Dry spraying method and dry spraying equipment

Abstract

To provide a dry spray method capable of suppressing a splash that occurs in spraying onto a spray target, as well as capable of quantitatively and stably transporting a powder material.SOLUTION: A dry spray method includes: a supply process of supplying a powder material containing cement to a flow channel of a transportation gas flowing towards a spray target; a transportation process of transporting the powder material supplied to the flow channel of the transportation gas towards the spray target by the transportation gas; and a spray process of mixing the powder material transported at the transportation process with a liquid material containing water to form a spray material while spraying the spray material to the spray target together with the transportation gas. The flow channel of the transportation gas includes a gas rise part in which the transportation gas flows from a bottom to a top. A pressure of the transportation gas flowing in the gas rise part is 0.010 to 0.050 MPa. The supply process is performed by supplying the powder material to the gas rise part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a dry spraying method in which a spray material consisting of a mixture of a powder material containing cement and a liquid material containing water is sprayed onto an object together with a gas, and to an apparatus used in the dry spraying method. [Background technology]

[0002] Conventionally, a method for applying a spraying material to a surface of an object to be sprayed by spraying a spraying material formed by mixing a powder material containing cement and a liquid material containing water onto the object to be sprayed is known. For example, in construction work of excavated tunnels and underground spaces, a rapid-hardening cement composition (specifically, concrete and mortar) is sprayed as a spraying material onto the excavated surface to prevent the excavated surface from collapsing.

[0003] As a method for spraying a spray material onto an object to be sprayed, a method is known in which the spray material is sprayed from a spray nozzle together with compressed gas compressed by a high-pressure compressor to the object to be sprayed. Specifically, a dry spraying method is known which includes a supplying step of supplying a powder material to a flow path of compressed gas flowing toward the object to be sprayed, a pressure-feeding step of pressure-feeding the powder material supplied to the flow path of compressed gas toward the object to be sprayed by the compressed gas, and a spraying step of mixing the powder material pressure-feeding step with a liquid material in the spray nozzle to form a spray material and spraying the spray material together with the compressed gas onto the object to be sprayed (see Patent Document 1). Also, as a powder supplying machine for supplying a powder material to a flow path of compressed gas in such a dry spraying method, a machine is known which supplies a powder material to a gas descending section of the flow path of compressed gas where the compressed gas flows from top to bottom (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-12867 A [Patent Document 2] Japanese Utility Model Application Publication No. 52-104954 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the spray material is sprayed from a spray nozzle together with compressed gas onto an object to be sprayed as described above, the impact of the spraying causes part of the spray material to bounce back and scatter around the object to be sprayed, which can lead to a deterioration of the working environment.

[0006] One possible method for suppressing rebound is to transport the powder material using low-pressure air supplied from a blower. However, if the powder material is supplied to the gas descending section of the low-pressure gas flow path, the powder material tends to accumulate in the flow path, making it difficult to transport the powder material in a quantitative and stable manner.

[0007] Therefore, the present invention aims to provide a dry spraying method that can suppress the rebound that occurs when spraying onto an object to be sprayed and can transport powder material in a stable, quantitative manner, and a dry spraying device for use in the dry spraying method. [Means for solving the problem]

[0008] The dry spraying method of the present invention is a dry spraying method comprising a supply process of supplying a powder material containing cement into a flow path of a conveying gas flowing toward an object to be sprayed, a transport process of transporting the powder material supplied into the flow path of the conveying gas toward the object to be sprayed by the conveying gas, and a spraying process of mixing the powder material transported in the transport process with a liquid material containing water to form a spray material and spraying the spray material together with the conveying gas toward the object to be sprayed, wherein the flow path of the conveying gas has a gas ascending section through which the conveying gas flows from bottom to top, and the pressure of the conveying gas flowing into the gas ascending section is 0.010 MPa or more and 0.050 MPa or less, and the supply process is carried out by supplying the powder material to the gas ascending section.

