Guide to Underwater Repair of Concrete

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ACI 546.2R-10

Reported by ACI Committee 546 --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`---

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First Printing June 2010

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Guide to Underwater Repair of Concrete

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ACI 546.2R-10

Guide to Underwater Repair of Concrete Reported by ACI Committee 546

Paul E. Gaudette* David W. Whitmore* Chair Secretary

James Peter Barlow Fred R. Goodwin John S. Lund Joe Solomon Paul D. Carter Harald G. Greve James E. McDonald* Michael M. Sprinkel Michael M. Chehab Ron Heffron Lawrence G. Mrazek Ronald R. Stankie Marwan A. Daye Robert F. Joyce Myles A. Murray Alexander M. Vaysburd* Peter H. Emmons Lawrence F. Kahn Jay H. Paul Kurt Wagner Michael J. Garlich* Brian F. Keane Richard C. Reed* Patrick M. Watson Timothy R. W. Gillespie Benjamin Lavon Johan L. Silfwerbrand Mark V. Ziegler* Yelena S. Golod Kenneth M. Lozen

*Subcommittee members who prepared this guide. --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`---

This document provides guidance on the selection and application of CONTENTS materials and methods for the repair and strengthening of concrete structures Chapter 1—General, p. 546.2R-2 under water. An overview of materials and methods for underwater repair 1.1—Introduction is presented as a guide for making a selection for a particular application. 1.2—Scope References are provided for additional information about selected materials 1.3—Underwater access technology and construction methods.

Keywords: anti-washout; cathodic protection; concrete removal; deteriora- Chapter 2—Notation and definitions, p. 546.2R-4 tion; diver; formwork; marine placement; pile-jackets; polymer(s); repair; 2.1—Notation surface preparation; tremie; underwater. 2.2—Definitions

Chapter 3—Causes of deterioration, p. 546.2R-5 3.1—Deficient construction practices 3.2—Marine organisms ACI Committee Reports, Guides, Manuals, and Commentaries 3.3—Chemical attack are intended for guidance in planning, designing, executing, 3.4—Corrosion and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the 3.5—Mechanical damage significance and limitations of its content and recommendations 3.6—Freezing and thawing damage and who will accept responsibility for the application of the 3.7—Salt scaling material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute 3.8—Scour shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in contract ACI 546.2R-10 supersedes ACI 546.2R-98 and was adopted and published June 2010. documents. If items found in this document are desired by the Copyright © 2010, American Concrete Institute. Architect/Engineer to be a part of the contract documents, they All rights reserved including rights of reproduction and use in any form or by any shall be restated in mandatory language for incorporation by means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduction the Architect/Engineer. or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

Copyright American Concrete Institute 546.2R-1 Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=wer, weqwe No reproduction or networking permitted without license from IHS Not for Resale, 01/26/2015 02:07:17 MST Daneshlink.com daneshlink.com

546.2R-2 ACI COMMITTEE REPORT

Chapter 4—Investigation and evaluation, effective, the evaluation procedure should begin with a review p. 546.2R-8 of historical information on the structure and its environment, 4.1—Introduction including any changes made to the structure over time and 4.2—Visual inspection the records of prior on-site inspections or repairs. Accurate 4.3—Tactile inspection repairs can be designed only after the extent of deterioration 4.4—Underwater nondestructive testing of concrete is documented and the failure mechanism is determined. In 4.5—Sampling and destructive testing addition, proper repair techniques and installation procedures 4.6—Evaluation should be followed to produce an optimum repair system. Underwater concrete deterioration is a serious economic Chapter 5—Preparation for repair, p. 546.2R-12 problem (Fig. 1.2 and 1.3). Water containing oxygen and 5.1—General contaminants can aggressively attack concrete. Selecting 5.2—Excavation and debris removal appropriate repair materials and methods, and maintaining 5.3—Concrete removal quality control not normally associated with repair above 5.4—Surface preparation water are critical when working in a marine environment. As 5.5—Reinforcement preparation such, underwater repair of concrete is a specialized and highly 5.6—Concrete anchors technical part of concrete repair technology. Successful repairs can be achieved when these factors are carefully implemented. Chapter 6—Formwork, p. 546.2R-14 This guide provides an overview of the current status of under- 6.1—General water repair technology to assist the design professional, 6.2—Rigid forms contractor, and owner in making repair decisions. 6.3—Semi-rigid forms 6.4—Flexible forms 1.2—Scope This guide covers the repair of concrete structures in the Chapter 7—Materials and methods, p. 546.2R-19 splash zone and underwater portions of structures located in 7.1—General considerations lakes, rivers, oceans, and groundwater. Concrete deterioration, 7.2—Anti-washout admixtures investigation and testing procedures, preparation, materials 7.3—Preplaced-aggregate concrete and methodology, and inspection procedures are described. 7.4—Tremie concrete Design considerations and references for underwater repair 7.5—Pumped concrete and grout of concrete bridges, wharves, pipelines, piers, outfalls, bulk- 7.6—Free dump through water heads, and offshore structures are identified. Scour repair, 7.7—Epoxy grouting however, is not included in this guide. 7.8—Epoxy injection One option for repairing underwater structures is to 7.9—Gloved-hand placement construct a cofferdam around the structure and remove the 7.10—Geomembrane systems water inside the cofferdam. Concrete repairs can then be 7.11—Cathodic protection installed in the dry, as discussed in ACI 546R. 7.12—Fiber-reinforced polymers 1.3—Underwater access technology Chapter 8—Inspection of repairs, p. 546.2R-28 Underwater work is generally classified into one of two 8.1—Introduction broad categories for accessing the work site: diving or a 8.2—Procedure remotely operated vehicle (ROV). 8.3—Documentation Diving is the traditional method of performing tasks under water. In this category, the diver is equipped with life- Chapter 9—References, p. 546.2R-29 9.1—Referenced standards and reports support systems that provide breathable air and protection 9.2—Cited references from the elements. Manned diving systems include SCUBA (self-contained underwater breathing apparatus) and CHAPTER 1—GENERAL surface-supplied air. When employing SCUBA, the diver is 1.1—Introduction supplied with breathing air (or gas) from a tank carried by the The repair of concrete structures under water presents many diver. In surface supply diving, the breathing medium is complex problems. Although the applicable basic repair supplied to the diver through a hose connected to the air (or procedures and materials are similar to those required in typical gas) supply above water. concrete repair, the harsh environmental conditions and specific Performance of duties at higher than one atmosphere problems associated with working under water or in the splash ambient pressure causes a multitude of physiological zone area (Fig. 1.1) create many differences. The repair of changes within the human body. For example, body tissues concrete under water is usually difficult, requiring specialized absorb and shed gases at different rates than those normally products and systems, and the services of highly qualified and experienced on the surface. Because of this, the time available experienced design professionals and contractors. to perform work under water decreases rapidly with Proper evaluation of existing structural condition is the increased water depth. For example, industry standards

essential first step in designing long-term repairs. To be most allow --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`---a diver using compressed air to work at 30 ft (10 m) for

UNDERWATER REPAIR OF CONCRETE 546.2R-3

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

Fig. 1.2—Deteriorated pile in tidal and exposed zones. Fig. 1.3—Advanced deterioration; pile has been cleaned. (Figure courtesy of Michael J. Garlich.) (Figure courtesy of Michael J. Garlich.)

an unlimited period of time. If work, however, is being When manned diving is used deeper than 180 ft (60 m) of performed at 60 ft (20 m), the diver can only work for water, most divers elect to use specially formulated mixtures approximately 60 minutes without special precautions to of gases rather than compressed air. To increase efficiency, prevent decompression sickness. The sophistication (and these diving operations are often enhanced with diving bells, hence, the cost) of the diving systems used on a project which are used to maintain the divers at working depths for increases with increased depth. extended periods of time. Divers may be supported at water --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=wer, weqwe No reproduction or networking permitted without license from IHS Not for Resale, 01/26/2015 02:07:17 MST Daneshlink.com daneshlink.com

546.2R-4 ACI COMMITTEE REPORT

Fig. 1.4—Remotely operated vehicle. (Figure courtesy of Michael J. Garlich.) Fig. 1.6—Work class remotely operated vehicle. (Figure courtesy of Oceaneering, Inc.)

observation activities. Work Class ROVs are also equipped with cameras, but can have manipulator arms, cutting tools, high-definition imaging sonar, and other equipment to assist in construction support (NRC 1996). More advanced tooling packages can be added for trenching, bolting pipeline flanges, and differential pressure work, such as hydroelectric facilities repairs. Advanced position systems are also being employed to increase the operation envelope on the ROVs, allowing real-time model-based positioning and enabling continued operations in zero visibility (Beck et al. 2008). Currently, many Work Class ROVs are rated to operate at depths up to 10,000 ft (3050 m).

CHAPTER 2—NOTATION AND DEFINITIONS Fig. 1.5—Flying eyeball remotely operated vehicle. (Figure 2.1—Notation courtesy of Sub-Atlantic, Inc.) Not used in this document.

depths where the work is performed for weeks at a time. The 2.2—Definitions technologies associated with mixed gas diving are changing ACI provides a comprehensive list of definitions through rapidly as people work at deeper depths. an online resource, “ACI Concrete Terminology,” http:// The One Atmosphere Diving Suit (Hard Suits, Inc. 1997) terminology.concrete.org. Definitions provided herein is capable of supporting divers at depths as great as 2100 ft complement that resource. (640 m) with an internal suit pressure of one atmosphere. admixture, anti-washout (AWA)—a concrete admixture The diver works in an ambient pressure equivalent to that on that reduces the loss of fine material from concrete when the surface; therefore, the time at depth is virtually unrestricted. placed in water. The suit looks much like a hollow robot. The arms are repair—to replace or correct deteriorated, damaged, or equipped with claw-like operating devices, which reduce faulty materials, components, or elements of a structure. manual dexterity. The suits are cumbersome and difficult to repair, nonstructural—halting or slowing deterioration position because mobility is provided by external propulsion without intending to affect the structural capacity of a member. devices, ballast tanks, or cables suspended from topside repair, structural—a repair that addresses deterioration support vessels. and re-establishes or enhances the structural capacity of a Remotely operated vehicles are underwater robots member. controlled by remote crews through an umbilical or tether repair systems—the combination of materials and (Fig. 1.4) (Vadus and Busby 1979; MTS 1984). The umbilical techniques used in the repair of a structure. carries power to the ROV, along with command and control strengthening—increasing the load-carrying capacity of signals from the crew. Remotely operated vehicles typically a structural component beyond its current capacity, or have free range of movement and range in size from small restoring a damaged structural component to its original “flying eyeball” (Fig. 1.5) models to larger Work Class design capacity. models (Fig. 1.6). Flying eyeball ROVs are typically surface preparation—the removal of deteriorated or

equipped with only a camera and used for inspection or contaminated concrete--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- or steel using a method, or combination

UNDERWATER REPAIR OF CONCRETE 546.2R-5

of methods, to roughen or clean the substrate to enhance bond of a repair material or protective coating. tremie—a pipe extending below water, generally with a funnel-shaped top, through which concrete can be deposited.

CHAPTER 3—CAUSES OF DETERIORATION 3.1—Deficient construction practices Underwater placement of concrete and other materials is often susceptible to deficient construction practices due to the difficult working conditions and the inability to provide adequate inspection during construction. Failure to follow specified procedures and good practice or outright carelessness may lead to a number of conditions that may be grouped together as construction errors. Typically, most of these errors do not lead directly to failure or deterioration of concrete. Instead, they enhance the adverse impacts of other Fig. 3.1—Failure of precast pile attributed to delayed mechanisms identified in Chapter 3. ettringite formation. (Figure courtesy of Tom Spencer.) Deficient practices include: 1. Exceeding the target water-cementitious material ratio

rock. These organisms, known as pholads, make shallow--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- (w/cm); oval-shaped burrows in the concrete. Rock-borers in warm- 2. Inadequate surface preparation; water areas are also able to dissolve and bore into concrete 3. Improper alignment of formwork; made with limestone aggregate, even if the aggregate and 4. Improper concrete placement and consolidation; concrete is dense. 5. Improper location of reinforcing steel; 3.2.2 Acid attack from acid-producing bacteria—Anaerobic, 6. Movement of formwork during placement; sulfate-reducing bacteria can produce hydrogen sulfide. 7. Premature removal of forms or shores; and Sulfur-oxidizing bacteria, if also present, can oxidize the 8. Settling of the concrete during hardening. hydrogen sulfide to produce sulfuric acid, common in Each of these construction errors is discussed in an sewers. Also, oil-oxidizing bacteria can produce fatty acids engineering manual prepared by the U.S. Army Corps of in aerobic conditions, such as in the splash zone, which Engineers (USACE) (1995). attacks the cement paste. In addition, the acids can reduce the One deficiency observed in marine structures is tension pH of the concrete to approximately 8 or lower, at which cracking of precast concrete piling, resulting from improper level the passive layer breaks down, and reinforcement driving practices. This problem is characterized by horizontal corrosion may occur (Thornton 1978; Khoury et al. 1985). cracks generally occurring in the below-water portion of the Deterioration is characterized by a loss of the cement matrix pile. Both under water and in the splash zone, cracks in and a rough surface of exposed concrete aggregate. concrete increase concrete permeability near the crack. Thus, Aggregate loss may occur in severe cases. in seawater, chloride penetration is amplified both in depth and concentration in the immediate location of the crack, leading to 3.3—Chemical attack the creation of an anode at the reinforcing bars. This usually Concrete under water is susceptible to deterioration does not lead to significant corrosion of steel reinforcement in caused by a wide range of chemicals. This deterioration may underwater concrete because of the low oxygen availability and be classified as that caused by chemicals outside the the sealing of the crack by lime, which leaches from the concrete, and that caused by chemicals present in the concrete and also comes from marine organisms. In the splash concrete constituents themselves. In cases of external attack, zone, however, the presence of such cracks can lead to the early the water frequently provides a continuous fresh supply of onset of local reinforcing steel corrosion. these chemicals. The water also washes the reaction products Failure of precast prestressed piles attributed to delayed away and removes loose aggregate particles, exposing new ettringite formation (Fig. 3.1) has been reported (Spencer concrete surfaces to further attack. and Blaylock 1997; Stark et al. 1999). This deterioration is Internal attack is accelerated by porous concrete, cracks, and attributed to improper high temperature curing practices in voids. Alkali-silica reactions and corrosion of reinforcement are manufacture. Concrete distress due to delayed ettringite examples of internal attack. Internal deterioration also results formation is characterized by cracking and softening of the when soluble constituents of concrete are leached out, resulting concrete along with disintegration and loss of concrete. in lower concrete strengths and higher porosity. Observed deterioration has included near-total loss of Splash-zone concrete is particularly susceptible to chemical concrete over substantial portions of affected piles. attack because of the abundant supply of oxygen and frequent wetting-and-drying cycles caused by daily wave or tidal action. 3.2—Marine organisms Chemicals present in water surrounding the concrete can 3.2.1 Rock borers—Marine organisms resembling ordinary cause deterioration that varies in rate from very rapid to very clams are capable of boring into porous concrete, as well as slow. The following are common forms of chemical attack.

546.2R-6 ACI COMMITTEE REPORT

Fig. 3.2—Failure of concrete pile attributed to alkali-silica reaction. (Figure courtesy of Collins Engineers, Inc.) Fig. 3.3—Spalled and cracked concrete attributed to corrosion of the steel reinforcement. (Figure courtesy of 3.3.1 Acid attack—Portland cement-concrete is not resistant Collins Engineers, Inc.) to attack by acids. In most cases, the chemical reaction between acid and portland cement results in the formation of and cracking. The most common of these internal reactions water-soluble calcium compounds that are then leached away. is the alkali-silica reaction (Fig. 3.2). In this case, the alkalis ACI 201.2R and 515.1R describe acid attack in further detail. present primarily in portland cement react with silica found Symptoms of acid attack are loss of the cement paste and in in certain aggregates. The reaction gel expands when it is severe cases, subsequent loss of coarse aggregate. If the acid has moistened, causing tensile stresses in the concrete. Alternating reached reinforcing steel, corrosion may be present. wetting and drying frequently associated with the aquatic 3.3.2 Sulfate attack—Sulfates of sodium, potassium, splash-zone accelerates this reaction. Also, salt in marine calcium, or magnesium are often found in seawater, ground- environments can accelerate alkali-aggregate reactions by water, rivers, and industrial water. The chemical reactions increasing the sodium ion concentration until it is above the that take place between sulfate ions and portland cement minimum level necessary for alkali reactivity (Neville 1983; result in reaction products that have a greater volume than Spencer and Blaylock 1997; ACI 201.2R) Symptoms of alkali- the reactants. This volume change causes the development of aggregate attack are map- or pattern-cracking and swelling of stresses in the concrete that eventually lead to cracking and the concrete. In prestressed piles, the horizontal cracks may not deterioration. ACI 201.2R describes additional details of the be present due to the precompression in the concrete. sulfate attack mechanism. Symptoms of sulfate attack include map-cracking and softening of the concrete. In 3.4—Corrosion prestressed piles, observed cracking is primarily vertical 3.4.1 Introduction—Corrosion of reinforcing steel is a cracking, as the prestress force tends to prevent formation of serious threat to the durability and load-carrying capacity of the horizontal cracks. concrete structures in marine environments. The serious 3.3.3 Magnesium ion attack—Magnesium ion concentrations nature of this problem is demonstrated by the many examples present in some groundwater and in seawater may react with of cracked and spalled concrete at coastal locations caused the calcium-silicate hydrate, replacing calcium ions with by corrosion of the reinforcing steel (Fig. 3.3). magnesium. When this reaction occurs, there is a reduction Corrosion occurs rapidly in permeable, porous concrete in the amount of calcium-silicate hydrate present in the with inadequate cover over the reinforcing steel that is cement matrix that leads to a reduction in the strength of the exposed alternately to saltwater splash and to air, as in tidal cementitious material (Mehta and Monteiro 1993). and splash zones. Chlorides of varying concentrations Magnesium ion attack is characterized by a softening of the penetrate the concrete and, upon reaching the reinforcing cement matrix of the outer concrete surface. steel, set up electrochemical reactions that corrode the 3.3.4 Soft water attack—Water with very low concentrations reinforcing steel. Corrosion products occupy several times of dissolved minerals may leach calcium from the cement the volume of the original metal and can develop internal paste or aggregate (DePuy 1994). This is a particular pressures, creating a stress greater than the tensile strength of problem with water that occurs with snow melt, but major the concrete. Cracks are developed along the reinforcing deterioration from this mechanism is not a common event. bars, and eventually the concrete cover spalls. This allows Some process waterflows, such as demineralized water used exposure to increased chlorides and causes corrosion of the for boilers, can also dissolve calcium from cement paste. steel reinforcement to accelerate. Symptoms of corrosion 3.3.5 Internal attack—Several chemical reactions can take include concrete cracking oriented parallel to the reinforcement, place between the constituents of the concrete. Typically, spalling over reinforcement, and rust staining. reaction products develop that occupy a volume greater than 3.4.2 The corrosion process—Steel in concrete is the original solid materials, --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`---resulting in increased stresses normally protected chemically by the alkalinity of the

