Concrete composition and method for manufacturing the concrete composition

Abstract

This invention provides a concrete composition that can reduce CO2 emissions and a method for manufacturing the same. [Solution] A concrete composition is adopted that contains blast furnace slag fine powder, carbonated steelmaking slag powder, water, fine aggregate and coarse aggregate, wherein the carbonated steelmaking slag powder contains calcium carbonate.

Description

[Technical Field]

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

[0002] Concrete is a hydraulic composition produced by mixing cement, water, aggregate, and small amounts of chemical admixtures, and is used in a wide variety of applications as a major construction material. However, with growing awareness of global environmental protection, there is a demand for low-carbon materials in construction materials as well.

[0003] Cement, a component of concrete compositions, plays a crucial role as a binder and is an important element that determines the performance of concrete. However, because cement production generates a large amount of carbon dioxide emissions, there is a growing need to reduce the amount of cement used in concrete compositions from the perspective of protecting the global environment.

[0004] Herein, Patent Document 1 describes a hydrated solidified body for underwater submersion, which is obtained by hydrating and hardening raw materials, with powdered steelmaking slag as the main aggregate and blast furnace slag fine powder as the main binder, and is characterized in that it contains nitrogen-containing organic matter as part of the raw materials.

[0005] Furthermore, Patent Document 2 describes a method for obtaining a hydrated solidified body by kneading and hardening a composition containing aggregate including steelmaking slag, a binder including blast furnace slag fine powder, and water, wherein the steelmaking slag includes steelmaking slag fine aggregate, and the calcium ion concentration in the test solution obtained by performing the "test in its usable form" described in JIS K 0058-1:2005 "Test methods for chemical substances of slags - Part 1: Elution test method" is 30 mg / L or higher, and the amount of steelmaking slag fine aggregate blended is 800 kg / m³. 3 The above describes a method for producing a hydrated solidified product.

[0006] However, the hydrated solidified concrete for underwater submersion described in Patent Document 1 is for use in marine areas. Furthermore, the hydrated solidified concrete described in Patent Document 2 is an invention that uses steelmaking slag powder as aggregate to obtain a hydrated solidified concrete with excellent durability, and does not describe any consideration from the perspective of reducing CO2 emissions. For this reason, Patent Documents 1 and 2 do not mention anything about reducing CO2 emissions as a concrete composition, and there is still room for improvement in reducing CO2 emissions. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2009-045006 [Patent Document 2] Japanese Patent Publication No. 2024-012841 [Overview of the project] [Problems that the invention aims to solve]

[0008] This invention has been made in view of the above circumstances, and aims to provide a concrete composition that can reduce CO2 emissions and a method for manufacturing the same. [Means for solving the problem]

[0009] To solve the above problems, the present invention adopts the following configuration. (1) A binder containing blast furnace slag fine powder and carbonated steelmaking slag powder, Water and, Fine aggregate and coarse aggregate, A concrete composition containing, The concrete composition is characterized in that the carbonated steel slag powder contains calcium carbonate. (2) The specific surface area of ​​the blast furnace slag fine powder is 3000 to 10000 cm². 2 / g The concrete composition described in (1) that satisfies the following formula (i). 20.0 ≦ W / (GGBFS + CGGSS)×100 ≦ 65.0 ···(i) However, in formula (i), GGBFS is the mass (kg) of the blast furnace slag fine powder, CGGSS is the mass (kg) of the carbonated steelmaking slag powder, and W is the mass (kg) of the water. (3) Furthermore, it contains a mixing agent, and the mixing agent is a chemical mixing agent containing one or more of lignin sulfonate, lignin sulfonic acid, oxycarboxylate, oxycarboxylic acid, polycarboxylate, polycarboxylic acid or silicofluoride. The concrete composition according to (1). (4) The particle size of the carbonated steelmaking slag powder is 600 μm or less. The concrete composition according to (1). (5) A part or all of the fine aggregate contained in the concrete composition is carbonated steelmaking slag. The concrete composition according to (1). (6) A part or all of the coarse aggregate contained in the concrete composition is carbonated steelmaking slag. The concrete composition according to (5). (7) The total blending amount of the blast furnace slag fine powder and the carbonated steelmaking slag powder in the concrete composition is 350 kg or more per 1 m 3 of the concrete composition. The concrete composition according to (1). (8) A method for manufacturing a concrete composition, characterized by kneading and manufacturing the concrete composition according to any one of (1) to (7) at a construction site.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a concrete composition capable of reducing CO2 emissions and a method for manufacturing the same.

