364.1R-94 Guide for Evaluation of Concrete Structures...

ACI 364.1 R-94(Reapproved 1999)

Guide for Evaluation of Concrete StructuresPrior to Rehabilitation

Reported by ACI Committee 364

Tony C. LiuChairman

Leonard MillsteinSecretary

Sam BhuyanRobert W. BobelBoris BreslerT. Z. ChastainJames R. CliftonGlenn W. DePuyAshok K. DhingraPeter EmmonsRussell S. FlingRobert Gevecker

Zareh B. GregorianRobert L. HenryLawrence F. KahnDov Kaminetzky*Stella L. MarusinKatharine MathertJames E. McDonaldRichard L. MillerMichael J. PaulSherwood P. Prawel

Ranjit S. ReelGajanan M. SabnisCarolyn L SearlsRobert E. ShewmakerAvanti C. ShroffMartin B. SobelmanRobert G. TracyVikas P. WaghJames WarnerHabib M. Zein Al-Abidien

*Technical review subcommittee.
t Deceased.
This report presents the guidelines and general procedures that may be usedfor evaluation of concrete structures prior to rehabilitation. Among the sub-jects covered are: preliminary investigation; detailed investigations docu-mentation; field inspection and condition survey; sampling and materialtesting evaluation; and final report. Seismic evaluation is considered be-yond the scope of this report.

Keywords: buildings: concrete; condition survey: evaluation; field observation; historic structures: nondestructive evaluation; rehabilitation: sampling; servicehistory: testing.

CONTENTS

Chapter l-Introduction, pg. 364.1-2l . l-General1.2-Definitions1.3-Purpose and scope

Chapter 2-preliminary investigation, pg. 364.1-32.1-Introduction2.2-Scope and methodology2.3-Results

Chapter 3-Detailed investigation, pg. 364.1R-53.1-Introduction

ACI Committee Reports, Guides, Standard Practices, andCommentaries are intended for guidance in designing, plan-ning. executing, or inspecting construction and in preparingspecifications. References to these documents shall not bemade in the Project Documents. If items found in thesedocuments are desired to be a part of the Project Docu-ments, they should be phrased in mandatory language andincorporated into the Project Documents.

364.1

3.2-Documentation3.3-Field inspection and condition survey3.4-Sampling and material testing3.5-Evaluation3.6-Final report

Chapter 4-Documentation, pg. 364.1R-64.1-Introduction4.2-Design information4.3-Materials information4.4-Construction information4.5-Service history4.6-Communication

Chapter 5-Field observations and condition survey, pg.364.1R-7

5.1-Introduction5.2-Preparation and planning5.3-Field verification of as-built construction5.4-Condition assessment5.5-Unsafe or potentially hazardous conditions

Chapter 6-Sampling and material testing, pg. 364.1R-96.1-Introduction6.2-Determination of testing requirements6.3-Testing and evaluation

ACI 364.1R-94 became effective Feb. 1. 1994.

Copyright 0 1993. American Concrete Institute.

All rights reserved including rights of reproduction and use in any form or byany means, including the making of copies by any photo process, or by any elec-tronic or mechanical device, printed. written, or oral, or recording for sound orvisual reproduction or for use in any knowledge or retrieval system or device.unless permission in writing is obtained from the copyright proprietors.

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364.11-2 ACI COMMITTEE REPORT

6.4-Nondestructive evaluation methods6.5-Sampling techniques

Chapter 7--Evaluation, pg. 364.1R-187.1-Introduction7.2-Dimensions and geometry7.3-Material evaluation7.4-Structural evaluation7.5-Evaluation of rehabilitation alternatives7.6-Cost evaluation

Chapter 8-Final report, pg. 364.lR-198.l-Introduction8.2-Purpose and scope of investigation8.3-Existing construction and documentation8.4-Field observations and condition survey8.5-Sampling and material testing8.6-Evaluation and repair alternatives8.7-Findings and recommendations

Chapter 9-References, pg. 364.1R-209.1-Recommended references9.2-Cited references

CHAPTER l-INTRODUCTION

l.l-GeneralThis report outlines procedures that may be used for

evaluation of concrete structures prior to rehabilitation.The procedures should be used as a guide and are not in-tended to replace judgment by the engineer responsiblefor the evaluation. The evaluation work is generally per-formed for one or several of the following purposes:

a) To determine the feasibility of changing the use ofa structure or retrofitting the structure to accommodatea different use from the present one. The feasibility ofenlarging the structure or changing the appearance of thestructure may also be determined.

b) To determine the structural adequacy and integrityof a structure or selected elements.

c) To evaluate the structural problems or distresswhich result from unusual loading or exposure condi-tions, inadequate design, or poor construction practices.Distress may be caused by overloads, fire, flood, foun-dation settlement, deterioration resulting from abrasion,fatigue effects, chemical attack, weathering, or inade-quate maintenance.

d) To determine the feasibility of modifying the exis-ting structure to conform to current codes and standards.

Many failures have taken place in rehabilitation pro-jects due to erroneous procedure and improper judg-ment. It should be recognized that there is no absolutemeasurement of structural safety in an existing structure,particularly in structures that have deteriorated due toprolonged exposure to the environment, or that havebeen damaged by a physical event. Similarly, there are nogenerally recognized criteria for evaluating serviceability

of an existing structure. Engineering judgment and closeconsultation with the owner regarding the intended useof the structure are required in the evaluation of struc-tures prior to rehabilitation.

It is important to clearly define the objective of the re-habilitation effort. The cost associated with items such asinterference with normal operations, or a complete shut-down of a structure can easily exceed those of the actualrehabilitation work. Although rehabilitation can oftenproceed with little, if any, interference with normal oper-ations, it is obviously more costly to carry out rehabil-itation work under such conditions. The owner should beconsulted and provided with relative costs for variouslevels of interference, so that an informed decision as tohow to proceed with the rehabilitation work can bemade.

Due to the many unknowns inherent in rehabilitationwork, it is essential to retain the services of consultantsexperienced in this type of work. It is also equally impor-tant to retain services of a well-experienced specialtycontractor on a negotiated basis so that a better controlin terms of total cost, level of disturbance to the users,and the quality of work can be achieved. If competitivebidding is used, consideration should be given to limitingbidding to prequalified contractors with an establishedrecord in completing similar rehabilitation projects.

1.2-DefinitionsThe following definitions are defined here as in ACI

116R:Preservation-The process of maintaining a structure

in its present condition and arresting further deterior-ation

Rehabilitation-The process of repairing or modifyinga structure to a desired useful condition

Repair-To replace or correct deteriorated, damaged,or faulty materials, components, or elements of a struc-ture

Restoration-The process of reestablishing the mater-ials, form, and appearance of a structure to those of aparticular era of the structure

Strengthening-The process of increasing the load-re-sistance capacity of a structure or portion thereof.

1.3-Purpose and scopeThe purpose of this report is to provide a source of

information on the evaluation of concrete structures (ex-cept those subjected to seismic effects) prior to rehabil-itation. This is of particular importance since there is asubstantial difference between the complexity of rehabili-tation design, as compared with the design of a newstructure. Evaluation of specialty structure types such asbridges, dams, and tunnels are considered beyond thescope of this report.

The report is presented as a series of recommendedguidelines, based on experience drawn from existingsources and past investigations. Case histories are notgiven so as not to deviate from a guideline approach.

EVALUATION OF STRUCTURES PRIOR TO REHABILITATION 364.1R-3

(For case histories, see ACI SP-85, ACI SCM 21, andConcrete International, March 1993.) The guidelines givenin this report are general in character, but specificenough for use as a format to model an evaluation pro-cedure for a structure.

The report is presented in the order in which aninvestigation would normally be conducted. The first andthe most important single effort in evaluation prior torehabilitation is the “preliminary investigation,” asdescribed in Chapter 2. After having the results of thepreliminary investigation, the detailed investigation canproceed, if deemed desirable. Chapter 3 outlines the ef-forts required for the detailed investigation which gen-erally consist of five major tasks: reviewing pertinentdocuments, performing a field inspection and conditionsurvey, sampling and material testing, evaluating andanalyzing the information and data, and preparing a finalreport. Chapter 4 identifies those documents and sourcesof information that would normally be reviewed duringthe evaluation. The efforts required in performing fieldobservations to verify and assess the structural conditionare described in Chapter 5. Chapter 6 provides informa-tion on practices and procedures for sampling and mater-ial testing, including visual examination, nondestructiveevaluation, and field and laboratory investigations. Chap-ter 7 contains discussions on review of all the accumu-lated information and data, material and structural eval-uation, identification and evaluation of rehabilitationalternatives, and costs. Guidelines for preparing the finalreport are presented in Chapter 8.

CHAPTER 2-PRELIMINARY INVESTIGATION

The goals of the preliminary investigation are to pro-vide initial information regarding the condition of thestructure, the type and seriousness of the problems af-fecting it, the feasibility of performing the intendedrehabilitation, and information on the need for a detailedinvestigation.

The preliminary investigation, once authorized by theowner, is based on an established objective or reason forperforming the rehabilitation. It is necessary to meet withthe owner to fully evaluate the owner’s needs and per-ceptions and to determine the objectives of the investi-gation. A written agreement, stating the objectives andthe scope of these studies, is recommended. It is impor-tant to recognize that preliminary investigations aretypically introductory in nature and are not comprehen-sive. Preliminary investigations commonly identify theneed for a more detailed and extensive study and for anadditional scope of services. However, in some cases, thepreliminary investigation may determine that it is notdesirable to proceed with a further detailed investigation,as in the case of excessive damage where the structuralintegrity cannot be economically restored or the owner’sobjectives cannot be satisfactorily met.

2.2-Scope and methodologyThe scope and methodology of a preliminary investiga-

tion can involve one or more of the following steps, de-pending on the size and complexity of the project.

a) Review of plans, specifications, and constructionrecords

b) Site observations of conditionsc) Measurement of geometry, deflections, displace-

ments, cracks, and other damaged) Nondestructive testinge) Exploratory removalf) Sampling, testing, and analysisIt should be noted that only a limited amount of in-

vestigation within each step is generally required toestablish the feasibility of the rehabilitation project.Detailed studies are generally deferred until the detailedinvestigation phase, if such investigation is deemeddesirable.

2.2.1 Plans, specifications, and construction records-The first task is to review available plans, specifications,and construction records. It may be necessary to searchmany sources to obtain these documents. For older struc-tures, the process can be tedious and difficult and canconsume far more time than the actual review. Theowner’s files, city archives, original designers, and originalcontractors are generally the best sources to search fordocuments and records. Testing agencies, building man-agement firms, or large subcontracting companies arealso possible avenues for obtaining construction docu-ments. Universities, libraries, historic societies, and statepreservation offices may have design documents and con-struction records for historic structures.

When original documents are not available, the studymust begin without precise knowledge of the structure.Special steps should be taken to compensate for themissing information. Nondestructive testing and physicalmeasurements can be used to supplement visual observa-tions. Nondestructive testing to locate reinforcement canbe a practical alternative to exploratory removals. Theuse of nondestructive techniques can yield valuable in-formation on which to base decisions regarding furthertesting and evaluation. Nondestructive tests must be cor-related with the testing of a sufficient number of samplesto confirm their reliability (ACI 437R).

Once the plans and specifications are obtained andfield checks have been performed to confirm that thestructure is in reasonable conformance with the con-struction drawings, then a study of the plans, specifi-cations, and other construction records can proceed.Checks of the critical design details, arrangement ofcritical members, and installation of any special featurescan then be accomplished. If variations from the draw-ings are noted or if scope changes occurred during con-struction, proper documentation should be made so thatsite observations can confirm or clarify features of theactual structure. It is important to check what code re-quirements were applicable at the time of design. Theseshould be compared to presently applicable codes and

364.1R-4 ACI COMMlTEE REPORT

standards. Critical data such as loading requirements andallowable stresses should be reviewed. It may also benecessary to determine the physical properties of theconstruction materials if such information is not availablefrom the existing documentation. If soils or foundationinformation is available, it should be retained for futureuse.

As the review progresses, parallel steps may be takento develop field observation record sheets for recordinginformation obtained during the field investigation. Suchrecord sheets should provide essential information onstructural features such as perimeter boundaries, column,beam, and wall locations and dimensions. If the structurebeing examined is a multifloor structure, one recordsheet may be developed for each floor. A list of items orquestions obtained during the records review concerningas-built status, alterations, or possible changes in struc-ture use since its original construction should be devel-oped and checked in the field. Alterations to existingstructures in service are common and must be carefullynoted and evaluated, because they represent potentiallysensitive areas in the structural system.

2.2.2 Field observations--A walk-through of the struc-ture may be adequate to establish the project scope andto serve the project needs. However, in instances ofextensive rehabilitation, more detailed checks of variousitems followed by preliminary tests may be required.

The principal focus of the preliminary investigationgenerally involves recording the nature and extent of ob-served problems and identifying the affected members.Frequency and severity of problems throughout the struc-ture must also be recorded. In the event that seriousdistress or deficiencies are discovered, which may resultin unsafe or potentially hazardous conditions, the ownershould be notified for immediate action. Temporary eva-cuation, temporary shoring measures, or any other emer-gency safety measures, if required, should be recom-mended to the owner. Monitoring of movements, cracks,and progressive distress should follow immediately.

Assessment of the conditions observed, and specificallythe need for follow-up and appropriate remedial actions,should be recorded. Initial impressions can be very val-uable; they often accurately characterize the nature of aproblem. If structural problems are suspected, specialattention should be given to connections, support regions,areas of abrupt geometric change, and areas in the struc-ture where load concentrations occur. Where cracks ofstructural significance are found, consideration should begiven to monitoring the movements of the cracks. Thisinformation will be of value for future investigations.

Photographic records or videotapes are valuable aidsin classifying and communicating information on the con-ditions and problems observed in the field (Buchanan1983). Where unusually severe deterioration or distressis observed, a photographic record of this information isessential.

2.2.3 Measurements-The field condition survey gener-ally requires measurements of member dimensions, span

lengths, and deflection magnitudes. Any displacement,cracks, separations, or distortion of the structural frame,curtain walls, or other load-bearing or enclosure systemsshould be noted and characterized. Existing floor or roofslopes should also be noted.

Additional measurements may be necessary where al-terations to a structure have been made without properdocumentation. It is common to encounter alterations ina structural system that have been made without anawareness of the significance that such alterations mayhave on the structural system. If there is reason tobelieve that alterations may be affecting a structuralsystem’s response or capacity, recommendations for re-medial action may be appropriate. The owner should benotified immediately if the nature and extent of problemsdiscovered require urgent action.

2.2.4 Nondestructive testing-Limited nondestructivetesting can supplement observations and measurements.Some of the most common techniques used during pre-liminary investigation are listed in the following:

a) Acoustic impact (sounding and chain dragging)b) Magnetic detection instrument (cover meters)c) Rebound hammerd) Penetration resistancee) Forced vibration testsIt is unlikely that all of these methods will be used

during a preliminary investigation. Preliminary nonde-structive testing can often help to identify locationswithin a structure where more comprehensive nonde-structive and destructive testing may be required. Adetailed description of nondestructive test methods andprocedures is included in Chapter 6 of this report.

2.2.5 Exploratory removal-Exploratory removal is usedwhen there is substantial evidence of serious deterior-ation or distress, when hidden defects are suspected, orwhen there is insufficient information. Exploratory re-movals help to determine existing features and to gainreliable information about the nature and extent ofexisting problems. During preliminary investigation,selected exploratory removals are considered the excep-tion and not the rule. It is more common to defer remo-vals until the detailed investigation phase.

2.2.6 Sampling testing, and analysis-sampling andtesting are not usually performed during the preliminaryinvestigation. When performed, sampling generally con-sists of extracting cores or small specimens, or collectingother readily obtainable samples for compressive strengthtesting and petrographic examination (ACI 437R). Pow-der samples may be extracted during the preliminary in-vestigation for chemical analysis and determinations ofchloride ion content. Reinforcing steel samples may beanalyzed to determine strength, hardness, and carboncontent.

2.3-ResultsThe results of the preliminary investigation should be

summarized in a report that will generally include struc-tural capacity check, project feasibility, identification of

EVALUATION OF STRUCTURES PRIOR TO REHABILlTATlON 364.1R-5

structural problems, strengthening requirements, andneeds for further investigation.

2.3.1 Structural capacity check-The structural capacitycheck generally produces one of three results: (1) Thestructure or individual members are adequate for the in-tended use; (2) The structure or individual members areadequate for the existing loads but may not be adequatefor intended use; (3) The analysis may be inconclusive.Depending on the results, the adequacy of the structuremust be established. It may also be necessary to proposeimmediate action to deal with a condition affecting thesafety or stability of the structure.

2.3.2 Project feasibility-An assessment based on tech-nical and cost considerations should indicate whether aproposed rehabilitation is feasible. Points that should beconsidered in reaching a conclusion regarding projectfeasibility include the expected effectiveness of the rehab-ilitation and its estimated life-cycle cost. The effects ofthe rehabilitation on the structural system and the anti-cipated impact on the operation of the structure shouldalso be considered.

2.3.3 Structural problems-when structural problemsare identified, they should be described in terms of theirseriousness and extent. Steps should be taken to verifythe significance of the structural problems discovered andto determine whether or not corrective action is requiredto remedy the existing conditions or to protect the exis-ting structural system. It is not unusual to encounter pro-blems that require immediate action to mitigate deficien-cies discovered. In such cases, the owner should be noti-fied for immediate action. Preliminary investigation,especially for older structures, frequently identifiesconditions which may be in marginal compliance with orin violation of current codes.

2.3.4 Strengthening requirements-Alternate strength-ening methods should be considered to satisfy the in-tended loading requirements and applicable code re-quirements. Actions taken to strengthen existingstructures must take into consideration the operation ofthe structure both in terms of current and possible futureuse. The investigation should also consider the costeffectiveness of repairing, replacing, or strengthening theexisting structural members.

2.3.5 Further investigation-The need for a furtherdetailed investigation should be identified. Frequently,the end product of a preliminary investigation is thedetermination that a detailed investigation is required.Issues that must be addressed in planning the next phaseof the work include the objectives of the detailed inves-tigation and the additional data or information requiredto satisfy these objectives. Other important issues are thetime required for investigation, the cost of investigation,and the intended use of detailed investigation.

CHAPTER 3-DETAILED lNVESTIGATlON

3.1-IntroductionThe detailed field investigation should only be per-

formed after the preliminary investigation is completed,the owner’s goals identified and tentatively determined tobe feasible, and the objectives of the detailed investi-gation properly defined. It is important before proceed-ing with the detailed investigation that the projectbudgets and costs of the detailed investigation be ap-proved by the owner.

The detailed investigation may be divided into fivemajor tasks:

a) Documentationb) Field observations and condition surveyc) Sampling and material testingd) Evaluatione) Final reportThe findings of the detailed investigation will directly

influence the final outcome of the evaluation process, thechoices of various rehabilitation methods to be consid-ered, the estimated cost associated with each rehabilita-tion alternative, and ultimately the selection of theappropriate rehabilitation method. Therefore, extremecare is required in planning and executing the detailedinvestigation.

3.2-DocumentationIntensive effort should be made to locate, obtain, and

review the pertinent documents relating to the structure.Thorough review of the available documentation will saveboth time and cost for any rehabilitation project. Chapter4 provides a guide describing the type of documentationneeded for various types of structures and where it maybe obtained.

