Icj Serviclife Article 105

8/2/2019 Icj Serviclife Article 105

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These columns of 1CJ affer.an opportunity to the engineeringfytern ity fo express thei r views'o'n ni ciri, ni"irecaces rndesign, constructlon and managem*rt iiig'rltr;wed in theindustry.::":::i::?::fi::2, *:th, our readers, you may send in yourinputs in abaut 1S0A words via e_mait io iJitofticiontine.com

Some issues reloled lo service tife of (,ncrele slruclures

avoid confusion in this article, fif","iri"a conceptsdefinitions of certain terminologi;;; presentedcomplexities invot?eJ il service lifeare illustrated and inaaeqracy in currentrzice life.modelling is described. ft"r"",i air"r."io,qurablltty performance specification of concrete incontext is presented.related concepts for concrete

rmodynamically onJy natu rally existing materialsDe stable over a Iong period of time as the-y would be

B. Bhofiochoriee

specification of concrete relies mostly on 2gstrength and mould-ability tnua is quantifiedrrr--e empirical indicatorJsu"fr r, "tr*p V"f"etc. The last mentioned indicators are determinedrespective lngineering tests. iie tong rermhowever is hindled ofiy through prescriptivesay, by specifying max w / critio, rnirri*trrncontent and minimum recommended grade:^"-.T1"r:.. .I d eaIy, durability "f,uf i U"' qu antif ie drerms of time during which the concrete elementto perform its -clesignat"d f;;;;;on withoutsigns of any unacieptable deterioration in aexpqsure condition. Defining life of structure isrmbiguous and confusi&r persists, as unlikebeings, clear-cut demarcation event of death, thatitself from the life, does not exist for structures.

in a state of minimum or nearly minimumpotential. Manmade materials those rr" prbdrr""d at tire expense ofenergy/ would tend to dissipate this energy and ""a"rg"hemical changes in reaciion. Concreie is producedwith a considerable expense of ur"igv and thusunder conducive conditions would ""d"'.;;il#l;hanges. Quite ofteru-during its service condition, the::ncrete gets exposed to the aggressive environmentthat causes deterioration. Deterilrati,on-is the processof becoming-impaired in quatiry urd ;;i";. A chemicalreaction leading to chang"i hulrirrg ro effect on concretegerforlance may not b=e consid&ed as deterioration.L.regractatton process in concrete may take place dueto sulphate attack, frost actiory action of acids, alkali_aggregate reaction and in steel reinforced concrete,the- degradation may also take plu"" ;;;urbonationand chlonde ingress leading to

"'"rr.rf"'r, of rebar. Asaresult g{ degradatioru detJrioration of concrete takesplace with time. Degradati,en by definition;;;;;;; v*lrnqecrease rn performance with time. With refe[nce to ]e.^:.or:r:t" structure, performance can be understood asrne Denavrour related to the use of the structure. Hence,the performance can be relared t. t;;;;g capacity,stability, and safety in.use, tightness against ingress,hygro-thermat propertier, "iriui upp;?;;." etc. Forconcrete, these behaviors are aynami" and changeswith time. Therefore performanc" i, u ftr*iion of timeand rs related to durability and degradation of concrete.Durability is a property expressing"the ability to maintain


