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 employed that comprises either cement or slaked lime, or both, blast furnace slag fine powder, steelmaking slag fine powder, water, fine aggregate and coarse aggregate, characterized in that the steelmaking slag fine powder contains a calcium composition.

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 solid for underwater immersion described in Patent Document 1 is used for marine applications. Further, the hydrated solid described in Patent Document 2 is an invention in which steelmaking slag powder is used as an aggregate to obtain a hydrated solid with excellent durability, and no consideration is given from the viewpoint of reducing CO2 emissions. Therefore, Patent Documents 1 and 2 do not mention anything about reducing the CO2 emissions of the concrete composition, and there is still room for improving the reduction of CO2 emissions.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a concrete composition capable of reducing CO2 emissions and a method for producing the same.

Means for Solving the Problems

[0009] To solve the above problems, the present invention employs the following configuration. (1) A binder containing either or both of cement and slaked lime, blast furnace slag fine powder, and steelmaking slag fine powder, water, fine aggregate and coarse aggregate, and a concrete composition comprising: A concrete composition characterized in that the steelmaking slag fine powder contains a calcium composition. (2) The specific surface area of the blast furnace slag fine powder is 3000 to 10000 cm 2 / g, The concrete composition according to (1), which satisfies the following formula (i). 20.0 ≦ W / (C + CH + GGBFS + GGSS) × 100 ≦ 65.0 ···(i) However, in formula (i), C is the mass (kg) of the cement, CH is the mass (kg) of the slaked lime, GGBFS is the mass (kg) of the granulated blast furnace slag fine powder, GGSS is the mass (kg) of the steelmaking slag fine powder, and W is the mass (kg) of the water. (3) Furthermore, it contains an admixture, and the admixture is an admixture in which any one or more of lignin sulfonate, lignin sulfonic acid, oxycarboxylate, oxycarboxylic acid, polycarboxylate, polycarboxylic acid or silicofluoride are used in combination. The concrete composition according to (1). (4) The specific surface area of the steelmaking slag fine powder is 4000 cm 2 / g or more, and the concrete composition according to (1) is characterized by this. (5) A part or all of the steelmaking slag fine powder contained in the concrete composition is carbonated steelmaking slag, and the concrete composition according to (1) is characterized by this. (6) A part or all of the fine aggregate contained in the concrete composition is carbonated steelmaking slag fine aggregate, and the concrete composition according to (1) is characterized by this. (7) A part or all of the coarse aggregate contained in the concrete composition is carbonated steelmaking slag coarse aggregate, and the concrete composition according to (6) is characterized by this. (8) The binder further contains carbonated steelmaking slag powder, and the carbonated steelmaking slag powder contains calcium carbonate, and the concrete composition according to (2) is characterized by this. (9) The particle size of the carbonated steelmaking slag powder is 600 μm or less, and the concrete composition according to (8) is characterized by this. (10) The total amount of cement, slaked lime, blast furnace slag powder, steelmaking slag powder, and carbonated steelmaking slag powder in the concrete composition is 3 The concrete composition according to (9), characterized in that it weighs 350 kg or more per unit. (11) A method for producing a concrete composition, characterized by mixing and manufacturing a concrete composition described in any one of items (1) to (10) at a construction site. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a concrete composition that can reduce CO2 emissions and a method for producing the same. [Modes 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 found that by using blast furnace slag powder and steelmaking slag powder in addition to cement and slaked lime, it is possible to reduce the amount of cement used and thus reduce CO2 emissions.

[0013] The inventors have further discovered that by using blast furnace slag powder and steelmaking slag powder as binders, calcium compounds contained in the 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 either cement or slaked lime, blast furnace slag fine powder and steelmaking slag fine powder, water, fine aggregate and coarse aggregate, characterized in that the steelmaking slag fine powder contains a calcium composition. In the following explanation, cement, slaked lime, blast furnace slag powder, and 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] The cement is preferably one of the following: ordinary Portland cement, ultra-rapid-strength Portland cement, rapid-strength Portland cement, moderate-heat Portland cement, or low-heat Portland cement. By mixing cement or slaked lime into the concrete composition, alkali is leached from the cement or slaked lime. The leached alkali stimulates the blast furnace slag fine powder, which is a glassy hydraulic material, and promotes hardening. This allows the concrete to exhibit the desired strength. Alternatively, a blended cement such as blast furnace cement or fly ash cement may be used as the cement. In addition, quicklime may be used instead of cement or slaked lime.

