Introduction of a full-range model for liquid and vapor transport properties of autoclaved aerated concrete
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Xella Technologie- und Forschungsgesellschaft, Section of Applied Research and Building Physics, Hohes Steinfeld 1, 14797 Kloster Lehnin, Germany
Publication date: 2011-12-01
Cement Wapno Beton (Special 2011 16) 53-59 (2011)
The hygric performance of autoclaved aerated concrete is a key determinant for many other material properties as e.g. thermal conduction, carbonation or shrinkage behavior. Laboratory determination of hygric material properties, i.e. moisture storage and moisture transport, is hence a prerequisite and a standard in production and process supervision. In this context, prediction and simulation of the hygric material performance based on numerical calculation models has become a widely used research and design tool. However, for assessment of the material behavior under variable climatic conditions, the hygric material properties have to be determined in a fi rst step. In a second step, these properties have to be transformed into the non-linear coeffi cients required by these numerical calculation models. This paper is the second of two focusing on the second step. It introduces a full-range hygric material model bridging the gap between measured material properties and the non-linear storage and transport coeffi cients in the transfer equation. The model is based on the conductivity approach and relies on a bundle of tubes approach to derive the transport function from the pore structure of the material. By extending this approach with a mechanistic treatment of serial and parallel structured transport, a semi-empirical material model is developed providing a high fl exibility and adjustability. The model is applied for an aerated autoclaved concrete. Input data are basic material properties obtained by the methods introduced in the fi rst paper [26]. The approximation procedure is described and the achieved accuracy is discussed. In conclusion, the model is very suitable for sophisticated research as well as for a broad application to autoclaved aerated concrete in particular, and to porous materials in general.
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