Concrete formwork panels

Abstract

To provide a concrete formwork panel that improves the flatness of the concrete surface after hardening and firmly holds nails without worsening the efficiency of the work when removing the concrete formwork panel. [Solution] The concrete formwork panel 1 is a concrete formwork panel used for the weir plate 3 of the concrete formwork 2, and comprises a pair of skin layers made of thermoplastic resin, a pair of intermediate layers laminated on each of the pair of skin layers and made of thermoplastic resin with a void ratio higher than that of the skin layers, and a layer laminated between the pair of intermediate layers and made of thermoplastic resin, middle This includes a core layer with a lower porosity than the porosity of the layer.

Description

[Technical Field]

[0001] The present invention relates to a resin concrete formwork panel that can be used as a formwork board for concrete pouring. [Background technology]

[0002] Conventional concrete formwork panels are described, for example, in Patent Document 1. Patent Document 1 describes a concrete formwork panel obtained by melt-kneading a polypropylene resin, a biomass filler, and an inorganic filler, adjusting the resulting composition so that its melt tension at 190°C is 10 mN to 100 mN and its melt flow rate (MFR) measured under conditions of 190°C and a load of 10 kg is 2 to 15, to which 0.3 to 0.8 parts by weight of a foaming agent is added, and then extruding and foam-molding the resulting pellets. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-176599 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When concrete formwork panels are used as the damming plates for concrete formwork, the concrete formwork panels are fixed to wooden vertical and horizontal battens with nails. In this case, if the strength of the concrete formwork panels is insufficient, the heads of the nails driven in will be embedded from one surface of the concrete formwork panel, creating multiple depressions on that surface. As a result, when concrete is poured, unhardened, fluid concrete flows into these depressions, and after curing, the surface of the hardened concrete will have raised areas from these depressions as transfer marks, reducing the flatness of the concrete surface.

[0005] Furthermore, since the poured concrete flows into the aforementioned multiple depressions and hardens, when the concrete formwork is dismantled after curing, the hardened concrete acts as an anchor, requiring a lot of effort to remove the concrete formwork panels, resulting in poor work efficiency.

[0006] Furthermore, when removing concrete formwork, workers may shake it, causing the formwork itself to warp or twist, which can cause the nails securing the concrete formwork panels to come loose. In such cases, the nails must be driven in again. Considering that concrete formwork panels are used multiple times, it is necessary for the concrete formwork panels to firmly hold the nails that have been driven in.

[0007] Conventional concrete formwork panels failed to address the aforementioned problems and satisfy the requirements.

[0008] The object of the present invention is to provide a concrete formwork panel that can firmly hold nails without improving the flatness of the surface of hardened concrete and without worsening the efficiency of the work when removing the concrete formwork panel. [Means for solving the problem]

[0009] The present invention relates to a concrete formwork panel used as a slab for concrete formwork, A pair of skin layers made of thermoplastic resin, A pair of intermediate layers are laminated on each of the aforementioned pair of skin layers, are made of thermoplastic resin, and have a porosity higher than that of the skin layers, Laminated between the pair of intermediate layers, made of thermoplastic resin, middle This concrete formwork panel is characterized by including a core layer with a void ratio lower than that of the layer.

[0010] Furthermore, the present invention provides that the skin layer has a porosity of 0.6 to 8%. The porosity of the pair of intermediate layers is 30-60%. The porosity of the core layer is 4-32%. The difference between the porosity of the pair of intermediate layers and the porosity of the core layer is set to 20% or more.

[0011] Furthermore, the present invention is characterized in that the concrete formwork panels are made of the same thermoplastic resin. [Effects of the Invention]

[0012] According to the present invention, a concrete formwork panel is constructed by comprising a pair of skin layers made of thermoplastic resin with a void ratio of 0.6 to 8%, each of which comprises a pair of intermediate layers made of thermoplastic resin with a void ratio of 30 to 60%, and a core layer made of thermoplastic resin with a void ratio of 4 to 32%, which is laminated between the pair of intermediate layers. This configuration provides adequate resistance to nailing by workers, as well as by pneumatic nail guns such as air tackers or electric nail guns. Therefore, even when these concrete formwork panels are fixed to wooden vertical and horizontal battens with nails, the nails can be driven in with a consistent amount of force so that the heads are positioned almost flush with the surface of the concrete formwork panels. This prevents the formation of the aforementioned multiple depressions on the surface of the concrete formwork panel, prevents the formation of multiple protrusions on the surface of the hardened concrete, and improves the flatness of the concrete surface. Furthermore, since it is possible to reduce the flow of unhardened, fluid concrete into depressions, the anchoring effect produced by hardened concrete can be reduced, and the efficiency of the work when removing concrete formwork panels can be prevented from being worsened. Furthermore, the combination of the skin layer and core layer allows for significant frictional force to be applied to the nail, enabling a firm hold on the nail.

