Method for constructing concrete structure

Abstract

To provide a method for constructing concrete structures that makes a concrete surface sufficiently moist during a wet curing period prior to formwork removal.SOLUTION: A method for constructing a concrete structure comprises: a concrete placement step of placing concrete C into a formwork 1 having a permeable sheet 5 installed on an inner surface thereof; and a concrete curing step of supplying water to the permeable sheet 5 in a state in which the formwork 1 is placed to cure the concrete C. In the concrete curing step, through water supply pipes 19 connected from the outside of the formwork 1 to a plurality of through holes 7 penetrating the formwork 1 at the height where the concrete C is present, a water pouring treatment is performed in which water to be supplied to the permeable sheet 5 is continuously injected into the formwork 1 from the through holes 7.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for constructing a concrete structure. [Background technology]

[0002] Conventionally, in order to construct highly durable concrete structures, moist curing is performed after pouring concrete in accordance with the Standard Specifications for Concrete. Such moist curing techniques are disclosed, for example, in Patent Documents 1 and 2 listed below. In the technique of Patent Document 1, a water-retaining portion that does not easily deform and its inner surface portion are present between the poured concrete and the formwork body. Moist curing is performed by supplying water from above the water-retaining portion while the formwork is in place. In the technique of Patent Document 2, a formwork having a water-retaining portion formed between two flat plates is used, and a permeable sheet is present between the formwork and the poured concrete. Then, water is poured from above the water-retaining portion while the formwork is in place, and water is supplied to the permeable sheet through the through-holes in the flat plates inside the formwork, thereby performing moist curing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 05565921 [Patent Document 2] Utility Model Registration No. 03177266 Summary of the Invention [Problem to be solved by the invention]

[0004] In such wet curing of concrete, it is important to keep the concrete surface sufficiently moist after pouring. However, according to the techniques of Patent Documents 1 and 2, the concrete surface may not necessarily be sufficiently moistened during wet curing. For example, when the technique of Patent Document 1 is applied to the underside of a concrete structure, the water in the water-retaining section tends to be concentrated toward the formwork due to the influence of gravity, and less water may be supplied to the surface. The technique of Patent Document 2 may also have a similar problem. Therefore, an object of the present invention is to provide a method for constructing a concrete structure that keeps the concrete surface sufficiently moist during wet curing before form removal. [Means for solving the problem]

[0005] The gist of the present invention lies in the following [1] to [5].

[0006] [1] A method for constructing a concrete structure, comprising: a concrete pouring step of pouring concrete into a formwork having a water-permeable sheet installed on the inner surface; and a concrete curing step of supplying water to the water-permeable sheet while the formwork remains in place and curing the concrete, wherein in the concrete curing step, a water injection process is carried out in which water to be supplied to the water-permeable sheet is continuously injected into the formwork from a plurality of through-holes that penetrate the formwork at a height where the poured concrete is present, through water supply pipes connected from the outside of the formwork to the through-holes.

[0007] [2] A method for constructing a concrete structure according to [1], wherein the water is injected under water pressure during the water injection process.

[0008] [3] A method for constructing a concrete structure described in [1] or [2], wherein the formwork is composed of a plurality of formwork plates, and during the water injection process, the water supplied to the water-permeable sheet is discharged outside the formwork through the gaps between the formwork plates.

[0009] [4] A method for constructing a concrete structure according to any one of [1] to [3], wherein the concrete curing step uses a water supply system having a water tank arranged so that the water level is higher than the top end of the poured concrete, and the water supply pipe that distributes water from the water tank to the plurality of through holes.

