Foamed quick-setting agent, sprayed concrete composition, sprayed concrete, and spraying method

Abstract

To provide an expandable accelerator capable of preventing acceleration inhibition of an accelerator caused by precipitation of natroalunite, and of exhibiting excellent workability, a spray concrete composition, sprayed concrete, and a spray construction method.SOLUTION: The expandable accelerator to be blended in a spray concrete composition containing cement concrete and polyethylene oxide of a mass average molecular weight of 100000 to 3000000, includes a liquid accelerator including aluminum, sulfur and sodium, with the natroalunite content therein being 0.3 to 3 mass% and the pH thereof being 1 to 4, and a powdery auxiliary containing an alkali carbonate.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a foaming quick-setting admixture, a sprayed concrete composition, a sprayed concrete, and a spraying method. [Background technology]

[0002] Conventionally, silicates, aluminates, chlorides, etc. have been known to be effective for reducing rebound in shotcrete, filling voids underground or behind tunnels, and instantly eliminating fluidity in areas where water is present or cracks exist, thereby preventing leakage, etc. However, most of these are highly alkaline liquid quick-setting admixtures, which pose problems in terms of handling and practical operation.

[0003] Therefore, various non-alkaline liquid quick-setting admixtures have been investigated. For example, Patent Document 1 proposes a cement quick-setting admixture containing a soluble aluminum salt and a fluoride, which exhibits good quick-setting properties and strength development, and realizes sufficient workability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-261393 Summary of the Invention [Problem to be solved by the invention]

[0005] However, liquid quick-setting admixtures generally produce precipitates depending on the storage temperature. Among these precipitates, insoluble ones (insoluble precipitates) cannot be redissolved, so if they are added to concrete or other materials as is, the quick-setting admixture's effectiveness is reduced, which can cause problems during construction. In Patent Document 1, insoluble precipitates (insoluble precipitates) as described above may occur after storage for a certain period of time, and these precipitates must be removed before application, which is one factor that reduces workability.

[0006] In light of these problems, the present inventors conducted various investigations and studies on the insoluble precipitates, and first discovered that the insoluble precipitates were natroalunite (sodium alum). They then newly discovered that the precipitated natroalunite inhibited the quick-setting of the accelerator-setting admixture, thereby reducing the workability when the accelerator-setting admixture was used.

[0007] In light of the above, an object of the present invention is to provide a foamed quick-setting admixture, a sprayed concrete composition, a sprayed concrete, and a spraying method that can prevent inhibition of quick-setting of the quick-setting admixture due to precipitation of sodium alunite and exhibit good workability. Another object of the present invention is to reduce the dust of the sprayed concrete from the viewpoint of the working environment. [Means for solving the problem]

[0008] As a result of various investigations aimed at solving the above-mentioned problems, the present inventors have found that the problems can be solved by controlling the amount of natroalunite precipitated in a liquid quick-setting admixture of a specific composition to a predetermined value or less.

[0009] [1] A foamed quick-setting agent to be mixed with a sprayed concrete composition containing cement concrete and polyethylene oxide having a mass average molecular weight of 100,000 to 3,000,000, the foamed quick-setting agent containing aluminum, sulfur, and sodium, a sodium alunite content of 0.3 to 3 mass% or less, and a pH of 1 to 4, and a powder auxiliary containing alkali carbonate. [2] The foamed quick-setting admixture according to [1], which contains the liquid quick-setting admixture, and after storing the liquid quick-setting admixture at 0 to 40°C for 48 hours, the content of the natroalunite is 0.3 to 3 mass% or less. [3] The foamable quick-setting admixture according to [1] or [2], wherein the natroalunite is derived from cryolite and / or sodium sulfate. [4] The foamable quick-setting admixture according to any one of [1] to [3], wherein the aluminum in the liquid quick-setting admixture is 1 to 20 parts by mass in terms of Al2O3, the sulfur is 10 to 30 parts by mass in terms of SO3, and the sodium is 0.1 to 3 parts by mass in terms of Na2O. [5] The foamed quick-setting admixture according to any one of [1] to [4], wherein the solid content concentration in the liquid quick-setting admixture is 20 to 50 mass %. [6] The foamed quick-setting admixture according to any one of [1] to [5], wherein the viscosity of the liquid quick-setting admixture at 20°C is 1,000 mPa·s or less. [7] The foamable quick-setting admixture according to any one of [1] to [6], wherein the liquid quick-setting admixture has a mass ratio (Al2O3 / SO3) of aluminum in terms of Al2O3 to sulfur in terms of SO3 of 0.3 to 0.7. [8] A sprayed concrete composition comprising the foamable quick-setting admixture according to any one of [1] to [7], cement concrete, and polyethylene oxide having a mass average molecular weight of 100,000 to 3,000,000. [9] The sprayed concrete composition according to [8], wherein the cement concrete and the polyethylene oxide are mixed in advance.

