JP7038600B2 - Surface modification method for hardened cement and surface modification device for hardened cement - Google Patents

Description

The present invention relates to a surface modification method for a hardened cement body and a surface modification device for a hardened cement body, and in particular, a surface modification method for a hardened cement body containing a reinforcing steel material inside and a surface modification for the hardened cement body. Regarding the device.

Hardened cement with steel inside, such as reinforced concrete, has high alkalinity because it produces calcium hydroxide as a by-product when the cement reacts with water to harden the ready-mixed concrete. Due to this high alkalinity, the reinforcing bar forms an inactive film and is protected from corrosion.

However, concrete deteriorates over time due to various factors such as salt damage and neutralization, and countermeasures against this deterioration have been conventionally proposed.

Patent Document 1 discloses a curing device for placed concrete. According to this, the curing sheet is in close contact with the concrete surface by a simple device, and the concrete surface can be prevented from cracking by intermittent watering and can be cured.

In Patent Document 2, a steel material inside concrete is used as an anode, a solution is held between the surface of the concrete and a sheet stacked on the surface, and an electrode is inserted into the solution to serve as a cathode, and the space between the anode and the cathode is used. Disclosed is a process in which an anion in a solution is electrochemically permeated from the surface of the concrete to the steel side inside the concrete by passing an electric current through the solution. According to this treatment, for example, when the neutralization of concrete progresses, anions such as hydroxide ions permeate the inside of the concrete and restore the internal environment of the concrete to a strongly alkaline state, thereby reinforced concrete. It is possible to extend the life of the structure.

Patent Document 3 discloses a corrosion inhibitor for steel materials, which easily penetrates into concrete without forming insoluble or sparingly soluble calcium salts. This corrosion inhibitor can be used for kneading into concrete, applying to a steel surface, or applying to a concrete surface.

Japanese Unexamined Patent Publication No. 2010-168804 Japanese Unexamined Patent Publication No. 2015-227578 Japanese Patent No. 4377403

According to the curing by the curing device of Patent Document 1, although it is possible to prevent cracking of the cast concrete surface, it is not possible to suppress dealkalization over time.

According to the electrochemical treatment of Patent Document 2, although the internal environment of concrete can be re-alkalined, the neutralization and the removal of the passivation film will progress over time, so that the electrochemical treatment is performed again. Will be required. In particular, in an environment where the neutralization of concrete progresses at an early stage due to sulfuric acid produced by sulfur-oxidizing bacteria, such as concrete structures used for sewerage, frequent electrochemical treatment becomes necessary, and electrochemical treatment becomes necessary. Processing cannot be an effective measure.

According to the corrosion inhibitor of Patent Document 3, a remarkable increase in polarization resistance is achieved in the same manner as the known corrosion inhibitor (calcium nitrite), so that a substantial effect as a corrosion inhibitor can be seen. However, if a corrosion inhibitor is kneaded into concrete in order to add the functionality of preventing corrosion of reinforcing bars in concrete, for example, when placing concrete with a width of 1 m or more, a huge amount of corrosion will occur. It requires the addition of inhibitors and is not acceptable from a cost-effectiveness perspective. In addition, when a corrosion inhibitor is mixed with concrete, it is necessary to evaluate that it complies with the requirements of JIS A 5308 (when using ready-mixed concrete).

To add corrosion inhibitors to the surface of the structure rather than the entire structure, add it only to the first concrete in the formwork for the ceiling and only to the last concrete to be launched for the floor. If added, a corrosion suppression layer will be formed on the surface, but in the case of a wall surface, concrete will rise from the bottom to the top, so it was not possible to form a corrosion suppression layer only on the surface.

In addition, when imparting functionality with a corrosion inhibitor to thick concrete, it is more economical to use a coating type lining agent than kneading into concrete, but for wet surfaces. It cannot be applied and therefore cannot be applied at the same time as curing.

The present invention has been made in view of the above problems, and an object thereof is to maintain the effect of modifying the surface of a hardened cement body for a long period of time in a hardened cement body containing a steel material, and after casting. It is an object of the present invention to provide a surface modification method and a surface modification device for a hardened cement body, which can be carried out regardless of the properties and positions of the surface of the hardened cement body.

