ACI 345 1R-2006 Guide for Maintenance of Concrete Bridge Members《混凝土桥梁构建的维护指南》.pdf

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1、ACI 345.1R-06 supersedes ACI 345.1R-92 and became effective March 14, 2006.Copyright 2006, 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, p

2、rinted, written, or oral, or recording for sound or visual reproductionor for use in any knowledge or retrieval system or device, unless permission in writingis obtained from the copyright proprietors.ACI Committee Reports, Guides, and Commentaries areintended for guidance in planning, designing, ex

3、ecuting, andinspecting construction. This document is intended for the useof individuals who are competent to evaluate the significanceand limitations of its content and recommendations and whowill accept responsibility for the application of the material itcontains. 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 by theArchitect/Engineer to be a part of the contrac

5、t documents, theyshall be restated in mandatory language for incorporation bythe Architect/Engineer.345.1R-1Guide for Maintenanceof Concrete Bridge MembersReported by ACI Committee 345ACI 345.1R-06Bridges represent a substantial investment of public funds, and areexpected to provide satisfactory per

6、formance and remain in service formany years. Design specifications typically require 75- or 100-year design lifefor new bridges. Neglecting or delaying bridge maintenance can result inreduced service life and increased costs due to repair, rehabilitation, orreplacement at an early age. Another cons

7、equence of neglecting maintenanceis that the condition of the bridge can become life-threatening to the public.It is believed that continuous and systematic maintenance of a bridge willextend its service life and reduce its overall operating cost.This document addresses typical problems and presents

8、 potentiallycost-effective maintenance techniques for concrete bridge elements. It providesguidance for engineers and maintenance staff. It does not cover repair,rehabilitation, reconstruction, or bridge inspection, and therefore, it doesnot include topics such as cathodic protection, repair with sh

9、otcrete, anddeck overlays. Detailed methods of repairing and inspecting bridges maybe found in the references.Concrete bridge maintenance is defined as those activities that arerelatively inexpensive and repeatable, performed when the concrete elementis still in good to fair condition, intended to p

10、revent or minimize deteriorationof the concrete. These activities may include sealing, washing, caulking,crack repair, and other minor repairs intended to prolong the functionalityof the bridge element.Keywords: bridge decks; cementitious; coating; maintenance; placement;polymer; sealant.CONTENTSCha

11、pter 1Bridge maintenance, p. 345.1R-21.1Introduction1.2Concrete bridge maintenance1.3Purpose of maintenance1.4Limitations1.5Timing of maintenanceChapter 2Concrete bridge deterioration,p. 345.1R-32.1Deterioration indicators2.2Causes2.3Contributing factorsChapter 3Considerations in bridge design,p. 34

12、5.1R-53.1General3.2Decks and curbs3.3Deck joints3.4Superstructure3.5SubstructuresChapter 4Drainage and washing, p. 345.1R-84.1General4.2Deck drainage4.3Washing exposed surfaces4.4Maintenance of deck drains4.5Other drain considerationsGerald H. Anderson Dena L. Guth Johan Silfwerbrand Paul St. JohnMi

13、chael C. Brown Alan B. Matejowsky Michael M. Sprinkel Jerzy ZemajtisRobert J. Gulyas Harold R. SandbergRichard E. WeyersChairPaul D. CarterSecretary345.1R-2 ACI COMMITTEE REPORTChapter 5Sealing, p. 345.1R-105.1General5.2Purpose5.3Sealing materials5.4What and when to seal5.5Recommended practice5.6Pro

14、duct selectionChapter 6Maintenance patching, p. 345.1R-126.1General6.2Purpose6.3Selecting durable patching materials6.4Recommended patching proceduresChapter 7Joints, cracks, and control joints,p. 345.1R-157.1General7.2Maintenance of joints7.3Cracks7.4Crack repair7.5Joint caulkingChapter 8Potentiall

15、y promising techniques for bridge maintenance, p. 345.1R-178.1General8.2Corrosion inhibitors for use in maintenance8.3Galvanic cathodic protection using sprayed zincChapter 9References, p. 345.1R-189.1Referenced standards and reports9.2Cited referencesCHAPTER 1BRIDGE MAINTENANCE1.1IntroductionBridge

16、s represent a substantial investment of public fundsand are expected to function for many years. United Statesdesign specifications typically require a 75- or 100-year designlife, and European specifications require a 120-year designlife. Neglecting or delaying bridge maintenance can result inreduce

17、d service life and increased life-cycle costs due torepair, rehabilitation, or replacement at an early age. Anotherconsequence of neglecting maintenance is that the condition ofthe bridge can become life-threatening to the public.When exposed to sufficiently aggressive environmentalconditions, struc

18、tural concrete members will eventuallydeteriorate and lose strength. Aggressive environmentalconditions for bridges involve cycles of freezing andthawing, and cycles of wetting and drying, with or withoutthe presence of chloride. Corrosion of reinforcing steel spallsthe cover concrete, reduces the c

19、ross-sectional area of thereinforcing steel, and therefore, its strength. The timerequired for deterioration to occur varies considerably,depending on the severity of the exposure conditions and thecharacteristics of the structural concrete. It is believed thatcontinuous and systematic maintenance o

20、f a bridge willextend its service life and reduce its overall operating cost.1.2Concrete bridge maintenanceBridge deterioration usually occurs slowly at first and isoften overlooked. In later stages of deterioration, however,sudden catastrophic events can occur, demanding immediateaction. Progressiv

21、e deterioration can be retarded and some-times avoided if proper systematic preventive maintenanceis practiced (Carter and Kaufman 1990). Concrete bridgemaintenance involves relatively inexpensive, repeatableactivities that either prevent or minimize concrete life ofbridge elements or are minor repa

22、irs that extend the serviceof the structural concrete members.Concrete bridge maintenance is performed when the struc-tural concrete member is still in good to fair condition, and canbe subdivided into preventive and responsive maintenance.1.2.1 Preventive maintenancePreventive maintenanceprocedures

23、 are done before deterioration is visible and thestructural concrete member is still in good condition, and areusually planned at the design stage and started accordingly.Procedures include sealing, washing, caulking, and crackrepair. A procedure not planned is installing retrofit drains.1.2.2 Respo

24、nsive maintenanceResponsive maintenanceprocedures are usually more extensive, and are done in theearly stages of the visible deterioration cycle. Proceduresinclude small repairs, establishment of positive deckdrainage systems, maintaining the functionality of deckjoints, and similar activities to ex

25、tend the service life ofstructural concrete members in bridges.1.3Purpose of maintenanceMaintenance activities are often more cost effective whenthe concrete is still in relatively good condition and isfocused on those parts of a structure that face the most severeexposure conditions. Preventive mai

26、ntenance addressescauses of the potential deterioration, as opposed to treatment,of the effects of deterioration. For example, sealing the decksurface reduces the infiltration of chloride. Proper preventivemaintenance activities can reduce the rate of deterioration,extend service life, and reduce fu

27、ture repair costs (Carter1989a). Responsive maintenance activities help to keepbridges operating safely and efficiently.1.4LimitationsMaintenance is no substitute for proper design andconstruction. Even proper maintenance will not producedesirable results when applied to improperly designed andconst

28、ructed concrete bridge elements. Examples of improperdesign include insufficient reinforcing steel cover depths,excessive surface cracking, and poor drainage characteristics,such as ponding of chloride-contaminated water on aconcrete bridge deck.1.5Timing of maintenanceMaintenance activities perform

29、ed at the proper time areextremely cost effective. Similarly, maintenance activitiesconducted at the wrong time can be a poor investment. Thewrong time for maintenance is after significant damage hasoccurred. Maintenance can prevent damage, but it cannotrestore deteriorated concrete. Damage such as

30、scaling,MAINTENANCE OF CONCRETE BRIDGE MEMBERS 345.1R-3reinforcing steel corrosion, or spalling is easy for the untrainedeye to see after it has occurred, but an understanding ofconcrete deterioration mechanisms is required to foreseedamage before it occurs. Foresight involves the ability toidentify

31、 the signs and symptoms that precede the developmentof damage. For example, an early signal is the presence ofleakage stains. Leakage stains usually precede frozen bearingsand rust stains, delamination, and spalling of reinforcedconcrete bridge superstructure and substructure elements.CHAPTER 2CONCR

32、ETEBRIDGE DETERIORATION2.1Deterioration indicators The visual manifestation of concrete deterioration mech-anisms is well documented in ACI 201.1R. Deteriorationmay be hastened by the synergistics of environmentalconditions and mechanical loading forces. The followingpresent some of the conditions r

33、elative to concrete bridges:Water ponding because of improper deck drainage(Fig. 2.1);Cracks, regardless of cause or type (Fig. 2.2, 2.3, and 2.4);Spalling due to inadequate reinforcing steel cover(Fig. 2.5);Porous, debonded, or cracked asphalt wearing surfaces(Fig. 2.6);Accumulation of deicing chem

34、icals (Fig. 2.7);Staining of concrete surfaces, regardless of cause ortype (Fig. 2.8); andErosion of headslope and sideslopes (Fig. 2.9).2.2CausesFactors contributing to concrete bridge deterioration aremainly moisture, chloride, acids and other aggressive chem-icals, oxygen, cyclic changes in moist

