Method and device for repairing a pre-tension cable sleeve

Description

[0001] The present invention relates to the technical field of maintenance, repair and / or sleeving of prestressing cable sheaths, used for example in the field of public works and the construction of prestressed concrete structures, in order to guarantee the functionality and mechanical integrity of said structures. The invention applies for example to the repair of stay cables or to the repair of external prestressing cables.

[0002] The invention relates more particularly to an innovative method for repairing a prestressing cable sheath, as well as a prestressing cable sheath repair assembly making it possible to implement said method, the repair assembly comprising in particular two cylindrical polymer sleeve parts intended to be welded to the cable sheath to be repaired. State of the art

[0003] Typically, a concrete prestressing cable comprises a bundle of metal strands and an outer protective sheath of generally tubular shape. This outer sheath is generally made of a polymer material.

[0004] For illustration purposes, the Figure 1 attached schematically illustrates the cross-section of a state-of-the-art prestressed concrete cable 1. The Figure 1 shows the interior of the cable 1, in particular its external protective sheath 2 having a generally elongated tubular shape, as well as its internal strands 5. The strands 5 are typically formed from steel. Such prestressing cables are widespread in civil engineering works, for example for supporting cables or bridge hangers.

[0005] During the life cycle of prestressed concrete structures, various deterioration phenomena of the protective sheaths of prestressing cable strands can commonly be observed, requiring rapid repair intervention. In particular, it is necessary to quickly control the corrosion of the internal elements of the cable, which can cause mechanical rupture of the strands. Preferably, a surface treatment of the protective sheath as well as a deep treatment should then be carried out in order to restore the functionality and durability of the prestressed concrete cable.

[0006] In particular, the following phenomena of local degradation of the external protective sheath are commonly observed in practice: localised voluntary opening of the sheath, to check the condition of the cables or the filling material, vandalism following an intrusion into the structure, longitudinal and / or transverse cracking of the material constituting the sheath, due for example to friction between two sheaths, local accidental tearing of the sheath, following the passage of prestressing cables, assembly of a defective protective sleeve around the sheath, non-compliant longitudinal end-to-end assembly of sheaths.

[0007] However, a defect in the mechanical integrity and / or sealing of the external protective sheath of the concrete prestressing cable is likely to cause corrosion and rapid oxidation of the strands, even if this defect is very localized. Such a defect therefore requires rapid intervention by the personnel responsible for the inspection and maintenance of the structure.

[0008] Document FR 2.911.382 A1 discloses a repair method comprising the following steps: positioning by winding around the sheath two end heating resistors, positioning, around the sheath and over the end heating resistors, a first portion of sleeve made of polymer material and a second portion of sleeve made of polymer material, the two said sleeve portions together forming a cylindrical sleeve, the said first portion having an injection socket, welding by electrofusion of the end heating resistors with the two sleeve portions by applying an electric current to the terminals of the end heating resistors. General description of the invention

[0009] In view of the above, there is a need for an improved method for repairing a protective sheath of a prestressing cable, for example a concrete prestressing cable. The repair method must be efficient and reliable, and its implementation must be simple and rapid, so that damage can be treated even in areas that are difficult to access.

[0010] The desired prestressing cable sheath repair process must be able to be implemented safely by the personnel responsible for the work.

[0011] The quality and watertightness of the duct repair must be guaranteed, so as to ensure the mechanical integrity and durability of the structure.

[0012] There is also a need for a versatile repair process, adaptable to a wide variety of prestressing cables regardless of their dimensions, specific materials, etc.

[0013] To meet these different needs, a first aspect of the invention relates to a method for repairing a damaged area of ​​a sheath of a prestressing cable, the prestressing cable comprising at least one strand extending substantially along a longitudinal axis, the method comprising the following steps: positioning, by winding around the sheath, two end heating resistors respectively on either side of the damaged area to be repaired, positioning, around the strand and over the end heating resistors, a first portion of sleeve made of polymer material and a second portion of sleeve made of polymer material, the two said sleeve portions together forming a cylindrical sleeve, said first portion or said second portion having a vent socket comprising a welded sleeve, said first portion or said second portion having an injection socket comprising an additional welded sleeve, electrofusion welding of the end heating resistors with the two sleeve portions by applying an electric current to the terminals of the end heating resistors, extrusion welding of the first sleeve portion with the second sleeve portion,so as to form a cylindrical sleeve around the damaged area, so as to allow the subsequent injection of a filling material inside the cylindrical sleeve thus formed via the injection port, in the vicinity of the damaged area of ​​the prestressing cable, so as to repair the sheath of the prestressing cable.