The surface modification method for a hardened cement body according to claim 1 for achieving the above object comprises a surface of the hardened cement body containing a reinforcing steel material inside and a covering body provided in advance to cover the surface. An anion supply step of supplying an electrolytic solution containing anions (excluding OH ⁻ ) that imparts functionality to the hardened cement body to the covering region between them, and the steel material as an anode in the electrolytic solution. The anion is permeated into the cement hardened body by energizing between both electrodes using the electrode inserted in the cement as a cathode, and the anion is cemented by the bond between the permeated anion and the cation in the cement hardened body. It is characterized by having a fixing step of fixing to the surface portion of the cured body.

According to this configuration, the anions in the electrolyte are bonded to the cations in the hardened cement on the surface of the hardened cement by energization and fixed on the surface of the hardened cement. As a result, the surface portion of the hardened cement is modified by imparting functionality according to anions such as antibacterial property, denseness, and water repellency to the surface portion of the cement cured product. Since the anions are fixed to the surface of the hardened cement, this reforming effect is maintained for a long period of time.

Further, since the surface modification method of the present invention is carried out by supplying an electrolytic solution to the coated region, it can be carried out regardless of whether the surface of the hardened cement body is in a dry state or a wet state. Further, since the surface portion of the hardened cement body may be covered, the surface of the hardened cement body can be modified at any position such as a ceiling surface, a floor surface, and a wall surface.

The preferred embodiment of the surface modification method for the hardened cement body of the present invention is as follows.

(1) The redox potential of the electrolytic solution is controlled to −800 mV or less when energization between both electrodes in the fixing step.

(2) The functionality imparted by anions is antibacterial.

( ₃ ) The anion is at least one selected from WO _4-2- , PbO ^4-4- , formic acid ion, dicarboxylic acid ion, ^hydroxy acid ion and silicate ion.

(4) The supplied electrolytic solution circulates between the covered region and the outside thereof.

(5) After the fixing step, a cation supply step of supplying another electrolytic solution containing other cations that imparts antibacterial properties to the cured cement to the coated region, and an energization direction between the two electrodes. It has a cation infiltration step of reversing the above and infiltrating the cation into the cured cement.

Further, the above object is to cement harden a covering body capable of covering the surface of a cement hardened body containing a reinforcing steel material inside, a covering region between the covering body and the surface of the cement hardened body, and the outside thereof. A circulation system capable of circulating an electrolytic solution containing anions that imparts functionality to the body, a cathode that can be inserted into the electrolytic solution in the covering region using the steel material as an anode, and between the anode and the cathode. It is also achieved by a surface modifier of a cement hardened body provided with a power source for passing an electric current between both electrodes.

According to the present invention, the anions in the electrolyte are bonded to the cations in the hardened cement body at the surface portion of the hardened cement body by energization and fixed to the surface of the hardened cement body. As a result, the surface portion of the hardened cement is modified by imparting functionality according to anions such as antibacterial property, denseness, and water repellency to the surface portion of the cement cured product. Since the anions are fixed to the surface of the hardened cement, this reforming effect is maintained for a long period of time, and it is not necessary to carry out the reforming treatment many times, which is economical.

Further, since the surface modification method of the present invention is carried out by supplying an electrolytic solution to the coated region, it can be carried out regardless of whether the surface of the hardened cement body is in a dry state or a wet state. Further, since the surface of the hardened cement body needs to be covered, the surface of the hardened cement body can be modified at any position such as a ceiling surface, a floor surface, a wall surface, etc., and is highly versatile. ..

It is a figure which shows an example of the electrode arrangement for carrying out the surface modification method of the cement hardened body of this invention. It is a figure which shows the other example of the electrode arrangement for carrying out the surface modification method of the cement hardened body of this invention. It is a potential-pH equilibrium diagram of iron. It is a schematic diagram which shows one Embodiment of the surface modification apparatus of the cement hardened body of this invention. FIG. 4 is a sectional view taken along line VV of FIG. It is an enlarged view of the part a of FIG. It is a perspective view of the test body (cement hardened body) which concerns on Example. It is explanatory drawing of the test system which performs the surface modification treatment of the cement hardened body which concerns on Example. It is a graph which showed the measurement result of the penetration depth of tungsten and the number of days of energization of the test body which concerns on an Example. It is a distribution map of tungsten in the cross section of the test body which concerns on an Example.

<Method of surface modification of hardened cement>
Next, the surface modification method of the hardened cement body of the present invention will be described in detail, but the method of the present invention is not limited to the following methods.

