JP2018028438A - Concrete measurement method and concrete evaluation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of directly and nondestructively measuring cured concrete.SOLUTION: A method involves obliquely transmitting radiation through a corner of a concrete wall 1 by placing a radiation source rod 30 on one outer wall surface 1A constituting the corner and placing a main body 20 on the other outer wall surface 1B. Density and moisture content of the concrete wall 1 is measured using the corner by irradiating the outer wall surface 1A with radiation from a radiation source 32 of the radiation source rod 30, detecting the radiation transmitting through to the outer wall surface 1B using a radiation detection unit of the main body 20, and computing density and moisture content based on a result of the detection using a processing unit.SELECTED DRAWING: Figure 3

Description

The present invention relates to a concrete measurement method and a concrete evaluation method.

  When measuring the physical properties of hardened concrete such as buildings (for example, unit volume mass and water content), simultaneously with the placing of the concrete, separately prepare a specimen using the concrete, and use the specimen Indirect measurement is performed (for example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 11-83846

  However, the actual concrete and the test specimen for management differ in conditions such as the temperature history and the degree of drying, and therefore the measurement results may not always match. In addition, if the actual physical property values of concrete can be measured directly in-situ, it is possible to take into account variations such as the compaction status of concrete and the influence of joints, and to capture changes in the physical property values of concrete over time. It becomes.

  This invention is made | formed in view of this subject, The main objective is to carry out the nondestructive measurement of the hardened concrete directly.

In order to achieve such an object, the concrete measuring method of the present invention includes a step of irradiating the hardened concrete with radiation, a step of detecting the radiation transmitted through the concrete, and a detection result of the radiation, And a step of obtaining a physical property value of the concrete.
According to such a concrete measuring method, the hardened concrete can be directly measured nondestructively.

In this concrete measuring method, the radiation may be gamma rays, and the physical property value may be a unit volume mass.
According to such a concrete measuring method, the unit volume mass of hardened concrete can be measured nondestructively.

In this concrete measuring method, the radiation may be a neutron beam, and the physical property value may be a water content.
According to such a concrete measuring method, the moisture content of the hardened concrete can be measured nondestructively.

In this concrete measurement method, it is preferable that the correspondence between the number of detected radiations and the magnitude of the physical property value is predetermined, and the physical property value is obtained using the correspondence relationship.
According to such a concrete measuring method, the physical property value can be easily calculated.

In this method of measuring concrete, the concrete may have a corner portion, and the radiation may be transmitted from one surface forming the corner portion to the other surface.
According to such a concrete measuring method, the concrete can be measured using the corner portion.

In this method for measuring concrete, the concrete may have a hole on a predetermined surface, and the radiation may be transmitted from the inside of the hole to the predetermined surface.
According to such a concrete measuring method, the concrete can be measured using the hole.

In this concrete measuring method, the concrete may have a width-thickness portion, and the radiation may be transmitted from one side of the width-thickness portion to the other side.
According to such a concrete measurement method, the measurement position of the concrete is not easily restricted.

Moreover, it is desirable to evaluate the shielding performance of the concrete against the radiation from the physical property values obtained by any one of the concrete measuring methods.
According to such a concrete evaluation method, the shielding performance against radiation can be directly evaluated nondestructively.

  According to the present invention, hardened concrete can be directly measured nondestructively.

