JP4781485B1 - Split kneading method - Google Patents

Abstract

[PROBLEMS] To produce high-quality concrete by a divided kneading method and to knead in a shorter time than before.
In the divided kneading method, the total time of half of the charging time for adding primary water to the aggregate and the adjusted kneading time after the completion of charging the primary water is set to 12 seconds or more and less than 18 seconds. Adjustment kneading is performed to uniformly attach primary water to the interface. Thereafter, the hydraulic substance powder containing cement is charged, and the total time of half of the charging time and the primary mixing time after completion of the charging of the hydraulic substance is set to 25 seconds or more and less than 36 seconds. High-quality concrete is produced by primary kneading to uniformly form a shell of a hydraulic substance powder in a state where the bonding force between particles of the powder is strong at the interface.
[Selection] Figure 2

Description

  When producing concrete containing mortar by mixing hydraulic substance powder such as cement and water, the present invention divides the total amount of mixing water into primary water and secondary water, and aggregates, cement, etc. In particular, the present invention relates to a divided kneading method in which concrete is produced by strengthening the shell by kneading with a hydraulic material powder of each other.

Conventionally, mortar and concrete consist of fine aggregate (sand) and cement, fine aggregate (sand), coarse aggregate (gravel) and cement, etc., and these composite mixtures are widely used in various civil engineering and construction works. Yes.
Usually, when producing concrete, which is a composite mixture, a batch kneading method is widely used in which concrete is produced by adding various materials at once and kneading and mixing.
Concrete subjected to compressive force has microcracks generated between the aggregate containing fine aggregate and coarse aggregate and the paste of hydraulic substance powder including cement and blast furnace slag, fly ash, etc. in contact with the interface. It is known to cause compression fracture by gradually connecting and growing. The concrete produced by the batch kneading method has a number of defects such as a large number of microcracks at the time of loading and insufficient compression strength after curing.
In addition, the concrete produced by the batch kneading method has a problem that a large amount of bleeding occurs until it hardens, or the flow friction of the concrete is large and the pumpability is reduced.

As a method for producing concrete in which such drawbacks are improved, for example, a divided kneading method (SEC (registered trademark) method) described in Patent Documents 1, 2, and 3 below has been proposed. According to this construction method, the aggregate of fine aggregates (which may contain coarse aggregates) is mixed with primary water, which is a part of the total amount of blended water, and adjusted and kneaded. Moisture is evenly attached to the interface, which is the circumferential surface. Then, add the powder of a hydraulic substance consisting of the required amount of cement (or blast furnace slag, fly ash, etc. to the cement) to the adjusted aggregate and knead it to the aggregate interface. A cement paste with a low water cement ratio is adhered and granulated.
Next, add secondary water (and necessary admixture) from which primary water is removed from the total amount of water to be added to the granulated aggregate. Concrete with good fluidity can be obtained.
The concrete obtained by this method has high water retention, so there is little bleeding, high compression strength, and there is little friction between aggregates, so pumpability is good.
In the following description, cement is used as a representative hydraulic material powder.

Here, in the granulated body obtained by attaching and granulating the hydraulic substance powder containing cement to the interface of the aggregate produced by the primary mixing of the divided kneading method, the hydraulic substance powder containing cement Forming a shell as a layer around aggregate is called shelling. The granulated body made up of shells is arranged in a three-dimensional network structure to suppress the rise of moisture in the fresh concrete and to reduce bleeding that causes separation and floating of water in the concrete.
The granulated shell layer is strengthened to adhere to the aggregate, and the paste diluted with the secondary water of hydraulic substance powder such as cement fills the space between the granulated bodies to give compressive strength, etc. The strength of is improved. Moreover, the shell-forming layer around the aggregate can reduce the friction between the aggregates, improve the fluidity under vibration, and improve the pumpability.
By forming a strong shell, performance improvements such as reduction of bleeding, improvement of strength, improvement of fluidity under vibration, and improvement of pumpability can be achieved. It is necessary to strengthen the shell.

Japanese Patent Publication No. 6-16035 Japanese Patent Publication No. 7-2329 Japanese Patent No. 2597835

However, the divided kneading method has a problem that the total kneading time becomes longer because the divided kneading method is divided into the adjustment kneading method, the primary kneading method, and the secondary kneading method. is there. For example, the mixing time of the divided kneading method is such that when the volume of the forced kneading mixer is 0.5 m ³ or more, the aggregate is added to the mixer in 5 seconds, and then the primary water is added in 10 seconds to adjust and mix. 13 seconds to 20 seconds, hydraulic material powder containing cement is charged in 15 seconds, primary mixing is performed for 28 seconds to 40 seconds, secondary water is charged in 10 seconds, and secondary mixing is performed for 30 seconds. If it is performed for ˜60 seconds, the average value of the mixing time is about 140 seconds in total.
For this reason, when compared only with the mixing time, the divided mixing method has a longer mixing time than the batch mixing method (usually about 60 seconds), so the concrete production efficiency is inferior. There is a problem.

 Therefore, considering the productivity and economic efficiency of the concrete, the mixing time should be shorter than the mixing time of the conventional divided mixing method while ensuring the excellent properties of the concrete obtained by the divided mixing method. Is required. However, if each kneading time is shortened too much, the characteristics of the divided kneading method cannot be fully demonstrated, but the limit of how far the kneading time can be shortened is unknown. It was set with a margin as described above. Therefore, there was a problem that the mixing time could not be shortened.

Also, in the divided kneading method, the kneading step can be divided into adjustment kneading, primary kneading, and secondary kneading, but each step kneading has its own purpose, and it is appropriate to meet that purpose. If kneading is not performed, performance as a divided kneading method cannot be secured.
For example, if the mixing time is too short or too long when adjusting and kneading, the performance of split kneading cannot be fully demonstrated, and the primary kneading is the same. Otherwise, there was a problem that excellent characteristics of the divided kneading method could not be obtained, such as a reduction in bleeding and an insufficient increase in compressive strength after curing as compared with batch kneading.
Furthermore, there is a problem that the mixing time becomes excessive because the mixing time of each concrete, which varies depending on the concrete manufacturing equipment, is not considered in the mixing time of each step.

