JPH0328444A - Method for preventing corrosion of pc steel stranded wire for prestress concrete - Google Patents

Abstract

PURPOSE:To produce a high corrosion preventing effect by a method wherein the twist of a stranded wire of a PC steel formed by twisting together a plurality of side wires around a core is slackened, and after the whole peripheries of the side wires and the core is covered with synthetic resin, a twisted state is restored. CONSTITUTION:The tip of a PC steel stranded wire 10 is pulled out from a rewinding device 31, and is ted to a slackening device 36 through a gap between endless belts 33a and 33b of an interrupting device 33, an adhered substance removing device 34, and a heating device 35. A twist is untwisted from the tip part of the PC steel stranded wire 10 by a manual work, and is spread into each of side wires 10a and a core 10b. The untwisted wires 10a and 10b are caused to pass a powdery material feed device 45 to spray synthetic powdery material paint, and a synthetic resin covering layer (a) with o uniform thickness is formed on the surface thereof. Thereafter, a twisted state is restored to an original state, and a secondary covering layer (b) is adhered to the outside of the synthetic resin covering layer (a). This method improves a corrosion preventing effect.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides the following features in the production of prestressed concrete:
Concerning a rust prevention method for PC steel strands used for prestressing. (Conventional technology and its problems) Conventionally, as a rust prevention method for PC steel stranded wire in which multiple four wires are twisted around a core wire, tension is applied to the PC steel wire in advance when manufacturing prestressed concrete. Later, this was embedded, concrete was poured, and the concrete
As shown in Fig. 19, the pre-tensioning method in which both ends of the PCw4 stranded wire are opened and a press l/res is introduced into the concrete after solidification in Steps 1 to 1 is as shown in Fig. 19.
A coating layer 1 is applied to the entire outer peripheral surface of the PC steel stranded wire 10 by a powder coating method using a synthetic resin powder material such as polyethylene or epoxy, or an extrusion method using the same material.
1 (Japanese Unexamined Patent Publication No. 59-1 30960). In this method, it is necessary to completely cover the inside of the spirally shaped part 13 between the side lines 10a, 10a of the p c f4 strand line ■0, to which the coating layer 1l is applied, with the coating layer 11. , it is necessary to increase the overall thickness of the covering layer 11 considerably, and in this case, the spirally shaped portion 14 appearing on the outer surface of the covering layer 11 must be made smaller. However, in the pretensioning method, the helical deformed portion 14 on the outer surface of the coating layer 11 is the most important part for obtaining adhesion to concrete, and the smaller the helical deformed portion 14 is, the more the adhesion to the concrete becomes. This leads to a decrease in the adhesion force. In addition, the PC steel stranded wire has an elliptical core wire and M
There is a gap between the j lines, which is 3 in the longitudinal direction! ! Since the end is not completely sealed, air and water will flow freely through this gap.
In addition, internal corrosion caused by penetration of water, etc. due to holes in the surface coating or damage to the coating during concrete pouring has become a problem. On the other hand, in order to increase the adhesion with concrete, the above-mentioned Japanese Patent Application Laid-Open No. 5-9-1. Publication No. 30960 discloses a method of forcing sand-like particles onto the surface of the coating layer to make them adhere to the surface of the coating layer, but there are only a few practical examples, and in fact, in the case of the pretensioning method, most of them are not suitable for rust prevention. Currently, untreated PC# stranded wire is used. In addition, after pouring concrete, wait for it to solidify before using P.C.
