Dry spraying method, dry spraying device, and spraying material

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 transporting a powder material.SOLUTION: A dry spray method includes: a transportation process of supplying a powder material containing cement to an air flow flowing towards a spray target so as to transport the powder material; and a spray process of supplying a liquid material containing water to the air flow containing the powder material formed at the transportation process and mixing the powder material and the liquid material to form a spray material while spraying the spray material to the spray target together with a gas. The powder material has an organic matter content of 10 mass% or less. In the transportation process, the powder material is supplied to an air flow of 70°C or higher.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Conventionally, there has been known a method for applying a spraying material to the surface of an object by spraying a spraying material formed by mixing a powder material containing cement with a liquid material containing water onto the object. For example, in construction work such as 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] A known method for spraying a spray material onto an object is to spray the spray material together with gas from a spray nozzle onto the object. Specifically, a powder material is transported by an airflow and supplied to the spray nozzle, and a liquid material is supplied to the spray nozzle separately from the powder material. The powder material and the liquid material are then mixed in the spray nozzle to form a spray material, which is then sprayed onto the object together with gas (a so-called dry spraying method) (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-12867 Summary of the Invention [Problem to be solved by the invention]

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

[0006] Furthermore, in the dry spraying method described above, there is a risk that the powder material may adhere to the inside of the pipe used to transport the powder material. If the powder material adheres to the inside of the pipe, this causes turbulence in the airflow and changes in the flow rate, making it difficult to transport the powder material quantitatively.

[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 quantitatively, a dry spraying device used in the dry spraying method, and a sprayed material sprayed by the dry spraying method. [Means for solving the problem]

[0008] The dry spraying method according to the present invention is as follows: a conveying step of conveying a powder material containing cement by supplying the powder material to an airflow flowing toward an object to be sprayed; a spraying step in which a liquid material containing water is supplied to an airflow containing a powder material formed in a conveying step, and the powder material and the liquid material are mixed to form a spray material, and the spray material is sprayed together with gas onto an object to be sprayed, The powder material has an organic matter content of 10% by mass or less, In the conveying process, the powder material is fed into an air current at 70°C or higher.

[0009] According to this configuration, a relatively high-temperature airflow, such as that in the above-mentioned temperature range, has a relatively high viscosity. Therefore, by using such an airflow to transport the powder material, the resistance to separation between the airflow and the powder material during the transport process is improved. This reduces the rebound caused by spraying. Furthermore, since the organic matter content in the powder material is within the above-mentioned range, the viscosity of the powder material is unlikely to increase even when the powder material is supplied to the above-mentioned relatively high-temperature airflow. This makes it difficult for the powder material to adhere to the inside of the pipe used to transport the powder material, allowing for quantitative transport of the powder material.

[0010] The dry spraying device according to the present invention comprises: A dry spraying device used in the above dry spraying method, a gas supplier that supplies gas to form an airflow that flows toward the object to be sprayed; a powder feeder that supplies powder material to an airflow flowing toward an object to be sprayed; It is equipped with The airflow flowing from the gas supply device toward the object to be sprayed is configured so that the temperature of the airflow between the gas supply device and the powder supply device is 70°C or higher.

[0011] The spraying material according to the present invention is A sprayed material sprayed onto an object by the above dry spraying method, The temperature is between 10°C and 50°C.

[0012] According to this configuration, the temperature of the sprayed material is within the above range, which promotes hydration of the cement, thereby suppressing splashback during spraying. [Effects of the Invention]

[0013] 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 that can transport powder material quantitatively, a dry spraying device used in the dry spraying method, and sprayed material sprayed by the dry spraying method. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described.

[0015] 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.

[0016] 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-rapid-hardening cements such as calcium aluminate, calcium sulfoaluminate, and calcium fluoroaluminate may be used, or a mixture of two or more may be used.

[0017] The powder material may contain aggregate. The aggregate may be a coarse aggregate and a fine aggregate, or only fine aggregate. In other words, when a coarse aggregate and a fine aggregate are used as aggregates, the sprayed material constitutes concrete, and when only fine aggregate is used as aggregate, the sprayed material constitutes mortar.

[0018] The coarse aggregate to be used may be of 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, and recycled aggregate. 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.

[0019] Fine aggregate can be used if it passes all 10 mm sieve openings and 85% or more by mass passes a 5 mm sieve opening. Specific examples of fine aggregate include natural sands such as mountain sand, river sand, land sand, and sea sand; crushed sand (more specifically, crushed limestone sand) formed by artificially crushing sandstone, limestone, etc.; lightweight aggregates such as crushed, granulated, and fired expansive shale; and crushed and heated perlite. The content of fine aggregate in the powder material is not particularly limited and may be, for example, 70% to 200% by mass or 200% to 300% by mass relative to the cement.

