JP2018145089A - Method for finely dividing air bubble in ready-mixed concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for finely dividing an air bubble in a ready-mixed concrete in which an air bubble on the surface or inside of a ready-mixed concrete can be finely divided, or de-foamed, and a good appearance, homogeneous and high quality precast concrete product can be produced.SOLUTION: Provided is a method for finely dividing air bubble in ready-mixed concrete for producing a precast concrete product in which an air bubble in a ready-mixed concrete is finely divided, and in which a fluctuating inertial force is given to a ready-mixed concrete, and depending on physical and/or chemical attributes of the ready-mixed concrete and/or physical and/or chemical attributes of the air bubble, the fluctuating inertial force is controlled by one or more conditions selected from the fluctuation range, the number of fluctuations per unit time, the repeatedly fluctuated time duration or fluctuation frequency, and the acceleration of the fluctuating inertial force.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for refining air bubbles for refining air bubbles in ready-mixed concrete.

  Conventionally, when a product or the like is manufactured using ready-mixed concrete, there is a case where it is necessary to process bubbles contained in the ready-mixed concrete from the viewpoint of quality and appearance. For example, when air bubbles are present in the ready-mixed concrete when the ready-mixed concrete is solidified, cavities and dents are generated inside and on the surface of the solidified body.

  Regarding such a problem, for example, Patent Document 1 discloses a concrete bubble reduction vibrator having a vibrating body that connects or incorporates an electric motor, a gutter plate, and a connecting portion that couples the vibrating body and the gutter plate. In addition, a method is described in which the bubble reduction vibrator is inserted in the vicinity of an uncured concrete mold and vibrated to reduce concrete bubbles.

  However, in the vibrator as described in Patent Document 1, due to the scattering or irregular reflection of the vibration due to the mixed viscosity of concrete, the properties such as cement paste and fine aggregate or coarse aggregate, the size or size, and the specific gravity. There is a problem that the vibration does not spread to the whole due to attenuation or the like, and the vibration can be given only locally. Moreover, labor and cost are excessively generated for the work of inserting the vibrator near the formwork. Furthermore, in the first place, there has been a problem that the given vibration conditions do not meet the defoaming conditions of the shaker and cannot be defoamed.

  Further, in Patent Document 2, a formwork placing table for placing a concrete molded product form is constituted by a frame made of shape steel or the like, and a base is also made by a frame made of shape steel or the like. A mold mounting table is mounted with a cushioning member such as rubber interposed, and a mold fixing device for mounting and fixing a concrete molded product mold on the mold mounting table is provided. There is described a table vibrator for molding a cement concrete product in which a vibration motor is attached to a portion of a mounting table.

  However, the table vibrator described in Patent Document 2 can only provide a predetermined vibration that is not fixed to the microbubble formation condition, and is a so-called entrapped air. There is a problem that it cannot be made fine until it disappears in appearance. That is, under the given vibration conditions, there was a problem that the foaming conditions were not met and the foaming could not be made.

  There is also a defoaming device for removing bubbles, which includes a defoaming treatment tank and an ultrasonic vibrator connected to the defoaming treatment tank.

  However, in the technology of defoaming using sound waves, particularly ultrasonic waves, the fluid is a viscous fluid or a hybrid fluid containing a plurality of objects having different specific gravity, hardness, size, and shape. Can be applied in the vicinity where the sound wave is input, the wave of the preset condition can be applied, but when the sound wave is moved away from the sound wave input source, the sound wave is significantly attenuated and the attenuated wave deviates from the set condition. There is a problem that it is non-uniform, does not spread evenly over the entire surface, and as a result, it cannot be defoamed to an acceptable level.

JP 2006-16868 A JP-A-5-318422

  The present invention has been made by the inventor's diligent research in view of such conventional circumstances, and can refine the surface and internal bubbles of the ready-mixed concrete, have a good appearance, and have a high quality. An object of the present invention is to provide a method for refining bubbles in ready-mixed concrete, which can efficiently produce a precast concrete product at low cost.

  One aspect of the present invention is a method for refining bubbles in a ready-mixed concrete for producing a precast concrete product obtained by refining bubbles in a ready-mixed concrete. Depending on the physical and / or chemical attributes of the gas and / or the physical and / or chemical attributes of the bubble, the fluctuation range of the variable inertial force, the number of fluctuations per unit time, the time or number of fluctuations repeatedly changed, The variable inertial force is controlled according to one or more conditions selected from acceleration.

  In addition, the method for refining the bubbles of ready-mixed concrete is characterized in that a variable inertial force is applied immediately after the start of the solidification reaction and / or before complete solidification.

  Further, the method for refining bubbles in ready-mixed concrete is characterized in that a variable inertial force is uniformly applied to the entire ready-mixed concrete simultaneously.

  Moreover, the method for refining bubbles in ready-mixed concrete is characterized in that a variable inertial force is applied in the vertical direction and / or the horizontal direction.

  In addition, the method for refining bubbles in ready-mixed concrete is characterized in that the variable inertial force is controlled according to one or more conditions selected from the viscosity, specific gravity, and bubble size of ready-mixed concrete.

  In addition, the method for refining bubbles in ready-mixed concrete is characterized in that the variable inertial force is controlled by simultaneously controlling the fluctuation range and the fluctuation number according to the time of repeated fluctuations or the passage of the number of fluctuations.

  ADVANTAGE OF THE INVENTION According to this invention, the surface of a ready-mixed concrete and an internal bubble can be refined | miniaturized or defoamed, and the precast concrete product of good appearance and a homogeneous and high quality can be manufactured efficiently.

