JPH0336087B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a metal sheath (also referred to as a duct) used in a prestressed concrete structure constructed by the post-tension method, the so-called post-tension method. The present invention relates to a metal sheath, and more particularly to a metal sheath that takes anti-rust measures, that is, a rust-proof metal sheath.

[Conventional technology]

Recently, measures have been taken to prevent the metal sheath from rusting in prestressed concrete structures by applying a synthetic resin coating layer to the inner and outer surfaces of this type of metal sheath. There is.

In manufacturing this rust-proof metal sheath, the sheath body is usually made by bending the side ends of thin steel strips to form mutually engaged joints, that is, bending seams, as shown in Fig. 1. After the steel strips are joined in the longitudinal direction, that is, in the direction of the tube axis, or are wound spirally and joined, the joined portion is subjected to tooth-shaped plastic deformation, that is, caulking. Thereafter, a synthetic resin coating layer is applied to the inner and outer surfaces of the sheath body by an appropriate method.

However, the rust-proof sheath manufactured by this caulking method has the following problems.

(a) If the coating layer on the outer or inner circumferential surface of the sheath body is thinned, the coating layer will not spread to the seams, resulting in coating defects.
Corrosive ions such as chlorine ions penetrate into the sheath through communication with the vent hole in the joint, corroding not only the sheath body but also the PC steel material within the sheath.

(b) As shown in Figure 2, if the coating layer B on the outer or inner circumferential surface of the sheath body A is made thicker, the defect of poor coating described in (a) above will not occur, but on the other hand, the seam portion C of the sheath body will be Coating layer B is unable to follow the bending deformation, cracking and even peeling of the coating layer occurs, and corrosive ions enter from this area, resulting in the above-mentioned (a).
The result is similar to . Note that forming a thick coating film itself is uneconomical and not practical.

Therefore, when considering the causes in (a) and (b) above,
For sheaths manufactured by caulking means,
It has been found that the above-mentioned problems are caused by the caulked joint having porosity such as pinholes, displacement, and large protrusion height.

[Problem that the invention seeks to solve]

The present invention has been made based on the above findings in order to eliminate the drawbacks of the rust-proof sheaths of the prior art. That is, the present invention requires that the joint portion be airtight, that there is no displacement, or that
The technical problem is to meet the requirement of a small protrusion height and to prevent cracking and peeling of the synthetic resin coating layer.

[Means for solving problems and their effects]

The first rust-proof metal sheath for post-tension construction method of the present invention (hereinafter referred to as the first invention)
will take the following technical measures to achieve the above technical challenges. That is, the sheath body is formed into a hollow tube shape with a seam in which both ends of thin-walled steel strips are continuously and airtightly joined to each other by welding or adhesive, and the seam is free from polymerization other than the butt joint. The protruding height of the sheath body is made as small as possible, and a synthetic resin coating layer is applied to the outer surface or inner and outer surfaces of the sheath body.

Here, the shape of the sheath main body may be a hollow tubular shape, and includes a circular tubular shape, a box-tubular shape, and other shapes. The seams of the sheath body are joined by bending, overlapping, or butting. Furthermore, welding also includes brazing. Furthermore, for the synthetic resin coating layer applied to the outer or inner surface of the sheath body, a material is selected that ensures the elasticity of the sheath body and is resistant to the alkalinity of concrete. As such a material, for example, epoxy resin, vinyl chloride resin, or furan resin is suitable.

The first invention has the following effects due to the above configuration.

The seams are continuously joined together, so
There is no shift or movement in this area, and there is no cracking or peeling of the synthetic resin coating layer, and the rust prevention effect is high.

The seam is airtightly joined, there is no discontinuity, and the protrusion height is as small as possible, so the thickness of the synthetic resin coating layer can be made thinner, which is not only economical, but also The toughness (resistance to cracking) of the sheath itself is increased, giving the sheath effective properties.

The first invention adopts the following embodiments.

Forming a seam in the sheath body in the longitudinal direction, that is, in the tube axis direction of the sheath. In this embodiment, the seams are joined by bending, overlapping, or butting. Further, this aspect is particularly effective when the sheath body has a box-tube shape.

Forming the seam of the sheath body in a spiral shape. The means for joining the seams in this embodiment is the same as described above. Moreover, this aspect is particularly effective when the sheath is cylindrical.

The sheath body has corrugated ribs or protrusions that bulge outward.
The ribs provide flexibility and appropriate rigidity (strength against impact or crushing) to the sheath, and also increase adhesion to concrete.

The sheath body has a spiral rib that bulges outward. The function of the rib is as described above.

Second rust-proof metal sheath for post-tension construction method of the present invention (hereinafter referred to as the second invention)
In addition to the configuration of the first invention,
A configuration is adopted in which a component is added in which a solid lubricant coating is applied to the inner surface of the sheath body.