  In view of such circumstances, the present invention specifies a mixing time for each step so that concrete with excellent performance can be produced, and a divided mixing method that enables mixing in a shorter time than before. The purpose is to provide.

 The split kneading method according to the present invention involves adjusting kneading to add primary water to the aggregate and uniformly adhering the primary water to the aggregate interface, and then adding hydraulic substance powder such as cement to perform the primary kneading. In addition, in the divided kneading method for producing concrete by adding secondary water from which the primary water amount has been removed from the total water amount and performing secondary kneading, an adjustment kneading step, a primary kneading step, In each of the above, each half of the time for feeding the primary water and the time for feeding the hydraulic substance powder measured at the concrete production equipment used is added to each mixing time after the addition, and each mixing is performed. It is characterized by setting time.

The divided kneading method according to the present invention is the same as the above-described divided kneading method in which the capacity is 0.5.
In the adjustment kneading process using a forced kneading mixer of m ³ or more, when adding the primary water after adding the aggregate to the mixer, the mixing time after charging is half of the time for adding the primary water. In addition to the time, the adjustment kneading time is set in a range of 12 seconds to less than 18 seconds.
According to the divided kneading method according to the present invention, in the adjusting kneading step, the charging time for adding the primary water to the aggregate is included in the adjusting kneading time, so the mixing time including this is set. This makes it possible to reduce the time required for the adjustment and kneading, and even if the charging time for charging the primary water measured in the concrete production equipment used for the aggregate is long or short, The adjustment kneading time can be adjusted within the range of 12 seconds to less than 18 seconds according to the total time of these adjustments. Can be shortened.

By adjusting the adjusted mixing time, including the primary water charging time described above, to a range of 12 seconds to less than 18 seconds, which is shorter than the conventional mixing time of 18 seconds to 25 seconds, Compared with the split kneading method, the proportion of the water content of the aggregate is unevenly distributed in a shorter time and the primary water is uniformly mixed in the aggregate. Therefore, the bleeding rate of concrete can be reduced.
On the other hand, when the adjustment kneading time is less than 12 seconds, the adjustment kneading time is too short and the primary water does not uniformly adhere around the aggregate interface. In addition, when the adjustment kneading time exceeds 30 seconds, the primary water amount is larger than the water amount that the aggregate is uniformly adhered to the interface as the surface water, so that some primary water settles downward. Concrete that is unevenly distributed and becomes excessively strong in the bonding force between particles of hydraulic substance powder, and the concrete obtained by performing the next primary mixing process and secondary mixing process for the same time as before There arises a problem that the bleeding rate is higher than in the case of the present invention.
In the above measurement, even if the primary water charging time fluctuates, the length of the adjustment mixing time after completion of the primary water charging can be adjusted. Can be set to a proper mixing time.

In the above-mentioned divided kneading method, in the primary kneading process after the completion of the adjusting kneading process, when the hydraulic substance powder is introduced, half of the time during which the hydraulic substance powder is introduced is added. In addition to the kneading time, the primary kneading time is set in a range of 25 seconds to less than 36 seconds.
According to the divided kneading method according to the present invention, in the primary kneading step after the adjusting kneading step described above, the charging time for feeding the hydraulic substance powder is included in the primary kneading time after the completion of the charging. The time required for the primary mixing can be shortened. Moreover, regardless of whether the charging time of the hydraulic material powder measured at the concrete production facility used is long or short, the primary mixing time after the hydraulic material powder has been charged is adjusted to determine the total time. Since the primary kneading time can be set in a range of 25 seconds to less than 36 seconds, the total primary kneading time can be shortened as compared with the conventional case even if the hydraulic material powder charging time changes.
Moreover, in the primary mixing step, the primary mixing time including the charging time of the hydraulic substance powder is equivalent to the mixing time of 36 seconds to less than 45 seconds, which has been conventionally practiced, and is less than 25 seconds to less than 36 seconds. Because the primary water is uniformly attached to the aggregate interface and the hydraulic substance powder is mixed with the primary water, the uniform interparticle bonding force becomes strong and adheres to the aggregate interface. In this state, a shell is formed to obtain a shell having a uniform thickness, and the concrete produced by the secondary kneading process is a high strength concrete having a low bleeding rate.
Here, if the primary kneading time is less than 25 seconds, the stirring of the hydraulic substance powder is insufficient, and the thickness of the shell-forming layer is not uniform, and the effect of divided kneading is not sufficiently exhibited. As a result, there is a disadvantage that the bleeding rate increases.

Further, in the above-mentioned divided kneading method, in the secondary kneading step after the completion of the primary kneading step, the secondary water is charged and half the time for charging the hydraulic substance powder is added. In addition to the mixing time, the proper mixing time is to set the secondary mixing time in the range of 30 seconds to 62 seconds.
After mixing and mixing in the mixer for the above-mentioned adjustment mixing time and primary mixing time, respectively, secondary water is added and the secondary mixing time is within the range of the above mixing time of 30 seconds to 62 seconds. By kneading in seconds, high-strength concrete with a low bleeding rate can be produced. Moreover, the total mixing time is shorter than that of the conventional divided mixing method, and the production efficiency of concrete can be improved.

