ACI CommitteeCommentaries signing, executinment is intendcompetent to eof its content aresponsibility fotains. The Amerall responsibilitynot be liable for Reference to thdocuments. If iby the Architectuments, they shincorporation by

This document provide

rials and methods fo

under water. An overv

is presented as a gui

References are provide

materials and constru

ACI 546.2R-98

——* , **

of the

†, ††

comm

Jo

G

M

Guide to Underwater Repair of Concrete

Reported by ACI Committee 546

Reports, Guides, Standard Practices, andare intended for guidance in planning, de-g, and inspecting construction. This docu-

ed for the use of individuals who arevaluate the significance and limitations

nd recommendations and who will acceptr the application of the material it con-

ican Concrete Institute disclaims any and for the stated principles. The Institute shallany loss or damage arising therefrom.is document shall not be made in contracttems found in this document are desired/Engineer to be a part of the contract doc-all be restated in mandatory language for the Architect/Engineer.

546.2R

s guidance on the selection and application of mate-

r the repair and strengthening of concrete structures

iew of materials and methods for underwater repair

de for making a selection for a particular application.

d for obtaining additional information on selected

ction methods.

———Members who served as the editorial subcommittee for this document, and editor, respectively. G.W. DePuy also served as a member editorial subcommittee.

Members, associate membersa, and former membersf who served on the Underwater Repair Subcommittee, and Chairman of the sub-ittee, respectively, that prepared the initial drafts of this document.

William Allen† Leon Glassgold† Kenneth Saucier†

Robert Anderson†a Harald G. Greve Johan L. Silfwerbrand

Peter Barlow Terry Holland†a W. Glenn Smoak

hn J. Bartholomew* Martin Iorns†a Martin B. Sobelman

eorg Bergemann†a Robert F. Joyce Joe Solomon

ichael M. Chehab Lawrence F. Kahn Michael M. Sprinkel

Gary Chynoweth†a Tony C. Liu Ronald R. Stankie

Marwan A. Daye Mark Luther†f Steven Tate†a

Floyd E. Dimmick† James E. McDonald Robert Tracy†f

Peter H. Emmons Kevin A. Michols Alexander Vaysburd†

Jack J. Fontana Joseph P. Miller D. Gerry Walters

Jerome H. Ford Thomas J. Pasko Jr. Patrick Watson

Michael J. Garlich† Jay H. Paul Mark V. Ziegler††

Steven H. Gebler Don T. Pyle**

Keywords: cementitious; concrete; concrete removal; deterioration; evalu-ation; formwork; investigation; inspection; jackets; joints; materials;marine placement; polymer; protection; reinforcement; repair; strengthen;surface preparation; underwater; water.

Myles A. Murray*Chairman

Paul E. GaudetteSecretary

CONTENTSChapter 1—General, p. 546.2R-2

1.1—Introduction and general considerations1.2—Scope1.3—Diving technology

Chapter 2—Causes of deterioration, p. 546.2R-42.1—Marine organisms2.2—Deficient construction practices2.3—Chemical attack2.4—Corrosion2.5—Mechanical damage

ACI 546.2R-98 became effective September 21, 1998.Copyright 1998, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by any

means, including the making of copies by any photo process, or by electronic ormechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission inwriting is obtained from the copyright proprietors.

-1

546.2R-2 MANUAL OF CONCRETE PRACTICE

on

el

en red

onr oengighan

ure Tocalngs or ex-airce-on-

sh

gres-is ach-

pairtrolngi-cts can andthengi-.

ashans,, in-tion, de-rwa-ers,.

of, a or a

gwithtec-cu-and

am-ngessorbperi-le tosedllow anr-xi-ent

2.6—Freezing and thawing damage2.7—Salt scaling2.8—Damage not included in this guide

Chapter 3—E valuations and i nvestigations, p. 546.2R-6

3.1—Introduction3.2—Visual inspection3.3—Tactile inspection3.4—Underwater nondestructive testing of concrete3.5—Sampling and destructive testing

Chapter 4—Preparation for repai r, p. 546.2R-94.1—Concrete removal4.2—Surface preparation4.3—Reinforcement rehabilitation4.4—Chemical anchors/dowels

Chapter 5—Form work, p. 546.2R-105.1—Rigid and semi-rigid forms5.2—Flexible forms

Chapter 6—Methods and materials, p. 546.2R-156.1—General considerations6.2—Preplaced aggregate concrete6.3—Tremie concrete6.4—Pumped concrete and grout6.5—Free dump through water6.6—Epoxy grouting6.7—Epoxy injection6.8—Hand placement6.9—Other underwater applications using concrete c

taining anti-washout admixtures

Chapter 7—Inspection of repai rs, p. 546.2R-217.1—Introduction7.2—Procedure7.3—Documentation

Chapter 8—D eveloping te chnologies, p. 546.2R-228.1—Precast concrete elements and prefabricated ste

ements

Chapter 9—References, p. 546.2R-229.1—Recommended references9.2—Cited references

CHAPTER 1—GENERAL1.1—Int roduction

The repair of concrete structures under water presmany complex problems. Although the applicable basicpair procedures and materials are similar to those requiretypical concrete repair, the harsh environmental conditiand specific problems associated with working under watein the splash zone area (Fig. 1.1) cause many differences. Threpair of concrete under water is usually difficult, requirispecialized products and systems, and the services of hqualified and experienced professionals. See ACI SP-8 SP-65.

Proper evaluation of the present condition of the structis the essential first step for designing long-term repairs.be most effective, long-term evaluation requires historiinformation on the structure and its environment, includiany changes, and the record of periodic on-site inspectionrepairs. Comprehensive documentation of the cause andtent of deterioration, accurate design criteria, proper reptechniques, and quality assurance of the installation produres and the repair will result in a better repair system. Lgevity of the repair is the ultimate indicator of success.

Underwater concrete deterioration in tidal and splazones is a serious economic problem (Fig. 1.2 and 1.3). Wa-ter that contains oxygen and contaminants can cause agsive attack on concrete. Underwater repair of concrete specialized and highly technical part of concrete repair tenology. It presents problems of selecting appropriate rematerials and methods, and of maintaining quality connot normally associated with repair above water. Sound eneering, quality workmanship and high-performance produand systems are extremely important. Successful repairsbe achieved when these factors are considered carefullyproperly implemented. This guide provides an overview of current status of underwater repair technology to aid the eneer, designer, contractor and owner in making decisions

-

el-

ts-insr

lyd

1.2—ScopeThis guide is limited to concrete structures in the spl

zone and underwater portions of typical lakes, rivers, oceand ground water. Concrete deterioration, environmentsvestigation and testing procedures, surface preparatypes of repair, repair methodology, and materials arescribed. Design considerations and references for undeter repair of concrete bridges, wharves, pipelines, pioutfalls, bulkheads, and offshore structures are identified

1.3—Diving technolo gyUnderwater work can be generally classified into one

the three broad categories of diving: manned divingone-atmosphere armored suit or a manned submarine,remotely-operated vehicle (ROV).

Manned diving is the traditional method of performintasks under water. In this category, the diver is equipped life-support systems that provide breathable air and protion from the elements. Manned diving systems include sba (self-contained underwater breathing apparatus) surface-supplied air.

Performance of duties at higher than one atmospherebient pressure causes a multitude of physiological chawithin the human body. For instance, body tissues aband shed gases at different rates than those normally exenced on the surface. Because of this, the time availabperform work under water decreases rapidly with increawater depth. For example, industry standards currently aa diver using compressed air to work at 30 ft (10 m) forunlimited period of time. However, if work is being peformed at 60 ft (20 m), the diver can only work for appromately 60 min without special precautions to prev

546.2R-3GUIDE TO UNDERWATER REPAIR OF CONCRETE

Fig. 1.1—Repair zones: submerged, tidal, exposed.

.

f M.

Fig. 1.2—Deteriorated piles in tidal and exposed zones. (Courtesy of I. Leon Glassgold.)

lilimp de

ws

Fig. 1.3—Advanced deterioration, pile has been cleaned(Courtesy of I. Leon Glassgold.)

m-

reivp

a o

ency,ells, for

quiv-s as- as

decompression sickness. The industry standard upperis 30 min work time at 90 ft (30 m) in seawater. If these its are exceeded, precautions must be taken to decomthe diver. The sophistication (and hence the cost) of theing systems used on a project increases with increased d

If manned diving is used deeper than 180 ft (60 m) ofter, most divers elect to use specially formulated mixture

it

ss-th.

-f

gases rather than compressed air. To increase efficithese diving operations are often enhanced with diving bwhich are used to maintain the divers at working depthsextended periods of time. Divers may be supported at ealent water depths for weeks at a time. The technologiesociated with mixed gas diving are changing rapidlypeople work at deeper depths.

Fig. 1.4—Remotely operated vehicle (ROV). (Courtesy oGarlich.)

546.2R-4 MANUAL OF CONCRETE PRACTICE

uipo in

in aforkswh

most.erosomrmana

k.un,a rca opershehiphyruspe

eds

s of-.

the) ra-t ofion,m- or

achy the

resop-one,r thefiedn ofcing un-d thereteone,early

ol-es intion

tion may

A recent development is the One Atmosphere Diving S(Hard Suits, Inc., 1997). These suits are capable of suping divers at depths as great as 2,100 ft (640 m), with anternal suit pressure of one atmosphere. The diver works ambient pressure equivalent to that on the surface; therethe time at depth is virtually unrestricted. The suit loomuch like a hollow robot. The arms are equipped with clalike operating devices, which reduce manual dexterity. Tsuits are cumbersome and difficult to position, because bility is provided by external propulsion devices, ballatanks or cables suspended from topside support vessels

Mini-submarines are occasionally used to perform undwater work. These typically have crews of two or three. Mare equipped with video and photographic equipment. Ssubmarines are also equipped with robotic arms for perfoing tasks outside of the submarine. The lack of dexterity limitations on the positioning capability of these vessels mhamper their effectiveness for inspection and repair wor

Remotely operated vehicles (ROVs) look much like an manned version of a submarine (Fig. 1.4) (Vadus and Busby1979). They are compact devices that are controlled by mote crew. The operating crew and the vehicle communithrough an umbilical cord attached to the ROV. The crewerates the ROV with information provided by transpondattached to the frame of the ROV. ROV’s may be launcdirectly from the surface or from a submarine mother sMost ROV’s are equipped with video and still photograpdevices. The vehicle is positioned by ballast tanks and thers mounted on the frame. Some ROV’s also are equipwith robotic arms, used to perform tasks that do not nehigh degree of dexterity. ROV’s have been used at depthapproximately 8,000 ft (2,400 m).

i- welloarmsol ev

lfide hyersro-te carceon ra

ffi-ion

con-crete, theeseucts new

cks,ce-tionare

gher

emi-aily

.reteid tolow

ore

is-ctionn ofhed

CHAPTER 2—CAUSES OF DETERIORATION2.1—Marine organisms

2.1.1 Rock borers—Marine organisms resembling ordnary clams are capable of boring into porous concrete asas rock. These animals, known as pholads, make shaoval-shaped burrows in the concrete. Rock borers in wwater areas such as the Arabian Gulf are also able to disand bore into concrete made with limestone aggregate,if the aggregate and concrete is dense.

2.1.2 Acid attack from acid-producing bacteria—Anaero-bic, sulfate reducing bacteria can produce hydrogen suSulfur-oxidizing bacteria, if also present, can oxidize thedrogen sulfide to produce sulfuric acid, common in sewAlso, oil-oxidizing bacteria can produce fatty acids in aebic conditions. These acids attack portland cement pasconcrete, dissolving the surface. In addition, the acidslower the pH of the concrete to a level where the reinfoment is no longer passivated. Once this occurs, corrosithe reinforcing steel can begin, often at an accelerated(Thornton, 1978; Khoury et al., 1985).

2.2—Deficient construction practices and errorsBecause of the difficult working conditions and the di

culty of providing adequate inspection during construct

trt--ne,

-e-

-te-dy

-

e-te-

d.

t-d

aof

llw,

veen

.-.

inn-inte

,

underwater placement of concrete and other materials iten susceptible to errors and poor construction practices

Deficient practices include the following: exceeding specified water-cement (or water-cementitious materialstio, inadequate surface preparation, improper alignmenformwork, improper concrete placement and consolidatimproper location of reinforcing steel, movement of forwork during placement, premature removal of formsshores, and settling of the concrete during hardening. Eof these practices is discussed in a manual prepared bCorps of Engineers (Corps of Engineers, 1995).

One specialized deficiency common to marine structuis tension cracking of concrete piling, resulting from imprer driving practices. Both under water and in the splash zcracks in concrete increase concrete permeability neacrack. Thus in seawater, chloride penetration is ampliboth in depth and concentration in the immediate locatiothe crack, leading to creation of an anode at the reinforbar. This usually does not lead to significant corrosion ofderwater concrete because of the low oxygen content ansealing of the crack by lime, which leaches from the concand also comes from marine organisms. In the splash zhowever, the presence of such cracks can lead to the onset of localized corrosion.

Construction or design errors can result in formwork clapse, blowouts of pressurized caissons, and breachcofferdams. These situations usually require reconstrucand are beyond the scope of this guide.

2.3—Chemical attackConcrete under water is susceptible to deteriora

caused by a wide range of chemicals. This deteriorationbe classified as that caused by chemicals outside thecrete, and that caused by chemicals present in the conconstituents themselves. In situations of external attackwater frequently provides a continuous fresh supply of thchemicals. The water also washes the reaction prodaway and removes loose aggregate particles, exposingconcrete surfaces to further attack.

Internal attack is accelerated by porous concrete, craand voids. Alkali-silica reactions and corrosion of reinforment are examples of internal attack. Internal deterioraalso results when soluble constituents of concrete leached out, resulting in lower concrete strengths and hiporosity.

Splash zone concrete is particularly susceptible to chcal attack because of the frequent wetting and drying, dwave or tide action, and the abundant supply of oxygen

Chemicals present in the water surrounding the conccan cause deterioration that varies in rate from very rapvery slow. Chemical attack is slowed considerably by temperatures. The following discusses several of the mcommon types of chemical attacks on concrete.

2.3.1 Acid attack—Portland cement concrete is not restant to attack by acids. In most cases the chemical reabetween acid and portland cement results in the formatiowater-soluble calcium compounds that are then leac

546.2R-5GUIDE TO UNDERWATER REPAIR OF CONCRETE

in

l- wahault rigeved tna, aln ousuACaw

reionad

-ommicakes

e-tionorigactheari-re-tedtioagtio

ac-ls.

