JP2023132217A - Method of evaluating strength of concrete structures and method of constructing buildings using concrete - Google Patents

Abstract

To provide a concrete structure strength evaluation method which enables on-site, non-destructive, easy, and accurate strength evaluation of a concrete structure cast in a formwork, and to provide a concrete building construction method that implements the strength evaluation method.SOLUTION: A concrete structure strength evaluation method is provided, comprising casting ready mix concrete into a formwork having a through-hole penetrating in a thickness direction thereof to fill the through-hole with mortar, and measuring a penetration depth into the mortar by performing a pin penetration test.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for evaluating the strength of concrete structures and a method for constructing buildings using concrete.

When constructing buildings using concrete, fresh concrete is poured into formwork, and once the concrete hardens and develops sufficient initial strength, the formwork is removed. Although the standard curing time for concrete to function as a structural member is 28 days, forms are typically removed in less time.

The formwork cannot be removed until the ready-mixed concrete poured into the formwork has developed sufficient initial strength. Therefore, in order to remove the formwork, it is necessary to check whether the strength of the young concrete within the formwork has reached a strength sufficient to remove the formwork.

Various methods have been proposed for testing concrete strength. For example, during pouring, a test piece is prepared separately from the pouring process, and the strength of this test piece is inspected. In addition, destructive tests such as concrete core tests; microdestructive tests such as tests using boss specimens and small-diameter core tests; non-destructive tests such as repulsion hardness method, ultrasonic method, and electromagnetic radar method are known (for example, patent (See Reference 1).

Japanese Patent Application Publication No. 2005-322582

In the above-described strength evaluation method using a test piece, a difference in strength inevitably occurs between the concrete in the actual formwork (object to be evaluated) and the test piece. Although corrections are made in anticipation of the intensity difference, there are limitations to improving the accuracy of intensity evaluation of the evaluation target.
On the other hand, destructive testing is a highly accurate method in that the strength of the evaluation object itself can be measured by directly taking a sample from the evaluation object and testing and analyzing it. However, there is a problem in that damage to the evaluation object cannot be avoided.
Similarly, in micro-destructive testing, even if the damage is only micro-destructive, repairs are required for damaged areas, and as the number of test samples increases, problems similar to those of the above-mentioned destructive testing may occur.
Furthermore, non-destructive testing has the advantage of being able to measure strength over a wide range without destroying the object to be evaluated. However, the measurement accuracy is not sufficient and it cannot be said to be an established evaluation method.
Furthermore, in strength tests based on the hardening reaction of concrete, it is reasonable to exclude the influence of the strength of the coarse aggregate itself contained in the concrete. That is, it is important to measure the strength of the mortar portion with high accuracy in evaluating the degree of hardening reaction of concrete.

When constructing a building using concrete, once the formwork is removed after concrete is poured, the next work (for example, installing insulation material, fittings (window frames, etc.), applying interior finishing materials, etc.) , work such as pasting exterior wall materials). Therefore, expediting the time for removing the formwork is an important element in meeting or shortening the construction period.
There is a strong social demand for strict adherence to or shortening construction schedules. For example, in the construction of a commercial facility, if the opening of a store is delayed by one day, sales will decrease by that amount, resulting in damage. If the scale of the commercial facility is large, the amount of damage will be significant. Furthermore, when constructing housing, the move-in date is often scheduled to coincide with the new school term or the business year of companies, etc., and delays in construction can have a significant impact on the social lives of residents.
Establishment of technology that allows the strength of young concrete in formwork to be easily and accurately measured on-site, non-destructively, and to quickly remove the formwork when the desired strength is reached is an important step in construction. This is an urgent issue in the industry.

In view of the above circumstances, the present invention provides a method for evaluating the strength of a concrete structure cast in a formwork on-site, non-destructively, simply and with high precision. The task is to provide an evaluation method. Another object of the present invention is to provide a method for constructing a building using concrete to which the strength evaluation method is applied.

