6.1 corrosion and corrosion protection

7/30/2019 6.1 Corrosion and Corrosion Protection

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268 CORROSION AND CORROSION PROTECTIONBreakdown due to oxidation will increase acidity and fluidity.From the results of Table 6-3 it appears that grease 1 is the most suitableof the three types tested. This grease has the following advantages: (a) ahigher drop point, affording better adhesion to the tendon at elevated tem-peratures; (b) higher penetration for easier pumping and better void-fillingproperties; (c) lower evaporation loss, diminishing the risk of hardening; and(d) much higher oxidation stability.Useful comparative data are shown in Table 6-4, and include basic prop-erties of greases according to the recommendations of the Geotechnical Con-trol Office of the Government of Hong Kong (Brian-Boys and Howells,1984).Tendon CoatingsTendon coatings should be applied under factory conditions, either by themanufacturer, or on site in special workshops where air-drying and cleanconditions are provided.Bo nded Metal l ic Coat ings . This process includes galvanizing, zinc spray-ing, and electroplating, all producing an absorbed surface coating. Theyshould be applied only in the factory by the tendon steel manufacturer.Sacrificial metallic coatings should be confined to temporary anchorages. Acoated tendon is always liable to damage; hence special care is necessaryduring handling. They should be chosen under sufficient information andcompetent advice, since there is some reservation about the effectivenessof a thin surface film under highly stressed cyclic loading, and possible flawsin surface treatment may enhance corrosion by creation of bimetallic cells.Bi tuminou s and Meta l lic Paints . Most authorities consider these fairlyunreliable for strands owing to difficulties in obtaining uniform coating, andbecause they are also subject to damage during handling. They are suitablefor tendon protection during storage and before use.Tapes. In this group are polypropylene or grease-impregnated fabric tapes,generally considered effective for temporary anchorages. Tapes should beapplied by wrapping with minimum 50 percent laps. During wrapping contactwith the tendon should be maintained, hence the latter must be greasedbefore wrapping to exclude atmosphere and give the tendon flexibility tomove within the coating.Plast ic Sheaths . Continuous-diffusion impervious polypropylene or poly-ethylene sheaths applied under factory conditions are used for temporaryand permanent anchorages. Their minimum thickness should be 1 mm, butwith 1.5 mm nominal thickness. Plastics susceptible to ultraviolet (UV)ightare suitable, provided that carbon black or U V inhibitors are incorporatedto resist degradation. With reference to potential exposure to fire when cor-

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6-9 PROTECTIVE SY STEMS OF THE FIXED LENGTH 269rosion-promoting chlorides are released, plastic sheathing is considered safesince this hazard is extremely unlikely.

Sheaths are effective as long as the internal annular space is filled duringmanufacture with an appropriate resin, cementitious material or grease toexclude atmosphere and create an appropriate electrochemical environment.A heat-shrinkable tube with a preapplied sealant may be used, but is notconsidered acceptable as double protection system.

When close-fitting sheaths are used together with grease or a sealant, itis essential to ensure that the coating clearance around the tendon is suf-ficient so that the tendon can be stressed without frictional resistance. Ifsetting fluids are used in combination with a sheath giving substantial clear-ance, provisions should likewise be made to ensure that the tendon canextend without restrictions; thus, an additional sheath or tube can be usedto act as bond-breaker.Metal Sheaths. Light corrugated metal sheaths should not be consideredfor protection, since they can be easily perforated by corrosion. Where met-als are chosen, their electrochemical characteristics must be compatible withthe tendon metal in order to avoid induction of corrosion potentials betweendiffering metals.Sheath Joints. Bars used for tendons are not transported in rolls, and theirsections must be therefore effectively connected in situ. Sheath or coatingjoints should not interfere with the continuity of the protective system alongthe entire tendon length, with respect to physical and electrochemical ef-fects.

Reliable joints can be obtained by overlapping at least 25 mm ( 1 in),combined with liberal use of solvent glues appropriate for the sheathingmaterial. Loose sleaves should have overlaps at least 50 mm (2 in) and fiteasily over the basic coating with clearance allowing injection or extrusionof the bonding agent.

Heat-shrinkable tubing is suitable for connecting sheaths, provided thecomponents are of the same quality approved for tendon protection. Normaloverlap should be 350 mm (14 in) minimum for butt joints without solvent.Any voids at joints within the sheath should be completely filled to excludeatmosphere. Joint details should accommodate injection of cementitious ma-terial or greases and similar sealing compounds with simultaneous displace-ment of air. Excess filler must be extruded during tightening of screwedconnections or during injection of the joint voids between t h e tendons orsheath.A typical sheathed joint detail for bar tendon is shown in Fig. 6-9.6-9 PROTECTIVE SYSTEMS OF THE FIXED LENGTHThe fixed anchor length must receive the same degree of protection as thefree length. Furthermore, materials as well as their structural configurations



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270 CORROSION AND CORROSION PROTECTION

Fig. 6-9 Coupler detail in the free length of bar tendon.

must be capable of receiving and transferring tensile loads from one mediumto another and eventually to the ground, and the only mechanism availableis by bond. Accordingly, strength and deformability features must be as-certained in terms of their structural behavior. From the study of bond dis-tribution discussed in the foregoing sections, it may be assumed that stressesare gradually transmitted to the ground along the entire fixed length until atsome point or near the end the stress remaining in the tendon is practicallyzero. Where the corrosion problem is critical, it is prudent to ensure thatthe distal end of the tendon is redundant and therefore unstressed but en-closed.

The deformation or associated distortion of individual elements of thecorrosion protective system should not be allowed to reach creep stage, norexpose the steel tendon through cracking. In practice, however, both crack-ing and creep of individual components is always likely, but the correspond-ing requirements of each mode are opposite, and few materials are availablewhich can satisfy both particularly under the stress intensity involved inanchor testing and stressing.

Cement GroutThis material is invariably the agent used to transmit the fixed anchor loadto the ground. This is not a reliable electrochemical barrier, although itsalkalinity must be recognized. The minimum cover specified for this zoneshould always be provided. Cement grout is brittle and either bonds to orencases the tendon; hence it will invariably crack following extension of thetendon when preloading the anchor.Caution is necessary when using washers at suitable intervals to inducelocal compression in front of the plate, since these systems are not proofagainst cracking. In this case, the entire fixed length does not necessarilyfunction in compression. Furthermore, these devices can cause decouplingof the tendon from the grout at the washer location; otherwise the grout willbond to the tendon in such a way that the load transfer will begin at theproximal end thereby reverting the grout to tension.



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6-9 PROTECTIVE SYSTEMS OF THE FIXED LENGTH 271EPOXYCertain nonmetallic coatings, especially epoxies, exhibit physicochemicaldurabilities3 s well as strength and protective qualities that make them suit-able for corrosion protection. The coating materials included for consider-ation in this section are restricted to organic formulations, he most importantcriteria being inertness toward the constituents of cement paste and alsochloride ions, favorable creep characteristics, film integrity and protectivequalities, and bond to steel. The abrasion resistance of suitable epoxy coatingis also acceptable. However, a large variation has been observed betweenthe relative flexibilities of epoxy coatings, with the powder systems givingbetter flexibilities than the liquid ones. Polyvinyl chloride coating, for ex-ample, has excellent flexibilities even in film thickness of 35 mils. Epoxiesare tough materials and therefore should be more resistant to abuse.

