JP5888847B2 - Spraying material and spraying method using the same - Google Patents

Description

The present invention relates to a quick setting agent, a quick setting slurry, a spraying material, and a spraying method using the same, which are sprayed onto a ground surface exposed in a tunnel or a slope such as a road, a railway, and a waterway.
The cement concrete of the present invention is a general term for paste, mortar, and concrete. Further, parts and% in the present invention are based on mass unless otherwise specified.

In order to prevent the collapse of exposed ground such as tunnel excavation, spraying method of quick setting concrete in which quick setting agent is mixed with concrete is performed. 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.
The quick-setting admixture, mixtures of calcium aluminate and an alkali carbonate, mixtures of calcium aluminate and 3CaO · SiO _2, calcium aluminate, mixture of alkali metal aluminate, and alkali carbonate, and the like, as well as, A mixture of a calcining van, aluminate, carbonate, slaked lime, sodium aluminate, sodium carbonate and the like are known (Patent Documents 1, 2, 3, 4, 5).
The quick setting agent is mixed with cement concrete and sprayed on the natural 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. (Patent Document 6). Since this method uses a highly alkaline liquid, it is difficult to handle, and when spraying, protective glasses or gloves are required, and there is a problem that workability is reduced. On the other hand, the quick setting construction method which improves a working environment by making a quick setting agent into slurry and mix | blending alums with cement concrete is proposed (patent document 7). In recent years, there has been proposed a quick setting method that improves workability and dust reduction effect and improves quick setting in terms of shortening the work period (Patent Document 8).

In recent years, there has been an increase in the spirit of building a recycling-oriented society that reuses waste, and the use of fly ash is the “Law Concerning Promotion of Effective Use of Resources” (Act No. 48 of 1991, a designated by-product). For promoting the effective use of coal ash as There is also a need for the development of a material with excellent quick setting and initial strength development even in mixed cement mixed with a large amount of fly ash.
Moreover, fly ash is mixed up to a maximum of 30% in the cement by using fly ash cement described in JIS. However, large-scale use is not expected, and further mass consumption of fly ash is required.
Furthermore, the demand for quick setting agents has been increasing under conditions where spring water and natural ground have deteriorated. Regarding the required performance of conventional quick setting agents for cement concrete, it is also necessary to secure initial setting time and reduce dust. There is a need for further improvements.

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 Japanese Patent Laid-Open No. 5-139804 JP-A-5-097491 JP 2003-81664 A

  As a result of various studies on the above-mentioned problems and requirements, the present invention has acquired the knowledge that it can be solved by spraying using a specific quick setting agent, and further improves the workability of tunnels and the dust reduction effect. In addition, the present invention provides a spraying material and a spraying method using the spraying material that exhibit high quick setting even under conditions where the spring water and the ground surface have deteriorated.

That is, the present invention is (1) a powder in which the total amount of cement and coal ash is 360 to 530 kg / m ³ , and coal ash is 35 to 60 parts by mass in a total of 100 parts by mass of cement and coal ash. Cement concrete formed by mixing 42 to 70 parts by mass of water with 100 parts by mass, and an amorphous product obtained by quenching a heat-treated product corresponding to a 12CaO · 7Al ₂ O ₃ composition having a Blaine specific surface area of 6,500 cm ² / g or more calcium aluminates 100 parts by weight of 35 parts by weight of sulphates is anhydrous gypsum, 10 parts by weight of the alkali-metal aluminate salts is sodium aluminate, 35 parts by weight of alkali metal carbonates are sodium carbonate and sodium gluconate the quick-setting admixture comprising a certain oxy acids 0.5 parts by mass, reduced a formalin condensate of naphthalene sulfonate Agent consists of a 5 weight parts and water was added to the slurry quick-setting admixture, the slurry quick-setting admixture of 70 parts by weight of water relative to the quick-setting admixture 100 parts by weight of cement and coal slurry quick-setting admixture is in cement concrete It is 12 parts by mass in terms of solid content with respect to 100 parts by mass of ash, and the compressive strength at 7 days of age is 81 % or more compared to the compressive strength of cement concrete without addition of a quick-setting agent. In a spraying material with a compressive strength value of 39.1 N / mm ² or more in 91 days, continuously add water to the quick setting agent to adjust the slurry quick setting agent, and mix and mix with cement concrete and spray. A spraying method wherein the rebound amount is 17.5% or less and the dust amount is 3.9 mg / m ³ or less .

