Method for evaluating the strength of concrete structures and method for constructing buildings using concrete

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

Technical Field

[0001] The present invention relates to a method for evaluating the strength of concrete structures and a method for constructing buildings using concrete.

Background Art

[0002] In the construction of buildings using concrete, fresh concrete is poured into a formwork, and when a hardening reaction occurs in the concrete and sufficient initial strength is developed, the formwork is removed. The standard hardening time for concrete to function as a structural member is 28 days, but the formwork is usually removed in a shorter time than that.

[0003] Until sufficient initial strength is developed in the fresh concrete placed in the formwork, the formwork cannot be removed. Therefore, in order to remove the formwork, it is necessary to check whether the strength of the young concrete in the formwork has reached a sufficient strength to remove the formwork.

[0004] As inspection methods for concrete strength, various methods have been proposed. For example, at the time of pouring, test pieces are prepared separately from the pouring, and the strength of these test pieces is inspected. Also known are destructive inspections such as concrete core tests; micro-destructive inspections such as tests using boss specimens and small-diameter core tests; and non-destructive inspections such as the rebound hardness method, ultrasonic method, and electromagnetic wave radar method (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] 注:原文中 至 部分似乎有误,按照要求保留原文未进行翻译,你可检查确认。In the strength evaluation method using test pieces described above, a strength difference inevitably occurs between the actual concrete in the formwork (the object being evaluated) and the test piece. Although a correction is made to account for this strength difference, there are limitations to improving the accuracy of the strength evaluation of the object being evaluated. In contrast, destructive testing is a highly accurate method because it can measure the strength of the object being evaluated by directly taking a sample from the object and testing and analyzing it. However, it has the problem that damage to the object being evaluated is unavoidable. Similarly, even with microdestructive testing, repairs are necessary to the damaged areas, and the more test samples there are, the more problems similar to those encountered with destructive testing can arise. Furthermore, non-destructive testing has the advantage of being able to measure the strength over a wide area without damaging the object being evaluated. However, its measurement accuracy is not sufficient, and it cannot be considered an established evaluation method. Furthermore, in strength testing based on the hardening reaction of concrete, it is reasonable to eliminate the influence of the strength of the coarse aggregate itself contained in the concrete. In other words, accurately measuring the strength of the mortar portion is important for evaluating the degree of the concrete's hardening reaction.

[0007] In the construction of buildings using concrete, once the concrete is poured and the formwork is removed, the next steps (for example, installing insulation, fittings (window frames, etc.), applying interior finishing materials, or applying exterior wall materials) can be carried out. Therefore, removing the formwork earlier is an important factor in adhering to or shortening the construction period. There is a strong social demand for strict adherence to or shortening of construction deadlines. For example, in the construction of commercial facilities, a one-day delay in opening a store results in a decrease in sales and a loss. If the commercial facility is large, the amount of loss can be enormous. Also, in the construction of residential buildings, move-in dates are often scheduled to coincide with the start of the new school year or the fiscal year of companies, so delays in construction can have a significant impact on the social lives of residents. Establishing a technology that allows for the non-destructive, simple, and accurate measurement of the strength of young concrete within formwork on-site, and enables the quick removal of the formwork once the desired strength is reached, is an urgent issue in the construction industry and other related fields.

[0008] In view of the above circumstances, the present invention aims to provide a method for evaluating the strength of a concrete structure that can evaluate the strength of a concrete structure poured into a formwork on-site, non-destructively, simply, and with high accuracy. Furthermore, the present invention aims to provide a method for constructing a building using concrete to which this strength evaluation method is applied. [Means for solving the problem]

