Spraying method and spraying device

Abstract

To provide a spray method and a spray device which can provide spray application with high strength development at an initial stage.SOLUTION: In a spray method to perform spraying to a target object after adding and mixing a set accelerating agent in a base concrete containing cement, a set accelerating aid including gypsums is added to the base concrete before adding the set accelerating agent. A spray device 10 has a force feed pipe 1 for forcibly feeding the base concrete containing cement, an air supply section 2 and a set accelerating agent supply section 3 which are sequentially disposed in a force feeding direction on a side portion of the force feed pipe 1, and a spray nozzle 4 at a terminal portion of the force feed pipe 1. The spray device has at least one set accelerating aid adding section 5 for adding the set accelerating aid including gypsums on a side portion of the air supply section 2 and / or a side portion of the force feed pipe 1 between the air supply section 2 and the set accelerating agent supply section 3.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a spraying method and a spraying device.

Background Art

[0002] In tunnels, mining shafts, underground spaces, etc., construction using sprayed concrete is carried out from the viewpoints of preventing the collapse of the excavation surface and reinforcing the ground during or after mining or excavation. Sprayed concrete ensures its adhesiveness to the construction object due to its rapid setting property, and contributes to the reinforcement of the construction object.

[0003] Rapid setting components are mixed in sprayed concrete to impart rapid setting properties. Among them, powder rapid setting agents containing calcium aluminate, sodium aluminate, etc. as active ingredients can impart strong rapid setting properties and can also obtain high strength. In the wet spraying method, which is a general construction method for sprayed concrete, for example, at least cement, water, and aggregates are weighed and mixed to produce base concrete, and then it is pumped to a spraying device during construction via an agitator truck or the like. In the spraying device, a separately fed powder or liquid rapid setting agent is added to the base concrete being pumped, and mixing proceeds in the spraying nozzle of the spraying device to form sprayed concrete, which is sprayed from the discharge hole at the nozzle end. While moving from the point where the rapid setting component in this spraying device comes into contact with water (the water contact point) to the discharge hole at the nozzle end, mixing is carried out to form sprayed concrete. The distance used for mixing is usually a distance of several tens of cm to several meters, and the movement time becomes the mixing time. Generally, the longer this distance, the more the mixing progresses, the higher the mixability, and it becomes easier to obtain more uniform concrete both organizationally and in terms of properties.

[0004] In order to obtain such sprayed concrete, the powdered quick-setting agent mixed into the base concrete generally has various components added to the above-described quick-setting components to adjust various properties. For example, in a typical conventional powdered quick-setting agent, calcium aluminate with a high CaO content as a chemical component is blended with gypsum for accelerating hardening, and sodium aluminate for enhancing early strength development and sodium carbonate for accelerating setting are added thereto (see, for example, Patent Documents 1 to 4). In addition to the above-described cement, water, and aggregate, the base concrete is also added with gypsum for raising the long-term strength and a water reducing agent for suppressing the amount of water leading to strength reduction, as necessary (see, for example, Patent Document 4).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in recent years, depending on the construction site of the sprayed concrete, higher early strength development within about 3 hours after spraying has been required. For this reason, it is considered that if the strength development can be enhanced not only by a powdered quick-setting agent showing high strength development but also by the construction procedure and the construction apparatus, a synergistic effect between the quick-setting agent and the construction procedure / apparatus can be obtained.

[0007] Therefore, an object of the present invention is to provide a spraying method and a spraying apparatus capable of performing spraying construction with high early strength development.

Means for Solving the Problems

[0008] As a result of intensive studies on the above problems, the present invention provides a spraying method excellent in initial strength development by adding a quick-setting aid containing gypsum to base concrete separately from the gypsum contained in the base concrete or the quick-setting material as needed before adding the quick-setting material to the base concrete. Furthermore, by adjusting the position where the quick-setting aid is added in the spraying device, it has been found that a spraying device suitable for the method can be obtained.

[0009] The present invention provides a spraying method in which, in a spraying method of adding and mixing a quick-setting material to base concrete containing cement and then spraying it onto an object to be constructed, a quick-setting aid containing gypsum is added to the base concrete before adding the quick-setting material.

