Cement composition and method for producing the same

Abstract

To provide a cement composition containing fibers, which exhibits excellent fluidity in a fresh state and excellent tensile strength and toughness after hardening.SOLUTION: A cement composition comprises a powder including cement, an aggregate, water, and fibers, wherein the fibers are at least one selected from the group consisting of a metal fiber, an organic fiber, an inorganic fiber, and a carbon fiber, and a value obtained by multiplying an aspect ratio of the fibers by a content ratio of the fibers in the cement composition is from 40 to 300. A method for producing the cement composition includes: a step of determining a planned aspect ratio of fibers to be used and a planned content ratio of the fibers in the cement composition such that a value obtained by multiplying the planned aspect ratio of the fibers to be used by the planned content ratio of the fibers in the cement composition to be used becomes 40 to 300; and a step of mixing each raw material at the aspect ratio and the content ratio of the fibers determined in the above step to obtain the cement composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cementitious composition and a method for producing the cementitious composition. [Background technology]

[0002] BACKGROUND ART Conventionally, cementitious compositions such as mortar containing fibers for the purpose of increasing toughness or the like (also referred to as "fiber-reinforced cementitious compositions" in this specification) have been known. For example, Patent Document 1 describes a low-shrinkage, ultra-high-strength fiber-reinforced cement composition that is characterized by containing specific amounts of cement, silica fume, coal gasification fly ash, gypsum, a specific expansive material, a specific shrinkage-reducing agent, and metal fibers. Furthermore, Patent Document 2 describes fiber-reinforced concrete obtained by mixing 0.5% to 6.0% by volume of short fibers, which are preheat-treated to give them shrinkage strain, and which contains organic short fibers cut to have an aspect ratio of 20 to 200. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-84095 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-102183 Summary of the Invention [Problem to be solved by the invention]

[0004] Increasing the amount of fibers in a fiber-reinforced cementitious composition can improve the toughness of the fiber-reinforced cementitious composition. On the other hand, an increase in the amount of fibers reduces the fluidity of the fiber-reinforced cementitious composition, making it difficult to ensure the desired workability. It is also known that the size of the fibers has a significant effect on the fluidity of the fiber-reinforced cementitious composition. An object of the present invention is to provide a cementitious composition that contains fibers and has excellent fluidity when fresh (unhardened), and excellent tensile strength and toughness after hardening, as well as a method for producing the same. [Means for solving the problem]

[0005] As a result of intensive research into solving the above problems, the present inventors have found that the above objects can be achieved by a cementitious composition comprising a cement-containing powder, aggregate, water, and fibers, wherein the fibers are at least one type selected from metal fibers, organic fibers, inorganic fibers, and carbon fibers, and the value obtained by multiplying the aspect ratio of the fibers by the fiber content is 40 to 300, and have completed the present invention. That is, the present invention provides the following [1] to

[11] . [1] A cementitious composition comprising a powder containing cement, aggregate, water, and fibers, wherein the fibers are at least one selected from metal fibers, organic fibers, inorganic fibers, and carbon fibers, and the value calculated using the following formula (1) is 40 to 300. Aspect ratio of the fiber × Content (volume %) of the fiber in the cementitious composition (1) [2] The cementitious composition according to [1], wherein the paste fine aggregate volume ratio is 1.60 to 6.00. [3] The cementitious composition according to [1], wherein the paste fine aggregate volume ratio is 1.00 or more and less than 1.60. [4] The powder has a BET specific surface area of ​​5 to 25 m 2 The cementitious composition according to any one of [1] to [3] above, containing pozzolanic fine powder in an amount of 1 / g.

[0006] [5] The above powder has a Blaine specific surface area of ​​3,500 to 10,000 cm 2 The cementitious composition according to any one of [1] to [4] above, containing / g of inorganic powder. [6] The cementitious composition according to any one of [1] and [2], wherein the flow value of the cementitious composition is within the range of 220 to 320 mm when 90 seconds have passed since the flow cone was removed, in the case where the 15-time drop motion is not performed in the flow value measurement method described in "JIS R 5201 Physical Testing Methods for Cement". [7] The cementitious composition according to [1] or [3], wherein the flow value of the cementitious composition is within the range of 110 to 190 mm 90 seconds after the flow cone is removed when the 15-time drop motion is not performed in the flow value measurement method described in "JIS R 5201 Physical Testing Methods for Cement". [8] The cementitious composition has a tensile strength of 4.5 to 15.0 N / mm2, measured in accordance with the Japan Concrete Institute standard "JCI-S-002-2003" (Test method for load-displacement curve of fiber concrete using notched beams). 2 The cementitious composition according to any one of [1] to [7] above, which is within the range. [9] A method for producing a cementitious composition according to the above [1] or [2], comprising: a fiber composition determination step of determining an aspect ratio of fibers to be used and a content of the fibers to be used in the cementitious composition so that a value calculated by the following formula (2) is 40 to 300; and a composition preparation step of mixing each raw material with the aspect ratio of the fibers and the content of the fibers determined in the fiber composition determination step to obtain the cementitious composition. Aspect ratio of the fiber to be used × Content (volume %) of the fiber to be used in the cementitious composition (2)

[10] A method for producing a cementitious composition according to [9], comprising: a curing step of curing the pre-hardened cementitious composition obtained in the composition preparation step in an atmosphere of 50°C or higher to obtain a hardened product of the cementitious composition.

[11] A method for producing a cementitious composition according to the above item [3], comprising: a fiber composition determination step of determining an aspect ratio of fibers to be used and a content rate of the fibers to be used in the cementitious composition so that a value calculated by the following formula (3) is 40 to 300; a composition preparation step of mixing raw materials with the aspect ratio of the fibers and the fiber content determined in the fiber composition determination step to obtain the cementitious composition; and a curing step of curing the cementitious composition before hardening obtained in the composition preparation step in an atmosphere of less than 50°C to obtain a hardened product of the cementitious composition. Aspect ratio of the fiber to be used × Content (volume %) of the fiber to be used in the cementitious composition (3) [Effects of the Invention]

[0007] The cementitious composition of the present invention contains fibers and has excellent fluidity when fresh (unhardened), and excellent tensile strength and toughness after hardening. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the relationship between the tensile strength and the value obtained by multiplying the aspect ratio of the fiber by the content of the fiber in Examples 1 to 15 and Comparative Examples 1 to 5. [Figure 2] FIG. 1 is a graph showing the relationship between the 90-second flow value and the value obtained by multiplying the aspect ratio of the fiber by the fiber content in Examples 1 to 15 and Comparative Examples 1 to 5. [Figure 3] FIG. 1 is a graph showing the relationship between the tensile strength and the value obtained by multiplying the aspect ratio of the fiber by the fiber content in Examples 16 to 27 and Comparative Example 6. [Figure 4] FIG. 1 is a graph showing the relationship between the 90-second flow value and the value obtained by multiplying the aspect ratio of the fiber by the fiber content in Examples 16 to 27 and Comparative Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0009] The cementitious composition of the present invention is a cementitious composition comprising a powder containing cement, aggregate, water, and fibers, wherein the fibers are at least one type selected from metal fibers, organic fibers, inorganic fibers, and carbon fibers, and the value calculated using the following formula (1) is 40 to 300. Aspect ratio of fiber × Content (volume%) of the fiber in the cementitious composition (1) A detailed explanation is provided below. Examples of cement contained in the cement-containing powder are not particularly limited, and include various types of Portland cement such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, and low-heat Portland cement; blended cements such as blast-furnace cement, silica cement, and fly ash cement; and ecocement.

[0010] Examples of powders other than cement contained in cement-containing powders include those with a BET specific surface area of ​​5 to 25 m 2 / g (hereinafter, sometimes abbreviated as "pozzolanic fine powder") and a Blaine specific surface area of ​​3,500 to 10,000 cm 2 / g of inorganic powder (hereinafter, sometimes abbreviated as "inorganic powder"). Examples of pozzolanic fine powders include silica fume, silica dust, fly ash, slag powder, volcanic ash, silica sol, precipitated silica, etc. These may be used alone or in combination of two or more. Among them, silica fume and silica dust have a BET specific surface area of ​​5 to 25 m 2 / g and does not require pulverization, and is therefore preferably used in the present invention.

[0011] The BET specific surface area of ​​the pozzolanic fine powder is 5 to 25 m 2 / g, preferably 7 to 20m 2 / g, more preferably 8 to 16 m 2 / g. This value is 5m 2When the value is 25m / g or more, the filling property of the pozzolanic fine powder in the cementitious composition is improved, and the strength (for example, tensile strength) of the hardened body of the cementitious composition is increased. 2 When the viscosity is 0.15 MPa or less, the amount of water required to obtain the desired fluidity can be reduced, and as a result, the strength (for example, tensile strength) of the hardened body of the cementitious composition can be increased. The amount of pozzolanic fine powder is preferably 40 parts by mass or less, more preferably 4 to 35 parts by mass, even more preferably 8 to 30 parts by mass, and particularly preferably 10 to 28 parts by mass, relative to 100 parts by mass of cement. When the amount is 40 parts by mass or less, the fluidity of the cementitious composition before hardening can be further improved.

[0012] Blaine specific surface area is 3,500 to 10,000 cm 2 / g of inorganic powder includes quartz powder, limestone powder, alumina powder, etc. The Blaine specific surface area of ​​inorganic powder is 3,500 to 10,000 cm 2 / g, preferably 5,000~9,500cm 2 / g, more preferably 6,500 to 8,500 cm 2 / g. The value is 3,500 cm 2 When the value is 10,000 cm / g or more, the difference in Blaine specific surface area with the cement becomes large, and the fluidity of the cementitious composition before hardening can be further improved. 2 When the content is 0.01 to 0.1g, the labor required for pulverization can be further reduced, and the fluidity of the cementitious composition before hardening can be further improved. The amount of inorganic powder is preferably 45 parts by mass or less, more preferably 4 to 40 parts by mass, even more preferably 8 to 35 parts by mass, and particularly preferably 10 to 30 parts by mass, relative to 100 parts by mass of cement. When the amount is 45 parts by mass or less, there is no need to excessively increase the amount of water contained in the cementitious composition in order to obtain the desired fluidity, and therefore a decrease in the compressive strength of the hardened product of the cementitious composition can be avoided. It should be noted that the inorganic powder does not include cement.

