JPH0752143A - Moisture measuring device for concrete - Google Patents

Abstract

PURPOSE:To measure the unit water content of cast concrete. CONSTITUTION:A neutron beam irradiation device 2 irradiating the outer surface of a pipe sending concrete under pressure with neutron beam to transmit neutron beam through the pipe 1 and the concrete sent under pressure, a moisture meter 3 measuring the attenuation factor of the neutron beam transmitted through the concrete sent under pressure, a gamma-ray irradiation device 4 irradiating the outer surface of the pipe 1 with gamma-rays to transmit the same through the pipe 1 and the concrete sent under pressure and a density meter 5 measuring the attenuation factor of gamma-rays transmitted through the pipe 1 and the concrete sent under pressure are provided. The measured attenuation factors of neutron beam and gamma-rays are inputted to a microcomputer 6 to continuously operate unit water quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water content measuring device for concrete.

[0002]

2. Description of the Related Art In recent years, the upper limit of the amount of water per cubic meter of concrete, that is, the upper limit of the unit amount of water, has decreased, and high-performance AE water reducing agents having higher water reducing performance than AE water reducing agents have come to be used. There is. In addition, high-strength concrete has come to be used mainly in RC super high-rise apartments, and high-performance AE is also used for manufacturing the high-strength concrete.
A water reducing agent is used.

In the conventional AE water reducing agent, since the standard addition amount was set, the slump of concrete fluctuated in proportion to the unit water amount. Therefore, in the case of concrete using the AE water reducing agent, the unit water amount could be measured by performing a slump test in the acceptance inspection at the time of delivery to a site such as a work place.

However, in the case of the high-performance AE water reducing agent, the high-performance AE water reducing agent is not specified because the standard addition amount is not clearly defined.
The concrete slump using the E water-reducing agent varies not only with the fluctuation of the unit water amount but also with the usage amount and effect of the high-performance AE water-reducing agent, making it difficult to measure the unit water amount by the slump test. .

Therefore, conventionally, the high-frequency heating method and the L-type flow test, which have been developed mainly for the purpose of measuring the unit water content of high-strength concrete, are applied to the construction work to measure the unit water content of the concrete.

[0006]

However, the high-frequency heating method and the L-type flow test in the conventional examples are all carried out by sampling a part of the concrete to be placed, and the unit water amount is set in all the concrete to be placed. However, there is a drawback that the quality of concrete cannot be adequately controlled. In addition, there is a drawback that it takes time to carry out the measurement work itself.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide one capable of measuring the unit water amount of all concrete to be placed.

[0008]

In order to achieve the above-mentioned object, a concrete water content measuring apparatus of the present invention irradiates a neutron beam from an outer surface of a pipe for pumping concrete, and the pipe and the pump are fed. Neutron irradiation device that transmits concrete, moisture meter that measures the attenuation rate of neutron rays that have penetrated pipes and pumped concrete, and gamma rays that irradiate γ rays from the outer surface of the pipes and that transmit pipes and pumped concrete The irradiation unit, the density meter that measures the attenuation rate of γ-rays that have passed through the pipes and pumped concrete, the attenuation rate of neutron rays measured by the moisture meter and the attenuation rate of γ-rays measured by the density meter And a water amount calculating means for calculating

[0009]

According to the structure of the concrete water content measuring apparatus of the present invention, the unit water content of the pumped concrete can be continuously measured by paying attention to the characteristics of each of neutron rays and γ rays. That is, the neutron beam projected from the neutron beam irradiation device, in the process of passing through the pumped concrete,
The amount of neutron rays measured by a moisture meter decreases exponentially in proportion to the amount of water contained in the concrete, which causes elastic scattering with hydrogen atoms that make up the water in the aggregate. On the other hand, the degree of absorption of γ-rays projected from the γ-ray irradiator in the process of passing through pumped concrete is proportional to the density of concrete, and the amount of γ-rays measured by a densitometer determines the wet density of concrete. It decreases exponentially in proportion. Focusing on these points, calculate the unit water volume from the attenuation rate of neutron rays measured with a moisture meter and the attenuation rate of γ rays measured with a density meter, and continuously measure the unit water volume of pumped concrete. You can

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a vertical cross-sectional view showing an embodiment of a water content measuring apparatus for concrete according to the present invention, in which a neutron beam is applied to a pipe 1 connected to a pipe for concrete pumping so as to face each other. The apparatus 2 and the moisture meter 3 are attached, and neutron rays are irradiated from the outer surface of the pipe 1 to allow the pipe 1 and the pumped concrete to pass therethrough, and the attenuation rate of the transmitted neutron beam is measured by the moisture meter 3. Is configured.

Further, the pipe 1 is arranged so as to face each other.
The γ-ray irradiation device 4 and the densitometer 5 are attached, and γ-rays are radiated from the outer surface of the pipe 1 to allow the pipe 1 and the pressure-fed concrete to pass through, and the attenuation rate of the γ-ray that has passed through the densimeter 5 It is configured to measure.