[0010] In addition, the present invention includes a pressure-feeding pipe (1) for pressure-feeding base concrete containing cement, an air supply part (2) and a quick-setting material supply part (3) for supplying a quick-setting material, which are arranged in order in the side part of the pressure-feeding pipe (1) with respect to the pressure-feeding direction, a spraying device (10) provided with a spraying nozzle (4) at the end part of the pressure-feeding pipe (1), and at least one quick-setting aid adding part (5) for adding a quick-setting aid containing gypsum is provided in the side part of the air supply part (2) and / or in the side part of the pressure-feeding pipe (1) between the air supply part (2) and the quick-setting material supply part (3). The present invention provides a spraying device.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a spraying method and a spraying device capable of performing a spraying construction with high initial strength development.

Brief Description of the Drawings

[0012]

Figure 1

Embodiments for Carrying Out the Invention

[0013] [Spraying Material] The spraying material (sprayed concrete) includes base concrete, accelerating material, and accelerating aid.

[0014] ·Base Concrete The base concrete contains cement. The cement is preferably Portland cement, and any type of Portland cement may be used. For example, various Portland cements such as ordinary, early strength, ultra-early strength, medium heat, low heat, and sulfate-resistant Portland cements can be mentioned. As the cement, for example, blended cements containing Portland cements such as blast furnace cement and fly ash cement can also be used. The cement may be used alone or in combination of two or more. When using Portland cement, the particle size is not particularly limited. For example, those with 2500 cm 2 / g or more according to JIS standard (JIS R 5210:2019) can be mentioned.

[0015] The base concrete can contain aggregates such as fine aggregates and coarse aggregates. The fine aggregate is not particularly limited as long as it is a fine aggregate that can be used in mortar or concrete. The coarse aggregate is not particularly limited as long as it is a coarse aggregate that can be used in concrete. From the viewpoint of easily ensuring a predetermined aggregate strength and having a small specific gravity difference from other contained components and being less likely to cause material separation, it is preferable to use aggregates with an apparent dry density of 2.3 to 2.9 g / cm 3 Specific examples of such aggregates include, for fine aggregates, natural aggregates such as silica sand and limestone sand, crushed sand such as andesite, sandstone, and basalt, and for coarse aggregates, crushed stones and gravel such as silica, limestone, andesite, sandstone, and basalt. The aggregates may be used alone or in combination of two or more.

[0016] The content of aggregates in the base concrete is not particularly limited. However, from the perspective of excellent pumpability of the concrete during construction, it is preferably 300 to 570 parts by mass, more preferably 380 to 550 parts by mass, and even more preferably 420 to 520 parts by mass in total of fine aggregates and coarse aggregates with respect to 100 parts by mass of cement content. When fine aggregates and coarse aggregates are used in combination, the mass ratio of fine aggregates (mass ratio of fine aggregates in all aggregates) is preferably 54 to 69% by mass, more preferably 55 to 65% by mass, and even more preferably 56 to 63% by mass.

[0017] The base concrete may contain a water reducing agent. The water reducing agent includes a dispersant, a high-performance water reducing agent, a high-performance AE water reducing agent, an AE water reducing agent, and a fluidizing agent. Examples of such water reducing agents include water reducing agents specified in JIS A 6204:2011 "Chemical admixtures for concrete". Examples of water reducing agents include polycarboxylic acid-based water reducing agents, naphthalene sulfonic acid-based water reducing agents, lignin sulfonic acid-based water reducing agents, melamine-based water reducing agents, and acrylic-based water reducing agents. Among these, polycarboxylic acid-based water reducing agents are preferred. The water reducing agent may be used alone or in combination of two or more. From the perspective of easily ensuring fluidity while suppressing the amount of water, the content of the water reducing agent is preferably 0.01 to 1 part by mass, more preferably 0.05 to 0.5 part by mass, and even more preferably 0.1 to 0.3 part by mass in terms of solid content with respect to 100 parts by mass of cement.

[0018] The base concrete can also contain components other than the above as long as the effects of the present invention are not impaired. Examples of components that can be contained include gypsum, thickeners, short fibers, pozzolanic reactive substances, and the like.

