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Effect of entrapped and entrained air on the workability and rheology of cementitious materials

Boekbijdrage - Boekhoofdstuk Conferentiebijdrage

The influence of air on the fresh properties of cementitious materials is still a point of discussion in concrete research. On the one hand, fluctuations of entrapped air can change the predicted properties in an undesirable way. On the other hand, it is known that the addition of air entrainment changes the rheology significantly. A profound research on the impact of different methods to change the air content, is necessary. We investigated the influence of vacuum mixing and air entrainment on the workability of paste and mortar. For self-compacting mortar also the influence on the rheology was examined. For vibrated paste and self-compacting mortar a clear decrease of the workability is determined when air is added. This was also found for the rheology of self-compacting mortar. In case of vibrated mortar an overall increase of the workability occurred, when the air content increased. In conclusion, vacuum mixing can control the air content and changes the workability and rheology in an acceptable way. A more important change of the slump flow and, if determined, the rheology, is obtained by air entrainment. Further research should be performed on the influence of air on the worability and the rheology of ultra-high performance concrete.
Boek: Rheology and Processing of Construction Materials, Proceedings
Volume: PRO 90
Pagina's: 179 - 188
Jaar van publicatie:2013