Concrete specimen framework, concrete specimen preparation method, early-age strength test method and concrete structure strength test method

Abstract

To prepare a concrete specimen having strength development properties close to those of a concrete structure, and to perform a strength test using the concrete specimen.SOLUTION: A framework 1 is composed of a plurality of (two in the figure) formwork members 1a and 1b each having a cylindrical half-split shape made of plastic or metal. The framework members 1a and 1b are fixed by a fixture 2 such as a hose band. A gap (g) is provided between each of the adjacent framework members 1a and 1b. A water-permeable sheet 3 (a water-permeable member) is attached to an inner peripheral surface of the framework 1, and a part of the water-permeable sheet 3 is exposed to the outside of the framework 1 through the gap g. The moisture contained in the concrete filling the inside of the framework 1 escapes from the gap (g) to the outside of the framework 1 by water permeation and moisture diffusion effects of the water permeable sheet 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for preparing a concrete specimen and using the concrete specimen to perform an early age strength test and a concrete structure strength test. [Background technology]

[0002] The slip form method is known, in which concrete is poured continuously while the formwork is raised. In this method, the concrete is demolded within a few hours after pouring, so the concrete must have a compressive strength (for example, 0.06 to 0.1 N / mm depending on the height of the structure) that can support its own weight when demolded. 2 degree) is necessary.

[0003] Concrete strength control is carried out, for example, by preparing cylindrical concrete specimens and measuring their compressive strength, and by having an expert insert reinforcing bars into the concrete structure (actual structure) at the casting site. Regarding formwork for concrete specimens, the technology disclosed in Patent Document 1, for example, is known.

[0004] However, such early-age compressive strength differs between concrete specimens prepared in steel forms according to the JIS A 1132 standard and concrete structures. Experiments conducted by the inventors of the present application showed that the strength development characteristics of concrete specimens and concrete structures differ, as illustrated in Figure 10, and that concrete structures constructed using the slip-form method tend to develop strength faster than concrete strength development in concrete specimens. This raises the risk that the accuracy of strength control using concrete specimens may be unreliable. In Figure 10, the vertical positions of the concrete specimens and concrete structures are represented by layer numbers, with the first layer representing the lowest position. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-53514 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above-mentioned background, and aims to prepare concrete specimens having strength development properties similar to those of concrete structures constructed by the slip form method, and to conduct strength tests using the concrete specimens. [Means for solving the problem]

[0007] The concrete specimen formwork of the present invention is a concrete specimen formwork for producing concrete specimens used in early-age strength tests using the slip form method, and has a structure on the side of the formwork that allows moisture in the concrete filled inside the formwork to escape to the outside of the formwork.

[0008] The structure may include a void extending from the inside to the outside in the axial direction of the formwork, and a water-permeable member, which may be arranged along the inner wall surface of the formwork and inserted into the void so that a portion of it is exposed to the outside of the formwork.

[0009] The formwork may be made up of a plurality of formwork members, and the gap may be located between adjacent formwork members.

[0010] The formwork member may have a half-cylindrical shape, the gap may be provided so as to extend from the upper end to the lower end between the two formwork members, and the permeable member may be inserted into the gap extending from the upper end to the lower end between the two formwork members.

[0011] Furthermore, the method for producing a concrete specimen according to the present invention uses the above-mentioned concrete specimen formwork to produce a concrete specimen to be used in an early age strength test in a slip form construction method.

[0012] The concrete specimen may be prepared by applying a load by a weight to the concrete poured into the concrete specimen formwork.

[0013] Furthermore, the early age strength testing method according to the present invention uses a concrete specimen produced using the above concrete specimen formwork to test early age strength in slip form construction.

[0014] In addition, the concrete structure strength testing method of the present invention uses a concrete specimen prepared using the above-mentioned concrete specimen formwork to test the strength of a concrete structure that is cast using a formwork with a gap at the bottom. [Effects of the Invention]

[0015] According to the present invention, a concrete specimen having strength development characteristics similar to those of a concrete structure can be prepared, and an appropriate demolding time can be determined by conducting a strength test using the concrete specimen. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a perspective view of a concrete specimen formwork according to one embodiment of the present invention; [Figure 2] Plan view of formwork for concrete specimens. [Figure 3] Side view of formwork for concrete specimens. [Figure 4] 1 is a flowchart showing a method for preparing a concrete specimen. [Figure 5] 1 is a diagram illustrating the process of preparing a concrete specimen. [Figure 6] 1 is a diagram illustrating the process of preparing a concrete specimen. [Figure 7] Table showing concrete mixes. [Figure 8] 10 is a graph illustrating the results of unconfined compressive strength for concrete specimens. [Figure 9]10 is a graph illustrating the amount of dewatering of a concrete specimen depending on whether or not a water-permeable sheet is present. [Figure 10] 2 is a graph illustrating the time required for concrete specimens and concrete structures to reach their demolding strength. [Figure 11] Schematic diagram explaining the principle of dewatering from a concrete specimen. [Figure 12] Graphs illustrating the time it takes for concrete specimens and concrete structures made using this formwork to reach their demolding strength. DETAILED DESCRIPTION OF THE INVENTION

[0017] As shown in Figure 10, the strength development characteristics of the concrete specimen and the concrete structure constructed by the slip form method differ, and the concrete structure tended to develop strength faster than the concrete specimen. The inventors of the present application hypothesized the following reason for this.

