Sorption kinetics of superabsorbent polymers (SAPs) in fresh Portland cement-based pastes visualized and quantified by neutron radiography and correlated to the progress of cement hydration |
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| Affiliation: | 1. Technische Universität Dresden, Fakultät Bauingenieurwesen, Institut für Baustoffe, DE-01062 Dresden, Germany;2. Paul Scherrer Institut, Laboratory for Neutron Scattering and Imaging, CH-5232 Villigen/AG, Switzerland;1. Empa, Swiss Federal Laboratories for Materials Science and Technology, Switzerland;2. Institute of Materials and Structures, Riga Technical University, Latvia;3. Department of Building Physics and Building Materials, Lodz University of Technology, Poland;4. Institute for Building Materials (IfB), ETH Zurich, Switzerland;1. Magnel Laboratory for Concrete Research, Department of Structural Engineering, Faculty of Engineering and Architecture, Ghent University, Technologiepark Zwijnaarde 904, B-9052 Gent, Belgium;2. DTU Byg, Department of Civil Engineering, Faculty of Civil Engineering, Technical University of Denmark, Building 118, Brovej, 2800 Kgs. Lyngby, Denmark |
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| Abstract: | Water sorption of two superabsorbent polymers in cement-based pastes has been characterized by neutron radiography. Cement pastes with W/C of 0.25 and 0.50 and one additionally containing silica fume (W/C = 0.42) were investigated. The SAPs differed in their inherent sorption kinetics in extracted cement pore solution (SAP 1: self-releasing; SAP 2: retentive).Desorption from SAP 1 started very early after paste preparation. Hence, its individual non-retentiveness governs its behavior only.SAP 2 released water into all matrices, but its kinetics were different. In the paste with the highest W/C, some moderate water release was recorded from the beginning. In the other two pastes, SAP 2 retained its stored liquid during the dormant period, i.e., up to the percolation threshold. Intense desorption then set in and continued throughout the acceleration period.These findings explain the pronouncedly higher efficiency of SAP 2 as internal curing admixture as compared to SAP 1. |
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