According to the divided kneading method according to the present invention, primary water is added to the aggregate to adjust the kneading so that the primary water uniformly adheres to the aggregate interface, and then a hydraulic substance powder such as cement is added to the primary kneading. In the divided kneading method to produce concrete by adding secondary water from which the primary water amount has been removed from the total amount of water and performing secondary kneading.
In the adjustment kneading process using a forced kneading mixer with a capacity of 0.5 m ³ or more, while adding the primary water to the aggregate, half the time of adding the primary water is added to the kneading time after the addition, The adjusted kneading time is set in the range of 12 seconds to less than 18 seconds, and in the primary kneading process after the adjusting kneading process is finished, the hydraulic substance powder is added and the hydraulic substance powder is charged. The primary mixing time is set in the range of 25 seconds to less than 36 seconds in addition to the mixing time after the addition.

The purpose of each kneading step and the concept of setting the time range in the divided kneading method according to the present invention are as follows.
The purpose of the adjustment kneading is to allow moisture to adhere uniformly to the surface of the aggregate.
If the water is not evenly distributed around the aggregate because the mixing time is short, the water will be unevenly distributed with respect to the aggregate. The shell and shell thickness by the body is not enough. In addition, the excessive water around the aggregate causes problems such as weak shell formation and a lot of lumps of hydraulic substance powder in the primary kneading process. Unless the moisture distribution on the surface of the aggregate is uniform, a strong shell cannot be formed in a state where the bonding force between particles of the hydraulic substance powder is strong.
Conventionally, since the shortest and optimal adjustment mixing time is unknown, when a relatively long adjustment mixing time is set, some primary water settles down and is unevenly distributed. Too much or too little of the powder has a strong bonding force between particles, and the concrete has a problem that the bleeding rate is higher than in the case of the present invention. Since the primary water is more than the amount of water that the aggregate can hold on the surface, the surface water is unevenly distributed again by the adjustment kneading, so there is an upper limit in the mixing time. The present invention is characterized in that the shortest adjustment kneading time that does not cause these problems is set.

In the present invention, the optimum adjustment kneading time was clarified at the shortest time, and the optimum primary kneading time was set at the shortest time in a range of time not conventionally practiced.
The purpose of primary kneading is to form a strong shell by attaching the hydraulic substance powder uniformly to the aggregate surface in a state where the bonding force between the particles of the powder is strong. Therefore, there is a minimum necessary time, and if it is too long, the effect of divided kneading, such as an increase in the amount of bleeding, is impaired due to the occurrence of a granulated nodule (bonding) of the shelled body.
In setting the kneading time, the kneading time cannot be set properly unless the material charging time is taken into consideration.

In the case of producing concrete with a mixer, the mixer is kneaded with the stirring blades continuously rotating during each step of adjusting kneading, primary kneading, and secondary kneading. For this reason, stirring was carried out during the charging of the primary water and hydraulic substance powder, and unless this time was taken into account, it was found that an appropriate mixing time could not be set, impairing the performance of divided mixing. .
For example, a mixer with a large capacity (2 to ³ m ³ ) has a large input amount and a long input time. Therefore, determining the mixing time without taking this into account makes the mixing time too long. Will impair the performance. For example, the charging time of hydraulic substance powder such as cement in the primary kneading process is usually 10 to 15 seconds in the case of a large mixer. Some older batcher plants took 20 seconds. The primary water charging time for adjustment kneading was about 10 seconds. These are not negligible lengths for each mixing time.
Therefore, a practically effective mixing time cannot be set unless the charging time is reasonably taken into consideration.

 According to the divided kneading method according to the present invention, in particular, in the adjusting kneading step and the primary kneading step, the time for feeding the primary water to the aggregate and the time for feeding the hydraulic substance powder are respectively half the time. In addition, the total mixing time is set in addition to the adjustment mixing time and the primary mixing time, so the mixing time in each process and the overall process is shorter than before, and even if each input time changes for a short time It can be adjusted by each total time with the mixing time after the end. In addition, the optimal mixing time has not been known so far, and in order to prevent shortage of mixing, the optimum mixing time that has been set relatively long considering empirical safety has to be set with the actual machine when setting the mixing time program. By measuring and setting, the inventors set the minimum and optimal adjustment mixing time and primary mixing time, so each mixing time was shortened and the conventional divided mixing method Compared with the above, the manufacturing efficiency and economy can be improved.

 Moreover, in the adjustment kneading step, if the total time of the adjustment kneading time is in the range of 12 seconds to less than 18 seconds, the proportion of the water content of the aggregate is unevenly distributed, and the primary water is uniformly mixed in the aggregate. It becomes a state. In the primary kneading step, if the primary kneading time is in the range of 25 seconds to less than 36 seconds, the primary water uniformly attached to the aggregate interface is mixed with the hydraulic substance powder and uniform. As a result, the bonding force between particles becomes strong, and a shell having a uniform thickness can be obtained in a state of being firmly fixed to the aggregate interface. According to the present invention, among these kneading time ranges, a shorter time range was obtained excluding the range that has been conventionally practiced.

The conventional mixing time range is expressed as mixing time including half of the actual charging time of each of the primary water and hydraulic substance powder, and the adjusted mixing time ranges from 18 to 25 seconds. The primary kneading time was in the range of 36 to 45 seconds.
The conventional mixing and primary mixing times are set with some allowance within the allowable range, taking this into consideration when the plant's production capacity is sufficient with respect to the required shipment amount of concrete per hour. It also included the case. Therefore, the mixing time was relatively long.

On the other hand, according to the present invention, it is possible to shorten the mixing time as compared with the prior art while securing the properties of the concrete excellent in divided mixing.
In normal batch mixing, it may be necessary to change the required mixing time with respect to the concrete mix (water cement ratio, powder amount).
On the other hand, in this construction method, it is not necessary to change the time of the adjustment mixing and the primary mixing with respect to the change in the concrete mixing. This is because, when using 0.5 m ³ or more forced kneading mixer, kneading subject aggregate in mixing adjustment kneaded (sand, gravel) only kneading shaft power does not include the hydraulic substance powders The mixing time is not affected by the blending because it is small and only requires a certain time for the moisture to uniformly adhere to the surface of the aggregate.

