JP3216631B2 - Rust-proof coated PC steel strand and method for producing 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 rust-proof coated PC steel strand used for prestressed concrete, cable-stayed bridges and rock / ground anchors, and a method for producing the same.

[0002]

2. Description of the Related Art As a method for preventing rust of PC steel strands used for prestressed concrete and cable-stayed bridges, Japanese Patent Application Laid-Open No. Hei 6-260,1992 is used.
Although there is a method using an epoxy resin as disclosed in Japanese Patent No. 504818, the resin is filled up to the inside of the twisted wire, and the resin is firmly adhered to the core wire and the side wire. Moisture penetrated from the terminal portion or the pinhole of the resin coating layer does not spread in the longitudinal direction of the wire, and exhibits a very excellent rust prevention effect. It also has excellent adhesion to concrete and cement grout. However, since the hard resin is used, there is a case where the wire is curled and the wire is curled when the drum is pulled out from the wound state and is difficult to perform.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 8-42061, there is a method of filling and covering a gap between a core wire and a side line and an outer surface of the side line with a polyethylene resin. Although the above-mentioned winding habit hardly occurs,
Since the adhesiveness between the core wire and the side wire and the resin is weak, the moisture that has penetrated from the terminal portion or the pinhole of the resin coating layer is more likely to spread in the longitudinal direction of the wire than the above-described epoxy resin, and the rust prevention effect. Was inferior.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a rust-proof coating which has no curling when used after being pulled out of a drum and is excellent in rust resistance and excellent in adhesion to concrete or cement grout. It is an object to provide a PC steel strand and a method for manufacturing the same.

[0005]

Means for Solving the Problems The present inventors have conducted various studies on a method for preventing rusting of a PC steel strand, and as a result, found that the inside of the strand, that is, the gap between the core wire and the side wire, and the The outer surface of the wire is filled and coated with an ethylene-acrylic acid copolymer resin, an ethylene-methacrylic acid copolymer resin, or a resin composed of a mixture thereof, and does not substantially contact the stranded wire. By having a structure having sand-like particles partially embedded in the coating so as to be partially exposed, there is no winding habit when pulled out from the drum winding state and used, and it has excellent rust prevention properties, and It has been found that a rust-proof coated PC steel strand having excellent adhesion to concrete or cement grout can be obtained, and the present invention has been completed. FIG. 1 shows a rust-proof coated PC steel strand having the above structure.

In the present invention, a thermoplastic resin is used. Examples of the ethylene-acrylic acid copolymer resin include "Primacol" manufactured by Dow Chemical Japan Co., Ltd. and "Novatech EAA" manufactured by Nippon Polychem Co., Ltd. Similarly, as the ethylene-methacrylic acid copolymer resin, “Nucrel” manufactured by DuPont-Mitsui Polychemicals Ltd. can be mentioned.

As the sand-like particles, silicon dioxide, magnesium oxide and the like are used. Also, the particle size of the sandy particles is
Those having a size of 200 μm or less are used.

The present inventors have also studied the method for producing the rust-proof coated PC steel strand of the present invention diligently, and have found that a product having good characteristics can be produced with good productivity by the following method. That is, the temperature of the PC steel strand is 150 to 300 ° C.
After heating in, while gradually loosening partly,
By extruding an ethylene-acrylic acid copolymer resin, or an ethylene-methacrylic acid copolymer resin, or a resin composed of a mixture thereof at the loosening position by extrusion molding, by returning the mating state before the resin is cured, After simultaneously filling the gap between the core wire and the side wire and coating the outer peripheral surface of the stranded wire, the sand-like particles are not substantially in contact with the stranded wire, and are partially applied to the outer surface of the coating. It is partially embedded in the coating so that it is exposed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the gap inside the stranded wire, that is, the gap between the core wire and the side wire, and the outer peripheral surface of the stranded wire are made of ethylene-acrylic acid copolymer resin or ethylene-methacrylic acid copolymer. Sand-like particles that are filled and coated with a resin or a resin consisting of a mixture thereof, and are not substantially in contact with the stranded wires and partially embedded in the coating so as to be partially exposed on the outer surface of the coating. By having, there is no winding habit when pulling out from the drum winding state and using it,
It is possible to obtain a rust-proof coated PC steel strand which is excellent in rust prevention and also excellent in adhesion to concrete or cement grout.

