Tedmic al Ciee Re阿 おω Dig Eiti, 91-1ωI C叩yn似⑥2閥均aCo間取I stJtu te Commi ttee Re port : JCI・ TC075B Technical Commttee on Autogenos Heaing匝Cementtous Maerials Shn-ichi GARASH, Mnoru KUND, Tomoya NSWKAbstract 91 百le Committee on Autogenous Heaing in Cementitious Meris (chain: Shinichi gashi, Kzawa University) hs cried out its activi esωreonlze pぉt studies on血e sef-heng!-reparingnco n of conc rete over t wo yes (2007-2008). A surey of 白E iterature ncuding the atest reserch位ends of the commitee members was conducted with a prtic叫r focus on由e mechism of sef-heing!repairing, in order to cassi骨粗d dene the phenomena. The Commitee so hed a workshop/pediscussion during也e nuconvention of JCI in 2008, at which vuabe owedge企om resechers i n vrious spheres ws accumuated, wit h discussions made on e requred direction of tre s佃dy. Keywordsactivated reparing, autonomic heng, crack, natraheaing, repr technique Introduc姐on Sefheaing of cracks i n concre旬is a generic term for phenomena incudng re-hydration of unhydrated cement, which hs been recoied as a phenomenon for a ong te, as mentioned by A. M. Nevie 1s‘autogenous heaing.' However, da回accumuaon組d qutitive evauation have not been sucient f or engneers to consider白is phenomenon 也e desi ste. T here fore, it hs n ot become av abe for desid use as a met hod of repair . JCI TechnicCommiton Autogenous Heng n Cementious Mris (JC・TC075B, channShni chi gashi, Kzawa Univer sity) hs cied out cvities to review past studies on sef-heaing!・re pairing of concrete over the ast two yes (200 72 008). 百e commit ee member s, who e ist ed n Table , ∞nduc 旬 d a ite rature surey incudng ther atest reserch resuts d hed discussions withe of achievng 也e qutication of se fheaing on vious scaes. Specic弘ese ncude a microscopi c eve(modeng usng cement hydraon modes), mesoscopic eve(evuation on a eveof constutive modes), d macroscopic eve(utiiz耳ion methods on a concre旬member eve). At a workshop/pediscussion hed durng the AnnuConvention of JCI in 2008, vauabe owedg e of res ec her s 企om vi ous ed s w accumuated, widiscussions hed
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8/14/2019 Technical Committee on Autogenous Healing in Cementitious Materials_TC075B_tcr09
S Igahi, M KW児a and T. Nihiwaki ! Tec加ical Cittee Rors 2ゆ Diest Editm, 91-102
1ble : Dra table of conents of e epot
Capter 1 IntroducionCapぬr 2 Sef. heag/repairing peomea ad deosCapter 3 Sef. heag/rep唱iring mecasms and crrent stae of techology
Capter4 Maぬria 即時田皿odels o se. ealing/repairgCapter 5 Eperea evalation of self hea酔epairing e飴ctsCapter 6 Applcaon exampes of sef heag/reparng nctonsCapt泡r7 τeame of sef heag/ep岨rg other 直dsCapter 8 Sef heag peomena of ceamc materas (Specal corbo)Capt泡r 9 JCI wokshop FokaCapter 10 ConclsosAppendx
. Classcaion o phenomena and de自国姐ons otems
93
The Commitee categorzed te concept of self-hengーreparing as shown n Fig. 1組d
Table 3, focusng on respecve phenomena. Tabe 4 gives exples of studies n each
c旬gory. The c蹴go白紙ion nd dierences of mechnisms betw閃ne c蹴goe温e
expled n e following praphs:
‘Recovery' which covers te entire ea shown in Fig. 1 is dened s event in gener
n which least one nion of concrete rωovers by whatever mes. Conventiona
repair/s仕engtenng corresponds to也is while it is expected也at self-heaing・reparing of
concrete det w由is report will be regded s a fesible mes for recovery.
‘Selfheaingrepairng' is demed悩n event n genera in which at lest one nction of
concrete recovers by mechnisms nherenty provided n concrete wi世0ut te need for
rep or s回ng世enng. Note紙‘heaing' d‘rep釦ing' e dierentiated om each oter
as follows: te foner refers to cloggng of cracks by phenomena found in convention
concrete s well suchrehydration of cement d deposion of cacium cbon旬 wheres
e l枕er refers to mens clog crackng by te addition of rtici device s a substitute
for convention repr/s回ng世enng. I oter words ‘heaing' mkes cracng of a
cementitious meria clogged by itself, utiizng its nne mechisms. Addition of a
supplement cementitious materia for nstnce appropri旬 proportion to accelerate
such a crackclogging mechism is aso ncluded in‘heng.世e oter hd,‘reprng'
adds devices such箇microcpsues nd heatgeneratng devices血a e outside of也E
category of conventiona supplementry cementitious materis to imprt a crackclogging
cpability s a new ncon.
