Water balance and pore structure development in cementitious materials in internal curing with modified superabsorbent polymer studied by NMR |
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Authors: | N. Nestle, A. Kü hn, K. Friedemann, C. Horch, F. Stallmach,G. Herth |
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Affiliation: | aBASF SE Ludwigshafen, GKP/P, G201, D-67056 Ludwigshafen, Germany;bUniversität Leipzig, Abteilung Grenzflächenphysik, Linnéstraße 4, D-04103 Leipzig, Germany;cBASF Construction Chemicals GmbH, GKI/A, D-83308 Trostberg, Germany |
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Abstract: | In this contribution, the water balance between modified superabsorbent polymer particles of various grain sizes and a hydrating cement matrix is studied both for ordinary and white Portland cements by means of NMR relaxometry. Different approaches for the evaluation of the experimental data are compared: inverse Laplace transforms and several multicomponent fitting models. Both evaluations provide well-comparable results with respect to the overall water quantities absorbed and re-released by the superabsorber. The experimental data indicate fast water uptake within less than 5 min after watering the superabsorber/cement mixture. The re-release of the water begins along with the onset of the hydration reaction and is finished after 1 day for superabsorber powders with a dry grain size below 125 μm and takes about 2 days for larger dry grain size. The water uptake of the superabsorber inside the cement matrix is quantified to about 2250% of its dry weight. |
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Keywords: | NMR relaxometry Cement Superabsorber Water balance Internal curing |
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