Patent Application
20200123666
This application claims the priority benefit of EP Pat. App. No. 18200953.0, titled “Gelege mit Primaranode”, filed Oct. 17, 2018, which is hereby incorporated by reference in its entirety.
The following is an accurate translation of the priority document into English.
This invention relates to an anode system for a cathodic corrosion prevention.
An exemplary embodiment of the invention is explained in detail by means of a drawing in which
Buildings made of reinforced concrete are integral parts of the infrastructure in almost all countries of the worlds. In addition to residential and commercial buildings, many trafficked buildings are built of reinforced concrete, e.g. parking blocks, garages, highways, bridges, tunnels, etc. A large number of these buildings are used for 50 to 100 years (and sometimes even longer). However, in addition to mechanical stress, above all dew salts affect the reinforced-concrete buildings. As a rule, dew salts contain chloride. Therefore, in combination with water, solutions are formed which cause corrosion in the buildings. Therefore, in many buildings, substantial, cost-intensive repair works have to the carried out on the reinforcement after 20-25 years already.
For this purpose, usually, the contaminated covering concrete is removed, the rein-forcing steel is cleaned and provided with a new corrosion prevention (e.g. based on polymer or cement). However, often the repaired region lasts only few years (due to mechanical, thermal and/or hygric incompatibilities), so that soon, another repair will be necessary, especially when the covering concrete is greatly stressed. This causes high costs, is a considerable intervention into the building and last, not least, leads to limitations of use during the repair works.
One possibility to suppress and, ideally, prevent corrosion, is the cathodic corrosion prevention (CCP) of buildings. Being a largely nondestructive repair method, the cathodic corrosion prevention is an increasingly important economical repair method for building components threatened or damaged by corrosion.
The principle of the electrochemical prevention method (cathodic corrosion prevention) consists in electrically influencing the corrosion process of unalloyed or low alloy steels (e.g. reinforcing steel) in an extensive electrolyte (grounds, seawater, in case of use in reinforced concrete: concrete) by introducing a direct current. The application of this direct current (protective current) causes a displacement of the electrochemical potential of the metal to be protected in negative direction, thus cathodically polarizing the metal surface and preventing a damaging corrosion.
To impress a protective current, one must first of all couple a permanent and corrosion-resistant anode to the concrete and fix it to the positive pole of a rectifier serving as a voltage source. The negative pole of the direct voltage is connected to the steel (in case of reinforced concrete, to the reinforcement) to be protected. After the direct voltage has been switched on, the steel will be cathodically polarized and the steel corrosion will be reduced to negligible rates.
Furthermore, it is possible to analyze, monitor and control the condition of the house, building or pipeline, or the corrosion of the steel, via a remote-monitoring system, by means of an inserted reference electrode, so that further corrosion or faults in the corrosion prevention can be detected and eliminated early.
To achieve as uniform and also safe a corrosion prevention as possible, it is desirable to design the anode system on the largest possible surface in the vicinity of the steel element, for example the reinforcement steel, serving as cathode. This is, however, very difficult to implement with the anode systems used so far, such as, for example, in case of use of rod anodes or titanium-band anodes, or it is very difficult to install, such as, for example, in case of use of a netlike titanium anode. It requires in particular a high amount of work and time to fix a netlike titanium anode for the protection of a reinforced-concrete building on the concrete, due to the inflexibility of the material and the necessary large layer thicknesses of the embedding mortar. In addition, this leads to a high load.
It is true that large-surface anode systems generate a more uniform electric field, but due to their defined structure, they can hardly be adapted to the locally changing electrical conditions, such as, for example, in the form of deviations of the concrete covering or a different content of steel, while band anodes are more flexible in this case, as they can be laid in a more narrow manner, if necessary.
When using rod anodes or else netlike anode systems, it has, furthermore, been usual up to now to feed in the current through a primary anode welded together with the anode system in one point. Not only must this connection of the primary anodes be effected in a further process step, but this point welding and feed-in of the current through a single welding point causes the functionality of the cathodic corrosion prevention to depend on the durability of the welding point and the contacting effected there. This makes the system very susceptible to weather influences and environmental changes.
