Spraying method

Abstract

To provide a spray method enabling spray application with high strength development at a very 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, the base concrete contains a water-reducing agent, the set accelerating agent contains alkali metal carbonate, and a set accelerating aid including gypsums is added to the base concrete before adding the set accelerating agent.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

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

[0003] Rapid setting components are mixed into 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 common construction method for sprayed concrete, for example, at least cement, water, and aggregates are weighed and mixed to produce base concrete, and then 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 the spraying device contacts water (water contact point) to the discharge hole at the nozzle end, mixing occurs and sprayed concrete is formed. The distance used for mixing is usually 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 accelerating agent mixed in the base concrete generally has various components added to the accelerating components described above to adjust various properties. For example, in a typical conventional powdered accelerating agent, calcium aluminate with a high CaO content as a chemical component is blended with gypsum for accelerating hardening, and sodium aluminate for enhancing the initial 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 increasing the long-term strength and a water reducing agent for suppressing the amount of water leading to a 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 sprayed concrete, extremely early strength development within 10 to 15 minutes after spraying has been increasingly required. For this reason, it is considered that if the strength development can be enhanced not only by a powdered accelerating agent showing high strength development but also by the construction procedure, a synergistic effect between the accelerating agent and the construction procedure can be obtained.

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

Means for Solving the Problems

[0008] As a result of intensive studies on the above problems, the present invention, in addition to containing a water reducing agent in the base concrete and an alkali metal carbonate in the accelerating material, before adding the accelerating material to the base concrete, a setting accelerator containing gypsum is added to the base concrete separately from the gypsum that may be contained in the base concrete or the accelerating material as needed, and it has been found that a spraying method excellent in extremely early strength development can be achieved.

[0009] The present invention provides a spraying method in which an accelerating material is added and mixed with a base concrete containing cement and then sprayed onto an object to be constructed, wherein the base concrete contains a water reducing agent, the accelerating material contains an alkali metal carbonate, and a setting accelerator containing gypsum is added to the base concrete before adding the accelerating material.

Effect of the Invention

[0010] According to the present invention, it is possible to provide a spraying method capable of performing a spraying construction with high extremely early strength development.

Brief Description of the Drawings

[0011]

Figure 1

Embodiment for Carrying Out the Invention

[0012] [Spraying Material] The spraying material (sprayed concrete) contains a base concrete, an accelerating material, and a setting accelerator.

[0013] ·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 types of Portland cement such as ordinary, early-strength, super-early-strength, moderate heat, low heat, and sulfate-resistant Portland cement can be mentioned. As the cement, for example, blended cement containing Portland cement 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 types. 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.

[0014] The base concrete contains 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. Such water reducing agents include those specified in JIS A 6204:2011 "Chemical admixtures for concrete". Examples of the water reducing agent 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 types. From the viewpoint of easily ensuring fluidity while suppressing the water amount, the content of the water reducing agent is preferably, for example, 0.01 to 1 part by mass in terms of solid content based on 100 parts by mass of cement, more preferably 0.05 to 0.5 part by mass, and even more preferably 0.1 to 0.3 part by mass.

[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. For both the fine aggregate and the coarse aggregate, 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, the apparent dry density is 2.3 to 2.9 g / cm 3It is preferable to use such aggregates. Specific examples of such aggregates include, as fine aggregates, natural aggregates such as silica sand and limestone sand, and crushed sand such as andesite, sandstone, and basalt. As coarse aggregates, crushed stones and gravel such as silica, limestone, andesite, sandstone, and basalt can be mentioned. The aggregates may be used alone or in combination of two or more kinds.

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

[0017] The base concrete can also contain components other than those described above as long as the effects of the present invention are not inhibited. Examples of the components that can be contained include gypsum, thickeners, short fibers, pozzolanic reactive substances, and the like.

[0018] The amount of water in the base concrete can be appropriately adjusted according to factors such as the purpose of use and the location. The water content is preferably 35 to 55 parts by mass, more preferably 40 to 50 parts by mass, and still more preferably 42 to 48 parts by mass with respect to 100 parts by mass of the cement. If the water content is within the above range, the strength development property in the very early stage tends to be excellent.

[0019] ·Quick-setting material As the quick-setting material, it may be a powder or a liquid. However, in the present invention, from the viewpoint of strength development at the very initial stage, it is necessary to contain a carbonate of an alkali metal. Examples of the powder quick-setting material include those containing calcium aluminate, a sulfate of an alkali metal, a sulfate of an alkaline earth metal, and aluminum sulfate in addition to the carbonate of an alkali metal. Examples of the liquid quick-setting material include those containing aluminum sulfate as a main component in addition to the carbonate of an alkali metal, and commercially available liquid quick-setting materials can also be used.

[0020] The carbonate of an alkali metal is not particularly limited, and any of them can be used. Since it has excellent reactivity, it is preferably an anhydride. Examples of the alkali metal include lithium, sodium, potassium, etc., and sodium is particularly 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 strength development at the very initial stage is further improved.

[0021] Calcium aluminate is an inorganic hydration active substance having CaO and Al 2 O 3 as main chemical components. The content molar ratio of CaO and Al 2 O 3 (CaO / Al 2 O 3 ) is preferably 1.8 to 2.7, more preferably 1.9 to 2.65, and still 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 easier to achieve both quick-setting property and workability. In calcium aluminate, CaO and Al derived from raw materials2 O 3 Impurities and other foreign components other than O may be included as long as they do not inhibit the effects of the present invention, regardless of their forms of existence.

[0022] Calcium aluminate can be used in any of crystalline, amorphous, and mixtures thereof. From the viewpoint of easily obtaining better flash setting properties, the vitrification rate, which is the degree of amorphization, of calcium aluminate is preferably 60% by mass or more, more preferably 80% by mass or more, and still more preferably 95% by mass or more. The powder fineness of calcium aluminate is not particularly limited, but since it is easy to obtain appropriate reaction activity 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 powder fineness of a Blaine specific surface area of 3000 to 6500 cm 2 / g can be mentioned.

[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 vitrification rate, 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 to 85% by mass, more preferably 65 to 83% by mass, and still more preferably 70 to 80% 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, more preferably 5 to 15 parts by mass, and still more preferably 6 to 14 parts by mass with respect to 100 parts by mass of calcium aluminate. 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 10 to 35 parts by mass in terms of anhydride, more preferably 11 to 30 parts by mass, and still more preferably 12 to 25 parts by mass with respect to 100 parts by mass of calcium aluminate. 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 1.1 to 2.5, more preferably 1.2 to 2.4, and still more preferably 1.3 to 2.35 in terms of anhydride. 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 may be in any form, such as the 16-hydrate, anhydride, etc., and among them, the 16-hydrate is preferred. The content of aluminum sulfate is preferably 0.1 to 10 parts by mass in terms of anhydride, more preferably 0.5 to 7 parts by mass, and still more preferably 1 to 5 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 initial setting property is enhanced in a low-temperature environment.

[0029] The mass ratio of the sulfate of alkali metal and aluminum sulfate in the initial setting material ([mass of aluminum sulfate] / [mass of the sulfate of 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 alkali metal and aluminum sulfate is within the above range, it is easy to obtain the initial setting property, mixability, and strength development property.

[0030] The initial setting material is produced by mixing the above components. The mixing method is not particularly limited, and for example, general mixers such as a tilting mixer, a pan mixer, a twin-shaft mixer, a grout mixer, a hopper mixer, and an omnimixer can be used.

[0031] The amount of the initial setting material added to the base concrete is preferably 5 to 15 parts by mass, more preferably 6 to 14 parts by mass, and still more preferably 7 to 13 parts by mass with respect to 100 parts by mass of cement. If the addition amount of the initial setting material is within the above range, it is easy to achieve both the initial setting property and the mixability.

[0032] ·Initial setting aid The accelerating aid used in the present invention contains gypsum materials. Examples of gypsum materials include anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, etc. 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 strength development at the very initial stage, the fineness of the gypsum materials is preferably 3500 - 18000 cm 2 / g in terms of Blaine specific surface area, more preferably 5000 - 15000 cm 2 / g, still more preferably 5500 - 14000 cm 2 / g, particularly preferably 7000 - 12000 cm 2 / g.

[0033] 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, water, etc. Examples of the carbonates of alkali metals are as 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 - 98 parts by mass, more preferably 65 - 90 parts by mass, and still more preferably 75 - 85 parts by mass with respect to 100 parts by mass of the solid content of the accelerating aid.

