JP2012091941A - Spray material and spraying method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spray material and a spraying method using it producible of concrete for spraying with small slump loss even if alumina cement with high hydration activity is incorporated in the concrete.SOLUTION: This spray material includes cement concrete and a liquid quick setting agent containing aluminum sulfate. The cement concrete includes: 2-20 pts.mass alumina cement with ≥4,000 cm/g Blaine specific surface area and containing 50-60 mass% AlO, 33-40 mass% CaO and ≤2.0 mass% FeOto 100 pts.mass portland cement or similar types thereof; and 0.5-20 pts.mass of a polymer emulsion in terms of solid content to 100 pts.mass of the alumina cement. Further the spray material includes cement concrete containing fly ash, and an acrylate-based polymer emulsion. The spraying method uses such the spray materials.

Description

  The present invention mainly relates to a spraying material used in the civil engineering and construction industry and a spraying method using the same.

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

Conventional quick-setting agents include calcium aluminate, a mixture of alkali metal aluminate and alkali metal carbonate, and a mixture of baked alum, alkali metal aluminate, alkali metal carbonate, etc. Further, a mixture of calcium aluminate and 3CaO · SiO ₂ , slaked lime, alkali metal aluminate, and a mixture of alkali metal carbonates are known (see Patent Documents 2 to 5).
These quick setting agents have a function of promoting the setting of cement, and all of them are mixed with cement concrete and sprayed on the ground surface. The quick setting agent is an admixture necessary for shotcrete to suppress loosening of natural ground at an early stage.
In recent years, there has been an increase in the use of liquid quick setting agents mainly composed of aluminum sulfate in consideration of a working environment that generates a small amount of dust and has little alkali irritation to the human body (Patent Documents 6 to 8). Liquid quick setting agents are superior in that they can suppress the generation amount of dust and have little alkali irritation to the human body, but the setting speed immediately after spraying is slower than general quick setting agents, such as spring water In some cases or when it was thickened, it could peel off. Also, spraying with a concrete mix with an increased amount of cement tends to solve the setting speed problem, but there is an economic demerit that material costs are significantly increased.
On the other hand, as a method of generating a small amount of dust, a technique is also known in which a powder quick-setting agent is added to slurryed concrete with water and sprayed (Patent Documents 9 to 11). However, this method can reduce the amount of dust generation and improve the initial setting properties, but the slurry-set quick-acting agent shows alkalinity and is not improved in terms of irritation to the human body due to alkali. is there.

  Therefore, cement concrete is pumped and mixed with a rapid setting agent containing calcium aluminate, alkali metal sulfate, gypsum and water-retaining substance, and slurry water containing aluminum and sulfur separately. A spraying material containing a slurry accelerating agent has been developed (Patent Document 11). This method is a method in which a quick setting agent containing calcium aluminate is slurried with acidic slurry water containing aluminum and sulfur and added to the concrete, so there is little irritation to the human body and the setting speed is also a general quick setting agent. Is excellent in terms of good initial strength development. However, a system for pneumatically conveying a powder quick-setting agent containing calcium aluminate and a system for pumping acidic slurry water are required, which complicates the spraying system and increases equipment costs. It was.

There is a spraying material containing a quick setting agent slurry containing water and a powder quick setting agent in cement concrete containing hydraulic material (containing calcium aluminate), polymer emulsion, aggregate and water (Patent Literature) 12). This method also requires a system that pneumatically conveys the powder accelerating agent and a system that pumps slurry water, making it a complicated spraying system and increasing equipment costs, and the calcium aluminate used. is the cement concrete side, hydration activity using weak Auin _{(4CaO · 3Al 2 O 3 ·} SO 3), a strong calcium aluminate hydration activity as quick-setting admixture (12CaO · _7Al 2 _{O 3)} It is fundamental to use a powder accelerating agent as a main component, and there is no actual example of applying calcium aluminate that can be hardened by mixing with cement.

