JP2021143944A - Method for evaluating concrete and separation resistance evaluation container - Google Patents

Abstract

To propose a method for evaluating a concrete which allows an evaluation of a separation resistance of a fresh concrete by an easy method for measurement, and a separation resistance evaluation container used for the method.SOLUTION: The method for evaluating a concrete includes: a container preparation step S1 of connecting a plurality of cylinders together vertically and forming a container; a filling step S2 of filling the container with a fresh concrete; a concrete collecting step S4 of collecting a fresh concrete which overflows because the cylinder in the uppermost part is removed; an aggregate amount measuring step S5 of measuring the mass of the coarse aggregate in the collected fresh concrete; and an evaluation step S6 of evaluating the material separation resistance of the fresh concrete by the mass of the coarse aggregate.SELECTED DRAWING: Figure 5

Description

The present invention relates to a method for evaluating concrete and a container for evaluating separation resistance used therein.

Concrete should be compounded and designed so that it will exhibit the required strength after hardening and ensure the workability required during construction. The workability of fresh concrete is evaluated by the slump test to evaluate the consistency of concrete.
However, even if concrete has the same slump value, there may be a difference in material separation resistance. The material separation resistance of concrete has a great influence on the compaction of concrete, pumping, and the like. On the other hand, there is no method for quantitatively evaluating the material separation resistance of concrete, and at present, it is common to visually confirm the sinking condition of the aggregate of concrete to determine the presence or absence of separation.
Patent Document 1 discloses a test method using a concrete sample after a slump flow test as a test method for evaluating the material separation resistance of concrete. In this test method, a concrete sample is divided into a plurality of regions in the radial direction by arranging a plurality of steel rings having different diameters on a base plate after the slump flow test so as to have a concentric positional relationship. Material separation resistance is evaluated by measuring the crude bone material amount ratio in the region.
However, in the test method of Patent Document 1, it is necessary to calculate the coarse bone material amount ratio for each region, which is troublesome. That is, it is necessary to measure the mass of the sample collected for each region and the mass of the coarse aggregate contained in the sample, and calculate the coarse aggregate material amount ratio by using the measurement result.

Japanese Unexamined Patent Publication No. 2003-322602

An object of the present invention is to propose a concrete evaluation method capable of evaluating the separation resistance of fresh concrete by a simple measurement method, and a container for separation resistance evaluation used in this evaluation method.

The concrete evaluation method of the present invention for solving the above-mentioned problems includes a container preparation step of preparing a container in which a plurality of cylinders are connected one above the other, a filling step of filling the container with fresh concrete, and the uppermost part. A concrete sampling step of collecting the fresh concrete that overflowed by removing the tubular body, an aggregate amount measuring step of measuring the mass of the coarse aggregate in the collected fresh concrete, and the coarse aggregate. It is provided with an evaluation step of evaluating the material separation resistance of the fresh concrete by mass. According to such a concrete evaluation method, a certain amount of fresh concrete can be collected from the upper part of the container only by removing the cylinder at the upper part of the container. In addition, the sinking condition of the aggregate can be confirmed by measuring the mass of the coarse aggregate in the collected fresh concrete. Therefore, it is possible to easily evaluate the material separation resistance of fresh concrete.
The plurality of containers filled with fresh concrete are compacted at different times for each container, and the material of the fresh concrete is based on the relationship between the mass of the coarse aggregate and the compaction time for each container. If the separation resistance is evaluated, the material separation resistance can be evaluated more accurately. In the evaluation step, the work of obtaining an approximate curve from the unit coarse aggregate amount calculated from the mass of the coarse aggregate and the compaction time, and the unit coarse aggregate amount when the compaction time is zero from the approximate curve are determined. It is desirable to do the desired work.

Further, the container for evaluating separation resistance of the present invention includes a bottom plate and a plurality of cylinders stacked vertically on the upper surface of the bottom plate, and the cylinder is the upper end or the lower end of the cylinder. It has an engaging member that protrudes from and is inserted into another adjacent cylinder.
According to the separation resistance evaluation container, since a plurality of cylinders can be separated, a certain amount of fresh concrete can be collected by removing the uppermost cylinder. Since the cylinders are engaged with each other via the engaging member, fresh concrete is prevented from flowing out from between the cylinders.
If a receiving material is further provided around the outer surface of the cylinder, the fresh concrete that overflows when the uppermost cylinder is removed stays on the receiving material, so that the fresh concrete can be easily collected. Is.

