Liquid quick-setting agent, shotcrete

Abstract

A liquid quick-setting agent that contains an aluminum component and a sulfur component and that is substantially free from fluorine components, the liquid quick-setting agent having a peak in the chemical shift range of more than -5.0 ppm and less than 0 ppm in a spectrum obtained by 27Al-NMR measured under the following conditions. (Conditions) Observation nucleus: 27Al. Sample tube rotation speed: 12 Hz. Measurement temperature: 25°C. Pulse width: 5 μsec (45° pulse). Waiting time: 5 seconds. External standard: aqueous aluminum chloride solution.

Description

[Technical Field]

[0001] The present invention relates to a liquid quick-setting admixture and a shotcrete containing the liquid quick-setting admixture. [Background technology]

[0002] Conventionally, to prevent the collapse of exposed ground such as in tunnel excavation, a method of spraying quick-setting concrete, in which an accelerator is mixed into the concrete, has been used. In this method, materials are measured and mixed in a measuring plant installed at the excavation site to prepare the shotcrete, which is then pumped out and mixed with accelerator pumped in from the other side of the confluence pipe, and sprayed onto the ground surface until it reaches a specified thickness.

[0003] The quick-setting admixtures used in the spraying method can be broadly classified into two types: powdered quick-setting admixtures whose main ingredients are calcium aluminate or alkali metal aluminate, and liquid quick-setting admixtures whose main ingredients are alkali metal aluminate or aluminum sulfate.

[0004] In recent years, from the perspective of ensuring the health of workers engaged in tunnel construction sites, etc., there has been a demand for the use of acidic liquid quick-setting admixtures whose main component is aluminum salt, which produce less dust when sprayed and are free from the risk of alkaline chemical burns.

[0005] On the other hand, liquid quick-setting admixtures have the problem of having lower quick-setting properties compared to powder quick-setting admixtures. To address this problem, measures have been taken to improve quick-setting properties by increasing the sulfate ion concentration, as shown in Patent Document 1, for example. However, when high-concentration liquid quick-setting admixtures are stored for long periods of time, precipitates may form in the liquid, the liquid may gel, or suspended particles may settle. The solubility of aluminum sulfate in water is 27% at 20°C, and this varies depending on the coexisting solutes and the liquid temperature. However, liquid quick-setting admixtures containing aluminum sulfate above the solubility limit have poor storage stability, making it difficult to maintain the properties they had immediately after production.

[0006] As a measure to improve strength, for example, liquid quick-setting admixtures have been proposed, such as those disclosed in Patent Document 2, which are composed of aluminum fluoride, an acidic or basic solution of aluminum containing aluminum hydrofluoric acid as a component, lithium silicate, and lithium aluminate.Also, as disclosed in Patent Document 3, liquid quick-setting admixtures have been developed which are composed of a fluoride-containing water-soluble aluminum salt obtained by the reaction of aluminum sulfate with hydrofluoric acid, aluminum hydroxide, and lithium hydroxide, lithium carbonate, lithium sulfate, etc. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-193388 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-130935 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-89276 Summary of the Invention [Problem to be solved by the invention]

[0008] While the above-mentioned technologies improve strength characteristics by adding fluorine compounds, measures to suppress fluorine elution have recently become necessary from the perspective of environmental conservation at construction sites. However, there has been a problem in that adding the above-mentioned compounds containing fluoride ions to liquid quick-setting admixtures raises concerns about fluorine elution from the hardened body.

[0009] In view of the above, an object of the present invention is to provide a liquid quick-setting admixture which has excellent quick-setting properties and storage stability, and which does not contain a fluorine component and therefore is free from the risk of fluorine elution. [Means for solving the problem]

[0010] As a result of extensive research conducted by the present inventors in light of the above-mentioned problems, they have discovered a novel fluorine-containing polymer composition containing an aluminum component and a sulfur component, and substantially no fluorine component, 27The inventors have found that a liquid quick-setting admixture having a peak at a specific chemical shift in an Al-NMR spectrum can solve the above problems, and have thus completed the present invention.

