JP7759615B2 - Method for vitrifying concrete members, concrete drainage structure, and vitrified repaired concrete member - Google Patents

Description

The present invention relates to a method for vitrifying concrete members, concrete drainage structures obtained by the vitrification method, and vitrified-repaired concrete members.

Because laser beams have no mass, laser processing can be performed essentially noiselessly and vibration-free. Laser processing is gaining attention not only for processing and welding metal materials, but also for processing concrete materials, and research into its potential application in the construction industry has begun.

Specifically, it has been reported that when a laser is irradiated onto concrete or rock containing silica, the silica in the irradiated area melts and vitrifies, and this phenomenon is being explored for use in rock cutting, drilling holes in concrete, and surface treatment.

For example, Patent Document 1 (JP 6-80485 A) proposes a surface treatment method in which a surface-attaching material primarily composed of an inorganic substance is placed on the surface of a building material substrate, and the surface layer is melted by irradiating it with a laser, resulting in a building material with a strong film formed on it.

The laser welding device described in Patent Document 1 above is capable of creating a strong hardened film by melting both the base material of the construction material and the surface-attached material, and is said to be able to easily form a colored hardened film on the surface of the construction material and to provide thermal and sound insulation to the surface of the construction material.

Patent Document 2 (JP Patent Publication No. 11-19785) proposes a method for drilling hardened cement bodies, which involves irradiating the hardened cement body with a laser to form a brittle layer that reduces the strength of the hardened cement body, and then removing the brittle layer to drill holes.

The drilling method for hardened cement bodies described in Patent Document 2 uses a low-noise, low-vibration device to form a brittle layer with a sufficiently reduced strength in the hardened cement body, which is the object to be drilled. The brittle layer can then be removed using a low-speed mechanical or manual tool. As a result, it is possible to minimize the generation of vibration and noise during drilling, thereby improving the working environment and surrounding environment during drilling.

The present inventor also disclosed a method for manufacturing a glass bulk body using laser irradiation in Patent Document 3 (WO 2020/026766). The invention aims to provide a simple method for manufacturing a glass bulk body by irradiating a sand grain aggregate, rock, or concrete with a laser and continuously forming a dense glass layer in a desired region using the silica (SiO ₂ ) component contained in the sand grain aggregate, rock, or concrete as a raw material. The method for manufacturing a glass bulk body includes a first step of irradiating the surface of the sand grain aggregate, rock, or concrete with a fixed _- point laser to form a molten zone, and a second step of moving the laser irradiation position at a scanning speed that continuously expands the molten zone to form a glass layer, wherein the first and second steps are performed continuously.

In the glass bulk manufacturing method described in Patent Document 3, a molten section that serves as the seed for the glass layer is formed by fixed-point laser irradiation, and then the molten section is continuously expanded by laser scanning, thereby obtaining a high-quality glass bulk.

Japanese Patent Application Publication No. 6-80485 Japanese Patent Application Publication No. 11-19785 International Publication No. 2020/026766

However, the construction material and surface treatment method described in Patent Document 1 above require the use of a surface attachment material whose main component is an inorganic substance whose composition has been adjusted for laser irradiation, and the surface attachment material is melted by laser irradiation and coated onto the surface of the construction material base material. In other words, the surface treatment method described in Patent Document 1 above is a method of coating an inorganic substance using laser irradiation, and does not vitrify any area of a concrete member.

Furthermore, the method of drilling holes in a hardened cement body described in Patent Document 2 uses laser irradiation to form a brittle layer in the hardened cement body, which is a technology with a completely opposite approach to methods that form a dense glass layer in any region with reduced defect formation. Furthermore, not only is the formation of the brittle layer limited to a narrow region corresponding to the drilled region, but the brittle layer does not need to be formed continuously.

