JP2003056121A - Anticorrosion method for post-tension steel for prestressed concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anticorrosion method for post-tension steel for prestressed concrete maintaining an environment not corroding a periphery of the PC steel by drying the PC steel so that no water contents such as moisture or dew condensation exist around the PC steel by a simple facility. SOLUTION: A prestressed concrete (hereinafter referred to as PC) member 6 of a post-tensioning system applying prestress by arranging the PC steel 5 in a sheath pipe 3 embedded in concrete 33 is characterized by that space is provided between the sheath pipe 3 and the periphery of the PC steel 5, and dry air A1 or anticorrosive gas A such as nitrogen gas is filled in the space.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a prestressed concrete (hereinafter referred to as PC) bridge, PC slab, P
The present invention relates to a post-tensioning method for preventing corrosion of PC steel materials used for PC structures such as C tanks or PC members.

[0002]

2. Description of the Related Art Post tension type P for PC bridges, etc.
Since the PC steel wire or PC steel stranded wire or PC steel material of the PC steel rod used in the C structure is a strength member,
It is extremely important to carefully prevent corrosion so as to prevent the PC member from having a predetermined tension throughout the service period.

[0003] Conventionally, as a method of preventing corrosion of the PC steel material of a PC structure using a precast concrete member or on-site cast concrete, as shown in Fig. 6, a sheath tube 3 provided with a PC steel material 5 is used. It was common to fill with grout material 20 to prevent corrosion.

Recently, in order to improve the corrosion resistance of PC steel,
Use a PC steel material whose surface is coated with an anticorrosion resin,
In some cases, special grease is adhered to the PC steel material, polyethylene or the like is coated on the PC steel material, and in an unbonded state, tension can be introduced into the PC steel material after hardening of the concrete poured around it.

[0005]

However, when the sheath tube 3 in which the PC steel material 5 is arranged is filled with the grout material 20, the gap D inside the sheath tube 3 is narrow and the filling property is poor.
There was a problem of incomplete grout. Further, in particular, as shown in FIG. 6, in the structure in which the sheath tube 3 is arranged to bend in the positive bending section and the negative bending section in the PC structure, the high level position of the intermediate portion of the sheath tube is provided. Then, there was a problem that it became an incomplete grout state.

Also, until the grout filling work is completed,
Since water equivalent to about 45% of the cement weight is mixed in the grout material 20 so that the grout material 20 maintains good fluidity, breathing may occur in the sheath pipe in which the PC steel material is arranged. . Further, there is a problem that it is extremely difficult to confirm the grout state in the sheath tube.

For this reason, recently, PC made of grout material
Anticorrosion of steel has been regarded as a problem. On the other hand, P
C steel material coated with anticorrosion resin on the surface or grease-filled has physical properties due to damage to the anticorrosion resin during on-site work or due to heat of hydration reaction during hardening of cast concrete on site. There was a problem of change.

An object of the present invention is to provide a method for preventing the corrosion of the PC steel material arranged in the sheath tube by using a means for keeping the environment around the PC steel material in a non-corrosive environment, unlike the idea of the conventional corrosion prevention method. It is what

[0009]

According to a first aspect of the present invention, there is provided a post-tension prestressed concrete in which a PC steel material is placed in a sheath tube embedded in concrete and prestressed. , PC) anticorrosion method for PC steel material, a gap is provided around the sheath tube and the PC steel material,
The gap is filled with an anticorrosive gas.

Further, the invention of claim 2 is characterized in that, in the invention of claim 1, a sensor is provided for monitoring a corrosion factor of a gap provided around the sheath tube and the PC steel material.

Further, the invention of claim 3 is characterized in that, in the invention of claim 2, the sensor for monitoring the corrosion factor is either a humidity sensor or an oxygen concentration sensor.

