JP7504824B2 - Apparatus and method for evaluating the risk of material separation in fresh concrete - Google Patents

Description

The present invention relates to an apparatus and method for evaluating the risk of material separation in fresh concrete.

Fresh concrete is produced by mixing the ingredients at a ready-mix concrete plant. The produced fresh concrete is poured into an agitator truck and transported to the pouring site. At the pouring site, the fresh concrete is pumped from the agitator truck to the construction site and poured.

After pouring fresh concrete, it is usually compacted to ensure that the concrete reaches every corner of the area to be filled. If compaction is insufficient, the concrete will not reach every corner of the area to be filled. If compaction is excessive, the fresh concrete may separate. Material separation is a phenomenon in which the distribution of constituent materials becomes uneven while the fresh concrete is being handled. For example, it refers to the phenomenon in which aggregates with a high specific gravity in fresh concrete settle in the paste, resulting in excessive aggregate concentration at the bottom. Material separation in fresh concrete may lead to defects such as poor filling in concrete structures and reduced durability.

Therefore, the extent to which compaction work is performed has been managed for some time. For example, Patent Document 1 and Patent Document 2 describe a method for determining the viscosity of poured concrete during compaction work and judging the compaction time, etc. Patent Document 3 describes a method for measuring the rheological constant related to viscosity using an inclined flow test and evaluating the workability, such as the compactability, of concrete at the concrete pouring site.

JP 2015-169003 A JP 2013-36162 A JP 2019-117093 A

The likelihood of material separation, which can lead to concrete defects, is not determined solely by the content of the compaction work. For example, it also differs depending on the characteristics of the fresh concrete itself. Specifically, the characteristics of the fresh concrete itself include the mix ratio of the components of the fresh concrete and the time that has elapsed since the components were mixed.

In Patent Documents 1 and 2, the viscosity of concrete after pouring is measured, so it is not possible to evaluate the degree of susceptibility of fresh concrete to segregation before pouring. Therefore, even if the fresh concrete before pouring has a high degree of susceptibility to segregation, pouring cannot be stopped. In Patent Document 3, it is time-consuming to collect and measure measurement samples of fresh concrete at the construction site.

The present invention was devised in consideration of the above circumstances, and aims to provide an evaluation device and evaluation method that can easily evaluate the degree of susceptibility of material separation in fresh concrete itself before pouring the fresh concrete.

The material separation risk assessment device of the present invention comprises: a vibrator that vibrates flowing fresh concrete;
A detector for detecting a degree of vibration propagation of the fresh concrete excited by the vibrator;
An evaluation unit that evaluates a risk of material separation of the fresh concrete based on a detection result of the detector;
and an output unit that outputs a result of the evaluation by the evaluation unit.

As a result of intensive research by the inventors, it has been discovered that it is possible to think of and evaluate the risk of material separation as the degree of likelihood of material separation, which can lead to concrete defects. The risk of material separation is an index of the likelihood of material separation occurring during handling of fresh concrete (concrete in an unhardened state from the time the ingredients are mixed until it hardens after pouring and compaction). The supplier of fresh concrete determines the evaluation method and control value of this index in consultation with the user as necessary. The supplier then controls the quality of the fresh concrete so that it satisfies the criteria for the index according to the determined evaluation method.

As will be described in more detail later, we have discovered that this risk of material separation is correlated with the degree of vibration propagation when flowing fresh concrete is vibrated. This discovery led us to realize that it is possible to detect the degree of vibration propagation when flowing fresh concrete is vibrated, and evaluate the risk of material separation. The degree of vibration propagation can be detected by utilizing a method for measuring viscosity under vibration. In other words, we have discovered that by measuring the viscosity of fresh concrete under vibration, it is possible to detect the degree of vibration propagation when it is vibrated, and to evaluate the risk of material separation in fresh concrete based on the detection results.

Before fresh concrete is poured, it is in a flowing state, for example, in the following conditions. First, at a pouring site, etc., it is being pumped through a pressure pipe. Second, at a ready-mix concrete plant, etc., it is being stirred in a container.

Therefore, by detecting the degree of vibration propagation in flowing fresh concrete while it is being pumped through a pressure pipe, or while it is being stirred in a container at a ready-mix concrete plant, etc., it is possible to evaluate the risk of material separation before the fresh concrete is poured.

Because there is no need to collect samples and measure them at the construction site to evaluate the risk of material separation, this evaluation method is easy and time-saving. Furthermore, it is also easy to constantly monitor the risk of material separation, which changes over time.

The flowing fresh concrete is pumped through a pipe,
The vibrator is attached to the piping,
The detector comprises:
A first pressure gauge for measuring the pressure of the fresh concrete in the pipe;
A second pressure gauge may be provided, which is located downstream of the first pressure gauge in the direction of pumping and measures the pressure of the fresh concrete in the pipe.

The principle of the so-called pressure loss type viscometer can be applied as a method for detecting the degree of vibration propagation of fresh concrete being pumped through a pipe. In other words, a first pressure gauge and a second pressure gauge are placed at two points along the pipe, a certain distance apart, and the pressure loss in the pipe is calculated from the measurements of the two pressure gauges. The pressure loss represents the viscosity of the fresh concrete flowing through the pipe.

