Concrete Construction

EXCELLENCE IN CONCRETE CONSTRUCTIONTHROUGH INNOVATIONPROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON CONCRETE CONSTRUCTION,KINGSTON UNIVERSITY, LONDON, UK, 910 SEPTEMBER 2008Excellence in ConcreteConstruction throughInnovationEditorsMukesh C. Limbachiya & Hsein Y. KewConcrete & Masonry Research GroupKingston University, London, UKCover photograph supplied originally by the Concrete Centre UKCRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business 2009 Taylor & Francis Group, London, UKTypeset by Charon Tec Ltd (A Macmillan Company), Chennai, IndiaPrinted and bound in Great Britain by Antony Rowe (A CPI Group Company), Chippenham, WiltshireAll rights reserved. No part of this publication or the information contained herein may be reproduced, storedin a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying,recording or otherwise, without written prior permission from the publishers.Although all care is taken to ensure integrity and the quality of this publication and the information herein, noresponsibility is assumed by the publishers nor the author for any damage to the property or persons as a resultof operation or use of this publication and/or the information contained herein.Published by: CRC Press/BalkemaP.O. Box 447, 2300 AK Leiden, The Netherlandse-mail: [email protected] www.taylorandfrancis.co.uk www.balkema.nlISBN: 978-0-415-47592-1 (Hardback)ISBN: 978-0-203-88344-0 (eBook)Excellence in Concrete Construction through Innovation Limbachiya & Kew (eds) 2009 Taylor & Francis Group, London, ISBN 978-0-415-47592-1Table of ContentsPreface XIOrganising Committee XIIIScientific and Technical Committee XVTheme 1: Innovation and development in concrete materials/designFoamed Concrete: Application and specification 3R.A. BarnesThe estimation of concrete quality by power functions 11B.K. NyameThe control of stable concrete quality 17B.K. NyameThe design of concrete mixes on limit surfaces 21B.K. NyameImprovement in the compressive strength of cement mortar by the use of a microorganism Bacillus megaterium 27V. Achal, R. Siddique, M.S. Reddy &A. MukherjeeNonlinear analysis of ultra high strength concrete RC structure 31H.G. Kwak, C.K. Na, S.W. Kim & S.T. KangStiffened deep cement mixing (SDCM) pile: Laboratory investigation 39T. Tanchaisawat, P. Suriyavanagul & P. JamsawangRelationship between compressive strength and UPV for high strength concrete containingexpanded Perlite aggregate 49M.B. Karako & R. Demirbo gaThe effects of the curing technique on the compressive strength of Autoclaved Aerated mortar 57T. Ungsongkhun, V. Greepala & P. NimityongskulMechanical properties of concrete encased in PVC stay-in-place formwork 63K.G. Kuder, C. Harris-Jones, R. Hawksworth, S. Henderson, J. Whitney & R. GuptaStudy and comparison between numerical and mathematical method for optimizing structures 73S.A.H. Hashemi & E. HashemiThe mathematical explanation of genetics algorithm method for optimizing structures 79S.A.H. Hashemi & E. HashemiOptimising 3D structure frames using GA 85S.A.H. HashemiExcellence in concrete construction through innovation 91S.K. ManjrekarDevelopment of eco earth-moist concrete 97G. Hsken & H.J.H. BrouwersVContaminated soil concrete blocks 107A.C.J. de Korte & H.J.H. BrouwersWho is the key decision maker in the structural frame selection process? 119H. Haroglu, J. Glass, T. Thorpe & C. GoodchildPerformance of surface permeability on high-performance concrete 127A. Naderi, A.H.H. Babei & N.S. KiaApplication of nano composites in designing and manufacturing of cement and concrete 131A. Bahari, J.R. Nasiri & O.J. FarzanehLightening and strengthening of building using structural lightweight concrete 135M. Mohammadi, S. Nanpazi, M. Ghassabi K. & D.B. ZadehThe role of nano particles in self Compacting concrete 143O.J. Farzaneh, J.R. Nasiri &A. BahariTheme 2: Composite materials in concrete constructionStrength properties of high-volume fly ash (HVFA) concrete incorporating steel fibres 149R. Siddique, J.M. Khatib, I. Yksel & P. AggarwalPermeability of high strength concrete 159S.M. Gupta, P. Aggarwal, Y. Aggarwal, V.K. Sehgal, R. Siddique & S.K. KaushikFormulation of Turonien limestone concrete of the Central Saharian Atlas (Algeria) 165Z. Makhloufi & M. BouhichaEffect of cumulative lightweight aggregate volume in concrete on its resistance tochloride-ion penetration 175X.M. Liu & M.H. ZhangEffect of bagasse ash on water absorption and compressive strength of lateritic soilinterlocking block 181P. Khobklang, K. Nokkaew &V. GreepalaLight-weight TRC sandwich building envelopes 187J. Hegger & M. HorstmannThermo-mechanical properties of HSC made with expanded perlite aggregate 195M.B. Karako & R. Demirbo gaComposition and microstructure of fly ash geopolymer containing metakaolin 201K. Pimraksa, T. Chareerat, P. Chidaprasirt, N. Mishima & S. HatanakaA computed-based model for the alkali concentrations in pore solution of hydratingPortland cement paste 207W. Chen, Z.H. Shui & H.J.H. BrouwersResearch on the absorbing property of cement matrix composite materials 215B. Li & S. LiuVisual examination of mortars containing flue gas desulphurisation waste subjected tomagnesium sulphate solution 221J.M. Khatib, L. Wright & P.S. MangatEffect of cement type on strength development of mortars containing limestone fines 227J.M. Khatib, B. Menadi & S. KenaiAdiabatic temperature rise of metakaolin mortar 233J.M. Khatib, S. Wild, R. Siddique & S. KenaiVICement-based composites for structural use: Design of reactive powder concrete elements 239G. Moriconi &V. CorinaldesiBiomass ash and its use in concrete mixture 245V. Corinaldesi, G. Fava, G. Moriconi & M.L. RuelloProperties of lightweight concretes made from lightweight fly ash aggregates 251N.U. Kockal &T. OzturanExperimental studies of the effectiveness of mortar modified with latexes 263M.Z. Yusof & M. RamliEffect of crystal cement on concrete 269H.K. Nezhad &A. NaderiProperties of FRP composite durability 271A. Bahari & J.R. NasiriUltra-high performance concrete 275D.B. Zadeh, A. Bahari & F. TirandazTheme 3: Design and construction in extreme conditionsSuitability of PTC heating sheets for curing foundation concrete in low temperatureenvironments 281M. SugiyamaImprovement of the durability of sand concrete to freezing-thaw and wet-dry cyclingby treatment of wood shavings 287M. Bederina, M.M. Khenfer, A. Bali, A. Goullieux & M. QuneudecMicrostructure characteristics of cementitious composites at elevated temperatures 293Y.F. Fu, W.H. Li, J.Q. Zhang, J.J. Feng & Z.H. ChenDurability of polyester polymer concrete under varying temperature and moisture 299M. Robles, S. Galn & R. AguilarMicrostructure degradation of concrete in extreme conditions of dry and high temperaturedifference 305A.M. She, Z.H. Shui & S.H. WangIntelligent exothermal Nano concrete with high thermal conductivity and designing andperforming the automatic road temperature monitoring system 311J. Poursharifi, S.A.H. Hashemi, H. Shirmohamadi & M. FeiziApplication of composite in offshore and marine structure 317Q. Jafarpour, M. Balaei & B.B. ZadehTheme 4: Protection against deterioration, repair and strengtheningLateral strength evaluation of seismic retrofitted RC frame without adhesive anchors 325T. Ohmura, S. Hayashi, K. Kanata &T. FujimuraAssessment of deformation capacity of reinforced concrete columns 335M. Barghi & S. YoussefiDuctility of confined reinforced concrete columns with welded reinforcement grids 339Tavio, P. Suprobo & B. KusumaOn the effect of FRP sheet composite anchorage to flexural behaviour of reinforcedconcrete beams 345C.B. Demakos & G. DimitrakisVIIFE modelling of the effect of elevated temperatures on the anchoring of CFRP laminates 351D. Petkova, T. Donchev & J. WenRehabilitation and strengthening of a hypar concrete shell by textile reinforced concrete 357R. Ortlepp, S. Weiland & M. CurbachCorrosion mitigation in concrete beams using electrokinetic nanoparticle treatment 365K. Kupwade-Patil, K. Gordon, K. Xu, O. Moral, H. Cardenas & L. LeeLong-term durability of reinforced concrete rehabilitated via electrokineticnanoparticle treatment 373K. Gordon, K. Kupwade-Patil, L. Lee, H. Cardenas & O. MoralThe use of glass-ceramic bonding enamel to improve the bond between concrete andsteel reinforcement 381C.L. Hackler, C.A. Weiss, Jr., J.G. Tom, S.W. Morefield, M.C. Sykes & P.G. MaloneA new design approach for plate-reinforced composite coupling beams 387R.K.L. Su &W.H. SiuAnalytical modeling of FRP-strengthened RC exterior beam-column joints 397T.H. Almusallam, Y.A. Al-Salloum, S.H. Alsayed & N.A. SiddiquiEnvironmentally-friendly self-compacting concrete for rehabilitation of concrete structures 403V. Corinaldesi & G. MoriconiShrinkage-free fiber-reinforced mortars 409S. Monosi & O. FavoniComparison between design codes and procedures for concrete beams with internal FRPreinforcement in balanced case failure 413M. Kadhim, T. Donchev, S. Al-Mishhdani & I. Al-ShaarbafExperimental behavior of repaired and strengthened self-compacted RC continuous beams 419K.M. HeizaPerformance-based durability testing, design and specification in South Africa:Latest developments 429M.G. Alexander & H. BeushausenMechanical properties and durability of FRP rods 435J.R. Nasiri, A. Bahari & O.J. FarzanehFRP composites in fabrication, rehabilitation and strengthening of structure 439Z. Aghighi & M. BabahaTheme 5: Environmental, social and economic sustainability credentialsEffect of GGBFS and GSS on the properties of mortar 445I. Yksel, R. Siddique, . zkan & J.M. KhatibComparative study on behaviour of concrete-filled steel tubular columns usingrecycled aggregates 453R. Malathy, E.K. Mohanraj & S. KandasamyA comparative study of using river sand, crushed fine stone, furnace bottom ash andfine recycled aggregate as fine aggregates for concrete production 459S.C. Kou & C.S. PoonFeasibility of using low grade recycled aggregates for concrete block production 465C.S. Poon, S.C. Kou & H.W. WanUtilization of glass cullet for the manufacture of binding material used in theproduction of concrete 473A.S. Belokopytova, P.A. Ketov, V.S. Korzanov &A.I. PuzanovVIIIMethodology for the prediction of concrete with recycled aggregates properties 477J. de Brito & R. RoblesGeopolymeric concrete based on industrial wastes 489F. Colangelo, R. Cioffi & L. SantoroRestoration mortars made by using rubble from building demolition 495F. Colangelo, R. Sommonte & R. CioffiHigh strength products made with high volume of rejected fly ash 501X.C. Qiao, B. Zhou & J.G. YuIndustrial symbiosis effective resource recovery within the UKs construction industry 505R. Kirton, D.H. Owen & E.J. ProbertEffects of different glasses composition on ecosustainable blended cements 511M.C. Bignozzi & F. SandroliniPossible utilisation of wheat husk ash waste in the production of precast concrete elements 517J. Zhang, J.M. Khatib, C. Booth & R. SiddiqueDeveloping viable products using recycled rubber tyres in concrete 523H.Y. Kew & M.J. KennyInvestigation into the potential of rubberised concrete products 533H.Y. Kew, K. Etebar, M.C. Limbachiya & M.J. KennySelf-cleaning surfaces as an innovative potential for sustainable concrete 545M. Hunger & H.J.H. BrouwersPervious concrete pavement: Meeting environmental challenges 553A.K. Jain & J.S. ChouhanInvestigation on the use of burnt colliery spoil as aggregate in low to normalstrength concrete 559T. Runguphan & P.M. GuthrieImprovement of characteristics in cement composite sheet with agriculture waste fibre 567M. Khorrami, E. Ganjian & M.A. KhaliliAuthor index 577IXExcellence in Concrete Construction through Innovation Limbachiya & Kew (eds) 2009 Taylor & Francis Group, London, ISBN 978-0-415-47592-1PrefaceThe Concrete industry has embraced innovation and ensured high levels of long-term performance and sustain-ability through creative applications in design and construction. As a construction material, the versatility ofconcrete and its intrinsic benefits mean that it is well placed to meet challenges of modern construction industry.Indeed, concrete has kept evolving to satisfy ever more demanding design requirements and relentless pressurefor change and improvement in performance. This is done through introduction of new constituent materials,technology and construction methods. The current challenges faced by concrete construction may not necessarilybe the same as those in the future. However, an ongoing programme of innovation and product developmentmeans that concrete should continue to provide cost effective sustainable solution that are able to turn a challengeinto an opportunity.The Concrete and Masonry Research Group (CMRG), part of the Sustainability Technology Research Centrewithin the Faculty of Engineering at Kingston University, organised this International Conference to discusshow concrete industry has addressed challenges from new materials, technologies, environmental concerns andeconomic factors to maintain its excellence. This is done by bringing together engineers, designers, researchersand scientists from 27 different countries to celebrate excellence in concrete construction and promote recentinnovations in science and engineering. This Conference dealt with key technical, as well as practical achieve-ments under concurrently proceeded five themes; (i) Innovations and Developments in Concrete Materials andDesign, (ii) Composite Materials in Concrete Construction, (iii) Design and Construction in Extreme Conditions,(iv) Protection Against Deterioration, Repair and Strengthening, and (v) Environmental, Social and EconomicSustainabilityCredentials. Over 80 papers were presented by authors during this Conference and these arecompiled in the CD and a hard bound single volume conference proceedings.The event was organised with co-sponsorship from the American Concrete Institute and support from AsianInstitute of Technology Thailand, Universit degli Studi di Napoli Parthenope Italy, The Hong KongPolytechnic University Hong Kong, University of Cape Town South Africa, Universita Politecnica delleMarche Italy, The Concrete Centre UK, British Cement Association UK and Wuhan University of Tech-nology, P R China. All there organisations are gratefully acknowledged for their invaluable support. The work ofConference was an immense undertaking and help from all those involved are gratefully acknowledged, in par-ticular, members of the Scientific and Technical Committee for their assistance from start to finish; the Authorsand the Chair of Technical Sessions for their invaluable contribution.The Proceedings have been prepared using camera-ready copy printed from the electronic manuscripts sub-mitted by the authors and editing has been restricted to minor changes where it was considered absolutelynecessary.Mukesh C. LimbachiyaHsein Y. KewKingston University LondonSeptember 2008XIExcellence in Concrete Construction through Innovation Limbachiya & Kew (eds) 2009 Taylor & Francis Group, London, ISBN 978-0-415-47592-1Organising CommitteeConcrete and Masonry Research Group Kingston UniversityProfessor M.C. Limbachiya (Chairman)Dr H.Y. KewDr K. EtebarDr T. DonchevProfessor S.B. Desai OBEDr A. CheahDr J. OmerMiss D. PetkovaFaculty of Engineering Research OfficeXIIIExcellence in Concrete Construction through Innovation Limbachiya & Kew (eds) 2009 Taylor & Francis Group, London, ISBN 978-0-415-47592-1Scientific and Technical CommitteeProfessor Dr Ir H.J.H. (Jos) BrouwersProfessor of Sustainable Building, University of Twente, THE NETHERLANDSProfessor Raffaele CioffiVice-Director, University of Parthenope of Naples, ITALYProfessor Peter ClaisseProfessor of Construction Materials, Coventry University, UKProfessor Jorge de BritoInstituto Superior Tcnico/Technical University of Lisbon, PORTUGALProfessor Satish Desai OBEVisiting Professor, Kingston UniversityPrincipal Structural Engineer Trenton Consultants, UKEur Ing Costas GeorgopoulosEducation &Training Manager, The Concrete Centre, UKDr Jamal KhatibReader in Civil Engineering Materials, University of Wolverhampton, UKProfessor Mukesh Limbachiya (Chairman)Research Professor, Faculty of EngineeringDirector Sustainable Technology Research Centre, Kingston University, UKDr Surendra ManjrekarChairman & Managing Director Sunanda Speciality Coating Pvt Ltd, INDIAProfessor Giacomo MoriconiDirector Department of Materials and Environment Engineering & Physics UniversitPolitecnica delle Marche, ITALYProfessor C.S. PoonProfessor The Hong Kong Polytechnic University, HONG KONG P.R. CHINAProfessor Rafat SiddiqueProfessor of Civil Engineering Thapar University, INDIAProfessor Dr Shui ZhongheProfessor Wuhan University of Technology, P.R. CHINAXVTheme 1: Innovation and development inconcrete materials/designExcellence in Concrete Construction through Innovation Limbachiya & Kew (eds) 2009 Taylor & Francis Group, London, ISBN 978-0-415-47592-1Foamed Concrete: Application and specificationR.A. BarnesThe Concrete Society, Camberley, UKABSTRACT: The Concrete Society has produced a new guide on foamed concrete, its range of applicationsand a specification (The Concrete Society, 2008), which this paper aims to summarise. Although foamed concretewas used some 2000 years ago it wasnt until recently that modern foamed concrete began to be developed. In1987 a full scale trial on the use of foamed concrete for trench reinstatement was conducted in the UK, whichled to a further increase in use in this country. Foamed concrete has the following properties: it is lightweight,free flowing and easy to level, it does not require compaction, has good thermal insulation and frost resistanceproperties, and it is easy to pump, both vertically and horizontally. Its uses include: Trench Reinstatement,Blinding, Filling (basements, pipes, tunnels, subways, mine workings), Building use (under floors and roofing),Soil stabilisation, Reductions in lateral loading, Sports fields and athletics tracks and Sandwich fill for precastunits. As well as the composition and production methods, this paper covers some of the practicalities andproperties of the material.1 INTRODUCTIONThe term Foamed Concrete may be somewhat mis-leading in that most do not contain large aggregates(indeedit maybeconsideredtobefoamedmortaror foamed grout). It is a lightweight concrete man-ufacturedfromcement, sandorflyash, wateranda preformed foam. Its dry density ranges from 300to 1600 kg/m3with 28 day strength normally rangingfrom 0.2 to 10 N/mm2or more.A widely cited definition of foamed concrete is:Acementitiousmaterial havingaminimumof20 per cent by volume of mechanically entrained foamin the plastic mortar or grout.Thisdifferentiatesit fromairentrainedconcretewhich has a far lower volume of entrained air (typically38%), retarded mortar systems (typically 1522%)and aerated concrete where the bubbles are chemicallyformed.In the production of foamed concrete, a surfactantis diluted with water and passed through a foam gen-erator which produces a stable foam. This foamis thenblended into a cementitious mortar or grout in a quan-tity that produces the required density in the foamedconcrete.Surfactants are also used in the manufacture of LowDensityFills(alsocalledControlledLowStrengthMaterial (CLSM)). Inthiscase, however, theyareadded directly into a sand rich, low cement contentconcretetogive15to25%air. Somewhat confus-ingly, somesuppliersofLowDensityFillsrefertothese materials as foamed concrete, but as the foam isnot formed separately to the concrete they are not truefoamed concretes.2 APPLICATIONSThe value offoamedconcrete lies inits good voidfilling ability with a rigid hardened structure whichwill not deflect under low loading and also the lowdensity where loading on other parts of the structureare critical. Although it will give enhanced thermal andfire rating properties, it is not usually the most costeffective solution for these applications unless accessis difficult.Some examples of the wide variety of applicationswhere foamed concrete has been used include:2.1 Trench reinstatementOne of the main causes of damage to road pavementsareexcavationscarriedout byutilitiescompanies.Settlement of backfill means that the surfacing is dam-aged and constant patching will be required. Foamedconcretemeetsthecriteriafortheidealbackfillingtechnique in that: it normally requires no compactiveeffortanddoesnotsettleafterplacing;itdoesnottransmit axleloads directlytotheservices inthetrench; final resurfacingis possible the next day;it is economic; it is readily available; it permitseasy re-excavation; it does not require unreasonablycomplicated equipment or skilled labour.3In order to satisfactorily compact the bitumi-nous surfacing foamed concrete with a compressivestrength of approximately 1 N/mm2is required. Fur-ther guidance on the design of foamed concrete fortrench reinstatement can be found in Foamed concretefor improved trench reinstatement (Taylor, 1991).In order to evaluate the suitability of foamed con-crete as an alternative to normal granular backfill atrenching trial was undertaken in Wickford in 1988.In2003 a long termassessmentofthe results sug-gested no significant difference in the predicted totallife of the carriageway since construction of thereinstatement (Steele et al, 2003).2.2 Void fillingAs foamed concrete is flowing, self levelling and selfcompacting it provides a rapid, effective and compet-itively priced solution for void filling, and has beenused for this application throughout the UK. Its rigid-ity, rangeofstrengthsanddensitiesalongwithitsthermal insulationandcontrolledwater absorptionproperties make it an ideal choice for a wide range ofvoid filling applications. Old mines and tunnels oftenlead to ground stability problems and many have beenfilledwithfoamedconcrete, alongwithsewers, servicetrenches and highway structures such as subways andculverts. Collapsed tunnels at the Heathrow ExpressrailLinkwerestabilisedwith13 500 m3offoamedconcrete.2.3 Replacement of existing soilIn areas of weak soil conditions the weight of a foamedconcrete layer and the construction on top of this layer(e.g. road or building) can be designed to equal theweightoftheexcavatedsoil(balancedfoundation).Therefore, the stress in the underlying soil layers isnot increased, minimising settlements. Densities in therange 300600 kg/m3tend to be used.Foamed concrete can be used as a foundation toroads where there are poor underlying ground condi-tions. It also provides a more stable foundation thanlight granular material. 