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Ocean Structures Construction, Materials, and Operations Srinivasan Chandrasekaran, Arvind Kumar Jain

Materials for Ocean Structures

Publication details https://www.routledgehandbooks.com/doi/10.1201/9781315366692-4 Srinivasan Chandrasekaran, Arvind Kumar Jain Published online on: 29 Dec 2016

How to cite :- Srinivasan Chandrasekaran, Arvind Kumar Jain. 29 Dec 2016, Materials for Ocean Structures from: Ocean Structures, Construction, Materials, and Operations CRC Press Accessed on: 27 Sep 2021 https://www.routledgehandbooks.com/doi/10.1201/9781315366692-4

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Though it is agreed upon that the the upon that it Though for is agreed offshore applications,particular. material in of suitability the rank shall characteristic is acomplex no single as material task environment for marine Selection the of materials structures. of marine construction polyvinyl have polythene, and also wide the applications chloride acrylic in their types, resin thermoplastic and Plastics of thermosetting structures. tion of ocean Moreover,- segments of construc in specific also fiber-reinforced used are plastics brass. and steel, copper, nonferrous: aluminum, mild and ferrous be can metals Further, structures. of ocean for construction the materials one primary ofas the However, environment. marine the never in possess they can concrete ignored be advantages due salient to times recent sideof the composites in increasing is on the (2)and namely,addition, nonmetals, use In andglass. fiberglass, concrete, wood, such (1) groups as different are so on. There and tection, nonferrous and ferrous pro corrosion rehabilitation, repair, construction, of for purposes: used avariety are They structures. of ocean construction the in used are of materials types Different 3.1 also presented. discussed. Recentadvancements withrespecttorepairofconcretestructuresare are of structural materials that are useful for construction, repair, and rehabilitation vention ofthestructure forrepairandrehabilitation.Inthischapter, different types not because of its limited accessibility for repair but also due to its undesirable inter structures isguaranteed.Repairofoceanamulticomplex phenomenon Material forconstructionshouldbecarefullychosensothattheservicelifeofocean can causeseriousdegradation ofmaterialandstrengththestructuralmembers. the designsuccessfully. Moreover, marineenvironment iscorrosive innature,which of actualconditionsstructuresduringtheirworking lifewould behelpfultodo save alarge sumofmaterialcostsandeaseouttheinstallationprocedures.Feedback above factors resultinheavy penaltyontheexisting weight.Otherwise,thiscould mated infew designcases.Fatigue andcorrosionarestilldebatablesubjects. All the severe thaninitiallypredicted values. Wave andcurrentloadshave beenunderesti- working life. Unfortunately, weatherconditionsand marine growth becomemore to besowelldesignedandbuilt sothatnoseriousfailure develops duringhisorher ­certification ofoffshore structures. Alternatively, onecouldrelyonthestructures ­installation, commissioning,andoperability. Legislation callsforperiodic The structuralformofoceanstructuresisuniqueandexpensive bydesign, INTRODUCTION 3 Structures Materials for Ocean 129 - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 FIGURE 3.1 suitable material aparticular make to properties codes; advanced international all by addressed commonly are that of materials properties of fundamental standing under aclear offshore in demands platforms failure on the based properties material of requirements special the acontinuous feedback loop ofFurther, understanding more complicated. task this make properties structural having similar materials for offshore of categorizations applications, materials various selectto appropriate helps offshore an of materials basic knowledge of structural characteristics 130 survivability (1) in case of any accidents (collision) and (2) in case of excessive loads (1) ­survivability biofouling effects. Hence,thesematerialsmusthave propertiesthatensure otherforcesduetochemical,fatigue, stressand corrosioneffects, and materials on few types ofenvironmental loads.Inaddition,themarineenvironment alsoexerts ­example, wind, waves, ocean currents coupled with thermal gradient, and ice are a guidethesuitabilityofmaterialsformarineenvironment.­combinations For important. conditions loading become and environmental particular under suitability their assess to properties suitable; advanced them make their later that properties fundamental their understanding after more preciselybe addressed of accordingly. can classification them process tions categorizes materials This of that areavailable inthemarket; suitabilityofthesematerialstooffshore applica of shows It materials also for types offshore different collage of structures. materials Figure 3.1 shows research. the of material domain unique it an making properties, material of required those for offshore learning advanced applications necessitates Chipboar Mahoga Offshore structuresareexposed todifferent environmental loads, andtheir Cotto Pl yw OA Wo Wr Pine ny oo n d K ought iro ol St MDF

d ainless st Silk Materials for marine applications. for marine Materials Man-made Natura Natura Dy n ee es Va Fa l Wo Te rnis bric l l od xtil Mild ste reads Pain h Fi s es nishes t Fe rr el ous MA Re Metals TERI cy En cling Nonferrous Sust vir AL onmen S ainable Rene t Copp wa ble Nonto ermopla er ermosetting Pl Aluminu as To xic tics xic Br as stic m s P P Ocean Structures Ocean oly olyester re for vin P sin Melamine oly P Ac maldeh yl chloride oly thene r ylic urethane ­ engineer engineer yde - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 cific propertiestosustaintheseloadsandtheircombinations. ocean systems. As materials are subjected to different types of loads, they require spe- vehicles, andsoon,aretheexamplessubmarine ofsuchnewly developed platforms, characteristics. Offshore drillingandproductionplatforms,surface buoys, instrument for surface ships; now newly developed ocean systems require materials with special ricanes, scouring,andtyphoons.Earlier, themajorapplicationofmaterialswas only complexity, structuresarealsoexposed toearthquakes, hur their to Adding pressure. during hurricanes; note also thathydrostatic withstand haveto structures underwater important decision. istics andperformanceunder different environmental conditionstomake suchan desired crosssectionandsize, itisvitaltounderstandtheirfundamentalcharacter priate factor ofsafety. Apart fromthe costofmaterialsandtheiravailability inthe allowance, eitherbyincreasingthethicknessofmembersor by usinganappro- various oceanconditions. This istaken careindesigntermsof material for ­controlled laboratoryconditions. This warrants changeinallowable stresslevels in theactualenvironment differs markedly fromthoseof any testsconducted in the literaturebasedondatataken fromstandardspecimens.Structureloading become equallyimportant.Notethatthephysical characteristicsarepresentedin nature ofenvironmental loads,fatigue performanceand fractureresistancealso is alsoimportantasstructuresareunder multiaxis loading.Duetothedynamic consideration, whereas Young’s modulusandductilityfollow it.Poisson’s ratio material (physical) characteristicsareimportant. Yield strengthbecomesthefirst stand hazards(includingthoseariseduringoperations). Duringselection,afew catastrophic failure. Besidesmeeting thedesignrequirements,they shouldwith- (3) fabrication facilities, and(4)maintenancecost.Chosenmaterialsshouldavoid accountedfor:(1)physical andchemicalpropertiesofmaterials,(2)cost,normally decision. engineering important an becomes structures for ocean choice materials the of appropriate conditions, complexities that high influence theperformanceofmaterialsundergiven environmental has environment marine the As literature. the in seen been also has embankments geotextiles for of and coastal slopebranes stabilization interest tooffshore engineeringprofessionals.Intherecenttimes,useofgeomem- areasrenewable afew toxic nontoxic are property, and important and nature of sustainability, recycling characteristics, issues their to related environmental from strength, Apart important. for applicationbecomes aspecific very materials of materials. Under the given wide choice of materials thatare available, selection of the it­recommendations as may limit is only desirable but not mandatory to theuseofmaterialsforsurface ships,materialselectionbasedonsuch respect of Bureau Shipping with by American made the set of recommendations the to Referring environment. for marine the selection of the materials process in agencies Variousguide of specifications/codes/regulatory offshore structures. type the exists aclose and There selection relationship the of between materials 3.2 Materials for Ocean Structures for Ocean Materials During the selection of materials for ocean structures,thefollowing factors are SELECTION OFMATERIALS ­selection 131 - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 property thatenables amaterialtoresistdeformation underload.Ultimate strengthof reversal of(natureof)forcesatthesamepointisknown asfatigue. Strengthisthe bent backandforth),therod cannot bebroken. Tendency ofamaterial tofail under times inthesameplace;however, ifthesameforceisappliedinasteadymotion (not example, athinsteelrodcanbebroken byhandbendingitbackandforthseveral is considerablybelow itsmaximum strengthintension,compression,orshear. For stressed repeatedly. Usually, itfails atacriticalsection­ sary tostatethetypeofloading.Fatigue isinducedinmembers(­ only 290MPa; therefore,whendealingwithmaximumstrength,itisalways neces- strength of386MPa intensionandcompressionbut ­ 14 MPa incompressionbut only3 MPa intension.Carbon steelhasa­ show marked differences; forexample, curedconcretehas a­ rials areequallystrongincompression,tension,andshear. However, many ­ — Underwhichtypeofloadshouldoneclassifythemaximum strength?Somemate- forces canseparatematerialsbyslidingthemapart. when external forcesareappliedalongparallellinesinoppositedirections.Shear the resistancetolongitudinalstressesorpull.Shearoccurwithinamaterial anchor thestructuretoseabedresultsinaxialtension.“Tensile strength”isdefinedas pulling load;forexample, usingawireropetoliftloadoritasguy compression. Tension (or tensile) stresses develop when a material is subjected to a beam is in compression, and the internal stresses that develop within the column are compress orcrushthematerial.For example, acolumnthatsupportsanoverhead such asfatigue. Compressionstressesaredeveloped withinthematerialwhenforces are compression,tension,shear, torsion,impact,oracombinationofthesestresses, subjected toenvironmental loadswillbecomeimportant.Commontypesofstress Followed bythis,thetypes offorces/stressthatarecommoninoffshore structures types offorcesorstressthatthematerialhastowithstandandhow arethey resisted. brittleness, ductility, and malleability. These propertiesaredescribedintermsofthe tions. Someoftheimportantpropertiesarestrength,hardness,elasticity, plasticity, the specialpropertiesthatarerequiredbyamaterialtoqualifyfor­ is stilladvantageous toreview itinthissection. This willhelponetounderstand to estimate their behavior literature, it under loads. Though it is well known in the rial choiceinadvertent. Mechanical propertiesofmaterialsareusedas­ design criterion),performance-basedofoffshore structuresmakes themate- strength maybeoneofthemostimportantcriteria(incases,itisonly tigated beforethechoiceofmaterialismade.Unlike land-basedstructureswhere their functionaldegradation inthecorrosive environment alsoneedstobeinves - forces areresisted.Inadditiontotheirhomogeneityandisotropic­ terms ofthetypesforcesorstressthatmetalmustwithstandaswellhow these ­behavior underdifferent typesofloads. These propertiesaregenerallydescribedin plasticity, brittleness, ductility, and malleability are useful to characterize their behavior of metals under loads. For example, strength, hardness, toughness, Mechanical propertiesaregenerallyconsideredimportantindicesforstudyingthe 3.3 132 A basicquestioncomestomindwhenselectingmaterialsfor offshore applications

FUNDAMENTAL PROPERTIES maximum shearstrengthof magnitude ofload,which maximum strengthof Ocean Structures Ocean material) thatare offshore applica- characteristics, measurements maximum ­elasticity, materials Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 strain curve determines the yield point as shown in the figure. This is also called also called is This yield figure. the shown as point the in determines curve strain stress– the with line of value. of point this intersection The strain maximum of the slope, 0.2 from by “offset initial the the to yield method.” parallel is drawn Aline determined typically yield is the strength yield materials, defined these point. For steel do not have is showncurve than Figure 3.2. in other a well- Most metals ductile stress; atypical uniaxial under plotted curve stress–strain the from well understood behaviorite ductile choice widely of The offshore steel and is in construction. used afavor such steel are as materials Ductile fatigue failure. result in (TLP), which can of tension tethers leg in platform arise can that tension variations tether dynamic be ous forces acomplex classic in results One example behavior material. of could the combination design. of The vari the in aspects most critical the tion are of stresses combina- safely to the disburse of capacity behavior material the the of and members Interestingly, torsion; occasional. shear, addition bending, forces and to in impact are into thinsheets. malleable materialisonethatcanbestamped,hammered, forged, pressed,orrolled enables a materialtodeform by compressive forces without developing defects. A stretch, bend,ortwistwithoutcrackingbreaking.Malleabilityisthepropertythat design ofstructures,ductilityplaysanimportantrole,whichenablesthememberto in comparisonwiththeirtensilestrength.Underthebracesofperformance-based good examples ofbrittle materials,brittlemetalspossesshighercompressive strength is theonethatbreaksorshattersbeforeitdeforms. Although castironandglassare construction. Brittleness is the opposite ofthepropertyplasticity. A brittlemetal members thatarecommonly used inmarine structural large manufacture to used is that ofstrength.Bycarefulalloying ofmetals,­ to deformpermanentlywithout­ recover itsoriginalshapeaftertheloadisremoved. However, plasticityistheability elastic limitofamaterialisthetowhichcanbeloadedandstill ability ofamaterialtoreturnitsoriginalshapeonremoval ofload. Theoretically, This isconsideredtobeacombinationofstrengthandplasticity. Elasticityisthe that enablesamaterialtowithstandshockandbedeformedwithoutrupturing. and thehardnessisindicatedbyaRockwell“B”­ a Rockwell“C”number. For nonferrousmetals,whicharesofter, ametalballisused harder thannonferrousmetals,adiamondtipisusedandthehardnessindicatedby penetration ismeasuredandcomparedtoscale.For ferrousmetals,whichareusually in theRockwelltestisthatahardmaterialcanpenetratesofterone;amountof tests, Rockwellhardnessistheonemostfrequentlyused. The basicprincipleused Rockwell, Vickers, orBrinellaresomeofthemethodstestingharness. Ofthese in termsoftheparticulartestthatisusedtomeasurethisproperty. For example, tion. Because there are several methods of measuring hardness, it is always specified applied loads.Hardnessisthepropertyofamaterialtoresistpermanentindenta- specified numberof cycles. Impactstrengthistheabilityofametaltoresistsuddenly or cyclic in nature and is expressed by the magnitude of an alternating stress for a load. “Fatigue strength”istheabilityofmaterialstoresiststressesthatarereversal is ameasurementoftheresistancetobeingpulledapartwhenplacedundertensile the materialismaximumstrengthacanwithstand,wheretensile Materials for Ocean Structures for Ocean Materials Compressive or tensile stresses are commonly generated on structural members members on structural generated Compressive commonly are stresses or tensile breaking orrupturing. This propertyisinconverse to combination ofplasticityandstrength number. Toughness istheproperty 133 % - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 134 ment platforms, andsubmarine vehicles thataredeveloped inthepast,require materials structures, suchasoffshore drilling andproductionplatforms,surface buoys, instru- Earlier, themajorapplication of materials isonlywithsurface ships. New offshore 3.4 index material. of of abscissa is an the toughness the to respect with curve stress–strain the underneath for Area members. same these the are strength ultimate and such rupture cases, In for materials. curve brittle shows stress–strain atypical awell-designated yield is point Figure 3.3 not or ceramics, such seen. concrete as materials of case brittle index In of absorption. is an ratio energy ductility large as governs ratio decision ductility for of the choicethe offshore of structures materials for design. However, important is also yield to strength, strength of ratio ultimate the plastic analysis. the ratio, Interestingly, in which sections is strength at critical the formed be to govern of capacity rotation plastic assumed will hinges, the This tures. design- of the offshore in struc property engineering ratio,” important which is an 0.2 FIGURE 3.3 0.2%). (typically (4) (5) limit; strain offset (3) proportional rupture; 3.2 FIGURE proof stress. The ratio of the maximum strain to that at yield“ductility that to is called strain maximum of ratio the The % proof stress. EFFECTS OFTHE MARINE ENVIRONMENT ON MATERIALS

