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Self- healing of cracks in concrete long-term exposed to different types of water : results after 1 year exposure

Fagerlund, Göran LU and Hassanzadeh, Manouchehr LU (2010) In Report TVBM 3156.
Abstract
SUMMARY

The aim of the project was to find out if cracks in concrete exposed to water can heal so that chloride ingress in the crack is effectively obstructed. If this is the case it might be possible to accept wider cracks in concrete than is allowed today.

18 concrete specimens with induced cracks, 0.2 and 0.4 mm wide, were exposed to sea water, brackish water and tap water for 1 year. For most specimens the crack width has been locked mechanically. For four specimens the crack had the possibility to relax.

Two types of water exposure have been used:

* Permanent immersion

* Cyclic immersion and drying in lab air

Photographs were taken of the crack before and after exposure. Photos are... (More)
SUMMARY

The aim of the project was to find out if cracks in concrete exposed to water can heal so that chloride ingress in the crack is effectively obstructed. If this is the case it might be possible to accept wider cracks in concrete than is allowed today.

18 concrete specimens with induced cracks, 0.2 and 0.4 mm wide, were exposed to sea water, brackish water and tap water for 1 year. For most specimens the crack width has been locked mechanically. For four specimens the crack had the possibility to relax.

Two types of water exposure have been used:

* Permanent immersion

* Cyclic immersion and drying in lab air

Photographs were taken of the crack before and after exposure. Photos are shown in APPENDIX 1 and 2. The photographs indicate that some healing has occurred, particularly for specimens permanently immersed in sea water. The effect of relaxation seems to be marginal.

After terminated exposure the chloride content in the crack walls on different depths was determined. The chloride content diminishes with the crack depth which indicates that the precipitation of minerals in the crack has the ability to somewhat obstruct chloride ingress. There was no big difference between cracks 0.2 mm and 0.4 mm wide or between locked and relaxed cracks.

SEM-EDS analyses of precipitations in the cracks showed that these mainly consisted of calcium hydroxide crystals of various size, and sometimes calcium carbonate crystals (calcite). In sea water needle-like sulphur containing crystals (e.g. ettringite) were frequent. For concrete that was exposed to cycles of sea water and drying magnesium hydroxide crystals (brucit) were found.

This report presents the results of part 1 of the project. In part 2 specimens will be exposed in sea water for about somewhat more than 2 years (28 months). (Less)
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author
organization
publishing date
type
Book/Report
publication status
published
subject
in
Report TVBM
volume
3156
pages
58 pages
publisher
Division of Building Materials, LTH, Lund University
external identifiers
  • other:TVBM-3156
ISSN
0348-7911
language
English
LU publication?
yes
id
ce7ab679-231a-480c-9a5e-dca4b77c12da (old id 1785153)
date added to LUP
2011-02-09 08:38:47
date last changed
2018-05-29 09:47:30
@techreport{ce7ab679-231a-480c-9a5e-dca4b77c12da,
  abstract     = {SUMMARY<br/><br>
The aim of the project was to find out if cracks in concrete exposed to water can heal so that chloride ingress in the crack is effectively obstructed. If this is the case it might be possible to accept wider cracks in concrete than is allowed today.<br/><br>
18 concrete specimens with induced cracks, 0.2 and 0.4 mm wide, were exposed to sea water, brackish water and tap water for 1 year. For most specimens the crack width has been locked mechanically. For four specimens the crack had the possibility to relax.<br/><br>
Two types of water exposure have been used:<br/><br>
* Permanent immersion<br/><br>
* Cyclic immersion and drying in lab air<br/><br>
Photographs were taken of the crack before and after exposure. Photos are shown in APPENDIX 1 and 2. The photographs indicate that some healing has occurred, particularly for specimens permanently immersed in sea water. The effect of relaxation seems to be marginal.<br/><br>
After terminated exposure the chloride content in the crack walls on different depths was determined. The chloride content diminishes with the crack depth which indicates that the precipitation of minerals in the crack has the ability to somewhat obstruct chloride ingress. There was no big difference between cracks 0.2 mm and 0.4 mm wide or between locked and relaxed cracks.<br/><br>
SEM-EDS analyses of precipitations in the cracks showed that these mainly consisted of calcium hydroxide crystals of various size, and sometimes calcium carbonate crystals (calcite). In sea water needle-like sulphur containing crystals (e.g. ettringite) were frequent. For concrete that was exposed to cycles of sea water and drying magnesium hydroxide crystals (brucit) were found.<br/><br>
This report presents the results of part 1 of the project. In part 2 specimens will be exposed in sea water for about somewhat more than 2 years (28 months).},
  author       = {Fagerlund, Göran and Hassanzadeh, Manouchehr},
  institution  = {Division of Building Materials, LTH, Lund University},
  issn         = {0348-7911},
  language     = {eng},
  pages        = {58},
  series       = {Report TVBM},
  title        = {Self- healing of cracks in concrete long-term exposed to different types of water : results after 1 year exposure},
  volume       = {3156},
  year         = {2010},
}