sprayed concrete

Abstract

To provide a spray concrete which shows high strength development and is hard to form cracks.SOLUTION: A spray concrete includes a concrete composition including a cement, an aggregate, and a strength enhancement material, a quick-setting admixture, and water, wherein the strength enhancement material is a gypsum analog and / or amorphous aluminosilicate, and a content of the strength enhancement material is 1-15 pts.mass to 100 pts.mass of the cement.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to sprayed concrete. [Background technology]

[0002] In tunnels, mining shafts, and underground spaces, sprayed concrete is used for construction to prevent collapse of the excavation surface and to reinforce the ground during or after excavation. Due to its rapid setting properties, sprayed concrete ensures adhesion to the construction site, contributing to the reinforcement of the structure.

[0003] To impart rapid setting properties to sprayed concrete, rapid setting agents are mixed in. Among these, powdered rapid setting agents containing calcium aluminate, sodium aluminate, etc., as active ingredients can impart strong rapid setting properties and achieve high strength. In the wet spraying method, a common method of applying sprayed concrete, for example, base concrete is prepared by weighing and mixing at least cement, water, and aggregate, and then pumped to the spraying device via an agitator truck or similar vehicle during application. Inside the spraying device, a separately delivered powdered or liquid rapid setting agent is added to the base concrete being pumped, and mixing proceeds within the spraying nozzle to form sprayed concrete, which is then sprayed from the nozzle end hole. Mixing occurs as the rapid setting agent moves from the point of contact with water (water contact point) to the discharge hole at the end of the spraying nozzle, forming the sprayed concrete. The distance used for mixing is usually several tens of centimeters to several meters, and this travel time constitutes the mixing time. Generally, the longer this distance, the more the mixing progresses, the better the mixability, and the easier it is to obtain concrete that is more uniform in terms of structure and properties.

[0004] To obtain such sprayed concrete, the powdered rapid-setting agent mixed into the base concrete generally consists of the aforementioned rapid-setting component with various components added to adjust its properties. For example, a typical conventional powdered rapid-setting agent is a calcium aluminate with a high CaO content as a chemical component, blended with gypsum to accelerate hardening, and to which sodium aluminate is added to enhance initial strength development, and sodium carbonate is added to accelerate setting (see, for example, Patent Documents 1-4). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-121763 [Patent Document 2] Japanese Patent Publication No. 2003-012356 [Patent Document 3] Patent No. 5129955 [Patent Document 4] Japanese Patent Publication No. 2020-11891 [Overview of the project] [Problems that the invention aims to solve]

[0006] In recent years, depending on the application and the environment of the construction site, there is a need for sprayed concrete that exhibits even higher strength development than conventional sprayed concrete. While methods such as increasing the cement content or decreasing the water content can achieve higher strength development, such sprayed concrete has sometimes been prone to cracking during hardening.

[0007] Therefore, the present invention aims to provide sprayed concrete that exhibits high strength development and is resistant to cracking. [Means for solving the problem]

[0008] As a result of intensive studies conducted by the present inventor on the above problem, it has been found that by using gypsum and / or amorphous aluminosilicate as a strength enhancer and adjusting the content thereof, sprayed concrete that exhibits high compressive strength and is less prone to cracking can be obtained.

[0009] That is, the present invention is as follows. [1] Sprayed concrete, comprising a concrete composition containing cement, aggregate and a strength enhancer, a quick-setting admixture, and water, wherein the strength enhancer is gypsum and / or amorphous aluminosilicate, and the content of the strength enhancer is 1 to 15 parts by mass relative to 100 parts by mass of the cement. [2] The sprayed concrete according to [1], wherein the quick-setting admixture comprises calcium aluminate, an alkali metal sulfate, an alkaline earth metal sulfate, and aluminum sulfate. [3] The unit volume mass of cement is 400 to 650 kg / m 3 , which is the sprayed concrete according to [1] or [2]. [4] The sprayed concrete according to any one of [1] to [3], wherein the fine aggregate ratio of the aggregate is 45 to 70% by volume. [5] The sprayed concrete according to any one of [1] to [4], wherein the water-cement ratio is 25 to 50% by mass. Effects of the Invention

[0010] According to the present invention, it is possible to provide sprayed concrete that exhibits high strength development and is less prone to cracking. Mode for Carrying Out the Invention

[0011] Hereinafter, one embodiment of the present invention will be described in detail. In the present specification, all contents such as content are calculated in terms of solid content and anhydride.

