Abstract
Two superabsorbent polymer (SAP) samples were studied with respect to their sorption kinetics in freshly prepared cement pastes that were exposed to evaporation. SAP 1 was a self-releasing type material when tested in extracted cement pore solution, whereas SAP 2 was a retentive type. These polymers had proven efficient to mitigate plastic shrinkage and its related cracking propensity, however, to different degrees. The observed difference in the performance was elucidated using neutron radiography imaging. Cement pastes with water-to-cement ratios of 0.25 and 0.50 were investigated which were exposed to two different climates: the one mimicking ordinary central European climate (20 °C, intermediate relative humidity) and the other one representing hot and dry weather conditions (40 °C, very low relative humidity).
It was found that SAP 1 released its absorbed aqueous solution right from the beginning, nearly independent of w/c and climatic conditions. This corresponded to its individual ab- and desorption behaviour in extracted pore solution. Contrarily, the inherently retentive SAP 2 desorbed water upon demand that arouse in the paste. While the cracking propensity of the pastes generally largely decreased in the presence of SAP, SAP 2 was found to be more efficient than SAP 1 in this aspect, which can be traced back to the temporally delayed supply of water by SAP 2 upon demand. Obviously, it did not matter much by which physico-chemical mechanism the water was extracted from the SAP particles, i.e. low w/c or hot and dry climate.
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Acknowledgements
The authors from TU Dresden gratefully thank SNF Floerger (Andrézieux Cedex, France) for the generous supply with the superabsorbent polymer samples. They as well thank PSI for the access to and support at NEUTRA.
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Schröfl, C., Mechtcherine, V., Mannes, D. (2020). Dewatering Kinetics from Fresh Cement Pastes Enriched with Superabsorbent Polymer (SAP) Samples at Ambient and Elevated Temperatures Visualised and Quantified by Neutron Radiography Imaging. In: Boshoff, W., Combrinck, R., Mechtcherine, V., Wyrzykowski, M. (eds) 3rd International Conference on the Application of Superabsorbent Polymers (SAP) and Other New Admixtures Towards Smart Concrete. SAP 2019. RILEM Bookseries, vol 24. Springer, Cham. https://doi.org/10.1007/978-3-030-33342-3_14
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DOI: https://doi.org/10.1007/978-3-030-33342-3_14
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