JP7790889B2 - Method for removing hardened cement - Google Patents

Description

The present invention relates to a method for removing hardened cement paste.

One technique proposed for reusing building materials removed from exterior walls involves immersing the building materials with hardened cement attached in an acid solution at room temperature for 40 days to remove the hardened cement (see, for example, Patent Document 1).

JP 2016-199458 A

However, as mentioned above, in the conventional technology, building materials with hardened cement attached are immersed in an acid solution at room temperature for 40 days, which requires a significant number of days to remove the hardened cement. Therefore, there is room for improvement in terms of shortening the time required to remove the hardened cement.

The present invention has been made in consideration of the above, and aims to provide a method for removing hardened cement bodies that can shorten the time required to remove hardened cement bodies.

In order to solve the above-mentioned problems and achieve the object, the method for removing a hardened cement body described in claim 1 is a method for removing a hardened cement body adhering to a construction member from the construction member , and includes a removal step of removing the hardened cement body adhering to the construction member by immersing the construction member in an acid solution at about 50°C to 90°C for a predetermined period of time, and in the removal step, after immersing the construction member in the acid solution for about 15 minutes, removing the hardened cement body from the construction member by a predetermined removal method is repeated multiple times, and the predetermined removal method includes applying hot air to the construction member and/or immersing the construction member in boiling water.

The method for removing a hardened cement body according to claim 2 is a method for removing hardened cement body adhering to a construction member from the construction member, and includes a removal step of removing the hardened cement body adhering to the construction member by immersing the construction member in an acid solution at about 50°C to 90°C for a predetermined period of time, and a pretreatment step carried out before the removal step for accelerating the removal of the hardened cement body in the removal step, in which the construction member is dried to an absolute dry state or a state close to it, and then the construction member is immersed in the acid solution at room temperature for a predetermined period of time, and/or the construction member is immersed in the acid solution at room temperature for a predetermined period of time.

The method for removing hardened cement bodies as set forth in claim 1 includes a removal step of removing the hardened cement bodies adhering to construction members by immersing the construction members in an acid solution at about 50°C to 90°C for a predetermined period of time. This makes it possible to remove the hardened cement bodies more quickly and shorten the time required to remove them compared to the conventional technique (technique in which building materials with hardened cement bodies adhering thereto are immersed in an acid solution at room temperature).
Furthermore, in the removal process, the construction member is immersed in an acid solution for about 15 minutes, and then the hardened cement body is removed from the construction member using a predetermined removal method, which is repeated multiple times. This makes it possible to remove the hardened cement body more effectively than when the construction member is simply immersed in an acid solution, and further shortens the time required to remove the hardened cement body.
Furthermore, since the specified removal method includes applying hot air to the construction member and/or immersing the construction member in boiling water, the hardened cement body can be easily and reliably removed from the construction member, making it possible to remove the hardened cement body more efficiently.

According to the method for removing hardened cement bodies as set forth in claim 2, a removal step is included in which the hardened cement bodies adhering to construction members are removed by immersing the construction members in an acid solution at about 50°C to 90°C for a predetermined period of time. This makes it possible to remove the hardened cement bodies more quickly and shorten the time required to remove the hardened cement bodies compared to the conventional technique (technique in which building materials with hardened cement bodies adhering thereto are immersed in an acid solution at room temperature).
Furthermore, in the pretreatment process, the construction members are immersed in an acid solution at room temperature for a predetermined period of time, which facilitates the removal of the hardened cement body in the removal process, thereby shortening the removal process and improving the workability of the removal process.

1A and 1B are diagrams conceptually showing a body according to an embodiment of the present invention, in which FIG. 1A is a front view and FIG. 1B is a cross-sectional view taken along the line AA. 10A and 10B are diagrams showing preparation steps of a method for removing a hardened cement body. 1A and 1B are diagrams showing a pretreatment step of a method for removing a hardened cement body, in which FIG. 1A shows a state in which a construction member is being dried, and FIG. 1B shows a state in which the construction member is being immersed in a first acid solution. 1A and 1B are diagrams showing the removal process of the method for removing a hardened cement body, in which FIG. 1A shows a state in which a construction member is immersed in a second acid solution, and FIG. 1B shows a state in which the construction member is scrubbed. FIG. 10 is a diagram showing test results of a first removal confirmation test. 1A and 1B are diagrams showing the test results of the second removal confirmation test, in which FIG. 1A is a diagram showing the relationship between the temperature of the second acid solution and the mass loss of each test specimen, and FIG. 1B is a diagram showing the relationship between the temperature of the second acid solution and the titration concentration of the second acid solution. FIG. 10 is a diagram showing test results of a third removal confirmation test. FIG. 10 is a diagram showing test results of the fourth removal confirmation test.