The effect of coated bars on structural integrity has been favorably as-sessed by pullout and creep tests. Epoxy coated bars with average filmthickness of 5-11 mils have shown acceptable bond strengths to concrete(and by extension to grout) as measured in pullout tests. Most epoxies havealso shown acceptable creep rates, that is, comparable to those of uncoatedbars. However, polyvinyl chloride-coated bars have unacceptable bond andcreep characteristics.Epoxy and polyester resins may be substituted for cementitious grouts,but generally are more expensive. When used alone as bonding agent be-tween the tendon and the ground resins can be formulated to deform withoutcracking and are thus suitable for corrosion protection without the necessityof sheathing (this is possible with rock bolts). A comprehensive report andstudy on epoxies is given by Clifton et al. (1975), following research spon-sored by the U .S. Department of Transportation. Considering flexibility,bond strength, creep characteristics, and corrosion protection requirements,this report concluded that the optimum film thickness of epoxy coatings onsteel bars is 7 mils, with acceptable deviation of 2 mils.

When epoxy and polyester resins are used to encapsulate fixed lengthsof tendon in combination with sheaths, compatibility of elastic properties ofall components of the anchor must be considered and ensured in order toavoid decoupling of the resin from the sheath or sheath from grout whenstressed.DetailsFigure 6-10 shows a bar anchor protected by a double protective system.The tendon, in this case, is a ribbed bar. Cement grout cracks adjacent tothe ribs are calculated to be less than 0.1 mm wide. Therefore, the groutand plastic corrugated sheath provide two physical barriers to corrosion.Longitudinal cracking should be given consideration, and depends on thelateral restraint. If uncontrolled longitudinal cracking is possible, the systemreverts to single corrosion protection.



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272 CORROSION AND CORROSIONPROTECTION

,2SECTION A-A

IS- aeianl)

13

Delani 01cenlte 01 Secbion A-A SECTION a-8I Ancnof ncra core, 9 PfobectW bar cowie:2 NU1 10 Eat Ienrmn3 Anbrcotrostonaieasa b I Cmnenb.aarea

? L abd WC Dona bWdUer

Fig. 6-10 Double corrosion protection for a bar anchor.

Figure 611 shows corrosion protection for a multiwire tendon with mon-obar jacking head. The protective system in the fixed (bond) length is clas-sified as double protection if cement cracks are controlled and shown to beless than 0.1 mm wide and uncontrolled longitudinal cracking can be ex-cluded. In the free length the system is classified as single protection sincethe anticorrosive paste is not considered a physical barrier.Figure 6-12 shows double corrosion protection for the fixed (bond) lengthof strand tendon. If, however, the grout within the corrugated sheath iscement-based, the tendon bond length protection reverts to a single system.Nonstressed elements of the tendon, that is, the threaded length of barsprotruding beyond the nuts, should always be enclosed within the protectedsystem. In instances where protection is not specified, cement grout coverover the fixed length may be considered adequate for temporary anchorsonly, and on the explicit understanding that more detailed protection is notnecessary.

Corrugated DuctsIn addition to protection, the plastic sheath forming the primary element ofprotection must also transmit stresses from the filler to the external groutwithout displacement, distortion, or distress. Effective shear transfer is ac-complished if the sheaths are corrugated. Established guidelines specify acorrugation pitch 6-12 times the sheath wall thickness, and corrugation am-plitude not less than three times the wall thickness, which should be 1 mmminimum. Duct materials must be impervious, and common types are pol-ypropylene, polyethylene and plastic. Duct joints may be screwed, and al-



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6-9 PROTECTIVE SYSTEMS OF THE FIXED LENGTH 273

i2315689

I O11

3

Fig. 6-11 Single protection for multiwire tendon with monobar jacking head.

Enlarged V ~ C Wx -xOtmenrionr are in milltmelrer

Enlargedy e w 2 - 2

Fig. 6-12 Double protection of fixed (bond) length for strand tendon.



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274 CORROSION AND CORROSION PROTECTIONways cemented to preclude ingress to fluids. Where the anchor length per-mits, unjointed ducts are preferred.

Where metal ducts, either plain or corrugated, are considered, they mustbe compatible with the tendon metal, and appropriate certification from themanufacturer should be requested. A double sheath protection of free andfixed anchor length of strand tendon, shown in Fig. 6-13, consists of twoconcentric high-strength plastic corrugated ducts.

6-10 PROTECTIVE SYSTEMS OF THE ANCHOR HEADCertain anchor-head details may be left with the manufacturer, or they maybe standardized. In either case, the system consists of a bearing plate, themain anchor head, a trumpet, and a protective cover. Custom-designed an-chor heads are frequently specified. In this context, they are not entirelyprefabricated. Furthermore, because of tendon elongation associated withprestressing, friction grips for strand and locking nuts on bars cannot lockthe system in a fixed position until the entire extension has been achieved.Locking devices and arrangements require exposed wire, strand, or bar onwhich to grip, and any preformed corrosion protection at this end must beremoved. This exposes tendon metal in two locations, above and below thebearing plate, which must be protected separately, as is the bearing plateand other exposed anchor head accessories.In aggressive circumstances early anchor head protection is indicated forboth temporary and permanent anchorages. The essence of protection in

inawaual polvpiooylenesneath around g reasecoalea stfan8 Two concenlric niqn. Leaa Inslrenqm plastic snoeIconugalea OUCISnSpacer. \I7

Flewole sacrilic~aIqouo oneath RPI CAL LONGITUDINAL SECTION THROUGHENCAPSUUTION I SH O WI N G 2 STRANOS ONLWFlea~ble Strand H~gn.slrengtn on.snrinh Spacersacrilicial locatmq rape encaprulalmn cement grout /grouo sneain

lnuwaual Strand aclofmationstrand sneatnI? w e ranui around umg w e13 per siranalSECTION * -A SECTION 8 -8 SECTION C-C SECTION 0-03 strand syslem 3 slrana system 5 Wanu svstem 8 s i m a svsiem

Fig. 6-13 Double protection for free and fixed length for strand tendon.



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6-10 PROTECTIVE SYSTEMS OF THE ANCHOR HEAD 275this case is to enclose the exposed metal parts and accessories while im-parting to the system freedom to extend under prestressing and thereafterunder the working stresses. Typical examples of anchor head protection areshown in Figs. 6-14, 6-15, and 6-16, and also in the illustration of corrosionprotection for the free and the fixed length./ m e r Head. Protection at this location is to ensure effective overlap withthe free-length protective system, protect the short tendon section belowthe bearing plate, and isolate the short section passing through the plate.These requirem ents may be satisfied with a telescopic section of sheathingand, after tensioning, fillers that will displace any water and injected bothwithin and outside the telescopic sheath.Cem ent grout is not suitable for inner head protection, and primary groutshould not be in contact with the structure, since it may crack during move-ment of the anchor against the structure. This area, therefore, must be pro-tected with deformable ductile m aterials impervious to w ater, and these maybe preplaced or injected but fully contained within surrounding ducts withan end seal.In saturated or damp conditions, it may be impracticable or difficult toexlude every vestige of water during the protection application; hence thedesign of the telescopic sheath must provide a full enclosure around the

Fig. 6-14 Typical corrosion protection detail for anchor head; double protection ofbar tendon.



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276 CORROSION AND CORROSION PROTECTIONRelurn hole

Greaseor polyester resin inleCIed through slressinghead and return lhrough spare notelastics or bilumenized,libre ring 10 conlainpolyester monar cap

Rubber 01 sot1 Dlastic iernporary seai cap

Cu~-otleve!01 strand Shealhalter stressingto oe abovewn 01 corrugalea lube

or mortar

extension-Single protection inlree length (Section 7 31 Polypropylenesheathed slrand

Fig. 6-15 Typical corrosion protection detail for anchor head; double protection ofstrand tendon.

steel-cap

Grease

Aaeouale slrand lengthto allow coupling forA ll sleel componenls 01 gussets. duclsbearing plates and caps coaled with twocoals 01 pilch epoay

Overourden collaDsedon lo wand lenaon onextraction01 casing

Gusset plates withsled ~UC Iweldedbetween

with grease I ing-Extent 01 oilesFree :englh classilied assinole ?r01ection. since Primarygrout not Ingrease 8sdiscounted as aproteclive barrier (Seclion 7 3 I cantact,*nth back 0 1struc!ure

Fig. 6-16 Typical corrosion protection detail for anchor head; double protection ofrestressable strand tendon.



