Formwork skin plate

Abstract

To provide a formwork skin plate that reliably reduces surface air bubbles in concrete and improves the quality of the concrete.SOLUTION: A thermal spray coating layer 12 is provided on a surface of a steel plate 11 that constitutes a formwork surface of a formwork for concrete placement. The surface roughness of the thermal spray coating layer 12 is 55.6 to 93.7 μm, more preferably 75 to 92 μm. The thermal spray coating layer 12 is preferably an arc spray layer of stainless steel. Further, it is preferable to use an antifoaming agent in combination with the release agent applied to the formwork surface of a formwork skin plate 10.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a formwork skin plate for a concrete casting formwork, in which a sprayed coating layer is provided on the surface of a steel plate constituting the formwork surface of the formwork. By setting the surface of the sprayed coating layer within a predetermined roughness range, the formwork skin plate reduces the surface bubbles of concrete.

Background Art

[0002] The quality of the concrete surface layer is important not only for improving the aesthetics but also for improving the durability of the structure. That is, when surface bubbles are formed in the concrete, the cover thickness of the concrete decreases, leading to a decrease in durability and the possibility of early deterioration.

[0003] Particularly in the placement of lining concrete in mountain tunnels, concrete is placed and compacted in a narrow space, and on the side wall below the spring line (SL), the finished surface is inclined with a negative gradient. Therefore, it has been pointed out that problems related to surface quality such as surface bubbles, floating and peeling are likely to occur.

[0004] As technologies for improving the quality of the concrete surface layer, for example, the following Patent Documents 1 to 4 can be cited.

[0005] Patent Documents 1 to 3 below describe a formwork panel in which a large number of slits are uniformly scattered and drilled in a panel steel plate, and a breathable substance layer such as ceramic is formed on the surface of the panel steel plate. By using this formwork panel for concrete casting, it is described that moisture and bubbles in the concrete can leach out to the outside through the porous breathable substance layer and the slits.

[0006] Furthermore, Patent Document 4, described below, describes how, by spraying stainless steel powder material onto the concrete casting surface of a formwork steel plate for concrete pouring using a gas plasma spraying machine, the stainless steel powder material sprayed onto the surface of the formwork steel plate forms a coating layer containing many voids on the surface of the formwork steel plate, thereby forming a porous metal layer on the surface. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 153470 / 1983 [Patent Document 2] Japanese Patent Application Publication No. 63-67373 [Patent Document 3] Japanese Patent Application Publication No. 63-67374 [Patent Document 4] Japanese Patent Publication No. 2006-207277 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, in the case of forming a porous ceramic layer on the surface of a steel panel as described in Patent Documents 1 to 3 above, the opening ratio of the ceramic layer is not very high, so the amount of water and air bubbles in the concrete that can seep out to the outside through the ceramic layer and slits is insufficient, and there is a risk that surface bubbles will easily form in the concrete. In Patent Document 4 above, it is also described that the void ratio of the porous metal layer is about 10%, and it is presumed that the amount of air bubbles that can flow out to the outside through these voids is insufficient to prevent surface bubbles.

[0009] Furthermore, Patent Document 4 describes a process in which a porous metal layer is formed by plasma spraying, and then a finishing process (such as sanding) is performed to adjust the roughness (surface roughness) of the formed porous metal layer. It is believed that such a surface finishing process is performed to reduce the surface roughness of the formwork surface, thereby forming concrete with a smooth surface. However, if the roughness of the formwork surface is too low, fine air bubbles can easily flow across the formwork surface, and in the process of flowing, these bubbles can combine to form larger bubbles, potentially degrading the quality of the concrete surface layer. Conversely, if the roughness of the formwork surface is too high, air bubbles can concentrate in the recesses of the formwork surface, forming larger bubbles, which also potentially degrades the quality of the concrete surface layer.

[0010] Thus, while the roughness of the formwork surface is a major factor affecting the quality of the concrete surface, conventionally, the focus has been solely on reducing the surface roughness of the formwork and creating a smooth formwork surface, without considering the optimal roughness range for the quality of the concrete surface.