[0009] The present inventor's above-mentioned problems are solved by the following means. [1] A method for evaluating the strength of a concrete structure, comprising pouring ready-mix concrete into a formwork having through-holes that penetrate in the thickness direction, filling the through-holes with mortar, and measuring the penetration depth into the mortar by a pin penetration test. [2] The method for evaluating the strength of a concrete structure according to [1], wherein the plan view diameter of the through hole for filling with the aforementioned mortar is 5 to 20 mm. [3] A method for evaluating the strength of a concrete structure according to [1] or [2], wherein the through-hole for filling with the aforementioned mortar is formed by a pipe. [4] The pipe has a protruding portion that extends from the outer surface of the formwork, The method for evaluating the strength of a concrete structure as described in [3], wherein in the pin penetration test, the penetration testing machine used to perform the pin penetration test is attached to the protruding portion. [5] A method for evaluating the strength of a concrete structure according to any one of [1] to [4], wherein the shape of the through-hole for filling with the aforementioned mortar corresponds to the shape of the through-hole for arranging separators in the formwork. [6] A method for evaluating the strength of a concrete structure according to any one of [1] to [5], wherein an intrusion prevention portion is provided on the side of the through hole into which the mortar is filled, to prevent coarse aggregate in the fresh concrete from entering the through hole. [7] A method for evaluating the strength of a concrete structure as described in any one of [1] to [6], wherein the pin penetration energy in the aforementioned pin penetration test is 0.6 to 60 J. [8] A method for evaluating the strength of a concrete structure according to any one of [1] to [7], wherein the formwork has a plurality of through holes for filling with the mortar, and a pin penetration test is performed in each of the plurality of through holes. [9] A method for evaluating the strength of a concrete structure according to any one of [1] to [8], wherein the shape of the through hole for filling with the aforementioned mortar is circular in plan view.

[10] A method for constructing a building using concrete, comprising evaluating the strength of a concrete structure within a formwork using the strength evaluation method for concrete structures described in any one of [1] to [9], and determining the timing for removing the formwork based on the evaluation.

[0010] In the present invention and this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits. For example, when it is written as "A~B", the numerical range is "A or greater and B or less".

[0011] In the present invention and this specification, the term "filling" is not limited to a form in which mortar is poured to completely fill a space without any gaps, but also includes a state in which a portion of the space remains empty even after the mortar has been poured. [Effects of the Invention]

[0012] According to the present invention's method for evaluating the strength of concrete structures, the strength of concrete structures cast in formwork can be evaluated on-site, non-destructively, simply, and with high accuracy.

Brief Description of the Drawings

[0013] [Figure 1] It is a flowchart including the procedure of the strength evaluation method for concrete structures. [Figure 2] It is a schematic diagram showing a configuration example of a formwork. [Figure 3] It is a schematic diagram showing a configuration example of a formwork. [Figure 4] It is a schematic diagram showing a configuration example of a formwork. [Figure 5] It is a cross-sectional view schematically showing an enlarged through-hole provided in a formwork. [Figure 6] It is a cross-sectional view schematically showing a configuration example of a penetrometer. [Figure 7] It is a cross-sectional view schematically showing a configuration example of a penetrometer. [Figure 8] It is a flowchart illustrating the details of the measurement process. [Figure 9] It is a cross-sectional view schematically showing an enlarged state where a through-hole is formed by a pipe in a mock-up manner. [Figure 10] It is a schematic diagram showing a configuration example of an intrusion inhibiting portion. [Figure 11] It is a schematic diagram showing a configuration example of an intrusion inhibiting portion. [Figure 12] It is an explanatory diagram for explaining the filling process. [Figure 13] It is an explanatory diagram for explaining the state of a penetrometer in a pin penetration test.

Best Mode for Carrying Out the Invention

[0014] While referring to the drawings, preferred embodiments of the present invention will be described. Note that, in the drawings, the dimensions and scales of each part may be different from the actual ones for the convenience of explanation. Also, the drawings may be schematically shown for easy understanding. Furthermore, the scope of the present invention is not limited to the following embodiments other than those defined by the present invention.

[0015] <First Embodiment> Figure 1 is a flowchart showing the procedure for the concrete structure strength evaluation method of the present invention. This strength evaluation method includes a concrete placement step (Step St01), a curing step (Step St02), a measurement step (Step St03), and a demolding determination step (Step St04). The details of each of the above steps will be explained below with reference to Figure 1 as appropriate.

[0016] (Step St01: Concrete pouring process) In step St01, for example, ready-mix concrete is transferred from a ready-mix concrete mixer truck to a concrete pump truck, and then the ready-mix concrete is poured into the formwork 10 via a pump from the pump truck. Next, the ready-mix concrete poured into the formwork 10 is compacted using, for example, a vibrator. This ensures that the ready-mix concrete reaches every corner of the formwork 10 and removes excess air and moisture that would otherwise be needed for the concrete to harden. Subsequently, the surface of the compacted ready-mix concrete is smoothed using a trowel or similar tool. This prevents cracks from forming on the surface.