[0019] The base concrete can appropriately adjust the amount of water according to factors such as the purpose of use and location. The water content is preferably 52 to 68 parts by mass, more preferably 53 to 67 parts by mass, and still more preferably 55 to 65 parts by mass with respect to 100 parts by mass of cement. If the water content is within the above range, the strength development tendency is excellent.

[0020] ·Quick-setting material The quick-setting material may be a powder or a liquid. Examples of the powder quick-setting material include those containing calcium aluminate, alkali metal sulfate, alkaline earth metal sulfate, and aluminum sulfate. Examples of the liquid quick-setting material include those mainly composed of aluminum sulfate, and commercially available liquid quick-setting materials can also be used.

[0021] Calcium aluminate is an inorganic hydration active substance having CaO and Al 2 O 3 as the main chemical components, and the content molar ratio of CaO and Al 2 O 3 (CaO / Al 2 O 3 ) is preferably 1.8 to 2.7, preferably 1.9 to 2.65, and more preferably 2.0 to 2.6. If the content molar ratio of CaO and Al 2 O 3 is within the above range, it is easy to balance quick-setting property and workability. Calcium aluminate may contain other components such as impurities other than CaO and Al 2 O 3 derived from raw materials, as long as the effects of the present invention are not inhibited regardless of their existence forms.

[0022] Calcium aluminate can be any of crystalline, amorphous, or a mixture thereof. From the perspective that better flash setting properties are more easily obtained, the degree of vitrification, which is the degree of amorphization, of calcium aluminate is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more. The powder fineness of calcium aluminate is not particularly limited, but since appropriate reaction activity is more easily obtained when used as a flash setting material for concrete, it is preferably of a powder fineness comparable to or higher than that of the cement in the base concrete to be mixed. For example, a Blaine specific surface area of 3000 - 6500 cm 2 / g can be mentioned as the powder fineness.

[0023] Calcium aluminate can be obtained, for example, by heating a raw material mixture in which a raw material serving as a CaO source and a raw material serving as an Al 2 O 3 source are blended so as to obtain a molar ratio of CaO and Al 2 O 3 as the target chemical components until melting. Also, due to differences in the cooling process after heating during production, various differences occur in the structural state of calcium aluminate after cooling. Therefore, the degree of vitrification, which is the degree of amorphization, can be adjusted according to cooling conditions such as the cooling rate.

[0024] The content of calcium aluminate is preferably 60 - 80% by mass, more preferably 65 - 78% by mass, and even more preferably 66 - 77% by mass based on the total mass of the flash setting material. If the content of calcium aluminate is within the above range, it is easy to achieve both flash setting properties and mixability.

[0025] The sulfate of an alkali metal is not particularly limited and any one can be used, and it is preferably an anhydride because of its excellent reactivity. Examples of the alkali metal include lithium, sodium, potassium, etc., and sodium is particularly preferred. The sulfate of an alkali metal may be used alone or in combination of two or more. The content of the sulfate of an alkali metal is preferably 4 to 16 parts by mass in terms of anhydride based on 100 parts by mass of calcium aluminate, more preferably 5 to 15 parts by mass, and still more preferably 6 to 14 parts by mass. If the content of the sulfate of an alkali metal is within the above range, it is likely to be excellent in flash setting property and strength development property.

[0026] The sulfate of an alkaline earth metal is not particularly limited and any one can be used, and it is preferably an anhydride because of its excellent reactivity. Examples of the alkaline earth metal include magnesium, calcium, etc., and calcium is particularly preferred. The sulfate of an alkaline earth metal may be used alone or in combination of two or more. The particle size and particle size distribution of the sulfate of an alkaline earth metal are not particularly limited, and for example, those having a Blaine specific surface area of about 4000 to 8500 cm 2 / g can be mentioned. The content of the sulfate of an alkaline earth metal is preferably 5 to 45 parts by mass in terms of anhydride based on 100 parts by mass of calcium aluminate, more preferably 7 to 40 parts by mass, and still more preferably 10 to 35 parts by mass. If the content of the sulfate of an alkaline earth metal is within the above range, it is likely to be excellent in long-term strength development property.