According to the concrete evaluation method and the separation resistance evaluation container of the present invention, it is possible to evaluate the separation resistance of fresh concrete by a simple measurement method.

It is a front view of the container for evaluation of separation resistance which concerns on this embodiment. It is a top view of the bottom plate. (A) is a plan view of the tubular body, and (b) is a cross-sectional view of the tubular body. (A) is a plan view of the receiving material, and (b) is a cross-sectional view of the receiving material. It is a flowchart which shows the procedure of the concrete evaluation method. (A) and (b) are graphs showing the results of experiments carried out on the concrete evaluation method. It is a graph for demonstrating the setting method of the compaction time using the container for evaluation of separation resistance.

In this embodiment, a concrete evaluation method for evaluating the separation resistance of concrete will be described. FIG. 1 shows a separation resistance evaluation container 1 used in the concrete evaluation method of the present embodiment. As shown in FIG. 1, the separation resistance evaluation container 1 includes a bottom plate 2, a plurality of cylinders 3, and a receiving material 4.
The bottom plate 2 has a square shape with a side of 360 mm and is made of a steel plate having a thickness of 5 mm. The bottom plate 2 is not limited as long as it is a plate material having a shape larger than the outer shape of the cylinder 3, and is not necessarily rectangular (square), for example, a circle having a diameter larger than the outer shape of the cylinder 3. It doesn't have to be. Further, the bottom plate 2 is not limited to a steel plate, and may be, for example, a synthetic resin plate or a glass plate.

The plurality of cylinders 3 are stacked vertically on the upper surface of the bottom plate 2. In the present embodiment, seven cylinders 3 (cylinders 31 to 37) are stacked on the bottom plate 2. The tubular body 3 of the present embodiment is made of a vinyl chloride pipe having an inner diameter of 250 mm, an outer diameter of 267 mm, and a height of 50 mm. The material constituting the tubular body 3 is not limited. Further, the shape and dimensions of the tubular body 3 are not limited, and for example, the inner diameter may be 200 mm or 300 mm.
An engaging member 5 is attached to a cylinder 3 (second to seventh cylinders 32 to 37 from the bottom) other than the lowermost cylinder 31. The engaging member 5 protrudes from the lower end of the tubular body 3 and is inserted into the tubular body 3 directly below. The engaging member 5 is made of a tubular member having an outer diameter equivalent to the inner diameter of the tubular body 3. By inserting the engaging member 5 of the tubular body 3 into the tubular body 3 directly below, the upper and lower tubular bodies 3 are engaged with each other. The protruding length of the engaging member 5 from the lower end of the tubular body 3 is not limited, and the size may be appropriately determined so as to be able to engage with the lower tubular body 3. The configuration of the engaging member 5 is not limited, and for example, a plurality of plate-shaped engaging members 5 may be arranged at intervals in the circumferential direction of the tubular body 3. It may cover the outer periphery of the abutting portion between the upper and lower cylinders 3.

The receiving material 4 is provided around the outer surface of the tubular body 3. The receiving material 4 is made of plastic resin, and includes a bottom portion 41 having an annular shape in a plan view, and an inner wall portion 42 and an outer wall portion 43 erected on the upper surface of the bottom portion 41. An opening 44 having an opening diameter (268 mm in the present embodiment) equivalent to the outer diameter of the tubular body 3 is formed in the central portion of the bottom portion 41. The inner wall portion 42 is erected along the inner edge of the bottom portion 41 (the edge of the opening 44). Further, the outer wall portion 43 is erected along the outer edge of the bottom portion 41. The height of the inner wall portion 42 and the outer wall portion 43 is 50 mm. The shape and dimensions of the receiving material 4 are not limited, but in the present embodiment, the volume of the space surrounded by the bottom portion 41, the inner wall portion 42, and the outer wall portion 43 is the inner space of one cylinder 3. It is larger than the volume. The receiving material 4 of the present embodiment is attached to the outer surface of the tubular body 3 (cylindrical body 36) in the second stage from the top. A jig may be used when the receiving material 4 is attached to the outer surface of the tubular body 3.

