Method for manufacturing precast concrete bodies and method for inspecting concrete.

Abstract

To provide a method of manufacturing a precast concrete body and a concrete inspection method which do not require the protrusion of a portion becoming a specimen outward from the side of the concrete.SOLUTION: A method of manufacturing a precast concrete body includes: a step of placing a pipe member 2 made of a material having a linear expansion coefficient larger than that of concrete in a manufacturing form 5 of the precast concrete body 1 so that the cavity direction of the pipe member 2 matches the direction perpendicular to the side surface of the precast concrete body 1 and placing fresh concrete 110 into the manufacturing form 5, including the inside of the pipe member 2; and a step of hardening fresh concrete 110 by high-temperature curing using water vapor to obtain a concrete part 11.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This invention relates to a method for manufacturing a precast concrete body and a method for inspecting concrete.

Background Art

[0002] In Patent Document 1, it is possible to eliminate the need for cutting out specimens from a structure after concrete hardening, and even after the formwork of the structure is removed, the formwork of the specimen can be made to stand independently in a state of protruding from the structure and cured until a predetermined age. A specimen sampling jig for managing the strength of structural concrete is disclosed. Using this technology, it is possible to perform a strength inspection by subjecting the specimen obtained by the above specimen sampling jig to a compression test without performing the operation of core drilling from the structural concrete, and to measure the neutralization depth with a phenolphthalein solution by splitting the above specimen.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above conventional technology, since the formwork of the specimen is created so as to protrude outward from the side surface of the structural concrete, this formwork of the specimen may become an obstacle to building construction.

[0005] This invention provides a method for manufacturing a precast concrete body and a method for inspecting concrete that do not require the formwork of the specimen to protrude outward from the side surface of the concrete.

Means for Solving the Problems

[0006] The present invention provides a method for manufacturing a precast concrete body, comprising the steps of: placing a pipe member made of a material having a coefficient of linear expansion greater than that of concrete within a precast concrete body formwork such that the direction of the cavity of the pipe member coincides with a direction perpendicular to the side surface of the precast concrete body; pouring fresh concrete into the formwork, including the inside of the pipe member; and hardening the fresh concrete by high-temperature curing using steam.

[0007] According to this method, a building can be constructed using a precast concrete body made by this method, and in later years, the concrete column inside the pipe member can be removed from the precast concrete body along with the pipe member, and this concrete column can be used as a concrete test specimen for strength testing and carbonation depth measurement. In other words, the work of extracting cores from the precast concrete body with a core drilling machine becomes unnecessary. Furthermore, there is no need to use the Schmidt hammer method for strength testing, nor the drill method for measuring carbonation depth. And since the pipe member is located inside the precast concrete body, it does not protrude from the precast concrete body and become an obstacle to transportation or building construction.

[0008] In the above method, reinforcing bars are placed within the fabricated formwork, and the pipe members may be placed at a distance from the reinforcing bars corresponding to the required concrete cover thickness. This prevents insufficient concrete cover over the reinforcing bars.

[0009] In the above method, the fabricated formwork may be positioned so that the direction of the rising section of the precast concrete body is horizontal, and the fresh concrete may be poured in. This makes it easier to stably position the pipe member.

[0010] In the above method, the pipe member may be a resin pipe. Since the coefficient of linear expansion of resin is significantly different from that of concrete, it becomes easier to remove the concrete column inside the pipe member, along with the pipe member itself, from the precast concrete body.

[0011] Furthermore, the concrete inspection method of this invention is characterized by performing construction using a precast concrete body manufactured by the above manufacturing method, and in later years, removing the concrete column body inside the pipe member along with the pipe member from the precast concrete body, and performing a destructive test on this concrete column body as a concrete test specimen. As a result of the destructive test, the precast concrete body will have holes where the concrete column body was removed, but if the precast concrete body is used, for example, in a partition section, there will be no deterioration in the aesthetic appearance of the building's exterior.