-ill iaferv,d boaal

eteir, atraemion

ina0 p

e ten- formovernt to

l-andtingent

th ofed re-pro-

ro-ladenwithand

ctro-lvedhuses-f therete notd.

con-tidesle op-ea-entsan in be

ble to

ayact

of aBe- great,H-

maytance, im-di-and

ants.a-ainstrface.still-d pil-ents.

away. ACI 201.2R and ACI 515.1R describe acid attackfurther detail.

2.3.2 Sulfate attack—Sulfates of sodium, potassium, cacium, or magnesium are often found in seawater, groundter rivers, or in industrial water. The chemical reactions ttake place between sulfate ions and portland cement resreaction products that have a greater volume than the onal solid constituents. This volume change causes the dopment of stresses in the concrete that eventually leacracking and deterioration. ACI 201.2R describes additiodetails of the sulfate attack mechanism. It points out thatthough seawater contains a high enough concentratiosulfate ions to cause concrete disruption, the reaction is ally less severe than would otherwise be expected. 201.2R indicates that the chloride ions also present in seter inhibit sulfate attack.

2.3.3 Magnesium ion attack—Magnesium ions present inground water may react with the calcium silicate hydrate,placing calcium ions with magnesium. When this reactoccurs, there is a reduction in cementitious properties, leing to deterioration.

2.3.4 Soft water attack—Soft water has very low concentrations of dissolved minerals and may leach calcium frthe cement paste or aggregate. This is a particular problewater flows continuously over the concrete so that chemequilibrium is not achieved. This attack apparently taplace very slowly (DePuy, 1994).

2.3.5 Internal attack—Several reactions can take place btween the constituents of the concrete. Typically, reacproducts develop that occupy a volume greater than the inal solid materials, resulting in increased stresses and cring. The most common of these internal reactions is alkali-silica reaction. In this case the alkalis present primly in portland cement react with silica found in certain agggates. Alternating wetting and drying frequently associawith the aquatic splash zone does accelerate this reacAlso, salt in marine environments can accelerate alkali-gregate reactions by increasing the sodium ion concentrauntil it is above the minimum level necessary for alkali retivity (Nevielle, 1983). ACI 201.2R gives additional detai

2.4—Corrosion2.4.1 Introduction—A significant number of cases indi

cate that corrosion of reinforcing steel has been and stthe most serious and critical threat to the durability and sty of concrete structures in marine environments (Gjo1968). The serious nature of this problem is demonstratethe many examples of cracked and spalled concrete at cal locations caused by corrosion of the reinforcing steel (Hstead and Woodworth, 1955).

Corrosion occurs rapidly in permeable, porous concrthat is exposed alternately to salt-water splash and to ain tidal and splash zones. Chlorides of varying concentions are deposited in the concrete, setting up electrochcal reactions and corroding the reinforcing steel. Corrosproducts occupy several times the volume of the origmetal and can develop internal pressures as high as 470

-tini-l-ol-f-

Ia-

-

-

ifl

-k-

n.-n

s-

yst--

s-i-

lsi

(30 MPa), creating a stress many times greater than thsile strength of the concrete (Rosa et al., 1913). Cracksalong the reinforcing bars and eventually the concrete cspalls. This allows the corrosion of the steel reinforcemeaccelerate.

2.4.2 The corrosion process—Steel in concrete is normaly protected chemically by the alkalinity of the concrete, is highly resistant to corrosion. This is due to a passivafilm that forms on the surface of embedded reinforcemand provides protection against corrosion. Greater depcover and less permeable concrete also provide increassistance to the ingress of chloride ions, which can commise the passivating film.

Corrosion of reinforcing steel is an electrochemical pcess that requires an electrolyte (such as moist, cation-concrete), two electrically connected metallic surfaces different electrical potentials, and free oxygen (Burke Bushman, 1988).

When the concrete is permeable, the entry of the elelyte and oxygen are facilitated. Water containing dissosalt provides an electrolyte of low electrical resistivity, tpermitting corrosion currents to flow readily. Oxygen is sential to the electrochemical reaction at the cathode ocorrosion cell. Consequently, steel in reinforced conccompletely and permanently immersed in water doescorrode appreciably because oxygen is virtually exclude

A severe exposure condition exists when part of the crete structure is alternately wetted by salt water, as by or sea spray. The part that is alternately wetted has ampportunity for contact with atmospheric oxygen. For this rson, reinforcing steel in concrete in aqueous environmcorrodes faster in the tidal zone and the spray areas thother areas. Additional information on corrosion mayfound in ACI 222R.

2.5—Mechanical damageConcrete structures in and around water are suscepti

various types of mechanical damage.2.5.1 Impact—Impact damage to a concrete structure m

range from the shallow spalling caused by a light impfrom a barge brushing against a lock wall to total loss structure caused by a ship colliding with a bridge pier. cause the range of damage caused by impact can be soit is not possible to define a typical set of symptoms (AASTO, 1991).

In cases of less than catastrophic impact, the damagebe under water and hence undetected. In such an insthe structure suffers not only from the direct result of thepact (typically cracking and spalling), but also from the inrect results of greater access to interior concrete reinforcing steel by the water and water-borne contamin

2.5.2 Abrasion—Abrasion is typically caused by wter-borne particles (rocks, sand, or rubble) rubbing agand to some degree impacting against a concrete suTypical underwater abrasion could include damage to ing basins of hydraulic structures, or damage to piers aning caused by abrasive particles being carried by curr

546.2R-6 MANUAL OF CONCRETE PRACTICE

ornr reiclelased sectehe ir of

iseamset re acreconinoranughusihenm-

ee fucea

ezmb

rispties

er-ivehenes tre

cycn o

wng iie-

anherienbe-se

t. In de in

f de-

awa-esulte un-

s ofnts.ture,rfacelt so-henpres-th the

portly in-nda-ir of

ual-nce

ecialvent,978;esti- test-

ersewa-rti-

ise

s thein-ost

med

ac-ovee in-rial in-ary

obvi-tifiesriousloca-e thesary.

Abrasion such as in a stilling basin typically produces a wand polished concrete surface with heavily exposed omoved coarse aggregate. Abrasion by water-borne parttypically produces an appearance similar to that of sandbed concrete. Abrasion damage to concrete is discussACI 201.2R and ACI 210R. Abrasion damage is also cauby the movement of ships moored to inadequately protestructures. Again, the damage allows greater access to tterior concrete. In cold climates, ice is a major contributoabrasion damage.

2.5.3 Cavitation—Cavitation damage to concrete caused by the implosion of vapor bubbles carried in a strof rapidly flowing water. The bubbles are formed and subquently destroyed by changing pressure conditions thasult from discontinuities in the flow path. Cavitation isserious problem since the force exerted upon the conwhen the bubbles implode is large enough to remove crete. Cavitation may result in damage ranging from msurface deterioration to major concrete loss in tunnels conduits. Cavitation damage initially appears as very roareas on a concrete surface. Since the mechanism cacavitation is self-supporting once initiated, damage tworsens in the direction of flow. Details of cavitation daage are discussed in ACI 210R.

2.5.4 Damage due to loads—A concrete structure may bdamaged by seismic forces or loads greater than thoswhich it has been designed. The typical symptoms of sdamage will be major structural cracking in tension or shareas and spalling in compression areas.

2.6—Freezing and thawing damageDeterioration of saturated concrete due to cycles of fre

ing and thawing action has been observed in a large nuof structures exposed to water and low temperatures.

The freezing of water in the pores of concrete can giveto stresses and cause rupture in the paste. The disruforces are due to the fact that as water freezes it increasvolume by about 9 percent.

Concrete that is continuously submerged will usually pform well. In the tidal zone, however, it is subject to actfreeze-thaw cycling in cold climates. Freezing occurs wthe tide drops, exposing wet concrete. The water freezthe concrete pores, expands, and tends to create large ses. When the tide eventually rises, the ice melts and the repeats. This cycling causes progressive deterioratioconcrete unless it is adequately air entrained.

Extensive field and laboratory investigations have shothat the rate of deterioration due to freezing and thawinconsiderably higher in salt water than in fresh water (Wbenga, 1985). This difference in resistance to freezingthawing is normally ascribed to the generation of a highydraulic pressure in the pore system due to salt gradand osmotic effects. Small air voids in the concrete will come water-filled after a long period of immersion. Thevoids may also be more easily filled when salt is presenspite of the low frost resistance of concrete in salt water,terioration normally takes place very slowly. However,

-st-inddn-

--

te-

d

ng

orhr

-er

eve in

inss-lef

s

d

ts

-

tidal zones the concrete is also exposed to other types oterioration processes (Klieger, 1994).

Concrete subjected to many freeze-thaw cycles in seter can increase in volume due to the micro-cracks that rfrom inadequate freeze-thaw resistance. This can causdesirable deformations in flexural members.

2.7—Salt scalingDamage due to salt scaling is usually limited to portion

the structure in the splash zone in marine environmeWhen water with dissolved salts splashes onto a strucsome of it migrates into the concrete through cracks, suvoids, pores and capillaries. As the concrete dries, the salution is concentrated and eventually crystals form. Wthe salt then changes to a higher hydrate form, internal sure results and the concrete disintegrates just beneasurface.

2.8—Damage not included in this guideScour occurs when water currents undermine the sup

of concrete structures. Correcting scour damage usualvolves repairs to earth or rock supporting concrete foutions rather than repairs to concrete. Therefore, repascour damage is not included in this guide.

CHAPTER 3—EVALUATIONS AND INVESTIGATIONS

3.1—IntroductionStructural investigations of underwater facilities are us

ly conducted as part of a routine preventive maintenaprogram, as an initial construction inspection, as a spexamination prompted by an accident or catastrophic eor as a method for determining needed repairs (Busby, 1Popovics, 1986; Sletten, 1997). The purpose of the invgation usually influences the inspection procedures anding equipment used.

Underwater inspections are usually hampered by advconditions such as poor visibility, strong currents, cold ter, marine growth, and debris buildup. Horizontal and vecal control for accurately locating the observationdifficult. A diving inspector must wear cumbersomlife-support systems and equipment, which also hamperinspection mission. This section will focus primarily on spection efforts conducted by a diving team. However, mof the discussion also applies to other inspections perforby ROV’s and submarines.

Underwater inspections usually take much longer tocomplish than inspections of similar structures located abthe water surface. This necessitates more planning by thspecting team to optimize their efforts. Inspection criteand definitions are usually established prior to the actuaspection, and the inspection team is briefed. The primgoal is to inspect the structural elements to detect any ous damage. If a defect is observed, the inspector identhe type and extent of the defect to determine how sethe problem may be. The inspector also determines the tion of the defect so repair crews can return later to makrepair, or another inspection team can reinvestigate if neces

546.2R-7GUIDE TO UNDERWATER REPAIR OF CONCRETE

ot Inpreiateinghe

tiontionon

he ofulderce

a-beoutthehe

ththe hic-l. I

n-

ustdi-uetheem

d ofblepa

life

bel-

artve-ff-a

atetere

fur-eri-

r in-ith at of rul-

ngths,n thepro-llytape

ica-th- of andmu-

well.par-ore ex-ords the

de,en-s ofet di-

allyd in-cord-e ofica-le orbili-ectsice de-ice.

thederily- be

par-ngally

armultyay

Many divers who perform structural inspections do nhave specific structural engineering training for this task.this case, a second person is normally employed to interthe results of the inspection and make the approprevaluations. Occasionally, this person will be present durthe inspection to direct the efforts of the diver or direct tuse of video equipment.

3.1.1 Planning the investigation—Once the scope of theinvestigation has been defined, the client and the inspecteam plan the mission. The purpose of the pre-inspecmeeting is to help identify the equipment, the inspectitechniques, and the type of documentation required.

Planning usually begins with a thorough review of toriginal design and construction drawings and a reviewthe previous inspections and repairs, if any. The team coplan to conduct the investigation during optimum weathconditions to minimize hazardous conditions and to reduthe effects of reduced visibility.

Inspection notes typically consist of a dive log with nottions of specific features. These notes may be transcrifrom a slate used by the diver, or from a work sheet filled by topside personnel if voice communication is used in operation. These notes may be supplemented with sketcphotographs, or video tape.

3.1.2 Evaluating the findings—As with any structural in-spection, evaluation of the inspection results is perhapsmost difficult task. The evaluator studies the contents of inspection report, then interprets the results based onknowledge of the facility. The skill of the diver as an inspetor is essential for the evaluation process to be meaningfuis the diver’s responsibility to qualify and quantify the codition and defect.

During this phase of the investigation, the evaluator mdecide if the observed defects are minor or major. In adtion, to help decide the actions required to ensure continservice of the facility, the evaluator also judges whether defect will continue to degrade the structure or if the problhas stabilized.

3.1.3 Deciding what actions to take—Deciding on the ap-propriate action to take after a defect has been discoveredpends on the potential hazard of the defect, the riskcontinued structural deterioration, the technology availato repair the defect, the cost associated with the needed reand the intended remaining life of the structure.

If the defect presents a hazard that threatens either thesafety of individuals working on or near the facility, or thcontinued operation of the facility, remedial action shouldtaken immediately. A critical structural condition is generaly repaired promptly.

The logistics of a repair problem often dictate at least pof the solution. For example, repair of a pier may be relatily straightforward, but the repair of similar defects on an oshore arctic structure, or repair of an outfall for hydroelectric structure, can be much more difficult.

If the defect does not threaten life safety or the immedioperation of a facility, the owner or operator of an underwastructure has more options. A minor defect is often merly

t

d

s,

e

s

t

d

e-

ir

e

monitored for continued deterioration. If none is noted, ther action may not be required. However, if a defect is sous, repair is usually needed.

3.2—Visual inspectionVisual inspections are the most common underwate

vestigations. These inspections are usually performed wwide variety of simple hand tools. Physical measuremena defect may be approximated using visual scaling, handers, tape measures, finger sizes or hand spans, body leand depth gages. The selection of the tools depends oaccuracy of measurement required. Visual inspections vide the information for the written report, which is usuasupplemented with photographic documentation, video documentation, or sketches.

If scuba is used as the primary diving mode, communtion with the surface is limited. The typical scuba moupiece does not allow the diver to speak. However, usefull face mask in place of the traditional mouthpiece amask can accommodate either hardwire or wireless comnication systems. Wireless systems do not always work The hardwire system, which does work well, requires a tial umbilical to the surface, and therefore it may be mpractical to provide surface-supplied air to give the divertended time under water. Customarily the dive team recresults of the inspection on slates and later transcribenotes onto an inspection form.