[0020] The sizes of the coarse aggregate and fine aggregate mentioned above are measured by the sieve test method for aggregates in accordance with JIS A 1102, and represent the test sieve openings of JIS Z 8801-1.

[0021] The powder material may further contain other materials, such as fiber materials (glass fiber, steel fiber, vinylon fiber, aramid fiber, polypropylene fiber, carbon fiber, etc.), admixtures (blast furnace slag, fly ash, silica fume, expansive additives, etc.), and additives (water-reducing agents, thickeners, antifoaming agents, accelerators, etc.).

[0022] The organic matter content of the powder material is 10% by mass or less, preferably 8% by mass or less, and more preferably 7% by mass or less. Examples of organic matter that can be contained in the powder material include polymers for polymer cement. The polymers for polymer cement are polymers that contribute to the formation of a binding phase in the composition together with cement, and examples include those that correspond to the re-emulsifiable powdered resins for cement admixture specified in JIS A 6203, and polymeric thickeners such as starch.

[0023] The water contained in the liquid material is not particularly limited, and ordinary 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 modifiers, accelerators, etc.

[0024] 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.

[0025] The compressive strength of the sprayed material when hardened is not particularly limited, but is preferably 20 N / mm 2 More preferably, 40N / mm 2 The compressive strength was measured in accordance with JSCE-F561 (how to prepare specimens for compressive strength tests of shotcrete) using a 40cm x 40cm x 25cm formwork (repair area: 0.16m). 2 After two days, the hardened core is removed and both ends are shaped (Φ10 x 20 cm) to obtain a hardened core. The hardened core is then cured in water at 20°C for up to 28 days, after which it can be measured in accordance with JIS A 1108.

[0026] 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 comprises a transport step of transporting the powder material by supplying the powder material to an airflow flowing toward the object to be sprayed, and a spraying step of spraying the spray material together with gas onto the object to be sprayed. The dry spraying method according to the present invention can also be carried out using a dry spraying device comprising a gas supply device, a powder supply device, and an injector, as described below.

[0027] In the conveying step, the powder material is supplied to an airflow at 70°C or higher, preferably 72°C or higher, and more preferably 75°C or higher. The conveying step can be performed using a gas supplying machine that supplies gas to form an airflow flowing toward the object to be sprayed, and a powder supplying machine that supplies the powder material to the airflow flowing toward the object to be sprayed. The gas supplying machine is not particularly limited, and low-pressure blowers such as ring blowers, roots blowers, and turbo blowers can be used. Powder supplying machines such as dry camber types and dry rotor types can be used. The temperature of the airflow refers to the temperature of the airflow between the gas supplying machine and the powder supplying machine, among the airflows flowing from the gas supplying machine toward the object to be sprayed. The method for changing the temperature of the airflow is not particularly limited, and examples include a method using a cooler that cools the airflow from the gas supplying machine toward the powder supplying machine or a heater that heats the airflow.

[0028] In the spraying process, a liquid material is supplied to an airflow containing powder material formed in the conveying process, and the powder material and liquid material are mixed to form a spray material, which is then sprayed together with the gas onto the object to be sprayed. The spraying process can be performed using an injector (e.g., a dry spraying nozzle) that injects the spray material together with the gas. Specifically, the powder material is supplied to the dry spraying nozzle together with the airflow in the conveying process. In addition, a liquid material is supplied to the dry spraying nozzle via a route separate from the powder material. The powder material and liquid material are then mixed in the dry spraying nozzle to form a spray material, which is then sprayed from the dry spraying nozzle together with the gas (e.g., an airflow conveying the powder material) and sprayed onto the object to be sprayed.

[0029] The temperature of the spray material obtained in the spraying step (the temperature immediately after spraying) is not particularly limited, but is preferably 10°C or higher and 50°C or lower, more preferably 15°C or higher and 40°C or lower.

[0030] As described above, the dry spraying method, dry spraying device, and spraying material according to the present invention can suppress the rebound that occurs when spraying onto an object, and can transport powder material quantitatively.

[0031] That is, since a relatively high-temperature airflow such as that in the above temperature range has a relatively high viscosity, using such an airflow to transport the powder material improves the resistance to separation between the airflow and the powder material during the transport process. This reduces rebound caused by spraying. Furthermore, since the organic matter content in the powder material is within the above range, the viscosity of the powder material is less likely to increase even when the powder material is supplied to a relatively high-temperature airflow such as that described above. This makes it difficult for the powder material to adhere to the inside of the piping used to transport the powder material, allowing for quantitative transport of the powder material. Furthermore, since the temperature range of the sprayed material formed using the above dry spraying method promotes cement hydration, rebound during spraying can be reduced.

