1、 Standard Practice Maintenance and Rehabilitation Considerations for Corrosion Control of Atmospherically Exposed Existing Steel-Reinforced Concrete Structures This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisio
2、ns. Its acceptance does not in any respect preclude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to be
3、construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum re
4、quirements and should in no way be interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE Internatio
5、nal assumes no responsibility for the interpretation or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of int
6、erpretations by individual volunteers. Users of this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard m
7、ay not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE International standard are also responsible for establishing appropriate he
8、alth, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to per
9、iodic review, and may be revised or withdrawn at any time in accordance with NACE technical committee procedures. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication and subsequently from the da
10、te of each reaffirmation or revision. The user is cautioned to obtain the latest edition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International First Service Department, 1440 South Cr
11、eek Dr., Houston, Texas 77084-4906 (telephone +1 281-228-6200). NACE SP0390-2009 (formerly RP0390) Item No. 21044 Revised 2009-11-08 Reaffirmed 2006-03-14 Revised 1998-06-26 Approved 1990-04-12 NACE International 1440 South Creek Drive Houston, Texas 77084-4906 +1 281/228-6200 ISBN 1-57590-059-9 200
12、9, NACE International SP0390-2009 NACE International i _ Foreword Corrosion of reinforcing steel in concrete is a serious problem in certain environments throughout the world. This corrosion is directly attributable to the presence of significant amounts of chloride or other aggressive substances at
13、 the steel surface. Parking structures, bridges and roadways, buildings, sanitary and water facilities, marine structures, concrete pipe, storage facilities, and other reinforced concrete structures are being damaged by corrosion. Corrosion of the reinforcing steel can weaken or destroy a structure.
14、 Corrosion of the reinforcing steel in concrete and the resulting cracking and spalling of concrete cost billions of dollars each year. These losses can be reduced if proper corrosion control factors are considered during rehabilitation and maintenance repair of reinforced concrete structures. The p
15、urpose of this standard is to give maintenance personnel, engineers, and facility owners the necessary considerations for corrosion control of existing atmospherically exposed steel-reinforced concrete structures. These considerations include guidelines to control corrosion of reinforcing steel in p
16、ortland cement concrete structures. The provisions of this standard should be applied under the direction of a registered professional engineer or a person certified by NACE as a corrosion specialist or cathodic protection (CP) specialist. His or her professional experience should include suitable e
17、xperience in corrosion control of reinforced concrete structures. This NACE standard was originally prepared in 1990 by NACE Task Group (TG) T-3K-5, a component of Unit Committee T-3K, “Corrosion and Other Deterioration Phenomena Associated with Concrete.” To provide the necessary expertise on all a
18、spects of the subject and to gain input from all interested parties, TG T-3K-5 was composed of corrosion consultants, consulting engineers, architect-engineers, CP engineers, researchers, structure owners, and representatives from industry and government. Unit Committee T-3K became Group Committee T
19、-11, “Corrosion and Deterioration of the Infrastructure,” and later Specific Technology Group (STG) 01, “Reinforced Concrete.” This standard was revised by TG T-11-4a in 1998 and reaffirmed by STG 01 in 2006. It was revised in 2009 by TG 324, “Reinforced Concrete: Maintenance and Rehabilitation Cons
20、iderations for Existing Structures.” It is published by NACE under the auspices of STG 01. In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual. The terms shall and must are used to state a requirem
21、ent, and are considered mandatory. The term should is used to state something good and is recommended, but is not considered mandatory. The term may is used to state something considered optional. _ SP0390-2009 ii NACE International _ NACE International Standard Practice Maintenance and Rehabilitati
22、on Considerations for Corrosion Control of Atmospherically Exposed Existing Steel-Reinforced Concrete Structures Contents 1. General 1 2. Definitions 2 3. Periodic Inspection and Routine Maintenance 3 4. Assessment of Reinforced Concrete Structures . 5 5. Corrosion Control Techniques and Repair Stra
23、tegy . 7 References 13 Bibliography 14 FIGURES Figure 1: Repair or Rehabilitation Strategy Flow Chart 4 _ SP0390-2009 NACE International 1 _ Section 1: General 1.1 This standard presents corrosion control guidelines that are applicable to existing atmospherically exposed structures made of concrete
24、conventionally reinforced with carbon steel (ASTM(1)A 6151). These guidelines may be used to develop specifications involving repair and rehabilitation of steel-reinforced concrete structures. These guidelines should be used primarily when repair or rehabilitation is being implemented because of det
25、erioration resulting from the corrosion of steel reinforcement. 1.1.1 Reinforcing steel is compatible with concrete, not only because of similar thermal expansion characteristics, but also because the highly alkaline portland cement allows a stable, protective oxide film to form on the surface of th
26、e encased steel. If the film does not form or is weakened or destroyed so that it does not protect the steel, corrosion can occur. The protective oxide film does not form or is destroyed if (1) the cement paste is not in contact with the reinforcing such as at voids and cracks; (2) alkalinity is los
27、t by reaction with certain gases and liquids; or (3) excessive amounts of chloride or other aggressive ions are present. It has been shown that chloride ion content as low as approximately 0.2 percent by weight of cement (or approximately 0.6 kg/m3 1 lb/yd3 of concrete, depending on the cement conte