Stress–strain curve for brittle material: (1) ultimate strength; (2) (1) strength; rupture. material: for ultimate brittle curve Stress–strain Stress–strain curve of mild steel: (1) ultimate strength; (2) (1) steel: of mild strength; yield curve strength; ultimate Stress–strain σ 3 2 1 σ 5 1 2 ε 4 ε Ocean Structures Ocean Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials withstanding the unforeseen hazards besides meeting the design requirements. the besides meeting hazards unforeseen the withstanding should rigs capable be and of such pipe lines as accessories other platformof the and successfully. Under for such selected acomplex construction materials operation, and exploration drilling perform to aspecific format in synchronized be to need is complex. It involves which equipment, electrical and alot of electromechanical production oil process because errors operational from arise that hazards be can or invested itdiate, may on offshore loss are to lead platforms. There that of assets even occurs, atalower atall if failure, probability, should sudden not or be imme properties thatguidetheselectionforvarious applications. given by various international codes. These codes indicate a variety of engineering Hence, selectionofmaterialsiscloselygoverned bytheadviceorrecommendations these kindsofstructuralsystemsinthecomplex oceanenvironment isvery important. important tonotetheexpected maintenancemustbelooked uponasthesurvivability of the offshore site, which is one of the major constraints in material selection. It is also Materials chosenformarineconstructionshouldbeeasyto fabricate andtransportto and the availability of fabrication facilities for the chosen shape, size, and geometry. cal andchemicalpropertiesofthematerials,costavailability in large quantity, ocean structures.Factors thatbecomevitalforselectionofmaterialsincludethephysi- properties, whicharedemandedfromthematerialsifthey have got to qualify for loads inthecriticalmarineenvironment, itisimportanttoknow aboutthosespecific of materialsthatarerequiredtosustainthecombinationdifferent environmental for such special applications. Apart from understandingthe list ofspecial properties nature, oneneedstounderstandthefactors basedonwhichmaterialscanbechosen As thealgorithmofselectionmaterialsforoceanstructuresgrows complex in special conditionsmake thechoiceofmaterialstoahighlylimited­ In addition,materialsshouldwithstandasevere hydrostatic pressure. All theabove sive ­ perform theirintendedfunctionunderspecialconditions:collision or impact, exces to able be ­properties thatensuresurvivabilityshould inthemarineenvironment. They the suitabilityofmaterialsformarineenvironment. on Materials musttation have general recommendationsbut notarequirementasthey mayimposeaseriouslimi- specifications suggestedbycodesandotherregulatory agencies are only desirable Variousstructure. tionship betweentheselectionofmaterialandtypeocean ­possess tobequalifiedforconstructionofoceanstructures. There exists acloserela- it isimperative tounderstandtheimportantcharacteristicsthatmaterialsshould ­different combinationsofforcesactingonthemembersoffshore structures, during hurricanes, they shouldbeabletowithstandhighhydrostatic pressure.Given ensure survivability incaseofany accidents(collision).Incaseofexcessive loads effects, andbiofoulingeffects. Itisdesiredthatmaterialsmusthave properties,which mental loads.Few ofthemarechemical,fatigue, stress­ Chapter 2. The materialstrengthdegrades undertheeffects causedbytheenviron are exposed to a combination of a variety of environmental loads, as fatigue resistanceinthematerialsusedforarticulatedjoints.Offshore structures as TLPs demandshighductility in tethermaterials. more Articulated towersdemand with specialcharacteristics.Large deformationinducedinthedesign­ Materials should be chosen not to initiate any catastrophic failure; this means that that means failure; this any catastrophic should chosen be not initiate to Materials loading thatoccursduringhurricanes,andspecialkindsofenvironmental forces. concentration, corrosion concept such ­discussed in situation. 135 - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 account foraccount such uncertainties. to factor safety for Alternatively, materials environment. partial use also one can ocean the conditions by in caused the change in are that of uncertainties care take to design the allowanceallowance.” in as is seen thickness in For example, increase an “material of through care is taken able and levels environment stress for marine the allow achange in It environment. therefore warrants marine the in those tions and testcondi under standard properties material the between difference is asignificant there that understand to conditions. other Therefore,of and it loading is important However, specimen. nature on the standard depending value reality, may in vary this ayield has value it indicative of is 250 onlyple, material value an MPa, the for if a only indicative. are For exam properties above the addition, In material resistance. (2) modulus of elasticity, (3) Poison’s ratio, (4) (5) and fracture fatigue performance, follows: as of order priority the in (1) important are characteristics yield strength, following (physical) applications, the for material marine amaterial selecting While 3.5 136 of carbonwhose yieldstrengthisabout1035 MPa. Itiswidelyused forfabricating instrument ancillaries,andbuoys. Medium-strengthsteel hasamediumpercentage of steeliswidelyrecommended forthehullstructureofplatforms,fittings,tanks, referred toaslow-strength steel whoseyieldstrengthislessthan415MPa. This type bon content.Carboncontentinfluences thestrengthofsteel;low carbonsteelisalso content varying from0.6%to1 %. Ultrahighcarbonsteelhasabout–2ofcar 1.25 has apercentageofcarbonvarying from0.3to0.6,whereas highcarbonsteelhasa contain otherelementssuchaschromium,cobalt,andnickel. Mediumcarbonsteel steel. Low carbonsteelcontainslessthan(orequalto)0.3% ofcarbonanddoesnot on carbon content, steel is classified as low, medium, high, and ultrahigh carbon according totheiryieldstrength.Lookingatthefurtherlevel ofclassificationbased on thecomponentofmemberandtypeloadcombinations, codesclassifythem desired shapesnamedaftertheshapeofcrosssectionas L, Tee, andsoon. on theproductform,itisclassifiedasbars,plates,sheets, strips,tubes,andother desired characteristics,itisclassifiedasannealing,quenching, andtempering.Based classify theminmany ways. Basedonheattreatmentcarried outonsteeltoachieve as ferritic,pearlitic,ormartensitic.Basedonthestrengthrequired,different codes fied eitherashotrollingorcoldrolling.Basedonthemicrostructure,itisclassified electric furnaceoropenhearthprocess.Basedonthefinishingmethods,itisclassi- low alloy, orstainlesssteel.Basedonthemanufacturing methods,itisclassifiedas treatment, and the product form. Based on the composition, it is classified as carbon, position, manufacturing methods, finishing methods, microstructure, strength, heat enables ustoidentifytheirareasofapplication.Steelisclassifiedbasedonitscom- for particularset of applicationsinthe ocean environment; in fact, classification used materialsinoceanstructures.Itisclassifiedseveral ways tomake it­ Steel isacommonmaterialusedformarineconstruction.Italsooneofthewidely 3.6 Classification ofsteelbasedonstrengthisintrinsicinthedesign codes.Depending

STEEL CLASSIFICATIONSTEEL DESIGN CONSIDERATIONS DESIGN Ocean Structures Ocean suitable - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials example, NORSOKrefers toprEN10225,whichitselfisbasedonBS7191. its applications,asrecommendedbyvarious codes,correspondstoeachother. For part oftheworld. Itisimportanttonotethatmostoftheclassificationsteeland and Asian regions, althoughthereisnobarofusingany specificstandardonany tries. American Petroleum Institute (API) standards are primarily used in American of NORSOK,whichisNorwegian standard,applicableprimarilyinEuropeancoun- used foroffshore constructionareprEN10225,BS7191,andMaterialDataSheets ment toimprove itsspecificpropertiessuchas ductility. Themajorstandardsthatare of 1–2GPa. This typeofsteelisrelatively ductileandmanufactured byheattreat- greater than1035MPa. For example, maragingsteelhasayieldstrengthintherange icebreakers andbuoys forarcticregions. High-strengthsteelhasayieldstrength based on the impact tests. They are grouped as class class as C, class B, C A. Class and grouped are They tests. impact on the based is usefulinprescribingthecritical stressintensityfactor required forthedesign. whereas fracturetoughnessis computedbasedonCTOD or J-integral test. The latter is theenergy measuredinjoulesand commonlyrelatedtotheCharpy V-notch test, Toughness isexpressed intermsofimpact andfracturetoughness.Impacttoughness relatively littleenergy ofdeformationisinvolved, andtheresultisabrittlefracture. if theapplicationofstresscauseselasticfailure ofatomicbondsatthecracktip, plastic deformationisrequiredatthecracktipbefore advances. Conversely, structural systems. A high toughness material is one where a considerable amount of exists ahighprobabilityofstressconcentrationatthejoinsmembersinoffshore tant requirementsforselectingamaterialtheoffshore structural systemasthere therefore ispreferredforoffshore steel. Therefore, thisbecomesasoneoftheimpor failure inthepresenceofacrack,notch, orsimilarstressconcentrator. Hightoughness ­selection of steel for marine applications. It is described as a measure of resistance to growth. crack the to of amaterial tance resis - measures that tests mechanics of is one CTOD of fracture afamily properties. displacement (CTOD) steel should opening tip crack good possess that demand also results. test They impact on Charpy based properties test impact the specify Codes avoid to of for metal weldedlow-temperature base toughness failure the joints. brittle applications. However, steel should superior possess that note to it important is also choice the decide to of steel for different characteristic most important the sidered as is con of grouping steel, strength the in design seen check. As routine of the a part of investigated group be steel should also for this with problems, fatigue-related as fabricated members fabrication. Further, during welding procedures special requires of group steel This MPa. 360 than SMYS steel with greater refers high-strength to of use low the hydrogen III Group requires weldingtures particular. in process, equivalent of carbon 0.45 and MPa 360 equivalent of carbon 0.4and yield (SMYS)strength minimum MPa or lessrefers 280 of aspecified steel to with level strength Group I the to welding and according characteristics. Steel is grouped 3.7 Steel is also grouped according to the notch toughness characteristics, computed computed characteristics, notch toughness the to according grouped Steel is also Toughness isanotherimportantstructuralpropertyofsteel,whichvitalin GROUPS OFSTEEL or less. Group II refers% or less. SMYS II steel to with Group less than - higher. struc % and steel for Using ocean this 137 - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 structures usesteelwithayieldstrengthofmorethan350MPa. Table 3.1 gives abrief mersible module offshore drilling units. On average, about more than 40% in compliancewithoffshore structuressuchas TLPs andformooringlinesinsemisub- and spud cans of jack-up platforms. High-strength steel is commonly used for tethers strength rangingfrom500to800MPa isusedtofabricate thelegs, racksandpinions, of high-strengthsteelisseeninthefabrication ofjack-upplatforms.Steelwithayield ously lackingincaseofhigh-strengthsteel.Intherecenttimes,increasedapplication is mainlybecauseofthebetterknow-how oftheirfatigue performance,whichisseri- bers (joints, in particular) are been fabricated using medium-strength steel only. This the NorthSea.However, todate,fatigue-sensitive componentssuchastubular mem- structed usingsteelwithayieldstrengthrangingfrom400to450MPa andinstalledin to-weight ratio,whichresultsinsavings ofcostmaterials.Jacket platformsarecon- strength steelsfortheseinstallations. The primarybenefitistheincreaseinstrength- prescriptive documentation. Inrecentyears,therehasbeenanincreasinguseofhigher of 350MPa. Existingcodes andstandardswidelycover thesegroups ofsteelthrough loads. encountered resist to the incapability material the from by offshore encountered risk structures the reduces cation. This specifi of which error, source is material wrong relieved one important off from are offshore structures provisions steel manufacturers, the on codal from update constant the to so on. Thanks and by members, the encountered loading process, of manufacturing members, of type terms prescriptive very in are codes ­different by made Recommendations structures. for ocean material of aconstruction steel as provisions selection Interestingly, the codal guide the temperatures. at subfreezing for use recommended so on. Arefersloading, Class are of and agroup to steel that impact concentration, stress high subjected to are and thickness larger with members for legs. recommended and B refers Class are of a to group beams, steeldeck that only. loading static Few jacket legs, in piles, bracings and examples platforms, are quasi- subjected to and concentration, modest stress low forming, moderate restraint, involving thickness, members limited structural primary to ofgroup steel is limited this Applicability of refers specified. of agroup to steel for are tests which no impact 138 Note: 850 750 650 550 (X80) 450 (X65) Structures andpipelines 350 (X52) Strength (MPa and Grade) Structures in Offshore Steels Used High-Strength 3.1 TABLE Fixed offshore structures usedmedium-gradestructuralsteelwithayieldstrength Q&T, quenchingandtempering; TMCP, thermomechanicalcontrolledprocessing. Q&T Q&T Q&T Q&T TMCP Q&T TMCP Normalized TMCP Process Route Jack-ups andmoorings Jack-ups andmoorings Jack-ups andmoorings Structures andmooringpipelines Structures andpipelines Structures Application Area Ocean Structures Ocean of offshore - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Quantitative results given by Charpy test indicate the energy required to fracture fracture to required energy the given indicate results test Quantitative by Charpy on results acomparative qualitative provide scale. quantitative tests and both These the notch by geometry. influenced results. test Results are the sample affects the in Notch fracture. before after and height in hammer of the difference the comparing by is inferred absorbed energy The material. of the specimen on the impact cause an (Kayano et length al., 1993).simple and of mass pendulum aknown to It is dropped consists of a procedure test impact Charpy onlyresults on acomparative scale. The gives test The transition. ductile–brittle temperature-dependent, a tool study the to It is is given energy index Absorbed of material. of an notch as ture. toughness the - frac during by material of the absorbed energy amount the determine to useful and test rate strain high It is astandardized of any material. strength impact the stand under to laboratory the simple is avery in test conducted impact experiment This 3.7.1 view ofthetestsetup. other thansteelisinsteadbasedonCharpy V-notch shows aschematic test.Figure 3.4 yielding arevery interestingly awidevariety offailure modes.Selectionofmaterial impact, mechanical overload, stress concentration, cracking, thermal shocks, wear, and structures. For example, buckling, corrosion, creep, fatigue, hydrogen, embrittlement, of failure modesareencounteredbythematerialwhenthey areexposed tooffshore steel withahigheryieldstrengthisusedforjack-upandmooringlines.Different types along withthelocationofusagearealsomentioned.Itcanbeseenfromtablethat summary ofsteelusedinoffshore structures;yieldstrengthandgradeofsteelused FIGURE 3.4 Materials for Ocean Structures for Ocean Materials C harpy Schematic view of a Charpy test setup. test view of aCharpy Schematic T es t SC/IIT M 139 - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 edge or shear lips, then it is considered a ductile material. Usually, fracture will be a be Usually, will it then lips, is material. considered aductile edge or fracture shear on a jagged breaks material the if material; then flat it consideredis a plane, brittle on a breaks material indirectly. the If material of the derive to ductility the useful gives It also some which results, qualitative are material. the fracture to required the energy in levelchange the whichsignificant is defined by sition temperature, tran gives test The aductile–brittle fails. material atwhich the studied be also can rate Strain material. of the toughness the measure to used be can This material. the 140 series, which are widely used in marine applications, varies from 100 to 200 MPa. MPa. 100 from 200 to applications, varies widely marine which in are series, used alloys of 5xxx of yield aluminum corrosion. The strength from protected be to steel anyneeds protective whereas coatings, not does require aluminum addition, In savingsdead in it significant weight. in results of aluminum, that more than times weight the reducing up about to 60 of of steel while equivalent that enables an strength with members design to the steel, which alloys of have mild that to comparable Aluminum strength aluminum. using 5xxx alloy of constructed are particular, in boats, equipment. High-speed and superstructure in property. of Passenger quantities aluminum large vessels utilize maintenance-free windows, due their to doors gratings, and tion of railings, ladders, covers hatch fabrica ships. and It in is used of deckhouses, commercial hulls, in used It is widely for offshore structures. material is a phenomenally attractive Aluminum 3.8 units. for offshorerecommended drilling combination of in steel, oneused check must for effects galvanic also before the it is are materials case In particular. in units, steel for offshore drilling recommending checked for be to criteria Formability, weldability, important the are toughness and equivalency given following as carbon the ity and in two equations: susceptibil by computed be cold-cracking can member. This offshore structural an for which is arequirement characteristic, Generally, weldability important is avery 3.7.2 offshore in applications. them use to prerequisites one which of is also the steel treated, should heat be of rolling. Further, direction the to Charpy’s parallel axis V-notch alongitudinal with should results obtained test be for reference two as results test offshorethese for construction. materials selecting well as test tensile Charpy’s as on the V-notch recommend codes International test. of steel should based be properties mechanical The failure. ductile and of brittleness percentage the combination ofand edges, flatjagged which is helpfuldetermine to

