JP3221988B2 - Concrete moisture meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, the amount of water per cubic meter of concrete, that is, the upper limit of the unit water amount has been reduced, and high-performance AE water reducing agents having higher water reducing performance than AE water reducing agents have been used. I have. In addition, high-strength concrete has been actively used mainly in RC high-rise apartment buildings, and high-performance AE has been used for the production of high-strength concrete.
Water reducing agents are used.

In the conventional AE water reducing agent, the slump of concrete fluctuates in proportion to the unit water amount because the standard addition amount is determined. For this reason, in the case of concrete using an AE water reducing agent, a unit amount of water could be measured by performing a slump test in an acceptance inspection at the time of transport to a work site or the like.

[0004] However, in the case of a high-performance AE water reducing agent, the standard addition amount is not clearly defined, so that the high-performance AE water reducing agent is used.
Concrete slumps using E water reducer not only vary in unit water volume, but also fluctuate depending on the amount and effect of high-performance AE water reducer, making it difficult to measure unit water volume by slump test. .

Therefore, conventionally, a high-frequency heating method or an L-shaped flow test developed mainly for measuring the unit water amount of high-strength concrete has been applied to the execution work to measure the unit water amount of concrete.

[0006]

However, in the conventional high-frequency heating method and the L-shaped flow test, a part of the concrete to be cast is sampled. Was not able to measure the quality of concrete, and there was a drawback that the quality of concrete could not be controlled sufficiently. In addition, there is a disadvantage that it takes time to perform the measurement operation itself.

The present invention has been made in view of such circumstances, and has as its object to provide a device capable of measuring a unit water amount of all concrete to be poured.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, a concrete moisture content measuring apparatus of the present invention irradiates a neutron beam from an outer surface of a pipe for feeding concrete to the concrete and pressurizes the pipe. A neutron irradiation device that transmits concrete, a moisture meter that measures the attenuation of neutron radiation that has passed through pipes and pumped concrete, and a γ-ray that irradiates gamma rays from the outer surface of pipes and penetrates pipes and pumped concrete obtained from the irradiation device, piping and density meter for measuring the attenuation factor of the transmitted γ-rays pumping concrete and the attenuation factor of the γ-rays measured by the rate of decay of neutrons measured by moisture analyzer the densimeter Depending on the wet density ρt
Therefore, based on the following formula,
And a water amount calculating means for calculating a unit water amount ρw ₀ in a product mass . ρw ₀ = ρw · ρt ₀ / ρt where ρw is the free water volume of the pressed concrete,
This is the amount of water in the moisture density ρt. ρt ₀ is the concrete
It is the unit volume mass in the preparation of G.

[0009]

According to the configuration of the concrete moisture content measuring device of the present invention, the unit water content of the pressed concrete can be continuously measured by focusing on the characteristics of the neutron beam and the gamma ray. In other words, the neutron beam projected from the neutron beam irradiation device, in the process of penetrating the pumped concrete,
Hydrogen atoms constituting the moisture in the aggregate cause elastic scattering, and the amount of neutron rays measured by the moisture meter decreases exponentially in proportion to the amount of moisture contained in the unit volume of concrete. On the other hand, the degree of absorption in the process of the γ-rays projected from the γ-ray irradiator passing through the pumped concrete is proportional to the density of the concrete, and the amount of γ-rays measured by the density meter indicates the wet density of the concrete. It decreases exponentially in proportion. Focusing on these facts, the unit water amount ρw ₀ is calculated based on the following equation ρw ₀ = ρw · ρt ₀ / ρt from the neutron beam attenuation rate measured by the moisture meter and the γ-ray attenuation rate measured by the density meter. calculated Te, preparation of concrete that is not subject to pressure to pumping concrete flowing in the pipe in compression
The unit water volume per unit volume mass above can be measured continuously.

[0010]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of a concrete moisture content measuring apparatus according to the present invention. A pipe 1 connected to a pipe for concrete pumping is irradiated with neutron beams so as to face each other. The apparatus 2 and the moisture meter 3 are attached, irradiate a neutron beam from the outer surface of the pipe 1 to transmit the pipe 1 and the pumped concrete, and measure the attenuation rate of the transmitted neutron beam with the moisture meter 3. Is configured.