It is process drawing which shows an example of the manufacturing process of the processing molded object using ready-mixed concrete to which the micronization method of the bubble of ready-mixed concrete concerning one embodiment of the present invention is applied. It is the schematic for demonstrating the direction which gives a variable inertia force in the refinement | miniaturization method of the bubble of the ready-mixed concrete which concerns on one Embodiment of this invention. It is the schematic which represented typically the 1st mechanism of bubble refinement | miniaturization in the bubble refinement | miniaturization method of the ready-mixed concrete concerning one Embodiment of this invention. It is the schematic which represented typically the 2nd mechanism of bubble refinement | miniaturization in the bubble refinement | miniaturization method of the ready-mixed concrete concerning one Embodiment of this invention. It is the schematic which represented typically the 3rd mechanism of bubble refinement | miniaturization in the bubble refinement | miniaturization method of the ready-mixed concrete concerning one Embodiment of this invention. It is a figure showing the state of the bubble of concrete when conditions are changed in an Example. It is a figure showing the state of the bubble of concrete when conditions are changed in an Example. It is a figure showing the state of the bubble of concrete when conditions are changed in an Example. It is a figure showing the state of the bubble of concrete when conditions are changed in an Example. It is a figure showing the state of the bubble of concrete when conditions are changed in an Example. It is a figure showing the state of the bubble of concrete when conditions are changed in other modes of an example.

  Hereinafter, a method for refining bubbles in ready-mixed concrete to which the present invention is applied will be described in detail with reference to the drawings. In addition, this invention is not limited to the following examples, It can change arbitrarily in the range which does not deviate from the summary of this invention.

  One embodiment of the present invention is a method for refining a bubble in a ready-mixed concrete for producing a precast concrete product obtained by refining a bubble in a ready-mixed concrete, and applying a variable inertia force to the ready-mixed concrete. Depending on the physical and / or chemical attributes of the ready-mixed concrete and / or the physical and / or chemical attributes before the refinement of the bubbles to be refined, the fluctuation range of inertial force, unit time, which is at least variable The variable inertial force is controlled by one or more conditions selected from the number of hits, the number of times to change or the time or acceleration at the time of change. By applying a variable inertial force to the entire ready-mixed concrete, bubbles existing inside and on the ready-made concrete can be refined and / or defoamed to a size that causes no problem in appearance and quality. The variable inertial force applied to the ready-mixed ready-mixed concrete is not particularly limited. However, the ready-mixed concrete is displaced irregularly or randomly, and positive acceleration or negative Can be generated (accelerated (decelerated)) or in the process of changing the direction, etc., and applied to the ready-mixed concrete.

  Further, in the embodiment of the present invention, the method of applying a variable inertial force to the ready-mixed concrete can be realized by applying a regular and / or variable inertial force to the ready-mixed concrete. Depending on the type of ready-mixed concrete and / or the size of the bubbles to be refined before refinement, the fluctuation range of the regular and / or variable inertial force, the number of repetitions per unit time and / or It is characterized in that the repetitive and / or variable inertial force is controlled by one or more conditions selected from the number of fluctuations, repeated iterations, and / or the time of fluctuation or the number of fluctuations. By applying repetitive and / or variable inertial force to the entire ready-mixed concrete, bubbles existing inside and on the ready-made concrete can be refined to a size that does not cause a problem in appearance and quality. .

  In one embodiment of the present invention, it is important to apply an inertial force to the ready-mixed concrete itself, particularly to repeatedly apply an inertial force. For example, it is effective to enter (irradiate) (ultra) sound waves by a sound source device. Not a reason. In the case of sonic waves, when the ready-mixed concrete is vibrated, the ready-mixed concrete itself is a medium that propagates the waves. As a result, there is a mechanism in which the ready-mixed concrete does not vibrate. In addition, due to the difference in size, specific gravity difference, mass difference, etc. of multiple objects that make up ready-mixed concrete, objects that vibrate and non-vibrated objects appear due to various conditions of sound waves, and the same effect is applied to the entire ready-mixed concrete. There is a problem that it is not possible to apply the action of collapsing bubbles over the entire ready-mixed concrete. In particular, ready-mixed concrete, which is a vibration body, contains solids of various shapes, masses, and specific gravities, so that the input sound wave is scattered and / or attenuated by viscous resistance, etc. on each surface and boundary surface. Therefore, there is a problem that the wave does not spread over the entire volume of the ready-mixed concrete.

  On the other hand, in one embodiment of the present invention, inertia is applied almost uniformly to the entire volume of the ready-mixed concrete to apply inertial force to all objects constituting the ready-mixed concrete, Depending on the physical and / or chemical attributes and / or the physical and / or chemical attributes of the bubbles to be refined, the fluctuation range of the variable inertial force, the number of fluctuations per unit time, By controlling the variable inertial force according to one or more conditions selected from the number of fluctuations and acceleration, an inertial force suitable for reducing bubbles is applied to the periphery of the bubble, and the inertial force generated in the bubble itself From the difference, the surface and internal air bubbles of the ready-mixed concrete can be made finer, thereby making it possible to efficiently produce a precast concrete product with a good aesthetic appearance. Of course, the inertial force that is applied to the ready-mixed concrete, which is to be oscillated, does not necessarily have to be reciprocal. And may be intermediate between irregularities.

  The means for applying the variable inertial force is not particularly limited. For example, it may be configured to obtain an inertial force that varies due to a centrifugal force in a rotating system that repeatedly alternates the rotation direction, Can be due to movement and vibration. Hereinafter, a case where a variable inertial force is applied by vibration will be described as one embodiment of the present invention. In this case, the fluctuation range of the variable inertial force corresponds to the amplitude, the number of fluctuations per unit time corresponds to the vibration frequency, and the time for repeated fluctuations corresponds to the vibration time.

  In one embodiment of the present invention, the ready-mixed concrete is solidified by reaction in itself. When the ready-mixed concrete is solidified with air bubbles contained therein, the internal bubbles remain as cavities and dents, so by applying the method for refining ready-mixed air bubbles according to an embodiment of the present invention. Even if it is solidified by refining the bubbles in the ready-mixed concrete to a size that does not cause any problems in appearance and quality, it remains as a large cavity inside the solidified body, or a depression is generated on the surface That can be solved. Here, the quality is required among the strength, rigidity, elasticity, mass distribution, denseness, homogeneity, etc. that define the properties of the ready-mixed concrete after the foam is refined or defoamed. In particular, it is preferable that the bubbles are refined or defoamed so that the required characteristics satisfy the required level.