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the required performance. Therefore, degradationis the opposite of performance and often serves asanother way to treat performance problem. Hence itis desired that concrete should not deteriorate in theenvisaged service environment at a rapid rate and mustcontinue to perform satisfactorily for a desired servicelife. Service life can be understood as the period afterinception of the structure, during which all the essentialproperties of the structure meet or exceed the minimumacceptable valuel'2. The long-term performance ofconcrete is related to its durability related properties.The concrete as a material shall therefore be so designed,that the structure where it is to be used should possesthe designed service life with minimum possiblemaintenance requirements. The economic objective ofthe material design can be minimization of life cyclecost that includes the maintenance cost as well. It maybe noted however that although manmade materialstend to deteriorate, the tendency does not necessarilymean deterioration would actually take place as; thesame is also governed by the kinetics or the rate of theprocess. For example; significant deterioration wouldrequire infinitely long time for an infinitesimally smalldeterioration rate. \Atrhile for faster rate of deterioration,the degradation of the structure would lead to rapidperformance failure.The answer to the questiory how long a structure isgoing to last or what is the life, is not straight forwardas end of life can be defined in several ways dependingupon context, for example; physical life, functional life,economic life and service life etc. Again there can beintended design life that is the life envisaged in the,design stage. It is the life during which structure isexpected or intended to be in servicb. Intended designlife is used in the context of design load calculation andit also represent the planninghorizon at the design stage.Physical life is the period of actual survival of structure.Most of the time, the physical life can be prolongeddesirably, with adequate maintenance, hence infinite fora1l practical purposes. Functional life relates to change offunction of the structure, e.g., acinema theatre convertedin to a shopping complex with some alteration in space.Occupancy class would change hence imposed loadand importance factor etc may change accordingly.Economic life relates to increased cost of its maintenancerenderingthe structure economically unworthy of futurecontinuance vis-d-vis analtemative option of demolitionand possible reconstruction. Physical life of a structurecan be very long before it collapses if properly designedand constructed, compared to economic life andfunctional life. The period during which the structurewould remaininservice is the minimum of physical and

economic life. Service life can be appropriately relatedto serviceability limit through the concept of limit statedesign. Design procedure of RCC structure is carriedout by sizing individual member elements and theirreinforcement contents. Similarly, pres-stressed concretemembers are designed by sizing the member and theircorresponding level of prestress. Serviceability limitsalso referrers to individual member, hence service lifeof RCC/PSC shall refer to elements. The time whendeterioration leadf $ldegradation of an element to anunacceptable servicedbility limit, is the service life ofthat element. This time can be considered from the timeof inception of the structural element. Overloading ofstructure causes damages over the short period loading,e.g., loading due to extreme earthquake and cyclone cancause almost instantaneous damage. As per prevailingdesign philosophy, structure is not expected to collapseeven in case of probable extreme events mentionedabovg therefore the limit state of collapse is consideredin the corresponding structural designs. Further suchevent is expected to occur not more than once duringintended design life. Design against deterioration on theother hand is not related to collapse as the process ofdeterioration is slow, can be detected early in most casesand the impending danger of collapse can be avoided byappropriate and timelyrepair of element. Servicelifethusis related to repair cycle of the element and maintenanceof the structure. In some cases the whole structure mayrequire rehabilitation. Service life thereforqcan also beconsidered from the time of last repair. To increase thereliability against loading, redundancy in terms of excesscapacity is always ensured in structure, so, even if onemember becomes incapable of carrying the load othermembers share it by redistribution. Thus the capacity toredistribute the load provide additional cushion againstfailure to collapse due to deterioration. Service lite ofconcrete elements therefore is related to maintenancecost rather than collapses; as deterioration rarelyleads to sudden collapse of the structure. Maintentrnceof concrete structures is a necessity; economic andappropriate maintenance policies and repair strategiesfor concrete structures can be formulated through servicelife2-s. The exposure environment, concrete material andquality etc., control the rate of degradation and hence theservice life of concrete structural member. Actual time ofattainment of serviceability timit relates to cover depthand varies from member element to member elemenfas;neither the exposure condition of all elements are samenor their resistance against deterioration is identical. Theuncertainties of exposureenvironment and material shallbe accounted for in service life design of structure.

