Fiber-reinforced mortar composition and fiber-reinforced mortar

Abstract

To provide a fiber-reinforced mortar composition which reduces the amount of cement to be used, is excellent in workability, and is also excellent in curing characteristics such as compressive strength, bending strength and split tensile strength.SOLUTION: A fiber-reinforced mortar composition comprising: a cement composition comprising cement, a pozzolanic substance comprising blast furnace slag, and fine aggregate; and polypropylene-based short fibers, wherein a mass ratio of the cement is 10 to 35 mass% with respect to a mass of the cement composition, A mass ratio of the pozzolanic material is 30 to 60% by mass with respect to a mass of the cement composition, a volume ratio of the polypropylene short fibers is 2.5 to 5% by volume with respect to a total volume of the cement composition, and an air content at the time of completion of mixing is 7 to 15%, the air content being measured at 20 °C according to "6.5 Air content test" described in JISA1171:2016 "Testing methods for polymer cement mortars".SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fiber-reinforced mortar composition and a fiber-reinforced mortar. [Background technology]

[0002] Cement materials containing large amounts of fibers are known as a technology that provides high toughness, meaning that hardened cement bodies are less likely to break and do not develop large cracks. In structures using such cement materials, even if cracks do occur, the presence of fibers prevents the formation of large cracks and allows for fine control of crack width, resulting in high toughness, elongation, and durability, thereby improving the durability of the structure.

[0003] As examples of cement materials containing large amounts of fibers, Patent Document 1 discloses a spray-on repair material using short PVA (polyvinyl alcohol) fibers, and Patent Document 2 discloses a cement fiber composite material using polypropylene fibers that have been surface-treated with a carboxyl-modified low-molecular-weight polyolefin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-193653 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-137119 Summary of the Invention [Problem to be solved by the invention]

[0005] Fiber-reinforced mortars containing large amounts of fibers can suffer from poor fiber dispersion and reduced mortar fluidity, resulting in poor filling (workability). Therefore, products must address these issues while also providing high durability and resistance to fracture during hardening. Furthermore, in recent years, carbon-neutral initiatives have become increasingly important worldwide as part of efforts to create a recycling-oriented society. Given this background, the cement used in premixed mortars is produced by firing limestone at high temperatures of 1400°C, resulting in significant carbon dioxide (CO2) emissions, which are considered one of the causes of global warming. Reducing the amount of cement used in premixed mortars, which are cement-based materials, is an extremely effective way to reduce CO2 emissions. However, reducing the amount of cement used in fiber-reinforced mortars can result in reduced strength and toughness during hardening.

[0006] Therefore, an object of the present invention is to provide a fiber-reinforced mortar composition and a fiber-reinforced mortar that reduce the amount of cement used, have excellent workability, and are also excellent in hardening properties such as compressive strength, flexural strength, and splitting tensile strength. [Means for solving the problem]

[0007] As a result of intensive research into the above-mentioned problems, the present inventors have found that by blending cement, a specific pozzolanic substance, fine aggregate, and specific fibers and adjusting the fiber content and the amount of air in the mortar, it is possible to obtain a fiber-reinforced mortar composition and a fiber-reinforced mortar that are excellent in various hardening properties while reducing the cement content.

[0008] That is, the present invention is represented by the following [1] to [5]. [1] A fiber-reinforced mortar composition comprising a cement composition including cement, a pozzolanic substance including blast furnace slag, and fine aggregate, and polypropylene-based short fibers, The mass ratio of the cement is 10 to 35 mass% relative to the mass of the cement composition, The mass proportion of the pozzolan substance is 30 to 60 mass% relative to the mass of the cement composition; The volume ratio of the polypropylene short fibers is 2.5 to 5% by volume relative to the total volume of the cement composition; A fiber-reinforced mortar composition having an air content of 7 to 15% when mixed, measured in a 20°C environment in accordance with "6.5 Air Content Test" described in JIS A 1171:2016 "Test Methods for Polymer-Cement Mortars." [2] The polypropylene short fiber has a strength of 270N / mm 2 The fiber-reinforced mortar composition according to [1], having a fiber tensile strength of the above, a fiber diameter of 35 to 70 μm, and a fiber length of 5 to 18 mm. [3] The fiber-reinforced mortar composition according to [1] or [2], further comprising an air content adjuster. [4] When hardened, the bending strength is 10N / mm at 28 days, measured at 20°C in accordance with JIS A 1106:2018 "Test method for bending strength of concrete." 2 The fiber-reinforced mortar composition according to [1] or [2] above. [5] [1] or [2], and water, The fiber-reinforced mortar has a water content of 13 to 35 parts by mass relative to 100 parts by mass of the cement composition. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a fiber-reinforced mortar composition and a fiber-reinforced mortar that can reduce the amount of cement used, have excellent workability, and are also excellent in hardening properties such as compressive strength, flexural strength, and splitting tensile strength. DETAILED DESCRIPTION OF THE INVENTION

[0010] A preferred embodiment of the present invention will be described below. The contents described in this specification are on a solids basis and an anhydrous basis, and if a liquid is contained, the water contained therein is included in the water content.

[0011] The fiber-reinforced mortar composition of the present embodiment contains a cement composition containing cement, a pozzolanic substance containing blast furnace slag, and fine aggregate, and polypropylene-based short fibers.

[0012] The cement composition includes cement, a pozzolanic material including blast furnace slag, and fine aggregate. Various cements can be used, including, for example, various Portland cements such as normal, early-strength, ultra-high-early-strength, low-heat, and medium-heat, ecocement, ultra-high-speed hardening cement, and fly ash cement. Normal Portland cement and early-strength Portland cement are preferred. One type of cement may be used alone, or two or more types may be used in combination.

[0013] The cement content is preferably 20 to 50 parts by mass, more preferably 22 to 48 parts by mass, even more preferably 25 to 45 parts by mass, and particularly preferably 27 to 44 parts by mass, per 100 parts by mass of the total of the cement and pozzolanic substance. If the cement content is within the above range, even better fluidity and hardening properties can be obtained.

[0014] The mass proportion of cement is 10 to 35 mass% relative to the mass of the cement composition. If the mass proportion of cement is outside this range, the fluidity and material separation resistance will decrease, and the hardening characteristics will decrease. From the viewpoint of further improving the fluidity and hardening characteristics, the mass proportion of cement is preferably 12 to 34.5 mass%, and more preferably 15 to 34 mass%, relative to the mass of the cement composition.

[0015] The pozzolanic substance includes blast furnace slag. Examples of pozzolanic substances other than blast furnace slag include fly ash, silica fume, amorphous aluminosilicate, volcanic ash, acid clay, and activated clay. Preferred pozzolanic substances other than blast furnace slag are silica fume, fly ash, and amorphous aluminosilicate.

[0016] The specific surface area of ​​blast furnace slag is 2000 to 10000 cm 2 / g, and 3000 to 9500 cm 2 / g, and more preferably 3500 to 9000 cm 2 When the Blaine specific surface area of ​​the blast furnace slag is within the above range, good fluidity is likely to be obtained.

[0017] The content of blast furnace slag is preferably 30 to 80 parts by mass, more preferably 40 to 70 parts by mass, even more preferably 45 to 65 parts by mass, and particularly preferably 50 to 62 parts by mass, per 100 parts by mass of the pozzolanic substance. If the content of blast furnace slag is within the above range, the CO2 reduction effect can be further improved.

[0018] When fly ash is included as the pozzolanic substance, the content of the fly ash is preferably 20 to 70 parts by mass, more preferably 30 to 60 parts by mass, and even more preferably 35 to 55 parts by mass, per 100 parts by mass of the pozzolanic substance. When the content of the fly ash is within the above range, good fluidity is likely to be obtained.

[0019] The content of the pozzolanic substance is preferably 50 to 80 parts by mass, more preferably 52 to 78 parts by mass, and even more preferably 55 to 75 parts by mass, per 100 parts by mass of the total of the cement and the pozzolanic substance. If the content of the pozzolanic substance is within the above range, even better fluidity and hardening properties can be obtained.

[0020] The mass proportion of the pozzolanic substance is 30 to 60 mass% relative to the mass of the cement composition. If the mass proportion of the pozzolanic substance is outside this range, the fluidity and material separation resistance will decrease, and the hardening characteristics will decrease. From the viewpoint of further improving the fluidity and hardening characteristics, the mass proportion of the pozzolanic substance is preferably 35 to 58 mass%, more preferably 40 to 55 mass%, and even more preferably 43 to 52 mass%, relative to the mass of the cement composition.

[0021] Examples of fine aggregates include silica sand, crushed sand, kansui stone, crushed limestone sand, and slag aggregate. Among these, it is preferable to use aggregates such as silica sand and crushed limestone sand, adjusted to a particle size that does not contain coarse aggregate, and their fine powders. Fine aggregates may be used alone or in combination. The maximum particle size of the fine aggregate is preferably 1.2 mm or less, more preferably 0.6 mm or less, and even more preferably 0.3 mm or less. The maximum particle size of the fine aggregate can be measured in accordance with JIS A 1102:2014, "Sieving Test Method for Aggregates." For example, fine aggregate with a maximum particle size of 0.3 mm or less refers to fine aggregate that passes through a 0.3 mm sieve.

[0022] The content of the fine aggregate is preferably 20 to 60 parts by mass, more preferably 22 to 55 parts by mass, and even more preferably 25 to 50 parts by mass, per 100 parts by mass of the total of the cement and the pozzolanic substance. If the content of the fine aggregate is within the above range, even better fluidity and hardening properties can be obtained.

[0023] The cement composition of this embodiment may contain a water-reducing agent. Examples of water-reducing agents include high-performance water-reducing agents, high-performance air-entraining water-reducing agents, air-entraining water-reducing agents, and superplasticizers. Examples of such water-reducing agents include those specified in JIS A 6204:2011 "Chemical admixtures for concrete." Examples of water-reducing agents include polycarboxylic acid-based water-reducing agents, naphthalene sulfonic acid-based water-reducing agents, lignin sulfonic acid-based water-reducing agents, and melamine-based water-reducing agents. Among these, polycarboxylic acid-based water-reducing agents are preferred. One type of water-reducing agent may be used alone, or two or more types may be used in combination.

[0024] The content of the water-reducing agent is preferably 0.01 to 1 part by mass, more preferably 0.02 to 0.7 parts by mass, and even more preferably 0.05 to 0.5 parts by mass, calculated as solid content, per 100 parts by mass of the total of cement and pozzolanic substance. If the content of the water-reducing agent is within the above range, better fluidity is likely to be obtained when the mortar is made into a mortar.

[0025] The cement composition of this embodiment may contain various admixtures (materials) within the range that does not impair the effects of the present invention. Examples of admixtures (materials) include expansive agents, gypsum, antifoaming agents, waterproofing agents, rust inhibitors, shrinkage reducing agents, thickeners, water retention agents, pigments, water repellents, and anti-efflorescence agents.

[0026] The cement composition of the present embodiment can be prepared by mixing the above-described components using a commonly used mixing tool, and the tool is not particularly limited. Examples of the mixing tool include a mortar mixer, a Hobart mixer, a hand mixer, a Henschel mixer, a tilting mixer, and a twin-shaft mixer.

[0027] The fiber-reinforced mortar composition of the present embodiment contains the above cement composition and polypropylene-based short fibers.

[0028] The length of the polypropylene short fibers is preferably 5 to 18 mm, more preferably 7 to 15 mm, and even more preferably 10 to 13 mm. The diameter of the polypropylene short fibers is preferably 35 to 70 μm, more preferably 37 to 65 μm, and even more preferably 40 to 50 μm. The fiber tensile strength of the polypropylene short fibers is 270 N / mm 2 It is preferable that the resistance is 300N / mm or more. 2 More preferably, it is 350N / mm 2 More preferably, it is equal to or greater than this. When the physical properties of the polypropylene short fibers are within the above ranges, the bending strength and splitting tensile strength when cured are further improved.

[0029] The volume ratio of the polypropylene short fibers is 2.5 to 5% by volume relative to the total volume of the cement composition. If the volume ratio of the polypropylene short fibers is outside this range, the bending strength and splitting tensile strength upon hardening cannot be ensured sufficiently. The volume ratio of the polypropylene short fibers is preferably 2.7 to 4.5% by volume, more preferably 3 to 4% by volume, relative to the total volume of the cement composition.

[0030] The fiber-reinforced mortar composition of this embodiment may further contain an air content adjuster. The air content adjuster is not particularly limited, and examples thereof include air entraining agents (AE agents) specified in JIS A 6204:2011, "Chemical admixtures for concrete." Examples of air content adjusters include anionic surfactants, nonionic surfactants, and resin acid salt surfactants, among which resin acid salt surfactants are preferred. In this specification, the term "air content adjuster" refers to the AE agents specified in JIS A 6204:2011, "Chemical admixtures for concrete." Air-entraining water-reducing agents and high-performance air-entraining water-reducing agents defined in the same standard are treated as the water-reducing agents described above.

[0031] The content of the air content adjuster is preferably 0.01 to 3 parts by mass, more preferably 0.1 to 2 parts by mass, even more preferably 0.2 to 1.5 parts by mass, and particularly preferably 0.3 to 1 part by mass, relative to 100 parts by mass of the cement composition. If the content of the air content adjuster is within the above range, it is easy to ensure the air content of the fiber-reinforced mortar, material separation is less likely to occur, and workability is further improved.

[0032] When the fiber-reinforced mortar composition of this embodiment is mixed with 27 parts by mass of water per 100 parts by mass of the cement composition, the air content at the time of mixing is 7 to 15%, as measured in a 20°C environment in accordance with "6.5 Air Content Test" described in JIS A 1171:2016 "Test Methods for Polymer-Cement Mortars." If the air content is outside the above range, material separation is likely to occur, workability is reduced, and hardening characteristics upon hardening are poor. From the viewpoint of further improving freeze-thaw resistance, material separation resistance, and workability, the air content is preferably 7.5 to 14%, more preferably 8 to 13%, and even more preferably 8.5 to 12%. The air content at the end of mixing can be measured in accordance with "6.5 Air Content Test" in JIS A 1171:2016 "Test Methods for Polymer-Cement Mortar." The air content can be controlled by adjusting the rotation speed and mixing time during mortar mixing, as well as the amount of air content regulator added, while measuring the air content as needed.

[0033] The fiber-reinforced mortar composition of this embodiment can be prepared as a fiber-reinforced mortar by mixing with water, and the water content can be adjusted appropriately depending on the application. From the viewpoint of more easily ensuring fluidity and easily suppressing the occurrence of material separation, the water content is preferably 13 to 35 parts by mass, more preferably 15 to 32 parts by mass, and even more preferably 20 to 30 parts by mass, relative to 100 parts by mass of the cement composition.

[0034] The fiber-reinforced mortar of this embodiment can be prepared using the same mixing equipment as that used for the above-mentioned fiber-reinforced mortar composition, and is not particularly limited. Examples of mixing equipment include a mortar mixer, a Hobart mixer, a hand mixer, a Henschel mixer, a tilting mixer, and a twin-shaft mixer. From the viewpoints of preventing material separation and facilitating adjustment of the air content, it is preferable to knead the fiber-reinforced mortar by kneading the cement composition with water to which an air content adjuster has been added, and then adding polypropylene short fibers and kneading the mixture.

[0035] The fiber reinforced mortar of this embodiment has a bending strength of 10 N / mm at 28 days, measured at 20°C in accordance with JIS A 1106:2018 "Test method for bending strength of concrete" when hardened. 2 It is preferable that the resistance is 12N / mm or more. 2 More preferably, it is 14N / mm 2 If the flexural strength of the fiber-reinforced mortar when hardened is within the above range, the deformability will be high and the durability will be even more excellent.

[0036] The fiber-reinforced mortar of this embodiment preferably has a unit volume weight of 1.5 to 2.2 kg / L, more preferably 1.6 to 2.0 kg / L, and even more preferably 1.7 to 1.9 kg / L. If the unit volume weight of the fiber-reinforced mortar is within the above range, it is lightweight and can further reduce the load on existing components when used for repair, reinforcement, etc. The unit volume weight can be measured in accordance with "6.4 Unit Volume Weight Test" described in JIS A 1171:2016 "Test Methods for Polymer-Cement Mortars."

[0037] The fiber-reinforced mortar composition and fiber-reinforced mortar of this embodiment reduce the amount of cement used, while exhibiting excellent workability and excellent hardening properties such as compressive strength, flexural strength, and splitting tensile strength. Because the fiber-reinforced mortar composition and fiber-reinforced mortar of this embodiment reduce the amount of cement used, they are excellent in CO2 reduction effects. Therefore, such fiber-reinforced mortar composition and fiber-reinforced mortar can be used in applications such as bridge and deck materials, repair and reinforcement members, and earthquake-resistant reinforcement materials, aimed at reducing greenhouse gas emissions and improving fatigue durability, for example, in the earth floors, joints, and gap filling of relatively large concrete structures, and in cross-sectional reinforcement areas of existing structures. [Example]

[0038] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. The examples were carried out in an environment of 20°C.

[0039] The materials used in the examples are as follows: Cement: Ordinary Portland cement (commercially available) Pozzolanic material A: Ground blast furnace slag for concrete (commercially available: Blaine, specific surface area 4000 cm) 2 / g) Pozzolanic material B: Fly ash for concrete (commercially available: JIS Type II) Fine aggregate A (limestone fine powder: passing through a 300 μm sieve) Fine aggregate B (commercially available: No. 7 silica sand, passing through a 300 μm sieve) Fiber: Polypropylene short fiber (commercially available: fiber tensile strength 390 N / mm 2 , fiber diameter 43 μm, fiber length 12 mm) Water reducing agent: Polycarboxylic acid water reducing agent (commercially available) Air content adjuster (commercially available: resinate surfactant)

[0040] [Experimental Example 1] <Production of cement composition> The materials were weighed according to the mixing ratios shown in Table 1 and charged into a Henschel mixer, and mixed for 6 minutes to produce a cement composition.

[0041] <Preparation of fiber-reinforced mortar> 3 kg of the prepared cement composition was gradually added to a mixing vessel containing water with added air content adjuster, and mixed for 2 minutes at a rotation speed of 1000 rpm using a basket-type hand mixer (Toshiba BMV-150A), followed by mixing for another 2 minutes with the fibers, to prepare fiber-reinforced mortar. The air content adjuster was blended in the range shown in Table 2 according to the target air content. The air content of the fiber-reinforced mortar was measured in a 20°C environment in accordance with "6.5 Air content test" described in JIS A 1171:2016 "Test methods for polymer-cement mortar," and the air content at the time of mixing was adjusted as shown in Table 2. The unit volume mass was measured in accordance with "6.4 Unit volume mass test" described in JIS A 1171:2016 "Test methods for polymer-cement mortar." Details of the prepared fiber-reinforced mortar are shown in Table 2.

[0042] [Table 1]

[0043] [Table 2]

[0044] <Evaluation of fresh properties of fiber-reinforced mortar> The fresh consistency (fluidity), material separation resistance, and workability of the prepared fiber-reinforced mortar were evaluated. The evaluation test methods are shown below. [Consistency] The fiber reinforced mortar immediately after mixing was filled into a cement paste container (flow cone) according to JIS R 5201:2015 "Physical Testing Methods for Cement," and the table flow value (mm) was measured after 15 hits of drop vibration. In assessing fluidity, fiber-reinforced mortar was evaluated as being able to be easily poured into the floor and to achieve a good trowel finish after filling. Those that met the table flow value of 150 to 250 mm were given a rating of ◯, while those that did not met the rating were given an X. [Material separation resistance] Resistance to material separation was evaluated as follows: Good: the fiber-reinforced mortar was uniform, the fine aggregate was not tactile on the bottom of the container, the fibers were uniformly dispersed, and there was no partial water floating; and Bad: the mixed fiber-reinforced mortar had a noticeable fine aggregate tactile on the bottom of the container, the fibers were unevenly distributed, and partial water floating on the surface of the mortar. [Workability] Workability was evaluated as follows: when the fiber-reinforced mortar was poured into a wooden formwork measuring 30 cm in length, 30 cm in width, and 15 cm in height with a hand shovel, the fibers were dispersed, no floating water was generated, and the mortar could be molded smoothly with a good finish; if the fibers were unevenly distributed, floating water was generated, and the mortar could not be molded smoothly with a good finish, then it was evaluated as "×."

[0045] The evaluation results of the fresh properties of the fiber-reinforced mortar are shown in Table 3. All of the fiber-reinforced mortars of the Examples showed good fluidity, with 15-attack flow values ​​of 179 to 210 mm immediately after mixing, and there were no problems with fiber dispersion or material separation resistance, confirming good workability. On the other hand, the fiber-reinforced mortars of the Comparative Examples had poor fluidity, with 15-attack flow values ​​that were either too small or too large, and separation of materials such as fibers was observed, resulting in poor workability.

[0046] [Table 3]

[0047] [Experimental Example 2] <Evaluation of hardening characteristics of fiber-reinforced mortar> The compressive strength, flexural strength and splitting tensile strength of the fiber reinforced mortar when hardened were measured and evaluated. The evaluation test methods are as follows. [Compression strength] The compressive strength of the specimens was measured at 28 days of age in accordance with JIS A 1108:2018 "Testing Method for Compressive Strength of Concrete." The specimen dimensions were φ50 x 100 mm. After molding, the specimens were wet-cured, demolded after 24 hours, and then underwater cured at 20°C until the specified age was reached. The compressive strength of ordinary concrete at 28 days of age was 24 N / mm 2 Those having the above value were evaluated as having good compressive strength. [Bending strength] The bending strength of the specimens was measured at 28 days of age in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement." The specimen dimensions were 4 x 4 x 16 cm. After wet curing, the specimens were demolded after 24 hours and then underwater cured at 20°C until the specified age was reached. The fiber-reinforced mortar had a bending strength of 10 N / mm at 28 days of age. 2 Those that met the above criteria were evaluated as being good. [Splitting tensile strength] The splitting tensile strength of the specimens was measured at 28 days of age in accordance with JIS A 1113:2018 "Testing method for splitting tensile strength of concrete." The specimen dimensions were φ100 x 200 mm. After molding, the specimens were wet-cured, demolded after 24 hours, and then underwater cured at 20°C until the specified age was reached. The fiber-reinforced mortar had a splitting tensile strength of 5 N / mm at 28 days of age. 2 Those that met the above criteria were evaluated as being good.

[0048] The evaluation results of the hardening characteristics of the fiber-reinforced mortar are shown in Table 4. In the test specimens of the examples, the compressive strength was 30 N / mm at 28 days. 2 The bending strength is 13N / mm 2 As shown above, the splitting tensile strength is also 5N / mm 2 The above results indicate good hardening characteristics. On the other hand, the specimens of the comparative examples were insufficient in compressive strength, bending strength, and splitting tensile strength.

[0049] [Table 4]

Claims

1. A fiber-reinforced mortar composition comprising a cement composition including cement, a pozzolanic substance including blast furnace slag, and fine aggregate, and polypropylene-based short fibers, The mass ratio of the cement is 10 to 35 mass% relative to the mass of the cement composition, The mass proportion of the pozzolan substance is 30 to 60 mass% relative to the mass of the cement composition; The volume ratio of the polypropylene short fibers is 2.5 to 5% by volume relative to the total volume of the cement composition; A fiber-reinforced mortar composition having an air content of 7 to 15% when mixed, measured in a 20°C environment in accordance with "6.5 Air Content Test" described in JIS A 1171:2016 "Test Methods for Polymer Cement Mortars."

2. The polypropylene short fiber has a viscosity of 270 N / mm ２ The fiber-reinforced mortar composition according to claim 1, having a fiber tensile strength of at least 1000 kJ / cm, a fiber diameter of 35 to 70 μm, and a fiber length of 5 to 18 mm.

3. The fiber-reinforced mortar composition according to claim 1 or 2, further comprising an air content adjuster.

4. When hardened, the bending strength at 28 days is 10 N / mm, measured at 20°C in accordance with JIS A 1106:2018 "Test method for bending strength of concrete". ２ The fiber-reinforced mortar composition according to claim 1 or 2.

5. A fiber-reinforced mortar composition according to claim 1 or 2, and water, The fiber-reinforced mortar, wherein the water content is 13 to 35 parts by mass per 100 parts by mass of the cement composition.

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