JP7190321B2 - Desalting method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technique for repairing steel structures such as steel bridges, and more specifically, to a desalination method for removing chloride ions by an electrochemical repair method.

It has been pointed out that the construction infrastructure (hereinafter referred to as "construction infrastructure"), which was intensively developed during the high economic growth period, has already deteriorated considerably. In 2014, the “Proposals for full-scale implementation of measures to deal with aging roads (Social Infrastructure Development Council)” were compiled. It will lead to a fatal situation related to the equipment," he warned, strongly advocating the importance of maintenance of construction infrastructure.

Against this background, the national government issued a ministerial ordinance to partially revise the Enforcement Regulations of the Road Act, and issued a regular ordinance indicating specific inspection methods for construction infrastructure, points to focus on major deformations, and photographs of judgment cases. We have established inspection guidelines. This periodical inspection guideline covers about 700,000 bridges with a length of 2.0m or longer, and the first inspection is to be carried out within two years after the start of service, followed by regular inspections once every five years. I'm doing it.

By the way, bridges are categorized according to their structural type (girder bridge, suspension bridge, etc.), their use (road bridge, railroad bridge, etc.), or the position of the main girder (upper bridge, underpass bridge, etc.). It is sometimes classified by focusing on In addition, it is sometimes classified by focusing on the main members (especially the main girder), and in this case, concrete bridges using concrete main girders and steel bridges using steel main girders are typical examples. be done. Of these, steel bridges use steel as the main material, so corrosion of members is one of the most important factors in maintenance.

As for the maintenance of steel bridges, it is common to perform regular (or temporary) inspections and repaint them according to the results. In the past, when deterioration was observed, the entire bridge was repainted. It may be repainted as a target.

The "Guidelines for Partial Repainting of Steel Highway Bridges" stipulate that partial repainting be carried out in order to maintain the anti-corrosion function of the entire paint and prevent the progress of corrosion. ing. Substrate preparation is the work to remove the old paint film and form a normal painted surface. .

Patent document 1 also discloses a technique for repairing steel bridges by repainting, and proposes a painting method in which the ends of main girders that are significantly deteriorated are coated with highly weather-resistant paint, and other general parts are painted at low cost. there is

JP 2006-144285 A

By the way, steel bridges built along the coast may be subject to airborne salt from seawater, and steel bridges constructed in cold regions may be subject to salt from antifreeze sprayed on the road surface. When repainting a steel bridge with salt attached in this way, the surface is adjusted as described above. /m ² ) has been reported. Especially in the bolt part, since sufficient cleaning cannot be performed, salt tends to remain. In addition, when repainting the damaged part of a weather-resistant steel girder, even if a type 1 cleaning is performed, salt remains inside the surface pitting corrosion peculiar to weather-resistant steel, so it cannot be removed sufficiently. Salt remains or requires a great deal of time and effort to be sufficiently removed.

Since salt promotes corrosion of steel materials, it is desirable to remove salt adhering to steel bridges. However, the conventional washing method cannot sufficiently remove the salt content, and as described above, even if one type of cleaning is performed, the salt content exceeding the standard value may remain. Therefore, a technique that can effectively remove the salt adhering to the steel material has been desired.

An object of the present invention is to solve the problems of the prior art, that is, to provide a technique capable of effectively removing salt adhering to steel materials.

The present invention was made with a focus on applying the electrochemical repair method, which is sometimes employed as a repair method for reinforced concrete structures, to steel materials, and is based on an unprecedented idea. It is an invention that has been made.

The desalting method of the present invention is a method for removing salt content from steel materials, and is a method comprising an electrode installation step and an energization step. In the electrode installation step, a planar electrode is installed so as to form a gap from the surface of the steel material. In one energization step, an electrolyte solution is supplied between the electrode and the surface of the steel material, and electricity is energized with the electrode on the anode side and the steel material on the cathode side. The steel material is desalted by electrophoresis of the chloride ions contained in the steel material to the electrode side.

The desalination method of the present invention can also be a method of arranging a spacer between the electrode and the surface of the steel material in the electrode installation step. In this case, due to the effect of arranging the spacers, it is possible to form a separation between the electrode sheet and the surface of the steel material.

The desalting method of the present invention can also be a method further comprising a watertight sheet installation step and a suction step. In this watertight sheet installation process, a watertight sheet is installed on the surface of the steel material so as to cover the electrodes. to In this case, the energization step is performed with a negative pressure between the watertight sheet and the surface of the steel material.

