Fresh concrete manufacturing apparatus, and method for manufacturing mortar or fresh concrete

Abstract

The present invention provides a fresh concrete manufacturing apparatus that can pre-mix fine aggregate and cement while limiting the amount of water. [Solution] Before mixing all materials in the second mixer 60, the fine aggregate and cement are pre-mixed in the first mixer 50. Since no mixing water is supplied to the first mixer 50, the amount of moisture adhering to the inner surface of the first mixer 50 can be suppressed. Therefore, the pre-mixing of the fine aggregate and cement in the first mixer 50 can be carried out with a limited amount of moisture.

Description

Technical Field

[0001] The present invention relates to a technique for producing mortar or fresh concrete.

Background Art

[0002] Concrete, which is a building material, is produced by kneading fine aggregate, coarse aggregate, cement, and water as main raw materials in a mixer. Fresh concrete (green concrete) immediately after production has fluidity, but as time passes, the hydration reaction progresses and it eventually hardens.

[0003] Conventionally, in order to increase the fluidity of fresh concrete, an admixture may be added to the above materials. A method for producing fresh concrete using an admixture is described in, for example, Patent Document 1.

[0004] In the production method of Patent Document 1, first, only fine aggregate and cement are pre-mixed for a predetermined time. As a result, cement particles form flocs due to the action of the surface water of the fine aggregate. Then, water and an admixture are added and kneading is performed. Then, the amount of the admixture adsorbed on the cement particles in the initial stage of kneading is suppressed, and an excess admixture remains in the liquid phase. And the excess admixture improves the fluidity of the fresh concrete produced by subsequent kneading.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the manufacturing method described in Patent Document 1, it is necessary to strictly limit the amount of water during the pre-mixing of the fine aggregate and cement. However, if the pre-mixing of the fine aggregate and cement and the subsequent mixing of all materials, including the mixing water, are performed in the same mixer, moisture will adhere to the inner wall of the mixer after the mixing of all materials. This could then affect the pre-mixing of the fine aggregate and cement when producing the next batch of fresh concrete.

[0007] Therefore, the present invention aims to provide a fresh concrete manufacturing apparatus that can pre-mix fine aggregate and cement while limiting the amount of water. [Means for solving the problem]

[0008] The first invention of this application is a fresh concrete manufacturing apparatus comprising: a fine aggregate supply unit for supplying fine aggregate; a cement supply unit for supplying cement; a coarse aggregate supply unit for supplying coarse aggregate; a mixing water supply unit for supplying mixing water; a first mixer for obtaining a mixed material of fine aggregate and cement by mixing the fine aggregate supplied from the fine aggregate supply unit and the cement supplied from the cement supply unit; and a second mixer for obtaining fresh concrete by mixing the mixed material discharged from the first mixer with the coarse aggregate supplied from the coarse aggregate supply unit and the mixing water supplied from the mixing water supply unit.

[0009] The second invention of this application is a fresh concrete manufacturing apparatus of the first invention, wherein the fine aggregate has surface water, the mixing water contains an admixture, and the fine aggregate and the cement are mixed in the first mixer so that the cement particles form flocs.

[0010] The third invention of this application is a fresh concrete manufacturing apparatus of the second invention, wherein, in the surface moisture content test method specified in JIS A 1111:2015, the surface moisture content of the fine aggregate is 2% or more and 5% or less.

[0011] The fourth invention of this application is a fresh concrete manufacturing apparatus according to the second or third invention, wherein the mixed material obtained in the first mixer is allowed to stand for a predetermined time before being supplied to the second mixer.

[0012] The fifth invention of this application is a fresh concrete manufacturing apparatus according to any one of the first to fourth inventions, further comprising a switching mechanism for switching the supply destination of the fine aggregate supply unit and the cement supply unit between the first mixer and the second mixer.

[0013] The sixth invention of this application is a fresh concrete manufacturing apparatus according to any one invention from the first invention to claim 5, wherein the first mixer is located above the second mixer, and the mixing material is supplied from the first mixer to the second mixer by its own weight.

[0014] The seventh invention of this application is a fresh concrete manufacturing apparatus according to any one of the first to fifth inventions, further comprising a feeder for transporting the mixed material from the first mixer to the second mixer.

[0015] The eighth invention of this application is a fresh concrete manufacturing apparatus according to any one of the first to seventh inventions, wherein the vertical dimension of the first mixer is smaller than the vertical dimension of the second mixer.