Furthermore, in the invention of claim 4,
In the invention according to any one of claims 1 to 3, a PC
An air supply port is provided at one end of the sheath pipe so as to be in communication with the gap between the one end of the steel material and the sheath pipe, and an exhaust port is provided at the other end of the PC steel product for communication with the sheath pipe. It is characterized in that dry air is sent from the air supply port, and the gap is constantly filled with the anticorrosive gas made of dry air.

Furthermore, the invention of claim 5 is characterized in that, in the invention of claim 4, the operation of supplying dry air is controlled by the data of the humidity sensor of claim 3.

Further, in the invention according to claim 6, in the invention according to any one of claims 1 to 3, an air supply port communicating with a gap between the one end portion of the PC steel material and the sheath tube is provided with one end portion of the sheath tube. An exhaust port is provided at the other end of the sheath tube, which is connected to the gap between the other end of the PC steel material and the sheath pipe, and nitrogen gas is sent from the air supply port to replace the air in the gap with nitrogen gas. After that, the air supply port and the exhaust port are sealed, and the gap is filled with an anticorrosive gas composed of nitrogen gas.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a post-tension PC member 6 with a post-tension PC of the present invention in order to explain a method of preventing corrosion of a post-tension PC steel material of the present invention.
The figure shows a state in which a method for preventing corrosion of steel is being performed, in which both ends of a sheath tube 3 integrally having an end-portion cylindrical expanded sheath portion 2 having an expanded diameter at both ends of the sheath tube body 1 are It is fitted and fixed inside a steel annular pressure bearing plate 9, and an anchor nut 10a having a female screw portion 8 is fitted and locked to each pressure bearing plate 9. An outer male screw portion of the tension pipe 10 having a steel wire insertion hole is screwed into each of the anchor nuts 10a.

Inside the sheath tube 3, a PC steel rod or a large number of PC steel wires 4 or a PC steel material 5 having strands is in a tensioned state and is separated from the inner peripheral surface of the sheath tube 3 to form a gap G. And a plurality of steel wires are twisted together to form a gap G for each strand.
And the both ends of the PC steel material 5 are inserted into the tension pipes 10 screwed and fixed to the bearing members 9 arranged at both ends of the concrete member 7. In addition, it is fixed by a wedge 11 press-fitted between the steel wire insertion hole and the PC steel wire 4.

Explaining further, the legs of the anchor nuts 10a are fitted into the central through holes of the pressure bearing plates 9 and are locked to the pressure bearing plates 9, and the inner surface of the taper is fixed through the anchor nuts 10a. The tension pipe 10 having the steel wire insertion hole is fixed, and the PC steel wire 4 inserted in the through hole of the tension pipe 10 is fixed by the split type wedge 11 having a tapered outer surface.

As shown in FIG. 1, in the concrete member 7, one end portion of the air supply pipe 12 is connected to the outer peripheral surface of the intermediate portion of the one end side end tubular cylindrical expanded sheath portion 2, and The other end of the air supply pipe 12 is located outside the one end side of the concrete member 7, and has the valve 13 and the air supply pipe 15a.
The air supply fan 15 is connected to the drying / dehumidifying machine 16 via a connecting pipe 16a.

Further, one end of a sheath exhaust pipe 14 is connected in the concrete member 7 to the outer peripheral surface of the intermediate portion of the end cylindrical tubular expanded sheath 2 on the other end side, and the sheath exhaust pipe The other end of the pipe 14 is located outside the other end of the concrete member 7 and is connected to an exhaust pipe 19 via a valve 18.

The air supply pipe 12 connected to the one end cylindrical expanded sheath 2 having the closed end, the on-off valve 13 and the air supply means constitute an air supply unit 23 which is electrically connected to the inside of the sheath pipe 3. Further, the exhaust pipe 14 connected to the other end cylindrical tubular expanded sheath 2 having the closed end, the opening / closing valve 18 and the like constitute an exhaust part 24 which is electrically connected to the inside of the sheath pipe.