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6-10 PROTECTIVE SYSTEMS OF THE ANCHOR HEAD 277exposed metal to ensure against the possibility of water flow through thecell during service.Where the protective materials are injected, a lower injection pipe andan upper vent pipe should be used for complete filling of the void and fullexpulsion of water and air (FIP , 1986). Injected materials should be conveyedby tremie to the lowest part of the duct, thereby displacing fluids upwardand toward the vent. If the space is restricted, simple grease gun techniquesare a good alternative.Frequently, the duct through the anchored structure is exposed to wetconditions, and in this case a brittle grout is fairly unreliable in providing awater seal outside the tube. Experience shows that the grout will probablybe squ eezed , displaced, moved, o r fractured as the structure deforms duringservice.Where standard anchor head details are applicable, some elements ofcorrosion protection may be prefabricated. These include a rigid plasticsheath, resin-bonded to a metal spigot welded in turn to the back of thebearing plate. During installation of the latte r, the plastic tube is slid exter -nally and telescopically over the tendon coatings, but adequate tolerancemust be provided.Outer Head. With restressable anchors, or with anchors subject to loadmonitoring, protection of par ts above the bearing plate (bare tendon, frictiongrips, and locking nuts) should recognize the requirement to remove boththe ancho r head c ap and the contents to allow tendon access for restressing.Th e protective system will depend on the details of the stressing and lockingmethod and equipment. Generally, however, grease is used with plastic orsteel caps. Additionally, a suitable seal and mechanical coupling betweenthe cap and the bearing plate should be included.If the tendon is not the restressable type, the cap and its contents maybe fixed. R esins and other setting sealants are suitable, and the mechanicalcoupling between the cap and the bearing plate may be omitted.If the design calls for the anchor head to be completely enclosed by thestructure (e + , conc rete blocks), the overhead componen ts can be encasedin good concrete, and rely on adequate cover if the environment is not ag-gressive and ingress to water and atmosphere is restrained.Bear lng Plate. Current practice calls for the bearing plate and other steelaccessories to be painted with bitumastic or similar protective materials.Prior to painting, all steel surfaces should be cleaned and all rust and de-leterious matter removed by sand blasting or acid pickling. The selectedcoatings should be compatible with the materials used for corrosion pro-tection of the ancho r head. Th e side of the bearing plate against the structureand other inaccessible parts should be treated before installation. It is quiteacceptable for bearing plates on concre te structure s to be set directly on aconc rete pad o r in a seating formed by epoxy o r polyester mortar.



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278 CORROSIONAND CORROSIONPROTECTION6-11 CATHODIC PROTECTIONCathodic protection is an acceptable method for underground pipelines andmarine structures. It consists of passing an artificial electric current throughthe ground with the intent t o polarize the metal cathodically. A diagrammaticrepresentation of the process is shown in Fig. 6-17.Cathodic protection may be considered for anchorages, but caution isnecessary in assessing its effectiveness and reliability because of the fol-lowing disadvantages:

1 .2 .

3.

4.5 .6.

The protection must be extended along the entire length of the anchor;otherwise intermediate corrosion centers may appear.For best results, the cathodic protection needs virtually complete sat-uration in electrolytes. The system must be used therefore in combi-nation with protected coverings where partially saturated soils are tobe traversed.Determination of the electric current required to maintain protectionduring service is still empirical and rather uncertain; hence it cannotbe predicted as well as the response of other protective systems.Full protection cannot be ensured, since there is the potential of dam-age by underwater corrosion to adjacent burried metals.An additional tendon must be inserted and fit in a system that is alreadycongested, and without interfering with the load-carrying capacity.The need to maintain and occasionally renew sacrificial anodes impliesa continuing cost. Furthermore, accessibility to replace such anodesis difficult for anchorages, and sometimes even impossible.

I-Sacri f lc lal Anode I pro tec to r 12- Insu la t ing Washer

current density m A l d m LI 4illFig. 6-17Hobst and Zajic, 1977.)Diagrammatic rep resentation of cathodic protection for an anch or. (From



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6-12 PREPROTECTED BOND LENGTH ANCHORS 2797. Stress corrosion in high-tensile steels cannot be precluded with the

same certainty as in the case of coatings.Portier (1974) mentions anchorage projects in zones where the differenceof potential of the soil attained 100 V, articularly in the vicinity of railwaystations In these cases cathodic protection might appear appropriate, butafter careful consideration it was excluded because of the risk of inducing

electroosmosis or electrodrainage in the soil, and because the cost of energyand supervision of the installation was estimated to be too high.Further reluctance to use this method relates to the risk of producing linesof current that may enter and leave the steel in relatively pervious environ-

ment, thereby creating microbatteries. Certain specialists also fear that thisoperation may in the long term create a more serious corrosion problemunder tension than other forms of protection.

6-12 PREPROTECTED BOND LENGTH ANCHORSAn example of preprotected bond anchor (factory applied) is shown in Fig.6-18. With this type, the steel tendon is protected over the entire bond lengthby a zibbed plastic sheath, with the annular space filled with epoxy pitchor cement mix at the manufacturing stage.

For this operation, the injection sleeve pipe is located beside the tendonsteel and maintained in position by spacers. The protective plastic ribbedsheath that covers the fixed length is elastic, rotproof, waterproof, and non-corrodable. It is also sufficiently strong to resist and transfer high bondstresses during service. An epoxy pitch or a cement-bentonite mix is injectedinto the annular space between the ribbed sheath and the steel tendon at themanufacturing stage and under factory-controlled conditions.

S l e e v e t u b cP r o t e c t i v e s h e a t h

n

S t e e lt en do n k n d o d l e n g t h L e - p r o t e c t i o nw i th eD o x v D i t ch- .endon F r e e l e n g t hP r o t e c t i v e shcathP r e - s e a l i n g g r o u tSealing Rrout

Fig. 6-18 Preprotected bond length ancho r; schematic section . (Soletanch e.)



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280 CORROSION AND CORROSION PROTECTION6-13 A B RIEF SURVEY OF CORROSION INCIDENTSThe permanence of ground anchorages and long-term effectiveness of cor-rosion protection systems is assessed in this section and also in Section 6-14 in terms of documented case histories.Cheurtas Dam. This structure was mentioned in Section 1-2, and a typicalcross section is shown in Fig. 1-2. Approximately 30 years after the IOOO-ton (metric) anchors were installed (between 1931 and 1935), a survey in-dicated that they were subject to considerable corrosion, despite the elab-orate protective system shown in Fig. 6-19. These conclusions were basedon three main observations: (a) a nearly steady average reduction of 5 per-cent the initial tension force on most anchors occurred between 1938 and1969; (b) a very substantial cumulative loss of tension was observed oncertain anchors, which were retensioned to IO00 tons (m etric), attributed tolong-term effects; and (c) a virtually complete failure was manifested at theanchor head of two units (Portier, 1974).Since most anchors were of the restressable type, their top part wasprojected beyond the bearing plate and was protected by a tarpaulin sheet

(1) 630 5-mm galvanized steel wires(2) Average diam eter of bound cable 15 cm(3) Average diam eter of finished cable 20 cm(4) Flint-kot coating(5 ) Bindings every 50 cm(6) Flint-kot-coated tarpaulin(7) Aloe rope(8) Plastic mattress (mixtur e of grease andbitumen)(9) Tarpaulin sheath with zip fastener(10) Cement stopper sealing wires and tarpaulin s(11) Scraped wires(12) White metal point(13) Sealing tube

Fig. 6-19 Corrosion protection for the 1000-ton anchor in Cheurfas Dam, Algeria.(FromCambefort, 1966.)



