Rust preventive composition and rust preventive treatment method

Abstract

To provide a rust inhibitor composition that is used to apply rust-inhibiting treatment, delaying the start of rust generation, and also improves flowability for improved workability.SOLUTION: A rust inhibitor composition contains cement and nitrite, and further contains at least one non-hydraulic compound selected from the group consisting of γ-2CaO SiO2, 3CaO 2SiO2, α-CaO SiO2 and calcium magnesium silicate.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rust preventive agent composition and a rust prevention treatment method thereof, and particularly to a rust preventive agent composition for suppressing corrosion of steel materials inside concrete, such as reinforcing bars, steel frames, steel plates, steel wires inside prestressed concrete, etc., and preventing the occurrence of rust, and a rust prevention treatment method thereof.

Background Art

[0002] In the repair work of concrete structures, cross-section repair work is carried out to remove the deteriorated part and newly apply repair mortar. At that time, a rust prevention treatment is performed for the purpose of preventing rusting of steel materials such as exposed reinforcing bars.

[0003] Conventional rust preventive agents include nitrites, chromates, silicates, and phosphates in the inorganic system, and organic phosphate esters, ester salts, organic acids, sulfonic acids, amines, alkylphenols, mercaptans, and nitro compounds in the organic system (see Non-Patent Document 1).

[0004] As a rust preventive agent for reinforcing bars when performing a cross-section repair method, nitrite-based rust preventive agents are often used, and they are used by directly applying them to the reinforcing bars, applying a mixture with a polymer emulsion, or applying a mixture with a hydraulic substance such as cement. When used in a mixture with cements, a polymer for cement admixture is blended for the purpose of retaining nitrite on the surface of the reinforcing bars for a long period of time and reducing the permeability of chloride ions and oxygen to maintain a better rust prevention effect, and in some cases, it is applied.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, although the nitrite-based rust inhibitor widely used in the cross-section repair method can be directly applied to the reinforcing bars, rust may occur if the cross-section is not repaired immediately after application. In addition, a mixture of cement and a polymer for mixing with cement is preferable in that rust hardly occurs on the reinforcing bars even if the cross-section is not repaired immediately after application, but a sufficient effect cannot be obtained. Furthermore, there was a problem of poor workability due to an increase in viscosity and a decrease in fluidity after kneading. Therefore, an object of the present invention is to provide a rust inhibitor composition that can prolong the time until rusting occurs and improve workability by increasing fluidity by performing rust prevention treatment.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventor has found that by using a rust inhibitor composition containing cement, nitrite, and one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate, the time until rusting occurs can be prolonged and the workability can be improved by increasing the fluidity.

[0008] The present invention is a rust inhibitor composition containing cement, nitrite, and one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate, and further a rust inhibitor composition containing Li in the non-hydraulic compound, and further a rust inhibitor composition containing a polymer for mixing with cement, and a rust prevention treatment method using the rust inhibitor composition.

Advantages of the Invention

[0009] The rust inhibitor composition of the present invention can prolong the time until rusting occurs and improve workability by increasing fluidity by performing rust prevention treatment using the composition.

Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail. In the present invention, parts and % are shown on a mass basis unless otherwise specified.

[0011] The rust preventive composition of the present invention contains cement and nitrite, and further contains one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate. Further, the rust preventive composition preferably further contains Li in the non-hydraulic compound, and the content rate of Li in the non-hydraulic compound is preferably 0.001 to 1.0% by mass in terms of oxide conversion. It is presumed that the production of vaterite, which is one of calcium carbonates, among the carbonations of C-S-H (calcium silicate hydrate) is promoted by this predetermined amount of Li, and it is considered that a denser hardened state can be obtained by carbonation (salt) and the rust preventive effect can be easily obtained. Further, the rust preventive composition preferably further contains a cement admixture polymer. Here, "containing Li in the non-hydraulic compound" means that Li2O is included as a chemical composition in the non-hydraulic compound (the presence can be confirmed by ICP emission spectroscopic analysis), but Li2O is not identified by X-ray diffraction measurement (no distinct peak of Li2O is observed), and it does not simply mean a state where the non-hydraulic compound and the Li compound are physically mixed. Such a state can be obtained by mixing the respective raw materials and performing heat treatment at a high temperature of 1,000 °C or higher. The rust preventive treatment method of the present invention is a rust preventive treatment method using the rust preventive composition described in any of the above. Hereinafter, each component of the above rust preventive composition will be described.

