Form with drain window and placement method of concrete using the same

Abstract

To easily and surely remove bleeding water.SOLUTION: A form is used when placing and joining concrete 3 on an upper layer of a layer of concrete 2 where a super retarding agent is added, and at the height position containing a placing and joining surface 4 of the concrete 2 where the super retarding agent is added, an openable / closable drain window 5 is provided. A lower end of the drain window 5 is positioned at the same height with or below the placing and joining surface 4 of the concrete 2 where the super retarding agent is added. The drain window 5 is switchable between a closed state where it is closed by a drain window closing body 8 and an open state where it is opened.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a formwork with drainage windows in which drainage windows are provided at a height including the joint surface of concrete to which an ultra-retardant has been added when concrete is poured in layers upward, and a concrete pouring method using the formwork. [Background technology]

[0002] Traditionally, when constructing large-scale concrete structures in civil engineering projects, concrete is poured in layers one after the other. In this case, once concrete pouring is completed on one day, concrete pouring will resume on the following day, so the treatment of the interface (horizontal pour joint) between the poured concrete and the new concrete is important to ensure the quality of the concrete.

[0003] Conventionally, the method used was to remove laitance from the surface of the lower layer concrete (which will become the horizontal joints) that had hardened to a certain extent using wire brushing or chipping (this is called green cut processing), and then pour concrete into the upper layer. However, this method was essentially done by hand, which was time-consuming and labor-intensive, and it also generated dust, which required environmental protection measures.

[0004] Therefore, in Patent Document 1 listed below, the applicant proposed a method of casting concrete to which an ultra-retarder has been added, thereby arbitrarily controlling the setting time of the concrete, and then, after a predetermined time has passed, casting concrete to which a hardening accelerator has been added, and stirring and mixing the layer of concrete to which the ultra-retarder has been added and the layer of concrete to which the hardening accelerator has been added, thereby ensuring the integrity of the overlapping parts. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-130982 Summary of the Invention [Problem to be solved by the invention]

[0006] However, concrete containing super-retarders has a problem of increased bleeding because the hydration reaction of cement is delayed.

[0007] The Standard Specifications for Concrete [Construction Section: Construction Standards] states, "If the water remaining on the cast surface due to concrete bleeding is not removed, the surface in contact with the formwork will be washed away, and there is a risk of sand streaks or a weak layer forming near the finished surface. The water must be removed using a sponge, ladle, small submersible pump, etc." However, removing bleeding water takes time and effort, and is not easy, so the development of a simple method of removal was desired.

[0008] Furthermore, if bleeding water is not removed sufficiently, it can lead to a decline in the quality of the concrete, such as the creation of voids inside the concrete, so it is important to remove bleeding water efficiently.

[0009] Therefore, the main object of the present invention is to provide a formwork with drainage windows that allows bleeding water to be removed easily and reliably, and a method for pouring concrete using the formwork. [Means for solving the problem]

[0010] In order to solve the above problem, the present invention according to claim 1 provides a formwork used when pouring concrete onto an upper layer of a concrete layer to which an ultra-retardant has been added, There is provided a formwork with drainage windows, characterized in that an openable and closable drainage window is provided at a height position including the joint surface of the concrete to which the ultra-retardant has been added.

[0011] In the invention described in claim 1 above, when a horizontal joint construction method using concrete containing ultra-retardant is adopted to arbitrarily control the setting time of concrete and ensure the integrity of the overlapping parts, an openable drainage window is provided at a height position including the joint surface of the concrete containing ultra-retardant. Therefore, before joining concrete to the upper layer of the concrete containing ultra-retardant, bleeding water accumulated on the joint surface can be removed by draining it from the drainage window, making it possible to remove the bleeding water easily and reliably.

[0012] As a second aspect of the present invention, the upper end of the drainage window is located above the joint surface of the concrete to which the ultra-retardant has been added, The formwork with drainage windows according to claim 1 is provided, wherein the lower end of the drainage window is positioned at the same level as or below the joint surface of the concrete to which the ultra-retarder has been added.