[10] A sprayed concrete composition according to [8] or [9], which is obtained by mixing the foamed quick-setting admixture with the cement concrete containing the polyethylene oxide.

[11] Shotcrete obtained by spraying the shotcrete composition according to any one of [8] to

[10] .

[12] A spraying method, which comprises spraying the sprayed concrete composition according to any one of [8] to

[10] . [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a foamed quick-setting admixture, a sprayed concrete composition, a sprayed concrete, and a spraying method that can prevent inhibition of quick-setting of the quick-setting admixture due to precipitation of sodium alunite and exhibit good workability. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. In this specification, "parts" and "%" are based on mass unless otherwise specified.

[0012] [Sprayed concrete composition and shotcrete] The shotcrete composition according to an embodiment (present embodiment) of the present invention and the shotcrete obtained by hardening the same contain a foaming quick-setting admixture, cement concrete, and polyethylene oxide. Hereinafter, embodiments of the shotcrete composition of the present invention, the liquid quick-setting admixture used in the shotcrete, the cement concrete, and the polyethylene oxide will be described.

[0013] [Foam-type quick-setting agent] The foamed quick-setting admixture according to the embodiment of the present invention (the present embodiment) is mainly composed of a liquid quick-setting admixture, and is used in combination with a powdery aid by mixing it therewith.

[0014] The content of the foaming quick-setting admixture contained in the shotcrete composition according to this embodiment is preferably 1 to 20 parts by mass, more preferably 4 to 14 parts by mass, per 100 parts by mass of cement in the cement concrete. When the content of the foaming quick-setting admixture is within the above range, a good quick-setting effect is exhibited, good early strength development can be achieved, low dust properties can be achieved, and low-rebound spraying can be made possible.

[0015] <Liquid quick-setting agent> The liquid quick-setting admixture according to the embodiment of the present invention contains aluminum, sulfur, and sodium, which can improve quick-setting properties and strength development.

[0016] Furthermore, the liquid quick-setting admixture according to this embodiment has a natroalunite content of 3% by mass or less. If the natroalunite content exceeds 3% by mass, the quick-setting properties that the liquid quick-setting admixture can exhibit in low-dust sprayed concrete are hindered, making it difficult to exhibit good workability. The natroalunite content is preferably 2.5% by mass or less, and more preferably 2% by mass or less. Although it is preferable that natroalunite is absent, since it is produced by thermal hydrolysis, in practice it may be present at about 0.3% by mass.

[0017] The natroalunite content preferably reaches 3% by mass or less at least after 48 hours of storage at 0 to 40°C immediately after preparation of the liquid quick-setting admixture. If the natroalunite content is 3% by mass or less at this point, inhibition of rapid hardening by natroalunite is suppressed during subsequent storage at 0 to 40°C. Note that "0 to 40°C" is the assumed temperature range during actual use of the liquid quick-setting admixture. The natroalunite content can be measured by the method described in the Examples.

