DE102018110533B4 - Sandwich laminate structure, its use and a method for using the sandwich laminate structure - Google Patents

Abstract

Sandwich laminate structure (1) having a first and a second surface facing each other, comprising
a core element (4) having a first surface and a second surface opposite the first surface,
at least two heating layers (3), of which at least one heating layer (3) is arranged on the first surface and at least one heating layer (3) on the second surface of the core element (4),
and at least two fabric layers (2), of which at least one fabric layer (2) is arranged on the side of the at least two heating layers (3) facing away from the core element (4), wherein the material of the core element (4) is designed as a honeycomb fleece which comprises polyester fibers, polyamide fibers, polyether fibers and/or mixtures thereof, wherein connections for a voltage source are arranged on the at least two heating layers (3) and the at least two heating layers (3) serve as conductivity sensors for leakage monitoring.

Description

The present invention relates to a sandwich laminate structure with a first and a second surface that are opposite one another, which comprises a core element that has a first surface and a second surface opposite the first surface, at least two heating layers, of which at least one heating layer is arranged on the first surface and at least one heating layer on the second surface of the core element, and at least two fabric layers, of which at least one fabric layer is arranged on the side of the at least two heating layers facing away from the core element. The invention further relates to the use of the sandwich laminate structure for lining, renovating, stabilizing and/or rehabilitating walls that delimit cavities and for leakage monitoring. In addition, the present invention relates to a method for lining, renovating, stabilizing and/or rehabilitating walls that delimit cavities and for leakage monitoring of walls that delimit cavities using the sandwich laminate structure.

The renovation of concrete pumping shafts that are subject to heavy media stress and that have leaks at the shaft connection and corrosion on the shaft wall due to mechanical and chemical influences during use represents a major technical challenge. The main cause of this damage is biogenic sulfuric acid corrosion. The liquid medium collected in the shaft often contains organic and inorganic sulfur compounds, from which bacteria form sulfides, which subsequently lead to hydrogen sulfide emissions into the gas space. Oxidation processes form sulfuric acid, which attacks the shaft material. In order to prevent the liquid medium from escaping from the shaft through damaged areas into the environment, renovation measures for cavities enclosed by concrete, such as concrete pumping shafts, are essential.

Section 60, paragraph 1 of the Water Resources Act stipulates that sewage systems are constructed, operated and maintained in accordance with generally accepted technical standards. This means that sewage systems are watertight, stable, durable and corrosion-resistant. The aim of renovating a concrete sewage shaft is therefore to ensure that these functions are maintained.

Various methods are known in the state of the art for the rehabilitation of concrete shafts. Possible rehabilitation methods for concrete sewage shafts include, for example, coating methods, which include spin-on methods (special mortar, polyurethane liquid resin), spraying methods (dry/wet spraying methods, shotcrete, polyurethane liquid resin) and coatings applied by hand, such as mineral mortar, plastic-modified mortar and bitumen coatings.

The rehabilitation methods available on the market, which are based on the surface coating of concrete structures, usually use styrene-containing, polyester resin-perforated textile layers and the welding integration of thermoplastic liners, the latter requiring considerable assembly effort, especially for small shaft diameters. Both approaches can be implemented without removing the shaft cone, but do not take on a load-bearing function in the context of structural rehabilitation. The rehabilitation of pump shafts with already impaired load-bearing capacity, on the other hand, is far more time-consuming and costly, as it usually requires civil engineering measures such as the dismantling of the shaft top and parts of the road.

This is how the US 2015/0190972 A1 for example, thermosetting, resin-impregnated wrapping devices for stabilizing load-bearing elements in buildings. Heating mats can be integrated into the reinforcement wrapping devices, which are used to harden the resin. However, these heating mats can also be placed on the reinforcement wrapping devices from the outside and removed later.

In general, repair work can usually only be carried out in the warmer spring and summer months. For example, thermosetting plastic solutions can only be processed at temperatures above 10 °C, as the necessary cross-linking reaction, which ultimately leads to the hardening of the layers, cannot take place below this critical processing temperature. Another significant disadvantage of the available solutions is the necessary dismantling of all installations (pumps, brackets, ladders) as well as the exposure and reworking of all connection points after repairs, which requires a high level of manual work.

Furthermore, lining methods are frequently used, which include the shaft-in-shaft system, using materials such as polyethylene/polypropylene and glass fiber reinforced plastic (GRP). The use of GRP modular systems and the use of modular systems made of high-density polyethylene (PEHD) are also described.

In addition, plate linings are used, which use welded polyethylene plates and GRP plates. Other well-known methods use film linings and so-called shaft lining.

The following is a brief description of the most important remediation methods known in the state of the art.

coating process

Mortar coatings are mainly used for the renovation of shaft structures. For shaft depths of up to 3.5 m, this can still be carried out economically by hand. In addition, after any manual reprofiling is required, spin-coating and spraying processes are used. Mortar coatings always require reliable protection against infiltrating groundwater, even in small quantities (previous injections) and guaranteed high humidity without drafts or post-treatment for shrinkage-free and therefore crack-free curing.

Organic film-forming coatings made of polyurethane are also used, which are applied using the spraying or spray-spinning process. In this case, extensive measures are usually required to ensure a dry substrate and to avoid condensation during application and curing in order to prevent the material from foaming when it comes into contact with water. Coating processes therefore place high demands on the surfaces and building preparation and require high quality standards when carrying out the measures.

