DE102021101138A1 - Process for the extrusion-based production of a reinforced concrete component - Google Patents

Abstract

The invention relates to a method for producing a reinforced concrete component (1), comprising a matrix material concrete (4, 4') and a reinforcement (2), the production of the concrete component (1) being extrusion-based additively, the reinforcement being produced in a first step (2) erected and layers of the concrete (4, 4') are formed by at least one concrete strand which is extruded from an extrusion nozzle (10). According to the invention, at least vertical first and second side surfaces (6, 6') of the concrete component (1) are formed by the concrete strand, which emerges from the extrusion nozzle (10) in a horizontal direction, lateral to the direction of movement of the print head, and presses against the reinforcement ( 2) is delivered.

Description

The invention relates to a method for producing a reinforced concrete component, comprising a matrix material concrete and reinforcement, the production of the concrete component being extrusion-based additively, with the reinforcement being erected in a first step and concrete layers being formed by at least one concrete strand which is pressed out of an extrusion nozzle becomes.

Additive manufacturing is the layered creation of a component based on an electronic data record, also referred to as a 3D printing process. As a rule, this data set is derived from a three-dimensional CAD model. In contrast to manufacturing processes that remove material, such as milling, components are created in additive manufacturing by adding material. This makes it possible to manufacture components that would not be easy to produce using conventional manufacturing technologies.

Additive manufacturing processes in the manufacture of concrete parts, including extrusion-based manufacturing processes, are well known. The publications are examples of this DE 10 2018 217 141 A1 and U.S. 2007/0138678 A1 called.

In the prior art, however, additive manufacturing with concrete is either carried out without reinforcement at all or it is inserted manually and discontinuously, as for example in the publications WO 2020/126701 A1 and WO 2020/126705 A1 described. Reinforcement lying perpendicular to the concreting level (generally vertical reinforcement) is subsequently positioned in cavities left free for this purpose, which are then filled with concrete or otherwise. The reinforcement can be installed tension-free or tensioned. A related variant is the additive manufacturing of an integrated concrete formwork into which a reinforcement cage is inserted. After the production of the integrated formwork or an element with vertical openings, the reinforcement and concreting are placed in the conventional way, ie with all the disadvantages in terms of productivity, flexibility and the possibility of automation. However, this contradicts the principle of additive manufacturing in particular.

According to a well-known method, published in B. Sevenson, "Shanghai-based WinSun 3D Prints 6-Story Apartment Building and an Incredible Home", 3DPrint.com / The Voice of 3D Printing / Additive Manufacturing, 18-Jan-2015, according to the Production of an integrated formwork (contour crafting process) introduced a reinforcement cage (cf. in the document). For this purpose, only the contour may be printed in advance, without a wavy or zigzag-shaped reinforcement inside the wall (cf. in the document). The process severely restricts the freedom of form of the concrete parts to be manufactured. The subsequent implementation of the reinforcement excludes a tapering, curvature or torsion of the component geometry in many cases.

From the pamphlet WO 2020/193150 A1 a method is known in which a thin vertical layer of concrete is attached to an additively manufactured component (cf. 3 and associated description). However, this layer is only used for the accompanying, protective enclosure and for the connection of a mandatory textile reinforcement fiber, which is to be attached as vertical reinforcement to improve the bending load-bearing capacity with a horizontal load direction. In addition, the layer of concrete is in turn held to the vertical wall by the embedded reinforcement fiber.

Other methods envisage that the reinforcement along the component axis (longitudinal reinforcement), including the welded shear force reinforcement, is placed manually on individual printed concrete filaments and then overprinted with a new layer of concrete. However, the discontinuous, especially manual integration of reinforcement leads to the interruption of the printing process, since the process has to be repeated several times. A vertical or inclined reinforcement cannot be integrated.

It is also known to use a forked head to enclose pre-installed rebar in concrete through the extrusion process. The process severely restricts the freedom of form of the components to be manufactured. Enclosing the entire rebar construction with the print head severely limits or makes it impossible to have flexibility in terms of taper, curvature or twisting. The print head must be very large or high in order to enclose the vertical reinforcement from both sides at the same time. This requires a very heavy and expensive construction of the manipulator (e.g. a robot). In any case, the height of the armor is limited by the length of the bifurcated print head.

In another method, the mesh reinforcement is applied to the previously 3D-printed concrete wall with subsequent concrete cover, either manually or by spraying and smoothing. This procedure adopts the processes from the repair technology for existing concrete structures. The technology achieves only a low level of productivity and automation.

Even spraying the concrete or mortar onto a previously installed reinforcement cage does not offer the desired result, especially since it is a spraying technique, not extrusion. The process is imprecise and unclean due to the rebound and the spray mist. The resulting rough surface requires post-processing. The method is also only suitable for fine-grain concrete, not for other types of concrete.

It is also known that a flexible, braided wire is continuously integrated into the concrete filament during extrusion for reinforcement. Reinforcement orientation is only possible in the direction of the concrete filaments (i.e. horizontal). The implementation of the vertical reinforcement still has to be carried out separately. The reinforcement is therefore not continuous.

Laying down the wire is problematic when changing direction, since the deflection radii are limited by the rigidity of the wire. The extremely smooth steel wires also have insufficient bonding properties to the concrete, which is why large anchoring lengths must be taken into account depending on the wire diameter. A braided wire has the additional disadvantage that, under load, a very high degree of deformation must occur before the strength is reached, since it is still structurally stretching. In order to keep crack widths in the component at a desired level, a larger reinforcement cross section is required than with straight elements.

It is therefore the object of the present invention to propose a method for the additive manufacturing of a reinforced concrete component, in which restrictions on the use and type of reinforcement are avoided and in particular a steel reinforcement is given sufficient coverage.

The object is achieved by a method for producing a reinforced concrete component, comprising a matrix material concrete and a reinforcement, the production of the concrete component being extrusion-based additive. In a first step, the reinforcement is erected and concrete layers are formed by at least one concrete strand, which is pressed out of an extrusion nozzle. According to the invention, at least first and/or second side surfaces of the concrete component that are vertical or inclined relative to the vertical are formed by the concrete strand. For this purpose, it emerges from the extrusion nozzle in a substantially horizontal direction, lateral to the direction of movement of the print head, and is released against the reinforcement. The inclination to the vertical is 0° to 45°, preferably 0 to 40°, particularly preferably 0 to 30°. It is also provided that the method is used on one side, on the first or the second side surface, for example when renovating the outer area of a concrete structure.

According to a first alternative, the reinforcement is filled with concrete by the concrete strand entering from the side and at the same time the reinforcement on the side surfaces is covered with concrete. It has proven to be advantageous if a middle layer is introduced between the two sides from which the concrete strand enters, which prevents the concrete strand entering from a first side from passing over into a second side and from exiting from the second side. Wire mesh is preferably used as the middle layer.

According to a second alternative, in a first step, an unreinforced construction is made of concrete by additive manufacturing. In a second step, it is reinforced by attaching reinforcement, preferably to anchors placed in the unreinforced structure. In a third step, the side surfaces of the construction are covered with concrete by the concrete strand that is fed in from the side. The reinforcement structure is preferably attached automatically. In particular, it is envisaged that the interior of the construction has previously been filled with concrete in an extrusion-based manner, for example through a conventional extrusion nozzle, in which the concrete is discharged vertically, for example downwards.

A first variant for discharging concrete in the horizontal orientation provided according to the invention provides flowable concrete to which an accelerator is added in the pressure head. This concrete then forms the concrete strand. To ensure an attractive surface quality, the flowable concrete can be supported with a slipform.

A second variant for pouring concrete in the planned horizontal orientation provides for highly tixotropic concrete to form the concrete strand, which is briefly subjected to excitation during the pouring process and thus has sufficient flowability to enclose the reinforcement and fill the wall cross-section. When the excitation ceases, the concrete stiffens again and loses its flowability. A kneading effect in the conveying device of the extruder, an ultrasonic effect, e.g. B. provided by ultrasonic vibration, or mechanical vibration.

The invention enables the integration of standardized and existing reinforcement elements ments for horizontal and especially vertical tensile force transmission in the 3D printing process with concrete. The concretes can largely correspond to the existing standard.

With the help of the present invention, for example, the fully automated production of concrete components with complete horizontal and vertical reinforcement, as is known from previous concrete construction methods, can be implemented. All previously known and approved calculation methods can therefore be used. This represents an essential step for the establishment of the 3D printing process in the concept of digital construction. The invention also enables the production of curved or tapered components. However, the method can also be used for extensive repair or reinforcement of existing structures. Because the outer covering of the reinforcement, in particular in the sense of the second alternative according to the invention, can be done in the same way with existing concrete components or buildings.

• 1: schematisch eine geschnittene Ansicht einer Ausführungsform eines Betonbauteils bei der Herstellung nach einer Ausführungsform eines erfindungsgemäßen Verfahrens und
• 2: schematisch eine geschnittene Ansicht einer Ausführungsform eines Betonbauteils bei der Herstellung nach einer weiteren Ausführungsform eines erfindungsgemäßen Verfahrens.

The invention is explained in more detail below on the basis of the description of exemplary embodiments and their representation in the associated drawings. Show it:

• 1 : schematically a sectional view of an embodiment of a concrete component during production according to an embodiment of a method according to the invention and
• 2 1: schematically shows a sectional view of an embodiment of a concrete component during production according to a further embodiment of a method according to the invention.

1 shows a concrete component 1 with a steel reinforcement 2, which is designed here in the form of a conventional reinforcement cage. A middle layer 8 is inserted between a first and a second side of the concrete component 1 in the inner area 5 between the two layers of the steel reinforcement 2 . When the concrete 4 is discharged from an extrusion nozzle 10 from a side surface 6 or 6', this prevents the undesired transfer to the other side or even out of the cubature of the concrete component 1 to be produced.

The first side of the concrete component 1, recognizable as an outside and referred to as side surface 6', has already been produced, fills the inner area 5 within the steel reinforcement 2 and covers the steel reinforcement 2 on the outside. The second side surface 6' is located in the Manufacturing by the extrusion nozzle 10 deposits a layer of concrete 4. This passes from the side surface 6 through the reinforcement 2 and reaches the middle layer 8, designed here as wire mesh, or up to the concreted first side of the inner area 5.

The extrusion nozzle 10 is designed in such a way that the concrete 4 can be discharged in the horizontal direction without immediately falling down. Two discharge principles are provided for this purpose. The first discharge principle is based on free-flowing concrete, to which an accelerator is added in a pressure head, part of which is the extrusion nozzle 10 , which results in rapid stiffening of the concrete 4 after it emerges from the extrusion nozzle 10 .

A sliding mold, not shown here, which can be moved together with the print head or separately, supports the method according to the invention and ensures a high surface quality.

An alternative design of the print head, which also serves to ensure that the extrusion nozzle 10 can output the concrete 4, 4' in a horizontal direction, is based on the use of a highly thixotropic concrete 4, 4'. In rheology, thixotropy describes a time dependence of the flow properties of non-Newtonian fluids, in which the viscosity decreases as a result of ongoing external influences and only returns to the initial viscosity after the stress has ended.

This highly tixotropic concrete 4, 4' is briefly excited during discharge and before exiting through the extrusion nozzle 10, giving it sufficient fluidity to enclose the reinforcement 2 or to fill the cross section within the reinforcement 2. As soon as the concrete 4, 4' has arrived there, the concrete 4, 4' stiffens again and loses its flowability since the excitation has ceased. Excitation mechanisms can be, among other things, an effect in the conveying device of an extruder, an ultrasonic effect or mechanical vibration.

2 shows a schematic sectional view of an embodiment of a concrete component 1 during production according to a further embodiment of a method according to the invention, in which concrete 4 is first introduced between the two layers of steel reinforcement 2 . According to the preferred embodiment shown, this is also provided in 3D printing, but a conventional print head with the delivery of concrete 4 vertically downwards is provided. The deposit of concrete 4 between the two layers of steel reinforcement 2 can also take place in the horizontal direction, but in any case parallel to the direction of movement of the print head, while in the inventive method the concrete outside layer 4 'on the side surface 6 is delivered laterally, perpendicularly or laterally to the direction of movement of the print head.

As an alternative to this, the concreting of the interior area can be a long time ago, for example part of an existing building that has to be renovated using the method according to the invention.

In a second step, a concrete outer layer 4' is applied to the side surface 6, as a result of which the reinforcement 2 is given a sufficiently protective cover. Here, too, the extrusion nozzle 10 is used, which is to 1 described measures in the upstream print head allows the horizontal delivery of the concrete 4 on the side surface 6.

Reference List

1

concrete component

2

Reinforcement, steel reinforcement

4

concrete

4'

concrete outer layer

5

interior

6

first face

6'

second side face

8th

middle position

10

extrusion die

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102018217141 A1 [0003]
• US 2007/0138678 A1 [0003]
• WO 2020/126701 A1 [0004]
• WO 2020/126705 A1 [0004]
• WO 2020/193150 A1 [0006]

Claims (10)

Method for producing a reinforced concrete component (1), comprising a matrix material concrete (4, 4') and a reinforcement (2), the production of the concrete component (1) being extrusion-based additively, the reinforcement (2) being erected in a first step and layers of the concrete (4, 4') are formed by at least one concrete strand which is pressed out of an extrusion nozzle (10), characterized in that at least vertical first and/or second side surfaces (6, 6') or inclined relative to the vertical of the concrete component (1) are formed by the concrete strand, which emerges from the extrusion nozzle (10) in a substantially horizontal direction, lateral to the direction of movement of the print head, and is delivered against the reinforcement (2). procedure after claim 1 An inner area (5) within the reinforcement (2) is filled with concrete (2) by the concrete strand entering the inner area (5) from the side and at the same time the reinforcement (2) is covered on the side surfaces (6) by concrete (4). . procedure after claim 1 or 2 , a middle layer (8) being introduced between the two side surfaces (6, 6') from which the concrete strand enters, which prevents the concrete strand entering from the first side surface (6) from passing over to the second side surface (6'). prevents. procedure after claim 3 , whereby wire mesh is used as the middle layer (8). procedure after claim 1 , wherein in a first work step an unreinforced structure is produced from concrete (4) by additive manufacturing, reinforced in a second work step by a reinforcement (2) being attached and in a third work step by the laterally supplied concrete strand on the side surfaces (6, 6' ) is covered by concrete (4'). procedure after claim 5 , whereby the inner area (5) is filled out based on extrusion. Method according to one of the preceding claims, in which flowable concrete (4, 4'), to which an accelerator is added in the pressure head, forms the concrete string. procedure after claim 7 , wherein the flowable concrete (4, 4 ') can be supported with a slip form. Procedure according to one of Claims 1 until 8th , whereby highly thixotropic concrete (4, 4'), which is briefly subjected to excitation during discharge and thus acquires sufficient flowability to enclose the reinforcement (2) with a concrete outer layer (4') and to fill the interior (5), the concrete strand forms. procedure after claim 9 , wherein a kneading effect in the conveying device of the extruder, an ultrasonic effect or a mechanical vibration are provided for excitation.

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