[0027] The mass ratio ([mass of sulfate of alkaline earth metal] / [mass of sulfate of alkali metal]) of the sulfate of an alkali metal and the sulfate of an alkaline earth metal in the flash setting material is preferably 0.5 to 7 in terms of anhydride, more preferably 0.8 to 4, and still more preferably 1 to 4. If the mass ratio of the sulfate of an alkali metal and the sulfate of an alkaline earth metal is within the above range, flash setting property, mixing property, and long-term strength development property can be easily obtained.

[0028] Aluminum sulfate can be in any form, such as the 16-hydrate, anhydride, etc., among which the 16-hydrate is preferred. The content of aluminum sulfate is preferably 0.5 to 15 parts by mass in terms of anhydride, more preferably 0.7 to 13 parts by mass, and still more preferably 1 to 10 parts by mass with respect to 100 parts by mass of calcium aluminate. If the content of aluminum sulfate is within the above range, it is easy to ensure long-term strength development even when the flash setting property is enhanced under a low-temperature environment.

[0029] The mass ratio of the sulfate of an alkali metal and aluminum sulfate in the flash setting material ([mass of aluminum sulfate] / [mass of the sulfate of an alkali metal]) is preferably 0.05 to 2 in terms of anhydride, more preferably 0.1 to 1.8, and still more preferably 0.2 to 1.5. If the mass ratio of the sulfate of an alkali metal and aluminum sulfate is within the above range, it is easy to obtain flash setting property, mixability, and strength development property.

[0030] The flash setting material may contain a carbonate of an alkali metal. The carbonate of an alkali metal is not particularly limited, and any one can be used. It is preferably an anhydride because of its excellent reactivity. Examples of the alkali metal include lithium, sodium, potassium, etc., among which sodium is preferred. The carbonate of an alkali metal may be used alone or in combination of two or more. The particle size of the carbonate of an alkali metal is not particularly limited. For example, a powder with a Blaine specific surface area of generally 3000 to 6500 cm 2 / g and a maximum particle size of 1 mm or less can be used. The content of the carbonate of an alkali metal is preferably 1 to 10 parts by mass in terms of anhydride, more preferably 1.5 to 9 parts by mass, and still more preferably 2 to 8 parts by mass with respect to 100 parts by mass of calcium aluminate. If the content of the carbonate of an alkali metal is within the above range, the initial strength development property is further improved.

[0031] The accelerating material is produced by mixing the above components. The mixing method is not particularly limited, and for example, general-purpose mixers such as tilting mixers, pan mixers, twin-shaft mixers, grout mixers, hover mixers, and omnimixers can be used.

[0032] The amount of the accelerating material added to the base concrete is preferably 5 to 15 parts by mass, more preferably 6 to 14 parts by mass, and even more preferably 7 to 13 parts by mass with respect to 100 parts by mass of cement. If the addition amount of the accelerating material is within the above range, it is easy to achieve both rapid setting property and mixability.

[0033] ·Accelerating aid The accelerating aid used in the present invention contains gypsum materials. Examples of gypsum materials include anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum. From the viewpoint of further improving the strength development property, anhydrous gypsum is preferred. The gypsum materials may be used alone or in combination of two or more. From the viewpoint of further improving the initial strength development, the fineness of the gypsum materials is preferably 3500 to 18000 cm 2 / g in terms of Blaine specific surface area, more preferably 5000 to 15000 cm 2 / g, even more preferably 5500 to 14000 cm 2 / g, particularly preferably 7000 to 12000 cm 2 / g.

[0034] The accelerating aid may contain components other than gypsum materials as long as the effects of the present invention are not inhibited. Examples of the components that can be contained include carbonates of alkali metals and water. Examples of the carbonates of alkali metals include those described above, and sodium carbonate is preferred among them. When the accelerating aid contains components other than gypsum materials, the amount of gypsum materials is preferably 55 to 98 parts by mass, more preferably 65 to 90 parts by mass, and even more preferably 75 to 85 parts by mass with respect to 100 parts by mass of the solid content of the accelerating aid.

[0035] The amount of the accelerating admixture added to the base concrete is preferably 1 to 15 parts by mass, more preferably 2 to 10 parts by mass, and still more preferably 3 to 8 parts by mass in terms of solid content with respect to 100 parts by mass of cement. If the addition amount of the accelerating admixture is within the above range, the strength development property from the initial stage to the long term can be further enhanced.