28、nt of the mix) at the steel depth can initiate the corrosion process. If one or more of these conditions are present, and moisture and oxygen are available to the embedded reinforcing steel, an electrochemical cell forms, resulting in corrosion. 1.1.2 Corrosion most commonly proceeds by the formatio
29、n of an electrochemical cell. This electrochemical cell is composed of four elements: (1) an anode; (2) a cathode; (3) an electrical connection between the two; and (4) an ionic connection provided by an electrolyte (concrete). Direct current (DC) caused by electrochemical potential differences, suc
30、h as between different metals or the same metal in different environments, flows from the anodic area to the cathodic area through the electrolyte. Corrosion occurs at the anode, where the current leaves the metal. If any one of the elements of the electrochemical cell is eliminated, corrosion can b
31、e prevented. Dissimilar metal couples and stray DC can initiate and accelerate corrosion. 1.1.3 The corrosion product of iron occupies several times the volume of the base metal. The expansive pressure exerts a significant tensile force on the surrounding concrete. The resulting cracks propagate eit
32、her to the surface or to nearby reinforcing steel, resulting in a delamination. Steel sectional losses, which may or may not have structural significance, can generate cracking of the concrete. Bond forces and corrosion both put concrete in tension and are additive. Relatively small amounts of metal
33、 loss at the surface of the reinforcing steel can be sufficient to crack the concrete cover and result in the loss of bond and anchorage. Other problems resulting from delamination and spalling include danger from falling concrete, increased corrosion, loss of fireproofing, and safety considerations
34、. 1.1.4 Other forms of corrosion, such as those caused by dissimilar metal couples and DC stray currents, can initiate or accelerate corrosion. 1.2 This standard describes various approaches that may be taken with respect to corrosion control of existing structures. The flow chart in Figure 1 deline
35、ates the repair or rehabilitation strategy covered in this standard. Because of the complexity of corrosion problems on individual structures, advice from a professional engineer or a corrosion specialist, whose professional qualifications include suitable experience in corrosion control of reinforc
36、ed concrete structures, should be sought before proceeding with repair and rehabilitation programs. Also, a structural engineer may be required if a decision on structural integrity is needed. 1.3 This standard does not cover pretensioned and post-tensioned reinforced concrete. (1) ASTM Internationa
37、l (ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959. SP0390-2009 2 NACE International _ Section 2: Definitions Anode: The electrode of an electrochemical cell at which oxidation occurs. Electrons flow away from the anode in the external circuit. Corrosion usually occurs and metal ions en
38、ter the solution at the anode. Cathode: The electrode of an electrochemical cell at which reduction is the principal reaction. Electrons flow toward the cathode in the external circuit. Cathodic Protection: A technique to reduce the corrosion of a metal surface by making that surface the cathode of
39、an electrochemical cell. Corrosion: The deterioration of a material, usually a metal, that results from a reaction with its environment. Corrosion Specialist: A person certified by NACE International through verification of experience and examinations that demonstrate an advanced understanding of co
40、rrosion theory and mechanisms, corrosion monitoring and control, management, and professional conduct as well as a high level of knowledge and ability in the area of specialization. Delamination: A separation of the concrete (usually in layers) from the reinforcing steel at the interface, usually as
41、 a result of corrosion. Disbondment: The loss of adhesion between a coating and the substrate. Dissimilar Metals: Different metals that could form an anode-cathode relationship in an electrolyte when connected by a metallic path. Efflorescence: A growth of salt crystals on the concrete surface cause
42、d by evaporation of salt-laden water. Electrochemical Cell: A system consisting of an anode and a cathode immersed in an electrolyte so as to create an electrical circuit. The anode and cathode may be different metals or dissimilar areas on the same metal surface. Electrolyte: A chemical substance c
43、ontaining ions that migrate in an electric field. For the purposes of this standard, electrolyte refers to the concrete, including moisture and other chemicals contained therein. Galvanic Corrosion: Accelerated corrosion of a metal because of an electrical contact with a more noble metal or nonmetal
44、lic conductor in a corrosive electrolyte. Macrocell: A corrosion cell composed of relatively large anodic and cathodic sites. Macroenvironment: The climate of an entire area as opposed to localized effects. Microclimate: The climate of a small area as contrasted with the climate of the entire area,
45、as a result of various factors such as local topography of a structural member and variations in the surface characteristics. Spalling: The spontaneous chipping, fragmentation, or separation of a surface or surface coating. Stray Current: Current through paths other than the intended circuit. SP0390
46、-2009 NACE International 3 _ Section 3: Periodic Inspection and Routine Maintenance 3.1 Periodic routine visual inspections of the structure should be carried out to note areas of distress. These inspections should include the following: 3.1.1 Visual Inspections 3.1.1.1 CracksCracking of the concret
47、e that appears to be coincident with reinforcement locations should be recorded. These cracks should be distinguished from structural and other types of cracks that are not corrosion related or likely to accelerate corrosion. 3.1.1.2 SpallsCorrosion-related and all other spalls should be noted. 3.1.
48、1.3 Rust stainsCorrosion products seen on the concrete surface may indicate corrosion of steel embedded in the concrete. 3.1.1.4 DrainagePonded areas can accelerate local corrosion of reinforced concrete structures. 3.1.1.5 Waterproofing systems should be inspected for deterioration as follows: 3.1.1.5.1 SealantsAreas of disbonding, cracking, crazing, or loss of elasticity should be noted. 3