Embodiments for Carrying Out the Invention

[0011] Conventional concrete compositions are hydraulic compositions produced by mixing cement as a binder, water, aggregate, and chemical admixtures, and are one of the main building materials used in various applications. However, since cement emits 755.5 kg of CO2 per ton during its production, it was necessary to reduce the amount of cement used in order to reduce the carbon content of concrete compositions.

[0012] The inventors of this invention diligently studied how to minimize the cement content in concrete compositions and discovered that CO2 emissions can be reduced by using blast furnace slag powder and carbonated steelmaking slag powder as binders.

[0013] The inventors have further discovered that by using blast furnace slag powder and carbonated steelmaking slag powder as binders, calcium compounds contained in the carbonated steelmaking slag powder dissolve as alkaline components, and these dissolved alkaline components stimulate the blast furnace slag powder, which is a glassy hydraulic material, thereby achieving a predetermined strength in the concrete composition. The concrete composition and its manufacturing method, which are embodiments of the present invention, will be described below.

[0014] The concrete composition of this embodiment is a concrete composition comprising a binder containing blast furnace slag fine powder and carbonated steelmaking slag powder, water, fine aggregate and coarse aggregate, wherein the carbonated steelmaking slag powder contains calcium carbonate. In the following explanation, blast furnace slag powder and carbonicated steelmaking slag powder may be collectively referred to as "binders." The concrete composition of this embodiment hardens after placement to form concrete. The following describes the compositional components of the concrete composition.

[0015] Blast furnace slag fine powder is obtained by rapidly cooling molten slag, which is formed simultaneously with pig iron in a blast furnace, with water to form water-granulated slag, and then crushing the water-granulated slag.

[0016] In this embodiment, blast furnace slag fine powder is used, with a specific surface area of ​​3000 cm². 2 / g or more, 10000cm 2 It is preferable that the specific surface area is in the range of / g or less. If the specific surface area is below the upper limit, the hardening reaction of the concrete composition will not proceed too rapidly, and excessive viscosity will not appear in the fresh properties immediately after mixing. If the specific surface area is above the lower limit, the hardening reaction of the concrete will proceed appropriately, the hardening time to reach the desired hardness will not be prolonged, and the fresh properties immediately after mixing will be favorably exhibited.

[0017] Carbonated steelmaking slag refers to steelmaking slag in which CO2 has been immobilized by reacting some or all of the calcium composition in the steelmaking slag with CO2. It is presumed that the CO2 is fixed in the steelmaking slag in the form of calcium carbonate. Examples of steelmaking slag used as a raw material for carbonated steelmaking slag include crushed various types of slag, such as pre-treatment slag generated in the molten iron pre-treatment process, converter slag generated in processes such as decarburization and desilicate in converters, electric furnace slag such as reduction slag and oxidation slag generated in electric furnace processes, ingot slag generated in the casting process, and secondary refining slag generated in the secondary refining process. These may be included individually or as a mixture of two or more types. Steelmaking slag contains one or more substances from among free lime, calcium hydroxide, calcium ferrite, calcium silicate, and dicalcium silicate. The CO2 content of carbonated steelmaking slag is not particularly limited, but it is acceptable as long as the amount of CO2 desorption detected in the 600°C to 800°C range when heated at 20°C / min under an inert gas atmosphere using thermogravimetric-differential thermal analysis (TG-DTA) is greater than 0% by weight. Furthermore, the CO2 used in the production of carbonated steelmaking slag should be the CO2 generated from each stage of steelmaking at a steelworks. In addition, carbonated steelmaking slag with a particle size of 75 μm or less as the raw material should be referred to as "carbonated steelmaking slag powder".