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WService life assessmentThe service-ability limit with respect to a specificdeterioration needs to be defined for estimation ofservice life. For example with respect to corrosion ofrebar, appearance of first visible crack is often definedas the service-ability limit. Consequently, the servicelife is defined as the time from inception to the time ofappearance of first visible crack. Similarly, service-abilitylimit and hence time for reaching the limit i.e., servicelife in the context of all other deterioration mechanismcan be defined. Service life can be estimated whenrate of deterioration is known. The time required forattainment of service-ability limit can be assessed fromthe knowledge of service-ability limit and deteriorationrate.Deterioration rates again depend on reaction kinetics andavailable concentrations of reactants in the concrete. Atleast one of the reactants must be present in the concreteand at least another reactant must be entering in to theconcrete by ingress. Most of the deterioration processesin concrete take place in presence of moisture and dueto ingress of aggressive chemical agents those causedeterioration. The aggressive agent again ingress in toconcrete usually in solution phases with water or are fluidthemselves. Concrete inherently is a capillary porousmaterial by nature. Thus its permeability and diffusionproperties are important from its durability performancepoint of view. Modelling of deterioration rates wouldinvolve considerations of ingress mechanisms such aspermeation, diffusion, capillary suction, reaction kineticsetc. First and foremost in this context is modelling formoisture profile. Quite often reaction occurs only in aconducive moisture condition e.g., carbonation occursmost rapidly at relative humidity ranging from 55-65%,and, do not occur either in fully saturated or completelydry concrete. Similarly rebar corrosion can occur onlyin a partially saturated concrete. Therefore modellingwetting and drying of concrete is most important inthe context of service-Iife assessment of concrete. Incase of exposed concrete wind driven rain is drivingforce for moisture ingress and modelling for moistureprofile in concrete in main three tropical climatic zonesof India would be quite relevant in this context. Secondaspect of service life models would be to model ingressof aggressive agent causing deterioration. The processinvolved may be concentration driven diffusion. Forexample, in case of carbonation, atmospheric CO2 maydiffuse in to concrete under concentration gradient.Ionic diffusion of chloride ion due to concentrationgradient can also be used to model (free) water solublechloride in saturated concrete. However, it is importantto recognize physical and chemical binding of chloride

in concrete; hence Fick's diffusion equation needsappropriate modification. Modelling of corrosionprocess however, is extremely complex involvingdiffusion of oxygen, Fe** ion,-moisture etc in additionto mass and chaige balances.6 Thus mass balance andstoichiometry of reacting species is the third aspect inmodelling deterioration process of concrete. The lastaspect is the estimation of stresses and resulting crackpropagation due to formation of expansive productwherever applicable. Thus service life assessment ofconcrete requires modelling of complex physical andchemical process involving several compounds. Atthe moment, modelling of most of the deteriorationprocesses is not well understood and hence most ofthe available deterioration models are inaccurate. Theinadequacy of deterioration models are discussedfurther in the next section.A second aspect of complexity in service life assessmentis the interaction of loading with deteriorationenvironment, while static or quasi-static imposedload may not significantly affect the deterioration,fatigue loads with stress reversals on the other handmay enhance the deterioration process through crackinitiation.'-" Shrinkage, thermal and other intrinsiccracks similarly *oia also enhance the progress ofdeterioration.Athird aspectinthis contextis the difficul$ of calibrationand validation of deterioration models against real lifebehaviour. The manifestation of deterioration is visibleonly aftervery long exposures and any validated modelsare not available. Determination of coefficient of themodel and material properties poses similar problemdue to lack of understanding of the phenomena. Forexample determination of chloride diffusion coefficientfrom a migration test under.electric field is meaningless,as, driving forces under natural concentration drivendiffusion and that under imposed electric field aredifferent. In the former Chloride and cation may movetogether in the same direction where as in the later theywould invariably move along opposite directions.Gurrent state of degradation modelsAn elaborate review on degradation phenomena withreference to durability of concrete is presented byGlasser et.el.7 In their article the authori first look into general transport mechanisms followed by chlorideingress and corrosion, carbonatiorU decalcification andsulfate attack. From their review, authors conclude thatresults of accelerated test proposed so far cannot beextrapolated to real life and progress towards analyticalmodelling is uneven. The authors further expect a