In addition, the pipe 1 is arranged so as to face each other.
A γ-ray irradiator 4 and a density meter 5 are attached, and γ-rays are radiated from the outer surface of the pipe 1 to transmit the pipe 1 and the conveyed concrete. It is configured to measure.

Each of the moisture meter 3 and the density meter 5 is connected to a microcomputer 6 as water amount calculating means, and calculates a unit water amount from a neutron beam attenuation rate and a γ-ray attenuation rate. explain.

First, in order to correct the attenuation at the time of transmission through the pipe 1, the attenuation rates of γ-rays and neutron rays in an empty state where no concrete is pumped are obtained in advance, and the obtained attenuation rates are used as a denominator. The calibration equations (1) and (2) using the densitometer count ratio Rρ and the moisture meter count ratio Rm using the decay rate measured by the moisture meter 3 as a numerator are stored in a memory.

(Equation 1)

(Equation 2)

In equation (1), ρt is a wet density, and A and B are calibration constants. In Equation (2), ρm is the water content, ρd is the dry density, C and D are calibration constants, respectively, and α is a correction coefficient. The water content ρm is 110
Ρm = ρw + ρq (3) where ρw is a free water amount (corresponding to a unit water amount in ρt), and ρq is It is the amount of water absorption. Further, 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 in the furnace drying and to some extent other than hydrogen atoms. It is for conversion into quantity.

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

(Equation 3)

(Equation 4)

That is, the water content ρm is obtained from the attenuation rates of the neutron rays and the γ rays measured by the moisture meter 3 and the density meter 5, respectively. Since the dry density ρd = ρt−ρm, the dry density ρd
Is determined from the wet density ρt and the water content ρm.

If the average water absorption Q including the aggregate and cement is known in advance, the water absorption ρq = Q · ρd.
The free water amount ρw is determined. Since this free water amount ρw is the amount of water in the wet density ρt, the unit water amount ρw ₀ at the unit volume mass ρt ₀ in the preparation of concrete is: ρw ₀ = ρw · ρt ₀ / ρt (6) 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 Q are each stored. By inputting, the unit water amount per unit mass of concrete can be obtained from the attenuation rates of neutron rays and γ rays measured by the moisture meter 3 and the density meter 5, respectively.

Next, a description will be given of a confirmation experiment performed using the above-described apparatus for measuring the moisture content of concrete. First, the materials used and the mix of concrete will be explained.
As the cement, ordinary Portland cement (manufactured by Sumitomo Cement) is used. As fine aggregate, sea sand from the main island (surface dry specific gravity: 2.56, water absorption: 1.64%) and crushed sand from Oyama (table dry specific gravity: 2.57, water absorption) : 1.41%) and 6: 4 mixed sand (surface dry specific gravity: 2.56, FM: 2.70), as coarse aggregate,
Oyama crushed stone (maximum size: 20mm, specific gravity of surface dryness: 2.61, actual rate: 58%, water absorption: 0.99%), and a high-performance AE water reducing agent (POZORIS NO. 70) as an admixture And three kinds prepared at the ratio of (a) in Table 1 were used as test specimens.

[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. In addition, (b) of Table 1 shows a measurement test result described later.

Each of the three specimens 1, 2, and 3 prepared as described above is placed in a first ready-mixed car 7 as shown in the plan view of the schematic configuration for the confirmation experiment shown in FIG. The concrete is put in, and the concrete is pumped to the second ready-mixed concrete truck 10 by the pump truck 8 through the pipe 1 and the boom truck 9. Then, at the position close to the discharge point of the pump car 8, the above-described concrete moisture content measuring device A is attached to the pipe 1.
And 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. The specimen 1, specimen 2, and specimen 3 were supplied, and their unit weight and unit water amount were measured.
When a comparison was made between the set values of the test pieces 2 and 3, the measurement test results shown in (b) of Table 1 were obtained. In addition,
With regard to the test piece 1, the concrete was closed during the low-speed pumping, so that the medium-speed and high-speed pumping was not performed.

