JP7132565B2 - Concrete kneading temperature control method - Google Patents

Description

The present invention relates to a concrete mixing temperature control method in a batcher plant.

Conventionally, in mountain tunnel construction, shotcrete has been used as wall support after excavation by a blasting method or the like. For mountain tunnel construction, if it is difficult to transport ready-mixed concrete from an existing concrete plant, a concrete manufacturing facility (hereinafter referred to as a batcher plant) should be installed near the construction site to supply shotcrete. There are many.

In shotcrete construction, since the temperature of each material drops especially in winter, the kneading temperature of shotcrete tends to drop and the amount of quick setting agent used tends to increase. Specifically, it is clear from the graph in FIG. 10 that shows the relationship between the elapsed time and the penetration resistance value for each shotcrete temperature under the condition that the addition rate of the quick-setting agent is constant at 5%. In addition, it has been found that the set hardening properties decrease as the temperature of the shotcrete decreases. Therefore, as shown in FIGS. 11(A) to 11(C), it is known that if the amount of quick-setting agent added is increased, the setting hardening property increases even if the temperature is lowered. In the case of shotcrete construction, the amount of quick-setting agent used was increased to ensure early strength development.

However, in the case of this method, an increase in the amount of quick-setting agent used leads to an increase in construction costs, and changes in the rate of addition of quick-setting agent have a large effect on strength development, resulting in quality fluctuations. there is Conventionally, therefore, the temperature at which concrete is kneaded has been raised by using warm water as kneading water, warming aggregates in a storehouse, or projecting high-temperature steam during transportation.

Furthermore, in recent years, several methods or devices have been proposed for increasing the mixing temperature of concrete. For example, in Patent Document 1 below, a mixer for adding aggregate to cement and kneading it, a heating water tank storing hot water for heating the aggregate supplied to the mixer to a predetermined temperature, and hot water in the heating water tank heating means for heating, agitating means for agitating the hot water in the heating water tank, immersion transfer means for immersing the aggregate in the hot water in the heating water tank and carrying out the immersed and heated aggregate, aggregate Equipped with a temperature sensor that detects the temperature of the hot water to heat the aggregate and controls the heating means to control the hot water temperature to a set value, and the immersion transfer means immerses the aggregate in the warm water of the heating water tank and heats it. An apparatus for producing warm ready-mixed concrete has been proposed which is configured to heat and discharge the warmed aggregate from a heating water bath and supply it to a mixer.

Further, in Patent Document 2 below, fine aggregates are soaked in water in a container, and the volumes and masses of these water and fine aggregates are measured to determine the mass of fine aggregates and the mass of water. In a concrete manufacturing method using a fine aggregate weighing method, a concrete manufacturing method has been proposed in which the temperature of the water in which the fine aggregate is soaked is adjusted to control the kneading temperature of the concrete.

Furthermore, in Patent Document 3 below, a cylindrical main body provided with an aggregate inlet at one end and an outlet at the other end, a hollow heating shaft installed between both ends of the main body and having a hollow portion as a steam passage, Concrete provided with heat transfer plates mounted perpendicularly to the heating shaft and arranged so as to stand on one side, a rotary drive device for rotating the heating shaft by at least 180°, and a drive device for reciprocating in the axial direction. Aggregate heating devices have been proposed.

JP-A-7-100821 JP 2006-327114 A Japanese Patent Publication No. 53-42336

However, the method of providing the aggregate storage with a heating function results in an increase in equipment investment. Moreover, in the case of the method of projecting high-temperature steam onto the aggregate, there is a problem that moisture adheres to the surface of the aggregate, making it difficult to adjust the water-cement ratio.

Further, in the case of the method of immersing the aggregate in hot water to heat the aggregate disclosed in the above-mentioned Patent Document 1, a large-scale dedicated device (heating water tank) is separately provided in order to immerse the aggregate in warm water while moving. necessary.

In the case of the method according to the above Patent Document 2, it is based on the premise of a concrete manufacturing method using the water immersion fine aggregate weighing method, and the structure of the batcher plant itself is significantly different from the existing one, so it cannot be adopted. It is rather difficult.

Furthermore, the aggregate heating apparatus according to Patent Document 3 can secure a contact area in the case of fine aggregates, but cannot secure a contact area with the heat transfer plate in the case of coarse aggregates due to the large particle size. There were problems such as poor aggregate heating efficiency.