Concrete protection coatings are themselves acid-resistant and protect the concrete component of the shaft underneath as a separating layer, provided the coating remains firmly attached to the substrate. A basic distinction is made between vapor-permeable and vapor-tight coatings. Gaseous water can hardly or not at all escape through the latter and condensation can form under the coating. This can lead to the coating detaching via various complex chemical and/or physical processes (increased alkali concentration, saponification of plastic coatings, osmotic blistering, alkali drift, frost heaves). In addition, in shafts, the component is always affected by the moisture in the ground. In the case of biogenic sulfuric acid corrosion, this can progress intensively, particularly under burst blisters and detachments. In addition, solvent-based coating materials are not diffusion- or osmosis-tight, which means that as a result of SO ₄ ^2- diffusion, ettringite can form again under the coating and accelerate its destruction. The disadvantage of these processes is that there is no structural maintenance or structural improvement. Furthermore, all fittings must be dismantled for renovation. This requires a high level of manual effort for building preparation, implementation and follow-up. Another disadvantage is that the renovation process is dependent on the season and temperature, as the work can only be carried out at temperatures of more than 5 °C. Overall, the coating processes are not a closed manufacturing process, which is why extensive occupational health and safety measures are required. Another disadvantage is that there is no integrated leak detection and therefore no condition monitoring.

lining process, shaft lining

To achieve a seal and ensure surface protection as well as to improve stability, ECR (electric corrosion resistant) glass fiber sheets, which are impregnated with a light-curing synthetic resin, are inserted into the cleaned, reprofiled and sealed shaft and cured using UV radiation. Unsaturated polyester resin (type 1140 group 3 according to DIN 18820-1) or vinyl ester resin (type 1310 group 5 according to DIN 18820-1) are used. The glass fiber sheets with a thickness of 0.7 mm are laid in several layers as a seamless, one-piece hose that extends from the upper edge of the berm to the top edge of the road. The hose is assembled specifically for the individual case in advance of the construction work. The hose is aligned, calibrated with compressed air and cured using a UV radiation source. The channel and the berm are renovated manually using prefabricated shaft bases or hand laminate. The annular gap that forms during hardening is sealed with an EPDM rubber profile. The duration of the work for a concrete shaft DN 1000 with a depth of 3.5 m is given as approximately 3 hours. This method can also be used to renovate square shafts and shafts with cross-sectional changes. The disadvantage of this method is that there is no structural maintenance or structural improvement and all fittings have to be dismantled for the renovation. This again involves a high level of manual effort for structural preparation, implementation and follow-up. This renovation method is also dependent on the season and temperature, as this work cannot be carried out at low temperatures and requires a minimum temperature of more than 5 °C. Another disadvantage is that there is no integrated leak detection and therefore no condition monitoring.

shaft rehabilitation / shaft-in-shaft system

The "Schacht + Trumme®" system is based on individual plastic elements made of PEHD, which fit together in a modular design, but can also be used individually (partial renovation). The prefabricated, flexible molded parts for the channel, connections, etc. as well as the on-site adaptable components for the shaft wall can be inserted through the shaft opening and are welded together. The tight connection of the connections and transitions is ensured by special nozzle solutions. After welding, hollow spaces are filled with a special early-strength insulation material. The anchor studs create a firm connection to the old shaft.

This method also has the disadvantage that it does not result in structural preservation or structural improvement and all installations must be dismantled beforehand. The manual effort required for structural preparation, implementation and follow-up is very high and here too, minimum temperatures of more than 5 °C are required for the method to be carried out. Integrated leak detection and condition monitoring are also not possible.

shaft rehabilitation

The HOBAS Shaft Rehabilitation® modular system based on glass fiber plastic (GRP) is also suitable for use on structurally load-bearing shafts. Channels and connections can be made to fit on site from semi-finished products. The shaft wall can be inserted through the shaft opening (no earthworks). This is then doweled and joints and edges are sealed with fiber filler. The annular space is dammed with flowable mortar and thus connected in a force-locking manner. This method also has the disadvantages already mentioned for the above methods. There is no structural maintenance or upgrading, all fittings must be dismantled, and a lot of effort is required for structural preparation, implementation and follow-up. Temperatures of more than 5 °C are required and no leak detection and condition monitoring are integrated.

shaft-in-shaft system

The "shaft-in-shaft" method enables renovation while the new structure takes over all static loads. Prefabricated shaft bodies made of GRP or polyethylene / polypropylene are used, which are inserted into the old shaft and mortared after the shaft cone has been dismantled. This results in a slight reduction in the shaft diameter. The old shaft remains in the ground as a permanent formwork. The road surface and shaft superstructure as well as the channel, base and climbing aids are dismantled. New prefabricated channels and base are used, which were incorporated into the prefabricated shaft insert according to the installation situation. The connections of the inlets and outlets can be adjusted on site and connected using hand laminate. The annular space between the new and old shaft is sealed with a flowable concrete mortar. A major disadvantage here is that the shaft cone has to be dismantled and costly civil engineering work is required in the road area. Furthermore, all fittings in the shaft have to be dismantled. This involves a lot of effort overall. The work can only be carried out at temperatures above 5 °C and there is no integrated leak detection or condition monitoring.

In the following, known leakage sensor units and damage detection systems are discussed in the state of the art.

There are currently no permanently functioning damage detection systems for sewage pump shafts. The functionality/tightness of shaft bodies is checked at regular intervals through inspections with and without access to the structures by visual inspection and directly after new construction/renovation of the shafts by means of complex leak testing in accordance with DIN EN 1610 and with country-specific deadlines for repeat testing of 10 - 30 years. Thus, efficient damage detection for the total of 10 million shaft structures in public traffic areas is currently inadequate due to a lack of technical options. Newer methods use digital image recognition and assessment and evaluation software, but also only result in visual snapshots of the structure's condition.

Leak monitoring systems are currently required according to TRwS (Technical Rules for Substances Hazardous to Water), for example for the storage of heating oil, fuels and other substances hazardous to water. Leak monitoring in underground, double-walled storage tanks is ensured here by leak detection devices that monitor a control space between the inner and outer tank walls. A leak fluid (level monitoring) or a vacuum generated by the leak detection device can be used as the monitoring medium. If a leak is detected, the leak detection device generates an alarm.

