Spray method

Abstract

To provide a spray method that enables spray construction with high initial strength development.SOLUTION: A spray method in which, after adding and mixing a quick-setting material into base concrete containing cement, spray application is performed on an object to be constructed, comprises a step of, prior to adding the quick-setting material, adding a quick-setting aid containing gypsum (however, excluding cases where it contains alkali metal aluminate, lime, and gypsum) to the base concrete.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Preventing collapse of excavated surfaces in tunnels, mining pits, underground spaces, etc., and preventing collapse of natural ground during or after excavation From the viewpoint of reinforcement, sprayed concrete is used for construction. The rapid setting properties of this adhesive ensure adhesion to the object being treated, contributing to the reinforcement of the object.

[0003] Shotcrete contains quick-setting ingredients to give it quick setting properties. Powdered quick-setting agents containing calcium aluminate, sodium aluminate, etc. as active ingredients have a strong It is possible to give quick setting and high strength. In the wet spraying method, which is a common construction method, for example, at least cement, water and aggregate are weighed and mixed. The concrete is mixed together to make the base concrete, which is then passed through an agitator vehicle, etc., and sprayed with a spraying device during construction. In the spraying equipment, the separately sent powder or liquid quick-setting agent is pumped into the base concrete. The mixture is added to the concrete in the spray nozzle of the spraying device to form a sprayed concrete. The quick-setting component is sprayed from the nozzle end hole. The point where the quick-setting component comes into contact with water (water contact point) As it moves from the nozzle to the discharge hole at the end of the spray nozzle, mixing occurs and sprayed concrete is formed. The distance used for mixing is usually several tens of centimeters to several meters, and the travel time is the mixing time. Generally, the longer this distance, the more the mixture progresses, the higher the mixability, and the more the structure and properties improve. This also makes it easier to obtain more uniform concrete.

[0004] In order to obtain such a sprayed concrete, powdered Accelerators generally consist of the aforementioned quick-setting components plus various components for adjusting various properties. For example, a typical conventional powder quick-setting admixture contains a large amount of CaO as a chemical component. The calcium aluminate is mixed with gypsum to accelerate hardening, and these are combined to develop early strength. Sodium aluminate is added to improve the viscosity and sodium carbonate is added to promote coagulation. (For example, see Patent Documents 1 to 4). The base concrete also contains the above-mentioned cement, In addition to water and aggregate, gypsum is used to increase the strength over the long term, and water content is used to reduce the strength of the concrete. For this purpose, a water-reducing agent or the like is added as necessary (for example, Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-121763 A [Patent Document 2] JP 2003-012356 A [Patent Document 3] Patent No. 5129955 [Patent Document 4] JP 2020-11891 A Summary of the Invention [Problem to be solved by the invention]

[0006] By the way, in recent years, depending on the location of the sprayed concrete, the initial time of about 3 hours after spraying is Therefore, the strength development of high strength is required. Strength development can be improved not only by the powder quick-setting agent, but also by the construction procedure and construction equipment. If possible, it is thought that a synergistic effect can be obtained between the quick-setting agent and the construction procedures and equipment.

[0007] Therefore, the present invention provides a spraying method and spraying equipment that allows spraying with high initial strength development. The purpose of this document is to provide a place where [Means for solving the problem]

[0008] As a result of intensive research into the above-mentioned problems, the present invention has been developed by adding a quick-setting material to base concrete. Before the concrete is cooled, a quick-setting agent containing gypsum is added to the base concrete or the quick-setting material as necessary. By adding it to the base concrete in addition to the gypsum that is used in the concrete, it is possible to improve the initial strength development. Furthermore, the position where the quick-setting aid is added in the spraying device is It has been found that by adjusting the above, a spraying device suitable for the above-mentioned method can be obtained.

[0009] In the present invention, a quick-setting material is added and mixed into base concrete containing cement, and then the concrete is applied to the construction site. In the spraying method in which the quick-setting material is sprayed onto an object, the base concrete is sprayed with the quick-setting material before the quick-setting material is added. The present invention provides a spraying method in which a quick-setting aid containing gypsum is added to the concrete.

[0010] The present invention also provides a pressure pipe (1) for pressure-feeding base concrete containing cement, An air supply section (2) and a quick-setting material are arranged in order in the direction of pumping on the side of the pumping pipe (1). a quick-setting material supply section (3) for supplying the quick-setting material; A spraying device (10) having a spray nozzle (4) at an end of the pressure pipe (1), The side of the air supply section (2), and / or the air supply section (2) and the quick-setting material supply section (3) A quick-setting aid for adding a quick-setting aid containing gypsum is provided on the side of the pressure pipe (1) between the At least one addition portion (5) is provided. A spraying device is provided. Effect of the Invention

[0011] According to the present invention, a spraying method and a spraying device capable of performing spraying with high initial strength development are provided. It can be provided. [Brief description of the drawings]

[0012] [Figure 1] 1(a) and (b) are schematic diagrams showing one embodiment of a spraying device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Spraying material] The sprayed material (sprayed concrete) includes base concrete, quick-setting material and quick-setting aid. .

[0014] Base concrete The base concrete contains cement, preferably Portland cement. Any type of Portland cement may be used, for example, normal, high-early-strength, ultra-high-early-strength, medium There are various types of Portland cement, including heat-resistant, low-heat, and sulfate-resistant. For example, mixed cement containing Portland cement such as blast furnace cement and fly ash cement. The cement may be used alone or in combination of two or more kinds. When using Portland cement, the particle size is not particularly limited. For example, the JIS standard IS R 5210:2019) 2500 cm 2 / g or more.

[0015] The base concrete can contain aggregates such as fine aggregate and coarse aggregate. Fine aggregate is a mortar. There is no particular restriction on fine aggregates as long as they can be used in concrete. There is no particular restriction on the coarse aggregate as long as it can be used for the concrete. The surface dry density is easy to ensure, and the difference in specific gravity with other components is small, making it difficult for material separation to occur. is 2.3~2.9g / cm 3 It is preferable to use the aggregate of the following. Specific examples of such aggregate include: Examples of fine aggregate include natural aggregates such as silica sand and limestone sand, and crushed sand of andesite, sandstone, basalt, etc. The coarse aggregate may be crushed stone or gravel such as silica, limestone, andesite, sandstone, or basalt. One type may be used alone, or two or more types may be used in combination.

[0016] The content of aggregate in the base concrete is not particularly limited, but From the viewpoint of excellent pumpability of concrete, The total amount of the fine aggregate and the coarse aggregate is preferably 300 to 570 parts by mass, and more preferably 380 to 550 parts by mass. It is more preferable that the content of the fine aggregate and the coarse aggregate is 420 to 520 parts by mass, and further more preferable that the content of the fine aggregate and the coarse aggregate is 420 to 520 parts by mass. When used in combination, the mass ratio of fine aggregate (mass ratio of fine aggregate to total aggregate) is 54 to 69 mass%. It is preferable that the content is 55 to 65 mass %, more preferably 56 to 63 mass %. Preferred.

[0017] The base concrete may contain a water-reducing agent. The water-reducing agent may be a dispersant, a high-performance water-reducing agent, a high-performance These include AE ​​water reducing agents, AE water reducing agents, and superplasticizers. Examples of water-reducing agents include those specified in the "Chemical Admixtures for Concrete". For example, polycarboxylic acid-based water reducing agents, naphthalene sulfonic acid-based water reducing agents, lignin sulfonic acid-based water reducing agents, etc. Water reducing agents, melamine-based water reducing agents, and acrylic-based water reducing agents. The water reducing agent may be used alone or in combination of two or more. The content of the water reducing agent is determined from the viewpoint of ensuring fluidity while suppressing the amount of water. Therefore, for example, the amount is preferably 0.01 to 1 part by mass in terms of solid content per 100 parts by mass of cement. The amount is preferably 0.05 to 0.5 parts by mass, more preferably 0.1 to 0.3 parts by mass. preferable.

