NACE GUD CORR MGT REIN CONC STR-2011 Guide to Corrosion Management of REINFORCED CONCRETE STRUCTURES.pdf

1、CORROSION MANAGEMENT SERIESCORROSION MANAGEMENT SERIESGuide to Corrosion ManagementofREINFORCED CONCRETE STRUCTURESAN OFFICIAL NACE PUBLICATIONAN OFFICIAL NACE PUBLICATIONThis book is the second in a series of corrosion management books published by NACE International. The series covers management o

2、f corrosion in various industries in a straightforward and readable form.Corrosion of metals embedded in the reinforced concrete structures is the leading cause of structural deterioration. This guide provides owners and maintenance practitioners with comprehensive guidelines for corrosion managemen

3、t in bridges. It serves as a good starting point for any user who is not familiar with corrosion of metal in concrete, but seeks effective corrosion management strategies and timely treatments at the lowest whole life cost. Seung-Kyoung Lee, Ph.D., Research Associate, Center for Advanced Infrastruct

4、ure and Transportation, Rutgers University This guide is a valuable tool for those responsible for highway structures to implement corrosion management on a case-by-case level. It covers the latest standards for bridge assessment and corrosion control, helping managers and engineers VLMZIVLPMZMWZKMP

5、MaVMMLQVMZUWN MXMZQMIVLVIVKMWKWMNNMKQMTaUIVIOMWZIOQVOJZQLOM2WPV8*ZWWUMTL8P,+WVTQVO+WZZWQWV-VOQVMMZThis guide was prepared by corrosion engineers well-versed in preserving reinforced concrete structures and detecting and mitigating corrosion of reinforcing steel. It focuses on reinforced concrete bri

6、dges but most, if not all, of the techniques discussed are suitable for all reinforced concrete structures. Management and technical personnel involved in the preservation WN PMQZQVNZIZKZMIM_QTTVLPQOQLMIVMKMTTMVZMWZKM;aTQI+0ITT8-6)+-1VMZVIQWVIT;/:MQVNWZKML+WVKZMM+PIQZ335399c-S.indd 1 2/18/12 1:57:34

7、 AMGuide to CorrosionManagement ofReinforced ConcreteStructures1440 South Creek DriveHouston, Texas 77084C2011 by NACE InternationalLibrary of Congress Cataloguing in Publication DataSohanghpurwala, Ali Akbar.Guide to corrosion management of reinforced concrete structures / Ali AkbarSohanghpurwala.p

8、. cm.Includes bibliographical references and index.ISBN 1-57590-244-31. Concrete bridgesCorrosion. 2. Reinforced concreteCorrosion.3. Reinforcing barsCorrosion.4. Concrete bridgesInspection. I. Title.TG414.S64 2011624.2dc23 2011046174ISBN: 1-57590-244-3Printed in the United States of America. All ri

9、ghts reserved. This book, or parts thereof,may not be reproduced in any form without permission of the copyright owners.Neither NACE International, its officers, directors, nor members thereofaccept any responsibility for the use of the methods and materials discussedherein. The information is advis

10、ory only, and the use of the materials andmethods is solely at the risk of the user.NACE International1440 South Creek DriveHouston, Texas 77084http:/www.nace.orgContentsForeword v1 Introduction 12 Bridge Inventory Management 113 Inspection Management 154 Preservation Strategy Development and Implem

11、entation 33References 39Index 43iiiForewordConsidering the capital that bridge owners must invest to build their struc-tures, it is imperative they make the structures last as long as possible. In thepast few decades, the desired service life of bridge structures has increasedfrom 50 years to 100 ye

12、ars. To preserve structures for that long, a concertedmaintenance and repair program must be in place. All components of a bridgestructure deteriorate and require maintenance and repair; however, corrosion ofreinforcement is one of the most important and costly problems for which mostbridge owners d

13、o not have a fully developed management system. Therefore,this guide was developed to assist bridge owners in understanding the basicrequirements for managing corrosion of reinforced concrete elements. It is notintended to provide step-by-step instructions for managing corrosion; insteadit provides

14、an outline and identifies the essential components for a corrosionmanagement program. Owners can develop their own programs based on theirneeds and the resources available to them.The primary goal of this guide is to encourage bridge owners to imple-ment a well-planned effort to control corrosion ra

15、ther than perform necessaryrepairs after a structure has suffered critical damage and cannot be ignoredany longer. It is understood that most bridge owners do not have the resourcesto allocate to a corrosion management program; however, not implementinga well-planned program for managing corrosion w