[0011] [1] A liquid quick-setting admixture containing an aluminum component and a sulfur component, and substantially no fluorine component, measured under the following conditions: 27 A liquid quick-setting admixture having a peak in the chemical shift range of more than -5.0 ppm and less than 0 ppm in the spectrum obtained by Al-NMR. (conditions) Observation kernel: 27 Al Sample tube rotation speed: 12Hz Measurement temperature: 25℃ Pulse width: 5 μsec (45° pulse) Wait time: 5 seconds External standard: Aluminum chloride aqueous solution [2] The liquid quick-setting admixture according to the above [1], wherein the half-width of the peak in the chemical shift range of more than -5.0 ppm and less than 0 ppm is 10.0 ppm or less. [3] The liquid quick-setting admixture according to [1] or [2] above, wherein the total alkali content R2O (R is an alkali metal) is 1.0 mass% or less. [4] The liquid quick-setting admixture according to any one of the above [1] to [3], which has a chloride ion concentration of 5.0 mass % or less. [5] Shotcrete obtained by using the liquid quick-setting admixture according to any one of [1] to [4] above in combination with a powder quick-setting admixture containing calcium aluminate as a main component. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a liquid quick-setting admixture which has excellent quick-setting properties and storage stability, and which does not contain a fluorine component and therefore is free from the risk of fluorine elution. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention (the present embodiment) will be described in detail, but the present invention is not limited to this embodiment. In this specification, "%" is based on mass unless otherwise specified.

[0014] [1. Liquid Accelerator] The liquid quick-setting admixture according to this embodiment contains an aluminum component and a sulfur component, and is substantially free of a fluorine component. The liquid quick-setting admixture is measured under the following conditions: 27 It is a liquid quick-setting admixture that has a peak in the chemical shift range of more than -5.0 ppm and less than 0 ppm in the spectrum obtained by Al-NMR. (conditions) Observation kernel: 27 Al Sample tube rotation speed: 12Hz Measurement temperature: 25℃ Pulse width: 5 μsec (45° pulse) Wait time: 5 seconds External standard: Aluminum chloride aqueous solution

[0015] The liquid quick-setting admixture is substantially free of fluorine components. Specifically, the fluoride ion concentration in the liquid quick-setting admixture is preferably less than 1.0 ppm. The lower limit is not limited, but may be 0 ppm. When the liquid quick-setting admixture is substantially free of fluorine components, it can be a liquid quick-setting admixture that is free from concerns about fluorine elution. The fluoride ion concentration in the liquid quick-setting admixture can be measured using a commercially available analyzer, for example, an ion chromatograph (ICS2100) manufactured by Thermo Scientific. The measurement can be performed by diluting the liquid in advance so that the fluoride ion concentration falls within the calibration curve.

[0016] Liquid quick-setting admixtures are 27 In a spectrum obtained by Al-NMR, the liquid quick-setting admixture has a peak in the chemical shift range of more than -5.0 ppm and less than 0 ppm, preferably in the range of -4.5 ppm or more and -1.0 ppm or less. 27If the spectrum obtained by Al-NMR does not have a peak in the chemical shift range of more than -5.0 ppm and less than 0 ppm, the compound may not exhibit rapid-setting properties.

[0017] In addition, liquid accelerator 27 The half-width of the peak in the chemical shift range of more than -5.0 ppm and less than 0 ppm in the spectrum obtained by Al-NMR is preferably 10.0 ppm or less, more preferably 7.0 ppm or less, and even more preferably 5.0 ppm or less. This further improves the storage stability of the liquid quick-setting admixture. The half-width may be, for example, 0.1 ppm or more.

[0018] Here, the liquid accelerator 27 The Al-NMR measurement can be performed using a commercially available measuring device, for example, a superconducting nuclear magnetic resonance device (ECX-400) manufactured by JEOL Ltd., under the following conditions. (conditions) Observation kernel: 27 Al Sample tube rotation speed: 12Hz Measurement temperature: 25℃ Pulse width: 5 μsec (45° pulse) Wait time: 5 seconds External standard: Aluminum chloride aqueous solution

[0019] From the viewpoint of worker safety, the total alkali content R2O (R is an alkali metal) in the liquid quick-setting admixture is preferably 1.0 mass% or less, more preferably 0.8 mass% or less, and even more preferably 0.5 mass% or less. It may also be 0 mass% or more. When preparing the liquid quick-setting admixture, for example, by using raw materials with a low concentration of total alkali content R2O, the total alkali content R2O in the liquid quick-setting admixture can be kept within the above range. The total alkali content R2O in the liquid quick-setting admixture can be measured by atomic absorption spectrometry.

[0020] From the viewpoint of preventing corrosion of steel, the chloride ion concentration in the liquid quick-setting admixture is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less. When preparing the liquid quick-setting admixture, the chloride ion concentration in the liquid quick-setting admixture can be adjusted to the above range, for example, by using raw materials with a low chloride ion concentration. The chloride ion concentration in the liquid quick-setting admixture can be measured using a commercially available analyzer, such as an ion chromatograph (ICS2100) manufactured by Thermo Scientific. For analysis, the measurement can be performed by diluting the liquid in advance so that the chloride ion concentration falls within the calibration curve.

[0021] Liquid quick-setting admixtures can be obtained by mixing an aluminum component raw material such as aluminum sulfate, various alums, or aluminum hydroxide with a sulfur component raw material such as sulfuric acid, and then reacting them at high heat. The heating temperature is preferably 70 to 100°C, more preferably 85 to 100°C, and even more preferably 85 to 95°C. The reaction time is preferably 30 to 150 minutes, more preferably 60 to 150 minutes, and even more preferably 90 to 120 minutes. That is, for example, the liquid quick-setting admixture can be prepared by mixing aluminum hydroxide and sulfuric acid and heating at 85 to 95°C for 90 to 120 minutes. Here, in terms of the ratio of the raw material of the aluminum component to the raw material of the sulfur component, if the ratio of the raw material of the aluminum component is increased, the chemical shift is more likely to fall within the desired range, and if the ratio of the raw material of the sulfur component is increased, the half-width is more likely to become smaller.

[0022] The liquid quick-setting admixture preferably contains 7.2 to 20.0 mass% of an aluminum component, calculated as Al2O3, more preferably 7.5 to 18.0 mass%, and even more preferably 8.0 to 15.0 mass%. In this embodiment, the aluminum component refers to a substance containing aluminum atoms, such as aluminum ions derived from the raw materials, or aluminum compounds such as aluminum hydroxide. By adjusting the amount of raw materials for the aluminum component used during preparation of the liquid quick-setting admixture, the aluminum component in the liquid quick-setting admixture, calculated as Al2O3, can be kept within the above range, thereby improving the quick-setting properties of the liquid quick-setting admixture.

[0023] The liquid quick-setting admixture preferably contains 17.0 to 30.0 mass% of sulfur components, calculated as SO3, more preferably 19.0 to 28.0 mass%, and even more preferably 20.0 to 26.0 mass%. In this embodiment, the sulfur component refers to a substance containing sulfur atoms, such as sulfate ions derived from the raw materials, or sulfates such as magnesium sulfate. By adjusting the amount of raw materials for the sulfur component used during preparation of the liquid quick-setting admixture, the sulfur component in the liquid quick-setting admixture, calculated as SO3, can be kept within the above range, thereby improving the quick-setting properties of the liquid quick-setting admixture.

[0024] The liquid quick-setting admixture preferably contains 0.05 to 0.5 mass % of magnesium component, calculated as MgO, more preferably 0.06 to 0.4 mass %, and even more preferably 0.07 to 0.3 mass %. In this embodiment, the magnesium component refers to a substance containing magnesium atoms, such as magnesium ions contained in raw materials or magnesium compounds such as magnesium oxide. By adding raw materials containing the magnesium component and adjusting the amount used during preparation of the liquid quick-setting admixture, the magnesium component in the liquid quick-setting admixture, calculated as MgO, can be adjusted to fall within the above range, thereby improving the quick-setting properties of the liquid quick-setting admixture.

[0025] The liquid quick-setting admixture preferably contains 0.5 to 5.0 mass %, more preferably 1.0 to 4.0 mass %, and even more preferably 1.5 to 3.0 mass % of ethanolamines. When the content of ethanolamines is within the above range, the storage stability of the liquid quick-setting admixture can be improved. Examples of ethanolamines include monoethanolamine, diethanolamine, and trimethanolamine, with diethanolamine being preferred from the viewpoint of storage stability.

[0026] In addition to the components described above, the liquid quick-setting admixture may contain various additives within the range that does not impair the effects of the present invention. However, from the viewpoint of ease of handling, it is preferable that the liquid quick-setting admixture does not contain sodium aluminate.

[0027] [2. Shotcrete] In the shotcrete according to this embodiment, it is preferable to use the liquid quick-setting admixture of the present invention in combination with a powder quick-setting admixture containing calcium aluminate as the main component.

[0028] In practice, cement is used in shotcrete, and examples of cement that can be used in this type of concrete include various types of Portland cement, such as normal, early strength, extra early strength, low heat, and medium heat; various types of mixed cements in which blast furnace slag, fly ash, or silica is mixed with these types of Portland cement; filler cements in which limestone powder or ground pulverized cooled blast furnace slag is mixed; and environmentally friendly cements (ecocements) made from municipal waste incineration ash and sewage sludge incineration ash.

[0029] Shotcrete actually uses aggregate, but the type of aggregate is not particularly limited; however, aggregates with low water absorption and high aggregate strength are preferred. The maximum size of the aggregate is not particularly limited as long as it can be shotcreted. River sand, mountain sand, sea sand, lime sand, and silica sand can be used as fine aggregate, while river gravel, mountain gravel, and lime gravel can be used as coarse aggregate, and crushed sand and crushed stone can also be used.

[0030] The powder quick-setting admixture is preferably a powder quick-setting admixture containing calcium aluminate as the main component, which can improve quick-setting properties and strength development. Here, "containing calcium aluminate as a main component" means that the content (by mass) of calcium aluminate is the highest among the components of the powder quick-setting admixture.

[0031] The content of calcium aluminate in the powder quick-setting admixture is 30% by mass or more, preferably 30 to 80% by mass, and more preferably 45 to 60% by mass. When it is 30% by mass or more, good setting properties are easily obtained. When it is 80% by mass or less, good long-term strength development is easily obtained.

[0032] Calcium aluminate is a general term for compounds that have CaO and Al2O3 as their main components and have hydration activity. They are compounds in which part of the CaO and / or Al2O3 is replaced with alkali metal oxides, alkaline earth metal oxides, silicon oxide, titanium oxide, iron oxide, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, alkaline earth metal sulfates, etc., or substances in which small amounts of these are dissolved in substances containing CaO and Al2O3 as their main components. Calcium aluminate may be either crystalline or amorphous.

[0033] Specific examples of crystalline materials include C3A and C, where CaO is C, Al2O3 is A, and R2O (Na2O, K2O, Li2O) is R. 14 RA5, CA, C 12 A7 and C 11 Examples include A7·CaF2, C4A·Fe2O3, and C3A3·CaSO4, but amorphous calcium aluminate is preferred due to its rapid setting properties. In addition, in the case of amorphous calcium aluminate, it is preferable that the vitrification rate is 80% or more.

[0034] The CaO / Al2O3 molar ratio of calcium aluminate is not particularly limited, but in consideration of the very early and long-term strength development, the molar ratio is preferably 2.0 to 3.0, more preferably 2.1 to 2.8. If the molar ratio is 2.0 or more, the very early setting properties can be improved, and if it is 3.0 or less, good long-term strength development is likely to be obtained.

[0035] Calcium aluminate can be obtained by heat treating a CaO raw material such as calcium carbonate or calcium hydroxide with an Al2O3 raw material such as bauxite in a rotary kiln, electric furnace, or the like. Specifically, the raw materials are mixed in a predetermined ratio, heated and melted in an electric furnace, and then quenched by contact with compressed air or water. The CaO / Al2O3 molar ratio can be adjusted by adjusting the ratio of the raw materials, and the vitrification rate can be adjusted by changing the temperature during heating and melting and the cooling method.

[0036] The Blaine specific surface area of ​​calcium aluminate is 4000-8000 cm 2 / g, and 5000 to 7000 cm 2 / g. It is more preferable that the Blaine specific surface area is 4000 to 8000 cm 2 / g, early strength development is easily achieved, and the handling properties of the mortar and / or concrete at the time of spraying can be improved. The Blaine specific surface area is measured based on the specific surface area test described in JIS R 5201:2015 "Physical testing methods for cement."

[0037] The amount of liquid quick-setting admixture added to the shotcrete can be adjusted so that the aluminum content in the liquid quick-setting admixture is preferably 0.1 to 10 parts by mass per 100 parts by mass of cement in the shotcrete. The amount of powder quick-setting admixture added can be adjusted so that the calcium aluminate content in the powder quick-setting admixture is preferably 1 to 15 parts by mass per 100 parts by mass of cement. The amounts of liquid quick-setting admixture and powder quick-setting admixture added can be adjusted as described above depending on the required strength of the shotcrete, thereby improving the initial and long-term compressive strength of the shotcrete. Regarding the blending ratio of the liquid quick-setting admixture to the powder quick-setting admixture, for example, when the natural ground is in poor condition, the amount of powder quick-setting admixture added can be increased to improve the early strength of the shotcrete, while when the natural ground is in stable condition, the amounts of both quick-setting admixtures used can be reduced.

[0038] The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention.

[0039] <Preparation of liquid quick-setting admixture> The various raw materials were adjusted and mixed so that the aluminum component, sulfur component, and fluorine component had the Al2O3 equivalent, SO3 equivalent, and fluoride ion concentrations shown in Table 1, respectively, and heated at 90°C for 2 hours to produce a liquid quick-setting admixture.

[0040] <Raw materials used> Aluminum component raw material: Aluminum hydroxide, for industrial use Sulfur component raw material: sulfuric acid, industrial use Fluoride ion source: cryolite, industrial grade, fluorine content 52-54% Solvent: Pure water

[0041] < 27 Al-NMR measurement> The prepared liquid quick-setting admixture was analyzed using a JEOL superconducting nuclear magnetic resonance spectrometer (ECX-400) under the following conditions to measure the chemical shift and half-width of the peak. The results are shown in Table 1 below.

[0042] < 27 Al-NMR measurement conditions> Observation kernel: 27 Al Sample tube rotation speed: 12Hz Measurement temperature: 25℃ Pulse width: 5 μsec (45° pulse) Wait time: 5 seconds External standard: Aluminum chloride aqueous solution

[0043] <Setting test / compression strength test> A test sample was obtained by mixing 100 parts by mass of ordinary Portland cement (pH 14, industrial product), 10 parts by mass of the prepared liquid quick-setting admixture, and 40 parts by mass of water (tap water). Setting tests and compressive strength tests were conducted using the obtained test sample. The tests were conducted in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement," and the initial and final setting times and compressive strength at each age were measured. The results are shown in Table 1 below.

[0044] <Dissolution test> Test samples were prepared in the same manner as in the setting test and compressive strength test, and a leaching test was conducted in accordance with "Concrete Library 11." The prepared test samples were immersed in pure water, and after 24 hours, the test samples were removed and the immersion water was subjected to quantitative analysis of fluoride ions using ion chromatography. The results are shown in Table 1 below.

[0045] <Storage test> A storage test was conducted to evaluate the storage stability of the liquid quick-setting admixture. When the storage stability deteriorates, precipitates form in the liquid quick-setting admixture, especially in low-temperature environments. The liquid quick-setting admixture was left to stand at 10°C for one month, and the precipitates were extracted with filter paper. The amount of precipitate per 100g of liquid quick-setting admixture was calculated. The results are shown in Table 1 below.

[0046] [Table 1]

[0047] From the results shown in Table 1, it is clear that the product contains aluminum and sulfur components, but does not substantially contain fluorine components, and is measured under the specified conditions. 27 It was confirmed that liquid quick-setting admixtures with peaks in the chemical shift range of more than -5.0 ppm and less than 0 ppm in the spectrum obtained by Al-NMR have excellent quick-setting properties and storage stability, and there is no concern about fluorine elution. Note that even though the fluoride ion concentration of the liquid quick-setting admixture is 0 ppm, fluoride ions were detected in the test sample in the elution test. This is presumably due to the trace amounts of fluoride ions contained in the cement and aggregate, as the measurement test method involves crushing and shaking the cement.

[0048] <Preparation of shotcrete> Cement 400 kg, water 200 kg, fine aggregate 1,100 kg, coarse aggregate (Niigata Prefecture Himekawa River system No. 6 crushed stone, density 2.67 g / cm 3 716 kg of concrete was prepared. 100 parts by mass of cement in this concrete was mixed with a liquid quick-setting admixture and a powder quick-setting admixture in the proportions shown in Table 2 to prepare shotcrete. The liquid quick-setting admixtures used were those of Examples 1 to 5 and Comparative Examples 1 and 2, and the powder quick-setting admixture used was calcium aluminate powder with a CaO / Al2O3 molar ratio shown in Table 2. The resulting shotcrete was subjected to a compressive strength test. The test results are shown in Table 2.

[0049] <Compression strength test> In accordance with JSCE-G561, the prepared shotcrete was sprayed onto a formwork, and the pull-out strength at 3 hours and 1 day of age was converted into compressive strength to measure the initial strength. In accordance with JSCE-F561, the prepared shotcrete was sprayed into a formwork, and cores were taken at 28 days old in accordance with JIS A 1107:2012 to measure the long-term strength.

[0050] [Table 2]

[0051] The results shown in Table 2 confirm that shotcrete made using a combination of liquid quick-setting admixture and powder quick-setting admixture whose main component is calcium aluminate exhibits excellent quick-setting and strength development. In particular, it was confirmed that the strength development in the very early stages can be improved by increasing the content of powder quick-setting admixture. [Industrial Applicability]

[0052] 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 liquid quick-setting admixture containing an aluminum component and a sulfur component and substantially no fluorine component, which is measured under the following conditions: ２７ In the spectrum obtained by Al-NMR, Chemical shift: A liquid quick-setting admixture having a peak in the range of more than 5.0 ppm and less than 0 ppm. (conditions) Observation kernel: ２７ Al Sample tube rotation speed: 12 Hz Measurement temperature: 25℃ Pulse width: 5 μsec (45° pulse) Wait time: 5 seconds External standard: Aluminum chloride aqueous solution

2. 2. The liquid quick-setting admixture according to claim 1, wherein the half-width of the peak in the chemical shift range of more than −5.0 ppm and less than 0 ppm is 10.0 ppm or less.

3. Total alkali amount R ２ 3. The liquid quick-setting admixture according to claim 1, wherein O (R is an alkali metal) is 1.0 mass % or less.

4. 3. The liquid quick-setting admixture according to claim 1, wherein the chloride ion concentration is 5.0 mass % or less.

5. 3. Shotcrete comprising a liquid quick-setting admixture according to claim 1 or 2 in combination with a powder quick-setting admixture containing calcium aluminate as a main component.

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