[0032] The dry spraying method, dry spraying device, and spraying material according to the present invention are not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention. Furthermore, the configurations, methods, etc. of the above-described multiple embodiments may be arbitrarily adopted and combined (the configurations, methods, etc. of one embodiment may be applied to the configurations, methods, etc. of other embodiments), and further, configurations, methods, etc. of various other modified examples may be arbitrarily selected and adopted in the configurations, methods, etc. of the above-described embodiments. [Example]

[0033] The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0034] <Materials used> Powder material: Cement (Sumitomo Osaka Cement Co., Ltd., product name: Ordinary Portland cement, density 3.15 g / cm 3 ), and No. 4 quartz sand (produced in Kochi Prefecture, density 2.51 g / cm 3) were mixed in a mass ratio of 4:6, and then a re-emulsifiable powder resin (powdered acrylic resin) was added. The organic matter content in the powder material is shown in Table 1 below. The organic matter content can be determined from the weight loss at 200 to 400°C by TG-DTA measurement. Liquid material: Tap water was used.

[0035] <Quantitative evaluation of transportation> An airflow was formed using a Roots blower (Anlet Co., Ltd., Model: 3-blade Anlet Roots Blower BH80) as a gas supply device, and this airflow was supplied to a powder supply device (Towa Refractory Industry Co., Ltd., Model: TOWA Rotary Gun) to supply the powder material to the airflow. The powder material was then transported at a rate of 5 kg / min for 3 minutes. A cooler was installed at the airflow outlet of the gas supply device to change the temperature of the airflow flowing from the gas supply device to the powder supply device (the temperature at the airflow inlet of the powder supply device). The pressure of the airflow containing the powder material was measured at each airflow temperature at the airflow outlet of the powder supply device. The average airflow temperature and pressure are shown in Table 1 below. The difference between the maximum and minimum pressure values ​​(pressure amplitude) was also calculated. A pressure amplitude of 0.005 MPa or less was evaluated as "Good," and a pressure amplitude of more than 0.005 MPa was evaluated as "Poor." The evaluation results are shown in Table 1 below.

[0036] <Measurement of rebound rate> A bounce rate test was conducted based on JSCE-F 563. Specifically, a formwork with a 100 cm × 100 cm bottom was used as the target for spraying, and the mass of the formwork (hereinafter also referred to as the initial formwork mass) was measured. The powder material was transported under the above-mentioned transport conditions and supplied to the dry spraying nozzle, and the liquid material was supplied to the dry spraying nozzle. The spray material was sprayed onto the target (formwork) for 3 minutes. The ratio of the liquid material to the powder material supplied to the dry spraying nozzle (liquid / powder ratio) was 14.0. The mass of the sprayed material that bounced back (the amount of bounce) was then measured. The bounce rate was calculated using the measurement results using the following formula (1). A bounce rate of 10% or less was evaluated as "Good," and a bounce rate of more than 10% was evaluated as "Poor." 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)

[0037] [Table 1]

[0038] <Summary> As can be seen from Table 1, the pressure amplitude and rebound rate are relatively small in each example. In other words, by supplying and transporting a powder material with an organic matter content within a predetermined range using a relatively high-temperature airflow, as in the present invention, the powder material can be transported quantitatively and rebound of the sprayed material can be suppressed.

Claims

1. a conveying step of conveying a powder material containing cement by supplying the powder material to an airflow flowing toward an object to be sprayed; a spraying step of supplying a liquid material containing water to an airflow containing a powder material formed in a conveying step, mixing the powder material and the liquid material to form a spray material, and spraying the spray material together with a gas onto an object to be sprayed, The powder material has an organic matter content of 10% by mass or less, In the conveying step, the powder material is supplied to an air flow having a temperature of 70° C. or higher. Dry spraying method.

2. A dry spraying device used in the dry spraying method according to claim 1, A gas supplier that supplies gas to form an airflow that flows toward the object to be sprayed; a powder feeder that feeds powder material into an airflow flowing toward an object to be sprayed; Equipped with The airflow between the gas supply device and the powder supply device is configured to have a temperature of 70° C. or higher among the airflows flowing from the gas supply device toward the object to be sprayed. Dry spraying equipment.

3. A conveying step of conveying a powder material containing cement by supplying the powder material to an airflow flowing toward an object to be sprayed; A method for producing a spray material to be sprayed onto an object by a dry spraying method, the method comprising: a spraying step of supplying a liquid material containing water to an airflow containing a powder material formed in a conveying step, mixing the powder material and the liquid material to form a spray material, and spraying the spray material together with a gas onto the object to be sprayed, The powder material has an organic matter content of 10% by mass or less, In the conveying step, the powder material is supplied to an air flow having a temperature of 70° C. or higher. Manufacturing method of spraying material.

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