[0011] Therefore, the main problem of the present invention is, When pouring lining concrete in mountain tunnels, This method effectively reduces surface air bubbles in concrete and improves the quality of the concrete. Ruko It is located there. [Means for solving the problem]

[0012] To solve the above problems, the present invention according to claim 1 is: A concrete pouring formwork for a center used for pouring lining concrete in a mountain tunnel, the aforementioned In a formwork skin plate in which a thermal spray coating layer is provided on the surface of a steel plate that constitutes the formwork surface of a concrete pouring formwork, The aforementioned thermal spraying coating The layers are made of stainless steel, When pouring the lining concrete Only a release agent is applied to the surface of the aforementioned formwork skin plate. use Use an antifoaming agent in combination with the condition or release agent. use Under the conditions, Surface roughness of the thermal spray coating layer (maximum height Rz in accordance with JIS B 0601) is 7There is provided a formwork skin plate characterized in that it has a range of 5 to 92 μm.

[0013] In the invention according to claim 1, in a formwork skin plate provided with a thermal spraying coating layer made of stainless steel on the surface of a steel plate, paying attention to the optimum roughness range for improving the quality of the concrete surface layer, the thermal spraying coating layer is composed of stainless steel, and When pouring the lining concrete only a release agent is applied to the surface of the formwork skin plate use or a defoaming agent is used in combination with the release agent use Under the conditions, the roughness (maximum height Rz conforming to JIS B 0601) of the surface of the thermal spraying coating layer is 7 is set to 5 to 92 μm. By setting the surface of the thermal spraying coating layer within this roughness range, from the results of the [Experiment] described later, the flaking rate can be reduced compared to the case of a steel plate without a thermal spraying coating layer, and the quality of the concrete can be reliably improved. If the roughness of the surface of the thermal spraying coating layer (stainless steel) is less than 75 μm, the flaking rate may increase compared to the steel plate, and the surface bubbles of the concrete cannot be sufficiently reduced. The same applies when the roughness of the surface of the thermal spraying coating layer is greater than 92 μm.

[0014] In the formwork skin plate according to the present invention, by optimizing the roughness of the surface of the thermal spraying coating layer, the fine granular bubbles adhering to the surface of the formwork surface do not easily flow due to the unevenness of the formwork surface, and the combination of the fine granular bubbles is suppressed. Since the concrete solidifies without growing into large bubbles, it is considered that the generation of visible surface bubbles is suppressed.

Effect of the Invention

[0015] As described in detail above, according to the present invention, A concrete pouring formwork for a center used for pouring lining concrete in a mountain tunnel, the aforementioned In a formwork skin plate provided with a thermal spraying coating layer on the surface of a steel plate constituting the formwork surface of a formwork for concrete placement, by setting the surface of the thermal spraying coating layer within a predetermined roughness range, the surface bubbles of the concrete can be reliably reduced, and the quality of the concrete can be improved.

Brief Description of the Drawings

[0016] [Figure 1] It is a perspective view of a tunnel showing the installation status of the center 3. [Figure 2] It is a cross-sectional view of the tunnel. [Figure 3] It is a perspective view of the formwork skin plate 10. [Figure 4] It is a graph showing the relationship between the stainless steel sprayed layer and the roughness. [Figure 5] (A) is a cross-sectional view showing an experimental apparatus, and (B) and (C) are plan views of the skin plate. [Figure 6] It is a graph showing the relationship between the roughness and the flanging rate, showing the results of Experiment 1. [Figure 7] It is a graph showing the relationship between the roughness and the flanging rate, showing the results of Experiment 2.

Embodiments for Carrying out the Invention

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiment examples, the case where the formwork skin plate 10 according to the present invention is applied to the formwork of the center (movable formwork for placing lining concrete) used when placing lining concrete in a mountain tunnel is taken as an example and described in detail. However, the formwork skin plate 10 according to the present invention can be widely adopted as the skin plate of the formwork used when placing concrete in addition to the formwork of the center.