[0018] Here, natroalunaite is also called soda-alumite, and is (NaAl3(SO4)2(OH)6, (Na,K)Al3(SO4)2(OH)6, or [Na + ][Al 3+ ][Al 3+ 2][(OH)6|(SO4)2] 10- According to the inventors, natroalunite is mainly derived from the raw material cryolite, and in particular, thiolite (Na5Al3F 14 It has been found that natroalunite is derived from sodium sulfate, which is a raw material, and since increasing the sodium sulfate content leads to a larger amount of precipitation in the liquid quick-setting admixture, the amount of sodium sulfate is preferably 0.5 parts by mass or more but less than 7 parts by mass, and more preferably 1 part by mass or more but less than 6 parts by mass. Therefore, in order to make the natroalunite content in the liquid quick-setting admixture 3% by mass or less, it is sufficient to carry out a treatment such as reducing the amounts of thiolite and elpasolite in the cryolite. Also, the temperature conditions when preparing the liquid quick-setting admixture may be adjusted as described below.

[0019] The liquid quick-setting admixture according to this embodiment is acidic with a pH of 1 to 4. Because the liquid quick-setting admixture is acidic, it is easier to handle than alkaline hardening accelerators.

[0020] The contents of aluminum, sulfur, and sodium in the liquid quick-setting admixture are not particularly limited, but from the viewpoint of rapid hardening, it is preferable that the aluminum content be 1 to 20 parts by mass in terms of Al2O3, the sulfur content be 10 to 30 parts by mass in terms of SO3, and the sodium content be 0.1 to 3 parts by mass in terms of Na2O. It is more preferable that the aluminum content be 5 to 10 parts by mass in terms of Al2O3. It is more preferable that the sulfur content be 12 to 25 parts by mass in terms of SO3. It is more preferable that the sodium content be 0.1 to 2 parts by mass in terms of Na2O.

[0021] Furthermore, from the viewpoint of the storage stability of the liquid quick-setting admixture and its mixability when added to paste, mortar, or concrete, the mass ratio of aluminum in terms of Al2O3 to sulfur in terms of SO3 (Al2O3 / SO3) is preferably 0.3 to 0.7, and more preferably 0.4 to 0.6.

[0022] The solids concentration of the liquid quick-setting admixture according to this embodiment is preferably 20 to 50 mass %, and more preferably 25 to 45 mass %, from the viewpoints of the storage stability of the liquid quick-setting admixture and the mixability when added to paste, mortar, or concrete.

[0023] Furthermore, the viscosity of the liquid quick-setting admixture according to this embodiment at 20°C is preferably 1,000 mPa·s or less, more preferably 1 to 900 mPa·s. A viscosity of 1,000 mPa·s or less improves mixability and provides stable physical properties. The viscosity can be measured by the method described in the examples.

[0024] The liquid quick-setting admixture according to this embodiment can be produced by mixing raw materials such as aluminum sulfate, various alums, aluminum hydroxide, sodium hydroxide, sulfuric acid, natural or synthetic cryolite, sodium fluoride, and aluminum fluoride in a liquid and heating at 80 to 95°C for 30 to 120 minutes. From the viewpoint of good productivity, it is preferable to use sulfuric acid, aluminum hydroxide, aluminum sulfate, or various alums and natural or synthetic cryolite as the raw materials. It is also preferable to use water or the like as the liquid.

[0025] Here, when cryolite is used as a raw material for preparing the liquid quick-setting admixture according to this embodiment, insoluble precipitates are likely to be generated. In particular, it is presumed that the thiolite and elpasolite contained in the cryolite contribute to the generation of insoluble precipitates. It has also been found that the generation of insoluble precipitates can be suppressed by carrying out a specific operation when preparing the hardening accelerator. Taking either of these factors into consideration, it is preferable to carry out, for example, the following operation (1) or (2) in order to make the natroalunite content in the liquid quick-setting admixture 0.3 to 3 mass%.

[0026] (1) When using cryolite as the raw material, the amount of thiolite and elpasolite contained in the cryolite is 3% by mass or less. (2) After heating at 80 to 95°C as described above, the mixture is rapidly cooled to room temperature (for example, 25°C) within 60 minutes.

[0027] The liquid quick-setting admixture prepared in the above manner is suitable for use in low-dust sprayed concrete, as will be described later.

[0028] <Powder Auxiliary Agent> The amount of powder aid used according to the embodiment of the present invention is preferably 10 to 400 parts by mass, more preferably 40 to 140 parts by mass, relative to 100 parts by mass of the liquid quick-setting admixture. By setting the amount of powder aid used within the above range, good low dust properties can be achieved and low rebound spraying can be achieved.

