JP2006016261A - Spraying composition, spraying paste, and method of rust prevention processing using them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spraying composition that is effective in rust prevention of reinforced concrete, a spraying paste, and a method of rust prevention processing. <P>SOLUTION: The spraying composition includes one or more compounds selected from a nitrite, an amine, a molybdic acid or its salt and a tungstic acid or its salt, and calcium aluminate comprising 63-21% CaO and 37-79% Al<SB>2</SB>O<SB>3</SB>as well as gypsum. It can further include a setting retarder, cement and/or an inorganic fine powder, a polymer, and water. The method of rust prevention processing comprises spraying the spraying paste onto a steel material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spray composition that suppresses corrosion of steel materials such as steel wires in reinforcing bars, steel frames, and prestressed concrete, and prevents rusting, and a rust prevention treatment method using the same. Unless otherwise specified, parts and% in the present invention are shown on a mass basis.

  In cross-section repair work and the like, a work of applying a rust prevention treatment to a steel material of a concrete structure deteriorated due to salt damage or the like is widely performed. Cross-section restoration work usually involves removing degraded concrete, exposing the internal reinforcing bars, applying rust-proofing material to the reinforcing bars by spraying or troweling, etc., and cross-sectioning with a durable cement composition. Covering and repairing work. A rust preventive material may be added to the cement composition.

  Examples of the rust preventive material include an organic solvent-based rust preventive material containing an organic solvent such as xylene, toluene, and thinner, and a hydrophilic rust preventive material. The organic solvent rust preventive has quick drying properties. Cement compositions containing nitrite are used as hydrophilic rust preventives that are not flammable and have little impact on health in repair work of concrete structures (see Non-Patent Document 1, Patent Documents 1 and 2, etc.) ).

  Examples of other rust preventive materials include compositions containing highly viscous amines (see Patent Documents 3 and 4, etc.) and compositions containing tungstic acid and molybdic acid (see Patent Document 5 etc.).

  Also included are silicates, phosphates, chromates, organic acids, ester salts, sulfonic acids, alkylphenols, mercaptans, nitro compounds, and organic phosphates (see Non-Patent Document 2, etc.).

  These rust-preventing substances are often used in combination with mortar or concrete in advance, but after applying a low-viscosity nitrite aqueous solution to the entire exposed steel bar surface, further apply polymer cement mortar, A method of repairing concrete deteriorated by salt damage has also been proposed (see Patent Document 6).

Synthetic rubber latex, 11CaO · 7Al ₂ O ₃ · CaX ₂ (X is a halogen atom), quick-hardening cement containing 3CaO · SiO ₂ and CaSO ₄ as essential components, aggregates, surfactants, etc. as necessary An anticorrosion and anticorrosion coating composition for steel obtained by adding an additive is known (Patent Document 7).

  In order to exhibit a sufficient rust prevention effect over a long period of time, a method of securely fixing the rust prevention substance inside the cement / concrete before diffusion or flow-out has been required.

  As a result of various studies to suppress a decrease in the concentration of the rust preventive component in the vicinity of the reinforcing bar due to the diffusion of the rust preventive component, the present inventor has come to solve the above problem by using a specific spray composition.

Japanese Patent Publication No. 02-28532 Japanese Patent Application Laid-Open No. 07-61852 Japanese Patent Application Laid-Open No. 07-173650 JP 2000-7401 A JP 2002-12458 A JP 2003-120041 A JP-A-56-84768 Takataka Hori, Satoshi Yamazaki, Yoshihiro Hamada: Research on rust mortar, Concrete Engineering, Vol. 5, no. 1, pp. 89-97, 1994 Norihiro Kudo, Hiroshi Ibe: Rust preventives used for sea sand reinforced concrete, cement concrete, No. 350, pp. 28-37, 1976

  The present invention provides a novel spray composition, spray paste, and a rust preventive treatment method using the same.

That is, the present invention is a calcium aluminate containing at least one selected from nitrite, amine, molybdic acid or a salt thereof, and tungstic acid or a salt thereof, CaO 63-21% and Al ₂ O ₃ 37-79%, A spray composition containing gypsum, the spray composition containing a setting retarder, the spray composition containing cement and / or inorganic fine powder, and the spray composition containing a polymer. A spraying composition comprising a spraying composition and water, wherein the spraying paste is sprayed onto a steel material.