[0018] As shown in FIG. 1, the formwork skin plate 10 according to the present invention is used in the construction of a mountain tunnel T. After excavation by blasting or the like for each span in the tunnel direction, shotcrete 1 is applied to the excavated inner wall surface of the tunnel by spraying. After driving the rock bolts, a waterproof sheet 2 is pasted on the surface, and the formwork 5 of the center 3 is installed along the circumferential direction with a distance from the natural ground side wall surface T1. When placing lining concrete 4 in the space between the natural ground side wall surface T1 and the formwork 5, it is arranged on the formwork surface of the formwork 5.

[0019] The centering device 3 is installed behind the heavy machinery used for tunnel construction and, as shown in Figures 1 and 2, mainly consists of a formwork 5 positioned to form a space of a predetermined width between it and the natural ground wall T1 of the tunnel T, a support frame 6 that supports the formwork 5, and a running rail 7 that the support frame 6 can run on and which is laid on the underside of the tunnel T. As shown in Figure 3, the formwork 5 is equipped with a formwork skin plate 10 consisting of a steel plate 11 that constitutes the formwork surface and a thermal spray coating layer 12 provided on the surface of the steel plate 11. The formwork 5 is divided into a plurality of parts in the circumferential direction of the tunnel T, and each part is connected to the others. The formwork skin plate 10 according to the present invention is used on the concrete pouring surface of each formwork 5. Although not shown, the formwork 5 is provided with a concrete pouring opening for pouring concrete near the tunnel entrance at the top, and inspection windows are provided at appropriate locations. As shown in Figures 1 and 2, the formwork 5 is attached to the support frame 6 via connecting members such as a hydraulic cylinder 6A so as to be movable in the left-right and up-down directions relative to the cross-section of the tunnel T. The support frame 6 consists of a gate-shaped frame 6B made of a roughly gate-shaped steel frame and other materials, and connecting members such as the hydraulic cylinder 6A to which the formwork 5 is attached. The aforementioned running rails 7 support the gate-type frame 6B so that it can run on them, and are laid in two rows along the longitudinal direction on the underside of the tunnel T.

[0020] Next, the formwork skin plate 10, which is placed on the formwork surface of the formwork 5, will be described in detail. The steel plate 11 that serves as the base material for the formwork skin plate 10 is generally made of steel plate with a thickness of about 9 mm and has a curved surface that follows the circumferential shape of the tunnel T. The steel plate 11 does not have any openings or slits that penetrate through to the front and back, except for concrete pouring openings and inspection windows, so that the poured concrete does not leak out.

[0021] The thermal spray coating layer 12 provided on the surface of the steel plate 11 is a surface treatment layer obtained by heating a thermal spray material to melt or soften particles, which are then sprayed onto a substrate and layered. As the molten material, metals such as stainless steel, aluminum, nickel, copper, and zinc, or ceramics can be used, but it is preferable to use metals because of their excellent durability, and among metals, it is more preferable to use stainless steel because it is highly elastic and provides a hard coating layer.

[0022] Thermal spraying methods include arc spraying and plasma spraying, but arc spraying is preferred due to its high spraying speed and low cost. When stainless steel (SUS316) wire is arc sprayed, the particle size of the molten material is 20 to 100 μm. When performing plasma spraying, it is preferable to use a spray material in powder form with a particle size of 20 to 30 μm.

[0023] The thermal spray coating layer 12 is preferably composed of only one layer, but it may also be composed of multiple layers in which coating layers differing in one or more of the thermal spray material, thermal spray method, and thermal spray conditions. For example, the first layer may be thermal spray method: arc spraying, thermal spray material: stainless steel (SUS316), and the second layer may be thermal spray method: plasma spraying, thermal spray material: ceramics. This allows for fine adjustment of the surface roughness by the surface ceramic layer, and because the stainless steel thermal spray coating layer 12 is interposed between the base steel plate 11 and the outer ceramic layer, the elasticity of the stainless steel layer increases the bonding strength to the ceramic layer, improving the durability of the ceramic layer.

[0024] The optimal surface roughness (maximum height Rz in accordance with JIS B 0601) of the thermal spray coating layer 12 is 55.6 to 93.7 μm. By setting the roughness within this range, as shown in the [experiment] described later, surface bubbles are less likely to form compared to those using steel plates on the surface, thereby improving the quality of the concrete. Also, as shown in the [experiment] described later, it is preferable to set the roughness to 75 to 92 μm.

[0025] There are no particular restrictions on the thickness of the thermal spray coating layer 12. However, if the thickness of the thermal spray coating layer 12 is too small, especially when blast treatment is applied, the surface irregularities of the steel plate 11 cannot be covered by the thermal spray coating layer, and areas where the base material is exposed will appear. Therefore, the minimum thickness should be 50 μm or more. Since the steel plate 11 and the thermal spray coating layer 12 are mechanically bonded, if the thickness of the thermal spray coating layer 12 exceeds 300 μm, distortion is likely to occur due to residual stress, and the thermal spray coating layer 12 may peel off from the surface of the steel plate 11. Therefore, the maximum thickness should be 300 μm or less. Preferably, it is 50 to 150 μm, more preferably 50 to 100 μm.

[0026] An example of thermal spraying conditions that can produce such a coating is as follows: using stainless steel (SUS316) wire as the spraying material, with a voltage of 25-35V, a current of 200-400A, and an air pressure of 3-5 kg / cm². 2 Arc spraying is performed at a distance of 100-500 mm from the substrate.

[0027] The surface roughness of the thermal spray coating layer 12 can be adjusted by one or more of the following means. The first means is to adjust the thickness of the thermal spray coating layer 12. Increasing the thickness increases the roughness, while decreasing it decreases the roughness. However, if it is too thin, the substrate cannot be covered with the thermal spray coating, so it is preferable to set it to 50 μm or more. The second means is to adjust the heating temperature of the thermal spray material. To adjust the heating temperature, the current or voltage can be adjusted in the case of arc spraying, and the plasma current can be adjusted in the case of plasma spraying. By heating the thermal spray material to a high temperature and melting it completely, the particles are dispersed by the impact when it hits the substrate, making it easier to smooth the surface. On the other hand, if the heating temperature of the thermal spray material is low and the thermal spray material is in a semi-molten state, irregularities will be formed by unmelted or partially molten particles even after hitting the substrate, resulting in a higher roughness. The third means is to adjust the distance between the tip of the thermal spray nozzle and the substrate. Increasing the spraying distance tends to increase the surface irregularities because the sprayed particles, once molten, cool down, reducing their flattening behavior upon impact and causing them to stack.

[0028] The surface of the steel plate 11 on which the thermal spray coating layer 12 is provided does not necessarily need to be surface-treated, but it is preferable to perform a blast treatment such as sandblasting in order to improve the bonding strength between the steel plate 11 and the thermal spray coating layer 12.

[0029] 〔experiment〕 An experiment was conducted to demonstrate the effect of surface roughness of the thermal spray coating layer 12 on surface air bubbles in concrete.

[0030] As a preliminary experiment, an experiment was conducted to investigate the relationship between the thickness of the thermal spray coating layer 12 and the roughness of the thermal spray coating layer 12. For the thermal spray coating, a stainless steel thermal spray layer was formed by arc spraying stainless steel onto a steel plate, and the surface roughness of each thermal spray coating layer was measured when the thickness of this thermal spray coating layer was varied to 50 μm, 100 μm, and 250 μm. The roughness was evaluated using the maximum height Rz in accordance with JIS B 0601.

