JPH08333182A - Temperature control in concrete kneading - Google Patents

Abstract

PURPOSE: To enable simple and exact measurement of the temperature of concrete surface without influence of fog by measuring its surface temperature using a radiation thermometer in a non-contact manner, after the concrete mix kneaded in a mixer is discharged in an open air vessel. CONSTITUTION: When an empty cart 5 stops under the concrete outlet of a batcher plant, a position sensor 9 outputs a signal that the cart stops at the prescribed position to a signal processor 12, and concrete is charged from the batcher plant in a bucket 6. When the concrete is charged over a certain level, a level sensor 10 inputs the completion of discharge and a radiation thermometer 11 inputs the surface temperature of the concrete in the bucket 6 through a signal processor 12 to a signal converter 13. After a prescribed time, in a controller 14 to which this temperature information has been inputted, the amount of liquefied gas which is needed for cooling the concrete down to a target temperature is calculated by using the above temperature information as well as other routine informations. Then, the calculated result is outputted to a discharge amount setter 15, which actuates a control valve 16 to charge the needed amount of liquefied gas into a mixer 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a concrete cooling temperature when a low temperature liquefied gas such as liquid nitrogen is brought into contact with concrete being mixed to obtain a cooled concrete kneaded product.

[0002]

2. Description of the Related Art Among the cooling techniques of concrete for preventing temperature cracking of mass concrete, etc., as a pre-cooling method for cooling the concrete before placing, contacting the concrete being mixed with a low temperature liquefied gas such as liquid nitrogen. There is known a method of making it possible, for example, JP-A-62-1460.
3, Japanese Patent Laid-Open No. 63-4169, Japanese Utility Model Publication 2-5.
4506-7 and the like describe a precooling method for concrete with liquid nitrogen. It has also been proposed to use liquid carbon dioxide as a cooling medium instead of liquid nitrogen. In the present specification, liquid nitrogen, liquid carbon dioxide gas and the like used for such precooling of concrete are simply referred to as “liquefied gas”.

Conventionally, when a liquefied gas is supplied into a mixer such as a batcher plant (normally, the liquefied gas is supplied into the mixer in a liquid state), a tentative standard is used to determine the amount of the liquefied gas to be supplied. Cooling unit of liquefied gas required to cool concrete, namely "concrete 1m
"The amount (weight) of liquefied gas required to cool ³ ° C by 1 ° C" is experimentally obtained, and this cooling intensity is multiplied by the kneading amount of one batch and the required temperature drop amount to determine manually. Was there.

FIG. 1 shows the measured values of the kneading temperature on a certain day when precooling was performed by determining the liquid nitrogen input amount from the cooling unit in a batcher plant at a dam construction site. It is a thing. Small fluctuations (waves) in the curve indicate changes in the kneading temperature for each batch.
The type and amount of materials to be fed to the batcher plant are almost constant, but since the operation started at 8:00 am, the kneading temperature rises slowly with the passage of time, and the target kneading temperature rises toward the daytime. It exceeds the value. The reason for this is that there are too many fluctuation factors based on environmental changes such as the amount of solar radiation, water temperature, air temperature, material temperature, equipment temperature, and waiting time.
Empirical methods have shown that it is difficult to control the kneading temperature accurately.

As described above, the cooling intensity varies depending on the temperature of each material and the amount of temperature drop due to the environmental change of the day. Therefore, in order to properly manage the concrete mixing temperature, the temperature should be monitored and input. Since it is necessary to set the amount frequently, work cannot be denied. In addition, at the setting site, it was difficult to assign measurement personnel exclusively to control these temperatures, and it was necessary to automate a series of operations.

[0006]

In automating the kneading temperature control, it is necessary to always accurately grasp the kneading concrete temperature after kneading, regardless of the method of determining the amount of liquefied gas input. is important. However, when trying to continuously and automatically measure the concrete mixing temperature in the batcher plant, there were the following problems.