In the present invention, the hardened cement body refers to a cement paste obtained by kneading cement and water and kneading it with an aggregate to harden it.

The hardened cement material includes not only concrete but also mortar. When the cement paste is kneaded with fine aggregate such as sand as an aggregate, it is mortar, and when both fine aggregate such as sand and coarse aggregate such as gravel are kneaded as aggregate, it is concrete.

In the structure formed by the hardened cement of the present invention, a reinforcing steel material is arranged inside. The steel material is not particularly limited, and includes, for example, various materials such as reinforcing bars, steel frames, round steel, deformed steel bars, PC steel materials, and welded wire mesh.

The distance from the surface of the hardened cement body to the reinforcing steel material (hereinafter, also referred to as cover thickness) is at least 2 cm, and the maximum is 7 cm. Further, the surface of the hardened cement body to which the method of the present invention is applied is not limited to a flat surface, but includes various shapes such as a curved surface, an uneven surface, and a bent surface such as an inner corner of a water tank.

The method for surface modification of a hardened cement body of the present invention includes the following steps.

[Anion supply process]
In this step, anions that impart functionality to the hardened cement body in the covering region between the surface of the hardened cement body containing a reinforcing steel material inside and the covering body that covers the surface provided in advance. Supply an electrolytic solution containing (however, OH ^- is excluded).

The coating material may be any material having watertightness capable of retaining the electrolytic solution in the coating region between the surface of the hardened cement body and flexibility capable of following the surface shape of the hardened cement body. You may. For example, a soft resin sheet such as vinyl chloride, polyethylene, or polypropylene can be used.

Further, from the viewpoint of preventing the coating material from sticking to the surface of the hardened cement body and ensuring cushioning properties, it is preferable that the surface of the coating material on the side in contact with the electrolytic solution has a flexible concavo-convex structure. As the covering body having this uneven structure, for example, a bubble wrap sheet formed by laminating a flat soft resin sheet with an uneven soft resin sheet having columnar protrusions arranged on one surface (coating in FIG. 6). Body 14) can be used.

Any functionality may be imparted to the surface of the concrete structure by anions, and examples thereof include antibacterial properties, water repellency, and denseness.

By imparting antibacterial properties to the surface of the concrete structure, the activity of sulfur-oxidizing bacteria (specifically, sulfur-oxidizing bacteria such as Acidithiobacillus ferrooxidans, Thiomonas intermedius, Halothiobacillus neapolitanus) on the concrete surface, that is, , The production of sulfuric acid is suppressed, and the neutralization that leads to the collapse of the concrete structure can be effectively suppressed.

Such antibacterial properties are particularly required in an environment rich in sulfur-oxidizing bacteria such as sewerage.

Examples of the anion that imparts antibacterial properties include WO _4-2 , PbO 444, formate ion ₍ ^{HCOO- )} , dicarboxylic acid ion, and ^hydroxy acid ion.

Dicarboxylic acid ions include citrate ion ((COO) ^22-2 ), succinate ion (C ₂ H ₄ (COO) ^2-2 ), methaconic acid ion (CH ₂ (COO) ₂ ^2-2 ), and glutarate ion (CH ₂ (COO) 22-2). C ₃ H ₆ (COO) ^22- ), maleate ion (C ₂ H ₂ (COO) ₂ ^2- ), fumaric acid ion (C ₂ H ₂ (COO) ₂ ^2- ), citraconic acid ion _{(C 3 )} ^At least one selected from H _{4 (COO) 22-), mesaconic acid ion (C 3 H 4 ( COO ) 2} ^2- ), and itaconic acid ion (C ₃ H ₄ (COO) ₂ ^2- ). be.

The hydroxy acid ions include tartrate ion (C ₂ H ₂ (OH) ₂ (COO) ₂ ^2-2 ), malate ion (C ₂ H ₃ (OH) (COO) ^{22 2} ₎ and tartronic acid ion (CH). At least one selected from (OH) ₍ COO) ^22- ).

These anions can be supplied in the form of alkali metal salts that are easily ionized. For example, WO _4-2 can be supplied in the form of tungstates such as sodium tungstate and sodium ^{paratungstate} , and ₍ COO) ²² can be supplied in the form of sodium oxalate, PbO. ⁴⁴⁴ can be supplied in the form of Pb _- containing sodium salts. Similarly, dicarboxylic acid ions, hydroxy acid ions, and formic acid ions other than oxalate ions can be supplied in the form of alkali metal salts.