[0016] 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.

[0017] In this embodiment, blast furnace slag fine powder is used, with a specific surface area of ​​3000 cm². 2 / g or more, 10000cm 2It 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.

[0018] Steelmaking slag fine powder can be exemplified by the pulverization of 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.

[0019] Steelmaking slag fine powder contains one or more of the following substances: free lime, calcium hydroxide, calcium ferrite, calcium silicate, and dicalcium silicate. By incorporating such steelmaking slag fine powder into a concrete composition, the calcium compounds contained in the steelmaking slag fine powder dissolve into the water as alkaline components. These dissolved alkaline components stimulate the glassy properties of the blast furnace slag fine powder, allowing it to exhibit its hydraulic properties. This makes it possible to form concrete that is suitable for the intended application and has excellent environmental friendliness.

[0020] In this embodiment, the steelmaking slag fine powder has a specific surface area of ​​3000 cm². 2 / g or more, 10000cm 3 It is preferable to use a specific surface area within 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 the fluidity necessary for construction can be maintained. If the specific surface area is above the lower limit, the hardening reaction of the concrete will proceed at a moderate pace, the hardening time to reach the desired hardness will not be prolonged, and the appropriate fluidity for construction will be exhibited.

[0021] Furthermore, in this embodiment, a portion of the steelmaking slag fine powder may be replaced with carbonated steelmaking slag powder. By including carbonated steelmaking slag powder, calcium carbonate can be leached out as an alkaline component from the carbonated steelmaking slag powder during mixing with water and blast furnace slag fine powder, and the leached alkaline component can further promote the hydration reaction. Moreover, by replacing the steelmaking slag fine powder contained in the binder (cement, slaked lime, blast furnace slag fine powder, and steelmaking slag fine powder) in the concrete composition with carbonated steelmaking slag powder, CO2 emissions can be further reduced.

[0022] Carbonated steelmaking slag powder refers to steelmaking slag powder in which CO2 has been immobilized by reacting some or all of the calcium composition in the fine powder of steelmaking slag with CO2. It is presumed that the CO2 is fixed in the steelmaking slag in the form of calcium carbonate. The CO2 content of carbonated steelmaking slag powder is not particularly limited, but it is sufficient if the amount of CO2 desorption detected in the 600°C to 800°C range when heated at 20°C / min using thermogravimetric analysis-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 steel mill.

[0023] 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.

[0024] The water used is not particularly limited; tap water, supernatant water produced during concrete mixing, and sludge water can 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.

[0025] Coarse aggregates and fine aggregates can use all kinds of aggregates, such as natural aggregates like mountain sand, land sand, sea sand, mountain sand gravel, land sand gravel, river sand gravel, artificial aggregates like crushed stone, crushed sand, lightweight aggregates, aggregates processed from waste concrete, recycled aggregates like slag aggregates, etc.

[0026] Coarse aggregates and fine aggregates can be distinguished by particle size. For example, those with a particle size of 5 mm or more can be used as coarse aggregates, those with a particle size of less than 5 mm and more than 75 μm can be used as fine aggregates, and those with a particle size of 75 μm or less can be used as fine powder.

[0027] Furthermore, in this embodiment, part or all of the coarse aggregates may contain carbonated steel slag. By using carbonated steel slag for the coarse aggregates, the CO2 emissions can be further reduced. The carbonated steel slag used for the coarse aggregates only needs to have a particle size of 5 mm or more. Furthermore, similarly for the fine aggregates, part or all of them may contain carbonated steel slag. By using carbonated steel slag for the fine aggregates, not only can the CO2 emissions be further reduced, but also the hydration reaction during the mixing with water and blast furnace slag fine powder can be further promoted. The carbonated steel slag used for the fine aggregates only needs to have a particle size of less than 5 mm and more than 75 μm.