ALUMINUM W eldabili pC cm t =+ y C eq =+ 30 SM in C ++ 20 MN 61 ni + % CN 20 . As the specific gravity of 2.5 aboutis specific steel the . As ui +++ + 55 60 CC ur + 20 CM ro ++ MV 15 o ++ 10 V % 5% B Ocean Structures Ocean - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials and 9xxx refers to unused series. As we understand that an alloy is simply a mixture alloy is simply an a mixture that we refersAs series. understand unused to 9xxx and 7xxx refers to aluminum– to ­aluminum– 1xxx referstopurealuminum,whosepurityis99%andabove; 2xxxindicates is unique. The following designationsofaluminumalloy clarifythe­ However, alloy variations. individual indicate but it no significance, has number the digits and fourth alloy;third the initial of the digit variations second signifies the alloyingconstituent(s); digit refers principal the first to namely, The XXXX. ­digits, its composition. alloying designation systemunderstand The consists of four applications. suit to marine to process manufacturing on the based customized are of aluminum properties structural the table that the It from is seen alloys. Table 3.2 alloys. aluminum designations in of used shows temper details the cold-worked the indicate to used conditions of or aluminum tions heat-treated are for applications. vital choosing for Temper them also deep-sea are These designa- aluminum. of characteristics desired the give to are polished high-reflective surfaces ity, conductor good corrosion, to electricity, of be resistance to heat, capability and malleabil components. Strength, aluminum which has unit, shows traction atypical Figure 3.5 crawler it structures. which suitable mining makes forfeatures, deep-sea is one most of attractive the of zone. aluminum Corrosion resistance heat-affected the in equipmentsuchimprove to used are in postweldthe wires strength alloys filler and of favorable is acandidate Suitable aluminum of use mining aluminum. deep-sea in lightweight crawlers have­applications. particular, that In attempted recently been for low-temperature is used conditions and for long-termbaric Aluminum operations. of hyper terms in limitations has mining Deep-sea mining. of deep-sea arena loss or transfer. temperature against where ships, it is insulated port - (LNG) gas trans vessels pressure natural liquid in in used is commonly Aluminum FIGURE 3.5 An alloy of aluminum has a unique designation a unique system, has which enables alloy of us to aluminum An the in for construction materials one alternate of as the used is also Aluminum fabricating the subcomponents in the mechanical equipment used in deep-sea deep-sea in equipment used mechanical the subcomponents in the ­fabricating copper alloys; 3xxx indicates aluminum–manganese alloy; refers 4xxx alloys;­copper aluminum–manganese 3xxx indicates R ubb Cross Typical traction unit for deep-sea mining. for deep-sea unit Typical traction aluminum–zinc alloys; 8xxx refers to aluminum with other elements; other with aluminum to refers alloys; 8xxx ­aluminum–zinc Rear dr silicon alloys; 6xxxreferstoaluminum–magnesium–silicon alloys; ­silicon er be be um lt within am volute te et h Drive dr Ve Rollers um hicle frame wor nomenclature: nomenclature: k 141 - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 142 of the alloying elements will precipitateat the grainboundaries at higherpercentageof sion resistance ofthealloy graduallydecreases. This isbecauseintermetallic particles sium contentaddsstrengthtothe alloy, but ifaddedbeyond 4% particles ofaluminum–magnesium, whichreinforcethealloy. An increaseinmagne- the principalreasonsforincrease instrengthisduetotheformationofintermetallic the mechanicalpropertiessuch asyieldstrength,tensileandductility. Oneof shipbuilding aswell. The magnesiumcontent of5xxxalloys significantlyinfluences tions. Corrosion resistance of these alloys makes them the mostsuitable materials for the mainalloying constituent,lends itselftoareasonablestrengthformarineapplica- (5xxx series)arethemostsuitablematerialsformarineapplications. Magnesium,as Among allthealuminumalloys, the non-heat-treatablealuminum–­ a substantialpercentageofcopperisusedaremoresusceptible tocorrosive action. nese, magnesium,chromium,andsilicon.However, thesealloys inwhich metal. Aluminum alloys containtheprincipalalloying ingredientssuchasmanga- Commercially purealuminumisa white, lustrous,lightweight,andcorrosion-resistant a 3.8.1 formability, conductivity. machinability, or electrical ductility, such strength, as characteristic aparticular alloys is maximize to designed of Each the of range materials. elements entire alloying givedifferent an to that rise with mixed aluminum, pure alloy is primarily Aluminum metals. parent ofthose the from differ melted whose togetherof anew form to characteristics metals metal, H O F Designation Alloys of Aluminum Temper Designations 3.2 TABLE T T T T T T T T T T W H H 6 5 4 3 2 1 10 9 8 7 3 2 1 lloying Annealed As fabricated Cooled fromanelevated temperature forshapingprocessandcoldworked and Solution heattreated,artificiallyaged,andthencold worked Solution heattreated,coldworked, andartificiallyaged Solution heattreatedandstabilized Solution heattreatedandartificiallyaged Cooled fromanelevated temperature forshapingprocessandartificiallyaged Solution heattreatedandnaturallyaged Solution heattreated,coldworked, andnaturallyaged Cooled fromanelevated temperature forshapingprocessandcoldworked andnaturallyaged Cooled fromanelevated temperature forshapingprocessandnaturallyaged Solution heattreated Strain hardenedandthermallystabilized Strain hardenedandpartiallyannealed Strain hardenedonly artificially aged E lemen ts Condition (approximately),corro- Ocean Structures Ocean magnesium alloys Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Note: AA6061 Plasma AA5083 TIG AA6082 MIG properties and dimensions of product. Table 3.3 shows aluminum materials with with 3.3 materials shows of dimensions Table product. and aluminum properties mechanical the helps also stabilize This release to stresses. residual alloy structures heat-treated and aluminum by workability in softening aids Annealing structure. improve workability. cast and the their in brittleness reduces It also structures cast segregation of chemical out reduce to or homogenizing is carried aging. Preheating of natural that to compared improves further cipitation its This strength accelerates. holding it, and pre above temperature room the atemperature to material treated the solution aging, by heating heat- of case artificial aging. In natural as is known quenching. solution and This treatment after heat when temperature atroom stored alloys aging. properties Heat-treatable their change artificial and aging ries: natural catego two into is divided main process Aging properties. improve mechanical their steel alloys to copper, some nickel, stainless and magnesium, on aluminum, used is age alternatively as to hardening, referred hardening, hot oil. Precipitation and water, blast, soap solutions, conditions. are air cal Most media quenching common or mechani adverseof without constituents metallurgical alloying introducing The faster rateofcoolingthealloy enablestoretainasupersaturatedsolidsolution abruptly. quenching then and for period, adesignated temperature high uents atthat solid solution. It involves constit holding the temperature, above heating critical the in constituents hardening of concentration the by practical developing maximum the ing pittingandweightloss;itmayalsoleadtostress–corrosioncracking. in electrochemicalimbalancethegrains. This leadstointergranular corrosion,caus- magnesium. These particlesareanodicwithrespecttoaluminumandthereforeresults AA5083 MIG Alloy Mining Materials for Deep-Sea Aluminum 3.3 TABLE Materials for Ocean Structures for Ocean Materials arc weld deep-sea mining preferred for Heat treatment is carried out to improve the mechanical properties of the alloy of the properties out improve to mechanical the is carried Heat treatment xx -notapplicable. Welded material Welded material Base material Weld with Weld with Base material Single-pass weld Multipass weld Base material ER5183 fillers ER4043 fillers Description Strength (MPa) Yield 155 200 245 170 175 285 158 180 245 Strength (MPa) Ultimate Tensile 205 335 350 205 200 305 265 320 350 Elongation (%) 20 20 10 14 16 20 8 8 7 Angle Bend 140 100 135 125 xx xx xx 65 60 Energy (kJ) Impact xx xx xx 30 15 18 22 26 35 143 - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 crawler structures in deep-sea mining. deep-sea in crawler structures AA5083-H116 that ­single-pass for weld. literature recommended the It in is seen are Multipass weldshave shown abettermicrostructureproperties compared to material. base of alloy multipass of with welds the that the with comparable strength are of about 90 highlighted. applications are mining for useful deep-sea of alloys are different that properties cal weldTIG weld. produce to anonconsumable uses mechani electrode tungsten The workpiece, up the melts, heats joins them. workpiece. and Electrode metal the and electrode a consumable between wire is formed arc electric which an in is a process (TIG) gas welding. welding (MIG) inert gas welding MIG tungsten and inert metal 144 monly used in small submersibles. small in monly strength-to-weight used most High attractive is the ratio cost is prohibitively even initial is com the though Titanium maintenance high. term toward contribute its long- cost reduction in of titanium resistance corrosion and nontoxic, whichmake thembiologicallycompatible. thermal conductivity, low coefficientofthermal expansion (about9–11ppm/ °C), and of titaniumalloys includenonmagnetic,goodheattransfer propertywithlow-heat have goodfatigue resistance and highfracturetoughness.Otherusefulproperties solutions andcompoundswithmetallic,ionic,covalent bonding. These alloys with almostallsubstituteelements. Titanium alloy resultsintheformationofsolid is atransitionmetal with anincomplete“d” shell;therefore, it formssolidsolutions titanium alloys. Titanium canreadily form analloy withotherelementsbecause it thermomechanical processingisthebasisfordevelopment ofawiderange of Manipulation ofthesecrystallographicvariations through alloying additionsand Therefore, a wide variety of microstructure can be produced by heat treatment. tion fromα-Ti toβ-Ti at882 °C; alloying elementsinfluencethis transformation. and itsalloys canbeusedupto540 °C. Titanium undergoes allotropic- transforma is betterthanthatofaluminumasitcannotbeusedathighertemperature. Titanium higher meltingpointandincreasedstrengthattemperature,itsapplicability atmospheric oxygentoformaprotective layer;thismakes itcorrosionfree. With titanium ishighlyreactive, onexposure tothemarineenvironment, itreactswith higher strength-to-weightratio,whichisvitalforoffshore applications.Even though 47.88 andanatomicnumberof22.Beingalightmetalwithlower density, ithas It hasanhexagonal closepacked (HCP)crystalstructurewithanatomicweightof of steel. The specific gravity of titanium is 4.5, which is about 55% of that of steel. space industries. The meltingpointoftitaniumis1678°C,whichhigherthanthat alloys are commonly available in wrought products; most of them are used in aero- with sodiumandmagnesiumunderinertatmosphere,was theprocessused. Titanium manufacturing titanium.Reductionoftitaniumchlorate,firstwithcalciumandlater tegic importanceinthe past60years.In1938,Dr. Krolldeveloped aprocessfor Titanium asanelementhasbeeninrecognitionforover 200years.Itgained stra- 3.9 As seen from the Table 3.3, the welds from MIG seen As AA5083 have shown ajoint efficiency Titanium is as strong as steel but strong as about is as 45Titanium TITANIUM based on UTS tests. Impact strength, bend, ductility and ultimate ultimate and ductility bend, strength, Impact tests. on UTS % based lighter. High strength, low% lighter. strength, density, High Ocean Structures Ocean - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 to-atom ratio equal to four are neutral (e.g., neutral four to are silicon). equal ratio and to-atom tin, zinc, 4(e.g., than greater molybdenum, manganese). iron, and electron- Elements an with by ratio elements electron-to-atom an with is stabilized aluminum). phase Beta and 4(e.g., less ratio elements than electron-to-atom an with oxygen, nitrogen, carbon, by is stabilized phase alpha The alpha. nontransition elementstion and stabilize to transi both alloys contain II type whereas beta, elementsonly transition stabilize to saturated saturated asuper to transformation undergo to adiffusionless atwhich βbegins temperature the indicate to includes of concentration aline ing addition element. diagram Phase α/(+β) andboundaries,aredepressedtolower temperatureswithincreas- α in solubility addition element βthan in greater has diagram, phase II element alloying of case the type by In concentrations. increasing peratures tance, beinga strong betastabilizer. Iron,ifalloyed withtitanium, reducescreep is alsosubsequentlyreduced. Niobiumimproves high-temperatureoxidation resis- to increasehardnessbut reduceslong-time, high-temperaturestrength;weldability and creepstrength.Molybdenum isastrongbetastabilizerand,ifalloyed, helps as itisaweakbetastabilizer. Ifaddedmorethan6%byweight,itreducesductility embrittlement. Zirconium,ifalloyed withtitanium,retardstherate oftransformation which resultsinsolidsolutionandhardensthealloy withaluminum,without­ alloyed withtitanium,dissolves inbothaphaandbeta.Itis aweakalphastabilizer, temperatures: α temperatures: two into transformation for elements equilibrium ing single divides temperature the transformation temperature of α temperature transformation the additions, or alloying of impurities amount and type nickel. on the Depending and tively. chromium, iron, manganese, with compounds form Eutectoid stabilizers eutectoidsuch and either form isomorphous solid as solutions- respec or compounds, solid result solutions, in such peritectoid stabilizers as beta whereas stabilizers Alpha classificationmicrostructure. the on depends beta; its and alpha–beta, groups: alpha, even heavily in seawater. polluted placed if three classifiedinto alloys are Titanium resistance corrosion outstanding an has Titanium handling. and strength mechanical for requirements minimum allowance,corrosion the equipment is satisfy to designed no valves, requires cold hotsuch special and propellers, pipes. and titanium as As be painted benefits. cannot which additional It is used surfaces, for ity are fabricating relatively and resistance corrosion good modulus of of high elastic titanium; features - by weight,anintermetalliccompoundcalledα and elasticmodulus.However, ifthecontentofaluminumincreasesmorethan6% Aluminum, asanalloy withtitanium, increasesthetensilestrength,creep e 3.9.2 in solubility addition element α in greater has diagram, Iphase type In type III. and II, type I, type as diagrams classifiedon phase alloys based are Titanium 3.9.1 Materials for Ocean Structures for Ocean Materials β . Addition α element stabilizes C α ffe lassifi , that is, α , that ct

-transus and β and -transus of c a A t ions lloying ʹ ; this occurs usually on rapid cooling. usually Type occurs Ialloys; this contain E -transus. lemen - to β - to , that is, ( , that ts -Ti or lowered. raised be Addition can of alloy α + β 2 isformed,whichbrittle. Tin, if ) region, is elevated tem higher to . It stabilizes β . It stabilizes , that is, , that causing than than 145 - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 The onlydemeritistheincreaseininitialinvestment, but byincludingthecostof Titanium has a very clear edge as a construction material for marine applications. almost resistanttoalltypesofcorrosionthatarecommoninthemarineenvironment. offshore construction. With referencetothetable,itisseenthattitaniumalloys are parison ofpropertiesthattitaniumposseswithothercompetitive materialsusedin modulus elasticityareadditionalbenefitsoftitaniumalloys. showsTable 3.4 acom- which is equivalent to that of steel. Good corrosion resistance and relatively high enables a maintenance-free system, its yield strength can be as high as 400 MPa, narios, titaniumalloys areusedforpipelinefittingsandsystems. Althoughtitanium to handletheconstructionandfabrication challenges.Inthepresenceofsuchsce- to thedifferent methodologiesoffabrication areavailable asatechnicalworkforce the fabrication experience. Peoplewithfabrication skillsintitaniumwithrespect price in the market. Oneoftheencouragingaspectstitaniumisavailability of at 10 ice corrosionuptoatleast70°Cinseawater, whereassteeltendstocorrodeeven whereas othermetalsandalloys corrodesignificantly. Titanium isimmunetocrev - seawater attemperaturesupto130°C,titaniumsurfaces areimmunetocorrosion, structural engineeringapplicationsaswell.Itisalsoevident thatinflowing orstatic availability ofinformation,designengineersareattractedtoward itsusefulnessfor composition andfabrication experience oftitaniumintherecenttimes.Dueto facturing industryforsharinginformationaboutthestructuralproperties,chemical the marineenvironment raisedaseriousconcernaboutsafety. Thanks tothemanu- ity. An increaseindisruptive failures ofstainlesssteelandcopper-based alloys in elements totheirchemicalcompositionincreasesstrengthanddecreasesductil- beta-­ strength, whereascarbonwidensthetemperaturerangebetweenalpha-transusand 146 Erosion corrosion Weld/heat-affected zone Microbiological corrosion Galvanic corrosion Corrosion fatigue Stress corrosion Pitting corrosion Crevice corrosion Mode ofCorrosion Comparison A Titanium: 3.4 TABLE General corrosion (HAZ) corrosion Pure titaniumhas low strengthandhighductility. Addition ofsmallamounts of transus; itisastrongaplhastabilizer. ° C. Inrecenttimes,titaniumhasbeenavailable atavery competitive andstable Susceptible Susceptible Susceptible Susceptible Susceptible Susceptible Susceptible Susceptible Resistant/susceptible Copper-Based Alloy Susceptible Susceptible Susceptible Susceptible Susceptible (>60°C) Susceptible Susceptible Susceptible Resistant Steel 316 Stainless Stainless Steel6 Mo andDuplex Resistant Susceptible Susceptible Resistant Susceptible Resistant Resistant Susceptible Resistant (>25°C) Ocean Structures Ocean Highly resistant Resistant Immune Immune Immune Resistant Immune Resistant up Resistant to 80°C Titanium Alloys Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 cooling and piping systems, and many other components in the ship design. ship the components piping in other and systems, many cooling and fasteners, yacht shipboard fittings, high-strength manipulators, underwater armors, navel exhaust liners, propellers, stack jet and propulsion systems, shafts propeller submersibles, valves, for deep-sea ball exchangers, heat pumps, water material hull for of majority rosion offshore submarine The applications resistance. titanium use cor phenomenal and toughness, high applications due strength, its to high marine in used increasingly is Titanium material. alternate an as used is titanium fleet; fishing an ongoing the is penalty for and Japanese cleaning fouling fiberboats repeated by easier removal and offor biofouling. painting hull Progressive of glass degradation improvedwith efficiency.fuel includecost the operational Savings no necessity in Weighing only 4.6 was boat 12.5 tons, the mlong, which could travel at30 knots sional andstructuralstability. Solutiontreatingandagingincreaseitsstrength. helps toproduceanoptimalcombinationofductility, machinability, anddimen- ual stressesdeveloped during fabrication; thisiscalledstressrelieving. Annealing toughness, fatigue strength,andhigh-temperaturestrength.Italsoreducesresid- removed afterhotworking. Heattreatmentisdoneontitaniumtoimprove fracture oxidizing atmospheretoavoid hydrogen absorption;oxygen-embrittledlayeris in larger quantitiesleadsto embrittlement.Hotworking isthereforedoneinan oxygen above 1300° gases isanimportantfactor inhotworking. Itabsorbshydrogen above 300° more ­ maintenance over a service life of about 15years,titanium andaluminumwillbecomea Pultruded glass or phenolic gratings are a particular type of GRE being commonly commonly being of GRE type aparticular are or phenolic glass gratings Pultruded water.portable and dredging, mains, fire plants, exploration, chemical desalination, suitable applications them such for oil as special make many characteristics These adverseand conditions. rosive soil, weather temperature, pressure, fluids at various cor highly offshore against offersystem They the environment. resistance good in epoxy Glass-reinforced (GRE) extensively composites are matrix. piping the in used forin epoxy fiberglass example, and multiple matrices, carbon and reinforcements of hybrid use composites varieties that are composites. There matrix metal reinforced (3)(4)matrix, fiber carbon fiber-reinforced andcomposites, polymeric particulate- (5) classifiedas are they (1) of matrices, type (2)matrix, onpolymer the matrix, metal continuous fiber, into grouped whiskers.fiber, andshort also Based composites are (2)and reinforced, (3)reinforced, flake fiber-reinforced composites. Fiber-reinforced classifiedas (1) further are they phase, reinforcing particulate of the geometry the on Based of matrices. types and phase reinforcing of the geometry on the based classified “matrix.” Composites the are is called is embedded phase reinforcing the phase.” “reinforcing the which one in constituent is called One The compound. cal not of soluble formation anew do not the are result also they in chemi other; each in physical individual and phases their keep they that such in amanner combined are consisting of constituents two or more constituents. The materials Composites are 3.10 Materials for Ocean Structures for Ocean Materials The first fishing boat, fabricated in all-titanium, was launched in Japan in inwas Japan 1998.launched all-titanium, in boat,fabricated fishing first The Titanium canbehotworked, but thereactionoftitaniumwithatmospheric COMPOSITES competitive, affordable, andreplaceablematerialincomparisonwithsteel. F, andnitrogenabove 1500° F. Absorption ofthesegases 147 F, F, - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 processing methods and product development,product and methods processing composites have attractive an become of offshore the industry.management techniques advancements in recent With the lower to leads construction assessment the in cycle life important which costs, is an safety. and helps corrosion to reliability improving in resistance It also Their titanium. byreplaced expensive such copper–nickel alloys as and metals corrosion-resistant systems, sewerage and systems, towers, systems. cooling draining seawater mains, intake for used cost fire-fighting reduction. also Compositein pipes are of ones composites, made lighter with results which replaced also are pipelines metal advantage. Heavy added longevity is an new the posites, construction increased in while cost replace to steelcom piping to use retrofit High applicationsprompted in handling. layouts line for process used the hydrocarbon application in ofthe made composites are in advances Significant two past decades. the since industry gas and oil the in seen are Extensive in applicationsinstallations. offshore applications increased Hence, find they and stiffness. ductivity, strength coefficientaxial lowhigherof and expansion, thermal con such low as features suit to thermal special of customized composites are Properties of fabrication. or by method the of either manufacturing by method the easily altered of be composites can characteristics mechanical and properties Structural lines. cess suitable them for make offshore pro production and tear and wear to resistance and exclusiveare extremes under temperature to advantages of composites. resistance Good cyclic to resistance and loads situations. resistance corrosion Superior environmental corrosive and proved high-pressure under worthy alternatives are They be forms. to of offshore construction plat the in used conventional other to materials compared ratio functionality even afterfire exposure; onevitalcharacteristicisthelow smoke emission. not onlyintheirperformanceduringfire but intheirabilitytoretainasignificant of level platforms wherefiresafetyisimportant. Themainadvantage ofphenolicgratingslies modified. Inrecenttimes,phenolicgratingsarealsoseenatlarger applicationsinoffshore sions of the floor or the plant requirements, pultruded grating panels can easily be cut and of theimportantcriteriafortopsideoffshore structures. To fitany modulardimen- offshore applications. They cansustainalongerspanwithlessdeflection,whichisone that ofthecomposites,pultrudedgratingshave anedgeover themoldedgratingsin members in offshore platforms. By comparing the performance of molded gratings with of acompositecanbeasgoodthatany othermaterial,whichisusedforstructural on thetopsideofoffshore platforms. Thus, load-bearingcapacityofapultrudedproduct compared tothatofthemoldedgratings. This isanaddedadvantage tousethemfordecks higher load-bearingcapacity. Pultrudedgratingshave longerspanwithlessdeflection ers. Pultrudedproducts,duetotheirhighfiber-to-resin ratio(70:30), help inachieving means. Pultrudedstructuralprofilesprovide extremely usefuloptionstooffshore design- preshaped FRPpultrudedsections,whicharejoinedtogetherbyvarious mechanical tion. For example, pultrudedfiber-reinforced polymer(FRP)gratingisan assemblyof sectors. infrastructural and transportation, pharmaceutical, cable chemical, ladders, so on trays, in and walkways, rails, hand industrial used commonly which are or compression gratings, and molded compositetruded grids pul Worldwide suchindustries. in manufacturing process used are industries many 148 The cost advantages of composite products are much greater when they are when cost are they advantagesmuch ofThe greater composite are products exhibit strength-to-weight Composites and high diverse meet design requirements Performance ofacompositeproductmainlydependsontheprocessitsfabrica- Ocean Structures Ocean - - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials shows topside application on the of of composite offshore atypical grating installation. additives for and bonding. used resins Figure 3.7 and formation product on the depend of such composites mainly temperature service and resistance Chemical preservations. therefore extensivelysystems are recovery for used and oil in firefighting systems systems system the such more reliable. pipes under piping shocks makes GRE GRE rupture-free The effect of mains. fire rosive the from expelled pressure under effects of are water that cor pipingfor capable recovery of systems GRE preserves. the of oil are withstanding injectionlines and steam fields oil pipes highcost.pressure Established use GRE for construction Availability help of the lightweight forms reduce GRE to and modular in offshore applications. waterlines drinking and ballasts, firefighting, fluids, drilling vent offshore in for rigs system systems, used air being seawater is also lines, cooling piping GRE relatively required. are withstand to and ability buildup,highpressure fin paraf oil, crude to where resistance transportation oil in used commonly pipes are GRE 3.10.1 so on. Figure 3.6and piping shows system GRE of atopside atypical installation. dredging, mains, widely fire plants, used exploration, oil chemical in desalination, are adverse weather conditions. and and soil GREs temperatures, pressures, various suitable corrosivesystems highly for fluids offshore are at against the environment chosencomposites for are topside piping offshore applications in platforms. GRE investigated are before that properties afew conditions are important environmental adverse under resistance loads, and impact shock to and includingties resistance proper when fluids. exposed aqueous to andSmoketoxicity mechanical resistance, of composites durability the roleof for asuitable plays imparting resin important an for topsidecandidate applications, Selection down-hole others. and subsea, in tubing FIGURE 3.6 g

