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1、ACI 546.2R-98 became effective September 21, 1998. Copyright 1998, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or o
2、ral, or recording for sound or visual reproduc- tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. ACI Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in planning, de- sign
3、ing, executing, and inspecting construction. This docu- ment is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it con- tains. The American Con
4、crete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom. Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be
5、a part of the contract doc- uments, they shall be restated in mandatory language for incorporation by the Architect/Engineer. 546.2R-1 This document provides guidance on the selection and application of mate- rials and methods for the repair and strengthening of concrete structures under water. An o
6、verview of materials and methods for underwater repair is presented as a guide for making a selection for a particular application. References are provided for obtaining additional information on selected materials and construction methods. Guide to Underwater Repair of Concrete ACI 546.2R-98 Report
7、ed by ACI Committee 546 *, * Members who served as the editorial subcommittee for this document, and editor, respectively. G.W. DePuy also served as a member of the editorial subcommittee. , Members, associate membersa, and former membersf who served on the Underwater Repair Subcommittee, and Chairm
8、an of the sub- committee, respectively, that prepared the initial drafts of this document. William AllenLeon GlassgoldKenneth Saucier Robert Andersona Harald G. Greve Johan L. Silfwerbrand Peter Barlow Terry Hollanda W. Glenn Smoak John J. Bartholomew* Martin Iornsa Martin B. Sobelman Georg Bergeman
9、na Robert F. Joyce Joe Solomon Michael M. Chehab Lawrence F. Kahn Michael M. Sprinkel Gary Chynowetha Tony C. Liu Ronald R. Stankie Marwan A. Daye Mark LutherfSteven Tatea Floyd E. Dimmick James E. McDonald Robert Tracyf Peter H. Emmons Kevin A. Michols Alexander Vaysburd Jack J. Fontana Joseph P. M
10、iller D. Gerry Walters Jerome H. Ford Thomas J. Pasko Jr. Patrick Watson Michael J. Garlich Jay H. Paul Mark V. Ziegler Steven H. Gebler Don T. Pyle* Keywords: cementitious; concrete; concrete removal; deterioration; evalu- ation; formwork; investigation; inspection; jackets; joints; materials; mari
11、ne placement; polymer; protection; reinforcement; repair; strengthen; surface preparation; underwater; water. CONTENTS Chapter 1General, p. 546.2R-2 1.1Introduction and general considerations 1.2Scope 1.3Diving technology Chapter 2Causes of deterioration, p. 546.2R-4 2.1Marine organisms 2.2Deficient
12、 construction practices 2.3Chemical attack 2.4Corrosion 2.5Mechanical damage Myles A. Murray* Chairman Paul E. Gaudette Secretary 546.2R-2 MANUAL OF CONCRETE PRACTICE 2.6Freezing and thawing damage 2.7Salt scaling 2.8Damage not included in this guide Chapter 3Evaluations and investigations, p. 546.2
13、R-6 3.1Introduction 3.2Visual inspection 3.3Tactile inspection 3.4Underwater nondestructive testing of concrete 3.5Sampling and destructive testing Chapter 4Preparation for repair, p. 546.2R-9 4.1Concrete removal 4.2Surface preparation 4.3Reinforcement rehabilitation 4.4Chemical anchors/dowels Chapt
14、er 5Formwork, p. 546.2R-10 5.1Rigid and semi-rigid forms 5.2Flexible forms Chapter 6Methods and materials, p. 546.2R-15 6.1General considerations 6.2Preplaced aggregate concrete 6.3Tremie concrete 6.4Pumped concrete and grout 6.5Free dump through water 6.6Epoxy grouting 6.7Epoxy injection 6.8Hand pl
15、acement 6.9Other underwater applications using concrete con- taining anti-washout admixtures Chapter 7Inspection of repairs, p. 546.2R-21 7.1Introduction 7.2Procedure 7.3Documentation Chapter 8Developing technologies, p. 546.2R-22 8.1Precast concrete elements and prefabricated steel el- ements Chapt
16、er 9References, p. 546.2R-22 9.1Recommended references 9.2Cited references CHAPTER 1GENERAL 1.1Introduction The repair of concrete structures under water presents many complex problems. Although the applicable basic re- pair procedures and materials are similar to those required in typical concrete
17、repair, the harsh environmental conditions and specific problems associated with working under water or in the splash zone area (Fig. 1.1) cause many differences. The repair of concrete under water is usually difficult, requiring specialized products and systems, and the services of highly qualified
18、 and experienced professionals. See ACI SP-8 and SP-65. Proper evaluation of the present condition of the structure is the essential first step for designing long-term repairs. To be most effective, long-term evaluation requires historical information on the structure and its environment, including