UNDERWATER REPAIR OF CONCRETE 546.2R-7

concrete and is highly resistant to corrosion. This is due to a passivating film that forms on the surface of embedded reinforcement that provides protection against corrosion. Greater depth of cover and less permeable concrete also provide increased resistance to the ingress of chloride ions, which compromise the passivating film. Corrosion of reinforcing steel is an electrochemical process that requires an electrolyte (such as moist, cation- laden concrete), two electrically connected metallic surfaces with different electrical potentials, and free oxygen (Burke and Bushman 1988). The entry of the electrolytes and oxygen are facilitated in more permeable concrete. Water containing dissolved salt provides an electrolyte of low electrical resistivity, thus permitting corrosion currents to flow readily. Oxygen is an essential ingredient to the electrochemical reaction at the Fig. 3.4—Concrete deterioration on a bridge pier attributed cathode of the corrosion cell. Consequently, steel in reinforced to cycles of freezing and thawing. (Figure courtesy of Collins concrete completely and permanently immersed in water Engineers, Inc.) corrodes much more slowly than in splash zones because oxygen is virtually excluded. Wave action or other activities movement of ships moored to inadequately protected structures. that mix the upper water surfaces with air may produce Again, the damage allows greater access to the interior oxygen levels in the water sufficient to initiate corrosion concrete, thus accelerating corrosion of reinforcement. In below the normal water levels. cold climates, ice movements can cause abrasion damage. A severe exposure condition exists when part of the 3.5.3 Cavitation—Cavitation is the formation of bubbles concrete structure is exposed to wetted cycles by salt water, or cavities in a liquid. The bubbles are formed and, subse- as by tides or sea spray. The part that is alternately wetted has quently, destroyed by changing pressure conditions that ample opportunity for contact with atmospheric oxygen. For result from discontinuities. Cavitation damage to concrete is this reason, reinforcing steel in concrete in aqueous environ- caused by the implosion of the bubbles, which generates an ments corrodes faster in the tidal zone and spray areas than extremely high pressure over a small area. Cavitation is a in other areas. Additional information on the mechanism of serious problem because the force exerted upon the concrete corrosion of steel in concrete is provided in ACI 222R. when the bubbles implode is large enough to remove concrete. Cavitation can result in damage ranging from 3.5—Mechanical damage minor surface deterioration to major concrete loss in tunnels Concrete structures in and around water are susceptible to and conduits. Cavitation damage initially appears as very various types of mechanical damage. rough pitted areas on a concrete surface. The mechanism 3.5.1 Impact—Impact damage to a concrete structure may causing cavitation is self-supporting. Once initiated, damage range from the shallow spalling caused by a light impact worsens in the direction of flow. Details of cavitation from a barge striking a lock wall to total loss of a structure damage are discussed in ACI 210R. caused by a ship colliding with a bridge pier. Because the range 3.5.4 Damage due to loads—A concrete structure may be of damage caused by impact can be so great, it is not possible to damaged by seismic forces or loads greater than those for define a typical set of symptoms (AASHTO 2009). which it was designed. The typical symptoms of such In cases of less-than-catastrophic impact, the damage may damage will be major structural cracking in tension or shear be under water and, hence, undetected. In such an instance, areas and spalling in compression areas. the structure suffers not only from the direct result of the impact (typically cracking and spalling), but also from the 3.6—Freezing and thawing damage indirect results of greater access to interior concrete and Deterioration of saturated concrete due to cycles of reinforcing steel by the water and water-borne contaminants. freezing and thawing has been observed in a large number of 3.5.2 Abrasion—Abrasion of underwater concrete is structures exposed to water and low temperatures (Fig. 3.4). typically caused by water-borne particles (rocks, sand, and Freezing of water in the pores of concrete can give rise to rubble) rubbing against and, to some degree, impacting concrete stresses that can rupture the cement paste. The against a concrete surface. Typical underwater abrasion disruptive forces are due to the fact that, as water freezes, it could include damage to stilling basins of hydraulic structures, increases in volume by approximately 9%. --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- or damage to piers and piling caused by abrasive particles Concrete that is continuously submerged will usually being carried by currents. Abrasion, such as in a stilling perform well. In the tidal zone, however, it is subject to basin, typically produces a worn and polished concrete cycles of freezing and thawing in cold climates. Freezing surface with heavily exposed or removed coarse aggregate. occurs when the tide drops, exposing wet concrete. The Abrasion damage to concrete is discussed in ACI 201.2R and water freezes in the concrete pores, expands, and tends to create ACI 210R. Abrasion damage may also be caused by the large stresses. When the tide eventually rises, the ice melts and

546.2R-8 ACI COMMITTEE REPORT

the cycle repeats. This cycling causes progressive deterioration cumbersome life-support systems and equipment, which of concrete unless it is adequately air-entrained. also hampers the inspection mission. This section will focus Extensive field and laboratory investigations have shown primarily on inspection efforts conducted by a diving team. that the rate of deterioration due to freezing and thawing is Most of the discussion, however, also applies to other considerably higher in salt water than in fresh water inspections performed by ROVs and manned submersibles. (Wiebenga 1980). This difference in resistance to freezing Underwater inspections usually take much longer to and thawing is normally ascribed to the generation of a accomplish than inspections of similar structures located higher hydraulic pressure in the pore system due to salt above the water surface. This necessitates more planning by gradients and osmotic effects. Small air voids in the concrete the inspecting team to optimize their efforts. Inspection will become water-filled after a long period of immersion. criteria and definitions are usually established before the These voids may also be more easily filled when salt is present. actual inspection and the inspection team is briefed. The In spite of the low frost resistance of concrete in salt water, primary goal is to inspect the structural elements to detect deterioration normally takes place slowly (Klieger 1994). any obvious damage. If a defect is observed, the inspector Concrete subjected to many freezing and thawing cycles in identifies and documents the type and extent of the defect. seawater can increase in volume due to the microcracks that The inspector also determines the location of the defect so result from inadequate freezing-and-thawing resistance. This repair crews can return later to make the repair, or another can cause increased deformations and stresses in flexural inspection team can reinvestigate, if necessary. members. Divers who perform structural inspections should be trained to recognize and describe defects, but may not have 3.7—Salt scaling specific structural engineering training. In this case, another Damage due to salt scaling in marine environments is person with the appropriate engineering background is usually limited to portions of the structure in the splash zone. normally employed to interpret the results of the inspection, When water with dissolved salts splashes onto a structure, evaluate the severity of the defects, and make the appropriate some of it migrates into the concrete through cracks, surface condition assessment. Preferably, this person will be present voids, pores, and capillaries. As the concrete dries, the salt during the inspection to direct the efforts of the divers or solution is concentrated, and, eventually, crystals form. direct the use of video equipment. When the salt then changes to a higher hydrate form, internal 4.1.1 Planning the investigation—Once the scope of the pressure results and the concrete disintegrates just beneath investigation has been defined, the client and the inspection the surface. team plan the mission. The purpose of the pre-inspection meeting is to help identify the equipment, the inspection 3.8—Scour techniques, and the type of documentation required. Scour occurs when water currents undermine the support Planning usually begins with a thorough review of the of concrete structures. Correcting scour damage usually original design and construction drawings, and a review of involves repairs to earth- or rock-supporting concrete founda- the previous inspections and repairs, if any. The team should tions rather than repairs to concrete. Therefore, repair of scour plan to conduct the investigation during optimum weather damage is not included in this guide. conditions to minimize hazardous conditions and the effects of reduced visibility. CHAPTER 4—INVESTIGATION AND EVALUATION 4.1.2 Recording inspection notes—Inspection notes typically 4.1—Introduction consist of a dive log with notations of specific features. Structural investigations of underwater facilities are These notes may be transcribed from a slate used by the diver, usually conducted as part of a routine preventive maintenance or from a work sheet filled out by topside personnel when voice program, an initial construction inspection, a special exami- communication is used in the operation. These notes may be nation prompted by an accident or catastrophic event, or a supplemented with sketches, photographs, or video. determination of the required repairs (Busby 1978; Popovics 1986; Sletten et al. 1977). The purpose of the investigation 4.2—Visual inspection usually influences the inspection procedures and testing Visual inspections are the most common underwater equipment used. The investigation and evaluation of investigations. These inspections are usually performed with underwater facilities should be directed by a licensed design a wide variety of simple hand tools. Physical measurement professional. Information on underwater inspection procedures, of a defect may be approximated using visual scaling, hand classifications of inspection types, structure cleaning require- rulers, tape measures, finger sizes or hand spans, body ments, diver qualifications, and other guidance on underwater lengths, and depth gauges. The selection of the tools depends inspections are found in the Underwater Investigation Standard on the accuracy of measurement required. Visual inspections Practice Manual (ASCE 2001). provide the information for the written report, which is Underwater inspections are usually hampered by adverse usually supplemented with photographic documentation, conditions such as poor visibility, strong currents, cold video documentation, or sketches. water, marine growth, and debris buildup. Horizontal and Hand tools, such as scrapers and wire brushes, are often vertical control for accurately locating the deteriorated or used for local cleaning to remove silt and marine growth damaged area is difficult. A diving inspector--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- wears during the inspection. Where large areas require cleaning to

UNDERWATER REPAIR OF CONCRETE 546.2R-9

properly assess their conditions, or where extensive marine and background noise. Soundings are the most elementary of growth is present, more aggressive cleaning systems, as NDT methods. discussed in Section 5.4, may be used. 4.4.2 Ultrasonic pulse velocity—Ultrasonic pulse velocity When SCUBA is used as the primary diving mode, (ASTM C597) is determined by measuring the time of trans- communication with the surface is limited. The typical mission of a pulse of energy through a known distance of SCUBA mouthpiece does not allow the diver to speak. Use concrete. Many factors affect the results, including aggregate of a full face mask in place of the traditional mouthpiece and content and reinforcing steel location. The results obtained are mask, however, can accommodate either hardwire or quantitative; however, they should be used only as an indication wireless communication systems. of the relative quality of concrete within a given structure. When surface-supplied air is used as the primary diving Ultrasonics can be used successfully under water to help mode, the dive team has much more flexibility with the evaluate the condition of concrete structures. Commercially documentation of the inspection. The diver can relay available instruments have been modified for underwater descriptions of the observations directly to the topside team use. Laboratory and field tests of the instruments have and also get direction from the team members on the surface. demonstrated that the modifications had no effect on the Video cameras are either self-contained or umbilically output data (Olson et al. 1994). Both direct and indirect served. The self-contained video camera is a hand-held transmission methods can be used in the field to evaluate the instrument that contains both the video camera and the uniformity of concrete and obtain a general condition rating. recorder, and is operated by the diving inspector. The other A special form of this technique is the pulse-echo method. type of video is served with a supplemental power and The pulse-echo method has been used for the in-place deter- communication cord, and is either attached to an underwater mination of the length and condition of concrete piles. Low- vehicle or held by the diver. The video image is sent along frequency, impact echo-sounding devices have proven the umbilical cord to a monitor and recorder. The surface effective for locating deep delaminations in thick concrete crew directs the diver or the ROV to position the camera. members in the splash zone (Olson 1996). When there is voice communication, the diver can describe 4.4.3 Magnetic reinforcing bar locator—A commercially the details of the defect while directing the camera lens. The available magnetic reinforcing bar locator has been modified diver’s voice may be recorded in real time with the image. for use under water (Fig. 4.1) (Smith et al. 1991). The magnetic reinforcing bar locator can be used to determine 4.3—Tactile inspection the location of reinforcing bars in concrete and either Tactile inspections (inspections by touch) are, perhaps, the measure the depth of concrete cover or determine the size of most difficult underwater inspections to perform, due to the reinforcing bar, if one or the other is known. Techniques conditions of extremely poor visibility. Tactile inspections are available for approximating each variable if neither is are typically performed in heavily silted rivers, settling known. Laboratory and field tests of the instrument ponds, pipelines, or where the element to be inspected is demonstrated that the modification for underwater use had totally or partially buried by silt. The diver merely runs his no effect on the output data. hands along the structural element to find a defect. The defect is usually quantified relative to the size of the 4.4.4 Rebound hammer—A standard rebound hammer inspector’s hand and arm lengths. Once a defect is observed, (ASTM C805/C805M), modified for underwater use, can be the diver should clearly describe the position of the defect so used for rapid surveys of concrete surface hardness (Fig. 4.2). that it may be located and repaired at a future date. Water-saturated concrete produces rebound readings that are approximately five points lower than for the same concrete 4.4—Underwater nondestructive testing of in a dry condition. This may make it difficult to test low- concrete strength concrete (Smith 1986). The use of nondestructive testing (NDT) for the evaluation of 4.4.5 Echosounders—Echosounders (specialty fathometers), concrete structures is described in ACI 228.2R, which can be useful for underwater rehabilitation work using includes details on a variety of NDT methods. Several of tremie concrete, both to delineate the void to be filled and to these methods have been modified to allow their use in confirm the level of the tremie concrete placed (USACE underwater testing. 2002; FHWA 1989). They are also effective in checking The following testing techniques and instruments are among scour depth in a stream bed. They consist of an ultrasonic those applicable to underwater work. Information regarding transducer, which is suspended in the water, a sending/ equipment is available from equipment manufacturers. receiving device, and a recording chart or screen output that 4.4.1 Soundings—Soundings are taken by striking the displays the water depth. High-frequency sound waves concrete surface to locate areas of internal voids or delami- emitted from the transducer travel through the water until nation of the concrete cover as might be caused by the effects they strike the bottom and are reflected back to the trans- of freezing and thawing or corrosion of reinforcement. ducer. The echosounder measures the transit time of these Although the results are only qualitative in nature, the waves and converts it to water depth shown on the display. method is rapid, economical, and enables an expeditious When an echosounder is used close to the structure, determination of the overall condition. The inspector’s however, erroneous returns may occur from the underwater ability to hear sound in water is reduced by waves,--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- currents, structural elements.

546.2R-10 ACI COMMITTEE REPORT

Fig. 4.1—Magnetic reinforcing bar locator. (Figure courtesy of SDS Company.)

