EP3302907A1

EP3302907A1 - Method and apparatus for producing multilayer, profiled noise barrier panels

Info

Publication number: EP3302907A1
Application number: EP16738537.6A
Authority: EP
Inventors: Tamás BALOGH
Original assignee: Sw Umwelttechnik Magyarorszag Kft
Current assignee: Sw Umwelttechnik Magyarorszag Kft
Priority date: 2015-05-29
Filing date: 2016-02-16
Publication date: 2018-04-11
Anticipated expiration: 2036-02-16
Also published as: WO2016193769A1; EP3302907C0; EP3302907A4; HUP1500260A2; EP3302907B1; HU230951B1

Abstract

The invention relates to a method for producing multilayer noise barrier panels, comprising the step of making the two layers in a single session from fresh concrete applying slipform construction technology, where one of the layers is a conventional gravel concrete layer comprising reinforcement, while the second layer is a wood concrete layer. The invention also relates to an apparatus for carrying out the method. The method according to the invention is characterised by laying, during a pre-profiling operation, a wood concrete layer (3) on the gravel concrete layer (1) at a height exceeding the final height and the profile outline of the noise barrier panel by 10-15%, and producing the final panel height and profile - in addition to applying a vibration motion known per se - by means of periodically distancing, for short intervals, the profiling plates from the wood concrete surface. The apparatus according to the invention is characterised in that it comprises a precompaction unit (15) adapted for laying a wood concrete layer (3) over the gravel concrete layer (1) in the fresh state thereof, a drive unit (16) for driving the precompaction unit (15), at least one profiling plate (18) adapted for producing the final profile of the wood concrete layer, resilient attachment elements (24) and resilient support members (25) adapted for attaching the profiling plate (18) to the fixed structural element of the apparatus, lifting rods (19) connected to the forward edge of the profiling plate with respect to the direction of travel (30), a drive unit (20) adapted for moving the lifting rods (19), and securing member(s) (29) securing the drive unit (20) to the frame (26).

Description

METHOD AND APPARATUS FOR PRODUCING MULTILAYER, PROFILED NOISE

BARRIER PANELS

Technical field

The invention relates to a method for producing multilayer noise barrier panels, comprising the step of making the two layers in a single session from fresh concrete applying slipform construction technology, where one of the layers is a conventional gravel concrete layer comprising reinforcement, while the second layer is a wood concrete layer.

The invention also relates to an apparatus for carrying out the method.

Background art

Noise barriers are more and more frequently applied along motorways in order to reduce the primarily transport-related noise pollution in residential areas.

To allow for quick and easy installation, these noise barriers, also termed as noise walls, usually consist of mostly prefabricated panels and supporting structures.

The panels comprise at least two layers having different functionality and different structural arrangement. The base layer is made of closed-texture dense concrete capable of bearing loads. Acoustic protection is provided by a lightweight concrete layer attached to the base layer.

The base layer is at least 5 cm thick and is made of C45/50 gravel concrete comprising steel strands and, if necessary, a steel mesh. The number, dimensions and pre-tensioning of the strands is determined, and the decision about the application of the optional steel mesh is made, on the basis of static calculations.

This base layer is adapted to bear the loads resulting from external forces exerted on the panel during its lifting, transport and on-site installation and also during its operation. Due to its closed texture it also acts as a barrier for airborne noise.

A 9-15 cm-thick lightweight concrete layer with high acoustic absorption capacity is attached to the base layer. The side of the lightweight concrete layer that faces the noise source is arranged to have a profiled surface formed by ribs and flutes of different shapes. Acoustic protection is provided by the lightweight concrete layer by absorbing a significant fraction of noise, while the profiled surface prevents non-absorbed noise from getting dispersed.

A number of building block prefabrication solutions can be applied for producing the above described dual-layer noise barrier panel. A well-known option is to apply two formwork parts that correspond to the dimensions of the product.

One of the formwork parts is applied for producing the base layer, the other for making the lightweight concrete layer, the two layers being integrated by adhesive bonding or by other means.

A more advantageous and more productive option is to produce the two layers by casting them, one after the other, in the same formwork part in a fresh state. The two layers, laid in a fresh state above each other and made of concrete types having different characteristics, will adhere to each other well.

Such a method is disclosed in the patent specification DE 3,632,394 Al .

