How to cut concrete components

Abstract

The purpose of the present invention is to provide an easy-to-use and efficient method for cutting a concrete member, in particular, a method that is for cutting a reinforced concrete member, that makes it easy to increase cutting depth and cutting width, and that is low in cutting cost. To achieve the purpose, the present invention provides a method for cutting a concrete member through irradiation of the concrete member with laser, the method being characterized in that: the concrete member includes a steel material; concrete is melted by scanning laser thereon to form a cutting region; the steel material is heated by means of laser to a temperature that causes progression of self-burning of the steel material; and the melting of the concrete is expedited by heat generation from said self-burning.

Description

[Technical Field]

[0001] The present invention relates to a method for cutting concrete members, and more particularly to an efficient method for cutting reinforced concrete members. [Background technology]

[0002] Because laser beams have no mass, laser processing can be performed essentially noiselessly and vibration-free. This has attracted attention not only for processing and welding metal materials, but also for processing concrete materials, and investigations into the possibility of applying this technology to the construction industry have begun.

[0003] For example, Patent Document 1 (JP 2017-25631 A) proposes a method for demolishing a structure that is made up of multiple combined concrete members, with the aim of providing a method for demolishing a structure that can easily maintain the posture of concrete members after cutting, and includes a cutting process in which the concrete members are cut by irradiating them with a laser from a laser device, and in this cutting process, the laser device cuts the concrete members diagonally upward and also forms an uncut portion in a portion of the cut surface.

[0004] The method for demolishing a structure described in Patent Document 1 above is said to be able to form an oblique cut surface, which can support the concrete member after cutting and maintain its posture. Furthermore, in the cutting process, the laser device forms a non-cut portion in a portion of the cut surface, which supports the gaps in the cut surface. This prevents the gaps in the cut surface from being blocked and hindering the cutting when the concrete member is cut obliquely upward, making it easier to cut. Furthermore, when using a laser, it is said that it is easier to form an non-cut portion in the cut surface than with other cutting methods.

[0005] Furthermore, Patent Document 2 (JP 2018-171628 A) proposes a laser cutting device for laser cutting an object with the aim of improving the removability of molten material and performing good laser cutting in relation to laser cutting of concrete structures, the laser cutting device comprising: a laser nozzle that irradiates laser light onto the cutting portion of the object; an assist gas spraying unit that sprays assist gas onto the molten material generated by melting the object at the cutting portion with the laser light; and a laser heating unit that irradiates the molten material with laser light to heat the molten material.

[0006] In the laser cutting device described in Patent Document 2, the temperature of the molten material melted by the laser light irradiated from the laser nozzle is reduced by the assist gas blown from the gas blowing unit, but by irradiating the molten material with laser light from the laser heating unit, the molten material is heated and a decrease in the fluidity of the molten material can be suppressed. Also, by moving the laser nozzle backward in the cutting direction and irradiating the molten material with laser light, the molten material can be heated and a decrease in fluidity can be suppressed, and by having the laser nozzle function as the laser heating unit, it is said that there is no need to provide a separate laser heating unit. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2017-25631 [Patent Document 2] Japanese Patent Application Publication No. 2018-171628 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the structure demolition method described in Patent Document 1 maintains the posture of the concrete members after cutting, and is not intended to efficiently cut the concrete members. The cutting direction of the concrete members is also limited. Furthermore, the laser cutting device described in Patent Document 2 ensures fluidity by reheating the molten material with laser irradiation, but even after reheating, the viscosity of molten concrete is relatively high, making it extremely difficult to achieve sufficient cutting efficiency and depth.

[0009] In view of the problems in the prior art as described above, an object of the present invention is to provide a simple and efficient method for cutting concrete members, in particular a method for cutting reinforced concrete members that allows easy increase in cutting depth and cutting width and has low cutting costs. [Means for solving the problem]

[0010] In order to achieve the above object, the inventors conducted extensive research into methods for cutting concrete members using lasers, and discovered that in concrete members using steel as reinforcement, it is extremely important to utilize the heat generated by the self-burning of the steel, leading to the present invention. In other words, the method for cutting concrete members of the present invention efficiently cuts concrete members by utilizing the self-burning phenomenon, which should be avoided when laser cutting steel.