[0009] According to this configuration, by supplying the powder material to the gas rising section where the conveying gas flows from bottom to top, the powder material is lifted up by the conveying gas, so that the powder material is easily dispersed in the conveying gas. This makes it difficult for the powder material to accumulate in the conveying gas flow path, so that the powder material can be transported stably and quantitatively. In addition, by keeping the pressure of the conveying gas flowing into the gas rising section within the above range, rebounding that occurs when spraying the material on the target can be suppressed.

[0010] In the conveying step, the pressure of the conveying gas containing the powder material is preferably 0.030 MPa or more and 0.10 MPa or less.

[0011] According to this configuration, in the conveying step, the pressure of the conveying gas containing the powder material is within the above range, so that rebound that occurs when spraying the powder material onto the object to be sprayed can be more effectively suppressed.

[0012] The dry spraying apparatus of the present invention is a dry spraying apparatus used in the above-mentioned dry spraying method, and is equipped with a conveying gas flow path for circulating the conveying gas toward the object to be sprayed, a gas supplying machine for supplying the conveying gas to the conveying gas flow path, a powder supplying machine for supplying powder material to the conveying gas flow path, and an injector for injecting the spraying material, wherein the conveying gas flow path has a gas ascending section in which the conveying gas flows from bottom to top, the powder supplying machine is capable of supplying powder material to the gas ascending section, and the pressure of the conveying gas flowing into the gas ascending section is 0.010 MPa or more and 0.050 MPa or less.

[0013] According to this configuration, the powder material is supplied to the gas rising section by the powder supplying device while the carrier gas is supplied to the carrier gas flow path, so that the powder material is easily dispersed in the carrier gas. This makes it difficult for the powder material to accumulate in the carrier gas flow path, so that the powder material can be transported stably and quantitatively. In addition, since the pressure of the carrier gas flowing into the gas rising section is within the above range, rebounding that occurs when spraying the material on the target can be suppressed. Effect of the Invention

[0014] As described above, according to the present invention, it is possible to provide a dry spraying method that can suppress the rebound that occurs when spraying onto an object to be sprayed and can transport powder material in a stable, quantitative manner, and a dry spraying device for use in the dry spraying method. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is a cross-sectional view showing an outline of an air current rising section and a powder feeder in the dry spraying device according to one embodiment of the present invention. [Diagram 2] FIG. 11 is a cross-sectional view showing an outline of an air current rising section and a powder feeder in a dry spraying device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described.

[0017] The dry spraying method according to the present invention involves mixing a powder material containing cement with a liquid material containing water to form a spray material, and then spraying the spray material together with gas onto an object.

[0018] The cement contained in the powder material is not particularly limited, and various cements available on the market can be used. Specifically, one selected from the group consisting of various Portland cements such as ordinary Portland cement and high-early-strength Portland cement, alumina cement, and ultra-fast-hardening cements such as calcium aluminate, calcium sulfoaluminate, and calcium fluoroaluminate may be used, or a mixture of two or more may be used.

[0019] The powder material may contain aggregate. As the aggregate, coarse aggregate and fine aggregate may be used, or only fine aggregate may be used. In other words, when coarse aggregate and fine aggregate are used as aggregate, the sprayed material constitutes concrete, and when only fine aggregate is used as aggregate, the sprayed material constitutes mortar.

[0020] The coarse aggregate to be used may be one having a size such that 85% by mass or more of the aggregate does not pass through a 5 mm sieve. Specific examples of the coarse aggregate include crushed sandstone, pebbles (river gravel), natural lightweight coarse aggregate (perlite, vermiculite, etc.), by-product lightweight coarse aggregate, artificial lightweight coarse aggregate, recycled aggregate, etc. The content of the coarse aggregate in the powder material is not particularly limited, and may be, for example, 70% by mass or more and 200% by mass or less, or 200% by mass or more and 300% by mass or less, relative to the cement.

