JP4805714B2 - Spraying method - Google Patents

Description

  The present invention relates to a spraying material and a spraying method using the same.

  Conventionally, in order to prevent the collapse of exposed ground such as tunnel excavation, a rapid setting concrete spraying method in which a quick setting agent is mixed with concrete has been performed (see Patent Document 1). This method usually involves preparing sprayed concrete at a cement, aggregate and water metering and mixing plant installed at the excavation site, transporting it with an agitator car, pumping it with a concrete pump, and using a confluence pipe installed in the middle. This is a method of mixing with a rapid setting agent fed from the other side and spraying it to the ground surface as a quick setting sprayed concrete until a predetermined thickness is reached.

Further, conventionally used quick setting agents include calcium aluminate, a mixture of alkali metal aluminate and alkali metal carbonate, etc., and calcium aluminate, alkali metal aluminate, and alkali metal carbonate. And mixtures of calcium aluminate and 3CaO · SiO ₂ are known (see Patent Documents 2 to 5).

  These quick setting agents have a function of promoting the setting of cement, and all of them are mixed with cement concrete and sprayed on the ground surface. The method of adding the quick setting agent is usually a method in which the amount of dust is increased due to powder mixing by pneumatic transportation. For this reason, the working environment may be deteriorated, and it is necessary to wear protective glasses, a dust mask, or the like when spraying, and a construction method with less dust is required.

  As a method of generating less dust, a method is proposed in which a quick setting agent is slurried and added to cement concrete, and then an alkali metal aluminate solution is separately pumped, mixed, and sprayed. (See Patent Document 6). However, since this method uses a highly alkaline liquid, it is difficult to handle, and when spraying it requires protective glasses, gloves, etc., and there is a problem that workability is reduced, and dust of the slurry quick-setting agent itself is generated. There was a case.

  On the other hand, the quick setting construction method which improves a working environment by making a quick setting agent into a slurry and mix | blending alums with cement concrete is proposed (refer patent document 7).

  However, in terms of shortening the construction period, it has been required to further improve the strength expression.

Japanese Patent Publication No. 60-4149 Japanese Patent Laid-Open No. 64-051351 Japanese Examined Patent Publication No. 56-27457 JP-A-61-026538 JP 63-2105050 A JP 05-139804 A JP 05-097491 A

  The present invention provides a spraying material capable of further improving strength development in the spraying method.

That is, the present invention comprises (1) cement concrete,
(2) Quick setting agent slurry containing (2-1) and (2-2) below (2-1) 100 parts of calcium aluminate, 2.5 to 40 parts of alkali metal sulfate, 20 to 20 gypsum 60 parts, a quick setting agent containing water-retaining substance 0.1-5.0 parts (2-2) slurry water containing aluminum element and sulfur element
It is a spraying method characterized by mixing and spraying. (2-2) The spraying method in which the solid content concentration in the slurry water is 15 to 50%, (1) the spraying method in which cement concrete contains a water reducing agent, (2-1) This is a spraying method in which the quick setting agent and (2-2) slurry water are continuously joined and mixed, and (2) the quick setting agent slurry is prepared. (2-2) The slurry water is ammonium alum. And a spray method that is slurry water containing at least one of aluminum sulfate and the amount of water used for cement concrete is 35% or more. The pressure is 0.2 to 0.5 MPa, the spraying speed is 4 to 20 m ³ / h, and the pressure of the pumping air for pumping the rapid setting agent slurry is the pumping pressure of cement concrete. 0.01 0.3MPa is a great該吹with method.

  By using the spray material of the present invention, there is an effect of improving strength development.

Hereinafter, the present invention will be described in detail.
The cement concrete referred to in the present invention is a general term for cement paste, mortar, and concrete. Further, parts and% in the present invention are based on mass unless otherwise specified.

  The quick setting agent slurry used in the present invention contains a quick setting agent and slurry water.

The quick setting agent used in the present invention contains 100 parts of calcium aluminate, 2.5 to 40 parts of alkali metal sulfate, 20 to 60 parts of gypsum, and 0.1 to 5.0 parts of water-retaining substance.