When the thermocouple or other temperature sensor is brought into contact with the concrete which has been mixed with the liquefied gas to be mixed and then the temperature is measured spot-wise, when the aggregate material, cement or the like, which is a mixed material, is stored Since there is a local temperature difference depending on the temperature history and the degree of mixing, there is a problem that the measurement system is complicated and the processing needs to be performed with a large number of measurement points and the average value of them is used as a representative value. Besides, there is a problem that the mortar adheres to the temperature sensor and equipment inserted in the concrete, which makes the measurement sensitivity dull and requires frequent cleaning to complicate the work.

Further, if the temperature of the concrete that has been kneaded in the mixer is to be measured in a non-contact manner by, for example, a radiation thermometer that detects infrared radiant energy, when liquefied gas is injected into the concrete to cool it. However, since moisture in the air is condensed and a large amount of fog is generated in the mixer, there is a problem that the absorption and emission of moisture in the fog greatly affect the temperature measurement value and the concrete temperature cannot be measured correctly. is there. The present invention aims to solve such a problem.

[0009]

According to the present invention, a liquefied gas is introduced into a concrete being mixed by a mixer of a batcher plant in a controlled amount to knead concrete cooled to a predetermined temperature. After discharging the kneaded material kneaded with the mixer into a container open to the atmosphere, the surface temperature of the concrete kneaded material in this container is measured by a radiation thermometer in a non-contact manner, and the measured temperature of the batch is measured during the next batch mixing. Provided is a concrete kneading temperature control method which is used for calculation of a liquefied gas input amount.

[0010]

In the present invention, the temperature of kneaded concrete is measured using a non-contact type radiation thermometer, and the measurement time is measured from the mixer of the batcher plant to the atmosphere open container,
Specifically, when it is discharged to a truck or concrete carrier. When the concrete is discharged from the mixer into a container open to the atmosphere, there is no mist in the container anymore. Therefore, the radiation thermometer can measure the surface temperature of the kneaded concrete in the container without the influence of fog.

[0011]

EXAMPLE As shown in FIG. 2, in an ordinary batcher plant, a concrete mixer 1 is charged with a kneading material from a charging chute 2. At that time, liquefied gas, for example, liquefied nitrogen, is dripped into the mixer 1 being kneaded in a liquid state through the injection pipe 3, and the amount of the liquefied gas is appropriately adjusted to obtain concrete cooled to a predetermined temperature. This kneading operation is performed in batch (batch) type,
Lower chute 4 for concrete mixed in each batch
Is temporarily stored in the bucket 6 of the carriage 5 for transportation.

At that time, it was found that when the kneaded material was discharged to the trolley bucket 6, the fog generated by the introduction of the liquefied gas did not substantially drift to the upper portion of the trolley. Further, the trolley 5 is set at the concrete receiving position and is stopped at that position for the concrete receiving time. However, before the vehicle starts after the receiving, although the concrete remains in the bucket 6 on the trolley for a short time, Exists. No fog is generated in this stationary time zone, and the measurement time is sufficient for temperature measurement with a radiation thermometer. The measurement position and time do not change for each batch. Therefore, the radiation thermometer enables non-contact and steady-state temperature measurement.

Further, according to the radiation thermometer, even if there is a temperature distribution in the kneaded concrete, the representative temperature of the whole can be measured almost accurately. This will be described below by actual measurement values.

As shown in FIG. 3, while the kneaded concrete 7 remains in the hopper 4, the temperature of the surface layer of the concrete is spotted by a thermocouple sensor at six points at substantially equal intervals. It was measured. Next, after discharging this concrete into the bucket 6 on the trolley, the surface temperature of the concrete 7 is reduced to about 1/3 of the total surface of the concrete.
The measurement was performed with a radiation thermometer having a measurement viewing angle of. These results are shown in comparison with Table 1.

