Cement composition and method for producing the same

Abstract

To provide a cement composition having excellent flowability (specifically, a slump flow value is 350 to 750 mm), in which material separation is reduced despite the fact that unit cement content is not excessively large (specifically, 200 to 500 kg / m3).SOLUTION: A cement composition comprises a cement, water, an aggregate, a cement dispersant, and fibers, wherein: a ratio of the fibers in the cement composition is 0.003 to 0.6% by volume; a unit volume of cement is 200-500 kg / m3; and a slump flow value of the cement composition, measured according to "JIS A 1150:2020 (Slump flow test method for concrete)", is 350 to 750 mm. Preferably, the fiber has a diameter of 0.010 to 0.3 mm, a length of 1 to 10 mm, and an aspect ratio (fiber length / fiber diameter) of 2 to 700.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] When pouring concrete into a formwork, it is common to perform a vibration compaction operation using a vibrator or the like in order to ensure that the concrete is sufficiently filled into the formwork. On the other hand, concrete with high fluidity can reduce or eliminate the need for vibration compaction work, thereby improving productivity in concrete construction. However, there is a problem with highly fluid concrete in that it is prone to material segregation. Patent Document 1 describes a self-compacting concrete composition that contains a high-performance water-reducing agent and pulp fiber and has a slump flow value (specified in JIS-A 1101) of 40 cm or more, has excellent resistance to material separation, has self-compacting properties, and has little delay in effectiveness, even when the slump flow value is 40 cm or more. Furthermore, as an example of highly fluid concrete with a reduced unit cement amount, Patent Document 2 describes highly fluid concrete containing cement, water, aggregate, a thickener, and a powdered high-performance water-reducing agent, wherein the thickener contains a water-soluble cellulose ether, an antifoaming agent, and gums, and the highly fluid concrete has a water-cement ratio of 46.1% or more and 65% or less, and a slump flow of 35 cm or more and 75 cm or less. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-115999 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-184330 Summary of the Invention [Problem to be solved by the invention]

[0004] As a method for preventing material separation of a highly fluid cement composition (mortar or concrete), a method for increasing the viscosity of the cement composition to ensure an appropriate viscosity is known. Increasing the unit cement content of a cement composition to improve its viscosity increases the temperature rise of the cement composition due to the hydration reaction of the cement, which increases the likelihood of thermal cracking and increases the autogenous shrinkage of the cement composition. The object of the present invention is to provide a concrete mixture having excellent fluidity (specifically, a slump flow value of 350 to 750 mm) and not having an excessively large unit cement amount (specifically, 200 to 500 kg / m 3 ) and yet, to provide a cement composition in which material separation is suppressed. [Means for solving the problem]

[0005] As a result of intensive research into solving the above problems, the present inventors have found a cement composition containing cement, water, aggregate, a cement dispersant, and fibers, wherein the ratio of fibers in the cement composition is 0.003 to 0.6% by volume, and the unit amount of cement is 200 to 500 kg / m 3 The present inventors have found that the above object can be achieved by a cement composition having a slump flow value of 350 to 750 mm, and have completed the present invention. That is, the present invention provides the following [1] to [8]. [1] A cement composition comprising cement, water, aggregate, a cement dispersant, and fibers, wherein the ratio of the fibers in the cement composition is 0.003 to 0.6% by volume, and the unit amount of the cement is 200 to 500 kg / m 3 and the slump flow value of the cement composition measured in accordance with "JIS A 1150:2020 (Concrete slump flow test method)" is 350 to 750 mm. [2] The cement composition according to [1], wherein the fibers have a diameter of 0.010 to 0.3 mm, a length of 1 to 10 mm, and an aspect ratio (fiber length / fiber diameter) of 2 to 700. [3] The cement composition according to [1] or [2], wherein the fibers are synthetic fibers. [4] The aggregate is fine aggregate and coarse aggregate, and the cement composition 1m 3 The amount of coarse aggregate per 0.38 m 3 The cement composition according to any one of the above [1] to [3], which is:

[0006] [5] In accordance with "JSCE-F 511-2012 (Draft method for filling test of high flow concrete)", the filling height measured using the flow obstacle R2 described in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]" is 300 mm or more, and the above cement composition 1 m 3 The amount of coarse aggregate per 3 The cement composition according to [4] above. [6] In accordance with "JSCE-F 511-2012 (Draft method for filling test of high flow concrete)", the filling height measured without using flow obstacles is 300 mm or more, and the above cement composition 1 m 3 The amount of coarse aggregate per unit is 0.30 to 0.38 m 3 The cement composition according to [4] above. [7] In accordance with "JSCE-F 511-2012 (Draft method for filling test of high flow concrete)", the filling height measured using the flow obstacle R1 described in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]" is 300 mm or more, and the above cement composition 1 m 3 The amount of coarse aggregate per 3 The cement composition according to [4] above. [8] A method for producing a cement composition according to any one of [1] to [7] above, comprising: a first mixing step of mixing the cement and the aggregate to obtain a first mixture; and a second mixing step of mixing the first mixture with the water, the cement dispersant, and the fibers to obtain a cement composition. [Effects of the Invention]

[0007] The cement composition of the present invention has excellent fluidity (specifically, a slump flow value of 350 to 750 mm) and does not have an excessively large unit cement amount (specifically, 200 to 500 kg / m 3 ), material separation was suppressed. DETAILED DESCRIPTION OF THE INVENTION

[0008] The cement composition of the present invention is a cement composition containing cement, water, aggregate, a cement dispersant, and fibers, wherein the ratio of fibers in the cement composition is 0.003 to 0.6% by volume, and the unit amount of the cement is 200 to 500 kg / m 3 The slump flow value of the cement composition measured in accordance with "JIS A 1150:2020 (Concrete slump flow test method)" is 350 to 750 mm.

[0009] Examples of cement 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, as well as blended cements such as blast-furnace cement and fly ash cement, and ecocement. These may be used alone or in combination of two or more. The unit amount of cement contained in the cement composition (1 m of cement composition) 3 From the viewpoint of improving the strength development of the cement composition, the mixing amount per 3 or more, preferably 230 kg / m 3 More preferably, 300 kg / m 3 More preferably, 380 kg / m3 More preferably, 450 kg / m 3 The above unit amount is 500 kg / m from the viewpoint of suppressing the increase in the temperature rise of the cement composition due to the hydration reaction of cement, thereby reducing the possibility of thermal cracking and reducing the autogenous shrinkage of the cement composition. 3 or less, preferably 490 kg / m 3 Less than or equal to 450 kg / m 3 or less, more preferably 380 kg / m 3 Particularly preferably 300 kg / m or less 3 The following is the result.

[0010] The water is not particularly limited, and examples thereof include tap water and recycled water as specified in "JIS A 5308:2019 (Ready-mixed concrete)". The amount of water to be blended is not particularly limited, and may be a general blending amount in cement compositions such as mortar and concrete, and may be adjusted appropriately depending on the desired quality. For example, the water-cement ratio of the cement composition (the mass ratio of water to cement (water / cement) contained in the cement composition, expressed as a percentage (%)) is preferably 30 to 70%, more preferably 35 to 65%, and particularly preferably 40 to 60%. If the ratio is 30% or more, the softness required for application of the cement composition before hardening can be ensured. If the ratio is 70% or less, the strength development of the cement composition is further improved.

[0011] 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. Examples of fine aggregate include river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, slag fine aggregate, lightweight fine aggregate, etc. These may be used alone or in combination of two or more. The unit amount of fine aggregate is not particularly limited, and may be a general unit amount in cement compositions such as mortar and concrete. For example, in the case of mortar, the unit amount of fine aggregate is preferably 400 to 1,800 kg / m 3, more preferably 500 to 1,600 kg / m 3 In the case of concrete, the unit amount of fine aggregate is preferably 600 to 1,300 kg / m 3 , more preferably 700 to 1,200 kg / m 3 is. Furthermore, when the cement composition contains coarse aggregate, the fine aggregate ratio is preferably 10 to 70%, more preferably 20 to 65%, even more preferably 30 to 60%, and particularly preferably 40 to 58%. If the fine aggregate ratio is within the above range, the workability and ease of molding of the cement composition are improved.