  It is preferable to give vibration to the ready-mixed concrete immediately after the start of the solidification reaction. If the solidification progresses to some extent, the bubbles are fixed as cavities, which are difficult to eliminate. In addition, excessive vibration is not preferable because, for example, a plurality of objects having different specific gravities constituting the ready-mixed concrete may be separated.

  In one embodiment of the present invention, the vibration is preferably applied so as to spread substantially uniformly over the entire ready-mixed concrete. As a method for uniformly applying vibration, for example, there is a method of vibrating the entire mold holding the ready-mixed concrete. In the vibrator described in Patent Document 1 as described above, vibration can be given only locally, and vibration can not be given or swung to the whole, and bubbles can be sufficiently eliminated. Therefore, it is preferable to apply vibration and rocking uniformly to the whole ready-mixed concrete.

  FIG. 1 is a process diagram showing an example of a process for producing a processed molded body using ready-mixed concrete, to which a method for refining fresh concrete bubbles according to an embodiment of the present invention is applied. When manufacturing a processed molded body etc. using ready-mixed concrete, for example, raw materials are mixed to prepare ready-mixed concrete (mixing step S1), and the ready-mixed concrete is transported to a forming place (transporting step S2), to a formwork. Raw concrete is injected (injection step S3) and molded in a mold (molding step S4). In order to eliminate the generated and / or mixed bubbles, a variable inertia force (for example, vibration) can be applied to the mold in the final molding step S4. When the mass is large, or when it is difficult to prepare equipment that gives a variable inertial force at the manufacturing site where the molding step S4 is performed, rocking is performed in any of the mixing step S1 to the injection step S3. Then, a variable inertia force may be applied.

  FIG. 2 is a schematic view for explaining a direction in which a variable inertial force is applied in the method for refining bubbles in ready-mixed concrete according to an embodiment of the present invention. In the method for refining bubbles in ready-mixed concrete according to an embodiment of the present invention, it is preferable that the variable inertial force is applied to the vertical direction with respect to ready-mixed concrete 11, that is, the z-axis direction in FIG. . Since gravity is applied to the vertical direction, by applying a variable inertial force to the same direction as gravity, the bubbles 12 can be more effectively made finer and disappear. It is also possible to move it upward in the vertical direction. In addition, even when a variable inertial force is applied to a large amount of ready-mixed concrete 11 having a scale of several tons to a few tens of tons, the configuration in which the variable inertial force is applied to the vertical direction is greater than the horizontal direction. Compared with a configuration that gives a variable inertial force, it is possible to take a reaction force using the ground, and the control of the mold 13 becomes easier. However, regarding the method for refining the bubbles of ready-mixed concrete according to an embodiment of the present invention, it does not exclude the application of a variable inertia force in the horizontal direction, and the x-axis direction or the y-axis direction in FIG. An inertial force in a direction combining the x axis and the y axis may be applied. Furthermore, in addition to the inertia force in the vertical direction, the inertia force in the horizontal direction may be given. Further, in addition to the application of the variable inertia force in the vertical direction and / or the horizontal direction, the vibrating body may be rotated in the vertical plane or in the horizontal plane. In this case, it is possible to reduce separation of a plurality of objects constituting the ready-mixed concrete. In addition, the method of applying the inertial force to ready-mixed concrete is not limited to the acceleration variation along the uniaxial direction, but changes by rotating the entire ready-mixed concrete regularly or irregularly while changing the rotation direction. You may comprise so that a centrifugal force may act.

  In the method for refining bubbles in ready-mixed concrete according to an embodiment of the present invention, the mechanism by which the bubbles are refined will be described below with reference to FIGS. 3 to 5, the direction of the variable inertia force coincides with the z axis of FIG. 2, and the vertical direction also coincides with the vertical direction of FIG. 2. Moreover, although this description demonstrates as an example what applied the variable inertia force to the ready-mixed concrete by a monotonous and reciprocating motion, a motion is not restricted to a monotonous and reciprocating motion.

  FIG. 3 is a schematic view schematically showing a first mechanism of bubble miniaturization in the bubble miniaturization method according to an embodiment of the present invention. The bubbles 20 in the ready-mixed concrete are formed by applying a tension Fs (hereinafter referred to as “interface tension”) acting on the interface between the ready-mixed concrete and the bubbles. Therefore, in the method for refining a bubble of ready-mixed concrete according to an embodiment of the present invention, when the direction of the variable inertial force is changed by applying a variable inertial force to the bubble and the ready-mixed concrete surrounding the bubble, Inertial force Fi acting in proportion to the mass of the element body constituting the ready-mixed concrete surrounding the bubbles (in particular, the inertial force acting on the element body constituting the ready-mixed concrete existing around the interface is referred to as the interface inertia force herein) Pressure is applied to the bubbles. Explaining in detail, the vertical movement of the ready-mixed concrete according to the monotonous and reciprocating movement is the acceleration movement in the upward direction, the deceleration movement in the upward direction, the change in the movement direction in the downward direction, and the acceleration movement in the downward direction. The deceleration movement in the downward direction and the change in the movement direction in the upward direction are repeated, and the inertia force Fi is applied to the bubble 20 in such a movement that repeatedly accelerates and decelerates (FIG. 3A). ). At this time, the bubble 20 can be deformed by applying a variable inertial force such that the magnitude of the inertial force Fi is larger than the interfacial tension Fs or the collapse resistance force described later (FIG. 3B). Eventually, a certain bubble 20 existing in the ready-mixed concrete can be divided into a plurality of bubbles 20A and 20B to be reduced in size (FIG. 3C). By repeating this miniaturization, the bubbles in the ready-mixed concrete are refined to such a size that there is no problem in appearance and quality, and the bubbles in the ready-mixed concrete can be disappeared in a state invisible to the naked eye. .

  Thus, in the method for refining bubbles according to an embodiment of the present invention, by applying a variable inertial force, the bubbles are collapsed by the inertial force difference caused by the mass difference between the bubbles and the ready-mixed concrete. The following bubble breakup, tertiary bubble breakup, and so on, promote the breakup to higher-order bubble breakup, and along with this, make the bubbles finer and reach the desired level of size Get vanishing effect. At this time, the total volume of the bubbles does not change so much before and after the higher-order bubble splitting, and the bubbles may remain finely divided in the ready-mixed concrete. Therefore, the fine bubbles generated as a result of the progress of higher-order bubble splitting below a predetermined level can be made into, for example, entrained air having a diameter of about 25 to 250 μm.