[0016] The ninth invention of this application is a fresh concrete manufacturing apparatus of the eighth invention, wherein the first mixer is a turbine mixer and the second mixer is a twin-screw forced mixer.

[0017] The tenth invention of this application is a method for producing mortar or fresh concrete using the fresh concrete production apparatus of the second invention, comprising: a pre-mixing step of mixing the fine aggregate and the cement in the first mixer to obtain the mixed material; and a first mixing step of adding the mixing water to the mixed material in the second mixer after the pre-mixing step and mixing further to obtain mortar, wherein the pre-mixing step is performed in the absence of the mixing water and in the presence of surface water already contained in the fine aggregate. [Effects of the Invention]

[0018] According to the first to tenth inventions, the fine aggregate and cement are pre-mixed in the first mixer before mixing all the materials in the second mixer. Since no mixing water is supplied to the first mixer, the amount of moisture adhering to the inner surface of the first mixer can be suppressed. Therefore, the pre-mixing of the fine aggregate and cement in the first mixer can be carried out with a limited amount of moisture.

[0019] In particular, according to the second invention, in the first mixer, surface water of the fine aggregate causes the cement particles to form flocs. As a result, the specific surface area of ​​the cement decreases, and in the second mixer, excess admixture remains without adsorbing to the cement particles. This excess admixture can improve the fluidity of the fresh concrete.

[0020] In particular, according to the third invention, flocs of an appropriate size can be formed in the first mixer.

[0021] In particular, according to the fourth invention, flocs in the mixed material can be grown by allowing the mixed material to stand.

[0022] In particular, according to the fifth invention, if pre-mixing of fine aggregate and cement is required, the fine aggregate and cement can be supplied to the first mixer. Also, if pre-mixing of fine aggregate and cement is not required, the fine aggregate and cement can be supplied directly to the second mixer.

[0023] In particular, according to the sixth invention, the supply of the mixing material from the first mixer to the second mixer can be realized without using power.

[0024] In particular, according to the seventh invention, it is not necessary to arrange the first mixer above the second mixer. As a result, the degree of freedom in arranging the first mixer is improved.

[0025] In particular, according to the eighth invention, the first mixer can be provided, and the vertical dimension of the fresh concrete manufacturing apparatus can be suppressed.

[0026] In particular, according to the ninth invention, the height of the first mixer can be suppressed. Also, sufficient kneading can be performed in the second mixer.

[0027] In particular, according to the tenth invention, the divided input of the mixing water is not required, and the flocs of cement particles can be stably formed.

Brief Description of the Drawings

[0028] [Figure 1] It is a diagram showing the configuration of a fresh concrete manufacturing apparatus. [Figure 2] It is a flowchart showing the manufacturing procedure of fresh concrete. [Figure 3] It is a diagram schematically showing the state of cement particles in the pre-mixing process. [Figure 4] It is a diagram schematically showing the state in which an admixture is adsorbed on cement particles without flocs formed. [Figure 5] It is a diagram schematically showing the state in which an admixture is adsorbed on cement particles with flocs formed. [Figure 6] It is a diagram showing the configuration of a fresh concrete manufacturing apparatus according to the first modification. [Figure 7] It is a diagram showing the configuration of a fresh concrete manufacturing apparatus according to the second modification.

Embodiments for Carrying Out the Invention

[0029] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0030] <1. Fresh Concrete Manufacturing Equipment> Figure 1 shows the configuration of a fresh concrete manufacturing apparatus 1 according to one embodiment of the present invention. This fresh concrete manufacturing apparatus 1 is a device that manufactures fresh concrete (ready-mixed concrete) by mixing fine aggregate, cement, water, admixture, and coarse aggregate. As shown in Figure 1, the fresh concrete manufacturing apparatus 1 includes a fine aggregate supply unit 10, a cement supply unit 20, a coarse aggregate supply unit 30, a mixing water supply unit 40, a first mixer 50, a second mixer 60, and a control unit 70.

[0031] The fine aggregate supply unit 10 is a mechanism for supplying fine aggregate to the first mixer 50. The fine aggregate supply unit 10 is located above the first mixer 50. The fine aggregate supply unit 10 has a hopper 11 and a gate 12. The fine aggregate before supply is stored inside the hopper 11. The gate 12 opens and closes a supply port 13 located at the bottom of the hopper 11. The fine aggregate supply unit 10 also has a measuring device (not shown) for measuring the amount of fine aggregate supplied.