[0011] That is, the present invention provides: A method for cutting a concrete member by irradiating a laser, comprising: the concrete member includes a steel material; The laser scans the concrete to melt the concrete and form a cutting area; The temperature of the steel material is raised by the heating with the laser to a temperature at which self-burning progresses, Promoting melting of the concrete by heat generated by the self-burning; The present invention provides a method for cutting a concrete member, characterized by the above.

[0012] The greatest feature of the concrete cutting method of the present invention is that in addition to melting the concrete using laser irradiation, the melting of the concrete is promoted by heat generated by self-burning of the steel material contained in the concrete. The temperature rise of the steel material to promote self-burning can be easily achieved by laser irradiation.

[0013] The self-burning phenomenon in laser cutting steel occurs when the steel reacts excessively with the assist gas (oxygen), resulting in a large kerf not only in the laser-irradiated area but also in the area where the assist gas (oxygen) is being sprayed, significantly reducing the roughness of the cut surface. In contrast, the "self-burning" phenomenon in the concrete member cutting method of the present invention does not require the use of an assist gas, and broadly includes the phenomenon in which the steel reacts with oxygen to generate heat due to the temperature rise caused by laser irradiation. In other words, to promote the self-burning phenomenon, it is preferable to use an assist gas containing oxygen, but even if an assist gas containing oxygen is not used, the self-burning phenomenon may progress due to, for example, atmospheric oxygen.

[0014] The self-burning phenomenon that occurs when laser cutting steel tends to occur in areas where heat is easily accumulated, such as corners of the steel, or when excessive heat is input by the laser. In the method for cutting concrete members of the present invention, the steel is surrounded by concrete with low thermal conductivity, creating a situation where self-burning of the steel is likely to occur. In addition, when cutting concrete members using a laser, the concrete region, which is a high-melting-point material, must be melted, so the laser scanning speed is slower than when laser cutting steel. In other words, the conditions are set such that the steel experiences excessive heat input, allowing for efficient use of self-burning.

[0015] As self-burning of steel progresses, the heat generated accelerates the melting of the concrete area, causing the concrete near the steel to melt significantly. As a result, the amount of molten concrete flowing out from the steel increases, making it easy to check whether or not the steel is self-burning by observing the discharge of molten concrete during cutting.

[0016] The type and shape of the steel material contained in the concrete member are not particularly limited as long as the effects of the present invention are not impaired, and various types of steel material and their shapes known in the art can be used, but commonly used reinforced concrete and reinforced steel concrete can be efficiently cut using the concrete member cutting method of the present invention.

[0017] In addition, in the method for cutting a concrete member of the present invention, it is preferable to form the cutting area using the side of the laser. When the laser is focused on the edge of the concrete member and irradiated in a spot shape, the concrete member melts from the irradiated area, and the molten concrete flows out, forming a point-like depression. The concrete member can then be cut by expanding the depression in the depth and / or width directions, but removing highly viscous molten concrete is not easy, and the cutting process is not smooth. In contrast, by cutting the concrete member by slicing it using the side of the laser, it is possible to efficiently remove the molten concrete and form a long cutting line in one go.

[0018] In the method for cutting a concrete member of the present invention, it is preferable to start cutting from the outer periphery of the concrete member. By starting cutting from the outer periphery of the concrete member, a wide opening is formed on the outer periphery of the concrete member, and the molten concrete can be efficiently removed from the opening, allowing the cutting to proceed smoothly.

[0019] In addition, in the method for cutting a concrete member of the present invention, it is preferable to abut the side of the laser with the outer peripheral surface of the concrete member at the cutting start position and fix the position of the laser until a molten region of the concrete is formed around the entire circumference of the laser. By forming a molten region of the concrete around the entire circumference of the laser with the side of the laser abutting the outer peripheral surface of the concrete member, it is possible to fully utilize the energy of the laser.

