JPS5944458A - Metal sheath for post-tension construction applied with anti-rust treatment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal sheath that has been subjected to anti-corrosion treatment in a sheath used in a prestressed concrete structure constructed by the boss tension construction method.

Generally, when constructing a prestressed concrete structure by the boss tension construction method, a metal sheath is usually used to arrange the prestressed steel members. This metal sheath serves as a kind of cover for the PC steel so that it can be tensioned from the concrete that is being poured. In addition, it must have the strength to prevent holes from forming, and even when the placed PC steel material is under tension (
Pre-stressing) requires low frictional resistance.

However, in addition to the above-mentioned requirements for the metal sheath, importance has recently been placed on the rust prevention (corrosion resistance) of the metal sheath. In other words, if concrete structures such as prestressed concrete structures (hereinafter referred to as PC structures) and reinforced concrete structures (hereinafter referred to as RC structures) are placed in the ocean or near the coast, or if sea sand is used as the concrete aggregate, is used, anions such as nitrogen ions (e.g. C
Z−$ B r −+ I ”−+ S 04−−t
S-, etc.), especially when the presence of chlorine ions is prevalent, the steel in concrete corrodes at an unexpectedly rapid rate, and there have been recent cases where the concrete structure itself is damaged through this corrosion. Regarding structures, as a result of the metal sheath covering the prestressing steel material being directly corroded by anions (these are called corrosive ions), the concrete and prestressing steel material in the vicinity of the metal sheath may be damaged or corroded. , leading to the weakening of the entire PC structure.In addition, in PC structures, electrochemical corrosion phenomena that occur due to contact or proximity between the metal sheath and the PC steel material are added, which is a factor that accelerates the deterioration of the PC structure. It is also accompanied by

Conventionally, as a rust prevention measure for metal sheaths, when the sheath is stored for several months near the coast, or when a long period of time is required between placing the sheath and pre-stressing, galvanizing has been used. It is known that anti-rust treatments such as However, in this known means, the main objective is to reduce the friction between the sheath and the prestressing steel placed within the sheath (that is, to prevent an increase in frictional resistance due to rust), and after concrete is poured, No consideration has been given to the corrosivity of the metal sheath due to the intrusion of chlorine ions etc. over many years. Furthermore, this plating process does not have the effect of sufficiently suppressing the electrochemical corrosion phenomenon that occurs due to contact or proximity between dissimilar metals in a chlorine ion atmosphere.

In view of the above-mentioned circumstances, the technical object of the present invention is to provide a metal sheath for the boss tension construction method which has a further improved anti-corrosion effect compared to the conventional metal sheath described above.

The metal sheath for the boss tension construction method of the present invention (3) adopts the following configuration (technical means) in order to achieve the above technical problem. Specifically, (1) the outer or inner and outer surfaces of the sheath body made of a thin steel plate are surface-treated with a phosphate coating, (2) a synthetic resin coating is formed on the outer surface of the sheath body that has been subjected to nuclear surface treatment, and (3) the sheath body is coated with a synthetic resin. - A solid lubricating film is formed on the inner surface of the main body.

Here, the phosphate coating has a thickness that does not inhibit the elasticity of the sheath body, and is essential to be chemically coated on the outer surface of the sheath body, but may be omitted from the inner surface of the sheath body as appropriate.

Furthermore, for the synthetic resin coating applied to the outer surface of the sheath body, a material is selected that ensures the elasticity of the sheath and is durable against the alkalinity of concrete. As the material, for example, Epoquine resin or vinyl chloride resin is suitable. Generally, phosphate coatings have good adhesion to synthetic resin coatings.

In addition, the solid lubricant coating applied to the inner surface of the sheath body has good adhesion to the inner surface of the metal sheath, has anti-rust properties in itself (4), and when the prestressing steel material is tensed, the solid lubricating coating coats the inner surface of the sheath and the A material is selected that reduces the sliding friction resistance generated on both surfaces with the steel material. Its materials include polytetrafluoroethylene resin (hereinafter referred to as PTFE), a binder,
Alternatively, compositions of PTFE and mixtures of soft metals and/or metal sulfides and binders are used.

The metal sheath of the present invention having the above structure exhibits the following rust prevention effect. In other words, the phosphate coating applied to the outer surface of the metal sheath body exhibits corrosion resistance that continuously resists corrosive ions in concrete, and furthermore, the synthetic resin coating such as Epoquin resin applied to the outer surface has corrosion resistance. It not only protects the phosphate coating, but also has the function of filling pinholes that occur during the chemical conversion treatment of the phosphate coating, providing double protection against corrosion from the outer surface of the sheath. In addition, the phosphate coating and solid lubricant coating applied to the inner surface of the sheath body not only exhibit corrosion resistance against corrosive ions in the concrete (grout) filled in the sheath, but also the metal sheath body and the PC steel. This has the effect of avoiding direct contact with the metal and suppressing metal corrosion caused by local current generated at the contact area over a long period of time. Furthermore, in addition to the rust-preventing effect of the sheath in concrete, the rust-preventing effect of the present sheath is sufficiently effective even when the sheath is exposed to the outside air for a long period of time during storage or pre-stressing.

Furthermore, each component of the metal sheath of the present invention has the following specific effects.

