JP6554208B2 - Property evaluation method of fresh concrete - Google Patents

Description

  The present invention relates to a method of evaluating the properties of fresh concrete.

The workability of fresh concrete is determined by the consistency and separation resistance of the concrete.
Conventionally, the workability of concrete is evaluated by the slump test.

  The slump test is a test to evaluate the consistency of concrete, but in the era when there were few types of admixtures and river sand and river gravel were used, the workability of concrete could be evaluated to some extent.

  However, in recent years, concrete materials such as fly ash and slag fine aggregate have been diversified, and even with concrete that has the same slump value, meshing between aggregates and material separation resistance Because there are many cases where differences in gender etc. appear, there is a risk that workability alone can not be accurately grasped only by the slump test.

  In addition to the slump test, it is necessary to evaluate the separation resistance of concrete in order to accurately grasp the workability of concrete. Since the viscosity of concrete greatly affects the separation resistance of concrete, the separation resistance of concrete can be evaluated to some extent by evaluating the viscosity of concrete.

  For example, Patent Document 1 measures the distance from the outer edge of the mortar of the concrete sample after the slump test and the center of gravity of the coarse aggregate, and if this measured value is within the set value, the material separation resistance is provided. There is disclosed an evaluation method for evaluating the

  Patent Document 2 discloses an evaluation method in which a concrete sample after a slump test is divided into a plurality of regions by a plurality of ring-shaped members having different diameters, and the material separation resistance is evaluated for the concrete sample collected from each region. It is disclosed.

  Furthermore, Non-Patent Document 1 describes an evaluation method for evaluating the material separation resistance of concrete by the number of times of tamping when a slump plate is hit against a concrete sample after a slump test until the circular shape on the top surface of the concrete sample disappears. Is disclosed.

  However, since the evaluation method described in Patent Document 1 needs to measure the position of the outer edge portion of mortar, measure the positions of a plurality of aggregates, calculate the average value, and the like, it requires labor. It was

  In addition, the material separation resistance evaluation method described in Patent Document 2 collects concrete samples from a plurality of regions, and measures and evaluates the coarse aggregate mass ratio for each sample collected. Was required.

Further, the evaluation method of Non-Patent Document 1 may cause an error in the test result due to a difference in the installation state of the slump plate or a difference in tamping strength for each operator.
Moreover, although it was possible to compare the material separation resistance between concrete samples, it was difficult to determine whether the samples were good or bad (determining whether the viscosity was excessive or insufficient).

  Therefore, for the purpose of easily obtaining a stable evaluation result, the present applicant gives vibration to the concrete sample after the slump test until the slump flow reaches the reference diameter, as shown in Patent Document 3, A property evaluation method for fresh concrete was developed to evaluate the viscosity of fresh concrete by confirming the shape of the top surface of the concrete sample whose flow became the reference diameter. In addition, a reference diameter is set based on the completion energy of compaction.

Japanese Patent Application Laid-Open No. 10-267921 Japanese Patent Application Publication No. 2003-322602 Patent No. 4981984

Atsushi Ishii and two others, “Study of simple evaluation method of workability in tamping test”, Concrete Engineering Annual Papers, Japan Concrete Institute, 2008, Vol. 30, No. 2, p. 37-40

  In the method for evaluating the properties of fresh concrete in Patent Document 3, it is necessary to confirm the spread of the concrete sample and the circular change of the upper surface of the concrete sample. There was a possibility that it might occur.

  This invention is made | formed in order to solve such a problem, and makes it a subject to provide the property evaluation method of the fresh concrete which can obtain a more stable evaluation result.

  In order to solve the above-mentioned problems, a method for evaluating the properties of fresh concrete according to the first invention includes a first step of applying vibration to a concrete sample subjected to a slump test until the slump flow reaches a reference diameter, and a slump flow. And a second step of confirming the shape of the upper surface of the concrete sample having the reference diameter, and before performing the slump test, the entire upper surface of the concrete sample is colored with a phenolphthalein solution. In the second step, when the outer edge shape of the colored portion on the upper surface of the concrete sample is not maintained in a circular shape, it is evaluated that the viscosity of the fresh concrete is insufficient.

  In the second step, when the outer edge shape of the colored portion on the top surface of the concrete sample is maintained in a circular shape, the slump flow is further increased with respect to the concrete sample until the second reference diameter is larger than the reference diameter. A third step of applying vibration and a fourth step of confirming the shape of the upper surface of the concrete sample where the slump flow becomes the second reference diameter are performed. In the fourth step, the colored portion of the upper surface of the concrete sample is checked. When the outer edge shape is held in a circular shape, it is evaluated that the viscosity of fresh concrete is excessive.

