JP6902248B2 - Rheological constant measurement method for concrete and its equipment - Google Patents

Description

The present invention relates to a method and an apparatus for measuring rheological constants at a concrete casting site for uncured fresh concrete, and uses the apparent yield value and the apparent plastic viscosity obtained by the present invention to create a concrete site. It is possible to evaluate the workability such as concrete filling property, compaction property, and pump pumping property in construction.

As a test method for evaluating the workability of uncured fresh concrete, the JIS A 1101 slump test method using a slump cone is widely used.

On the other hand, high-fluidity concrete has too high fluidity to be supported by the conventional slump test, so the JIS A 1150 slump flow test method is used for high-fluidity concrete.

Further, as an improved version of the slump flow test method, there is an L-shaped flow test method, which is standardized as a test method for high-fluidity concrete together with the slump flow test method.

When the behavior of fresh concrete is modeled as the behavior of Bingham fluid, the slump value and slump flow value are mainly used to evaluate the yield value, and the 500 mm arrival time and V funnel test in the slump flow test including the time element are performed. It is used to evaluate plastic viscosity.

On the other hand, in Patent Document 1 by the inventors of the present application, in order to properly evaluate the workability of semi-high fluid concrete and soft-kneaded concrete, which could not be accurately evaluated by the conventional slump test and slump flow test. As a method and an apparatus, a concrete test method and an apparatus using an inclined flow of a sample are disclosed.

In the test method described in Patent Document 1, a tubular tank portion, an inclined flow portion that communicates with an opening formed on the lower side surface thereof, and an inclined flow portion that can open and close the opening are partitioned from the lower portion of the tank portion. Using an inclined flow tester equipped with a partition plate, a sample of uncured fresh concrete is put into the tank part from the top, packed to a predetermined height, and then the partition plate is opened to incline from the opening. The workability of the sample is evaluated by letting the sample flow down to the flow section and measuring the flow-down speed of the sample on the inclined surface at that time.

However, in the case of the test method and apparatus described in Patent Document 1, there are the following problems.
(1) How to evaluate the fluidity of the Bingham fluid from the flow tip velocity, especially how to evaluate the yield value and the plastic viscosity, which are the properties of the Bingham fluid, is not set.
(2) Since the normal stress of the vertical sample box is applied, the flow turbulence occurs even at the corners of the sample box.

On the other hand, as disclosed in Non-Patent Documents 1 and 2, the inventors of the present application have a structure in which a sample tank portion linearly continuous with the inclined flow portion is partitioned by a gate plate instead of the vertical sample box portion. The tilt flow test was performed at a plurality of different tilt angles, and the apparent yield value and the apparent plastic viscosity corresponding to the rheological constants of the fresh concrete were obtained from the test results. We have developed a test method for evaluating fluidity.

Further, in Patent Document 2 by the inventors of the present application, the sample tank portion for collecting and holding the fluid to be measured input from the sample inlet and the bottom surface are linearly continuous with the bottom surface of the sample tank portion. It is equipped with a tilted flow section with a variable tilt angle and a gate plate that can be opened and closed to vertically partition the sample tank section and the tilted flow section, and the gate plate is erected outside the boundary between the sample tank section and the tilted flow section. It was decided to measure the rheology constant of the fluid as follows by using a leology constant measuring device capable of ascending and descending in the vertical direction while being supported by the gate plate support provided with the support column.

That is, as the rheology constant, the apparent shear stress τ (Pa) of the sample is obtained by the following equation.
τ = W × h × g × sin θ… (1)

Here,
W: Unit volume mass of sample (kg / m ³ )
h: Average height (m) of the sample when passing between sensors
g: Gravity acceleration (9.807m / sec ² )
θ: Tilt angle

Then, the three or more different inclination angles calculated for the flow front velocity v _a (m / sec) or strain rate (/ sec) and obtained from the shear stress tau (Pa) apparent obtained on the regression line flow tip speed v _a becomes zero shear stress apparent in sections tau yield value of apparent _{(Pa) τ y (Pa)} , plastic viscosity of apparent slope of the regression line η (Pa · s / m or Pa · s) Ask as.
Strain rate (/ sec) is obtained by dividing the flow front velocity v _a a (m / sec) in the sample height (m).

