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From nano to macro - modelling freeze-thaw characteristics of cementitious materials
Surface physics and chemistry acting in the nano-scale affect fundamental properties of concrete such as strength, ductility, creep and shrinkage, fracture behaviour and here highlighted the durability against freeze-thaw. Recent data prove that the characteristic properties of both solid gel matrix and of pore water are essentially changed by surface interaction in the nano-scale. It is crucial to handle hardened cement paste as a linked system of both components characterised by naming SLGS ('Solid-Liquid Gel System'). The model comprises the nano-effects in a smeared microstructure. On this basis the findings of Powers, Feldman and Sereda or the Munich model can be improved essentially. In this contribution the properties of the submicroscopic SLGS model are embedded in a macroscopic multi-phase and multi-scale model. At the macroscopic scale transient conditions with long relaxation times must be handled e.g water-uptake and heat transport. The macroscopic aspects are processed by a thermomechanical model based on the TPM (Theory of Porous Media) consisting of a mixture of 5 interacting constituents. The TPM is a combination of the Theory of Mixtures and the Concept of Volume Fractions. This multiscale model describes the characteristic freeze-thaw phenomena of cementitious materials like frost shrinkage, frost heave and artificial saturation during melting, been obviously 2 to 3 times greater than isothermal capillary suction. The methodology can be adopted to other properties.
From nano to macro - modelling freeze-thaw characteristics of cementitious materials
Surface physics and chemistry acting in the nano-scale affect fundamental properties of concrete such as strength, ductility, creep and shrinkage, fracture behaviour and here highlighted the durability against freeze-thaw. Recent data prove that the characteristic properties of both solid gel matrix and of pore water are essentially changed by surface interaction in the nano-scale. It is crucial to handle hardened cement paste as a linked system of both components characterised by naming SLGS ('Solid-Liquid Gel System'). The model comprises the nano-effects in a smeared microstructure. On this basis the findings of Powers, Feldman and Sereda or the Munich model can be improved essentially. In this contribution the properties of the submicroscopic SLGS model are embedded in a macroscopic multi-phase and multi-scale model. At the macroscopic scale transient conditions with long relaxation times must be handled e.g water-uptake and heat transport. The macroscopic aspects are processed by a thermomechanical model based on the TPM (Theory of Porous Media) consisting of a mixture of 5 interacting constituents. The TPM is a combination of the Theory of Mixtures and the Concept of Volume Fractions. This multiscale model describes the characteristic freeze-thaw phenomena of cementitious materials like frost shrinkage, frost heave and artificial saturation during melting, been obviously 2 to 3 times greater than isothermal capillary suction. The methodology can be adopted to other properties.
From nano to macro - modelling freeze-thaw characteristics of cementitious materials
Von der Nano- zur Makromodellierung der Gefrier- und Auftaueigenschaften von Zementwerkstoffen
Kruschwitz, J. (author)
2009
7 Seiten, 1 Bild, 1 Tabelle, 30 Quellen
Conference paper
English
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