However, the rehabilitation of sewage shafts does not require the construction of a double-walled shaft container that allows the option of creating a permanent vacuum or introducing a leakage fluid. The use of such systems is therefore not possible.

Another option for leakage monitoring is the installation of sensor cables or point sensors in the area of possible water leakage. For shaft structures, in the case of exfiltration of wastewater, these are located in the area below the floor and the outside of wetted wall surfaces. These are not accessible when renovating existing shafts. Infiltration events cannot be detected because the inside of the shaft is wet anyway.

moisture measurement in buildings

Another option for leak detection can be moisture measurement in buildings. Common methods are resistance moisture measurement and capacitive (dielectric) moisture measurement. These enable the local, non-destructive determination of moisture, even in mineral building materials. Resistance moisture measurement uses two electrodes to determine the electrical resistance of a building material. The resistance changes depending on the moisture content of the test material and is displayed on the measuring device in manufacturer-specific units (digits).

The manufacturers' building material-specific measurement tables and the technicians' many years of experience enable the measurement ranges to be divided into dry, damp and wet, with the electrical resistance of the building material in the dry state forming the basis for the calculation. Capacitive moisture measurement enables measurements of building materials at depths of up to 7 cm. Its application is suitable for all types of materials and is used primarily for the initial assessment or limitation of moisture damage. Capacitive moisture measurement actually measures the capacitance of a capacitor, which is the heart of the measuring device. The capacitance of the capacitor changes depending on the dielectric (separating material of the capacitor plates). If there is material with a higher moisture content in the stray field of the capacitor, this is reflected in a higher dielectric constant, which also changes the capacitance of the capacitor.

Neither method is suitable for leak detection in shaft structures in its conventional application, as a shaft body is permanently damp on the inside due to its function of absorbing moisture from the wastewater medium and on the outside due to ambient humidity. An increase in moisture caused by a leak only occurs locally and can only be detected directly at the damaged area. However, comprehensive detection across the entire shaft body is not possible.

Damage Monitoring in Composite Materials

By measuring the electrical resistance, it is possible to show both load-related strain changes and damage in carbon fiber reinforced plastics. The load-bearing carbon fibers can therefore be used directly as sensors for fiber failure and delamination growth. With the help of electrical impedance tomography (EIT), a path has been recorded that makes it possible to detect not only the damage as such but also the location of the damage in components made of carbon fiber reinforced plastics. However, this method still requires further experimental and theoretical development.

The state-of-the-art renovation measures are associated, among other things, with restrictions on the use of the shaft and, in the area around the shafts, with closures due to construction work.

The rehabilitation methods currently used in the state of the art are time-consuming and costly and require civil engineering work with a high level of manual and physical effort. These rehabilitation methods are also dependent on the season because they include materials and process steps that can only be used or carried out at certain minimum temperatures. Another disadvantage of the state of the art methods is that although the damaged surfaces are sealed, the original stability of the shaft is not restored or improved. These methods are therefore not suitable for structural rehabilitation.

Furthermore, in the context of the renovation, the state of the art does not provide integrated leak detection and condition monitoring.

With conventional methods, no integrated leak detection and condition monitoring is possible and damage detection on shaft structures is only possible to a limited extent through visual inspection with on-site inspection. The common, very complex leak test is only required and carried out after new construction, renovation or within long periods of time and the leak test only allows an overall statement about the structure, a It is not possible to localize the damage or to isolate the area of damage.

From the CN 102940424 A An electric heating element is known which simultaneously fulfils the function of a heat storage device. A layered structure of the system is disclosed, with the core element being designed as a heat storage device and/or energy storage device.

In the DE 39 20 723 A1 discloses a sensor designed as a profile body which has at least two electrically conductive zones, wherein a switching pulse is triggered when the zones come into contact with electrically conductive media, in particular liquids such as water, acids or alkalis.

The object of the invention is to overcome the disadvantages of the prior art and to provide materials and methods for temperature- and thus season-independent structural rehabilitation in existing buildings, whereby materials and methods can be provided or carried out cost-effectively and with comparatively little effort.

Furthermore, the object of the invention is to provide a system that enables integrated leakage monitoring of shaft and container systems. In the state of the art, there is a need for segmented condition/leakage monitoring without the inspection personnel having to enter the shaft, which significantly reduces the inspection time per shaft including leak testing. Furthermore, the use of digital, wireless data transmission systems should be possible in order to also allow remote monitoring.

The object of the present invention is therefore to enable the renovation of concrete shafts, pipes and containers by providing materials and a method. The material used in the renovation according to the invention can bear at least the static loads of the original system or, if the use changes, can also bear a higher load.

The object of the invention is achieved by providing a sandwich laminate structure and the use of this sandwich laminate structure.

The object of the invention is achieved by a sandwich laminate structure with a first and a second surface that are opposite one another: The sandwich laminate structure comprises a core element that has a first surface and a second surface opposite the first surface, at least two heating layers, of which at least one heating layer is arranged on the first surface and at least one heating layer on the second surface of the core element, and at least two fabric layers, of which at least one fabric layer is arranged on the side of the at least two heating layers facing away from the core element, wherein the material of the core element is designed as a honeycomb fleece that comprises polyester fibers, polyamide fibers, polyether fibers and/or mixtures thereof, wherein connections for a voltage source are arranged on the at least two heating layers and the at least two heating layers serve as conductivity sensors for leak monitoring.

Preferred is a sandwich laminate structure which comprises at least one barrier layer arranged on one of the two surfaces of the sandwich laminate structure.

Also preferred is a sandwich laminate structure in which the heating layer is a textile material in or on which heating conductors in the form of electrically conductive wires and/or fibers are arranged.

