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Impregnation of concrete structures - introduction to a PhD-project
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.ORCID iD: 0000-0002-1526-9331
2005 (English)In:  Proceedings Hydrophobe IV: water repellent treatment of building materials, Freiburg, Switzerland: Aedification Publishers , 2005, 59-68 p.Conference paper, Published paper (Refereed)
Abstract [en]

Moisture is the source of most damage in concrete bridges, such as frost damage and reinforcement corrosion. Experiments and field investigations show that impregnation with silanes and siloxanes provide good protection against moisture for at least eight to ten years. But most of the research only verifies this without providing a reason for the positive results. This project analyses how common impregnation substances work in concrete. Additionally, the authors develop models in order to explain these effects. As a first step, it is important to obtain reliable data on how the moisture diffusion coefficient is affected by hydrophobic treatments. Some of the factors investigated are how the water-cement ratio and the impregnation depth will influence moisture transport. One of the goals is to create a computer model to predict the moisture and chloride content over time when the geometry, the material properties of the concrete structure and the environmental conditions are known.

Place, publisher, year, edition, pages
Freiburg, Switzerland: Aedification Publishers , 2005. 59-68 p.
Keyword [en]
Hydrophobization, Concrete, Model, Mathematic model
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-6300ISBN: 3-931681-81-5 (print)OAI: oai:DiVA.org:kth-6300DiVA: diva2:10978
Conference
4th International Conference on Water Repellent Treatment of Building Materials, Stockholm, Sweden, April 12-13 2005
Note
QC 20101117Available from: 2006-10-25 Created: 2006-10-25 Last updated: 2010-11-17Bibliographically approved
In thesis
1. Impregnation of concrete structures: transportation and fixation of moisture in water repellent treated concrete
Open this publication in new window or tab >>Impregnation of concrete structures: transportation and fixation of moisture in water repellent treated concrete
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Water repellent agents, today mainly consisting of alkylalkoxysilanes, are often used on concrete to prolong the service life of the structure. This is accomplished by protecting the reinforcement bars from chlorides or by changing the moisture content inside. When the concrete is treated with a water repellent agent the properties of the surface layer turn from hydrophilic to hydrophobic and thereby water droplets are stopped from entering, still allowing water vapour to pass through. This property change can reduce chloride ingression and stop heavy rain from penetrating through the surface layer.

This thesis presents results concerning how the moisture transport and fixation in the surface layer of the concrete is affected by a water repellent treatment. It also presents an investigation in which the effective penetration depth and the factors that influence it are studied. The methods used covers uni-dimensional transport of moisture using the so called cup method, measurements on moisture fixation using climate boxes with saturated salt solutions, penetration depth by cracking samples and spraying water on them, and field tests in a harsh tunnel environment.

The moisture diffusion coefficient for a water repellent treated concrete is close to constant and not nearly as dependent on the relative humidity (RH) as for untreated concrete. Unlike untreated concrete, where capillary suction plays an important role for the moisture transport at high RH, the vapour transport is the dominant transport mechanism even at high RH for water repellent treated concrete.

The moisture fixation is affected by a water repellent treatment and the effect is clearest at high moisture levels. There is, however, a certain amount of moisture present in a concrete treated with a water repellent agent. It can also be seen that the main reason for this is that the capillary porosity is affected by the treatment to a relatively high degree while the gel porosity to a large extent remains unaffected.

The three most important factors for the penetration of any water repellent agent into concrete is time, porosity and degree of saturation. An empirical equation is derived that gives an idea on how much these factors affect the efficient penetration depth of the water repellent agent.

Measures prolonging the service life of a concrete structure will lead to savings of natural resources and thus both economical and environmental savings for the community. The aim with the PhD-project is to develop explanation models to the promising results that have been obtained from the empirical research during the last decade and by doing this also create a better knowledge about when and how to apply a water repellent agent in order to benefit as much as possible from the product. The results presented in this Lisenciate thesis will be used as input in these models in the planned second phase of this project.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. x, 38 p.
Series
Trita-BKN. Bulletin, ISSN 1103-4270 ; 84
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-4160 (URN)
Presentation
2006-10-13, Sal L1, KTH, Drottning Kristinas väg 30, Stockholm, 13:10
Opponent
Supervisors
Note
QC 20101117Available from: 2006-10-25 Created: 2006-10-25 Last updated: 2012-02-21Bibliographically approved

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Silfwerbrand, Johan

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