Cement composition, method of producing cement composition, and method of absorbing / fixing co2
The cement composition, featuring cement, aggregate, clinker ash, and water with controlled moisture content, addresses the challenge of maintaining compressive strength while absorbing and fixing CO2, achieving effective CO2 fixation and moldability.
Patent Information
- Application Number
- JP2023182329
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-10-24
- Publication Date
- 2025-05-09
AI Technical Summary
Increasing the water-cement ratio (W/C) of concrete or mortar to enhance CO2 absorption and fixation leads to a decrease in compressive strength, limiting its practical application.
A cement composition comprising cement, aggregate, clinker ash, and water, with a moisture content of clinker ash at 21.2% or less, is developed to absorb and fix CO2 while maintaining the compressive strength of concrete or mortar.
The cement composition effectively absorbs and fixes CO2, suppressing the decrease in compressive strength of concrete or mortar, and exhibits excellent moldability despite the fixed CO2 amount.
Smart Images
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Abstract
Description
[Technical field]
[0001] The present invention relates to a cement composition, a method for producing the cement composition, and a method for producing the cement composition. 2 This relates to absorption and fixation methods. [Background technology]
[0002] The production of cement uses large amounts of carbon dioxide (CO 2 ) is emitted. 2 In light of the current situation regarding emission reduction, concrete or mortar may be directly or indirectly 2 Technology has been developed to absorb and fix CO in concrete or mortar. 2 By absorbing and fixing the CO generated during cement production, 2 is indirectly captured, and the CO in the cement manufacturing and use process is 2 The total emissions will be reduced.
[0003] Non-Patent Document 1 discloses that increasing the water-cement ratio (W / C) of concrete or mortar increases the carbonation depth of concrete or mortar. In general, as the carbonation depth of concrete or mortar increases, the carbonation of the entire concrete or mortar 2 It is known that the amount of fixation increases. [Prior art documents] [Non-patent literature]
[0004] [Non-Patent Document 1] Factors affecting the rate of carbonation of concrete, Proceedings of the Japan Society of Civil Engineers, No. 451, Vol. 17, pp. 119-128, August 1992 (Taketo Uomoto, Yoshiaki Takada) Summary of the Invention [Problem to be solved by the invention]
[0005] However, as the W / C ratio increases, the compressive strength of the concrete or mortar decreases, limiting the applications of such concrete or mortar.
[0006] The present invention has been made in view of the above circumstances, 2 While absorbing and fixing CO 2 Cement composition that suppresses the decrease in compressive strength of concrete or mortar in proportion to the amount of fixation, its manufacturing method, and CO 2 The objective of the present invention is to provide an absorption and fixation method. [Means for solving the problem]
[0007] The cement composition according to the present invention is a cement composition comprising cement, aggregate, clinker ash, and water, The moisture content of the clinker ash is 21.2% or less.
[0008] The cement composition according to the present invention has the above-mentioned constitution. 2 While absorbing and fixing CO 2 Considering the amount of fixation, the decrease in compressive strength of concrete or mortar is suppressed.
[0009] In the cement composition according to the present invention, the water content of the clinker ash may be 5.0% or more and 21.2% or less.
[0010] The cement composition according to the present invention has such a constitution that it is more effective in preventing CO 2 While absorbing and fixing CO 2 Considering the amount of fixation, the decrease in compressive strength of concrete or mortar is suppressed.
[0011] The cement composition according to the present invention has a mixing amount of the water of 138 kg / m 3 More than 190kg / m 3 It may be the following.
[0012] The cement composition according to the present invention has such a constitution that it is more effective in preventing CO2 While absorbing and fixing CO 2 Considering the amount of fixation, the decrease in compressive strength of concrete or mortar is suppressed, and further, the moldability is excellent.
[0013] In the cement composition according to the present invention, the amount of the clinker ash mixed may be 15 mass % or more and 60 mass % or less relative to the amount of the cement mixed.
[0014] The cement composition according to the present invention has such a constitution that it is more effective in preventing CO 2 While absorbing and fixing CO 2 Considering the amount of fixation, the decrease in compressive strength of concrete or mortar is suppressed.