16、ill result in a greater strainon the owners resources as their structures age and reach the critical damagestage. To maximize service life and to minimize preservation costs, bridgeowners need to change their modus operandi from responding to damage topreventing the damage.To properly implement a co

17、rrosion control program, bridge owners needto acquire skill sets in this subject area. Without trained, experienced, andknowledgeable personnel it is not possible to implement such a program.vvi FOREWORDThis guide was developed by Task Group (TG) 400, “Reinforced Con-crete: Corrosion Management,” wh

18、ich is administered by Specific TechnologyGroup (STG) 01, “Reinforced Concrete.” It is also sponsored by STG 46,“Building Management.” This guide is published by NACE under the auspicesof STG 01.CHAPTER 1IntroductionReinforced concrete is the material of choice for construction of the majorityof hig

19、hway bridge structures in the United States. This is evident in the recordsof the National Bridge Inventory (NBI) database maintained by the FederalHighway Administration (FHWA),(1)an agency of the U.S. government. Thisdatabase is a compilation of records submitted to FHWA by all State Depart-ments

20、of Transportation (DOTs) for bridges located on public roads in the U.S.In 2009, this database had records of 586,000 bridges existing on public roadsin the U.S. Of these, 235,000 are listed as reinforced concrete structures, andanother 108,000 are identified as prestressed concrete structures. Thus

21、, 59% ofbridge structures in the database are reinforced concrete structures. The remain-ing 41% of the structures may not be listed as reinforced concrete or prestressedconcrete; however, many are likely to contain one or more reinforced concreteelements.Concrete is a very durable material; however

22、, its durability is compro-mised by corrosion of reinforcement in certain environments or exposure con-ditions. Corrosion of conventional reinforcement results in cracking, delam-ination, and spalling of the cover concrete, and in extreme cases can resultin significant loss of reinforcement cross-se

23、ction, as is apparent in Figure 1.This degradation has an impact on the operation of the structure and/or resultsin the reduction of overall structural integrity. Consequences of corrosion ona stressed (both pre- and post-tensioned) reinforcement are far more severeand can result in the failure of t

24、he stressed high-strength steel element. Failureof a critical number of stressed elements can result in failure of that bridgeelement.(1)Federal Highway Administration (FHWA), U.S. Department of Transportation (DOT), 1200New Jersey Ave. SE, Washington, DC 20590.12 GUIDE TO CORROSION MANAGEMENT OF RE

25、INFORCED CONCRETEFIGURE 1 Loss of Cross-Section of Reinforcement as a Result of CorrosionCorrosion of reinforcement significantly increases the cost of bridgepreservation. With the limited availability of maintenance and preservationfunds, controlling corrosion has become a top priority for many bri

26、dge owners.In addition, corrosion of the reinforcement can result in catastrophic failures,with accompanying loss of human life and significant impact on the localeconomy.Several catastrophic bridge failures have occurred as a result of corrosionof metallic members of bridges that are classified as

27、reinforced concrete bridges.The most tragic incident was the failure of the Silver Bridge over the OhioRiver in 1967, when a total of 46 people died. This prompted President LyndonB. Johnsons administration to mandate regular bridge inspections and thedevelopment of the NBI database. The death of a

28、motorist resulting from thefailure of the Anclote River Bridge in Pinellas County, Florida, in 1968 ledthe Florida Department of Transportation (FDOT) to start a corrosion group topreserve bridges in that state. In 1983, a 100 ft (30 m) section of the MianusRiver Bridge in Connecticut collapsed, kil

29、ling three people.There are several cases of catastrophic failures of bridge structures inother parts of the world from corrosion of stressed reinforcement, both pre-stressed and post-tensioned. The first known failure occurred in 1967; theBrickton Meadows Foot Bridge collapsed in Hampshire, U.K., b

30、ecause of cor-rosion of post-tensioned tendons. Corrosion of post-tensioning also resulted inthe failures of the Ynys-y-Gwas Bridge located in Wales in 1985 and the MalleBridge in Belgium in 1992. Similarly, corrosion of prestressing strands resultedin the collapse of a five-year-old Lowes Motor Spe

31、edway Bridge in Charlotte,Introduction 3FIGURE 2 Lowes Motor Speedway CollapseNorth Carolina, in 2000. Figure 2 displays a photograph of the failed bridge.A 45-year-old overpass on Interstate 70 (I-70) located in Washington County,Pennsylvania, failed in 2005, as shown in Figure 3.These failures pro

32、mpted many bridge owners to ascertain the conditionof their post-tensioned structures. The state of Florida, one of the leading statesin the construction of post-tensioned bridges, especially segmental concretebridges, surveyed all of their post-tensioned bridge elements. Failed tendonswere discover