The above-mentioned problem of the present inventors is solved by the following means.
[1]
A concrete structure comprising placing fresh concrete in a formwork having a through hole penetrating in the thickness direction, filling the through hole with mortar, and measuring the penetration depth of the mortar by a pin penetration test. A method for evaluating the strength of objects.
[2]
The method for evaluating the strength of a concrete structure according to [1], wherein the through hole filled with the mortar has a diameter in a plan view of 5 to 20 mm.
[3]
The method for evaluating the strength of a concrete structure according to [1] or [2], wherein the through hole filled with the mortar is formed by a pipe.
[4]
The pipe has a protrusion that protrudes from the outer surface of the formwork,
The method for evaluating the strength of a concrete structure according to [3], wherein in the pin penetration test, a penetration testing machine for performing the pin penetration test is hung on the protrusion.
[5]
The strength of the concrete structure according to any one of [1] to [4], wherein the shape of the through hole filled with the mortar corresponds to the shape of the through hole for arranging the separator in the formwork. Evaluation method.
[6]
[1] to [5] An intrusion inhibiting portion is provided on the side of the through hole filled with the mortar on which the ready-mixed concrete is placed, which prevents coarse aggregate in the ready-mixed concrete from entering the through-hole. ] The method for evaluating the strength of a concrete structure according to any one of the above.
[7]
The method for evaluating the strength of a concrete structure according to any one of [1] to [6], wherein in the pin penetration test, the driving energy of the pin is 0.6 to 60 J.
[8]
The concrete structure according to any one of [1] to [7], wherein the formwork has a plurality of through holes filled with the mortar, and a pin penetration test is conducted in each of the plurality of through holes. Strength evaluation method.
[9]
The method for evaluating the strength of a concrete structure according to any one of [1] to [8], wherein the through hole filled with the mortar has a circular shape in plan view.
[10]
Evaluating the strength of the concrete structure in the formwork by the method for evaluating the strength of a concrete structure according to any one of [1] to [9], and determining the timing to remove the formwork based on the evaluation. A method of constructing buildings using concrete, including

In the present invention and this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as lower and upper limits. For example, when "A to B" is written, the numerical range is "A to B".

In the present invention and this specification, the term "filling" is not limited to a form in which mortar is inserted so as to fill a space without any gaps, but a part of the space remains as an empty space even after mortar is inserted. It is used to include the state of being.

According to the method for evaluating the strength of a concrete structure of the present invention, it is possible to evaluate the strength of a concrete structure cast in a formwork nondestructively, simply, and with high precision on site.

It is a flowchart including the procedure of the strength evaluation method of a concrete structure. FIG. 2 is a schematic diagram showing a configuration example of a formwork. FIG. 2 is a schematic diagram showing a configuration example of a formwork. FIG. 2 is a schematic diagram showing a configuration example of a formwork. FIG. 2 is an enlarged cross-sectional view schematically showing a through hole provided in a formwork. FIG. 2 is a cross-sectional view schematically showing a configuration example of a penetration testing machine. FIG. 2 is a cross-sectional view schematically showing a configuration example of a penetration testing machine. It is a flowchart illustrating details of a measurement process. FIG. 2 is an enlarged cross-sectional view schematically showing a state in which a through hole is formed by a pipe. FIG. 2 is a schematic diagram showing a configuration example of an invasion inhibiting section. FIG. 2 is a schematic diagram showing a configuration example of an invasion inhibiting section. It is an explanatory view for explaining a filling process. It is an explanatory view explaining the state of a penetration testing machine in a pin penetration test.

Preferred embodiments of the present invention will be described with reference to the drawings. Note that in the drawings, the dimensions and scale of each part may differ from the actual size for convenience of explanation. Further, the drawings may be shown schematically to facilitate understanding. Furthermore, the scope of the present invention is not limited to the forms shown below except as specified in the present invention.

