JP3511054B2 - Embedding method of PC steel stranded wire for partial unbonding - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for burying a PC steel twisted wire for partial unbonding used for tensioning prestressed concrete (hereinafter referred to as "PC concrete").

[0002]

2. Description of the Related Art Conventionally, a PC steel stranded wire coated with a synthetic resin sheath for the unbond method has a grease-like anticorrosive lubricant and a synthetic resin coating layer over its entire length. Cut the length to form a set with the fixing unit,
The sheath of the coating layer and the grease-like rust preventive lubricant were removed so that the fixing portion sufficiently adhered to the grout material.

However, the work of removing the grease-like rust preventive lubricant is very time-consuming, and it is difficult to completely remove it, and the adhesion between the grout and the PC steel stranded wire tends to be insufficient, There was also a quality problem.

In order to solve the above-mentioned drawbacks of the prior art, the PC steel stranded wire covered with a sheath has no adhesion of grease-like rust preventive lubricant to the fixing portion of the PC steel, and PC steel has improved adhesion to grout. Stranded wire is known.

There is also known an unbonded PC steel twisted wire in which a grease-like rust preventive lubricant is applied to the outer peripheral surface of the fixing portion of the PC steel twisted wire at regular intervals in the lengthwise direction.
FIG. 3 is a longitudinal cross-sectional view showing an example of a conventional unbonded PC steel twisted wire which is intermittently provided with a grease-like antirust lubricant at regular intervals. 11 is a PC steel stranded wire, 15 is a synthetic resin sheath, and 14 is a grease-like rust preventive lubricant applied intermittently at regular intervals.

However, in the case of this unbonded PC steel twisted wire, the grease-like anticorrosive lubricant flows out through the space of the strands of the steel twisted wire to the PC strand portion not coated with the grease-like anticorrosive lubricant. , Because the adhesion to concrete deteriorates and an accident is caused by poor fixing,
A countermeasure against this drawback is strongly desired.

That is, the work of removing the grease-like anticorrosive lubricant near the boundary between the unbonded portion and the fixing portion, the work of removing the grease-like anticorrosive lubricant that has flowed out to the fixing portion, and the grease-like prevention of the groove portion of the strand. The work of removing the rust lubricant is difficult and likely to be incomplete in the actual work, which causes a lack of fixing after the concrete milk is injected and fixed.

[0008]

In view of the above circumstances, the present invention prevents a grease-like lubricant from entering the space around the central core wire in a strand, and in a PC steel twisted wire for partial unbonding. An object of the present invention is to provide a method for burying a PC steel twisted wire for partial unbonding, which can eliminate insufficient fixing.

[0009]

In order to achieve the above object, the present invention applies a fat-and-oil type rust preventive agent to the surface of a PC steel stranded wire, and applies a pressure-sensitive adhesive to the surface of the rust preventive agent. The tape layer coated on the inner surface is wrapped and wound, the surface of the tape layer is filled with a grease-like lubricant, and a coating layer of thermoplastic synthetic resin is further arranged on the surface of the lubricant to fix it. Part, the coating layer of thermoplastic synthetic resin is peeled off, and the grease-like lubricant is also removed together with the tape layer, and it is embedded in concrete, which constitutes a method for burying PC steel twisted wire for partial unbonding. It is a thing.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A PC steel twisted wire for partial unbonding of the present invention is a PC steel twisted wire including a fixing portion, which is wrapped around a tape layer and wrapped around a tape layer. This prevents the grease-like lubricant from flowing into the space around the core wire inside the strand of the twisted wire and flowing out to the fixing portion through this space. The filled grease-like lubricant can be easily removed by removing the tape layer.

In the present invention, the tape layer having the pressure-sensitive adhesive applied to the inner surface is, for example, polyester tape of about 50 μm.
This is a tape layer in which a pressure-sensitive adhesive film is formed on the inner surface of the tape by applying an adhesive composed of a polyolefin-based emulsion on the surface having a thickness of about m to 100 μm and drying it.
When this is superposed on the surface of the PC steel twisted wire while wrapping the surface while wrapping the surface while applying a grease-based rust preventive, the inner surface of the next tape to be superposed on the outer surface of the tape, Since the pressure-sensitive adhesive which has been applied is pasted together and wound, the grease-like lubricant on the surface of the tape layer does not penetrate into the interior and complete sealing can be achieved.