  By adopting the spraying material of the present invention and the spraying method using the same, the workability is improved by suppressing the generation of dust generated by the spraying work such as tunnels, and the spring water and natural ground surface deteriorated. Even under circumstances, high quick setting is obtained, and there is an effect that a large amount of coal ash can be used.

  Unless otherwise specified, parts and% in the present invention are shown on a mass basis.

  The quick setting agent of the present invention contains calcium aluminates, sulfates, alkali metal aluminates, alkali metal carbonates, and oxycarboxylic acids.

The calcium aluminates used in the present invention are obtained by mixing a raw material containing calcia, a raw material containing alumina, etc., and performing a heat treatment such as firing in a kiln or melting in an electric furnace, and CaO and It is a general term for substances having hydration activity, mainly composed of Al ₂ O ₃ . Some of CaO and Al ₂ O ₃ are alkali metal oxides, alkaline earth metal oxides, silicon oxides, titanium oxides, iron oxides, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, and These are substances in which a small amount of these are dissolved in a compound substituted with alkaline earth metal sulfate or the like, or in which CaO and Al ₂ O ₃ are the main components.
As the mineral form, either crystalline or amorphous can be used. Among these, amorphous calcium aluminates are preferable in terms of reaction activity, and amorphous heat-treated products corresponding to the composition of 12CaO · 7Al ₂ O ₃ (hereinafter referred to as C ₁₂ A ₇ ) are rapidly cooled. Calcium aluminate is more preferred.
The particle size of the calcium aluminates is 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, more preferably at least 5,000 cm ² / g . If it is less than 3,000 cm < ² > / g, the quick setting property and initial strength expression property of the spray material which mixed the quick setting agent and cement concrete may fall.

The sulfates used in the present invention improve the setting property and strength development of the spray material, for example, delay the curing time of the quick setting agent slurry in which the quick setting agent and water (hereinafter referred to as slurry water) are mixed. To mix. Sulfates are sodium sulfate, potassium sulfate, aluminum sulfate, alum, and anhydrous gypsum, semi-water gypsum, gypsum of dihydrate gypsum, etc., one or more of these depending on the purpose of use It is possible to use together. Among these, the use of sodium sulfate and gypsum is preferable from the standpoint that sufficient quick setting properties can be obtained, initial strength development properties, and suitable for on-site construction.
The amount of sulfate used is preferably 10 to 50 parts, more preferably 25 to 45 parts, per 100 parts of calcium aluminate. If the amount is less than 10 parts, the viscosity of the quick setting agent slurry increases, so that the workability and the setting property of the spray material may be reduced, and it may be difficult to promote long-term strength development. If the amount exceeds 50 parts, the initial setting is delayed. In some cases, the initial strength developability may decrease.

Alkali metal aluminate (hereinafter referred to as aluminate) used in the present invention is to promote the initial setting of cement. Aluminum hydroxide and alkali metal hydroxide are mixed and dissolved, dried, and powdered. It is obtained as a shape. Examples of the aluminate include sodium aluminate, potassium aluminate, and lithium aluminate, and one or more of these can be used. Among these, sodium aluminate is preferably used in terms of the setting property and initial strength development property of the quick setting sprayed cement concrete.
The amount of alkali metal aluminate used is preferably 3 to 30 parts, more preferably 5 to 15 parts, per 100 parts of calcium aluminates. If it is less than 3 parts, the initial setting may be delayed and the initial strength development may be reduced. If it exceeds 30 parts, the viscosity of the rapid setting slurry may increase, and the workability of the spray material and the long-term strength development may be reduced. is there.

