Reinforcing bar holding member

Abstract

To provide a reinforcement holding member having both inorganic physical properties such as high load resistance performance and a precise outer shape by injection molding.SOLUTION: A reinforcing bar holding member 1 of the present invention includes a support base 10 and a holding base 20 provided on the support base 10, in which the support base 10 and / or the holding base 20 is made of a composite molded material A, and the composite molded material A includes an inorganic powder A1, an organic binder A3, and a compatibilizer A3, and has an outer shape molded by a mold for thermoforming.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reinforcing bar holding member, and more particularly to a reinforcing bar holding member that combines inorganic physical properties such as high load-bearing capacity with a precise outer shape achieved by injection molding. [Background technology]

[0002] BACKGROUND ART In pouring the framework of reinforced concrete structures, in the manufacturing process of secondary concrete products, and the like, reinforcing bar retaining members are used to support reinforcing bars embedded in concrete and ensure a covering thickness of concrete. Patent Documents 1 and 2 disclose rebar retaining members made of mortar. According to the Standard Specifications for Concrete published by the Japan Society of Civil Engineers, rebar retaining members that support the weight of rebars should preferably be made of concrete or mortar, and mortar is the overwhelming majority of products. Mortar rebar retaining members are manufactured by pouring mortar into a formwork at normal pressure, similar to the manufacturing of ordinary concrete products. Patent Documents 3 and 4 disclose reinforcing bar holding members made of synthetic resin such as polypropylene. Reinforcing bar holding members made of synthetic resin are specified in JISA5390. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-179309 [Patent Document 2] Utility Model Registration No. 3204073 [Patent Document 3] Japanese Patent Publication No. 2020-172807 [Patent Document 4] Utility Model Registration No. 3246187 Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional reinforcing bar retaining members made of mortar (hereinafter, "mortar" is used to include concrete) have the following problems. <1> Because the mold filling ability during manufacturing is low, there is little freedom in the shape, resulting in a simple shape and low functionality. <2> Its low impact resistance makes it susceptible to cracking when struck by rebar or dropped. In addition, the compressive strength depends on the mortar mix, so strength can vary from product to product. <3> Because of its weight, it takes effort to transport and is difficult to handle. <4> Since the production process involves pouring mortar into a formwork, removing the formwork, and curing, productivity is low.

[0005] The prior art reinforcing bar holding members made of synthetic resin have the following problems. <1> It has low load-bearing capacity and is prone to buckling and cracking due to the load of rebar. For this reason, it cannot be used in large concrete products with heavy rebars. <2> Because the linear expansion coefficient is different from that of concrete, gaps may appear between the concrete and steel bars after use, which could become a route for water and salt to enter.

[0006] An object of the present invention is to provide a reinforcing bar holding member that reduces the above-mentioned problems. [Means for solving the problem]

[0007] The reinforcing bar holding member of the present invention comprises a support base and a holding base provided on the support base, wherein the support base and / or the holding base is made of a composite molding material, the composite molding material is made of an inorganic powder, an organic binder, and a compatibilizer, and has an outer shape formed by a mold for hot molding.

[0008] In the reinforcing bar holding member of the present invention, the support base may include a base, a plurality of legs supporting the base, and insertion holes communicating vertically with the base.

[0009] The reinforcing bar holding member of the present invention may have legs each having a hemispherical shape with the lower end facing downward.

[0010] In the reinforcing bar holding member of the present invention, the holding base may be integral with the support base.

[0011] In the reinforcing bar holding member of the present invention, the holding base may be a separate member from the support base.

[0012] In the reinforcing bar holding member of the present invention, the weight ratio (A:B) of the inorganic powder (A) to the organic binder (B) may be 30:70 to 70:30.

[0013] In the reinforcing bar holding member of the present invention, the organic binder may contain a polyamide resin.

[0014] In the reinforcing bar holding member of the present invention, the inorganic powder may contain powder made of cement, concrete, blast furnace slag, and / or ceramic.

