1、 Standard Practice Inspection Methods for Corrosion Evaluation of Conventionally Reinforced Concrete Structures 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 precl
2、ude 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 construed as granting any right, by implication
3、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 requirements and should in no way be interpreted a
4、s 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 International assumes no responsibility for the interpreta
5、tion 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 interpretations by individual volunteers. Users of
6、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 may not necessarily address all potential health
7、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 health, safety, and environmental protection pract
8、ices, 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 CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withdrawn at
9、 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 date of each reaffirmation or revision. The user i
10、s 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 FirstService Department, 1440 South Creek Dr., Houston, Texas 77084-4906 (telephone +1
11、281-228-6200). Approved 2008-06-20 NACE International 1440 South Creek Drive Houston, Texas 77084-4906 +1 281-228-6200 ISBN 1-57590-220-6 2008, NACE International SP0308-2008 Item No. 21128 SP0308-2008 NACE International i _ Foreword This NACE International standard practice provides testing procedu
12、res and investigative techniques for the evaluation of conventionally reinforced concrete structures. The investigation and evaluation techniques described in this standard focus on degradation resulting from corrosion of the reinforcing steel. When distress of a structure is evident, it is importan
13、t to determine the nature of the degradation to select the best restoration strategy. Although this standard does not specifically address restoration options, additional information on repairs and corrosion mitigation techniques can be found in other NACE International standard practices, test meth
14、ods, and state-of-the-art reports, and other publications.1-17This standard is intended for use by corrosion specialists, civil engineers, and structural engineers involved with evaluating corrosion of reinforcing steel in concrete. It also may be useful to owners of reinforced concrete structures w
15、hose service life may be affected by reinforcing steel corrosion. NACE Task Group (TG) 055 prepared this standard. The TG is composed of manufacturers, users, consulting engineers, and other interested parties, and this standard represents a consensus of those members. This standard is not intended
16、to be all encompassing. However, it provides information that allows the user to perform testing and evaluation of atmospherically exposed reinforced concrete structures that are believed damaged from corrosion of the reinforcing steel. Note that the information gathered during this investigation ma
17、y require subsequent investigation and evaluation by qualified structural engineering personnel, depending on the nature and extent of degradation. This standard was prepared in 2008 by NACE TG 055, a component of Specific Technology Group (STG) 01Reinforced Concrete, and is also sponsored by STG 62
18、Corrosion Monitoring and Measurement: Science and Engineering Applications. It is published 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 mu
19、st 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 considered optional. _ SP0308-2008 ii NACE International _ NACE International Standard Practi
20、ce Inspection Methods for Corrosion Evaluation of Conventionally Reinforced Concrete Structures Contents 1. General 1 2. Definitions. 1 3. Technique Selection 1 4. Corrosion Survey. 2 5. Evaluation and Report. 16 References 16 _ SP0308-2008 NACE International 1 _ Section 1: General 1.1 Inspecting an
21、d monitoring the condition of reinforced concrete involves the use of a number of evaluation techniques, ranging from simple visual inspections that identify rust staining, cracks, and delamination, to physical and chemical inspection methods, which use hammer rebound, ultrasonic testing, electrical
22、 resistance, chemical analyses, or electrochemical potential and corrosion rate measurements. A number of relevant standards and overview technical papers that discuss issues germane to corrosion inspection of reinforced concrete structures are available.18-32 In 1993, a manual related to this topic
23、 was published.331.2 The purpose of this standard is to provide the corrosion specialist, engineer, or owner a framework for evaluating the corrosion condition of a reinforced concrete structure beyond simple visual inspection and basic sounding techniques. Evaluation techniques that identify genera
24、l and localized corrosion of conventional reinforcement are provided. Although this standard specifically addresses conventionally reinforced structures, many of the techniques also apply to prestressed and post-tensioned reinforcement. Commentary is included for screening corrosion control methods
25、that might be considered as part of recommendations for restoration of the reinforced concrete structure being evaluated. However, it is beyond the scope of this standard to fully address all factors associated with the design, criteria, and implementation of such corrosion control measures. _ Secti
26、on 2: Definitions Electrode Potential: The potential of an electrode in an electrolyte as measured against a reference electrode. (The electrode potential does not include any resistance losses in potential in either the electrolyte or the external circuit. It represents the reversible work to move
27、a unit of charge from the electrode surface through the electrolyte to the reference electrode.) Electrometer: A highly sensitive electronic voltmeter whose input impedance is so high that the current flowing into it can be considered, for practical purposes, to be zero. To obtain accurate potential
28、 measurements in high-resistivity concrete, the required impedance may exceed 109 . Fickian Behavior: A process that follows Ficks laws of diffusion. Laitance: A milky white deposit of fine particles on the surface of cement or concrete. Pozzolan: A material that, when combined with water and calciu
