JP7208078B2 - Fiber amount measuring device and fiber amount measuring method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fiber amount measuring apparatus and a fiber amount measuring method for fiber reinforced concrete, which can easily measure the amount of steel fibers in steel fiber reinforced concrete.

Concrete, which is used for construction of structures, has a characteristic of being strong against external force in the compressive direction but weak against external force in the tensile direction. Fiber-reinforced concrete, which is made by uniformly dispersing synthetic fibers, steel fibers, etc. into concrete before hardening and hardening, is known as a technique for improving the tensile strength of concrete. According to fiber reinforced concrete, it is possible to improve the strength in the tensile direction and suppress the occurrence of cracks. Since the strength of fiber-reinforced concrete changes depending on the fiber content, it is necessary to accurately grasp the fiber content during the manufacturing process.

At construction sites of buildings, it is required to measure the mixing rate of steel fibers in steel fiber concrete before hardening and adjust the mixing rate to a specified value. The content of steel fiber in steel fiber concrete is calculated by taking a sample of mixed concrete, measuring the weight, washing the concrete to remove the steel fiber, and using the result of measuring the weight of the steel fiber. However, performing such a washing operation requires labor for washing the sample, and washing the concrete may result in discharge of turbid water, which may deteriorate the environment. In addition, there is a risk that the fibers will flow out during the washing process, making it impossible to accurately calculate the mixing ratio of the steel fibers.

Patent Literature 1 describes a measuring device for measuring the mixing ratio of steel fibers in steel fiber concrete mixed with steel fibers. This measuring device comprises a transmitting/receiving coil for applying a magnetic field to steel fiber concrete and detecting changes in magnetic flux, and means for calculating the amount of steel fiber mixed in based on the detected value. According to this measuring device, the amount of metal fibers mixed in the steel fiber reinforced concrete structure can be measured based on the waveform of the detected magnetic flux.

JP-A-10-054824

The measuring device described in Patent Literature 1 is a technique for measuring the amount of steel fibers contained in hardened steel fiber reinforced concrete, and cannot be measured when the concrete is fresh before hardening.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and aims to provide a fiber amount measuring device and a fiber amount measuring method that can calculate the mixing ratio of steel fibers in steel fiber concrete by a simple method. aim.

In order to achieve the above objects, the present invention provides a fiber amount measuring device for measuring the mixing ratio of steel fibers contained in steel fiber concrete before hardening, comprising a pair of electrodes, the pair of electrodes and the steel fibers a container for containing concrete; a measuring unit for measuring the impedance of the steel fiber concrete based on the value of the current flowing through the pair of electrodes and having predetermined frequency characteristics; and the impedance value measured by the measuring unit. and a calculation unit for calculating the mixing rate of the steel fiber in the steel fiber concrete based on the above.

According to the present invention, by measuring the impedance of the steel fiber concrete by applying an alternating current from a pair of electrodes to a container containing the steel fiber concrete before hardening, the previously known impedance and the steel fiber of the steel fiber concrete are measured. The mixing rate can be calculated based on the relationship with the mixing rate of .

Further, in the present invention , the calculating unit calculates the mixing rate by applying the measured impedance value to a relational expression showing the relationship between the steel fiber mixing rate and the impedance set in advance. may be configured to

According to the present invention, the relationship between the impedance and the steel fiber mixing ratio of the steel fiber concrete is obtained in advance by a predetermined relational expression, so that the steel fiber content can be determined simply by measuring the impedance of the steel fiber concrete before hardening. A mixing rate can be calculated.

The present invention is a fiber amount measuring method for measuring the mixing ratio of steel fibers contained in steel fiber concrete before hardening , wherein the steel fiber concrete is poured into a container containing a pair of electrodes, and the pair of electrodes is measured. contacting the steel fiber concrete; measuring the impedance of the steel fiber concrete based on the value of current having a predetermined frequency characteristic flowing through the pair of electrodes; and measuring the impedance value based on the measured impedance value. and calculating the mixing ratio of the steel fibers in the steel fiber concrete.

According to the present invention, by measuring the impedance of the steel fiber concrete by applying an alternating current from a pair of electrodes to a container containing the steel fiber concrete before hardening, the previously known impedance and the steel fiber of the steel fiber concrete are measured. The mixing rate can be calculated based on the relationship with the mixing rate of .

According to the present invention, the mixing ratio of steel fibers in steel fiber concrete can be calculated by a simple method.

It is a figure which shows the structure of the fiber amount measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of the meter with which a fiber amount measuring apparatus is provided. FIG. 4 is a diagram showing measured values of steel fiber mixing ratio and impedance; FIG. 4 is a diagram showing the relationship between the mixing ratio of steel fibers and impedance. FIG. 4 is a diagram showing a washing-out operation for measuring the mixing ratio of steel fibers;

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the fiber amount measuring apparatus 1 which concerns on this invention, and a fiber amount measuring method is described, referring drawings. The fiber amount measuring device 1 measures the mixing rate of steel fibers contained in the steel fiber concrete S before hardening. Steel fibers are metallic fibrous chips used to reinforce concrete. The steel fibers are processed such that they are formed into a corrugated shape so as to be entwined with the concrete after hardening.

