries, hence the fact that most of the CAS

staff are engineers.

Case StudiesThere is a huge range of case studies that

could be quoted but here is a selection of a few

which may be of interest:

• Slippery floor: A floor in Glasgow was

apparently made extremely slippery by a

product used in the factory. In affected

areas the surface was like ice.

• Bridge deck soffit spalling: Arcing from

an overhead traction power cable (25KV)

over a main railway line, to a damp bridge

deck soffit had caused spalling of the

soffit. Pieces the size of dinner plates had

spalled off.

• Substandard slab thickness: The cutting

out of a section of a floor for proposed

changes to a retail unit found that found

that the floor was about 30 to 35 mm

under thickness. This case lead to an

article on slab thickness tolerance

published in CONCRETE magazine.

• Cracking in suspended ground slabs:

The investigation of several cases of

extensive cracking in suspended ground

floor slabs, indicated that these slabs have

a high risk of surface cracking due to

restrained overall and differential drying

shrinkage.

• Cracking in composite decks: The

investigation of several cases of cracking

in composite decks (which were left with a

power trowelled finish) indicated the usual

design and detailing of these gave a very

high risk of cracking over supporting

beams, due to bending and shrinkage.

• Cube/core strength studies: The CAS

has been asked many times to comment

upon cube/core result strength results. In

virtually all cases considered the concrete

66

has been deemed acceptable, even if it

may not have strictly complied/conformed.

What is apparent from these studies is

that there are problems with the current

core strength assessment methods, in that

they can ‘fail’ a conforming concrete.

• Demolished columns: On a scheme in

Edinburgh a few years ago the resident

engineer decided, against advice, to

remove three columns with suspect

concrete, after several floors had been

built on top of these columns. When one

column was being demolished movement

occurred, causing panic, the site was

closed, and a main road in central

Edinburgh was also closed temporarily

(until sanity returned) causing chaos.

• Moisture in floors: The potential

problem of concrete floors not being dry

enough for the applications of floorings is

one that the CAS receives enquiries on a

regular basis. One engineer received four

different enquiries on this topic in one

day. In fact in many cases this potential

problem could be eradicated if the

flooring industry could be persuaded to

use non-moisture sensitive adhesives.

• Constructional tolerances: A significant

number of cases of problems associated

with the specification of completely

unattainable and unrealistic constructional

tolerances have been brought to the CAS.

Whether the specification of grossly

unrealistic constructional tolerances is due

to ignorance or a cynical misuse of the

contract process is open to question in

some cases.

• Surface mottling: For many years the

CAS has been asked to comment upon

cases of mottling due to the use of shiny

impermeable form faces. In one case in

Douglas, Isle of Man, a trough slab soffit

cast against GRP forms was virtually black,

much to the annoyance of the architect. In

this case the surfaces were painted.

67

Mike Grantham is a Chartered

Chemist and a Fellow of the

Royal Society of Chemistry. He

has worked in the field of

construction materials testing

since 1976, following earlier

work in polymer and adhesive research. He is a

Director of MG Associates and is the current

chairman of the SCI’s Construction Materials

Group. He is also a Director of GR Technologie

Ltd., the organisers of the “Concrete Solutions”

conferences on concrete repair.

ABSTRACT Concrete testing remains a useful tool in the

armoury of methods to resolve reasons for

concrete failure. Many engineers are familiar

with the basic methods, but possibly not with

some of the pitfalls they can entail. A detailed

understanding of the capabilities and limitations

of the different concrete test methods is critical

to getting the correct information. This paper

addresses the more common test methods and

discusses possible errors that can occur if they are

not fully understood. Some information on new

test procedures is also given.

KEYWORDS Concrete, Testing, Desk study, Visual survey,

Covermeter, Carbonation, Chloride testing,

Phenolphthalein, UPV, PUNDIT, Half-cell, Llinear

polarisation, Corrosion rate, Schmidt hammer,

Petrography, Radar, Impact-echo, Corrosion

monitoring.

INTRODUCTIONWhen I was asked to write something for

presentation at the ICT Symposium, I was faced

with a dilemma. I could, of course, have

regurgitated all of the stuff that most of us

already know regarding procedures for the

testing and inspection of buildings and structures.

I didn’t feel that was especially helpful, so I

decided to tackle the presentation in two phases.

Firstly, I felt it was worth discussing how best to

approach surveys, what potential pitfalls there

can be and what techniques give the best

information. Secondly I felt it would be useful to

tackle what new techniques are available and

how these might be employed to solve problems.

TECHNIQUES AVAILABLEWhen examining a structure, we have found

the following to be a consistently good approach

in determining the condition and in appraising

the possibility of deleterious materials or

processes occurring in the concrete:

1. Desk study. What information already

exists? Drawings, manuals, previous

inspection reports? These can be used as a

guide, but should not be taken as gospel! I

recall working on one job where HAC (high

alumina cement) had been identified, and a

company had been revisiting every 5 years

to investigate the degree of conversion of

the HAC and its condition. We examined

the building at the 15-year point only to

find that it wasn’t HAC at all! Nevertheless,

the previous testing laboratory had (rather

poor and ambiguous) Differential Thermal

Analysis (DTA) traces to support the fact

that this was HAC concrete. So don’t

always believe everything you are told.

2. Visual survey. Probably the most useful

part of any survey is to go over the structure

with a trained eye, looking for all those tell-

tale signs of defects. These can include

areas where the concrete is a different

colour, is damp, has algal or moss growth

and, of course any obvious signs of spalling

or incipient spalling. The latter, of course,

needs hammer rapping, or on a deck, chain

dragging, to determine hollow areas. It is

not usually too time-consuming to visually

survey the whole structure (provided

elevation drawings are available). If no

drawings are available, it is possible to

produce sketch elevations, but this can be

quite a task for larger structures. The visual

survey should be supported with good

quality photographs. Modern digital

cameras are getting better and better at

this.

WHERE ARE WE GOING WITH TESTING OF STRUCTURES?

Mr. Michael Grantham BA, EurChem, CChem, FRSC,

IEng, MIQA, MICT

MG Associates Construction Consultancy Ltd.

68

3. Covermeter survey. Covermeters are still

not fully understood by many engineers.

The cheaper ones are only as good as the

information you give them: you have to tell

them the bar size and they will work out

the cover. If you then encounter lapped

bars, the machine draws the obvious

conclusion that the steel must be nearer the

surface, if the bar size you gave it was

correct. In a recent legal dispute, our

opposition, proudly brandishing their

Kolectric microcovermeter (a nice and

reasonably priced machine, if you

understand its limitations) told us that it

was accurate to within 2 mm! We proved

that it was up to 8 mm out in places. The

Protovale CM9, which we used on the same

job, has been found to be consistently good

at correcting for bar size variations and

lapped bars.

The average

error on the

legal job was

0.5 mm, with

the worst

error 3 mm

in one

isolated case.

Of course the

CM9 is twice

the price of

the Kolectric machine. We also use the Hilti

Ferroscan for jobs that require a detailed

knowledge of the placement of the steel

reinforcement. This machine gives an image

of the reinforcement under the concrete

surface. Its ability to give bar size, however,

is often questionable.

4. Carbonation testing. The test is

performed using phenolphthalein solution,

sprayed on a freshly broken concrete

surface. Since we are usually removing

dust-drilled samples for chloride testing, we

usually drill twin holes to get sufficient dust

for testing purposes. Breaking the bridge

between the holes with a club hammer and

chisel then gives a freshly exposed concrete

surface to measure carbonation from.

Attempting to measure carbonation in a

drilled hole can be fraught with difficulty

because the drilled dust can contaminate

the edges of the hole. A broken surface

avoids this problem. Carbonation testing

should go hand in hand with covermeter

tests, so that the risk of reinforcement

corrosion can be linked to the measured

cover. It is surprising how often we are

asked by Engineers to perform carbonation

tests without covermeter measurements?

Another problem with carbonation testing is

the effect of patchy diffuse carbonation that

can occur in some materials, notably

reconstituted stone and white concrete.

Both have shown a frequent tendency to

carbonate patchily. When tested, the pink

colour develops gradually instead of

immediately and spreads slowly throughout

the concrete despite it being partially

carbonated in reality. The partial

carbonation is quite enough to cause

corrosion problems, so the phenolphthalein

result can be very misleading. The key is in

the speed of colour change, which should

be immediate.

5. Chloride sampling. This is best done by

removal of drilled dust samples, often taken

in a gradient fashion with increments taken

at different depths. To ensure a

representative sample, a minimum of 25 g

of dust needs to be taken for each sample

increment. If 25 mm increments are used,

this means that twin holes must be drilled

to get sufficient sample. The chloride test

itself actually only requires about 5 g of

sample, but it is normal to report the results

as a percentage of some assumed cement

content. If too small a sample is taken, the

assumptions on cement content can be

wildly inaccurate, compromising the whole

test result. In 1995, in conjunction with

Makers, we carried out a round-robin survey

to test the accuracy of laboratories in

measuring chloride content. The results

Figure 1: Protovale CM9.

Figure 2: Hilti Ferroscan image ofreinforcement.

69

were appalling with over 50% of the

laboratories seriously in error in the reported

results. It is high time that the industry was

tested again. This might make a useful ICT

project for someone, if the appropriate

funding could be found. It is important that

the testing is undertaken blind, with the

laboratory unaware that they are being

tested, in our view.

6. Petrographic examination. In our view

this technique should always be included as

part of a survey. It involves the preparation

of a transparent section of the concrete, on

a glass slide and also one or more polished

plates of the concrete. The thin section

provides the following useful information:

(a) The presence and position of

reinforcement.

(b) The extent to which reinforcement is

corroded.

(c) The nature of the external surfaces of

the concrete.

(d) The features and distribution of macro

and fine cracks.

(e) The distribution and size range and

type of the aggregate.

(f) The type and condition of the cement

paste.

(g) Any superficial evidence of deleterious

processes affecting the concrete.

This is supplemented by the polished plate

examination which adds:

(a) The size, shape and distribution of

coarse and fine aggregate.

(b) The coherence, colour, and porosity of

the cement paste.

(c) The distribution, size, shape, and

content of voids.

(d) The composition of the concrete in

terms of the volume proportions of

coarse aggregate, fine aggregate,

paste and void.

(e) The distribution of fine cracks and

microcracks. Often the surface is

stained with a penetrative dye, so that

these cracks can be seen.

A good petrographic examination will also

determine the mix proportions and estimate

the original free water to cement ratio.

Supplemented by EDAX scanning using an

electron microscope, microscopy becomes an

unrivalled tool for the diagnosis of

chemically induced concrete problems.

7. Half-cell potential testing. This technique

has been around for some while now, but is

worth a mention as we find it to be a

consistently useful tool when used properly.

The technique involves measuring the

electrical activity of the reinforcement by

measuring the voltage of the steel with

reference to a standard cell, typically a

copper/copper sulfate half-cell or a

silver/silver chloride half-cell. The latter is

considerably more robust, but gives results

some 80mV shifted from the copper/copper

sulfate cell.

According to the ASTM C876 method,

corrosion can only be identified with 95%

certainty at potentials more negative than -

350 mV (Cu/CuSO4). For the silver/silver

chloride/0.5M KCl half cell (Ag/AgCl) the

critical value is –270mV, since this type of

cell gives values about 80mV more positive

than the copper/copper sulfate cell.

Figure 3: ASR can be reliably diagnosedusing petrographic examination.

Figure 4: Petrographic examination ofconcrete.

70

Experience has shown, however, that

passive structures tend to show values more

positive than -200 mV (-20mV Ag/AgCl) and

often, positive potentials. Potentials more

negative than -200 mV (-120mV) may be an

indicator of the onset of corrosion. The

patterns formed by the contours can often

be a better guide in these cases.

In any case, the technique should never be

used in isolation, but should be coupled

with measurement of the chloride content

of the concrete and its variation with depth

and also the cover to the steel and the

depth of carbonation.

Large scale half-cell potential maps can

provide an extremely useful guide to the

corrosion condition of a structure. The

technique is especially suited to car parks,

bridges and marine structures.

The plot in Figure 5 shows a survey of a

complete post tensioned car park deck.

The white areas are where no conventional

reinforcement exists. The areas of high

corrosion activity are clearly visible.

There are two potential pitfalls with half-cell

potential measurements. Firstly, it only

measures what is happening on the day the

measurements are taken. During summer

months, it is quite possible for a structure to

dry out and for corrosion cells to shut down.

This can result in significantly reduced half-

cell potential activity. It is easy then to look

at the data for a structure, which clearly has

a corrosion problem, and conclude that the

half-cell test is useless because it says (quite

correctly) the structure isn’t corroding!

The other possible problem occurs when the

concrete is very damp or where a polymer-

modified concrete is used, for example. In

these situations, oxygen access to the steel

can be restricted. This causes the passive

oxide layer on the bar to become unstable

and the bar can then commence corrosion,

but at an infinitesimally slow rate, in the

absence of oxygen. The half-cell potential

test indicates very high negative potentials,

but these relate to the low oxygen

availability, not to high levels of corrosion

activity. Measurement of resistivity can be

very helpful here. If high negative rest

potentials in the steel reinforcement

correspond to areas of high resistivity,

significant corrosion activity can be ruled

out. The rogue results are more likely to be

due to oxygen starvation.

It is said that the technique is only really

applicable to chloride-contaminated

concrete. This is true to an extent, as

carbonation induced corrosion tends to be

more general and the intense contour build

up that occurs with chlorides does not tend

to happen. Nevertheless, in our experience,

carbonated concrete with sufficient moisture

will show potentials in the active zone. If

the concrete is dry, the resistivity tends to be

high and low or positive potentials are

found. If the moisture content is that low,

however, corrosion is unlikely in any case. In

common with chloride-induced corrosion,

very damp concrete can again suffer the

oxygen starvation effect.

As a tool to aid the location of repairs to

large structures this technique is extremely

useful.

Figure 5: Large scale half cell potential map of a post-tensioned car park.

71

8. Corrosion monitoring

The extent of corrosion-induced deterioration

of reinforced concrete structures around the

world has led to increasing interest and

concern in the durability and performance of

reinforced concrete. Equations and models

have been used to predict the ability of

concrete to resist chloride ingress and to

estimate the time to corrosion, cracking and

concrete spalling.

These models require empirical data to validate

them. In addition, owners of large, prestigious

structures require assurance that their structure

is behaving as predicted and that maintenance

requirements can be foreseen and scheduled

without major disruption to the use of their

facilities. Permanent corrosion monitoring is a

very useful tool for ensuring that the

vulnerable elements are performing as required

with respect to the long-term durability of the

structure. It is also valuable where problems

have been identified. It can be used to ensure

that the optimum repair is applied to the right

area at the right time, ensuring the most cost

effective repair.

Broomfield, in a recent paper[1], presented

details of monitoring of the bridge deck in a

road tunnel. In Phase 1 of this project, thirty-

seven corrosion-monitoring probes were

installed in the reinforcement cages before

casting the concrete. After the concrete was

cast and cured, the formwork was stripped off,

exposing a capped socket on the soffit of the

deck unit. The deck units were installed

overnight and at weekends in the tunnel and,

on completion, the corrosion monitoring

probes were checked and the system

commissioned manually using a hand held

logging instrument. In phase 2, the second

tunnel was de-decked and 35 similar probes

were installed. A remote monitoring system

was then networked to 69 probes and

commissioned in 2001.