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 Laying-Open No. 2005-60201 JP 2005-89276 A JP 2008-30999 A JP 05-139804 A JP 05-097491 A JP 2007-277051 A JP 2002-137993 A

  The present invention allows a concrete to contain an alumina cement having high hydration activity by applying a liquid setting agent mainly composed of aluminum sulfate to cement concrete containing a specific alumina cement and a specific polymer emulsion. Can produce spray concrete with low slump loss, and when mixed with a liquid accelerator mainly composed of aluminum sulfate, the hydration activity is drastically improved, unlike when using a general retarder. Therefore, it is possible to realize spraying construction with low dusting, low rebound, and little alkali stimulation to the human body. Furthermore, since it is possible to provide a spray material having excellent setting properties without using concrete containing an excessive amount of cement, it is economically advantageous.

That is, the present invention provides (1) 50 to 60% Al ₂ O ₃ , 33 to 40% CaO, 2.0% or less Fe ₂ O ₃ , and a Blaine specific surface area with respect to 100 parts of Portland cement. Cement concrete containing 2 to 20 parts of alumina cement of 4000 cm ² / g or more, 0.5 to 20 parts of polymer emulsion in solid content with respect to 100 parts of the alumina cement, and a liquid quick-setting agent containing aluminum sulfate (2) Further, the cement concrete contains fly ash, (1) the spray material, (3) the polymer emulsion is an acrylate emulsion (1) ) Or (2) spraying material, (4) and the liquid accelerator contains fluorine and / or lithium. Spraying material Zureka is put method, using any of the spraying material (5) (1) to (4).

  By using the spray material of the present invention and the spray method using the same, it is possible to produce spray concrete with low slump loss even when alumina cement having high hydration activity is contained in cement concrete, and the main component is aluminum sulfate. Unlike when using a general retarder when mixing a liquid quick-set agent, the hydration activity is drastically improved, resulting in low dusting, low rebound, and low alkali stimulation to the human body. Can be realized. Furthermore, since it is possible to provide a spray material having excellent setting properties without using concrete containing an excessive amount of cement, it is economically advantageous. In addition, the spraying system does not require a powder transport device, and can be applied with a liquid quick-setting agent pressure pump.

Hereinafter, the present invention will be described in detail.
Unless otherwise specified, parts and% in the present invention are shown on a mass basis.

Portland cements used in the present invention include various portland cements such as normal, early strength, ultra-early strength, low heat, and moderate heat, and various blends obtained by mixing blast furnace slag, fly ash, or silica with these portland cements. Environmentally friendly cement made from cement, filler cement mixed with limestone powder with a Blaine specific surface area of 2000 cm ² / g or more, blast furnace chilled slag fine powder, etc. Portland cement such as eco-cement) can be used, and one or more of these can be used.

The alumina cement of the present invention has the characteristics that Al ₂ O ₃ is 50 to 60%, CaO is 33 to 40%, Fe ₂ O ₃ is 2.0% or less, and Blaine specific surface area is 4000 cm ² / g or more. Therefore, it corresponds to alumina cement No. 1 which is usually marketed. A rapid setting action is exhibited by mixing with a liquid setting agent mainly composed of aluminum sulfate.
Alumina cement is more cemented than calcium aluminate and gypsum compositions represented by 12CaO · 7Al ₂ O ₃ (hereinafter referred to as C ₁₂ A ₇ ) and 3CaO · Al ₂ O ₃ (hereinafter referred to as C ₃ A) compositions. Hydration activity is slow when added to. Therefore, it is advantageous for securing working time. However, it is difficult to secure a working time of 1 hour or more in the addition region that exhibits quick setting performance when sprayed. Therefore, it has been found that the use of the polymer emulsion together can ensure working time and good quick setting. When calcium aluminate and gypsum as shown above were used and a polymer emulsion was applied, the retardation action was hardly exhibited, and it was found that the effect was unique to alumina cement.
The alumina cement of the present invention may be used in combination with, for example, Alumina Cement No. 2 and fondue having a higher iron content than the alumina cement of the present invention. Furthermore, a high-purity alumina cement in which components other than aluminum and calcium are reduced as much as possible can be used in combination.
The amount of the alumina cement used in the present invention is preferably 2 to 20 parts, more preferably 5 to 15 parts, relative to 100 parts of Portland cement. If it is less than 2 parts, it is difficult to improve the setting property when the liquid quick-setting agent is added, and if it exceeds 20 parts, it may be difficult to maintain the fluidity of the concrete.

