JPS61274209A - Apparatus for detecting omission of concrete - Google Patents

Abstract

PURPOSE:To make it possible to detect the presence of an omission part prior to the solidification of concrete, by utilizing that a microwave is transmitted through a panel such as plywood and reflected from the surface of concrete not hardened. CONSTITUTION:A microwave is transmitted through a wooden panel P and reflected from the layer of concrete C not hardened. Therefore, a standing wave W is generated in a wave guide 2 and an antenna 3 by the synthesis of the reflected wave and a radiation wave and the imaginary reflective surface Ro of the standing wave W comes to the surface present in the vicinity of the boundary of the wooden panel P and the concrete C. When the position of a standing wave detection part 4 is set to the voltage min. point position Mo of the standing wave, the current flowing to a detection diode 7 comes to a definite value Io. When the state of the standing wave W in such a case that there is no void inside the panel P is set to a reference state, the state of the standing wave W changes with respect to said reference state if there is a void inside the panel P and a point other than the voltage min. point M corresponds to a standing wave detection part 4. By this method, a detection current exceeds the definite value Io and is displayed on a display part 5.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is mainly used at the construction site of buildings and other structures when ready-mixed concrete is poured into a formwork made of plywood called a concrete panel. The present invention relates to a detection device for detecting a defective part of concrete that occurs on the inner surface of a panel.

<Prior art> The frame construction of a concrete structure involves formwork work for walls, floors, columns, and beams, and as mentioned above, the formwork work is performed using panels made of panels such as plywood. This is done by pouring fresh concrete into formwork.

By the way, when pouring the fresh concrete, depending on the flow of the fresh concrete, voids or missing portions that are not filled with concrete may occur on the inner surface of the panel.

Conventionally, there was no way to detect this defect from the outside of the panel, and the defect was discovered only after the concrete had hardened and the plywood was removed.

<Problems to be solved by the invention> If such a defective part is found after the concrete has hardened, the defective part must be repaired and then exterior work such as tiling must be carried out, which requires a lot of time and effort for the exterior work. It takes.

If such defective parts of the concrete can be discovered before the concrete hardens, the defective parts can be eliminated by means such as applying vibration to the fresh concrete or stirring the ready-mixed concrete.
It is possible to shorten the construction period by eliminating the need for troublesome repair work on the exterior.

From this point of view, the present invention makes it possible to detect missing parts of concrete from the outside of panels constituting formwork, especially wooden panels, so that the missing parts can be eliminated during pouring of fresh concrete. The purpose is to

Means for Solving the Problems> The present invention was made by focusing on the fact that microwaves pass through panels such as plywood and are reflected on the surface of fresh concrete. In order to achieve this, a microwave oscillator, a microwave antenna provided to the microwave oscillator via a waveguide, a standing wave detector projecting into the middle of the waveguide, and A device for detecting defects in concrete, etc. was constructed by including a display unit that displays the status of detection of standing waves by the standing wave detection unit.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings. FIG. 1 is a block diagram of a concrete defect detection device according to the present invention, which includes a microwave oscillator 1, a waveguide 2, a microwave antenna 3, and a standing wave detection section 4. , and a display section 5.

The microwave oscillator l may be one that continuously oscillates microwaves at a frequency that can pass through the wooden panel with attenuation below a predetermined allowable attenuation amount, and according to experiments, 10G
A gun-type microwave oscillator in the Hz band may be used. This microwave oscillator l is attached to one end of the waveguide 2,
A microwave antenna 3 is attached to the other end of the waveguide 2.

Reference numeral 6 is a power source for the microwave oscillator l. The microwave antenna 3 is intended to be brought into contact with the outer surface of the panel, which is the detection target area, and is an electromagnetic horn in this embodiment. The standing wave detection section 4 is a rod-shaped conductor, and is provided in the middle of the waveguide 2, with its tip end protruding into the tube. This standing wave detection section 4 is made movable along the length direction of the waveguide 2 by means such as being provided in a slit formed in the length direction of the waveguide 2 . The standing wave detection current detected by the standing wave detection section 4 is detected by the detection diode 7,
The signal is amplified to a required level by an amplifier 8 in the next stage, and then supplied to the display section 5. The amplifier 8 may perform modulation at approximately I KHz. The display unit 5 includes a meter 9 and an indicator lamp 1.
It consists of 0.

In the above configuration, if the microwave oscillator l oscillates a microwave with the tip of the antenna 3 in contact with the outer surface of the wooden panel P, this microwave will pass through the wooden panel P, but the ready-mixed concrete C The fresh concrete C can be regarded as a reflector for microwaves. Therefore, inside the waveguide 2 and antenna 3, as shown in FIG. 2(A),
A standing wave W is generated by combining the reflected wave and the radiated wave, and a virtual reflection surface Ro of this standing wave W is a surface near the boundary between the wooden panel P and the concrete C. and,
The position of the standing wave detector 4 is set to the minimum voltage point position Mo of the standing wave.
When set to , the current flowing through the detection diode 7 becomes equal to or less than a constant value Io.