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ffitransition of durability research from empirical state toquantitative basis in future. In the next sub-section twodeterioration phenomena namely; chloride ingress andcarbonation are considered to illustrate the current stateof deterioration models. These two phenomena are notdeteriorations of concrete per se, however depassivationof rebar resulting from these processes initiate corrosionleading to serviceability failure of RCC elements. Therebar corrosion being the major durability concernin RCC structures these phenomena had attractedmaximum attention in practice.GarbonationThe carbonation model essentially relate depth ofpenetration of carbonation front with time. Mostcommonly used and simplest form of semi-empiricaldegradation model for carbonation is d = k" t"' ;where d is the depth of penetration of carbonationfront, t is the time and k" is a coefficient depend uponconcrete material as well as environment and can bedetermined empirically.l Service life of concrete withrespect to carbonation is defined as the time when depthof penetration of carbonation front becomes equals tocover depth of rebar. Thus time t at which this depth dbecomes same as cover depth can be easily estimatedfrom above formula. More elaborate models are basedon diffusion equation and can be written as:7tu_P_*(*_,,o.$rco,1) _

r, =o (1)where $ is the porosity, w is the volumetric watercontent, [CO2] is the carbon dioxide'concentratior; D"is the diffusion coefficient and f" is a sink term dealingwith reaction of carbon dioxide with alkaline materialsin concrete. Two issues were highlighted by the authorsnamely; phenolphthalein indicator based measurementtends to under estimate the carbonation depth. Secondlymost of the models ignore the pH drop by overlookingOH- concentration. Actually pH drop is responsible fordepassivation. However, sgqle experimental evidencestends to justify d = k" t1/2 reiationship althoughrealistic models dealing with depassivation are non-existance.z8Chloride lngressChloride ingress again is not a deterioration per se, butin RCC, chloride concentration above a threshold levelcan initiate rebar corrosion. Service life with respect tochloride ingress is considered as the time required forchloride concentration at the rebar depth to reach thethreshold level. The mechanisms involved in chloride

ingress can be ionic transport and capillary suctionin unsaturated concrete. The driving force for ionictransport may be concentration gradient, chemicalactivity, potential difference due to ionic concentrationetc.'q", = D.,(9*C",!P!**c",{)*c",q- (z)"ldx '' dx RT"d*)In equation 2, g.t" is flux, "D.1" is chloride diffusioncoefficient, "w" stands for moisture, "C"1" is watersoluble chloride concentr atiott, " a" is activity an d "Y" ispotential due to interaction of various ionic species. q* issolution flux and can be obtained from extended Darcy'slaw for unsaturated porous materials.l0 Consideringmass balance:^.6C, _6q"r - -^ (3)dl dr

y is a chloride binding term, and combining equations 2and 3 one would get the equation for chloride ingressin unsaturated concrete. All the material coefficientsfor use in equation 2 andS are not available. Thereforeuse of these equations at the current state is precluded.Quite often people use the following equation neglectingelectrica,l coupling, chemical activity ant chloridebinding.'Y:'",Qoo* (4)

D"r(app) stands for apparent chloride diffusioncoefficient. Equation 4 is only valid for saturated concreteand obviously it does not represent the real situation inmy manner. Yet this equation is often used in service lifeprediction of real structure with following set of specificinitial and boundary conditions for which closed formsolution is available in heat transfer.llFor a inJinitely thick wall; for t< 0; C"1(x,t)=Co; and t2 0;C",(0,t)= C; C"1(a,t)=Cs; the solution is:rr

where,2G

(s)