Here, the solid lubricant coating applied to the inner surface of the sheath body has rust prevention properties by itself, and reduces the sliding friction resistance that occurs between the inner surface of the sheath and the PC steel material when the prestressing steel material is tensed. The material is selected. Such materials include polytetrafluoroethylene resin (hereinafter referred to as PTEE), a binder,
Alternatively, compositions of PTEE and soft metals and/or metal sulfides and binders are used.

Due to this configuration, the second invention has the following effects in addition to the effects of the first invention.

The solid lubricant coating has a good rust prevention effect by itself, and also exhibits an even better rust prevention effect in cooperation with the synthetic resin coating layer.

Due to the lubricating action of the solid lubricating film, tensioning of the prestressing steel material is performed smoothly, and therefore, direct contact between the metal sheath body and the prestressing steel material is suppressed as much as possible.
Metal corrosion caused by local current generated at the contact portion can be suppressed.

Third rust-proof metal sheath for post-tension construction method of the present invention (hereinafter referred to as the third invention)
has the same structure as the first invention, but the inner and outer surfaces of the sheath body are surface-treated with a phosphate coating, and a synthetic resin coating layer is applied on the phosphate coating, and A structure in which a solid lubricant film is applied on a synthetic resin coating layer on the inner surface of the sheath body is added to each component.

Here, the phosphate coating has a thickness that does not impair the elasticity of the sheath body, and is coated on the inner and outer surfaces of the sheath body. Further, the selection of the material for the synthetic resin coating layer and the selection of the material for the solid lubricant film are in accordance with the configurations of the first and second inventions.

Due to this configuration, the third invention has the following effects in addition to the effects of the first invention.

The phosphate coating adheres firmly to the metal sheath body and is easy to process. Furthermore,
The anticorrosion effect of the phosphate coating is not easily affected by chemical effects, and the effect is sustained over a long period of time, making it suitable as a material for use in concrete structures.

Since the synthetic resin coating is applied to the inner and outer surfaces of the metal sheath via the phosphate coating, the adhesion of the synthetic resin coating layer to the sheath is good in terms of strength. In addition, it has a compensating function in case a pinhole is generated during the chemical conversion treatment of the phosphate film, and provides multiple protection against corrosion from the outer surface of the sheath body.

〔Example〕

Examples of the rust-proof metal sheath for post-tension construction according to the present invention will be described below.

The main body of the metal sheath is made of a thin band steel plate, and is formed into a hollow tube by bending the steel plate into a cylindrical or box-tube shape, or by winding it spirally.

3 to 5 show a metal sheath main body H manufactured by spirally winding thin-walled steel strips and joining the side ends by welding.

FIG. 3 shows a mode in which the side end portions of the steel strips 1 are overlapped and joined by fillet welding 2A. Moreover, FIG. 4 shows a mode in which the side ends of the steel strips 1 are brought into contact with each other and joined by butt welding 2B.
Furthermore, FIG. 5 shows an embodiment in which the joints are joined by fillet welding 2C along the sides of the folded seams.

In these embodiments, the weld is applied continuously and airtight at the joint. The ones in FIGS. 3 and 5 form a superimposed joint, but it should be noted that the protrusion height is kept as small as possible. Reference numeral 11 denotes a rib protruding from the outer surface of the sheath body H and provided in a spiral shape.

Further, instead of welding, it is also possible to adopt an embodiment in which the steel strips are joined using an adhesive.

The outer surface or inner and outer surfaces of the metal sheath body are appropriately surface-treated with a phosphate coating. The phosphate coating is chemically treated by an appropriate method such as a manganese phosphate method, a zinc phosphate method, or an iron phosphate method, but the rust prevention property is further improved by applying a post-treatment method using the enzyurion method. It is something. The thickness of this film is suitably about 5 to 10 microns, and the film can be formed by any appropriate means such as dipping or spraying.

The phosphate coating adheres firmly to the metal sheath body and is easy to process. Furthermore, the rust-preventing effect of the phosphate coating is resistant to chemical effects, and this effect is sustained over a long period of time, making it suitable as a material for use in concrete structures.

A synthetic resin coating of epoxy resin is applied onto this phosphate coating or directly onto the surface of the metal sheath body. The epoxy resin used for the synthetic resin coating is Aron Powder (Toagosei Co., Ltd.,
(trade name) or Araldite (Ciba Products Co., Ltd., trade name) is recommended.

The epoxy resin coating is applied to the outer surface of the sheath by brushing, thermal spraying, spraying, electrostatic coating, or fluid dipping, and to the inner surface of the sheath by spraying, electrostatic coating, or fluid dipping. It is formed to a thickness of about 30 to 200 microns.

Since this synthetic resin coating is applied to the inner and outer surfaces of the metal sheath via the phosphate coating, the adhesion of the synthetic resin coating layer to the metal sheath is good in terms of strength.

