Field performance of bacteria-based repair system: Pilot study in a parking garage

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Case

Study

Field

performance

of

bacteria-based

repair

system:

Pilot

study

in

a

parking

garage

§

V. Wiktor

*

,

H.M.

Jonkers

DelftUniversityofTechnology,Delft,TheNetherlands

1. Introduction

Concreteisthemostusedconstructionmaterialworldwide.Indeed,evenifexposedtoanumberofdegradationprocesses suchascarbonationorchlorideingress,concretestructurescanreachaservicelifeofmorethan50years(Emmonsand Sordyl,2006).Howeverthepresenceofcracks,andthesubsequentingressofaggressivecorrodingsubstances,isamajor limitationforthedurability.Thisleadstotheprematurecorrosionofthereinforcementandearlyfailureofthestructure.Asa result,costlymeasuresformaintenanceandrepairareundertaken.Nowadaysawiderangeofrepairproducts,suchasfor instanceepoxy-basedﬁllersorsilane-basedwaterrepellent,isavailableforconcrete.However,theshorttermefﬁciencyand negativeimpactontheenvironmentareanissuefortherepairindustry.

Biodeposition,amethodbywhichcalciumcarbonate(CaCO3)precipitationisinducedbybacteria,hasbeenproposedas

aninteresting alternativeapproachtoprotectbuildingmaterials.Variouspathwaysareinvolvedin MicrobialInduced Precipitation(MIP)process.Amongthem,enzymatichydrolysisofureainacalciumrichenvironmentisthemostcommonly

A R T I C L E I N F O

Articlehistory:

Availableonline9January2015

Keywords: Concrete Repair Bacteria-basedsystem Crack A B S T R A C T

Thispaperpresentsthefieldperformanceinaparkinggarageoftherecentlydeveloped bacteria-basedrepairsystemforconcrete.Thisliquid-basedrepairsystemaimsatthe sealingofcracksanddecreaseoftheporosityduetotheproductionofacalcium-based biomineral.The systemcombinesadvantagesof botha traditionalrepairsystemfor concrete (fast reacting and short term efficiency), and bio-based methods (more sustainable,slowprocess,andlong-termefficiency).

Thebacteria-basedrepairsystemhasbeensprayedontothesurfaceofcracksandon concretepavement.Thecrack-sealingefﬁciencyandimprovementoffrostsaltscaling wereassessedbywaterpermeabilityandfreeze/thawresistancetestsrespectively.The resultswereverypromisingasonlycracksthathadnotbeentreatedwiththe bacteria-basedrepairsystemwerestillheavilyleaking.Inaddition,thefreeze/thawresistanceof concretethatwastreatedwiththebio-basedrepairsystemwashigherthantheuntreated concrete.

ß2015TheAuthors.PublishedbyElsevierLtd.ThisisanopenaccessarticleundertheCC BY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

§

ThispaperwaspresentedatConcreteSolutions,the5thInternationalConferenceonConcreteRepair.Itcanbefoundintheconferenceproceedings:

MichaelGrantham,P.A.MuhammedBasheer,BryanMagee,MariosSoutsos,ConcreteSolutions2014,CRCPress,2014.

* Correspondingauthor.

E-mailaddress:v.a.c.wiktor@tudelft.nl(V.Wiktor).

ContentslistsavailableatScienceDirect

Case

Studies

in

Construction

Materials

j our na lh ome p a ge : w ww . e l se v i e r. co m/ l oc a te / c scm

http://dx.doi.org/10.1016/j.cscm.2014.12.004

2214-5095/ß2015TheAuthors.PublishedbyElsevierLtd.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/

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usedsystem(Dhamietal.,2012).Successfullyappliedasasurfacetreatmentinpracticetolimestonemonuments,ithasbeen consideredonlyonalaboratoryscaleforcementitiousmaterialandcrackrepair.

Also,besidescostissues,MIPusingureolyticbacteriamightgenerateotherproblems,suchasenvironmentalnitrogen loadingduetotheproductionofammoniaduringthehydrolysisofureaornegativeeffecttothematerialitselfduechemical reactionswithammoniumsalt(Dhamietal.,2012).Inaddition,thetimerequiredforasubstantialamountofbacterially inducedcalciumcarbonatemayholdbacktheacceptanceofMIPasanefﬁcientrepairtechniquebythebuildingindustry. Bacteriallymediatedcalciteprecipitationthankstometabolicconversionofcalciumlactateinsteadofureahydrolysishas beensuccessfullyappliedinself-healingconcrete(WiktorandJonkers,2010).Theauthorsimplementedthisconceptforthe developmentofbio-basedrepairsystemforarealconcretestructure.Thenoveltyofsuchasystemistocombineadvantages ofbothatraditionalrepairsystemforconcreteandbio-basedmethods(WiktorandJonkers,2011,2012a).

Inthisway,asilicate-basedcompound,whichhasacompositionsimilartoconcrete,isassociatedwithMIPwithout involvingaureahydrolysispathway.Instead,themetabolicconversionoforganicsaltsthroughbacterialrespirationisused forMIP.