[0015] In the reinforcing bar holding member of the present invention, the compatibilizer may contain a silane coupling agent. [Effects of the Invention]

[0016] The reinforcing bar holding member of the present invention has at least one of the following effects due to the above-mentioned configuration. <1> Injection molding allows for the manufacture of precise shapes and complex structures that were previously impossible with conventional mortar rebar retaining members, allowing for multiple functions such as retaining rebar, venting air, and reducing weight. <2> It is resistant to damage because it combines the load-bearing capacity of rebar with the impact resistance against collisions and falls. <3> Because its linear expansion coefficient is close to that of concrete, it behaves in sync with concrete and reinforcing bars, reducing the occurrence of gaps and ensuring high watertightness. <4> Since it can be manufactured using a plastic thermoforming device, there is a high degree of freedom in shape and productivity is high. [Brief explanation of the drawings]

[0017] [Figure 1] Illustration of rebar holding member [Figure 2] Illustration of the support stand [Figure 3] Explanation of the holding part [Figure 4A] Reinforcement bar holding member product examples [Figure 4B] Reinforcement bar holding member product examples [Figure 4C] Reinforcement bar holding member product examples [Figure 4D] Reinforcement bar holding member product examples [Figure 4E] Reinforcement bar holding member product examples [Figure 4F] Reinforcement bar holding member product examples [Figure 5] Product evaluation test diagram [Figure 6] Product evaluation test results [Figure 7] Material evaluation test results [Figure 8] Explanatory diagram of Example 2 [Figure 9] Explanatory diagram of Example 2 DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the reinforcing bar holding member of the present invention will be described in detail with reference to the drawings. [Example]

[0019] <1> Reinforcement bar retaining member (Fig. 1) The reinforcing bar holding member 1 is a member that holds reinforcing bars R that are embedded in concrete when concrete is poured. Pouring concrete includes not only pouring concrete at a construction site but also manufacturing secondary concrete products. The reinforcing bar holding member 1 includes at least a support base 10 and a holding base 20 provided on the support base 10, and at least one of the support base 10 and the holding base 20 is made of the composite molded material A. In this example, both the support base 10 and the holding base 20 are made of the composite molded material A. One of the features of the reinforcing bar holding member 1 is that it combines inorganic physical properties such as high load-bearing capacity and a linear expansion coefficient similar to that of concrete, thanks to the composite molding material A, with a precise outer shape formed using a mold for hot forming. Conventional mortar reinforcing bar support bases have limited flexibility in shape and cannot be molded into complex shapes, and have problems such as low impact resistance, prone to cracking, and being heavy. Furthermore, synthetic resin reinforcing bar support bases have low load-bearing capacity and are prone to buckling (cracks), and due to differences in linear expansion coefficients, gaps may form between the concrete and reinforcing bars after use, creating a path for water and salt to penetrate. In contrast, the reinforcing bar retaining member 1 of the present invention can be provided with complex structures such as arms 23 and insertion holes 14 using a plastic heating and molding device, and since its linear expansion coefficient is close to that of concrete, it behaves in harmony with the surrounding concrete and reinforcing bars R even after it is put into service, thereby maintaining high watertightness.

[0020] <2> Support stand (Figure 2) The support base 10 is the base of the reinforcing bar holding member 1. In this example, the support base 10 comprises a base 11, four legs 12 that support the base 11, a first connecting portion 13 provided in the center of the top surface of the base 11, and four insertion holes 14 that connect the base 11 vertically. In this example, the support base 10 is made of the composite molding material A, and therefore has high formability, and can be provided with the insertion holes 14 that cannot be formed in conventional mortar spacing members. By connecting the top and bottom of the base 11 with the insertion hole 14, air pockets are prevented from forming at the bottom of the support base 10 when concrete is poured, thereby improving the quality of the concrete. The structure of the support base 10 is not limited to the above, and for example, the number of legs 12 may be three or five or more. Also, the support base 10 does not have to be provided with the insertion holes 14.

[0021] <2.1> Legs The legs 12 are members that support the base 11 . In this example, the lower end of the leg 12 is formed into a downward-facing hemispherical shape. This allows the lower end of the leg 12 to come into point contact with the installation surface, minimizing the area of ​​the reinforcing bar holding member 1 exposed from the concrete surface after the concrete has hardened, thereby improving the watertightness of the concrete.