As shown in FIG. 1, the fiber amount measuring device 1 includes a container 2 for containing steel fiber concrete S before hardening, a pair of electrodes 5 provided in the container 2, and a pair of electrodes 5. and a meter 10 electrically connected.

The storage container 2 is, for example, a bottomed container made of a non-conductive material such as vinyl chloride. The storage container 2 is formed with an upper opening. The container 2 is, for example, circular. The container 2 may be formed in a rectangular shape. The circular storage container 2 is formed so that its diameter is three times or more the length of the steel fibers mixed in the concrete. The rectangular storage container 2 is formed so that the length of one side is three times or more the length of the steel fibers mixed in the concrete. A pair of electrodes 5 are provided on opposite side walls of the container 2 .

The electrode 5 is formed in, for example, a rectangular plate-like body. Electrode 5 may be formed in a circular shape. The electrodes 5 are desirably made of the same conductive material as the steel fiber, such as metal, but may be made of any conductive material. In the case of a rectangle, the electrode 5 is formed so that the length of one side thereof is at least three times the length of the mixed steel fiber. The electrode 5 is formed to have a length that is at least three times as long as the length of the steel fiber in which the length of the diameter is mixed in the case of a circular shape. A meter 10 is connected to the pair of electrodes 5 via a lead wire W. As shown in FIG.

The meter 10 is a device for calculating the impedance value of the steel fiber concrete S inside the container 2 . Meter 10 may be, for example, a commercially available LCR meter. An LCR meter is a device that measures parameters such as inductance, capacitance, resistance, impedance, etc., of components that generally constitute an electronic circuit using alternating current.

Meter 10 is electrically connected to a pair of electrodes 5 . The meter 10 is configured so as to contact a specimen (steel fiber concrete S) to be measured with two terminals consisting of a pair of electrodes 5 . The meter 10 may be realized not only by an LCR meter, but also by connecting a measurement interface to a personal computer, a tablet terminal, a smartphone, or the like, or by combining an LCR meter and the above terminal.

As shown in FIG. 2, the meter 10 includes, for example, a power supply unit 11 for applying current to the test piece, obtains measured values of the current and voltage applied to the test piece, and based on the obtained measured values, A measurement unit 12 for calculating the impedance of the test piece, a calculation unit 13 for calculating the mixing ratio of steel fibers in the test piece based on the calculated impedance, a storage unit 14 for storing measured values and various data, and calculation results. and a display unit 15 for displaying.

The power supply unit 11 serves as the power supply for the meter 10, is connected to the pair of electrodes 5 via the conducting wire W, and has a predetermined frequency characteristic (for example, 1 [kHz]) in the steel fiber concrete S in the container 2. Energize current. The measurement unit 12 acquires data on the current value and the voltage value of the current supplied by the power supply unit 11 . The measurement unit 12 stores the acquired data in the storage unit 14 . The measurement unit 12 reads the data from the storage unit 14 and calculates the impedance of the steel fiber concrete S based on each data. Impedance is calculated, for example, using a general AC impedance measurement technique.

The calculation unit 13 calculates the mixing ratio of steel fibers in the steel fiber concrete S based on the calculated impedance value. The inclusion rate is the ratio of the volume of steel fibers to the volume of the container. Detailed content of the calculation method of the calculation unit 13 will be described later.

The computing unit 13 is implemented by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of these components are hardware (circuit part; circuitry) or by cooperation of software and hardware.

The program may be stored in advance in a storage device such as a HDD (Hard Disk Drive) or flash memory, or may be stored in a removable storage medium such as a DVD or CD-ROM. It may be installed by being worn. Alternatively, the computer program may be distributed to a computer via a communication line, and the computer receiving the distribution may execute the program.

The storage unit 14 stores the data of each value acquired by the measurement unit 12 and the data of each parameter of the later-described mathematical expression used by the measurement unit 12 to calculate the impedance. The storage unit 14 is implemented by, for example, a storage device such as flash memory or HDD. The display unit 15 displays the computation results of the computation unit 13 . A display device such as a liquid crystal display, an LED display, an organic EL display, or the like is used for the display unit 15 .

ここで、Ｒは繊維補強コンクリートのインピーダンス、ｒは鋼繊維の混入率である。式（１）はインピーダンスと混入率との関係を示す近似式の一例であり、インピーダンスと混入率との関係を表せるのであればどのような式を用いてもよい。 Next, the calculation method of the calculation unit 13 will be described. The relationship between the steel fiber mixing ratio of the steel fiber concrete S and the impedance is shown by the formula (1). By setting the coefficients (parameters) a, b, and c of the formula (1), the mixing ratio of steel fibers in the steel fiber concrete S arbitrarily blended can be calculated.

where R is the impedance of the fiber reinforced concrete and r is the steel fiber content. Formula (1) is an example of an approximation formula showing the relationship between impedance and mixing ratio, and any formula may be used as long as it can express the relationship between impedance and mixing ratio.

