JPH07291767A - Reforming method of concrete - Google Patents

Abstract

PURPOSE:To remarkably increase the reforming effect of concrete by heating the surface and/or surroundings of the concrete in a method for reforming the concrete by impressing current between an external electrode provided on the surface of the concrete and the steel in the concrete as an internal electrode. CONSTITUTION:At least a part of the concrete to which current is impressed is heated by supplying steam or a heated electrolyte solution to the surface and/or surroundings of the concrete and further providing a heating element. In the case of supplying steam, the generating pressure of steam is preferably 1-10kg/cm<2>. And in the case of supplying the heated electrolyte solution, the concrete is rapidly reformed since the temp. of the concrete is kept at 20-60 deg.C. In the electric heating element, the quantity of electric energy is optionally and accurately controlled. The raised temp. is preferably >=30 deg.C. The impressed current for the purpose of removing salt matter in the concrete or recovering alkalinity is preferably 0.5-5A/cm<2> per the surface area of the concrete.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electrochemically modifying concrete containing a steel material inside, and more particularly to a method for modifying concrete for electrochemically removing salt in the concrete. The present invention relates to a method for modifying concrete, in which an alkaline solution is supplied to neutralized concrete to restore alkalinity.

[0002]

[Prior art and its problems] Concrete is generally
Due to its strong resistance to various environments and its strong alkalinity, the steel material inside it is protected from corrosion by forming a passivation film on the steel surface, which makes the concrete structure durable. It has been considered to be a permanent structure.

However, the durability of the concrete structure, which has been considered to be the permanent structure, is deteriorated due to causes such as neutralization and salt damage, and the life of the structure has been questioned. .

As a method for repairing such a deteriorated concrete structure, a repairing method using an electrochemical method has been proposed (JP-A-1-176287 and JP-A-2-302384).

However, when the concrete is modified by using these methods, for example, the method of removing salt from the concrete requires a long treatment time of 2-3 months. Was needed.

Therefore, it goes without saying that the construction period associated therewith also becomes long, and various restrictions on the surrounding residents and the environment, such as the prohibition of traffic on roads and the use of buildings due to construction, must be continued for a long period of time. There was a problem that it had to be done and that costs increased due to the prolonged construction.

The main purpose of the electrochemical treatment of concrete is to move chlorine ions in the concrete by an electric current applied to the concrete or to electrolyze the alkaline solution supplied to the concrete surface into the concrete. Therefore, if the value of the electric current applied to the concrete is increased, the treatment can be performed quickly, and as a result, the construction period can be shortened.

However, since the voltage is directly proportional to the current, increasing the current inevitably increases the voltage, and if the processing voltage is increased, the safety such as an electric shock will be impaired and the precious human life will be increased. There is a risk that it may lead to loss of voltage, and in practice it was impossible to raise the voltage.

The present inventor has solved the above problems and conducted various tests in order to shorten the treatment period as much as possible. As a result, by adopting a specific method, the above problems were solved and the concrete structure was solved. The present invention has been completed based on the knowledge that modification processing of a product can be performed quickly.

[0010]

That is, according to the present invention, an external electrode is installed on a surface portion of concrete, and a steel material inside the concrete is used as an internal electrode, and at least a concrete portion to which an electric current is applied is heated and the external electrode is heated. A method for modifying concrete, characterized in that a current is applied between electrodes and / or between an external electrode and an internal electrode, wherein steam or a heated electrolyte solution is supplied to the surface of the concrete and / or its periphery. Further, a heating element is installed to raise the temperature of at least a concrete portion to which an electric current is applied, and an electric current is applied between the external electrodes and / or between the external electrode and the internal electrode. It is a modification treatment method,
Furthermore, the method of modifying concrete (salt removal method) that electrochemically removes the salt in the concrete using them, and the modification of concrete that recovers the alkalinity by supplying an alkaline solution to the neutralized concrete. It is a treatment method (re-alkalizing method).

Hereinafter, the present invention will be described in detail as a representative of concrete, but it can be applied to mortar and paste.

Saturated calcium hydroxide aqueous solution is abundantly present inside the hardened concrete as pore water. When an electric current is applied to the concrete, the pore water acts as an electrolyte and the concrete itself has. A current corresponding to the resistance is applied. Also, on this concrete,
A method of supplying an electrolyte solution to facilitate the application of an electric current is also preferable, and in reality, it is usual to supply the electrolyte solution.