[0015]

[Table 1]

As can be seen from the measurement results in Table 1, the average value of the spot-like measurement results in the hopper and the measurement value in the bucket of the radiation thermometer having a relatively wide measurement viewing angle are in good agreement. There is. Therefore, according to the radiation thermometer,
Even if there is a local temperature distribution in the concrete, its representative value can be measured almost accurately. In this case, it is important to measure the concrete surface in the trolley bucket as wide as possible and to measure with a measurement field of view that does not receive measurement errors around the sides of the bucket, but in the experiments conducted by the inventors, It was found that the representative value of concrete temperature could be measured almost accurately if a measurement field of view covering approximately 1/4 or more of the concrete surface in the trolley bucket could be secured.

That is, the opening of the bucket has various shapes such as a circle, a square, and a rectangle depending on the plant, but any shape having a viewing angle sufficient to cover an area of 1/4 or more of the concrete surface is sufficient. . In order to further improve the measurement accuracy, it is desirable to select the model and installation location of the radiation thermometer so as to secure a wider viewing angle, for example, an area of 1/2 or more.

As described above, according to the present invention, the concrete temperature after kneading can be measured accurately and simply. However, in order to reflect these measurement results in the liquefied gas input amount, the liquefied gas input required It is necessary to calculate the quantity using this measurement result. For this purpose, first of all, the timing for setting the amount of liquefied gas input and the timing for measuring the concrete temperature after mixing must be appropriately selected.

However, in general, at the time when concrete is discharged to a carrier truck, when the truck moves to the setting site,
At the time of kneading with the mixer in the plant, etc., it is not always linked at a constant interval depending on the situation of the casting site and various other factors. Therefore, the timing for performing the above arithmetic processing should be set. Requires complicated signal exchanges with the liquefied gas charging device, the batcher plant operation device, the start and stop of the carrier truck, etc., which complicates automatic control.

Therefore, the present invention has solved these problems by the following equipment configuration. FIG. 4 shows the equipment configuration of this apparatus. Further, FIG. 5 shows a time chart of these devices and output signals of measured values.

In FIG. 4, 9 is a position detection sensor of the truck, 10 is a level sensor of concrete, and 11
Indicates a radiation thermometer. All of these detection signals are transmitted to the signal converter 13 via the signal processor 12.

The position detecting sensor 9 is for detecting whether or not the truck 5 is stopped at a position where concrete is discharged from the batcher plant, and the concrete level sensor 10 is used for concrete in the bucket 6 on the truck. It is for detecting whether or not is filled. When the empty truck 5 stops just below the concrete outlet of the batcher plant, the position detection sensor 9 outputs to the signal processor 12 that the truck has stopped at a predetermined position. After that, when the bucket 6 of the truck is filled with concrete from the batcher plant and the bucket 6 is filled to a certain level or more, the level sensor 10 outputs the concrete loading completion information to the signal processor 12. Then, radiation thermometer 1
1 is a signal processor for the concrete surface temperature in the bucket 1
Output to 2.

The signal processor 12 processes the measurement time points of the respective sensors in this way, and outputs the signal of the concrete surface temperature input to the signal processor 12 to the next signal converter 13. The temperature signal received by the signal converter 13 is sent to the controller 14 as temperature information for determining the amount of liquefied gas input at the time of concrete mixing in the next batch. If the control signal is immediately output, the operation of the next batch has not started yet. Therefore, the signal converter 13 holds the temperature information until just before the operation of the next batch.

When the temperature information is input to the controller 14 (personal computer) after a lapse of a predetermined time, the controller 14 receives this temperature information and other routine information (material input amount and its temperature). , Temperature, its time zone, etc.) is used to calculate the input amount of liquefied gas required to cool the concrete to the target cooling temperature, and the calculation result is output to the input amount setter 15, and this setter 15 Sends an operation signal to the control valve 16 of the liquefied gas inlet pipe, and the control valve 16
The required amount of liquefied gas is introduced into the mixer 1 during kneading by operating the opening degree and time. Note that the controller 14 may calculate not only the temperature information measured this time, but also the average value of the stock temperature information two times before and further, and the current information, and perform arithmetic processing using this average value.