The desalination method of the present invention can also be a method that includes an electrode box installation step and uses the electrode box to remove salt content from a steel material having protrusions on its surface. This electrode box has a box having an open surface, a planar electrode fixed to a part of the inner surface of the box, and an inlet for allowing liquid to flow into the box. In the electrode box installation step, the electrode box is installed so that the open surface faces the steel material and accommodates the protrusions, and a gap is formed between the electrodes and the protrusions. In the energizing step in this case, the electrolytic solution is supplied from the inlet into the electrode box, and the electrodes are energized with the anode side and the steel material with the cathode side. The steel material is desalted by electrophoresis of the chloride ions contained in the steel material to the electrode side.

The desalination method of the present invention can also be a method of removing salt content from a steel material including a watertight sheet installation step and a suction step, and including projections and flat portions on the surface using an electrode box.

In the watertight sheet installation process, a watertight sheet is installed on the steel material surface so as to cover the electrode box and the electrodes, and in the suction process, the air between the watertight sheet and the steel material surface is sucked to to negative pressure. In this case, the electrode installation process is performed on the flat part of the steel material, and the electrode box installation process is performed on the projecting part of the steel material. In the energization step, an electrolyte solution is supplied between the electrode and the surface of the steel material, and the electrolyte solution is supplied into the electrode box from the inlet, and current is supplied with the electrode on the anode side and the steel material on the cathode side.

The desalting method of the present invention has the following effects.
(1) Since salt content can be removed easily and effectively, significant labor savings, cost reductions, and quality improvements can be achieved in steel bridge repair work.
(2) Scraping and blasting work can be suppressed, and as a result, noise and vibration can be reduced.
(3) The bolts protruding from the girders are also made of steel and can be used as cathodes in the desalting method, so salt can be effectively removed even at relatively intricate bolt locations.

Sectional drawing explaining the desalination method of this invention. FIG. 2 is a flow chart showing the main steps of the desalting method of the present invention. The side view which shows the condition which implements the desalination method of this invention. (a) is a front view showing an external electrode in which steel wires are combined in a mesh shape, and (b) is a cross-sectional view showing an energization range when an external electrode in which steel wires are combined in a mesh shape is used. A partial cross-sectional view showing the side of a steel girder with bolts installed. Sectional drawing which shows an electrode box. The side view which shows the state which installed the electrode box in the projection part. The side view which shows the state which installed the planar external electrode in the flat part, and installed the electrode box in the projection part.

An embodiment of the desalting method of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view for explaining the desalting method of the present invention. The desalting method of the present invention is a method of removing the salt content of the target steel material MT using electrochemical treatment. Specifically, as shown in FIG. 1, the external electrode 10 is connected to the anode (+ electrode) of the power source 20, a part of the steel material MT is connected to the cathode (- electrode) of the power source 20, and the external electrode 10 In this method, the electrolyte solution SL is supplied to the space 30 between the steel material MT and the steel material MT, and then a DC current is applied, and this state is continued for a predetermined period to remove the salt content of the steel material MT. Chloride ions Cl ⁻ contained in the steel material MT are electrophoresed toward the external electrode 10 side, thereby removing the chloride ions Cl ⁻ contained in the steel material MT (that is, desalting).

Hereinafter, the desalting method of the present invention will be described in detail with reference to FIGS. 2 and 3. FIG. FIG. 2 is a flow chart showing the flow of main steps of the desalting method of the present invention, and FIG. 3 is a side view showing the state of carrying out the desalting method of the present invention. For the sake of convenience, a steel main girder (hereinafter simply referred to as "steel girder GM") will be described as an example, but the desalination method of the present invention is not limited to steel girder GM, but can be applied to any steel material MT. can be implemented.

First, the target range of the steel girder GM is determined, and depending on the scale of construction, division of work sections and the order of construction are planned. Then, cleaning and cleaning are performed as necessary, and necessary preparations such as installation of scaffolding and equipment to be used and confirmation of construction procedures are prepared (Step 101).

Subsequently, the prepared external electrodes 10 are installed (Step 102). It is desirable that the external electrode 10 has a shape (planar shape) in which the surface dimensions (length x width) are extremely large compared to the thickness dimension. It can have various shapes such as plate-like or mesh-like. In addition, it is possible to use the external electrode 10 that can cover the target range with one sheet, that is, the desalination method can be performed with one external electrode 10, and as shown in FIG. A plurality of external electrodes 10 may be arranged and connected to each other by connecting wires 11 before the desalting method.

