Abstract
The leaching process when water attacks concrete, and the effect of leaching on the strength and durability of a concrete structure, is analysed theoretically. Technique for prediction of the future leaching
and structural stability is outlined. The analysis is to a certain extent supported by data from literature. The leaching process is divided in five different types: 1: Pure surface leaching 2: Surface leaching involving erosion
3: Homogeneous leaching over the entire structure
4: Semi-homogeneous leaching over the entire structure
5: Leaching in defects within the structure
For each type, the physical leaching process is outlined. Consideration is taken to the increase in
permeability caused by leaching making it theoretically possible to predict the future leaching from an
analysis of the water flow and degree of leaching at the time of inspection of the structure.
The effect of leaching on strength and E-modulus of the concrete is analysed showing that the effect can
be substantial.
A short discussion is made on the effect of leaching on the structural stability and on the changes in
structural stability in the future. Important mechanical factors discussed are changes in compressive
strength, tensile strength and bond strength between reinforcement and concrete. The increased risk of
reinforcement corrosion and frost damage in leached concrete is discussed and found to be big. The
effect of changes in the internal uplift pressure in dams due to changed flow paths inside the dam and the
effect of these changes on the dam stability are mentioned.
Finally, in an APPENDIX, a simple method is outlined for how to assess the concrete strength from
information of the physical composition of the cement paste. By this theory it is also possible to assess
the effect of leaching on the concrete strength.
and structural stability is outlined. The analysis is to a certain extent supported by data from literature. The leaching process is divided in five different types: 1: Pure surface leaching 2: Surface leaching involving erosion
3: Homogeneous leaching over the entire structure
4: Semi-homogeneous leaching over the entire structure
5: Leaching in defects within the structure
For each type, the physical leaching process is outlined. Consideration is taken to the increase in
permeability caused by leaching making it theoretically possible to predict the future leaching from an
analysis of the water flow and degree of leaching at the time of inspection of the structure.
The effect of leaching on strength and E-modulus of the concrete is analysed showing that the effect can
be substantial.
A short discussion is made on the effect of leaching on the structural stability and on the changes in
structural stability in the future. Important mechanical factors discussed are changes in compressive
strength, tensile strength and bond strength between reinforcement and concrete. The increased risk of
reinforcement corrosion and frost damage in leached concrete is discussed and found to be big. The
effect of changes in the internal uplift pressure in dams due to changed flow paths inside the dam and the
effect of these changes on the dam stability are mentioned.
Finally, in an APPENDIX, a simple method is outlined for how to assess the concrete strength from
information of the physical composition of the cement paste. By this theory it is also possible to assess
the effect of leaching on the concrete strength.
| Original language | English |
|---|---|
| Publisher | Division of Building Materials, LTH, Lund University |
| Number of pages | 51 |
| Volume | 3091 |
| Publication status | Published - 2000 |
Publication series
| Name | Report TVBM |
|---|---|
| Volume | 3091 |
| ISSN (Print) | 0348-7911 |
Bibliographical note
This work is part of a European research project CONTECVET; A Validated Users Manual for Assessing the Residual Service Life of Concrete Structures.The project involves partners from U.K., Spain and Sweden.
(Research on leaching and its effect on the structural stability has also been published in the report:
T. Ekström: Leaching of concrete. Experiments and modelling. Div. of Building Materials, Lund Institute of
Technology. Report TVBM-3090, Lund, 2001)
Subject classification (UKÄ)
- Materials Engineering