JP2009078934A - Quick setting cement concrete, and spraying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide quick setting cement concrete whose dust prevention effect improves. <P>SOLUTION: Disclosed is quick setting cement concrete comprising (1) and (2): (1) (1-1) cement and (1-2) dust preventive of 0.01 to 2 pts.mass to cement of 100 pts.mass; and (2) a quick setting agent. The dust preventive comprises (1-2-1) polyethylene oxide of 100 pts.mass and (1-2-2) inorganic fine power of 10 to 300 pts.mass composed of talc and/or pyrophyllite. It is preferable that the weight average molecular weight of the polyethylene oxide is 1,000,000 to 5,000,000, the grain size of the inorganic fine powder is ≤45 μm, the ratio of fine aggregates is 50 to 80 vol.%, the surface moisture percentage of the fine aggregates is ≤10 mass%, and the surface moisture percentage of coarse aggregates is ≤2 mass%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a quick setting cement concrete and a spraying method thereof.

  Conventionally, concrete spraying methods have been used to reinforce natural ground in tunnel excavation work and stabilize the excavation surface. For example, the compressed air sent from the compressor is supplied into the transport pipe that transports concrete sent by a piston pump, etc., and the concrete is pneumatically transported. A wet method in which concrete is rapidly sprayed from a nozzle after supplying a body setting agent and mixing the concrete and the quick setting agent is generally performed.

  In addition, water is added during the pneumatic feeding of dry mix concrete, and then the powder quick setting agent supplied by air from the quick setting agent supply equipment is supplied to the branch pipe of the merge pipe, and the concrete and the quick setting agent are mixed. A dry method of spraying concrete from a nozzle has been proposed.

  These spraying methods may generate a large amount of dust when spraying pneumatically conveyed concrete. As a countermeasure, there has been proposed a method in which water-soluble cellulose and polyethylene oxide are added to concrete before kneading the concrete. Compressed air sent from the compressor is supplied into the transport pipe that transports the concrete sent by a piston pump, etc., and the concrete is pneumatically transported, and the powder is rapidly transported to the branch pipe of the merging pipe from the quick setting agent supply equipment. There has been proposed a method of reducing dust by spraying concrete from a nozzle after supplying an agent and mixing concrete and a rapid setting agent (cited document 1, cited document 2).

  However, in this spraying method, it was necessary to adjust the polyethylene oxide to an appropriate particle size in order to increase the solubility in order to obtain a dust reduction effect. A defoamer was also used in order to entrain air when mixing concrete. In addition, since conventional dust reducing agents dissolve in the concrete aggregate surface water, they easily adhere to the aggregate hopper, and the dust preventing agent tends to be ball-shaped when mixed. Therefore, the dust prevention agent is not uniformly dispersed, so that a sufficient dust prevention effect cannot be obtained. This was particularly noticeable when the surface water of the aggregate was high. For this reason, there has been a demand for a dust prevention agent that can provide a sufficient dust prevention effect. In addition, because of its high hygroscopicity, there are problems such as solidification at the time of discharging from the adding device and fluctuation of the addition rate, and handling is required.

  There has been proposed a method of reducing dust by spraying a cement composition using a coated fine aggregate obtained by coating fine aggregate with cement (Cited document 3). However, the cited document 3 does not describe the use of polyethylene oxide and inorganic fine powder composed of talc and / or pyrophyllite.

JP-A-58-15056 JP 2004-189529 A JP 2000-72503 A

  The problem to be solved by the present invention is to improve the dust prevention effect.

