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Chloride initiated reinforcement corrosion in marine concrete

Sandberg, Paul LU (1998) In Report TVBM 1015
Abstract (Swedish)
Popular Abstract in Swedish

Korrosion av stålarmering i betong orsakade höga reparationskostnader för Ölandsbron, och är en grundläggande fråga vid val av material och utförande för Öresundsbron. Avhandlingen behandlar hur val av betongkvalité och tjocklek hos betongen som skyddar armeringen påverkar



dels



hur fort saltvatten tränger in i betong för att till slut nå armeringen,



dels



hur mycket salt armeringen tål innan den börjar rosta.



Parametrar som fukthalt och temperatur, betongens ålder, täthet och sprickbenägenhet, val av cement, förhållande mellan mängden vatten och cement i betongen, påverkar starkt både hur snabbt salt... (More)
Popular Abstract in Swedish

Korrosion av stålarmering i betong orsakade höga reparationskostnader för Ölandsbron, och är en grundläggande fråga vid val av material och utförande för Öresundsbron. Avhandlingen behandlar hur val av betongkvalité och tjocklek hos betongen som skyddar armeringen påverkar



dels



hur fort saltvatten tränger in i betong för att till slut nå armeringen,



dels



hur mycket salt armeringen tål innan den börjar rosta.



Parametrar som fukthalt och temperatur, betongens ålder, täthet och sprickbenägenhet, val av cement, förhållande mellan mängden vatten och cement i betongen, påverkar starkt både hur snabbt salt tränger in i betong, och hur mycket salt som krävs för att armeringen ska börja rosta.



Parametrar som luftblåsor mellan stål och betong, typ av armeringsstål och typ av bearbetning, påverkar också hur mycket salt som krävs för att armeringen ska börja rosta. (Less)
Abstract
Factors affecting the total chloride threshold for initiation of pitting corrosion in reinforced concrete were investigated by means of field and laboratory exposure tests. Factors affecting the chloride penetration into concrete were also investigated by means of field tests. The thesis consists of a summary (86 p.) and 11 papers attached.



Measured total chloride thresholds for uncracked concrete based on sulfate resisting portland cement with w/c ratio 0.3-0.5 and exposed in the splash zone were in the range of 1.1-1.5 % total chloride by weight of binder. The effect of replacing the portland cement with 5 % silica fume on the chloride threshold was insignificant. Defects in the concrete micro structure and the steel... (More)
Factors affecting the total chloride threshold for initiation of pitting corrosion in reinforced concrete were investigated by means of field and laboratory exposure tests. Factors affecting the chloride penetration into concrete were also investigated by means of field tests. The thesis consists of a summary (86 p.) and 11 papers attached.



Measured total chloride thresholds for uncracked concrete based on sulfate resisting portland cement with w/c ratio 0.3-0.5 and exposed in the splash zone were in the range of 1.1-1.5 % total chloride by weight of binder. The effect of replacing the portland cement with 5 % silica fume on the chloride threshold was insignificant. Defects in the concrete micro structure and the steel surface at the steel-concrete interface were found to have a major negative effect on the chloride threshold.



A linear relationship between free and total chlorides was found in concrete submerged in sea water. Concentration profiles measured for the free chloride and hydroxide ions indicated that these ions penetrate concrete in opposite directions but at approximately the same rate. It was suggested that hydroxide counter diffusion increases the chloride binding close to the exposed uncarbonated surface, which leads to an almost linear chloride binding.



The effective chloride diffusivity calculated by fitting experimentally obtained total chloride concentrations to a solution to Fick´s second law of diffusion, decreases over time in field exposed concrete. The results after 5 years of field exposure indicated that the effective chloride diffusivity can be reduced by a factor of 8-10 by using 5 % silica fume in the binder and by reducing the w/c ratio from 0.40 to 0.30, as compared to a typical Swedish bridge concrete with w/c 0.40 and no pozzolan in the binder. The corresponding reduction of the required minimum cover would be 50 % for an initiation time of 100 years. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Doc. Fidjestol, Per, Kristiansand
organization
publishing date
type
Thesis
publication status
published
subject
keywords
w/c ratio, cover thickness, chloride penetration, service life prediction, corrosion cells, chloride thresholds, field exposure tests, marine concrete, pozzolans, reinforcement corrosion, chloride binding, Building construction, Byggnadsteknik
in
Report TVBM 1015
pages
86 pages
publisher
Division of Building Materials, LTH, Lund University
defense location
Room V:A, Civil Engineering
defense date
1998-08-20 10:15
external identifiers
  • other:ISRN: LUTVDG/TVBM--98/1015--SE(1-86)
ISSN
0348-7911
language
English
LU publication?
yes
id
737d1ae3-cf63-417f-89de-ac5e3a92a1ae (old id 38785)
date added to LUP
2007-08-01 11:28:07
date last changed
2016-09-19 08:44:58
@phdthesis{737d1ae3-cf63-417f-89de-ac5e3a92a1ae,
  abstract     = {Factors affecting the total chloride threshold for initiation of pitting corrosion in reinforced concrete were investigated by means of field and laboratory exposure tests. Factors affecting the chloride penetration into concrete were also investigated by means of field tests. The thesis consists of a summary (86 p.) and 11 papers attached.<br/><br>
<br/><br>
Measured total chloride thresholds for uncracked concrete based on sulfate resisting portland cement with w/c ratio 0.3-0.5 and exposed in the splash zone were in the range of 1.1-1.5 % total chloride by weight of binder. The effect of replacing the portland cement with 5 % silica fume on the chloride threshold was insignificant. Defects in the concrete micro structure and the steel surface at the steel-concrete interface were found to have a major negative effect on the chloride threshold.<br/><br>
<br/><br>
A linear relationship between free and total chlorides was found in concrete submerged in sea water. Concentration profiles measured for the free chloride and hydroxide ions indicated that these ions penetrate concrete in opposite directions but at approximately the same rate. It was suggested that hydroxide counter diffusion increases the chloride binding close to the exposed uncarbonated surface, which leads to an almost linear chloride binding.<br/><br>
<br/><br>
The effective chloride diffusivity calculated by fitting experimentally obtained total chloride concentrations to a solution to Fick´s second law of diffusion, decreases over time in field exposed concrete. The results after 5 years of field exposure indicated that the effective chloride diffusivity can be reduced by a factor of 8-10 by using 5 % silica fume in the binder and by reducing the w/c ratio from 0.40 to 0.30, as compared to a typical Swedish bridge concrete with w/c 0.40 and no pozzolan in the binder. The corresponding reduction of the required minimum cover would be 50 % for an initiation time of 100 years.},
  author       = {Sandberg, Paul},
  issn         = {0348-7911},
  keyword      = {w/c ratio,cover thickness,chloride penetration,service life prediction,corrosion cells,chloride thresholds,field exposure tests,marine concrete,pozzolans,reinforcement corrosion,chloride binding,Building construction,Byggnadsteknik},
  language     = {eng},
  pages        = {86},
  publisher    = {Division of Building Materials, LTH, Lund University},
  school       = {Lund University},
  series       = {Report TVBM 1015},
  title        = {Chloride initiated reinforcement corrosion in marine concrete},
  year         = {1998},
}