<First embodiment>
FIG. 1 is a flowchart including the steps of the method for evaluating the strength of a concrete structure according to the present invention. The strength evaluation method includes a casting process (Step St01), a curing process (Step St02), a measuring process (Step St03), and a demolding determination process (Step St04). The details of each of the above steps will be described below with reference to FIG. 1 as appropriate.

(Step St01: pouring process)
In step St01, for example, fresh concrete is transferred from a fresh concrete mixer truck to a pressure truck, and the fresh concrete is poured into the formwork 10 from the pressure truck via a pump. Next, the fresh concrete poured into the formwork 10 is compacted using, for example, a vibrator. As a result, the fresh concrete spreads to every corner within the formwork 10, and unnecessary air and moisture are discharged while the fresh concrete hardens. Next, the surface of the compacted fresh concrete is smoothed using a trowel. This prevents cracks from forming on the surface.

2 to 4 are schematic explanatory diagrams showing configuration examples of the formwork 10, and FIGS. 2, 3, and 4 are a front view, a side view, and a perspective view of the formwork 10, respectively.
The formwork 10 is provided with a plurality of through holes 11, as shown in FIGS. 2 to 4. The plurality of through holes 11 are provided in each of the plurality of side walls 12 that define the internal space E of the formwork 10, and communicate with the internal space E. That is, the plurality of through holes 11 are provided on the front, back, and side surfaces of the formwork 10, and are arranged in a grid pattern.
The plurality of through holes 11 are, for example, through holes formed by drilling the formwork 10 with a drill or the like. In this case, the diameter D2 (see Figure 5) of the through-hole 11 matches the diameter of the through-hole (usually 9 mm) for installing the separator (a metal fitting that keeps the width of the formwork constant and gives it strength). It is preferable to do so. Since the diameter of the through hole for separator installation and the diameter D2 of the through hole 11 match, the through hole 11 can be formed in the formwork 10. Therefore, the convenience in carrying out the pin penetration test described later is improved.
Alternatively, the plurality of through holes 11 may be through holes that are previously provided in the formwork 10 for arranging separators. Since the through-hole 11 is a through-hole for arranging a separator, the step of separately providing a through-hole in the formwork 10 can be omitted, so that the penetration depth, which will be described later, can be easily and easily measured.
In the present invention, the number of through holes 11 provided in the formwork 10 is not limited to the number shown in FIGS. 2 to 4, and in reality, for example, about 20 to 30 holes are provided. Furthermore, the arrangement of the through holes 11 is not limited to the arrangement shown in FIGS. 2 to 4.

FIG. 5 is a schematic cross-sectional view showing the through hole 11 in an enlarged manner. At construction sites, formwork with a thickness of 12.5 mm is usually used. Therefore, the dimension D1 of the through hole 11 in the thickness direction of the side wall portion 12 is normally 12.5 mm. The shape of the through hole 11 in plan view is typically circular. By making the through hole 11 circular, the mortar is filled into the through hole 11 more efficiently than when the through hole 11 has a shape different from a circular shape in plan view. Further, a circular shape is preferable because the through hole for arranging the separator can be used. Note that the shape of the through hole 11 in plan view is not limited to a circle, and may have a shape different from a circle.

When the through hole 11 has a circular shape in plan view, the circular shape is not limited to a perfect circle. For example, when the through hole 11 has a circular shape in plan view, its circularity can be 0.7000 to 1.0000, preferably 0.8000 to 1.0000, and 0.9000 to 1.0000. It is also preferable to set it to 0000, it is also preferable to set it to 0.9500 to 1.0000, and it is also preferable to set it to 0.9800 to 1.0000. Circularity is calculated by the following formula (1). In the present invention, all shapes having a circularity of 0.7000 to 1.0000 in plan view are included in the concept of "circular" in plan view shape. This also applies to the second embodiment described below.