The following describes in detail an embodiment of the method for removing hardened cement bodies according to the present invention, with reference to the accompanying drawings. First, [I] the basic concept of the embodiment will be explained, followed by [II] specific details of the embodiment, and finally, [III] modified examples of the embodiment will be explained. However, the present invention is not limited to the embodiment.

[I] Basic Concept of the Embodiment First, the basic concept of the embodiment will be described. The embodiment generally relates to a removal method for removing a hardened cement body adhering to a construction member from the construction member.

Here, the specific structure and type of "construction component" is arbitrary, but the concept includes, for example, exterior materials (e.g., tile-based exterior materials, brick-based exterior materials, stone-based exterior materials) and interior materials (e.g., tile-based interior materials, brick-based interior materials, stone-based interior materials) attached to the framework of a structure (e.g., pillars, walls, floors, or ceilings), but in this embodiment, it will be described as tile-based exterior materials for walls.

Furthermore, the specific structure and type of "structure" can be arbitrary, but the concept includes, for example, architectural structures such as office buildings, commercial facilities, public facilities, and apartment complexes such as apartment buildings and condominiums, as well as civil engineering structures such as tunnels and dams. However, in this embodiment, we will explain it as an office building.

Furthermore, the term "hardened cement body" refers to a material used to attach construction components to the main body of the building structure described below, and is a concept that includes, for example, base materials and/or adhesive materials that contain at least cement as an ingredient. In the embodiments, it will be described as including base materials and adhesive materials made of mortar.

Furthermore, the specific use of the construction components from which the hardened cement has been removed using this removal method is arbitrary, but examples include reusing the construction components as exterior or interior materials on the skeleton of the structure to which they were attached or on the skeleton of a different structure, or using them for purposes other than exterior or interior materials (such as fencing for flower beds, for example).

[II] Specific Contents of the Embodiment Next, specific contents of the embodiment will be described.

(composition)
First, the structure of the skeleton of a structure (specifically, an office building) including construction members to which the method for removing a hardened cement body according to the embodiment is applied will be described.

Figure 1 is a conceptual diagram of a body according to an embodiment of the present invention, where (a) is a front view and (b) is a cross-sectional view taken along the line A-A.

In the following explanation, the X direction in Figure 1 will be referred to as the left-right direction of the body (-X direction will be the left direction of the body, and +X direction will be the right direction of the body), the Y direction in Figure 1 will be referred to as the front-to-back direction of the body (+Y direction will be the front direction of the body, and -Y direction will be the rear direction of the body), and the Z direction in Figure 1 will be referred to as the up-down direction of the body (+Z direction will be the top direction of the body, and -Z direction will be the bottom direction of the body).

The skeleton 1 is a wall (e.g., an exterior wall) that constitutes a structure, and as shown in Figure 1, it comprises a skeleton body 10, construction members 20, and a hardened cement body 30.

(Structure - Main body)
The main body 10 is the basic structure of the main body 1. The main body 10 is formed of a long rectangular plate made of, for example, concrete (for example, reinforced concrete or prestressed concrete), and as shown in Fig. 1, is arranged so that its longitudinal direction is along the vertical direction, and is fixed to an installation target (for example, a floor, etc.) not shown.

(Configuration - Construction Materials)
The construction member 20 is constructed using, for example, a known tile-based exterior material, and as shown in Figure 1, is arranged outside the main body 10 so as to cover the entire outer surface of the main body 10 (in Figure 1, the entire front surface), and has a construction member main body 21.

(Configuration - Construction component - Construction component body)
The construction member body 21 is the basic structure of the construction member 20. This construction member body 21 is made of, for example, known tile material (one example is a rectangular tile material having a tile portion and a joint portion), and as shown in Fig. 1, a plurality of construction member bodies 21 are arranged side by side substantially along the left-right direction so as to cover the framework body 10, and a plurality of construction member bodies 21 are arranged side by side substantially along the up-down direction.

In addition, the specific configuration of the construction member main body 21 in this embodiment is as follows:

That is, as shown in Figure 1, the entire outer surface of the construction member main body 21 (in Figure 1, the entire front surface) is formed flat. However, this is not limited to this, and it may be formed non-flat, for example. Furthermore, the entire inner surface of the construction member main body 21 (in Figure 1, the entire rear surface) is formed non-flat, and specifically, is formed so as to have multiple convex portions that protrude rearward.