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6-13 A BRIEF SURVEY OF CORROSION INCIDENTS 281and bitumen in order to fascilitate their individual retensioning at any time.Floodwaters and repeated restressing rapidly destroyed the fabric, and thesun melted the bitumen. The heads were left in this conditionfor many years,and some corroded to failure.The 5 percent load loss observed over a period of 30 years is by currentstandards nominal and reflects relaxation and long-term loss in the steeltendon, irrespective of any corrosion effects. The very high time yield ob-served with certain anchors might have been the combined result of improperhandling during tensioning and corrosion attack in the presence of swellingmarls and water in the body of the dam.Portier (1974) suggests that the problems encountered with the anchorheads can be avoided if they are not placed in spillways, and if their deten-sioning is not performed at the expense of protection.Jo ux -Tarare Dam. This incident was among the first documented casesinvolving stress corrosion cracking (SCC), iscussed in Section 6-3, andexemplifies the combined action of high static tensile stress and localizedcorrosion.

Between June and October 1952, eight 1300-ton anchors of the Cheurfastype were installed and tensioned in the upper works of the Joux dam inFrance. The tendons were stressed to 67 percent f p u . Controls performedseveral months after installation indicated that the residual tension had beenreduced from 0.67fp, o practically zero. On exposing the tendon, brokenstrands were noticed, (see Fig. 6-20), apparently the result of SCC initiatedby high tensioning, groundwater aggressivity, and poor storage conditions.Recognizing the effect of high tension on the steel tendon in a corrosiveenvironment, a direct recommendation that followed the study of this in-cident was to reduce the stress level in the steel by limiting the working loadof permanent anchors to 55 percent the failure strength.World Trade Cent er. In this example, slurry (diaphragm) walls 70 ft deepwere temporarily braced by six rows of tiebacks, stressed to 100 percenttheir design (working) load, and installed at 45". The walls are keyed intounderlying bedrock, mainly for the transfer of the considerable vertical loadimposed on the structure during the service of the temporary bracing. Thefinal permanent lateral support is provided by the underground floor system,and the tiebacks were eventually distressed.Since the tiebacks were temporary, corrosion protection was omitted,although monitoring was specified and carried out. During service the tie-backs showed certain corrosion effects, and an expensive system of cathodicprotection was installed (Feld and White, 1974). Although zinc loss wasconsiderable, elimination of corrosion was not accomplished. A view of theexcavation and the anchorage system is shown in Fig. 1-14.



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282 CORROSION AND CORROSION PROTECTION

Fig. 6-20 Joux Dam (1952); (a) view of dam crest during floor period; (b) failure o ftendons by stress corrosion cracking (SCC). (From Portier, 1974.)



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6-14 DOCUMENTED PERFORMANCE OF ANCHORAGES 2836-14 DOCUMENTED PERFORMANCE OF ANCHORAGESInterestingly , the subject of corrosion protection may never be placed in theright perspective, since corrosion failures are either not reported or seldomwell docum ented.To date, however, about 35 case histories of failure by tendon corrosionhave been collected and fairly documented. One led to collapse of the com -plete structure-anchor-ground system , but under the combined effect ofinstallation procedures and corrosion protection, neither of which is ac-ceptable by current standards (FIP, 1986).Of these cases, 24 related to permanent installations (protected or un-protected), and 11 were temporary anchorages with no protection specifiedother than cement grout cover along the fixed length and occasionally adecoupling sheath do ng the free length. Included in this group are the C heur-fas and Joux dams discussed in Section 6-13.Various pertinent d ata for these ca ses are summarized in Table 6-5 basedon reported case histories of tendon corrosion by Portier (1974), Herbst(1978), Nurnburger (1980), Weatherby (19821, and personal communicationsby FIP (1986).Relevance of Tendon Type and Locat ion. It appears that corrosion islocalized. N o tendon type is exempt from the process, and no special systemhas immunity to corrosion. Nine incidents involved bar, 19 involved wire,and 7 involved strand. Fo r each tendon type, the service period before failureextended from several weeks to many years. Failures occurring a few weeksafter installation have been caused by stres s corrosion cracking or hydrogenembrittlement.The case histories confirm that quenched and tempered plain carbon steelsand high-strength alloy steels are more susceptible to hydrogen embrittle-ment than other varieties, hence these steels should be selected with extrem ecaution where environmental conditions are known to be dangerous andaggressive.Interestingly, in this survey corrosion incidents are associated with certainanchor components more frequently than with others. Thus 19 incidentsoccurred at or within 1 m (3.5 f t ) of the anchor head, 21 incidents involvedthe free length, and only two occurred in the fixed length. In terms of causethere is no specific pattern, and these incidents are fairly random with pos-sible exception of the choice of steel.Corros ion T ime. The duration of service at failure is extremely variable,ranging from a few weeks to 31 years. The following observations are ap-propriate:

Nine incidents occurred within six months after installation, namely,cases 2 , 8 , 11, 15, 18 ,23 ,24 ,30 ,and 33. Of these, four were permanentanchorages with some or full protection.



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AnchorageCategory Corrosion Rotection Corrosion No. Failure Location Remarks and/or DiagnosisPermanent

Permanent

Permanent

Permanent

Permanent

Temporary

Permanent

Permanent

Permanent

Permanent

Coated tarpaulin coveredby mixture o f greaseand bitumen with outertarpaulin sheath overfree length; cementgrout cover in fixedkngth'Coated tarpaulin coveredby mixture of greaseand bitumen with outertarpaulin sheath overfree length; cementgrout cover i n RxedlengthGrease-impregnatedglassfiber bandage and outerasphalt wrapping overfree length; cementgrout cover i n fixedlength

Bitumen coating of a nchor head; cementgrout cover over tendonlength

No protection at anchorhead; jute wrapping-im-pregnated bitumen infree length

No protection over freelength; cement groutcover in fixed length

Tendon encased in ce-ment grout

Road oil loaded with redlead but anchor headwaiting several weeksbefore protective fillingplacedBituminous infilling as asurround for the freelength (piped in hot):cement grout cover infixed lengthTendon painted with bitu-men over free length:cement grout cover infixed length

4 anchorages

Wires in 2 anchorages

4 anchorages

One anchorage

17 anchorages

A few anchorages

3 anchorages

Several individual wires

24 wires in 3 anchoragesa further 13 wires insame anchorages 2years later3 anchorages

Beneath the anchor head



I n fully bonded length 2 . 5m up from crane beamanchor head

5 in anchor head: I2 infree length of which 5were within 0.5 m ofanchor head

Free length

85% of ruptured wiresfailed in vicinity of con-crete deadman-tendoninterface

Button headed wires a1anchor head

0.6-1 m beneath anchorhead

Free length

Floodwaters and repeated ten-sioning tore the tarpaulin fab-ric and the exposed internalbitumen cover melted underhigh ambient temperatures.thereby removing protection;localized corrosionCorrosion failure under tensionlinked to type o f steel: deci-sion taken to limit workingstresses to SS% UTS there.after. but to increase proofloading up to 1 . J times work-ing load on occasionsFully corroded wires exposed inspite of protective wrapping;by contrast. on the same siteand in the same location. steeltendons comprising 37 bundlesof 19 wires o f 2.9 mm dia.were undamaged-here the in-ternal spaces of the ropeswere filled in the factory withred lead sealing compoundcover: significant pitting andtypical reduction in cross-sec.lional area was 6.8%; depth ofdeepest crack 1.3 mm; failureattributed to intergranularstress corrosion: steel judgedto be sensitive l o cracking

