1、 Standard Practice Design Considerations for Corrosion Control of Reinforcing Steel in 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, whet
2、her 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, to
3、 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 restriction
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7、ems 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 consult
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9、ordance 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 date of each reaffirmation or revision. The user is cautioned to o
10、btain 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 FirstService Department, 1440 South Creek Dr., Houston, TX 77084-4906 (telephone +1 281-228-6200). Revi
11、sed 2008-06-20 Reaffirmed 2005-04-07 Revised 1996-03-30 Reaffirmed 1990-09 Approved 1987-04 NACE International 1440 South Creek Drive Houston, Texas 77084-4906 +1 281-228-6200 ISBN 1-57590-012-2 2008, NACE International NACE SP0187-2008 (formerly RP0187-2005) Item No. 21034 SP0187-2008 NACE Internat
12、ional i _ Foreword Corrosion of reinforcing steel in concrete is a serious problem in certain environments. The major cause of reinforcing steel corrosion is the presence of significant amounts of chloride or other aggressive ions at the surface of the steel. Reinforced concrete parking structures,
13、bridges and roadways, buildings, wastewater and water facilities, marine structures, pipe, storage facilities, and other reinforced concrete structures are being damaged by the corrosion of the reinforcing steel. The purpose of this standard is to give designers and facility owners design considerat
14、ions for controlling corrosion of proposed reinforced concrete structures. These considerations include guidelines that provide the designer with information about the causes of and control methods for the corrosion of reinforcing steel in portland cement concrete structures. This NACE standard was
15、originally prepared in 1987 by NACE Task Group (TG) T-3K-5, a component of Unit Committee T-3K on Corrosion and Other Deterioration Phenomena Associated with Concrete. To provide the necessary expertise on all aspects of the subject and to provide input from all interested parties, Task Group T-3K-5
16、 was composed of corrosion consultants, consulting engineers, designers, cathodic protection (CP) engineers, researchers, structure owners, and representatives from industry and government. This standard was reaffirmed in 1990 and revised in 1996. It was reaffirmed by Specific Technology Group (STG)
17、 01Reinforced Concrete in 2005. This standard was revised in 2008 by TG 290Reinforced Concrete: Design Considerations for Corrosion Control. It is published by NACE International under the auspices of STG 01. In NACE standards, the terms shall, must, should, and may are used in accordance with the d
18、efinitions of these terms in the NACE Publications Style Manual. The terms shall and must are used to state a requirement, 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 consid
19、ered optional. _ SP0187-2008 ii NACE International _ NACE International Standard Practice Design Considerations for Corrosion Control of Reinforcing Steel in Concrete Contents 1. General 1 2. Definitions 2 3. Achieving Service Life by Design 4 4. Site History and Environmental Survey. 8 5. Design Co
20、nsiderations 10 6. Selection of Construction Materials. 11 7. Preventive Measures Applied to Concrete 12 8. Preventive Measures on Steel 13 9. Cathodic Protection. 13 10. Corrosion Monitoring System 14 11. Construction Practices 15 12. Monitoring and Maintenance. 16 References 16 Bibliography 18 _SP
21、0187-2008 NACE International 1 _ Section 1: General 1.1 This standard presents corrosion control guidelines that are applicable to structures made of steel-reinforced portland cement concrete. 1.2 State of Steel in Concrete 1.2.1 Reinforcing steel is compatible with concrete not only because of simi
22、lar thermal expansion properties, but also because the highly alkaline pore solution in portland cement pastes allows a stable, protective oxide film to form on the surface of the encased steel. 1.2.2 If the protective oxide film does not form on the steel surface or if it does not protect the whole
23、 surface of the steel, corrosion can occur. Corrosion of the reinforcing steel can cause cracking and spalling of concrete, weaken its load-bearing capacity, or even destroy a structure. 1.2.3 The protective oxide film on the steel surface is not formed or can be destroyed if (1) the concrete does n
24、ot fully encase the steel, (2) alkalinity is lost by reaction with aggressive substances, or (3) excessive amounts of chloride or other aggressive ions are present in the vicinity of the steel. If any of these conditions occurs, and both sufficient moisture and oxygen are in contact with the steel,
25、corrosion can occur. 1.2.4 Corrosion proceeds by the formation of an electrochemical cell, including anodic and cathodic areas that are electrically coupled on the metal, with the pore solution of the cement paste acting as the electrolyte. If any one of the elements of the electrochemical cell is e
26、liminated, corrosion can be prevented. 1.2.5 Other forms of corrosion such as those caused by dissimilar metal couples and direct current (DC) stray currents can initiate or accelerate corrosion. 1.3 Damage to Concrete Caused by Steel Corrosion The corrosion process can damage concrete in several wa
27、ys, including cracking, loss of bond, and localized corrosion. 1.3.1 Cracking The corrosion products of steel often occupy several times the volume of the base metal. The expansive pressure because of this volume increase exerts a significant tensile force on the surrounding concrete. Resulting crac
28、ks propagate toward either the concrete surface or nearby reinforcing steel, causing delamination. A small loss of steel can cause concrete delamination, but structural integrity remains undiminished until corrosion has removed a significant amount of reinforcing steel. 1.3.2 Loss of Bond Bond stres