When using the post-tensioning method, which tensions the S-wire and introduces prestress, the adhesion between the PC steel wire and the concrete is not a problem when introducing prestress; Since the steel strands must be able to move in the axial direction, the 20th
PC as shown! A method of applying an oil-based anti-rust lubricant 15 to the surface of the IiI stranded wire 10, and covering the outer curve with a synthetic resin cylinder 16 by extrusion molding (U.S. Pat. No. 3,646,748, Japanese Patent Publication No. 53-47609) Publication No.). In this method, the anti-rust lubricant 15 applied to the surface of the PC@stranded wire deteriorates over time, the application tends to be incomplete, and furthermore, if the synthetic resin tube 16 cracks, However, there is a problem in that the rust prevention effect is significantly reduced. In order to solve these problems, in recent years, as shown in Figure 21, a powder coating method has been applied to the surface of the PC steel stranded wire IO using a synthetic resin material such as polyethylene or epoxy, which is crushed due to its adhesion to iron. The coating layer 17 is formed by forming the coating layer 17, and then the synthetic resin 1 is formed on the outside by extrusion molding. A method has been developed to cover the PC steel strands with il8, but in this method as well, there are gaps between the core wires and side wires that make up the PC steel strand, and the cut end surface or the coating The problem of water infiltrating through the bottle holes and damaged parts of layer 17 has not been resolved. Furthermore, as shown in FIGS. 22 and 23, a coating layer 18 made of synthetic resin is applied to the side wire 10a and core wire 10b of the PC@ stranded wire before being twisted, and then these are twisted to form a stranded wire. None, a method of applying one grease to the surface and providing a synthetic resin coating layer 20 on the outer curve, and a method of applying a synthetic resin coating layer 21 to the outer surface of the wire without using grease 1-1 4 4 1 2
Publication No. 1) has been proposed. In this method, the core wires and open wires that make up the PC steel stranded wire are each coated with synthetic resin, which provides more complete rust prevention. , and forming a coating layer on each of the side lines,
These wires are twisted together to form a stranded wire, and because it has a synthetic resin coating layer, heat treatment (blueing) cannot be applied to remove residual stress after the stranding process. That is, normally, after the stranded PC steel wire is twisted, it is heated to about 400°C to remove the residual stress after the processing.
This stabilizes the twisted state, but in the case of PCw4 wire, the twisting is done with almost only elastic deformation, so if blueing is not done, the ends of There is a problem with it coming apart. Furthermore, if a process were to be applied to maintain the strands even without bluing, the synthetic resin coating layer would be damaged during the process, resulting in problems such as the rust prevention effect not being maintained. (Problems to be Solved by the Invention) In view of the above-mentioned conventional problems, the present invention solves the following problems for a PC steel stranded wire that has been blued and is in a stable twisted state.
The purpose of the present invention is to provide a rust prevention method for PC steel stranded wires, each of which is coated with a synthetic resin, which can be processed without damaging the FW layer during processing, and which has a high rust prevention effect. ．． (Means for Achieving the Object) The feature of the rust prevention method for PC steel stranded wire of the present invention for achieving the above-mentioned objects is first that the method is formed by twisting a plurality of side wires around a core wire. While partially untwisting the PC steel stranded wires, a synthetic resin paint is supplied to the loosened positions to form a synthetic resin coating around the entire circumference of each of the four wires and core wires, and then the twisted wires are twisted. The second step is to gradually loosen the twist of the PC steel stranded wire, which is formed by twisting multiple side wires around the core wire, and then apply synthetic resin to the loosened position. The purpose is to supply a paint to form a synthetic resin coating around the entire circumference of the side wires and the core wire, restore the twisted state to its original state, and then further apply a synthetic resin coating treatment to the surface. (Operation) In this method, by partially loosening the already twisted PC steel strands, the spaces between each side wire and core wire are opened, which allows the synthetic resin paint to be applied to each wire. It becomes a state. In this state, on the entire surface of each line,
For example, coating is performed using a powder coating method such as an electrostatic method or a dipping method.

After painting, the stranded state is restored to its original state, resulting in a PC@stranded wire with anti-rust coating applied to each side wire and core wire. In addition, in the PCM stranded wire that has been rust-proofed in this way, the depth of the spirally erased portion between each side wire is greater than that before the rust-proofing coating, so when used for pretensioning, it is difficult to concrete 1. The adhesion force to the material increases. Also, after forming a synthetic resin coating on each side wire and core wire, the loosening was canceled and the twisted state was restored to its original state. Furthermore, by applying a synthetic resin coating to the surface, a strong coating that is resistant to damage during prestressed concrete construction can be obtained. (Example) Next, implementation 1 of the present invention will be explained with reference to FIGS. 1 to 23. Figure 1 shows the arrangement of equipment used in the first embodiment. In the figure, 3l is a rewinding device, and as shown in the cross section shown in FIG. 8, a measuring line 10a. 10a・
A coil 32 wound with wire 10 made of twisted PC steel is rotatably supported.
33 is a celestial feeding device, which presses a pair of driving endless belts 33a, 33b against each other, and clamps the PC steel strand 10 pulled out from the unwinding device W 3 1 between them to drive both bells 1 33a, 33b. I am trying to force it to be sent. 34 is a deposit removal device;
In this example, shot blasting is used, and sand is blasted onto 4t10 from PC steel to remove oil and other contaminants. 35 is a heating device, in which a high-frequency induction heating device is used to heat the PC steel strands to the temperature required for subsequent powder coating. 36 is p
From ct, loosen the rising of wire 10 and open wires 10a, 10a...