[0031] The results are shown in Table 1 and Figure 4. From these results, it was found that increasing the thickness of the thermal spray coating layer (stainless steel thermal spray layer) tends to linearly increase the roughness. [Table 1]

[0032] Next, we conducted an experiment to measure the surface quality (pitter rate) of the concrete by pouring concrete using two types of skin plates: one made only of steel plate without a thermal spray coating layer on the concrete pouring surface, and another made of steel plate with thermal spray coating layers of different roughness levels on the surface.

[0033] As shown in Figure 5(A), the experimental apparatus is designed to pour concrete inside skin plates installed on both sides. Each of the skin plates has a roughly trapezoidal cross-section with a negative slope (inclination angle of 70°) to simulate the concrete side walls of a tunnel lining. As shown in Figures 5(B) and (C), each skin plate has the same dimensions, 1000 mm in height and 1144 mm in width, but the surface specifications differ in the two equally divided regions in the width direction. Specifically, as shown in Figure 5(B), one region of the surface of one skin plate is a steel plate without a thermal spray coating layer, while the other region is "Stainless Steel 50," which has a thermal spray coating layer of stainless steel with a thickness of 50 μm applied by arc spraying stainless steel. As shown in Figure 5(C), the surface of the other skin plate 1 is "stainless steel 100" in one area in the width direction, where a thermal spray coating layer of stainless steel is provided with an arc spraying method to a thickness of 100 μm, and "ceramics 50" in the other area, where a thermal spray coating layer of ceramics is provided with a thickness of 50 μm. When the length of the upper base of the trapezoidal cross-section (the distance between skin plates at the top of the formwork) is 300 mm, the length of the lower base (the distance between skin plates at the bottom of the formwork) is approximately 984 mm. In addition, both ends and the bottom of this formwork are closed with wooden formwork, and concrete is poured in from the open top surface.

[0034] The concrete mix design is as shown in Table 2 below. In the table, C: Blast furnace cement type B, manufactured by Sumitomo Osaka Cement Co., Ltd., density 3.04 g / cm³. 3 S1: Sand from Namegata City, Ibaraki Prefecture, surface dry density 2.58 g / cm³ 3 S2: Crushed sand from Aizawa, Sano City, Tochigi Prefecture, surface dry density 2.69 g / cm³ 3 G: Tsukuba City, Ibaraki Prefecture, 2005, crushed stone, surface dry density 2.69 g / cm³ 3 AD:AE water-reducing agent, Floric S, manufactured by Floric Co., Ltd. [Table 2]

[0035] After the concrete was poured, a 50mm diameter rod-shaped vibrator was inserted into the open top surface and vibrated at a total of eight locations for 10-15 seconds each. In addition, the outer surface of each skin plate was vibrated at eight locations for 10 seconds each using a formwork vibrator to compact it.

[0036] The experiment was conducted in two patterns, depending on the type of release agent applied to the formwork surface of the skin plate. Specifically, in Experiment 1, only a concrete release agent (Jet Coat G-MAX, manufactured by Chukyo Kasei Kogyo Co., Ltd.) was applied to the formwork surface of the skin plate, while in Experiment 2, the same concrete release agent was applied in combination with an antifoaming agent (Surface Screen, manufactured by Nippon Sika Co., Ltd.) to the formwork surface of the skin plate. For Experiments 1 and 2, concrete was poured, cured, and then the pitting rate of the demolded concrete surface was measured.

[0037] The aforementioned pitting ratio was measured by photographing the concrete surface with an imaging device, processing the images with a computer, and dividing the sum of the areas of the measured pitted portions by the measured area.

[0038] The measurement results are shown in Tables 3 and 4. Table 3 shows the results of Experiment 1 (when only the release agent was applied to the surface of the skin plate), and Table 4 shows the results of Experiment 2 (when the release agent was used in combination with an antifoaming agent). In the tables, "Ratio to steel plate (%)" indicates the percentage when the pitting rate of the steel plate in Experiment 1 is set to 100 (%). [Table 3]

[0039] [Table 4]

[0040] Furthermore, Figures 6 and 7 show graphs illustrating the relationship between roughness and pitting rate for Experiment 1 (when only the release agent was applied to the skin plate surface) and Experiment 2 (when the release agent was used in combination with an antifoaming agent). Note that the technical lower limit for the film thickness that can be formed by arc spraying stainless steel is 50 μm, and the roughness at this point is approximately 80 μm as shown in Figure 4. Since a lower roughness could not be obtained with the arc sprayed stainless steel layer, the values ​​for "Ceramics 50," which yields a lower roughness than "Stainless Steel 50," were used to consider the overall trend between roughness and pitting rate.