[0028] The blending amount of the fine aggregates in the concrete composition according to this embodiment is preferably 300 kg or more and 1500 kg or less per 1 m 3 of the concrete composition. When the amount of the fine aggregates is 300 kg or more per 1 m 3 of the concrete composition, the concrete after hardening can have more appropriate strength as a on-site structure. Also, when the amount of the fine aggregates is 1500 kg or less per 1 m 3 of the concrete composition, the fluidity of the concrete composition is ensured, and it becomes easier to fill without gaps during placement.

[0029] The blending amount of the fine aggregates in the concrete composition according to this embodiment is preferably 500 kg or more and 2000 kg or less per 1 m 3 of the concrete composition. When the amount of the coarse aggregates is...3 Having an aggregate weight of 500 kg or more per cubic meter of concrete composition allows the hardened concrete to have more appropriate strength for use as a site structure. 3 By keeping the weight below 2000 kg per square meter, the fluidity of the concrete composition is ensured, making it easier to fill gaps without creating voids during placement.

[0030] In the concrete composition of this embodiment, the proportion of water is preferably such that it satisfies the following formula (i) with respect to the amount of binder (total amount of cement, slaked lime, blast furnace slag powder, and steelmaking slag powder).

[0031] 20.0≦W / (C+CH+GGBFS+GGSS)×100≦65.0 (i)

[0032] However, in equation (i), C is the mass of cement (kg), CH is the mass of slaked lime (kg), GGBFS is the mass of blast furnace slag powder (kg), GGSS is the mass of steelmaking slag powder (kg), and W is the mass of the water (kg).

[0033] When W / (C+CH+GGBFS+GGSS)×100 is 20 or more, that is, when the ratio of water to the total amount of binder is 20% or more, the moisture 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 / (C+CH+GGBFS+GGSS)×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 steelmaking slag fine powder is replaced with carbonated steelmaking slag powder, GGSS in formula (i) may be the total amount of steelmaking slag fine powder and carbonated steelmaking slag powder.

[0034] The proportion of steelmaking slag powder in the binder of the concrete composition (total amount of cement, slaked lime, blast furnace slag powder, and steelmaking slag powder) preferably satisfies the following formula (ii).

[0035] 5≦GGSS / (C+CH+GGBFS+GGSS)×100≦50 (ii)

[0036] If GGSS / (C+CH+GGBFS+GGSS)×100 is 5 or more, that is, if the proportion of steelmaking slag powder in the binder is 5% or more, appropriate strength can be obtained due to the calcium ions leached from the steelmaking slag powder. If GGSS / (C+CH+GGBFS+GGSS)×100 is 50 or less, that is, if the proportion of steelmaking slag powder in the binder is 50% or less, the amount of steelmaking 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 GGSS / (C+CH+GGBFS+GGSS)×100 may be between 7 and 40, or between 9 and 30. Furthermore, if a portion of the steelmaking slag fine powder is replaced with carbonated steelmaking slag powder, GGSS in formula (ii) may be the total amount of steelmaking slag fine powder and carbonated steelmaking slag powder.

[0037] The proportions of cement and slaked lime in the binder (total amount of cement, slaked lime, blast furnace slag powder, and steelmaking slag powder) in the concrete composition preferably satisfy the following formula (iii).

[0038] 3≦(C+CH) / (C+CH+GGBFS+GGSS)×100≦25 (iii)

[0039] If (C+CH) / (C+CH+GGBFS+GGSS)×100 is 3 or more, that is, if the proportion of cement and slaked lime in the binder is 3% or more, then appropriate strength can be obtained by the alkali leaching from the cement and slaked lime. If (C+CH) / (C+CH+GGBFS+GGSS)×100 is 25 or less, that is, if the proportion of cement and slaked lime in the binder is 25% or less, then the amount of cement and slaked lime is appropriate, and CO2 emissions can be significantly reduced compared to conventional technology. Note that (C+CH) / (C+CH+GGBFS+GGSS)×100 may be between 5 and 20, or between 7 and 15. Furthermore, if a portion of the steelmaking slag fine powder is replaced with carbonated steelmaking slag powder, GGSS in formula (iii) may be the total amount of steelmaking slag fine powder and carbonated steelmaking slag powder.