27000 m3of foamed concretewas placed from a purpose built barge to form a roadfoundation as part of the London Docklands project(S van Dijik, 1991).2.4 Lateral load reductionThis application has been used in harbour quays (e.g.diaphragmwall orsheet pileretainingwall)wherefoamed concrete is used as a lightweight backfill mate-rial behindthequay. Vertical loadsandhencethelateral load are reduced. Settlements are also reducedand maintenance is minimized. Densities in the range400600 kg/m3tend to be used.2.5 Soil stabilizationTo improve the slope stability of embankments partof thesoil isreplacedwithfoamedconcrete. Thisreduces the weight which is a major factor in the insta-bility of slopes. Densities in the range 400600 kg/m3tend to be used.2.6 Bearing capacity enlargementCast-in-place piles of foamed concrete can be used asskin friction piles in weak soils. Densities in the range1200 kg/m3tend to be used.2.7 Raft foundationThis application has been used in housing. The foamedconcrete acts as a lightweight raft foundation and ther-mal insulatinglayer. Thisisprotectedwithafloorscreedoraconcreteblindingwhichalsoactsasaload spreading layer. Densities in the range 500 kg/m3tend to be used, average thickness 0.2 m (R Jones &AGiannakou. 2002). Another applicationisaraftfoundationmanufacturedwith400600 kg/m3foamedconcrete, 0.75 m thick for dwellings to be built that siton water in dykes (in Holland mostly). These are alsoused as floating pontoons in marinas.2.8 Roof slopesLow density foam concrete has many roofing appli-cationsbutisparticularlysuitableforprofilingthepositiveslopetodrainsonflat concreteroofs. Byadding sand to the mix slopes of 16 mm/m are achiev-able and the foam concrete surface can be finishedwith a tolerance of 10 mm relative to the requiredlevel while maintaining the required slope (L Cox &S van Dijik, 2003).2.9 Floor levellingRaising the level of an old floor can be expensive whenusing conventional concrete but placing a foamed con-crete sub base on top of the old floor before laying anew concrete floor on top can be more cost efficient.Different densities tend to be used for different layerthickness.2.10 BlindingFoamedconcrete has the advantage of highworkabilityand flexibility of placing over conventional concretefor blinding. Densities of approximately 1200 kg/m3areusedifthermal insulationisnot important and500 kg/m3if it is.42.11 Sports fields and athletic tracksToachievearapiddrainingsports fieldaperme-able foamed concrete (density: 600650 kg/m3) witha high drainage capacity is used (Darcy permeabil-ity 300 mm/hour). The foamed concrete serves as alightweight foundationandis coveredwithgraveland/or a synthetic turf for sports fields used for hockey,football and tennis.2.12 Filling of pipesUnderground fuel tanks, pipelines and sewers whichare out of use can cause fire hazards or can collapse.Once filled these structures are supported and blockedby the foamed concrete. Densities in the range 6001100 kg/m3tend to be used.2.13 Support of tank bottomsFoamed concrete can be poured under steel storagetanks, which ensures that the whole tank bottomis sup-ported. Densities in the range 5001000 kg/m3tend tobe used.2.14 Shock-absorbing concrete (SACON) (U.S.Army Environmental Center, 1999)Shock-absorbing concrete (SACON) is a low-density,fibre-reinforcedfoamedconcretedevelopedintheUSA to be used in live fire military training facilities.It was developed to minimise the hazard of ricochetsduring urban training. As well as reducing ricochets,the shock absorbing properties of this foamed con-crete also function to create a medium for capturingsmall-arms bullets.3 COMPOSITIONIngeneral, foamedconcreteswithdensitiesbelow600 kg/m3consist of cement, foamand water, with thepossible addition of fly ash or limestone dust. Higherdensitiesareachievedbyaddingsand. Forheavierfoam concrete the base mix is typically between 1:1 to3:1 filler to Portland Cement (CEM I). At higher den-sities (above 1500 kg/m3) there is higher filler loadingand a medium concreting sand may be used. As thedensity is reduced the amount of filler should also bereduced and at densities below about 600 kg/m3fillermaybe completelyeliminated. The filler size must alsobe reduced, first to a fine concreting or mortar sand,and then to limestone dust, pfa or ggbs at densitiesbelow about 1100 kg/m3.3.1 Cement and combinationsPortlandCement (CEMI)isnormallyusedasthebinder but other cements could be used including rapidhardening cement. A wide range of cement and com-binations can also be used e.g. CEM I 30%, fly ash60% and limestone 10%. Cement contents tend to bein the range of 300 to 400 kg/m3.3.2 SandSand up to 5 mm maximum particle size may be usedbut a higher strength is obtained using finer sands upto 2 mm with 6095% passing a 600 micron sieve.3.3 FoamThe most commonly used foams are based onhydrolised proteins or synthetic surfactants. Syntheticbased foaming agents have longer storage times andare easier to handle and cheaper. They also requireless energy to produce foam, however protein basedfoaming agents have higher strength performance.The preformed foam can be divided into two cate-gories: wet foam and dry foam.Wet foam has a large loose bubble structure andalthoughstable, is not recommendedfor thepro-ductionof foamedconcretes withdensities below1000 kg/m3. It involves sprayingasolutionof theagent and water over a fine mesh, leading to a foamwith bubbles sized between 25 mm.Dry foam is extremely stable, a characteristic thatbecomes increasingly important as the density of thefoamed concrete reduces. It is produced by forcing asolution of foaming agent and water through restric-tions whilst forcing compressed air into the mixingchamber. The resulting bubble size is smaller than wetfoamat less than 1 mmin diameter and of an even size.Foaming admixtures are covered by BS 8443:2005Specification for establishing the suitability of specialconcrete admixtures (BSI, 2005).3.4 Other aggregates and materialsCoarse normal weight aggregates cannot be used infoamed concrete as they would sink in the lightweightfoam.3.5 Mix detailsThe properties of foamed concrete are mostly depen-dent on the following aspects: volume of foam, cementcontent, filler and age.Water/cement ratiohasrelativelylittleeffect onstrengthbut other factors like filler content andparticlesize do.4 PRODUCTIONTherearetwomainmethodsofproducingfoamedconcrete, namely the inline and pre-foam methods.54.1 InlineIn this case the base mix is put into a unit where it isblended with the foam. The mixing process is morecontrolled and greater quantities can be more easilyproduced. It can be split into two processes:4.2 Inline system (wet method)The base materials are the same as those used in thepre-foam system but are generally wetter. The basematerial and the foam (dry type see above) are fedthrough a series of static inline mixers where the twoaremixedtogether. Thefoamandthebasemateri-als are blended together and checked with a continualon-board density monitor. The output volume is notgovernedbythesizeof theready-mixedconcretetruck, but by the density of the foamed concrete one8 m3delivery of base material can produce 35 m3of a500 kg/m3foamed concrete.4.3 Inline system (dry method)This method is widespread in Europe and is also usedin the UK. Dry materials are loaded into on-board silosfrom where they are batched weighed and mixed on-site as required using on-board mixers. The base mixis then pumped into a mixing chamber where the foamis then added in the same way as the wet inline system.They require large amounts of water at site for mixing.One delivery of cement/fly ash blend can produce upto 130 m3of foamed concrete.4.4 Pre-foamInthismethodthebasematerialsaredeliveredtosite in a ready-mixed concrete truck. The pre-formedfoamis then injected directly into the back of the truckwhilst the mixer is rotating. This method has the advan-tage that relatively small quantities can be ordered, fortrench fill, for example, however, it does rely on themixing action of the concrete truck. Densities in therange of 3001200 kg/m3can be achieved. These sys-tems are typically foamed air in the range 20 to 60%air. As this normally takes place in a ready-mix truck,the volume of base mortar or concrete mixed in thedrum must be reduced to allow for the final volume offoamed concrete. The amount of stable air and hencedensity is difficult to control precisely so a degree ofboth under and over yield must be allowed for whenestimating deliveries.Once the foam is formed it is added to the sandcement mortar that normally has a water cement ratioof 0.4 to 0.6. Too wet a mortar leads to an unstablefoam, too dry and the pre-foam may not be able toblend with the mortar.5 PRACTICALITIES5.1 GeneralOn exposed surfaces there will be some shrinkage butthis tends to be in the formof micro cracking. Abrasionresistance is not high, especially at the lower densitiesso a surface coating is usually needed. The air cellsare closed and do not immediately fill with water butat lower densities this will progressively occur if thereis any pressure head. Foamed concrete is not used inconjunction with steel reinforcement.5.2 FormworkFormwork needs to be waterproof and able to resistthe pressure exerted by the foamed concrete. If cablesand pipework are to be incorporated in the foamedconcrete, they may need to be loaded or anchored toprevent themfrommoving and floating. Considerationmust be given to the fact that foamed concrete willfill every accessible space and that the surface willbe practically horizontal after setting. When castingfoamed concrete against the ground it may well bebeneficial to use a geomembrane or geotextile.5.3 Health and safetyAll the parties involved with the use of foamed con-crete should ensure that all works are carried out inaccordance with current health and safety regulations.In particular it is important to protect against drown-ing, which is a risk whilst the foamed concrete remainsfluid. Measures to be taken include: the use of warningsigns, guarding the construction site and covering thefoamed concrete.5.4 Pour depthsIn general, the depth of a pour should be limited to amaximumof 1.5 m, thicker pours increasing the risk ofsegregation and settlement. Where greater depths arerequired, pours should be carried out in approximatelyequal layers.5.5 PumpingFoamed concrete may be placed by pump but pressureinvolved in pumping reduces the air content and theproperties of the foamedconcrete shouldbe assessedatthe point of placement (i.e. once it has left the pump).For long pump distances the grout and the foamingagent can be pumped separately. The foam can thenbe formed and pumped up to 100 m then blended withthe grout to form the foamed concrete at the point ofapplication.65.6 SpecifyingIf strength and or density are critical to the applica-tion, ensure that they are adequately