Furthermore, while the glass bulk manufacturing method described in Patent Document 3 can form a favorable vitrified region on the surface of a concrete member, it requires expanding the molten area created by fixed-point laser irradiation through laser scanning, making it difficult to locally vitrify any desired region. In addition, because laser irradiation is performed on a relatively large area, it is difficult to completely suppress spalling of the concrete member, limiting the concrete members and working environments to which it can be applied. It is particularly difficult to apply this method to existing concrete members, such as concrete drainage structures, to impart sufficient corrosion resistance. It is also difficult to accurately and efficiently repair cracks with openings on the surface of concrete members. In other words, there is no simple and efficient vitrification method that can be suitably used for the internal treatment of concrete drainage structures or the repair of cracks in concrete members.

In light of the problems with the prior art described above, the object of the present invention is to provide a simple and efficient vitrification method for vitrifying any region of a concrete member by laser irradiation, which not only eliminates the need to form a molten area (a seed of a glass layer) by fixed-point laser irradiation, but also enables localized vitrification and suppresses concrete spalling. Another object of the present invention is to provide concrete drainage structures and vitrified-repaired concrete members that have excellent corrosion resistance and low hydraulic conductivity, which can be obtained by the vitrification method of the present invention.

In order to achieve the above objective, the inventors conducted extensive research into methods of irradiating the surface of concrete members with a laser, and discovered that controlling both the laser beam diameter and output is extremely important, leading to the development of this invention.

That is, the present invention provides:
A method for vitrifying any area of a concrete member, comprising:
Irradiating a laser onto the surface of the concrete member;
The beam diameter of the laser on the surface is set to 10 to 100 μm,
The output of the laser is 100 to 1000 W;
The present invention provides a method for vitrifying a concrete member, characterized by the above.

In the concrete member vitrification method of the present invention, by setting the laser beam diameter to 10 μm or more, it is possible to ensure industrially applicable vitrification speed and efficiency. On the other hand, by setting the laser beam diameter to 100 μm or less, it is possible to suppress concrete spalling. The laser beam diameter is preferably 20 to 90 μm, more preferably 30 to 80 μm, and most preferably 40 to 70 μm.

In addition, in the concrete member vitrification method of the present invention, by setting the laser output to 100 W or more for a beam diameter of 10 to 100 μm, the concrete member in the laser scanning area can be vitrified without forming a molten zone (a seed of a glass layer) due to fixed-point laser irradiation. On the other hand, by setting the laser output to 1000 W or less, spalling of the concrete can be suppressed. The laser output is preferably 200 to 900 W, more preferably 300 to 800 W, and most preferably 400 to 700 W.

Furthermore, in the method for vitrifying a concrete member of the present invention, it is preferable to set the power density of the laser to 10 to 50 MW/ ^cm² . By setting the power density to 10 MW/cm² or ^more , the concrete member in the laser scanning area can be more reliably vitrified without forming a molten zone (a seed of a glass layer) due to fixed-point laser irradiation. In addition, it is possible to ensure an industrially usable vitrification speed and efficiency. Furthermore, by setting the power density to 50 MW/cm² or ^less , it is possible to more reliably suppress concrete spalling. A power density of 15 to 45 MW/ ^cm² is more preferable, and a power density of 20 to 40 MW/ ^cm² is most preferable.

In addition, in the concrete member vitrification method of the present invention, it is preferable to set the laser scanning speed to 100 to 1,000 mm/sec. By setting the laser scanning speed to 100 mm/sec or more, it is possible to ensure the speed and efficiency of vitrification while simultaneously suppressing spalling. Furthermore, by setting the laser scanning speed to 1,000 mm/sec or less, it is possible to form a vitrified region stably and continuously. It is more preferable to set the laser scanning speed to 300 to 800 mm/sec, and most preferably to set it to 500 to 600 mm/sec.

Furthermore, it is preferable to use a fiber laser in the concrete member vitrification method of the present invention. The type of laser used in the concrete member vitrification method of the present invention is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known lasers can be used. However, by using a fiber laser, a beam diameter of 10 to 100 μm and a laser output of 100 to 1,000 W can easily be achieved.