[0014] The innovative sheath repair method according to the invention has the advantage of allowing rapid and reliable repair of a damaged area of ​​a prestressing cable sheath. A perfect seal is obtained between the cylindrical sleeve made of polymer material and the various components of the prestressing cable, which ensures the durability and mechanical integrity of the cable, particularly in the repaired area.

[0015] Furthermore, the innovative method according to the invention ensures the cohesion of the assembly after repair, since the radial expansion or retraction of the repaired area and the radial expansion or retraction of the rest of the prestressing cable are substantially identical.

[0016] Furthermore, the method of the invention is capable of treating damage even for prestressing cables located in areas that are difficult to access.

[0017] Optional features of the repair method according to said first aspect of the invention, not limiting to the scope of the invention, are the following considered alone or in any technically possible combination: the first sleeve portion and / or the second sleeve portion are formed from polyethylene or polypropylene. the electrofusion welding comprises, for each end heating resistor, connecting a welding machine to the connection lugs of said end heating resistor. the electrofusion welding comprises, for each end heating resistor, heating said end heating resistor to an electrofusion temperature of between 190 degrees Celsius and 230 degrees Celsius. the electrofusion welding comprises, for each end heating resistor, cooling said end heating resistor for a predetermined cooling time. the vent port and / or the injection port comprises a socket welded by polyfusion to the polymer material of the cylindrical sleeve.the step of injecting the filling material comprises an injection of a concrete grout and / or an injection of a petroleum wax. the repair method comprises an additional step of plugging the vent outlet using a first plug and / or plugging the injection outlet using a second plug, subsequent to the injection of the filling material.

[0018] A second complementary aspect of the present invention relates to an assembly for repairing a prestressing cable sheath having a degraded area, comprising: a first sleeve portion made of polymer material, in the shape of a cylinder sector, comprising one of a vent outlet or an injection outlet, a second sleeve portion made of polymer material, in the shape of a cylinder sector, comprising the other of a vent outlet or an injection outlet, configured to be assembled with the first sleeve portion and thus form a cylindrical sleeve, at least two end heating resistors, configured to be wound around a longitudinal axis of extension of a prestressing cable sheath, below the first sleeve portion and the second sleeve portion.

[0019] Optional and non-limiting technical characteristics of the repair assembly according to this second aspect of the invention are the following, considered alone or in any technically possible combination: the repair assembly is provided for implementing a method for repairing a prestressing cable sheath according to the first aspect of the invention as defined above. the cylindrical sector of the first sleeve portion extends over a circumference interval of between 50% and 90% of a total circumference of the cylindrical sleeve. the cylindrical sector of the second sleeve portion extends over a circumference interval of between 10% and 50% of the total circumference of the cylindrical sleeve. at least one lateral edge of the first sleeve portion has a chamfer. at least one complementary lateral edge of the second sleeve portion has a chamfer complementary to the chamfer of the lateral edge of the first sleeve portion. at least one of the end heating resistors comprises a grid resistor.the outer diameter of the wall of the first cuff portion and / or the wall of the second cuff portion is between 90 millimeters and 200 millimeters. the thickness (along a plane perpendicular to the longitudinal axis) of the first cuff portion and / or the second cuff portion is between 6.0 millimeters and 12 millimeters. the length (along the longitudinal axis) of the first cuff portion and / or the second cuff portion is between 300 millimeters and 2000 millimeters. General description of the figures

