Your most visited
- Sorry, this tool will only work with Javascript available.
| Title | Chloride initiated reinforcement corrosion in marine concrete |
| Author/s | Paul Sandberg |
| Department/s |
Building Materials
|
| Full-text | Available as PDF |
| Defence date | 1998-08-20 |
| Defence time | 10:15 |
| Defence place | Room V:A, Civil Engineering |
| Opponent | Doc. Per Fidjestol |
| Publication/Series | Report TVBM 1015 |
| Publishing year | 1998 |
| Pages | 86 |
| Document type | Dissertation |
| Language | English |
| Publisher | Div of Building Materials, LTH, Lund University |
| Popular science abstract 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. |
| Abstract English |
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. |
| Subject |
Technology and Engineering |
| Keywords | cover thickness, w/c ratio, chloride penetration, service life prediction, corrosion cells, chloride thresholds, field exposure tests, marine concrete, pozzolans, reinforcement corrosion, chloride binding, Building construction, Byggnadsteknik |
| ISBN/ISSN/Other |
ISSN: 0348-7911 ISRN: LUTVDG/TVBM--98/1015--SE(1-86) |
| Part of | Factors affecting the chloride thresholds for uncracked reinforced concrete exposed in a marine environment Part I: Field exposure tests of reinforced concrete |
| Part of | Factors affecting the chloride thresholds for uncracked reinforced concrete exposed in a marine environment Part II: Laboratory - and field exposure of corrosion cells |
| Part of | The effect of defects at the steel - concrete interface, exposure regime and cement type on pitting corrosion in concrete |
| Part of | Studies of chloride binding in concrete exposed in a marine environment |
| Part of | Recurrent studies of chloride ingress in uncracked marine concrete at various exposure times and - elevations |
| Part of | Recurrent studies of chloride ingress in uncracked marine concrete at various exposure times and - elevations |
| Part of | Field studies of chloride transport into high-performance concrete |
| Part of | Field study of the penetration of chlorides and other ions into a high quality concrete marine bridge column |
| Part of | Cost-effective design of high performance concrete structures exposed in saline environment |
| Part of | Service life prediction of reinforced concrete structures in saline environment |
| Part of | Critical evaluation of factors affecting chloride initiated reinforcement corrosion in concrete |