Furthermore, the method for vitrifying a concrete member of the present invention preferably includes a first step of identifying the position, shape, and size of a crack present on the surface of the concrete member, and a second step of irradiating the crack with the laser. If a crack exists on the surface of a concrete member, the position, shape, and size of the crack can be determined in advance in the first step, and the crack can be accurately irradiated with the laser in the second step, thereby efficiently and effectively repairing the concrete member by vitrifying the crack.

Furthermore, in the method for vitrifying a concrete member of the present invention, it is preferable that the concrete member is a concrete drainage structure, and that the irradiation is applied to the upper surface of the base slab and/or the inner wall surface of the concrete drainage structure. By irradiating the upper surface of the base slab and/or the inner wall surface of the concrete drainage structure with a laser to vitrify it, a concrete drainage structure with excellent corrosion resistance can be produced extremely efficiently. The concrete drainage structure is not particularly limited as long as it does not impair the effects of the present invention, and can be any of a variety of conventionally known concrete drainage structures, such as concrete manholes, concrete gutters, and concrete Hume pipes.

Furthermore, for example, when lining the interior of an existing concrete drainage structure with plastic, dirt on the surface of the concrete member due to sludge and other contaminants and moisture can hinder adhesion. However, with the concrete member vitrification method of the present invention, the surface of the concrete drainage structure, including the sludge, is melted and vitrified by laser irradiation, and the moisture instantly evaporates, so these effects are hardly felt. As a result, existing concrete drainage structures can also be treated effectively.

Furthermore, in the method for vitrifying a concrete member of the present invention, it is preferable to set the hydraulic conductivity of the concrete member to 1×10 ⁻⁷ cm/s or less. By vitrifying the surface of the concrete member, particularly the surface having cracks, the hydraulic conductivity of the concrete member can be set to 1×10 ⁻⁷ cm/s or less, thereby obtaining a concrete member with excellent reliability and long-term stability. The hydraulic conductivity of the concrete member is more preferably 0.5×10 ⁻⁷ cm/s or less, and most preferably 0.1×10 ⁻⁷ cm/s or less.

The present invention also provides a concrete drainage structure characterized by the formation of a vitrified layer on at least a portion of the top surface of the base slab and/or the inner wall surface. Note that the "vitrified layer" and "vitrified area" in this invention refer to the vitrified surface of a concrete member, and do not refer to a glass layer formed using a material other than the concrete member.

The concrete drainage structure of the present invention has a vitrified layer formed on at least a portion of the top surface of the base slab and/or the inner wall surface, and has dramatically improved corrosion resistance compared to conventional concrete drainage structures. It is preferable that the vitrified layer be formed in an area of the concrete drainage structure that is constantly in contact with acidic water.

Concrete drainage structures deteriorate when they react with acid. Furthermore, when alkaline wastewater is discharged from beverage factories and other facilities, reinforced plastic pipes must be used, and in areas where it is difficult to use plastic components such as manholes, the concrete components must be lined with plastic to prevent the acid from acting on them. In contrast, in the concrete drainage structure of the present invention, the areas that come into contact with acidic water are covered with a glass layer that has excellent chemical stability, providing good corrosion resistance.

In the concrete drainage structure of the present invention, the thickness of the vitrified layer is preferably 100 to 20,000 μm. A vitrified layer thickness of 100 μm or more can impart extremely good corrosion resistance to the concrete drainage structure, while a thickness of 20,000 μm or less can reduce the embrittlement of the concrete drainage structure and the cost of vitrification treatment. A more preferred thickness of the vitrified layer is 200 to 15,000 μm, and the most preferred thickness is 300 to 10,000 μm.

The concrete drainage structure of the present invention can be suitably obtained by the concrete member vitrification method of the present invention.

Furthermore, the present invention also provides a vitrified-repaired concrete member, characterized in that a vitrified layer is formed on at least a portion of the surface of the concrete member, and the concrete member having the vitrified layer has a water permeability coefficient of 1 x 10 ^-7 cm/s or less.

