Hochtief Aktiengesellschaft Vorm. Gebr.helfmann

Hochtief Ag Vorm. Gebruder Helfmann

Bernd Hillemeier

Siegmund Hflm Babendererde

Otto Braach

Richard Pohl

Gunter Brockmann

Claus Flohrer

Andreas Schaab

Rolf Wichern

A surface of a fresh concrete body is dried by first covering the surface to be dried with a layer of bibulous granules having a great internal surface area for a time sufficient to draw generally all of the water out of the body via the surface and then preventing water from entering the layer from its side turned away from the body. The granules are finely divided hygroscopic particles, with an internal surface area of at least 200 m.sup.2 /g, preferably at least 800 m.sup.2 /g. The hydrophilic particles take up the moisture from the concrete and hold it in the layer of particles lying on the surface. This reduces the partial vapor pressure on the surface of the concrete body which effectively draws further liquid out of the concrete. The particles are a mixture of a cross-linked polymer that only swells in water and silica. The particles are carried in a coherent mat and are applied as a layer to the surface by laying the mat thereon. This mat has a moisture-pervious face and a moisture-impervious face so that water is prevented from entering the layer from the side turned away from the body by orienting the moisture-impervious face away from the body. The moisture-impervious face is formed by a synthetic-resin sheet.

Drying the surface of a fresh concrete body

The apparatus for applying a sprayed concrete layer to a surface comprises a concrete feed pipe for a pumpable and sprayable concrete mixture made with water, a sprayer and a compressed air feed device for compressed air under a pressure of several bar from a compressed air source. The concrete feed pipe opens into the sprayer which has a compressed air connector device. The concrete mixture is sprayable with the compressed air. The compressed air feed device comprises a register including several compressed air chambers which connect to and open into the compressed air connector device. The individual compressed air chambers are connected with the help of control valves in alternating sequence to a power silo for loading a powdery concrete additive, particularly silica powder, or for blowing through a compressed air partial flow.

Method of and apparatus for applying a sprayed concrete layer to a

A spray concrete composition which is sprayed with driving-air pressure has its setting time accelerated by incorporation in the driving air of amorphous silica dust having an inner surface (specific surface area) of at least 25 m.sup.2 /g.

Method and apparatus for the spray placing of concrete layers

An apparatus for making a tunnel lining from concrete in a single operation with a tunnel excavator comprises a tunnel lining form consisting of a plurality of tunnel lining form segments and a form front adjacent the tunnel excavator and a tunnel lining circular space between the form and the ground. The concrete is selected so that it remains workable for more than two hours at a temperature of about 20.degree. C. but sets to a nonworkable state after 10 to 30 minutes upon heating to a temperature in the range of substantially 40.degree. C. to substantially 70.degree. C. The concrete is heated in a pipe section proximal to the compartment into which it is introduced by direct introduction of electrical energy into the pipe section.

Method of and apparatus for concrete tunnel lining

An apparatus for making a tunnel lining from concrete in a single operation with a tunnel excavator comprises a tunnel lining form consisting of a plurality of tunnel lining form segments and a form front adjacent the tunnel excavator and a tunnel lining circular space between the form and the ground. In order to heat the concrete as it is pumped into the tunnel lining circular space to accelerate hardening, transmitting antennae for electromagnetic radiation are mounted in the tunnel lining form segments and/or the feed pipes for the concrete. Similarly a process for making a tunnel lining from concrete comprises pumping concrete into the tunnel lining circular space and accelerating the hardening of the concrete by heating it with electromagnetic radiation. The tunnel form is rapidly repositioned after the concrete being hardened reaches a sufficient strength.

A process for providing a corrosion resistant synthetic plastic resin coating on a surface of a concrete structure comprises cleaning the surface of the concrete structure, forming a fiber containing sprayed concrete layer having a plurality of fiber components therein, for example glass fibers or plastic fibers, on the surface of the concrete, and subsequently applying a synthetic plastic resin thereto, whereby the fiber components projecting from the fiber containing sprayed concrete layer act to anchor the synthetic plastic resin to form the corrosion resistant coating. The corrosion resistant synthetic plastic resin coating preferably contains a polyester resin, and a polymer-cement-concrete base layer may be used to help bond the fiber containing sprayed concrete layer to the cleaned concrete surface.

Process for providing a synthetic resin coating on a concrete structure

A method of determining location and orientation of metallic reinforcing members in reinforced concrete whereby the members are heated inductively, e.g. by a spiral coil lying in a plane parallel to the plane of the reinforced concrete slab, and the heating of the members is detected by thermally sensitive means, such as a camera (e.g. thermovision), film or paper responsive to infrared radiation. The heat pattern represents the pattern of reinforcement.

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Wiesbaden, Germany

Bernd Hillemeier