Cement composition, mortar composition, and method for repairing concrete structures

Abstract

To provide a cement composition capable of improving sulfuric acid resistance, a mortar composition, a repair method of a concrete structure.SOLUTION: A cement composition according to the present invention includes: a binder (B) comprising a Portland cement, a blast furnace slag fine powder, and Shirasu fine powder; an electric furnace oxide slag fine aggregate (S); and a polymer for cement admixture (P).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cement composition, a mortar composition, and a method for repairing a concrete structure using the mortar composition. [Background technology]

[0002] Polymer cement mortars, in which various polymers are mixed into mortar, have been widely used as repair and reinforcing materials for concrete structures. For example, Patent Documents 1 and 2 disclose polymer cement mortars that can be used as repair and reinforcing materials for concrete structures, which contain rapid-setting cement, gypsum, quicklime, a cement polymer, and fine aggregate having a specific particle size. The polymer cement mortars described in Patent Documents 1 and 2 contain a predetermined amount of cement polymer, thereby ensuring sufficient adhesive strength of concrete and suppressing a decrease in strength development.

[0003] Meanwhile, corrosion and deterioration of concrete structures caused by sulfates contained in sewage has become a problem in sewerage-related facilities and the like. Sulfates contained in sewage are reduced by sulfate-reducing bacteria to produce hydrogen sulfide. This hydrogen sulfide is then oxidized by sulfur-oxidizing bacteria to produce sulfuric acid. As a result, the surface of the concrete structure is continuously exposed to an acidic atmosphere, causing corrosion and deterioration. Repair materials for such corroded and deteriorated concrete structures are usually required to be sulfuric acid resistant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-154511 [Patent Document 2] Patent Publication No. 2021-119115 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the sulfuric acid resistance of the polymer cement mortars described in Patent Documents 1 and 2 has not been studied, and there is room for improvement. In particular, in polymer cement mortars using Portland cement such as high-early-strength Portland cement, slaked lime is produced in large amounts, and therefore gypsum production is not sufficiently suppressed, so further improvement in sulfuric acid resistance is necessary.

[0006] The present invention has been made in view of the above-described current situation, and an object of the present invention is to provide a cement composition, a mortar composition, and a method for repairing a concrete structure that can improve sulfuric acid resistance. [Means for solving the problem]

[0007] The cement composition of the present invention contains a binder (B) consisting of Portland cement, ground granulated blast furnace slag, and ground shirasu, an electric furnace oxidized slag fine aggregate (S), and a polymer for cement admixture (P).

[0008] The cement composition contains a binder (B) consisting of Portland cement, ground granulated blast furnace slag, and ground shirasu, an electric furnace oxidized slag fine aggregate (S), and a polymer for cement admixture (P), thereby improving sulfuric acid resistance.

[0009] In the cement composition according to the present invention, the polymer for cement admixture may have a glass transition temperature of −8° C. or higher.

[0010] With this constitution, the cement composition can further improve its sulfuric acid resistance.

[0011] The cement composition according to the present invention may have a fine aggregate to binder ratio (S / B) of 0.67 or more and 1.8 or less.

[0012] The cement composition has excellent workability due to this configuration. More specifically, the cement composition can be easily mixed and the sagging of the cement composition during construction can be suppressed. Furthermore, unevenness of the aggregate is less likely to appear on the surface of a concrete structure to which the cement composition is applied, thereby improving the surface condition of the concrete structure after construction.

[0013] In the cement composition according to the present invention, the electric furnace oxidizing slag fine aggregate may have a coarse particle ratio of 2.3 or more and 4.3 or less.

[0014] The cement composition has excellent workability due to this configuration. More specifically, the cement composition can be easily mixed and the cement composition can be prevented from sagging during application. Furthermore, the surface of a concrete structure to which the cement composition is applied is less likely to have uneven aggregate, and the surface condition of the concrete structure after application can be improved.

[0015] The cement composition according to the present invention is characterized in that the specific surface area of ​​the ground granulated blast furnace slag is 3,500 cm 2 / g or more 8,000cm 2 / g or less.

[0016] With this constitution, the cement composition can further improve its sulfuric acid resistance.

[0017] The cement composition according to the present invention is characterized in that the specific surface area of ​​the shirasu fine powder is 4,000 cm 2 / g or more 15,000cm 2 / g or less.

[0018] With this constitution, the cement composition can further improve its sulfuric acid resistance.

[0019] The cement composition according to the present invention may have a polymer (solid content) to binder ratio (P / B) for cement admixture of 1% or more and 10% or less.

[0020] With this constitution, the cement composition can further improve the sulfuric acid resistance and can suppress the decrease in compressive strength.

[0021] The mortar composition according to the present invention contains the above-mentioned cement composition and water.

[0022] The mortar composition can have improved sulfuric acid resistance by containing the above-mentioned cement composition.

[0023] In the method for repairing a concrete structure according to the present invention, the above-mentioned mortar composition is filled or applied to a portion of the concrete structure to be repaired.

[0024] The method for repairing a concrete structure includes filling or applying a mortar composition containing the above-mentioned cement composition to the repair area of ​​the concrete structure, thereby repairing the corroded and deteriorated concrete structure and obtaining a concrete structure with excellent sulfuric acid resistance. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide a cement composition, a mortar composition, and a method for repairing a concrete structure that can improve sulfuric acid resistance. DETAILED DESCRIPTION OF THE INVENTION

[0026] <Cement composition> The cement composition according to this embodiment will be described below.

[0027] The cement composition according to this embodiment contains a binder (B), an electric furnace oxidizing slag fine aggregate (S), and a polymer for cement admixture (P). The binder is made of Portland cement, ground granulated blast furnace slag, and ground shirasu.

[0028] The Portland cement is not particularly limited, and examples thereof include ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement, which are specified in JIS R 5210. One type of Portland cement may be used alone, or two or more types may be used in combination.

[0029] From the viewpoints of increasing early strength and suppressing slaked lime formation, the amount of Portland cement blended is preferably 10% by mass or more and 25% by mass or less, and more preferably 13% by mass or more and 20% by mass or less, based on the total cement composition. When two or more types of Portland cement are used, the blending amount is the total blending amount of Portland cement.

[0030] As the ground granulated blast furnace slag, for example, one conforming to the provisions of JIS A 6206:2013 can be used. The Blaine specific surface area of ​​the ground granulated blast furnace slag is set to 3,000 cm from the viewpoint of suppressing the decrease in sulfuric acid resistance and facilitating kneading. 2 / g or more 8,000cm 2 / g or less, and 2 / g or more 6,000cm 2 / g or less is more preferable. The Blaine specific surface area refers to a value measured in accordance with 8.1 of JIS R 5201:2015.

[0031] The amount of ground blast furnace slag to be added is preferably 100 parts by mass or more and 200 parts by mass or less, and more preferably 145 parts by mass or more and 165 parts by mass or less, per 100 parts by mass of Portland cement, from the viewpoint of preventing a decrease in sulfuric acid resistance and facilitating mixing.

[0032] The fine shirasu powder may be, for example, one that conforms to the specifications of JIS A 6209:2020. The Blaine specific surface area of ​​the fine shirasu powder is set to 3,000 cm from the viewpoint of suppressing a decrease in sulfuric acid resistance and facilitating kneading. 2 / g or more 15,000cm2 / g or less, and 2 / g or more 6,000cm 2 It is more preferable that the saturation coefficient is 1 / g or less.

[0033] In order to prevent a decrease in sulfuric acid resistance and facilitate mixing, the amount of fine shirasu powder to be blended is preferably 5 parts by mass or more and 50 parts by mass or less, and more preferably 10 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of Portland cement.

[0034] For example, electric furnace oxidizing slag fine aggregate conforming to the specifications of JIS A 5011-4 can be used. From the viewpoint of improving workability, the coarse particle ratio of the electric furnace oxidizing slag fine aggregate is preferably 2.3 to 4.3, more preferably 2.8 to 3.8. The coarse particle ratio can be determined based on the method described in JIS A 1102:2014.

[0035] The amount of electric furnace oxidizing slag fine aggregate to be mixed is preferably 67 parts by mass or more and 180 parts by mass or less, and more preferably 100 parts by mass or more and 130 parts by mass or less, per 100 parts by mass of binder, from the viewpoint of suppressing a decrease in sulfuric acid resistance and facilitating mixing.

[0036] The fine aggregate to binder ratio (S / B) of the electric furnace oxidizing slag fine aggregate to the binder is 0.67 or more and 1.8 or less, preferably 1.0 or more and 1.3 or less, from the viewpoint of suppressing a decrease in sulfuric acid resistance and compressive strength.

[0037] Examples of polymers that can be used for cement admixture include polymer dispersions such as liquid resin emulsions, and powdered re-emulsified powdered resins. Examples of resin emulsions include polyacrylic esters, polyvinyl acetate, vinylidene chloride vinyl chloride, polyvinyl propionate, and ethylene vinyl acetate. Examples of re-emulsified powdered resins include ethylene vinyl acetate and vinyl acetate vinyl versatate. One type of polymer for cement admixture may be used alone, or two or more types may be used in combination.

[0038] From the viewpoint of suppressing a decrease in sulfuric acid resistance, the glass transition temperature of the polymer for cement admixture is preferably −8° C. or higher, and more preferably 0° C. or higher and 9° C. or lower. The glass transition temperature can be measured by a method in accordance with JIS K 7121.

[0039] The amount of the polymer for cement admixture is preferably 1 to 10 parts by mass, more preferably 3 to 7 parts by mass, calculated as solid content, per 100 parts by mass of the binder. When two or more types of polymer for cement admixture are contained, the amount mentioned above is the total amount of the polymer for cement admixture.

[0040] The ratio (P / B) of the polymer (solid content) for cement admixture to the binder for cement admixture is 1% or more and 10% or less, and more preferably 3% or more and 7% or less, from the viewpoint of suppressing a decrease in sulfuric acid resistance and compressive strength.

[0041] The cement composition according to this embodiment may contain binders other than the binders described above from the viewpoint of controlling durability and workability. Examples of other binders include alumina cement, ultra-rapid hardening cement, various mixed cements obtained by mixing the Portland cement with blast furnace slag, fly ash, etc., and silica cement. One type of other binder may be used alone, or two or more types may be used in combination.

[0042] From the viewpoint of controlling durability and workability, the amount of the other binders to be mixed is preferably 1 part by mass to 20 parts by mass, and more preferably 1 part by mass to 10 parts by mass, per 100 parts by mass of Portland cement. When two or more types of other binders are contained, the amount mentioned above is the total amount of the other binders.

[0043] The cement composition according to this embodiment may contain fine aggregates other than the electric furnace oxidizing slag fine aggregate in order to control durability and workability. Examples of other fine aggregates include naturally occurring sands such as mountain sand, river sand, land sand, sea sand, and crushed sand, as specified in JIS A 5308 Appendix A Aggregates for Ready-Mixed Concrete, and sands derived from slags such as ferronickel slag. These other fine aggregates may be used alone or in combination of two or more.

[0044] From the viewpoint of controlling durability and workability, the amount of the other fine aggregate to be mixed is preferably 1 part by mass to 20 parts by mass, and more preferably 1 part by mass to 10 parts by mass, per 100 parts by mass of binder. When two or more types of other fine aggregate are contained, the amount mentioned above is the total amount of the other fine aggregates to be mixed.

[0045] The cement composition according to the present embodiment may contain an admixture. Examples of the admixture include air-entraining agents, air-entraining water-reducing agents, superplasticizers, separation-reducing agents, set retarders (e.g., tartaric acid, etc.), set accelerators (e.g., aluminum sulfate, etc.), quick-setting admixtures, shrinkage-reducing agents, thickeners, thixotropy adjusters, waterproofing agents, and antifoaming agents. One type of admixture may be used alone, or two or more types may be used in combination.

[0046] The cement composition according to this embodiment may contain an admixture. Examples of admixtures include inorganic fine powders such as silica fume, fly ash, cement kiln dust, blast furnace fume, ground converter slag, anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, expansive additives, limestone fine powder, and dolomite fine powder, as well as inorganic fillers such as bentonite, attapulgite, sepiolite, activated clay, acid clay, allophane, imogolite, shirasu balloon, kaolinite, metakaolin (calcined clay), and zeolite. One type of admixture may be used alone, or two or more types may be used in combination.

[0047] The cement composition according to this embodiment may contain short fibers. Examples of short fibers include vinylon fibers, polypropylene fibers, aramid fibers, polyethylene fibers, acrylic fibers, and nylon fibers. One type of short fiber may be used alone, or two or more types may be used in combination.

[0048] The cement composition according to this embodiment contains a binder (B) made of Portland cement, ground granulated blast furnace slag, and ground shirasu, an electric furnace oxidized slag fine aggregate (S), and a polymer for cement admixture (P), which can suppress the intrusion of sulfate ions while suppressing the production of calcium hydroxide, thereby improving sulfuric acid resistance.

[0049] The cement composition according to this embodiment can further improve sulfuric acid resistance by using a polymer for cement admixture having a glass transition temperature of −8° C. or higher.

[0050] The cement composition according to this embodiment has a fine aggregate to binder ratio (S / B) of 0.67 or more and 1.8 or less, and therefore has excellent workability. More specifically, the cement composition can be easily mixed and the cement composition can be prevented from sagging during construction. Furthermore, the surface of a concrete structure to which the cement composition is applied is less likely to have uneven aggregate, and the surface condition of the concrete structure after construction can be improved.

[0051] The cement composition according to this embodiment has excellent workability because the coarse particle ratio of the electric furnace oxidizing slag fine aggregate is 2.3 or more and 4.3 or less. More specifically, the cement composition can be easily mixed and the cement composition can be prevented from sagging during application. Furthermore, the surface of a concrete structure to which the cement composition is applied is less likely to have unevenness due to the aggregate, and the surface condition of the concrete structure after application can be improved.

[0052] The cement composition according to this embodiment is characterized in that the specific surface area of ​​the ground granulated blast furnace slag is 3,500 cm 2 / g or more 8,000cm 2 / g or less, it is possible to further improve the sulfuric acid resistance and improve the workability. More specifically, it is possible to easily mix the cement composition and to suppress sagging of the cement composition during construction. Furthermore, it is possible to prevent the appearance of unevenness of the aggregate on the surface of a concrete structure to which the cement composition is applied, and it is possible to achieve a good surface condition of the concrete structure after construction.

[0053] The cement composition according to this embodiment is characterized in that the specific surface area of ​​the shirasu fine powder is 4,000 cm 2 / g or more 15,000cm 2 / g or less, it is possible to further improve the sulfuric acid resistance and improve the workability. More specifically, it is possible to easily mix the cement composition and to suppress sagging of the cement composition during construction. Furthermore, it is possible to prevent the appearance of unevenness of the aggregate on the surface of a concrete structure to which the cement composition is applied, and it is possible to achieve a good surface condition of the concrete structure after construction.

[0054] The cement composition according to this embodiment has a polymer (solid content) to binder ratio (P / B) of 1% to 10%, which suppresses the generation of calcium hydroxide and inhibits the penetration of sulfate ions over the long term, thereby further improving sulfuric acid resistance and inhibiting a decrease in compressive strength.

[0055] <Mortar composition> The mortar composition according to this embodiment will be described below.

[0056] The mortar composition according to this embodiment contains the above-mentioned cement composition and water.

[0057] The water is not particularly limited, and examples of water that can be used include tap water, industrial water, recycled water, groundwater, river water, and rainwater.

[0058] The amount of water to be added is preferably 20 parts by mass or more and 40 parts by mass or less, and more preferably 30 parts by mass or more and 35 parts by mass or less, relative to 100 parts by mass of the binder.

[0059] The water-to-binder ratio (W / B) of the water to the binder is preferably 20% or more and 40% or less, and more preferably 30% or more and 35% or less, from the viewpoint of improving workability.

[0060] The mortar composition according to the present embodiment can be produced by mixing the above-described cement composition and water. The mixing method is not particularly limited, and for example, the mortar composition can be produced by a conventionally known method using a conventionally known mixer or the like.

[0061] The mortar composition according to the present embodiment contains the above-described cement composition and water, and therefore can suppress the penetration of sulfate ions while suppressing the amount of calcium hydroxide produced, thereby improving sulfuric acid resistance.

[0062] <Methods for repairing concrete structures> The concrete structure repair method according to this embodiment will be described below.

[0063] In the method for repairing a concrete structure according to this embodiment, the above-described mortar composition is filled or applied to a repaired portion of the concrete structure. Specifically, the above-described mortar composition is filled or applied by spraying or plastering to a repaired portion that has been subjected to surface preparation such as removal of corroded and deteriorated portions.

[0064] The filling or application method is not particularly limited, and examples thereof include a filling method, a plastering method, and a spraying method. In the filling method, a formwork is constructed at the repair location and poured into the formwork. In the plastering method, a craftsman places an appropriate amount of mortar on a mortarboard and applies the mortar composition to the repair location of the concrete structure using a trowel or the like. In the spraying method, the mortar composition is sprayed onto the repair location of the concrete structure using a device such as a mortar pump.

[0065] In the method for repairing a concrete structure according to this embodiment, the mortar composition is filled or applied to the repair area of ​​the concrete structure, thereby repairing the corroded and deteriorated concrete structure and obtaining a concrete structure with excellent sulfuric acid resistance. [Example]

[0066] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0067] Mortar compositions of each Example and Comparative Example were prepared according to the formulations shown in Table 1. Test specimens were prepared using the mortar compositions of each Example and Comparative Example according to a method in accordance with JIS A 1171. The prepared test specimens were tested for compressive strength and acid resistance.

[0068] Details of each component shown in Table 1 are as follows: The pulverized product is a product obtained by pulverizing a coarse-grained product in a mill and adjusting the Blaine specific surface area. Cement (HC): High-early-strength Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.) Cement (NC): Ordinary Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.) Ground granulated blast furnace slag: specific surface area 3000cm 2 / g, ground preparation Specific surface area 3500cm 2 / g, ground preparation Specific surface area 6000cm 2 / g, Fine Cerament 20A (D (Made by Sea) Specific surface area 8000cm 2 / g, Fine Cerament 10A (D (Made by Sea) Shirasu fine powder: specific surface area 3000cm 2 / g, ground preparation Specific surface area 4000cm 2 / g, ground preparation Specific surface area 6000cm 2 / g, ground preparation Specific surface area 15000cm 2 / g, ground preparation Electric furnace oxidizing slag fine aggregate: mixed sand Dry silica sand: mixed sand Emulsion (polymer for cement blending): Styrene acrylic polymer emulsion with glass transition temperatures (Tg) of -8°C, 0°C, and 9°C

[0069] [Table 1]

[0070] [Compression strength] The compressive strength of the specimens of each example and each comparative example, which were 3 days old, was measured in accordance with the test method shown in the Japan Sewage Works Agency's "Manual for Corrosion Inhibition and Anticorrosion Technology for Sewerage Concrete Structures." 2 Those with a compressive strength of 25N / mm or more are marked as "○" 2 More than 30N / mm 2 Those with a compressive strength of less than 25N / mm are marked "△" 2The measured values ​​of compressive strength and the evaluation thereof are shown in Table 2. In Example 21, the compressive strength was 25 N / mm at the age of 4 days. 2 Achieve a compressive strength of at least 10 ...

[0071] [Acid resistance (sulfuric acid penetration depth)] In accordance with the test method described in the Japan Sewage Works Agency's "Manual for Corrosion Inhibition and Prevention Techniques for Sewerage Concrete Structures," specimens from each Example and Comparative Example were immersed in a 5% sulfuric acid solution for 28 days and 112 days, and then the sulfuric acid penetration depth of each specimen was measured. For specimens immersed for 28 days, those with a sulfuric acid penetration depth of 2.4 mm or less were evaluated as "Good," those with a sulfuric acid penetration depth of more than 2.4 mm and less than 3 mm were evaluated as "Good," those with a sulfuric acid penetration depth of more than 3 mm were evaluated as "Poor," and those with a sulfuric acid penetration depth of more than 3 mm were evaluated as "Poor." For specimens immersed for 112 days, those with a sulfuric acid penetration depth of 5.4 mm or less were evaluated as "Good," those with a sulfuric acid penetration depth of more than 5.4 mm and less than 6 mm were evaluated as "Good," and those with a sulfuric acid penetration depth of more than 6 mm were evaluated as "Poor." The measured sulfuric acid penetration depths and their evaluations are shown in Table 2.

[0072] [Acid resistance (mass change rate)] The mass change rates of specimens of each Example and Comparative Example after 28 days and 112 days of immersion were measured in accordance with the test method set forth in the Japan Sewage Works Agency's "Manual for Corrosion Inhibition and Anticorrosion Technology for Sewerage Concrete Structures." Specifically, the mass of each Example and Comparative Example specimen was first measured. Subsequently, these specimens were immersed in a 5% sulfuric acid aqueous solution for 28 days and 112 days, respectively. The masses of the specimens of each Example and Comparative Example after 28 days of immersion and 112 days of immersion were then measured again, and the ratio of the mass after immersion to the mass before immersion (mass change rate) was calculated. For specimens immersed for 28 days, a mass change rate within ±4.9% was evaluated as "Good," a mass change rate greater than ±4.9% but less than ±10% was evaluated as "Average," and a mass change rate greater than ±10% was evaluated as "Poor." For the specimens immersed for 112 days, those with a mass change rate of ±7.4% or less were evaluated as "Good," those with a mass change rate of more than ±7.4% but less than ±10% were evaluated as "Good," and those with a mass change rate of more than ±10% were evaluated as "Poor." The mass change rates and their evaluations are shown in Table 2.

[0073] [Table 2]

[0074] As can be seen from the results in Table 2, the mortar compositions of the examples which satisfy all of the constituent requirements of the present invention have improved sulfuric acid resistance and are excellent in long-term sulfuric acid resistance.

Claims

1. A binder (B) consisting of Portland cement, blast furnace slag powder, and shirasu powder; Electric furnace oxidizing slag fine aggregate (S); A polymer for cement admixture (P), Including, The cement composition has a coarse particle ratio of the electric furnace oxidizing slag fine aggregate of 2.3 or more and 4.3 or less.

2. 2. The cement composition according to claim 1, wherein the glass transition temperature of the polymer for cement admixture is −8° C. or higher.

3. 3. The cement composition according to claim 1, wherein the fine aggregate to binder ratio (S / B) is 0.67 or more and 1.8 or less.

4. The specific surface area of ​​the ground blast furnace slag is 3,500 cm ２ / g or more 8,000cm ２ The cement composition according to any one of claims 1 to 3, wherein the SiO2 content is 0.1g or less.

5. The specific surface area of ​​the shirasu fine powder is 4,000 cm ２ / g or more 15,000cm ２ The cement composition according to any one of claims 1 to 4, wherein the SiO2 content is 0.01g or less.

6. 6. The cement composition according to claim 1, wherein the polymer (solid content) to binder ratio (P / B) for cement admixture is 1% or more and 10% or less.

7. A mortar composition comprising the cement composition according to any one of claims 1 to 6 and water.

8. A method for repairing a concrete structure, comprising filling or applying the mortar composition according to claim 7 to a portion of the concrete structure to be repaired.

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