A typical unit consisted of a three electrode

linear polarisation (LPR) unit with a mild steel

working electrode of known dimensions, a

silver/silver chloride/ 0.5M potassium chloride

reference electrode and two stainless steel

auxiliary electrodes. A platinum resistance

thermometer was an integral part of the

probe. Other probes were installed to

measure the electrical resistivity of the

concrete. An identity chip with a unique

address also formed part of each unit to avoid

confusion when taking manual readings and

when setting up the remote monitoring unit.

The unit also had a connection to the

reinforcement so that the polarisation

resistance of the actual reinforcement could be

measured as well as that of the isolated

working electrode.

Corrosion rates were calculated from the

polarisation resistance using a Stern and Geary

B value of 60 mV. The surface area of the

mild-steel working electrode was 20 cm2.

Figure 6 shows the corrosion rates of four

probes out of the 35 installed in the West

Tunnel. After the first few readings, the

corrosion rate stays below the warning alarm

level set at 1.0 μm/y. Corrosion rates less than

Figure 6: Typical Corrosion Rate Plot with Time for the West Tunnel.

72

this (approximately 0.1 μA/cm2) are considered

to reflect a passive condition. Probe 10/28

shows “noisier” results than the other three

probes. There is a general downward trend in

corrosion rate with time, stabilising over winter

2001, with a slight rise toward the end of the

data, around July 2002.

Figure 7 shows similar data but using the

reinforcement connection to polarise the steel

around the probe rather than its own isolated

working electrode. The results have been

calibrated against the isolated electrode.

These show a less “noisy” set of results, when

working from the larger surface area of the

reinforcement network. There is a similar

trend as in Figure 5 of a decrease in rates with

a slight rise toward the summer of 2002. The

trend is more apparent here. Temperature

measurements are shown in Figure 8. These

show how the decrease in corrosion rate with

time was influenced by the seasonal

temperature variations.

9. Ultrasonic pulse velocity

In the author’s view, both this technique and

the Schmidt hammer are under-used

techniques. On training courses we regularly

demonstrate how sensitive both methods are

to changing concrete strength. A simple

demonstration is conducted to show that

Figure 7: Trace Improved for Noise.

Figure 8: Temperature Monitoring of Structure.

73

adding water to a mix in a series of increments

lowers the cube strength. The students are

then shown that the cubes can very quickly be

tested with Schmidt Hammer and UPV, and a

clear trend of results with the falling strength

occurs. Building up such a library of data on

real contracts would enable anyone to quickly

assess whether failed cubes really reflected a

fault in the concrete, by testing the in situ

structure, or whether poor cube making or

sampling was the problem.

Its use in structures relies on the fact that the

velocity of ultrasonic pulses travelling in a solid

material depends on the density and elastic

properties of that material.

The quality of some materials is sometimes

related to their elastic stiffness so that

measurement of ultrasonic pulse velocity in

such materials can often be used to indicate

their quality as well as to determine their

elastic properties.

Materials which can be assessed in this way

include, in particular, concrete and timber

10. Schmidt hammer

The Swiss engineer Ernst Schmidt first

developed a practicable rebound test hammer

in the late 1940s and modern versions are

based on this. A spring controlled hammer

mass slides on a plunger within a tubular

housing. The plunger retracts against a spring

when pressed against the concrete surface and

this spring is automatically released when fully

tensioned, causing the hammer mass to

impact against the concrete through the

plunger. When the spring controlled mass

rebounds, it takes with it a rider, which slides

along a scale and is visible through a small

window in the side of the casing. The rider can

be held in position on the scale by depressing

the locking button. The equipment is very

simple to use and may be operated either

horizontally or vertically either upwards or

downwards.

The plunger is pressed strongly and steadily

against the concrete at right angles to its

surface, until the spring loaded mass is

triggered from its locked

position. After the

impact, the scale index is

read while the hammer is

still in the test position.

Alternatively, the locking

button can be pressed to

enable the reading to be

retained or results can

automatically be recorded

by an attached paper

recorder. The scale

reading is known as the

rebound number, and is

an arbitrary measure since

it depends on the energy

stored in the given spring

and on the mass used.

Figure 10: Graph showing relationship between UPV and strength.

Figure 9: PUNDIT Plus UPV machine. Figure 11: Digital Schmidt hammer in use.

Correlation Between Strength and UPV

UPV measured on beam then beam broken and both halves tested in compression

Str

eng

th(N

/mm

2 )

74

This version of the equipment is most

commonly used, and is most suitable for

concrete in the 20-60 N/mm2 strength range.

Electronic digital reading versions of the

equipment are available.

We have mentioned above a good practical

use for this equipment. Provided its limitations

are understood (and that means ripping off

the “calibration” graph on the side of the

machine) it is a very useful tool. Used in

comparison mode, or with proper calibration

on the concrete to be tested, it is useful and

reasonably priced tool in concrete testing.

11. Radar

GPR is an echo sounding method where an

antenna (transmitter/receiver) is passed over

the structure under investigation. Low power

radio pulses are fired into the structure and

reflections are recorded from material

boundaries or features such as voids or

embedded metal. Sampling is so rapid that the

collected data effectively forms a continuous

cross section, enabling rapid assessment of

thickness, arrangement and condition over

large areas. By assessing the strength and the

scatter of signals it is often possible to find

cracking, corrosion and changes in

compaction, bond and moisture content.

Surveys of buildings and structures are typically

conducted by a two-person team. One

member will operate the control instruments

and log the data, while the other sweeps the

antenna over the surface in a series of profiles.

The position of each profile is recorded and

distance along a profile is measured using an

odometer wheel that controls the sampling

rate of the radar system. The equipment is

rugged, self powered and is suitable for use in

confined spaces and at height using mobile

hoists or access cradles. Using advanced digital

systems mounted in vehicles, large areas such

as runway and highway pavements can be

rapidly assessed. Detailed pavement surveys

are conducted at 5–10 km/h and inventory

surveys at 50–70 km/h.

Radar is very good at determining voids under

slabs and finding voids in walls.

Reinforcement is detected with ease.

Determine major construction features

Assess element thickness

Locate reinforcing bars

Locate moisture

Locate voids, honeycombing, cracking

Locate chlorides

Size reinforcing bars

Size voids

Estimate chloride levels

Locate rebar corrosion

Table 1: Structural Applications of Radar.

Greatest Least

Figure 12: Radar in use to detectreinforcement in a bridge.

Reliability:

75

However, small voids can be much more

difficult or impossible to find with any

reliability, and mapping of foundation details

has proven too to be fraught with difficulty.

Given the expense of radar surveys,

consideration must be given as to whether

they are a cost effective approach for

structures. In some situations radar has clear

benefits, but in others, information can often

be gained effectively using lower cost, less

complex methods. (Author’s note – a large

breaker is a very sound tool for some types of

survey!!)

NEW TECHNIQUESAll of these methods have been around for a

while. So what is new in the field of concrete

testing? The answer is very little. The above

techniques remain the tried and tested way of

establishing problems with structures and

providing the essential information to deal with

them.

Some recently published work has however

highlighted a few new methods worthy of

mention.

Impact Echo-TechniquePrinciples of the method

A small steel sphere generates an impact on

one of the faces of the tested element, which

produces dilatational waves that propagate

through the material. These waves are reflected

by the external limits of the structure and by

voids, metallic sheaths, crack interfaces between

materials, etc. The amplitude of the reflected

waves is measured by means of an accelerometer

located adjacent to the point of impact. The time

signal is converted into a frequency signal whose

analysis gives indications as to the location and

the type of flaws detected.

In a recent paper by Toussaint[2], presented at

the Concrete Solutions Conference in St Malo in

2003, a typical application was shown. Heating

pipes buried in a concrete floor had frozen,

fractured and delaminated the concrete. It was

necessary to find the extent of the problem.

A 1-metre grid was painted on the controlled

slab. In order to obtain reproducible and reliable

measurements, the concrete had to be rubbed

down at each of the nodes of the grid. Certain

damp areas had to be dried before testing. A

steel sphere of 8 mm diameter was used to

produce the impacts that generate frequencies

allowing flaw detection at more than 6 cm depth.

The presence of cable trays embedded in the slab

or zones with a higher density of pipes disrupted

the measurements and complicated their

interpretation. The signals measured above cross

beams were also difficult to interpret. The non-

uniformity of the lower faces likewise

complicated the reflected signal.

As far as one of the slabs was concerned, the

presence of a tower crane working near the

building foundation resulted in extraneous

vibrations that disrupted data acquisition. The

measurements had to be carried out during the

weekend. One signal alone was sometimes

difficult to interpret and it was often necessary to

corroborate the hypotheses put forward by

analyzing the signals measured at adjacent

points. That is the reason why an area was

marked as damaged when the measurements

carried out at two adjacent points, at least,

presumed the presence of a cracking plane.

Acoustic monitoringWhile on the subject of listening to structures,

an interesting new application of monitoring of

Figure 13: Example of core carried out ina damaged area.

Figure 14: Marking of the cracked areasby means of paint.

76

structures has been listening for tendon breaks in

both bonded and unbonded post-tensioned

structures[3].

Continuous acoustic monitoring has been used

since 1994 to monitor failures in bonded and

unbonded tendons in post-tensioned structures,

where it has shown major benefits in confirming

the performance of structures. To extend the

application of this technology to the monitoring

of concrete cracking required that the

effectiveness of the principles and methods were

evaluated for each structural type. For acoustic

monitoring technology to function in a particular

environment it must be shown that the signals

generated by wire failure can be detected above

general noise levels and distinguished from events

which are not of interest. Furthermore, to assess

the structural implication of each event it is

generally important to be able to locate the

source of each emission.

Provided with high quality data of this type,

the engineer can appraise a structure with

knowledge of the actual failures in damaged

elements, and their location, in the entire

structure over the monitoring period. The

alternative, to base the assessment on a physical

inspection at a sample of locations, leads to

uncertainty when for practical and economic

reasons the number of inspection points is

limited. Monitoring the entire structure may also

reveal failures not detectable by a conventional

investigation. In many applications the acoustic

data is transmitted over the Internet for

processing and analysis. After processing and

quality control checks, the data can be made

available on a secure section of a web site,

allowing owners rapid independent access to

their database of results.

The technology is useful in providing cost-

effective long-term surveillance of both unbonded

and grouted post-tensioned structures.

Papers have been published on the possibility

of monitoring other acoustic events in structures,

such as the cracking resulting from reinforcement

corrosion. Given the levels of probable

extraneous noise on most structures, we think

this remains as an interesting research tool at

present.

So where next? Could anyone come up with

a reliable means to determine chloride in concrete

in situ? Or can someone devise a safer and

cheaper way of X-raying structures, to determine

structural details. A reliable way of determining

how fast reinforcement is corroding would be

welcomed. Techniques based on linear

polarisation resistance do provide useful data as

in the tunnel example, but has shown

considerable variation in data quality when used

in the way half-cell potential is used, for example.

In the meantime, the present arsenal of tools

continues to serve well and in experienced hands

will usually determine the problem.

REFERENCES

1 Broomfield J, Davies K, et al. Monitoring ofReinforcement Corrosion in ConcreteStructures in the field. Proceedings ofConcrete Solutions, 1st InternationalConference on Concrete Repair, Pub. GRTechnologie Ltd, Barnet, Herts. 2003.

2 Toussaint, P. Examples of the application ofImpact-Echo and Acoustic Emissiontechniques for the inspection of concretestructures. Proceedings of ConcreteSolutions, 1st International Conference onConcrete Repair, Pub. GR Technologie Ltd,Barnet, Herts. 2003.

3 Paulson P et al “The use of AcousticMonitoring to Manage ConcreteStructures” Proceedings of ConcreteSolutions, 1st International Conference onConcrete Repair, Pub. GR Technologie Ltd,Barnet, Herts. 2003.

Figure 15: Standard sensor for buildings,bridges and parking structures.

Figure 16: Time domain and frequencyspectrum plots of wire break detectedby sensor 10.0 m from event.

77

Bob Berry, for more than 35

years, has been involved at

senior level in the construction

industry, both with specialist

contracting organisations and

an international chemical

building product manufacturer. Currently Acting

Chairman of the Concrete Repair Association, his

involvement with the refurbishment of reinforced

concrete buildings and structures stretches back

over 25 years. His experience includes

representation on a number of Concrete Society

technical working groups, industry working

parties and Euro standards development. As

Senior Business Development Manager of

Concrete Repairs Limited, he continues to be

heavily involved in all market sectors of the

concrete refurbishment industry.

ABSTRACT This paper presents an overview on the basic

causes of reinforced concrete deterioration,

current repair methods and more recently

accepted systems supplied and used by Concrete

Repair Association members.

KEYWORDS Concrete Repair Association, Construction

Skills Certification Scheme (CSCS), Trained

personnel and operatives, Quality Assured

accreditation, Health & Safety, Environment,

Corrosion control systems & inhibitors, Structural

strengthening with composites, Specialist

discipline & skills activity, Communication,

Teamwork

INTRODUCTIONConcrete, as we all know, is a very successful

construction material. It is versatile, relatively

low in cost and readily available. Yet despite, or

maybe because of these attributes, we have

witnessed many examples of its failure to perform

over the last decade or more.

Typical problems include carbonated concrete

and chloride (calcium chloride) attack. New

concrete has a pH value of around twelve or

thirteen, which forms a protective passivating

layer over the surface of steel reinforcement.

Attack and penetration into concrete substrates

by carbon dioxide gas and other atmospheric

pollutants reduces the concrete’s alkalinity.

Eventually, with the pH value at neutral (pH7) the

passivating layer is broken down, corrosion

begins and its expansive by-products result in the

cracking and subsequent spalling of the concrete

cover over the steel reinforcement. The action of

chloride ions and oxygen, following the break

down of the protective passivating barrier around

the steel, attacks the steel and after time often

results in a loss of section of significant area. This

can seriously affect the integrity of a structure or

building and some car parks and similar

structures have been known to collapse as a

result. Chlorides are commonly introduced into

concrete via de-icing salts, but also in marine

environments such as seafront locations and

marine jetty and pier structures. Permanently

submerged seawater structures do not suffer

from this problem due to the absence of free

oxygen. Many precast concrete panels, columns,

beams and window elements contain chloride

material, although this is no longer permitted for

use as an accelerating admixture.

AN OVERVIEW OF CURRENT CONCRETE REPAIR SYSTEMS

Mr Bob Berry, Acting Chairman, Concrete Repair Association

Concrete Repairs Ltd

Figure 2: Carbonation.

Figure 1: Low Cover.

78

The implementation of CDM (Construction,

Design & Management), the requirements of

RIDDOR (Reporting of Injuries, Diseases and

Dangerous Occurances) and a culture of safety

awareness should encourage all building owners

or, on their behalf, those responsible for their

maintenance monitoring, to regularly inspect their

structures. When necessary and when identified,

remedial action should be promptly implemented.

Once the repair process is underway, the safety of

the structure and its expected long term

structural condition should also be

comprehensively undertaken.

So, when faced with concrete refurbishment

problems what action and considerations need to

be taken before proceeding ?