[0013] In the invention described in claim 2, the drainage window is installed at a height where the joint surface of the concrete containing ultra-retardant is located at the bottom end of the drainage window or halfway up and down based on the concrete pouring plan. This makes it easy to remove bleeding water that has accumulated on the joint surface.

[0014] As the present invention according to claim 3, there is provided a formwork with a drainage window according to claim 1, in which the drainage window can be switched between a closed state in which it is blocked by a drainage window blocking body and an open state in which it is open.

[0015] In the invention described in claim 3 above, the drainage window is closed while concrete is being poured and is opened when bleeding water is to be removed, so that the drainage window can be switched between a closed state in which a drainage window blocking body is installed on the drainage window, and an open state in which it is open.

[0016] As a fourth aspect of the present invention, the drainage window can be opened and closed by attaching and detaching a drainage window blocking body, A formwork with a drainage window is provided as claimed in claim 1, wherein the drainage window blocking body is fixed to the surrounding formwork with bolts and nuts via a gasket.

[0017] In the invention described in claim 4 above, the drainage window can be opened and closed by attaching and removing the drainage window blocking body, and the drainage window blocking body is fixed to the surrounding formwork with bolts and nuts via gaskets, so that when the drainage window is blocked by the drainage window blocking body during concrete pouring, leakage of sludge from the drainage window can be prevented.

[0018] The present invention according to claim 5 provides a formwork with a drainage window according to claim 1, wherein the drainage window can be opened and closed by a shutter-type drainage window blocking body whose blocking height can be adjusted in the vertical direction.

[0019] In the invention described in claim 5 above, a shutter-type drainage window blocking body whose blocking height can be adjusted in the vertical direction is installed on the drainage window, and the opening height of the drainage window can be adjusted by adjusting the blocking height of the shutter.

[0020] As a sixth aspect of the present invention, there is provided a method for pouring concrete using the formwork with drainage windows according to any one of the first to fifth aspects, After the drainage window is closed and concrete containing the ultra-retardant is poured, A concrete pouring method is provided, characterized in that the drainage window is left open so that bleeding water can be constantly discharged from the drainage window until concrete is poured on top of it, or only the drainage window near the location where bleeding water has accumulated is opened to discharge the bleeding water from there before concrete is poured on top of the concrete to which the ultra-retarder has been added.

[0021] In the invention described in claim 6, the drainage windows are closed during the pouring of the concrete containing the ultra-retarder to prevent the concrete from flowing out through the drainage windows. After the concrete containing the ultra-retarder is poured, the drainage windows may be opened to allow bleeding water to be constantly discharged from the drainage windows until the concrete on top is poured. Alternatively, if the amount of bleeding water is small, the drainage windows may be left closed after the concrete containing the ultra-retarder is poured, and after a predetermined time has passed, only the drainage windows near the areas where bleeding water has accumulated may be opened to allow the bleeding water to be discharged from there before the concrete on top of the concrete containing the ultra-retarder is poured.

[0022] As a seventh aspect of the present invention, there is provided a method of pouring concrete as described in claim 6, in which the height of the joint surface of the layer of concrete to which the ultra-retardant has been added is adjusted so that it slopes downward toward the drainage window.

[0023] In the invention described in claim 7, the height of the joint surface of the concrete layer containing the ultra-retardant is adjusted so that it slopes downward toward the drainage window, so that the bleeding water naturally flows toward the drainage window. This makes it possible to remove the bleeding water more easily and reliably. [Effects of the Invention]