Deep localized corrosion wherebitumen protection was miss-ing (differential aeration postu-lated); this protection couldnot withstand damage duringinstallation or environmentalattack: steel judged to be sen-sitive to corrosionBrittle failure: groundwater wascorrosive due to presence ofsulfuric acid formed from cin.ders falling for many yearsfrom steel locomotives: brinemay also have contributedSurface corrosion and pitting ob.served in tendons: insutlicientgrout cover and presence ofchlorides noted; stress corro-sion and cracking also located:tendon bending due to groundmovement

Virtually no trace o f grout

Brittle failure under tension: but.ton heads were cold forged onsite

Stress corrosion due to anaqueous environment

Although no corrosion-producingelements found, stress corro-sion postulated where bitumenprotection had broken down:surface corrosion and heavyDittinn on wires: some Dits had;mallfissures( c o n t i n u e d )

285



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TABLE 6-5 (Continued)Time in Ser- WorkingCase Date of In- vice at Fail- Geographic Type of General Envi- Ground Con - Type of Ten- Load o rNo. stallation ure Location Structure ronment ditions don Stres s Level

I I

12

13

14

IS

Quenched and (67% UTS)960s 3 months U.K. Anchored Temperate Rockfloor of dry climate and tempe reddock saline atmw low vlloysphere bur (1500Nlmm)

I8 Gm md ia. WO-1700 kN%7-68 6-18 month s W est Ger. Underground Tem perate Rockm n y pumped climate wiresstorage (1500-1700scheme Nlmm)

12 S-m mdia . 650 kN968 Within 3 Switzer land Underground Ternp erate Rockyenrs power ria- climate winstion1968 I I years France Anchored Temp erate Coal mine 8-12-m mdia. 1720 kN (67%foundation climate waste fill: oval ribbed of elasticblocks above wires ( l 4 W limit)wnter table 1600 N Imm)

d i . wiresBefore 1969 A few day s West Ger- Anchor ed re- Tem perate Soil fi l l 6 12.2-mm- -and 100 many taining wall climatedays suppottinpa rail track

16 1968-69 - U.S.A. Ancho red re- -taining wall

17 1969 10 years U.S.A. Anchored re- Acidic; adja-waste acidwutraliza.tion plant

taining wall cent to

18 1969 A fe w weeks France Anchored re- Temperatetaining wall climate

19 1969 5 years Malaysia Rock Humidstrengthen-ing

Landfill withhk h or-ganic con-tent overiy-ing micaschist;brackishgroundwa-terFill ( clays andsilts)

Above watertable; c h brides andsulfates inwater fromsewer leak-agesRock

12.7-mmdia. s2640 kNr t n n d of4.2-mmwire (270 KW )

32-mmdia. 636 kNhigh-slrcn@hb u r (1033Nlmm ult i-mate)8 12-mm-dip. 1030 kN (63%ribbed of elasticwire r (I45W limit)I600 Nlmm)

36 7-mmdia. 700 kNwires

20 1970 28 months New Zcaland Anchored re- -!Pining wall Clay overly- 42 7.mm dia. UTS = 2570inasand. wirer kN: initialstone tensioningto 48%UTS; ten-don de-signed towork at up



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AnchorageCategory Corrosion P rotection Corrosion No. Failure Location Remarks and/or DiagnosisPermanent

Permanent

Test

Permanent

Temporary

Temporary

Permanent

Permanent

Permanent

Permanent

Bare bar, ungrouted overfree length; cementgrout cover in fixedlength

A chemical filler (oil-based unsaturated fattyacid polymer) surround-ing the free length; ce-ment grout cover infixed lengthTendon installed in bore-hole with anchor headsat either end; no pro-tection by design fortest purposesOrdinary P ortland cementand polyethylene outertube over free lengthTendon unprotected overfree length; cementgrout cover in fixedlength

Bentonite-cement groutcover plus outer steelpipe in free length; inaddition. a sacrificialzinc ribbon anode wasinstalled with each ten-don; cement groutcover in fixed lengthNoprotection of anchorhead; in free-lengthgrease. paper wrappingand plastic sleeveembedded in cementgrout; cement groutcover in fired lengthOrdinary P ortland cementgrout and mild steelouter tube in freelength; cement groutcover in fixed length

Anchor outer head pro-tected by sealing capinfilled with grease andinjected under pressure:polypropylene sheathedwires surrounded by bi-tumen placed in situover free length; poly-propylene sheathedwires with stainlesssteel end barrels sur-rounded by cementgrout in fixed lengthPolypropylene extrudedsheathingof individualwires with outer phstictube if lt lkd with a mas.tic aeahnt; ribbed nl-kathenc tube and epoxyresin cover in fixedlength

1 anchorages

Majority of the 133 an-chorages installed

2 anchorages ( I 1 wiresand IO wires)

4 anchorages

3 anchorages

8 anchorages

6 anchorages

I anchorage comprising36 wires, of which 33were broken

5 wires

Free length

Free length

Corrosion pitting leading to hy-drogen-induced stress corro.sion cracking at failure: free-length grouting actioned in1977, since when no corrosionfailures have been observedStress corrosion due to leachingout of nitrate ions from chemi.cal protective filler

Stressed length betweenanchor heads Presence of sulfides caused ern-brittlement o f the steel

0.2-2.5 m beneath anchorhead

Free length



0.1-0.5 m beneath anchorhead

Underside of anchor headand at bare section ofwires immediatelyabove plastic

I n free length 1-8 mbelow anchor head

Brittle failure under tension. mi-tiated at surface oxidized localdefects

Tendons not heavily corroded;failure judged to be due locorrosion fatigue as a result ofbending due to fluctuatingloads from railway beingtransmitted through frozenground; cracks in steel notedat failure locationBrittle corrosion failure of ten.don where bentonite-cemeentgrout cover had dropped 1-1.2m; hydrogen sulfide waspresent in the soil and the sac-rificial anode was consumednear the anchor head of thefailed tendons

Heavy pitting leading to brittlefailure of unprotected tendon

Brittle lailure under tension: de-carboned steel at wire perime-ter: incomplete fil ling o f pro-tective grout beneath anchorhead

Stress corrosion cracking ofwires; inadequate filling ofinner head region with bitu-men; exposed bare wires sub.ject to wetting and drying cy-cles; groundwater of low pHsuspected

Surface corrosion cracking: mas.tic filler found to be hygro-scopic and it was suspectedthat the mineral oil softenedthe polypropylene sheathing;also speculated that the poly-propylene sheathing may havebeen damaged during trans-( c o n t i n u e d )

287



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TABLE 6-5 (Continued)Time in Scr - WorkingCa se Date of In- vice at Fail- Geograp hic Type of Genera l Envi- Ground Con- Type of Ten- LoedorNo. stallation UTC Location S tructure ronment ditions don Stress Level

to 66%UTS

21 Be fore 1971 - West Ger- Ancho red re- Temp erate -many taining wall clim ate22 Before 1971 Within a year West Ger - Anc hore d re- Tem pera te -many taining wall climate

23

24

25

1971 6w ee ks U.S.A.

1971 4 wee ks U.S.A .

Anchored re- -taining wall Acidic soilembank-ment com-prisingmainly blastfurnaceslag; soilmoist adja-cent to ten.do nPH

Anchored re- - Moist soiltaining wall with low

1972 2 years South Africa Restraint for Seasonal wet- Fillcantilevered ling andgrandstand drying

26 1972-73 I n the earlystages ofcontract27 1973 I 1 years

i a 1974 -

29 1974 5 years

New Zealand Anchored re- -taining wallU.K. Anchorage re- Temperatestraint of climateabutmentwhich was

yielding ini-tiallybridge abut.men!