[0022] <3> Holding table (Fig. 3) The holder 20 is a part that holds the reinforcing bar R. In this example, the holding base 20 comprises a main body 21, a holding recess 22 provided on the upper surface of the main body 21, a pair of arm portions 23 provided on the upper surface of the main body 21, a second connecting portion 24 provided on the lower part of the main body 21, and a pair of connecting portions 25 that partially connect the holding recess 22 and the arm portions 23. The holding recess 22 has a substantially U-shape when viewed from the front. The pair of arms 23 are located on both sides of the holding recess 22 in the width direction, extend upward from the top surface of the main body 21, and have their tips bent toward the holding recess 22 and facing downward. The pair of connecting portions 25 linearly connect the outer surface of the holding recess 22 and the inner surface of the arm portion 23 . In this example, the holder 20 is made of the composite molding material A, which has high moldability and allows the arm portions 23, the connecting portions 25, and the like to have complex external shapes. The structure of the holder 20 is not limited to the above, and for example, the holding recess 22 may be a generally inverted C-shape with an open top. Also, it may not be provided with the connecting portion 25. Furthermore, instead of a structure that holds the body of the reinforcing bar R, a structure that holds the tip of the reinforcing bar R in a sheath shape and ensures a concrete covering thickness on the tip side of the reinforcing bar R may be used.

[0023] <3.1> Reinforcement The reinforcing bar holding member 1 holds the reinforcing bar R, for example, as follows. The reinforcing bar R is lowered from above the holding base 20 and pushed into the holding recess 22 between the pair of arms 23. When the reinforcing bar R is pushed in, the upper part of the holding recess 22 is elastically pushed open, and the restoring force of this pushes the outer periphery of the reinforcing bar R. At the same time, the tips of the pair of arms 23 elastically press the reinforcing bar R from above, positioning the reinforcing bar R at the center of the holding recess 22. At this time, the connecting part 25 linearly connects the arms 23 and the holding recess, increasing the restoring force of the arms 23. In this example, since the holder 20 is made of the composite molding material A having a high flexural modulus, the reinforcing bar R can be securely held by utilizing the elasticity of the holding recess 22 and the arm portion 23.

[0024] <4> connection structure In this example, the support base 10 and the holder base 20 are constructed from separate members. In detail, the support base 10 is provided with a first connecting portion 13 consisting of a grooved hole, and the holding base 20 is provided with a second connecting portion 24 consisting of a protrusion that can fit into the first connecting portion 13. Alternatively, the first connecting portion 13 may be a protrusion, and the second connecting portion 24 may be a grooved hole. By constructing the support base 10 and the holding base 20 from separate components, a hybrid structure is possible, for example, in which the support base 10 is made of composite molding material A and the holding base 20, which prioritizes bending elasticity, is made of synthetic resin.

[0025] <5> Composite molding material Composite molding material A is a material that combines the high compressive strength of concrete with the high moldability of thermoplastic resin. The composite molding material A is formed by binding inorganic powder A1 and organic binder A2 via compatibilizer A3. The weight ratio of the inorganic powder A1 to the organic binder A2 can be set arbitrarily depending on the application, but is preferably approximately 30:70 to 70:30.

[0026] <5.1>Inorganic powder The inorganic powder A1 is a powder that is the main material of the reinforcing bar holding member 1. In this example, ordinary Portland cement is used as the inorganic powder A1. However, the inorganic powder A1 is not limited to this, and may be cementitious powder such as various types of Portland cement such as high-early-strength Portland cement, blast-furnace cement mixed with fly ash or blast-furnace slag, concrete powder, sludge cake powder obtained by high-pressure dehydration of concrete sludge, etc. In addition to cementitious powders, the inorganic powder A1 may be industrial by-products such as ground blast-furnace slag and fly ash, mineral powders such as ceramics, calcium carbonate, talc, mica, and whiskers, metal powders such as ferrite and copper, or a combination of the above powders.