In the past years, anode systems consisting, at least partially, of carbon have increasingly been used. While carbon offers some advantages for the generation of an electric field in the mortar for cathodic corrosion prevention, such anode systems often present problems with the electric contacting and feed-in of the current, because carbon cannot electrically be welded or soldered. Therefore, the electric contacting is only possible by gluing the primary anode to the carbon elements or by mechanical connections, which up to now were either very work-intensive or little durable.
The invention is, therefore, based on the problem to provide an anode system with a particularly simple and durable connection of the primary anode.
This problem is solved according to the invention by the anode system comprising a biaxial or multiaxial nest with a number of threads, wherein at least a partial number of the threads comprise carbon multifilaments and wherein at least one thread comprises a primary anode
The invention starts out on the consideration that in particular, the contacting of the primary anode on the carbon anode should be facilitated and improved, in order to improve the feed-in of the current into the anode system. At the same time, however, a stable, large-surface anode structure should be used to enable an easy laying. It has been found that a particularly good feed-in can be effected if the primary anode is incorporated or integrated into the anode structure. To also simplify the production of the anode system, no fabric is used into which the individual threads and, thus, also the primary anodes would have to be woven. Therefore, according to the invention, a nest is used in which the individual threads are present in stretched shape, so that no additional stretching of the structure exists and the orientation of the threads can also be defined specifically for the application in question. In such a carbon nest or in a nest with a number of threads comprising carbon multifilaments, the conductivity may, however, deviate from one thread to the other, because said conductivity depends on the number of fractures in the carbon multifilaments. The conductivity of the entire nest is, thus, greatly determined by the node points and fractures in the carbon multifilaments. It has been found that the feed-in of current in a single point of the nest may lead to the fact that the nest is supplied with current in a very poor or non-uniform manner if, due to a lack of fractures in the carbon multifilaments, individual threads lie substantially insulatingly relative to the adjacent thread. To provide a uniform and large-surface feed-in, the latter should, therefore, be effected over the entire length of the nest. Therefore, at least one thread of the nest comprises a primary anode. The primary anode is substantially formed over the entire length of the thread.
By nest, one understands within the framework of the present application a surface body consisting of several layers of substantially parallel stretched threads. The individual layers are placed one on top of the other and fixed to each other in the crossing points. If the threads of different layers are oriented in two different directions, a biaxial nest is given, if several layers with several orientations are provided, as can be the case, for example in a 3D nest, a multiaxial nest is given. Within the framework of the present application, one also understands, therefore, by the term “nest” a grid which also has a corresponding structure.
By the thread of a nest, one understands an individual stretched string. This thread may consist of a number of carbon multifilaments forming together a thread or string.
In a preferred embodiment, the primary anode is made of platinum or titanium and possibly coated with a mixed-metal oxide. In a preferred embodiment, the primary anode is in this case sewn into a thread consisting of carbon multifilaments or sewn onto such a thread. It is also possible in this case that the primary anode is wound around a thread. Alternatively or additionally, a primary anode can also rest on the gaps or meshes. Accordingly, the primary anode can, therefore, also be designed as a round, flat-band or grid anode. In principle, it is also possible that the primary anode substitutes a thread consisting of carbon multifilaments.
For a particularly simple and stable connection between the individual layers, the threads of adjacent layers are, in a preferred embodiment, sewn together in the crossing points. This mechanical connection enables, depending on the pull of the sewing thread, both the production of a rigid nest and a mobility of the nest threads in the crossing points, so that, according to the case of application, both a rigid and a flexible nest, which can be subdivided into any stages, are possible. In individual cases, an exclusive or additional thermofixing of the threads of adjacent layers in the crossing points is possible.