,u l rr. TNDTAN coNcRErE J.,RNALJANUAR'2oI2

*f(y): ll "-' au


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The boundary conditions mentioned above is rarelyencountered in real life situations and use of the abovlmodel for estimation of cover depth for a given servicelife of concrete element can provide onlf intellectualsatisfaction of using a model and wouid be totallyunreliable. The cover depth proposed on the basis ofexperience and consensus of many experts is far morereliable. For example, using this modeifor determiningsaJe cover {epth against chloride ingress for 125 yearlfor a tunnel lining at 20m below ground level, whereacid soluble chloride concentration in soil was knowr;is totally erroneous. The chloride flux deals with freewater soluble chloride not acid soluble ones, furtherthe concrete is unsaturated, hence neglecting solutionflux is incorrect. It may be noted thit solution fluxcontributes much more than the diffusion flux. Chlorideconcentration C, at the surface is not same as that in thesoil and would depend upon surface current. Temporalconstancy of C, over 125 years is also questionable. Sofar as the inappropriateness of use of the equation 5 toa specific case. In general following are the additionalproblems associated with modelling of chloride ingressin general, more so when modelled through "qrulior,,and 5.First of all, there is complete uncertainty regardingthreshold chloride that is the backbone-of c-hloridlingress modelling. The threshold chloride concentrationdepend upon cement"type, steel type etc, hence no singlevalue is available. 12'lt Secondiy, tnere is no reliableway of measurement of diffusion coefficient as it is notpossible to isolate the phenomena involved, besides,diffusion coefficient cannot be measured reliably overa short period of time.Degra-dation models for other deterioration processesare still in the development stage and as such service lifeassessment concept is yet to mature sufficiently before itbecomes possible for its use in real life practical designsituation.Service life design philosophyReliability based design concepts are well acceptedprinciple and one can describe the failure event in terms oftwo variables i.e., load variable S and resistance variableR. The failure than can be defined as: ffailure)={R0. In,the stochastic approach the requirementcorresponding to performance based principle can beexpressed as: P{failure},r=p{(R-S)0 respJctively forperformance and service life principles respectiveiy.The design concepts discussed above have been appliedin many fields of mechanical and structural deslgn,however their applicability in case of service life designof concrete element is limited by limitations of the ba;icdegradation models mentioned earlier. This is becausethe degradation models are the basic tool for eltimationof either R or t1etc.Residual service LifeAtmany instances duringthe service period of structure,one may be interested to estimate the remaining orresidual service life of concrete elements as weil aJforthe structure as a whole. Residual service life assessmentrequires obtaining first hand information regarding thecurrent condition of the structure through i thoroughcondition survey. Such condition survey-involves no-n-destructive and semi-destructive tests to obtain thestrength and other properties of the concrete. Thoroughvisual survey and document surveys are essential lncondition survey for getting a cleai picture about thetype of distresses existing in the struiture, if any. Thistype of investigation of existing condition is intended todetermine the state of the health of the structure, establisha diagnosis and to arrive at a prognosis. Through theprognosis one can estimate the expected residual "-"*i""ife using.some of the degradation models mentionedearlier.'"'" For an existing structure condition of

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elements can be expressed in terms of condition indexthrough inspection and survey and condition index ofall elements can be combined to obtain overall conditionindex for the structure as a whole.16-17 Su"h conditionindex indicate the repair priority. Through prognosischange of condition index with time can be estimated.However, prognosis is limited by limitations of servicelife assessment, although this may be easier than servicelife assessment of new structure as one can make morerealistic assumption regarding exposure environment.Material properties and state of degradation can beknown through condition assessment. When conditionassessment is done atregular interval through a plannedinspection scheme, performance can be related to timeeither empirically or through model or using bothconcepts together. One may take advantage of Markov'stheory to piedict the future state in suchiituations.l'l4When expected service life of structure as wholeis desired, the safety against load also needs to beconsidered. For the available strength the safe windpressure that can be withstood can be estimated andiorresponding design wind speed, basic wind speedetc ani the return period of the later can be determinedusing appropriate distribution.ls The expected servicefife *ould have a bearing on the above retum period.Similarly, for the given materials and structuralsystem determined and identified through appropriatecondition assessment, the degree of tolerable groundmotion (acceleratioo velocity and displacement etc)and the resulting tolerable forces, moments and overalltolerable hazards for the structure can be estimated, andhence corresponding size of the earthquake in termsintensity and magnitude can also be dstimated. Throughprobabilistic seismic hazardanalysis the period of timeduring which this hazard would not like$ to occur morethan once canbe estimated, this period will also limit theexpected residual service life of the structure".Closing remarks and discussionsDiscussions presented makes it clear that adoption ofservice life design in practice for practical construction ispremature at this stage because of (i) conceptual limitationsin the degradation models, lack of understanding of thephenomena involved, (ii) lack of real time validationor calibration against performance in actual structuresand lastly, (iii) difficulty in determination of materialcoefficients and other parameters in the model. Further,assessment of service life through accelerated testalthough had been attempted in past needs further,"r"ur"i prior to their adoption in practice.z2o

