Pre-splitter

A pre-molded , pre-injector or Spritzbewurf is a thin liquid sprayed- mortar for the preparation of the ground for a subsequent plastering .

A distinction must be spritz of spray plaster . While the method of application and layer thickness are similar, spray plaster serves as a decorative finishing plaster. To avoid cracks, spray plaster should develop less strength than spray grout when it sets.

It can perform several tasks:

1. In the case of surfaces that are too smooth (e.g. smooth concrete or plaster with sintered skin ) and insufficiently absorbent substrates (e.g. compacted concrete from around C10 or cement plaster ) , the spray grout serves as an adhesion promoter and is sprayed on in a network. The underground remains partially visible.
2. In the case of substrates that are too absorbent (such as clay plaster , clay bricks and bricks that are burnt low ), the spray grout serves as a primer, which protects the subsequent plaster layers from too rapid dehydration. In this case, it is sprayed on thinly but over the entire surface.
3. In the case of a substrate made of different materials, the spray grout serves as a primer, which balances the absorbency of the plaster base in order to enable an even application of the subsequent plaster layers. In this case, it is also sprayed over the entire surface.

Basically, the pre-splash consists of binding agent and broken sand with a grain size of up to 4 mm or, in rare cases, up to 8 mm. The grain size of the sand should not be too fine in order to achieve good interlocking of the subsequent plaster layers with the substrate.

Spray grout can be produced with a wide variety of binders. Frequently, cement used as the low elasticity of cement plaster when thin and non-solid order does not constitute a disadvantage. The low water permeability of cement plaster is also desirable if the absorbency is to be reduced. The disadvantage is the stiff cement plaster on soft substrates, especially if the surfaces are exposed to the sun or driving rain, since the resulting stresses can lead to the formation of peeling and detachment from the substrate. A lime plaster with little or no cement should be selected here.

The pre-spray is made up as a liquid and thrown onto the surface as a thin layer or sprayed by machine. Due to the kinetic energy and the liquid consistency of the pre-spraying mortar, the binding agent penetrates the pores better and digs into the fine structure of the substrate than is the case with applied plastering mortar. If the existing subsurface is very uneven, deeper areas should first be ejected with mortar and roughly leveled off. The thin spray grout can only fill uneven areas to a limited extent. In order to avoid the formation of cracks later on, framework beams are often decoupled from the subsequent plaster layers by a layer of expanded metal or a special plaster base grid with an inserted cardboard layer before the spray grout is applied. In this case, the plaster base should extend at least 15 cm beyond the framework beams and, if possible, be attached not to these but to the surrounding masonry.

With very highly absorbent substrates such as gypsum plaster , plasterboard and aerated concrete , it may be necessary to apply a primer with synthetic or natural resin components in addition to or instead of the sprayed grout.

Before the plastering of non-absorbent or very smooth surfaces or those on which mineral Spritzbewurf other reasons not adhere well, one can primer , Primer or a bonding agent to be applied, which are usually less fluid as primers, and contained surcharges a create a rough surface.