[0040] Also, 1 m of concrete composition 3 The amount of binder per unit (total amount of cement, slaked lime, blast furnace slag powder, and 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 steelmaking slag fine powder is replaced with carbonated steelmaking slag powder, the amount of carbonated steelmaking slag powder may be included in the amount of binder. Furthermore, the binder in the concrete composition of this embodiment may also contain quicklime or other calcium compositions. The inclusion of these further enhances the alkaline stimulation of the blast furnace slag fine powder, thereby activating the hydration reaction.

[0041] 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. By keeping the value below this threshold, the amount of water contained in the concrete becomes appropriate, allowing it to exhibit the appropriate strength as a site structure.

[0042] 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 composition. Furthermore, the admixtures may be formulated for the purpose of reducing the amount of water while maintaining fluidity.

[0043] 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.

[0044] The mixing ratio of admixtures to the amount of binder in concrete (cement, slaked lime, blast furnace slag powder, and steelmaking slag powder) preferably satisfies the following formula (iv).

[0045] 0≦SP / (C+CH+GGBFS+GGSS)×100≦5 …(iv)

[0046] In equation (iv), SP is the mass (kg) of the admixture.

[0047] SP / (C+CH+GGBFS+GGSS)×100 may be 0, but it may be 0.1 or more 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 steelmaking slag fine powder is 0.1% or more, 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 / (C+CH+GGBFS+GGSS)×100 exceeds 5, that is, if the mixing ratio of the admixture to the total amount of blast furnace slag fine powder and steelmaking slag fine powder exceeds 5%, the effect of adding the admixture becomes saturated. The range of SP / (C+CH+GGBFS+GGSS)×100 may be 0.1 or more, or 0.2 or more and 4 or less, or 0.5 or more and 3 or less, or 1 or more and 2 or less. Furthermore, if a portion of the steelmaking slag fine powder is replaced with carbonated steelmaking slag powder, GGSS may be the total amount of steelmaking slag fine powder and carbonated steelmaking slag powder.

[0048] 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.

[0049] The concrete composition used in this embodiment is preferably expected to exhibit the following properties.

[0050] [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 required strength is as above. If it is lower than this, the foundation structure will not be able to maintain adequate strength. 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 as follows, 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.

[0051] [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.

[0052] 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 is acceptable.

[0053] As described above, the concrete composition of this embodiment contains blast furnace slag fine powder and steelmaking slag fine powder. Therefore, the amount of material used that emits a large amount of CO2 during the manufacturing process can be reduced, and CO2 emissions can be kept low. In addition, the strength of the concrete after hardening can be controlled by the amount of binder added, and a concrete composition that can exhibit the necessary performance depending on the application can be obtained.

[0054] According to the concrete composition of this embodiment, by using a chemical admixture in which one or more of polycarboxylic acids, polycarboxylic acid salts, ligninsulfonic acid, ligninsulfonate salts, oxycarboxylic acids, oxycarboxylic acid salts, or silicogenic compounds are used in combination as admixtures, particularly effective performance can be achieved in terms of fluidity and strength.

[0055] Furthermore, according to the concrete composition of this embodiment, by mixing and blending the concrete composition at the construction site, it is possible to blend 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 manufacturing 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.

[0056] Furthermore, 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]

[0057] [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 and the CO2 concentration are inversely proportional. 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 using thermogravimetric-differential thermal analysis (TG-DTA analysis), as shown in Table 2.