29、m hydroxide or alkali oxides, exhibits cementitious properties. _ Section 3: Technique Selection 3.1 The selection and application of specific techniques depends on the particular structure and the purpose of the survey. A detailed program of inspection for one structure is not necessarily directly
30、applicable to a different structure. 3.2 Basic surveys, carried out at regular intervals, e.g., every one or two years, normally rely on relatively simple inspection methods. However, if corrosion or premature deterioration is suspected, or has occurred, a detailed survey involving additional techni
31、ques is required to ascertain the extent and degree of damage. In some cases, this may require sophisticated techniques to identify the nature and cause of the deterioration, highlight areas of particular damage or concern, and estimate the remaining life expectancy. 3.3 Procedures for inspecting co
32、ncrete structures on site include: (a) Visual inspection techniques; (b) Crack inspection; (c) Delamination survey; (d) Cover thickness survey and reinforcement location; (e) Assessment of concrete strength and condition; (f) Corrosion potential measurements; (g) Corrosion rate measurement; SP0308-2
33、008 2 NACE International (h) Carbonation depth measurement; (i) Concrete resistivity measurement; (j) Electrical continuity testing of reinforcement; (k) Chloride content measurement and chloride profile determination in the concrete; and (l) Other advanced techniques. 3.4 Evaluation Evaluation of s
34、urvey findings is defined in large part by the type of structure being inspected. Given the wide range of reinforced concrete structures that may suffer corrosion distress, it is not possible to provide a single evaluation protocol. Rather, it is important that the findings of the corrosion survey b
35、e reviewed by corrosion specialists with in-depth experience in the area of reinforcement corrosion, and that the specialists discuss those findings with appropriate structural or civil engineers and architects. 3.5 Repair History Previous repairs should be investigated. Often, cosmetic or “fill the
36、 hole” patching can aggravate corrosion. Some repairs, such as epoxy injection, may present problems, and should be noted if cathodic protection (CP) is considered as a corrosion control strategy. All previous repairs, and the success or failure of the repairs, should be identified. _ Section 4: Cor
37、rosion Survey 4.1 Scope A corrosion survey of a reinforced concrete structure is often a component of a large condition and rating process. It is important that the information collected during the corrosion survey is concise and clearly presented. To achieve that, investigators coming from a corros
38、ion paradigm must become familiar with the basics of reinforced concrete construction. Likewise, if an investigator comes from a civil engineering or architectural paradigm, they must become familiar with reinforcing steel corrosion processes. 4.2 Environmental Factors A number of environmental fact
39、ors should be considered when a corrosion survey is performed. Descriptions of some of the most important factors follow. Some indication as to their effects on design or feasibility of restoration methods is given. 4.2.1 Temperature Temperature is a significant factor in the observed reinforcement
40、corrosion rate. The mean temperature, average temperature range, and extremes that can be encountered, as well as diurnal cycles of temperature, are all important and should be documented. In nonarid environments, freezing and thawing of concrete may be destructive to concrete structures. In arid en
41、vironments, although freezing of water may not be a problem, temperature cycling may result in differential thermal stress effects. In extremely warm and humid environments, reinforcing steel corrodes at a faster rate than in cooler and drier environs. In extremely low temperatures, the corrosion ra
42、te may become very small, and some tests may not provide meaningful results. 4.2.2 Precipitation Precipitation or condensation affects the moisture content of the top layer of concrete. This influences transport of aggressive ions into the bulk concrete. At times of low precipitation or high evapora
43、tion rates, moisture conditions may not be uniform in the outer layers of concrete. In very wet areas, it may be necessary to provide additional attention to corrosion control methods and components. In areas where freezing occurs, expansion of ice may exert pressures on components; therefore, consi
44、deration should be given to additional protection of components in such environments. Wetting the concrete reduces the concrete resistivity, making passage of corrosion currents easier. 4.2.3 Load Factors Imposed mechanical stresses potentially aggravate corrosion. These may include stresses generat
45、ed by traffic (especially trucks) loading, wind load, seismic effects, and wave or ice action. In areas where such stresses are significant, cracking may be present. Load factors should be taken into account when an inspection is planned, and sufficient time should be allocated to investigate if loa
46、d is facilitating corrosion activity. 4.2.4 Environments with Submerged or Saturated Elements 4.2.4.1 Seawater environments with submerged elements require special considerations. Tide and splash zone effects create microenvironments with differing moisture, chloride, and oxygen contents. This is es
47、pecially true in vertical members such as piers and columns. SP0308-2008 NACE International 3 4.2.4.2 Corrosion is generally highest in the splash zone and upper tidal zone. Generally, fully saturated elements do not suffer serious corrosion problems. However, with prestressed piles or poorly consol
48、idated conventionally reinforced piles, initial installation may create serious problems. If reinforcing steel that is directly exposed to the surrounding seawater, e.g., from spalling during driving, is installed, a large cathode/small anode situation may exist, causing the exposed steel to corrode at an accelerated rate.