[0010] [5] The method for constructing a concrete structure according to any one of [1] to [4], wherein a mesh material is placed between the inner surface of the formwork and the water-permeable sheet. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for constructing a concrete structure in which the concrete surface is kept sufficiently wet during wet curing before form removal. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a column capital of a bridge pier, which is an example of a concrete structure to which the method for constructing a concrete structure of the first embodiment is applied. [Figure 2] FIG. 10 is a cross-sectional view showing a part of a formwork installed in a formwork installation process. [Figure 3] FIG. 10 is a cross-sectional view showing the state in which concrete has been poured into a formwork during the concrete pouring process. [Figure 4] FIG. 1 is a diagram showing a water supply system used in the concrete curing process. [Figure 5] FIG. 2(a) is a perspective view showing a part of a mold in which a through-hole is formed, and FIG. 2(b) is a cross-sectional view thereof. [Figure 6] 10 is a cross-sectional view showing an example of a connection structure for connecting a water supply pipe to each through-hole. FIG. [Figure 7] FIG. 7 is an enlarged cross-sectional view showing one of the connection structures of FIG. 6. [Figure 8] FIG. 10(a) is a cross-sectional view showing a formwork in a second embodiment, and FIG. 10(b) is a diagram showing a net material attached to the formwork. [Figure 9]Graphs (a) to (c) respectively show the results of tests conducted by the present inventors. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First embodiment] A first embodiment of a method for constructing a concrete structure according to the present invention will be described in detail below with reference to the drawings. A concrete structure 101 constructed by the method for constructing a concrete structure according to this embodiment is a column capital of a bridge pier as shown in FIG. 1. This column capital has a size of, for example, approximately 12 m in width and approximately 6 m in height, and this type of mass concrete is particularly in need of measures to prevent cracks and the like during curing. The concrete structure 101 has vertical side surfaces 103 and a bottom surface 105 facing downward. Note that the side surfaces 103 do not have to be completely vertical and may be inclined surfaces. Furthermore, the bottom surface 105 does not have to be completely vertical and may be a surface facing diagonally downward.

[0014] The concrete structure construction method of this embodiment includes a formwork installation process for installing a formwork, a concrete pouring process for pouring concrete into the formwork, a concrete curing process for curing the concrete, and a demolding process for demolding the formwork.

[0015] (Formwork installation process) In the formwork installation process, as shown in Figure 2, formwork 1 is installed at the location where concrete will be poured. Figure 2 includes a formwork portion of formwork 1 that corresponds to the corner between side surface 103 and bottom surface 105 of concrete structure 101 (Figure 1). Formwork 1 is made up of multiple formwork plates 3. Each formwork plate 3 is rectangular, for example, 1800 mm long and 900 mm wide, and multiple formwork plates 3 are combined to form a formwork 1 of the required size. Note that the multiple formwork plates 3 do not all need to be the same size or shape; formwork plates 3 of different sizes and shapes may be mixed together. The material of formwork plates 3 is not limited, but wooden formwork plates, for example, are used as formwork plates 3.

[0016] A permeable sheet 5 is attached to each form plate 3. The permeable sheet 5 covers the entire inner surface of the form plate 3 (the surface on which concrete is poured) and extends continuously to cover the end faces and part of the outer surface of the form plate 3, and is fastened to the edge of the outer surface of the form plate 3.

[0017] The permeable sheet 5 is a sheet with a thickness of approximately 0.05 to 2.0 mm, which is generally referred to as a "permeable formwork sheet." Although a detailed illustration of the layer structure is omitted, the permeable sheet 5 has a multi-layer structure having a drainage layer that contacts the inner surface of the formwork 1 and a permeable layer that contacts the concrete to be poured. The drainage layer is made of, for example, nonwoven fabric, and allows water to pass in the in-plane direction. The drainage layer has higher permeability in the in-plane direction than the permeable layer, and has a thickness of 0.05 mm to 2.0 mm and a basis weight of 25 g / m 2 ~250g / m 2 , density is 0.05g / cm 3 ~1.0g / cm 3 The water-permeable layer is made of, for example, a woven fabric or a perforated sheet of a thermoplastic resin, and allows water to pass through in the thickness direction but prevents or restricts water from passing in the in-plane direction. The mesh of the woven fabric or the holes of the perforated sheet are sized to allow water to pass through and prevent the passage of concrete particles. Examples of the thermoplastic resin include polypropylene (PP) and polyethylene terephthalate (PET). Commercially available permeable formwork sheets can also be used as the water-permeable sheet 5. An example of a commercially available permeable formwork sheet is "Filter Sheet Tough" (registered trademark) manufactured by Fujimori Kogyo Co., Ltd.

[0018] In the assembled formwork 1, adjacent formwork plates 3 are arranged lengthwise and widthwise with their end faces butted against each other, with both permeable sheets 5 sandwiched between the end faces. Similarly, at locations where adjacent formwork plates 3 intersect at a predetermined angle, such as at the corners between the side surface 103 and the underside 105 (Figure 1), both permeable sheets 5 are also sandwiched between the formwork plates 3. This formwork installation process results in the construction of a formwork 1 with permeable sheets 5 installed on the entire inner surface.