[0024] As explained above in detail, according to the present invention, bleeding water can be removed simply and reliably. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view of concrete using a formwork 1 with drainage windows according to the present invention. [Figure 2] 1A is an enlarged cross-sectional view of the joint surface, showing the drainage window 2 in a closed state, and FIG. 1B is an enlarged cross-sectional view of the drainage window 2 in an open state. [Figure 3] FIG. 2 is a front view of the formwork 1 with drainage windows. [Figure 4]FIG. 10 is an enlarged front view of the drainage window 5 portion. [Figure 5] 1A shows a drainage window blocking body 8, where (A) is a front view, (B) is a view taken along line BB in (A), and (C) is a view taken along line CC in (A). [Figure 6] This is a procedure diagram (part 1) for pouring concrete. [Figure 7] This is a procedure diagram (part 2) for pouring concrete. [Figure 8] This is a procedure diagram (part 3) for pouring concrete. [Figure 9] This is a procedure diagram (part 4) for pouring concrete. [Figure 10] This is a procedure diagram (part 5) for pouring concrete. [Figure 11] This is a procedure diagram (part 6) for pouring concrete. [Figure 12] FIG. 10 is a cross-sectional view showing a modified example of a drainage window blocking body 8A. [Figure 13] FIG. 10 is a cross-sectional view showing a variation of a layer of concrete with added ultra-retardant. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0027] (Formwork with drainage windows) The formwork 1 with drainage windows of the present invention is a formwork used when pouring concrete 3 on top of a layer 2 of concrete to which an ultra-retardant has been added, and is provided with an openable and closable drainage window 5 at a height position including the pouring joint surface 4 of the layer 2 of concrete to which an ultra-retardant has been added.

[0028] The final layer of concrete on the lower side, leading up to the joint surface 4, is layer 2 of concrete with added super retarder. In Figure 1, on the first day of pouring work, five layers of standard concrete 6 are poured in succession, followed by layer 2 of concrete with added super retarder as the final layer, and then, after a predetermined time has passed, on the second day of pouring work, five layers of standard concrete 7 are poured in succession. However, the number of layers of standard concrete 6 and 7 can be arbitrarily determined, and the concrete pouring schedule is determined in advance based on the size and shape of the structure, taking into account the daily concrete pouring capacity.

[0029] Since the concrete pouring work for one day is usually done while compacting using a vibrator, it is common to pour the concrete in two or more layers. In this case, the concrete pouring height for each layer is determined taking into consideration the compaction capacity, etc., but the height h1 of one layer of poured concrete is typically 40 to 50 cm or less.

[0030] The type of cement used in the concrete is not particularly limited, but various types of Portland cement, such as ordinary Portland cement, high-early-strength Portland cement, extra-high-early-strength Portland cement, moderate-heat Portland cement, white Portland cement, sulfate-resistant Portland cement, and low-heat Portland cement, as well as blended cements such as blast-furnace slag cement, fly ash cement, and silica cement, can be used. It is desirable to use common water-reducing agents, such as lignin sulfonate-based, polyol-based, and oxycarboxylate-based, as well as high-performance water-reducing agents and super-adjusted air-entraining agents. Among these, high-performance water-reducing agents with high water-reducing rates, such as polyalkylarylsulfonate-based and melamine resin sulfonate-based, and polycarboxylate-based super-adjusted air-entraining agents, are preferred. Note that the drawings omit the illustrations of reinforcing bars and formwork, and only show the concrete portion.

[0031] The super retarder is an additive that can adjust (slow) the setting rate of concrete as desired by adding it; it adsorbs to the surface of cement particles, temporarily blocking contact between water and cement, thereby delaying the setting of concrete. JIS A 0203 defines a set retarder as an admixture used to slow the hydration reaction of cement and extend the time required for setting. Set retarders are generally classified into retarders and super retarders, with admixtures that exhibit a short-term delaying effect of within a few hours being called retarders, and admixtures that exhibit a long-term delaying effect of several hours to several days being called super retarders. The admixture used in this invention is the latter "super retarder."

[0032] Ultra-retarders are generally classified into inorganic compounds and organic compounds. Examples of inorganic ultra-retarders include zinc chloride, zinc carbonate, lead monoxide, phosphates, silicofluorides, borax, and magnesia salts. Examples of organic ultra-retarders include sugars and their derivatives, lignin sulfonates, organic acids and their acid salts, hydroxycarboxylates such as citrates and gluconates, cellulose derivatives, and water-soluble polymers such as polyvinyl alcohol. Generally, organic compound retarders are larger than inorganic compounds, and organic compounds are considered advantageous when used as ultra-retarders.