Considerations to be taken into account:

• Safety

• Deterioration & diagnosis

• Client’s objectives

• Methods & materials

• Specification criteria

• Contract documents

• Contractor selection

• Site activity & supervision

• Electrochemical & other options.

Concrete problems need to be assessed,

identified and understood, but how does one go

about assessing what damage has been and is

being subjected to an area of concrete? Visual

inspection of the damage is the obvious pre-

requisite, but on its own is insufficient. To ensure

a successful concrete repair, more thorough and

comprehensive testing is necessary.

Testing usually includes some or all of the

following procedures:

• Visual survey

• Hammer testing

• Chloride testing

• Chemical analysis

• Reinforcement cover assessment

• Half-cell potential surveys

• Carbonation testing using phenolphthalein

solution to ascertain the depth and

location of carbonation relative to the

steel rebar.

Before any project proceeds, however,

consideration must also be given to the client's

circumstances.

The following should be taken into account:

• Financial constraints

• Tenant considerations

• Future requirements for the structure

• Weather and time of year.

So, let us assume we now understand the

cause of the problem, the client’s needs and the

tenant’s requirements. Where do we go from

here?

Design and specification of repair work should

include evaluation of the following.

• Compliance to BS EN ISO 9001 – 2000

• Client & material manufacturer approval

status etc.

• Health & safety

• BBA approval

• Other appropriate standards such as CSCS

operative registration

• Constructionline accreditation

• Appearance of repair

• Effects of repair on environment

• Weather conditions.

On a practical level consider health and safety

implications, the appearance of the structure and

the method of repair. For example, what effect

will preparation dust and noise have on the local

environment? Will adverse weather conditions

have a negative impact on the chosen repair

method?

The physical repair process will involve most of

the following elements. Firstly and extremely

important is preparation, cleaning and breaking

out of the deteriorated or contaminated concrete.

The steel reinforcement must be cleaned and

protected.

The entire area is primed and reinstated with

hand applied, spray applied, or flowable mortars,

grouts, or concretes.

Figure 3: HP water jetting.

79

Fairing coats will give repaired areas a clean,

smooth and uniform surface, whilst protective

coatings will protect, increase resistance to future

deterioration and provide an attractive finish.

CONTRACT DOCUMENTS &TENDER STAGE

The preparation of concise contract documents

is vital in order to achieve a successful concrete

refurbishment project. Reports of any survey &

diagnosis works together with drawings, if

available, should be provided. Consideration must

be given to the type of access, protection on site

and co-ordination with other trades. The use of

the CRA’s Method of Measurement document will

assist and, together with the

detailed survey, will provide a

realistic cost projection. When

complete, the specification should

encompass the method, the

materials, contingencies, weather

precautions and application

recommendations. Finally, verify

third party accreditations.

Having decided the materials

required and the method of

repair, the next stage is to select

appropriate contractors for the

project. The specifier should be

satisfied that the contractors are

financially sound and able to devote the

necessary management, technical and trained

labour resources to the contract. This procedure

is usually carried out through the tendering

selection process, but evaluation should also take

account of the following criteria. Is the

Contractor a CRA member? Does the company

have ISO 9001 - 2000 Quality Assurance

accreditation, employ trained operatives (CSCS),

has it provided technical references and third

party referees and has previous experience of the

proposed works? Does it have product

manufacturer recommended or approved

contractor status?

- CRA member

- ISO 9001 - 2000 Quality Assurance

- Trained operatives

- Product manufacturer recommendation

- Financial status

- Technical references

- Previous experience.

Finally, on contract award, ensure adequate

work supervision is in place during all stages of

the contract period.

ALTERNATIVE REPAIR METHODSFOR REFURBISHING REINFORCEDCONCRETE

In addition to conventional repair techniques,

there are a number of electrochemical and other

remedial options that should be considered.

Chloride Extraction& Re-Alkalisation

Chloride extraction is designed to draw

chloride ions away from the steel reinforcement,

whilst re-alkalisation is intended to re-establish

alkalinity of the concrete around the steel.

Figure 4: Protecting prepared steel.

Figure 5: Dry process sprayed concrete.

Figure 6: Chloride extraction technique.

80

Corrosion inhibitorsCorrosion inhibitors are designed as a

preventative measure providing corrosion

protection of reinforcement in all types of

concrete structures above and below ground.

During repair and maintenance as a treatment of,

as yet, undamaged reinforced concrete where

steel is corroding or in danger of corroding due

to the effects of carbonation or chloride attack.

The materials can be applied to the surface of

existing repairs and the surrounding areas to

prevent the setting up of incipient anodes. The

solution impregnates concrete to provide

corrosion protection of the steel reinforcement.

The materials are generally applied by brush, low-

pressure spray equipment or “ponded” on the

concrete substrate and allowed to penetrate to

the steel interface. The need to break out

concrete with the associated noise and dust

creation can be greatly reduced when using these

materials.

Cathodic protectionCathodic protection is a permanent system,

designed to remotely monitor and inhibit the

corrosion of reinforcement in structures where

chlorides are ever present. These systems use

proven technology, have become accepted and

now widely used for protecting all types of

reinforced concrete buildings and structures.

For further information on the use of cathodic

protection of reinforced concrete, contact the

Corrosion Prevention Association (CPA).

Association members incorporate all the major

UK contractors, consultants and material suppliers

involved in electrochemical remediation of steel

reinforcement in concrete and steel framed

structures.

Sacrificial anodes,corrosion control anddiscrete CP anode systemsSacrificial anodes are easy to install in

reinforced concrete during the repair

process. The system prevents the

transfer of corrosion into areas

adjacent to a patch repair by

establishing a protective current that

restores electrochemical equilibrium.

Alternative sacrificial corrosion control

systems are installed into pre-drilled

holes and interconnected in a grid

formation over the structure.

Impressed current systems are available for

protecting reinforced concrete elements subject

to severe exposure conditions.

STRUCTURAL STRENGTHENINGWITH COMPOSITES SYSTEMS

Carbon fibre plates and mesh materials are

being increasingly adopted for structural

strengthening.

Since the early 1990s the UK has witnessed an

increasing requirement for the strengthening and

upgrading of many structures and commercial

buildings. The escalation in demand has been due

in some respect to concrete failure, inadequate

design, poor quality construction, structural and

fire damage, or change of use, etc. All have

influenced the increase, but in the main it has

been brought about through the need to

accommodate increased loading.

In the civil bridge market the introduction of

heavier vehicles has meant that the entire UK

bridge stock has, or is being, structurally

reassessed to accommodate new European

legislation i.e: 40 tonne loading. This on-going

exercise, which includes impact loadings on the

bridge piers, has either established the need for

strengthening, or confirmed the need for load

Figure 7: Re-alkalisation technique.

Figure 8: Installation of sacrificial anodes.

81

restrictions. In addition, growing demand has

also been experienced in the building market,

which is often driven as a result of the need to

increase floor loading capacity; for example when

a change of use for a building is intended.

Not surprisingly, the significant interest in the

new technology has spawned the development of

a number of new strengthening systems. Traditional

methods, utilising additional reinforced concrete or

heavy steel plates, are quickly being supplemented

by fibre reinforced polymers, or FRPs as they are

now referred to. In addition to increasing the load

carrying capacity of the structure, FRPs are

demonstrating significant advantages in increasing

flexural strength, redistributing loads around

openings, improving shear and impact resistance.

The new technology is also contributing

significantly toward reducing the adverse visual

impact of strengthening, accelerating project

times, minimising disruption to services and

resolving access difficulties and detailing problems.

Before the introduction of composites,

strengthening would have necessitated the

installation of additional reinforced concrete, or

the use of steel plates, bonded and bolted to the

structure.

STEEL PLATE CONSIDERATIONS- Additional dead load

- Limited plate lengths

- Possible future corrosion

- Drilling & bolting issues

- Longer installation time

- Health and safety implications.

With the introduction of modern composites

and some innovative installation techniques,

however, such elaborate structural endeavour is

fast declining.

The industry’s lack of enthusiasm for the steel

plate procedure was easy to appreciate. Problems

included dead load, plate lengths, possible

corrosion, drilling and bolting issues, longer

installation times and health and safety

implications.

At first, it was found that in most cases the

costs of both the old and the new systems were

comparable. This was because the high cost of

composites was usually offset by a reduction in

Figure 9: Comparison of techniques.

Figure 10: Steel plate application. Figure 11: Application of FRP mesh.

82

labour and plant. Within a couple of years,

however, clients began to accept composites as

their preferred solution to structural

strengthening.

More importantly, composites were also

beginning to be considered as a solution for

strengthening metallic structures.

This development helped to fuel the market,

encouraged the industry to further adopt the

technology, spawned more material suppliers and

provided better choice.

It was recognised from the beginning that to

establish the composites market in the

construction industry, stringent quality control

procedures were needed to encourage

confidence in the product. In the first instance

the relevant steel plate bonding test procedures

were used, but now, quality control testing is

routinely undertaken on a project-to-project basis

by CRA members.

Pull off tests are undertaken on the concrete

bond surfaces and plate samples are tested,

under laboratory conditions, to check conformity.

As a result, there is now a wide variety of

carbon fibre composite plates available, as well as

glass, aramid and fabrics.

In addition, free-formed wet and dry lay

composite fibre wrapping systems, which can be

used to strengthen complex profiles, have also

evolved. Several CRA members have also

introduced alternative fibres, resins and

pultrusions to meet niche markets.

Before any decision on the most suitable

strengthening material is made, however, the

extremely important issue of system design needs

consideration. System design is available

through CRA members, or through specialist

structural engineers. Many important aspects

need to be considered, such as the flatness and

quality of the substrate, the possibility of on-

going corrosion, the current state of stress in the

element and future loading requirements.

SYSTEM DESIGNCONSIDERATIONS

- Flatness of substrate

- Quality of substrate

- Possibility of ongoing corrosion

- State of stress in the element

- Future loading requirements.

The degree of strengthening possible is often

limited by the strength of the concrete, but it is

more usually governed by the adequacy of bond

between the concrete and the composite. It is

therefore essential that the structure is thoroughly

surveyed, tested and assessed prior to the design

process commencing.

The Concrete Society Technical Reports 55 and

57 give guidance on the design process, quality

control, inspection and testing on site, but it is

important to appreciate that issues such as fire,

cracking and fibre de-bonding need to be

considered in more detail than for conventional

reinforced concrete structures.

In all situations, an adhesive with a glass

transition temperature at least 10˚ Celsius above

the maximum temperature to which the structure

is likely to be exposed, should be selected. The

designer must also ensure that the structure will

not collapse due to delamination of the fibre

reinforcement in the event of a fire, or that

serious damage, impact for example, does not

occur to the composite.

The accurate installation of composites is also

critical. So, what is the process?

At the outset it is extremely important to

establish good quality control on all

strengthening projects. Cleanliness, surface

preparation, product mixing techniques and

application at the right temperature are all

critical. It is essential to get it right first time.

Too little adhesion and/or incorrect installation

will create significant subsequent problems –

problems that you could do without. An

experienced contractor with suitably trained and

supervised staff, such as those CRA members

established in this specialist activity, should always

be the first port of call.

On site, the concrete surface to receive the

strengthening plate is usually prepared by needle

gunning or dry grit blasting and then vacuumed

to remove all dust contaminants.

The composite plates are cut to length using a

guillotine before the plate bond surface is

prepared by degreasing, or the peel ply-backing

strip is removed.

The adhesive is applied uniformly to the plate

surface by drawing it under a profile board,

which is loaded on one side with the adhesive.

The plate is then offered up to the concrete

surface and installed using a hard rubber roller.

Excess resin is removed before the exposed

plate surface is wiped clean. Finally, possible voids

in the adhesive are checked for by light tapping

of the plates.

83

Composite fibre wrapping systems use either

the dry or the wet laid process. With the dry

process, the dry fibre material is cut to shape on

site and applied to the primed bond surface,

which has also received an initial coating of

adhesive.

The material is rolled to remove air bubbles

and to ensure good contact. A further coating of

adhesive is applied, another layer of fabric

applied, and so on. The procedure is repeated as

many times as necessary to achieve the required

strength.

The wet process is similar except that the

adhesive is applied to the fibre material before it

is rolled into position.

The fibre installation can finally be painted if

required.

The first commercial use of pultruded

composite plate in the UK was in 1996. The

installation, at Kings College Hospital, was to

strengthen a floor slab, where the deck beams

were 75mm wide and 13m long. At the time,

very few alternative techniques existed and this

pathfinder project clearly demonstrated the

advantages of composite plates compared to

steel plates.

Further projects followed, some using

combinations of both composite plate and fibre

wrapping.

It can be said that the use of composites in the

construction industry is still in its infancy. But as

new fibre and resin technology is developed the

possibilities for its use in construction become

infinite. It is only a matter of time before the

technology is employed on new construction

projects as a matter of course.

The initial reticence of designers to adopt the

technology has now been surmounted and major

clients such as the Highways Agency, Network

Rail and British Nuclear Fuels Ltd have recognised

the considerable benefits that such materials are

able to provide.

The Concrete Society views the introduction of

fibre composite materials for strengthening

concrete structures as a major advance. It is

proving to be a cost-effective technique,

providing benefits due to speed of installation

and less disruption, says the Society.

It is, however, highly dependent on the quality

of workmanship and it’s vital that an experienced

repair contractor is appointed. This, along with

the importance of regular inspection, is one of

the key points identified in the Concrete Society

Technical Report, TR57, which covers acceptance,

inspection and monitoring of concrete structures

strengthened with fibre composites.

CONCLUSIONWhatever the system chosen or the concrete

activity required, it is accessible through a

member of the Concrete Repair Association. CRA

Members’ work is proven on all types of

structures, such as high-rise residential buildings,

river, rail and road bridges, commercial premises,

unique and unusual buildings and more

conventional structures. The CRA exists to

promote and advance the practice of this

specialist activity. Its rules and Codes of Practice

are stringent, thereby ensuring only competent

organisations are accepted into membership.

85

Shaun Hurley trained as a

chemist and has over 30 years

experience in the construction

industry, predominantly

concerned with polymer-based

materials. He has been

employed by Taylor Woodrow in various

capacities since 1987 and is presently a Senior

Materials Consultant.

ABSTRACTThis paper gives an overview of coatings and

related surface treatments that are commonly

applied to concrete. It discusses the type of

products available, their properties and the

benefits that they can provide. Several new

European Standards that address this area are

also discussed.

KEYWORDSCoatings, Penetrants, Pore-blocking sealers,

Hydrophobic impregnation, Product types and

classification, European Standards, Specification,

Reasons for use and benefits, Properties,

Durability, Maintenance.

INTRODUCTIONThis paper gives an overview of coatings and

related products that are commonly applied to

reinforced and mass concrete and discusses the

benefits that can be obtained from their use.

Three types of system are considered, as follows:

• Penetrants that convert the surfaces of the

pores/capillaries to a hydrophobic state

• Sealers that physically block the

pores/capillaries

• Coatings that form a continuous layer,

thereby shielding the concrete’s surface.

The following aspects of these treatments are

discussed (the context should convey where the

term ‘coating’ is being used to cover all the

system types):

• Reasons for use

• Product types

• Material properties

• Achievable benefits.