35、ure and temperature,freezing, wear, and abrasion (ACI 201.1R and 222R). Themost economically significant direct cause of bridgeconcrete deterioration is exposure to moisture and chlorides,which is why directly exposed decks and curbs deterioratesooner than sheltered superstructure members. Leaking j

36、ointsdo not shelter superstructure elements.Deterioration of concrete decks can also result fromconcrete fatigue. Tests (Suresh 2005) indicate that compressivestrength of concrete under cyclic loading can be drasticallyreduced. Concrete bridge decks are often exposed to highcyclic loading, which may

37、 result in cracking, and whichfacilitates the infiltration of chloride and results in progressivecorrosion of reinforcement and disintegration of the deck slab.2.3Contributing factorsIn general, the causes and rates of deterioration depend onthe relationship between design, construction, materialsel

38、ection, and exposure condition.2.3.1 DesignSkeet and Kriviak (1994) found that designcould be the primary determinant to service life of bridgedeck overlays and other protection systems. It is easier andless expensive to maintain a bridge that has been designedwith sufficient cover, protective syste

39、ms, and positivedrainage. Long-term maintenance costs are sometimesincreased by focusing on low initial construction costs.Fig. 2.1Water ponding from improper deck drainage.Fig. 2.2Map cracking on underside of deck.Fig. 2.3Transverse crack in deck.345.1R-4 ACI COMMITTEE REPORTSimple examples are bri

40、dges that are flat, do not have deckdrains, have inadequate cover over reinforcing steel, or havepoor-quality concrete. Common examples, widely used inthe 1950s and 1960s, were simple-span bridges used forgrade separations in heavily deiced urban locations. Simple-span bridges require maintenance of

41、 deck joints. Withoutsuch maintenance, the superstructure and substructureelements prematurely deteriorate. Present practice innorthern regions of the U.S. is to reduce bridge maintenancecosts by using continuous spans that reduce or avoid deckjoints (Hambly and Nicholson 1990). Compared with earlie

42、rdesigns, bridge design codes typically require increasedFig. 2.4Map cracking in parapet.Fig. 2.5Shallow cover depth spalling.Fig. 2.6Deteriorated asphalt wearing surface.Fig. 2.7Application of deicing chemicals to roadways.Fig. 2.8Rust staining of curb.Fig. 2.9Erosion and settlement of slopewall.MA

43、INTENANCE OF CONCRETE BRIDGE MEMBERS 345.1R-5concrete cover, a reduced water-cement ratio (w/c) andpermeability, use of air-entrained concrete, corrosion protec-tion systems, and eliminated simple spans and deck joints toincrease service life and durability.2.3.2 ConstructionImproper construction te

44、chniquesthat contribute to deterioration include insufficient compaction,inadequate cover over the reinforcement, inadequatelyentrained air, or increases in the concretes water-cementitiousmaterial ratio (w/cm) during placement. Improper surfacefinishing techniques, such as direct application of wat

45、er tothe surface, reduce durability and service life. Inadequate orlate curing increases shrinkage cracking and permeability tochlorides.2.3.3 MaterialsMaterial factors that contribute todeterioration include incompatibility between air-entrainingand other admixtures, high w/cm concrete, and nondura

46、bleaggregates vulnerable to aggregate-alkali reactions andcycles of freezing and thawing.2.3.4 Climate-related exposure conditionsEnvironmentand climatic conditions contribute to varying rates ofdeterioration. For example, the deterioration of coastalbridges is entirely different from that of high e

47、levationmountain bridges. The mountain bridges are subjected tosnow, moisture, cycles of freezing and thawing, and deicingchemicals (Fig. 2.10), whereas coastal bridges may involvechloride exposure from salt water. The design, construction,and maintenance of bridges in one environment and climatenee

48、ds to take into account many conditions not relevant toanother environment and climate. Concrete maintenancematerials are generally sensitive to ambient temperature andmoisture conditions during application. Many productsrequire moderate weather conditions, and are not suitable forapplication in ext

49、reme conditions (Carter 1989a; Departmentof Transport 1990a; Federal Highway Administration 1994;Bean 1988).CHAPTER 3CONSIDERATIONSIN BRIDGE DESIGN3.1GeneralGood bridge design details prevent or delay componentdeterioration. Some design issues related to reducing futurebridge repair and rehabilitation costs are discussed in thefollowing sections.3.2Decks and curbs3.2.1 FunctionBridge decks support traffic and transmitstructural loads to girders, bearings, and substructurecomponents. Curbs, medians, and parapets defi