A sandwich laminate structure is advantageous in which the fabric layers comprise glass fiber, carbon fiber, aramid fiber, natural fiber and/or mixtures thereof.

Particularly advantageous is a sandwich laminate structure in which the material of the barrier layer is selected from polyethylene, ethylene-propylene-diene rubber, tetrafluoroethylene-perfluoropropylene, silicone rubber and mixtures thereof.

Also preferred is a sandwich laminate structure in which the sandwich laminate structure comprises a cured resin material which is embedded in the core element, the heating layers, the fabric layers and the spaces between the layers of the sandwich laminate structure.

Particularly advantageous is a sandwich laminate structure in which the resin material is a thermosetting resin material and is selected from vinyl ester resin, cyanate ester resin, epoxy resin, polyester resin, phenolic resin and mixtures thereof.

Particularly preferred is a sandwich laminate structure in which the respective heating layers are subdivided into two or more sub-areas, wherein each individual sub-area of the respective heating layers has connections for a voltage source.

Furthermore, the object of the invention is achieved by the use of the sandwich laminate structure according to the invention for lining, renovating, stabilizing and/or rehabilitating walls surrounding cavities and for leak monitoring. The cavity is preferably a shaft, a pipe or a container.

• a) Größe und Struktur des Hohlraums mit einem 3D-Erfassungssystem bestimmt, b) die Sandwichlaminatstruktur entsprechend der in Schritt a) ermittelten Abmessungen und Struktur zuschneidet und konfektioniert, c) die konfektionierte Sandwichlaminatstruktur in den Hohlraum einbringt, d) die Sandwichlaminatschicht im Hohlraum positioniert,
• e) in die Sandwichlaminatstruktur Harzmaterial einbringt und das Harzmaterial härtet und
• f) mittels der mindestens zwei Heizschichten den Zustand der ausgehärteten Sandwichlaminatstruktur überwacht.

Furthermore, the object of the invention is achieved by providing a method for lining, renovating, stabilizing and/or rehabilitating walls surrounding cavities and for leakage monitoring of walls surrounding cavities using a sandwich laminate structure according to the invention, wherein

• a) the size and structure of the cavity is determined using a 3D detection system, b) the sandwich laminate structure is cut and assembled according to the dimensions and structure determined in step a), c) the assembled sandwich laminate structure is introduced into the cavity, d) the sandwich laminate layer is positioned in the cavity,
• e) introducing resin material into the sandwich laminate structure and curing the resin material and
• f) the condition of the cured sandwich laminate structure is monitored by means of at least two heating layers.

Preferred is a method in which the sandwich laminate structure is positioned in step d) by applying a vacuum to the sandwich laminate structure.

Also advantageous is a method in which the sandwich laminate structure is positioned in step d) by exerting an overpressure on the sandwich laminate structure.

• 1 eine Explosionsdarstellung des schematischen Aufbau einer Ausführungsform der erfindungsgemäßen Sandwichlaminatstruktur;
• 2a eine Explosionsdarstellung der erfindungsgemäßen Sandwichlaminatstruktur mit Wassereintritt in den Schacht;
• 2b eine Explosionsdarstellung der erfindungsgemäßen Sandwichlaminatstruktur mit Wassereintritt in die Sandwichlaminatstruktur;
• 3a - 3e eine schematische Ansicht der Verfahrensschritte einer Ausführungsform des erfindungsgemäßen Verfahrens;
• 4 ein schematische Darstellung des Verfahrens zur Herstellung einer Ausführungsform der erfindungsgemäßen Sandwichlaminatstruktur;
• 5 einen Querschnitt einer Ausführungsform der erfindungsgemäßen Sandwichlaminatstruktur, und
• 6a - 6c verschiedene Anordnungsvarianten der Heizschichten der erfindungsgemäßen Sandwichlaminatstruktur.

The present invention is explained in more detail with the accompanying drawings. It shows:

• 1 an exploded view of the schematic structure of an embodiment of the sandwich laminate structure according to the invention;
• 2a an exploded view of the sandwich laminate structure according to the invention with water ingress into the shaft;
• 2b an exploded view of the sandwich laminate structure according to the invention with water ingress into the sandwich laminate structure;
• 3a - 3e a schematic view of the method steps of an embodiment of the method according to the invention;
• 4 a schematic representation of the process for producing an embodiment of the sandwich laminate structure according to the invention;
• 5 a cross-section of an embodiment of the sandwich laminate structure according to the invention, and
• 6a - 6c different arrangement variants of the heating layers of the sandwich laminate structure according to the invention.

The sandwich laminate structure according to the invention has a first and a second surface which are opposite one another. The core element consists of a chemical-resistant material, which is preferably a glass fiber reinforced plastic material. In order to support the absorption of resin material for the curing step, the core material according to the invention is a material which has honeycombs. Preferably, a honeycomb fleece made of polyester fiber is used as the core material. In further embodiments, the core material consists of polyamide fibers, polyether fibers and/or mixtures thereof, also as mixtures with polyester fibers.

In a preferred embodiment, all layers of the sandwich laminate structure, except for the optionally present barrier layer, are preferably made of materials that are prepared for a vacuum infusion process. For this purpose, these layers can additionally comprise infusion channels. Furthermore, the sandwich laminate structure is preferably prepared for the introduction of infusion lines for vacuum infusion.

Furthermore, the sandwich laminate structure 1 comprises at least two fabric layers 2. 5 shows a cross-section of an embodiment of the sandwich laminate structure 1 according to the invention with two fabric layers 2 and two heating layers 3. As in 1 As shown, in a preferred embodiment, the laminate structure can also comprise further fabric layers 2.

The material of the fabric layers preferably comprises glass fiber, carbon fiber, aramid fiber, natural fiber or mixtures thereof. ECR glass fiber material is preferably used as a corrosion-resistant and chemical-resistant, glass fiber reinforced plastic.

