JP7337734B2 - Concrete evaluation method - Google Patents

Description

The present invention relates to a concrete evaluation method .

Concrete is mixed and designed so that it exhibits the necessary strength after hardening and ensures the necessary workability during construction. The workability of fresh concrete has been evaluated by the slump test for evaluating the consistency of concrete.
However, even with concrete having the same slump value, there may be a difference in material separation resistance. Material segregation resistance of concrete has a great influence on concrete compaction and pumping. On the other hand, there is no method for quantitatively evaluating the material separation resistance of concrete, and at present, it is common to determine the presence or absence of separation by visually confirming the sinking condition of concrete aggregates.
Patent Document 1 discloses, as a test method for evaluating material separation resistance of concrete, a test method using a concrete sample after a slump flow test. In this test method, by placing multiple steel rings with different diameters concentrically on the bed plate after the slump flow test, the concrete sample is divided radially into multiple regions, and each Material segregation resistance is evaluated by measuring the coarse bone mass ratio in the region.
However, in the test method of Patent Document 1, it is necessary to calculate the coarse bone mass ratio for all regions, which is time-consuming. 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 use the measurement results to calculate the coarse aggregate mass ratio.

Japanese Patent Application Laid-Open No. 2003-322602

An object of the present invention is to propose a concrete evaluation method that enables evaluation of the separation resistance of fresh concrete by a simple measurement method.

The concrete evaluation method of the present invention for solving the above problems includes a container preparation step of preparing a container in which a plurality of cylindrical bodies are arranged vertically, a filling step of filling fresh concrete in the container, and a top A concrete collection step of collecting the fresh concrete overflowing by removing the cylindrical body of, an aggregate amount measurement step of measuring the mass of coarse aggregate in the collected fresh concrete, and the coarse aggregate and an evaluation step of evaluating material separation resistance of the fresh concrete by mass. According to this concrete evaluation method, a certain amount of fresh concrete can be collected from the upper part of the container simply by removing the cylindrical body at the upper part of the container. In addition, by measuring the mass of coarse aggregate in the sampled fresh concrete, it is possible to confirm the degree of sinking of the aggregate. Therefore, it is possible to easily evaluate the material separation resistance of fresh concrete.
A plurality of containers filled with fresh concrete are compacted at different times for each container. By evaluating the separation resistance, the material separation resistance can be evaluated more accurately. In the evaluation process, the work of obtaining an approximate curve from the unit coarse aggregate amount calculated from the mass of coarse aggregate and the compaction time, and the unit coarse aggregate amount when the compaction time is zero from the approximate curve It is desirable to do the work you ask for.

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

1 is a front view of a separation resistance evaluation container according to the present embodiment; FIG. It is a top view of a baseplate. (a) is a plan view of a cylinder, and (b) is a sectional view of the cylinder. (a) is a plan view of the receiving material, and (b) is a sectional view of the receiving material. It is a flowchart which shows the procedure of a concrete evaluation method. (a) and (b) are graphs showing the results of an experiment conducted for a concrete evaluation method. It is a graph for demonstrating the setting method of the compaction time using the container for separation resistance evaluation.

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. The separation resistance evaluation container 1 includes a bottom plate 2, a plurality of cylinders 3, and a receiving member 4, as shown in FIG.
The bottom plate 2 is made of a steel plate having a square shape with a side of 360 mm and 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 cylindrical body 3. For example, the bottom plate 2 is not necessarily rectangular (square) such as a circular shape with a diameter larger than the outer shape of the cylindrical body 3. does not have to be Also, the bottom plate 2 is not limited to a steel plate, and may be, for example, a synthetic resin plate or a glass plate.