[0019] (Concrete pouring process) In the subsequent concrete pouring process, with the permeable sheet 5 installed on the inner surface of the formwork 1 as described above, concrete C is poured immediately inside the permeable sheet 5, as shown in Figure 3. Pouring of concrete C into formwork 1 may be carried out by a known method. Reinforcing bars may be placed inside formwork 1. Excess water generated during the hardening process of the poured concrete C travels through the permeable sheet 5 as a water path and leaks out of formwork 1 through the gaps 4 between the formwork plates 3.

[0020] (Concrete curing process) The subsequent concrete curing process is a process of wet curing the vertical side surface 53 and the downward-facing underside 55 of the poured concrete C by supplying water. Note that the side surface 53 is not limited to being completely vertical, but may be an inclined surface. Furthermore, the underside 55 is not limited to being a surface facing completely vertically downward, but may be a surface facing diagonally downward. For example, the side surface 53 will ultimately form the side surface 103 (FIG. 1) of the concrete structure 101, and the underside 55 will ultimately form the underside 105 (FIG. 1) of the concrete structure 101.

[0021] The concrete curing process is started after excess water has been sufficiently drained, for example, about 24 hours after the concrete C is poured. In the concrete curing process, before the formwork 1 is removed, i.e., while the formwork 1 is still in place, water is supplied to the permeable sheet 5 inside the formwork 1, thereby performing water supply and wet curing of the concrete C. In order to supply water in this manner, a water supply system 11 is constructed and used in the concrete curing process to supply water into the formwork 1, as shown in FIG. 4.

[0022] The configuration of the water supply system 11 will be described. As part of the water supply system 11, as shown in FIGS. 5(a) and 5(b), a circular through-hole 7 is formed in each of the form plates 3 constituting the formwork 1, penetrating the form plate 3 in the thickness direction. The diameter of the through-hole 7 is, for example, about 1 to 2 cm, and the through-hole 7 is formed, for example, in the center of the form plate 3. All of the through-holes 7 are located at a height where the concrete C poured in the concrete pouring process exists. In other words, all of the through-holes 7 are located at a position lower than the upper end 8 (FIG. 6) of the concrete C, and face the side surface 53 or the underside 55 of the concrete C in the thickness direction of the formwork 1, with the permeable sheet 5 sandwiched therebetween.

[0023] The through holes 7 are used as water injection holes for injecting water from the outside into the formwork 1 during the concrete curing process. According to experiments by the inventors, it is considered sufficient that such water injection holes are present at intervals of one or more within an area of ​​2 m × 2 m of the formwork 1, but in this embodiment, for example, one through hole 7 is formed for each formwork plate 3. Note that multiple through holes 7 may be formed for each formwork plate 3.

[0024] The work of forming the through holes 7 may be carried out before the start of water supply. For example, the through holes 7 may be formed before the water-permeable sheet 5 is attached to the form plate 3 in the form setting process, or the through holes 7 may be formed immediately before water is supplied into the form 1 after the concrete pouring process.

[0025] As shown in FIG. 4, the water supply system 11 further includes a raw water tank 13 for storing raw water obtained from a water supply system, and a water temperature control unit 15 for adjusting the temperature of the water sent from the raw water tank 13. The raw water tank 13 can obtain water not only from the water supply system but also from a river. The water supply system 11 further includes a water tank 17 for storing water sent from the water temperature control unit 15 as water to be supplied to the formwork 1, and a water supply pipe 19 for distributing the water sent from the water tank 17 and injecting it into each through-hole 7 of the formwork 1. The water supply system 11 further includes a water collection section 21 for collecting water discharged from the formwork 1, and a treated water tank 23 for storing the water collected in the water collection section 21. The water from the treated water tank 23 is sent to the water temperature control unit 15 in parallel with the water from the raw water tank 13. The water supply system 11 is appropriately equipped with hoses and pumps for transporting water between the above-mentioned elements, valves for adjusting the flow rate, and the like.

[0026] The water temperature control unit 15 has a chiller for lowering the water temperature to an appropriate temperature in summer, or a heater for raising the water temperature to an appropriate temperature in winter. For example, the water temperature control unit 15 may have both a chiller and a heater, and use them depending on conditions such as the outside air temperature.

[0027] The capacity of the water tank 17 is, for example, approximately 200 L. The water tank 17 is positioned so that the water level is higher than the upper end 8 (Figure 6) of the concrete C to be poured into the formwork 1. For example, the water tank 17 is positioned so that the bottom of the water tank 17 is higher than the planned construction location of the concrete structure 101. A submersible pump 31 is provided inside the water tank 17 to send water from the water tank 17 to the water supply pipe 19. Heat insulating material is installed on the tank walls of the water tank 17. Furthermore, a lid made of plywood or the like is placed on the top of the water tank 17. The presence of such heat insulating material and lid reduces the influence of the outside temperature and stabilizes the temperature of the water supplied to the formwork 1.

[0028] The water supply pipe 19 is constructed mainly along the outer wall surface of the formwork 1 and constitutes a water supply path for distributing water from the submersible pump 31 to each through-hole 7. Note that the water supply path of the water supply pipe 19 shown in FIG. 4 is a simplified schematic diagram and does not accurately represent the actual water supply path. The water supply pipe 19 branches the water supply path from the submersible pump 31, and there are at least as many downstream ends 37 of the water supply pipe 19 as there are through-holes 7. The water supply pipe 19 includes, for example, a hose 35 for conveying water and branch joints and valves V for connecting the hoses 35. For example, a water hose is used as the hose 35. The components of the water supply pipe 19 may include, for example, a branch unit having one inlet port and multiple outlet ports with valves. Each of the branched downstream ends 37 of the water supply pipe 19 is connected to each of the through-holes 7 from the outside of the formwork 1, one for each. By operating each valve V (for example, a ball valve) appropriately arranged in the water supply pipe 19, the distribution of water to each through-hole 7 and the injection pressure can be adjusted.

[0029] An example of the connection structure between the water supply pipe 19 and each through-hole 7 is shown in Figures 6 and 7. Figure 7 is an enlarged view of one through-hole 7 and its vicinity in Figure 6. As also shown in Figure 5, each through-hole 7 is fitted with a hard T-shaped pipe 41, for example made of resin. For each through-hole 7, one branch pipe of one T-shaped pipe 41 is inserted into the through-hole 7 to fasten the T-shaped pipe 41. Sealing tape may be wrapped around the outer periphery of the inserted branch pipe to prevent water leakage. Then, hoses 35, 35 routed along a predetermined water supply path are connected to two other branch pipes of the T-shaped pipe 41 protruding from the outer wall surface of the formwork 1, thereby completing the water supply path for the water supply pipe 19. One of the hoses 35 delivers water W from the submersible pump 31 to the T-shaped pipe 41, and the other delivers a portion of the water W to the adjacent T-shaped pipe 41. Note that Figure 6 does not show the hoses 35 and other components connected to the T-shaped pipe 41. The branch pipe of the T-pipe 41 inserted into the through hole 7 constitutes the aforementioned downstream end 37. In this way, the use of rigid T-pipes 41 makes it easy to connect each downstream end 37 of the water supply pipes 19 to each through hole 7. Water injected into the formwork 1 through the through hole 7 by the water supply pipes 19 passes through the permeable sheet 5 and leaks out of the formwork 1 through the gaps 4 between the formwork plates 3.

[0030] The water collection section 21 shown in FIG. 4 is, for example, a tray-like or gutter-like member arranged below the formwork 1. This water collection section 21 receives water flowing out from gaps 4 (FIG. 6) between the formwork plates 3 and sends it to a treatment water tank 23. If there are gaps 4 among the many gaps 4 that are particularly prone to water leakage, the water collection section 21 may be arranged below the gap 4. Such gaps 4 that are particularly prone to water leakage may be gaps 4 that are intentionally made slightly wider during the formwork installation process. Furthermore, drainage slits (not shown) for draining water may be provided at predetermined positions on the formwork 1, separate from the gaps 4, and the water collection section 21 may be arranged below the drainage slits.

[0031] In the concrete curing process, the water supply system 11 as described above performs a water injection process in which water is continuously injected into the formwork 1 from each of the multiple through-holes 7. This water injection process will now be described. When the water supply system 11 shown in FIG. 4 is in operation, water from the mains water supply is supplied to the raw water tank 13. If there is a problem with the water supply from the mains water supply, water from a river is supplied to the raw water tank 13. The water from the raw water tank 13 and the treated water tank 23 is then temperature-adjusted by the water temperature control unit 15 and sent to the water storage tank 17. The submersible pump 31 in the water storage tank 17 continuously sends water to each of the through-holes 7 via the water supply pipe 19, and the water is continuously injected into the formwork 1 through each of the through-holes 7.