[0032] The fine aggregate supply unit 10 operates the weighing device and gate 12 according to the control signal input from the control unit 70. This supplies the fine aggregate stored in the hopper 11 to the first mixer 50 at the specified timing and in the specified amount. The fine aggregate falls into the first mixer 50 from the supply port 13 of the hopper 11 by its own weight.

[0033] Fine aggregate is aggregate with a smaller particle size than coarse aggregate, which will be discussed later. Examples of fine aggregate include natural sand (sea sand, mountain sand, river sand, etc.), crushed sand, and crushed limestone sand. Crushed sand conforming to JIS A 5005:2009 is preferably used. Natural sand conforming to JIS A 5308:2019 is preferably used. However, the types of fine aggregate are not limited to the examples above. Fine aggregate may also be recycled aggregate, slag-based aggregate, or other alternative aggregates.

[0034] As will be understood by those skilled in the art, fine aggregate is produced and manufactured in a quarry or crushing plant, but by the time it is delivered to the batching plant equipped with the fresh concrete manufacturing apparatus 1, the fine aggregate already contains a considerable amount of surface water. Reasons for this include, for example, exposure to rainwater due to open-air storage, undergoing wet classification and washing processes, and the addition of a small amount of water in a post-dry classification process for dust control. Furthermore, the surface water content of the fine aggregate may be adjusted in advance to a predetermined value.

[0035] The cement supply unit 20 is a mechanism for supplying cement to the first mixer 50. The cement supply unit 20 is located above the first mixer 50. The cement supply unit 20 has a hopper 21 and a valve 22. The cement before supply is stored inside the hopper 21. The valve 22 opens and closes the supply port 23 located at the bottom of the hopper 21. The cement supply unit 20 also has a measuring device (not shown) for measuring the amount of cement supplied.

[0036] The cement supply unit 20 operates the measuring device and valve 22 according to the control signal input from the control unit 70. This supplies the cement stored in the hopper 21 to the first mixer 50 at the specified timing and in the specified amount. The cement falls into the first mixer 50 from the supply port 23 of the hopper 21 by its own weight.

[0037] Cement is a powder composed of fine calcareous particles. Examples of cements used include ordinary cement, rapid-hardening cement, moderate-heat cement, or low-heat cement. Furthermore, cement may be a mixture of two or more types of cement. In addition, "cement" in this invention may refer to cement substitute materials such as fly ash, blast furnace slag, or geopolymers used in environmentally friendly concrete. That is, as "cement" in this invention, various hydraulic binders (binding agents) that exhibit a hydration reaction and hardening action, either alone or in the presence of an stimulant, can be used.

[0038] The coarse aggregate supply unit 30 is a mechanism for supplying coarse aggregate to the second mixer 60. The coarse aggregate supply unit 30 is located above the second mixer 60. The coarse aggregate supply unit 30 has a hopper 31 and a gate 32. The coarse aggregate before supply is stored inside the hopper 31. The gate 32 opens and closes a supply port 33 located at the bottom of the hopper 31. The coarse aggregate supply unit 30 also has a measuring device (not shown) for measuring the amount of coarse aggregate supplied.

[0039] The coarse aggregate supply unit 30 operates the weighing device and gate 32 according to the control signal input from the control unit 70. This supplies the fine aggregate stored in the hopper 31 to the second mixer 60 at the specified timing and in the specified amount. The coarse aggregate falls into the second mixer 60 from the supply port 33 of the hopper 31 by its own weight.

[0040] Coarse aggregate is aggregate with a larger particle size than the fine aggregate mentioned above. For example, crushed stone, natural gravel (such as river gravel), or recycled aggregate can be used as coarse aggregate.

[0041] The mixing water supply unit 40 is a mechanism that supplies mixing water, which contains water and an admixture, to the second mixer 60. The mixing water supply unit 40 is connected to the second mixer 60 via piping 41. The mixing water supply unit 40 consists of a water tank, an admixture tank, a measuring device, valves, a pump, etc. The mixing water supply unit 40 mixes the water and admixture in a specified ratio according to the control signal input from the control unit 70 and supplies it to the second mixer 60.