Each of the moisture meter 3 and the densitometer 5 is connected to a microcomputer 6 as a water amount calculating means, and the unit water amount is calculated from the attenuation rate of neutron rays and the attenuation rate of γ rays. explain.

First, in order to correct the attenuation during transmission through the pipe 1, the attenuation rates of γ-rays and neutron rays in an empty state in which concrete is not pumped are obtained in advance, and these are used as the denominator, and the density meter 5 Further, calibration formulas (1) and (2) using the density meter count ratio Rρ and the moisture meter count ratio Rm, which have the attenuation rate measured by the moisture meter 3 as a numerator, are stored in the memory.

[Equation 1]

[Equation 2]

In equation (1), ρt is the wet density, and A and B are calibration constants. Further, in the equation (2), ρm is a water content, ρd is a dry density, C and D are calibration constants, and α is a correction coefficient. The water content ρm is 110
It is the amount of water that evaporates in 24 hours when dried in a furnace at ℃, ρm = ρw + ρq (3) where ρw is the free water amount (corresponding to the unit water amount in ρt) and ρq is The amount of water absorption. In addition, since the moisture meter 3 is basically a hydrogen concentration meter, the correction coefficient α is affected by the amount of hydrogen that does not evaporate during furnace drying and other than hydrogen atoms to some extent. It is for converting into quantity.

Since the density meter count ratio Rρ is obtained from the attenuation rate of γ rays measured by the density meter 5, ρt can be obtained from the equation (1). On the other hand, since the moisture meter count ratio Rm is obtained from the attenuation rate of the neutron beam measured by the moisture meter 3, the formula (2)
Therefore, ρm + α · ρd can be obtained. Where the dry density ρ
Since d = ρt−ρm, the water content ρm is obtained by the following equations (4) and (5).

[Equation 3]

[Equation 4]

That is, the water content ρm is obtained by the attenuation rate of each of the neutron ray and the γ ray measured by the moisture meter 3 and the density meter 5 described above. Further, since the dry density ρd = ρt−ρm, this dry density ρd
Is also determined from the wet density ρt and the water content ρm.

If the average water absorption rate Q including the aggregate and cement is known in advance, the water absorption amount ρq = Q · ρd.
The free water amount ρw is obtained. Since this free water amount ρw is the water amount in the wet density ρt, the unit water amount ρw ₀ in the unit volume mass ρt _{0 when} mixing concrete is

[Equation 5] Becomes

As described above, in the microcomputer 6, the calibration equations (1) and (2) are stored in the memory, and the calibration constants A, B, C and D, the correction coefficient α and the average water absorption rate Q are respectively stored. By inputting it, the unit water amount per unit volume mass of concrete can be obtained by the attenuation rate of each of neutron ray and γ ray measured by the moisture meter 3 and the densitometer 5, respectively.

Next, a confirmation experiment carried out using the concrete water content measuring apparatus will be described. First, when explaining the materials used and the mixing of concrete,
As the cement, ordinary Portland cement (made by Sumitomo Cement) was used, and as the fine aggregate, the main island sea sand (surface dry specific gravity: 2.56, water absorption rate: 1.64%) and Oyama crushed sand (surface dry specific gravity: 2.57, water absorption rate) : 1.41%) and sand mixed at a ratio of 6: 4 (surface dry specific gravity: 2.56, FM: 2.70), as coarse aggregate,
Oyama crushed stone (maximum size: 20 mm, surface dry specific gravity: 2.61, actual rate: 58%, water absorption rate: 0.99%) and a high-performance AE water reducing agent (Pozoris NO. 70) were used as admixtures. , Three types prepared in the proportion of (a) in Table 1 were used as test pieces.

[Table 1] In Table 1 (a), C indicates the amount of cement, S indicates the amount of fine aggregate, and G indicates the amount of coarse aggregate. Moreover, (b) of Table-1 shows the measurement test result mentioned later.

Each of the three types of specimen 1, specimen 2, and specimen 3 prepared as described above is placed in the first ready-mixed concrete truck 7 as shown in the plan view of the schematic configuration used for the confirmation experiment in FIG. The concrete is put in and pumped by the pump car 8 through the pipe 1 and the boom car 9 to the second ready-mixed concrete car 10. Then, the water content measuring device A for concrete described above in the pipe 1 at a position near the discharge point of the pump car 8
And the first and second pressure gauges 11 and 12 are attached before and after.

