JP2018162196A - Spraying material for wet-spraying construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spraying material for a wet-spraying construction method, which has quick-setting properties and early strength-developability, has sufficient strength developability for a medium-to-long period, and has good workability.SOLUTION: A spraying material for a wet spraying construction method consists of: a base concrete [B]; and a powder quick-setting material [A] to be added to the base concrete. The powder quick-setting material [A] comprises 1.5-5 mass% of sodium aluminate, 4-8 mass% of alkali metal carbonate, and a balance comprising an amorphous calcium aluminate and the base concrete [B] comprises 100 pts.mass of Portland cement, 7-14 pts.mass of an anhydrous gypsum having an average water content of 0.3-0.6 mass%, 3.8-4.8 pts.mass of an aggregate, and a mixing water.SELECTED DRAWING: None

Description

  The present invention relates to a cement-based spray material used in a wet spraying method.

  In tunnels, mining pits, underground spaces, etc., mortar and concrete cement-based spray materials are used to prevent collapse of exposed excavated surfaces, reinforcement of natural ground structures, prevention of spring water from natural ground surfaces, and surface finishing of these construction surfaces. Is sprayed on the target surface. Cement-based spraying materials ensure rapid adhesion by using quick setting materials, but those using powder quick setting materials have higher initial strength than those using liquid quick setting materials. Strength development is easy to obtain. When using powder quick setting materials, at least base concrete or base mortar (hereinafter collectively referred to as base concrete unless otherwise specified), which is a pre-kneaded mixture of cement, aggregate and water, is pumped to the spraying device. The wet spraying method is adopted, and a powder quick setting material is added to the base concrete being pumped at a position near the spraying material discharge part of the spraying device to make a spraying material. Furthermore, anhydrous gypsum is required to improve not only high initial strength but also strength over the medium to long term. When anhydrous gypsum is added, it is desirable to add it together with the powder rapid setting material immediately before spraying to the base concrete because there is no blockage due to consolidation in the transport route and excellent supply stability. However, with this addition method, mixing with base concrete and quick setting material tends to be insufficient, so when increasing the amount of anhydrous gypsum, it is generally pre-mixed on the base concrete side, giving priority to mixing. (For example, see Patent Document 1). When gypsum is blended on the base concrete side, kneaded water is also blended in advance, so that the hydration reaction of gypsum progresses gradually, and there is a risk of aggregation when time progresses. As the gypsum agglomerates, the distribution of gypsum becomes uneven, and the strength development of the sprayed concrete may become uneven, and shrinkage cracks may occur in places where the gypsum distribution is dilute. If dispersants are added to the base concrete (see, for example, Patent Document 2), it may contribute to the dispersion of hydration-reactive particles such as cement. Since there is a possibility of delaying, there is a concern that the required performance as a spraying material cannot be obtained sufficiently.

JP 2004-123535 A JP 2001-316150 A

  For this reason, in the spray material for the wet spray method, the present invention hardly causes aggregation or uneven distribution even when anhydrous gypsum is blended on the base concrete side, in addition to the provision of rapid setting and high initial strength, It is an object to provide a spray material for a wet spraying method with sufficiently high long-term strength and good workability.

  Accordingly, as a result of various studies to solve the above problems, the present inventor has used a specific gypsum for gypsum, Portland cement, aggregate, base concrete gypsum containing quick setting aid and kneaded water, If calcium aluminate powder quick setting material is added to concrete, it will not cause aggregation or uneven distribution on the base concrete side, and quick setting and high initial strength can be obtained. It discovered that the spraying material for wet spraying methods was obtained, and completed this invention.

  That is, the present invention provides the following inventions (1) to (5).

(1) A spray material for a wet spray method comprising the following [B] base concrete and [A] a powder quick-setting material added thereto.
[A] A powder quick-setting material comprising 1.5 to 5% by mass of sodium aluminate, 4 to 8% by mass of alkali metal carbonate, and the balance amorphous calcium aluminate.
[B] Base concrete containing 100 parts by weight of Portland cement, 7 to 14 parts by weight of anhydrous gypsum having a total water content of 0.3 to 0.6% by weight, 3.8 to 4.8 parts by weight of aggregate and kneaded water.
(2) Anhydrous gypsum in the base concrete does not contain dihydrate gypsum and hemihydrate gypsum, The spray material for wet spraying method according to (1) above.
(3) Anhydrous gypsum with a total moisture content of 0.3 to 0.6% by mass in the base concrete is 1.5 to 4.8% by mass of anhydrous gypsum with a moisture content of 0.7% by mass or more, and the balance is moisture content. The spraying material for wet spraying method according to (1) or (2), which comprises 0.5% by mass or less of anhydrous gypsum.
(4) Any of the above (1) to (3), wherein the amorphous calcium aluminate in the powder rapid setting material contains 3.0 to 4.0 mass% of SiO ₂ as a chemical component. Spray material for wet spraying method.
(5) Any of (1) to (4) above, wherein the amount of the powder rapid setting agent added to the base concrete is 6 to 14 parts by mass with respect to 100 parts by mass of the cement in the base concrete. Spray material for the wet spray method.

  According to the present invention, agglomeration of anhydrous gypsum in the base concrete that contributes to the improvement of curability and strength development can be suppressed without using any dispersants, so that it acts uniformly on the material without unevenness. It is possible to obtain a spray material for a wet spraying method in which an increase in overall strength is achieved together with an excellent initial high strength by using a quick setting agent. Moreover, the risk of setting delay can be eliminated by not using dispersants, and high spray adhesion can be stably obtained.

  The spray material for the wet spraying method of the present invention is composed of a base concrete in a broad sense and a powder quick-setting material added thereto. The base concrete that constitutes the spray material for the wet spray method is a fresh concrete composition or mortar composition that does not contain a quick setting component such as a quick setting agent and contains at least Portland cement, aggregate, and kneaded water. The base concrete also includes anhydrous gypsum.

The Portland cement used for the base concrete may be any Portland cement, and specific examples include various ordinary Portland cements such as normal strength, early strength, ultra-high strength, moderate heat, low heat, and sulfate resistance. Moreover, mixed cement containing Portland cement such as blast furnace cement may be used. Of these, ordinary Portland cement is preferred from the viewpoint of economy and versatility. The particle size of Portland cement is not particularly limited as long as it satisfies 2500 cm ² / g or more of the JIS standard (JIS R 5210). Preferably, the particle size should be comparable to that of general commercial products (for example, approximately 2900 to 3400 cm ² / g).

  The aggregate used for the [B] base concrete is composed of fine aggregate and coarse aggregate in the case of concrete blending, and is composed of only fine aggregate in the case of mortar blending. The fine aggregates and coarse aggregates are not limited in terms of materials as long as they can be used for concrete and mortar. Preferably, natural or artificial ordinary aggregate can be mentioned. Specifically, examples of the fine aggregate include river sand, mountain sand, sea sand, ore powder such as silica powder and limestone powder, rock crushed sand, and slag aggregate. Examples of coarse aggregates include gravel, crushed stone, and artificial ore. The content ratio of the fine aggregate and the coarse aggregate in the case of blending with concrete is not particularly limited. Preferably, when obtaining a dense and homogeneous sprayed construction, the content of coarse aggregate in the aggregate is 1.4 to 2.1% (in terms of mass). The aggregate content in the base concrete is 4 to 4.8 parts by mass as the total aggregate amount regardless of the concrete composition or mortar composition with respect to 100 parts by mass of the Portland cement content in the base concrete. An aggregate amount exceeding 4.8 parts by mass is not preferable because the strength decreases, and an aggregate amount less than 4 parts by mass tends to reduce the kneadability after water pouring, and the sprayed material construction after spraying. This is not preferable because shrinkage increases and cracks may occur.