The alkali metal carbonate (hereinafter referred to as alkali carbonate) used in the present invention is to accelerate the initial setting of cement, and includes sodium carbonate, potassium carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate. Among these, sodium carbonate is preferable in terms of promoting initial setting.
The amount of alkali carbonate used is preferably 5 to 60 parts, more preferably 10 to 50 parts, per 100 parts of calcium aluminates. If it is less than 5 parts, the initial setting of the spray material may be delayed and the initial strength development may be reduced. If it exceeds 60 parts, the viscosity of the quick setting slurry may increase, and the workability and long-term strength development may be reduced. is there.

Examples of oxycarboxylic acids (hereinafter referred to as oxyacids) used in the present invention include gluconic acid, tartaric acid, citric acid, malic acid, salicylic acid, lactic acid, and salts thereof. Examples of the salt include alkali metal salts such as sodium and potassium. Among these, sodium gluconate is preferable in terms of initial strength development.
The amount of oxycarboxylic acids used is preferably 0.01 to 2 parts, more preferably 0.1 to 1 part, per 100 parts of calcium aluminates. If it is less than 0.01 part, the setting property and initial strength expression of the spray material may be inhibited, and if it exceeds 2 parts, the setting property and strength development property may be inhibited.

The water reducing agent used in the present invention is used to improve the dispersion stability of the quick setting agent or to give the cement concrete an appropriate viscosity at the time of spraying to reduce the rebound of the spray material and the amount of dust. Is.
As a water reducing agent, a powdery thing can be used. Examples of water reducing agents include polyol derivatives, lignin sulfonates and derivatives thereof, and high-performance water reducing agents, and one or more selected from these can be used. Among these, a high-performance water reducing agent is preferable in terms of high strength expression and dispersion stability. By using a high-performance water reducing agent, the amount of rapid setting material can be reduced, and the amount of dust generated and / or the rebound rate can be extremely reduced.
High performance water reducing agents include formalin condensate of alkyl allyl sulfonate, formalin condensate of bisphenolic acid, formalin condensate of naphthalene sulfonate, formalin condensate of melamine sulfonate, polycarboxylic acid polymer compound, etc. Can be used in either liquid or powdery state, and one or more selected from these can be used. Among these, a formalin condensate of naphthalene sulfonate, a formalin condensate of bisphenolic acid, a formalin condensate of melamine sulfonate, or a polycarboxylic acid polymer compound is preferable because of its great effect.
The amount of water reducing agent used is preferably 0.5 to 10 parts, more preferably 1 to 8 parts, per 100 parts of calcium aluminate. If it is less than 0.5 part, when adding a quick-setting agent and water and making it a slurry, a quick-setting agent and water cannot mix well, it may not become a slurry state, and it may be unable to mix well with cement concrete. If it exceeds 10 parts, the reaction of the quick setting agent itself may be dispersed and delayed, and the strength development may be reduced.

  The amount of water used in the present invention is preferably 30 to 100 parts, more preferably 50 to 80 parts, relative to 100 parts of the quick setting agent. If the amount is less than 30 parts, the rapid setting agent may not be in a slurry state, and the amount of dust may increase. If the amount exceeds 100 parts, the coagulability and strength development may be reduced.

  The amount of the slurry accelerating agent used in the present invention is preferably 3 to 20 parts, more preferably 5 to 15 parts, and more preferably 10 to 15 parts in terms of solid content with respect to a total of 100 parts of cement and coal ash. Most preferred. If it is less than 3 parts, it may be difficult to promote initial setting of the spray material, and if it exceeds 20 parts, long-term strength development may be inhibited.

  The cement concrete used in the present invention is formed from cement, coal ash, water, aggregate, etc., and blast furnace slag, limestone fine powder, silica fume, water reducing agent, AE water reducing agent according to temperature conditions and construction conditions. High performance water reducing agents, high performance AE water reducing agents, retarders, setting accelerators and the like can be used.

  Examples of the cement used in the present invention include various ordinary Portland cements such as normal, early strength, moderate heat, and ultra early strength, and various mixed cements obtained by mixing blast furnace slag with these various Portland cements. These can be used in the form of fine powder. It is also possible to use fly ash cement in which fly ash is pre-blended with Portland cement.

  The coal ash used in the present invention is fly ash, classified, or unclassified raw powder satisfying the provisions of JIS A6201, and contains the types of coal ash and chemical components contained in the coal ash. The ratio and physical properties are not particularly limited.