[0017] Figures 2-4 are schematic diagrams illustrating examples of the formwork 10's configuration. Figures 2, 3, and 4 are the front, side, and perspective views, respectively, of the formwork 10. As shown in Figures 2-4, the formwork 10 is provided with multiple through-holes 11. The multiple through-holes 11 are provided in each of the multiple side wall portions 12 that define the internal space E of the formwork 10 and communicate with the internal space E. That is, the multiple through-holes 11 are provided on all four sides of the formwork 10, on the front, back, and sides, and are arranged in a grid pattern. The multiple through holes 11 are formed, for example, by drilling holes in the formwork 10 with a drill or the like. In this case, it is preferable that the diameter D2 of the through holes 11 (see Figure 5) matches the diameter of the through holes for arranging separators (metal fittings that make the width of the formwork constant and give the formwork strength) (usually 9 mm). By matching the diameter of the through holes for arranging separators with the diameter D2 of the through holes 11, the through holes 11 can be easily formed in the formwork 10 on-site using the separator arranging tools without having to prepare any special tools. Therefore, the convenience of conducting the pin penetration test described later is improved. Alternatively, the multiple through holes 11 may be through holes that have been pre-provided in the formwork 10 for arranging separators. Since the through holes 11 are through holes for arranging separators, the process of separately providing through holes in the formwork 10 can be omitted, and the penetration depth, which will be described later, can be measured easily and without hassle. In this invention, the number of through-holes 11 provided in the formwork 10 is not limited to the number shown in Figures 2-4, and in practice, for example, 20 to 30 holes are provided. Furthermore, the arrangement of the through-holes 11 is not limited in any way to the arrangement shown in Figures 2-4.

[0018] Figure 5 is a schematic cross-sectional view showing a magnified view of the through-hole 11. 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 usually 12.5 mm. The shape of the through-hole 11 in plan view is typically circular. By making it circular, mortar can be filled into the through-hole 11 more efficiently than if the shape of the through-hole 11 in plan view were a different shape. Furthermore, a circular shape is preferable because it allows the through-hole to be used for the placement of the separator. Note that the shape of the through-hole 11 in plan view is not limited to a circle and may be a different shape.

[0019] When the plan view shape of the through hole 11 is circular, this circle is not limited to a perfect circle. For example, when the plan view shape of the through hole 11 is circular, its circularity can be 0.7000 to 1.0000, preferably 0.8000 to 1.0000, preferably 0.9000 to 1.0000, preferably 0.9500 to 1.0000, and preferably 0.9800 to 1.0000. The circularity is calculated by the following formula (1). In this invention, all plan view shapes with a circularity of 0.7000 to 1.0000 are included in the concept of a "circular" plan view shape. The same applies to the second embodiment described later.

[0020] Roundness = 4π × (area) ÷ (perimeter) 2 (1)

[0021] The plan view diameter of the through hole 11 (diameter D2 if the through hole 11 is a perfect circle in plan view) is preferably 5 to 20 mm, more preferably 6 to 20 mm, even more preferably 6 to 15 mm, even more preferably 6 to 12 mm, and also preferably 7 to 10 mm, from the viewpoint of preventing coarse aggregate from entering the through hole 11. In this invention, if the plan view shape of the through hole 11 is not a perfect circle, the plan view diameter of the through hole 11 means the equivalent diameter of a circle (the diameter of a perfect circle with the same area).

[0022] In step St01, the diameter D2 of the through-hole 11 is set to the diameter described above. This prevents coarse aggregate (for example, aggregate with a diameter of 10 mm or more) contained in the ready-mixed concrete from entering the through-hole 11 when the ready-mixed concrete is poured into the formwork 10, and instead allows mortar, from which the coarse aggregate has been removed, to enter the through-hole 11. In other words, by performing step St01, in which ready-mixed concrete is poured into the formwork 10, mortar enters the through-hole 11, and the through-hole 11 is filled with mortar.

[0023] (Step St02: Curing Process) In step St02, the fresh concrete poured into the formwork 10 in step St01 is allowed to cure for a predetermined number of days until it reaches a predetermined age (predetermined initial strength), thereby allowing the hardening reaction to proceed. The number of days is determined appropriately depending on the material of the fresh concrete, but it is preferable to set it to, for example, half a day or more and 14 days or less.

