JPH05111912A - PC steel stranded wire and its manufacturing method - Google Patents

Abstract

PURPOSE:To manufacture a PC steel twist wire excellent in bonding properties with mortar and corrosion resistance by forming a number of recesses and projections and also a plastic coated layer of rough surface state on the surface of a twisted wire composed of a plurality of strands. CONSTITUTION:Strands are surface treated by a formation device or the like as a pretreatment device 1, and then said strands are heated up to the temperature required for melting plastic powder and making the same adhered in the following process by heater 2 of high frequency heating or the like. The surfaces of heated strands are plastic coated at coating device 3. Said coating is the powder coating such as static powder coating or the like and a coated layer is formed in a manner of exposing twisted pattern on the surface. Then the plastic coated layer is cured and hardened by a cooling device 4 such as water cooling or the like, and spraying is carried out by a shot blast device 5 to form surface roughness on the surface of plastic coated layer and forming a number of recesses and projections.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art The corrosion resistant PC steel stranded wire conventionally used for prestressed concrete structures and the like includes the following. Cross-sectional views of the following PC steel twisted wires are sequentially shown in FIGS. 4 to 6. Apply a lubricant 21 such as grease 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). A plastic coating layer 31 is provided on the outer circumference of the wire 30, a slip prevention layer 32 is provided on the coating layer 31, and a plastic sheath 33 is further coated thereon (see Japanese Utility Model 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 sandy particles 42 protrudes from the surface of the coating layer (Japanese Patent Publication No. 28551/1991). (See the official gazette).

[0003]

Among these, and are the so-called unbonded PC steel materials for the post-tensioning method used for slabs of buildings, tanks made of prestressed concrete, and the like. These have a lubricant or the like 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 PC steel stranded wire, the wire does not behave integrally with the concrete, so that there is a problem that the fracture resistance of the structure is reduced. In addition, after the structure is completed, if a load is applied from the outside, the wire can slide freely, so the load is repeatedly transmitted directly to the fixing part that holds the tension of the wire, and long-term reliability is considered. Is not enough. For this reason, it was not used for important members such as required to have earthquake resistance, and its use was limited.

On the other hand, when the type 1 PC steel stranded wire is used in a building requiring durability such as a marine structure, a sheath is previously arranged, concrete is cast, and after hardening,
Insert this PC steel stranded wire into the sheath, and after tensioning the sheath and P
Inject grout between the C steel stranded wire. When using it as a suspension material such as a cable-stayed bridge, insert one PC steel stranded wire into the protection tube to make a cable consisting of many PC steel stranded wires, and then strain the cable Inject mortar between the tube and the protective tube. By the way, the sand-like particles of the PC steel twisted wire are provided to improve the adhesion to grout, mortar and the like. However, when it is inserted into the sheath or the protection tube as described above, it may come off considerably due to the contact or friction between these and the previously inserted PC steel twisted wire, or the particles may be rounded, so 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 an object thereof is to provide a PC steel stranded wire having excellent adhesion to mortar and the like and excellent corrosion resistance, and a method for producing the same. Is.

[0006]

In order to achieve the above object, the PC steel twisted wire of the present invention is a PC steel twisted wire having a plastic coating layer on the surface of a wire rod formed 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 of the coating layer 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 rod formed by twisting a plurality of strands by powder coating so that the twists of the strands appear on the outer surface, and after curing, the surface of the coating layer is cured. It is characterized in that a large number of irregularities are provided by performing shot blasting on the.

The plastic coating layer may be made of polyester resin or the like, but epoxy resin is suitable in view of versatility as plastic, corrosion resistance, and chemical resistance. The coating method is powder coating (fluid immersion powder coating,
Electrostatic powder coating). This coating method is to heat the wire rod to a predetermined temperature, and dip or spray the wire rod in a fluidized dipping tank or electrostatic powder coating tank.
The powder coating is fused onto the surface of the wire. According to this method, the strength of the coating layer is high, and the wire can be firmly adhered.

[0008]

As described above, by forming a highly solid plastic coating layer having high adhesion on the wire material by powder coating, a PC steel twisted wire having high corrosion resistance can be obtained. The thickness of this coating layer is preferably 400 μm or more in consideration of the presence of pinholes and the fact that a large number of irregularities are formed 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, it is possible to obtain a PC steel stranded wire having excellent adhesion to mortar and the like. Unlike the conventional example, this unevenness does not cause sand-like particles to be fixed, but causes rough skin on the surface of the plastic coating layer, so it does not fall off like sand-like particles. The adhesiveness does not decrease even after the sheath is inserted.

[0009]

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

The surface of the heated wire is coated with plastic at the coating device 3. This painting is
Powder coating such as fluid immersion powder coating and electrostatic powder coating is used, and the coating layer is formed so that the twists of the wire appear on the outer surface. Then, the plastic coating layer is cured and cured by a cooling device 4 such as water cooling. After doing this curing,
This time, the shot blasting device 5 is used for spraying,
Rough skin is formed on the surface of the plastic coating layer to form a large number of irregularities. In this example, the shot blasting device 5 is provided between the cooling device 4 and the winding device. However, after the curing and curing by the cooling device is completed, it is once wound and then performed in a different step in the same manner as described above. You may spray by shot blast.