[0029] The powder aid according to this embodiment contains an alkali carbonate. The alkali carbonate refers to an alkali metal carbonate salt, which can significantly improve the setting properties and early strength development of a powdered quick-setting admixture. The alkali carbonate is not particularly limited, but examples include lithium carbonate, sodium carbonate, sodium sesquicarbonate, potassium carbonate, sodium bicarbonate, and sodium bicarbonate. Sodium carbonate, potassium carbonate, sodium sesquicarbonate, sodium bicarbonate, and sodium bicarbonate are particularly effective in setting properties and early strength development, and one or more of these can be used in combination. Preferably, at least one selected from the group consisting of sodium carbonate, sodium sesquicarbonate, sodium bicarbonate, and potassium carbonate is used.

[0030] The content of the alkali carbonate is preferably 0.3 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the powder auxiliary. When the content of the alkali carbonate is equal to or greater than the lower limit, it is easy to obtain an effect of improving setting and early strength. Furthermore, when the content of the alkali carbonate is equal to or less than the upper limit, it is possible to ensure good quick-setting properties.

[0031] The average particle size (D50) of the alkali carbonate is preferably 10 to 100 μm, more preferably 20 to 50 μm. If the average particle size (D50) of the alkali carbonate is 100 μm or more, the effects of promoting setting and enhancing strength development may not be obtained, and if it is 10 μm or less, storage stability may decrease. Here, in this specification, the average particle size (D50) can be determined as the median diameter D50 (volume basis) using a laser diffraction / scattering particle size distribution measuring device.

[0032] [Cement concrete] The cement concrete according to the embodiment of the present invention is blended with polyethylene oxide. Here, cement concrete is a general term for cement paste, cement mortar, and concrete.

[0033] The cement for cement concrete is not particularly limited, and examples include various types of Portland cement: normal, high-early-strength, ultra-high-early-strength, medium-heat, and low-heat; filler cements made by mixing these Portland cements with blast furnace slag, fly ash, and limestone powder; and environmentally friendly cements (eco-cements) made from municipal waste incineration ash and sewage sludge incineration ash. These can also be used in finely powdered form. There are no particular limitations on the ratio of admixture to cement in blended cement, and it is also possible to use blends containing more of these admixtures than are specified in the JIS.

[0034] The cement concrete of this embodiment contains cement and aggregate, and the aggregate preferably has low water absorption and high aggregate strength. The aggregate is not particularly limited as long as it can be sprayed, but examples of fine aggregate that can be used include river sand, mountain sand, sea sand, lime sand, and silica sand, and examples of coarse aggregate that can be used include river gravel, mountain gravel, and lime gravel, and crushed sand and crushed stone can also be used.

[0035] [Polyethylene oxide] The polyethylene oxide according to this embodiment is blended into a shotcrete composition as a dust-reducing component. If the mass-average molecular weight of polyethylene oxide is high, the viscosity of concrete increases and the mixability with the accelerator tends to deteriorate, resulting in a decrease in dust-reducing performance. If the mass-average molecular weight is low, the polyethylene oxide is unable to affect the viscosity of concrete and therefore decreases dust-reducing performance. Therefore, in the present invention, the mass-average molecular weight of polyethylene oxide is preferably 100,000 to 3,000,000, more preferably 300,000 to 2,500,000, and even more preferably 500,000 to 2,000,000. The mass average molecular weight of polyethylene oxide can be determined by gel permeation chromatography (GPC) under the following measurement conditions. <Measurement conditions> Device: Product name "LC-10AD" (Shimadzu Corporation) Detector: Refractive index detector (RID) Column: Product name "SHODEX KF-804" (Showa Denko K.K.) ·Measurement temperature: 30℃ ·Eluent:THF ·Flow rate: 1.0mL / min Sample concentration: 0.2% by mass (THF) Sample injection volume: 100 μL Conversion standard: Polyethylene oxide

[0036] The content of polyethylene oxide according to the present embodiment as described above is, for example, preferably 0.02 to 0.4 parts by mass, more preferably 0.05 to 0.3 parts by mass, and even more preferably 0.05 to 0.3 parts by mass, relative to 100 parts by mass of water used in cement concrete. When the content of polyethylene oxide is equal to or greater than the above-mentioned lower limit, dust reduction performance is easily achieved. Furthermore, when the content of polyethylene oxide is equal to or less than the above-mentioned upper limit, miscibility with the liquid quick-setting admixture is improved, the initial adhesion properties are good, and rebound can be suppressed. By using the liquid quick-setting admixture of the present invention in combination, thick spraying and spraying under spring water, which have been issues with previous liquid quick-setting admixtures, become possible.