The textile fiber materials in the sandwich laminate structure according to the invention preferably consist of a type or a combination of continuous fibers (> 50 mm) or long and short fibers (< 50 mm).

The at least two heating layers are preferably glass fibre materials on or in which electrically conductive wires of the fibers are arranged. Such heating foils are known in the prior art and are widely produced by embroidering copper wire onto glass fiber materials. This makes these heating layers thin, relatively flexible and usable in sandwich laminates.

The heating layers make it possible for curing to take place even at ambient temperatures below the temperatures required for curing the resin material. To do this, the heating layers are switched on and the sandwich laminate is brought to the curing temperature. These heating layers are provided with connections to which a voltage can be applied.

The heating layers also serve to determine the condition of the sandwich laminate, particularly for leak monitoring. Damage to the sandwich laminate structure can then be detected by measuring the resistance between the heating layers when voltage is applied. This enables the condition of the heating layers in the cavity to be monitored and thus also the condition of the cured sandwich laminate to be monitored. Damage to the sandwich laminate structure is accompanied by a change in the conductivity of the heating layers and thus by a leak.

A further object of the present invention is to provide an integrated leakage monitoring system. According to the invention, heating layers are arranged on both sides of the core element of the sandwich laminate structure. The purpose of the heating layers is initially to cure the resins introduced into the sandwich laminate structure by means of heat. Since the heating layers remain as lost layers in the then cured sandwich laminate structure, they are used according to the invention as conductivity sensors. Continuous monitoring therefore makes it possible to detect impending leaks at an early stage.

According to one embodiment, it is further provided to provide precise leak detection in addition to the integrated leak monitoring. This makes it possible to narrow down the area in which a leak has occurred. This makes it easier to repair the lined shaft, as the leak can be found more quickly. To make this possible, according to one embodiment, the respective heating layers are divided into several sub-areas. In contrast to the layers of the sandwich laminate structure according to the invention, which ensure sealing, the heating layers do not have to be arranged over the entire surface of the sandwich laminate structure.

In the 6 Arrangement variants of the heating layers 3 are shown. In the 6a the heating layers 3 are arranged horizontally one above the other. This is particularly advantageous when ring-shaped shaft elements are present. It is also planned to install a sandwich laminate structure 1 according to the invention inside the shaft segments during the initial installation of such shafts. Each shaft element or each individual shaft ring can then be individually heated and then monitored. Equipping the shaft rings separately with separate heating elements also has the advantage that they can be individually heated during operation. This makes it possible to regulate the temperature inside the shaft in order to optimize fermentation processes, for example.

In the 6b a vertical, strip-shaped arrangement of the heating layers 3 is shown. 6c finally shows a field-wise arrangement of the heating layers 3. This arrangement is particularly advantageous when a targeted and precise location of leaks is necessary. This is the case when the substances present in the shaft are highly hazardous to water or are dangerous substances.

Each individual heating layer 3 is connected to a monitoring system (not shown) by means of electrical lines. Such monitoring systems are known to those skilled in the art. The monitoring and control of the systems is preferably carried out by means of suitable, computer-aided devices, which are also known per se to those skilled in the art.

The resin material used in one embodiment of the present invention is a thermosetting resin material. In a preferred embodiment, this resin material is adapted to vacuum infusion with a low viscosity. A combination of resin and hardeners is used as the resin material. This resin material is commercially available. For example, epoxy resins from GURIT can be used, which provide resin material for vacuum infusion for a wide variety of applications. Furthermore, vinyl ester resin, cyanate ester resin, epoxy resin, polyester resin, phenolic resin and mixtures thereof can be used as the thermosetting resin. In the present invention, vinyl ester resin is used as the resin material in a preferred embodiment.

The optional barrier layer serves to seal the sandwich laminate structure airtight to the interior of the cavity so that a vacuum can be applied to the sandwich laminate structure - without a pressure bag. The material of the barrier layer is preferably selected from poly ethylene, ethylene-propylene-diene rubber, tetrafluoroethylene-perfluoropropylene, silicone rubber and their mixtures.

In a further preferred embodiment, a pressure bag is provided which serves to position the sandwich laminate structure in the cavity. The pressure bag is manufactured according to the geometry of the cavity. The data from the 3D capture of the cavity is used for this purpose. It is particularly advantageous here that the pressure bag is also manufactured in such a way that it is adapted to any fittings in the cavity. The pressure bag will have indentations where fittings protrude from the wall in the cavity. The indentations of the pressure bag then correspond to the dimensions and position of the fittings. Plastic films that are stretchable and tear-resistant are suitable materials for the pressure bag. Films made of polyethylene, ethylene-propylene-diene rubber, tetrafluoroethylene-perfluoropropylene, silicone rubber and mixtures thereof are preferred.

A schematic representation of the process for producing an embodiment of the sandwich laminate structure according to the invention is shown in 4 shown. First, the material is fed in at position 12 and the core element and the fabric panels are cut at position 13.

At the same time, the heating foil is manufactured at position 19. However, the heating foils can also be purchased from well-known suppliers. The heating foils are stacked together with the material cut from position 13 in position 14. The materials are sewn together in position 15. The pressure bag produced in position 21 and the infusion lines cut in position 22 are fed to the sewn layers and these elements are assembled together in position 16. The sandwich laminate with pressure bag is packed in position 17 and transported, which is marked with position 18. The material cutting of the pressure bag takes place in position 20 and the pressure bag is manufactured in position 21.

