ACI 365.1R-2000 Service-Life Prediction - State-of-the-Art Report《使用期限预测.技术发展水平报告》.pdf

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1、ACI 365.1R-00 became effective January 10, 2000.Copyright 2000, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by anymeans, including the making of copies by any photo process, or by electronic ormechanical device, printed, written, or oral, o

2、r recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission inwriting is obtained from the copyright proprietors.ACI Committee Reports, Guides, Standard Practices, andCommentaries are intended for guidance in planning, de-signing, execut

3、ing, and inspecting construction. This docu-ment is intended for the use of individuals who arecompetent to evaluate the significance and limitationsof its content and recommendations and who will acceptresponsibility for the application of the material it con-tains. The American Concrete Institute

4、disclaims any andall responsibility for the stated principles. The Institute shallnot be liable for any loss or damage arising therefrom.Reference to this document shall not be made in contractdocuments. If items found in this document are desired bythe Architect/Engineer to be a part of the contrac

5、t docu-ments, they shall be restated in mandatory language for in-corporation by the Architect/Engineer.365.1R-1Service-Life PredictionState-of-the-Art ReportACI 365.1R-00This report presents current information on the service-life prediction ofnew and existing concrete structures. This information

6、is important to boththe owner and the design professional. Important factors controlling theservice life of concrete and methodologies for evaluating the condition ofthe existing concrete structures, including definitions of key physical prop-erties, are also presented. Techniques for predicting the

7、 service life of con-crete and the relationship between economics and the service life ofstructures are discussed. The examples provided discuss which service-lifetechniques are applied to concrete structures or structural components.Finally, needed developments are identified.Keywords: construction

8、; corrosion; design; durability; rehabilitation;repair; service life.CONTENTSChapter 1Introduction, p. 365.1R-2 1.1Background1.2Scope1.3Document useChapter 2Environment, design, and construction considerations, p. 365.1R-3 2.1Introduction2.2Environmental considerations2.3Design and structural loadin

9、g considerations2.4Interaction of structural load and environmental effects2.5Construction-related considerationsChapter 3In-service inspection, condition assessment, and remaining service life, p. 365.1R-11 3.1Introduction3.2Evaluation of reinforced concrete aging or degrada-tion effects3.3Conditio

10、n, structural, and service-life assessments3.4Inspection and maintenanceChapter 4Methods for predicting the service life of concrete, p. 365.1R-17 4.1Introduction4.2Approaches for predicting service life of new concrete4.3Prediction of remaining service life4.4Predictions based on extrapolations4.5S

11、ummaryChapter 5Economic considerations, p. 365.1R-245.1Introduction5.2Economic analysis methods5.3Economic issues involving service life of concretestructuresReported by ACI Committee 365S. L. Amey*M. Geiker D. G. ManningJ. P. ArchibaldC. J. Hookham P. K. MukherjeeN. R. Buenfeld W. J. Irwin J. Pomme

12、rsheimP. D. Cady*A. Kehnemui M. D. ThomasC. W. DolanR. E. Weyers*Report chapter coordinatorsDeceasedReport coordinatorJames R. Clifton*ChairmanDan J. Naus*Secretary365.1R-2 ACI COMMITTEE REPORTChapter 6Examples of service-life techniques, p. 365.1R-27 6.1Example IRelationship of amount of steel corr

13、o-sion to time of concrete spalling6.2Example IIComparison of competing degradationmechanisms to calculate remaining life6.3Example IIIUtilization of multiple input to calcu-late the life of a structure6.4Example IVWhen to repair, when to rehabilitate6.5Example VUtilization of reaction rate to calcu

14、latethe life of a sewer pipe6.6Example VIEstimating service life and mainte-nance demands of a diaphragm wall exposed to sa-line groundwater 6.7Example VIIApplication of time-dependent reli-ability concepts to a concrete slab and low-rise shearwallChapter 7Ongoing work and needed developments, p. 36

15、5.1R-36 7.1Introduction7.2Designing for durabilityChapter 8References, p. 365.1R-37 8.1Referenced standards and reports8.2Cited referencesCHAPTER 1INTRODUCTION1.1BackgroundService-life concepts for buildings and structures dateback to when early builders found that certain materials anddesigns laste

