JP3325316B2 - Concrete regeneration method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing concrete such as a reinforced concrete structure and a prestressed concrete structure using reinforcing steel or PC steel as a reinforcing material.

[0002]

2. Description of the Related Art Concrete is generally
It has strong resistance to the environment such as water, fire, and sunlight, and its pH is about 12 which is strongly alkaline.Therefore, the steel inside the concrete forms a passive film on its surface to prevent corrosion. Protected, concrete structures have been considered to be durable permanent structures.

[0003] However, the durability of the concrete structure, which has been considered as a permanent structure, has been reduced due to various causes, and the life of the structure has been questioned.

[0004] One of the causes of deterioration of concrete structures is the neutralization of concrete and salt damage.

[0005] Neutralization is a phenomenon in which the pH of concrete decreases for some reason, corrosion of steel in the concrete occurs, and the concrete deteriorates. Examples thereof include carbonation caused by carbon dioxide. Can be

[0006] Carbonation is a phenomenon in which calcium hydroxide produced by a hydration reaction of cement reacts with carbon dioxide in the atmosphere to form calcium carbonate. Therefore, the alkalinity of concrete decreases. , Its pH is 12
It is a phenomenon that becomes lower.

[0007] In general, when the pH of concrete drops to about 10, the passive material coating of steel in the concrete is destroyed, corrosion of the steel starts, the strength balance as a concrete structure is lost, and its durability is greatly reduced. Is what you do.

[0008] In addition, salt damage is a phenomenon in which salt penetrates into concrete, breaks a passive film of steel material in concrete, and tends to cause corrosion. At this time, since the rust of the steel material expands, cracks are generated in the concrete due to the expansion pressure, and the cracks further progress, causing a situation where the concrete is lost, and the concrete structure is deteriorated.

When sea sand is used as the fine aggregate used as a concrete material, if the salt content is insufficiently removed, the concrete contains a large amount of chloride from the time of concrete kneading. As a result, the formation of the passive material film of the steel material in the concrete becomes insufficient,
Corrosion occurs.

Conventionally, such a method of repairing a deteriorated concrete structure has "removed" the surrounding concrete for steel rust and the concrete for cracked or missing portions of the concrete. Later, the so-called cross-section restoration method of filling with new concrete or mortar was mainly used.

This cross-section repair method repairs only visible deterioration phenomena such as rust of steel in concrete and cracking or chipping of concrete, and the portion where the deterioration phenomenon has not been confirmed at the time of repair, that is, Although the deterioration of the concrete is potentially progressing, it is not possible to take any measures for the dangerous part where the deterioration is not apparent on the surface.

Furthermore, this cross-section repair method does not deal with the root cause of the deterioration of concrete at all, and it cannot be expected that the deterioration phenomenon is fundamentally solved.

[0013] In order to solve the problem of such a potentially dangerous portion and the problem of the root cause, a direct current is passed between the steel material in the concrete and the electrode on the concrete surface, whereby the alkalinity is reduced. Moves substances and salts to reduce the pH of concrete degraded by neutralization.
A repair method using an electrochemical method has been proposed in which the concentration is increased to 12 or more or salt is removed to the outside of the concrete (Japanese Patent Application Laid-Open Nos. 1-176287 and 2-302384).

However, the effects of these methods depend on the magnitude of the direct current with respect to the surface area of the concrete, and there have been problems such as requiring a large current to obtain a sufficient effect.

Further, in these methods, a direct current is passed through concrete to move alkaline substances and salts, but the voltage for that purpose increases with the passage of time, and sometimes a voltage exceeding 100 volts is required. It was something.

In general, many concrete structures are exposed outdoors and can be easily touched by anyone. Therefore, it is not preferable to apply a high voltage to concrete in order to prevent an electric shock accident by a third party when a current is passed through a concrete structure.

It is generally said that if the voltage is 40 volts or less, even if a person receives an electric shock, death does not occur. Considering the safety of life, it is necessary to reduce the voltage to 40 volts or less when supplying current to concrete. is there.

Therefore, the conventional method has a problem that if priority is given to safety, a sufficient processing effect cannot be obtained.

The present inventor has made various studies to solve the above-mentioned problems, and as a result, has found that by adopting a specific method, the above-mentioned problems can be solved and the concrete structure can be sufficiently regenerated. As a result, the present invention has been completed.