[0020] Other aims and advantages of the invention will emerge on reading the detailed description below, which is supplemented by the figures annexed below which are given for illustrative and non-limiting purposes, among which, in addition to the Figure 1 introduced above: [ Fig.2 ] There Figure 2 schematically represents, for illustration purposes, two examples of types of degradation that can be observed at the level of the sheath of a prestressing cable. Fig.3 ] There Figure 3 is a schematic perspective view of the first portion and the second portion of a cylindrical sleeve, which belong to a cable sheath repair assembly according to an exemplary embodiment. Fig.4 ] There Figure 4 is a schematic view in longitudinal section of the first portion and the second portion of said cylindrical sleeve, before the positioning of said cylindrical sleeve on a prestressing cable sheath at a degraded area. Fig.5 ] There Figure 5 is a schematic cross-sectional view (along plane BB of the Figure 4 ) of said first portion and second portion of sleeve, said view showing longitudinal welding zones as well as a filling material injection point. Fig.6 ] There Figure 6 is a schematic view in longitudinal section of the cable and of the first portion and the second portion of said cylindrical sleeve, after positioning of said cylindrical sleeve at the level of the degraded zone of the cable, and before electrofusion welding of the end resistors. Fig.7 ] There Figure 7 is a schematic view in longitudinal section of the cable and the cylindrical sleeve, after electrofusion welding of the resistors with the sleeve and the sheath. Fig.8 ] There Figure 8 is a schematic cross-sectional view (along plane BB of the Figure 7 ) of the cable and the cylindrical sleeve, prior to the injection of filling material aimed at restoring the sheath of the prestressing cable. Fig.9 ] There Figure 9 is a schematic cross-sectional view (along plane BB of the Figure 7 ) of the cable and the sleeve, illustrating the result after filler injection. [ Fig.10 ] There Figure 10 represents, in a perspective view, a prestressing cable at the end of the repair process of its external sheath. Detailed description of embodiments of the invention

[0021] The following description concerns the repair of a prestressing cable sheath (in particular an external concrete prestressing cable), using a sleeve constituting a tubular envelope placed at the level of the damaged area.

[0022] It will be understood that the invention can be applied, with the same advantages, to any type of external or additional prestressing cable (concrete or non-concrete), stay cable, etc. Damage to the external sheaths of prestressing cables

[0023] For illustrative purposes, the Figure 2 attached, two examples of prestressing cables 1 whose respective external protective sheaths 2 have a degraded area requiring rapid repair.

[0024] The prestressing cable shown on the upper part of the Figure 2 has a degraded zone Z, at the level of a voluntary rectangular opening. This opening could have been made, for example, to check the condition of the strands, and / or the condition of the filling material between the strands and the sheath.

[0025] The prestressing cable shown on the lower part of the Figure 2 presents, for its part, a degraded zone Z' at the level of a transverse crack in the external sheath. This crack could have been created by friction between two cable protection sheaths.

[0026] In the two examples illustrated, some metal strands 5 are exposed to the external environment, due to the deterioration and partial degradation of the external sheath 2. More generally, many types of degradation of the cable sheath can occur (vandalism, accidental tearing of the sheath, etc.)

[0027] The integrity and mechanical functionality of the prestressing cable 1 are called into question. Such alteration of the outer sheath 2 requires rapid action, otherwise the strands 5 are exposed not only to external damage and impacts, but also to corrosion. Surface and in-depth treatment is necessary.

[0028] Below we describe and illustrate in relation to the Figures 3 à 10 attached a method and device for repairing a sheath according to an example. - Cylindrical repair sleeve

[0029] The repair of the sheath 2 at the level of zone Z (or Z') is carried out by the installation of a sleeve of generally cylindrical shape, assembled by welding to the sheath 2, allowing the subsequent injection of a filling material 4.

[0030] Here we describe, in relation to the view of the Figure 3 and according to an exemplary embodiment, the elements of a repair device comprising the unassembled sleeve.

[0031] There Figure 4 is a schematic view in longitudinal section of the first portion 1A and the second portion 1B of said sleeve, before the positioning of said sleeve on a prestressing cable sheath, and the Figure 5 is a schematic cross-sectional view of said sleeve along the section plane BB indicated on the Figure 4 .

[0032] The repair device comprises a first cuff portion 1A and a second cuff portion 1B initially dissociated, intended to be assembled together, and to be assembled to the sheath. Preferably, the first portion 1A and the second portion 1B are both formed from a polymer material, even more preferably from polyethylene or polypropylene.

[0033] If the selected material is polyethylene, the material preferably complies with the French standard NF 114 and / or the European standard NF EN 12201 managed by AFNOR.

[0034] The geometry of the first portion 1A and the second portion 1B is designed to form, after assembly, a substantially cylindrical sleeve that can be placed around the sheath 2 and then welded. Here, each of the two portions 1A and 1B forms a cylinder sector extending parallel to a longitudinal axis L. Preferably, the first portion 1A and / or the second portion 1B have symmetry with respect to a transverse median plane, perpendicular to the longitudinal axis L.