16、d longer than others (Davey 1961). Throughouthistory, service-life predictions of structures, equipment, andother components were generally qualitative and empirical.The understanding of the mechanisms and kinetics of manydegradation processes of concrete has formed a basis formaking quantitative pr

17、edictions of the service life of struc-tures and components made of concrete. In addition to actualor potential structural collapse, many other factors can gov-ern the service life of a concrete structure. For example, ex-cessive operating costs can lead to a structures replacement.This document rep

18、orts on these service-life factors, for bothnew and existing concrete structures and components.The terms “durability” and “service life” are often errone-ously interchanged. The distinction between the two terms isevident when their definitions, as given in ASTM E 632, arecompared:Durability is the

19、 capability of maintaining the serviceabil-ity of a product, component, assembly, or construction overa specified time. Serviceability is viewed as the capacity ofthe above to perform the function(s) for which they are de-signed and constructed. Service life (of building component or material) is th

20、e pe-riod of time after installation (or in the case of concrete,placement) during which all the properties exceed the mini-mum acceptable values when routinely maintained. Threetypes of service life have been defined (Sommerville 1986).Technical service life is the time in service until a defined u

21、n-acceptable state is reached, such as spalling of concrete, safetylevel below acceptable, or failure of elements. Functional ser-vice life is the time in service until the structure no longer ful-fills the functional requirements or becomes obsolete due tochange in functional requirements, such as

22、the needs for in-creased clearance, higher axle and wheel loads, or road wid-ening. Economic service life is the time in service untilreplacement of the structure (or part of it) is economicallymore advantageous than keeping it in service.Service-life methodologies have application both in thedesign

23、 stage of a structurewhere certain parameters areestablished, such as selection of water-cementitious materi-als ratios (w/cm), concrete cover, and admixturesand inthe operation phase where inspection and maintenancestrategies can be developed in support of life-cycle costanalyses. Service-life desi

24、gn includes the architectural andstructural design, selection and design of materials, mainte-nance plans, and quality assurance and quality control plansfor a future structure (CEB/RILEM 1986). Based on mixtureproportioning, including selection of concrete constituents,known material properties, ex

25、pected service environment,structural detailing (such as concrete cover), constructionmethods, projected loading history, and the definition of end-of-life, the service life can be predicted and concrete with a rea-sonable assurance of meeting the design service life can bespecified (Jubb 1992, Clif

26、ton and Knab 1989). The acceptanceof advanced materials, such as high-performance concrete, candepend on life-cycle cost analyses that consider predictions oftheir increased service life. Methodologies are being developed that predict the servicelife of existing concrete structures. To predict the s

27、ervice lifeof existing concrete structures, information is required on thepresent condition of concrete, rates of degradation, past andfuture loading, and definition of the end-of-life (Clifton1991). Based on remaining life predictions, economic deci-sions can be made on whether or not a structure s

28、hould berepaired, rehabilitated, or replaced.Repair and rehabilitation are often used interchangeably.The first step of each of these processes should be to addressthe cause of degradation. The distinction between rehabilita-tion and repair is that rehabilitation includes the process ofmodifying a s

29、tructure to a desired useful condition, whereasrepair does not change the structural function.To predict the service life of concrete structures or ele-ments, end-of-life should be defined. For example, end-of-life can be defined as:Structural safety is unacceptable due to material degra-dation or e

30、xceeding the design load-carrying capacity;Severe material degradation, such as corrosion of steelreinforcement initiated when diffusing chloride ionsattain the threshold corrosion concentration at thereinforcement depth;Maintenance requirements exceed available resourcelimits;Aesthetics become unac

31、ceptable; orFunctional capacity of the structure is no longer suffi-cient for a demand, such as a football stadium with adeficient seating capacity.365.1R-3SERVICE-LIFE PREDICTIONSTATE-OF-THE-ART REPORTEssentially all decisions concerning the definition of end-of-life are combined with human safety

32、and economic con-siderations. In most cases, the condition, appearance, or ca-pacity of a structure can be upgraded to an acceptable level;however, costs associated with the upgrade can be prohibi-tive. Guidance on making such decisions is included in thisreport.1.2ScopeThis report begins with an ov

