1、ACI 555R-01 became effective October 1, 2001.Copyright 2001, American Concrete Institute.All rights reserved including rights of reproduction and use in any form or by anymeans, including the making of copies by any photo process, or by electronic ormechanical device, printed, written, or oral, or r
2、ecording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission inwriting is obtained from the copyright proprietors.ACI Committee Reports, Guides, Standard Practices,and Commentaries are intended for guidance in planning,designing, executing,
3、and inspecting construction. Thisdocument is intended for the use of individuals who arecompetent to evaluate the significance and limitations ofits content and recommendations and who will accept re-sponsibility for the application of the material it contains.The American Concrete Institute disclai
4、ms any and all re-sponsibility for the stated principles. The Institute shallnot be liable for any loss or damage arising therefrom.Reference to this document shall not be made in con-tract documents. If items found in this document are de-sired by the Architect/Engineer to be a part of the contract
5、documents, they shall be restated in mandatory languagefor incorporation by the Architect/Engineer.555R-1Removal and Reuse of Hardened ConcreteACI 555R-01This report presents information on removal and reuse of hardened con-crete. Guidance for assessment of concrete structures for complete or par-ti
6、al demolition is provided. The applicability, advantages, limitations, andsafety considerations of various types of concrete removal methods, includ-ing hand tools, hand-operated power tools, vehicle-mounted equipment,explosive blasting, drills and saws, nonexplosive demolition agents,mechanical spl
7、itters, heating and thermal tools, and hydrodemolition(water-jet blasting), are provided. The available surface removal systems,their probable applications, and advantages and disadvantages of varioustypes of surface removal systems are discussed. Considerations for evaluat-ing and processing waste
8、concrete for production of aggregates suitable forreuses in concrete construction are presented.Keywords: aggregates; concrete removal; condition survey; demolition;diamond saw; drop hammer; explosive blasting; hardened concrete; hydro-demolition; impact breaker; jet-flame cutter; mechanical spltter
9、; mixtureproportion; nonexplosive demolition agent; recycled aggregates; recycledconcrete; rotating cutter head; spring-action breaker; thermal lance; water-jet blasting; wrecking ball.CONTENTSChapter 1Introduction, p. 555R-21.1Scope1.2ObjectiveChapter 2Kinds of concrete and degree of removal, p. 55
10、5R-22.1Introduction2.2Assessment of concrete structures for complete orpartial demolition2.3Types and degrees of removal2.4Types of concrete and effects on removal and reuse2.5Monitoring and safety considerationsChapter 3Removal methods, p. 555R-63.1Introduction3.2Hand tools3.3Hand-operated power to
11、ols3.4Vehicle-mounted equipment3.5Explosive blasting3.6Drills and saws3.7Nonexplosive demolition agents3.8Mechanical splitters3.9Demolition of concrete structures by heat3.10Hydrodemolition (water-jet blasting)Chapter 4Surface removal, p. 555R-114.1Introduction4.2Purpose of surface removal4.3Systems
12、 available for surface removal4.4Definition of final surface4.5Requirements for surface preparation4.6Concrete pavement surface removal4.7Influence of surface conditions on bond propertiesChapter 5Production of concrete from recycled concrete, p. 555R-185.1IntroductionReported by ACI Committee 555Jo
13、seph F. Lamond*ChairmanRoy L. Campbell, Sr. Almerigo Giraldi Nichloas J. T. JenkinsTimothy R. Campbell William Halczak Raymond MillerJoseph A. Cazares Herbert C. Hale, Jr. Philip T. Seabrook*Tony C. Liu, member and chairman of ACI Committee 555 as of March 30, 2001, also contributed significantly to
14、 the completionof this document.555R-2 ACI COMMITTEE REPORT5.2Aggregate production process5.3Aggregate quality5.4Effects of recycled aggregates on concrete properties5.5Mixture proportioning5.6Concrete production Chapter 6References, p. 555R-246.1Referenced standards and reports6.2Cited referencesCH
15、APTER 1INTRODUCTION1.1ScopeThis report provides available information on concrete re-moval methods with detailed discussions on surface remov-al. Reuse of removed concrete as concrete aggregate is alsoaddressed. The type and kind of concrete and its locationwithin a structure directly affect the rem
16、oval methods to beused. Selection of proper tools and equipment are critical fora cost-effective and safe concrete removal project.1.2ObjectiveDriven by cost, need, and limited resources, the technolo-gy for concrete removal and reuse is rapidly advancing. Par-tial removal of critical structural com
17、ponents for repairrather than replacement, geographical constraints, access tostructures planned for removal, environmental regulations,and worker and structure safety will continue to effect anevolution of developing methods and equipment.With safety as a foremost consideration, thorough plan-ning