For the quick and economical production of structural concrete units the so-called slipform prefabrication technology has recently become widespread.

The essential feature of this technology is that elongated structural concrete units, such as beams and floor slabs are not made utilising unique formwork parts, but are produced at a length multiple times greater than the length of the final product, by forming the entire cross section of the product in a single session, in a continuous manner.

After the desired bonding strength has been reached, the products are cut to the desired final length from the preform that is multiple times longer than the final product.

This solution requires the application of a special fabrication line and a manufacturing machine proceeding along the line.

The line is essentially a strip made from steel sheet that at both of its lateral extremities has rail-like edges adapted for receiving the manufacturing machine. This steel strip performs the same function as the base plate of conventional formworks.

For reasons of economies of scale, the width of the line is 1-1.5m, while its length is usually greater than 100m. In case of tensioned reinforced concrete products, steel strands are placed above the line at an appropriate height, and the steel strands are pre-tensioned.

To apply control of the setting process of the concrete, the fabrication line comprises controllable heating means at the bottom.

The manufacturing machine has the following generic structure:

• A rigid frame structure, with driven wheels adapted to be fitted on the rails of the manufacturing line, being disposed in the four corners of the frame structure

• A reinforcement (strand) guide unit

• At least two concrete containers, having feed openings at the bottom and comprising means for controlling the outflow of concrete • A side formwork adapted to delimit the width of the product

• A driving mechanism for the side formwork

• A concrete spreading and precompaction mechanism connected to the first concrete container, usually adapted for producing the mid-height of the product.

• A concrete spreading and compaction mechanism connected to the second concrete container - the last component of this mechanism is adjusted such that at the end of the compaction phase the prescribed height of the product (as measured from the plane of the fabrication line) is generated accurately.

• Components related to electric energy supply, distribution and automatic operation.

The manufacturing process is the following:

After performing the necessary preparations the manufacturing machine is placed on the edge rails of the fabrication line.

The two containers of the manufacturing machine are filled up with concrete mixed according to the formulation corresponding to the product.

The drive adapted for advancing the apparatus along the line is turned on,

the drive adapted for moving the slipforms forward and backwards, the drive of the spreading and alternating precompaction unit (connected to the first concrete container), and the vibrators of the compaction mechanism are turned on.

While the machine advances along the line, the concrete flowing from the container on the line takes up the space delimited in width by the moving formwork parts, encompasses the pre-tensioned strands, while the desired bulk density is provided by the compaction units.

The approximate mid-height of the product is thus produced.

As the machine continuously proceeds forward, the concrete spreading means of the second concrete container reaches the beginning of the half-height layer, and the feeding and compaction of concrete is started also from this container, and is continued as long as the full height of the finished product is reached.

The full cross section of the panel is thus produced. The manufacturing machine continuously proceeds along the line, while the concrete containers are filled as necessary.

When the manufacturing machine reaches the end of the line, the casting of a preform having a length multiple times greater than the length of the product is completed. After reaching the sufficient bonding strength the pre-tensioning of the strands is removed, the products are cut to size and are removed from the line.

The manufacturing line is thus freed up for the next production run.

The above described process includes the manufacturing steps of a generic panel, where both containers are filled with gravel concrete of identical quality, and thereby the entire cross section of the product is made of the same concrete quality.

Such apparatuses and complete technology solutions are offered by a number of manufacturers, such as PCE, ELEMATIC, Weiler Italia.

For making multilayer noise barrier panels the first container is filled with C45/50 gravel concrete, and the second one with lightweight concrete.

The manufacturing process is similar to the one described above, but there are significant differences due to the two layers having different materials, characteristics, structure, and surface configuration.

The entire cross section of the base layer is prepared from gravel concrete fed from the first container, the base layer also including the pre-tensioned strands. The vertical position of the surface forming elements of the compaction unit connected to the first container is adjusted such that the elements produce the final height of the base layer with respect to the plane of the manufacturing line.

The vertically alternating component of the precompaction unit connected to the second container follows the approximate contour line of the top face of the lightweight concrete layer's profile.

The operating surface of the final compaction unit is configured to match the final profile contour, its height being adjusted to the height of the final product.

The term "lightweight concrete layer", referring to the layer of the noise barrier panel which has favourable acoustic characteristics, has been used in the context of this description to refer to a concrete material having porous texture and lower bulk density compared to the gravel concrete base layer, but it is still a mineral-based concrete.