FIG. 2 shows a sectional view of the PC steel stranded wire thus obtained. If a lubricant such as grease is applied to the surface of the PC steel stranded wire and a plastic outer cover is formed on the surface of the PC steel stranded wire by extrusion, an unbonded PC steel stranded wire having excellent corrosion resistance can be obtained. Furthermore, the PC
By filling the gap 8 between the individual strands 6 of the steel material with plastic, it is possible to effectively prevent corrosive water infiltration from the end of the PC steel strand. The method of filling the gaps between the individual wires with plastic is performed by temporarily untwisting the PC steel stranded wire at the coating device in the manufacturing process and coating the plastic on each individual wire. This means that the twisted strands are passed through a mesh plate having holes corresponding to the number of strands, and when this mesh plate is rotated, the twisted wires that have passed through the holes are returned to the original twist.

[0012]

[Test Example] An adhesion test with concrete was actually performed using the PC steel twisted wire of the present invention. The test material is a wire rod (A) in which seven strands are twisted together, a coating layer of epoxy resin is provided on the wire rod A so that the twists of the strands appear on the outer surface, and a large number of sand-like layers are formed in this coating layer. The one in which particles were fixed (B) was used as a comparative example, and a coating layer of epoxy resin was provided on the wire A so that the twists of the strands appeared on the outer surface, and many irregularities were provided on this surface by shot blasting. The thing (C) was made into the Example. Then, for each of these, an adhesion test with concrete was carried out with and without insertion into a 100 m metal sheath by a pushing machine.

The test method was the pull-out test method of Japan Concrete Institute. This is as shown in FIG.
Strength: 300 ± 30 Kg / cm ² , the test material 10 fixed in a 20 cm cubic concrete block 11 is pulled out, and the load at that time is measured. The test results are shown in Table 1.

[0014]

[Table 1]

As shown in the table, both the test materials B and C, which are not inserted into the sheath, show higher adhesion than the test material A. However, the adhesiveness of B inserted into the sheath deteriorated considerably, probably because the sand-like particles fell off considerably during this insertion. On the other hand, in the examples of the present invention, the effectiveness of the present invention was confirmed with almost no decrease in the adhesiveness even after insertion into the sheath.

[0016]

As described above, since the PC steel stranded wire of the present invention is roughened by providing a large number of irregularities on the plastic coating layer, the irregularities enhance the adhesiveness with mortar and the like. You can Since the irregularities are not the ones in which sandy particles are fixed as in the conventional example, there is no problem that they fall off, and the adhesiveness does not deteriorate when inserting into a sheath or the like. Further, since the plastic coating layer is formed so that the twists of the strands appear on the outer surface, the unevenness of the twists further secures the adhesiveness with the mortar and the like.

Further, since the plastic coating layer on the surface of the wire is firmly adhered by powder coating, even if the corrosive water permeates from the mortar, the plastic coating layer serves as a partition wall, and particularly long-term reliability is ensured. Even in, the sufficient corrosion resistance can be secured. Further, by filling the gaps between the individual wires forming the wire rod with plastic, it is possible to prevent the corrosive water from penetrating from the tip portion of the PC steel stranded wire due to the capillary phenomenon, and to obtain higher corrosion resistance.

Further, the conventional PC steel stranded wire is a bare PC
Since the steel stranded wire is fixed directly by the wedge and fixed, it was not sufficient in terms of fatigue characteristics when a repeated load was applied for a long period of time. In this regard, in the PC steel twisted wire of the present invention, since the wires are fixed by a wedge from above the twisted wires, oxygen does not directly reach each wire and the fatigue characteristics are improved.

[Brief description of drawings]

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

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

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

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

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

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

[Explanation of symbols]

 1 Pretreatment Device 2 Heating Device 3 Coating Device 4 Cooling Device 5 Shot Blasting Device 6 Element Wire 7 Plastic Covering Layer 8 Gap 10 Test Material 11 Concrete Block 12 Reinforcing Bars 20, 30, 40 Wire Rod 22, 31, 41 Plastic Covering Layer 21 Lubricant 32 Anti-slip agent 42 Sandy particles

Claims (2)

[Claims] 1. A PC steel stranded wire having a plastic coating layer on the surface of a wire rod formed by twisting a plurality of strands, wherein the coating layer is formed such that the twists of the strands appear on the outer surface. Moreover, the PC steel stranded wire is characterized in that its surface is rough due to a large number of irregularities. 2. A plastic coating layer is formed by powder coating on the surface of a wire rod formed by twisting a plurality of strands so that the twists of the strands appear on the outer surface, and after curing, shots are made on the surface of the coating layer. A method for producing a PC steel stranded wire, which comprises spraying by blasting to form a large number of irregularities.