The present invention is a rapid setting cement concrete containing (1) and (2),
(1) Cement concrete containing (1-1) and (1-2) (1-1) Cement (1-2) (1-2-1) 100 parts by mass of polyethylene oxide (1-2) 2) 0.01-0.2 parts by mass of (2) quick setting of dust inhibitor comprising 10-300 parts by mass of inorganic fine powder composed of talc and / or pyrophyllite with respect to 100 parts by mass of cement Agent The rapid setting cement concrete in which the weight average molecular weight of polyethylene oxide is 1 million to 5 million, and the rapid setting cement concrete in which the particle size of the inorganic fine powder composed of talc and / or pyrophyllite is 45 μm or less. And the rapid setting cement concrete in which the powder rapid setting agent contains calcium aluminate, and the fine aggregate ratio of the cement concrete is 50 to 80% by volume. This is a hard-setting cement concrete, and the surface water content of fine aggregate of cement concrete is 10% by mass or less, and the surface water rate of coarse aggregate of cement concrete is 2% by mass or less. (1) 100 parts by mass of polyethylene oxide and (1-2-2) talc and / or in a fine aggregate having a surface water content of 10% by mass or less. Or the cement which added the cement after adding 0.01-0.2 mass part with respect to 100 mass parts of cement for the dust prevention agent containing the inorganic fine powder 10-300 mass parts which consist of pyrophyllite It is a spraying method characterized in that (2) a quick setting agent is added to concrete to form a quick setting cement concrete, and the quick setting cement concrete is sprayed. (1) In a fine aggregate having a surface water ratio of 10% by mass or less, inorganic powder 10 to 300 composed of (1-2-1) 100 parts by mass of polyethylene oxide and (1-2-2) talc and / or pyrophyllite. After adding 0.01 to 0.2 parts by mass of the dust inhibitor containing 100 parts by mass with respect to 100 parts by mass of cement, a coarse aggregate having a cement and a surface water content of 2% by mass or less was added. It is a spraying method characterized by adding (2) a quick setting agent to cement concrete to form a quick setting cement concrete, and spraying the quick setting cement concrete, and the weight average molecular weight of polyethylene oxide is 1,000,000 to 500 This spraying method is characterized in that the particle size of the inorganic fine powder composed of talc and / or pyrophyllite is 45 μm or less. And is a 該吹 with how quick-setting admixture is characterized by containing a calcium aluminate.

  According to the present invention, the dust prevention effect is improved.

  In the present invention, paste, mortar, and concrete are collectively referred to as cement concrete.

The amount of cement in the cement concrete is preferably 300 to 500 kg / m ³ , more preferably 350 to 450 kg / m ^{3 in} terms of cement unit. The water / cement ratio in cement concrete previously mixed with water is preferably 45 to 65% by mass, and more preferably 50 to 60% by mass.

   The polyalkylene oxide (hereinafter referred to as PAO) used in the present invention gives viscosity to cement concrete and prevents dust from being sprayed immediately after spraying. Examples of the polyalkylene oxide include polyethylene oxide, polypropylene oxide, and polybutylene oxide. Among these, polyethylene oxide is preferred because it has a great effect of imparting viscosity to cement concrete and preventing dust during spraying.

  The weight average molecular weight of PAO is preferably 1 million to 5 million, and more preferably 1.5 to 2.5 million. If the weight average molecular weight of PAO is small, the viscosity of cement concrete is small and the effect of preventing dusting during spraying may not be expected. If the weight average molecular weight of PAO is large, strength development will be hindered. There is a case where the pumpability of rapid setting cement concrete mixed with cement concrete is lowered.

  The inorganic fine powder used in the present invention is composed of talc and / or pyrophyllite. It prevents PAO from coming into contact with moisture in the atmosphere or directly from the surface water of the aggregate, and facilitates cutting out from the hopper of the adding machine. Talc and pyrophyllite are preferable because they are rich in lubricity and low in hygroscopicity. When inorganic fine powders other than talc and pyrophyllite are used, cutting out from the hopper of the adding machine is poor, and the inorganic fine powder may form a bridge and cannot be discharged stably.

  It is preferable to preliminarily mix PAO and inorganic fine powder in that the inorganic fine powder covers the surface of PAO, prevents a decrease in hygroscopicity, and facilitates cutting out from the hopper of the adding machine. Moreover, it is preferable also in the point which prevents contact with the surface water of the aggregate of cement concrete, and becomes a ball shape.