The region where the vitrified layer is formed is not particularly limited as long as it does not impair the effects of the present invention, but by forming a region having defects such as cracks into a vitrified layer, water permeation is effectively suppressed and the water permeability coefficient is 1×10 ⁻⁷ cm/s or less, more preferably 0.5×10 ⁻⁷ cm/s or less, and most preferably 0.1×10 ⁻⁷ cm/s or less.

In addition, in the vitrification-repaired concrete member of the present invention, it is preferable that the bond strength between the vitrified layer and the concrete member is 98 N/cm ² or more. With a bond strength of 98 N/cm ² or more, the vitrification-repaired concrete member can be suitably used in applications where reliability is required.

The concrete member vitrification method of the present invention not only eliminates the need to form a molten area (a seed of a glass layer) by fixed-point laser irradiation, but also enables localized vitrification, providing a simple and efficient vitrification method that can suppress concrete spalling. Furthermore, the present invention can provide concrete drainage structures and vitrified-repaired concrete members that have excellent corrosion resistance and low hydraulic conductivity, achieved by the vitrification method of the present invention.

1 is a schematic diagram of a method for vitrifying a concrete member (a method for manufacturing a concrete drainage structure) according to the present invention. FIG. 1 is a schematic diagram of a method for vitrifying a concrete member (a method for repairing a concrete member) according to the present invention. 1 is a schematic diagram of a concrete drainage structure (vitrified concrete drainage structure) of the present invention. FIG. 1 is a schematic diagram of a vitrification-repaired concrete member of the present invention. 1 is a photograph showing the appearance of a concrete member used in Example 1. 1 is a photograph showing the appearance of a concrete member after laser irradiation in Example 1. 1 is a photograph showing the appearance of a test specimen in a hydrochloric acid resistance test in Example 1. 1 is a photograph showing the appearance of a concrete member used in Example 2. 10 is a photograph showing the appearance of a concrete member after laser irradiation in Example 2.

Representative embodiments of the present invention's method for vitrifying concrete members, concrete drainage structures, and vitrified repaired concrete members will be described in detail below with reference to the drawings, but the present invention is not limited to these. In the following description, identical or equivalent parts will be designated by the same reference numerals, and duplicate explanations may be omitted. Furthermore, because the drawings are intended to conceptually explain the present invention, the dimensions and ratios of the components shown may differ from the actual dimensions.

(1) Method for Vitrifying Concrete Members The method for vitrifying concrete members of the present invention involves irradiating the surface of a concrete member with a laser to vitrify any region of the concrete member, and in addition to eliminating the need to form a molten area (a seed of a glass layer) by fixed-point laser irradiation, it enables localized vitrification and can also suppress concrete spalling. Below, we will explain in detail the manufacturing of a concrete drainage structure and the repair of a concrete member using the method for vitrifying concrete members of the present invention as representative examples.

(1-1) Manufacturing of a concrete drainage structure Fig. 1 shows a schematic diagram of a concrete drainage structure manufactured using the method for vitrifying a concrete member of the present invention. In Fig. 1, the concrete drainage structure is a concrete manhole, and an existing concrete drainage structure is shown.

The concrete drainage structure 2 is buried underground and is typically covered on top by a manhole 4. The concrete drainage structure 2 is also connected to a drainage pipe 6 made of polyvinyl chloride or the like.

By irradiating the inner surface of the concrete drainage structure 2 with a laser at a beam diameter of 10 to 100 μm and a laser output of 100 to 1000 W, it is possible to form a favorable vitrified area in the irradiated area. Even if the concrete drainage structure 2 is already installed and connected to a drainage pipe 6, the treatment can be easily carried out by scanning the laser from the laser oscillator 8. Note that when the treatment is carried out in a factory on the concrete drainage structure 2, the concrete drainage structure 2 may be rotated or the laser may be scanned.

