JP3199421B2 - Concrete production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing concrete capable of reducing temperature cracks occurring in mass concrete and hot concrete.

[0002]

2. Description of the Related Art Conventionally, in order to reduce temperature cracks generated in mass concrete or hot concrete, ice (so-called flake ice) is required when kneading concrete.
A method of cooling concrete or aggregate using liquid or liquid nitrogen is used.

[0003]

However, in the method using ice, a large-scale ice-making plant is required separately from a kneading apparatus, and ice whose temperature is reduced only to the freezing point is converted to concrete W / C (water). Its cooling capacity is very limited because it must be mixed into the concrete so as not to increase the cement ratio). In addition, in the method using liquid nitrogen, it takes a very long time to cool the liquid mixer, since it is used by spraying the whole of the mixer filled with the concrete after kneading, and the liquid nitrogen has an extremely low temperature of -196 ° C. However, the cooling heat cannot be utilized sufficiently effectively, that is, the cooling efficiency in this method is 30 to 4
0% is very inefficient. Therefore, a method has been proposed in which a ready-mixed plant is modified so that aggregates such as sand and gravel are cooled in advance by a cooling facility using liquid nitrogen before kneading. However, since such aggregate cooling equipment requires a large-scale and complicated device dedicated to liquid nitrogen, it is proposed to install such aggregate cooling equipment in an existing ready-mixed plant having limited space and economy. Is difficult to adopt. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a concrete manufacturing method capable of efficiently cooling concrete with a small facility without requiring a significant improvement of a raw concrete plant. .

[0004]

That is, according to the present invention, a refrigerant (13) composed of a liquefied gas stored in a storage tank (15) under pressure is added to a pressure release zone (5) of a kneading device (2).
A), the powdered refrigerant (13 ′) is generated by being discharged into the adiabatic expansion, and the powdered refrigerant (13 ′) and the aggregate (19) are mixed in the kneading region (2) of the kneading device (2). 5B) kneading in the air, the endothermic sublimation of the powdered refrigerant (13 ') to lower the temperature of the aggregate (19) to produce the kneaded cooling aggregate (19'), The powdered refrigerant (13 ′) vaporized by the endothermic sublimation is discharged from the kneading region (5B) of the kneading device, and the cooling aggregate in the kneaded state is removed in the kneading region (5B) of the kneading device (2). (1
The concrete (26) is manufactured by putting the cement (20) and the water (25) into the 9 ') and kneading it again. The numbers and the like in parentheses are for convenience and indicate the corresponding elements in the drawings.
Therefore, the description is not limited to the description on the drawings. below

The same applies to the column of [Action].

[0005]

According to the above-mentioned structure, the present invention acts so that the cooling aggregate (19 ') in the dry kneaded state cools the cement (20) and the water (25).

[0006]

1 is a diagram showing an example of a kneading plant used in the method for producing concrete according to the present invention, and FIG. 2 is a flowchart showing an example of a method for producing concrete according to the present invention.

As shown in FIG. 1, a kneading plant 1 for kneading concrete has a mixer body 2 formed by a forced biaxial kneading mixer, and the mixer body 2 is connected via a leg 21 to a frame of the concrete plant. 3 and so on. Inside the mixer main body 2 is provided a kneading space 5 formed in a double-cave shape so as to be able to store concrete, and at the upper end of the mixer main body 2 is an input port for inputting a material constituting the concrete. A kneading space 22 is provided so as to be openable and closable, for example, so that the kneading space 5 can be opened upward in the drawing. In the kneading space 5, mixing rotors 6, 6 shown in a pair on the left and right in the figure are provided so as to be respectively arranged in left and right cavities 5 </ b> B, 5 </ b> B formed in a double sinusoidal shape of the kneading space 5. Each mixing rotor 6 is provided with two kneading blades 61 so as to be rotatable around a rotating shaft 62 along the plane of the drawing. A drive source (not shown) for rotationally driving each mixing rotor 6
Is fixed to the outside of the mixer main body 2, and a discharge port (not shown) for discharging the kneaded concrete is provided at a lower portion of the mixer main body 2 so as to be openable and closable. In addition, at the upper part of the mixer body 2, inspection windows 7, 7 having a shape shown in a pair on the left and right in the figure are provided so that the kneading space 5 is opened, and the inspection window 7 is formed in a plate shape, for example. The window member is mounted in a manner that can be opened and closed via a hinge or the like, and the state in the kneading space 5 can be visually checked by opening the window member.