In this way, the air supply section 2 is provided on both ends of the sheath tube 3.
3 and the exhaust part 24, and when the corrosion prevention gas A consisting of dry air A1 is filled around the PC steel material 5 to prevent corrosion, for example, the valve 18 on the exhaust pipe 14 side and the air supply pipe 12 side In the state where the valve 13 is opened, the moisture in the air is removed by the dry dehumidifier 16 to form dry air, and then the air supply fan 15 is operated to send the dry air as shown by an arrow in FIG. Then, the dry air flows into the sheath tube 3 from the air supply port 26 of the one end tubular expanded sheath 2 and the inflowing dry air flows between the inside of the sheath tube 3 and the PC steel material 5. Flow is discharged from the exhaust port 27 of the other end cylindrical tubular expanded sheath 2 and a steady flow of dry air is created in the sheath tube 3. If the air supply pressure of the dry air is such that the air pressure is equal to or higher than the outside air pressure, there is no risk that moisture, humidity, etc. will enter the sheath tube 3 from the outside to the inside. .

By the flow of the dry air A1, the moisture present in the sheath tube 3 and the condensed water are removed,
When the inside of the sheath tube 3 is improved from a wet state to a dry state, and in this improved state, the valve 18 on the exhaust side is closed and then the valve 13 on the air supply side is closed, the inside of the sheath tube 3 is dried. It can be filled with A1 (A) and sealed. Thus, when the sheath tube 3 is filled with the dry air A1, it is possible to prevent the PC steel material 5 from being corroded in the sheath tube 3.

In the above case, the valves 13 and 18 of the air supply unit 23 and the exhaust unit 24 are closed to fill the dry air, but the valves 13 and 18 of the air supply unit 23 and the exhaust unit 24 are opened. Then, the anticorrosion gas A such as dry air having a low flow rate is constantly continuously operated from the air supply unit 23 or the air supply fan 1
5 may be intermittently fed into the gap by intermittent operation to be filled with a continuous or intermittent anticorrosive gas flow, or the sensor 21 (21a) may be used for anticorrosion after filling the gap. The anticorrosive gas A may not be supplied and may remain filled with the anticorrosive gas until the decrease in the filled state of the anticorrosive gas A is detected.

When dry air A1 is used as the anticorrosive gas A as in this embodiment, the cylindrical expanded sheath 2 is formed on the outer peripheral surface of the end cylindrical expanded sheath 2 on the other end side. A sensor 21 composed of a humidity detecting sensor 21a is provided inside the diameter sheath portion 2, and when nitrogen gas A2 is used as the anticorrosive gas A as described later, the sensor 21 is replaced with the oxygen concentration detecting sensor 21b. You can do this. The humidity detection sensor 21b may be fed back based on the data, and the control device may operate the air supply fans 15 and 34 continuously or intermittently to supply the dry air or the nitrogen gas. .

Further, each of the sensors 21 (21a, 21a
b) is connected to the sensor monitor 22 arranged outside the PC member 6, and the signal from the sensor 21 such as the humidity sensor 21a or the oxygen concentration sensor 21b is P
The data is monitored by being recorded on the monitor 22 installed outside the C member 6. Further, a control device (not shown) is connected to the monitor 22, or a control device (not shown) is incorporated in the monitor 22, and the control device causes the air supply side fan 15 and the drying device 15 to dry. Operate the dehumidifier 16 as appropriate to dry air A1 or nitrogen gas 35
The air can be supplied by the air supply fan 34 to fill the gap with the anticorrosive gas. Also, with the monitor 22,
The atmosphere in the gap can be constantly grasped, and the atmosphere in the sheath tube can be kept in an anticorrosive gas by automatic operation or artificially.

