EP2984197A2

EP2984197A2 - Method for building prestressed concrete structures by means of profiles consisting of a shape-memory alloy, and structure produced using said method

Info

Publication number: EP2984197A2
Application number: EP14716745.6A
Authority: EP
Inventors: Christian Leinenbach; Masoud MOTAVALLI; Benedikt WEBER; Wookjin Lee; Rolf BRÖNNIMANN; Christoph CZADERSKI
Original assignee: Re-Fer AG; EMPA
Current assignee: Re-Fer AG; EMPA
Priority date: 2013-04-08
Filing date: 2014-03-17
Publication date: 2016-02-17
Also published as: KR102293794B1; US20160053492A1; CN105378129A; WO2014166003A3; CA2908895C; US9758968B2; WO2014166003A4; CN105378129B; CH707301B1; KR20160037836A; WO2014166003A2; CA2908895A1

Abstract

The invention relates to a method according to which a profile consisting of a shape-memory alloy is placed into concrete, or a concrete to be reinforced is roughened on the outside, then profiles (2) consisting of a shape-memory alloy are fastened to the roughened outside (9) of the structure (6) and a cementitious matrix is applied to the roughened outside (9) to cover the profiles (2). After the cementitious matrix has set, said profiles (2) produce a contraction force and thus a tension as a result of the input of heat. The mortar covering layer (16) thereby acts as a reinforcement layer owing to the interlocking of the mortar covering layer (16) with the roughened outside (9) of the structure (6). The profiles (2) run in an outer mortar as a reinforcement layer (16) of the outside of a structure along the outside of the structure inside the mortar or reinforcement layer (16). A structure can also be prepared for a prestress in the equipped mortar or reinforcement layer by the input of heat, in that electrical cables (3) are routed from the end regions thereof to the outside of the mortar or reinforcement layer (16) or the end regions of the electrical cables (3) are accessible by removing inserts (5).

Description

Method for the production of prestressed concrete structures by means of profiles from a shape memory arrangement, as well as

Structure made by the process

This invention relates to a method for producing prestressed concrete components in new constructions (cast in situ on the construction site) or in the prefabrication and for the subsequent reinforcement of existing structures by means of cementitious mortars, in which profiles of shape memory alloys, among professionals often referred to as shape memory alloy profiles, in short SMA profiles, for preloading. With this preload system, subsequent attachments can be attached to an existing structure under prestress. In addition, the invention also relates to a concrete structure that created using this method or subsequently reinforced resp. to which attachments were docked by this method. As a special feature, shape memory alloys based on steel in the form of profiles are used for generating a prestress.

A bias within a building generally increases its serviceability by reducing cracks or preventing cracking at all. Such a bias is already today Reinforcement against the bending of concrete parts or for lashing example of columns to increase the axial load resp. used for shear reinforcement. Another application of the prestressing of concrete are pipes for liquid transports and silos respectively. Tank container, which are tied to produce a bias voltage. For prestressing, in the state of the art round bars or cables are inserted into the concrete or subsequently fixed externally on the surface of the component on the tension side. The anchoring and force from the biasing element in the concrete is very complex in all these known methods. High costs for anchoring elements (anchor heads) are incurred. For external prestressing, the prestressing steels resp. In addition, by means of a coating to protect against corrosion. This is necessary because conventionally used steels are not corrosion resistant. If the pretensioning cables are inserted into the concrete, they must be protected from corrosion with much effort by means of cement mortar, which is introduced by means of an injection into the cladding tubes. An external bias is also generated in the prior art with fiber composites which are adhered to the surface of concrete. In this case, the fire protection is often very expensive, since the adhesives have a low glass transition temperature. The corrosion protection is the reason that in traditional concrete a minimum overlap of the steel inserts of approx. 3cm must be kept. As a result of environmental influences (namely C0 ₂ and S0 ₂ in the air) a carbonation takes place in the concrete. Because of this carbonation, the basic environment in the concrete (pH 12) falls to a lower value, ie to a pH of 8 to 9. If the internal reinforcement is in this carbonated area, the corrosion protection of conventional steel is no longer guaranteed , The 3cm overlap of the steel accordingly guarantees a corrosion resistance for the inner reinforcement over a lifetime of the structure of about 70 years. Carbonation is much less critical when using the novel shape memory alloy because the novel shape memory alloy has significantly higher corrosion resistance compared to ordinary structural steel. As a result of the bias of the concrete part resp. Mortar cracks are closed and accordingly that becomes Penetration of pollutants greatly reduced. Correspondingly, the concrete cover can be massively reduced with the new development, and correspondingly components such as balcony projections, balcony railings, pipelines, etc. can be dimensioned thinner. The components are thereby lighter and more economical to use.