An embodiment of the present invention will be described below in more detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of a PC stranded wire for partial unbonding of a rust preventive coating produced by the method of the present invention, and FIG. 2 is a vertical cross-sectional view of the same embodiment.

As shown in FIGS. 1 and 2, the PC untwisted wire for partial unbonding of the present invention has a surface of PC steel twisted wire 1 coated with a fat-and-oil rust preventive agent 2, and the surface of the rust preventive agent 2 is applied. In the case of this example, a pressure-sensitive adhesive (not shown) having a thickness of 60 μm was wrapped with the polyester tape layer 3 coated on the inner surface, wrapped, and completely sealed. The surface of the tape layer 3 was filled with a grease-like lubricant 4.

On the outer periphery of the grease-like lubricant 4, a coating layer 5 made of a thermoplastic synthetic resin sheath is further arranged to constitute the PC steel twisted wire 7 for partial unbonding of the present invention. In the case of the present invention, the grease is applied to the entire length, but the fixing portion is stripped of the thermoplastic synthetic resin coating layer 5, and further the grease layer-like lubricant 4 is removed together with the tape layer 3 and embedded in the concrete. To do. However, since the tape-like layer 3 is provided, the grease-like lubricant 4 does not leak through the internal space 6 of the strand 1 of the twisted wire to the fixing portion, and this is prevented.

The tape layer 3 having the pressure-sensitive adhesive applied to the inner surface is automatically bonded and sealed at the position where the tapes are superposed on each other in the winding. The thickness of the tape layer 3 is preferably 50-100 μm. If it is less than 50 μm, it is too thin and weak, and conversely 100 μm.
If it is more than m, it is too thick and difficult to wind.

[0016]

Since the PC steel twisted wire for partial unbonding of the present invention has the tape layer provided between the grease-like lubricant and the steel twisted wire, even if the rust preventive agent or the like in the fixing portion is removed, the grease can be removed. -Like lubricant did not leach into the fixing portion, the adhesion between the PC steel twisted wire and the concrete was good, and the insufficient fixing in the PC steel twisted wire for partial unbonding could be eliminated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing an embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a conventional unbonded PC twisted wire for which a grease-like rust preventive lubricant is intermittently applied at regular intervals.

[Explanation of symbols]

1 PC steel stranded wire 2 rust inhibitor 3 tape layers 4 Grease-like rust preventive lubricant 5 Coating layer made of synthetic resin sheath 6 internal space 7 Part unbonded PC steel stranded wire 11 PC steel stranded wire 14 Grease-like rust preventive lubricant 15 Synthetic resin sheath

─────────────────────────────────────────────────── --- Continuation of front page (56) Reference JP-A-7-189149 (JP, A) JP-A-57-146861 (JP, A) JP-A-5-179586 (JP, A) JP-A-54- 106652 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) E04G 21/12 104 E04C 5/08 D07B 1/16

Claims (2)

(57) [Claims] 1. A surface of a PC steel stranded wire is coated with an oil-based rust preventive, and the surface of the rust preventive is wrapped with a tape layer coated with a pressure-sensitive adhesive on the inner surface and wound. A grease-like lubricant is filled on the surface of the tape layer, and a coating layer of thermoplastic synthetic resin is further provided on the surface of the lubricant. The fixing portion is stripped off the coating layer of thermoplastic synthetic resin, and the tape layer is further formed. A method for burying PC steel stranded wire for partial unbonding, characterized in that it also removes grease-like lubricant and bury it in concrete. 2. The method for burying a PC steel twisted wire for partial unbonding according to claim 1, wherein the tape layer coated with a pressure-sensitive adhesive on the inner surface is a polyester tape having a thickness of 50 to 100 μm.