Fiber-reinforced mortar composition and method for repairing concrete structures

Abstract

To provide a fiber-reinforced mortar composition that maintains high compressive strength while exhibiting excellent tensile strength, and a method for repairing concrete structures using the fiber-reinforced mortar composition. [Solution] The fiber-reinforced mortar composition according to the present invention is a fiber-reinforced mortar composition containing Portland cement, a binder containing silica fume fine powder, fine aggregate, steel fibers, organic fibers, and water, wherein the specific surface area of ​​the silica fume fine powder is 15 to 20 m². 2 The amount is / g, the silica fume fine powder content is 5 to 30 parts by mass per 100 parts by mass of the Portland cement, the steel fiber content is 2.5 to 4.5 volume% of the entire fiber-reinforced mortar composition, the organic fiber content is 0.2 to 2.0 volume% of the entire fiber-reinforced mortar composition, the water binder ratio is 16 to 22%, and the fine aggregate binder ratio is 0.25 to 0.70.

Description

[Technical Field]

[0001] The present invention relates to a fiber-reinforced mortar composition and a method for repairing concrete structures. [Background technology]

[0002] Fiber-reinforced mortar compositions, used as building materials for concrete structures such as skyscrapers and road structures, are known for their high compressive strength and high toughness, including tensile strength.

[0003] Fiber-reinforced mortar compositions generally consist of a binder containing Portland cement or ultrafast-setting cement, silica fume, slag powder, and admixtures (e.g., fly ash powder), fine aggregate, short fibers (e.g., organic fibers, steel fibers), a polycarboxylic acid-based water-reducing agent, and water. Here, fiber-reinforced mortar compositions containing steel fibers as short fibers tend to have excellent compressive strength but low toughness, while fiber-reinforced mortar compositions containing organic fibers as short fibers tend to have excellent toughness but low compressive strength. Therefore, in recent years, fiber-reinforced mortar compositions containing a mixture of steel fibers and organic fibers have been investigated in order to achieve both sufficient compressive strength and toughness (see Non-Patent Documents 1 and 2). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Study on the material properties of HFRCC using straight steel fibers and PVA fibers. Proceedings of the Architectural Institute of Japan Annual Meeting (Hokuriku), September 2010 (Takashi Kikuta, Hiromitsu Mihashi, Tomoya Nishiwaki) [Non-Patent Document 2] Effect of steel fiber shape on the tensile performance of fiber-reinforced cement composite materials containing steel and synthetic fibers. Annual Proceedings of the Concrete Engineering Society, Vol. 34, No. 1, 2012 (Risa Yoshida, Takatsune Kikuta, Tomoya Nishiwaki, Hiromitsu Mihashi) [Overview of the project] [Problems that the invention aims to solve]

[0005] However, conventional fiber-reinforced mortar compositions have difficulty improving tensile strength while maintaining high compressive strength. Therefore, there is a need to improve tensile strength in conventional fiber-reinforced mortar compositions.

[0006] This invention has been made in view of the above circumstances, and aims to provide a fiber-reinforced mortar composition that maintains high compressive strength while exhibiting excellent tensile strength, and a method for repairing concrete structures using the fiber-reinforced mortar composition. [Means for solving the problem]

[0007] The fiber-reinforced mortar composition according to the present invention is a fiber-reinforced mortar composition comprising a binder (B) containing Portland cement and silica fume fine powder, fine aggregate (S), steel fibers, organic fibers, and water (W), The specific surface area of ​​the aforementioned silica fume fine powder is 15 m². 2 / g or more 20m 2 It is less than / g The content of the silica fume fine powder is 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the Portland cement. The steel fiber content is 2.5% by volume or more and 4.5% by volume or less relative to the entire fiber-reinforced mortar composition. The content of the organic fibers is 0.2% by volume or more and 2.0% by volume or less relative to the entire fiber-reinforced mortar composition. The water-to-binder ratio (W / B) is between 16% and 22%. The fine aggregate-to-binder ratio (S / B) is between 0.25 and 0.70.

