Guide to ConcreteRepair
Reported by ACl Committee 546
Guide to ConcreteRepair
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American ConcreteInstitute38800 Country ClubDrive Farmington Hills MI 48331Fax:1.248.848.3701 Phone:1.248.848.3700
GuidetoConcreteRepair
Reported byACl Committee546
John S. Lund Chair
David W: Whitmoee Secretary
James Peter Barlow Michael M. ChehabMarwan A. Daye Michael J. Garlich Timochy R. W. Gillspie Paal E. GaudetteFred R. Goodwin Yelena S. GolodHarald G. Greve
Robert F Joyce Roe HeffronLawrence F. Kahn Brian F. KeaneKenneth M. Lozen Benjamin LavonJames E. McDonald Myles A. MurrayJay H. Paal
Johan L Silfwerbrand Richard C. ReedMichael M. Sprinkel Joe SolomonRonald R. Stankie Joseph E TomesAleunder M. Vayshurd David A. VanOckerKut Wagner
Patrick M. Watson Mark V. Ziegler
Consalring MembersNoel P Mailvaganam Peter EmmonsKevin A. Michols Richard MontaniDon T. Pyle
This guide presents remendations for the selectiom and appli- cation of materials und methods for repairing protecting andstrengrhening concrete stracheres. An overview of materials andmethods is presented as α gide for selecting α particular applica- tion. References are provided for obtaining in-depth informatiom ontihte selected materiais or methods.
3.2-Concrete removal. p. 6 3.3-Surface preparation p. 143.4-Quality control and assurance p. 17
CHAPTER 4-REPAIRMATERIALS p.17
4.2--Concrete replacements and overlays p. 17 4.1-Introduetion. p. 174.3-Crack repair materials p. 274.4--Bonding materials p. 31 4.5-Coatings on reinforcement p. 324.6--Reinforcement p. 32 4.7-Material selection p. 33
Keywords: anchorage; coating: concrete repair: joint sealant:; placement: polymer ptetive syes; repair matrials; stuctural strenthning.
CONTENTS
CHAPTER1-INTRODUCTION p.2
1.1--Guide use p. 21.2-Repair methodology p. 2 1.3-Sustainability p. 6
REPAIR TECHNIQUES p.34 CHAPTER5-CONCRETEANDREINFORCEMENT
5.1-Introduction p. 34 5.2-Crack repair p. 345.3-Conerete replacement p. 375.5-Anchorage. p. 44 5.6Quality control and assurance p. 45
CHAPTER 2-DEFINITIONS p.6
SURFACE PREPARATION p.6 CHAPTER3-CONCRETEREMOVALAND3.1-Introduction. p. 6
CHAPTER6-PROTECTIVESYSTEMS p.46
6.1Introduction and selection factors p. 46tion systems p. 46 6.2-Typical problems that can be mitigated with protec-6.3Total system concept p. 47 6.4Surface treatments p. 48
intended for guidance in plnning designing executing and ACI Committee Reports Guides and Commentaries areinspecting constrution This document is intended for the useand limitations of its content and remendations and who will accept responsibility for the application of the material itcontains. The American Concrete Institute disclaims any and all reponsibility for the stated principles. The Institute shllnot be liable for any loss or damage arising therefrom.
Reference to this document shall not be made in contractthe Architect/Engineer to be a part of the contract documents documents. If items found in this document are desired byby the Architect/Engineer. they shall be restated in mandatory language for incorporation
6.5-Concrete surface preparation and installationrequirements p. 536.7-Cathodic protection p. 54 6.6Joints p. 546.8Chloride extraction p. 55 6.9Realkalization p. 56
STRENGTHENING p.56 CHAPTER7-STRUCTURALREPAIRAND
7.1General. p. 56 7.2-Internal structural repair (restoration to originalmember strength) p. 567.3-External reinforcement (encased and exposed) p. 57 7.4-External post-tensioning p. 597.6-Supplemental members p. 61 7.5--Jackets and collars p. 60Special considerations for repair of structural clements. p.61 7.7--Repair of concrete columns p. 617.9-Repair of conerete structural slabs p. 64 7.8-Repair of concrete beams girders and joists p. 63
CHAPTER8-REFERENCES p.65 Authored documents p. 69
CHAPTER1-INTRODUCTION
1.1-Guide use
This document provides guidance on removal and prepa-ratin selecting material and application methods for repair protection and strengthening of concrete structures. Theinformation is applicable to repairing deteriorated or damagedconcrete structures; correcting design or construction defi- ciencies; and strengthening the structure for new uses or toply with current more restrictive building codes.
Current practices in concrete repair are summarized andinformation provided for the initial planning of repair work conditions. and selecting repair materials and methods for various
1.2-Repair methodology
The methodology for repairing a concrete structure typi-cally includes a condition assessment of the structure designing repairs developing construction documents bidding and negotiation processes and performing the dad astructure is also remended. A basic understanding ofthe causes of concrete distress deterioration or deficien- cies is essential to performing meaningful evaluations andof deterioration or deficiency is detemined the appropriate pleting successful repairs (ACI 364.1R). Once the causerepair program can be selected to address these conditions.Depending on the cause and extent of the damage repair is not always warranted.
of the deterioration or deficiency and not focus only on the Assessment of the structure should determine the causesymptoms. For example cracking can be a symptom ofdistress that may have a variety of causes such as restraint
of drying shrinkage restraint of movement due to thermalcycling verloading corrosion of embedded metal or nad-cquate design or construction. The cause of distress should be assessed for proper selection and implementation of anappropriate repair program (Fig. 1.2).
