1、 Standard Practice Electrochemical Realkalization and Chloride Extraction for Reinforced Concrete This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone, wh
2、ether 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 construed as granting any right, by implication or otherwise,
3、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 requirements and should in no way be interpreted as a restrictio
4、n 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 International assumes no responsibility for the interpretation or use of
5、 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 interpretations by individual volunteers. Users of this NACE Int
6、ernational 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 may not necessarily address all potential health and safety pr
7、oblems 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 health, safety, and environmental protection practices, in cons
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9、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. The user is cautioned to obtain the latest edition. Purchasers of NACE International sta
10、ndards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Dr., Houston, Texas 77084-4906 (telephone +1281228-6200). Approved 2007-03-10 NACE International 1440 South Creek Drive Hou
11、ston, Texas 77084-4906 +1 281/228-6200 ISBN 1-57590-210-9 2007, NACE InternationalNACE SP0107-2007 Item No. 21113 SP0107-2007 NACE International i _ Foreword This NACE standard practice presents the requirements for electrochemical chloride extraction and electrochemical realkalization of reinforcin
12、g steel in atmospherically exposed concrete structures. The standard provides the design engineer and contractor with the requirements for control of corrosion of conventional reinforcing steel in Portland cement concrete structures through the application of chloride extraction or realkalization. T
13、his standard is aimed at owners, engineers, architects, contractors, and all those concerned with rehabilitation of corrosion-damaged reinforced concrete structures. These electrochemical techniques are related to the use of impressed current cathodic protection of steel in concrete as described in
14、NACE SP0290.1State-of-the-art reports on the techniques were previously published by the task group and are available from NACE.2,3For more information on design, maintenance, and rehabilitation of reinforcing steel in concrete, refer to NACE Standard RP01874and NACE Standard RP0390.5To provide for
15、the necessary expertise on all aspects of the subject and to provide input from all interested parties, Task Group (TG) 054 is composed of corrosion consultants, consulting engineers, architect engineers, cathodic protection engineers, researchers, structure owners, and representatives from both ind
16、ustry and government. The provisions of this standard should be applied under the direction of a registered Professional Engineer or a person certified by NACE International as a Corrosion Specialist or Cathodic Protection Specialist. His or her professional experience should include suitable experi
17、ence in corrosion control of reinforced concrete structures. This standard was prepared in 2007 by NACE TG 054, a component of Specific Technology Group (STG) 01 on Reinforced Concrete, and is published under the auspices of STG 01. In NACE standards, the terms shall, must, should, and may are used
18、in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements. The term should is used to state something good and is recommended but is not mandatory. The term may is used to state somethi
19、ng considered optional. _ SP0107-2007 ii NACE International _ NACE International Standard Practice Electrochemical Realkalization and Chloride Extraction for Reinforced Concrete Contents 1. General 1 2. Electrochemical Chloride Extraction 2 3. Electrochemical Realkalization 6 References 10 Bibliogra
20、phy 11 _ SP0107-2007 NACE International 1 _ Section 1: General 1.1 Background 1.1.1 Following this General section, this standard is divided into two stand-alone sections, the first on electrochemical chloride extraction and the second on electrochemical realkalization. This will help the user by en
21、suring that all the relevant provisions are in one place. 1.1.2 Reinforcing steel is compatible with concrete because of similar coefficients of thermal expansion and because concrete normally provides the steel with excellent corrosion protection. The corrosion protection is the result of the forma
22、tion of a highly alkaline passive oxide film on the surface of the reinforcement by Portland cement contained in the concrete. This passive oxide film is compromised by (1) excessive amounts of chloride or other aggressive ions and gases such as carbon dioxide, or (2) the concrete not fully encasing
23、 the steel. 1.1.3 Corrosion occurs as a result of the formation of an electrochemical cell. An electrochemical cell consists of four components: an anode, where oxidation occurs; a cathode, where reduction occurs; a metallic path, where the electrons flow; and an electrolyte (concrete), where the io
24、ns flow. The anodic and cathodic areas occur as a result of coupling of dissimilar metals, exposure to differential environmental conditions, or both. If any one of the four elements of the electrochemical cell is eliminated, corrosion can be prevented. 1.1.4 Corrosion of reinforcing steel in concre
25、te is a serious problem in certain environments throughout the world. This corrosion is directly attributable to the presence of significant amounts of aggressive substances at the steel surface. Parking structures, bridges and roadways, buildings, sanitary and water facilities, marine structures, c
26、oncrete pipe, storage facilities, and other reinforced concrete structures are being damaged by corrosion. Corrosion of the reinforcing steel can weaken or destroy a structure. Corrosion of the reinforcing steel in concrete and the resulting cracking and spalling of concrete costs billions of dollar
27、s/euros, etc., each year. These losses can be reduced if proper corrosion control factors are considered during rehabilitation and maintenance repair of reinforced concrete structures. 1.1.5 Carbonation of concrete is a major cause of reinforcement corrosion. Carbonation is a process by which atmosp