Fig. 4.3—Scanning sonar image of a bridge pier. (Figure courtesy of Bradley A. Syler.)

software is used to stitch these slices together to form a contiguous image. The primary benefit of scanning sonar is the ability to produce highly detailed images of the channel bottom and vertical components of submerged structures. Near-photo quality images can be generated for inclusion into inspection reports (Fig. 4.3). The primary limitation of Fig. 4.2—Rebound hammer. (Figure courtesy of the U.S. Navy.) scanning sonar is the inability to quickly and efficiently generate detailed images of large areas of the channel 4.4.6 Side-scan sonar—A side-scan sonar system is bottom. As a result, side-scan sonar is a better solution for similar to the standard bottom-looking echo sounder, except overall channel bottom-mapping or searching for a that the signal from the transducer is directed laterally, submerged object (Syler and Stromberg 2008). producing two side-looking beams (Clausner and Pope 4.4.8 Multi-beam sonar—Multi-beam sonar is essentially 1988). The system consists of a pair of transducers mounted scanning sonar that does not rotate. Scanning sonar consists in an underwater housing, or “fish,” and a dual-channel of one beam that mechanically moves to build an image. recorder connected to the fish by a conductive cable. In the Multi-beam sonar consists of numerous beams side-by-side. past several years, the side-scan technique has been used to Computer software is used to stitch the beam returns map surfaces other than the ocean bottom. Successful trials together to form a real-time contiguous image. Similar to have been conducted on the slopes of ice islands and break- scanning sonar, the primary benefit of multi-beam sonar is waters, and on vertical pier structures. Although the side- the ability to produce highly detailed images of the channel scan sonar technique permits a broad-scale view of the bottom and submerged structures. The real-time images underwater structure, the broad beam and lack of resolution generated by multi-beam sonar can be used to produce near- make it unsuitable for obtaining the kind of data required photo quality videos. Scanning sonar can be used to produce from inspections of concrete structures (USACE 1994; near-photo quality stills. The primary limitation of multi- Garlich and Chrozastowski 1989; Hard Suits, Inc. 1997). beam sonar is range, due to higher operating frequencies. As 4.4.7 Scanning sonar—Scanning sonar is similar to side- a result, side-scan sonar is a better solution for overall scan sonar in that the transducer emits acoustic pulses channel-bottom mapping or searching for submerged

through the water perpendicular to the base; however, unlike objects, and scanning sonar is a better solution for producing --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- side-scan sonar, which requires vessel movement to develop highly detailed still images of large submerged structures an image, the scanning sonar works best when it remains (Syler and Stromberg 2008). stationary. The acoustic images, which are representative of 4.4.9 Radar—Certain types of radar have been used to the echoed (backscattered) target intensity within the evaluate the condition of concrete up to 30 in. (800 mm) geometric coverage of the beam, are recorded in a series of thick. Radar has been used successfully as an underwater slices generated by the rotation of the transducer. Computer inspection tool, and is being developed for possible future

UNDERWATER REPAIR OF CONCRETE 546.2R-11

use. Radar with the antenna contained in a custom water- 4.5.3 Sampling considerations for cores used in petro- proof housing was used in 1994 in conjunction with pulse graphic, spectrographic, and chemical analysis—When velocity testing to investigate the structural integrity in a samples are used to detect changes in the chemical composition concrete plug submerged 150 ft (46 m) in a water supply or microstructure of the concrete, they are usually rinsed tunnel (Garlich 1995). with distilled water after they reach the surface, then dried, 4.4.10 Underwater acoustic profilers—Because of known then wrapped in a towel wetted with distilled water and prior developmental work on an experimental acoustic sealed in containers. Cores should not be allowed to dry system, acoustic profiling has been considered for mapping preferentially before testing and any surface growth should underwater structures. Erosion and down faulting of be retained. If a core sample is of adequate size, the exterior submerged structures have always been difficult to accurately portions of the sample, which may have been contaminated map using standard acoustic (sonic) surveys because of with seawater during the sampling operation, are removed limitations of the various systems. Sonic surveys, side-scan and the interior sections are sent to the laboratory for petro- sonar, and other underwater mapping tools are designed graphic examination. If chloride content measures are primarily to see targets rising above the plane of the sea floor. needed, the exposed end surface of the sample is not In 1978, the USACE, in conjunction with a private removed because it represents the degree of contamination in contractor, investigated a high-resolution acoustic mapping the original concrete. Cuttings and powder from concrete system for use on a river lock evaluation (Thornton and Alex- coring also can be analyzed, although recognition should be ander 1987). The first known attempt to develop an acoustic given to the fact that the material may have been contami- system suitable for mapping the surface contours of stilling nated by surface deposits (Dolar-Mantuani 1983). basins, lock chamber floors, and other underwater structures, 4.5.4 Sampling considerations for cores for testing to this system is similar to commercial depth sounders or echo ASTM C42/C42M—After arriving at the surface, each sounders, but has a greater degree of accuracy. The floor slabs sample should be wrapped in a wet towel and placed in a of the main and auxiliary lock chambers were profiled, and sealed container. Upon arrival at the lab, cores should remain defects previously located by divers were detected. Features in a wet condition until testing. Cores should not be placed of the stilling basin, such as the concrete sill, the downstream in lime water. diffusion baffles, and some abrasion-erosion holes, were mapped and profiled. The accuracy of the system appeared to 4.6—Evaluation be adequate for defining bottom features in the field. As with any structural inspection, evaluation of the inspection The system contains an acoustic subsystem, a positioning results is perhaps the most difficult task. The skill of the subsystem, and a compute-and-record subsystem. The diver as an inspector is essential for the evaluation process to system’s capabilities allow it to “see” objects rising above be meaningful. It is the diver’s responsibility to qualify and the plane of the bottom, extract data from narrow depressions quantify the condition of each defect. and areas close to vertical surfaces, provide continuous real- During this phase of the investigation, the design professional time data on the condition of the bottom surface, and record should decide if the observed defects are structural or and store all data. nonstructural. A structural defect causes a reduction in the load-carrying capacity of the member or structure. A 4.5—Sampling and destructive testing nonstructural defect may affect appearance, adversely affect In some cases, visual or nondestructive inspections do not a structure’s function (for example, a leaking joint in a water adequately indicate the internal condition of a structure. tank), or reduce durability. In addition, to help decide the Collecting concrete samples may be necessary. actions required to ensure continued service of the facility, the 4.5.1 Cores—Concrete cores are the most common type of design professional also judges whether the defect will continue samples. Conventional electric core drilling equipment is not to degrade the structure or when the problem has stabilized. --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- readily adaptable for underwater use. Conventional core 4.6.1 Deciding what actions to take—Deciding on the appro- drilling frames, however, have been modified for underwater priate action to take after a defect has been discovered and use by replacing electric power with hydraulic or pneumatic evaluated depends on the potential hazard of the defect, the risk power. Drill base plates are usually bolted to the structure. of continued structural deterioration, the technology Rather than have the operator apply thrust to the bit, as is the available to repair the defect, the cost associated with the usual case in above-water operation, pressure-regulated needed repair and the intended remaining life of the structure. rams or mechanical levers are used to apply this force. When the defect presents a hazard that threatens either the Core holes should be repaired after the core specimen is life safety of individuals working on or near the facility, or removed. the continued operation of the facility, remedial action 4.5.2 Other sampling techniques—Pneumatic- or hydraulic- should be taken immediately. A critical structural condition powered saws and impact breakers also can be used to take is generally repaired promptly. concrete samples from underwater structures. Samples of The logistics of a repair problem often dictate at least part reinforcing bar are usually taken by cutting the bar with a of the solution. For example, repair of a pier may be relatively torch, although a pneumatic- or hydraulic-powered saw with straightforward, but the repair of similar defects on an an abrasive or diamond blade can be used. Some high- offshore arctic structure or repair of an outfall for a hydro- pressure water jets can cut concrete and reinforcing steel. electric structure can be much more difficult.

546.2R-12 ACI COMMITTEE REPORT

When the defect does not threaten life safety or the immediate The working depth of the equipment is limited by excavator operation of a facility, the owner or operator of an under- arm length and crane cable length. Cameras and acoustic water structure has more options. A minor defect is often positioning systems have been used to a limited extent to merely monitored for continued deterioration. When none is monitor hydraulic excavators, although in most cases the noted, further action may not be required. Defects that have operator works by “feel,” along with boom markings and affected, or will potentially affect, the structural integrity and buoys. This equipment is best suited for rough excavation work. durability of the structure, should be repaired to prevent further 5.2.2 Airlifting—The airlift operates on the principle of deterioration, to restore the structural integrity, or both. differential density. Air is introduced at the lower end of a partly submerged pipe. The resulting air/water mixture is CHAPTER 5—PREPARATION FOR REPAIR less dense than the surrounding water and rises. As it does so, 5.1—General it creates a suction that transports material up with it from the The intent of preparation for repair is similar for under- lower end of the pipe. Airlifts consist of a discharge pipe, water and above-water repairs. Additional information on typically 3 to 12 in. (75 to 300 mm) in diameter, an air preparation of concrete and reinforcing steel for repairs is chamber where the air enters, and an air compressor, located provided in the ACI 546R. above water. Airlifts shorter than 30 ft (9 m) are inefficient. • Additional sound concrete is removed to provide sufficient Airlifts can be used to remove sediment and debris from gaps to facilitate placement of concrete around exposed water depths of up to approximately 75 ft (25 m). reinforcing bars; Airlifts are diver controlled, allowing accurate material • Exposed concrete and steel surfaces are cleaned; removal. They are best at removing mud, sand, silt, clay, and • Supplemental steel is installed as necessary; and gravel. Excavated material is deposited relatively close to • Concrete anchors are installed to anchor the repair the point of excavation, so some may settle back onto the material to the substrate concrete (when necessary). excavation site. All marine growth, sediment, debris, and deteriorated 5.2.3 Jetting—This technique uses the flow of pressurized concrete should be removed before repair concrete is placed. water pumped from a pump located above water to the jetting This cleaning is essential for good bond to occur between the tool. The pressure of the water jet on the soil breaks up and newly placed concrete and the existing concrete. Various displaces the material. Because the water flow from the jetting cleaning tools and techniques, such as high-pressure water jets, tool creates a force on the diver operating the jetting nozzle, an hydraulic breakers, abrasive jetting equipment, and mechanical oppositely directed reaction force is provided by a balancing jet. scrubbers, have been designed specifically for cleaning and Otherwise, the pressure from the water jet would cause the preparing the surface of submerged portions of underwater operator to be pushed through the water. structures (Keeney 1987). The selection of equipment is deter- Jetting can be used in any water depth. It is good for moving mined by the extent and type of material that is to be removed. local areas of mud, sand, silt, and clay over short distances. The Water jets operated by divers or fixed to self-propelled vehicles technique can create poor visibility for the diver and significant have been effective in most cleaning applications. Tools for turbidity, particularly in higher current areas. removing underwater debris are also available. 5.2.4 Dredging—Diver-controlled dredging equipment is available. One type of equipment consists of a flexible 5.2—Excavation and debris removal suction hose connected to a pump located above water. Excavation and removal of debris may be accomplished Another type uses a water jet connected to a pipe near the by various techniques, used either singly or in combination. intake end. As the water jet, aimed at the discharge end, Common techniques include using conventional excavating enters the pipe, it creates suction at the intake, carrying equipment, airlifting, jetting, and dredging. material off the bottom. Factors to be considered in selecting a method for a given Dredging is good for moving soft or loose mud, sand, silt, situation include type and quantity of material to be removed, or clay. It can operate in all water depths, including shallow water depth, horizontal distance the material should be moved, depths where an airlift is inefficient. vertical distance the material should be lifted, currents, and topside support equipment available. Excavation may create 5.3—Concrete removal turbidity, disturb spawning areas, and cause other potentially General practice is to remove only the concrete necessary adverse environmental conditions. Installation of silt fences, to expose sound concrete. This procedure minimizes the cost turbidity curtains, or other mitigating measures may be of the repair. required. This should be evaluated on a site-specific basis. 5.3.1 High-pressure water jets—High-pressure water jets 5.2.1 Conventional excavation equipment—Hydraulic provide an efficient procedure for removing deteriorated excavators and cranes with clam shell buckets can be used concrete, especially where the concrete’s compressive for excavation--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- and removal of debris below water. It may be strength is less than 3000 psi (20 MPa). Water is supplied by necessary to position them on a barge to access various areas a pump to a nozzle at pressures exceeding 10,000 psi (70 MPa). of a site, resulting in the need for support equipment and When used below water, nozzles should be capable of crews. Hydraulic excavators can be equipped with pneumatic developing an equivalent thrust in the opposite direction of jaws and breakers for demolition and removal of rock or the main nozzle to minimize the force exerted by the diver. concrete. This reduces diver fatigue, provides a safer work environment,

UNDERWATER REPAIR OF CONCRETE 546.2R-13

and lowers concrete removal costs. Standard orifice nozzles impingement angle of 40 to 90 degrees. When operating with are well suited to cutting concrete, but at high pressure, a equipment that has a flow rate of 26 gal./min. (100 L/min.), standard orifice nozzle may cause cavitation bubbles at the cleaning rates of 4 to 7 ft2/min. (0.35 to 0.65 m2/min.) can be surface of the concrete. achieved on fouled concrete surfaces. Ultra-high pressure (UHP) water jet/abrasive systems High-pressure water jets operating at 5000 psi (35 MPa) have been used for concrete cutting and removal below using a fan jet nozzle, can clean previously prepared surfaces water (Hendershot et al. 2002). These systems use a highly that have been contaminated by muddy or silty water. focused UHP water jet (60,000 psi [420 MPa]) that aspirates 5.4.2 Abrasive blasting—Abrasive blasting involves a fine abrasive into the water jet stream. projecting a natural or man-made abrasive by pneumatic 5.3.2 Pneumatic- or hydraulic-powered impact breakers— pressure at the removal surface. It can be used as a final Pneumatic- or hydraulic-powered impact breakers designed surface preparation for areas that have been prepared by for surface repairs are easily modified for underwater use. To pneumatic or hydraulic tools. The procedure will help to absorb the reaction force of the impact breaker, the diver remove any fractured surfaces, and also cleans any sound should be tied off to the structure or another fixed element. surfaces that have been contaminated by muddy or silty waters. Pneumatic- or hydraulic-powered impact breakers on the Abrasive blasting provides an effective and efficient ends of surface-mounted booms with TV cameras provide an method of removing corrosion product from the surfaces of efficient concrete removal system without the need for a the reinforcing steel. This procedure is beneficial to the long- diver when underwater visibility is good. The booms are term performance of the repair operation. commonly mounted to a stable structure to assure the necessary 5.4.3 Mechanical scrubbers—Pneumatic or hydraulic stability and operating safety. The TV camera allows the mechanical scrubbers can remove contamination and marine operator to see and remove the deteriorated concrete. growth. Although these tools can clean surfaces effectively, 5.3.3 Pneumatic- or hydraulic-powered saws—Pneumatic- they are not as efficient as high-pressure water jets or or hydraulic-powered saws designed for surface use can also abrasive blasting for cleaning large areas. be used under water. The necessary force to execute the work can be applied without the use of an external support. When 5.5—Reinforcement preparation this work is carried out in muddy or silty water, a mechanical Removing loose rust is the first step in preparation of guide is employed, allowing the operator to continue even in reinforcement, and can be done with high-pressure water low-visibility conditions. jets or abrasive blasting. The back surfaces are difficult to 5.3.4 Wire saws—Diamond wire saws are composed of clean, especially where the reinforcement is congested; diamond-impregnated beads mounted on a continuous nevertheless, steel bars should be cleaned all around. length of steel wire. The wire is looped around pulleys that When the cross section of the reinforcing steel has been pull the wire saw continuously thorough the material to be reduced, the situation should be evaluated by a licensed cut. Originally developed for marble and granite quarrying, design professional who should determine if additional steel they are effective in cutting concrete above and below water, bars are required. Additional bars should be developed including cutting through reinforcing steel. Cutting of under- beyond the deteriorated sections, either by lap splices, water walls (Kilnbridge Construction Services 2007) and mechanical reinforcing bar couplers, or welding to the pipes (Cutting Edge Services Corp. 2007) are common existing bars. For lap splices, additional lengths of the applications. The wire driving equipment can be mounted existing bars may need to be exposed, which is a costly

--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- above, as well as below, water. procedure in underwater applications. It may be desirable to use smaller bars to reduce lap lengths. A variety of mechanical 5.4—Surface preparation reinforcing bar couplers can be installed under water. The intent of the surface preparation is to remove any Bar chairs or spacers should be used to provide minimum remaining pieces of loose concrete and any contaminants clearances from existing concrete surfaces and formwork. from the exposed concrete and steel surfaces. Welding new bar to existing bar is possible, but is rarely The type of surface preparation and the required procedure done. Because the carbon content or chemical composition varies with the site conditions as well as the specified of the existing and new reinforcing steel may not be known, objectives. It is essential that the repair procedure be carried welding is not recommended without a detailed evaluation. out the same day that the surface preparation has been Reinforcement steel in repair areas, particularly around the completed to minimize further surface contamination, periphery of the repair, can be subject to an increased rate of particularly in muddy or silty waters. corrosion due to the differential chloride concentrations 5.4.1 High-pressure water jet—High-pressure water jets between the new repair material and the existing concrete. can be used to clean exposed concrete and steel surfaces. Techniques to mitigate this effect include installation of Fractured pieces of concrete can also be removed from the embedded passive galvanic anodes on existing reinforcement concrete surface. and the application of zinc silicate coating on new reinforce- Fan jet nozzles on 10,000 psi (70 MPa) high-pressure ment. Zinc silicate can be applied to existing reinforcement water jets are an efficient method of removing marine when conditions allow for drying. growth and fouling. The optimum standoff distance for Stainless steel reinforcing bars may also be used as reinforce- cleaning surfaces is 1/2 to 3 in. (10 to 80 mm), with an ment in repairs. They are more expensive than normal steel

546.2R-14 ACI COMMITTEE REPORT

anchor capacity. Adhesive anchors placed in adhesive-filled holes can be used where control of the hole size is of concern. Pulloff testing using hydraulic jacks are performed to verify anchor capacity.

CHAPTER 6—FORMWORK 6.1—General Forms for underwater repairs are similar to those used for above-water repairs. Rigid, semi-rigid, and flexible forms are used. The forms are anchored to the concrete member using drilled or grouted anchors, clamps, or other methods and sealed with gaskets or caulked to minimize material loss. All forms are used to confine the repair material; rigid and semi-rigid forms may also be integral, permanent components of the repair system. In the latter case, the forms are

Fig. 5.1—Underwater view of hollow rock bolts grouted mechanically attached to the repair system. Information on --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- into existing construction. (Courtesy of Michael J. Garlich.) formwork design are found in ACI 347 and ACI SP-4. bars, but resist corrosion and require less cover. Various grades Rigid forms may be left in place or removed and, possibly, of stainless steel reinforcing bars, including 304 and 316 psi (2.1 reused; semi-rigid and flexible forms are generally left in place. and 2.18 MPa), have been shown to be effective (McGurn When left in place, a form of oxygen and chlorides to the 1998). The use of stainless steel reinforcing in the vicinity of concrete surface may reduce the exposure of the concrete carbon steel bars will not increase the corrosion risk on the surface to oxygen and chloride and can increase the abrasion carbon steel reinforcing (Quin et al. 2006). resistance of the structure. When intended to provide such benefits, the long-term durability of the form should be 5.6—Concrete anchors evaluated. The consequences of potential dislodgement and In many repairs, the formwork or replacement material is environmental concerns, however, should also be considered. anchored to the existing concrete substrate (Fig. 5.1). The selection of a forming system is often based on the Adhesive and mechanical (expansion) anchors are used. desired geometric tolerances of the final repair. Most under- Similar to above-water installations, holes are drilled into the water formwork is rather small or prefabricated into small concrete with hydraulic or pneumatic drills, the holes individual pieces that require only one or two divers to cleaned, and the anchors installed. Materials and procedures secure in place. Coordinating more than two divers and a should be specifically developed for use in underwater hoist operator on the surface is usually difficult. Large forms applications. For example, the pullout strengths of anchors can be cumbersome and difficult to place due to their mass embedded in polyester resin under submerged conditions and the form area exposed to currents. Cleaning existing were as much as 50% less than the strength of similar concrete and reinforcing steel surfaces should be completed anchors installed under dry conditions (Best and McDonald before the forms are installed as further cleaning is not 1990). A two-step anchor installation procedure that uses possible after the forms are in place. When required, rigid, vinylester resin in both bulk and capsule form to displace the semi-rigid, and flexible forms can be designed to accommo- water in a drill hole before anchor insertion and spinning, date a reinforcing cage. Spacers should be used between the eliminated the poor performance (McDonald 1990; USACE form and the structure to correctly position the form. In some 1995). Injection of selected epoxies under submerged instances, the forms are dewatered before placing the repair conditions resulted in poor performance compared to dry material. Proper consolidation of repair materials may be installation, whereas anchors embedded with cementitious difficult with some forming systems. Form cleaning and capsules exhibited excellent performance under submerged release agents may be an environmental concern in areas of conditions (McDonald 1998). Anchors should only be sensitive marine life or public water supply. installed in thoroughly cleaned holes. The forming system is generally selected by the Underwater installation of mechanical anchors in contractor, based on: conformance with manufacturer’s requirements may be 1. Performance; difficult to achieve. The effects of currents on the diver’s 2. Cost; ability to control the drill’s position makes drilling accurately sized holes difficult. This is further complicated by the need 3. Ease of installation; for the diver to provide a restraining force to the drill’s reac- 4. Ability to perform within the construction tolerances; and tion. The quality of the concrete into which the anchor is 5. Chemical compatibility with the repair medium. placed may also be difficult to readily determine. Currents, as Formwork should be designed by a licensed design well as reduced visibility, may hamper confirming that proper professional, usually retained by the contractors. Integral, installation torques have been achieved. permanent, forming systems that are designed to act compositely The designer should consider then potential installation with the final repair require special consideration and should difficulties when selecting an appropriate safety factor for be specified by the licensed design professional.

UNDERWATER REPAIR OF CONCRETE 546.2R-15

6.2—Rigid forms 6.2.1 Definition and description—Rigid forms for underwater repairs are much like traditional forms used for above-water repair. The forms inherently maintain a given shape, making them suitable for molding repairs into a final geometric shape. Some rigid form systems are characterized by a semi-rigid, smooth-surfaced form backed by a series of stiffeners that restrict the deflection of the forming system. Rigid forms normally provide neat and clean outlines for the repairs. Properly designed, rigid forms will perform well within specified construction tolerances. Most rigid forms are prefabricated and lowered into position with appropriate hoist equipment. The forms are often attached to the concrete substrate with concrete anchors (Fig. 6.1). Rigid forms can often be reused, which can be a significant cost-savings for repetitive repair work. Fig. 6.1—Rigid wood/metal panel forms secured to existing Typical form materials include plywood, timber, steel, concrete. (Figure courtesy of Michael J. Garlich.) polymer-based materials, and precast concrete. Rigid wooden forms are relatively lightweight and easy to work pulled completely out of the substrate concrete. Subsequent with under water. When intended for reuse, the wood can be underwater inspections indicated continuing loss of the steel lined with plastic to act as a bond breaker. Precast concrete plate until the stilling basin was dewatered for inspection and forms are designed to remain in place and act compositely repair in 1987. At that time, approximately 90% of the steel with the repair material; the forms are rather heavy, possibly plate was missing. Failure of the steel plates was primarily restricting their deployment into final position. Fiberglass or attributed to underestimating the magnitude of the vibration and polymer forms may be more cost-effective for certain appli- uplift forces. Panel design should account for the maximum cations. Plywood or steel forms are frequently used for flat local uplift pressures, as opposed to average uplift. Anchor rods surfaces, such as wall repairs. should be detailed such that nuts do not protrude above the 6.2.2 Typical applications—Rigid forms are most plates, as they are susceptible to being sheared off by rocks or commonly used to form flat surfaces, walls, caissons, debris in the water (Rail and Haynes 1991). seawalls, spillways, and foundations. In addition, they may 6.2.2.2 Precast concrete forms—A precast concrete be used to form columns and piles. Rigid forms can also be stay-in-place forming system for lock-wall rehabilitation fabricated in many geometric shapes. Prefabricated steel, was developed by the U.S. Army Corps of Engineers Water- precast concrete, and composite steel-concrete panels can be ways Experiment Station (ABAM 1987a,b, 1989; McDonald used for repair of stilling basins (Rail and Haynes 1991). 1988). A number of navigation locks have been successfully Each material has inherent advantages, and several factors, rehabilitated using precast concrete forms (McDonald and including abrasion resistance, uplift, anchors, joints, and Curtis 1995). weight, should be considered when designing panels for a In addition to resurfacing lock chambers, precast concrete specific project. form panels were used for overlaying the back side of the river 6.2.2.1 Prefabricated steel plates—Design details for wall at the Troy Lock in Troy, NY (Fig. 6.2) (Petronis and Ellin- prefabricated steel plates should ensure that the steel panels wood 1993). The original plan for repair of this mass concrete remain serviceable under uplift forces from the high velocity gravity wall included construction of a cofferdam, dewatering, flow and avoid water infiltration between the steel panel and extensive removal of deteriorated concrete, and replacement the repair concrete surfaces. with shotcrete. Application of the precast concrete stay-in- Prefabricated modules of steel plate anchored to the top of place form system eliminated the need for a cofferdam and the end sill and to the floor slab directly behind the down- minimized the need for concrete removal. stream row of baffles were used as formwork in the repair of Three rows of precast concrete panels were used to form the stilling basin at the Old River Control Structure in Louisiana. the overlay. The bottom row of panels was partially Thirty modules, 24 ft (7.3 m) long and varying in width from submerged during formwork installation and infill concrete 3 to 22 ft (0.9 to 6.7 m) were fabricated from 1/2 in. (13 mm) placement (Miles 1993). An anti-washout admixture thick steel plate and installed underwater (McDonald 1980). allowed the infill concrete to be placed under water without Vertical diaphragm plates were welded to the horizontal a tremie seal having to be maintained. The application of plates, both to stiffen the plates and to provide formed voids in precast concrete forms resulted in significant cost-savings,

--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- which to place the fiber-reinforced infill grout. compared to the original cofferdam plan. Also, the durability An underwater inspection conducted 8 months after the and appearance of the precast concrete should be superior to repairs showed that seven of the 30 form modules had lost shotcrete, which has a generally poor performance for lock portions of their steel plate ranging from 20 to 100% of the wall repairs. Spalling at the downstream edge of draft tube surface area. A number of anchor bolts had fractured either portals at the Gavins Point Dam near Yankton, SD, was flush with the plate or flush with the grout surface, or had repaired using precast concrete stay-in-place forms installed

546.2R-16 ACI COMMITTEE REPORT

Fig. 6.3—Schematic showing “wet” pile repair. (Figure courtesy of I. Leon Glassgold.)

6.3—Semi-rigid forms 6.3.1. Description and materials—Similar to rigid forms, Fig. 6.2—River wall repaired at the Troy Lock in Troy, NY. semi-rigid forms inherently maintain a given shape, making Note that the lower tier of formwork is partially submerged. them suitable for molding repairs into a final geometric (Figure courtesy of J. McDonald.) shape. Semi-rigid forms differ from rigid forms in that they are flexible enough to be wrapped around an existing struc- and anchored under water, and with preplaced-aggregate ture (such as pile), yet are rigid enough to retain their shape concrete (Harris et al. 1991). This approach enabled engineers during placement of the repair material. to provide a durable and cost-effective repair with minimal Semi-rigid forms are typically used to form cylindrical impact on project operations. shapes such as jackets around piles and columns. Thin- 6.2.2.3 Underwater rigid forms for piles—Rigid forms walled steel pipe, waterproofed cardboard, fiberglass, high-

for pile--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- repairs are generally prefabricated in two mated density polyethylene (HDPE), polyvinyl chloride (PVC), halves. A form support bracket consisting of a friction collar and acrylonitrile-butadiene-styrene (ABS) plastics are that is set on the pile, and a base plate (usually plywood) is frequently used to form cylindrical shapes. These materials secured onto the collar (Fig. 6.3). When reinforcement is do not require stiffeners and may be designed as thin-shell, included in the repair, it is normally set down on the base free-standing units. Semi-rigid forms can also be used as plate using the appropriate chairs to keep it off the bottom of bottom forms for flatwork and as general formwork for the form. Spacers are installed on the reinforcing cage to set irregularly-shaped structures. Fiberglass and PVC and ABS the clear cover to the form. The two halves of the pile form plastics can be preshaped in the factory to nearly any are lowered into position individually, aligned, and fastened geometric design and to accommodate steel reinforcement, together. Normally, each half is positioned and secured by when necessary. one diver, who either coordinates the form lift with a crane 6.3.2 Typical applications—Semi-rigid forms for pile operator, or maneuvers the form by himself, sometimes using repairs are generally prefabricated in one piece. Forms are air bags to aid in the lifting. The concrete repair material available in various sizes, and fabricated sections may be (grout, concrete, or epoxy mortar) is then pumped into the spliced together to extend the overall length. The form is form. After the repair has been completed, the form and friction wrapped loosely around the pile above the water line where collar are generally removed. Some applications allow these overhead clearance permits, and the diver then pulls the form elements to be left in place. Figure 6.4 shows an example of an into position. The form is then tightened around the structure, underwater repair using rigid forms and a portable cofferdam, the vertical seam is locked, and the form is firmly attached to where shotcrete is used above the waterline. the structure.

UNDERWATER REPAIR OF CONCRETE 546.2R-17

Fig. 6.4—Schematic showing “dry” pile repair. (Figure courtesy of I. Leon Glassgold.)

6.4—Flexible forms 6.4.1 Description—Flexible forming systems lack bending stiffness and resist internal material pressures through membrane tension. Examples of these types of systems include fabric pile jacketing forms, membrane plastics, and fabric bags (Fig. 6.5 and 6.6). Flexible forms are fabricated from a multitude of materials, including burlap, membrane plastic, and synthetic fiber fabric. 6.4.2 Materials—Commercially available flexible forming systems come in a wide variety of materials, including burlap, membrane plastic, and synthetic fiber fabric. The physical Fig. 6.5—Underwater view of fabric form repair. (Figure properties of these materials may restrict their usage in certain courtesy of Michael J. Garlich.) applications. The tensile strength of typical fabrics is 200 to 400 psi (1.4 to 2.8 MPa) (Lamberton 1989). It is not uncommon for the form material to stretch as much as 10% under loads equal to 50% of the tensile breaking load. Therefore, allowance should be made either for the form to stretch during pumping operations (and the required volume of repair material increased), or this stretching should be restricted by installing external supports, such as hoops. Some commercially available forms have fabric mesh that allows cement paste particles to escape through the form. This can increase the w/cm near the formed surface and, hence, reduce the strength and increase the outside surface permeability of the repair. In addition, the release of the alkaline cement paste through the fabric weave into the free water may be an environmental concern in localities that support fish, mollusk, and crustacean populations. Fabric form materials that allow water to pass through the weave without allowing significant amounts of cement grains to pass are Fig. 6.6—Fabric form repair on timber pile. (Figure courtesy available. These materials reduce the disadvantages of loss of Michael J. Garlich.) of cement paste and may be required by environmental agencies. Impermeable membrane plastics usually fill may or may not be reinforced. For wall repairs, the completely contain the cement particles. finished shape is generally uneven or corrugated in appearance. 6.4.3 Typical applications—Applications for most flexible For groin and breakwater repairs, the finished product is forms include the repair of piles, although these forming typically a mass with only a generally definable shape. materials can be used for new construction of flat surfaces 6.4.4 Advantages—Flexible forms offer many advantages, such as walls or mass-concrete elements such as groins. For including low initial cost, low weight, and ease and speed of pile repairs, the final product is typically an approximately installation. Most flexible forms are factory manufactured cylindrical shape that surrounds the pile and extends for and field adjustable to meet the job requirements. Formed

several feet (meters) above and below the damaged area. The fabric jackets with--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- a zipper on one face are sometimes used

546.2R-18 ACI COMMITTEE REPORT

Fig. 6.8—Flexible fabric form with removable stiffening grid. (Figure courtesy of Barry McGill.)

zippers and seams on these forms) have ruptured during the filling process due to excessive pressure in the repair material. In some instances, it may be necessary to restrict the rate of placement of the repair material. The surfaces of flexible-formed concrete are generally Fig. 6.7—Laterally deformed pile repair with flexible form. irregular in appearance. Because fabrics or membranes offer (Figure courtesy of Michael J. Garlich.) no bending strength, formed surfaces are curved, although some flexible forms have been used for semi-flatwork appli- in pile repairs. One diver usually deploys and erects a fabric cations. When a truly flat surface is desired, rigid forms form without the assistance of surface-based lifting equipment. should be used. Because the fabric form adheres to the surface of the repair 6.4.6 Installation procedures—For pile repairs, the material, the toughness of the fabric provides some supple- majority of flexible forms are shop prefabricated to the mental abrasion resistance. However, prolonged exposure to required length of the repair. The form jacket is then field ultraviolet light, abrasion, or impact may cause the form modified as required and deployed by a diver to the repair material to decompose or delaminate from the repair surface. zone. The diver completes the cylindrical shape by zipping Hence, the surface will take on a ragged appearance with up the bag. The form typically extends several feet (meters) pieces of the form material dangling from the repair medium. above and below the damaged area. The top and bottom of When the fabric form is allowed to rest on the free surface the jacket are then secured to the pile, often with wire or of the repair material placement, the material/water interface large hose clamps. The repair material is then injected into is partially protected from dilution. This helps reduce the the bag using one of several techniques, such as pumping laitance characteristic of typical tremie concrete. concrete from the bottom, pumping from a hose located 6.4.5 Disadvantages—Fabric forms are difficult to maintain inside of the repair cavity while slowly withdrawing the in a proper alignment, and once filled with repair material, hose, or using preplaced aggregates (Thaesler et al. 2005). In they are very difficult to manipulate. Unless care is taken, the most cases, a diver monitors the filling operation and may try form and repair material may shift to one side, resulting in an to maintain the fabric form shape. asymmetric repair and, possibly, insufficient cover over the For wall repairs, the flexible forms require a supplemental reinforcement on the thin side (Fig. 6.7). Shifting can be support system. The support system may consist of timber or exacerbated by uneven material placement (concrete rising steel wales, ribs formed by reinforcing mesh that are, in turn, more rapidly on one side of a pile jacket), or placement of supported by wales, or even supplemental piles driven near nonvertical repairs, such as batter piles where the repair the repair zone. On one project, 2 in. (50 mm) diameter steel material displaces the form to the underside of the pile. It pipes driven vertically into the river bottom were used as might be possible to mitigate these problems by using added support for fabric used to form a bridge pier repair. closely-spaced standoffs; however, because flexible forms The external supports are usually removed after the repair have no inherent ability to maintain a given shape, they are has been completed. not particularly well-suited for the use of standoffs or chairs Some mass concrete placements are constructed with indi- to maintain clear cover. Temporary supplemental stiffening vidual fabric bags or flexible fabric mattresses that encapsulate systems can also be used (Fig. 6.8). Symmetric placement of an entire element. Mass placements are seldom reinforced. the repair material can help to minimize lateral distortions. After the element has been cleaned and prepared for repair, The overall weight of the repair material may pose problems a flexible form is placed around the feature and secured into and should be carefully considered. Some fabric forms (or position. The repair material is then injected into the form --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114, User=wer, weqwe No reproduction or networking permitted without license from IHS Not for Resale, 01/26/2015 02:07:17 MST Daneshlink.com daneshlink.com

UNDERWATER REPAIR OF CONCRETE 546.2R-19

until the desired shape has been achieved. Pieces of reinforcing Table 7.1—Intake velocity cap concrete proportions steel can be placed through adjacent fabric forms to tie the Constituent Quantity mass concrete together. Some leakage of the repair material Cement [C], lb/yd3 (kg/m3) 600 (354) is commonly observed when this technique is used. Fly ash [FA], lb/yd3 (kg/m3) 90 (53.10) CHAPTER 7—MATERIALS AND METHODS Silica fume [SF], lb/yd3 (kg/m3) 43 7.1—General considerations Water/[C+FA+SF]* 0.40 The design objective of the repair largely dictates the type of Fine aggregate, lb/yd3 (kg/m3) 1467 (870.90) repair used on a project. For a minor spall or crack, a simple 3 3 1550 (920.10) surface patch or crack-injection system may be adequate to Coarse aggregate, lb/yd (kg/m ) provide protection to the reinforcing steel. For major damage Anti-washout admixture, gal./yd3 (L/m3) 0.60 (3.58) where the load-carrying capacity of the element is High-range water-reducing admixture, gal./yd3 (L/m3) 1.90 (11.34) compromised, the repair may either re-establish the strength Slump, in. (mm) 10 (254) of the original element, or perhaps even establish a new load 24-hour strength, psi (MPa) 1960 (13.50) path around the damaged area. The severity of the damage *Water-cementitious material ratio (w/cm). often determines the type of surface preparation, forming system, reinforcement arrangement, and repair medium used for the repairs. ACI 546R contains considerable information Development of these admixtures was initially concentrated on repair design that is applicable to underwater repair. in northern Europe, but has spread to Japan and the U.S. Underwater repair materials include portland cement and (Straube 1982). The admixtures contain some or all of the other hydraulic-cement concretes and grouts, as well as a following ingredients: high-molecular-weight polymers, variety of polymer grouts, adhesives, and mortars. Epoxy HRWRAs, cellulose derivatives, and gums. When added to systems are used for patching, grouting, and crack repair. fresh concrete, the AWAs improve the flow and cohesion They are also used to bond such items as anchor bolts, characteristics of the concrete. reinforcing steel, and protective safety devices to underwater The USACE has developed a test method (CRD-C61) to concrete. Underwater-curable epoxy coatings are used to measure the amount of cement paste that washes out of a sample provide protection to concrete and other construction materials of confined, freshly mixed concrete upon contact with water, as from erosion and aggressive waters. Due to the generally well as a specification (CRD-C661) for AWAs. severe environment for underwater repairs, materials should Anti-washout admixtures are often included in concrete be selected to provide desirable durability and ease of placement mixtures proportioned for underwater placement (Maage (Thaesler et al. 2005). Fly ash and silica fume are often used 1984; Underwater Concrete 1983b). The concrete also may to reduce repair concrete permeability and provide improved contain abrasion-resistant materials, silica fume (Makk and resistance to sulfate attack or chloride intrusion in seawater. Tjugum 1985), or other admixtures (Maage 1984; Under- Repairs to concrete damaged by abrasion-erosion, such as water Concrete 1983b). To achieve maximum benefit from can occur in hydraulic structures, should be proportioned for AWAs, an HRWRA should be included in the mixture (Yao --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- improved abrasion-erosion resistance. Mixtures are often and Gerwick 2004a). An example of a mixture proportion proportioned with silica fume and high-range water-reducing using an AWA for the rehabilitation of an intake velocity cap admixtures (HRWRAs) to improve abrasion resistance by is shown in Table 7.1 (Hasan et al. 1993). attaining high compressive strengths. The use of hard, coarse Typical dosage rates for AWAs are 0.5 to 1.5% by mass of aggregate such as basalt, chert, trap rock, granite, quartz, or cementitious materials for powdered AWAs and 0.05 to diorite can also improve abrasion-erosion resistance (Khayat 0.15 gal. (0.019 to 0.057 L) per 100 lb (45 kg) of cementitious 1991). Guidance on specifying and proportioning durable material for liquid form admixtures (Makk and Tjugum concrete are found in ACI 201.2R. ACI 546.3R provides 1985). Refer to Yao and Gerwick (2004b), Khayat and guidance on material selection for repairs, including various Assad (2003), and Khayat (1995, 1996) for information on polymer materials. mixture proportioning and the effects of AWA on the properties While placement of repair materials under water may be of fresh and hardened concrete. Concrete made with AWA is similar to that above water with some modification, such as often tacky, sensitive to slight changes in the w/cm and deposition by pump line, other techniques have been certain other admixtures (Gerwick 1988), and sticky and developed specifically for underwater placement, such as the difficult to remove from equipment (Maage 1984). tremie technique. Because of diver, material, and equipment Concretes containing AWAs are typically very rich in limitations, all repairs should be planned carefully. In some cementitious materials, and the potential to create thermal cases, construction of dry land mockups is advisable. stress problems in large placements should be evaluated. Long setting times associated with some AWAs should be 7.2—Anti-washout admixtures considered in planning the concrete placement. Refer to Yao Anti-washout admixtures (AWAs) are chemical admixtures and Gerwick (2004a), Bury et al. (2001), Hasan et al. (1993), that bind up the free water in the concrete mixture and reduce Khayat (1991), and Neeley and Wickensham (1989) for the loss of the fine materials into the water during under- additional information on the behavior of concrete with water concrete placement. AWA under various field conditions and temperatures.

546.2R-20 ACI COMMITTEE REPORT

Concretes containing AWAs also can be placed under enlarged to increase capacity to accommodate heavier deck water by tremie, pump, or slipform (Saucier and Neeley loads, or to resist masses of floating ice or the impact of 1987; Kepler 1990). The highest quality underwater concrete runaway river traffic. The method also has been widely placement can be achieved when the concrete contains a applied to the repair of piers supporting control gates on moderate dosage of AWA and is placed by either tremie or spillways and hydroelectric outlet structures that have pump (Underwater Concrete 1983a; Kajima Corp. 1985) suffered damage from ice abrasion or freezing and thawing. directly to the point of placement. Concrete containing anti- Preplaced-aggregate concrete was also used for underwater washout admixtures has been successfully placed by tremie repair of erosion damage in the stilling basin at Chief Joseph and by pump in numerous applications in the U.S., Europe, Dam (McDonald 1980). and Japan. These applications have been in new construction 7.3.4 Selection considerations—The quality of preplaced- and in repair of existing concrete structures. The USACE has aggregate concrete is not significantly reduced by placement conducted extensive research into repair applications using under water. The grout displaces the water in the voids of the concretes containing AWA and placed by tremie and pump aggregate with minimal intermixing. Preparation of the (Neeley 1988; Neeley et al. 1990; Khayat 1991; Yao et al. repair area, setting forms and aggregate, and grout placement 1999). The concrete can be proportioned to be self-consoli- can be performed by divers. This eliminates the costs for dating and to flow around reinforcing steel and other objects. The increased cohesiveness imparted by the AWA makes the cofferdams. concrete pumpable. These concretes can also be placed in In water that is polluted by organic materials, the prepared areas surrounded by slowly flowing water. Anti-washout concrete surface and coarse aggregate resting in the forms admixtures in combination with certain water-reducing and may become contaminated if placement is delayed more than air-entraining admixtures should be checked for compatibility. a few days. The type and extent of contaminants in the water, Any potentially troublesome problems with the fresh as well as their effects on the concrete repairs, should be concrete can be detected in trial batches before the actual determined through water sampling and testing. Water placement. containing clay or other settleable fines may need to be excluded from the forms, either by using tight formwork or 7.3—Preplaced-aggregate concrete by flooding them with clean water to prevent inflow. In 7.3.1 Definition and description—Preplaced-aggregate Japan, algae have been limited successfully by treating the concrete is defined in ACI Concrete Terminology as water with inhibitors and placing a cover over the top of open --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- “Concrete produced by placing coarse aggregate in a form forms to shut out sunlight. and later injecting a portland cement-sand grout, usually 7.3.5 Installation procedures—All damaged or weakened with admixtures, to fill the voids between the coarse aggregate concrete is first removed to a predetermined depth or to particles.” Preplaced-aggregate concrete is suitable for sound material, whichever is greater. Where reinforcement underwater repair and modifications of concrete structures is corroded, loose rust is removed or the bars are replaced or as described in this section. Detailed material requirements supplemented as the situation requires. The time required to and procedures on proportioning, mixing, handling, and place aggregate and forms will almost always exceed a placing concrete, along with references, are given in ACI bonding agent’s working time. The installation pressure on 304R and ACI 304.2R. the grout and flowing action over the substrate results in a 7.3.2 Materials—The physical properties of preplaced- good bond between the repair and substrate. In addition, the aggregate concrete are essentially the same as convention- effectiveness of below-water bonding agents is questionable. ally mixed and placed concrete with respect to strength, Forms are placed and carefully sealed at joints and at points modulus of elasticity, and thermal characteristics. The of contact with concrete surfaces. Coarse aggregate is placed permeability of preplaced-aggregate concrete can be significantly reduced when fly ash or silica fume is added to into the formed areas, usually in 2 to 4 ft (0.6 to 1.2 m) lifts the grout. Of particular interest in connection with under- as the forms are set. Placing aggregate from above the form water repairs is the fact that the quality and properties of may result in the larger aggregate falling to the bottom and preplaced-aggregate concrete are not affected by whether it the smaller aggregate segregating to the top. Finally, the is placed above or below water. The bond between grout is pumped into the preplaced aggregate, starting at the preplaced-aggregate concrete and a roughened existing lowest point(s), either through the forms or through concrete surface has been reported to be excellent, and where preplaced vertical pipes, as described in ACI 304R. When drying shrinkage can occur, as in repairs that extend some the forms are full, it is good practice to spill a small portion distance above water, it is reduced to approximately half that of grout over the top of the form if it is open, or through vent of conventional concrete (USACE 1992). holes or a venting section at the top of the form, to ensure 7.3.3 Typical applications—Preplaced-aggregate concrete that any trapped water, air, or diluted grout is expelled. Form has been used extensively for repairing railway (Colle 1992) removal should follow the requirements of the contract and highway bridge piers for many years, particularly for documents. Guidance on form removal is contained in encasing and underpinning piers weakened by such factors ACI 347. Underwater concrete repairs do not require special as weathering, riverbed scour, exposed piling or cribbing, curing, as they are continuously wet; any above-water floating ice, and overloading. In many cases, piers have been portions of the repairs are cured normally.

UNDERWATER REPAIR OF CONCRETE 546.2R-21

7.4—Tremie concrete is held stationary while concrete is cast at a single location, 7.4.1 Definition and description—Tremie concrete is and then relocated. Whenever possible, the bottom of the placed under water using a pipe, commonly referred to as a tremie pipe should be embedded in freshly placed concrete tremie or tremie pipe. Tremie concrete differs from pumped (Neeley et al. 1990; Khayat 1991; Khayat et al. 1993). concrete in that the concrete flows away from the tremie pipe A second limitation is that water flow across the placement by gravity acting on the concrete mass in the tremie and not site should be stopped during the placement until the by pump pressure. concrete has gained enough strength to resist being washed 7.4.2 Materials—Tremie concretes typically have a high out of place. Flow control has been achieved by closing gates cementitious materials content, which results in adequate of structures, building diversion boxes, or placing the compressive strengths for most underwater repair work. concrete under an upper form, such as a heavy steel plate or Concrete proportioned according to accepted guidelines weighted canvas with a hole to accommodate the tremie. for tremie placement generally gives excellent results Where the flow velocity of water across the placement is (Holland 1983). slow and laminar (approximately 3 ft/s [1 m/s]], AWA may Concretes ranging from fine grouts to those with 1-1/2 in. prevent the concrete from being washed out of place. A small (40 mm) aggregates can be placed by tremie. Materials test placement made during the investigation or design phase requirements and mixture proportioning are discussed in of the repair can determine the suitability of AWA for a ACI 304R. particular project. 7.4.3 Typical uses—Tremie concrete has been used in a 7.4.5 Installation procedures—Successful tremie placement variety of applications for underwater repair. At Tarbela depends on keeping the concrete in the tremie separate from Dam, more than 90,000 yd3 (68,800 m3) of tremie concrete the water. Once the placement is started, the mouth of the was placed to repair damage caused by cavitation (Holland tremie should remain embedded in the concrete to prevent 1976). The USACE has used tremie concrete to repair concrete from dropping directly through water and damage to stilling basins at several of its structures becoming dispersed. Tremie placements for repair do not (McDonald 1980). Tremie concrete is probably best suited differ significantly from placements for new underwater for larger-volume repair placements where the tremie does construction. ACI 304R contains recommendations for not need to be relocated frequently, or for deeper placements tremie placement. where pumping is impractical. Tremie methods, however, have successfully been used for small grout placements, 7.5—Pumped concrete and grout such as filling cavities. A large tremie placement approxi- 7.5.1 Definition and description—Pumped concrete is mately 5 ft (1.5 m) thick was used to repair the stilling basin manufactured above water and pumped into place under of the Lower Monumental Dam, while placements ranging water during a repair. This concrete depends upon the pressure from 2 in. (50 mm) to approximately 5 ft (1.5 m) thick were of the pump and sometimes upon gravity flow to reach its used to restore coral reef damage in the Florida Key Marine final position in the repair. Sanctuary (Yao and Gerwick 2004a). Grouts are more fluid than concrete and generally do not 7.4.4 Selection considerations—The tremie method is contain coarse aggregate. Most grouts consist of portland relatively simple if well-established guidelines are followed. cement and sand, and may contain fly ash and silica fume. The equipment used in placing tremie concrete is rugged and Proprietary grouts may contain selected admixtures for simple; therefore, it seldom malfunctions. Nevertheless, the pumping, adhesion, acceleration, dimensional stability, or tremie method still requires proper equipment and experienced other properties. Fluid grouts used to penetrate fissures, personnel. lenses, and small defects are made from very finely ground The major limitation for conventional vertical tremie- cement known as microfine cement. placed concrete is caused by the mechanics of the technique. 7.5.2 Materials—For concrete and grouts proportioned To seal the mouth of the tremie, a mound of concrete is built according to the generally accepted guidelines for pumped up at the beginning of the placement. The mouth of the placement (ACI 304.2R), satisfactory results can be tremie should remain embedded in this mound throughout expected. Concrete containing fibers should not be used as it the placement. The width of the placement is, therefore, does not meet the high fluidity requirements for pumped dictated by the depth of this mound and the slope at which concrete (Khayat 1991). Pumped concretes typically have the concrete flows away from the tremie. Thin overlay place- high ratios of fine-to-coarse aggregate, and cohesiveness ments under water usually cannot be accomplished using a will be improved. Grouts used under water sometimes have vertical tremie pipe. faster setting times to reduce loss due to erosion and wash-out. An inclined tremie pipe has been used successfully for Materials should be selected that are relatively dimensionally placements as thin as several inches (millimeters). Typical stable in both the wet and dry environments to avoid the tremie pipe diameters range between 6 and 10 in. (150 to development of stress at the bond line. When the underlying 250 mm). Tremie pipes placed at a 45-degree angle have materials have been properly cleaned, bond strength to --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- given good results, though the angle should be adjusted hardened concrete has been shown to be satisfactory. based on initial placement results. During placement, the Concrete and grout pumps now available can pump a wide concrete should be supplied without interruptions to assure variety of mixtures comprised of cementitious materials with flow and allow the concrete to spread and self level. The pipe little difficulty. The cementitious mixtures should be

546.2R-22 ACI COMMITTEE REPORT

proportioned with the specifics of the repair in mind and then for new underwater work. Underwater concrete placement reviewed for suitability for underwater pumping. by pumping was used to fill voids in a bridge pier and widen 7.5.3 Typical uses—Pumped concrete is the most common the pier shelf for a bridge in Washington. Open-top rigid method of placing concrete in underwater repairs, including forms were set around and approximately 1 ft (0.3 m) outside those that are formed. It can be used in most applications of the pier. The space between the form and pier was then where tremie concrete is applicable, but has the added filled with concrete using a diver-held pump line. Concrete advantage of having a smaller, more flexible hose that can placement started at the bottom of one corner of the repair reach difficult locations. The USACE has pumped concrete area and progressed up and around until the formwork was under water to repair stilling basins (Neeley and Wicker- full. Water was displaced as cement filled the formwork. sham 1989; Khayat 1991). Other uses include filling voids in Additional guidance can be obtained in ACI 304R. or under structures. Pump placement is often used to fill pile jackets with grout Grouts are most commonly used to fill voids between or small-aggregate concrete (Khayat 1992). Elimination of concrete and forms or jackets, such as in pile repair. They water from the forms and reduction in material dilution is have also been used to repair smaller voids and larger cracks accomplished by a symmetrical placement of material, often in and under concrete structures. using two or more pump lines. Such techniques also minimize 7.5.4 Selection considerations—Pumped cementitious lateral distortions in fabric pile jacket forms. concrete and grout provide repair material with physical properties that are essentially the same as the concrete being 7.6—Free dump through water repaired. 7.6.1 Definition and description—Free dump through Differences in modulus of elasticity and thermal expansion water is the placement of freshly mixed concrete by allowing are negligible for most underwater work. Uncured cementitious it to fall through water without the benefit of confinements materials are less hazardous than uncured epoxies. such as a tremie pipe or pump line. Anti-washout admixtures Cementitious materials are easier to work with and less may or may not be used. This method is applicable to filling trouble-prone than polymers because they are less sensitive eroded pockets in spillways. to temperature variations during mixing, placing, and curing. 7.6.2 Materials—It is recommended that concrete that is They are also less likely than epoxy systems to leak from to be allowed to freefall through water contains AWA. small defects in forms and jackets. Pumping under water eliminates the equipment associated Unless the concrete mixture is proportioned properly and with a tremie placement because the pump delivering the the proper amount of AWA is used in the mixture, significant concrete or grout is also the placement device. The use of a washout and segregation can occur during placement. pump with a boom may facilitate relocating the pump outlet Mixture proportions guidelines proposed by Khayat (1991) site if the repair consists of a series of small placements. include use of cementitious materials contents with approxi- 3 3 As with tremie placements, successful underwater placement mately 850 lb/yd (505 kg/m ), maximum w/cm of 0.35 or less, of concrete by pump requires the proper combination of high concentrations of AWA, and HRWRA. The washout appropriate concrete proportions and equipment, and weight loss should be limited to 1% after 10 test drops in water. personnel trained in underwater concrete placement. The shorter the fall through water, the greater the chance for In the past, some environmental agencies, such as the success. When the freefall is limited to approximately 1 ft National Oceanographic and Atmospheric Agency (NOAA), (0.3 m), the probability for successful application is excellent have expressed concern about the effects of alkalis and (Underwater Concrete 1983a; Kajima Corp. 1985). washed-out cement particles on coral reefs and fish. On one Conflicting evidence exists on the quality of the in-place project in the Florida Keys for the USACE, these concerns concrete when placed by the free-dump method. Neeley et were addressed, at least in part, by using AWA (Concrete al. (1990) reported that concrete without AWA exhibited no Products 1995; McKain and McKain 1996). bond to hardened concrete when allowed to freefall through The same limitations regarding underwater placements in 3 ft (1 m) of water. Similar placement of concrete with AWA thin sections and the requirement to eliminate water flow resulted in a bond strength of 185 psi (1.3 MPa). In comparison, across a placement site that applied for tremie placements AWA concrete placed under water at the point of use by also apply for pumping under water. One problem inherent bottom-dump bucket, pump, and inclined tremie exhibited in pumped concrete is that it is discharged in surges, which bond strengths of 210, 300, and 265 psi (1.4, 2.1, and 1.8 MPa), can result in more cement washout and laitance formation respectively. Other laboratory work has indicated that, once than tremie concrete. These surges can be reduced by using the free-dump concrete is in place and set, its physical accumulators in the pumping system. properties are equal to those of high-quality concrete placed 7.5.5 Installation procedures—Successful placement by conventional tremie or pump (Underwater Concrete under water by pumping depends upon separating the initial 1983a; Kajima Corp 1985). In fact, there is some evidence concrete or grout that is placed at the start of the pumping that strength, bond, and impermeability are actually from the water and maintaining that separation throughout improved, compared with normally placed underwater the placement. The separation should be re-established concrete (Maage 1984; Makk and Tjugum 1985). Another whenever the pump outlet is relocated. Underwater place- problem that can occur with this method is that water may be --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`---ments for repairs do not differ significantly from placements entrapped within the dumped concrete. The freefall height