[0035] It is preferable that the cylindrical sector of the first portion 1A extends over an interval whose circumference is between 50% and 90% of the total circumference of the cylindrical sleeve around the axis L, and / or that the cylindrical sector of the second portion 1B extends over an interval of circumference between 10% and 50% of said total circumference of the sleeve. In the present example, the first portion 1A covers 80% of said total circumference, and the second portion 1B covers 20% of said total circumference.

[0036] The dimensions of the first portion 1A and the second portion 1B are advantageously selected according to the dimensions of the sheath 2 of the prestressing cable. By way of non-limiting example, the dimensions may be as follows: The outer diameter of the wall of the first portion 1A and / or of the wall of the second portion 1B, in a radial direction orthogonal to the longitudinal axis L, is preferably between 90 millimeters and 200 millimeters; The thickness of the wall of the first portion 1A and / or of the wall of the second portion 1B, in a plane orthogonal to the longitudinal axis L, is preferably between 6.0 millimeters and 12 millimeters; The axial length of the wall of the first portion 1A and / or of the wall of the second portion 1B, parallel to the longitudinal axis L, is preferably between 30 centimeters (300 millimeters) and 2 meters (2,000 millimeters).

[0037] The two sleeve portions 1A and 1B are designed to allow, after the welds, the injection and circulation of a filling material (preferably concrete grout, and / or petroleum wax) inside the formed cylindrical sleeve. An annular space 6 is formed between the inner surfaces of the two sleeve portions 1A and 1B on the one hand, and the outer sheath 2 on the other hand. This space can be filled with the filling material. To allow the injection, one of the sleeve parts 1A or 1B comprises a vent outlet 7, and the other sleeve part 1A or 1B comprises an injection outlet 8.

[0038] In the present example, the mechanical structures of the vent port 7 and the injection port 8 are similar. The port 7 which is located upstream of the prestressing sheath during injection serves as the “vent port” and the port 8 which is located downstream of the prestressing sheath during injection serves as the “injection port”.

[0039] Here, the injection socket 8 is located in the low position on the first portion 1A intended to be placed at the bottom of the sheath 2, and the vent socket 7 is located in the high position on the second portion 1B intended to be placed at the top of the sheath 2.

[0040] Each of the two sockets 7 and 8 preferably comprises a hollow cylindrical sleeve 10, of small dimensions (for example a few millimeters long). The sleeve 10 is fixed on the outer surface of the corresponding sleeve part, and extends axially outwards. The sleeve 10 is for example formed from polyethylene or polypropylene.

[0041] Each sleeve 10 defines a respective passage channel 12, opening on the inner side of the sleeve parts 1A and 1B, allowing passage of air or filling material.

[0042] Each socket 10 has preferably been polyfusion welded to the polymer material of the cylindrical sleeve, as shown in FIG. Figure 3 .

[0043] Furthermore, the sleeve portions 1A and 1B preferably have a chamfer, intended to facilitate the longitudinal extrusion welding of said two sleeve portions. At least one lateral edge of the first portion 1A has a chamfer edge (angled cut). The lateral edge opposite the second portion 1B then has another complementary angled cut. The two angled cuts form a chamfer 13 between them.

[0044] Preferably, each of the two side edges of the sleeve portion 1A has a chamfer edge, and the edges of the sleeve portion 1B have a complementary chamfer edge, as illustrated in Figure 5 . - End heating resistors

[0045] As illustrated on the Figures 3 à 5 attached, the prestressing cable sheath repair device comprises, in addition to the cylindrical sleeve parts described above, at least two end heating resistors 3.

[0046] The heating resistors 3 are intended to be welded by electrofusion with the cylindrical sleeve, and with the external sheath 2 comprising the degraded zone Z to be repaired.

[0047] The heating resistors 3 are designed to be placed radially around the sheath 2 to be repaired, and below the two sleeve parts 1A and 1B, in order to carry out electrofusion welding. Preferably, the resistors are continuous and do not have any breakage, in order to allow homogeneous electrofusion welding on the sheath 2.

