JPS5942828B2 - Cavity exploration device in concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for detecting cavities in concrete that can check the degree of filling of concrete placed inside the formwork from outside the formwork before it hardens. be.

In recent years, alkali-resistant glass fiber reinforced cement (F, R, C) has been used as formwork (shedding boards) in concrete works.
Concrete surface finishing materials or finishes, such as veneer, F, R, and C sprayed onto wood wool cement boards or composite boards of wood wool cement boards and heat insulating materials, composite boards of heat insulating materials and plywood, etc. A construction method has been proposed that uses a base material to eliminate the need for dismantling and removing formwork after concrete is poured.

Since this construction method does not involve dismantling and removing the formwork, it can be expected to have great advantages in terms of simplifying the construction process, shortening the construction period, and reducing construction costs. Since it is not possible to visually check the presence or absence of the filling, there is a risk that the construction will be completed without being repaired even though the degree of filling is poor, and this is a bottleneck preventing the spread of this method. By the way, even in a fluid state before hardening is complete, the concrete poured inside the formwork has a natural frequency that corresponds to the degree of hardening, just like in the case of soft ground. If there is a cavity in the concrete, the cavity exhibits different natural frequencies due to air compression waves.

That is, while the former is a vibration of a solid, the latter is a vibration of a gas, and there is a considerable difference in the frequency of the vibrations.

Therefore, when an impact is applied to concrete from outside the formwork, there is a considerable difference in the sound (frequency of vibration) generated between a solid part of the concrete and a part with hollow parts.

Therefore, the present invention makes use of the above-mentioned phenomenon to explore cavities in concrete from outside the formwork, and refills the discovered cavities (areas with insufficient filling) to form dense concrete. The object of the present invention is to provide an apparatus for detecting cavities in concrete, which enables the above-mentioned construction method to be widely used.

In other words, a nondestructive strength testing method has been proposed for a long time that measures the compressive strength of concrete by directly applying an impact to hardened concrete and measuring the vibration frequency and sound propagation velocity of the concrete. It is difficult to apply the method to the exploration of cavities surrounded by concrete and formwork.

This is because this method measures the vibration of solid objects, and it also captures the faint vibrations caused by slight impacts.
They are inherently susceptible to vibrations caused by external factors. on the other hand,
Cavity exploration in a concrete body where the formwork is used as a finishing material or finishing base material for the concrete surface can be performed while the poured concrete has not yet completely hardened, meaning that the cavity can be refilled with concrete. It has no practical significance unless it is carried out at the appropriate time, and therefore, it is extremely necessary to carry out this work in parallel with the concrete pouring that is being carried out in the adjacent construction area.

Therefore, in an environment such as during concrete pouring,
In addition to the vibration caused by the concrete pouring work itself in the adjacent construction area, there is also an extremely large amount of vibration caused by the running of heavy machinery, the walking of workers, the handling of materials, etc., and the effects of these external vibrations cannot be eliminated.

Also, as seen in Utility Model Application Publication No. 52-10383,
There is also known a device that strikes a wall tile and detects peeling of the wall tile based on the sound of the strike.

This device prevents the concrete and tiles from coming into contact with each other (i.e., creating a cavity on the back side of the tile).
Since separation is detected by capturing sounds that vary considerably from part to part, the influence of vibrations caused by external causes is small compared to the method of measuring the propagation velocity of solid vibrations described above. In practice, it is difficult to use this method to detect cavities inside formwork during concrete pouring.
In other words, this device was devised with the assumption that it would be used in buildings that have been completed for many years. The structure is such that a vertical rod is attached so as to be movable up and down, and a means for hitting the wall tiles and a sensor for catching the sound of hitting are attached to the lower end of the vertical rod in an exposed manner. Therefore, during the construction process where concrete is poured sequentially from the lower floor to the upper floor, not only for the inner walls, beams, and columns, but also for the outer wall, there are parts of the wall that serve as guide rails for the trolley. The device cannot be set.