19、any changes, and the record of periodic on-site inspections or repairs. Comprehensive documentation of the cause and ex- tent of deterioration, accurate design criteria, proper repair techniques, and quality assurance of the installation proce- dures and the repair will result in a better repair sys
20、tem. Lon- gevity of the repair is the ultimate indicator of success. Underwater concrete deterioration in tidal and splash zones is a serious economic problem (Fig. 1.2 and 1.3). Wa- ter that contains oxygen and contaminants can cause aggres- sive attack on concrete. Underwater repair of concrete is
21、 a specialized and highly technical part of concrete repair tech- nology. It presents problems of selecting appropriate repair materials and methods, and of maintaining quality control not normally associated with repair above water. Sound engi- neering, quality workmanship and high-performance prod
22、ucts and systems are extremely important. Successful repairs can be achieved when these factors are considered carefully and properly implemented. This guide provides an overview of the current status of underwater repair technology to aid the engi- neer, designer, contractor and owner in making dec
23、isions. 1.2Scope This guide is limited to concrete structures in the splash zone and underwater portions of typical lakes, rivers, oceans, and ground water. Concrete deterioration, environments, in- vestigation and testing procedures, surface preparation, types of repair, repair methodology, and mat
24、erials are de- scribed. Design considerations and references for underwa- ter repair of concrete bridges, wharves, pipelines, piers, outfalls, bulkheads, and offshore structures are identified. 1.3Diving technology Underwater work can be generally classified into one of the three broad categories of
25、 diving: manned diving, a one-atmosphere armored suit or a manned submarine, or a remotely-operated vehicle (ROV). Manned diving is the traditional method of performing tasks under water. In this category, the diver is equipped with life-support systems that provide breathable air and protec- tion f
26、rom the elements. Manned diving systems include scu- ba (self-contained underwater breathing apparatus) and surface-supplied air. Performance of duties at higher than one atmosphere am- bient pressure causes a multitude of physiological changes within the human body. For instance, body tissues absor
27、b and shed gases at different rates than those normally experi- enced on the surface. Because of this, the time available to perform work under water decreases rapidly with increased water depth. For example, industry standards currently allow a diver using compressed air to work at 30 ft (10 m) for
28、 an unlimited period of time. However, if work is being per- formed at 60 ft (20 m), the diver can only work for approxi- mately 60 min without special precautions to prevent 546.2R-3GUIDE TO UNDERWATER REPAIR OF CONCRETE decompression sickness. The industry standard upper limit is 30 min work time
29、at 90 ft (30 m) in seawater. If these lim- its are exceeded, precautions must be taken to decompress the diver. The sophistication (and hence the cost) of the div- ing systems used on a project increases with increased depth. If manned diving is used deeper than 180 ft (60 m) of wa- ter, most divers
30、 elect to use specially formulated mixtures of gases rather than compressed air. To increase efficiency, these diving operations are often enhanced with diving bells, which are used to maintain the divers at working depths for extended periods of time. Divers may be supported at equiv- alent water d
31、epths for weeks at a time. The technologies as- sociated with mixed gas diving are changing rapidly as people work at deeper depths. Fig. 1.1Repair zones: submerged, tidal, exposed. Fig. 1.2Deteriorated piles in tidal and exposed zones. (Courtesy of I. Leon Glassgold.) Fig. 1.3Advanced deterioration
32、, pile has been cleaned. (Courtesy of I. Leon Glassgold.) Fig. 1.4Remotely operated vehicle (ROV). (Courtesy of M. Garlich.) 546.2R-4MANUAL OF CONCRETE PRACTICE A recent development is the One Atmosphere Diving Suit (Hard Suits, Inc., 1997). These suits are capable of support- ing divers at depths a
33、s great as 2,100 ft (640 m), with an in- ternal suit pressure of one atmosphere. The diver works in an ambient pressure equivalent to that on the surface; therefore, the time at depth is virtually unrestricted. The suit looks much like a hollow robot. The arms are equipped with claw- like operating
34、devices, which reduce manual dexterity. The suits are cumbersome and difficult to position, because mo- bility is provided by external propulsion devices, ballast tanks or cables suspended from topside support vessels. Mini-submarines are occasionally used to perform under- water work. These typical