(Structure - hardened cement body)
The hardened cement body 30 is used to attach the construction member 20 to the skeleton main body 10. As shown in FIG. 1(b), the hardened cement body 30 is provided between the skeleton main body 10 and the construction member main body 21.

The specific configuration of the hardened cement body 30 is optional, but in this embodiment, as shown in Figure 1(b), it includes a base portion 31 and an attachment portion 32.

Of these, the base portion 31 is used to level out any unevenness in the main body 10. This base portion 31 is constructed using, for example, a known mortar base material, and is provided so as to cover substantially the entire outer surface of the main body 10, as shown in Figure 1(b).

The adhesive portion 32 is used to attach the construction member 20 to the base material. This adhesive portion 32 is constructed using, for example, a known adhesive material made of mortar, and is provided so as to cover substantially the entire outer surface of the base portion 31, as shown in Figure 1(b).

(Method for removing hardened cement body)
Next, a method for removing the hardened cement body 30 according to the embodiment will be described.

Figure 2 shows the preparatory steps of the method for removing hardened cement body 30. Figure 3 shows the pretreatment steps of the method for removing hardened cement body 30, where (a) shows the construction member 20 being dried, and (b) shows the construction member 20 being immersed in a first acid solution AL1, which will be described later. Figure 4 shows the removal steps of the method for removing hardened cement body 30, where (a) shows the construction member 20 being immersed in a second acid solution AL2, which will be described later, and (b) shows the construction member 20 being scrubbed.

The method for removing hardened cement body 30 according to the embodiment is a method for removing hardened cement body 30 attached to a construction member 20 from the construction member 20, and includes a preparation process, a pretreatment process, and a removal process, as shown in Figures 2 to 4.

(Method for removing hardened cement body - preparation process)
Returning to FIG. 2, the preparation step will be described first.

The preparation process is a process for preparing the hardened cement body 30 for removal from the construction member 20.

Specifically, as shown in FIG. 2, first, a known cutting tool (not shown) is used to cut a portion of the construction member 20 together with the hardened cement body 30, and then a known peeling tool (not shown) is used to peel the cut construction member 20 and the hardened cement body 30 from the main body 10 of the building structure. In this case, for example, to increase the reusability of the construction member 20, it is desirable to cut the construction member 20 so that the cut region includes at least one tile portion of the main body 21 of the construction member, and to cut the joint portion of the main body 21 of the construction member without cutting the tile portion of the main body 21 of the construction member.

(Method for removing hardened cement body - pretreatment process)
Next, the pretreatment step will be described.

The pretreatment process is performed after the preparation process and before the removal process to facilitate the removal of the hardened cement body 30 in the removal process.

The processing details of the pretreatment process are optional, but in this embodiment, the construction member 20 is dried to an absolute dry state or a state close to it, and/or the construction member 20 is immersed in an acid solution AL1 (hereinafter referred to as the "first acid solution AL1") at room temperature for a predetermined period of time.

The reason for drying the construction member 20 until it reaches an absolute dry state or a state close to it is to remove moisture from the interior of the hardened cement body 30 adhering to the construction member 20, thereby making it easier for the first acid solution AL1 in the pretreatment process or the second acid solution AL2 described below to penetrate into the interior of the hardened cement body 30. Note that "an absolute dry state or a state close to it" refers to, for example, a state in which the moisture content of the construction member 20 is approximately 5% or less.

The reason for immersing the construction member 20 in the first acid solution AL1 at room temperature for a predetermined period of time is to allow the first acid solution AL1 to penetrate into the hardened cement body 30 attached to the construction member 20, thereby shortening the penetration time of the second acid solution AL2 (described below) into the hardened cement body 30.

Regarding the details of the pretreatment process, first, as shown in Figure 3(a), based on the test results of the third removal confirmation test described below, the construction material 20 is dried at approximately 100°C for approximately three hours using a known drying device 41. Next, as shown in Figure 3(b), the dried construction material 20 is placed in a first container 42 containing a first acid solution AL1 at room temperature, and the construction material 20 is immersed in the first acid solution AL1 for approximately 20 hours.

However, this is not limiting. For example, the construction member 20 may be dried at a temperature exceeding 100°C for more than 3 hours (or less than 3 hours), and then the construction member 20 may be immersed in the first acid solution AL1 for less than 20 hours or more than 20 hours. Alternatively, the construction member 20 may simply be dried at about 100°C (or a temperature exceeding 100°C) for about 3 hours (or more than 3 hours, or less than 3 hours, etc.) using the drying device 41. Alternatively, the construction member 20 may simply be immersed in the first acid solution AL1 at room temperature for about 20 hours (or less than 20 hours, or more than 20 hours).

The amount of first acid solution AL1 stored in the first container 42 can be any amount as long as it is sufficient to immerse the entire hardened cement body 30. In this embodiment, however, as shown in FIG. 3(b), the amount may be set to an amount that completely immerses both the construction member 20 and the hardened cement body 30. However, this is not limited to this, and the amount may be set such that, for example, the hardened cement body 30 is completely immersed, but not all of the construction member 20 is immersed in the first acid solution AL1 (note that the same applies to the amount of second acid solution AL2 stored in the second container 52 described below).

The type of acid contained in the first acid solution AL1 may be any as long as it can react with at least some of the components of the hardened cement body 30 to dissolve the hardened cement body 30. For example, hydrochloric acid, nitric acid, sulfuric acid, citric acid, hydroiodic acid, perchloric acid, hydrobromic acid, chloric acid, bromic acid, iodic acid, perbromic acid, metaperiodic acid, permanganic acid, thiocyanic acid, aqua regia, malic acid, lactic acid, glycolic acid, oxalic acid, malonic acid, succinic acid, phthalic acid, acetic acid, formic acid, tartaric acid, benzoic acid, propionic acid, butyric acid, valeric acid, etc. may be used (note that the same applies to the type of acid contained in the second acid solution AL2 described below).

Furthermore, the acid concentration of the first acid solution AL1 can be set by any method, but in this embodiment, it is set to the same concentration as the acid concentration of the second acid solution AL2, which will be described later. However, this is not limited to this, and for example, it may be set to a concentration lower than the acid concentration of the second acid solution AL2, which will be described later, or it may be set to a concentration higher than the acid concentration of the second acid solution AL2, which will be described later.

This pretreatment process can facilitate the removal of the hardened cement body 30 in the removal process, shortening the removal process while also improving the workability of the removal process (e.g., reducing the number of times or time required to scrub the construction member 20).

(Method for removing hardened cement body - Removal step)
Next, the removal step will be described.

The removal process is a process that follows the pretreatment process, in which the construction member 20 is immersed in an acid solution AL2 (hereinafter referred to as the "second acid solution AL2") at approximately 50°C to 90°C for a predetermined period of time to remove the hardened cement body 30 adhering to the construction member 20.

The reason why the temperature of the second acid solution AL2 was set to approximately 50°C to 90°C is as follows. Specifically, as shown in the test results of the second removal confirmation test described below, if the temperature of the second acid solution AL2 was set at or near the boiling point, the acid concentration of the second acid solution AL2 (specifically, the acid titration concentration) would decrease over the immersion period, potentially making it impossible to maintain the acid concentration of the second acid solution AL2. Furthermore, if the temperature of the second acid solution AL2 was set below 50°C, the effect of removing the hardened cement body 30 would be lower than if the temperature of the second acid solution AL2 was set at 50°C or higher, potentially making it difficult to shorten the time required to remove the hardened cement body 30. Therefore, these problems were avoided.

The processing details of this removal process are optional, but in this embodiment, the construction member 20 is immersed in the second acid solution AL2 for approximately 15 minutes, and then the hardened cement body 30 is removed from the construction member 20 multiple times using a specified removal method.

The specific type of specified removal method can be any method as long as it allows the hardened cement body 30 to be easily and reliably removed from the construction member 20. In this embodiment, however, the method is described as scrubbing the construction member 20. However, this is not limited to this method, and other methods may include, for example, scrubbing the construction member 20, applying hot air to the construction member 20, immersing the construction member 20 in boiling water, or a combination of these.

As shown in Figure 4(a), the details of the removal process are as follows: Based on the results of the first removal confirmation test, the second removal confirmation test, and the fourth removal confirmation test, the construction material 20 is placed in a second container 52 containing a second acid solution AL2 heated to approximately 80°C using a known heating device 51 (e.g., a gas heating device), and the construction material 20 is immersed in the second acid solution AL2 for approximately 15 minutes. Then, as shown in Figure 4(b), the immersed construction material 20 is scrubbed in a third container 54 containing water W (e.g., fresh water) using a known brush 53 or the like, thereby removing the dissolved hardened cement body 30 from the construction material 20. This series of steps is then repeated four times (i.e., the construction material 20 is immersed in the second acid solution AL2 for a total of 60 minutes while being scrubbed).

This allows the hardened cement body 30 to be removed more effectively than simply immersing the construction member 20 in the second acid solution AL2.