[0013] Also, according to the present invention, since the concrete formwork panel is made of the same thermoplastic resin, it can be manufactured by an extrusion foam molding machine by adjusting the foaming ratio for each layer, and an increase in cost can be suppressed.

Brief Description of Drawings

[0014] [Figure 1] It is an enlarged cross-sectional view of a part of the concrete formwork panel according to an embodiment of the present invention. [Figure 2] It is a perspective view showing an example of the concrete formwork 2. [Figure 3] It is a cross-sectional view of a part of the concrete formwork 2. [Figure 4] It is a cross-sectional view schematically showing the configuration of the five-layer concrete formwork panels 1a to 1c of Example 1 of the present invention. [Figure 5] It is a cross-sectional view schematically showing the configuration of the three-layer concrete formwork panels 20a to 20c of Comparative Example 1. [Figure 6] It is a cross-sectional view schematically showing the configuration of the single-layer concrete formwork panels 30a to 20c of Comparative Example 2. [Figure 7] It is a diagram showing the results of the nail head immersion test. (a) is a diagram showing the state where a nail is driven into the concrete formwork panel 1a using a nail driving machine, (b) is a diagram showing the state where a nail is driven into the concrete formwork panel 20a using a nail driving machine, and (c) is a diagram showing the state where a nail is driven into the concrete formwork panel 30a using a nail driving machine.

Modes for Carrying Out the Invention

[0015] FIG. 1 is an enlarged cross-sectional view of a part of the concrete formwork panel 1 according to an embodiment of the present invention. In FIG. 1, the voids are shown as black portions.

[0016] The concrete formwork panel 1 of this embodiment includes a pair of skin layers A and E made of thermoplastic resin with a void ratio of 0.6 to 8%, a pair of intermediate layers B and D made of thermoplastic resin with a void ratio of 30 to 60% and laminated on each of the pair of skin layers A and E, and a core layer C made of thermoplastic resin with a void ratio of 4 to 32% and laminated between the pair of intermediate layers B and D. Here, the difference between the void ratio of the pair of intermediate layers B and D and the void ratio of the core layer C is set to 20% or more.

[0017] For the sake of convenience in the following explanation, one of the pair of skin layers A and E mentioned above may be referred to as the first skin layer A, the other as the second skin layer E, one of the pair of intermediate layers B and D may be referred to as the first intermediate layer B, and the other as the second intermediate layer E.

[0018] For example, the thickness T1 of the first skin layer A is 0.4 to 0.5 mm, the thickness T2 of the first intermediate layer B is 4.6 to 5.6 mm, the thickness T3 of the core layer C is 0.1 mm, the thickness T4 of the second intermediate layer D is 5.1 to 6.4 mm, and the thickness T5 of the first skin layer E is 0.3 to 0.6 mm.

[0019] In this embodiment, the thermoplastic resins constituting the pair of skin layers A and E, the pair of intermediate layers B and D, and the core layer C are acrylonitrile, butadiene, and styrene copolymer resins (abbreviated as ABS resin). However, the invention is not limited to these, and for example, polypropylene resin, polyethylene resin, polystyrene resin, etc. may also be used.

[0020] For reference, the porosities of the pair of skin layers A and E, the pair of intermediate layers B and D, and the core layer C are as follows: The porosity of the first skin layer A is 4.84%, the porosity of the first intermediate layer B is 14.89%, the porosity of the core layer C is 3.28%, the porosity of the second intermediate layer D is 18.18%, and the porosity of the second skin layer E is 2.47%. The surface hardness of skin layers A and E is selected to be 25 to 35, preferably 30, on the Rockwell hardness scale.