3.3-Field observations and condition surveyEven with complete documentation and construction

information, investigation is required to verify reliabilityand accuracy in the field. Field observations should notonly address the as-built geometry and materials of con-struction, but also the present condition of the structure,its environment, and the loads to which it is subjected.The guidelines for field observation and condition surveyare given in Chapter 5.

3.4-Sampling and material testingMaterial testing is often required to determine the

existing material properties and conditions. The testingmay be destructive or nondestructive and may be per-formed both in the field and in the laboratory. Chapter6 describes the types of testing and the methods of sam-pling that may be performed during the detailed investi-gation.

3.5-EvaluationChapter 7 identifies the major types of evaluations

that should be performed to reach a conclusion to pro-ceed with the rehabilitation project or to choose analternative plan.

364.1R-6 ACI COMMllTEE REPORT

3.6-Final reportThe final report should include the results of all

phases of the investigation field observations, testing, andevaluation, and should also include conclusions and rec-ommendations to the owner on how to proceed with therehabilitation project. It should include an action plan,cost estimates, and tentative design and constructionschedules. Guidelines for preparing the final report areincluded in Chapter 8.

CHAPTER 4-DOCUMENTATION

4.1-IntroductionThis chapter identifies documents and sources of in-

formation that should be reviewed during the evaluationof structures prior to their rehabilitation. This reviewprocess is necessary to minimize the assumptions neces-sary to evaluate the structure. Details of the rehabilita-tion project and the type of structure being rehabilitatedwill dictate the nature and quantity of information thatshould be reviewed.

4.2-Design information4.2.1 Structures-Documentation that may contain use-

ful structural information includes:a) Design drawings, specifications, and calculationsb) Shop drawings of assemblies and steel framingc) Placing drawings of concrete reinforcementd) Alteration plans, addenda, and change orderse) As-built drawings, photographs, job field records,

and correspondencef) Building codesg) Manufacturer’s technical information, descriptions

of construction materials, patents, and test dataInformation regarding original construction or alter-

ation plans may be obtained from the owner, the archi-tect or engineer, local building departments or regulatoryagencies for the political subdivision in which thestructure is located, the general contractor, the subcon-tractors, and the fabricators. Local building departments’records may be valuable in locating alteration plans andpossible violations.

The assembly of all this information can be time-consuming, but it is extremely important for a successfulrehabilitation project.

4.2.2 Historic structures-Buildings-Buildings desig-nated as historic structures are required to be preserved,and their rehabilitation may fall under federal, state, orcity preservation statutes or acts (HUD 1982). Often,rigid rules must be observed, and these should be care-fully studied.

When working on historic structures, it is important torelate the structural system used in the project to thedesign practices existing at the time of construction. For-tunately, on many older structural designs, there is a sub-stantial amount of available information. Reinforced con-crete designs often were developed in a competitive com-

mercial atmosphere. As a result, there were many rein-forcement systems, including many reinforcing bar de-formation patterns that were protected by patents. Manyof these systems were illustrated in catalogs. Not onlywere design calculations often presented in tabular form,but often the strength of the system was validated byload tests, and the results of tests included in thecatalogs. Early textbooks and handbooks also includedmuch of this information and are especially helpful.Newspaper clippings and old photographs may be helpfulduring the process of planning for the preservation ofhistoric structures.

The Historic American Building Survey (HABS),National Park Service, U.S. Department of the Interior,Washington, D. C., has drawings and reports on manyhistoric buildings (McKee 1970). HABS publishes anindex of all drawings that are stored in the Library ofCongress. The state historic preservation office may alsohave drawings and reports.

Much of the general information on early concretesystems can be found in the ACI Bibliography on theHistory of Concrete (ACI B-14), and in ConcreteReinforcing Steel Institute Publication CDA-24.

4.2.3 Historic structures-Bridges-The discussion inParagraph 4.2.2 on historic structures is also applicableto reinforced concrete bridges. Bridges almost alwayshave been public structures built under the aegis ofcounty and local governments, or state highway depart-ments. Thus, public records, including drawings of aparticular bridge, may be found in the archives. Often, ifdetails of a particular bridge are lacking, documents maybe available for a bridge designed and built by the sameengineering group or agency at the same time and to thesame specifications.

Drawings of existing historic bridges may be obtainedfrom the Historic American Engineering Record(HAER), National Park Service, U.S. Department of theInterior, Washington, D.C.

Beginning about 1905, hundreds of bridges were builtaccording to catalog designs. A careful review of suchdesigns may prove beneficial in documenting the designof a particular bridge. In addition, a number of railroadbridges were built by railroad companies. These railroadcompanies generally keep good records. Possibilities ofobtaining original design plans and inspection and main-tenance records from the railroad companies should beinvestigated.

4.3-Materials informationThe following information on the materials used in a

particular structure may be available, especially for morerecently constructed structures, and should be sought:

a) Concrete mixture components, proportions, and testresults

b) Mill test reports on cement and reinforcing andprestressing steel

c) Material specifications and drawings, includingthose prepared by material suppliers and used to place

EVALUATION OF STRUCTURES PRIOR TO REHABlLlTATlON 364.1R-7

their products in the original construction

4.4-Construction informationVarious construction documents from the original

construction may have been retained and may be helpfulin documenting the construction methods, materials, andproblems encountered. If available, this information willprove to be valuable in the rehabilitation process.

The following records should be sought:a) Correspondence between members of the construc-

tion team, design team, and owner or developerb) Results of tests on fresh and hardened concretec) Quality control data and field inspection reportsd) Diaries or journals kept by the construction teame) Job progress photographsf) As-built drawingsg) Survey notes and recordsh) Reports filed by building inspectorsi) Drawings and specifications kept on the job, in-

cluding modifications and change ordersj) Material test reports for all structural materials usedk) Information concerning the foundation and soil-

bearing capacity, including soil-bearing reports preparedprior to construction; allowable soil-bearing pressuresused in the design; and soil and foundation work, includ-ing backfill and compaction conducted during construc-tion. Pile driving records and pile cap modificationdrawings may be helpful. The soils and foundation re-cords may be useful when foundation loadings are to beincreased during the rehabilitation or whenever foun-dation settlements have been noted. Also, local geo-technical engineers may be aware of soil information forrecently built and adjacent structures

Other possible sources of information regarding re-cently constructed structures may be the constructionsuperintendent and the owner’s representative. Moreinformation can often be obtained through a personalinterview. Local newspaper and trade publications mayhave provided coverage of the original construction.

4.5-Service historyDocuments which relate to the service history of a

structure should be reviewed to learn as much as possibleabout any distress, damage, deterioration, and subsequentrepairs which may have occurred. The types of informa-tion that may be available include:

a) Records of current and former owners, or users ofthe structure, their legal representatives, and theirinsurers

b) Maintenance, repair, and remodeling recordsc) Reports maintained by owners of adjacent struc-

turesd) Weather recordse) Interviews with operation and maintenance person-

nelf) Logs of seismic activity, geologic activity, etc.g) Insurance reports and records of damage to the

structure by fire, wind, snow, overloads, earthquake,

fatigue, etc.h) Information on operation, occupancy, instances of

overloading, and load limitsi) Records from government or local building depart-

ments or departments of licenses and inspection. Inspec-tion reports and reports of violations are often useful

j) Photographsk) Local newspapers and trade publications

4.6-CommunicationAll documentation obtained should be kept in separ-

ately organized files. These files should identify the originof the documents and data obtained.

Copies of all documents should be made available tothe owner for his information. These documents may alsobe made available to the contractor selected for therehabilitation project.

CHAPTER 5-FIELD OBSERVATIONSAND CONDlTION SURVEY

5.1-IntroductionOnce the available design, construction, and materials

information, and service history of the structure havebeen collected and reviewed, the next step is to performfield observations to verify the previously obtained infor-mation, and to survey and assess the condition of theas-built construction.

The field observations can be divided into the fol-lowing four major efforts:

a) Preparation and planningb) Verification of as-built constructionc) Condition assessment of the structured) Summary reportEach of these efforts may be modified depending on

the type, size, complexity, age, intended future use, andthe overall nature of a particular project.

5.2-Preparation and planningThe scope of the field observation effort is, in part,

dictated by the availability of funds and time, but it mustbe sufficient to include relevant information consistentwith project goals. Before a detailed field observation isundertaken, the conclusions of the preliminary investiga-tion should be reviewed thoroughly. Additionally, theavailable documentation should be reviewed to determinethe type and extent of information that is to be obtainedor verified during field inspection. Recording proceduresand appropriate forms should be developed to documentproperly information obtained in the field.

When original documents are not available, specialsteps should be taken to compensate for the missing in-formation. Nondestructive testing (ACI 228.1R) and phy-sical measurements should be used to supplement visualobservations.

A reconnaissance should be made to establish generalsite conditions and to decide if special access equipment

364.1R-8 ACI COMMITTEE REPORT

or permits are required, if any finishes have to beremoved, if services of subcontractors are required toprovide the appropriate means of access, or if specializedinspection services such as rigging, underwater inspection,etc., are required. In addition, photographs or a video-recording of critical areas should be taken during thefield observations to assist in planning of equipment,access, and inspection methodology.

5.3-Field verification of as-built construction5.3.1 Geometry and structural materials--Spans and

cross sections of the structural members should bemeasured, particularly at critical locations, becauseas-built conditions may vary considerably from thoseshown on available drawings. Variations may be due tolater design modifications or field changes. In particular,unrecorded alterations may be critical because they maybe the cause of reduced strength of the structure. It isessential that location and size of openings in structuresand holes through members be measured and recorded.

