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Vacuum mixing: a new way of air content reduction in UHPC

Author(s): J. Dils, V. Boel , G. D. Schutter
Paper category: Proceedings
Book title: Proceedings of the Seventh International Conference on Concrete under Severe Conditions – Environment and Loading
Editor(s): Z.J. Li, W. Sun, C.W. Miao, K.Sakai, O.E. Gjřrv, N.Banthia
ISBN: 978-2-35158-124-7
e-ISBN: 978-2-35158-134-6
Publisher: RILEM Publications SARL
Publication year: 2013
Pages: 870-878
Total Pages: 9
Language : English

Abstract: The production of ultra-high performance concrete is made possible by a combination of an optimal packing density, a suitable mixing procedure and an effective match between a third generation superplasticizer and the binders. By increasing the level of performance, it is questionable how the robustness of the mixture evolves. What is the impact of a change in proportioning. An undesirable increase in air content can alter the fresh and hardened properties. For this, vacuum mixing can help. Because little is known about this new technology, research is necessary. We tested the influence of a reduced air pressure in the mixing pan on the microstructure and the mechanical performance of ultra-high performance concrete. This paper reports the impact on the hardened air content, the specific pore surface, the spacing factor and the compressive strength.
The hardened air content decreased for all mixtures tested in this program. A reduction of the air pressure to 50 mbar, reduced the air cavities. Depending on the workability of the mixture, this led to an increase in the specific pore surface and the spacing factor. The improved microstructure led to a higher compressive strength. An average gain between 8% and 18% was determined. In conclusion, the air content can be controlled and a higher performance is achieved. Further research, should be focussed on the influence of vacuum mixing on the durability of ultra-high performance concrete.

Online publication : 2013
Publication type : full_text
Public price (Euros) : 0.00

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