In a further aspect, the invention relates to a rehabilitation process for cavities, for example silos, areas in biogas plants, sewer pipes, sewage treatment plants and industrial containers. Even if the invention is described below using pump shafts as an example, it is not limited to their rehabilitation. The invention can generally be used for the rehabilitation and structural regeneration of underground and above-ground media-loaded shafts or containers made of concrete or any other material (sewage treatment plants, biogas plants). In addition to the application in the field of wastewater treatment, the sandwich laminate structure according to the invention and the method according to the invention can also be used in the rehabilitation of tanks and silos for fuel, chemicals, bulk goods, building materials and food in a stationary as well as mobile sense, such as in freight transport by road, rail or sea.

In one embodiment of the invention, the provision of a fiber-plastic composite material for lining the inner wall of a cavity, for example the inner wall of a shaft, is disclosed. An active sandwich structure with a load-bearing effect is provided, which is integrated into the cavity on site and, in one embodiment of the invention, is solidified, i.e. hardened, there by means of the economical vacuum infusion process.

The invention enables flexible and short-term structural rehabilitation of, for example, existing concrete pumping shafts that are in need of renovation. Mechanical and chemical-biological stress can cause damage to shafts made of precast concrete elements, which can impair the load-bearing capacity and function of the overall structure. The process is intended to completely rehabilitate the damaged concrete pumping shafts without replacing them, so that the original load-bearing capacity and the associated service life of the system are restored at the same time.

The rehabilitation process according to the invention comprises the following steps, including the production and adaptation of the sandwich laminate structure: In the first step, the actual condition of the shaft 9, pipe or container is analyzed using a 3D shape detection system 7. The inner contour of the cavity is recorded. Furthermore, any installations and damaged areas, such as spalling, are localized and digitally recorded. The recording of the digital geometry data is followed by its processing. This is shown schematically in 3a shown.

Preferably, the shaft 9 or another cavity is cleaned in advance to remove foreign bodies before the 3D shape is captured. This is followed by planning and designing the repair. The surface leveling required and desired for the repair and its implementation are planned. The required material requirements and the cutting geometries of the sandwich laminate structure according to the invention are calculated. In addition, work instructions for assembly can be provided. Then the components of the sandwich laminate structure according to the invention, namely the fiber textiles, heating foils and other foils, are cut to size. The cutting is preferably carried out close to the final shape, for example using CNC programs. This is followed by marking and joining the sandwich laminate segments. The sandwich laminate is then assembled and transported to the site.

In the second step, the sandwich laminate structure 1, which is individually provided for the shaft 9 or container to be renovated, is placed in the cavity, i.e. in the shaft 9, pipe or container, and then positioned. This shows 3b .

In the third step, the sandwich laminate structure 1 is optimally aligned in the cavity by bringing it into contact with the inner walls of the cavity in such a way that the area of the sandwich laminate 1 prefabricated for a wall area also rests against the corresponding area of the cavity wall 5 and lines it. This means that the sandwich laminate structure 1 adapted to the geometry of the cavity also rests against the wall with the partial area provided for it and adapted to the corresponding part of the wall. In a preferred embodiment, this positioning and alignment of the sandwich laminate structure 1 follows by exerting an overpressure on the sandwich laminate structure 1, whereby it is pressed against the cavity inner walls. In this embodiment of the invention, the overpressure can be achieved, for example, by inflating a pressure bag 10 adapted to the cavity geometry. In this embodiment, the pressure bag 10 is not an integral part of the sandwich laminate structure 1. The pressure bag 10 is manufactured in accordance with the geometry data of the cavity recorded in the first step. The step-by-step inflation of the pressure bag 10 enables flexible positioning of the sandwich laminate structure 1 in the cavity and thus enables optimal alignment of the sandwich laminate structure 1 according to the geometry of the cavity. The process step using a pressure bag 10 is shown in 3c . Here Pü means overpressure.

In a further preferred embodiment of the invention, the sandwich laminate structure positioned in the cavity comprises at least one barrier layer which is arranged on one of the surfaces of the sandwich laminate structure. In this embodiment of the invention, the sandwich laminate structure is positioned in the cavity such that the barrier layer is directed towards the interior of the cavity. In this embodiment, the sandwich laminate structure is positioned by applying a negative pressure to the area between the barrier layer and the cavity wall.

In the fourth step, the sandwich laminate structure 1 is prepared for the curing step in order to produce a cured sandwich laminate structure 1 in the cavity. In the embodiment in which a pressure bag 10 is used, this is converted into a vacuum bag by sealing the edge area of the pressure bag 10 on the cavity, for example on the shaft cone, with an application-specific sealing tape. This is shown in 3D shown.

In the embodiment in which no separate pressure bag is used, the at least one barrier layer of the sandwich laminate is sealed at the edge region of the cavity with a sealing tape.

In the fifth step, the hardening of the sandwich laminate structure 1 is carried out. For this purpose, resin material is introduced into the laminate. In a preferred embodiment of the invention, the resin material is introduced by means of vacuum infusion. After the sandwich laminate structure 1 has been positioned, the area between the pressure bag 10 and the cavity wall, i.e. the area in which the sandwich laminate structure 1 is arranged, is evacuated. Resin material is introduced into the sandwich laminate structure 1 by the negative pressure. The matrix material (resin) is fed to the sandwich laminate structure 1 and infiltrated with the help of the negative pressure forces. A schematic representation of this process step shows 3e . Here P _u means negative pressure.

In a preferred embodiment, cable channels are integrated into the sandwich laminate structure.

If a separate pressure bag was used, it can be removed after the resin has hardened. To ensure that the pressure bag can be removed without damaging the hardened laminate structure, the material of the pressure bag is selected in such a way that it can be removed from the hardened resin material.

In the case of thermosetting resin material, the curing of the resin material is assisted by heat, which can be generated by integrated heating layers.

Once the sandwich laminate structure has cured, the cavity contains a sandwich structure that has been optimized for production, which not only lines the cavity walls but also supports them. The support effect can be individually adjusted by the materials selected in the sandwich laminate structure used. This means that the cured sandwich laminate structure can have the stability and give the cavity walls the same stability as the original, undamaged structure.