[0032] The flow rate of the water injected here is 1m2 per 1m2 of formwork area. 2 For example, if the concrete structure 101 is the column capital of a bridge pier, the total flow rate of water injected into the formwork 1 is about 600 to 1000 L / hour. The injection pressure of the water injected here is, for example, 0.15 to 0.74 MPa.

[0033] Water from the water tank 17 is pumped out by a submersible pump 31, and pressure from the submersible pump 31 is applied to the water injected into the formwork 1. In addition, because the water level in the water tank 17 is higher than the upper end 8 (Figure 6) of the poured concrete C, head pressure is also applied to the water injected into the formwork 1. Therefore, water from the water tank 17 is continuously injected into the formwork 1 with water pressure applied through the water supply pipe 19. The injection flow rate and injection pressure of water into each through-hole 7 are individually and appropriately adjusted by operating each valve V. For example, the injection flow rate and injection pressure into all through-holes 7 may be adjusted to be approximately equal. Alternatively, for example, the injection flow rate and injection pressure may be adjusted to be greater the higher (or lower) the through-hole 7 is.

[0034] Water injected into the formwork 1 through each through-hole 7 is continuously supplied to the permeable sheet 5 within the formwork 1, moistening the surface of the concrete C. The water in the permeable sheet 5 is then continuously discharged to the outside of the formwork 1 through the gaps 4 between the formwork plates 3. Note that the formwork plates 3 have a predetermined water-proofing property, so very little of the water injected into the formwork 1 passes through the formwork plates 3 themselves and is discharged to the outside of the formwork 1.

[0035] As described above, the water discharged from the gaps 4 between the formwork plates 3 is collected in the water collection section 21 and sent to the treated water tank 23. The water in the treated water tank 23 is sent to the water temperature control unit 15 in parallel with the water in the raw water tank 13, so that a portion of the water used for moist curing is circulated within the water supply system 11, thereby reducing water consumption. If the water collected in the water collection section 21 is not suitable for circulation, the water in the treated water tank 23 may not be circulated, and only the water in the raw water tank 13 may be used for the water injection treatment. An example of a case where the water collected in the water collection section 21 is likely to contain laitance-treated water or the like.

[0036] In the water supply system 11, the water temperature in the water temperature control unit 15 may be feedback-controlled so that the temperature of the water injected into the formwork 1 becomes an appropriate temperature for wet curing of concrete (for example, about 20°C). That is, for example, a measuring instrument (not shown) that measures the water temperature may be provided at any position in the water supply pipe 19, and the temperature of the water delivered from the water temperature control unit 15 may be controlled based on the measured value.

[0037] The water injection process as described above in this concrete curing process may be performed continuously without interruption throughout the entire period of the concrete curing process. That is, water may be constantly injected into each through-hole 7 without interruption throughout the entire period of the concrete curing process. Alternatively, the water injection process may be interrupted for a certain period of time during the concrete curing process, as long as it does not significantly deteriorate the wet state of the water-permeable sheet 5 or the concrete C. An example of a case in which the water injection process is interrupted in this manner is when water injection from some or all of the through-holes 7 is temporarily stopped by operating the valve V, etc. After the concrete curing process as described above has been performed for a predetermined curing period (e.g., five days), the operation of the water supply system 11 is stopped to stop the water supply, and the concrete curing process is completed.

[0038] (Demolding process) After the concrete curing process is completed, the formwork 1 is removed. By removing the formwork, the surface of the cured concrete C is exposed, and the concrete structure 101 is completed.

[0039] Next, the effects of the concrete structure construction method of this embodiment as described above will be described.

[0040] In the concrete curing step of the concrete structure construction method of this embodiment, as shown in Figures 6 and 7, through-holes 7 are provided at the height where the poured concrete C is present, and a water injection process is performed in which water is continuously injected into the formwork 1 from each through-hole 7 via a water supply pipe 19 connected to each through-hole 7 from the outside of the formwork 1. Since the injected water is continuously supplied to the water-permeable sheet 5, water flows through the water-permeable sheet 5 after injection and is always present within the water-permeable sheet 5 until it is discharged outside the formwork 1. Therefore, the surface of the concrete C is always maintained in a wet state. Therefore, the surface of the concrete C can be sufficiently wetted in the concrete curing step before demolding, resulting in the construction of a highly durable concrete structure 101. Furthermore, since the water injected into the formwork 1 eventually leaks out of the formwork 1 through the gaps 4 between the formwork plates 3, there is no need to provide a special drainage outlet or the like.