[0042] The water used for mixing is, for example, tap water, groundwater, or river water. However, the mixing water may also contain recovered water, such as the supernatant liquid of concrete sludge. Admixtures (chemical admixtures) are industrial chemicals that adsorb to cement particles and cause the cement particles to repel each other. Admixtures used include water-reducing agents, high-performance water-reducing agents, or combinations thereof, which are types of surfactants. Admixtures mainly consist of, for example, polycarboxylic acid-based water-reducing agents that have steric hindrance, or naphthalene-based or melamine-based water-reducing agents that have electrostatic repulsion. As bases for admixtures, for example, polystyrene sulfonates, polycarboxylates, naphthalene sulfonates, or melamine sulfonates are used.

[0043] The first mixer 50 is a mixer that mixes the fine aggregate supplied from the fine aggregate supply unit 10 with the cement supplied from the cement supply unit 20. The first mixer 50 is positioned above the second mixer 60 and below the fine aggregate supply unit 10 and the cement supply unit 20.

[0044] The first mixer 50 has a container 51 capable of containing fine aggregate and cement, and a blade 52 that rotates inside the container 51. The container 51 contains the fine aggregate and cement. The first mixer 50 mixes the fine aggregate and cement in the container 51 by rotating the blade 52. This yields a mixture of fine aggregate and cement. In this embodiment, the first mixer 50 does not have a function to supply mixing water. That is, the piping 41 of the mixing water supply unit 40 does not branch out into the inside of the first mixer 50. Furthermore, the first mixer 50 does not have any other liquid supply mechanism.

[0045] The first mixer 50 mixes only the fine aggregate and cement from the fresh concrete materials. Therefore, the first mixer 50 has a smaller capacity than the second mixer 60. For example, the vertical dimension of the first mixer 50 is smaller than that of the second mixer 60. Also, the power required for the first mixer 50 is less than that of the second mixer 60. The first mixer 50 can be equipped with, for example, a turbine mixer, a Smith mixer, a twin-screw forced mixer, a screw feeder, a centrifuge, etc.

[0046] For example, a turbine mixer rotates blades 52 around a vertically extending axis within a flat, cylindrical container 51. Therefore, using a turbine mixer allows for a reduction in the vertical dimension of the first mixer 50. Consequently, the overall vertical dimension of the fresh concrete manufacturing apparatus 1, including the first mixer 50, can be reduced.

[0047] The bottom of the first mixer 50 is provided with an outlet 53 for discharging materials and a gate 54 for switching the opening and closing of the outlet 53. The gate 54 is movable between a closed position that closes the outlet 53 and an open position that opens the outlet 53. The first mixer 50 mixes fine aggregate and cement with the gate 54 in the closed position. After the mixing of the fine aggregate and cement is complete, the gate 54 is moved to the open position, thereby discharging the mixed material inside the first mixer 50 from the outlet 53 to the second mixer 60. The mixed material falls from the outlet 53 of the first mixer 50 to the second mixer 60 by its own weight.

[0048] The second mixer 60 is a mixer that mixes all the materials for fresh concrete. The second mixer 60 is located below the first mixer 50 and the coarse aggregate supply unit 30. The second mixer 60 is supplied with fine aggregate and cement mixture materials from the first mixer 50. Mixing water is also supplied to the second mixer 60 from the mixing water supply unit 40. Coarse aggregate is also supplied to the second mixer 60 from the coarse aggregate supply unit 30.

[0049] The second mixer 60 has a container 61 and a blade 62 that rotates inside the container 61. The container 61 contains fine aggregate, cement, coarse aggregate, and mixing water. The second mixer 60 mixes the fine aggregate, cement, coarse aggregate, and mixing water inside the container 61 by rotating the blade 62. This produces fresh concrete.

[0050] The second mixer 60 mixes all the materials for the fresh concrete. For this reason, the container 61 of the second mixer 60 has a larger capacity than the container 51 of the first mixer 50. Also, the power of the second mixer 60 is greater than that of the first mixer 50. For example, a twin-shaft forced mixer is used for the second mixer 60. A twin-shaft forced mixer has two sets of blades 62 that rotate around a horizontally extending rotation axis inside the container 61. However, the second mixer 60 may be a mixer other than a twin-shaft forced mixer.

[0051] The control unit 70 is a unit that controls the operation of each part of the fresh concrete manufacturing apparatus 1. The control unit 70 is composed of a computer having, for example, a processor such as a CPU, memory such as RAM, and a storage unit such as a hard disk drive.