However, this is not limiting, and the above series of steps may be repeated five or more times. Alternatively, the construction member 20 may be immersed in the second acid solution AL2 at a temperature higher than (or lower than) 80°C for more than 15 minutes (or less than 15 minutes) until the hardened cement body 30 is completely removed, and then the construction member 20 may be scrubbed and washed, which may be repeated four or more times (or less than four times). Alternatively, the scrubbing of the construction member 20 may be omitted, and the construction member 20 may simply be immersed in the second acid solution AL2 for 60 minutes (or more than 60 minutes).

Furthermore, the acid concentration of the second acid solution AL2 can be set by any method, but in this embodiment, it is set to approximately 3% to 35% by weight based on the test results of the second removal confirmation test described below, and specifically, it is set to 35% by weight.

This allows the hardened cement body 30 to be removed effectively, ensuring the removal process is carried out reliably.

This removal process allows for quicker removal of the hardened cement body 30 than conventional techniques (techniques in which building materials with hardened cement body attached are immersed in an acid solution at room temperature), thereby shortening the time required to remove the hardened cement body 30.

The above-described removal method can shorten the time required to remove the hardened cement body 30, thereby reducing the work time required to reuse the construction member 20.

(Test results)
Next, the results of various tests conducted by the applicant of the present invention will be described. Here, the test results of the first removal confirmation test to the fourth removal confirmation test will be described.

(Test results - First removal confirmation test - Overview)
First, an outline of the first removal confirmation test will be described.

The first removal confirmation test is a test to confirm the amount of hardened cement body 30 removed from each test specimen under various test conditions (specifically, temperature conditions and acid concentration conditions of the second acid solution AL2).

The test method for this first removal confirmation test is optional, but is as follows: First, the mass of each test specimen is measured using a known mass measuring device. Next, each test specimen is placed in the corresponding second container 52 containing the second acid solution AL2 (specifically, an acid solution containing hydrochloric acid), and the test specimen is immersed for a predetermined period of time. Then, during and after the immersion, the mass of each test specimen is measured using the mass measuring device.

Here, the temperature of the second acid solution AL2 is set to room temperature for test specimens A1 and A2, which will be described later, and to 80°C for test specimen A3, which will be described later.

Furthermore, the acid concentration of the second acid solution AL2 is set to approximately 3% by weight (1 mol/L) for test specimen A1, which will be described later, and approximately 35% by weight (11.38 mol/L) for test specimens A2 and A3, which will be described later.

Furthermore, the test specimens used in the first removal confirmation test are divided into test specimens A1 to A3.

Specifically, specimens A1 to A3 are specimens in which the construction member 20 is a tile material with a planar shape of 45 mm x 45 mm, and the cement hardened body 30 attached to the construction member 20 is a mortar base material and adhesive material with a thickness of approximately 40 mm.

(Test Results - First Removal Confirmation Test - Details of Test Results)
Next, the test results of the first removal confirmation test will be described in detail. Fig. 5 is a diagram showing the test results of the first removal confirmation test.

As shown in Figure 5, it was confirmed that the mass of specimens A1 to A3 decreased as the immersion period progressed. It was also confirmed that the mass of specimens A2 and A3 decreased over a shorter immersion period than specimen A1. In particular, it was confirmed that the amount of mortar dissolved until the mass of specimen A3 was approximately 85% was approximately 72 times the amount of mortar dissolved until the mass of specimen A1 was approximately 85%.

From the above, the effectiveness of immersing the construction member 20 in the second acid solution AL2, which has an acid concentration of approximately 3% to 35% by weight and is at approximately 80°C, was confirmed.

(Test results - Second removal confirmation test - Overview)
Next, an outline of the second removal confirmation test will be described.

The second removal confirmation test is a test to confirm the amount of hardened cement body 30 removed from each test specimen under various test conditions (specifically, temperature conditions and acid concentration conditions of the second acid solution AL2).

The test method for this second removal confirmation test is optional, but is as follows: First, the mass of each test specimen is measured using a known mass measuring device. Next, each test specimen is placed in the corresponding second container 52 containing the second acid solution AL2 (specifically, an acid solution containing hydrochloric acid) and immersed for 60 minutes. After immersion, the mass of each test specimen is measured again using the mass measuring device, and the mass loss, which indicates the difference in mass before and after immersion, is calculated. Additionally, the titration concentration of the second acid solution AL2 in each second container 52 is measured using a known measurement method.

Here, the temperature of the second acid solution AL2 is set to the boiling point temperature of the second acid solution AL2 for specimens B1 to B3 (described below), 80°C for specimens C1 to C3 (described below), 50°C for specimens D1 to D3 (described below), and 20°C for specimens E1 to E3 (described below).

