Architectural concrete

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Under architectural concrete a is concrete understood, are placed on the high architectural requirements. The German Precast Construction Association defines the term in its leaflet “ Precast concrete parts made of architectural concrete ” as follows: “The term architectural concrete includes both the designs that aim to achieve the most perfect, uniform surface and color possible, as well as projects that are natural and lively of the building material concrete should be approved and consciously emphasized. The precast concrete elements made of architectural concrete are conceived as a design element of the architecture and must be manufactured with particular care in terms of surface, color and shape. "Architectural concrete thus represents a high-quality form of exposed concrete and is usually only produced in precast concrete plants, because the high requirements the construction site can only be reached with great difficulty. Architectural concrete is mainly used in facades and in very representative interior areas of buildings.

Composition of the concrete

Special aggregates such as light marble , dark stones such as dolomite or special chippings (e.g. glass chippings) or gemstones are almost always used. The cement used also plays a major role. So z. B. white cement has a positive effect on the uniformity of the color shade. The additives also play a major role. Pigments are often used for coloring. But fly ash and rock powder are usually added to the concrete. The color and the appearance of the concrete can thus be strongly influenced, so that the later processed and treated concrete, for example, can look confusingly similar to natural stones. However, effects can also be achieved that do not occur in natural rock.

Surface treatment

Processing the concrete is a central component of the manufacturing process for architectural concrete.

  • In the past, exposed aggregate concrete was a very popular way of processing concrete surfaces. The setting of the concrete is delayed on the surface. The surface of the cement that has not set is then washed out with water and a broom, now often also with high pressure water jets, so that the aggregates are clearly visible. Today, fine washing can also produce structures that can no longer be compared with the earlier exposed aggregate concrete.
  • Acidification: Acids artificially roughen the concrete surface so that a structure is created that cannot be dissimilar to sawn sandstone.
  • Sandblasting : sandblasting removes the top layer of concrete, similar to acidification, so that similar effects are achieved.
  • Stonemason-like processing: There are numerous methods of processing natural stone surfaces . Typical are, for example, pointed, stick or scratch. The concrete surface is worked on with a pointed iron or a special hammer (e.g. stick hammer ).
  • Sanding and polishing: the concrete surface can only be sanded or also polished. The processing is therefore comparable to the steps in the production of terrazzo , so that the concrete surface can look very similar to polished granite, for example.
  • Flames: the concrete surface is treated with a gas burner. This creates a surface structure that looks similar to roughly hewn rock.

In some cases, several procedures are used in succession.

Surface treatment

The surface of architectural concrete is usually treated finally. The options for surface treatment are also dealt with in DIN V 18500. The goals of such treatment can be:

literature

  • Heeß, S .: fair-faced concrete with Dyckerhoff Weiss, Dyckerhoff AG