Any appropriate means can be adopted as the sealing means for preventing the leakage of the anticorrosive gas such as the dry air A1 or the nitrogen gas A2 from the air supply part 23 side or the exhaust part 24 side. In the embodiment, the leakage preventing cap 28 is screwed into the male screw portion of the tension pipe 10, and the end face of the tension pipe 10 is crimped by the annular rubber plate 30 arranged on the inner surface of the head portion of the leakage preventing cap 28. In this way, leakage is prevented. The anchor nut 10
When it is necessary to leak air from the contact surface between the pressure support plate 9a and the pressure support plate 9, an air leak prevention rubber ring 29 is provided on the flat side surface of the pressure support plate 9 as in this embodiment. It may be attached to the distal end of the tubular leg portion of 28 to be crimped.
Further, the leak preventing cap 28 may be attached in a state where the inside of the tension pipe 10 is appropriately filled with a filling material.

On the outside of the end of the sheath tube 3, a reinforcing spiral reinforcing bar 31 is embedded and fixed in the concrete member 7 for reinforcement.

As described above, according to the present invention, the air supply section 23 and the exhaust section 24, which are electrically connected to the inside of the sheath tube 3, are provided at the end of the sheath tube 3 in which the PC steel material 5 is disposed, and the dry dehumidifier 16 is provided. An air supply / drying device 32 including an air supply fan (blower) 15 is installed, and the dry gas A is flown into the metal or plastic sheath tube 3 in which the PC steel material is disposed. Air supply unit 2
The dry gas flowing into the sheath tube 3 from the sheath tube 3
It flows inside and in the gap G of the PC steel material 5, is discharged from the exhaust port 27 of the exhaust unit 23, and a steady flow of dry gas can be made in the sheath tube 3. The flow of the dry gas removes moisture, dew condensation (moisture) and the like existing in the sheath tube 3 to improve the moist environment in the sheath tube 3.

According to the present invention, as described above, when dry gas or nitrogen gas is caused to flow through the clearances of the PC steel material constituting the sheath tube 3 and the PC steel material 5, when there is moisture or condensation remaining inside the sheath tube. Is to remove them to a dry state or replace the air with nitrogen gas to protect the PC steel from corrosion over the entire length of the PC steel.

[0030]

EXAMPLES Examples of the present invention will be described below. When constructing the post-tension type PC structure according to the present invention, as in the case of manufacturing a conventional PC member, for example, the sheath tube 3 is provided in a form frame (not shown) arranged across the piers or abutments 36. After the concrete 33 has been embedded and has reached a predetermined strength, the PC steel material 5 arranged in the sheath tube 3 is tensioned by a jack (not shown) connected to an internal thread portion inside the tension pipe 10. PC steel 5
After fixing the end of the, press prestressing to open the jack. After that, the anticorrosive gas is sent from the air supply section by using the air supply section 23 and the exhaust section 24 which are provided in advance in the sheath tube 3 embedded in the PC member 6. When a dry gas is used as the anticorrosive gas, the dry gas is sent from the air supply unit 23 and discharged from the exhaust unit 24. As the dry gas as the anticorrosive gas, it is better to use air having a relative humidity as low as possible, and it is necessary to use dry air having a relative humidity of 60% RH or less.

The reason for this is that, as shown in the relationship diagram between iron corrosion and relative humidity shown in FIG. 4, the corrosion rate of metal becomes very slow in an environment where the relative humidity is 60% RH or less. It is necessary to use dry air with humidity.

Further, the humidity of the exhaust gas is detected and monitored by the sensor 21 and the monitor 22 to monitor the anticorrosion condition in the sheath tube 3 in which the PC steel material 5 is arranged. As a result, when the humidity of the gap G in the sheath tube 3 becomes 60% or more of the relative humidity, the air supply fan 15 is automatically operated and the sheath tube 3 is operated.
ON / to automatically stop the operation of the air supply fan 15 when the relative humidity of the inner gap G becomes less than 60% (for example, 55%).
It may be controlled to be turned off.