[0021] <Method for measuring porosity> The aforementioned method for measuring porosity will be explained using the example of measuring the porosity of intermediate layer B. First, using a contour machine, cuts are formed from each end of the concrete formwork panel in the width direction perpendicular to the longitudinal direction, up to partway through the intermediate layer B. Next, the concrete formwork panel is gripped so that a crack surface is formed between the cuts (stress is concentrated), and a bending moment is applied in the direction that brings each end in the width direction closer together to cause it to break. The cross-section of intermediate layer B, excluding the portion cut with a contour machine, was imaged using a KEYENCE Corporation microscope (product name "VHX-8000") with a magnification of 150x to 200x. During this process, "high-resolution depth stacking" was used to correct for focus misalignment of the surface irregularities in the imaged cross-section. The image analysis software included with the microscope manufactured by Keyence Corporation is used to calculate the porosity of the obtained image data. Specifically, "automatic area measurement" → "manual" → "filter processing" is performed to remove uneven brightness, remove noise, and extract contours. Then, "specify extraction area" → "specify brightness (extraction range)" is performed to calculate the porosity as the ratio of the area of ​​voids within the extracted area (area). In other words, the void area in intermediate layer B is calculated, and the ratio of the void area to the total area is calculated as the void ratio of intermediate layer B. The method for measuring void ratio described above is the same when measuring the void ratio of each layer.

[0022] When the porosity of the first skin layer A was measured, the obtained image data contained voids No. 1 to No. 13, which are the basis for calculating the porosity of the first skin layer A. Table 1 shows the area, perimeter, maximum diameter, and minimum diameter of voids No. 1 to No. 7, which are representative examples. As shown in Table 1, the total area of ​​voids No. 1 to No. 13 is 418.15 μm². 2 The total area of ​​the first skin layer A in the excised region is 65054.50 μm². 2These results were obtained. Using these, the area of ​​voids in the total area of ​​the first skin layer A was expressed as a percentage, which was 0.64%.

[0023] [Table 1]

[0024] When the porosity of the first intermediate layer B was measured, the obtained image data contained voids No. 1 to No. 901, which are the basis for calculating the porosity of the first intermediate layer B. Table 2 shows the area, perimeter, maximum diameter, and minimum diameter of voids No. 1 to No. 7, which are representative examples. As shown in Table 2, the total area of ​​the voids from No. 1 to No. 901 is 809152.21 μm². 2 Therefore, the total area of ​​the first intermediate layer B in the extracted region is 2,169,198.96 μm². 2 These results show that the area of ​​voids in the total area of ​​the first intermediate layer B, expressed as a percentage, was 37.30%.

[0025] [Table 2]

[0026] When the porosity of core layer C was measured, the obtained image data contained voids No. 1 to No. 199, which are the basis for calculating the porosity of core layer C. Table 3 shows the area, perimeter, maximum diameter, and minimum diameter of voids No. 1 to No. 7, which are representative examples. As shown in Table 3, the total area of ​​the voids from No. 1 to No. 199 is 0.080 mm². 2 Therefore, the total area of ​​core layer C in the extracted region is 0.752 mm². 2 These results show that the area of ​​voids in the total area of ​​core layer C, expressed as a percentage, was 10.662%.

[0027] [Table 3]

[0028] When measuring the porosity of the second intermediate layer D, in the obtained image data, there were voids numbered from No.1 to No.1253 that served as the basis for calculating the porosity of the second intermediate layer D. Table 4 shows the areas, perimeters, maximum diameters, and minimum diameters of the voids numbered from No.1 to No.7, which are representative examples among them. As shown in Table 4, the total area of the voids numbered from No.1 to No.1253 was 0.881 mm 2 and the total area of the second intermediate layer D in the cut-out region was 2.292 mm 2 Using these values, when expressing the area of the voids as a percentage of the total area of the second intermediate layer D, it was 38.464%.

[0029] [Table 4]

[0030] When measuring the porosity of the second skin layer E, in the obtained image data, there were voids numbered from No.1 to No.106 that served as the basis for calculating the porosity of the second skin layer E. Table 5 shows the areas, perimeters, maximum diameters, and minimum diameters of the voids numbered from No.1 to No.7, which are representative examples among them. As shown in Table 5, the total area of the voids numbered from No.1 to No.106 was 0.017 mm 2 and the total area of the second skin layer E in the cut-out region was 1.282 mm 2 Using these values, when expressing the area of the voids as a percentage of the total area of the second skin layer E, it was 1.315%.

