Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Relative permeabilities of cement-based materials: influence of the tortuosity function
The macroscopic physical modeling of humidity-, energy-, and air-coupled transport in unsaturated porous materials requires their water retention characteristics and transport coefficients to be known. Among the most sensitive properties are the air and liquid permeabilities. As their direct determination is often difficult and time consuming, relations for prediction of the relative permeabilities for cement-based materials have long been proposed starting from experimental properties that are easier to obtain, such as water pressure head as a function of the degree of saturation or isothermal sorption curves. In the first part, existing model relationships (van Genuchten's relations validated for soil mechanics) are compared with experiments. The data obtained show that the exponent coefficient p in these relationships has to be modified. In the second part of the study, this approach is generalized by starting from the porosity of the cement-based materials studied here. Expressions for the relative permeabilities are given as functions of tortuosity and capillary pressure, which can be deduced from the pore size distribution. An expression is proposed for the tortuosity. The relative influence of the porosity and the tortuosity of the cement-based materials on gas and liquid permeabilities, according to the relative degree of saturation, are discussed.
Relative permeabilities of cement-based materials: influence of the tortuosity function
The macroscopic physical modeling of humidity-, energy-, and air-coupled transport in unsaturated porous materials requires their water retention characteristics and transport coefficients to be known. Among the most sensitive properties are the air and liquid permeabilities. As their direct determination is often difficult and time consuming, relations for prediction of the relative permeabilities for cement-based materials have long been proposed starting from experimental properties that are easier to obtain, such as water pressure head as a function of the degree of saturation or isothermal sorption curves. In the first part, existing model relationships (van Genuchten's relations validated for soil mechanics) are compared with experiments. The data obtained show that the exponent coefficient p in these relationships has to be modified. In the second part of the study, this approach is generalized by starting from the porosity of the cement-based materials studied here. Expressions for the relative permeabilities are given as functions of tortuosity and capillary pressure, which can be deduced from the pore size distribution. An expression is proposed for the tortuosity. The relative influence of the porosity and the tortuosity of the cement-based materials on gas and liquid permeabilities, according to the relative degree of saturation, are discussed.
Relative permeabilities of cement-based materials: influence of the tortuosity function
Relative Permeabilitäten von zementbasierten Werkstoffen: Einfluss der Tortuositätsfunktion
Wardeh, George (Autor:in) / Perrin, Bernard (Autor:in)
Journal of Buildings Physics ; 30 ; 39-57
2006
19 Seiten, 8 Bilder, 1 Tabelle, 18 Quellen
Aufsatz (Zeitschrift)
Englisch
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