[0012] Examples of coarse aggregate include river gravel, mountain gravel, land gravel, sea gravel, crushed stone, slag coarse aggregate, lightweight coarse aggregate, etc. These may be used alone or in combination of two or more. The unit amount of coarse aggregate is not particularly limited, and may be a general unit amount in cement compositions such as concrete, but is preferably 500 to 1,200 kg / m 3 , more preferably 600 to 1,100 kg / m 3 be. In addition, in terms of the filling property (gap passing property) of high-flow concrete, in order to satisfy the self-filling property Rank 1 specified in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]", the cement composition 1m 3 The amount of coarse aggregate per unit area is preferably 0.25 to 0.33 m 3 , more preferably 0.28 to 0.30 m 3 is. In addition, in terms of the filling property of high-flow concrete, in order to satisfy the self-filling property Rank 2 specified in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]", the cement composition 1 m 3 The amount of coarse aggregate per unit area is preferably 0.28 to 0.35 m 3 , more preferably 0.30 to 0.33 m 3 is. Furthermore, in terms of the filling property of high-flow concrete, in order to satisfy the self-filling property rank 3 specified in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]", the cement composition 1 m 3 The amount of coarse aggregate per unit area is preferably 0.30 to 0.38 m 3 , more preferably 0.33 to 0.35 m 3 is.

[0013] From the viewpoint of improving the strength development of the cement composition, the dimensions of the fibers are preferably a diameter of 0.010 to 0.3 mm and a length of 1 to 10 mm, more preferably a diameter of 0.011 to 0.25 mm and a length of 2.5 to 8 mm, even more preferably a diameter of 0.012 to 0.2 mm and a length of 3 to 7 mm, and particularly preferably a diameter of 0.012 to 0.2 mm and a length of 3 to 6 mm. Fibers having a diameter of less than 0.010 mm are difficult to manufacture, and if the diameter is 0.3 mm or less, material separation of the cement composition can be further suppressed. If the length is 1 mm or more, material separation of the cement composition can be further suppressed. If the length exceeds 10 mm, the cement composition may not have the desired fluidity (high fluidity such that the slump flow value is 350 mm or more), and the amount of cement dispersant used may become excessive.

[0014] The aspect ratio of the fibers (fiber length / fiber diameter) is preferably 2 to 700, more preferably 10 to 600, even more preferably 15 to 400, and particularly preferably 20 to 300. When the aspect ratio is 2 or more, material separation of the cement composition can be further suppressed. When the aspect ratio exceeds 700 mm, the amount of cement dispersant required to ensure the desired fluidity of the cement composition (high fluidity such that the slump flow value is 350 mm or more) may become excessively large.

[0015] Examples of the fibers include synthetic fibers, metal fibers, carbon fibers, and glass fibers, etc. Among these, synthetic fibers are preferred from the viewpoint of further suppressing material separation of the cement composition. Examples of synthetic fibers include aramid fibers, vinylon fibers, polypropylene fibers, polyethylene fibers, polyamide fibers, and PBO fibers, etc. Among these, vinylon fibers, polypropylene fibers, and aramid fibers are preferred from the viewpoint of further suppressing material separation of the cement composition. Examples of metal fibers include steel fibers, stainless steel fibers, amorphous fibers, etc. Among these, steel fibers are preferred from the viewpoints of strength development, cost, and ease of availability. Examples of carbon fibers include PAN-based carbon fibers and pitch-based carbon fibers. Examples of glass fibers include alkali-resistant glass fibers. These fibers may be used alone or in combination of two or more.

[0016] From the viewpoint of suppressing material separation of the cement composition, the proportion of fibers in the cement composition is 0.003 to 0.6 volume %, preferably 0.004 to 0.55 volume %, more preferably 0.005 to 0.4 volume %, even more preferably 0.006 to 0.35 volume %, and particularly preferably 0.007 to 0.3 volume %.

[0017] Examples of cement dispersants include 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 and high-performance air-entraining water reducing agents are preferred from the viewpoint of further improving the fluidity of the cement composition. These may be used alone or in combination of two or more. The amount of cement dispersant to be added (the total amount when multiple types are used) per 100 parts by mass of cement is not particularly limited, but in the case of a liquid, it is preferably 0.05 to 3.0 parts by mass, more preferably 0.10 to 2.5 parts by mass, even more preferably 0.50 to 2.0 parts by mass, and particularly preferably 0.80 to 1.8 parts by mass, and in the case of a solid such as a powder, it is preferably 0.005 to 1.5 parts by mass, more preferably 0.010 to 1.2 parts by mass, even more preferably 0.050 to 1.0 part by mass, and particularly preferably 0.08 to 0.8 parts by mass.

[0018] The cement composition preferably contains an air entraining agent, which improves the workability and freeze-thaw resistance of the cement composition by entraining fine air bubbles. The amount of AE agent (usually liquid) to be added per 100 parts by mass of cement is not particularly limited and can be determined appropriately depending on the type of material, the composition, the application, etc., but is preferably 0.0002 to 1.0 part by mass, more preferably 0.002 to 0.8 part by mass, even more preferably 0.01 to 0.6 part by mass, and particularly preferably 0.05 to 0.4 part by mass. The air content of the cement composition is preferably 3 to 7 volume %, more preferably 3.5 to 6.5 volume %, and particularly preferably 4 to 6 volume %. If the air content is 3 volume % or more, the freeze-thaw resistance of the cement composition can be further improved. By introducing fine air bubbles into concrete in an amount such that the air content is 7 volume % or less, the workability of the cement composition can be further improved with a small unit amount of water due to a ball bearing-like effect.

[0019] Furthermore, the cement composition of the present invention may not contain a thickener from the viewpoint of achieving both cost reduction for materials and durability of the cement composition. For example, when attempting to improve the viscosity of the cement composition by adding a thickener, the unit water content required to increase the fluidity of the cement composition may increase significantly depending on the type and quality of the aggregate contained in the cement composition (for example, when the unit water content of concrete is 175 kg / m). 3In such cases, from the viewpoint of reducing costs while suppressing a decrease in durability due to a significant increase in the unit water content, it is preferable that the cement composition does not contain a thickener. Furthermore, depending on the type and quality of the aggregate, a thickener may be included from the viewpoint of appropriately suppressing material separation. Whether or not to include a thickener can be determined appropriately in consideration of the mix design of the cement composition.

[0020] The slump flow value of the cement composition measured in accordance with "JIS A 1150:2020 (Test method for slump flow of concrete)" is 350 to 750 mm (preferably 400 to 700 mm, more preferably 500 to 600 mm). The slump flow value may be adjusted appropriately depending on the application of the cement composition (the reinforcement state of the target structure, the required workability and fillability).

[0021] The cement composition of the present invention satisfies, for example, any one of the following conditions (i) to (iii). (i) In accordance with "JSCE-F 511-2012 (Draft method for filling test of high flow concrete)", the filling height measured using the flow obstacle R1 described in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]" as a flow obstacle is 300 mm or more, and 3 The amount of coarse aggregate per 3 (Meets the self-compacting rank 1 specified in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]") (ii) In accordance with "JSCE-F 511-2012 (Draft method for filling test of high flow concrete)", the filling height measured using the flow obstacle R2 described in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]" as a flow obstacle is 300 mm or more, and the above cement composition 1 m 3 The amount of coarse aggregate per 3(Meets the self-compacting grade 2 specified in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]") (iii) In accordance with "JSCE-F 511-2012 (Draft method for filling test of high flow concrete)", the filling height measured without using flow obstacles is 300 mm or more, and 3 The amount of coarse aggregate per unit is 0.30 to 0.38 m 3 (Meets the self-compacting grade 3 specified in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]")

[0022] An example of a method for producing a cement composition of the present invention includes a first mixing step of mixing cement and aggregate to obtain a first mixture, and a second mixing step of mixing the first mixture with water, a cement dispersant, and fibers to obtain a cement composition. In the first mixing step, the materials may be simultaneously or separately charged into the mixer and mixed. The order in which the materials are charged does not matter. In the second mixing step, the water, cement dispersant, and fibers may be simultaneously charged into the mixer and mixed, or may be charged separately into the mixer and mixed. The order in which the water, cement dispersant, and fibers are charged does not matter, but from the viewpoint of ensuring a stable effect of the dispersant, it is preferable to charge the water and cement dispersant as a premixed mixture. [Example]

[0023] 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: Ordinary Portland cement manufactured by Taiheiyo Cement Corporation, density: 3.16 g / cm 3 (2) Fine aggregate; mountain sand, density: 2.58g / cm 3 (3) Coarse aggregate: crushed stone 2005, density: 2.65 g / cm 3 (4) Fiber A: Kuraray Co., Ltd., Vinylon fiber, diameter: 0.2 mm, length: 6 mm, aspect ratio: 30 (5) Fiber B: Kuraray Co., Ltd., Vinylon fiber, diameter: 0.045 mm, length: 4 mm, aspect ratio: 90 (6) Fiber C: manufactured by Barchip, polypropylene fiber, diameter: 0.043 mm, length: 6 mm, aspect ratio: 140 (7) Fiber D: Teijin Co., Ltd., aramid fiber, diameter: 0.012 mm, length: 3 mm, aspect ratio: 250 (8) Fiber E: Teijin Co., Ltd., aramid fiber, diameter: 0.012 mm, length: 6 mm, aspect ratio: 500 (9) Cement dispersant; high-performance water reducer, manufactured by Pozzolith Solutions, product name "Mastergranium SP8SV" (10) Air content adjuster; manufactured by Pozzolith Solutions, trade name "Master Air 303A" (11) Water; tap water

[0024] [Examples 1 to 14] Coarse aggregate, fine aggregate in an amount that was half of the total amount of fine aggregate mixed, cement, and the remaining amount of fine aggregate were charged in that order into a forced twin-shaft mixer, and then dry-mixed for 30 seconds. Next, water and an air content adjuster that had been mixed with a high-performance water-reducing agent were added and mixed for 60 seconds, after which any mixture adhering to the inner wall of the mixer was scraped off, and the fibers were added and mixed for another 60 seconds.The mixture was then left to stand for 5 minutes and mixed for another 30 seconds to produce concrete (cement composition). The amounts of each material and the types of fibers are shown in Table 1. The physical properties of the resulting concrete, such as the slump flow value, were measured according to the following methods. The separation of materials immediately after the concrete mixing was visually evaluated on a three-point scale: "Excellent: Excellent," "Good: Good," and "Poor: Material separation occurred."

[0025] [Slump flow value] The slump flow value of concrete was measured in accordance with JIS A 1150:2020 (Concrete slump flow test method). The time to reach 50 cm and the time to stop flow were also measured. [Air content] The air content of the concrete was measured in accordance with "JIS A 1128:2019 (Test method for air content of fresh concrete by pressure - Air chamber pressure method)". [Temperature] The temperature of the concrete was measured in accordance with "JIS A 1156:2006 (Method for measuring temperature of fresh concrete)". [Filling height] The filling height of the concrete was measured in accordance with "JSCE-F 511-2012 (Draft filling test method for high-flow concrete)" (i) without using a flow obstacle, (ii) using the flow obstacle R1 described in "2017 Standard Specifications for Concrete [Construction section: Special concrete]", or (iii) using the flow obstacle R2 described in "2017 Standard Specifications for Concrete [Construction section: Special concrete]". In Table 2, the word "none" in the flow obstruction type item indicates that the concrete filling height was measured using the above method (i), the word "R1" indicates that the concrete filling height was measured using the above method (ii), and the word "R2" indicates that the concrete filling height was measured using the above method (iii). [Compressive strength] The compressive strength of concrete at 7 days and 28 days was measured in accordance with JIS A 1108:2018 (Test method for compressive strength of concrete).

[0026] [Comparative Examples 1 to 4] Concrete was produced in the same manner as in Example 1, except that no fibers were used. The mortar flow value of the obtained concrete was measured and the separation of materials was evaluated in the same manner as in Example 1. [Comparative Examples 5 to 6] Concrete was produced in the same manner as in Example 1. The mortar flow value of the obtained concrete was measured and the separation of materials was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0027] [Table 1]

[0028] [Table 2]

[0029] It can be seen from Table 2 that the evaluation of material separation in Examples 1 to 14 was "A" or "Good", while the evaluation of material separation in Comparative Examples 1 to 6 was "Poor". In particular, when Examples 1 and 2 are compared with Comparative Example 1 (which does not use fibers and has the same formulation as Examples 1 and 2 except for a different amount of cement dispersant), it is found that Examples 1 and 2 are evaluated as "◎" for material separation, while Comparative Example 1 is evaluated as "×". A similar tendency is also seen in comparisons of Examples 3 to 5 with Comparative Example 2, Examples 6 to 8 with Comparative Example 3, and Examples 9 and 10 with Comparative Example 4. Furthermore, when comparing Example 5 with Comparative Example 5 (which has the same composition as Example 5 except that the fiber content is 0.0010% by volume), it can be seen that the material separation evaluation of Example 5 is "◎", while the material separation evaluation of Comparative Example 5 is "×". Furthermore, when comparing Example 9 with Comparative Example 6 (which has the same composition as Example 9 except that the fiber content is 0.800% by volume and the amount of cement dispersant is 1.20 parts by mass), it can be seen that the material separation evaluation of Example 9 is "◎", while the material separation evaluation of Comparative Example 6 is "×".

Claims

1. A cement composition comprising cement, water, aggregate, a cement dispersant, and fibers, The proportion of the fiber in the cement composition is 0.003 to 0.6% by volume, The unit amount of the cement is 300 to 500 kg / m ３ and The slump flow value of the cement composition measured in accordance with "JIS A 1150:2020 (Concrete Slump Flow Test Method)" is 500 to 750 mm, The water-cement ratio is 30 to 60%, The aggregate is a fine aggregate and a coarse aggregate, The unit amount of the fine aggregate is 700 to 1,200 kg / m 3 , The fine aggregate ratio is 40 to 65%. The cement dispersant is liquid, and the amount of the cement dispersant mixed with 100 parts by mass of the cement is 1.30 to 2.0 parts by mass; A cement composition characterized in that the filling height measured in accordance with "JSCE-F 511-2012 (Draft method for filling test of high-fluidity concrete)" using flow obstacle R2 described in "Standard Specifications for Concrete [Construction section: Special concrete] established in 2017" as a flow obstacle is 300 mm or more, and the amount of the coarse aggregate per 1 m3 of the cement composition is 0.28 to 0.35 m3.

2. A cement composition comprising cement, water, aggregate, a cement dispersant, and fibers, The proportion of the fiber in the cement composition is 0.003 to 0.6% by volume, The unit amount of the cement is 300 to 500 kg / m ３ and The slump flow value of the cement composition measured in accordance with "JIS A 1150:2020 (Concrete Slump Flow Test Method)" is 500 to 750 mm, The water-cement ratio is 30 to 60%, The aggregate is a fine aggregate and a coarse aggregate, The unit amount of the fine aggregate is 700 to 1,200 kg / m 3 , The fine aggregate ratio is 40 to 65%. The cement dispersant is liquid, and the amount of the cement dispersant mixed with 100 parts by mass of the cement is 1.30 to 2.0 parts by mass; A cement composition characterized in that the filling height measured without using flow obstacles in accordance with "JSCE-F 511-2012 (Draft method for filling test of high-fluidity concrete)" is 300 mm or more, and the amount of the coarse aggregate per 1 m 3 of the cement composition is 0.30 to 0.38 m 3 .

3. A cement composition comprising cement, water, aggregate, a cement dispersant, and fibers, The proportion of the fiber in the cement composition is 0.003 to 0.6% by volume, The unit amount of the cement is 300 to 500 kg / m ３ and The slump flow value of the cement composition measured in accordance with "JIS A 1150:2020 (Concrete Slump Flow Test Method)" is 500 to 750 mm, The water-cement ratio is 30 to 60%, The aggregate is a fine aggregate and a coarse aggregate, The unit amount of the fine aggregate is 700 to 1,200 kg / m 3 , The fine aggregate ratio is 40 to 65%. The cement dispersant is liquid, and the amount of the cement dispersant mixed with 100 parts by mass of the cement is 1.30 to 2.0 parts by mass; A cement composition characterized in that the filling height measured using flow obstacle R1 described in the "2017 Standard Specifications for Concrete [Construction Section: Special Concrete]" in accordance with "JSCE-F 511-2012 (Draft Filling Test Method for High-Flow Concrete)" is 300 mm or more, and the amount of the coarse aggregate per 1 m3 of the cement composition is 0.25 to 0.33 m3.

4. The cement composition according to any one of claims 1 to 3, wherein the fibers have a diameter of 0.010 to 0.3 mm, a length of 1 to 10 mm, and an aspect ratio (fiber length / fiber diameter) of 2 to 700.

5. The cement composition according to any one of claims 1 to 4, wherein the fibers are synthetic fibers.

6. A method for producing the cement composition according to any one of claims 1 to 5, a first mixing step of mixing the cement and the aggregate to obtain a first mixture; a second mixing step of mixing the first mixture with the water, the cement dispersant, and the fibers to obtain a cement composition; A method for producing a cement composition comprising:

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