Therefore, the main object of the present invention is to manage and adjust the concrete kneading temperature in a batcher plant, while reducing the equipment burden and cost burden, and efficiently managing and adjusting the kneading temperature to a predetermined temperature. to propose a temperature control method for

In order to solve the above problems, the present invention according to claim 1 is a concrete mixing temperature control method in a batcher plant,
The batcher plant includes at least a coarse aggregate storage, a fine aggregate storage, and a kneading water tank, and coarse aggregate for measuring the weight of coarse aggregate and the weight of fine aggregate to be fed into the concrete mixer. Equipped with a weighing bucket and a fine aggregate weighing bucket,
In the coarse aggregate weighing bucket, a coarse aggregate heating facility is provided in which a plurality of perforated pipes are arranged inside the bucket and a hot air generator for supplying hot air to the perforated pipes. The coarse aggregate is heated to a predetermined temperature in the process in which the hot air blown out from the perforated pipe flows between the aggregates in a state in which a predetermined amount of coarse aggregate is charged,
In the fine aggregate weighing bucket, a plurality of bar-shaped cartridge heaters are arranged with the heater portion facing the inside of the bucket from the bucket wall surface, and a stirring for stirring the fine aggregate is provided between the cartridge heaters. A fine aggregate heating facility having blades is provided. With a predetermined amount of fine aggregates added, the fine aggregates are agitated by rotating the stirring blades and heat is released from the cartridge heater. The fine aggregate is heated to a predetermined temperature,
After the coarse aggregate is filled in the coarse aggregate weighing bucket and heated to a predetermined temperature, and the fine aggregate is filled in the fine aggregate weighing bucket and heated to a predetermined temperature,
A concrete kneading method characterized in that the coarse aggregate and fine aggregate are put into a concrete mixer, and a predetermined amount of cement and kneading water are put into the concrete mixer and stirred to produce concrete at a predetermined kneading temperature. A temperature control method is provided.

In the invention according to claim 1, the coarse aggregate weighing bucket has a plurality of perforated pipes disposed inside the bucket, and is provided with a hot air generator for supplying hot air to the perforated pipes. A coarse aggregate heating facility is provided, and the coarse aggregate is heated to a predetermined temperature in the process in which the hot air blown out from the perforated pipe flows between the aggregates in a state where a predetermined amount of coarse aggregate is charged. In the fine aggregate weighing bucket, a plurality of bar-shaped cartridge heaters are arranged with the heater portion facing the inside of the bucket from the wall surface of the bucket, and a thin cartridge heater is provided between the cartridge heaters. A fine aggregate heating facility having a stirring blade for stirring the aggregate is provided, and the fine aggregate is stirred by rotationally driving the stirring blade in a state in which a predetermined amount of fine aggregate is added. Meanwhile, the fine aggregate is heated to a predetermined temperature by heat radiation from the cartridge heater.

In this way, the coarse aggregate weighing bucket and the fine aggregate weighing bucket in the batcher plant are equipped with an aggregate heating function. It becomes possible to manage and adjust the rising temperature.

Further, in the present invention, the aggregate heating equipment is optimized according to the form of the aggregate. That is, for coarse aggregate, a coarse aggregate heating facility comprising a plurality of perforated pipes arranged inside a bucket and a hot air generator for supplying hot air to the perforated pipes. is applied. Since coarse aggregates have large gaps between aggregates, it is possible to efficiently heat the aggregates while the hot air blown out from the perforated pipes flows through the aggregates.

On the other hand, as for the fine aggregate, since the gaps between the aggregates are small, a plurality of bar-shaped cartridge heaters are arranged with the heater portion facing the inside of the bucket from the wall surface of the bucket. Efficient heating can be achieved by applying fine aggregate heating equipment having stirring blades for stirring fine aggregate . In this way, by heating the coarse aggregate and the fine aggregate in the optimum manner according to their respective forms, both can be efficiently heated at low cost.

As the present invention according to claim 2 , the concrete kneading according to claim 1 is performed by first charging the coarse aggregate, fine aggregate and hot water into a concrete mixer and stirring them, and then adding cement and stirring. A temperature control method is provided.

In the method of claim 2 , as the stirring procedure, first, the coarse aggregate, fine aggregate and hot water are charged into a concrete mixer and stirred, and then cement is charged and stirred. As a result, even if the aggregate is heated unevenly, the temperature of the cement can be raised smoothly, and the temperature rise of the cement can be suppressed.