29、ses and corrosion both put concrete in tension and are additive. Even minor metal loss at the surface of the reinforcing steel can be sufficient to crack the concrete cover and cause loss of bond. Other problems caused by loss of cover include spalling and falling concrete, increased steel corrosion
30、, and reduction in the structural integrity of the structure. 1.3.3 Localized Corrosion Localized corrosion of the reinforcement can also occur. Localized corrosion can result in significant reinforcement section loss without generating the tensile hoop stresses necessary to crack or delaminate the
31、concrete. Typically, this problem occurs at construction joints, non-corrosion-related cracks (e.g., from early removal of formwork), or where the structural steel exits the concrete. The high section loss possible in localized corrosion carries serious structural implications. 1.4 Scope and Limitat
32、ions 1.4.1 Because of the concrete damage caused by the corrosion products formed on reinforcing steel, the designer should consider certain corrosion criteria during the design of the structure. Design and construction considerations should be based on good engineering practices to eliminate condit
33、ions conducive to corrosion. The guidelines in this standard give the designer several alternative methods of controlling the corrosion of a proposed atmospherically exposed, submerged, or buried reinforced concrete structure. 1.4.2 This standard does not designate specific design practices for the
34、control of corrosion because of the complexity of corrosion mechanisms in individual structures. This standard does not cover areas such as welding of reinforcement for which other professional societies have published pertinent standards. Although many of the statements in this standard are applica
35、ble to prestressed concrete structures, this standard does not address this type of reinforcing system. 1.4.3 The standards mentioned here (American Concrete Institute ACI,(1) ASTM International _ (1) American Concrete Institute (ACI), P.O. Box 9094, Farmington Hills, MI 48333. SP0187-2008 2 NACE In
36、ternational ASTM,(2)and American Association of State Highway and Transportation Officials AASHTO(3), have been prepared for applications in the U.S. The international practitioner should refer to local standards, if such are available. 1.4.4 During the design phase of a reinforced concrete structur
37、e that could be affected by corrosion, the services of a qualified Professional Engineer or qualified Corrosion Specialist shall be obtained so that proper materials selection and engineering practices for corrosion control are included in the design. Professional qualifications shall include suitab
38、le experience in corrosion control of reinforced concrete structures. The provisions of this standard shall be applied under the responsible charge of said Professional Engineer or Corrosion Specialist. 1.5 Significance of Corrosion Control Corrosion of the reinforcing steel in concrete and the resu
39、ltant cracking and spalling of concrete cost billions of U.S. dollars or euros each year.1These losses can be reduced if proper corrosion control factors are considered during the design phase. When the designer considers corrosion of reinforcing steel to be a potential problem, provisions should be
40、 made for a cost-effective corrosion control system. _ Section 2: Definitions Admixture: A material or combination of materials (other than water, aggregates, hydraulic cement, and fiber reinforcement), used as an ingredient of concrete or mortar, and added to the batch immediately before or during
41、its mixing. 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 enter the solution at the anode. Assorted Hardware: A device or piece of material that is attached to the concret
42、e surface, such as handrails, anchor bolts, light poles, and signs. Bond Stress: The shear stress at the surface of a reinforcing steel bar, which prevents relative movement between the steel bar and the surrounding concrete. Carbonation (of Concrete): A process by which the carbon dioxide of the at
43、mosphere reacts with calcium hydroxide in the concrete pore solution, forming calcium carbonate and reducing the pH of the pore solution in concrete. Cathode: The electrode of an electrochemical cell at which reduction is the principal reaction. Electrons flow toward the cathode in the external circ
44、uit. (For the purposes of this standard, typical cathodic processes are cations taking up electrons and being discharged, oxygen or water being reduced, or the reduction of an element or group of elements from a higher to a lower valence state.) Cathodic Protection: A technique to reduce the corrosi
45、on of a metal surface by making that surface the cathode of an electrochemical cell. Cathodic Protection Specialist (CP Specialist): A person certified by NACE International through examinations and verification of experience to possess an advanced understanding of design, installation, and maintena
46、nce of cathodic protection systems, to possess a high level of knowledge and ability in his or her area of specialization, and to exhibit professional conduct. Chemical Admixture: An admixture, usually dispersed in the mixing water, that includes accelerating admixtures, air entraining admixtures, r
47、etarding admixtures, and water-reducing and high water-reducing admixtures. Concrete Consolidation: A compaction procedure followed after placement of concrete in order to eliminate voids and entrapped air. Conductive Coating: (1) A coating that conducts electricity. (2) An electrically conductive,
48、mastic-like material used as an impressed current anode on reinforced concrete surfaces. Corrosion Monitoring System: Testing equipment that may include reference cells, coupons, wire connections, or corrosion rate probes in or on the surface of reinforced concrete to determine levels of corrosion or cathodic protection. Corrosion Rate Probe: A testing device made of the same material as the reinforcing material that is pla