Circularity = 4π x (area) ÷ (perimeter) ² (1)

The diameter of the through hole 11 in plan view (diameter D2 when the through hole 11 is a perfect circle in plan view) is preferably 5 to 20 mm from the viewpoint of preventing coarse aggregate from entering the through hole 11. , more preferably from 6 to 20 mm, even more preferably from 6 to 15 mm, even more preferably from 6 to 12 mm, and even more preferably from 7 to 10 mm. In the present invention, when the planar view shape of the through hole 11 is not a perfect circle, the planar view diameter of the through hole 11 means an equivalent circle diameter (diameter of a perfect circle having the same area).

In step St01, the diameter D2 of the through hole 11 is set to the above-described diameter, so that when the ready-mixed concrete is poured into the formwork 10, coarse aggregate (for example, with a diameter of 10 mm or more) contained in the ready-mixed concrete is (aggregate) is inhibited from entering into the through hole 11, and mortar from which coarse aggregate has been removed from the fresh concrete enters into the through hole 11. That is, by executing step St01 of pouring fresh concrete into the formwork 10, mortar enters the through hole 11, and the through hole 11 is filled with mortar.

(Step St02: Curing process)
In step St02, the ready-mixed concrete cast in the formwork 10 in the previous step St01 is cured for a predetermined number of days to advance a hardening reaction until it reaches a predetermined age (predetermined initial strength). The number of days is appropriately determined depending on the material of the ready-mixed concrete, etc., but is preferably, for example, not less than half a day and not more than 14 days.

(Step St03: Measurement process)
In step St03, a pin penetration test is performed on the through holes 11 provided in the formwork 10. The pin penetration test may be performed on one of the through holes 11. If the through holes 11 are filled with mortar from which coarse aggregate has been removed without any gaps, it is possible to achieve a certain degree of measurement accuracy by simply performing a pin penetration test on one of the through holes 11. . Further, by performing a pin penetration test on a plurality of through holes 11 and averaging the results, measurement accuracy can be further improved.
Here, in the present invention, when "the formwork has a plurality of through holes filled with mortar, and a pin penetration test is carried out in each of the plurality of through holes," two of the plurality of through holes that the formwork has, This means performing a pin penetration test on more than one through hole. In other words, in addition to performing a pin penetration test on all of the multiple through holes of the formwork, pin penetration tests are performed on some of the through holes (two or more through holes) of the multiple through holes of the formwork. This term includes the manner in which the test is carried out.
In the pin penetration test, the pin P of the penetration tester 40 is penetrated into the mortar filled in the through hole 11, and the penetration depth of the pin P (the shortest distance between the surface 42S and the tip of the pin P) [mm] is determined. This is a measurement test, and the compressive strength σ [MPa] of the mortar is calculated from this penetration depth. It is widely known that when mortar is subjected to a pin penetration test, there is a correlation between the penetration depth (penetration resistance) and the compressive strength of the mortar (for example, Concrete Engineering Annual Transactions, 2004, Vol. (See Vol. 26, No. 1, p. 1833-1838). As the penetration tester 40, a penetration tester is used in which the driving energy of the pin into the mortar entering the pipe 20 is, for example, 0.6 to 60 J, preferably 3 to 12 J, more preferably 4 to 8 J. Further, in the pin penetration test, the driving energy of the pin P is controlled so that the penetration depth of the pin P does not exceed the thickness of the formwork 10.

FIG. 6 is a cross-sectional view schematically showing a configuration example of the penetration testing machine 40, and is a diagram showing a state in which the holding portion 411 is at the bottom dead center. The penetration tester 40 used in step St03 has, for example, a pin penetration tester 41 and a plate-like member 42. The pin penetration tester 41 includes a holding part 411 that holds a pin P, a cylindrical housing 412, and a cylindrical pin P that extends in the longitudinal direction of the housing 412. The diameter of the pin P is smaller than the diameter D2 of the through hole 11. The shape of the tip of the pin P (the shape of the end that is not held by the holding part 411) may be set as appropriate, and may be configured to have a cylindrical shape or a conical shape, for example. The holding portion 411 is configured to be movable in the longitudinal direction of the housing 412 while being housed in the housing 412 . As the pin penetration tester 41, for example, a commercially available product (trade name: Pirodin D6J, manufactured by FTS Co., Ltd.) that drives a pin into wood and measures the degree of deterioration of the wood from the penetration depth may be used. The plate member 42 is an annular flat plate and has a through hole 42h. The plate member 42 is provided to face the end surface 41S of the pin penetration tester 41, and may be attached to the end surface 41S using adhesive means such as double-sided tape.