Thebio-basedrepairsystemaspresentedinthispaperisaliquid-basedsystemwhichtransportsthebio-basedagentinto concrete. Thispaper investigates and discusses the ﬁeld performance of thebacteria-based system developedin the laboratory.

2. Materialsandmethods

2.1. Bacteria-basedrepairsystem

Therepairsystemconsistsofconcretecompatiblebacteria(WiktorandJonkers,2012b)andfeedwhichproduce calcite-basedmineralsdecreasingconcreteporosity.Thissystemiscomposedoftwosolutions:

(i)Solution A – sodium-silicate (alkaline buffer), sodium-gluconate (carbon source for bacteria growth), alkaliphilic bacteria.

(ii)SolutionB–calcium-nitrate(nitratesourcefordenitriﬁcationwhenO2isdepletedandcalciumforCaCO3precipitation),

alkaliphilicbacteria.

Thedenitriﬁcationisthebiologicalreductionofnitrogenousoxidestogaseousproductsduringanaerobic(nooxygen) bacterialgrowth.Thismeansthatunderthemetabolicconversionofcalciumnitrate,N2andCaCO3areproduced.

Thesilicate-basedcompound,sodiumsilicate,ensuresanalkalinepHinthesystemandtheformationofagelinsidethe crack. Although not very strong, this gel allows a rapid sealing of thecrack (within a few hours) and an optimum environmentforbacteriatoprecipitatecalciumcarbonate.Bythetimethegelbecomestooweak,asubstantialamountof CaCO3hasbeenprecipitatedtosealthecrack.

2.2. Testlocation:parkinggarage

Thetestlocationwasa2storeyundergroundparkinggaragewithacapacityof300parkingplaces.

Theconcretedeckwassufferingfromcrackingwhichresultedinsigniﬁcantleakageofthestructure(Fig.1a).Also,the concretepavementoneachsideoftheaccessrampwasdamagedduetofreeze/thaw(Fig.1b).

2.3. Applicationofthebacteria-basedrepairsystem

Part of the concrete pavement (area of 2m0.5m) and three cracks (1–3mm wide)of the concrete deck were impregnatedwiththebacteria-basedrepairsystem.SolutionAandsolutionBwereeachpouredinasprayer,andmanually appliedatthesurfaceoftheconcreteinlayersuntilsaturationoftheconcretetreatedarea.

2.4. Evaluationoftheefﬁciencyoftherepairsystem

Twomonthsaftertheapplicationofthebacteria-basedrepairsystem,6coresweredrilled(Fig.2aandb)fromtwo differentlocationsontheconcretepavement:3fromthetreatedareaand3fromanuntreatedpartonthesamesideofthe accessrampascontrolspecimens.Theresistanceofthetreatedand untreatedconcretetofreeze/thaw conditionsand deicingsaltwasthenevaluatedinlaboratory.

Thecrack-sealingefﬁciencyofthebacteria-basedrepairsystemwasassessedbymeansofawaterpermeabilitytest performedonsiteon3treated-and3untreatedcracks(Fig.2c).

2.4.1. Resistancetofreeze/thawanddeicingsalt

The6concretecoresweretestedaccordingtheNPR-CEN/TS1239-9(Testinghardenedconcrete–Part9:Freeze/thaw– scaling)andNEN-EN13877-2(Concretepavement–Part2:Functionalrequirementsforconcretepavements).Thetestwas

V.Wiktor,H.M.Jonkers/CaseStudiesinConstructionMaterials2(2015)11–17

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Fig.1.Testlocationfortheapplicationofthebacteria-basedrepairsystem.(a)Cracksontheconcretedeck,(b)pavementonthesideoftheaccessramp.

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performedindependentlybyCuglaB.V.(Breda,TheNetherlands).Ifthespecimensaredamagedinsuchawaythatthe masslossis>1kg/m2_,_the_test_is_stopped._Indeed,_a_mass_loss_>1_kg/m2_means_that_the_concrete_has_a_poor_resistance_to

freeze/thawandﬁtsinthelowestcategory(FT0)accordingtoNEN-EN13877-2.

2.4.2. Waterpermeabilitytest

Thegoalofthistestwastohavearapidandpracticalevaluationofthecracksealingonsite.Forthispurpose,rectangular woodenframes(1m0.5m)wereplacedontopoftheconcretedeckinsuchawaythatthecrackwentthroughthefull lengthoftherectangle(Fig.2c).Thewoodenframeswerepositionedontopof3crackstreatedwiththebacteria-basedrepair systemand3non-treatedcracksforcontrol.

Thewoodenframesweresealedwithsilicongluepriortopouringin5Loftapwater.Asthecrackwentthroughthe wholethicknessofthedeck,thesealingefﬁciencywasassessedbymonitoringvisually,fromtheothersideofthedeck, howmuchwaterwasdrippingthroughthecrack(Fig.3).