[0031] [Table 5]

[0032] Figure 2 is a perspective view showing an example of concrete formwork 2, and Figure 3 is a cross-sectional view of a part of concrete formwork 2. Concrete formwork panel 1 is used for the weir board 3 of concrete formwork 2. Concrete formwork 2 includes a plurality of vertical bars 4, a plurality of horizontal bars 5, and a weir board 3 fixed to the vertical bars 4 and horizontal bars 5 by nails 6. The plurality of vertical bars 4 and the plurality of horizontal bars 5 are made of wooden square timbers. The plurality of vertical bars 4 extend in the vertical direction, which is the up and down direction in Figure 3, and are arranged horizontally perpendicular to the plane of paper in Figure 3 at intervals of about 300 to 500 mm from each other.

[0033] The concrete formwork 2 further includes a separator 7, a pair of fasteners 8 also called cones, two support pipes 9, pipe holders 10 that hold each pair of support pipes 9, connecting bolts 11 that connect the fasteners 8 and the pipe holders 10, a first lock nut 12 that secures the pipe holders 10 to the connecting bolts 11, and a second lock nut 13 that secures the connecting bolts 11 to the fasteners 8.

[0034] The concrete formwork panel 1 can be manufactured using an extrusion foam molding machine. First, pellets made of thermoplastic resin, which are the raw material, are heated and melted. A foaming agent is then mixed into the raw material to form a pair of skin layers A and E, a pair of intermediate layers B and D, and a core layer C. The panel is then obtained by extrusion foam molding, with the core layer C in the center, sandwiched between intermediate layers B and D, and intermediate layers B and D sandwiched between skin layers A and E.

[0035] <Examples> Figure 4 is a schematic cross-sectional view showing the configuration of the five-layer concrete formwork panels 1a to 1c of Examples 1 to 3 of the present invention; Figure 5 is a schematic cross-sectional view showing the configuration of the three-layer concrete formwork panels 20a to 20c of Comparative Example 1; and Figure 6 is a schematic cross-sectional view showing the configuration of the one-layer concrete formwork panels 30a to 30c of Comparative Example 2.

[0036] In this example, ABS resin "EX74J" manufactured by Techno UMG was used as the raw material, and "Vinihole AC#3" manufactured by Eiwa Kasei Kogyo Co., Ltd. was used as the foaming agent.

[0037] The inventors created concrete formwork panels 1a to 1c with different foaming ratios for intermediate layers B and D to confirm how the degree of nail head embedding in concrete formwork panel 1 changes by varying the foaming ratio of intermediate layers B and D. Furthermore, to confirm the superiority of the present invention, which consists of a five-layer concrete formwork panel, the inventors compared it with Comparative Examples 1 and 2. The thickness of the example and Comparative Examples 1 and 2 were identical and set to 12 mm.

[0038] Concrete formwork panel 1a has a foaming ratio of 1.5 times for intermediate layers B and D, with skin layers A and E set to 1. Concrete formwork panel 1b has a foaming ratio of 1.8 times for intermediate layers B and D. Concrete formwork panel 1c has a foaming ratio of 2.0 times for intermediate layers B and D.

[0039] Comparative Example 1 consists of three-layer concrete formwork panels 20a to 20c, where the foaming ratio of the intermediate layer F differs from that of the skin layers A and E. Concrete formwork panel 20a has an intermediate layer F foaming ratio of 1.5 times, with skin layers A and E set to 1. Concrete formwork panel 20b has an intermediate layer F foaming ratio of 1.8 times. Concrete formwork panel 20c has an intermediate layer F foaming ratio of 2.0 times.

[0040] Comparative Example 2 consists of single-layer (intermediate layer G) concrete formwork panels 30a to 30c, where concrete formwork panel 30a is made only from concrete formwork panel 20a of Comparative Example 1, concrete formwork panel 30b is made only from concrete formwork panel 20b of Comparative Example 1, and concrete formwork panel 30c is made only from concrete formwork panel 20c of Comparative Example 1.

[0041] For each of the specimens in Example 1, Comparative Example 1, and Comparative Example 2, the flexural modulus, maximum strength, maximum point displacement, porosity, and thickness of each layer were measured, and the measurement results are shown in Tables 6 to 11 below. For the porosity of the high-foaming layer, the porosity was measured at three locations, and the average was also calculated.