The inner surface of the metal sheath body has a solid lubricating coating containing polytetrafluoroethylene resin (PEFE).
This is carried out in the following manner. In other words, PTFE is in the form of a fine powder of 5 microns or less, and its apparent density is
Those with a specific gravity of 0.3 to 0.5 gr/cm ² and a specific gravity of 2.10 to 2.29 (for example, Fluon (trade name) manufactured by ICI in the UK and Hostaflon (trade name) manufactured by Hoechst in West Germany) are preferably used. As a carrier for PTFE
Suitable examples include finely powdered soft metals (e.g. lead, tin, zinc, cadmium, etc.) that pass through the 250 mesh, and/or finely powdered metal sulfides (e.g. molybdenum disulfide, tungsten disulfide) of about 5 to 8 microns. used. In addition, as a binder for this PTFE or a mixture of PTFE and a soft metal and/or metal sulfide, alkyd resin (in particular, styresol (Dainippon Ink Chemical Manufactured by Kogyosha (product name) is recommended.) is used.

Then, the above-mentioned binder is added to the above-mentioned PTFE or a mixture of PTFE and soft metal and/or metal sulfide, and this is suspended in a volatile solvent (usually xylene, mineral turbene, etc.). A suspension is prepared, and this suspension is applied as a thin film with a thickness of 20 to 100 microns on the inner surface of a metal sheath by spraying. The blending amounts of each of the above components (excluding the solvent) are expressed as a volume ratio (VOL%), and are, for example, 50 to 70% of the PTFE fine powder and 30 to 70% of the styrenated alkyd resin.

Therefore, this solid lubricating coating has a good rust-preventing effect by itself, and when used in cooperation with the above-mentioned phosphate film and synthetic resin coating, the rust-preventing effect is further increased. Furthermore, according to this solid lubricating film,
The sliding friction resistance (0.1 to 0.15 in terms of friction coefficient) generated between the inner surface of the metal sheath coated with the film and the PC steel material when the PC steel material is tensioned is compared to that of the conventional one (approximately 0.4 in terms of friction coefficient). can be reduced significantly, so that large prestressing forces can be introduced. In addition, since the solid lubricant coating is extremely thin, it does not impair the flexibility of the metal sheath itself, and despite its thinness, it has good adhesion and is therefore difficult to peel off. It has particularly good film properties.

FIG. 6 is a schematic cross-sectional view of an embodiment of the rust-proof metal sheath S of the present invention. H is a main body of the hollow cylindrical metal sheath described above, and 3 is a phosphate resin film which has been subjected to film conversion treatment on the inner and outer peripheral surfaces of the metal sheath main body H. 4 is a synthetic resin coating such as epoxy resin, 4a is the outer synthetic resin coating, and 4b is the inner synthetic resin coating. 5 is a solid lubricating film containing polytetrafluoroethylene resin.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a seam in a conventional metal sheath body, FIG. 2 is a sectional view of a seam in a conventional rust-proof sheath, and FIG. 3 is a sectional view of an embodiment of a seam in a metal sheath body of the present invention. FIG. 4 is a cross-sectional view of another embodiment, FIG. 5 is a cross-sectional view of still another embodiment, and FIG. 6 is a schematic cross-sectional view of the metal sheath of the present invention.

Claims (1)

[Scope of Claims] 1. The sheath body is formed into a hollow tube shape with a seam in which both ends of thin-walled steel strips are continuously and airtightly joined to each other by welding or adhesive, and the sheath body includes: The post tension is characterized in that the protruding height of the overlapping portion other than the butt joint portion is made as small as possible, and a synthetic resin coating layer is applied to the outer surface or inner surface of the sheath body. Shion method metal sheath. 2. The metal sheath for post-tension construction method according to claim 1, wherein the seams of the sheath body are formed in the longitudinal direction. 3. The metal sheath for post-tension construction method according to claim 1, wherein the seam of the sheath body is formed in a spiral shape. 4. The metal sheath for post-tension construction according to claim 2, wherein the sheath body is formed with ribs that bulge outward in a wavy manner. 5. Claims 2 or 3, wherein the sheath body is formed with a rib that bulges outward in a spiral shape.
The metal sheath for post-tension construction method according to any of paragraphs. 6. The metal sheath for post-tension construction according to any one of claims 1 to 5, wherein the synthetic resin is an epoxy resin. 7. The sheath body is formed into a hollow tube shape with a seam in which both ends of thin-walled steel strips are continuously and airtightly joined to each other by welding or adhesive, and the seam is other than a butt joint. The protruding height of the overlapping portion of the sheath body is made as small as possible, and a synthetic resin coating layer is applied to the outer or inner surface of the sheath body, and the inner surface of the sheath body is coated with a solid material containing polytetrafluoroethylene. A metal sheath for post-tension construction, characterized by being coated with a lubricating film. 8. The sheath body is formed into a hollow tube shape through a seam in which both ends of thin-walled steel strips are continuously and airtightly joined to each other by welding or adhesive, and the seam is a joint other than a butt joint. In the polymerization part, the protrusion height is made as small as possible, the inner and outer surfaces of the sheath body are surface-treated with a phosphate coating, and a synthetic resin coating layer is applied on the phosphate coating, and A metal sheath for post-tension construction, characterized in that a solid lubricant film containing polytetrafluoroethylene is applied on a synthetic resin coating layer on the inner surface of the sheath body.