. . . This is a loosening device for mutually expanding the space between the cores 1a10b, and as shown in FIG. The loosening guide plate 39 is rotated by a motor 41 via a chain 40. As shown in FIGS. 3 and 4, the loosening guide plate 39 has a core wire guide hole 42 at its center, and side wire guide holes 43 arranged on the same circumference at intervals around the core guide plate 39.・A chain wheel 44 is integrally molded on the outer periphery. 45 is a powder coating supply device, and as shown in FIG.
is inserted, and its vI. Synthetic resin powder coating 11 is sprayed with air from spray cans 4747, 47 from three directions toward the solution part 1.0C. Reference numeral 48 is a light source device, which uses an infrared lamp. 49 is a cooling device that circulates cold air to prevent rust from PC.
The #l stranded wire 10A is cooled to room temperature. Reference numeral 50 denotes an output drawing device, which has a pair of endless belts 50a and 50b that are pressed against each other and driven, and a rust-proofed PC# stranded wire 10A is held between the belts and forcibly drawn out. Reference numeral 51 denotes a winding device, which rotates a reel 52 to wind up the anti-corrosion treated PC* up line 10A. 53 is a leading wire winding device for preparatory work. Next, we will explain the rust prevention treatment performed using this equipment. Prior to continuous operation of this equipment, preparatory work will be carried out. First, the tip of the PC steel strand 10 is pulled out from the unwinding device 31 and fed through between the endless belts 33a and 33b of the interrupting device 33, through the deposit removing device 34 and the heating device 35 to the loosening device 36. Next, manually insert the sixth
Loosen the twist as shown in the figure, and each round line 10a'?
: Insert the core wire 10 into the same-line guide hole 43 of the M-solution guide plate 39.
b into the core wire guide tube 42. And the 7th! 7th!
As shown in I, create a loosening part 10c of a certain length,
Twist the ends together again by hand. In this twisting, each ■ wire 10a is permanently deformed, so
This can be done without any particular effort. Next, a leading wire 54 is fixed to the twisted ends as shown in FIG. The leading wire 54 is passed through the powder coating supply device 45, the post-curing device 48, the cooling device 49, and the drawing device 51, and then wound around the leading wire winding device ff53. In this state, all equipment starts continuous operation. As a result, the PCI stranded wire lO is continuously drawn out from the unwinding device 33 to the feeding device 33, passed through each device, subjected to rust prevention treatment, and then drawn out by the drawing device 50. When the completely rust-proofed portion is pulled out of the drawer 49, the incompletely treated portion is cut and the rust-proofed PCM wire 10A, which is successively drawn out, is transferred to the reel 52 of the winding device 51. Wind it up. Next, this rust prevention treatment step will be explained. The PC steel stranded wire 10 is prevented from rotating in the circumferential direction by the unwinding device 33 and the pulling device 50, and is moved only in the axial direction.
First, in the heating device 36, the powder paint supply device 4
In Step 5, the resin powder coating is heated to a temperature that maintains the temperature at which it melts and adheres to the surface when it adheres. In this state, the PC steel stranded wire 10 is sent to the loosening device 36, where the loosening guide plate 39 is rotated by the motor 41 in the twisting direction in accordance with the twisting pitch of the PC steel stranded wire 10. The wires are constantly unraveled by a certain length L, and are automatically twisted again after moving by L. This fixed length is set in advance to a length that will maintain the unraveled state for a certain period of time after the synthetic resin powder coating described later is sprayed and until it begins to harden. In this way, the loosened state enters the spray booth 46 of the powder supply device 45 and is heated by the spray gun 47.
A synthetic resin powder coating with a charge value of
This is adhered to the surface of each side wire 10a and core wire 1ob to which a charge value of ■ is given in the loosening device 36, and is melted.
As shown in FIG. 9, each line 10a, . A synthetic resin coating layer a is formed to a uniform thickness on the surface of 10b. Then, the first
As shown in Figure 0, the space between each 4!10a and 10b is densely filled, and the wire 10A is made of rust-proof treated PC steel with a synthetic resin coating layer a applied to the outer surface, and the post-heating device 49
The surface of the coating layer is prepared by being heated again in the cooling device 5.