[0008] According to such a configuration, in the fiber-reinforced mortar composition, since the steel fibers and the organic fibers are sufficiently mechanically adhered to the binder (B), the fine aggregate (S), etc., the materials are firmly bonded to each other. Therefore, the fiber-reinforced mortar composition is excellent in tensile strength while maintaining high compressive strength.

[0009] In the fiber-reinforced mortar composition according to the present invention, the fiber diameter of the steel fibers may be 100 μm or more and 400 μm or less.

[0010] According to such a configuration, in the fiber-reinforced mortar composition, since the steel fibers are more likely to be mechanically adhered to the binder (B), the fine aggregate (S), etc., it is more excellent in tensile strength.

[0011] In the fiber-reinforced mortar composition according to the present invention, the fiber length of the steel fibers may be 10 mm or more and 20 mm or less.

[0012] According to such a configuration, in the fiber-reinforced mortar composition, since the steel fibers are more likely to be mechanically adhered to the binder (B), the fine aggregate (S), etc., it is more excellent in tensile strength.

[0013] In the fiber-reinforced mortar composition according to the present invention, the tensile strength of the steel fibers may be 1,800 MPa or more.

[0014] According to such a configuration, in the fiber-reinforced mortar composition, since the tensile strength of the steel fibers is sufficiently high, it is more excellent in tensile strength.

[0015] In the fiber-reinforced mortar composition according to the present invention, the fiber diameter of the organic fibers may be 10 μm or more and 200 μm or less.

[0016] According to such a configuration, in the fiber-reinforced mortar composition, since the organic fibers are more likely to be mechanically adhered to the binder (B), the fine aggregate (S), etc., it is more excellent in tensile strength.

[0017] In the fiber-reinforced mortar composition according to the present invention, the fiber length of the organic fiber may be 6 mm or more and 15 mm or less.

[0018] According to such a configuration, in the fiber-reinforced mortar composition, since the organic fiber is more likely to mechanically adhere to the binder (B), the fine aggregate (S), etc., it is more excellent in tensile strength.

[0019] In the fiber-reinforced mortar composition according to the present invention, the tensile strength of the organic fiber may be 900 MPa or more.

[0020] According to such a configuration, in the fiber-reinforced mortar composition, since the tensile strength of the organic fiber is sufficiently high, it is more excellent in tensile strength.

[0021] In the fiber-reinforced mortar composition according to the present invention, the organic fiber may be at least one selected from the group consisting of polyvinyl alcohol fiber, polyethylene fiber, and aramid fiber.

[0022] According to such a configuration, in the fiber-reinforced mortar composition, since the adhesion of the organic fiber to the binder (B), the fine aggregate (S), etc. is sufficiently high, it is more excellent in tensile strength.

[0023] In the fiber-reinforced mortar composition according to the present invention, the maximum particle size of the fine aggregate (S) may be 2.5 mm.

[0024] According to such a configuration, in the fiber-reinforced mortar composition, since the fine aggregate (S) is easily kneaded sufficiently with other materials, it is more excellent in tensile strength.

[0025] In the fiber-reinforced mortar composition according to the present invention, the coarse grain ratio of the fine aggregate (S) may be 1.3 or more and 3.0 or less.

[0026] According to such a configuration, in the fiber-reinforced mortar composition, since the fine aggregate (S) is easily kneaded sufficiently with other materials, it is more excellent in tensile strength.

[0027] The method for repairing concrete structures according to the present invention involves filling or applying the above-described fiber-reinforced mortar composition to the repair area of ​​the concrete structure.

[0028] The method for repairing the concrete structure described above, by using the fiber-reinforced mortar composition described above, can maintain high compressive strength at the repaired location while exhibiting excellent tensile strength. [Effects of the Invention]

[0029] According to the present invention, it is possible to provide a fiber-reinforced mortar composition that maintains high compressive strength while exhibiting excellent tensile strength, and a method for repairing concrete structures using the fiber-reinforced mortar composition. [Modes for carrying out the invention]

[0030] The fiber-reinforced mortar composition and the method for repairing concrete structures according to this embodiment will be described below.

[0031] <Fiber-reinforced mortar composition> The fiber-reinforced mortar composition according to this embodiment comprises a binder (B), fine aggregate (S), steel fibers, organic fibers, and water (W).