The position where the vibrator applies vibrations to the pipe may be located downstream of the first pressure gauge in the direction of pumping, and upstream of the second pressure gauge in the direction of pumping. This allows vibrations to be applied effectively to the fresh concrete between the positions where the first pressure gauge and the second pressure gauge are attached.

A vibration absorbing section may be provided to absorb vibrations transmitted to at least one of the first pressure gauge and the second pressure gauge. By making at least one of the first pressure gauge and the second pressure gauge less susceptible to vibrations, accurate pressure measurement is possible.

The vibration absorbing section may include at least one of a first vibration isolation joint provided between the vibrator and the first pressure gauge, and a second vibration isolation joint provided between the vibrator and the second pressure gauge.

A container of the fresh concrete;
A rotor that fluidizes the fresh concrete in the container;
A drive unit that rotates the rotor at an arbitrary rotation speed,
The detector may include a torque meter that measures the rotation torque of the rotor. The rotation torque reflects the plastic viscosity of fresh concrete at a certain distance from the vibrator. The degree of vibration propagation can be detected from the measurement result of the rotation torque.

The present invention is a transport vehicle for transporting the fresh concrete, which is equipped with the above-mentioned evaluation device.

The method for evaluating a risk of material separation in fresh concrete of the present invention comprises:
The flowing fresh concrete is vibrated,
Detecting the degree of vibration propagation of the fresh concrete during vibration application;
Based on the detected results, a risk of material separation of the fresh concrete is evaluated.

The fresh concrete is fluidized by pumping through a pipe,
The vibration of the flowing fresh concrete is performed by a vibrator attached to the piping,
The detection of the degree of vibration propagation in the fresh concrete includes measuring the pressure of the fresh concrete in the pipe with a first pressure gauge;
A second pressure gauge located downstream of the first pressure gauge measures the pressure of the fresh concrete in the pipe,
This may be performed by determining the pressure loss of the fresh concrete from the measurement results of the first pressure gauge and the measurement results of the second pressure gauge.

The fresh concrete is stored in a container,
The detection of the degree of propagation of the vibration of the fresh concrete includes:
The fresh concrete is fluidized by rotating a rotor inserted in the fresh concrete in the container.
The flowing fresh concrete is vibrated by a vibrator inserted into the fresh concrete in the container,
This may be done by measuring the rotation torque of the rotor.

The measurements are repeated,
The degree of vibration propagation may be detected based on a representative value of the results of the repeated measurements. Fresh concrete is an inhomogeneous fluid, and therefore pressure measurements are prone to fluctuate. By using the representative value of the results of the repeated measurements, accurate pressure loss can be obtained. In this specification, the term "representative value" may include concepts including the average value, mode, and median of a set of measurement results. Furthermore, the term "average value" may include various concepts of average value, such as the arithmetic mean and geometric mean.

The measurement results may be compared with preset standard values to evaluate the risk of material separation of the fresh concrete. This makes it possible to clarify the pass/fail judgment of the fresh concrete based on the risk of material separation.

The pumping or production of the fresh concrete may be managed based on the risk of material separation evaluated using the above-mentioned evaluation method. For example, when the risk of material separation is evaluated to be high, the pumping or production of the fresh concrete may be stopped.

This makes it possible to provide an evaluation device and evaluation method that can easily evaluate the risk of material separation in fresh concrete before the concrete is poured.

FIG. 2 is a schematic diagram showing how fresh concrete is pumped at a pouring site. FIG. 2 is an enlarged schematic diagram showing the vicinity of the piping of the material separation risk assessment device. FIG. 4 is a diagram showing a vibration application period and a pressure measurement period. FIG. 13 is a schematic diagram of a material separation risk assessment device according to a second embodiment. 1 is a graph showing the relationship between pressure loss and material separation risk value determined by visual observation for each sample. 1 is a graph showing the relationship between the rotational torque and the material separation risk value determined by visual observation for each sample.

The fresh concrete material separation risk assessment device and assessment method according to the present invention will be described with reference to the drawings. Note that the drawings disclosed in this specification are merely schematic illustrations. In other words, the dimensional ratios on the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match.

First Embodiment
1 is a top view showing a state in which fresh concrete is pumped from a pump 8 through pumping pipes (11a, 11b) and a discharge pipe 12 to a pouring location 9 at a pouring site. The pumping direction of the fresh concrete is indicated by an arrow 13.

The pressure pipes (11a, 11b) are hollow flow paths closed from the surroundings. The pressure pipes (11a, 11b) are not necessarily integral pipes, but may be formed by connecting multiple pipes. Furthermore, as shown in FIG. 1, the pressure pipes (11a, 11b) may include bent pipes in addition to straight pipes without bends.

The pump 8 is used to pump the fresh concrete. The pump 8 may be mounted on a transport vehicle. As the pump 8, various pumps such as a squeeze type, a piston type, or a screw type can be used. Note that the pump 8 is not an essential component. As a pumping method other than a pump, for example, a pressure-feeding method using gravity by using a difference in elevation may be used.

In this embodiment, medium-fluidity concrete, which has higher fluidity than general concrete, is used for the fresh concrete. Medium-fluidity concrete can easily reach every corner, even in places where rebar is arranged in a complex or dense manner, or where formwork of a complex shape is present. On the other hand, medium-fluidity concrete poses a higher risk of material separation than general concrete. Therefore, it is particularly desirable to frequently evaluate the risk of material separation for medium-fluidity concrete.