When the concentration of anions in the electrolytic solution is antibacterial, the total concentration of anions that impart antibacterial properties is the maximum solubility (unit: g / per 100 g of saturated solution). It is 1/1000 or more and 1/1 or less, preferably 1/100 or more and 1/10 or less. When the added functionality is antibacterial, the anion that imparts the functionality to the hardened cement is selected from WO _4-2 and oxalate ion ( ₍ ^COO ) ^2-2- ). It is preferably at least one.

Further, by imparting the denseness, it is possible to prevent CO ₂ from permeating into the hardened cement body, and it is possible to reduce the progress rate of neutralization leading to the collapse of the concrete structure.

Further, by imparting water repellency, the infiltration of acidic water into the hardened cement body is suppressed, and the neutralization of the reinforcing bar is suppressed.

Examples of anions that impart denseness and water repellency include orthosilicate ion (SiO _4-4- ), ^pyrosilicate ion (Si _{2O 7} ^6- ), metasilicate ion (SiO _3-2- ), and ^metanicate . ^Examples thereof include silicate ions such as acid ions (Si ₂ O _5-2 ). The silicate ion can be supplied in the form of sodium silicate. The total concentration of silicate ions (anions) that impart denseness and water repellency in the electrolytic solution is 1/1000 or more and 1/1 or less of the maximum solubility (unit: g / per 100 g of saturated solution), and is preferable. , 1/100 or more and 1/10 or less.

In addition, in the present invention, since the anion is intended to exert the functionality by an action different from the strong alkalinization by the hydroxide ion, the anion imparts the functionality to the cured cement body in the present invention. Hydroxide ions (OH ⁻ ) are excluded from the anions (above, the anion supply step).

[Fixing process]
In this step, the steel material is used as an anode, the electrode inserted in the electrolytic solution is used as a cathode, and the anion is permeated into the hardened cement body by energizing between both electrodes, and the permeated anion and the hardened cement body are permeated. The anion is fixed to the surface of the hardened cement body by binding with the cation inside.

In the present invention, a steel material in a hardened cement body is used as an anode.

The cations in the hardened cement are Ca ²⁺ derived from cement.

The electrode inserted into the electrolytic solution has a size that covers substantially the entire surface of the hardened cement body in the covering region between the hardened cement body and the hardened cement body from the viewpoint of allowing anions to permeate the entire surface of the hardened cement body. It is preferable to use a net-shaped, mesh-shaped, or sheet-shaped electrode having the above. However, the electrode is not limited to these widths and shapes, but may be rod-shaped or plate-shaped, and if treatment is to be performed locally, the entire surface of the hardened cement is covered. It does not have to be large enough to be used. As the material of the electrode, iron, titanium, stainless steel, carbon fiber or the like can be used.

As the arrangement of the electrodes, for example, the arrangement shown in FIGS. 1 and 2 can be adopted. That is, as shown in FIG. 1, when the thickness of the hardened cement body 20 is small, the cathode 16 may be arranged on both the front surface 20a and the back surface 20b of the hardened cement body 20 with the steel material 18 as an anode. Specifically, the front surface 20a and the back surface 20b are coated with the covering bodies 14 and 14, respectively, in the electrolytic solution of the covering region between the covering body 14 and the front surface 20a, and the covering region between the covering body 14 and the back surface 20b. The cathodes 16 and 16 are inserted into the electrolytic solution of the above, respectively.

Further, as shown in FIG. 2, when the thickness of the hardened cement body 20 is large, the cathode 16 may be arranged only on the surface 20a side of the hardened cement body 20 close to the steel material 18 with the steel material 18 as the anode.

The energization between the two electrodes can be performed by using the power supply 12, and the current flows from the cathode 16 through the power supply 12 toward the anode (steel material 18). On the other hand, the anions permeate the surface of the cement hardened body 20 from the electrolytic solution and move toward the anode (steel material 18). In the process, it is ionically bonded to the cations (Ca ²⁺ ) existing on the surface of the hardened cement body 20 and fixed on the surface of the hardened cement 20 (the above is the fixing step).