[0013] The aggregate may be fine aggregate alone or a combination of fine and coarse aggregate. Natural aggregate, artificial aggregate, or recycled aggregate may all be used. The fine aggregate is not particularly limited, and examples thereof include river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, limestone fine aggregate, slag fine aggregate, lightweight fine aggregate, clinker fine aggregate, and CCU fine aggregate (fine aggregate in which carbon dioxide is fixed in one or more types selected from recycled aggregate, waste concrete, blast furnace slag, and steelmaking slag), etc. These may be used alone or in combination of two or more types. The amount of fine aggregate is preferably 180 parts by mass or less, more preferably 10 to 150 parts by mass, even more preferably 20 to 120 parts by mass, and particularly preferably 30 to 100 parts by mass, relative to 100 parts by mass of the cement-containing powder. When the amount is 180 parts by mass or less, it is possible to avoid shortening the usable life of the cementitious composition.

[0014] The coarse aggregate is not particularly limited, and examples thereof include river gravel, mountain gravel, land gravel, sea gravel, crushed stone, limestone coarse aggregate, slag coarse aggregate, lightweight coarse aggregate, clinker coarse aggregate, and CCU coarse aggregate (coarse aggregate in which carbon dioxide is fixed in one or more selected from recycled aggregate, waste concrete, blast furnace slag, and steelmaking slag), etc. These may be used alone or in combination of two or more. The amount of coarse aggregate is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and particularly preferably 20 parts by mass or less, relative to 100 parts by mass of the cement-containing powder. When the amount is 60 parts by mass or less, the strength (e.g., tensile strength) of the hardened body of the cementitious composition can be increased. When the cementitious composition contains coarse aggregate, the fine aggregate ratio (s / a) is preferably 5 to 70%, more preferably 10 to 60%, and particularly preferably 20 to 50%. If the fine aggregate ratio is within the above range, the workability and ease of molding of mortar or concrete are improved. The fine aggregate ratio refers to the volume ratio of fine aggregate to the total amount of fine aggregate and coarse aggregate.

[0015] The water is not particularly limited, and examples thereof include tap water and sludge water. The mass ratio of water to cement-containing powder (water / cement-containing powder) is preferably 0.10 to 0.30, more preferably 0.11 to 0.28, even more preferably 0.12 to 0.25, and particularly preferably 0.14 to 0.22. When the ratio is 0.10 or more, the fluidity of the cementitious composition before hardening is further improved. When the ratio is 0.30 or less, material separation of the cementitious composition is less likely to occur.

[0016] The hydraulic composition of the present invention may contain various admixtures such as a cement dispersant, an air-entraining agent, a shrinkage reducing agent, and an antifoaming agent, as required. Examples of cement dispersants include lignin-based, naphthalene sulfonic acid-based, melamine-based, and polycarboxylic acid-based water-reducing agents, air-entraining water-reducing agents, high-performance water-reducing agents, and high-performance air-entraining water-reducing agents. Among these, high-performance water-reducing agents are preferred because of their large water-reducing effect. In particular, polycarboxylic acid-based high-performance water-reducing agents are more preferred because they improve the fluidity of the cementitious composition before hardening. The amount of cement dispersant is preferably 0.3 to 3.3 parts by mass, more preferably 0.4 to 3.0 parts by mass, even more preferably 0.5 to 2.5 parts by mass, and particularly preferably 0.9 to 1.8 parts by mass, relative to 100 parts by mass of the cement-containing powder. When the amount is 0.3 parts by mass or more, the water-reducing effect is enhanced. When the amount is 3.3 parts by mass or less, the strength development of the cementitious composition is further improved.

[0017] Examples of fibers include metal fibers, organic fibers, inorganic fibers, and carbon fibers, which may be used singly or in combination of two or more. In addition, the size of the fibers may be such that the value calculated using the formula (1) described below falls within a range of 40 to 300, from the viewpoint of improving the fluidity of the cementitious composition before hardening and the tensile strength of the hardened body after hardening. Examples of metal fibers include steel fibers. The dimensions of the metal fibers are preferably 0.008 to 1.0 mm in diameter and 1 to 30 mm in length, more preferably 0.05 to 0.5 mm in diameter and 5 to 25 mm in length, from the viewpoints of preventing material separation of the metal fibers in the cementitious composition and increasing the tensile strength of the hardened body of the cementitious composition. The aspect ratio (fiber length / fiber diameter) of the metal fibers is preferably 10-200, and more preferably 40-150.