[0021] Fine aggregates of a size that passes all 10 mm sieve openings and 85% or more by mass of those that pass 5 mm sieve openings can be used. Specifically, examples of fine aggregates include natural sands such as mountain sand, river sand, land sand, and sea sand, crushed sand (more specifically, crushed limestone sand, etc.) formed by artificially crushing sandstone, limestone, etc., lightweight aggregates obtained by crushing, granulating, and burning expansive shale, etc., and crushing and heating and foaming perlite, etc. The content of fine aggregate in the powder material is not particularly limited, and may be, for example, 70% by mass or more and 200% by mass or less, or 200% by mass or more and 300% by mass or less, relative to the cement.

[0022] The sizes of the above coarse aggregate and fine aggregate are measured by the sieve test method for aggregate in accordance with JIS A 1102, and represent the test sieve openings of JIS Z 8801-1.

[0023] The powder material may further include other materials. For example, the powder material may include fiber materials (glass fibers, steel fibers, vinylon fibers, aramid fibers, polypropylene fibers, carbon fibers, etc.), admixtures (blast furnace slag, fly ash, silica fume, expansive materials, etc.), and admixtures (water reducers, thickeners, defoamers, quick-setting agents, etc.).

[0024] The water contained in the liquid material is not particularly limited, and for example, general tap water can be used. The liquid material may also contain materials other than water. For example, the liquid material may contain admixtures such as water-reducing agents used when mixing mortar or concrete, polymer dispersion liquids, shrinkage reducing agents, setting regulators, accelerators, and the like.

[0025] The mass ratio of the liquid material to the powder material (liquid / powder ratio) is not particularly limited, but is preferably 10 mass % or more and 24 mass % or less, and more preferably 12 mass % or more and 16 mass % or less.

[0026] The compressive strength of the spray material when it hardens is not particularly limited, but is preferably 20 N / mm 2 More preferably, 40N / mm 2 The compressive strength was measured using a 40cm x 40cm x 25cm formwork (repair area: 0.16m2) in accordance with JSCE-F561 (how to prepare specimens for compressive strength tests of shotcrete). 2 After 2 days, a core was removed and both ends were molded (Φ10×20 cm) to obtain a hardened core. The hardened core was aged in water at 20°C for up to 28 days, after which it was measured according to JIS A 1108.

[0027] The dry spraying method according to the present invention is carried out using the powder material and liquid material configured as described above. Specifically, the dry spraying method according to the present invention includes a supplying step of supplying the powder material to a flow path of a carrier gas flowing toward the object to be sprayed, and a transporting step of transporting the powder material supplied to the flow path of the carrier gas toward the object to be sprayed by the carrier gas. The dry spraying method according to the present invention also includes a spraying step of mixing the powder material transported in the transporting step with a liquid material to form a spraying material and spraying the spraying material together with the carrier gas toward the object to be sprayed.

[0028] In the supply step, the powder material is supplied to the gas ascending part of the flow path of the carrier gas where the carrier gas flows from bottom to top. The supply amount of the powder material is not particularly limited, and is preferably 1 kg / min to 20 kg / min, more preferably 2 kg / min to 12 kg / min. The pressure of the carrier gas flowing into the gas ascending part is 0.010 MPa to 0.050 MPa, preferably 0.015 MPa to 0.047 MPa, more preferably 0.020 MPa to 0.045 MPa.

[0029] In the conveying step, the pressure of the conveying gas containing the powder material is preferably 0.030 MPa or more and 0.10 MPa or less, more preferably 0.040 MPa or more and 0.080 MPa or less, and further preferably 0.050 MPa or more and 0.075 MPa or less.

[0030] The above-mentioned supply process, conveying process, and spraying process can be carried out using a dry spraying device that includes a carrier gas flow path for circulating the carrier gas toward the object to be sprayed, a gas supplying machine for supplying the carrier gas to the carrier gas flow path, a powder supplying machine for supplying powder material to the carrier gas flow path, and an injector for injecting the spraying material.

[0031] The gas supplying device is not particularly limited, and for example, a low pressure type blower such as a ring blower, a roots blower, a turbo blower, etc., can be used. Among these, it is preferable to use a roots blower as the low pressure type blower from the viewpoint of increasing the air volume.