[0052] The control unit 70 outputs control signals to each part of the fresh concrete manufacturing apparatus 1 according to the computer program and various setting values. As a result, the supply of fine aggregate from the fine aggregate supply unit 10 to the first mixer 50, the supply of cement from the cement supply unit 20 to the first mixer 50, the mixing of materials in the first mixer 50, the supply of mixed materials from the first mixer 50 to the second mixer 60, the supply of mixing water from the mixing water supply unit 40 to the second mixer 60, the supply of coarse aggregate from the coarse aggregate supply unit 30 to the second mixer 60, and the mixing of materials in the second mixer 60 are performed.

[0053] <2. Method for manufacturing fresh concrete> Next, we will explain how to manufacture fresh concrete using the fresh concrete manufacturing apparatus 1 described above. Figure 2 is a flowchart showing the fresh concrete manufacturing procedure. The manufacturing procedure in Figure 2 is realized by the control unit 70 described above controlling the operation of the fine aggregate supply unit 10, the cement supply unit 20, the coarse aggregate supply unit 30, the mixing water supply unit 40, the first mixer 50, and the second mixer 60.

[0054] The fresh concrete manufacturing apparatus 1 first supplies fine aggregate from the fine aggregate supply unit 10 into the container 51 of the first mixer 50, and simultaneously supplies cement from the cement supply unit 20 into the container 51 of the first mixer 50 (first supply step S1). At this time, the amount of fine aggregate and cement supplied is appropriate to the mix of the fresh concrete. Furthermore, the fine aggregate supplied from the fine aggregate supply unit 10 is not completely dry, but contains water (surface water) on its surface.

[0055] Next, the first mixer 50 rotates its blades 52. This mixes the fine aggregate and cement in the container 51 of the first mixer 50 (pre-mixing step S2). Then, by continuing the mixing of the materials in the first mixer 50 for a predetermined time, a mixture of fine aggregate and cement is obtained.

[0056] Figure 3 is a schematic diagram showing the state of cement particles in the pre-mixing step S2. When fine aggregate and cement are mixed in the pre-mixing step S2, surface water of the fine aggregate comes into contact with the cement particles. Then, due to the action of water moving from the surface of the fine aggregate to the cement particles, the cement particles aggregate together to form flocs F, as shown in Figure 3. This is thought to be because a positive charge is generated on the surface of the cement particles during the hydration reaction caused by the addition of water, and this charge attracts the cement particles to each other.

[0057] Floc F is an aggregate with a particle size of approximately 10 to several tens of micrometers. The average particle size of floc F is larger than the average particle size of cement (approximately 10 μm). When cement particles form floc F, the specific surface area of ​​the cement becomes smaller compared to when floc F is not formed.

[0058] The mixing time of the materials in the pre-mixing step S2 is set to a time sufficient to suppress the specific surface area of ​​the cement by allowing the cement particles to form flocs F. For example, by setting the mixing time of the materials in the pre-mixing step S2 to 30 seconds or more, the growth of flocs F is promoted, and the specific surface area of ​​the cement can be significantly reduced.

[0059] After the pre-mixing step S2 for a predetermined time is completed, the fresh concrete manufacturing apparatus 1 may stop the rotation of the blades 52 and allow the obtained mixed material to stand in the first mixer 50 for a predetermined time. By allowing the mixed material to stand, the flocs F in the mixed material can grow. For example, after the completion of the pre-mixing step S2, the mixed material may be allowed to stand for 1 minute or more.

[0060] Subsequently, the first mixer 50 opens its discharge port 53 by operating its gate 54. This allows the mixed aggregate and cement to be supplied from the container 51 through the discharge port 53 into the container 61 of the second mixer 60. The fresh concrete manufacturing apparatus 1 also supplies mixing water containing water and admixtures from the mixing water supply unit 40 into the container 61 of the second mixer 60 (second supply step S3). At this time, the amount of mixed materials and mixing water supplied is set to match the proportions of the fresh concrete.

[0061] Next, the second mixer 60 starts rotating its blades 62. This mixes the fine aggregate, cement, and mixing water inside the second mixer 60 (first mixing step S4). By continuing the mixing of the materials in the second mixer 60 for a predetermined time, a mortar consisting of fine aggregate, cement, water, and admixtures is obtained.

[0062] Figure 4 schematically shows how the admixture is adsorbed onto cement particles in which floc F has not been formed. Figure 5 schematically shows how the admixture is adsorbed onto cement particles in which floc F has been formed.