The pressure for supplying concrete is adjusted by the first and second pressure gauges 11 and 12, and the pumping speed is changed to a low speed of 20 m ³ / hr, a medium speed of 40 m ³ / hr and a high speed of 80 m ³ / hr. Each of the specimen 1, the specimen 2, and the specimen 3 was supplied, and the unit weight and the unit water amount thereof were measured to obtain each specimen 1,
When compared with the set values of each of the specimen 2 and the specimen 3, the measurement test results shown in (b) of Table-1 were obtained. In addition,
For sample 1, the concrete was blocked during the low-speed pressure feeding, and therefore the medium-speed and high-speed pressure feeding was not performed.

Further, the change with time of the average value of all the data of the unit weight and the unit water amount of each of the test piece 1, the test piece 2, and the test piece 3 was obtained. Unit weight] and (b) [Unit water amount of Specimen 1], (a) [Unit weight of Specimen 2] and (b) [Specimen 2] of FIG.
The unit water amount], and the graphs of (a) [unit weight of sample 3] and (b) [unit water amount of sample 3] in FIG. 5 were obtained. In addition, the measured values of the unit weight and the unit water amount are the moisture meter 3 and the density meter 5, respectively.
Attenuation rate of each neutron ray and γ ray measured in each is input every 1 second, unit weight and unit water amount are respectively calculated by the value every 10 seconds, and further, for the calculated value, for example, 12 at 120 seconds after starting measurement
The average of the measured values is used as the measured value for the first 10 seconds, and the next
The average value of 12 measured values in 10 to 130 seconds is calculated as the next 10 to 20.
It was calculated by taking the average of 12 times, such as the measured value for 2 seconds.

From the above results, stable measured values can be obtained as the unit weight and the unit water amount, respectively, and there is only an error of about 1% when compared with the set value. It was clear that the water content and the unit water content were continuously measured with high accuracy.

[0025]

As described above, according to the water content measuring apparatus for concrete of the present invention, it is possible to continuously measure the unit water content of pumped concrete by paying attention to the characteristics of neutron rays and γ rays. Therefore, it is possible to measure the unit water amount of all the concrete to be placed and perform good quality control of the concrete, and it is possible to provide a concrete water content measuring device that is extremely useful in constructing a concrete structure of stable quality. It became so.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a concrete water content measuring apparatus according to the present invention.

FIG. 2 is a plan view showing a schematic configuration used in a confirmation experiment.

FIG. 3 (a) is a graph showing a change with time of a measurement unit weight of the sample 1, and FIG. 3 (b) is a graph showing a change with time of a measurement unit water amount of the sample 1.

FIG. 4 (a) is a graph showing a change with time of a measurement unit weight of the sample 2, and FIG. 4 (b) is a graph showing a change with time of a measurement unit water amount of the sample 2.

5 (a) is a graph showing a change with time of a measurement unit weight of the sample 3, and FIG. 5 (b) is a graph showing a change with time of a measurement unit water amount of the sample 3. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Piping 2 ... Neutron beam irradiation device 3 ... Moisture meter 4 ... γ-ray irradiation device 5 ... Density meter 6 ... Microcomputer as water amount calculation means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Iwashimizu 2-5-14 Minamisuna, Koto-ku, Tokyo Inside the Takenaka Corporation Technical Research Institute (72) Inventor Nobunao Murakami 2-chome, Minamisuna, Koto-ku, Tokyo 5-14 No. 14 in Takenaka Corporation Technical Research Institute (72) Inventor Sadatoshi Ono 2-5-14 Minamisuna, Koto-ku, Tokyo Incorporated Takenaka Corporation Technical Research Institute (72) Inventor Takashi Nishizaki Tokyo 2-5-14 Minamisuna, Koto-ku, Ltd. Takenaka Corp. Technical Research Institute (72) Inventor Yasuhiko Yoshioka 2-5-14 Minamisuna, Koto-ku, Tokyo Incorporated Takenaka Corp. Technical Research Institute (72) Inventor Masao Otake 2-21-1, Shonai-cho, Toyonaka-shi, Osaka Soil and Rock Engineering Co., Ltd. In-house (72) Inventor Yoshifumi Kumahara Shoei-cho, Toyonaka-shi, Osaka Chome No. 21 No. 1 source yl and lock engineering shares meeting-house (72) inventor Hiroshi Tamura Suita, Osaka Prefecture Fujishirodai 5-chome No. 8 No. 1 Foundation Japanese architecture comprehensive test house

Claims (1)

[Claims] 1. A neutron beam irradiation device for irradiating neutron rays from the outer surface of a pipe for pumping concrete so as to pass through the pipe and the pump concrete, and an attenuation rate of the neutron beam passing through the pipe and the pump concrete. Moisture meter, a γ-ray irradiation device that irradiates γ-rays from the outer surface of the pipe, and transmits the pipe and the pumped concrete, and a density meter that measures the attenuation rate of the γ-ray that has passed through the pipe and the pumped concrete. And a water content calculation means for calculating a unit water content from the attenuation rate of neutron rays measured by the moisture meter and the attenuation rate of γ rays measured by the density meter, and the water content of concrete. measuring device.