JP4908818B2 - Mixing method of ready-mixed concrete using a twin screw mixer - Google Patents

Description

  The present invention relates to a method for mixing ready-mixed concrete using a twin-screw mixer.

Conventionally, various types of twin-screw mixers have been known, and those described in Patent Documents 1 to 3 are examples thereof.
For example, in a twin-screw mixer for ready-mixed concrete as described in Patent Document 1, two horizontal shafts are arranged in parallel in a mixing tank so as to be rotatable, and kneading blades are attached in the longitudinal direction of the shaft, Mixing was performed while turning the shaft back and forth by rotating the kneading blades. At this time, the material in the mixing tank was moved in a circular or diagonal manner (Patent Document 3) repeatedly in the horizontal plane in the mixing tank, and the ready-mixed concrete was mixed and mixed.

Further, in order to improve the circulation mobility of the material, the kneading blade is formed in a spiral shape, and the material movement speed is increased by continuously moving the material in the longitudinal direction of the shaft.
Further, the mixing and conveying unit and the mixing turning unit are provided in the kneading blade, and when the material sent in the longitudinal direction of the shaft by the mixing and conveying unit is sent to the mixing turning unit, the mixing and turning unit defines the mixing and conveying unit. The conveyance force in the reverse direction is applied, and the material that has lost its destination is changed to the lateral direction and sent to the adjacent shaft side.

However, in the mixing using the conventional twin-screw mixer, the mixing does not proceed while the material circulates and moves in the mixing tank, and the moving speed of the material is particularly high even when mixing raw concrete with low viscosity. However, there was a problem that sufficient mixing was not performed for the increased size.
Further, WO 2005/000455 A1, which is Patent Document 2, describes a twin-screw mixer according to an application filed by the same applicant as the applicant of the present invention. The same publication also discloses a method for mixing ready-mixed concrete using the twin-screw mixer.

This gazette discloses a twin-screw mixer whose configuration is considerably different from that of Patent Document 1, and similarly shows a part of a method for mixing ready-mixed concrete. Is moved from one shaft side to the other shaft side. And according to such a mixing method, for example, a part of the material on one side of the mixing tank is pushed upward by one kneading blade, and the other side by the other turning blade with respect to the space formed immediately after that. This is a type of mixing in which a part of the material is pushed in, centering on the so-called reverse mixing action.
For this reason, a part of the material cut by each blade is alternately moved into the mixing tank on the opposite side by the opposed kneading blades and the turning blades rotating on the two rotating shafts. It is quite effective in terms of the mixing action.

However, the inside of the material lump cut off by each of the kneading blade and the turn-back blade has been found to be problematic in that the adjacent materials to be mixed are not mixed so much that the time required for mixing becomes longer as a whole.
Therefore, the present inventors have heretofore known that generally the best mixing state can be generally obtained in order to mix raw concrete material having a relatively low viscosity in a short time and with little variation in the mixing degree. I have been studying with reference to hand-kneading techniques.

  As a result, the greatest advantage of the hand-kneading mixing is that, for example, when a part of a material lump cut by an excavator is turned upside down and dropped, the inside of the cut material collapses when dropped. I noticed that adjacent materials to be mixed are in a point where they are mixed with each other. In addition, the mixing action due to the collapse at the time of the fall (hereinafter referred to as collapse) is utilized to the maximum, and the action is performed at high speed using a twin-screw mixer, thereby simultaneously reducing the mixing time. The mixing method that can obtain extremely homogeneous ready-mixed concrete was completed.

Here, in order to understand the characteristic action in the mixing method of the present invention, the behavior of the mixed material in the conventionally well-known hand-kneading mixing is analyzed using FIGS. 7 and 8 as follows.
FIG. 7 shows different materials such as sand (represented by black circle 02 for illustration) and cement (represented by white circle 03 for explanation) separately to be mixed in the flat container 01. This is schematically shown in a state in which the components are alternately turned back and mixed by the excavators 04 and 04 by human power from both side surfaces of the container 01. That is, the sand 02 and the cement 03, for example, appropriately put into the container 01 become an integral large lump 05 at the time of charging, which are alternately cut out by the shovels 04 and 04 shown in the figure, and sequentially as small lumps 06 and 07. It cuts back in the direction of the arrow.

FIGS. 8A to 8D are views of the two-time turning operation in the description of FIG. 7 as seen from the XX direction of FIG. As shown in FIGS. 8A and 8B, the small lump 06 cut from the large lump 05 is reversed in the up-down direction by the reversing operation of the shovel 04 by the first turn-back by the shovel 04, and then the container When falling into 01, it collapses as shown in FIG. At this time, the upper and lower sand portions and the cement portion collapse and become a lump 08 which is widely developed, and both of the minute portions naturally come close to each other in a wide range.
Also, in FIGS. 2C and 2D, the sand and cement blob 07 to be mixed with the same action is developed widely, and the crevice 09 is formed in which the minute portions are close to each other. .

That is, a lump of low-viscosity material is naturally developed by lifting, flipping and collapsing it, and can be mixed very reasonably and rapidly by repeating this operation.
JP 2003-126668 A WO 2005/000455 A1 publication JP-A-2-303805

The present invention provides a mixing method in which the behavior of the material to be mixed generated by the hand kneading operation as described above is executed by using a twin-screw mixer, and a homogeneous ready-mixed concrete can be quickly produced.
In this case, for example, a mixer having a structure basically similar to that of the known twin-screw mixer described in Reference 2 is used.

The present invention relates to a method for mixing ready-mixed concrete using a biaxial mixer comprising a pair of mixing tools having a kneading blade and a turning blade rotating on the respective rotational shaft cores. The kneading blade and the turning blade provided opposite to each other are rotated synchronously or delayed with respect to the preceding kneading blade and either one of the mixing tanks or It is characterized by repeating the step of throwing from one corner to the other or the other corner on the opposite side to collapse the mixed material.
Further, the delay angle of the turning blade that is rotated with respect to the preceding kneading blade is about 30 ° to 60 °, and the operation speed of the process of throwing and collapsing the mixed material by the biaxial mixer is as follows. One round trip in about 2 seconds.
Furthermore, each mixing tool used in the present invention has a kneading blade twisting of about 170 °, a turning blade twisting of about 110 °, and an inner angle of the bent portion of the connecting member bent in a U shape. It is characterized by being about 165 °.

According to the mixing method of the ready-mixed concrete of the present invention, the mixed material is thrown from one side to the other side on the diagonal line in the mixing tank, and further from the other side to the one side. Adjacent dissimilar materials in the mixed material were quickly mixed together, and a homogeneous ready-mixed concrete could be made efficiently.
Further, since the mixture is thrown from one side to the other side in the mixing tank and further from the other side to the one side, and a collapsing mixing operation is performed for each process, extremely rapid mixing is possible.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a perspective view of a twin-screw mixer used in the method for mixing ready-mixed concrete according to the present invention, and FIG. 2 is a plan view of the mixer.
In these two-shaft mixers 10 shown in FIG. 1 and FIG. 2, the mixing tank 11 is opened upward to serve as a material inlet, and has a discharge port provided with a gate (not shown) that can be opened and closed at the bottom. . In addition, two horizontal and parallel rotation axes B ₁ and B ₂ are provided inside the mixing tank 11, and two mixing tools 12 (12a and 12b) each having the rotation axis as a rotation center are provided. It is provided on the rotating shaft cores B ₁ and B ₂ .

The two mixing tools 12a and 12b are rotatably provided in the mixing tank 11 so as to rotate in opposite directions around the rotation axis, respectively, and rotate downward from the outside to the inside and upward. Each mixing tool 12a, 12b includes kneading blades 13a, 13b formed in a spiral with respect to the rotation shafts B ₁ , B ₂ , and turning blades 14a, 14b formed in a spiral that twists in the opposite direction to the kneading blades. The kneading blades 13a, the turning blades 14a, the kneading blades 13b, and the turning blades 14b are opposed to each other and are arranged alternately in the direction of the rotation axis.

Adjacent ends of the kneading blade 13a and the turnback blade 14b and the kneading blade 13b and the turnback blade 14a arranged on the rotary shaft cores B ₁ and B ₂ are connected by connecting members 15 and 15, respectively. 15 are disposed in a substantially radial direction with respect to the rotation axis B _1, B ₂ bent in shape "dogleg".

The kneading blades 13a and the turnback blades 14b and the turnback blades 14a and the kneading blades 13b connected on the rotation axis by the connecting member 15 are fixed to the rotation support members 16 and 16 at both ends that are not connected to each other. These rotation support members 16 and 16 are provided so as to slightly protrude inward from both side walls 11a and 11b in the mixing tank 11, and are provided so as to be rotatable around the rotation shafts B ₁ and B ₂ .

As described above, each of the two mixing tools 12 (12a, 12b) has the kneading blades 13 (13a, 13b), the turnback blades 14 (14a, 14b), the connecting member 15, and the rotation support members 16, 16. And is rotatably supported on the rotation axis (B ₁ , B ₂ ), and is provided in the mixing tank 11 in a horizontal and parallel manner.

Here, the biaxial mixer used for the ready-mixed concrete mixing method according to the present invention will be described in more detail.
In one embodiment of the twin screw mixer used in the mixing method described later, the details of the two mixing tools 12a and 12b in the twin screw mixer 10 are as follows.
First, in the mixing tool 12b, the kneading blade 13a is fixed to the rotation support member 16 of the side wall 11a in the mixing tank 11 which is the rotation driving means. The kneading blade 13a is twisted about 170 ° upward from the side wall 11a side end portion 13aX and extends to the connecting member 15 side end portion 13aY.

  The kneading blade 13a is fixed to one end of the "U" -shaped connecting member 15 in the vicinity of the connecting member side end 13aY, and the other end of the connecting member 15 is connected to the turn-back blade 14b. The member side end portion 14bY is fixed, and the turning blade 14b is twisted to the opposite side to the kneading blade 13a, and the twist angle is about 110 °. And the mixing tool 12b is comprised by the rotation support member 16 side of the turned-back blade | wing 14b twisted about 110 degrees, ie, the side wall 11b side edge part 14bX being fixed to the rotation support member 16 of the side wall 11b.

  Next, the mixing tool 12a will be described. The kneading blade 13b and the turning blade 14a constituting the mixing tool 12a completely correspond to the kneading blade 13a and the turning blade 14b constituting the mixing tool 12b. However, the kneading blade 13a, the kneading blade 13b, the turning back blade 14a, and the turning back blade 14b are provided at diagonal positions in the mixing tank 11, and are rotated in opposite directions.

Therefore, for example, regarding the mixing tool 12b, the support member side end portion 13aX fixed to the rotation support member 16 on the side wall 11a side of the kneading blade 13a has a substantially horizontal direction toward the outside of the mixing tank 11 as shown in FIG. In the positioned state, the rear end portion 13aY of the kneading blade 13a is at a position delayed by about 170 °, and the shape of the connecting member 15 is “shaped” at about 10 ° above the inside of the mixing tank 11 (mixing tool 12a side). It is fixed on one side. Further, the inner end portion 14bY of the turning blade 14b is fixed to the other side of the connecting member 15 whose inner angle is bent at about 165 ° at about 25 ° below the mixing tank 11, and further, the turning blade 14b. Since the end portion 14bX on the side wall 11b side is twisted by about 110 ° in the opposite direction, the fixed position of the turning blade 14b with the rotation support member 16 on the side wall 11b side is about 45 ° inward and downward from the horizontal direction. It will be in the direction.
(Note that each blade shown in FIG. 2 does not strictly represent the torsion angle as described above.)

As described above, the two mixing tools 12a and 12b provided in the mixing tank 11 are configured so that the blades at the opposing positions are different, for example, the kneading blade 13b is provided at one side end of one mixing tool 12a. In the opposite side end of the other mixing tool 12b, a turning blade 14b is provided. Similarly, a kneading blade 13a is provided at one side end of one mixing tool 12b, and a turning blade 14a is provided at the opposite side end of the other mixing tool 12a.
In addition, although the rotation drive of each mixing tool 12a, 12b in FIG. 2 is made into the motor M, M, for example, a conventionally well-known drive means can also be utilized and these detailed description is abbreviate | omitted.

Next, the method for mixing ready-mixed concrete according to the present invention using the twin-screw mixer 10 having the above-described structure will be described in detail with reference to FIGS.
FIG. 3 is a plan view showing the inside of the mixing tank 11 of the biaxial mixer 10 shown in FIG. 1 and FIG. 2 described above. For example, a mixed material for raw concrete to be mixed (hereinafter referred to as a mixture) is central. The position (hereinafter referred to as G) and the rotational positional relationship of the mixing tools 12a and 12b at that time are shown in the order of (a) to (f) over time. However, in each blade of the twin-screw mixer 10 shown in FIGS. 1 and 2 and each blade of the twin-screw mixer described below in FIG. 3, the twist angle and the deviation of the mixing tools 12a and 12b are not necessarily the same. Not.

4 (a) to 4 (f) show cross sections in the direction of the rotation axis of the mixing tank 11 of FIG. 3, and the mixing tools start from the center of the rotation axes B ₁ and B ₂ of the mixing tools 12a and 12b. It is the side cross section which looked at the 12b side. That is, the positional relationship between the central position G of the mixture and the mixing tool (only one mixing tool 12b is shown) in the steps corresponding to (a) to (c) of FIG. 3 is shown in more detail. .

FIGS. 5A to 5F are cross-sectional views in a direction perpendicular to the rotation axis of the mixing tank 11 at points corresponding to FIGS. 4A to 4F, respectively. In the cross section viewed from the side of the driving devices M and M at the position where the central position G of the mixture exists at the time corresponding to (a) to (f) in FIG. And the cross-sectional shape corresponding to the G position of each blade of the mixing tools 12a and 12b are shown together with their relative relationships.
Note that the cross-section of the mixture at 5 represents a G ₂ are hatched, are displayed with G ₃ shows the outline of the mixture located behind a small circle.

Subsequently, the pair of mixing tools 12a and 12b, the central position G of the mixture, and the schematic shape thereof in the mixing method of the present invention will be described in detail.
As is apparent from FIG. 3, the pair of mixing tools 12a and 12b is set in a state where the kneading blade 13b and the turning blade 14a and the kneading blade 13a and the turning blade 14b are shifted from each other by about 45 ° in the rotation direction. ing. As shown in FIG. 5 (a), when the kneading blade 13a is at a position below the vertical direction in the figure, the turn-back blade 14a is in the direction of 45 ° outwardly downward from the lower vertical direction.
Therefore, as each mixing tool is rotated from (a) to (f) in FIG. 3, first, each blade on the mixing tool 12b side is first rotated in FIG. Each blade on the side of the mixing tool 12a is rotated in the opposite direction with a delay of °.

  For this reason, for example, at the time shown in FIG. 3 (a), the mixture (G) is first swirled from the lower right side of the drawing by the kneading blade 13a of the mixing tool 12b, and then the mixing tool 12a is delayed by about 45 °. The turn-back blade 14a rotates so as to scoop up from the lower left of the drawing. Along with this, the mixture (G) first starts moving in the direction of the arrow in the figure, and it is as if it is scooped up with both palms (actually about 45 ° misalignment) by the kneading blade 13a and the turning blade 14a. It moves and shifts to the next state of FIG.

  FIG. 3B shows a state in which each mixing tool 12a, 12b is rotated by about 60 ° from the state shown in FIG. 3A, and the mixture (the mixture scooped up by the kneading blade 13a and the turning blade 14a ( G) is also moved in the direction of the arrow in the figure. At this time, since the mixture (G) is lifted at a considerable speed, the shape of the mixture lump is expanded in a plane as will be described later. However, the center position G is moving in a direction away from the blade surfaces of the kneading blade 13a and the turning blade 14a.

  FIG.3 (c) has shown the state which each mixing tool 12a, 12b rotated about 60 degrees from the state of the same (b). At this time, the lump of the mixture is completely separated from the kneading blade 13a and the turn-back blade 14a, and dropped to a place where a gap is formed between the kneading blade 13b and the turn-back blade 14b of each mixing tool 12a, 12b. Is shown. At this time, the lump of the mixture that has been scooped up and dropped collapses, the planar shape expands, and the behavior peculiar to the present invention as described later is exhibited.

  At this time, since the blades of the mixing tools 12a and 12b are in the relationship as described in FIG. 2, the mixture (G) is mixed with the mixing tank 11 as shown in FIG. It should be noted that it falls between the kneading blade 13b and the cut-back blade 14b located on the outer side and collapses.

  Thereafter, each mixing tool 12a, 12b continues to rotate and changes to the state shown in FIG. It can be seen that this state corresponds to the state shown in FIG. That is, the mixture (G) that has fallen and collapsed in FIG. 3C is rotated by the mixing tools 12a and 12b following the state of FIG. As shown in FIG. 3D, the mixture (G) is scooped up as shown in FIG. 3 (d) in cooperation with the rotation of the turn-back blade 14b that is collected approximately in the center by rotation from the side and continues with a delay of about 45 °. Progresses. This is exactly the same operation as the state of FIG.

  Therefore, (e) and (f) following FIG. 3 (d) are exactly the same as the operations of FIG. 3 (b) and (c) described above, and only the mixture (G) in FIG. 3 (c). Is at the upper left position in the drawing of the mixing tank 11, and the kneading blade 13b rotates in advance of the turning blade 14b, so that the mixture (G) is turned through the turning blade 14a through the states shown in FIGS. And the kneading blade 13a fall to the lower right position in the figure of the mixing tank 11, and collapse at this position at the same time.

  What is important here is that the moving state of the mixture shown in FIG. 3 is such that each mixing tool 12a, 12b in the twin-screw mixer 10 shown in FIG. The movement timing of the mixture (G) is shown by changing the axial length of each blade 13a, 13b, 14a, 14b, the twist degree of each blade, and the like. To change.

  Further, such a change in the moving timing of the mixture (G) is caused by a shift angle between the mixing tools 12a and 12b, that is, a delay of about 45 ° of the mixing tools 12a and 12b in the description with respect to FIG. It should be noted that these changes are also caused by changes, for example, due to the viscosity characteristics of the ready-mixed concrete as a mixture or the mixed material thereof.

  4 (a) to (f) and FIG. 5 (a) to (f) show the operating states corresponding to the above-mentioned FIGS. 3 (a) to 3 (c), particularly the behavior of the mixture therebetween. This will be described in more detail. 4 (a) to (f) and FIG. 5 (a) to (f) show the relationship between each blade and the mixture at the same time point, as described above. 4 (a) to 4 (f) show the side surface of the mixing tool 12b in FIGS. 2 and 3 together with the mixture center position G at that time, and FIGS. 5 (a) to 5 (f) 4 (a) to (f), the blades and the cross section of the mixture itself in the cross section orthogonal to the rotation axis corresponding to the mixture center position G are viewed from the rotational drive means M and M side. Show.

The shape of the mixture in FIG. 5 displays the whole with G _1, the section cut along a corresponding plane and displays put hatched by displaying the G ₂ to the mixture center position G in FIG. 4, the the material moved to the rear direction on the drawing from the surface indicated as G _3, it is expressed by a population of small circles. Moreover, each blade | wing which appears in the applicable cross section in FIG. 5 has described the code | symbol of the applicable blade | wing with the cross-sectional shape and the rotation direction position.

First, as is clear from FIG. 4A and the corresponding FIG. 5A, the mixture represented by the center position G or the entire G ₁ is below the drive units M and M side of the mixing tank 11. The kneading blade 13a is first collected in the substantially central portion of the mixing tank 11 in cooperation with the turn-back blade 14a. As the mixing tools 12a and 12b rotate, the operation proceeds with the turning blades 14a being added while scooping up by the kneading blades 13a, as shown in FIGS. 4B and 5B. In FIG. 5C and FIG. 5C, the mixture is completely scooped up by the kneading blade 13a and the turn-back blade 14a, and the center position G of the mixture is moved to the side opposite to the mixing tank 11a. At this time, as clearly shown in FIG. 4 (c), the mixture (G) is considerably lifted and moved toward the side opposite to the side wall 11 b of the mixing tank 11.

  As apparent from FIGS. 4D and 5D, at this point, the mixture (G) starts to leave the kneading blade 13a. However, particularly as shown in FIG. It is still moving to the upper side of the mixing tank 11 and the side wall 11a, and is almost in a state of being thrown out.

  When the rotation of the mixing tools 12a and 12b further proceeds, the center position (G) of the mixture is completely thrown into the air, as is apparent in FIGS. 4 (e) and 5 (e), and the position is the mixing tank. 11 near the side wall 11b and close to the mixing tool 12a in plan view, and as shown in FIG. 4 (e), the center position G of the mixture starts to fall.

Then, at the end of the movement process of the mixture (G), as is clear from FIGS. 4 (f) and 5 (f), the mixture (G) separated from all the blades falls and then collapses. However, as is apparent from FIG. 3C, the position is in the vicinity of the rotation support member 16 (see FIG. 3) of the kneading blade 13b.
Although the description of the steps corresponding to (d) to (f) in FIG. 3 is omitted, the states shown in FIGS. 4 (a) to (f) and FIGS. 5 (a) to (f) are completely different. The operation proceeds in the same state, and collapsing mixing action is performed.