The calcium aluminate used in the present invention is, for example, CaO obtained by mixing a raw material containing calcia and a raw material containing alumina and performing a heat treatment such as firing in a kiln or melting in an electric furnace. It is a general term for substances having Al ₂ O ₃ as a main component and having hydration activity. CaO and part of Al ₂ O ₃ are alkali metal oxides, alkaline earth metal oxides, silicon oxide, titanium oxide, and oxidation. To compounds containing iron, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, alkaline earth metal sulfates, or the like, or containing CaO and Al ₂ O ₃ as main components, Is a substance in a small amount. As the mineral form, either crystalline or amorphous can be used. Among these, amorphous calcium aluminate is preferable in terms of reaction activity, and amorphous calcium obtained by quenching a heat-treated product corresponding to a composition of 12CaO · 7Al ₂ O ₃ (hereinafter referred to as C ₁₂ A ₇ ). More preferred is aluminate.

The particle size of the calcium aluminate, in terms of quick-setting property and the initial strength development, Blaine specific surface area (hereinafter, referred to as Blaine) 3,000 cm ² / g or more is preferable, 5,000 cm ² / g or more is more preferable. If it is less than 3,000 cm < ² > / g, the quick setting property and initial strength expression property of the quick setting spray cement concrete which mixed the quick setting agent and the spray cement concrete may fall.

Examples of the alkali metal sulfate used in the present invention include sodium sulfate, potassium sulfate, and lithium sulfate. The alkali metal sulfate is not particularly limited, but an anhydrous product is preferable. Blaine value is preferably at least ^{500cm 2 / g, 1,000cm 2 /} g or more is more preferable. If it is less than 500 cm < ² > / g, the quick setting property and initial strength expression property of the quick setting spray cement concrete which mixed the quick setting agent and the spray cement concrete may fall.

  Although the usage-amount of an alkali metal sulfate is not specifically limited, 2.5-40 parts are preferable with respect to 100 parts of calcium aluminates, and 10-30 parts are more preferable. If it is less than 2.5 parts, the middle and long-term strength of the concrete may be difficult to obtain. If it exceeds 40 parts, the quick setting property is weakened, and the adhesive properties such as the rebound rate and the amount of dust may be reduced.

  Examples of the gypsum used in the present invention include anhydrous gypsum, semi-aqueous gypsum, and dihydrate gypsum, and one or more of these can be used in combination depending on the purpose of use. Among these, the use of anhydrous gypsum is preferable in terms of sufficient quick setting, initial strength development, and suitable for on-site construction.

  Although the usage-amount of gypsum is not specifically limited, 20-60 parts are preferable with respect to 100 parts of calcium aluminates, and 30-50 parts is more preferable. When the amount is less than 20 parts, sufficient strength development may not be obtained. When the amount exceeds 60 parts, the quick setting is weak, the quick setting is weak, and the adhesiveness such as the rebound rate and the amount of dust is reduced. There is.

The water-retaining substance used in the present invention is not particularly limited, but includes inorganic substances such as bentonite and silica gel, water glass and a gelling agent for water glass such as sodium chloride and sodium aluminate, and further, den powder, methylcellulose, carboxymethylcellulose , Ethyl cellulose, polyvinyl alcohol, polyethylene oxide, polyacrylamide, vinyl alcohol-acrylate copolymer, polyacrylonitrile hydrolyzate and general formula RO (AO) _n H (R is an alkyl group, A is one or two types) The above-mentioned alkyl group, and n is an integer).

Among these, in order to exhibit particularly sufficient dust suppression, methylcellulose, polyethylene oxide, vinyl alcohol-acrylate copolymer, polyacrylonitrile hydrolyzate, and general formula RO (AO) _n H (R is an alkyl group) , A preferably contains one or more of the raw materials of the polymer material represented by one or two or more alkyl groups, and n is an integer), and has a good strength development property. Is more preferable. The weight average molecular weight of polyethylene oxide is preferably 1 million to 5 million.

  Although the usage-amount of a water retention substance is not specifically limited, 0.1-5.0 parts are preferable with respect to 100 parts of calcium aluminates, 0.3-3.0 parts are more preferable, 1.0- 2.0 parts is most preferred. If it is less than 0.1 part, the rebound rate and the amount of dust of the quick setting slurry itself may be generated at the time of spraying, and if it exceeds 2.0 part, the mixability with cement concrete may deteriorate. There is a case where the quick setting property is weakened, and the adhesiveness such as the rebound rate and the dust amount is lowered.

  The slurry water used in the present invention contains aluminum and sulfur.