[0036] [Spraying method] The spraying method of the present invention is to add an accelerating admixture containing gypsum to the base concrete containing cement, and then add and mix an accelerating material and spray it onto the object to be constructed. That is, it is characterized in that, separately from the gypsum contained in the base concrete or the accelerating material as required conventionally, an accelerating admixture containing gypsum is added before adding the accelerating material to the base concrete. According to the spraying method of the present invention, spraying construction excellent in initial strength development property can be performed. Therefore, it can be suitably applied not only to the spraying on ordinary tunnel walls and slopes but also to the construction in an environment where the adhesion is poor and early setting property is required, such as a place with a lot of water.

[0037] [Spraying device] Hereinafter, an embodiment of the spraying device of the present invention will be described with appropriate reference to the drawings. Each drawing is a schematic diagram, and the size and the like of each component are not limited to those shown in the drawings.

[0038] FIGS. 1(a) and (b) are schematic diagrams showing an embodiment of the spraying device of the present invention. The spraying device 10 of this embodiment includes a pressure feeding pipe 1 for pressure-feeding the base concrete containing cement, an air supply unit 2, an accelerating material supply unit 3 for supplying an accelerating material, and a spraying nozzle 4. On the side portion of the pressure feeding pipe 1, the air supply unit 2 and the accelerating material supply unit 3 are arranged in order with respect to the pressure feeding direction. Further, at least one accelerating admixture addition unit 5 for adding an accelerating admixture is provided on the side portion of the air supply unit 2 and / or on the side portion of the pressure feeding pipe 1 between the air supply unit 2 and the accelerating material supply unit 3.

[0039] The pressure conveying pipe 1 is not particularly limited as long as it is a pressure-resistant pipe, and it may be a metal pressure-resistant pipe, a pressure-resistant hose, or a composite of these. The length of the pressure conveying pipe 1 can be appropriately adjusted according to the distance to the construction site. The inner diameter of the pressure conveying pipe 1 is not particularly limited, and for example, it can be 5 to 13 cm. The pressure conveying pipe 1 receives base concrete containing cement from a concrete material supply machine such as an agitator truck or a mortar mixer, and pressure-conveys the base concrete by the air supplied from the air supply unit 2.

[0040] The air supply unit 2 is not particularly limited as long as it can convey air, and examples include an air compressor. By adjusting the amount of air supplied by the air supply unit, the discharge pressure of the spraying material can be controlled. The spraying material includes base concrete, a quick-setting material, and a quick-setting aid. From the viewpoint of further improving the workability during spraying, the installation position of the air supply unit 2 is preferably 6 to 18 m, more preferably 8 to 15 m, from the tip of the spraying nozzle 4.

[0041] The quick-setting material supply unit 3 conveys the quick-setting material, and a suitable one can be selected according to the shape of the quick-setting material. When the quick-setting material is in powder or slurry form, an air compressor or the like can be used. When it is in liquid form, an annular member in which the liquid is supplied in the central direction of a ring called a shower ring, a water ring, an O-ring, etc. can be used. From the viewpoint of facilitating sufficient mixing of the base concrete, the quick-setting material, and the quick-setting aid, the installation position of the quick-setting material supply unit 3 is preferably 0.5 to 5 m, more preferably 0.8 to 4.5 m, and even more preferably 1 to 3 m, from the tip of the spraying nozzle.

[0042] The spraying nozzle 4 is not particularly limited as long as it is usually used for spraying or the like. The length of the spraying nozzle 4 is preferably 10 to 50 cm, more preferably 15 to 40 cm, and even more preferably 20 to 35 cm. If the length of the spraying nozzle 4 is within the above range, the discharge range can be more easily controlled, and the amount of generated dust can be further reduced.

[0043] The quick-setting aid supply unit 5 pumps the quick-setting aid using an air compressor or the like. The quick-setting aid may be in powder form or in slurry form. The quick-setting aid supply unit 5 may be connected to the air supply unit 2 as shown in Fig. 1(a), or may be connected to the pressure feed pipe 1 between the air supply unit 2 and the quick-setting aid supply unit 3 as shown in Fig. 1(b). Alternatively, the quick-setting aid supply unit 5 may be connected to both the air supply unit 2 and the pressure feed pipe 1 by combining the configurations shown in Figs. 1(a) and (b). By using such a spraying device, the quick-setting aid is added during the spraying process without being added to the base concrete in advance, thereby improving the initial strength development property and suppressing the use of a water reducing agent because it does not affect the fresh properties of the base concrete.