specified, bothmaximum and minimum values if necessary. Densitymeasured on site will be wet density but a cube or corewill be an air dry density. Air dry density is typically100 to 150 kg/m3lower than wet density. Compressivestrength is measured on dry cubes.Strength and density can be accurately controlledbut this will cost more, especially for pre-foam pro-duction. In most cases where strength/density are notspecified as a critical requirement, control of foamedconcrete is quite loose.6 PROPERTIES6.1 Visual appearanceThe foamthat is added to the mortar to produce foamedconcrete closely resembles shaving foam. Once this ismixed with the mortar the foamed concrete is liquidwith a consistency similar to yoghurt or milkshake.In its hardened state foamed concrete is similar inappearance to aerated autoclaved blocks (or an Aerochocolate bar).6.2 Fresh propertiesThe foam has a strong plasticising effect and foamedconcrete is normally of high workability with slumpsranging from 150 mm to collapse. For most applica-tions of foamed concrete this is an advantage and itcan be difficult to make a low slump if this is what isrequired. Foamed concrete is quite thixotropic and itcan be quite difficult to restart the flow once the con-crete has been static for several minutes (although thisis not always the case).The high air content of foamed concrete eliminatesany tendency to bleed. With its good insulation prop-erties, as the mix temperature increases during setting,the air expands slightly which ensures good filling andcontact in confined voids.If a foamed concrete mix is over sanded or uses anover-coarse sand, segregation or bubble collapse canoccur leading to volume loss and/or a weak top sur-face. Foamed concrete can be pumped but care shouldbe taken to avoid a significant free fall down the lastlengthofpumplineasturbulencemaydestroythebubble structure.6.3 Hardened propertiesAs can be seen inTable 1 belowthe physical propertiesof hardened foamed concrete relate to the dry den-sity. Thermal conductivity ranges from 0.1W/mk toTable 1. Typical properties of foamed concrete.Dry Compressive Tensile Waterdensity strength strength Absorptionkg/m3N/mm2N/mm2kg/m2400 0.51.0 .050.1 75600 1.01.5 0.20.3 33800 1.52.0 0.30.4 151000 2.53.0 0.40.6 71200 4.55.5 0.61.1 51400 6.08.0 0.81.2 51600 7.510.0 1.01.6 5The guide value indicates the total quantity of water in kgthat permeates a 1 m2foam concrete surface during 10 years,if this surface is constantly exposed to water with the samepressure as a 1 m water column. The water absorption mayvary according to the type of foam used.0.7W/mk, whilst drying shrinkage ranges from 0.3%at 400 kg/m3to 0.07% at 1600 kg/m3.It should be noted that foamed concrete is, in gen-eral, not asstrongasautoclavedblocksof similardensity. If the concrete is saturated at the time of com-pressive strength testing, a low result will be obtaineddue to the internal hydraulic pressures set up as thesample deforms under load.The cellular structure of foamed concrete gives itgood resistance to the effects of freeze thaw action.Foamed concrete does not appear to be vulnerable infreeze-thaw situations and specimens of foamed con-crete with densities ranging from 400 to 1400 kg/m3showed no signs of damage when subjected to a freezethaw regime with a temperature range of 18C to+25C.If a lowdensity foamed concrete has been specifiedfor its lightweight properties then the effect of possiblewater absorption on the final density should be takeninto consideration.7 QUALITY CONTROL7.1 Foam density and stabilityThe properties of foamed concrete are highly depen-dent on the quality of the foam. The wet density of thefoam can be simply determined through weighing aknown volume of foam e.g. using a glass measuringcylinder or a bucket, and should be done routinely.The stabilityof a foamcanbe assessedbymeasuringits collapse with time, using a glass measuring cylinderbut a wide plastic pipe may be better as it reduces siderestraint.7.2 Plastic density of the foamed concreteThe plastic density of the foamed concrete can again besimply determined through weighing a known volume7of foamed concrete e.g. using a bucket. The methodis outlined in BS EN 12350:Part 6:2000. Testing freshconcrete: Density (BSI, 2000e).7.3 Consistence and segregationAs slumpis normallyhigh, theslumptest is notideal but can be used to indicate whether the foamedconcrete workability is too low.The consistence of foamed concrete can be quan-tified by the slump flow test to BS EN 12350-5:2000TestingfreshconcretePart 5Flowtabletest, (BSI,2000d) but without jolting the table.Segregation of foamed concrete in the fresh statecan be detected by foam rising to the surface of themix, or by the formation of a separate paste at thebottom of the mixer (only noticeable when mixing).Segregation can be quantified through difference inoven dry densities of 25 mmthick slices taken fromthetop and bottom of a 100 mm diameter core. Anothermethodtoquantifysegregation is throughdifference inoven dry densities of horizontal cores taken at differentheights.7.4 Cube strengthThe foamed concrete should be sampled in accordancewithBSEN123501:2000Testingfreshconcrete,sampling (BSI, 2000b). Compressive strength can bemeasured in accordance with BS EN 123503:2000Testinghardenedconcrete. Compressivestrengthoftest specimens (BSI, 2000c).To manufacture the test specimens 150 mm ratherthan100 mmcubesmayberequiredtoensuresuf-ficient accuracy. Disposable polystyrene moulds areoften used as the concrete can be left in the mould(with a suitable lid) until testing. The foamed concreteshould not be tamped or vibrated into the mould. Hav-ing been left covered for at least 3 days the cubes canbe demoulded and immediately sealed in plastic bagsand cured at 20 2C.Onlowdensityfoamedconcreteacoreisoftentaken the following day for curing and testing along-side the cubes.It should be noted that the variability in strengthof a foamed concrete is greater than that of a normalconcrete.7.5 SoundnessThe soundness of the surface of the foamed concretecanbeusedtoassessitsstrengthdevelopment. Toassess the soundness the BREscreed tester can be usedtodetermine the insitucrushingresistance. For screedsthe test is described in BS8204-1:2003 Annex D (BSI,2003), however, for foamed concrete the penetration ofa single drop of the weight should be measured ratherthan the four successive blows.8 SPECIFICATIONThere is currently no standard specificationfor foamedconcrete in the UK although there are some guidancedocuments available (Brady et al, 2001). BS EN 206-1:2000 Concrete Part1: Specification, performance,production and conformity (BSI, 2000a) specificallystates that it does not apply to foamed concrete.8.1 Strength and density requirementsThe specification gives requirements for strength anddensity limits.8.2 Constituent materialsConstituent materials are covered by the specification,for example:Anyfoamingadmixturesshall complywithBS8443:2005 Specification for establishing the suitabil-ity of special purpose concrete admixtures. (BSI,2005).8.3 ProductionAs well as specification details covering production,notes are also given, such as:Note: It is known that there is a correlation betweenthe density and compressive strength of foamed con-crete. Comparing the wet density of the foamedconcrete at the point of discharge, with the wet den-sity determined during development testing gives anestimate of the likely strength at a given age.8.4 GeneralGeneral specification clauses are included in this sec-tion, andit is notedthat for some applications specialistadvice should be sought.8.5 SafetyThe specification clause on safety is reproducedbelow:Foamed concretes are likely to provide minimalload bearing capacity for several hours after mixing;during this time unguarded concreting works can rep-resent a drowning hazard for site operatives, childrenand animals.9 CONCLUSIONSThe Concrete Society has produced a new guide onfoamed concrete, which introduces the material, cov-ers its wide range of applications, gives informationon its composition and production, includes practical-ities of its use, summarises its properties, advises onquality control and includes a specification.8ACKNOWLEDGEMENTSThis paper is based upon The Concrete Society doc-ument, FoamedConcrete:applicationsandspecifi-cations, theproductionofwhichwassponsoredbyFoam Concrete Ltd, Propump Engineering Ltd, TheHighways Agency, London Concrete and the CementAdmixtures Association.REFERENCESBrady, K.C., Watts, G.R.A. & Jones, M.R. 2001. Specifica-tion for foamed concrete, Highways agency ApplicationGuide AG39. TRL, Crowthorne.British Standards Institute. 2000a BS EN 206-1:2000 Con-crete Part1: Specification, performance, production andconformity. BSI, London.British Standards Institute. 2000b. BS EN 12350 1:2000Testing fresh concrete, sampling. BSI, London.British Standards Institute. 2000cBSEN123503:2000Testing hardened concrete. Compressive strength of testspecimens. BSI, London.BritishStandards Institute. 2000d. BSEN12350-5:2000Testing fresh concrete Part 5 Flowtable test. BSI,London.British Standards Institute. 2000e. BS EN12350:Part 6:2000.Testing fresh concrete: Density. BSI, London.British Standards Institute. 2003. BS8204-1:2003 Annex D(BSI, 2003). Screeds, bases and in situ floorings Part 1.BSI, London.British Standards Institute. 2005. BS 8443:2005 Specifica-tionforestablishingthesuitabilityof special concreteadmixtures. BSI, London.Cox, L. & van Dijik, S. 2003. Foam concrete for roof slopesand floor levelling. CONCRETE. February. pp. 3739.Jones, R. &Giannakou, A. 2002. Foamedconcrete forenergy-efficient foundations andgroundslabs. CON-CRETE. March. pp. 1417.S van Dijik. 1991 FoamConcrete. CONCRETE, July/August.U.S. ArmyEnvironmental Center. 1999. Shock-AbsorbingConcrete (SACON), Bullet Traps for Small Arms Ranges.Cost and Performance Report. U.S. Army EnvironmentalCenter. Report No. SFIM-AEC-ET-TR-99019.Steel, D.P., McMahon, W. &Burtwell, M.H. 2003. Long-termperformanceof reinstatedtrenchesandtheiradjacentpavements. Part 2: Long term performance of reinstate-ments in the highway. TRLReport TRL573. TRL,Crowthorne.Taylor, R.W. 1991. Foamedconcreteforimprovedtrenchreinstatements. British Cement Association, Camberley.The Concrete Society. 2008. Foamed Concrete: applicationand specification. The Concrete Society, Camberley.9Excellence in Concrete Construction through Innovation Limbachiya & Kew (eds) 2009 Taylor & Francis Group, London, ISBN 978-0-415-47592-1The estimation of concrete quality by power functionsB.K. NyameConsultant, London, UKABSTRACT: Concrete is the main composite material. The need arises to rationalize computer mix designsfor multi-phase concrete. There are only two simple two-phase models for composites the upper and lowerbounds, with quality estimated by the expected values. Otherwise, the models are free two-phase models withvaried geometric configurations and whose quality is estimated by power functions. In these 3 papers, two-phasemodels are (i) used to simply describe the complex distribution of material quantity qi, and quality Qi. and (ii)interpolated by the interparticle model the IM -, using its variable interface vector m. The overall objective isto estimate and control to design for the composite property. Power functions are empirically used to estimatenon-linear behavior by curve fitting. This 1st of 3 papers, deals with power function estimations of the concreteproperty, Q0,. Firstly, expected values are expressed as power series and analysed for uniqueness. Next, powerfunctions are derived by eliminating the characteristic IM interface vectors. The power mean value is the mean,mode and median of the conventional mean values. The power function, Q0=