[0032] The powder feeder is not particularly limited, and for example, a dry rotor type, chamber type, or other powder feeder can be used. As an example of the dry rotor type powder feeder, as shown in FIG. 1, there is a powder feeder 10 that includes a plurality of cylinders 1 and repeatedly fills the cylinders 1 with powder material X and supplies the powder material X from the cylinders 1 to a flow path 2 of a carrier gas. Specifically, the dry rotor type powder feeder 10 includes a gas rising section 2a in which a carrier gas supplied from a gas supplying device (not shown) flows from bottom to top. Then, the cylinder 1 filled with the powder material X is disposed in the gas rising section 2a, so that the carrier gas flowing through the gas rising section 2a flows inside the cylinder 1 and lifts up the powder material X in the cylinder 1 from bottom to top. As a result, the powder material X is supplied to the flow path 2 of the carrier gas and transported.

[0033] In addition, when using another powder feeder, as shown in Fig. 2, a powder feeder 10' may be connected to the gas ascending section 2a via a pipe 20, and the powder material X may be supplied from the powder feeder 10' to the gas ascending section 2a via the pipe 20. The method of supplying the powder material X from the powder feeder 10' to the gas ascending section 2a via the pipe 20 is not particularly limited, and may be, for example, a method of transporting the powder material to the gas ascending section 2a by wind pressure, or a method of dropping the powder material X from the powder feeder 10' to the gas ascending section 2a depending on the connection state between the powder feeder 10' and the gas ascending section 2a.

[0034] The spraying device is not particularly limited, and for example, a dry spraying nozzle (not shown) can be used. The dry spraying nozzle is configured to be supplied with the powder material transported in the transport process. The dry spraying nozzle is also configured to be supplied with the liquid material via a route separate from the powder material. Furthermore, the dry spraying nozzle is configured to mix the powder material and the liquid material inside to form a spray material, and to spray the spray material together with a transport gas onto the object to be sprayed.

[0035] As described above, the dry spraying method and dry spraying device according to the present invention can suppress rebound that occurs when spraying onto an object, and can transport powder material quantitatively.

[0036] That is, by supplying the powder material X to the gas ascending section 2a where the carrier gas flows from bottom to top, the powder material X is stirred up by the carrier gas from bottom to top, and the powder material X is easily dispersed in the carrier gas. This makes it difficult for the powder material X to accumulate in the flow path of the carrier gas, and the powder material X can be transported stably and quantitatively. In addition, by keeping the pressure of the carrier gas flowing into the gas ascending section 2a within the above range, rebounding that occurs when spraying the material onto the target can be suppressed.

[0037] Furthermore, in the conveying step, by setting the pressure of the conveying gas containing the powder material X within the above range, rebound that occurs when the powder material X is sprayed onto the target object can be more effectively suppressed.

[0038] The dry spraying method and the dry spraying device according to the present invention are not limited to the above-mentioned embodiment, and various modifications are possible without departing from the gist of the present invention. In addition, the configurations and methods of the above-mentioned embodiments may be arbitrarily adopted and combined (the configurations and methods of one embodiment may be applied to the configurations and methods of other embodiments), and further, the configurations and methods of other various modified examples may be arbitrarily selected and adopted in the configurations and methods of the above-mentioned embodiments. EXAMPLES

[0039] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0040] <Materials used> Cement: Ordinary Portland cement manufactured by Sumitomo Osaka Cement Co., Ltd. ·Fine aggregate: Silica sand No. 3, Silica sand No. 4, Silica sand No. 6 Water: Water supply Liquid admixture: Lion Bond A manufactured by Sumitomo Osaka Cement Co., Ltd.

[0041] <Spraying material composition> The composition of the spray material is shown in Table 1 below.