[Outline of the material separation risk assessment device]
A material separation risk assessment device 10 that assesses the risk of material separation is disposed in the pressure pipes (11a, 11b). When fresh concrete is pressure-transported through the pressure pipes (11a, 11b), the fresh concrete is in a fluid state. When the fluidized fresh concrete passes through the material separation risk assessment device 10, the risk of material separation of the fresh concrete is assessed.

The material separation risk assessment device 10 includes a vibrator 1 attached to a pipe 4 located between the pressure pipe 11a and the pressure pipe 11b downstream of the pressure pipe 11a, a detector that detects the degree of propagation of the vibration of the fresh concrete excited by the vibrator 1, an evaluation unit 5 that evaluates the material separation risk of the fresh concrete based on the detection result of the detector, an output unit 7 that outputs the result of the evaluation by the evaluation unit 5, and a control unit 6 that controls the evaluation unit 5 and the output unit 7. In this embodiment, the detector includes a first pressure gauge 2 that measures the pressure of the fresh concrete in the pressure pipe 11a, and a second pressure gauge 3 that measures the pressure of the fresh concrete in the pressure pipe 11b.

The first pressure gauge 2 and the second pressure gauge 3 are each electrically connected to the evaluation unit 5 and send the fresh concrete pressure measurement results as electrical signals to the evaluation unit 5. The evaluation unit 5 determines the pressure loss from the pressure measurement results of the pressure gauges (2, 3). The reason for this will be explained below.

[Viscosity of fresh concrete and risk of material separation]
As a result of intensive research, the inventors have found that the risk of material separation is correlated with the degree of vibration propagation when vibrating fresh concrete in flow. The degree of vibration propagation indicates the ease with which vibration propagates.

Fresh concrete is known to behave like a Bingham fluid. A Bingham fluid is a fluid that does not flow when the pressure, called shear force, is below a value called the yield value, but when the shear force exceeds the yield value, it flows with a viscosity that correlates with the increment of shear force relative to the yield value. In fresh concrete, this Bingham fluid-like behavior occurs mainly due to friction between the paste (generally a mixture of water, cement, and sand) and the aggregate (gravel).

When flowing fresh concrete is vibrated, the vibration reduces the friction between the paste and aggregate. As a result, the viscosity of the flowing fresh concrete decreases.

In fresh concrete with a low risk of material separation, when the fresh concrete is vibrated, the degree of vibration propagation is large (vibrations propagate easily) and the vibration propagates over a wide area. When vibrations propagate over a wide area, friction between the paste and aggregate decreases over a wide area. As a result, the viscosity of the fresh concrete decreases significantly overall. In fresh concrete with a high risk of material separation, when the fresh concrete is vibrated, the degree of vibration propagation is small (vibrations propagate less easily) and the range over which the vibration propagates is narrow. Because the vibrations are limited to a narrow range, friction between the paste and aggregate decreases over a narrow range. As a result, the viscosity of the fresh concrete does not decrease easily overall.

Based on the findings presented above, the inventors have come up with the idea that the risk of material separation can be evaluated by using a method for measuring the viscosity of flowing fresh concrete. In this embodiment, we have decided to use a method for measuring pressure loss, which is one method for measuring the viscosity of fresh concrete.

[Method for assessing risk of material separation according to the first embodiment]
The method for evaluating the risk of material separation according to the first embodiment will be described in detail with reference to Fig. 2. Fig. 2 is a schematic diagram showing an enlarged view of the vicinity of the pipe 4 to which the vibrator 1 is attached in the material separation risk evaluation device 10 shown in Fig. 1. In Fig. 2, a semicircle shown by a dotted line with the vibrator 1 at its center indicates how the vibration of the vibrator 1 is transmitted to the surroundings. As a method for detecting the degree of transmission of vibration of fresh concrete pumped through the pipe 4, the principle of a so-called pressure loss type viscometer can be applied.

The piping 4 is connected to the pressure pipe 11a on the upstream side via a first vibration-proof joint 15a, and to the pressure pipe 11b on the downstream side via a second vibration-proof joint 15b. A first pressure gauge 2 is attached to the end of the upstream pressure pipe 11a, and a second pressure gauge 3 is attached to the end of the downstream pressure pipe 11b.

The pressure is measured using the first pressure gauge 2 and the second pressure gauge 3. The pressure difference between the pressure of the first pressure gauge 2 and the pressure of the second pressure gauge 3 indicates the pressure loss caused by the fresh concrete between the position where the first pressure gauge 2 is attached and the position where the second pressure gauge 3 is attached. This pressure loss represents the viscosity of the fresh concrete flowing through the pressure pipes (11a, 11b) and the piping 4. In other words, a large pressure loss indicates that the viscosity of the fresh concrete is large and that the vibrations are not propagating over a wide area. A small pressure loss indicates that the viscosity of the fresh concrete is small and that the vibrations are propagating over a wide area.

When fresh concrete is pumped by gravity, the pressure will differ between the position where the first pressure gauge 2 is attached and the position where the second pressure gauge 3 is attached due to the difference in the weight of the fresh concrete. Therefore, in such a case, it is advisable to correct the measurement value of the first pressure gauge 2 or the second pressure gauge 3 for the weight of the fresh concrete.