   The particle size of the inorganic fine powder is preferably 45 μm or less, and the average particle size is preferably 10 to 15 μm.

10-300 mass parts is preferable with respect to 100 mass parts of PAO, and, as for the usage-amount of inorganic fine powder, 50-200 mass parts is more preferable. If the amount of inorganic fine powder used is small, the fine inorganic powder will come into contact with the surface water of the aggregate, and the PAO will tend to be ball-shaped. In addition, if the amount of inorganic fine powder used is large, it may be difficult to dissolve when kneading cement concrete, and the dust prevention effect may be easily reduced. The particle size was measured with a laser diffraction / scattering particle size distribution meter manufactured by Horiba Ltd.

  0.01-0.2 mass part is preferable with respect to 100 mass parts of cement, and, as for the usage-amount of the dust inhibiting agent which mixed PAO and inorganic fine powder, 0.03-0.1 mass part is more preferable. If the amount of dust prevention agent used is small, the viscosity of the quick setting cement concrete may be small and the amount of dust may be large.If the amount of dust prevention agent used is large, the viscosity of the cement concrete will be large. The pumpability of the mixed quick setting cement concrete may decrease.

  In the present invention, a dust inhibitor is added to the aggregate of cement concrete, for example. It is preferable to add a dust prevention agent to the fine aggregate in advance. By adding in advance to the fine aggregate, the inorganic fine powder composed of talc and / or pyrophyllite is in direct contact with the surface water of the polyalkylene oxide and aggregate, and the cement is not formed into a polyalkylene oxide. It uniformly disperses in concrete and improves the dust prevention effect. For example, it is preferable to add a dust prevention agent at the time of measuring the fine aggregate. For example, add an anti-dust agent on the belt conveyor that is put into the weighing hopper from the aggregate bin, knead the cement, aggregate, anti-dust agent, and water with a commercially available mixer for 60-90 seconds, then drop it on the agitator car. And carry it into the mine. Cement concrete is supplied from the agitator wheel to the piston pump, air is inserted along the way, air is transported through the transport pipe, and transported to the junction pipe where the powder quick-setting agent is mixed.

  50-80 volume% is preferable and, as for the fine aggregate rate of the cement concrete used by this invention, 55-70 volume% is more preferable. When the fine aggregate ratio is small, the dust prevention effect may be reduced, and when the fine aggregate ratio is large, the pumpability of the quick setting cement concrete may be reduced.

  The surface water content of the fine aggregate is preferably 10% by mass or less, more preferably 1 to 10% by mass, and most preferably 2 to 5% by mass. If the surface water ratio is low, the cost may increase, and if the surface water ratio is high, the dust prevention agent dissolves and forms a ball shape, which may reduce the dust prevention effect.

  The surface water content of the coarse aggregate is preferably 2% by mass or less, more preferably 0.3 to 2% by mass, and most preferably 0.5 to 1% by mass. If the surface water ratio is low, the cost may increase, and if the surface water ratio is high, the dust prevention agent dissolves and forms a ball shape, which may reduce the dust prevention effect.

  As the cement concrete used in the present invention, ordinary sprayed cement concrete can be used, and is not particularly limited. Also, spray cement concrete containing steel fibers can be used.

  The quick setting agent used in the present invention is preferably a powder quick setting agent. The powder quick-setting agent is pressure-fed by the quick-setting agent supply device to the branch pipe of the merging pipe through the quick-setting agent transport pipe. For example, a hose having an inner diameter of 3 / 4B (20 mm) or 1B (25 mm) can be used as the quick setting agent transport pipe.

  The powder quick-setting agent preferably contains calcium aluminate, and more preferably contains calcium aluminate, gypsum, and alkali metal aluminate.