Nondestructive testing methods such as a magneticdetection instrument, radiography, ultrasonic pulsevelocity, or other methods may be used to estimate eithernumber, size, length, or spacing of reinforcing steel inconcrete. If the reinforcing details are available, thenondestructive testing methods can be used to verily theinformation at a few random locations (ACI 228.lR, Car-ino and Malhotra 1991). If they are not available, non-destructive testing methods may have to be used exten-sively to establish reinforcing steel sixes and locations atcritical sections. An adequate number of tests at otherlocations should also be made to establish a reliableestimate (ASTM E 122). The results of nondestructivetesting methods should always be verified by removal ofconcrete cover at some locations.

Nondestructive testing can be used to identify areas ofreinforcing corrosion, delamination, or cracking. Nondes-tructive testing can also be used to estimate the concretestrength and overall concrete quality. Results of nondes-tructive tests are most useful when supplemented by alimited number of destructive test procedures.

Exploratory removal of portions of a structure may berequired when it is not possible to fully evaluate visibleevidence of a seriously deteriorated or distressed condi-tion. Removal may also be required when there is a lackof information about a portion of a structure. Sinceremoval and replacement of portions of a structure mayrequire services of a subcontractor, this work should beplanned well in advance with the owner’s approval. Fur-thermore, since most rehabilitation projects requireextensive removal during construction, it may be moreefficient and more convenient to plan inspection ofhidden areas or conditions during early phases of theconstruction.

5.3.2 Loadings and environment-The existing loads,loading combinations, soil pressures, and environmentalconditions acting on a structure may be different fromthose assumed and provided for at the time of design.

The inspection should note any changes that can affectthe total load-carrying capacity of the structure.

5.3.2.1 Dead loads--Differences between design andactual dead loads may arise from variations in the dimen-sions, and the density and moisture content of the con-struction materials. Change in architectural finishes, addi-tion of partition walls, changes in facade construction, oraddition of nonstructural elements can also affect theactual dead loads.

5.3.2.2 Imposed Loads-Since the imposed loadsdepend on the use of the structure, a full description ofcurrent and proposed usage should be obtained from theowner. The imposed loads should be verified during thefield observations. Code requirements for wind andseismic loads may now be more stringent than when thestructure was originally constructed. Roth static anddynamic effects of the imposed loads should be con-sidered.

5.3.2.3 Warehouse loading and storage-In awarehouse, attention should be given to the current andproposed methods and patterns of storage. Mechanicalstacking may induce dynamic effects and thus increaseloading. It is necessary to confirm whether the materialsstored are of similar characteristics to those assumed inthe original design. Overloading is a common problem inwarehouses.

5.3.3.4 Loads from equipment and machinery-Staticand dynamic loadings induced by mechanical equipmentto the structure should be field-verified. Attention shouldbe given to the loads applied during the installation,relocation, or replacement of equipment. The size, loca-tion, and direction of application of point loads fromlifting equipment may be of significance. Dynamic effectsof mobile equipment, e.g., forklift trucks, should beinvestigated. Observations should be made of impactresponses from presses, hammers, compressors, and simi-lar equipment, producing cyclic loads that may inducedynamic effects. The fatigue properties of the supportingmembers should be investigated. Loads from pipes,valves, and other services should be examined to confirmthat the loads used in the design are adequate.

5.3.2.5 Snow and ice loadings-Consideration shouldbe given to the buildup of snow and ice, particularly inroof valleys and snow drift accumulation against verticalsurfaces.

5.4-Condition assessmentACI 201.1R should be followed in assessing the condi-

tion of the concrete. The condition of a structure shouldbe considered without prejudging the cause and type ofdefects. There is a danger that defects outside of pre-vious experience of the investigator will be missed, andthat significant effort may go into trying to find a type ofdefect that is not present. Therefore, it is necessary todescribe the conditions adequately so they can be eval-uated objectively. Photographs and videotapes can be val-uable in this regard.

A visual inspection should be carried out to document

EVALUATlON OF STRUCTURES PRlOR TO REHABlLlTATlON 364.1R-9

the extent and severity of any distress or deteriorationwhich could affect the load-carrying capacity or servicelife of the structure. Previously repaired or modifiedportions of the structure should also be included in theinspection. The inspection records should be supplemen-ted with sketches, photographs, and videotapes, as appro-priate. Cracks, spalls, corrosion of reinforcing steel, etc.,should be identified as follows (ACI 201.1R and Con-crete Society 1982):

a) Cracks should be measured and recorded for width,depth, length, location, and type (i.e., structural ornonstructural). Structural cracks should be further iden-tified, as flexure, shear, or direct tension, if known. Crackpatterns should be plotted. Results of crack monitoringor recommendations for such monitoring should be con-sidered

b) Spalling, scaling, honeycombing, efflorescence, andother surface defects should be measured and recorded

c) Corrosion of reinforcing bars, including the extentand amount of lost cross section, should be measuredand recorded

d) Loose, corroded, or otherwise defective connectorsfor precast concrete elements, or ties to architecturalelements or cladding should be noted

e) Deformations, whether permanent or transientunder loads, out-of-plumb columns, and other misalign-ments, should also be measured and recorded. Continu-ous monitoring should be considered, as appropriate

f) Signs of foundation settlement or heave, and relateddistress, should be noted

g) Water leakage, ponding areas, areas of poor drain-age, or other indications of water problems should benoted

h) Evidence of aggressive chemical deterioration suchas sulfate attack and acid attack should be noted

In general, the visual inspection should include themeasurement and assessment of three basic conditions:visible damage, visible deviations and deformations, andfoundation settlement.

5.4.1 Visible damage-It is generally difficult to quanti-fy the visible damage since it depends on subjective cri-teria and the experience of the inspectors. Moreover,damage which is acceptable in one region or one type ofstructure may not be acceptable in another circumstance.Therefore, before commencing the field observations,some guidelines should be established in assessing theobservations so that a consistent representation andunderstanding of the significance of the damage is pos-sible. A six-point assessment classification is recom-mended as follows:

a) Unsafeb) Potentially hazardousc) Severed) Moderatee) Minorf) Good conditionAny of the components of the structure can then be

evaluated using this rating system.

The condition assessment using the preceding classifi-cations should be supplemented by sketches, photo-graphs, videotapes, measurements, and brief descriptions.It is important to note the extent and severity of deter-iorated areas with respect to the entire structure beingassessed. For example, if extensive spalling of a concretebeam is observed, it is important to note what percentageof the beam is spalled and what is the condition of thebeam that is not spalled.

5.4.2 Visible deviations and deformations-Unintendedvisible deviations of members from the vertical or hori-zontal should be measured and recorded. Appraisal ofrelative movement is often guided by comparisons withneighboring or adjacent structures or members. Devia-tions from the vertical or horizontal in excess of aboutL/250 are likely to be noticed where L represents thespan length. For horizontal members, a slope exceedingL/50 (¼ in./ft) would be visible, as would a deflec-tion-to-length ratio of more than about L/240.

5.4.3 Foundation settlement-The field investigationshould include an assessment of any foundation settle-ments. The movements, tilts, and separations of struc-tural elements and cracks that result from differentialsettlements should be measured and recorded. Beforecommencing the field investigation of foundation settle-ment, the existing foundation design drawings should bereviewed for type of foundations, types of soils, designwater table, surrounding terrain, site drainage, andadjacent structures.

The field investigation should note any changes in thewater table, any signs of erosion and scour, and the addi-tion of structures in the vicinity. If signs of differentialsettlement are present, it may be necessary to carry outa more detailed gee-technical investigation to assess fullythe impact of the observed conditions.

5.5-Unsafe or potentially hazardous conditionsWhen unsafe or potentially hazardous conditions are

discovered, the owner must be immediately notified ofthe potential consequences of these conditions. Tempor-ary evacuation, temporary shoring measures, or any otheremergency safety measures, if required, should be rec-ommended to the owner. If public safety is involved, afollow-up of the conditions discovered should continuewith the owner until satisfactory safety measures areimplemented.

CHAPTER 6-SAMPLING ANDMATERIAL TESTING

6.1-IntroductionThis chapter contains information on practices and

procedures for assessing the condition and properties ofstructural materials in an existing structure. These prac-tices and methods include visual examination, nondes-tructive evaluation (NDE) tests, and destructive testswhich include field and laboratory procedures.

364.1R-10 ACI COMMlTTEE REPORT

6.2-Determination of testing requirementsThe requirements for testing will depend on the

findings during the preliminary investigation, the study ofavailable documents, and the requirements of the pro-posed rehabilitation.

There is no need for testing where the available infor-mation is sufficient to complete the evaluation with con-fidence. A structure may clearly be in sound conditionand without defects, and the dimensions measured duringthe investigation may allow analysis to confirm suitabilityfor its intended future use.

Requirements for testing will arise in situations wherethere is inadequate information about the materials pre-sent in a structure or where deterioration or deleteriousmaterials are suspected.

Where testing is required, it is necessary to make anassessment of what specific information is needed. Thepurpose of each test and the information that it can pro-vide must be understood so that the appropriate tests arecarried out. Test methods range widely in cost, reliability,and complexity. Some tests require little or no distur-bance, while others are destructive and require that aportion of the structure be removed from service whilethey are conducted. In some circumstances, the cost oftesting may be so high that remedial action may be themore economic solution. Appropriate experience is nec-essary so that the required tests are performed properlyand interpreted correctly.

The selection of the proper test methods (ACI228.1R), and the number of tests and their locations willdepend on:

a) Variation in material properties within the structureb) Critical locationsc) Probable error in a test resultd) Extent of the structure over which a property is

measured, e.g., ultrasonic-pulse-velocity measurementsindicate the average quality through the entire depth ofa member, whereas a core test measures only the condi-tion of the material in the core

6.3-Testing and evaluationEvaluation of existing concrete should include deter-

minations of strength and quality (NRMCA 1979, ACI228.1R, and Shroff 1986 and 1988). Proper assessmentand subsequent evaluation should provide some under-standing of the structural ability to sustain the loads andenvironmental conditions to which the structure is beingor will be subjected (Mather 1985).