Next, a concrete evaluation method using the separation resistance evaluation container 1 will be described. As shown in FIG. 5, the concrete evaluation method includes a container preparation step S1, a filling step S2, a compaction step S3, a concrete sampling step S4, an aggregate amount measuring step S5, and an evaluation step S6.
The container preparation step S1 is a step of preparing the separation resistance evaluation container 1. The separation resistance evaluation container 1 is formed by vertically connecting a plurality of cylinders 3, 3, ... On the bottom plate 2 (see FIG. 1). At this time, the receiving material 4 is attached to the outer circumference of the tubular body 35 in the second stage from the top. In this embodiment, four separation resistance evaluation containers 1 are prepared. The number of separation resistance evaluation containers 1 assembled in the container preparation step S1 is not limited.

The filling step S2 is a step of filling the separation resistance evaluation container 1 with fresh concrete. Fresh concrete is poured from above the separation resistance evaluation container 1. The upper surface of the fresh concrete is aligned with the upper end surface of the separation resistance evaluation container 1. The composition of concrete is appropriately determined.

The compaction step S3 is a step of compacting the fresh concrete filled in the separation resistance evaluation container 1. In the compaction step S3, the compaction time is different for each container. In the present embodiment, the vibration times applied to the four separation resistance evaluation containers 1 are 5 seconds, 10 seconds, and 20 seconds, respectively. The fresh concrete is compacted by an internal vibrator (vibrator) inserted in the separation resistance evaluation container 1. The compaction of the fresh concrete may be performed by applying vibration from the outer surface of the separation resistance evaluation container 1 or shaking the separation resistance evaluation container 1. Further, the vibration time of the container is not limited to the above, and may be appropriately determined.

The concrete sampling step S4 is a step of sampling fresh concrete from the upper part of the separation resistance evaluation container 1. Fresh concrete is collected by removing the uppermost cylinder 3 (cylinder 37). The uppermost cylinder 37 is removed by pulling it upward. When the uppermost cylinder 37 is removed, the volume (a certain amount) of fresh concrete of the cylinder 37 overflows. Since the overflowed fresh concrete flows into the receiving material 4 attached to the outer periphery of the tubular body 36 in the second stage from the top, the fresh concrete that has flowed into the receiving material 4 is collected. In addition, fresh concrete is collected in a state where the concrete immediately after compaction has fluidity before hardening.

The aggregate amount measuring step S5 is a step of measuring the mass of the coarse aggregate in the collected fresh concrete. First, coarse aggregate is collected from the collected fresh concrete, and the cement paste adhering to the coarse aggregate is washed off. The coarse aggregate may be collected by sieving the fresh concrete collected from the receiving material 4 and washing it with water on the sieve. Next, the mass of the collected coarse aggregate is measured. The coarse aggregate may be washed using a container different from the sieve.

The evaluation step S6 is a step of evaluating the material separation resistance of fresh concrete based on the mass of the coarse aggregate. In the evaluation of the material separation resistance, first, the unit coarse aggregate amount is calculated by dividing the mass of the coarse aggregate by the volume of the tubular body 3. Then, by comparing the calculated unit coarse aggregate amount (measurement unit coarse aggregate amount) with the unit coarse aggregate amount at the time of blending (blending unit coarse aggregate amount), the tendency of concrete material separation is determined. do.
In the present embodiment, the material separation resistance of fresh concrete is evaluated based on the relationship between the mass of the coarse aggregate and the compaction time. In the evaluation step S6 of the present embodiment, when the ratio of the measurement unit coarse aggregate amount to the compounding unit coarse aggregate amount is equal to or more than the threshold value (for example, 95%), it is determined that the separation is not performed. The size of the threshold value may be appropriately determined. Moreover, the method for determining the tendency of material separation is not limited. For example, the tendency of material separation may be determined by the following method. First, the relationship between the unit amount of coarse aggregate calculated from the mass of coarse aggregate and the compaction time is plotted (see FIG. 6). Next, an approximate curve is created from the plot by, for example, the least squares method. Read the unit coarse aggregate amount when the compaction time is zero from the approximate curve. When the ratio of the unit coarse aggregate amount to the unit coarse aggregate amount at the time of compounding design is zero and the ratio of the unit coarse aggregate amount is equal to or more than the threshold value (for example, 95%), it is judged that the particles are not separated.