The powder used in the present invention is composed of cement and coal ash. In cement concrete, the total amount of cement and coal ash is preferably 360 to 550 kg / m ³ . If it is less than 360 kg / m ³ , the initial strength may decrease, and if it is 550 kg / m ³ or more, the amount of cement increases and the cost increases.

  The coal ash used in the present invention is preferably 35 to 60 parts in a total of 100 parts of cement and coal ash. If it is less than 35 parts, it is not preferable from the viewpoint of mass use of fly ash, and if it exceeds 60 parts, the initial strength development is greatly reduced.

  The aggregate used in the present invention is not particularly limited, but those having low water absorption and high aggregate strength are preferred. The maximum size of the aggregate is not particularly limited as long as it can be sprayed. As fine aggregate, river sand, mountain sand, sea sand, lime sand, quartz sand, etc. can be used, and as coarse aggregate, river gravel, mountain gravel, lime gravel, etc. can be used, crushed sand, Crushed stone can also be used.

  The amount of water in the cement concrete used in the present invention is preferably 42 to 70 parts with respect to a total of 100 parts of powder of cement and coal ash. If it exceeds 70 parts, peeling or strength may be insufficient during spraying, and if it is less than 42 parts, the concrete is strongly sticky, the workability deteriorates, the slurry quick-setting agent does not mix well, and the amount of dust increases. There is a case.

  The slump of cement concrete used in the present invention is not particularly limited as long as good workability can be obtained. Generally, when the slump is less than 6 cm, the viscosity tends to become very strong, and the construction becomes difficult.

The spray material of the present invention has a compressive strength ratio of 7 days of age of 80% or more and a compressive strength of 91 days of age of 18 N / mm ² or more as compared with a material to which no slurry quick-setting agent is added.

  In the spraying method using the spraying material of the present invention, conventionally used spraying equipment can be used. Specifically, for example, the product name “MKW-25SMT” manufactured by Shintech Co., Ltd. is used for pumping spray cement concrete, and the quick setting agent pumping device “Natom Cleat” is used for pumping quick setting agents. It can be used.

As a spraying method using the slurry quick-setting agent of the present invention, various spraying methods corresponding to required physical properties, economy, workability, etc. are possible, but wet spraying methods are possible. .
As the wet spraying method, for example, cement concrete, fine aggregate, coarse aggregate, and cement concrete kneaded by adding water are pumped, and a Y-shaped pipe is provided in the middle. The method of spraying the spraying material obtained by combining and mixing the pressure-accelerated slurry quick-setting agent is mentioned.

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.
The pressure of the pumping air for pumping the rapid setting agent may be 0.01 to 0.3 MPa higher than the pumping pressure of the cement concrete so that the inside of the pumping pipe is not blocked when the cement concrete is mixed into the pumping pipe of the quick setting agent slurry. preferable.

  In the spraying method using the slurry quick-setting agent of the present invention, in order to reduce dust and rebound, water is added to the quick-setting agent to continuously slurry the quick-setting agent, It is preferable to mix with spray cement concrete and spray at the discharge port tip. As a method of continuously slurrying the quick setting agent, for example, a hole is made around a pressure feeding pipe for pneumatically feeding the powder quick setting agent, and high pressure water is added into the pressure feeding pipe from the hole to make a slurry. The method of sending etc. can be used.