Since the external electrode 10 functions as an anode, it is made of an electrically conductive material such as titanium, steel, stainless steel, carbon fiber, or conductive rubber. Desirably, the external electrodes 10 are made of a material with a volume resistivity of 1.0×10 ⁻¹⁰ to 10 (Ω·cm).

As will be described later, an electrolyte solution SL is supplied between the external electrodes 10 and the steel girder GM. Therefore, as shown in FIGS. 1 and 3, the external electrodes 10 are arranged so that a separation 30 is formed between them and the steel girder GM. In FIG. 3, the distance 30 is shown with a slightly large width for the sake of convenience, but in practice it is sufficient if the external electrodes 10 and the steel girder GM are not in contact with each other. can be When using the external electrode 10 in which steel wires WR are combined in a mesh form as shown in FIG. It is desirable that the dimension be 1/2 or more of the interval L between the steel wires WR.

A spacer may be used to form a predetermined distance 30 between the external electrode 10 and the steel girder GM. That is, spacers having a width approximately equal to the planned width of the space 30 are prepared, and the external electrodes 10 are arranged with the spacers interposed therebetween. Note that the spacers may be arranged in a dot shape at a plurality of locations, or may be arranged in planar form such as a hydrophilic non-woven fabric. In the case of planar spacers, if a material with high water retentivity is used, it is preferable to have the function of flooding (impregnating) the electrolyte solution SL in addition to the function of the spacer. The external electrodes 10 and the spacers can be prepared separately, or the external electrodes 10 and the spacers can be integrated by attaching a non-woven fabric to one side of the external electrodes 10 .

As shown in FIG. 1, in the case where the external electrode 10 is arranged on the upper surface of a horizontal steel material such as a floor surface, the electrolyte solution SL is supplied below the external electrode 10 (that is, the distance 30) without using other materials. However, when the side surface or the bottom surface of the steel girder GM is targeted, the electrolyte solution SL may leak if only the external electrodes 10 are arranged. Therefore, in the case where the external electrodes 10 are arranged from the side or below the steel girder GM, it is preferable to use the watertight sheet 40 shown in FIG. Specifically, as shown in FIG. 3, the external electrode 10 is arranged at a predetermined position on the surface side (right side in the drawing) of the steel girder GM, and the back side of the external electrode 10 (opposite side of the steel girder GM, The watertight sheet 40 is laid (installed) so as to cover from the right side in this figure (Step 103 in FIG. 2). Therefore, the watertight sheet 40 is preferably a sheet-like sheet (for example, a vinyl sheet) that is watertight enough to prevent leakage of the electrolyte solution SL.

When laying the watertight sheet 40 as shown in FIG. 3, the Aqua Curtain (registered trademark) construction method can be used in combination. The Aqua Curtain (registered trademark) method is a method widely known as a water supply curing method for concrete. This is a water supply curing method in which the inside of the curing sheet is set to a negative pressure, and curing water flows down between the concrete surface and the curing sheet in that state. To apply the method to the desalination method of the present invention. As shown in FIG. 3, the space between the watertight sheet 40 and the surface of the steel girder GM is reduced by sucking the air between the watertight sheet 40 and the surface of the steel girder GM using an intake means PA such as a pump. pressure (Step 104 in FIG. 2). By creating a negative pressure between the watertight sheet 40 and the surface of the steel girder GM, the watertight sheet 40 is brought into close contact with the steel girder GM, and accordingly the external electrodes 10 are firmly fixed, and leakage of the electrolyte solution SL is further prevented. It can be suppressed.

By the way, the steel girder GM is often spliced in the direction of the bridge axis, or connected to a cross girder or horizontal structure, or attached to other facilities, and bolts BT are often installed as shown in FIG. . That is, the surface (for example, side surface) of the steel girder GM may have a flat portion or may have projections such as bolt BT installation portions. If the flat portion and the protrusion are used as a series of objects, that is, if the same external electrode 10 (indicated by the dashed line in the figure) is used for the flat portion and the protrusion, the arrangement depends on the protrusion such as the bolt BT, and the flat portion is flat. In some parts, the distance 30 more than necessary is formed. Alternatively, depending on the state of damage to the steel girder GM, it may be sufficient to remove the salinity only from the protrusions.