New Zealand Anchored -

Algeria Concre te dam Dry airraising

Clays endsilts overly.ing sand-stoneFill overlyingclay andweak rock

Rock

Concrete

I5 5.2-mm- -dip. wires(alloy steel)5.2-mmdia. -wires (alloysteel)

32-mmdia. -bar hot-rolled,drawn. andstTCss-TC-lieved (1100Nlmm' ulti-m t e )

35-mmdia. -bar, hot-rolled,drawn. andstress-re-lieveddia. strandsS 12.2-mm- 450 kN

Multiwirc ten- 490-lOSO kNdon (50% UTS)

4-5 15.2-mm- 350 kN ( 5 0%dip, strands UT S max.)

34 7-m md ia. too0 kN (50%wirer UTS)

36 15.2-mm. -dia. strands



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AnchorageCategory Corrosion Protection Corrosion No. Failure Location Remarks and/or Diagnosis.port and installation; Im ofpolypropylene sheathingstripped off below anchorhead before tendon installationand stressingHeavy pitting and occasionalcrackinn of wires noted:Temporary Tendon unprotected over 2 anchoragesfree length; cementgrout cover in fixedlength

Temporary Tendon encased in ce- 5 anchoragesment grout

Temporary Tendon unprotected over 4 anchoragesfree length; cementgrout cover i n fixedlength

Temporary

Permanent

Temporary

Permanent

Permanent

Permanent

Tendon unprotected overfree length: cementgrout cover in fixedlengthPolypropylene sheathedand greased strands infree length; cementgrout cover in fixedlength

Unprotected in freelength; cement groutcover in fixed lengthNo anchor head protec-tion: greased andsheathed strands overfree length; cementgrout cover in fixedlengthPolypropylene sheathingover wires with a rec-ondary protection ofouter tube and masticinfilling in free length:corrugated tube-groutencapsulation overfixed length

grouted with acrylamidechemical: cement groutcover in fixed length

Free-length annulus

No failure, but one ten-don located with unac-ceptable corrosion, i.e.pitting, and all 9 an-chorages condemned

One strand in each of 2anchorages

Free length

Free length

Free length

Free length

chemical analysis of corrosionproducts indicated 0.25% SUI-fur content but no chloridesHeavy corrosion and pitting incertain zones where there wasno adhering cement grout;other sections of tendon thatwere completely grout-freedisplayed general corrosion;no corrosion where tendonstill bonded to grout; brittlefailure recorded; tendon bend-ing and overstressing also in-duced by ground deforma-tions; analysis of corrosionproducts indicated 0.63% sul-fates but no chlorides or SUI-fidesStress corros ion cracking postu-lated

Stress corrosion cracking postu-lated

Fixed anchor zone Some doubts were expressedover the efllcacy of the grout-ing of the fixed anchor lengthwhere no special precautionshad been taken; when one an.chorage was excavated. groutcover in fixed zone rangedfrom nil to 6 mm, and pittingup to I mm in depth was mea-suredw e verloading of tendons incenain locations; corrosion oftendon

- Ground movements created se-

Beneath the anchor head Failure due to stress corrosion

Protective ducting in free lengthdamaged during transwrla-lion. permitting leakage o fmastic filler that had softenedat the high ambient tempera-ture; protected tendons storedseveral months on site beforeinstallationWhere duct had not been filledproperly with acrylamidegrout. a tar epoxy was pouredin to f i l l upper 0.5 m; failureoccurred at the base of the tarepoxy

Beneath anchor head

( c o n t i n u e d )289



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TABLE 6-5 (Con t inued)Time in Ser- WorkingCase Date of In- vice at Fail- Gco#raphic Type of Gemml Envi- Ground Con- Type of Ten- Load or

No. au lh t ion UIC Location SI NC IU ~C ronment ditions don Stress LevelM 1975 6 m o n t h s France Anchored re. Temperate Above water 32-mmdia. 610 kN (74%taining wall clim ate table: m t h - ribbed ~ W S of elastic)ing ruspi- (1079- 1275cious N/mmz)

abutment8 climate sands and d i. steelfor pipeline gravels str and sbridge overlying31 1976 5 year s Switzerland Anchored Temperate Fill overlying IO 12.7-mm- IIU)-llSOkN

rock

32 1977 Within 3 Hong Kong Anchored re- Humid and No nag er a- 7 12.9-mm- 1050 k NYa rn mininp wall slightly ss- sivc fill dia. Supsline overlying strandscompletelyweatheredgranite thatimpmveswith depthto moder-ately stronggranite

33 1977 4 months West Ger. Ancho red re- Tem perate Fill consislingmany taining wall climate of slag andash; sulfatecontent =200 m a i l e r

34 1978 4 years South Africa Slop e stabili- Humid Weath eredzation xdimcnlaryrock

35 1980 1-3 years Hong Kong Stabilization Humid and Rockof rock slightly sa-line

32 mm dia. -hot-rolkdandthreadedbars (1100Nlmm'UTS)

4 o r 6 15.2 590 kNmmdia . 890kNstrands ( W b U T S )

Hi@-tensile 5Ml-650 kNstrl bars

From FIP (1%).

290



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AnchorageCategory Corrosion Rote ction Corrosion No. Failure Location Rem arks andlor DiagnosisTemporary

Permanent

Permanent

Polyethylene oute r tubeover free length: ce.ment p o u t cover infixed lengthPolyethylene sheathedstrands in free lengthwith asphalt filling; ce-ment pout cover infixed kngth

Anchor head encased inconcrete; grease andplastic sheathing overfree length; cementgrout cover in fixedlength

2 anchorages

3 anchorages

I anchorage (2 strands)

Temporary No proteclion at anchor 2 anchorageshead, polythene tubeover free kngth; ce-ment pout cover infixed length

Permanent Grease-fdled or cement. 2 inchoragespou ted Outer anchorhead; PVC sheathedand greased s trands infree lencth; cementgrout cover and epoxyresin coaling over tiredlength

Permanent Cement grout plus sheath 10 anchoragesover free length andtendon bond length;grease at bar couplers

3 m and 8 m beneath an-chor head

In fixed anchor lengthwithin 500 mm of freekngth

Beneath the anch or headand in the free kngth

50 nun beneath anchorhead; middle of freelength

Underside of anchor head

Up to 20 m beneath an.chor head but dway rg a c e n t to a couplingp i n t

Brittle failure under tension

Bridpe collapse due to failure ofanchored abutment: reverecorrosion of strands in proxi-mal zone of fixed anchorlength that was only parliallygrouted: tendon exposed toaggressive groundwater con-taining sulfides and chloridesin fill and u n d y gravel; poorconstruction practice and lackof quality controls. such aswater testing. led to inade-quate pouting; fixed anchorstraddled permeable soil androckvided immediately beneath an-chor head; considerable delaysexperienced between stressingand concrete encasem ent ofanchor hea d; metallographicexamination of tendon wiresin 45 anchorages showed up to2.7% and 125% loss of diameterfor delay periods of 1-8months and 16-36, months re-spectively; it was also specu-lated that rtrandr had beenstored on site for som e time(allowing corrosion to de.velop) before greasing andsheathing of free lengthFailure adjacent to anchor headdue to brittle fracture at adeep pit; second failure attrib-uted to hydrogen embrittle-ment; ground deformationsalso present. lerding to bend-ing and overstressing: lack ofprotection and use of corro-sion-susceptible steel high-lighted overall; sulfur com-pounds present as corrosionproductsGround movement Dner serviceincreased tendon loads by upto 2046; grease filling and c a pping of anch or head inade-quate to stop infiltration ofsurface water to inner head;stray currents from adjacentelectrifed mil line (15-20mdistance) identified; sulfate-re-ducing bacteria l ou te d in an-nulus between strand and PVCsheathing in some cases

All fractures occurred over asmal l u e a where neither groutnor g r e w was in contact withthe bar-this small air void re-sulted from th e method of en-capsulation: metallurgicd ex.amination showed pittingcorrosion and hydrogen em-briltkmnt: traces of chloridesdtr were present on the barDner assembly. which probr-bly initiated pitting

No orrosion protection pro-

291



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292 CORROSION AND CORROSION PROTECTIONFive corrosion failures occurred within the period 6- 18 months,namely, cases 5 , 12, 16, 22, and 26. Two of these were permanentinstallations.The majority of failures (2 1 incidents) occurred during the period from18 months to 31 years, which is the upper time limit for the casesstudied. Although limited statistical value can be inferred from thesefigures, it appears that the 18-month or longer service period used todefine permanent anchors is not inconsistent with this record. How-ever, the relative large number of failures recorded within 6 monthsafter anchorage installation raises the question of serviceability of un-protected anchors, even those of very short duration.