  FIG. 4 is a schematic view schematically showing a second mechanism of bubble refinement in the method for refined bubble of ready-mixed concrete according to an embodiment of the present invention. By applying the variable inertial force, the ready-mixed concrete 30 is moved at the intermediate position between the peak of the monotonous and reciprocal motion to be applied. Specifically, the ready-mixed concrete 30 is moved from the upward movement to the downward direction. When the direction of movement is changed to start downward acceleration and coincides with the speed of free fall of the ready-mixed concrete 30, the state instantaneously becomes close to zero gravity. At this time, the large-diameter coarse aggregate 31 a and the small-diameter coarse aggregate 31 b (coarse aggregate 31) constituting the ready-mixed concrete 30, the fine aggregate 32 existing between the coarse aggregates 31, and these coarse aggregates 31. And the friction force due to gravity acting between the cement paste 33 interposed between the fine aggregate 32 and the fine aggregate 32 becomes almost zero (FIG. 4A). At the next moment, when the peak of the variable inertia force (position where the moving direction of the ready-mixed concrete 30 changes the moving direction from the downward direction to the upward direction), the coarse aggregate 31, the fine aggregate 32, and the cement paste 33 are , The rearrangement is made as a distribution in contact with each other. In this process, the frictional force acting between each other gradually fluctuates toward the maximum value. It flows down toward the stable state where the energy state is low (FIG. 4B). This flow-down occurs in the vicinity of the bubbles 34 as a flow from the raw concrete 30 into the bubbles 34 around the cement paste 33 and the fine aggregate 32, and the bubbles 34 that flow in are shifted in the direction of filling and flow into the raw material. On the concrete 30 side, replacement with the gas present in the bubbles 34 occurs. If such a ready-mixed / gas exchange flow occurs in one place for one bubble 34, the original bubble collapses and the gas is displaced further upward. It seems to have moved up. In addition, when the ready concrete / gas exchange flow for one bubble 34 occurs at a plurality of locations, the one bubble 34 is originally displaced upward so as to be divided into a plurality of smaller bubbles. By repeating the flow collapse in this way, the bubbles are refined or reach the uppermost part and pass through the ready-mixed concrete 30.

  FIG. 5 is a schematic view schematically showing a third mechanism of bubble miniaturization in the bubble miniaturization method according to one embodiment of the present invention. There may be air bubbles 41 that are not lost by the first mechanism and the second mechanism of fine air bubbles in the green concrete 40 described above. However, such bubbles 41 hardly exist in the case of mortar that does not include coarse aggregate. Therefore, it is considered that the main cause of the generation of the bubbles 41 is generated by the presence of the coarse aggregate 42. That is, the bubble 41 can exist in the vicinity of the coarse aggregate 42, and there is a space surrounded by several coarse aggregates 42, and air is trapped in the coarse aggregate 42. it is conceivable that. The air bubbles 42 having such a structure are aggregates in which coarse aggregates 42 having relatively close densities gather together and mortar (fine aggregate 43 and cement paste 44) having a density close to that of the coarse aggregates 42 is used as a binder material. Is made. From this, it is considered that the bubbles 41 are not collapsed by the first mechanism and the second mechanism, or are extremely difficult to collapse. As a mechanism for the disappearance of the bubble 41 having such a configuration, it is effective to apply a resonance vibration having a natural frequency to the coarse aggregate 42 constituting the bubble 41.

  Actually, it is considered that the bubbles are made finer as a form in which the first mechanism, the second mechanism, and the third mechanism are combined, but here, in the bubble refinement method according to one embodiment of the present invention, The setting of conditions for applying the variable inertia force will be described in more detail. Hereinafter, the first mechanism will be mainly described in mind, but the parts applicable to the second and third mechanisms may be appropriately replaced and understood. As described above, in order to reduce the size of the bubbles, a force greater than the force (hereinafter referred to as “bubble collapse resistance force”) that maintains the state of the bubbles acting on the bubbles is vibrated. , Impact, and centrifugal force (however, even if inertial force such as steady centrifugal force is applied, it is often impossible to collapse the bubbles. It is preferable to give to the bubbles by, for example, a state.

  Bubble collapse resistance is the presence of gas trapped by solid concrete viscosity, specific gravity, component mass, bubble size, bubble interfacial tension, bubble internal pressure, aggregates, etc. The degree of surrounding of the gas by the solid is used as a parameter. Therefore, it can be set or estimated as appropriate depending on the size, shape, form, etc. of the ready-mixed concrete and / or bubbles. In the method for refining a bubble of ready-mixed concrete according to an embodiment of the present invention, the variable inertia force is controlled so that a force exceeding the bubble collapse resistance force is applied to the bubble.

The waveform of the variable inertial force to be applied is not particularly limited. As an example, simple vibration is realistic and efficient. In this case, for example, if the displacement of the vibration wave on the z-axis in FIG. 2 at time t is f (t),
It can be expressed as Here, A is the amplitude, ω is the angular frequency corresponding to the frequency, and t is the vibration time. Therefore, in the method for refining a bubble of ready-mixed concrete according to an embodiment of the present invention, vibration can be controlled by one or more conditions selected from amplitude, frequency (or wavelength), and vibration time. In consideration of the existence of bubbles without collapsing in the presence of gravity, it is preferable to apply vibration so that an acceleration exceeding at least 1 G (gravity acceleration), preferably about several G or more, is applied to the bubbles.

