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Author:Tiirikainen, Suvi
Title:Monitoring of reinforcement corrosion by use of the galvanostatic pulse method
Galvanostaattiset pulssivirtamittaukset betoniraudoitteiden korroosiomonitoroinnissa
Publication type:Master's thesis
Publication year:2004
Pages:98 + 4      Language:   eng
Department/School:Materiaali- ja kalliotekniikan osasto
Main subject:Korroosionestotekniikka   (Mak-85)
Supervisor:Aromaa, Jari
Instructor:Pehkonen, Antero ; Laurila, Timo
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark TKK  100   | Archive
Keywords:concrete
corrosion
galvanostatic pulse
potential transient
steel reinforcement
betoniteräs
korroosio
galvanostaattinen pulssi
korroosio
potentiaalimuutos
Abstract (eng): Interpretation of corrosion risk in reinforced concrete structures has been performed with a number of electrochemical techniques ever since the first half-cell potential mapping measurements were developed.
The maintenance and repair of the structures requires a monitoring technique that can reliably locate the corroding areas and estimate corrosion rates.
The galvanostatic pulse technique introduced in 1988 has been lately investigated as an easy, rapid and non-destructive method to assess corrosion rate of rebar steel.

The aim of the study was to determine the usability of galvanostatic pulse measurement applications on corrosion monitoring of reinforced steel in concrete to assess corrosion rates.
The laboratory tests were performed in simulated pore water solutions with varying chloride concentrations.
The purpose of tests was to define parameters, which give the most reliable and comprehensive information of the condition of rebar steel rods.
The traditional electrochemical methods as well as the galvanostatic pulse method were used to specify parameters in laboratory and they were tested using the GPM method on site.
The main interest was to examine reinforced concrete structures guarded by cathodic protection.

The tested galvanostatic pulse method was proved to be suitable to separate active and passive state of steel.
The measurements performed in laboratory confirmed that there is one decade difference in corrosion current density values between active and passive steel.
The results showed that the magnitude of the cathodic protection current and the applied measurement current do not have an excessive influence on the determined resistances.
However the determination of resistance values may be disturbed related to the small applied currents if corrosion rate is high and deviations occur in the measured transient.
Therefore the interrupted GPM method was more applicable because the time constants could also be used to determine the corrosion state of steel.
Abstract (fin): Korroosioriskin arviointia betonirakenteissa on suoritettu käyttäen lukuisia elektrokemiallisia menetelmiä aina ensimmäisistä kennopotentiaalimittauksista lähtien.
Rakenteiden ylläpito ja korjaus vaatii monitorointitekniikan, jolla pystytään luotettavasti paikantamaan vaurioitunut betoniteräsalue ja arvioimaan korroosionopeus.
Galvanostaattinen pulssivirtamittausmenetelmä, joka on ollut tutkimuksen kohde jo vuodesta 1988, on viime aikoina herättänyt kiinnostusta nopeana ja helppona keinona määrittää betoniteräksen korroosionopeus vaurioittamatta terästä.

Työn tavoitteena oli tutkia galvanostaattisten pulssivirtamittausten sovellusten käyttökelpoisuutta betoniteräksen korroosiomonitoroinnissa.
Laboratoriossa tehdyt mittaukset suoritettiin simuloidussa huokosvedessä vaihtelevilla kloridipitoisuuksilla.
Laboratoriotesteillä määriteltiin parametrit, jotka antavat luotettavimman arvion betoniterästen tilasta.
Perinteisiä elektrokemiallisia mittausmetodeja käytettiin galvanostaattisten pulssivirtamittausten ohella parametrien määrittämiseen laboratoriossa ja niitä testattiin GPM metodilla kenttäolosuhteissa.
Pääkiinnostuksen kohde oli katodisesti suojattujen rakenteiden tutkiminen.

Mittaustulokset todistivat, että galvanostaattisella pulssivirtamittausmetodilla pystytään erottamaan aktiivinen ja passiivinen teräs toisistaan.
Laboratoriomittaukset vahvistivat aktiivisen ja passiivisen teräksen korroosiovirrantiheystulosten eroavan kymmenkertaisesti.
Katodisen suojavirran tai syötetyn mittavirran suuruus ei vaikuttanut merkittävästi määriteltyjen resistanssien arvoihin.
Hyvin pienillä syyottovirroilla saattoi esiintyä häiriöitä mitatuissa potentiaalimuutoskäyrissä vaikeuttaen resistanssiarvojen laskemista, kun korroosiovirrat olivat suuria.
Tämän vuoksi keskeytetyn virran GPM menetelmä on käyttökelpoisempi, koska myös aikavakioiden avulla voidaan arvioida teräksen korroosiotilaa.
ED:2005-03-04
INSSI record number: 28124
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