1、1ACI 364.6T-02(11)ConCrete removal in repairs involving Corroded reinforCing steelKeywords: corrosion; reinforcing steel; repair; ring anode effect; surface preparation.TechNoteIntroductionThe performance of a reinforced concrete repair depends significantly on the condition of concrete in the reinf
2、orcement vicinity and on the quality of (re-)encapsulation. The extent of concrete removal prior to repair must be adjusted in accordance with the degree of contamination and the nature of distresses affecting the member or structure.Questionnullhen corroded reinforcing steel is encountered in a rep
3、airnullshould the bar be undercutnull ow far should the bar be exposed along its lengthnullAnswernulloncrete should be removed around the reinforcing barnullleaving in all directions a clear distance of at least nullnullnullin. (nullmm) plus the dimension of the repair material maximum sinulle aggre
4、gate. nulln additionnullconcrete removal along the reinforcing bar shall continue until the bar is essentially free from corrosion products.Discussionnullhen a portion(s) of the electrically continuous reinforcing bar is exposed to a chloride-free repair material and the rest of the bar remains in c
5、ontact with chloride-contaminated andnullor carbonated concretenullcorrosion in areas adjacent to the repair may be accelerated. This condition is often referred to as the nullring effectnullor nullhalo effect.null encenullwhen corrosion problems are encountered in a repairnullthe chloride ion conce
6、ntration and the depth of carbonation in the existing concrete should first be determined.The decision to undercut the reinforcing bar should be made based on the chloride ion concentration andnullor extent of carbonation in the surrounding concrete. There is a high risnullof continuing corrosion wh
7、enevernullat the reinforcing steel levelnullthe acid-soluble chloride content by weight of cement exceeds nullnull(nullnullTnullnullnullnullnull) or cement paste is carbonated. nullignificant contamination may require the removal of existing concrete surrounding the bar. nulluch a removal will avoid
8、 creating an environment where part of the circumference is depassivated and another part is still passivenulla combination that may lead to accelerated corrosion.The sinulle of the repair shall be based on both technical and economic considerations. nullinimallynullif corroded reinforcement in the
9、repair is exposed and found to have loose oxidation products or is not bonded to the surrounding concretenullit is recommended that the concrete be removed from around the bar (nullig. null). The clear space behind the reinforcing steel should be not less than nullnullnullin. (nullmm) plus the dimen
10、sion of the maximum sinulle aggregate in the repair materialnullas shown in nullig. null.nullnullnullnulln additionnullconcrete removal along the reinforcing bar shall continue until the bar is essentially free from corrosion products. nulln some cases of advanced corrosionnullit may be appropriate
11、to replace the affected reinforcement and concrete along the entire length of the member.Summarynullhen corroded reinforcing steel is encountered in a repairnullsurrounding contaminated concrete should be removed and the bars should be undercut and exposed along their entire affected length.Referenc
12、esnull. nullnullnullnullnull nullnulluide for nullurface nullreparation for the nullepair of nulleteriorated nulloncrete nullesulting from nulleinforcing nullteel nullorrosion (nullnullnullnull nullnull.nullnull-nullnullnullnull) nullformerly null. nullnullnullnullnullnullnullnull nternational nullo
13、ncrete nullepair nullnstitutenull osemont null nullnullnullnullnullnullnullnullnullpp.null2 CONCRETE REMOVAL IN REPAIRS INVOLVING CORRODED REINFORCING STEEL (ACI 364.6T-02)Fig. 1Typical concrete removal around reinforcing bar.Fig. 2Removal of concrete from around reinforcing bar (adapted from ICRI 3
14、1null1Rnullnullnull formerly No. nullnullnull.null. nullnullnull ommittee nullnullnullnull nulloncrete nullepair nulluide (nullnullnull nullnullnull-nullnull)nullnull merican nulloncrete nullnstitutenull armington nullillsnullnullnullnullnullnullnullnullnullnullnullpp.nullCONCRETE REMOVAL IN REPAIRS
15、 INVOLVING CORRODED REINFORCING STEEL (ACI 364.6T-02) 3nullnullnull Technullotes are intended for reference for the design and construction of concrete structures. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and w
16、ho will accept responsibility for the application of the information it contains. The nullerican nullncrete nullstitute disclaims any and all responsibility for the accuracy of the content and shall not be liable for any loss or damage arising therefrom. nullference to this document shall not be mad
17、e in contract docu-ments.nullnullnullnullnull-null was adopted and published nullly nullnull.nullpyright nullnullnullnullnullerican nullncrete nullstitute.nullll rights reserved including the rights of reproduction and use in any form or by any meansnull including the manulling of copies by any phot
18、o processnull or by electronic or mechanical devicenullprintednullwrittennullor oralnullor recording for sound or visual reproduction or for use in any nullowledge or retrieval system or devicenullunless permission in writing is obtained from the copyright proprietors.For additional copies, please c
19、ontact: American Concrete Institute, 38800 Country Club Drive, Farmington Hills, MI 4833null nullone: null8null48nullnull0, Fanull 348null48nullnullnull nullnullnullconcretenullorgReported by ACI Committee 364nulled null nullodwinnullairnulljorie null nullynchnullcretarynullndall null nullardnullnoi
20、t nullssonnettenullristopher null nullownnulluglas nullrnullnullyan nullexander nullrrisnulluce null nullllinsnullian nulle nullpenullris nullagunsnullnullter null nullmonsnullul null nulludetteTimothy null null. nullllespienullreh null nullegoriannullwan null nullptanullmes null nullnullnaldnullill
21、iam null nullshnully null nullulnull nullm nulliuThomas null nullencernullhn null Tannernullalery Tonullrnullvid null nullannullnullrnullexander null nullaysburdnullrt null. von nullynullmes nullarnernullvid null. nullitmorenullhn null nullusfeldnulln nullffronnullbert null nullnrynulll null nullndo
22、nullarles null nullonullamnullhonullnull nullnulldenullmes null nullspernullory null nullmpnullith null nullsnernullicnullnull nullrsonnullhn null nullndnullitpal null nullngatnullrendra null nullnjrenullrConnullulting membernullnullbert null. nullvecnullrnullephen null nullhansonnullward null nullwlon null.nulleilan nullngnullla Tharmabalanullbert Tracynullilliam null. nullescott