The acceleration at time t when applying a variable inertial force by applying vibration to the ready-mixed concrete is G (t), and the gravitational acceleration on the earth is G≈9.8 [m / sec / sec]. The acceleration G (t) [G] based on this is not particularly limited,
Setting so as to satisfy the relationship is effective, efficient and preferable. Further, if the amplitude at time t is A (t) [mm] and the angular frequency is ω (t) = 2πν [rad / sec] (where ν [Hz] is the frequency), the acceleration G (T) [G] is
It is expressed. From this, the frequency ν (t) is
It is expressed. When determining the frequency ν (t), for example, if G (t) = 5/2 · G [G] is set, the frequency ν (t) is
And obtained. Here, when the amplitude at time t = 0 is A ₀ > 0, and an arbitrarily set proportional constant is −A ₁ <0, it is assumed that the amplitude A (t) decreases with time. As
From the equation (6), the frequency ν (t) is
Therefore, the angular frequency ω [rad / sec] is
Given in. Therefore, it can be seen that the frequency ν or the angular frequency ω increases with the increase of the time t from the formula (7) or the formula (8). As described above, when the acceleration G (t) is set as a constant that does not depend on time, when the amplitude is decreased with the passage of time, the frequency and the angular frequency increase with the passage of time. It can be said that it is required to set so as to. Therefore, when the acceleration G (t) is set to increase with the passage of time, the frequency ν and the angular frequency ω are expressed by the following formulas (7) and (8). It can be seen that the increase is significantly greater than shown.

  The amplitude is not particularly limited, but may be, for example, about 1/10 or more of the diameter of the bubble, and preferably about a width equal to or less than the diameter of the bubble. If the amplitude is too small or too large than this range, the inertial force applied to the ready-mixed concrete will be insufficient and the force for collapsing the bubbles will be weakened, and the force for minimizing the bubbles will not be sufficiently applied, or Excessive vibration energy is applied, which is inefficient in terms of energy, and it is unreasonable that the components of the ready-mixed concrete may be separated. In addition, when ready-mixed concrete is a mixture of a plurality of materials having different specific gravities, if excessive vibration is applied, components may be separated. By applying vibration, the bubbles are gradually divided and miniaturized, so that the amplitude may be gradually decreased with the passage of time.

  By the way, if the inertial force with respect to the whole ready-mixed concrete system, which is a vibration body, is constant, the force per unit area acting everywhere in the system, that is, the surface pressure can be regarded as substantially constant. Therefore, a large diameter bubble has a large surface area, and the force received as the entire surface of the bubble is relatively large. On the other hand, a small diameter bubble has a small surface area, and the force received as the total surface area of the bubble is relatively small. That is, small diameter bubbles are less likely to collapse than large diameter bubbles. Therefore, it can be said that it is preferable to increase the inertial force as a result of increasing the acceleration that causes the inertial force in the process in which the inertial force is applied to the ready-mixed concrete and the bubbles are fragmented. At this time, if the amplitude is gradually decreased in accordance with the target bubble size, the acceleration can be increased by increasing the frequency accordingly.

  In one embodiment of the present invention, vibration can be controlled by the frequency (frequency). Although the frequency is not particularly limited, for example, vibration of about several tens of Hz may be given. An excessively high frequency is not preferable because there is a possibility that the objects constituting the ready-mixed concrete may be separated. Further, as described above, since bubbles are gradually reduced when vibration is applied, the frequency is set to be gradually increased in accordance with equations (2) to (8). May be.

  In one embodiment of the present invention, vibration can be controlled by the vibration time or the number of vibrations. Although the vibration time is not particularly limited, for example, it can be in the range of several tens of seconds to several minutes. Further, when the ready-mixed concrete is solidified, it is necessary to set the vibration conditions so that the refinement of bubbles is completed before the solidification reaction is completed. Of course, there is also a fluid in which solidification does not proceed while rocking, and in this case, it may be vibrated at an appropriate time. In addition, even if it is vibrated over a certain period of time, depending on conditions, there may be bubbles that remain without defoaming, and in that case, it will lead to loss of energy to be input, so stop for about the required time Is preferred.

  Furthermore, in one embodiment of the present invention, vibration may be controlled by further setting conditions other than those described above. For example, fresh concrete may be pressurized or depressurized during vibration. Further, during vibration, an impact may be applied by applying an impulse and / or impact to the ready-mixed concrete. When an impact is applied, the bubbles in the ready-mixed concrete are subjected to striking pressure, and thus are more likely to collapse. Impulse can be generated by making the vibration applied to the ready-mixed concrete into a vibration having a waveform such as a rectangular wave or a sawtooth wave. In addition, a shock wave may be applied. The impact can also be realized by configuring the system so that an object that vibrates together with the ready-mixed concrete causes a collision between the ready-mixed ready-mixed concrete and a relatively displaced object.

  Thus, the vibration is controlled according to one or more conditions selected from the amplitude, the frequency, and the vibration time according to the size of the bubble. When a bubble is split by vibration and becomes a bubble smaller than a certain size, it may not be possible to further miniaturize the bubble that has become smaller in amplitude and frequency until then. Accordingly, the amplitude and frequency may be controlled simultaneously as the vibration time elapses, and an acceleration G that sufficiently exceeds the bubble collapse resistance may be applied to a small-sized bubble.

Furthermore, in one embodiment of the present invention, in order to efficiently miniaturize a plurality of bubbles having different sizes, or to obtain a desired combined waveform, a vibration obtained by combining a plurality of vibration waves may be added. That is, the diameter _{d 1,} d 2 a plurality of different, ..., for each of the bubbles having a d _n, the optimum amplitudes _{A 1, A 2, ···,} A n and a vibration number omega _1, omega ₂ , ..., using a combination of ω _n , the synthesized wave f (t) is
May be set. By applying vibration by such a synthetic wave, bubbles can be efficiently miniaturized simultaneously in a short time with respect to bubbles of various sizes. Further, it may be close to its limit (that is, n → ∞ in equation (9)).