If surface-supplied air is used as the primary diving mothe dive team has much more flexibility with the documtation of the inspection. The diver can relay descriptionthe observations directly to the topside team, and also grection from the team members on the surface.

Video cameras are either self-contained or umbilicserved. The self-contained video camera is a hand-helstrument that contains both the video camera and the reer, and is operated by the diving inspector. The other typvideo is served with a supplemental power and communtion cord, and is either attached to an underwater vehicheld by the diver. The video image is sent along the umcal cord to a monitor and recorder. The surface crew dirthe diver or the ROV to position the camera. If there is vocommunication, the diver can describe the details of thefect as while directing the camera lens. The driver’s vomay be recorded in real time with the image on the tape

3.3—Tactile inspectionTactile inspections (inspections by touch) are perhaps

most difficult underwater surveys. Usually conducted unconditions of extremely poor visibility, such as in a heavsilted river, a settling pond, or a pipeline, they may alsorequired where the element to be inspected is totally ortially buried by silt. The diver merely runs his hands alothe structural element to find a defect. The defect is usuquantified relative to the size of the inspector’s hand andlengths. Once a defect is found, the diver may have difficproperly describing the position of the defect so that it mbe located and repaired at a future date.

546.2R-8 MANUAL OF CONCRETE PRACTICE

vap

emel-o

rmoaD

s oreoe.e

alteempis

ifoec fa

odrmreete

e prr

oxndca

fo uda bfo t

the de-

er un-h totheWA, in andeddingHighavellect-s the

epther isoccur

i-t thatcing sys-rwa-ctedears, otherduct- ver-ique, the ob-retezas-

tom)

acks,terial.spec- Ra-roofcityretear-

sys- un-of

rate-se ofscand pri-oor.tiontion

3.4—Underwater nondestructive testing of concrete

Studies of nondestructive testing (NDT) of concrete hashown that the following techniques and instruments are plicable to underwater work. Information regarding equiment is available from equipment manufacturers.

3.4.1 Soundings—Soundings are taken by striking thconcrete surface to locate areas of internal voids or delanation of the concrete cover as might be caused by the effof freezing and thawing or corrosion of reinforcement. Athough the results are only qualitative in nature, the methis rapid and economical and enables an expeditious detenation of the overall condition. The inspector’s ability thear sound in water is reduced by waves, currents, and bground noise. Soundings are the most elementary of Nmethods.

3.4.2 Ultrasonic pulse velocity—Ultrasonic pulse velocity(ASTM C 597) is determined by measuring the time of tranmission of a pulse of energy through a known distanceconcrete. Many factors affect the results, including agggate content and reinforcing steel location. The results tained are quantitative, but they are only relative in natur

Ultrasonics can be used successfully under water to hevaluate the condition of concrete structures. Commerciavailable instruments have been modified for underwause. Laboratory and field tests of the instruments have donstrated that the modifications had no effect on the outdata (Olson et al., 1994). Both direct and indirect transmsion methods can be used in the field to evaluate the unmity of concrete and obtain a general condition rating. Dirultrasonic transmission measurements generally canmade by an individual, while indirect measurements arecilitated by the use of two or more people.

A special form of this technique is the pulse-echo methThe pulse-echo method has been used for the in-situ detenation of the length and condition of concrete piles. Low fquency, impact echo sounding devices have proven veffective for locating deep delaminations in thick concremembers in the splash zone (Olson, 1996).

3.4.3 Magnetic reinforcing bar locator—A commerciallyavailable magnetic reinforcing bar locator (or pachomethas been successfully modified for underwater use. Thechometer can be used to determine the location of reinfoing bars in concrete, and either measure the depth of conccover or determine the size of the reinforcing bar, if onethe other is known. Techniques are available for appromating each variable if neither is known. Laboratory afield tests of the instrument demonstrated that the modifition for underwater use had no effect on the output data.

3.4.4 Impact hammer—A standard impact hammer(ASTM C 805), modified for underwater use, can be usedrapid surveys of concrete surface hardness. However, thederwater readings are generally higher than comparable obtained in dry conditions. These higher readings couldeliminated by further redesigning of the Schmidt hammer underwater use. Data also can be normalized to eliminateeffect of higher underwater readings. However, measurement

ep--

i-cts

di-

ck-T

-f-

b-

lplyr-

ut-r-t

be-

.i-

-ry

r)a-c-eteri-

-

rn-taerhe

of low compressive strength concrete is limited becausemodifications required for under water use lowered thetection threshold (Smith, 1986).

3.4.5 Echosounders—Another ultrasonic device, thechosounders (specialty fathometers), can be useful foderwater rehabilitation work using tremie concrete, botdelineate the void to be filled and to confirm the level of tremie concrete placed (Corps of Engineers, 1994; FH1989). They are also effective in checking scour depthstream bed. They consist of a transducer which is suspein the water, a sending/receiving device, and a recorchart or screen output which displays the water depth. frequency sound waves emitted from the transducer trthrough the water until they strike the bottom and are refed back to the transducer. The echosounder measuretransit time of these waves and converts it to water dshown on the display. However, when an echosoundused very close to the structure, erroneous returns may from the underwater structural elements.

3.4.6 Side-scan sonar—A side-scan sonar system is simlar to the standard bottom-looking echo sounder, excepthe signal from the transducer is directed laterally, produtwo side-looking beams (Clausner and Pope, 1988). Thetem consists of a pair of transducers mounted in an undeter housing, or “fish,” and a dual-channel recorder conneto the fish by a conductive cable. In the past several ythe side-scan technique has been used to map surfacesthan the ocean bottom. Successful trials have been coned on the slopes of ice islands and breakwaters, and ontical pier structures. Although the side-scan sonar technpermits a broad-scale view of the underwater structurebroad beam and lack of resolution make it unsuitable fortaining the kind of data required from inspections of concstructures (Corps of Engineers, 1994; Garlich and Chrtowski, 1989; Hard Suits, Inc., 1997; Lamberton, 1989).

3.4.7 Radar—Certain types of radar have been usedevaluate the condition of concrete up to 30 in. (800 mthick. Radar can detect delaminations, deteriorations, crand voids. It can also detect and locate changes in maRadar has been used successfully as an underwater intion tool, and is being developed for possible future use.dar with the antenna contained in a custom waterphousing was used in 1994 in conjunction with pulse velotesting to investigate the structural integrity in a concplug submerged 150 ft (46 m) in a water supply tunnel (Glich, 1995).

3.4.8 Underwater acoustic profilers—Because of knownprior developmental work on an experimental acoustic tem, acoustic profiling has been considered for mappingderwater structures. Erosion and down faulting submerged structures have always been difficult to acculy map using standard acoustic (sonic) surveys becaulimitations of the various systems. Sonic surveys, side-sonar, and other underwater mapping tools are designemarily to see targets rising above the plane of the sea fl

In 1978, the U.S. Army Corps of Engineers in conjuncwith a private contractor investigated a high resolu

546.2R-9GUIDE TO UNDERWATER REPAIR OF CONCRETE

io tae

ec

m

b

aolo

ti

no

o ea

esst

oe l

s

dp i

o

pe.f a

eriortiga-osedepre-rete.ana-t thenated

ustdure

stedsive sup-0 psipabletiondiv-iron-rificeres-bles

m-ersater, theents ofeffi-iver.re toe TVs the

usedan bethis

icaln in

eri-ete isoode ex-ues,tting

ignedthe

acoustic mapping system for use on a river lock evaluat(Thornton and Alexander, 1987). The first known attemptdevelop an acoustic system suitable for mapping the surfcontours of stilling basins, lock chamber floors, and othunderwater structures, this system is similar to commercdepth sounders or echo sounders but has a greater degraccuracy. The floor slabs of the main and auxiliary lochambers were profiled, and defects previously locateddivers were detected. Features of the stilling basin suchthe concrete sill, the downstream diffusion baffles, and soabrasion-erosion holes were mapped and profiled. The acracy of the system appeared to be adequate for defining tom features in the field.

Work has continued on the system, which contains acoustic subsystem, a positioning subsystem, and a cpute-and-record subsystem. The system’s capabilities alit to “see” objects rising above the plane of the bottom, etract data from narrow depressions and areas close to versurfaces, provide continuous real-time data on the conditof the bottom surface, and record and store all data.

3.5—Sampling and destructive testingIn some cases, visual or nondestructive inspections do

adequately indicate the internal condition of a structure. Clecting concrete samples may be necessary.

3.5.1 Cores—Concrete cores are the most common typesamples. Conventional electric core drilling equipmentnot readily adaptable for underwater use. However, convtional core drilling frames have been modified for underwter use by replacing electric power with hydraulic opneumatic power drills. Drill base plates are usually boltto the structure. Rather than have the operator apply thruthe bit as is the usual case in above-water operation, presregulated rams or mechanical levers are used to apply force.

A diver-operated coring apparatus can drill horizontal vertical cores to a depth of 4 ft (1.2 m). The core diametare up to 6 in. (150 mm). The equipment is light enoughbe operated from an 18 ft. (5.5 m) boat. Larger cores amay be taken, brought to the surface, and sectioned inlaboratory to obtain test specimens of the proper dimensio

Core holes should be patched after the core specimen imoved.

3.5.2 Other sampling techniques—Pneumatic or hydraulicpowered saws and chipping hammers also can be usetake concrete samples from underwater structures. Samof reinforcing bar are usually taken by cutting the bar withtorch, although a pneumatic or hydraulic powered saw wan abrasive or diamond blade can be used. Some high-psure water jets can cut reinforcing steel.

3.5.3 Sampling considerations for cores used in petrgraphic, spectrographic, and chemical analysis—Whensamples are used to detect changes in the chemical comtion or microstructure of the concrete, they are usually rinswith distilled water after they reach the surface, then drieda case sample is of adequate size, the exterior portions osample, which may have been contaminated with seawter

nocer

iale ofkby as

ecu-ot-

nm-w

x-icalon

otl-

fisn--

rdt tourehis

rrstosothens. re-

tolesathres-

-

osi-d

Ifthe

during the sampling operation, are removed and the intsections are sent to the laboratory for petrographic investion. If chloride content measures are needed, the expend surface of the sample is not removed, because it rsents the degree of contamination in the original concCuttings and powder from concrete coring also can be lyzed, although recognition must be given to the fact thamaterial has been mixed and may have been contamiby surface deposits (Dolar-Mantuani, 1983).

CHAPTER 4—PREPARATION FOR REPAIR4.1—Concrete removal

General practice is to remove only the concrete that mbe replaced while exposing sound concrete. This proceminimizes the cost of the repair.

4.1.1 High-pressure water jets—High-pressure water jetprovide an efficient procedure for removing deterioraconcrete, especially where the concrete’s compresstrength is less than 3000 psi (20 MPa). Fresh water isplied to the pump and transferred to a nozzle at 10,00(70 MPa). To achieve success, the nozzles must be caof developing an equivalent thrust in the opposite direcof the main nozzle to minimize the force exerted by the er. This reduces diver fatigue, provides a safer work envment, and lowers concrete removal costs. Standard onozzles are well suited to cutting concrete, but at high psure, a standard orifice nozzle may cause cavitation bubat the surface of the concrete.

4.1.2 Pneumatic or hydraulic powered chipping hamers—Pneumatic or hydraulic powered chipping hammdesigned for surface repairs are easily modified for underwuse. To absorb the reaction force of the chipping hammerdiver must be tied off to the structure or another fixed elem.

Pneumatic or hydraulic chipping hammers on the endsurface-mounted booms with TV cameras provide an cient concrete removal system without the need for a dThe booms are commonly mounted to a stable structuassure the necessary stability and operating safety. Thcamera lets the operator see below the surface and allowoperator to remove the deteriorated concrete.

4.1.3 Pneumatic or hydraulic-powered saws—Pneumaticor hydraulic saws designed for surface use can also beunder water. The necessary force to execute the work capplied without the use of an external support. When work is carried out in muddy or silty water a mechanguide is employed, allowing the operator to continue evelow-visibility conditions.

4.2—Surface preparationTypically, all marine growth, sediment, debris, and det

orated concrete should be removed before repair concrplaced into a structure. This cleaning is essential for gbond to occur between the newly placed concrete and thisting concrete. Numerous cleaning tools and techniqsuch as high-pressure water jets, chippers, abrasive jeequipment, and mechanical scrubbers have been desspecifically for cleaning and preparing the surface of

546.2R-10 MANUAL OF CONCRETE PRACTICE

deteles foans

ujecaiream

ee

wathc

itn),

Pac

sar to srsodgo.

th rerm

rina

ffes o

in-s te re

ce Thn

behe re-s areone

ngn be

elyn ofwn,

an- pro-ten the un-

s thanonsty is al-n an of

gi-chor

hor-de-routsions

uit-mi-n ca-ent.

ionuchpairmer de-ct as

te oro the

as theec-d,rete.

submerged portions of underwater structures.11 The type ofequipment required for an effective cleaning operation is termined by the type of fouling that is to be removed. Wajets operated by divers or fixed to self-propelled vehichave been effective in most cleaning applications. Toolsremoving underwater debris are also available. Air-lifts cbe used to remove sediment and debris from water depthup to about 75 ft (25 m).

The type of surface preparation and the required procedvaries with the site conditions as well as the specified obtives. In muddy or silty waters it is essential that the repprocedure be carried out the same day that the surface paration has been completed to minimize the surface contination that follows the cleaning operation.

4.2.1 High pressure water jet—High-pressure water jetscan remove loose corrosion product from reinforcing stduring the concrete removal or cleaning process.

Fan jet nozzles on 10,000 psi (70 MPa) high-pressure ter jets are an efficient method of removing marine growand fouling on the surface. The optimum standoff distanfor cleaning surfaces is 1/2 to 3 in. (10 to 80 mm) with an im-pingement angle of 40 to 90 degrees. When operating wequipment that has a flow rate of 26 gal/min (100 l/micleaning rates of 4 to 7 ft2/min (0.35 to 0.65 m2/min) can beachieved on fouled concrete surfaces.

High-pressure water jets operating at 5000 psi (35 Musing a fan jet nozzle can clean previously prepared surfathat have been contaminated by muddy or silty water.