FIG. 5 schematically shows the relationship between the advancing / retreating of the trolley during operation and the measurement time point of each sensor, and the horizontal axis represents time. As shown in the figure, the position sensor (eg photoelectric switch) when the truck enters and is set at a predetermined position
Will continue to output while is in its set position. Then, when concrete is supplied to the bucket and filled to a certain level or more, a level sensor (for example, an ultrasonic position detector) continues to output the concrete level. The radiation thermometer measures the temperature when the position sensor and level sensor outputs are obtained. When the supply of concrete to the truck ends and the truck exits, the temperature measurement ends and each sensor does not output until the next batch. However, the measured temperature value of this batch is held in the converter 13 as described above until just before the mixing of the next batch starts. As a result, the control computer of the batcher plant can always receive the concrete temperature measurement value necessary for calculating the liquefied gas input amount required for cooling, and automatic control can be realized.

[0026]

As described above, according to the present invention, the concrete mixing temperature can be constantly monitored with a relatively simple device configuration, and the temperature rises to the target temperature when cooling concrete by liquefied gas. Cooling can be controlled automatically.

[Brief description of drawings]

FIG. 1 is a diagram showing an actual measurement value of a kneading temperature on a certain day when precooling is performed by determining a liquid nitrogen input amount from a cooling unit in a batcher plant at a dam construction site. .

FIG. 2 is a schematic cross-sectional view showing an example of a batcher plant.

FIG. 3 is a view showing a spot-like temperature measurement position of a concrete in a hopper of a batcher plant by a thermocouple and a position where a surface of concrete in a trolley bucket is measured by a radiation thermometer.

FIG. 4 is a flow chart of control according to the method of the present invention.

FIG. 5 is a diagram showing a relationship between advancing / retreating of a cart for control according to the method of the present invention and measurement time points of respective sensors.

[Explanation of symbols]

 1 mixer 2 chute 3 liquefied gas injection pipe 4 hopper 5 dolly 6 dolly on dolly 7 concrete mixing 9 position detection sensor 10 level sensor 11 radiation thermometer 12 signal processor 13 signal converter 14 controller (personal computer) 15 liquefaction Gas input setting device 16 Control valve

Front page continuation (72) Inventor Masahiro Mangi 2-19-1 Tobita, Tokyo, Chofu City, Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Naoyuki Katayama 4-8-10 Tajima, Urawa-shi, Saitama (72) Inventor Yasushi Fukuda 2-690 Sachi-cho, Sachi-ku, Kawasaki City, Kanagawa Prefecture (72) Inventor Shio Sugawara 1-40-19 Kitasenka, Ota-ku, Tokyo Toko Building 302 (72) Tsutomu Yamashita Sachi-ku, Kawasaki City, Kanagawa Prefecture 2-690 Saiwaicho

Claims (4)

[Claims] 1. When kneading concrete in a mixer of a batcher plant with a controlled amount of liquefied gas to knead concrete cooled to a predetermined temperature, the kneaded mixture kneaded by the mixer is opened to the atmosphere. After discharging it into the container, measure the surface temperature of the concrete kneaded material in this container with a radiation thermometer in a non-contact manner, and use the measured temperature of the batch to calculate the liquefied gas input amount during the next batch mixing. A method for controlling concrete kneading temperature, characterized by: 2. The container opened to the atmosphere is a bucket on a trolley that moves in and out of a batcher plant, and after detecting the entry of this trolley and the completion of loading of the kneaded material into the bucket, the concrete in the bucket is released. The method for controlling concrete kneading temperature according to claim 1, wherein the surface temperature of the kneaded product is measured by a radiation thermometer. 3. The temperature information measured by the radiation thermometer is stored until just before the start of the kneading operation of the next batch and is output to the liquefied gas input amount controller.
The method for controlling concrete kneading temperature according to. 4. The method for controlling concrete mixing temperature according to claim 1, 2 or 3, wherein the radiation thermometer is set at a position having a viewing angle of at least 1/4 or more of the concrete surface area of the concrete in the container. .