Calcium aluminate has a hydration activity mainly composed of CaO and Al ₂ O ₃ obtained by mixing calcia raw material and alumina raw material and performing heat treatment such as baking in a kiln or melting in an electric furnace. It is a general term for substances that have it. When CaO is abbreviated as C and Al ₂ O ₃ is abbreviated as A, C ₃ A, C ₁₂ A ₇ , C ₁₁ A ₇ · CaF ₂ , C ₁₁ A ₇ · CaCl ₂ , C ₂ A · SiO ₂ , CA, and C ₂ A and the like, and a part of CaO and Al ₂ O ₃ is alkali metal oxide, alkaline earth metal oxide, silicon oxide, titanium oxide, iron oxide, alkali metal halide, alkaline earth metal halogen. A compound in which a small amount of these compounds is contained in a compound substituted with a chemical compound, an alkali metal sulfate, an alkaline earth metal sulfate or the like, or a compound containing CaO and Al ₂ O ₃ as main components is also included.

As a form of calcium aluminate, either crystalline or amorphous can be used. Among these, amorphous calcium aluminates are preferable from the viewpoint of reaction activity, and amorphous calcium aluminates obtained by quenching the heat-treated product corresponding to the C ₁₂ A ₇ composition are more preferable.

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) 3000 cm ² / g or more is preferable, 5000 cm ² / g or more is more preferable. If the brane value is small, the rapid setting property and initial strength development property of the quick setting cement concrete may decrease.

  For example, anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum can be used as the gypsum. Among these, the use of anhydrous gypsum is preferable in terms of setting properties and strength development.

The particle size of gypsum may be the level usually used for cement or the like, but it is preferably at least 3000 cm ² / g of brane in terms of rapid setting properties and initial strength development properties of the quick setting cement concrete. When the brane value is small, the setting property and strength development property of the rapid setting cement concrete may be lowered.

  The amount of gypsum used is preferably 20 to 150 parts by mass and more preferably 25 to 100 parts by mass with respect to 100 parts by mass of calcium aluminate. If the amount of gypsum used is small, the setting properties of rapid setting cement concrete may be reduced, and it may be difficult to promote long-term strength development. If the amount of gypsum used is large, initial setting is delayed and the initial strength development is reduced. May decrease.

  The alkali metal aluminate of the present invention (hereinafter referred to as aluminate) is obtained by mixing and dissolving aluminum hydroxide and an alkali metal hydroxide, and drying to obtain a powder.

  Examples of the aluminate include sodium aluminate, potassium aluminate, and lithium aluminate, and one or more of these can be used. In these, use of sodium aluminate is preferable at the point of the setting property of rapid setting cement concrete, and initial stage strength development property.

  10-50 mass parts is preferable with respect to 100 mass parts of calcium aluminate, and, as for the usage-amount of aluminate, 15-45 mass parts is more preferable. If the amount of aluminate used is small, the initial setting may be delayed, and the initial strength development may be reduced. If the amount of aluminate used is large, the long-term strength development of the rapid setting cement concrete may be reduced. There is.

  It is preferable that the powder rapid setting agent further contains an alkali metal carbonate.

  Examples of the alkali metal carbonate (hereinafter referred to as alkali carbonate) of the present invention include 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 15 to 45 parts by mass and more preferably 20 to 40 parts by mass with respect to 100 parts by mass of calcium aluminates. If the amount of alkali carbonate used is small, the initial setting may be delayed and the initial strength development may be reduced. If the amount of alkali carbonate used is large, the long-term strength development of the rapid setting cement concrete may be reduced. .

  The amount of the rapid setting agent is preferably 3 to 15 parts by mass, and more preferably 5 to 10 parts by mass with respect to 100 parts by mass of cement in the cement concrete. If the amount of the powder quick-setting agent is small, the effect may not be obtained, and even if the amount of the powder quick-setting agent is large, the addition effect may not be obtained.

  The quick setting cement concrete to which the quick setting agent is added is pumped while being mixed with the powder quick setting agent by the expansion and flow of compressed air in the transport pipe, discharged from the nozzle, and the ground is the spraying surface. It is sprayed to.