4.2.2 Abrasive blasting—Abrasive blasting can be used aa final surface preparation for areas that have been prepby pneumatic or hydraulic tools. The procedure will helpremove any fractured surfaces, and also cleans any soundfaces that have been contaminated by muddy or silty wate

Abrasive blasting offers the contractor an efficient methof cleaning marine growth and fouling from existinsurfaces. However, crustaceans firmly attached to the ccrete surface are not easily removed by abrasive blasting

Abrasive blasting provides an effective and efficient meod of removing corrosion product from the surfaces of theinforcing steel. This procedure is beneficial to the long-teperformance of the repair operation.

4.2.3 Mechanical scrubbers—Pneumatically or hydrauli-cally-operated mechanical scrubbers can remove macrustaceans efficiently and effectively, as well as clean smsurface areas. Although these tools can clean surfaces etively, they are not as efficient as high-pressure water jetabrasive blasting for cleaning large areas.

4.3—Rehabilitation of reinforcementRemoving loose rust is the first step in rehabilitating re

forcement and can be done with high-pressure water jetabrasive blasting. The back surfaces of the reinforcing sare the most difficult places to clean, especially where theinforcement is congested.

If the cross section of the reinforcing steel has been reduthe situation should be evaluated by a structural engineer.reduced section often can be strengthened with the additio

-r

r

of

re-rp--

l

-

e

h

)es

ed

ur-.

n-

--

ellc-r

orel-

d,e

of

new reinforcing bars, but the original reinforcement has toexposed beyond the corroded section a distance equal to tquired design lap-splice length. Since the preparation costhigh, several small bars are frequently specified in lieu of large bar to reduce the design lap-splice length.

Splicing new reinforcing bars onto the existing reinforcisteel is also possible. A variety of mechanical splices cainstalled under water.

Welding new bar to existing bar is possible, but is rardone. Since the carbon content or chemical compositiothe existing and new reinforcing steel may not be knowelding is not recommended without further evaluation.

4.4—Chemical anchorsIn many repairs, the forming or replacement material is

chored to the existing concrete substrate. Materials andcedures that perform well in dry applications are ofinadequate for underwater applications. For example,pullout strengths of anchors embedded in polyester resinder submerged conditions are as much as 50 percent lesthe strength of similar anchors installed under dry conditi(Best and McDonald, 1990). This reduced tensile capaciprimarily attributed to the anchor installation procedure,though saponification can also be a factor. For details oanchor installation procedure that eliminates the problemresin and water mixing in the drill hole, see Corps of Enneers (1995). The cleanliness of the holes also effects anbond. When used in drilled holes that have not been toughly cleaned, chemical grouts can have significantly creased bond strengths. Polyester resins and cement ghave achieved acceptable bond in comparable condit(Best and McDonald, 1990).

CHAPTER 5—FORMWORK5.1—Rigid and semi-rigid forms

5.1.1 Definition and description—Rigid and semi-rigidforms inherently maintain a given shape, making them sable for molding repairs into a final geometric shape. Serigid forms differ from rigid forms in that they maintaisome surface rigidity or stiffness when in place, but arepable of being bent into rounded shapes during placemBoth types of forms may be sacrificial, required to functonly long enough to allow the repair material to cure. Sforms do not function as a structural element after the rematerial has cured. Forms made of fiberglass or polymaterials are often used as part of the repair design tocrease the overall costs. When forms are designed to acomposite portions of the repair, such as epoxy concreprecast concrete forms, they are mechanically attached tfinal repair system and become an integral part of it.

5.1.2 Physical properties—As with traditional, above-wa-ter forming systems, the ability of the form to perform needed during the repair is the primary concern, whilespecific choice of material used to construct the form is sondary. Typical materials for rigid forms include, plywootimber, steel, polymer based materials, and precast conc

546.2R-11GUIDE TO UNDERWATER REPAIR OF CONCRETE

rfohinith

thed aer

eof touc

y crming d

ntlyion,

siteepa hasasiocon-

fory

ss-ac-ed ty,

re-cing re- Us-rete

Theted-

illhe

av-.

lneda-ereC toein-

m-tedctorm

e

The forming system is generally selected based on pemance, cost, ease of installation, ability to perform witthe construction tolerances, and chemical compatibility wthe repair medium. However, material selection for forming systems that are designed to remain in place ancompositely with the final repair requires special considation.

5.1.3 Typical applications—The specific geometry of thdesired repair surface usually dictates the selection forming system. Rigid forms are most commonly usedform flat surfaces, and are suitable for flat wall surfaces sas caissons, seawalls, spillways, and foundations. Thealso be fabricated in many geometric shapes. Rigid foare typically characterized by a semi-rigid smooth formsurface backed by a series of stiffeners that restrict theflection of the forming system. Plywood and steel frequeare used to form flat surfaces for wall repairs. In additthey may be used to form columns.

Prefabricated steel, precast concrete, or composteel-concrete panels can be used during underwater rof stilling basins (Rail and Haynes, 1991). Each materialinherent advantages, and several factors, including abrresistance, uplift, anchors, joints, and weight should be sidered when designing panels for a specific project.

A precast concrete, stay-in-place, forming system lock-wall rehabilitation was developed by the U.S. ArmEngineer Waterways Experiment Station (Fig. 5.1) (Abam,1987a,b, 1989). A number of navigation locks were succefully rehabilitated using the system. In addition to resurfing the lock chamber, precast concrete panels were usoverlay the back side of the river wall at Troy Lock in TroN.Y. The original plans for repairing this area requiredmoving the extensively deteriorated concrete and replait with shotcrete. To accomplish a dry repair would havequired construction of a cofferdam to dewater the area.ing the precast concrete form panels minimized concremoval and eliminated the need for a cofferdam.

Fig. 5.1—“Symonds” forms in place underwater for pumped repair. (Courtesy of M. Garlich.)

ir

n

o

Three rows of precast panels were used in the overlay. bottom row of panels was installed and the infill concrewas placed under water (Miles, 1993). An anti-washout amixture allowed effective underwater placement of the infconcrete without a tremie seal having to be maintained. Tapplication of precast concrete resulted in a significant sings compared with the originally proposed repair method

Semi-rigid forms are typically used to form cylindricashapes. They do not require stiffeners and may be desigas thin-shell, free-standing units. Thin-walled steel pipe, wterproofed cardboard, fiberglass, and polyvinyl chlorid(PVC) and acrylonitrile butadiene styrene (ABS) plastics afrequently used to form cylindrical shapes. Fiberglass, PVand ABS plastics also can be preshaped in the factorynearly any geometric design and to accommodate steel rforcement, if necessary.

For pressure grouting, plastic jackets are the most comonly used forms. Wooden forms are also used for isolaor flat wall placements. The wood is lined with plastic to aas a bond breaker; after the grout has cured, the entire fis removed from the structure.

r-

ct-

a

hans

e-

Fig. 5.2—Lower of three tiers of panels used to overlay thTroy Lock river wall wre placed and infilled under partiallysubmerged conditions. (Courtesy of J. McDonald.)

546.2R-12 MANUAL OF CONCRETE PRACTICE

de-ted

ent.can

forsed

caland

ed asforigidentngac-ibleh as

ringable;t beent. bysion stopm,re.teelre,

pair

of

y

Fig. 5.5—Underwater view fabric form repair. (Courtesy of M. Garlich.)

5.1.4 Selection considerations—Rigid forms normallyprovide neat and clean outlines for the repairs. Properlysigned, rigid forms will perform well within normal construction tolerances. Most rigid forms can be prefabricaand lowered into position with appropriate hoist equipmMany rigid forms can be reused, which can be a signifi

-

t

cost savings for repetitive repair work. Most rigid forms underwater repairs are much like the traditional forms ufor above-water repair.

Semi-rigid forms are most commonly used in a cylindriconfiguration, such as jackets around piles, columns, other aquatic structures; however, they can also be usbottom forms for flatwork and as general formwork multi-shaped structures. Most repairs using semi-rforms do not require the incorporation of steel reinforcemwithin the form. However, if required, the jackets (includirigid, semi-rigid, and flexible forms) can be designed to commodate a reinforcing cage. Semi-rigid forms are flexenough to be wrapped around an existing structure (suca pile), yet are rigid enough to retain their shape duplacement of the repair materials. Some jackets are reushowever, for most grouts and mortars the jackets cannoremoved and must be left in place as a sacrificial elemWhen left in place a sacrificial form may provide benefitsencapsulating the concrete structure, which slows diffuof oxygen and chlorides to the concrete surface, helps tothe growth of any marine life unintentionally left in the forand may increase the abrasion resistance of the structu

Cleaning existing concrete surfaces and reinforcing safter the forms are installed is extremely difficult. Therefothe integrity of the repair can be compromised if the re

Fig. 5.3—Schematic showing “dry” pile repair. (Courtesy I. Leon Glassgold.)

Fig. 5.4—Schematic showing “wet” pile repair. (Courtesof I. Leon Glassgold.)

546.2R-13GUIDE TO UNDERWATER REPAIR OF CONCRETE

af-e re-erer-di-andted

a-inale orthan too

toathesi-

uires

venn be

ndhor istion

f re-wn

it offforc-es of in-ese

, whotor,

d in ep-m-

ved leftairrete

at-formlinecked the

irm-in atop), po-ter-ut,

henorm

pen-etricc pile

ofetic

-onsghch asle re-in-veral

Fig. 5.6—Fabric form repair on timber pile. (Courtesy of M. Garlich.)

zone becomes contaminated with silts or marine growthter the forms are in place but prior to the placement of thpair material. With some rigid forming systems, propconsolidation of repair materials may be difficult. Most undwater formwork is rather small or segmented into small invidual pieces. Large rigid forms can be cumbersome difficult to place due to their mass, which must be manipulaby a diver.

The limitations of each of the forming systems are primrily related to the desired geometric tolerances of the frepair. Most forms are prefabricated to require only ontwo divers to secure them in place. Coordinating more two divers with a hoist operator on the surface is usuallydifficult to be effective.

Rigid wooden forms are relatively lightweight and easywork with under water. Precast concrete form panels are rheavy, possibly restricting their deployment into final potion. Placement of both types of panels under water reqgood communication to reduce the hazards to the divers.

Underwater forms must be sealed by gaskets to precement paste from leaking out through the joints. This caespecially serious in flowing water or waves.

5.1.5 Installation procedures—Rigid forms for flatworkor walls are typically prefabricated, lifted into position, aattached to the substrate using drilled-in expansion anc(Fig. 5.2). After the repair concrete has cured, the formgenerally removed, but can be left in place at the discreof the designer.

msin-iftedel iseceam,

ind a

maygen- andass

asean-

Rigid, stay-in-place, precast-concrete, wall-panel forare designed to perform monolithically with the cast-place concrete repair material. Wall panels are precast, linto position, and attached to the substrate. After the pansecured, the space behind the wall panel is sealed as nsary to receive the fresh cast-in-place concrete (Ab1987b).

Rigid forms for pile repairs are generally prefabricatedtwo mated halves. A friction collar is set on the pile, an

base plate (usually plywood) is secured onto the collar. Iinforcement is included in the repair, it is normally set doon the base plate using the appropriate chairs to keepthe bottom of the form. Spacers are installed on the reining cage to set the clear cover to the form. The two halvthe pile form (steel pipe, PVC) are lowered into positiondividually, aligned, and fastened together. Normally, thforms are positioned and secured by one diver at a timeeither coordinates the lift of the form with a crane operaor maneuvers the form by himself or with air bags to aithe lifting. The concrete repair material (grout, concrete,oxy mortar) is pumped into the form. After the repair is copleted, the form and friction collar generally are remo(Fig. 5.3). Some applications allow these elements to bein place. Fig. 5.4 shows an example of an underwater repusing rigid forms and a portable cofferdam, where shotcis used above the waterline.

r

t

s

s-

Semi-rigid forms for pile repairs are generally prefabriced in one piece and are available in various sizes. The is wrapped loosely around the pile above the water where overhead clearance permits. Sections may be lotogether to extend the overall length. The diver then pullsform into position and completes the locking process to fly attach the form to the structure. Many forms contacompressible foam seal at the bottom (optional at the with spacers between the form and structure to correctlysition the form. At this point some materials require dewaing, while others may not. The repair material (groconcrete, epoxy mortar, or epoxy injection resin) is tpumped into the form. After the repair is completed the fmay be left in place as a jacket.

5.2—Flexible forms5.2.1 Definition and description—Flexible forming sys-

tems do not have the internal stiffness required to indedently form the surface of concrete to a precise geomshape. Examples of these types of systems include fabrijacketing forms, membrane plastics and fabric bags (Fig. 5.5and 5.6). Flexible forms are fabricated from a multitudematerials, including burlap, membrane plastic, and synthfiber fabric.

5.2.2 Typical applications—For many years, piles commonly have been repaired using flexible forms. Applicatifor most flexible forms include the repair of piles, althouthese forming materials can be used for flat surfaces suwalls or mass-concrete elements such as groins. For pipairs, the final product is typically an approximately cyldrical shape that surrounds the pile and extends for sefeet above and below the damaged area. The fill may ornot be reinforced. For wall repairs, the finished shape is erally uneven or corrugated in appearance. For groinbreakwater repairs, the finished product is typically a mwith only generally definable shape.

5.2.3 Selection consideration—Flexible forms offer manyadvantages, including low initial cost, low weight, and eand speed of installation. Most flexible forms are factory mufactured and field adjusted to meet the job requirements.

546.2R-14 MANUAL OF CONCRETE PRACTICE

manasacide

theiala

stitairly

irr omabe

e Pracnan lin

n auainolderer

ric t

threa thea loular tont

vep-a

inesns

(1. o

e ttri

h asnsileade

thehingh as

e re-tical

ight

pre-nedometeelcing mayiles

hen-

ved.ned are the

forl-di-ce offacerspair.de- thetomf thesed.e of bot-vityag-

thewithman-ases,ain is un-rom

areapsu-ts are andfea-

ed.

Formed fabric jackets with a zipper on one face are sotimes used in pile repairs. One diver usually deploys erects a fabric form without the assistance of surface-blifting equipment. Since the fabric form bonds to the surfof the repair concrete, the toughness of the fabric provsome supplemental abrasion resistance.

If a fabric form is allowed to rest on the free surface of concrete placement, the concrete/water interface is partprotected from dilution. This helps reduce the laitance chacteristic of typical tremie concrete. Impermeable plamembranes for forming systems usually completely conthe cement particles, which may escape from similaformed fabric systems.