[0012] The sprayed concrete of the present embodiment comprises a concrete composition containing cement, aggregate and a strength enhancer, a quick-setting admixture, and water.

[0013] [Concrete Composition] The concrete composition includes cement, aggregate, and strength enhancer. Portland cement is preferred, and any type of Portland cement may be used, such as ordinary, rapid-hardening, very rapid-hardening, moderate-heat, low-heat, and sulfate-resistant Portland cements. As cement, blended cements containing Portland cement, such as blast furnace cement and fly ash cement, can also be used. One type of cement may be used alone, or two or more types may be used in combination. The particle size when using Portland cement is not particularly limited, for example, 2500-7000 cm² as per JIS standard (JIS R 5210:2019). 2 Examples include those that weigh / g.

[0014] The unit volume mass of cement is 400-650 kg / m³. 3 Preferably, it is 450-600 kg / m 3 It is more preferable that it be 470-580 kg / m 3 It is even more preferable that the unit volume mass of cement is within the above range, which further improves the strength development.

[0015] Aggregates are a mixture of fine aggregate, coarse aggregate, etc. The fine aggregate is not particularly limited as long as it can be used in mortar and concrete. The coarse aggregate is not particularly limited as long as it can be used in concrete. Both the fine and coarse aggregates are chosen with a surface-dry density of 2.3 to 2.9 g / cm³ from the viewpoint of easily ensuring the required aggregate strength and minimizing material segregation due to a small difference in specific gravity with other components. 3 It is preferable to use aggregates of the following types. Specific examples of such aggregates include fine aggregates such as natural aggregates like silica sand and limestone sand, and crushed sands such as andesite, sandstone, and basalt, and coarse aggregates such as crushed stone and gravel like silica, limestone, andesite, sandstone, and basalt. Aggregates may be used individually or in combination of two or more types.

[0016] The unit volume mass of fine aggregate is 700-1200 kg / m³. 3 Preferably, it is 800-1100 kg / m 3more preferably 900 to 1050 kg / m 3 and even more preferably . When the unit volume mass of the fine aggregate falls within the above range, strength development is further improved. The unit volume mass of the coarse aggregate is 400 to 750 kg / m 3 preferably 500 to 700 kg / m 3 more preferably 550 to 650 kg / m 3 and even more preferably . When the unit volume mass of the coarse aggregate falls within the above range, strength development is further improved.

[0017] The fine aggregate ratio of aggregate ([volume of fine aggregate / volume of total aggregate] × 100) is preferably 45 to 70% by volume, more preferably 50 to 68% by volume, and even more preferably 55 to 65% by volume. When the fine aggregate ratio of the aggregate falls within the above range, pumpability during construction is further improved, and strength development is also further enhanced.

[0018] The strength enhancer is gypsum and / or amorphous aluminosilicate. For the strength enhancer, gypsum may be used alone, amorphous aluminosilicate may be used alone, or both gypsum and amorphous aluminosilicate may be used in combination.

[0019] Examples of gypsum include anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum. From the viewpoint of further improving strength development, anhydrous gypsum is preferable as the gypsum. One type of gypsum may be used alone, or two or more types may be used in combination. From the viewpoint of further improving initial strength development, the fineness of gypsum is 3200 to 18000 cm 2 / g, preferably 5000 to 15000 cm 2 / g, more preferably 5500 to 14000 cm 2 / g, even more preferably 7000 to 12000 cm 2 / g, and particularly preferably

[0020] Amorphous aluminosilicates are derived from clay minerals and are not particularly limited as long as they contain an amorphous portion; any type can be used. Examples of clay minerals used as raw materials include (1) kaolin minerals, (2) mica clay minerals, (3) smectite-type minerals, and mixed-layer minerals formed by mixing these. Amorphous aluminosilicates can be obtained by amorphousizing these crystalline aluminosilicates, for example, by calcination and dehydration. From the viewpoint of superior reactivity, amorphous aluminosilicates derived from kaolin minerals such as kaolinite, halosite, and dickite are preferred, and metakaolin obtained by calcining kaolinite is even more preferred. Amorphous aluminosilicates may be used individually or in combination of two or more types. The BET specific surface area of ​​amorphous aluminosilicates is 1 to 22 m². 2 It is preferable that the value be / g, and 1.5 to 16m 2 It is more preferable that it be / g. In this specification, "amorphous" means that, as measured by a powder X-ray diffractometer, peaks originating from the clay mineral raw material are almost completely absent. The amorphous aluminosilicate mineral powder according to this embodiment only needs to have an amorphous content of 70% by mass or more, preferably 90% by mass or more, and more preferably 100% by mass, i.e., it is most preferable that no peaks are observed at all when measured by a powder X-ray diffractometer. Here, the amorphous content is a value obtained by the standard addition method. Aluminosilicate with a high amorphous content, i.e., aluminosilicate with a low crystalline content, tends to exhibit even better strength development at the same amount of mixing compared with aluminosilicate with a low amorphous content. Heating for amorphousization of aluminosilicate can be performed by firing in an external kiln, internal kiln, electric furnace, etc., and melting in a melting furnace.

[0021] The strength-enhancing agent content is 1 to 15 parts by mass per 100 parts by mass of cement. If the unit volume mass of the strength-enhancing agent is outside the above range, sufficient initial and long-term strength development cannot be obtained, and cracking is likely to occur during hardening. From the viewpoint of obtaining even higher strength development and reducing the likelihood of cracking, the strength-enhancing agent content is preferably 1.5 to 12 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of cement. When gypsum and amorphous aluminosilicate are used in combination as strength-enhancing agents, the total unit volume mass of these can be adjusted to fall within the above range.

[0022] The concrete composition according to this embodiment may contain a water-reducing agent. The water-reducing agent includes high-performance water-reducing agents, high-performance AE water-reducing agents, AE water-reducing agents, and superplasticizers. Examples of such water-reducing agents include those specified in JIS A 6204:2011 "Chemical admixtures for concrete". Examples of water-reducing agents include polycarboxylic acid-based water-reducing agents, naphthalene sulfonic acid-based water-reducing agents, lignin sulfonic acid-based water-reducing agents, and melamine-based water-reducing agents. Among these, polycarboxylic acid-based water-reducing agents are preferred. A single water-reducing agent may be used alone, or two or more may be used in combination.

[0023] The water-reducing agent content is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 3 parts by mass, and most preferably 0.5 to 1.5 parts by mass, based on solid content, per 100 parts by mass of cement. When the water-reducing agent content is within the above range, good fluidity is easily obtained and strength development is easily improved.

[0024] Various admixtures may be added to the concrete composition, provided that the effects of the present invention are not impaired. Examples of admixtures include expansive agents, defoamers, waterproofing agents, rust inhibitors, shrinkage reducing agents, thickeners, water-retaining agents, pigments, water-repellent agents, efflorescence inhibitors, fibers, and pozzolanic substances.

[0025] Concrete compositions can be prepared by mixing the above-mentioned components using commonly used mixing equipment, and such equipment is not particularly limited. Examples of mixing equipment include concrete mixers.

[0026] [Quick setting admixture] The rapid-setting admixture may be in powder or liquid form, but it is preferable to use a powder from the viewpoint of high rapid-setting properties. Examples of powdered rapid-setting admixtures include those containing calcium aluminate, alkali metal sulfates, alkaline earth metal sulfates, and aluminum sulfate. Examples of liquid rapid-setting admixtures include those containing aluminum sulfate as the main component in addition to alkali metal carbonates, and commercially available liquid rapid-setting admixtures can also be used.

[0027] Calcium aluminate is an inorganic hydrating active substance whose main chemical components are CaO and Al2O3. The molar ratio of CaO to Al2O3 (CaO / Al2O3) is preferably 1.8 to 2.7, preferably 1.9 to 2.65, and more preferably 2.0 to 2.6. If the molar ratio of CaO to Al2O3 is within the above range, it becomes easier to achieve both rapid setting and workability. Calcium aluminate may also contain impurities and other foreign components other than CaO and Al2O3 derived from the raw materials, regardless of their form, as long as they do not hinder the effects of the present invention.

