JP2020196217A - Method for producing spraying concrete - Google Patents

Abstract

To provide a method for producing spraying concrete where, when a kneading temperature of spraying concrete is managed in a batcher plant in the cold season, the kneading temperature is efficiently managed and adjusted to a prescribed kneading temperature while a facility load and a cost load are reduced.SOLUTION: In a method for producing spraying concrete by a split kneading procedure, primary kneading temperature control is performed in which a kneading temperature of spraying concrete discharged from a concrete mixer 4 is measured, and a concrete kneading temperature is increased by increasing a primary water temperature under the condition where a kneading temperature immediately before the charge of cement becomes 40°C or lower in the case that the measured kneading temperature does not reach a kneading target temperature. Then, in the case that the kneading temperature of the spraying concrete does not reach the kneading target temperature even by the primary kneading temperature control, secondary kneading temperature control is performed in which a temperature of the mixer body is increased by mixer heating means 23 installed in an outer face of the concrete mixer 4 to increase the concrete kneading temperature.SELECTED DRAWING: Figure 6

Description

The present invention relates to a method for producing sprayed concrete in a batcher plant during the cold season.

Conventionally, in mountain tunnel construction, sprayed concrete has been used as wall support after excavation by a blasting method or the like. In 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 batcher plant) for supplying sprayed concrete will be installed near the construction site. There are many.

In the conventional sprayed concrete work, the temperature of the mixed water is uniformly set to about 40 ° C. to manufacture concrete. However, in this method, since the temperature of each material is lowered especially in winter, the kneading temperature of the sprayed concrete is lowered, and the amount of the quick-setting admixture tends to be increased. Specifically, as is clear from the graph of FIG. 12, which shows the relationship between the elapsed time and the penetration resistance value for each sprayed concrete temperature under the condition that the addition rate of the quick-setting admixture is constant at 5%. In addition, it is known that the coagulation hardening property decreases as the temperature of the sprayed concrete decreases. Therefore, as shown in FIGS. 13 (A) to 13 (C), it is known that when the amount of the quick-setting admixture is increased, the coagulation-curing property increases even if the temperature decreases. In the sprayed concrete work, the amount of quick-setting admixture used was increased to ensure early strength development.

However, in the case of this method, an increase in the amount of the quick-setting admixture used causes an increase in the construction cost, and a change in the quick-setting admixture addition rate has a great influence on the strength development, which causes quality fluctuation. There is. Therefore, conventionally, the kneading temperature of concrete has been raised by using hot water as kneading water, warming aggregates in a storage, or projecting high-temperature steam during transportation.

Further, in recent years, some methods or devices for raising the kneading temperature of concrete have been proposed. For example, in Patent Document 1 below, a mixer in which aggregate is added to cement and kneaded, a heating water tank for storing hot water for heating the aggregate supplied to the mixer to a predetermined temperature, and hot water in the heating water tank are used. A heating means for heating, a stirring means for stirring the hot water in the heating water tank, an immersion transfer means for immersing the aggregate in the warm water of the heating water tank and carrying out the soaked and heated aggregate, and an aggregate. It is equipped with a temperature sensor that detects the temperature of the hot water to be heated and controls the heating means to control the hot water temperature to the set value, and the aggregate is immersed in the hot water of the heating water tank by the immersion transfer means. A device for producing warmed ready-mixed concrete has been proposed, which is configured to discharge warmed aggregate from a warming water tank and supply it to a mixer.

Further, in Patent Document 2 below, in a state where the fine aggregate is immersed in water in a container, the volume and mass of these water and the fine aggregate are measured to obtain the mass of the fine aggregate and the mass of water. In the concrete manufacturing method using the fine aggregate weighing method, a concrete manufacturing method has been proposed in which the temperature of the water in which the fine aggregate is immersed is adjusted to control the kneading temperature of the concrete.

Further, in Patent Document 3 below, a cylindrical main body having an aggregate inlet at one end and an outlet at the other end, and a hollow heating shaft erected between both ends of the main body and having the hollow portion as a steam passage. Concrete equipped with a heat transfer plate attached so as to stand at right angles to the heating shaft and be biased to one side so that a large number of them are aligned, 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.