[0018] In this embodiment, the particle size of the carbonated steelmaking slag powder is preferably 600 μm or less. This particle size promotes the hydration reaction during mixing with water and blast furnace slag fine powder. For example, the particle size can be sorted using a 26-mesh sieve as specified in JIS Z 8801:2019.

[0019] The water used is not particularly limited; tap water, supernatant water produced during concrete mixing, and sludge water can all be used. Using supernatant water or sludge water during mixing is especially preferable from an environmental standpoint, as it involves the reuse of industrial waste.

[0020] Coarse and fine aggregates can be of any type, including natural aggregates such as mountain sand, land sand, sea sand, mountain gravel, land gravel, and river gravel; artificial aggregates such as crushed stone, crushed sand, and lightweight aggregates; and recycled aggregates such as aggregates processed from waste concrete and slag aggregates.

[0021] Coarse aggregate and fine aggregate can be distinguished by particle size; for example, aggregate with a particle size of 5 mm or more is considered coarse aggregate, aggregate with a particle size of 5 mm or less but greater than 75 μm is considered fine aggregate, and aggregate with a particle size of 75 μm or less is considered fine powder.

[0022] Furthermore, in this embodiment, part or all of the coarse aggregate may contain carbonated steelmaking slag. By using carbonated steelmaking slag as coarse aggregate, CO2 emissions can be further reduced. The carbonated steelmaking slag used as coarse aggregate only needs to have a particle size of 5 mm or more. Furthermore, the fine aggregate may also contain, in part or in whole, carbonated steelmaking slag. Using carbonated steelmaking slag in the fine aggregate not only further reduces CO2 emissions but also further promotes the hydration reaction during mixing with water and blast furnace slag fine powder. The carbonated steelmaking slag used in the fine aggregate should have a particle size of 5 mm or less and greater than 75 μm.

[0023] The amount of fine aggregate in the concrete composition according to this embodiment is 1 m of concrete composition3 per cubic meter of the concrete composition, it is preferably 300 kg or more and 1500 kg or less. When the amount of fine aggregate is 300 kg or more per cubic meter of the concrete composition, the concrete after curing can have more appropriate strength as a on-site structure. Also, when the amount of fine aggregate is 1500 kg or less per cubic meter of the concrete composition, the fluidity of the concrete composition is ensured, and it becomes easier to fill without gaps during placement. 3 per cubic meter of the concrete composition, it is preferably 300 kg or more. When the amount of fine aggregate is 300 kg or more per cubic meter of the concrete composition, the concrete after curing can have more appropriate strength as a on-site structure. Also, when the amount of fine aggregate is 1500 kg or less per cubic meter of the concrete composition, the fluidity of the concrete composition is ensured, and it becomes easier to fill without gaps during placement. 3 per cubic meter of the concrete composition, it is preferably 1500 kg or less. When the amount of fine aggregate is 1500 kg or less per cubic meter of the concrete composition, the fluidity of the concrete composition is ensured, and it becomes easier to fill without gaps during placement.

[0024] The blending amount of coarse aggregate in the concrete composition according to this embodiment is preferably 500 kg or more and 2000 kg or less per cubic meter of the concrete composition. When the amount of coarse aggregate is 500 kg or more per cubic meter of the concrete composition, the concrete after curing can have more appropriate strength as a on-site structure. Also, when the amount of coarse aggregate is 2000 kg or less per cubic meter of the concrete composition, the fluidity of the concrete composition is ensured, and it becomes easier to fill without gaps during placement. 3 per cubic meter of the concrete composition, it is preferably 500 kg or more. When the amount of coarse aggregate is 500 kg or more per cubic meter of the concrete composition, the concrete after curing can have more appropriate strength as a on-site structure. Also, when the amount of coarse aggregate is 2000 kg or less per cubic meter of the concrete composition, the fluidity of the concrete composition is ensured, and it becomes easier to fill without gaps during placement. 3 per cubic meter of the concrete composition, it is preferably 500 kg or more. When the amount of coarse aggregate is 500 kg or more per cubic meter of the concrete composition, the concrete after curing can have more appropriate strength as a on-site structure. Also, when the amount of coarse aggregate is 2000 kg or less per cubic meter of the concrete composition, the fluidity of the concrete composition is ensured, and it becomes easier to fill without gaps during placement. 3 per cubic meter of the concrete composition, it is preferably 2000 kg or less. When the amount of coarse aggregate is 2000 kg or less per cubic meter of the concrete composition, the fluidity of the concrete composition is ensured, and it becomes easier to fill without gaps during placement.