As the present invention according to claim 3, in order to make concrete at a desired mixing temperature, the amount of aggregate heating (Δθa) in the coarse aggregate weighing bucket and the fine aggregate weighing bucket based on the following formula (1) A temperature control method for mixing concrete according to any one of claims 1 and 2 is provided.

The third aspect of the invention provides a specific example of calculating the aggregate heating amount (Δθa) in the aggregate heating bucket.

As described in detail above, according to the present invention, when managing the mixing temperature of concrete in a batcher plant, it is possible to efficiently manage and adjust the temperature to a predetermined kneading temperature while reducing the burden on equipment and costs. become.

1 is a front view of a batcher plant 1; FIG. It is the top view. Its right side. FIG. 2 is a view taken along line IV-IV in FIG. 1 (a side view of a weighing and kneading part). It is a cross-sectional view showing a temperature sensor provided on the belt conveyor. 1(A) is a vertical sectional view and (B) is a horizontal sectional view showing a coarse aggregate weighing bucket 5 with an aggregate heating function. FIG. 1(A) is a vertical cross-sectional view and (B) is a cross-sectional view showing a fine aggregate weighing bucket 6 with an aggregate heating function. FIG. FIG. 4 is a cross-sectional view showing an aggregate weighing bucket with an aggregate warming function; It is a structural drawing in the case of providing an aggregate bucket. It is a penetration resistance change chart according to kneading temperature. (A) to (C) are penetration resistance value change diagrams when the addition rate of quick-setting agent is changed.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Batcher plant 1 structure example]
First, based on FIGS. 1 and 2, a structural example of a batcher plant 1 for shotcrete to be constructed near a mountain tunnel construction site will be outlined.

The batcher plant 1 normally comprises at least a coarse aggregate storage 2, a fine aggregate storage 3 and a kneading water tank 8, and measures the weight of coarse aggregate and the weight of fine aggregate fed into the concrete mixer 4. A coarse aggregate weighing bucket 5, a fine aggregate weighing bucket 6, and a cement weighing bucket 7 for weighing the cement to be put into the concrete mixer 4 are provided. These weighing buckets 5 to 7 are supported by load cells so as to measure the weight of the charged materials. The cement silo is provided adjacent to the batcher plant 1, and conveyed to the cement weighing bucket 7 by a belt conveyor (not shown).

In the illustrated example, a coarse aggregate storage 2 and a fine aggregate storage 3 are installed on one side (the right side in FIG. 1), and a coarse aggregate weighing bucket is installed on the other side (the left side in FIG. 1). 5 and a fine aggregate weighing bucket 6 are arranged, a cement weighing bucket 7 is arranged between these buckets 5 and 6, and a concrete mixer 4 is arranged below these bucket groups. The kneading water tank 8 is provided adjacent to the weighing bucket groups 5-7. A hot water tank 15 equipped with a boiler is installed so that the kneading water heated to a predetermined temperature is used. It is stored and supplied to the concrete mixer 4 from here.

Coarse and fine aggregates from the coarse aggregate storage 2 and fine aggregate storage 3 are conveyed to a coarse aggregate weighing bucket 5 and a fine aggregate weighing bucket 6 by belt conveyors 9 and 10, respectively. .

In addition, in FIG. 1, the aggregate receiving hopper 11 is provided in the central part, and the coarse and fine aggregates fed into this hopper are fed by the belt feeder 12 and the belt conveyors 13 and 14 to the coarse aggregate storage 2 or It is transported to the fine aggregate storage 3.

A hopper 16 for temporarily storing the kneaded shotcrete is provided directly below the concrete mixer 4, and a space below the hopper 16 is a space into which a ready-mixed concrete vehicle can enter. The shotcrete is put into ready-mixed concrete trucks and transported to the construction site.

In this batcher plant, in order to control the temperature of various materials, the coarse aggregate belt conveyor 9 and the fine aggregate belt conveyor 10 are provided with coarse aggregate weighing buckets 5 as shown in FIG. A temperature sensor 20 is provided for measuring the temperature of coarse aggregate (θa1) before charging, and the temperature of fine aggregate (θa2) before charging to the fine aggregate weighing bucket 6 . As the temperature sensor 20, a radiation thermometer using infrared rays that can measure the surface temperature without contact can be preferably used.

As shown in FIG. 4, the cement weighing bucket 7 is provided with a temperature sensor 17 for measuring the temperature of the filled cement, and the temperature of the mixing water in the mixing water tank 8 is measured. A temperature sensor 18 is provided.

Furthermore, as shown in FIG. 4, a temperature sensor ( radiation thermometer) 19 is provided.