[0015] The cement composition according to the present invention may have a water-cement ratio (W / C) of the cement to the water of 50 mass % or more and 65 mass % or less.
[0016] The cement composition according to the present invention has such a constitution that it is more effective in preventing CO 2 While absorbing and fixing CO 2 Considering the amount of fixation, the decrease in compressive strength of concrete or mortar is suppressed.
[0017] The method for producing a cement composition according to the present invention is a method for producing a cement composition by mixing cement, aggregate, clinker ash, and water, The moisture content of the clinker ash before mixing is 21.2% or less.
[0018] The method for producing a cement composition according to the present invention has the above-mentioned constitution. 2 While absorbing and fixing CO 2 It is possible to obtain a cement composition which, relative to the amount of the binder, suppresses the decrease in compressive strength of concrete or mortar.
[0019] CO according to the present invention 2 The absorption and fixation method is CO 2 An absorption and fixation method comprising the steps of: CO2 CO used in absorption and fixation methods 2 The absorbing and immobilizing material is a cement composition obtained by mixing cement, aggregate, clinker ash, and water, The moisture content of the clinker ash before mixing is 21.2% or less.
[0020] CO according to the present invention 2 The absorption and fixation method is as follows: 2 While absorbing and fixing CO 2 Considering the amount of fixation, the decrease in compressive strength of concrete or mortar is suppressed. Effect of the Invention
[0021] According to the present invention, CO 2 A cement composition capable of absorbing and fixing CO while suppressing a decrease in the compressive strength of concrete or mortar, a method for producing the same, and 2 It is possible to provide an absorption fixation method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The cement composition according to this embodiment, the method for producing the cement composition, and CO 2 The absorption and fixation method will be explained.
[0023] <Cement composition> The cement composition according to this embodiment contains cement, aggregate, clinker ash, and water.
[0024] The cement is not particularly limited, and for example, Portland cement such as ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, moderate-heat Portland cement, sulfate-resistant Portland cement, and white Portland cement as specified in JIS R 5210:2019; mixed cement such as blast furnace cement, fly ash cement, and silica cement; ultra-fast-hardening cement, alumina cement, and other known cements can be used. Note that one type of cement may be used alone, or two or more types may be used in combination.
[0025] The amount of the cement blended is, for example, a unit amount (kg / m 3 : Cement composition 1m 3 Mass per unit: 250 kg / m 3 More than 400kg / m 3 In addition, when two or more types of cement are contained, the above blending amount is the total blending amount of the cements.
[0026] Fine aggregate and / or coarse aggregate can be used as aggregate. Fine aggregate refers to aggregate that passes entirely through a 10 mm mesh sieve and 85% or more of its mass passes through a 5 mm mesh sieve, and coarse aggregate refers to aggregate that is retained by 85% or more of its mass on a 5 mm mesh sieve (JIS A 0203:2019).
[0027] Examples of fine aggregates include river sand, land sand, mountain sand, sea sand, crushed sand, limestone crushed sand, and other natural sands as specified in JIS A 5308:2019 Appendix A Aggregates for Ready-Mixed Concrete, and blast furnace slag. Silica sand produced by crushing and classifying silica may also be used. Note that one type of fine aggregate may be used alone, or two or more types may be used in combination.
[0028] The amount of the fine aggregate to be mixed is, for example, unit amount (kg / m 3 : Cement composition 1m 3 Mass per unit, 600 kg / m 3 More than 900kg / m 3 In addition, when two or more types of fine aggregate are contained, the above blending amount is the total blending amount of the fine aggregate.
[0029] Examples of coarse aggregates include natural aggregates such as river gravel, mountain gravel, and sea gravel, as specified in JIS A 5308:2019 Appendix A Aggregates for Ready-Mixed Concrete, artificial aggregates such as crushed stone such as sandstone, hard limestone, basalt, andesite, and recycled aggregates. Note that one type of coarse aggregate may be used alone, or two or more types may be used in combination.
[0030] The amount of the coarse aggregate mixed is, for example, a unit amount (kg / m 3 : Cement composition 1m 3 Mass per unit: 850 kg / m 3 More than 1100kg / m 3 When two or more types of coarse aggregate are contained, the above blending amount is the total blending amount of the coarse aggregate.