  The aluminum feedstock used in the present invention is not particularly limited, and examples thereof include aluminum sulfate, aluminate, other inorganic aluminum compounds, organic aluminum compounds, and aluminum complexes.

  Examples of the aluminum sulfate include sodium alum, potassium alum, ammonium alum, hydroxysulfuric acid, aluminum, and aluminum sulfate. The aluminate includes lithium aluminate, sodium aluminate, potassium aluminate, and calcium aluminate. And other inorganic aluminum compounds such as bauxite, aluminum oxide, aluminum hydroxide, aluminum chloride, aluminum phosphate, aluminum nitrate, aluminum fluoride, polyaluminum chloride, aluminum carbonate hydroxide, Examples thereof include synthetic hydrosartite and aluminum metasilicate.

  In the present invention, one or two or more of these aluminum feedstocks can be used, and an aluminum sulfate that is also a sulfur feedstock is preferred, and aluminum sulfate is more preferred.

  The sulfur feedstock used in the present invention is not particularly limited, but in addition to sulfur in the elemental state such as sulfur and sulfur flower, sulfides, sulfuric acid or salts thereof, sulfites, thiosulfates, and organic sulfur compounds, etc. Is mentioned.

  Examples of the sulfide include magnesium sulfide, calcium sulfide, iron sulfide, and phosphorus pentasulfide. Examples of the sulfate include aniline sulfate, aluminum sulfate, ammonium sulfate, magnesium sulfate, manganese sulfate, barium sulfate, calcium sulfate, and sodium alum. Potassium alum, ammonium alum, and hydroxylamine sulfate. Examples of sulfites include ammonium bisulfite and calcium sulfite. Examples of thiosulfates include ammonium thiosulfate and barium thiosulfate.

  In the present invention, one or two or more of these sulfur feedstocks can be used, the solubility in water is high, the condensing properties are further improved, and both aluminum and sulfur can be supplied. One or more of ammonium alum and aluminum sulfate are preferred, and aluminum sulfate is more preferred.

  The slurry water used in the present invention preferably has an effect of reducing the dust of the quick setting agent. From the aspect of suppressing the alkali amount of the quick setting agent, any slurry containing aluminum, sulfur or the like can be used. Is possible.

  The solid content concentration in the slurry water is preferably 15 to 50%, more preferably 20 to 40%. If it is less than 15%, strength development may be reduced, and if it exceeds 50 parts, the viscosity of the slurry water itself may increase and workability may be reduced.

  The amount of slurry water used in the present invention is preferably 100 to 400 parts, more preferably 200 to 300 parts, relative to 100 parts of the quick setting agent. If it is less than 100 parts, the viscosity of the quick setting slurry increases, the mixing with cement concrete becomes poor, the initial strength developability decreases, the rebound rate increases, and the amount of dust may increase, exceeding 400 parts. In some cases, the coagulability and strength development may be reduced.

  The amount of the rapid setting agent slurry is preferably 4 to 30 parts, more preferably 6 to 24 parts, and most preferably 8 to 17 parts in terms of solid content with respect to 100 parts of cement. If it is less than 4 parts, it may be difficult to promote the initial setting of the sprayed cement concrete, and if it exceeds 30 parts, long-term strength development may be hindered, which may not be preferable from the viewpoint of cost.

  Here, the cement includes various ordinary Portland cements such as normal, early strength, moderate heat, and ultra-early strength, and various mixed cements obtained by mixing these various Portland cements with fly ash, blast furnace slag, and the like. These can be used in the form of fine powder.

  In the slurry of this invention, it is also possible to use a water reducing agent etc. further as needed.

  The water reducing agent is used to improve the fluidity of cement concrete, and can be used in liquid or powder form. As the water reducing agent, for example, known water reducing agents such as lignin sulfonic acid, naphthalene sulfonic acid, and polycarboxylic acid can be used.

  The amount of water reducing agent used is preferably 0.05 to 2 parts with respect to 100 parts of cement.

  The cement concrete used in the present invention contains cement and aggregate. As the aggregate, one having a low water absorption rate and high aggregate strength is preferable. The maximum dimension of the aggregate is not particularly limited as long as it can be sprayed. River sand, mountain sand, lime sand, quartz sand, and the like can be used as the fine aggregate, and river gravel, mountain gravel, lime gravel, and the like can be used as the coarse aggregate.