The base concrete contains anhydrous gypsum having a total water content of 0.3 to 0.6% by mass (in terms of mass). Although the specific surface area of the anhydrous gypsum contained is not particularly limited, it is preferable to have a higher reaction activity. Therefore, the specific surface area of the brane is preferably 10,000 cm ² / g or more, more preferably 20000 cm ^2. / G or more. The anhydrous gypsum having a total water content of 0.3 to 0.6% by mass may be one type of anhydrous gypsum, or two or more types of anhydrous gypsum. In particular, when two or more types of anhydrous gypsum are used, the water content is calculated from the total water content of all the anhydrous gypsum used, and this is used as the total water content. When only one kind of anhydrous gypsum is used, the moisture content is taken as the total moisture content. By using anhydrous gypsum having such a total water content, anhydrous gypsum hardly aggregates in the base concrete even after pouring water, it is easy to uniformly disperse, and a relatively high reaction activity can be maintained for a long time. Thereby, the promotion effect of hardening and the improvement effect of strength expression over the medium to long term can be provided uniformly over the entire spray material.
Preferably, the anhydrous gypsum has a moisture content of 0.7% by mass or more, more preferably 1.5 to 4.8% by mass with a moisture content of 0.7 to 1.5% by mass, and the balance being the moisture content. The thing of 0.5 mass% or less, Preferably the thing of 0.1-0.5 mass% of water content is used. By combining two or more types of anhydrous gypsum having different moisture contents at a specific ratio, the above-described action is more accurately and strongly expressed.
If the anhydrous gypsum in the base concrete is less than 0.3% by mass of the total moisture content, it is not preferable because the initial strength development is reduced. If the anhydrous gypsum in the base concrete exceeds 0.6% by mass, In addition to the possibility that the powder fluidity is lowered and the workability is deteriorated or the property stability is impaired, the medium-to-long-term strength development property is lowered, which is not preferable. The content of such anhydrous gypsum in the base concrete is 7 to 14 parts by mass with respect to 100 parts by mass of the Portland cement content in the base concrete. An anhydrous gypsum content exceeding 14 parts by mass is not preferred because it may cause overexpansion and setting delay, and an anhydrous gypsum content of less than 7 parts by mass is not preferred because strength improvement and hardening cannot be sufficiently obtained. Absent. The anhydrous gypsum having a total water content of 0.3 to 0.6% by mass does not include hydrated gypsum such as dihydrate gypsum and hemihydrate gypsum. Specifically, it is composed of, for example, natural crystals such as type II anhydrous gypsum and moisture in which no chemical bond relationship is found.
Portland cement contains a small amount of gypsum, but since it is a constituent of Portland cement, it is included in Portland cement itself and not included in anhydrous gypsum blended in base concrete.

  Moreover, the said base concrete can contain a component other than the above, if it does not inhibit the effect of this invention. Examples of components that can be used include powdery thickeners, setting accelerators, pozzolanic reactive substances, and short fibers that are used in mortar and concrete.

  Among these, those containing short fibers are preferable. The short fiber is not particularly limited as long as it is a fiber made of a material such as organic polymer, carbon, steel, glass, and ceramics that can be used for mortar and concrete. Preferably, an organic polymer is used because it has folding resistance and corrosion resistance and is relatively inexpensive. The length of the short fiber is not particularly limited, but is preferably 5 to 20 mm, more preferably 10 to 12 mm. The fiber diameter is not particularly limited, but is preferably 1 mm or less for obtaining a sufficient fiber blending effect. By containing short fibers, the cracking resistance of the sprayed concrete construction is improved. In addition, the toughness of the construction is improved. In order to express such an operational effect, the content when short fibers are included is preferably about 0.03 to 0.25% by volume of the entire base concrete.

  Further, the amount of the kneading water contained in the base concrete is not particularly limited as long as it can react with a component having a hydration reaction activity such as cement and the like almost without excess or deficiency. If the standard of the amount of kneading | mixing water is illustrated, it will be 35-60 mass parts of kneading | mixing water with respect to 100 mass parts of Portland cement content. Preferably, the amount of the kneaded water is 45 to 55 parts by mass in order to improve the kneadability at the time of pouring water and enhance the strength development property of the spray material.

The amorphous calcium aluminate in the [A] powder quick-setting material constituting the spray material for wet spraying method of the present invention is an inorganic hydration active substance containing CaO and Al ₂ O ₃ as main chemical components. It is obtained by heating a raw material mixture considering a raw material to be a CaO source and a raw material to be an Al ₂ O ₃ source so as to have a desired content molar ratio (CaO / Al ₂ O ₃ ) until it is preferably melted. Preferably, the amorphous calcium aluminate has a molar ratio of CaO to Al ₂ O ₃ as a chemical component to be contained (CaO / Al ₂ O ₃ ) of 1.9 to 2.8, more preferably. Has a molar ratio (CaO / Al ₂ O ₃ ) of 2.2 to 2.4. When the content molar ratio (CaO / Al ₂ O ₃ ) is in the range of 1.9 to 2.8, adhesion and strength development are improved, and the setting time is appropriate. Further, for example, when manufactured using a natural mineral raw material, impurities other than CaO and Al ₂ O ₃ mainly derived from the raw material used are in a range that does not hinder the effects of the present invention regardless of the form of the impurities. Amorphous calcium aluminate containing is acceptable. Preferably, the content of SiO ₂ as a chemical component is 4.3% by mass or less among the impurities because higher initial strength development can be obtained. More preferably, the content of SiO ₂ as a chemical component is 3.0 to 4.3% by mass because the elongation of strength development in the medium to long term is improved. Further, the amorphous calcium aluminate does not have to be completely in a glass state, and may have a structure in which vitrification has advanced. Specifically, the vitrification rate is preferably 50% or more, more preferably 90% or more. The higher the activity of vitrification, the higher the reaction activity. The adjustment of the vitrification rate can be performed, for example, by a cooling process from a high temperature that has reached a molten state. In general, the faster the quenching rate, the higher the vitrification rate of calcium aluminate. Moreover, by using such an amorphous calcium aluminate as an essential component, it is possible to sufficiently compensate for the shortage of rapid setting force when using a quick setting agent that is not so strong in rapid setting.

Sodium aluminate contained in the powder rapid-setting material is necessary as a quick-setting aid, and in particular, has the effect of accelerating the setting time and promoting the hardening. Any sodium aluminate may be used, and an anhydride is preferably used. The content of sodium aluminate necessary for imparting the above action to the concrete spray material is set to 1.5 to 5% by mass. If the amount is less than 1.5% by mass, the above-mentioned effects are hardly obtained, which is not preferable. If the amount exceeds 5% by mass, an increase in strength cannot be obtained and the medium- to long-term strength is sluggish. A more preferable content of sodium aluminate is 2 to 4% by mass.
Moreover, components other than sodium aluminate and alkali metal carbonate in the powder quick-setting material are the amorphous calcium aluminate.

  The alkali metal carbonate contained in the powder rapid setting material is also necessary as a quick setting aid, and particularly imparts an action of increasing strength in a short time of a minute unit. Examples of the alkali metal carbonate include lithium carbonate, potassium carbonate, and sodium carbonate, any of which can be used, or any two or more of them can be used. The content of the alkali metal carbonate necessary for imparting the action to the concrete spray material in the powder quick-setting material is 4 to 8% by mass. If it is less than 4% by mass, the above-mentioned action is hardly obtained, which is not preferable. A more preferable content of alkali metal carbonate is 5 to 7% by mass.

  The addition amount of the [A] powder rapid setting material to the [B] base concrete is preferably 6 to 14 parts by mass, more preferably 100 parts by mass of Portland cement content in the base concrete. The added amount is 8 to 12 parts by mass. If the amount added is within this range, not only the quick setting performance is high, but also rapid solidification can be prevented at the junction between the base concrete and the quick setting material, the pumping path is not blocked, and long-term strength is developed. Sex is also obtained. Moreover, the high intensity | strength expressiveness from the very initial stage is obtained.

  Water injection and kneading of the base concrete for obtaining the spray material for the wet spraying method of the present invention can be performed with a normal kneading apparatus, and for example, a forced biaxial mixer or the like can be used. In addition, the obtained base concrete can be transported for a relatively long distance to the construction site using, for example, an agitator car, etc., but at the construction site, from a tank or the like for storing the transported material from the site plant or agitator car, The base concrete is conveyed by pumping to the spraying device via a hose or a transport pipe. The powder quick-setting material is added to the base concrete being conveyed. Regarding the addition of the powder quick-setting material, for example, a method is recommended in which a Y-tube or the like is provided, and the powder quick-setting material sent from another place by compressed air or the like and the pumped base concrete are merged. It is desirable that the merging point of both is relatively close to the nozzle of the spraying device.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the described examples. The examples were performed in an environment of 20 (± 1) ° C. unless otherwise specified.