Furthermore, even if the device is set using some kind of support member, the impact means and the sensor are attached to the lower end of the vertical rod so that they are exposed to the outside, so the impact of noise generated during construction can be avoided. Not only is it easy to receive vibrations, but the vibration of the vertical rod caused by the operation of the striking means is likely to affect the sensor. From the above points of view, the present invention is a simple method that can be applied to any of external walls, internal walls, beams, and columns.
We have developed a device that can explore cavities from outside the formwork before the contours harden, without being affected by noise or vibrations caused by the means of striking the formwork.

That is, the cavity exploration device during contouring according to the present invention includes a barrel-shaped portion in which a striking rod is inserted so as to be movable in the axial direction, and a grip portion. A bowl-shaped member made of an elastic material that can be closely attached to the outer surface of the formwork and that also serves as a surface finishing material or finishing base material and has vibration-proofing and sound-insulating effects is provided, and faces the internal space of the bowl-shaped member. A sensor for sensing vibrations of the air in the internal space caused by hitting the outer surface of the formwork with the striking rod is provided in a state where it is elastically supported by the bowl-shaped member, and the sensor has a It is connected to a meter that determines the presence or absence of a cavity surrounded by concrete and formwork based on the output signal.

Examples of the present invention will be described below.

First, a method for detecting cavities in concrete will be explained step by step.

() Concrete surface finishing material or finishing base material is applied to the formwork (
Before the concrete has completely hardened, that is, while it is possible to refill the defective areas, a slight impact is applied to the outside of the formwork to loosen the concrete and the formwork. Air compression waves are generated in the cavity surrounded by the frame, and the formwork is vibrated by the internal vibrations caused by the compression waves.

() The vibration of the formwork described above is captured as vibration (sound) using the surrounding air as a medium.

That is, a highly sensitive microphone senses vibrations in the external air caused by vibrations of the formwork due to compressional waves in the air in the cavity. (1) While measuring the frequency of the output signal from the above-mentioned microphone, similar frequencies obtained from multiple pieces of concrete with different filling degrees are experimentally obtained in advance as data, and this data and the above-mentioned measurement frequency are obtained experimentally in advance. Based on this, the degree of concrete filling (presence or absence of a cavity) is determined from the outside of the formwork.

(5) If the existence of a cavity is detected, the cavity is refilled with concrete, thereby obtaining a solid concrete body without dismantling and removing the formwork.

Next, an embodiment of a cavity exploration device in concrete that can be suitably used in the above method will be described based on the drawings.

The drawings show an example of a device for detecting cavities in concrete, where A is poured concrete and B is a formwork that also serves as a concrete surface finishing material or a finishing base material.

1 includes a barrel-shaped portion 2, a grip portion 3, a trigger 4, etc.,
The main body of the exploration device is portable with one hand, and the barrel-shaped portion 2 is biased to slide forward by a compression spring 5, and by pulling the knob 6a at the rear end backward against the compression spring 5. , trigger 4 (or a member interlocked therewith).

) A striking rod 6 having a locking portion 6b that engages with a part of the rod is inserted so as to penetrate from the front and back. Also, the barrel-shaped part 2
A bowl-shaped member 7 made of an elastic material such as rubber that has a vibration-proofing effect and a sound-insulating effect is attached to the tip of the mold B, and the trigger 4 can be pulled while the bowl-shaped member 7 is in close contact with the outer surface of the formwork B. According to
The tip of the striking rod 6 applies a slight impact to the outer surface of the formwork B facing the internal space S of the bowl-shaped member 7, and this impact generates an elastic wave accompanied by the natural vibration of the concrete A. If there is a cavity in the concrete A, the construction is such that air compression waves are generated in the cavity. When applying the impact, the compression spring 5 is used to prevent the impact rod 6 from repeatedly colliding against the outer surface of the formwork B in small increments due to the rebound of the outer surface of the formwork B and the force of the compression spring 5. When the compression spring 5 is fully extended, a small gap is formed between the tip of the striking rod 6 and the outer surface of the formwork B, and after the compression spring 5 is fully extended, the striking rod 6 is forced to release the compression spring due to inertia. It is desirable that the molding member move forward against the force of 5, collide with the outer surface of the formwork B, and then come to rest at a position away from the surface.