The polymer emulsion of the present invention has a function of suppressing the hydration activity of the alumina cement, and unlike a general retarder such as an oxycarboxylic acid, when a liquid accelerator mainly composed of aluminum sulfate is mixed. The delaying action disappears instantaneously, and it has the characteristic of exhibiting a rapid setting effect. In addition, it is possible to suppress the conversion of the hardened alumina cement in an environment of 35 ° C. or higher.
As the type of polymer emulsion, for example, a cement-mixing polymer (polymer dispersion) defined in JIS A 6203 can be used, and rubber latex such as acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, and natural rubber. , Ethylene / vinyl acetate copolymer, vinyl acetate vinyl versatate copolymer, polyacrylate homopolymer, acrylate ester / vinyl acetate vinyl versatate copolymer, and styrene / acrylate copolymer And acrylic acid ester copolymers typified by acrylonitrile / acrylic acid esters, epoxy resins, liquid polymers typified by unsaturated polyester resins, and the like, and one or more of these can be used. From the viewpoint of initial strength development when a liquid accelerator is added, it is preferable to use an acrylic ester copolymer.
The polymer emulsion of the present invention may be liquid or powdered.
The amount of the polymer emulsion of the present invention to be used is preferably 0.5 to 20 parts, more preferably 2 to 15 parts by solid content with respect to 100 parts of alumina cement. If it is less than 0.5 part, it may be difficult to maintain fluidity, and if it exceeds 20 parts, the coagulability when a liquid quick-setting agent is added may not be improved.

The fly ash of the present invention is a powder mainly composed of spherical particles obtained by cooling the ash melted when pulverized coal is burned at a coal-fired power plant, and is a by-product collected by an electric dust collector or the like. is there. Since fly ash varies in quality, the quality specified in JIS A 6201 is preferred, and the quality equivalent to or higher than the Class II equivalent is more preferred. By applying fly ash to the concrete of the present invention, it is possible to improve the adhesion and long-term strength development of the concrete when sprayed.
The amount of fly ash used is preferably 2 to 30 parts, more preferably 5 to 20 parts, per 100 parts of Portland cement. If the amount of fly ash used is small, the effect of fly ash may not be exhibited. If the amount of fly ash used is excessive, fluidity retention may be reduced.

The liquid quick-setting agent based on aluminum sulfate of the present invention is a component that accelerates the setting of Portland cement or alumina cement, and commercially available ones can be used. For example, liquid aluminum sulfate commercially available as a water flocculant, or powdered aluminum sulfate (anhydrous salt or hydrated salt) dissolved or slurried in any concentration can be used.
When a liquid accelerator containing aluminum sulfate as a main component is added to concrete in which the hydration activity of the alumina cement is suppressed by the polymer emulsion, the emulsion particles adsorbed on the surface of the alumina cement particles are rapidly agglomerated to form water. It is thought that a rapid condensing action is exhibited due to an increase in contact area. This is an action that cannot be seen when a retarder such as oxycarboxylic acids or other inorganic salts (phosphates, silicofluorides) having a retarding effect is used in combination.

The fluorine and lithium of the present invention are compounds containing fluorine and lithium, and exhibit an action of further improving the initial cohesive force when used in combination with aluminum sulfate.