It is a schematic explanatory drawing which shows the structure of the measuring apparatus 10 used by this embodiment. 2A and 2B are schematic explanatory views of the measurement principle of the measurement apparatus 10. FIG. 2A is an explanatory diagram for measuring the density, and FIG. 2B is an explanatory diagram for measuring the moisture content. 3A and 3B are schematic explanatory views of the corner method. 3A is a perspective view, and FIG. 3B is a top view of FIG. 3A. 4A and 4B are schematic explanatory views of the sleeve method. 4A is a perspective view, and FIG. 4B is a view of FIG. 4A as viewed from above. 5A and 5B are schematic explanatory diagrams of the transmission method. 5A is a perspective view, and FIG. 5B is a view of FIG. 5A as viewed from above. It is a figure which shows the use material of concrete (test body). It is a figure which shows the mixing conditions of concrete (test body). FIG. 8A is a diagram showing measurement results of unit volume mass, and FIG. 8B is a diagram showing measurement results of water content. 9A and 9B are diagrams showing a correspondence relationship between a measured value (count rate ratio) of the unit volume mass of concrete by the measuring device 10 and the unit volume mass. FIG. 9A is a diagram showing the measurement result of the corner method, and FIG. 9B is a diagram showing the measurement result of the sleeve method.

=== Embodiment ===
<< About measuring equipment >>
FIG. 1 is a schematic explanatory diagram showing the configuration of a measuring apparatus 10 used in the present embodiment.

In this embodiment, the unit volume mass (hereinafter also referred to as density) and the water content (hereinafter also referred to as moisture content) of the concrete are measured using the measuring device 10. The measuring device 10 is a nondestructive measuring device using a sealed radioisotope (radioisotope: RI), and is a device (device for measuring soil quality) used for earthwork such as roads, dams, and dikes. .
The measuring device 10 includes a main body 20 and a radiation source rod 30.

  The main body 20 is an apparatus main body of the measurement apparatus 10 and includes a radiation detection unit 21 and a processing unit 22.

  The radiation detection unit 21 is a part that detects and counts (counts) the radiation that has passed through the measurement object among the radiation irradiated by the radiation source 32 (described later) of the radiation source rod 30. The radiation detection unit 21 of the present embodiment includes a gamma ray detection unit 21a that detects gamma rays (γ rays) and a neutron beam detection unit 21b that detects neutron rays.

  The processing unit 22 performs various data processing and the like based on the detection result of the radiation detection unit 12. For example, the difference (attenuation amount) between the radiation amount (count value) detected by the radiation detection unit 12 and the radiation generated by the radiation source 32 of the radiation source rod 30 is calculated. Then, a ratio (count rate ratio) between the attenuation amount and the radiation attenuation amount of the standard substance is calculated.

  Moreover, the main body 20 has a storage unit (not shown) for storing measurement results and various data, and the storage unit shows a correspondence relationship between the measurement results (counting rate ratio) and the density. Relational expressions (calibration curves: see FIGS. 9A and 9B) are stored in advance. The processing unit 22 calculates the density from the measurement result using the above relational expression. By using the relational expression in this way, the magnitude of the density can be easily calculated. Since radiation also exists in the natural world, the radiation measurement amount (background) in the natural world is counted and corrected by subtracting it from the calculated attenuation amount.

  Similarly, in the case of the moisture content, a relational expression indicating the correspondence between the measurement result (counting rate ratio) and the magnitude of the moisture content is stored in the storage unit, and the processing unit 22 uses the relational expression to determine the moisture content. Is calculated.

  Further, the main body 20 includes an output unit (not shown) that outputs the calculation result of the processing unit 22. As the output unit, a display mechanism such as a display and a printing mechanism such as a printer are provided.

The radiation source rod 30 is a rod-shaped elongated member (cylindrical body), and is provided so as to be detachable from the main body 20. A radiation source 32 in which ⁶⁰ Co (cobalt 60) and ²⁵² Cf (californium 252) are sealed is provided at the tip of the radiation source rod 30. Cobalt 60 is a gamma ray source, and californium 252 is a neutron ray source.

<< About the measurement principle >>
2A and 2B are schematic explanatory views of the measurement principle of the measurement apparatus 10. FIG. 2A is an explanatory diagram for measuring the density, and FIG. 2B is an explanatory diagram for measuring the moisture content. 2A and 2B show the case where the source rod 30 is inserted into the soil and the density and moisture content of the soil are measured.

