JP2710888B2 - PC steel stranded wire and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stranded PC steel wire suitable for use in a severe corrosive environment such as a seaside area, and a method for manufacturing the same.

[0002]

2. Description of the Related Art The followings are examples of corrosion-resistant stranded PC steel wires conventionally used for prestressed concrete structures and the like. Sectional views of the following stranded PC steel wires are shown in FIGS. 4 to 6 in order. A lubricant 21 such as grease is applied to the outer periphery of the wire 20,
A plastic coating layer 22 is provided thereon by extrusion (see Japanese Patent Publication No. 53-47609). The wire 30 is provided with a plastic coating layer 31 on the outer periphery thereof, an anti-slip layer 32 provided on the coating layer 31, and further covered with a plastic sheath 33 (see Japanese Utility Model Application Laid-Open No. 61-69318). A plastic coating layer 41 is provided on the outer periphery of the wire 40 by powder coating, and sand-like particles 42 are fixed to the coating layer 41 so that a part of the particles protrudes from the surface of the coating layer (Japanese Patent Publication No. 3-28551). Reference).

[0003]

Of these, the so-called unbonded PC steel for the post-tensioning method is used for building slabs, prestressed concrete tanks and the like. In these, a lubricant or the like is interposed between the outer plastic coating layer and the wire, so that the wire can slide freely even when embedded in a concrete structure. However, in this type of stranded PC steel wire, since the wire does not behave integrally with concrete, there is a problem that the fracture strength of the structure is reduced. In addition, if a load is applied from the outside after the completion of the structure, the wire can slide freely, so the repeated load is transmitted directly to the fixing part that holds the tension of the wire, and long-term reliability is improved. Is not enough. For this reason, they are not used for important members such as those requiring earthquake resistance, and their applications are limited.

[0004] On the other hand, when the type of stranded PC steel wire is used for a building requiring durability, such as an offshore structure, a sheath is placed in advance, and concrete is cast and hardened.
This PC steel stranded wire is inserted into the sheath, and after tensioning, the sheath and P
Grout is injected between the C steel strands. Also, when using the cable for cable-stayed bridges, insert a stranded PC steel wire into the protective tube one by one, make a cable consisting of many stranded PC steel wires, and then tighten the cable. Mortar between the tube and the protective tube. By the way, the sand-like particles of the PC steel stranded wire are provided in order to improve the adhesion to grout, mortar and the like. However, when inserted into the sheath or the protective tube as described above, due to contact or friction with these or with the previously inserted PC steel stranded wire, the material may fall off considerably or the particles may be rounded, It is not possible to obtain the same adhesiveness as the previous PC steel stranded wire.

The present invention has been made in view of the above circumstances, and has as its object to provide a stranded PC steel wire having excellent adhesion to mortar and the like and excellent corrosion resistance, and a method for producing the same. It is.

[0006]

In order to achieve the above object, a stranded PC steel wire according to the present invention is a stranded PC steel wire having a plastic coating layer on the surface of a wire obtained by twisting a plurality of strands. The coating layer is formed so that the twists of the wires appear on the outer surface, and the surface thereof is roughened by a large number of irregularities.
Further, the manufacturing method is such that a plastic coating layer is formed on the surface of a wire obtained by twisting a plurality of wires so that the twist of the wires appears on the outer surface by powder coating, and after curing, a plastic coating layer is formed on the surface of the coating layer. Is provided with a large number of irregularities by spraying with a shot blast.

Here, the plastic coating layer may be a polyester resin or the like, but epoxy resin is suitable in consideration of general versatility, corrosion resistance and chemical resistance as plastic. The coating method is powder coating (fluid immersion powder coating,
(Electrostatic powder coating). In this coating method, the wire is heated to a predetermined temperature, and the wire is immersed or sprayed in a fluid immersion tank or an electrostatic powder coating tank,
The powder coating is fused to the surface of the wire. According to this method, the strength of the coating layer is high, and the coating layer can be firmly adhered to the wire.

[0008]

As described above, by forming a very firm plastic coating layer with high adhesion on the wire by powder coating, a stranded PC steel wire having high corrosion resistance can be obtained. The thickness of the coating layer is preferably 400 μm or more in consideration of the existence of pinholes and the provision of a large number of irregularities on the surface by shot blasting. Further, by forming a large number of irregularities on the surface of the plastic coating layer by shot blasting, a stranded PC steel wire having excellent adhesion to mortar or the like can be obtained. Unlike the conventional example, the unevenness does not cause the sand-like particles to be fixed, but rather causes the surface of the plastic coating layer to be rough, so that it does not fall off like the sand-like particles. Adhesiveness does not decrease even after insertion of the sheath.

[0009]

Embodiments of the present invention will be described below. First, FIG.
The manufacturing method will be described based on FIG. FIG. 3 is a schematic view showing the steps of the manufacturing method of the present invention. As shown in the figure, the element wire constituting the wire is first subjected to a surface treatment by a shot blast or chemical conversion treatment device as a pretreatment device 1. Next, the plastic powder is heated to a temperature required for melting and adhering in the next step by a heating device 2 such as high-frequency heating. The heating temperature at this time is appropriately set according to the type of plastic used.