[0018] In the slip form method, a small gap (for example, about 3 to 4 mm) is left at the bottom of the formwork, and concrete is poured continuously while the formwork is raised (for example, about 25 mm at a time, every 15 minutes). As shown in Figure 11, as the formwork rises, a gap appears between the formwork and the concrete, and water from bleeding and other sources escapes through this gap, dehydrating the concrete, which is thought to increase the strength of the concrete. Furthermore, the concrete in the lower layer is consolidated by the weight of the concrete in the upper layer, and this consolidation is thought to also cause dehydration.

[0019] On the other hand, regular concrete cylindrical specimens are made in formwork with sealed sides and bottoms that prevent water from leaking out. Therefore, it is expected that the amount of water lost over time will differ between concrete structures cast using the slip form method and regular concrete cylindrical specimens.

[0020] Therefore, the inventors of the present application have invented a formwork having a structure that promotes the dehydration effect when preparing concrete specimens. Fig. 1 is a perspective view of a concrete specimen formwork for preparing concrete specimens used in early-age strength tests using the slip-form construction method. Fig. 2 is a plan view of the concrete specimen formwork, and Fig. 3 is a side view of the concrete specimen formwork.

[0021] 1 to 3, formwork 1 is composed of multiple (two in the figure) formwork members 1a and 1b each having a half-cylindrical shape and made of, for example, plastic or metal. These formwork members 1a and 1b are fixed together with fasteners 2 such as hose bands. The bottom of formwork 1 is integrated with the half-cylindrical formwork members 1a and 1b by, for example, gluing. Note that formwork 1 does not necessarily have to be cylindrical.

[0022] Between adjacent formwork members 1a, 1b, there is a gap g that runs from the inside to the outside in the axial direction of the cylindrical shape. This gap g is provided on the side of formwork 1 so as to reach from the upper end to the lower end between the two formwork members 1a, 1b. When preparing a concrete specimen, concrete is filled into formwork 1, and the moisture contained in that concrete (i.e., the concrete specimen) is designed to escape through this gap g to the outside of formwork 1. The width of gap g needs to be wide enough to allow the moisture contained in the concrete filled inside formwork 1 to pass through, but it should be wide enough to prevent the concrete itself filled inside formwork 1 from leaking out.

[0023] Furthermore, a water-permeable sheet 3 (water-permeable member) (for example, Abanon manufactured by Maeda Kogyo Steel Co., Ltd.) may be attached to the inner peripheral surface of the formwork 1, with a portion of the water-permeable sheet 3 exposed to the outside of the formwork 1 through the gap g. In other words, the water-permeable sheet 3 is arranged along the inner wall surface of the formwork 1, and both ends thereof are inserted into the gap g extending from the upper end to the lower end between the two formwork members 1a, 1b, with a portion of the sheet exposed to the outside of the formwork 1. The water-permeable member does not necessarily have to be in sheet form. The water-permeable sheet 3 may also be attached to the inner peripheral surface of the formwork 1 with double-sided adhesive tape.

[0024] The moisture contained in the concrete filled inside the formwork 1 is released through the permeable sheet 3 to the outside of the formwork 1 through the gap g due to the permeability effect of the permeable sheet 3 and the drainage effect of the permeated excess water.

[0025] Fig. 4 is a flow chart showing a concrete specimen fabrication method for fabricating a concrete specimen. In Fig. 4, an operator assembles formwork 1 having the above-described structure (step S1).

[0026] Next, the worker fills the created formwork 1 with concrete c from above into the interior thereof (step S2), as illustrated in Fig. 5. An example of the mix proportions of the concrete c used at this time is illustrated in Fig. 7.

[0027] Next, as shown in Fig. 6, the worker places a weight w on the concrete c filled in the formwork 1 and applies a load to the concrete c (step S3). At this time, the weight of the weight w is, for example, approximately the same as the weight of the filled concrete c. As a predetermined time passes and the concrete c hardens, the moisture contained in the concrete c filled inside the formwork 1 escapes to the outside.

[0028] After a predetermined time has elapsed, the worker caps the top surface of the prepared concrete specimen to make it smooth (step S4). After the capping has hardened, the worker removes the concrete specimen from the formwork 1 (step S5).

[0029] Next, the worker performs a uniaxial compression test on the concrete specimen (step S6). This uniaxial compression test is one of the tests for early-age strength in the slip form construction method.

[0030] Then, the worker determines whether the concrete structure can be removed from the form based on the results of the uniaxial compression test (Step S7). As mentioned above, in the slip form method, there is a small gap at the bottom of the form, so the determination in Step S7 corresponds to a test on the strength of the concrete structure that is poured using formwork with a gap at the bottom.