6.3.1 Evaluation procedures for concrete-The functionof concrete material in a structure is twofold. First, theconcrete functions as one component of the compositestructural material that constitutes the load-carryingelement. Second, the concrete provides an overall protec-tion against fire and environmental forces. Specifically,the concrete cover provides protection against corrosionof the embedded steel reinforcement, insulates it againstthe effects of fire, and thereby provides durability.

For concrete to function as a load-carrying structural

element, the following three coincidental characteristicsare required: adequate strength, adequate cross-sectionalarea of both concrete and reinforcing steel, and adequatebond of concrete to steel. If the combination of thesethree characteristics is not adequate, the concrete isunacceptable.

For concrete to function as an effective cover for rein-forcing or prestressing steel and to provide durability, itmust a) be relatively dense, b) be nonporous, c) have lowcapillarity, d) have low permeability, and e) contain ag-gregates and cement that are nonreactive with each otherand with the environment. Although some of these pro-perties are related to compressive strength, the desiredproperties are usually achieved by controlling the amountand type of cement, degree of air entrainment, slump,water-cementitious materials ratio, type of aggregate andtypes of admixtures, and by controlled procedures formixing, placing, and curing.

The preceding concepts indicate that concrete proper-ties and physical conditions tabulated in Tables 6.1(a)and 6.1(b) may be considered in evaluating the accepta-bility of existing concrete and its future performance(ASCE 11). These tables should be used as a guide bythe engineer performing the investigation based on pastexperience and judgment.

6.3.2 Evaluation procedures for steel reinforcement--Thefunction of the embedded steel reinforcement in a con-crete structure is to carry tensile and compressive forces.Not only must the properties and physical conditions ofthe steel be determined to evaluate this load-carryingability, but the means of transmitting and distributing thestresses to the concrete structure must also be deter-mined. These requirements indicate that the propertiesor physical conditions tabulated in Table 6.2 (ASCE 11)may be considered in evaluating the acceptability of theembedded steel reinforcement.

6.4-Nondestructive evaluation methodsThe available nondestructive evaluation methods that

may be used in the field or in the laboratory to assess theproperties and physical conditions of structural materialsare summarized in Table 6.3(a) through (e) (ASCE ll),in which each test is briefly explained along with its re-quirements, advantages, and limitations (Carino and San-salone 1990, Clifton et al. 1982, Clifton 1985, Malhotra1976, and Carino and Malhotra 1991).

6.5-Sampling techniques6.5.1 Concrete-Samples of concrete in an existing

structure may be used to determine strength as well asphysical and chemical properties, as discussed earlier. Itis essential that the samples be obtained, handled, iden-tified (labeled), and stored in a proper fashion to preventdamage or contamination (Stowe and Thornton 1984).

Guidance on developing an appropriate sampling pro-gram is provided by ASTM C 823. Samples are usuallytaken to obtain statistical information about the proper-ties of concrete in the structure or to characterize some

364.1R-11

Table 6.1(a)-Evaluation of properties of concrete

CHEMICAL ANDPHYSICAL

COMPRESSIVE STRENGTH l l l l lCONTAMINATEDAGGREGATE 0 lCONTAMINATEDMIXING WATER l 0

CORROSION ENVIRONMENT l 0

CREEP 0

DENSITY l 0

ELONGATION l

FROZEN COMPONENTS lMODULUS OFELASTICITY 0 0

MODULUS OF RUPTURE l 0

MOISTURE CONTENT 0 l lPERMEABILITY aa

PULL OUT STRENGTH lQUALITY OF AGGREGATE lRESISTANCE TO FREEZINGAND THAWlNG l 0 l

SOUNDNESS l l lSPLlTTING TENSILESTRENGTH lSULFATE RESISTANCE l 0

TENSILE STRENGTH 0 0

UNIFORMITY l 0 0 a

WATER-CEMENT RATIO l


Table 6.1(b)-Evaluation of physical conditions of concrete

EVALUATIONPROCEDURE

PHYSICALCONDITION

BLEEDING CHANNELS l 0CHEMICAL DETERIORATION l 0 0

CORROSION OF STEEL 00 0 0

CRACKING .a .a 0 0.0 .a.

CROSS SECT PROPERTIESAND THICKNESS 0 0 0 0

DELAMINATION 0 .a*. 0 0 .a*

DISCOLORATION 0 0 0

DISINTEGRATION 0 00 0 0 0

DISTORTION 0

EFFLORESCENCE l a 0EROSION a l

FREEZE-THAW DAMAGE 0 0

HONEYCOMB •~.. 0 0 0

POPOUTS 0

SCALING 0

SPALLING 0 00 0

STRATIFICATION l 0 00STRUCTURAL PERFORMACE l 0 lUNIFORMITY OF CONCRETE 0 0 l . l .


Table 6.2-Evaluation of properties of reinforcing steel

PROPERTIES AND

I I I I I I I I I I I


Table 63-Description of nondestructive (event as noted) evaluation methods for concreteMethod

Acoustic emission(Clifton et al., 1982;

Acoustic impact(Clifton et al., 1982)

Core testing (ASTMC 42)

Cover meters/Pach-ometers (Malhotra1976)

Electrical potentialmeasurements(Mathey and Clifton1988)

Electrical resistancemeasurements(Mathey and Clifton1988)

Applications

Continuous monitoringof structure during ser-vice life to detect impen,ding failure; monitoringperformance of structureduring proof testing.

Used to detect debonds,delaminations. voids, andhairline cracks.

Direct determination ofconcrete strength; con-crete evaluation of con-dition type and qualityof aggregate, cement,and other components.

Measure cover, size, andlocation of reinforce-ment and metal embed-ments in concrete ormasonry.

Indicating condition ofsteel reinforcing bars inconcrete masonry. Indi-cating the corrosion ac-tivity in concrete pave-ments.

Determination of mois-ture content of concrete.

Principle of operation

During crack growth orplastic deformation, therapid release of strainenergy produces acoustic(sound) waves that can bedetected by sensors incontact with or attachedto the surface of a testobject.

Surface of object is struckwith an implement. Thefrequency and dampingcharacteristics of resultingsound, giving an indica-tion of the presence ofdefects; equipment mayvary from simple hammeror drag chain to sophisti-cated trailer-mountedelectronic equipment.

Drilled cylindrical core isremoved from structure;tests may be performedon core to determinecompressive and tensilestrength, torsional pro-perties, static modulus ofelasticity, etc.

Presence of steel inconcrete or masonry af-fects the magnetic field ofa probe. The closer theprobe is to steel, thegreater the effect.

Electrical potential ofconcrete indicates prob-ability of corrosion.

Determination of mois-ture content of concrete isbased on the principlethat the conductivity ofconcrete changes withchanges in moisture con-lent.

User expertise

Extensive knowledgerequired to plan testand to interpret results.

Low level of expertiserequired to use audi-tory system but theelectronic systemrequires training.

Special care not todamage cores must betaken in obtainingdrilled cores; moderatelevel of expertiserequired to test andevaluate results.

Moderate; easy to op-erate; training neededto interpret results.

Moderate level of ex-perience required, usermust be able to recog-nize problems.

High level of expertiserequired to interpretresults; equipment iseasy to use.

Advantages

Monitors structural re-sponse to applied load;capable of locatingsource of possible fail-ure; equipment is por-table and easy to oper-ate, good for load tests.

Portable equipment; easyto perform with auditorysystem; electronic devicerequires more equip-ment.

Most widely acceptedmethod to determine re-liably the strength andquality of in-placeconcrete. Good for ex-aminations of cracks,embedded reinforcingbars, and for sample forchemical tests.

Portable equipment,good results if concreteis lightly reinforced.Good for locating rein-forcing or prestressingtendons and wires toavoid damage in coring.

Portable equipment,field measurementsreadily made; appears togive reliable information

Equipment is auto-mated and easy to use.

Limitations

Expensive test torun; can be usedonly when structureis loaded and whenflaws are growing;interpretation ofresults required anexpert; currentlylargely confined tolaboratory; limitedtrack record, furtherwork required.

Geometry and massof test object in-fluence results; poordiscrimination forauditory system; ref-erence standards re-quired for electronictesting.

Coring damagesstructures andrepairs may berequired. Destruc-tive test.

Difficult to interpretresults if concrete isheavily reinforced orif wire mesh is pre-rent. Not reliable forcover of 4 in.; andform ties often mis-taken for anchors.

Information on rateof corrosion is notprovided; access toreinforcing barsrequired.

Equipment is expen-sive and requireshigh-frequency spe-cialized applications;dielectric propertiesalso depend on saltcontent and temper-ature of specimen,which poses prob-lems in interpre-tation of results. Nottoo reliable.

EVALUATION OF STRUCTURES PRIOR TO REHABILlTATION 364.1R-15

Table 6.3 cont.-Description of nondestructive evaluation methods for concrete


iber optic probe consis-ing of flexible opticalibers. lens, and illumin-ting system is insertednto a crack or drilledole in concrete; eyepieces used to view interior toook for flaws such asracks, voids, or aggregateebonds, commonly usedo look into areas whereores have been removedr bore boles have beenrilled. Examination ofavity walls and othermasonry boles.

laws detected by usingelective infrared fre-quencies to detect variousassive heat patternshich can be identified aselonging to certain de-eds. Through cracks inoncrete and masonry ma:be detected on cold days.

Test load is applied tostructure in a manner thatwill simulate the load pat-

tern under design condi-tions.

Moisture content in con-crete determined based onthe principle that mater-ials (such as water) de-cease the speed of fastneutrons in accordancewith the amount of hydro-gen produced in testspecimen.

- Used in conjunction withother tests. chemical andPhysical analysis of con-

Crete samples is per-formed by qualified petrographer.

easure the force re-uired to pull out theteel rod with enlargedlead cast in concrete;ullout forces produceensile and shear stressesn concrete.