[0037] The sprayed concrete composition and sprayed concrete of the present invention can be made using bentonite, stone powder, and various cement admixtures and cement admixtures in addition to liquid quick-setting admixtures, cement concrete, and polyethylene oxide. In particular, when constructing in places where water is present, such as underground or behind a tunnel, or where leakage into cracks must be prevented, the combined use of fine powders such as bentonite and stone powder, and underwater anti-segregation admixtures is effective in improving underwater anti-segregation resistance.

[0038] The foamed quick-setting agent of the present invention is also effective in producing quick-setting aerated mortar. Typically, the quick-setting action of the accelerator is faster than necessary, e.g., instantaneously, causing the bubbles in the aerated mortar to break while the accelerator is being added and mixed, making it difficult to achieve the desired physical properties, such as specific gravity and strength. The foamed quick-setting agent of the present invention has a setting time of several seconds to several tens of seconds, allowing for the production of quick-setting aerated mortar without breaking the bubbles, making it fully applicable for construction and exhibiting excellent quick-setting properties after setting. This prevents the previously considered drawbacks of aerated mortar, such as leakage into cracks and separation of materials when poured in areas where water is present.

[0039] The water used in cement concrete is not particularly limited, and the amount of water used is also not particularly limited, but usually, 40 to 150 parts by mass per 100 parts by mass of cement is preferred. If the amount is 40 to 150 parts by mass, good fluidity and strength development are likely to be exhibited.

[0040] In the present invention, when a foamed quick-setting agent, which is a mixture of a liquid quick-setting agent and a powder aid, is mixed with cement concrete kneaded with water, the fluidity may be lost within a few seconds after mixing. Therefore, when a long pumping distance is required or when workability is a consideration, it is preferable to feed the foamed quick-setting agent and the cement concrete kneaded with water separately and then mix them together at the tip of the delivery pipe during construction.

[0041] In the present invention, the method for mixing the foamable quick-setting admixture, cement concrete, and polyethylene oxide to prepare a concrete composition is not particularly limited, and examples include a method of mixing and joining the foamable quick-setting admixture and the cement concrete containing polyethylene oxide. Specific mixing and joining methods include, for example, a method using a mixing pipe such as a Y-shaped pipe, a method using a double pipe, and a method using an inlet piece that mixes and joins the liquid quick-setting admixture in a shower-like manner. Further mixing can also be performed by installing a spiral mixer in the pipe after joining and mixing. If the liquid quick-setting admixture and cement concrete are mixed sufficiently, adhesion and plasticity are achieved, improving workability. However, if the mixing is insufficient, partial fluidity may occur, making complete construction difficult.

[0042] [Spraying construction method] The sprayed concrete composition according to this embodiment is mainly used in a spraying method, although simply pouring it into voids in the basement or behind a tunnel is sufficient for filling them. In the spraying method according to this embodiment, when spraying in areas where water is present or where leakage into cracks must be prevented, it is also effective to use compressed air to blow the sprayed concrete composition away. The point where the compressed air is introduced is not particularly limited, but it is preferable to introduce it into a mixing pipe. [Example]

[0043] The present invention will be explained in more detail below based on experimental examples, but the present invention is not limited to these examples.

[0044] (Examples 1 to 11) Aluminum sulfate, an aluminum source, a sulfur source, a fluorine source, and a sodium source were mixed with water so that the proportions of aluminum (calculated as Al2O3), sulfur (calculated as SO3), and sodium (calculated as Na2O) were as shown in Table 1, and the mixture was heated at 90°C for 60 minutes. After heating, the mixture was rapidly cooled to 25°C in 50 minutes using a circulating cooling device to produce a liquid quick-setting admixture as a hardening accelerator. The solids concentration and viscosity of the liquid quick-setting admixture at 20°C were measured as described below. The pH of the supernatant of the liquid quick-setting admixture was also measured using a pH meter. The results are shown in Table 1.