[0048] Advantageously, the heating resistors 3 are formed by grid resistors. Thus, with reference to the Figure 3 , each heating resistor 3 here comprises an annular surface in a grid with metal crosspieces, intended to increase in temperature.

[0049] Each heating resistor 3 also comprises here a transverse attachment clip 18, as well as a pair of connection lugs 19 with an automaton to ensure the temperature rise of said resistors.

[0050] The heating resistors 3 are designed not to pass under the vent outlet 7 of the cylindrical sleeve, nor under the injection outlet 8, so that said resistors are not blocked during the injection of the filling material. - Pre-stressing cable sheath repair process

[0051] The steps of a method for repairing a prestressing cable sheath (here an external prestressing cable) are described below by way of illustration, according to a possible example of embodiment. This repair method is for example implemented using a sheath repair assembly comprising a first sleeve part 1A, a second sleeve part 1B and two end heating resistors 3 as described above.

[0052] In the present example, prior to the installation of the two sleeve parts 1A and 1B and the heating resistors 3, two sockets 10 have already been welded respectively on the first sleeve part 1A and on the second sleeve part 1B, in order to form an injection port 8 and a vent port 7. This welding of the sockets 10 has preferably been carried out by polyfusion.

[0053] Alternatively, the vent and injection ports could be formed on the sleeve following the positioning of the sleeve parts 1A and 1B on the outer sheath 2 to be repaired.

[0054] The process of repairing the degraded zone Z of the outer sheath 2 begins here by positioning, by winding around the outer sheath 2, the two end heating resistors 3. The heating resistors 3 are here grid resistors.

[0055] The two heating resistors 3 are positioned on either side of the zone Z. A first resistor 3 is positioned axially upstream of the zone Z (along the longitudinal axis L) and a second resistor 3 is positioned axially downstream of the zone Z. In addition, the first resistor 3 is positioned upstream of the location of the vent outlet 7, and the second resistor 3 is positioned downstream of the location of the injection outlet 8. Preferably, the respective meshed annular sectors of the two resistors 3 extend all around the outer sheath 2.

[0056] Then, the first sleeve portion 1A and the second sleeve portion 1B are positioned around the prestressing cable. The two sleeve portions 1A and 1B are intended to cover the outer sheath 2 (here at the level of the degraded zone Z) and to cover the two heating resistors 3.

[0057] The left and right axial edges of the first sleeve part 1A are aligned with the left and right axial edges of the second sleeve part 1B. Thus, the sheath 2 is encircled by the first sleeve part 1A (here placed at the bottom) and by the first sleeve part 1B (here placed at the top).

[0058] We have represented, on the Figure 6 attached, a longitudinal sectional view of a prestressing cable 1 after positioning the two heating resistors 3 and the two sleeve parts 1A and 1B. In this example, the first sleeve part 1A which includes the injection socket 8 is assembled on the cable 1 from below, and the second sleeve part 1B which includes the vent socket 7 is assembled on the cable 1 from above.

[0059] The two sleeve portions 1A and 1B together form a cylindrical sleeve 9 which surrounds the outer sheath 2 of the prestressing cable.

[0060] Furthermore, the two sleeve portions 1A and 1B provide an annular space 6 between the lateral outer surface of the sheath 2 and the inside of the sleeve. As illustrated in the Figure 6 , the annular space 6 and the void at the level of the strands 5 are intended to be closed by the subsequent injection of the filling material via the injection port 8, while allowing air to be expelled at the level of the vent port 7.

[0061] The sheath repair process continues by electrofusion welding the end heating resistors 3 with each of the two sleeve portions 1A and 1B. Electrofusion welding is carried out by applying an electric current to the terminals of the heating resistors 3, while the latter are in contact with the sleeve portions 1A and 1B made of polymer material. Electrofusion welding makes it possible to secure each of the heating resistors 3 on the one hand with the outer sheath 2, and on the other hand with each of the two sleeve portions 1A and 1B.

[0062] In the present example, the electrofusion welding is carried out as follows, successively on one then the other of the heating resistors 3. A welding machine is first connected to the terminals of the heating resistor 3, for example via the connection tabs 19 of the resistor 3. The welding is preferably carried out in an accessible position.