mi=1 Qqiidefines central tendencyas the power mean value.1 INTRODUCTIONModern structures are designed for a wide range ofloading and concrete quality as described in table 1.Along time before two-phase models, concrete wasregarded (Troxell et al. 1968) as a mixture of gran-ular materials, with water added merely for fluidity.The properties of concrete were popular as empiricalTable 1. Quality for concrete construction.Loading Structure QualityHumidity Pavement Slabs DeformationTemperature Power Stations, Cracking &hot & cold. Refractories, ThermalLNG tanks ResistancePrestress & Buildings and Bridges Tension,Vibrations Deformation,Damping.Hydraulic Offshore, pipelines, Durability &tanks, tunnels, dams, Permeabilityfoundations, marineShock waves Hardened ImpulseStructures Response.Acoustic Buildings & Studios Acousticwaves ImpedanceRadiation Power Stations Absorptionpower functions or power laws. Powers differentiatedthe water content as evaporable and non-evaporable at105Cand then explained the deformation of concrete.Power functions are popular as empirical equationswhich describe non-linear behavior of systems.In 1960, Hansen (1960) introduced the simpletwo-phasemodelsintoconcretetechnology, fortheestimations of elastic modulus by linear elastic anal-ysis. Later, workerssuchasHirsch(1962), Counto(1964), Hobbs (1971) andCampbell-Allen(1963) esti-mated deformation with what was then a new openingto two-phase models.Interfaces affect strength and fracture mecha-nisms. Barnes(1976), Alexanderet al. (1998), Yeh(1992)andHughes& Ash(1969), describedinter-face effects by measurements and morphology. Since1960, two-phase models have only been used as esti-mation models (Illston et al. 1979) for the concretedeformation.Illston et al. (1979) outlined some limitationsfor slow progress of two-phase models as measure-ment techniques, starting data, moisture contents, theinterfaceeffects, thealgebraiccomplications, non-linearity, high strength aggregate have little effect onconcrete strengths, or universal non-acceptability ofmodels. Counto (1964) and Hobbs (1971) derived non-linear estimators. For the design of concrete nuclear11Figure 1. Logical flowdiagramfor qualityestimation,design and control.heat shields, Browne (1972), point estimated the coef-ficients of thermal expansion by assuming linearityat normal aggregate volumes concentrations of 60%to 80%.Thispapershowsthatinterfacevectorsarevari-ables to eliminate from two-phase models on figs 1 &2 (a). One problem identified was the hope to esti-matethenon-linear effectsusingthelinear elasticanalysis.Another problemis that upper bounds on phase Q+1ishowdirect compositequalityincreases. However,the lower bounds on phase Q1ido not predict directquality increases as the phase quality is increased.Firstly, the upper and lower bound expected qual-ityof two-phase models andthe micro-chipIMare identified by interface vectors m=+1 or 1 onfig 1 (read from base up) and by configurations onfig 2 (a).Next, interface vectors are eliminated by applyingthe uniqueness theorem (Rade & Westergren 1990) toderive power functions for estimation. Using conver-gence criteria (Rade & Westergren 1990), stable mixcompositions are deduced in the 2nd of 3 papers.Finally, by combining the estimation and the controlof stable mix compositions, limit surfaces for designare described. Fig 1 outlines the logical mix design.Figure 2(a). The IM(G) interpolates the Upper (A) &Lower(B) Bounds.Figure 2(b). The power function for the IM (G) interpo-lates the Upper (A) and Lower (B) bound permeability.2 POWER SERIES ANALYSISThe expected quality of simple two-phase models bysuperposition from figure 1 isInterface vector, m=+1 upper, m=1 lower bound.The expected quality is evaluated by linear flow andlinear elastic analyses (Illston et al. 1979). The powerseries areHence the power series for the expected quality oftwo-phase models from eqn 1 isThis vital power series for the expected quality aseqn 4 is investigated for uniqueness (Rade & Wester-gren 1990), in this paper for quality estimation. It will12then be investigated for convergence (Rade & West-ergren1990), inthe2ndpaperforqualitycontrol.The important equation 4 sums up the linear flow orlinear elastic analysis (Illston et al. 1979) of simpletwo-phase models for the mix design described in the3rd paper.Bylinear elastic analysis, uniqueness of eqn4yieldsthe response to loads, which has limits as strengths -theresistance to loads. However, the convergence of vitalequation 4 yields the stable response to loads. Thislinks equation 4 to real structural analysis and design(Kong&Evans1975, Allen1988), nowappliedtoconcrete mix design.2.1 The power mean value PMVUniqueness (Rade &Westergren 1990), is investigatedfor equation 4, so as to derive the power function thatestimates the power mean value PMV which ascentral tendency, is the mean, mode andmedianof con-ventional means, as the rms, arithmetic and harmonicmeans on fig 4.Applying the uniqueness theorem, (Rade & West-ergren1990)bycomparingcoefficientsof(mn/n!)on both sides of equation 4, eliminates the randominterface vector m, so that the expected quality isFrom eqn 5, if n =1, then power mean value Q0 fromthe power function isPower mean values are powerful 3 in 1 non-linear esti-mators of the mean, median and mode values as shownon figure 4, but are independent on interface vectors,m and geometric configurations. Except for the upperand lower bounds, free two-phase models, such as theIM, obey the power functions.2.2 Transcendental power functionsThe transcendentals are deduced by comparing eqn 1to eqn 5, as superposition of phase effects, so that Qiand m of eqn 1 are replaced by ln Qi and n at eqn 5.By applying the uniqueness theorem(Rade &Westergren1990) toeqn5, the1st transcendentalpower function for the two-phase composites isIn effect, applying the uniqueness theorem14to thepower series of expected values, theY superpositionis transformed toH factors of phase effects in powerfunctions and the 1st transcendental power function.In lubrication engineering7empirical transcenden-tal power functions are used to blend grades of oil. Soas a liquid, fresh concrete may obey transcendentals.Deviations frompower functions occur as non-linear effects of by-pass flow around aggregate par-ticles.In this respect, exclusive powers function, where theexclusion factor h depends on levels of by-pass flow.h =1 for impermeable aggregate on full by-pass flowh =0 for permeable aggregate with no by-pass flowIf h =1 or no flow occurs through the aggregate, theexclusive power function becomes simply3 QUALITY ESTIMATIONS Q0Everyone can estimate. Those estimating nothing haveestimated zero. Those estimating with the least errorsfrom accepted values give the better estimates. Thereare 3 types of quality for concrete.3.1 Steady state linear flow or no flowProperties in this group, such as density and poros-ity are structural and if there are any flows for theirmeasurement, they are linear. Steady state quality offree wc 0.47 mortar samples (Nyame 1985) cured for28days are described by power functions on figure 3.3.2 Steady state non-linear flowProperties in this group, such as the elastic modulus,permeability and thermal conductivity are structuraland depend on the flow of substances or energy, sothey have by-pass flow around aggregate particles.Fig 3 shows that permeability obeys power func-tions and the 1st transcendental, but with slightdeviations.3.3 Ultimate state strengthStrengthhas manyways for estimation. Themostimportant by Weibulls theory (Weilbull 1939) fromfailure theories and fracture mechanics is that, failureof the weakest links, leads to total failure. This theoryexplains why high strength aggregate have little effecton concrete strengths (Illston et al. 1979). The 168 yearold concept of Ferets law (Feret 1892) that cementconcentrations affect concrete strengths remains goodestimators. Thecontinuouscement paste, dispersed13Figure 3. Power functions &the 1st transcendental fitdensity, porosity and permeability data.with aggregate, is the weakest link in concrete to affectthe ultimate composite strength.The192datafor 28daystrengths (ACI 1997,Mehta &Aitchin 1990, Jambor 1976, Domone &Sout-sos 1995, Parrott 1995, Mangat & Molloy 1995, Egan1994, Watson & Oyeka 1981, Karihaloo et al. 2001)were analyzed for best fit on figs 5 & 6. The data pre-sented 137 years after the Feret law (Feret 1892) waspublished and in the 25 years from1976 to 2001, lacksexperimental bias (Illston et al. 1979) in the empiri-cal relations discovered. Volume concentrations basedon a unit volume of concrete, cement paste and thefree water have been related to the 28 day compres-sive strength data (ACI 1997, Mehta & Aitchin 1990,Jambor 1976, Domone & Soutsos 1995, Parrott 1995,Mangat & Molloy 1995, Egan 1994, Watson & Oyeka1981, Karihaloo et al. 2001).Figure 5shows non-unique linear relations forstrength based on concentrations in a unit volume ofconcrete. Line (1) for concrete (65%75% aggregatevolume)andcement pasteline(3)(0%aggregate)bothindicatethat concentrations, definedinaunitvolume of concrete, is not appropriate for both, butshould include additional variables for the aggregate.However, line (2) for fibre and (35%45% aggregatevolume) suggests an extension of line (1) despite theconsiderable fibre content in the concrete.Figure 6 shows linear relations for concretestrength, if concentrationisdefinedbyvolumeofeither the cement paste, or the free water matrix.Figure 4. The power mean value is the mean, median andmodeoftheconventionalmeansi.e. RMS, harmonicandarithmetic means.Figure5. Theinfluenceofactivecementinconcreteonstrength.Figure6. Theinfluenceof activecement inmatrixonconcrete strength.14The linear correlation92%, basedonconcentrationsper unit volume of the cement paste matrix was:-The linear relation of correlation 93% based on theconcentrations per unit volume of water matrix wasFigure6showslessscatterforequation10than11. Asthefreewctendstozero, equation10pre-dicts limited strengths of 825(LS) MPa, but equation11 predicts unlimited strength, which is unrealistic, soequation 10 was preferred. The most appropriate defi-nitions of the cement concentration are based on a unitvolume of cement paste matrix eqn 10 & 12.Equation 12 superposes the pozolanic activity of thelime, silica and alumina by [(LS) &(LA)] on the28 day compressive strength of concrete correlationcoefficient of 91% as:where L=% lime in cementS =% silica of in cementA=% alumina in cementvc =specific volume of