Cement composition manufacturing method, concrete composition and manufacturing method thereof, and hardened concrete

Abstract

To provide a cement composition capable of reducing CO2 emissions and capable of obtaining a concrete composition having high resistance to thermal cracking.SOLUTION: A cement composition comprises a binder containing cement, ground granulated blast furnace slag, and anhydrous gypsum. The cement has: a C3S content of more than 50.0 mass% and 70.0 mass% or less; and a C2S content of 5.0 mass% to 15.0 mass%. A content of the ground granulated blast furnace slag in the binder is more than 70 mass% and 89 mass% or less.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present disclosure relates to a cement composition and a method for producing the same, a concrete composition and a method for producing the same, and a hardened concrete body. [Background technology]

[0002] In recent years, with the increasing demand for measures to combat global warming, there has been a demand for reducing CO2 emissions during concrete production. One possible method for reducing CO2 emissions is to replace cement, which generates a large amount of CO2 during production, with other binder components. Patent Document 1 proposes reducing the cement content of concrete materials to 20% by weight or less by setting the total amount of fly ash and ground granulated blast furnace slag within a specified range.

[0003] When blended cement with a high content of cement admixtures such as fly ash and ground granulated blast furnace slag is used as a concrete material, the cement hydration reaction and concrete shrinkage continue for a long period of time, so cracks may occur in the concrete even after a certain age.Patent Document 2 proposes a method for evaluating crack resistance by determining the minimum value of the thermal cracking index through temperature stress analysis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-269786 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-9384 Summary of the Invention [Problem to be solved by the invention]

[0005] Mass concrete applications use large amounts of concrete composition, which has a significant impact on CO2 emissions. Therefore, using a concrete composition with a reduced cement content for mass concrete can significantly reduce CO2 emissions. However, because mass concrete is constructed in thick layers, it is prone to cracking due to the temperature difference between the surface and interior of the concrete (cracking due to internal restraint), and cracking due to restraint at the joints between the concrete and the ground and the existing concrete when the concrete temperature drops and shrinks (cracking due to external restraint). For this reason, excellent resistance to cracks that can occur due to temperature differences is required.

[0006] The present disclosure provides a concrete composition that can reduce CO2 emissions and has high thermal crack resistance, and a method for producing the same. It also provides a cement composition that can obtain such a concrete composition, and a method for producing the same. It also provides a hardened concrete body that can reduce CO2 emissions and has suppressed cracking. [Means for solving the problem]

[0007] One aspect of the present disclosure provides [1] to

[14] .

[0008] [1] A cement composition comprising cement, ground granulated blast furnace slag, and a binder containing anhydrous gypsum, The cement has a C3S content of more than 50.0 mass% and not more than 70.0 mass%, and a C2S content of 5.0 to 15.0 mass%, A cement composition, wherein the content of the ground granulated blast furnace slag in the binder is more than 70 mass % and not more than 89 mass %. [2] The cement composition according to [1], wherein the ground granulated blast furnace slag contains gypsum dihydrate. [3] The cement composition according to [2], wherein the total amount of the anhydrous gypsum is 55 to 100 parts by mass per 100 parts by mass of the total amount of the anhydrous gypsum contained in the binder and the gypsum dihydrate. [4] The Blaine specific surface area of ​​the cement is 3500 cm 2 / g or more of the cement composition according to any one of [1] to [3]. [5] The cement composition according to any one of [1] to [4], wherein the cement is ordinary Portland cement or high-early-strength Portland cement. [6] The cement composition according to any one of [1] to [5], wherein the content of the hardening accelerator in terms of solid content is less than 0.9 mass % based on the binder. [7] A concrete composition comprising the cement composition according to any one of [1] to [6] above, water, fine aggregate, coarse aggregate, and a chemical admixture, and having a water-binder ratio of 0.25 to 0.6. [8] The unit amount of water is 150-190 kg / m 3 , the unit amount of the binder is 250 to 800 kg / m 3 , fine aggregate unit weight 650~1050kg / m 3 , and the unit amount of coarse aggregate is 700 to 1100 kg / m 3 [7] The concrete composition according to [7]. [9] The concrete composition according to [7] or [8], wherein the initial setting time measured in accordance with "JIS A 1147:2019 Test method for setting time of concrete" is 8 hours or less under the condition that the water-binder ratio is 0.4 to 0.5.

[10] When the water-binder ratio is 0.4 to 0.5, the bleeding amount measured in accordance with "JIS A 1123:2022 Concrete Bleeding Test Method" is 0.4 cm 3 / cm 2 The concrete composition according to any one of [7] to [9] below.

[11] The structural strength correction value ( 28 S 91 ) is 5.0N / mm 2 The concrete composition according to any one of [7] to

[10] below.

[12] A hardened concrete body obtained by hardening the concrete composition according to any one of [7] to

[11] above.

[13] A method for producing a cement composition, comprising a step of mixing raw materials including cement having a C3S content of more than 50.0 mass% and not more than 70.0 mass% and a C2S content of 5.0 to 15.0 mass%, ground granulated blast furnace slag containing gypsum dihydrate, and anhydrous gypsum, to obtain a cement composition having a binder containing the ground granulated blast furnace slag in an amount of more than 70 mass% and not more than 89 mass%.

[14] A method for producing a concrete composition, comprising a step of mixing the cement composition according to any one of [1] to [6] above or the cement composition obtained by the production method according to

[13] above with raw materials containing water, fine aggregate, coarse aggregate, and a chemical admixture to obtain a concrete composition having a water-binder ratio of 0.25 to 0.6. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a concrete composition that can reduce CO2 emissions and has high thermal crack resistance, and a method for producing the same. It is also possible to provide a cement composition that can obtain such a concrete composition, and a method for producing the same. It is also possible to provide a hardened concrete body that can reduce CO2 emissions and has suppressed cracking. [Brief explanation of the drawings]