User expertiseApplications Advantages

Gives clear high-resolution images of remoteobjects. Camera attach-ment for photos is avail-able. Flexible hose en-ables multidirectionalviewing.

Method

Fiber optics (Matheyand Clifton 1988)

To view portions of astructure that are in-accessible to the eye.

Equipment is easy tohandle and operate.

Equipment expen-sive; many boreboles are required togive adequate access.Mortar in masonrywalls binders view.

Infrared thermo-graphy (Mathey andClifton 1988)

Detection of internalflaws, crack growth, de-lamination, and internalvoids.

Requires special skill

and equipment. Ef-fective where tem-perature differentialbetween surfaces ishigh.

Has potential for be-coming a relatively inex-pensive and accuratemethod for detectingconcrete defects; canover large areas quickly

High level of expertiserequired to interpretresults.

Load testing (ACI4371)

Determine performanceof a structure under asimulation of actualloading conditions, usingoverload factors.

Provides highly reliableHigh level of expertiserequired to formulateand conduct the testprogram and to evalu-ate the results. Protec-ion shoring is required‘or safety.

Expensive and time-consuming; testingmay cause limited oreven permanentdamage to the struc-

ture or some of itselements.

- prediction of structure’sability to perform satis-factorily under expectedloading conditions.

Nuclear moisturemeter (ASTMD 3017)

Estimation of moisturecontent of hardenedconcrete.

Must be operated byrained and licensedpersonnel.

Portable moisture esti-mates can be made ofin-place concrete.

Equipment sophisti-cated and expensive;NRC License re-quired to operate;moisture gradients inspecimen may giveerroneous results.Measures all nitro-gen in concrete aswell as nitrogen inwater.

Petrographic analysis(ASTM C 856)

Used to determine a variety of properties of con-crete or mortar sampleremoved from structure;some of these include 1)denseness of cement. 2)homogeneity of concrete3) location of cracks, 4)air content, 5) propor-tions of aggregate, cc-ment, and air voids, and6) curing.

High level of skill andraining required toperform and analyzetest results.

Provides detailed andreliable information ofconcrete ingredients.paste, aggregates, curing,possible damage, andfreezing

Qualified exper-ienced petrographerrequired; relativelyexpensive and time-consuming.

Pullout testing(ASTM C 900)

Estimation of compres-sive and tensile strengthsof existing concrete.

Low level of expertiserequired, can be usedby field personnel.

Directly measures in-place strength of con-crete; appears to givegood prediction of con-crete strength.

Pullout devices mustbe inserted duringconstruction; cone ofconcrete may bepulled out, necessi-tating minor repairs.



Method I Applications

Pull-off testing Estimation of the com-(Long and Murray pressive strength of1984) existing concrete.

Radar (Mathey andClifton 1988)

Detection of substratumvoids, delaminations. andembedments. Measure-meat of thickness ofconcrete pavements.

Gamma radiography Estimation location, size,(Malhotra 1976) sad condition of rein-

forcing bars; voice inconcrete; density.

Rebound hammer(ASTM C 805)

Ultrasonic pulse(ASTM C 597)

Visual examination(ACI 2O1.1R andASTM C 823)

crete from differentareas of specimen; esti-mates of concretestrength based on cali-bration curves withlimited accuracy.

Gives estimates of uni-formity, quality. com-pressive strength. (whenpreviously correlated) ofconcrete; internal dis-continuities can belocated sad their sizeestimated; most widelyused stress wave methodfor field use.

(a) Evaluation of thesurface condition ofconcrete (finish, rough-ness, scratches cracks,color). (b) Determiningdeficiencies in joints. (c)Determining deforma-tions and differentialmovements of structure.


Circular steel probe isbonded to concrete. Ten-sile force is applied usingportable mechanical sys-tem until concrete fails.Compressive strength canbe estimated using cali-bration charts.

Uses transmitted electro-magnetic impulse signalsfor void detection.

Based on principle thatthe rate of absorption ofgamma rays is affected bydensity sad thickness oftest specimen; gamma rayare emitted from source.penetrate the specimen,exit on opposite side, endare recorded on file.

Springdriven mass strikessurface of concrete sadrebound distance is givenin R-values; surface hard-ness is measured andstrength estimated fromcalibration curves pro-vided by hammer manu-lecturer.

Operates on principle thatstress wave propagationvelocity is affected byquality of concrete; pulsewaves are induced inmaterials sad the time ofarrival measured at thereceiving surface with areceiver.

Visual examination withor without optical aids,measurement tools, photographic records, or oth-er low-cost tools, differ-ential movement deter-mined over long periodswith surveying methodsand other instrumenta-tion

User expertise

HighIy skilled operatoris not required.

High level of expertiserequired to operateequipment sad inter-pret results.

Use of gamma-producing isotopes isclosely controlled byNRC, equipment mustbe operated by licensedinspectors.

Simple to operate; canbe readily operated byfield personnel.

Varying level of ex-pertise required toInterpret results.Operator requires afair degree of training.

Experience required toletermine what to lookfor, what measurementto take, interpretationof conditions, and whatfollow-up testing tospecify.

Advantages

Simple sad inexpensive.

Expedient methods canlocate reinforcing barsand voids regardless ofdepths. May be usedwhen only one surface isavailable.

Internal defects can bedetected; applicable tovariety of materials; per-manent record on film,gamma-ray equipmenteasily portable.

Equipment is light-weight simple to oper-ate, and inexpensive,large amount of data canbe quickly obtained,good for determininguniformity of concreteand stress potentially lowstrength.

Equipment relatively in-expensive and easy tooperate; accurate mea-surement of uniformitysad quality. By corre-lating compressivestrength of cores andwave velocity, in-situstrength can be esti-mated.

Generally low costs;rapid evaluation ofconcrete conditions.

Standard test proce-dure not yet avail-able. Limited trackrecord. Concretemust be repaired attest locations.

Equipment is expen-sive; reliability ofvoid detention great-ly reduced if rein-forcement present;procedure still underdevelopment.

Equipment is ex-pensive; gamma-raysource is health andsafety hazard; re-quires access to bothsides of specimen.

Results effected bycondition of concretesurface; does notgive precise predic-tion of strength; esti-mates of strengthshould be used withgreat care; frequentcalibration ofequipment required.

Good coupling be-tween transducer andconcrete is critical;interpretation of re-sults can be difficultdensity, amount ofaggregate, moisturevariations. and pre-sence of metal rein-forcemeat may affectresults; calibrationstandards required.

Trained evaluationrequired, primaryevaluation confinedto surface ofstructure.



Method

Penetration resis-tance (ASTM C 803)

Ultrasonic pulse-echo (Thornton andAlexander 1987)

Resonant frequencytesting (Carino andSansalone 1990)

Applications

Estimates of compressivestrength. uniformity. andquality of concrete mayhe used for estimatingstrength prior to formremoval.

Gives estimates of com-pressive strength, unifor-mity, and quality of coo-crete. Can locate rein-forcing bar. defects,voids delamination, saddetermine thickness.

Is used in the laboratorytO determine variousfundamental modes ofvibration for calculatingmoduli; used in field todetect voids, delamin-ations.


Probes are gun-driveninto concrete; depth ofpenetration converted toestimates of concretestrength by using cal-ibration curves.

Operates on principle thatoriginal direction, ampli-tude, sad frequency con-teat of stress waves introduced into concrete aremodified by the presenceof interfaces such ascracks, objects, sad sec-tions which have differentacoustic impedance.

A resonant frequency con-dition is set up betweentwo reflecting interfaces.Energy can be introducedby hammer impact oscilla-tor-amplifier-electromag-netic driver system.

User expertise

Simple to operate, canbe readily operated inthe field with littletraining. Safety requireoperator certificate.

High level of expertiserequired to interpretresults. Operatorshould have consider-able training to useequipment and know-ledge of electronics,and should have consi-derable training in thearea of condition sur-

vey of concrete struc-lures.

High level of expertiserequired to interpretresults. Operator canbe easily trained forlaboratory measure-meats as specimenshave simple geometry.

Advantages Limitations

Equipment is simple, May not yield accur-durable. and requires ate estimates of con-little maintenance, useful crete strengths; inter-in assessing the quality pretation of resultsand relative strength of depends on correla-concrete; does relatively tion curves. Difficultylittle damage to speci- in removing themen. probes, which are

often broken anddamaging to coverconcrete.

Can operate where only Is still in developoat surface is accessible. mental stage. NeedsCan operate in dry (in development of mea-theory - never saw pub- surement criteria.licized material). Allows Not presently a stan-one to “see” inside dard test method.concrete. Digital signal pro

cessing can improveinterpretation butdata must be re-turned to laboratoryfor processing atpresent.

Allows one to “see in-side” concrete structures,can penetrate to depthsof a number of feet; anewly developed trans-ducer receiver can im-prove results over anaccelerometer.

Operates in sonic range and does nothave resolution ofultrasonics. Still in

developing stage.

unusual or extreme conditions in specific portions of thestructure. In the first case, sample locations should berandomly distributed throughout the structure. The num-ber and size of samples depend on the laboratory testsand the degree of confidence desired in the average val-ues obtained from the tests.

The sampling plan depends on whether the concreteis generally believed to be uniform, or if there are likelyto be two or more regions different in composition, con-dition, or quality. The results of the preliminary inves-tigation and the review of other sources of informationshould be considered before a detailed sampling plan isprepared. Where a property is believed to be uniform,sampling locations should be distributed randomlythroughout the area of interest, and all data treated asone group. Otherwise, the study area should be subdi-vided into regions believed to be relatively uniform, witheach region sampled and analyzed separately.