Hitherto, the coating of concrete has not

received dedicated and comprehensive coverage

in British Standards. Consequently, the current

production of new European Standards that

address this area, within the wider context of the

repair and protection of concrete structures, is

particularly notable. It is not the purpose here to

review these Standards in detail. Nevertheless,

the content of this paper acknowledges the

extensive scope of these new Standards, both

published and presently in draft form. Thus, it

may serve as an introduction to the more

comprehensive treatment of coatings that is now

becoming available.

WHY COAT CONCRETE?A summary of the common reasons for

applying these products to concrete is given in

Table 1.

The benefits of these applications are well

proven, but specific local conditions can affect

performance significantly. Consequently,

particular requirements should always be

discussed with suppliers.

Although presented in a different format, most

of the examples given in Table 1 can be

correlated with the ‘principles and methods’

defined in the European Prestandard DD ENV

1504-9: 1997[1]. They are also related, therefore,

to the generic Standard (prEN 1504-2) that deals

specifically with systems for surface protection[2].

Uncoated concrete provides a long service life

in many environments. In overly aggressive

conditions requiring additional surface protection,

it can remain an attractive construction material

due to its versatility and relatively low cost. For

some cases, protection against deterioration

and/or ingress may be essential; for others, it may

be optional, giving increased assurance of

satisfactory durability. However, coatings should

not be viewed as a basis for reducing cover or for

inadequate mix design, placement and curing.

Wherever surface coating/treatment is

optional, increased initial costs, and inevitable

maintenance costs, must be balanced against the

projected in-service benefits.

The potential benefits of protective surface

barriers can also be related to the age and

condition of the concrete, as follows:

COATINGS AND THEIR BENEFITS

Dr. Shaun Hurley, BSc, PhD, MRSC

Taylor Woodrow

86

(i) ‘Normal specification’ for new concreteof satisfactory quality. Here, surface

treatments would usually be specified at the

design stage when there is an obvious

incompatibility between the performance of

the concrete and a particular service

environment or demand, e.g. chemical

attack.

In exceptionally aggressive environments,

they may be used to enhance the resistance

to indirect deterioration due to

reinforcement corrosion, although other

options may be considered, for example:

improved concrete mix design, increased

cover or alternative forms of reinforcement.

For other circumstances, any of the

applications given in Table 1 could be

relevant.

(ii) ‘Remedial specification’ for newconcrete of unsatisfactory quality. It is

well established that proprietary products

can provide effective chloride and

carbonation barriers over long service

periods. Consequently, surface treatments

can alleviate potential deterioration due to

an inadequate mix design, insufficient cover

or poor compaction/curing of reinforced

concrete.

(iii) ‘Repair specification’ for concreteundergoing deterioration. Here, a

distinction must be made between the

likely effectiveness of surface treatments

applied before/after the initiation of

reinforcement corrosion; and between

carbonation and chloride ingress.

Coating can considerably extend the

service life of a structure where carbonated

concrete in the cover zone has not reached

the reinforcement. However, the value of

surface treatments is more debatable when

significant chloride ingress has occurred, as

it is generally unlikely that corrosion will be

prevented in the longer term – or even in

the short/medium term where there is a

high level of ingress.

After the initiation of corrosion, due to

Reasons for Surface Coating/Treatment Examples/Comments

To prevent directdeterioration

To prevent indirectdeterioration due toreinforcementcorrosion

To limit or controlingress/contact

To enhance/maintainappearance

To enhance safety

Chemical attack

Physical effects

Loss of concrete alkalinity andsteel passivation due to theingress of acidic gases

Premature initiation of corrosiondue to ionic ingress

Waterproofing

Vapour/gas barriers

Ease of cleaning anddecontamination

Colour and texture

Reflectance

Prevention of mould growthand dirt staining

Anti-graffiti treatment

Uniformity after repair

Anti-slip/skid

Anti-static/electrically conductivesystems

Road/floor markings

Attack by aggressive chemicals such as acids,sulphates, sugars and fertilisers

Deterioration due to erosion/abrasion, saltcrystallisation and freeze-thaw action

Carbonation

Ingress of chlorides in coastal environmentsor from de-icing salts

Barriers to liquid water. Some systems areapproved for contact with potable water

Barriers to moisture vapour, methane, radonand acidic gases, e.g. CO2, SO2 (NO)

Floors, walls in food processing areas,hospitals and nuclear installations

Building facades

Road tunnels and car parks

Walls and floors

Assisting removal

Following patch repairs

Used with a scatter of fine aggregate onfloors/roads

Floor coatings in manufacturing areas

Defining specific areas by colour

Table 1: Common reasons for using surface coatings/treatments.

87

carbonation or chlorides, surface

treatments are likely to be cost effective

only where a relatively short extension of

service life is required. Effectively limiting

the ingress of oxygen and/or moisture

presents a number of practical difficulties,

even where a highly impermeable surface

treatment is applied.

WHAT TYPE OF COATING?The draft European Standard for surface

protection systems applied to concrete, prEN

1504–2[2], adopts a classification scheme that is

based upon function, i.e. hydrophobic

impregnation (penetrants), impregnation (sealers)

and coatings. For each of these functions, the

Standard provides performance criteria for

different applications. Consequently, once this

Standard becomes established, it seems likely that

the need for many practitioners to be concerned

with the generic basis of these products will be a

much reduced.

Coating materials/systems are also dealt with

in a non-harmonized European Standard, EN

1062–1[3], in this case for application to a wide

variety of substrates under the general description

“masonry and concrete”. The objectives of this

Standard, which may be viewed as dealing

predominantly with ‘architectural issues’, is to

avoid misuse and misunderstanding/

overstatement of claims by providing a common

framework for communication between suppliers

and users. It is, therefore, less prescriptive than

prEN 1504–2 and does not support CE marking.

A general system of classification is specified in

EN 1062-1, based on the following alternatives:

• End use – preservation, decoration or

protection

• Chemical type of binder – which may be

inorganic, organic or a hybrid organo-

silicon derivative

• The state of dissolution/dispersion of the

binder – water or solvent-dilutable or

solvent-free.

An overview of product types, according to the

classification method used in each Standard, is

given below.

Product TypesA basis for classifying proprietary products

according to the main generic component (i.e.

the binder) is given in Figure 1.

The systems based on thermoplastics and

synthetic rubbers undergo film formation by

physical processes only, i.e. drying and the

coalescence of dispersed particles. Thermosetting

products are characterised by chemical curing

reactions that lead to molecular growth and the

formation of cross-linked network structures.

Various processes apply to the remaining systems

shown in Figure 1, including reaction with the

concrete substrate.

Figure 1: A classification of surface treatments.

88

It is particularly important to note that,

although the main generic component

contributes significantly to the performance of a

product, there are also many formulation

variables that can have a major influence on the

application and service properties.

Some typical product types that can be

assigned to the functional classification system

used in prEN 1504-2 are given below.

(i) Hydrophobic impregnation: silanes,

siloxanes and some silicones. These

products chemically modify the surfaces of

the pores/capillaries, thus preventing the

absorption of aqueous media by surface

tension effects. There is usually little, if

any, change in appearance of the concrete

and, as the pores remain open, there is

negligible effect on the transmission of

vapours/gases. The ingress of liquids can

occur if the repellent effect is exceeded by

hydrostatic pressure – this could include

ponding, wave action and wind driven

conditions.

(ii) Impregnation (pore-blocking sealers):solvented thermoplastic and thermosetting

systems; some water-borne dispersions and

low viscosity, solvent-free thermosetting

products may also be suitable for

particularly absorbent substrates. As pore

blocking occurs, there is generally enhanced

resistance to ingress under a hydraulic

gradient and, in addition, improved

resistance to abrasive wear. A distinct, if

not necessarily continuous, surface film can

be formed if the application rate is

sufficient or if the concrete is particularly

dense and impermeable.

(iii) Coatings: polymer-modified cementitious

products, pigmented silicates, bituminous

systems, alkyds/drying oils and an

extremely wide variety of products based

on thermoplastics and thermosetting

resins. The attainable thickness per coat

depends upon the particular product type

and can extend to several millimetres.

Heavy-duty linings, membranes, renders

and floor toppings are also based on some

of these binder types. In general, coatings

will provide the highest level of

performance where resistance to aggressive

service conditions is required, viz:

weathering, ingress, chemical attack and

mechanical effects.

WHAT PROPERTIES ARE RELEVANT?

A key section of the draft European Standard,

prEN 1504-2[2], provides a basis for the selection

of appropriate products/systems. Various

performance characteristics (and the

corresponding test methods) are tabulated

against the relevant principles from ENV 1504-

9[1]. The tabulation then shows which

performance characteristics are required for “all

intended uses” within the selected principle and

which may be required only for “certain intended

uses”.

Thus, the Standard acknowledges that the

primary reason for applying a surface treatment

may be supplemented by other requirements that

vary from one project to another. It also

acknowledges that the characteristics specified

for “certain intended uses” are extensive and

that the approach presupposes a very sound

knowledge of the subject by the

designer/specifier.

Given that these new Standards do not seek to

replace the experience of the engineer with a

routine procedure for selection, an appreciation

of many performance properties remains

essential. It is not possible here to discuss specific

properties in any detail, as those of relevance are

extensive. However, a summary of the

characteristics that may have to be considered for

various applications is given in Table 2 and some

general comments regarding performance issues

follow below.

The tasks of specification and selection for a

particular application will generally be

concentrated, at least initially, on the short and

long-term properties given in Table2, as it is here

that the benefits will be obtained. Appropriate

information may be found on technical data

sheets, although it is usually advisable to treat

these documents as an introduction to the

product, as information may be incomplete or

simplified. Consequently, more detailed

discussions with suppliers will often be necessary

and, on occasion, more specific, and possibly

independent, testing may need to be

commissioned.

89

At this point, and particularly for the more

demanding requirements/conditions, due

consideration must be given to the following:

• The exact relevance of laboratory test

results and case histories, and their

relationship to the long-term requirements

of the particular project

• The on-site conditions anticipated at the

time of application

• Maintenance issues.

In the laboratory, both preparation and testing

are invariably conducted under well-defined and

controlled conditions. On external sites in

particular, such standards can be achieved very

rarely, if ever. Furthermore, for various (and

acceptable) reasons, the testing details may differ

from, or at best may only approximate to, the

service environment.

This is not to imply that test results are

irrelevant; rather, that they show the potential

benefits of the product and should be used in the

context of a particular application with some

degree of judgement – more, rather than less,

testing assists this process.

The influence on performance of

substrate/ambient conditions at the time of

application/cure is frequently given insufficient

attention, although it is here that many failures

originate. While it is not unreasonable to assume

that a specialist applicator would be aware of,

and take responsibility for, such matters, risks can

only be reduced by stipulations that are clearly

stated in the specification.

The value of test results is increased

significantly if they are obtained not just on the

freshly prepared coating, but also after some

form of exposure; for instance, thermal cycling,

artificial (accelerated) weathering or mechanical

treatment – impact or abrasion, for example, may

precede an assessment of barrier performance or

chemical resistance. Artificial weathering regimes

bring increased benefits if they are matched to

particular climates of interest.

Such testing is often viewed as providing a

close estimate of the anticipated service life but,

Unmixed and FreshlyMixed

Shelf-life

Storage requirements,particularlytemperature

Flash point

Volatile components

Health, safety andenvironmentalconsiderations

Taint, e.g. of nearbyfoodstuffs

Density and coveragerate

Need for priming

Mixing requirements

Application propertiesand methods

Transition to theDry/Cured State

Effects ofambient/substratetemperature

Sensitivity toambient/substratemoisture

Usable (pot) life

Gel time

Reaction exotherm (forsome systems)

Rate and extent ofcure/drying vs time

Cure shrinkage (only forcertain systems)

Over-coating interval

Short Term

Dry film thickness

Adhesion

Colour, texture, hidingpower, gloss andreflectance

Barrier properties

Mechanical properties

Fire performance

Electrical properties

Slip/skid resistance

Effect on potable water

Ease of cleaning andnuclear decontamination

Resistance to graffiti andthe ease of its removal

Long Term

Change of short termproperties on exposureto service conditions

Accommodation ofcrack formation andmovement

Abrasion resistance

Effects of thermalcycling/shock

Resistance to water,chemicals, biologicalattack/mould growth,radiation

Resistance toweathering

Cleanability

Ease of maintenance

Fully Cured

Table 2: Properties of surface coatings/treatments.

90

generally, this is not the case, as service

environments are usually complex and difficult to

reproduce in the laboratory, notwithstanding the

use of sophisticated equipment. However, the

test results do give an invaluable view of the

manner in which the performance is likely to

change in service, both in direction and extent.

Consequently, they add to the confidence with

which a product can be selected.

General case histories have to be treated with

some caution, as seemingly similar applications

can often vary in significant detail and product

formulations may be changed. The laboratory

assessment of specimens taken from trial areas or

real structures can represent a useful supplement

to more conventional data. Unfortunately,

various constraints tend to limit the availability of

such information.

In summary, when selecting coatings and

surface treatments, it is important that a broad

view is maintained and that all the relevant

factors are considered.

WHAT BENEFITS CAN BE OBTAINED?

For a coating or related treatment to perform

satisfactorily, surface preparation and application

must be carried out strictly in accordance with

the requirements dictated by the particular

product. These issues are not dealt with here,

but they have been discussed in detail

elsewhere[4,5]. Additionally, a recently published

European Standard, EN 1504-10[6], gives extensive

detail on all aspects of on-site work, including

associated tests and observations.

The main benefits provided by surface

coatings, and related treatments, have been

summarised earlier (see Table 1). Some particular

aspects of each functional type are discussed

further below.

Hydrophobic ImpregnationIn addition to their benefits for preventing the

ingress of water and saline liquids, these products

generally require minimal surface preparation and

are simple to apply. Although their durability may

be difficult to ascertain, they have demonstrated

cost-effectiveness on many UK highway structures

subject to the ingress of de-icing salts; re-

application poses little difficulty.

The volatility of some products, and the

consequent material loss in hot/windy conditions,

is a disadvantage, but this can be alleviated with

more recently developed materials that have a

paste-like consistency. Such products also assist

in achieving good penetration.

Concerns have arisen that penetrants, such as

silanes, will encourage carbonation by

maintaining an optimum internal moisture state

(50-70% RH). This does not appear to be

supported by experience.

A number of laboratory studies seemingly

support the use of silanes/siloxanes to maintain

concrete in a sufficiently dry state for the

inhibition of ASR. However, there appears to be

little, if any, documented evidence from real

structures for the effectiveness of this approach.

Various factors, including the low resistance to

moisture vapour transmission, could be

responsible for a lack of success.

Impregnation (Pore-BlockingSealers)

Provided that their limitations are clearly

recognized, these products can be extremely cost-

effective. They can provide useful resistance to

weathering, water ingress and abrasion, while

requiring little surface preparation, and they do

not depend on maintained adhesion – perhaps

the major downfall of many coating applications.

They can also be used effectively as

primers/stabilisers prior to coating porous or

friable surfaces.