"Experiment 1"
100 parts of calcium aluminate, and 100 parts of calcium aluminate, the amount of sulfate, aluminate, alkali carbonate, oxyacids and water reducing agent shown in Table 1 and 100 parts of quick setting agent 70 parts of water was mixed and stirred to prepare a slurry rapid setting agent. Also, the total amount of cement and coal ash is 400 kg / m ³ , out of 100 parts total of cement and coal ash, 55 parts powder of coal ash, water is 100 parts total of cement and coal ash Prepare mortar by removing coarse aggregate from 56 parts of concrete mix α, add 12 parts of slurry quick-setting agent to 100 parts of cement and coal ash in total to make quick setting mortar, setting time and compression The strength was measured.
For comparison, the results of measuring mortar properties under the following conditions are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, commercial product, Blaine value 3,200 cm ² / g, specific gravity 3.16
Fine aggregate: Himekawa water system river sand, Itoigawa City, Niigata Prefecture, surface dry state, specific gravity 2.62
Coarse aggregate: Himekawa Sakegawa gravel, Itoigawa City, Niigata Prefecture, surface dry condition, specific gravity 2.68, maximum dimension 20mm
Coal ash: fly ash for JIS A6201 concrete, coal ash corresponding to fly ash quality type II, commercial product, brain value 4,500 cm ² / g, specific gravity 2.20
Calcium aluminates: corresponding to C ₁₂ A ₇ composition, amorphous, Blaine value 6,500 cm ² / g
Sulfate: commercially available anhydrous gypsum pulverized product, brain value 5,900 cm ² / g
Aluminate: Sodium aluminate, Commercially available alkali carbonate: Sodium carbonate, Commercially available oxyacids: Sodium gluconate, Commercially available water reducing agent: Naphthalene sulfonic acid formalin condensate, Commercially available comparative quick setting agent 1: Natomic TYPE-5 , Denki Kagaku Kogyo Co., Ltd. comparative quick setting agent 2: acidic liquid quick setting agent whose solid content concentration of aluminum sulfate is 27%

<Concrete mix α>
Cement 180 kg / ^{m 3,} coal ash 220 kg / ^{m 3,} water 224 kg / ^{m 3,} fine aggregates 973kg / ^{m 3,} coarse aggregate 664kg / ^{m 3}

<Measurement method>
Setting time: Measure mortar according to the Japan Society of Civil Engineers Standards "Quality Code for Rapid Setting Concrete (JSCED-102)" Compressive strength: Measure mortar according to JIS R 5201

<Comparison>
Comparative Example 1: Cement 400 kg / ^{m 3,} fine aggregates 995kg / ^{m 3,} coarse aggregate 679kg / ^{m 3,} Kyuyuizai mortar excluding the coarse aggregate from concrete water 240 kg / ^{m 3} (Natomikku TYPE-5 Comparative Example 2: Cement 180 kg / m ³ , Coal ash 220 kg / m ³ , Water 224 kg / m ³ , Fine aggregate 973 kg / m ³ , Coarse bone Comparative example 3 without adding a quick setting agent to mortar obtained by removing coarse aggregate from concrete of 664 kg / m ³ of material: cement 180 kg / m ³ , coal ash 220 kg / m ³ , water 224 kg / m ³ , fine aggregate 973 kg / M ³ , coarse aggregate 664kg / m ³ concrete mortar with a rapid setting agent (Natomic TYPE-5) to 100 parts of cement and coal ash Comparative Example 4: Concrete of cement 180 kg / m ³ , coal ash 220 kg / m ³ , water 224 kg / m ³ , fine aggregate 973 kg / m ³ , coarse aggregate 664 kg / m ³ 8 parts of acidic liquid quick-setting agent is added to 100 parts of cement to mortar from which coarse aggregate has been removed, and mixed and stirred.

From Table 1, it can be seen that if no sulfates are added, the completion time of setting is delayed and the compressive strength is low. It can be seen that if the aluminate or alkali carbonate is not added, the setting (starting or stopping) is delayed. If oxyacids are not blended, when the quick setting agent and water are combined, solidification occurs immediately and the test cannot be performed. If a water reducing agent is not blended, even if the quick setting agent and water are combined, a slurry state is not obtained, and a test cannot be performed. For this reason, if even one composition of the quick setting agent of the present invention is missing, satisfactory spraying cannot be performed.
Comparative Example 1 is a mortar that does not contain coal ash, and a powder quick-setting agent is added, and the strength expression of the setting and material ages 1 day and 7 days is high, but the long-term strength is lower than the physical properties of the examples. As a result. Comparative Example 2 is a base mortar, but has a low strength for 7 days. Comparative Example 3 is obtained by adding a powder accelerating agent to the mortar of the example. However, the initial strength is low, the elongation of the strength for one or seven days is small, and if the composition of the present invention is not used, the comparative example It is not equivalent to 1 cement simple powder quick-setting agent. In Comparative Example 4, an acidic liquid quick-setting agent was added, but the physical properties were not improved.