lass GRE piping system. piping GRE - R einfor c ed

E poxy

SC/

II

TM 149 - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 150 mat is widely used in the production of small boats and buoys. and advantage of boats production is of widelymat The major the small in used Fiberglass polyester process. manufacturing on the depends of FRP binder. strength The an epoxypolyester fiberwith or is most the glass phenolics, common The silicon. and epoxies, polyesters, typically are materials Bonding materials. reinforcing as tungsten and boron, aluminum, graphite, suchas nylon, steel, or metals carbon fibers, glass silica, composite. the to gives Composites strength consist of material reinforcing together; the are bind that of composites, whichvariety consistmaterials of reinforcing plasticas fibers buoys of and FRP. made boats one of are Small the plastic with are They (FRP). reinforced applications is for fiberglass, which is ocean material nonmetallic most prominent The 3.12 only basedontheirstrengthbut alsobasedonthedesiredperformancecriteria. note unlike otherstructures,materials foroffshore structureapplicationsareselectednot material thatisrequiredfortheservicelifeofanoffshore a variety ofthesematerialsasdiscussedabove make anengineertoselectthesuitable copper and10 other materialsexcluding aluminumandtitanium.Bronze,whichisanalloy with90 nickel–copper 400alloy, whichconstitutes66 of 65 single inlet and multiple outlets or vice versa. K-Monel alloy, which is a combination such astubes,tubesheets,andmanifolds. The term“manifold”referstoapipewith for offshore applications.Cupronickel alloy iswidelyusedforcondenser applications Cupronickel alloy, whichismixtureof69 There areothernonferrousmaterials,whichalsosuitableforoffshore construction. 3.11 FIGURE 3.7

% nickel and30 NONFERROUS METALS FIBERGLASS

Topside applications. % zinc,findsincreasingapplicationsintheoffshore industry. However, % copperisanotheralternative. The next competitorisMONEL SC/IIT % copperand30 % M nickel and32 % application. It is important to application. Itisimportantto ­ nickel, is a popular alternate nickel, isapopularalternate % copper with rest from copperwithrestfrom Ocean Structures Ocean %

Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 safety norms of the safety directorate; GRP passes such stringent fire safety norms. safety such fire passes stringent GRP directorate; safety of the norms safety Materials for Ocean Structures for Ocean Materials tempered glass without glass defect istempered one major of the concerns. However,methods. of of nonavailability sections large the that note to it is important manufacturing modified. Thisisdonebythechoiceofresinsandadoptingappropriate of glassneedstobe characteristics of mechanical a combination loads, the of variety by encountered are compression. when in used offshore Because structures a material tempered glassisoneofsuchvarieties. Tempered as promise glassshows substantial environment. For example, ofmarine the fiberglassto suit characteristics fundamental the chosento modify carefully are fiberglasscomposites manufacture to Resins used highly ­ are fiberglass manufacture to used are that resins many as necessary, are methods manufacturing upon application of High-quality heat. itas gets laminated compressive reduces exposure ultraviolet to absorption strength, rays brittleness, causes when seen continuouslyreduction is also exposed ultraviolet to rays. water Although over of water by absorption when long strength the loses immersed glass strength period; cern to the offshore the to ­ cern con lower of ratio 0.25; important fatigue strength tensile to the is an than this making cycles. fast-changing to stress cycles,jected 10 in It its fatigue reaches million strength up when heats sub characteristics, damping conditions. Fiberglass, owing its to internal of operating avariety durable under highly and free it is that is maintenance material this are wood and gasoline whose specific gravities are 0.5 and 0.7,are gravities 0.5 whose gasoline specific wood and respectively. are buoys, mostbuoyancy pipes, so deep-sea on.common The and well drill oil submarines, small Few buoyancyas applications are common materials. used havegravity that considerably aspecific Materials are that lower of water than 3.15 aboutof 1200 temperature and a kerosene flames 30-m-high about withstand to required are crafts survival that note to important Itins. is also - res is fire-retardant attains GRP what the property GRP. as them important One using GRP, manufactured for which we are They rescue operations. call industry offshore in oil used which are enclosed,righting, motor-propelled, crafts, survival self- of are for Lifeboats lifeboats. construction recommended is essentially GRP 3.14 when theloadisappliedparalleltograinswiththatof perpendiculardirection. grain orientationwithrespecttotheloadingdirection;itshows asignificantdifference important drawbacks ofwood isitssignificantchangeinstrengthcharacteristics and serious limitationsofwood as thechoiceof construction material. One of the most size, anddeteriorationofstrengthundercontinuousexposure toseawater areafew of being usedasstructuralmembers.Flammabilitycharacteristics,nonavailability inlarge pilings, docks, and similar applications. In the recent times, wooden laminates are also it is the onlymaterial used for ship building. Currently, wood isextensively usedfor One oftheoldestmaterialsusedinmarineenvironment iswood; formany years, 3.13 WOOD

GLASS-REINFORCED PLASTICS GLASS-REINFORCED BUOYANCY MATERIALS engineers and naval architects. In the marine environment, fiber environment, marine the In naval and architects. engineers ° C, as a part of the of the apart as C, flammable. flammable. materials ­materials 151 - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 low water absorption. They can easily be handled with woodworking with tools.low handled easily be can They water absorption. epoxy binder. an resin with have They with compressive ahigh strength shear and micro-balloons called spheres of glass use foams extremely diameter syntactic small most efficient The a plastic hollow in matrix. essentially spheresare dispersed glass They offshore in engineering. needs special certain to cater that buoyancy materials are foams Syntactic material. ues for matrix foam epoxy with the syntactic as resin Table 3.5 shows val material. typical matrix on the foam of depends the strength tensile The micro-balloons. as microspheres glass and material base epoxy the as shows favorableliterature composition: the with foams of syntactic characteristics more reliable. the becomes in Recent studies mining of the vibration response, and amplitude the abuoyancyas reduces operation, system. system, in the to while The by itself acts buoyancy. and of structure strength the and corrosion, from It is free advantages combine the can they structures, cement concrete reinforced to similar of (80 concrete that MPa). than used, When strength higher 3 times possess pressure bar at600 lower foams low Syntactic in results strength. particles higher density and of presence hol The micro-balloons. hollow with called particles matrix a ceramic polymer, a a metal, or by filling synthesized composite materials are foams Syntactic s 3.15.1 (2) nocompression.under and absorption dis-configuration Buoyancy materialsshouldpossesscertaindesirableproperties:(1)nowater 152 coating, neoprene, and other rubber coatings. rubber other coating, and neoprene, epoxy, tar coal anticorrosive epoxy, are coatings vinyl anticorrosive polyurethane, Most environment. ­ marine the wood in protecting in successful are coatings thick. mm Polyurethane about upapplied five of to film in a 0.25–0.5 resulting coats, are coatings Protective degradation. from prevent and materials barrier chemical a physical for as serve used Coatings protection. a corrosion also and are coatings epoxy Certain protection. for antifouling times recent the in used plastic are coatings new water temperature, in increase the with increases fouling As sea. of the nants spray, salt contami from other deterioration pollution, corrosion, all and barnacles, against surfaces protect to environment extensively are Coatings marine the in used 3.16 COATINGS yn t a ct Hardener density Resin density Microsphere density Density Young’s modulus Properties Resin Epoxy of with Syntactic Foam Properties 3.5 TABLE i c F oams 1050 kg/m 1120 kg/m 349 kg/m 640 kg/m 2.1 GPa Value Ocean Structures Ocean 3 3 3 3 common common - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials ents inthemarineenvironment. one hastobecareful in treatingconcreteifitisusedatdifferent temperature gradi - corrosion resistance,itsuffers deteriorationduringfreezingandthawing. Therefore, sels forLNGstorage. Although concreteperformscomparatively better thansteelin very high compressive and tensile strength, are the best candidates for pressure ves - to improve tensilestrengthandstability. Prestressedconcrete,which canwithstand widely usedtoconstructbarges, boats,andsoon, whichisreinforcedwithwiremesh prestressing andferrocementconcretesarealsodesirable.Ferrocementconcreteis come by reinforcing concrete with steel to form reinforced cement concrete (RCC); as thefirstchoiceformarineconstriction.Problemsoflow tensilestrengthare over Excellent compressive strength and high resistance to seawater attack make concrete environment make concreteasthemost-preferredchoiceofoffshore designers. tion. Various typesofcementthatarespeciallymanufactured tocaterthemarine Concrete is seenasastrong competitor tosteelandwidely used inmarineconstruc- 3.17 CONCRETE FIGURE 3.8 merged shown zone, as Figure 3.8. in zones: zone, different splash atmospheric in zone (tidal grouped zone),be sub and member. of length the on its can consequences, the based Corrosion, throughout is not environment uniform marine the place in takes Corrosion that environment. complex undergoes marine problems materials, the in construction most preferred one of as Concrete, the of processes. a number physical deterioration chemical and exposed action of seawater to are simultaneous directly, the which in results tures - struc Ocean environment. marine the in is a subject of especially major concern, durability strength, from corrosive under apart environment; are structures Marine 3.18 CONCRETE IN THE MARINE ENVIRONMENT Corrosion zones on a concrete pile in the marine environment. marine the in pile onaconcrete zones Corrosion SC/IITM Atmospheric Submerged Tidal zone zone zone 153 - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 concentrations ofcarbondioxidepresentin seawater. This is alsoacceleratedinthe cement paste duetothecarbonicacidattack. Loss ofmaterial is associated with the of uncombinedcalciumhydroxide after curing. cement usuallyoutperformsthe referenceconcrete. This is duetothelower presence In seawater, well-cured concretecontaininglarge amountsofslagorpozzolonain corrosion asadeterioratedprocessshouldbeaddressedvery carefully. strength ordegrades fromitsfunctionalpurposeforwhichitisdesigned. Therefore, to lossofdesiredthicknessinthemembers. The memberalsosubstantiallylosesits corrosion resultsinlossofmetal(materialfromthe surface). This willlead Control methodsare generally cathodic protection or some coatings. As seenabove, corrosion rateofhalfthatthesplashzone,whichisabout25millsperyear. methods prevalent arecoatingsoradditionalcladding. The submerged zonehasthe This ismainlyduetoalternatewettinganddryingcausedbysplashwaves. Control The corrosionrateinthesplashzoneisabout55millsperyear, whichisvery high. coatings are generally epoxy-based resins or chlorinated rubber vinyl or zinc sulfate. retard thecorrosionrateinatmosphericzone,arethroughexternal coatings. These 0.025 mm(about25 microns). Control methods,whichare generally employed to sion rateis5–10 mills per year;one mill is about (1/1000)th of an inch, which is about and oxygencontent. The atmosphericzoneistheuppermostlayer, whosecorro- the splashandtidalzoneswherealternate wetting anddryingresultin high chloride ture contentlimitthecorrosionrateabove hightide.Corrosionismostsevere within water level islimitedbylow oxygenavailability. Conversely, lower chlorideandmois- zone dependsonthewave heightsandvariations intides. The corrosionratebelow the wetting anddryingwaves, dependingonthewave actions. The extension ofthesplash tidal zonevaries between0and15m. The splashzoneischaracterizedbyrandomly in thetidalzonearemostlywetwithalimitedaccessofoxygen. The extension ofthe ized byperiodicalwettinganddrying,possiblefreeze–thaw actions. The surfaces concrete, high moisture content, and oxygen availability. The tidal zone is character include highchlorideconcentrationlevels fromtheseawater, wet/drycycling ofthe are especiallypronetocorrosionofreinforcingsteeldueavariety ofreasons. These waves. Reinforcedconcretestructuresthatarepartiallyorfullysubmerged inseawater of theconcretestructureinthiszoneisrandomlyexposed tosprayfrombreaking limited bytheextent ofsprayfrombreakingwaves above thesplashzone. The surface crete structureinthiszoneisrandomlyexposed toseawater. The atmosphericzoneis the extent ofsplashfrombreakingwaves above thetidalzone. The surface ofthecon- is exposed toseawater inacyclic mannerinthis zone. The splashzoneislimitedby zone islimitedbytheextent ofthetidalactions. The surface oftheconcretestructure structure iscontinuouslyandconstantlyexposed toseawater inthiszone. The tidal 154 of whitedepositsMg(OH) ter, ithasbeenseenthatmagnesiumionattackiswellestablishedbythepresence From long-termstudiesofPortlandcementmortarandconcrete exposed toseawa - d 3.18.1 There isapotentiallossofconcrete massbyleachingaway calciumfromhydrated The submerged zoneisbelow thesurface ofthewater. The surface ofthe­ e t eriora t ion

of C 2 , alsocalledbruciteandmagnesiumsilicatehydrate. on c re t e Ocean Structures Ocean concrete concrete - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4

age duetocorrosion. This isseenhigheron thesurface ofcoastalstructures. case studies reported by researchers show that chloride profiles indicate greater dam- The majordeteriorationisobserved inthesampleshaving greater thaumisite.Several derived fromdeterioratedconcrete,whichisexposed toseawater foralongertime. The presenceofthaumasite,hydrocalumite, andaragoniteisreportedincement pastes

chemical reactionsexplain thedeterioration ofconcreteinseawater: carbonate) is responsible for deterioration of concrete in seawater. The following bonate), hydrocalumite (calciumcarboaluminate hydrate), andaragonite(calcium presence ofdissolved carbondioxide.Presenceofthaumasite(calciumsilicocar

Materials for Ocean Structures for Ocean Materials ↓SO 2. 4. 3. 5. 1.

Mg Action of Magnesium chloride CaCl Action of chloride calcium [Coating] [Leaching] Soluble Precipitate gypsum Action of secondary Ca(OH) Action of carbon-di-oxide: Mg Action of Magnesium sulphate MgCl MgSO Ettringite CaSO ↓ 2+ 2+ →Ca →Ca 2 [Expansion] [Coating] Gypsum [Leaching] Soluble Precipitate Solid secondary

+C 4 +C 2 + CO + 2 4 Precipitate [Coating] Calcite Aragonite +Ca(OH) + Ca(OH) CaCO 2+ 3 2+ A +10H substitution substitution 2 +H 3 A +32 H 2 →CaSO Ettringite Thaumasite C Chloro aluminate Chloro 2 O →CaCO 2 2 →CaCl O →C ↓

2 O →C 4 ↓ ↓ + Mg(OH) + ↓

3 2 +2H + Mg(OH) + 3 ↓ A.3CaSO 2 O 3 3 A.3CaSO A.CaCl 3 .CaSO 4 .32 H .32 2 .10H 4 4 .32H .CaSiO CO 2 2 O 2 2 O 2 2 O 3 + SiO + 3 .15H 2 2 O 155 - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 retrofitted with galvanic cathodicprotection. nical factors. Figure 3.9 shows atypicalspillway, whichiscorrodedbut subsequently quality ofmaterials,poorconstruction,corrosioninrebar, andothertech- tion ofconcreteinthemarineenvironment aredesignandconstructiondefects,poor presence ofaggressive elements presentinseawater. Otherreasonsfordeteriora- Environmental factors arisefromexposure conditions,temperature,humidity, and frost anddeicingsalts.Chemicalprocessarisesfromacid,sulfate, andalkaliattacks. logical processes.Physical processincludescracking,abrasion,andattackcausedby ing cement.Deteriorationofconcreteismainlyduetophysical, chemical,andbio- of seawater fairly well.However, blastfurnacecementcannotbealways thegovern- shown that blast furnace slag cement, especially when well cured, resists the action of freelime,reducingpermeability, andprotectingthereinforcement.Studieshave addition ofpozzolonacanimprove thedurability ofconcretebyremoving apart effective incontrollingthemigrationofchloride ionsisstilldebatable.Calculated of theordinaryPortlandcement.However, the issue ofwhichtypecementismost Sulfate-resisting cementsuffers lesschemicaldecompositioninseawater thanthat s 3.18.2 156 FIGURE 3.9 following the in sequence: advocated are methods repair inspection, successful After growth. extent of marine components, (3)exposed metal conditions of (4) foundation, and the by observing (1) are They struction. (2) conditions of inspection, cracking visual the by observing of con concrete failure by the of assess which methods one can avariety are There i 3.18.3 nspe ele Corroded spillway. Corroded ct ct ion ion