In the primary mixing, a large amount of shaft power is applied to form a strong shell by attaching hydraulic substance powder (such as cement as a binder) uniformly to the aggregate surface with a strong interparticle bonding force. Therefore, the mixer for dividing and kneading has a motor having a power 1.3 to 1.5 times that of a general mixer power for kneading. When a forced kneading mixer of 0.5 m ³ or more is used, the necessary power for kneading with the strongest binding force of the powder particles is large, and the power to the change in mixing (mainly powder amount change) Since the influence is small, it is not necessary to change the mixing time for bringing the hydraulic substance powder into a state where the bonding force between the powder particles is strong, depending on the amount of the hydraulic substance powder.
Therefore, the material composition per m ^{3 of} concrete is 90 to 200 kg of total mixed water (including 35 to 160 kg of primary water), 120 to 600 kg of hydraulic powder such as cement, 500 to 1300 kg of fine aggregate, and coarse bone The mixing time is not changed for the composition in the range of 600 to 1700 kg (total aggregate amount 1400 to 2200 kg).
Furthermore, the mixing capacity and mixing time depending on the mixer capacity, type, and manufacturer differ, so long as it is a forced kneading (biaxial and pan type) type with a capacity of 0.5 m ³ or more and 3.0 m ³ or less. . The mixer is supposed to meet the mixing performance specifications in Table 2 of JIS A8603-1994 (2006 confirmation) “Concrete Mixer”. The kneading time at this time is the same as the condition of 60 seconds in the JIS 6.2 section.
Naturally, the mixers of each manufacturer are compatible with this and have almost the same mixing performance. Therefore, in divided kneading, the adjustment kneading and primary kneading times do not need to be changed when using a forced kneading (biaxial and pan type) type mixer having a capacity of 0.5 m ³ or more.

 According to the divided kneading method according to the present invention, in the adjustment kneading step and the primary kneading step, the time for feeding the primary water, the time for feeding the hydraulic substance powder, measured by the concrete production equipment used. Since each mixing time is set by adding half of each time to each mixing time after charging, concrete and mortar can be manufactured in a shorter time than before even though it is a divided mixing method. And kneading time excellent in performance improvement and economy can be obtained. In addition, the hydraulic material powder, which has been brought into a state where the interparticle bonding force of the powder is strong against the aggregate interface by the adjustment kneading and the primary kneading, adheres with a uniform thickness to form a strong shell. realizable.

According to the divided kneading method according to the present invention, the total time of half of the charging time for adding primary water to the aggregate and the adjusting kneading time after the completion of charging of the primary water is smaller than the adjusting kneading time that has been conventionally performed. By setting it within the range of 12 seconds to less than 18 seconds, the primary water can be uniformly attached to the surrounding interface of the aggregate, and the subsequent primary kneading such as administration of hydraulic substance powder thereafter. Even if mixing and secondary kneading are performed, a uniform and strong shell formation is possible with a strong bonding force between particles of the powder.
Therefore, concrete containing mortar with less bleeding can be produced. And although it is divided kneading | mixing, concrete can be manufactured by the adjustment kneading time shorter than before.

Further, according to the divided kneading method according to the present invention, in the primary kneading step after the adjustment kneading step, half of the charging time of the hydraulic substance powder and the primary kneading time after completion of the charging of the hydraulic substance, Is set in the range of 25 seconds to less than 36 seconds, which is smaller than the primary kneading time, which has been conventionally carried out, so that the hydraulic substance powder is made uniform and strong with a strong interparticle bonding force. A granulated body that can be shelled and has a shell-forming layer having a uniform thickness can be produced.
Therefore, even if the subsequent secondary mixing step is performed in the same manner as in the past, it is possible to produce concrete containing mortar with little bleeding. Moreover, it is possible to produce concrete in a shorter time than before while being divided and kneaded.

According to the divided kneading method according to the present invention, the adjusted kneading time is set to a range of 12 seconds to less than 18 seconds, and the primary kneading time is set to a range of 25 seconds to less than 36 seconds. Although it is a construction method, concrete and mortar can be produced in a shorter time than before, and a mixing time excellent in performance and economy can be obtained.
In addition, the hydraulic material powder, which has been brought into a state where the interparticle bonding force of the powder is strong against the aggregate interface by the adjustment kneading and the primary kneading, adheres with a uniform thickness to form a strong shell. realizable. And by secondary kneading, a thin paste of hydraulic substance powder can be evenly distributed between the shelled aggregates, and there is less bleeding than the conventional divided kneading method, and the slump value is stable. Can produce concrete with high performance mortar.

It is a schematic block diagram of the batcher plant for implementing the division | segmentation kneading method in embodiment of this invention. In each of the adjustment mixing process, primary mixing process, and secondary mixing process in the divided mixing method, the relationship between the material mixing time and the mixing time after the completion of charging It is a schematic diagram shown. It is a figure which shows the relationship between the adjustment kneading time in an adjustment kneading process, and the deviation of a fine aggregate moisture content. It is a figure which shows the relationship between the adjustment kneading time and the deviation of the bleeding rate of the manufactured concrete. It is a figure which shows the relationship between the primary kneading time and the bleeding rate of the manufactured concrete. It is a figure which shows the relationship between the secondary mixing time and the slump value by the slump test of the concrete after completion of mixing.

Next, the divided kneading method according to the embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a batcher plant for producing concrete by a divided kneading method according to an embodiment of the present invention.
A batcher plant 1 shown in FIG. 1 includes a mixer 2 provided with a stirring blade (not shown) for mixing mainly constituent materials of concrete, and a peripheral device 3 for transporting these constituent materials from a storage state, weighing them, and feeding them. And a control unit 4 for controlling them. Above the mixer 2, a water reservoir 6 that stores the blended water W, a cement reservoir 7 that stores cement, a fine aggregate reservoir 8 that stores fine aggregates such as sand, and a coarse aggregate such as gravel. And a coarse aggregate reservoir 9 for storing aggregates.
The cement storage 7 is supplied with cement from the cement silo 10 and stored. Aggregates such as fine aggregates and coarse aggregates are also supplied to and stored in the storage units 8 and 9 by a conveyor or the like.