The present exposure conditions given in IS 456:20fi)needs a relook. Exposure classification can be moreelaborate and India specific. For example the temperature,the relative humidity and rainfall pattem govern themoisture conditions and reaction rates in exposedstructures. Such conditions would depend upon climaticzottes, namely, hot-dry climate as in ]odhpur/ warmhumid climate as in Kolkata and composite monsoonclimate of Delhi. A concrete exposed in warm humidclimate is likely to have a conducive moist conditionfor deterioration for a longer period of time with itslonger duration of rainy season annually compared tothat in hot-dry desert climate where rainy season is forshort duration." G"ogruphical location and geologicalconditions again are the other considerations thoseshall go in to exposure classification. Exposure incoastal areas would be different than locations awayfrom cost. There again, the surface facing sea may bemore conducive for deteriorationcompared to oppositeface. Analysis of current deterioration pattern may notalways provide reliable answer to above requirements.Quite often concrete structures in north India had beenconstructed withchloride ri{{en ground water resultingin early corrosion distress.zz Thus analysis of currentdistress would indicate most of the northern Indiabeing rebar corrosion Prone due to chloride, there byleading to erroneous inferences. Loading conditionssuch as static or fatigue loading also shall be taken into consideration. tThe present prescriptive practice recommended in IS456:2b00 also needs a relook. While, options of cement/cementitious combinations and other ingredients ofconcrete, limits of water cementitious ratio etc., may besuggested, inclusion of some measureable performanceparameter in specification of concrete may provide areliable way of ensuring adequate durability of concreteat present . A number of qualitative tests such as waterabsorption, Initial Surface Absorption Test (ISAT),Figg's air permeability, etc are available for relativeevaluation of permeation quality of concrete. Limitsof such permeation prop"tty may be proposed. 23'24Determination of properties involved in models wouldrequire consideration of micro structure and theirrelationship with permeation and diffusion properties.Attempts have been made to relate these properties tomicro parameters-suchas pore size parameters and mixfactors as well. b30 The irn-portance of the structure mayalso be considered while proposing the prescriptiverecommendations on material options, cover depth etc.,as intended maintenance free service life may vary fromstructure to structure.

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Lastly, with sustainability concern the specificationof concrete may include specification with regardto sustainability also. This is because sustainabilityencompasses durability as well. A sustainability indexis presented recently that incorporates implicationsof iepair cycles in the index itself together with other'slconcelns.References1. Sarja A. and Vesikari, 8' Durabiti$ design of conuete structures, E & FNSpon.1996.2. Bhaftacharjee, B., Durability and service life of concrete stflrctures (Key noteaddress) Proc. Of National mnference on Repair and Rehabilitation of Concrcte

Structuies,Noidn,lndia, Eits. Rajitt GoelandA.K.Shama,May 6-7,2ll\'IndianConcrete Institute . PP 3241.3. Campbell-alten, D. and Roper, H .: Concrete Structures: Mnterials, Maintenanceand Repair. Longmm Scientific and Technical. 1991'4. Mays, G., Durability of Concrete Structure- inaestigation, repair, protection' E& FN Spon.1992.5. Bhattacharjee, 8., Blended Cement In The Context Of Seroice LiJe OfConcrete Structur e. Proceeding of seminar on- Eco-Fimdly Bbnfud Cemmts FotEmnomical And Durable Ctsncietc ln The Nats Millenniam, Feb 2000 Mumbai'pp.7+82.2000.