If nitrogen gas is used as the dry gas, the air around the metal wire such as the PC steel wire 4 or the PC steel material 5 can be expelled and replaced, and the gap can be made oxygen-free, so that the PC steel material 5 is corroded. It is possible to create an environment that does not cause Next, a mode of using this nitrogen gas will be described.

Also in the case of nitrogen gas, it is possible to use the structural equipment shown in FIGS. 1 and 2 to fill the gap with nitrogen gas as an anticorrosive gas, as in the case of filling the gap with dry air. it can.

In this case, as shown on the right side of FIG. 1, the nitrogen gas A2 in the nitrogen gas cylinder 35 is sent from the air supply port 26 by the air supply fan 34 to replace the air in the gap G with the nitrogen gas A2. After that, the air supply port 26 and the exhaust port 27 are sealed, and the gap G is filled with the anticorrosive gas A composed of the nitrogen gas A2. The air supply pipe 34a may be connected to the valve 13, or the air supply pipe 15a may be used also as the air supply pipe 34a and the air supply fan 34 may be connected thereto.

When nitrogen gas A2 is used as the anticorrosive gas, the sensor 21 uses the oxygen concentration sensor 21b.

Dry air or nitrogen gas is fed to the sheath tube 3 and P.
When air is supplied to the gap G of the C steel material 5 and the air supply side and the exhaust side end are sealed after being filled, the air supply / drying device 32, the nitrogen gas supply fan 34, and the nitrogen gas cylinder 35 are
They may be sequentially relocated or removed. As described above, the air supply port 26 and the exhaust port 27 are sealed by closing the valve 13 and the valve 18 on the other end side. The valves 13 and 18 are
If necessary, it may be fixed to the concrete member 7 with appropriate metal fittings.

The present invention can be applied to post-tension type PC bridge girders, PC tanks for fluid storage, PC structures such as PC girders in the field of construction, and other post-tensioned PC (prestressed concrete) structures. You can Post tension PC structure
The structure may be arranged vertically or horizontally, or may be arranged diagonally.

In the present invention, the term "filling the gap with the anticorrosive gas" means that the gap is continuously filled with the anticorrosive gas, or the anticorrosive gas is intermittently filled. It may be filled by flowing, or may be in a static state in which the anticorrosive gas is not forcedly flowed in the gap.

In carrying out the present invention, as the fixing means of the PC steel material, in addition to the wedge-type fixing method of the above-mentioned embodiment, a screw type fixing method in which a screw portion is provided at the end of the PC steel material and is fixed by a nut A suitable fixing method such as a method, a sleeve-type fixing method using a threaded sleeve, or the like may be adopted.

When the present invention is carried out, a pressure pump may be used in place of the air supply fan 15, and dry air or nitrogen gas is sucked by a suction pump on the exhaust side to form a gap in the sheath tube 3. Alternatively, the anticorrosive gas may be filled.

The present invention can also be applied to the corrosion prevention of a precast concrete member having a sheath pipe embedded therein or a PC steel material used for a post tension type PC member using a cast-in-place concrete member.

When the present invention is carried out, the inert gas other than dry air and nitrogen gas may be used as the anticorrosive gas.

[0044]

According to the present invention, since a gap is provided around the sheath tube and the PC steel material and the gap is filled with the anticorrosive gas, the corrosion factor is removed from the environment around the PC steel material. Therefore, it is possible to reliably prevent the PC steel material from being corroded, and it is possible to exert stable strength on the PC member for a long period of time. Further, by providing a sensor for monitoring the corrosion factor such as humidity or oxygen concentration in the gap, and monitoring these corrosion factors, it is easy to determine whether the atmosphere in the gap has a good anticorrosion property. Can be monitored.

If the air supply operation is controlled by the data obtained from the sensor, the running cost can be reduced.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional side view showing a state in which a post-tensioned PC steel material is subjected to a corrosion prevention method according to an embodiment of the present invention to protect the PC steel material from corrosion.

