JPH0543018B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to pre-tensioning concrete structures, such as cable-stayed bridges and offshore structures, which require durability in severe corrosive environments, using the post-tension method. The present invention relates to a method for manufacturing stranded PC steel wire that has excellent corrosion resistance and good integration with concrete, making it suitable for applying stress.

[Conventional technology]

Conventional examples of PC steel stranded wires with corrosion resistance include JP-B No. 53-47609, JP-A-61-122360,
No. 61-122361, No. 61-69318, Special Publication No. 1983-
There is an unbonded type as shown in each publication of No. 36264, and a bonded type.

Figure 2 is a typical example of the unbonded type.
1 is steel stranded wire, 3 is extruded plastic coating,
4 indicates grease. Bond type PC
The steel stranded wire may be galvanized only, or a plastic paint coating layer may be provided directly on the outer periphery of the steel stranded wire (Fig. 3 shows this, and 5 shows the paint coating layer), or the steel stranded wire may be galvanized in place of the above paint coating. Stranded wire is a structure with a non-adhesive extruded coating layer. The extruded coating layer 3 in this case has a perfect circular outer periphery as shown in FIG.

[Problem to be solved by the invention]

In the unbonded type, the steel strands do not adhere to the concrete and good lubricity is maintained between the outermost covering material and tension can be maintained even after the concrete has been placed and hardened. Furthermore, as shown in FIG. 2, a wire in which anti-corrosion or lubricant such as grease is applied directly to the steel wire is resistant to corrosion because it is difficult for water to enter from the wire end. However, since this type of structure has a permanently unbonded structure, when a live load is applied to a concrete structure, the load is always applied to the anchoring end, which has the disadvantage of accelerating fatigue of that part. ing.

On the other hand, with respect to the bond type, the method of forming the covering material or the adhesion of the covering material to the concrete (the sheath is buried in the concrete, and the sheath placed inside the sheath is Although there are some differences in adhesion with mortar), a considerable effect can be expected, and since the concrete and PC steel wire behave as one when a live load is applied, the load on the anchoring end is reduced. There is no concentration.

However, the back side of this bond type PC steel wire is galvanized, which has the problem of reduced strength due to the plating process.

In addition, when a plastic coating layer is provided, the plastic during coating or extrusion does not have enough fluidity to pass through the minute clearance between the side lines, so as shown in Figures 3 and 4, the center The gap g between the strands 1a and the side wires 1b is not filled with plastic, and as a result, there is a problem in that water, etc. enters through the gap g from the end of the PC steel stranded wire, causing faster corrosion of the wire than the steel wire. .

Therefore, the object of this invention is to provide a method for manufacturing a PC steel stranded wire that has only the advantages of the unbonded type and the bonded type, that is, it has excellent corrosion resistance and integration with concrete.

[Means to solve the problem]

In order to eliminate the above-mentioned problems, in the present invention, as shown in FIG. Further, when applying the time-curable resin 2, a relatively fluid one is used, and the resin is allowed to flow into the gaps between the wires as shown in the figure.

[Effect]

Time-hardening resins, such as tar epoxy mixed with a hardening agent, which is used as a rust preventive and anticorrosion paint for steel structures, exhibit considerable fluidity when applied to PC steel wires. It is forcibly pushed between the side lines 1b by the extrusion pressure of the layer 3, and lateral pressure is always applied to the coating 3 during storage or transportation. 1b
The center strand 1 gradually passes through the minute clearance between
It flows into the gap between a and the side line 1b and completely fills the gap. Therefore, there is no path for water etc. to enter from the terminal portion.

Note that, after applying the coating 3, if it is attempted to flow the time-curable resin only by the above-mentioned lateral pressure, the flow will be insufficient and the gap will not be filled sufficiently. Therefore, in order to completely fill the gap, it is extremely important to use the extrusion pressure of the plastic coating to force the plastic coating.

In addition, since the tar epoxy adheres and hardens to both the extruded plastic coating 3 and almost the entire surface of the strands except for the parts where the strands are in contact with each other, the stranded PC steel wire 1 is integrated with the concrete and mortar. It becomes possible to behave as follows. Even if the adhesion of the tar epoxy to the PC steel wire 1 is insufficient, the tar epoxy will sufficiently fill the valley between the side wires 1b and harden, so the integrity with the concrete and mortar will be quite low. therefore, concentration of loads on the fixing end is avoided in any case.

It should be noted that the time-curable resin 2 may be a two-component mixed resin consisting of a base resin and a curing agent, as long as it exhibits appropriate fluidity during application, without any hindrance to achieving the object of the invention. Considering the cost, it is desirable to use an inexpensive tar epoxy or the like.

〔effect〕

As mentioned above, the method of this invention can obtain
Because the PC steel strands can behave as one with the concrete, local fatigue at the anchoring end due to live loads does not occur.

In addition, the outer periphery of the steel stranded wire is double coated with an extruded coating of time-curing resin and plastic.
The plastic coating is forcibly pushed in by the extrusion pressure to fill the gaps in the steel wire and prevent water from entering from the terminals, so it exhibits excellent corrosion resistance without the need for plating, which can reduce strength. Ru.

Therefore, it is particularly suitable for applications that require a high degree of corrosion resistance and high fatigue strength, such as PC cables used in cable-stayed bridges, offshore structures, or other structures susceptible to salt damage, and are suitable for applications that require a high degree of corrosion resistance and high fatigue strength. Even the structures installed underneath can be hardened to greatly improve their durability.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing a specific example of the PC steel stranded wire of this invention, and Figure 2 is a cross-sectional view of a conventional unbonded type wire.
Cross-sectional diagrams showing an example of PC steel stranded wire, Figures 3 and 4
The figure is a cross-sectional view showing an example of a conventional bond type PC steel stranded wire. 1...PC steel stranded wire, 1a...Central strand, 1b
... Side line, 2 ... Time-curable resin, 3 ... Plastic coating layer.

Claims (1)

[Claims] 1. By successively applying a layer of time-hardening resin and a coating layer of plastic extrusion on the outer circumference of the steel stranded wire, the time-hardening resin is applied between the strands of the steel stranded wire. A method for producing a highly corrosion-resistant PC steel stranded wire, which is characterized by flowing the wire into the wire.