Quantification and Modelling of the Saturation Behaviour of Hardened Cement Paste During Frost Attack By Means of Innovative NMR Imaging

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Frost resistance of concrete is significantly influenced by water transport in the matrix of hardened cement paste as a consequence of freezing and thawing action. The intensity of exposure is a direct function of degree of saturation of the pore system. Every freeze-thaw-cycle leads to an increased saturation. Upon reaching a critical value of saturation structural damage occurs. The presented project aims at a quantification of this so called frost-suction process as a function of hardened cement-pasted quality and prevalent environmental conditions considering the underlying physical mechanisms. Frost suction will be analyzed non-destructively using methods of one-dimensional NMR imaging. Thereby for the first time a basis for the derivation of an engineering model for the prediction of saturation process as a function of frost exposure will be provided. Investigations will be conducted in situ in a low-field NMR apparatus equipped with single-sided temperature control. Using two-dimensional NMR methods, a good spatial resolution as well as a monitoring of fast signal decay is to be achieved. Signal decay is governed by state of aggregation as well as surface interaction of the observed water molecules. Advancements of NMR methodology will be of general interest for research on porous media.