Furthermore, the acid concentration of the second acid solution AL2 is set to 8.75% by weight for specimens B1, C1, D1, and E1, which will be described later; 20% by weight for specimens B2, C2, D2, and E2, which will be described later; and 35% by weight for specimens B3, C3, D3, and E3, which will be described later.

The specimens used in the second removal confirmation test are divided into specimens B1 to B3, specimens C1 to C3, specimens D1 to D3, and specimens E1 to E3. Here, specimens B1 to B3, specimens C1 to C3, specimens D1 to D3, and specimens E1 to E3 are specimens in which the construction member 20 is a tile material with a planar shape of 45 mm x 45 mm, and the hardened cement body 30 attached to the construction member 20 is a mortar adhesive material with a thickness of approximately 20 mm.

(Test Results - Second Removal Confirmation Test - Details of Test Results)
6A and 6B are diagrams showing the results of the second removal confirmation test, in which (a) is a diagram showing the relationship between the temperature of the second acid solution AL2 and the mass loss of each test specimen, and (b) is a diagram showing the relationship between the temperature of the second acid solution AL2 and the titration concentration of the second acid solution AL2.

As shown in Figure 6(a), it was confirmed that the mass loss from specimens B1 to B3, specimens C1 to C3, and specimens D1 to D2 was greater than that from specimens D3 and E1 to E3. Based on the mass loss from specimens B1 to B3, specimens C1 to C3, and specimens D1 to D2, it is estimated that if the temperature of the second acid solution AL2 is approximately 50°C to 90°C, the mass loss will be 15 g or more.

Furthermore, as shown in Figure 6(b), it was confirmed that the titration concentration of the second acid solution AL2 for test specimens B1, C1, D1, and E1 was approximately the same as the original concentration of 8.75 wt%, and that the titration concentration of the second acid solution AL2 for test specimens B2, C2, D2, and E2 was approximately the same as the original concentration of 25 wt%. On the other hand, the titration concentration of the second acid solution AL2 for test specimens C3, D3, and E3 was approximately the same as the original concentration of 35 wt%, but the titration concentration for test specimen B3 was significantly lower than 35 wt% due to the evaporation of the components of the second acid solution AL2.

From the above, the effectiveness of immersing the construction member 20 in the second acid solution AL2, which has an acid concentration of 8% to 35% by weight and a temperature of approximately 50°C to 90°C, was confirmed.

(Test results - Third removal confirmation test - summary)
Next, an outline of the third removal confirmation test will be described.

The third removal confirmation test is a test to confirm the amount of hardened cement body 30 removed from each test specimen under various test conditions (specifically, conditions with or without a pretreatment process).

The test method for this third removal confirmation test is optional, but is as follows: First, the mass of each test specimen is measured using a known mass measuring device. Next, a pretreatment process (specifically, using a drying device 41 to dry test specimen F2 described below at approximately 100°C for approximately three hours) is performed on only test specimen F2. Next, each test specimen is placed in the corresponding second container 52 containing a second acid solution AL2 (specifically, an acid solution containing hydrochloric acid) with an acid concentration of 35% by weight and at 80°C, and the test specimen is immersed for 15 minutes. After immersion, the mass of each test specimen is measured again using the mass measuring device, and the mass loss, which indicates the difference in mass before and after immersion, is calculated.

Furthermore, the test specimens used in the third removal confirmation test are divided into test specimens F1 and F2. Test specimens F1 and F2 are constructed in a manner substantially identical to test specimen B1.

(Test Results - Third Removal Confirmation Test - Details of Test Results)
Next, the test results of the third elimination confirmation test will be described in detail. Fig. 7 is a diagram showing the test results of the third elimination confirmation test.

As shown in Figure 7, it was confirmed that the mass loss of specimen F2 was greater than that of specimen F1. Specifically, it was confirmed that the mass loss of specimen F2 was approximately four times that of specimen F1.

From the above, the effectiveness of performing a pretreatment process before the removal process was confirmed.

(Test results - Fourth removal confirmation test - summary)
Next, an outline of the fourth removal confirmation test will be described.

The fourth removal confirmation test is a test to confirm the amount of hardened cement body 30 removed from each test specimen under various test conditions (specifically, the immersion period and whether or not the hardened cement body 30 is removed).