of M C e t emen hods t SC/IIT M Ocean Structures Ocean - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 testing (NDT), as applicable to marine structures, are discussed in Chapter 5. Chapter in discussed are structures, applicable as marine to (NDT), testing (4)(3) and Nondestructive method, measurement. pulse potential galvanized half-cell (1) are They (2) environment. test, adhesion tester, hammer portable Schmidt marine Various deployed are conditions the field of in situ concrete the in methods assess to which results in the development Concrete the which in results macrocracks. and of micro- may be volume, changes and shrinks concrete it As pores. dries, and network of capillaries for cement of hydration, water. bleeding action leaves in required results that This a water:cementworkable, its to ratio. limiting water is added More water, than added if it cement.and making For sand, aggregates, fine aggregates, ofcomposes coarse Figure 3.11ronment. shows of concrete. Concrete composition the characteristics and envi marine the of in concrete performance the affect will possibilities of This pores. photograph ofconcrete,whichverifies thisstatement. showsand permeable.Figure 3.10 a5000-timescannedelectronmicroscope(SEM) able towithstandany worst environment. However, thefact isthatconcreteporous already imperviousand has enoughstrength, itisbelieved that concrete should be of concreteusedinthemarineenvironment. As itiscommonlyfeltthatconcrete Crystalline techniqueisoneoftheinterestingandrecentadvancements inprotection concrete isattempted,itimportanttounderstandthelevel ofstrengthdegradation. help toenhancestructuralintegrity ofdeterioratedmembers.Beforeprotection of crete. Suchtreatmentswillonlyprotectconcreteinasuperficial manner but donot able coatingsorvapor barriercoatingsareappliedonthesurface ofdegraded con- a deterioratedconditiontobasic acceptable level. Different typesofvapor perme- ment. This isacosmetictypeofrepaircarriedouttoimprove theserviceabilityfrom principal structure. Alternatively, many practicingengineersattemptedsurface treat- rehabilitation ofmarinestructurescanbeeven higherthanthatofthecost is abetteralternative but asexpensive asconstructinganew structure. Therefore, members, especiallyintheseaenvironment. Replacementofconcrete,course, in different capacities,allover theworld toimprove theperformanceofconcrete using different chemical components has also been attempted by various engineers crete isimportantwhilecarryingouttherepairofoceanstructures.Sealingcracks the marineenvironment, concretealsodeteriorates.Removal ofdeterioratedcon- Concrete isoneofthepromisingconstructionmaterialsforoffshore structures.In 3.19 Materials for Ocean Structures for Ocean Materials In reality, as concrete is not a homogeneous impervious material, there are alot of are there reality, is not material, ahomogeneous concrete In as impervious • • • • • Restoration of structures treatment Surface Replacement of concrete of cracks Sealing Removal concrete of deteriorated • Desalination • Realkalization • • PROTECTING CONCRETE Vapor coatings barrier Vapor coatings permeable 157 - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 158 Figure 3.13 shows the formation of macrocracks by structural, thermal, drying, and and drying, thermal, Figure 3.13 by shows structural, of formation macrocracks the aggregates. around by by induced loads or by caused stresses shrinkage further are of 0.01 size 1 to 0.1 less than which are 100 to microcracks, result in also It can μ ofrange 70–400 μ 100 from 3000 to varies cracks of the to from μ voids10,000 scales of entrapped the 1000 size vary figure, the path. primary this problems through cause durability and concrete into penetrate residue the of essentially water-filledare spaces. aggressiveand other Water ions can voids of of concrete. Capillary deterioration degree role the in ferent their and sizes shows sizes. Figure 3.12 scale on of several different pores dif permeable and the FIGURE 3.11 FIGURE 3.10 Concrete may be permeable on several different size scales as well. as from on scales several seen size As may permeable different Concrete be Composition and characteristics of concrete. characteristics and Composition SEM photograph of concrete. photograph SEM μ m. If you look at the entrained air, it can vary from 70 to 400 μm. 70 to 400 μm. from vary it air, can you If m. entrained look atthe m are responsible for making concrete permeable. Microcracks Microcracks permeable. responsible concrete m are for making SC/IITM SC/IITM m, whereas that of the entrained air is in the the is in air entrained of the that whereas m, μ m. Capillary pores pores Capillary m. Ocean Structures Ocean m. The size size The m. - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials capillary voids. Concrete is a good performing material, which is widely for preferred material, voids. is performing agood Concrete capillary these in ity problems. when For water example, is entrained corrode reinforcements ment, it enables aggressive causing durabil concrete, serious into ions penetrate to environ sea content the or from moisture the water from attracting voids started are capillary this water-filledWhen residue the spaces. originally of essentially the are voids Capillary permeable. it and porous make concrete present in pores Capillary 3.19.1 ingression of due the to aggressive chemicals. structures Figure 3.14 whereas plastic shrinkage, shows of on marine concrete deterioration the FIGURE 3.13 FIGURE 3.12 C rys t Formation of macrocracks. Formation performance. on influence their and Pores Entrapp alline Ca Entraine Micro pillar Crac T ed crack y po k d air e void c re hnology SC/IIT 1000–10,000 μm M 100–3000 μm <0.1–100 μm 70–400 μm 0.01–1 μm 159 - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 160 FIGURE 3.15 Figure 3.17rial. without crystallization. and of shows with concrete comparison the mate crystalline of the that and adhesive concrete the chemical present in the between reaction result the is of chemical This closed. completelypermanently and are lier filled were that present ear pores capillary structure, crystalline permanent offormation this Figure 3.16. in seen as structure, sage the develop to they of Due time, acrystalline into “crystallization.” initiate to reactive chemicals crystalline hydration the with react by-products concrete. These of fresh of cement tracts capillary the into precipitates of concrete. Figure 3.15 showsstructure by-products the of cement hydration, which pore the in fixed which formation, is permanently nonsoluble in results crystalline cium hydroxide hydration of by-products, the cement. process other This and during Areactive cal with component when concrete reacts to it prepared. isis being added which ingredient, it nor that is an note neither to acoating It is important impervious. make theit up fill and to voids concrete in mixed be to which is particle, a fine is material technology, problem. concrete ments in Crystalline this which addresses advance is technology one recent of the Crystalline structures. of ocean construction 3.14FIGURE Crystalline formation sticks onto the pores of permanently.- sticks pores formation pas concrete onto With the the Crystalline SC/IIT

Deterioration due to the ingression of chemicals. ingression the due to Deterioration By-products filling capillary tracts. capillary By-products filling M SC/IIT M SC/IIT Ocean Structures Ocean M - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials ing from − from ing rang variations thermal significant sustain can treatment crystalline with Concrete contact. 11 3to 12 2to from periodic of and in contact pHcals ranging constant in chemi to resistant highly also and hydrostatic high pressure capable of withstanding layer. or amembrane acoating than concrete. It is It therefore the is better within it as is or damaged punctured be cannot formation Crystalline impervious. truly concrete making of chemical, formation permanent the with up filled gradually are FIGURE 3.17 FIGURE 3.16 checks carried out are permeability, chemical resistance, crack sealing, compressive sealing, crack resistance, permeability, chemical out are carried checks Common environment. marine behavior the in its performance accept to tested be should concrete issues. Crystalline important very are concrete tics of crystalline - oxygen in ultraviolet characteris variation and light, Performance concentration. (a) Crystalline treatment ensures permeability; pores and voids and pores concrete present in permeability; ensures treatment Crystalline 32 ° F to 265F to Comparison of crystalline concrete: (a) concrete: before; (b) of crystalline after. Comparison Crystalline formation. Crystalline ° F. Crystalline-treated concrete is not affected by humidity, is not affected concrete F. Crystalline-treated (b ) 161 - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 surface temperature must above be 33 temperature surface cold overnight. In weather, surface the the soak to hot weather, it may necessary be In condition treatment. apply to adamp should this in be surface the and saturated, must thoroughly foreign be other surface matter. and oil Concrete from it free make to thoroughly should cleaned be coated, be to which needs surface, substrate. Concrete the into transfer such chemical admit readily will themselves. surface pore open Any solution the in of lower of equalize diffuse them both readily densitywhich until can of have concrete. Coatings preparation concentration, the high during concrete green out surface. on concrete carried mon problem treatments most with chemical of the any volatile which compounds, is a com do organic not products contain Crystalline it as is nontoxic product” “green fumes. not as does produce and is termed concrete Crystalline parallel. in maintenance periodic proper with is ensured this structures; sion by advantage for initiation aboutwhich double is agreat marine time, of this showed for concrete codes severetional adelay corro the exposure. in Crystalline cover aconcrete with - of such 70 cover by high interna mm; many is recommended of years construction 40 approximately after conditions, is corrosion initiated normal rebar. the embedded Under in initiation delay corrosion the is asignificant in there of showed aprotective that with coating. also Studies compared that concrete line out by Iwate University, Tokyo, of crystal Japan, show performance satisfactory the carried tests durability. durability Results chemical of the freeze–thaw and strength, 162 the original metal, which results in aloss which component in of results of or system. the function metal, original the from anew less produces desirable and material Corrosion process refers metals. to of refers wood, plastics, but also degradation to generally and concrete, term This environment. the with interaction by chemical ofCorrosion is material deterioration 3.20 ment is significantly reduced, as the service life of the structure is enhanced. lifethe structure of service the as mentreduced, is significantly invest initial as maintenance the to member. cost added Construction astructural as compressive the of concrete increases strength It also cracking. shrinkage the reduces and member. impermeable the concrete therefore It throughout and makes concrete the throughout distribution auniform batch plant ensures atthe admixture crystalline for so on. used Adding and slump commonly control, rapidwhich are hardening, by design. It weight is compatible admixtures, mix other the with of in cement used itself. of dosage is about 1 batching rate The time atthe concrete in mixed directly be can admixture The form. available readymade the which is in commercially ture, admix Alternatively, an as applied be voids the can structure. in concrete of this the happens formation up before crystalline not does get the dried surface the that ensure should done for be atleast couple cold of hot and days is weather. to both under This h of application. Curing 3–4 after formation crystalline coating, initiates cement and the It controls hardens evaporation, and treatment. cures of this performance proper for water with of is necessary Moist coating or using gun. ahopper curing painting Subsequently, of that to mixture. by by applied similar be it this either a brush can formed consistency the slurry of ensure to the thoroughly water by volume stirred and of of powder of ataratio 2parts to 5parts is mixed material Crystalline treatment. Crystalline treatment can be done either by coating or by mixing the product in the the in product the done either be by or by can coating mixing treatment Crystalline CORROSION ° F for at least 24 h before start applying this applying this F for hbefore atleast 24 start Ocean Structures Ocean % - - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials cally bonded,theanode is positively charged and the cathodeisnegatively charged. between theanodeandcathode. When boththeanodeandcathodeareelectri a measurabledirectcurrent(DC)voltage, which can bereadinthemetallicpath medium. electrolyte an and acathode, components: anode, an basic is three shown cell corrosion Figure 3.18. basic in needs cell corrosion The of product The is corrosion “rust,” common steel surface. The which on the is formed FIGURE 3.19 FIGURE 3.18 are continuouslyexposed toseawater; (2)oxygentoactivate theprocess,whichis (1) a medium to move, which is water in case of ocean structures as the members ions areinvolved. For corrosion totake place,three basic requirementsare necessary: corrosion occursattheanodeandnotcathode detrimental effect on theanodeknown as“corrosion.” Itisimportanttonotethat returns fromthecathodetoanodethroughanelectricalpath. This flow hasa from theanodeandispicked upatthecathodethroughelectrolyte.Current Conventional currentflows frompositive tonegative, andthus,currentdischarges Electron flow Therewill be during acorrosionprocess isshown in Figure 3.19.

Electron flow during the corrosion process. corrosion the flow during Electron A basic corrosion cell. A basic corrosion 2M Corrosion Ele Ca Ano 2M th ctr Me od de 2 onegative + tal + e Me 4e 1 tallic conn − Ele Ele curr ctrica ctr Cu Ele Ele en SC/IIT on flowinmeta rr ctr t ct ent flow re ec l ro oly Corrosion action tion chemical M O te 2 + 2H El 2 l . ec O Ca Corrosionisaprocessinwhich Me trop + th 4e tal od ositiv An − e 2 od SC/IIT e 4OH e − M 163 - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 formed onthemetalsurface. bimetallic couple(galvanic couple),or, asinthecaseofrustingsteel,they maybe in acorrosionprocessmaybeontwo different metalsconnectedtogetherforminga may reactagain orcouldbeprotective oftheoriginalmetal. The anodeandcathode to starttheprocess.Corrosionprocessresultsinformationofanew material,which present inabundance; and(3)ametal,whichshouldbewillingtogive upelectrons 164 FIGURE 3.20 is product corrosion ferrous atwhich the rate the to is related atmosphere marine of the steel rate in region. corrosion The for this in corrosion candidate vulnerable region; soffit this the deck placethe most in slab is of takes condensation process and salt, precipitated generally It present. contains are modules deck and where derrick is ata lower film probability. barrier water. thin of or washing Hence, the leaching with contact direct not in are members the of fact due that corrosion rate the mum to mini zone the experiences This located. are modules deck and zone where derricks atmospheric top offshore zone is the platform. an The place in takes corrosion the shows figure regionsdifferent The at which marked. zones corrosion different with shows offshore removed platformbe atypical Figure 3.20 by or spalling. leaching with less tendencyof a film to helpmation. They atighter, produce to barrier denser for film barrier of the structure the by altering resistance corrosion their enhances low nickel, the of and in presence copper even alloy quantities steel, The small in impossible. becomes sion soluble, film becomes of formation aprotective the barrier Whenproducts the corro one of of rust. of film or washed isproduct leached from atwhich corrosion aferrous rate the to is related environment marine the steel in extent,large is governed by oxygen the content of seawater. of rate corrosion The offshore the industry. in a to of Corrosion, construction basicSteel is the material 3.20.1 Atmospheric sea exposure is sea alwaysAtmospheric topside of the top portion present on the C orrosion Offshore jacket platform with various corrosion zones. corrosion various with jacket platform Offshore Do co Corrosion

Hot risers in F fa rr wnhole ouling tig S osion t ue eel A Spla Immerse tmospheri Mu zone sh zone dline d c Ocean Structures Ocean - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials form aprotective coatingautomatically, and thatprotectsthemembers in thisregion. films, oncethey areformedinthisregion, arerelatively undisturbed. Therefore,they below themudlinebecauseof lower availability ofdissolved oxygen content.Barrier compared totheremainingpart andgetcorroded. The corrosion ratereduceswell sulfur compoundinthevicinity ofthemudline.Duetothis,they becomeanodic presence of marine organisms, which can generate additional concentration cells and in thevicinityofmudline,but furtherdown, itisvery less. This isduetothe gradient in seawater with the increase in water depth. The corrosion rate may go up velocity. Kindlynotethatrateofcorrosionisnotdeterminedbythetemperature organisms. The corrosion rate is not influenced by the seawater temperature and tidal cipally governed bytherateofdiffusion ofoxygenthroughlayersrustandmarine reduced duetothedecreaseinoxygenconcentration.Inthis zone,corrosionisprin- below. immersed regions, which the are in growth of marine or formation aeration zone automatically. by differential is caused tidal the the This in the members enablesto protection sufficient cathodic This environment. sea the in areas this zone in which is tidal cathode, which is the submerged to anode, surface, flowsthe current from zone. The tidal the present in members the faster than rode may get growth cor less and oxygen anodic they become and content surface, on the covered are oxygen-shielding with example, that members marine the like organisms oxygen severely. therefore, and it content anodic, is less gets corroded becomes For adjacent where the the submerged surface corrodes, member of the part anodic the seawater, only As aerated cathodic. therefore highly with becomes contact and is in zone a tidal in region. Steeloxygen surface this present in currents cell concentration seawater.regions, in which is continuously immersed other of the that than higher several region as times is seen this of in corrosion rate fast. very Therefore, process corrosion the activates electrolyte of the presence an the cathodic; other the and anodic becomes member of the couple. part One bimetallic legs) development regions the different in of resulting corrosion, through passes of a (say, member same member. of the the that note to It is interesting part e.g., jacket continuous of immersion the that than splash greater sion zone is several this times in oxygen of presence of abundant of the region.corro rate because The content this in automatically.be off leached is aggravated theywill This may be formed, films rust continuously. drying and wetting Even zone is alternate subjected to the though this as dry become to zonehave this splashlittle in opportunity the a zone. Rust films in be corrosion washed this awayexpedites will evenimmediately; if film, formed, barrier force, of continuous to contact Due seawater thin lateral ahigher with area. tidal the in corrosion pitting It in results sea. the in variations of tidal because ing impossible. is film offormation aprotective barrier soluble, becomes be Whenproducts the corrosion oneof off.washed of can the film this is aleast possibility that zone, of there case atmospheric activated. In be can process corrosion the or be then off leached off,washed can film barrier this ity that member, top of the the is apossibil aby-product as there If process. corrosion of the on created being is film rust.protective A barrier or film or washedleached off from In theimmersedzonewherejackets andmudlinesarepresent,corrosionis protective of action of the because aminimum zone, reaches corrosion tidal the In Severe splash dry the zone due and continuous to in wetting is corrosion seen 165 - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 parison with 24 with parison 4 less to than drops 1800 temperature the m, than ofa water greater depth little amountofcorrosion. line below, nospecial methods ofcorrosionprotectionareadvocated asthereisa sacrificial anodetechniqueorcathodicprotectionmethodsareemployed. In themud is recommendedasacorrosionprotectionmeasure.Incaseoftheimmersionzone, zone, special methods such as providing extra steel, Monel wrapping or sheathing splash spheric andtidalzonescanbeprotectedbypainting.For thosepresentinthe corrosion protection,themajorityofmembersplatformpresentin atmo in current velocity increases the rate of corrosion. Considering different methods of current velocity playsanimportantroleinacceleratingthecorrosionrate;increase tion becomesthinnerandiseasilybroken underhighercurrentvelocity. Therefore, on members.However, whentheplatformmotionislarger, thebarrierlayerforma- any gentlemotionwillnotaffect ordisturbtheformationofprotective barrier Considering the effect of current velocity on the corrosion rate, it is understood that 166 from one part of the reinforcement of (anode) (cathode). the one part part from another to of Because this flowspassive Corrosion current process. corrosion the layer initiates is broken. This by ingression, this steel surface reach apassive chlorides is in concrete. If in state Steel easily understood: be can RCC in faster. structures mechanism corrosion The areas other to but spreads not corroding does stop from areas of damaged Patching RCC in whenever ofaccelerated members chloride. source is exposure the to there is rate corrosion by life The years. 20 its service reduce bycaused can corrosion weakening Structural RCC most in cause of serious is the deterioration structures. assist preventive corrosion plan to can activity corrosion Chloride-induced measures. corrosion of of detection the concrete. Early delamination and spalling, cracking, in results of vicinity steel the in sufficient forcement. of in quantities chloride Presence steel to rein protection it provides nature, barrier in rosion. is alkaline concrete As cor against of protection degree ahigh steel, has embedded whichConcrete, has 3.20.2 mon candidates of such problems.mon candidates com are lines which mooring is a long-line line, mooring of effect. Galvanized the length segments along the different of in corrosion rate the alters This concentration. layers is different subjected to oxygen long lines of varied of length mooring attack, “long-line oxygen is called effect.” typical dueThis the to concentration Mainly cell level local is corrosion set atthe cathodic, mooring. of length the along the becoming line mooring of the ferent problem. part to of zones Due face acritical corrosion, which extend lines, dif to Mooring decrease. to tend also fouling with associated pitting and Fouling decreases. temperature the as water depth atgreater decreases by contents. oxygen Corrosion different layers differentiated various salinity are and layers not homogeneous; Ocean are concentration. surface the with comparison in is significant belowoxygen raise again but 820 rises This m. depth along the drops biofouling relatively below are of marine Dissolvedsurfaces m. 700 free Metal rate. The effect of water depth on the corrosion rate is also an interesting viewpoint. At interesting an is also effect rate corrosion of onThe the water depth Various factors influencethecorrosionrateofsteelmembersinoffshore ­ C orrosion ° C at the surface. This results in substantial reduction in the corrosion corrosion the reduction in substantial in results This surface. C atthe

