JP2001337074A - Device for determining compaction of fresh concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the degree of compaction inside concrete simultaneously with compaction work. SOLUTION: This device for determining the compaction of fresh concrete is comprised of ultrasonic wave transmitting/receiving means 5 and 6 arranged outside an oscillating tube 2 which constitutes a vibrator 1, a reference setting means 12 in which output according to the energy attenuation ratio of a wave reception signal to a wave transmission signal when concrete is compacted is previously set, a comparing means 11 to compare the output of the wave receiving means 6 with the output of the setting means 12 to output a compaction completion signal when the output of the wave receiving means 6 is in a state equal to or larger than the value set in the setting means 12, and a display means 14 to receive the output from the comparing means 11 to display the completion of the compaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for judging compaction of fresh concrete.

[0002]

2. Description of the Related Art Fresh concrete that has just been cast is often in a state of being entrapped with air. Immediately after casting, compacting works to remove bubbles and make the concrete denser and more uniform. Generally, in this compaction work, the vibrator is inserted into the concrete by hand, heavy equipment or an automated machine and forcedly vibrated to discharge the air bubbles trapped inside, thereby achieving a uniform and dense material distribution. ing. Judgment of the concrete state in this compaction work relies exclusively on visual confirmation and feeling by workers,
At present, it is roughly determined that the compaction has been completed based on the work time, and the work has been completed.

[0003]

However, in actuality, there are cases where a hollow portion called a nest after demolding and a portion where a large amount of coarse aggregate called a bean board or junka is distributed are found. Since such a portion causes a partial weakness, it is necessary to remove the corresponding portion and fill it with a repair material such as concrete, mortar, epoxy, or the like.

[0004] Therefore, if the compaction is insufficient, partial repair work must be performed, extra work such as additional work must be performed, and a problem also arises in the integrity of these repaired parts and surrounding parts. Was.

[0005] By the way, ultrasonic waves have the property of being reflected between materials having greatly different acoustic impedances and not propagating through the materials. Since the acoustic impedance of fresh concrete is significantly higher than the acoustic impedance of air, when the amount of air entrained in the fresh concrete is large, the scattering increases, and the energy reaching the receiver decreases. Conversely, if the air bubbles in the concrete decrease, the received energy increases and the state becomes steady.

The present invention has been made based on the above-mentioned characteristics of ultrasonic waves. The object of the present invention is to add an ultrasonic sensor function to a vibrator for compaction so that concrete can be produced simultaneously with compaction work. It is an object of the present invention to provide a fresh concrete compaction judging device capable of accurately detecting an internal compaction degree.

[0007]

In order to achieve the above object, the present invention provides an ultrasonic wave transmitting / receiving means disposed inside or outside a vibrating tube constituting a vibrator, and an ultrasonic wave transmitting / receiving means for transmitting a signal at the time of compacting concrete. The reference setting means presetting the output according to the energy attenuation ratio of the received signal, the output of the receiving means and the output of the setting means are compared, and the output of the receiving means is the same as the value set in the setting means. In this case, the comparison means outputs a compaction end signal in a state of exceeding, and a display means for receiving the output from the comparison means and displaying the end of compaction. Therefore, in the present invention, the compacted state of fresh concrete can be accurately and accurately determined by utilizing the above-described properties of the ultrasonic wave.

Further, the comparing means in the present invention may output a compaction end signal when the output level of the wave receiving means is a steady output for a certain period of time. This is suitable for the end determination at a place where the compacting conditions are different.

[0009]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows a vibrator to which the present invention is applied. The vibrator 1 basically includes a vibrator driving unit 3 such as a motor and an eccentric pendulum inside a slender hollow vibrating cylinder 2 having a closed end, and vibrates the vibrating cylinder 2 by driving the driving unit 3. If it is of the size, it can be manually operated, if it is medium or large, it can be attached to the tip of heavy equipment such as a shovel car, etc. There are various sizes and operation methods.

In the present invention, although suitable for any size and operation method, an ultrasonic wave transmitting / receiving section is provided at the tip of the vibrating cylinder 2 in addition to these basic structures. The transmission / reception unit separates the oscillation-side ultrasonic probe 5 and the reception-side ultrasonic probe 6 each having a built-in ultrasonic vibrator inside the outer periphery of the vibrating cylinder 2 in the length direction, and moves the sensor surface thereof. The probes 5 and 6 are attached to the outside, and each of the probes 5 and 6 includes a transmission drive unit 7, a reception amplification unit 8, a time axis unit 9, and a timing thereof arranged outside the vibration tube 2 via a high-frequency cable 4 or the like. Is connected to the synchronization control unit 10 for adjusting The signal output from the receiving amplifier 8 is input to one of the comparators 11. The other input terminal of the comparator 9 is connected to the reference setting unit 12.