Next, the results of experiments carried out on the concrete evaluation method of the present embodiment will be described.
First, two types of concrete samples (Sample A and Sample E) having different formulations are put into the separation resistance evaluation container 1 and compacted for 0 seconds, 5 seconds, 10 seconds, and 20 seconds, and then the cylinder 3 Coarse aggregate was collected every (every depth). Next, the mass of the coarse aggregate collected for each of the cylinders 3 was measured, and the unit amount of coarse aggregate for each of the cylinders 3 was calculated. Then, the ratio of the calculated unit coarse aggregate amount to the unit coarse aggregate amount at the time of compounding was calculated. Table 1 and FIG. 6 (a) show the ratio of the amount of coarse aggregate for each cylinder 3 of sample A, and Table 2 and FIG. 6 (b) show the ratio of the amount of coarse aggregate for each cylinder 3 of sample E. show.

As shown in Table 1 and FIG. 6A, in sample A, when the compaction time was 0 seconds, 5 seconds, and 10 seconds, the unit coarse aggregate amount having a height of 350 mm (top cylinder 37) was 350 mm. It was around 80%, and in the range of other heights, it was in the range of about 90% to 110%. When the compaction time is 20 seconds, the amount of unit coarse aggregate having a height of 350 mm is significantly reduced by 41%, and the unit coarse aggregate having a height of 100 mm (the second cylinder 32 from the bottom) is used. Although the amount of material increased to about 130%, it was in the range of about 90% to 120% at other heights.
As shown in Table 2 and FIG. 6 (b), in sample E, the unit coarse aggregate amount was significantly reduced at a height of 350 mm (top cylinder 37), and the height was 300 mm (two from the top). Although the columnar cylinder 36) also showed 100% or less, at other heights, the alignment was close to horizontal, and the results were almost evenly dispersed.
Therefore, in both cases of sample A and sample E, the amount of coarse aggregate in the uppermost cylinder 37 is significantly reduced, and if the amount of coarse aggregate in the uppermost cylinder 37 is measured, the material can be separated. It was confirmed that it could be evaluated.
In the sample E, even at a position of 300 mm in height, a difference in the progress of material separation appears for each compaction time. Therefore, if the separation resistance evaluation container 1 in which a plurality of cylinders 3 are laminated is used, the position of material separation can be evaluated by measuring the amount of coarse aggregate for each cylinder 3.

As described above, according to the concrete evaluation method of the present embodiment, a certain amount of fresh concrete can be collected from the upper part of the container only by removing the cylinder 3 (the cylinder 36) at the upper part of the container. In addition, by measuring the mass of the coarse aggregate in the collected fresh concrete, it is possible to confirm the sinking condition of the aggregate, and as a result, it is possible to easily evaluate the material separation resistance of the fresh concrete. Become.
Further, since the cylinders 3 are engaged with each other via the engaging member 5, the cylinders 3 do not shift when the fresh concrete is put in, and the fresh concrete does not flow out.
Further, since the fresh concrete that overflows when the uppermost cylinder 3 is removed by the receiving material 4 is received by the receiving material 4, the fresh concrete can be easily collected.

Further, the separation resistance evaluation container 1 of the present embodiment can also be used for setting a guideline for the compaction time of concrete. For example, after putting concrete having a predetermined composition into the separation resistance evaluation container 1 and compacting it, coarse aggregate is collected from the uppermost cylinder 37 to calculate the unit coarse aggregate amount. Next, the relationship between the ratio of the measured coarse aggregate amount to the compound coarse aggregate amount and the compaction time is plotted, and an approximate curve is created from this plot. Then, the permissible value of the remaining amount of coarse aggregate can be set according to the concrete structure, and the guideline of the compaction time can be set from the intersection of the permissible value of the remaining amount of coarse aggregate and the approximate curve. .. Table 3 and FIG. 7 show the results of experiments carried out on six types of concrete samples (samples A to F) having different formulations. In this experiment, the samples A to F were put into the separation resistance evaluation container 1 and compacted for 0 seconds, 5 seconds, 10 seconds, and 20 seconds, and then the coarse aggregate was collected from the uppermost cylinder 37. , The unit coarse aggregate amount (measurement unit coarse aggregate amount) was calculated. Next, the ratio of the measurement unit coarse aggregate amount to the compounding unit coarse aggregate amount is calculated, and the relationship between the measurement unit coarse aggregate amount ratio and the compaction time to the compounding unit coarse aggregate amount is plotted and this is performed. An approximate curve was created from the plot. By using this graph, it is possible to set a guideline for the concrete compaction time according to the structure. For example, when the threshold value of the remaining amount of coarse aggregate is set to 80%, the standard compaction time of each sample is about 4 to 5 seconds for samples A, C, and D, and about 2 to 3 seconds for sample B. The sample E may be set to about 1 second, and the sample F may be set to about 7 seconds.