In the present invention, the total amount of the compressed air to the air transporting rapid setting cement concrete to the nozzle is preferably 5 to 30 m ³ / min at atmospheric pressure conversion value, 10 to 20 m ³ / min is more preferred. If the total amount of compressed air is small, the amount of air will be insufficient, the compaction of the quick setting cement concrete to the spraying surface will be insufficient, and it may be difficult to obtain strength, and the pumpability of the quick setting cement concrete will be poor. In some cases, the quick-setting cement concrete may block in the piping. If the total amount of compressed air is large, the amount of compressed air may be excessive, which may increase the amount of dust.

   In the present invention, the spray pressure of cement concrete is preferably 0.2 to 0.5 MPa. The pressure of the pumping air for pumping the quick setting agent may be about 0.01 to 0.3 MPa higher than the pumping pressure of cement concrete in that the quick setting agent does not block when mixed in the cement concrete merge pipe or transport pipe. preferable.

  The spraying equipment is not particularly limited as long as the spraying is sufficiently performed. For example, the product name “MKW-25SMT” of Shintech Co., Ltd. is used for the pumping of the sprayed cement concrete. The quick setting agent pressure feeding device “Natom Cleat” can be used.

  According to the present invention, the dust prevention effect is improved and the mixing property of the quick setting agent and cement concrete is improved. There is an effect of reducing troubles caused by blockage during spraying.

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

Experimental example 1
A dust inhibitor prepared by mixing 100 parts by mass of PAO Lee and inorganic parts of the inorganic powder shown in Table 1 was prepared, and the moisture absorption amount, the powder state after 3 days, and the discharge state were evaluated. The results are also shown in Table 1.

<Materials used>
PAO B: polyethylene oxide, weight average molecular weight 2 million, commercially available inorganic fine powder A: talc, average particle size 10 μm, commercially available inorganic fine powder B: pyrophyllite, average particle size 12 μm, commercially available inorganic fine powder C: gypsum , Anhydrous gypsum, average particle size 15μm, commercial product

<Evaluation method>
Moisture absorption: 100 g of a dust prevention agent was placed in a vat and left in a constant temperature and humidity chamber at a temperature of 35 ° C. and a relative humidity of 90 mass% for a predetermined period. The moisture absorption amount was calculated by measuring the mass before entering the constant temperature and humidity chamber, measuring the mass after 3 days, dividing the increased mass by the mass before entering the constant temperature and humidity chamber, and calculating the percentage.
Powder state after 3 days: 100 g of a dust prevention agent was placed in a vat and allowed to stand in a constant temperature and humidity chamber at a temperature of 35 ° C. and a relative humidity of 90% by mass for 3 days, and the subsequent powder state was evaluated. The case where it was in a powder state and having fluidity was marked with ◯, the case where it was ball-shaped and slightly dumpling, and the case where it was in a block state and in a dumpling state were marked with ×.
Discharge state: Dust inhibitor with 80% capacity of hopper capacity is added to an addition device with a screw feeder attached to the bottom of a hopper with a height of 40 cm, width of 30 cm, length of 40 cm, and angle of 60 degrees, and continuously discharged. After that, the discharge state in the hopper was evaluated. The case where almost the entire amount of the dust prevention agent was discharged was indicated as “◯”, the case where a small amount of the dust prevention agent partially remained was indicated as “Δ”, and the case where the dust prevention agent became bridging and remained as “x”.

  The results in Table 1 are as follows. When an appropriate amount of inorganic fine powder was used, even when left for a predetermined period, the amount of moisture absorption of the dust inhibitor was small, and the powder state, fluidity, and discharge state were good. When inorganic fine powders such as talc and pyrophyllite were used, the powder state and discharge state were good.