The laser irradiation area (vitrification area) is preferably the top surface of the base slab and the inner wall surface of the concrete drainage structure 2, encompassing the entire area that comes into contact with water, and more preferably extending above the designed water level in the manhole. By irradiating the top surface of the base slab and the inner wall surface of the concrete drainage structure with a laser to vitrify them, a concrete drainage structure with excellent corrosion resistance can be produced extremely efficiently. The concrete drainage structure is not particularly limited as long as it does not impair the effects of the present invention, and can be any of a variety of conventionally known concrete drainage structures, such as concrete manholes, concrete gutters, and concrete fume pipes.

By setting the laser beam diameter on the surface of the concrete drainage structure 2 to 10 μm or more, it is possible to ensure an industrially usable vitrification speed and efficiency. For example, even when treating an existing concrete drainage structure 2, it is possible to carry out the treatment only at night. On the other hand, by setting the beam diameter to 100 μm or less, it is possible to suppress concrete spalling and ensure sufficient safety even during on-site construction. The laser beam diameter is preferably 20 to 90 μm, more preferably 30 to 80 μm, and most preferably 40 to 70 μm.

Furthermore, by setting the laser output to 100 W or more for a beam diameter of 10 to 100 μm, it is possible to vitrify the concrete component in the laser scanning area without forming a molten zone (a seed of a glass layer) due to fixed-point laser irradiation. On the other hand, by setting the laser output to 1000 W or less, it is possible to suppress concrete spalling. Laser output is preferably set to 200 to 900 W, more preferably 300 to 800 W, and most preferably 400 to 700 W.

Furthermore, the laser power density is preferably 10 to 50 MW/ ^cm² . By setting the power density to 10 MW/ ^cm² or more, the inner surface of the concrete drainage structure 2 in the laser scanning area can be more reliably vitrified without forming a molten area (a seed of a glass layer) due to fixed-point laser irradiation. In addition, it is possible to ensure an industrially applicable level of vitrification speed and efficiency. Furthermore, by setting the power density to 50 MW/ ^cm² or less, concrete spalling can be more reliably suppressed. The power density is more preferably 15 to 45 MW/ ^cm² , and most preferably 20 to 40 MW/ ^cm² .

The laser scanning speed is preferably 100 to 1000 mm/sec. By setting the laser scanning speed to 100 mm/sec or higher, it is possible to ensure the speed and efficiency of vitrification while simultaneously suppressing explosions. Furthermore, by setting the laser scanning speed to 1000 mm/sec or less, it is possible to form a vitrified region stably and continuously. A laser scanning speed of 300 to 800 mm/sec is more preferable, and a speed of 500 to 600 mm/sec is most preferable.

Furthermore, it is preferable to use a fiber laser for laser irradiation. There are no particular restrictions on the type of laser used for irradiation as long as it does not impair the effects of the present invention, and various conventionally known lasers can be used. However, by using a fiber laser, it is possible to easily achieve a beam diameter of 10 to 100 μm and a laser output of 100 to 1000 W.

Furthermore, the thickness of the vitrified layer formed on the inner surface of the concrete drainage structure 2 is preferably 100 to 20,000 μm. A vitrified layer thickness of 100 μm or more can provide the concrete drainage structure 2 with extremely good corrosion resistance, while a thickness of 20,000 μm or less can reduce the embrittlement of the concrete drainage structure 2 and the cost of vitrification. A more preferred thickness of the vitrified layer is 200 to 15,000 μm, and the most preferred thickness is 300 to 10,000 μm.

(1-2) Repair of Concrete Members FIG. 2 is a schematic diagram showing the case where a concrete member is repaired using the method for vitrifying a concrete member of the present invention.

When repairing a concrete member using the concrete member vitrification method of the present invention, it is preferable to have a first step of identifying the position, shape, and size of a crack 12 present on the surface of the concrete member 10, and a second step of irradiating the crack 12.