28、heric carbon dioxide reacts with the alkalis in the pore water of the concrete. A carbonation front proceeds through the cover concrete to the reinforcement, where it leads to the breakdown of the passive oxide layer, allowing corrosion to proceed. Electrochemical realkalization can be used to rever
29、se this process and restore the alkaline environment to the reinforcement, preventing further corrosion. 1.1.6 Chloride-induced corrosion is the other major cause of reinforcement corrosion. It has been shown that chloride ion content as low as approximately 0.2 percent by weight of cement (or appro
30、ximately 0.6 kg/m3 1 lb/yd3 of concrete, depending on the cement content of the mix) at the steel depth can initiate the corrosion process. Electrochemical realkalization can be used to move chloride ions away from the steel surface and reestablish the protective passive oxide layer. 1.2 Electrochem
31、ical Treatments 1.2.1 Electrochemical treatments for reinforced concrete include cathodic protection (CP), electrochemical chloride extraction (ECE), and electrochemical realkalization (ER). ECE and ER are short-term treatments with a temporary installation that is removed after treatment. Treatment
32、 is intended to remove the cause of corrosion. On the other hand, CP is a permanent installation. CP of atmospherically exposed steel in concrete is described in NACE SP0290.1Many of the practices described in SP0290 are relevant to ECE and ER in terms of preparation of the structure, testing, and w
33、iring. 1.3 Scope and Limitations 1.3.1 The provisions of this standard shall be applied under the direction of a registered Professional Engineer or a person certified by NACE International as a Corrosion Specialist or certified as a Cathodic Protection Specialist. The persons professional experienc
34、e shall include suitable experience in CP, ECE, and ER. 1.3.2 The requirements presented here are limited to impressed current ECE and ER systems for new or existing atmospherically exposed reinforced concrete elements; they are not applicable to prestressed concrete. 1.3.3 Normal reinforcement in p
35、ost-tensioned elements with the post-tensioning strands fully protected in ducts can be treated as long as adequate precautions are taken to ensure that the prestressed steel is not susceptible to hydrogen embrittlement and that it is protected such that the potential of the steel does not rise abov
36、e the hydrogen evolution potential. SP0107-2007 2 NACE International _ Section 2: Electrochemical Chloride Extraction 2.1 Suitability for Treatment A structure shall be suitable for ECE if: 2.1.1 There is sufficient chloride contamination to warrant generalized or localized treatment to retard furth
37、er chloride attack. 2.1.2 Water ingress can be controlled during treatment so that the current density to the steel can be maintained and accurately monitored, especially in marine conditions. ECE is not suitable for application to the elements of structures in splash and tidal zones. 2.1.3 There is
38、 no prestressed steel susceptible to hydrogen embrittlement in the area to be treated. Any prestressed steel shall be monitored to ensure that its potential does not go more negative than -1,100 mV vs. a copper/copper sulfate reference electrode. 2.1.4 Any susceptibility to alkali silica reaction (A
39、SR) is addressed by analysis of the risk of further ASR expansion and, if necessary, by the use of a suitable electrolyte as discussed in Paragraph 2.3.2. 2.2 End Point Criteria 2.2.1 The criteria in this section have been found to achieve corrosion control for reinforcing steel embedded in atmosphe
40、rically exposed concrete after the application of ECE. Compliance with these criteria is dependent on analysis of representative data in each situation. The number and locations of measurements made during data collection shall be commensurate with the complexity of the structure being protected. Sa
41、mpling plans shall be in accordance with ASTM(1)E105.6Sample size shall be determined in accordance with ANSI(2)/ASQ(3)Z1.47with the unit of product typically being 0.836 m2 (1.00 yd2) of protected metal surface area. For structures in which ECE or ER systems are divided into discrete zones, testing
42、 inspection lots shall be defined. Acceptable quality and confidence levels shall also be defined. Potentials of reinforcing steel or other embedments measured against portable reference electrodes shall be obtained in accordance with the techniques described in ASTM C876.8 Sign conventions for pote
43、ntial and current density as well as conventions for graphical presentation of data shall be in accordance with ASTM G3-89.92.2.2 NACE TG 054 developed these criteria through evaluation of data obtained from successfully operated ECE systems. NOTE: Those using this standard shall review data made av
44、ailable after this standards publication to determine whether more effective criteria have been established. It is not intended that those responsible for corrosion control be limited to these criteria if it can be demonstrated by other means that adequate corrosion control can be achieved. A combin
45、ation of criteria can be used on a single structure. 2.2.3 In all cases, the current density shall not exceed 4 A/m2(0.4 A/ft2) of steel surface area, and the voltage shall be in the range of 30 to 50 V direct current (DC). 2.2.4 Electrochemical Chloride Extraction Criteria At least one of criterion
46、 A, B, or C below (Paragraphs 2.2.4.1, 2.2.4.2, and 2.2.4.3) shall be used: 2.2.4.1 Criterion AChloride content within the concrete: Treatment shall be continued until the chloride content within the concrete in the vicinity of the reinforcing steel is reduced to a predetermined level. A suitable te
47、st method for chloride determination is ASTM C1152/C1152M-04e1.10Treatment is halted when the target chloride value is reached. Samples are collected carefully to prevent contamination and are located relative to the location of the rebar. Because of the inhomogeneous nature of embedded concrete, sa
48、mples are statistically analyzed to account for natural variations in chloride content. NOTE: Typical target values used for these measurements are acid-soluble chloride content of less than 0.2 to 0.4% by weight of cement (when corrected for background levels of chloride permanently bound in aggregates, if appropriate) within 25 mm (1.0 in.) or one diameter of the reinforcing steel. 2.2.4.2 Criterion BAmp hours (A-h) per square meter (per square foot): Th