Due to the inventive integration of a heating system, it is possible to renovate the walls of hollow spaces regardless of temperature and therefore season. The sandwich laminate has connections to which a voltage source can be connected.

In addition to lining, supporting and renovating the shaft, container or pipe, the sandwich laminate structure according to the invention also enables active condition monitoring with regard to the tightness of the system, for example the shaft. For this purpose, the condition of the heating layers of the laminate structure is recorded. Damage to the walls surrounding the cavity, which are lined with the sandwich laminate structure, is detected if this damage affects the conductivity of the heating layers.

Only damage that extends into the depth of the sandwich laminate structure will ultimately become relevant in relation to a leak. This means that determining damage to the heating layers also allows conclusions to be drawn about an impending or already occurring leak in the shaft, container or pipe.

To detect leaks and thus monitor leaks, the condition of the heating layers is monitored by carrying out resistance measurements between at least two heating layers. Damage to the heating layers is detected by a change in resistance. For this purpose, the sandwich laminate has connections to which a voltage source can be connected.

Overall, it is therefore advantageous that using the sandwich laminate structure according to the invention enables short-term renovation of existing shafts, pipes and containers, i.e. without civil engineering work. The method according to the invention using the sandwich laminate structure according to the invention enables renovation and structural rehabilitation independent of temperature and season. The proposed vacuum infusion method enables the renovation to be carried out without the employees entrusted with the renovation coming into contact with resin material and solvents. This provides a closed and environmentally friendly renovation method.

Another advantage is that inexpensive and lightweight materials are used, which can be brought to the site of renovation with low transport costs and easy handling. Also, no precautions are required with regard to handling chemicals, because untreated, i.e. not pre-impregnated sandwich laminate is provided. This enables a reduction in manual and risky work.

Overall, the process and rework times are significantly shorter because the sandwich laminate structure is individually adapted to the geometry of the cavity and fittings are already taken into account during the production of the sandwich laminate structure.

The method according to the invention also has a positive effect on the costs of renovation because it allows the material requirements to be individually adapted to the structure to be renovated. This means that waste can be avoided.

The integrated leakage monitoring can be carried out with the support of wireless data transmission as lifetime monitoring by determining resistance values and transmitting them wirelessly to a data acquisition system where they are evaluated. In a preferred embodiment, smart technologies are integrated here.

A particular advantage is that the rehabilitated shaft has a longer service life than shafts rehabilitated using conventional lining methods.

Essential aspects of the invention are now briefly summarized again in a discussion of a common prior art method. DE 600 07 525 T2 describes a process for the in-situ renovation of shafts, in particular sewage shafts, and prefabricated lining for this purpose. In this patent, the lining is wound, woven or braided onto a rubber form coated with foil. The glass fiber material used is already pre-impregnated with the corresponding matrix or plastic (polyester or epoxy resin).

In contrast, in the method according to the invention, the shaft to be renovated (for example a pump shaft or a building in general) is scanned using a 3D laser scanner. Digital surface models are generated from this data, which precisely represent the inner surface of the shaft. On this basis, the textile fiber materials are individually cut to size using CNC processes. The individual cuts are then joined together using sewing and gluing techniques. It should be noted that, in contrast to the prior art method, all fiber materials are completely dry, i.e. without a matrix (resin). It is also important that the sandwich laminate structure according to the invention is ideally adapted to the shaft in question due to the scanning. In the patent DE 600 07 525 T2 The adaptability is realized by changing the inclination angle.

In the patent DE 600 07 525 T2 a pre-impregnated material is used that is in direct contact with the environment and people. It should be noted that the resin is a hazardous substance. To prevent premature hardening of the matrix, the pre-impregnated fiber material must be conditioned (cooled) during production and processing. Furthermore, the adaptability by changing the inclination angle is geometrically limited, so that fine or complex bulges may not be able to be reproduced.

After DE 600 07 525 T2 The lining is placed on the inner wall of the building using an elastic pressure bag. In the method according to the invention, in a preferred embodiment, the pressure bag is made to measure for the existing shaft analogously to the fiber material. In this case, the pressure bag consists of a thin and stretchable multi-layer composite plastic film. The individual cuts of the pressure bag are welded and glued together so that the pressure bag is gas-tight. The pressure bag is then assembled with the sandwich laminate structure to form a “hose package”. The disadvantage of the DE 600 07 525 T2 that the elastic expansion of the tubular rubber bag is limited to a certain extent. Complex or difficult to access geometries cannot be correctly reproduced in this way. This problem is solved by the ideal adaptation of the pressure bag in the method according to the invention. As mentioned above, DE 600 07 525 T2 Pre-impregnated semi-finished fiber products (so-called “prepregs”) are used. The material is cured by tempering with steam or warm water.

In one embodiment of the method according to the invention, a dry sandwich laminate structure is used. After this is positioned in the shaft and evacuated, the matrix material is injected via infusion lines in the resin infusion process. The fiber material is completely impregnated. The curing of the matrix material can take place with or without tempering. However, tempering accelerates the curing process and is therefore more economical. The tempering of the fiber structure and the matrix material takes place with the help of the integrated heating system (heating layers). The advantage of this embodiment of the method according to the invention is that the resin infusion process is a closed process carried out under vacuum, in which the resin does not come into contact with the environment or people at any point. The curing process can be influenced in a targeted or local manner by controlling the electrical power through the heating layers. The structural load-bearing capacity of the structure is increased by the process of DE 600 07 525 T2 not restored, but only the structure is lined and a smooth internal surface is provided.