[0024] (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 only one of the through-holes 11. If the mortar, from which the coarse aggregate has been removed, is filled without any gaps in the through-holes 11, it is possible to achieve a certain level of measurement accuracy by performing the pin penetration test on only one of the through-holes 11. Furthermore, the measurement accuracy can be further improved by performing the pin penetration test on multiple through-holes 11 and averaging the results. In this invention, when we say that "the formwork has multiple through holes for filling with mortar, and a pin penetration test is performed in each of the multiple through holes," it means that a pin penetration test is performed on two or more of the multiple through holes in the formwork. In other words, it includes not only the form in which a pin penetration test is performed on all of the multiple through holes in the formwork, but also the form in which a pin penetration test is performed on some of the multiple through holes (two or more through holes) in the formwork. The pin penetration test is a test in which a pin P of a penetration tester 40 is driven into the mortar filled in a 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 measured, 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 (see, for example, Annual Proceedings of the Concrete Engineering, 2004, Vol. 26, No. 1, pp. 1833-1838). As the penetration tester 40, a penetration tester is used in which the energy of the pin driven 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. In addition, in the pin penetration test, the energy of the pin driven into the mortar is controlled so that the penetration depth of the pin P does not exceed the thickness of the formwork 10.

[0025] Figure 6 is a schematic cross-sectional view showing an example of the configuration of the penetration test machine 40, and shows the state in which the holding part 411 is at the bottom dead center. The penetration test machine 40 used in step St03 is configured to have, for example, a pin penetration test machine 41 and a plate-shaped member 42. The pin penetration test machine 41 has 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 tip shape of the pin P (the shape of the end on the side not held by the holding part 411) can be set as appropriate, for example, to be cylindrical or conical. The holding part 411 is configured to be movable in the longitudinal direction of the housing 412 when housed in the housing 412. As the pin penetration tester 41, for example, a commercially available product (product name: Pyrodin D6J, manufactured by FTS Co., Ltd.) that drives a pin into wood and measures the degree of wood deterioration from the depth of penetration may be used. The plate-shaped member 42 is an annular flat plate and has a through hole 42h. The plate-shaped member 42 is provided so as to face the end face 41S of the pin penetration tester 41 and may be attached to the end face 41S by an adhesive means such as double-sided tape.

[0026] Figure 7 is a schematic cross-sectional view showing the state in which the retaining portion 411 is at its top dead center. When the pin P is fully released by the operator, the end face 411S of the retaining portion 411 is located substantially flush with the surface 42S of the plate-shaped member 42. On the other hand, when the pin P is pulled up by the operator, the through hole 42h of the plate-shaped member 42 is exposed, as shown in Figure 6.

[0027] Figure 8 is a flowchart illustrating the procedure of step St03. This flowchart assumes that there is a significant variation in the degree of mortar filling into the through-holes 11, and is merely one example of the procedure for step St03. For example, if the mortar filling into multiple through-holes 11 can be performed substantially uniformly, step St03 can be appropriately modified or simplified accordingly. The procedure to be adopted can be determined appropriately according to the site conditions. Below, an example of step St03 will be described with reference to Figure 8 as appropriate, but the present invention is not limited in any way to the following embodiments.

[0028] First, pins P are sequentially driven into the mortar in each of the multiple pipes 20 with a constant force, and the penetration depth is measured (Step St13). Next, for each of the multiple measurements obtained in Step St13, the absolute value of the difference from the median is calculated (Step St23). Subsequently, from the multiple measurements obtained in Step St13, the measurements with the largest absolute values ​​are removed in order, based on the number calculated using the following formula (2) (Step St33). Next, the average value of the measurements that were not removed in Step St33 is calculated as the penetration depth d [mm] (Step St43).

[0029] k + N × 0.2 ... (2) N is the number of measurements, and k is the number of through-holes 11 in which the mortar defect rate is 20% or more. The defect rate is the percentage of the area of ​​the mortar that enters the through-hole 11 in a plan view (S2) to the area of ​​the through-hole 11 in a plan view (S1) ((S2 / S1) × 100).

