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Title:
METHOD FOR MANUFACTURING CONCRETE ELEMENTS AND MANUFACTURING SYSTEM THERETO
Document Type and Number:
WIPO Patent Application WO/2020/160768
Kind Code:
A1
Abstract:
A method for efficiently manufacturing concrete elements (10, 110), wherein at least one operational functional element (3, 103a, 103b), which has functions after completion of the concrete element (10, 110), is provided, the method comprising: - embedding the at least one operational functional element (3, 103a, 103b) in non-cured concrete (2), and - irradiating heat from the at least one operational functional element (3, 103a, 103b) to the surrounding concrete (2) to support the curing of the surrounding concrete (2).

Inventors:
VON LIMBURG FELIX (DE)
SCHNEIDERS KLAUS-DIETER (DE)
Application Number:
PCT/EP2019/052920
Publication Date:
August 13, 2020
Filing Date:
February 06, 2019
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
BT INNOVATION GMBH (DE)
International Classes:
B28B11/24; C04B40/02; F24D19/10
Foreign References:
EP0000298A11979-01-10
US4899031A1990-02-06
GB1076333A1967-07-19
CN108000680A2018-05-08
Other References:
None
Attorney, Agent or Firm:
GRÜNECKER PATENT- UND RECHTSANWÄLTE PARTG MBB (DE)
Download PDF:
Claims:
CLAIMS

1. A method for manufacturing concrete elements (10, 1 10), wherein at least one operational functional element (3, 103a, 103b), which has functions after completion of the concrete ele ment (10, 110), is provided, the method comprising:

embedding the at least one operational functional element (3, 103a, 103b) in non-cured concrete (2), and

irradiating heat from the at least one operational functional element (3, 103a, 103b) to the surrounding concrete (2) to support the curing of the surrounding concrete (2).

2. The method according to claim 1 , wherein the at least one operational functional element (3, 103a, 103b) protrudes at least at one location toward the outside of the non-cured concrete (2).

3. The method according to claim 1 or 2, wherein the at least one operational functional element (3, 103a, 103b) is a reinforcement, preferably comprising an electrically conductive material which has preferably a metal component.

4. The method according to claim 1 or 2, wherein the at least one operational functional element is a thermal tube, which has a function of cooling or heating after completion of the concrete element.

5. The method according to any of the preceding claims, wherein irradiating heat is caused by a heating medium flowing through the at least one operational functional element.

6. The method according to any of the preceding claims, wherein the at least one operational functional element (3, 103a, 103b) preloads the concrete element (10, 1 10) after completion thereof preferably with a compression load, wherein the at least one operational functional el ement (3, 103a, 103b) has preferably a rod shape.

7. The method according to claim 6, wherein the at least one operational functional element (3, 103a, 103b) protrudes at minimum two locations to the outside of the non-cured concrete (2) and is attached to clamping blocks (5) which apply a tension force to the at least one operational functional element (3, 103a, 103b). 8. The method according to any of the preceding claims, wherein irradiating heat is caused by an electric current flowing through the at least one operational functional element (3, 103a, 103b).

9. The method according to claim 8, wherein the non-cured concrete (2) is supported at least partially by an electrically conductive bed (4) and an electric circuit comprises a power source (6), the at least one operational functional element (3), and the electrically conductive bed (4).

10. The method according to claim 8 or 9, wherein a plurality of operational functional elements (103a, 103b) are provided and an electric current flowing through each operational functional element (103a, 103b) can be controlled individually.

1 1. The method according to claim 7 and 8 or 7, 8 and 9, wherein the at least one operational functional element (3) is electrically conductively attached to at least one of the clamping blocks (5).

12. The method according to claims 7 to 10, wherein the at least one operational functional ele ment (103a, 103b) is attached in an electrically insulating manner to the clamping blocks (5).

13. The method according to any of claims 6 to 10, wherein the electric current amount and a temperature of the at least one operational functional element (3, 103a, 103b) are monitored and the electric current flowing through the at least one operational functional element (3, 103a, 103b) is regulated.

