JP2014181165A - Accelerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an accelerator capable of improving the setting quickness and strength development potential.SOLUTION: The provided accelerator includes: calcium aluminate including at least 60 vol.% of particles having diameters of 5-15 μm; gypsum including at least 60 vol.% of particles having diameters of 5-50 μm; alkali metal aluminates; and alkali metal carbonates. A method for manufacturing the accelerator by mixing a pre-classified calcium aluminate, a pre-classified gypsum, a pre-classified sodium aluminate, and pre-classified alkali metal carbonates is also provided.

Description

  The present invention relates to, for example, a quick setting agent, a spraying material, and a spraying method using the rapid spraying agent 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 cement paste, mortar, and concrete.

  Parts and% in the present invention are based on volume in the integrated value of particles, and are based on mass in other cases.

  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.

Accelerating agents include calcium aluminate, a mixture of alkali metal aluminate and alkali carbonate, etc., a mixture of calcium aluminate, alkali metal aluminate, and alkali carbonate, calcium aluminate and 3CaO, etc. A mixture with SiO ₂ is known (see Patent Documents 2 to 6).

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 Application Laid-Open No. 11-12008 JP 2000-233955 A JP 2003-292354 A Japanese Patent Laid-Open No. 2004-210552 JP 2006-152733 A JP 2006-182617 A International Publication No. 2005/123620 Pamphlet

  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. However, these quick setting agents have a problem that concrete is easily stripped or collapsed in a natural ground where there is a lot of spring water or a small amount of rock. Furthermore, in recent years, in order to reduce costs, there is a demand for a spray material that shortens the construction cycle and ensures safety even when the spray thickness is thin.

  From the above, improvement of quick setting property and strength development property of shotcrete is demanded, and a new cement quick setting agent has been developed (see Patent Documents 7 to 12). These cement quick-setting agents and cement compositions are mainly the result of examining the ratio of calcium aluminate, gypsum and other subcomponents in the quick-setting agent, and by examining the appropriate particle size range, There is no description about improving the quick setting property and reducing the rebound and dust of shotcrete.

The particle size is an index of reaction activity, and the evaluation method includes specific surface area, particle size distribution, pore distribution and the like. For example, the Blaine specific surface area in Patent Document 7 (hereinafter, Blaine the drawing) and 4500cm ² / g or more calcium aluminates, the use of the plaster of Blaine value 4000 cm ² / g, the Blaine values for the entire powder Because of the surface area, the particle size distribution is different even at the same brain value, and the reaction activity is different. Patent Document 7 proposes a concrete quick setting agent using calcium aluminate and gypsum having a brain value of 4500 cm ² / g or more. In calcium aluminate having a brain value of 5000 cm ² / g measured according to JIS R 5201, when not classified, 45% by volume is distributed in a particle diameter of 5 to 15 μm, but when classified, the particle diameter is 5 The activity is stronger when the particle size range is narrowed by classifying even with calcium aluminate having the same brain value of 5000 cm ² / g. If the plain value is high, the activity becomes strong, but it takes time to grind and increases the cost. Therefore, classification in advance is preferable in terms of economy. In the present application, it is possible to reduce the rebound by classifying and setting the appropriate particle size range to increase the quick setting property. In the prior art, the particle size of calcium aluminate and gypsum is defined by a plain value, but there is no definition of particle size distribution. Depending on the substance, the particle size distribution is different even with the same brain value, and therefore it may not be possible to uniquely define the particle size with a plain value.

  When the calcium aluminate in the concrete quick-setting agent is not classified, the content of particles having a particle diameter of 5 to 15 μm is less than 60% by volume. When the gypsum in the concrete quick-setting agent is not classified, the content of particles having a particle diameter of 5 to 50 μm is less than 60% by volume.

  As a result of various studies on the above-mentioned problems and requirements, the present inventor can improve the quick setting property of the quick setting agent by, for example, classifying the raw materials constituting the quick setting agent and adjusting them to an appropriate particle size range. It was possible to obtain the knowledge that rebound and dust of spray cement concrete can be reduced, and the present invention has been completed.