Therefore, according to the method for modifying a hardened cement body of the present invention, an anions in the electrolyte are ionically bonded to Ca ²⁺ in the hardened cement body 20 on the surface of the hardened cement body 20 by energization to form an insoluble salt. It is formed and fixed to the front surface 20a and the back surface 20b of the cement hardened body 20. As a result, the surface portion of the cement hardened body 20 is modified by imparting functionality according to anions such as antibacterial property, denseness, and water repellency to the surface portion. Since the anions are fixed to the surface of the hardened cement body 20, this reforming effect is maintained for a long period of time.

Further, since the method for modifying the surface of the hardened cement body of the present invention is carried out by supplying an electrolytic solution to the coated region, it can be carried out regardless of whether the surface of the hardened cement body 20 is in a dry state or a wet state. .. Further, since the surface portion of the cement hardened body 20 may be covered, the surface of the cement hardened body can be modified at any position such as a ceiling surface, a floor surface, and a wall surface.

Further, according to the surface modification method of the hardened cement body of the present invention, it is possible to impart functionality after placing the cement. There is no need to consider the effect on strength. For example, although Pb is useful as an antibacterial agent, it is difficult to mix it before placing cement because it causes a decrease in strength after hardening when mixed with ready-mixed concrete. Anions of Pb can be fixed to the surface of the hardened cement without causing a problem of strength decrease.

Since the steel material 18 is used as the anode when energizing between the two electrodes, the metallic iron of the steel material 18 may be ionized and corrosion may proceed depending on the energization conditions.

FIG. 3 is a potential-pH equilibrium diagram of iron. The vertical axis is the standard redox potential (V vs. SHE), and the horizontal axis is pH. This figure shows the Removal of ammonium, iron and manganese from potable water in biofiltration units: A review (Athanasia G. Tekerlekopoulou et al., Journal of Chemical Technology and Biotechnology, Vol. 88, No. 5, pp. 751-773, 2013. Figure 2 (issued in May) is quoted, and some additions have been made. As shown in the figure, in the range of pH 11 or higher corresponding to the strong alkaline environment in the hardened cement, the region where iron continues to be metallic iron having an oxidation number of 0 is the region shown by the broken line, and the redox potential is-. It is a region of 800 mV or less. That is, from the viewpoint of promoting the fixation of anions while preventing the corrosion of the steel material, the redox potential of the electrolytic solution is controlled to -800 mV or less in the fixing step, and in particular, it is controlled to -1200 mV or more and -800 mV or less. Is preferable.

The control of the redox potential can be realized, for example, by inserting a redox potential meter into the covering region R and adjusting the voltage in the power supply 12 while observing the indicated value. Further, the control may be performed by a computer (electronic computer).

Further, the depth of penetration of the anion into the surface of the hardened cement body may be any depth as long as it can exhibit the imparted functionality. From the viewpoint of protecting the steel material 18 in the hardened cement body 20, it is preferably at least 5 mm or more, and preferably at most the cover thickness or less. The depth of anion penetration into the surface of the hardened cement can be controlled by the composition of concrete, the concentration of anions in the electrolytic solution, the redox potential, the energization time, and the like.

The surface modification method of the hardened cement body of the present invention is preferably performed, for example, at the time of curing after placing the ready-mixed concrete. By performing the curing at the time of curing, the electrolytic solution supplied to the covering body and the covering area promotes hardening by the hydration reaction of the cement, and at the same time, the surface of the hardened cement body can be modified, which is efficient.

Further, the method for modifying a hardened cement body of the present invention may include the following cation supply step and cation infiltration step after the fixing step.

[Cation supply process]
After the fixing step, in this step, another electrolytic solution containing other cations that impart antibacterial properties to the hardened cement is supplied to the coated region.

Examples of the functionality imparted to the surface of the concrete structure by other cations include antibacterial properties as in the case of the above-mentioned anions.

Examples of the cation that imparts antibacterial properties include Ni ²⁺ , Zn ²⁺ , Co ²⁺ , and Sn ²⁺ , and Ni ²⁺ is preferable. Cations can be supplied in the form of sulfates, nitrates and chlorides, respectively. When supplied as fine powder, it can be supplied in the form of a metal (zero oxidation number). When supplied as a metal, it is ionized in the liquid by energization.

The concentration of cations in the other electrolytic solution is 1/1000 or more and 1/1 or less of the maximum solubility (unit: g / per 100 g of saturated solution), preferably 1/100 or more and 1/10 or less (1/100 or more and 1/10 or less). Above, cation supply process).