[0031] 8 is a graph illustrating the results of the uniaxial compressive strength of concrete specimens. The graph shows a graph of a concrete specimen made using a formwork without a permeable sheet and without a weight load (the graph "without permeable sheet" in the figure), a graph of a concrete specimen made using a formwork with a permeable sheet and without a weight load (the graph "with permeable sheet" in the figure), a graph of a concrete specimen made using a formwork without a permeable sheet and with a weight load (the graph "weight only" in the figure), and a graph of a concrete specimen made using a formwork with a permeable sheet and with a weight load (the graph "with permeable sheet + weight" in the figure).

[0032] As can be seen from these graphs, the compressive strength of the concrete specimen made using a formwork with a water-permeable sheet and with a weight load was the highest, followed by the compressive strength of the concrete specimen made using a formwork with a water-permeable sheet and without a weight load, the compressive strength of the concrete specimen made using a formwork without a water-permeable sheet and with a weight load was high, and the compressive strength of the concrete specimen made using a formwork without a water-permeable sheet and without a weight load was the lowest. Therefore, it can be inferred that the dewatering effect of the water-permeable sheet and the weight load is high.

[0033] Fig. 9 is a graph illustrating the results of measuring the amount of dewatering of concrete specimens with and without a permeable sheet. The graph shows a graph of a concrete specimen made using a formwork with a permeable sheet and without a weight load (the graph "with permeable sheet" in the figure), and a graph of a concrete specimen made using a formwork with a permeable sheet and with a weight load (the graph "with permeable sheet + weight" in the figure). As can be seen from these graphs, it is estimated that the dewatering effect of the weight load is high.

[0034] Figure 12 compares the strength development characteristics of concrete specimens fabricated using this formwork with those of a concrete structure constructed using the slipform method. Because compressive strength tests cannot be performed on actual concrete structures, the compressive strength of the concrete structure was measured using rebar insertion, as in Figure 10, and the concrete specimens were fabricated using the method described above. A comparison of the compressive strength times of the concrete specimen fabricated using this formwork and the concrete structure in Figure 12 shows that the values ​​are nearly identical, confirming the effectiveness of this formwork. Therefore, strength tests using concrete specimens fabricated using this formwork make it possible to determine the appropriate demolding time. In Figure 12, the vertical positions of the concrete specimens and concrete structures are represented by layer numbers, with the first layer representing the lowest position.

[0035] Although the embodiments for carrying out the present invention have been described above, the present invention is not limited to these, and various modifications are possible within the scope of the technical concept of the present invention. For example, although the bottom surface of formwork 1 is fixed to half-split formwork members 1a and 1b by adhesive, it may be fixed by fitting uneven grooves provided below the inner peripheral surfaces of formwork members 1a and 1b into uneven grooves provided on the outer periphery of the bottom surface.

[0036] Alternatively, the semicircular bottom surfaces may be fixed to the half-split formwork members 1a and 1b by welding.

[0037] Furthermore, the gap g that connects the inside to the outside of the formwork 1 does not have to be arranged so as to reach from the upper end to the lower end between the formwork members 1a and 1b, and multiple gaps g having a predetermined length in the axial direction of the formwork 1 may be arranged.

[0038] Furthermore, in the embodiment, two formwork members 1a and 1b are used, but three or more formwork members may be used.

[0039] According to the embodiment described above, it is possible to prepare a concrete specimen having strength development properties similar to those of a concrete structure, and to carry out a strength test using the concrete specimen. [Explanation of symbols]

[0040] 1: formwork, 1a, 1b: formwork members, 2: fixings, 3: permeable sheet, g: void, c: concrete, w: weight.

Claims

1. A concrete specimen formwork for producing concrete specimens used in early age strength tests in slip form construction, A formwork for concrete specimens that has a structure on the side that allows moisture in the concrete filled inside the formwork to escape to the outside of the formwork.

2. The structure includes a void communicating from the inside to the outside in the axial direction of the formwork, and a water-permeable member, 2. A form for a concrete specimen according to claim 1, wherein the water-permeable member is disposed along the inner wall surface of the form and inserted into the gap so that a part of the water-permeable member is exposed to the outside of the form.

3. The formwork is composed of a plurality of formwork members, 3. A formwork for a concrete specimen according to claim 2, wherein said gap is located between adjacent said formwork members.

4. The formwork member has a cylindrical half-split shape, the gap is provided so as to extend from the upper end to the lower end between the two formwork members, 4. A form for a concrete specimen according to claim 3, wherein the water-permeable member is inserted into a gap extending from the upper end to the lower end between the two form members.

5. A method for producing a concrete specimen using the concrete specimen formwork according to any one of claims 1 to 4, for producing a concrete specimen to be used in an early age strength test in a slip form method.

6. 6. A method for producing a concrete specimen according to claim 5, wherein the concrete specimen is produced by applying a load by a weight to the concrete poured into the concrete specimen formwork according to any one of claims 1 to 4.

7. An early age strength testing method for testing early age strength in a slip form method using a concrete specimen produced using the concrete specimen formwork described in any one of claims 1 to 4.

8. A concrete structure strength testing method for testing the strength of a concrete structure cast using a formwork with a gap at the bottom, using a concrete specimen prepared using the formwork for concrete specimens according to any one of claims 1 to 4.

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