[0020] In the method for cutting a concrete member of the present invention, it is preferable that at least a part of the bottom surface of the concrete member is included in the cutting start position. By providing a cutting area on at least a part of the bottom surface of the concrete member at the start of cutting, molten concrete can be efficiently drained by gravity.

[0021] In addition, in the method for cutting a concrete member of the present invention, it is preferable that the laser be scanned from the lower side of the concrete member in the direction of gravity to the upper side in the direction of gravity to form a cutting area, and that the molten concrete be ejected from the cutting area by gravity. By scanning the laser from the lower side of the concrete member in the direction of gravity to the upper side in the direction of gravity to form a cutting area, the concrete melted by the laser is gradually ejected downward in the direction of gravity, thereby achieving extremely efficient cutting.

[0022] In the method for cutting a concrete member of the present invention, it is preferable that the laser scanning direction is substantially vertical, which makes it possible to make maximum use of gravity in terms of discharging the molten concrete.

[0023] In the method for cutting concrete members of the present invention, the laser output and power density can be appropriately set depending on the desired cutting speed and the size and material of the workpiece, but it is preferable to set the power density to a value greater than or equal to the laser beam diameter. More specifically, when the beam shape in the irradiated area is approximately circular, and when the beam radius is 1.2 mm, the power density is 3.5 kW / mm.2 Power density above 1.0kW / mm for a beam radius of 2.2mm 2 Power density above 0.5kW / mm for a beam radius of 3.2mm 2 Power density above 0.3kW / mm for a beam radius of 4.2mm 2 Power density above 0.2kW / mm for a beam radius of 5.2mm 2 It is preferable to set the power density to the above values. By setting the power density to these values, the concrete member can be melted efficiently.

[0024] Furthermore, in the method for cutting concrete members of the present invention, the laser scanning speed can be set appropriately depending on the output and power density of the laser used, the size and material of the materials to be joined, etc., but it is preferable that the laser scanning speed be 5 to 50 mm / min. By setting the laser scanning speed to 5 mm / min or more, a practical cutting speed for cutting concrete members can be ensured, and by setting it to 50 mm / min or less, the progress of self-burning and the discharge of molten concrete can be promoted. [Effects of the Invention]

[0025] The method for cutting concrete members of the present invention is a simple and efficient method for cutting concrete members, and in particular, it is possible to provide a method for cutting reinforced concrete members that allows for easy increase in cutting depth and cutting width and has low cutting costs. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram showing a state before cutting in the method for cutting a concrete member of the present invention. FIG. [Figure 2] 3 is a schematic diagram showing the laser contact step in the method for cutting a concrete member of the present invention. FIG. [Figure 3] 1A to 1C are schematic diagrams showing cutting progress stages in the method for cutting a concrete member of the present invention. [Figure 4]3 is a schematic diagram showing the self-burning stage in the method for cutting a concrete member of the present invention. FIG. [Figure 5] 1 shows the arrangement of a laser head and a reinforced concrete block in an embodiment. [Figure 6] 3 is a schematic diagram showing a cutting state in Example 1. FIG. [Figure 7] 1 is a photograph of the appearance of a reinforced concrete block immediately after laser irradiation was stopped in Example 1. [Figure 8] 1 is a photograph showing the appearance of a reinforced concrete block divided into two pieces in Example 1. [Figure 9] 10 is a photograph showing the appearance of a reinforced concrete block that has been air-cooled after laser irradiation has been stopped in Example 2. [Figure 10] 10 is a photograph of the appearance of a reinforced concrete block immediately after laser irradiation was stopped in Example 3. [Figure 11] FIG. 10 is a schematic diagram showing a cutting state in Example 4. [Figure 12] 10 is a photograph showing the appearance of a reinforced concrete block that has been air-cooled after laser irradiation has been stopped in Example 4. [Figure 13] 1 is a photograph showing the appearance of a concrete block that has been air-cooled after laser irradiation has been stopped in Comparative Example 1. [Figure 14] 10 is a photograph showing the appearance of a concrete block that has been air-cooled after laser irradiation has been stopped in Comparative Example 2. [Figure 15] 1 is a graph showing the relationship between beam radius and power density for obtaining a good cut. DETAILED DESCRIPTION OF THE INVENTION

[0027] Representative embodiments of the method for cutting concrete members of the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to these. In the following description, the same or equivalent parts will be designated by the same reference numerals, and duplicate explanations may be omitted. Furthermore, since the drawings are intended to conceptually explain the present invention, the dimensions and ratios of the components shown may differ from the actual dimensions.