Fixed Length. The two incidents involving the fixed anchor length werecaused by inadequate grouting of the tendon bond length. In one case, thislack of protection exposed 3 m (10 ft) of tendon to aggressive groundwatercontaining chlorides and sulfides. This incident (case 31 in Table 6-5) in -volved the failure of three rock anchors bracing an abutment, and occurredafter 5 years in service. This failure caused the collapse of a pipeline bridge.The following conditions during construction were recorded: (a) no boreholewas drilled at this location, and the rock stratum was inferred from a borehole25 m (80 ft) away; (b) drilling for the anchors was poorly supervised, anddrill records were not kept; (c) water or pregrouting tests were not carriedout prior to tendon homing; and (d) grout injection procedures were notmonitored, and instead a fixed quantity of grout was preplaced sufficientonly for the tendon bond.This problem could have been detected by water or pregrouting tests,and prevented if one protective sheath had been applied over the tendonbond length.Free Length. The relatively high number of incidents in the free length,compared to only few at the fixed length, suggests more aggressive or com-bined causes augmenting intensified failure of the anchor system. In thissurvey, free length failures were caused by the following reasons: (a) tendonoverstressing due to ground movement initiating pitting corrosion or cor-rosion fatigue; (b) absence of cement grout or inadequate grout cover intendons exposed to chlorides in industrial waste fills or organic materials;(c) disruption of bitumen cover because of lack of elasticity; (d) poor choiceof protective materials, incompatible with the anchor system and its corn-ponents; (e) poor storage conditions on site and for periods long enough tocause initial corrosion damage; and (0 oor execution of the protection sys-tem and its details.Anchor Head. Documented causes of anchor-head failure are (a) lack ofprotection (extended even for only a few weeks in aggressive conditions);



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REFERENCES 293(b) incomplete protection, such as inadequate cover due to improper tilling;and (c) damage to the protective filler during service.

In case 32 of Table 6-5, there was considerable delay between tendonstressing and concrete capping of the anchor head. For a delay between 16and 36 months, a loss of wire diameter I2 percent was recorded.

Exposure of the anchor head to the atmosphere contributes to the cor-rosion risk and increases the corrosion potential. This simple fact suggeststhat the anchor head should be protected with at least the same standardsthat are applied to the free and fixed anchor length. Noting that 19 failuresoccurred within 18 months after installation, early protection of the anchorhead is always indicated, and at best i t should be applied after grouting,irrespective of the service life. Where a delay is unavoidable, the anchorhead should be protected temporarily with the use of plastic paint, grease-impregnated tape, or other suitable cover.

REFERENCESAmerican Society for Testing and Materials, 1979: Underground Corrosion,

ASTM Symp. on Corrosion of Metals, Williamsburg, Virginia.Arup, H., 1979: A Recording Instrument for Measuring Corrosivity in OffshoreSeawater. Offshore Tech. Conf., Houston, Paper OTC 3602, 2129-2134.Beeby, A. W., 1978: Corrosion of Reinforcing Steel in Concrete and Its Relationsto Cracking, Strucr. Eng ., 54 (31, 77-81.Bird, C. E., and F. J. Strauss, 1967: Metallic Coatings for Reinforcing Steel,Materials Protection, 6 , 48.Brian-Boys, K. C., and D. J. Howells, 1984: Model Specification for PrestressedGround Anchors, Geotech. Control Office. Hong Kong, GCO Pub]. (3/84).British Standards Institution, 1982: Recommendations for Ground Anchorages,Draft for Development DD81, BSI, Lond.Burdekin, F. M., and G. . Rothwell, 1981: Survey of Corrosion and Stress Cor-rosion in Prestressing Components Used in Concrete Structures with ParticularReference to Offshore Applications, Cement & Con crete Assoc., Slough.Bureau S ecuritas, 1972: Recom mendations Regarding the Design, Calculation, In-stallation and Inspection of Ground Anchors, Editions Eyrolles, 5 1 BoulevardSaint-Germain, Paris (Ref. TA 72).Cambefort, H., 1966: The Ground Anchoring of Structures, Travaux, 46 (April-May), 15 PP.Caron, C . , 1972: Corrosion et Protection d es Ancrages D efinities, Construction,(Feb.), pp. 52-56.Champion, F. A ,, 1962: Corrosion Testing Procedu res, Chapman & Hall, London.Clifton, J. R., H . F. Beeghly, and R. G. Mathley, 1975: Nonmetallic Coatings forCo ncrete Reinforcing Ba rs, U.S.Dept. of Co mm erce, National Bureau of Stan -dards, Washington, D.C.



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294 CORROSION AND CORRO SION PROTECTIONComte, C., 1971: Tech. des Tirants, Inst. Research Found. Kolibrunner/Rodio,

119 pp. Zurich.Cornet, I., and B. Bresler, 1966: Corrosion of Steel and Galvanized Steel in Con-

crete, Mate r i a l s P ro tec t i on , 5.Coyne, A., 1930: Perfectionnement aux barrages-poids par Iadjonction de tirantsen acire, (Genie Civil, Aout).Duffaut, Duhoux, et Heuze, 1973: Corrosion des aciers dans le beton arme. Essaisrealises dans Iestuaire de la Rance de 1959 a 1971, Annales ITBTP (May).Environmental Degradation by De-Icing Chemicals and Effective Countermeasure-ments, 1973: page 25. Highway Research Record No. 425.Federation Internationale de la Precontrainte, 1976: Report of Prestressing Steel,

1. Types and Properties (FIP/5/3), Slough.Feld, J., and R. E. White, 1974: Prestressed Tendons in Foundation Construction,Pres t r . Conc rete Foun d . and Ground Ancho rs . 7 FIP. Cong., pp. 25-32, NewYork.

Fidjestol, P., and N. Nilsen, 1980: Reinforcement Corros ion in Concr ete , Vedas,Bergen.FIP, 1986: Corrosion and Corrosion Protection of Prestressed Ground Anchor-ages.FIP, 1972: Draft of the Recommendations and Replies to FIP Questionnaire,(1971). FIP Subcommittee on Prestressed Ground Anchors.FIP, 1973: Final Draft of Recommendations FIP Subcommittee on PrestressedGround Anchors.Frazier, K . S., 1965: Value of Galvanized Reinforcing in Concrete Structures,

Mate r i a l s P ro tec t i on 4, 53.Goto, Y., 1971: Cracks Formed in Concrete Around Deformed Tension Bars, J .