The object of the present invention is therefore to provide a method for tempering new concrete structures and concrete components or cement-bonded Vermörtelungen for the reinforcement of existing structures, either to improve the serviceability and stability of the structure, to ensure a more flexible use of Building for subsequent overhanging attachments, or to increase the durability and fire resistance of the building. Further, it is an object of the invention to provide a concrete structure having biases or gains generated using this method.

The object is first of all solved by a method for creating prestressed concrete structures by means of profiles of a shape memory alloy, be it of new concrete structures and concrete components or cement-bonded Vermörtelungen for the reinforcement of existing structures, which is characterized in that profiles a steel-based shape memory alloy of a polymorphic and polycrystalline structure having a ribbed surface or having a surface in the form of a thread which can be brought to its permanent state as austenite by elevating its temperature from its state as martensite to the concrete or the cementitious mortar be optionally with additional end anchorages, so that they either due to a subsequent active and controlled heat input with heating means or or by heat in a fire, a contraction force and thus generate a tensile stress and e ntsprechend a bias on the concrete resp. generate the Vermortelung, with the introduction of force into the concrete or mortar on the surface structure of the profile and / or on the end anchors of the profile takes place.

The object is further achieved by a concrete structure, created using one of the preceding methods, which is characterized in that it contains profiles of a shape memory alloy in a new concrete or in a grouting applied as a reinforcing layer of a building exterior, the run along the outside of the building within the Vermettelung or reinforcing layer and are biased or prepared for a bias by heat input by electric cables are led out of their end portions of the grouting or reinforcing layer or their end portions are accessible by removing deposits.

The method is described and explained with reference to the drawings. There are applications for new construction resp. described and explained in the prefabrication and applications for the subsequent reinforcement of existing concrete structures.

It shows

Figure 1: A concrete beam or a concrete slab poured on the

Construction site or in the prefabrication plant, with inserted electrically heatable profiles made of a shape memory alloy;

Figure 2: A concrete beam, poured on the site or in

Prefabrication movement, with inserted profile made of a shape memory alloy, both ends of which are edged with inserts;

FIG. 3: shows a cross-section of a concrete structure with an internal, traditional steel reinforcement, prepared for applying a reinforcement as a reinforcement layer, which contains profiles of a shape memory alloy; FIG. 4 shows a cross section of this building wall according to FIG. 3, after attaching profiles made of a shape memory alloy;

FIG. 5 shows a cross-section of this building wall according to FIGS. 3 and 4, after covering the attached profiles of a shape-memory alloy with shotcrete or cement mortar;

6 shows a cross-section of this building wall according to FIGS. 3 and 4, with the molded-in and covered profiles made of a shape-memory alloy, with two variants for the heat input for heating the profiles, a) by electric resistance heating via cast-in electric cables, or via a recess for connecting electric cables;

Figure 7 is a cross section of this building wall according to Figures 3 to 6, with the molded and covered profiles of a shape memory alloy, after the heat input and after filling the access to the profiles.

FIG. 8 shows a cross-section of an existing concrete component (building wall), which is reinforced with a profile of a shape-memory alloy on the surface, during the application of a cementitious layer by means of shotcrete / sprayed mortar;

FIG. 9 shows a cross-section of an existing concrete component which is reinforced with a profile of a shape memory alloy on the surface when a cementitious layer is applied by hand;

FIG. 10 shows a detail of a concrete slab provided on its underside with a pegged and prestressed reinforcing layer containing profiles of a shape memory alloy; FIG. 11: shows a cross section through the existing concrete slab according to FIG. 10, with the conventional reinforcement as well as the full-surface doweled and prestressed mortar reinforcement layer with profiles of a shape-memory alloy;

Figure 12: An existing concrete slab with subsequently applied below

Mortar as reinforcing layer with profiles of a shape memory alloy in the interior, and which is only locally doweled at both ends of the profile;

Figure 13: A cantilevered concrete slab with profiles from a

Shape-memory alloy in its interior, which was attached to a concrete structure, which was prepared for this purpose when creating with already set profiles made of a shape memory alloy.