18、is essential when engaged in a removal project. Thescope and type of concrete to be removed should be evaluat-ed and examined in detail to determine the most advanta-geous system(s). This report provides information onselecting the most appropriate systems.Concrete reuse is primarily related to a pr
19、ojects location.For example, limited availability of materials in a particularregion may result in a cost-effective use of equipment andmanpower to remove nearby concrete structures with theintent of reusing the removed materials as a roadway baseor as coarse aggregate for concrete. This report is c
20、onfinedto the evaluation and processing of hardened concrete usedas concrete coarse aggregates.Work continues in a number of countries to improveequipment and methods, including the use of robotics. Pro-ceedings from the RILEM Symposium held in October 1993in Odense, Denmark, and other RILEM publica
21、tions provideadditional information. These publications include: Demoli-tion and Reuse of Concrete and Masonry (Kasai 1988),Demolition and Reuse of Concrete and Masonry (Lauritzen1993), “Disaster Planning, Structural Assessment, Demoli-tion and Recycling” (De Pauw and Lauritzen 1993), “Recy-cling of
22、 Demolished Concrete and Masonry” (Hansen 1992),and “Specification for Concrete With Recycled Aggregates”(RILEM Technical Committee 121 1993). The StrategicHighway Research Program (SHRP) in the United Statesstudied problems that have an influence on the removal ofconcrete for bridges (Vorster et al
23、. 1992).CHAPTER 2KINDS OF CONCRETE AND DEGREE OF REMOVAL2.1IntroductionThis chapter addresses complete and partial removal fromdifferent types of structures and assessment of structure con-sidering safety, stability, cost, constructibility, and environ-mental impact. The complete or partial removal
24、ofprestressed, reinforced, and unreinforced concrete structuresshould be assessed by a competent team experienced in allphases of the concrete removal operation.One should identify sound concrete and examine whateffect the removal may have on remaining concrete andreinforcement when partial removal
25、is undertaken. Mostimportantly, concrete removal or demolition should beperformed under appropriate supervision, regardless ofthe project size. 2.2Assessment of concrete structures for complete or partial demolition2.2.1 General considerationsGuidance on performing acondition survey of concrete stru
26、ctures is covered extensive-ly in ACI 201.1R. Listed below are other general items toconsider before either partial or complete concrete removal.If the decision to remove concrete is based on economic orreasons other than concrete deterioration, a detailed condi-tion survey might not be necessary.2.
27、2.1.1 SafetyA predemolition survey should be per-formed to determine if the planned work could cause anystructure to collapse. Before to starting work, a survey of thejob site should be made to determine the hazards and thesafeguards necessary to ensure that work is performed safely.Continually chec
28、k for hazards due to weakening of thestructure.2.2.1.2 Environmental impactA work plan requiring theremoval of a structure, either partially or totally, should addressthe impact on the surrounding environment. Impacts on theenvironment include: neighboring tenants and surroundingstructures; noise po
29、llution; dust pollution; water runoffs due towork, storms, or both; and other environmental factors such asasbestos and hazardous chemicals. An inventory of potentialenvironmental impacts should be developed and used as achecklist during concrete removal operations.2.2.1.3 Plans provided or drawn fo
30、r assessment documen-tationDuring the condition survey of the concrete structure,prepare drawings or sketches that reflect existing conditions.These drawings or sketches become part of the condition sur-vey report to provide preremoval documentation.2.2.1.4 Complete set of structural and architectur
31、aldrawingsIn performing a condition survey of concretestructures, the use of as-built structural and architecturaldrawings is strongly recommended for work plan development.The drawings can be reviewed and evaluated for assessingexisting conditions, areas of distress or potential hazards, devel-opme
32、nt of work plans, and concrete removal operations. Withaccurate and thorough drawings, a work plan can be developedsafely and effectively, while minimizing environmentalimpacts and costly errors. If original drawings are not avail-able or if modifications appear to have been made, spot de-REMOVAL AN
33、D REUSE OF HARDENED CONCRETE 555R-3structive exploration may need to be done to ascertainreinforcement location, size, and condition.2.2.1.5 Budgetary and logistic constraintsBudgetaryand logistic constraints should be identified and incorporatedinto the work plan.2.2.2 Evaluation of concrete2.2.2.1
34、 Field documentation (visual examination)Referto ACI 201.1R to develop a checklist for field documentationof the structure. ACI 201.1R provides information on exami-nation of uniformity and rating of distress manifestations.2.2.2.2 Detailed examination(i) PetrographyThe usefulness of any petrographi
35、cexamination procedure on the objectives of the investigation,proposed or underway, can be determined by a discussionwith an experienced petrographer. ASTM C 457 can be usedto develop data that will explain why freezing-and-thawing-related damage has occurred. ASTM C 856 gives the follow-ing purpose
36、s for petrographic examination of concrete: Determine, in detail, the condition of concrete in astructure; Determine inferior quality, distress, or deterioration ofconcrete in a structure; Determine whether alkali-silica or alkali-carbonatereaction, or cement-aggregate reaction, or reactionsbetween
37、contaminants and the matrix have taken place,and their effects upon the concrete; Determine whether the concrete has been subjected toand affected by sulfate attack, other chemical attack,early freezing, or to other harmful effects of freezingand thawing; and Determine whether concrete subjected to
38、fire is essen-tially undamaged or moderately or seriously damaged.(ii) Nondestructive testing (NDT)There are numer-ous nondestructive test methods for estimating strength ofconcrete, a few of which are listed as follows:a) Surface hardness methods;b) Penetration resistance techniques;c) Pullout test
39、s; andd) Ultrasonic pulse velocity method.There are also other nondestructive test methods fordetermining properties other than strength: a few arelisted as follows:a) Magnetic methodsreinforcement cover and location;b) Electrical methodsreinforcement corrosion, thick-ness of concrete pavements, moi
40、sture content, and moisturepenetration;c) Radioactive methodsdensity, voids, composition, andsegregation; andd) Ultrasonic pulse velocity and pulse echo techniquesto determine cracks and voids in mass concrete.For additional test methods and their application and limita-tions, refer to ACI 228.1R an
41、d ACI SP-82 (Malhotra 1984). 2.2.2.3 Cause of distressIn developing removal proce-dures, consider the cause of distress on the removal processas it may affect the structures integrity.2.2.2.4 Reuse of concrete rubbleRefer to Chapter 5.2.2.2.5 Transport and deposit of waste materialVerylittle of the
42、approximately 135 million tons (123 milliontonnes) of removed concrete rubble in European communi-ties, United States, and Japan is reused. Due to the decliningavailability of disposal sites, recycling alternatives should beevaluated as quality aggregate sources.2.2.3 Report2.2.3.1 Summary of scope
43、of workDefine purpose andlimitations of preliminary investigation and findings, con-crete removal work plan, safety, schedule requirements,environmental aspects, or recycling plan.2.2.3.2 FindingsDescribe the structure, its presentcondition, nature of loading and detrimental elements, origi-nal cond
44、ition of the structure, materials used in construction,and practices used in constructing the structure. Photographsshould be used to illustrate the conditions.2.2.3.3 RecommendationsInclude complete or partialdemolition, salvage, removal methods, safety and environ-mental considerations, and furthe
45、r investigation or testing asrequired.2.2.3.4 Total estimated costProvide cost estimates forvarious removal methods, partial or complete concrete re-moval, reuse, transportation and waste disposal, and addi-tional inspection and testing. Other associated costs shouldbe identified and estimated where
46、 practical, including pro-tection of adjacent construction.2.2.3.5 Photos and drawingsUse of drawings illustrat-ing as-built, current conditions and areas of concern (for ex-ample, concrete quality, distress, loading, and utilities) isrequired to demonstrate the need for concrete removal, thelogic f
47、or the method, and amount of removal recommended.Photographs can illustrate distress manifestations and providedocumentation of existing conditions. Where possible, in-clude some means for identifying scale, such as including aruler or other recognized object like a pencil or coin.2.2.3.6 Supporting
48、 data in comprehensive formTosupport findings and recommendations, the data developedthrough visual examination, coring, nondestructive testing,petrography, photographs, drawings, and sketches should bearranged in a comprehensive format that can readily be fol-lowed. For example, plans could be labe
49、led with symbolsidentifying where samples or photos were taken, with eachsample or photo containing a brief but concise description. Itis essential that the extent of damage be established, regard-less of the cause. Whether concrete quality of the remainingstructure is sufficient to support a sound repair should be de-termined.2.2.4 Engineering surveyBefore starting any demolitionoperations, an engineering survey of the structure conductedby a competent individual is required. The purpose of thesurvey is to determine t
