Release agent (formwork)

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Release agent application

Concrete formwork is treated with special release agents before use . In this way, the formwork can later be removed from the concrete easily and usually without damage . At the same time, the release agents are used to maintain the formwork.

Mode of action

By applying the release agent, the water absorption capacity of the formlining is reduced (pore closure) and thus the adhesion between concrete and formwork is reduced. As a result, the stripping process requires less effort and damage to both the concrete surface and the formwork is avoided.

Release agents are also used to maintain the formwork. The treated formwork parts are protected from corrosion and rot and can be cleaned of concrete residues more easily after use. This leads to a significantly longer service life for the formlining.

species

There are basically five different types of release agents:

  • water-soluble formwork oils
  • water-insoluble formwork oils
  • Formwork pastes
  • Formwork wax
  • Chemically reacting release agents

application

The selection of the release agent depends primarily on the absorbency of the formlining and the required surface quality. Formwork oils are used as standard. They are thin and are usually applied to the formlining with high pressure tips. The quality of the concrete surface is negatively affected by overdosing.

Formwork pastes and formwork waxes, on the other hand, have a thick to solid consistency and are applied thinly with brushes, rags or by machine. Compared to the formwork oils, the adhesion to the formlining is better and particularly high-quality exposed concrete surfaces can be achieved. Overdosing also has a negative effect on the quality of the concrete surface.

Environmental protection and pollutants

Release agents made from renewable raw materials are available, but release agents made from petroleum are mostly used for cost reasons . In Germany, for example, around 25,000 tons of formwork oil were used in 2007. With around 2,500 t, biogenic forming oils make up 10% of this.

Until the ban on use in open applications in 1978, PCBs were used in formwork oils. These formwork oils led to the contamination of the formwork and the concrete, which today can still have high PCB values. According to the PCB Directive NRW, building materials with a PCB content of more than 50 mg / kg must be classified as containing PCB and therefore disposed of as hazardous waste according to the Waste Catalog Ordinance .

literature

  • Roland Schmitt: The formwork technology . John Wiley & Sons, 2001, ISBN 3-433-01346-2 , pp. 27-29
  • Construction engineering . 10th edition. Europa-Lehrmittel, 2003, ISBN 978-3-8085-4460-0 , pp. 273 .

Individual evidence

  1. ↑ Horst Becker: Structural Engineering III . Springer-Verlag, 2013, ISBN 3-642-95264-X , page 395
  2. ^ FNR - Agency for Renewable Raw Materials eV (2007): Data and facts on renewable raw materials, 1st edition 2007, Rostock: Weidner GmbH. PDF file
  3. ↑ Bavarian State Office for the Environment, Pollutant Advisor - Building Dismantling, Chapter 512: Polychlorinated Biphenyls (PCB), https://www.lfu.bayern.de/abfall/schadstoffratgeber_gebaeuderueckbau/suchregister/doc/512.pdf

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