First, the nature of shape memory alloys must. Shape Memory Alloy (SMA)]. These are alloys that have a specific structure that can be changed depending on the heat, but that returns to their initial state after heat dissipation. Like other metals and alloys, shape memory alloys (SMA) contain more than one crystal structure, so they are polymorphic and thus polycrystalline metals. The dominating crystal structure of shape memory alloys (SMA) depends on the one hand on their temperature, on the other hand on the externally acting tension - be it train or pressure. At high temperature it is an austenite, and at the low temperature it is a martensite. The special feature of these shape memory alloys (SMA) is that they resume their initial structure and shape after raising the temperature to the high temperature phase, even if they were previously deformed in the low temperature phase. This effect can be exploited to apply prestressing forces in building structures. If no heat is artificially introduced into the shape memory alloy (SMA) or removed from it, so it is at the ambient temperature. The shape memory alloys (SMA) are stable within a species-specific temperature range, ie their structure does not change within certain limits of mechanical stress. For applications in the construction industry in the outdoor area, the fluctuation range of the ambient temperature of -20 ° C to + 60 ° C is required. Within this temperature band, a shape memory alloy (SMA) used here should not change its structure. The transformation temperatures at which the structure of the shape memory alloy (SMA) changes may vary considerably depending on the composition of the shape memory alloy (SMA). The transformation temperatures are also load-dependent. With increasing mechanical load of the shape memory alloy (SMA) also its transformation temperatures rise. If the shape memory alloy (SMA) is to remain stable within certain load limits, then great attention must be paid to these limits. When shape memory alloys (SMA) are used for structural reinforcement, the fatigue quality of the shape memory alloy (SMA), in addition to corrosion resistance and relaxation effects, must be taken into account, especially if the loads vary over time. A distinction is made between structural fatigue and functional fatigue. Structural fatigue involves the accumulation of microstructural defects as well as the formation and propagation of surface cracks until the material eventually breaks. Functional fatigue, on the other hand, is the result of the gradual degradation of either the shape memory effect or the damping capacity due to microstructural changes in the shape memory alloy (SMA). The latter is associated with the modification of the stress-strain curve under cyclic loading. The transformation temperatures are also changed. Shape memory alloys (SMA) based on iron Fe, manganese Mn and silicon Si are suitable for taking up permanent loads in the construction sector, with the addition of up to 10% chromium Cr and nickel Ni making the SMA a similar one Corrosion behavior brings like stainless steel. It is found in the literature that the addition of carbon C, cobalt Co, copper Cu, nitrogen N, niobium Nb, niobium carbide NbC, vanadium nitrogen VN and zirconium carbide ZrC can improve the shape memory properties in various ways. Particularly good properties are exhibited by a shape memory alloy (SMA) made of Fe-Ni-Co-Ti, which absorbs loads of up to 1000 MPa, is highly resistant to corrosion, and has an upper temperature of about 100 ° C. to convert it to an austenite state is.

The present reinforcement system utilizes the properties of shape memory alloys (SMAs), and preferably those of a shape memory alloy (SMA) based on steel much more corrosion resistant than structural steel, because such shape memory alloys (SMAs) are essential are cheaper than about SMAs made of nickel-titanium (NiTi). The steel-based shape memory alloys (SMAs) are used in the form of round steels with rough surfaces, for example with coarse threaded surfaces, and embedded in a mortar, ie a mortar layer, which subsequently acts as a reinforcing layer through a toothing with an underlying concrete. When heat is applied, the alloy contracts permanently back to its original state. Thus, heating the SMA profiles to the austenite state temperature will restore and retain their original shape, even under load. The effect achieved is that the molded memory alloy profiles cast into the grout layer after heating due to the conformation-inhibited recovery of their shape memory alloy (SMA) create a preload on the entire cured mortar layer extends this bias uniformly or linearly over the entire length of the profile of a shape memory alloy. [001 1] In principle, a steel profile made of a shape memory alloy, in short a SMA steel profile, preferably made of round steel with ribbed surface or with a coarse thread surface as new construction or in the prefabrication instead of a traditional reinforcing steel or in addition to the concrete is inserted. After the concrete has hardened, the SMA steel profile is heated by supplying electricity. This leads to a shortening of the SMA steel profile and accordingly causes a bias on the cured concrete part. For subsequent reinforcement, the SMA steel profile is attached to the roughened surface of the concrete structure in any direction, but mainly in the direction of pull, and pegged with the same, and then fully enclosed and covered with a cementitious mortar or shotcrete. After hardening of the cementitious grouting or mortar layer, the SMA steel profiles are heated by means of electricity, which leads to the shortening of these SMA steel profiles. The shortening causes a bias of cement mortar or mortar layer. From the mortar layer, the forces are then introduced into the existing concrete due to the rough surface of the concrete structure and the adhesion.