[0020]

That is, the present invention provides a steel material inside concrete as an internal electrode, electrodes provided at two or more locations on the concrete surface as external electrodes, and a space between the internal electrode and the external electrode or the external electrode. During this time, the electrolyte solution is applied to the concrete surface area of 1 m ^2.
This is a method for regenerating concrete characterized by supplying 1 to 100 liters / day per day .

Hereinafter, the present invention will be described in detail.

The internal electrode according to the present invention is a steel material existing inside the concrete, and may be a reinforcing bar, or a steel material specially installed in the concrete may be used. There is no particular limitation.

The external electrodes used in the present invention are electrodes placed on the surface of concrete, and two or more external electrodes may be required depending on the condition of the concrete to be modified.

The distance between these electrodes is not particularly limited as long as the current flows normally.

The use of an external electrode fixed in advance to the electrolyte solution holding material is preferable from the viewpoint of saving labor, since it is not necessary to install the electrode on the concrete surface.

Here, the electrolyte solution holding material is a material that plays a role of holding the electrolyte solution given to the concrete surface on the concrete surface.
There are fibrous, porous and water-absorbing materials.

In the present invention, a current flows between the internal electrode and the external electrode or between the external electrodes.

The current in the present invention may be either DC or AC. It is also possible to arbitrarily change the polarity of the direct current during energization.

The present invention is directed to providing an electrolyte solution while an electric current is flowing, in particular, intermittently and / or continuously one or more times while an electric current is flowing. It is characterized by supplying a solution.

The term "while the current is flowing" means a period from immediately after the start of energization until the end of the energization, and also includes a period during which the energization is temporarily stopped to confirm the processing effect. .

The electrolyte solution is a solution that has ions that carry electrons in the solution and can conduct electricity. For example, there are an alkaline aqueous solution, a neutral aqueous solution, and water.

The method of supplying the electrolyte solution is a method of supplying the electrolytic solution once or twice or more intermittently while the current is flowing, and / or continuously supplying the electrolytic solution while the current is flowing. further,
Regardless of whether the supply is continuous or intermittent,
You can supply it daily, but you don't necessarily have to supply it every day.

That is, while a direct current is flowing through the concrete in order to move alkaline substances and salts, the electrolyte solution supplied immediately before the start of energization permeates the concrete with time, and as a result, the electrolyte solution near the electrode The electric resistance increases, and the voltage required to flow a predetermined current increases with the passage of time.To prevent this increase in voltage, that is, in order to prevent an increase in electric resistance near the electrode, an electrolyte solution is used. Is to supply.

Specifically, the electrolyte solution supplied immediately before the start of energization permeates into concrete immediately after the start of energization, so that the amount of the electrolyte solution near the electrodes decreases, and the electrolyte solution is reduced within approximately 48 hours. About 20 to 30% penetrate into concrete, and the resistance near the electrode starts to increase, and as a result, the voltage increases.

In order to prevent this high voltage, there is a method of supplying a large amount of electrolyte solution immediately before the start of energization.
Electrolyte required amount of the solution of concrete surface area 1 m ² per 10
0 liters or more, in order to hold the electrolyte solution on the concrete surface, there are problems such as the need for large equipment and extensive construction, but in the method of the present invention, immediately before the start of energization, an appropriate amount of electrolyte solution Is simply held on the concrete surface, and relatively simple equipment and construction can be used.

The method of supplying the electrolyte solution includes, for example, watering or spraying with a spray or the like, supply by a pump, and the like, but is not limited thereto, and any other method can be used.

The supply amount of the electrolyte solution varies depending on the condition of the concrete surface, the condition of the electrolyte solution holding member provided on the concrete surface, the ambient temperature and humidity, and the like.

However, in general, when supplied continuously, 1 to 100 liters / day is preferable per 1 m ^{2 of} concrete surface area. For example, when there is no electrolyte solution holding material on the concrete surface, the electrolyte solution is 10 to 100 liters / m ² ·
When the electrolyte solution holding material on the concrete surface is a cloth such as a nonwoven fabric, the electrolyte solution is about 1 to 100 liters / m ² · day, and when the electrolyte solution is fibrous such as cellulose fiber, the electrolyte solution is preferably When about 1 to 50 liter / m ² · day and contains a water-absorbing polymer, the electrolyte solution is 1
50 l / m of about ² · day, and more, when the hydraulic porous material, the solution is preferably about ² day 1 to 100 l / m. 1
If it is less than 1 liter / m ² · day, the resistance value near the electrode may increase.If it exceeds 100 liter / m ² · day, it becomes saturated and water is wasted, or the electrolyte solution The holding material may be washed away.