[0063] In the case of Figure 4, the admixture is adsorbed onto individual cement particles. Therefore, in the case of Figure 4, excess admixture is less likely to be generated in the liquid phase. In contrast, in the first mixing step S4 of this embodiment, as shown in Figure 5, the admixture is adsorbed onto cement particles whose specific surface area has been reduced by the formation of floc F. Therefore, the amount of admixture adsorbed onto cement particles is less in the case of Figure 5 than in the case of Figure 4. As a result, in the first mixing step S4 of this embodiment, some of the supplied admixture remains in the liquid phase as excess admixture without being adsorbed onto the cement particles.

[0064] Once the first mixing process S4, which has been completed for a predetermined time, is finished, the fresh concrete manufacturing apparatus 1 then supplies coarse aggregate from the coarse aggregate supply unit 30 into the container 61 of the second mixer 60 (third supply process S5). At this time, the amount of coarse aggregate supplied is set to match the mix of the fresh concrete.

[0065] Then, the second mixer 60 continues to rotate the blades 62. This mixes the fine aggregate, cement, mixing water, and coarse aggregate within the second mixer 60 (second mixing step S6). By continuing the mixing of the materials in the second mixer 60 for a predetermined time, fresh concrete consisting of fine aggregate, cement, water, admixture, and coarse aggregate is obtained.

[0066] As described above, some of the admixtures added in the second supply process S3 remain as excess admixtures without being adsorbed onto the cement particles. These excess admixtures improve the fluidity of the mortar obtained in the first mixing process S4 (for example, the flow value measured using the test method described in JIS R 5201:2015) and the fluidity of the fresh concrete obtained in the second mixing process S6 (for example, the flow value measured using the test method specified in JIS A 1150:2007).

[0067] In other words, in the manufacturing method of this embodiment, the fine aggregate and cement are mixed in the pre-mixing step S2 before the mixing water is supplied. As a result, the cement particles form flocs F, and the specific surface area of ​​the cement decreases. Consequently, the amount of admixture adsorbed in the first mixing step S4 is reduced. Therefore, even without using a large amount of admixture, excess admixture that does not adsorb to the cement particles can be generated in the initial stage of the first mixing step S4. This excess admixture then improves the fluidity of the mortar produced in the first mixing step S4 and the fresh concrete produced in the second mixing step S6. Thus, it is possible to improve the fluidity of mortar and fresh concrete while suppressing the amount of admixture used.

[0068] Furthermore, at least a portion of the flocs F generated in the pre-mixing step S2 may be decomposed into multiple cement particles in the second mixing step S6. However, it is thought that the decomposed cement particles will also be well dispersed by the adsorption of the excess admixture mentioned above. Alternatively, in the first mixing step S4 and the second mixing step S6, hydration products are sequentially generated when the mixing water and cement particles come into contact. If the admixture already adsorbed on the cement particles (or hydration products) is incorporated into these hydration products, the dispersion effect of the admixture will be weakened. However, it is thought that the excess admixture mentioned above will sequentially adsorb onto the surface of the newly generated hydration products, thereby maintaining these hydration products in a dispersed state. As a result, it is thought that the fluidity of the fresh concrete can be improved compared to when there is no excess admixture.

[0069] In the first supply process S1, the surface moisture content of the fine aggregate supplied is preferably 2% or more and 5% or less according to the surface moisture content test method specified in JIS A 1111:2015, as described in Patent Document 1. By setting the surface moisture content of the fine aggregate to 2% or more, in the pre-mixing process S2, the cement particles become flocs F of an appropriate size of about 10 to several tens of micrometers. Furthermore, excessively enlarged flocs F can actually impair the fluidity of fresh concrete, but by setting the surface moisture content of the fine aggregate to 5% or less, the generation of such excessively enlarged flocs F in the pre-mixing process S2 can be suppressed. As a result, the mixing time required to break up the flocs F in the first mixing process S4 or the second mixing process S6 can be shortened.

[0070] The mixing time in the pre-mixing step S2 may be adjusted according to the surface moisture content of the fine aggregate. For example, the control unit 70 may be configured to accept input for the surface moisture content of the fine aggregate, and the control unit 70 may set the mixing time based on the input surface moisture content. Specifically, if the surface moisture content of the fine aggregate is higher than a predetermined value, it is advisable to set a longer mixing time in the pre-mixing step S2. As mentioned above, if the surface moisture content of the fine aggregate is higher than a predetermined value, the flocs F tend to become excessively enlarged, but by setting a longer mixing time in the pre-mixing step S2, the enlarged flocs F can be broken down. This allows for an appropriate size of flocs F. For example, if the surface moisture content of the fine aggregate is 4% or higher, it is advisable to set the mixing time in the pre-mixing step S2 to 60 seconds or more.