(Density measurement)
Cobalt 60 emits gamma rays. When gamma rays pass through the material, a part of the energy is given to the orbital electrons due to the interaction with the orbital electrons of the atoms, and the traveling direction is changed to a small energy. Since the total number of electron orbits of atoms constituting the measurement object is the same as the number of protons, it is generally proportional to the density (unit volume mass). For example, as shown in FIG. 2A, when the radiation source 32 (gamma ray source in this case) is arranged in the ground, the larger the density of the soil, the less the gamma rays that reach the ground surface.

  Thereby, as shown in FIG. 2A, the density (soil density) can be measured by counting (counting) the gamma rays reaching the gamma ray detector 21a of the radiation detector 21 on the ground surface.

(Measurement of water content)
The californium 252 emits neutrons with large energy called fast neutrons. When fast neutrons collide with nuclei in matter, they gradually lose their kinetic energy and are converted to low energy neutrons called thermal neutrons. The slowing ability of hydrogen atoms (the ability to convert fast neutrons into thermal neutrons) is very high compared to other atoms, so the more hydrogen atoms there are in the material, the faster neutrons will collide with hydrogen atoms. By losing energy. Therefore, as shown in FIG. 2B, when the radiation source 32 (neutron source in this case) is placed in the ground, moisture is counted by counting thermal neutrons that pass through the soil and reach the neutron beam detector 21b. The amount can be measured.

  In this way, the density and moisture content of the soil can be measured using the measuring device 10. In this embodiment, this measuring apparatus 10 is applied to the measurement of the density (unit volume mass) and moisture content (water content) of the hardened concrete.

<< About measurement method >>
As shown in FIGS. 2A and 2B, when the soil quality is measured by the measuring apparatus 10, the source rod 30 is inserted into the soil. However, in the case of hardened concrete, the source rod 30 cannot be inserted as shown in FIGS. 2A and 2B.

  Therefore, in this embodiment, in order to directly measure the hardened concrete, the following three measurement methods (corner method, sleeve method, transmission method) were examined.

<Corner method>
3A and 3B are schematic explanatory views of the corner method. 3A is a perspective view, and FIG. 3B is a top view of FIG. 3A. An object to be measured is a concrete wall 1, and the concrete wall 1 has a corner formed by an outer wall surface 1A and an outer wall surface 1B. Further, the outer wall surface 1A and the inner wall surface 1C inside thereof, and the outer wall surface 1B and the inner wall surface 1D inside thereof form a width-thickness portion of the concrete wall 1.

  In the corner angle method, the source rod 30 is pressed against one surface (outer wall surface 1A in the figure) forming the corner portion, the main body 20 is pressed against the other surface (outer wall surface 1B in the figure), and the concrete wall 1 In this method, radiation is transmitted obliquely through the corner. That is, the radiation source 32 emits radiation from the radiation source 32 to the outer wall surface 1A, and the radiation transmitted through the outer wall surface 1B is detected by the radiation detection unit 21 of the main body 20. Then, based on the detection result, the processing unit 22 calculates the density and water content. Thereby, the density and moisture content of the concrete wall 1 can be measured using a corner part. Since the radiation source rod 30 is fixed to the main body 20, the distance (radiation distance) between the radiation source 32 and the radiation detector 21 (gamma ray detector 21a or neutron beam detector 21b) is always constant. .

<Sleeve method>
4A and 4B are schematic explanatory views of the sleeve method. 4A is a perspective view, and FIG. 4B is a view of FIG. 4A as viewed from above. 4A and 4B is provided with a sleeve hole 1a (corresponding to a hole) for piping penetrating from the outer wall surface 1B (corresponding to a predetermined surface) to the inner wall surface 1D.

  In the sleeve method, the source rod 30 is inserted into the sleeve hole 1a provided in the outer wall surface 1B of the concrete wall 1, the main body 20 (radiation detection unit 21) is pressed against the outer wall surface 1B, and from the inside of the sleeve hole 1a, In this method, radiation is transmitted through the outer wall surface 1B. Thereby, the density and moisture content of the concrete wall 1 can be measured using the sleeve hole 1a. Also in this case, since the radiation source rod 30 is fixed to the main body 20, the distance (radiation distance) between the radiation source 32 and the radiation detector 21 (gamma ray detector 21a or neutron beam detector 21b) is Always constant.