Eight levels of fiber inclusion rates of 0.0%, 0.3%, 0.5%, 0.7%, 0.9%, 1.1%, and 1.5% in a certain formulation A concrete Steel fibers are added to the mixture and stirred sufficiently. Then, a pair of electrodes 5 are brought into contact with the steel fiber concrete CA in the container 2, and the impedance of each of the eight test pieces of the steel fiber concrete S is measured.

FIG. 3 shows measured values indicating the relationship between the steel fiber mixing ratio and the impedance, which were obtained from measurements performed in advance. The measurement for confirming the mixing ratio of steel fibers is carried out, for example, by washing out steel fiber concrete specimens as described later (see FIG. 5). As the mixing ratio of steel fibers increases, the increase in steel fibers makes it easier for current to flow, and the impedance of the steel fiber concrete S decreases. The coefficients a, b, and c in equation (1) are determined based on the results obtained from the measurements. For example, when the determined coefficients are applied to the equation (1), the relationship between the steel fiber mixing ratio r _A and the impedance R _A of the steel fiber concrete S produced by the formulation A is expressed by the equation (2) is indicated by

Similarly, in the case of producing steel fiber concrete S with concrete of other formulations, a plurality of specimens of steel fiber concrete S are produced in advance at a predetermined mixing ratio, and the impedance of each specimen is measured to obtain the formula (1). By determining each coefficient, the relational expression (2) between the steel fiber mixing ratio of the steel fiber concrete S and the impedance is obtained.

As shown in FIG. 4, the formula (2) represented by the measured values agrees with the relationship between the steel fiber mixing ratio and the impedance shown by the formula (1). Based on the calculated formula (2), even if the steel fiber mixing rate of the steel fiber concrete S produced by the mix A is unknown, the steel fiber mixing rate can be calculated. For example, the storage container 2 is filled with a pre-hardened steel fiber concrete S sample having an unknown steel fiber mixing ratio. Next, a current of a predetermined frequency is applied from the meter 10 to the specimen through the pair of electrodes 5 in the container 2 .

At this time, the measurement unit 12 acquires the current value and the voltage value. The measurement unit 12 calculates the impedance _RA of the specimen based on the acquired current value and voltage value. Based on the calculated impedance value, the calculation unit 13 refers to the equation (2) to calculate the steel fiber mixing ratio r _A of the specimen.

As shown in FIG. 5, in order to verify the calculated contamination rate, the sample was washed out. First, after measuring the weight and volume of the specimen, the specimen is placed on the sieve. Water is run over the sieve to wash away the concrete in the specimen, and the steel fibers contained in the specimen are taken out. After drying the removed steel fibers, the weight and density are measured. Based on the measured weight and density of the steel fibers and the volume of the specimen, the steel fiber mixing rate is calculated. The measured value of the mixing rate and the calculated value of the mixing rate based on the impedance substantially match (see FIG. 4).

As described above, according to the fiber amount measuring device 1, the amount of steel fibers mixed in the steel fiber reinforced concrete can be calculated by a simple method by measuring the impedance of the specimen before hardening at the site. According to the fiber amount measuring device 1, the mixed amount of steel fibers can be calculated regardless of the type of steel fibers. According to the fiber amount measuring device 1, compared with the conventional method of actually measuring the amount of mixed fiber by washing work, problems such as the labor of washing the sample at the site, the discharge of muddy water, and the concern of fiber outflow are solved, and it is easy to use. In addition, the mixing rate of steel fibers in the steel fiber concrete S can be calculated without discharging turbid water.

An embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the scope of the invention.

1 Fiber amount measuring device 2 Container 5 Electrode 10 Meter 11 Power supply unit 12 Measurement unit 13 Calculation unit 14 Storage unit 15 Display unit S Steel fiber concrete W Lead wire

Claims (3)

A fiber amount measuring device for measuring the mixing ratio of steel fibers contained in steel fiber concrete before hardening,
a pair of electrodes;
a container containing the pair of electrodes and the steel fiber concrete;
a measuring unit that measures the impedance of the steel fiber concrete based on the value of the current flowing through the pair of electrodes and having predetermined frequency characteristics;
a calculation unit that calculates the mixing ratio of the steel fiber in the steel fiber concrete based on the impedance value measured by the measurement unit,
Fiber quantity measuring device. The calculation unit calculates the mixing ratio by applying the measured impedance value to a relational expression showing the relationship between the steel fiber mixing ratio and the impedance set in advance.
The fiber amount measuring device according to claim 1. A fiber amount measuring method for measuring the mixing ratio of steel fibers contained in steel fiber concrete before hardening, comprising:
a step of pouring the steel fiber concrete into a container containing a pair of electrodes to bring the pair of electrodes into contact with the steel fiber concrete;
measuring the impedance of the steel fiber concrete based on the value of the current flowing through the pair of electrodes and having predetermined frequency characteristics;
and calculating the mixing rate of the steel fiber in the steel fiber concrete based on the measured impedance value,
Fiber content measurement method.

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