[0010] [Figure 1] Graphs (A) and (B) show the measured and estimated values ​​of autogenous shrinkage strain in Comparative Example 1 and Comparative Example 2. [Figure 2] Graphs (A) and (B) show the measured and estimated values ​​of autogenous shrinkage strain in Comparative Examples 3 and 4. [Figure 3] Graphs (A) and (B) show the measured and estimated values ​​of autogenous shrinkage strain in Comparative Examples 5 and 6. [Figure 4] Graphs (A) and (B) show the measured and estimated values ​​of autogenous shrinkage strain in Comparative Examples 7 and 8. [Figure 5] Graphs (A) and (B) show the measured and estimated values ​​of autogenous shrinkage strain in Comparative Examples 9 and 10. [Figure 6] Graphs (A) and (B) show the measured and estimated values ​​of autogenous shrinkage strain in Comparative Example 11 and Example 1. [Figure 7] Graphs (A) and (B) show the measured and estimated values ​​of autogenous shrinkage strain in Comparative Examples 12 and 13. [Figure 8] Graphs (A) and (B) show the measured and estimated values ​​of autogenous shrinkage strain in Examples 2 and 3. [Figure 9] Graphs (A) and (B) show the measured and estimated values ​​of autogenous shrinkage strain in Examples 4 and 5. [Figure 10] 10 is a graph showing the measured and estimated values ​​of autogenous shrinkage strain in Example 6. [Figure 11] 1 is a graph showing the relationship between CO2 reduction rate and minimum crack index. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are merely examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content. The symbol "to" used in a numerical range indicates a numerical range that includes the upper and lower limit values. For example, "X to Y" indicates a numerical range "greater than or equal to X and less than or equal to Y." Numerical ranges in which the upper and / or lower limits are replaced with numerical values ​​described in the examples are also included in the content of the present disclosure. Multiple exemplified components or materials may be used alone or in combination.

[0012] In the present specification, numerical ranges in which the upper or lower limit of one numerical range is replaced with the upper or lower limit of another numerical range are also included in the present disclosure. In the present specification, numerical ranges in which the upper or lower limit of a numerical range is replaced with a value shown in the examples are also included in the present disclosure.

[0013] [Cement composition and method for producing the same] A cement composition according to one embodiment includes cement, ground granulated blast furnace slag, and a binder containing anhydrous gypsum (CaSO4). A binder is a material that functions to bind and solidify aggregates in a concrete composition. The binder hardens upon reacting with water, and after hardening, it constitutes a part of the hardened cement body or hardened concrete body. Examples of anhydrous gypsum include natural anhydrous gypsum and hydrofluoric anhydrous gypsum. The binder may contain, for example, gypsum dihydrate (CaSO4·2H2O) and / or gypsum hemihydrate (CaSO4·1 / 2H2O). Examples of dihydrate gypsum include dehydrated gypsum dihydrate, gypsum phosphate dihydrate, gypsum hydrofluoride dihydrate, and natural gypsum dihydrate. Examples of hemihydrate gypsum include α-type hemihydrate and β-type hemihydrate.

[0014] <Cement> The cement may be any of the Portland cements specified in JIS R 5210:2009 "Portland Cement." The mineral composition of the cement is such that the C3S content in the cement is greater than 50.0 mass% and not more than 70.0 mass%, and the C2S content is 5.0 to 15.0 mass%. The lower limit of the C3S content may be 55.0 mass%, 60.0 mass%, or 63.0 mass%. This allows the unit amount of binder in the concrete composition to be reduced while still achieving sufficiently high thermal crack resistance, thereby further reducing CO2 emissions during the production of the concrete composition. The upper limit of the C3S content may be 68.0 mass%.

[0015] The lower limit of the C2S content in the cement may be 7.0% by mass or 8.0% by mass. The upper limit of the C2S content may be 12% by mass or 10% by mass. By including C2S in such a range, it is possible to further improve thermal crack resistance. The C3A content in the cement may be, for example, more than 6.0% by mass and less than 15% by mass, or more than 8.0% by mass and less than 12% by mass.

[0016] The mineral composition of cement in this specification is calculated using the Bogue formula. The Bogue formula is a widely used formula for calculating the content of major minerals in cement from the content of its chemical components. By using the Bogue formula shown below, the contents of C3S (tricalcium silicate (3CaO SiO2)), C2S (dicalcium silicate (2CaO SiO2)), C3A (tricalcium aluminate (3CaO Al2O3)), and C4AF (tetracalcium aluminate ferroferrate (4CaO Al2O3 Fe2O3)) in cement can be calculated. In the Bogue formula below, the chemical formulas represented by CaO (aluminum oxide), SiO2 (silicon dioxide), Al2O3 (aluminum oxide), Fe2O3 (iron oxide), and SO3 (sulfur trioxide) represent the content (mass%) of each chemical component in cement measured in accordance with JIS R 5202:2015 "Methods for chemical analysis of cement" or JIS R 5204:2019 "Methods for X-ray fluorescence analysis of cement." In addition, "%" in the Bogue formula below represents "mass%."

[0017] ·Bogue style C3S[%]=(4.07×CaO[%])-(7.60×SiO2[%])-(6.72×Al2O3[%])-(1.43×Fe2O3[%])-(2.85×SO3[%]) C2S[%]=(2.87×SiO2[%])-(0.754×C3S[%]) C3A[%]=(2.65×Al2O3[%])-(1.69×Fe2O3[%]) C4AF[%]=3.04×Fe2O3[%]

[0018] The cement is preferably high-early-strength Portland cement or ordinary Portland cement, among the cements specified in JIS R 5210:2009 "Portland cement." This allows the unit amount of binder in the concrete composition to be reduced while still achieving sufficiently high thermal crack resistance, thereby further reducing CO2 emissions during the production of the concrete composition.

[0019] Although high-early-strength Portland cement tends to have a greater increase in adiabatic temperature than other Portland cements, the cement composition of this embodiment contains a sufficiently high content of ground granulated blast furnace slag in the binder, which prevents a significant increase in adiabatic temperature and ensures sufficiently high thermal crack resistance. Furthermore, in addition to thermal crack resistance, the inclusion of high-early-strength Portland cement as a binder in the cement composition improves the strength development of the concrete composition and shortens the setting time. It also reduces the amount of bleeding. Thus, the inclusion of high-early-strength Portland cement as a binder in the cement composition achieves high levels of both thermal crack resistance and fresh properties, thereby reducing CO2 emissions and sufficiently improving the workability and reliability of the concrete composition. Such a concrete composition is particularly useful for mass concrete.

[0020] When a cement composition contains ordinary Portland cement as the cement, it can sufficiently minimize the change in the fluidity of the concrete composition over time. This allows the concrete composition to be poured with high uniformity even in large-scale pouring. Furthermore, the inclusion of ordinary Portland cement can reduce the production costs of the cement composition and the concrete composition.

[0021] The cement may contain cement clinker and gypsum. Examples of gypsum include gypsum dihydrate, gypsum hemihydrate, and anhydrous gypsum. The content of SO3 in the cement may be, for example, 1.5 to 4.0 mass% or 2.0 to 3.5 mass%. In addition to the above-mentioned gypsum, examples of SO3 in the cement include alkali sulfates derived from cement clinker.