14. A manufacturing system for manufacturing concrete elements (10, 110) suitable for any method according to claims 7 to 12, comprising:

at least one operational functional element (3, 103a, 103b), which has functions after comple tion of the concrete element (10, 1 10) and which is to be embedded in non-cured concrete; at least two clamping blocks (5), to which the at least one operational functional element (3, 103a, 103b) is attached and which are configured to apply a tension force to the at least one operational functional element (3, 103a, 103b); and

a power source (6, 106) configured to supply an electric current to the at least one operational functional element (3, 103a, 103b).

Description:
Method for manufacturing concrete elements and manufacturing system thereto

Hollow-core slabs are standardized concrete finished elements in which a hollow-core is formed preferably along a longitudinal axis of the concrete element in order to reduce weight. Thereby, transport costs and material usage can be reduced.

Concrete materials are suitable to support high compression loads. However, under tension loads they have the tendency to cracking. Hence, their tensile strength is rather small. In order to im prove the tensile strength, concrete elements are often reinforced. Basically, there are two kinds of reinforcements. In case of a non-preloading reinforcement, there might be placed, for example, wires or metallic rods along a longitudinal direction of the concrete elements, in which the rein forcement mainly absorbs the tension load whilst the tensile strength of the reinforced concrete elements is increased.

On the other hand, the concrete element might be preloaded with a compression load by means of the reinforcement. For this purpose, wires are subjected to a tensile stress by means of clamp ing blocks which clamp the wires at both ends thereof and apply a tension force. The wires are embedded in non-cured concrete between the clamping blocks such that a part of the wires pro trudes to the outside of the non-cured concrete. After curing of the concrete, the tension force applied from the clamping blocks is removed on the outside of the concrete. As the cured concrete inhibits a reformation of the stretched wires, the tensile stress of the wires provokes a compression stress in the concrete. An externally applied tension load is superimposed on the preload com pression stress of the concrete such that the concrete can support higher tension loads. The ap plication of the tension force to the wires preferably takes place after embedding the wires in the non-cured concrete, but may also be carried out before or while embedding them in concrete.

Manufacturing of such reinforced hollow-core slabs is typically carried out on casting beds of about 100 to 120 m. The reinforcement wires are stretched at predetermined locations above the casting beds. Non-cured concrete is discharged from, for example, an extruder to the casting beds wherein the wires are embedded in the non-cured concrete.

A method for accelerating the curing process of the concrete is the application of heat to the curing concrete. From the prior art, it is known to apply heat to the curing concrete from below the con crete, namely from the casting bed. Thereby, a system of tubes and hoses is routed below the casting bed through which a liquid or steam as a heating medium passes. This kind of heating, however, requires an expensive preheating in order to provide a uniformly heated casting bed. In addition, energy loss arises from heat escaping to the lower side of the casting bed and, hence, cannot be used for heating of the concrete. Furthermore, the lower side of the concrete is inevitably heated more than an upper side thereof, which could lead to structural defects and deformation. The tubes and hoses transporting the heating medium require a high effort for ensuring leakproof ness and, if necessary, cumbersome measurements for sealing the tube and hose system.

To overcome the above mentioned drawbacks, a uniform and direct heat input into the concrete element is desired. Thereby, the heating costs and the manufacturing time can be reduced which increases the productivity of the installations.

For this purpose, a special heating technique has occasionally been applied to in situ curing at construction sites, in particular under cold environmental conditions. Thereby, electric wires have been inserted in the non-cured concrete. A current passes through these electric wires at a low voltage wherein energy is input into the concrete to support the curing.

Indeed, this technique leads to an improved heating process of the concrete. However, the fin ished concrete element includes material, which is unnecessary for its function, in form of the heating electric wires. Hence, material is used excessively and the dimensions of the concrete element might increase with this technique.

It is therefore an object of the present invention to increase the efficiency of manufacturing of concrete elements.

This object is achieved by a manufacturing method according to claim 1 and a manufacturing system according to claim 14.

According to a first aspect disclosed herein, a method for manufacturing concrete elements, wherein at least one operational functional element, which has functions after completion of the concrete element, is provided, comprises: embedding the at least one operational functional ele ment in non-cured concrete and irradiating heat from the at least one operational functional ele ment to the surrounding concrete to support the curing of the surrounding concrete.