Experimental example 2
Concrete and powder quick setting agent were mixed to prepare quick setting concrete. Concrete, the unit quantity of each material, cement 360 kg / ^{m 3,} the water 216 kg / ^{m 3,} and a value indicating the fine aggregate ratio in Table 1. A fine aggregate on a belt conveyor for supplying aggregates, with a dust prevention agent consisting of 100 parts by mass of PAO and a mass part of inorganic fine powder A shown in Table 2 as shown in Table 2 for 100 parts by mass of cement. The surface water content was added to 3.0% by mass). Coarse aggregate (surface water ratio 0.8% by mass), cement and water were mixed with fine aggregate to which a dust prevention agent was added, and kneaded for 60 seconds to prepare concrete.
This concrete was pneumatically fed by a concrete pumping machine “MKW-25SMT”. The total amount of compressed air was 15 m ³ / min, and the spray pressure was 0.4 MPa. During the pressure feeding, 7 parts by mass of a powder quick-setting agent was added to 100 parts by mass of cement in the concrete. The powder quick-setting agent was pneumatically fed using a quick-setting agent adding apparatus “NATOM CLEAT” under the condition of a pumping pressure of 0.45 MPa. The resulting quick setting concrete was sprayed. Dust amount, pumpability, finished surface, and compressive strength were evaluated. The results are shown in Table 2.

<Materials used>
Cement: Normal Portland cement, Blaine specific surface area value 3200 cm ² / g, specific gravity 3.15
Fine aggregate: Himekawa sand from Niigata prefecture, specific gravity 2.62
Coarse aggregate: Gravel from Himekawa, Niigata Prefecture, surface dry condition, specific gravity 2.65, maximum dimension 13mm
Powder setting agent: 100 parts by mass of calcium aluminate (amorphous calcium aluminate rapidly quenched from heat-treated product corresponding to C ₁₂ A ₇ composition, brain specific surface area 6000 cm ² / g), gypsum (anhydrous gypsum, brain ratio) Surface area 5500 cm ² / g) 50 parts by mass, alkali metal aluminate (sodium aluminate) 20 parts by mass, alkali metal carbonate (sodium carbonate) 25 parts by mass PAOro: polyethylene oxide, weight average molecular weight 1 million, commercially available PAO C: Polyethylene oxide, weight average molecular weight 5 million, commercial product

<Evaluation method>
Surface water content of fine aggregate: Measured according to JIS A 1111.
Coarse aggregate surface water ratio: Measured according to JIS A 1110.
Dust amount: measured at a fixed position of 5 m from the spraying place after 10 minutes of spraying. The measuring device uses a digital dust meter P-5L manufactured by Shibata Kagaku.
Pumpability: The transportation situation of quick setting concrete was observed. The case where the merging pipe or the transport pipe was not clogged was marked as “◯”, the case where the concrete was squeezed and the quick setting concrete was discharged intermittently, and the case where the merging pipe or the transport pipe was clogged and could not be sprayed was marked as “X”.
Finished surface: The finished surface of quick setting concrete was observed. ○ when the thickness of the quick setting concrete is uniform and smooth, △ when the finished surface of the quick setting concrete is uneven, and when the entire finished surface of the quick setting concrete is uneven Was marked with x.
Compressive strength: The daily strength is determined by covering a pin placed on a 25cm wide x 25cm long pullout formwork with fast-setting concrete from the pullout surface, pulling the pin out of the formwork surface, and obtaining the pullout strength at that time Compressive strength = (Pullout strength) × 4 / (Specimen contact area) The compressive strength at the age of 28 days was measured with a 20-ton pressure machine on a specimen having a diameter of 5 cm and a length of 10 cm, which was sprayed with rapidly setting concrete on a form having a width of 50 cm, a length of 50 cm and a thickness of 20 cm.

  The results in Table 2 are as follows. When an appropriate amount of inorganic fine powder was used, the dust reduction effect was improved and the initial strength and long-term strength were improved. When an appropriate amount of dust inhibitor was used, when the fine aggregate ratio was appropriate, and when the weight average molecular weight of PAO was appropriate, the dust reduction effect, pumpability and finished surface were improved, and the initial strength and long-term strength were enhanced.

Experimental example 3
The surface shown in Table 3 with a fine aggregate ratio of 60% by volume, and adding 0.05 parts by mass of a dust prevention agent consisting of 100 parts by mass of PAO and 100 parts by mass of inorganic fine powder to 100 parts by mass of cement. Evaluation was performed in the same manner as in Experimental Example 2 except that a fine aggregate having a water ratio was used. The results are also shown in Table 3.