According to the present invention, an external electrode is installed on the surface of concrete, and the steel material inside the concrete is used as the internal electrode.
A concrete is modified by applying an electric current between the external electrodes, between the external electrode and the internal electrode, and between the external electrodes and between the external electrode and the internal electrode.

The external electrode used in the present invention is installed on the surface of the concrete in order to apply an electric current to the inside of the concrete, and it is usually a temporary electrode which is removed after the treatment. Is, for example,
It is composed of a combination of a metal mesh, an electrolyte solution, an electrolyte solution holding material and the like.

The amount of temperature rise of the concrete temperature in the present invention is preferably 10 ° C. or higher, more preferably 20 ° C. or higher, 30
Most preferably, the temperature is not lower than 0 ° C, and the effect is remarkable. If the temperature rise of concrete temperature is less than 10 ° C, it is not possible to expect the treatment effect just by raising the temperature.

For the purpose of raising the temperature of the concrete, only the concrete portion to which the electric current is applied may be used. However, in reality, it is difficult to raise the temperature of only the necessary portion. It is usual to raise the temperature of the concrete including the concrete portion to be heated. Of course, it is also possible to raise the temperature of the entire concrete.

In the usual method for electrochemically modifying concrete, not only external electrodes but also electrolyte solution, electrolyte solution holding material, etc. are installed on the concrete surface. It is also possible to raise the temperature of concrete.

Here, the electrolyte solution is a solution having good electric conductivity supplied to the concrete surface, including ordinary water, and facilitates the application of an electric current as it penetrates into the concrete. It is intended to promote the modification treatment effect.

The electrolyte solution holding material serves to keep the electrolyte solution on the concrete surface.

In the present invention, as means for raising the temperature of the concrete, it is possible to supply water vapor to the surface of the concrete and / or its surroundings, to supply a heated electrolyte solution, and to install a heating element. is there.

When water vapor is supplied, it is possible to maintain the temperature of the concrete at a relatively high temperature of 40 to 80 ° C., and it is possible to more rapidly perform the electrochemical reforming treatment of the concrete. is there.

The method of supplying water vapor to the concrete surface is not particularly limited, but a method of covering the concrete surface with a sheet or plate and spraying it through a steam pipe or the like is preferable. In addition, there is also a method of circulating in piping or radiator.

When steam is supplied, steam generated by a boiler or the like can be used, and the generated pressure, which is the pressure in the boiler or the pipe, is the surface area of concrete or its volume. Although it varies depending on the case, usually, 1 to 10 kg / cm ² is preferable, and ² to 10 kg / cm ² is more preferable. If it is less than 1 kg / cm ² , it is difficult to raise the concrete temperature sufficiently, and if the generated pressure exceeds 10 kg / cm ² , the temperature is high, so there is a risk of cracking the concrete if it comes into direct contact with the concrete surface. There is. In the method of supplying water vapor, since water can be further supplied to the concrete surface portion, it becomes easy to apply an electric current to the concrete. In addition, by installing a pipe-shaped object on the surface of and / or around the concrete,
It is also possible to raise the temperature of the concrete by passing steam through it.

When supplying a heated electrolyte solution, that is, when supplying warm water or another heated electrolyte solution, the temperature of the concrete can be maintained at about 20 to 60 ° C. It is possible to perform the reforming process quickly. Furthermore, since the electrolyte solution whose temperature has been raised can be circulated, it is possible to save the energy required for raising the temperature by circulating it.

As a method of supplying the heated electrolyte solution to the concrete surface, a method of circulating the concrete surface through a pipe or the like, a method of spraying or spraying the concrete surface, and a method of A method such as dripping is possible. Among them, the method of circulating the concrete through a pipe or the like is most preferable from the viewpoint of increasing the temperature of the concrete. The method of watering, spraying, or dripping can maintain the wet state by separately supplying the electrolyte solution to the concrete surface while warming the concrete.

As a method of warming the electrolyte solution, there is a method of collecting them in a water storage tank and warming them with a pipe heater, warm air, steam, electron beam irradiation, dielectric heating and the like.

Examples of the heating element used in the present invention include an electrical heating element that generates heat by passing electricity, a chemical heating element typified by a hydration reaction of a hydraulic substance and an oxidative reaction, and the like. Is mentioned.

Here, examples of the electric heating element include nichrome wire, ceramic heater, heater cable, pipe heater and the like, and examples of the chemical heating element include quick lime and iron powder.