[0063] Then, an electric current is applied to the terminals of said resistor, the intensity of which is controlled so as to obtain a sufficient electrofusion temperature. The selected electrofusion temperature is preferably between 190 degrees Celsius and 230 degrees Celsius to achieve a durable weld without damaging the sleeve or the sheath. Due to the axial positioning of the heating resistors 3, the electrofusion weld does not block the vent and injection ports.

[0064] Finally, after disconnecting the welding machine, the heating resistors 3 are left to cool for a predetermined cooling time at the end of the welding, for example a cooling time of more than 10 minutes.

[0065] We have represented, on the Figure 7 attached, a longitudinal sectional view of the prestressing cable 1 and the sleeve 9 at the end of the step of electrofusion welding of the two heating resistors 3 with the sleeve and with the outer sheath of the cable. The heating resistors are melted into the mass of the sheath 2 and the sleeve portions 1A and 1B. The sheath repair method continues here by longitudinal extrusion welding of the first sleeve portion 1A with the second sleeve portion 1B, so as to form a sleeve 9 (preferably cylindrical) around the degraded zone Z of the sheath 2. As described above, preferably, the longitudinal extrusion welding zone is defined by at least one lateral edge of the first portion 1A having a chamfer edge (angled cut) as illustrated in the Figure 5 commented previously. The lateral edge opposite the second portion 1B then preferably has a complementary angle cut, so as to define a chamfer 13 along the axis L. The longitudinal extrusion weld is then carried out along the two lateral edges opposite, forming welds 11, here at the level of the chamfers 13.

[0066] Preferably, two chamfers 13 are defined on both sides, on the two pairs of lateral edges opposite the two sleeve portions 1A and 1B. The welds 11 produced fuse the two sleeve portions 1A and 1B to form the cylindrical sleeve 9. These welds are preferably also produced in an accessible position.

[0067] Preferably, the two longitudinal extrusion welds are implemented as follows. An extruder, preferably equipped with a welding shoe (for example made of Teflon) corresponding to the desired weld profile, is used to crush the extrusion material. Thus, under the effect of heat and crushing, the extrusion material melts into the thicknesses of the two sleeve portions 1A and 1B. The extrusion weld is preferably carried out from one axial end of the two sleeve portions, to the other end, along the entire lateral edges to be welded together. A final sanding can finally be carried out, to improve the finish of the weld and to allow a visual check of the quality of the weld. It is shown on the Figure 8 attached is a longitudinal sectional view of the cable 1 and the sleeve 9 produced at the end of the longitudinal extrusion welding step. The various welds produced at this stage have not closed the annular space 6.

[0068] It will be noted that, alternatively, the step of welding by longitudinal extrusion of the lateral edges of the sleeve portions 1A and 1B could be implemented before the step of welding by electrofusion of the heating resistors 3.

[0069] The two stages of welding the resistors by electrofusion, and of welding the lateral edges of the shells by longitudinal extrusion, are carried out before filling the interior of the sleeve.

[0070] The method of repairing the sheath 2 continues here with the step of injecting a filling material 4, into the degraded zone Z and into the space 6 formed between the sheath 2 and the inside of the sleeve 9.

[0071] Preferably, the filling material used comprises a concrete grout and / or a petroleum wax. Any other filling material known to the person skilled in the art in the field of prestressing cable sheath repairs may be used.

[0072] It will be noted that the step of injecting the filling material can be implemented either immediately after the completion of the electrofusion and extrusion welds, or later. Before said injection, the degraded zone Z is temporarily protected from atmospheric corrosion by the contact of the sleeve 9; however, it is very preferable to inject a filling material to complete the repair of the cable sheath.

[0073] The injection is advantageously carried out via the injection port 8, preferably from below. The injected filling material 4 gradually fills the annular space 6 until it fills the internal volume of the degraded zone Z. A volume of repair material 14 is formed at the location where the degraded zone Z was located, below the internal surface of the sleeve 9. During the injection, the air is expelled towards the vent port 7, which acts as a purge.

[0074] The injection of the filling material 4 is preferably carried out by operators authorized to install and maintain prestressing. The injection can be carried out under a predetermined pressure selected according to the chosen operating mode.

[0075] Finally, preferably, it is possible to plug the vent outlet 7 and / or to plug the injection outlet 8 using a plug closing the corresponding passage channel 12. The plugs 15 used here are tapped and threaded plugs.