[0027] <5.1.1> Reuse of waste materials When concrete powder is used as inorganic powder A1, waste concrete can be reused. Here, "waste concrete" includes leftover concrete, returned concrete, concrete rubble, and test pieces used in concrete compression tests. Waste concrete is generated at ready-mix concrete plants, demolition sites, etc., and is generally disposed of at high disposal costs. Therefore, by reusing this waste concrete as the inorganic powder A1 of the composite molding material A, waste disposal costs can be reduced and resources can be recycled. Concrete also reacts with carbon dioxide in the atmosphere and adsorbs it (Ca(OH)2 + CO2 → CaCO3 + H2O). Powdered concrete in particular has a large surface area, so by adsorbing a large amount of carbon dioxide, composite molding material A can also function as a carbon dioxide storage (CCS).

[0028] <5.2> Organic binders The organic binder A2 is a binder that binds the inorganic powder A1. In this example, polyamide resin such as PA6 or PA66 is used as the organic binder A2. However, the organic binder A2 is not limited to this, and may also be a thermoplastic resin such as polypropylene resin, polycarbonate resin, elastomer resin, polyethylene resin, polyvinyl chloride resin, polystyrene resin, acrylic resin, polyester resin, polyurethane resin, polypropylene resin, or a combination thereof. In particular, polyamide resins and polycarbonate resins are self-extinguishing (flame-retardant) resins, making them suitable for use in building materials.

[0029] <5.3> Compatibilizer The compatibilizer A3 is a compound that makes the inorganic powder A1 and the organic binder A2 compatible with each other. In this example, a silane coupling agent is used as the compatibilizer A3. However, the compatibilizer A3 is not limited to a silane coupling agent, and various acid-modified polypropylenes, hydrogenated styrene-based thermoplastic elastomers (SEBS), etc. may also be used as long as they can make the inorganic powder A1 and the organic binder A2 compatible.

[0030] <6> Manufacturing method The reinforcing bar holding member 1 is manufactured using a plastic thermoforming device, which may include, for example, a cylinder with a built-in heater, a hopper attached to the cylinder, a screw conveyor installed inside the cylinder, and a mold installed at the tip of the cylinder. The reinforcing bar holding member 1 is manufactured, for example, by the following procedure. Inorganic powder A1, pellet-shaped, lumpy, or powdery organic binder A2, and compatibilizer A3 are mixed in a predetermined ratio using a mixer, tumbler, etc., kneaded, melted, and pelletized to produce mixture A4. In the mixture A4, the weight ratio of the inorganic powder A1 to the organic binder A2 is within the range of 30:70 to 70:30. The compatibilizer A3 can be blended in a weight ratio of 1 to 8% relative to the inorganic powder A1, for example. The pellet-like mixture A4 is placed into the hopper of an injection molding machine, dropped into the cylinder, and then heated and kneaded inside the cylinder before being extruded toward the mold by a screw conveyor and injected into the mold. During this process, the organic binder A2 melts and mixes uniformly with the inorganic powder A1, and the chemical bonding function of the compatibilizer A3 integrates the inorganic powder A1 and the organic binder A2. The injection molding machine can be a twin-screw extruder, kneader-mixer, small kneader-mixer, Banbury mixer, etc. The mold is cooled, disassembled, and the reinforcing bar holding member 1 is removed. The above steps make it possible to easily manufacture a rebar retaining member 1 that combines the characteristics of inorganic materials, such as high load resistance and affinity with concrete, with the characteristics of organic materials, such as a dense surface and precise shape. However, the manufacturing method for the composite molded member is not limited to the above, and other methods such as the free blend method (registered trademark), which simultaneously performs mixing and molding, may also be used.

[0031] <7> Reinforcement bar holding member product examples 4A to 4F show examples of products of the reinforcing bar holding member 1. FIG. Figure 4A shows products made with four different blends: cement:PA6 = 70:30, cement:PP = 70:30, blast furnace slag:PP = 70:30, and waste concrete:PP = 70:30. Figure 4B shows a product made with a blend of waste concrete:PP = 70:30. Figure 4C shows four shapes of products made with a blend of blast furnace slag:PA6 = 70:30. Figure 4D shows a product made with a blend of blast furnace slag:PA6 = 70:30. Figure 4E shows a product made with a blend of blast furnace slag:PA6 = 70:30. Figure 4F shows products made with three different blends: blast furnace slag:PA6 = 70:30, blast furnace slag:PA6 = 30:70, and blast furnace slag:PA6 = 40:60. Both products achieve precise shapes through injection molding that could not be achieved with conventional mortar products, such as thin, long arms 23 that hold the reinforcing bars R and multiple insertion holes 14 that connect the support base 10 from top to bottom.