in C on c re t e Ocean Structures Ocean ° structures. C in com C in ------Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials accelerates corrosion. for ingression and chloride exposes areas more steel contact further concrete. This of delamination and spalling, cracking, result in volume. will of its normal This of that times expand 4–5 steel can Corroded stresses. encountered the withstanding steel develops oxide which state, is not capable atendency revert to its to of natural reinforcing result, As a rust. andproduces flow, anode current the at corrodes steel in abundance. in of oxygenisnotadvisableinthe openenvironment because ofthepresenceoxygen presence the of reduce oxygen can Removalsulfites environment. sea the content in corrosion. Removal achieved be strong-reducing by can agents. adding For example, Removal process. corrosion activateto the of oxygen of rate the help can retard to control corrosion. Oxygen componentsment, one required can is one main of the corrosive Bysteel is alloyed the conditioning environ nickel with chromium. and alloy.a corrosion-resistant which ordinary steel in Aclassical example is stainless Alternatively, produce environment. to sea the to metal alloy the also threat one can but aserious pose rate corrosion help the also reduce can ametal Coating used. also are greases oxide; and oil, enamel, plastics, such resins, coatings as paints, organic aluminum with coated be of can amember surface Forapplied. example, metal the be also itself can surface metal the derived Aprotective from coating surface. ing coat external coating. It an on applied steel as is generally or tin zinc in mon case com is the surface metal existing coat to an Using metal method. another anode sacrificial is called prevented. be This can structure of members existing the on the member,additional the corrosion By allow it and member sacrificing corrode. to additional an create corrosion, reduce actually to sion that, corrosion. It with means prevention any corrosion is fight to behind method corro or protection aim principle The reaction. cathodic or the anodic either the by retarding reduced be can corrosion of corrosion;with (5) rate (6) The and metal; metal. by by the the alloying coating which reaction, is responsibleelectrochemical for corrosion; (4) by corrosion fighting (2) surface; metal the corrosive by (3) the conditioning environment; the by controlling ways different are prevented: by be There which can corrosion (1) by conditioning 3.21 protective oxideover film rebar. natural of formation the initiate to concrete place in takes rebar. Realkalization through concrete into alkali draw paste, alkali-rich in solution. embedded nodes, Surface Electrolyte covering isdoneby spraying cellulous fiber, saturatedin sodium carbonate 7days. 3to from of vary application period can steel reinforcement. The and concrete of surface low-voltage on the anodes sustained ing temporary the between current involves of- pass technique of electrochemical steel reinforcement. Realkalization an losswhich in results of passive corrosion rebar. to the accelerates protection It also lower with concrete alkalinity, carbonated dioxideIngression of creates carbon which provides passive alkalinity, steel. to inherent protection has Fresh concrete r 3.20.3 CORROSION PREVENTION ealkaliza t ion 167 - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 commonly deployedcommonly splash the zone, is copper–nickel in alloy of either 70 which is also material, alternative Another stiffness. of weldability increased and degree high splash applications advantages the of zone. are in these The members of over the surface wrapped the be steel, can stainless alloy of chromium–nickel an Alternatively, which steel 304, is material. of the surface stainless austenitic parent may the even off from sheathing off or tear the peel is a tendency that There thin. too However, is sheathing forces the or impact as it by is tearing likely get to damaged process. installation by caused conditions, this stress which are the under damaged ormember by not get welding. modulus of high will elasticity has and Monel-400 parent on the is Moneldone splash either by the the zone. sheathing bonding in This gauge member (approximately thick 18 1.02 to tubular the to equal mm) is attached severe, one can use Monel-400 or other metal cladding. Monel-400, an alloy of splash is very rate the corrosion zone, where the In members. the protect to coatings use can zone is One one where high. is corrosion not severe, very but marginally corrosion. Atmospheric from offshore protect to structures methods many are There 3.22 168 mon methods of corrosion protection in the marine environment. In principle, it In environment. marine the in of protection corrosion mon methods one com of and the important is an protection Cathodic metal. inside the current or cathodic is done by anodic passing an technique This for process. corrosion the types ofcorrosioninhibitors. sion andsplashzones. Anodic inhibitorsaremorepopularamongallofthese three Corrosion inhibitorsarecommonlydeployed indeepwater platformsintheimmer the member;they physically blockthesurface fromthecorrosive environment. ple. Adsorption-type corrosioninhibitorsgenerallyformafilmonthesurface of at anodes. They suppressthecathodicreactionsthat occuronabimetalliccou- the rateofcorrosion. Anodic inhibitorsinterferewiththereaction thattakes place corrosive aqueousenvironment, interfereswiththechemicalreactionandreduces members ofoceanstructures. These arechemicaladditives, whenaddedtothe and mixed. Corrosioninhibitorsareotheralternatives forcorrosionprotectionof rosion. Corrosioninhibitorsareofdifferent types:anodic, cathodic,adsorption, zone. splash the in measures of protection corrosion Table 3.6 showssheathing. summary the Monel of the that with comparison in which is high 13 mm, 5to from varies ally usu Thickness material. more or less homogeneous parent of the that action with in becomes strongly very and material parent the to Itwhen adheres it is hardened. strength abuse. tearing high It very has mechanical and corrosion to resistant highly It members. is the to which is braced sheathing, elastomericSplashtron rubber is an zone. products, whichcanbeusedasasheathinglayeronthemembersnearsplash of two varieties the are rubber neoprene large. very Splashtron vulcanized be and can variations regions, temperature where the Arctic the application in is more common loads. This impact against improve resistance and members their the to stiffness and strength add also They thickness. plates of steel wear use 6–13 mm also can One 90 even Another effective method is to control the electrochemical reaction responsible reaction effective electrochemical is control to Another the method Use ofcorrosioninhibitorsisalsoonetheeffective methodsofreducingcor % CORROSION PROTECTION –10 composition. This adds stiffness to the members during installation. installation. during members the to stiffness adds % composition. This Ocean Structures Ocean % –30 or % or - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials 1 Corrosion Protection in the Splash Zone Splash in the Protection Corrosion 3.6 TABLE FIGURE 3.21 shows figure The surface. on ametal reactions cathodic viewmatic and of anodic shows asche Figure 3.21 measure. of protection corrosion suitable kind for this condition is not drying and wetting zones; splash atmospheric alternate the and in applied be water, in hence cannot and soil or immersed in geous for buried members advanta- is This the electrolyte. as acts and chemicals of sulfites impurities with seawateras in case of offshore structures condition fulfilled is automatically This electrolyte. bulk the with contact is in that surface any metallic to applied be can 2 3 4 5 6 7 Monel alloy 400sheathing Austenitic stainlesssteeltype Cu–Ni alloy of70/30and90/10 Steel wearplates Rubber Splashtron Vulcanized neoprene stainless steel 304(18 Cr, 8NI)chrome–nickel composition Materials Cathodic and anodic reactions on the metal surface. metal onthe reactions anodic and Cathodic Ano dic reaction +2e Fe 2+ ee Me Normally, Monelalloy 400of18guage(1.02mm) These materialsarealsowrappedinthesplashzone, This gives adequatespaceforinstalling. These areusedwithathicknessontheorderof6–13mm An elastomerrubbersheathingmaterialcalledsplashtron Normally usedassheathingmaterial. Normally usedinlayersofprotection. rigidity forfieldinstallation. impact. Ithasahighmodulusofelasticity, whichgives light gauge, Monelsheathingisvulnerabletotearingon zone eitherbybondingorwelding.Becauseofits thickness isattachedtotubular membersinthesplash and stiffness toqualitythemfromsheathing. which gives necessarycorrosionresistance,weldability, high-velocity silt-ladenwater. structure fromanticipatederosionduetoiceor geater impactresistance. They areusedtoprotectthe in ordertoaddstiffness andstrength,therebyproviding Neoprene of5–13mmthicknessisused. section. Itishighlyresistanttomechanicalabuse. is generallyusedtosendblastedleg andbracing ta Ca l tho −2e dic reaction H + H 2 Uses 169 - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 from the anode to the pipeline through earth or water, electrolyte bulk which is the earth through pipeline the to anode the from flows current pipe. remote the to The connected externally are a steel pipeline. Anodes zone. immersion the of in members protection corrosion as is used This structures. RCC and ocean storage tanks metallic to applied commonly and protection cathodic of the that to similar are Connections surface. cathodic onto the anode external an from power current low DC the external impress to dissolution an use They anodes. systems employ current or Impressed either zero metal. on the current impressed the proves method anodes;therefore,be this to expensive. sometimes, morehence sacrificial say and for more current example, of structure, demands coatings, deterioration the resistivity the flow in A electrolyte. of changethe electrical on depends of electrons surveys. voltage. Amonitor system in sensitive variation is highly small The record to system agalvanic monitoring for under effective difficult is very protection corrosion output available current is relatively the is that disadvantages Therefore, main small. the One of float-out. Moreover, structures. with neighboring interaction has less this available effective is highly on protection immediately power. and source Localized Big blockscaneitherbeboltedorweldedtothestructure. in theformofrods,bigblocks,orwiresthatcanbewounded aroundthemembers. monly usedassacrificialanodesarealuminum,zinc,andmagnesium. They areused termed assacrificialanodetechniqueofcathodicprotection.Metalsthatarecom- tion.” As anew metal, whichisprovided, actsasananodethatcorrodes,thisisalso cathodic, isprotectedasitnegatively charged. This istermedas“cathodic protec- which resultsincorrosionofanode. Thus, thewholesurface ofsteelwhichisnow in thepresenceofelectrolyte. The currentflows fromtheanodetoparentmetal, the electrochemicalseries,willmake thenew materialanodic;corrosionisinitiated between theanodeandparentsteel,asindicatedbytheirrespective positionsin member isintroducedtoactasagalvanic anodedeliberately. The potentialdifference the steelsurface, whichistobeprotected,shouldmadeasacathode. An additional directly connectedtothemetal,whichisbeprotected. Therefore, thememberor powerDC metal. on the source couple agalvanic forms well; as external alternatively, an from is impressed current It two between metals. difference is aresult potential of the current where the anode, which is provided, may agalvanic metal, be external The current. DC electric an to when reaction connected achemical release in to electrons is ready Anode anode. as is connected metal external an whereas cathode, as is connected protected be to and Metal method. (2)technique, anode current impressed by sacrificial as termed is sacrificed. anode case, this in metal; couple parent the with bimetallic of forming which is capable anode, as member, parent onethe should material provide another To protection. cathodic name the hence protect is protection, part cathodic but the is continuously negative. becomes corroded, and electron part anodic Therefore, the positive, the receives reaction becomes tion releases and electron cathodic whereas - reac electrolyte. of Anodic couple presence bulk the in offormation bimetallic the 170 Figure 3.22 for applied as shows method, current aschematic view impressed of the is by protection passing cathodic use by also method which one can alternate An no external requires and system it is advantageous as simple isThis very install to The galvanic anodesystemsemploy reactive metalsasauxiliaryanodesthatare achieved be two ways: in can protection Cathodic (1) by using anodes, galvanic Ocean Structures Ocean Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 requires no external power advantages. no it external source, one main of is considered be to the requires robust systems. are it As and install to easy systems platforms.ity Galvanic of are the for Sea of Mexico major North Gulf or the the in techniques protection galvanic use prefer offshore to high, is very engineers maintenance cost in of the coating Because is found platforms cost-effective. very be to uncoated large against method protection galvanic the Sea, North largely is very the tection deployed In times. recent the in examples pro common where cathodic are subseaoffshore structures and platforms foundation piles. and Floating jacket joints in structures, tubular structures, harbor and jetties of of base ships, hull storage pipelines, tanks, are Examples protection. cathodic by protected are structures of ocean surfaces Exterior structures. stage of ocean system. of protection kind this in important is very or monitoring nance elements feasible. in highly members is also mainte Regular structural the between available interaction it for As surfaces, is uniformly protection larger structures. other with interaction the minimize to ­example, intensive should taken an be care However, members. system. of some the demerits For structural are the in there it is capable of providing aflexiblerespective changes output, mayit accommodate of electrolytes. As most types in voltages used be provide driving can DC and high It is able feasible mechanism. to is highly current mechanism trol by the impressing of effective systems, galvanic that with an of con monitoring comparison in current environment. sea the present in get chemicals washed off due or leached the to or splash atmospheric example, zone have the in members atendency for to coatings For damaged. being coating of this probability is high there and coated, surface are that members to applied is commonly protection tiveness Cathodic treatment. of the effec - the index which measure to is the terminals, cathodic and anodic the between of flow electronic amount the record can One circuit. aDC possible by maintaining is its effectiveness treatments offorms anticorrosion monitor to continuously. is This over protection advantages of cathodic other main of One the process. activateto the electrolyte of contact bulk the requires method this medium; the in immersed fully is effective method are only members when This the it cathodic, is protected. remains it is as laid; location pipeline where atthe (medium). the is passed current Impressed FIGURE 3.22 Materials for Ocean Structures for Ocean Materials Cathodic protection is a common phenomenon that is implemented in the design phenomenon the is implemented is acommon in protection that Cathodic few has supply it method As merits. can current relatively impressed The alarger Impressed current method of cathodic protection. of cathodic method current Impressed Po St sitive currentfromtheano ee l pip e throug Ele h ea ctr − rt ons Ano h orwate + de (usuallyremotefrompi de tothepipe r wa Ground or ter le line ve l pe ) 171 - - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 for generatingtherequiredDCpower forimpressedcurrent. areas, power sourceincludethermoelectricgeneratorsandsolarorwind supply; alternatively, onecanuseeitherdiesel-orgas-driven alternators.Inremote ensured byusingrectifiersoftransformerunitsinconjunctionwithan existing AC source ofDCpower, which isvitalincaseoftheimpressedcurrentmethod,canbe and securedconnectionbetweentheanodes,conductors,power source. The source andelectricallywithawell-insulatedsystemtoensureminimumresistance anodes connectedtogetherofteninabackfill.Italsorequiresan external DCpower ensured. An impressed current system requires inert anodes, which are cluster of with aminimumresistancebetweentheconductorandstructureistobealso tively, aconductorcanalsoconnecttheanodetostructure. A securedconnection requires asacrificialanode,whichshouldbedirectweldedtothestructure;alterna- members thatareincontactwithbulk electrolyte.Inaddition,agalvanic system completely of be it not, corrosion; rate if can controlto the prevented. method most preferred is the protection cathodic temperature, water differential under of or coolant continuous uses circulation that industry rosion aprocess In protection. of cor method of this candidates common also are of storage oil large tanks surface inner ships. The in tanks ballast and pipelines of diameter large surface internal the protect to used is also protection Cathodic is instantaneous. of protection corrosion Moreover, method this on float-out it providesthe immediately structure; protection of 172 approach of supporting the deck on a new set of piles, although the dockyard was on deck anew dockyard the set of the piles, although approach of supporting involved times recent the in a new outdockyard on the carried Figure 3.23). Repair Pennsylvania,(see, shown as of dockyard, in ship of for repair example, details the These typesofstructurescannot bedismantledorreconstructedbut onlybe repaired. ability under critical load combinations encountered by them are a very prescriptive tofunctionalfailure. Insuchcases,specialissues relatedtotheirsurviv- ties. Moreover, the repair of ocean structures is not preventive in general but only limited period; constraints may arise from the weather window or functional priori- is becausethedowntime available forrepairofoceanstructuresisgenerallya speedy constructionandattainthedesired strength attheearliestpossibletime. This important ­ although they areundertheinfluenceof various environmental loads,whichisan mental loadsduringrepair. This means that oceanstructures need toundergo repair, routine. Furthermore,they cannotberelieved off fromtheencounteredenviron- of oceanstructuresisrequiredtobecarriedoutwithout affecting theirfunctional Repair specific tothetypeofchosenstructuralsystem,asdiscussed inChapter2. structures are­ ­limitation, theforemostisthatmaterialchoiceforrepaircasespecific.Ocean and ­ ommendation of international codes. These codes only suggest repair procedures Materials forrepairandrehabilitationofoceanstructuresarenotundertherec- 3.23 The cathodicprotectionsystemhascertainrequirements. This canbeappliedto There are instances where an extensive repair needs to be carried out water under carried be to extensive where an needs instances repair are There desirable characteristicsofmaterialsforrepair. Among several reasonsforthis MATERIALS FOR REPAIR AND REHABILITATION challenge. The characteristicsofamaterialchosenforrepairshouldenable constructed foravariety offunctionalrequirements,whicharevery Ocean Structures Ocean ­critical issue. - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials installed to replace the deficient piles on the front end (Figure 3.25). From the abovethe deficient (Figure 3.25). frontFrom replace to the end the piles on installed piles was showedPower anew Philadelphia, that set of steel auxiliary Corporation, Exelon out in works carried repair of fender the systems. state-of-art Details with equipped also are bulkheads concrete using prestress new boardwalks constructed (Figure 3.24). Jetty of capacity Designed the ferry-handling the enhancing in resulted May, Cape in Jetty New Jersey, berthing May Cape of Ferry the Repair service. in FIGURE 3.24 FIGURE 3.23