Although surface sealers do not form a highly

impermeable barrier to the ingress of carbon

dioxide or chlorides, their performance can be

more than adequate in marginal situations, i.e.

those where some upgrading will delay

reinforcement corrosion for a useful period. From

experience, such benefits often apply to exposed

aggregate concrete panels, as possibly awkward

issues associated with coatings (appearance,

surface preparation and maintenance) can then

be avoided.

Caution is required if surface sealers are

considered for protection against chemical attack,

for example, acids on floors, as it is difficult to

ensure that a complete barrier has been obtained,

while the slightest imperfection can lead to attack

that spreads below the surface.

CoatingsCoatings can provide any of the benefits given

or implied in Table 1, including such seemingly

opposed demands as resistance to liquid water

ingress but transparency to moisture vapour

transmission – a requirement for many facades.

Given a versatility that exceeds that of

91

hydrophobic and pore-blocking impregnants, and

the wide range of product types, it can be

difficult to achieve an optimum balance between

satisfactory performance and initial/maintenance

costs. The need for re-coating is inevitable,

although the lifetime costs will depend on a

number of factors, for example: ease of access,

surface preparation requirements and the

frequency of re-coating.

Many coating types can be re-applied with

relatively little preparation but, with the exception

of methacrylate systems, the thermosetting

products generally need to be abraded for good

new/old intercoat adhesion. The frequency of re-

coating will vary, depending on function and

other requirements, and could range anywhere

between 5 and 20+ years.

In some cases, coatings are used sacrificially –

for example, on bunds or floors where accidental

spillage of very aggressive chemicals can occur.

Short-term resistance to breakdown is seen as a

benefit here, as coating re-application is

preferable to extensive concrete replacement.

In contrast to impregnants, some coatings can

be applied to very damp/wet surfaces;

underwater application is also possible with

specific systems. This capability is now commonly

utilized in ‘fast track’ flooring applications, where

a ‘surface damp-proof membrane’ allows vinyl

sheet/tiles to be laid on base slabs or screeds that

have a very high moisture content. Perhaps less

commonly, some products can be applied to

‘green’ concrete, acting as both a curing

membrane and a permanent coating.

The evaluation of some uses that, in principle,

are well proven, such as chemical resistance or

resistance to chloride ingress, can present

experimental difficulties. Intermittent contact,

common with chemicals on floors or salt

solutions on highway structures, can be simulated

relatively easily, but the timescale for testing can

become unacceptably protracted. Consequently,

recourse is often taken to ponding or complete

immersion, conditions that can give a distorted

view of performance where a product is not

designed for prolonged contact.

For chloride ingress, a particularly important

property for many coating applications, there is a

more fundamental difficulty, as very long test

periods can be required even under immersed

conditions. This problem, which is discussed

elsewhere in more detail[7], has delayed the

agreement of a satisfactory procedure for use as

a European Standard.

CONCLUSIONSAn extensive range of coatings and related

products is available for application to concrete.

Successful use over many years has established

that these systems can provide significant benefits

for concrete of widely varying age and condition.

Typical applications include the prevention of

various forms of deterioration and ingress, the

enhancement of appearance and improvements

in safety for trafficked surfaces.

New European Standards, dealing with the

protection and repair of concrete structures,

should assist in the specification, selection and

site use of these products.

REFERENCES

1. BSI, DD ENV 1504-9. Products and systemsfor the protection and repair of concretestructures – Definitions – Requirements -Quality control and evaluation ofconformity. Part 9: General principles forthe use of products and systems, 1997.

2. prEN 1504-2. Products and systems for theprotection and repair of concrete structures– Definitions – Requirements - Qualitycontrol and evaluation of conformity. Part 2:Surface protection systems (presently indraft form only).

3. BSI, EN 1062-1. Paints and varnishes –Coating materials and coating systems forexterior masonry and concrete. Part 1:Classification, 1997.

4. CONCRETE SOCIETY, Guide to surfacetreatments for protection and enhancementof concrete. Technical Report No. 50. TheConcrete Society, U.K, 1997.

5. HURLEY, S. A. Coatings. Chapter 17 inAdvanced Concrete Technology – Processes.Newman, J. and Choo, B. S. (editors).Elsevier, Oxford, 2003, pp 17/1 – 17/14.

6. BSI, EN 1504-10. Products and systems forthe protection and repair of concretestructures – Definitions – Requirements -Quality control and evaluation ofconformity. Part 10: Site application ofproducts and systems and quality control ofthe works, 2003.

7. HURLEY, S. A. Coatings for concrete – therole of new European Standards. Paper 3 inCoatings for masonry and concrete.Brussels, 30 June – 1 July 2003, Conferencepapers. The Paint Research Association,Teddington, 2003.

93

Peter Robery is Head of

Infrastructure Maintenance in

FaberMaunsell and a visiting

Professor at The University of

Leeds, from where he

graduated and returns to teach

on concrete repair and maintenance strategy.

Peter represents the UK as principal technical

expert for BSI on the CEN Standards Working

Group TC104/SC8/WG2, developing standards for

mortars and concretes for structural and non-

structural concrete repair.

ABSTRACTMore than 50% of UK construction

expenditure is now attributable to refurbishment

projects. Yet asset inspection, maintenance and

repair is still the poor relation to new build in the

construction sector.

Accurate whole life costing of the

maintenance and repair of an asset over its life is

one of the most difficult and technically

challenging problems facing the industry today. It

is in demand, because industry is being asked to

predict expenditure profiles for older assets, such

as for PFI projects. In short, tomorrow’s asset

managers need to be “deteriorologists”, who

understand why infrastructure assets of various

kinds fail over the service life.

This Paper reviews the common deterioration

processes at work that affect our concrete assets

and reviews the repair methods available,

including a brief review of the forthcoming

standards on concrete repair (BS EN 1504).

KEYWORDSConcrete repair, Maintenance, Strategy,

Deterioration modelling, Monitoring, Research

and development, Education.

INTRODUCTIONThe past 100 years has seen considerable

changes in the nature of construction work,

particularly reinforced concrete structures. The

use and abuse of reinforced concrete as a

construction material has led to a backlog of

deteriorating structures, particularly those in the

most severe exposure environments, such as road

bridges and car parks. Although more than 50%

of UK construction expenditure is now

attributable to refurbishment projects,

maintenance and repair is still the poor technical

relation in the construction sector. While

designers have sat back and praised their new

buildings and bridges that rise out of the ground

like gleaming diamonds, they have often ignored

the planned inspection and maintenance of their

designs. Perhaps this is because maintenance

and repair is not perceived as an attractive

discipline: however, the science of deteriorology,

harnessed to save our crumbling infrastructure, is

a challenging field of bespoke, “prototype” repair

solutions, using the latest materials and methods

to solve corrosion problems. Asset inspection,

maintenance and repair are as essential as new

build design if the industry is truly to offer

concrete structures as a sustainable construction

method.

A lack of understanding regarding durability

and exposure classifications led to a multitude of

structures built in the 1960s and 1970s that

required major maintenance work well short of

their intended service life. Worse still, the defects

were treated without any real understanding of

the causes of the problem, leading to a catalogue

of unsuccessful repairs. These failures fostered an

attitude among engineers that concrete repair

products were “no good”, because the patches

always fell off. Not that the formulators were

completely blameless; the issue was a widespread

lack of understanding of why the repairs were

required and how to repair them successfully.

Some good examples are included in the

following list:

• Concrete repair products bonded with

materials that are attacked by the alkali

and moisture naturally present in concrete

• Use of materials with additives that speed

up both the setting of the mix and the

corrosion rate of the embedded steel onto

which they are applied (e.g. calcium

chloride)

• Use of ultra fast setting repair materials

that cure by exothermic reaction, leading

to cracking as they cool down (e.g.

polyester resin mortars)

• Failure to use these “new” concrete repair

products properly – the horror stories of

A CONSULTING ENGINEER’S VIEW OF REPAIRS

Professor Peter Robery, BSc, PhD, CEng, MICE, MICT, MCS

FaberMaunsell

94

allowing bonding coats to dry (making a

de-bonding layer) and adding water to

epoxy resin because the mortar was too

stiff.

Some engineers have learned from the

mistakes of the past and have taken to challenge

the manufacturer’s claims for every new product

and system; but even case histories can be

misleading, referring to structures with very

different diurnal temperature, precipitation and

humidity exposure than the current candidate

structure in need of repair.

It is important therefore for engineers of

tomorrow to understand the problems of the

past, challenge the “common knowledge” advice

of the present and think about providing lasting

reinforced concrete structures that will be both a

credit to the industry in 100 years and be still

standing!

THE LESSONS FROM THE PASTTo understand the future for concrete repair

and maintenance, an appreciation is needed as to

how the industry has ended up in the current

position of having a multitude of failing

structures.

Concrete Durability FactorsIt remains an unfortunate truth about the

history of reinforced concrete design and

specification that had we learned our lessons

from the early research into the performance of

reinforced concrete, many of the problems facing

us today would not have occurred[1].

In the 1920s, research into the effects of

exposing reinforced concrete to seawater led to

very firm conclusions about keeping the two

apart. When concrete structures were designed

for use in seawater, extreme care was taken. In

fact, some of the most durable reinforced

concrete maritime structures were built in the

period from 1910 to 1950. A good example is

the concrete used in the Mulberry Harbour units,

which were conceived by Guy Maunsell and

designed by Oscar Faber (among others). These

floating structures were built during 1939-1945

using no more sophisticated concrete technology

than a cement-rich, watertight concrete (1:1:2 by

weight of cement : sand : 10mm coarse

aggregate)[2]. The units have survived exposure in

seawater for over 60 years[3]. With a cement

content equivalent to over 550kg/m3, far too high

by today’s “modern” standards, and with high

cover to the reinforcement, chloride ions have

hardly penetrated into the concrete at all and are

certainly well away from the deep-set

reinforcement.

A lesson from this 1940s’ structure is that by

using large quantities of coarse-ground cement,

necessary to get sensible strengths, a highly

durable structure would result. Yet the trends of

the 1950s to 1970s very much changed the

design concepts and hence the durability of

structures. Driven by the need to build quickly,

industry required that concrete for both precast

and insitu works should be fast setting, which

resulted in changes to the cement chemistry and

an increase in the fineness and hence reactivity of

the cement. With the use of the high reactivity

cement, it was found that less cement was

needed to get the same compressive strength at

28-days – that well-known time horizon of

obscure origin that takes no heed of the materials

being used or their rate of strength gain.

In the building sector, architectural pressures

were also contributory, as these dictated the need

for an increasingly slender form of construction

and reduced concrete cover. With pressure to

shorten the construction programme, a concrete

“anti-freeze” began to be introduced, based on

calcium chloride, which was added to the mix to

accelerate the set and allow concrete to be cast

under low temperature conditions. To keep costs

down, poorly washed marine-sourced aggregates

were used, boosting the insitu chloride ion

content. Allied to these factors were a workforce

and a supervisory team that generally did not

understand the importance of cover, compaction

and curing. Therefore, structures of this era were

commonly built using low cement contents (some

barely over 300kg/m3) low cover (anywhere from

0 mm upwards) and poor quality concrete.

The result was a large number of building

structures suffering from premature

reinforcement corrosion, resulting in cracking,

spalling and loss of section of the bar, caused by

one or both of the following corrosion initiators:

• Chloride ions, either added to the mix,

from contaminated marine sourced

aggregates or calcium chloride accelerator

• Carbonation, arising from a weak and

porous concrete matrix, due to low

cement content, high water/cement ratio

and poor compaction and curing of the

concrete, coupled with low cover

protection to the reinforcement.

Added to these in-built problems, there was

also a lack of appreciation of the exposure

95

environment. Many building structures, such as

car parks, were designed with a low strength

requirement and therefore had poor inherent

durability. Yet these structures were exposed to a

chloride ion build-up that was as severe as that

found for bridge decks. Bridges were designed

to take much higher stress levels than car parks

and therefore used a higher strength of concrete

and had better durability performance. Was it

therefore just a quirk of fate, in an era when

structures were designed for strength alone, that

highly stressed structures such as bridge decks

had more resistance to chloride ions?

Concrete repairsTo combat the problem of reinforcement

corrosion, the ubiquitous patch repair was born.

The name itself gives some idea as to how

concrete repair works were generally specified

and used – “patched up” by the maintenance

man.

While in theory patching up an area of spalled

concrete with new cementitious material appears

to be the correct approach, variations on this

theme soon led to problems, some of which are

listed below:

• Mortar mixes of cement, sand and water

(CC) were found to crack and fall off, due

to high shrinkage and lack of bond,

leading to the development of polymer-

modifier dispersions for adding to the mix

(PCC) to improve bond and reduce

shrinkage - although woe-betide anyone

who let the bonding coat dry out!

• High flow concrete mixes were specified

for repairs to beam soffits, based on

plasticising admixtures, but these tended

to fail by collection of air and bleed water

at the upper concrete interface. Concrete

technologists had to learn about the inter-

relationship between cement fineness,

water/cement ratio and the rate and

duration of bleed – T.C Powers explained

the process perfectly in 1939![4]

• Polymer-based mortars and concretes that

used epoxy or polyester resin as the binder

(PC), began to crack and fall off – the

realisation soon dawned that strongest

was not best, as the different thermal,

elastic modulus and tensile strength

properties created high tensile strains in

the concrete around the patch

• Certain types of PC and PCC mortars

began to fail, because the products were

either affected by the continued presence

of moisture in concrete or the strong alkali

in the pore water – concrete could not be

repaired like a stone or brick

• Special fast-setting mortars were

developed - but these had a high

temperature rise during cure, and

sometimes a high chemical shrinkage

during cure, leading to the repairs pulling

themselves off the concrete as they set.

However, even with the best materials and

workmanship, some concrete repairs began to

fail, whereas others did not – some even on the

same beam or column that had been repaired to

Figure 1: Typical anode-cathode relationship in chloride-contaminated concrete,showing the corrosion site (Anode) which sacrificially protects the cathode (that is,until it is repaired!).

96

the same standard and at the same time. Soon,

industry began to understand the destructive

power of the chloride ion in concrete. Terms like

incipient anode, electrochemical corrosion

currents and chloride ion corrosion threshold

began to be used, explaining why patch repairs

to damaged areas of chloride-contaminated

concrete lasted only a few years, before either

the patch repair failed again, or new spalling

appeared alongside the existing repair. The

corrosion cell was born (Figure 1)[5].

Over the past 25 years, methods for effective

control of electro-chemical corrosion have taxed

the minds of many researchers. A wide range of

imaginative solutions have developed for the

repair of reinforced concrete, including:

• impressed current cathodic protection

• electrochemical chloride extraction

• anodic and/or cathodic corrosion

inhibitors

• high resistivity repair products

• protective coatings to keep the concrete

dry and free from contamination.

Industry now has a better understanding of

the deterioration processes at work and the best

methods of combating them. Widespread

guidance is available on the methods of testing,

diagnosis and repair: the next step is to

standardise the products and systems for repair.

STANDARDISATION OF REPAIRSAll of the above techniques, and others

besides, have now been incorporated in a new

standard for concrete repair (BS EN 1504 series),

with Part 9 of this series[6] setting out the

principles to be used for repairing concrete that is

either damaged, under strength or insufficiently

durable for its conditions of exposure.