Further, in the previous patent application (Patent Document 4 below), the applicant is a method for controlling the mixing temperature of concrete in a batcher plant.
The batcher plant is provided with at least a coarse aggregate storage, a fine aggregate storage, and a mixing water tank, respectively, and is a coarse aggregate for measuring the coarse aggregate weight and the fine aggregate weight to be put into the concrete mixer, respectively. It is equipped with a weighing bucket and a fine aggregate weighing bucket.
An aggregate heating bucket, which is provided with one or more perforated pipes for coarse aggregate and fine aggregate, and is provided with a hot air generator for supplying hot air to the perforated pipes, 1. Alternatively, a plurality of cartridge heaters are arranged, an aggregate heating bucket provided with stirring blades for stirring the aggregate, and a spiral heating plate are arranged around the rotation axis. After heating to a predetermined temperature by any of the aggregate heating buckets provided with a drive device for rotating the rotating shaft,
We propose a concrete kneading temperature control method for producing concrete with a predetermined kneading temperature by putting the coarse aggregate and fine aggregate into a concrete mixer and adding a predetermined amount of cement and kneading water and stirring. did.

Japanese Unexamined Patent Publication No. 7-100821 Japanese Unexamined Patent Publication No. 2006-327114 Tokukousho No. 53-42336 Japanese Patent Application No. 2018-79532

However, the above-mentioned method of providing the aggregate storage with a heating function requires a large amount of capital investment. Further, in the case of the above-mentioned method of projecting high-temperature steam onto the aggregate, there is a problem that water adheres to the surface of the aggregate, which makes it difficult to adjust the water content of the water-cement ratio.

Further, in the case of the method of immersing the aggregate disclosed in Patent Document 1 in warm water to heat it, a large-scale dedicated device (heating water tank) is separately required to immerse the aggregate in warm water while moving. You will need it.

In the case of the method according to Patent Document 2, the concrete manufacturing method using the water-immersed fine aggregate weighing method is premised, and the structure of the batcher plant itself is significantly different from the existing one. It's difficult.

Further, the aggregate heating device according to Patent Document 3 can secure a contact area in the case of fine aggregate, but cannot secure a contact area with the heat transfer plate in the case of coarse aggregate as a whole. There were problems such as poor heating efficiency of the aggregate.

On the other hand, the kneading temperature control method according to Patent Document 4 has an advantage that the equipment burden and the cost burden can be reduced because the bucket in the batcher plant is provided with an aggregate heating function. Heating the aggregate in a bucket was not heat efficient and required many heat sources and time to heat the aggregate to the desired temperature.

In addition, in the concrete standard specification [2017 version] construction edition, "If the aggregate is heated to 65 ° C or higher, it becomes difficult to handle it and there is a risk of urgent cement. Generally, a mixture of water and aggregate. If the temperature is set to 40 ° C or lower, there is no such concern. ”It is a prerequisite that the kneading temperature immediately before the cement is added is 40 ° C or lower.

Therefore, the main subject of the present invention is to efficiently control and adjust the kneading temperature to a predetermined kneading temperature in a batcher plant in the cold season, although the equipment burden and cost burden are small in controlling the kneading temperature of the sprayed concrete. The purpose is to propose a method for producing sprayed concrete that can be used.

In order to solve the above-mentioned problems, as the present invention according to claim 1, in the cold season, in a batcher plant, first fine aggregate, coarse aggregate and primary water are put into a concrete mixer and stirred, and then cement is added. In the method of producing sprayed concrete by a split kneading procedure in which secondary water and an admixture are added and stirred, and then charged and stirred.
The kneading temperature of the sprayed concrete discharged from the concrete mixer is measured, and if this kneading temperature does not reach the kneading target temperature, the kneading temperature immediately before the cement is added is 40 ° C. or less. Then, the primary kneading temperature control for raising the concrete kneading temperature by raising the temperature of the primary water while keeping the temperature of the secondary water as it is is performed.
If the kneading temperature of the sprayed concrete does not reach the kneading target temperature even with the primary kneading temperature control, the concrete mixer is operated under the condition that the kneading temperature immediately before the cement is added is 40 ° C. or less. Provided is a method for producing sprayed concrete, which comprises performing secondary kneading temperature control in which the temperature of the mixer body is raised by a mixer heating means installed on the outer surface to raise the concrete kneading temperature. ..

