Matches in UGent Biblio for { ?s ?p Ultrasonic measurements can be used to monitor concrete setting. To relate these measurements with fundamental structural changes in the cement paste, the results are compared with the microstructure development as simulated with an adjusted version of the pixel model Cemhyd3D. Mixtures in which the Portland cement was replaced by different dosages of blast-furnace slag and fly ash were tested. The fraction of percolated solid particles is het most important microstructure parameter determining the change of the wave velocity during setting. However, the measured wave velocity starts to increase earlier than the solid percolation, which is by other researchers assumed to be caused by the formation of early-age- C-S-H and AFt. The simulations could not confirm the latter. After percolation, the formation of additional hydration products increases the elastic moduli and thus the wave velocity. This becomes especially visible for the high-volume slag mixture. After approximately 24h, the presence of slag causes a second acceleration of both the hydration product formation and the wave velocity increase. The pore space depercolation seems unimportant in the study of the setting of concrete or mortar.. }
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- aggregation abstract "Ultrasonic measurements can be used to monitor concrete setting. To relate these measurements with fundamental structural changes in the cement paste, the results are compared with the microstructure development as simulated with an adjusted version of the pixel model Cemhyd3D. Mixtures in which the Portland cement was replaced by different dosages of blast-furnace slag and fly ash were tested. The fraction of percolated solid particles is het most important microstructure parameter determining the change of the wave velocity during setting. However, the measured wave velocity starts to increase earlier than the solid percolation, which is by other researchers assumed to be caused by the formation of early-age- C-S-H and AFt. The simulations could not confirm the latter. After percolation, the formation of additional hydration products increases the elastic moduli and thus the wave velocity. This becomes especially visible for the high-volume slag mixture. After approximately 24h, the presence of slag causes a second acceleration of both the hydration product formation and the wave velocity increase. The pore space depercolation seems unimportant in the study of the setting of concrete or mortar.".