[0045] <Materials used> Water: Tap water Aluminum sulfate: aluminum sulfate powder, reagent (aluminum source, sulfur source) Cryolite: Reagent (sodium source, fluorine source), Chiolite: 2%, Elpasolite: 0.5% (measured by XRD) Sodium sulfate: Reagent, anhydrous, (sodium source)

[0046] <Measurement method> Solid content: The total amount of SO3, Al2O3, Na2O, and F from the raw materials was calculated. Viscosity (20°C): Measured using a B rotational viscometer.

[0047] 50 g of the liquid quick-setting admixture was stored at 20°C for 48 hours. After that, the amount of natroalunite precipitated was measured as follows. The results are shown in Table 1.

[0048] <Measurement method> Natroalunite content 50g of the stored liquid quick-setting admixture was poured into a glass filter, suction filtered, and then dried in a vacuum desiccator for 24 hours. The sample was then subjected to X-ray diffraction measurement. The peak intensity of the natroalunite alone was compared with the peak intensity of the natroalunite sample, and the content was calculated.

[0049] Next, the liquid quick-setting admixture was mixed with a powdered auxiliary containing alkali carbonate in the proportions shown in Table 1 to form a foamed quick-setting admixture.

[0050] <Materials used> Alkaline carbonate: sodium carbonate, average particle size 30 μm, commercially available

[0051] Next, 100 parts by mass of cement, 50 parts by mass of water, 200 parts by mass of sand, and 0.15 parts by mass of polyethylene oxide per 100 parts by mass of water were mixed in a mixer to produce cement mortar milk. The produced cement mortar milk and the foamed quick-setting admixture were separately fed into a mixing pipe, and the mixture was continuously mixed in a non-driven line mixer so that the liquid quick-setting admixture was 10 parts by mass per 100 parts of cement, thereby producing quick-setting mortar, which is quick-setting cement concrete. The quick-setting mortar was subjected to a setting test as described below to evaluate its quick-setting properties and mixability. The results are shown in Table 1.

[0052] <Materials used> Cement: Commercially available ordinary Portland cement (manufactured by Denka Co., Ltd., density 3.15 g / cm 3 ) Water: Tap water Sand: River sand from the Himekawa River system in Niigata Prefecture, density 2.61 g / cm 3 Polyethylene oxide: Mass average molecular weight 1.8 million, commercially available

[0053] <Evaluation method> -Evaluation of quick setting and mixability According to ASTM C403, a Proctor needle was inserted 10 times into the quick-setting mortar 2 minutes after adding the foaming accelerator. 2 Those who met all 10 criteria were given an "A," those who met 7 to 9 criteria were given a "B," those who met 4 to 6 criteria were given a "C," and those who met less than 4 criteria were given a "D."

[0054] Example 12 A liquid quick-setting admixture was produced under the same conditions as in Example 1, except that the amount of cryolite was reduced to two-thirds. The results are shown in Table 1.

[0055] Example 13 A liquid quick-setting admixture was produced under the same conditions as in Example 1, except that the amount of cryolite was reduced to one-third. The results are shown in Table 1.

[0056] Example 14 A liquid quick-setting admixture was produced under the same conditions as in Example 1, using one-sixth the amount of cryolite. The results are shown in Table 1.

[0057] (Comparative Example 1) In the same manner as in Example 1, aluminum sulfate, an aluminum source, a sulfur source, a fluorine source, and a sodium source were mixed with water and heated at 90°C for 60 minutes. After heating, the mixture was allowed to stand and cooled to 25°C over 240 minutes to produce a liquid quick-setting admixture. The solids concentration of the liquid quick-setting admixture and the viscosity of the liquid quick-setting admixture at 20°C were measured. The pH of the supernatant of the liquid quick-setting admixture was also measured using a pH meter. The results are shown in Table 1.

