EP2861805A1

EP2861805A1 - Construction element and method to manufacture such a construction element

Info

Publication number: EP2861805A1
Application number: EP20130806191
Authority: EP
Inventors: Markus Andersson; Martin Persson
Original assignee: MMAP Holding AB
Current assignee: MMAP Holding AB
Priority date: 2012-06-19
Filing date: 2013-06-11
Publication date: 2015-04-22
Also published as: SE536597C2; EP2861805A4; SE1250653A1; WO2013191615A1

Abstract

The invention relates to a construction element (1) in concrete comprising an upper surface (2) and a lower surface (3) and two end surfaces (4a, 4b) and at least one reinforcing tensioning member (5) stretching between the end surfaces (4a, 4b). The invention is characterized in that the tensioning member (5) is enclosed by a pipe (6) which is embedded into the concrete and wherein the at least one tensioning member (5) have a length (I1) longer than the pipe (I2) and is arranged moveable in relation to the pipe (6) and is arranged to stay moveable in relation to the pipe (6). The invention also relates to method to manufacture such a construction element (1).

Description

CONSTRUCTION ELEMENT AND METHOD TO MANUFACTURE SUCH A

CONSTRUCTION ELEMENT

Technical field

[0001] The present invention relates generally to a construction element in concrete, which for example may be used as a prefabricated floor element. The invention further relates to a method to manufacture such a construction element.

Background art

[0002] During today's industrialized construction, prefabrication is to a great extent used to decrease work performed at the construction site and to receive the advantages of production methods from the stationary industry. Properties and houses are today often manufactured as readymade modules in factories and are transported to the building site for assembly. Wall and floor elements are manufactured in different factories specialized in their own products.

[0003] In order to decrease the weight of these readymade modules they may be manufactured as a construction element having the shape of a hollow concrete block. To build with hollow block modules is a thoroughly tested building method used all over Europe and in the industrialized world. Hollow blocks are today used to a large extent as an entablature between different floors or as a roof.

[0004] Hollow concrete blocks are today manufactured for the construction industry by a few manufacturers in the country. All hollow blocks comprise, as the name indicates, hole having the shape of longitudinal channels. These channels are decreasing the weight of the element and are a possible way of wire installations.

[0005] The channels in the hollow blocks are not only of good, they often lead to a decreased sound and fire resistance which often mean that an additional storey must be added to the construction. This may for example be done by an extra in situ casting or with large alternative superstructures in wood and insulation in the floor. Thus, it is desirable to be able to produce construction elements which sometimes not include channels. [0006] The hollow blocks are casted on a casting bed which is between 60-100 meter long, where it in the lower part of the cast compound is arranged

reinforcement pre-tensioned with a certain force. When the cast compound is set, the pre-tensioned reinforcement is casted into the material. After casting the element is sawn into the desired dimensions.

[0007] The technique of using pre-tensioned reinforcement when producing hollow blocks is old and thoroughly tested and requires large machine parks for aftertreating in order for the product to suit the final customer. Further, casting comprising reinforcement require high quality concrete since it need to set quickly to a certain strength value before the element can be lifted out and cut. Cutting is preferably done as soon as the day after casting. If the concrete has not obtained the required strength, the reinforcement will be able to split out of the concrete.

[0008] Unfortunately concrete is one of the building materials least favorable relating to CO2 emissions. Today's technique with high quality values lead to very high CO2 emissions. By using recycled material of lower quality it is possible to decrease the CO2 emissions. This is today not possible with the technique using pre-tensioned reinforcement and with a stationary production facility.

[0009] There are a number of patents and patent applications relating to hollow blocks and production of hollow blocks. See for example WO0212649A2 and US5114617 showing hollow blocks comprising pre-tensioned reinforcement arranged in the top and/or bottom part of the hollow block. Here they have tried to solve the problem by adding different types of materials to strengthen the concrete.

[0010] WO2005010292A1 is another patent application describing a

construction comprising several hollow block modules comprising thorough going holes where reinforcement bars are inserted last. The reinforcement bars are stretching through several modules and are tensioned after insertion in order to hold the modules together and to increase the strength of the entire construction. In this solution no pre-tensioned reinforcement is used. This will however decrease the strength of the separate modules and make production of large modules more difficult.

Summary of invention

[0011] An object of the present invention is to solve the above mentioned problems with the production methods of today of prefabricated concrete construction elements. This object is achieved with a construction element as defined in patent claim 1.

[0012] The invention consequently relates to a construction element in concrete with possible additatives comprising an upper surface and a lower surface and two end surfaces and at least one, between the end surfaces running, reinforcing tensioning member. The invention is characterized in that the tensioning member is enclosed by a pipe which is embedded into the concrete and where the tensioning member have a length longer than the pipe, is arranged moveable in relation to the pipe and is arranged to stay moveable in relation to the pipe.