The electric heating element can control the concrete temperature arbitrarily and accurately by controlling the amount of electric energy supplied. The electrical heating element
It can be installed on the concrete surface portion, its peripheral portion, and / or the electrolyte holding material.

Since the amount of heat generated by the chemical heating element varies depending on the degree of progress of the chemical reaction, the concrete temperature cannot be controlled accurately, but the external energy required to generate heat is unnecessary. Quicklime, reduced iron powder, etc. may be applied or applied to the surface of the concrete or its periphery at the beginning of the electrochemical modification of the concrete. After that, it is also possible to add by spraying or the like depending on the degree of progress of the reaction.

The applied current is usually preferably 0.5 to 10 A / m ² per surface area of concrete. Below 0.5 A / m ² ,
There is no treatment effect, and if it exceeds 10 A / m ² , cracking tends to occur due to the gas pressure generated near the electrode.

[0032]

EXAMPLES Hereinafter, examples will be described based on the present invention.

Example 1 Using a diffusion cell container made of vinyl chloride as shown in FIG. 1, the mobility of chlorine ions when electrochemically modifying the concrete was measured. On the negative electrode side of the diffusion cell container, put powdered calcium chloride and fill it with a saturated calcium chloride aqueous solution, and on the positive electrode side of the diffusion cell container,
It was filled with deionized water containing no chlorine ion. The test piece was attached to the diffusion cell container with bolts and nuts.
Hardened cement that is a disc with a thickness of 10 cm and a thickness of 1 cm.
Cement = 60%, cement / sand = 1/2 mortar was used for molding, which was cured in water at 20 ° C. for 28 days. The diffusion cell container was placed in a thermostatic chamber at 5, 20, 30, 50, and 70 ° C., and the temperature was kept constant. The electrode of the diffusion cell container was connected to a constant-voltage constant-current DC power source, a constant-voltage current of 10 V was applied, and the amount of chlorine ions moving from the negative electrode side to the positive side through the test body was measured over time. The results are shown in FIG. 2 and Table 1.

<Materials used> Calcium chloride: Reagent first grade cement: Denki Kagaku Kogyo's ordinary Portland cement Sand: Himekawa production sand, specific gravity 2.62, FM = 2.75 Electrode: Platinum plated titanium electrode DC power supply: Constant voltage constant current DC power supply Product name "MSA 180-015" manufactured by Japan Stabilizer Industry Co., Ltd.

[0035]

[Table 1]

From FIG. 2 and Table 1, when the temperature rises by about 30 ° C., the amount of chlorine ions moved to the positive electrode side becomes about twice, and the rise of the reforming treatment temperature is caused by the increase of the electrochemical concrete. It shows that the reforming process is accelerated.

Example 2 Cement 280 kg / m ³ , water 168 kg / m ³ , sand 860 kg / m ³ , gravel 1,00
Fig. 3 shows a test piece of 15 × 15 × 50 cm prepared using concrete with unit amounts of 2 kg / m ³ and 10 kg / m ³ of sodium chloride.
Installed in the test equipment as shown in Fig.5, put it in a thermostatic chamber at 5, 20, 30, 50, and 70 ℃, keep the temperature constant, and perform the electrochemical modification treatment of the concrete. The ease of movement was measured. Connect the titanium mesh electrode of the device and the rebar in the test body to a constant voltage and constant current DC power supply,
A constant voltage current was applied for 2, 4, 6, and 8 weeks, and the amount of salt contained in the concrete near the reinforcing bars was measured over time. The results are shown in FIG. 4 and Table 2.

<Materials used> Sodium chloride: Reagent first grade Gravel: Himekawa crushed stone, Gmax = 20mm, specific gravity 2.62, FM
= 2.75 Electrode: Titanium mesh electrode, product name "L-Guard Mesh # 210" manufactured by Eltec Asia Service Co., Ltd. DC power supply: Constant-voltage constant-current DC power supply, product name "MSA 36-1" manufactured by Japan Stabilizer Industry Co., Ltd.

[0039]

[Table 2]

It can be seen from FIG. 4 and Table 2 that the amount of salt that escapes from the concrete increases sharply as the temperature rises. From this, it is shown that also in the case of concrete, an increase in the modification treatment temperature accelerates the electrochemical modification treatment of concrete.