Therefore, if the state of the standing wave W in the case where there is no air gap inside the panel P as shown in FIG. On the other hand, the state of the standing wave W changes.

That is, as shown in FIG. 2(B), when a gap S exists between the panel P and the concrete C, the virtual reflection surface R of microwaves is changed from the virtual reflection surface Ro(
(hereinafter referred to as the reference reflective surface), it deviates to Fugo. In this case, it is deviated in the direction away from the antenna 3. When the virtual reflective surface R shifts in this manner, the voltage minimum point position M of the standing wave W also shifts, and the standing wave detection section 4 corresponds to a point other than the voltage minimum point M. As a result, the detected current exceeds the above-mentioned constant value io, and this is displayed on the display section 5.

However, even if the virtual reflecting surface R of the air gap S is displaced, the minimum voltage point M of the standing wave W may face the standing wave detection section 4. This means that the distance between the position of the displaced virtual reflecting surface R and the position of the reference reflecting surface RO is (n/2) of the wavelength of the standing wave W.
).

However, before reaching the gap S, the area around the gap S must be searched, and when the surrounding area is searched, a point other than the minimum voltage point M of the standing wave 4, at which time the detected current exceeds the constant value 1o, so that the presence of the gap S is detected.

Furthermore, as shown in FIG. 2(C), if the air gap S is larger than the opening of the antenna 3, the amount of microwave leakage will increase, the appearance will be higher, and the amplitude of the standing wave W will be lower. becomes smaller,
Even if the position of the minimum voltage point M is on the standing wave detector 4, the detected current exceeds the constant value IO, and the presence of the gap S is thereby detected. Even when the gap S extends to the back panel P and the concrete layer drops back and forth in this area, the amount of microwave leakage increases as well, so that the detected current exceeds the constant value 1o.

In the above explanation, the standing wave detector 4 detects the minimum voltage point M of the standing wave W, but even if the maximum voltage point is detected, the void S in the concrete C can be detected in the same way. sell.

In addition, in the above explanation, the operation when detecting the void S in the ready-mixed concrete C was described, but by the same operation,
It is possible to detect the presence of water pipes, gas pipes, heating and cooling pipes, etc. hidden behind exterior panels such as wooden panels and plastic panels.

Note that in order to increase the stability of the microwave oscillator 1, an isolator may be interposed between the microwave oscillator 1 and the waveguide 2. In addition, by connecting the waveguide 2 and antenna 3 with a flexible coaxial cable via a converter, the antenna 3 can be freely swung relative to the waveguide 2, making it easier to handle during detection. can be facilitated. Furthermore, by providing the antenna 3 with a matching element for canceling reflected waves from the panel P, the detection sensitivity of the standing wave W can be improved. As the antenna 3, in addition to an electromagnetic horn, various antennas can be used, such as a slit antenna in which a slit of a desired size is formed in a metal plate that is the end plate of the waveguide 2.

Furthermore, although a conductor was used as the standing wave detection section 4 in the above embodiment, a detection diode is arranged inside the waveguide 2 with each lead part thereof oriented in the same direction as the electric field. The detector may serve both as a detection section and a detection section.

Furthermore, although the standing wave detection section 4 is movable along the length direction of the waveguide 2 as described above, a phase adjuster is provided between the standing wave detection section 4 and the antenna 3. This phase adjuster may be adapted to accommodate deviations in the minimum voltage point position M due to differences in the thickness of the panel P. As the phase adjuster, for example, there is a knife-shaped dielectric inserted into a slit formed in the waveguide 2.

<Effects of the Invention> As described above, according to the present invention, the standing waves generated inside the waveguide and antenna vary depending on the condition of the ready-mixed concrete inside the panel such as plywood, and this variation is detected by the standing wave detection part and displayed on the display part, so it is possible to detect the condition of the fresh concrete inside the panel from the outside of the panel, that is, the presence or absence of a defective part. It is possible to take effective measures to solve this problem, and the troublesome exterior work that was conventionally done after concrete hardening is no longer necessary.

In addition, since the structure is simple, the entire device can be made compact and portable, allowing it to be used even in places with poor footing at construction sites.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 (A) (B)
")CC) are explanatory diagrams of the operating states. ■...Microwave oscillator, 2...Waveguide, 3...
Microwave antenna, 4... Standing wave detection unit, 5...
・Display section.

Claims (1)

[Claims] (1) A microwave oscillator, a microwave antenna provided to the microwave oscillator via a waveguide, a standing wave detector projecting into the middle of the waveguide, and a standing wave detector provided in the middle of the waveguide; What is claimed is: 1. A detection device for concrete defects, etc., comprising: a display section that displays the detection status of standing waves by the wave detection section.