[0028] Calcium aluminate can be crystalline, amorphous, or a mixture thereof. From the viewpoint of obtaining better rapid setting properties, the vitrification rate, which is the degree of amorphousness, is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 95% by mass or more. The fineness of the calcium aluminate is not particularly limited, but in order to obtain appropriate reaction activity when used as a rapid setting admixture in concrete, it is preferable that the fineness is similar to or greater than that of the cement in the base concrete to be admixed, for example, a Blaine specific surface area of ​​3000 to 6500 cm². 2 One example of a powderiness level is / g.

[0029] Calcium aluminate can be obtained, for example, by heating a mixture of raw materials, which are formulated to obtain the desired molar ratio of CaO and Al2O3, until it melts. Furthermore, because differences in the cooling process after heating during manufacturing result in various differences in the structural state of the calcium aluminate after cooling, the degree of amorphization, or vitrification rate, can be adjusted according to cooling conditions such as the cooling rate.

[0030] The calcium aluminate content is preferably 60-85% by mass, more preferably 65-83% by mass, and even more preferably 70-80% by mass, based on the total mass of the rapid-setting admixture. If the calcium aluminate content is within the above range, it is easier to achieve both rapid-setting properties and mixability.

[0031] The alkali metal sulfate is not particularly limited and any type can be used, but it is preferable that it be anhydrous due to its excellent reactivity. Examples of alkali metals include lithium, sodium, and potassium, with sodium being the most preferred. One type of alkali metal sulfate may be used alone, or two or more types may be used in combination. The alkali metal sulfate content is preferably 4 to 16 parts by mass, more preferably 5 to 15 parts by mass, and even more preferably 6 to 14 parts by mass, on an anhydrous basis, per 100 parts by mass of calcium aluminate. When the alkali metal sulfate content is within the above range, it tends to exhibit excellent rapid setting and strength development.

[0032] The alkaline earth metal sulfate is not particularly limited and any type can be used, but it is preferable that it be anhydrous due to its excellent reactivity. Examples of alkaline earth metals include magnesium and calcium, with calcium being particularly preferred. The alkaline earth metal sulfate may be used alone or in combination of two or more types. The particle size and particle size of the alkaline earth metal sulfate are not particularly limited, for example, a Blaine specific surface area of ​​4000 to 8500 cm² is acceptable.2 Examples include amounts of approximately / g. The content of alkaline earth metal sulfate is preferably 10 to 35 parts by mass, more preferably 11 to 30 parts by mass, and even more preferably 12 to 25 parts by mass, on an anhydrous basis, per 100 parts by mass of calcium aluminate. If the content of alkaline earth metal sulfate is within the above range, it tends to exhibit excellent long-term strength development.

[0033] The mass ratio of alkali metal sulfates to alkaline earth metal sulfates in the rapid-setting admixture ([mass of alkaline earth metal sulfates] / [mass of alkali metal sulfates]) is preferably 1.1 to 2.5 on an anhydrous basis, more preferably 1.2 to 2.4, and even more preferably 1.3 to 2.35. If the mass ratio of alkali metal sulfates to alkaline earth metal sulfates is within the above range, rapid setting, mixability, and long-term strength development are easily obtained.

[0034] Aluminum sulfate can be in any form, such as 16-hydrate or anhydrous, with 16-hydrate being preferred. The aluminum sulfate content is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and even more preferably 1 to 5 parts by mass, on an anhydrous basis, per 100 parts by mass of calcium aluminate. If the aluminum sulfate content is within the above range, it is easier to ensure long-term strength development even when rapid setting is enhanced in a low-temperature environment.

[0035] The mass ratio of alkali metal sulfate to aluminum sulfate in the rapid-setting admixture ([mass of aluminum sulfate] / [mass of alkali metal sulfate]) is preferably 0.05 to 2 on an anhydrous basis, more preferably 0.1 to 1.8, and even more preferably 0.15 to 1.5. If the mass ratio of alkali metal sulfate to aluminum sulfate is within the above range, rapid setting, mixability, and strength development are easily obtained.

[0036] Rapid-setting admixtures are manufactured by mixing the above-mentioned components. The mixing method is not particularly limited, and general-purpose mixers such as tilt mixers, pan mixers, twin-screw mixers, grout mixers, Hobart mixers, and omni mixers can be used.