Depending on the length of the loosened and loosened part 10C, the synthetic resin paint applied by cooling in step 1 is completely cured.
As shown in Figure 1, each line 10a, 10b is coated with synthetic resin 1a.
can also be made independent. Further, the post-ripening device 49 in the above-described embodiment is not necessarily necessary depending on the type of synthetic resin powder coating. In addition, in the above example, the PCgA strands were coated with powder paint.
Electrostatic powder coating is used, in which the PCIlA strands are preheated and a fluidized powder coating is sprayed onto them, which is the so-called method. Powder coating using fluidized dipping may also be used. Furthermore, as shown in FIG. 12, an electrostatic powder paint supply device 55 for secondary coating is installed between the powder paint supply device 45 and the post-heating device 48, and as shown in FIG. After both strands 10a and 10b are stranded, a secondary coating layer b is further attached to the outer surface of the synthetic resin coating layer a on the surface thereof, whereby a static-proof treated PC steel stranded wire 10B with even higher reliability can be obtained. (Test example) I. l) Rust strength test (1) Type of test piece a) Conventional surface-only rust prevention method b) Rust prevention method of the present invention (2) Rust prevention coating resin type and thickness a) Conventional type epoxy (Resin 700 microns) Invention Epoxy resin 300 microns + 3) PCjl1 Type of stranded wire A) Conventional one SWPRB 12.7W from 7 wires) Invention SWPR8 12.7W from 7 wires (4
) Test method Salt spray test (5) Test piece length 200 cm (6) Test method a. Five pieces each of the conventional product and the present invention product were cut off at both ends with a cutter as shown in Figure 14, and immersed in salt water.
Corrosion caused by salt water penetration inside the area can be seen from both ends. b. As shown in Fig. 15, 5 each of the conventional product and the present invention product were sealed at both ends with synthetic resin F, and a spiral shape was sandwiched in the center of the test piece, with a width of about 3 cm and a length of about 50 cm. Cut off the coating and look at the corrosion caused by saltwater penetration inside from the cut section G. (7) Test time: 2,000 hours (8) Judgment method: Peel off the surface coating layer and loosen the open wires one by one.
After washing with running water, leave it for 2 hours and observe with the naked eye. (9) Test results a) Conventional surface-only rust prevention method a. Salt water penetrates from both cut surfaces @open surface, and rust occurs inside the stranded wire, covering the entire surface coating layer! There was rust all over the survey line and core line. b. Salt water penetrated from the part where the coating layer was removed (width: 3 cm, length: 50 cm), and the entire surface coating layer expanded due to the occurrence of rust inside the stranded wire, and rust was generated throughout both the open wire and the core wire.

(a) In the case of the rust prevention method of the present invention, rust was observed only on the side surfaces of both ends of the cut surface which had not been subjected to rust prevention treatment, and no rust was observed on the wire or core wire. b. Covering layer removed part (3 meters wide, 50 meters long)
) Rust was observed only in areas where anti-rust treatment was not applied, but no rust was observed on the survey lines or core wires. ■． Concrete adhesion test O (fixation test 1tl!) (1
) Standard mix design basic strength of concrete (krf/ad). 400
Strength when demolding (kgf/ad) 30
0 Cement type Early strength boltland cement Maximum dimension of coarse aggregate (fi) 25 slump range (cm) 6 ± 1.5 air content range (
%) 3±1 Most rain water cement ratio (%) 45 Unit cement! (kr) 400 (2)
Concrete specimen length (distance) 115 Width (lIm+) 115 Length (distance) 3,000 (4) Test method 1) As shown in Figure 16, 60 parts of the concrete specimen were tested with pcm before pouring the concrete. A stranded wire 61 is placed, and a jack 62 applies a predetermined tensile load to the PCa stranded wire 6l in the direction of the arrow. 2) Concrete is poured into the concrete specimen 60 section, and after the concrete hardens (after the concrete compressive strength reaches 300 kg/1 or more), gradually loosen the tension applied by the jack 62. 3) PC steel stranded wire 61 shrinks and concrete specimen 6
The state in which stress is introduced at 0 is measured using strain gauges 63, 63, etc. attached to the surface of concrete 1 and the specimen. (5) Test results The results were as shown in the graph shown in Figure 17. The graph shows a slightly higher value for the PC steel wire treated with the method of the present invention than for the bare PC steel wire without rust prevention. The reason for this is that in the method of the present invention, a rust-preventing coating layer is formed on each of the survey line and the core wire, so that the following conditions are observed: d1: core wire diameter d2: side wire diameter h: clear Depth j1: open line spacing (circumferential distance) j2: @ line spacing (straight line distance) 1) In the case of no coating... d + "d2 = 4.25 φ j + = 6.6766 J 2 = 6.375 h = 2.694 2) When the core wire and side wire are coated with a thickness of 300μ...d
．． = d2 = 4, s”i φ J , = 7.618 1 − = 7.275 Mh
=3. 075, the outer diameter, spiral spring width, and spring depth become larger.