That is, the present invention contains calcium aluminate containing 60% by volume or more of particles having a particle diameter of 5 to 15 μm, gypsum containing 60% by volume or more of particles having a particle diameter of 5 to 50 μm, alkali metal aluminate, and alkali metal carbonate. A quick setting agent, wherein the alkali metal aluminate is an alkali metal aluminate containing 60% by volume or more of particles having a particle diameter of 7 to 100 μm, and the alkali metal carbonate is a particle. Alkali metal carbonates containing 60% by volume or more of particles having a diameter of 70 to 300 μm are the quick setting agent, and the quick setting agent has a vitrification ratio of calcium aluminate of 90% or more. a said acute admixture is the molar ratio of CaO and _{Al 2 O 3 (CaO / Al} 2 O 3) is 1.7 to 2.3, a said acute admixture gypsum is anhydrous gypsum, alk The molar ratio of _{R 2} O and _Al 2 _{O 3} in the metal aluminate _{(R 2 O / Al 2 O} 3, R is an alkali metal)) is the sudden admixture is 0.8 to 1.2, The quick setting agent wherein the alkali metal aluminate is sodium aluminate, comprising 100 parts of calcium aluminate, 150 parts or less of gypsum, 5 to 40 parts of sodium aluminate, 40 parts or less of alkali metal carbonate Quick setting agent, calcium aluminate, gypsum, sodium aluminate, alkali metal carbonate is the pre-classified quick setting agent, pre-classified calcium aluminate, pre-classified gypsum, A method for producing the quick-setting agent comprising mixing sodium aluminate that has been pre-classified and alkali metal carbonate that has been pre-classified, comprising cement and the quick-setting agent A cement composition comprising 100 parts of cement and 3 to 20 parts of the quick setting agent, and a spraying material comprising the cement composition. And the quick setting agent are mixed and sprayed.

  By using the cement quick setting agent of the present invention, the quick setting property and the strength development property of the quick setting spray cement concrete are improved.

  Hereinafter, the present invention will be described in detail.

The calcium aluminate used in the present invention is a mixture of a raw material containing calcia and a raw material containing alumina, and obtained by heat treatment such as firing in a kiln or melting in an electric furnace. ₂ O ₃ is a general term for substances having hydration activity, and a part of CaO and Al ₂ O ₃ is an alkali metal oxide, alkaline earth metal oxide, silicon oxide, titanium oxide, oxidation To compounds containing iron, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, alkaline earth metal sulfates, etc., or those containing CaO and Al ₂ O ₃ as main components, Is a substance that is dissolved in a small amount.

In terms of reaction activity, the mineral form is preferably rapidly cooled and vitrified after melting in an electric furnace, and the vitrification rate is preferably 90% or more, more preferably 93% or more. If it is less than 90%, excellent rapid setting properties and initial strength development may not be obtained. The vitrification rate is determined by measuring the main peak area S of the crystalline mineral in advance by powder X-ray diffraction of the sample before heating, heating at 1000 ° C. for 2 hours, and then gradually cooling at a cooling rate of 1-10 ° C./min. The main peak area S ₀ of the crystal mineral after heating by the X-ray diffraction method is obtained, and further, the vitrification rate χ is calculated by using the following formula using the values of S ₀ and S.
Vitrification rate χ (%) = 100 × (1−S / S ₀ )

The calcium aluminate CaO to Al ₂ O ₃ molar ratio (CaO / Al ₂ O ₃ ) is preferably 1.7 to 2.3, more preferably 1.9 to 2.2. If the molar ratio is outside this range, excellent rapid setting properties and initial strength development may not be obtained.