[0032] The binder (B) contains Portland cement and silica fume powder.

[0033] Examples of Portland cement include ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, moderate-heat Portland cement, low-heat Portland cement, sulfate-resistant Portland cement, and white Portland cement, as specified in JIS R 5210.

[0034] Silica fume fine powder means fine particles (specifically, amorphous spherical fine particles) mainly composed of silicon dioxide collected from exhaust gas generated during the production of metallic silicon or ferrosilicon in an arc furnace, as defined in JIS A 6207, and refers to silica fume in a form where no treatment is carried out to increase the unit volume mass or to suspend it in water while it remains in the collected state.

[0035] The composition of the silica fume fine powder may be, for example, 85% by mass or more and 98% by mass or less of silicon dioxide, and 0.6% by mass or more and 2.0% by mass or less of magnesium oxide.

[0036] From the viewpoint of obtaining excellent crack generation strength, the specific surface area of the silica fume fine powder is 15 m 2 / g or more and 20 m 2 / g or less, preferably 16 m 2 / g or more and 19 m 2 / g or less, more preferably 17 m 2 / g or more and 18 m 2 / g or less. The specific surface area of the silica fume fine powder is measured by the method defined in JIS A 6207 "Silica fume for concrete, 7 Test methods, 7.9 Specific surface area".

[0037] The bulk density of the silica fume is not particularly limited. For example, from the viewpoint of reducing the autogenous shrinkage of concrete, it may be 0.25 g / cm 3 or more and 0.50 g / cm 3 or less. The bulk density means the density when a powder is filled in a container of a certain volume and the internal volume is taken as the volume, and is synonymous with the apparent density defined in JIS Z 8901.

[0038] From the viewpoint of obtaining excellent crack generation strength, the content of the silica fume fine powder is 5 parts by mass or more and 30 parts by mass or less, preferably 5 parts by mass or more and 25 parts by mass or less, and more preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the Portland cement.

[0039] In addition to the Portland cement mentioned above, the binder (B) may also include, for example, a blended cement such as blast furnace cement, fly ash cement, or silica cement; or known cements such as ultrafast-setting cement or alumina cement.

[0040] Furthermore, the binder (B) may also contain admixtures. Examples of admixtures include inorganic powders such as fly ash, cement kiln dust, blast furnace fume, blast furnace granulated slag powder, blast furnace decooked slag powder, converter slag powder, hemihydrate gypsum, expansive agents, limestone powder, quicklime powder, dolomite powder, sodium-type bentonite, calcium-type bentonite, attapulgite, sepiolite, activated clay, acid clay, allophane, imogolite, shirasu (volcanic ash), shirasu balloon, kaolinite, metakaolin (calcined clay), synthetic zeolite, artificial zeolite, mordenite, clinoptilolite, and other inorganic fillers. Note that one type of admixture may be used alone, or two or more types may be used in combination.

[0041] Fine aggregate (S) refers to aggregate that, as defined in JIS A 0203:2019, completely passes through a 10mm mesh sieve and passes through a 5mm mesh sieve by mass at a rate of 85% or more. Examples of fine aggregate (S) include sands derived from natural materials such as river sand, land sand, mountain sand, sea sand, crushed sand, and crushed limestone sand, as defined in Annex JA of JIS A 5308:2024 for ready-mixed concrete, as well as sands derived from slags such as blast furnace slag, electric furnace oxidized slag, and ferronickel slag, recycled aggregate, artificial lightweight aggregate, and recovered aggregate. Silica sand produced by crushing and classifying silica can also be used. Fine aggregate may be used alone or in combination of two or more types.

[0042] The maximum particle size of the fine aggregate (S) is preferably 2.5 mm, from the viewpoint of facilitating sufficient mixing with other materials. The maximum particle size of the fine aggregate (S) refers to the largest mesh opening of the sieve that the fine aggregate (S) remains in when the fine aggregate (S) is sieved in accordance with the method described in JIS A 1102.