■ The phosphate coating adheres firmly to the metal sheath body and is easy to treat. Furthermore, the rust-preventing effect of the phosphate coating is difficult to be 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 attached to the outer surface of the metal sheath via the phosphate coating, the adhesion of the synthetic resin coating layer is good in terms of strength and workability, and it also has good adhesion to concrete. This improves the sheath's adhesion to concrete.

■ The solid lubricant coating itself has anti-corrosion properties, and
It cooperates with the phosphate coating to further enhance its rust prevention effect, and has a large friction reduction effect with the PC steel material, making it possible to introduce a large prestressing force.

Examples of the present invention will be described below.

The main body of the metal sheath is made of a thin steel plate, and is usually made by winding a strip of steel into a spiral and caulking the joints.

The phosphate coating applied to the inner and outer surfaces of the metal sheath body can be applied using a manganese phosphate method (main component Mn(H2PO4)2), a zinc phosphate method (main component Mn(H2PO4)2), or an iron phosphate method (main component Mn(H2PO4)2). ) (Other methods are omitted) and other appropriate methods are used for chemical conversion treatment, but if this is subjected to a post-treatment method using the Endurion method, the rust prevention properties will be further improved. The thickness of this coating is approximately 5 to 10 microns, and the coating may be formed by dipping or spraying as appropriate.

The use of Araldite (Ciba Products Co., Ltd., trade name) as the Epoquine resin used for synthetic resin coating (7) is recommended. In particular, Araldite AY103 as the main resin is recommended.
(Shape: Low viscosity resin) and hardening agent is HY953F.
(Shape: viscous liquid) or Araldye as the main ingredient) AW1'06 (Shape: High viscosity resin) and HV953U as the hardening agent (Shape: Fluid paste)
It is preferable to use these materials; after curing, these materials form a flexible coating layer that blends well with concrete.

A solid lubricating coating containing polytetrafluoroethylene resin (PTFE) is applied to the inner surface of the metal sheath body in the following manner.In other words, the PTFE is in the form of a fine powder of 5 microns or less, and the apparent density is 0. 3-0.5? r/c
r/l and specific gravity of 2.10 to 2.29, such as 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 this finely powdered PTFE, finely powdered soft metals (such as lead, tin, zinc, cadmium, etc.) that pass through the 250 mesh and/or finely powdered metal sulfides (such as 1, molybdenum disulfide, etc.) of about 5 to 8 microns are used. , binary (8) tungsten oxide) is preferably used as a binder for the mixture of PTFF or PTFE with soft metals and/or metal sulfides. Styresol (trade name, manufactured by Dainippon Ink and Chemicals), a styrenated alkyd resin with styrene grafted onto it, 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 turpentine, etc.) to form a suspension. and spray this suspension onto the inner surface of the metal sheath to a thickness of 20 to 1
It is applied as a thin film of 0.00 microns. The blending amounts of each of the above components (excluding the solvent) are expressed as volume ratios (voL%), for example: ■ PTFE fine powder 50-70%, styrenated alkyd resin 30-50%, ■ PTFE fine powder 20-60%.
%, soft metal and/or metal sulfide 10 to SOS, and styrenated alkyd resin 30 to 70%.

Therefore, this solid lubricating coating has a good rust-preventing effect by itself, and when used in cooperation with the above-mentioned phosphate coating, the rust-preventing effect is further increased. Furthermore, this solid lubricating coating reduces the sliding frictional resistance (0.11 to 0.14 in friction coefficient) that occurs between the inner surface of the metal sheath coated with the coating and the PC steel when the PC steel is tensed. This can be significantly reduced compared to the conventional one (approximately 0.4 friction coefficient), and since the solid lubricant coating is extremely thin, it does not impair the flexibility of the metal sheath itself. In addition, it has good adhesion despite its thinness and is therefore difficult to peel off.
It has good coating properties for metal sheaths.

The figure is a schematic cross-sectional view of the metal sheath S of the present invention.

1 is a main body of a cylindrical metal sheath. Reference numeral 2 denotes a talinate coating formed on the inner and outer surfaces of the metal sheath main body 1, and the coating on the inner surface may be omitted. 3 is a synthetic resin coating such as Epoquin resin, and 4 is a solid lubricating coating containing polytetrafluoroethylene resin.

[Brief explanation of the drawing]

The drawing is a schematic cross-sectional view of the metal sheath S of the present invention. 0 ■...Metal sheath body, 2... Phosphate coating,
3...Synthetic resin coating, 4...Solid lubricating coating Patent applicant Japanese National Railway Oiles Industry Co., Ltd. Agent Patent attorney Ike 1) Hitoshi Ike

Claims (1)

[Scope of Claims] The outer surface or inner and outer surfaces of a sheath body made of a 1° thin steel plate are surface-treated with a phosphate coating, and a synthetic resin coating is formed on the surface-treated outer surface of the sheath body. A metal sheath for a boss tension construction method, characterized in that a solid lubricant film is formed on the inner surface of the sheath body. 2. The metal sheath for the boss tension construction method according to claim 1, wherein the synthetic resin coating is an epoxy resin. 3. The metal sheath O for the boss tension construction method according to claim 1 or 2, wherein the solid lubricant coating contains a polytetrafluoroethylene resin.