[0028] One embodiment of the process for cutting a concrete member using the method for cutting a concrete member of the present invention is shown schematically in Figures 1 to 4. Figure 1 shows the pre-cutting stage, Figure 2 shows the laser contact stage, Figure 3 shows the cutting progress stage, and Figure 4 shows the self-burning stage.

[0029] The material to be cut is a concrete member 2, which contains concrete 4 and steel material 6. The composition of the concrete 4 is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known concretes can be used. Furthermore, the type and shape of the steel material 6 are also not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known steel materials and shapes can be used. However, if the concrete member 2 is commonly used reinforced concrete or reinforced steel concrete, the concrete 4 and steel material 6 will be present in an appropriate ratio, allowing for efficient cutting.

[0030] 1. Pre-cutting stage As shown in Figure 1, the laser head 8 is positioned so that the antinode (side surface) of the laser 10 emitted from the laser head 8 is located near the surface to be cut of the concrete member 2. Here, since gravity is used to expel the molten concrete 4 from the cutting area, it is preferable that the surface to be cut is the bottom surface (the surface below in the direction of gravity) of the concrete member.

[0031] As long as the effect of the present invention is not impaired, the type of laser 10 is not particularly limited, and various conventionally known lasers can be used, but it is preferable to use, for example, a semiconductor laser or a fiber laser.

[0032] The output and power density of the laser 10 may be adjusted as appropriate depending on the desired cutting speed and the size, shape, and composition of the concrete member 2. However, it is preferable to set the power density to a value greater than or equal to an appropriate value depending on the laser beam diameter. More specifically, when the beam shape in the irradiated area is approximately circular, and the beam radius is 1.2 mm, the power density is set to 3.5 kW / mm. 2 Power density above 1.0kW / mm for a beam radius of 2.2mm 2 Power density above 0.5kW / mm for a beam radius of 3.2mm 2 Power density above 0.3kW / mm for a beam radius of 4.2mm 2 Power density above 0.2kW / mm for a beam radius of 5.2mm 2 It is preferable to set the power density to the above values. By setting the power density to these values, the concrete member can be melted efficiently.

[0033] The scanning speed of the laser 10 may also be adjusted as appropriate depending on the output and power density of the laser 10 and the size, shape, and composition of the concrete member 2, but it is preferable that the scanning speed of the laser be 5 to 50 mm / min. By setting the scanning speed of the laser to 5 mm / min or more, a practical cutting speed for cutting the concrete member can be ensured, and by setting it to 50 mm / min or less, the progress of self-burning and the discharge of molten concrete can be promoted.

[0034] 2. Laser contact stage As shown in Figure 2, this is the stage where the side of the laser 10 is brought into contact with the surface of the concrete member 2. At the cutting start position of the concrete member 2, it is preferable to bring the side of the laser 10 into contact with the outer peripheral surface of the concrete member 2 and fix the position of the laser 10 until a melted region of the concrete 4 is formed all around the laser 10. By forming a melted region of the concrete 4 all around the laser 10 while the side of the laser 10 is in contact with the outer peripheral surface of the concrete member 2, the energy of the laser 10 can be fully utilized.

[0035] The time for which the laser 10 is held in contact with the outer peripheral surface of the concrete member 2 can be adjusted as appropriate, but a holding time of several seconds to several tens of seconds can form a melted area of ​​the concrete 4 around the entire circumference of the laser 10.

[0036] 3. Cutting Progression Stage As shown in Figure 3, this is the stage where the laser 10 is scanned in the cutting direction. The concrete member 2 can be cut by scanning the laser 10 in any direction from the outer peripheral surface of the concrete member 2. Here, from the viewpoint of utilizing gravity to expel the molten concrete 4 from the cutting area, it is preferable to operate the laser 10 upward in the direction of gravity, but for example, the laser 10 may be scanned diagonally upward, or may be scanned upward and then laterally, etc.