The main requirement from this Standard is to

ensure that the mistakes of yesterday, such as

using incompatible, untried, or “wishful”

solutions are eliminated, and requiring that that

all construction products sold for concrete repair

works meet a series of minimum performance

standards and are therefore “CE-marked” as fit

for purpose.

The CEN Standards are designed to fulfil

several functions, with perhaps the most

important being:

• to provide identification tests, by which a

product may be sampled, checked and

confirmed to be in accordance with a

manufacturer's specification

• to provide relevant performance tests, by

which the designer/specifier can select the

most appropriate product for the repair

• to specify minimum performance levels so

that a product can attain approval for sale

in Europe (the CE mark) for a given

application

• to define requirements for quality control

and safety

• to remove technical barriers to trade, with

a repair product being deemed to satisfy

specification requirements by meeting the

defined performance levels, whatever the

country of manufacture

• to achieve the above, by having a single

method of test agreed across participating

CEN members for each performance and

identification test.

The technical performance requirements for

the products, such as mortars and coatings, are

contained in the various parts of the EN 1504

series, with test methods given in new test

standards that are currently being drafted and

finalised.

Eleven Repair Principles have been identified in

DD ENV 1504-9[6], split into 37 Repair Methods,

as summarised in Table 1. As repair products and

systems are tested and approved for use in each

of the one of the 37 Repair Methods (e.g.

Principle 1.2: Surface coating to protect against

ingress) then the product or system will be

certified and approved to carry a CE mark for that

Repair Method or Methods. This approach is

intended to ensure that all products which carry

the CE mark and which have the correct

performance for a particular application, may be

sourced with confidence from all CEN member

countries.

As an example, consider reinforcement

corrosion caused by carbonation: under Repair

Principle 7 (Table 1) DD ENV-1504-9 gives five

Repair Methods (7.1 to 7.4) suitable for restoring

passivity due to carbonation. The concrete

surface can then be treated with a surface

protection system to prevent a recurrence of the

problem (e.g. Repair Method 1.2, Table 1).

97

1 PI

2 MC

3 CR

4 SS

5 PR

6 RC

7 RP

8 IR

9 CC

10 CP

11 CA

1.1

1.2

1.3

1.4

1.5

1.6

1.7

2.1

2.2

2.3

2.4

3.1

3.2

3.3

3.4

4.1

4.2

4.3

4.4

4.5

4.6

4.7

5.1

5.2

6.1

6.2

7.1

7.2

7.3

7.4

7.5

8.1

9.1

10.1

11.1

11.2

11.3

Impregnation

Surface coating with and without crack bridging ability

Locally bandaged cracks

Filling cracks

Transferring cracks into joints

Erecting external panels

Applying membranes

Hydrophobic impregnation

Surface coating

Sheltering or over cladding

Electrochemical treatment

Applying mortar by hand

Recasting with concrete

Spraying concrete or mortar

Replacing elements

Adding or replacing embedded or external reinforcing

steel bars

Installing bonded rebars in pre-formed or drilled holes in

the concrete

Plate bonding

Adding mortar or concrete

Injecting cracks, voids or interstices

Filling cracks, voids or interstices

Prestressing - (post tensioning)

Overlays or coatings

Impregnation

Overlays or coatings

Impregnation

Increasing cover to reinforcement with additional

cementitious mortar or concrete

Replacing contaminated or carbonated concrete

Electrochemical realkalisation of carbonated concrete

Realkalisation of carbonated concrete by diffusion

Electrochemical chloride extraction

Limiting moisture content by surface treatments, coatings

or sheltering

Limiting oxygen content (at the cathode) by saturation or

surface coating

Applying electrical potential

Painting reinforcement with coatings containing active

pigments

Painting reinforcement with barrier coatings

Applying inhibitors to the concrete

Protection against ingress

Moisture Control

Concrete Restoration

Structural Strengthening

Physical Resistance

Resistance to chemicals

Preserving or restoring

passivity

Increasing Resistivity

Cathodic Control

Cathodic Protection

Control of Anodic Areas

Repair Principle Repair Method

Note: Methods in italics may make use of products and systems that are outside the scope of the

EN 1504 series.

Table 1: Summary of repair principles and methods for concrete repair to BS ENV 1504-9[6].

98

Supporting DD ENV 1504-9[6] are the

performance test requirements in forthcoming BS

EN-1504 Parts 2 to 6, each referring to new and

existing methods of test to determine the

performance and identification test results.

The selection of test methods followed CEN

rules[7]:

• first, consider whether the test methods

could be selected and adapted from

existing CEN Standards

• then consider ISO Standards

• then consider CEN member National

Standards

• finally, if no existing Standard test method

is suitable, develop a method from a non-

standard procedure (e.g. RILEM) or

develop from first principles.

For example, within Europe, several National

Standards existed for methods of test that could

be applied to concrete repair mortars, such as

compressive strength. However, no standard

existed for the compatibility performance of the

mortar when bonded onto a concrete substrate

(e.g. under thermal cycling).

For information, the list of

performance test

requirements for repair

mortars are shown in Table

2.

In many cases, the final

selection process for the test

methods was based on the

presentation of technical

information and experience

by the representatives of the

different countries, among

other factors. A good

example is the Highways

Agency flow trough test for

flowing concrete, as used in

the UK for over 15 years.

On the Continent, this type

of product is not used, yet it

did not prevent the Working

Group from developing the

Highways Agency test from

an Advice Note into a full

Standard (BS EN 13395-3)[8].

Progress towards getting full agreement on the

methods of test is often slow and compromises

often have to be made, both on technological

grounds and in the light of experience from other

countries. While every method of test is prepared

with the utmost care, it is accepted that

conflicting views will exist within a country and

between countries, with the compromise solution

not necessarily being the best test.

This limitation is recognised by CEN and a

process of Standards revision has been initiated to

follow the initial drafting effort. This will provide

the opportunity for new and modified methods

to be proposed and assessed alongside reaction

from industry on the suitability and practicability

of the existing methods.

The Standards are designed for characterising

pre-batched products, which inherently contain

precise quantities of materials prepared under a

factory-controlled production system. These

products may be expected to exhibit performance

criteria that lie between narrow limits and are CE

marked accordingly. Site-batched products are

outside these requirements, meaning that to

Table 2: Summary of minimum performance requirementsfor repair mortars, to BS ENV 1504-9[6].* BS EN 1766: Products and systems for the protection and repair ofconcrete structures - Test methods - Reference substrates for testing.

99

conform the mixed

components must be

shown to produce the

required performance

criteria consistently, using

the locally-sourced

materials (e.g. aggregates

and cements) in

combination with the

formulated components

such as special polymers,

admixtures and additives.

Confirming continued

satisfactory performance

on a site therefore requires

consistency in the base

materials as well as an expensive programme of

regular conformance testing.

The issue of repair products batched on the

site has yet to be addressed by the CEN

committees. However, in many European

countries, site batched mixes are in any case not

permitted for critical repairs.

The BS EN 1504 series should greatly assist

engineers in CEN member States, by ensuring

that products and systems sold for concrete repair

meet a series of minimum performance criteria

and that single methods of test exist for assessing

compliance with those criteria (as opposed to

national Standards that vary between countries).

However, the BS EN 1504 series specifically

excludes the key areas of investigation, testing,

residual life prediction and whole life costing as

the basis for option selection.

WHAT THEFUTURE BRINGS

In practice, the proper maintenance and

lasting repair of an asset over its life is one of the

most difficult technical challenges facing the

industry today.

Increasingly, whole-life

expenditure profiles

need to be determined

for an asset, such as for

the 20-year concessions

commonplace in the

private financing of new

or renovated

developments. If

engineers are uncertain

about the rate of future

deterioration of

structural elements, then

the expenditure required

over the life of the concession will remain

uncertain and financially weighted accordingly,

possibly making the opportunity unviable.

Before the future life and maintenance costs

can be predicted, the design life of the asset

needs to be defined and the required

performance of each element over its life needs

to be established. The necessary technologies

include the following[9]:

• Deterioration modelling that considers

local macroclimates and takes account of

the properties of the concrete materials

used around the original structure (Figure

2). Considerable research work is needed

in this area if industry is to move forward

with deterioration and life prediction,

using statistical approaches such as

reliability analysis, as current techniques

rely heavily on establishing actual time-

performance curves.

• Whole life costing of the various

approaches to deal with future

deterioration, based on the intended

service life (Figure 3).

Figure 2: Typical T0-T1 curve for deteriorating reinforcedconcrete structures subject to chloride ion exposure.

Figure 3: Typical Life cycle costing of different repair optionsto combat carbonation of a reinforced concrete building.

100

• Predictive Planned repairs andmaintenance regimes, targeted only to

the key areas of the structure that are

critical to the future performance, rather

than just following an arbitrary list of

works and “cosmetic” repairs, while

missing the unplanned major events.

Options include a variety of measures that

suppress the rate of corrosion, thereby

delaying any necessary repair works

(Figure 4).

• Performance assurance, using advanced

monitoring and control techniques to

provide feedback that all is well in the

critical areas of a structure, or early

warning of impending problems[10].

Only with significant research and

development in the above areas can the

expenditure over the life of an asset be effectively

predicted and managed, giving confidence to

clients and financiers alike and recognising whole

life cost savings.

CONCLUSIONSTo tackle the problems of tomorrow, asset

managers need to be “deteriorologists”, who

understand why infrastructure assets of various

kinds fail over the service life. Such

understanding goes beyond general building and

civil engineering and delves into specialist areas

of materials, deterioration modelling, monitoring,

assessment and strengthening and repair scheme

specification. The future can unlock many of the

difficult issues through training, research and

development; but we will first have to overcome

the negative attitudes about maintenance and

repair that pervade the industry. This will require

close collaboration between industry, Universities

and funding organisations to ensure the repair

and maintenance industry is prepared to tackle

the problems that will arise in the future.

ACKNOWLEDGEMENTThe author would like to express his thanks to

the Infrastructure Maintenance team in

FaberMaunsell for helping to contribute to the

concepts and conclusions in this paper, born of

many years of field research into reinforced

concrete deterioration.

REFERENCES

1. LOOV, R.E., Reinforced Concrete at the Turnof the Century, Concrete International, Dec1991, pp 67-73.

2. HARTCUP, G., Code Name Mulberry – Theplanning, building and operation of theNormandy Harbours, 1968.

3 CIRIA UEG TN.5/1, Concrete in the Oceans:Marine durability survey of the tonguesands tower, Report 5652, CIRIA UEG,London, 1979.

4. POWERS, T.C., Bleeding of Cement Pastes,PCI, Skokie, 1939.

5. CURRIE, R.J. & ROBERY, P.C., Repair andMaintenance of Reinforced Concrete,Building Research Establishment Report NoBR 254, Apr. 1994, 34pp.

6. BS ENV 1504-9, Products and systems forthe protection and repair of concretestructures - Definitions, requirements,quality control and evaluation of conformity- Part 9 : General principles for use ofproducts and systems, BSI.

7. ROBERY, P.C., Standards for Concrete Repairand Protection, Proc 4th South AfricanConference on Polymers in Concrete, 20 –23 June 2000, South Africa.

8. BS EN 13395-3, Products and systems forthe protection and repair of concretestructures - Test methods - Determination ofworkability - Part 3: Test for flow of repairconcrete, BSI.

9. ROBERY, P.C., Maintenance strategies forhighway structures, Journal of the Instituteof Highways, October 1997, pp 14-16.

10. ROBERY, P.C., Remote monitoring andcontrol systems for steel reinforced concretestructures, ICRI Spring Convention, Seattle,April 1997.

Figure 4: Schematic representation ofdelayed repair works displacing theexpenditure profile.

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P de Vries F 73ENCI Netherlands