  By using the spray composition of the present invention, the spray paste, and the antirust treatment method using the same, it is possible to obtain sufficient strength in a short time with a short setting time and an appropriate viscosity. Therefore, the outflow of the rust preventive component when applied can be suppressed. And since an active ingredient is fix | immobilized around a reinforcing bar in a short time, the fall of the active ingredient density | concentration near a reinforcing bar can be suppressed. Furthermore, since it is only applied to the exposed reinforcing bars, the amount used is small and advantageous in terms of cost, and has a sufficient antirust effect over a long period of time. In addition, a large construction area can be repaired in a short period of time.

  In the present invention, for example, a mixture of calcium aluminate and gypsum, cement, and inorganic fine powder are used as the binder. The inorganic fine powder is not particularly limited. For example, silica fume, fly ash, blast furnace slag, blast furnace gradual cooling are effective in improving the material separation resistance by increasing the viscosity of the kneaded product and densifying the hardened structure. It is preferable to use one or more fine powders such as slag and electric furnace reduction period slag, and to use one or more fine powders of granulated blast furnace slag, silica fume, and fly ash that show latent hydraulic or pozzolanic properties. More preferred.

  Calcium aluminate is obtained, for example, by calcining a mixture of a CaO raw material or an Al2O3 raw material in a kiln or melting in an electric furnace or the like. Calcium aluminate in the range of 37-79% is used as Al2O3. The mineral component of calcium aluminate is not particularly limited, but when CaO is C and Al2O3 is A, for example, pulverized calcium aluminate represented by C3A, C12A7, CA, CA2, etc. One or more aluminates can be used.

As the calcium aluminate, calcium aluminate in which an oxide of an alkali metal such as sodium, potassium and lithium, SiO ₂ , SO ₃ or the like is dissolved can be used.

  Calcium aluminate can be either crystalline or amorphous, but amorphous calcium aluminate is preferred in terms of reaction activity.

Without limitation calcium granularity of aluminate is particularly preferable 3,000 cm ² / g or more in Blaine value, 5,000 cm ² / g or more is more preferable. If coarse calcium aluminate is used, the coagulation properties may be reduced.

  Gypsum is used to improve strength development. Although gypsum is not specifically limited, For example, an anhydrous gypsum, a semi-water gypsum, a two-water gypsum, etc. are mentioned, 1 or more types of these gypsum can be used. Among these gypsums, anhydrous gypsum is preferable in terms of strength development.

  The amount of gypsum used is preferably 20 to 300 parts, more preferably 50 to 200 parts, per 100 parts of calcium aluminate. If the amount of gypsum used is small, strength development may be insufficient, and if used excessively, initial strength development may be insufficient.

  The cement is not particularly limited. For example, various portland cements defined in JIS R 5210, eco-cement, various mixed cements defined in JIS R 5211, JIS R 5213, and JIS R 5213. Examples thereof include blast furnace cement, fly ash cement, silica cement, filler cement mixed with limestone powder and the like manufactured at the above admixture mixing rate, and one or more of these cements can be used. Cement is preferably used if it is necessary to improve the long-term strength development.

  The amount of cement used is preferably 10 to 2,000 parts, more preferably 50 to 1,500 parts, with respect to 100 parts in total of calcium aluminate and gypsum. If the amount of cement used is small, the effect of improving the strength may not be expected, and if used excessively, the initial strength may be weakened.

The particle size of the inorganic fine powder is preferably at 4,000 cm ² / g or more at normal Blaine specific surface area, and more preferably 10,000 cm ² / g or more.

  The amount of the inorganic fine powder used is preferably 0.5 to 100 parts, more preferably 2 to 50 parts with respect to 100 parts in total of calcium aluminate and gypsum. If the amount of the inorganic fine powder is small, there is a possibility that improvement in material separation resistance and densification of the hardened structure may not be expected. If it is used excessively, strength development may be reduced.

  Nitrite has a rust prevention effect on steel in an environment where chloride ions are present. The nitrite is not particularly limited, and examples thereof include lithium nitrite, sodium nitrite, potassium nitrite, calcium nitrite, magnesium nitrite, and barium nitrite, and one or more of these nitrites can be used. . Among these nitrites, lithium nitrite and / or calcium nitrite are preferable because they are inexpensive and easily available and do not adversely affect the alkali-aggregate reaction.

  The amount of nitrite used is preferably 2 to 100 parts and more preferably 7 to 70 parts with respect to 100 parts of the binder. If the amount of nitrite is small, there is a possibility that the anticorrosive effect of the reinforcing bars cannot be expected, and if it is used excessively, strength development may be reduced.

  As the nitrite, a powder or an aqueous solution may be used.

  The amine is not particularly limited. For example, benzotriazole, N, N-dimethyl-ethanolamine, N-methyl-ethanolamine, monoethanolamine, diethanolamine, triethanolamine, N-cured tallow alkyl-1.3-diaminopropane , Octadecylamine, and octadecylamine acetate, and one or more of these amines can be used. Among these amines, triethanolamine is preferable because it is inexpensive and easily available.

  The amount of amine used is preferably 0.05 to 5 parts, more preferably 0.2 to 3 parts, relative to 100 parts of the binder. If the amount of amine is small, there is a possibility that a sufficient effect cannot be exhibited, and even if it is used excessively, a further effect cannot be expected, which may be uneconomic.

  Tungstic acid or a salt thereof has a rust preventive effect on steel in an environment where chloride ions are present. The tungstate is not particularly limited, and examples thereof include tungstic acid, calcium tungstate, magnesium tungstate, sodium tungstate, potassium tungstate, lithium tungstate, and the like. The above can be used.

  The amount of tungstic acid or a salt thereof used is preferably from 0.1 to 20 parts, more preferably from 0.3 to 10 parts, based on 100 parts of the binder. If the amount of tungstic acid or a salt thereof used is small, there is a possibility that a sufficient rust prevention effect cannot be exhibited, and even if it is used excessively, a further effect cannot be expected, which may be uneconomical.

  The molybdic acid or a salt thereof is not particularly limited, and examples thereof include molybdic acid, calcium molybdate, magnesium molybdate, sodium molybdate, potassium molybdate, and lithium molybdate. More than species can be used.

  The amount of molybdic acid or a salt thereof used is preferably from 0.1 to 20 parts, more preferably from 0.3 to 10 parts, based on 100 parts of the hydraulic component. If the amount of morbiddenic acid or a salt thereof used is small, there is a possibility that a sufficient rust prevention effect cannot be exhibited, and even if it is used excessively, no further effect can be expected, which may be uneconomical.

  In the present invention, it is possible to use one or more nitrites, amines, tungstic acid or salts thereof, and molybdic acid or salts thereof, which have a rust-proofing effect on steel materials in the presence of chloride ions.

  The setting retarder is not particularly limited, and examples thereof include oxycarboxylic acids such as citric acid, tartaric acid, gluconic acid, and malic acid, phosphoric acid, boric acid, and lithium oxycarboxylic acid, phosphoric acid, and boric acid. Sodium, potassium, calcium, magnesium, and barium salts, and sugars such as sucrose and fructose, and one or more of these setting retarders can be used.

  Combinations of these setting retarders with carbonates, sulfates, nitrates, aluminates, silicates, and the like can also be used.

  Furthermore, oxycarboxylic acid and its salt have the effect | action which forms a complex with the tungstate and molybdate etc. which have a rust prevention effect, and coat | covers the steel material surface, and have a synergistic rust prevention effect.

  0.1-2 parts are preferable with respect to a total of 100 parts of calcium aluminate and gypsum, and 0.3-1 part is more preferable. If the amount of setting retarder used is small, sufficient pot life may not be ensured, and if used excessively, strength development may be hindered.

  The polymer is not particularly limited. For example, rubber latex such as acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, and natural rubber, polyacrylate ester, styrene-acrylate copolymer, and acrylonitrile-acrylate ester. Acrylic ester copolymer such as ethylene-vinyl acetate copolymer, vinyl acetate-veova copolymer, resin emulsion such as vinyl acetate-veova-acrylic copolymer, etc., and one of these polymers The above can be used. Examples of the polymer form include a re-emulsification type powder type and a liquid type. The polymer is used for preventing the mortar from rebounding, improving the adhesion to the base portion, and further improving the durability of the mortar.

  Among these polymers, acrylate ester copolymers, styrene-butadiene rubbers, ethylene-vinyl acetate copolymers, vinyl acetate-versaic acid vinyl copolymers, and vinyl acetate-veova-acrylic copolymers. 1 or more types are preferable, and 1 or more types of an acrylic ester copolymer, a vinyl acetate-veova, and a vinyl acetate-veova-acrylic copolymer are more preferable.