These two types of concrete have different laying characteristics but the differences are not so great that would disallow the application of slipform fabrication technology.

This technology is therefore also applied in practice for producing noise barrier panels.

Pressed forms made from cement-bonded wood fibre material, precast wall panels, and pressed panels combined with concrete slabs have been successfully applied as noise barriers for a long time. Cement-bonded wood shavings or wood fibre, or by a more general term, wood concrete, satisfies all functional requirements of application as components of a noise wall, while it is also favourable from the aspect of environmental load. Noise barrier panes made using wood concrete have lower specific weight and lower material costs.

The applied wood shavings (wood fibre) material can be provided by recycling or from renewable natural sources, which also constitutes an advantage.

However, there are some difficulties related to the manufacturing of such panels.

The behaviour of wood concrete during the laying operation is significantly different from load-bearing structural concretes comprising mineral aggregates, and also from lightweight concretes also comprising mineral aggregates but having a bulk density of 2000 - 2500 kg/m³.

The bulk density of wood concrete - falling in the range of 200 - 600 kg/m³ - is significantly lower than the density of mineral-based concretes. An issue related to this is that the material's self-levelling capacity and space-filling capacity is low.

Due to the presence of fibres, wood concrete material is difficult to cast with passages having sharp turns. It has a tendency to adhere to shaping profiles, and thus it tends to accumulate even at places with low flow resistance, while at other places there will not be enough material.

Because only a limited fraction of the energy exerted by the vibrators reaches the deeper layers of the product, compaction through vibration has a limited effect.

Urged by economic considerations, structural blocks production is trending towards the application of slipform technology for the prefabrication of identical components in large numbers.

It would be especially advantageous if this efficient technology could be applied for manufacturing noise wall panels using a combination of a gravel concrete base layer and a wood concrete acoustic absorption layer.

The object of the present invention is to provide an apparatus and method for producing, applying slipform technology, noise barrier panels having a gravel concrete base layer and an acoustic absorption layer.

Disclosure of invention

The object of the invention is accomplished by a method comprising the step of making the two layers in a single session from fresh concrete applying slipform construction technology, where one of the layers is a conventional gravel concrete layer comprising reinforcement, while the second layer is a wood concrete layer, the method according to the invention being characterised by laying, during a pre-profiling operation, a wood concrete layer at a height exceeding the final height and the profile outline of the noise barrier panel by 10- 15%, and producing the final panel height and profile - in addition to applying a vibration motion known per se - by means of periodically distancing, for short intervals, the profiling plates from the wood concrete surface.

In a preferred way of carrying out the method according to the invention a wood pulp- based wood concrete material having a bulk density of 200-600 kg/m³ is applied, the bulk density of the gravel concrete base layer being 2000-2500 kg m³.

In another preferred way of carrying out the method according to the invention the frequency of periodically distancing the profiling plate applied for profiling the wood concrete layer is 1-5% of the vibration frequency of the compaction vibrator, i.e. expediently 1-3 Hz, the amplitude being 5-25 mm, and the profiling plate is only partially distanced from the wood concrete material by the periodical motion of the profiling plate, the amplitude of periodic distancing being the greatest in the area near the forward edge of the profiling plate with respect to the direction of travel, said amplitude gradually decreasing rearward therefrom.

The object of the invention is further realized by and apparatus for producing a multilayer noise barrier panel consisting expediently of a reinforced gravel concrete layer as base layer and a wood concrete layer having a profiled surface, comprising a structural unit known per se that is movable on edge rails along a fabrication line, containers, a filler/feeder unit, a compaction unit and a vibrator, the apparatus according to the invention being characterised in that it comprises a precompaction unit adapted for laying a wood concrete layer over the gravel concrete layer in the fresh state thereof, a drive unit for driving the precompaction unit, at least one profiling plate adapted for producing the final profile of the wood concrete layer, resilient attachment elements and resilient support members adapted for attaching the profiling plate to the fixed structural element of the apparatus, lifting rods connected to the forward edge of the profiling plate with respect to the direction of travel, a drive unit adapted for moving the lifting rods, and securing member(s) securing the drive unit to the frame.