[0042] <Evaluation of blockage of carrier gas flow path> A low pressure blower (Anlett Co., Ltd., product name: 3-blade Anlett Roots Blower BH80) and a compressor (Hokuetsu Industries Co., Ltd., product name: PDS265SD-5C3) were used as the gas supplying machine. A dry rotor type device (Towa Fireproofing Co., Ltd., product name: TOWA type rotary gun) with the configuration shown in Figure 1 was used as the powder supplying machine. In the examples, the powder supplying machine was configured so that a gas ascending section was formed at the supply position where the powder material was supplied in the flow path of the conveying gas, and in the comparative examples, the powder supplying machine was configured so that a gas descending section was formed at the supply position where the conveying gas flows from top to bottom. The powder material was then supplied to the conveying gas flow path so as to convey the powder material at a speed of 5 kg / min for 1 minute, and the presence or absence of blockage of the conveying gas flow path was evaluated. Specifically, if there was no blockage within 1 minute from the start of spraying, it was marked as "Good", and if powder conveyance was not possible due to blockage, it was marked as "Poor". The pressure of the conveying gas flowing into the gas ascending section or gas descending section (the pressure of the conveying gas in the conveying gas flow path connecting the gas supply machine and the powder supply machine), the outlet pressure of the powder supply machine at the start of conveyance (the pressure of the conveying gas containing the powder material), and the presence or absence of blockage are shown in Table 2 below.

[0043] <Rebound rate measurement> Based on JSCE-F 563, the bounce rate test was conducted. Specifically, a formwork with a bottom surface of 100 cm x 100 cm was used as the object to be sprayed, and the mass of the formwork (hereinafter also referred to as the initial formwork mass) was measured. In addition, the powder material was transported under the above-mentioned transport conditions and supplied to the dry spray nozzle, and the liquid material was supplied to the dry spray nozzle, and the spray material was sprayed onto the object (formwork) for 3 minutes. Then, the mass of the spray material that bounced back by spraying (the amount of rebound) was measured. Furthermore, the bounce rate was calculated using the obtained measurement results according to the following formula (1). Then, a bounce rate of 10% or less was evaluated as "good", and a bounce rate of more than 10% was evaluated as "bad". The evaluation results are shown in Table 1 below. Rebound rate = rebound amount ÷ (transported amount of powder material + supplied amount of liquid material) × 100 (1)

[0044] [Table 1]

[0045] [Table 2]

[0046] <Summary> From Table 2, it can be seen that in each of the Examples, the flow path of the conveying gas is less likely to be clogged (powder material is less likely to accumulate) and the rebound rate is lower than in each of the Comparative Examples. In other words, as in the present invention, the pressure of the conveying gas is configured to be within a predetermined range in the gas rising section where the conveying gas flows from bottom to top, and the powder material is supplied to this gas rising section, whereby the powder material can be conveyed quantitatively and rebound of the spray material can be suppressed.

Claims

1. A supplying step of supplying a powder material containing cement into a flow path of a carrier gas flowing toward an object to be sprayed; a conveying step of conveying the powder material supplied to a conveying gas flow path toward a target object by the conveying gas; A dry spraying method including a spraying step in which the powder material transported in the transporting step is mixed with a liquid material containing water to form a spray material, and the spray material is sprayed onto an object to be sprayed together with a transport gas, The flow path of the carrier gas includes a gas rising portion through which the carrier gas flows from bottom to top, The pressure of the carrier gas flowing into the gas ascending section is 0.010 MPa or more and 0.050 MPa or less, The supply step is performed by supplying the powder material to the gas rising section. Dry spraying method.

2. In the conveying step, the pressure of the conveying gas containing the powder material is 0.030 MPa or more and 0.10 MPa or less. The dry spraying method according to claim 1.

3. A dry spraying device used in the dry spraying method according to claim 1 or 2, a flow path for a carrier gas that flows the carrier gas toward the object to be sprayed; a gas supplier that supplies a carrier gas to a carrier gas flow path; a powder feeder for feeding a powder material into a flow path of the carrier gas; A sprayer for spraying the spray material; It is equipped with The flow path of the carrier gas includes a gas rising portion through which the carrier gas flows from bottom to top, The powder feeder is capable of feeding powder material to the gas rising section; The pressure of the carrier gas flowing into the gas rising section is 0.010 MPa or more and 0.050 MPa or less. Dry spraying equipment.

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