[0022] The Blaine specific surface area of ​​cement is, for example, 3500 cm 2 / g or more, or 4000 cm 2 / g or more. By increasing the Blaine specific surface area of ​​cement, the strength development of the concrete composition can be improved and the setting time can be shortened. In addition, the amount of bleeding can be reduced. The Blaine specific surface area of ​​cement can be, for example, 10,000 cm 2 / g or less, 8000cm 2 / g or less, or 5000cm 2 / g or less. By reducing the Blaine specific surface area of ​​cement, it is possible to reduce production costs and further reduce CO2 emissions during cement production. The Blaine specific surface area in this specification is measured in accordance with JIS R 5201:2015 "Physical Testing Methods for Cement."

[0023] The cement content in the binder may be 25% by mass or less, 20% by mass or less, or 19% by mass or less. This allows for sufficient reduction in CO2 emissions during production of the cement composition and concrete composition. The cement content in the binder may be 5% by mass or more, 10% by mass or more, or 15% by mass or more. This allows for sufficient increase in the compressive strength of the hardened cement body and hardened concrete body.

[0024] <Ground granulated blast furnace slag> The ground granulated blast furnace slag may be, for example, commercially available, or slag equivalent to the ground granulated blast furnace slag may be prepared. The ground granulated blast furnace slag preferably contains gypsum, and more preferably contains gypsum dihydrate. In this specification, the gypsum dihydrate contained in the ground granulated blast furnace slag is referred to as "gypsum dihydrate BDS."

[0025] The inclusion of gypsum dihydrate BDS in the ground granulated blast furnace slag facilitates the development of strength in the concrete composition, enabling the compressive strength of the hardened concrete (structure) to be sufficiently high. This allows the structural strength correction value (S value) measured in accordance with "JASS 5 T-606:2022 Method for Estimating Structural Concrete Strength Using Simplified Adiabatic Cured Specimens" to be sufficiently reduced. Furthermore, the amount of bleeding in the concrete composition can be reduced. The cement composition of this embodiment has the highest content of ground granulated blast furnace slag. Therefore, the inclusion of gypsum dihydrate in the ground granulated blast furnace slag allows the proportion of gypsum dihydrate in the entire cement composition to be sufficiently increased. This makes the above-mentioned effects even more pronounced.

[0026] The content of gypsum dihydrate BDS may be 0.5% by mass or more, 1.0% by mass or more, or 1.4% by mass or more, based on the total amount of binder. This ensures that a sufficient amount of gypsum dihydrate is contained in the cement composition, further reducing CO2 emissions. The content of gypsum dihydrate BDS may be 3.0% by mass or less, or 2.0% by mass or less, based on the total amount of binder.

[0027] The ground granulated blast furnace slag may contain anhydrous gypsum BAS together with dihydrate gypsum BDS. In this specification, "anhydrous gypsum BAS" refers to anhydrous gypsum contained in the ground granulated blast furnace slag. Anhydrous gypsum BAS has the effect of further increasing the thermal crack resistance of the hardened concrete body. By including anhydrous gypsum BAS in the ground granulated blast furnace slag, the proportion of anhydrous gypsum in the entire cement composition can be sufficiently increased. Therefore, the above-mentioned effects can be made even more remarkable.

[0028] The content of anhydrous gypsum BAS may be 0.5% by mass or more, 1.0% by mass or more, or 1.4% by mass or more, based on the total amount of binder. This ensures that a sufficient amount of anhydrous gypsum is contained in the cement composition, thereby further reducing CO2 emissions. The content of anhydrous gypsum BAS may be 3.0% by mass or less, or 2.0% by mass or less, based on the total amount of binder.

[0029] The gypsum content in the ground granulated blast furnace slag, calculated as SO3, may be 0.5% by mass or more, 1.0% by mass or more, or 1.5% by mass or more, based on the total amount of binder. This ensures that a sufficient amount of gypsum is contained in the cement composition, thereby further reducing CO2 emissions while sufficiently increasing thermal crack resistance. The gypsum content in the ground granulated blast furnace slag, calculated as SO3, may be 3.0% by mass or less, or 2.0% by mass or less, based on the total amount of binder.

[0030] The content of Al2O3 (aluminum oxide) in the ground granulated blast furnace slag may be, for example, 14.5% by mass or less, 14.0% by mass or less, 13.5% by mass or less, or 13.0% by mass or less. This sufficiently prevents a decrease in the long-term strength development when the concrete composition is hardened. The content of Al2O3 in the ground granulated blast furnace slag may be, for example, 8.0% by mass or more, 10.0% by mass or more, or 12.0% by mass or more. This allows the latent hydraulic properties of the ground granulated blast furnace slag to be more fully exhibited.

[0031] The SiO2 (silicon dioxide) content in the ground granulated blast furnace slag may be, for example, 30.0 mass% or more, 31.0 mass% or more, or 32.0 mass% or more. This can further suppress the deterioration of initial and long-term strength development. The SiO2 content in the ground granulated blast furnace slag may be, for example, 40.0 mass% or less, 38.0 mass% or less, 36.0 mass% or less, or 35.0 mass% or less. This can further suppress the deterioration of initial strength development.

[0032] The CaO (calcium oxide) content in the ground granulated blast furnace slag may be, for example, 38.0 mass% or more, 40.0 mass% or more, or 42.0 mass% or more. This can further improve the initial strength development. The CaO content in the ground granulated blast furnace slag may be, for example, 50.0 mass% or less, 48.0 mass% or less, or 46.0 mass% or less. This can further suppress the decrease in long-term strength development.

[0033] The content of MgO (magnesium oxide) in the ground granulated blast furnace slag may be, for example, 3.0% by mass or more, 4.0% by mass or more, or 4.5% by mass or more. This can further suppress the decrease in initial and long-term strength development when the concrete composition is hardened. The content of MgO in the ground granulated blast furnace slag may be, for example, 10.0% by mass or less, 8.0% by mass or less, or 6.0% by mass or less. This can further suppress the decrease in initial strength development when the concrete composition is hardened.

[0034] The ground granulated blast furnace slag may contain other components such as NaO2 (sodium oxide), K2O (potassium oxide), TiO2 (titanium oxide), and the like.

[0035] In this specification, the chemical composition of the ground blast furnace slag is measured in accordance with the description of JIS R 5202:2015 "Method for chemical analysis of cement" or JIS R 5204:2019 "Method for fluorescent X-ray analysis of cement."

[0036] The Blaine specific surface area of ​​ground granulated blast furnace slag is, for example, 2500 to 10000 cm 2 / g, 2500-8000cm 2 / g, 2500-6000cm 2 / g, 2500-5000cm 2 / g, 3000-5000cm 2 / g, or 4000 to 5000 cm 2 / g.

[0037] The content of ground granulated blast furnace slag in the binder is more than 70% by mass and not more than 89% by mass. This reduces CO2 emissions and makes it easier to obtain a concrete composition with high thermal crack resistance. From the viewpoint of further reducing CO2 emissions, the lower limit of the content of ground granulated blast furnace slag in the binder may be 73%, 75%, or 78% by mass. From the viewpoint of further increasing thermal crack resistance, the upper limit of the content of ground granulated blast furnace slag in the binder may be 85% or 83% by mass.

[0038] <Gypsum> The binder contains anhydrous gypsum. Examples of anhydrous gypsum include natural anhydrous gypsum, hydrofluoric anhydrous gypsum, and recycled anhydrous gypsum recycled from waste gypsum boards. The anhydrous gypsum referred to here is added separately from the anhydrous gypsum contained in cement and ground granulated blast furnace slag. In this specification, anhydrous gypsum added separately from other components is referred to as "anhydrous gypsum ANH." By including anhydrous gypsum ANH in the binder, it is possible to smoothly adjust the total content of anhydrous gypsum in the binder and the ratio of the total amount of anhydrous gypsum to the sum of the total amount of anhydrous gypsum and gypsum dihydrate BDS.

[0039] The content of anhydrous gypsum (ANH) may be 0.5 to 8.0 mass%, 1.0 to 6.0 mass%, or 1.5 to 5.0 mass% based on the total amount of the binder, from the viewpoint of further improving thermal crack resistance. The total amount of anhydrous gypsum may be 2.0 to 10.0 mass%, 2.5 to 8.0 mass%, or 3.0 to 7.0 mass% based on the total amount of the binder, from the viewpoint of further improving thermal crack resistance. The total amount of anhydrous gypsum refers to the total amount of anhydrous gypsum (e.g., anhydrous gypsum BAS) already contained in the components contained in the binder, such as cement and ground granulated blast furnace slag, and anhydrous gypsum (ANH).

[0040] The total amount of anhydrous gypsum relative to a total of 100 parts by mass of the total amount of anhydrous gypsum contained in the binder and the gypsum dihydrate BDS contained in the ground granulated blast furnace slag is preferably 55 to 100 parts by mass, more preferably 60 to 85 parts by mass, and even more preferably 65 to 80 parts by mass. This makes it possible to further promote the development of strength in the concrete composition while sufficiently increasing thermal crack resistance.

[0041] <Components other than binder> In a cement composition, the binder is the main component. The content of the binder in the cement composition may be, for example, 90% by mass or more, 95% by mass or more, 98% by mass or more, 99% by mass or more, or 100% by mass. The cement composition may contain components other than the binder. Such components include a hardening accelerator.

[0042] The hardening accelerator is a compound that accelerates the reaction of ground granulated blast furnace slag and improves early strength. The strength-improving effect of the hardening accelerator is particularly effective in winter (for example, when the average daily temperature is 10°C or less). The hardening accelerator may contain at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts. Examples of alkali metals include sodium and potassium. Examples of alkaline earth metals include magnesium and calcium. The hardening accelerator may contain a salt having a monovalent anion. The hardening accelerator may contain at least one selected from the group consisting of nitrites, nitrates, and chlorides.

[0043] Specific examples of the hardening accelerator include calcium nitrite, calcium nitrate, calcium chloride, calcium hydroxide, sodium nitrite, potassium nitrite, sodium nitrate, potassium nitrate, sodium chloride, and potassium chloride.

[0044] The content of the hardening accelerator, calculated as solid content, is preferably less than 0.9% by mass, more preferably less than 0.45% by mass, and even more preferably less than 0.23% by mass, based on the binder. The cement composition (concrete composition) may not contain a hardening accelerator. That is, cement compositions and concrete compositions containing a hardening accelerator may be excluded. By making the cement composition with such a reduced hardening accelerator content, it is possible to suppress the temperature rise during hardening of the concrete composition and reduce autogenous shrinkage, for example, when used in an environment where the average daily temperature exceeds 10°C (summer and standard seasons (spring and autumn)). As a result, the thermal cracking resistance of the concrete composition can be further improved.

[0045] The cement composition of this embodiment can suppress the temperature rise due to the hydration reaction and sufficiently suppress autogenous shrinkage. A concrete composition containing such a cement composition has high thermal crack resistance. Furthermore, since the cement content of this cement composition is sufficiently reduced, CO2 emissions can be reduced.

[0046] A method for producing a cement composition according to one embodiment includes a step of preparing and mixing the above-described components as raw materials. This step may involve, for example, blending and mixing raw materials for a binder to prepare a binder, and then mixing the binder with raw materials other than the binder to prepare the cement composition. The contents of the cement composition are as described above, and the mixing method is not particularly limited. The raw materials may be mixed in such a manner that the mixing ratio is the above-described content or content ratio. In this way, a cement composition having the above-described properties can be obtained.

[0047] [Concrete composition and method for producing the same] A concrete composition according to one embodiment includes a cement composition, water, fine aggregate, coarse aggregate, and chemical admixtures. The concrete composition may also include other components.

[0048] <Cement composition> The cement composition used is the one described above. 3 The content (unit B amount) of the binder (the binder contained in the cement composition) based on this is 250 to 800 kg / m 3 , 300~700kg / m 3 , or 350 to 600 kg / m 3 It may be.

[0049] <Water> Examples of water include tap water, distilled water, and deionized water. 3 The water content (unit amount of water) based on this is 150 to 190 kg / m 3 , or 160-180 kg / m 3 The mass ratio of water to the binder (water-binder ratio) may be 0.25 to 0.6, 0.3 to 0.55, or 0.4 to 0.5.

[0050] <Fine and coarse aggregate> The fine aggregate can be any of those specified in JIS A 5005:2020 "Crushed Stone and Crushed Sand for Concrete." Examples of fine aggregate include river sand, land sand, sea sand, crushed sand, silica sand, copper slag fine aggregate, and electric furnace oxidizing slag fine aggregate. 3 The content of fine aggregate (unit S content) based on this is 650 to 1050 kg / m 3 , 700~1000kg / m 3 , or 750 to 950 kg / m 3 It may be the following:

[0051] The coarse aggregate may be any of those specified in JIS A 5005:2020 "Crushed Stone and Crushed Sand for Concrete." Examples of coarse aggregate include gravel and crushed stone. 3 The coarse aggregate content (unit G amount) based on this is 700 to 1100 kg / m 3 , 800~1000kg / m 3 , or 850 to 950 kg / m 3 It may be the following:

[0052] <Water reducing agent> Examples of water-reducing agents include water-reducing agents, AE (Air Entraining) water-reducing agents, high-performance water-reducing agents, and high-performance AE water-reducing agents. Standard, delayed, and accelerated types of AE water-reducing agents can be used as AE water-reducing agents and high-performance AE water-reducing agents, with delayed types being preferred. Type I, II, and III types of AE water-reducing agents can be used as AE water-reducing agents and high-performance AE water-reducing agents, with type I being preferred. The water-reducing agent may include a high-performance AE water-reducing agent or may be a high-performance AE water-reducing agent.