In the invention according to claim 1, the kneading temperature of the sprayed concrete discharged from the concrete mixer is measured, and when the kneading temperature does not reach the kneading target temperature (generally 20 to 25 ° C.), cement is added. Under the condition that the kneading temperature immediately before the concrete kneading temperature is 40 ° C. or less, the primary kneading temperature for raising the concrete kneading temperature by raising the temperature of the primary water while keeping the temperature of the secondary water as it is. It is in control. As a result, even if the temperature of the fine aggregate and coarse aggregate drops in the cold season, the temperature of the primary water is heated to higher than 40 ° C and put into the concrete mixer, so that the fine aggregate in the concrete mixer These aggregates are heated by the primary water during stirring with the aggregates and coarse aggregates, so that the concrete kneading temperature can be raised.

However, in the severe winter when the outside air temperature becomes even lower, it may not be possible to maintain the target kneading temperature only by heating the primary water due to the further lowering of the aggregate temperature and the temperature drop of the concrete mixer during kneading. is there. Therefore, in the present invention, if the kneading temperature of the sprayed concrete does not reach the kneading target temperature even with the above-mentioned primary kneading temperature control, the kneading temperature immediately before the cement is added is 40 ° C. or less. Under the above, the mixer heating means installed on the outer surface of the concrete mixer is made to function, and the secondary kneading temperature control for raising the temperature of the mixer main body to raise the concrete kneading temperature is performed. In this way, since the concrete mixer is provided with a heating function, the kneading temperature of the sprayed concrete is efficiently managed and adjusted to the predetermined kneading target temperature, although the equipment burden and cost burden are small. It becomes possible to do.

According to a second aspect of the present invention, the mixer heating means is provided with the method for producing sprayed concrete according to claim 1, which is a hot water tank installed on the outer surface of a concrete mixer.

In the invention according to claim 2, a hot water tank is used as one of the specific configurations of the mixer heating means installed on the outer surface of the concrete mixer. The concrete mixer is heated by the heat conduction from the hot water put into the hot water tank.

As the present invention according to claim 3, the mixer heating means is provided with the method for manufacturing sprayed concrete according to claim 1, which is a heater installed on the outer surface of a concrete mixer.

In the invention according to claim 3, a heater such as a heating wire is used as another configuration of the mixer heating means. In this embodiment, the outer surface of the concrete mixer is directly heated by the heater.

According to the fourth aspect of the present invention, in the primary kneading temperature control, the temperature of the secondary water is maintained at 40 ° C., and the temperature of the primary water is variably controlled between 40 and 90 ° C. The method for producing a sprayed concrete according to any one of Items 1 to 3 is provided.

In the invention according to claim 4, if the temperature of the secondary water is higher than 40 ° C., the cement may be rapidly formed. Therefore, the temperature of the secondary water is set to 40 ° C. The kneading temperature is raised by variably controlling the temperature between about 90 ° C.

上記請求項５記載の発明は、１次水の温度（θw1）を算定する具体例を示したものである。 As the present invention according to claim 5, in the primary mixing up temperature control, in order to the kneading upstream temperature theta ₀ 'immediately before turning on the cement at a predetermined temperature, the primary water based on the following equation (2) The method for producing sprayed concrete according to any one of claims 1 to 4, wherein the temperature (θw1) of the above is calculated.

The invention according to claim 5 shows a specific example of calculating the temperature (θw1) of the primary water.

As described in detail above, according to the present invention, in controlling the kneading temperature of sprayed concrete in a batcher plant during the cold season, the kneading temperature is efficiently controlled to a predetermined kneading temperature while the equipment burden and cost burden are small.・ It becomes possible to adjust.

It is a front view of the batcher plant 1. It is the plan view. It is the right side. FIG. 1 is a view taken along the line IV-IV of FIG. 1 (side view of the weighing and mixing portion). It is a cross-sectional view which shows the temperature sensor 20 provided in the belt conveyor 9 (10). It is a kneading flow diagram of sprayed concrete. It is a front view of the concrete mixer 4. It is the side view. It is a front view of the concrete mixer 4. It is the side view. It is a graph which shows the change of the initial strength development when the temperature of the kneading water is changed. It is a penetration resistance change diagram for each kneading temperature. (A) to (C) are graphs of changes in penetration resistance when the rate of addition of the quick-setting admixture is changed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Batcher plant 1 structural example]
First, a structural example of a batcher plant 1 for sprayed concrete constructed in the vicinity of a mountain tunnel construction site will be outlined based on FIGS. 1 and 2.