[0031] Clinker ash is a porous ash obtained by dehydrating and crushing the lumps of coal ash particles generated by burning coal inside a boiler that accumulate in a water tank at the bottom of the boiler into a sand-like mass. Clinker ash is easy to obtain because it is an industrial waste product discharged from coal-fired power plants, etc.
[0032] The moisture content of the clinker ash is calculated from the following formula (1). Moisture content (%) = 100 x (mass of moisture in clinker ash) / (mass of bone dry clinker ash) (1)
[0033] The moisture content of the clinker ash is 2 While absorbing and fixing CO 2 From the viewpoint of suppressing the decrease in the compressive strength of concrete or mortar relative to the fixed amount, the water content of the clinker ash is 21.2% or less, preferably 19.7% or less, and more preferably 15.0% or less. 2 While absorbing and fixing CO 2 From the viewpoint of suppressing the decrease in the compressive strength of concrete or mortar relative to the fixed amount, the water content is preferably 3.0% or more, and more preferably 5.0% or more. Note that the water content of the clinker ash refers to the water content before mixing in the production of the cement composition described below.
[0034] The amount of clinker ash blended is CO 2 While absorbing and fixing CO 2From the viewpoint that the decrease in compressive strength of concrete or mortar is suppressed relative to the fixed amount, the unit amount (kg / m 3 : Cement composition 1m 3 per unit mass), preferably 50 kg / m 3 More than 150kg / m 3 More preferably, it is 100 kg / m or less. 3 More than 150kg / m 3 In addition, when the clinker ash contains moisture, the blending amount of the clinker ash refers to the blending amount of the clinker ash including moisture.
[0035] The amount of clinker ash mixed is 2 While absorbing and fixing CO 2 From the viewpoint of suppressing a decrease in the compressive strength of concrete or mortar relative to the fixed amount, the amount of the clinker ash is preferably 15% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 50% by mass or less, relative to the amount of cement. Note that, in the case where the clinker ash contains moisture, the amount of the clinker ash refers to the amount of the clinker ash including moisture.
[0036] The water is not particularly limited, and may be, for example, tap water, industrial water, recycled water, groundwater, river water, rainwater, etc. It is preferable that the water does not contain organic matter, chloride ions, sodium ions, potassium ions, etc., which have adverse effects on the hydration reaction of the cement composition and concrete, or contains only trace amounts of them. It is more preferable that the water be tap water or industrial water of stable quality.
[0037] The amount of water blended is CO 2 While absorbing and fixing CO 2 From the viewpoint of suppressing the decrease in compressive strength of concrete or mortar relative to the fixed amount and obtaining a cement composition with excellent moldability, the unit amount (kg / m 3 : Cement composition 1m 3 per unit mass), preferably 138 kg / m 3More than 190kg / m 3 More preferably, 138 kg / m 3 More than 180kg / m 3 The following is the result.
[0038] The water-cement ratio (W / C) of the cement composition is CO 2 While absorbing and fixing CO 2 From the viewpoint of suppressing the decrease in compressive strength of concrete or mortar relative to the fixed amount, it is preferably 50 mass% or more, more preferably 55 mass% or more. From the same viewpoint, it is preferably 65 mass% or less, more preferably 60 mass% or less. The water-cement ratio is the mass percentage of water to cement.
[0039] The cement composition may contain an admixture. Examples of other admixtures include air-entraining agents, air-entraining water-reducing agents, high-performance water-reducing agents, high-performance air-entraining water-reducing agents, fluidizing agents, separation-reducing agents, setting retarders (e.g., tartaric acid, etc.), setting accelerators (e.g., aluminum sulfate, etc.), quick-setting agents, shrinkage-reducing agents, foaming agents, foaming agents, waterproofing agents, etc. The admixtures may be used alone or in combination of two or more.
[0040] The amount of the admixture may be 0.0005% by mass or more and 3.0% by mass or less with respect to the cement. When two or more kinds of admixtures are included, the amount is the total amount of the admixtures.