[0030] Next, based on the estimated strength function that correlates the penetration depth d with the compressive strength σ, the compressive strength σ of the mortar in the through-hole 11 is calculated from the penetration depth d calculated in step St43 (step St53). The estimated strength function is expressed by, for example, the following equation (3). For example, in a preliminary experiment in which mortar was subjected to a pin penetration test using a pin penetration tester (product name: Pirrodin D6J, manufactured by FTS Co., Ltd.), it was confirmed that there is a correlation between the penetration depth d and the compressive strength σ of the mortar within the range of 3 to 30 MPa. The initial strength of the mortar portion of the concrete structure required to remove the formwork 10 is assumed to be around 5 to 15 MPa, and if it is possible to measure within the above range of compressive strength σ, it is possible to determine whether or not the mortar of the concrete structure inside the formwork 10 has reached the desired initial strength. In the following equation (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.

[0031] σ = s / (dt)···(3) s and t are constants.

[0032] (Step St04: Demolding Determination Process) In step St04, it is determined whether the compressive strength σ calculated in step St03 is equal to or greater than the demolding standard strength. The demolding standard strength is an indicator used to determine whether or not to demold (remove) the formwork 10, and is, for example, 5 to 15 MPa. If the compressive strength σ is equal to or greater than the demolding standard strength (YES in step St04), it is determined that the strength of the concrete structure poured into the formwork 10 is sufficient to remove the formwork 10, and the formwork 10 is demolded by the operator (step St05). On the other hand, if the compressive strength σ is less than the demolding standard strength (NO in step St04), the concrete structure poured into the formwork 10 is further cured (hardened) until the formwork 10 can be demolded. Note that step St04 and step Stn3 (n=2~5) shown in Figure 8 above may be performed by the operator or by an information processing device such as a computer.

[0033] As can be understood from the above explanation, according to the present invention, since the pin penetration test is performed on the mortar that has entered the through-hole 11, it is possible to prevent the pin P from directly striking the coarse aggregate in the fresh concrete during the penetration test. Therefore, the penetration depth can be measured with high accuracy. In addition, since the through-hole 11 into which the mortar enters is formed in advance in the formwork 10, the pin penetration test can be easily performed at the site where the fresh concrete has been poured through this through-hole 11 without demolding the formwork 10. Furthermore, since the mortar that enters the through-hole 11 in which the pin penetration test is performed hardens in the shape of a small-diameter protrusion that follows the shape of the through-hole 11, it can easily break off when the formwork 10 is demolded and be easily removed together with the formwork 10. In other words, the concrete structure strength evaluation method according to the present invention allows for the evaluation of the initial strength of a concrete structure poured into formwork 10 on-site, non-destructively, simply, and with high accuracy. Therefore, it is more convenient than conventional methods to determine whether the strength has reached a level that allows for the removal of formwork 10, making it possible to remove the formwork 10 at a more appropriate time and earlier, thereby contributing to a reduction in construction time.

[0034] <Second Embodiment> Figure 9 is a cross-sectional view that simulates an enlarged view showing a through-hole, into which mortar is filled, formed by a pipe. In the following description, the same configuration as in the first embodiment will not be described.

[0035] In the second embodiment, the formwork 10 has a plurality of side wall portions 12 and a pipe 20, and each of the plurality of through holes 24 into which mortar is filled is formed by the pipe 20. That is, the pipe 20 is inserted through the formwork 10, and the cavity inside the pipe 20 forms the through hole 24 into which mortar is filled. By inserting the pipe 20 through the through hole 11, for example, the diameter of the through hole 11 can be stabilized. Furthermore, as will be described later, there are advantages such as making it easier to determine the installation position of the pin penetration test machine by the shape of the pipe, and providing an intrusion obstruction portion in the pipe to more reliably prevent the intrusion of coarse aggregate. 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 advance in the formwork 10, and the pipe 20 is inserted through this through-hole 11 to form the through-hole 24 to which mortar is filled. The shape of the through-hole 24 in plan view is typically circular. Because the shape of the through-hole 24 in plan view is circular, mortar is filled into the through-hole 24 more efficiently than if it were a shape other than circular. Note that the shape of the through-hole 24 in plan view is not limited to circular and may be a shape other than circular. The following describes the case where the shape of the through-hole 24 in plan view is circular.