The test method for this fourth removal confirmation test is optional, but is as follows: First, the mass of each test specimen is measured using a known mass measuring device. Next, each test specimen is placed in the corresponding second container 52 containing a second acid solution AL2 (specifically, an acid solution containing hydrochloric acid) with an acid concentration of 35% by weight and at 80°C, and the test specimen is immersed for a predetermined period of time (note that for test specimen G3, described below, test specimen G3 is scrubbed a total of four times during and after the immersion). Then, after the immersion, the mass of each test specimen is measured again using the mass measuring device, and the mass loss, which indicates the difference in mass before and after immersion, is calculated.

Here, the immersion period in the second acid solution AL2 is set to 15 minutes for test specimen G1 (described later), 60 minutes for test specimen G2 (described later), and 15 minutes x 4 times for test specimen G3 (described later) (i.e., a total immersion period of 60 minutes).

Furthermore, the test specimens used in the fourth removal confirmation test are divided into test specimens G1 to G3. Test specimens G1 to G3 are constructed substantially identically to test specimen B1.

(Test Results - Fourth Removal Confirmation Test - Details of Test Results)
Next, the details of the test results of the fourth elimination confirmation test will be described. Fig. 8 is a diagram showing the test results of the fourth elimination confirmation test.

As shown in Figure 8, it was confirmed that the mass loss of specimen G3 was greater than that of specimens G1 and G2. Specifically, it was confirmed that the mass loss of specimen G3 was approximately 1.5 times that of specimen G2.

From the above, it was confirmed that it is effective to immerse the construction member 20 in the second acid solution AL2 for approximately 15 minutes and then remove the hardened cement body 30 from the construction member 20 multiple times using a specified removal method.

(Effects of the embodiment)
As described above, according to the embodiment, the method includes a removal step of removing the hardened cement body 30 adhering to the construction member 20 by immersing the construction member 20 in the second acid solution AL2 at a temperature of about 50°C to 90°C for a predetermined period of time. Therefore, compared to the conventional technique (technique in which a building material to which the hardened cement body is adhering is immersed in an acid solution at room temperature), the hardened cement body 30 can be removed more quickly, and the time required to remove the hardened cement body 30 can be shortened.

In addition, the acid concentration of the second acid solution AL2 is set to approximately 3% to 35% by weight, which allows the hardened cement body 30 to be removed effectively and ensures that the removal process is carried out reliably.

In addition, in the removal process, the construction member 20 is immersed in the second acid solution AL2 for approximately 15 minutes, and then the hardened cement body 30 is removed from the construction member 20 using a specified removal method multiple times.This allows the hardened cement body 30 to be removed more effectively than when the construction member 20 is simply immersed in the second acid solution AL2, and makes it possible to further shorten the time required to remove the hardened cement body 30.

Furthermore, since the specified removal method includes scrubbing the construction member 20, applying hot air to the construction member 20, and/or immersing the construction member 20 in boiling water, the hardened cement body 30 can be easily and reliably removed from the construction member 20, making it possible to remove the hardened cement body 30 more efficiently.

In addition, in the pretreatment process, the construction member 20 is dried to an absolute dry state or a state close to it, and then immersed in the first acid solution AL1 at room temperature for a predetermined period of time. This facilitates the removal of the hardened cement body 30 in the removal process, shortening the removal process while improving workability.

[III] Modifications to the Embodiments The embodiments of the present invention have been described above, but the specific configurations and means of the present invention can be modified and improved as desired within the scope of the technical ideas of each invention as set forth in the claims. Such modifications will be described below.

(About the problem to be solved and the effects of the invention)
First, the problems that the invention aims to solve and the effects of the invention are not limited to those described above, and the present invention may solve problems that are not described above or achieve effects that are not described above, or may solve only some of the problems that are described or achieve only some of the effects that are described.

(shape, numbers, structure, time series)
The components illustrated in the embodiments and drawings may be modified and improved as desired within the scope of the technical concept of the present invention in terms of shape, numerical value, or the structure or chronological relationship of multiple components.

(Regarding the acid concentration of the acid solution)
In the above embodiment, the acid concentrations of the acid solutions (specifically, the first acid solution AL1 and the second acid solution AL2) are set to approximately 3% by weight to 35% by weight, but this is not limiting. For example, if it is acceptable that the time required to remove the hardened cement body 30 is longer than in the above embodiment (provided that the time required to remove the hardened cement body 30 can be shortened compared to the prior art), the acid concentration may be set to less than 3% by weight. Alternatively, the acid concentration may be set to more than 35% by weight.

(Method for removing hardened cement paste)
In the above embodiment, the method for removing the hardened cement body 30 has been described as including a preparation step and a pre-treatment step, but this is not limited thereto. For example, if the construction member 20 and the hardened cement body 30 have already been removed from the main body 10, the preparation step may be omitted. Alternatively, if the hardened cement body 30 is made of a material that is easily removed from the construction member 20, the pre-treatment step may be omitted.