[0013] By arranging the tensioning member moveable in relation to the embedded pipe it is possible to embed a tensioning member in the mould which is not under tension but is loosely arranged in the cast compound and which stays moveable even after the set of the cast compound. In order to increase the strength it is instead possible to re-tension the tension member when the construction element is fully set. This is particularly advantageous for prefabricated construction elements, which then is possible to tension both directly after fabrication and re-tension when they are laid in place in the building construction. The concrete used in a re-tensioned construction element may be of a

considerably lower strength when the tensioning element not is under tension before casting is performed. Since the tensioning member is slack in the concrete compound the risk of splitting is also minimized.

[0014] According to a first embodiment of the invention, the pipe is essentially straight and arranged closer to the lower surface of the construction element that its upper surface. [0015] By arranging the pipe and the by the pipe enclosed tensioning member in the lower part of the construction element, a pre-tensioning is created in the construction element when the tensioning member is re-tensioned and a certain upwards directed bending of the element, which partly counteract the deflection which otherwise occur due to the plastic deformation of the hollow block due to its dead weight, is also created.

[0016] According to a second embodiment of the invention, the pipe has a middle part arranged between the first and the second end of the pipe. This middle part is arranged closer to the lower surface of the construction element than the first and second end of the pipe so that the pipe adapt to a bow shape.

[0017] By embedding the pipe in the cast so that it from the beginning has a bow shape, the pulling forces of the tensioning member will work straight opposite the moment forces. This lead to that the mounting of the tensioning member is optimized in relation to the deflection of the element.

[0018] In another embodiment the first and second end of the pipe is arranged in the vicinity of the upper surface of the construction element and the middle part of the pipe is arranged in the vicinity of the lower surface of the construction element.

[0019] By using the larger part of the height of the building element when the pipe and the tension member is mounted, additional moment forces can be inhibited and the construction element can be made longer if so is desired.

[0020] In another embodiment, the tensioning member is firmly attached in the first end surface of the construction element and is arranged loosely laying in the pipe at the second end surface of the pipe.

[0021] By having one end of the tensioning element loose and one firmly attached, the re-tensioning of the tensioning member is facilitated since pulling forces only have to be added in one end of the tensioning member. [0022] In another embodiment the tensioning member is a reinforcement made by a bar or a wire. The tensioning member may also be made of metal or composite material.

[0023] By using a bar or a wire in metal as a tensioning member, the

construction is durable and is easy to re-tension and lock in a tensioned state. If the reinforcement is made of a composite material, for example carbon fiber or glass fiber, the construction is lighter and more moisture resistant since these materials do not rust.

[0024] In another embodiment the construction element comprises at least one through going channel stretching between the end surfaces of the construction element, essentially parallel with the upper and lower surface of the construction element.

[0025] By arranging channels in the construction element the weight of the element is decreased and it is also possible to use the channels for cable run and similar. A hollow block has then been created.

[0026] In another embodiment the used concrete is mixed GGBS and/or fly ash and/or other material giving a puzzolanic effect. This in order to even further decrease the amount of CO2 during manufacturing. It is also possible to add non- tensioned reinforcement and a crack and bend-up reinforcement in the element if so is desired.

[0027] The invention also relates to a method to manufacture a construction element according to any of the above embodiments, characterized in that it comprises the steps: attaching both ends of a pipe, which encloses a, in relation to the pipe, moveable tensioning element, in a casting mould, attend to that the tensioning element have a length even longer than the length of the pipe, adding casting compound in the casting mould, removing the construction element after it has cured.

[0028] By the above mentioned method a construction element is created comprising a tensioning member which is possible to re-tension after it has cured. Then, it is also possible to use a concrete of a lower tensile properties,

reinforcement that is optimized mounted and a technique which makes it possible to move the production site when needed at the same time as the blocks are cast one by one. Thus, the construction element may with advantage be pre-produced. This means that the technique require much less resources. Thus, large

environmental benefits are made, like less volumes of cement for production, shorter transports and an optimized production where the markets demands on a modern construction element are met.

[0029] In another embodiment the method also comprises the step of attending to that the length of the pipe is longer than the length of the casting mould so that the pipe hangs in the shape of a bow in the mould.

[0030] By mounting a pipe longer than the casting mould and which hangs in the shape of a bow, the tensioning member is so arranged that when it is re-tensioned it will act against the moment forces and counteract the deflection of the

construction element where the deflection is largest. This also lead to that the element better remain its shape.

[0031] In another embodiment, the method also comprises the step of attending to that both ends of the tensioning member protrudes from the first and second end surfaces of the pipe and so that they at least partly protrudes through the edges of the mould or so that the at least partly is inserted into the edges of the mould.

[0032] Through this step it is attended to that both ends of the tensioning member are possible to grip, which makes it possible to re-tension from both directions of the construction element.

