JP2007032154A - Protective sheath for pc steel material and coated pc steel material using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent, with reliability, a PC steel material from being corroded by a protective sheath by improving the airtightness of the protective sheath. <P>SOLUTION: The protective sheath 1 for PC steel material is formed by applying a resin coating 3 onto the outer surface of a bendable and stretchable metal tube 2 having pleats on the surface thereof. The PC steel material is covered by the protective sheath 1 for PC steel material to prevent the PC steel material from being corroded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a protective sheath for reliably preventing corrosion of PC steel used for reinforcing concrete and a coated PC steel combined with the sheath.

  For example, in a post-stressed concrete post-tension method, a sheath is disposed in a mold before placing concrete, and after placing the concrete, a PC steel material is inserted into the sheath to be tensioned and fixed. A filler such as cement milk is injected between the sheath and hardened to adhere and integrate the PC steel and concrete.

  The sheath employed in this method includes a metal sheath and a resin sheath made of polyethylene, polypropylene, or the like. The former metal sheath is a flexible tube made by winding a galvanized band iron in a spiral and mechanically caulking the seam, and is most frequently used. Moreover, the latter resin sheath is disclosed by the following patent documents 1-3.

  Since the durability of the PC structure depends greatly on the durability of the PC steel as a reinforcing material, it is important that the PC steel that reinforces the concrete be treated so as not to rust.

  In the post-stressed concrete post-tension method, as described above, the PC steel material inserted into the sheath is tensioned and fixed, and then a filler is injected between the PC steel material and the sheath. As a result, the PC steel material is protected by the sheath and the filler. However, it is not easy to fill the narrow space between the PC steel material and the sheath with a filler such as cement milk without any gaps. The probability of being able to do is high. Therefore, it is necessary to consider the corrosion protection of PC steel mainly with the sheath.

  However, the above-described conventional metal sheath is not hermetically sealed at the seam of the band iron, and therefore, corrosion factors such as rainwater may flow into the interior from the seam and corrode the PC steel material. In addition, since the existing sheath is used by connecting a standard product, the inflow of moisture from the connecting portion can be considered, and the reliability of corrosion prevention is low.

  In addition, the resin sheath has no joints but has a problem in strength, and there is a concern that the resin sheath may be broken due to a catch of an external member. In addition, polyethylene and the like are gas permeable and cannot completely block the permeation of water vapor.

Although it can be easily considered that the outer periphery of the metal sheath is coated with a synthetic resin to provide airtightness, as described above, polyethylene and the like are gas permeable, and thus better anticorrosion properties are required. If this is the case, this method will be insufficient.
JP-A-1-260083 Japanese Patent Publication No. 6-136883 Japanese Patent Publication No. 9-144210

  An object of the present invention is to improve the airtightness of the protective sheath and to reliably prevent corrosion of PC steel by the protective sheath.

  In order to solve the above problems, in the present invention, a resin coating is applied to the inner surface, the outer surface, or both the inner and outer surfaces of a metal tube that has a pleated surface and can be bent and stretched and is sealed without gaps at both ends. Thus, a protective sheath for PC steel was constructed.

  The metal pipe is preferably a welded pipe that is easy to produce a coated PC steel material. In terms of cost, a tube in which an anticorrosion plating layer is provided on the surface of a tube formed of an iron-based material is preferable.

  Further, the resin coating is preferably made of a thermoplastic resin such as polyethylene or polypropylene.

  The present invention provides a coated PC steel material in which a PC steel material is coated with the above-described protective sheath for PC steel material composed of a metal tube and a resin coating, or a delayed curable material in a void portion in the protective sheath after the PC steel material is coated with the protective sheath. Coated PC steel filled with is also provided. The delayed curable material used may be a delayed curable resin or a cement grout to which a setting retarder is added.

  Since the protective sheath of the present invention includes the metal tube, there is no fear of breaking, and rain water and water vapor can be reliably prevented from entering. Furthermore, since the outer surface, inner surface, or both inner and outer surfaces of the metal tube are covered with resin, the corrosion resistance performance due to the presence of holes due to the corrosion of the metal tube, which can be considered when using inexpensive iron-based materials, is remarkable. The decrease is also suppressed.

  Further, the metal pipe uses a pipe (corrugated pipe) which is given flexibility by attaching a fold to a welded pipe or the like, and can be wound around a drum. Therefore, it is also possible to supply a long sheath that is continuous in the longitudinal direction without a connecting portion.

  The metal tube constituting the protective sheath of the present invention may be a seamless tube. However, the seamless tube needs to be inserted into the tube after the tube is manufactured, and the long coated PC steel material is manufactured. Becomes difficult. On the other hand, the welded pipe can produce the pipe while putting the PC steel inside, and has an effect of facilitating the production of the long coated PC steel.

  Further, when a thermoplastic resin is used as the coating resin, continuous coating by an extruder advantageous in terms of productivity can be performed.

  1 and 2 show an embodiment of a protective sheath for PC steel material according to the present invention. The protective sheath 1 for PC steel material of FIG. 1 is configured by providing a pleat on the pipe surface and providing a resin coating 3 on the outer surface of the pleated metal pipe 2. Further, the protective sheath 1A for PC steel material in FIG. 2 is configured by providing resin coatings 3 and 4 on both the inner and outer surfaces of a metal tube 2 having the same configuration as in FIG.