Dr D Evans F 55Rugby Cement

J P H Frearson F 3Consultant

N Greig F 70CCS Associates Ltd

R E T Hall F 10QSRMC

Prof T A Harrison F 12QPA

A M Hartley F 61RMC R&D

A J M Horton F 28Contest South Africa

P M Latham F 60RMC Materials

Prof A E Long F 44Queen’s University Belfast

D J Macrae F 65Mass Transit Railway CorpHong Kong

R J Majek F 62Degussa

Dr B K Marsh F 64Arup

E W Miller F 24Consultant

P C Oldham F 45Christeyns UK Ltd

P L Owens F 8Consultant

S D Pepper F 27Castle Cement

G Prior F 43Castle Cement

INSTITUTE OF CONCRETE TECHNOLOGY

MEMBERSHIP DIRECTORY - SUMMER 2004

102

C B Richards F 39Tarmac Precast Concrete

Dr L K A Sear F 67UK Quality Ash Association

G Taylor F 22ICT

J V Taylor F 33Castle Cement

Dr J F Troy F 53Tarmac

D R Vaughan F 41Barcon Precast Ltd /Consultant

A J Walker F 42Consultant

S M Walton F 68Grace

D M Wetherill F 57Canary Wharf Contractors Ltd

W Wild F 48Tarmac Southern

R A Wilson F 52Consultant

MEMBERS

R Albers M 382ENCI Netherlands

M R Aldam M 518Morgan EST

J M Aldred M 467GHD Materials Tech GpAustralia

Prof M G Alexander M 390University of Cape TownSouth Africa

C F Allen M 475Hanson Premix

S M Amos M 404RMC

A J Andrews M 202Technotrade

S J Angel M 405Rugby Cement

A Arateeb M 436Brown & Root NA Ltd

R T Austin M 400Delmon Readymix Bahrain

R Avenell M 66Angelus Block Inc USA

Khaled W Awad M 432Advanced ConstructionTechnology Services (ACTS)Lebanon

T D Balmer M 472Hanson Aggregates

C A Bannon M 217Irish Cement LtdRepublic of Ireland

M E Barker M 461Concrete Ideas South Africa

P F Barker M 266Lafarge Aggregates

S J Basnett M 269Hoddam Contracting Co Ltd

Prof A W Beeby M 441University of Leeds

H B Bell M 346Roshcon (Pty) Ltd South Africa

J G Bell M 328Plean Precast Ltd

A Benitez M 483INTI Argentina

I R Berrie M 421Degussa

R A Binns M 212 Tony Binns TrainingWorkshops

Dr S J Bloomer M 399Castle Cement Ltd

C Bolan M 169C C Geotechnical

R F Bolton M 309Cockburn Cement LtdAustralia

R G Boult M 465Omya UK Ltd

R A Boulton M 281Minelco Minerals

G C Bouquet M 410Association of theNetherlands ConcreteIndustry (VNC)Netherlands

D S Bowerman M 343MBT Middle EastSharjah U A E

A Bromwich M 397Chryso UK Ltd

A D R Brown M 336W R GraceU S A

R C Brown M 413Tarmac Northern

P R Browne M 519Ready Use Concrete

M G Bruce M 179Brett Concrete Ltd

Prof N R Buenfeld M 257Imperial College London

A Bustami M 401Arabian Mix Co llcDubai UAE

P H Butlion M 419Port Elizabeth TechnikonSouth Africa

Dr E A Byars M 508University of Sheffield

A K Campbell M 492SNC-Lavalin (M) Sdn BhdEast Malaysia

Chan Wai Wing M 367Tsing Ma Management LtdHong Kong

Dr P Chana M 498British Cement Association

Prof B S Choo M 501Napier University

Chow Kin Keung M 462Pioneer Concrete (HK) LtdHong Kong

P M Clarke M 379Enterprise IrelandRepublic of Ireland

H Clay M 174Tarmac Precast Concrete

103

J Cokart M 520HolcimSouth Africa

T Coleman M 210Lafarge Cement UK

C R Cooper M 209Lafarge Cement UK

H Corporaal M 510ENCINetherlands

S J Crompton M 341RMC Materials Ltd

S F Crosswell M 489PPC CementSouth Africa

D Crowley M 366John A Wood LtdRepublic of Ireland

P N Davey M 248McNicholas Construction Ltd

D R Davies M 503Multi Design Consultants

T F Davis M 391Roadston Dublin LtdRepublic of Ireland

J S Dawes M 403Lafarge CementFrance

R I Day M 275The Concrete Society

T de Veer M 438ENCIThe Netherlands

M P Dean M 236Civil & Marine (Holdings) Ltd

P Deegan M 482Banagher Concrete LtdRepublic of Ireland

S Dibani M 468Brown & Root NA Ltd

M W J Dolan M 273Marshalls Mono

Dr P L J Domone M 386University College London

N C Dowie M 334 RMC Admixtures

Dr A J Dowson M 452Consultant

T J Dowson M 406North East Slag Cement

H T R du Preez M 324C&CI / ConsultantSouth Africa

J Dudden M 431BSI Management Systems

C Eastwood M 439RMC

R Egan M 480Mattest (Ireland) LtdRepublic of Ireland

E Elliott M 417 Tarmac Southern

G P Ellis M 302Materials Testing Ltd

D J Eriksen M 139Holcim (South Africa) Pty LtdSouth Africa

S E Fawcett M 335MWH

T Fawcett M 337Sir Robert McAlpine Ltd

L Fernandez Luco M484IETcc, Spain and University ofBuenos Aires, Argentina

F J Fitzgerald M 442Roadstone Provinces LtdRepublic of Ireland

C R Foord M 316RMC South East

P J Foskin M 385Roadstone Provinces LtdRepublic of Ireland

A D Foster M 278Rugby Cement

R Gaimster M 433RMC Readymix Ltd

M J Gatfield M 204Laing O’Rourke Ltd

J A Gauld M 481RMC

I Gibb M 363RMC

J C Gibbs M 288University of Paisley

C M Gibson M 105Lafarge Cement UK

J R Givens M 279Buxton Lime Industries

Dr C Goodier M 511Loughborough University

H J Goodman M 355Cement & Concrete InstSouth Africa

M G Grantham M 502M G Associates

F Gray M 285Hanson Aggregates

Dr G R H Grieve M 356Cement & Concrete InstSouth Africa

S M Haider Abidi M 163Dubai ReadyMix ConcreteDubai U A E

K M Halloran M 380ForbaistRepublic of Ireland

O R Hansen M 144COWIconsultDenmark

N A Harries M 211RMC TopmixDubai UAE

E Heikkilä M 506Finnsementti OyFinland

D W Hendry M 164RMC Readymix

T Hloele M 485Lesotho

D G Hooper M 56RMC Readymix

R D Hossell M 347Grace Construction ProductsDubai UAE

Dr K C Hover M 251Cornell UniversityUSA

D H Howarth M 325Tarmac Southern Ltd

104

A Hulett M 493Face Consultants Ltd

D M Hutton M 213Hyundai Chung Lin JVTaiwan

S I Jackman M 387Regional Railways

G Jackson M 111Rugby Cement

P Jackson M 55

A D Jensen M 113DTI ByggeriDenmark

P E F Jensen M 232MT HøjgaardDenmark

B R Jones M 463Hanson Premix

C N Jones M 91Hanson plc

J D Jones M 300Tarmac Southern

K J Juvas M 297Consolis TechnologyFinland

S Kandasami M 521University of Dundee

D A Kay M 282

C Keeley M 62

J S Keighley M 255RMC Western Ltd

Dr S Kelham M 308Lafarge Cement UK

J Kennedy M 293Consultant

Ms U Kjaer M 119RambøllDenmark

Dr A J Klemm M 469Glasgow CaledonianUniversity

L Kotrys M 368Laing Construction Services Ltd

H Kouwenhoven M 514Exterra BVThe Netherlands

W Krieg M 522Saudi Readymix ConcreteSaudi Arabia

Kshemendranath P M 504ElkemIndia

A C W Kwok M 445K Wah Concrete Co LtdHong Kong

S M Laffan M 214Concrete Technical Consultant

A Lamont M 342The Highlands Council

Lau Mei-Tong M 296Chun Wo Construction & Engineering Co LtdHong Kong

J Lay M 427RMC Materials Ltd

R E Lee M 219

A Legg M 460Tarmac Southern

M Lephoma M 384Coega Development Corp.South Africa

S E Lesurf M 440Civil & Marine Slag Cement

R C Lewis M 470Elkem Materials

C Lillis M 477Readymix (SW) LtdRepublic of Ireland

Lim Seng Huat M 464Jurong Readymix ConcreteSingapore

M Limbachiya M 497Kingston University

C G Lloyd M 227Flexcrete Ltd

B A Lord M 458CTRL

B G Lynch M 381Irish Cement LtdRepublic of Ireland

M C Mackenzie M 395Hanson ConstructionMaterialsAustralia

K Macleod M 509Lafarge Cement UK

Dr B J Magee M 517The Concrete Centre

T P Mahlo M 499Lesotho H T PLesotho

P L Mallory M 357Lafarge Cement UK

J Marrison M 262Appleby Group Ltd

A McGibney M 295Civil & Marine Slag Cement

J G McLoughlin M 473Galway County CouncilRepublic of Ireland

D A McQuaid M 233The Pathumthani Concrete CoThailand

G McWhannell M 260Concrete Grinding (UK) Ltd

M R Messham M 313Jacobs

A Miller M 286Sandberg llp

W Milligan M 507Natal Portland CementSouth Africa

M Mitchell M 349Adfil UK

J M Mollart M 430South Yorkshire Laboratory

J E J Molloy M 157Tarmac Northern

F E Montesin M 189University of MaltaMalta

P C Morton M 258RMC

H F Mostert M 360University of PretoriaSouth Africa

P E Mulligan M 487SikaRepublic of Ireland

105

C J Munn M 263CCA(NZ)New Zealand

V Selvan Naidoo M 372Lafarge South AfricaSouth Africa

C D Nessfield M 434Tarmac Special Products

P H Newby M 329Lafarge Aggregates

Dr J B Newman M 141Imperial College London

M J Newson M 254Slough Building Control

A J Nicklinson M 340Archirodon Group NVSharjah U A E

P S Nokes M 294BAE SystemsGuernsey

M J Norfolk M 455Appleby Abrasives

M S Norton M 186RMC Rugby

D G O’Brien M 446Irish CementRepublic of Ireland

F O’Byrne M 516National Standards Authorityfor Ireland (NSAI)Republic of Ireland

N J Papenfus M 451Dams for AfricaSouth Africa

G G Parnell M 49Appleby Group

B C Patel M 435Rugby Cement

Ms Z Perks M 515Holcim (South Africa) Pty LtdSouth Africa

B F Perry M 333Grace

D L Pickwell M 315RMC

D C Pitcher M 99Hanson Premix

R J Potter M 160Testing & ConsultancyServices Ltd

M N Prendergast M 424Roadstone DublinRepublic of Ireland

A R Price M 398Rugby Ltd

Dr W F Price M 409Lafarge Cement UK

Dr R G D Rankine M 490Cement & Concrete InstSouth Africa

M F Rash M 345Lancaster PrecastSouth Africa

A S Read M 496Ove Arup & Pts HK LtdHong Kong

P R Rhodes M 121RMC Readymix Ltd

P W Richards M 203Fortress Health & SafetyServices

R I Richards M 205RMC South East

Dr M Richardson M 375Univerity College DublinRepublic of Ireland

S C E Rickett M 321Appleby Group

J F Rigg M 249BSI

M R Roberts M 241Magnox Electric plc

M Roberts M 112QSRMC

Prof J J Roberts M 361Kingston University

Prof P C Robery M 488FaberMaunsell Ltd

E M Roche M 393University College CorkRepublic of Ireland

A M Rogers M 513Price Brothers (UK)Libya

A R Rogers M 320Consultant

R A Rogerson M 456Sandberg llp

M J Ryan M 429Rugby Cement

P J Sayers M 256Brett Concrete Ltd

R Scales M 95Al Hoty-Stanger Ltd CoSaudi Arabia

S R Schulte M 422Concrete Management South Africa

R C Schutte M 414Natal Portland CementSouth Africa

H S Sehmi M 314Lafarge Aggregates

J Seller M 284Beton Services Ltd

Seow Kiat Huat M 344MBT (Singapore) Pte LtdSingapore

K M Sharpe M 466RMC Eastern

T Sherriff M 61Al Hoty-Stanger LaboratoriesDubai UAE

C A Simpson M 180

Dr I Sims M 354STATS Limited

B N Smith M 3`83B D Flood LtdRepublic of Ireland

I M Smith M 277Fosroc Ltd

P Snook M 486Samsung, Doosen, IE&E JVTaiwan

M Sopeng M 500Mohale Consultant GroupLesotho

Dr M N Soutsos M 505 University of Liverpool

W G Sparksman M 140Retired

106

P Strange M 225C V Buchan Ltd

A Stubbs M 107Sika

K C Sutherland M 396Tarmac Central Ltd

W L Sutherland M 193Degussa

P J Sweeney M 274Emrill Services llcDubai UAE

N M Tait M 474British Nuclear Fuels Ltd

H D Taylor M 304National Laboratory ServicesEnvironment Agency

T Tente M 512Mohale Consultant GroupLesotho

M Thakholi M 494Lesotho Highlands TunnelsPartnershipLesotho

C G Thompson M 471Con-Tech Associates Ltd

J Thomson M 310AWG Construction Services

M J Tiernan M 423Tara Mines LtdRepublic of Ireland

Ting Hong Yew M 389Mega Pascal BehadMalaysia

G F True M 118GFT Materials Consultancy

D R Turner M 194Hanson Central Premix

M Turner M 318Lagfarge Cement UK

M Van Halderen M 476ENCINetherlands

H L Van Heerden M 454Blue Circle LtdSouth Africa

J K Virtanen M 208Finnsementti OyFinland

S C S Wainwright M 216Lafarge Aggregates

Com O B Wallace M 377Irish ArmyRepublic of Ireland

R W M Wan M 364Cement Connections LtdHong Kong

Dr R P West M 378Trinity College Dublin Republic of Ireland

S J Willis M 145RMC

A T Wilson M 261C&G Concrete Ltd

D E Wimpenny M 495Halcrow Group Ltd

S J Wolfe M 428Hanson Premix

J Wood M 339Hanson plc

J Wright M 353Tarmac Northern Ltd

A Wu Yuk Tak M 358Hong Kong Concrete Co Ltd

ASSOCIATE MEMBERS

L S K Abbey A 546Tube Lines

M A U Z Abu Saleh A 629DegussaSingapore

B Alavi A 622Kier Group

G Al-Talal A 650Concrete Information Ltd

W M Armstrong A 332ScotAsh

T Asiedu-Agyei A 646Kuottam Constr Works LtdGhana

G Attree A 631Adfil Construction Fibres

V S Azizian A 429Hanson plc

M B Babadi A 623National Iranian S Oil CoIran

P D Bartys A 348USA

C I Batty A 450Sandberg llc

P Baughan A 53Hanson Aggregates

C Bennett A 537ScotAsh Ltd

S G Benson A 502Hanson Aggregates

D Berrill A 643Bureau Veritas

D Billington A 521Concrete Consultant

D G Birchall A 373Amec Capital Projects Ltd

A R Bourne A 328Brett Concrete Ltd

M Bowman A 614Tarmac TopPave

S P D Brennan A 549Tarmac Central Ltd

A K Bright A 619RMC

M J Bunny A 128Quickmix Concrete

S Burton A 603Kirton Concrete Services

N T Bustami A 595Stevin Rock QuarriesRas al Khaimah U A E

P Butterworth A 246Lafarge

M G Carleton A 252TBV Stanger LtdRepublic of Ireland

D A S H Carslaw A 407Thames Valley ProbationService

D P Cawdron A 309Ground Engineering, Xplor Ltd

107

Chan Kwai Tong A 496Alliance Precast IndustriesMalaysia

Chan Wan Tong A 457City University of Hong KongHong Kong

S D Cheeseman A 41Hong Kong

Cheung Chuk L A 298Hong Kong Testing CoHong Kong

L Chisholm A 612Border Readymix Ltd

Chow Pui Ching A 543Hong Kong Airport AuthorityHong Kong

D Clarke A 540Grace

A C Close A 641C & H Quickmix

P Copestake A 600Tarmac Central Ltd

C W Coton A 319Hanson Premix

H T Cowan A 67Bardon Concrete

A P Cox A 577Gleitbau GmbH

T P F Coyne A 145Grace Construction Products

A B Crofts A 597Hanson Premix

A Cross A 648Rugby Cement

D A Cullen A 510Taywood Engineering Ltd

D J Dance A 437Stonbury Ltd

I G Dare A 445Aggregate Industries UK Ltd

I M Davenport A 635RMC Readymix East

M E Davey A 339Grace Cement Additives

G W David A 544Testing & ConsultancyServices Ltd

Dr G Diorazio A 601Tarmac Central Ltd