Although the embodiments according to the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-mentioned components can be appropriately modified without departing from the spirit of the present invention.
For example, in the above embodiment, the case where the separation resistance evaluation container 1 is formed by stacking six cylinders 3 has been described, but the number of cylinders 3 constituting the separation resistance evaluation container 1 is limited. It is not something that is done. For example, it may be composed of two cylinders 3 of an upper cylinder and a lower cylinder. At this time, it is desirable that the lower cylinder has a height larger than that of the upper cylinder.
Further, in the above embodiment, the case where the sedimentation state of the coarse aggregate is estimated by measuring the amount of coarse aggregate on the upper part of the fresh concrete has been described, but the amount of coarse aggregate for each depth may be measured. .. In this case, the cylinder 3 of the separation resistance evaluation container 1 is removed in order from the top, and the amount of coarse aggregate in the collected concrete is measured each time the cylinder 3 is removed.
Further, the receiving material 4 may be installed as needed.
In the above embodiment, the case where the engaging member 5 is attached to the lower end of the tubular body 3 has been described, but the engaging member 5 protrudes from the upper end of the tubular body 3 and is inserted into another tubular body 3 directly above. It may be one. The engaging member 5 may be a portion integrally molded with the tubular body 3. Further, the engaging member 5 may be provided as needed or may be omitted.
In the above embodiment, the case where a part of the concrete is collected after compaction has been described, but the compaction step S3 may be omitted.
In the above embodiment, the case where the relationship between the unit coarse aggregate amount and the compaction time is plotted and an approximate curve is created from this plot has been described, but it is not always necessary to plot the unit coarse aggregate amount and the compaction. The formula of the approximate curve may be calculated from the relationship with time. By using this formula, the unit coarse aggregate amount when the compaction time is zero can be calculated.

1 Separation resistance evaluation container 2 Bottom plate 3 Cylinder 4 Receiving material 5 Engagement member S1 Container preparation process S2 Filling process S3 Compaction process S4 Concrete sampling process S5 Aggregate amount measurement process S6 Evaluation process

Claims (5)

A container preparation process that prepares a container in which multiple cylinders are connected vertically,
The filling process of filling the container with fresh concrete and
A concrete sampling process for collecting the fresh concrete that overflowed by removing the uppermost cylinder, and
An aggregate amount measuring step for measuring the mass of the coarse aggregate in the collected fresh concrete, and
A method for evaluating concrete, which comprises an evaluation step of evaluating the material separation resistance of the fresh concrete based on the mass of the coarse aggregate. It further includes a compaction step of compacting the plurality of containers filled with fresh concrete.
In the compaction step, the compaction time is different for each container.
The concrete evaluation method according to claim 1, wherein in the evaluation step, the material separation resistance of fresh concrete is evaluated based on the relationship between the mass of the coarse aggregate and the compaction time. In the evaluation step, the work of obtaining an approximate curve from the unit coarse aggregate amount calculated from the mass of the coarse aggregate and the compaction time, and
The method for evaluating concrete according to claim 2, wherein the work of obtaining a unit coarse aggregate amount when the compaction time is zero from the approximate curve is performed. With the bottom plate
A plurality of cylinders stacked vertically on the upper surface of the bottom plate are provided.
A container for evaluating separation resistance, wherein the cylinder body includes an engaging member that protrudes from the upper end or the lower end of the cylinder body and is inserted into another adjacent cylinder body. The container for evaluating separation resistance according to claim 4, further comprising a receiving material that is provided around the outer surface of the cylinder.

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