UNDERWATER REPAIR OF CONCRETE 546.2R-23

should be limited to that required for opening the bucket so as to reduce the velocity of impact. 7.6.3 Typical uses—The free-dump method is used for placing concrete containing AWA under water in new construction and to repair old concrete. 7.6.4 Selection considerations—Freefall concrete has been most successful in shallow water applications, where self- leveling concrete is not required. Research results strongly suggest that freefall concrete is cohesive and not harmful to the environment (Underwater Concrete 1983a; Kajima Corp. 1985). Since the 1970s, the Sibo group in Osnabruck, Germany, has successfully placed thousands of cubic yards (meters) of concrete with an AWA by first spreading the concrete uniformly on pallets on the deck of a special barge, and then dropping the concrete through the water by tilting the pallets (Freese et al. 1978). The primary advantage is, of Fig. 7.1—Semi-rigid fiber-reinforced plastic pile jacket being course, the capability to place quality concrete under water filled with epoxy grout. (Figure courtesy of Fred Goodwin.) without the use of cumbersome tremies and pumps. 7.6.5 Installation procedure—Underwater concretes eliminated. Pumpable epoxy mortars contain a larger quantity containing AWA can be batched and mixed in conventional of silica sand than pourable mortars. They require a pumping concrete plants or concrete trucks (Underwater Concrete system that allows larger particles (sand and, possibly, stone) 1983a; Kajima Corp. 1985). Placement may be by pump or to pass through the pump without causing segregation of the inclined or vertical pipe without the need to maintain a epoxy/aggregate mixture. Epoxy resins, blended with a select tremie seal (Underwater Concrete 1983a; Kajima Corp. gradation of silica sands, silica or quartz flour, or other fillers 1985) or special equipment (Underwater Concrete 1983b; to make a non-sag consistency, can be placed by gloved hand. Freese et al. 1978). The AWA in powder form is prebatched These are used for small-quantity placements between the into the concrete (Makk and Tjugum 1985). The admixture concrete structure and a permanent jacket system. in liquid form is normally added to the concrete after all Epoxy grout is designed to bond to the concrete, eliminating other ingredients have been blended together. a cold joint between the concrete and jacket system. The entire system provides additional reinforcement to the structure. The 7.7—Epoxy grouting damaged area may be repaired with or without the inclusion of 7.7.1 Definition and description—Epoxy grouts are used reinforcing steel. When reinforcement is used, epoxy mortars for splash zone and underwater repairs. The materials typically are intended to encapsulate and protect it. consist of an epoxy resin that is curable under water. The When epoxy resins are used in repair it is intended that resin is used either without aggregate for narrow void these materials become bonded with the concrete structure. grouting, or mixed with specially graded silica sands, and Because the underwater environment creates unique challenges sometimes with larger aggregates, to form an epoxy-polymer for these materials, documented performance history and mortar or concrete for larger voids or placements. testing in accordance with ASTM C881/C881M methods are The epoxy grouting process usually includes the epoxy advised. grout and a jacket, creating a composite system (Fig. 7.1). The epoxy formulations are selected based on the The jackets, concrete, and epoxy grouts have different physical temperature at the time of application and on the anticipated properties. Adhesion of the epoxy grout to the concrete is temperature range during the service life. Epoxy is mixed important to the overall composite design (Thaesler et al. with aggregate or other fillers to form the epoxy grout. The 2005). The jacket system protects the outer surface of the filler extends the epoxy to reduce the overall costs of the concrete structure against abrasion, reduces oxygen flow into polymer grouting repair and reduce heat buildup and to the damaged area, and protects the structure from physical and produce an epoxy concrete that has an elastic modulus (E) chemical attack. and coefficient of thermal expansion (CTE) close to that of Guidelines used for void grouting are typically divided the original concrete. into two categories: a wide void is defined as a space 7.7.3 Typical uses—Plastic jackets and underwater-curable, between the jacket and concrete larger than 3/4 in. (20 mm), epoxy-resin systems are used for the repair of eroded or and a narrow void is defined as a 1/8 to 3/4 in. (3 to 20 mm). structurally damaged splash zone concrete and underwater 7.7.2 Materials—Pourable epoxy grout materials usually concrete structures. Epoxy jacket systems are widely used contain silica sands. The amount of sand is dependent on the for pile repairs, but are also applicable to flat surfaces. epoxy material, void size, and ambient temperatures. 7.7.4 Selection considerations—Using epoxy grouts for These materials may be either poured into place, filling the the repair of splash zones and underwater areas of concrete --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- void between the jacket and the existing concrete, or pumped has several advantages. The jacket system is light and does into place. Placing grouts by pouring should be performed not add significant additional weight to the structure. A carefully if water pockets and bleed channels are to be properly selected, designed, and installed system provides

546.2R-24 ACI COMMITTEE REPORT

long-term protection from sand erosion, wave erosion, wet- 7.7.5 Installation procedures—For jacket-type repairs, the dry cycles, floating debris, marine organisms, freezing and jacket is usually installed immediately after the surface thawing damage, and salt and chemical intrusion. preparations have been completed, including the removal of The jacket repair method is fast and easy to install. loose or broken concrete and rust, and then the epoxy is Manufacturers of jacket systems offer standard sizes and placed. A two-step surface preparation procedure is sometimes shapes. Special shapes and sizes may be available upon used, where the major material preparation is completed and request. The epoxy portion of the system is the most critical then a second cleaning is performed just before jacket in terms of application and cure. Good quality-control standards installation. Jacket placement is often accomplished from for mixing and handling of the epoxy are essential for a above the waterline on a barge or scaffolding. The jacket is successful application. The epoxy grout should be capable of wrapped around the structure and loosely locked so that it being placed by pouring, pumping, or hand packing, and will not reopen in a strong current or waves. The jacket is cured in the presence of fresh, brackish, or salt water at then slipped down the structure into the water, where the temperatures from 38 to 120°F (3 to 50°C) to accommodate diver pulls it into place. By pulling the locking device, the placement in most North American water areas. jacket is secured to the pile. A similar procedure is used for Epoxy grouts possess physical properties much different flat surface forming. than those of the concrete being repaired. The compressive The epoxy should be carefully mixed according to the and tensile strengths of epoxies are typically greater than manufacturer’s directions and with the specified amount of those of the concrete substrate and are not usually a critical sand and coarse aggregate. Most manufacturers recommend issue in repair design. The modulus of elasticity of epoxies is immediate product placement after mixing by pouring or lower than the concrete with which they will act compositely. pumping the material into the jacket cavity and displacing all Due to their low moduli of elasticity, the epoxy will not carry water. Epoxy mortar or concrete should be rodded or a load proportional to their sectional area when acting mono- vibrated during installation to remove air pockets. lithically with a stiffer material such as concrete. Pumpable epoxy mortars are typically placed with a hose or pipe (1 to 1-1/2 in. [25 to 35 mm] diameter), which is The coefficient of thermal expansion is another important inserted between the concrete structure and the permanent physical property of epoxies. Underwater repairs are generally jacket system. The pipe is then slowly removed as the epoxy subjected to lower variations in temperature than above- mortar fills the cavity and displaces the water. The mortar water repairs. Some underwater structures, however, such as may also be placed by pumping through ports in the side of those associated with power plants, may be subjected to the forms or jackets, beginning at the bottom of the place- large variations in temperature. Expected temperature ranges ment. For some installations, multiple ports are used due to should be compared to manufacturer data for acceptable height or lateral extent of the repair. temperature exposure. Epoxy repair materials generally For many of these systems, good performance requires reach higher temperatures when they cure than cementitious bond of the epoxy mortar to both the concrete substrate and mortars and concretes reach. These temperature rises can be jacket. Thus, both the concrete surface and the jacket interior significant when large voids are being filled. Because of this should be well cleaned and properly prepared. Due to the and cost considerations, epoxy repairs are generally limited possibility of contamination from marine organisms, mortar to filling smaller voids or cracks. placement should preferably take place the same day the When the narrow-void jacket system is used in an effort to surfaces are prepared and the forms are set. fill cracks in piles, the cracks are usually not filled, and the Narrow voids are grouted with formulations of neat epoxy internal crack surfaces are not bonded together. In most resin. The material is placed by a positive displacement cases, only the adjacent surface is encapsulated and pump, which mixes and sometimes heats the two-component protected. If the crack extends beyond the jacket coverage resin system. The epoxy resin is pumped into the space area, deterioration will develop or continue, possibly even between the concrete and jacket surfaces until all water is under the jacket area. displaced. Placement should start at the bottom of the jacket Epoxy mortar installation requires workers with more so that the epoxy displaces the water as the jacket is filled. specialized training and equipment than cementitious-based After the jacket is filled, it is capped with a trowellable repairs. Both the uncured resin and solvents that are epoxy mortar, which is beveled at a 45-degree angle upward commonly used are hazardous chemicals that require special from the outer edge of the jacket to the surface of the structure. --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- handling and safety precautions. Epoxy is also more sensitive Experience has shown that, in both freezing and warm environ- than portland-cement-based materials to mixing, application, ments, this technique improves the durability of the protective and curing temperature. For example, epoxy mortars that are system. workable when mixed in warm conditions on the surface could become very stiff when being applied in colder conditions 7.8—Epoxy injection under water. In addition, the shelf life and temperature range 7.8.1 Description and definition—Injection of epoxy during storage are more limited for epoxies. When filling resins into splash zone and underwater cracks and honey- forms with epoxy mortars, care should be taken to minimize combs in concrete structures has been successfully practiced or prevent the material from leaking out of small separations since the 1960s in fresh and salt water environments. The or defects in the forming system. injection process may be accomplished from the interior of

UNDERWATER REPAIR OF CONCRETE 546.2R-25

pipes, tunnels, shafts, dams, floating-precast-box bridges, there is adequate adhesion to the surfaces of the crack and and piers. Piles and backfilled walls should be serviced from when at least 90% of the crack is filled. the water side. The following text will concentrate on the Nonmoving joints can be bonded together with epoxy water-side application methods of repair, even though dry- resins, just like a crack. Anchor bolts and reinforcing steel side applications are very similar. can be grouted into concrete structures in the splash zone and The purpose of crack injection is to restore the integrity under water with the injection process. of the concrete or to seal cracks. Honeycombed areas 7.8.4 Selection considerations—Materials that meet the within the concrete also can be repaired by the injection criteria for ASTM C881/C881M and are verified to exhibit process. The injected epoxies fill the cracks and bond the sufficient bond strength in a wet and saturated condition are crack surfaces together, restoring, at least in part, the excellent initial choices for material selection. Much of the concrete’s original integrity and preventing any further underwater work done in North America is in water with water intrusion into the structure. temperatures at or below 50°F (10°C). The epoxy material The physical properties of concrete repaired with epoxy selected should be tested and verified to cure and bond at the injection are similar to the original concrete. The repair of anticipated ambient temperatures. In addition, the viscosity concrete by epoxy injection will not increase the structure’s of the material needs to be compatible with the selected load-carrying ability above the level of the original design. pumping equipment at the anticipated temperatures to ensure 7.8.2 Materials—Epoxies for resin injection are formulated that the material will be able to penetrate the size of cracks in low viscosity and gel consistencies. The materials are to be repaired. 100% solid and 100% reactive, and have low shrinkage upon Epoxy injected into cracks will act as an electrical insu- curing. The low-viscosity injection resin is used for voids lator, possibly preventing the effective use of cathodic narrower than 1/4 in. (6 mm). An epoxy gel may be used for protection. Epoxies may not provide full bond to contaminated larger voids, from 1/4 to 3/4 in. (7 to 20 mm). The physical crack surfaces, thereby limiting the epoxy’s ability to fully strength properties for both epoxy consistencies are typically seal a crack or transfer forces across the crack. equal. The resin is required to displace water within the 7.8.5 Installation procedure—Several types of epoxy void, adhere to a wet or moist surface, and then cure in that pumping systems are used: (1) positive displacement pumps; environment. (2) pressure pots; or (3) progressive cavity pumps. Type (1) Not all epoxies are capable of bonding cracked concrete pumps mix the epoxy just before entry into the crack, whereas together, especially under water. An underwater concrete crack Types (2) and (3) require mixing the epoxy before pumping. contains materials such as dissolved mineral salts, silt or The exposed concrete surfaces on both sides of the crack clay, and debris from the corroding metal, in addition to are typically cleaned by high-pressure water blasting, abrasive water. All of these materials interfere with good bond develop- blasting, or other mechanical methods. Entry ports are used ment unless they are removed. Ideally, the epoxy injection as inlets to carry the epoxy injection resin into the crack or resin has two main duties: first, it should displace all free void. The entry ports can be attached to the concrete surface water from within the crack or void; second, it should cure and bonded into place with a hydraulic cement or epoxy and adhere to wet concrete and steel reinforcement surfaces. paste. Ports may also be established by drilling into the crack As a result, special epoxy formulations that do not react with and setting an entry port into the drilled hole. The size of the water are required for underwater work. cavity to be injected, concrete thickness, and crack length all A surface sealer is applied over the cracks to prevent determine the proper spacing of the entry ports. Spacing of leakage of the injection resin. Injection ports are set at intervals injection ports should be at least equal to the thickness of the in the seal to allow resin to enter the cracks. The surface cracked member being repaired, or, if the crack depth has been sealer should be capable of adhering to the concrete, set previously determined, then the spacing should be a minimum rapidly at the expected ambient temperatures, and confine of the crack depth. The remainder of the exposed crack is the epoxy injection resin while it is being injected and cured. sealed with fast-setting hydraulic cement or epoxy paste. It is usually of either a hydraulic cement base or a paste The rapid-setting cement formulations for surface sealing consistency epoxy specially formulated to be placed and over cracks may have a working life of 3 to 5 minutes and a bond in the underwater environment. The selection of either set time of an additional 3 to 15 minutes, depending on the a cement or epoxy formula is dependent on water tempera- water temperature. When a cement sealer is used, the crack ture, currents, setting time, and previous work experience of is injected as soon as possible, because the bond strength to the divers or injection technicians. the existing concrete surface may be affected by surface 7.8.3 Typical uses—Limitations of the underwater contaminants. The surface seal can either be left in place or environment such as visibility, currents, temperature, and removed after the injection resin has cured. contaminants on or in the crack limit the size of crack that can The epoxy is injected at the lowest entry port and injection be injected from a practical standpoint. Considering these continues until all air, water, and epoxy mixed with water is limitations, a low-viscosity epoxy may penetrate cracks forced out of the next adjacent port with clear epoxy resin. This 0.015 in. (0.38 mm) and larger; when the crack size is 0.10 in. process is continued until the entire crack length is injected. (2.5 mm) or larger, a gel-consistency epoxy resin may be used. The pressure used for epoxy injection needs to be sufficient Both consistencies of materials are generally considered to displace materials at temperatures and depths anticipated

capable of bonding and repairing a cracked section when and to completely fill the crack. Typical pumping pressures --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`---

546.2R-26 ACI COMMITTEE REPORT

Fig. 7.3—Hand placing underwater patch. (Figure courtesy Fig. 7.2—Stitch bolting. of Michael J. Garlich.)

are from 20 to 150 psi (0.34 to 1.0 MPa) above the ambient surface of a concrete structure to prevent the passage of water pressure. Care should be taken not to use pressures that water into cracks or joints beneath the geomembrane. could rupture the surface seal. Excessively high pressures 7.10.2 Materials—A geomembrane system designed for have been known to damage concrete elements when the use on dams consists of a high-density polyethylene (HDPE) epoxy in the crack has no point of exit. Special care should geonet drainage layer and a PVC geomembrane backed with be given during epoxy injection into laminar cracks where geotextile reinforcement. The geomembrane is anchored to --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- there is little or no reinforcement across the crack. The injection the surface and sealed around the perimeter with stainless pressure should be kept low to prevent hydraulic fracturing steel on bars secured with stainless steel anchors. An open- from widening or extending the crack. Stitch bolts across the cell neoprene gasket is placed between the geomembrane crack are the only positive means of repairing such laminar and concrete and compressed by the stainless steel bars cracks (Fig. 7.2). (Christensen et al.1995; Marcy et al. 1996; McDonald 1997). 7.10.3 Typical uses—Geomembrane systems have been used 7.9—Gloved-hand placement on the upstream faces of dams to greatly reduce leakage through 7.9.1 Description and definition—In locations where the cracks (McDonald 1993). The first underwater application was repair area is small, patching by gloved-hand placement may on the upstream face of Lost Creek Dam, a thin-arch concrete be preferable to other methods (Fig. 7.3). As with other dam in Northern California. An acceptance criterion for leakage repair methods, the surface should be cleaned before placing was 25 gpm. After installation, the rate was 1.2 gpm, and 5 years new material. Repairs made using this method may not be as later had reduced to 0.2 gpm (Onken 1998). durable as with other methods, but the cost may be less. A 5 in. (40 mm) HDPE geomembrane system was used to Hand-placed materials often fail because of poor workman- stop leakage through a 320 ft (97 m) wide paper mill dam in ship. When carefully selected materials are used, along with Michigan. Twenty-five ft (7.5 m) HDPE panels were good surface preparation and material application, satisfactory deployed from rolls on a barge. Adjacent panels were joined repair performance can be achieved. by fusion bonding (Vallance 1999). 7.9.2 Cementitious products—Accelerating admixtures can Localized repair of leaking cracks and joints has been facilitate gloved-hand placement of cementitious mixtures. accomplished on concrete-faced rock fill and concrete gravity Concrete can be modified by hydrophilic, epoxy-resin mixtures dams. Underwater installation to a depth of 312 ft (95 m) on that can be used for hand patching of thin sections. Concrete can the upstream face of Platanovrissi Dam essentially stopped all also be modified with AWAs and dropped through the water to leakage through an existing crack (Wilkes et al. 2003). divers waiting to apply it by gloved hand. Conventional 7.10.4 Selection considerations—Geomembranes are concrete has been placed in plastic bags with twist ties and good alternatives to crack sealing, particularly where extensive dropped to waiting divers. cracking is present. They are also a means for stopping 7.9.3 Epoxy mortar products—Epoxy mortars made with leakage through moving cracks because the membrane fine aggregate have also been applied by gloved hand. These materials are flexible. Installation over rough surfaces may materials are typically mixed on the surface and lowered require surface preparation to achieve a good seal or reduce through the water to the work area below in a covered the possibility of puncture. They can be damaged by impact bucket. Refer to Section 7.7 for further information. from flooding debris or vessel impact. 7.10.5 Installation procedures—Geomembranes are 7.10—Geomembrane systems installed by divers assisted by a topside crew to dispense the 7.10.1 Description and definition—Geomembrane systems membrane materials off of rolls. For large areas, sheets of the consist of an impervious synthetic barrier secured to the PVC geomembrane are joined by fusion bonding. The

UNDERWATER REPAIR OF CONCRETE 546.2R-27

barrier should be securely anchored to the concrete for support and to affect a seal between the geomembrane and concrete. The anchor system developed by the USACE uses a 1/4 in. (6 mm) thick stainless steel flat bar secured with resin grouted stainless steel anchor bolts on 12 in. (300 mm) centers (McDonald 1997). A 1 in. (25 mm) thick open cell neoprene gasket is compressed by the stainless bar. Before anchorage, loose material is removed from the anchoring/ sealing area.