[0032] <8> Product evaluation test A product evaluation test was carried out on the reinforcing bar holding member of the present invention. [Composition] Ordinary Portland cement (inorganic powder) and nylon 6 (organic binder) were mixed in a weight ratio of 70:30, and 1% by weight of a silane coupling agent (compatibilizer) was added to the ordinary Portland cement. [Evaluation items] (1) Test piece: density, linear expansion coefficient, tensile strength, flexural strength, flexural modulus, impact strength, compressive strength (2) Product model: Compressive strength, water permeability evaluation [Evaluation Procedure] The product model (support part) and test specimens of the rebar holding member were molded using an injection molding machine and then cured for at least 48 hours after molding. The flexural modulus was evaluated by measuring the cross section with a 3D shape measuring device, and other measures were taken according to each evaluation method. [Compression strength of product model] A D13 rebar was placed on top of the product model and compressed at a speed of 10 mm / min (Fig. 5(a)). [Permeability evaluation] The rebar retaining members are placed inside the concrete formwork, and concrete (ordinary Portland cement concrete) is poured so that the top and bottom ends of the rebar retaining members are exposed. After pouring, the concrete is cured for a specified period of time, and then the formwork is removed to obtain the specimen (Figure 5(b)). A water pressure of 0.1 MPa is applied to the top surface of the test specimen, and after 15 minutes it is checked to see if water is seeping out from the bottom of the test specimen (Figure 5(c)(d)). If water is not seeping out, the water pressure is increased by 0.1 MPa and the test is continued for another 15 minutes to check if water is seeping out from the bottom of the test specimen. This process is repeated until water seeps out from the bottom.

[0033] <9> Product evaluation test results (Fig. 6) The results of the product evaluation test are shown in Figure 6. In the test piece of the present invention, the linear expansion coefficient is 35.8 × 10 -6 / ℃, and the temperature of 72 × 10 -6 / ℃, Polypropylene (PP) 58~100 × 10 -6 / ℃, which is closer to the linear expansion coefficient of ordinary concrete. In addition, the impact strength (Charpy impact value: unnotched) is 17.8kJ / m 2 The impact strength was comparable to that of ordinary concrete. In the permeability evaluation, no water leakage was observed up to 0.3 MPa, ensuring high watertightness.

[0034] <10> Material Evaluation Test A material evaluation test was carried out on the composite molded member of the present invention. Examples 1 to 18 are examples of combinations of the type of inorganic powder, the type of organic binder, the weight ratio of the inorganic powder to the organic binder, the weight ratio of the compatibilizer to the inorganic powder and the organic binder, and the method of mixing the materials. Note that Example 11 uses the same material as in the product evaluation test described above. Comparative Examples 1 to 5 are examples using only an organic binder, and Comparative Example 6 is an example in which a combination of inorganic powder and an organic binder was kneaded without using a compatibilizing agent. [Evaluation items] (1) Density: JIS-K7112 (2) Tensile stress: JIS-K7161 (3) Nominal breaking strain: JIS-K7161 (4) Bending stress: JIS-K7171 (5) Flexural modulus: JIS-K7171 (6) Charpy impact value: JIS-K7111 (with notch) (7) Compressive stress: See JIS-A1108 (8) Linear expansion coefficient: JIS-K7197 (9) Shrinkage rate: proprietary method (10) Water permeability: Original method [Evaluation Procedures (1) to (8)] Test pieces of composite molded components were molded using an injection molding machine and then cured for at least 48 hours. The flexural modulus was evaluated by measuring the cross section using a 3D shape measuring device, and other evaluation methods based on JIS standards were also performed. [Evaluation Procedure (9)] In general plastic molding, the molded product shrinks as heat dissipates, and the amount of shrinkage is roughly constant depending on the material at a constant temperature, and this is defined as the shrinkage rate. The shrinkage rate is measured by molding a test specimen of the material to be measured using a test specimen mold, curing it for three days after molding, and storing it in a 23°C environment for at least 24 hours.Then, the mold dimensions of the test specimen are compared with the actual dimensions of the molded product to measure the amount of shrinkage per 1000 mm. [Evaluation Procedure (10)] The test piece is placed in a concrete formwork and concrete is poured in. After pouring, it is cured for one day, removed from the formwork, and then cured underwater for at least 14 days to produce a specimen in which the test piece penetrates both sides of the concrete from top to bottom. A water pressure of 0.1 MPa is applied to the top surface of the test specimen, and after 15 minutes it is checked to see if water is seeping out from the bottom of the test specimen. If water is not seeping out, the water pressure is increased by 0.1 MPa and the test is continued for another 15 minutes to see if water is seeping out from the bottom of the test specimen. This process is repeated until water seeps out from the bottom.