This is because the adhesion force of concrete increases. (Effect of the invention) As described above, the method for preventing rust of PC steel strands of the present invention
c* By applying a synthetic resin coating to the entire circumferential surface of each side wire and core wire while partially loosening the stranded wire, it is possible to prevent the PC steel stranded wire from opening after bluing. A complete synthetic resin coating that leaves no voids between the wire and the core wire is achieved, and the wire is made from rust-proof PC steel that has a high rust-preventing effect and is in a stable twisted condition. Furthermore, in the present invention, since each side wire and the core wire are coated with resin, the outer diameter of the stranded wire becomes larger, and the spiral shape between each side wire is reduced. Because the depth of the part becomes large, the anchorage of the PC steel strands is maintained by the adhesion force to the concrete, for example, when used in greastress concrete construction methods such as the pretensioning method, the adhesion force to the concrete is increased. This has the effect of increasing the bond length and shortening the attachment length.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the arrangement of devices used in the embodiment of the present invention, Fig. 2 is a sectional view of the loosening device, Fig. 3 is a front view of the loosening guide plate, Fig. 4 is the same sectional view, and Fig. 4 is a sectional view of the loosening guide plate. Figure 5 is a partial cross-sectional view of the powder coating supply device, Figure 6 is an open view of the tip of the PC steel stranded wire loosened during slading, and Figure 7 is the tip attached to the same <1 solution guide plate. side view, No. 8
The figure is a cross-sectional view of the PC steel stranded wire before rust prevention treatment, Figure 9 is a cross-sectional view of the synthetic resin paint coating state in the decomposed part, and Figures 10 and 11 are PCG after rust prevention treatment! ! Cross section of stranded wire,
Fig. 12 is a block diagram showing the arrangement of the equipment used in the pond example, Fig. 13 is a cross-sectional view of the pcgA stranded wire treated with the same vt'JIt for rust prevention, and Figs. 14 and 15 are shown separately. Figure 17 is a graph showing the test results, Figure 18 (a) is a cross-sectional view comparing the shape before and after rust prevention treatment, Figures 19 to 23 are respectively These are cross-sectional views of separate conventional examples. 10...pc@stranded wire, 10A...rust-proofed PCI stranded wire, 10a...
... Side wire, 10b ... Core wire, 1. Oc
... Relaxing part, 31 ... Rewinding device, 32 ... Coil, 33 ... Feeding device, 33a, 33b ... Endless belt , 34・
... Deposit removal device, 35 ... Heating device, 36 ... Relaxation device, 37 ... Frame,
38... Rotating body, 39... Relaxation guide plate, 40... Chain 541... Motor, 42... Core wire guide tube. , 43...
・Side wire guide hole, 44... Chain wheel, 45... Electrostatic powder paint supply device, 46...
...Spray Poose, 47...Spray Gun,
48...Added later! ! ! Device, 49...Cooling device, 50...Drawer device, 51...
... Winding device, 52... Reel, 53... Leading wire winding device, 54...
・・・Leading wire

Claims (2)

[Claims] (1) Partially and sequentially loosening the twist of the PC steel stranded wire, which is formed by twisting multiple side wires around the core wire,
Rust prevention for PC steel stranded wire, characterized in that a synthetic resin coating is supplied to the loosened position to form a synthetic resin coating around the entire circumference of each of the side wires and core wires, and then the twisted state is restored to its original state. Method. (2) Partially and sequentially loosening the twist of the PC steel stranded wire, which is formed by twisting multiple side wires around the core wire,
A synthetic resin coating is supplied to the loosened position to form a synthetic resin coating around the entire circumference of the side wires and the core wire, and then the twisted state is restored to its original state, and then the surface is further coated with a synthetic resin. A rust prevention method for PC steel strands for prestressed concrete.