  The results in Table 3 are as follows. When the surface water content of the fine aggregate was appropriate, the dust reduction effect, pumpability, and finished surface were improved.

Experimental Example 4
The surface shown in Table 4 with a fine aggregate ratio of 60% by volume and addition of 0.05 part by mass of a dust prevention agent consisting of 100 parts by mass of PAO and 100 parts by mass of inorganic fine powder to 100 parts by mass of cement. Evaluation was performed in the same manner as in Experimental Example 2 except that a coarse aggregate having a water ratio was used. The results are also shown in Table 4.

  The results of Table 4 are as follows. When the surface water content of the coarse aggregate was appropriate, the dust reduction effect, pumpability and finished surface were improved.

  According to the experimental example, the present invention has the following effects. Prevents dust-preventing agents from forming balls when in contact with moisture in the air or directly on the surface water of the aggregate. Cutting out from the hopper of the dust additive adding machine becomes easy. Dust reduction effect, rebound rate reduction effect, transportability, and finished surface are improved. Increases initial strength and long-term strength.

Claims (13)

Rapid setting cement concrete containing (1) and (2).
(1) Cement concrete containing (1-1) and (1-2) (1-1) Cement (1-2) (1-2-1) 100 parts by mass of polyethylene oxide (1-2) 2) 0.01-0.2 parts by mass of (2) quick setting of dust inhibitor comprising 10-300 parts by mass of inorganic fine powder composed of talc and / or pyrophyllite with respect to 100 parts by mass of cement Agent   The rapid setting cement concrete according to claim 1, wherein the polyethylene oxide has a weight average molecular weight of 1,000,000 to 5,000,000.   The quick setting cement concrete according to claim 1, wherein the inorganic fine powder composed of talc and / or pyrophyllite has a particle size of 45 µm or less.   The quick setting cement concrete according to claim 1, wherein the quick setting agent contains calcium aluminate.   The quick setting cement concrete according to claim 1, wherein the fine aggregate ratio of the cement concrete is 50 to 80% by volume.   2. The rapid setting cement concrete according to claim 1, wherein the surface water content of the fine aggregate of cement concrete is 10% by mass or less.   The rapid setting cement concrete according to claim 1, wherein the surface water content of the coarse aggregate of cement concrete is 2 mass% or less.   (1) Inorganic fine powder comprising (1-2-1) 100 parts by mass of polyethylene oxide and (1-2-2) talc and / or pyrophyllite in a fine aggregate having a surface water content of 10% by mass or less. After adding 0.01 to 0.2 parts by mass of a dust prevention agent comprising 10 to 300 parts by mass to 100 parts by mass of cement, (2) a quick setting agent A spraying method characterized by adding quick-setting cement concrete and spraying the quick-setting cement concrete.   (1) Inorganic fine powder comprising (1-2-1) 100 parts by mass of polyethylene oxide and (1-2-2) talc and / or pyrophyllite in a fine aggregate having a surface water content of 10% by mass or less. After adding 0.01 to 0.2 parts by mass of a dust prevention agent containing 10 to 300 parts by mass with respect to 100 parts by mass of cement, the coarse aggregate with a cement and a surface water content of 2% by mass or less (2) A spraying method characterized in that a rapid setting cement concrete is added by adding a quick setting agent to the cement concrete to which is added, and then sprayed with the quick setting cement concrete.   The spraying method according to claim 8 or 9, wherein the polyethylene oxide has a weight average molecular weight of 1,000,000 to 5,000,000.   The spraying method according to claim 8 or 9, wherein the inorganic fine powder composed of talc and / or pyrophyllite has a particle size of 45 µm or less.   The spraying method according to claim 8 or 9, wherein the quick setting agent contains calcium aluminate.   The spraying method according to claim 8 or 9, wherein the fine aggregate ratio of cement concrete is 50 to 80% by volume.