Further, when the average value of all the data of the unit weight and the unit water amount of each of the specimen 1, the specimen 2, and the specimen 3 was determined with the lapse of time, (a) of FIG. Unit weight] and (b) [Unit water amount of specimen 1], (a) of FIG. 4 [Unit weight of specimen 2] and (b) [Sample 2]
And the results shown in the graphs of (a) [unit weight of specimen 3] and (b) [unit water amount of specimen 3] in FIG. 5 were obtained. Note that the measured values of the unit weight and the unit water amount were measured with the moisture meter 3 and the density meter 5 respectively.
The neutron and γ-ray attenuation rates measured respectively are input every 1 second, and the unit weight and the unit water amount are calculated based on the values obtained every 10 seconds. Further, for the calculated values, for example, 12 at 120 seconds after the start of measurement
The average of the measured values is taken as the measured value for the first 10 seconds.
The average of the 12 measured values from 10 to 130 seconds is calculated in the next 10 to 20
An average of 12 measurements was obtained, such as a measurement value for seconds.

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

[0025]

As described above, according to the concrete moisture content measuring apparatus of the present invention, the unit water content of the pressed concrete can be continuously measured by focusing on the characteristics of the neutron beam and the gamma ray. And concrete
Because it is converted into unit water volume per unit volume mass in the formulation,
To be able to perform concrete quality control well by measuring the unit water amount of all concrete to be poured, and to provide a concrete moisture content measuring device which is extremely useful for constructing a concrete structure of stable quality. became.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a concrete moisture content measuring device according to the present invention.

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

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

4A is a graph showing a change over time of a unit weight of a test piece 2 and FIG. 4B is a graph showing a change over time of a unit water amount of a test piece 2.

5 (a) is a graph showing the change over time of the measurement unit weight of the sample 3, and FIG. 5 (b) is a graph showing the change over time of the 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 ... Gamma ray irradiation device 5 ... Density meter 6 ... Microcomputer as a water amount calculation means

Continuing from the front page (72) Nobuo Murakami, Inventor 2-5-1-14 Minamisuna, Koto-ku, Tokyo Inside the Technical Research Center, Takenaka Corporation (72) Inventor Sadatoshi Ohno 2-5-14-Minamisuna, Koto-ku, Tokyo Stock Takenaka Corporation Technical Research Institute (72) Inventor Takashi Nishizaki 2-5-1 Minamisuna, Koto-ku, Tokyo Stock Company Takenaka Corporation Technical Research Institute (72) Inventor Yasuhiko Yoshioka 2-5-Minamisuna, Koto-ku, Tokyo No. 14 Takenaka Corporation Technical Research Institute (72) Inventor Masao Otake 2-21-1, Shonai Sakaemachi, Toyonaka City, Osaka Prefecture Inside Soil and Rock Engineering Co., Ltd. (72) Inventor Yoshifumi Kumahara Shonai, Toyonaka City, Osaka Prefecture 2-21-1, Sakaemachi Inside Soil and Rock Engineering Co., Ltd. (72) Inventor Hiroshi Tamura 5-8-1, Fujishirodai, Suita-shi, Osaka Pref. Japan Building Research Institute (56) References 4-47253 (JP, A) 89094 (JP, A) JP Akira 50-16595 (JP, A) JitsuHiraku Akira 60-82257 (JP, U) (58 ) investigated the field (Int.Cl. ^7, DB name) B28C 7/00 G01N 9 /twenty four

Claims (1)

(57) [Claims] 1. A neutron beam irradiation device for irradiating a neutron beam from the outer surface of a pipe for feeding concrete and transmitting the tubing and the pumping concrete, and measuring an attenuation rate of a neutron beam passing through the pipe and the pumping concrete. Moisture meter, a γ-ray irradiator that irradiates gamma rays from the outer surface of the pipe to penetrate the pipe and the pumped concrete, and a density meter that measures an attenuation rate of the γ-ray transmitted through the pipe and the pumped concrete. And the neutron attenuation rate measured by the moisture meter and the γ-ray attenuation rate measured by the density meter
From the wet density ρt obtained from
Unit water in unit volume and mass when mixing concrete
An apparatus for measuring the amount of water in concrete, comprising: a water amount calculating means for calculating the amount ρw ₀ . ρw ₀ = ρw · ρt ₀ / ρt where ρw is the free water volume of the pressed concrete,
This is the amount of water in the moisture density ρt. ρt ₀ is the concrete
It is the unit volume mass in the preparation of G.