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

Jeroen Dils (UGent) , Veerle Boel (UGent) and Geert De Schutter (UGent)
(2013) PRO 84. 2. p.1782-1790
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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.
Keywords
Vacuum mixing, UHPC, compressive strength, air void analysis

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Chicago
Dils, Jeroen, Veerle Boel, and Geert De Schutter. 2013. “Vacuum Mixing: a New Way of Air Content Reduction in UHPC.” In PRO 84, ed. ZJ Li, W Sun, CW Miao, K Sakai, OE Gjorv, and N Banthia, 2:1782–1790. Bagneux, France: RILEM Publications S.A.R.L.
APA
Dils, J., Boel, V., & De Schutter, G. (2013). Vacuum mixing: a new way of air content reduction in UHPC. In ZJ Li, W. Sun, C. Miao, K. Sakai, O. Gjorv, & N. Banthia (Eds.), PRO 84 (Vol. 2, pp. 1782–1790). Presented at the Concrete under Severe Conditions : Environment and Loading (CONSEC - 2013), Bagneux, France: RILEM Publications S.A.R.L.
Vancouver
1.
Dils J, Boel V, De Schutter G. Vacuum mixing: a new way of air content reduction in UHPC. In: Li Z, Sun W, Miao C, Sakai K, Gjorv O, Banthia N, editors. PRO 84. Bagneux, France: RILEM Publications S.A.R.L.; 2013. p. 1782–90.
MLA
Dils, Jeroen, Veerle Boel, and Geert De Schutter. “Vacuum Mixing: a New Way of Air Content Reduction in UHPC.” PRO 84. Ed. ZJ Li et al. Vol. 2. Bagneux, France: RILEM Publications S.A.R.L., 2013. 1782–1790. Print.
@inproceedings{4150508,
  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.},
  author       = {Dils, Jeroen and Boel, Veerle and De Schutter, Geert},
  booktitle    = {PRO 84},
  editor       = {Li, ZJ and Sun, W and Miao, CW and Sakai, K and Gjorv, OE and Banthia, N},
  isbn         = {9782351581247},
  keyword      = {Vacuum mixing,UHPC,compressive strength,air void analysis},
  language     = {eng},
  location     = {Nanjing, China},
  pages        = {1782--1790},
  publisher    = {RILEM Publications S.A.R.L.},
  title        = {Vacuum mixing: a new way of air content reduction in UHPC},
  volume       = {2},
  year         = {2013},
}