Blinding layer
In the building industry , the terms blinding layer ( SKS for short ) or sub- concrete refer to a thin layer of lean concrete that is located between the base of the excavation pit and the building foundation .
purpose
The main purpose of installing a blinding layer is to maintain a clean, level and dry surface for subsequent work. This is an effective way of preventing the reinforcement and spacers from being pressed into the subsoil and thus no longer adhering to the required minimum concrete cover . When building a black tank , the necessary sealing layer is applied directly to the blinding layer.
Furthermore, a blinding layer has the advantage that the base of the construction pit is protected from harmful weather influences. This is particularly important if the subsoil is sensitive to moisture (such as cohesive soils ).
properties
The blinding layer consists of concrete with a low strength class (mostly C 8/10 with exposure class X0), which is installed as flat as possible. Reinforcement is not required. The thickness is at least 5 cm. If the requirements are higher (for example in the case of chemically aggressive soil) or when building a black tank, a thickness of 10 cm should be selected.
Alternatives
In order to save time and money, in some cases the production of a blinding layer is dispensed with and instead PE films or thick-walled dimpled sheets are used. However, both products are not a completely equivalent substitute, as they can hardly compensate for any unevenness in the base of the excavation and there is also the risk that the reinforcement or the spacers will be penetrated and the minimum concrete cover will no longer be observed.
A blinding layer cannot be omitted if unreinforced foundations (e.g. strip foundations with earth cladding ) are to be created or if perimeter insulation is provided under the floor slab. This would lead to inadmissible stress on the insulation. In both cases, the base of the excavation must only have very slight unevenness.
Norms and standards
- DIN EN 1992-1 - Eurocode 2: Dimensioning and construction of reinforced concrete and prestressed concrete structures
- DIN 1045-3 - Structures made of concrete, reinforced concrete and prestressed concrete - Part 3: Construction - Application rules for DIN EN 13670
Individual evidence
- ↑ Wormuth Schneider: Building encyclopedia . Bauwerk Verlag, Berlin 2009, ISBN 978-3-89932-159-3 , p. 233 .
- ↑ Gottfried Lohmeyer: Reinforced concrete construction . Springer-Verlag, 2013, ISBN 3-663-01539-4 , p. 438 .
- ↑ Ulf Hestermann: Frick / Knöll building construction theory 1 . Vieweg + Teubner Verlag, 2009, ISBN 3-8348-0837-7 , p. 50 .