[0018] The base concrete contains components other than those mentioned above, provided that the effects of the present invention are not impaired. Possible ingredients include gypsum, thickeners, short fibers, pozzolanic reactive substances, etc. Examples include:

[0019] The amount of water in the base concrete can be adjusted depending on the purpose of use, location, and other factors. The content of water is preferably 52 to 68 parts by mass relative to 100 parts by mass of cement. It is preferable that the content is 53 to 67 parts by mass, and more preferable that the content is 55 to 65 parts by mass. If the water content is within the above range, the strength development tends to be excellent.

[0020] ·Quick setting material The quick-setting material may be in the form of a powder or a liquid. , e.g., calcium aluminate, sulfates of alkali metals, sulfates of alkaline earth metals and aluminum sulfate. Examples of the material include those containing aluminum as a main component, and commercially available liquid quick-setting materials can also be used.

[0021] Calcium aluminate is composed of CaO and Al 2 O3 It is an inorganic hydrated active substance whose main chemical component is , CaO and Al 2 O 3 The molar ratio of CaO / Al 2 O 3 ) is preferably 1.8 to 2.7, more preferably 1.9 to 2.65 It is preferable that the content of CaO and Al is 2.0 to 2.6. 2 O 3 The molar ratio of Within the above range, it becomes easier to achieve both quick setting and ease of application. is CaO and Al derived from the raw materials. 2 O 3 Other components such as impurities are also included in the present invention, regardless of their form. It may be contained within a range that does not impair the light-emitting effect.

[0022] Calcium aluminate can be used in either crystalline or amorphous form or in mixtures thereof. Calcium aluminate is preferred because it has a better quick-setting ability. The vitrification rate, which is the degree of amorphization, is preferably 60% by mass or more, and more preferably 80% by mass or more. More preferably, the content is 95% by mass or more, and even more preferably, 95% by mass or more. There is no particular restriction on the fineness of the nate, but when used as a quick-setting material for concrete, Since it is easy to obtain a high reaction activity, it is easy to mix it with the cement in the base concrete. It is preferable that the powder size is equal to or greater than the above. For example, the Blaine specific surface area is 3000 to 6500 cm 2 The powder size is 0.1 to 1.0 μm / g.

[0023] Calcium aluminate is, for example, a raw material that is a CaO source and Al 2 O 3 The raw materials are CaO and Al as chemical components 2 O3 The raw material mixture was mixed so as to obtain the molar ratio of It is obtained by heating it until it melts. Also, depending on the cooling process after heating during production, Since various differences occur in the structure of calcium aluminate after cooling, the cooling rate, etc. The vitrification rate, which is the degree of amorphization, can be adjusted depending on the cooling conditions.

[0024] The content of calcium aluminate is 60 to 80 mass% based on the total mass of the quick-setting material. It is preferable that the content is 65 to 78% by mass, and more preferable that the content is 66 to 77% by mass. If the content of calcium aluminate is within the above range, the quick setting property and the mixing property are improved. It is easy to balance gender.

[0025] There is no particular limitation on the alkali metal sulfate, and any sulfate can be used. The anhydride is preferable because it has excellent reactivity. Examples of alkali metals include lithium, sodium, and potassium, and among these, sodium is preferred. The sulfates of the alkali metal group may be used alone or in combination of two or more. The content of sulfate of the metal is 4 to 1 in anhydrous equivalent per 100 parts by mass of calcium aluminate. Preferably, it is 6 parts by mass, more preferably 5 to 15 parts by mass, and more preferably 6 to 14 parts by mass. If the content of the alkali metal sulfate is within the above range, rapid crystallization can be achieved. It tends to have excellent properties and strength expression.

[0026] The alkaline earth metal sulfate is not particularly limited and any sulfate may be used. The anhydride is preferable because it has excellent reactivity. Examples of the alkali include magnesium and calcium, and among these, calcium is preferable. The sulfates of earth metals may be used alone or in combination of two or more. The particle size and grain size of the potassium earth metal sulfate are not particularly limited. For example, the Blaine ratio Surface area is 4000~8500cm 2 The content of alkaline earth metal sulfates is about 1000 mg / g. is 5 to 45 parts by mass, calculated as an anhydrous equivalent, per 100 parts by mass of calcium aluminate. is preferable, 7 to 40 parts by mass is more preferable, and 10 to 35 parts by mass is even more preferable. If the content of the alkaline earth metal sulfate is within the above range, it is preferable that the long-term strength development is good. Easy to excel.