A plurality of cylindrical bodies 3 are vertically stacked on the upper surface of the bottom plate 2 . In this embodiment, seven cylindrical bodies 3 (cylindrical bodies 31 to 37) are stacked on the bottom plate 2. As shown in FIG. The cylindrical body 3 of this embodiment is made of a vinyl chloride pipe with an inner diameter of 250 mm, an outer diameter of 267 mm, and a height of 50 mm. In addition, the material which comprises the cylinder 3 is not limited. Moreover, the shape and size of the cylindrical body 3 are not limited, and for example, the inner diameter may be 200 mm or 300 mm.
Engagement members 5 are attached to the cylinders 3 (the cylinders 32 to 37 in the second to seventh stages from the bottom) other than the cylinder 31 in the lowest stage. The engaging member 5 protrudes from the lower end of the cylindrical body 3 and is inserted into the cylindrical body 3 directly below. The engaging member 5 is a tubular member having an outer diameter equal 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 projection length of the engaging member 5 from the lower end of the cylindrical body 3 is not limited, and may be appropriately determined to a size that allows engagement with the cylindrical body 3 on the lower side. The configuration of the engaging member 5 is not limited. For example, a plurality of plate-like engaging members 5 may be arranged at intervals in the circumferential direction of the cylindrical body 3, It may cover the outer periphery of the butted portion of the upper and lower cylinders 3 .

The receiving material 4 is provided around the outer surface of the cylindrical body 3 . The receiving member 4 is made of plastic resin, and includes a bottom portion 41 that is annular in 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 equivalent to the outer diameter of the cylindrical body 3 (268 mm in this embodiment) 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. Although the shape and dimensions of the receiving material 4 are not limited, 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 equal to the inner space of one cylindrical body 3. larger than its volume. The receiving material 4 of this embodiment is attached to the outer surface of the cylindrical body 3 (the cylindrical body 36) in the second stage from the top. A jig may be used to attach the receiving material 4 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 process S1, a filling process S2, a compaction process S3, a concrete extraction process S4, an aggregate amount measurement process S5, and an evaluation process S6.
The container preparation step S1 is a step of preparing the separation resistance evaluation container 1 . A container 1 for evaluating separation resistance is formed by vertically connecting a plurality of cylindrical bodies 3, 3, . . . on a bottom plate 2 (see FIG. 1). At this time, the receiving material 4 is attached to the outer circumference of the cylindrical 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 to be assembled in the container preparation step S1 is not limited.

The filling step S2 is a step of filling fresh concrete into the separation resistance evaluation container 1 . Fresh concrete is poured from above the separation resistance evaluation container 1 . The top surface of the fresh concrete is aligned with the top surface of the container 1 for evaluating separation resistance. In addition, the mixing ratio of the concrete is determined appropriately.

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 varied for each container. In this embodiment, the vibration times applied to the four separation resistance evaluation containers 1 are 5 seconds, 10 seconds, and 20 seconds, respectively. Compaction of fresh concrete is performed by an internal vibrator (vibrator) inserted in the container 1 for evaluating separation resistance. The fresh concrete may be compacted by applying vibration from the outer surface of the separation resistance evaluation container 1 or by shaking the separation resistance evaluation container 1 . Also, the vibrating time of the container is not limited to the above, and may be determined as appropriate.

The concrete extraction step S4 is a step of extracting 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 cylindrical body 37 is removed by pulling it upward. When the uppermost cylinder 37 is removed, the volume of the cylinder 37 (fixed amount) of fresh concrete overflows. Since the overflowed fresh concrete flows into the receiving material 4 attached to the outer periphery of the cylindrical 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 fluid state before the concrete immediately after compaction hardens.

The aggregate amount measurement step S5 is a step of measuring the mass of coarse aggregate in the sampled fresh concrete. First, coarse aggregate is collected from fresh concrete, and the cement paste adhering to the coarse aggregate is washed off. 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 other than the sieve.