[0037] By providing a cutting region on at least a part of the bottom surface of the concrete member 2 at the start of cutting, the molten concrete can be efficiently discharged by gravity.

[0038] When the laser 10 is in contact only with the concrete 4 of the concrete member 2, there is almost no position dependency in the discharge of the molten concrete, and the same amount of molten concrete is discharged sequentially from the entire cutting area.

[0039] 4. Self-burning stage As shown in Figure 4, this is the stage where the heat input from the laser 10 causes self-burning of the steel material 6 and promotes melting of the concrete 4. When the effect of the laser 10 reaches the steel material 6 and the heat input from the laser 10 causes the steel material 6 to heat up and promote self-burning, the heat generated promotes melting of the concrete 4 near the steel material 6, increasing the amount of molten concrete 4 flowing out from near the steel material 6 and allowing the concrete member 2 to be cut efficiently.

[0040] The presence or absence of self-burning of the steel material 6 can be easily confirmed from the discharge state of molten concrete during cutting. Specifically, as shown in Figure 4, the amount of molten concrete discharged from the vicinity of the steel material 6 becomes significantly large.

[0041] Representative embodiments of the present invention have been described above, but the present invention is not limited to these, and various design modifications are possible, all of which are included in the technical scope of the present invention. [Example]

[0042] Example 1 An attempt was made to cut a reinforced concrete block using a semiconductor laser with a maximum output of 50 kW. The arrangement of the laser head and reinforced concrete block is shown in Figure 5. A schematic of the cutting situation is shown in Figure 6. The reinforced concrete block is a rectangular parallelepiped measuring 100 mm x 150 mm x 500 mm, and the laser head was placed opposite the longitudinal side of the reinforced concrete block.

[0043] The distance between the edge of the reinforced concrete block and the laser head was 100 mm, and the laser focal position was 220 mm from the edge of the reinforced concrete block in the depth direction. The antinode of the laser was held in contact with the surface to be welded for 30 seconds, forming a melted area of ​​the concrete around the entire circumference of the laser, and then the laser was scanned in the cutting direction. The cutting conditions, such as laser power and laser scanning speed, are shown in Table 1.

[0044] [Table 1]

[0045] The laser was scanned 80 mm directly above the bottom of the reinforced concrete block, and then the laser irradiation was stopped. Figure 7 shows a photograph of the appearance of the reinforced concrete block immediately after the laser irradiation was stopped. It can be seen that the molten concrete was being discharged downward in the direction of gravity, and that a good cut had been made in accordance with the laser scanning.

[0046] After the reinforced concrete block shown in Figure 7 was air-cooled, external stress was applied manually using a chisel and hammer, and the block was easily divided into two pieces. Figure 8 shows a photograph of the appearance of the reinforced concrete block after division.

[0047] Example 2 An attempt was made to cut a reinforced concrete block in the same manner as in Example 1, except that the laser output was set to 30 kW. Figure 9 shows a photograph of the appearance of the reinforced concrete block after the laser was scanned 80 mm directly upward from the bottom of the block and then the laser irradiation was stopped and the block was allowed to air-cool. In the photograph in Figure 9, the top and bottom surfaces of the reinforced concrete block are reversed, and it can be seen that the ejection of molten concrete is promoted near the area where the rebar is present. This result indicates that the cutting was promoted by the self-burning of the rebar.

[0048] Example 3 An attempt was made to cut a reinforced concrete member in the same manner as in Example 1, except that the conditions shown as Example 3 in Table 1 were used. The laser was scanned 80 mm upward at an angle of 60° from the bottom of the reinforced concrete block, and then the laser irradiation was stopped. Figure 10 shows a photograph of the appearance of the reinforced concrete block immediately after the laser irradiation was stopped. Even when cutting at an angle, a good cut was made, and it can be seen that molten concrete is being discharged from the opening in the bottom of the concrete block.