As described above, in the method for refining bubbles in ready-mixed concrete according to an embodiment of the present invention, the inertial force F (t) is applied as vibration under a predetermined condition to ready-mixed concrete as a vibration body. As vibration conditions, vibration frequency ν (t) (or angular frequency ω (t)), amplitude A (t), vibration time t, and the like can be considered, and vibration frequency ν (t) (or angle As an effective viewpoint as the frequency ω (t)) and the amplitude A (t), it is calculated from the frequency ν (or the angular frequency ω) and the amplitude A and set to exceed the gravitational acceleration 1G of the earth. There is a preferable acceleration G (t), and this acceleration G (t) can define a variable inertia force F (t), for example, an inertia force F (t) whose direction is reversed up and down. In terms of the relationship between the inertia force F (t) and the time t at which the inertia force F (t) is applied, the time t at which the inertia force F (t) should be applied to the ready-mixed concrete that is the vibration body is necessary. In addition, it is necessary to exceed a sufficient predetermined time τ. Of course, since exceeding the predetermined time τ significantly results in energy loss, it is preferable to stop around the predetermined time τ. Here, the essential meaning of the time t in the vibration system is that when the vibration continues at the frequency ν (t) from the time t = 0 to the time t = τ, This is a parameter that gives the number of times the upper and lower ends of the vibration are reached, where inertial force acts on the concrete. Therefore, for ready-mixed concrete, Since the inertia force acts twice at the lower end, the acceleration at the frequency ν _k with respect to the amplitude A _k for the bubble B _k of a certain size is expressed as G _k (G _k (t)> 1 [G]. ), And τ _k is a necessary and sufficient time for the target bubble B _{k to} be divided and subdivided,
It is also possible to think. However, where, N is a measure value of the dimensionless relative bubble B _k of each size, 1 or a for consideration from the sum of the inertial force by acceleration in excess of [G] has enough times applied It is an indicator.

  As described above, by repeatedly applying an inertial force to the ready-mixed concrete, most of the bubbles are subdivided, and by repeating such subdivision, the refinement of the bubbles is realized. By miniaturization to a required area, the bubbles in the ready-mixed concrete are refined or defoamed to a necessary and sufficient level with no aesthetic or quality problems. However, there may be bubbles that are not miniaturized by the above means. The structure and collapse method of this type of bubbles (hereinafter referred to as residual bubbles) will be described below.

  As described above, the residual bubbles are often formed by being surrounded by a plurality of relatively large solids such as coarse aggregates, and the paste being interposed between the coarse aggregates (third). Mechanism). In this case, the coarse aggregate surrounding the remaining bubbles does not collapse the relative position between the coarse aggregates even if an inertial force sufficiently exceeding 1 [G] is generated, and the remaining bubbles are generated. Therefore, in order to disintegrate and subdivide the remaining bubbles under such conditions, the coarse aggregates surrounding these remaining bubbles are respectively swung and displaced, or the relative positional relationship is changed. Thus, it is necessary to destroy the structure formed by the coarse aggregate (hereinafter referred to as a bubble trapping structure).

Therefore, if the mass of the coarse aggregate η surrounding the residual bubbles is m _η , the natural frequency ν _η of the coarse aggregate _η is
By inputting a vibration V corresponding to this natural frequency ν _η to the ready- _mixed concrete, the coarse aggregate whose mass existing in the _ready-mixed concrete is close to m _η becomes the forced vibration V from the outside. Unlike other pastes, fine aggregates, coarse aggregates, etc., which cause resonance, they vibrate violently. Among them, the coarse trapping that is a part of the bubble trapping structure formed by the coarse aggregate surrounding residual bubbles By swinging the aggregate η greatly, the interface inertia force proportional to the mass of the coarse aggregate, which is the element body existing in the vicinity of the interface of the remaining bubbles, can be applied, and the bubble trapping structure can be collapsed. As described above, the remaining bubbles formed by the bubble trapping structure can also be destroyed.

Here, k in the equation (11) is derived from viscoelasticity or the like due to the mutual relationship in the bubble trapping structure of paste, fine aggregate, coarse aggregate, etc. constituting the ready-mixed concrete, Assuming that it is almost uniform in the system, this can be clarified by experiments or the like in advance, and if the value is known, the natural frequency ν _η is the value of each element η in the ready-mixed concrete. As it is proportional to the reciprocal of the square root of the mass m _η , it can be known in advance by measurement, etc. In the case of an object such as coarse aggregate, the natural frequency ν _η is a relatively small value, In the case of a thing, it becomes a relatively large value. Therefore, since it is efficient to proceed with fragmentation from large bubbles, the natural frequency ν _η applied to the ready- _mixed concrete is targeted to a larger coarse aggregate among the elements existing in the ready- _mixed concrete. It is preferable to set a corresponding value, and gradually change the target coarse aggregate to a lighter object and change the frequency input as the forced vibration V. At this time, the forced vibration V to be input does not necessarily have to be along the direction of the vibration giving the inertial force to the ready-mixed concrete, and may be parallel or orthogonal to this direction, You may do it.

  The method for refining ready-mixed concrete according to an embodiment of the present invention can be used in the production of precast concrete. Conventionally, in the production of concrete, when solidified due to the inclusion of entrapment air or the like during molding, it remains as a dent or cavity on the surface or inside of the concrete. Since it is not preferable, for example, a makeup process or the like is performed manually on the concrete surface, which requires considerable effort and cost.

  In the method for refining bubbles in ready-mixed concrete according to an embodiment of the present invention, since the bubbles can be made finer and disappear, the bubbles on the concrete surface can also be made finer and can be brought into a state with no problem in appearance. Moreover, by setting an appropriate amplitude, vibration frequency, and vibration time, bubbles can be efficiently eliminated in a short time. Furthermore, in the method for refining bubbles in ready-mixed concrete according to an embodiment of the present invention, the bubble diameter when the bubbles are assumed to be spherical is about Entrend air, which is about 0.025 mm to 0.25 mm. Can eliminate bubbles with a conspicuous size of 1 mm or more without causing adverse effects. The method for refining bubbles in ready-mixed concrete according to an embodiment of the present invention can be applied to the production of several tons to tens of tons such as a so-called cement tunnel precast concrete product used for tunnel lining. Is possible.

  The concrete described above includes concrete such as roman concrete, fiber reinforced concrete, polymer concrete, and the like in addition to concrete that can be hardened by adding water, a filler (filler), ordinary aggregate, or the like to cement. As the aggregate, any material that is usually used for concrete or a conventionally known material may be used, and sand, gravel, crushed stone, crushed glass, debris, artificial materials, waste, etc. can be used. is there. Further, the cement is not particularly limited, and for example, Portland cement, Roman cement, resin cement and the like can be used.