[0025] The mixing ratio of water in the concrete composition of this embodiment preferably satisfies the following formula (i) with respect to the amount of binder (total amount of ground granulated blast-furnace slag powder and carbonated steel slag powder).

[0026] 20.0≦W / (GGBFS + CGGSS)×100≦65.0 ···(i)

[0027] However, in formula (i), GGBFS is the mass (kg) of ground granulated blast-furnace slag powder, CGGSS is the mass (kg) of carbonated steel slag powder, and W is the mass (kg) of water.

[0028] When W / (GGBFS+CGGSS)×100 is 20 or more, that is, when the ratio of water to the total amount of binder is 20% or more, the water content is appropriate, the concrete composition has a suitable fluidity, and it becomes easier to fill the concrete composition without gaps during placement. Also, when W / (GGBFS+CGGSS)×100 is 65 or less, that is, when the ratio of water to the total amount of binder is 65% or less, there is no excess water, and the hardened concrete can fully exhibit the strength required for the on-site structure. Furthermore, if a portion of the carbonated steelmaking slag powder is replaced with fine steelmaking slag powder, CGGSS in formula (i) may be the total amount of carbonated steelmaking slag powder and fine steelmaking slag powder.

[0029] In concrete compositions, the proportion of carbonated steel slag powder in the binder (total amount of blast furnace slag fine powder and carbonated steel slag powder) preferably satisfies the following formula (ii).

[0030] 5.0≦CGGSS / (GGBFS+CGGSS)×100≦50.0 (ii)

[0031] If CGGSS / (GGBFS+CGGSS)×100 is 5 or more, that is, if the proportion of carbonated steel slag powder in the binder is 5% or more, appropriate strength can be obtained due to the calcium ions leached from the carbonated steel slag powder. If CGGSS / (GGBFS+CGGSS)×100 is 50 or less, that is, if the proportion of carbonated steel slag powder in the binder is 50% or less, the amount of carbonated steel slag powder is appropriate, the hardening reaction of the concrete composition does not proceed excessively, and excessive viscosity does not appear in the fresh properties immediately after mixing. Note that CGGSS / (GGBFS+CGGSS)×100 may be between 10 and 45, or between 15 and 40. Furthermore, if a portion of the carbonated steelmaking slag powder is replaced with fine steelmaking slag powder, CGGSS in formula (ii) may be the total amount of carbonated steelmaking slag powder and fine steelmaking slag powder.

[0032] Also, 1 m of concrete composition 3 The amount of binder per unit (total amount of blast furnace slag powder and carbonated steelmaking slag powder) is preferably 350 kg or more. This value or higher allows the hardened concrete to have more appropriate strength as a site structure. Furthermore, if a portion of the carbonated steelmaking slag powder is replaced with fine steelmaking slag powder, the amount of fine steelmaking slag powder may be included in the amount of binder. Furthermore, the binder in the concrete composition of this embodiment may also include cement, slaked lime, quicklime, steelmaking slag powder, and other calcium compositions. The inclusion of these further enhances the alkaline stimulation to the blast furnace slag powder, thereby activating the hydration reaction.

[0033] Furthermore, the unit water content in the concrete composition is 200 kg / m³. 3 The following is preferable. More preferably, 185 kg / m 3 The following applies. Keeping the value below this level ensures that the water content in the concrete is appropriate, making it easier for the structure to exhibit sufficient strength.