  The amount of the polymer used is preferably 2 to 15 parts, more preferably 4 to 10 parts, relative to 100 parts of the hydraulic component. If the amount of the polymer used is small, the adhesion strength may be insufficient and rebound may increase, and even if used excessively, further improvement in the effect may not be expected.

  In this invention, for example, it sprays and applies to a reinforcing bar as a spraying paste which added water to the spraying composition. Although the usage-amount of water is not specifically limited, Even if it applies to steel materials, it should just not flow down significantly. Specifically, 20 to 200 parts of water is preferable with respect to 100 parts of the hydraulic component, and 35 to 100 parts is more preferable. If the amount of water is too small, it may be too hard to be applied, and even if it is used excessively, the viscosity is too small and it may fall off the steel.

  The antirust treatment method of the present invention is not particularly limited as long as the spray paste can be sprayed onto the steel material. For example, there is a method in which the deteriorated part of concrete is removed, the steel material is exposed, and a spray paste is sprayed on the steel material using a ricin gun, or a method of applying with a trowel, spatula, brush, roller, etc. Can be mentioned. In addition, a Y-tube is connected in front of the spray nozzle, a composition obtained by removing calcium aluminate and gypsum from the spray paste is transported from one side, and a mixture of calcium aluminate and gypsum is pneumatically transported from the other side. A method of mixing and spraying may also be mentioned. The coating thickness is not particularly limited, but when applied to a deformed reinforcing bar or the like, it may be applied to the extent that the irregularities of the deformed portion are not lost. Generally 0.1 to 0.5 mm is appropriate.

  The mixing method of the spray composition and spray paste of the present invention is not particularly limited, but all raw materials may be mixed at once, a part of the material may be mixed in advance, and other components may be mixed. Good. For example, when using a lithium nitrite aqueous solution, dry-mix powder components such as calcium aluminate, gypsum, and cement as a method of mixing a part of the material in advance and further mixing other components. , Dry mixing method that kneads, pumps and merges with water or lithium nitrite aqueous solution, wet mixing that mixes calcium aluminate and gypsum mixture into paste kneaded with cement, water and lithium nitrite aqueous solution Law.

  The present invention relates to known cement additives such as water reducing agents, AE agents, AE water reducing agents, high performance water reducing agents, high performance AE water reducing agents, antifoaming agents, shrinkage reducing agents, antifreezing agents, thickeners, fibers. In addition, an antibacterial agent, a water repellent and the like may be used in combination as long as the effects of the present invention are not impaired.

  Add 100 grams of gypsum to 100 parts of calcium aluminate, 0.8 parts of a set retarder to 100 parts of calcium aluminate and gypsum, 10 parts of nitrite in solids, 70 parts of water, Using a spatula, the mixture was stirred by hand for 20 seconds to obtain a spray paste, and the curing time of the resulting spray paste was measured. Furthermore, compressive strength and rust resistance were measured using a sample sampled from a cured product sprayed with a lysing gun. The results are shown in Table 1.

(Materials used)
Calcium aluminate A: mainly composed of amorphous calcium aluminate having a C12A7 composition, CaO 48%, Al ₂ O ₃ 52%, Blaine specific surface area 6,000 cm ² / g
Calcium aluminate B: mainly composed of CA calcium amorphous alumina, CaO 35%, Al ₂ O ₃ 63%, SiO ₂ 2%, Blaine specific surface area 6,000 cm ² / g
Calcium aluminate C: mainly composed of amorphous calcium aluminate having a C3A composition, CaO 61%, Al ₂ O ₃ 37%, SiO ₂ 2%, Blaine specific surface area 6,000 cm ² / g
Calcium aluminate D: mainly composed of crystalline calcium aluminate having a composition of C12A7, CaO 47%, Al ₂ O ₃ 51%, SiO ₂ 2%, Blaine specific surface area 6,000 cm ² / g
Calcium aluminate E: C2.5 Amorphous calcium aluminate of 5A composition, mainly CaO 56%, Al ₂ O ₃ 42%, SiO ₂ 2%, Blaine specific surface area value 6,000 cm ² / g
Calcium aluminate F: C1, mainly composed of amorphous calcium aluminate with 2A composition, CaO 39%, Al ₂ O ₃ 59%, SiO ₂ etc. 2%, Blaine specific surface area 6,000 cm ² / g
Calcium aluminate G: mainly composed of amorphous calcium aluminate having a CA ₂ composition, CaO 22%, Al ₂ O ₃ 78%, Blaine specific surface area 6,000 cm ² / g
Gypsum: Anhydrous gypsum, a commercial product, Blaine specific surface area value 4,000 cm ² / g
Setting retarder: sodium citrate, commercially available nitrite: lithium nitrite aqueous solution, solid content 40%, commercially available product

(Test method)
Curing time: The time from when the spray composition was kneaded in the cup until it could not be applied with a brush was measured.
Compressive strength: measured in accordance with JIS R 5201 using a 4 cm × 4 cm × 16 cm rectangular parallelepiped specimen.
Rust prevention: Conforms to the method of rust prevention test of JHS 415 (Japan Highway Public Corporation standard, quality standard test method for reinforcing steel rust prevention material). The steel was checked for rust, blistering, peeling and cracking. The case where there was considerable rust, blistering, peeling, and cracking was rated as x, the case where there was a little was △, and the case where there was not.

  Implemented except that 100 parts of gypsum was added to 100 parts of calcium aluminate A, and the amount of setting retarder shown in Table 2 was added to 100 parts of binder (total of calcium aluminate, gypsum, cement and inorganic fine powder). Performed as in Example 1. The results are shown in Table 2.

  The same procedure as in Example 1 was conducted except that 100 parts of gypsum was added to 100 parts of calcium aluminate A, 0.8 part of the setting retarder was added to 100 parts of the binder, and the amount of nitrite shown in Table 3 in terms of solid content was added. It was. The results are shown in Table 3.

  The same procedure as in Example 1 was conducted except that 100 parts of gypsum was added to 100 parts of calcium aluminate A, 0.8 part of a setting retarder was added to 100 parts of binder, and the amount of amine shown in Table 4 was added. The results are shown in Table 4.

(Materials used)
Amine: Triethanolamine, commercial product

  The same procedure as in Example 1 was performed except that 100 parts of gypsum was added to 100 parts of calcium aluminate A, 0.8 part of the setting retarder was added to 100 parts of the binder, and the amount of tungstate shown in Table 5 was added. The results are shown in Table 5.

(Materials used)
Tungstate: Potassium tungstate, commercial product

  The same procedure as in Example 1 was conducted except that 100 parts of gypsum was added to 100 parts of calcium aluminate A, 0.8 parts of a setting retarder was added to 100 parts of binder, and the amount of molybdate shown in Table 6 was added. The results are shown in Table 6.

(Materials used)
Molybdate: potassium molybdate, commercial product

  100 parts of gypsum for 100 parts of calcium aluminate A, 100 parts of cement and inorganic fine powder in the amount shown in Table 7 for a total of 100 parts of calcium aluminate and gypsum, 0.8 part of setting retarder, and 100 parts of binder In the same manner as in Example 1 except that 10 parts of nitrite and 70 parts of water were added as solid contents. The results are shown in Table 7.

(Materials used)
Cement: ordinary Portland cement, commercially available inorganic fine powder: silica fume, commercially available product, BET specific surface area of 10 m ² / g

  Example 1 except that 100 parts of gypsum was added to 100 parts of calcium aluminate A, 0.8 part of a setting retarder was added to 100 parts of binder, 10 parts of nitrite in solid content, and the amount of polymer shown in Table 8 was added. As well as. The results are shown in Table 8.

(Materials used)
Polymer: Vinyl acetate-veova-acrylic copolymer, commercial product

(Measurement item)
Adhesive strength: A steel plate (JIS G 3141 SPCC-SB) with a thickness of 0.8 mm x length 150 mm x width 70 mm is sanded and fixed around a PVC pipe with an inner diameter of 50 mm and a thickness of 10 mm. The inside was filled to a thickness of about 5 mm. It was cured for 28 days at a temperature of 20 ° C. and a humidity of 60%, and the adhesion strength was measured. Adhesion strength was measured by the Kenken method.

  Table 9 shows 100 parts of gypsum for 100 parts of calcium aluminate A, 0.8 parts of a set retarder, 100 parts of binder, nitrite (solid content), amine, tungstate, and molybdate. The procedure was the same as in Example 1 except for the addition. The results are shown in Table 9.

  100 parts of gypsum for 100 parts of calcium aluminate A, 0.8 part of setting retarder for 100 parts of calcium aluminate and gypsum, 100 parts of cement, inorganic fine powder and polymer, and amount of binder shown in Table 10 The same procedure as in Example 1 was conducted except that 10 parts of nitrite and 70 parts of water were added as solids. The results are shown in Table 10.

  In a cylindrical mold having a diameter of 10 cm and a height of 20 cm, a mold for filling a cross-sectional repair material was prepared in which a D13 reinforcing bar having a length of 30 cm was fixed at the center. Experiment No. 1 shown in Table 11 is formed on the reinforcing bar surface. After 15 minutes, the cross-sectional restoration material (water / cross-section restoration material ratio = 10%) was filled. The active ingredient density | concentration which can exhibit the rust prevention effect to 5 mm from the reinforcing bar surface was measured after 28 days of material age, 3 months, 6 months, and 1 year. The results are shown in Table 11.

  For comparison, when a material exhibiting a rust prevention effect (hereinafter referred to as a rust prevention material) is applied alone or as an aqueous solution to a reinforcing bar, the cement paste (water / cement ratio = 70%) contains the rust prevention material. The case where the prepared composition was applied to the reinforcing bar was also evaluated.

(Materials used)
Cross-section restoration material: polymer cement mortar, commercial product

(Measuring method)
Concentration of anticorrosive component: Cylindrical test specimen filled with cross-sectional repair material and hardened is split in the axial direction of the reinforcing bar, exposing the surface of the reinforcing bar embedded in the center, and repairing the cross section between 5 and 10 mm from the surface of the reinforcing bar Part of the mortar was removed with a chisel and collected. The collected mortar was finely pulverized, treated with hot water, the active ingredient was extracted, and the active ingredient concentration was measured by the following method.
In the case of nitrite, the nitrite ion concentration was measured by ion chromatography.
In the case of an amine salt, the amine concentration was measured by a liquid chromatography method.
Tungstate and molybdate were measured for potassium ion concentration by ion chromatography.

(Materials used)
Antirust material A: 40% aqueous solution of lithium nitrite, commercially available antirust material B: triethanolamine, reagent grade 1 antirust material C: cement paste, 1.0 parts of potassium tungstate containing 100 parts of cement Rust material D: Cement paste, containing 1.0 part of potassium molybdate per 100 parts of cement Rust prevention material E: Cement paste, containing 1.0 part of solid content of lithium nitrite per 100 parts of cement

  Experiment No. shown in Table 12 Kneading the composition excluding calcium aluminate, gypsum, and setting retarder from the blended composition of the above, while pumping with a squeeze pump, while pneumatically transporting a powder of 100 parts calcium aluminate and 100 parts gypsum, Both were merged and mixed by a Y-shaped tube provided in front of the nozzle, and sprayed, and measured for compressive strength and rust prevention performance test. The results are shown in Table 12.

By using the spray composition of the present invention and the rust prevention treatment method using the same, it is possible to shorten the setting time, have an appropriate viscosity, and obtain sufficient strength in a short time. The rust preventive component can be prevented from flowing out when applied. Moreover, since the active ingredient is fixed around the reinforcing bar in a short time, it is possible to suppress a decrease in the active ingredient concentration in the vicinity of the reinforcing bar. Furthermore, since the composition of the present invention is only applied to exposed reinforcing bars, the amount used is small and advantageous in terms of cost, and since it exhibits a sufficient antirust effect over a long period of time, it is effective for rust prevention of reinforced concrete for civil engineering and construction applications. is there.

Claims (6)

One or more kinds selected from nitrite, amine, molybdic acid or a salt thereof, and tungstic acid or a salt thereof, calcium aluminate containing 63 to 21% CaO and 37 to 79% Al ₂ O ₃ , and a blow containing gypsum Moisturizing composition.   The spraying composition according to claim 1, comprising a setting retarder.   The spraying composition of Claim 1 or Claim 2 containing a cement and / or inorganic fine powder.   The spraying composition according to any one of claims 1 to 3, comprising a polymer.   The spraying paste containing the spraying composition of any one of Claims 1-4, and water. 6. A rust preventive treatment method comprising spraying the spray paste according to claim 5 onto a steel material.