"Experimental example 2"
Concrete is prepared using the composition shown in Table 2 consisting of cement, coal ash, fine aggregate, coarse aggregate, and water, and the concrete is pumped under conditions of a spraying pressure of 0.4 MPa and a spraying speed of 10 m ³ / h. Pumped by a machine “MKW-25SMT”. On the other hand, rapid setting under the condition of a pumping pressure of 0.5 MPa so that the rapid setting agent having the blending ratio of Experiment No. 1-9 in Experimental Example 1 is 12 parts with respect to 100 parts in total of cement and coal ash. Pneumatically fed using the agent addition device “Natom Cleat” and rapidly connected with 5 parts of water reducing agent to 100 parts of calcium aluminate from holes provided in several places around one of the Y-shaped pipes provided in the middle 70 parts of water was added to 100 parts of the agent to form a quick setting slurry. This quick setting slurry was mixed with the shotcrete fed from the other side of the Y-shaped tube to obtain quick setting shotcrete. Concrete compression strength, rebound rate, and dust amount of this quick setting shot concrete were measured. The results are shown in Table 3.

<Measurement method>
Concrete compressive strength: The compressive strength at 1 hour of age is that the pin placed in the pullout formwork 25cm wide x 25cm long is covered with the quick setting sprayed concrete from the surface of the pullout formwork, and the pin from the back side of the formwork The pullout 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. In addition, on the 7th day of age, specimens of base concrete were also collected and the strength ratio with the base 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 sprayed concrete was sprayed on the simulated tunnel at a pumping speed of 10 m ³ / h for 10 minutes. Thereafter, the amount of dust was measured at a fixed position of 3 m from the spraying place.

  From Table 2 and Table 3, no influence is seen in compressive strength expression property in 35 to 60 parts of coal ash in a total of 100 parts of cement and coal ash. However, when the amount was 65 parts, a significant decrease in strength was confirmed. Moreover, rebound and the amount of dust increased remarkably when the amount of water was less than 42 parts with respect to 100 parts of cement and coal ash in total, and strength development, rebound, and the amount of dust deteriorated when 75 parts. It can be seen that good physical properties can be obtained by using concrete prepared within the scope of the present invention.

  By adopting the spraying material of the present invention and the spraying method using the same, the workability is improved by suppressing the generation of dust generated by the spraying work such as tunnels, and the spring water and natural ground surface deteriorated. Even under the circumstances, high quick setting properties and strength development properties can be obtained, and it is possible to use a large amount of coal ash.

Claims (1)

The total amount of cement and coal ash is 360 to 530 kg / m ³ , and the total amount of cement and coal ash is 100 parts by mass. 70 parts by mass of cement concrete and 100 parts by mass of amorphous calcium aluminates obtained by quenching a heat-treated product corresponding to a 12CaO · 7Al ₂ O ₃ composition having a Blaine specific surface area of 6,500 cm ² / g or more , 35 parts by weight sulfate salts are anhydrous gypsum, 10 parts by weight of the alkali-metal aluminate salts is sodium aluminate, 35 parts by weight of alkali metal carbonates are sodium carbonate, and oxycarboxylic acids 0.5 parts by weight sodium gluconate the quick-setting admixture comprising a, was added water reducing agent 5 parts by mass and water are formalin condensate of naphthalene sulfonate Consists Larry quick-setting admixture, is 70 parts by weight of water relative to the slurry quick-setting admixture is quick-setting admixture 100 parts by weight, the slurry quick-setting admixture is per 100 parts by weight of cement and coal ash in the cement concrete It is 12 parts by mass in terms of solid content, and the compressive strength at 7 days of age is 81 % or more as compared with the compressive strength of cement concrete without the addition of a quick-setting agent, and the compressive strength value 39.1 at 91 days of age. it is N / mm ² or more, the spraying material, continuously adding water to adjust the slurry quick-setting admixture in quick-setting admixture, and wherein the spraying joins mixed with cement concrete, the rebound amount 17 A spraying method in which the amount is 5% or less and the amount of dust is 3.9 mg / m ³ or less .