[0042] [Table 6]

[0043] [Table 7]

[0044] [Table 8]

[0045] [Table 9]

[0046] [Table 10]

[0047] [Table 11]

[0048] As is clear from Tables 6-11, even with the same thickness, Examples 1a-1c have higher flexural modulus and maximum strength, and lower maximum point displacement compared to Comparative Examples 20a-20c and 30a-30c. Therefore, when manufacturing concrete formwork panels by foaming the same resin, the configuration of the present invention can produce the most rigid concrete formwork panel.

[0049] <Nail head immersion test> Figure 7 shows the results of the nail head immersion test, where (a) shows the state in which nails have been driven into concrete formwork panel 1a using a nail gun, (b) shows the state in which nails have been driven into concrete formwork panel 20a using a nail gun, and (c) shows the state in which nails have been driven into concrete formwork panel 30a using a nail gun.

[0050] In the concrete formwork panels 1a-1c of the example, concrete formwork panels 20a-20c of comparative example 1, and concrete formwork panels 30a-30c of comparative example 2, vertical battens were placed on top of each other. Ten nails were then driven in consecutively from one surface using a nail gun, and it was observed whether or not depressions were formed around the nail heads. The results of the test are shown in Table 12. Test conditions Nail gun: Product name "High-pressure air nail gun AN534HM" Manufactured by Makita Corporation Air compressor: Product name "MAX 9700E" Manufactured by Makita Corporation Nails: Product name "NC21-50" Head diameter: 4.8mm, Shank diameter: 2.1mm, Length: 50mm Manufactured by Daido Hunt Co., Ltd. Supply pressure: 1.8 MPa

[0051] [Table 12]

[0052] As is clear from Figure 7 and Table 12, the concrete formwork panels 1a to 1c of the embodiment can significantly reduce the formation of depressions compared to Comparative Examples 1 and 2. This makes it possible to obtain a highly flat surface with fewer protrusions on the surface of the hardened concrete. Furthermore, since the formation of depressions on the surface of the concrete formwork panel 1 can be reduced, the efficiency of the work when removing the concrete formwork panel after the concrete has hardened is not worsened.

[0053] <Nail pull-out strength test> Nails were driven into the concrete formwork panels 1a-1c of the example, concrete formwork panels 20a-20c of comparative example 1, and concrete formwork panels 30a-30c of comparative example 2 under the same conditions, and the pull-out distance, which is the distance from the start of pulling out the nail when the maximum test force was reached, was measured. The test results are shown in Table 13.

[0054] [Table 13]

[0055] As shown in Table 13, when equipped with a high-foaming layer with the same foaming ratio, the concrete formwork panels 1a to 1c of the example exhibit a greater pull-out distance compared to the concrete formwork panels 20a to 20c of Comparative Example 1 and the concrete formwork panels 30a to 30c of Comparative Example 2. Therefore, it can be seen that the concrete formwork panels 1a to 1c of the example have a higher nail holding force.

[0056] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various modifications and improvements are possible without departing from the spirit of the invention. It goes without saying that all or part of each of the above embodiments can be combined as appropriate and in a non-contradictory manner. [Explanation of Symbols]

[0057] 1. Concrete formwork panel 2. Concrete formwork 3 Weir plate 4 vertical bars 5 horizontal bars 6 nails 7 Separator 8 Fasteners 9 Support pipes 10 Pipe holders 11 Connecting bolts 12. First lock nut 13. Second lock nut A, E skin layer C Core Layer B,D Middle layer

Claims

1. A concrete formwork panel used as a dam board for concrete formwork, A pair of skin layers made of thermoplastic resin, A pair of intermediate layers are laminated on each of the aforementioned pair of skin layers, are made of thermoplastic resin, and have a porosity higher than that of the skin layers, A concrete formwork panel characterized by comprising a core layer laminated between the pair of intermediate layers, made of a thermoplastic resin, and having a porosity lower than that of the intermediate layers.

2. The aforementioned skin layer has a porosity of 0.6 to 8%. The porosity of the pair of intermediate layers is 30 to 60%. The porosity of the core layer is 4 to 32%. The concrete formwork panel according to claim 1, characterized in that the difference between the void ratio of the pair of intermediate layers and the void ratio of the core layer is set to 20% or more.

3. The concrete formwork panel according to claim 1, characterized in that the concrete formwork panel is made of the same thermoplastic resin.

Images