FIG. 6 schematically shows the movement of the center position G of the mixture described in FIG. 3, and FIG. 6A shows that the deviation angle between the kneading blade 13a and the turning blade 14a described above is about 45. (The kneading blade 13b and the turn-back blade 14b are the same), and FIG. 6 (b) shows the case where the misalignment angle of both blades is about 0 °.
That is, in the case of FIG. 6 (a), the mixture (G) scooped up by the kneading blade 13a and the turning blade 14a in the steps (a) to (c) of FIG. 3 (d) to (f) in FIG. 3 is crushed up by the kneading blade 13b and the turnback blade 14b and thrown out in the same manner as the previous steps and operations. 6 (a) collapses at the Gx position, and as a result, the constituent materials of the mixture are effectively mixed by the falling collapse at the diagonal position of the mixing tank 11.

That is, according to the mixing method in one embodiment of the present invention, the center position G of the mixture moves at high speed between the positions Gx and Gy in FIG. 6A, and repeatedly collapses each time. This is where efficient mixing takes place.
In FIG. 6B, the moving position of the mixture (G) that has been scooped up when there is no deviation angle between the kneading blade 13a and the turning blade 14a (the same applies to the kneading blade 13b and the turning blade 14b) as described above. In this case, it is scooped up and thrown out between Gx and Gy in FIG.

Here, one embodiment of the mixing according to the present invention will be described. The time required for one reciprocation between the Gx position and the Gy position in FIG. When the mixing time is about 2 seconds, when mixing high-viscosity concrete with low viscosity, especially when mixing low-viscosity sand and cement, the adhesiveness between materials is small and the material tends to collapse. Mixing due to the collapse of the material was promoted, the material was easily mixed, and good mixing could be performed in an extremely short time.
Further, the delay between the kneading blade 13a and the turning blade 14a and the kneading blade 13b and the turning blade 14b at this time is 45 ° in this embodiment. It also shows the case where there is no delay between them.

It is a perspective view of the twin-screw mixer utilized in order to implement the mixing method of this invention. It is a top view of the twin-screw mixer shown in FIG. FIG. 3 is a plan view of a mixing tank showing a positional relationship between a moving state of a mixture and each mixing tool in the twin-screw mixer shown in FIGS. 1 and 2. It is explanatory drawing which shows the movement state of the mixing tool 12b and a mixture corresponding to the process of Fig.3 (a)-(c). It is explanatory drawing which shows the positional relationship of each blade | wing and a mixture in the cross section orthogonal to the rotating shaft of each blade | wing in the mixture position corresponding to Fig.4 (a)-(f). 6 (a) and 6 (b) are explanatory views showing the moving state of the mixture in the mixing method of the present invention in the mixing tank according to two examples. It is explanatory drawing of the mixing method of the ready-mixed concrete by the conventional hand kneading mixing. It is explanatory drawing which shows the behavior of the mixture in the mixed state in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Twin-shaft mixer 11 Mixing tank 11a, 11b Mixing tank side wall 12a, 12b Mixing tool 13a, 13b Kneading blade 14a, 14b Turning-back blade 15 Connection member 16 Rotation support member G Central position of mixture

Claims (5)

A method for mixing ready-mixed concrete using a biaxial mixer comprising a pair of mixing tools having a kneading blade and a turning blade rotating on each rotating shaft core, facing the biaxial shaft core. The ready-mixed concrete is characterized by repeating the step of rotating the kneading blade and the turning blade provided and throwing it from one of the mixing tanks to the other while scooping up the mixed material with both blades. Mixing method. A method for mixing ready-mixed concrete using a biaxial mixer comprising a pair of mixing tools having a kneading blade and a turning blade rotating on each rotating shaft core, facing the biaxial shaft core. The kneading blade and the turning blade provided are rotated with a delay with respect to the preceding kneading blade, and the mixed material is scooped up by both blades from one corner of the mixing tank to the other corner on the diagonal side. A method for mixing ready-mixed concrete characterized by repeating the process of throwing and collapsing the mixed material. 3. The method for mixing ready-mixed concrete according to claim 2, wherein the delay angle of the turning blade that is rotated with respect to the preceding kneading blade is about 30 ° to 60 °. Method. The method for mixing ready-mixed concrete according to any one of claims 1 to 3, wherein the operation speed of the step of throwing and collapsing the mixed material by the biaxial mixer is one reciprocation in about 2 seconds. Mixing method of ready-mixed concrete. 5. The mixing method of ready-mixed concrete according to claim 3, wherein each mixing tool in the twin-screw mixer used has a kneading blade twisting about 170 ° and a turning blade twisting about 110 °. And the inner angle of the bent portion of the connecting member bent in a U-shape is about 165 °.