JPH07198629A - Water content measuring method for concrete or mortar - Google Patents

Abstract

PURPOSE:To measure the water content correctly, in a short measurement time and directly by radiating neutrons to concrete or mortar, the water content of which is to be measured, and measuring capture gamma rays generated by radiation of neutrons. CONSTITUTION:Neutrons are made to irradiate the concrete or mortar. Capture gamma rays of the same number as that of hydrogen atoms for forming water in concrete or mortar are generated by radiation of neutrons. Capture gamma rays of the same number are radiated equally in any direction of concrete and mortar. At this time, measurement of capture gamma rays is better at a plane than at a point to reduce the measurement time. Subsequently, the number of capture gamma rays generated by radiation of netrons is measured. The number of capture gamma rays can be measured by a scintillation counter or the like. As the measured number of capture gamma rays corresponds to the number of hydrogen atoms, the half of the number of capture gamma rays is equal to the number of one molecule of water. Thus, the water content can be measured substantially directly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete used for walls, floors, etc. of buildings, concrete such as mortar, or a method for measuring the water content of mortar.

[0002]

2. Description of the Related Art Measuring the water content of concrete or mortar such as concrete and mortar is extremely important for knowing the hardening state and quality control of building structures.

As a conventional method for measuring the water content of concrete or the like, a fast neutron source is placed near a detector having high sensitivity to slow neutrons, and the fast neutrons gradually lose energy due to surrounding substances to become thermal neutrons. There is known a neutron moisture meter or the like that measures the water content and indirectly measures the water content. The neutron moisture meter has the advantage that the time required for measurement is short and continuous measurement is possible without the need for sampling.

However, in the neutron moisture meter, it is necessary to create a calibration curve in order to obtain the water content from the measured thermal neutron ratio, and what is the standard when creating the calibration curve is the simplest and the easiest to reproduce. It is unknown whether there is a
In addition, since it is necessary to increase the effective volume (the volume necessary for sufficiently converting fast neutrons into thermal neutrons), the area of the object to be measured must be increased accordingly. Further, when the object to be measured contains iron, boron, cadmium, etc., there is a drawback that an accurate measurement result cannot be obtained due to the influence of these elements.

On the other hand, it is generally known that when a substance is irradiated with neutrons, the same number of captured γ-rays as the number of hydrogen atoms contained in the substance is generated. This phenomenon is measured by measuring the water content. The fact is that nothing is known about how to use it.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a method for measuring the water content of concrete or mortar which can measure the water content directly and accurately with a short measurement time. To provide.

Another object of the present invention is to obtain a precise content without being affected by other components other than water in concrete or mortar, and without being affected by the area or the like of the concrete or mortar as an object. It is to provide a method for measuring the water content of concrete or mortar capable of measuring the water content.

[0008]

According to the present invention, there is provided a method for directly measuring the water content of concrete or mortar, which comprises irradiating concrete or mortar for measuring water content with neutrons, and irradiating the neutrons. Capture γ generated by
A method for measuring the water content of concrete or mortar is provided, characterized in that it measures the number of lines.

The present invention will be described in more detail below.

The concrete or mortar to be the object in the measuring method of the present invention may be a normal one containing cement, not only a cured product which has been completely cured, but also a curing reaction in progress. However, it is not particularly limited as long as it is in a solid state as a whole. In this case, components other than water containing hydrogen atoms in concrete or mortar are merely trace components even if they are contained, and can be ignored in the measuring method of the present invention.

In the measuring method of the present invention, concrete or mortar is first irradiated with neutrons. The method of irradiating the neutrons can be performed by using a device using a known radiation nuclide, a device using an artificial accelerator, a device using a nuclear fission chain reaction by a nuclear reactor, and the like. Um-252, americium-beryllium, etc. can be mentioned. At this time, irradiation conditions are preferably such that neutrons are irradiated in a beam shape and the measurement time is 5
It can be done in about a minute.

By the irradiation of the neutrons, trapped γ-rays of the same number as hydrogen atoms constituting water (H ₂ O) in concrete or mortar are generated. The captured gamma rays are emitted in the same direction in any direction of concrete or mortar, that is, in the range of 360 degrees. Therefore, the capture γ described later
The measurement of the number of rays may be the surface of the concrete or mortar irradiated with neutrons, or may be the back side of the irradiated surface, and the measurement location of the captured γ-rays is not particularly limited. . At this time, the measurement of the captured γ-rays is preferably performed on the surface rather than at the point in order to shorten the measurement time.

In the measuring method of the present invention, the number of captured γ rays generated by the irradiation of the neutrons is then measured. The capture γ
The number of lines can be measured by using a scintillation counter or the like which is usually used in a radiation measuring instrument. The installation location of the scintillation counter or the like is not particularly limited as described above.

Since the number of captured γ-rays measured in this manner corresponds to the number of hydrogen atoms in water (H ₂ O), 1/2 of the number of captured γ-rays becomes equal to the number of one molecule of water. Therefore, the water content can be directly measured.

[0015]

EFFECT OF THE INVENTION In the method for measuring the water content of concrete or mortar of the present invention, since the neutron is used, the water content can be measured in a short time, and the number of captured γ rays generated by the irradiation of neutrons can be measured. Therefore, even if it is a test piece of concrete, etc., an accurate water content can be obtained without being affected by components other than water in concrete or mortar, and without being affected by the area of concrete or mortar. Can be measured.

[0016]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[0017]

Example 1 Contained elements other than water (calcium, sulfur,
Silicon, potassium, titanium, aluminum, iron, manganese, sodium, manganese, oxygen) are the same, and concrete A and B of two kinds of compositions with different mixing ratios of each element
On the other hand, concrete test pieces shown in Tables 1 and 2 having different water contents of 0% to 7% by 1% were prepared. The shape of the test piece was a 100 × 100 × 100 cm rectangular parallelepiped. Each of the obtained test pieces was placed on a table, and a calforonium-252 neutron source installed at a position 1 m away from one surface of the concrete was used to cause spontaneous emission of calfornium-252 over the entire one surface of the concrete. Irradiation with fission neutrons for 5 minutes. Simultaneously with the irradiation, the number of captured γ rays generated by a NaI scintillation counter (manufactured by Bycron Co., Ltd.) installed on the other surface (back surface) of the concrete was measured. The results are shown in Table 3.
Further, FIG. 1 shows a plot of the measurement results of the number of captured γ rays in Table 3.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

From the results of Table 3 and FIG. 1, concrete A
In B and B, the number of captured γ-rays similarly increases as the water content (water content) increases regardless of the difference in composition.
It can be seen that this increase in the number of captured γ-rays depends on the amount of water in concretes A and B. Also concrete A
It can be seen that the difference (error) in the number of captured γ-rays at each water content in B and B is within ± 0.06 and does not depend on the difference in the composition of concrete.

[0022]

[Example 2] For each of the test pieces prepared in Example 1, the NaI scintillation counter (manufactured by Bycron Co., Ltd.) was installed at a position diagonally above the neutron irradiation surface side of the test piece. The number of captured γ rays was measured in the same manner as in 1. As a result, the same measurement results as in Example 1 were obtained. From this, it can be seen that it does not matter where the scintillation counter is installed.

[Brief description of drawings]

FIG. 1 is a graph in which the measurement results of the number of captured γ rays of each concrete measured in Example 1 are plotted.

Claims (1)

[Claims] 1. A method for directly measuring the water content of concrete or mortar, in which the concrete or mortar whose water content is to be measured is irradiated with neutrons, and the number of captured γ rays generated by the irradiation of the neutrons is measured. A method for measuring the water content of concrete or mortar, characterized by: