JPH05277436A - Rust-preventive coating of pc strand - Google Patents

Abstract

PURPOSE:To apply rust-preventive coating to the whole of a PC strand by allowing a synthetic resin material to penetrate into the PC strand formed by intertwisting a plurality of single strands. CONSTITUTION:A PC strand 5 formed by intertwisting single strands is heated to be passed through a pressure tank 3 having a synthetic resin material received therein. The pressure tank 3 is packed with the synthetic resin material 13 showing high flowability by heating in a highly flowable state while a pressurized state is held and the synthetic resin material is allowed to penetrate into the PC strand 5 during the passage of the strand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method for introducing stress in prestressed concrete (hereinafter referred to as "PC") and a rust preventive coating method for PC strands used for suspension materials such as cable-stayed bridges.

[0002]

2. Description of the Related Art In recent years, the outer surface of a PC strand is covered with a synthetic resin layer having adhesiveness, which is inserted into a synthetic resin sheath to be used in a post-tension unbonding method, or a synthetic resin coating. What has been developed to be used in a pre-tensioning bond method of embedding the product subjected to tensioning and then burying it in concrete (JP-A-1-
215528).

Even if such a conventional PC strand is coated with a synthetic resin, there is a gap between each of the simple wires forming the strand, and water or air intrudes into the gap from the end, There was a problem of corroding PC strands.

In order to solve this problem, in the production of PC strands, each single wire is coated with a synthetic resin in advance,
It has been proposed that these are twisted together to form a strand, and the outside thereof is coated with a synthetic resin (Shokaisho 61).
No. 144121).

However, since this conventional PC strand is not subjected to the bluing treatment, there is a problem that the processing strain of the material due to the twisting process remains, it is easy to unravel and the strength is not stable, and each single strand Since the entire circumference is separately covered, the total synthetic resin is interposed between each single wire, and when pulled, this synthetic resin layer is compressed and the distance between the single wires is reduced. There was a problem that it was narrowed and the elongation of the PC strand was increased.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and the inner voids between the individual element wires are completely filled with a synthetic resin material to prevent corrosion both inside and outside. It is an object of the present invention to provide a rust preventive coating method for a PC strand which can be handled as a conventional rust preventive PC strand.

[0007]

The gist of the present invention for solving the above-mentioned conventional problems and achieving the intended object is to have adhesiveness and high fluidity by heating. A synthetic resin material having a is supplied under pressure to a pressure tank in a heated state with improved fluidity, and a PC strand obtained by twisting a plurality of single wires in the pressure tank is stored in the pressure tank. A PC characterized in that the synthetic resin material is allowed to penetrate into the single strands by heating so as to cover the entire surface of each single strand of the PC strand by being passed through while being heated to a temperature substantially equal to the temperature. It lies in the method of rust-proof coating of strands.

In this method, the PC strand may be heated during the bluing process by using the heating for the bluing process as it is,
Alternatively, the bluing-treated PC strand may be heated by dielectric heating.

[0009]

According to this method, the synthetic resin material is heated and melted in a heated state, and the synthetic resin material is passed through the pressurized tank filled with the pressurized synthetic resin material. While being intimately contacted with, and permeating into the inside through twisting from the gaps between the individual strands, the internal space is filled with the synthetic resin material, and the entire peripheral surface of all the single strands is covered.

Further, since the twisted state is not loosened or loosened, an unnecessary amount of synthetic resin does not enter between the contact portions between the single wires, and the twisted state does not change.

[0011]

EXAMPLE An example of the present invention will be described with reference to FIGS.

FIG. 1 shows a first embodiment of the present invention,
In the figure, 1 is a PC strand twist processing device,
2 is a brewing heating furnace, 3 is a pressure tank, and 4 is a cooling device. Although the twisting device is not shown in detail in the figure, a plurality of single wires wound around a reel are spirally wound around the single core wire 5a and the side wires 5b, 5b ... The PC strand 5 having a cross section as shown in FIG. 3 is formed. The brewing heating furnace 2 houses an induction heating coil 2a therein, and by connecting an AC power supply thereto, the PC strand 5 passing through the center of the induction heating coil 2a is about 40.
It is designed to be heated to 0 ° C to 450 ° C.