  The particle size of calcium aluminate is preferably sieved to various particle sizes with a classifier. The calcium aluminate preferably contains 60% by volume or more of particles having a particle diameter of 5 to 15 μm, more preferably 70% by volume or more of particles having a particle diameter of 5 to 15 μm, in terms of rapid setting and initial strength development. preferable. If it is less than 60 volume%, the quick setting property and initial strength development property of the quick setting spray cement concrete which mixed the quick setting agent and the spray cement concrete may fall. When many particles with a particle diameter of less than 5 μm are included, the reaction occurs immediately after contact with water, so that a hydrate may be formed on the surface of the calcium aluminate particles and the reaction may be suppressed. Is good. If many particles having a particle diameter exceeding 15 μm are included, the reaction activity may be reduced, and the rapid setting property and the initial strength development property may be reduced.

  The particle size distribution was measured using a laser diffraction particle size distribution measuring instrument (for example, HORIBA LA-920) using ethanol as a sample dispersion medium. The integrated value of the particles is indicated by volume%.

  The gypsum used in the present invention is blended in order to improve the quick setting property and strength development of the quick setting sprayed cement concrete. Among the gypsum, anhydrous gypsum is preferable. The particle size of gypsum may be the level usually used for cement or the like, but it is preferable to screen the particles with a classifier. The gypsum preferably contains 60% by volume or more of particles having a particle size of 5 to 50 μm, and 70 volumes of particles having a particle size of 5 to 15 μm from the viewpoint of rapid setting and initial strength development of the quick setting sprayed cement concrete. It is more preferable that it contains more than%. If it is less than 60 volume%, the quick setting property and initial strength development property of the quick setting spray cement concrete which mixed the quick setting agent and the spray cement concrete may fall. When many particles with a particle diameter of less than 5 μm are included, the reaction between calcium aluminate and gypsum may be suppressed, and the rapid setting of the cement may be reduced, and the amount of dust may be increased. Good to do. When many particles having a particle diameter exceeding 50 μm are contained, the reaction activity of calcium aluminate and anhydrous gypsum may be lowered and the reaction may be delayed.

The amount of gypsum used in the quick setting agent is preferably 150 parts or less, more preferably 20 to 150 parts, and most preferably 40 to 120 parts with respect to 100 parts of calcium aluminate. Gypsum can be added to cement concrete without being premixed with the quick setting agent. If it exceeds 150 parts, the setting may be delayed and the initial strength development may be reduced.

The alkali metal aluminate used in the present invention (hereinafter sometimes referred to as aluminate) is, for example, one that promotes the initial setting of cement, and mixes slurry of aluminum hydroxide and alkali metal hydroxide, It is obtained by heating and dissolving at 60 to 140 ° C., reacting, and drying at 200 to 300 ° C. to obtain a powder. The R ₂ O / Al ₂ O ₃ molar ratio (R is an alkali metal) of the alkali metal aluminate is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. If it is less than 0.8, the hygroscopicity decreases, but the rapid setting of the cement may also decrease. When it exceeds 1.2, the hygroscopicity is increased, and the storage property may be lowered. In R, Na is preferable.

  Of the aluminates, sodium aluminate is preferred. The aluminate particle size is preferably sieved to various particle sizes using a classifier, and preferably contains 60% by volume or more of particles having a particle size of 7 to 100 μm in terms of rapid setting and initial strength development. More preferably, 70 volume% or more of particles having a diameter of 7 to 100 μm are included. If it is less than 60 volume%, the quick setting property and initial strength development property of the quick setting spray cement concrete which mixed the quick setting agent and the spray cement concrete may fall. When many particles having a particle diameter of less than 7 μm are contained, the hygroscopicity is increased and the storage stability may be lowered. If many particles exceeding 100 μm are contained, the solubility may be lowered and the rapid setting property and the initial strength development property may be lowered. Therefore, it is preferable to cut at 200 μm.

  In Patent Document 6, 0.05 to 0.2 mm is more preferable for the particle size range of sodium aluminate, but there is no definition of a particle size of less than 0.05 mm because it is not classified. In the present invention, the particles having a particle size of 2 μm or less are classified and cut, so that a quick setting agent having good storage stability can be obtained even if particles of less than 0.05 mm are included.