[0071] Alternatively, a sensor for measuring the surface moisture content of the fine aggregate may be installed inside the fresh concrete manufacturing apparatus 1, and the measured value of the surface moisture content may be input from the sensor to the control unit 70.

[0072] Furthermore, as described above, when adjusting the mixing time of the pre-mixing step S2, the mixing time of the first kneading step S4 may be shortened as the mixing time of the pre-mixing step S2 increases. Alternatively, the sum of the mixing time in the pre-mixing step S2, the kneading time in the first kneading step S4, and the kneading time in the second kneading step S6 may be kept constant. In this way, even if the mixing time in the pre-mixing step S2 is long, it is possible to suppress an increase in the total time of all steps.

[0073] As described above, in this embodiment, the fresh concrete manufacturing apparatus 1 does not perform the pre-mixing process S2, the first mixing process S4, and the second mixing process S6 in a single mixer. Instead, the pre-mixing process S2 is performed in the first mixer 50, and then the first mixing process S4 and the second mixing process S6 are performed in the second mixer 60. In other words, in this embodiment, the fresh concrete manufacturing apparatus 1 pre-mixes the fine aggregate and cement in the first mixer 50 before mixing all the materials in the second mixer 60.

[0074] In this way, while the first kneading process S4 and the second kneading process S6 are being performed in the second mixer 60, the pre-mixing process S2 for the next batch can be performed in the first mixer 50. This reduces the time required to process multiple batches.

[0075] Furthermore, since no mixing water is supplied to the first mixer 50, the amount of moisture adhering to the inner surface of the container 51 of the first mixer 50 can be suppressed. In other words, the amount of moisture supplied to the first mixer 50 is not considered to exceed the amount of surface water equivalent to that of the fine aggregate. Therefore, the mixing of the fine aggregate and cement in the first mixer 50 can be carried out with a limited amount of moisture. This allows for strict control of the amount of moisture in the first mixer 50. As a result, flocs F can be formed well in the pre-mixing step S2.

[0076] The above manufacturing method uses high-strength concrete (with a design strength of 36 N / mm² as defined by the Architectural Institute of Japan). 2 This method is particularly suitable for producing fresh concrete for the above-mentioned types of concrete. Fresh concrete for high-strength concrete has a relatively low water-to-cement ratio and is therefore high in powder content, which tends to result in low fluidity. However, according to the above manufacturing method, even with high-powder content fresh concrete, it is possible to improve fluidity while reducing the amount of admixture used.

[0077] <3. Variant> Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. Below, several modifications will be described, focusing on the differences from the above embodiments.

[0078] <3-1. First variation> Figure 6 shows the configuration of a fresh concrete manufacturing apparatus 1 according to the first modified example. The fresh concrete manufacturing apparatus 1 in Figure 6 is equipped with a switching mechanism 80 that switches the supply destination of fine aggregate and cement. The switching mechanism 80 is located below the fine aggregate supply unit 10 and the cement supply unit 20, and above the first mixer 50 and the second mixer 60.

[0079] The switching mechanism 80 has a switching damper 81 inside. The switching damper 81 can switch between a first state in which fine aggregate supplied from the fine aggregate supply unit 10 and cement supplied from the cement supply unit 20 are poured into the first mixer 50, and a second state in which fine aggregate supplied from the fine aggregate supply unit 10 and cement supplied from the cement supply unit 20 are poured into the second mixer 60.

[0080] When a pre-mixing step S2 of fine aggregate and cement is required, the switching mechanism 80 is set to the first state. This allows the fine aggregate and cement to be supplied to the first mixer 50. On the other hand, when the pre-mixing step S2 is not required, the switching mechanism 80 is set to the second state. This allows the fine aggregate and cement to be supplied directly to the second mixer 60 without going through the first mixer 50. Therefore, according to the structure in Figure 6, it is possible to select whether or not to perform the pre-mixing step S2 in a single fresh concrete manufacturing apparatus 1.

[0081] <3-2. Second variation> Figure 7 shows the configuration of a fresh concrete manufacturing apparatus 1 according to a second modified example. In the embodiment described above, the first mixer 50 was positioned above the second mixer 60. The mixed material of fine aggregate and cement was supplied from the first mixer 50 to the second mixer 60 by gravity. In contrast, in the example of Figure 7, the mixed material discharged from the first mixer 50 is transported to the second mixer 60 by a feeder 90. The feeder 90 can be, for example, a screw feeder, a belt conveyor, an airflow conveyor, or other transport means.