The pressure tank 3 has a cylindrical shape as shown in FIG. 2, and has an inlet 6 for introducing the PC strand 5 at one end and an outlet cylinder 7 at the other end. .. A seal tool 8 that swivels along the spiral of the PC strand 5 as it moves is fitted in the inlet port 6, and a die 9 for molding the outer surface is fitted in the lead-out tube 7. Further, a synthetic resin material extruding device 10 is connected to the pressure tank 3, and a synthetic resin material 13 melted by a pressure pump 12 through a supply passage 11 as shown in FIG.
The pressure in the pressurizing tank 3 is adjusted by press-fitting and pressurizing the internal pressure adjusting valve 15 of the discharge passage 14. A wind tunnel type cooling device 4 is provided continuously to the outlet cylinder 7 of the pressure tank 3. In the figure, 16 is a winding device for winding the PC strand after the coating treatment.

A PC using the device thus constructed
The rust preventive coating of the strands is performed. First, the PC strands 5 twisted together by the twisting device 1 have residual strain due to processing, and the side wires 5b, 5b. It does not completely adhere, leaving a slight gap. Then, the residual strain is removed by passing it through the brewing heating furnace 2 to heat it to about 400 ° C. to 450 ° C. and gradually cooling it at room temperature.

During the bluing process, the heated PC strands 5 are passed through the pressure tank 3 at a position where the temperature required for the coating process of the synthetic resin material is maintained.
The pressure tank 3 is heated to a temperature at which the viscosity of the synthetic resin material used is the lowest. As the synthetic resin material, a silicon-based material or a polyethylene-based material is used, and the processing is performed at a temperature position matching the softening temperature.

The PC strand 5 is inserted into the pressure tank 3 while being cooled to a temperature substantially equal to the temperature of the synthetic resin material in the pressure tank 3.

In this way, the viscosity of the synthetic resin material is lowered in the pressure tank 3 to increase the fluidity thereof, and the PC strand 5 having a temperature corresponding to the temperature is inserted in a pressurized state. During the passage, the synthetic resin material 13 is filled into the inner space through the space between the side lines 5a, 5a.
The outer peripheral surfaces of all the single wires are coated, gradually cooled in the lead-out tube 7 to increase the viscosity, and cooled in the cooling device 4 to a temperature at which the fluidity disappears, and an anticorrosive coating having a cross-sectional shape as shown in FIG. P
C strand 5A is obtained.

[0018]

As described above, according to the method of the present invention, the PC strand is supplied in the pressure tank into the pressure tank in which the synthetic resin material which is heated and melted to improve the fluidity is supplied under pressure. By allowing the material to pass through in a heated state in accordance with the temperature, the synthetic resin material with high fluidity entered between the element wires, and the outer surface of all the element wires was covered. Since the twist of the PC strand does not need to be unraveled as in the conventional case, the twisted state does not change, and therefore the elongation does not increase. Further, if the heating during the bluing treatment is utilized, the rust preventive coating treatment can be continuously performed on the same line as the twisting of the PC strand.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of implementation of the present invention.

FIG. 2 is a sectional view of a pressure tank portion of the above.

FIG. 3 is a cross-sectional view of an example of PC strands to be coated according to the present invention.

FIG. 4 is a cross-sectional view of a PC strand coated according to the present invention.

[Explanation of symbols]

 1 PC Strand Twisting Device 2 Brewing Heating Furnace 2a Heating Coil 3 Pressurizing Tank 4 Cooling Device 5 PC Strand 5a Core Wire 5b Side Wire 5A Anticorrosion Coated PC Strand 6 Inlet 7 Derivation Cylinder 8 Sealing Tool 9 Dice 10 Synthetic Resin Material Extruder 11 Supply path 12 Pressurizing pump 13 Synthetic resin material 14 Discharge path 15 Internal pressure adjustment valve 16 Winding device

Claims (3)

[Claims] 1. A synthetic resin material having adhesiveness and having high fluidity by heating, is pressurized and supplied into a pressure tank in a heated state with increased fluidity, and is supplied into the pressure tank. The synthetic resin material is permeated between the single strands by passing a PC strand in which a plurality of single strands are twisted together while being heated to a temperature substantially the same as the temperature in the pressure tank. An anticorrosion coating method for a PC strand, which comprises coating the entire surface of each single strand of the strand. 2. The rust preventive coating method for a PC strand according to claim 1, wherein the heating of the PC strand is heating for bluing after twisting the PC strand. 3. The rust preventive coating method for a PC strand according to claim 1, wherein the PC strand is heated by induction heating immediately before passing through the pressurized tank.