Example 3 When concrete was mixed, the concrete was prepared by mixing concrete with a salt content of 3 kg / m ³ dissolved in water and having a height of 1.
The test was conducted using a concrete prewall, which is an L-shaped retaining wall with a width of 2.0 m and a width of 2.0 m. As shown in FIG.
On the wall surface of this concrete prewall, using cellulose fiber as an electrolyte solution holding material, after spraying a mixture of it and an electrolyte solution, a titanium mesh was attached as an electrode, and further, a mixture of cellulose fiber and an electrolyte solution was sprayed again. . Next, the titanium mesh was used as a positive electrode, and the reinforcing bar inside the concrete prewall was used as a negative electrode, and connected to a DC power source. Also,
A steam pipe was installed near the concrete prewall, and the wall surface was covered with a curing sheet along with the pipe. 7 kg
While supplying steam of / cm ² into the curing sheet through the steam pipe, the temperature of the concrete wall surface during the energization period is about 70
Hold at ~ 85 ℃, and apply 20V constant current from DC power supply to 2
Applied for a week. Two weeks after the start of energization, the amount of salt content in the concrete was measured and found to be 0.6 kg / m ³ on average. In a similar test at room temperature, this value is equivalent to an energization time of 5 to 6 weeks, and it was found that the electrochemical concrete modification treatment effect was remarkable.

<Materials used> Electrolyte solution holding material: Excel Industries, cellulose fiber electrolyte solution: calcium hydroxide aqueous solution DC power supply: constant voltage constant current DC power supply, product name "MSA 36-5" manufactured by Japan Stabilizer Industry Co., Ltd. Other than the same as Example 2.

Example 4 A concrete prewall similar to that used in Example 3 was used as a test body for testing. As shown in Fig. 6, a diameter of 1.5 mm
Example 3 except that a circulation pipe for supplying an electrolyte solution in which the holes are opened at 15 cm intervals and a receiving gutter for collecting the electrolyte solution are installed under the concrete wall surface so that the electrolyte solution can be circulated. I went the same way. The electrolyte solution is collected in a solution tank through a receiving gutter, and there is a pipe heater A type throw heater manufactured by Yako Electric Co., Ltd.
The temperature was raised to 50 ° C., and again supplied to the concrete surface through the circulation pipe to raise the concrete surface temperature to 40 to 45 ° C. In this state, a constant-voltage current of 20 V was applied from a DC power source, and after 2 weeks, the amount of salt content in the concrete was measured. The average value was 0.9 kg / m ³ . In a similar test at room temperature, this value is a value corresponding to an energization time of 4 to 5 weeks, and it was found that the electrochemical concrete modification treatment effect was remarkable.

Example 5 A concrete prewall similar to that used in Example 3 was used as a test body for testing. As shown in FIG. 7, a heating cable manufactured by Raychem Co., Ltd. under the trade name of “1
0BTV "was installed to allow the temperature of the concrete, the cellulose fiber, and the electrolyte solution to be raised to 35 to 40 ° C, and the same procedure as in Example 3 was performed. In this state,
A constant-voltage current of 20 V was applied from a DC power source, and two weeks later, the amount of contained salt in the concrete was measured. As a result, the average value was 1.1 kg / m ³ . In a similar test at room temperature, this value is equivalent to a power-on time of 4 weeks, and it was found that the electrochemical modification treatment effect of concrete is remarkable.

Example 6 A concrete prewall having a height of 1.5 and a width of 2.0 m having a neutralization depth of 20 to 25 mm (23 mm on average) from the surface of concrete was tested as a test body. Cellulose fiber was used as an electrolyte solution holding material on the wall surface of this concrete prewall, and 1 mol / l Na
After spraying a mixture with an alkaline electrolyte solution, which is a ₂ CO ₃ aqueous solution, a titanium mesh was placed as an electrode, and then a mixture of cellulose fiber and the alkaline electrolyte solution was sprayed again. Next, the titanium mesh was used as a positive electrode, and the reinforcing bar inside the concrete prewall was used as a negative electrode, and connected to a DC power source. FIG. 6 of Example 4
In the same manner as in the sprayed cellulose fiber,
A circulation pipe for supplying an alkaline electrolyte solution having 1.5 mm holes at 15 cm intervals and a receiving gutter for collecting the alkaline electrolyte solution were installed at the bottom of the concrete wall surface so that the alkaline electrolyte solution could be circulated. The alkaline electrolyte solution is collected through a trough into a solution tank, where it is heated to 50 ° C with a pipe heater, a type A throw-in heater manufactured by Yako Electric Co., Ltd. To
The temperature was raised to 40 to 45 ° C. In this state, a constant-voltage current of 12 V was applied from the DC power source, and after 5 days, the neutralization depth in the concrete was measured and found to be 0 mm. This value is
In a similar test at room temperature, the value was equivalent to the energization time of 7 to 10 days, and it was found that the electrochemical concrete modification treatment effect was remarkable.