The apparent yield value τ _y and the apparent plastic viscosity η have been confirmed to have a high correlation with the yield value and plastic viscosity of the fluid measured by other measuring means, and it is useful for grasping the fluid characteristics as a rheological constant of the fluid. It can be used.

Further, in Patent Document 3, the inventors of the present application use the tilt flow device shown in FIG. 4 to obtain the flow tip velocity obtained for a plurality of tilt angles or the strain rate calculated using the flow tip velocity, and the apparent strain rate. The apparent shear stress τ (Pa) in the section where the flow tip velocity of the regression line obtained from the shear stress τ (Pa) is 0, the apparent yield value τy (Pa), and the slope of the regression line the apparent plastic viscosity η ( An invention is described in which the workability of fresh concrete is evaluated based on the measured apparent yield value τ and the apparent plastic viscosity η, which are obtained as Pa · s / m or Pa · s).

Further, Patent Document 4 describes a test method and device for fresh concrete that automatically inspects the consistency of fresh concrete of a concrete agitator truck and the presence or absence of material separation at the time of unloading to prevent construction defects and quality accidents. Are listed.

Specifically, a camera attached to the chute of an agitator car is used to photograph the concrete surface flowing through the chute at regular intervals, and at the same time, the cross-sectional shape of the concrete at a certain position and the inclination of the chute are measured and measured. Calculate the flow velocity of concrete from, calculate the cross-sectional area of concrete from the cross-sectional shape, then calculate the flow rate per unit time from the flow velocity and cross-sectional area of concrete, and finally, calculate the calculated flow rate for each tilt of the chute. It describes a test method for fresh concrete that is judged to be acceptable if it is within the permissible range of the standard flow rate by comparing it with the specified standard flow rate.

In addition, as devices, a camera that photographs the concrete surface flowing through the chute at regular intervals, a plane laser rangefinder that measures the height of the concrete surface inside the chute, an inclinometer that measures the tilt of the chute, and these cameras. The data from the plane laser rangefinder and the inclinometer are processed, the flow rate per unit time is calculated from the flow velocity and cross-sectional area of the concrete flowing through the chute, and the calculated flow rate is the standard determined for each chute tilt. A test device for fresh concrete is described, which comprises a computer for judging pass / fail, which is judged to be acceptable if the standard flow rate is within the permissible range of the flow rate, and displaying the judgment result.

On the other hand, as a means for measuring the three-dimensional shape of an object and its change, for example, a three-dimensional image processing system as shown in Non-Patent Document 3 has been put into practical use, and the scope of application has been expanded in various fields.

Japanese Patent No. 3963800 Japanese Unexamined Patent Publication No. 2016-176890 JP-A-2017-223490 Japanese Patent No. 5715040

Hiroyuki Sasakura, Yoshihiro Masuda, Eiran Lee: Experiments on fluidity evaluation of fresh concrete using an inclined flow tester, Architectural Institute of Japan Technical Report, Vol. 18, No. 36, pp.11-14, February 2012 Hiroyuki Sasakura, Yoshihiro Masuda, Eiran Lee: Effect of formulation on rheological constants by inclined flow tester, Architectural Institute of Japan Technical Report, Vol. 19, No. 42, pp.387-392, June 2013 "Three-dimensional image processing enables inspections that were previously impossible!" [Online], KEYENCE Co., Ltd., [Search on November 14, 2017], Internet <URL: https://www.keyence .co.jp/landing/req/vision/xg-x_1126_06.jsp>

(1) In order to obtain the apparent yield value and the apparent plastic viscosity using the apparatus described in Patent Document 1 or Patent Document 2 described above, using an inclined flow tester having three or more different angles, or The inclined flow part of the inclined flow tester must be set at three or more different angles to measure the flow tip velocity of concrete, which takes time and effort for the test.