[0041] Here, instead of injecting water through the through-holes 7, it is also possible to periodically supply water to the upper end of the permeable sheet 5 from inside the formwork 1 at the height of the upper end 8 of the concrete C. However, in this case, the water flows naturally down within the permeable sheet 5, so the higher the position, the less water there tends to be within the permeable sheet 5. This may result in the side surface 53 of the concrete C near the upper end 8 being insufficiently wet. Furthermore, this method is difficult to apply to curing the underside 55 of the concrete C (for example, the underside of an overhanging part of a concrete structure, the underside of a beam, the underside of a slab, etc.).

[0042] In contrast, in the concrete curing step of the concrete structure construction method of this embodiment, water pressure is applied to inject water into the formwork 1, and the water is supplied to the water-permeable sheet 5 under the water pressure. Therefore, the water not only flows downward through the through-holes 7 naturally within the water-permeable sheet 5, but also spreads upward through the through-holes 7 due to the water pressure. Therefore, for example, sufficient water is supplied to the water-permeable sheet 5 via the highest through-hole 7, even on the side surface 53 near the upper end 8 of the poured concrete C. Note that, in order to efficiently obtain this effect, it is preferable that the highest through-hole 7 be located at a height of 30 cm or less from the upper end of the poured concrete C. Furthermore, it is preferable that the horizontal distance between the through-holes 7 be 90 cm or less.

[0043] Furthermore, because water pressure is applied and water is injected into the formwork 1, even when applied to the underside 55 of the concrete C, water is sufficiently supplied to the permeable sheet 5 located on the formwork 1, and water comes into sufficient contact with the underside 55 of the concrete C located above the permeable sheet 5. Therefore, the concrete structure construction method of this embodiment can also be suitably applied to the underside 55 of the concrete C. For example, when the concrete structure 101 is a column capital as shown in FIG. 1, the downward-facing underside 105 can also be cured well. The method can also be suitably applied when the underside of an overhanging portion of a concrete structure, the underside of a beam, the underside of a slab, etc. is to be cured alone.

[0044] Furthermore, the pressure of the water injected through the through-holes 7 is the sum of not only the head pressure due to the height of the water tank 17 but also the pressure due to the submersible pump 31. If water were injected into each through-hole 7 using only head pressure, the injection pressure would fluctuate depending on the height of the water surface in the water tank 17, and the injection pressure for each through-hole 7 would differ depending on the height position of that through-hole 7. In contrast, in the water injection process of this embodiment, the injection pressure into each through-hole 7 can be stabilized by applying pump pressure in addition to the natural flow due to head pressure from the water tank 17. Furthermore, in the water injection process of this embodiment, not only the pressure of the submersible pump 31 but also the head pressure due to the height of the water tank 17 is used, so the capacity required of the submersible pump 31 can be reduced, and a relatively small submersible pump 31 can be used.

[0045] In the concrete curing step of the concrete structure construction method of this embodiment, water is supplied into the form 1 while the form 1 is in place, and the concrete C is kept moist by the water-permeable sheet 5. Therefore, compared to a curing method in which a sheet is installed on the surface of the concrete after the form is removed, it is possible to avoid the surface of the concrete C being exposed to the outside air during the curing period from after the form is removed until the sheet is installed.

[0046] Second Embodiment Next, a second embodiment of the method for constructing a concrete structure will be described in detail. As shown in Fig. 8(a), the method for constructing a concrete structure of this embodiment differs from the first embodiment in that a mesh material 9 is installed between the inner surface of the formwork 1 and the permeable sheet 5. Since the method is otherwise similar to the first embodiment, a duplicated description will be omitted. Components that are the same as or equivalent to those of the first embodiment are designated by the same reference numerals in the drawings.