cementwc =free water/ cement ratiofcm=28day strength.and Q0=concrete qualityQ1=matrix qualityQ2=particle qualityq1=matrix quantity as volume concentrationq2=particle quantity as volume concentrationUsing the power function for density and porosity,and the power functions with the by-pass flows forpermeability, the estimators cited help mix designs forconcrete and for its several qualities and strength.4 CONCLUSIONS1. Thepower functionsandtheempirical strengthestimators are deduced to design concrete mixes.2. ThepowermeansvaluesPMVnon-linearlydescribe all 3 in 1, mean, median and mode values.3. Power functions estimate concrete quality with theinterparticle model the IM.4. Power functions non-linearlyinterpolate simpletwo-phase models, which estimate on lineareffects.REFERENCESALEXANDER K, WARDLAW J , GILBERT D Aggregate-cement paste bond and the strength of concrete. Proceed-ingsofaninternationalconferenceonthestructureofconcrete. Editors AE Brooks, K Newmann, C&CA, 198,p 59ALLENAH Reinforced Concrete Design to BS 8110:E & FN Spon, 1988, p 1, Chpt 1AMERICANCONCRETEINSTITUTEManual of ConcretePractice, 1997, part 1, p 233BARNES BD Morphology of the paste-aggregate interface.PhD thesis, Vol 1, p 125, Purdue University, Lafayette,Indiana, 1976, JHRP76-13BROWNE RDThermal movements of concrete. Cur PracticeSheet 3PC/06/1, Concrete 6, 1972, 51CAMPBELL-ALLENDandTHORNE CPThe thermal con-ductivity of concrete Magazine of Concrete Research, 15,43, 1963, pp 39COUNTO UJ The effect of elastic modulus of the aggre-gate on the elastic modulus, creep and creep recovery ofconcrete. Mag of Concrete Research, 16, 1964, 129DOMONEPLand SOUTSOS MNProperties of highstrength concrete mixes containing pfa and ggbs Maga-zine of Concrete Research, 47, 173, Dec 1995, p 35567,table 1,3EGANPJ, Benefitsofsuperplasticisingadmixtures, Con-crete, May/June 1994, Vol 28, No 3, p 1821FERET RAnnales des Ponts et Chausses, Series 7, 4, 5 -164,1892.HIRSCHTJ Modulus of elasticity of concrete as affected byelastic moduli of cement paste matrix and aggregate. ProcACI, 59, 1962, 427HOBBS JW The dependence of the bulk modulus, Youngsmodulus, creep, shrinkage, and thermal expansion uponaggregate volume concentration. Materiaux et Construc-tion, 4, 1971, 107HUGHESBPand ASHJE Watergainanditseffectsonconcrete. Concrete Vol 3, 1969, p 494ILLSTONJM, DINWOODIEJM, SMITH AAConcrete,Timber and Metals, Van Nostrand Reinhold Co, 1979,p 280285JAMBOR J Influence of water-cement ratio on the structureand strength of hardened cement paste. Proc of conferenceon hydraulic cement pastes, Sheffield, 1976, p175KARIHALOO BL, ALAEE FJ, BENSON SD A new tech-nique for retrofitting damaged concrete structures, Con-crete Communication Conference 2001, p 293304KONG FK, EVANS RH Reinforced &Prestressed Concrete,Nelson, 1975, p 11, Magazine of Concrete Research, 37,130, 1985, pp 4648MANGAT PS and MOLLOY BT, Chloride binding in con-cretecontainingpfa, gbs, silicaflumeunderseawaterexposure. Magazine of Concrete Research, 47, 173, Jun1995, p 129MEHTAPKandAITCHINPCMicrostructural basis of selec-tion of materials and mix proportions for high strengthconcrete. Proceedings 2nd International Symposium onhigh strength concrete, Detroit, 1990NYAMEBKPermeabilityof normal andlightweight mortars.PARROTTLJ, Influenceof cement typesandcuringonthe drying and air permeability of cover concrete.Magazine of Concrete Research, 47, 171, Jun 1995,p 10311115POWERS TC, The physical properties of Portland cementpastes. in TheChemistryofCements, TAYLORHFW,Editor, Academic Press, Vol 1, Chp 10, pp 392 HANSENTCCreep and Stress relaxation of concrete Proc ofSwedish Cement and Concrete Res Inst, pp 31, 1960RADE L and WESTERGREN B Beta Mathematics Hand-book, 2nd edition, Chartwell-Bratt, 1990, pp 111112TROXELL GE, DAVIS HE, KELLY JW Composition andproperties of concrete, 2nd edition, McGrawHill, London1968, pp 3, 75-, 429-WATSON AJandOYEKACC, Oilpermeabilityofhard-ened cement paste and concrete. Magazine of ConcreteResearch, 33, 115, Jun 1981, p 85WEIBULL W A statistical theory of the strength of mate-rials. Proc. ofRoyalSwedishInstituteforEngineeringResearch, Stockholm, 1939, 151, 5.YEHJR Theeffectofinterfaceonthetransverseproper-tiesofcomposites. InternationalJournalofSolidsandStructures, 29, 20, 1992, p 24932502.16Excellence in Concrete Construction through Innovation Limbachiya & Kew (eds) 2009 Taylor & Francis Group, London, ISBN 978-0-415-47592-1The control of stable concrete qualityB.K. NyameConsultant, London, UKABSTRACT: It is generally accepted that too much or too little of anything is not good. It means theextremes, like the maximum or minimum quantities control stable quality. His 2nd of 3 papers deals with thecontrol of stable concrete quality. The expected values of simple two-phase models are investigated as powerseries for convergence to deduce the stable mix compositions. This is the stable quality theory. Concrete hasstable quality, if any or all the mix compositions are the basic 1/ (e-1) to a critical ln 2 aggregate volumeconcentration i.e. (1) Aggregate volume, AgVol, from 58% to 69%. (2) Water content, W, from 155 kg/m3to210 kg/m3, (3) Cement content, C, from 480 kg/m3to 650 kg/m3(4) Free w/c ratio, wc, from 0.24 to 0.44. Thesecompositions fromthe stable quality theory and IMconfigurations are compared with mix design specifications.The stable mix compositions help to draw limit surfaces for mix design in the final of 3 papers.1 INTRODUCTIONThe reduction of variability in quality, particularly theconcrete compressive strength, is an important aim inconstruction quality control (BSI 1992, ACI 1973, BSI1985). 28 daystrengthvariations (Kong&Evans 1975)bystandard deviations,of45 N/mm2signify goodcontrol, 57 N/mm2show fair control and 78 N/mm2indicatespoor control. Variabilityisinfluencedbyproperties. Permeabilityhas largest scatter anddensity,the least variability. Scatter is usuallydue toinadequateequipment and site production practice. However, thescatters, now deduced, arise from unstable design offresh mixes.In general, stability means firm, secure, robust, andnot fickle, or the tendency to maintain or return tosteady conditions, after small disturbances or loads.Mechanical stability is a tendency to resist collapse.Mathematical convergence is the tendency to a point.From the word tendency in mechanics, mathematicsand everyday use, stability also means convergence.In the 1st of 3 papers on estimation the expectedquality is transformed to the power mean value by apower series analysis, which tests for uniqueness.This 2nd of 3 papers derives the theoretic conditionsto rectify instability in the designed quality but now,power series analysis with convergence tests for theseries, so as to define the stable quality conditions.The concrete is regarded as a two-phase model ofcement paste matrix and aggregate particles. The sta-ble quality of concrete is due to the matrix binding theparticles to resist failure or collapse and the particlesrestraining deformation and the flowof fluids, heat andstrain energy. These two factors should be optimizedto determine stable quality, by the control of mix com-positions for the min/max and stable matrix or particlevolume concentrations.The simple relation for the volume concentrationsof matrix and particles in two-phase models is thatthey add up to unity or 1. This means that stabilizingthe matrix also effectively stabilizes the particles.2 POWER SERIES ANALYSISFrom the chart, 1st of 3 papers, figure 1 (read it frombase upwards)- analysis of the expected quality is bythe linear flow or linear elastic analyses (Illston et al.1979) of simple two-phase models, to sumup the vitalpower series.This convergence of the power series of the expectedquality is the stable quality theory. It is intuitively sat-isfactory because convergence is tendency to a singlepoint and a stable behaviour.3 STABLE QUALITYTHEORYThe expected quality Q0 is represented byQ0 for the expected quality has the power series of17The non-dimensional form of equation 1 isThe power series of this non-dimensional eq 3 isThis is the vital power series, but now, it is tested forconvergence5to control stable quality. It sums up thelinear elastic analysis7or response to loads.3.1 Stable Relative Quality Q21=Q2/Q1Using the root test5equation 4 converges ifsince m1 for two-phase models, the stable relativequality of aggregate to paste Q21 is in the interval3.2 The Basic StabilityIf m of equation 6 is replaced in equation 3, then thestable relative quality of the concrete to paste Q01 isThe value of Q01 converges as a binomial series5ifAggregate volume concentration qb, is basic stabilityin a concrete mix. To sum for the basic stability,3.3 The Critical StabilityMaximumrelativequalityofconcretetopasteQ01above is 2,Therefore the critically stable concrete mix has3.4 The extreme min/max Mix CompositionsAny 2 of the 3 main ingredients, cement, water andaggregatedefinethemixcompletely. Cement andwater is the matrix, and aggregates are the particles.3.5 The min/max free wcThefreshpastehasmin/maxconcentrationsofthecement or water up to ln 2.For phase 1, the water: wc/(wc +vc) ln2 For phase 2,the cement vc/(wc +vc) ln2 If specific volume of thecement is vc =0.32is the min/max range of free wc which varies withcement blending that changes its specific volume vcand the water demand of the blended cement mix.3.6 The Min/max Cement ContentThe volume concentration of matrix cement paste isFor the min/max free wc 0.14 to 0.72, if vc =0.32, themin/max cement contents areThe non-dimensional units are based on unit densityof water as in relative density concepts.3.7 The Min/max Water ContentsThe two-phase model is matrix water and particles ofthe total solids (cement +aggregate).Close-pack volume concentration of solids is 0.864This implies the min/max water contents of3.8 The Stable Mix CompositionsThe cement content is the power series ofThe water content is the power series ofDivide these stable water and cement contents toget the stable free wc range of wc =0.24 to 0.44.Table 1. Stabilizes the Water and Cement Contents.Condition Water CementPower Series Equation 18 Equation 17Converges if W12(1-q) C12(1-q)/vcBasic q =1/(e-1) W0.209 C0.653Critical q =ln 2 W0.154 C0.480Optimal range 0.154 to 0.209 0.480 to 0.653Optimal PMV 0.179 0.560184 STABLE PARTICLE STRUCTURESThe IM interpolated the upper and lower bound two-phase models to derive the power functions for theestimations of quality (figure 2 in paper 1 of 3).StableIMreturntooriginal after small distur-bances. Figure 2describes the IMequations andvectors. Figure 3 shows 2 IM fault lines that controlstrength.