Upgradation of Cape May, of Cape Upgradation New Jersey. Ship dockyard, Pennsylvania. SC/IITM SC/IITM 173 Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 174 situation; enough timeisnotavailable fordetailedstudies andverification. Hence, cesses become more complicated as they are generally requested only on an emergency practice inmany oftheoceanstructurescommissioned aroundtheworld, repairpro- cannot beintervened forrepairfrequently. As preventive maintenanceisnotausual be evaluated under an economic perspective, but foravalid reason that ocean structures effective and(2)long-termsolutionisdemanded.It notbecausesuchrepairsneedto during repair. Other factors areasfollows: (1)therepairprocessshouldalsobecost- of time for carrying out repair, and (2) to minimize the damage on existing structures minimize theshutdown timeofthestructureduringrepair duetolimitedavailability tures. Specializedmethodsandequipmentaregenerallyused fortwo reasons:(1)to capacity shouldnotbechallengedwhenrepairsarebeing attempted onoceanstruc- that thestructurehastoremaininserviceduringrepair. Therefore, theload-carrying steel members,underwater photography/video, andmarineborerassessment. ment, side-scansonarimaging,instrumentstomeasurethe ultrasonicthicknessof before andafterrepair. These equipmentstudiesincludehydrographic survey equip- repairs. Italsorequiresstate-of-artelectronicsystemstomap underwater conditions set ofspecializedequipment,chemicals,andconstructionexpertise tocarryoutsuch tures, ocean structures need to be repaired in the hostile environment. It requires a analysis.” Repairofoceanstructuresisfullchallenges.Unlike land-basedstruc- on whichrepairmethodologyissuggested,thenthestudytermedas“integrity of theproposedrepairwork. Ifalltheabove factors areincludedinthestudybased (3) costfactor, (4)shutdown timeoftheservicestructure,and(5)feasibility lished: (1)existing strength ofthestructure,(2)magnitudeproposedrepair, to be fulfilled. factors, namely, required the Both serviceability, are and deteriorated. strength are that of materials performance forments but degraded compensate should the also ity. design existing require on the is not chosen based for repair Hence, material - capac load-carrying enhanced and characteristics on functional demand update the due to procedure is astate-of-art structures of ocean examples, repair it that is clear FIGURE 3.25 Repair of ocean structures also poses a set of unique challenges; the foremost is Repair of ocean structures also poses a set of unique challenges; the foremost is Before the actual repair can be carried out, the following factors need to be estab- Schematic view of steel auxiliary piles, replacing damaged piles. damaged replacing piles, view auxiliary of steel Schematic SC/IITM Ocean Structures Ocean - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials generally usedforrepairsarecasespecific. international codes. This isduetothefact thatvarious chemicaladmixturesthatare generally prescribed in the standard literature and are not generally recommended by ment arethecommonmethodsusedduringrepairprocess.Repairprocessesnot imaging equipment.Underwater videography, photography, andmarineborerassess- ocean structures. They includehydrographic survey equipmentsitescanners,andsonar They alsorequirestate-of-artelectronicsystemstomapunderwater conditionsofthe ment, chemicals,andconstructionexpertise tocarryouttherepairofoceanstructures. structures mostlyhave lessorremoteaccesstoland. They requirespecializedequip- land-based structures, ocean structures need to be repaired inthehostile condition as ologies andchemicalsavailable tocarryoutrepaironemergency situation.Unlike offshore engineersshouldhave athoroughunderstandingofvarious repairmethod- FIGURE 3.26 material specificationand even incorrectchoiceofmaterialamountsclosetoabouthalf It isseenfromthefigurethatmajor factor thatcauses failure arises from improper structures ingeneralbut notspecifictothe failure ofoceanstructures(Gettu,2015). 3.27shows thecausesfor failureofconcrete influences tothemaximum.Figure percentage (Gettu,2015).Itisseenfromthefigurethatpresenceof external chlorides that influencedeteriorationofconcretealongwiththeirsignificance, expressedin shows agraphicalrepresentationofvarioussteel reinforcement.Figure 3.26 factors degradation ofrebarin reinforced concretestructures,whichisduetocorrosionof that occurinthemarineenvironment. Lossofstrengthismainlyassociatedwith of damageconcrete.Concretestructuresdeteriorateduetochemicalreactions reinforced concretestructuresinparticular, itisimperative tounderstand theprocess Before reviewing different methodsofrepairconcretestructuresingeneraland 3.24 REPAIR OFCONCRETE STRUCTURES Chemical attack Factors for deterioration of concrete. forFactors deterioration 4% Abra Ex te sion/erosion 10% rnal c 33% hloride Alkali agg s 9 % Inbuilt chloride regate 5% Infre Carb 7% quen Fr 17% s onation ee z t ing/tha 10% Shrinkage and set tlemen wing 5% t 175 Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 176 reaction are as follows: in the first step, the release of alkali from cement during of dolomiticlimestoneaggregates withalkaline material. The steps involved inthe of bondstrengthanddevelops microcracking;this is theconsequenceofreaction shows thedamageofcolumns andbeamsofaportstructure. of gelleaves thecracksinopencondition,thisfurtherdeteriorates concrete. Figure 3.28 all poresarefilledwith water, further expansion causescracking. Although dehydration aggregates toform“silicategel,” whichabsorbswater andfurtherexpands. Although hydroxides ofsodiumandpotassiumthatarepresentincement. They reactwithsilica reasons fordeteriorationofconcrete. Alkali–silica reactionoccursinthepresenceof the cementingeffect inconcrete;further, alkali–silicareactionisoneoftheimportant is formedfromthereaction,replacescalciumionswiththose ofmagnesium.Itdestroys attack bymagnesiumsulfate ismore damagingbecausemagnesiumhydroxide, which humid weatherconditions,whichinturninitiatessevere corrosioninsteel.Inaddition, rosive marineenvironment. This furtheradmitsthepenetrationofchlorides underthe volume but initiated from the surface. Once initiated, concrete is exposed to a cor compounds toform“ettringite,” whichresultsinexpansion ofconcreteinmanifold hydroxide toformacompoundcalled“gypsum.” Gypsum,inturn,reactswithhydrated corrosion. causes and concrete rebar-embedded with reacts concrete. It further the ingression of the aggressive facilitate agents also into of and concrete strength the well. as on Extensive its surface and core could decrease concrete leaching within a white powder, forms This dioxide which carbonate. calcium form is to deposited Dissolved reactions. chemical under hydroxideconcrete calcium carbon with reacts problems serious considered be to for of are deterioration attack sulfate and Leaching d 3.24.1 of concrete structures,ingeneral. material, bothconstructionandrepair, playsamajorroleinsuccessfulfunctioning totalfactors thatinfluencethe of the failure ofconcretestructures.Hence,selection of FIGURE 3.27 Alkali–carbonate reactioninconcrete inthemarineenvironment initiatestheloss Sulfate attackdeterioratesthestrengthofconcrete.Sulfates react with calcium e t eriora Causes for failure of concrete structures. of concrete for failure Causes workmanship Po Po or qualityconcrete 7% t or ion 2% D Insufficient water ue

t o Wr C 13% hemi ong sp 26% c pro ec al ification ofing R Wr ea ct ong materialsel ion Low cover 15% 21% ec tion Ocean Structures Ocean - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 in the expulsion of liquid gel through cracks. Figure 3.29 shows thedamagedjetty expulsion ofliquidgelthroughcracks.Figure 3.29 in the tion ofalkalisilicategeltakes placeduetofurtherinhibitionofwater. This results the internalpressure,whichresultsincrackingofconcrete.Finally, liquefac of alkalisilicategelbyinhibitionwater. This causeslocalswellingandincreases highly alkalinesolution,destroys theintegrity ofaggregates. This resultsinswelling second step,theinitialhydrolysis ofsiliceous fractionofaggregate, presentinthe hydration increasestheconcentrationofhydroxide ionsintheporesolution.In FIGURE 3.29 FIGURE 3.28 Materials for Ocean Structures for Ocean Materials

Damaged concrete jetty in the marine environment. marine the in jetty concrete Damaged Damage in columns and beams due to chloride attack. chloride due to beams and columns in Damage

SC/IIT SC/IIT

M M 177 - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 178 lower water:cement ratio. which protectssteelfromdirect access.Corrosioninhibitorsprovided resistanceat compounds. They resultintheformationofaprotective ferricoxidelayeronsteel, nature ofconcrete. The mostcommonlyusedcorrosion inhibitors arenitrite-based to prevent corrosionofsteelreinforcement;protection isprovided bythe alkaline the resistancetoabrasion.Corrosion inhibitorsprovide thesecondlineofdefense by providing additionalresistancetorebar. High-strength superplasticizersimprove concerned. Corrosion-inhibitingadmixturesincreasethecorrosion thresholdofsteel setting ofconcrete,whichisnotdesirableasfar asoceanstructuralconstructionis workability whenconcretingisdone athighertemperature.Itwillresultinquick from bleeding water. Retarding and plasticizing admixtures will help to achieve rapid In thepresence of plasticizers, the toplayerof concrete willremaindenseandfree yield concretewithlow permeability, bettercontraction,andgoodqualitytoplayer. promising onstrength,plasticizershelptolimitthewater:cement ratio. This can concrete undervarious compositionsandtheirroleiscase specific. Without com- forcement embeddedinconcrete. They influence theperformancebehavior of Admixtures playanimportantroleininculcatingcorrosion resistancetotherein- r 3.24.2 attack inconcrete,asthisinitiatesaseriesoffailure, followed inorder. attack. Exposureofsteelreinforcementisthemostseriousconsequence­ shows thedeteriorationoffendersjettyduetochloride roded. Figure 3.30 resulted inspallingofcover. As seeninthefigure,reinforcementis extensively cor in themarineenvironment. Duetoalkali–carbonate reaction, anexpanded concrete FIGURE 3.30 ole Damaged fender of a concrete jetty. fender of aconcrete Damaged

of De jet C ty fenders ter reinforcemen hemi Ex iorate posed st c al d A ee dmix l t t ures

in R epair SC/IIT M Ocean Structures Ocean chemical - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials rebar embedded in concrete is protected. concrete in embedded rebar the allowed whereas are corrode, to anodes ribbon All figure. the in seen as concrete to prior RCC in used beam is also anode Ribbon protection. by cathodic protected earlier, now rebar, which are they was embedded corroded the to is connected anode supplemented the reinforcement. As embedded the to anode an as which is acting supplement flowan from external node, current the is enabledprotection through cathodic figure, the in of seen As RCC rebar to shows protection beam. cathodic the Figure 3.31 therefore protected. and cathodic becomes rebar rebar, the the and anode cover. concrete in flowthe electrons supplementalis embedded between the in When that anode the through source external an from DC the uses method concrete. This It is one effective of the stop to in of corrosion reinforcement methods bar structures. major avery of forms role concrete protection protection corrosion in Cathodic 3.25.1 3.25 FIGURE 3.31 the cathode. This makes thesteelcorrodeandproducesrust.Itis important to note steel, whichbecomestheanodethroughconcreteintoanotherpart, corrosion toprogressfreely. Therefore, corrosioncurrentflows fromonepartof chlorides, thepassive layer formedonthesteelsurface isattacked. This enables tion. Embeddedsteelremainsinthepassive stateinconcrete.Inthepresenceof The electrochemicalprotectionsystems(EPS)isanadvanced methodofprotec- e 3.25.2 ADVANCED METHODS OFREPAIR C le a t ct hodi Cathodic protection to a rebar. to protection Cathodic ro c c hemi P ro c t al e ct P ion ro t e ct ion S ys t ems 179 Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 toring ­ thepossiblesolutionscouldbeawell-designedcorrosionmoni- measures. One of corrosion, therefore,isavery importantstageinplanningcorrosionprevention exposes thesteelfurtherandacceleratescorrosionprocess.Earlydetectionof ­concrete. This canresultinspallinganddelamination ofconcrete. This, inturn, that corrodedsteelcanexpand 4–5timesthatofitsnormalvolume, whichcracks 180 and ConplastP505. ticizers. Typical commercial brands available in the Asian market are Conplast P211 recommended dosagedepending onthevariety andchemicalcompositionoftheplas- cement dependingonthetype ofadmixtures.Generally, manufacturers advisethe dosageofthese admixturesisabout100–300mLperbagof concrete. A typical of can resultinsaving ofcementwithoutaffecting theworkability andthestrength concrete isrequired.Useoftheseadmixturesintheconstruction ofoceanstructures surface. Water-reducing admixturesareusedwhereimproved densityandqualityof poured intotheformwork. A few oftheadmixturescanalsobesprayedonconcrete inhibitors, arecommonly used admixtures. They are addedtogreenconcretewhen superplasticizers, retardingplasticizers,accelerators,surface retarders,andcorrosion fresh and hardened concrete. Water-reducing admixtures, also called plasticizers, market. Although they have different functions,allofthemmodifytheproperties crete. There aredifferent typesofadmixtures,whichareavailable inthecommercial Admixtures areaddedtoconcretemodifythepropertiesof freshandhardenedcon- 3.26 surface ofsteelbythesubmerging method. surface preparationisdoneusingtitaniumoxide,nanocoatingthenappliedonthe polymeric reactionstotake place,thepreparedsolutionisleftforabout6h. After it isstirredwell;whilestirring,somedropsofdistilledwater arealsoadded.For at roomtemperature. Tetra-n-butyl orthotitanate(TBT)isaddedtothesolution,and termed asnanolayered coating. Ethanol and ethyl acetoacetate are mixed together uniformity oftheappliedcoating.Itformsavery thinfilmonapplication,andhence gel, itcanbeeasilyapplied;itsadvantages aresimplicity, homogeneity, andhigh tetra-n structured coatingsareaformofgelsolution,whichpreparedusingalkoxide Nanostructured coatingsenhancesurface resistanceagainst corrosion.Nano­ n 3.25.3 electrochemical polarizationtechnique. sion ratebymeasuringthereinforcementpotentialofembeddedsteelusing current betweencarbonsteelandstainlesselectrodes.Itmeasuresthecorro- ing unitsembeddedinconcreteitself.Itdetectscorrosionbymeasuringthegalvanic part of the corrosion monitoring system. This system consists of corrosion monitor is corroded.Earlydetectionofchloridecontaminationconcretealsoanintegral -butyl orthotitanate (also named as TNT). As the coating is in the form of a system. This ­ ADMIXTURES FOR REPAIR anolayered provides informationwithrespecttotherateatwhichrebar C oa t ings Ocean Structures Ocean - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials are usedassuperplasticizersformarinestructuralsystems. brands available inthe Asian market areConplastSP337andconplastSP430,which dosageisabout200–500mLperbagofcement. A typical A few ofthecommercial penetration, whichisvery importanttoprotectthereinforcementfromcorrosion. of flow anddrypacking.Itresultsinlow porosityandimproved resistance to water cohesion betweentheaggregates. They aidpumpingofconcrete byreducingfriction in reinforcementdenseshuttering.However, they alsoimprove theworkability and superplasticizers areaddedtoconcrete. They improve thecompactionofconcrete To enableeasycompactionofconcreteintheheavily reinforcedprecastelements, and (3)repetitive sizeofmembersthatmakes constructioneasyandwellorganized. tory cast,(2)speedyconstructionasthereisnodelaytimeforcastingandcuring, are mostlypreferredduetomany reasons:(1)goodqualitycontrolasthey arefac- major roleinoffshore constructionasthey areusedinlarge scale.Precastmembers used inprecastconstructionofoffshore structures.Precastelementsplayavery Higher rangeofwater-reducing admixtures,alsocalledsuperplasticizers,are s 3.26.1 of concretestructures in oceanenvironment. Accelerators are essentially required Accelerators and surface retarderscanbealso usedasadmixtures in theconstruction a 3.26.4 bag of per cement. 10 mL agent from varies 200 to air-entraining dosage ofmal this is Conplast market available PA21(S). Asian the in product A commercially nor The (GBS)example, of case gravity-based jetties. structures in seawalls, platforms, and for massive requirement foundation; for a fundamental as gates. It may required be agents improve cohesiveness aggre Air-entraining harsh with structures. ocean for outcome which of is an low-permeable important is also concrete, structures, coastal and marine salt in to improved of concrete. The resistance low permeability ensure concrete, fresh to admixtures agents, as when added ability. Air-entraining it as improved service structures forLow-permeable is preferred ocean concrete a 3.26.3 is Conplast market RP264. Asian the in plasticizers available of retarding brands commercially and used commonly ofcement. One the bag of per is about concrete, 10–300 mL fresh to added plasticizers, of retarding dosage usual The of offshore piles in structures. construction the in useful are They “cold as joints.” termed are delayed offshore activities in engineering construction delayed the of placement. time Such during green help remain to and concrete time setting the retard admixtures These states. by weathersea windowcontrolled and the it problem is delayed. as common isconcrete is offshore avery in construction This when placing state of afresh in concrete retain to used are plasticizers Retarding r 3.26.2 uperplas e cc ir t - arding elera E n t raining t t ors P i c izers las

and A t i c gen S izers urfa ts c e R e t arders 181 - - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 of cement. Conplast-SR, whichisaretarder. The recommendeddosageisabout1–2Lperbag products available inthe Asian market areConplast-NC,whichisanaccelerator, and allow enoughmoisturetobeavailable forconcretetohave afreshfinish.Commercial wind inopenseacanbecontrolledusingthesekindsofretarders. Therefore, they the concretefinishin facedown ofprecastmembers. Accelerateddryingdueto form theintendedfunction.Surface retarders,whenaddedtoconcrete,canimprove earlier thanthescheduledtime,whichensurespreparednessofstructuretoper they reducethetimeof hardeningofconcrete.Concreteattainsthedesiredstrength of construction. Accelerators areadmixtures;whenaddedtothequickrepairprocess, repairs. One hastotherefore undertake the repairofsuch structures ina quick mode example, jettiesusedbynaval bases,have very lessshutdown timeavailable for ing aquickrepaironoceanstructures.Coastalstructuresofstrategic importance,for to beusedinconcreteplaceitcoldweather. They arealsorequiredwhenattempt- window varies unsuitablyfortheconstructionprocess,thenacceleratorsarerequired weather window varies drastically. During the constructionprocess,ifweather for concreteplacedincoldweather. As weallknow, intheocean­ 182 jetties. They also aid placing of concrete in underwater construction very fast. Commercial compact concrete.Generally, they areusedinnarrow formwork, forexample, inrepairof hyper plasticizersare addedtofreshconcrete.Itisaninevitable admixtureincase ofself- Pumping of large volume of concrete can therefore becomes essential; to aid pumping, batching plantscannotbelocated asclosetotheconstructionsiteofoffshore structures. ­compressive strength andimprove workability. They aid pumpingofconcretebecause Hyper plasticizersareadmixturesusedinfreshconcrete toachieve highearly h 3.26.7 bag ofcement. construction. The usualdosageofsprayedconcrete acceleratorsisabout23Lper sprayset HBLisacommercialproductavailable andcommonlyusedinmarine time. This is a very useful admixture for underwater applications. For example, Sprayed concreteaccelerators,whenaddedtofreshconcrete, acceleratethesetting Shotcrete andGunitearehighlycommonintherepair ofmarinestructures. s 3.26.6 bag ofcement. Conplast X4211Cand WP90, WP112. The usualdosageisabout125–200mLper of concreteandminimizeshrinkagecracks.Commercialproductsavailable are concrete and protect therebarfromcorrosion. They also improve theworkability rosion ofreinforcement;waterproofing compoundsreducethepermeabilityof protect itfromthepenetrationofwater. Continuousmoisturewillinitiatethecor Integral waterproofing compoundsareaddedasadmixturestofreshconcrete i 3.26.5 n prayed yper t egral P C las W on t a i c t c izers erproofing re t e A cc elera C ompounds t ors Ocean Structures Ocean environment, the - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials 270 mL per square meter area of application. area meter square per 270 mL to 200 from varies dosageadmixtures ofusual surface 90. The LP and WB Concrete for are, example, market available Asian products the in advantageous. Commercial be can compounds of is curing exposed, slabs concrete of where area a large jetties for concrete of effective in case deck moisture In the curing. retain it will surface, the aspray As onto applied treatment. surface as used are compounds Curing structures. of concrete finish exposed improve to surface the required serviceability. are They and capacity out improve to load-carrying the carried are They shore structures. of off integrity the for maintaining important equally also are treatments Surface 3.26.8 ommended dosagebythemanufacture isabout0.25–1.5Lperbagofcement. products ofhyper plasticizersare,forexample, Structro-100 andStructro-485. The rec- rary patchingis donerapidlyasitisessential toplugtheconcretesegments from under lateralloadsoroperation oftheequipment.Insuchspecialrepairs,tempo- restricted onnewly placedmaterials ormembersundergoing excessive vibration such specialrepairsistoaccess suchkindofrepairs.Suchrepairsaregenerally from theparentmember. This istermedas“spalling.” The problem associatedwith in external pressureonthecover ofconcrete, whichmakes thecover towitheroff essential factor. In the splash zone, when rebar corrodes, it expands. This results to asevere corrosive environment; presence of salt and continuous moisture is the Spalling ofconcreteisavery commonprobleminmarinestructuresasitisexposed 3.27 available products foranchorgrouts. equipment. For example, Lokfix andConbextra EUWare afew ofthecommercially are specificallyusedincase ofrockbed anchors, fenders,andfixingof any marine resin-based grouts aremoreeffective. Polyesterresin-based chemical anchor grouts of concrete.Incasetheoccurrencewherechemicalspillage mayoccur, epoxy preferred forinjectiongroutingofrepairswheretherearenarrow gaps onthesurface span oftime.Epoxy-basedresinsareusedasinjectedgrouts. They aregenerally that these kinds of admixtures ensure rapid setting to attain strength within shorter have highstrengthasanchorgroutsaresubjectedtoaxialpull.Itisalsorequired material inanarrow holeavailable fortheboltsbecomesdifficult. They shouldalso the liquidorplasticstate. They shouldnotbeasolidmaterialascompactionofgrout acteristics similartothoseofshrinkage-compensatedadmixturesandareavailable in bounding withconcrete,whichisbeingrepaired.Inaddition,they shouldhave char should becementitious. This isduetothefact thatcementitious productshave agood be nonshrinking;(2)they shouldbefreeflowing; and(3)preferablythematerial The essentialrequirementsofanchorsandgroutsareasfollows: (1) They should Anchors areanintegral partofany mooringsystem,provided inocean structures. g 3.26.9 SPECIAL REPAIRS OFCONCRETE MEMBERS C uring rou ts C