[0053] The content of the water-reducing agent is 0.5 parts by mass or more and 3.0 parts by mass or less relative to 100 parts by mass of the binder (the binder contained in the cement composition). The content of the water-reducing agent may be, for example, 0.6 parts by mass or more, 0.7 parts by mass or more, or 0.8 parts by mass or more. By including a water-reducing agent content of 0.5 parts by mass or more, the fluidity of fresh concrete can be further improved. The content of the water-reducing agent may be 2.5 parts by mass or less, 2.0 parts by mass or less, 1.5 parts by mass or less, or 1.0 part by mass or less. By including a water-reducing agent content of 3.0 parts by mass or less, material separation resistance can be imparted without impairing the fluidity of fresh concrete.

[0054] <Chemical admixtures> The chemical admixture may include those specified in JIS A 6204:2011. For example, it may include an air entraining agent and a high-performance air entraining water reducing agent. The content of the air entraining agent may be, for example, 0.0005 to 0.01 mass% based on the total amount of the binder. The content of the high-performance air entraining water reducing agent may be, for example, 0.2 to 1.5 mass% based on the total amount of the binder. The chemical admixture may also include components other than these.

[0055] The concrete composition may contain a shrinkage-reducing agent, but its content is preferably low. That is, concrete compositions containing a shrinkage-reducing agent may be excluded. Shrinkage-reducing agents (also called drying shrinkage-reducing agents) such as polyalkylene glycol monoalkyl ethers typically function to suppress shrinkage and reduce cracking in hardened concrete. However, when the concrete composition of this embodiment contains a shrinkage-reducing agent, delays in setting and increased bleeding tend to occur. For this reason, the content of the shrinkage-reducing agent in the concrete composition is preferably less than 0.2 parts by mass, more preferably less than 0.1 parts by mass, and even more preferably 0 parts by mass, per 100 parts by mass of binder. In this way, by reducing the content of the shrinkage-reducing agent, delays in setting are less likely to occur, and a concrete composition with a sufficiently reduced amount of bleeding can be obtained.

[0056] <Properties of concrete composition> The concrete composition has a water-binder ratio of 0.4 to 0.5, and the initial setting time measured in accordance with "JIS A 1147:2019 Testing Method for Concrete Setting Time" is preferably 8 hours or less, more preferably 7 hours or less, even more preferably 6 hours or less, and particularly preferably 5 hours and 30 minutes or less. Such a concrete composition has excellent workability. From the viewpoint of shortening the construction period, the final setting time measured in a similar manner is preferably 14 hours or less, more preferably 12 hours or less, and even more preferably 11 hours or less. From the same viewpoint, the difference between the final setting time and the initial setting time may be within 7 hours, or may be within 6 hours. The initial setting time may be 3 hours or more, or 4 hours or more. The final setting time may be 5 hours or more, or 6 hours or more.

[0057] The concrete composition has a water-binder ratio of 0.4 to 0.5, and the bleeding amount measured in accordance with "JIS A 1123:2022 Concrete bleeding test method" is preferably 0.4 cm 3 / cm 2 Less than 0.3cm, preferably 0.3cm 3 / cm 2 Less than 0.2 cm, more preferably 3 / cm 2 Less than 0.15 cm, particularly preferably 3 / cm 2 Such a concrete composition has excellent workability. From the viewpoint of ease of preparation, the bleeding amount is set to 0.05 cm or less. 3 / cm 2 It may be more than that.

[0058] The concrete composition is measured in accordance with the structural strength correction value ( 28 S 91 ) but preferably 5.0N / mm 2 More preferably, it is 4.5 N / mm 2 or less, and more preferably 4.0 N / mm2 Such a concrete composition can reduce the difference between the compressive strength of the hardened concrete body in a structure and the compressive strength of the hardened concrete body after standard underwater curing. Therefore, the compressive strength of the structure can be sufficiently increased. m S n ) is a correction value that indicates the difference between the compressive strength of a standard cured specimen at an age of m days, which is used as the basis for determining the mixed strength, and the structural concrete strength (compressive strength of a core specimen) at an age of n days for columns, beams, etc.

[0059] The concrete composition of this embodiment can suppress the temperature rise due to the hydration reaction and sufficiently suppress autogenous shrinkage. Therefore, it has high resistance to thermal cracking. Furthermore, since the cement content is sufficiently reduced, it can reduce CO2 emissions.

[0060] A method for producing a concrete composition according to one embodiment includes preparing and mixing the above-described components as raw materials. The contents of the raw materials are as described above, and the mixing method is not particularly limited. The raw materials may be mixed in proportions such that the above-described contents or content ratios are achieved. In this manner, a concrete composition having the above-described properties can be obtained.

[0061] [Hardened concrete] A hardened concrete body according to one embodiment is obtained by hardening the above-described concrete composition. Curing conditions may be selected as appropriate. This hardened concrete body is sufficiently crack-suppressed and has excellent reliability. It also has excellent workability, making it suitable for use as mass concrete.

[0062] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. [Example]

[0063] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

[0064] 1.Materials used The materials used are shown in Table 1, the chemical compositions of the cement and ground granulated blast furnace slag in Table 2, and the mineral composition of the cement in Table 3. The chemical compositions of the cement and ground granulated blast furnace slag were measured in accordance with JIS R 5202:2015 "Methods for chemical analysis of cement" or JIS R 5204:2019 "Methods for X-ray fluorescence analysis of cement." The mineral composition of the cement was calculated using the Bogue formula. Note that "ig.loss" in Table 2 means loss on ignition. Loss on ignition was measured in accordance with the method described in JIS R 5202:2015.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] 2. Preparation of Cement Composition The formulation of the cement composition is shown in Table 4. In Table 4, the numerical values ​​of each component of binder B and the numerical values ​​of the hardening accelerator are the solid content (unit: mass%) based on the total amount of binder B. The SO3 content in Table 4 is the SO3 content (unit: mass%) in binder B. Cement compositions of each example and comparative example were prepared by kneading each component shown in Table 4. In the preparation, for those that did not contain a hardening accelerator, the components were kneaded to prepare the cement composition. For those that contained a hardening accelerator, the components of binder B were first mixed, and then the hardening accelerator was further added and mixed to prepare the cement composition.

[0069] [Table 4]

[0070] Table 5 shows the SO3 equivalent values ​​of each gypsum content in ground granulated blast furnace slag based on the total amount of binder B in each example and comparative example. The rightmost column of Table 5 shows the SO3 equivalent values ​​of the total content of all gypsum components (gypsum dihydrate BDS + anhydrous gypsum BAS) in ground granulated blast furnace slag based on the total amount of binder B.

[0071] [Table 5]

[0072] Table 6 shows the content of anhydrous gypsum (ANH) added when preparing binder B and its SO3 equivalent value based on the total amount of binder B, as well as the total content of anhydrous gypsum based on the total amount of binder B. The values ​​in the rightmost column of Table 6 show the parts by mass of the total amount of anhydrous gypsum per 100 parts by mass of the total amount of anhydrous gypsum contained in binder B (anhydrous gypsum ANH + anhydrous gypsum BAS) and the dihydrate gypsum BDS contained in the ground granulated blast furnace slag.

[0073] [Table 6]

[0074] 3. Mixing of concrete composition Concrete compositions were prepared using the cement compositions of each example and each comparative example shown in Table 4. Two types of concrete compositions were prepared using each cement composition, as shown in Table 7. For one concrete composition, the ratio of water to binder B (water-binder ratio) was 0.5 (W / B50), and for the other concrete composition, the ratio of water to binder B (water-binder ratio) was 0.4 (W / B40). The amount of AE (air-enhancing agent) added was adjusted appropriately within the range of 0.0005 to 0.01 (B x mass%) so that the air content when the concrete composition was mixed would be the value shown in Table 7. The reason why there are ranges in the fine aggregate ratio and unit S content in Table 7 is that the amount of fine aggregate mixed is such that the concrete composition becomes 1m 3 This is because the value was adjusted to be:

[0075] [Table 7]

[0076] 4. Test Results (4-1) Measurement of various fresh properties and compressive strength Table 8 shows the test results for compressive strength of concrete composition (W / B50) under various fresh properties and standard underwater curing, and Table 9 shows the test results for compressive strength of concrete composition (W / B40) under various fresh properties and standard underwater curing. Slump, air content, concrete temperature immediately after mixing, setting time, bleeding amount, and compressive strength under standard underwater curing were measured in accordance with JIS A 1101:2020, JIS A 1128:2019, JIS A 1156:2014, JIS A 1147:2019, JIS A 1123:2022, and JIS A 1108:2018, respectively. The ambient temperature was 20°C, and compressive strength specimens were demolded after 1 day and then underwater cured at 20°C until testing.

[0077] [Table 8]

[0078] [Table 9]

[0079] (4-2) Measurement of autogenous shrinkage strain The autogenous shrinkage strain of each concrete composition shown in Tables 8 and 9 was measured. The autogenous shrinkage strain was measured in accordance with "Appendix 1 (tentative title) Autogenous Shrinkage Test Method for High-Fluidity Concrete" described in "Japan Concrete Institute: Super-Fluidity Concrete Research Committee Report (II), pp. 209-210, 1994." Table 10 shows the autogenous shrinkage strain values ​​at an age of 91 days. Positive values ​​for autogenous shrinkage strain indicate expansion, and negative values ​​indicate contraction.

[0080] The measurement results (actual measured values) of autogenous shrinkage strain for each comparative example and each example are shown in (A) and (B) of Figures 1 to 9, and in Figure 10. The "mixture name" shown above each graph is the mix name of the cement composition shown in Tables 4 and 10.

[0081] [Table 10]

[0082] (4-3) Measurement of linear expansion coefficient As shown in Table 11, the coefficient of linear expansion was measured for some concrete compositions (W / B: 50 or 40). The coefficient of linear expansion was measured in accordance with "Reference Material 1" in "Japan Concrete Institute: Guidelines for Crack Control in Mass Concrete 2008, p. 96, 2008." Table 11 also shows the average values ​​of the measured values ​​when W / B was 50 and when W / B was 40.

[0083] [Table 11]

[0084] (4-4) Measurement of structural strength correction value The structural strength correction value ( m S nThe structural strength correction value was measured in accordance with JASS 5 T-606:2022 "Method for estimating structural concrete strength using simple adiabatic cured specimens." The results are shown in Table 12.

[0085] [Table 12]

[0086] The concrete compositions shown in Table 13 were prepared using the cement compositions of Example 2 and Example 6 shown in Table 4. The amount of AE (AE agent) added was adjusted appropriately within the range of 0.0005 to 0.01 (B x mass%) so that the amount of air when the concrete composition was prepared would be the value shown in Table 13. "W / B55" in Table 13 indicates that the ratio of water to binder was 0.55, and "W / B35" and "W / B30" indicate that the ratio was 0.35 and 0.30, respectively. The structural strength correction values ​​( m S n ) was measured. The structural strength correction value was measured in accordance with JASS 5 T-606:2022 "Method for estimating structural concrete strength using simplified adiabatic cured specimens" as with the concrete compositions in Table 12. The results are shown in Table 14.

[0087] [Table 13]

[0088] [Table 14]

[0089] 5. Temperature stress analysis (5-1) Overview A temperature stress analysis was performed using the three-dimensional finite element method with temperature stress analysis software (ASTEA MACS Ver.10, manufactured by Computational Mechanics Research Center, Inc.). The analysis conditions were set with reference to the Architectural Institute of Japan: Guidelines and Commentary for Thermal Crack Control Design and Construction of Mass Concrete, 2019. The analysis model assumed that a mat slab would be poured into the ground in one go, and the shape of the mat slab was a rectangular parallelepiped with a height of 2m and a width of 60m. The analysis parameters for the concrete into which the mat slab will be poured and the ground are shown in Table 15. The analysis period was set at two months, based on the age of the concrete.

[0090] [Table 15]

[0091] (5-2) Water-to-Binder Ratio W / B and Compressive Strength Design standard strength (28 days) is 33N / mm 2 The compressive strength of each concrete composition at 28 days of standard underwater curing (hereinafter referred to as the target strength) was calculated using the following formulas (1) and (2). 28 S 91 The values ​​are for W / B50 and W / B40 for each concrete composition in Table 12. 28 S 91 The average value of this 28 S 91 The average values, the mixture control strength calculated by formula (1), and the target strength calculated by formula (2) are shown in Table 16.