The above resin is moderately flexible and easily deformable, and is excellent in adhesion to a PC steel wire. For this reason, even when the stranded wire using the resin is bent at an acute angle, the resin can be stretched and the deformation can be absorbed by stretching the resin without separating the core wire and the side wire from the resin, thereby suppressing the curl.

In order to exhibit the above characteristics, it is necessary that the resin has a low elastic modulus and good elongation. Polyolefin resins have relatively low elastic modulus, good elongation, and low cost. However, general polyethylene hardly adheres to PC steel wires and cannot be used. Therefore, as a result of examining various adhesive polyolefin resins, ethylene-acrylic acid copolymer resin or ethylene-methacrylic acid copolymer resin has low cost, low elasticity, good elongation, and excellent adhesion with PC steel wire. I found something. In addition, these resins showed a small decrease in adhesive strength even after spraying with salt water.

Japanese Patent Application Laid-Open No. 5-163796 discloses a method in which a polyethylene-based polyolefin resin having a functional group represented by "Admer" manufactured by Mitsui Chemicals, Inc. is used as a part of the coating resin. , A polyethylene-based polyolefin resin having a functional group is expensive,
Although the initial adhesive strength was good, the adhesive strength after spraying with salt water was greatly reduced, and sufficient corrosion resistance was not obtained.

In the present invention, it is effective that the thickness of the resin at the peak of the outer peripheral surface of the strand is 300 to 700 μm. Hereinafter, the thickness of the resin is the thickness at the peak of the outer peripheral surface of the wire. If it is less than 300 μm, the sand-like particles will come into contact with the strands. It is not suitable when is emphasized.

In the present invention, by partially embedding the sand-like particles in the resin coating so that the resin coating does not substantially contact the stranded wire and is partially exposed on the outer surface of the coating,
Adhesion with concrete and cement grout is improved. The sand-like particles are partially embedded in the coating before the resin cures, by spraying the resin-laden PC steel strand or passing through a layer of sand-like particles.

[0015]

EXAMPLES (Example 1) PC steel strands heated to 250 ° C. were partially loosened sequentially, and Dow Chemical Japan-made “Primacol” was adhered to the loosened portions by extrusion molding, and the twist was returned. . Subsequently, before the resin was cured, sand having a particle size of 100 μm was partially embedded in the coating so that the sand was not in contact with the stranded wires but was partially exposed on the outer surface of the coating. A rust-proof coated PC steel wire was obtained.

Table 1 shows the evaluation results of the produced rust-proof coated PC steel strands.

[0017]

[Table 1]

The curl is determined by measuring the amount of curling of the rust-proof coated PC steel strand before winding on the drum and after holding it for one month by winding it on a drum having a diameter of 1 m, as shown in FIG.
Was evaluated. Corrosion resistance is determined by observing the PC steel wire by spraying salt water on a 15 cm long rust-prevention coated PC steel stranded wire with pinholes, both ends sealed with resin for 1000 hours, then removing the coating resin. evaluated. Adhesive strength, the rust-proof coated PC steel wire is embedded in cubic concrete with a side of 20 cm, and after the concrete hardens,
The wire was drawn from the rust-proof coated PC steel, and the maximum drawing force was evaluated by dividing the maximum drawing force by the surface area of the rust-proof coated PC steel wire in the concrete.

As shown in Table 1, the obtained rust-proof coated PC
The steel strand had a small winding habit and was excellent in corrosion resistance and adhesion.

(Comparative Example 1) Rust-proof coating PC manufactured in the same manner as in Example 1 except that sand was not buried in the coating.
A steel strand was obtained. The produced rust-proof coated PC steel strand was evaluated in the same manner as in Example 1. As shown in Table 1, the obtained anticorrosion-coated PC steel strand had a small winding habit and excellent corrosion resistance, but was inferior in adhesion.