[0034] The concrete composition of this embodiment may contain admixtures. In this embodiment, the admixtures may be formulated primarily for the purpose of improving fluidity. The admixtures may also be formulated for the purpose of reducing the hardening rate of the concrete. Furthermore, the admixtures may be formulated for the purpose of reducing the amount of water while maintaining fluidity.

[0035] The admixture is more preferably a chemical admixture containing one or more of the following: lignin sulfonate, lignin sulfonic acid, oxycarboxylate, oxycarboxylic acid, polycarboxylate, polycarboxylic acid, or silicogenic fluoride. By using the above chemical admixture as an admixture, the hardening rate of the concrete composition is reduced, the viscosity after mixing the materials is suitably controlled, and favorable fluidity for placement is achieved.

[0036] The mixing ratio of admixtures in a concrete composition is preferably such that it satisfies the following formula (iii) in relation to the amount of binder (total amount of blast furnace slag fine powder and carbonated steelmaking slag powder).

[0037] 0≦SP / (GGBFS+CGGSS)×100≦5 …(iii)

[0038] However, in equation (iii), SP is the mass (kg) of the admixture.

[0039] SP / (GGBFS+CGGSS)×100 may be 0, but it may be 0.1 or higher in order to obtain the desired effect of the admixture. That is, if the mixing ratio of the admixture to the total amount of blast furnace slag fine powder and carbonated steelmaking slag powder is 0.1% or higher, the effects of the admixture in reducing the hardening speed, improving fluidity, and reducing the amount of water can be fully exerted. On the other hand, if SP / (GGBFS+CGGSS)×100 is 5 or less, that is, if the mixing ratio of the admixture to the total amount of blast furnace slag fine powder and carbonated steelmaking slag powder is 5% or less, the effect of adding the admixture can be utilized without saturation. The range of SP / (GGBFS+CGGSS)×100 may be 0.1 or higher, or 0.2 or higher and 4 or lower, or 0.5 or higher and 3 or lower, or 1 or higher and 2 or lower. Furthermore, if a portion of the carbonated steelmaking slag powder is replaced with fine steelmaking slag powder, CGGSS may be the total amount of carbonated steelmaking slag powder and fine steelmaking slag powder.

[0040] Furthermore, as admixtures, in place of or in conjunction with the above-mentioned chemical admixtures, or together with the above-mentioned chemical admixtures, admixtures, expansive agents, colorants, polymers, etc. may be added to improve strength, such as pozzolanic materials like fly ash, silicate clay, and diatomaceous earth; by-products such as silica fume, waste concrete, and woody biomass; and admixtures, expansive agents, colorants, and polymers, such as limestone powder and siliceous powder. Furthermore, polypropylene fibers or ceramic matrix composite (CMC) materials may be added as admixtures to improve the fire resistance of the concrete composition.

[0041] The concrete composition used in this embodiment is preferably expected to exhibit the following properties.

[0042] [Compressive strength at 28 days of age] It is desirable to vary the application of the concrete composition depending on its compressive strength. For example, when applying a concrete composition to building structures, the compressive strength of the concrete at 28 days of age, measured in accordance with JIS A 1108:2018 "Test Method for Compressive Strength of Concrete", is 18 N / mm², according to the "Standard Specifications and Commentary for Building Construction JASS5 Reinforced Concrete Construction 2022". 2 The above is required. On the other hand, for concrete structures that are not subjected to large loads (for example, those used in pavement work, landscaping, etc., and wave-dissipating blocks), the design is carried out based on the expected load, and if the concrete strength is sufficient, then 18 N / mm² is used. 2 Even if the compressive strength is below the specified level, it can still be used. For example, in the case of concrete within the embankment of a gravity dam structure, no large external forces are generated, and no strength specifications are set. However, for concrete within the embankment of a gravity dam, it is required to apply a concrete composition with sufficient strength considering the stresses acting on it. Therefore, the compressive strength of the concrete at 28 days of age, measured in accordance with JIS A 1108:2018 "Test Method for Compressive Strength of Concrete", can be, for example, 10 N / mm². 2 Anything above that is acceptable.