[0012] Furthermore, the concrete inspection method of this invention is characterized by performing construction using a precast concrete body manufactured by the above manufacturing method, removing the concrete column body inside the pipe member along with the pipe member from the precast concrete body in a later year, performing a non-destructive test on this concrete column body as a concrete test specimen, and returning the pipe member and the concrete column body to the precast concrete body after this non-destructive test. With this method, it becomes possible to remove the concrete column body that has been returned to the precast concrete body in a later year and perform another inspection on this concrete column body as a concrete test specimen. [Effects of the Invention]

[0013] With this invention, the concrete portion used as the test specimen does not protrude outward from the side of the precast concrete body, thus facilitating the transportation of the precast concrete body and the construction of the building. Furthermore, it eliminates the need to extract cores from the precast concrete body using a core drilling machine for concrete inspection, and also eliminates the need to use the Schmidt hammer method for strength testing and the drill method for measuring carbonation depth. [Brief explanation of the drawing]

[0014] [Figure 1] This is an explanatory diagram showing a schematic front view and side view of a precast concrete body manufactured by the method of the embodiment. [Figure 2] Figure 1 is an explanatory diagram showing a cross-section of the precast concrete body and its fabrication formwork. [Figure 3] This is an explanatory diagram showing the method for manufacturing a precast concrete body according to the embodiment. [Figure 4] Figure 1 is an explanatory diagram illustrating the formation of gaps due to the expansion and contraction of pipe members in a precast concrete structure. [Modes for carrying out the invention]

[0015] Hereinafter, an embodiment according to one aspect of this invention will be described based on the attached drawings. Figure 1 illustrates a precast concrete body 1 manufactured by the manufacturing method according to the embodiment. Within the concrete portion 11 (shown by dashed lines) of this precast concrete body 1, there are upper reinforcement bars 12, web reinforcement bars 13, and portions of the vertical reinforcement bars (stirrups) 14 other than the lower side. Below the concrete portion 11, the lower side of the vertical reinforcement bars 14 and the lower reinforcement bars 15 are exposed. This precast concrete body 1 is the rising portion of the concrete foundation and is positioned above the area where the footing portion of the concrete foundation is formed at the construction site. When the poured concrete that will form the footing portion hardens, it integrates with the footing portion and can become a strip foundation. However, the foundation portion in which the precast concrete body 1 is used is the partition foundation portion located on the inside of the building.

[0016] And, inside the concrete part 11 of the precast concrete body 1, there is a cylindrical pipe member 2. The wall thickness of this pipe member 2 is, for example, about 1 to 2 mm. Also, this pipe member 2 is positioned such that the cavity direction of the pipe member 2 coincides with the direction orthogonal to the side surface of the precast concrete body 1 (the thickness direction of the precast concrete body 1). Also, inside the pipe member 2, there is a concrete column body 11A made of the same fresh concrete as the concrete part 11. The end face of the pipe member 2 exists substantially flush with the side surface of the concrete part 11. Also, the pipe member 2 is made of a material having a linear expansion coefficient larger than the linear expansion coefficient of concrete (about 1×10 -5 (1 / °C)). The linear expansion coefficients of polypropylene, polyethylene, etc., which are used as the material of the resin pipe, are about 11×10 -5 (1 / °C).

[0017] For the production of the precast concrete body 1, the production formwork 5 shown in FIG. 2 is used. In this production formwork 5, the rising direction of the precast concrete body 1 that becomes the rising part of the foundation is set to the horizontal direction, and the height (depth) direction of this production formwork 5 coincides with the thickness direction of the precast concrete body 1. That is, the production method of the precast concrete body 1 is a flat-placement type.

[0018] For example, as shown in FIG. 3, in the production formwork 5, a combination of upper-end bars 12, web bars 13, and longitudinal bars 14 is horizontally arranged, and the pipe member 2 is arranged such that the cavity direction of the pipe member 2 coincides with the thickness direction of the precast concrete body (the height direction in the production formwork 5). Also, each pipe member 2 is arranged at a distance corresponding to the required cover thickness of concrete with respect to the web bars 13, longitudinal bars 14, etc. Then, fresh concrete 110 is poured into the production formwork 5 including inside the pipe member 2.