5. Bazant, Z.P, Physical model for steel corrosion in sea shuctures-theory'loumal of structural diaision ASCE, lttne 1979. Vol' 705, pp' 7137'7153'7. Glasser F.P., Marchand, t. and SAMSON, E., Durability of concrete -degradation phenomena involving detrimental chemic a7 rcactions' Cunentand Concrete Research, 2C[l8. Y o1. 38, pp.225-246.8. Schiessl, P. Con'osion Of Steel ln Concrete, Aapmanand HaIl,1988'9. Newm, J. and Choo, Ban Sang. Advanced concrete technology-concreteproperties. Elsevier 2003

10. Nagesh.M,andBhattacharjee.B., Modellingofchloridediffusioninconcrete*id"t"t.rrinutior, of diffuiion coeffic ients. ACI material joumalsMarclvApril1998. Vol. 95, No.2. PP. 113-120.

11. ]akob, M. and Hawkins, G .A., Elemmts of heat transfer, Wiley IntemationalEdition.1957.12. Pradhan, B. and Bhattacharjee, B', Role of steel and cement type onchlorideinduced conosion in concrete. ACI m ateilals ioumal.Nov-Dec 2007' Vol' 104,No.6. pp. 612-619.13. Pradharu B. and Bhattacharjee, B., Half- cell potential as an indicator o{

c1rloride induced rebar corroiion initiation in RC. loumal of Materitls in Ciz.tilEngineering, ASCE. October 2009. VoL21, No.:10, pp' 543-552'

14. Bhattacharjee, 8., Evaluation Of Health Of Concrete Structures And, Prognosis Of Disttess. Proceding of National seminnr on- Engineereil BuildingI Mairials and theit Performance,Jan2O03 Mumbai.Indim National Academyof Engineering. pp. 85-97.15. Gaharwar, S.S. and Bhattacharjee. 8., Residual Life Assessment of Structures'

Proceeding of National s*ninat on- Engineeted Building Materials and theirfeformaia lan 2003 Mumbai. lndian National Academy of Engineering'pp.98-121.16. Mitra, G., Jain, K.K. and Bhattacharjee, B., Condition assessment of corrosiondistressed reinforced concrete buildings rsing htzzy logic' lournal of

Performance for Constructed Facilities, ASCE. Nov-Dec 2010' Vo24, No':6'pp.:562-570.17. Jairu K.K. and Bhattacha4ee, B., Application of fuzzy concepts to the-

visual assessment of deteriorating reinforced concrele stnrctwes' loumal ofConstruction Engineeing and Marugemmt, ASCE. March 2012' Available online http:/ /ascelibrary.org/coo/ resource/3/ jcemxx18. Liu,H.,Wind Engineering,Prenhce Hall Inc. 1991.19. Kramer, S.L., Geotechnical Earthquake Engineeing. Prentice Hall Inc'1996'20. Ahmad, S., Bhattachariee, B. and WasorL R., Experimental service lifeprediction of rebar corroded r/c structure. ACI materials journal' July-Aug1997. Vol.94 No.4. PP.311-316.

21. Gaharwa, S.S. and Bhattacharje. B. Moisture Diffusion and Seroice Lifeprediction of concrete Structures. Proceeding of lnternational SymposiumOn lnnotsatioe woild of Concrete-98'. 1998. Indian Concrete Institute. PPL.99-7.1.06..

22. Bhattachajee, B., RCC structues distressed due to rebar corrosion-somecase studies. Cioil EngineeingToilny (loumal of ASCE- lndia Section). Dec-Jan2005, Vol.3. pp.3-12

23. Bhattachajee, B., Testing of concrete in structue -duability related tests'Non-destructioe testing of concrete structures. Proceedings of the INDO-USWorkshop OnNon-Desiruitit:eTesting, Eds. S.K.Kaushik, S.P.Shnhand A'KMaiLAugust 1.997, Indian Concrete Institute . pp 729- 1'40.