[0043] [Fluidity of concrete composition] The required fluidity of a concrete composition varies depending on the structure. For example, when forming arc-shaped structures such as tunnel segments using a concrete composition, if the fluidity is too high, it will be difficult to form the desired shape. On the other hand, for structures with a wide planar surface, such as building floor slabs, higher fluidity is desirable. Therefore, it is necessary that the fluidity can be appropriately adjusted by the type and amount of chemical admixtures. For this reason, it is preferable that the slump value of the concrete composition immediately after mixing, as measured by the "Slump Test Method for Concrete" in JIS A 1101:2020, be 25 cm or less. This value indicates that the concrete composition has appropriate fluidity, allowing the concrete composition to fill the structure without gaps during construction.

[0044] Regarding the amount of bleeding, the "Standard Specifications for Building Construction and Commentary JASS5 Reinforced Concrete Construction 2022" specifies 0.30 cm. 3 / cm 2 The following is stipulated. However, this value is determined from the perspective of resistance to frost damage, and the bleeding amount is 0.30 cm. 3 / cm 2 Even if the amount exceeds this, performance issues can be resolved by taking special measures during construction, such as removing bleeding water. Furthermore, as mentioned above, bleeding is often not a problem in structures with small loads. Therefore, a bleeding amount of 0.50 cm is considered sufficient. 3 / cm 2 The following level is acceptable.

[0045] As explained above, the concrete composition of this embodiment does not contain any materials that emit large amounts of CO2 during the manufacturing process. Carbonated steel slag powder and the carbonated steel slag used as fine aggregate and coarse aggregate carry CO2, allowing for permanent CO2 fixation in the hardened concrete. Therefore, CO2 emissions can be kept low. Furthermore, since all the binders that contribute to the hardening of the concrete are industrial by-products, the use of the concrete composition of this embodiment can reduce the environmental burden. In addition, the strength of the hardened concrete can be controlled by adjusting the amount of binders used, making it possible to obtain a concrete composition that exhibits the necessary performance depending on the application.

[0046] Furthermore, according to the concrete composition of this embodiment, by using a chemical admixture whose main component is one or more of polycarboxylic acids, polycarboxylic acid salts, ligninsulfonic acid, ligninsulfonate salts, oxycarboxylic acids, oxycarboxylic acid salts, or silicogenic compounds, particularly effective performance can be achieved in terms of fluidity and strength.

[0047] Furthermore, according to the concrete composition of this embodiment, by mixing the concrete composition at the construction site, it is possible to mix a concrete composition that is suitable for the detailed soil conditions of the site, which become clear during the construction phase, and to carry out construction with a concrete composition that is more appropriate for the ground conditions at the site. The equipment used in the manufacture of the concrete composition of this embodiment is not particularly limited and can be manufactured using equipment found in a general concrete plant or a concrete mixer for on-site mixing.

[0048] In addition, the concrete composition of this embodiment can be applied to any structure in which part or all of the structure is formed by the concrete composition, such as reinforced concrete structures, steel-concrete composite structures, steel-reinforced concrete composite structures, and unreinforced concrete structures. [Examples]