[Temperature control for mixing shotcrete]
In the mixing temperature control of shotcrete according to the present invention, the coarse aggregate weighing bucket 5 is provided with one or more perforated pipes 22, 22, . . . In addition, a coarse aggregate heating facility 21 comprising a hot air generator 23 for supplying hot air to the perforated pipe 22 is provided. By supplying hot air to the perforated pipe 22, the coarse aggregate G is heated to a predetermined temperature. Coarse aggregate G is defined as aggregate containing 85% or more by weight of particles of 5 mm or more (so-called gravel, etc.). Since it is large, it becomes possible to heat the coarse aggregate G efficiently in the process in which the hot air blown out from the perforated pipe 22 circulates between the aggregates.

On the other hand, in the fine aggregate weighing bucket 6, as shown in FIG. 7, one or a plurality of cartridge heaters 25, 25, . 26 is provided, and in a state in which a predetermined amount of fine aggregate S is charged, the stirring blade 26 is rotationally driven to agitate the fine aggregate S to a predetermined amount. It is designed to heat up to a temperature of Fine aggregate S is defined as aggregate (so-called sand, etc.) that has passed through a 10 mm sieve and contains 85% or more by weight of 5 mm or less. can not be effectively heated by the method of supplying and heating. Therefore, the fine aggregates S are heated by heat radiation from the cartridge heater 25 while stirring the filled fine aggregates S. As shown in FIG.

The cartridge heater is a rod-shaped heater in which a nichrome wire, which is a heating element, is covered with a metal pipe (sheath). As shown in FIG. It is fixed while facing the inside. However, since it is difficult to circulate the heat to the entire fine aggregate only with these cartridge heaters 25, 25 . The stirring blade 26 is a device in which a rotary shaft 28 having blades is rotatably supported by bearings 27 , 27 and the rotary shaft 28 is rotated by a driving device 29 . One or a plurality of stirring blades 26 are provided between the cartridge heaters 25, 25, . . .

Further, as a heating mechanism in the fine aggregate weighing bucket 6, as shown in FIG. The fine aggregate heating equipment 30 may be provided with an electric heating plate 32 spirally arranged on the peripheral surface of the shaft and provided with a driving device 34 for rotating the rotating shaft 31 .

As the electric heating plate 32 , a spiral processed hot plate for industrial use can be preferably used. The structure of the industrial hot plate employs stainless steel and/or aluminum as a material, and can be heated by inserting a cartridge heater or casting a sheath heater.

When the coarse aggregate G and the fine aggregate S are heated to a predetermined temperature by the aggregate heating buckets (the coarse aggregate weighing bucket 5 and the fine aggregate weighing bucket 6), the coarse aggregate G, The fine aggregate S is put into the concrete mixer 4, and a predetermined amount of cement and kneading water heated to a predetermined temperature are also put into the concrete mixer 4, and these materials are stirred to obtain a predetermined kneading temperature. It becomes possible to produce shotcrete.

<Temperature setting management for various materials>
First, the temperature of the shotcrete immediately after kneading (for example, θ ₀ =20° C.) is set. In order to achieve this kneading temperature, the amount of aggregate heating (Δθa) in the aggregate heating buckets (the coarse aggregate weighing bucket 5 and the fine aggregate weighing bucket 6) is calculated based on the following formula (1): calculate. The following formula (1) is based on an excerpt from the Concrete Engineering Handbook.

The kneading water is heated to an arbitrarily set temperature (θw) in the hot water tank 15 and then sent to the kneading water tank 8 where the temperature is measured by the temperature sensor 18 . Also, the cement is measured by a temperature sensor 17 provided on the cement weighing bucket 7 . Therefore, the heating amount (Δθa) of the coarse aggregate and the fine aggregate in the coarse aggregate weighing bucket 5 and the fine aggregate weighing bucket 6 can be changed from the set aggregate temperature (θa) to the belt conveyor before charging the weighing bucket. It can be calculated by subtracting the aggregate temperatures (θa1, θa2) measured by the temperature sensor 20 above.

A temperature sensor 19 installed at the gate of the concrete mixer 4 is used to check the temperature at the final and actual kneading completion. The amount of heating in 6 and the temperature of the kneading water are adjusted.

[Other form examples]
(1) In the above embodiment, the coarse aggregate is a coarse aggregate heating facility comprising one or more perforated pipes 22 and a heat generator 23 for supplying hot air to the perforated pipes 22. 21, and the fine aggregate is heated by a fine aggregate heating device 24 comprising one or more cartridge heaters 25 and agitating blades 26 for agitating the aggregate, or around a rotating shaft 31. Heating is performed by a fine aggregate heating equipment 30 having an electric heating plate 32 disposed spirally and a driving device 34 for rotating the rotating shaft 31. Any warming device 21, 24, 30 may be applied to the aggregate.

(2) In the above embodiment, the aggregate weighing buckets 5, 6 are provided with the heating equipment 21, 24, 30. The aggregate may be heated. For example, in the example of fine aggregate, as shown in FIG. , into the fine aggregate weighing bucket 5 for weighing. By separating the bucket for weighing and the bucket for heating, the aggregates that have been heated are sequentially put into the bucket for weighing, so that the next batch of aggregates can be heated continuously. Therefore, the heated aggregate can be continuously supplied to the concrete mixer 4 .

(3) In the above embodiment, the coarse aggregate and fine aggregate are put into the concrete mixer 4, and a predetermined amount of cement and kneading water are added and stirred to produce shotcrete at a predetermined mixing temperature. I made it In other words, all the materials are put in at once and stirred, but first, the coarse aggregate, fine aggregate and hot water are put into the concrete mixer and stirred, and then the cement is put in and stirred. As a result, even if the aggregate is heated unevenly, the temperature of the cement rises smoothly, and the temperature rise of the cement can be suppressed.

(4) In the above embodiment, the concrete mixing temperature control method according to the present invention is applied to shotcrete in mountain tunnel construction. The method can be applied to general concrete other than shotcrete.

DESCRIPTION OF SYMBOLS 1... batcher plant, 2... coarse aggregate storage, 3... fine aggregate storage, 4... concrete mixer, 5... coarse aggregate weighing bucket, 6... fine aggregate weighing bucket, 7... cement weighing bucket, 8... kneading Mixing water tank 9 Belt conveyor (coarse aggregate) 10 Belt conveyor (fine aggregate) 11 Aggregate receiving hopper 12 Belt feeder 13/14 Belt conveyor 15 Warm water tank 16 Hopper 17 to 20 Temperature sensor 21 Coarse aggregate heating equipment 22 Perforated pipe 23 Hot air generator 24 Fine aggregate heating equipment 25 Cartridge heater 26 Stirring blade 30 ... fine aggregate heating equipment, 31 ... rotating shaft, 32 ... electric heating plate

Claims (3)

A concrete mixing temperature control method in a batcher plant,
The batcher plant includes at least a coarse aggregate storage, a fine aggregate storage, and a kneading water tank, and coarse aggregate for measuring the weight of coarse aggregate and the weight of fine aggregate to be fed into the concrete mixer. Equipped with a weighing bucket and a fine aggregate weighing bucket,
In the coarse aggregate weighing bucket, a coarse aggregate heating facility is provided in which a plurality of perforated pipes are arranged inside the bucket and a hot air generator for supplying hot air to the perforated pipes. The coarse aggregate is heated to a predetermined temperature in the process in which the hot air blown out from the perforated pipe flows between the aggregates in a state in which a predetermined amount of coarse aggregate is charged,
In the fine aggregate weighing bucket, a plurality of bar-shaped cartridge heaters are arranged with the heater portion facing the inside of the bucket from the bucket wall surface, and a stirring for stirring the fine aggregate is provided between the cartridge heaters. A fine aggregate heating facility having blades is provided. With a predetermined amount of fine aggregates added, the fine aggregates are agitated by rotating the stirring blades and heat is released from the cartridge heater. The fine aggregate is heated to a predetermined temperature,
After the coarse aggregate is filled in the coarse aggregate weighing bucket and heated to a predetermined temperature, and the fine aggregate is filled in the fine aggregate weighing bucket and heated to a predetermined temperature,
A concrete kneading method characterized in that the coarse aggregate and fine aggregate are put into a concrete mixer, and a predetermined amount of cement and kneading water are put into the concrete mixer and stirred to produce concrete at a predetermined kneading temperature. Temperature control method. 2. A concrete mixing temperature control method according to claim 1, wherein said coarse aggregate, fine aggregate and hot water are first charged into a concrete mixer and stirred, and then cement is charged and stirred. Calculate the amount of aggregate heating (Δθa) in the coarse aggregate weighing bucket and the fine aggregate weighing bucket based on the following formula ( 1 ) in order to make the concrete at the desired mixing temperature. The temperature control method for kneading concrete described above.

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