According to the first aspect, operational functional elements are used to irradiate heat to the surrounding concrete. Thereby, the curing process is supported and accelerated by heat transfer from the operational functional elements to the surrounding curing concrete. The operational func tional elements are elements which have functions in the finished concrete element, namely after completion of the concrete element. Hence, no additional elements need to be used in order to accelerate the curing process. Rather, elements are used for the acceleration of the curing pro cess, which are provided for functions in the finished concrete element anyway. Hence, the man ufacturing of the concrete element can be carried out efficiently, saving material and heating costs. In particular, the method according to the first aspect can be easily applied, requiring a low instal lation effort. In addition the method can be carried out with existing installations for concrete man ufacturing.

According to another aspect, the at least one operational functional element may protrude at least at one location toward the outside of the non-cured concrete.

As a result, the accessibility of the at least one operational functional element is improved. Hence, a medium which causes the heat irradiation of the at least one operational functional element can be easily supplied to the at least one operational functional element.

Preferably the at least one operational functional element is a reinforcement, comprising prefera bly an electrically conductive material which has preferably a metal component.

Thus, the function of the at least one operational functional element is to reinforce the concrete element. Such reinforcement may increase, for example, the tensile strength of the concrete ele ment, but it may also increase the shear strength or durability of the concrete element. With an electrically conductive material, electric current can be used as a medium causing heat irradiation. A metal component further combines good strength, stiffness, electric as well as thermal conduc tivity properties. A material with a high thermal conductivity facilitates the heat irradiation along the at least one operational functional element.

According to another aspect, the at least one operational functional element may be a thermal tube, which has a function of cooling or heating after completion of the concrete element.

According to this aspect, the properties of a thermal tube which provide the function of cooling or heating in use of the concrete element, are also used during manufacturing of the concrete ele ment.

Furthermore, irradiating heat may be caused by a heating medium flowing through the at least one operational functional element.

Consequently, a heating circuit comprises the at least one operational functional element, wherein a heated heating medium flows through the at least one operational functional element and dis charges the heat which is irradiated to the surrounding concrete. The at least one operational functional element may be a thermal tube or a reinforcement, which has an inner channel through which the heating medium is allowed to pass. The heating medium may be a liquid like oil circu lated by a pump or steam.

In still another aspect, the at least one operational functional element may preload the concrete element after completion thereof preferably with a compression load, wherein the at least one operational functional element has preferably a rod shape.

According to this aspect, the function of the at least one operational functional element is to pre load the concrete element after completion thereof. Hence, an external load acting in an opposite direction to the preload can be better supported by the concrete element. The tensile strength of the concrete element can be enhanced if the concrete element is preloaded by a compression load. A rod shape of the at least one operational functional element facilitates the handling thereof and improves the heat irradiation from the at least one operational functional element to the sur rounding concrete.

According to another aspect, the at least one operational functional element may protrude at min imum two locations to the outside of the non-cured concrete and may be attached to clamping blocks which apply a tension force to the at least one operational functional element.

This configuration allows an easy preloading of the concrete element wherein a load is applied to the at least one operational functional element from the outside of the non-cured concrete during manufacturing of the concrete element. Hence, the clamping blocks can be installed easily.

Preferably, irradiating heat is caused by an electric current flowing through the at least one oper ational functional element.

Thereby, the heat irradiation is achieved with low effort, as no pipes and pumps for a heating medium need to be provided. Rather, the at least one operational functional element is directly used within an electric circuit. Hence, manufacturing of the concrete element can be carried out efficiently, wherein no effort incurs for ensuring leakproofness of tubes or pipes.

Preferably, the non-cured concrete is supported at least partially by an electrically conductive bed and an electric circuit comprises a power source, the at least one operational functional element, and the electrically conductive bed. If the support, on which the non-cured concrete is put, is at least partially an electrically conductive bed, the manufacturing effort can further be reduced. For example, the manufacturing casting bed can partially be configured as an electrically conductive bed. The manufacturing casting bed as a whole can also be configured as an electrically conductive bed. Hence, at least a part of the in stallations, which are provided anyway for the manufacturing process can be used to be part of an electric circuit which provides the at least one operational functional element with electric cur rent. Thus, manufacturing of the concrete element can be carried out more efficiently.