Comparative Example 2 A strand of PC steel heated to 250 ° C. was partially loosened sequentially, and powder epoxy resin E90 manufactured by Nippon Paint Co. was applied to the loosened portion by electrostatic coating, melted, and the twist was returned. And further heated at 250 ° C. for 1 minute. As described above, a rust-proof coated PC steel wire was obtained in which the gap between the core wire and the side wire and the outer peripheral surface of the side wire were completely filled and covered. The produced rust-proof coated PC steel strand was evaluated in the same manner as in Example 1. As shown in Table 1, the obtained rust-proof coated PC steel strand was excellent in corrosion resistance and adhesion, but poor in curl.

(Comparative Example 3) After heating a PC steel strand to 250 ° C, the strand was partially relaxed sequentially, and a polyethylene polyolefin “Admer” having a functional group manufactured by Mitsui Chemicals, Inc. was used in the relaxed portion. After being attached by extrusion, the mating state was returned to the original state. Subsequently, before the resin was cured, sand having a particle diameter of 100 μm was partially embedded in the coating so that the sand did not come into contact with the strands and was partially exposed on the outer surface of the coating. A coated PC strand was obtained. The produced rust-proof coated PC steel strand was evaluated in the same manner as in Example 1. As shown in Table 1, the obtained rust-proof coating P
The C steel strand had a small winding habit and good adhesion, but was inferior in corrosion resistance.

(Comparative Example 4) After heating a PC steel stranded wire to 250 ° C, the strand was partially loosened sequentially, and the loosened portion was subjected to polyethylene “HIZEX53” manufactured by Mitsui Chemicals, Inc.
05E "was adhered by extrusion, and then returned to the original state. Subsequently, before the resin was cured, sand having a particle diameter of 100 μm was partially embedded in the coating so that the sand did not come into contact with the strands and was partially exposed on the outer surface of the coating. A coated PC strand was obtained. The produced rust-proof coated PC steel strand was evaluated in the same manner as in Example 1. Table 1
As shown in the above, the obtained anticorrosion-coated PC steel strand had a small winding habit, but was inferior in corrosion resistance and adhesion.

[0024]

As described above, according to the present invention,
By limiting the resin and partially embedding the sand-like particles in the coating, this anti-corrosion coated PC steel strand has a small winding habit when used by pulling it out of the drum winding state and has excellent rust resistance. Excellent adhesion to concrete and cement grout.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a rust-proof coated PC steel stranded wire according to the present invention.

FIG. 2 is an explanatory view of a curl test method.

[Explanation of symbols]

 1 PC steel wire 2 Resin 3 Sand 4 Rust-proof coated PC steel wire

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-195602 (JP, A) JP-A-5-200825 (JP, A) JP-A-8-49354 (JP, A) JP-A-10-1998 196049 (JP, A) JP-A-8-226191 (JP, A) JP-A-9-173941 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) E04C 5/00-5 / 20

Claims (3)

(57) [Claims] 1. A stranded wire, a gap between a core wire and a side wire, and an outer peripheral surface of the stranded wire are ethylene-acrylic acid copolymer resin,
Alternatively, the resin is filled and coated with an ethylene-methacrylic acid copolymer resin or a resin comprising a mixture thereof, and does not substantially contact with the stranded wire, and is partially exposed on the outer surface of the coating so as to be partially exposed to the outer surface of the coating. A rust-proof coated PC steel stranded wire having sandy particles embedded in the wire. 2. The thickness of the ethylene-acrylic acid copolymer resin, the ethylene-methacrylic acid copolymer resin, or a mixture thereof at the peak of the outer peripheral surface of the stranded wire is 300 to 700.
The rust-proof coated PC steel strand according to claim 1, wherein the diameter is μm. 3. After the PC steel strand is heated, the strand is partially loosened sequentially, and is extruded at the loosened position by extrusion molding to form an ethylene-acrylic acid copolymer resin or an ethylene-methacrylic acid copolymer resin, or After adhering a resin consisting of a mixture of the above and returning the twisted state to the original state, simultaneously filling the gap between the core wire and the side wire, and coating the outer peripheral surface of the strand, sand-like particles are formed. A method for producing a rust-proof coated PC steel stranded wire, wherein the stranded wire is partially embedded in the coating so as not to substantially contact the stranded wire and partially exposed to the outer surface of the coating.