[0036] The outer diameter D3 of the pipe 20 preferably matches the diameter of the through-hole for separator installation. By matching the diameter of the through-hole for separator installation with the outer diameter D3, the through-hole for installing the pipe 20 can be easily formed in the formwork 10 on-site using the separator installation tool without the need to prepare any special tools. The inner diameter D4 of the pipe 20 (the diameter of the through-hole 24 into which the mortar is filled) is not particularly limited, but from the viewpoint of preventing coarse aggregate in the fresh concrete from entering the pipe 20, it is preferably 5 to 20 mm, more preferably 5 to 14 mm, even more preferably 5 to 11 mm, and also preferably 6 to 9 mm. The dimension D5 of the pipe 20 in the thickness direction of the side wall 12 is preferably thicker than the thickness of the side wall 12, for example, about 15 mm.

[0037] The pipe 20 has a projection 23 that protrudes from the outer surface S of the side wall 12. The dimension D6 of the projection 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 be made of resin or the like.

[0038] In the second embodiment, the pipe 20 is provided with an intrusion obstruction section 30, as shown in Figure 9. The intrusion obstruction section 30 is provided to block the inlet 21 of the pipe 20. A cap 50 may be provided on the outlet 22 side opposite to the inlet 21 (see Figure 12). The cap 50 is removed before the measurement process (step St03) is performed. The cap 50 may be provided with pores 50h to allow excess mortar to escape so that the pipe 20 is densely packed with mortar.

[0039] Figures 10 and 11 are schematic diagrams showing examples of the configuration of the penetration obstruction section 30. The penetration obstruction section 30 may include a pair of bridging members 31 that span the periphery of the inlet 21 of the pipe 20, as shown in Figure 10. In this case, it is preferable that the distance between one bridging member 31 and the other bridging member 31 is greater than the diameter of the pin P of the penetration tester 40. Alternatively, the penetration obstruction section 30 may have a configuration including an annular body 32 with a diameter smaller than the inner diameter D4 of the pipe 20, and a plurality of bridging members 33 that span the annular body 32 and the periphery of the inlet 21, as shown in Figure 11. It is preferable that the central axis of the annular body 32 and the central axis of the through hole 24 are on the same straight line, and it is preferable that the diameter of the annular body 32 is greater than the diameter of the pin P of the penetration tester 40.

[0040] Next, the method for evaluating the strength of a concrete structure according to the second embodiment will be described with reference to Figure 1 as appropriate. Procedures similar to those in the first embodiment will be omitted or simplified in their explanation.

[0041] (Step St01: Concrete pouring process) In step St01 according to the second embodiment, the pipe 20 is provided with an intrusion-inhibiting portion 30, which more reliably prevents coarse aggregate contained in the ready-mixed concrete from entering the pipe 20 when the ready-mixed concrete is poured into the formwork 10, so that only mortar from which the coarse aggregate has been removed enters the pipe 20. That is, when step St01, in which ready-mixed concrete is poured into the formwork 10, is performed, only mortar from which the coarse aggregate has been removed enters the pipe 20, and the through-hole 24 is filled with mortar.

[0042] (filling process) Figure 12 is an explanatory diagram illustrating the filling process. In the second embodiment, a filling process may be performed between the casting process (step St01) and the curing process (step St02) to eliminate the voids H in the mortar filled inside the pipe 20. In this process, vibration is applied to the pipe 20, for example, by a vibrator or other vibration exciter, so that the mortar is densely packed inside the pipe 20.

[0043] (Step St03: Measurement process) In step St03 of the second embodiment, a pin penetration test is performed on the mortar-filled through-hole 24, similar to the pin penetration test performed on each of the mortar-filled through-holes 11 in the first embodiment. Then, as in the first embodiment, the compressive strength σ is calculated from the penetration depth d.

[0044] Figure 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 Figure 13, the operator pulls up the pin P to expose the through-hole 42h, which is then hooked onto the protruding part 23 of the pipe 20, and the pin P is driven into the mortar inside the pipe 20. This positions the penetration testing machine 40 relative to the formwork 10, making it possible to reliably drive the pin P into the mortar and improving the efficiency of the pin penetration test. The aforementioned "hooking" means that the through-hole 42h is hooked onto the protruding part 23, thereby fixing the penetration testing machine 40 to the formwork 10.