If a crack 12 exists on the surface of the concrete member 10, the position, shape, and size of the crack 12 are determined in advance in the first step, and the crack 12 is accurately irradiated with a laser in the second step. This closes the opening of the crack 12 by vitrifying the concrete, preventing water from entering through the crack 12 and causing rust on the reinforcing steel 14.

The concrete member 10 preferably has a hydraulic conductivity of 1×10 ⁻⁷ cm/s or less. By vitrifying the surface of the concrete member 10, particularly the surface having cracks 12, the concrete member 10 can have a hydraulic conductivity of 1×10 ⁻⁷ cm/s or less, thereby obtaining a concrete member 10 with excellent reliability and long-term stability. The concrete member 10 more preferably has a hydraulic conductivity of 0.5×10 ⁻⁷ cm/s or less, and most preferably has a hydraulic conductivity of 0.1×10 ⁻⁷ cm/s or less.

The laser irradiation conditions are the same as when manufacturing a concrete drainage structure, but laser irradiation may be superimposed on the same area to more reliably seal the opening of the crack 12. Furthermore, since repairs to the concrete member 10 are carried out on-site, reducing the time required for repairs and preventing concrete spalling are extremely important.

(2) Concrete Drainage Structure Fig. 3 is a schematic diagram of a concrete drainage structure (vitrified concrete drainage structure) of the present invention. Fig. 3 shows a concrete drainage structure in the form of a concrete manhole.

The vitrified concrete member 20 preferably has a vitrified area 22 formed on the top surface of the base slab and the inner wall surface of the concrete drainage structure 2, and it is more preferable that the vitrified area 22 encompasses the area that comes into contact with water. Furthermore, it is preferable that the area that comes into contact with water be above the design water level in the manhole.

The formation of a vitrified area 22 on the top surface of the base slab and the inner wall surface of the concrete drainage structure 2 imparts excellent corrosion resistance to the vitrified concrete member 20. The concrete drainage structure 2 is not particularly limited as long as it does not impair the effects of the present invention, and can be any of a variety of conventionally known concrete drainage structures, such as concrete manholes, concrete gutters, and concrete Hume pipes.

(3) Vitrification-repaired concrete member Fig. 4 shows a schematic diagram of a vitrification-repaired concrete member of the present invention. In the vitrification-repaired concrete member 30, the opening of a crack 12 that reaches the surface of a concrete member 10 is closed by a vitrified region 22.

If a crack 12 exists on the surface of the concrete member 10, the position, shape, and size of the crack 12 are determined in advance in the first step, and the crack 12 is accurately irradiated with a laser in the second step. This closes the opening of the crack 12 by vitrifying the concrete, preventing water from entering through the crack 12 and causing rust on the reinforcing steel 14.

The coefficient of permeability of the vitrified-repaired concrete member 30 is preferably 1×10 ⁻⁷ cm/s or less. By vitrifying the surface of the concrete member 10, particularly the surface having the cracks 12, the coefficient of permeability of the vitrified-repaired concrete member 30 can be set to 1×10 ⁻⁷ cm/s or less, thereby obtaining a vitrified-repaired concrete member 30 with excellent reliability and long-term stability. The coefficient of permeability of the vitrified-repaired concrete member 30 is more preferably 0.5×10 ⁻⁷ cm/s or less, and most preferably 0.1×10 ⁻⁷ cm/s or less.

Furthermore, in the vitrification-repaired concrete member 30, the bond strength between the vitrified layer and the concrete member 10 is preferably 98 N/cm ² or more. With a bond strength of 98 N/cm ² or more, the vitrification-repaired concrete member 30 can be suitably used in applications where reliability is required.

The above describes representative embodiments of the present invention, but the present invention is not limited to these. Various design modifications are possible, and all such design modifications are included within the technical scope of the present invention.