[0018] In particular, when the metal fibers are steel fibers, the length of the steel fibers is preferably 1.0 mm or more, more preferably 3.0 mm or more, even more preferably 6.0 mm or more, and particularly preferably 8.0 mm or more, from the viewpoint of increasing the tensile strength of the hardened body of the cementitious composition. Also, the length is preferably 30 mm or less, more preferably 25 mm or less, even more preferably 20 mm or less, and particularly preferably 18 mm or less, from the viewpoint of enabling the fibers to be uniformly distributed in the cementitious composition and improving the fluidity of the cementitious composition before hardening. From the viewpoint of improving the fluidity of the cementitious composition before hardening, the diameter of the steel fibers is preferably 0.008 mm or more, more preferably 0.050 mm or more, even more preferably 0.10 mm or more, even more preferably 0.12 mm or more, and particularly preferably 0.20 mm or more. From the viewpoint of increasing the tensile strength of the hardened body of the cementitious composition, the diameter is preferably 1.0 mm or less, more preferably 0.8 mm or less, even more preferably 0.6 mm or less, even more preferably 0.4 mm or less, and particularly preferably 0.3 mm or less. From the viewpoint of increasing the tensile strength of the hardened body of the cementitious composition, the aspect ratio of the steel fibers (fiber length / fiber diameter) is preferably 10 or more, more preferably 30 or more, even more preferably 40 or more, and particularly preferably 60 or more. From the viewpoint of improving the fluidity of the cementitious composition before hardening, the above ratio is preferably 300 or less, more preferably 200 or less, even more preferably 150 or less, and particularly preferably 80 or less.

[0019] Examples of organic fibers include vinylon fibers, polypropylene fibers, aramid fibers, high-strength aramid fibers, high-strength polyethylene fibers, high-strength polyarylate fibers, and PBO fibers. Examples of inorganic fibers include basalt fibers. Examples of carbon fibers include PAN-based carbon fibers and pitch-based carbon fibers. From the viewpoints of preventing material separation of these fibers in the cementitious composition and improving the fracture energy of the cementitious composition, the dimensions of the organic fibers, inorganic fibers, and carbon fibers are preferably 0.005 to 1.0 mm in diameter and 2 to 30 mm in length, more preferably 0.01 to 0.5 mm in diameter and 5 to 25 mm in length. The aspect ratio (fiber length / fiber diameter) of the organic fibers, inorganic fibers, and carbon fibers is preferably 20 to 200, more preferably 30 to 150.

[0020] The content of fibers in the cementitious composition is preferably 0.5% by volume or more, more preferably 1.0% by volume or more, even more preferably 2.0% by volume or more, even more preferably 3.0% by volume or more, and particularly preferably more than 4.0% by volume, from the viewpoint of increasing the tensile strength of the hardened body of the cementitious composition. Also, from the viewpoint of improving the fluidity of the cementitious composition before hardening, the content is preferably 10.0% by volume or less, more preferably 9.0% by volume or less, even more preferably 8.0% by volume or less, even more preferably 7.0% by volume or more, even more preferably 5.0% by volume or less, even more preferably 3.0% by volume or less, and particularly preferably less than 1.5% by volume.

[0021] In the cementitious composition of the present invention, the numerical value calculated using the following formula (1) is 40 to 300. Aspect ratio of fiber × fiber content in cementitious composition (volume %) (1) The units of the values ​​calculated in formula (1) are omitted. When the above numerical value is within the numerical range of 40 to 300, the cementitious composition can be made excellent in fluidity before hardening and strength development after hardening. From the viewpoint of increasing the tensile strength of the hardened body of the cementitious composition, the above numerical value is 40 or more, preferably 70 or more, more preferably 100 or more, even more preferably 120 or more, even more preferably 150 or more, and particularly preferably 200 or more. In addition, from the viewpoint of further improving the fluidity of the cementitious composition before hardening, the above numerical value is 300 or less, preferably 250 or more, more preferably 200 or less, even more preferably 150 or less, even more preferably 120 or less, and particularly preferably 100 or less. The above numerical range may be changed as appropriate within the numerical range of 40 to 300 depending on the desired physical properties (quality) of the cementitious composition.

[0022] The paste fine aggregate volume ratio of the cementitious composition is preferably 1.00 or more, more preferably 1.10 or more, even more preferably 1.60 or more, even more preferably 1.62 or more, even more preferably 1.65 or more, even more preferably 1.80 or more, and particularly preferably 2.00 or more, from the viewpoints of further improving the strength development of the cementitious composition, further improving the kneadability, and making it less likely that fiber balls and the like will be generated during kneading. Also, the paste fine aggregate volume ratio is preferably 6.00 or less, more preferably 5.80 or less, even more preferably 5.50 or less, even more preferably 5.25 or less, even more preferably 5.00 or less, even more preferably less than 1.60, and particularly preferably 1.50 or less, from the viewpoints of further improving the fluidity and workability before hardening, and making it less likely that material separation will occur. Here, the paste fine aggregate volume ratio is the ratio of the volume of 1 m of concrete to the volume of fine aggregate. 3 The ratio of the paste volume (volume of a mixture of powder and water containing cement) to the volume of fine aggregate in the paste (volume of paste / volume of fine aggregate).

[0023] The cementitious composition of the present invention has the following physical properties. In this specification, the cementitious composition includes a form having fluidity before hardening and a form after hardening. (1) Physical properties before hardening (fresh state) In the flow value measurement method described in "JIS R 5201 Physical Testing Methods for Cement," when the 15 drop motions are not performed, the flow value 90 seconds after the flow cone is removed is preferably 110 mm or more, more preferably 120 mm or more, even more preferably 140 mm or more, even more preferably 220 mm or more, even more preferably 240 mm or more, and particularly preferably 250 mm or more, from the viewpoint of further reducing the viscosity of the cementitious composition and further improving fluidity. The above flow value is preferably 320 mm or less, more preferably 300 mm or less, even more preferably 290 mm or less, even more preferably 190 mm or less, even more preferably 180 mm or less, and particularly preferably 170 mm or less, from the viewpoint of making separation of the material (fiber) less likely to occur. The preferable range of the flow value also varies depending on the value of the paste fine aggregate volume ratio of the cementitious composition. For example, when the paste fine aggregate volume ratio of the cementitious composition is 1.60 to 6.00, the flow value is preferably 220 to 320 mm. When the paste fine aggregate volume ratio of the cementitious composition is 1.00 or more and less than 1.60, the flow value is preferably 110 to 190 mm. The reason why the time to measure the flow value was set as "90 seconds after the flow cone was removed" is that, generally, the change in the flow value after 90 seconds is significantly smaller than before 90 seconds. The air content of the cementitious composition is preferably 5.0% or less, more preferably 4.8% or less, and particularly preferably 4.5% or less. If the air content is 5.0% or less, the strength (tensile strength) of the hardened body of the cementitious composition can be increased.

[0024] (2) Physical properties after hardening The tensile strength of the hardened cementitious composition measured in accordance with the Japan Concrete Institute standard "JCI-S-002-2003" (Test method for load-displacement curve of fiber concrete using notched beam) is preferably 4.5 N / mm 2 More preferably, 5.0N / mm2 More preferably, 6.0 N / mm 2 More preferably, 8.5N / mm 2 More than 9.0N / mm 2 The upper limit of the tensile strength is not particularly limited, but is preferably 20 N / mm 2 , more preferably 15N / mm 2 is. The compressive strength of the hardened cementitious composition measured in accordance with "JIS A 1108:2018 (Testing method for compressive strength of concrete)" is preferably 80 to 300 N / mm 2 More preferably, 90 to 280 N / mm 2 , and more preferably 100 to 250 N / mm 2 is. In addition, when the paste fine aggregate volume ratio of the cementitious composition is 1.60 to 6.00, the compressive strength of the hardened body of the cementitious composition is preferably 150 to 300 N / mm 2 , more preferably 200N / mm 2 Exceeds 250N / mm 2 The following is the result. In addition, when the paste fine aggregate volume ratio of the cementitious composition is 1.00 or more and less than 1.60, the compressive strength of the hardened body of the cementitious composition is preferably 100 to 200 N / mm 2 , more preferably 120 to 195 N / mm 2 is.

[0025] An example of the method for producing the cementitious composition of the present invention includes: (A) a fiber composition determination step of determining the aspect ratio of fibers to be used and the content of fibers to be used in the cementitious composition so that the value calculated by the following formula (2) is 40 to 300; and (B) a composition preparation step of mixing each raw material at the fiber aspect ratio and fiber content determined in the fiber composition determination step to obtain the cementitious composition. Aspect ratio of the fiber to be used × Content (volume%) of the fiber to be used in the cementitious composition (2) Each step will be explained in detail below.

[0026] [(A) Fiber composition determination step] This step is a step of determining the aspect ratio of the fibers to be used and the content of the fibers to be used in the cementitious composition so that the value calculated by the following formula (2) is 40 to 300. Aspect ratio of the fiber to be used × Content (volume%) of the fiber to be used in the cementitious composition (2) The units of the values ​​calculated in formula (2) are omitted. The fiber to be used may be one type or two or more types. When there are multiple types of fiber to be used, the numerical value is calculated for each of the multiple types of fiber using the above formula (2). In this step, by appropriately adjusting the aspect ratio of the fibers and the content of the fibers in the cementitious composition so that the value calculated by formula (2) is 40 to 300, it is possible to produce a cementitious composition that has excellent fluidity when fresh (unhardened) and excellent tensile strength (toughness) after hardening. When two or more types of fibers are used, the aspect ratio of the fibers to be used in the above formula (2) is the average value of the aspect ratios of the two or more types of fibers, and the content of the fibers to be used is the sum of the content of the two or more types of fibers. As a result, even if the fiber has a size that has been conventionally determined to be unsuitable from the viewpoints of fluidity and tensile strength, the fiber content that enables a cementitious composition excellent in fluidity, tensile strength, and toughness to be obtained can be determined from the value calculated by formula (2), and a wide range of fibers can be used.

[0027] Before the step (A), a reference value setting step may be performed to appropriately set the range of the value calculated by the above formula (2) within a range of 40 to 300 according to the desired physical properties (quality) of the cementitious composition. For example, from the viewpoint of producing a cementitious composition having superior tensile strength, the lower limit of the range of the value calculated by the above formula (2) may be set to preferably 70, more preferably 100, even more preferably 120, still more preferably 150, and particularly preferably 200. Furthermore, from the viewpoint of producing a cementitious composition having superior fluidity, the upper limit of the range of the value calculated by the above formula (2) may be set to preferably 250, more preferably 200, even more preferably 150, still more preferably 120, and particularly preferably 100.

[0028] [(B) Composition preparation process] This step is a step of obtaining the cementitious composition by mixing the respective raw materials in amounts that will achieve the fiber aspect ratio and fiber content determined in the fiber composition determination step. The raw materials contained in the cementitious composition include the above-mentioned cement-containing powder, aggregate, fiber, water, and the like. The mixing method is not particularly limited, and examples include a method in which part of the materials (e.g., cement, other powders, and aggregates) are put into a mixer and mixed (dry mixed), then part of the remaining materials (e.g., water and cement dispersant) are put into the mixer and mixed, and finally the remaining part of the materials (e.g., fibers) are put into the mixer and mixed.

[0029] [(C)Curing process] After the step (B), a curing step may be provided in which the pre-hardened cementitious composition obtained in the composition preparation step is cured to obtain a hardened cementitious composition. The curing method is not particularly limited, and general curing methods such as air curing, moist air curing, underwater curing, hot water curing, sealed curing, and autoclave curing can be used. The curing time varies depending on the curing method, but is, for example, preferably 1 hour or more, more preferably 2 to 96 hours, and particularly preferably 12 to 84 hours. In addition, in the curing step, from the viewpoint of increasing the tensile strength and toughness of the hardened body of the cementitious composition, the curing conditions may be determined depending on the value of the paste fine aggregate volume ratio. For example, when the paste fine aggregate volume ratio of the cementitious composition is 1.60 to 6.00, the cementitious composition before hardening obtained in the composition preparation step is used to harden the cementitious composition so that the compressive strength of the hardened body of the cementitious composition is 40 to 50 N / mm 2 It is preferable to leave the mixture in an atmosphere of 5 to 40°C until the temperature reaches 50°C, and then cure the mixture in an atmosphere of 50°C or higher (preferably 60 to 300°C, more preferably 70 to 250°C). More specifically, it is more preferable to leave the cementitious composition before hardening in an atmosphere of 5 to 40°C for 12 to 36 hours, and then perform either or both of steam curing or hot water curing at 70°C or higher but lower than 100°C for 6 hours or more, and autoclave curing at 100 to 200°C for 1 hour or more. According to such curing conditions, the compressive strength of the hardened cementitious composition after being left standing in an atmosphere of 5 to 40°C is 40 to 50 N / mm 2 The compressive strength of the hardened cementitious composition obtained in the end is 150 to 250 N / mm 2 (Preferably 200N / mm 2 Exceeds 250N / mm 2 or less) and tensile strength of 5.0 to 15.0 N / mm 2 The numerical range can be:

[0030] Furthermore, when the paste fine aggregate volume ratio of the cementitious composition is 1.00 or more and less than 1.60, it is preferable to cure the cementitious composition before hardening obtained in the composition preparation step in an atmosphere of 5 to 50°C (preferably 10 to 40°C, more preferably 15 to 35°C). Examples of methods for curing in an atmosphere of less than 50°C include air curing, moist air curing, underwater curing, and sealed curing. Under these curing conditions, the compressive strength of the hardened cementitious composition is 100 to 200 N / mm 2 (Preferably 120 to 195 N / mm 2 ) and the tensile bending strength is 5.0 to 15.0 N / mm 2 The numerical range can be: Furthermore, before the curing step, a casting step of casting the pre-hardened cementitious composition into a formwork may be provided. The casting method is not particularly limited, and a conventional method such as pour molding can be used. When the casting step is performed, a demolding step of demolding the hardened body of the cementitious composition in the formwork from the formwork is performed after the curing step. [Example]

[0031] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Cement: Pacific Cement Corporation, moderate heat Portland cement (2) Pozzolanic fine powder (shown as "fine powder" in Tables 2 and 4); silica fume (BET specific surface area: 11 m 2 / g) (3) Inorganic powder: quartz powder (Blaine specific surface area: 7,500 cm 2 / g) (4) Fine aggregate: silica sand (5) Fibers A to G: Steel fibers (details are shown in Table 1). (6) Cement dispersant; polycarboxylic acid-based high-performance water reducer

[0032] [Table 1]

[0033] [Examples 1 to 15, Comparative Examples 1 to 5] Cementitious compositions were prepared using the types of fibers shown in Table 2 and the amounts of fibers corresponding to the content (volume ratio) in the cementitious composition, as well as the amounts of cement, pozzolanic fine powder, and inorganic powder shown in Table 2. Specifically, cement, pozzolanic fine powder, inorganic powder, and fine aggregate were put into a pan mixer (volume: 55 liters) and dry-mixed, then water and a cement dispersant were added and kneaded, and finally, fibers were added to the mixer and further kneaded to obtain a cementitious composition (volume: 20 liters). The amount of cement dispersant added was 10 ... 3The amount was set to 21 kg per 100 parts by mass of the powder containing cement (amount in the range of 0.3 to 3.3 parts by mass). The blending ratios of Examples 1 to 15 were adjusted so that the paste fine aggregate volume ratio of the cementitious composition was within the range of 1.6 to 6.0. The paste fine aggregate void ratios of the cementitious compositions of Examples 1 to 15 and Comparative Examples 1 to 5 are shown in Table 2. Furthermore, a numerical value (shown as "ASf x Vf" in Tables 1 and 2) was calculated by multiplying the aspect ratio of the fiber by the content of the fiber in the cementitious composition.

[0034] The flow value of the obtained cementitious composition was measured 90 seconds after the flow cone was removed in the case where the 15-time dropping motion was not performed in the flow value measurement method described in "JIS R 5201 Physical Testing Methods for Cement." (hereinafter, also referred to as "90-second flow value") Furthermore, the obtained cementitious composition was cast into a form, and then the unhardened cementitious composition was subjected to sealed curing in an atmosphere at 20°C for 24 hours, and then removed from the form and subjected to steam curing in an atmosphere at 90°C for 48 hours to obtain a test specimen of the hardened cementitious composition. Using the obtained test specimen, the tensile strength was measured in accordance with the Japan Concrete Institute standard "JCI-S-002-2003" (Test method for load-displacement curve of fiber concrete using notched beams). In addition, the compressive strength of the obtained specimens was measured in accordance with "JIS A 1108:2018 (Test method for compressive strength of concrete)". Furthermore, the air content of the cementitious composition was measured using a mortar air meter. The results are shown in Table 3. Furthermore, from the data of the 20 kinds of cementitious compositions produced in Examples 1 to 15 and Comparative Examples 1 to 5, a multiple regression analysis was performed with the values ​​calculated using the formula (1) as independent variables and the measured values ​​of tensile strength as dependent variables, and a relational expression between the values ​​calculated using the formula (1) and the measured values ​​of tensile strength was obtained. The results are shown in Figure 1. In addition, multiple regression analysis was performed in the same manner, except that the measured 90-second flow value was used instead of the measured tensile strength value, and a relationship equation between the value calculated using equation (1) and the measured 90-second flow value was obtained. The results are shown in Figure 2.

[0035] [Table 2]

[0036] [Table 3]

[0037] From Table 3, it can be seen that the 90-second flow values ​​(240 to 293 mm) of Examples 1 to 15 are greater than the 90-second flow values ​​(161 to 197 mm) of Comparative Examples 1 to 5, and the cementitious compositions of the present invention have excellent fluidity. The tensile strength of Examples 1 to 15 was 5.1 to 11.6 N / mm 2 Among them, the tensile strengths of Examples 1 to 11, in which the values ​​calculated by the formula (1) are 110.0 to 272.7 (8.8 to 11.6 N / mm 2 ) is the tensile strength (5.1 to 8.1 N / mm 2 ) is found to be larger than 1 and 2, it can be seen that there is a high positive correlation between the value calculated using formula (1) (the value obtained by multiplying the aspect ratio of the fiber by the content of the fiber in the cementitious composition) and the 90-second flow value. It can also be seen that there is a high negative correlation between the value calculated using formula (1) and the tensile strength. From this, it can be seen that by determining the aspect ratio of the fibers used and the content of the fibers in the cementitious composition so that the value calculated using formula (1) falls within a specific range (for example, 40 to 300), it is possible to produce a cementitious composition that has excellent fluidity when fresh (unhardened) and excellent tensile strength (toughness) after hardening.

[0038] [Examples 16 to 27, Comparative Example 6] The types of fibers shown in Table 4 and the amounts of fibers corresponding to the content (volume ratio) in the cementitious composition, and the amounts of cement, pozzolanic fine powder, and inorganic powder shown in Table 4 were used to prepare cementitious compositions in the same manner as in Example 1. The blending ratios of Examples 16 to 27 were adjusted so that the paste fine aggregate volume ratio of the cementitious composition was in the range of 1.0 or more and less than 1.60. The paste fine aggregate void ratios of the cementitious compositions of Examples 16 to 27 and Comparative Example 6 are shown in Table 4. Furthermore, a numerical value (shown as "ASf x Vf" in Tables 4 and 5) was calculated by multiplying the aspect ratio of the fiber by the content of the fiber in the cementitious composition.

[0039] The 90-second flow value of the obtained cementitious composition was measured in the same manner as in Example 1. In addition, the obtained cementitious composition was cast into a form, and then the unhardened cementitious composition was subjected to sealed curing in an atmosphere of 20°C for 24 hours, and then removed from the form to obtain a test specimen of the hardened cementitious composition. Using the obtained test specimen, the tensile strength and compressive strength were measured in the same manner as in Example 1. Furthermore, the air content of the cementitious composition was measured using a mortar air meter. The results are shown in Table 5. Furthermore, from the data of the 13 types of cementitious compositions produced in Examples 16 to 27 and Comparative Example 4, a multiple regression analysis was performed with the values ​​calculated using formula (1) as independent variables and the measured values ​​of tensile strength as dependent variables, and a relational expression between the values ​​calculated using formula (1) and the measured values ​​of tensile strength was obtained. The results are shown in Figure 3. In addition, multiple regression analysis was performed in the same manner, except that the measured 90-second flow value was used instead of the measured tensile strength value, and a relationship equation between the value calculated using equation (1) and the measured 90-second flow value was obtained. The results are shown in Figure 4.

[0040] [Table 4]

[0041] [Table 5]

[0042] From Table 5, it can be seen that the 90-second flow values ​​(112 to 180 mm) of Examples 16 to 27 are greater than the 90-second flow value (100 mm) of Comparative Example 6, and the cementitious compositions of the present invention have excellent fluidity. 3 and 4, it can be seen that there is a high positive correlation between the value calculated using formula (1) (the value obtained by multiplying the aspect ratio of the fiber by the content of the fiber in the cementitious composition) and the 90-second flow value. It can also be seen that there is a high negative correlation between the value calculated using formula (1) and the tensile strength. From this, it can be seen that by determining the aspect ratio of the fibers used and the content of the fibers in the cementitious composition so that the value calculated using formula (1) falls within a specific range (for example, 40 to 300), it is possible to produce a cementitious composition that has excellent fluidity when fresh (unhardened) and excellent tensile strength (toughness) after hardening.

Claims

1. A cementitious composition comprising a powder containing cement, aggregate, water, and fibers, the fibers are at least one selected from metal fibers, organic fibers, inorganic fibers, and carbon fibers; A cementitious composition characterized in that the value calculated using the following formula (1) is 40 to 300. Aspect ratio of the fiber × Content (volume%) of the fiber in the cementitious composition (1)

2. 2. The cementitious composition according to claim 1, wherein the paste fine aggregate volume ratio is 1.60 to 6.

00.

3. 2. The cementitious composition according to claim 1, wherein the paste fine aggregate volume ratio is 1.00 or more and less than 1.

60.

4. The powder has a BET specific surface area of ​​5 to 25 m ２ 4. The cementitious composition according to claim 1, wherein the pozzolanic fine powder is present in an amount of 0.1 to 0.2g.

5. The powder has a Blaine specific surface area of ​​3,500 to 10,000 cm ２ The cementitious composition according to any one of claims 1 to 3, comprising / g of inorganic powder.

6. The cementitious composition according to claim 1 or 2, wherein the flow value of the cementitious composition is within the range of 220 to 320 mm when 90 seconds have elapsed since the flow cone was removed, in the case where the 15 times of dropping motion is not performed in the flow value measurement method described in "JIS R 5201 Physical Testing Methods for Cement".

7. The cementitious composition according to claim 1 or 3, wherein the flow value of the cementitious composition is within the range of 110 to 190 mm when 90 seconds have elapsed since the flow cone was removed, in the case where the 15 times of dropping motion is not performed in the flow value measurement method described in "JIS R 5201 Physical Testing Methods for Cement".

8. The cementitious composition has a tensile strength of 4.5 to 15.0 N / mm2 as measured in accordance with the Japan Concrete Institute standard "JCI-S-002-2003" (Test method for load-displacement curve of fiber concrete using notched beams). ２ The cementitious composition according to any one of claims 1 to 3, wherein the composition is in the range of

9. A method for producing the cementitious composition according to claim 1 or 2, A fiber composition determination step of determining the aspect ratio of the fibers to be used and the content of the fibers to be used in the cementitious composition so that the value calculated by the following formula (2) is 40 to 300; A composition preparation step of mixing each raw material with the fiber aspect ratio and fiber content determined in the fiber composition determination step to obtain the cementitious composition; A method for producing a cementitious composition comprising: Aspect ratio of the fiber to be used × Content (volume%) of the fiber to be used in the cementitious composition (2)

10. a curing step of curing the pre-hardened cementitious composition obtained in the composition preparation step in an atmosphere of 50°C or higher to obtain a hardened product of the cementitious composition; A method for producing the cementitious composition of claim 9, comprising:

11. A method for producing the cementitious composition according to claim 3, A fiber composition determination step of determining the aspect ratio of the fibers to be used and the content of the fibers to be used in the cementitious composition so that the value calculated by the following formula (3) is 40 to 300; A composition preparation step of mixing each raw material with the aspect ratio of the fiber and the content of the fiber determined in the fiber composition determination step to obtain the cementitious composition; a curing step of curing the pre-hardened cementitious composition obtained in the composition preparation step in an atmosphere of less than 50°C to obtain a hardened body of the cementitious composition; A method for producing a cementitious composition comprising: Aspect ratio of the fiber to be used × Content (volume%) of the fiber to be used in the cementitious composition (3)

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