[0033] The addition rate of the super retarder is set so that the penetration resistance of layer 2 of the concrete to which the super retarder has been added during stirring and mixing is 0.1 N / mm 2 It is desirable to determine the value based on the following criteria: When performing horizontal joints, the penetration resistance value must be 0.1 N / mm 2 It is said that cold joints occur when the concrete layer 2 containing the ultra-retarder has a penetration resistance of 0.1 N / mm or more at the start of concrete pouring after a predetermined time has elapsed. 2 It is desirable to manage it so that the following occurs:

[0034] The interval (time) between joints is generally 24 to 72 hours, which is a wide range. The penetration resistance of the concrete layer 2 to which the ultra-retardant was added was 0.1 N / mm2 In order to control the penetration resistance to below 0.1N / mm, a laboratory test was conducted in advance. 2 It is desirable to obtain a graph showing the relationship between the time required to obtain this value and the rate of addition of super-retarder used. By obtaining such a graph, it becomes possible to easily determine the rate of addition of super-retarder even when the interval between joints changes. The penetration resistance value can be measured according to JIS A 1147, the test method for setting time of concrete.

[0035] In addition, in order to prevent an increase in the unit water content due to the addition of the ultra-retarder solution, it is desirable to convert the amount of ultra-retarder solution to be added into part of the unit water content and mix it into the concrete.

[0036] Furthermore, for concrete 2 to which an ultra-retardant has been added, the slump of the poured concrete can be adjusted to an appropriate level by adjusting the addition rate of admixtures such as water reducers, AE water reducers, high-performance water reducers, and high-performance AE water reducers.

[0037] The slump of the concrete 2 containing the ultra-retarder can be set arbitrarily without any particular limitation, but is preferably set to about 10 to 30, and particularly about 15 to 20. By setting the slump within this range, the concrete will not flow out of the drainage window 5 even if the drainage window 5 is left open after pouring. The slump can be measured in accordance with JIS A 1101 Slump Test Method for Concrete.

[0038] The height h2 of the concrete layer 2 to which the ultra-retardant has been added is desirably set to be smaller than the height h1 of one layer of standard concrete 6, 7, taking into consideration mixing with the concrete 3 to be poured on top.

[0039] The formwork 1 with drainage windows has a height that includes the pouring height of the layer 2 of concrete containing ultra-retardant and the standard concrete 3 to be poured on top of that layer, and as shown in Figure 1, it is preferable that the height is equal to or greater than the pouring height of the concrete from the first day to the second day of the pouring work.

[0040] The formwork 1 with drainage windows according to the present invention has drainage windows 5 at a height including the joint surface 4 of the concrete 2 to which an ultra-retardant has been added. The drainage windows 5 are openings that penetrate the front and back of the formwork, and one or more may be provided depending on the size and shape of the structure. When multiple drainage windows 5 are provided, they are arranged at approximately the same height at a predetermined horizontal interval.

[0041] There are no particular limitations on the shape of the opening of the drainage window 5, but it is preferable that it be formed as a horizontally long rectangle with a height of 10 to 50 cm and a width of 20 to 70 cm so that bleeding water can be removed effectively.

[0042] The upper end of the drainage window 5 is located above the joint surface 4 of the concrete 2 to which super retarder has been added, and the lower end of the drainage window 5 is located approximately at the same level as or lower than the joint surface 4 of the concrete 2 to which super retarder has been added. In other words, the installation height of the drainage window 5 is adjusted so that the joint surface 4 of the concrete 2 to which super retarder has been added is located at the lower end of the drainage window 5 in the vertical direction or halfway therebetween.

[0043] As shown in FIG. 2, the height difference h3 between the bottom end of the drainage window 5 and the joint surface 4 of the concrete 2 to which the super-retarder has been added is preferably 0 to 10 cm.

[0044] As shown in Figure 2, the drainage window 5 can be switched between a closed state ((A)) in which it is blocked by a drainage window blocking body 8, and an open state ((B)) in which it is open. The closed state and open state can be switched as needed, and the window is kept in the closed state at least during concrete pouring work, and in the open state at least during bleeding water removal work.