In a preferred embodiment of the apparatus according to the invention the drive unit adapted for moving the precompaction unit is an eccentric mechanism driven by an electric motor drive, and the active surface of the precompaction unit follows the final profile of the product in an approximately parallel manner, the shape of the precompaction unit being narrower and wider than the final profile at the flutes and the ribs thereof, respectively. In another preferred embodiment of the apparatus according to the invention only a portion of each profiling plate is oriented parallel with the plane of the fabrication line, with approximately the forward 1/3 portion thereof (with respect to the direction of travel of the machine) lying at an acute angle (preferably 10°-30°) to the horizontal, and the resilient securing members of the profiling plate are disposed at the rearward portion of the profiling plate, and the resilient support members are disposed at the forward portion of the profiling plate with respect to the direction of travel.

In a further preferred embodiment of the apparatus according to the invention the resilient securing members are rubber springs comprising screwed joints at their two parallel planes, while the resilient support members are rubber support members comprising screwed joints on one side, the other side thereof being flat.

In all preferred embodiment of the apparatus according to the invention the drive unit adapted for periodically distance the profiling plates from the concrete surface is an eccentric mechanism driven by an electric motor drive.

Brief description of the drawings

Preferred embodiments of the apparatus according to the invention are explained in detail referring to the attached drawings, where

Fig. 1 shows a sectional view of the noise barrier panel and the fabrication line,

Fig. 2 shows a side elevation view of the apparatus according to the invention on the fabrication line,

Fig. 3 is a section taken along the plane X-X of Fig. 2,

Fig. 4 is a section taken along the plane Y-Y of Fig. 2,

Fig. 5 is a section taken along the plane Z-Z of Fig. 2,

Fig. 6 is a section taken along the plane A- A of Fig. 4, and

Fig. 7 is a section taken along the plane B-B of Fig. 4.

Modes for carrying out the invention

Fig. 1 shows the cross-section of the noise barrier panel that can be produced applying the apparatus according to the invention. The panel consists of a gravel concrete layer 1 comprising reinforcement 2, a wood concrete layer 3 that is laid over the gravel concrete layer 1 in the fresh state of the latter and is connected therewith during setting, with the upper profiled surface 4 of the wood concrete layer 3 being constituted by flutes 4 and ribs 5. The multilayer noise barrier panel is laid on a fabrication line 7 comprising edge rails 6.

Fig. 2 shows the side elevation view of the apparatus, which consists of a frame structure 8 driven by wheels 9 adapted to be fitted on the edge rails 6, a strand guide unit 10 adapted for guiding the strands of the frame structure 2, a gravel concrete container 1 1 adapted for supplying the material of the gravel concrete layer 1, and a wood concrete container 12 adapted for supplying material for the upper, profiled wood concrete layer of the noise barrier panel.

A structural unit 13 known per se, adapted for forming the gravel concrete layers 1 of the noise barrier panel 1, is connected to the gravel concrete container 11 , and comprises spreading, precompaction and decompaction units known per se.

A filler/feeder unit 14 is connected to the wood concrete container 12, the filler/feeder unit 14 being adapted for controlling the outflow and performs laying of the wood concrete layer applying components known per se.

A wood concrete precompaction unit 15, built on the filler/feeder unit 14, is shown in the section X-X of Fig. 3.

An eccentric mechanism 16, fitted with an electric drive, is connected to the precompaction unit 15.

In Fig. 3 there is also shown a side formwork 17 that is fitted against the edge rails 6 of the fabrication line 7, the side formwork 17 determining the lateral dimensions of the noise barrier panel.

Fig. 4 shows a section of the apparatus according to the invention taken along plane Y- Y of Fig. 2, depicting the profiling plates 18 adapted to form the upper profiled portion of the wood concrete layer of the noise barrier panel, lifting rods 19 connected to the profiling plates 18, and an electric motor-driven eccentric mechanism 20 adapted for driving the rods 19.

Fig. 5 shows the apparatus according to the invention in a sectional view taken along plane Z-Z of Fig. 2. As it is readily apparent in Fig. 5, the profiling plates 18 form a rigid unit with a connecting member 21 and an attachment plate 22 adapted to close the connecting member 21.

A vibrator 23 is mounted on the upper surface of the attachment plates 22, while a pair of resilient securing members 24 (as shown in Fig. 6) and a pair of resilient securing members 25 are attached to the underside of the attachment plate in the corners thereof.