According to still another aspect, a plurality of operational functional elements may be provided and an electric current flowing through each operational functional element can be controlled in dividually.

Hence, the plurality of operational functional elements are configured as parallel circuits. Accord ing to the required heat, an electric current can be controlled individually. In this manner, the heat ing process can be carried out even more efficiently.

According to still another aspect, the at least one operational functional element may be electrically conductively attached to at least one of the clamping blocks.

With this configuration the manufacturing system can be simplified. As the attachment of the at least one operational functional element to the clamping block is electrically conductive, an electric current can easily flow between the clamping block and the at least one operational functional element without additional elements. Thereby, one electrochemical potential can be applied to the clamping blocks, which drives the electric current through the at least one operational functional element. Hence, the manufacturing process can be carried out efficiently.

In another aspect, the at least one operational functional element may be attached in an electri cally insulating manner to the clamping blocks.

This configuration is, in particular, advantageous if an electric current flowing through each oper ational functional element is controlled individually. In this manner, a bridging of the individual electric circuits via the clamping blocks is suppressed. Hence, the electric current flowing through each operational functional element can easily be controlled individually. Preferably, the electric current amount and temperature of the at least one operational functional element are monitored and the electric current flowing through the at least one operational func tional element is regulated.

Therefore, the manufacturing is carried out efficiently. The temperature and electric current are used as feedback quantities which allow the regulation of the electric current flowing through the at least one operational functional element. Hence, a desired heating behavior can be realized which supports the efficiency of the manufacturing process.

Another aspect disclosed herein provides a manufacturing system for manufacturing concrete el ements, comprising: at least one operational functional element, which has functions after com pletion of the concrete element and which is to be embedded in non-cured concrete; at least two clamping blocks, to which the at least one operational functional element is attached and which are configured to apply a tension force to the at least one operational functional element; and a power source configured to supply an electric current to the at least one operational functional element.

The manufacturing system according to this aspect allows an efficient manufacturing of a concrete element. Thereby, the manufacturing system provides some of the advantageous effects pre sented above. In particular, the at least one operational functional element preloads the concrete element after completion thereof and the curing process is supported by heat irradiated from the at least one operational functional element. The heat is generated by an electric current in this manufacturing system which allows an installation at low cost. In particular, the manufacturing system according to this aspect can be easily adopted by already existing installations for concrete manufacturing.

In the following, the invention will be explained in more detail by making reference to the accom panying drawings. The presented embodiments do not intend to limit the present invention. Ra ther, they only present some ways to realize the present invention. However, there are other ways to realize the present invention which are obvious for the person skilled in the art.

Fig. 1 shows a manufacturing system 1 according to a first embodiment of the invention

Fig. 2 shows a front view of a clamping block in Fig. 1 and a sectional view along a line A-A in the front view

Fig.3 shows a manufacturing system 101 according to a second embodiment of the invention Fig. 4 shows a front view of a clamping block in Fig. 3 and a sectional view along a line B-B in the front view

Fig. 5 shows a front view of a concrete element 10, which can be manufactured with a system according to the first embodiment

Fig. 6 shows a front view of a concrete element 1 10, which can be manufactured with a system according to the second embodiment

<Detailed description of embodiments>

Fig. 1 shows a manufacturing system 1 according to the invention, which is capable to apply a manufacturing method according to the invention. In the manufacturing system 1 , a support 4 is provided in form of a casting bed, on which non-cured concrete 2 is placed down. The concrete 2 may be place down on the support 4, for example, by means of an extruder. In particular, in man ufacturing of hollow-core slabs extruders are used in order to form the hollow space. However, the concrete 2 may also be placed on the support 4 from a concrete mixer via a pump and may be supported on the sides by a framework.