As shown in FIG. 2, the position where the vibrator 1 is attached in the piping 4 is located downstream of the first pressure gauge 2 in the direction of pumping, and is located upstream of the second pressure gauge 3 in the direction of pumping. In other words, the vibrator 1 is located between the two pressure gauges (2, 3). This allows the fresh concrete between the position where the first pressure gauge 2 is attached and the position where the second pressure gauge 3 is attached to be effectively vibrated.

The material separation risk assessment device 10 of this embodiment can assess the risk of material separation in fresh concrete being pumped. Therefore, the assessment of the risk of material separation can be carried out before the fresh concrete is poured. Also, it is not necessary to collect samples just to assess the risk of material separation. Furthermore, this assessment method can easily be carried out to constantly monitor the change in the risk of material separation over time. The material separation risk assessment device 10 may be provided in a transport vehicle that transports fresh concrete (including a pump vehicle that pumps fresh concrete).

[Anti-vibration joint]
2, the vibration-proof joints (15a, 15b) function as vibration absorbers and suppress the vibration of the vibrator 1 from propagating to the pressure pipes (11a, 11b). This makes the first pressure gauge 2 and the second pressure gauge 3, which are respectively arranged in the pressure pipes (11a, 11b), less susceptible to vibration from the vibrator 1. This allows the first pressure gauge 2 and the second pressure gauge 3 to accurately measure pressure.

In addition, the pipe 4 to which the vibrator 1 is attached is susceptible to deterioration due to vibration. By connecting the pipe 4 to the pressure pipe (11a, 11b) via anti-vibration joints (15a, 15b), the pipe 4 to which the vibrator 1 is attached and the anti-vibration joints (15a, 15b), which are susceptible to deterioration, can be replaced independently of the pressure gauges (2, 3), which has the effect of simplifying the replacement work. However, the anti-vibration joints (15a, 15b) are not essential components, and it is not necessary to use the anti-vibration joints.

[Vibrator]
The vibrator 1 can be, for example, a device that converts the centrifugal force generated by attaching an eccentric weight to a motor into vibration, and in particular, a device that can apply vibration with an acceleration of 20 m/ ^s2 or ^more can be preferably used. When applying vibration using the vibrator 1, it is preferable to apply vibration such that the acceleration of the vibration of the vibrator surface at the surface of the vibrator 1 that contacts the concrete is 20 m/s2 or more. By applying such strong vibration, the viscosity of the fresh concrete can be greatly reduced as a whole, and as a result, the risk of material separation of the flowing fresh concrete can be more accurately evaluated. Furthermore, it is more preferable that the acceleration of the applied vibration is within the range of 20 to 50 m/ ^s2 . Since the value is close to the acceleration of the vibrator used in the compaction work, the reproducibility of material separation during compaction is improved.

The vibration frequency is preferably 100 to 300 Hz, which is similar to that of the vibrator used in compaction work. In particular, 200 to 260 Hz is more preferable. The vibration amplitude is determined based on the diameter of the pressure pipe. The value of pipe diameter/vibration amplitude is preferably 500 to 20,000, and more preferably 1,000 to 10,000. If it is within this range, the difference in the range of vibration propagation due to differences in material separation risk will be easily apparent, making it easier to evaluate the material separation risk.

There are no particular limitations on the material of the piping 4 to which the vibrator 1 is attached and the pressure pipes (11a, 11b) as long as they are strong enough to be used as pressure pipes for a concrete pump.

[Pressure gauge]
It is preferable that the pressure gauges (2, 3) have a convex pressure-receiving portion as shown in Fig. 2. It is also preferable that the pressure gauges (2, 3) be flush diaphragm type pressure gauges that are resistant to pressure fluctuations.

[Evaluation Department]
The evaluation unit 5 determines the pressure loss from the measurement results of the pressure gauges (2, 3). The evaluation unit 5 then evaluates the risk of material separation of the fresh concrete from the determined pressure loss. The risk of material separation may be evaluated based on the determined pressure loss and a preset standard value for pressure loss. For example, when the pressure loss determined from the measurement results of the pressure gauges falls below the preset standard value for pressure loss, the fresh concrete is judged to be unacceptable.

[Output section]
The output unit 7 outputs the results of the evaluation by the evaluation unit 5. Specifically, it outputs a pressure value, a pressure loss, or a material separation risk evaluation. One example of the output unit 7 is an interface for communicating the evaluation results to an operator. Possible examples of such an interface include a display, an alarm that generates an alarm sound or light, a printer, etc.

[Control unit]
The control unit 6 outputs the evaluation result by the evaluation unit 5 to the output unit 7. For example, the control unit 6 causes the output unit 7 to output a failure message to inform the worker. The worker manages the pumping of the fresh concrete to stop. The control unit 6 may also stop the pumping of the fresh concrete. As a specific example, the control unit 6 may switch the flow path of the pumping pipe so that the fresh concrete is not discharged from the discharge pipe 12.

[Method of applying vibration and measuring pressure]
The vibration application method and pressure measurement method will be described with reference to Fig. 3. Fig. 3 is a diagram showing a vibration application period and a pressure measurement period. In Fig. 3, the horizontal axis represents the passage of time T. The vibration application periods are represented as V1, V2, and V3. The pressure measurement periods are represented as M1, M2, and M3. Periods other than the vibration application period are vibration rest periods. That is, in this embodiment, vibration is applied intermittently. By providing a vibration rest period, deterioration of the device caused by continuous exposure to vibration is suppressed, and material separation due to excessive vibration of fresh concrete is prevented.