At least part of the threads, preferably, however, all threads except the primary anodes, comprise carbon multifilaments. To bundle the carbon multifilaments into a thread, said carbon multifilaments are, in a preferred embodiment, glued together and/or sewn together with a circumferential positioning thread. To increase the electric conductivity and in particular the charge transition to the surrounding concrete and also for reinforcement, the carbon filaments and/or the carbon multifilaments and/or the threads and/or the nest as a whole are, in a preferred embodiment, impregnated and/or coated in an upstream process step. It is another advantage of an impregnation that a better contacting between the primary anode and the threads or the nest is achieved through shrinking of the basic medium used for impregnation.
It has turned out that the nest of the textile reinforcement can be adapted to the environmental conditions prevailing on the site of application in a particularly easy manner if the impregnation and, there, the basic medium used for the impregnation, is modified by admixing additives to increase the electrical, mechanical and thermal properties. It is possible, for example, by admixing carbon nanotubes, metal particles, salts (or ionic compounds) or graphite, to increase the electrical properties, in particular the conductivity, while the thermal properties can be influenced by admixing metals, carbon particles and graphite particles. To improve the mechanical properties, in particular also the composite with the solid mortar, it is possible to admix hard materials, for example in the form of silicon carbite, quartzes and ceramics.
It is, furthermore, possible to modify the process parameters and the possible processability of the nest, in particular of a carbon nest, by admixing additives. It is imaginable to use plasticizers, retarders or thickeners to influence also the properties of the fresh and solid mortar.
By admixing additives, it can in particularly be achieved that the solidity of the mortar is particularly high in the area of the nest, while it is relatively low on the surface. This solidity gradient, decreasing in the direction facing away from the nest, allows a particularly flexible use of the nest.
For a particularly flexible and manifold possibility of modification, the basic material is, in a preferred embodiment, synthesized by radical polymerization from a monomer and a starter. In this case, it is possible to admix the additive to the monomer and/or the starter already prior to the synthesization. This enables a modification of the impregnation already prior to the synthesization of the basic material. Additionally or alternatively, it is, however, also possible to admix the additive to the already synthesized basic material before, during and/or also after the impregnation in the form of spreading it onto the impregnated nest.
In a special form of impregnation or else in connection with the subsequent coating, the starter is applied in a first process on the nest and the monomer is only applied afterwards, so that the synthesization of the basic material is effected directly on the nest.
It has turned out to be particularly advantageous to use a polymethylmethacrylates as a basic material for the impregnation because due to its low density, this basic material can be introduced particularly well into the interspaces of the nest, but also into the interspaces of the fiber strings. In addition to using polymethylmethacrylates as basic material, it is, however, also imaginable in general to use the above-mentioned epoxy resins, styrene-butadiene rubbers and acrylates or polyurethanes.
To produce a solid composite between the impregnated textile reinforcement and the surrounding concrete, the surface of the impregnated carbon nest is, in a preferred embodiment, roughened and thus enlarged. For this purpose, additives are admixed to the coating medium in the form of particles which cause such an enlargement of the surface. In particular, granite, quartz powder, hydrated cement or conductive particles can be used. The enlarged surface results in a force and form-locking composite (reinforcing effect). By admixing conductive particles, the charge transition can be optimized in order to improve the cathodic corrosion prevention. Alternatively or additionally, ionic compounds or concrete admixtures influencing the kinetics of the hardening reaction can be used, in order to increase, in case of using salts, the conductivity in the border area, on the one hand, and the solidity of the mortar in the environment of the nest, on the other hand.
In addition to enlarging the surface of the carbon nest by admixing particles, it is also possible, in an advantageous embodiment, to apply a coating on the already impregnated carbon nest, which coating, like the particles, enlarges the surface. This coating may then either form the carrier medium for the particles or provide itself for a better composite. In a preferred embodiment, additives are admixed to this coating medium, too, to improve the electrical, thermal or mechanical properties before, during or after its application on the impregnated carbon nest.
The impregnation or else the coating can be applied in particular by the immersion-bath method, an emulation process, a spray process or may also be painted or rolled on.