[Cation infiltration process]
In this step, the direction of energization between the two electrodes is reversed to allow other cations to permeate into the hardened cement (above, the cation infiltration step).

Therefore, according to the surface modification method of the hardened cement body of the present invention to which the cation supply step and the cation infiltration step are added, functional anions are bound to Ca ²⁺ on the surface portion of the hardened cement body. Since the insoluble salt is formed and fixed, it is substantially not ionized again and returned to anions even if the energization direction is reversed.

In addition, since cations having further antibacterial properties can be supplied to the surface portion of the hardened cement body to which anions are fixed, the antibacterial properties of the hardened cement body are further improved.

<Surface modification device for hardened cement>
Next, the surface modification device for the hardened cement body of the present invention will be described with reference to FIGS. 4 to 6, but the surface modification device for the hardened cement body is not limited to this.

4A and 4B are schematic views showing an embodiment of a surface reforming apparatus for a hardened cement body of the present invention, FIG. 5 is a sectional view taken along line VV of FIG. 4, and FIG. 6 is a portion a of FIG. It is an enlarged view. In FIGS. 4 to 6, the same elements as those shown in the electrode arrangement diagrams of FIGS. 1 and 2 described above are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 4, the surface reforming apparatus 10 for a hardened cement according to the present embodiment includes a covering body 14, a circulation system 30, a steel material 18, a cathode 16, and a power supply 12.

The circulation system 30 is an electrolytic solution containing anions that can impart functionality to the cement hardened body 20 inside and outside the covering region R between the covering body 14 and the surface 20a of the cement hardened body 20. To circulate.

The circulation system 30 has a covering region via a supply unit 34 for supplying an electrolytic solution to the water supply pipe 32 and the water suction pipe 32 connected to the covering region R, and a suction pipe 36 and a suction pipe 36 connected to the covering region R. It has a suction unit 38 for sucking the electrolytic solution in R.

In the present embodiment, the supply unit 34 includes a solution tank 35 that serves as a place for producing an electrolytic solution, and a water supply pump 33 that sends the solution in the solution tank 35 to the water supply pipe 32. Then, sodium tungstate or the like is added to the solution tank 35 and mixed to produce an electrolytic solution.

In the present embodiment, the suction unit 38 has a suction machine 40 and sucks the electrolytic solution from the covering region R to the suction unit 38 via the suction pipe 36. Further, the suction unit 38 has a water removal / dust removal machine 42 provided between the suction machine 40 and the suction pipe 36, whereby dust and liquid are removed, and only the remaining exhaust gas passes through the suction machine 40. Is discharged to the outside.

On the other hand, the electrolytic solution from which the gas and dust have been removed is sent to the supply unit 34.

Further, it is preferable that a thin film 45 (see FIG. 6) capable of impregnating the electrolytic solution and having a predetermined air permeability is laminated on the surface 20a of the cement cured body 20. According to the thin film 45, the surface 20a of the cement hardened body 20 can be maintained in a wet state, and anions can be more effectively supplied to the surface 20a. Examples of the thin film 45 include non-woven fabrics and woven fabrics.

According to the surface modification device 10 for the hardened cement according to the present embodiment of the present invention, the above-mentioned surface modification method for the hardened cement can be carried out, the same effect can be obtained, and the circulation system 30 can be provided. Since the electrolytic solution circulates through the solution tank 35, the electrolyte in the electrolytic solution reduced by energization can be replenished.

Further, the suction machine 40 can effectively remove air bubbles in the electrolytic solution in the covering region R, and the fixing speed of the anion on the surface of the cement hardened body 20 even by a long-term reaction coupled with the replenishment of the electrolyte. Does not decrease.

Hereinafter, the present invention will be described in more detail with reference to Examples.

1. 1. Manufacture of hardened cement (test piece) containing reinforcing bar (steel) inside 1: 2 Add water to 20 parts by mass of mortar at a ratio of 3 parts by mass and mix, and mix the mixed mortar with rod-shaped reinforcing bar 18 (φ). : 10 mm) was poured into a pre-arranged mold to prepare a test piece 100 having dimensions of 40 mm × 40 mm × 80 mm. The reinforcing bar 18 is arranged in the test body 100 so that the long axis direction of the test body is the longitudinal direction of the reinforcing bar 18.