A m . C o n c . I n s t . , 68 (4) , 244.Graber, F., 1980: Excavation of a VSL Rock Anchor at Tarbela, VSL SilverJubilee Symp., Losinger Ltd., Bern, unpubl. work.Gutt, W. H., and W . H. Harrison, 1977: Chemical Resistance of Concrete, BRECurrent Paper 23/77, Bldg. Research Establishment, Garston.Hadley, R. F., 1939: Microbiological Anaerobic Corrosion of Steel Pipe Lines,

O i l G a s J., 38 (19) , 32.Hamner, N. E., 1970: Coatings for Corrosion Protection, Chapter 14 in NACEBas ic Cor ros ion Course , A. des Brasunas and N. E. Hamner, eds., NationalAssoc. Corrosion Engineers. Houston, Tex.Hausman, D. A., 1967: Steel Corrosion in Concrete, Mate r i a l s P ro tec t i on , 6, 19.Herbst, T. F. , 1978: Safety and Reliability in Manufacture of Rock Anchors, Int .Hilf, J. W ., 1973: Reply to Aberdeen Questionnaire, (l972), Unpublished.Hobst, L., and J. Zajic, 1977: Anchoring in Rock, Development in GeotechnicalEngineering, Vol. 13, Elsevier Scient. Publ., Amsterdam.Houston, J. T., et al., 1972: Corrosion of Reinforcing Steel Embedded in StructuralConcrete, Report N o. CFHR-3-5-68-112-1. Centre of Hwy. Research. Univ.Texas.

Symp. on Rock Mech. Related to Dam Foundations, Rio de Janeiro.



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REFERENCES 295King, R. A., 1977: A Review of Soil Corrosiveness with Particular Reference toReinforced Earth , TR RL Supplementary Report 3 16. Tran spo rt and Road Re-search L aboratory, Crowthom e.Koch, J., 1972: Reply to FIP Question naire, Unpublished.Larson, T. D., P. D. Cady, and J. C. Theisen, 1969: Durability of Bridge DeckConcrete, Report No. 7, College of Engineering, Pennsylvania State Univ.,April.Lee, H., and K . Neville, 1967: Handbook of Epoxy Resins, McGraw-Hill, New York,Littlejohn, G. S.,1973: Report on Tendon Corrosion of Ground Anchorages Ad-jacent to Bridge No. 5, Clear Water Bay Road, Hong Kong, Unpublished.Longbottom, K. N ., and G. P. M allett, 1973: Prestressing Steels, T he StructuralEngineer, 51, (121, pp. 455-471.Littlejohn, G. ., nd D. A. Bruce, 1977: Rock Anchors-State o f t he A r t , Found.Publ. Ltd., Essex, England.Mayne, J. E. O., J. W. Menter, and M. J. Pryor, 1960: The Mechanism and In-hibitions of the Corrosion of Iron by Sodium Chloride Solution, Part I , J. C h e m .

S o c . , 3229.Meyer, A., 1977: Report on Discussion to Session VI by J. M. Mitchell. A Review

of Diaphragm Walls, Thomas Telford Ltd., London.Mitchell, J. M., 1974: Some Experiences with Ground Anchors in London, I C EConf. on Diap hr agm Wal ls and An cho rages, London, Sept., pp. 129-133.

Modern Electrical Methods for Determining Corrosion, 1973: Rates, NACETech. Unit Comm. T-3D on Instrum ents for Measuiing Corrosion , NACE Publ.3D170.Mozer, J. D., A. C. Bianchini, and C. E. Kelser, 1965: Corrosion of ReinforcingBars in Concrete, J. A m . C o nc r et e I n s t . Pr o c , 62, 909.Naus, D. J., 1979: An evaluation of the effectiveness of selected corrosion inhibitorsfor protection of prestressing steels in PCPVs. Oak Ridge National Laboratory,Tennessee.ONeill, E. F., 1980: Study of reinforced concrete beams exposed to marine envi-ronments. Performance of concrete in marine en viron ments, Report SP-65, Amer-ican Con crete Institute.Nurnberger, U., 1980: Analysis and Evaluation of Failures in Prestressed Steel,

Forschung. Strabenbau und Strabenverkehrstechnik , 308, 1-95.Ostermayer, H., 1974: Construction, Carrying Behavior and Creep Characteristicsof Ground Anchors, Pro c . Diaphragm Wal ls and Anchorage Conf ., Inst. CivilEng., London, pp. 141-151.Palmer, J. D., 1974: Soil Resistivity-Measurement and Analysis , Mater ia ls Per-

fo rmance (Jan .), 41-46.Pascoe, W. R., 1%8: Plast ic Coat ing s for Met a ls , Modern Plast ics Encyclopedia

Issue, McGraw-Hill, New York.PCI Post-Tensioning Committee, 1974: Tentative Recommendations for Pre-stressed Rock and Soil Anchors, PCI, Chicago, 32 pp.

pp. 6-45 to 6-52.



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296 CORROSION AND CORROSION PROTECTIONPender, E., A. Hosking, and B. Mattner, 1963: Grouted Rock Bolts for PermanentSupport of Major Underground Works, J . Inst. Eng. Austral., 35, 129-150.Phelps, E. H., 1967: A Review of the Stress-Corrosion Behaviour of Steels with

High Yield Strength, Conf. on Fundamental Aspec ts of Stress Corrosion Crack-ing, Ohio State Univ., Columbus, Sept. 11-15.Portier, J., 1974: Protection of Tie-Backs Against Corrosion, Prestressed Con-crete Found. and Ground Anchors, 7th FIP Congress, pp. 39-53, New York.Pourbaix, M . , 1966: Atlas of Electrochem ical Equilibria in Aqueous Solutions, Per-gamon Press, New York, pp. 409-410.Rehm, G., 1968: Corrosion of Prestressing Steel, Proc. Symp. on Prestressing,Madrid (June).Robinson, R. C., 1972: Design of Reinforced Concrete Structures for CorrosiveEnvironments, Materials Performance, 11, 15.Ryell, J., and B,. S.Richardson, 1972: Cracks in Concrete Bridge Decks and TheirContribution to Corrosion of Reinforcing Steel and Prestressing Cables, ReportIR51, Ontario Ministry of Transport and Communication.Schiessl, P., 1975: Admissible Crack Width in Reinforced Concrete Structures,Contribution 11, 3-17, Inter-Assoc. Colloqu. on the Behavior of In-Service Con-crete Structures, Liege.Schrier, L. L., 1976: Corrosion, Newnes-Buttenvorths, London.Soletanche Co., Ltd., 1970: Other Types of Anchor, Suppl. Ground Anchors,Cons. Eng. (May), 13, 15.Spellman, D. L., and R. F. Stratfull, 1969: Chlorides and Bridge Deck Deterio-ration, Research Report No. M&R 635116-4, Division of Highways, State ofCalif.Stern, M., 1958: A Method for Determining Corrosion Rates From Linear Polar-ization Data, Corrosion, 14, 440t.Stratfull, R. F., 1957: The Corrosion of Steel in a Reinforced Concrete Bridge,

Corrosion, 13, 173t.Test for Indentation Hardness of Organic Coatings, 1974: ASTM DesignationTimblin, L. O., and T. E. Backstrom, 1969: A Study of Depassivation of Steel inTripler, A . B., E. L. White, F. H. aynie, and W . K. Boyd, 1966: Methods forUhlig, H. H., 1971: Corrosion and Corrosion Control, Wiley, New York.Weatherby, D. E ., 1982: Tiebacks, Report FHWA/RD-82/047,U.S.Dept. Transp.

D 1474-68.Concrete, Report No. ChE-86, Bureau of Reclamation, Denver, Col.Reducing Corrosion of Reinforcing Steel, NCHRP Report 23.

Fed. Hwy. Admin., Washington, D.C.

6.1 corrosion and corrosion protection

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