Operational functional elements 3 pass through the concrete 2 along the longitudinal direction of the support 4, as can be seen in Fig. 1. In other words, the operational functional elements 3 are embedded in the non-cured concrete 2 placed on the support 4. In the present first embodi ment, the operational functional elements are reinforcements which increase the tensile strength of the concrete element after completion thereof. The reinforcement comprises preferably an elec trically conductive material, which has preferably a metal component, such as steel.

The operational functional elements 3 protrude at both end sides in the longitudinal direction of the support 4 to the outside of the non-cured concrete. The operational functional elements 3 are attached to clamping blocks 5 on the outside of the concrete 2 at both end sides of the operational functional elements 2. The clamping blocks 5 apply a tension force to the respective operational functional elements 3 which are therefore stretched. After curing of the concrete 2, the tension force applied from the clamping blocks is removed on the outside of the concrete 2. Then, the cured concrete 2 supports the stretching of the operational functional elements 3 and, as a con sequence, is preloaded by a compression load. The application of the tension force to the wires preferably takes place after embedding the wires in the non-cured concrete, but may also be car ried out before or while embedding them in concrete. In the manufacturing system, a power source 6 is further provided. One pole of the power source 6 is connected to one clamping block 5 at one end side of the operational functional elements 3 and the support 4 via an electric cable 7. The cable 7 might be attached to the clamping block via a terminal 7. However, there are many other possibilities to connect the clamping block 5 with the power source 6.

The other pole of the power source 6 is connected to the support 4 via another cable 7. In the first embodiment, the support 4 is an electrically conductive bed. At the other end side of the support 4, still another cable 7 connects the support 4 to the other clamping block 5 at the other end side of the operational functional elements 3.

In Fig. 2, the attachment of the operational functional elements 3 to the clamping blocks 5 is shown. The left side in Fig. 2 shows a front view of a clamping block in Fig. 1. The right side in Fig. 2 shows a sectional view along the line A-A in the left side. As can be seen from Fig. 2, the operational functional elements 3 pass through a through hole of the clamping block 5. On the end side of the clamping block 5 opposite to the concrete 2, the operational functional elements are clamped by a clamping cone 9. The clamping cones 9 are attached to the clamping block 5 with a washer 8 interposed between. The clamping block 5, the clamping cone 9, and the washer 8 are made of electrically conductive materials, preferably steel. Hence, the operational functional ele ments 3 are electrically conductively attached to the clamping block 5. Furthermore, adjacent washers 8 contact each other. Hence, the electric resistance is small. The use of washers is op tional and alleviates the adjustment of the tension force.

Once the power source 6 is switched on, the electrochemical potential of the respective pole of the power source 6, which is connected to the respective clamping block 5, is transferred to the clamping block 5. The washers 8 and the clamping cones 9 transmit the electrochemical potential to the operational functional elements 3. As the clamping block 5 on the one end side of the sup port 4 is connected to one pole of the power source 6 via a cable 7, and the clamping block 5 on the other end side is connected to the other pole of the power source 6 via two cables 7 and the support 4 in form of an electrically conductive bed, an electric current flows through the operational functional elements, which are disposed in parallel in the first embodiment. In other words, an electric circuit comprises the power source 6, the operational functional elements 3, and the sup port 4 in form of the electrically conductive bed. The electric current is driven by the voltage be tween the clamping block 5 on the one end side of the support 4 and the clamping block 5 on the other end side. In order to avoid a short circuit, at least one clamping block 5 must be electrically separated from the support 4 if the support is made electrically conductive. The support 4 need not necessarily be part of the electric circuit, but a cable may be used instead.

In the first embodiment, the operational functional elements 3 are rod-shaped reinforcements such as wires. Therefore, the operational functional elements 3 can be easily clamped by the clamping cones 9 and have a low electric resistance. If the rod further has a circular cross-section the heat transfer from the operational functional elements 3 to the surrounding concrete can be enhanced.

In the first embodiment, the individual operational functional elements 3 have the same cross shape, the same sectional area, and the same length. Hence, the electric resistance of the indi vidual operational functional elements is approximately the same and the same amount of electric current flows through the individual operational functional elements 3. Therefore, the system can be maintained simple and approximately the same amount of electric current can flow through the individual operational functional elements, if the whole clamping blocks 5 are supplied with the electrochemical potential of the respective poles of the power source 6.

The electrochemical potential need not necessarily be provided to the operational functional ele ments 3 via the clamping blocks 5, but may be provided, for example, via bus bars which connect the individual operational functional elements with each other on the outside of the clamping blocks 5. In such a case, the clamping blocks 5, washers 8, and clamping cones 9 may be formed of an electrically insulating material.

Finally, Fig. 5 shows a front view of a concrete element 10, which can be manufactured with a system according to the first embodiment. The concrete element 10 is a hollow-core slab which comprises the concrete 2 and a layer of operational functional elements 3 in form of reinforcements which preload the concrete element 10. As can be seen from Fig. 5, the operational functional elements are preferably equally spaced from each other in order to provide an uniform heat input into the concrete 2 during curing.

In the first embodiment, an electrochemical chemical potential is supplied to the clamping block 5, from which it is transferred to operational functional elements 3 via the washers 8 and the clamping cones 9. The first embodiment is preferable for operational functional elements 3 which have the same electric resistance. However, it might be desired to provide operational functional elements with different electric resistances and to control the current flowing through each of them individ ually. Therefore, in the second embodiment shown in Figs. 3 and 4, operational functional elements 103a and 103b are provided in a manufacturing system 101 which have different electric re sistances from each other. The second embodiment is similar to the first embodiment, wherein only the differences are explained in detail in the following. Same elements are provided with the same reference signs in the second embodiment. As can be seen from Fig. 4, the cross sections of the individual operational functional elements 103a and 103b are different from each other. If, in the second embodiment, an electrical chemical potential were supplied to the clamping blocks 5 and the washers 108 and clamping cones 109 provided electrically conductive attachment of the operational functional elements 103a and 103b to the clamping blocks 5, the current would mainly flow through the operational functional elements 103a with the bigger cross sectional area, as the electric resistance of the operational functional elements 103a is smaller than the one of the op erational functional elements.

Therefore, the operational functional elements 103a and 103b are attached in an electrically insu lating manner to the clamping blocks 5. That is, the washers 108 and optionally the clamping cones 109 are made of an electrically insulating material such as ceramic or a resin. That is, the clamping cones 109 may be electrically conductive as a direct contact between the clamping cones 109 and the clamping blocks 5 is prevented by the electrically insulating washers 108.

As can be seen in Fig. 3, a plurality of electric cables 7 connect the individual operational functional elements 103a and 103b on one end side thereof with one pole of a power source 106. Another plurality of electric cables 7 connect the operational functional elements 103a and 103b on the other end side thereof with the other pole of the power source 106. If a current distributor is used as the power source 106 in the second embodiment, a voltage and an electric current of each parallel electric circuit, which is formed of each individual operational functional element 103a and 103b respectively and the respective cables 7 connected to the poles of the current distributor, can be controlled individually. Thereby, the heat input into the curing concrete 2 can be controlled according to the heat requirement at the respective locations. Furthermore, it is possible to secure a uniform heat input into the curing concrete 2, even if operational functional elements 103a and 103b with different cross sections are provided because of, for example, constructional reasons such as adjusting the preload.

In the second embodiment, a bridging or short circuiting of the individual electric circuits is sup pressed by the electrically insulating attachment of the operational functional elements 103a and 103b to the clamping blocks 5. For this purpose, an electrically insulating bushing 1 1 is interposed between the individual operational functional elements 103a and 103b and the respective through holes of the clamping blocks 5 in order to reduce the danger of a voltage flashover.

In the second embodiment, the support 4 is not used as part of an electric circuit to conduct the electric current to the power source 106. Hence, the danger of a short circuit within the support 4 is avoided. However, even if it is not shown in Fig. 3, it is possible to use the support 4 to let an electric current flow therethrough instead of an electric cable 7 in one of the individually controlled parallel electric circuits of the second embodiment. Thus, material usage can be reduced. It is further possible to split the support 4 into several electrically conductive areas, each of which forms part of one individually controlled parallel electric circuit. For example, the support 4 may comprise electrically insulating material in its longitudinal directions, which divides the support 4 into parallel electrically conductive areas comprising an electrically conductive material.