[0027] The mass ratio of alkali metal sulfates and alkaline earth metal sulfates in the quick-setting material ([ [mass of sulfate of alkaline earth metal] / [mass of sulfate of alkali metal] is calculated on an anhydrous basis. It is preferably 0.5 to 7, more preferably 0.8 to 4, and more preferably 1 to 4. It is more preferable that the mass ratio of the alkali metal sulfate and the alkaline earth metal sulfate is within the above range. Within this range, rapid setting, mixability, and long-term strength development are likely to be obtained.

[0028] The aluminum sulfate may be in any form, for example, 16-hydrate, anhydrous, etc. Among them, 16-hydrate is preferable. The content of aluminum sulfate is 100% calcium aluminate. The amount is preferably 0.5 to 15 parts by mass, and more preferably 0.7 to 13 parts by mass, calculated as an anhydride. The content of aluminum sulfate is more preferably 1 to 10 parts by mass, and further preferably 1 to 10 parts by mass. If the content is within the above range, long-term strength is maintained even when the quick setting property is increased in a low temperature environment. It is easy to ensure the quality.

[0029] The mass ratio of alkali metal sulfate and aluminum sulfate in the quenching material ([Al sulfate The ratio of mass of the alkali metal sulfate to mass of the aluminum is 0.05 to 2 on an anhydrous basis. It is preferable that the ratio is 0.1 to 1.8, and more preferable that the ratio is 0.2 to 1.5. If the mass ratio of the alkali metal sulfate and aluminum sulfate is within the above range, the quick setting property is improved. , mixability, and strength development are easily achieved.

[0030] The quick-setting material may include an alkali metal carbonate. Any of these can be used, and anhydrous is preferred due to its excellent reactivity. The alkali metal is preferably lithium, sodium, potassium, etc. Among them, sodium is preferred. The carbonate of an alkali metal may be used alone. The particle size of the alkali metal carbonate is not particularly limited. For example, the Blaine specific surface area is approximately 3000 to 6500 cm 2 / g for powders with a maximum particle size of 1 mm or less The content of alkali metal carbonate is 100% calcium aluminate. The amount of the anhydride is preferably 1 to 10 parts by mass, and more preferably 1.5 to 9 parts by mass. More preferably, the content is 2 to 8 parts by mass, and further preferably, 2 to 8 parts by mass of the alkali metal carbonate. If the content is within the above range, the initial strength development is further improved.

[0031] The quick-setting material is produced by mixing the above-mentioned components. The mixing method is not particularly limited. For example, tilting mixer, pan mixer, twin-shaft mixer, grout mixer, Hobart mixer, A general-purpose mixer such as a mixer, an omni mixer, or the like can be used.

[0032] The amount of quick-setting material added to the base concrete is 5 to 15 parts by mass per 100 parts by mass of cement. It is preferable that the amount of the glycerol is 6 to 14 parts by mass, and more preferably 7 to 13 parts by mass. If the amount of the quick-setting material added is within the above range, both quick-setting property and mixability are achieved. Easy to stand.

[0033] ·Quick-setting aid The quick-setting aid used in the present invention contains gypsum. Examples of gypsum include For example, gypsum anhydride, gypsum hemihydrate, gypsum dihydrate, etc. can be mentioned. From this viewpoint, anhydrous gypsum is preferred. The gypsums may be used alone or in combination of two or more. The fineness of gypsum is important from the viewpoint of improving the initial strength development. The specific surface area of ​​the blaine is 3500 to 18000 cm 2 / g, and 5000 to 15000 cm 2 / g More preferably, the wavelength is 5500 to 14000 cm. 2 / g, and more preferably 7000 to 12000 cm 2 / g It is particularly preferred that:

[0034] The quick-setting aid may contain components other than gypsum as long as the effect of the present invention is not impaired. Possible components include alkali metal carbonates and water. Examples of carbonates of the group include those mentioned above, and among them, sodium carbonate is preferable. If the agent contains ingredients other than gypsum, the amount of gypsum per 100 parts by mass of the solid content of the quick-setting agent is preferably 55 to 98 parts by mass, more preferably 65 to 90 parts by mass, and more preferably 75 to 85 Parts by weight are even more preferred.

