JPH116797A - Measurement of moisture quantity of placed concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the measurement of moisture quantity in a short time as a whole. SOLUTION: A formwork (30) for placing concrete C has a bottom formwork and a pair of side formworks 30b. At the surfaces of the side formworks 30b, a plurality of measuring window parts 32, which are scattered in the approximately grid shape, are provided. The window part 32 is the cylindrical part, whose tip side is closed and formed of a member, which can pass infrared rays. When the moisture in the placed concrete C is measured, a holder 18 of a moisture meter is individually inserted into the measuring window part 32, and the infrared rays are emitted on the concrete through the window part 32. The infrared rays have the wavelength that is absorbed into water. The moisture quantity of the concrete of obtained from the reflected amount of the irradiated infrared rays.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the moisture content of cast concrete, and more particularly to a method for directly and entirely measuring the moisture content of concrete cast in a formwork at a construction site. Things.

[0002]

BACKGROUND OF THE INVENTION Managing the quality of concrete involves:
In order to improve the reliability and economic efficiency of concrete construction in recent years where high strength and high quality are required, it is extremely important work. Various tests are conducted by collecting fresh concrete from such sources.

[0003] Among the quality control items for concrete, the compressive strength, particularly the compressive strength at the age of 28 days, is very important, but it takes too much time to obtain a measurement result, and the quality control before casting is performed. This is not a suitable method.

As a method of determining the compressive strength in a short time,
A quality control method based on an accelerated strength test for an age of 5 to 28 hours by boiling curing, an accelerated strength test for an age of 40 to 50 hours by warm water curing, or an age of 3 to 7 by normal temperature curing
A quality control method based on early strength testing of Japan has been proposed.

[0005] However, even if the period for measuring the compressive strength is shortened by such means, the method cannot be applied to quality control of fresh concrete before casting because of lack of quickness.

In view of the above, a quality control method that focuses on the water-cement ratio of fresh concrete, which is closely related to the compressive strength, determines the water-cement ratio, and estimates the compressive strength at the age of 28 days from the results, , Is considered to be the most effective quality control method.

[0007] In such a quality control method, it is necessary to measure the moisture content of fresh concrete.
Conventionally, the JIS "washing concrete concrete analysis test method" (JIS1112),
Measurement methods such as drying in a microwave were used.

However, the method for measuring the moisture content of fresh concrete has the following technical problems.

[0009]

That is, the conventional methods for measuring the amount of water described above are all methods of sampling and measuring a sample, and cannot measure the amount of water in the entire fresh concrete. 10 to measurement
It took about 20 minutes.

Further, in order to accurately grasp the water content in the whole fresh concrete, the number of times of sampling must be increased. However, when the number of times of sampling is increased, there is a problem that much more labor and time are required.

The present invention has been made in view of the above problems, and has as its object to measure the water content of cast concrete in which the water content can be measured in a short time and entirely. It is to provide a method.

[0012]

In order to achieve the above object, the present invention relates to a method of measuring the moisture content of concrete cast in a mold, wherein infrared rays are transmitted to appropriate portions of the mold. Forming a measurement window, irradiating the concrete with infrared light having a wavelength that is absorbed by water through the measurement window, and calculating the moisture content of the concrete from the reflected amount of the irradiated infrared light. I made it. Moisture has a specific wavelength, for example, 1.2, 1.45, 1.94, 2..
It has a property of absorbing infrared rays of 95 μm, and the absorption amount increases in proportion to the amount of water contained. Therefore, by irradiating the measurement target fresh concrete with infrared light having a wavelength that can be absorbed by water and measuring the reflection amount of the irradiated infrared light, the moisture content of the fresh concrete can be obtained. By applying the principle, a measuring window for transmitting infrared light is provided at an appropriate position of the mold, and the poured concrete is irradiated with infrared light through the measuring window to measure the moisture content. According to such a measuring method, it is not necessary to perform sampling, so that the water content can be obtained quickly and entirely. In the measuring method according to the present invention, the infrared ray can be applied to the fresh concrete to be measured from the tip of the optical fiber bundle. According to this configuration, the infrared light can be guided to an arbitrary position by propagating the infrared light in the optical fiber bundle, and the degree of freedom of the measurement place is increased. In the measuring method of the present invention, the measuring window may be formed so as to penetrate into the concrete. When this configuration is adopted, the amount of water inside the poured concrete can also be measured.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG.
FIG. 2 is a diagram showing the measurement principle of the infrared moisture meter 10 used in the method for measuring fresh concrete according to the present invention.

The moisture meter 10 shown in FIG.
An optical filter 12 provided on the front side of the light source 11,
It has a light projecting fiber 14 for receiving light emitted from the optical filter 12 and a light receiving fiber 16 for receiving light reflected from an object to be measured.

The light emitting and receiving fibers 14, 16 are
Each is composed of multiple fiber bundles,
These are integrated, and the distal end side is inserted and held in the holder 18 so that the open end faces of the fibers 14 and 16 are directed toward the object to be measured.

A photoelectric conversion element 20 such as a phototransistor is provided on the emission end side of the light receiving fiber 16. An electric signal converted by the photoelectric conversion element 20 is input to an analog operation circuit 24 via a sampling circuit 22. Is done.

In the moisture meter 10 configured as described above, the light emitted from the light source 11 is divided into reference light in the infrared region, measurement light, and visible light by passing through the optical filter 12.