<Transmission method>
5A and 5B are schematic explanatory diagrams of the transmission method. 5A is a perspective view, and FIG. 5B is a view of FIG. 5A as viewed from above.

  In the transmission method, the source rod 30 is pressed against one of the thick and thick parts of the concrete wall 1 (inner wall surface 1D in the figure), and the main body 20 (radiation detection part 21) is pushed into the other of the thick and thick parts (outer wall surface 1B in the figure). And the radiation is transmitted from the inner wall surface 1D side to the outer wall surface 1B side. This transmission method is less subject to measurement position restrictions than the corner method and sleeve method. In the case of this measurement method, the source rod 30 is removed from the main body 20 as shown in the figure. For this reason, it is necessary to adjust the distance (radiation distance) between the radiation source 32 and the radiation detection unit 21 (gamma ray detection unit 21a or neutron beam detection unit 21b) to be constant.

  The density and moisture content of the concrete wall 1 can be measured with the measuring device 10 by the above measuring method. That is, radiation is irradiated to the concrete wall 1 from the radiation source 32 of the measuring apparatus 10, and the radiation transmitted through the concrete wall 1 is detected by the radiation detection unit 21, and the concrete wall 1 is detected by the processing unit 22 based on the detection result. The physical property values (density, moisture content) of Thereby, the concrete wall 1 can be measured directly and non-destructively.

  Further, the shielding performance against radiation (gamma rays, neutron rays) of the concrete wall 1 can be evaluated from the calculated density and moisture content. For example, as the density of the concrete wall 1 increases, the shielding performance against gamma rays increases. Moreover, the shielding performance with respect to a neutron beam becomes large, so that the moisture content of the concrete wall 1 is large. Thereby, the shielding performance of the concrete wall 1 can be evaluated directly and non-destructively.

<< Experiment >>
Experiments using test specimens were conducted on the application of the above three measurement methods (corner angle method, sleeve method, and transmission method) to concrete measurement.

<Test body>
FIG. 6 is a diagram showing materials used for concrete (test body), and FIG. 7 is a diagram showing mixing conditions for concrete (test body).

As shown in FIG. 7, four types of specimens having different target unit volume mass (kg / m ³ ) of concrete were produced. Specifically, specimens having target unit volume masses of 3800 (Formulation No. 1), 3400 (Formulation No. 2), 3000 (Formulation No. 3), and 2400 (Formulation No. 4) were produced. The shape of the test body was a rectangular parallelepiped of 600 (mm) × 600 (mm) × 400 (mm), and a sleeve hole of φ42 mm × 600 mm penetrating the side surface was formed in the test body. The age was evaluated on the 7th, 28th, and 91st days.

<Measurement item>
The density (unit volume mass) and water content (water content) of each specimen were measured using the measuring apparatus 10 by the above-described three measurement methods (corner method, sleeve method, transmission method). Moreover, the density was measured using the load cell as an actual value of the density.

<Result>
FIG. 8A is a diagram showing measurement results of unit volume mass. FIG. 8B is a diagram showing a measurement result of water content. In order to compare the water content with the unit water content in preparation, the water content contained in the aggregate was calculated and subtracted from the water absorption rate of the aggregate shown in FIG. In addition, since the dispersion | variation with respect to a measurement was almost equivalent irrespective of the difference in mixing conditions and material age, in FIG. 8A and FIG. The horizontal axis of the figure is the number of measurements.

  Regarding the unit volume mass, the measurement results of the corner method and the sleeve method were almost the same, and the transmission method was slightly lower than those. It is considered that the unit volume mass can be measured with respect to concrete with little variation due to five measurements.