M J Dobbie A 592Sandsfield RMC Ltd

P Doddington A 608Lafarge Aggregates

R P Dowle A 111Conceit Investments Pty LtdAustralia

C D Dowson A 624Brett Landscaping Ltd

M R Edwards A 515Lafarge Aggregates Ltd

HR Effendi-Atkinson A 462M/s Premier Structure SdnBhdMalaysia

C R Evans A 609Jacobs

I Evans A 602Hanson Product Technology

Mrs S J Fairclough A 489Derwent Cast Stone Co

I F Ferguson A 455Marshalls plc

M A Fitzgerald A 376Borregaard UK Ltd

Ms M Flores A 638Concrete Colour SysyemsAustralia

P J S Ford A 364Self-employed

B P Gaten A 31Master Builders TechnologiesUSA

J George A 446Young EngineeringConsultancy ServicesDubai U A E

T Geraghty A 542Weeks Laboratories

C S Gibson A 477Pell Frischmann Group

P G Gillard A 325

M R Gillespie A 395Hanson Aggregates

V Gogol A 517Adcon CC

M Gorji A 610Brown & Root NA Ltd

R J Greenfield A 562RMC Materials

J E Greenhalgh A 403Bekaert Building Products

M Greig A 178RMC Readymix

L G Guise A 527Lafarge North AmericaUSA

J Hall A 583Tarmac

S Handscomb A 423Appleby Group

M V Harris A 599Tarmac Northern Ltd

P J Hawkins A 185

P E Haynes A 312Durox Building Products

K W Head A 286Grace

A D Heath A 616Tremco Europe Ltd

N A Henderson A 551Mott Macdonald Ltd

Dr I Heritage A 645Lafarge Cement UK

M A Hickingbottom A 539North East Slag Cement

P K Hinchcliffe A 571Sika Ltd

W Hudson A 70

S R Hughes A 358Douglas Technical Services

Dr S A Huntley A 637Marshalls Mono

108

J B Jackson A 7MC-BauchemieGermany

H D Jairam A 572S C L (Trinidad) LtdTrinidad

B C James A 554Q P A

S A M Jawad A 647Al HashemiDubai

Prashant G Jha A 627RMC India LtdIndia

C D Johnson A 195Patersons Quarries

R JonesA 441Bison Concrete Products Ltd

N Jowett A 625Christeyns UK Ltd

W M Kay A 564WAK Consultants Pte LtdSingapore

W G Kennedy A 101StonCor Middle East llcAbu Dhabi UAE

T Kenyon A 304Batchmix Ltd

R P Kershaw A 587RMC

A Kirby A 330C&CANZNew Zealand

J C Knights A 557Halcrow Group Ltd

Koo Shu Wah A 536Kowloon & Canton RailwayHong Kong

D Kruger A 471The University ofJohannesburgSouth Africa

R R Kumar A 607Boral ResourcesAustralia

P C Lau A 439Consultant to MD AssociatesHong Kong

D R Lavender A 224Intech Services Ltd

J K C Lee A 242Giant City Concrete LtdHong Kong

R Lewis A 568Marshalls

P Livesey A 238Castle Cement Ltd

S Loh A 426W R Grace (Singapore) Singapore

E N Longworth A 333Longworth ConsultingWorldwide Ltd

G B Lory A 106The Dudman Group

A C Macdonald A 486W R Grace & CoUSA

N M MacRitchie A 61Sandberg llp

M R Maguire A 228Fife Council

P L Male A 188Hydronix Ltd

R J Mangabhai A 346Consultant

K R Marfleet A 281M C BauchemieMalaysia

B Massie A 345Hunter Construction Ltd

A J McDonald A 447Shire Cast Stone Ltd

G McGovern A 334RMC

L D McLennan A 379Sika Ltd

L K Moore A 356Smiths Concrete Ltd

T J Mulcahy A 634RMC Readymix

P Mundell A 310R A K Materials ConsultantsSingapore

R J Musgrave A 596Doncaster College

K Muston A 32Hanson plc

G J Mutch A 422Hanson Premix

K Naidoo A 495Natal Portland CementSouth Africa

R K Nar A 582RMC

C Newberry A 566RMC Readymix Ltd

G F Norman A 406

Dr B K Nyame A 354Consultant

A Orr A 630RMC Readymix Scotland

T L Ostler A 606Tarmac Central Ltd

D W Ovington A 553UMA Ltd

I L Owen A 501Chryso UK Ltd

Dr B D Perrie A 385Cement & Concrete InstSouth Africa

D Petts A 500Brett Concrete Ltd

J P Platt A 109RMC Materials

P L Pretorius A 417Alpha Stone & ReadymimxSouth Africa

M A Price A 497Marshalls Mono

S V Price A 398Pioneer Concrete

M A Pullan A 578

B A Raath A 483ContestSouth Africa

D J Rankin A 55Alfa Aggregates

109

C Rathbone A 154J P N Cast Stone

G F Richardson A 161Lafarge Aggregates

B H Robertson A 113Unique Mortar Products Ltd

S Rodgers A 644Lafarge Cement UK

A K Rogers A 642Meadowstone (Derbyshire)Ltd

J N Rumford A 8Supreme Concrete

Ms R R Rupert A 465USA

J Rust A 633RMC

D W Sackett A 134Brett Concrete Ltd

S Sadler A 605British Board of Agrément

V V Santhosh A 632Gulf Concrete & BlocksRas al Khaimah U A E

D Schooling A 498Atkins (Somerset Highways)

Ms A Scothern A 639The Concrete Centre

B J Sealey A 594Tarmac Tech Services

J S Shearing A 368Tarmac Topfloor Ltd

V Sibbald A 649Appleby Group Ltd

B J Simpson A 139Babtie EngineeringLaboratories

D Simpson A 234Aggregate Industries

M T Simpson A 636RMC

S R Sindhu A 485London Concrete Ltd

C D Smith A 343Vetco Saudi Arabia LtdSaudi Arabia

J V Smith A 82ConcreteWorksNew Zealand

C P Sofianos A 357Group Five CivilsSouth Africa

S M Speers A 342Sika Armorex

V H Spindler A 526Zambezi River Authority

A Stables A.525Caledonian Slag Cement

M J Staff A 143Lytag Ltd

A J Stammers A 367Grace

J F Stenton A 257Miller Construction Ltd

M J Steptoe A 315Castle Cement

J R Stockbridge A 615Technotrade

J P Stothard A 444Techrete (UK) Ltd

C E Surridge A 552Castle Cement

J B Sutherland A 96Castle Cement

M G Taylor A 307British Cement Association

A J Teagle A 628Hanson Premix

Teh Boon Kim A 535Sun Mix ConcreteMalaysia

K T Thamaha A 528Lesotho Highlands T PLesotho

Q M Thöle A 448SNALABSouth Africa

S E Thorpe A 474Lafarge Readymix

D H Tite A 382CTS (Pty) LtdSouth Africa

D C Tomlinson A 434Castle Cement Ltd

A Trueman A 90Austin Trueman Associates

I Tupling A 279RMC Concrete Products

M Valentine A 581Sterling Precast Ltd

A M Venn A 513Ferro Monk Systems Ltd

I T Waddell A 201MBT Middle East llcDubai U A E

G Wake A 618RMC Readymix

C B Wakelin A 640Morgan-Vinci 31

T Ward A 604Tarmac Central Ltd

C Waterhouse A 503

J C Watkinson A 28NBS Stone Products Ltd

K Whalley A 613Civil & Marine Slag CementLtd

R Whitty A 351University of Glamorgan

M J Wildmore A 479Lafarge Aggregates

H G Williams A 217Tarmac Northern

J Wilson A 507Marshalls Mono Ltd

K R Winder A 302A R L Group

Wong Foo Keung A 538Ground Research Co LtdHong Kong

R J Woodhead A 504Castle Cement Ltd

R S Young A 391Grace

I Zejma A 499T5 Project

Dr G S Ziadat A 454Robert Benaim & AssocQatar

110

TECHNICIANMEMBERS

J Ackroyd T 7Skanska

B Anarfi T 13Highways AuthorityGhana

G D Campbell T 3N W Concrete Testing

R P Drew T 10University of W of England

S G Stewart T 12Leiths Montrose Precast

R Stride T 11Roger Bullivant Ltd

GRADUATE MEMBERS

M A Cowley G 1RMC Readymix

S G N Guerineau G 3Roadston Dublin LtdRepublic of Ireland

M Watson G 2Marshalls plc

STUDENT MEMBERS

G Abdyli S 154

D Afoke S 225

M Afridi S 118

D Almond S 138

M C Anderson S 201

M H Apadile S 111

G Aqel S 161

V Arvanitis S 54

M Athamanathan S 18

Au E Chun-Wing S 16

M Avgerinos S 75

R Baland S 98M J Bardin S 70

J A Barnes S 159

M Barrett S 34

P Barry S 165

C Barton S 187

J Bassett S 191

C M Bell S 203

S J Bell S 219

K Bitsikokos S 49

R G Borgust S 173

G W Bouwens S 224

L Brocklehurst S 51

J R Brown S 128

M Browning S 22

M Bunyan S 223

T Butler S 11

O Calvert S 32

Chan Kheng Seow S 116

A B Chappidi S 95

Chen Qing Feng S 78

Cheng Chung Kam S 144

Cheung L M S 20

D D Christie S 221

R Christie S 27

C Christodoulou S 110

Chua Chee Kiong S 81

Chung Ho-Fai S 125

T R Chuttur S 114

C J Coffey S 19

T Z N Cookson S 87

C Crawford S 113

N Crowley S 135

P Cuschieri S 47

M G Davies S 123

R Davies S 206

W M Davison S 215

P Dawson S 209

N de Battista S 48

J D Dickinson S 205

M Dillon S 211

S Dixon S 185

A Dominguez Lage S 66

S Dougan S 200

A M Doyle S 31

M J Doyle S 53

Duan F S 134

R J Eagles S 137

G Eborall S 169

N G Edwards S 156

O C Erewele S 148

J Evans S 68

P Farshim S 107

B Fekaiki S 237

I Fernandez S 65

R Finnimore S 184

A P Fisher S 177

R E Fuller S 56

A S Gadsby S 136

E M Gee S 84

I Georgiou S 170

E Giakoumakis S 64

T Gill S 71

S Gilliland S 23

J Gilman S 190

M Glover S 46

J Godman S 186

Goh Chin Heng S 99

P Goodlad S 83

111

T Gorringe S 183

B Groves S 232

S Gulliver S 182

J Gunu S 103

E Gxesos S 40

D P Hagan S 52

D Hamilton S 8

Han Wei S 86

D P G Harrison S 238

T J Harrison S 230

M J Harvey-Broake S236

L E Hawkins S 93

A W Heffer S 196

J C Hewett S 121

C Higgins S 204

C Hoare S 157

J E Hogg S 217

L Hogg S 212

J Holden S 218

N Holmes S 92

A Howlett S 127

J Hughes S 226

Hui Chi Wai S 89

Hung Fai Tsang S 21

G C Irving S 195

U I Isiadinso S 100

A B Jahromi S 106

B Jones S 115

S C Jordan S 102

J Kapetanidis S 73

T Kapeti S 104

N Karafillides S 90

D Karametos S 120

R Kemp S 180

A Khan S 105

H H Khansahib S 158

E S L King S 163

A Kokias S 91

C Kouros S 43

K Kourtidis S 62

Kwong Kin Man S 59

C Kythicotis S 58

J O Labiran S 101

Lam C-Y S 160

M Landrum S 139

G Latham S 213

Lau K Y S 145

A Leathard S 194

R Lee S 168

R J Lee S 55

Z Lee S 7

G J Leighton S 235

A Lever S 189

H C Lewis S 176

S Lewis S 28

Li G S 155

Li Wai-Kin S 124

Lock Wei Siong S 82

D J Lowery S 199

J S Macaulay S 146

K Mainwaring S 150

S Margaritidis S 44

N Marinos S 79

L Mason S 234

J Matlapeng S 109

L McAuliffe S 33

P McCann S 39

C McGivern S 119

C P McMahon S 229

G McMahon S 5

D McNair S 122

S R B Meddings S 222

T Mifsud S 3

S J Miller S 143

N Mills S 192

Z Misbah S 1

P Moalosi S 151

M M Mojadife S 153

L B Motshwaedi S 152

J Morgan S 50

S C F Morley S 15

J Morris S 214

J G Morris S 179

R Morris S 37

T Mothoka S 108

Mo-Yung Chun Wai S 13

K J Mulvey S 197

S Neal S 36

O Nevett S 231

N Ntouniapilen S 171

C O’Kane S 4

Oh Say Yong S 80

S Papatzani S 94

N Parkin S 210

Z Parvizi S 85

J Patching S 174

Peh H Z S 133

J M Peacher S 2

G Phiri S 149

112

M J Pinder S 25

G Prempeh S 167

M J Primrose S 164

P Prunty S 188

R Qamhiyeh S 162

S Qureshi S 117

P Richardson S 198

A Rigby S 67

C Roberts S 129

D E Roberts S 112

I Roberts S 147

P C Roberts S 202

E K Ruxton S 76

R Sabatino S 97

C Sanders S 207

Shao H S 132

J Sharkey S 140

M Shaw S 193

A Shepherd S 38

J Sivasundram S 35

A Skordelis S 41

N Snowdon S 208

R A Spencer S 141

J Stedman S 233

C Stevenson S 228

M J Stewart S 26

T Sutton S 29

D J Swift S 24

S Tabone S 12

Tam Kam Fai S 77

Tang K P S 6

Tang Y P S 60

J Thomas S 216

G Thomopouloi S 42

I M Thomson S 220

W Thorne S 9

S J Threadingham S 172

D Tierney S 45

E Tsafos S 72

I Tsoupakis S 96

M Vavli S 74

Wang L S 130

D J Webb S 175

E J Welsby S 142

T Wichall S 178

A J Williamson S 69

Wong C Ka Ho S 17

K M Xenos S 14

E Ximeris S 63

Xiu Wen Liang S 30

S Young S 181

T Young S 10

Yung E W H S 166

Yung Sai Man S 57

Zhou H S 131

Zhou X Y S 126

P Zografos S 61

113

INSTITUTE OF CONCRETE TECHNOLOGY

DIRECTORY OF RETIRED MEMBERS - SUMMER 2004

RETIRED FELLOWS

D W Bath F 29South Africa

Dr A N Crossley F 59

J F Dixon F 20

J W Figg F 11

K Hafizuddin F 30

W K Hall F 25

R Hutton F 9

Dr M Levitt F 63

S J Martin F 51

M G Monk F 36

D G Nash F 72South Africa

J C Payne F 49

J G Richardson F 6

R Ryle F 21

F Walker F 4

K F C Weston F 37

J D Wootten F 1

RETIRED MEMBERS

M A Adams M 14

S R Arnold M 132

A E Ashman M 69

G D Ault M 9

T Bach M 182Denmark

L R Baker M 85

B V Brown M 237

D J Burrell M 4

A T Corish M 84

J A Curtis M 12

R M Edmeades M 292

R Garstone M 90

Z George M 183India

C F P Justesen M 191Denmark

R E Lavery M 81Portugal

S Mac Craith M 305Republic of Ireland

L H McCurrich M 412

Dr G K Moir M 426

D Parkinson M 89

D R Russell M 101

Dr G Somerville M 289

P T Spencer M 43

D C Spooner M 449

D C Teychenné M 146

C J G Travis M 153

Dr U A Trüb M 60

RETIRED ASSOCIATEMEMBERS

J Hymers A 108

E L Moss A 120Australia

O Rostam A 352

F E Spence A 153

C D Turton A 42

B R Tutt A 6

Unless otherwise stated, listedindividuals are resident in the UK.

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.concreterepair.org.uk

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



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 ASSOCIATION156 Buckingham Palace RoadLondon SW1W 9TRTel: 020 7730 8194www.mortar.org.uk

QSRMCQuality Scheme for ReadyMixed Concrete3 High StreetHamptonMiddlesex TW12 2SQTel: 020 8941 0273www.qsrmc.co.uk

QUARRY PRODUCTS ASSOCIATION156 Buckingham Palace RoadLondon SW1W 9TRTel: 020 7730 8194www.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

97

Published by:THE INSTITUTE OF

CONCRETE TECHNOLOGY4, Meadows Business Park

Blackwater Camberley Surrey GU17 9AB

Tel/Fax: 01276 37831Email: [email protected]

Website: www.ictech.org

ICT YEARBOOK 2004-2005

EDITORIAL COMMITTEE

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

& UNIVERSITY OF DUNDEE

Peter C. OldhamCHRISTEYNS UK LIMITED

Dr. Philip J. NixonBUILDING RESEARCH ESTABLISHMENT

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.

Engineering CouncilProfessional Affiliate

Yearbook: 2004-2005


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TheINSTITUTE OF CONCRETE TECHNOLOGY

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

Tel/Fax: 01276 37831Email: [email protected] 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.

concrete technology institute ofict.concrete.org.uk/downloads/yearbooks/ict_2004.pdf · concrete...

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