[0034] The amount of the accelerating aid added to the base concrete is preferably 5 - 20 parts by mass, more preferably 6 - 18 parts by mass, and still more preferably 7 - 15 parts by mass as the solid content with respect to 100 parts by mass of cement. If the addition amount of the accelerating aid is within the above range, the strength development property from the very initial stage to the long term can be further enhanced.

[0035] [Spraying method] The spraying method of the present invention is to add a quick-setting aid containing gypsum to the base concrete containing cement and a water reducing agent, and then add and mix a quick-setting material containing an alkali metal carbonate, and spray it onto the object to be constructed. That is, conventionally, separately from the gypsum contained in the base concrete or the quick-setting material as required, a quick-setting aid containing gypsum is added before adding the quick-setting material to the base concrete, and it is characterized in that it is essential to contain a water reducing agent in the base concrete and an alkali metal carbonate in the quick-setting material. According to the spraying method of the present invention, spraying construction excellent in extremely early strength development can be performed. Therefore, it can be suitably applied not only to spraying on ordinary tunnel walls and slopes, but also to construction in an environment where adhesion is poor and early quick-setting is required, such as in a place with a lot of water.

[0036] [Spraying device] The spraying method of the present invention can be carried out using the spraying device shown in the following example. Hereinafter, an embodiment of the spraying device will be described with appropriate reference to the drawings. Each figure is a schematic diagram, and the size etc. of each component are not limited to those shown in the drawings.

[0037] Figs. 1(a) and (b) are schematic diagrams showing an embodiment of the spraying device. The spraying device 10 of this embodiment includes a pressure feeding pipe 1 for pressure feeding base concrete containing cement, an air supply unit 2, a quick-setting material supply unit 3 for supplying a quick-setting material, and a spraying nozzle 4. On the side portion of the pressure feeding pipe 1, the air supply unit 2 and the quick-setting material supply unit 3 are arranged in order in the pressure feeding direction. Further, at least one quick-setting aid adding unit 5 for adding a quick-setting aid 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 quick-setting material supply unit 3.

[0038] The pressure delivery 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 delivery pipe 1 can be appropriately adjusted according to the distance to the construction site. The inner diameter of the pressure delivery pipe 1 is not particularly limited, and for example, it can be 5 to 13 cm. The pressure delivery pipe 1 receives base concrete containing cement from a concrete material supply machine such as an agitator truck or a mortar mixer, and pressure-feeds the base concrete by the air supplied from the air supply unit 2.

[0039] The air supply unit 2 is not particularly limited as long as it can pressure-feed 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.

[0040] The quick-setting material supply unit 3 pressure-feeds 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.

[0041] 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.

[0042] The quick-setting aid supply unit 5 pumps the quick-setting aid by means of 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), or 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 of Fig. 1(a) and (b). By using such a spraying device, the quick-setting aid is added during the spraying process without adding it to the base concrete in advance, so that the early strength development property is improved, and since it does not affect the fresh properties of the base concrete, the use of a water reducing agent can be suppressed.

[0043] 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

[0044] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. The examples were carried out in an environment of 20 ± 1°C unless otherwise specified.

[0045] Examples 1 to 3, Comparative Examples 1 to 3 [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) Sodium carbonate reagent Quick-setting aid: anhydrous gypsum, Blaine specific surface area 11000 cm 2 / g 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) Water reducing agent: Polycarboxylic acid based high performance water reducing agent

[0046] [Preparation of base concrete] For 100 parts by mass of cement, 260 parts by mass of fine aggregate, 180 parts by mass of coarse aggregate, 45 parts by mass of water, and the amount of water reducing agent shown in Table 1 were mixed in a concrete mixer for 2 minutes to prepare base concrete. For Comparative Examples 1 - 3, in addition to the above materials, an accelerating admixture was mixed (internally added) at the ratio shown in Table 1 to prepare base concrete. [Preparation of accelerating material] Based on 100 parts by mass of calcium aluminate, the formulation was designed to be 2.7 parts by mass of aluminum sulfate, 10.8 parts by mass of sodium sulfate, 20 parts by mass of calcium sulfate, and 2.7 parts by mass of sodium carbonate. These were mixed in a Henschel mixer to prepare an accelerating material.