The reference setting unit 12 sets in advance the output according to the energy attenuation ratio of the received signal with respect to the transmitted signal during compaction of the concrete. The output from the amplifying unit 8 is compared, and when the output from the amplifying unit 8 is equal to or higher than the reference output, a compaction completion signal is output, and the indicator 14 such as a lamp or a buzzer is operated. When the output from the reception amplification unit 8 is the same for a certain period of time by a timer or the like, a compaction completion signal is output similarly,
The display 14 is operated.

In the above configuration, when the apparatus is turned on to enter the measurement mode, a command signal is transmitted from the synchronous control section 9 several tens of times or more per second. A voltage is generated and transmitted to the transducer in the transmission-side probe 5, which receives an electric pulse and generates mechanical ultrasonic vibration. This vibration is transmitted through the probe 5 and into the fresh concrete.

The ultrasonic pulse transmitted from the transmitting probe 5 propagates through the fresh concrete, and is diffused, scattered, and attenuated. When the attenuated ultrasonic pulse reaches the receiving probe 6, the transducer in the probe is vibrated by the ultrasonic wave, and as a result, the transducer expands and contracts. A high frequency voltage is generated between the two poles in proportion to the intensity of the ultrasonic pulse.

This voltage is amplified by the amplifier 8 and compared with the reference output by the comparator 11. In general, densification of fresh concrete is to eliminate the air entrapped in the fresh concrete and bring the weight of the fresh concrete per unit volume closer to the theoretical weight. On the other hand, ultrasonic waves have the property of being reflected between materials having greatly different acoustic impedances and not propagating through the materials.

That is, the acoustic impedance of fresh concrete is significantly larger than the acoustic impedance of air. Therefore, when the amount of air entrained in the fresh concrete is large, the scattering becomes large, and the receiving side probe 6 The energy that reaches is small. Conversely, if the number of bubbles in the concrete that reflects ultrasonic waves is reduced, the received energy increases.

Therefore, if the received energy in the state where the concrete is densified is measured in advance and this output is set in the setting unit 12 as a reference output, the display unit 14 can display the received energy in a state in which it matches the value. Completion of compaction is output.

In addition, as the compaction of the fresh concrete increases, the ultrasonic wave receiving energy increases, and at a certain value, it is almost in a steady state. Therefore, the comparator 11 determines the steady state by holding the same level of output for a certain time even if it does not match the reference value by the built-in timer function, and thereby the compaction end signal Is output. In this case, it is suitable for the measurement of the degree of compaction at a casting place where conditions such as a casting depth are different.

Incidentally, when high-frequency ultrasonic waves are oscillated on fresh concrete, energy is greatly attenuated, and measurement becomes impossible. Further, the higher the frequency of the ultrasonic wave, the higher its directivity, and when the ultrasonic wave oscillates from the side of the vibrator, the received energy decreases. From experience, it is desirable that the ultrasonic oscillation to the fresh concrete be 1 MHz or less, preferably 50 KHz or less.

Further, when the measurement is performed simultaneously with compaction of the fresh concrete, a filter circuit for removing noise accompanying the measurement of the ultrasonic pulse is provided, or the operation of the vibrator is stopped and the measurement is alternately performed. Can also.

In the above embodiment, the compaction end signal is merely displayed. For example, in the case of an automatic machine for compaction, the work by the vibrator is automatically stopped in response to the end signal. Can be used for a control signal to move to the next compaction location.

[0021]

As is apparent from the above description, according to the fresh concrete compaction judging device of the present invention, an ultrasonic sensor function is added to the compacting vibrator so that the compacting work can be performed simultaneously. With this, the degree of compaction inside the concrete can be accurately detected.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a vibrator provided with a compaction determination device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vibrator 2 Vibration cylinder 5, 6 Ultrasonic wave transmitting / receiving part (5 Oscillation side ultrasonic probe, 6
(Receiver ultrasonic probe) 11 Comparison unit 12 Reference setting unit 14 Display unit

Claims (2)

[Claims] 1. An ultrasonic wave transmitting / receiving means disposed inside or outside a vibrating tube constituting a vibrator, and an output corresponding to an energy attenuation ratio of a received signal to a transmitted signal during compaction of concrete is set in advance. Reference setting means, and comparing means for comparing the output of the receiving means and the output of the setting means, and in a state where the output of the receiving means is equal to or higher than the value set in the setting means, outputs a compaction end signal. Display means for receiving an output from the comparing means and displaying the end of compaction. 2. The fresh concrete according to claim 1, wherein the comparing means outputs a compaction end signal when the output level of the wave receiving means is a steady output for a certain period of time. Compaction judgment device