It is an advantage that through use of an impregnation of the nest, in case of a carbon nest, in particular of the carbon fibers, carbon threads or the entire nest containing carbon, which is adapted to the application range in question and modified by an additive, it is possible to influence the properties of the reinforcement, but also of the mortar, in the immediate environment of the reinforcement. In this way, it is possible to protect, in addition to plane surfaces, also curved, freely weathered and trafficked buildings permanently against steel corrosion and, at the same time, to mechanically reinforce them. It is in this case a particular advantage that it can be achieved, by suitably modifying the mechanical properties, that the carbon nest used in this case, being a thin-layer textile concrete, can provide a sufficient load-bearing capacity or a load increase even without the combination with a cathodic corrosion prevention. Together with the removal of thin former coats which are not needed for load bearing (such as screed, asphalt or less solid concrete), this may, therefore, reduce the load, increase the load-bearing capacity and enlarge the overhead clearances in parking blocks.
Thus, the increase of solidity in the vicinity of the fibers leads to an improved performance without causing a very high crack formation. Furthermore, the admixture of plasticisers on the fiber can improve the penetration into the fabric.
In detail, the essential advantages of the coating medium used lie in improving the electrical, chemical and mechanical properties of the entire system, in particular the high mechanical load-bearing or load-carrying capacity of the materials used (e.g. in case of static and dynamic tensile, adhesive-pull and shearing stresses), the long-term resistance against environmental influences, i.e. chemical inertia as well as thermal stability in a temperature range of −20° C. to 80° C. The load-carrying behavior in a larger temperature range can also be improved. Furthermore, the advantages lie in the flexible processability and ductility (drapability) and, at the same time, sufficient rigidity for laying the textile reinforcement. Connections over corners and edges can be produced in a force-locking and electrically conductive manner. Furthermore, the rigidity enables an easy application in the laying process. Further advantages are the high bond strength between the concrete and the textile reinforcement (possibly due to the additional use of a coating) and the optimized conductivity in the “metallic” conductor (carbon, conductor of 1st order) and the good charge transition to the ionic conductor (concrete; conductor of 2nd order).
For an optimum embedding of the anode system in the concrete and, thus, a particularly good current transmission, the threads of a layer are, in an advantageous embodiment, arranged spaced from each other. In this way, interspaces are formed between the threads, which can be filled with concrete, whereby the threads are completely covered by concrete. A spacing between the threads of 5-100 mm is particularly advantageous, in order to create, on the one hand, enough clearance for mortar or concrete in the interspaces and to be able, on the other hand, to provide an anode nest which is sufficiently dense to fulfill the required electrical properties. In one embodiment of the invention, the nest comprises two layers, the threads of each layer being arranged spaced from each other. This biaxial arrangement of the layers results, therefore, in rectangular interspaces defined by the adjacent threads of the two layers and can be filled with concrete.
In order to be able to provide, on the one hand, an anode system which is particularly easy to lay, but which is, on the other hand, also particularly stable and robust against external influences and mechanical stresses, the nest has, in an advantageous embodiment, an area weight per layer of 100-1000 g/m2, preferably in the range of 350-650 g/m2.
The advantages achieved with the invention consist in particular in the fact that by embedding the primary anode in the nest, a particularly safe and oxidation-free feed-in of currents into the anode system in several points is possible. The use of a nest enables a particularly simple manufacture of the anode system in the preliminary stages as well as a particularly easy laying on site. At the same time, the anode system can particularly easily be adapted to the case of application and the conditions prevailing there, by means of using special coatings, different spacings of the threads and variations in the number of layers.
The nest 1 according to
Of course, the planes of the nest 1 need not necessarily be arranged orthogonal to each other, but can also be arranged, depending on the intended application, at another angle. It is also imaginable to provide more than two planes.
In the exemplary embodiment according to
To increase the mechanical, electrical and thermal properties, in particular to improve the layability and activation of the mechanical properties of the nest 1 and also of the anode system embedded in the mortar, an impregnation 10 and afterwards, a coating is applied on the nest 1. By suitably choosing the recipe of the impregnation and the coating and by admixing corresponding additives, it is possible in this case to provide a nest 1 for an anode system, which possesses optimum mechanical, electrical and thermal properties for the application and operating site in question.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18200953.0 | Oct 2018 | EP | regional |