7.11—Cathodic protection 7.11.1 Definition and description—Cathodic protection systems provide a means of mitigating corrosion damage in reinforced concrete structures including the splash zone and underwater portions of marine structures. Cathodic protection involves the passage of DC current from an anode system to the reinforcing steel. Sufficient current needs to be passed to the steel to provide complete corrosion protection. Cathodic protection--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- has particularly been used for pile and bridge pier rehabilitation in salt water environments (Fig 7.4). Additional information on cathodic protection is provided in ACI 222R. 7.11.2 Materials—There are two types of cathodic protection systems: galvanic and impressed current. The materials Fig. 7.4—Pile jacket incorporating cathodic protection. for these systems are different. (Figure courtesy of David Whitmore.) Galvanic cathodic protection systems use sacrificial anodes made of zinc, aluminum, or magnesium, which corrode over time to protect the reinforcing steel. Impressed anodes (metalizing), activated embedded galvanic anodes current systems require an external DC power supply and (distributed and/or discrete anodes), and mixed metal oxide generally use inert anodes, such as titanium. titanium systems in a variety of forms. 7.11.3 Typical uses—Cathodic protection systems are 7.11.4 Selection considerations—Factors to consider used on marine structures to extend the service life and when deciding what type of system to use include: desired prevent corrosion of the reinforcing steel. Cathodic protection service life, extent of concrete repair required, resistivity of can be used on structures that are chloride contaminated and the existing concrete, ability to perform regular maintenance are actively corroding. and monitoring, location of the area to be protected (below To protect the underwater portion of a structure that is in water or in the splash zone), and cost. good condition, galvanic or impressed current anodes may 7.11.5 Installation procedures—Installation procedures be installed in the water. vary depending on the type of system to be installed. To protect areas subject to periodic wetting such as tidal and splash zones, a common approach is to use concrete jackets that contain galvanic or impressed current anodes. 7.12—Fiber-reinforced polymers Examples of this technique include galvanic pile jackets, 7.12.1 Definition and description—Fiber-reinforced which act as the anode and incorporate zinc mesh or activated polymer (FRP) systems used for concrete rehabilitation zinc strip anodes or impressed current jackets. The anodes consist of a fiber-reinforcing material, such as carbon or may be secured to the concrete surface or they may be glass fibers, combined with adhesive resin to form a secured to the inside face of the forming system. For composite material. By controlling the fiber type, volume forming, temporary forms, reusable forms or stay-in-place ratio, and orientation and resin type, FRP systems with forms may be used. The form is installed and secured around specific properties can be developed for a given repair or the section to be jacketed, and the space between the structure strengthening application. and jacket is filled with cement mortar or concrete, as Applications of FRP for underwater concrete repair of required. Reinforcing steel may be included in the jacket if piles have been reported (Sen et al. 2005; Chaallali et al. additional structural capacity is required. In some applications 2006). Additional information is provided in ACI 440R. a supplemental bulk anode may be installed to protect the 7.12.2 Materials—Resins used for underwater applications submerged section of the pile below the jacket (Kessler et al. should be specifically formulated for proper applications, 1998; Leng 2002; Ball and Whitmore 2005). curing, and durability. Epoxy resins are commonly used. To protect atmospherically exposed areas such as pile caps Glass and carbon fibers have been used for underwater and and decks, a variety of cathodic protection systems are splash zone repairs (Chaallali et al. 2006; Mullins et al. available. A partial list of systems that have been used on 2006). Glass material should be E-glass and well covered marine structures would include thermally applied galvanic with resin to preclude deterioration from water absorption.

546.2R-28 ACI COMMITTEE REPORT

7.12.3 Typical uses—Externally bonded FRP systems procedure has unique problems. Guidance for developing an have been used to restore pile strength where damage or inspection program are found in ACI 311.4R. The quality- deterioration has occurred (Mullins et al. 2006), and also for control activities and checklists for above-water inspections seismic strengthening. are applicable to underwater work as well. 7.12.4 Selection considerations—FRP systems can be formulated and designed to provide specific strengthening 8.2—Procedure properties for the repair application. Design guidance is An engineer or independent agency can perform the found in ACI 440.2R. inspections. The use of externally bonded FRP systems to strengthen 8.2.1 Inspection techniques—Most inspections are visual, corrosion-deteriorated piles is not recommended due to the with some use of small hand tools such as hammers or rulers. possibility of concrete cover spalling, rendering the FRP Occasionally, a core sample is taken to verify the adequacy of system ineffective. the repair. For further information regarding specific techniques Where full-encasement FRP systems are used on corrosion- used for the inspections, refer to Chapter 4. deteriorated piles, careful consideration should be given to Video is especially helpful to the owner when the inspection the potential for future reinforcement corrosion of the steel is being performed by a diving agency that does not have reinforcement within the repaired area. ACI Committee 440 specific expertise in construction inspection. An owner’s guidelines caution that the installation of FRP systems does representative may direct the diver and the video from the not stop ongoing corrosion. The removal of an FRP pile surface when communication is available. Video equipment, jacket on the Gandy Bridge in Florida revealed reinforcing however, requires reasonably clear water. corrosion within the jacketed pile (Collins and Garlich 8.2.2 Inspection during construction—Inspections that are 1998). Information of field monitoring of corrosion within performed during construction are normally phased so the FRP pile repairs is given in Mullins et al. (2006). inspection team can observe certain critical tasks as they are Engineers do not all agree if the adhesive resin can fully performed. In the case of a large spall repair, the inspections bond to a porous saturated surface such as concrete. Design may be phased so that the inspection team can observe the values for adhesion should be based on test results of the drilling and placement of dowels, surface preparation, specific material to be used. reinforcing bar arrangement, and the completed product. If Adhesive resin should be able to be placed and cure in the repair involves epoxy injection of small cracks, the water temperatures expected at the repair side. The ability to inspectors may check the following: install the system in poor visibility or currents should be 1. The cleaning; considered. 2. Placement of the injection ports; 7.12.5 Installation procedures—Installation procedures 3. Placement of the surface crack sealer; for FRP will vary with individual manufacturers’ product 4. Actual injection; and requirements. Concrete substrates to receive FRP application 5. Completed repair. should be clean, with sound concrete surfaces. Local If inspections are performed during construction, they substrate repair may be required before FRP application. should be timed so the progress of the contractor is not For systems using resin-impregnated reinforcing mats, unduly interrupted and subsequent phases of work do not the mats are pre-impregnated with resin above water and obscure the item to be inspected. taken below water for installation. Resins that are water 8.2.3 Post-construction inspection—A post-construction

activated--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- are taken below water in sealed bags to delay the inspection is performed at the completion of repairs. The initiation of curing. actual timing of this type of inspection may not be especially As part of a repair and seismic upgrade at the Fort Mason critical; however, it should normally be performed soon after Pier 2 in San Francisco, CA, prefabricated FRP sections construction has been completed. It may form the basis for were placed around 4 ft (1.5 m) diameter concrete columns payments to the contractor. Cores or nondestructive testing after working from above water. The sections were placed and the work has been completed may be used to determine accept- wrapped with the composite strengthening materials and, as ability of the repair. Post-construction inspection does not sections were completed, the composite shell was lowered hamper the contractor; however, it only verifies that work was into the water. The annulus between the reinforced shell and done. It does not confirm that all phases of the work were column was then grouted (Fyfe Co. LLC 2005). performed in accordance with the contract documents.

CHAPTER 8—INSPECTION OF REPAIRS 8.3—Documentation 8.1—Introduction 8.3.1 A written report should be prepared to document all Construction inspections are performed to verify that construction inspection activities. Where underwater repairs have been made in accordance with the construction construction inspection is an ongoing activity, each individual documents. This is poor practice to skip inspections, which report may be brief, covering perhaps a single activity such as verify conformance and quality of work. Inspections may be inspection of concrete removal. A post-construction inspection performed either during the course of the construction phase report should be comprehensive for all performed repairs. or after all of the work has been completed. There are The report should document what was inspected, the inspec- advantages and disadvantages to each, because each inspection tion techniques used, deficiencies found, recommendations

UNDERWATER REPAIR OF CONCRETE 546.2R-29

for corrective measures if needed, and recommendations for ASTM International changes in inspection frequencies based on observed C42/C42M Standard Test Method for Obtaining and (partially) completed work. For underwater inspections, the Testing Drilled Cores and Sawed Beams following data should also be included: of Concrete • Dive team members’ names; C597 Standard Test Method for Pulse Velocity • Lead inspector’s name; through Concrete • Type of dive equipment used; C805/C805M Standard Test Method for Rebound • Type of inspection equipment used; Number of Hardened Concrete • Water temperature; C881/C881M Specification for Epoxy-Resin-Base Bonding Systems for Concrete • Water currents (ft [m] per second); • Water surface elevation to a standard datum; U.S. Army Corps of Engineers (USACE) • Underwater visibility; and CRD-C61 Test Method for Determining the Resis- • Time the inspectors enter and leave the water. tance of Freshly Mixed Concrete to All inspections should be documented with detailed notes, Washing out in Water dimensional sketches, and photographs. Video cameras can CRD-C661 Specification for Antiwashout Admix- also be used. The inspection report should include labeled tures for Concrete photographs. The underwater inspection report should reference any related concurrent inspection activity being The above publications may be obtained from the performed above water. For instance, the underwater following organizations: inspection may be documenting concrete placement, whereas concrete mixture quality assurance tests are being American Concrete Institute conducted above water. 38800 Country Club Drive Farmington Hills, MI 48331 CHAPTER 9—REFERENCES www.concrete.org 9.1—Referenced standards and reports The documents of the various standards producing organi- American Society of Civil Engineers zation referred to in this document are listed below with their 1801 Alexander Bell Drive serial designations: Reston, VA 20191 www.asce.org American Concrete Institute (ACI) 201.2R Guide to Durable Concrete ASTM International 210R Erosion of Concrete in Hydraulic Structures 100 Bar Harbor Drive 222R Protection of Metals in Concrete Against West Conshohocken, PA 19428 Corrosion www.astm.org 228.2R Nondestructive Test Methods for Evaluation of Concrete in Structures U.S. Army Corps of Engineers (USACE) 304R Guide for Measuring, Mixing, Transporting, and 441 G. Street, NW Placing Concrete Washington, DC 20314-1000 304.2R Placing Concrete by Pumping Methods www.usace.army.mil 311.4R Guide for Concrete Inspection 347 Guide to Formwork for Concrete 9.2—Cited references AASHTO, 2009, “Guide Specification and Commentary 440R Report on Fiber-Reinforced Polymer (FRP) for Vessel Collision Design of Highway Bridges,” second Reinforcement for Concrete Structures edition, American Association of State Highway and Trans- 440.2R Guide for the Design and Construction of Exter- portation Officials, Washington, DC, Feb. nally Bonded FRP Systems for Strengthening ABAM Engineers, Inc., 1987a, “Design of a Precast Concrete Structures Concrete Stay-in-Place Forming System for Lock Wall 515.1R Guide to the Use of Waterproofing, Damp- Rehabilitation,” Technical Report REMR-CS-7, U.S. Army proofing, Protective, and Decorative Barrier Corps of Engineers Waterways Experiment Station, Vicks- --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- Systems for Concrete (withdrawn) burg, MS, July. 546R Concrete Repair Guide ABAM Engineers, Inc., 1987b, “A Demonstration of the 546.3R Guide for the Selection of Materials for the Constructability of a Precast Concrete Stay-in-Place Repair of Concrete Forming System for Lock Wall Rehabilitation,” Technical SP-4 Formwork for Concrete (synopsis) Report REMR CS-14, U.S. Army Corps of Engineers Water- ways Experiment Station, Vicksburg, MS, Dec. American Society of Civil Engineers (ASCE) ABAM Engineers, Inc., 1989, “Concepts for Installation Underwater Investigations: Standard Practice Manual of the Precast Concrete Stay-in-Place Forming System for

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Lock Wall Rehabilitation in an Operational Lock,” Tech- ASTM STP 169C, ASTM International, West Conshohocken, nical Report REMR-CS-28, U.S. Army Corps of Engineers PA, Chapter 27, pp. 263-281. Waterways Experiment Station, Vicksburg, MS, Dec. Dolar-Mantuani, L., 1983, Handbook of Concrete Aggre- American Concrete Institute, 1964, Symposium on gates—A Petrographic and Technological Evaluation, Concrete Construction in Aqueous Environments, SP-8, Noyes Publications, Park Ridge, NJ, 345 pp. Farmington Hills, MI, 116 pp. FHWA, 1989, “Underwater Inspection of Bridges,” ASCE, 2001, Underwater Investigation Standard Practice Report FHWA-DP-80-1, Federal Highway Administration, Manual, American Society of Civil Engineers, Reston, VA. U.S. Department of Transportation, Springfield, VA. Ball, J. C., and Whitmore, D. W., 2005, “Innovative Freese, V. D.; Hofig, W.; and Grotkopp, U., 1978, “Neuar- Corrosion Mitigation Solutions for Existing Concrete Struc- tige Betone fur den Wasserbau,” Beton, June. tures,” International Journal of Materials and Product Tech- Fyfe Co. LLC, 2005, “Tyfo® for Mason System,” Fyfe Co. nology, V. 23, No. 3 and 4, pp. 219-239. LLC, San Diego, CA, 2 pp. Beck, R.; Davis, J.; Butcher, R.; Burhke M.; Clarke, J.; Garlich, M. J., 1995, “Application of Nondestructive Simpson, R.; Benitez, L.; O’Leary, J.; and Smith, P., 2008, Testing in Underwater Evaluation of Bridge and Related “Integration of Solid Modeling into Real Time Navigation,” Structures,” Proceedings, SPIE Nondestructive Evaluation Offshore Technology Conference, May. of Aging Infrastructure, June. Best, J. F., and McDonald, J. E., 1990, “Evaluation of Garlich, M. J., and Chrozastowski, M. J., 1989, “An Polyester Resin, Epoxy, and Cement Grouts for Embedding Example of Side Scan Sonar in Waterfront Facilities Evalu- Reinforcing Steel Bars in Hardened Concrete,” Technical ation,” PORTS ’84, K. M. Childs, ed., American Society of Report REMR-CS-23, U.S. Army Corps of Engineers, Jan. Civil Engineers, Reston, VA, pp. 84-94. Burke, N. D., and Bushman, J. B., 1988, “Corrosion and Gerwick, B. C., 1988, “Review of the State of the Art for Cathodic Protection of Steel Reinforced Concrete Bridge Underwater Repair Using Abrasion-Resistant Concrete,” Decks,” FHWA-IP-007, Federal Highway Administration, Technical Report REMR-CS-19, U.S. Army Corps of Engi- Washington, DC. neers Waterways Experiment Station, Vicksburg, MS. Bury, M. A.; Nmai, C. K.; Amekuedi, G.; and Bury, J., Hard Suits, Inc., 1997, “Systems Information Package,” 2001, “Unique Applications of a Cellulose-Based Anti- --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- American Oilfield Divers, Inc., Houston, TX. Washout Admixture,” Concrete International, V. 23, No. 4, Harris, B. N.; Palma, J. F.; and Miller, D. F., 1991, Apr., pp. 24-30. “Underwater Repair of Concrete Based on REMR Technical Busby, R. F., 1978, “Underwater Inspection/Testing/ Information, “ The REMR Bulletin, V. 8, No. 4, U.S. Army Monitoring of Offshore Structures,” U.S. Government Corps of Engineers Waterways Experiment Station, Vicks- Printing Office, Washington, DC, Feb. burg, MS. Chaallali, O.; Shahawy, M.; and Hassan, M., 2006, “CFRP Repair and Strengthening of Structurally Deficient Piles: Hasan, N.; Faerman, E.; and Berner, D., 1993, “Advances Design Issues and Field Application,” Journal of Composites in Underwater Concreting: St. Lucie Plant Intake Velocity High Performance Concrete in Severe for Construction, ASCE, Jan.-Feb., pp. 26-34. Cap Rehabilitation,” Environments, SP-140, P. Zia, ed., American Concrete Christensen, J. C.; Marcy, M. A.; Scuero, A. M.; and Institute, Farmington Hills, MI, pp. 187-213. Vaschetti, G. L., 1995, “A Conceptual Design for Under- water Installation of Geomembrane Systems on Concrete Hendershot, B.; Enderlin, T.; and Reynolds, T., 2002, Hydraulic Structures,” Technical Report REMR-CS-50, U.S. “Taking it One Block at a Time,” Underwater, Jan.-Feb., Army Corps of Engineers Waterways Experiment Station, pp. 15-19. Vicksburg, MS, 102 pp. Holland, T. C., 1976, “Tremie Concrete Techniques Used at Clausner, J. E., and Pope, J., 1988, “Side Scan Sonar Tarbela,” International Water Power and Dam Construction, Applications for Evaluating Coastal Structures,” Technical V. 28, No. 1, pp. 21-24. Report CERC-88-16, U.S. Army Corps of Engineers, Vicks- Holland, T. C., 1983, “Tremie Concrete for Massive burg, MS, Nov. Underwater Construction,” University of California, Colle, E. R., 1992, “Preplaced Aggregate Concrete Berkeley, CA. Repairs 63-Year Old Railroad Bridge,” Concrete Repair Kajima Corp., 1985, “Use of Hydrocrete for Repair of Digest, V. 2, pp. 61-64. Stilling Basin,” Japan, p. 49. Collins, T. J., and Garlich, M. J., 1998, “Pile Jackets: Keeney, C. A., 1987, “Procedures and Devices for Under- Issues in Design and Performance,” Proceedings Ports ’98, water Cleaning of Civil Works Structures,” Technical ASCE, Reston, VA, pp. 682-691. Report REMR CS-8, U.S. Army Corps of Engineers Water- Concrete Products, 1995, “A Few Good Pieces Tackle ways Experiment Station, Vicksburg, MS, Nov., 46 pp. Marine Jobs,” Dec., pp. 32A-32E. Kepler, W. F., 1990, “Underwater Placement of a Cutting Edge Services Corp., 2007, “It’s a Dirty Job, but Concrete Canal Lining,” Concrete International, V. 12, Someone Has to Do it,” Cutting Edge Services, Batavia, OH. No. 6, June, pp. 54-59. DePuy, G. W., 1994, “Chemical Resistance of Concrete,” Kessler, R. J.; Powers, R. G.; and Lasa, I. R., 1998, Significance of Tests and Properties of Concrete and “History and Performance of Marine Substructure Cathodic Concrete-Making Materials, P. Klieger and J. F. Lamond, eds., Protection Systems in Florida,” Proceedings, International