The batcher plant 1 usually includes at least a coarse aggregate storage 2, a fine aggregate storage 3, and a mixing water tank 8, and measures the weight of the coarse aggregate and the weight of the fine aggregate to be charged into the concrete mixer 4, respectively. It is provided with a coarse aggregate measuring bucket 5 and a fine aggregate measuring bucket 6 for measuring the weight of cement to be put into the concrete mixer 4, and a cement measuring bucket 7 for measuring the weight of cement to be put into the concrete mixer 4. These measuring buckets 5 to 7 can measure the weight of the charged material by being supported by the load cell. The cement silo is provided adjacent to the batcher plant 1 and is conveyed to the cement measuring bucket 7 by a belt conveyor (not shown).

In the illustrated example, the coarse aggregate storage 2 and the fine aggregate storage 3 are installed on one side (right side in FIG. 1), and the coarse aggregate measuring bucket 5 and fine aggregate 3 are installed on the other side (left side in FIG. 1). A measuring bucket 6 is arranged, a cement measuring bucket 7 is arranged between these buckets 5 and 6, and a concrete mixer 4 is arranged under the bucket group. The mixing water tank 8 is provided at a position adjacent to the measuring bucket groups 5 to 7.

In order to use the mixing water that has been heated to a predetermined temperature, a primary water hot water tank 15 and a secondary water hot water tank 16 equipped with a boiler device are provided, respectively, and the water is heated to a predetermined temperature. The primary water and the secondary water are once stored in the mixing water tank 8 and are supplied to the concrete mixer 4 from here.

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

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

Immediately below the concrete mixer 4, a hopper 21 for temporarily storing the kneaded sprayed concrete is provided, and the lower side thereof is a space where a ready-mixed concrete vehicle can enter, and is kneaded here. The sprayed concrete is put into the ready-mixed concrete car 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, respectively, have the coarse aggregate measuring bucket 5 as shown in FIG. A temperature sensor 20 for measuring the coarse aggregate temperature before charging and the fine aggregate temperature before charging is provided in the fine aggregate measuring bucket 6. As the temperature sensor 20, a radiation thermometer using infrared rays capable of measuring the surface temperature without contact can be preferably used.

Further, as shown in FIG. 4, the cement measuring bucket 7 is provided with a temperature sensor 17 for measuring the temperature of the filled cement, and the primary water or 2 stored in the mixing water tank 8. A temperature sensor 18 for measuring the temperature of the next water is provided.

Further, as shown in FIG. 4, in order to measure the kneading temperature of the sprayed concrete discharged from the concrete mixer 4 at the completion of kneading, a temperature sensor (radiation temperature) is provided around the gate portion of the concrete mixer 4. A total of 19 is provided.

Further, as shown in FIG. 4, in order to measure the temperature of the water / aggregate mixture during kneading in the concrete mixer 4, the kneading is performed at a position above the water / aggregate mixture in the concrete mixer 4. A temperature sensor (radiation thermometer) 22 for measuring the temperature of the water / aggregate mixture in the middle of mixing is provided.

[Manufacturing method of sprayed concrete]
In the method for producing sprayed concrete according to the present invention, as shown in FIG. 6, in the above-mentioned batcher plant 1, first, coarse aggregate, fine aggregate and primary water are first charged into the concrete mixer 4 in the cold season. Then, add cement and stir, and then add secondary water and admixtures such as water reducing agent, AE water reducing agent, high performance water reducing agent, high performance AE water reducing agent, and fluidizing agent and stir. This is a split kneading procedure. In the method for producing sprayed concrete by this split kneading method, sprayed concrete at a predetermined temperature is produced by changing the temperatures of the primary water and the secondary water, and the amount of quick-setting admixture used during spraying is reduced. doing.