[0019] Next, the fresh concrete 110 is cured (steam curing) at a high temperature of about 60°C using steam to form the concrete part 11.

[0020] Here, as described above, when steam curing is performed on the fresh concrete 110, as shown in FIG. 4, the fresh concrete 110 hardens in a state where the pipe member 2 is greatly expanded and becomes the concrete part 11. If the outer diameter of the pipe member 2 at room temperature is R1, the outer diameter of the pipe member 2 during steam curing is represented by R1 + ΔR.

[0021] Then, when the concrete part 11 returns to room temperature, the pipe member 2 greatly shrinks and its outer diameter returns to R1. Therefore, a gap (ΔR / 2) occurs between the outer peripheral surface of the pipe member 2 and the part of the concrete part 11 facing the outer peripheral surface. For example, if the room temperature is 20°C, the steam curing temperature is 60°C, and the linear expansion coefficient of the resin pipe member 2 with an outer shape Φ of 60 mm is 10×10 -5 (1 / °C), then the above gap (ΔR / 2) is about 0.1 mm. Further, when the pipe member 2 shrinks, the inner peripheral surface of the pipe member 2 and the outer peripheral surface of the concrete column 11A are in close contact, so the neutralization of the outer peripheral surface (interface) of the concrete column 11A is less likely to occur.

[0022] The produced precast concrete body 1 is transported to the construction site and constructed as a strip foundation of a building.

[0023] In the concrete inspection method of the embodiment, after several decades have passed since the construction, the concrete column 11A in the pipe member 2 is taken out together with the pipe member 2 from the precast concrete body 1 constructed as described above, and this concrete column 11A is used as a concrete specimen for concrete inspection.

[0024] Here, after several decades have passed since construction, a certain amount of shrinkage occurs in the precast concrete body 1. For example, if the length of the precast concrete body 1 is 4P (4 × 910 mm = 3640 mm) and the shrinkage rate is 0.03%, then 3640 mm × 0.03% = 1.1 mm. Furthermore, if there are three pipe members 2 arranged horizontally, a gap of approximately 0.2 mm will be created around the pipe members 2. Therefore, adding the 0.1 mm gap created during the manufacturing of the precast concrete body 1, there will be a gap of approximately 0.3 mm around the pipe members 2, making it easy to remove the concrete column body 11A together with the pipe members 2 from the precast concrete body 1.

[0025] When the strength of the concrete column 11A is confirmed by destructive testing using the concrete column as a concrete specimen, the pipe member 2 is removed using a cutter or the like, and pressure is applied to the concrete column 11A alone using a compressor. Similarly, when the carbonation depth is measured by destructive testing using the concrete column 11A as a concrete specimen, the pipe member 2 is removed, and the fractured concrete column 11A is sprayed with phenolphthalein solution for measurement.

[0026] On the other hand, when measuring the carbonation depth using non-destructive testing on the concrete column 11A as a concrete specimen, the pipe member 2 is not removed, and the carbonation depth is measured on the concrete column 11A together with the pipe member 2 using a non-destructive testing device such as an X-ray CT scanner. After the non-destructive testing, the concrete column 11A together with the pipe member 2 is returned to the precast concrete body 1. Then, when measuring the carbonation depth again several years later, the concrete column 11A together with the pipe member 2 is similarly removed from the precast concrete body 1, and after non-destructive testing, the concrete column 11A together with the pipe member 2 is returned to the precast concrete body 1.

[0027] As explained above, with a precast concrete body 1 manufactured using this method, a gap of approximately 0.3 mm will be formed between the pipe member 2 and the concrete section 11 during concrete inspection. For example, the concrete column 11A can be removed together with the pipe member 2 by tapping the pipe member 2 with a wooden mallet. In other words, the work of extracting cores from the precast concrete body 1 using a core drilling machine becomes unnecessary. Precast concrete bodies 1 are typically stronger than concrete cast in place, making core drilling of precast concrete bodies 1 difficult. Furthermore, there is no need to use the Schmidt hammer method for strength testing, nor the drill method for measuring carbonation depth. And since the pipe member 2 is located inside the precast concrete body 1, it does not protrude from the precast concrete body 1 and become an obstacle to transportation or building construction.