FIG. 7 is a cross-sectional view schematically showing a state in which the holding portion 411 is at the top dead center. When the pin P is completely released by the operator, the end surface 411S of the holding portion 411 is located on substantially the same plane as the surface 42S of the plate member 42. On the other hand, when the pin P is pulled up by the operator, the through hole 42h of the plate member 42 is exposed, as shown in FIG.

FIG. 8 is a flowchart illustrating the procedure of step St03. Note that this flowchart is based on the premise that there are non-negligible variations in the degree of mortar filling into the through holes 11, and is merely an example of the procedure of step St03. For example, if the plurality of through holes 11 can be filled with mortar substantially uniformly, step St03 can be changed or simplified accordingly. The procedure to be adopted can be determined as appropriate depending on the situation at the site. An example of step St03 will be described below with reference to FIG. 8 as appropriate, but the present invention is not limited to the form described below.

First, the pin P is sequentially penetrated with a constant strength into the mortar that has entered each of the plurality of pipes 20, and the penetration depth is measured (Step St13). Next, for each of the plurality of measured values obtained in the previous step St13, the absolute value of the difference from the median value is calculated (step St23). Subsequently, from the plurality of measured values obtained in the previous step St13, measured values are omitted by the number calculated based on the following formula (2) in order of decreasing absolute value (step St33). Next, the average value of the measured values that were not omitted in the previous step St33 is calculated as the penetration depth d [mm] (step St43).

k+N×0.2...(2)
N is the number of measurements, and k is the number of through holes 11 with a mortar defect rate of 20% or more among the plurality of through holes 11. The defect rate is the percentage ((S2/S1)×100) of the area (S2) of the mortar that enters the through hole 11 in plan view relative to the area (S1) of the through hole 11 in plan view.

Next, based on the estimated strength function in which the penetration depth d and the compressive strength σ are associated, the compressive strength σ of the mortar in the through hole 11 is calculated from the penetration depth d calculated in the previous step St43. (Step St53). The estimated intensity function is expressed, for example, by equation (3) below. For example, in a preliminary experiment in which mortar was subjected to a pin penetration test using a pin penetration tester (trade name: Pirodin D6J, manufactured by FTS Corporation), the penetration depth was It has been confirmed that there is a correlation between d and compressive strength σ. The initial strength of the mortar part of the concrete structure required to remove the formwork 10 is assumed to be about 5 to 15 MPa, and if it is possible to measure the compressive strength σ in the above range, the concrete in the formwork 10 It can be determined whether the mortar of the structure has reached the desired initial strength. In the following formula (3), the constants s and t can be individually determined, for example, through preliminary tests, depending on the type of cement used, the mixing ratio with sand, etc.

σ=s/(d-t)...(3)
s and t are constants.

(Step St04: demolding determination step)
In step St04, it is determined whether the compressive strength σ calculated in the previous step St03 is greater than or equal to the demolding reference strength. The demolding reference strength is an index for determining whether or not to demold the mold 10 (remove the mold 10), and is, for example, 5 to 15 MPa. If the compressive strength σ is equal to or higher than the demolding reference strength (YES in step St04), it is determined that the strength of the concrete structure placed in the formwork 10 is sufficient to remove the formwork 10, The formwork 10 is demolded by the operator (step St05). On the other hand, if the compressive strength σ is less than the demolding reference strength (NO in step St04), the concrete structure placed in the formwork 10 is further cured (hardened) until the formwork 10 can be demolded. . Note that step St04 and step Stn3 (n=2 to 5) shown in FIG. 8 described above may be executed by an operator or may be executed by an information processing device such as a computer.