[0043] The coarseness ratio of the fine aggregate (S) is preferably 1.3 to 3.0, and more preferably 1.5 to 2.5, from the viewpoint of facilitating sufficient mixing with other materials. The coarseness ratio of the fine aggregate (S) can be measured according to the method described in JIS A 1102.

[0044] The fine aggregate binder ratio (S / B) is 0.25 to 0.70, preferably 0.25 to 0.60, and more preferably 0.25 to 0.50, from the viewpoint of facilitating sufficient mixing with other materials.

[0045] The steel fibers are not particularly limited and include, for example, steel cord (SC fiber), cut wire (CW fiber), straight steel fiber (OL fiber), hooked steel fiber (DR fiber), embossed steel fiber, three-dimensional corrugated steel fiber, piano wire, etc. Straight steel fibers are preferably those without end processing. Hooked steel fibers may have only one end hooked, or both ends may have hook processing.

[0046] From the viewpoint of obtaining excellent tensile strength, the fiber diameter of the steel fiber is preferably 100 μm to 400 μm, and more preferably 150 μm to 250 μm.

[0047] From the viewpoint of obtaining excellent tensile strength, the fiber length of the steel fibers is preferably 10 mm to 20 mm, and more preferably 13 mm to 15 mm.

[0048] From the viewpoint of obtaining excellent tensile strength in the fiber-reinforced mortar composition, the tensile strength of the steel fibers is preferably 1,800 MPa or higher, and more preferably 2,300 MPa or higher. However, the tensile strength of the steel fibers may be 4,000 MPa or lower, or 3,500 MPa or lower.

[0049] From the viewpoint of obtaining excellent tensile strength, the steel fiber content is 2.5% by volume or more and 4.5% by volume or less of the total fiber-reinforced mortar composition, preferably 3.0% by volume or more and 4.5% by volume or less, and more preferably 3.0% by volume or more and 3.5% by volume or less.

[0050] Examples of organic fibers include polyvinyl alcohol fibers (PVA fibers), polyethylene fibers, aramid fibers, polypropylene fibers, and nylon fibers. Among these, from the viewpoint of obtaining excellent tensile strength, the organic fiber is preferably at least one selected from the group consisting of polyvinyl alcohol fibers, polyethylene fibers, aramid fibers, and nylon fibers, and more preferably at least one selected from the group consisting of polyvinyl alcohol fibers, polyethylene fibers, and aramid fibers. The shape of the organic fiber is preferably a straight shape without end processing. Furthermore, the surface of the organic fiber may be embossed.

[0051] From the viewpoint of obtaining excellent tensile strength, the fiber diameter of the organic fiber is preferably 10 μm to 200 μm, and more preferably 12 μm to 200 μm.

[0052] From the viewpoint of obtaining excellent tensile strength, the fiber length of the organic fiber is preferably 6 mm to 15 mm, and more preferably 6 mm to 12 mm.

[0053] From the viewpoint of obtaining excellent tensile strength in the fiber-reinforced mortar composition, the tensile strength of the organic fibers is preferably 900 MPa or higher, and more preferably 2,000 MPa or higher. However, the tensile strength of the organic fibers may be 4,000 MPa or lower, or 3,500 MPa or lower.

[0054] From the viewpoint of obtaining excellent tensile strength, the organic fiber content is 0.2% to 2.0% by volume relative to the entire fiber-reinforced mortar composition, preferably 0.2% to 1.5% by volume, and more preferably 0.2% to 1.0% by volume.

[0055] The water (W) is not particularly limited, and for example, tap water, industrial water, recovered water, groundwater, river water, rainwater, etc. can be used. Preferably, the water does not contain organic matter, chloride ions, sodium ions, potassium ions, etc. that adversely affect the hydration reaction of the cement composition and concrete, or if it does contain them, it is in extremely small amounts. It is more preferable that the water be tap water or industrial water of stable quality.

[0056] The water-to-binder ratio (W / B) is 16% to 22%, preferably 17% to 21%, and more preferably 18% to 20%, from the viewpoint of obtaining excellent tensile strength.

[0057] The fiber-reinforced mortar composition according to this embodiment may contain admixtures. Examples of admixtures include air-entraining agents, air-entraining water-reducing agents, high-performance air-entraining water-reducing agents, fluidizing agents, separation-reducing agents, thickeners, thixotropic agents, setting retarders (e.g., tartaric acid), setting accelerators (e.g., aluminum sulfate), rapid setting agents, shrinkage-reducing agents, foaming agents, defoaming agents, and waterproofing agents. One type of admixture may be used alone, or two or more types may be used in combination.

[0058] The fiber-reinforced mortar composition according to this embodiment can be manufactured by the following method. Specifically, first, a premix powder obtained by mixing a binder (B) and fine aggregate (S) is mixed with water (W) and, if necessary, an admixture to obtain a slurry. Then, steel fibers and organic fibers are added to the slurry and mixed further to obtain the fiber-reinforced mortar composition according to this embodiment.

[0059] Furthermore, the fiber-reinforced mortar composition according to this embodiment can also be manufactured by the following method. Specifically, first, a premix powder is obtained by mixing a binder (B) and fine aggregate (S), to which steel fibers and organic fibers are added and dry-kneaded to obtain a powder mixture. Then, water (W) and, if necessary, an admixture are added to the powder mixture and kneaded to obtain the fiber-reinforced mortar composition according to this embodiment.

[0060] The fiber-reinforced mortar composition according to this embodiment may also be manufactured using a premixed powder obtained by mixing a binder (B), fine aggregate (S), and organic fibers.

[0061] Furthermore, the mixing machine used in the production of the fiber-reinforced mortar composition according to this embodiment is not particularly limited, and examples include a twin-screw forced mixer, a pan-type mixer, a fiber-reinforced material mixer, a hand mixer, and the like.

[0062] The fiber-reinforced mortar composition according to this embodiment can be used, for example, as building material for concrete structures such as skyscrapers and road structures, and as a repair material for such concrete structures.

[0063] The fiber-reinforced mortar composition according to this embodiment is a fiber-reinforced mortar composition comprising a binder (B) containing Portland cement and silica fume fine powder, fine aggregate (S), steel fibers, organic fibers, and water (W), The specific surface area of ​​the aforementioned silica fume fine powder is 15 m². 2 / g or more 20m 2 It is less than / g The content of the silica fume fine powder is 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the Portland cement. The steel fiber content is 2.5% by volume or more and 4.5% by volume or less relative to the entire fiber-reinforced mortar composition. The content of the organic fibers is 0.2% by volume or more and 2.0% by volume or less relative to the entire fiber-reinforced mortar composition. The water-to-binder ratio (W / B) is between 16% and 22%. The fine aggregate-to-binder ratio (S / B) is between 0.25 and 0.70.

[0064] In the aforementioned fiber-reinforced mortar composition, the steel fibers and organic fibers are mechanically and sufficiently adhered to the binder (B), the fine aggregate (S), etc., thus the materials are firmly bonded together. Therefore, the fiber-reinforced mortar composition exhibits excellent tensile strength while maintaining high compressive strength.

[0065] The fiber-reinforced mortar composition according to this embodiment has superior tensile strength because the steel fibers have a fiber diameter of 100 μm or more and 400 μm or less, which allows the steel fibers to adhere more easily to the binder (B), the fine aggregate (S), etc.

[0066] The fiber-reinforced mortar composition according to this embodiment has superior tensile strength because the steel fibers have a fiber length of 10 mm or more and 20 mm or less, which allows the steel fibers to adhere more easily to the binder (B), the fine aggregate (S), etc.

[0067] The fiber-reinforced mortar composition according to this embodiment has superior tensile strength because the tensile strength of the steel fibers is sufficiently high, as the tensile strength of the steel fibers is 1,800 MPa or higher.

[0068] The fiber-reinforced mortar composition according to the present invention has superior tensile strength because the organic fibers have a fiber diameter of 10 μm or more and 200 μm or less, which allows the organic fibers to adhere more easily mechanically to the binder (B), the fine aggregate (S), etc.

[0069] The fiber-reinforced mortar composition according to this embodiment has superior tensile strength because the organic fibers have a fiber length of 6 mm or more and 15 mm or less, which allows the organic fibers to adhere more easily mechanically to the binder (B), the fine aggregate (S), etc.