1.2.1 Condirion assessmentThe process of repairinga concrete structure starts with the evaluation of existingconditions. The evaluation can be divided into several steps:
a) Reviewing available design and construction docu-ments previous reports repair/maintenance records and testdata if available;
b) Visually examining the existing structure;
or the structure in its deteriorated condition: c) Performing structural analysis of members in question
d) Evaluating corrosion activity:
e) Performing invasive or nondestructive testing or both;
f) Reviewing physical chemical and petrographic anal-ysis results of laboratory-tested concrete samples.
Aditional information on conducting condition surveys can be found in ACI 201.1R 207.3R 222R 224.1R 228.2R 364.1R 437R and 562.
1.2.1.1 Unsafe conditionsDuring the condition assess-ment conditions discovered that pose an immediate safety issue should be identified and reported to the owner for miti-gation. Local building codes may require that the licensed design professional (LDP) report unsafe conditions to the authorities and typically require that the owner take measuresto protect the public safety where hazardous conditions exist. For example if loose concrete on overhead or verticalsurfaces is discovered access should be limited in the areas adjacent to and below until the hazards are removed or stabi-lized If structural members exhibit promised integrity.these members should be stabilized or the affected areas removed from service.
depends on maintaining the integrity of the structure and 1.2.1.2 Global issuesThe performance of a structureenvelope of the building. If the LDP bees aware of anitem of concern outside the assigned scope of work that could promise the integrity of the structure or jeopardizepublic safety the appropriate parties shuld be notified for implementation of remedial action.
1.2.1.3 Determination of cause and extentDuring thecondition assessment of a structure the cause of distress deterioration or deficiency should be determined. Becausea basic understanding of the causes of concrete deterioration many deficiencies are caused by more than one mechanism is essential to determine what has happened to a particularable remedial action plan can be developed repair appli- concrete structure. After pleting the assessment a suit-prepared If a delay occurs between the condition survey cations and materials selected and contract documentsand performing the repair work aditional deteriorationand distress could occur and consideration should be given to updating the condition survey to minimize variationsbetween estimated and actual quantities of repair work.
1.2.2 Design considerationsWhen designing a concreterepair strengthening system or protective system the LDshould consider the safety and serviceability of the structure
Fig. 1.2-Repair methodology.
during construction and its performance at pletion. At aminimum the repaired structure should satisfy the building code requirements for which it was designed. If required bythe governing agency the repaired structure may have to satisfy current building code requirements and be repairedand strengthened to meet these criteria. In any case it is thefor all structural ponents within the LDP's scope of work. LDP's responsibility to satisfy applicable code requirements318 may not be directly applicable to the current situation. In Structural code provisions such as those contained in ACIsuch cases ACI 562 requirements should be followed. TheLDP should apply basic principles of structural mechanics and have an understanding of material behavior to evaluateor a protective system. Several design considerations are and design a structural repair a strengthening procedure discussed 1.2.2.1 through 1.2.2.6.
condition a structural member or system may distribute 1.2.2.1 Caurrent load distribution-In a deteriorateddead and live loads differently than when the structure was undamaged. Cracking deteriorated concrete and corrodedreinforcement can alter the behavior of members leadingto changes in shear moment and axial load distribution. As concrete and reinforcement are removed and replacedbe further modified. To understand the final behavior of the during the repair operation these redistributed forces maystructural system the engineer should evaluate the redistri-bution a member can be relieved of the load by jacking or bution of the forces. To reestablish the original load distri-not jacked and the dead load is not relieved the repaired and other means before repair implementation. If the structure isadjacent members may support loads differently than wasassumed in the original design of the structure.
1.2.2.2 Comparibiliry of materialsIf a repair and theexisting substrate materials have the same stiffness or modulus of elasticity the behavior of the repaired membermay be assumed to be the same as the original member before triorationordamageonersely ifthe stifessesdiffer then the posite nature of the repaired systemacteristis further exacerbates the effects of thermal change should be considered. A mismatch of other material char-vibration long-tem creep and shrinkage. If the coefficient of thermal expansion of the repair material differs from thatof the original material stresses will be generated in both therepair and original material by temperature changes.
1.2.2.3 Creep and shrinkageReduction in length area or volume of both the repair and original materials due to creep shrinkage or both affect the structure’s serviceabilityand durability. As an example pared with the original material high creep or shrinkage of repair materials results in loss of stiffness of the repair redistributed forces andincreased deformations. Controlled-shrinkage cementitious repair materials and systems can contribute to the reductionof the volume change effects.
a plastic state or until adequate strength has been developed 1.2.2.4 VibrationWhen the installed repair material is invibration of a structure can result in reduced bonding of the repair material. Isolating the repairs or eliminating the vibra-tion may be a design consideration.
migration through a concrete structure can degrade a repair. 1.2.2.5 Water and vapor migrationWater or vaporshould be a repair design consideration. Understanding the cause of the migration and controlling it
1.2.2.6 Material behavior characteristicsAfter a repairis executed the structural behavior of the repaired section