[0047] FIG. 8(b) is an enlarged view of the mesh material 9 as viewed from a direction perpendicular to the inner surface of the formwork 1. As shown in FIG. 8(b), the mesh material 9 is composed of warp and weft threads made of resin (e.g., high-density polyethylene). In the formwork installation process of this embodiment, the mesh material 9 is placed on top of the permeable sheet 5 so as to cover the entire inner surface of the formwork plate 3. The thickness of the warp and weft threads constituting the mesh material 9 is, for example, about 0.5 to 1 mm, and the pitch of the warp and weft threads is, for example, about 2 to 3 mm. The warp and weft threads themselves have almost no water permeability. In the water injection process of the concrete curing process of this embodiment, as in the first embodiment, water from the water tank 17 (FIG. 4) is continuously injected into the formwork 1 through each through-hole 7 while water pressure is applied via the water supply pipe 19. At this time, due to the presence of the mesh material 9, gaps are formed between the inner surface of the formwork 1 and the permeable sheet 5, which can become water channels, allowing excess water generated after concrete is poured to be efficiently drained, and improving the circulation of water injected through the through holes 7 during the concrete curing process.

[0048] The following describes the tests conducted by the present inventors. In these tests, the surfaces of five types of concrete structures (Examples 1 to 4 and Comparative Example) with different curing methods were evaluated. The test results are shown in Figures 9(a) to 9(c).

[0049] In Example 1, a water-permeable form sheet was installed on the inner surface of the formwork that contacted the vertical side of a concrete structure. The curing of this vertical side was carried out for 28 days after the concrete was poured, in the same manner as in the concrete curing process of the first embodiment.

[0050] In Example 2, a vertical side of a concrete structure was used, and a mesh material and a water-permeable form sheet were placed on the inner surface of the formwork in contact with the vertical side. The curing of this vertical side was carried out for 28 days after the concrete was poured, in the same manner as in the concrete curing process of the second embodiment described above.

[0051] In Example 3, the horizontal underside of a concrete structure was covered with a permeable formwork sheet on the inner surface of the formwork that was in contact with the horizontal underside. The curing of this horizontal underside was carried out for 28 days after the concrete was poured, in the same manner as in the concrete curing process of the first embodiment.

[0052] In Example 4, the horizontal underside of a concrete structure was covered with a mesh material and a permeable formwork sheet on the inner surface of the formwork that was in contact with the horizontal underside. The curing of this horizontal underside was carried out for 28 days after the concrete was poured, in the same manner as in the concrete curing process of the second embodiment.

[0053] The vertical side surfaces formed in Examples 1 and 2 were 1.40 m high and 0.90 m wide, and the horizontal lower surfaces formed in Examples 3 and 4 were 1.40 m long and 0.90 m wide. 2 Through holes (water injection holes) are formed almost evenly at a rate of one per 1m of the formwork. 2 Water was supplied to each through-hole at a flow rate of 0.5 L / min per through-hole.

[0054] The permeable formwork sheet used in Examples 1 to 4 was "Filter Sheet Tough" (registered trademark) manufactured by Fujimori Kogyo Co., Ltd. The mesh material used in Examples 2 and 4 was a net made of high-density polyethylene. The warp threads of the mesh material had a thread width of 0.5 mm, a thread thickness of 0.5 mm, and an arrangement pitch of the warp threads of 1.8 mm. The weft threads of the mesh material had a thread width of 0.5 mm, a thread thickness of 0.4 mm, and an arrangement pitch of the weft threads of 2.8 mm.

[0055] The comparative example is the vertical side of a concrete structure, and no permeable formwork sheet or mesh material was installed on the inner surface of the formwork corresponding to this vertical side, so that the vertical side was in direct contact with the inner surface of the formwork. The formwork for this vertical side was left for 12 days after the concrete was poured, and then removed. No water was supplied to the formwork during these 12 days before removal. The vertical side after removal was left until the day of measurement of the surface layer air permeability coefficient, etc., which will be described later (28 days after the concrete was poured). The vertical side formed in the comparative example is 1.40 m high and 0.90 m wide. During the curing in the comparative example, a 1 m thick layer was placed on the formwork.2 Through holes (water injection holes) are formed almost evenly at a rate of one per 1m of the formwork. 2 Water was supplied to each through-hole at a flow rate of 0.5 L / min per through-hole.

[0056] For the vertical side surfaces or horizontal undersides of Examples 1 to 4 and the Comparative Example, the surface air permeability coefficient was measured using the Trent method, the estimated compressive strength using a test hammer, and the surface water absorption rate was measured using the SWAT method 28 days after concrete was poured. Figure 9(a) shows the measurement results for the surface air permeability coefficient, Figure 9(b) shows the measurement results for the estimated compressive strength, and Figure 9(c) shows the measurement results for the surface water absorption rate.