<Materials used> Sodium carbonate: first-grade reagent DC power supply: constant-voltage constant-current DC power supply, product name “MSA 36-5” manufactured by Japan Stabilizer Industry Co., Ltd.

[0047]

According to the present invention, when the concrete is subjected to the electrochemical modification treatment, the modification treatment effect can be made remarkable by raising the modification treatment temperature. Therefore, it became possible to solve in a short period of time various constraints on the surrounding inhabitants and the environment due to the work involved in the electrochemical modification of concrete. In addition, since it is possible to lower the voltage value, it is possible to avoid the risk of electric shock due to the application of electric current to the concrete structure, and it is safe not only for the construction itself but also for third parties. Greatly improved. Further, in the method of supplying water vapor or the method of supplying a heated electrolyte solution, it is possible to supply water to the concrete at the same time, so that it is possible to reduce the electric resistance value of the concrete. As a result, the voltage required for the reforming process can be reduced, resulting in further improvement in safety.

[Brief description of drawings]

FIG. 1 of the present invention is a cross-sectional view of a diffusion cell container testing apparatus used to measure the mobility of chlorine ions when electrochemically modifying concrete. .

FIG. 2 is a graph showing the relationship between the test time for each temperature tested in Example 1 and the amount of permeated chlorine ions.

FIG. 3 is a cross-sectional view of a test apparatus for an electrochemical modification treatment method tested in Example 2.

FIG. 4 is a graph showing the relationship between the test time for each temperature tested in Example 2 and the amount of salt content in concrete.

[Fig. 5] Fig. 5 is a test apparatus of an electrochemical concrete reforming treatment method, in which a concrete prewall is used as a test body and steam is supplied to heat the concrete wall surface for testing in Example 3. FIG.

[Fig. 6] Fig. 6 is an electrochemical modification treatment of concrete in Example 4, in which a concrete prewall was used as a test body and a heated electrolyte solution was supplied to test the temperature of a concrete wall surface. FIG. 3 is a cross-sectional view of a test device of the method.

[Fig. 7] Fig. 7 is a test of an electrochemical modification treatment method of concrete, in which a concrete prewall was used as a test body and a heating element was installed and a concrete wall surface was heated in Example 5 for testing. It is sectional drawing of an apparatus.

[Explanation of symbols]

 1 DC power supply 2 Test body 3 Diffusion cell container 4 Electrode 5 Container 6 Ion-exchanged water 7 Saturated calcium chloride aqueous solution 8 Calcium chloride powder 9 Electrolyte solution 10 Rebar in test body 11 Electrolyte solution-containing electrolyte solution holding material 12 Steam curing sheet 13 Steam piping 14 Electrolyte circulation pipe 15 Receiving gutter 16 Heating element

Claims (6)

[Claims] 1. An external electrode is installed on a surface portion of concrete, and a steel material inside the concrete is used as an internal electrode, and at least a concrete portion to which an electric current is applied is heated, and between the external electrodes and / or the external electrode-internal electrode. A method for modifying concrete, characterized by applying an electric current between them. 2. The method for modifying concrete according to claim 1, wherein steam is supplied to the surface of the concrete and / or its periphery to raise the temperature of the concrete portion. 3. The method for modifying concrete according to claim 1, wherein the temperature of the concrete portion is raised by supplying a heated electrolyte solution to the surface of the concrete and / or the periphery thereof. 4. The method for modifying concrete according to claim 1, wherein a heating element is installed on the surface of and / or around the surface of the concrete to raise the temperature of the concrete portion. 5. An external electrode is installed on the surface of concrete containing salt, the steel material inside the concrete is used as an internal electrode, and at least the concrete portion to which an electric current is applied is heated to increase the temperature between the external electrodes and / or the external electrode. A method for modifying concrete for removing salt in concrete, characterized by applying an electric current between an electrode and an internal electrode. 6. An external electrode is installed on a surface portion of neutralized concrete and / or concrete including a neutralized portion, a steel material inside the concrete is used as an internal electrode, and at least a concrete portion to which a current is applied is raised. A method of modifying concrete for recovering the alkalinity of neutralized concrete, which comprises heating and applying an electric current between the external electrodes and / or between the external electrode and the internal electrode.