[0058] Surface moisture content = (((Mass of aggregate in wet state) - (Surface-dry mass of aggregate)) / (Surface-dry mass of aggregate)) × 100 ... (A)

[0059] [Table 1]

[0060] [Table 2]

[0061] [Evaluation results of concrete composition] Concrete compositions No. 1 to No. 7 shown in Table 3 were produced by mixing cement, slaked lime, blast furnace slag powder, steelmaking slag powder, carbonated steelmaking slag powder, water, admixtures, and aggregate in predetermined mixing ratios 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. 2The composition used was one with a concentration of / g. Note that Nos. 1-4 and 7 are concrete compositions of the present invention, while Nos. 5 and 6 are concrete compositions of ordinary concrete (prior art) using ordinary Portland cement as a binder. Nos. 1, 3, 5, and 7 have a relatively high amount of powder (materials contributing to hardening), while Nos. 2, 4, and 6 have a relatively low amount of powder. Regarding steelmaking slag, Nos. 1 and 2 use finely powdered steelmaking slag, while Nos. 3 and 4 use carbonated steelmaking slag fine aggregate as part of the fine aggregate in Nos. 1 and 2. No. 7 uses both finely powdered steelmaking slag and carbonated steelmaking slag powder. Specific examples of cement, blast furnace slag powder, steelmaking slag powder, water, admixtures, and aggregates are shown in Table 4.

[0062] The obtained concrete composition was cured by sealing and curing at a temperature of 20°C under 60% RH. The compressive strength (σ) of the hardened concrete after 28 days was measured. c 28d) was evaluated. The method for measuring intensity was as described above. The results are shown in Table 3.

[0063] 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.

[0064] 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.

[0065] 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).

[0066] CO2 emissions (kg / m 3 ) = {755.5 × cement mix ratio (kg / m 3 )+755.5×slaked lime content (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)

[0067] [Table 3]

[0068] [Table 4]

[0069] As shown in Table 1, the concrete composition of the present invention has a CO2 emission (kg / m³). 3 ) is 100 (kg / m 3 The amount has been reduced to below ), making it an environmentally friendly material. Although the compressive strength of the concrete composition of the present invention tends to be lower than that of the conventional technology (No. 5, 6), all are 18 N / mm². 2 As described above, the concrete composition exhibits strength that allows it to be widely used in structural materials. Furthermore, the concrete composition of the present invention does not show abnormal values ​​in terms of fluidity, air content, and temperature compared to the comparative examples. The amount of bleeding is also kept low in all examples and is equivalent to that of the prior art.

[0070] Based on these results, it was found that the concrete composition of the present invention can reduce CO2 emissions and exhibit excellent performance.

[0071] Steelmaking slag fine powder is produced by finely grinding steelmaking slag of any particle size. Fine grinding can be carried out using industrial methods such as ball mills, roller mills, vibratory mills, planetary mills, and jet mills.

Claims

1. A binder containing either cement or slaked lime, or both, blast furnace slag powder and steelmaking slag powder, Water and, Fine aggregate and coarse aggregate, A concrete composition containing, A concrete composition characterized in that the steelmaking slag fine powder contains a calcium composition.

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 / (C+CH+GGBFS+GGSS)×100≦65.0...(i) However, in formula (i), C is the mass of the cement (kg), CH is the mass of the slaked lime (kg), GGBFS is the mass of the blast furnace slag powder (kg), GGSS is the mass of the 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 an admixture obtained by combining one or more of the following: lignin sulfonate, lignin sulfonic acid, oxycarboxylate, oxycarboxylic acid, polycarboxylate, polycarboxylic acid, or silicophilic acid.

4. The specific surface area of ​​the aforementioned steelmaking slag fine powder is 4000 cm². ２ The concrete composition according to claim 1, characterized in that it is 1 / g or more.

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

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

7. The concrete composition according to claim 6, characterized in that part or all of the coarse aggregate contained in the concrete composition is carbonated steel slag.

8. The concrete composition according to claim 2, further comprising carbonated steel slag powder in the binder, wherein the carbonated steel slag powder contains calcium carbonate.

9. The concrete composition according to claim 8, characterized in that the particle size of the carbonated steel slag powder is 600 μm or less.

10. The total amount of cement, slaked lime, blast furnace slag powder, steelmaking slag powder, and carbonated steelmaking slag powder in the concrete composition is ３ The concrete composition according to claim 9, characterized in that it is 350 kg or more per unit.

11. A method for producing a concrete composition, characterized by mixing and manufacturing the concrete composition described in any one of claims 1 to 10 at a construction site.

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