In one embodiment of the method according to the invention, the proportion and orientation of the fiber reinforcement can be calculated and designed individually for each structure using the data recorded in the 3D scan based on the finite element method (FEM). Depending on the load case (e.g. location and depth of the structure, structural condition, environmental conditions), the sandwich laminate structure can be designed to be sufficiently rigid. In addition, the laminate structure was chosen in the form of a sandwich construction, as this offers high rigidity and strength with low material usage. Another advantage here is that exactly the amount of material that is needed is used, thus significantly improving the cost-effectiveness of the process.

The method according to the invention is independent of the season due to the heating layers in the sandwich laminate structure. Due to its flexibility, the sandwich laminate structure can be inserted through standard shaft openings and dismantling the shaft cone is not necessary. Costly civil engineering work in the road area is not required. Due to the object-specific, computer-aided prefabrication of the flexible sandwich laminate structure in the modular system, the method can be carried out without dismantling all of the fittings. Furthermore, the use of the sandwich laminate structure according to the invention in the method according to the invention ensures a high level of tightness, durability and BSK (biogenic sulphuric acid corrosion) resistance of the shaft. The in-situ resin introduction without people entering the shaft is another positive effect in terms of occupational safety. The method according to the invention for renovation can be carried out in a shorter period of time compared to the prior art methods. For example, the rework is also significantly reduced because no re-lamination or welding of the connections and material transitions, joints and edges is required. This reduces the period of usage restriction due to media blockage. And the functional integration, namely the integration of leak detection and condition monitoring, is a further advantage of the sandwich laminate and method according to the invention.

list of reference symbols

1

sandwich laminate structure

2

fabric layer

3

heating layer

4

core element

5

concrete wall

6

damaged area

7

shape detection system

8

Street

9

concrete shaft

10

pressure backpack

11

resin infusion

12

material supply process step

13

cutting process step

14

stacking process step

15

sewing step

16

assembly process step

17

packaging process step

18

transport process step

19

Process step Provision of heating layer

20

Process step cutting printed bag

21

Process step manufacturing pressure bag

22

Process step cutting infusion lines

23

barrier layer

100

hardened sandwich laminate structure

Claims (15)

Sandwich laminate structure (1) with a first and a second surface that are opposite each other, comprising a core element (4) that has a first surface and a second surface opposite the first surface, at least two heating layers (3), of which at least one heating layer (3) is arranged on the first surface and at least one heating layer (3) on the second surface of the core element (4), and at least two fabric layers (2), of which at least one fabric layer (2) is arranged on the side of the at least two heating layers (3) facing away from the core element (4), wherein the material of the core element (4) is designed as a honeycomb fleece that comprises polyester fibers, polyamide fibers, polyether fibers and/or mixtures thereof, wherein connections for a voltage source are arranged on the at least two heating layers (3) and the at least two heating layers (3) serve as conductivity sensors for leak monitoring. Sandwich laminate structure (1) according to claim 1 , characterized in that the sandwich laminate structure comprises at least one barrier layer (23) which is arranged on one of the two surfaces of the sandwich laminate structure. Sandwich laminate structure (1) according to one of the preceding claims, characterized in that the heating layer (3) is a textile material in or on which heating conductors in the form of electrically conductive wires and/or fibers are arranged. Sandwich laminate structure (1) according to one of the preceding claims, characterized in that the fabric layers (2) comprise glass fiber, carbon fiber, aramid fiber, natural fiber and/or mixtures thereof. Sandwich laminate structure (1) according to claim 2 , characterized in that the material of the barrier layer (23) is selected from polyethylene, ethylene-propylene-diene rubber, tetrafluoroethylene-perfluoropropylene, silicone rubber and mixtures thereof. Sandwich laminate structure (1) according to one of the preceding claims, characterized in that the sandwich laminate structure comprises a cured resin material which is embedded in the core element (4), the heating layers (3), the fabric layers (2) and the spaces between the layers of the sandwich laminate structure. Sandwich laminate structure (1) according to claim 6 , characterized in that the resin material is a thermosetting resin material and is selected from vinyl ester resin, cyanate ester resin, epoxy resin, polyester resin, phenolic resin and mixtures thereof. Sandwich laminate structure (1) according to one of the preceding claims, characterized in that the respective heating layers (3) are subdivided into two or more sub-regions, wherein each individual sub-region of the respective heating layers (3) has connections for a voltage source. Use of a sandwich laminate structure according to one of the preceding claims for lining, renovating, stabilising and/or rehabilitating walls enclosing cavities and for leakage monitoring. Use according to claim 9 , characterized in that the cavity is a shaft, a pipe or a container. Method for lining, renovating, stabilising and/or rehabilitating walls enclosing cavities and for leakage monitoring of walls enclosing cavities using a sandwich laminate structure according to one of the Claims 1 until 8 , characterized in that one successively a) determines the size and structure of the cavity with a 3D detection system, b) cuts and assembles the sandwich laminate structure according to the dimensions and structure determined in step a), c) introduces the assembled sandwich laminate structure into the cavity, d) positions the sandwich laminate layer in the cavity, e) introduces resin material into the sandwich laminate structure and hardens the resin material and f) monitors the state of the hardened sandwich laminate structure by means of the at least two heating layers. procedure according to claim 11 , characterized in that the sandwich laminate structure is positioned in step d) by applying a vacuum to the sandwich laminate structure. procedure according to claim 11 , characterized in that the sandwich laminate structure is positioned in step d) by exerting an overpressure on the sandwich laminate structure. procedure according to claim 13 , characterized in that in step d) the overpressure is exerted by a pressure bag which is exerted by a pressure bag introduced into the cavity or by a pressure bag formed by the barrier layer, wherein the pressure bag introduced into the cavity is manufactured according to the dimensions and structure of the cavity. Procedure according to one of the Claims 11 until 14 , characterized in that the introduction of the resin material in step e) is carried out by means of vacuum infusion.

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