33、ed on the Niles Channel Bridge near Key West and the MidwayBridge in Destin. On the Midway Bridge, two of the three tendons on one sideof the segmental box girder had failed. Two failed tendons were also observedin the hollow columns of the Sunshine Skyway Bridge in Tampa.4 GUIDE TO CORROSION MANAGE

34、MENT OF REINFORCED CONCRETEFIGURE 3 Collapse of I-70 Overpass as a Result of Prestressing Cable CorrosionGenerally, corrosion of conventional reinforcement provides sufficientearly warning to allow remediation measures to be implemented. For example,the superstructure of the historic Jefferson Stree

35、t Bridge in Fairmont, WestVirginia, shown in Figure 4, had developed significant corrosion-induced dam-age. Although the reduction in operating capacity and the resulting dangerposed to the driving public is clearly observable, it was not expected to catas-trophically fail. However, rehabilitation c

36、ost approximately $25 million.Several cost analyses have been performed to estimate the cost of cor-rosion. In a 1986 report the National Cooperative Highway Research Program(NCHRP)(2)estimated that the unfunded liability to correct corrosion-induceddistress in bridges in the United States was $20 b

37、illion and was increasing byabout $500 million annually.1The U.S. Secretary of Transportations reportin 1982 estimated there were nearly 213,000 deteriorating bridges alone witha repair cost of $41.1 billion, with corrosion being the primary cause of thedeterioration.2A recent cost-of-corrosion stud

38、y determined that the annual costof corrosion to all bridges is $8.29 billion, and the indirect cost to the user re-sulting from traffic delays and lost productivity can be more than 10 times thedirect cost of corrosion. This study also estimated that of the $8.29 billion,(2)The National Cooperative

39、 Highway Research Program (NCHRP) conducts research in problemareas that affect highway planning, design, construction, operation, and maintenance in theU.S., under the auspices of the Transportation Research Board of the National Academy ofSciences, 500 Fifth St. NW, Washington, DC 20001.Introducti

40、on 5FIGURE 4 Corrosion-Induced Damage on Bridge Deck$3.8 billion are for the annual cost to replace structurally deficient bridgesover the next 10 years, plus $2.0 billion for maintenance and the capital costof concrete bridge decks, and $2.0 billion for maintenance and capital cost ofsubstructure e

41、lements.3Conventional reinforcing steel in concrete does not corrode unless theprotection afforded by the high alkalinity of the concrete pore solution is com-promised by chloride ions or carbonation. In North America, this primarilyresults from exposure to chloride ions from deicing salt and/or the

42、 marine en-vironment. When the chloride ion concentration at the steel-concrete interfaceexceeds the threshold, corrosion is initiated. The timefrom constructionrequired to initiate corrosion is termed time to initiation. Once corrosion isinitiated, corrosion products are formed. The products of the

43、 corrosion process(iron oxides, such as rust) occupy a greater volume than the original steel.4,5The expansive products of the corrosion process generate tensile stresses in theconcrete. Because the tensile capacity of concrete is relatively limited, thesestresses result in cracking, delamination, a

44、nd eventually spalling. The time fromcorrosion initiation to formation of delamination is referred to as the time topropagation. The reinforcing continues to corrode even after the delaminationhas occurred and with time can incur sufficient cross-section loss to adverselyaffect the overall integrity

45、 of the element.6 GUIDE TO CORROSION MANAGEMENT OF REINFORCED CONCRETEFactors that affect the initiation of corrosion on prestressing embeddedin concrete are very similar to those of conventional reinforcement. The typeof corrosion most likely to occur on prestressed tendon, however, is somewhatdiff

46、erent. Pitting corrosion and environmentally induced cracking are morelikely to occur rather than the general corrosion normally observed on con-ventional steel. Pitting corrosion can result in localized loss of cross-section,which results in a stress riser at that location. This can subsequently re

47、sult inthe failure of the wire and ultimately the tendon. Pitting corrosion can alsogenerate hydrogen, which, when absorbed by the high-strength steel, can resultin hydrogen embrittlement (HE). Environmentally induced cracking can resulteither from stress corrosion or HE and can result in the failur

48、e of the wire andeventually the tendon or cable. Corrosion of prestressed reinforcement has amore immediate and a greater impact on the structural integrity of the concreteelement than that of conventional reinforcement.In addition to the presence of chloride ions and lower pH, corrosioninitiation on bonded post-tensioned tendons occurs because of voids in groutswhere water and oxygen can collect, contact with dissimilar metals can occur,and excessive bl