8/14/2019 Technical Committee on Autogenous Healing in Cementitious Materials_TC075B_tcr09
ωconcreteωeact i脂latent po旬ntial,or by includng short bers n concrete to suppress
the widenng of crack wid血s. The latr direction aso ncludes a methoda utilzes bacteria
livng orgisms, having them deposit CaC03 in cracks to clog them 百e foer drection is
dened here s‘na加ra heang,悩
with no tici mes. This corresponds to ea A in Fg. 1.百e latter direction is dened
here s‘autonomic heang, in view of也e ct也at,血ough supplementry cementitious
materials nd/or renforcing bers紅白added to concrete, these have been ∞nvenonly
added to concrete not for self-healing/-repairng but to be in旬a pt of世e s飢re
constutng concæ旬.百e 旬rmautonomic' was adopted ωexpress concretes own hengeect, because the s佐ct町e of concrete itself accelerates clogging of cracks. This corresponds
to ea B n Fig. L‘Autogenous healing is deed as the concept encompassing eas A d
B. I refers ω a phenomenon in genera n which crackng is clogged by
mechisms/capabilities possessed by the sucture of concrete itself, regdls of wheer or
not ay supplementry cementitious materiachemical adm区re is added
In the entre ea of‘recover shown n Fg. 1,e ea outside of e category of
‘healing represents‘reparng.' Area C in也e gure is deedぉ‘activd rep創ngJemphaszng 由e pont紙the healing nction is developed by a stmulus企om outside. Tis
8/14/2019 Technical Committee on Autogenous Healing in Cementitious Materials_TC075B_tcr09
96 S Igahi, M KW児a and T. Nihiwaki ! Tec加ical Cittee Rors 2ゆ Diest Editm, 91-102
ea includes study cases atempting ωmic clogging of cracks by incorporating something
di島rent om conventiona1 concrete s回Cre,such as concrete w抽 embedded devi∞for
automac repring by a specic igger including rticia1 ones to aively imprting a
selιrepairng eect s a new nction. Specica1y,也is nc1udes the nstnces of embedding mcrocps由s or glass pipesntninge above-mentionrepr mia1s,as well as these
combned wi a heatng device.
In addition since‘autonomic hea1ing' d aivated repa廿ing e investiged in白
se direcon of addng a new釦nction,世e rea nc1uding bo曲目deed with a term
‘engneered he1ng!rep創rng.
3 Examples of se-healing-repaiing31 Natural healg
Fgue 2 shows n exple of natura1 hea1ing in concreぬ ). This is a conぽete specimen
havng aticia1 crackng induced d then eposed t a tida zone enviromnent for 15 yes.
Most cracks with a sm11 width (ound 0.5 m or less have been natura11y heed. The
substces c10gging the cracks re reporedω be primaily et位g旬with needlelke crystas
nd maesium hyoxide.
8/14/2019 Technical Committee on Autogenous Healing in Cementitious Materials_TC075B_tcr09
s Igarashi, M. Kieda d Nishiwaki I Technical C叩niee Repα 2叩9 -Dige泣Et叩, 91-102 99
33 Activated repairing
Concree in which a glass pipe en伺psulating a epai material nd a hea-geneating
device e embedded6) as sho Fig. 5 is a epresenative exmple of activated repairing.
The occrence of a crack aivates a mechnism白紙selecively heas he紅ea ner the crack, thereby auomatically suppying e epai mateial企om te pipe embedded in the concree
material
New crack due to re-Ioading
Figure 5: Actvated repairng by supplying a repair material
(courtesy ofT Nishiwak)
4. Summary of experimental nvestigation
Tale 5 gives epresentave exmples of exising meods of inoducing dmge nd
ev山富士ing selfhealing・repairing, as wel a evalu富士ion indices. Snce selιheingrep即時
is generay reevnt to ‘cracks,' most expeiments induce tensie o bending cracks
concree to a specied crack widh. hen, te concrete is recred,組d subjeced o s出il
tests to con批estorion of批帥ng血 rigidity, and absorbed energy (te蹴a under
働oaddispacement cuet9).刀ere e so mny exmples which micocrcks wiin
concree induced by企eezing nd thawing ωt e c10gged by autonomic heing, for ins旬nce,
which is evuated by relaive atios of dynmodulus of elぉiciザ 10) d ose in which
8/14/2019 Technical Committee on Autogenous Healing in Cementitious Materials_TC075B_tcr09
100 S Igahi, M KW児a and T. Nihiwaki ! Tec加ical Cittee Rors 2ゆ Diest Editm, 91-102
chnges n the water permeability accordng to chngng crack width are measured 3, 11)
Exmples of evaluatng the resistnce to mass sfer伽oug clogged cracks other 世
w旬r incude也ose evalu組ng也e resistce ω chloride ion仕sfer12. However mo唱t of
these nvestigaons currenty reman on a research level Furthermore it is also hoped白紙self-healng of other tpes of dage will be nvestigated d that eistng nondes佐ctive test
methods will be applied to由e evalution of selfhealing
Table 5: pes of damage, resto叫on mechanisms, and evauaon
mehods/indces relevant o sel-healng (exampes)
Method of nducing damage Lang tes {ense, exrreezand thawimtes
102 S Igahi, M KW児a and T. Nihiwaki ! Tec加ical Cittee Rors 2ゆ Diest Editm, 91-102
on由e systeatzation of self-he1ng technology for ceentious aeria1s chared by Prof.
Shn-ichi Igashi ofKnawa University for 2009 d 2010 to deve1opent11y te over
由e activities of由e present cottee百e new coittee pcully ntends t sit
resech infoation d acculate d翻on selfhea1ing/repairing technology
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