[0033] In another embodiment the method also comprises the step of, with a tool re-tension the tensioning member with a pulling force.

[0034] Re-tensioning of the tensioning member will increase its strength and decrease its deflection. [0035] All of the above embodiments or parts of an embodiment are possible to combine as long as the combination not is contradictory.

Brief description of drawings

[0036] The invention is now described, by way of example, with reference to the accompanying drawings, in which:

[0037] Fig. 1a shows a side view of a first embodiment of the inventive construction element,

[0038] Fig. 1 b shows an end view of a first embodiment of the inventive construction element,

[0039] Fig. 2a shows a side view of a second embodiment of the inventive construction element,

[0040] Fig. 2b shows an end view of a second embodiment of the inventive construction element,

[0041] Fig. 2c shows a cut view in cut A-A in fig. 2a of a second embodiment of the inventive construction element,

[0042] Fig. 3 shows a third embodiment of the inventive construction element, [0043] Fig. 4 shows the construction element during its manufacturing. Description of embodiments

[0044] In the following, a detailed description of embodiments of the inventive construction element. All examples shall be seen as parts of the general description and are therefore generally possible to combine.

[0045] Figures 1a and 1 b shows a construction element 1 in concrete in which it is casted at least one straight pipe 6, which encloses a tensioning member 5. The construction element 1 has an upper surface 2 and a lower surface 3 and two end surfaces 4a, 4b. The construction element 1 also has a height H, a length L and a width B. The height H is preferably between 200 and 600 mm, the length L between 1200 and 3500 mm and the width is preferably less than 2400 mm, which is the maximum width of a commercial vehicle. If the construction element 1 is manufactured on site, other dimensions are also possible.

[0046] The pipe 6 has a first and a second end 6a, 6b and a, between the ends arranged middle part 6c. The pipe 6 stretches between the two end surfaces 4a, 4b of the construction element and its first and second ends 6a, 6b are preferably in line with the end surfaces 4a, 4b so that the hollow part of the pipe stretches through the entire construction element 1. The length I2 of the pipe 6 is in this embodiment essentially the same as the length L of the construction element 1. The tensioning member 5 has a length 11 which is longer than the length I2 of the pipe 6 and protrudes a certain distance from the end surfaces 4a, 4b, thus are therefore possible to grip from both sides of the construction element 1 and to re- tension with a force F. The tensioning member 5 is arranged moveable in relation to the pipe 6 and will so remain even after molding, which makes re-tensioning possible.

[0047] The pipe 6 and the tensioning member 5 are arranged in an essentially straight line next to each other in the lower part of the construction element, thus closer to the lower surface 3 of the construction element 3. However, it is also possible to offset the pipes 6 and the tensioning members 5 in relation to each other in the height direction H of the construction element.

[0048] Figure 2a-2c shows a second embodiment of the construction element, where the pipes 6 and the tensioning members 5 are arranged in a bow shape in the construction element 1. Thus, the middle part 6c of the pipes are arranged closer to the lower surface 3 of the construction element than the first and second end 6a, 6b of the pipes. Further, the first and second end 6a, 6b of the pipes 6 are arranged in the vicinity of the upper surface 2 of the construction element and the middle part 6c of the pipe is arranged in the vicinity of the lower surface 3 of the construction element.

[0049] The length I2 of the pipes are longer than the length L of the construction element. Here the tensioning member 5 is firmly attached in the first end surface 4a of the construction element and arranged loosely laying in the pipe by the second end surface 4b of the construction element. Re-tensioning of the tensioning member 6 with a pulling force F then occur by the second end surface 4b.

[0050] Figure 2b shows a view towards the end surface 4b of the construction element and illustrates that the pipes 6 and the tensioning member 5 protrudes from the end surface near the upper surface 2 of the construction element.

[0051] In that end 4a of the construction element where the tensioning member 5 is firmly attached, the tensioning member 5 itself may be casted into or in another way attached in the concrete in its upper part. This is not shown in any figure, but can of course also be applied in the embodiment shown in figures 1a and 1 b.

[0052] Figure 2c shows a cut view through the cut A-A in figure 2a. Here it is illustrated that the middle part 6c of the pipes are arranged closer to the lower surface 3 of the construction element.

[0053] Figure 3 shows an embodiment having the shape of a hollow block where channels 7 runs through the entire construction element 1. Between the channels 7 are the pipes 6 and tensioning members 5 arranged.

[0054] Figure 4 shows a casting mould M in which a casting compound C of concrete is about to be added. In the edges/walls of the mould M, both ends 6a, 6b of at least one pipe 6 are attached. The pipes 6 encloses a, in relation to the pipe, moveable and un-tensioned tensioning member 5. The length I2 of the pipes are longer than the inner length L of the casting mould, i.e. the length of the ready construction elements.