The evaluation step S6 is a step of evaluating the material separation resistance of fresh concrete based on the mass of coarse aggregate. In evaluating 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 cylindrical 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 mixing (mixing unit coarse aggregate amount), the tendency of concrete material separation is determined. do.
In this embodiment, the material separation resistance of fresh concrete is evaluated based on the relationship between the mass of coarse aggregate and the compaction time. In the evaluation step S6 of the present embodiment, if the ratio of the unit coarse aggregate amount to the blending unit coarse aggregate amount is equal to or greater than a threshold value (for example, 95%), it is determined that the aggregates are not separated. Note that the size of the threshold may be determined as appropriate. Also, the method of determining the tendency of material separation is not limited. For example, the following method may be used to determine the tendency of material separation. 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 plots by, for example, the method of least squares. Read the unit coarse aggregate amount when the compaction time is zero from the approximation curve. If the ratio of the unit coarse aggregate amount when the compaction time to the unit coarse aggregate amount at the time of mixing design is zero is equal to or greater than a threshold value (for example, 95%), it is determined that the aggregates are not separated.

Next, the results of an experiment conducted with respect to the concrete evaluation method of this embodiment will be described.
First, two types of concrete samples (Sample A and Sample E) with different formulations were put into the separation resistance evaluation container 1 and compacted for 0, 5, 10, and 20 seconds. Coarse aggregate was collected every (every depth). Next, the mass of the coarse aggregate sampled for each cylinder 3 was measured, and the unit coarse aggregate amount for each cylinder 3 was calculated. Then, the ratio of the calculated unit coarse aggregate amount to the unit coarse aggregate amount at the time of blending was calculated. Table 1 and FIG. 6(a) show the ratio of the coarse aggregate amount for each cylinder 3 of sample A, and Table 2 and FIG. 6(b) show the ratio of the coarse aggregate amount for each cylinder 3 of sample E. show.

As shown in Table 1 and FIG. 6( a ), in sample A, the unit coarse aggregate amount with a height of 350 mm (the uppermost cylindrical body 37 ) is It was about 80%, and in other height ranges, it was in the range of about 90% to 110%. In addition, when the compaction time is 20 seconds, the amount of unit coarse aggregate with a height of 350 mm is significantly reduced by 41%, and the unit coarse aggregate with a height of 100 mm (second cylinder 32 from the bottom) Although the material weight increased to about 130%, it was within 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 is significantly reduced at a height of 350 mm (the uppermost cylindrical body 37), and at a height of 300 mm (second from the top) At the other heights, the linearity was close to horizontal, and the results were almost evenly distributed, although the result was 100% or less even at the stepped cylindrical body 36).
Therefore, in both cases of sample A and sample E, the decrease in the amount of coarse aggregate in the uppermost cylinder 37 is remarkable, and if the amount of coarse aggregate in the uppermost cylinder 37 is measured, material separation can be performed. It was confirmed that it can be evaluated.
In addition, in sample E, even at a height of 300 mm, a difference in progress of material separation appears for each compaction time. Therefore, by using the separation resistance evaluation container 1 in which a plurality of cylinders 3 are stacked, 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 cylindrical body 3 (the cylindrical body 36) at the upper part of the container. In addition, by measuring the mass of coarse aggregate in the sampled fresh concrete, it is possible to check the degree of sinking of the aggregate, and as a result, it is possible to easily evaluate the material separation resistance of fresh concrete. Become.
Further, since the cylinders 3 are engaged with each other via the engaging member 5, the cylinders 3 are not displaced when the fresh concrete is poured, and the fresh concrete does not flow out.
Moreover, since fresh concrete overflowing when the uppermost cylindrical body 3 is removed is received by the receiving material 4, it is easy to collect the fresh concrete.