(2) A large amount of sample is required for measurement at 3 or more different tilt angles. For example, if about 9 liters of sample is used in one test, at least 27 liters of sample is required.

(3) Since the flow height was measured visually by installing a scale on the inner side surface of the inclined flow tester, an error may be large, which may affect the final result.

(4) In the method and apparatus described in Patent Document 4, the flow velocity and volume of concrete flowing through the discharge chute of an agitator truck are automatically and non-contactly measured using an image to measure fluidity and material separation resistance. Although it is said that it can be measured, the flow velocity of concrete discharged from the agitator truck is not constant, and if it is discharged vigorously, it will flow down while sliding on the chute. The lower the fluidity of concrete (the smaller the slump value), the stronger the tendency, and it is not possible to accurately measure the fluidity and separation resistance.

The present invention has been developed based on the above background, and uses a device that can be attached to the chute of a truck agitator as a tilt flow test device, and quickly measures the rheology constant of concrete in the field. It is an object of the present invention to provide a rheological constant measuring method and an apparatus capable of the present invention.

In the method and apparatus for measuring the rheology constant of concrete of the present invention, the sample charging section connected to the chute section for discharging the concrete of the truck agitator and the measurement target continuously connected to the sample loading section and charged from the sample loading section. A sample tank portion for storing and holding a sample, an inclined flow portion whose bottom surface is linearly continuous with the bottom surface of the sample tank portion, and an openable / closable portion that vertically partitions the sample charging portion and the sample tank portion. An inclined flow test apparatus including a first gate plate and a second gate plate that can be opened and closed to vertically partition the sample tank portion and the inclined flow portion is used.

For on-site measurement of the rheology constant, the sample injection part of the above-mentioned inclined flow test device is connected to the chute part for discharging the concrete of the truck agitator, and fresh concrete as a sample discharged from the truck agitator is used as the first gate plate and With the second gate plate closed, the sample was flowed to the sample charging section, and the sample flowed to the sample loading section was opened in the first gate plate and stored in the sample tank section, and then stored in the sample dunk section. By opening the second gate plate in a state where a certain amount of sample is stored, the sample is allowed to flow down along the inclined flow portion, and any plurality of measurement points of the inclined flow portion are allowed for the sample flowing down the inclined flow portion. Find the flow tip velocity and sample height at.

Based on the measured values, the apparent shear stress τ (Pa) of the sample is obtained for each measurement point by the following equation.
τ = W × h × g × sin θ… (1)
Here,
W: Unit volume mass of sample (kg / m ³ )
h: Sample height (m) when passing through the measurement point of flow tip velocity
g: Gravity acceleration (9.807m / sec ² )
θ: Tilt angle

In the section where the flow tip velocity obtained for each of the plurality of measurement points or the strain rate calculated using the flow tip velocity and the flow tip velocity of the regression line obtained from the apparent shear stress τ (Pa) are 0. The apparent shear stress τ (Pa) is calculated as the apparent yield value τy (Pa), and the slope of the regression line is calculated as the apparent plastic viscosity η (Pa · s / m or Pa · s).

The flow tip speed of the sample flowing down the inclined flow part and the height of the sample are determined by, for example, three-dimensional image processing of the image taken by the 3D camera by photographing the fresh concrete flowing down with a 3D camera. Can be done.

In the present invention, unlike the invention described in Patent Document 2, it is not necessary to set three or more different inclination angles to measure the flow tip velocity of concrete, and when a 3D camera is used, it is possible to take a picture with the 3D camera. The test can be performed quickly in a single operation, and the amount of sample required can be reduced.

Further, in the present invention, the three-dimensional image processing based on the image information taken by the 3D camera is performed by a terminal device such as a computer terminal, a personal computer terminal, or a tablet PC connected to the 3D camera by a wired or wireless line. Then, the data processing can be performed instantly. That is, the rheology constant can be calculated almost automatically and instantly based on the flow tip velocity of the sample obtained from the three-dimensional image processing and the height of the sample for the image of the 3D camera.