By the way, a coolant supply port 9 for dropping the coolant into the kneading space 5 is provided at an upper portion of the mixer main body 2, for example, as shown in the center of an inlet 22 in the figure.
A supply pipe 16 of the refrigerant supply mechanism 11 is inserted into the refrigerant supply port 9 in a gas-tight manner via a seal (not shown) or the like.
Liquefied carbonic acid (LCO ₂ ) 13 is provided inside the refrigerant supply mechanism 11.
Is fixed at a predetermined pressure P, that is, a tank 15 in which the liquefied carbonic acid 13 is stored in a liquid state at a predetermined temperature, for example, -20 ° C., is fixed to an appropriate place such as the frame 3 of the concrete plant. The feed pipe 16 is connected to the tank 15 so as to feed the liquefied carbonic acid 13 stored in the tank 15. A nozzle 12 is provided at a distal end portion of the feed pipe 16 through a valve 17 for liquefied carbonic acid 13 stored in the tank 15.
The nozzle 12 is disposed in the upper part 5A of the kneading space 5.

Since the kneading plant 1 has the above configuration, when producing concrete using the kneading plant 1, concrete materials are kneaded one by one according to a flow chart shown in FIG. Manufacture concrete in shape. That is, first, in ST1 in FIG. 2, lightweight aggregates 19 such as sand and gravel are put into the kneading space 5 from the input port 22 through a hopper or the like of a concrete plant. A coolant for cooling the aggregate 19 is dropped into the kneading space 5. That is, in ST2, when the valve 17 of the refrigerant supply mechanism 11 is opened by a predetermined amount, the liquefied carbonic acid 13 is sent out from the tank 15 to the supply pipe 16 in such a manner that the pressure corresponding to the opening amount of the valve 17 is released from the tank 15. Come. Then, the liquefied carbonic acid 13 sent out in a form where the pressure is released from the tank 15 is sent through the feed pipe 16 under pressure, and is ejected downward from the tip of the nozzle 12 in the figure to form the kneading space 5. Is released to the upper part 5A. Then, the liquefied carbonic acid 13 which has been kept in a liquid state at about −20 ° C. by applying a predetermined pressure P in the tank 15 is discharged into the kneading space 5 and solidified by adiabatic expansion, That is, the dry ice 13 ′ exhibits a temperature state of about −80 ° C. Then, when the dry ice 13 'is discharged to the upper part 5A of the kneading space 5 in the form of being ejected from the tip of the nozzle 12 having a downward shape in the figure,
The jet force and the dry ice 13 ′ are dropped onto the aggregates 19 in the left and right cavities 5 B and 5 B in a form of falling quickly due to the weight of the dry ice 13 ′. When the aggregate 19 and the dry ice 13 ′ as the refrigerant are dropped into the kneading space 5 in this way, the aggregate 19 and the dry ice 1
3 ′ is kneaded through the mixing rotor 6. Then, in the embodiment, since the mixer main body 2 is a forced biaxial kneading mixer, at the time of the idle kneading, the mixer main body 2 remains fixed to the frame 3 and the like in the left and right cavities 5B, 5B of the kneading space 5. Only the kneading wings 61 rotate about the rotation axis 62 in a direction parallel to the plane of the drawing to knead the aggregate 19 and the dry ice 13 ′. Then, during the dry kneading step in ST3, the dry ice 13 ′ exhibiting −80 ° C. undergoes endothermic sublimation, so that the temperature of the aggregate 19 is significantly reduced. That is, since the dry ice 13 ′ is in a solid state, the dry ice 13 ′ is uniformly mixed with the rotating aggregate 19 via the mixing rotor 6 without floating in the kneading space 5 to efficiently cool the aggregate 19. Thus, a sufficiently low temperature state can be provided. The amount of the dry ice 13 ′ can be arbitrarily set by simply adjusting the open / close state of the valve 17, so that the aggregate 19 is cooled to the most economical temperature state. Kneading can be easily performed. That is, since the dry ice 13 'becomes carbon dioxide gas by endothermic sublimation and does not remain in the fresh concrete 26 after kneading, an arbitrary amount of the kneading space is obtained regardless of the W / C (water-cement ratio) of the concrete. 5 can be dropped. The amount of the dry ice 13 ′ to be dropped is determined based on the concrete temperature, cement temperature, aggregate particle size, and the like, which are specified in advance in the specifications and the like, so that the aggregate 19 has a predetermined temperature state (for example, −10 ° C., Further, the temperature may be arbitrarily adjusted so as to be a predetermined temperature state of, for example, 0 ° C. or less.