[0092] Mixing control strength = Design standard strength (33N / mm 2 )+ 28 S 91 Value (1) Target strength = Mixture control strength × 1.2 (2)

[0093] The coefficients (a3 and b3) in the following formula (3) for each concrete composition were calculated using Formula I, in which the W / B50 (B / W=2.0) and compressive strength (at 3 days' age) of each concrete composition shown in Table 8 were substituted into f'3 in the following formula (3), and Formula II, in which the W / B40 (B / W=2.5) and compressive strength (at 3 days' age) of each concrete composition shown in Table 9 were substituted into f'3 in the following formula (3). Similarly, the coefficients (a7 and b7, a7) in the following formulas (4), (5), and (6) for each concrete composition were calculated using the compressive strength (at 7 days' age, 28 days' age, or 91 days' age during standard underwater curing. 28 and b 28 , a 91 and b 91 ) was calculated. f'7 and f' in the following formula (4), the following formula (5), and the following formula (6) 28 , f' 91 are the compressive strengths at standard underwater curing ages of 7, 28, and 91 days, respectively. In this way, the relationship between the binder-water ratio (B / W) at each age of each concrete composition and the compressive strength f' at standard underwater curing was determined. The values ​​of each coefficient in the following equations (3) to (6) for each concrete composition were as shown in Table 17.

[0094] f'3=a3×(B / W)+b3 (3) f'7=a7×(B / W)+b7 (4) f' 28 =a 28 ×(B / W)+b 28 ···(5) f' 91 =a 91 ×(B / W)+b 91 ···(6)

[0095] The relation (f') of equation (5) obtained as described above 28 -B / W relation) f' 28 The target strength of each concrete composition calculated by the above formula (2) was substituted into the above formula to calculate the B / W of each concrete composition when the target strength was achieved. The water-binder ratio W / B (the reciprocal of B / W) of each concrete composition calculated in this way is shown in Table 16.

[0096] The reciprocal (B / W) of the water-binder ratio W / B of each concrete composition shown in Table 16 was calculated using the relationship formulas (3), (4), and (6) (f'3-B / W, f'7-B / W, f' 91 -B / W) and the compressive strengths f'3, f'7 and f' of each concrete composition at standard underwater curing ages of 3, 7 and 91 days were calculated. 91 The compressive strengths f'3, f'7, and f' at the standard water curing stage for the four ages were calculated as described above. 28 and f' 91 Using the following formula (4.7) described in the "Architectural Institute of Japan: Thermal Crack Control Design and Construction Guidelines and Commentary for Mass Concrete, 2019," the compressive strength prediction formula was obtained for each concrete composition using the least squares method, and used as the input value for the thermal stress analysis. The s and s in the compressive strength prediction formula for each concrete hardened body obtained by hardening each concrete composition are f , and f c28 is shown in Table 18.

[0097]

number

[0098] In equation (4.7), f c (t e ) is the compressive strength of the hardened concrete (N / mm 2 ), t e is the age of the hardened concrete (days), t n is a value that makes time dimensionless, and f is a value that makes time dimensionless. c28 is the compressive strength (N / mm 2 ), s is a constant related to the cement type, s f is the correction term (days) for the hardening origin. s, s substituted into equation (4.7) f ,f c28 are shown in Table 17. In addition, "S f The correction term for the hardening origin (days) was the average value of the initial setting time for each mix of W / B50 and W / B40 for each concrete composition shown in Tables 8 and 9.

[0099] (5-3) Autogenous shrinkage strain The autogenous shrinkage strain of W / B50 at 91 days and the autogenous shrinkage strain of W / B40 at 91 days shown in Table 10 were substituted into the following formula (7) to determine the coefficients c and d for each concrete composition. 91 is the autogenous shrinkage strain at 91 days (×10 -6 ) W / B is the water-to-binder ratio (mass ratio), and c and d are coefficients. ε 91 =c×exp{d×(W / B)} (7)

[0100] The relational expression (ε 91 The W / B mass ratio of each concrete composition shown in Table 16 was substituted into the W / B formula (relationship formula - W / B) to estimate the autogenous shrinkage strain at 91 days of age for that W / B. The estimated results are shown in Table 16 as "91-day autogenous shrinkage (× 10 -6 ) column. The estimated values ​​of autogenous shrinkage strain in W / B for each concrete composition shown in Table 16, estimated using the above method, are shown by dotted lines in Figures 1 to 10. The estimated values ​​of the change in autogenous shrinkage strain over time for each concrete composition at ages 0 to 91 days shown in Figures 1 to 10 were used as input values ​​for the temperature stress analysis.

[0101] (5-4) Linear expansion coefficient The linear expansion coefficient of concrete compositions is affected by the cement, chemical admixtures, aggregates, etc. that are commonly used, and concrete compositions containing ground granulated blast furnace slag tend to have a larger linear expansion coefficient. Taking this into consideration, the Architectural Institute of Japan: Guidelines and Commentary on Thermal Crack Control Design and Construction of Mass Concrete, 2019, states that when Portland cement is used, the linear expansion coefficient is 10(x10 -6 / ℃), and when using blast furnace cement type B, 12 (× 10 -6 / ℃) can be used as a standard value.

[0102] For this reason, it was assumed that the linear expansion coefficient is affected by the content of ground granulated blast furnace slag, and the linear expansion coefficient of concrete compositions containing the same amount of ground granulated blast furnace slag as the concrete compositions shown in Table 11 was considered to be the same as the linear expansion coefficient in Table 11. Specifically, the concrete compositions of Comparative Examples 4 to 10 were set to have the same linear expansion coefficient as Comparative Example 3, the concrete compositions of Comparative Examples 11 and 13 were set to have the same linear expansion coefficient as Comparative Example 12, the concrete compositions of Examples 1 and 3 were set to have the same linear expansion coefficient as Example 2, and the concrete composition of Examples 4 and 6 was set to have the same linear expansion coefficient as Example 5. In other words, the linear expansion coefficient of each concrete composition was set to be as shown in Table 16.

[0103] (5-5) Adiabatic temperature rise curve Adiabatic temperature rise tests were conducted for each concrete composition (W / B50, W / B40) shown in Tables 8 and 9. The adiabatic temperature rise tests were conducted using an air-circulating test device in accordance with JCI-SQA3 "Test Method for Adiabatic Temperature Rise of Concrete (Draft)." The sample container was cylindrical with an inner diameter of 400 mm and an inner height of 400 mm, and the sample volume was approximately 50 L. The ambient temperature and the temperature of the mixed concrete were both set at 20°C.