The supplied amount of the electrolyte solution is the amount of the solution actually supplied to the concrete surface. If the solution flowing out of the concrete surface is reused, the amount of the prepared electrolyte solution can be reduced. .

When the supply is performed intermittently, it is necessary to determine the supply amount per time so that the total of the day becomes a prescribed value.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below.

Example 1 A reinforcing rod inside concrete of a reinforced concrete wall having a height of 4 m, a length of 49 m and a thickness of 30 cm was used as an internal electrode.
After fixing a titanium mesh and an Elgard mesh manufactured by Eltec Asia Service Co., Ltd. as external electrodes to the concrete surface, cellulose fibers containing an aqueous solution of saturated calcium hydroxide as an electrolyte solution were sprayed. The wall length 49m is divided into 7 sections of 7m each, and the inner electrode and the outer electrode are installed in each section.
The electrolyte solution was sprayed as shown in FIG. A direct current was applied between the inner electrode and the outer electrode so that the current density became 1 A / m ² per concrete surface area, and the voltage at that time was measured for 28 days. The results are also shown in Table 1. The electrolyte solution was reused after storing the electrolyte solution flowing out of the concrete in a water tank. During the test period,
The concrete surface was covered with a sheet to prevent rainwater from hitting it, and the sheet was removed during spraying.

[0043]

[Table 1]

Example 2 1.5 m high, 2 m long, 20 cm thick reinforced concrete
Reinforcing bars inside the concrete of the retaining wall were used as internal electrodes. Con
Reinforcing bar with a diameter of 3mm on the cleat surface at 50mm pitch
5mm thick non-woven fabric made by Teijin Co., Ltd.
After fixing it on the `` Teijin Keeper '' (Part No.
Then, this non-woven fabric is put in two layers and sandwiched by the welding wire mesh,
Attach this nonwoven and welded wire mesh to the concrete surface
After that, 1 mol / liter of sodium carbonate aqueous solution was used as an electrolyte solution.
The solution containing the solution was supplied and used as an external electrode. Rebar
Prepare eight concrete retaining walls, each with internal electrodes and external
Electrode solution is installed in each section as shown in Table 1.
With a pump for 1 hour and then rest for 30 minutes
Supplied. Current density between the internal and external electrodes
0.8A / m per concrete surface area ^TwoDC power
The procedure was performed in the same manner as in Example 1 except that the flow was performed. The result
It is shown in Table 2.

[0045]

[Table 2]

Example 3 Made of reinforced concrete 1.5 m high, 2 m long and 20 cm thick
Titanium mesh fixed on concrete surface on both sides of retaining wall
And Arakawa Chemical Industries, Ltd.
Tap water to cellulose fiber containing "Arasorb"
Was sprayed to form an external electrode. Rebar
Prepare seven concrete retaining walls, each with internal electrodes and external
Install electrodes and apply electrolyte solution to each section as shown in Table 1.
A fixed amount was supplied by a pump. Between this internal electrode and external electrode
The current density is 1.2A / m per concrete surface area ^TwoWhen
Same as Example 1 except that a DC current was passed
I went to. The results are also shown in Table 3.

[0047]

[Table 3]

[0048]

According to the present invention, when a constant current is applied to concrete, the required voltage value can be suppressed to a low level. Can be prevented, and safer concrete regeneration work becomes possible. Also, since a specified current can be supplied even at a low voltage, a method for removing salt from concrete, a method for supplying an alkaline solution to concrete, a method for removing moisture from concrete, a method for suppressing alkali-aggregate reaction, and a method for removing concrete from concrete. In this case, the effect of reliably preventing the steel material from being regenerated can be ensured.

Claims (1)

(57) [Claims] 1. A steel material inside concrete is used as an internal electrode, electrodes provided at two or more locations on the concrete surface are used as external electrodes, and a current flows between the internal electrode and the external electrode or between the external electrodes. an electrolyte solution between are, co
Nkurito surface area 1 m ² per 1 to 100 l / day of a method of reproducing concrete and supplying.