Further, if the inclinometer is provided in the inclining flow portion, the inclining angle of the inclining flow portion at the time of conducting a test can be automatically measured, and the work when it is necessary to evaluate the inclining angle becomes easy.

When an inclinometer is provided in the inclination flow unit, data can be organized quickly by similarly sending the measured value of the inclinometer to the terminal.

In addition, the measurement of the flow tip velocity of the sample flowing down the inclined flow section is not limited to photography with a 3D camera, and the flow tip velocity measuring device (used by various sensors) provided at multiple points of the inclined flow section at intervals. It can also be done by (possible). The height of the sample may be measured on a scale based on, for example, the marks left by the concrete adhering to the inner wall portion of the inclined flow portion during the flow of fresh concrete.

Using the apparent yield value and the apparent plastic viscosity obtained by the method and apparatus of the present invention, it is possible to evaluate the workability such as concrete filling property, compaction property, and pump pumping property in the field construction of concrete.

The rheological constant measuring method and the inclined flow test apparatus of the present invention use the inclined flow test apparatus as a track agitator to determine the flow tip velocity and the height of the sample in the inclined flow part for obtaining the apparent yield value and the apparent plastic viscosity. It is made possible to measure with an inclined flow test device attached to the chute, and this device can quickly measure the rheological constant of concrete in the field.

In the present invention, the flow tip velocity and the sample height are measured at any plurality of measurement points of the inclined flow portion, and the flow tip of concrete is set to three or more different inclination angles in the conventional inclined flow test. Compared to measuring the speed, the measurement can be performed in one operation without changing the tilt angle, so the test can be performed quickly and the amount of sample required can be reduced. be able to.

High measurement accuracy can be obtained by measuring the flow state of the sample concrete with a 3D camera. Further, if the data measured by a 3D camera or the like is transmitted to a tablet PC or the like brought to the site by IoT or the like, the data can be organized instantly.

It is a perspective view which shows the state which attached the inclined flow tester of this invention to the chute part of a truck agitator. It is a perspective view which shows one Embodiment of the inclined flow tester of this invention. It is a side view which shows the working procedure by the rheological constant measuring method of concrete of this invention. It is a side view and a plan view which shows the inclined flow tester described in Patent Document 3.

Hereinafter, specific embodiments of the present invention will be described with reference to FIGS. 1 to 3.
(1) Test apparatus FIG. 1 shows a state in which the inclined flow tester 1 of the present invention is attached to the chute portion 12 of the truck agitator 11, and FIG. 2 shows a specific example of the inclined flow tester 1 attached to the chute portion 12. An example is shown.

The main body of the inclined flow tester 1 has a groove shape as shown in FIG. 2, and is used to store and hold a sample (fresh concrete) to be measured, which is input from the sample input port 2 on the upstream side. It is composed of a sample tank portion 3 and an inclined flow portion 4 whose bottom surface is linearly continuous with the bottom surface of the sample tank portion 3.

A first gate plate 5 that can be opened and closed to vertically partition these is provided between the sample charging section 2 and the sample tank section 3, and these are provided between the sample tank section 3 and the inclined flow section 4. A second gate plate 6 that can be opened and closed is provided. Note that partitioning in the vertical direction here means a vertical positional relationship, and the first gate plate 5 and the second gate plate 6 themselves do not necessarily have to be vertical and may be inclined.

Further, in the illustrated example, an inclinometer 7 for automatically measuring the inclining angle is attached to the inclining flow portion 4.
In the figure, reference numeral 8 is a 3D camera for photographing a sample flowing through the inclined flow portion 4, and determining the flow tip velocity and the height of the sample at any plurality of measurement points, and reference numeral 9 is photographed by a 3D camera. A terminal device such as a tablet PC for performing three-dimensional image processing based on image information is shown.