(Primary kneading temperature control)
In this manufacturing method, the kneading temperature of concrete discharged from the concrete mixer 4 is measured by the temperature sensor 19 (FIG. 4) provided around the gate portion of the concrete mixer 4, and this kneading temperature is the kneading target. If the temperature is not reached, the concrete kneading temperature rises by raising the temperature of the primary water while keeping the temperature of the secondary water as it is under the condition that the kneading temperature immediately before adding cement is 40 ° C or less. The primary kneading temperature is controlled. The kneading target temperature can be set to approximately 20 to 25 ° C.

セメント投入時の温度を４０℃より高くするとセメントが急結するおそれがあるため、セメントを投入する直前のコンクリートミキサ４内で練混ぜ中の水・骨材混合物の練上り温度θ₀’を所定の温度（例えば、θ₀’=４０℃以下）にするため、下式(2)に基づいて１次水の温度θw1を算出する。

一次的練上り温度制御において、２次水の温度は４０℃に保持する一方で、１次水の温度を４０〜９０℃の間で可変制御することによって、吹付けコンクリートの練上り温度が所定の練上り目標温度となるようにしている。 The kneading temperature θ ₀ of the sprayed concrete is expressed by the following equation (1). Equation (1) below is an excerpt from the Concrete Engineering Handbook.

Since the cement when the temperature in cement turned higher than 40 ° C. there is a risk of rapid setting, given the kneading upstream temperature theta ₀ 'water-aggregate mixture in the kneading of concrete mixer within 4 immediately before turning on the cement (For example, θ ₀ '= 40 ° C. or less), the temperature θw1 of the primary water is calculated based on the following equation (2).

In the primary kneading temperature control, the temperature of the secondary water is maintained at 40 ° C., while the temperature of the primary water is variably controlled between 40 and 90 ° C. to determine the kneading temperature of the sprayed concrete. The temperature is set to the target temperature for the concrete.

In a conventional batcher plant, if the temperature of the secondary water is higher than 40 ° C, cement may be formed suddenly. Therefore, the temperature of the primary water and secondary water is uniformly set to about 40 ° C to manufacture concrete. Was common. However, since the temperature of each material is lowered in winter, it is difficult to produce sufficiently heated concrete if the temperature of the mixing water is uniformly 40 ° C. Therefore, in this production method, the temperature of the primary water is variably controlled between 40 and 90 ° C., and the water becomes hotter than the conventional one by mixing and stirring with the fine aggregate / coarse aggregate. Produce an aggregate mixture and mix with cement. The temperature of the secondary water is maintained at 40 ° C. as before to prevent sudden cement formation.

It is also possible to measure the outside air temperature, the room temperature, the temperature of the fine aggregate and the coarse aggregate, and control the temperature of the primary water.

The primary water and the secondary water are once heated to a temperature arbitrarily set by a boiler device provided in the primary water hot water tank 15 and the secondary water hot water tank 16, respectively, and then mixed water. It is sent to the tank 8 where the temperature is measured by the temperature sensor 18. Further, the temperature of cement is measured by a temperature sensor 17 provided in the cement measuring bucket 7.

The temperature of the water / aggregate mixture being kneaded in the concrete mixer 4 is constantly measured by the temperature sensor 22 provided in the concrete mixer 4, and based on this, the temperature is added in the primary water hot water tank 15. The temperature of the primary water in the next batch to be warmed is adjusted.

The final and actual temperature at the completion of kneading is checked from beginning to end by the temperature sensor 19 installed at the gate portion of the concrete mixer 4, and based on this, the temperature is heated in the primary water hot water tank 15. The temperature of the primary water is adjusted.

(Secondary kneading temperature control)
Further, in the present manufacturing method, if the kneading temperature of the sprayed concrete does not reach the kneading target temperature even with the primary kneading temperature control, the kneading temperature immediately before the cement is added is 40 ° C. or less. Then, as shown in FIGS. 7 to 10, the temperature of the mixer main body is raised by the mixer heating means 23 installed on the outer surface of the concrete mixer 4, and the temperature of the concrete kneading is raised. Temperature control is performed.