[0041] The cement composition may also contain an admixture. Examples of the admixture include inorganic fine powders such as fly ash, silica fume, cement kiln dust, blast furnace fume, ground granulated blast furnace slag, ground granulated blast furnace slag, ground granulated converter slag, hemihydrate gypsum, expanding agent, ground limestone, ground quicklime, and ground dolomite, and inorganic fillers such as sodium bentonite, calcium bentonite, attapulgite, sepiolite, activated clay, acid clay, allophane, imogolite, shirasu (volcanic ash), shirasu balloon, kaolinite, metakaolin (calcined clay), synthetic zeolite, artificial zeolite, artificial zeolite, mordenite, and clinoptilolite. The admixture may be used alone or in combination of two or more kinds.
[0042] <Method of manufacturing cement composition> Hereinafter, a method for producing the cement composition according to this embodiment will be described.
[0043] The method for producing the cement composition according to this embodiment involves mixing cement, aggregate, clinker ash, and water.
[0044] Prior to the mixing, the clinker ash may be dried in advance to adjust the moisture content of the clinker ash to the above-mentioned range. Examples of the drying method include drying in the sun, natural drying, drying with a dryer, etc.
[0045] The method of mixing is not particularly limited, and for example, the components can be mixed by a conventionally known method using a forced twin-shaft mixer, forced single-shaft mixer, tilting mixer, pan-type forced mixer, or the like.
[0046] The method for producing a cement composition according to the present embodiment is a method for producing a cement composition by mixing cement, aggregate, clinker ash, and water, and the water content of the clinker ash before mixing is 21.2% or less, so that the amount of CO 2 While absorbing and fixing CO 2It is possible to obtain a cement composition which, relative to the amount of the binder, suppresses the decrease in compressive strength of concrete or mortar.
[0047] <CO 2 Absorption fixation method> Hereinafter, the CO 2 The absorption and fixation method will be explained.
[0048] CO according to this embodiment 2 The absorption and fixation method is CO 2 The method for absorbing and fixing CO 2 CO used in absorption and fixation methods 2 The absorbing and immobilizing material is a cement composition obtained by mixing cement, aggregate, clinker ash, and water.
[0049] The water content of the clinker ash contained in the cement composition is as described above.
[0050] CO 2 The absorption and fixation method is 2 The method includes a casting process of casting the absorbent fixation material into a formwork, and a curing process of removing the material from the formwork and curing the material after casting.
[0051] In the casting step, 2 The absorbing and immobilizing material is poured into a mold and vibration molding is performed. The method of vibration molding is not particularly limited, and a conventionally known method can be used.
[0052] In the curing step, the hardened kneaded material is removed from the mold and cured outdoors, etc. The curing method is not particularly limited, and a conventionally known method can be used.
[0053] CO according to this embodiment 2 The absorption and fixation method is CO 2 The method for absorbing and fixing CO 2 CO used in absorption and fixation methods 2The absorption and immobilization material is a cement composition in which cement, aggregate, clinker ash, and water are mixed, and the water content of the clinker ash before mixing is 21.2% or less. 2 While absorbing and fixing CO 2 Considering the amount of fixation, the decrease in compressive strength of concrete or mortar is suppressed. EXAMPLES
[0054] Examples of the present invention will be described below, but the present invention is not limited to the following examples.
[0055] <Preparation of cement composition> Using the materials shown in Table 1 and according to the formulations shown in Table 2, cement compositions of each Example and Comparative Example were prepared.
[0056] Specifically, first, cement, clinker ash, and fine aggregate were dry-mixed for 15 seconds using a mixing mixer (a mechanical mixer specified in JIS R 5201), and then water and admixtures were added and mixed for 90 seconds to obtain a cement composition. Using the obtained cement composition, the following fluidity evaluation and test specimens were prepared.
[0057] [Table 1]
[0058] [Table 2]
[0059] <Preparation of test specimen> The cement compositions of each Example and Comparative Example were cast into a cylindrical formwork (φ50×100 mm) to prepare test specimens. The test specimens obtained were demolded the next day and cured under conditions of 20°C and 60% RH until the material age of 3 days. Thereafter, they were subjected to a 20°C, 60% RH, CO 2 The specimens were subjected to accelerated carbonation for 5 weeks at a concentration of 10%. The following compressive strength, carbonation depth, and CO2 The amount of fixation was evaluated.