A cycle is taken as a period from the start of any vibration application period, including one vibration pause period, to the start of the next vibration application period. In this embodiment, a cycle C1 is taken as a period from the start time _t1 of a vibration application period V1 to the start time _t3 of the next vibration application period V2. This cycle is repeated multiple times. Although only part of cycle C3 is shown in FIG. 3, the cycle may be repeated four or more times.

Within one cycle, there is one pressure measurement period. During each vibration application period (V1, V2, V3), the vibrator 1 is constantly applying vibration, whereas during each pressure measurement period (M1, M2, M3), measurements are taken multiple times. The lower half of Figure 3 shows an enlarged view of pressure measurement period M1 and vibration application period V1. Within pressure measurement period M1, small cycles of measurement and rest are repeated. The first measurement is shown as m1, and the second measurement as m2. The hatched areas (m1, m2, ...) represent the actual measurement time.

It is advisable to perform 10 or more measurements (m1, m2, ...) during one pressure measurement period (e.g., M1). Fresh concrete is a non-uniform fluid, so pressure measurements are prone to variation. By repeatedly measuring the pressure within a certain period of time and calculating a representative pressure value (e.g., arithmetic mean value), an accurate pressure value for fresh concrete can be obtained.

It takes time from the start of vibration application until the pressure drop in the fresh concrete due to the application of vibration occurs. Therefore, it is advisable to provide an offset time that delays the start of pressure measurement (M1, M2, M3) from the start of vibration application (V1, V2, V3). For example, the start time _t2 of pressure measurement is delayed by 0.5 seconds or more from the start time _t1 of vibration. This allows pressure measurement to start after the pressure drop in the fresh concrete due to the application of vibration is reflected, making it possible to perform accurate measurement.

The total vibration application time (V1 + V2 + V3 + ...) should be 10% or less of the total time during which the fresh concrete is pumped. The period of one cycle (e.g., cycle C1) should be 1 to 5 minutes. The vibration application period (e.g., the length of V1) should be 1 to 10 seconds. This makes it possible to suppress material separation of the fresh concrete due to vibration.

Second Embodiment
A second embodiment will be described. The second embodiment is a method for detecting the degree of vibration propagation of fresh concrete that is flowing by being stirred in a container. This method can also be adopted in a ready-mix concrete plant, and the risk of material separation of fresh concrete can be evaluated in the ready-mix concrete plant. If the evaluation is unsatisfactory, for example, the production or shipment of fresh concrete can be stopped. Note that the method can be implemented in the same manner as the first embodiment, except for the points described below.

[Method for assessing risk of material separation according to the second embodiment]
A method for assessing the risk of material separation according to a second embodiment will be described with reference to Fig. 4. The device 20 for assessing the risk of material separation shown in Fig. 4 is a method for measuring rotational torque using a rotor. The value of the rotational torque reflects the plastic viscosity of fresh concrete at a position a certain distance away from the vibrator. Since the change in viscosity is brought about by vibration, the degree of vibration propagation can be detected by measuring the rotational torque.

In FIG. 4, fresh concrete F1 is stored in a container 23. A rotor 22 and a vibrator 21 are arranged inside the container 23. The vibrator 21 is arranged between the rotor 22 and the bottom of the container 23. In this embodiment, the vibrator 21 is rod-shaped and is attached to the tip of a rod 24 having the same diameter as the vibrator 21. The rod 24 is inserted from the side of the container 23 toward the inside of the container 23. In this embodiment, the central axis of the rotor 22, the central axis of the container 23, and the central axis of the vibrator 21 are set to be coaxial.

The rotor 22 is rotated by the drive unit 25. The rotor 22 also has a torque meter 26 that measures rotational torque as a detector for detecting the degree of vibration propagation. The drive unit 25 can set the rotation speed and rotate the rotor 22. The torque meter 26 can measure the rotational torque when the rotor 22 is rotated at a predetermined rotation speed.

The vibration of the vibrator 21 makes the fresh concrete easier to flow. In the case of fresh concrete with a low risk of material separation, the degree of vibration propagation is large, so the viscosity of the fresh concrete decreases over a relatively wide area from the vibrator 21. As the viscosity of the fresh concrete located near the rotor 22 decreases, the rotational torque of the rotor 22 decreases. In the case of concrete with a high risk of material separation, the degree of vibration propagation is small, so the vibration from the vibrator 21 attenuates and the decrease in the viscosity of the fresh concrete by the vibrator 21 is limited. Therefore, the rotational torque of the rotor 22 remains large. Therefore, the value of the rotational torque of the torque meter represents the degree of vibration propagation of the flowing fresh concrete F1.

The method for evaluating the risk of material separation in the second embodiment described above can be carried out in the same manner as in the first embodiment. A specific example of the method for evaluating the risk of material separation in the second embodiment will be described with reference to FIG. 3, which was used in the method for evaluating the risk of material separation in the first embodiment.