[0028] Furthermore, if the pipe member 2 is positioned at a distance from the vertical reinforcement bars 14, etc., that corresponds to the required concrete cover thickness, it is possible to prevent insufficient concrete cover for the vertical reinforcement bars 14, etc.

[0029] Furthermore, by producing the precast concrete body 1 using the flat casting method described above, it becomes easier to stably position the pipe member 2.

[0030] Furthermore, if the outer diameter of the pipe member 2 is 60 mm or more, it is desirable to provide reinforcing bars in the precast concrete body 1. On the other hand, if the outer diameter of the pipe member 2 is less than 60 mm, it is not necessary to provide reinforcing bars in the precast concrete body 1.

[0031] If the pipe member 2 is made of a resin such as polypropylene, the coefficient of linear expansion of this resin is several times larger than that of concrete, making it easy to remove the concrete column 11A inside the pipe member 2 along with the pipe member 2 from the precast concrete body 1.

[0032] However, the pipe member 2 is not limited to being made of resin. The coefficient of linear expansion of aluminum metal is 2.4 × 10⁻⁶. -5 Since the temperature is (1 / °C), the pipe member 2 may be made from this aluminum metal. Furthermore, the pipe member 2 is not limited to a single layer; a multi-layer structure can be adopted in which the outer layer is a metal pipe and the inner layer is a resin pipe, or the outer layer is a resin pipe and the inner layer is a metal pipe, or both the outer and inner layers are resin pipes. In addition, a coating or film may be provided on the outer surface of the pipe member 2 to assist in separating the pipe member 2 from the concrete part 11.

[0033] Although embodiments of this invention have been described above with reference to the drawings, this invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the illustrated embodiments within the same scope as this invention, or within the equivalent scope. [Explanation of symbols]

[0034] 1: Precast concrete body 2: Pipe member 5: Formwork 11: Concrete section 11A: Concrete column 12: Upper end muscle 13: Abdominal muscles 14: Vertical stripes 15: Lower end reinforcement 110: Fresh concrete

Claims

1. A method for manufacturing a precast concrete body, comprising the steps of: placing a pipe member made of a material having a coefficient of linear expansion greater than that of concrete within a precast concrete body formwork such that the direction of the cavity of the pipe member coincides with a direction perpendicular to the side surface of the precast concrete body; pouring fresh concrete into the formwork, including the inside of the pipe member; and hardening the fresh concrete by high-temperature curing using steam.

2. A method for manufacturing a precast concrete body according to claim 1, characterized in that reinforcing bars are arranged within the formwork, and the pipe member is arranged at a distance from the reinforcing bars corresponding to the required concrete cover thickness.

3. A method for manufacturing a precast concrete body according to claim 1, characterized in that the manufacturing formwork is arranged such that the direction of the rising of the precast concrete body is horizontal, and the fresh concrete is poured in.

4. A method for manufacturing a precast concrete body according to claim 1, characterized in that the pipe member is a resin pipe.

5. A concrete inspection method characterized by performing construction using a precast concrete body manufactured by the method for manufacturing a precast concrete body described in any one of claims 1 to 4, and in later years removing the concrete column inside the pipe member along with the pipe member from the precast concrete body, and performing a destructive test on this concrete column as a concrete test specimen.

6. A concrete inspection method characterized by performing construction using a precast concrete body manufactured by the method for manufacturing a precast concrete body described in any one of claims 1 to 4, and in later years removing the concrete column inside the pipe member together with the pipe member from the precast concrete body, performing a non-destructive test on the concrete column as a concrete test specimen, and returning the pipe member and the concrete column to the precast concrete body after the non-destructive test.

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