  About water content, although the dispersion | variation by a permeation | transmission method is a little large, all have grasped | ascertained generally the unit water amount on the mixing of concrete.

  9A and 9B are diagrams showing the correspondence between the measured value (count rate ratio) of the unit volume mass of concrete by the measuring apparatus 10 and the unit volume mass. FIG. 9A is a diagram showing the measurement result of the corner method, and FIG. 9B is a diagram showing the measurement result of the sleeve method. In the figure, a calibration curve (calibration curve stored in the measuring apparatus 10) used in the soil material is indicated by a broken line. The calibration curve is a relational expression showing the correspondence between the measured value (counting ratio) of the measuring device 10 and the unit volume mass.

As shown in the figure, both the corner method and the sleeve method are established in a manner that continuously complements the calibration curve (broken line) of the soil material in the region where the unit volume mass exceeds 2300 kg / cm ³ ). It was confirmed.

=== About Other Embodiments ===
The above embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About measuring equipment>
In the above-described embodiment, the measuring apparatus 10 can measure both the density and the moisture content of the measurement object, but is not limited thereto. For example, a measuring device capable of measuring only the density may be used, or a measuring device capable of measuring only the water content may be used.

<About measurement items>
In the above-described embodiment, the density and moisture content of the concrete are measured using the measuring device 10, but either density or moisture content may be measured.

<Measurement target>
In the above-described embodiment, the concrete wall 1 is measured, but is not limited thereto. For example, when measuring by a sleeve method or a transmission method, there may be no corner portion.

<About radiation sources>
In the above-described embodiment, cobalt 60 is used as the gamma ray radiation source and californium 252 is used as the neutron radiation source. However, other materials may be used.

<About radiation distance>
In the above-described embodiment, when the corner method and the sleeve method are performed, the source rod 30 is fixed to the main body 20 (the radiation distance is constant). May be removed from the main body 20 and the radiation distance may be adjusted for measurement.

<Calibration curve>
In the above-described embodiment, the calibration curve is limited to FIG. 9, but is not limited to this as long as the correspondence between the measured value (count rate ratio) and the unit volume mass can be obtained separately.

DESCRIPTION OF SYMBOLS 1 Concrete wall 1a Sleeve hole 1A Outer wall surface 1B Outer wall surface 1C Inner wall surface 1D Inner wall surface 10 Measuring device 20 Main body 21 Radiation detection part 21a Gamma ray detection part 21b Neutron beam detection part 22 Processing part 30 Radiation source rod 32 Radiation source

Claims (8)

Irradiating the hardened concrete with radiation;
Detecting the radiation transmitted through the concrete;
A step of obtaining a physical property value of the concrete based on the detection result of the radiation;
A method for measuring concrete, comprising: The method for measuring concrete according to claim 1,
The radiation is gamma rays;
The physical property value is a unit volume mass.
A method for measuring concrete characterized by the above. The method for measuring concrete according to claim 1,
The radiation is a neutron beam;
The physical property value is water content.
A method for measuring concrete characterized by the above. A method for measuring concrete according to any one of claims 1 to 3,
A correspondence method between the number of detected radiations and the magnitude of the physical property value is predetermined, and the physical property value is obtained using the correspondence relationship. A method for measuring concrete according to any one of claims 1 to 4,
The concrete has corners;
Transmitting the radiation from one surface forming the corner to the other surface;
A method for measuring concrete characterized by the above. A method for measuring concrete according to any one of claims 1 to 4,
The concrete has a hole on a predetermined surface,
The method for measuring concrete, wherein the radiation is transmitted from the inside of the hole to the predetermined surface. A method for measuring concrete according to any one of claims 1 to 4,
The concrete has a width-thickness part,
The method for measuring concrete, wherein the radiation is transmitted from one side of the width-thickness portion to the other side. The shielding performance against the radiation of the concrete is evaluated from the physical property values obtained by the concrete measuring method according to any one of claims 1 to 7.
Concrete evaluation method characterized by the above.

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