The surfaces of flexible-formed concrete are generallyregular in appearance. Since fabrics or membranes offebending strength, formed surfaces are curved, although sflexible forms have been used for semi-flatwork applictions. If a truly flat surface is desired, rigid forms must used.

Fabric and membrane forms usually bond to the surfacthe repair material during the concrete curing process. longed exposure to ultra-violet light, abrasion, or impmay cause the form material to decompose or delamifrom the repair surface. Hence the surface will take oragged appearance with pieces of the form material dangfrom the repair medium.

Since flexible forms have no inherent ability to maintaigiven shape, they are not particularly well suited for sittions where standoffs or chairs are needed to maintain mmum clear cover. Regardless of the configuration orientation of the structure, fabric forms are difficult to hoin proper alignment, and once filled with concrete are vdifficult to manipulate. This can result in insufficient covdue to form displacement.

Some commercially available forms have wide fabmesh that allows cement paste particles to escape fromform. This can increase the water-cement ratio nearformed surface, and hence reduce the strength and incthe outside surface permeability of the repair. In addition,release of the alkaline cement paste through the fabric winto the free water may be an environmental concern incalities that support fish, mollusk, and crustacean poptions. Conversely, some fabric form materials allow watepass through the weave without allowing significaamounts of cement grains to pass.

Flexible forms are light and easily managed by one dibut difficult to align true and plumb during the pumping oeration. The overall weight of the concrete-filled system mpose problems and needs to be carefully considered.

Commercially available flexible forming systems comea wide variety of materials. The physical properties of thmaterials may restrict their usage for certain applicatioThe tensile strength of typical fabrics are 200 to 400 psi to 2.8 MPa). Some fabric forms (or zippers and seamsthese forms) have ruptured during the filling process duexcessive pressure in the repair medium. This may resthe rate of placement for repair materials.

e-dedes

lyr-cn

-no

e-

ofo-tteag

-i-r

y

heese

eve--

r,

y

e.4noct

It is not uncommon for the material to stretch as muc10 percent under loads equal to 50 percent of the tebreaking load. Therefore, allowance should either be mfor the form to stretch during pumping operations (andrequired volume of concrete increased), or this stretcshould be restricted by installing external supports, suchoops around piling repairs.

5.2.4 Installation procedures—Flexible-formed concretecan be classified into three generic geometric shapes. Thpaired surface can be flatwork, such as wall repairs; vercylinders, such as a pile repair; or mass cast, such as mbe used to encapsulate groins or breakwater features.

After vertical surfaces of concrete walls have been pared to receive a repair, flexible forms may be positiousing a multitude of supplemental support methods. Sflexible forms have been supported with timber or swales, while others have been supported by reinformeshes forming ribs on the outer surface. The meshesin turn be supported by wales or even supplemental pdriven near the repair zone. The repair material is tpumped into the form. Typically, the flexible-form membrane is left in place, but the external supports are remo

When repairing piles, repair surfaces are normally cleato remove marine growth and other contaminants, andoccasionally roughened to enhance the bond betweenpile and the repair material. Any reinforcement requiredthe repair is installed first and secured to the pile. Smalameter PVC pipe is sometimes attached to the outer fathe reinforcement to maintain the required cover to the of the form. The majority of flexible forms for pile repaiare shop prefabricated to the required length of the reThe form jacket is then field modified as required and ployed by a diver to the repair zone. The diver completescylindrical shape by zipping up the bag. The top and botof the jacket is then secured to the respective sections opile repair zone. Wire or large hose clamps are often uThe repair material is then injected into the bag using onseveral techniques, such as pumping concrete from thetom, pumping from a hose located inside of the repair cawhile slowly withdrawing the hose, or using preplaced gregates. The concrete is usually batched using 3/8 in. (10mm) maximum size coarse aggregate, which helps inplacement process. Using concrete or grout mixtures small aggregate enables the diver to use smaller, more ageable hoses for placing the repair material. In most ca diver monitors the filling operation and may try to maintthe fabric form shape. After the repair zone is filled, itcommon to continue pumping the concrete or grout untilcontaminated concrete or grout is observed extruding fthe top of the form.

Individual fabric bags and flexible fabric mattresses sometimes used in mass-placement applications to enclate an entire element in mass concrete. Mass placemenseldom reinforced. After the element has been cleanedprepared for repair, a flexible form is placed around the ture and secured into position. Grout or concrete is then inject-ed into the form until the desired shape has been achiev

546.2R-15GUIDE TO UNDERWATER REPAIR OF CONCRETE

ceinom

ypsimuamomth loaa

inus

e bor

thed an d

aning no

g-nauluy oucrticfaccolo

e apusite

tenveon

. T

tewa ung, ndo to ve

re- hy-from

ent bypre-rms canit vi-rk inmps todurerd mayruc-ck-

ater,se oftem- pre-

the in theder-e theblerms,ac- hasibi-t.

dr toent

r sup-inglacedwitho theingt iswestver- areerr aanyrmsuate

ured

Pieces of reinforcing steel can be placed through adjafabric forms to tie together the mass concrete in adjoinzones. Some amount of mortar or concrete leakage is cmonly observed when this technique is used.

CHAPTER 6—METHODS AND MATERIALS6.1—General considerations

The design objective of the repair largely dictates the tof repair used on a project. For a minor spall or crack, a ple surface patch or crack injection system may be adeqto provide protection to the reinforcing steel. For major daage, where the load-carrying capacity of the element is cpromised, the repair may either re-establish the strengthe original element, or perhaps even establish a new path around the damaged area. The severity of the damoften determines the type of surface preparation, formsystem, reinforcement arrangement, and repair medium for the repairs.

6.2—Preplaced aggregate concrete6.2.1 Definition and description—Preplaced aggregat

concrete is defined in ACI 116R as concrete producedplacing coarse aggregate in a form and later injecting a pland cement-sand grout, usually with admixtures, to fill voids between the coarse aggregate particles. Preplacegregate concrete is suitable for use in effecting repairsmaking additions to concrete structures under water asscribed in this section. Detailed materials requirementsprocedures on proportioning, mixing, handling and placconcrete, and references are given in ACI 304R and willbe repeated here.

6.2.2 Materials—The physical properties of preplaced agregate concrete are essentially the same as conventiomixed and placed concrete with respect to strength, modof elasticity, and thermal characteristics. The permeabilitpreplaced aggregate concrete can be significantly redwhen fly ash or silica fume are added to the grout. Of paular interest in connection with underwater repairs is the that the quality and properties of preplaced aggregate crete are not affected by whether it is placed above or bewater. The bond between preplaced aggregate concreta roughened existing concrete has been shown in unlished reports to be better than 80 percent of the tenstrength (modulus of rupture) of the weaker concreWhere drying shrinkage can occur, as in repairs that exsome distance above water, it is less than half that of contional concrete. The durability of preplaced aggregate ccrete appears to be excellent, based on informal reportsprocedure was developed in about 1950.

6.2.3 Typical applications—Preplaced aggregate concrehas been used extensively for repairing railway and highbridge piers for many years, particularly for encasing andderpinning piers weakened by such factors as weatherinverbed scour, exposed piling or cribbing, floating ice, aoverloading. In many cases, piers have been enlarged tcrease capacity to accommodate heavier deck loads, or sist masses of floating ice or the impact of runaway ri

ntg

-

e-te--

ofdgeged

yt-

ag-de-d

t

llysfed-t

n-wndb-le.dn--he

y-

ri-

in-re-r

traffic. The method also has been widely applied to thepair of piers supporting control gates on spillways anddroelectric outlet structures that have suffered damage ice abrasion or freezing and thawing.

6.2.4 Selection considerations—The quality of preplacedaggregate concrete is not significantly reduced by placemunder water because the grout is not significantly dilutedthe water it displaces from the voids in the aggregate placed in the forms. Therefore, the cost of water-tight foand dewatering may be eliminated and preparatory workbe done under water. If cofferdams are desired to permsual inspection and the performance of preparatory wothe dry, the cofferdam need only be tight enough for puto hold the water down temporarily, then flooded priorplacing the preplaced aggregate concrete. This proceeliminates the harmful effect of water moving upwathrough the preplaced aggregate concrete. The methodbe used to fill relatively inaccessible voids under the stture or to consolidate the interiors of timber-crib or rofilled piers.

When inspection and preparation are done under wthe cost of divers must be balanced against the expencofferdams that can be dewatered. Additionally, at least porary dewatering may be required when inspection andparatory work performed by divers is not adequate.

In water that is strongly polluted by organic materials, prepared concrete surface and coarse aggregate restingforms may become unacceptably coated if grouting of unwater aggregate is delayed more than a few days. Whersurrounding water is turbid with clay or other settleafines, such water may need to be excluded from the foeither by using tight cofferdams or by flooding them with ceptably clean water to prevent inflow. In Japan, algaebeen limited successfully by treating the water with inhtors and placing a cover over the top to shut out sunligh

6.2.5 Installation procedures—All damaged or weakeneconcrete is first removed to a predetermined depth osound material, whichever is greater. Where reinforcemis corroded, loose rust is removed or the bars replaced oplemented as the situation requires. Applying bondagents is neither necessary nor desirable. Forms are pand carefully sealed at joints and at points of contact concrete surfaces. Coarse aggregate is dropped intformed areas, usually in 2 to 4 ft (0.6 to 1.2 m) lifts, takcare to avoid excessive segregation. Finally, the groupumped into the preplaced aggregate, starting at the lopoint(s), either through the forms or through preplaced tical pipes, as described in ACI 304R. When the formsfull, it is good practice to spill a small portion of grout ovthe top of the form if it is open, or through vent holes oventing section at the top of the form, to ensure that trapped water, air or diluted grout are expelled. The foare removed when the concrete has gained adeqstrength; the above-water portions of the repairs are cnormally.

546.2R-16 MANUAL OF CONCRETE PRACTICE

ass id bt b

ha

or fndn

uir4R

ae

antere

iteoeendsu

-d. aesxpicu

sef t thdthunthn

ce thshatthte

e.t inin

the the

ar

-arateh ofventm-

sig-R

wa-sure its

not ce-

Pro-for orlens- ce-

dpedted.to-routso re-d be theressrop-been

ideithl-re-

oningions ad-canrs

sinscts,ilicaes.

on-ave

6.3—Tremie concrete6.3.1 Definition and description—Tremie concrete is

placed under water using a pipe, commonly referred to tremie or tremie pipe. The pipe is commonly referred to atremie. Tremie concrete differs from pumped concretethat the concrete flow away from the tremie pipe is causegravity acting on the concrete mass in the tremie and nopump pressure.

6.3.2 Materials—Tremie concretes typically have a higcementitious-materials content, which results in adequcompressive strengths for most underwater repair wConcrete proportioned according to accepted guidelinestremie placement generally gives excellent results (Holla1983). If underlying materials are properly cleaned, bostrength to concrete has been shown to be excellent.

Concretes ranging from fine grouts to those with 11/2-in.(40mm) aggregates can be placed by tremie. Materials reqments and mixture proportioning are discussed in ACI 30Also see section 6.5.6.

6.3.3 Typical uses—Tremie concrete has been used inwide variety of applications for underwater repair. At Tarbla Dam more than 90,000 yd3 (68,800 m3) of tremie concretewere placed to repair damage caused by cavitation (Holl1996). The Corps of Engineers has used tremie concrerepair damage to stilling basins at several of its structu(McDonald, 1980). Tremie concrete is probably best sufor larger-volume repair placements where the tremie dnot need to be relocated frequently, or for deeper placemwhere pumping is impractical. However, tremie methohave successfully been used for small grout placements as filling cavities.

6.3.4 Selection considerations—The tremie method is relatively simple if well-established guidelines are followeThe equipment used in placing tremie concrete is ruggedsimple, and therefore seldom malfunctions. Neverthelthe tremie method still requires proper equipment and erienced personnel. These requirements may be more diffto meet than if ordinary pumped concrete is used.

The major limitation for tremie placed concrete is cauby the mechanics of the technique. To seal the mouth otremie, a mound of concrete is built up at the beginning ofplacement. The mouth of the tremie must remain embedin this mound throughout the placement. The width of placement is therefore dictated by the depth of this moand the slope at which the concrete flows away from tremie. Thin overlay placements under water usually canbe accomplished using a tremie.

A second limitation is that water flow across the plament site must be stopped during the placement untilconcrete has gained enough strength to resist being waout of place. Flow control has been achieved by closing gof structures, by building diversion boxes, or by placing concrete under an upper form such as a heavy steel plaweighted canvas, with a hole to accommodate the tremi

Where the flow velocity of water across the placemenslow and laminar [approximately 3 ft/sec (1 m/sec)], ati-washout admixtures may prevent the concrete from be

a anyy

tek.or,

d

e-.

-

d, tos

dsts

sch

nds,e-lt

dhee

ededeot

-eed

ese or

s-g

washed out of place. A small test placement made duringinvestigation or design phase of the repair can determinesuitability of anti-washout admixtures for a particulproject.

6.3.5 Installation procedures—Successful tremie placement depends on keeping the concrete in the tremie sepfrom the water. Once the placement is started, the moutthe tremie must remain embedded in the concrete to preconcrete from dropping directly through water and becoing dispersed. Tremie placements for repair do not differ nificantly from placements for new construction. ACI 304contains recommendations for tremie placement.

6.4—Pumped concrete and grout6.4.1 Definition and description—Pumped concrete is

manufactured above water and pumped into place underter during a repair. This concrete depends upon the presof the pump, and sometimes upon gravity flow, to reachfinal position in the repair.

Grouts are more fluid than concrete and generally docontain coarse aggregate. Most grouts consist of portlandment and sand, and may contain fly ash and silica fume. prietary grouts may contain selected admixtures pumping, adhesion, acceleration, dimensional stability,other properties. Fluid grouts used to penetrate fissures, es, and small defects are made from very finely groundment, known as “microfine cement.”

6.4.2 Materials—For concrete and grouts proportioneaccording to the generally accepted guidelines for pumplacement (ACI 304.2R), excellent results may be expecPumped concretes typically have high ratios of fine-coarse aggregate and cohesiveness will be improved. Gused under water sometimes have faster setting times tduce loss due to erosion and wash-out. Materials shoulselected that are relatively dimensionally stable in bothwet and dry environments to avoid the development of stat the bond line. If the underlying materials have been perly cleaned, bond strength to hardened concrete has shown to be excellent.

Concrete and grout pumps now available can pump a wvariety of mixtures comprised of cementitious materials wlittle difficulty. The cementitious mixtures should be deveoped with the specifics of the repair in mind and then viewed for suitability for underwater pumping.