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Conference on Corrosion and Rehabilitation of Reinforced REMR-CS-33, U.S. Army Corps of Engineers Waterways Concrete Structures, FHWA, Dec. Experiment Station, Vicksburg, MS. Khayat, K. H., 1991, “Underwater Repair of Concrete McDonald, J. E., 1993, “Geomembranes for Repair of Damaged by Abrasion-Erosion,” Technical Report REMR- Concrete Hydraulic Structures,” The REMR Bulletin, CS-37, U.S. Army Corps of Engineers Waterways Experi- USACE, V. 10, No. 4, pp. 1-6. ment Station, Vicksburg, MS. McDonald, J. E., 1997, “Development of a Geomembrane Khayat, K. H., 1992, “In Situ Properties of Concrete Piles System for Underwater Repair of Concrete Structures,” The Repaired Under Water,” Concrete International, V. 14, No. 3, REMR Bulletin, http://www.wes.army.mil/REMR/bulls/ Mar., pp. 42-49. vol14/no1/text/geomem.html (accessed Apr. 5, 2010). Khayat, K. H., 1995, “Effects of Antiwashout Admixtures McDonald, J. E., and Curtis, N. F., 1995, “Applications of on Fresh Concrete Properties,” ACI Materials Journal, V. 92, Precast Concrete in Repair of Civil Works Structures,” No. 2, Mar.-Apr., pp. 164-171. Technical Report REMR-CS-49, U.S. Army Corps of Khayat, K. H., 1996, “Effects of Antiwashout Admixtures Engineers Waterways Experiment Station, Vicksburg, MS. on Properties of Hardened Concrete,” ACI Materials McDonald, W. E., 1998, “Evaluation of Grouting Materials Journal, V. 93, No. 2, Mar.-Apr., pp. 134-146. for Anchor Embedments in Hardened Concrete,” Technical Khayat, K. H., and Assad, J., 2003, “Relationship between Report REMR-CS-56, U.S. Army Corps of Engineers Water- Washout Resistance and Rheological Properties of High- ways Experiment Station, Vicksburg, MS. Performance Underwater Concrete,” ACI Materials Journal, McGurn, J. F., 1998, “Stainless Steel Reinforcing Bars in V. 100, No. 3, May-June, pp. 185-193. Concrete,” International Conference on Corrosion and Reha- Khayat, K. H.; Gerwick, B. C.; and Hester, W. T., 1993, bilitation of Reinforced Concrete Structures, FHWA, Dec. “Concrete Placement With Inclined Tremie for Small McKain, D. W., and McKain, V. E., 1996, “Unique Reef Underwater Repairs,” Concrete International, V. 15, No. 4, Replication,” ON&T, May-June, p. 32. Apr., pp. 48-56. Mehta, P. K., and Monteiro, P. J. M., 1993, Concrete: Microstructure, Properties, and Materials Khoury, G. A.; Sullivan, P. J. E.; Dahan, R. A.; and , McGraw-Hill Onabolu, O. A., 1985, “Organic Acid Intake of Crude Oil in Companies, Inc., pp. 144-146. North Sea Oil Storage Tanks as Affected by Aerobic Bacterial Miles, W. R., 1993, “Comparison of Cast-in-Place Activity,” Petroleum Review, Sept., pp. 42-45. Concrete versus Precast Concrete Stay-in-Place Forming Systems for Lock Wall Rehabilitation,” Technical Report Kilnbridge Construction Services, Ltd., 2007, Concrete REMR-CS-41, U.S. Army Corps of Engineers Waterways Cutting, McDermott House, South Crescent, London, UK. Experiment Station, Vicksburg, MS, Oct. Klieger, P., 1994, “Air-Entraining Admixtures,” Significance MTS, 1984, “Operational Guidelines for ROVs,” Marine of Tests and Properties of Concrete-Making Materials, ASTM Technology Society, Columbia, MD. STP 169C, P. Klieger and J.F. Lamond, eds., ASTM Interna- Mullins, G.; Sen, R.; Suh, K. S.; and Winters, D., 2006, “A tional, West Conshohocken, PA, pp. 484-490. Demonstration of Underwater FRP Repair,” Concrete Inter- Lamberton, B. A., 1989, “Fabric Forms for Concrete,” national, V. 28, No. 1, Jan., pp. 70-73. Concrete International, V. 11, No. 12, Dec., pp. 58-67. Neeley, B. D., 1988, “Evaluation of Concrete Materials Leng, D. L., 2002, “Zinc-Mesh Jacket System Improves for Use in Underwater Repairs,” Technical Report REMR- Corrosion Control,” Better Roads, Nov. CS-18, U.S. Army Corps of Engineers Waterways Experi-

--`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- Maage, M., 1984, “Underwater Concrete,” Nordic ment Station, Vicksburg, MS. Concrete Research, Trondheim, Norway. Neeley, B. D.; Saucier, K. L.; and Thornton, H. T., 1990, Makk, O., and Tjugum, O., 1985, “Pumped Underwattens- “Laboratory Evaluation of Concrete Mixtures and Tech- betong (Pumped Underwater Concrete),” Nordisk Betong, niques for Underwater Repairs,” Technical Report REMR- V. 2. CS-34, U.S. Army Corps of Engineers Waterways Experi- Marcy, M. A.; Scuero, A. M.; and Vashetti, G. L., 1996, ment Station, Vicksburg, MS. “A Constructibility Demonstration of Geomembrane Systems Neeley, B. D., and Wickersham, J., 1989, “Repair of Installed Underwater on Concrete Hydraulic Structures,” Tech- Red Rock Dam,” Concrete International, V. 11, No. 10, nical Report REMR-CS-51, U.S. Army Corps of Engineers Oct., pp. 36-39. Waterways Experiment Station, Vicksburg, MS, 60 pp. Neville, A. M., 1983, Properties of Concrete, Longman McDonald, J. E., 1980, “Maintenance and Preservation of Scientific & Technical, third edition. Concrete Structures; Repair of Erosion Damaged Struc- NRC, 1996, “Undersea Vehicles and National Needs,” tures,” Technical Report C-78-4, Report 2, U.S. Army Corps National Research Council, Committee on Undersea Vehicles of Engineers Waterways Experiment Station, Apr., Vicks- and National Needs, National Academies Press, Wash- burg, MS. ington, DC. McDonald, J. E., 1988, “Precast Concrete Stay-in-Place Olson, L. D., 1996, “Nondestructive Testing of Unknown Forming System for Lock-Wall Rehabilitation,” Concrete Subsurface Bridge Foundations—Results of NCHRP Project International, V. 10, No. 6, June, pp. 31-37. 21-5,” NCHRP Research Results Digest, No. 213, Dec. McDonald, J. E., 1990, “Anchor Embedment in Hardened Olson, L. D.; Law, M.; Phelps, G. C.; Murthy, K. N.; and Concrete Under Submerged Conditions,” Technical Report Ghadiali, B. M., 1994, Proceedings, Federal Highway

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Administration Conference on Deep Foundations, Orlando, Thaesler, P.; Kahn, L.; Oberle, R.; and Demers, C. E., FL, Dec. 2005, “Durable Repairs on Marine Bridge Piles,” Journal of Onken, S. C., 1998, “Installing an Underwater Geomem- Performance of Constructed Facilities, ASCE, V. 19, No. 1, brane at Lost Creek Dam,” Hydro Review, V. XVII, No. 3, Feb., pp. 88-92. HCI Publications, Kansas City, MO, pp. 34-38. Thornton, H. T., 1978, “Acid Attack on Concrete Caused Petronis, W., and Ellinwood, A., 1993, “REMR-Designed by Sulfur Bacteria Action,” ACI JOURNAL, Proceedings, Precast Concrete Stay-in-Place Forming System Used for V. 75, No. 11, Nov., pp. 577-584. Concrete Repair at Troy Lock and Dam,” The REMR Thornton, H. T., and Alexander, A. M., 1987, “Development Bulletin, USACE, V. 10, No. 1, Vicksburg, MS. of Nondestructive Testing Systems for In Situ Evaluation of Popovics, S., 1986, “Underwater Inspection of the Concrete Structures,” Technical Report REMR-CS-10, U.S. Engineering Condition of Concrete Structures,” Technical Army Corps of Engineers Waterways Experiment Station, Report REMR-9, U.S. Army Corps of Engineers Waterways Vicksburg, MS, Dec. Experiment Station, Vicksburg, MS, July. Underwater Concrete, 1983a, “Hydraulic Sea Water Quin, S.; Qu, D.; and Coates, G., 2006, “Galvanic Coupling Intake,” Hydrocrete Underwater Concrete, Underwater between Carbon Steel and Stainless Steel Reinforcements,” Concrete Limited, London. NRCC-48715, National Research Council Canada, Ottawa, Underwater Concrete, 1983b, “Hydrocrete, Cable Peak ON, Canada. Pure Station, Hong Kong,” Hydrocrete Underwater Rail, R. D., and Haynes, H. H., 1991, “Underwater Stilling Concrete, Underwater Concrete Limited, London. Basin Repair Techniques Using Precast or Prefabricated U.S. Army Corps of Engineers (USACE), 1992, “Special- Elements,” Technical Report REMR-CS-38, U.S. Army ized Repair Technique: Preplaced-Aggregate Concrete,” Corps of Engineers Waterways Experiment Station, Vicks- REMR Technical Note CS-MR-9.4, 3 pp. burg, MS, Dec. USACE, 1994, “Hydrographic Surveying,” EM-1110-2- Saucier, K. L., and Neeley, B. D., 1987, “Antiwashout 1003, Washington, DC. Mixtures in Underwater Concrete,” Concrete International, USACE, 1995, “Evaluation and Repair of Concrete Struc- V. 9, No. 5, May, pp. 42-47. tures,” EM 1110-2-2002, Washington, DC, June. Sen, R.; Mullins, G.; Suh, K.; and Winters, D., 2005, USACE, 2002, “Hydrographic Surveying,” EM 1110-2- “FRP Applications in Underwater Repair of Corroded 1003, Washington, DC, 572 pp. Piles,” 7th International Symposium on Fiber-Reinforced Polymer (FRP) Reinforcement for Concrete Structures, Vadus, J. R., and Busby, R. F., 1979, “Remotely Operated SP-230, C. K. Shield et al., eds., American Concrete Insti- Vehicles: An Overview,” NOAA Technical Report 00E6, Dec. tute, Farmington Hills, MI, pp. 1139-1156. Vallance, C. A., 1999, “Underwater Repair of Dams,” Sletten, R.; Fjeld, S.; Roland, B.; Det norske, V., 1977, ASDSO Annual Dam Safety Conference. “In-Service Inspection of North Sea Structures,” Offshore Wiebenga, J. G., 1980, “Durability of Concrete Structures Technology Conference, OTC 2980, May. Along the North Sea Coast of the Netherlands,” Perfor- Smith, A. P., 1986, “Underwater Nondestructive Testing mance of Concrete in Marine Environment, SP-65, V. M. of Concrete: An Evaluation of Techniques,” NCEL Tech- Malhotra, ed., American Concrete Institute, Farmington nical Note, Feb. Hills, MI, pp. 437-452. Smith, A.; Goff, D.; and Rhoads, C., 1991, “Underwater Wilkes, J.; Larson, E.; Vaschetti, G.; and Scuero, A., 2003, Concrete Inspection Equipment,” Technical Note N-1828, “Synthetic Liners for Rehabilitation of Cracks and Joints: Naval Civil Engineering Laboratory, Port Hueneme, CA, 94 pp. Two Case Histories, One Executed in the Dry and One Spencer, T. E., and Blaylock, A. J., 1997, “Alkali-Silica Underwater,” Dam Safety 2003 Proceedings, Association of Reaction in Marine Piles,” Concrete International, V. 19, State Dam Safety Officials, Lexington, KY. No. 1, Jan., pp. 59-62. Yao, S. X.; Berner, D. E.; and Gerwick, B. C., 1999, Stark, D. C.; Horeczko, G.; and Rowghani, M., 1999, “Assessment of Underwater Concrete Technologies for In- “Cracking of Prestressed Concrete in Seawater,” Concrete the-Wet Construction of Navigation Structures,” Technical International, V. 21, No. 12, Dec., pp. 51-55. Report INP-SL-1, U.S. Army Corps of Engineers Waterways Straube, P., 1982, “Evaluation of Hydrocrete for Use as Experiment Station, Vicksburg, MS, 91 pp. Reinforced Concrete in Offshore Structures,” Technical Yao, S. X., and Gerwick, B. C., 2004a, “Underwater Report No. 82-0204, Det Norske Veritas, Oslo, Norway. Concrete Part 1: Design Concepts and Practices,” Concrete Syler, B. A., and Stromberg, D. G., 2008, “Comparison of International, V. 26, No. 1, Jan., pp. 79-83. New Advances in Underwater Bridge Inspection Tech- Yao, S. X., and Gerwick, B. C., 2004b, “Underwater nology,” International Bridge Conference Paper IBC-08-82, Concrete Part 2: Proper Mixture Proportioning,” Concrete June, Pittsburgh, PA. International, V. 26, No. 2, Feb., MI, pp. 77-82.

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American Concrete Institute® Advancing concrete knowledge

As ACI begins its second century of advancing concrete knowledge, its original chartered purpose remains “to provide a comradeship in finding the best ways to do concrete work of all kinds and in spreading knowledge.” In keeping with this purpose, ACI supports the following activities:

· Technical committees that produce consensus reports, guides, specifications, and codes.

· Spring and fall conventions to facilitate the work of its committees.

· Educational seminars that disseminate reliable information on concrete.

· Certification programs for personnel employed within the concrete industry.

· Student programs such as scholarships, internships, and competitions.

· Sponsoring and co-sponsoring international conferences and symposia.

· Formal coordination with several international concrete related societies.

· Periodicals: the ACI Structural Journal and the ACI Materials Journal, and Concrete International.

Benefits of membership include a subscription to Concrete International and to an ACI Journal. ACI members receive discounts of up to 40% on all ACI products and services, including documents, seminars and convention registration fees.

As a member of ACI, you join thousands of practitioners and professionals worldwide who share a commitment to maintain the highest industry standards for concrete technology, construction, and practices. In addition, ACI chapters provide opportunities for interaction of professionals and practitioners at a local level.

American Concrete Institute 38800 Country Club Drive Farmington Hills, MI 48331 U.S.A. Phone: 248-848-3700 Fax: 248-848-3701 www.concrete.org

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The AMERICAN CONCRETE INSTITUTE was founded in 1904 as a nonprofit membership organization dedicated to public service and representing the user interest in the field of concrete. ACI gathers and distributes information on the improvement of design, construction and

maintenance of concrete products and structures. The work of ACI is conducted by --`,`,,```,,`,```,`,`,```,``,,,,-`-`,,`,,`,`,,`--- individual ACI members and through volunteer committees composed of both members and non-members.

The committees, as well as ACI as a whole, operate under a consensus format, which assures all participants the right to have their views considered. Committee activities include the development of building codes and specifications; analysis of research and development results; presentation of construction and repair techniques; and education.

Individuals interested in the activities of ACI are encouraged to become a member. There are no educational or employment requirements. ACI’s membership is composed of engineers, architects, scientists, contractors, educators, and representatives from a variety of companies and organizations.

Members are encouraged to participate in committee activities that relate to their specific areas of interest. For more information, contact ACI.

www.concrete.org

American Concrete Institute® Advancing concrete knowledge