8 is a sensor that detects the vibration of the formwork due to air compression waves generated in the cavity as vibration using air as a medium (vibration of the air inside the bowl-shaped member), and specifically, it is a sensor with high sensitivity. Microphones are used.

As shown in the figure, this sensor 8 is provided in a state where it is elastically supported by a bowl-shaped member 7 so as to avoid picking up extra vibrations caused by sliding of the striking rod 6, swinging of the trigger 4, etc. as much as possible. ing. 9 is an amplifier for the output signal of the sensor 8; 10 is a frequency analyzer for comparing and analyzing the amplified output signal with data stored in advance; 11 is a filling degree indicator; , 11 is also configured to be portable and is electrically connected to the sensor 8.

13 is a spring force adjustment nut, and 14 is a position adjustment tube for the striking rod 6.

By using the above-mentioned device, by pressing the bowl-shaped member 7 against a location on the formwork B and pulling the trigger 4, a cavity in the concrete can be explored.

The device for detecting cavities in concrete according to the present invention has the above-mentioned configuration, and has a bowl-shaped member made of an elastic material with vibration-proofing and sound-insulating effects on the outer surface of the formwork, which also serves as a finishing material for the concrete surface or a finishing base material. The outer surface of the formwork is struck in the inner space of the bowl-shaped member isolated from the outside, and the air vibrations in the inner space of the bowl-shaped member are transmitted to a sensor elastically supported by the bowl-shaped member. In order to detect cavities surrounded by concrete and formwork, the system detects vibrations caused by concrete pouring in adjacent areas, vibrations caused by heavy machinery running, workers walking, material handling, etc. during construction. The cavity can be explored without being influenced by vibrations and noise caused by various external factors, and without the vibration of the exploration device body caused by the operation of the striking rod having an adverse effect on the sensor. Moreover, it can be easily done by grasping the grip part of the exploration device body with one hand, pressing the bowl-shaped member against any position on the outside of the formwork, and applying a striking force to the outside surface of the formwork facing the internal space of the bowl-shaped member. Cavities can be searched by operation, including outer walls, inner walls, beams,
It can be applied to any pillar.

In addition, the bowl-shaped member is made of an elastic material, and has the role of isolating the impact area on the outer surface of the formwork and the sensor from the outside to provide vibration and sound insulation, as well as preventing vibration propagation from the main body of the exploration device to the sensor. In order to fulfill the role of a vibration device, the structure of the device is simplified by using multiple members.

[Brief explanation of drawings]

The drawing is a configuration diagram of a cavity exploration device in concrete showing an embodiment of the present invention. A: Concrete, B: Formwork, S
...Inner space, 1...Exploration device main body,
2... Barrel-shaped part, 3... Grip part,
6...Blowing stick, 7... Bowl-shaped part, 8.
...sensor, 12...meter.

Claims (1)

[Claims] 1. At the tip of the gun barrel part 2 of the exploration device body 1, which is equipped with a gun barrel part 2 into which a striking rod 6 is movably inserted in the axial direction, and a grip part 3, there is provided a material that also serves as a concrete surface finishing material or a finishing base material. A bowl-shaped member 7 made of an elastic material that can be brought into close contact with the outer surface of the formwork B and has a vibration-proofing effect and a sound-insulating effect is provided, and the outer surface of the formwork B facing the internal space S of the bowl-shaped member 7 is provided. A sensor 8 for sensing the vibration of the air in the internal space S caused by hitting with the striking rod 6 is provided in a state where it is elastically supported by the bowl-shaped member 7, and the sensor 8 is provided with: This is a cavity exploration device in concrete, which is connected to an instrument 12 that determines the presence or absence of a cavity surrounded by concrete and formwork based on the output signal.