Thus, the aggregate 1 is obtained from ST1 to ST3.
When the temperature of the mixture 9 is reduced to a predetermined value, the aggregate 19 is formed of a material having a large particle size such as sand or gravel, and has a large heat storage capacity as compared with powders such as the cement 20 and the admixture 23. Therefore, in the kneading space 5, a cooling aggregate 19 ′ having a large cooling heat is generated and arranged. Therefore, next, in ST4 in FIG. 2, the cement 20 and the admixture 2 which have been previously compounded and weighed through a concrete plant.
3 and water 25 are charged into the kneading space 5 through the charging port 22.
In the step of charging the cement 20, the admixture 23, and the water 25 in ST4, this is performed while the rotation driving operation of the mixing rotor 6 in ST3 is still continued. When all the materials for one batch constituting the concrete have been dropped into the kneading space 5, the process then proceeds to ST5 in FIG. 2 to perform the main mixing of these materials. That is, in the left and right same portions 5B and 5B of the kneading space 5, while the rotation driving operation of the mixing rotor 6 is continued, the cooled kneaded aggregate 19 'which has been sufficiently cooled through the dry ice 13' is put in. , ST4, the cement 20, the admixture 23, and the water 25 are dropped. Then, the rotational driving of the mixing rotor 6 is continued until a predetermined property is obtained for these materials, whereby the fresh concrete 26 is kneaded. Then, since the cement 20 dropped in ST4 was stored in a cement silo or the like before dropping, the cement 20 exhibited an outside air temperature or a temperature state of 40 ° C. to 50 ° C. in some cases, and the water 25 was substantially at an outside air temperature. Therefore, the temperature of the concrete is relatively high with respect to the temperature of the concrete after kneading as defined by the above specifications. Therefore, when the main kneading is performed in ST5, as described above, the cooling aggregate 19 ′ having a large cooling heat is in the relatively high temperature state and the powder or fluid cement 20 and the admixture are mixed. The material 23 and the water 25 are efficiently cooled in a short period of time, and these materials are uniformly mixed to produce fresh concrete 26. After performing the main mixing until the predetermined properties are obtained in the fresh concrete 26 in this manner, then, the fully mixed fresh concrete 26 is discharged in ST6. Then, from the discharge port of the mixer body 2, sufficiently cooled and high-quality fresh concrete 26 is discharged, whereby the manufacturing process of one batch of fresh concrete 26 is completed.

Therefore, the cooling aggregate 19 'is obtained from the aggregate 19 having a large heat storage capacity by the latent heat of cooling of the liquefied carbonic acid 13 (dry ice 13') dropped into the kneading space 5 in ST2. The cement 20 and the admixture 23 and the water 25 are cooled by the
Is discharged to the outside of the mixer main body 2 and the like, so that 70 to 80% (experimental value) thereof is effectively used to cool the fresh concrete 26. Therefore, when mass concrete or hot concrete is molded from the low-temperature fresh concrete 26 thus kneaded and discharged, a solid structure having a greatly reduced possibility of temperature cracking can be obtained. In addition, dry ice 13 '
Is sublimated into carbon dioxide gas. If the carbon dioxide gas is discharged to the outside of the mixer main body 2 through the input port 22 or another exhaust port during or after the step of kneading the aggregate 19 in the ST3, It is possible to avoid such a danger that carbon dioxide gas is mixed into the fresh concrete 26 and becomes a hindrance in the main mixing step in ST5 or a factor that promotes the neutralization after the concrete is hardened. At this time, since the dry ice 13 ′ sublimes in a sufficiently short time and all of it becomes carbon dioxide, it is very easy to discharge the dry ice 13 ′ from the kneading space 5 only by exhausting it while rotating the mixing rotor 6. Can be done. In addition, since the refrigerant supply mechanism 11 can be freely removed from the mixer main body 2 by extracting the feed pipe 16 through the refrigerant supply port 9 of the mixer main body 2, the kneading plant 1 can be operated as described above. It is naturally possible to use not only for kneading the cooled concrete but also for kneading ordinary concrete or other concrete. Further, when the feed pipe 16 and the nozzle 12 are deteriorated or broken, etc., the kneading plant 1 is cooled again by replacing only the feed pipe 16 and the nozzle 12 without replacing the mixer body 2. Since it can be used for concrete kneading, the maintenance of the apparatus is easy, that is, economical concrete kneading can be performed using a simple apparatus. Further, in the above-described embodiment, the example in which the liquefied carbonic acid 13 is used as the refrigerant for cooling the aggregate 19 has been described.
The refrigerant dropped into the kneading space 5 is not limited to this, and may be another liquefied gas. Further, when the refrigerant composed of the liquefied gas is dropped into the kneading space 5 to knead the aggregate 19 with the aggregate 19, it is not necessary to drop the aggregate 19 into the kneading space 5 as described above. For example, before the aggregate 19 is dropped into the kneading space 5, or the aggregate 1
9 at the same time, or while the aggregate 19 is rotating via the mixing rotor 6, and so on.