(A) If 1=90 then fault line FF1 is verticalConfiguration =Vertical-fault & 2 lower boundsLow compressive strengths fcmParticle Volume Concentration, q1V=11%(B) If 2=0then fault line FF2 is horizontalConfiguration =Horizontal-fault & 2 upperbounds High compressive strengths fcmParticle Volume Concentration, q2H=56%(C) If the 2 particles touch each other thenConfiguration =Close-pack & Discontinuousmatrix Low compressive strengths fcmHighly brittle fracture mechanismParticle Volume Concentration, qCP=86%Note that the 50%:50% PMV Square Root ()For basic stable particle volume concentration,qb=1(e-1), hence q2H=56%1/(e-1).The PMV of q1V=11% & qCP=86%(1 ln 2)i.e. the matrix is critical stable or 1 q =ln 2Now, the PMV ofq2H=56% & qCP=86%critical stable ln 2.Finally, the PMV ofq1V=11% & q2H=56%25%This represents the quarter particle structure, as thePMV of the strong horizontal-fault line and the weakvertical-fault line particle structures. The basic stabil-ity is definitely the strong double upper bound stableconfiguration, qb1/ (e- 1), fig 4. The critical sta-bilityisthePMVofthestrongbasicstabilityandthe economy close-pack brittle unstable configuration,qcln 2, fig 4.Thisvalidatesstablequalitytheoryandparticlestructures are retained after small load disturbances.The combinations of the 3 particle configurationsare shown on fig 4 and also summarized in table 2.Table 2. The equivalence to the PMVof 3 particlestructures.q2H=56%q1V=11% qb1/(e 1) qCP=86%q1V=11% identical quarters q =(1 ln 2)q2H=56% quarters identical qcln 2qb1/(e 1)qCP=86% q =(1 ln 2) qcln 2 identical5 DISCUSSIONIt is often considered that too little or too muchofanythingisnottoogood. Thisviewappliestothe design of concrete mixes. The extreme min/maxFigure 1. The Min/Max and Stable Mix Compositions.Figure 2. The IM Configuration.Figure 3. The IM Particle Tangents.19Figure 4. The IM Stable Configurations.and stable mix compositions, on the staircase diagramsof figure 1, indicate the action limits when the mixcompositions will definitely cause mix problems.For instance, if the aggregate volume exceeds thecritical ln 2 or 69%, then mix problems of cohesion andsegregation are likely because of insufficient cementpaste matrix to bind the aggregate particles.Similarly, if the water content is below the mini-mum of 135 km3, as on figure 1, then the mix is likelyto be unworkable, because of the insufficient water,cement paste and any admixtures to lubricate the par-ticles. Such logical If . Then deductions have led tocomputer algorithms to detect the designed concretemix problems in the final of these 3 papers.The min/max cement contents in the old CP110,BS8110 and BS5328 of 250 kg/m3to 650 kg/m3allagree with 295 to 665 kg/m3by stable quality theory.Water is virtually free. There was the old tendencyto increase it on sites to get workable mixes to place.Water is important for quality control as it affects thefinal concrete porosity, permeability and durability.Teychenne et al. reported a survey of water contentsused for ready mix as 170 kg/m3to 230 kg/m3. Thesevalues agree within 20 kg/m3or 18% of the figure 1stable water contents of 155 kg/m3to 210 kg/m3.The free wc is more important thanthe water contentfor engineering properties of concrete. For completehydration, minimum free wc is 0.25. This is withinthe min/max range of 0.14 to 0.72. However, as theunhydratedcementgrainsenhancequality, bytheirrestraints, a lower limit than free wc 0.14 will be6 CONCLUSIONSThe stable quality theory, as convergence of the vitalpowerseriesfortheexpectedqualityoftwo-phaseconcrete derives the stable mix compositions.The stable quality theory is validated by an analysisof the particle tangents of the IM. The stable concretemix compositions are:(1)Aggregate volume concentrations from the basic1/(e-1) to critical ln 2, which is 58% to 69%.(2) Water Contents from 155 kg/m3to 210 kg/m3(3) Cement Contents from 480 kg/m3to 650 kg/m3(4) free wc from 0.24 to 0.44The min/max concrete mix compositions are:(1)Aggregate volume concentrations from 0 to 86%(2) Water Contents from 135 kg/m3to 305 kg/m3(3) Cement Contents from 295 kg/m3to 665 kg/m3(4) free wc from 0.14 to 0.72Concrete quality increases with the number of sta-ble and min/max mix compositions to be used for themix design in the final of these 3 papers.REFERENCESACI Committee, 704, Enchiridion E704-4 Concrete Quality,Detroit, 1973, 26 pp.BSI BS7850 Total Quality Management Part 1: 1992 Guideto quality improvement methods.BSI CP110, 1985, Part 1Table50, p103, 20 mmmaxaggregate sect 6.7.6.1.ILLSTONJM, DINWOODIEJM, SMITH AAConcrete,TimberandMetals, VanNostrandReinholdCo, 1979,p 280284.KONG FK and EVANS RH Reinforced & Prestressed Con-crete, p 42, table 2.8-1 Thomas Nelson & Sons Ltd, 1975.RADE L and WESTERGREN B Beta Mathematics Hand-book, 2nd edition, Chartwell-Bratt, 1990, pp 111112.TEYCHENNEDC, FRANKLINRE, ENTROYHC, HOBBSDW, NICHOLSJC, Designofnormalconcretemixes.BRE Report, Dept of Environment.20Excellence in Concrete Construction through Innovation Limbachiya & Kew (eds) 2009 Taylor & Francis Group, London, ISBN 978-0-415-47592-1The design of concrete mixes on limit surfacesB.K. NyameConsultant, London, UKABSTRACT: Graphicallimitsurfacesshowhowparametricfactorscontrolthedesignofsystems. Limitsurfaces, therefore, facilitate visual control by point estimations in systems design. This final of 3 papers dealswith the design of concrete mixes on limit surfaces. The estimation and control of quality of two-phase modelsare used to generate limit surfaces for mix design. The limit surfaces are drawn on axes of free wc and aggregatevolume concentration (Wc, AgVol). There are intersecting networks of water, W, and cement contents, C, sothat all mix variables are at particular points on the limit surface. Using stable mix compositions, quality mapsare classified for the strengths of concrete. A graphical hypothesis to detect and pre-determine concrete mixproblems is advanced.1 INTRODUCTIONConcretetechnologistshaveabundant accumulatedmix designs that proved successful for constructionprojects. As computer memory can now be increasedeasily to store substantial concrete mix data, the ready-mixedconcreteindustrynowtendsforsimplemixselections rather than the complex mix designs.The aims of concrete mix design (Kong & Evans1975) are to deduce the quantities of cement, aggre-gate, water, admixtures and additives that satisfy therequiredstrength, workability, durabilityandecon-omy. Similarly, theaimsofstructuraldesignaretodeduce a structure that is safe to satisfy its purposeof use and to be economical. Safety, from limit statephilosophy (Kong & Evans 1975, Allen 1988), is thatthe structure, with very low probability risks, will notviolate limit states of collapse, deflections, cracking,vibrations or fire resistance.The type of structure must be chosen and structuralmembers designed to be safe, durable and economic.Structural selections exist, rather like mix selections.The progress is to design mixes from their responseand resistance to loads, by eqn 4 1st & 2nd papers,just as economic membersections, by the structuraldesigns and to select from stored mix design data.Since Abrams laws (Abrams 1981) of 1918, con-crete mixes have been described in quite a few ways,by cement, water and aggregate contents as shown byequation 1, with the parameters Z and n, deduced intable 1.Table 1. Equation 1 parameters (Z, n) values for estimatingthe aggregate volume concentrations.Design Mixcodes specifications Z nAny Code ( C, A, W ) full specification.BS8110 (wc, C) C +1CP110 (C, A) use mix specs.CP114 (wc, 1:a:b) by vol. D2/(a +b) 1CP114 (wc, 1:a:b)by weight Dc/(a +b) 1Road Notes (wc, Ac) D2/Ac1Euro codes min C producer decisionIn the 3 papers, aggregate volume concentrations,q, are calculated from equations 2.whereD2=density of aggregate (kg/m3)Dc=density of cement (kg/m3)C=Cement Content (kg/m3)W=Water Content (kg/m3)A=Aggregate Content (kg/m3)wc =free water/cement ratio1: a: b =1: fines: coarse ratio for aggregateAc=aggregate/cement ratio2 RESPONSE & RESISTANCE TO LOADSThe response to loads is by the power series analysisof two-phase models (eqn 4 in 1st & 2nd papers). By21Figure 1. The interparticle model is tessellatedfromasurface of concrete.Figure 2. The volume composition of two phase concrete.linear elastic analysis (Illston et al. 1979), it showssteady state upper and lower bound responses toloads by deformation or flow/no flow by permeability,porosity or density.Instructural design, loadsimposedonall struc-tural elements are estimated by linear elastic or plasticanalyses with beams as horizontal lines, columns asvertical and struts as inclined lines. For mix design, theinterparticle model the IM as on figure 1 is the tes-sellated structural element which models the concretemix just as beams, columns and the struts.The IM non-linearly interpolates upper and lowerbounds to represent the mix at the engineering, phys-ical andchemical levels, bytwo-phasemodels, asshownonfig2, withparticleandmatrixvolumeconcentration relations in rows 2 & 4 of figure 2.The(steel +concrete) model hasviablealterna-tives. The (aggregate +cement paste) and(lime +silica)or (lime +alumina) models are nowviable here so thate.g. CEMENT 4933 has 49% lime and 33% silica.2.1 Mix composition and particle structureThe particle volume concentration q is calculated bythe scale factoring principle, that if a volume is q, thenq13is the linear scale factor, and q23is the area scalefactor, so that as shown on figure 1:Generally, for any particles in the matrix, since both and vary, it follows thatWhere is ultrafine particle size factor in the IM. is interparticle spacing factor in the IM. is interparticle centres angle in the IM.Specifically, for uniformly mixed similar particlesin the matrix, if =60 and =1 thenAssume that the IM for uniform mixes has =60then cos sin =3/4.The function for the composition and structure bythe volume concentration of cement particles in thecement paste matrix and ultrafine size factor is2.2 Mix composition and concrete qualityQualityhas 2steady states: linear andnon-linearthat are estimated by power functions and the exclu-sive power functions, which take account of by-passflowsaroundparticles. Thereistheultimatestatecompressive strength, fcm, to estimate empirically.For the mix design, equation 10, (1st of 3 papers) isre-structured toequation 12, (1st of 3 papers) is re-structured toThe free wc for any cement with L% lime, S% sil-ica and A% alumina is calculated in mix design fromequations 7 & 8 for 28 day required strengths fcm.22Table 2. Min/max and Stable Mix Compositions.Min Stable range MaxComposition ACTWARNINGACTWater kg/m3135 155 to 210 305Cement kg/m3290 480 to 650 665Aggregate %vol 0% 58% to 69% 86%free wc 0.14 0.24 to 0.44 0.72ACT for ACTION prevents low unpredictable qualityWARNINGprevents uncontrollable, but secures stablequality.2.3 Concrete quality and particle structureThis is the design of the Particle Structure the IM.Eqs 6 &7 for 28 day strength femare re-structured toand re-structured to include the alumina A% as3 LIMIT SURFACES FOR MIX DESIGNFigures 4, 5 and 6 are limit surfaces for concretes.Alimit surface is used to designby point estimation.It complies with theAction andWarning Limits of mixcompositions obtained by power series analysis orlinear elastic analysis summarized on table 2.It has 2 of 4 mix variables (q, wc, C, W), as x-y axesfor the (aggregate, free wc, cement, water) as shownon figure 3. The 3 shown have (wc, q) as x-y axeswith intersecting network contours of (C, W) for theCement and Water Contents of the designed mix.3.1 Mix