To open and close the first gate plate 5 and the second gate plate 6, for example, a groove for a guide is provided on the inner surface of the main body of the inclined flow tester 1, and both sides of the first gate plate 5 and the second gate plate 6 are guided. A structure or the like that slides along the above can be adopted.

The track agitator 11 of the inclined flow tester 1 may be attached to the chute portion 12 by a structure that can be easily removed, such as a screw type or a clip type, but the sample does not substantially spill from the connection portion. It needs to be a structure.

FIG. 1 shows a state in which the inclined flow tester 1 is attached to the chute portion 12 of the truck agitator 11. In this example, a foldable tip chute 13 that can be used at the time of placing concrete is attached to the chute portion 12 in advance. The inclined flow tester 1 is attached with the tip chute 13 folded.

(2) Test method Fig. 3 shows an example of the work procedure by the method for measuring the rheological constant of concrete of the present invention, and the work is carried out according to the following procedure.

About 1 to 2 cups of concrete (fresh concrete) is discharged from the truck agitator 11 to the unicycle.

After that, the inclined flow tester 1 is attached to the chute portion 12 with the tip chute 13 removed.

With the first gate plate 5 and the second gate plate 6 closed, a small amount of concrete is discharged and the concrete C is allowed to flow up to the first gate plate 5 (to the sample charging section 2) (see FIG. 3 (a)). ..

The first gate plate 5 is opened, and a required amount of concrete C is stored between the first gate plate 5 and the second gate plate 6 (that is, the sample tank portion 3) (see FIG. 3 (b)).
Next, the first gate plate 5 is closed and the concrete is compacted a predetermined number of times (see FIG. 3 (b)).

The second gate plate 6 is opened to allow the sample concrete C to flow along the inclined flow portion 4 (see FIGS. 3 (d) to 3 (f)).

As shown in FIG. 3, if the flow state of the concrete C is measured with a 3D camera, the flow tip velocities V ₁ , V ₂ , V ₃ , and the height h ₁ at any position can be measured by one measurement of the inclined flow. h ₂ , h ₃
Can be measured, and the apparent yield value and plastic viscosity can be obtained by acquiring data of three or more points. At this time, the inclining angle is also automatically measured by the inclinometer 7.

(3) Calculation of apparent yield value and plastic viscosity Flow tip velocities of multiple measurement points (3 points in this example) V ₁ , V ₂ , V ₃ , heights h ₁ , h ₂ , h ₃
The calculation of the apparent yield value and the plastic viscosity after the measurement is performed is the same as the method described in Patent Document 2, and the apparent shear stress τ (Pa) of the sample is calculated by the following equation based on the measured values. Obtained for each measurement point.
τ = W × h × g × sin θ… (1)
Here,
W: Unit volume mass of sample (kg / m ³ )
h: Sample height (m) when passing through the measurement point (position is arbitrary) of the flow tip velocity.
g: Gravity acceleration (9.807m / sec ² )
θ: Tilt angle

_{The apparent shear stress τ (P a} ) acting on fresh concrete in the inclined flow test is calculated by Eq. (1), and the apparent shear strain rate (1 / sec) is the flow tip velocity (m / sec). It can be calculated by dividing by (m).

The relationship between the apparent shear strain rate and the apparent shear stress obtained at each of the three measurement positions is a linear relationship. When this is linearly regressed, the intercept of the regression line is considered to correspond to the yield value because the apparent shear strain rate is 0, and this is referred to as the apparent yield value (hereinafter abbreviated as τy).

On the other hand, the slope of the regression line is considered to correspond to the plastic viscosity because it is the change in the apparent shear stress with respect to the apparent shear strain rate, and this is referred to as the apparent plastic viscosity (hereinafter abbreviated as η). In practice, the effect of sliding frictional resistance during flow is small and can be ignored.