35、ly have crews of two or three. Most are equipped with video and photographic equipment. Some submarines are also equipped with robotic arms for perform- ing tasks outside of the submarine. The lack of dexterity and limitations on the positioning capability of these vessels may hamper their effective
36、ness for inspection and repair work. Remotely operated vehicles (ROVs) look much like an un- manned version of a submarine (Fig. 1.4) (Vadus and Busby, 1979). They are compact devices that are controlled by a re- mote crew. The operating crew and the vehicle communicate through an umbilical cord att
37、ached to the ROV. The crew op- erates the ROV with information provided by transponders attached to the frame of the ROV. ROVs may be launched directly from the surface or from a submarine mother ship. Most ROVs are equipped with video and still photography devices. The vehicle is positioned by ball
38、ast tanks and thrust- ers mounted on the frame. Some ROVs also are equipped with robotic arms, used to perform tasks that do not need a high degree of dexterity. ROVs have been used at depths of approximately 8,000 ft (2,400 m). CHAPTER 2CAUSES OF DETERIORATION 2.1Marine organisms 2.1.1 Rock borersM
39、arine organisms resembling ordi- nary clams are capable of boring into porous concrete as well as rock. These animals, known as pholads, make shallow, oval-shaped burrows in the concrete. Rock borers in warm water areas such as the Arabian Gulf are also able to dissolve and bore into concrete made w
40、ith limestone aggregate, even if the aggregate and concrete is dense. 2.1.2 Acid attack from acid-producing bacteriaAnaero- bic, sulfate reducing bacteria can produce hydrogen sulfide. Sulfur-oxidizing bacteria, if also present, can oxidize the hy- drogen sulfide to produce sulfuric acid, common in
41、sewers. Also, oil-oxidizing bacteria can produce fatty acids in aero- bic conditions. These acids attack portland cement paste in concrete, dissolving the surface. In addition, the acids can lower the pH of the concrete to a level where the reinforce- ment is no longer passivated. Once this occurs,
42、corrosion in the reinforcing steel can begin, often at an accelerated rate (Thornton, 1978; Khoury et al., 1985). 2.2Deficient construction practices and errors Because of the difficult working conditions and the diffi- culty of providing adequate inspection during construction, underwater placement
43、 of concrete and other materials is of- ten susceptible to errors and poor construction practices. Deficient practices include the following: exceeding the specified water-cement (or water-cementitious materials) ra- tio, inadequate surface preparation, improper alignment of formwork, improper concr
44、ete placement and consolidation, improper location of reinforcing steel, movement of form- work during placement, premature removal of forms or shores, and settling of the concrete during hardening. Each of these practices is discussed in a manual prepared by the Corps of Engineers (Corps of Enginee
45、rs, 1995). One specialized deficiency common to marine structures is tension cracking of concrete piling, resulting from improp- er driving practices. Both under water and in the splash zone, cracks in concrete increase concrete permeability near the crack. Thus in seawater, chloride penetration is
46、amplified both in depth and concentration in the immediate location of the crack, leading to creation of an anode at the reinforcing bar. This usually does not lead to significant corrosion of un- derwater concrete because of the low oxygen content and the sealing of the crack by lime, which leaches
47、 from the concrete and also comes from marine organisms. In the splash zone, however, the presence of such cracks can lead to the early onset of localized corrosion. Construction or design errors can result in formwork col- lapse, blowouts of pressurized caissons, and breaches in cofferdams. These s
48、ituations usually require reconstruction and are beyond the scope of this guide. 2.3Chemical attack Concrete under water is susceptible to deterioration caused by a wide range of chemicals. This deterioration may be classified as that caused by chemicals outside the con- crete, and that caused by ch
49、emicals present in the concrete constituents themselves. In situations of external attack, the water frequently provides a continuous fresh supply of these chemicals. The water also washes the reaction products away and removes loose aggregate particles, exposing new concrete surfaces to further attack. Internal attack is accelerated by porous concrete, cracks, and voids. Alkali-silica reactions and corrosion of reinforce- ment are examples of internal attack. Internal deterioration also results when