Therefore, when the desalination method of the present invention is performed on the projecting portion, it is preferable to use the electrode box 50 shown in FIG. As shown in this figure, the electrode box 50 is mainly composed of the planar external electrode 10 and the box 51 . The box 51 has a hollow box shape, and one surface (upper surface in the figure) is an open surface (hereinafter referred to as "open surface"). Then, the electrode box 50 is formed by fixing the external electrodes 10 to one of the inner surfaces of the box 51 (bottom surface in the drawing) and attaching the inlet 52 penetrating the box 51 . The inlet 52 allows the electrolytic solution SL to flow into the box 51 , and the box 51 may be provided with an outlet 53 for discharging the electrolytic solution SL to the outside of the box 51 .

FIG. 7 is a side view showing a state where the electrode box 50 is installed on the protrusion. As shown in this figure, the electrode box 50 is arranged such that the open surface of the box 51 faces the projection (steel girder GM) side and the bolt BT (projection) is accommodated in the box 51, and the steel girder GM (Step 105 in FIG. 2). However, in a state in which the electrode box 50 is fixed, it is necessary to form a predetermined distance 30 between the external electrode 10 in the box 51 and the head of the bolt BT (to the extent that they do not come into contact with each other). Electrode housing 50 (especially housing 51) is designed and constructed such that such spacing 30 is formed.

As shown in FIG. 7, the electrode box 50 can be installed alone for only the projections, or as shown in FIG. A box 50 can also be installed. Specifically, the planar external electrode 10 is installed on the flat portion, and the electrode box 50 is installed on the protrusion. Moreover, when installing the external electrode 10 and the electrode box 50, the watertight sheet 40 can also be laid so that the external electrode 10 and the electrode box 50 may be covered (Step 103 of FIG. 2). Furthermore, when installing the watertight sheet 40, the Aqua Curtain (registered trademark) construction method is also used, and by sucking the air in the watertight sheet 40 with the suction means PA, the gap between the watertight sheet 40 and the surface of the steel girder GM The space between the watertight sheet 40 and the surface of the box 51 can be made negative pressure (Step 104 in FIG. 2).

When the planar external electrode 10 and the electrode box 50 are installed, the electrolyte solution SL is supplied to the separation 30 formed between the external electrode 10 and the steel girder GM surface (bolt BT head) (Step 106 in FIG. 2 ). This electrolyte solution SL is, of course, a liquid containing electrolytes, and a solution containing a relatively large amount of electrolytes such as an aqueous potassium carbonate solution can be used as the electrolyte solution SL. can also be used as

When supplying the electrolyte solution SL to the separation 30, the separation 30 can be flooded by directly pouring the electrolyte solution SL into the separation 30, or water can be sprinkled onto a highly water-retentive material (such as a mat) installed in the separation 30. can. Also, as shown in FIG. 3, the electrolyte solution SL can be caused to flow continuously. Hereinafter, based on FIG. 3, a method for continuously flowing down the electrolytic solution SL will be described.

In FIG. 3, an external electrode 10 is arranged on the surface of the target steel girder GM, a watertight sheet 40 is laid so as to cover the external electrode 10, and a solution supply pipe SP is installed above the external electrode 10. It is A water tank TW for storing the electrolyte solution SL is also installed separately. A submersible pump PW installed in the water tank TW pumps up the electrolyte solution SL and feeds it to the solution supply pipe SP. A large number of small holes are provided in the solution supply pipe SP arranged so as to extend in the depth direction of the drawing, and the electrolyte solution SL that has been fed is discharged from these small holes and flows down within the separation 30. is. In this figure, the solution supply pipe SP is installed inside the watertight sheet 40, but if the electrolyte solution SL can flow down within the separation 30, the solution supply pipe SP can be installed outside (for example, above) the watertight sheet 40. You can also For example, by providing a plurality of communication holes in the upper portion of the watertight sheet 40 and introducing the electrolyte solution SL discharged from the small holes of the solution supply pipe SP into the watertight sheet 40 through the communication holes, the electrolyte solution SL is introduced into the space 30. can flow down to

The electrolytic solution SL that has flowed down in the separation 30 can be discharged as it is and a new electrolytic solution SL can be constantly supplied (hereinafter referred to as a "discharge method"), or the electrolytic solution SL can be circulated to continue. It is also possible to adopt a method that is used for a purpose (hereinafter referred to as a “circulation method”). In particular, when the Aqua Curtain (registered trademark) construction method is used together, it is easy to adopt this circulation system because the intake means PA is installed. That is, as shown in FIG. 3, when the intake means PA intakes air in the watertight sheet 40 through the intake pipe IP, since the electrolyte solution SL is also mixed in the intake air, the electrolyte solution SL is sorted out. The water is sent to the water tank TW and stored in the water tank TW again for continued use.