  In the spraying method using the quick setting agent slurry of the present invention, conventionally used spraying equipment or the like can be used. Specifically, for example, a product name “MKW-25SMT” manufactured by Shintech Co., Ltd. can be used for pumping sprayed cement concrete. A quick-setting agent pumping device “Natom Cleat” or the like can be used for pumping the quick-setting agent.

  As the spraying method using the quick setting agent slurry of the present invention, various spraying methods corresponding to the required physical properties, economy, workability and the like are possible. As a spraying method using the quick setting slurry of the present invention, a dry spraying method can also be constructed, but since the amount of dust may increase, water should be put on the cement concrete side in advance before using the quick setting agent. In addition, it is preferable to use a kneaded wet spraying method.

  The amount of water used for cement concrete is preferably 35% or more, and more preferably 40 to 55% from the viewpoint of workability. If it is less than 35%, cement concrete may not be sufficiently mixed. If it exceeds 55%, strength development may be reduced.

In the spraying method using the quick setting agent slurry of the present invention, the spraying pressure is usually preferably 0.2 to 0.5 MPa, and the spraying speed is preferably 4 to 20 m ³ / h.

  Moreover, the pressure of the pumping air for pumping the rapid setting agent slurry is 0.01 to 0.3 MPa from the pumping pressure of the cement concrete so that the inside of the pumping pipe is not blocked when the cement concrete is mixed in the pumping pipe of the quick setting agent slurry. Larger is preferred.

  In the spraying method using the quick setting agent slurry of the present invention, in order to reduce dust and rebound, slurry water is added to the powder quick setting agent to continuously slurry the quick setting agent. It is preferable to spray the slurry mixed with spray cement concrete at the discharge port tip.

  As a method of continuously slurrying the quick setting agent, for example, a hole is formed around a pressure feeding pipe for pneumatically feeding the powder quick setting agent, and slurry water is added into the pressure feeding pipe from the hole to make the slurry, The method of sending etc. can be used.

As the wet spraying method, for example, cement, fine aggregate, coarse aggregate, and water are added and kneaded, pumped, and a Y-shaped tube is provided in the middle, and the rapid adjustment is continuously adjusted from one of them. A method of spraying a fast-setting wet spray concrete obtained by merging and mixing binder slurries is mentioned.

  Hereinafter, the present invention will be described in detail based on examples. The experiment and measurement were performed at 20 ° C. and a humidity of 60%.

100 parts of calcium aluminate, alkali metal sulfate in the amount shown in Table 1, 40 parts of gypsum, 100 parts of quick setting agent containing 1.0 part of water retaining material, solid content concentration containing aluminum and sulfur A rapid setting agent slurry was prepared by mixing and stirring 250 parts of 25% slurry water. A sulfur / aluminum feed was used to contain aluminum and sulfur.
Further, a mortar having a fine aggregate / cement ratio = 3 and a water / cement ratio = 50% was prepared.
To 100 parts of cement in the mortar, 12 parts of the quick setting agent slurry was added in terms of solid content to form a quick setting mortar, and the setting time and compressive strength were measured. The results are also shown in Table 1.

<Materials used>
Calcium aluminate: Corresponding to C ₁₂ A ₇ composition, amorphous, Blaine value 6,500 cm ² / g
Gypsum: Commercial anhydrous gypsum pulverized product, Blaine value 5,900 cm ² / g
Alkali metal sulfate: sodium sulfate, commercially available product, anhydrous product, brain value 1,000 cm ² / g
Sulfur / aluminum feedstock a: Aluminum sulfate, commercial cement: ordinary Portland cement, commercial product, Blaine value 3,200 cm ² / g, specific gravity 3.16
Water-retaining substance: Polyethylene oxide, weight average molecular weight 2 million, commercially available fine aggregate: Himekawa production river sand, Itoigawa City, Niigata Prefecture, surface dry state, specific gravity 2.62

<Measurement method>
Setting time: Quick setting mortar was measured according to Japan Society of Civil Engineers standard "Quality setting quality for sprayed concrete (JSCED-102)". Compressive strength: Quick setting mortar was measured according to JIS R5201.
Brain value: The specific surface area test of JIS R 5201 was followed.