FIG. 2 is a partially longitudinal side view showing one end portion (left side) of FIG. 1 in an enlarged manner.

FIG. 3 (a) is a view showing a PC member having a plurality of spans,
It is a partially longitudinal side view showing a state in which a steel material is arranged.
(B) is a sectional view taken along the line AA of FIG. 1.

FIG. 4 is a graph showing the relationship between iron corrosion and relative humidity.

FIG. 5 is an explanatory view showing a conventional method for preventing corrosion of a PC steel material of a PC bridge, in which (a) is a longitudinal side view and (b) is a sectional view taken along the line BB of (a) showing the inside of the sheath pipe. It is a figure which shows the state which filled up with the grout material.

[Explanation of symbols]

1 sheath tube 2 End diameter expansion cylindrical part 3 sheath tube 4 PC steel wire 5 PC steel 6 Post tension PC member 7 Concrete members 8 Female thread 9 bearing plate 10 Tension pipe 11 wedges 12 Air line 13 valves 14 Exhaust pipe 15 Air delivery fan 15a Air supply pipe 16 Dry dehumidifier 16a connecting pipe 18 valves 19 Exhaust pipe 20 grout 21 sensor 21a Humidity sensor 21b Oxygen concentration sensor 22 Monitor device 23 Air supply unit 24 Exhaust section 26 Air outlet 27 Exhaust port 28 Leak prevention cap 29 Rubber ring for leak prevention 30 annular rubber plate 31 Spiral reinforcement for reinforcement 32 Air dryer 33 concrete 34 Nitrogen gas blower fan 34a Air supply pipe 35 nitrogen gas cylinder 35a connecting pipe

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hidemitsu Matsuda             2-6-3 Otemachi, Chiyoda-ku, Tokyo New Japan             Steelmaking Co., Ltd. (72) Inventor Tatsuya Eguchi             2-6-3 Otemachi, Chiyoda-ku, Tokyo New Japan             Steelmaking Co., Ltd. F-term (reference) 2D059 BB39 GG02 GG23 GG61                 2E164 DA03 DA12

Claims (6)

[Claims] 1. A post-tension prestressed concrete in which a PC steel material is placed in a sheath tube embedded in concrete and prestressed (hereinafter,
In the method of anticorrosion of PC steel material in PC), a space is provided around the sheath tube and the PC steel material, and an anticorrosive gas is filled in the space, and the anticorrosion method of post-tension PC steel material. 2. The post-tension PC steel material anticorrosion method according to claim 1, further comprising a sensor for monitoring a corrosion factor in a gap provided around the sheath tube and the PC steel material. 3. The post tension PC according to claim 2, wherein the sensor for monitoring the corrosion factor is either a humidity sensor or an oxygen concentration sensor.
Anticorrosion method for steel materials. 4. An air supply port, which is connected to a gap between one end of the PC steel material and the sheath pipe, is provided at one end of the sheath pipe, and an exhaust port is connected to a gap between the PC steel material and the sheath pipe at the other end. The post according to any one of claims 1 to 3, wherein the post is provided at the other end of the sheath tube, dry air is sent from an air supply port, and the gap is constantly filled with an anticorrosive gas made of dry air. Tension PC Steel anticorrosion method. 5. The method for preventing corrosion of a post-tension PC steel material according to claim 4, wherein the air supply operation of dry air is controlled by the data of the humidity sensor according to claim 3. 6. An air supply port communicating with a gap between one end of PC steel and a sheath pipe is provided at one end of the sheath pipe, and an exhaust port communicating with a gap between the other end of PC steel and a sheath pipe is sheathed. Provided at the other end of the pipe, nitrogen gas is sent from the air supply port, the air in the gap is replaced with nitrogen gas, the air supply port and the exhaust port are sealed, and the anti-corrosion property consisting of nitrogen gas in the gap The post-tension PC steel material anticorrosion method according to claim 1, wherein the post-tension PC steel material is filled with gas.