On the other hand, in the case where the electrode box 50 is installed alone as shown in FIG. When replacing the electrolyte solution SL, the electrolyte solution SL in the box 51 is discharged from the discharge port 53 , and after the discharge port 53 is closed, the electrolyte solution SL is newly injected from the inlet 52 . In the case where the planar external electrode 10 and the electrode box 50 are provided side by side as shown in FIG. 8, the electrolytic solution SL can be continuously flowed down as shown in FIG. It is also possible to adopt a discharge method that has been used in a similar manner, or to adopt a circulation method.

When preparations for supplying the electrolyte solution are completed, the external electrode 10 (the external electrode 10 of the electrode box 50) is connected to the anode (+ electrode) of the power supply 20, and a part of the steel girder GM is connected to the cathode (- pole) (Step 107 in FIG. 2). Then, while the electrolyte solution SL is supplied to the space 30 between the external electrode 10 and the surface of the steel girder GM (the head of the bolt BT), a direct current is applied (Step 108). When the Aqua Curtain (registered trademark) construction method is used together, the electrolyte solution SL is supplied to the separation 30, and a direct current is applied with a negative pressure between the watertight sheet 40 and the steel girder GM. At this time, the steel girder GM should be energized in the range of 0.001 A/m ² or more and 10 A/m ² or less.

Electricity is continued for a planned period (for example, several weeks to several months) or until a planned residual salt content (for example, an amount below the standard value) is confirmed, and the salt content is appropriately removed from the steel girder GM.

The desalination method of the present invention can be effectively used for various steel structures using steel materials in addition to steel bridges, and the present invention contributes to the extension of the service life of steel bridges, which are one of the social infrastructures. Considering the above, it can be said that the invention is not only industrially applicable but also expected to make a great contribution to society.

REFERENCE SIGNS LIST 10 external electrode 11 connection line 20 power source 30 spacing 40 watertight sheet 50 electrode box 51 box (of electrode box) 52 inlet (of electrode box) 53 outlet (of electrode box) SL electrolyte solution MT steel GM Steel girder WR Steel wire BT Bolt PA Intake means TW Water tank PW Submersible pump SP Solution supply pipe IP Intake pipe

Claims (2)

A method for removing salt from a steel material having projections on its surface using an electrode box, comprising:
The electrode box includes a box having an open surface, a planar electrode fixed to a bottom surface of the inner surface of the box facing the open surface, and an inlet for introducing a liquid into the box. , and a discharge port for discharging the liquid from the box,
With the open surface facing the steel material, the inflow port is configured to accommodate the protrusion projecting horizontally from the side surface of the steel material and to form a gap between the electrode and the protrusion. an electrode box installation step of installing the electrode box so that the discharge port is downward and the discharge port is downward ;
An energization step of supplying an electrolyte solution from the inlet into the electrode box and energizing the electrode with the anode side and the steel material with the cathode side;
and an electrolyte solution replacement step of discharging the electrolyte solution flooded in the box from the discharge port, closing the discharge port, and injecting the electrolyte solution from the inflow port. Desalting of the steel material by electrophoresis of material ions to the electrode side,
A desalting method characterized by: A method for removing salt content from a steel material containing projections and flat portions on the surface using an electrode box, comprising:
The electrode box has a box having an open surface, a planar electrode fixed to a part of the inner surface of the box, and an inlet for allowing liquid to flow into the box,
an electrode installation step of installing the planar electrode such that a gap is formed between the flat portion of the steel material and the surface of the steel material;
The electrode box is installed so that the projecting portion of the steel material accommodates the projecting portion with the open surface facing the steel material, and a gap is formed between the electrode and the projecting portion. an electrode box installation step;
a watertight sheet installation step of installing a watertight sheet on the surface of the steel material so as to cover the electrode box and the electrode;
a suction step of sucking the air between the watertight sheet and the steel material surface to create a negative pressure;
an energization step of supplying an electrolyte solution between the electrode and the surface of the steel material, supplying the electrolyte solution into the electrode box from the inlet, and energizing the electrode with the anode side and the steel material with the cathode side; and desalting the steel material by causing chloride ions contained in the steel material to electrophoresis toward the electrode side,
A desalting method characterized by:

Images