The profiling plates 18, lifting rods 19, connecting members 21, attachment plates 22, and vibrator 23, mentioned in relation to Figs. 4 and 5, are connected to a frame 26 via the resilient securing members 24 and the resilient support members 25. The frame 26 is adapted to provide connection with the frame structure 8 of the apparatus.

In the sections A-A and B-B shown in Fig. 4 there is depicted the arrangement of the resilient securing members 24 (rubber springs), the resilient support members 25 (rubber supports) and further structural components with respect to the longitudinal axis and the direction of travel 30 of the apparatus according to the invention.

Fig. 6 shows a sectional view taken along plane A-A of Fig. 4. As it is clearly seen in the drawing, the resilient securing members 25 are disposed on the side of the profiling plates 18 opposite the direction of travel 30 (rearward side), while the resilient support members 25 are disposed on the side thereof corresponding to the direction of travel 30 (forward side). The resilient securing members 24 are configured at their top and bottom part to include screw threads 27, the top surface of the resilient support members 25 being flat, and their underside comprising screw threads 28.

The lifting rods 19 are attached to the forward edges of the profiling plates 18 with respect to the direction of travel 30, the lifting rods 19 being operated by an electric motor- driven eccentric mechanism 20.

Fig. 7 shows a section of Fig. 4 taken along the plane B-B, where there can be seen the manner in which the eccentric mechanism 20 is attached to the frame 26 by an attachment element 29.

The operation of the apparatus according to the invention and the production of the noise barrier panel are described as follows:

As a first step, preparations involving the fabrication line 7 are carried out. The reinforcement 2 (strands) of the gravel concrete layer 1 of the noise barrier panel are placed on the fabrication line 7 and are pre-tensioned. The apparatus according to the invention is set up and is placed on the edge rails 6 of the fabrication line 7. The containers 11 and 12 are filled with gravel concrete and wood concrete, respectively, and the production of the noise barrier panel is then started.

As the machine advances, the structural unit 13 starts to form the gravel concrete layer 1 in a manner known per se.

Feeding of wood concrete from the container 12 is started as soon as the filler/feeder unit 14 arrives above the prepared gravel concrete layer 1. By the vertical alternating motion of the precompaction unit 15, wood concrete is laid on the gravel concrete layer at a height exceeding the final height and the profile outline of the noise barrier panel by 10-15%.

Next, the profiling plates 18 adapted for creating the profile and the final height of the noise barrier panel are brought into motion, simultaneously with the vibrators 23 and lifting rods 19, by means of the eccentric mechanism 20.

The vibrators 23 are adapted for exerting the same effect as in the known and conventionally applied slipform panel construction technology. By means of the lifting rods 19 and the eccentric mechanism 20 the profiling plates 18 are exerted to further motion such that the resilient securing members 24 are acting as a virtual pivot point, with the lifting rods 19 periodically distancing the forward surface portion of the profiling plate 18 (with respect to the direction of travel) from the wood concrete surface by rotating about this pivot point.

Due to the nature of the lifting - turning motion, this distancing effect is not uniform along the entire width of the profiling plate 18, but it is the greatest at the location where the raising-up of the wood concrete can be prevented most efficiently.

During the thus produced short distancing intervals the manufacturing machine is continuously advancing, the excess material being thereby carried under the profiling face of the profiling plate 18, and being compacted under the profiling face as it returns to its initial height.

The edge of the profiling plate 18 opposite the direction of travel is practically unaffected by this additional motion, and is thereby dominated by the functionality adapted to calibrate the profiled surface to its final shape and determine the height of the finished product.

It has to be noted that only a portion of the profiling plates 18 lies parallel with the fabrication line 7. Approximately the forward 1/3 portion (with respect to direction of travel 30 of the machine) thereof lies at an acute angle - preferably at 10-30° - to the horizontal.

Passing along the entire length of the fabrication line 7 the manufacturing machine produces the noise barrier panel by repeatedly carrying out the above described motion types.

The noise barrier panel thus produced is cut to the desired size after its concrete layers have set completely.