[0044] From the viewpoint that the base concrete and the quick-setting aid are easily mixed sufficiently, the length from the quick-setting aid addition part to the quick-setting material supply part is preferably 3 to 18 m, more preferably 4 to 15 m, and still more preferably 4 to 12 m for the installation position of the quick-setting aid supply unit 5.

Examples

[0045] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. The examples were conducted under an environment of 20 ± 1°C unless otherwise specified.

[0046] Examples 1 to 6, Comparative Example 1 [Materials] Calcium aluminate: CaO / Al 2 O 3 is 2.5, Blaine specific surface area 5400 cm 2 / g, Vitrification rate 95 mass% Sodium sulfate reagent (anhydrous mirabilite) Calcium sulfate reagent (anhydrous gypsum) Aluminum sulfate reagent (hexadecahydrate) Quick-setting aid: Anhydrous gypsum, Blaine specific surface area 11000 cm 2 / g, When adding as a slurry, adjust with water so that it becomes a slurry with a solid content of 75% by mass Cement: Ordinary Portland cement, Blaine specific surface area 3200 cm 2 / g, Density 3.15 g / cm 3 Fine aggregate: Limestone fine aggregate (SSD density; 2.65 g / cm 3 , Median particle size; 0.6 mm) Coarse aggregate: Crushed stone (SSD density; 2.74 g / cm 3 , Particle size 5 - 15 mm)

[0047] [Production of base concrete] For 100 parts by mass of cement, 300 parts by mass of fine aggregate, 200 parts by mass of coarse aggregate, and 60 parts by mass of water were mixed with a concrete mixer for 2 minutes to produce base concrete. When using a slurry-like accelerating admixture, the water contained in the slurry was adjusted so that the total amount of water was also 60 parts by mass

[0048] [Production of accelerating material] Based on 100 parts by mass of calcium aluminate, the formulation was designed to be 5.7 parts by mass of aluminum sulfate, 12.8 parts by mass of sodium sulfate, and 26 parts by mass of calcium sulfate, and these were mixed with a Henschel mixer to produce an accelerating material

[0049] [Production of sprayed concrete] Immediately after kneading the base concrete, it was put into a supply tank and pumped through a resin hose about 10 m long and 6 cm in inner diameter to a spraying device. The spraying device is a commercially available product with a basic configuration consisting of a pressure pipe with an inner diameter of 2 inches through which the base concrete is pumped, a cylindrical side pipe (air supply section) for supplying and adding air to the base concrete that communicates with the side of the pressure pipe at an inclination angle of about 30 degrees, a cylindrical side pipe (accelerating material supply section) for supplying and adding an additive (accelerating material) to the base concrete that communicates with the side of the pressure pipe at an inclination angle of about 30 degrees, and a spraying nozzle with an inner diameter (tip aperture diameter) of 2 inches for spraying the sprayed concrete The side pipe, which is the quick-setting material supply section, is formed by connecting a steel T-shaped pipe (three-way pipe) between the main pumping pipe and the injection nozzle. The main pumping pipe and the injection nozzle are respectively connected to the two pipe openings located on the straight line of the T-shaped pipe, and the supply pipe for the separately fed quick-setting material is connected to the remaining pipe opening. The mixing of the base concrete and the quick-setting material is carried out within the distance from the addition position of the quick-setting material to the base concrete (the confluence point of the base concrete and the quick-setting material) in the T-shaped pipe to the end of the injection nozzle hole, and that distance (hereinafter referred to as the mixing distance) is set to 2 m. Also, the quick-setting aid supply section is connected to the air supply section via the T-shaped pipe. The length from the quick-setting aid supply section to the quick-setting material supply section is set to 6 m. The quick-setting material is pneumatically fed in a predetermined amount by compressed air and added to the base concrete being pumped in the spraying device. The added concrete is mixed while traveling a predetermined mixing distance, and the sprayed concrete is produced. The addition amount of the quick-setting material is as shown in Table 1. Here, for Examples 1 to 6, the quick-setting aid was added from the quick-setting aid supply section at the ratio shown in Table 1.