  From the results shown in Table 1, it is shown in Experiment No. 2 that balanced results are obtained at two points of setting properties and strength properties. It turned out to be 1-5. If the alkali metal sulfate is less than 2.5 parts, the setting time is accelerated, but the compression strength is not obtained. If the alkali metal sulfate exceeds 40 parts, the compression strength is increased, but the setting time is slow. It became the result. Therefore, the amount of alkali metal sulfate used is preferably 2.5 to 40 parts with respect to 100 parts of calcium aluminate.

Example 1 except that 100 parts of calcium aluminate, 25 parts of alkali metal sulfate, gypsum in the amount shown in Table 2 and 100 parts of quick setting agent containing 1.0 part of water-retaining substance were used. Went to. The results are shown in Table 2.

From the results shown in Table 2, it is shown in Experiment No. 2 that balanced results are obtained at two points of setting properties and strength properties. It turned out to be 1-5. When the gypsum is less than 20 parts, the setting time is accelerated, but the compression strength cannot be obtained. When the gypsum exceeds 60 parts, the compression strength is increased, but the setting time is delayed. Therefore, the amount of gypsum used is preferably 20 to 60 parts with respect to 100 parts of calcium aluminate.

Shot concrete is used as unit amount of each material, cement 400kg / m ³ , fine aggregate 1,058kg / m ³ , coarse aggregate 710kg / m ³ , water 200kg / m ³ , and high-performance water reducing agent 4kg / m ³ The sprayed concrete was pumped by a concrete pumping machine “MKW-25SMT” under conditions of a spraying pressure of 0.4 MPa and a spraying speed of 10 m ³ / h. On the other hand, a quick setting agent adding device comprising 100 parts of calcium aluminate, 25 parts of alkali metal sulfate, 40 parts of gypsum, and a water holding substance in an amount shown in Table 3 under the condition of a pumping pressure of 0.5 MPa. Solid content concentration containing aluminum and sulfur with respect to 100 parts of quick setting agent from holes provided in several places around one of Y pipes provided on the way using “Natom Cleat” 250 parts of 25% slurry water was hydrated to obtain a quick setting slurry. A sulfur / aluminum feed was used to contain aluminum and sulfur.
This quick setting slurry was mixed with the sprayed concrete fed from the other side of the Y-shaped pipe so that it became 13 parts in terms of solid content with respect to 100 parts of cement to obtain a quick setting sprayed concrete. . Concrete compression strength, rebound rate, and amount of dust were measured for this quick setting shot concrete. The results are also shown in Table 3.

<Materials used>
High-performance water reducing agent: polycarboxylic acid, commercially available coarse aggregate: Himekawa Sakegawa gravel, Itoigawa-shi, Niigata, surface dry state, specific gravity 2.64, maximum dimension 10mm

<Measurement method>
Concrete compressive strength: The compressive strength at the age of 3 hours and 24 hours is to cover the pin placed on the pull-out formwork 25cm wide x 25cm long with the quick-setting shotcrete from the surface of the pullout formwork. The pin was pulled out from the back side, the pulling strength at that time was determined, and the compressive strength was calculated from the formula of (compressive strength) = (pullout strength) × 4 / (test specimen contact area). The compressive strength after 1 day of age is 20 tons pressure-resistant machine by spraying quick setting sprayed concrete on a form of width 50cm x length 50cm x thickness 20cm, and collecting the specimen 5cm in diameter x 10cm in length. And the compressive strength was determined.
Rebound rate: Quick setting shotcrete was sprayed on a simulated tunnel having a height of 3.5 m and a width of 2.5 m created in an arch shape with an iron plate at a pumping speed of 10 m ³ / h for 10 minutes. After that, (Rebound rate) = (Amount of quick setting sprayed concrete dropped without adhering to the simulated tunnel) / (Amount of quick setting shot concrete sprayed to the simulated tunnel) x 100 (%) did.
Dust amount: Quick setting shot concrete was sprayed to the simulated tunnel at a pumping speed of 10 m ³ / h for 10 minutes. The amount of dust was measured with a dust meter (Shibata Chemical Co., Ltd., measurement range 0.01-100 mg / m ³ , P-5L type) at a fixed position of 5 m from the spraying place.