[0035] The amount of quick-setting agent added to the base concrete is the solid content per 100 parts by mass of cement. The amount is preferably 1 to 15 parts by mass, more preferably 2 to 10 parts by mass, and It is more preferable that the amount of the quick-setting aid added is within the above range. This further improves the long-term strength development.

[0036] [Spraying method] The spraying method of the present invention is a method of spraying a quick-setting agent containing gypsum onto a base concrete containing cement. After adding the agent, the quick-setting material is added and mixed, and the mixture is sprayed onto the object to be worked on. In other words, gypsum, which has traditionally been included as necessary in base concrete and quick-setting materials, Separately, a quick-setting aid containing gypsum is added to the base concrete before adding the quick-setting material. The spraying method of the present invention is characterized by the fact that spraying construction with excellent initial strength development can be performed. Therefore, in addition to spraying onto normal tunnel walls and slopes, It is also suitable for construction in environments where adhesion is poor and quick setting is required, such as in places with poor adhesion. It is possible.

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

[0038] 1(a) and (b) are schematic diagrams showing one embodiment of a spraying device of the present invention. The spraying device 10 includes a pressure pipe 1 for pressure-feeding base concrete containing cement, and an air supply. The apparatus is equipped with a supply section 2 for supplying the quick-setting material, a quick-setting material supply section 3 for supplying the quick-setting material, and a spray nozzle 4. An air supply section 2 and a quick-setting material supply section 3 are arranged on the side of the pipe 1 in this order in the direction of pumping. Furthermore, the side of the air supply section 2 and / or between the air supply section 2 and the quick-setting material supply section 3 At least one quick-setting aid adding section 5 for adding a quick-setting aid is provided on the side of the pressure pipe 1. .

[0039] The pressure pipe 1 is not particularly limited as long as it is a pressure-resistant pipe, and may be a pressure-resistant pipe made of metal. The length of the pressure pipe 1 is The inner diameter of the pressure pipe 1 is not particularly limited, and may be, for example, 5 to 10 mm. The pressure pipe 1 is a pipe for conveying base concrete containing cement by an agitator. - Receive base concrete from concrete material supplying machines such as trucks and mortar mixers, The base concrete is pumped using air supplied from the air supply section 2.

[0040] The air supply unit 2 may be any device capable of compressing and feeding air, such as an air compressor. The discharge pressure of the spray material can be controlled by adjusting the amount of air supplied by the air supply section. The spraying material includes base concrete, quick-setting material and quick-setting aid. The position of the air supply unit 2 is set so as to further improve the workability when spraying. Therefore, it is preferable that the distance from the tip of the spray nozzle 4 is 6 to 18 m, and more preferably 8 to 15 m. This is more preferable.

[0041] The quick-setting material supplying section 3 is for pumping the quick-setting material, and is adapted to supply the quick-setting material in a suitable manner depending on the shape of the quick-setting material. If the quick-setting material is in powder or slurry form, an air compressor can be used. For liquids, shower rings, water rings, O-rings, etc. can be used. A ring-shaped member, such as a ring, can be used to supply liquid toward the center of the ring. The setting material supplying section 3 is installed at a position where the base concrete, the quick-setting material and the quick-setting aid are thoroughly mixed. From the viewpoint of easy application of the spray nozzle, the distance from the tip of the spray nozzle is preferably 0.5 to 5 m, and more preferably 0.8 It is more preferably up to 4.5 m, and further preferably 1 to 3 m.

[0042] The spray nozzle 4 is not particularly limited as long as it is a nozzle that is normally used for spraying. The length of the wire is preferably 10 to 50 cm, more preferably 15 to 40 cm, and more preferably 20 to 35 It is more preferable that the length of the spray nozzle 4 is within the above range. It is easy to control and the amount of dust generated can be further reduced.