descriptionsFigure 4 describes mixes using engineers jargon.Workability Water Contents (w-contours)It is a Normal mixor Dry if W160 kg/m3andWet if W200 kg/m3Economy Cement Contents (c-contours)It is a Medium mix or Lean if C 350 kg/m3andRich if C 450 kg/m3Response to Loads -Aggregate Contents (y-axis)It is an Optimum stable mixor Basic if q 1/(e-1) and Critical stable if q ln 2Durability- free wc (x-axis).It is Durable if wc0.46 or not Durable if wc0.46.Figure 3. Limit Surface Axes and the Power Functions.Figure 4. Limit surface for mix descriptions.If the need is for a Dry, Durable, Normal, Rich Mixa likely point estimate is Mix (0.31, 67%). i.e. OPCC60, 50 mm slump, W=160, C=515 kg/m3.3.2 Mix strengthsFigure 5 is a 28 day strength limit surface. It showsthe strengths at network junctions for the mix waterand cement contents. Its boundaries are the min/maxmix compositions, indicate theACTIONLIMITSto prevent unpredictably low strengths. The internalboundaries indicate the WARNING LIMITS for mixcompositions to prevent uncontrollable strengths but23Figure 5. Limit surface for 28 days strengths of concrete.secure stable quality as on table 2. Alimit surface, likea fish, shows high & low strength and high & low costregions as cement and water contents vary. There is avery low strength region at the fish tail and very highstrengths at the fish head. Mix designs lying outsidethe limit surface or not inside the fish shape will satisfyresearch & development interests.3.3 Detection of mix problemsFig 6 is the limit surface that detects the extent andtype of mix problems. The 4 problems occur near themin/max mix composition boundary at the 4 corners.All 4 mix problems are:-prevented by those mix point estimates within theinternal boundaries of stable mix composition.Segregation, Compaction, Sedimentation, Crack-ingoccurs as themixpositionvectors, Rcis,satisfy the conditions laid down on table 3 below.The central problem-free mix is (wc =0.46,q =65%). A mix positioned in the 10% to 15% tar-get circles violates the min/max mix compositions sothe extents of mix problems are major to severe. Themixes in the 10%target circle have stable compositionsso the extents of problems, if any, are minor.Relative to problem-free (0.45, 65%), mix (wc, q)has polar co-ordinates Rcis to detect the problemtype, by and its extent, by R as defined in table 3.where n =1, and if wc 0.45, then n =0.On figure 6, mix (wc =0.35,q =53%) shown by the(+) has severe cracking problems severe cracking?Adjust to (wc =0.35, q =65%) causes majorcrack-ing. It is economic, but its resistance toloads is reducedFigure 6. Limit surface with target circles detects concretemix problems.Table 3. The 4 Concrete Mix Problems.Mix problem Angle Extent R valueSegregation 0 to 90None 5%Compaction 90 to180Minor 5% 10%Sedimentation 0 to 90Major 10% 15%Cracking 90 to 180Severe 15%with the higher aggregate volume from 53% to 65%.Using mix position vector, R cis, the limit surface,figure 6, detects mix problems after each mix design.4 POWER FUNCTIONS FOR MIX DESIGNThe mix designer decides the production control typeas Research, Ready-Mixed, Good, Fair or Poor in orderto assign safety factors of 1 to 1.5, for the publishedstrength equations used for programming.Thefreewciscalculatedfromequations7&8for the required strength fcm. The water content Wis calculated by power functions and two-phase IMthat assume the concrete cone slumps by self-weight.24Admixtures are added to control the Water, Cementor Aggregate contents, as well as the response to elasticloads, brittleness and chemical reliability to indicatedurability as 1 (free wc/lime). If wc > lime, then thenegatives are chemically unreliable mixes.The aggregate is proportioned by power functionsand two-phase IM which use stochastic fractions thatfit theBS882aggregategradingcurves(Kong&Evans 1979).The range of loads for no cracks is predictedby power functions of stress-strain derived from thetwo-phase IM for a decreased elastic matrix, but anincreased cracks/inelastic inclusions at higher loads.The cements are blended on a risk diagramdeducedby linear algebra which warns of unstable cements asstrengthening pozolanic reactions occur in two-phaseIM cements type (L, S) or (L, A). The risk diagram isdrawn on x-y axes of Lime vs. (Silica +Alumina)Limit surfaceswithC-W, C-wc, asexternal x-yaxesandinternalintersectingcontoursoftheothertwo mix variables on fig 3, are drawn for other qualityand costs. Designs must specify strength, age, slump,aggregate type with density and blend the cements.Curing temperature relations will be included later.5 CONCLUSIONSExcept for strength and aggregate, two similar mixesconclude the mix design with power functions and thetwo-phase IM.MIX COMPOSITIONDesigned mix to Research Control.C 50/150 mm/ 28 day/Cement 4933, vc =0.34Lightweight Concrete Batch Vol =1 m3CEMENT 4933 565 R-> 475 kg/m3free WATER 293 R-> 21020 mm ssd Lytag 65010 mm ssd Lytag 3705 mm ssd Sand 205FEBFLOW SP3 for 28% wR-> 4.3 litres/m3CEMENT 4933 OPC csf pfa ggbs metka +?kg/m3335 50 50 50 0.0 0.03RELATIVE DENSITIES 3Cement CoarseFine 33Fresh MixFresh Paste34933 Agg Agg331.91 1.8532.951.60 2.603MIX QUALITY CONTROL2.1 fcu =50 MPa fcm=55 to 60 MPaDesigned mix with 3 stable ingredientsMix Adjustments (kg/m3)WATER=85, CEMENT=90, AGGREGATE=+225Reduced free Wc from 0.52 to 0.442.2 Composition: [Wc, AgVol] =[0.44, 62%]Collapse SLUMP of 150 mm. Very high. Self-levelling2.3 Major sedimentation 0.10 cis 11CEMENT 4933 reduces thermal effects by 25%FEBFLOW SP3 enhances workability.2.4 NORMAL, MixChemical Reliability is 11 % and Brittlenessis 3.3Linear elastic range [ 0 MPa to 15 MPa]uncracked2.5 USE for Plain Concrete, for R.C, for P.C.Major Sedimentation, 0.10 cis 11MIX COMPOSITIONDesigned mix to Research Control.C100/150 mm/ 28 day/Cement 4933, vc =0.34Normalweight Concrete Batch Vol =1 m3CEMENT 4933 970 R-> 820 kg/m3free WATER 363 R-> 26010 mm ssd Gravel 8155 mm ssd Sand 390FEBFLOW SP3 for 28 % wR-> 7.4 litres/m3CEMENT 4933 OPC csf pfa ggbs metka +?kg/m3575 80 80 80 0.0 0.03RELATIVE DENSITIES3Cement Coarse Fine 33Fresh Mix Fresh Paste 34933 Agg Agg 332.28 2.0132.95 2.60 2.603KEY: =unstable, R->=reductionMIX QUALITY CONTROL2.1 fcu =100 MPa fcm=110 to 115 MPaMix Adjustments (kg/m3)WATER=105, CEMENT=150,AGGREGATE=+405Reduced free Wc from 0.38 to 0.322.2 Composition: [Wc, AgVol] =[0.32, 46%]Collapse SLUMP of 150 mm. Very high. Self-levelling2.3 Severe cracking 0.19 cis 263CEMENT 4933 reduces thermal effects by 25%FEBFLOW SP3 enhances workability2.4 WET, Rich MixChemical Reliability is 36 % and Brittlenessis 4.4Linear elastic range [ 0 MPa to 45 MPa]uncrackedWARNING CEMENT is over 600 kg/m32.5 USE for Plain Concrete, for R.C, for P.C.Severe Cracking, 0.19 cis 26325REFERENCESABRAMSDADesign of Concrete Mixtures, StructuralMaterials, Res Lab. Lewis, Institute Bulletin, 1, Chicago1918ALLENAH Reinforced Concrete Design to BS 8110: E & FN Spon, 1988, p 1, Chpt 1.ILLSTONJM, DINWOODIEJM, SMITH AAConcrete,Timber & Metals, Van Nostrand, 1979, pp. 280285.KONG FK, EVANS RH Reinforced & Prestressed Concrete,Nelson, 1975, p11 & 19.26Excellence in Concrete Construction through Innovation Limbachiya & Kew (eds) 2009 Taylor & Francis Group, London, ISBN 978-0-415-47592-1Improvement in the compressive strength of cement mortar by theuse of a microorganism Bacillus megateriumV. Achal, R. Siddique, M.S. Reddy &A. MukherjeeThapar University, Patiala (Punjab), IndiaABSTRACT: This study reports the results of compressive strength of cement mortars incorporating microor-ganism. The effect of addition of microorganism, Bacillus megaterium, on the compressive strength of cementmortar cube has been studied. Ordinary Portland cement (OPC) was used to prepare mortar with different cellconcentration of microorganismin the mixing water. Asignificant increase in the compressive strength of cementmortar cube at different ages (3, 7, 14 and 28 days) was achieved with the addition of B. megaterium. Increasesin compressive strength were observed maximumin case of 105cells/ml of microorganism. This improvement incompressive strength is due to deposition on the microorganismcell surfaces and within the pores of cementsandmatrix.1 INTRODUCTIONPortland cement concrete has clearly emerged as thematerial of choice for the construction in the worldtoday. Thisismainlyduetolowcost of materialsand construction for concrete structure as well as lowcost of maintenance. Therefore, much advancementof ConcreteTechnology have occurred dependingon(i)the speed ofconstruction(ii)the strength ofconcrete (iii) the durability of concrete and (iv) theenvironmental friendliness of industrial material like,fly ash, blast furnace slag, silica fume, metakaolin etc.(Mehta 1999).Compressive strength is one the important param-eters in determining the strength of building materialsand structures. Compressive strength is relatively easyto measure, and it commonly relates to some otherproperties, suchastensilestrengthandabsorptionof themortar. Thecompressivestrengthof mortardepends largelyuponthecement content andthewater-cementratio. Themeancompressivestrengthrequiredataspecifiedage, usually28days, deter-mines the nominal water-cement ratio of the mix. Thewater-cement ratio determines the porosity of hard-enedcement pasteat anystageofhydration. Thusthe water-cement ratio affects the volume of voids inconcrete thereby influencing the strength of concrete.Microbial inducedcarbonate mineralizationhasbeen proposed as a novel and eco-friendly strat-egy for the protection and remediation of stone andmortar (Adolphe et al. 1990). Microbial mineral pre-cipitation (biodeposition) involves various microbes,pathwaysandenvironments. Ureolyticbacteriaarefoundsuitablefor carbonate(calcite) precipitation.Thesebacteriaareabletoinfluencetheprecipita-tionofcalciumcarbonatebytheproductionofanenzyme, urease(ureaamidohydrolase, EC3.5.1.5).This enzyme catalyzes the hydrolysis of urea to CO2and ammonia, resulting in an increase of the pH andcarbonate concentration in the bacterial environment(Stocks-Fischer et al. 1999). There are few Bacillusspecies which are considered to produce high amountof urease which helps in calcite precipitation. Bacillusmegaterium is a rod-shaped, Gram-positive species ofbacteria. B. megaterium is generally considered a soilmicrobe (Vary 1994) and has been shown to precipitatecarbonate minerals (Cacchio et al. 1993).Ghosh et al. (2005) reported a significant improve-ment in compressive strength of cement mortar usingShewanella species.The present work deals with the compressivestrength of cement mortars, which is one of themost important parameters influencing the strength ofbuilding materials and structures and finally its per-formance. An attempt also has been made to observetheeffectofdifferentconcentrationofmicroorgan-ism, Bacillus megaterium on the compressive strengthof cement mortars.2 MATERIALS AND METHODS2.1 Mortars and concrete specimensOrdinaryPortlandcement(OPC)conformingtoIS12269 (Bureau of Indian Standard, New Delhi, 1987)27Table 1. Chemical compositions of ordinary Portlandcement (OPC) used in this study.Chemical Constituent