  From the results of Table 3, it is shown in Experiment No. 3 that balanced data is obtained at three points of compressive strength, rebound amount, and dust amount. It turned out to be 3-7. It was found that when the water-retaining substance was less than 0.1 part, a high compressive strength was obtained, but the rebound rate and the amount of dust increased. When the water-retaining substance exceeds 5.0 parts, the amount of rebound and the amount of dust increase, resulting in failure to obtain compressive strength. Therefore, the amount of the water-retaining substance used is preferably 0.1 to 5.0 parts with respect to 100 parts of calcium aluminate.

  100 parts of calcium aluminate, 25 parts of alkali metal sulfate, 40 parts of gypsum, 100 parts of quick setting agent consisting of 1.5 parts of water-retaining substance, aluminum and sulfur 250 of solid content concentration shown in Table 4 The same procedure as in Example 3 was performed, except that the part was hydrated to obtain a quick setting slurry. The results are also shown in Table 4.

<Materials used>
Sulfur and aluminum feedstock b: Ammonium alum, commercial product

<Measurement method>
Workability: The inside of the Y-shaped pipe where the quick setting slurry and the concrete pipe were mixed was checked to determine whether the pumpability of the quick setting slurry was deteriorated due to fluctuations in the slurry water solid content concentration, and the workability was judged. The case where the inside of the Y-shaped tube was completely consolidated was impossible, the case where it was slightly consolidated was good, and the case where it was not consolidated was accepted.

From the results in Table 4, when the solid content concentration of the slurry water was less than 15%, the compressive strength could not be obtained. When the solid content concentration of the slurry water exceeded 50%, the workability was not obtained. Therefore, the solid content concentration of the slurry water is preferably 15 to 50%.
Comparing ammonium alum and aluminum sulfate, aluminum sulfate is preferred in terms of compressive strength.

Comparison with Patent Document 7 was performed. Unit amount of each material, cement 400 kg / ^{m 3,} fine aggregates 1,058kg / ^{m 3,} coarse aggregate 710 kg / ^{m 3,} water 200 kg / ^{m 3,} superplasticizer 4 kg / ^{m 3,} 100 parts of cement to Add 7 parts of sulfur / aluminum raw material a to prepare shotcrete, 100 parts of calcium aluminate, 25 parts of alkali metal sulfate, 40 parts of gypsum, rapid setting agent consisting of water-retaining substances in the amounts shown in Table 3 Was carried out in the same manner as in Example 3, except that slurry water containing no aluminum or sulfur and having a solid content concentration of 0% was added to obtain a quick setting slurry. The results are also shown in Table 5.

  From the results of Table 5, when using slurry water containing aluminum and sulfur (Experiment No. 3-7), higher compression than when using shotcrete containing aluminum and sulfur (Patent Document 7) A very good result was obtained that the strength was obtained and the rebound rate and the amount of dust were small.

By using the spray material of the present invention, it is possible to minimize the amount of dust generated, and since high strength is obtained at the initial stage of spraying, there is an effect of improving safety. Workability can be further improved, and quick setting and strength development can be further improved in terms of shortening the work period.

Claims (8)

(1) cement concrete,
(2) Quick setting agent slurry containing (2-1) and (2-2) below (2-1) 100 parts of calcium aluminate, 2.5 to 40 parts of alkali metal sulfate, 20 to 20 gypsum 60 parts, rapid setting agent containing water-retaining substance 0.1-5.0 parts (2-2) Mixing and spraying slurry water containing aluminum element and sulfur element Spraying method. (2-2) spraying method of claim 1, wherein the solid concentration of the slurry water is 15 to 50%. (1) The spraying method according to claim 1 or 2, wherein the cement concrete contains a water reducing agent. The blowing according to any one of claims 1 to 3 , wherein (2-1) the quick setting agent and (2-2) the slurry water are continuously combined and mixed, and (2) the quick setting agent slurry is adjusted. Attaching method. (2-2) The spray method according to one of claims 1 to 4, wherein the slurry water is slurry water containing one or more of ammonium alum and aluminum sulfate. The spraying method according to claim 1, wherein the amount of water used for the cement concrete is 35% or more. In cement concrete, the spraying pressure is 0.2 to 0.5 MPa, and the spraying speed is 4 to 20 m. ³ The spraying method according to claim 1, which is / h. The spraying method according to claim 1, wherein the pressure of the pumping air for pumping the rapid setting agent slurry is 0.01 to 0.3 MPa greater than the pumping pressure of cement concrete.