[0076] We have represented, on the Figures 9 et 10 attached, the result after the injection of the filling material, at the end of the cable sheath repair process. Certain strands 5, previously exposed to the outside atmosphere, are now protected from atmospheric corrosion thanks to the repair implemented.

[0077] Furthermore, there is a continuity of material between the sheath 2 and the sleeve 9, making it possible to avoid differential shrinkage or differential expansion between the sheath and the sleeve.

Claims

1. Method for repairing a degraded zone (Z) of a sheath (2) of a prestressed wire, the prestressed wire comprising at least one strand (5) extending substantially along a longitudinal axis (L), the method comprising the following steps: - positioning, by means of winding them around the sheath (2), two end heating resistors (3) on either side of the degraded zone (Z) to be repaired, respectively, - positioning, around the sheath (2) and over the end heating resistors (3), a first sleeve portion (1A) made of polymer material and a second sleeve portion (1B) made of polymer material, the two sleeve portions together forming a cylindrical sleeve tube, said first portion (1A) or said second portion (1B) having a vent connector (7) comprising a welded bushing (10), said first portion (1A) or said second portion (1B) having an injection connector (8) comprising an additional welded bushing (10), - electrofusion-welding the end heating resistors (3) to the two sleeve portions (1A, 1B) by applying an electric current to the terminals of the end heating resistors (3), - extrusion-welding the first sleeve portion (1A) to the second sleeve portion (1B) so as to form a cylindrical sleeve tube around the degraded zone (Z) to allow subsequent injection of a filling material (4) via the injection connector (8) inside the cylindrical sleeve tube (9) formed, in the vicinity of the degraded zone (Z) of the prestressed wire, so as to repair the prestressed wire sheath (2).

2. Repair method according to claim 1, wherein the first sleeve portion (1A) and the second sleeve portion (1B) are formed from polyethylene or polypropylene.

3. Repair method according to either claim 1 or claim 2, wherein electrofusion welding comprises, for each end heating resistor (3): - connecting an automatic welding machine to the connection lugs (19) of said end heating resistor (3); - heating said end heating resistor (3) to an electrofusion temperature of between 190 degrees Celsius and 230 degrees Celsius; - cooling said end heating resistor (3) for a predetermined cooling time.

4. Repair method according to any of claims 1 to 3, wherein the vent connector (7) and / or injection connector (8) comprises a bushing (10) which is polyfusion-welded to the polymer material of the cylindrical sleeve tube.

5. Repair method according to any of claims 1 to 4, wherein the step of injecting filling material (4) comprises injecting a concrete grout and / or injecting a petroleum wax.

6. Repair method according to any of claims 1 to 5, comprising an additional step of resealing the vent connector (7) by means of a first end cap (15) and / or resealing the injection connector (8) by means of a second end cap after injecting the filling material.

7. Assembly for repairing a prestressed wire sheath (2) having a degraded zone (Z), the repair assembly comprising: - a first sleeve portion (1A) which is made of polymer material, in the shape of a cylinder sector, and comprises one of a vent connector (7) or an injection connector (8), - a second sleeve portion (1B) which is made of polymer material, in the shape of a cylinder sector, comprises the other of a vent connector (7) or an injection connector (8), and is designed to be assembled with the first sleeve portion (1A) and thus form a cylindrical sleeve tube (9), - at least two end heating resistors (3) which are designed to be wound around a longitudinal axis (L) of extension of a prestressed wire sheath (2), below the first sleeve portion (1A) and the second sleeve portion (1B), the prestressed wire sheath repair assembly being intended to implement a prestressed wire sheath repair method according to any of claims 1 to 6.

8. Wire sheath repair assembly according to claim 7, wherein the cylindrical sector of the first sleeve portion (1A) extends over a circumferential range of between 50% and 90% of a total circumference of the cylindrical sleeve tube, and wherein the cylindrical sector of the second sleeve portion (1B) extends over a circumferential range of between 10% and 50% of the total circumference of the cylindrical sleeve tube.

9. Wire sheath repair assembly according to either claim 7 or claim 8, wherein at least one side edge of the first sleeve portion (1A) has a chamfer (13), and wherein at least one complementary side edge of the second sleeve portion (1B) has a complementary chamfer.

10. Wire sheath repair assembly according to any of claims 7 to 9, wherein the end heating resistors (3) comprise grid resistors.