Spremljanje in karakterizacija korozijskih procesov jekla v betonu

doktorska disertacija

Aleš Česen (Author), Violeta Bokan-Bosiljkov (Mentor), Matjaž Mikoš (Thesis defence commission member), Zvonko Jagličić (Thesis defence commission member), Stane Pejovnik (Thesis defence commission member), Valter Doleček (Thesis defence commission member), Andraž Legat (Co-mentor)

Abstract

Keywords

gradbeništvo;disertacije;korozija jekla;beton;malta;elektrokemijske metode;električni uporovni senzorji;mreža sklopljenih elektrod;rentgenska računalniška tomografija;

Data

Language:	Slovenian
Year of publishing:	2013
Source:	Ljubljana
Typology:	2.08 - Doctoral Dissertation
Organization:	UL FGG - Faculty of Civil and Geodetic Engineering
Publisher:	[A. Česen]
UDC:	691.328.1:543.428.3:77.026.34(043.3)
COBISS:	6435937
Views:	2480
Downloads:	543
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Monitoring and characterization of corrosion processes on steel in concrete
Secondary abstract:	The aim of this thesis was to perform a critical comparison of a number of different electrochemical and physical methods for the monitoring of steel corrosion in concrete. Initially, some tests were performed on medium-sized reinforced-concrete columns located in a natural marine environment, into which electrical resistance probes were embedded. Electrochemical noise was measured using a five-electrode assembly, and corrosion potentials and rates were determined by the galvanostatic pulse technique. Since the results obtained in the case of these in situ measurements proved to be relatively unreliable, further research was performed in the laboratory on small-scale test specimens using electrical impedance spectroscopy in addition to the previously described test methods. The small size of the specimens made it possible to also perform X-ray micro tomography analysis, which proved to be highly important for our research results. These laboratory measurements were performed on different types of steel, which were embedded in carbonated mortar. The specimens were cyclically wetted with distilled water or a 3.5 % NaCl solution. The most reliable method for corrosion monitoring proved to be a coupled multi-electrode array. However, this method is difficult to install in actual structures, and a large amount of recorded data has to be processed. Good results were also obtained on similar test specimens using a simpler method with electrical resistance probes, which, however, has some disadvantages in chloride environments at high corrosion rates. The galvanostatic pulse technique, which is one of the most commonly used techniques for in situ corrosion monitoring, proved, on the basis of these laboratory tests, to be less reliable in the case of chloride contaminated concrete or mortar. On the other hand, X-ray computed micro-tomography turned out to be an extremely reliable non-destructive laboratory technique for the detection of corrosion type and the extent of corrosion damage. This technique was therefore used to evaluate the accuracy of the other used methods.
Secondary keywords:	civil engineering;thesis;steel corrosion;concrete;mortar;electrochemical techniques;electrical resistance probe;coupled multi-electrode array;X-ray computed tomography;
URN:	URN:NBN:SI
File type:	application/pdf
Type (COBISS):	Dissertation
Thesis comment:	Univ. v Ljubljani, Fak. za gradbeništvo in geodezijo, Podiplomski študij gradbeništva, Doktorski študij
Pages:	XXIV, 123 str.
Type (ePrints):	thesis
Title (ePrints):	Monitoring and characterization of corrosion processes on steel in concrete
Keywords (ePrints):	korozija jekla;beton;malta;elektrokemijske metode;električni uporovni senzorji;mreža sklopljenih elektrod;rentgenska računalniška tomografija
Keywords (ePrints, secondary language):	steel corrosion;concrete;mortar;electrochemical techniques;electrical resistance probe;coupled multi-electrode array;X-ray computed tomography
Abstract (ePrints):	Glavni cilj doktorskega dela je kritična primerjava različnih elektrokemijskih in fizikalnih metod za spremljanje korozijskih procesov jekla v betonu. V okviru in situ preiskav smo tako izvajali meritve na srednje velikih vzorcih v naravnem obalnem okolju z vgrajenimi električnimi uporovnimi senzorji, z merjenjem elektrokemijskega šuma na vgrajenih elektrodah ter z merjenjem korozijske hitrosti z metodo galvanostatskega pulza. Zaradi številnih problemov z nezanesljivimi meritvami na in situ vzorcih smo glavni del preiskav izvajali na manjših laboratorijskih vzorcih, na katerih smo poleg omenjenih metod izvajali še elektrokemijsko impedančno spektroskopijo. Majhna velikost laboratorijskih vzorcev je omogočala tudi analizo z rentgensko mikro-tomografijo, ki je dala našim raziskavam posebno dodano vrednost. Laboratorijske meritve korozije so potekale na različnih vrstah ogljičnega jekla, vgrajenega v cementno malto, ki je bila pred začetkom preiskav pospešeno karbonatizirana. Vzorce smo ciklično močili z destilirano vodo oziroma 3,5 % raztopino NaCl. Kot najzanesljivejša metoda merjenja korozijske hitrosti se je izkazala metoda z elektrodno mrežo, ki pa je tudi najkompleksnejša tako z vidika vgradnje ter obdelave velike količine podatkov. Dobre rezultate smo dobili tudi s preprostejšo vgradnjo električnih uporovnih senzorjev, kateri pa lahko odpovejo pri intenzivnejši lokalni koroziji. Splošno razširjena elektrokemijska tehnika galvanostatskega pulza, s katero merimo korozijske hitrosti betonskega jekla, se je izkazala za najmanj točno v primerih kontaminacije betona s kloridi. Uporaba razmeroma nove tehnike rentgenske računalniške mikrotomografije se je izkazala za izjemno zanesljivo neporušno metodo pri ugotavljanju vrste in obsega korozijskih poškodb na dovolj majhnih laboratorijskih vzorcih. S tovrstno analizo smo lahko zanesljivo ovrednotili natančnost ostalih uporabljenih metod.
Abstract (ePrints, secondary language):	The aim of this thesis was to perform a critical comparison of a number of different electrochemical and physical methods for the monitoring of steel corrosion in concrete. Initially, some tests were performed on medium-sized reinforced-concrete columns located in a natural marine environment, into which electrical resistance probes were embedded. Electrochemical noise was measured using a five-electrode assembly, and corrosion potentials and rates were determined by the galvanostatic pulse technique. Since the results obtained in the case of these in situ measurements proved to be relatively unreliable, further research was performed in the laboratory on small-scale test specimens using electrical impedance spectroscopy in addition to the previously described test methods. The small size of the specimens made it possible to also perform X-ray micro tomography analysis, which proved to be highly important for our research results. These laboratory measurements were performed on different types of steel, which were embedded in carbonated mortar. The specimens were cyclically wetted with distilled water or a 3.5 % NaCl solution. The most reliable method for corrosion monitoring proved to be a coupled multi-electrode array. However, this method is difficult to install in actual structures, and a large amount of recorded data has to be processed. Good results were also obtained on similar test specimens using a simpler method with electrical resistance probes, which, however, has some disadvantages in chloride environments at high corrosion rates. The galvanostatic pulse technique, which is one of the most commonly used techniques for in situ corrosion monitoring, proved, on the basis of these laboratory tests, to be less reliable in the case of chloride contaminated concrete or mortar. On the other hand, X-ray computed micro-tomography turned out to be an extremely reliable non-destructive laboratory technique for the detection of corrosion type and the extent of corrosion damage. This technique was therefore used to evaluate the accuracy of the other used methods.
Keywords (ePrints, secondary language):	steel corrosion;concrete;mortar;electrochemical techniques;electrical resistance probe;coupled multi-electrode array;X-ray computed tomography
ID:	8313075