Vacuum concrete
Fresh concrete , which is treated flatly with negative pressure after installation , is called vacuum concrete . The negative pressure causes a particularly tight storage of the concrete components as well as the drainage of the water not required for hydration . This leads to additional static compaction with a simultaneous reduction in the water-cement ratio by around 10 to 20%.
properties
Concrete surfaces treated with negative pressure have several positive properties. You get a particularly dense and wear-resistant surface. At the same time, there is less shrinkage cracking . This means that the concrete has a lower water penetration depth and increased frost resistance. By removing the excess water, the concrete also hardens many times faster and can therefore be removed and used much earlier.
Work steps
In the first step, the concrete is installed, compacted and leveled according to the profile. The concrete surface is then given a cover made of perforated plastic filter mats with air-filled knobs on the top. This is followed by a water- and air-impermeable vacuum carpet made of a special synthetic fabric. The required negative pressure is generated by a vacuum pump that is connected to the vacuum carpet with a hose line beforehand. Due to the pressure of about 0.09 N / mm² generated by the vacuum pump, part of the water in the fresh concrete migrates to the surface and reaches the collecting container at the vacuum pump via the vacuum carpet and the hose line. After the treatment has ended, the concrete surfaces are finally processed with the rotary trowel.
See also
Individual evidence
- ^ Hans-Gustav Olshausen: VDI-Lexikon civil engineering . Springer-Verlag, 2013, ISBN 978-3-6623-0424-2 , page 572 ff.
- ^ Hansjörg Frey: Structural engineering - specialist knowledge of construction . Europa-Lehrmittel Verlag, Haan-Gruiten 2003, ISBN 3-8085-4460-0 , p. 301 .