In this case, the reference light is infrared light having a wavelength that is not affected by moisture, for example, the wavelength is 1.8 μm.
Is set to On the other hand, the measurement light is infrared light having a wavelength that is absorbed by moisture, and the wavelength is set to 1.94 μm, for example.

The measuring light and the reference light are applied to the object to be measured via the light emitting fiber 14. The irradiated light generates different amounts of reflected light for each wavelength according to the water content of the measurement object, and the reflected light is received by the light receiving fiber 16 and converted into an electric signal by the photoelectric conversion element 20. Is done.

In the moisture meter 10 having such a configuration, the amount of moisture can be measured only by irradiating the measurement target with only the measuring light.
It is affected by color and surface condition.

Therefore, the reference light receiving the same influence as above is simultaneously irradiated, and such a variation factor is calculated by the analog arithmetic circuit 24 to perform a correction for excluding it from the measured value, thereby enabling more accurate measurement. Like that.

In the present invention, the moisture meter 10 based on such a measurement principle is applied to concrete cast in a mold. FIG. 2 shows an experimental result when an experiment is performed to determine whether or not the moisture content of concrete can be measured by the moisture meter 10 using infrared rays.

In this experiment, a plurality of concretes having a known water-cement ratio were prepared, and the holder 18 of the moisture meter 10 was immersed in each concrete to determine an output voltage value. In FIG. 2, the horizontal axis is the water-cement ratio of the concrete to be measured, and the vertical axis is the output voltage value of the moisture meter 10.

As can be seen from the experimental results, the difference between the water-cement ratio of concrete and the output voltage value of
A certain correlation is recognized, and the relationship between the water-cement ratio or moisture content of fresh concrete and the output voltage of the moisture meter 10 is measured in advance, and a calibration curve is created. From the value, the water-cement ratio or the water content of the fresh concrete can be obtained.

FIGS. 3 and 4 show a more specific embodiment of the present invention. In the embodiment shown in these figures, the formwork 30 for placing the concrete C includes a bottom formwork 30a,
And a pair of side molds 30b.
A plurality of measurement windows 32 scattered in a cheek grid on the surface b
Is provided.

The measurement window 32 is provided on one side of the mold 3.
0b, it may be provided on the other side mold, and in some cases, may be provided on the bottom mold 30a.

The measuring window 32 is a cylindrical one whose front end is closed, and is made of, for example, transparent plastics, which can transmit infrared rays, and is provided on the side mold 30B. And has a length that penetrates into the concrete C to be poured.

The inner diameter of the measurement window 32 is
The holder 18 is set to a size that can be fitted therein.

When measuring the water content of the concrete C poured into the formwork 30,. A method of individually inserting the holder 18 of the moisture meter 10 into each measurement window 30 and irradiating the concrete with infrared rays through the window 30, It is possible to adopt a method in which the holder 18 is inserted into each of the measurement windows 30 and the measurement is performed by sequentially switching the irradiation of the infrared rays by the changeover switch.

When the water content is measured in this manner, the entire water content of the concrete C placed in the formwork 30 can be measured without sampling, and the distribution of the water content with respect to the placement position can be measured. The state can also be grasped.

In the case of this embodiment, the measuring window 3
Since 0 penetrates into the concrete C, it is possible to measure the amount of water inside the cast concrete C.

In this case, if a reflecting mirror 34 is provided at the front end of the measuring window 32 at an angle or a similar reflecting mirror is provided on the front side of the holder 18, infrared rays can be transmitted to the measuring window 32. Since it can be guided to the side of 32, a wider range of water content can be measured.

In the above-described embodiment, the case where the output of the moisture meter 10 is taken out in an analog form is shown. However, the embodiment of the present invention is not limited to this. It can be converted to a format and the subsequent arithmetic processing can be performed by a personal computer or the like.

In this case, if the water content of the concrete C is measured over time, for example, from immediately after the casting to the hardening, the change in the water content in the hardening process of the concrete C can be grasped. The analysis of the amount of moisture with respect to the hardening of the concrete C can also be performed.

[0035]

As described above in detail in the embodiments,
According to the method for measuring the moisture content of cast concrete according to the present invention, the moisture content can be measured in a short time and entirely.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a measurement principle of a measurement method according to the present invention.

FIG. 2 is a graph showing a relationship between a measured value in the measuring method of the present invention and a water-cement ratio of concrete.

FIG. 3 is an explanatory diagram of one embodiment of a measuring method according to the present invention.

FIG. 4 is an explanatory sectional view of a main part of FIG. 3;

[Explanation of symbols]

 Reference Signs List 10 moisture meter 14 light emitting fiber 16 light receiving fiber 18 holder 30 formwork 30a bottom formwork 30b side formwork 32 window for measurement

Claims (3)

[Claims] 1. A method for measuring the moisture content of concrete cast in a mold, comprising: forming a measurement window through which infrared light is transmitted at an appropriate position of the mold; Irradiating the concrete with infrared light having a wavelength that can be absorbed by water, and calculating the water content of the concrete from the reflected amount of the irradiated infrared light. 2. The method according to claim 1, wherein the infrared ray is applied to the fresh concrete to be measured from an end of an optical fiber bundle. 3. The method according to claim 1, wherein the window for measurement is formed so as to penetrate into the concrete.