[0049] [Manufacturing of carbonated steelmaking slag] The present invention will be specifically described below with reference to examples. First, the manufacturing process of carbonated steelmaking slag according to this embodiment will be described. Table 1 shows the mineral composition of the steelmaking slag targeted for carbonation. Note that this steelmaking slag is the same as that used in the formulation in the example test. Other steelmaking slags containing calcium composition can also be similarly carbonated, providing alkaline stimulation to blast furnace slag powder and fixing CO2. The steelmaking slag is a fine powder (in this example, with a particle size of 75 μm or less (specific surface area of ​​4110 cm²)). 2 Carbonation was performed on fine aggregate (85% or more passing through a 5mm sieve) and coarse aggregate (85% or more remaining on a 5mm sieve). Water was added to each steelmaking slag beforehand, spread on a stainless steel pad, and placed in an environment of 20°C, 60RH%, and 5% CO2 concentration to start carbonation. Carbonation was carried out for 14 days, with three removals and water added each time. Removal was performed approximately once every 3-4 days. The amount of water added in the pre-carbonation stage and during the intermediate stage was as follows for fine powder, fine aggregate, and coarse aggregate, respectively. Fine powder: When the powder mass of steelmaking slag fine powder is P and the mass of water is W, water was added so that W / P = 20%. Here, W / P = 20% is a guideline, and W / P = 10-30% or even more is acceptable. Fine aggregate and coarse aggregate: Water was added to achieve a surface moisture content of approximately 1-6%. The surface moisture content was calculated using the following formula (A). The duration of carbonation is inversely proportional to the CO2 concentration. Carbonation is easier at higher CO2 concentrations, but even at low CO2 concentrations comparable to atmospheric concentrations, carbonation is possible by ensuring a sufficiently long treatment period. The amount and timing of water supply should be set in the same manner as described above. The amount of CO2 fixed after carbonation was evaluated by measuring the weight of calcium carbonate calculated from the amount of CO2 desorbed, as shown in Table 2, using thermogravimetric-differential thermal analysis (TG-DTA analysis).

[0050] Surface moisture content = (((Mass of aggregate in wet state) - (Surface-dry mass of aggregate)) / (Surface-dry mass of aggregate)) × 100 ... (A)

[0051] [Table 1]

[0052] [Table 2]

[0053] [Evaluation results of concrete composition] Concrete compositions No. 1 to No. 8 shown in Table 3 were produced by mixing blast furnace slag powder, carbonated steelmaking slag powder, water, admixtures, and aggregates in predetermined proportions at an ambient temperature of 20°C. The blast furnace slag powder had a surface area of ​​4110 cm². 2 The sample used was one containing 1g of steelmaking slag. The steelmaking slag fine powder had a surface area of ​​4110 cm². 2 The composition used was one that was equal to / g. Compositions No. 1 to 6 are the concrete compositions of the present invention, while No. 7 and No. 8 are concrete compositions of ordinary concrete (prior art) that use ordinary Portland cement as a binder. Compositions No. 1, 3, 5, and 7 have a relatively large amount of powder (materials that contribute to hardening), while No. 2, 4, 6, and 8 have a relatively small amount of powder. For carbonated steelmaking slag, only powder is used in No. 1 and 2, powder and fine aggregate are used in No. 3 and 4, and powder, fine aggregate and coarse aggregate are used in No. 5 and 6. Specific examples of cement, blast furnace slag fine powder, steelmaking slag fine powder, water, admixtures, and aggregates are shown in Table 4.

[0054] The obtained concrete composition was cured by sealing at a temperature of 20°C under 60% RH. The compressive strength of the hardened concrete was evaluated after 28 days. The strength measurement method was as described above. The results are shown in Table 3.

[0055] Furthermore, the slump (SL (cm)) and air entrainment (Air (%)) were measured for the concrete composition immediately after mixing. In addition, the temperature (CT (°C)) of the concrete immediately after preparation was measured. Furthermore, the amount of bleeding was measured. In addition, the CO2 emissions for each mix design in the examples were calculated.

[0056] The slump (SL (cm)) was measured according to JIS A 1101:2020, the slump test method for concrete. The amount of air entrained (Air (%)) was measured according to JIS A 1128:2019, the pressure test method for air content in fresh concrete. Furthermore, the concrete temperature (CT (°C)) was measured according to JIS A 1156:2014, the method for measuring the temperature of fresh concrete. In addition, the amount of bleeding was measured according to JIS A 1123:2012, the bleeding test method for concrete. The results are shown in Table 3.

[0057] Table 3 also shows the CO2 emissions during the manufacturing of each concrete composition. The CO2 intensity for cement is based on the cement variety inventory data list in "Overview of Cement LCI Data," published on April 1, 2024, by the Japan Cement Association. The CO2 intensity for blast furnace slag powder and aggregate is based on the Japan Concrete Institute's Research Committee Report on Environmental Impact Assessment of Cement and Concrete, published in September 2024. Since the CO2 intensity for carbonated steelmaking slag powder is not defined, it was assumed to be the same as for blast furnace slag powder, 40.21 kg-CO2 / t, and then the CO2 fixation amount (average value) shown in Table 4 was subtracted. Similarly, since the CO2 intensity for carbonated steelmaking slag fine aggregate and coarse aggregate is not defined, it was set as shown in Table 4, using the same approach as for fine aggregate. Using the CO2 intensity set as described above, the CO2 emissions during the production of each concrete composition were calculated using the following formula (B).