[0050] [Evaluation of Strength Development of Sprayed Concrete] Using the above spraying device, the sprayed concrete was sprayed into a forming mold with an inner dimension of 30×40×20 cm so as to fill the inside of the mold. This was placed in a constant temperature chamber at 20°C (±1°C), and after a predetermined time had elapsed, a cylindrical specimen with a diameter of 5 cm and a height of 10 cm was collected from the hardened concrete in the mold by a core drill to obtain a specimen at an age of 28 days. The uniaxial compressive strength of this specimen at an age of 28 days was measured with an Amthaler type compression strength tester. Also, using the formwork and embedment tool specified in the Japan Society of Civil Engineers Standard JSCE-G561, the sprayed concrete prepared in the same manner was subjected to a pull-out test in accordance with JSCE-G561. The compressive strength of the sprayed concrete at an age of 15 minutes, 3 hours, and 24 hours was measured by this test. The results of the strength measurement of each specimen are shown in Table 1.

[0051]

Table 1

[0052] Examples 1a - 4a, Comparative Example 1a (Evaluation of Quick Setting) In the above - mentioned base concrete mix, the total content of coarse aggregate and fine aggregate was all changed to the content of fine aggregate, and the mortar mix was prepared without coarse aggregate while keeping other components and their contents unchanged, following the same procedure as for the base concrete. For Examples 1a - 4a, first, a quick - setting aid was added and mixed at the ratios shown in Table 2 to the obtained base mortar, then a quick - setting material was added at the ratios shown in Table 2 and mixed for 5 seconds with a high - speed mixer to prepare a mortar kneaded product. For Comparative Example 1a, a quick - setting material was added at the ratio shown in Table 2 to the obtained base mortar and mixed for 5 seconds with a high - speed mixer to prepare a mortar kneaded product. The Proctor penetration resistance values of the mortar kneaded products were measured 30 seconds and 60 seconds after the addition of the quick - setting material to evaluate the quick - setting property. The method for measuring the Proctor penetration resistance conforms to the "Method for Measuring the Setting Time by Penetration Resistance of Mortar Added with Quick - Setting Agent" in the appendix of the "Quality Standard for Quick - Setting Agents for Sprayed Concrete" in the Concrete Standard Specification of the Japan Society of Civil Engineers, using a Proctor needle with a cross - sectional area of 0.125 cm 2 . The measurement results of this penetration resistance value are shown in Table 2. Also, the description ">16 (N / mm 2 )" in the table means that the Proctor needle could be driven in, but it exceeded the measurement limit (maximum 16 N / mm 2 ) of the equipment used this time.

[0053]

Table 2

[0054] According to the present invention, the sprayed concrete shows sufficient quick - setting property, and the initial strength development at 3 - hour and 24 - hour ages is improved, and sufficient strength development is maintained even in the long term.

Explanation of Signs

[0055] 1 Pressure - feeding pipe 2 Air - supply part 3 Quick - setting material supply part 4 Spray Nozzle 5 Quick Freezing Aid Additive Section 10 Spraying Device

Claims

1. A pumping pipe (1) for pumping base concrete containing cement, On the side of the pumping pipe (1), an air supply part (2) and a quick-setting material supply part (3) for supplying quick-setting material, which are arranged in order with respect to the pumping direction, At the end of the pumping pipe (1), a spraying device (10) provided with a spraying nozzle (4), At least one quick-setting aid addition part (5) for adding a quick-setting aid containing gypsum is provided on the side of the air supply part (2) and / or on the side of the pumping pipe (1) between the air supply part (2) and the quick-setting material supply part (3), Spraying device.

2. The spraying device according to Claim 1, wherein the length from the quick-setting aid addition part (5) to the quick-setting material supply part (3) is 3 to 18 m.

3. The spraying device according to Claim 1 or 2, wherein the addition amount of the quick-setting aid is 1 to 15 parts by mass with respect to 100 parts by mass of the cement.

4. A spraying method for spraying a construction object using the spraying device according to any one of Claims 1 to 3.

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