  The amount of aluminate used is preferably 5 to 40 parts, more preferably 10 to 30 parts, per 100 parts of calcium aluminate. If it is less than 5 parts, the initial setting may be delayed, and the rapid setting and initial strength may be reduced. If it exceeds 40 parts, the workability and long-term strength of the quick setting sprayed cement concrete 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 the initial setting. In the conventional technique, there is no regulation on the particle size of the alkali metal carbonate, but it is possible to improve the quick setting property by classifying and defining the particle size range. The particle size of the alkali carbonate is preferably sieved to various particle sizes with a classifier, and preferably contains 60% by volume or more of particles having a particle size of 70 to 300 μm in terms of rapid setting and initial strength development. More preferably, 70% by volume or more of 70 to 300 μm particles are contained. If it is less than 60 volume%, the quick setting property and initial strength development property of the quick setting spray cement concrete which mixed the quick setting agent and the spray cement concrete may fall. If many particles having a particle diameter of less than 70 μm are contained, the reaction between calcium aluminate and anhydrous gypsum may be delayed. When many particles exceeding 300 μm are contained, the rapid setting property and the initial strength development property may be lowered.

  The amount of alkali carbonate used is 40 wt. Per 100 parts of calcium aluminate, although the amount of anhydrous gypsum used is high or when used at low temperatures, the reaction of the cement is delayed and alkali carbonate may not be blended. The following is preferable, 10 to 30 parts are more preferable, and 15 to 25 parts are most preferable. If it exceeds 40 parts, workability and long-term strength development may be reduced.

  The quick setting agent of the present invention can be formulated with oxycarboxylic acids, such as gluconic acid, tartaric acid, citric acid, malic acid, salicylic acid, and lactic acid, or alkali metal salts thereof such as sodium and potassium.

  The rapid setting agent used in the present invention can be added to cement concrete in the form of a slurry.

  The amount of the quick setting agent used is preferably 3 to 20 parts, more preferably 5 to 15 parts with respect to 100 parts of cement. If it is less than 3 parts, it may be difficult to promote initial setting of rapid setting sprayed cement concrete, and if it exceeds 20 parts, long-term strength development may be hindered. There is.

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

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

  The cement concrete used in the present invention contains cement and aggregate. Here, the aggregate preferably has a low water absorption rate and a high aggregate strength. 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.

  The amount of water used for the cement concrete is preferably 35% or more, more preferably 40 to 65% in terms of strength development. If it is less than 35%, cement concrete may not be sufficiently mixed.

  In the spraying method using the quick setting agent of the present invention, conventionally used spraying equipment or the like can be used. Specifically, for example, a spray pump equipped with a concrete pump manufactured by Shintech Co., Ltd. can be used for pumping sprayed cement concrete, and a quick setting agent pumping device “NATOM CLEAT” can be used for pumping quick setting agent.

  As a spraying method using the quick setting agent of the present invention, various spraying methods according to required physical properties, economy, workability and the like are possible. As a spraying method using the quick setting agent of the present invention, a dry spraying method can also be constructed, but since the amount of dust may increase, water should be added to the cement concrete side before using the quick setting agent. It is preferable to use a wet spraying method that has been kneaded.

  As a wet spraying method, for example, cement, fine aggregate, coarse aggregate, and water are added and kneaded, pneumatically fed, a Y-shaped tube is provided in the middle, and pumped from one of them by a quick setting agent supply device. There is a method of spraying a quick setting wet spray concrete by merging and mixing quick setting agents.

In the spraying method using the quick setting agent of the present invention, usually, the spraying pressure is 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 is preferably 0.01 to 0.3 MPa larger than the pumping pressure of the cement concrete so that the pumping pipe is not blocked when the cement concrete is mixed in the pumping tube of the quick setting agent. .

  Hereinafter, the present invention will be described in detail based on experimental examples.