[0010] The heated element wire is coated with a plastic coating at the coating device 3. This painting is
It is formed by powder coating such as fluid immersion powder coating and electrostatic powder coating. The coating layer is formed so that the twist of the wire appears on the outer surface. Thereafter, the plastic coating layer is cured and hardened by a cooling device 4 such as water cooling. After performing this curing,
This time, spraying is performed by the shot blasting device 5,
The surface of the plastic coating layer is roughened to form many irregularities. In this example, the shot blasting device 5 is provided between the cooling device 4 and the winding, but after curing and hardening by the cooling device are finished, once the winding is performed, and in a separate process, the same process as described above is performed. Spraying by shot blast may be performed.

FIG. 2 is a cross-sectional view of the stranded PC steel wire thus obtained. If a lubricant such as grease is applied to the surface of the twisted PC steel wire and a plastic jacket is formed thereon by extrusion, an unbonded twisted PC steel wire having excellent corrosion resistance can be obtained. Further, the PC
If the gap 8 between the wires 6 constituting the steel material is filled with plastic, it is possible to effectively prevent corrosive water from entering from the end of the stranded PC steel wire. In addition, the method of filling the gap between the individual wires with plastic is performed by once opening the twist of the PC steel stranded wire and coating the plastic for each individual wire at the coating apparatus in the manufacturing process. This means that each twisted wire is passed through a perforated board having holes according to the number of strands, and when the perforated board is rotated, each twisted wire passing through the hole is again twisted.

[0012]

Test Example An adhesion test with concrete was actually performed using the stranded PC steel wire of the present invention. The test material was a wire (A) in which seven strands were twisted, an epoxy resin coating layer was provided on the wire A so that the twists of the wires appeared on the outer surface, and a large number of sandy layers were formed on the coating layer. Using the particles (B) having the particles fixed thereon as a comparative example, an epoxy resin coating layer was provided on the wire A so that the twists of the wires appeared on the outer surface, and a number of irregularities were provided on the surface by shot blasting. The product (C) was used as an example. Then, for each of these cases, an adhesion test with concrete was performed for a case where it was inserted into a metal sheath of 100 m by a pushing machine and a case where it was not inserted.

The test method was based on the pullout test method of the Japan Concrete Institute. This is shown in FIG.
Strength: A test material 10 fixed in a concrete block 11 of 300 cm ± 30 kg / cm ² and 20 cm 3 is pulled out, and the load at that time is measured. Table 1 shows the test results.

[0014]

[Table 1]

As shown in the table, the test materials B and C, which are not inserted into the sheath, show higher adhesiveness than the test material A. However, the adhesiveness of B inserted into the sheath was considerably reduced, probably because the sand-like particles dropped off during the insertion. On the other hand, in the example of the present invention, the effectiveness of the present invention was confirmed without substantially reducing the adhesiveness even after insertion into the sheath.

[0016]

As described above, the PC steel stranded wire according to the present invention is provided with a large number of irregularities on the plastic coating layer and is roughened. Can be. Since the irregularities do not adhere the sand-like particles as in the conventional example, there is no problem that the irregularities fall off, and the adhesiveness does not decrease when inserted into a sheath or the like. Furthermore, since the plastic coating layer is formed so that the twist of the strand appears on the outer surface, the unevenness of the twist further ensures adhesion to mortar or the like.

Further, since the plastic coating layer on the surface of the wire is firmly adhered by powder coating, even if corrosive water penetrates from the mortar, the plastic coating layer becomes a partition wall, and particularly, has a long-term reliability. In this case, sufficient corrosion resistance can be secured. In addition, if plastic is filled in the gaps between the wires constituting the wire, corrosion water can be prevented from penetrating from the tip portion of the stranded PC steel due to capillary action, and higher corrosion resistance can be obtained.

Furthermore, the conventional stranded PC steel wire is a bare PC steel.
Since the steel stranded wire is directly fixed and fixed by a wedge, it cannot be said that the fatigue characteristics are sufficient when a repeated load is applied for a long period of time. In this regard, in the stranded PC steel wire of the present invention, since the strands are fixed with a wedge from the twisted strands, oxygen does not directly reach each strand, and the fatigue properties are improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the steps of the production method of the present invention.

FIG. 2 is a cross-sectional view of the twisted PC steel wire of the present invention.

FIG. 3 is an explanatory view of an adhesion strength test with concrete.

FIG. 4 is a cross-sectional view of a conventional stranded PC steel wire.

FIG. 5 is a cross-sectional view of a conventional stranded PC steel wire.

FIG. 6 is a cross-sectional view of a conventional stranded PC steel wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pre-processing apparatus 2 Heating apparatus 3 Coating apparatus 4 Cooling apparatus 5 Shot blast apparatus 6 Element wire 7 Plastic covering layer 8 Gap 10 Test material 11 Concrete block 12 Reinforcement 20, 30, 40 Wire rod 22, 31, 41 Plastic covering layer 21 Lubricant 32 Anti-slip agent 42 Sandy particles

Claims (2)

(57) [Claims] 1. A stranded PC steel wire having a plastic coating layer on the surface of a wire obtained by twisting a plurality of wires, wherein the coating layer is formed such that the twist of the wires appears on the outer surface, A stranded PC steel wire whose surface is roughened by a number of irregularities. 2. A plastic coating layer is formed on the surface of a wire obtained by twisting a plurality of strands by powder coating so that the twists of the strands appear on the outer surface, and after curing, a plastic coating layer is formed on the surface of the coating layer. A method for producing a stranded PC steel wire, characterized by providing a large number of irregularities by spraying with blast.