In order to rotate the rotor 22 stably, first, the rotor 22 is rotated from time _t0 without applying vibration to the vibrator 21. Vibration is started after a certain time has elapsed since the rotor 22 started to rotate. Measurement of the rotational torque is started from time _t2 , a certain period of time after the vibration start time _t1 . It is advisable to perform the torque meter measurement multiple times and use a representative value of the measurement results (for example, an arithmetic mean value). In the case of a rotary vane type viscometer, it tends to take a long time for the rotor 22 to stabilize. Therefore, it is advisable to make the offset time between the vibration start time _t1 and the rotational torque measurement start time _t2 longer than the offset time between the vibration start time _t1 and the pressure measurement start time _t2 in the first embodiment.

In this embodiment, the fresh concrete F1 is put into the container 23 to measure the viscosity, but the container 23 and the rotor 22 may be used for a batch mixer. For example, the constituent materials of the fresh concrete F1 are put into the container 23, and the rotor 22 is rotated to mix. After mixing, the rotation torque is measured using the vibrator 21 and the rotor 22. The fresh concrete F1 after measurement is discharged from the container 23. The material separation risk assessment device 20 of this embodiment can also be applied to the aspect of pumping fresh concrete to the construction site by the pump 8, as described in the first embodiment. For example, a fresh concrete retention section may be provided upstream of the pump 8, and a small rotor may be installed in the retention section, or a rotor may be installed in a transport vehicle connected to the pump 8. A torque meter may also be provided on a rotatable drum mounted on the transport vehicle.

Two embodiments have been described above. However, the present invention is not limited to the above-described embodiments, and various improvements and modifications are possible without departing from the spirit and scope of the present invention.

Although examples have been described in which the principles of a pressure loss type viscometer and a rotary vane type viscometer are used to evaluate the risk of material separation in fresh concrete, the method of evaluating the risk of material separation in the present invention is not limited to the above two. In addition to the two measurement methods described above, for example, a viscosity measurement method using a ball-pulling viscometer may be used. In the case of a viscometer in which the distance between the detection unit and the vibration unit changes, such as a ball-pulling viscometer, the risk of material separation can be detected with high accuracy by understanding the change in viscosity in response to the change in the distance between the detection unit and the vibration unit.

Example 1
An experiment was conducted to confirm whether the risk of material separation can actually be evaluated using the method for evaluating the risk of material separation according to the first embodiment. The experimental conditions were as follows.

Pump 8: Vacuum squeeze type concrete pump (maximum discharge rate 25 ^m3 /h)
Pressure pipes (11a, 11b): The pipe diameter is 4 inches. The pressure pipes include a 3 m straight pipe and a 90° bend pipe with r=0.35 m.
Discharge pipe 12: A 5m flexible hose.
Pipe 4: Pipe diameter 4 inches, length 40 cm. Both ends are flanged. A rod-shaped vibrator is attached to the middle of the pipe.
Anti-vibration joints (15a, 15b): Nominal diameter 4 inches, length approximately 15 cm.
Pressure gauges (2, 3): Flush diaphragm type pressure gauges are used. The pressure gauges (11a, 11b) are arranged so that the distance between the first pressure gauge 2 and the second pressure gauge 3, including the pipe 4, is 1.0 m.
Vibrator 1: Using a portable vibration meter, Model 1332-B manufactured by Showa Sokki Co., Ltd., the acceleration and displacement of the vibrator 1 in a direction perpendicular to the extension direction of the pipe 4 were measured at eight points. The average acceleration at the eight points was 34 m/ ^s2 , and the average displacement was 0.027 mm. The ratio of the nominal diameter of the pipe 4 to the vibration amplitude was 3700.

Ten samples were prepared, with different constituent materials of fresh concrete or different time elapsed from mixing the raw materials to the start of pump operation. Table 1 shows the raw material mix, actual measured fresh properties, and elapsed time for the 10 samples. In Table 1, W is water, C is cement, S is fine aggregate, G is coarse aggregate, W/C is the weight ratio of water to cement, and s/a is the volume ratio of fine aggregate to the total aggregate. Flow indicates the results of the slump flow test.

The pump was set to an average discharge rate of 15 ^m3 /h and operated for 195 seconds for each sample. In order to stabilize the discharge rate, vibration was not applied until 60 seconds had elapsed from the start of operation. After 60 seconds (time _t1 ), vibration was applied for 3 seconds. That is, the vibration application period V1 was 3 seconds. Pressure measurement was started 1 second after the start of vibration. That is, the pressure measurement start time _t2 was 61 seconds. The pressure measurement period M1 was 2 seconds. During this time, pressure (unit: N/ ^mm2 ) was measured at 20 points on the upstream and downstream sides with a response speed of 100 ms.

The pressure measurement value is converted to pressure loss by finding the difference between the arithmetic mean values on the upstream and downstream sides and dividing this difference by the distance (unit: m) between the first pressure gauge 2 and the second pressure gauge 3. In this embodiment, the distance between the first pressure gauge 2 and the second pressure gauge 3 is 1.0 m, so the difference between the arithmetic mean values on the upstream and downstream sides is the pressure loss.

No vibration or pressure measurement was performed between 1 minute 3 seconds and 2 minutes after the start of operation. This is cycle C1. Cycle C2 started 2 minutes later. The vibration and pressure measurement conditions for cycle C2 were the same as those for cycle C1. After cycle C2 was completed, cycle C3 was performed. Vibration and pressure measurement ended with cycle C3.