[0035] <11> Test results The results of the material evaluation test are shown in Figure 7. Items for which results have not yet been obtained at the time of application are left blank. In Examples 1 to 18, the inorganic powder and organic binder were effectively mixed together by the presence of the compatibilizer, and test pieces could be produced by injection molding. On the other hand, in Comparative Example 6, the inorganic powder and the organic binder were not mixed together, and it was not possible to manufacture a test piece by injection molding. The tensile stress and bending stress were generally good in all examples, and particularly in Examples 1 to 3 and 11 to 17, which used PA6 as the organic binder, and Example 18, which used PA66, the values ​​were at a high level. In addition, the impact strength (Charpy impact value: notched) is 0.9 to 3.4 kJ / m 2 and the impact strength of ordinary concrete (1 kJ / m 2 The range was above (around 100°C). The linear expansion coefficient is 10.1 to 61.8 × 10 in all examples. -6 / °C, and 73.9 to 97.1 × 10 -6 / ℃, the linear expansion coefficient of ordinary concrete (10 × 10 -6 Therefore, in the water permeability evaluation, no water leakage was observed up to 0.3 to 0.5 MPa, particularly in Examples 1 to 3, 11, and 12, which used PA6 as the organic binder, and high watertightness was ensured by conforming to the concrete. [Example]

[0036] [Example of integrally molded type] In the first embodiment, the support base 10 is a separate member from the holder 20, but the support base 10 and the holder 20 may be integrally formed (FIGS. 8 and 9). In this example, the arm portion 23 of the holder 20 extends directly from the upper surface of the base 11 of the support table 10 . By integrating the support base 10 and the holding base 20, further effects can be achieved, such as reducing manufacturing costs, improving fire resistance, reducing the impact on the strength of concrete products, and reducing the amount of sorting work required during recycling. [Explanation of symbols]

[0037] 1 Reinforcement bar holding member 10 Support stand 11 Base 12 Legs 13 1st connection part 14 Insertion hole 20 Holding stand 21 Main body 22 Retaining recess 23 Arm 24 2nd connection part 25 Connection A Composite molding material A1 Inorganic powder A2 Organic binder A3 Compatibilizer A4 mixture R rebar

Claims

1. A reinforcing bar holding member that is embedded in concrete when pouring concrete, A support base; a holding table provided on the support table, The support base and / or the holding base are made of a composite molding material, The composite molding material comprises an inorganic powder, an organic binder, and a compatibilizer, The outer shape is formed by a mold for hot forming. Rebar holding member.

2. The support base is A base and a plurality of legs supporting the base; and an insertion hole that communicates with the base portion from above to below. The reinforcing bar retaining member according to claim 1 .

3. The lower end of the leg is a downward-facing hemispherical shape. The reinforcing bar retaining member according to claim 2.

4. The holding base is integral with the support base. The reinforcing bar retaining member according to claim 1 .

5. The holding table is a separate member from the support table. The reinforcing bar retaining member according to claim 1 .

6. The weight ratio (A:B) of the inorganic powder (A) to the organic binder (B) is 30:70 to 70:30, The reinforcing bar holding member according to any one of claims 1 to 5.

7. The organic binder contains a polyamide resin. The reinforcing bar holding member according to any one of claims 1 to 5.

8. The inorganic powder includes powder made of cement, concrete, blast furnace slag, and / or ceramic. The reinforcing bar holding member according to any one of claims 1 to 5.

9. The compatibilizer contains a silane coupling agent. The reinforcing bar holding member according to any one of claims 1 to 5.

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