24. Bungey, J.H. and Millard, S.G., Testing of Concrete in Structures, Thirdedition, Chapman and Hall, 199625. Kuma, R. and Bhattacharjee, B. Assesment of Permeation quality of concretetluough mercury porosimetry. Cern ent and Concrete Research,Febrtxy 2004'vol.uQ), pp.3\-328.26. Kumar, R. and Bhattacharjee, B. Porosity, pore sire distribution and in situstrength of concrete. Cemmt and Concrete Research,Jaruary 2003' Vol' 33(1),pp.155-164.Z7.Prudhan, B., Nagesh, M. and Bhattacharlee, B. Prediction of hydraulicdiffusivity from pore size distribution of concrete. Cement and C-onclete

Research, kptember 2005. Vol' 35(9), pp.1724-7733.28. Patil. S.G. snd Bhattacharjee, B., Size and volume relationship of porefor coretruction maleials. lournal of Mateials in Ciuil Engineering, ASCE'lune 2008. Vol.2O No.:5, pp.410-418.29. Bhattacharjee, B. and Krishnamoorthy, S., Permeable porosity and thermal

conductiviiy of corskuction materials. /ou mal ofMateritls in Ciail Engineering,ASCE. July-August 20O1. Vol. 16, No.:4'pp.322-330.30. Kondraivendhan. B and Bhattacharjee, B', Effect of age, w f c ratio on sizeand dispersion of pores in OPC paste" ACI materials ioumal' March-April

2010. Vol. 107, No.2. pP. 147-154.31. Bhattacharjee, B. Sustainability Performance Index fot Concrete. lnternationalConcrete S'ustainability Conference, August 9-11,2011, Boston, MA, USA'http:/ /www.nrmcaevents.org

Dr. Bishwajit Bhattachariee is Professor at theDepartment of Civil Engineering, Indian Instituteof Technotogy Delhi-India. After obfrining B.Tech(Hons.) degree from IIT Kharagpur, he worked. forM/s Gammon India Limited for a short period oftwo years. Subsequently he obtained M.Tech. andPhD d'egrees from IIT Delhi' His areas of active researchinteres[ includes corrosion of rebar in concrete, high-performance concrete, microstructure modelling of concrete, chlorideingress, service life prediction and life cycle costing of concretestiuctures besides condition evaluation and health monitoringof structures. Minor area of research and teaching interests areBuilding Physics and Building Engineering, Construction Technologyand Construction management. He ls Fellow of Indian Association ofStructural Engineers. He is Life member of 1) Indian Concrete Institute,2) Indian Society for construction Materials and Structure. 3) IndianSociety for Technical Education. 4) American Society of Civil EngineersIndia Section (ASCE-IS) 5) Maharastra ChapterofAmerican ConcreteInstitute (ACIj etc. He has authored more than 90, well cited, journaland conference papers in leading International journals such asACI materials Journal, lournal of Materials in Civil Engineering,ASCE; Cement and Concrete research and The Indian ConcreteJournals and others, besides authoring state of the art report, lecturenotes and articles in workshop proceeding etc. He also had a visiting

position in EPFL Switzerland and involved in collaborative researchprograms with German Universities and University of Dundee UK. HehaJhandled more than 200 consultancy and research projects andis actively involved in various national committees. Dr. Bhattacharjeehas supervised 125 M. Tech. and 11 Ph.D. thesis till date and currentlygulding 7 M.Tech. thesis work besides 10 ongoing Ph.D. researchprojec[s. He is also member of the editorial board of Magazine ofConcrete Research and International Journal of 3Rs. IJANUARY2ol2 THEINDIAN CoNGRETEJOUnNAT- | zs

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Icj Serviclife Article 105