The compound containing a fluorine atom of the present invention is not particularly limited as long as it is a compound that dissolves or disperses in water. Fluoride, silicofluoride, boron fluoride, organic fluorine, and hydrogen fluoride Fluorine compounds such as acids can be mentioned, and one or more of these can be used.
Examples of the fluoride salt include lithium fluoride, sodium fluoride, potassium fluoride, calcium fluoride, aluminum fluoride, and cryolite. Cryolite can be either natural or synthetic. Examples of the silicofluoride include ammonium silicofluoride, sodium silicofluoride, potassium silicofluoride, and magnesium silicofluoride. Boron fluoride salts include boron fluoride, boron trifluoride, boron trifluoride monoethylamine complex, boron trifluoride acetic acid complex, and boron trifluoride triethanolamine, ammonium borofluoride, sodium borofluoride, borofluoride Examples thereof include potassium and ferrous borofluoride. In the present invention, a fluoride salt is preferred from the viewpoints of high safety, low production cost, and excellent coagulation properties.
The amount of the compound containing a fluorine atom is preferably 2 to 20 parts with respect to 100 parts of aluminum sulfate. If it is less than 2 parts, the elongation of condensation cannot be expected and adhesion under spring water may be bad, and if it exceeds 20 parts, condensation may be inhibited and adhesion may be poor.

The lithium-containing compound of the present invention is a compound that dissolves or disperses in water, and nitric acid, organic acid, sulfuric acid, phosphoric acid, boric acid, silicic acid, carbonic acid, bicarbonate, aluminate, halogen (fluorine, chlorine, Bromine, iodine), and lithium salts of hydroxides. Among these, it is preferable to use lithium sulfate or lithium nitrate that exhibits high activity against the hydration of alumina cement.
0.5-20 parts is preferable with respect to 100 parts of aluminum sulfate, and, as for the usage-amount of the compound containing lithium, 2-15 parts is more preferable.

The solid content of the liquid accelerator mainly composed of aluminum sulfate of the present invention is preferably 22 to 40%. If it is less than 22%, it may be difficult to obtain a sufficient coagulation force. If it exceeds 40%, precipitates are generated due to temperature changes, and storage stability may be deteriorated.
The use amount of the liquid quick-setting agent of the present invention is preferably 0.5 to 8 parts, more preferably 1 to 6 parts in solid content with respect to 100 parts of cement. If it is less than 0.5 part, it may be difficult to give sufficient setting force, and if it exceeds 8 parts, the water-cement ratio will increase too much, inhibiting the toughness immediately after addition of the liquid quick-setting agent and long-term strength. May decrease too much.

The cement concrete of the present invention is not particularly limited as long as spraying is possible. As a general composition, slump is about 10 cm, W / C = about 60%, s / a = about 60%, cement amount is about 360 kg / m ³ , and gravel has a maximum dimension of 13 mm in many cases. In the strength type, the slump is about 20 cm, the slump flow is about 25 to 35 cm, W / C = about 40-50%, s / a = about 60%, the cement amount is about 400-500 kg / m ³ , and the maximum gravel dimension is 13 mm. It is often done.
The aggregate used in the present invention is not particularly limited, and any commercially available aggregate can be used, and there is no problem as long as it does not hinder spray construction.

  In the present invention, a water reducing agent, an AE water reducing agent, a high performance water reducing agent, a high performance AE water reducing agent, cellulose ethers, polyacrylamides, polyethylene, as long as the performance of sprayed construction and hardened shotcrete is not hindered. Thickeners such as oxides, polysaccharides, antifoaming agents, rust preventives, antifreeze agents, shrinkage reducing agents, polymer flocculants, vinylon fibers, steel fibers, fibers represented by polypropylene fibers, bentonite, etc. Various additives such as clay minerals and anion exchangers such as hydrotalcite, blast furnace slow-cooled slag, inorganic powders such as γ-type dicalcium silicate, gypsums such as anhydrous gypsum, ni water gypsum, half water gypsum, alumina cement It is possible to use together 1 type, or 2 or more types in the group which consists of calcium aluminates other than.

  The spraying method of the present invention is not particularly limited, but a wet spraying method in which a rapid setting agent is combined and sprayed into cement concrete mixed by adding water that is pumped and mixed, or concrete in a dry state. It is possible to use a dry spraying method in which the liquid quick setting agent is combined and sprayed before being pumped and before the nozzle.