Since the outside air temperature is low in the cold season, even if the primary water is heated to a predetermined temperature due to the temperature decrease of the concrete mixer 4 main body and the temperature dissipation during kneading, the temperature remains high during the kneading with the concrete mixer 4. It could be reduced. Therefore, the concrete mixer 4 is heated (heated) by the mixer heating means 23 as needed to raise the kneading temperature of the concrete.

As shown in the illustrated example, the mixer heating means 23 is preferably arranged so as to cover at least the lower half of both side surfaces of the concrete mixer 4. During kneading in the concrete mixer 4, the water / aggregate mixture is mainly located in the lower half of the concrete mixer 4, so by heating this part, the water / bone in the concrete mixer 4 can be efficiently used. The material will be heated.

As a specific example of the mixer heating means 23, as shown in FIGS. 7 and 8, it can be configured by a hot water tank 24 installed on the outer surface of the concrete mixer 4. The hot water tank 24 is arranged so as to cover at least a part of the outer surface of the concrete mixer 4, and hot water adjusted to a predetermined temperature is passed through the hot water tank 24, or an injection heater is charged into the tank. By heating the filled water to a predetermined temperature, the temperature of the outer surface of the concrete mixer 4 can be adjusted. As the hot water to be charged into the hot water tank 24, hot water heated in the primary water hot water tank 15 or the secondary water hot water tank 16 may be used.

Further, as a modification of the mixer heating means 23, as shown in FIGS. 9 and 10, a heater 25 installed on the outer surface of the concrete mixer 4 may be used. Specifically, one or a plurality of linear heaters 25, 25 ... (Heating wires) in the illustrated example are arranged along the horizontal direction at predetermined intervals in the vertical direction of the concrete mixer 4. There is.

Whether or not the mixer heating means 23 is activated and the set temperature of the mixer heating means 23 are determined based on the temperature measured by the temperature sensor 19 installed at the gate portion of the concrete mixer 4.

Sprayed concrete was manufactured by changing the temperature of the kneading water and the amount of the quick-setting admixture used, and the change in the initial strength development was measured. The result is shown in FIG. Comparing Comparative Example 1 and Example 1, by raising the primary water temperature, substantially the same strength can be obtained even if the amount of the quick-setting admixture used is reduced.

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 ... Primary water temperature Water tank, 16 ... Hot water tank for secondary water, 17-20 ... Temperature sensor, 21 ... Hopper, 22 ... Temperature sensor, 23 ... Mixer heating means, 24 ... Hot water tank, 25 ... Heater

Claims (5)

In the cold season, in the batcher plant, first, fine aggregate, coarse aggregate and primary water are added to the concrete mixer and stirred, then cement is added and stirred, and then secondary water and admixture are added. In the method of producing sprayed concrete by a split kneading procedure that stirs
The kneading temperature of the sprayed concrete discharged from the concrete mixer is measured, and if this kneading temperature does not reach the kneading target temperature, the kneading temperature immediately before the cement is added is 40 ° C. or less. Then, the primary kneading temperature control for raising the concrete kneading temperature by raising the temperature of the primary water while keeping the temperature of the secondary water as it is is performed.
If the kneading temperature of the sprayed concrete does not reach the kneading target temperature even with the primary kneading temperature control, the concrete mixer is operated under the condition that the kneading temperature immediately before the cement is added is 40 ° C. or less. A method for producing sprayed concrete, which comprises performing secondary kneading temperature control for raising the temperature of the concrete kneading temperature by raising the temperature of the mixer body by a mixer heating means installed on the outer surface. The method for manufacturing sprayed concrete according to claim 1, wherein the mixer heating means is a hot water tank installed on the outer surface of the concrete mixer. The method for manufacturing sprayed concrete according to claim 1, wherein the mixer heating means is a heater installed on the outer surface of the concrete mixer. The third to third aspect of the present invention, wherein in the primary kneading temperature control, the temperature of the secondary water is maintained at 40 ° C. and the temperature of the primary water is variably controlled between 40 and 90 ° C. How to make sprayed concrete. In the primary mixing up temperature control, in order to the kneading upstream temperature theta ₀ 'immediately before turning on the cement at a predetermined temperature, wherein for calculating the temperature (Shitadaburyu1) of the primary water based on the following equation (2) Item 4. The method for producing sprayed concrete according to any one of Items 1 to 4.

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