[0104] Using the measured values ​​of the adiabatic temperature rise curves of each concrete composition (W / B50, W / B40) obtained by the adiabatic temperature rise test, the following equation (8) was used to approximate K, α, and β for W / B50 and W / B40, respectively. Assuming that K, α, and β are each proportional to the unit amount of binder (unit B amount), the W / B50 mix (unit B amount: 346 kg / m 3 ) and W / B40 (unit B amount: 433 kg / m 3 ) were used to determine K, α, and β when the unit B content was the value shown in Table 16. The unit B content in Table 16 is the unit amount of binder calculated from W / B in Table 16. The determined K, α, and β are shown in the "Adiabatic Temperature Rise Characteristics" column in Table 16. Q(t) = K × {1-exp(-α × t} β )} (8)

[0105] In equation (8), t is the age of the material (days), Q(t) is the adiabatic temperature rise up to age t days (°C), K is the final adiabatic temperature rise (°C), and α and β are coefficients that represent the rate of adiabatic temperature rise. The values ​​K, α, and β shown in Table 16 were substituted into equation (8) to obtain the input value for the temperature rise of concrete in the thermal stress analysis.

[0106] [Table 16]

[0107] [Table 17]

[0108] [Table 18]

[0109] (5-6) Temperature stress analysis results A thermal stress analysis was performed using the analysis parameters shown in Table 15 and the input values ​​mentioned above, and the maximum member temperature and minimum crack index were obtained as output values. These results are shown in Table 21. The maximum member temperature is the highest temperature that occurs in the concrete member of the model, and is the temperature at the center of the mat slab. The minimum crack index indicates the minimum value of the ratio of the tensile strength of the hardened concrete to the tensile stress that occurs in the hardened concrete at the point where the maximum member temperature occurs; the smaller this value, the higher the probability of crack occurrence.

[0110] 6. Concrete composition 1m 3 Derivation of CO2 emissions per unit 1m of concrete composition 3 The CO2 emissions per unit of concrete were calculated from the mixing conditions for each concrete composition at the water-binder ratio W / B shown in Table 16 and the CO2 emissions intensity of each material. The mixing conditions for the concrete compositions are shown in Table 19, and the CO2 emissions intensity of each material is shown in Table 20.

[0111] [Table 19]

[0112] [Table 20]

[0113] Calculated concrete composition 1m 3 CO2 emissions per 1 m3 of concrete composition when ordinary Portland cement of Comparative Example 1 was used as the cement composition. 3 The CO2 reduction rate of each concrete composition, based on the CO2 emissions per unit of concrete, is shown in the "Low Carbon" column of Table 21.

[0114] 7. Overall evaluation of temperature stress analysis results and CO2 reduction rate [Table 21]

[0115] Figure 11 shows the relationship between CO2 reduction rate and minimum crack index. Only Examples 1 to 6 achieved a CO2 reduction rate of 70% or more and a minimum crack index exceeding the 1.00 level of Comparative Example 3 (blast-furnace cement type C). It was found that even with binders that use a large amount of ground granulated blast-furnace slag, adding anhydrous gypsum reduces autogenous shrinkage strain and increases the minimum crack index, i.e., improves thermal crack resistance. The use of a hardening accelerator increases compressive strength and allows for a higher water-binder ratio at the same design strength, but it also leads to increased autogenous shrinkage and temperature rise, resulting in a tendency for the minimum crack index to decrease overall.

Claims

1. A concrete composition containing a cement composition including a binder containing cement, ground granulated blast furnace slag, and anhydrous gypsum, water, fine aggregate, coarse aggregate, and a chemical admixture, The cement is C ３ The content of S is more than 50.0 mass% and not more than 70.0 mass%, and C ２ The S content is 5.0 to 15.0 mass %, The content of the ground granulated blast furnace slag in the binder is more than 70% by mass and 89% by mass or less, The total amount of anhydrous gypsum in the binder is 2.0% by mass or more based on the total amount of the binder, A concrete composition having a water-binder ratio of 0.4 to 0.5, and an initial setting time of 8 hours or less as measured in accordance with "JIS A 1147:2019 Test method for setting time of concrete."

2. A concrete composition comprising a cement composition containing cement, ground granulated blast furnace slag, and a binder containing anhydrous gypsum, water, fine aggregate, coarse aggregate, and a chemical admixture, The cement has a C 3 S content of more than 50.0 mass% and not more than 70.0 mass% and a C 2 S content of 5.0 to 15.0 mass%, The content of the ground granulated blast furnace slag in the binder is more than 70% by mass and 89% by mass or less, The total amount of anhydrous gypsum in the binder is 2.0% by mass or more based on the total amount of the binder, A concrete composition having a bleeding amount of 0.4 cm 3 / cm 2 or less when measured in accordance with "JIS A 1123:2022 Test method for bleeding of concrete" under the condition that the water-binder ratio is 0.4 to 0.

5.

3. The Blaine specific surface area of ​​the cement is 3500 cm ２ The concrete composition according to claim 1 or 2, wherein the Cr content is 1 / g or more.

4. 3. The concrete composition according to claim 1, wherein the cement is ordinary Portland cement or high-early-strength Portland cement.

5. A concrete composition as described in claim 1 or 2, containing a hardening accelerator including at least one selected from the group consisting of nitrites, nitrates, and chlorides.

6. The unit amount of water is 150 to 190 kg / m ３ , the unit amount of the binder is 250 to 800 kg / m ３ , the unit amount of the fine aggregate is 650 to 1050 kg / m ３ , and the unit amount of the coarse aggregate is 700 to 1100 kg / m ３ 3. The concrete composition according to claim 1 or 2, wherein

7. A hardened concrete product obtained by hardening the concrete composition according to claim 1 or 2.

8. C ３ The content of S is more than 50.0 mass% and not more than 70.0 mass%, and C ２ The method includes a step of mixing raw materials including cement having an S content of 5.0 to 15.0% by mass, ground granulated blast furnace slag containing gypsum dihydrate, and anhydrous gypsum, to obtain a cement composition in which the content of the ground granulated blast furnace slag in a binder is more than 70% by mass and 89% by mass or less, and the total amount of anhydrous gypsum in the binder is 2.0% by mass or more based on the total amount of the binder, The method for producing a cement composition, wherein the content of the gypsum dihydrate in the ground granulated blast furnace slag is 0.5 to 3.0 mass% based on the total amount of the binder.

9. A method for producing a concrete composition, comprising the step of mixing the cement composition obtained by the production method described in claim 8 with raw materials including water, fine aggregate, coarse aggregate, and a chemical admixture, to obtain a concrete composition having a water-binder ratio of 0.25 to 0.6.

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