and ompounds A n c hors 183 - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 characteristic. Itshouldalsobewaterproof. material shouldenablecracksealingcompletelyandhave arapidsetting and (6)they shouldbe cementitious materials,preferably. Inaddition,thechosen (4) they shouldbenonshrinking compounds;(5)they shouldhave highstrength; available inaprepacked mode; (3)they shouldremainasanti-washout materials; repair areasfollows: (1) They shouldbelightinweightgrade;(2)they arereadily as itwas earlier. A few importantrequirementsforspecialmaterialsusedsuch are originallydesigned. After repair, structuralmembershouldremainfunctional have thesame(oreven higher, ifpossible)load-carryingcapacityforwhichthey structures isnotacosmetictaskbut afunctionaltask.Repairedmembers needto tious material.Itisimportanttounderstandthattherepairattemptedinocean repair shouldhave highergradeofconcreteandshouldbepreferablyacementi- grade ofconcreterecommendedforoceanstructuresisM45. A materialchosenfor grade ofconcreteusedinthemarineenvironment isgenerallyvery high. The basic chosen. The chosen materials should have a proper structural grade as the parent porary patching.” Materialstocarryoutsuchspecialrepairsarebecarefully part ofthestructureisrepairedinasmallpossibletime;thistermedas“tem- avoided inthenearfuture. Therefore, theemergency reinstatementofthedamaged eliminate suchminorirregularities, sothatmajorrepairsofthestructurecanbe undergoing furtherdamage; blow holesarealsofilledinparallel.Itisrequiredto 184 erosion. Figure 3.32 erosion shows case. coastal atypical coastal the from hinterland the essentially protect to coastline of length the along the constructed are cyclone embankments and activities. Saline unforeseen which are for connectivity of saving establish case flood people also in embankments saline addition, ingression. In by tidal seriously the affected are sector coastal of the imity prox near in cultivable located are lands Many locations where agricultural India. of peninsular problem is common a very coastline along the This coastlines. the objectivealong paddy fields, is prevent ingression to adjoining into tidal located the embankment “saline as is termed such embankment embankment; trapping uplanddams. of seawalls andrevetments. Itcanalsoresultfromtheconstructionofsediment- works neartheshorearea,andalso duetohardeningofshorelinesbyconstruction tection structuressuchasgroinsandjetties,construction ofriverwater regulatory entrance, ­ cal changes. Various anthropogenicreasonsareasfollows: dredgingatthetidal ­seabed compaction, and due to instantaneous sea-level rise becauseof geographi- slope deteriorationalongthecoastalline,vertical movements that arisedueto and wind,new-shore current,tidalandstorm,catastrophicevents suchastsunami, and anthropogenicreasons. Various naturalcausesareasfollows: actionofwaves structures. Coastalstructuresaresubjectedtosevere erosionduetonaturalcauses understand thevarious reasonsforstrengthandfunctionaldegradation ofcoastal Prior totheselectionofmaterialsforrepaircoastalstructures,itisimportant 3.28 The primary solution erosion for problem of coastal an the is construction primary The PROTECTION OFCOASTAL EMBANKMENT construction ofharborinthenearshorearea, ofotherpro- Ocean Structures Ocean . ” The primary primary The - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 tics of the site govern the design of embankment and material selection. It istics site of material the and govern common design of the embankment - solution. geological characteris effective such critical not cases, In an technical and which is providedwooden improve to poles are embankment, of slope the stability Alternatively, embankment. Figure 3.33, in seen coastal as temporary the protect to FIGURE 3.33 FIGURE 3.32 Materials for Ocean Structures for Ocean Materials As seen from the figure, a heap of sandbags are placed along the embankment alongthe embankment are placed aheap of figure, sandbags the from seen As Temporary arrangement to improve to slope stability. arrangement Temporary A typical coastal erosion case. coastal A typical SC/IIT M 185 Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 to maintain the slope the stability. shows Figure 3.35 maintain to aschematic view Geotube of the gabionunits boxeswith stones.Gabbionarmour filled boxestogethertied with are effective very wave dissipating are they in construction, speedy by energy using enabling from Apart strength. tensile high durable with are and environment marine cost-effective are have noncorrosive and Geotubes in long life. remain They service 3.34 shows embankment. of section cross a geotube atypical problems. Figure sion high. is very rate applicable.as effective not Conventional be will for sandbagging sites ero where the regulations coastal appropriate selection the meet should also Material embankment. aflexiblerigid rubble-moundsystemof a systeminstead warrants pressure suchas low avery instability. has result in it Excessive slope will gradient, embankment pore constructed the If soil column. the layer, in pressure pore impervious high creating an as acts soil embankment complication. retardant the to which The adds potential, groundwater with enriched such also and regions are of gypsum, enrichment with 7 such sitesthat have clay, content arich of montmorillonite about from which varies 186 FIGURE 3.35 FIGURE 3.34 to 21 % to Geotube embankment is an alternative solution alternative such is an site-specific address to embankment Geotube La nd side % . Soil has a very high moisture content. Porehighly moisture corrosive fluid high avery is . Soil has Geotube embankment with layers with of gabion boxes. embankment Geotube Cross section of geotube embankment. of geotube section Cross SC/IITM Ocean Structures Ocean Se a side - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials Figure 3.36 shows anembankmentconstructedwithgeosynthetictubes. SoilTain tubesaregeotubesmanufactured byHUESKERSyntheticGmbH,Germany. SoilTain tubesareonesuchcommonapplication beingwidelyusedinpractice. and current.Geosynthetictubesareusedasartificialdunes,reefs,dyes,orgroins. of aconventional that with rubble-mound embankment. embankment geotube layered gabion with embankment, boxes. Table 3.7 of comparison shows atechnical FIGURE 3.36 Geotechnical considerations Inspection andmaintenance Time of construction Eco-friendliness Design adaptability Risk ofsoilerosionto Suitability ofsitewithhigh Description Comparison of Geotube and Rubble-Mound Embankments TABLE 3.7 adjacent unprotectedarea pore pressure Geosynthetic tubesareusedasbreakwaters toprevent soilbeingerodedbywaves

Embankment with geosynthetic tubes. geosynthetic with Embankment SC/IITM Suitable formud-slidingsoil Easy toinspectandcarryout Comparatively faster Remain noncorrosive inthe Most suitableduetoextensive Minimizes theriskasitdissipates Suitable asitisaflexible system periodic repair marine environment flexibility offered bygeotubes the wave energy effectively Geotube Embankment Not suitableforsuchsites No effective proceduresare Comparatively slower Remain noncorrosive inthe Rubble-mound designisstiff No suchmechanismisinplace No asthesystemisrigid Rubble-Mound Embankment devised andpracticed marine environment 187 Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 188 interesting tonotethatinsuch situations,itisnotpossibletorefuse/constrainthe ity withrespecttothenew crane ofdoublethecapacityexisting ones.Itis members isusedintheanalytical modelforcheckingtheload-carryingcapac- NDT anddestructive testsaswell.Deducedstrength ofthereinforcedconcrete Assessment oftheinsitustrengthreinforcedconcrete membersisdonethrough as appliedtostructuralassessmentandfailure analysisofamarinestructure. classical examples, whichintegrated experimental andanalyticalinvestigations jetty withthematerialcharacteristicsofinsitucondition. This isoneofthe enhanced capacity. The study demands adetailedmathematicalmodelingofthe of thedeckiscarriedoutasadditionalloadsareexpected fromthecranewith dynamic) analysisofajetty. Assessment forenhancingloadcarryingcapacity In thissection,wewilldiscussacasestudythatnecessitated adetailedstatic(and 3.29 spoil. dredge and it slurry convenient the makes dispose process and escapes; handle to this water inside and is captured Slurry material. volumereduction in dredging of the sludge. of asignificant the in results drainage This which execute gravimetric the geo-textiles, of special made are tubes These for material. clear-offtimes dredged 3.37, recent the in used are dewatering tubes shown As of Figure dredgers. in capacity problems handling and disposal dredge the addresses This disposal. FIGURE 3.37 Dewatering of dredged material is necessary for its effective compact is necessary and material ofDewatering dredged LOAD-CARRYING CAPACITY: STUDY CASE STRUCTURAL FOR ASSESSMENT ENHANCING OFAJETTY Dewatering tubes for clearing dredged material. dredged for clearing tubes Dewatering

SC/IIT

M Ocean Structures Ocean Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials e 3.29.1 concrete panelsaremodeledusingafinite-elementsoftware. the originalstrength.Existingreinforcementdetailsofbeamandreinforced of view. No conventional repairscanenhancethestrengtheven ifitcouldrestore enhanced loadcapacityofthejettyasthisisanobligation fromastrategic point the NDT/destructive testsonvarious concretemembersofthejetty. Inadditionto exceedance levels areseenintheanalysisnotvicinityofcrane rails. detailed insightofstressexceedance nodes.Itisseenthatthenodeswhere thestress slab isgoverned predominantly bybendingandnotshear. shows a Figure 3.40 is not a governing criterion for the current problem under investigation as the deck closer to principal stresses. Shear stress yield criterion, shown by Tresca stresses, Mises stressvalues, indicatingtheyieldcriterionfordeck slab,alsoshow values bution of these stresses as the structure has very high degree of indeterminacy. von slab resultingfromtorsion.However, itisseenthatthereapossibilityofredistri- ners aremorethanthepermissiblevalues duetotheuplifting ofcornersthedeck destructive testsshows 20–27MPa; theseareusedintheanalysis.Stressesatcor is computedbasedontheequivalent cubestrengthofRCC samplesobtainedfrom in thedeckplatearewithinpermissiblelimits. The actualinsitustrengththat analytical studies. shows theresultsof in themembersandconclusionsaredrawn. Figure 3.39 the figure. Adetailed3Danalysisiscarriedouttoascertainthecriticalstresses details ofthestructuralmodelandcorrespondingloadingareshown in showsFigure 3.38 thedetailsofanalyticalmodelgeneratedforstudy. The a 3.29.2 for strengthrestoration. ofsufficientalkalinityintheconcrete,whichisagoodsign indicate the availability 20–27 MPa. Carbonation testrevealed thatthepenetrationofCO of thecoresamplesshowed equivalent cubecompressive strengthsintherangeof sive strengthoftheconcrete inRCCwalls isintherangeof11–48MPa. Majority concrete aregood.Resultsofthecoretestsindicatethatequivalent cubecompres- Results of the rebound hammer test indicate that the near-surface characteristics of in thecoresindicatethatintegrity ofconcretemaybeconsideredaseven “good.” the integrity ofconcreteinRCCwalls willbeconsideredas“medium.” UPVvalues conditionofthejetty. Ultrasonic pulsevelocity (UPV)valuesin situ indicatethat Detailed experimental investigations werecarriedoutonthejettytoassess are below the threshold limit of 0.6 kg/m chemical analysisofthepowder samplesinRCCwalls indicatethatchloridecontents ability ofcorrosionishighinthedeckslabandRCCwalls aswell.Results ofthe most ofthelocations.Results the half-cellpotential tests indicate thattheprob- Based ontheabove study, itisseenthat strengthassessmentisdonebasedon Based onthefailure analyses carried out, it is seenthat the maximum stresses xperimen naly t i c al t al I nves I nves t iga t iga t ions t ions 3 . pH values of the concrete powder samples 2 isnegligible in 189 - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 190 FIGURE 3.38 Details of an analytical model. analytical of an Details Ocean Structures Ocean Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials load combinations. the deckbeamdonotshow undesirable stressvalues undertheconsideredloadsand is governed predominantly bybendingandnotshear. RCCwalls, tiebeams,and criterion forthecurrentproblem underinvestigation duetothefact thatthedeckslab crane rails.Shearstressyield criterion,shown by Tresca stresses,isnotagoverning show values closertoprincipalstresses; thesenodesarenotseeninthevicinityof values. Von Misesstressvalues, indicating theyieldcriterionfordeckslab,also RCC walls. Principalstressesinthe deckatafew critical nodesexceed desirable minate. This isprobablyimposedduetotherigidconnectionof the deckwith sible values. These stresseswillgetredistributed asthestructure ishighlyindeter within thepermissiblelimits;however, stressesatcornersaremorethanthepermis- the enhanced crane capacity. Itisalsoseen that thestress levels inthe deck slabare the deadloadofstructure,wheelloadsarealsoapplied ontothecranerailsfor 3.39 FIGURE

Results of analytical studies. of analytical Results 191 - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 192 monitoring probes and sensors, and high durability anode and steel connections. connections. steel and anode durability high and sensors, and probes monitoring anodes, includeproblems. activated titanium components construction of EPS afresh such problems.addressing such It aproactive has durability address to approach found effective be to been has that in methods is one recent EPS of the ronment. envi marine the in RCC major in the of causes deterioration structures concrete is corrosion one of of Chloride-induced new protection corrosion RCC structures. valueson selected of multiple employed be also reference can EPS electrodes. for based of mode automatic adjustment controlstatic allow current an circuit of the potentio and control corrosion using current EPSs. and Constant of afull-monitoring system. monitoring It control corrosion consists and is one advanced of the Australia, control system, developed RECON The by SAVCOR steel structures. and Ltd, Group development is arecent This structures concrete of for reinforced protection cathodic e 3.30.1 structures. ocean of ­ afew repair discuss we section, the advancements in will recent this In 3.30 FIGURE 3.40 CHEMICAL ADMIXTURES REPAIR OFOCEAN STRUCTURES USING le ct Stress exceedance levels in the deck slab. levels deck the in exceedance Stress ro c hemi c al P ro t e ct No ion de859 S ys No t em de660 Ocean Structures Ocean No de959 methodologies - - Downloaded By: 10.3.98.104 At: 14:38 27 Sep 2021; For: 9781315366692, chapter3, 10.1201/9781315366692-4 Materials for Ocean Structures for Ocean Materials formed, which offers protection against corrosion of corrosion which rebar. offers against formed, protection protective (passive concrete. Anatural layer) the then is film realkalize turn which in rebars, reaches and concrete the into is drawn alkali paste, alkali-rich this in ded - embed are anodes surface As surface. covering electrolyte concrete the an as used (3–15time days). solution, carbonate is in sodium of Paste cellulous fibers, saturated of over of concrete surface period on the ashort anodes temporary rent the between low-voltage involves of passing asustained technique This electrochemical an cur of rehabilitation. is concrete one nondestructive of methods the rebar. Realkalization loss the of in passive resulting of corrosion the accelerates layer;alkalinity, also this of concrete lower acarbonated dioxide of creates rebar. to carbon tection Ingress which offers passive alkalinity, pro inherent New natural environment. has concrete most marine effective is the concrete the ofin in of concrete rehabilitation method restoration of modeling. predictive It alkalinity that deterioration and is seen tests, reaction ment of of steel, cover resistivity measure testing, rebar, to alkali–aggregate of mapping RCC, measure resistance rate corrosion and potential half-cell rebars, of testing surveys, continuity electric delamination and using visual environment marine condition the out of in the assess to concrete carried are Many studies rated. passive when this of layer concrete. Corrosion occurs nature is destroyed or perfo by corrosion from a passive protected layer, alkaline which due high is to formed RCC initially in due corrosion. to Rebars members are and of materials radation deg cause of before strength corrosion the addressing understand to It is important after the test period and the concrete is cleaned with water. with is cleaned concrete the and period test the after disconnected Cables are tested. pHreadings; levels periodically also of are concrete voltage and of by current means period test the during is monitored arrangement power. switching off the whole after The realkalized be can surface concrete the required, if period, testdensity. to unit the supply designthe current rectifier During mesh (anode)and negative to positive connected and are poles transformer of the (cathode) rebars Cables the from period. repair the during ensured iselectrolyte be to alkaline an lulousthe fiber is fiber of with sprayedwetting the mesh.regular A onto celthe and the battens meshto is fixed anode mesh. The anode the and concrete the between as spacers act which surface, concrete the to fixed Wooden are battens be sprayed surface. acellulous is use concrete to the can that ontomon fiber practice com electrolyte. The alkaline mesh and anode house to the is used Areservoir unit. rectifier cables, subsequently using red transformer whichmade extended are the to then are connections Anode which is vital. established, checked and is be to rebar the Continuity of circuit. rectifier extended a transformer to cables rebar. are the These cables color) (black by in concrete connecting the in to is installed connection Rebar (4) cover tests. reaction (5) survey, rebars, to delamination (6) and alkali–aggregate (1)of treatment: (2) inspection, (3) visual of carbonation, depth analysis, chloride nature the out ascertain to following carried the are tests realkalization, to Prior m 3.30.2 e t hodology

of R ealkaliza t ion 193 ------