(Additional Note)
The method for removing a hardened cement body of Appendix 1 is a method for removing a hardened cement body adhering to a construction member from the construction member, and includes a removal step of removing the hardened cement body adhering to the construction member by immersing the construction member in an acid solution at about 50°C to 90°C for a predetermined period of time.

The method for removing hardened cement body in Appendix 2 is the same as the method for removing hardened cement body described in Appendix 1, except that the acid concentration of the acid solution is approximately 3% to 35% by weight.

The method for removing a hardened cement body in Appendix 3 is the method for removing a hardened cement body described in Appendix 1 or 2, in which, in the removal step, the construction member is immersed in the acid solution for approximately 15 minutes, and then the hardened cement body is removed from the construction member using a predetermined removal method multiple times.

The method for removing a hardened cement body in Appendix 4 is the method for removing a hardened cement body described in Appendix 3, wherein the specified removal method includes scrubbing the construction member, applying hot air to the construction member, and/or immersing the construction member in boiling water (e.g., fresh water).

The method for removing a hardened cement body of Appendix 5 is the method for removing a hardened cement body of any one of Appendixes 1 to 4, and includes a pretreatment step performed before the removal step to promote removal of the hardened cement body in the removal step, in which the construction member is dried to an absolute dry state or a state close to that, and/or the construction member is immersed in the acid solution at room temperature for a predetermined period of time.

(Effect of supplementary notes)
The method for removing hardened cement bodies described in Appendix 1 includes a removal step of removing the hardened cement bodies attached to construction members by immersing the construction members in an acid solution at about 50°C to 90°C for a predetermined period of time. This makes it possible to remove the hardened cement bodies more quickly and shorten the time required to remove them compared to the conventional technique (technique in which a construction material with hardened cement bodies attached thereto is immersed in an acid solution at room temperature).

In the method for removing hardened cement bodies described in Appendix 2, the acid concentration of the acid solution is set to approximately 3% to 35% by weight, which allows for effective removal of the hardened cement bodies and ensures that the removal process is carried out reliably.

According to the method for removing hardened cement bodies described in Appendix 3, the removal process involves immersing the construction member in an acid solution for approximately 15 minutes, and then removing the hardened cement body from the construction member using a specified removal method, which is repeated multiple times. This allows for more effective removal of the hardened cement body than simply immersing the construction member in an acid solution, and further shortens the time required to remove the hardened cement body.

According to the method for removing hardened cement bodies described in Appendix 4, the specified removal method includes scrubbing the construction components, applying hot air to the construction components, and/or immersing the construction components in boiling water. This allows the hardened cement bodies to be easily and reliably removed from the construction components, making removal of the hardened cement bodies even more efficient.

According to the method for removing hardened cement bodies described in Appendix 5, in the pretreatment step, the construction members are dried to an absolute dry state or a state close to it, and/or the construction members are immersed in an acid solution at room temperature for a predetermined period of time. This facilitates the removal of the hardened cement bodies in the removal step, shortening the removal step while improving workability.

REFERENCE SIGNS LIST 1 Structural body 10 Structural body main body 20 Construction member 21 Construction member main body 30 Hardened cement body 31 Base part 32 Attachment part 41 Drying device 42 First container 51 Heating device 52 Second container 53 Brush 54 Third container AL1 First acid solution AL2 Second acid solution W Water

Claims (2)

A method for removing a hardened cement body adhering to a construction member from the construction member, comprising:
a removing step of removing the hardened cement body adhering to the construction member by immersing the construction member in an acid solution at about 50°C to 90°C for a predetermined period of time,
In the removing step, the construction member is immersed in the acid solution for about 15 minutes, and then the hardened cement body is removed from the construction member by a predetermined removing method, and this is repeated several times;
The predetermined removal method includes applying hot air to the construction element and/or immersing the construction element in boiling water.
Method for removing hardened cement. A method for removing a hardened cement body adhering to a construction member from the construction member, comprising:
a removing step of removing the hardened cement body adhering to the construction member by immersing the construction member in an acid solution at about 50°C to 90°C for a predetermined period of time,
a pretreatment step carried out before the removing step, for facilitating removal of the hardened cement body in the removing step;
In the pretreatment step, after the construction members are dried to an absolute dry state or a state close to it, the construction members are immersed in the acid solution at room temperature for a predetermined period of time, and/or the construction members are immersed in the acid solution at room temperature for a predetermined period of time.
Method for removing hardened cement.