1、1Use of Hydrodemolition for ConCrete removal in Unbonded Post-tensioned systemsKeywords: demolition; hydrodemolition; post-tensioning; repair.QuestionShould hydrodemolition be used to remove concrete when unbonded post-tensioned systems are exposed in the removal process?AnswerHydrodemolition is not
2、 recommended for concrete removal if there is a possibility that unbonded post-tensioned systems are within the concrete removal zone. Currently, the only viable method of concrete removal in this situation is concrete chipping using lightweight nullacnullhammers or needle scalers.DiscussionHydrodem
3、olition is one of many methods available for concrete removal on horizontal, vertical, and over-head surfaces. nullhis techninullue uses very high-pressure water nullnullnull,nullnullnullto nullnull,nullnullnullpsi nullnullnullnullto nullnullnull nullanullnullto remove concrete. Hydrodemolition has
4、some advantages over other methods, including speed. nullased on available evidence,null,nullit does not cause signinullcant microcracnulling or bruising of the concrete substrate, and it provides a good surface with partially exposed aggregate for amplitude usually in excess of nullnullnullin. null
5、 mmnullto bond new concrete on.nulllthough hydrodemolition will not physically damage steel tendons, it is not considered to be a viable concrete removal techninullue if there is a possibility of the high-pressure water coming into contact with tendons, anchorages, or both. nulleasons that hydrodemo
6、lition is not considered to be a viable techninullue includenullnull Hydrodemolition of post-tensioned concrete elements may cause a safety problem. nullt is potentially dangerous because it may accidentally undercut embedded anchors and result in explosive release of prestressing force;null nullf a
7、ny part of the tendon is exposed to high water pressure, water may penetrate into the tendon. nullhe water nullets will linullely destroy the sheathing on the tendons, whether it is wrapped in paper, plastic, tubing, or extruded plastic. nullf the sheathing is damaged, the water has a direct path to
8、 the prestressing strand or wire, and corrosion may result; andnull Concrete repair pronullects commonly include replacement of post-tensioning strand. nullhe water pressure used in hydrodemolition enulluipment can force slurry into the sheathing. nullhen slurry and other debris exist within the she
9、athing, installation of a new strand becomes very difnullcult. nullhen the new strand is pushed into the existing sheathing, debris within the sheathing builds up ahead of the advancing strand. nullhis buildup of debris can cause the sheathing to rip and nullball upnullin front of the leading edge o
10、f the strand. nullhis scenario manulles strand replacement very difnullcult and compromises the corrosion protection or sheathing over the prestressing steel.nullore information can be found in nullCnullnullnullnull.nullnull.nullSummarynulluring concrete removal around reinforcement, including unbon
11、ded post-tensioned systems, potential collateral damage to the repaired structure must be considered relative to future performance. Consenulluently, selection of the appropriate method of concrete removal is crucial. Hydrodemolition is not recommended for concrete removal if there is a possibility
12、that unbonded post-tensioned systems are within the concrete removal zone.Referencesnull. Sprinnullel, null. null., nullnullreparing nullridge nullecnulls for nullverlays,null Concrete Repair Digest, null. null, null. null, nullnullnullnull, pp. nullnullnull-nullnullnull.null. nullssonnette, null.;
13、Courard, null.; nullaysburd, null. null.; and nullnulllair, null., nullConcrete nullemoval nullechninulluesnullnullnnulluence on nullesidual Cracnulling and nullond Strength,nullConcrete International , null. nullnull, null. nullnull, nullec. nullnullnullnull, p. nullnull-nullnull.ACI 364.8T-02(11)T
14、echNoteAmerican Concrete Institute Copyrighted nullterianullnullnull.concrete.org2 USE OF HYDRODEMOLITION FOR CONCRETE REMOVAL IN UNBONDED POST-TENSIONED SYSTEMS (ACI 364.7T-02)null. nullCnullCommittee nullnullnull, nullCorrosion and nullepair of nullnbonded Single Strand nullendons nullnullCnull nu
15、llnull.nullnull-nullnullnull,null merican Concrete nullnstitute, nullarmington Hills, nullnull, nullnullnullnull, nullnullpp.Referenced Standards and ReportsnullCnull nullnull ulletin nullnull, nullnullnullnull, nullConcrete nullemoval nullsing Hydrodemolition,null ield nulluide to Concrete nullepai
16、r nullppli -cation nullrocedures, nullmerican Concrete nullnstitute, nullarmington Hills, nullnull, nullpp.nullCnullnull, nullnullnullnull, nullnulluideline for the nullreparation of Concrete Surfaces for nullepair nullsing Hydrodemolition nullethods nullnullCnullnullnullnullnull.null-nullnullnullnu
17、llnull,nullnullnternational Concrete nullepair nullnstitute, nullosemont, nullnull, nullnullpp.Reported by ACI Committee 364nulled null nullodwinChairnullnullrie null nullynchSecretarynullndall null nullardnullnoit nullssonnetteChristopher null nullownnulluglas nullrnullnullyan nullexander Carrisnul
18、luce null Collinsnullian nulle Copenullris nullagunsnullnullter H. nullmonsnullul null nulludettenullimothy null null. nullllespienullreh null nullegoriannullwan null nullptanullmes null nullnullnaldnullilliam null nullshnully H. nullulnull nullm Shiunullomas null Spencernullhn null nullannernullale
19、ry nullonullrnullvid null nullannullnullrnullexander null nullaysburdnullrt null. von nullynullmes nullarnernullvid null. nullitmorenullhn null Hausfeldnulln Heffronnullbert null Henrynulll null HindoCharles null Hoonullamnullhonullnull nullnulldenullmes null nullspernullory null nullmpnullith null
20、nullsnernullicnullnull nullrsonnullhn S. nullndnullitpal S. nullngatSurendra null nullnnullenullrConsulting membersnullbert null. nullvecnullrStephen null nullhansonHoward H. nullwlon null.nulleilan Songnullla nullarmabalanullbert nullracynullilliam null. nullescottnullCnull nullechnullotes are inte
21、nded for reference for the design and construction of concrete structures. nullhis document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and who will accept responsibility for the application of the information it contains. null
22、he nullmerican Concrete nullnstitute disclaims any and all responsibility for the accuracy of the content and shall not be liable for any loss or damage arising therefrom. nulleference to this document shall not be made in contract documents.nullnullnullnullnull-null was adopted and published nully
23、nullnull.Copyright nullnullnull, nullerican Concrete nullstitute.nullll rights reserved including the rights of reproduction and use in any form or by any means, including the manulling of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for
24、 sound or visual reproduction or for use in any nullowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.For additional copies, please contact: American Concrete Institute, 38800 Country Club Drive, Farmington Hills, MI 4833null nullone: null8null48nullnull0, Fanull 348null48nullnullnull nullnullnullconcretenullorg