[0055] The tensioning members 5 may have a length 11 even shorter than the pipes 6 so that they at least partly protrude out through the edges/walls of the mould M or so that they protrude at least a certain distance into the edge/wall of the casting mould. This ensures that only the pipes 6 and not the tensioning members 5 are casted into the concrete when the construction element cures so that the tensioning members remain moveable in relation to the pipes.

[0056] When the construction element is cured the tensioning members 5 are re-tensioned with an appropriate tensioning force F. The re-tensioning is preformed with a suitable tool, for example a jack. The tensioning member may be re-tensioned at the construction site or at a storage site. The tensioning member 5 remains moveable after the first re-tensioning.

[0057] The casting compound C used may be recycled or have a lower quality since the tensioning members 5 are arranged loosely in the casting compound C when it cures and are therefore not inducing any stress to the concrete. Since this method also makes it possible to cast separate individual elements on site the curing time is not decisive for the choice of concrete quality.

[0058] With this method where all elements are manufactured separately it is also possible to customize the elements so that some comprises channels 7 and some comprises other cavities or where the elements have a deviating shape.

Claims

1. A construction element (1 ) in concrete with possible additatives comprising an upper surface (2) and a lower surface (3) and two end surfaces (4a, 4b) and at least one reinforcing tensioning member (5)stretching between the end surfaces (4a, 4b), characterized in that the tensioning member (5) is enclosed by a pipe (6) which is embedded into the concrete and where the at least one tensioning member (5) have a length (11 ) longer than the pipe (I2) and is arranged moveable in relation to the pipe (6) and is arranged to stay moveable in relation to the pipe (6).

2. The construction element (1 ) according to claim 1 , wherein the pipe (6) have a first and a second end (6a, 6b) which are so arranged to that they coincide with the two end surfaces (4a, 4b) of the construction element (1 )

3. The construction element (1 ) according to claim 1 or 2, wherein the pipe (6) is essentially straight and arranged closer to the lower surface (3) of the construction element (1 ) than its upper surface (2).

4. The construction element (1 ) according to claim 1 or 2, wherein the pipe (6) also has a middle part (6c) arranged between the first and the second end (6a, 6b) and wherein this middle part (6c) is arranged closer to the lower surface (3) of the construction element than the first and second end (6a, 6b) of the pipe so that pipe (6) adapt to a bow shape.

5. The construction element (1 ) according to claim 4, wherein the first and second end (6a, 6b) of the pipe are arranged in the vicinity of the upper surface (2) of the construction element and the middle part (6c) of the pipe is arranged in the vicinity of the lower surface (3) of the construction element.

6. The construction element (1 ) according to any of the above claims, wherein the at least one tensioning member (5) is firmly attached in the first end surface (4a) of the construction element and arranged loosly laying in the pipe by the second end surface (4b) of the pipe.

7. The construction element (1 ) according to any of the above claims, where the tensioning member (5) is arranged at least partly protruding through at least one of the first and second end surfaces (6a, 6b) of the pipe.

8. The construction element (1 ) according to any of the above claims, wherein the tensioning member (5) is a reinforcement made of a bar or a wire.

9. The construction element (1 ) according to any of the above claims, wherein the tensioning member (5) is made of metal or composite material.

10. The construction element (1 ) according to any of the above claims, wherein the construction element (1 ) comprises at least one through going channel (7) stretching between the end surfaces (4a, 4b) of the construction element (1 ), essentially parallel with the upper and lower surface (2, 3) of the construction element (1 ).

11. The construction element (1 ) according to any of the above claims, where it in the concrete is mixed GGBS and/or fly ash and/or other material giving a puzzolanic effect.

12. A method to manufacture a construction element (1) according to any of the above claims, characterized in that it comprises the steps:

• attaching both ends (6a, 6b) of a pipe (6), which encloses a, in relation to the pipe, moveable and un-tensioned tensioning element (5), in a casting mould (M)

• attend to that the tensioning element (5) have a length (11 ) longer than the length (I2) of the pipe (6)

• adding casting compound (C) in the casting mould (M)

• removing the construction element (1 ) after it has cured.

13. The method according to claim 12, wherein the method also comprises the step of: • attending to that the length (12) of the pipe (6) is longer than the length (L) of the casting mould (M) so that the pipe (6) hangs in the shape of a bow in the mould (M).

14. The method according to claim 12 or 13, wherein the method also comprises the step of:

• attending to that both ends of the tensioning member (5) protrudes from the first and second end surfaces (6a, 6b) of the pipe and so that they at least partly protrudes through the edges of the mould or so that the at least partly is inserted into the edges of the mould.

15. The method according to claim 12, 13 or 14, wherein the method also comprises the step of:

• with a tool tension the tensioning member (5) with a pulling force (F).