As understood from the above description, according to the present invention, the pin penetration test is performed on the mortar that has entered the through hole 11, so the pin P directly hits the coarse aggregate in the fresh concrete during the penetration test. This can be prevented. Therefore, the penetration depth can be measured with high precision. Furthermore, since the through-holes 11 into which the mortar enters are pre-formed in the formwork 10, pins can be easily pinned through the through-holes 11 at the site where fresh concrete is poured without removing the formwork 10. Penetration tests can be performed. Furthermore, the mortar that enters the through hole 11 where the pin penetration test is performed hardens in the shape of a small diameter protrusion that follows the shape of the through hole 11, so it easily breaks when the formwork 10 is demolded. Therefore, it can be easily removed together with the formwork 10.
That is, according to the method for evaluating the strength of a concrete structure according to the present invention, the initial strength of a concrete structure cast in the formwork 10 can be evaluated non-destructively, simply and with high precision on site. . Therefore, compared to conventional methods, it is more convenient to judge whether the strength has reached a level that allows the formwork 10 to be removed from the mold, and the formwork 10 can be removed at a more appropriate time. This makes it possible to remove the mold early, contributing to shortening the construction period.

<Second embodiment>
FIG. 9 is an enlarged sectional view schematically showing a state in which a through hole filled with mortar is formed of a pipe. In the following description, descriptions of configurations similar to those in the first embodiment will be omitted.

In the second embodiment, the formwork 10 has a plurality of side walls 12 and a pipe 20, and each of the plurality of through holes 24 filled with mortar is formed by the pipe 20. That is, the pipe 20 is inserted into the formwork 10, and the cavity inside the pipe 20 forms a through hole 24 that is filled with mortar. By inserting the pipe 20 into the through hole 11, for example, the diameter of the through hole 11 can be stabilized. In addition, as described later, it is possible to easily determine the installation position of the testing machine for pin penetration testing based on the shape of the pipe, and to more reliably prevent the intrusion of coarse aggregate by providing an intrusion prevention part in the pipe. There are also advantages to becoming
In order to form the through hole 24 with the pipe 20, a through hole 11 corresponding to the outer diameter D3 of the pipe 20 is formed in the formwork 10 in advance, and the pipe 20 is inserted into the through hole 11 and filled with mortar. A through hole 24 is formed. The shape of the through hole 24 in plan view is typically circular. Since the through-hole 24 has a circular shape in plan view, mortar is filled into the through-hole 24 more efficiently than when the through-hole 24 has a shape different from a circle. Note that the shape of the through hole 24 in plan view is not limited to a circle, and may be a shape different from a circle. Hereinafter, a case will be described in which the through hole 24 has a circular shape in plan view.

It is preferable that the outer diameter D3 of the pipe 20 matches the diameter of the through hole for arranging the separator. By matching the diameter of the through hole for separator installation with the outer diameter D3, the pipe 20 can be easily installed on site using a separator installation tool without preparing any special tools. Through holes can be formed in the formwork 10. The inner diameter D4 of the pipe 20 (the diameter of the through hole 24 filled with mortar) is not particularly limited, and from the viewpoint of preventing coarse aggregate in the ready-mixed concrete from entering the pipe 20, it is preferably 5 to 20 mm. The length is preferably from 5 to 14 mm, even more preferably from 5 to 11 mm, and even more preferably from 6 to 9 mm. The dimension D5 of the pipe 20 in the thickness direction of the side wall portion 12 is preferably thicker than the thickness of the side wall portion 12, and is, for example, about 15 mm.

The pipe 20 has a protrusion 23 that protrudes from the outer surface S of the side wall 12 . The dimension D6 of the protrusion 23 in the thickness direction of the side wall 12 is not particularly limited, but is, for example, about 3 mm. The pipe 20 is typically made of a metal material (such as aluminum), but may also be made of resin or the like.