The advantage of the method and apparatus according to the invention is that it can be applied for producing a dual layer (gravel concrete layer, wood concrete layer) noise barrier panel in a single session utilising state-of-the-art slipform technology, with a structural bond being formed between the two layer, and with the finished panel suited to be cut to the size that suits specific needs. LIST OF REFERENCE NUMERALS

gravel concrete layer

reinforcement

wood concrete layer

flutes (grooves)

ribs

edge rail

fabrication line

frame structure

wheels

strand guide unit

container (for gravel concrete)

container (for wood concrete)

structural unit

filler/feeder unit

precompaction unit

eccentric mechanism

side formwork

profiling plates

lifting rods

eccentric mechanism

connecting member

attachment plate

vibrator

resilient securing members

resilient support member

frame

screw thread

securing member

Claims

1. Method for producing multilayer noise barrier panels, comprising the steps of making the two layers in a single session from fresh concrete applying slipform construction technology, where one of the layers is a conventional gravel concrete layer (1) comprising reinforcement (2), while the second layer is a wood concrete layer (3), characterised by laying, during a pre-pro filing operation, a wood concrete layer (3) on the gravel concrete layer (1) at a height exceeding the final height and the profile outline of the noise barrier panel by 10-15%, and producing the final panel height and profile - in addition to applying a vibration motion known per se - by means of periodically distancing, for short intervals, the profiling plates from the wood concrete surface.

2. The method according to Claim 1, characterised in that a wood pulp-based wood concrete material having a bulk density of 200-600 kg/m³ is applied, the bulk density of the gravel concrete base layer (1) being 2000-2500 kg/m³.

3. The method according to Claim 1 or 2, characterised in that the frequency of periodically distancing the profiling plate (18) applied for profiling the wood concrete layer is 1-5% of the vibration frequency of the compaction vibrator (23), i.e. expediently 1-3 Hz, the amplitude being 5-25 mm.

4. The method according to any one of Claims 1-3, characterised in that the profiling plate is only partially distanced from the wood concrete material by the periodical motion of the profiling plate, the amplitude of periodic distancing being the greatest in the area near the forward edge of the profiling plate with respect to the direction of travel (30), said amplitude gradually decreasing rearward therefrom.

5. Apparatus for producing a multilayer noise barrier panel consisting expediently of a reinforced (2) gravel concrete layer (1) as base layer and a wood concrete layer (3) having a profiled surface, comprising a structural unit (13) known per se that is movable on edge rails (6) along a fabrication line (7), containers (11, 12), a filler/feeder unit (14), a compaction unit and a vibrator, characterised in that it comprises a precompaction unit (15) adapted for laying a wood concrete layer (3) over the gravel concrete layer (1) in the fresh state thereof, a drive unit (16) for driving the precompaction unit (15), at least one profiling plate (18) adapted for producing the final profile of the wood concrete layer, resilient attachment elements (24) and resilient support members (25) adapted for attaching the profiling plate (18) to the fixed structural element of the apparatus, lifting rods (19) connected to the forward edge of the profiling plate with respect to the direction of travel (30), a drive unit (20) adapted for moving the lifting rods (19), and securing member(s) (29) securing the drive unit (20) to the frame (26).

6. The apparatus according to Claim 5, characterised in that the drive unit (16) adapted for moving the precompaction unit (15) is an eccentric mechanism driven by an electric motor drive.

7. The apparatus according to Claim 5 or 6, characterised in that the active surface of the precompaction unit (15) follows the final profile of the product in an approximately parallel manner, the shape of the precompaction unit being narrower and wider than the final profile at the flutes (4) and the ribs (5) thereof, respectively.

8. The apparatus according to any one of Claims 5-7, characterised in that only a portion of each profiling plate (18) is oriented parallel with the plane of the fabrication line (7), with approximately the forward 1/3 portion thereof (with respect to the direction of travel (30) of the machine) lying at an acute angle (preferably 10°-30°) to the horizontal.

9. The apparatus according to any one of Claims 5-8, characterised in that the resilient securing members (24) of the profiling plate (18) are disposed at the rearward portion of the profiling plate (18), and the resilient support members (25) are disposed at the forward portion of the profiling plate (18) with respect to the direction of travel (30).

10. The apparatus according to any one of Claims 5-9, characterised in that the resilient securing members (24) are rubber springs comprising screwed joints at their two parallel planes, while the resilient support members (25) are rubber support members comprising screwed joints on one side, the other side thereof being flat.

11. The apparatus according to any one of Claims 5-10, characterised in that the drive unit (20) adapted for periodically distancing the profiling plates (18) from the concrete surface is an eccentric mechanism driven by an electric motor drive.