[0060] <Compressive strength evaluation> The compressive strength of test specimens prepared from the cement compositions of each Example and Comparative Example and subjected to accelerated carbonation was measured in accordance with the method of JIS A 1108. The measured values are shown in Table 3.
[0061] <Evaluation of carbonation depth> The carbonation depth was measured for test specimens prepared from the cement compositions of each Example and Comparative Example and subjected to accelerated carbonation in accordance with a method in accordance with JIS A 1152. The measured values are shown in Table 3.
[0062] <CO 2 Evaluation of fixation amount> Test specimens prepared from the cement compositions of each of the Examples and Comparative Examples and subjected to accelerated carbonation were split. The entire surface of the split accelerated carbonation test specimen was pulverized, and the CO2 content was measured by simultaneous thermogravimetry and differential thermal analysis using a STA 2500 (TG-DTA simultaneous measurement device; manufactured by NETZSCH Japan). 2 The amount of immobilization was measured and the measured values are shown in Table 3.
[0063] [Table 3]
[0064] As can be seen from Table 3, the cement compositions of the Examples, by containing clinker ash, have a higher carbonation depth and CO2 reduction rate at the same level of compressive strength compared to the cement compositions of the Comparative Examples, which do not contain clinker ash. 2 From this, the cement compositions of the examples that satisfy all the constituent requirements of the present invention can be seen to have a fixed amount of CO 2 While absorbing and fixing CO 2 It was found that the decrease in compressive strength of concrete or mortar was suppressed in proportion to the amount of fixation.
[0065] <Moisture content and amount of clinker ash and CO 2 Relationship with fixed amount> From each Example and Comparative Example 1, the moisture content and blending amount of clinker ash and CO 2 The relationship with the fixed amount is shown in Table 4.
[0066] [Table 4]
[0067] Furthermore, Table 5 shows the relationship between the moisture content and blending amount of clinker ash and the compressive strength in each Example and Comparative Example 1 when W / C=60%.
[0068] [Table 5]
[0069] As can be seen from Table 4, when the moisture content of clinker ash is in the range of 5 to 15%, CO 2 The fixed amount tended to be high. Also, the clinker ash content was 50-150kg / m 3 Within the range of CO 2 The fixed amount tended to be high.
[0070] As can be seen from Table 5, the decrease in compressive strength was suppressed when the moisture content of the clinker ash was in the range of 5 to 15%. In addition, when the mixing ratio of the clinker ash was 50 to 150 kg / m 3 Within this range, the decrease in compressive strength was suppressed.
[0071] For this reason, the cement composition of the present invention can be more effectively used for preventing CO2 generation by adjusting the water content and the blending amount of the clinker ash. 2 While absorbing and fixing CO 2 It was found that the decrease in compressive strength of concrete or mortar was suppressed in proportion to the amount of fixation.
Claims
1. A cement composition comprising cement, aggregate, clinker ash, and water, A cement composition, wherein the moisture content of the clinker ash is 21.2% or less.
2. 2. The cement composition according to claim 1, wherein the moisture content of the clinker ash is 5.0% or more and 21.2% or less.
3. The amount of water blended is 138 kg / m ３ More than 190kg / m ３ 3. The cement composition according to claim 1 or 2, wherein:
4. The cement composition according to claim 1 or 2, wherein the amount of the clinker ash is 15 mass % or more and 60 mass % or less with respect to the amount of the cement.
5. The cement composition according to claim 1 or 2, wherein a water-cement ratio (W / C) of the cement to the water is 50 mass% or more and 65 mass% or less.
6. A method for producing a cement composition comprising mixing cement, aggregate, clinker ash, and water, A method for producing a cement composition, wherein the moisture content of the clinker ash before mixing is 21.2% or less.
7. CO ２ An absorption and fixation method comprising the steps of: The CO ２ CO used in absorption and fixation methods ２ The absorbing and immobilizing material is a cement composition obtained by mixing cement, aggregate, clinker ash, and water, The moisture content before mixing of the clinker ash is 21.2% or less. ２ Absorption fixation method.