In the second embodiment, the pipe 20 is provided with an intrusion inhibiting portion 30 as shown in FIG. The invasion inhibiting part 30 is provided so as to block the entrance 21 of the pipe 20. A cap 50 may be provided on the outlet 22 side opposite to the inlet 21 (see FIG. 12). The cap 50 is removed before the measurement process (step St03) is performed. The cap 50 may be provided with pores 50h that allow excess mortar to escape so that the pipe 20 is tightly packed with mortar.

10 and 11 are schematic diagrams showing a configuration example of the invasion inhibiting section 30. As shown in FIG. 10, the invasion inhibiting portion 30 may include a pair of bridging members 31 that bridge around the periphery of the inlet 21 of the pipe 20. In this case, the distance between one bridge member 31 and the other bridge member 31 is preferably larger than the diameter of the pin P of the penetration tester 40. In addition, as shown in FIG. 11, the penetration inhibiting portion 30 includes an annular body 32 whose diameter is smaller than the inner diameter D4 of the pipe 20, and a plurality of bridging members 33 that bridge the annular body 32 and the periphery of the inlet 21. The configuration may include the following. The central axis of the annular body 32 and the central axis of the through hole 24 are preferably on the same straight line, and the diameter of the annular body 32 is preferably larger than the diameter of the pin P of the penetration tester 40.

Next, a method for evaluating the strength of a concrete structure according to a second embodiment will be described with reference to FIG. 1 as appropriate. Note that descriptions of procedures similar to those in the first embodiment will be omitted or simplified.

(Step St01: pouring process)
In step St01 according to the second embodiment, the intrusion inhibiting portion 30 is provided in the pipe 20, so that when the ready-mixed concrete is poured into the formwork 10, the coarse aggregate contained in the ready-mixed concrete is prevented from entering the pipe 20. Only the mortar from which coarse aggregate has been removed from the fresh concrete enters into the pipe 20. That is, by executing step St01 of pouring fresh concrete into the formwork 10, only the mortar from which coarse aggregate has been removed from the fresh concrete enters the pipe 20, and the through holes 24 are filled with mortar. Ru.

(Filling process)
FIG. 12 is an explanatory diagram for explaining the filling process. In the second embodiment, a filling process for eliminating the void H of the mortar filled in the pipe 20 may be performed between the casting process (step St01) and the curing process (step St02). In this step, the pipe 20 is vibrated by an exciter such as a vibrator so that the pipe 20 is densely packed with mortar.

(Step St03: Measurement process)
In step St03 according to the second embodiment, a pin penetration test is performed on the through holes 24 filled with mortar, similar to the pin penetration test performed on each of the through holes 11 filled with mortar in the first embodiment. Execute. Next, similarly to the first embodiment, the compressive strength σ is calculated from the penetration depth d.

FIG. 13 is an explanatory diagram illustrating an example of the state of the penetration testing machine 40 in a pin penetration test. In the pin penetration test according to the second embodiment, as shown in FIG. Drive the pin P into the mortar inside the pipe 20. Thereby, the penetration testing machine 40 is positioned with respect to the formwork 10, so it becomes possible to reliably drive the pin P into the mortar, and the efficiency of the pin penetration test is improved. In addition, the above-mentioned "hanging" means that the penetration tester 40 is fixed to the formwork 10 by hooking the through hole 42h on the protrusion 23.

[Modified example]
Although an example of a preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes may be made within the scope of the present invention. Examples of specific modifications that can be made to the above-mentioned embodiments are given below. Two or more aspects arbitrarily selected from the examples below may be combined as appropriate to the extent that they do not contradict each other. Note that the present invention is not limited to the following modifications other than what is specified in the present invention.

<Modification 1>
In the embodiment described above, a plurality of through holes 11 are provided in the formwork 10, but the present invention is not limited to this, and only one through hole may be provided.