According to the property evaluation method for fresh concrete, it is possible to easily evaluate the excess or deficiency (material separation resistance) of the viscosity of fresh concrete. In other words, because the slump is colored on the top surface of the concrete sample before the test, it is easy to check the outer edge shape of the top surface of the sample when the slump cone is pulled out, and the change in the shape of the sample that has been vibrated is visually observed The properties of fresh concrete can be evaluated simply with
In addition, if it is recognized that there is a tendency of material separation (separation, breakage, paste advancement, etc.) before the diameter of the slump flow reaches the reference diameter, it is regarded as inappropriate concrete that cannot be used for construction work. .

  In addition, since the evaluation is performed by confirming the colored portions, it is possible to minimize the variation caused by the different workers.

  Further, the method for evaluating the properties of fresh concrete according to the second invention includes a first step in which vibration is applied to a concrete sample subjected to a slump test until the slump flow reaches a reference diameter, and the slump flow becomes the reference diameter. And a second step of confirming the shape of the upper surface of the concrete sample, wherein the upper surface of the concrete sample is colored before performing the slump test. The first determination index by measuring the colored area which is the area of the colored portion, the work of measuring the diffusion area which is the area of the range in which the colored portion is diffused, and dividing the colored area by the diffusion area Characterized in that it has an operation of calculating the value and an operation of evaluating the separation resistance of fresh concrete based on the first judgment index. That.

  In the second step, when it is determined that the fresh concrete has a desired separation resistance, the slump flow with respect to the concrete sample is a second reference diameter larger than the reference diameter. Further, a third step for applying vibration and a fourth step for confirming the shape of the upper surface of the concrete sample whose slump flow becomes the second reference diameter are performed. In the fourth step, the upper surface of the concrete sample is colored. Calculate the second determination index by measuring the colored area that is the area of the part, measuring the diffusion area that is the area in which the colored part has diffused, and dividing the colored area by the diffusion area. And an operation of evaluating the separation resistance of fresh concrete based on the second determination index.

  According to the property evaluation method for fresh concrete, it is possible to quantitatively evaluate the property of fresh concrete and obtain a more stable evaluation result.

  According to the method for evaluating the properties of fresh concrete of the present invention, it is possible to minimize the variation due to the tester and obtain stable evaluation results.

(A)-(c) is a perspective view which shows each implementation stage of the property evaluation method of the fresh concrete which concerns on embodiment of this invention. It is a top view which shows typically the condition after vibration of the concrete sample from which mixing | blending differs, Comprising: When (a) is vibrated until the concrete of standard mixing becomes the 1st standard diameter, (b) When the concrete is vibrated to the second reference diameter, (c) is when the coarse blended concrete is vibrated to the first reference diameter, and (d) is the coarse blended concrete having the second reference diameter. (E) is when high viscosity concrete is vibrated to the first reference diameter, and (f) is when high viscosity concrete is vibrated to the second reference diameter. is there.

First Embodiment
The property evaluation method for fresh concrete according to the first embodiment is performed on fresh concrete (concrete sample 1) subjected to a slump test using a slump cone 2, as shown in FIG. , A first step, a second step, a third step, and a fourth step.

In the first step, as shown in FIG. 1B, the concrete sample 1 subjected to the slump test is struck by striking the slump plate 3 until the slump flow D reaches the first reference diameter (reference diameter). It is a process of giving. In the present embodiment, the first reference diameter is 470 mm.
The slump test is performed using a slump cone 2 having an upper surface inner diameter of 10 cm, a lower surface inner diameter of 20 cm, and a height of 30 cm.

In the present embodiment, vibration is given by hitting the slump plate 3 on which the concrete sample 1 is mounted with the mallet 4.
At this time, the concrete sample 1 is hit evenly around the concrete sample 1 so that the center line in the vertical direction of the concrete sample 1 is not biased (so as not to tilt).

As shown in FIG. 1A, the concrete sample 1 is colored on the upper surface before the slump test.
Although the coloring method is not limited, in this embodiment, the phenolphthalein solution is sprayed on the upper surface of the concrete sample 1. The phenolphthalein solution sprayed on the concrete sample 1 turns reddish purple in response to the alkalinity of the concrete.

  If the concrete sample collapses or moisture flows around the concrete sample 1 before the slump flow D reaches 470 mm when the concrete sample 1 is vibrated, the concrete sample 1 tends to separate. Therefore, it is judged that the material is inadequate concrete that cannot be used for construction work.