[0082] In this way, it is not necessary to place the first mixer 50 above the second mixer 60. Therefore, as shown in Figure 7, the first mixer 50 can be placed to the side of the second mixer 60. This increases the flexibility of the placement of the first mixer 50. In addition, it prevents multiple hoppers from being densely packed above the second mixer 60.

[0083] Preferably, the height at which the lower end of the discharge port 53 of the first mixer is located and the height at which the upper end of the container 61 of the second mixer 60 is located are substantially equal, and the feeder 90 is a horizontal conveying means that supplies the mixed material to the second mixer 60 by horizontal conveying. In this way, the first mixer 50 can be installed by extending the floor frame of the existing batching plant, making retrofitting easier and thus more readily adopted.

[0084] <3-3. Others> The elements that appear in the above embodiments and modifications may be combined or partially deleted as appropriate, to the extent that no inconsistencies arise. [Industrial applicability]

[0085] This invention can be used in fresh concrete manufacturing equipment and in methods for manufacturing mortar or fresh concrete of various formulations. [Explanation of Symbols]

[0086] 1: Fresh concrete manufacturing equipment 10: Fine aggregate supply section 20: Cement Supply Department 30: Coarse aggregate supply section 40: Mixing water supply unit 50: First Mixer 60: Second Mixer 70: Control Unit 80: Switching mechanism 90: Feeder F: Flock

Claims

1. A fine aggregate supply unit that supplies fine aggregate, The cement supply unit that supplies cement, The coarse aggregate supply unit supplies coarse aggregate, A mixing water supply unit that supplies mixing water, A first mixer that obtains a mixture of fine aggregate and cement by mixing fine aggregate supplied from the fine aggregate supply unit with cement supplied from the cement supply unit, A second mixer that obtains fresh concrete by mixing the mixed material discharged from the first mixer, the coarse aggregate supplied from the coarse aggregate supply unit, and the mixing water supplied from the mixing water supply unit, A fresh concrete manufacturing apparatus equipped with the following features.

2. A fresh concrete manufacturing apparatus according to claim 1, The fine aggregate has surface water, The aforementioned mixing water contains an admixture, A fresh concrete manufacturing apparatus wherein the fine aggregate and the cement are mixed in the first mixer, causing the cement particles to form flocs.

3. A fresh concrete manufacturing apparatus according to claim 2, A fresh concrete manufacturing apparatus in which, according to the surface moisture content test method specified in JIS A 1111:2015, the surface moisture content of the fine aggregate is 2% or more and 5% or less.

4. A fresh concrete manufacturing apparatus according to claim 2 or claim 3, A fresh concrete manufacturing apparatus that supplies the mixed material obtained in the first mixer to the second mixer after being allowed to stand for a predetermined time.

5. A fresh concrete manufacturing apparatus according to any one of claims 1 to 3, A switching mechanism that switches the supply destination of the fine aggregate supply unit and the cement supply unit between the first mixer and the second mixer. A fresh concrete manufacturing device that is further equipped with these features.

6. A fresh concrete manufacturing apparatus according to any one of claims 1 to 3, The first mixer is located above the second mixer. A fresh concrete manufacturing apparatus in which the mixed material is supplied from the first mixer to the second mixer by its own weight.

7. A fresh concrete manufacturing apparatus according to any one of claims 1 to 3, A feeder that transports the mixed material from the first mixer to the second mixer. A fresh concrete manufacturing device that is further equipped with these features.

8. A fresh concrete manufacturing apparatus according to any one of claims 1 to 3, A fresh concrete manufacturing apparatus wherein the vertical dimension of the first mixer is smaller than the vertical dimension of the second mixer.

9. A fresh concrete manufacturing apparatus according to claim 8, The first mixer is a turbine mixer, The second mixer is a twin-shaft forced-mix mixer, a fresh concrete manufacturing apparatus.

10. A method for producing mortar or fresh concrete using the fresh concrete production apparatus described in claim 2, A pre-mixing step is performed in the first mixer to mix the fine aggregate and the cement to obtain the mixed material, Following the aforementioned pre-mixing step, the first mixing step involves adding the mixing water to the mixed material in the second mixer and further mixing to obtain mortar. Includes, A method for producing mortar or fresh concrete, wherein the pre-mixing step is carried out in the absence of the mixing water and in the presence of surface water already contained in the fine aggregate.

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