[0047] [Preparation 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 - feeding pipe with an inner diameter of 2 inches through which the base concrete is pressure - fed, a cylindrical side pipe (air supply part) for supplying and adding air to the base concrete communicating with the side of the pressure - feeding pipe at an inclination angle of about 30 degrees, a cylindrical side pipe (accelerating material supply part) for supplying and adding an additive (accelerating material) to the base concrete communicating with the side of the pressure - feeding pipe at an inclination angle of about 30 degrees, and a spraying nozzle with an inner diameter (tip hole 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 this distance (hereinafter referred to as the mixing distance) is set to 2 m. In addition, 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 sprayed concrete is produced. The addition amount of the quick-setting material is as shown in Table 1. Here, for Examples 1 to 3, the quick-setting aid was added (externally added) from the quick-setting aid supply section at the ratio shown in Table 1.

[0048] [Evaluation of Strength Development of Sprayed Concrete] Using the above spraying device, sprayed concrete was sprayed into a molding formwork with an inner dimension of 30×40×20 cm to fill the inside of the formwork. This was placed in a constant temperature chamber at 20°C (±1°C), and after a predetermined time had elapsed, cylindrical specimens with a diameter of 5 cm and a height of 10 cm were collected from the hardened concrete in the formwork by a core drill to obtain specimens at a material age of 28 days. The uniaxial compressive strength of these specimens at a material age of 28 days was measured using an Amthauer type compressive strength testing machine. In addition, using the formwork and embedment tool for the pull-out test 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 a material age of 15 minutes and 3 hours was measured by this test. The results of the strength measurement of each specimen are shown in Table 1.

[0049]

Table 1

[0050] Examples 1a to 3a (Evaluation of quick setting) In the above-described base concrete mixture, all of the amounts corresponding to the total content of coarse aggregate and fine aggregate contained therein were made the content of fine aggregate, and no coarse aggregate was included. Also, the other components and their contents were not changed, and a base mortar changed to a mortar mixture was produced in the same procedure as the base concrete. For the obtained base mortar, first, a quick-setting aid was added and mixed at the ratios shown in Table 2, and then a quick-setting material was added at the ratios shown in Table 2 and mixed with a high-speed mixer for 5 seconds to produce a mortar kneaded product. After 30 seconds and 60 seconds had elapsed since the addition of the quick-setting material, the Proctor penetration resistance values of the mortar kneaded product were measured to evaluate the quick setting property. The method for measuring the Proctor penetration resistance conforms to the "Method for Measuring the Instantaneous Setting Time by the Penetration Resistance of Mortar Added with a Quick-Setting Agent" attached to the "Quality Standard for Quick-Setting Agents for Sprayed Concrete" in the Standard Specifications for Concrete of the Japan Society of Civil Engineers, and a Proctor needle with a cross-sectional area of 0.125 cm 2 was used. The measurement results of this penetration resistance value are shown in Table 2. Also, in the table, the description ">16 (N / mm 2 )" 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.

[0051]

Table 2

[0052] According to the present invention, the sprayed concrete exhibited sufficient quick setting property, improved early strength development property at an extremely early age of 15 minutes, and maintained sufficient strength development property even in the long term.

Explanation of Signs

[0053] 1 Pressure delivery pipe 2 Air supply unit 3 Quick-setting material supply unit 4 Spraying nozzle 5 Quick-setting aid addition unit 10 Spraying device

Claims

1. In a spraying method in which a quick-setting material is added to and mixed with base concrete containing cement and then sprayed onto an object to be constructed, the base concrete contains a water reducing agent, and the quick-setting material contains an alkali metal carbonate, before adding the quick-setting material, a quick-setting aid containing gypsum is added to the base concrete, a pressure conveying pipe (1) for pressure conveying the base concrete, on the side of the pressure conveying pipe (1), an air supply part (2) and a quick-setting material supply part (3) for supplying the quick-setting material, which are arranged in order with respect to the pressure conveying direction, at the end of the pressure conveying pipe (1), a spraying nozzle (4) is provided, using a spraying device (10) provided with at least one quick-setting aid addition part (5) for adding a quick-setting aid on the side of the air supply part (2) and / or on the side of the pressure conveying pipe (1) between the air supply part (2) and the quick-setting material supply part (3), spraying is performed on an object to be constructed, Spraying method.

2. The spraying method 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 method according to claim 1 or 2, wherein the addition amount of the quick-setting aid is 5 to 20 parts by mass with respect to 100 parts by mass of the cement.

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