[0037] The amount of rapid-setting admixture is preferably 5 to 15 parts by mass, more preferably 6 to 14 parts by mass, and even more preferably 7 to 13 parts by mass, per 100 parts by mass of cement. Adding rapid-setting admixture within the above range makes it easier to achieve both rapid-setting properties and good mixability.

[0038] [Sprayed concrete] Shotcrete may be manufactured by a wet spraying method, for example, in which each material except for the rapid-setting admixture is mixed with water in a concrete mixer to form a base concrete, and the base concrete and rapid-setting admixture are mixed at the tip of a spraying nozzle and sprayed. Alternatively, it may be manufactured by a dry spraying method, in which each material including the rapid-setting admixture is mixed to form a base composition, and the base composition and water are mixed at the tip of a spraying nozzle and sprayed. Shotcrete is preferably manufactured by a wet spraying method from the viewpoint that dust and rebound are more easily reduced and each material can be mixed more uniformly.

[0039] The amount of water used in sprayed concrete can be adjusted as appropriate depending on factors such as the purpose and location of use. The unit volume mass of water is 100 to 300 kg / m³. 3 Preferably, it is 150-250 kg / m 3 It is more preferable that it be 170-220 kg / m 3 It is even more preferable that the unit volume mass of water is within the above range. If the pumpability during construction is further improved, it is easier to ensure high strength development. The amount of water can be adjusted within the above range whether using a wet spraying method or a dry spraying method.

[0040] The water-cement ratio ([mass of water / mass of cement] × 100) of sprayed concrete is preferably 25 to 50% by mass, more preferably 30 to 45% by mass, and even more preferably 32 to 42% by mass. If the water-cement ratio is within the above range, the pumpability during construction is further improved, and it is easier to ensure high strength development.

[0041] The compressive strength of sprayed concrete at 28 days of age is 68 kN / m². 2 Preferably, it is 70 kN / m 2 It is more preferable that the value be 75 kN / m 2 It is even more preferable that the above is true. The upper limit of the compressive strength of sprayed concrete is, for example, 150 kN / m 2 The following may also apply. If the compressive strength of the sprayed concrete is within the above range, it can maintain its strength development over a longer period, further improving the durability of the sprayed concrete. The compressive strength of the sprayed concrete can be evaluated by the uniaxial compressive strength measured using an Amsler compressive strength tester.

[0042] The sprayed concrete of this embodiment exhibits high strength development and is resistant to cracking. Therefore, the sprayed concrete of this embodiment can be suitably used for spraying on tunnel walls, slopes, environments with groundwater seepage, and environments with soft ground. [Examples]

[0043] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, the examples were conducted under conditions of 20±1℃. In the examples, all content and other figures are based on solid content and anhydrous weight.

[0044] [material] ·Rapid setting admixture Calcium aluminate: CaO / Al2O3 ratio is 2.5, Blaine specific surface area 5400 cm² 2 / g, vitrification rate 95% by mass Sodium sulfate reagent: Anhydrous Glauber's salt Calcium sulfate reagent: Anhydrous gypsum Aluminum sulfate reagent: 16-hydrate • Base concrete Cement: Ordinary Portland cement, Blaine specific surface area 3200 cm² 2 / g, density 3.15g / cm 3 Aggregate: Mixed aggregate of fine and coarse aggregate (fine aggregate ratio 62% by volume) Fine aggregate: Limestone fine aggregate (surface dry density: 2.65g / cm 3 , center grain size; 0.6mm) Coarse aggregate: Crushed stone (surface dry density: 2.74 g / cm³) 3 , particle size 5~15mm) Strengthening material 1: Anhydrous gypsum, Blaine specific surface area 11000 cm² 2 / g Strengthening material 2: Metakaolin, BET specific surface area 2.1 m² 2 / g Water-reducing agent: Polycarboxylic acid-based water-reducing agent

[0045] [Preparation of rapid-setting admixture] A formulation was designed with 1.7 parts by mass of aluminum sulfate, 10.8 parts by mass of sodium sulfate, and 20 parts by mass of calcium sulfate per 100 parts by mass of calcium aluminate. These were then mixed in a Henschel mixer to produce a rapid-setting admixture.