33、erview of important factorscontrolling the service life of concrete, including past andcurrent design of structures; concrete materials issues; fieldpractices involved with placing, consolidating, and curing ofconcrete; and in-service stresses induced by degradationprocesses and mechanical loads. Me

34、thodologies used toevaluate the structural condition of concrete structures andthe condition and properties of in-service concrete materialsare presented. Methods are reviewed for predicting the ser-vice life of concrete, including comparative methods, use ofaccelerated aging (degradation) tests, ap

35、plication of mathe-matical modeling and simulation, and application of reliabil-ity and stochastic concepts. This is followed by a discussionof relationships between economics and the life of struc-tures, such as when it is more economical to replace a struc-ture than to repair or rehabilitate. Exam

36、ples are described inwhich service-life techniques are applicable to concretestructures or structural components. Finally, needed devel-opments to improve the reliability of service-life predictionsare presented.1.3Document useThis document can assist in applying available methodsand tools to predic

37、t service life of existing structures andprovide actions that can be taken at the design or construc-tion stage to increase service life of new structures. CHAPTER 2ENVIRONMENT, DESIGN, AND CONSTRUCTION CONSIDERATIONS2.1IntroductionReinforced concrete structures have been and continue tobe designed

38、in accordance with national or international con-sensus codes and standards such as ACI 318, Eurocode 2, andComit Euro International du Bton (1993). The codes are de-veloped and based on knowledge acquired in research andtesting laboratories, and supplemented by field experience.Although present des

39、ign procedures for concrete are domi-nated by analytical determinations based on strength princi-ples, designs are increasingly being refined to addressdurability requirements (for example, resistance to chlorideingress and improved freezing-and-thawing resistance). In-herent with design calculation

40、s and construction documentsdeveloped in conformance with these codes is a certain levelof durability, such as requirements for concrete cover to pro-tect embedded steel reinforcement under aggressive environ-mental conditions. Although the vast majority of reinforcedconcrete structures have met and

41、 continue to meet their func-tional and performance requirements, numerous examplescan be cited where structures, such as pavements and bridges,have not exhibited the desired durability or service life. In ad-dition to material selection and proportioning to meet con-crete strength requirements, a c

42、onscious effort needs to bemade to design and detail pavements and bridges for long-term durability (Sommerville 1986). A more holistic ap-proach is necessary for designing concrete structures basedon service-life considerations. This chapter addresses envi-ronmental and structural loading considera

43、tions, as well astheir interaction, and design and construction influences onthe service life of structures.2.2Environmental considerationsDesign of reinforced concrete structures to ensure adequatedurability is a complicated process. Service life depends onstructural design and detailing, mixture p

44、roportioning, concreteproduction and placement, construction methods, and mainte-nance. Also, changes in use, loading, and environment are im-portant. Because water or some other fluid is involved inalmost every form of concrete degradation, concrete perme-ability is important.The process of chemica

45、l and physical deterioration of con-crete with time or reduction in durability is generally depen-dent on the presence and transport of deleterious substancesthrough concrete,*and the magnitude, frequency, and effect ofapplied loads. Figure 2.1 (CEB 1992) presents the relationshipbetween the concept

46、s of concrete durability and performance.The figure shows that the combined transportation of heat,moisture, and chemicals, both within the concrete and in ex-change with the surrounding environment, and the parameterscontrolling the transport mechanisms constitute the principalelements of durabilit

47、y. The rate, extent, and effect of fluidtransport are largely dependent on the concrete pore structure(size and distribution), presence of cracks, and microclimate atthe concrete surface. The primary mode of transport in un-cracked concrete is through the bulk cement paste pore struc-ture and the tr

48、ansition zone (interfacial region between theparticles of coarse aggregate and hydrated cement paste). Thephysical-chemical phenomena associated with fluid move-ment through porous solids is controlled by the solids perme-ability (penetrability). Although the coefficient ofpermeability of concrete d

49、epends primarily on the w/cm andmaximum aggregate size, it is also influenced by age, consol-idation, curing temperature, drying, and the addition of chem-ical or mineral admixtures. Concrete is generally morepermeable than cement paste due to the presence of microc-racks in the transition zone between the cement paste and ag-gregate (Mehta 1986). Table 2.1 presents chloride diffusionand permeability results obtained from the 19 mm maximumsize crushed limestone aggregate mixtures presented in Table2.2.Additional information o