[0012]

As described above, according to the present invention,
A refrigerant composed of a liquefied gas such as liquefied carbon dioxide 13 stored in a storage tank such as a tank 15 under pressure is mixed with the mixer body 2.
The powdered refrigerant such as dry ice 13 ′ is generated by releasing into the pressure release area such as the upper part 5A of the kneading space of the kneading device of the kneading device and the like, and the powdered refrigerant and the aggregate 19 are kneaded. The kneading device of the device is kneaded in a kneading region such as a cavity 5B and the like, and the powdered refrigerant is absorbed and sublimated to lower the temperature of the aggregate 19 to generate the kneaded cooling aggregate 19 ′. The powdered refrigerant vaporized by endothermic sublimation is discharged from the kneading region of the kneading device, and in the kneading region of the kneading device, the cement 20 and the water 25 are put into the cooling aggregate 19 ′ in the kneaded state. Since the concrete such as the fresh concrete 26 is manufactured by kneading again, the cooling aggregate 19 ′ in an empty kneaded state is formed.
Can cool the cement 20 and the water 25. At this time, the aggregate 19 has a large heat storage capacity due to its large particle size as compared with the cement 20, the water 25, and the like. Therefore, the kneaded cooling aggregate 19 'cooled by the refrigerant generates a large cooling heat. When the cement 20 and the water 25 are charged into the cooling aggregate 19 ', the cement 20 and the water 25 can be efficiently cooled in a short time. When the hot concrete or the mass concrete is cast using the concrete that has been sufficiently cooled in this way, a solid structure with a low risk of occurrence of temperature cracks can be constructed. The powdered refrigerant that is kneaded with the aggregate 19 is obtained by adiabatically expanding the liquefied gas, so that the powdered refrigerant sublimates during kneading, that is, only its cold heat is used to produce a gaseous substance. Is eventually discharged from the concrete. Therefore, the refrigerant has no effect on the concrete W / C (water-cement ratio) which must be taken into consideration when cooling the concrete using ice or the like. This can be used freely. Also,
The present invention utilizes an existing suitable mixer, and only feeds the refrigerant together with the aggregate 19 into the mixer.
Cooling concrete can be produced economically without the need for large-scale equipment and complicated equipment, so that there is no need to make significant improvements to existing ready-mixed plants even if they already exist. Therefore, the ready-mixed concrete plant can be efficiently used by diverting the ready-mixed plant to both the production of the cooled concrete and the production of other concrete, for example.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a kneading plant used in a method for producing concrete according to the present invention.

FIG. 2 is a flowchart showing an example of a method for producing concrete according to the present invention.

[Explanation of symbols]

 2 Mixer body (kneading device) 5A Upper part of kneading space (pressure release area of kneading device) 5B ... kneading space cavity (kneading region of kneading device) 13 Liquid carbonic acid (refrigerant) 13 'dry Ice (pulverized refrigerant) 15 Tank (storage tank) 19 Aggregate 19 'Cooling aggregate 20 Cement 25 Water 26 Fresh concrete (concrete)

Continuing from the front page Examiner Mitsuo Teramoto (56) References JP-A-2-292003 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B28C 1/00-9/04

Claims (1)

(57) [Claims] 1. A powdered refrigerant is generated by discharging a refrigerant composed of a liquefied gas stored in a storage tank in a pressure-applied form into a pressure release region of a kneading device and adiabatically expanding the refrigerant. The kneaded refrigerant and the aggregate are kneaded in the kneading region of the kneading apparatus, and the temperature of the aggregate is reduced by absorbing and sublimating the powdered refrigerant to generate the cooled aggregate in the kneaded state and heat absorption. The powdered refrigerant vaporized by sublimation is discharged from the kneading region of the kneading device, and in the kneading region of the kneading device, cement and water are added to the cooling aggregate in the kneaded state and kneaded again to mix concrete. A method for producing concrete, configured to produce a concrete.