JPH074812B2 - Method for producing cooled concrete mixture - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a cooled concrete kneaded product.

[Conventional technology]

It is said that the pre-cooling method that lowers the kneading temperature of concrete is effective for suppressing the temperature cracks generated in the mass concrete structure.

For example, in JP-A-62-74603, JP-A-62-77907, and JP-A-63-4169, it is attempted to utilize the cooling capacity for vaporizing liquefied nitrogen for precooling of concrete. An invention has been proposed.

[Object of the Invention]

One object of the present invention is to avoid the adverse effect on the physical properties of concrete, which is a problem when the cooling capacity for vaporizing liquefied nitrogen is used for precooling of concrete,
Another object is to sufficiently draw the cooling capacity of liquefied nitrogen in the existing equipment and to obtain uniform cooling of the material.

[Structure of Invention]

The object of the present invention to achieve the above object is to produce a cooled concrete kneaded product.
First, while solid kneading the solid compound material before adding compounding water in a mixer, a solid mixture cooled by spraying liquefied nitrogen from a spray nozzle to the solid material in this compounding is produced, and then obtained. Compounding water is added to the obtained cooled solid mixture and kneading is performed.

[Detailed Description of the Invention]

The present invention can be carried out using an ordinary concrete mixer for producing a concrete kneaded product. First
As shown in the figure, the lid 2 is attached to the concrete mixer 1, the exhaust duct 3 is attached to the lid 2, and the spray nozzle 4 is installed. This spray nozzle 4 has a disk body 6 at the tip of a fixed pipe 5 as schematically shown in FIG.
Is rotatably mounted around the axis of the pipe 5, and the rotating disk body 6 is provided with a nozzle opening 7 whose discharge direction is directed in the tangential direction of the disk. It has a structure that leads to the fixed pipe 5 via a passage 8 in 6. Therefore, when liquefied nitrogen is supplied into the fixed pipe 5, it is discharged from the nozzle port 7 into the atmosphere through the passage 8 in the disc body 6. At that time, the liquefied nitrogen is instantaneously expanded and vaporized in the atmosphere and jetted from the nozzle port 7 at high speed, and the jet pressure causes the disc body 6 to rotate around the axis of the fixed pipe 5. The spray nozzle 4 and the exhaust duct 3 which rotate by such injection pressure are installed in a normal concrete mixer 1, and in the present invention, first, in the mixer 1,
Solid materials such as cement, sand, and gravel are charged, and an empty kneading operation is performed without adding water. During the empty kneading operation, liquefied nitrogen is supplied to the spray nozzle 4 from the liquefied nitrogen container through the flow rate adjusting valve 9. To supply. As a result, low-temperature nitrogen gas is sprayed from the spray nozzle 4 onto the solid material flowing in the mixer 1. At that time, the spray nozzle 4 continues to rotate by the injection pressure of liquefied nitrogen as described above. Therefore, the liquid nitrogen is not sprayed on one specific place, but is sprayed uniformly over a large area of the solid material. Moreover, since the solid material continues to flow due to the rotation of the mixer blades 10, uniform cooling over the entire material is achieved rather than local cooling. As long as this injection of liquefied nitrogen is continued, the temperature of the solid material will continue to be cooled to zero degrees Celsius without problems of freezing or cement denaturation. In practice, the temperature of the bottom inner wall of the mixer 1 is continuously detected by the temperature sensor 11, and when the inner wall temperature is lowered to an appropriate temperature, the kneading and the liquefied nitrogen injection operation may be stopped.

When this operation is completed, then compounding water is added to the mixer 1 in which the low temperature solid material is present, and kneading is performed. If necessary, an admixture or the like is also added. After adding the compounding water, injection of liquefied nitrogen is not performed except in special cases.
That is, a low temperature kneading material is manufactured by kneading the low temperature fixing material and water. At that time, it is of course advantageous to cool the water in advance and use low-temperature water as the compound water.
For cooling this water, it is also possible to introduce nitrogen gas discharged from the exhaust duct 3 to a water-to-gas heat exchanger and cool the water with this heat exchanger.

A person skilled in the art can easily estimate the kneading temperature by using a predetermined relational expression by knowing the temperature of the cooled solid material and the temperature of the mixed water by the temperature sensor 11. Therefore, according to the present invention, the kneading temperature can be estimated relatively easily and the temperature control is easy.

〔The invention's effect〕

According to the present invention, the cooling ability when liquefied nitrogen vaporizes is exhibited in the kneading of the concrete material. Since the cooling is performed in the absence of water, the problem of freezing is eliminated. And with a little modification to the existing concrete mixer, it can be converted into a concrete pre-cooling facility. Also, even if you change it to a pre-cooling facility, you can freely return it to the original mixer. Therefore, it is possible to selectively perform the precooling operation only when the ambient temperature is high throughout the year. In addition, since cooling is performed in the mixer using a spray nozzle while performing kneading, it is possible to avoid the presence of a cooled portion and an uncooled portion, and to cool the solid material uniformly. Moreover, the degree of cooling can be made extremely strong and the kneading temperature can be easily controlled. Therefore, it is possible to easily and rationally prevent the problem of temperature cracking when constructing a mass concrete structure such as dam construction, depending on the site situation.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a concrete mixer for carrying out the present invention, and FIG. 2 is a perspective view showing an example of a spray nozzle attached to the mixer of FIG. 1 …… Concrete mixer, 2 …… Lid, 3 …… Exhaust duct, 4 …… Spraying nozzle, 5 …… Fixed pipe, 6 …… Disc body, 7…
… Nozzle port, 9… Flow control valve.

Claims (1)

[Claims] 1. When manufacturing a cooled concrete kneaded product, while liquefying the solid compounding material before adding compounding water in a mixer, liquefied nitrogen is sprayed from the spray nozzle to the solid material in this compounding. A method for producing a cooled concrete kneaded product, which comprises producing a cooled solid mixture by spraying, and adding compounding water to the cooled solid mixture and kneading.