  The bubble miniaturization method according to an embodiment of the present invention can be suitably used for so-called concrete secondary products. For example, pile, pipe, flat plate, retaining wall, floor slab, floor board, wall rail, concrete block, box culvert, arch culvert, culvert, fume pipe (pipe using reinforced concrete), flume, cable trough, joint groove, curtain wall (Curtain wall, book wall), outer wall, concrete bridge, bridge, tunnel segment (shield tunnel), water distribution pipe, drain pipe, storage tank, water tank, drainage tank, street lamp, radioactive waste container, nuclear shelter, utility pole , Pavement (road), side gutter, gutter lid, manhole, assembly manhole, manhole lid, box manhole, boundary block, curbstone, car stopper block, root anchor block, interlocking block, vegetation block, protective fence, sheet pile, soundproof material, extinguishing Applicable to wave block, revetment block, sleeper, and object (image). In addition to the above-described examples, the present invention can be suitably applied to various products, for example, products molded using a mold (precast product). For example, it can be applied to the production of artificial stone, artificial marble, tiles, and the like. By applying the method for refining bubbles in ready-mixed concrete according to an embodiment of the present invention, the bubbles are removed to not only improve the appearance, but also prevent the strength from being reduced due to the generation of cavities, and high quality precast. Concrete products can be provided.

  Hereinafter, the present invention will be described more specifically using examples.

  The procedure for producing ready-mixed concrete, the procedure for vibration, and the procedure for recording and recording are described below. Of course, the ready-mixed concrete described below does not limit the blending ratio, production amount, and the like, and may be appropriately manufactured according to standards such as ISO and JIS, work procedure manuals, protocols, recipes, and the like. Further, the vibration procedure and the recording procedure are only examples.

[Procedure 1]
Cement, fine aggregate, coarse aggregate, and water were well kneaded at a weight ratio shown in Table 1 to obtain ready-mixed concrete.
[Procedure 2]
A cylindrical concrete specimen forming mold having a diameter of 100 mm and a height of 100 mm was placed in a dedicated mold holder.
[Procedure 3]
About 2 kg of the required weight of ready-mixed ready-mixed concrete was poured into the mold.
[Procedure 4]
It is a conventional procedure to level the injected ready-mixed concrete well with a stick, but when applying the process of stirring and leveling with a stick, air bubbles may or may not remain depending on the mixing method. It also affects the difference in bubble size, making it difficult to quantify, and in measuring bubble micronization, if the original bubble is too defoamed by agitation, the bubble refinement effect Since the purpose of measuring the defoaming effect cannot be fulfilled, the stirring step with a stick was not carried out. Therefore, as the procedure 4, as for the ready-mixed concrete poured into the formwork, the polystyrene foam piece is sandwiched between the formwork and the dedicated formwork holder, and the outside of the dedicated formwork holder is removed. By hitting the side with a wooden mallet, a minute impact vibration was indirectly applied so that the ready-mixed concrete was almost distributed throughout the formwork.
[Procedure 5]
A specimen was obtained in this uncured state. When applying vibration or the like, the specimen was placed on the vibration stage of the shaker together with the mold and fixed to the vibration stage.
[Procedure 6]
In this state, a single vertical vibration was applied to the specimen along the vibration conditions set in advance.
[Procedure 7]
After the vibration, the fluid was quickly removed from the vibration stage together with the formwork and allowed to stand for a necessary and sufficient curing period in a non-vibration system.
[Procedure 8]
When removing the mold, the mold was placed on a table, and the specimen was removed from the mold while breaking the mold along the half cut of the mold.
[Procedure 9]
The removed specimen is placed on the center of the rotary stage, and each time the rotary stage is rotated at a predetermined rotation angle within the horizontal plane, a photograph of the peripheral surface of the specimen is taken from a fixed point from the front. I took photos over the equivalent of a lap and recorded them.
[Procedure 10]
Of the images photographed for the entire circumference of each specimen, the circumferential images from the phase where the largest bubbles remained are arranged in a table for each vibration condition.

  The total amplitude was vibrated in increments of 0.5 mm from 1.0 to 5.0 mm for each frequency condition of frequencies 10, 20, and 30 Hz with constant time. The results are summarized in FIG. As can be seen from FIG. 6, under the vibration condition of 1 [G] or less or close to 1 [G], the bubbles are hardly refined and remain as they are. In addition, when an acceleration of a predetermined level or more is applied, there are no large-sized bubbles that were originally present, and on the other hand, subdivided relatively small bubbles remain. The amplitude here means the total amplitude (peak to peak), which corresponds to twice the so-called normal amplitude.

  Next, in FIG. 6, the vibration time is 30 seconds from 30 seconds to 60 seconds with respect to vibration conditions with a total amplitude of 3.5 mm at frequencies of 20 Hz and 30 Hz, which is a condition in which the bubbles are refined relatively cleanly. At intervals, vibration was performed from 60 seconds to 300 seconds in increments of 60 seconds. The results are summarized in FIG. As can be seen from FIG. 7, at the frequency of 20 Hz, it can be seen that the bubbles having the size remaining at the time of 30 seconds remain almost uniformly from the subsequent 60 seconds to 300 seconds. In other words, even if the vibration of a certain frequency corresponding to this with a certain amplitude and constant acceleration is continuously applied, the size is larger than that originally existed (a relatively large size targeted before excitation). It can be seen that although the bubbles are uniformly defoamed, smaller bubbles of a certain size or smaller can remain.

  Next, in FIG. 6, the total amplitude is further increased with respect to the previous stroke in which the vibration condition of the total amplitude of 3.5 mm at the frequency of 30 Hz, which is a condition in which the bubbles are made finer in a relatively clean manner, is applied for 30 seconds. While decreasing to 0.4 mm, the vibration frequency was set to an appropriate value from 30 Hz to 262 Hz, and the vibration was applied for 30 seconds in the subsequent process. The results are summarized in FIG. As can be seen from FIG. 8, although it seems that it is partially refined or defoamed partially, in practice, bubbles of the size that remained in the previous process remain after the subsequent process. It is thought that there is. That is, it can be seen that if the amplitude at the time of vibration is too small compared to the bubble size, it will not be refined or defoamed even if a vibration with a significantly large frequency or acceleration is applied.