[Preparation of calcium aluminate]
Using commercially available industrial chemicals CaCO ₃ and Al ₂ O ₃ , the weight ratio of CaO and Al ₂ O ₃ (CaO / Al ₂ O ₃ ) was evaluated so that the calcium aluminate represented below was obtained. The raw material formulation was prepared with a Henschel mixer. The raw material mixture was baked at about 1600 ° C. (± 50 ° C.) for 60 minutes using an electric furnace, and immediately after the baking time, the raw material mixture was taken out of the furnace. Nitrogen for cooling was blown onto the surface of the taken-out calcined mass (clinker) at a flow rate of about 30 mL / second to quench it, and a cooled product was obtained. In order to adjust the vitrification rate, some clinker was sprayed with the flow rate of nitrogen gas lowered. Furthermore, the Al ₂ O ₃ industrial chemicals used were also changed for some of the formulations. Each clinker was pulverized with a ball mill made of all steel, and sized with a classifier to a Blaine specific surface area of about 5000 cm ² / g. Calcium aluminate powder represented by the following CA1 to CA6 was obtained as the sized powder. The obtained calcium aluminate was quantitatively analyzed for the SiO ₂ content (% by mass) in the calcium aluminate clinker using a powder X-ray diffractometer by an internal standard method. In addition, the vitrification rate of calcium aluminate was determined by using a powder X-ray diffractometer and quantifying the mass of each mineral contained in the calcium aluminate clinker having a mass of M1 using an internal standard method, etc. Mass: M2 was calculated, the remainder was regarded as a pure glass phase, and the vitrification rate was calculated by the following formula.
Vitrification rate (%) = (1-M2 / M1) × 100

[Prepared calcium aluminate]
CA1; content molar ratio (CaO / Al ₂ O ₃ ) 2.8, vitrification rate 90%, SiO ₂ content rate 3.5% by mass
CA2; content molar ratio (CaO / Al ₂ O ₃ ) 2.3, vitrification rate 90%, SiO ₂ content rate 3.6% by mass
CA3; molar ratio (CaO / Al ₂ O ₃ ) 2.3, vitrification rate 50%, SiO ₂ content rate 3.6% by mass
CA4; content molar ratio (CaO / Al ₂ O ₃ ) 1.9, vitrification rate 90%, SiO ₂ content rate 3.6% by mass
CA5; content molar ratio (CaO / Al ₂ O ₃ ) 2.3, vitrification rate 90%, SiO ₂ content rate 3.0% by mass
CA6; content molar ratio (CaO / Al ₂ O ₃ ) 2.3, vitrification rate 90%, SiO ₂ content rate 4.3 mass%

[Preparation of powder quick-setting material]
A material selected from calcium aluminate powder represented by CA1 to CA6, sodium aluminate represented by AN (commercial reagent), sodium carbonate represented by NC (commercial reagent), and lithium carbonate represented by LC (commercial reagent). It put into the Henschel mixer so that it might become the compounding quantity shown in Table 1. This mixer was dry-mixed for about 1 minute to produce a powder quick setting material.

[Production of base concrete]
Ordinary Portland cement (commercial product, Blaine specific surface area 3200 cm ² / g), anhydrous gypsum represented by the following CS1 to CS4, dihydrate gypsum (commercial reagent, Blaine specific surface area 20000 cm ² / g), fine aggregate (land sand from Kakegawa The material selected from the surface dry density of 2.58 g / cm ³ ) and the kneaded water (clean water) are put into a forced biaxial mixer so as to have the composition shown in Table 2, and kneaded for 2 minutes. Concrete was produced. In addition, the anhydrous gypsum (CS1-CS4) investigated the crystal phase by powder X-ray diffraction, and confirmed that there was no crystal phase of gypsum compounds other than the type II anhydrous gypsum. In addition, the water content of anhydrous gypsum was examined using a combination of suggested thermal analysis and a thermobalance.

[Used gypsum]
CS1: anhydrous gypsum, Blaine specific surface area 20000 cm ² / g, moisture content 0.1%
CS2: anhydrous gypsum, Blaine specific surface area 20000 cm ² / g, water content 0.5%
CS3: anhydrous gypsum, Blaine specific surface area 20000 cm ² / g, moisture content 0.7%
CS4: anhydrous gypsum, Blaine specific surface area 20000 cm ² / g, water content 1.2%

[Production of spraying material with mortar]
The produced base concrete was pumped through a resin hose pipe having a length of about 30 m and an inner diameter of 4.0 cm to a spraying device by pumping. With the Y pipe installed in the spraying device, the powder quick-setting material pneumatically fed from another place was added to the base concrete that had been pressure-fed so as to have an addition amount shown in Table 3. From the addition point, the spray material was sprayed through the nozzle for injection provided about 50 cm ahead.

[Evaluation of quick setting of spray material containing mortar]
For the spray material produced as described above, after 30 seconds from the addition of the powder rapid setting agent, the Procter penetration resistance value after 60 seconds was measured, and the rapid setting property was evaluated. The measurement method of Proctor penetration resistance is based on the Japan Society of Civil Engineers Standard Specification “Quality Standards for Sprayed Concrete” appendix “Method for Measuring Instantaneous Setting Time of Mortar Using Penetration Resistance” and has a cross-sectional area of 0.125 cm ² . A proctor needle was used. Table 4 shows the measurement results of the penetration resistance value. Here, “−” described in the table indicates that the measurement object was hardened and the proctor needle could not be driven through. Further, according to become "> 16 (N / mm ^2)" is possible is driving the Proctor needle, but beyond the measurement limit of the fleet (maximum 16N / mm ^2). Moreover, the thing which was not condensing and was not worth measuring was displayed as "x".

[Evaluation of spray fixability of spray material]
The spray material produced as described above was subjected to spraying using a commercially available mortar spray gun immediately after production. The spray construction was sprayed toward the following objects. That is, the spraying mortar was sprayed at a flow rate of 160 mL / min toward a concrete plate surface of 3 mm square with a thickness of 9 mm installed vertically at a point about 100 cm away from the nozzle hole of the mortar spraying gun. The evaluation of the fixability of the sprayed product is determined by visual observation, with the mortar sprayed on the flat plate surface determined not to sag or peel off, and the adherence was judged to be “good”, and the other states All of those that were evaluated as having poor adhesion. After such spraying for 3 minutes, after stopping the supply of base concrete for 30 minutes and stopping the spraying, when the base concrete supply is resumed and sprayed again, the base concrete is pumped. If there is a problem with spraying or if there is a spraying failure such as a decrease in the spraying amount of the spraying material, it is judged that the pumpability is “bad”, these phenomena are not seen, smooth pumping is possible, and fluctuations in the spraying amount are also observed. Those that could not be determined were judged to have good pumpability. The results are shown in Table 5.

[Evaluation of strength development of spray material]
Immediately after production, the spray material produced as described above was filled into a molding mold having an inner size of 40 × 40 × 160 mm. This was allowed to stand in indoor air for 20 minutes and then demolded. Specimens having a material age of 30 minutes, 1 day and 28 days were obtained. The uniaxial compressive strength of each specimen was measured with an Amsler type compressive strength tester. This result is also shown in Table 5. In addition, what was not hardened | cured with the predetermined material age was described as "x", and the strength test could not be performed.

  From the results of Tables 4 and 5, the spray material of the present invention has a quick setting property that can sufficiently secure the adhesion during spraying, provides high strength development from the beginning, and the elongation of strength is very high. It turns out that it is good.

Claims (5)

A spray material for a wet spraying method comprising the following [B] base concrete and [A] a powder quick-setting material added thereto.
[A] A powder quick-setting material comprising 1.5 to 5% by mass of sodium aluminate, 4 to 8% by mass of alkali metal carbonate, and the balance amorphous calcium aluminate.
[B] Base concrete containing 100 parts by weight of Portland cement, 7 to 14 parts by weight of anhydrous gypsum having a total water content of 0.3 to 0.6% by weight, 3.8 to 4.8 parts by weight of aggregate and kneaded water.   [B] The spray material for wet spraying method according to claim 1, wherein the anhydrous gypsum in the base concrete does not contain dihydrate gypsum and hemihydrate gypsum.   [B] The total moisture content of the base concrete is 0.3 to 0.6% by mass of anhydrous gypsum, 1.5 to 4.8% by mass of anhydrous gypsum having a moisture content of 0.7% by mass or more, and the balance is 0% of moisture content. The spraying material for wet spraying methods according to claim 1 or 2, comprising anhydrous gypsum of 5% by mass or less. [A] The amorphous calcium aluminate in the powder quick-setting material contains 3.0 to 4.0% by mass of SiO ₂ as a chemical component. Spray material for wet spraying method.   The amount of [A] powder quick setting material added to [B] base concrete is 6 to 14 parts by mass with respect to 100 parts by mass of cement in the base concrete. Spray material for wet spraying method.