[0045] One means for switching the drainage window 5 between the closed state and the open state is to attach and detach a drainage window blocking body 8 shown in FIGS.

[0046] Such a removable drainage window blocking body 8 is formed with external dimensions slightly smaller than the opening dimensions of the drainage window 5, and is attached to the drainage window 5 by being fixed to the ribs provided on the surrounding formwork via a gasket 9 made of rubber or resin, etc., with a plurality of bolts and nuts 10 arranged at predetermined intervals around the circumference, as shown in Figure 4.

[0047] To explain the structure of the drainage window blocker 8 in more detail, as shown in Figure 5, it comprises a skin plate 8a placed on the surface facing the concrete, ribs 8b extending from its periphery to the opposite side of the surface facing the concrete, and a cylindrical handle 8c straddling the upper rib 8b and the lower rib 8b. When attaching or detaching the drainage window blocker 8 to or from the drainage window 5, the handle 8c can be held by hand from outside the formwork.

[0048] (Concrete pouring method) Next, a method for pouring concrete using the above-mentioned formwork 1 with drainage windows will be described with reference to FIGS.

[0049] First, on the first day of pouring work, layer 2 of concrete with added super retarder is poured in the pouring of the final layer of concrete on the lower side up to joint surface 4. During the pouring of layer 2 of concrete with added super retarder, drainage window blockers 8 are attached to the drainage window 5 to close the drainage window 5 and prevent the poured concrete from leaking out of the drainage window 5.

[0050] When layer 2 of concrete containing the ultra-retardant is poured, vibration compaction is performed using a vibrator 11. When a separator 12 is embedded in layer 2 of concrete containing the ultra-retardant, as shown in Figure 6, the vibrator 11 is inserted to a depth at least such that the bottom end of the vibrator 11 is positioned approximately 10 cm below the separator 12.

[0051] Once compaction is complete, as shown in Figure 7, the drainage window blocker 8 is removed to open the drainage window 5. This allows bleeding water to be discharged from the drainage window 5. However, if the amount of bleeding water is small, only the drainage window 5 near the area where bleeding water has accumulated is opened before the second vibration on the second day of concrete pouring, and the bleeding water is discharged from there. The amount of bleeding water can be determined based on the amount of bleeding water that has accumulated on the surface after the vibration of the vibrator 11 and the amount of bleeding obtained from a preliminary test.

[0052] After a predetermined time has passed, i.e., after the time between pouring joints has passed, layer 2 of the concrete to which the super-retardant has been added is re-vibrated by vibrator 11, as shown in Figure 8. The depth of insertion of vibrator 11 at this time is set to a position 10 cm above the bottom end of layer 2 of the concrete to which the super-retardant has been added, as shown in Figure 8. Re-vibration reduces voids and excess water in the concrete, improving the strength of the concrete and also improving the integrity of the poured joints, which is also effective in preventing cracks.

[0053] Once the re-vibration of the layer 2 of concrete containing ultra-retardant has been completed, the bleeding water is removed as shown in Figure 9. The bleeding water will naturally flow out of the drainage windows 5 if they are left open, but some of it may accumulate on the joint surface 4. To remove the bleeding water that has accumulated on the surface, as shown in Figure 9, a worker can absorb and remove the bleeding water from atop scaffolding 20 set up above the formwork 1 with drainage windows using a rod 21 with a water-absorbing material 22 such as a sponge or cloth attached to the tip. Alternatively, the bleeding water that has accumulated on the surface may be discharged from the drainage windows 5 using a blower or wiper.

[0054] Thereafter, a drainage window blocking body 8 is attached to the drainage window 5 to close the drainage window 5, and the first layer of concrete 3 is poured starting from the joint surface 4, as shown in Figure 10. The concrete 3 poured here may be standard concrete, or may be concrete to which a hardening accelerator has been added, as shown in the above-mentioned Patent Document 1 (JP 2021-130982 A).