To confirm that it is possible to derive the risk of material separation from pressure loss, the risk of material separation was determined using a method based on the vibration deformation test method defined in NEXCO Test Method 773-2008 (hereinafter referred to as "Test Method 773").

A vibration deformation tester conforming to Test Method 773 (tabletop size 700 × 700 mm, vibrator nominal diameter 32 mm, maximum vibration frequency 41 m/ ^s2 ) was installed on a horizontal surface, and a slump test was performed on the vibration deformation tester according to JIS A 1101:2020 "Test method for slump flow of concrete". Subsequently, the flow of concrete was measured according to JIS A 1150:2020 "Test method for slump flow of concrete".

Next, the rod-shaped vibrator was turned on and vibration was applied for 9.3 seconds. When the unit volume mass of fresh concrete is 2.25 kg/L, this vibration gives a vibration energy of 3.7 J/L acting on the plate. After vibration was applied, the flow of the concrete was measured and visual observation was performed in that state.

Visual observations were conducted as follows. Three judges, selected in advance from among the test participants, visually selected from three levels: "material separation has occurred (1.0 point)," "material separation is likely (0.5 point)," and "material separation has not occurred (0 point)." A score of 1.0 indicates that there is a risk of material separation even without compaction during pouring. A score of 0 indicates that material separation is unlikely even if excessive compaction is performed. The arithmetic mean of the scores of each judge was determined as the material separation risk value for the sample. The higher the material separation risk value, the higher the possibility of material separation. The judges were not informed of information about each sample, so as not to form preconceived ideas based on information such as the sample's mixture ratio. In addition, judges were prohibited from consulting each other to ensure that their evaluations were not influenced by the opinions of other judges.

The pressure loss and material separation risk assessment results for the 10 samples are shown in Table 2. C1 to C3 represent the pressure loss obtained in each cycle.

5 is a graph in which the average pressure loss is plotted on the horizontal axis and the risk of material separation as determined by visual observation is plotted on the vertical axis for the 10 samples shown in Table 2. As shown in this graph, it can be seen that when the pressure loss exceeds the threshold value of 4×10 ^-2 (N/mm ² /m), the risk of material separation as determined by visual observation increases significantly. In other words, there is a correlation between pressure loss and the risk of material separation as determined by visual observation. This confirms that it is possible to evaluate the risk of material separation in fresh concrete using the pressure loss when flowing fresh concrete is vibrated as an index. The threshold value obtained in the above manner may be adopted as a standard value for evaluating the risk of material separation.

Example 2
It will be confirmed whether or not the risk of material separation can be evaluated using the method for evaluating the risk of material separation according to the second embodiment. The conditions used in the evaluation are as follows (see FIG. 4).

Container 23: A cylindrical container having a diameter of 600 mm, a height of 500 mm, and a wall thickness of 1.6 mm. A hole having a diameter of 40 mm is provided at a position 150 mm from the bottom of the cylindrical container so that a rod-shaped vibrator can be inserted.
Vibrator 21: Attached to the tip of a cylindrical rod 24. It is cylindrical with a length of 175 mm and a diameter of 28 mm. The vibrator 21 is inserted to a position where it is at the center of the container 23. When the vibrator 21 is vibrated with the container empty, the acceleration at the center position of the vibrating part is 28 m/ ^s2 , and the displacement is 0.024 mm. To prevent vibrations from being transmitted directly from the rod 24 to the container 23, the gap between the container 23 and the rod 24 is filled with vibration-proof rubber.
Rotor 22: The rotor 22 is attached to the tip of a rod 27 with a diameter of 4 mm. The rotor 22 has a diameter of 100 mm, a height of 20 mm, and a thickness of 2 mm. The distance between the lower end of the rotor 22 and the upper end of the vibrator 21 is 65 mm. The ratio of the distance (65 mm) between the lower end of the rotor 22 and the upper end of the vibrator 21 to the displacement of the vibration of the vibrator 21 is 2708. This ratio corresponds to the ratio between the pipe diameter of the piping 4 and the displacement of the vibrator 1 in the first embodiment.
Fresh concrete: Ten samples of sample numbers 1 to 10 under the same conditions as in Example 1 are poured into the container 23 to a height of 350 mm.

As explained in the second embodiment, the rod 27 is equipped with a drive unit 25 for rotating the rotor and the rod, and a torque meter 26 for measuring the rotational torque. With the vibrator 21 vibrating, the rotor is rotated at 20 rpm, and the rotational torque is measured.

At this time, the vibration of the vibrator 21 makes the fresh concrete more likely to flow. If the fresh concrete has a low risk of material separation, the viscosity of the fresh concrete around the rotor 22 drops significantly, and the torque of the rotor 22 drops significantly. Conversely, if the fresh concrete has a high risk of material separation, the vibration transmitted to the fresh concrete at the rotor 22 is attenuated, and the drop in the viscosity of the fresh concrete is limited. As a result, the drop in the torque of the rotor 22 is small.