Experimental example 1
100 parts of calcium aluminate having a vitrification ratio and CaO / Al ₂ O ₃ (molar ratio) shown in Table 1 and containing 70% by volume of particles having a particle diameter of 5 to 15 μm, and 70 volumes of particles having a particle diameter of 5 to 50 μm. Anhydrous gypsum containing 60%, Na ₂ O / Al ₂ O ₃ (molar ratio) is 1.0, 20 parts of sodium aluminate containing 70% by volume of particles having a particle size of 7-100 μm, and particle size of 70-300 μm A rapid setting agent was prepared by mixing 20 parts of alkali carbonate a containing 70% by volume of particles. Further, a mortar having a sand / cement ratio = 2.89 and a water / cement ratio = 62% was kneaded and kneaded for 30 minutes. To 100 parts of the mortar cement, 7 parts of a quick setting agent was added to form a quick setting mortar, and its setting time and compressive strength were measured. The results are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, commercial product, brain value 3200 cm ² / g, specific gravity 3.15
Sand (fine aggregate): Niigata Prefecture Itoigawa City Himekawa River river sand, surface dry state, specific gravity 2.62
Calcium aluminate: Alumina raw material and calcia raw material are mixed, melted at 1600 ° C. in an electric furnace, the cooling rate is adjusted, and calcium having a predetermined vitrification ratio and a predetermined CaO / Al ₂ O ₃ (molar ratio) Aluminate is synthesized, pulverized with a pulverizer such as a ball mill, and the particle size is adjusted by classification, classified anhydrous gypsum: pulverized with a commercially available anhydrous gypsum pulverized product, ball mill or other pulverizer, and the particle size is adjusted by classification Sodium aluminate: Aluminium hydroxide and alkali metal hydroxide were mixed so as to have a predetermined Na ₂ O / Al ₂ O ₃ (molar ratio) of 1.0, and then added to make a slurry. It was made to react by heating and dissolving at ~ 140 ° C. The slurry was dried at 200 to 300 ° C., and the powdered product was pulverized with a pulverizer such as a ball mill, and the particle size was adjusted by classification, classified product alkali carbonate a: sodium carbonate, commercially available product in a ball mill Pulverized with a pulverizer, etc., and the particle size adjusted by classification, classified product

<Measurement method>
Setting time: The quick setting mortar was measured according to the Japan Society of Civil Engineers standard "Quality standard for quick setting agent for shotcrete (JSCED-102)".
Compressive strength: Quick setting mortar was measured according to JIS R5201.
Particle size distribution: Using a laser diffraction particle size distribution analyzer (HORIBA LA-920), measurement was performed using ethanol as a sample dispersion medium.

Experimental example 2
100 parts of calcium aluminate having a vitrification rate of 95% and a CaO / Al ₂ O ₃ (molar ratio) of 2.0, and an integrated value of each particle size shown in Table 2. 60 parts of anhydrous gypsum consisting of integrated values of each particle size shown in Table 2, 20 parts of sodium aluminate having a Na ₂ O / Al ₂ O ₃ (molar ratio) of 1.0, and each particle size shown in Table 2 Experiments were conducted in the same manner as in Experimental Example 1 except that 20 parts of alkali carbonate a composed of integrated values were mixed to prepare a quick setting agent. The setting time and compressive strength were measured in the same manner as in Experimental Example 1. The results are shown in Table 2.

Experimental example 3
The vitrification rate is 95%, CaO / Al ₂ O ₃ (molar ratio) is 2.0, 100 parts of calcium aluminate containing 70% by volume of particles having a particle size of 5 to 15 μm, and particles having a particle size of 5 to 50 μm. 60 parts of anhydrous gypsum containing 70% by volume, 20 parts of sodium aluminate having Na ₂ O / Al ₂ O ₃ (molar ratio) shown in Table 3 and containing 70% by volume of particles having a particle size of 7 to 100 μm, particle size of 70 An experiment was conducted in the same manner as in Experimental Example 1 except that 20 parts of alkali carbonate a containing 70 volume% of particles of ˜300 μm was mixed to prepare a quick setting agent. The setting time and compressive strength were measured in the same manner as in Experimental Example 1. The results are also shown in Table 3. Sodium aluminate was synthesized in the same manner as in Experimental Example 1.