6.4.3 Typical uses—Pumped concrete is the most commmethod of placing concrete in underwater repairs, includthose that are formed. It can be used in most applicatwhere tremie concrete is applicable, but has the addedvantage of having a smaller, more flexible hose that reach difficult locations. The U. S. Army Corps of Engineehas pumped concrete under water to repair stilling ba(Neeley and Wickersham, 1989). On several such projethe pumped concrete contained steel fibers and/or sfume. Other uses include filling voids in or under structur

Grouts are most commonly used to fill voids between ccrete and forms or jackets such as in pile repair. They h

546.2R-17GUIDE TO UNDERWATER REPAIR OF CONCRETE

s

ysea

re lteen

thtelos

ctiopeice

N)a on-rt

s oweningefo

-oooh fw

tsre

ees

tedd the fol-er-d tothe

in-ete,tanter

3b).ix-ol-

ceabo-te ise of

or. Inper-llyandve

d andoc-hinited ve-

rder

ere

te ister

thecedout

also been used to repair smaller voids and larger crackand under concrete structures.

6.4.4 Selection considerations—The main advantage ofpumped cementitious concrete and grout is that their phcal properties are essentially the same as the concrete brepaired. Differences in modulus of elasticity and thermexpansion are negligible for most underwater work. Uncucementitious materials are less hazardous than uncuredoxies. They are also easier to work with and less troubprone than polymers because they are less sensitive to perature variations during mixing, placing and curing. Thare also less likely to leak from small defects in forms ajackets than epoxy systems.

Pumping under water has the advantage of eliminatingequipment associated with a tremie placement, since pump delivering the concrete or grout is also the placemdevice. The use of a pump with a boom may facilitate recating the pump outlet site if the repair consists of a seriesmall placements.

As with tremie placements, successful underwater plament of concrete by pump requires the proper combinaof appropriate concrete proportions and equipment, and sonnel trained in underwater concrete placement. Typpump contractors or pump operators may not have expence in underwater concrete placements.

In the past, some environmental agencies, such as thetional Oceanographic and Atmospheric Agency (NOAAhave expressed concern about the effects of alkalis washed-out cement particles on coral reefs and fish. Onproject in the Florida Keys for the U.S. Army Corps of Egineers, these concerns were addressed, at least in pausing anti-washout admixtures (Concrete Products, 1995;McKain and McKain, 1996).

The same limitations regarding underwater placementthin sections and the requirement to eliminate water flacross a placement site that applied for tremie placemalso apply for pumping under water. A special problem herent in pumped concrete is that it is discharged in surwhich can result in more cement wash-out and laitance mation than tremie concrete.

6.4.5 Installation procedures—Successful pump placement under water, depends upon separating the initial ccrete or grout that is placed at the start of the pumping frthe water and upon maintaining that separation throughthe placement. The separation must be reestablished wever the pump outlet is relocated. Underwater placementsrepairs do not differ significantly from placements for nework. Additional guidance can be obtained ACI 304R.

6.5—Free dump through water6.5.1 Definition and description—Free dump through wa-

ter is the placement of freshly mixed concrete by allowingto fall through water without the benefit of confinemensuch as a tremie pipe or pump line. Anti-washout admixtumay or may not be used.

6.5.2 Materials—Concrete that is to be allowed to frefall through water should contain anti-washout admixtur

in

i-ingldep-e-m-yd

ehent-of

e-nr-

alri-

a-,ndne

, by

in

ts-s,r-

n-muten-or

it

s

.

Development of these admixtures was formerly concentrain northern Europe, but has recently spread to Japan anU.S. (Straube). The admixtures contain some or all of thelowing ingredients: high molecular weight polymers, supplasticizers, cellulose derivatives, and gums. When addefresh concrete, the anti-washout admixtures improve flow characteristics of the concrete.

Anti-washout admixtures are often used in concrete tended for underwater (Maage, 1984; Underwater Concr1983b). The concrete also may contain abrasion resismaterials, silica fume (Makk and Tjugum, 1985), or othadmixtures (Maage, 1984; Underwater Concrete, 198An example of a mix design using an anti-washout admture for the rehabilitation of an intake velocity cap is as flow (Hasan et al., 1993):

Conflicting evidence exists on the quality of the in-placoncrete when placed by the free dump method. Some lratory work has indicated that once the free dump concrein place and set, its physical properties are equal to thosgood quality concrete placed by conventional tremiepump (Underwater Concrete, 1983a; Kajima Corp, 1985)fact, there is some evidence that strength, bond and immeability are actually improved, compared to normaplaced underwater concrete (Maage, 1984; Makk Tjugum, 1985). However, other large-scale field trials habeen less successful, with the concrete being segregatewith wash-out of the cement. Another problem that can cur with this method is that water may be entrapped witthe dumped concrete. The free-fall height should be limto that required for opening the bucket so as to reduce thelocity of impact.

6.5.3 Typical uses—The free dump method is used foplacing concrete containing anti-washout admixture unwater in new construction and to repair old concrete.

6.5.4 Selection considerations—Free-fall concrete hasbeen most successful in shallow water applications, whself-leveling concrete is not required.

Research results strongly suggest that fee-fall concrecohesive and is not harmful to the environment (UnderwaConcrete, 1983a; Kajima Corp, 1985). Since the 1970s,Sibo group in Osnabruck, Germany, has successfully plathousands of cubic meters of concrete with an anti-wash

Cement, C, pcy 600 [354 kg/m3]

Fly Ash, FA, pcy 90 [53.10 kg/m3]

Silica Fume, SF, pcy 43 [27.10 kg/m3]

Water/[C+FA+SF]* 0.40

Fine Agg., pcy 1,467 [865.60 kg/m3]

Coarse Agg., pcy 1,550 [678.50 kg/m3]

Anti-washout admixture, gcy

0.60 [3.58 l/m3]

High range water reducing admixture, gcy

1.90 [11.34 l/m3]

Slump, in. 10 [254 mm]

24-hr Strength, psi 1,960 [13.50 MPa]

*Water to cementitious materials ratio.

546.2R-18 MANUAL OF CONCRETE PRACTICE

pal- co

ofigrseout

edeshof ane. As inbleon.ckyentick

entious

and the

durate

oxi-tionorp,

n-ed irwa-y b tojima

reteed per Theete. Th

kg)

typi-ter;oidnd

mer

oxykets,per-tantectssion,s the

edbe-

lypon

res.theped

ntitypingone)f the se-her byeen

at- Theruc-t re-are

thatture.hal-tory

tem-tededhethe

r-ed orater

o

admixture by first spreading the concrete uniformly on lets on the deck of a special barge, and then dropping thecrete through the water by tilting the pallets (Freese, Hand Grotkopp, 1978). The primary advantage is, of couthe capability to place quality concrete under water withthe use of cumbersome tremies and pumps.

Large doses of anti-washout admixture are usually neto provide concrete of adequate cohesion to prevent waand segregation during placement. Large amounts oti-washout admixture increase the cost of the concretconcrete mixture that is cohesive enough to maintain ittegrity while free-falling through water and yet is flowaenough to be self-leveling can be difficult to proportiConcrete made with anti-washout admixtures is often ta(Straube), sensitive to slight changes in the water-cemtious materials ratio and certain other admixtures (Gerw1988), and sticky and difficult to remove from equipm(Maage, 1984). Information about its behavior under varfield conditions and temperatures is limited.

Unless the concrete mixture is proportioned properly the proper amount of anti-washout admixture is used inmixture, significant washout and segregation can occuring placement. The shorter the fall through water, the grethe chance for success. If the free fall is limited to apprmately 1 ft (0.3 m), the probability for successful applicais excellent (Underwater Concrete, 1983a; Kajima C1985).

6.5.5 Installation procedure—Underwater concretes cotaining anti-washout admixtures can be batched and mixconventional concrete plants or ready-mix trucks (Undeter Concrete, 1983a; Kajima Corp, 1985). Placement maby pump or inclined or vertical pipe without the needmaintain a tremie seal (Underwater Concrete, 1983a; KaCorp, 1985) or special equipment (Underwater Conc1983b; Freese et al., 1978). The admixture is pre-batchpowder form into the concrete mixer by about 0.5 to 1.5 cent by mass of the cement (Makk and Tjugum, 1985).admixture in liquid form is normally added to the concrafter all other ingredients have been blended together

n-,,

dut-

-

i-,

-r

n

e

,in-

e

normal dosage is 0.05 to 0.15 gal/100 lb (0.4 to 1.1 l/100of cementitious material.

6.6—Epoxy grouting6.6.1 Definition and description—Epoxy grouts are used

for splash zone and underwater repairs. The materials cally consist of an epoxy resin that is curable under wathe resin is used either without aggregate for narrow vgrouting, or mixed with specially graded silica sands asometimes with larger aggregates to form an epoxy-polymortar or concrete.

The epoxy grouting process usually includes the epgrout and a jacket, creating a composite system. The jacconcrete, and epoxy grouts have different physical proties. Adhesion of the epoxy grout to the concrete is importo the overall composite design. The jacket system protthe outer surface of the concrete structure against abrareduces oxygen flow into the damaged area, and defendstructure from physical and chemical attack.

The guidelines used for void grouting are typically dividinto two categories. A wide void is defined as a space tween the jacket and concrete larger than 3/4 in. (20 mm). Anarrow void is defined as a 1/8 to 3/4 in. (3 to 20 mm).

6.6.2 Materials—Pourable epoxy grout materials usualcontain silica sands. The amount of sand is dependent uthe epoxy material, void size and ambient temperatuThese materials may be either poured into place filling void between the jacket and the existing concrete, or puminto place. Pumpable epoxy mortars contain a larger quaof silica sand than pourable mortars. They require a pumsystem that allows larger particles (sand and possibly stto pass through the pump without causing segregation oepoxy/aggregate mixture. Epoxy resins, blended with alect gradation of silica sands, silica or quartz flour, or otfillers to make a non-sag consistency, may be placedhand. These are used for small quantity placements betwthe concrete structure and a permanent jacket system.

Epoxy grout is designed to bond to the concrete, elimining a cold joint between the concrete and jacket system.entire system provides additional reinforcement to the stture. The damaged area may be repaired with or withouinforcing steel. If reinforcement is used, epoxy mortars intended to encapsulate and protect it.

When epoxy resins are used in repair it is intended these materials become bonded with the concrete strucBecause the underwater environment creates unique clenges for these materials, documented performance hisand testing per ASTM C 881 methods is advised.

The epoxy formulations are selected based upon the perature at the time of application, and on the anticipatemperature range during the service life. Epoxy is mixwith aggregate or other fillers to form the epoxy grout. Tfiller extends the epoxy to reduce the overall costs of polymer grouting repair and reduce heat buildup.

6.6.3 Typical uses—Plastic jackets and underwater-cuable, epoxy-resin systems are used for the repair of erodstructurally damaged splash zone concrete and underw

Fig. 6.1—Underwater view of hollow rock bolts grouted intexisting construction. (Courtesy of M. Garlich.)

546.2R-19GUIDE TO UNDERWATER REPAIR OF CONCRETE

hinsuc-

-cu t ag

and areur-

lderra-hen

concrete structures. Epoxy systems are used for patcgrouting, and crack repair. They are also used to bond items as anchor bolts (Fig. 6.1), reinforcing steel, and protective safety devices to concrete under water. Underwaterable epoxy coatings are used to provide protectionconcrete and other building materials from erosion and

cre doop-ondryam

nuapet. inanl fole andtemce

renssiate c

th. N

illlly

anairstur sueden

me risusral

cksna, onf tatireape- reondlitha

toall

erep-e oracketrline the

in a thece.the thet ofmend or allrat-

rge-jacketmor-

oxyentnente be- dis- a an-

ce of andility

ombssincection tun-iers.ter-idelica-

y ofin the

g,h

r-o-

tees

g-

-

-s.

-rof

--

tver

rit-eo

t

ech to-n-esely

lly

heon.

-lyngn

portland cement-based materials to mixing, application curing temperature. For example, epoxy mortars thatvery workable when mixed in warm conditions on the sface could become very stiff when being applied in coconditions under water. In addition, shelf life and tempeture range during storage are more limited for epoxies. Wfilling forms with epoxy mortars, care should be takenminimize or prevent the material from leaking out of smseparations or defects in the forming system.

6.6.5 Installation procedures—For jacket-type repairs, thjacket is usually installed immediately after the surface parations are completed, including the removal of loosbroken concrete and rust, and the epoxy is placed. Jplacement is often accomplished from above the wateon a barge or scaffolding. The jacket is wrapped aroundstructure and loosely locked so that it will not reopen strong current or waves. The jacket is then slipped downstructure into the water, where the diver pulls it into plaBy pulling the locking device, the jacket is secured to pile. A similar procedure is used for flat surface forming.

The epoxy should be carefully mixed according to manufacturer's directions and with the specified amounsand and coarse aggregate. Most manufacturers recomimmediate product placement after mixing, by pouringpumping the material into the jacket cavity and displacingwater. Epoxy mortar or concrete should be rodded or vibed during installation to remove air pockets.

Pumpable epoxy mortars are typically placed with a ladiameter hose or pipe (11/2 in. [25-35 mm]), which is inserted between the concrete structure and the permanent system. The pipe is then slowly removed as the epoxy tar fills the cavity and displaces the water.

Narrow voids are grouted with formulations of neat epresin. The material is placed by a positive displacempump, which mixes and sometimes heats the two-comporesin system. The epoxy resin is pumped into the spactween the concrete and jacket surfaces until all water isplaced. After the jacket is filled, it is capped withtrowelable epoxy mortar which is beveled at a 45 degreegle upward from the outer edge of the jacket to the surfathe structure. Experience has shown that in both freezingwarm environments, this technique improves the durabof the protective system.

6.7—Epoxy injection6.7.1 Description and definition—Injection of epoxy res-

ins into splash zone and underwater cracks and honeycin concrete structures has been successfully practiced the 1960s in fresh and salt water environments. The injeprocess may be accomplished from the interior of pipes,nels, shafts, dams, floating-precast-box bridges, and pPiles and backfilled walls must be serviced from the waside. The following text will concentrate on the water-sapplication methods of repair, even though dry-side apptions are very similar.