The flow tip velocity obtained for each of the plurality of measurement points or the strain rate calculated using the flow tip velocity and the flow tip velocity of the regression line obtained from the apparent shear stress τ (Pa) become 0. It can be obtained as the apparent shear stress τ (Pa) in the section as the apparent yield value τy (Pa) and the slope of the regression line as the apparent plastic viscosity η (Pa · s / m or Pa · s).

1 ... Measuring device body, 2 ... Sample loading section, 3 ... Sample tank section, 4 ... Tilt flow section, 5 ... 1st gate plate, 6 ... 2nd gate plate, 7 ... Tiltmeter, 8 ... 3D camera, 9 ... Tablet,
11 ... Track agitator, 12 ... Shoot part, 13 ... Tip chute (foldable),
C ... Fresh concrete

Claims (5)

A sample charging section connected to the chute section that discharges concrete from the truck agitator, and a sample tank section that is continuous with the sample loading section and stores and holds the sample to be measured that is loaded from the sample loading section. An inclined flow portion whose bottom surface is linearly continuous with the bottom surface of the sample tank portion, a first gate plate that can be opened and closed to vertically partition the sample charging portion and the sample tank portion, and the sample tank portion and the inclined portion. The first gate plate and the second gate plate were closed with fresh concrete as a sample discharged from the track agitator using an inclined flow test device provided with a second gate plate that can be opened and closed to partition the flow portion in the vertical direction. A state in which a predetermined amount of sample is stored in the sample dunk part by opening the first gate plate and storing the sample that has been flowed to the sample charging part in the state and flowing to the sample charging part. By opening the second gate plate, the sample is allowed to flow down along the inclined flow portion, and for the sample flowing down the inclined flow portion, the flow tip velocity and the sample at any plurality of measurement points of the inclined flow portion. Seeking the height of
The apparent shear stress τ (Pa) of the sample was obtained for each measurement point by the following equation.
τ = W × h × g × sin θ… (1)
Here,
W: Unit volume mass of sample (kg / m ³ )
h: Sample height (m) when passing through the measurement point of flow tip velocity
g: Gravity acceleration (9.807m / sec ² )
θ: Inclination angle The flow tip velocity obtained for each of the plurality of measurement points or the strain rate calculated using the flow tip velocity and the flow tip velocity of the regression line obtained from the apparent shear stress τ (Pa) are 0. The apparent shear stress τ (Pa) in the section is the apparent yield value τy (Pa), and the slope of the regression line is obtained as the apparent plastic viscosity η (Pa · s / m or Pa · s). How to measure the plasticity constant of concrete. In the method for measuring the rheology constant of concrete according to claim 1, the sample concrete flowing down the inclined flow portion is photographed by a 3D camera, and the inclined flow portion is processed by three-dimensional image processing of the image taken by the 3D camera. A method for measuring a rheological constant of concrete, characterized in that the flow tip velocity of the sample and the height of the sample are obtained for any plurality of measurement points. In the method for measuring the rheology constant of concrete according to claim 1 or 2, the image information taken by the 3D camera is subjected to three-dimensional image processing by a terminal device connected to the 3D camera by a wired or wireless line, and 3D. A method for measuring a rheological constant of concrete, characterized in that a rheological constant is calculated based on the flow tip velocity of the sample and the height of the sample obtained from three-dimensional image processing. The method for measuring the rheology constant of concrete according to claim 1, characterized in that the flow tip speed of a sample flowing down the inclined flow portion is measured for each flow tip speed measuring device provided at a plurality of intervals. Rheology constant measurement method for concrete. A sample charging section connected to the chute section that discharges concrete from the truck agitator, and a sample tank section that is continuous with the sample loading section and stores and holds the sample to be measured that is loaded from the sample loading section. An inclined flow portion whose bottom surface is linearly continuous with the bottom surface of the sample tank portion, a first gate plate that can be opened and closed to vertically partition the sample charging portion and the sample tank portion, and the sample tank portion and the inclined portion. An inclined flow test apparatus including a second gate plate that can be opened and closed to partition the flow portion in the vertical direction.

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