[0058] CO2 emissions (kg / m 3) = {755.5 × cement mix ratio (kg / m 3 ) + 40.21 × amount of steelmaking slag powder (kg / m 3 ) + 40.21 × amount of blast furnace slag fine powder added (kg / m³ 3 )-75.49 × Carbonated steel slag powder blending amount (kg / m 3 )+7.09×fine aggregate content (kg / m 3 )+7.09×coarse aggregate content (kg / m 3 )-34.01 × Carbonated steel slag fine aggregate content (kg / m 3}-3.11 × Carbonated steel slag coarse aggregate content (kg / m 3 ) / 1000 …(B)

[0059] [Table 3]

[0060] [Table 4]

[0061] As shown in Table 3, the concrete composition of the present invention has a lower CO2 emission (kg / m³) compared to a comparative example with the same amount of powder. 3 The amount of ) has been reduced to less than one-tenth, making it an environmentally friendly material. Although the compressive strength of the concrete compositions of the present invention is lower than that of the conventional technology (No. 7 and 8), all except No. 2 exhibit strength that can be widely used for structural materials. Furthermore, even No. 2 can be used, for example, as concrete inside the embankment of a gravity dam structure by appropriate design. In addition, the concrete compositions of the present invention do not show abnormal values ​​in terms of fluidity, air content, and temperature compared to the comparative examples. Regarding the amount of bleeding, No. 2 showed a larger amount compared to the other examples. This is thought to be related to the lower compressive strength resulting from the lower amount of hydration products produced, and therefore, more water became free water compared to the other cases, resulting in a larger amount of bleeding. However, as mentioned above, this excess bleeding water is within the range that can be removed during construction, and measures can be taken to minimize its adverse effects on performance.

[0062] Based on these results, it was found that the concrete composition of the present invention can reduce CO2 emissions and exhibit excellent performance.

Claims

1. A binder containing blast furnace slag fine powder and carbonated steelmaking slag powder, Water and, Fine aggregate and coarse aggregate, A concrete composition containing, The concrete composition is characterized in that the carbonated steel slag powder contains calcium carbonate.

2. The specific surface area of ​​the aforementioned blast furnace slag fine powder is 3,000 to 10,000 cm². ２ / g, The concrete composition according to claim 1, satisfying the following formula (i). 20.0≦W / (GGBFS+CGGSS)×100≦65.0...(i) However, in formula (i), GGBFS is the mass of the blast furnace slag powder (kg), CGGSS is the mass of the carbonated steelmaking slag powder (kg), and W is the mass of the water (kg).

3. The concrete composition according to claim 1, further comprising an admixture, wherein the admixture is a chemical admixture comprising one or more of ligninsulfonates, ligninsulfonic acids, oxycarboxylates, oxycarboxylic acids, polycarboxylates, polycarboxylic acids, or silicophiles.

4. The concrete composition according to claim 1, characterized in that the particle size of the carbonated steel slag powder is 600 μm or less.

5. The concrete composition according to claim 1, characterized in that a portion or all of the fine aggregate contained in the concrete composition is carbonated steel slag.

6. The concrete composition according to claim 5, characterized in that a portion or all of the coarse aggregate contained in the concrete composition is carbonated steelmaking slag.

7. The total amount of blast furnace slag fine powder and carbonated steelmaking slag powder in the concrete composition is 1 m of the concrete composition. ３ The concrete composition according to claim 1, characterized in that it weighs 350 kg or more per unit.

8. A method for producing a concrete composition, characterized by mixing and producing the concrete composition described in any one of claims 1 to 7 at a construction site.

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