In the prefabrication of reinforced concrete components, such as balcony or façade panels or pipes in which the new SMA steel profiles are inserted and biased, there are further advantages. Thanks to the prestressing of these prefabricated concrete components, the cross sections of the component can be reduced. Since the component is formed free of cracks due to internal bias, is much more protection against chloride penetration, respectively. Carbonation before. This means that such components are not only lighter but much more resistant and accordingly more durable.

The invention can also be applied to better protect a building in case of fire, for which purpose the direct contraction of the SMA steel profiles by heat input is initially deliberately omitted. In case of fire, however, the installed SMA steel profiles contract due to the heat of the fire. A building envelope made of concrete, which with SMA steel profiles was amplified, thus automatically generates in case of fire, a bias and thus an improvement in fire resistance.

The method will be described and explained below with reference to FIGS. 1 shows a cross section of a concrete slab or a concrete beam 1. Therein one or more SMA steel profiles 2 are embedded. Steel-based SMA profiles 2 of polymorphic and polycrystalline structure are always used, with a ribbed otherwise textured surface, or with a thread as the surface. By raising their temperature, these SMA steel profiles can be brought out of their state as martensite to their permanent state as austenite. Such a concrete component can be produced on site at the construction site or even in a prefabrication. The built-in SMA profiles 2 in the form of round steels have a coarse surface structure 4, so that they can dig into the concrete intimately with the same. After the concrete in which the SMA steel profiles 2 have been cast in is hardened, the SMA steel profiles 2 are heated by heat input. This is advantageously done electrically by establishing a resistance heating by applying a voltage to the cast-in heating cable 3 so that the SMA steel profile 2 heats up as a current conductor. Because with long SMA profile bars the heating would take up too much time by means of electrical resistance heating, and then too much heat would be introduced into the concrete, several power connections are established over the length of the SMA profile bar. The SMA steel profile can then be heated in stages by applying a voltage to two adjacent heating cables, and then to the next two adjacent ones, and so on, until the entire SMA profile bar is brought to the austenite state short-term high voltages and currents required, so that a normal mains voltage of 220V / 1 10V is not sufficient, even a voltage source of 500V not, as it is often set up on construction sites. Rather, the voltage is supplied by an on-site mobile energy unit that generates the voltage with a number of series connected lithium batteries with sufficiently thick power cables so that a high amperage current can be sent through the SMA steel profile. The heating should be done only for a short time, so you have within 2 to 5 Seconds throughout the required temperature of about 150 ° to 300 ° in the SMA steel profile 2 achieved and thus generates its contractile force. This prevents the subsequent concrete from being damaged. For this purpose, two conditions must be adhered to, namely firstly about 10-20 A per mm ^{2 of} cross-sectional area and secondly about 10-20 V per 1 m of profiled rod length in order to reach the condition of the profiled rod as austenite within seconds. The batteries must be connected in series. The number, the size and the type of batteries must be selected accordingly, so that the required current (ampere) and the required voltage (volts) are available, and the energy reference must be controlled by a controller, so at the touch of a button - tuned to a certain profile steel length and profile steel thickness, just the right period of time the profile bar is under tension and the necessary current flows. For long profiled bars of several meters, the heating can be done in stages by power connections are provided after certain sections, that is, out of these heating cables from the device to be created are led into the open, where then the voltage can be applied. In this way, in sections - one section after the other over the total length of a profile bar, the heat needed to be used to finally put the entire length in the state of an austenite.