[0049] Example 4 An attempt was made to cut a reinforced concrete member in the same manner as in Example 1, except that the conditions shown as Example 4 in Table 1 were used. The cutting state is shown schematically in Figure 11. The laser was scanned 80 mm directly across the side of the reinforced concrete block, and then the laser irradiation was stopped. Figure 12 shows a photograph of the appearance of the reinforced concrete block after the laser irradiation was stopped and the block was allowed to air-cool. Even when the laser was scanned directly across the side of the reinforced concrete block, a cut could be made, but the removal of molten concrete and cutting did not proceed as smoothly as when there was an opening on the bottom.

[0050] Comparative Example 1 An attempt was made to cut a concrete block in the same manner as in Example 1, except that a solid concrete block was used as the material to be cut and the laser scanning speed was set to 6 mm / min. The laser was scanned 15 mm directly upward from the bottom of the concrete block, and then the laser irradiation was stopped. Figure 13 shows a photograph of the appearance of the concrete block after laser irradiation was stopped and it was allowed to air-cool. Although a cut area was formed, it can be seen that the amount of molten concrete discharged was less than in the Examples, even when the laser scanning speed was slowed.

[0051] Comparative Example 2 An attempt was made to cut a concrete block in the same manner as in Example 2, except that a solid concrete block was used as the material to be cut. Figure 14 shows a photograph of the concrete block's appearance after the laser was scanned 80 mm directly above the bottom surface of the block and then the laser irradiation was stopped and the block was allowed to air cool. In the photograph in Figure 14, the top and bottom surfaces of the concrete block are reversed, but compared to the results of Example 2 (Figure 9) under the same cutting conditions, it can be seen that the amount of molten concrete discharged was less, and the cutting efficiency was inferior.

[0052] [Effects of laser spot diameter and power density on cutting of concrete materials] The relationship between beam radius and power density was measured under the laser irradiation conditions described in Example 1, which resulted in a good cut corresponding to the laser scanning. Specifically, since the beam diameter increases with increasing distance from the focal position, the beam radius and power density were measured at distances from the focal position of -250 mm, -200 mm, -150 mm, -100 mm, -50 mm, 0 mm, 50 mm, 100 mm, 150 mm, 200 mm, and 250 mm. These measurements were performed using a Primes beam profiler. The results are shown in Table 2. The relationship between beam radius and power density is also shown in Figure 15.

[0053] [Table 2]

[0054] The graph in Figure 15 shows the boundary conditions for the laser to obtain a good cut. By setting the beam radius and power density so that they fall in the upper right area of ​​the curve connecting the plots, concrete can be melted efficiently. [Explanation of symbols]

[0055] 2. Concrete members, 4. Concrete, 6...Steel materials, 8. Laser head, 10...laser, 20...cutting area.

Claims

1. A method for cutting a concrete member by irradiating a laser, comprising: the concrete member includes a steel material; The laser scans the concrete to melt the concrete and form a cutting area; The temperature of the steel material is raised by the heating with the laser to a temperature at which self-burning progresses, The heat generated by the self-burning promotes melting of the concrete, forming the cutting region using a beam profile in the optical axis direction of the laser; abutting the beam profile on the outer peripheral surface of the concrete member at a cutting start position, and fixing the position of the laser until a melted region of the concrete is formed around the entire circumference of the laser; A method for cutting concrete members, comprising:

2. Starting cutting from the outer periphery of the concrete member; 2. The method for cutting a concrete member according to claim 1, wherein:

3. At least a part of the bottom surface of the concrete member is included in the cutting start position; 3. The method for cutting a concrete member according to claim 1 or 2,

4. The laser is scanned from the lower side of the concrete member in the direction of gravity toward the upper side in the direction of gravity to form a cutting region. Discharging the molten concrete from the cutting area by gravity; 4. The method for cutting a concrete member according to claim 1, wherein the cutting force is 0.001 to 0.

001.

5. The scanning direction of the laser is set to a substantially vertical direction; 5. The method for cutting a concrete member according to claim 1, wherein the cutting tool is a cutting tool for cutting a concrete member.

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