Finally, Fig. 6 shows a front view of a concrete element 1 10, which can be manufactured with a system according to the second embodiment. The concrete element 1 10 is a hollow-core slab which comprises the concrete 2 and a layer of operational functional elements 103a with a bigger cross section than the one of operational functional elements 103b in a second layer. As can be seen from Fig. 6, the operational functional elements of each layer are preferably equally spaced from each other in order to provide an uniform heat input into the concrete 2 along the respective layer during curing. However, due to the different electric resistances and the individual control of the individual layers, the amount of heat irradiation from the individual layers can be adjusted appropriately during curing.

<Further modifications and effects>

Of course, the system of the second embodiment can also be applied to the first embodiment with operational functional elements having approximately the same electric resistance.

In particular, the clamping blocks of the second embodiment may be covered by an electrically insulating housing in order to avoid a voltage flashover to the operational functional elements. However, also in the first embodiment the clamping blocks may be provided with an electrically insulating housing in order to avoid any leak of electrochemical potential to the environment.

As already mentioned above, the support preferably comprises at least partially an electrically conductive bed to conduct electric current. At least partially means that either the whole support comprises an electrically conductive material and is configured to be electrically conductive, or the support is divided into several electrically conductive areas. However, the electric current need not necessarily pass the support, but may be conducted to the power source via cables, wherein the support can be made electrically insulating. Thus, the danger of a short circuit is reduced.

A standardized 400 V connector having five poles with a frequency of 50 to 60 Hz and carrying an electric current of approximately 32 A is preferably used as an input for the power sources. A rectifier might be provided to change the input alternating voltage into a direct voltage. With a direct voltage and a direct current, respectively, the heat can be provided to the concrete 2 in a constant manner. The electric current then is supplied to the individual operational functional ele ments at a voltage preferably between 0 and 16 V, more preferably between 4 and 12 V, and the electric current amount flowing through each operational functional elements is preferably high with preferably up to 1500 Ampere.

The operational functional elements can be heated up preferably to a temperature of 60 degrees Celsius. If reinforcements are used, which preload the concrete 2 after completion thereof, the temperature of the reinforcements is preferably set to approximately 40 degrees Celsius in order not to impair the preloading stress by thermal stresses.

Preferably, the current amount flowing through each operational functional element as well as the temperature thereof are monitored during the curing process. In addition, the temperature of the curing concrete 2 may be measured at several locations. A current and temperature display means may provide a user with the monitored information. Then, the user can adjust the electric current flowing through each operational functional element by adjusting the voltage of the power source. Preferably, the monitored electric current amounts and temperatures are used as feedback quan tities which allow the automatic regulation of the electric current flowing through each of the oper ational functional elements.

In the above embodiments, the operational functional elements are rod-shaped reinforcements. However, the operational functional elements may be of other shape, such as a mesh-type rein forcement structure. Furthermore, the operational functional elements may not protrude to the outside of the non-cured concrete. In such a case, for example, electrodes are connected to the operational functional elements inside of the non-cured concrete 2 in order to provide the electric current. The operational functional elements may protrude at only one location or at more than two locations to the outside of the non-cured concrete 2.

The operational functional elements need not necessarily be reinforcements but may be, for ex ample, thermal tubes which have a function of cooling or heating after completion of the concrete element. Thereby, an electric current might be supplied to the walls of such tubes or a heating medium might be forced to flow through the tubes during curing of the concrete 2.

Furthermore, the heat irradiation is preferably switchable between an on- and off-state. So, the electric current flowing through each operational functional element can be switched on and off, or a pump conveying a heating medium can be switched on and off. With a current distributor, the plurality of parallel electric circuits may further be switched on and off individually.

In a simple configuration, the operational functional elements are preheated before they are em bedded in non-cured concrete and heat irradiation is caused by the preheated operational func tional elements.

<Reference signs>

1 , 101 manufacturing system

2 concrete

3, 103a, 103b operational functional elements

4 support

5 clamping blocks

6, 106 power source

7 cables

8, 108 washers

9, 109 clamping cones

10, 1 10 concrete element

1 1 electrically insulating bushing