Figure 2 shows a cross section of an alternative embodiment of such a concrete component. For the heat input to be carried out after curing, the end regions of the SMA steel profiles are packed with inserts 5, which extend to the surface of the concrete part 1. These inserts 5 may be, for example, pieces of wood which are inserted over the end regions of the SMA round steel bars 2, or styrofoam pieces or the like. After hardening of the concrete, these inserts 5 can be removed and then the access to the end regions of the SMA steel profiles 2 is exposed. They can then be heated by applying the electrical cables of the energy unit to these end areas via large-area terminals. Optionally, the immediate heat input can be dispensed with. Then, such a concrete part 1 is preconditioned to a certain extent. If the effect of heat is later caused by the fire heat in a fire, the SMA profiles 2 generate a Contraction force and thus a tensile stress and thus generate a bias of the concrete, which leads to a significant improvement in the fire resistance of the building. In the event of fire, this will be clasped all around and will collapse much later, if at all.

In the figures 3 to 9, another application is shown, namely the creation of a reinforcing layer on a building. FIG. 3 shows a cross-section of a building wall 6, which in turn is traditionally reinforced with a conventional reinforcement 7, 8. The outside 9 of the building wall 6 is executed rough here or subsequently roughened. This can be done for example by means of a wet sandblasting. A better variant is the hydromechanical treatment with the high-pressure water jet. Different systems with different amounts of water and water pressures of at least 500bar to 3000bar are used in practice. With such systems, the desired roughness of the concrete surface of at least 3mm is ensured. In the application of the hydromechanics is additionally ensured that the ground support concrete is capillary water saturated. This is a condition for good adhesion between the existing concrete and the cement-based mortar layer to be applied.

Figure 4 shows how then the SMA profiles 2 are attached in the form of round steel with a corresponding alloy on the rough surface 9. They can be fastened with dowels 10 in the concrete wall. If necessary, the dowels 10 can also reach behind the first reinforcement 7, 8. The two end portions of the individual SMA profiles 2 are each connected to electric cables 3. Although only a single SMA profile 2 is visible here, which extends vertically, it is understood that horizontally extending, indeed running in any direction SMA profiles 2 can be installed, as well as the reinforcement in the concrete wall 6 here horizontally extending reinforcing bars 8, which intersect with the vertically extending reinforcing bars 7.

Next, the SMA profiles, as shown in Figure 5, completely wrapped by applying shotcrete or cement mortar, through Spraying, pouring or topping. The cement mortar can also be applied by hand.

As Figure 6 shows, here at one point on the SMA profile 2, a recess 1 1 can be seen, in which an insert 5 was used. After this has been removed after curing of the concrete or mortar, the SMA profile 2 is exposed there. The heat input then takes place via a there to be connected by means of a terminal heating cable in conjunction with another heating cable, which is connected to a similar recess point via a terminal to the SMA profile. Here, the SMA profile 2 is placed on the two marked heating cable 3 under an electrical voltage, so that a resistance heating is formed. The heating leads to a contraction force of the SMA profiles 2, which thus generate a tensile stress and thus a bias of the entire grouting or reinforcing layer 16, and their bias is transmitted via the teeth with the rough surface 9 of the concrete wall 6 on the same. Overall, a significant reinforcement of the structure is achieved.

Figure 7 shows a cross section of this building wall after generating the contraction force and tensile stress of the SMA profiles 2 within the grouting or reinforcing layer 16. The recess 1 1, which was used for the heat input be, is now with cement mortar filled. In the case of heating cables 3, these are cut flush with the surface.

Figure 8 shows a cross section of a steel-reinforced building wall 6, which is reinforced on a vertical outside with a sprayed layer, which in turn is biased by means of SMA profiles 2. For this purpose, a grid of SMA profiles 2 is attached to the roughened surface of the concrete 6, for example by means of suitable dowels 10. Afterwards, this grid is as shown by means of shotcrete from a spray gun 21 sheathed and covered. After curing of this shotcrete, the SMA profiles 2 of the grid are contracted by heat input, so that the whole shotcrete layer is biased as a reinforcing layer 21. The generated preload is over the teeth with the roughened surface of the structure 6 transferred to the same and thus significantly increases its stability and fire resistance.

FIG. 9 shows an application on a horizontal concrete slab. Here, after placing the SMA profiles 2 on the roughened surface of the concrete slab, these SMA profiles 2 can be cast with a manually applied liquid mortar. In the case of a cementitious Giessmörtels this still has to be compacted or vibrated with the trowel. As an alternative, a self-compacting and self-leveling cementitious mortar may be used. Thereafter, the cast-in SMA profiles 2 are heated by heat input and produce a nationwide bias of the mortar layer, which transfers to the concrete slab.

Figure 10 shows a section of a concrete slab 12, namely a corner thereof seen in a perspective view from below, which is provided on its underside with a pegged and prestressed reinforcing layer 19 containing SMA profiles. The reinforcing layer 19, which contains SMA profiles as described, is non-positively connected to the concrete slab 12 by means of a plurality of dowels 13. Only after such a successful dowelling and frictional connection between the concrete slab 12 and the hardened mortar or concrete layer, which is to act as a reinforcing layer 19, and softer the SMA profiles are, the SMA profiles by heat input to generate a contraction force and thus brought to a tensile stress, so that the reinforcing layer 19 is biased, and transmits this bias on the dowelling and connection to the concrete slab 12.

Figure 1 1 shows the internal structure of this reinforcement with a cross section through the concrete slab 12 of Figure 10, with the conventional reinforcement made of reinforcing steels 7.8, as well as the doweled and prestressed reinforcing layer 19 with SMA profiles 2. The underside the concrete slab 12 is rough, and the SMA profiles 2 are embedded in the sprayed-on reinforcing layer 19. After hardening, the dowelling takes place by means of long concrete dowels 13, which reach behind the first reinforcement 7,8 in the concrete slab 12. Then, the bias of the SMA profiles 2, which transmits to the reinforcing layer 19, and from there via the teeth with the rough surface of the concrete slab 12 and the doweling on the same. The thus prestressed concrete slab 12 has a significantly higher load capacity and so existing concrete slabs can be efficiently reinforced from below.

Figure 12 shows a concrete beam with a subsequently applied reinforcing layer 19, the two ends is pegged. In this application, the bias should act only in one direction, namely between the two support points of the concrete beam.

Another interesting application is shown in Figure 13. Here is a structure with embedded SMA profiles 2 or ordinary reinforcing steel biased. The outer end of the reinforcement, which faces towards the building outside, is equipped with a coupling member 22. In the case of SMA profiles 2 leads an electric cable 3 in the concrete to the rear, concreted end of the SMA profile 2. These coupling members 22 may be double nuts, for example. They are embedded in concrete and only slightly covered with concrete. If you want to later dock a cantilevered concrete slab 15 to the structure 14, the coupling members 22 are exposed and a concrete slab 15, in which SMA profiles 2 were poured, is connected to the concrete plant 14. For this purpose, the protruding from her SMA profiles 2, which are provided in the end with a coarse thread, connected by means of the coupling members 22 with the SMA profiles or the ordinary reinforcing bars in this building tensile strength or screwed. After this mechanical coupling, the gap between the structure 14 and the cantilevered concrete slab 15 is filled. After hardening of the backfilling 3 heat is introduced into the SMA profiles 2 via electric cables, so that they generate a contraction force and thus a tensile stress. Thus, the whole system is biased, that is, the cantilevered concrete slab 15 is internally biased, and also stretched by means of a bias to the structure 14, and if the entering into the structure reinforcements are also SMA profiles 2, so These also generate a prestress in the interior of the structure 14, which leads to a high stability and load capacity of the projection.

Claims

claims

A method of producing prestressed concrete structures by means of shape memory alloy profiles, whether of new structures and components or of cementitious mortars for the reinforcement of existing concrete structures, characterized in that profiles (2) of a steel-based shape memory alloy of polymorphic and polycrystalline structure, with a ribbed surface or with a surface in the form of a thread, which are brought by their temperature increase from their state as martensite to their permanent state as austenite, in the concrete or the cementitious mortar (1) are inserted, optionally with additional end anchors, so that they either due to a subsequent active and controlled heat input with heating means or by heat in a fire, a contraction force and thus generate a tensile stress and accordingly a bias on the concrete resp. produce the mortar (1), wherein the force is introduced into the concrete or the mortar (1) on the surface structure of the profile (2) and / or on the end anchors of the profile (2).

2. A method for creating prestressed concrete structures by means of profiles of a shape memory alloy according to claim 1, characterized in that the active, controlled heat input into the profiles (2) made of a shape memory alloy by these at the end portions of the profiles (2 ) or at intermediate points of the profiles (2) are provided with inserts (5) such that they protrude from the same or the same after curing of the concrete or the mortar (1), and these deposits (5) are removed mechanically or by burning away as required , and afterwards for the active, controlled Heat input electric cable (3) are connected to the exposed areas of the profiles (2) and are put under electrical voltage to generate a resistance heating of the profiles (2), after which the exposed end portions (1 1) of the profiles (2) from a shape memory Alloy be filled with cementitious mortar.

3. A method for producing prestressed concrete structures by means of profiles of a shape memory alloy according to claim 1, characterized in that

a. the outer side of the existing structure to be reinforced is roughened,

b. Profiles (2) made of a shape memory alloy on the roughened outside (9) of the building (6, 12) are attached,

c. a capillary saturation of the exterior of the building (6, 12) with water is generated, and then a cementitious matrix is applied as a mortar to this exterior, for covering the profiles (2) of a shape memory alloy,

d. after curing of the cementitious matrix, the profiles (2) are brought from a shape memory alloy by heat input to generate a contraction force and thus tensile stress, whereby the Vemörtelung generated as reinforcing layer (16,19) via the teeth with the roughened outside (9) of the building (6, 12) causes a bias voltage of the same.

4. A method for creating prestressed structures by means of profiles of a shape memory alloy according to claim 1, characterized in that

a. the outer side (6, 12) of the existing structure to be reinforced is hydromechanically roughened with a pressure of at least 500 bar or by means of sandblasting to a surface roughness of at least 3 mm, so that the substrate becomes water-saturated,

b. Profiles (2) of a shape memory alloy on the roughened outside (9) of the structure (6, 12) are fastened by means of anchors or profiles made of steel, c. a capillary saturation of the building exterior (6,12) is generated with water, and then applied as a reinforcing layer (16,19) a cementitious matrix as Vermörtelung by hand or sprayed dry or wet as a shotcrete, or horizontal outer surfaces as a mortar Reinforcing layer (6, 19) by means of applying self-leveling Fiiessmörtel and covering the profiles (2) is made of a shape memory alloy, with either anchoring the grouting or reinforcing layer (16,19) by attaching dowels (13), which behind a extend the foremost reinforcement (7, 8) of the structure (12) behind the attached grouting layer (16, 19),

d. after curing of the applied mortar or

Reinforcing the profiles (2) are brought from a shape memory alloy by heat input to generate a contraction force and thus a tensile stress, whereby the applied grouting or reinforcing layer (16,19) via the teeth with the roughened outside (9) of the building a bias causes the same.

5. A method for producing prestressed concrete structures by means of profiles of a shape memory alloy according to claim 1, characterized in that for the preparation of a later possible attachment of a new concrete component (15) to a currently created building (14) profiles (2 ) are placed from a shape memory alloy based on steel in the concrete of the currently building to be created (14) so that they are perpendicular to the building exterior (18) and ends are provided with a coarse thread (20) and below the surface of the building exterior side (18) end, wherein the end portions are bordered with a removable insert (5) and then covered with mortar, so that in case of need later a cantilevered concrete component (15) on the then already created concrete structure (14) can be anchored and prestressed by the concrete component to be attached (15) even with profiles (2) made of a shape memory alloy with coarse thread (20) in Endberei ch is provided and in the direction of the outside of the building exterior (18) of the already created concrete structure (14) directed towards the end portions of the exposed profiles (2) of a shape memory alloy in the existing concrete structure (14) by coupling elements (22) is connectable by traction and afterwards it can be concreted on, so that after hardening by means of heat input, its profiles (2) produce a contraction force from a shape-memory alloy and in this way the attached concrete component (15) experiences its own prestressing and is prestressed against the existing concrete structure (14).

6. A method for producing prestressed concrete structures by means of profiles of a shape memory alloy according to any one of the preceding claims, characterized in that the profiles (2) of a shape memory alloy for the heat input from a voltage source in the form of an energy unit of a series in series Switched batteries are connected via permanently or temporarily connected electric cables (3) under electrical voltage of 10-20 V per m profile length to generate a current of 10-20A per mm ² cross-sectional area, so that they form a resistance heating and within 2 to 10 seconds from their State as martensite be brought to their permanent state as austenite,

7. A method for creating prestressed concrete structures by means of profiles of a shape memory alloy according to claim 6, characterized in that over the profile length several power connections are provided with heating cables leading to the outside, and the heat input in sections successively by applying a voltage to two adjacent power connections is generated.

8. concrete structure, created using the method according to claim 1.

9. concrete structure, created using the method according to claim 5.

10. concrete structure, created using the method according to claim 6.