[0070] The fiber-reinforced mortar composition according to this embodiment has superior tensile strength because the tensile strength of the organic fibers is sufficiently high, as the tensile strength of the organic fibers is 900 MPa or higher.

[0071] The fiber-reinforced mortar composition according to this embodiment has superior tensile strength because the organic fibers are selected from the group consisting of polyvinyl alcohol fibers, polyethylene fibers, and aramid fibers, and the organic fibers have sufficiently high adhesion to the binder (B), the fine aggregate (S), etc.

[0072] The fiber-reinforced mortar composition according to this embodiment has superior tensile strength because the fine aggregate (S) has a maximum particle size of 2.5 mm, which allows the fine aggregate (S) to be easily mixed with other materials.

[0073] The fiber-reinforced mortar composition according to this embodiment has superior tensile strength because the fine aggregate (S) has a coarseness ratio of 1.3 to 3.0, which allows the fine aggregate (S) to be easily mixed with other materials.

[0074] <Repair methods for concrete structures> The concrete structure repair method according to this embodiment involves filling or applying a fiber-reinforced mortar composition to the repair area of ​​the concrete structure.

[0075] The fiber-reinforced mortar composition is the same as the fiber-reinforced mortar composition according to the present embodiment described above.

[0076] The method of filling or applying is not particularly limited and includes, for example, filling methods, plastering methods, and spraying methods. In the filling method, a formwork is assembled at the repair site and an appropriate amount of fiber-reinforced mortar composition is poured in. In the plastering method, a craftsman places an appropriate amount of fiber-reinforced mortar composition on a trowel board and applies the mortar composition to the repair site of the concrete structure using a trowel or similar tool. In the spraying method, the fiber-reinforced mortar composition is sprayed onto the repair site of the concrete structure using a device such as a mortar pump.

[0077] Furthermore, in the concrete structure repair method according to this embodiment, before filling or applying the fiber-reinforced mortar composition to the repair area of ​​the concrete structure, the repair area may be pre-treated by removing corroded or deteriorated parts.

[0078] The concrete structure repair method according to this embodiment involves filling or applying the above-described fiber-reinforced mortar composition to the repair area of ​​the concrete structure, thereby achieving excellent tensile strength while maintaining high compressive strength at the repair area.

[0079] Furthermore, the fiber-reinforced mortar composition and the method for repairing concrete structures according to the present invention are not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the present invention.

[0080] The present invention includes the following embodiments. [1] A fiber-reinforced mortar composition comprising a binder (B) containing Portland cement and silica fume powder, fine aggregate (S), steel fibers, organic fibers, and water (W), The specific surface area of ​​the aforementioned silica fume fine powder is 15 m². 2 / g or more 20m 2 It is less than / g The content of the silica fume fine powder is 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the Portland cement. The steel fiber content is 2.5% by volume or more and 4.5% by volume or less relative to the entire fiber-reinforced mortar composition. The content of the organic fibers is 0.2% by volume or more and 2.0% by volume or less relative to the entire fiber-reinforced mortar composition. The water-to-binder ratio (W / B) is between 16% and 22%. A fiber-reinforced mortar composition having a fine aggregate binder ratio (S / B) of 0.25 or more and 0.70 or less. [2] The fiber-reinforced mortar composition according to [1], wherein the fiber diameter of the steel fibers is 100 μm or more and 400 μm or less. [3] The fiber-reinforced mortar composition according to [1] or [2], wherein the fiber length of the steel fibers is 10 mm or more and 20 mm or less. [4] The fiber-reinforced mortar composition according to any one of [1] to [3], wherein the tensile strength of the steel fibers is 1,800 MPa or more. [5] The fiber-reinforced mortar composition according to any one of [1] to [4], wherein the fiber diameter of the organic fiber is 10 μm or more and 200 μm or less. [6] The fiber-reinforced mortar composition according to any one of [1] to [5], wherein the fiber length of the organic fiber is 6 mm or more and 15 mm or less. [7] The fiber-reinforced mortar composition according to any one of [1] to [6], wherein the tensile strength of the organic fiber is 900 MPa or more. [8] The fiber-reinforced mortar composition according to any one of [1] to [7], wherein the organic fiber is at least one selected from the group consisting of polyvinyl alcohol fiber, polyethylene fiber and aramid fiber. [9] The fiber-reinforced mortar composition according to any one of [1] to [8], wherein the maximum particle size of the fine aggregate (S) is 2.5 mm.

[10] A fiber-reinforced mortar composition according to any one of [1] to [9], wherein the coarseness ratio of the fine aggregate (S) is 1.3 or more and 3.0 or less. A method for repairing a concrete structure, comprising filling or applying a fiber-reinforced mortar composition described in any one of items

[11] [1] to

[10] to the repair area of ​​the concrete structure. [Examples]

[0081] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0082] (Preparation of fiber-reinforced mortar composition) Using the materials shown in Table 1, fiber-reinforced mortar compositions for each example and comparative example were prepared according to the formulations shown in Tables 2 and 3. Specifically, the mixture was first prepared using a mixing machine (Makita Corporation 550 min)... -1Using a premix powder, a binder (B) (Portland cement and silica fume) and fine aggregate (S) were mixed, and water (W) and an admixture were added and mixed for 2 minutes to obtain a slurry. Steel fibers and organic fibers were added to the slurry and mixed for 2 minutes to obtain a fiber-reinforced mortar composition. The obtained fiber-reinforced mortar composition was used to evaluate the state of mixing and to prepare specimens as described below. In addition, the mixability of the obtained slurry before fiber mixing was evaluated as described below. Slurries that received a × for mixability evaluation and a △ or × for the state of mixing evaluation were not used to prepare fiber-reinforced mortar compositions.

[0083] [Table 1]

[0084] [Table 2]

[0085] [Table 3]

[0086] <Preparation of test specimens> The fiber-reinforced mortar compositions of each example and comparative example were poured into steel formwork (10 × 50 × 300 mm), removed the next day, and cured at 20°C and 60% RH for 28 days to obtain 10 × 50 × 300 mm flat specimens. The tensile performance of the obtained specimens was evaluated as follows.

[0087] <Evaluation of mixability before fiber mixing> For each example and comparative example, the slurry used as the raw material for the fiber-reinforced mortar composition was visually inspected for the presence or absence of unmixed portions (lumps), and the mixability before fiber mixing was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 4 and 5. • Evaluation criteria ○: There were no clumps. ×: There was a clump.

[0088] <Evaluation of the finished product> (1) Check for the presence or absence of fiber balls (FB) Using a spoon, the fiber-reinforced mortar compositions of each example and comparative example were mixed and visually inspected for the presence or absence of clumps of steel fibers and / or organic fibers (fiber balls; FB). The results are shown in Tables 4 and 5.

[0089] (2) Confirmation of material separation For each example and comparative example of fiber-reinforced mortar composition, a JIS flow (0 pound) test was performed to confirm whether or not the mortar and fibers (steel fibers and / or organic fibers) had separated. The results are shown in Tables 4 and 5.

[0090] (3) Evaluation Based on the confirmation results in (1) and (2) above, the mixed state of the fiber-reinforced mortar compositions of each example and comparative example was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 4 and 5. • Evaluation criteria ◎: No FB (feedback) was present, and no material separation occurred. ○: FB was present, and there was no material separation. △: No FB (feedback) was present, and material separation occurred. ×: There was FB (feedback) and material separation occurred.

[0091] <Evaluation of compressive strength> First, cylindrical specimens measuring φ50 × 100 mm were prepared using the fiber-reinforced mortar compositions of each example and comparative example. Then, the compressive strength of the obtained cylindrical specimens was measured according to the method described in JIS A 1108. The measurement results are shown in Tables 4 and 5.

[0092] <Evaluation of tensile performance> (1) Measurement of maximum load For each example and comparative example, the maximum load was measured for 10 × 50 × 300 mm flat specimens obtained using the fiber-reinforced mortar composition, based on the notched direct tensile test described in JSCE Library 113. The measurement results are shown in Tables 4 and 5.

[0093] (2) Calculation of load reduction rate For 10 × 50 × 300 mm flat specimens obtained using the fiber-reinforced mortar compositions of each example and comparative example, the load at the opening displacement of +0.5 mm at the maximum load and the load at the opening displacement of +1.0 mm at the maximum load were measured based on the notched direct tensile test described in JSCE Library 113. From the obtained measurement results and the measurement results of the maximum load obtained in (1) above, the load reduction rate was calculated using the following formula (I). The calculation results are shown in Tables 4 and 5.

[0094]

number

[0095] (3) Evaluation Based on the results of (1) and (2) above, the tensile performance of specimens obtained using the fiber-reinforced mortar compositions of each example and comparative example was evaluated based on the following evaluation criteria. The evaluation results are shown in Tables 4 and 5. • Evaluation criteria ○: The maximum load was 5.0kN or more, and the load reduction rate was 60% or more. △: The maximum load was 5.0kN or more, or the load reduction rate was less than 60%, or the maximum load was less than 5.0kN, or the load reduction rate was 60% or more. ×: The maximum load was less than 5.0 kN, and the load reduction rate was less than 60%.

[0096] [Table 4]

[0097] [Table 5]

[0098] As can be seen from Table 4, the specimens obtained using the fiber-reinforced mortar composition satisfying the configuration of the present invention have a strength of 100 N / m 2 Despite demonstrating high compressive strength, all evaluations of its tensile performance were positive (○).

[0099] On the other hand, as can be seen from Table 5, the specimens obtained using the fiber-reinforced mortar compositions of Comparative Examples 1 and 2, for which specimens could be prepared, had a density of 100 N / m². 2 Although it showed high compressive strength as described above, its tensile performance was rated as △ or ×.

[0100] Based on the above, the fiber-reinforced mortar composition according to the present invention exhibits excellent tensile strength while maintaining high compressive strength.

Claims

1. A fiber-reinforced mortar composition comprising a binder (B) containing Portland cement and silica fume powder, fine aggregate (S), steel fibers, organic fibers, and water (W), The specific surface area of ​​the aforementioned silica fume fine powder is 15 m². ２ / g or more 20m ２ / g or less, The content of the silica fume fine powder is 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the Portland cement. The steel fiber content is 2.5% by volume or more and 4.5% by volume or less relative to the entire fiber-reinforced mortar composition. The content of the organic fibers is 0.2% by volume or more and 2.0% by volume or less relative to the entire fiber-reinforced mortar composition. The water-to-binder ratio (W / B) is 16% or more and 22% or less. A fiber-reinforced mortar composition having a fine aggregate binder ratio (S / B) of 0.25 or more and 0.70 or less.

2. The fiber-reinforced mortar composition according to claim 1, wherein the fiber diameter of the steel fibers is 100 μm or more and 400 μm or less.

3. The fiber-reinforced mortar composition according to claim 1, wherein the fiber length of the steel fibers is 10 mm or more and 20 mm or less.

4. The fiber-reinforced mortar composition according to claim 1, wherein the tensile strength of the steel fibers is 1,800 MPa or more.

5. The fiber-reinforced mortar composition according to claim 1, wherein the fiber diameter of the organic fiber is 10 μm or more and 200 μm or less.

6. The fiber-reinforced mortar composition according to claim 1, wherein the fiber length of the organic fiber is 6 mm or more and 15 mm or less.

7. The fiber-reinforced mortar composition according to claim 1, wherein the tensile strength of the organic fibers is 900 MPa or more.

8. The fiber-reinforced mortar composition according to claim 1, wherein the organic fiber is at least one selected from the group consisting of polyvinyl alcohol fiber, polyethylene fiber, and aramid fiber.

9. The fiber-reinforced mortar composition according to claim 1, wherein the maximum particle size of the fine aggregate (S) is 2.5 mm.

10. The fiber-reinforced mortar composition according to claim 1, wherein the coarseness ratio of the fine aggregate (S) is 1.3 or more and 3.0 or less.

11. A method for repairing a concrete structure, comprising filling or applying a fiber-reinforced mortar composition according to any one of claims 1 to 10 to a repair location in the concrete structure.

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