The purpose of crack injection is to restore the integritthe concrete or to seal cracks. Honeycombed areas with

gressive waters.6.6.4 Selection considerations—Using epoxy grouts for

the repair of splash zones and underwater areas of conhas several advantages. The jacket system is light andnot add significant additional weight to the structure. A prerly selected, designed, and installed system provides lterm protection from sand erosion, wave erosion, wet-cycles, floating debris, marine organisms, freeze-thaw dage, and salt and chemical intrusion.

The jacket repair method is fast and easy to install. Mafacturers of jacket systems offer standard sizes and shSpecial shapes and sizes may be available upon reques

The epoxy portion of the system is the most criticalterms of application and cure. Good quality control stdards for mixing and handling of the epoxy are essentiaa successful application. The epoxy grout must be capabbeing placed by pouring, pumping, or hand packing, cured in the presence of fresh, brackish, or salt water at peratures from 38 F (3 C) to 120 F (50 C) to satisfy plament in most North American water areas.

Epoxy grouts possess physical properties much diffethan those of the concrete being repaired. The compreand tensile strengths of epoxies are typically much grethan those of the concrete substrate and are not usually aical issue in repair design. The modulus of elasticity andcreep coefficient of the epoxies are more of a concernmatter how high their strength, more flexible materials wnot carry their portion of the load when acting monolithicawith a stiffer material such as concrete.

The coefficient of thermal expansion is another importphysical property of epoxies. Although underwater repare generally subjected to lower variations in temperathan above-water repairs, some underwater structures,as those associated with power plants, may be subjectlarge variations in temperature. Epoxy repair materials gerally reach higher temperatures when they cure than cetitious mortars and concretes reach. These temperaturecan be significant when large voids are being filled. Becaof this and cost considerations, epoxy repairs are genelimited to filling smaller voids or cracks.

When the narrow-void jacket system is used to fill crain piles, the cracks are usually not filled and the intercrack surfaces are not bonded together. In most casesthe adjacent surface is encapsulated and protected. Icrack extends beyond the jacket coverage area, deteriorwill develop or continue, possibly even under the jacket a

Epoxy mortar installation requires workers with more scialized training and equipment than cementitious basedpairs. Both the uncured resin and solvents that are commused are hazardous chemicals that require special hanand safety precautions. Epoxy is also more sensitive

546.2R-20 MANUAL OF CONCRETE PRACTICE

Tcel i

the

ox ore.

t- arin foe

aloidn

rere, s toetiocre

s. t

co aed

santhepenc

-am bm5 erc

aes t

escad

it

aretheithl se-e andtion, thetures size

nt.allyore

thepled

la-tec-

ackl ationnvi-ablever

ymps; (1)ile

ng. crackbra- arerack sur-oxyrack theh allg off thepre-m ofealed

ling setateris in-to oldnts.d af-

tionr is

concrete also can be repaired by the injection process.injected epoxies fill the cracks and bond the crack surfatogether, restoring, at least in part, the concrete's originategrity and preventing any further water intrusion into structure.

The physical properties of concrete repaired with epinjection are similar to the original concrete. The repairconcrete by crack injection will not increase the structuload-carrying ability above the level of the original design

6.7.2 Materials—Epoxies for resin injection are formulaed in low viscosity and gel consistencies. The materials100 percent solid, 100 percent reactive, and have low shage upon curing. The low-viscosity injection resin is usedvoids narrower than 1/4 in. (6 mm). An epoxy gel may bused for larger voids, from 1/4 in. to 3/4 in. The physicalstrength properties for both epoxy consistencies are typicequal. The resin is required to displace water within the vadhere to a wet or moist surface, and then cure in that eronment.

Not all epoxies are capable of bonding cracked conctogether, especially under water. An underwater conccrack contains materials such as dissolved mineral saltsor clay, and debris from the corroding metal in additionwater. All of these materials interfere with good bond devopment unless they are removed. Ideally, the epoxy injecresin has two main duties to perform: first, it must displaall free water from within the crack or void; then it must cuand adhere to wet concrete and reinforcing steel surfacea result, special epoxy formulations that are insensitivewater are required for underwater work.

The surface sealer must be capable of adhering to thecrete, set rapidly at the expected ambient temperaturesconfine the epoxy injection resin while it is being injectand cured.

It is usually of either a hydraulic cement base or a paconsistency epoxy specially formulated to be placed bond in the underwater environment. The selection of eia cement or epoxy formula is dependent upon water temature, currents, setting time, and previous work experieof the divers or injection technicians.

6.7.3 Typical uses—Limitations of the underwater environment such as light, currents, temperature and contnants on or in the crack limit the size of crack that caninjected from a practical standpoint. Considering these litations, a low viscosity epoxy may penetrate cracks 0.01(0.38 mm) and larger; when the crack size is 0.10 or larggel consistency epoxy resin may be used. Both consistenof materials are generally considered capable of bondingrepairing a cracked section when there is adequate adhto the surfaces of the crack and when at least 90% ofcrack is filled.

Non-moving joints can be bonded together with epoxy rins, just like a crack. Anchor bolts and reinforcing steel be grouted into concrete structures in the splash zone ander water with the injection process.

6.7.4 Selection considerations—Materials that meet thecriteria for ASTM C 881, and can be verified to exhib

hes

n-

yf's

rek-r

ly,

vi-

teteilt

l-n

e

Aso

n-nd

tedrr-e

i-ei-in aiesndionhe

-nun-

sufficient bond strength in a wet and saturated conditionexcellent initial choices for material selection. Much of underwater work done in North America is in water wtemperature at or below 50 F (10 C). The epoxy materialected should be tested and verified to be capable to curbond at the anticipated ambient temperatures. In addithe viscosity of the material needs to be compatible withselected pumping equipment at the anticipated temperato ensure that the material will be able to penetrate theof cracks to be repaired.

Selection of the correct epoxy formulation is importaMost epoxies will not bond or cure under water, especibelow 50 F (10 C). At lower temperatures, it becomes mdifficult to pump the epoxies into fine cracks because ofincreased viscosity. Correct equipment selection, couwith the proper epoxy, is essential.

Epoxy injected into cracks will act as an electrical insutor, possibly preventing the effective use of cathodic protion.

Epoxies may not provide full bond to contaminated crsurfaces, thereby limiting the epoxy's ability to fully seacrack or to transfer forces across the crack. Epoxy injecwill not stop corrosion once it has started. In aqueous eronments, especially seawater, epoxy coatings in permeconcrete may delaminate from the reinforcing bars otime, allowing corrosion to proceed.

6.7.5 Installation procedure—Several types of epoxpumping systems are used: (1) positive displacement pu(2) pressure pots; or (3) progressive cavity pumps. Typepumps mix the epoxy just prior to entry into the crack, whtypes (2) and (3) require mixing the epoxy prior to pumpi

The exposed concrete surfaces on both sides of the are typically cleaned by high-pressure water blasting, asive blasting or other mechanical methods. Entry portsused as inlets to carry the epoxy injection resin into the cor void. The entry ports can be attached to the concreteface and bonded into place with a hydraulic cement or eppaste. Ports may also be established by drilling into the cand setting an entry port into the drilled hole. The size ofcavity to be injected, concrete thickness, and crack lengtdetermine the proper spacing of the entry ports. Spacininjection ports should be at least equal to the thickness ocracked member being repaired or if the crack depth is viously determined then the spacing should be a minimuthe crack depth. The remainder of the exposed crack is swith fast setting hydraulic cement or epoxy paste.

The rapid setting cement formulations for surface seaover cracks may have a working life of 3 to 5 min and atime of an additional 3 to 15 min, depending on the wtemperature. When a cement sealer is used, the crack jected as soon as possible because the bond strength concrete surface may be affected by surface contamina

The surface seal can either be left in place or removeter the injection resin has cured.

The epoxy is injected at the lowest entry port and injeccontinues until all air, water and epoxy mixed with wate

546.2R-21GUIDE TO UNDERWATER REPAIR OF CONCRETE

sin.ject

ienpateres tak seaag

pointionent verx- onl

mentheracinbe alessan

n becierder-crete andete,e-

been ap-e ap-r of hassingd byyat,lingith

wash-con-owlyn

resu-ed in

rifytruc-der-

n anringork each,

as-rolthe

.

forced out of the next adjacent port with clear epoxy reThis process is continued until the entire crack length is in

The pressure used for epoxy injection need to be sufficto displace materials at temperatures and depths anticiand to completely fill the crack. Typical pumping pressuare from 20 to 150 psi (0.34 to 1.0 MPa). Care should been not to use pressures that could rupture the surfaceExcessively high pressures have been known to damconcrete elements when the epoxy in the crack has no of exit. Special care should be given during epoxy injecinto laminar cracks where there is little or no reinforcemacross the crack. The injection pressure must be keptlow to prevent hydraulic fracturing from widening or etending the crack. Stitch bolts across the crack are thepositive means of repairing such laminar cracks.

6.8—Hand placement6.8.1 Description and definition—In an isolated location

where the repair area is small, patching by hand placemay be preferable to other methods (Fig. 6.2). As with orepair methods, the surface should be cleaned before plnew material. Repairs made using this method may not durable as with other methods, but the cost may be Hand placed materials often fail because of poor workmship.

Fig. 6.2—Hand placing underwater patch. (Courtesy of MGarlich.)

es.ix-retndby ba

atughSe

per-

l,lers.acy

ch-

isncypec- thew-

6.8.2 Cementitious products—Accelerating admixturescan facilitate hand placement of cementitious mixturConcrete can be modified by hydrophobic, epoxy-resin mes that can be for hand patching of thin sections. Conccan also be modified with anti-washout admixtures adropped through the water to divers waiting to apply it hand. Conventional concrete has been placed in plasticwith twist ties and dropped to waiting divers. See Section 6.5for further information.

6.8.3 Epoxy mortar products—Epoxy mortars made withfine aggregate have also been applied by hand. These mrials are typically mixed on the surface and lowered throthe water to the work area below in a covered bucket. Section 6.6 for further information.

.

td

-l.

et

y

y

t

gs.

-

e

g

e-

e

6.9—Other underwater applications using concrete containing anti-washout admixtures

Concretes containing anti-washout admixtures also caplaced under water by tremie or pump, or slipform (Sauand Neeley, 1987; Kepler, 1990). The highest quality unwater concrete placement can be achieved when the concontains a moderate dosage of anti-washout admixturesis placed by either tremie or pump (Underwater Concr1983a; Kajima Corp, 1985) directly to the point of placment. Concrete containing anti-washout admixtures has successfully placed by tremie and by pump in numerousplications in the United States, Europe, and Japan. Thesplications have been in new construction and in repaiexisting concrete structures. The Corps of Engineersconducted extensive research into repair applications uconcretes containing anti-washout admixtures and placetremie and pump (Neeley, 1988; Neeley et al., 1990; Kha1991). The concrete can be proportioned to be self-leveand to flow around reinforcing steel and other objects wease. The increased cohesiveness imparted by the anti-out admixtures makes the concrete pumpable. These cretes can also be placed in areas surrounded by slflowing water. Anti-washout admixtures in combinatiowith certain water-reducing and air-entraining admixtushould be checked for compatibility. Any potentially troblesome problems with the fresh concrete can be detecttrial batches prior to the actual placement.

CHAPTER 7—INSPECTION OF REPAIRS7.1—Introduction

Ideally, construction inspections are performed to vethat repairs have been made in accordance with the constion documents. Due to the expense associated with unwater inspections, they are not always performed. Wheinspection is conducted, it may be performed either duthe course of the construction phase or after all of the wis complete. There are advantages and disadvantages tosince each procedure has unique problems.

7.2—ProcedureAt the discretion of the owner, the contractor may be

signed the responsibility for performing the quality contof the project without further review by the engineer, owner or an independent agency.

Alternatively, an engineer or independent agency can form the inspections.

7.2.1 Inspection techniques—Most inspections are visuawith some use of small hand tools such as hammers or ruOccasionally, a core sample is taken to verify the adequof the repair. For further information regarding specific teniques used for the inspections, see Chapter 3.

Video is especially helpful to the owner if the inspectionbeing performed by the contractor, or by a diving agethat does not have specific expertise in construction instion. An owner's representative may direct the diver andvideo from the surface, if communication is available. Hoever, video equipment requires reasonably clear water.

546.2R-22 MANUAL OF CONCRETE PRACTICE

ee iy atioe , thetealllacfacir.t bdusc

i-pa

neomcee

speeds fotio

ifief thcu

onnde i.

l eirin emhl

ingte

truuiai bos oovev st-vesissi

e toatnd8;

ght,t is

le-ionhanin.tionas

atioout andn En-hesys-

ani-eir

g, s

7.2.2 Inspection during construction—Inspections that arperformed during construction are normally phased so thspection team can observe certain critical tasks as theperformed. In the case of a large spall repair, the inspecmay be phased so that the inspection team can observdrilling and placement of dowels, the surface preparationreinforcing bar arrangement, the form, and the complproduct. If the repair involves epoxy injection of smcracks, the inspections may check the cleaning, the pment of the injection ports, the placement of the surcrack sealer, the actual injection, and the completed repainspections are performed during construction, they mustimed closely so the progress of the contractor is not uninterrupted and so subsequent phases of work do not obthe item to be inspected.

7.2.3 Post-construction inspection—Some owners are prmarily concerned with the outward appearance of the reand do not plan to own the structure for long. Other owrely on cores or non-destructive tests after the work is cplete to determine the quality of the repair. In these instanonly post-construction testing or inspections are performThe actual timing of this type of inspection may not be ecially critical; however, it should normally be performsoon after construction is complete. It may form the basipayments to the contractor. Post-construction inspecdoes not hamper the contractor; however, it only verthat work was done. It does not confirm that all phases owork were performed in accordance with the contract doments.

7.3—DocumentationDocumentation for the construction inspection should c

sist of a report accompanied by appropriate sketches aphotographs, as appropriate. If video is used during thspection, a copy of the video tape may also be included

CHAPTER 8—DEVELOPING TECHNOLOGIES8.1—Precast concrete elements and prefabricated steel elements

Precast concrete elements and pre-fabricated steements have been used on a very limited basis for repaconcrete structures under water. Difficulty of handling theements under water, the need to secure effective attachto the in-place concrete, the requirement for thorougcleaning the area to be repaired, and the design and sizthe elements are obstacles to the application of these niques.