[0045] [Differentiation] 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 modifications can be made without exceeding the scope of the present invention. Specific examples of modifications that can be applied to the above-described embodiment are given below. Two or more embodiments arbitrarily selected from the following examples may be combined as appropriate, within the scope that they do not contradict each other. Furthermore, the present invention is not limited in any way to the following modifications, except as provided in the present invention.

[0046] <Example 1> In the above embodiment, the formwork 10 is provided with multiple through holes 11, but it is not limited to this, and may be provided with only one.

[0047] <Modification 2> In the second embodiment described above, typically the pipe 20 is inserted through all of the multiple through holes 11, but it is not limited to this, and the pipe 20 may be inserted through only some of the multiple through holes 11.

[0048] <Variation 3> The penetration testing machine used for the pin penetration test is not limited to the penetration testing machine 40 exemplified in the above embodiment. For example, a Windsor pin device or a pneumatic penetration testing machine may be used. In other words, there are no restrictions on the type of penetration testing machine used for the pin penetration test, as long as it can drive in a pin of a desired size with a desired driving energy.

[0049] <Modification 4> The intrusion obstruction portion 30 is not limited to the embodiment illustrated above. For example, the intrusion obstruction portion 30 may be a needle (stake) driven into the inner surface of the formwork 10 so as to intersect with the entrance 21 of the pipe 20.

[0050] The method for evaluating the strength of a concrete structure according to the above embodiment is a method for determining whether or not to remove the formwork, but is not limited thereto, and the applications of the method for evaluating the strength of a concrete structure according to the present invention are not particularly limited.

[0051] The concrete structure strength evaluation method according to the present invention is applicable to various concrete building construction methods, which include evaluating the strength of the concrete structure within the formwork and determining the timing for removing the formwork based on this evaluation.

[0052] Furthermore, the effects described herein are merely descriptive or illustrative and not limiting. In other words, the present invention may produce other effects that a person skilled in the art can recognize from the description herein, in addition to or instead of the effects described herein.

[0053] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples. It is clear to any person with ordinary skill in the art of the present invention that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these are also understood to fall within the technical scope of the present invention. [Explanation of symbols]

[0054] 10...Formwork, 11,24,42h...Through-hole, 21...Entrance, 12...Side wall, 20...Pipe, 22...Exit, 23...Protruding part, 30...Intrusion obstruction part, 40...Penetration tester, 41...Pin penetration tester, 42...Plate-shaped member, 50...Cap, P...Pin.

Claims

1. A method for evaluating the strength of a concrete structure, comprising pouring ready-mix concrete into a formwork having through-holes that penetrate in the thickness direction, filling the through-holes with mortar, and measuring the penetration depth into the mortar by a pin penetration test without removing the formwork.

2. The method for evaluating the strength of a concrete structure according to claim 1, wherein the plan view diameter of the through hole for filling with the aforementioned mortar is 5 to 20 mm.

3. The method for evaluating the strength of a concrete structure according to claim 1 or 2, wherein the through-hole for filling with the aforementioned mortar is formed by a pipe.

4. The pipe has a protruding portion that extends from the outer surface of the formwork, 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 attached to the protruding portion.

5. A 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 for filling with the aforementioned mortar corresponds to the shape of the through-hole for arranging a separator in the formwork.

6. A method for evaluating the strength of a concrete structure according to any one of claims 1 to 5, wherein an intrusion prevention portion is provided on the side of the through hole into which the mortar is filled, to prevent coarse aggregate in the fresh concrete from entering the through hole.

7. A method for evaluating the strength of a concrete structure according to any one of claims 1 to 6, wherein the pin penetration energy in the pin penetration test is 0.6 to 60 J.

8. A method for evaluating the strength of a concrete structure according to any one of claims 1 to 7, wherein the formwork has a plurality of through holes for filling with mortar, and a pin penetration test is performed in each of the plurality of through holes.

9. A method for evaluating the strength of a concrete structure according to any one of claims 1 to 8, wherein the shape of the through hole for filling with the aforementioned mortar is circular in plan view.

10. A method for constructing a building using concrete, comprising evaluating the strength of a concrete structure within a formwork using the method for evaluating the strength of a concrete structure described in any one of claims 1 to 9, and determining the timing for removing the formwork based on the evaluation.

Images