3. Resultsanddiscussion

3.1. Resistancetofreeze/thawanddeicingsalt

TheresultsofthelaboratorytestingforscalingresistancewithdeicingsaltaregiveninFigs.4and5.

The test was stopped after only 7 cycles as specimens treated with the bacteria-based repair system and the controlones,both exhibiteda massloss>1kg/m2_._The_concrete_tested_had _a_very_poor_resistance_to_freeze/thaw _with

de-icingsalt.

Fig.4.Scalingafter7freeze/thawcycles.

Fig.3.Schematicrepresentationofthewaterpermeabilitytestperformed.

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However, a closerlook toFigs.4 and5showsthatthespecimens treatedwith thebacteria-basedrepairsystem hada signiﬁcantly lowermassloss (scaling) comparedto thecontrol,1.90.3kg/m2_and_3.6

1.3kg/m2 _on_average

respectively.

Thoughtreatedanduntreatedconcretespecimensfallsintothelowestcategory(FT0)forscalingresistance,theresults howeversuggestthatthetreatmentwiththebacteria-basedsystemtendedtoimprovetheresistanceoftheconcreteto freeze/thaw.

Of course,otherparametersshouldalsobetakenintoaccountwhile interpretingtheseresultssuchasthetypeof cement, mixcomposition orenvironmentalfactors.However, it shouldbenoticedthatverylittle isknown aboutthe history ofthisconcrete.Toourknowledge,theparkinggaragewasbuiltin2005.Theconcretehasbeenexposedover theyearstosigniﬁcantcarbonationandfreeze/thawepisodes.

ConsideringthattheparkinggarageislocatedintheNetherlandsandonacoastalarea,mostprobablyblastfurnaceslag cementwasused.

Moreover,concreteswithhighslagcontentareknowntohavealowercarbonationresistancecomparedtoOrdinary PortlandCement(OPC)whichmakesitmorevulnerabletofrostsaltscaling(Copuroglu,2006).Indeed,carbonationofslag cementresultsnotonlyincalciteformationasforOPC,butleadsalsotoaragoniteandvateriteformation.Thecombined attack offrost and chlorideresultsinthedissolution ofaragonite andvaterite and thusin microstructurecoarsening (Richardson,2006).

Therefore,basedontheavailableinformationandpresentresults,theapplicationofthebacteria-basedrepairsystem appearsasapromisingapproachtoimprovetheresistanceofconcretetofreeze/thawwithde-icingsalt.Itislikelythatthe decreaseinporosityanddensiﬁcationoftheporesystemisduetobiomineralprecipitation.However,furtherinvestigation onthemicrostructureoftheconcreteshouldbeperformedinordertoconﬁrmthisstatement.

3.2. Waterpermeabilitytest

Thecrack-sealingefﬁciencywasvisuallyassessedonsite.Theresultswereveryencouragingasthe3controlcrackswere heavilyleaking(Fig.6a–c)alongthefulltestedlengthwhile2crackstreatedwiththebacteria-basedrepairsystemexhibited onlyafewlocalizeddrippingspots(Fig.6dande).Thethirdtreatedcrackwasnotleakingatall.

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4. Conclusion

Thispaperpresentsthefieldperformanceoftherecentlydevelopedbacteria-basedrepairsystemforconcrete.The systemcombinesadvantagesofbothatraditionalrepairsystemforconcrete(fastreactingandshorttermefficiency),and bio-basedmethods(moresustainable,slowprocess,andlong-termefficiency).

Thebacteria-basedrepairsystemhasbeensprayedonthesurfaceofcracksandonaconcreteslabinanundergroundcar park.Thecrack-sealingefﬁciencyandimprovementoffrostsaltscalingwereassessedbywaterpermeabilityandfreeze/ thawresistance testsrespectively.Theresultswereverypromising asonlycracksthathad notbeentreatedwiththe bacteria-basedrepairsystemwerestillheavilyleaking.Inaddition,thefreeze/thawresistanceofconcretethathadbeen treatedwiththebio-basedrepairsystemwassigniﬁcantlyhigherthantheuntreatedconcrete.

Theseresultsareveryencouragingfortheapplicationinpracticeofthebacteria-basedrepairsystem.Thesystemis currentlybeingoptimizedinordertoraiseitsperformancestocompletesealingofthecracksandtodevelopbetterfrost saltscalingresistance.Anextstepisalsotoassessthelongtermperformanceofthebacteria-basedrepairsystem.

Acknowledgments

TheauthorswouldliketothankCuglaB.V.(Breda,TheNetherlands)fortesting theresistanceoftheconcretecores tofreeze/thaw.

FinancialsupportfromAgentschapNL(IOPGrantSHM012020)forthisworkisgratefullyacknowledged. References

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Fig.6.Observationofwaterleakingthroughthecracksduringwaterpermeabilitytest–(a–c)controlnontreatedcracks,(dande)crackstreatedwiththe

bacteria-basedrepairsystem.

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