[0055] As shown in Figure 10, when pouring the concrete 3, the vibrator 11 is inserted to a depth where the bottom end of the vibrator 11 reaches the layer 2 of concrete to which an ultra-retardant has been added, specifically, to a depth where the bottom end of the vibrator 11 is positioned about 10 cm below the joint surface 4. This improves the integrity of the poured joint.

[0056] Thereafter, as shown in Figure 11, concrete 7 is poured in layers in the upward direction on top of the concrete layer 3 in accordance with standard concrete pouring. The standard height of each layer of concrete 7 is 40 to 50 cm or less.

[0057] (Variation) Next, a modified example will be described. In the above embodiment, a detachable drainage window blocking body 8 was used, which was fixed to the surrounding formwork with bolts and nuts 10 via packing 9, but as shown in Figure 12, a shutter-type drainage window blocking body 8A whose blocking height can be adjusted in the vertical direction may also be used. This shutter-type drainage window blocking body 8A is a modified example of the means for switching the drainage window 5 between the closed state and the open state.

[0058] As shown in Figure 12, the shutter-type drainage window blocking body 8A is configured so that the opening of the drainage window 5 can be gradually made smaller from the bottom end of the drainage window 5 upward, and the bottom end of the opening formed by the drainage window 5 can be adjusted to any height. This makes it possible to switch between the closed state of Figure 12(A) and the open state of (B), and also to adjust to any height according to the pouring height of the layer 2 of concrete to which an ultra-retardant has been added, as shown in (C).

[0059] Next, as a modification of the construction joint surface 4 (upper surface) of the layer 2 of concrete to which the ultra-retardant has been added, while in the above example it was formed almost flat and horizontal, it may also be adjusted in height so as to slope downwards towards the drainage windows 5, as shown in Figure 13. That is, when formwork 1 with drainage windows is installed on both the left and right sides as shown in Figure 13, the construction joint surface 4 is formed with a mountain-shaped cross section by making the pouring height of the center higher than that of the left and right sides. This allows bleeding water that occurs on the construction joint surface 4 to naturally drain out through the drainage windows 5, reducing the burden of the work of removing the bleeding water. [Explanation of symbols]

[0060] 1...Formwork with drainage window, 2...Layer of concrete with added super retarder, 3...Concrete, 4...Construction joint surface, 5...Drainage window, 6 and 7...Standard concrete, 8...Drainage window blocker, 9...Packing, 10...Bolts and nuts, 11...Vibrator, 12...Separator

Claims

1. A form used when pouring concrete onto an upper layer of a layer of concrete to which an ultra-retardant has been added, A formwork with a drainage window, characterized in that an openable and closable drainage window is provided at a height position including the joint surface of the concrete to which the ultra-retardant has been added.

2. The upper end of the drainage window is located above the joint surface of the concrete to which the ultra-retardant has been added, 2. A formwork with drainage windows according to claim 1, wherein the lower end of the drainage window is positioned at the same level as or below the joint surface of the concrete to which the ultra-retardant has been added.

3. 2. A formwork with drainage windows according to claim 1, wherein the drainage windows are switchable between a closed state in which they are closed by a drainage window closing body and an open state in which they are open.

4. The drainage window can be opened and closed by attaching and detaching a drainage window blocking body, 2. A formwork with drainage windows according to claim 1, wherein the drainage window blocking body is fixed to the surrounding formwork with bolts and nuts via a packing.

5. 2. A formwork with drainage windows according to claim 1, wherein the drainage windows can be opened and closed by shutter-type drainage window closing bodies whose closing height can be adjusted in the vertical direction.

6. A method for pouring concrete using a formwork with drainage windows according to any one of claims 1 to 5, After the drainage window is closed and concrete containing the ultra-retardant is poured, A method of pouring concrete, characterized in that the drainage window is left open so that bleeding water can be constantly discharged from the drainage window until concrete is poured on top of it, or before concrete is poured on top of the concrete to which the ultra-retarder has been added, only the drainage window near the location where bleeding water has accumulated is opened so that bleeding water can be discharged from there.

7. 7. A method for pouring concrete according to claim 6, wherein the height of the joint surface of the layer of concrete containing the ultra-retardant is adjusted so that it slopes downward toward the drainage window.

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