  When using the wet spray method, for example, Portland cement, aggregates, alumina cement, and polymer emulsion are lightened by a predetermined amount in a kneading plant, kneaded with a mixer, and the mixed concrete is sprayed to an agitator truck. Carry. In addition, there is a method in which concrete mixed with a piston-type or air-conveying-type concrete pump is transported, and the liquid quick-setting agent is merged and mixed with the concrete from a liquid quick-setting agent insertion tube provided in front of the nozzle.

In the case of construction by the dry spray method, for example, a predetermined amount of Portland cement, aggregate, alumina cement, and polymer emulsion (using powder emulsion) are weighed and mixed with a mixer without adding water. In that case, the amount of generated dust can also be suppressed by adding about 0.5 to 2% of water or a dust reducing agent. The mixed dry concrete is transported to the spraying point by an agitator truck. The obtained dry concrete may be air-conveyed with an air-conveying pump, and the liquid quick-setting agent may be merged and mixed with the dry concrete from a liquid quick-setting agent insertion tube provided in front of the nozzle.
The transportation of the liquid quick-setting agent is not particularly limited, but it is preferable to use a plunger-type liquid pump for both methods and add it to the concrete together with compressed air.

"Experiment 1"
Portland cement such 400 kg / ^{m 3,} fine aggregates 1,058kg / ^{m 3,} coarse aggregate 710 kg / ^{m 3,} water 200 kg / ^{m 3,} 5 parts of the polymer emulsion against portland cement component 100 parts table alumina cement In addition to the above, 4 kg / m ³ of a high-performance water reducing agent was further added to prepare cement concrete. The cement concrete was pumped by a concrete pump “MKW-25SMT” under a spraying pressure of 0.4 MPa and a spraying speed of 10 m ³ / h. The liquid quick-setting agent misted with compressed air of 5 m ³ / min was mixed and sprayed with concrete fed by a merging pipe connected to a position 0.6 m from the nozzle tip. The liquid quenching agent was added at a solid content of 3 parts with respect to 100 parts of Portland cement.
Adhesion and concrete compressive strength were measured for the slump of cement concrete before adding the liquid quick-setting agent and the sprayed cement concrete. The results are shown in Table 1. Experiments Nos. 1-19 to 1-21 are the results of evaluation by adding 0.1 part of sodium citrate, which is a general retarder, to 100 parts of Portland cement instead of the polymer emulsion.

(Materials used)
High-performance water reducing agent: polycarboxylic acid, commercially available coarse aggregate: Himekawa Sakegawa gravel, Itoigawa City, Niigata Prefecture, surface dry state, specific gravity 2.66, maximum dimension 13mm
Fine Aggregate: River sand from Himekawa, Itoigawa City, Niigata Prefecture, surface dry condition, specific gravity 2.62
Portland cements: ordinary Portland cement, commercially available alumina cement: CaO: 54.4%, Al ₂ O ₃ : 36.2%, Fe ₂ O ₃ : 1.1%, Blaine specific surface area: 4900 cm ² / g, commercially available goods _C 12 _{a 7} of amorphous calcium aluminate and anhydrous gypsum which corresponds to the composition 1: 1 _{mixture: C} 12 _{a 7} Blaine specific surface area of 5800cm ² / g of the amorphous calcium aluminate corresponding to the composition, anhydrous gypsum Blaine specific surface area of 5300 cm ² / g
Polymer emulsion a: Acrylic ester-vinyl acetate-vinyl versatic acid copolymer (re-emulsified powder polymer), commercial product polymer emulsion b: Styrene-butadiene latex (liquid dispersion), solid content 45%, commercial product Liquid accelerating agent A: aluminum sulfate aqueous solution, solid content 26.8%, commercially available product

