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Cryogenic suction pump mechanism for combined salt-and frost exposure

Borgnakke, C. and Hansen, W. and Kang, Y. and Liu, Z. and Koenders, E. A. B. (2012):
Cryogenic suction pump mechanism for combined salt-and frost exposure.
In: Second International Conference on Microstructural-related Durability of Cementitious Composites, RILEM Proceedings pro083, 11-13 April, 2012, Amsterdam, The Netherlands, RILEM Publications, ISBN 978-2-35158-129-2,
[Online-Edition: http://resolver.tudelft.nl/uuid:ebc6e80e-3c9e-46a5-80be-c729...],
[Conference or Workshop Item]

Abstract

Freezing of water can be explained by the thermodynamic properties of the water due to the influence of temperature, pressure and special effects such as surface tension and salt solution. Gibbs free energy curves for ice and pore liquid containing different concentrations of NaCl (0-6%) are presented. These curves explain the onset of freezing in pores when the energy level for solid ice and pore liquid containing salt are equal. Upon further cooling a nonequilibrium condition develops since the Gibbs function for pure ice is less than the Gibbs function for the liquid. The theory also explains why ice nucleation is developing in the largest pores containing liquid, including air-voids. Below the nucleation temperature, a vacuum with low partial pressure of the water develops around the ice which starts a cryogenic suction pump. For a closed system (i.e. no external liquid) partial pore-drying develops leading to specimen shrinkage. In air-entrained concrete the ice growth may be accommodated within the pore system without structural damage. In the case external liquid is present, such as when the surface contains a salt solution, pore suction attracts surface liquid, and additional ice growth may not be accommodated within the pore system. Thus, a net expansion occurs. Frost expansion due to crystal growth is time-dependent and progresses as long as liquid is available and until thermodynamic equilibrium is re-established at a given temperature.

Item Type: Conference or Workshop Item
Erschienen: 2012
Creators: Borgnakke, C. and Hansen, W. and Kang, Y. and Liu, Z. and Koenders, E. A. B.
Title: Cryogenic suction pump mechanism for combined salt-and frost exposure
Language: English
Abstract:

Freezing of water can be explained by the thermodynamic properties of the water due to the influence of temperature, pressure and special effects such as surface tension and salt solution. Gibbs free energy curves for ice and pore liquid containing different concentrations of NaCl (0-6%) are presented. These curves explain the onset of freezing in pores when the energy level for solid ice and pore liquid containing salt are equal. Upon further cooling a nonequilibrium condition develops since the Gibbs function for pure ice is less than the Gibbs function for the liquid. The theory also explains why ice nucleation is developing in the largest pores containing liquid, including air-voids. Below the nucleation temperature, a vacuum with low partial pressure of the water develops around the ice which starts a cryogenic suction pump. For a closed system (i.e. no external liquid) partial pore-drying develops leading to specimen shrinkage. In air-entrained concrete the ice growth may be accommodated within the pore system without structural damage. In the case external liquid is present, such as when the surface contains a salt solution, pore suction attracts surface liquid, and additional ice growth may not be accommodated within the pore system. Thus, a net expansion occurs. Frost expansion due to crystal growth is time-dependent and progresses as long as liquid is available and until thermodynamic equilibrium is re-established at a given temperature.

Title of Book: Second International Conference on Microstructural-related Durability of Cementitious Composites, RILEM Proceedings pro083, 11-13 April, 2012, Amsterdam, The Netherlands
Publisher: RILEM Publications
ISBN: 978-2-35158-129-2
Uncontrolled Keywords: cryogenic suction, frost expansion, Gibbs-free energy, salt frost attack
Divisions: 13 Department of Civil and Environmental Engineering Sciences
13 Department of Civil and Environmental Engineering Sciences > Institute of Construction and Building Materials
Date Deposited: 08 Jun 2015 14:54
Official URL: http://resolver.tudelft.nl/uuid:ebc6e80e-3c9e-46a5-80be-c729...
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