If it is determined in the first step that the concrete does not tend to separate (appropriate concrete), the second step is continued.
On the other hand, when it is determined in the first step that the concrete sample 1 has a tendency to separate, it is desirable not to accept the concrete or to reconsider the mix of the concrete.

  The second step is a step of confirming the shape of the upper surface of the concrete sample 1 in which the slump flow D is 470 mm, as shown in (c) of FIG.

  The upper end surface of the concrete sample 1 is formed into a circular shape by the upper end opening edge of the slump cone 2, but the upper end surface of the concrete sample 1 that does not tend to separate immediately after the slump cone 2 is pulled up in the slump test maintains a circular shape. There is. In the process of performing the first step, the circular shape of the upper end surface of the concrete sample 1 expands. In the second step, is the outer edge shape of the colored portion 5 on the upper surface of the concrete sample 1 after the first step maintained circular? Check if it is not.

  When “circular” is held on the upper surface of the concrete sample 1 (when the outer edge shape of the colored portion 5 is circular), it is evaluated that the fresh concrete has a viscosity necessary for construction. When the “circular” is not held on the upper surface of the material (when the outer edge shape of the colored portion 5 is not circular), it is evaluated that the viscosity of the fresh concrete is insufficient. If the viscosity is evaluated as low, be careful not to over-compact the concrete (do not apply excessive vibration). Here, whether or not “circular” is held is determined from the outer edge shape of the colored portion 5.

  If it is evaluated in the second step that the viscosity of the fresh concrete is insufficient, the compacting operation when placing the concrete is performed with care so that the concrete does not separate. In addition, you may adjust the mixing | blending of concrete as needed.

In the third step, the diameter of the slump flow D relative to the concrete sample 1 is the first reference diameter (470
This is a step of applying vibration by hitting the slump plate 3 until the second reference diameter is larger than (mm) (see FIG. 1B). The third step is performed when the outer edge shape of the colored portion 5 on the upper surface of the concrete sample 1 is held in a circular shape in the second step. In the present embodiment, the second reference diameter is 520 mm.

  The method of applying vibration to the concrete sample 1 in the third step is the same as the method performed in the first step, and thus the detailed description is omitted.

  The fourth step is a step of confirming the outer edge shape of the colored portion 5 on the top surface of the concrete sample 1 where the slump flow D is 520 mm (see FIG. 1C).

  In the fourth step, when the outer edge shape of the colored portion 5 on the upper surface of the concrete sample 1 is held in a circular shape, it is evaluated that the viscosity of the fresh concrete is excessive, and the outer edge shape of the colored portion 5 on the upper surface of the concrete sample is circular. If it disappears, it is evaluated that the blend of fresh concrete is a blend with optimum separation resistance.

  In the fourth step, when it is evaluated that the viscosity of the concrete is excessive, it is desirable to carefully perform the compacting work (particularly around the reinforcing bars) when placing the concrete.

  According to the property evaluation method for fresh concrete of the present embodiment, the property of fresh concrete can be easily evaluated simply by visually observing the change in the shape of the concrete sample 1 subjected to vibration. It is simple because it is possible to evaluate the excess or deficiency (material separation resistance) of fresh concrete simply by observing the presence or absence of a circle formed on the upper surface of the concrete sample 1 when the slump cone 2 is pulled out. . Since the upper surface of the concrete sample 1 is colored, it is easy to confirm the shape of the upper surface of the concrete sample 1.

In addition, since the management is based on the diameter of the slump flow D, not the number of tampings, it is possible to minimize variations caused by different operators.
Since the material separation resistance is evaluated as it is for the concrete sample 1 whose fluidity is measured by the slump test, it is excellent in workability and can be evaluated more accurately.

Second Embodiment
The property evaluation method for fresh concrete according to the second embodiment is to confirm the property of fresh concrete by using the area of the colored portion on the upper surface of the concrete sample 1.
The property evaluation method for fresh concrete according to the second embodiment includes a first step, a second step, a third step, and a fourth step.

In the first step, as shown in FIG. 1B, the concrete sample 1 subjected to the slump test is struck by striking the slump plate 3 until the slump flow D reaches the first reference diameter (reference diameter). It is a process of giving.
Note that details of the first step are the same as the contents shown in the first embodiment, and thus detailed description thereof is omitted.

  The second step is a step of confirming the shape of the upper surface of the concrete sample 1 in which the slump flow D becomes the first reference diameter (470 mm) as shown in (c) of FIG.

In the second step, first, the concrete sample 1 is photographed from above.
Next, on the photographed image, the outer edge of the colored portion 5 on the top surface of the concrete sample 1 (the range in which the colored portion 5 has diffused) is surrounded by a polygonal colored range line 6 (see FIG. 2).

Subsequently, image processing such as binarization processing is performed on the photographed image, and thereafter, a colored area A1 that is an area of the colored portion 5 on the upper surface of the concrete sample 1 is measured (calculated).
Further, along with the measurement of the colored area A1, the diffusion area A2, which is the area of the portion surrounded by the colored range line 6 (the range where the colored portion 5 has diffused), is also measured (calculated) by image processing.

  Once the coloring area A1 and the diffusion area A2 are measured, the first determination index B1 (= A1 / A2) is calculated by dividing the coloring area A1 by the diffusion area A2.

And when 1st determination index | exponent B1 is 0.7 or more, it evaluates that fresh concrete has the separation resistance required for construction, and when 1st determination index | exponent B1 is 0.7 or less It is evaluated that the separation resistance of fresh concrete is insufficient.
Note that the threshold value of the first determination index B1 when evaluating the separation resistance of fresh concrete is not limited to 0.7, and is set as appropriate according to the purpose of use, strength, mixed material, and the like.

  When it is evaluated that the fresh concrete does not have the desired separation resistance in the second step, the compacting operation at the time of placing the concrete is performed with care so that the concrete does not separate. In addition, you may adjust the mixing | blending of concrete as needed.

In the third step, when it is determined in the second step that the fresh concrete has a desired separation resistance, the diameter of the slump flow D with respect to the concrete sample 1 is greater than the first reference diameter (470 mm). Is a step of applying vibration by further striking the slump plate 3 until a large second reference diameter (520 mm) is reached (see FIG. 1B).
Note that details of the third step are the same as the contents shown in the first embodiment, and thus detailed description thereof is omitted.

  The fourth step is a step of confirming the shape of the colored portion 5 on the upper surface of the concrete sample 1 where the slump flow D becomes the second reference diameter (see FIG. 1C).

In the fourth step, first, the concrete sample 1 is photographed from above.
Next, on the photographed image, the outer edge of the colored portion 5 on the top surface of the concrete sample 1 (the range in which the colored portion 5 has diffused) is surrounded by a polygonal colored range line 6 (see FIG. 2).

  Subsequently, image processing such as binarization processing is performed on the photographed image, and then a colored area A1 that is an area of the colored portion 5 on the top surface of the concrete sample 1 is measured (calculated), and the colored range line 6 A diffusion area A2 that is an area of a portion surrounded by (a range in which the colored portion 5 is diffused) is measured (calculated).

  After the coloring area A1 and the diffusion area A2 are measured, the second determination index B2 (= A1 / A2) is calculated by dividing the coloring area A1 by the diffusion area A2.

And when the 2nd determination index | exponent B2 exists in the range of 0.7-0.5, it evaluates that fresh concrete has the separation resistance required for construction, and the 2nd determination index | exponent B2 is 0.00. In the case of 7 or more, it is evaluated that the viscosity (separation resistance) of fresh concrete is excessive.
In addition, the threshold value of the second determination index B2 when evaluating the separation resistance of fresh concrete is not limited to 0.7 to 0.5, and is appropriately determined according to the purpose of use, strength, mixed material, and the like. Set

  In the fourth step, when the viscosity of the concrete is evaluated to be excessive, it is desirable to carefully carry out the compacting operation at the time of placing the concrete.

According to the property evaluation method for fresh concrete of the present embodiment, it is possible to quantitatively evaluate by measuring the change in the shape of the concrete sample 1 subjected to vibration, and obtain a more stable evaluation result. it can.
Therefore, errors due to the degree of experience of the examiner and individual differences can be reduced.

Further, since the management is based on the diameter of the slump flow D rather than the number of tampings, variations caused by different operators can be minimized.
Since the material separation resistance is evaluated as it is for the concrete sample 1 whose fluidity is measured by the slump test, it is excellent in workability and can be evaluated more accurately.

  Next, the experimental result performed about the judgment criteria of the isolation | separation resistance in the property evaluation method of the fresh concrete of 2nd embodiment is shown.

  In this experiment, concrete samples with proper (standard) viscosity (cases 1 and 4), concrete samples with rough mix (cases 2 and 5), and concrete with high viscosity (viscosity is too high) For the samples (cases 3 and 6), the first determination index B1 and the second determination index B2 were calculated and compared.

  The formulations of Case 1 to Case 6 are shown in Table 1. In addition, in this experiment, when the target slump was 8 cm (cases 1 to 3) and 12 cm (cases 4 to 6), the experiments were performed.

Each of the concrete samples of cases 1 to 6 was vibrated, and the slump flow was 470 mm (see (a), (c), (e) of FIG. 2) and 520 mm ((b), (d) of FIG. 2). , (F))), the colored area A1 and the diffusion area A2 are measured, and the first determination index B1 and the second determination index B2 of each case are calculated from the coloring area A1 and the diffusion area A2. did.
Table 2 shows the first determination index B1 and the second determination index B2 of cases 1 to 6.

As shown in Table 2, in cases 1 and 4 of the standard blend and cases 3 and 6 of the highly viscous blend, the first determination index was 0.7 or more. On the other hand, in cases 2 and 5 having a rough blend, the first determination indices were 0.30 and 0.17, respectively.
Therefore, if the first determination index B1 is 0.7 or more, it can be said that the necessary viscosity is secured.

Further, as shown in Table 2, in the case of standard blending cases 1 and 4, the second determination index is 0.56 and 0.65, respectively, and in the case of high viscosity blending 3 and 6, the second determination index is 0.75 respectively. , 0.73.
Therefore, when the second determination index B2 is 0.7 or more, it can be evaluated that the viscosity (separation resistance) of the fresh concrete is excessive.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiments, and the above-described components can be appropriately modified without departing from the scope of the present invention.

  For example, in each of the above embodiments, the first reference diameter and the second reference diameter are set to 470 mm and 520 mm, respectively, based on the concrete compaction completion energy. It is not limited.

  In each of the above embodiments, the concrete sample 1 is vibrated by hitting the slump plate 3 with the mallet 4, but the method of imparting vibration to the concrete sample 1 is not limited.

  The measuring method (calculation method) of the colored area A1 and the diffusion area A2 in the second embodiment is not limited to that by image processing.

DESCRIPTION OF SYMBOLS 1 Concrete sample 2 Slump cone 3 Slump board 4 Kiso 5 Colored part 6 Colored range line D Slump flow

Claims (4)

A first step of applying vibration to a concrete sample subjected to a slump test until the slump flow reaches a reference diameter;
A second step of confirming the shape of the upper surface of the concrete sample in which the slump flow becomes the reference diameter, and a method for evaluating concrete comprising:
Prior to performing the slump test, the entire top surface of the concrete sample is colored with a phenolphthalein solution,
In the second step, when the outer edge shape of the colored portion on the upper surface of the concrete sample is not maintained in a circular shape, the fresh concrete property evaluation method is evaluated as being insufficient in viscosity. . In the second step, when the outer edge shape of the colored portion on the top surface of the concrete sample is held in a circle,
A third step in which vibration is further applied to the concrete sample until a slump flow becomes a second reference diameter larger than the reference diameter;
Performing a fourth step of confirming the shape of the upper surface of the concrete sample in which the slump flow becomes the second reference diameter,
2. The fresh according to claim 1, wherein, in the fourth step, when the outer edge shape of the colored portion on the upper surface of the concrete sample is held in a circular shape, it is evaluated that the viscosity of the fresh concrete is excessive. Evaluation method of concrete properties. A first step of applying vibration to a concrete sample subjected to a slump test until the slump flow reaches a reference diameter;
A second step of confirming the shape of the upper surface of the concrete sample in which the slump flow becomes the reference diameter, and a method for evaluating concrete comprising:
The upper surface of the concrete sample is colored before the slump test is performed,
In the second step, an operation of measuring a colored area that is an area of a colored portion on the top surface of the concrete sample;
An operation of measuring a diffusion area which is an area of a range in which the colored portion is diffused;
Calculating a first judgment index by dividing the colored area by the diffusion area;
The property evaluation method of fresh concrete characterized by having the operation | work which evaluates the separation resistance of fresh concrete based on said 1st determination index | exponent. In the second step, when it is determined that the fresh concrete has a desired separation resistance,
A third step of further vibrating the concrete sample until a slump flow becomes a second reference diameter larger than the reference diameter;
Performing a fourth step of confirming the shape of the upper surface of the concrete sample in which the slump flow becomes the second reference diameter,
In the fourth step, an operation of measuring a colored area that is an area of a colored portion on the upper surface of the concrete sample;
An operation of measuring a diffusion area which is an area of a range in which the colored portion is diffused;
Calculating a second determination index by dividing the colored area by the diffusion area;
The property evaluation method for fresh concrete according to claim 3, further comprising: an operation for evaluating separation resistance of fresh concrete based on the second determination index.

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