[0046] [Preparation of base concrete] The cement, aggregate, water, and strength enhancer were used in the unit volume masses shown in Table 1, and the water-reducing agent was added at a ratio of 1 part by mass per 100 parts by mass of cement. The base concrete was prepared by mixing each material in a concrete mixer for 2 minutes. The amount of strength enhancer is given per 100 parts by mass of cement. [Preparation of sprayed concrete] Immediately after mixing the base concrete, it was placed in a supply tank and then pumped to the spraying device via a resin hose approximately 10m long and 6cm in diameter. The spraying device is a commercially available product with a basic configuration consisting of a 2-inch inner diameter pumping pipe through which the base concrete is pumped, a cylindrical side pipe (air supply section) connected to the side of the pumping pipe at an angle of approximately 30 degrees for supplying and adding air to the base concrete, a cylindrical side pipe (rapid-setting admixture supply section) connected to the side of the pumping pipe at an angle of approximately 30 degrees for supplying and adding additives (rapid-setting admixtures) to the base concrete, and a 2-inch inner diameter (tip hole diameter) spray nozzle for spraying the sprayed concrete. The side pipe, which serves as the supply section for the rapid-setting admixture, was formed by connecting the main pressure pipe and the injection nozzle with a steel T-shaped pipe (three-way pipe). The main pressure pipe and the injection nozzle were connected to two pipe openings located on a straight line of the T-shaped pipe, and the supply pipe for the separately delivered rapid-setting admixture was connected to the remaining pipe opening. Mixing of the base concrete and rapid-setting admixture occurred in the distance from the point where the rapid-setting admixture was added to the base concrete within the T-shaped pipe (the point where the base concrete and rapid-setting admixture merge) to the end of the injection nozzle hole, and this distance (hereinafter referred to as the mixing distance) was set to 2m. The rapid-setting admixture is added to the base concrete being pumped in the spraying device by air-pressure delivery in a predetermined amount using compressed air. The added concrete is mixed as it travels a predetermined mixing distance, and sprayed concrete is produced. The amount of rapid-setting admixture added is 9 parts by mass per 100 parts by mass of cement.

[0047] [Evaluation Method] The various evaluation methods for sprayed concrete are as follows. The evaluation results are shown in Table 1. • Strength development Using the spraying apparatus described above, sprayed concrete was applied to a molding formwork with internal dimensions of 30 × 40 × 20 cm, filling the formwork completely. This was then placed in a constant temperature chamber at 20°C (±1°C), and after a predetermined period of time, cylindrical specimens with a diameter of 5 cm and a height of 10 cm were taken from the hardened concrete inside the formwork using a core drill, obtaining specimens that were 7 or 28 days old. The uniaxial compressive strength of these specimens was measured using an Amsler compressive strength tester. • Crack evaluation Concrete slabs were prepared by spraying sprayed concrete onto a 60 x 60 x 6 cm flat formwork to create a smooth surface. The concrete slabs were cured for 28 days at 20°C and 60% humidity. The cured concrete slabs were visually inspected for cracks. Those with no cracks were marked with ◎, those with cracks less than 0.5 mm wide and less than 10 cm long, and two or fewer cracks were marked with ○, and those with cracks wider than 0.5 mm, longer than 10 cm, or with three or more cracks were marked with ×.

[0048] [Table 1]

[0049] The sprayed concrete in the example showed high compressive strength on the 28th, and almost no cracks were observed. On the other hand, the sprayed concrete in the comparative example had low compressive strength, or even with high compressive strength, cracks occurred.

Claims

1. A concrete composition containing cement, aggregate and strength enhancer, a rapid-setting admixture, and water, The strength-enhancing material is gypsum and / or amorphous aluminosilicate. The content of the aforementioned strength-enhancing agent is 1 to 6 parts by mass per 100 parts by mass of cement. The unit volume mass of the cement is 450 to 600 kg / m³ ３ And, The aforementioned rapid-setting admixture contains calcium aluminate, alkali metal sulfate, alkaline earth metal sulfate, and aluminum sulfate, and is used to create sprayed concrete.

2. The sprayed concrete according to claim 1, wherein the fine aggregate content of the aggregate is 45 to 70% by volume.

3. The sprayed concrete according to claim 1 or 2, wherein the water-cement ratio, which is the ratio of the mass of water to the mass of cement, is 25 to 50% by mass.

4. The sprayed concrete according to any one of claims 1 to 3, wherein the strength-enhancing material includes amorphous aluminosilicate.

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