<Measurement method>
Storage property (setting time after storage): The quick-setting agent mixed with each material was sealed in a plastic bag and stored in a storage room at 35 ° C. and 95% humidity for one month. The setting time was measured in the same manner as in Experimental Example 1 using a quick setting agent before and after storage.

Experimental Example 4
The vitrification rate is 95%, CaO / Al ₂ O ₃ (molar ratio) is 2.0, 100 parts of calcium aluminate containing 70% by volume of particles having a particle size of 5 to 15 μm, and particles having a particle size of 5 to 50 μm. 70% by volume, anhydrous gypsum in the amount shown in Table 4, Na ₂ O / Al ₂ O ₃ (molar ratio) is 1.0, 70% by volume of particles having a particle diameter of 7 to 100 μm, and shown in Table 4 The experiment was conducted in the same manner as in Experimental Example 1 except that the amount of sodium aluminate and 70% by volume of particles having a particle diameter of 70 to 300 μm were contained, the alkali carbonate shown in Table 4 was mixed, and a quick setting agent was prepared. The setting time and compressive strength were measured in the same manner as in Experimental Example 1. The results are also shown in Table 4.

<Materials used>
Alkali carbonate b: potassium carbonate, commercial product, each classified product containing 70% by volume of particles having a particle size of 70 to 300 μm

Experimental Example 5
Calcium aluminate, anhydrous gypsum, sodium aluminate, and sodium carbonate were mixed to prepare a quick setting agent. A quick setting mortar was prepared by adding 100 parts of cement and an amount of the quick setting agent shown in Table 5. The setting time and compressive strength of the quick setting mortar were measured in the same manner as in Experimental Example 1. The materials using quick setting agents such as calcium aluminate, anhydrous gypsum, sodium aluminate, and sodium carbonate were the same as those in Experimental Example 4. The results are also shown in Table 5.

<Materials used>
Accelerating agent a: 100 parts of calcium aluminate, 20 parts of sodium aluminate, 20 parts of sodium carbonate, quick setting agent b: 100 parts of calcium aluminate, 60 parts of anhydrous gypsum, 20 parts of sodium aluminate, carbonic acid Quick setting agent mixed with 20 parts of sodium c: Quick setting agent mixed with 100 parts of calcium aluminate, 100 parts of anhydrous gypsum and 20 parts of sodium aluminate

Experimental Example 6
The unit quantity of each material, cement 360 kg / ^{m 3,} fine aggregates 1,042kg / ^{m 3,} the shotcrete was prepared as coarse aggregate 708kg / ^{m 3,} the water 223kg / ^{m 3,} spray the shotcrete Under the conditions of a pressing pressure of 0.4 MPa and a spraying speed of 10 m ³ / h, it was pumped by a concrete pump manufactured by Syntex, and 10 m ³ / min of air was inserted 8 m behind the tip of the spraying nozzle and pumped. On the other hand, it consists of the integrated value of each particle size shown in Table 6, and the vitrification rate is 95%, CaO / Al ₂ O ₃ (molar ratio) is 2.0 parts calcium aluminate 100 parts, each particle size shown in Table 6 60 parts of anhydrous gypsum composed of integrated values, 20 parts of sodium aluminate having Na ₂ O / Al ₂ O ₃ (molar ratio) of 1.0, each composed of integrated values of each particle size shown in Table 6, and each shown in Table 6 The quick setting agent adding device “Natom Cleat” under the condition of a pressure of 0.5 MPa so that the quick setting agent composed of 20 parts of sodium carbonate having an integrated value of particle size is 7 parts with respect to 100 parts of cement. Was added to the concrete from a Y-tube provided in the middle and sprayed. Concrete compression strength, rebound rate, and amount of dust were measured for this quick setting shot concrete. The results are also shown in Table 6. The material used for the quick setting agent was the same as in Experimental Example 4.