[0057] As shown in Figure 9(a), the air permeability coefficients of Examples 1 to 4 were all significantly smaller than those of the Comparative Example. Furthermore, as shown in Figure 9(b), the estimated compressive strengths of Examples 1 to 4 were all 20% or more higher than those of the Comparative Example. Furthermore, as shown in Figure 9(c), the surface water absorption rate of Examples 1 to 4 was approximately 1 / 10 that of the Comparative Example. Therefore, it was confirmed that the curing method of the first or second embodiment improves the quality of both the vertical and underside surfaces of a concrete structure.

[0058] 9(a) to 9(c), Example 1 and Example 2 are compared, and it can be said that Example 2 is slightly superior in terms of estimated compressive strength and surface water absorption rate. Similarly, it can be said that Example 4 is slightly superior in terms of surface water absorption rate when Example 3 and Example 4 are compared. Therefore, it was confirmed that the use of the mesh material (second embodiment) in the concrete curing method slightly improves the quality of both the vertical surface and the underside of the concrete structure.

[0059] The present invention can be implemented in various forms, including the above-described embodiment, with various modifications and improvements based on the knowledge of those skilled in the art. It is also possible to configure modified examples by utilizing the technical matters described in the above-described embodiment. The configurations of the respective embodiments may be used in appropriate combination.

[0060] For example, in the embodiment, one through hole 7 is provided in the center of each form plate 3, but this is not limited to this. The through holes 7 may be formed in any position on each form plate 3, as long as there are one or more through holes 7 spaced apart within a 2 m x 2 m area on the surface of the form 1. In particular, near the top end 8 ( FIG. 6 ) of the poured concrete C, the through hole 7 may be provided in the upper part of the form plate 3 so as to be close to the top end 8 of the concrete C. This makes it easier for water poured through the through hole 7 to reach the side surface 53 near the top end 8 of the concrete C. Furthermore, multiple through holes 7 may be formed in one form plate 3.

[0061] The concrete curing step in the embodiment involves wet curing the side surface 53 and underside 55 of the concrete C, but is not limited to this. The concrete curing step in the concrete structure construction method of the present invention can be applied to wet curing not only the side surface and underside of the concrete, but also various other surfaces.

[0062] In addition, in the embodiment, the water tank 17 is arranged so that the water level is higher than the upper end of the poured concrete C, but this is not essential. For example, water pressure may be applied to the water injected from the through-hole 7 using a pump with sufficient capacity to achieve the required injection pressure. In this case, there is no need to place the water tank 17 at a high position, and the degree of freedom in arranging each element of the water supply system 11 is improved. [Explanation of symbols]

[0063] 1...formwork, 3...formwork board, 4...gap, 5...permeable sheet, 7...through hole, 9...mesh material, 11...water supply system, 17...water tank, 19...water supply pipe, 101...concrete structure, C...concrete, W...water.

Claims

1. a concrete pouring process in which concrete is poured into a formwork with a permeable sheet installed on the inner surface; and a concrete curing step of supplying water to the water-permeable sheet with the formwork remaining in place to cure the concrete, In the concrete curing step, A method for constructing a concrete structure, in which a water injection process is performed in which water to be supplied to the water-permeable sheet is continuously injected into the formwork from a plurality of through holes that penetrate the formwork at the height where the poured concrete is present, through water supply pipes connected from outside the formwork to the through holes.

2. The method for constructing a concrete structure according to claim 1 , wherein in the water injection treatment, the water is injected under water pressure.

3. The formwork is composed of a plurality of formwork plates, 3. The method for constructing a concrete structure according to claim 2, wherein in the water injection treatment, the water supplied to the water-permeable sheet is discharged to the outside of the formwork through gaps between the formwork plates.

4. In the concrete curing step, A water tank arranged so that the water surface is located at a position higher than the upper end of the poured concrete; the water supply pipe distributing water from the water tank to the plurality of through holes; 4. The method for constructing a concrete structure according to claim 3, wherein a water supply system having the following structure is used.

5. The method for constructing a concrete structure according to any one of claims 1 to 4, wherein a mesh material is installed between the inner surface of the formwork and the permeable sheet.

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