[0043] The quick-setting aid supplying section 5 is for feeding the quick-setting aid under pressure using an air compressor or the like. The auxiliary may be in the form of a powder or a slurry. 1(b), or may be connected to the air supply unit 2 as shown in FIG. 1(a) and 1(b) may be combined. In addition, a quick-setting aid supply section 5 may be connected to both the air supply section 2 and the pressure transport pipe 1. By using a spraying device such as this, the quick-setting agent can be added to the base concrete in advance. Adding it during the spraying process without any additives improves the initial strength development and also improves the base core. Since it does not affect the fresh properties of concrete, the use of water-reducing agents can be reduced. do.

[0044] The installation position of the quick-setting aid supplying part 5 is determined so that the base concrete and the quick-setting aid can be mixed sufficiently. From the viewpoint of ease of use, the length from the quick-setting aid adding section to the quick-setting material supply section is 3 to 18 m. It is preferable that the length is 4 to 15 m, more preferable that the length is 4 to 12 m. stomach. EXAMPLES

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

[0046] Examples 1 to 6, Comparative Example 1 [material] Calcium aluminate: CaO / Al 2 O 3 2.5, Blaine specific surface area 5400cm 2 / g, vitrification rate 95 mass% Sodium sulfate reagent (anhydrous sodium sulfate) Calcium sulfate reagent (anhydrous gypsum) Aluminum sulfate reagent (16-hydrate) Quick-setting aid: anhydrous gypsum, Blaine specific surface area 11000cm 2 / g, if added as a slurry, solids Adjust with water to make a 75% by weight slurry. Cement: Ordinary Portland cement, Blaine specific surface area 3200cm 2 / g, density 3.15g / cm 3 Fine aggregate: Limestone fine aggregate (surface dry density: 2.65g / cm 3 , center grain size; 0.6mm) Coarse aggregate: crushed stone (surface dry density: 2.74 g / cm 3 , particle size 5~15mm)

[0047] [Preparation of base concrete] Concrete 100 parts by weight of cement, 300 parts by weight of fine aggregate, 200 parts by weight of coarse aggregate, and 60 parts by weight of water. The mixture was mixed for 2 minutes in a Riet mixer to prepare the base concrete. When using a slurry of this type, the amount of water contained in the slurry was adjusted to 60 parts by mass. .

[0048] [Preparation of quick-setting material] For 100 parts by mass of calcium aluminate, 5.7 parts by mass of aluminum sulfate and 5.7 parts by mass of sodium sulfate The mixture was designed to contain 12.8 parts by mass of calcium sulfate and 26 parts by mass of calcium sulfate. The mixture was mixed in a mixer to prepare a quick-setting material.

[0049] [Preparation of sprayed concrete] Immediately after mixing the base concrete, it is placed in a supply tank, from which a pipe about 10 m long and with an inner diameter of 6 The concrete was pumped through a 1.5 cm resin hose to the spraying device. The pressure pipe has an inner diameter of 2 inches, and the base is connected to the side of the pressure pipe at an inclination angle of about 30 degrees. A cylindrical side pipe (air supply section) for supplying air to the concrete and a pressure pipe on the side To supply and add additives (fast-setting materials) to the base concrete that is connected at an inclination angle of about 30 degrees The cylindrical side pipe (quick-setting material supply part) and the inner diameter (tip hole diameter) for spraying the shotcrete are 2 It is a commercially available product that basically consists of an inch injection nozzle. The side pipe, which is the quick-setting material supply section, is a steel T-shaped pipe (three-way) between the main pressure pipe and the injection nozzle. The main pressure pipe and the injection pipe are connected to the two ends of the T-shaped pipe, which are located in a straight line. The nozzles for injection are connected to each of them, and the remaining nozzles are connected to the supply pipes for the quick-setting material that are sent separately. The position where the quick-setting material is added to the base concrete inside the T-shaped pipe (base concrete Between the point where the cleat and the quick-setting material meet and the end of the nozzle hole for injection, The slag and the quick-setting material were mixed, and the distance (hereinafter referred to as the mixing distance) was 2 m. The quick-setting aid supply section was connected to the air supply section via a T-shaped pipe. The length to the sintering material supply section was 6 m. The quick-setting material is compressed by air and sent in a specified amount, so that the base material being compressed in the spraying device The concrete is mixed while moving along a specified mixing distance. The amount of quick-setting material added is shown in Table 1. In Examples 1 to 6, the quick-setting aid was added from the quick-setting aid supply section in the proportions shown in Table 1. .