Also, a primary water metering tank 12a and a secondary water metering tank 12b are provided below the water reservoir 6 to divide the amount of water to be fed into the mixer 2 into primary water W1 and secondary water W2, respectively. ing. Similarly, a cement metering tank 13, a fine aggregate metering tank 14, and a coarse aggregate metering tank 15 are disposed below the cement reservoir 7, the fine aggregate reservoir 8, and the coarse aggregate reservoir 9, respectively. An appropriate constituent material is selected by the control unit 4 and dropped onto the mixer 2.
The secondary water meter 12b is mixed with an admixture from the admixture reservoir 17 as necessary.
The mixer 2 is rotated by a stirring blade (not shown). Aggregates such as sand and gravel and hydraulic substance powders such as cement are charged and stirred and kneaded. Then, the fresh concrete produced by performing the adjustment kneading, primary kneading, and secondary kneading in the mixer 2 is discharged through the hopper 16.

Here, the terms used in this specification will be described. The hydraulic substance powder is a powder that is cured by water and a hydration reaction to become a substance that is not soluble in water. Cement is a typical hydraulic material, but there are others that can be employed. That is, among hydraulic substance powders, there are cement having a fast hydraulic reaction, and blast furnace slag, fly ash, silica fume and the like having a relatively slow hydraulic reaction. Limestone fine powder and the like are those that do not have a hydraulic reaction.
Limestone fine powder is a substance that helps harden other substances and improves strength, and does not harden itself. An appropriate hydraulic substance other than cement can be mixed with cement and used as the hydraulic substance.
The hydraulic substance powder used in this embodiment is composed of cement alone, or in addition to cement, at least one or more kinds of blast furnace slag, fly ash, silica fume, and limestone fine powder are added and mixed. Any of those made of mixed powder is used. Therefore, a hydraulic substance powder made of a mixed material may be stored in the cement reservoir 7 instead of cement, and in the following description, it is referred to as a hydraulic substance powder including the case of only cement.

Shell making is a mixture of a hydraulic substance powder mixed with water and having a strong bonding force between powder particles at the interface of the aggregate composed of fine aggregate S and coarse aggregate G. It shall mean the layer adsorbed as a shell.
Primary water is a part of the total amount of water added to produce concrete, and the water adsorbed on the surface of the aggregate and the hydraulic substance powder have a strong binding force between the powder particles. It is the amount of water (primary water amount) corresponding to the sum of the water necessary for obtaining the state.
The secondary water is a water amount obtained by subtracting the primary water amount from the total blended water amount, and means a water amount that can obtain a specified slump value by secondary kneading.

In this batcher plant 1, control is performed according to the timing at which each component material measured according to each step of the adjustment kneading step, the primary water kneading step, and the secondary water kneading step in the divided kneading method is to be input. The operation panel electrically connected to the unit 4 is dropped into the mixer 2. The capacity of the mixer 2 to be used is in the range of 0.5 m ³ or more. In this embodiment, for example, a 1.0 m ³ capacity biaxial forced kneading type mixer 2 is used.
First, the kneading time in each process set in advance is determined as follows. In FIG. 2, the horizontal axis represents time T, and the vertical axis represents aggregate input amount Vo of aggregate, primary water W1, hydraulic substance powder, and secondary water W2. Then, for example, aggregate S, primary water amount W1, hydraulic substance powder C, and secondary water amount W2 are selected as each constituent material to be input per unit time, and the input amount of the constituent material per unit time is made constant. A predetermined charging time To corresponding to the total charging amount Vo in each step and a mixing time T1 from the end of charging of the constituent materials are set.

  The mixer 2 has been rotated at a constant speed before the constituent materials are charged, and the mixing time is included in the substantial mixing time because the mixing is performed by the stirring blades even when the constituent materials are charged. And As shown in FIG. 2, regarding the relationship between the cumulative input amount Vo and the input time T when the constituent materials are input, as shown in FIG. When the amount Vo is reached, the charging is finished. After that, the mixer 2 is mixed with the set cumulative input amount Vo.

For this reason, the kneading effect can be considered as the product of the amount Vo of the constituent material charged and the kneading time T. Therefore, the kneading effect at the charging time To corresponds to the area of a right isosceles triangle. Since the same area is a square area that is the product of (1/2) To and the cumulative input amount Vo, the relationship between the cumulative input amount Vo and the mixing time T is expressed by the following formula: To × Vo × 1/2 + T1 × Vo = (1/2) Vo (To + 2T1)
Is required. The substantial effective mixing time T is roughly calculated by the following formula.
T = 1 / 2Vo (To + 2T1) / Vo = (1/2) To + T1
In this way, the necessary mixing time T according to the constituent materials can be defined.
The charging time To of each constituent material varies depending on the batcher plant 1. In the plant 1, when determining the mixing program, the input time To is measured to determine the substantial mixing time T of each of these constituent materials.

Next, the divided kneading method according to the embodiment of the present invention will be described.
First, in the divided kneading method, for example, fine aggregate and coarse aggregate are used as the aggregate, and the primary water W1 is uniformly distributed on the interface (surface) of the aggregate for a strong shell formation. Most important. In order to fix the hydraulic substance powder containing cement to the fine aggregate, an optimum amount of moisture is required at the interface of the aggregate to make the hydraulic substance powder have a strong interparticle bonding force. Is most effective.

On the other hand, in the divided kneading method, even if the hydraulic substance powder and the primary water W1 are kneaded and the powder has a strong interparticle bonding force, the aggregate is mixed. If the interface is dry, the degree of fixation with the aggregate decreases, which is not preferable. Also, even if primary water W1 is added and kneaded in a state where the aggregate and hydraulic substance powder are mixed, the shell formation is insufficient because moisture is not adsorbed on the interface of the aggregate, and the divided kneading method The feature of is not demonstrated.
From these explanations, in the divided kneading method according to the present embodiment, the primary water W1 is uniformly attached to the interface (around the surface) between the fine aggregate and the coarse aggregate used as the aggregate, and thereafter the hydraulic substance powder The procedure to shell the body is most effective.

In addition, since the primary water amount W1 is larger than the amount of water that the aggregate can hold at the interface as surface water, if adjustment kneading is performed for a longer time than necessary, moisture is unevenly distributed in the lower portion, which is not preferable. Therefore, an upper limit and a lower limit are set for the adjustment kneading time.
Moreover, unless primary water is evenly distributed on the surface of the aggregate, the lumps due to uneven distribution of powder such as cement increase. In the mortar test, in the comparison between the mixed kneaded mixed and primary kneaded mixed kneaded and the aggregate (sand), cement and primary water added at the same time, the latter is more Occurrence is about 4 times. This is a difference due to the presence or absence of appropriate adjustment. If the adjustment kneading time is too short, the water distribution on the surface of the aggregate will not be uniform. The same is true even when the adjustment kneading time is too long. In particular, a portion where the primary water amount is excessive is generated around some aggregates, and the powder of hydraulic substance powder such as cement is generated. Therefore, the occurrence of lumps can be reduced by appropriately setting the adjustment kneading time.

Therefore, in the divided kneading method according to the present embodiment, in the adjustment kneading process to be processed first, a predetermined amount of fine aggregate made of sand and coarse aggregate made of gravel are put in the mixer 2 in advance and set in advance. The primary water W1 is added in a constant amount per unit time while being stirred with the stirring blades of the mixer 2 and adjusted and mixed. In addition, the determination method of the primary water W1 is disclosed in the above-described prior art, and the description thereof is omitted here (see Japanese Patent Nos. 4249176 and 1521715).
And after completion | finish of injection | throwing-in of the primary water W1 for the predetermined time To, adjustment kneading is further performed for the predetermined time T1.
The effective mixing time T (= 1 / 2To + T1) is set in the range of 12 seconds to 30 seconds, where Ta is the effective mixing time T by the adjustment mixing.

Here, the effective mixing time Ta in the adjustment mixing process is set, for example, as follows by a test in consideration of the charging time To of the primary water W1.
For example, when the mixer 2 having a capacity of 1 m ³ is used, 885 kg of aggregate is put into the mixer 2, and 1 kg of primary water W1 is charged at 16.6 kg per second at a charging time To (= total 5 seconds). Adjustment kneading was carried out including the water charging time To. The moisture content of a 100 g sample was measured at a plurality of locations (for example, 2 locations) in the mixer 2 every time the adjusted kneading time Ta passed a predetermined time. From the deviation of the obtained data, the mixing time and the time required for the primary water W1 to be uniformly distributed at the aggregate interface were determined. The result is shown in FIG.

FIG. 3 is a diagram showing the relationship between the adjusted mixing time (sec) obtained in the test and the proportion of the moisture content of the aggregate unevenly distributed. The adjusted mixing time Ta is in the range of 12 seconds to 30 seconds, The ratio of the moisture content of the aggregate being uneven is about 0.3% or less, which is the smallest, indicating that the primary water W1 is uniformly mixed in the aggregate. On the other hand, when the effective adjustment mixing time Ta is less than 12 seconds, the primary water W1 is not sufficiently uniformly adhered to the aggregate interface, and when the adjustment mixing time Ta exceeds 30 seconds, Since the amount of primary water W1 is larger than the amount of water in which the aggregate is uniformly adhered to the interface as surface water and retained, temporary adjustment of water for a long time exceeding 30 seconds causes the water to settle downward and become unevenly distributed. Therefore, the amount of the hydraulic substance powder becomes excessive to make the bonding force between particles strong, which is not preferable in the next primary mixing step.
In the above-described test, even when the charging time To of the primary water W1 is shorter or longer than the above-described case, the length of the adjustment mixing time T1 after completion of the charging of the primary water W1 can be adjusted. The substantial adjustment kneading time Ta is substantially the same length.

Next, in FIG. 4, in order to investigate whether or not the divided mixing effect appears by changing the adjustment mixing time Ta, the relationship with the bleeding rate of the concrete manufactured by this divided mixing method was examined. For example, 300 kg of cement C is added as a hydraulic substance powder to the sample after adjusting and mixing the time Ta, and the amount of water W composed of the primary water W1 (= 83 kg) and the secondary water W2 is (195) kg, (165) kg. , (135) kg of 3 types of concrete, and by charging each, the ratio of water input W to cement C W / C = 65%, 55%, 45% of the concrete is produced as a sample, bleeding The rate deviation was measured.
From FIG. 4, when the preferable bleeding rate deviation of the concrete manufactured by the division mixing method is 1% or less, the uneven distribution of the bleeding amount is small if the adjusted mixing time Ta is in the range of 12 seconds to 36 seconds. Admitted. Therefore, if the adjustment kneading time Ta is in the range of 12 seconds to 30 seconds that satisfies both of FIGS. 3 and 4, the aggregate moisture content deviation is small and uniform and strong shell formation is possible. It can be confirmed that good concrete with a small bleeding when producing concrete can be produced.
Thus, from the test results shown in FIGS. 3 and 4, the necessary effective mixing time Ta considering the charging time To of the primary water W1 and the adjusted mixing time T1 after the charging is completed is 12 to 30 seconds. I found out.

Next, the primary kneading step will be described.
After completion of the adjustment kneading step, kneading to uniformly fix the hydraulic substance powder containing cement C to the aggregate surface in a state where the primary water W1 is uniformly adhered and distributed on the aggregate interface. As such, primary mixing is required.
In the primary kneading step, an effective primary kneading time including the charging time To of the hydraulic substance powder and the mixing time T1 of the primary water after the charging is completed is defined as Tb. In the primary kneading step, a hydraulic substance powder is put into the mixer 2 and adhered to the entire circumferential interface of the aggregate to form a granulated body.
Therefore, the effective primary mixing time Tb = (1/2) To + T1 is set.

As an example of the primary kneading step, the one shown in FIG. 5 is presented. For example, the hydraulic substance powder C made of cement is stirred while being charged into the mixer 2 for 30 kg × 10 seconds per unit time = total 300 kg, and the primary mixing is performed during the primary mixing time T1 after the completion of the charging time To. Do.
Based on this example, in FIG. 5, the primary mixing time Tb shown on the horizontal axis and the concrete obtained by performing secondary mixing by adding secondary water W2 to the kneaded material after the primary mixing. The relationship with the bleeding rate is shown. In FIG. 5, the effective primary mixing time Tb is defined as a total time Tb of 1/2 of the hydraulic material charging time To and the primary mixing time T1 after completion of the charging, and a preferable bleeding rate of the manufactured concrete is shown. When it was 4% or less, a range of 25 seconds to 46 seconds was obtained as a range having a divided kneading effect.

In FIG. 5, if the primary mixing time Tb is in the range of 25 seconds to 46 seconds, the hydraulic substance powder is obtained by the primary mixing while the primary water W1 is uniformly attached to the aggregate interface. When C is mixed with the primary water W1 and the uniform interparticle bonding force becomes strong, the shell is formed in a state of being firmly fixed to the interface of the aggregate S, and a shell is obtained.
Here, if the primary kneading time Tb is less than 25 seconds, the stirring of the hydraulic substance powder is insufficient, and the thickness of the shell-forming layer is not uniform, and the effect of divided kneading is not sufficiently exhibited. . Therefore, the produced concrete has a disadvantage that the bleeding rate increases as compared with the concrete having a primary mixing time Tb in the range of 25 seconds to 46 seconds.
On the other hand, when the primary kneading time Tb exceeds 46 seconds, the kneading time is too long, so that the shells are combined and granulated to form a nodule, and the effect of the divided kneading is impaired. For this reason, the problem that the bleeding rate increases similarly occurs.

Next, the secondary kneading step will be described.
Secondary kneading is performed for the purpose of obtaining a slump value for filling the paste between granulations and maintaining workability.
Upon completion of the primary kneading process, secondary water W2 is further added to the primary kneaded product obtained by uniformly adhering the hydraulic substance powder C having a strong interparticle bonding force to the aggregate interface, The secondary mixing is performed for the effective secondary mixing time Tc. The secondary mixing time Tc means an effective secondary mixing time Tc including 1/2 of the charging time To of the secondary water W2 and the mixing time T1 of the secondary water after the charging is completed. Therefore, the secondary mixing time Tc = (1/2) To + T1 is set.
In order to determine the secondary kneading time Tc, the interface of the primary kneaded aggregate is an aggregate particle formed by a shell of a hydraulic substance powder in which the powder has a strong interparticle bonding force. Secondary water W2 was added to the granules, and secondary kneading was performed, and the slump value of the obtained fresh concrete was measured.
In the sample subjected to the primary kneading described above, the secondary water W2 is set to, for example, W / C = 55%, and the total water W (for example, 165 kg) is subtracted from the primary water W1 (= 83 kg). Yes, W2 = 82kg.

In FIG. 6, the slump test was performed on each of the obtained fresh concretes with the secondary kneading time set to 20 seconds to 10 seconds, and the measured slump values were plotted in FIG. In FIG. 6, the horizontal mixing time Tc is taken on the horizontal axis, and the slump value (cm) of fresh concrete obtained in the slump test is taken on the vertical axis.
In FIG. 6, when the secondary mixing time Tc is between 30 seconds and 62 seconds, the slump value of the concrete is 15 cm or more, which is substantially constant and large compared to the area outside this, and less than 30 seconds and exceeding 62 seconds. In some cases, it was confirmed that the slump value decreased with a steep slope. Therefore, the effective secondary mixing time Tc was obtained in the range of 30 seconds to 62 seconds. This secondary kneading time Tc partially overlaps the above-described secondary kneading time that has been conventionally set.
If the secondary kneading time Tc is within the above range, the hydraulic substance powder thinned in a paste form with the secondary water W2 between the shells by the secondary kneading after the secondary water W2 is charged. A high-performance concrete with a stable slump value in which the bodies C are uniformly distributed can be manufactured.
On the other hand, if the secondary mixing time Tc is less than 30 seconds, the secondary mixing is insufficient, and the manufactured fresh concrete cannot obtain a sufficient slump value. Moreover, when the secondary mixing time Tc exceeds 62 seconds, the slump value is lowered due to the decrease in the amount of air contained and the workability of the concrete is lowered.

As described above, the paste of the hydraulic substance powder that is nearly uniform can be distributed between the shelled aggregates by the secondary mixing time Tc in the range of 30 seconds to 62 seconds. By setting the optimal secondary mixing time Tc, it is possible to prevent the amount of air from being reduced by long-time mixing, which has been conventionally performed, to prevent fluctuations in the slump value, and to maintain high concrete strength.
In this embodiment, in the description of the mixing time T in the adjustment mixing process, the primary mixing process, and the secondary mixing process, each charging time To and each mixing time T1 after completion of charging are different from each other. It may be the same or partially or entirely the same.

As described above, according to the divided kneading method according to the present embodiment, when performing the adjustment kneading step, the primary kneading step, and the secondary kneading step sequentially, the primary water charging time, the charging of the hydraulic substance powder By including 1/2 of each time in each mixing time, the mixing time can be reduced as compared with the conventional divided mixing method as a whole, and the mixing time closer to the batch mixing time. The kneading time which is excellent in economy can be obtained.
That is, by setting the adjustment kneading time Ta within the range of 12 seconds to 30 seconds, it can be processed in a shorter time than the adjustment kneading time of the conventional divided kneading method, and the deviation of the aggregate content rate Provides a uniform and strong shell. In addition, it can be confirmed that the concrete obtained by the divided kneading method including this adjustment kneading can produce good concrete having a small bleeding rate deviation of 1% or less. In addition, the ratio of the moisture content of the aggregate being unevenly distributed is the smallest, and a configuration in which the primary water W1 is uniformly adhered to the aggregate can be obtained, and the excess primary water is not unevenly distributed downward.

Furthermore, in addition to the adjustment kneading time described above, the primary kneading time Tb is set in the range of 25 seconds to 46 seconds, so that it can be processed in a shorter time than the primary kneading time of the conventional divided kneading method. It can be confirmed that good concrete having a bleeding rate of 4% or less can be produced.
In addition, granulation with a uniform thickness shell that can form a uniform and strong shell at the interface of the aggregate with a strong mixing force of the hydraulic substance powder by primary kneading. The body can be manufactured. Therefore, good concrete with suppressed bleeding can be produced.

Moreover, by properly setting the secondary kneading process in addition to the adjustment kneading process and the primary kneading process, the overall kneading time is shorter than the conventional divided kneading method, which is close to the batch kneading method. The production efficiency of concrete can be improved. In addition, the effect of reducing the number of microcracks and sufficient compressive strength and adhesion strength after curing can be obtained.
In addition, according to the divided kneading method according to the present embodiment, although it is a divided kneading method, the total sum of each kneading time can be made shorter than before and mortar and concrete can be manufactured. Since it is close to the kneading time, it is possible to obtain a kneading time excellent in performance and economy. In addition, the bleeding rate of the obtained concrete can be reduced, and high-performance concrete with a stable slump value can be obtained.

  In the above-described embodiment, when a biaxial forced kneading mixer is used, fine aggregate and coarse aggregate are added as aggregates, and the adjustment kneading step, the primary kneading step, and the secondary kneading step are sequentially performed. Concrete is manufactured by doing this, but when using a pan-type mixer, fine aggregate is added as the aggregate, the adjustment mixing step and the primary mixing step are performed, and the coarse aggregate is input. The next kneading process can also be performed. Moreover, it is good also as a manufacturing method of mortar by throwing in only a fine aggregate as an aggregate. Even in this case, high-performance mortar can be produced.

However, since the mixing performance of the mixer 2 varies depending on the capacity of the mixer 2, there is a range of application.
The small laboratory mixer 2 (for example, a capacity of about 50 liters) is different from the mixer used for concrete production in that the similarity law is not established and the mixing performance is different. However, the forced mixing mixer used for the production of concrete of 0.5m ³ / batch or more has the same mixing performance as specified in JIS A8603-1996 (2006 confirmation), and the mixing performance is almost equivalent. It is.
In addition, a mixer having a size of 3.0 m ³ or more has been manufactured with an increase in size and size of the mixer. However, since the above-mentioned JIS standard is applied to the mixing performance, it can be specified as 0.5 m ³ or more in the present invention.
From this, it can be said that there is little difference between the mixer type (biaxial forced kneading and bread type forced kneading) and the manufacturer, so that it is not limited to the mixer 2 with a capacity of 1 m ³ per batch used in the above-described embodiment, but 0.5 m ³ Even when the above mixer 2 is used, the same result as that obtained by using the adjusting kneading time Ta, the primary kneading time Tb, and the secondary kneading time defined by the divided kneading method in the above-described embodiment can be obtained.

1 Batcher plant 2 Mixer

Claims (4)

Add primary water to the aggregate and adjust the kneading so that the primary water adheres uniformly to the aggregate interface, then add hydraulic material powder such as cement and mix the primary water, and then add the primary water volume from the total water volume. In the divided kneading method to make concrete by adding the removed secondary water and performing secondary kneading,
In the adjustment kneading process and the primary kneading process, each half time of the time to put in the primary water and the time to put in the hydraulic substance powder, measured by the concrete production equipment to be used, respectively, In addition to the kneading time, each kneading time is set and divided kneading method. In the divided kneading method according to claim 1,
When the primary water is added to the aggregate and kneaded to make the adjustment kneading, the total time of half of the charging time for adding the primary water to the aggregate and the adjusting kneading time after the primary water charging is finished is 0.5 m. ³ / A divided kneading method characterized in that when a forced kneading mixer of batch or more is used, the mixing kneading method is set to 12 seconds or more and less than 18 seconds. In the divided kneading method according to claim 1,
After adding primary water to the aggregate and adjusting and kneading, when adding the hydraulic substance powder and performing the primary kneading, half of the time for adding the hydraulic substance powder and after the completion of the injection of the hydraulic substance A divided kneading method characterized in that the total mixing time with the primary kneading time is set to 25 seconds or more and less than 36 seconds when a forced kneading mixer of 0.5 m ³ / batch or more is used. In the divided kneading method according to claim 1,
When using a forced kneading mixer of 0.5 m ³ / batch or more,
Set the total time of the half of the charging time for charging the primary water to the aggregate and the adjustment kneading time after the primary water is charged to 12 seconds or more and less than 18 seconds, and mix the aggregate and the primary water. Adjustment kneading process to be performed,
The hydraulic substance powder is charged after the adjustment kneading step, and the total time of half of the hydraulic substance powder charging time and the primary mixing time after the hydraulic substance charging is finished is 25 seconds or more and less than 36 seconds. A divided kneading method characterized by performing a primary kneading step in which kneading is carried out by setting.

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