For tests intended to measure the average value of aconcrete property, such as strength, elastic modulus, orair content, the number of samples should be determinedin accordance with ASTM E 122. The required numberof samples generally depends on:

a) Maximum difference (or error) that one is willingto accept between the sample average and the true aver-age

b) Variability of the test resultsc) Risk that one is willing to accept that the allowable

difference is exceededSince the variability of test results is usually not known

in advance, an estimate should be made and adjusted astest results become available. Cost should also be con-sidered in the selection of sample sizes. In some cases,increasing the sample size may result in only a minimaldecrease in the risk that the error is exceeded. The costof additional sampling and testing would not be justifiedunder these situations.

It should be recognized that concrete is not an iso-tropic material and properties will vary depending on thedirection that samples are taken. Particular attentionshould be given to vertical concrete members, such ascolumns, walls, and deep beams, because concrete pro-perties will vary with elevation due to differences inplacing and compaction procedures, segregation, orbleeding.

6.5.1.1 Core sampling-The procedures for properlyremoving concrete samples by core drilling are given inASTM C 42. The number, size, and location of core sam-ples should be carefully selected to permit all necessarylaboratory tests. If possible, use virgin samples for alltests so that there will be no influence from prior tests.Where cores are taken to determine a strength property,at least three cores should be removed at each locationin the structure. The strength value should be taken asthe average of the three cores. A single core should notbe used to evaluate or diagnose a particular problem.


For determining compressive strength or static ordynamic modulus of elasticity, the diameter of the coreshould not be less than three times the nominal maxi-mum size of aggregate.

6.5.1.2 Sampling of concrete with sawed beams-Where appropriate, sampling by sawing beams in accor-dance with ASTM C 42 may be used as an alternative todrilled core sampling. However, research has shown thatsignificant reductions in strength may be encounteredwhen using sawed beam samples. This should be takeninto consideration in the final analysis of the results.

6.5.1.3 Random sampling of broken concrete-Sam-pling of broken concrete generally should not be usedwhere a strength property of concrete is in question. Thismethod is most frequently used when evaluating chemicalor physical properties of deteriorated concrete members.

6.5.2 Steel reinforcement-Samples of steel reinforce-ment from existing members may be retrieved to deter-mine the strength, physical or chemical properties, orboth. The removed reinforcing bars should be replacedif required by design. The characteristics, selection, andpreparation of samples are discussed in ASTM A 370.Some of the important considerations are:

a) Specimens should be removed at locations of mini-mum stress in the reinforcement. Not more than onespecimen should be removed from the same cross sectionof a structural member

b) Locations of specimens in continuous concrete con-struction should be separated by at least the developmentlength of the reinforcement to avoid excessive weakeningof the member

c) For structural elements having a span of less than25 ft (7.5 m) or a loaded area of less than 625 ft2 (60m2), at least one specimen should be taken from themain longitudinal reinforcement (not stirrups or ties)

d) For longer spans or larger areas, more specimensshould be taken from locations well distributed throughthe portion being investigated, to determine whether thesame strength of steel was used throughout the structure

e) Information from Grade Marks and Mill Marksshould be collected when possible and used as appropri-ate in guiding sample collection

CHAPTER 7-EVALUATION

Evaluation is a process of determining the adequacyof a structure or component for its intended use by anal-yzing systematically the information and data assembledfrom reviews of existing documentation, field inspection,condition survey, and material testing. This investigativeprocess of evaluation cannot be generally standardizedinto a series of well-defined steps because the numberand type of steps vary depending on the specific purposeof the investigation, the type and physical condition ofthe structure, the completeness of the available designand construction documents, and the strength and quality

of the existing construction materials. Only generalguidelines are presented in this chapter.

Structural evaluations should be performed to deter-mine the load-carrying capacity of all critical elements ofthe structure, and the structure as a whole. The ability ofthe structure to support all present and anticipated loadsaccording to current code requirements or standardsshould be considered. Where these code requirementsare not met with the structure in its current condition,appropriate strengthening methods and techniquesshould be determined.

Ihe need to meet architectural requirements shouldalso be evaluated. Both changes in architectural layoutand modifications to the facades of the structure shouldbe evaluated. Final schemes should be selected by theowner from various design alternatives. The cost of var-ious alternatives should be estimated and the implicationsevaluated.

7.2-Dimensions and geometryThe actual dimensions of the structure and archi-

tectural layout should be evaluated for use, access, andneeded space. The field-measured cross sections of thecritical structural components should be reviewed. Dis-crepancies between the field-measured dimensions andthose indicated on available drawings should be evalu-ated.

7.3-Materials evaluationField and laboratory test results should be studied so

that components of the structure that require repair canbe identified. The structural components which requiretotal replacement should be identified and new materialsselected. All existing materials should be evaluated forstrength, quality, and satisfactory performance in termsof life expectancy, future loads, and intended usage.

Where rehabilitation is required, the appropriatematerials should be studied and recommendations made.The materials should be selected based on the environ-ment, type of use, life expectations, and compatibilitywith existing materials. After evaluation of the existingconditions, it may be determined that protection fromfurther deterioration is required. Methods such ascoating, shielding, or specialized systems (e.g., cathodicprotection) should be considered.

7.4-Structural evaluationUsing the information obtained from the field survey,

dimension and geometry evaluation, and material evalu-ations, the load-carrying capacity of the structure orportion of the structure undergoing evaluation should bedetermined. The choice of the evaluation method is de-pendent on such factors as the nature of the structureand the amount of information known about its existingcondition. The typical choices are 1) evaluation byanalysis, 2) evaluation by analysis and full-scale loadtesting, or 3) evaluation by analysis and structuralmodeling (ACI 437R).


Evaluation by analysis, the most common method, isrecommended when sufficient information is availableabout the physical characteristics, material properties,structural configuration, and loadings to which thestructure has been and will be subjected.

Evaluation by analysis and full-scale load testing orstructural modeling or both is recommended when thecomplexity of the design concept and lack of experiencewith the structural system make evaluation solely by anal-ytical methods unreliable, or when the nature of existingdistress introduces significant uncertainties into the mag-nitude of the parameters necessary to perform an analy-tical evaluation, or when the geometry and the materialcharacteristics of the structural elements being evaluatedcannot be readily determined.

Critical structural components including members andconnections should be identified for evaluation based onthe document review, dimension and geometry check,and material evaluation.

The capacities of the critical structural componentsshould be determined preferably by the strength designmethod. Sophisticated methods such as finite elementanalyses may be used. All existing and expected deadloads and live loads, equipment and piping loads, andcode-mandated wind and earthquake requirements mustbe considered.

Where applicable, the nonstructural componentsshould also be evaluated to insure that they are capableof resisting the prescribed loads and deformations. Iheeffect of nonstructural components on the overall per-formance of the structure should also be considered.

7.5 Evaluation of rehabilitation alternativesEven if the existing structure appears to meet all the

strength requirements, cosmetic or other types of repairsmay stiIl be required to restore the structure to an ap-propriate condition. Alternate repair methods, as well asthe possibility of using the “do nothing approach,” shouldbe evaluated based on comparative cost estimates, sched-ules, and relative levels of interference with the oper-ations.

When the existing structure (or components) does notmeet the strength requirements, alternate methods ofstrengthening should be evaluated, comparative cost esti-mates should be prepared for the various alternates, anda recommendation for the selected method or methodsshould be made for the owner’s approval.

Where the structure to be restored is occupied, theeffect of repair or strengthening procedures on the nor-mal operations of the structure must be considered. Thisincludes effects such as noise, dust, and physical inter-ruption of operations. The possibility of work during off-hours, (nights and weekends) should be evaluated be-cause it often proves to be desirable and cost effective.

7.6-Cost evaluationA cost evaluation should be conducted for all feasible

repair or rehabilitation alternatives. The cost of rehabil-

itation is subject to many factors; however, the cost forcertain types of structural repair or strengthening workcan often be reasonably estimated based on previous ex-perience. Such an estimate can form the basis for an ini-tial decision regarding the appropriate alternative to beselected and the overall economic feasibility of the pro-ject.

A more detailed cost of rehabilitation should be docu-mented, taking into account the location of the projectand the existing and available labor and skilled con-tractors. These costs should be computed for the approx-imate time of the actual construction schedule. It mustbe recognized that unanticipated conditions requiringextra cost are common in many rehabilitation projectsand adequate contingencies should be provided.

In the event the estimated costs exceed the availablebudget, another cycle of possible reductions should bestudied. The final rehabilitation program then can bemodified and approved by the owner, who should be ad-vised that actual costs can be determined only afterpreparation of detailed contract documents (drawingsand specifications) and after obtaining firm bids fromcontractors.

If the cost of upgrading is determined to be prohi-bitive, possible alternate uses of the structure should bestudied, or a recommendation made for continuing itspresent use or for phasing out its use.

CHAPTER 8 FINAL REPORT

8.l-IntroductionThe results of the entire investigation should be sum-

marized in a final report. This report generally includesa brief description of the following basic areas addressedduring the evaluation process:

a) Purpose and scope of investigationb) Existing construction and documentationc) Field observations and condition surveyd) Sampling and material testinge) Evaluationf) Findings and recommendations

8.2-Purpose and scope of investigationThis section of the report should describe the purpose

and scope of the investigation as agreed with the owner,including any modifications made during the course ofthe evaluation.

8.3-Existing construction and documentationA brief summary of information on the existing struc-

ture including location, size, history, architectural andstructural details, etc., should be included in this section.The results of the documentation review should be sum-marized and supplemented by photographs, copies ofdrawings, and any other pertinent information as appli-cable. A list of all the documents collected and theirsources should be included.


8.4-Field observations and condition surveyThe results of the inspection and condition survey for

all portions of the structure, including its envelope andfoundations, should be included. The report should brief-ly describe methods and equipment used, results of as-built verification efforts, including all deviations, majordeficiencies that require remedial work, and all portionsof the structure that are to be altered for change of useor appearance. The report should also include photo-graphs, sketches, drawings, and other pertinent informa-tion prepared during the inspection and field surveyoperations.

8.5-Sampling and material testingThe locations, methods, and results of the nondestruc-

tive and destructive testing performed during the detailedinvestigation should be summarized. The results may besupplemented with photographs and copies of laboratorytest reports as appropriate. The results should indicateadequacy in terms of physical condition, strength, andfuture performance of all structural and architecturalmaterials tested.

8.6-EvaluationThe report should summarize the results of the

strength evaluation of the structure. All assumptionsmade and methods used in the evaluation process shouldbe clearly documented. A brief description of each repairalternate (Corps of Engineers 1986) or strengtheningmethod studied, along with sketches showing typicaldetails, cost estimates, and the impact of the repairmethod, should be included.

8.7-Findings and recommendationsThe findings from each preceding task discussed

should be summarized in this section of the report. Thefindings should include a discussion of the condition ofthe structure and the feasibility of the rehabilitation. Therecommendations must address the following topics: ac-tion plan, cost estimates, scheduling, and determiningconstraints and feasibility.

8.7.1 Action plan-The recommendation should clearlypoint out an appropriate course of action, such as 1)accept the structure as-is, 2) strengthen the structure tocorrect deficiencies identified, 3) change the use of thestructure, or 4) phase the structure out of service. Thecourse of action that will best satisfy the owner’s objec-tives should be considered and an appropriate and cost-effective solution for the rehabilitation should bedeveloped. Effective plans should address what actionshould be taken and how it should best be accomplished.Where budget constraints are severe, it may be necessaryto assign priorities to repairs and to stage the programaccordingly over several years. Feasible alternatives tothe recommended plan of action should be identified in-cluding estimated costs and payback periods.

8.7.2 Cost estimates--Project costs often influenceevery aspect of a recommended rehabilitation plan and,

while not necessarily controlling the final recommenda-tions, can have a major influence on them. Cost esti-mates should address the owner’s requirements and con-sider the effects of interruptions of normal operations.Additionally, it is helpful to study possible phasing (orstaging) of the project and to identify the influence thatdeferring of a particular phase would have on future re-habilitation costs. Inflation rates and interest rates shouldboth be taken into account when evaluating the impactof a deferment on a rehabilitation program. Finally, thelife expectancy of various systems and alternate repairschemes, and the life expectancy of the entire structure,should be considered. The total cost estimate should alsoinclude cost of the required engineering services, testingservices, and contingencies.

8.7.3 Scheduling--Project schedule may be determinedby the urgency of the rehabilitation needs, the availabilityof funds, the effects on ongoing operations, and the opti-mal construction conditions. If rehabilitation work is re-quired outdoors, work may be delayed until the weatheris suitable, or temporary protection measures may haveto be considered. The schedule must consider the leadtime for engineering and for preparation of constructiondocuments. Sufficient time should be allowed for contrac-tor selection and mobilization. Where unknown condi-tions exist, sufficient time should be allowed for possiblemodifications and additional engineering services if newlydiscovered deficiencies are found during rehabilitation.Adequate delivery time for special materials, new orreplacement equipment, or prefabricated componentsshould be considered.

8.7.4 Constraints and feasibility determination-Rehabil-itation often involves the constraints associated withworking around existing operations. Special considera-tions are warranted for construction operations that pro-duce dust, noise, odor, vibrations, or involve hazardousmaterials. Site access and materials handling problemsshould also be considered. Special project planning meet-ings are often helpful in determining the most appropri-ate way of handling these constraints. It is of criticalimportance to insure that any constraints mandated bythe owner be considered and incorporated into the re-habilitation plan.

CHAPTER 9-RECOMMENDED REFERENCES

9.1-Recommended referencesThe documents of the various standards-producing or-

ganizations referred to in this document are listed withtheir serial designations.

American Concrete Institute116R Cement and Concrete Technology201.1R Guide for Making a Condition Survey of Con-

crete in Service228.1R In-Place Methods for Determination of Strength

of Concrete


437R

B-14SP-85

ASTMA 370

A751

A 775

C 42

C 457

C 597

C 666

C 803

C 805

C 823

C 856

C 900

C 1084

D 3017

E 122

G 12

G 14

G 20

Strength Evaluation of Existing ConcreteBuildingsHistory of ConcreteRehabilitation, Renovation, and Preservation ofConcrete and Masonry Structures

Test Methods and Definitions for MechanicalTesting of Steel ProductsMethods, Practices, and Definitions for ChemicalAnalysis of Steel ProductsSpecification for Epoxy-Coated Reinforcing SteelBarsMethods of Obtaining and Testing Drilled Coresand Sawed Beams of ConcretePractice for Microscopical Determination of Air-Void Content and Parameters of the Air-VoidSystem in Hardened ConcreteTest Method for Pulse Velocity Through Con-creteTest Method for Resistance of Concrete toRapid Freezing and ThawingTest Method for Penetration Resistance ofHardened ConcreteTest Method for Rebound Number of HardenedConcretePractice for Examination and Sampling of Hard-ened Concrete in ConstructionsPractice for Petrographic Examination of Hard-ened ConcreteTest Method for Pullout Strength of HardenedConcreteTest Method for Portland-Cement Content ofHardened Hydraulic-Cement ConcreteTest Method for Moisture Content of Soil andSoil Aggregate in Place by Nuclear Methods(Shallow Depths)Practice for Choice of Sample Size to Estimatethe Average Quality of a Lot or ProcessMethod for Nondestructive Measurement ofFilm Thickness of Pipeline Coatings on SteelTest Method for Impact Resistance of PipelineCoatings (Falling Weight Test)Test Method for Chemical Resistance of PipelineCoatings

Other standardsASCE 11-90 Guideline for Structural Condition Assess-

ment of Existing BuildingsCRD C 48 Method of Test for Water Permeability of

Concrete, U.S. Army Corps of EngineersStandard

The preceding references are available from:

American Concrete InstituteP.O. Box 19150Detroit, MI 48219.0150

ASTM 1916 Race St.Philadelphia, PA 19103

American Society of Civil Engineers345 East 47th St.New York, NY 10017

U.S. Army Engineer Waterway Experiment StationVicksburg, MS 391809.

9.22-Cited referencesBuchanan, T., 1983. “Photographing Historic Buildings

(London: Royal Commission on Historical Monuments),(Available from Her Majesty’s Stationery Office, 49 HighHolborn, London WCIV 614B).

Carino, N.J., and Malhotra, V.M., 1991. “Handbook ofNondestructive Testing of Concrete,” CRC.

Carino, N.J., and Sansalone, M., 1990. “Impact-Echo:A New Method for Inspecting Construction Materials,”Nondestructive Testing and Evaluation for Manufacturingand Construction, Henrique L.M. DOS Reis, ed., Hemis-phere Publishing Corporation, New York.

Clifton, J.R., 1985. “Nondestructive Evaluation inRehabilitation and Preservation of Concrete and Mason-ry Materials,” Rehabilitation, Renovation, and Preservationof Concrete and Masonry Structures, SP-85, AmericanConcrete Institute, Detroit, pp. 19-29.

Clifton, J.R.; Carino, N.J.; and Howdyshell, P., 1982,“In-Place Nondestructive Evaluation Methods for QualityAssurance of Building Materials,” U.S. Army Corps ofEngineers Construction Research Laboratory TechnicalReport M-305.

Concrete Reinforcing Steel Institute, “Evaluation ofReinforcing Steel Systems in Old Reinforced ConcreteStructures,” DA-24.

Concrete Society, 1982, “Non-Structural Cracks inConcrete,” Technical Report No. 22, England.

Corps of Engineers, 1986, “Evaluation and Repair ofConcrete Structures,” Engineer Manual, EM 1110-2-2002.

HUD, 1982, “Rehabilitation Guideline--StructuralAssessment,” U.S. Department of Housing and UrbanDevelopment, Washington, D.C.

Long, A.E., and Murray, A., 1984, “Pull-Off PartiallyDestructive Test for Concrete,” In Situ/NondestructiveTesting of Concrete, SP-82, American Concrete Institute,Detroit, pp. 327-350.

Malhotra, V.M., ed., 1976, Testing Hardened Concrete:Nondestructive Methods, Monograph No. 9, AmericanConcrete Institute, Detroit, 204 pp.

Mather, K., 1985, “Preservation Technology: Evalua-ting Concrete in Structures,” Concrete International:Design & Construction, V. 7, No. 10, Oct., pp. 33-41.

Mathey, R.G., and Clifton, J.R., 1988. “Review ofNondestructive Evaluation Methods Applicable to Con-struction Materials and Structures,” NBS Technical Note1247, U.S. Department of Commerce.

McKee, H-I., 1970, “Recording Historic Buildings,"Historic American Buildings Survey, Washington, D.C.


Rp

NRMCA, 1979, “In-Place Concrete Strength Evalua-tion-A Recommended Practice,” Committee on Re-search Engineering and Standards, Publication No.133-79, National Ready Mixed Concrete Association,Silver Spring, MD.

Shroff, 1986, “Old Concrete Arches,” Concrete Inter-national Design & Construction, V. 8, No.5, May, pp.52-57.

Shroff, 1988, “Evaluating a 50 Year Old ConcreteBridge,” Concrete International: Design & Construction, V.10, No. 5, May, pp. 56-62.

Stowe, R.L., and Thornton, H.T., 1984, “EngineeringCondition Survey of Concrete in Service,” Technical

eport REMR-CS-1, U.S. Army Engineer Waterways Ex-eriment Station, Vicksburg, MS.

Thornton, H.T., Jr., and Alexander, A.M., 1987,“Development of Nondestructive Testing Systems for In-Situ Evaluation of Concrete Structures,” Technical ReportREMR-CS-10, U.S. Army Engineer Waterways Experi-ment Station, Vicksburg, MS.

This report was submitted to letter ballot of Committee 364.

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