[0012] [Cement] The cement used in the present invention is not particularly limited, and examples include various Portland cements such as ordinary, early-strength, ultra-early-strength, low-heat, and moderate-heat Portland cements, and various blended cements obtained by blending blast furnace slag, fly ash, or silica with these Portland cements, filler cements blended with limestone powder, gypsum, or fine powder of slowly cooled blast furnace slag, and Portland cements such as environment-friendly cement (eco-cement) manufactured using municipal solid waste incineration ash or sewage sludge incineration ash as raw materials, as well as commercially available cement-based solidifying materials used in ground improvement work and commercially available fine particle cements. One or more of these can be used. Also, those adjusted by increasing or decreasing the amount of components usually used in cement can also be used.

[0013] [Nitrite] The nitrite used in the present invention is a substance that imparts a rust prevention effect. Examples include lithium nitrite, sodium nitrite, potassium nitrite, calcium nitrite, magnesium nitrite, and barium nitrite. Among these, it is preferable to use lithium nitrite or calcium nitrite, which have a low price and no influence on the alkali-aggregate reaction. The nitrite is preferably used in an amount of 5 to 30 parts by mass, more preferably 10 to 25 parts by mass, and even more preferably 15 to 20 parts by mass with respect to 100 parts by mass of cement as an aqueous solution having a solid content of 40% by mass. Setting the amount to 5% or more and 30% or less can obtain a sufficient rust prevention effect, which is preferable.

[0014] [Non-hydraulic compound] The non-hydraulic compound used in the present invention is one or more selected from the group consisting of γ-2CaO·SiO2, 3CaO·2SiO2, α-CaO·SiO2, and calcium magnesium silicate. By mixing these, the fluidity is increased, natural carbonation is promoted to make it dense, and it has an excellent rust prevention effect.

[0015] (γ-2CaO·SiO2) γ-2CaO·SiO2 is a compound represented by 2CaO·SiO2 and is known as a low-temperature phase, which is completely different from the high-temperature phases such as α-2CaO·SiO2, α’-2CaO·SiO2, and β-2CaO·SiO2. Although all of these are represented by 2CaO·SiO2, their crystal structures and densities are different.

[0016] (3CaO·2SiO2) 3CaO·2SiO2 is a mineral containing CaO in pseudo-wollastonite and is called rankinite. It is a mineral that is chemically stable without hydration activity, but has a large carbonation promotion effect and excellent rust prevention effect.

[0017] (α-CaO·SiO2) α-CaO·SiO2 (α-type wollastonite) is a compound represented by CaO·SiO2 and is known as a high-temperature phase, which is completely different from the low-temperature phase β-CaO·SiO2. Although all of these are represented by CaO·SiO2, their crystal structures and densities are different.

[0018] Naturally occurring wollastonite is the low-temperature phase β-CaO·SiO2. β-CaO·SiO2 has acicular crystals and is used as an inorganic fibrous substance such as wollastonite fiber, etc., but it does not have the carbonation promotion effect like α-CaO·SiO2 according to this embodiment.

[0019] (calcium magnesium silicate) Calcium magnesium silicate is a general term for CaO-MgO-SiO2 based compounds. In this embodiment, it is preferably Merwinite represented by 3CaO·MgO·2SiO2 (C3MS2). According to Merwinite, a large carbonation promotion effect can be achieved.

[0020] [Li] The above non-hydraulic compound may be one kind or two or more kinds. However, the content of Li in the non-hydraulic compound is 0.001 to 1.0% in terms of oxide conversion, preferably 0.005 to 1.0%, more preferably 0.010 to 0.90%, and even more preferably 0.015 to 0.80%. If the content of Li is less than 0.001% in terms of oxide conversion, the carbonation promotion effect cannot be obtained. If it exceeds 1.0%, the cost will increase. The content of Li in terms of oxide conversion can be measured by the method described in the examples. In addition, when there are two or more non-hydraulic compounds, the content of Li refers to the content of Li in terms of oxide conversion with respect to the total of two or more non-hydraulic compounds.

[0021] Among the above non-hydraulic compounds, particularly γ-2CaO·SiO2 is preferable because it is accompanied by a pulverization phenomenon called dusting during production, so it requires less energy for pulverization compared to other compounds, has a large carbonation (salt) promotion effect over a long period, and on the other hand, has a large rust prevention effect when combined with blast furnace cement at a low water binder ratio.

[0022] The non-hydraulic compound according to this embodiment is obtained by blending a CaO raw material, a SiO2 raw material, an MgO raw material, and, if necessary, an Li raw material in a predetermined molar ratio and then performing heat treatment. Examples of the CaO raw material include calcium carbonate such as limestone, calcium hydroxide such as slaked lime, by-product slaked lime such as acetylene by-product slaked lime, and fine powder generated from waste concrete blocks. Examples of the SiO2 raw material include silica stone, clay, and various silica dusts generated as industrial by-products typified by silica fume and fly ash. Examples of the MgO raw material include magnesium hydroxide, basic magnesium carbonate, and dolomite. Examples of the Li raw material include lithium carbonate. When Li is contained in the CaO raw material, the SiO2 raw material, and the MgO raw material, it is not necessary to newly add an Li raw material. From the viewpoint of reducing non-energy-derived CO2 emissions during heat treatment, one or more selected from industrial by-products containing CaO, such as by-product slaked lime, fine powder generated from waste concrete blocks, municipal solid waste incineration ash, and sewage sludge incineration ash, can be used. Among them, it is more preferable to use by-product slaked lime, which has a smaller amount of impurities compared to other industrial by-products.

[0023] As by - product slaked lime, there are by - product slaked lime by - produced in the manufacturing process of acetylene gas by the calcium carbide method (depending on the acetylene gas manufacturing method, there are wet products and dry products), and by - product slaked lime contained in the dust captured in the wet dust collection process of the calcium carbide electric furnace, such as acetylene by - product slaked lime. The by - product slaked lime contains, for example, 65 - 95% (preferably 70 - 90%) of calcium hydroxide, and in addition, 1 - 10% of calcium carbonate and 0.1 - 6.0% (preferably 0.1 - 3.0%) of iron oxide. These ratios can be confirmed by the mass loss obtained by fluorescence X - ray measurement and differential thermal gravimetric analysis (TG - DTA) (Ca(OH)2: around 405°C - 515°C, CaCO3: around 650°C - 765°C). The volume - average particle diameter measured by the laser diffraction / scattering method is about 50 - 100μm. Further, in JIS K 0068 "Method for Measuring Moisture in Chemical Products", the moisture content measured by the drying loss method is preferably 10% or less. Also, it may contain sulfur compounds such as CaS, A12S3, and CaC2·CaS, but preferably 2% or less.

[0024] The heat treatment at a high temperature of 1,000°C or higher described above is not particularly limited, but can be carried out, for example, by a rotary kiln or an electric furnace. The heat treatment temperature is not uniquely determined, but is usually carried out in the range of about 1,000 - 1,800°C, and often in the range of about 1,200 - 1,600°C.

[0025] This embodiment can also use industrial by - products containing the non - hydraulic compound described above. In this case, impurities coexist. Such industrial by - products include steelmaking slag and the like.

[0026] The CaO raw material, SiO2 raw material, and MgO raw material may contain impurities, but there is no particular problem as long as the effects of the present invention are not inhibited. Specific examples of the impurities include, for example, Al2O3, Fe2O3, TiO2, MnO, Na2O, K2O, S, P2O5, F, B2O3, chlorine, and the like. Further, examples of the coexisting compounds include free calcium oxide, calcium hydroxide, calcium aluminate, calcium aluminosilicate, calcium ferrite, calcium aluminoferrite, calcium phosphate, calcium borate, magnesium silicate, leucite (K2O, Na2O)·Al2O3·SiO2, spinel MgO·Al2O3, magnetite Fe3O4, the aforementioned CaS, A12S3, and sulfur compounds such as CaC2·CaS.

[0027] Among these impurities, the content of S (sulfur) in the non-hydraulic compound is preferably 1.0% or less, more preferably 0.7% or less, and still more preferably 0.5% or less in terms of oxide (SO3) conversion. By being 1.0% or less, a sufficient carbonation promotion effect can be obtained, and the setting and hardening properties can be made within an appropriate range. The content of S in terms of oxide (SO3) conversion can be measured by fluorescent X-ray measurement. Incidentally, S (sulfur) in the non-hydraulic compound may be present if it is about 2% in terms of oxide conversion.

[0028] In this rust preventive agent composition, the content of the non-hydraulic compound (the content in the total amount when a plurality of types are included) is preferably 1 to 50%, more preferably 2 to 25%, and still more preferably 3 to 15% with respect to 100 parts by mass of the cement. It is also possible that hydraulic 2CaO·SiO2 other than γ-2CaO·SiO2 is mixed, and the maximum mixing amount can be up to 35%.

[0029] The content rate of γ-2CaO·SiO2 in the non-hydraulic compound is preferably 35% or more, more preferably 45% or more. Also, the upper limit value of the content rate of γ-2CaO·SiO2 is not particularly limited. Among steelmaking slags, electric furnace reduction period slag or stainless steel slag with a high content rate of γ-2CaO·SiO2 is preferable.

[0030] Also, from the viewpoint of more easily expressing its effects in the non-hydraulic compound, as chemical components, in 100 parts by mass of the non-hydraulic compound, it is preferable to contain 0.001 to 1.0 part by mass of Li2O, 45 to 70 parts by mass of CaO, 30 to 55 parts by mass of SiO2, and 0 to 10 parts by mass of Al2O3. The content of Li2O can be measured by the method described in the examples below. Also, CaO, SiO2, and Al2O3 can be measured by fluorescent X-ray analysis. As chemical components, in 100 parts by mass of the admixture for rust preventive agent (non-hydraulic compound), it is more preferable to contain 0.002 to 0.5 part by mass of Li2O, 60 to 70 parts by mass of CaO, 30 to 45 parts by mass of SiO2, and 0.5 to 5 parts by mass of Al2O3. Furthermore, as chemical components, in 100 parts by mass of the non-hydraulic compound, the total of Li2O, CaO, SiO2, and Al2O3 is preferably 90 parts by mass or more, more preferably 95 to 100 parts by mass.

[0031] Examples of the method for quantifying the non-hydraulic compound in this rust preventive composition include the Rietveld method by powder X-ray diffraction.

[0032] The Blaine specific surface area of this rust preventive composition is not particularly limited, but is preferably 1,500 cm 2 / g or more, and the upper limit is preferably 8,000 cm 2 / g or less. Among them, 2,000 to 6,000 cm 2 / g is more preferable, and 4,000 to 6,000 cm 2 / g is most preferable. When the Blaine specific surface area is 2,000 cm 2 / g or more, good fluidity can be obtained, the carbonation promotion effect becomes large, and a sufficient rust preventive effect can be obtained. Also, 8,000 cm2 When it is below / g, the grinding power during grinding does not increase, which is economical, and weathering is suppressed, and deterioration of quality over time can be suppressed.

[0033] [Polymer for cement admixture] The polymer for cement admixture (hereinafter referred to as cement polymer) used in the present invention is a polymer that has been generally used for cement admixture, and is used for the purpose of improving durability such as neutralization, salt damage, and freezing damage. For example, rubber latex such as acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, and natural rubber, synthetic resin emulsions such as ethylene-vinyl acetate copolymer, polyacrylate copolymer, vinyl acetate versatate copolymer, styrene-acrylate copolymer, and liquid polymers represented by epoxy resins and unsaturated polyester resins can be mentioned, and a mixture of one or more of these can also be used. The amount of the cement polymer used is preferably 5 to 70 parts by mass, more preferably 10 to 60 parts by mass with respect to 100 parts by mass of cement. When it is 5 parts by mass or more, the rust prevention effect is excellent when used in combination with cement, and when it is 70 parts by mass or less, the workability is excellent.

[0034] [Mixture] In the rust preventive composition of the present invention, pozzolanic substances that are stimulated and cured by alkalis, which are hydraulic substances other than cement, and calcium aluminates that can impart rapid hardening can be used in combination within a range that does not adversely affect the quality of these mixtures.

[0035] [Aggregate] Furthermore, it is also possible to use sand as an aggregate and use it as a rust preventive composition in which sand is appropriately mixed to form mortar.

[0036] [Others] In addition, within a range that does not adversely affect the quality, the rust preventive composition of the present invention can be used in combination with various additives such as calcium carbonate, magnesium silicate, slag powder, clay powder, carbon black, surfactant, fibers, thickener, clay mineral, setting accelerator, setting retarder, waterproofing agent, water reducing agent, defoaming agent, quick hardening material, foaming agent, pigment, gas foaming substance, expansive material, shrinkage reducing agent, and chelating agents such as sodium ethylenediaminetetraacetate, water-soluble sulfur-containing organic compounds or their salts, fragrances, deodorants, antibacterial agents, preservatives, etc.

[0037] The construction method of the rust preventive composition of the present invention is not particularly limited. For example, it may be sprayed onto the reinforcing bars using a sprayer or applied with a brush.

Examples

[0038] Hereinafter, the present invention will be further described based on experimental examples of the present invention, but the present invention is not limited thereto.

[0039] Experimental Example 1 A rust preventive composition was prepared with the formulation shown in Table 1 with respect to 100 parts by mass of cement. With respect to 100 parts by mass of the obtained rust preventive composition, water was added so that the water-cement ratio was constant (water-cement ratio: 53%) to prepare a rust preventive agent. The fluidity of the prepared rust preventive agent and the time until rusting occurred were tested using the prepared rust preventive agent. The results are shown in Table 1 below.

[0040] [Materials Used] · Cement: Ordinary Portland cement (commercially available product) · Nitrite aqueous solution: Lithium nitrite aqueous solution, solid content 40% by mass (commercially available product) · Non-hydraulic compound A: Li-containing γ-2CaO·SiO2. Reagent grade calcium carbonate and reagent grade silicon dioxide were mixed at a molar ratio of 2:1, and further, reagent grade lithium carbonate was mixed so that the Li content in the mixture was 0.0005 to 1.1% (internal substitution) in terms of oxide (Li2O). The mixture was heat-treated at 1,400 °C for 2 hours, allowed to cool to room temperature, and then pulverized to a Blaine specific surface area of 4,000 cm2 It was set as / g. · Blending agent B for rust preventive: α-CaO·SiO2 containing Li. Calcium carbonate of the first grade reagent and silicon dioxide of the first grade reagent were mixed at a molar ratio of 1:1, and further lithium carbonate of the first grade reagent was mixed so that the Li content in the mixture was 0.0005 to 1.1% (internal substitution) in terms of oxide (Li2O). The mixture was heat-treated at 1,500 °C for 2 hours, allowed to cool to room temperature, and then pulverized to obtain a Blaine specific surface area of 4,000 cm 2 / g. · Blending agent C for rust preventive: β-2CaO·SiO2. Calcium carbonate of the first grade reagent and silicon dioxide of the first grade reagent were mixed at a molar ratio of 2:1. The mixture was heat-treated at 1,400 °C for 2 hours, allowed to cool to room temperature, and then pulverized and subjected to XRD. The same heat treatment was repeated until the peak of γ-2CaO·SiO2 was no longer confirmed. After only the peak of β-2CaO·SiO2 was confirmed, it was pulverized to obtain a Blaine specific surface area of 4,000 cm 2 / g. In addition, the Li content in terms of oxide conversion in the blending agents A to C for rust preventive was measured by an ICP emission spectroscopic analyzer (manufactured by Hitachi High-Technologies Corporation, VISTA-PRO). And from the absolute calibration curve method using the ICP mixed solution (manufactured by SPEX, XSTC-22) diluted and used, it was confirmed that the Li content was the same as the charged amount. The measurement conditions are as follows. · Li measurement wavelength: 670.783 nm · BG correction: Fitting curve method · Standard solution for calibration curve: Dilute and use the ICP mixed solution (manufactured by SPEX, XSTC-22) · Calibration curve range: 0 to 5 mg / L (five-point calibration curve of 0 mg / L, 0.1 mg / L, 0.5 mg / L, 1 mg / L, 5 mg / L) · Quantification by the absolute calibration curve method · Polymer for cement mixing: Vinyl acetate·vinyl versatate copolymer (powder, commercially available product) · Water: Tap water

[0041] [Measurement method] [Fluidity] JIS flow: Conforms to JIS R 5201. <Time until rusting> On the surface of the reinforcing bar (SD295 of JIS standard product) of D16, the prepared rust preventive agent was applied with a brush so that the application amount was approximately 150 g / m 2 and placed in a constant temperature and high humidity chamber at a temperature of 20°C and a relative humidity of 100%. The time from when it was applied until rust was visually confirmed on the reinforcing bar was measured. The number of tests was 3 for one example, and the average value of the measured time was taken as the time until rusting.

[0042]

Table 1

[0043] From the results in Table 1, it was confirmed that by containing the admixture for rust preventive agent containing a specific non-hydraulic material, the fluidity can be further increased and the time until rusting is improved.

Industrial applicability

[0044] The rust preventive agent composition of the present invention contains a specific non-hydraulic material, so that the fluidity is increased and the time until rusting can be improved, and it can be widely used for corrosion inhibition of steel materials inside concrete, such as reinforcing bars, steel skeletons, steel plates, steel wires inside prestressed concrete, and prevention of rust generation.

Claims

1. A rust preventive composition containing cement and nitrite, further containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO·SiO ２ , 3CaO·2SiO ２ , α-CaO·SiO ２ and calcium magnesium silicate, containing Li in the non-hydraulic compound, and the content rate of Li in the non-hydraulic compound being 0.001 to 1.0% by mass in terms of oxide.

2. Furthermore, the rust preventive composition according to claim 1, which contains a polymer for cement admixture.

3. A rust preventive treatment method using the rust preventive composition according to claim 1 or 2.

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