To allow the rotor 22 to rotate stably, vibration was not applied for 60 seconds after the rotor 22 started to rotate. After 60 seconds had elapsed since the start of rotation, vibration was applied for 30 seconds. That is, the time _t1 was 60 seconds, and the vibration application period V1 was 30 seconds. 20 seconds after the vibration application, measurement of the rotational torque was started. The measurement period M1 of the rotational torque was 10 seconds. During the measurement period M1 of the rotational torque, 20 points were measured with a response speed of 500 ms. The arithmetic mean value of the rotational torque measurement values at the 20 points was then calculated to obtain the rotational torque (N·m).

The relationship between the torque value and the material separation risk assessment results for each sample is shown in Table 3. Note that each sample was the same as in Example 1, and therefore the material separation risk assessment results for each sample were also the same as those in Example 1.

Figure 6 is a graph in which the average torque is plotted on the horizontal axis and the material separation risk value as determined by visual observation is plotted on the vertical axis for the 10 samples shown in Table 3. As shown in this graph, it can be seen that the risk of material separation increases significantly when the torque threshold exceeds 0.75 (N·m). In other words, there is a correlation between the rotational torque and the risk of material separation as determined by visual observation. This confirms that it is possible to evaluate the risk of material separation in fresh concrete using the rotational torque as an index when fresh concrete is vibrated by a rotor that has been fluidized with a rotor. The threshold value obtained in the above manner may be adopted as the standard value for evaluating the risk of material separation.

Reference Signs List 1, 21: Vibrator 2: First pressure gauge 3: Second pressure gauge 4: Piping 5: Evaluation unit 6: Control unit 7: Output unit 8: Pump 9: Pouring location 10, 20: Material separation risk evaluation device 11a, 11b: Pressure pipe 12: Discharge pipe 15a: First vibration-proof joint 15b: Second vibration-proof joint 22: Rotor 23: Container 24: Rod 25: Drive unit 26: Torque meter 27: Rod

Claims (13)

A vibrator that vibrates the flowing fresh concrete;
A detector for detecting a degree of vibration propagation of the fresh concrete excited by the vibrator;
An evaluation unit that evaluates a risk of material separation of the fresh concrete based on a detection result of the detector;
and an output unit that outputs a result of the evaluation by the evaluation unit. The flowing fresh concrete is pumped through a pipe,
The vibrator is attached to the piping,
The detector comprises:
A first pressure gauge for measuring the pressure of the fresh concrete in the pipe;
The evaluation device according to claim 1, further comprising: a second pressure gauge located downstream of the first pressure gauge in the direction of pumping, the second pressure gauge measuring the pressure of the fresh concrete in the pipe. The evaluation device according to claim 2, characterized in that the position where the vibrator applies vibrations to the piping is located downstream of the first pressure gauge in the direction of the pumping and is located upstream of the second pressure gauge in the direction of the pumping. 4. The evaluation device according to claim 2 or 3, further comprising a vibration absorbing section that absorbs vibrations from the vibrator that are transmitted to at least one of the first pressure gauge and the second pressure gauge, and suppresses the vibrations from propagating to piping arranged in at least one of the first pressure gauge and the second pressure gauge . The evaluation device according to claim 4, characterized in that the vibration absorbing unit includes at least one of a first vibration-proof joint provided between the vibrator and the first pressure gauge, and a second vibration-proof joint provided between the vibrator and the second pressure gauge. The evaluation device according to claim 1 further comprises:
A container of the fresh concrete;
A rotor that fluidizes the fresh concrete in the container;
A drive unit that rotates the rotor at an arbitrary rotation speed,
The vibrator vibrates the fresh concrete in the container,
The evaluation device, wherein the detector includes a torque meter that measures a rotational torque of the rotor. A transport vehicle for transporting the fresh concrete, the transport vehicle being characterized by being equipped with the evaluation device according to any one of claims 1 to 6. Allow the fresh concrete to flow,
The flowing fresh concrete is vibrated,
Detecting the degree of vibration propagation of the fresh concrete during vibration application;
A method for evaluating a risk of material separation in fresh concrete, comprising: evaluating the risk of material separation in the fresh concrete based on the detected results. The fresh concrete is fluidized by pumping through a pipe,
The vibration of the flowing fresh concrete is performed by a vibrator attached to the piping,
The detection of the degree of vibration propagation in the fresh concrete includes measuring the pressure of the fresh concrete in the pipe with a first pressure gauge;
A second pressure gauge located downstream of the first pressure gauge measures the pressure of the fresh concrete in the pipe,
9. The evaluation method according to claim 8, characterized in that the evaluation is performed by determining a pressure loss of the fresh concrete from the measurement results of the first pressure gauge and the measurement results of the second pressure gauge. The fresh concrete is stored in a container,
The detection of the degree of propagation of the vibration of the fresh concrete includes:
The fresh concrete is fluidized by rotating a rotor inserted in the fresh concrete in the container.
The flowing fresh concrete is vibrated by a vibrator inserted into the fresh concrete in the container,
9. The evaluation method according to claim 8, wherein the evaluation method is carried out by measuring a rotation torque of the rotor blades. The measurements are repeated,
The evaluation method according to claim 9 , further comprising detecting a degree of the vibration propagation based on a representative value of the results of the repeated measurements. The evaluation method according to any one of claims 9 to 11, characterized in that the measurement results are compared with a preset standard value to evaluate the risk of material separation of the fresh concrete. A management method for managing the pumping or production of the fresh concrete based on the risk of material separation evaluated by the evaluation method described in claim 12.