<Modification 2>
In the second embodiment described above, the pipe 20 is typically inserted into all of the plurality of through holes 11, but the pipe 20 is not limited to this, and the pipe 20 is inserted into only some of the through holes 11 among the plurality of through holes 11. It may also be an embodiment in which the

<Modification 3>
The penetration testing machine that performs the pin penetration test is not limited to the penetration testing machine 40 exemplified in the above embodiment, and for example, a Windsor pin device or a penetration testing machine using air pressure may be used. That is, as long as a pin of a desired size can be driven in with a desired driving energy, there is no restriction on the type of penetration testing machine that performs the pin penetration test.

<Modification 4>
The invasion inhibiting section 30 is not limited to the embodiments exemplified in the above embodiments. For example, the penetration inhibiting portion 30 may be a needle (pile) driven into the inner peripheral surface of the formwork 10 so as to intersect the entrance 21 of the pipe 20.

The method for evaluating the strength of a concrete structure according to the above embodiment is a method for determining whether or not to demold the formwork, but is not limited to this, and the application of the method for evaluating the strength of a concrete structure according to the present invention is not limited to this. is not particularly limited.

The method for evaluating the strength of a concrete structure according to the present invention includes evaluating the strength of a concrete structure within a formwork, and determining the timing to remove the formwork based on this evaluation. Applicable to construction methods.

Further, the effects described in this specification are merely explanatory or illustrative, and are not limiting. That is, the present invention can have other effects that can be recognized by those skilled in the art from the description of this specification, in addition to or in place of the above effects.

Although preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field of the present invention can come up with various changes or modifications within the scope of the technical idea stated in the claims. It is understood that these also naturally fall within the technical scope of the present invention.

10...Formwork, 11,24,42h...Through hole, 21...Inlet, 12...Side wall part, 20...Pipe, 22...Outlet, 23...Protrusion part, 30...Intrusion inhibiting part, 40...Penetration tester, 41... Pin penetration tester, 42...Plate member, 50...Cap, P...Pin.

Claims (10)

A concrete structure comprising placing fresh concrete in a formwork having a through hole penetrating in the thickness direction, filling the through hole with mortar, and measuring the penetration depth of the mortar by a pin penetration test. A method for evaluating the strength of objects. The method for evaluating the strength of a concrete structure according to claim 1, wherein the diameter of the through hole filled with the mortar in plan view is 5 to 20 mm. The method for evaluating the strength of a concrete structure according to claim 1 or 2, wherein the through hole filled with the mortar is formed of a pipe. The pipe has a protrusion that protrudes from the outer surface of the formwork,
4. The method for evaluating the strength of a concrete structure according to claim 3, wherein in the pin penetration test, a penetration testing machine for performing the pin penetration test is hung on the protrusion. The method for evaluating the strength of a concrete structure according to any one of claims 1 to 4, wherein the shape of the through hole filled with the mortar corresponds to the shape of a through hole for arranging a separator in the formwork. . According to any of claims 1 to 5, an intrusion inhibiting portion is provided on the side of the through hole to be filled with the mortar on which the ready-mixed concrete is cast, to prevent coarse aggregate in the ready-mixed concrete from entering into the through-hole. A method for evaluating the strength of a concrete structure according to any one of the items. The method for evaluating the strength of a concrete structure according to any one of claims 1 to 6, wherein in the pin penetration test, the driving energy of the pin is 0.6 to 60 J. Strength evaluation of a concrete structure according to any one of claims 1 to 7, wherein the formwork has a plurality of through holes filled with the mortar, and a pin penetration test is conducted in each of the plurality of through holes. Method. The method for evaluating the strength of a concrete structure according to any one of claims 1 to 8, wherein the through hole filled with the mortar has a circular shape in plan view. The method for evaluating the strength of a concrete structure according to any one of claims 1 to 9 includes evaluating the strength of the concrete structure within the formwork, and determining the timing for removing the formwork based on the evaluation. methods of constructing buildings using concrete, including

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