In developing underwater repair concepts, both constion methods and prefabricated panel designs reqattention. Divers are likely to be an integral part of repprojects, but for depths greater than 40 ft (12 m), severetom time limitations are placed on divers. Steel panelcomposite steel-concrete panels would be preferred concrete panels if abrasion resistance is important. Howif steel is selected, design details must assure that thepanels remain serviceable under uplift forces from highlocity water flow. Other approaches include abrasion-retant, epoxy-coated steel or concrete panels. One de

n-re

nstheed

e-e Ife

lyure

irrs-s,

d.-

rnse-

-/orn-

le-g

l-enty of

ch-

c-rert-r

erer,eel--

gn

philosophy would be to use panels as large as possiblminimize joints between panels. The number of joints thare transverse to water flow should be minimized (Rail aHaynes, 1991; Abam, 1987a,b, 1989; McDonald, 198Miles, 1993).

Precast ferrocement elements are strong and light weiwhich is an advantage in underwater repairs. Ferrocementhin-shell concrete reinforced with closely-spaced, multipmesh layers of either wire fabric or expanded metal. Sectthickness seldom exceeds 2 in. (50 mm), is usually less thalf that, and may be as thin as 3/8 in. (10 mm). A 1/8-(3-mm) cover has been found to provide adequate protecfor the mesh in marine environments when the mortar wmade with a 1:2 cement/sand ratio and a water/cement rbelow 0.4. Ferrocement can undergo large strains withcracking. When cracks do appear they are closely spacedlimited in extent. See ACI 549.1R for more information oferrocement. Ferrocement elements have been used ingland to repair sewer inverts under water without taking tsystem out of service. Patents are pending on a similar tem for use in the U.S.

CHAPTER 9—REFERENCES9.1—Recommended references

The documents of the various standards producing orgzation referred to in this document are listed below with thserial designations:

American Concrete Institute (ACI)116R Cement and Concrete Terminology201.2R Guide to Durable Concrete210R Erosion of Concrete in Hydraulic Structures222R Corrosion of Metals in Concrete304R Guide for Measuring, Mixing, Transporting and

Placing Concrete304.2R Placing Concrete by Pumping Methods515.1R Guide to the Use of Waterproofing, Dampproofin

Protective and Decorative Barrier Systemfor Concrete

549.1R Guide for the Design, Construction, and Repair of Ferrocement

American Society for Testing and Materials (ASTM)C 597 Standard Test Method for Pulse Velocity

Through ConcreteC 805 Standard Test Method for Rebound Number of

Hardened ConcreteC 881 Specification for Epoxy-Resin Base Bonding

Systems for Concrete

The above publications may be obtained from the followingorganizations:

American Concrete InstituteP.O. Box 9094Farmington Hills, MI 48333-9094

ASTM100 Bar Harbor DriveWest Conshohocken, PA 19428

546.2R-23GUIDE TO UNDERWATER REPAIR OF CONCRETE

seln

ton,

-in-ortta-

il-al

of

ast an of

us

t

sinardMR

Proed-

oni-ng-

s foica

pe

bs,

-2-

rucers

TPking

t-

P-rta-

ne

es-

r-

terCScks

inater

edAfr34

Oil-

rwa-

la,”24.on-

,”

Lin-

byers

A.nks

rch,

g,”

retert C-Sta-

Sys-

,”

susilita-ers

inrps

ryirs,”ter-

m,”

&

.n

cearch

ndi-gi-

innicaleri-

in

in

ruc-

9.2—Cited referencesAASHTO (1991). “Guide Specification and Commentary for Ves

Collision Design of Highway Bridges,” V. 1, Final Report, AmericaAssociation of State Highway and Transportation Officials, WashingD.C., Feb.

ABAM Engineers, Inc. (1987). “Design of a Precast Concrete StayPlace Forming System for Lock Wall Rehabilitation,” Technical RepREMR-CS-7, US Army Corps of Engineers Waterways Experiment Stion, Vicksburg, Miss., Jul.

ABAM Engineers, Inc. (1987). “A Demonstration of the Constructabity of a Precast Concrete Stay-in-Place Forming System for Lock WRehabilitation,” Technical Report REMR CS-14, U.S. Army Corps Engineers Waterways Experiment Station, Vicksburg, Miss., Dec.

ABAM Engineers, Inc. (1989). “Concepts for Installation of the PrecConcrete Stay-in-Place Forming System for Lock Wall Rehabilitation inOperational Lock,” Technical Report REMR-CS-28, U.S. Army CorpsEngineers Waterways Experiment Station, Vicksburg, Miss., Dec.

ACI SP-8 (1964). Symposium on Concrete Construction in AqueoEnvironments, American Concrete Institute, Farmington Hills, Mich.

ACI SP-65 (1980). Performance of Concrete in Marine Environmen,American Concrete Institute, Farmington Hills, Mich.

Best, J. F., and McDonald, J. E. (1990). “Evaluation of Polyester ReEpoxy, and Cement Grouts for Embedding Reinforcing Steel Bars in Hened Concrete,” U.S. Army Corps of Engineers, Technical Report RECS-23, Jan.

Burke, N. D., and Bushman, J. B. (1988). “Corrosion and Cathodic tection of Steel Reinforced Concrete Bridge Decks,” FHWA-IP-007, Feral Highway Administration, Washington, D.C.

Busby, R. Franks Assoc. (1978). “Underwater Inspection/Testing/Mtoring of Offshore Structures,” U.S. Government Printing Office, Washiton, D.C.

Clausner, J. E., and Pope, J. (1988). “Side Scan Sonar ApplicationEvaluating Coastal Structures,” U.S. Army Corps of Engineers TechnReport CERC-88-16, Nov.

Collins, T. J. (1988). “Underwater Inspection: Documentation and Scial Testing,” Public Works, V. 119, No. 1, Jan.

Concrete Products (1995). “A Few Good Pieces Tackle Marine JoConcrete Products, Dec.

Corps of Engineers (1994). “Hydrographic Surveying,” EM-11101003, Headquarters U.S. Army Corps of Engineers, Washington D.C.

Corps of Engineers (1995). “Evaluation and Repair of Concrete Sttures,” EM 1110-2-2002, Headquarters U.S. Army Corps of EngineWashington, D.C., Jun.

DePuy, G. W. (1994). “Chemical Resistance of Concrete,” ASTM S169C Significance of Tests and Properties of Concrete and Concrete-MaMaterials, P. Klieger and J. F. Lamond eds., Chapter 26, pp. 263-281.

Dolar-Mantuani, L. (1983). Handbook of Concrete Aggregates—A Perographic and Technological Evaluation, Noyes Publications.

FHWA (1989). “Underwater Inspection of Bridges,” Report FHWA-D80-1, Federal Highway Administration, U.S. Department of Transpotion, Springfield, Va.

Freese, V. D.; Hofig, W.; and Grotkopp, U. (1978). “Neuartige Betofur den Wasserbau,” Beton, June.

Garlich, M. J., and Chrozastowski, M. J. (1989). “An Example of Sidcan Sonar in Waterfront Facilities Evaluation,” PORTS ’84, Kenneth M.Childs, ed., American Society of Civil Engineers, pp. 84-94.

Garlich, M. J. (1995). “Application of Nondestructive Testing in Undewater Evaluation of Bridge and Related Structures,” Proceedings, SPIENondestructive Evaluation of Aging Infrastructure, June.

Gerwick, B. C. (1988). “Review of the State of the Art for UnderwaRepair Using Abrasion-Resistant Concrete,” Technical Report REMR-19, U.S. Army Corps of Engineers Waterways Experiment Station, Viburg, Miss.

Gjorv, O. E. (1968). “Durability of Reinforced Concrete Wharves Norwegian Harbors,” Norwegian Committee on Concrete in Sea WIngeniorforlaget A/S, p. 208.

Halstead, S., Woodworth, L. A. (1955). “Deterioration of ReinforcConcrete Structures under Coastal Conditions,” Transactions, South can Institution of Civil Engineers, Johannesburg, No. 4, Apr., pp. 115-1

Hard Suits, Inc. (1997). “Systems Information Package,” American field Divers, Inc. Houston, Tex.

l

,--

-

rl

-

”

-,

--

,

i-.

Hasan, N.; Faerman, E.; and Berned, D., (1993). “Advances in Undeter Concreting: St. Lucie Plant Intake Velocity Cap Rehabilitation,” HighPerformance Concrete in Severe Environments, ACI SP-140, pp. 187-213.

Holland, T. C. (1976). “Tremie Concrete Techniques Used at TarbeInternational Water Power and Dam Construction, V. 28, No. 1, pp. 21-

Holland, T. C. (1983). “Tremie Concrete for Massive Underwater Cstruction,” University of California, Berkeley.

Kajima Corp. (1985). “Use of Hydrocrete for Repair of Stilling BasinKajima Corp., Japan, p. 49.

Kepler, W. F. (1990). “Underwater Placement of a Concrete Canal ing,” Concrete International: Design and Construction, June, pp. 54-59.

Khayat, K. H. (1991). “Underwater Repair of Concrete DamagedAbrasion-Erosion,” Technical Report REMR-CS-37, U.S. Army EngineWaterways Experiment Station, Vicksburg, Miss.

Khoury, G. A.; Sullivan, P. J. E.; Dahan, R. A.; and Onabolu, O.(1985). “Organic Acid Intake of Crude Oil in North Sea Oil Storage Taas Affected by Aerobic Bacterial Activity,” Petroleum Review, Sept., pp.42-45.

Klieger, P. (1994). “Air-Entraining Admixtures,” Significance of Testsand Properties of Concrete-Making Materials, ASTM STP 169C, P.Klieger and J. F. Lamond, eds., Chapter 44, pp. 484-490.

Lamberton, B. A. (1989). “Fabric Forms for Concrete,” Concrete Inter-national, Dec. 1989, pp. 58-67.

Maage, M. (1984). “Underwater Concrete,” Nordic Concrete ReseaTrondheim, Norway.

Makk, O., and Tjugum, O. (1985). “Pumped UnderwattensbetonPumped Underwater Concrete, Nordisk Betong, V. 2.

McDonald, J. E. (1980). “Maintenance and Preservation of ConcStructures; Repair of Erosion Damaged Structures,” Technical Repo78-4, Report 2, U.S. Army Corps of Engineers Waterways Experiment tion, Vicksburg, Miss., Apr.

McDonald, J. E. (1988). “Precast Concrete Stay-in-Place Forming tem for Lock-Wall Rehabilitation,” Concrete International, V. 10, No. 6,June, pp. 31-37.

McKain, D. W., and McKain, V. E. (1996). “Unique Reef ReplicationON&T, May-June, p. 32.

Miles, W. R. (1993). “Comparison of Cast-in-Place Concrete verPrecast Concrete Stay-in-Place Forming Systems for Lock Wall Rehabtion,” Technical Report REMR-CS-41, U.S. Army Corps of EngineWaterways Experiment Station, Vicksburg, Miss., Oct.

Neeley, B. D. (1988). “Evaluation of Concrete Materials for UseUnderwater Repairs,” Technical Report REMR-CS-18, U.S. Army Coof Engineers Waterways Experiment Station, Vicksburg, Miss.

Neeley, B. D.; Saucier, K. L.; and Thornton, H. T. (1990). “LaboratoEvaluation of Concrete Mixtures and Techniques for Underwater RepaTechnical Report REMR-CS-34, U.S. Army Corps of Engineers Waways Experiment Station, Vicksburg, Miss.

Neeley, B. D., and Wickersham, J. (1989). “Repair of Red Rock DaConcrete International: Design and Construction, V. 11, No. 10, Oct.

Neville, A. M. (1983). “Properties of Concrete,” Longman Scientific Technical, 3rd ed.

Olson, L. D.; Law, M.; Phelps, G. C.; Murthy, K. N.; and Ghadiali, B. M(1994). Proceedings, Federal Highway Administration Conference oDeep Foundations, Orlando, Fla., Dec.

Olson, L. D., (1996). “Nondestructive Testing of Unknown SubsurfaBridge Foundations—Results of NCHRP Project 21-5,” NCHRP ReseResults Digest, No. 213, Dec.

Popovics, S. (1986). “Underwater Inspection of the Engineering Cotion of Concrete Structures,” Technical Report REMR-9, U.S. Army Enneers Waterways Experiment Station, Vicksburg, Miss., July.

Rail, R. D., and Haynes, H. H. (1991). “Underwater Stilling BasRepair Techniques Using Precast or Prefabricated Elements,” TechReport REMR-CS-38, U.S. Army Corps of Engineers Waterways Expment Station, Vicksburg, Miss., Dec.

Rosa, E. B.; McCollum, B.; and Peters, O. S. (1913). “ElectrolysisConcrete,” Technical Paper No. 18, U.S. Bureau of Standards.

Saucier, K. L., and Neeley, B. D. (1987). “Antiwashout Mixtures Underwater Concrete,” Concrete International: Design and Construction,V. 9, No. 5, May, pp. 42-47.

Sletten, Rune et al. (1977). “In-Service Inspection of North Sea Sttures,” Offshore Technology Conference, OTC 2980, May.

546.2R-24 MANUAL OF CONCRETE PRACTICE

te

e ias

ur

e-s,

er-

tion,

An

he

,

Smith, A. P. (1986). “Underwater Nondestructive Testing of ConcreAn Evaluation of Techniques,” NCEL Technical Note, Feb.

Straube, P., “Evaluation of Hydrocrete for Use as Reinforced ConcretOffshore Structures,” Technical Report No. 82-0204, Det Norske VeritOslo, Norway.

Thornton, H. T. (1978). “Acid Attack on Concrete Caused by SulfBacteria Action,” ACI JOURNAL, pp. 577-584, Nov.

Thornton, H. T., and Alexander, A. M. (1987). “Development of Nondstructive Testing Systems for In Situ Evaluation of Concrete StructureTechnical Report REMR-CS-10, U.S. Army Corps of Engineers Watways Experiment Station, Vicksburg, Miss., Dec.

:

n,

”

Underwater Concrete (1983a). “Hydraulic Sea Water Intake,” Hydro-crete Underwater Concrete, Underwater Concrete Limited, London.

Underwater Concrete (1983b). “Hydrocrete, Cable Peak Pure StaHong Kong,” Hydrocrete Underwater Concrete, Underwater ConcreteLimited, London.

Vadus, J. R., and Busby, R. F. (1979). “Remotely Operated Vehicles:Overview,” NOAA Technical Report 00E6, Dec.

Wiebenga, J. G. (1980). “Durability of Concrete Structures Along tNorth Sea Coast of the Netherlands,” ACI SP-65, Performance of Concretein Marine Environment, American Concrete Institute, Farmington HillsMich. pp. 437-452.