[0050] [Evaluation of strength development of sprayed concrete] Using the spraying device, spray concrete into a molding form with inner dimensions of 30 x 40 x 20 cm. The mold was filled with the mixture. This was placed in a thermostatic chamber at 20℃ (±1℃) and after a specified time had passed, A cylindrical specimen with a diameter of 5 cm and a height of 10 cm was then extracted from the hardened concrete in the formwork using a core drill. The unconfined compressive strength of the 28-day-old specimen was measured using Amsla Measurements were taken using a type compressive strength testing machine. In addition, the pull-out test formwork and embedding tool specified in the JSCE-G561 standard were used. The sprayed concrete prepared in the same manner was subjected to a pull-out test in accordance with JSCE-G561. The test measured the compressive strength of the shotcrete after 15 minutes, 3 hours, and 24 hours of application. The results of the strength measurements of the specimens are shown in Table 1.

[0051] [Table 1]

[0052] Examples 1a to 4a and Comparative Example 1a (Evaluation of quick setting ability) In the above-mentioned base concrete mix, the total content of coarse aggregate and fine aggregate is The amount equivalent to the content is the content of fine aggregate, does not include coarse aggregate, and does not include other components and their contents. The amount of base mortar was not changed, but the mortar mix was changed to the same amount as the base concrete. For Examples 1a to 4a, the obtained base mortar was first subjected to a quick After adding and mixing the setting aid in the ratio shown in Table 2, add the quick-setting material in the ratio shown in Table 2 and mix at high speed. The mixture was mixed for 5 seconds in a mixing bowl to prepare a mortar mixture. Add the quick-setting material to the mortar in the ratio shown in Table 2, mix with a high-speed mixer for 5 seconds, and A ruthenium kneaded material was prepared. Proctor penetration resistance of mortar mixture 30 seconds and 60 seconds after addition of quick-setting material The Proctor penetration resistance was measured and the rapid setting property was evaluated. Standard Specifications "Quality Standards for Accelerator for Sprayed Concrete" Annex "Mortar with Accelerator Added" In accordance with the "Method of Measuring Instantaneous Heating Time by Penetration Resistance of 0.125 cm2" 2 Uses Proctor needles The results of the measurement of the penetration resistance are shown in Table 2. 2 )" is a Although the Loctor needle could be driven in, the measurement limit of the equipment used this time (maximum 16N / mm 2 ) That is why.

[0053] [Table 2]

[0054] According to the present invention, the shotcrete exhibits sufficient quick setting and has a material life of 3 hours and 24 hours. The initial strength development is improved and sufficient strength development is maintained over the long term. Ta. [Explanation of symbols]

[0055] 1 Pressure Pipe 2 Air supply section 3 Rapid setting material supply section 4 Spray nozzle 5. Quick-setting agent addition section 10 Spraying equipment

Claims

1. In the spraying method, a quick-setting material is added and mixed into a base concrete containing cement, and then sprayed onto the construction object. Prior to the addition of the quick-setting material, a quick-setting aid containing gypsum (excluding cases where alkali metal aluminate, lime, and gypsum are contained) is added to the base concrete. Spraying method.

2. The spraying method according to claim 1, wherein the amount of the quick-setting aid added to the base concrete is 1 to 15 parts by mass as solid content per 100 parts by mass of the cement.

3. The spraying method according to claim 1 or 2, wherein the quick-setting material is a powder quick-setting material.

4. The Blaine specific surface area of ​​the gypsum in the quick-setting aid is 3500 to 18000 cm ２ The spraying method according to any one of claims 1 to 3, wherein the molar ratio is 1:1 or more.

5. The spraying method according to any one of claims 1 to 4, wherein the amount of quick-setting material added to the base concrete is 5 to 15 parts by mass per 100 parts by mass of the cement.

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