In addition, the separation resistance evaluation container 1 of the present embodiment can also be used to set a rough standard for the compaction time of concrete. For example, after putting concrete of a predetermined composition into the separation resistance evaluation container 1 and compacting it, coarse aggregate is collected from the uppermost cylindrical body 37 and the unit coarse aggregate amount is calculated. Next, plot the relationship between the ratio of the measured coarse aggregate amount to the blended coarse aggregate amount and the compaction time, and create an approximate curve from this plot. Then, according to the concrete structure, the allowable value of the remaining amount of coarse aggregate can be set, and the standard of compaction time can be set from the intersection of the allowable value of the remaining amount of coarse aggregate and the approximation curve. . Table 3 and FIG. 7 show the results of experiments conducted on six types of concrete samples (Samples A to F) with different formulations. In this experiment, samples A to F were put into the separation resistance evaluation container 1 and compacted for 0, 5, 10, and 20 seconds, and then coarse aggregate was collected from the uppermost cylindrical body 37. , the unit coarse aggregate amount (measurement unit coarse aggregate amount) was calculated. Next, the ratio of the unit coarse aggregate amount to the mixing unit coarse aggregate amount is calculated, and the relationship between the ratio of the measuring unit coarse aggregate amount to the mixing unit coarse aggregate amount and the compaction time is plotted. A fitted curve was created from the plot. By using this graph, it is possible to set a guideline for concrete compaction time according to the structure. For example, when the threshold for the remaining amount of coarse aggregate is set to 80%, the compaction time for each sample is about 4 to 5 seconds for samples A, C, and D, and about 2 to 3 seconds for sample B. Sample E should be about 1 second, and sample F should be 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 the constituent elements described above can be appropriately modified without departing from the scope of the present invention.
For example, in the above embodiment, the case of forming the separation resistance evaluation container 1 by stacking six cylinders 3 was described, but the number of cylinders 3 constituting the separation resistance evaluation container 1 is limited. not to be For example, it may be composed of two cylinders 3, an upper cylinder and a lower cylinder. At this time, it is desirable that the lower cylinder has a greater height than the upper cylinder.
Further, in the above-described embodiment, the case of estimating the sedimentation state of coarse aggregate is described by measuring the amount of coarse aggregate in the upper part of the fresh concrete, but the amount of coarse aggregate for each depth may be measured. . In this case, the cylindrical bodies 3 of the separation resistance evaluation container 1 are removed in order from the top, and the amount of coarse aggregate in the sampled concrete is measured each time the cylindrical bodies 3 are removed.
Moreover, the receiving material 4 may be installed as needed.
In the above embodiment, the engagement member 5 is attached to the lower end of the cylinder 3, but the engagement member 5 protrudes from the upper end of the cylinder 3 and is inserted into another cylinder 3 directly above. can be anything. In addition, the engagement member 5 may be a portion integrally formed with the cylindrical body 3 . Moreover, the engaging member 5 may be provided as required, and may be omitted.
In the above-described embodiment, a case where a part of the concrete is sampled after compaction has been described, but the compaction step S3 may be omitted.
In the above embodiment, the relationship between the unit coarse aggregate amount and the compaction time is plotted, and the case of creating an approximate curve from this plot has been described. An approximate curve formula may be calculated from the relationship with time. Using this formula, it is possible to calculate the unit coarse aggregate amount when the compaction time is zero.

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

Claims (3)

a container preparation step of preparing a container in which a plurality of cylindrical bodies are arranged vertically;
a filling step of filling fresh concrete into the container;
a concrete collecting step of collecting the fresh concrete that has overflowed by removing the uppermost cylindrical body;
an aggregate amount measuring step of measuring the mass of coarse aggregate in the collected fresh concrete;
and an evaluation step of evaluating material separation resistance of the fresh concrete based on the mass of the coarse aggregate. Further comprising a compaction step of compacting the plurality of containers filled with fresh concrete,
In the compaction step, the compaction time is varied for each container,
2. The concrete evaluation method according to claim 1, wherein, in said evaluation step, material separation resistance of fresh concrete is evaluated based on the relationship between the mass of coarse aggregate and compaction time. In the evaluation step, an operation of obtaining an approximate curve from the unit amount of coarse aggregate calculated from the mass of coarse aggregate and the compaction time;
3. The concrete evaluation method according to claim 2, further comprising the step of obtaining a unit coarse aggregate amount when the compaction time is zero from the approximation curve.

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