[0041] When the measurement points for "Ceramics 50," "Stainless Steel 50," and "Stainless Steel 100" are connected by a smooth curve, the roughness range in which the pitting rate is lower than that of steel plates is 55.6 μm or higher in Experiment 1, and 57.8 to 93.7 μm in Experiment 2. Therefore, although it depends on the release agent applied to the formwork surface of the formwork skin plate, by setting the surface roughness of the thermal spray coating layer 12 to 55.6 to 93.7 μm, the pitting rate can be kept lower than that of steel plates, and surface air bubbles in the concrete can be reliably reduced, thereby improving the quality of the concrete. The thickness of the stainless steel thermal spray layer required to achieve this roughness range (93.7 μm or less) is 112.5 μm or less, as shown in Figure 4.

[0042] Furthermore, the results of each experiment revealed that the roughness levels that minimized the pitting rate were 84.5 μm and 82.1 μm, respectively. From this, it can be said that the average value of these values, 83.3 μm, is the optimal surface roughness of the thermal spray coating layer that can minimize surface air bubbles in concrete. Moreover, assuming a variation of ±10% due to experimental and construction errors, the optimal roughness range of the thermal spray coating layer that can minimize surface air bubbles in concrete is approximately 75 to 92 μm. The thickness of the stainless steel thermal spray layer required to achieve this roughness range (92 μm or less) is 100.5 μm or less, as shown in Figure 4. Also, assuming a variation of ±5%, the optimal roughness range of the thermal spray coating layer is approximately 79 to 87 μm, and the thickness of the stainless steel thermal spray layer required to achieve a roughness range of 87 μm or less is 65.4 μm or less, as shown in Figure 4.

[0043] Considering the mechanism by which surface bubbles in concrete are suppressed by setting the roughness range described above, it is thought that within this roughness range, fine bubbles adhering to the surface of the formwork are less likely to flow due to the irregularities of the formwork surface, and as the concrete hardens without the fine bubbles combining with each other to grow into larger bubbles during the flow process, the generation of visible surface bubbles is suppressed.

[0044] Furthermore, comparing Experiment 1 (where only the release agent was applied to the skin plate surface) and Experiment 2 (where the release agent was used in combination with an antifoaming agent), Experiment 2 showed a lower overall pitting rate. Therefore, applying an antifoaming agent in combination with the release agent to the formwork surface of the skin plate, rather than applying only the release agent, can further reduce the pitting rate, reliably reducing surface bubbles in the concrete and improving the quality of the concrete. [Explanation of Symbols]

[0045] 1...Sprayed concrete, 2...Waterproofing sheet, 3...Centering, 4...Lining concrete, 5...Formwork, 6...Support frame, 7...Running rail, 10...Formwork skin plate, 11...Steel plate, 12...Thermal spray coating layer

Claims

[Claim 1] A concrete casting formwork for a center used for pouring lining concrete in a mountain tunnel, wherein a thermal spray coating layer is provided on the surface of a steel plate constituting the formwork surface of the concrete casting formwork, The aforementioned thermal spray coating layer is made of stainless steel, and under usage conditions in which only a release agent is applied to the surface of the formwork skin plate when pouring the lining concrete, or under usage conditions in which a release agent is used in combination with an antifoaming agent, A formwork skin plate characterized in that the surface roughness (maximum height Rz in accordance with JIS B 0601) of the thermal spray coating layer is in the range of 75 to 92 μm.

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