CS198375B1 - Method of hollow making in concrete prefabricated elements - Google Patents

Description

(54)

Method of cavity formation in prefabricated concrete

It is known that the bending and turkey profiles which are the most advantageous in terms of strength and economy are circumferentially closed, hollowly lightweight in their interior.

This is true for concrete bridge structures, both reinforced concrete and especially for prestressed beams.

It is laborious and costly to form a hinge in closed hens.

These methods are known to form cavities in precast concrete.

Either a core is inserted into the beam or column production mold, which is forcefully pulled out of the concrete element at a certain point in time, or a core is used which can be reduced in volume at the required time when the concrete already fades. (assembly of wedges or loosening of the core spacers) from the cavity.

Alternatively, the cavity is formed by a formwork or sheet metal structure that is left permanently in the product - the so-called lost formwork.

All of these methods are labor-intensive and the right time to pull them out of the product. In addition, lost formwork of wood or other materials or metal baldness is expensive and increases the non-functional weight of the product.

In the production of prefabricated parts of the described type pre-tensioned on a long track, where on the tensioned patented wires or ropes from them are concreted just behind

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the core cannot be removed from the long run before the concrete is fully matured and the parts are disconnected.

This further complicates the choice of the described core methods and hence the cost of its long-distance procurement and installation.

All of these disadvantages are overcome by the process according to the invention, which consists in using an easily fusible material such as paraffin to form the core. It is poured into the core mold by heat-liquefied and allowed to cool and solidify therein.

After removal from this mold, the solidified core is inserted into a mold for the production of a concrete product.

In individual molds or on a long run.

After a certain delay in which the precast concrete is vibrated or otherwise compacted, the precast form is heated, primarily in order to heat the concrete of the article, which greatly facilitates its maturation and hardening.

In a particular heat condition of a concrete, paraffin or other easily fusible material, e.g. at 6 ° C, becomes liquid and can flow by gravity through a hole formed during concreting in the bottom wall of the precast and through a hole in the floor of the precast form. again into core forms, where it solidifies again into a solid core for further concreting.

Instead of gravity, the liquid, easily fusible material can be pumped from the cavity through another opening, for example, in the top wall or side walls.

Claims (1)

P S E D OF THE INVENTION A method for forming cavities in precast concrete, characterized in that the core is made of a low-melting material, which core is placed in the precast mold and when the precast is heated both in and out of the mold as a molten liquid through the orifice or drained and poured into re-solidifying and forming a new core into a shaped core.