Then, after moist curing for 28 days, the upper surface 100a was left as shown in FIG. 7, and the other 5 surfaces were coated with epoxy resin. A total of 5 test bodies 100 were manufactured.

2. 2. Surface modification treatment of the test piece The coated test piece 100 was placed in a beaker 101 having a volume of 1000 mL containing 500 mL of a 10% sodium tungstate (Na ₂ WO ₄ ) solution, and the reinforcing bar 18 was used as an anode as shown in FIG. Using the electrode plate 102 inserted in the solution side as a cathode, a current was passed from the power source while controlling the redox potential to be -1 V on the cathode side.

Then, the test piece 100 was pulled up from the beaker 4 days, 7 days, 9 days, 12 days, and 14 days after the energization.

3. 3. Measurement of Tungsten Concentration Distribution and Penetration Depth In the cross section of the test piece after surface modification treatment, the test piece was cored in the direction of arrow X (see FIG. 7) and cored using an electron probe microanalyzer (EPMA). The concentration distribution of tungsten was measured. JXA-8230 (manufactured by JEOL Ltd.) was used for measuring the concentration distribution of tungsten.

The results are shown in FIGS. 9 and 10. FIG. 9 is a diagram showing the number of energization days (days) and the penetration depth (m) of tungsten, and FIG. 10 is a diagram showing the concentration distribution of tungsten after 14 days of energization.

As shown in FIG. 10, after 14 days of energization, tungsten permeated from the upper surface 100a of the test piece not covered with the epoxy resin to a depth of about 0.020 m, and tungsten was present in a high concentration near the surface. I found that I could make it.

Further, the penetration depth of tungsten is preferably 5 mm or more, which is the minimum design thickness of the repair mortar. However, according to FIG. 9, the tungsten permeates beyond 5 mm 3 days after the energization treatment under the test conditions of this example. You can see that it is doing.

10 Surface reformer for hardened cement 12 Power supply 14 Coating 16 Cathode 18 Steel 20 Hardened cement 20a Surface 30 Circulation system R Covered area

Claims (6)

Anions (however, OH) that impart functionality to the hardened cement body in the covering region between the surface of the hardened cement body containing a reinforcing steel material inside and the covering body that covers the surface provided in advance. Anion supply process for supplying an electrolytic solution containing (excluding-) ^and
With the steel material as the anode and the electrode inserted in the electrolytic solution as the cathode, the anions are permeated into the hardened cement body by energizing between the two electrodes, and the permeated anions and the cations in the hardened cement body are used. A fixing step of fixing the anion to the surface of the hardened cement body by binding with ions, and
Have,
The surface modification of a hardened cement product, wherein the anion is at least one selected from WO 4-2-, PbO 4-4-, formic acid ion, dicarboxylic acid ion, hydroxy acid _{ion and} silicate ^{ion .} Method. The method for surface modification of a hardened cement body according to claim 1, wherein the redox potential of the electrolytic solution is controlled to −800 mV or less when electricity is applied between the two electrodes in the fixing step. The method for surface modification of a hardened cement product according to claim 1 or 2, wherein the functionality imparted by the anion is antibacterial. The method for surface modification of a hardened cement body according to any one of claims 1 to 3 , wherein the supplied electrolytic solution circulates between the coated region and the outside thereof. After the fixing step, a cation supply step of supplying another electrolytic solution containing other cations that imparts antibacterial properties to the hardened cement to the coated region,
A cation infiltration step of reversing the energization direction between the two electrodes to allow the other cations to permeate into the hardened cement body.
The method for surface modification of a hardened cement product according to any one of claims 1 to 4 , wherein the cement is hardened. A covering that can cover the surface of a hardened cement body that contains a reinforcing steel material inside,
At least one selected from both antibacterial properties, denseness and water repellency with respect to the hardened cement body in the covering area between the covering body and the surface of the hardened cement body and the outside thereof. A circulatory system that circulates an electrolytic solution containing anions (excluding OH- ⁾ that impart functionality, and
With the steel material as the anode, a cathode that can be inserted into the electrolytic solution in the covering region, and
A power supply provided between the anode and the cathode for passing a current between the electrodes, and
Have,
The surface modification of the hardened cement product, wherein the anion is at least one selected from WO 4-2-, PbO 4-4-, formic acid ion, dicarboxylic acid ion, hydroxy acid _{ion and} silicate ^{ion .} Quality equipment.

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