  The metal pipe 2 is a welded pipe with no gap formed by bending the metal sheet in the width direction while continuously flowing the metal sheet and butting both side edges of the sheet and welding the seam with a seam welding machine. It has been. When pleats 5 (undulations such as waves) are formed on the tube surface of the metal tube 2 at a constant pitch in the longitudinal direction with a molding machine, and then a thermoplastic resin is extruded to the outer periphery of the metal tube 2 with an extruder, the PC of FIG. A protective sheath 1 for steel is obtained. Further, a tube formed of a thermoplastic resin having a heat sealing layer on the outer surface is drawn through the inside of the protective sheath 1 shown in FIG. 1, and the tube is inflated with steam or hot air and attached to the inner surface of the metal tube 2. The protective sheath 1A for PC steel material in which the resin coating 4 is also formed on the inner surface is obtained. If the metal tube 2 is formed of an iron sheet having a corrosion prevention layer (not shown) such as galvanization on the surface, the metal tube 2 can be made at low cost.

  The material of the resin coatings 3 and 4 is preferably a thermoplastic resin such as polyethylene or polypropylene.

  Further, the pleat 5 may be a pleat in which concave and convex portions are alternately and independently arranged in the longitudinal direction. However, the pleat 5 is preferable because it is easier to process continuous pleats forming a spiral. In short, any pleats that can impart flexibility to the metal tube 2 for bending and stretching may be used. The height of the folds 5 and the depth of the valleys are preferably set in consideration of the integration with the concrete to be reinforced. In addition, although the pleat 5 formed in the metal tube 2 shown in the figure has a gentle undulation, it can be considered to have an angular wave.

  FIG. 3 shows an example of the coated PC steel material of the present invention. The coated PC steel material 6 in FIG. 3 is configured by coating a PC steel material (PC steel strand wire in the figure) 7 with the protective sheath 1 for PC steel material in FIG. This coated PC steel material 6 wraps the PC steel material 7 continuously supplied by a metal sheet that is continuously bent while being supplied, and then welds the butt portion of the metal sheet to form a straight metal tube, and then the metal It can be manufactured by pleating the tube and then extruding the resin coating 3 on the outer periphery of the tube with an extruder.

  The coated PC steel material 6 can insert the PC steel material 7 into the protective sheath 1 without any trouble, and can also take up the finished product. Therefore, the long product can be produced without any trouble. It is possible to further enhance the corrosion resistance of the PC steel without the connection part.

FIG. 4 shows a coated PC steel material that is formed by including the delayed-curing material 8 in the coated PC steel material 6 of FIG. The coated PC steel material 6A is made by coating a PC steel material 7 with a protective sheath 1 and then filling a space in the protective sheath 1 with a delayed curable material 8.

  The delayed curable material 8 employs a delayed curable resin such as an epoxy afterbond resin, a cement grout to which a setting retarder is added, or the like according to the use of the coated PC steel material. Cement grout to which the latter setting retarder is added is preferable because it is inexpensive and the effect of integrating the PC steel and cement is high. The setting retarder may be sodium oxycarboxylate, which is employed in the well-known super delayed curable grout. As the cement grout to which a setting retarder is added, a cement grout having good adhesion to the PC steel material 7 is used.

  The delayed curable material 8 may be filled at the site (place where the steel material is applied), or may be pre-filled at the factory, and the completed coated PC steel material 6A may be carried to the site and applied. . After the filling, both ends of the protective sheath 1 are sealed with a cap 9 shown in FIG. 5 to prevent the delayed curable material 8 from flowing out. The cap 9 can be fixed by the tape winding layer 10 or the like.

Half sectional view showing an example of the protective sheath for PC steel of the present invention Half sectional view showing another example of the protective sheath for PC steel of this invention Sectional drawing which shows an example of the covering PC steel material of this invention Sectional drawing which shows the other example of the covering PC steel material of this invention Sectional drawing which shows the process state of the terminal part of the covering PC steel material of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A Protective sheath for PC steel material 2 Metal tube 3, 4 Resin coating 5 Pleed 6, 6A Coated PC steel material 7 PC steel material 8 Delay curable material 9 Cap 10 Tape winding layer

Claims (7)

  A protective sheath for PC steel, which is formed by applying a resin coating to the outer surface, inner surface, or both inner and outer surfaces of a metal tube that can be bent and stretched with a pleat on the surface and is sealed without gaps except for both ends.   The protective sheath for PC steel according to claim 1, wherein the metal pipe is a pipe formed by processing a pleat in a welded pipe.   The protective sheath for PC steel according to claim 1 or 2, wherein the metal tube is a tube formed of an iron-based material and has a corrosion-proof plating layer on a surface thereof.   The protective sheath for PC steel materials in any one of Claims 1-3 which formed the said resin coating with the thermoplastic resin.   A coated PC steel material obtained by coating a PC steel material with the protective sheath for PC steel material according to any one of claims 1 to 4.   A coated PC steel material obtained by coating a PC steel material with the protective sheath for PC steel material according to any one of claims 1 to 4, and further filling a space portion in the protective sheath with a delayed curable material.   The coated PC steel material according to claim 6, wherein the delayed curable material is a cement grout to which a delayed curable resin or a setting retarder is added.

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