  Further, in FIG. 6, the vibration condition is that the total amplitude is 3.5 mm at a frequency of 20 Hz, that is, an acceleration of 2.8 [G], which is a condition in which the bubbles are made relatively fine in FIG. In contrast to the condition where the vibration process is vibrated over a period of time, ie, 180 seconds, with the previous stroke as the previous stroke, the total amplitude is changed from 1.8 mm to 1 under the vibration condition where the acceleration is constant at 2.8 [G]. It was lowered in steps of 0.2 mm to 0.0 mm, and was shaken for an additional 120 seconds as a subsequent process. The results are summarized in FIG. As can be seen from FIG. 9, the acceleration is set to 2.8 [G], which is moderately larger than 1 [G], in both the pre-process and the post-process, and the amplitude of the post-process is set to about half of the pre-process. As a result, although it was subdivided from the maximum size bubbles that existed in the non-vibration state that would have remained in the previous step, the bubbles of the size that remained as subdivided bubbles After the post-process, it can be seen that further subdivision has progressed almost uniformly and has been refined. On the other hand, it can be seen that in addition to other specimens that have undergone a process with others, further fine bubbles remain. That is, it can be said that bubbles with a small size remain so as not to react under vibration conditions with an amplitude of about 1.0 mm to 1.8 mm. In order to further miniaturize these fine bubbles, it is only necessary to apply a vibration having a smaller amplitude and a constant acceleration or higher.

  In FIG. 9, the relatively large size bubbles in the specimen having an amplitude of 1.8 mm in the post-process are bubbles that remain after the pre-process and post-process and are residual bubbles. The types of bubbles that can remain without being refined are those that are rarely found especially when the fluid, which is a vibration body, contains fine aggregate or coarse aggregate in a paste-like fluid It is. In order to collapse this kind of residual bubbles, it is effective to destroy the aggregate surrounding the residual bubbles, particularly the bubble trapping structure formed by the coarse aggregate. It is preferable to resonate by applying vibrations of the natural frequency of the aggregate.

  Next, in FIG. 6, in the previous stroke in which the vibration condition of a total amplitude of 3.5 mm at a frequency of 30 Hz, that is, an acceleration of 6.3 [G], which is a condition in which the bubbles are made relatively fine in FIG. On the other hand, the frequency is set to 42 Hz as a condition for maintaining the acceleration at 6.3 [G] while further reducing the total amplitude to 1.8 mm which is about half of the amplitude in the previous stroke. Vibrated for 120 seconds. The results are summarized in FIG. As can be seen from FIG. 10, the acceleration in the pre-process and the post-process is both set to 6.3 [G], which is sufficiently larger than 1 [G], and the amplitude of the post-process is set to about half of the pre-process. As a result, although it was subdivided from the maximum size bubbles that existed in the non-vibration state that would have remained in the previous step, the bubbles of the size that remained as subdivided bubbles After the post-process, it can be seen that further subdivision has progressed almost uniformly and has been refined. Of course, if the surface is crushed, you can see the remaining refined bubbles as a result of sufficiently advanced miniaturization. The size of the remaining fine bubbles is less than 0.7 mm, which is sufficiently acceptable as a precast concrete product. Further, as can be seen from the results of FIG. 9 and FIG. 10, on the premise that the vibration condition is appropriate, the vibration condition, that is, the amplitude is reduced in accordance with the target bubble size as the excitation time elapses. It can be said that it is effective to change the frequency so as to keep the acceleration at a certain level or more while going.

  As another example, a fluid made of only cement, fine aggregate, and water and not containing coarse aggregate is injected into a rectangular parallelepiped mold, and immediately after that, the total amplitude is 2.0 mm and the frequency is 30 Hz. FIG. 11 shows the results of applying vibration in the vertical direction for each formwork and applying vibration. In this example, it can be seen that, since there is no coarse aggregate in the fluid, if the vibration is continued for a predetermined time or more, the bubbles are refined and defoamed to such an extent that they are hardly visible.

11 Raw concrete, 12 Bubbles, 13 Formwork, 20 (20A, 20B) Bubbles, 30 Raw concrete, 31 Coarse aggregate, 32 Fine aggregate, 33 Cement paste, 34 Bubbles, 40 Fluid, 41 Bubbles, 42 Coarse bone Material, 43 fine aggregate, 44 cement paste

Claims (6)

A method for refining bubbles in ready-mixed concrete to produce a precast concrete product obtained by refining bubbles in ready-mixed concrete,
Giving the above-mentioned ready-mixed concrete variable inertial force,
Depending on the physical and / or chemical attributes of the ready-mixed concrete and / or the physical and / or chemical attributes of the air bubbles, the fluctuation range of the variable inertial force, the number of fluctuations per unit time, and the time for repeated fluctuations Alternatively, the method for miniaturizing bubbles in ready-mixed concrete, wherein the variable inertial force is controlled according to one or more conditions selected from the number of fluctuations and acceleration.   The method for refining bubbles according to claim 1, wherein the variable inertial force is applied immediately after the start of the solidification reaction and / or before the complete solidification.   3. The method according to claim 1 or 2, wherein the variable inertia force is uniformly applied to the whole of the ready-mixed concrete simultaneously.   The method for refining bubbles in ready-mixed concrete according to any one of claims 1 to 3, wherein the variable inertial force is applied in a vertical direction and / or a horizontal direction.   The variable inertial force is controlled according to one or more conditions selected from the viscosity, specific gravity, and size of the bubbles of the ready-mixed concrete. A method for miniaturizing bubbles in ready-mixed concrete. 6. The variable inertial force is controlled by simultaneously controlling the fluctuation range and the number of fluctuations in accordance with the time of the repeated fluctuation or the number of fluctuations. To refine bubbles in fresh concrete.