[0058] (Comparative Example 2) A liquid quick-setting admixture was produced under the same conditions as in Comparative Example 1, except that sodium sulfate was used instead of cryolite. The results are shown in Table 1.

[0059] (Comparative Example 3) A liquid quick-setting admixture was produced under the same conditions as in Comparative Example 1, except that the amount of cryolite was reduced to half and the amount of sodium sulfate was reduced to half. The results are shown in Table 1.

[0060] Comparative Example 4 A liquid quick-setting admixture was produced under the same conditions as in Comparative Example 1, except that the amount of cryolite was reduced to one-twentieth of that in Comparative Example 1. The results are shown in Table 1.

[0061] (Comparative Example 5) A liquid quick-setting admixture was produced under the same conditions as in Comparative Example 1, except that the amount of cryolite was reduced to 1 / 40 of that in Comparative Example 1. The results are shown in Table 1.

[0062] [Table 1] [Industrial Applicability]

[0063] The liquid quick-setting admixture of the present invention can be suitably used for cement concrete to be sprayed onto exposed natural ground surfaces such as tunnels for roads, railways, and waterways, and slopes.

Claims

1. A foaming quick-setting agent to be mixed with a shotcrete composition containing cement concrete and polyethylene oxide having a mass average molecular weight of 100,000 to 3,000,000, a liquid quick-setting admixture containing aluminum, sulfur, and sodium, with a natroalunite content of 0.3 to 3 mass%, and a pH of 1 to 4; and a powder aid containing an alkali carbonate; The aluminum in 100 parts by mass of the liquid quick-setting admixture is Al ２ O ３ and the sulfur is 1 to 20 parts by mass in terms of SO ３ 10 to 30 parts by mass in terms of sodium, ２ 0.1 to 3 parts by mass in terms of O, the content of the alkali carbonate is 0.3 to 20 parts by mass relative to 100 parts by mass of the powder auxiliary; According to ASTM C403, 100 parts by mass of ordinary Portland cement, 50 parts by mass of water, 200 parts by mass of sand, and 0.15 parts by mass of polyethylene oxide per 100 parts by mass of water were mixed in a mixer, and the foamy quick-setting agent was added to the cement mortar milk. Two minutes after the addition, a Proctor needle was inserted into the quick-setting mortar 10 times, and the initial value of 3.5 N / mm was obtained. ２ A foaming quick-setting agent that meets the above requirements at least seven times.

2. 2. The foamed quick-setting admixture according to claim 1, wherein the liquid quick-setting admixture contains 0.3 to 3 mass% of natroalunite after storage at 0 to 40°C for 48 hours immediately after preparation of the liquid quick-setting admixture.

3. The foamable quick-setting admixture according to claim 1 or 2, wherein the natroalunite is derived from cryolite and / or sodium sulfate.

4. The foamed quick-setting admixture according to any one of claims 1 to 3, wherein the solids concentration in the liquid quick-setting admixture is 20 to 50 mass%.

5. The foamed quick-setting admixture according to any one of claims 1 to 4, wherein the viscosity of the liquid quick-setting admixture at 20°C is 1,000 mPa·s or less.

6. The liquid quick-setting admixture is Al ２ O ３ Aluminum and SO in terms of ３ Mass ratio to sulfur (Al ２ O ３ / SO ３ 6. The foamable quick-setting admixture according to claim 1, wherein the value of (a) is 0.3 to 0.

7.

7. A sprayed concrete composition comprising the foamable quick-setting admixture according to any one of claims 1 to 6, cement concrete, and polyethylene oxide having a mass average molecular weight of 100,000 to 3,000,000.

8. A method for producing the sprayed concrete composition according to claim 7, mixing the polyethylene oxide into the cement concrete; and mixing the foaming quick-setting admixture with the cement concrete containing the polyethylene oxide.

9. 9. The method for producing a sprayed concrete composition according to claim 8, wherein in the step of blending the foamed quick-setting admixture with the cement concrete blended with the polyethylene oxide, the foamed quick-setting admixture and the cement concrete blended with the polyethylene oxide are mixed together.

10. A sprayed concrete obtained by spraying the sprayed concrete composition according to claim 7.

11. A spraying method comprising spraying the sprayed concrete composition according to claim 7.

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