<Materials used>
Coarse aggregate: Gravel from Himekawa, Itoigawa City, Niigata Prefecture, surface dry condition, specific gravity 2.67, maximum dimension 13mm

<Measurement method>
Concrete compressive strength: The compressive strength of 1 hour of age and 1 day of age is determined by covering a pin placed on a pullout formwork with a width of 25 cm x length of 25 cm with a quick setting sprayed concrete from the surface of the pullout formwork. The pin was pulled out from the back side of the frame, 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).
Compressive strength after 7 days of age is 20 tons pressure-resistant machine by spraying quick setting sprayed concrete on a form of width 50cm × length 50cm × thickness 20cm and collecting 5cm diameter × 10cm length specimen. And the compressive strength was determined.
Rebound rate: Rapid setting shot concrete 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 5 minutes. Then, (rebound rate) = (mass of quick setting sprayed concrete dropped without adhering to the simulated tunnel) / (mass of quick setting shot concrete sprayed to the simulated tunnel) x 100 (%) did.
Dust amount: Quick setting sprayed concrete was sprayed on a simulated tunnel at a pumping speed of 10 m ³ / h for 5 minutes. Thereafter, the amount of dust was measured at a fixed position of 5 m from the spraying place.

  From the table, it can be seen that the present invention has an excellent effect. In the conventional case, for example, when calcium aluminate is not classified, the content of particles having a particle diameter of 5 to 15 μm is less than 60% by volume in the calcium aluminate in the concrete quick-setting agent and does not have the effect of the present invention. (Experiment No. 2-1, Experiment No. 6-1). In the conventional case, for example, when gypsum is not classified, the gypsum in the concrete quick-setting agent has a particle content of 5 to 50 μm and less than 60% by volume, and does not have the effect of the present invention (Experiment No. 1). 2-3, Experiment No. 6-4).

Claims (15)

Calcium aluminate containing 60% by volume or more of particles having a particle diameter of 5 to 15 μm, gypsum containing 60% by volume or more of particles having a particle diameter of 5 to 50 μm, an alkali metal aluminate, and an alkali metal carbonate . The rapid setting agent according to claim 1, wherein the alkali metal aluminate is an alkali metal aluminate containing 60% by volume or more of particles having a particle diameter of 7 to 100 µm. The rapid setting agent according to claim 1 or 2, wherein the alkali metal carbonate is an alkali metal carbonate containing 60% by volume or more of particles having a particle diameter of 70 to 300 µm. The rapid setting agent according to claim 1, wherein the vitrification rate of calcium aluminate is 90% or more. The quick setting agent according to claim 1, wherein a molar ratio of CaO to Al ₂ O ₃ (CaO / Al ₂ O ₃ ) in calcium aluminate is 1.7 to 2.3. The quick setting agent according to claim 1, wherein the gypsum is anhydrous gypsum. The molar ratio of R ₂ O to Al ₂ O ₃ (R ₂ O / Al ₂ O ₃ , R is an alkali metal) in the alkali metal aluminate is 0.8 to 1.2. The quick setting agent described in one of them. The rapid setting agent according to claim 1, wherein the alkali metal aluminate is sodium aluminate. The quick setting agent according to claim 1, comprising 100 parts of calcium aluminate, 150 parts or less of gypsum, 5 to 40 parts of sodium aluminate, and 40 parts or less of alkali metal carbonate. The quick setting agent according to claim 1, wherein calcium aluminate, gypsum, sodium aluminate, and alkali metal carbonate are classified in advance. The calcium aluminate previously classified, the preclassified gypsum, the preclassified sodium aluminate, and the preclassified alkali metal carbonate are mixed. A method for producing a quick setting agent. A cement composition comprising cement and the quick setting agent according to claim 1. A cement composition comprising 100 parts of cement and 3 to 20 parts of the quick setting agent according to claim 1. A spray material comprising the cement composition according to claim 12 or 13. A spraying method for mixing and spraying cement and the quick setting agent according to claim 1.