(Measuring method)
Slump: Measured according to JIS A 1101. The measurement was performed immediately after kneading and after 60 minutes.
Adhesiveness: If spray concrete is sprayed on the ceiling surface while repeatedly moving the spray nozzle in the range of 1 m, it will be ○ if it can be sprayed with a thickness of 15 cm or more, and it will drop off during spraying or if it cannot be sprayed with a thickness of 15 cm or more Is x.
Concrete compressive strength: The compressive strength of 1 hour and 24 hours of age is to cover the pin placed on the pullout formwork with 25cm width x 25cm length with the quick setting sprayed concrete from the surface of the pullout formwork. The pin was pulled out from the back side, the pulling strength at that time was determined, and the compressive strength was calculated from the formula of (compressive strength) = (pullout strength) × 4 / (test specimen contact area). The compressive strength at the age of 28 days was obtained by spraying quick setting sprayed concrete on a mold of width 50 cm x length 50 cm x thickness 20 cm, and a specimen 5 cm in diameter x 10 cm in length taken with a core drill one day later. The compressive strength was determined by measuring with a 20-ton pressure machine. Curing up to the measurement was water curing at 20 ° C.

"Experimental example 2"
The test was conducted in the same manner as in Experimental Example 1, except that 10 parts of alumina cement was added to 100 parts of Portland cement, and polymer emulsion a was added to 100 parts of alumina cement as shown in the table. The results are shown in Table 2.

"Experiment 3"
Except for 100 parts of Portland cement, 10 parts of alumina cement, 5 parts of polymer emulsion a with respect to 100 parts of alumina cement, and the same procedure as in Experimental Example 1 except that the liquid quick-setting agent was added as shown in the table. It was. The results are shown in Table 3.

(Materials used)
Liquid accelerating agent B: Aqueous solution liquid accelerating agent C dissolved in aluminum sulfate solid content 25%, sodium fluoride solid content 3% C: aluminum sulfate solid content 25%, lithium sulfate solid content 3% Dissolved aqueous solution quick setting agent D: Aqueous solution dissolved so that the solid content of aluminum sulfate is 25%, the solid content of sodium fluoride is 2%, and the solid content of lithium sulfate is 2%

"Experimental example 4"
Cement concrete was prepared by adding 10 parts of alumina cement to 100 parts of Portland cement, 5 parts of polymer emulsion a with respect to 100 parts of alumina cement, and adding fly ash as shown in the table. The same procedure as in Experimental Example 1 was performed except that 3 parts of a liquid quick-setting agent was added to 100 parts of cement. The results are shown in Table 4.

(Materials used)
Fly Ash: Tohoku Electric Power Industry Co., Ltd. Fly Ash JIS II

  By using the spray material of the present invention and the spray method using the same, it is possible to produce spray concrete with low slump loss even when alumina cement having high hydration activity is contained in cement concrete, and the main component is aluminum sulfate. Unlike when using a general retarder when mixing a liquid quick-set agent, the hydration activity is drastically improved, resulting in low dusting, low rebound, and low alkali stimulation to the human body. Can be realized. Furthermore, since it is possible to provide a spraying material with excellent setting properties without using concrete containing an excessive amount of cement, it is economical and can be widely used as an environment-friendly spraying work in the civil engineering and construction fields.

Claims (5)

Al ₂ O ₃ is 50 to 60% by mass, CaO is 33 to 40% by mass, Fe ₂ O ₃ is 2.0% by mass or less, and Blaine specific surface area is 4000 cm ² / g or more with respect to 100 parts by mass of Portland cements. 2-20 parts by weight of alumina cement, cement concrete containing 0.5-20 parts by weight of a polymer emulsion in solid content with respect to 100 parts by weight of the alumina cement, and a liquid setting agent containing aluminum sulfate Become spray material. Furthermore, cement concrete contains fly ash, The spraying material of Claim 1 characterized by the above-mentioned. The spray material according to claim 1 or 2, wherein the polymer emulsion is an acrylate emulsion. Furthermore, a liquid quick-setting agent contains a fluorine and / or lithium, The spraying material of any one of Claims 1-3 characterized by the above-mentioned. The spraying construction method using the spraying material of any one of Claims 1-4.