Example 1
Using a single-mode fiber laser, the surface of a disk-shaped concrete member having the composition shown in Table 1 was irradiated with laser. A photograph of the concrete member's appearance is shown in Figure 5. The laser beam diameter on the surface of the concrete member was 43 μm, and the laser output was 500 W (power density: 34.45 MW/cm ² ). The laser scanning speed was 260 mm/sec, and the entire surface of the concrete member was irradiated with laser. The pitch width of the laser scanning was 0.05 mm, and fixed-point laser irradiation was not performed.

Figure 6 shows a photograph of the appearance of the concrete member after laser irradiation. The entire surface of the concrete member has discolored, and it is clear that the entire surface has been vitrified. The vitrified concrete member was cut for evaluation purposes, and the three vertical lines in the photograph are due to this cutting.

To evaluate the corrosion resistance of the vitrified region, the vitrified region was crushed and separated from the concrete component and subjected to a hydrochloric acid resistance test. Specifically, the weight of the crushed vitrified region fragments was measured in an air-dry state, and then the fragments were immersed in laboratory hydrochloric acid (10%) in a petri dish for 30 minutes to observe the reaction. It was confirmed that there was only slight foaming from the crushed vitrified region fragments and that the reaction was mild. The weight of the crushed vitrified region fragments was then measured in an air-dry state after 30 minutes of immersion, and the weight change was evaluated. These evaluations were performed on five crushed vitrified region fragments. The weight change results are shown in Table 2.

For comparison, the corrosion resistance of non-vitrified concrete members was evaluated in the same manner as above. Crushed concrete pieces were immersed in laboratory hydrochloric acid (10%) for 30 minutes and the reaction status was observed. Numerous bubbles were generated from the crushed concrete pieces, indicating that the reaction was progressing vigorously. The weight change results are shown in Table 2.

Figure 7 shows photographs of the appearance of vitrified and non-vitrified concrete components before, during, and after immersion in experimental hydrochloric acid (10%). In the non-vitrified concrete components, the surface of the concrete components after immersion is roughened by dissolution, but in the vitrified concrete components, there is almost no change. Regarding the weight change in Table 2, there is also little change in the vitrified components, demonstrating that the vitrified region has extremely good corrosion resistance.

Example 2
The concrete member having a crack on its surface as shown in Figure 8 was irradiated with laser light to form a vitrified region at the opening of the crack. The composition of the concrete member was the same as in Example 1.

As a preliminary step to laser irradiation, the position, shape, and size of the crack on the surface of the concrete member were identified (first step), and the laser was then irradiated along the crack using the same laser irradiation conditions as in Example 1 (second step). Figure 9 shows a photograph of the appearance of the concrete member after laser irradiation. It can be seen that a vitrified region has formed along the crack, sealing the opening.

2... Concrete drainage structures,
4...manhole,
6...Drain pipe,
8...laser oscillator,
10...Concrete member,
12...cracks,
14...reinforcing bars,
20... Vitrified concrete member,
22... Vitrification region,
30... Vitrified repair concrete member.

Claims (5)

A method for vitrifying any area of a concrete member, comprising:
Irradiating a laser onto the surface of the concrete member;
The beam diameter of the laser on the surface is set to 10 to 100 μm,
The output of the laser is 100 to 1000 W,
The power density of the laser is 10 to 50 MW/cm ² ;
The scanning speed of the laser is set to 100 to 1000 mm/sec.
A method for vitrifying concrete members, characterized by: Using a fiber laser;
2. The method for vitrifying a concrete member according to claim 1, wherein the vitrification step comprises: a first step of identifying the location, shape, and size of cracks present on the surface of the concrete member;
a second step of irradiating the crack;
3. The method for vitrifying a concrete member according to claim 1 or 2 , wherein: The concrete member is a concrete drainage structure,
applying the irradiation to the upper surface of the bottom slab and/or the inner wall surface of the concrete drainage structure;
The method for vitrifying a concrete member according to any one of claims 1 to 3 , characterized in that: The concrete member has a coefficient of permeability of 1×10 ⁻⁷ cm/s or less.
The method for vitrifying a concrete member according to any one of claims 1 to 4 , characterized in that: