Liquid accelerator, shotcrete

Abstract

The present invention is a liquid quick-setting agent containing 2.5 to 21.0% by mass of aluminum, 7.5 to 30.0% by mass of sulfur, and 50 to 15,000 ppm by mass of silicon, respectively, when converted by oxides.

Description

Liquid Accelerator, Shotcrete The present invention relates to a liquid accelerator and shotcrete. Conventionally, in order to prevent the collapse of mountainous areas exposed by tunnel excavation cutting, etc., a spraying method of quick-setting concrete obtained by mixing an accelerator with concrete has been used. In this method, shotcrete is prepared by metering and mixing materials using a metering platform installed at the excavation cutting site, pumped by a pump, and then mixed with an accelerator pumped from the other side of the confluence pipe on the way, and then sprayed onto the mountain surface until a predetermined thickness is reached. The accelerators used in the spraying method can be roughly classified into two types: a powder accelerator mainly composed of calcium aluminate, alkali metal aluminate, etc., and a liquid accelerator mainly composed of alkali metal aluminate, aluminum sulfate, etc. In recent years, from the perspective of ensuring the health of workers at tunnel construction sites, etc., there is a desire to use an acidic liquid accelerator mainly composed of aluminum salts with less dust during spraying and no concern about alkaline agent damage. On the other hand, compared with powder accelerators, liquid accelerators have the problem of low quick-setting properties. Thus, as a countermeasure for improving quick-setting properties, for example, a countermeasure for improving quick-setting properties by increasing the sulfate ion concentration as shown in Patent Document 1 has been implemented. Also, as a countermeasure for improving strength, for example, a liquid accelerator composed of an acidic or alkaline solution of aluminum containing aluminum fluoride and aluminum hydrofluoric acid, lithium silicate, and lithium aluminate as described in Patent Document 2 has been proposed. Or a liquid accelerator composed of a fluoride-containing water-soluble aluminum salt obtained by the reaction of aluminum sulfate and hydrofluoric acid, aluminum hydroxide, and lithium hydroxide, lithium carbonate, lithium sulfate, etc. as described in Patent Document 3 has been proposed. [Prior Art Documents] [Patent Documents] [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 [Problems to be Solved by the Invention] However, although the above-mentioned technologies improve strength characteristics, sometimes the surface of the concrete after spraying becomes rough and uneven, resulting in a problem of poor finish. In summary, the object of the present invention is to provide a liquid accelerator having excellent quick-setting properties, strength exhibition properties, and finish. [Means for Solving the Problems] As a result of in-depth discussions by the inventors of the present invention in view of the above problems, it has been found that a liquid accelerator containing specific amounts of aluminum, sulfur, and silicon in terms of oxide conversion can solve the above problems, and thus the present invention has been completed. That is, the present invention is as follows. [1] A liquid accelerator contains, in terms of oxide conversion, 2.5 to 21.0% by mass of aluminum, 7.5 to 30.0% by mass of sulfur, and 50 to 15,000 ppm by mass of silicon. [2] The liquid accelerator as described in [1] above further contains 1 to 4,000 ppm by mass of calcium in terms of oxide conversion. [3] The liquid accelerator as described in [1] or [2] above is such that in the spectrum obtained by Al-NMR under the following conditions 27 it has a peak in the range of chemical shift of 0 ppm or more and 2.0 ppm or less. (Condition) Observed nucleus: 27 Al Sample tube rotation speed: 12 Hz Measurement temperature: 25 °C Pulse amplitude: 5 μsec (45° pulse) Waiting time: 5 seconds External standard: Aluminum chloride aqueous solution [4] The liquid accelerator as described in any one of [1] to [3] above, wherein the half-value width of the peak in the range of chemical shift of 0 ppm or more and 2.0 ppm or less is 2.0 ppm or less. [5] The liquid accelerator as described in any one of [1] to [4] above, wherein the mass ratio (Al 2 O 3 / SiO 2 ) of the aforementioned aluminum and silicon in terms of oxide conversion is 3 to 1,000. [6] The liquid accelerator as described in any one of [1] to [5] above, wherein the pH is 4.0 or less. [7] A shotcrete is prepared by using in combination the liquid accelerator as described in any one of [1] to [6] above and a powder accelerator mainly composed of calcium aluminate. [Advantages of the Invention] According to the present invention, a liquid accelerator with excellent quick-setting property, strength development property, and finish can be provided. Hereinafter, embodiments of the present invention (these embodiments) will be described in detail, but the present invention is not limited to these embodiments. In addition, in this specification, "%" is defined on a mass basis unless otherwise specified. [1. Liquid accelerator] The liquid accelerator of these embodiments is a liquid accelerator containing, in terms of oxide conversion, 2.5 to 21.0% by mass of aluminum, 7.5 to 30.0% by mass of sulfur, and 50 to 15,000 ppm by mass of silicon. In the liquid accelerator, aluminum in terms of oxide conversion (Al 2 O 3In terms of conversion, it contains 2.5 to 21.0% by mass, preferably contains 3.5 to 18.0% by mass, more preferably contains 4.5 to 15.0% by mass, and still more preferably contains 5.0 to 12.0% by mass. If the amount of aluminum oxide in the liquid accelerator in terms of conversion is less than 2.5% by mass, there is a concern that the quick-setting property cannot be exhibited. If it exceeds 21.0% by mass, there is a concern about poor strength development and finish. In the liquid accelerator, sulfur is in terms of oxide conversion (SO 3 In terms of conversion, it contains 7.5 to 30.0% by mass, preferably contains 8.5 to 28.0% by mass, more preferably contains 12.0 to 27.0% by mass, and still more preferably contains 13.5 to 20.0% by mass. If the amount of sulfur oxide in the liquid accelerator in terms of conversion is less than 7.5% by mass, there is a concern that the strength development property cannot be exhibited. If it exceeds 30.0% by mass, there is a concern about poor quick-setting property and strength development property. In the liquid accelerator, silicon is in terms of oxide conversion (SiO 2 In terms of conversion, it contains 50 to 15,000 ppm by mass, preferably contains 150 to 9,000 ppm by mass, more preferably contains 500 to 7,000 ppm by mass, and still more preferably contains 1,000 to 5,000 ppm by mass. If the amount of silicon oxide in the liquid accelerator in terms of conversion is less than 50 ppm by mass or exceeds 15,000 ppm by mass, there is a concern about poor finish. In the liquid accelerator, it is preferably further contained with 1 to 4,000 ppm by mass of calcium in terms of oxide conversion (CaO conversion), more preferably contains 100 to 3,800 ppm by mass, and still more preferably contains 750 to 3,500 ppm by mass. If the amount of calcium oxide in the liquid accelerator in terms of conversion falls within the above range, the quick-setting property, strength development property, and finish are more likely to be good. The mass ratio of aluminum and silicon in the liquid accelerator in terms of oxide conversion respectively (Al 2 O 3 / SiO 2 ) should be 3 to 1,000, more preferably 5 to 500, and still more preferably 10 to 150. Al 2 O 3 / SiO 2 If it falls within the above range, the quick-setting property, strength development property, and finish are more likely to be good. The utilization of the liquid accelerator 27In the spectrum obtained by Al-NMR, a peak should be present in the range of chemical shift above 0 ppm and below 2.0 ppm. Also, the half-width at half maximum of this peak should be, for example, 2.0 ppm or less, more preferably 1.8 ppm or less, and still more preferably 1.5 ppm or less. Thereby, the storage stability of the quick-setting agent can be improved. Additionally, the half-width at half maximum can also be, for example, 0.1 ppm or more. Here, for the liquid quick-setting agent 27 Al-NMR measurement can be carried out using a commercially available measuring device, such as a superconducting nuclear magnetic resonance device (ECX-400) manufactured by JEOL Ltd., and implemented under the following conditions. (Conditions) Observed nucleus: 27 Al Sample tube rotation speed: 12 Hz Measurement temperature: 25 °C Pulse amplitude: 5 μsec (45° pulse) Waiting time: 5 seconds External standard: Aluminum chloride aqueous solution The pH of the liquid quick-setting agent should be 4.0 or less, more preferably 3.5 or less. If the pH is 4.0 or less, the effect of reducing the environmental load can be exerted, and the adverse effects on the human body can be suppressed. Also, the pH should be 1.5 or more. Additionally, the pH of the liquid quick-setting agent can be measured using a pH meter. Regarding the fluoride ion concentration in the liquid quick-setting agent, from the perspective of reducing the elution of fluoride ions, it should be 1.0 - 500 ppm, more preferably 1.0 - 450 ppm, and still more preferably 1.0 - 350 ppm. If the fluoride ion concentration falls within the above range, the false setting caused by the intense hydration due to the addition of the quick-setting agent can be easily alleviated, and good workability can be easily obtained. The total alkali content R in the liquid quick-setting agent 2 O (where R is an alkali metal), from the perspective of the safety of the operator, should be 1.0 mass% or less, more preferably 0.8 mass% or less, and still more preferably 0.5 mass% or less. Also, it can be 0 mass% or more. When preparing the liquid quick-setting agent, for example, by using a raw material with a low concentration of total alkali content R 2 O, the total alkali content R in the liquid quick-setting agent can be controlled within the above range. Additionally, the total alkali content R 2 O in the liquid quick-setting agent can be measured by atomic absorption spectrometry. 2 O can be measured by atomic absorption spectrometry. The chloride ion concentration in the liquid accelerator, from the perspective of preventing corrosion of steel, should preferably be 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 accelerator, for example, the chloride ion concentration in the liquid accelerator can be controlled within the above range by using raw materials with a low chloride ion concentration. In addition, the chloride ion concentration in the liquid accelerator can be measured using a commercially available analytical device, such as an ion chromatograph (ICS2100) manufactured by Thermo Scientific. During analysis, the chloride ions can be diluted to within the calibration curve in advance for measurement. The liquid accelerator can be obtained, for example, by mixing raw materials containing aluminum components such as aluminum sulfate, aluminum hydroxide, various alums, fine powders of blast furnace slag, aluminum slag residues, etc., raw materials containing sulfur components such as sulfuric acid, and raw materials containing silicon components such as fly ash, silica fume, fine powders of blast furnace slag, amorphous silica, aluminum slag residues, etc., and reacting them at high heat. Also, raw materials containing calcium components such as calcium oxide, calcium hydroxide, fine powders of blast furnace slag, carbide slag, etc. can be used. The heating temperature should preferably be 70 - 100 °C, more preferably 85 - 100 °C, and even more preferably 85 - 95 °C. The reaction time should preferably be 30 - 150 minutes, more preferably 60 - 150 minutes, and even more preferably 90 - 120 minutes. That is, for example, it can be prepared by mixing aluminum hydroxide, sulfuric acid, and fine powders of blast furnace slag and heating them at 85 - 95 °C for 90 - 120 minutes. Here, the utilization of the liquid accelerator 27 The position and half-value width of the peaks in the spectrum obtained by Al-NMR are affected by the ratios of the raw materials of aluminum, sulfur, and silicon components. For example, in the ratio of the raw material of aluminum component to the raw material of sulfur component, if the ratio of the raw material of aluminum component is large, the chemical shift is likely to fall within the desired range, and if the ratio of the raw material of sulfur component is large, the half-value width is likely to become smaller. In addition to containing the above components, the liquid accelerator can contain various additives within the range that does not hinder the effects of the present invention. From the perspective of operability, it is preferably free of sodium aluminum dioxide. [2. Shotcrete] The shotcrete of this embodiment is preferably used in combination with the liquid accelerator of the present invention and a powder accelerator mainly composed of calcium aluminate. Cement is actually used in shotcrete. Examples of the cement used in this shotcrete include various Portland cements such as ordinary, early strength, ultra-early strength, low heat, and medium heat, or various blended cements obtained by mixing blast furnace slag, fly ash, or silica into these Portland cements, filler cements obtained by mixing limestone powder, fine powders of blast furnace slowly cooled slag, etc., and environmentally friendly cements (eco-cements) made from municipal dust incineration ash and sewage sludge incineration ash as raw materials. Shotcrete actually uses aggregates, which are not particularly limited, but preferably those with low water absorption and high aggregate strength. The maximum size of the aggregates is not particularly limited as long as spraying can be carried out. Fine aggregates can be river sand, mountain sand, sea sand, lime sand, silica sand, etc., and coarse aggregates can be river sand gravel, mountain sand gravel, lime sand gravel, etc., and crushed sand and crushed stone can also be used. The powder accelerator is preferably a powder accelerator mainly composed of calcium aluminate. By containing calcium aluminate as the main component, good quick-setting property and strength development property can be improved. Here, "containing calcium aluminate as the main component" means that among the accelerator components in the powder accelerator, the content (mass basis) of calcium aluminate is the highest. The content of calcium aluminate in the powder accelerator is 30% or more in the powder accelerator, preferably 30 - 80%, and more preferably 45 - 60%. If it is 30% or more, good setting properties can be easily obtained. In addition, if it is 80% or less, good long-term strength development property can be easily obtained. Calcium aluminate is a general term for compounds that are the main components and have hydration activity, and is a compound in which a part of CaO and / or Al 2 O 3 is replaced by alkali metal oxides, alkaline earth metal oxides, silicon oxide, titanium oxide, iron oxide, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, and alkaline earth metal sulfates, etc., or a substance in which these components are solid-solved in a small amount among those having CaO and Al 2 O 3 as the main component, and calcium aluminate can be either crystalline or amorphous. 2 O 3 Specific examples of the crystalline form, if CaO is C, Al and Al 2 O 3 is A, and R 2 O(Na 2 O, K 2 O, Li 2 O) is R, then C 3 A, or C 14 RA 5 , CA, C 12 A 7 , C 11 A 7 ･CaF 2 , C 4 A･Fe 2 O 3 , and C 3 A 3 ･CaSO 4 etc. Considering the viewpoint of good quick-setting property, it should be amorphous calcium aluminate. Also, when it is amorphous calcium aluminate, the vitrification rate should be 80% or more. The CaO / Al of calcium aluminate 2 O 3 The molar ratio has no particular limitation. Considering the initial and long-term strength development, the molar ratio should be 2.0 - 3.0, and 2.1 - 2.8 is better. If the molar ratio is 2.0 or more, the initial setting property can be good. If it is 3.0 or less, good long-term strength development can be easily obtained. The methods for obtaining calcium aluminate include: using CaO raw materials such as calcium carbonate and calcium hydroxide, and Al such as bauxite 2 O 3 raw materials, etc., and performing heat treatment using a rotary kiln, an electric furnace, etc. Specifically, it includes: mixing the raw materials at a predetermined ratio, heating and melting using an electric furnace, etc., and rapidly cooling by contacting with compressed air, water, etc. By adjusting the ratio of the raw materials, the above-mentioned CaO / Al 2 O 3 molar ratio can be adjusted. Also, the vitrification rate can be adjusted by the temperature during heating and melting and the cooling method. The Blaine specific surface area of calcium aluminate should be 4,000 - 8,000 cm 2 / g, and 5,000 - 7,000 cm 2 / g is better. By being 4,000~8,000 cm 2 / g, the initial strength exhibition can be easily obtained, and the workability of the mortar and / or concrete during spraying can be made good. In addition, the Blaine specific surface area is measured based on the specific surface area test described in JIS R 5201:2015 "Physical Test Methods for Cement". The addition amount of the liquid accelerating agent in the shotcrete is adjusted so that the aluminum component in the liquid accelerating agent becomes 0.1 to 20 parts by mass relative to 100 parts by mass of the cement in the shotcrete. Also, the addition amount of the powder accelerating agent is adjusted so that the calcium aluminate in the powder accelerating agent becomes 1 to 15 parts by mass relative to 100 parts by mass of the cement. The addition amounts of the liquid accelerating agent and the powder accelerating agent can be adjusted as described above according to the strength required for the shotcrete, and the initial and long-term compressive strengths of the shotcrete can be improved. The blending ratio of the liquid accelerating agent and the powder accelerating agent, for example, in the case of poor mountain conditions, by increasing the addition amount of the powder accelerating agent, the early strength of the shotcrete can be improved, and in the case of stable mountain conditions, the usage amounts of both accelerating agents can be reduced. [Examples] Hereinafter, the present invention will be described more specifically using examples and comparative examples, but the present invention is not limited to the following examples as long as it does not deviate from its gist. [Experimental Example 1 (Experiment No. 1-1~19)] <Preparation of Liquid Accelerating Agent> Various raw materials were adjusted and mixed in such a way that the oxides of aluminum, sulfur, silicon, and calcium were converted into Al 2 O 3 conversion, SO 3 conversion, SiO 2 conversion, and CaO conversion, and heated at 90 °C for 2 hours to obtain a liquid accelerating agent. <Raw Materials Used> Raw material for aluminum: Aluminum hydroxide, for industrial use. Raw material for sulfur: Sulfuric acid, for industrial use. Raw material for silicon: Amorphous silica, for industrial use. Raw material for calcium: Slaked lime, for industrial use. Solvent: Pure water. < 27 Al-NMR Measurement> The obtained liquid accelerating agent was used with a superconducting nuclear magnetic resonance device (ECX-400) manufactured by JEOL Ltd., and carried out under the following conditions to measure the chemical shift and half-value width of the peak part. The results are shown in Table 1 below. < 27Al-NMR measurement conditions > Observed nucleus: 27 Rotation speed of Al sample tube: 12 Hz, Measurement temperature: 25 °C, Pulse amplitude: 5 μsec (45° pulse), Waiting time: 5 seconds, External standard: Aqueous aluminum chloride solution <Concrete spraying test> The concrete prepared under the mixing conditions described in Table 2 below is sprayed using a concrete pump "MKW-25SMT" (manufactured by SHINTECH Co., Ltd.) at a pump spraying setting of 10 m 3 / hr, and each liquid accelerator for mixing shown in Table 1 below is quantitatively transported by a pump from another system immediately before spraying, and is made to merge and mix with the concrete so as to be 10% by mass with respect to the cement in the concrete, and is sprayed onto the respective objects in the setting test, compressive strength test, and finish evaluation as shown below. <Materials used> ･ Ordinary Portland cement: Commercially available product, Blaine’s value 3,200 cm 2 / g ･ Fine aggregate: Sand from the Himekawa River system in Iwamizawa City, Niigata Prefecture, with a maximum size of 5 mm or less and a density of 2.62 g / cm 3 。 ･ Coarse aggregate: No. 6 crushed stone from Iwamizawa, Niigata Prefecture, with a maximum size of 15 mm and a density of 2.67 g / cm 3 。 ･ Water: Tap water. ･ Water reducing agent: Commercially available product, high-performance water reducing agent. <Setting test> Spray concrete onto a wooden frame with a length of 30 cm, width of 30 cm, and depth of 10 cm. Use a Proctor penetrometer (spring type) for the sprayed concrete to measure the Proctor penetration resistance value over time after spraying, and set the time when it becomes 3.5 N / mm 2 or more as the initial time, and set the time when it becomes 28.0 N / mm 2 as the end time. The results are shown in Table 1 below. <Compressive strength test (at 3 hours and 1 day of age)> In accordance with JSCE-G 561-2010 "Test method for initial strength of sprayed concrete by pull-out method", measure the compressive strength at 3 hours and 1 day of age. The results are shown in Table 1 below. <Completion Evaluation and Compressive Strength Test (Age 28 days)> Concrete was sprayed onto a wooden frame measuring 30 cm in length × 50 cm in width × 20 cm in depth. At the age of 28 days, from the sprayed concrete, in accordance with JIS A 1107:2022 "Method for Taking Cores from Concrete and Method for Compressive Strength Test", five test specimen cores of φ100×200 mm were taken in a parallel manner on a horizontal straight line passing through the center of the concrete. After grinding the bottom surface of each test specimen with a test specimen edge surface processing machine (manufactured by Marui Co., Ltd.), using a digital vernier caliper with a precision of 1 / 100 mm (manufactured by Mitutoyo Corporation), with the center of the top surface of the five test specimens obtained by taking cores as the reference point, the height of the test specimens on the φ100 mm circumference centered on this reference point was measured at 6 points every 60° × 5 test specimens, a total of 30 points, and the standard deviation of the height was calculated. The smaller the standard deviation value, the smaller and better the unevenness of the completion degree was judged. After the completion evaluation, in accordance with JIS A 1107:2022 "Method for Taking Cores from Concrete and Method for Compressive Strength Test" and JIS A 1132:2020 "Method for Making Test Specimens for Strength Tests of Concrete", the top surface of the test specimens was ground, and the compressive strength at the age of 28 days was measured. [Table 1] [Table 2] As confirmed by the results shown in Table 1, a liquid accelerator containing a specific amount of aluminum, sulfur, and silicon in terms of oxides has excellent accelerating property, strength development property, and finish. Also, it was confirmed that when the liquid accelerator contains a specific amount of calcium in terms of oxides, an accelerator with even better accelerating property, strength development property, and finish can be produced. [Experimental Example 2 (Experiment Nos. 2-1 to 3)] <Concrete Spraying Test> Immediately before spraying, calcium aluminate powder (CaO / Al 2 O 3 molar ratio 2.3, Blaine value 6,000 cm 2 / g) as a powder accelerator and the liquid accelerator used in Experimental Example 1 were mixed in a combined manner at 5% by mass and 7% by mass relative to the cement in the concrete. Except for this, the concrete spraying test was carried out in the same manner as in Experimental Example 1, and various evaluations were carried out. The results are shown in Table 1. As confirmed by the results shown in Table 1, the shotcrete obtained by using a liquid accelerator and a powder accelerator mainly composed of calcium aluminate in combination exhibits excellent accelerating property, strength development property, and finish. [Industrial Applicability] The liquid accelerator of the present invention can be ideally used for, for example, cement concrete sprayed onto exposed mountain surfaces such as tunnels, slopes, etc. of roads, railways, and water conduits.

Claims

1. A liquid quick-setting agent containing 2.5 to 21.0% by mass of aluminum, 7.5 to 30.0% by mass of sulfur, and 50 to 7,000 ppm by mass of silicon, respectively, when converted to oxides.

2. The liquid quick-setting agent as claimed in claim 1 further contains calcium at a concentration of 1 to 4,000 ppm by mass, converted from oxides.

3. The liquid quick-setting agent as requested in item 1 or 2 has a peak in the range of chemical shift above 0 ppm and below 2.0 ppm in the 27Al-NMR spectrum obtained by measuring under the following conditions: (Conditions) Observation nucleus: 27Al Sample tube rotation speed: 12 Hz Measurement temperature: 25 ℃ Pulse amplitude: 5 μsec (45° pulse) Waiting time: 5 seconds External standard: Aqueous aluminum chloride solution.

4. Liquid quick-setting agent as requested in item 1 or 2, wherein, The half-width of the peak in the range of chemical shift above 0 ppm and below 2.0 ppm is below 2.0 ppm.

5. The liquid quick-setting agent as requested in item 1 or 2, wherein, The mass ratio (Al2O3 / SiO2) of the respective oxides of aluminum and silicon is 3 to 1,000.

6. The liquid quick-setting agent as requested in item 1 or 2, wherein, pH below 4.

0.

7. A shotcrete comprising the use of a liquid accelerator as described in claim 1 or 2, and a powder accelerator with calcium aluminate as the main component.