Co2 fixation material, co2 fixation material-containing composition, co2 fixation material-containing concrete, and co2 fixation cured body

Abstract

The present invention involves a CO2 fixation material in which the CO2 fixation percentage during carbonation curing under conditions of a temperature of 40°C, a humidity of 40% RH, and a CO2 concentration of 20% is 40-80%.

Description

CO2 immobilization material, CO2 immobilization material-containing composition, CO2 immobilization material-containing cement concrete, CO2 immobilization hardened body

[0001] The present invention is ２ Immobilization material, CO ２ Immobilizing agent-containing composition, CO ２ Cement concrete containing fixative, CO ２ This relates to a fixed hardened body.

[0002] Concrete uses a large amount of cement as a raw material, so CO ２ This is mainly due to the large amount of fossil fuels used to generate combustion energy in the furnace during the cement production process, as well as the decarbonation reaction of limestone (CaCO ３ →CaO+CO ２ ) is generated. ２ Reducing emissions has become an important theme as part of measures to combat global warming.

[0003] CO emitted during the production of concrete products ２ In order to reduce the total amount of cement used, it is effective to reduce the amount of cement used by incorporating large amounts of special additives or industrial by-products (ground granulated blast furnace slag, fly ash, etc.) as cement substitutes, and various research projects are being conducted on this topic.

[0004] On the other hand, γ-C ２ S(γ-2CaO・SiO ２ By forcibly carbonating (curing) concrete containing non-hydraulic compounds such as belite (also called gamma phase belite) as admixtures, CO ２ There is a known technique for obtaining a highly durable concrete product by densifying the surface layer through the absorption of γ-C (see, for example, Patent Document 1). ２ S does not undergo hydration reaction, and CO ２ Reacts with CaCO ３ and SiO ２ These products fill the voids in the cement matrix and dramatically improve the durability of the surface layer of the concrete product. In this case, the CO absorbed by the concrete during carbonation (salt) curing is ２The total CO2 required to obtain concrete products is ２ Emissions will be reduced.

[0005] Japanese Patent Application Laid-Open No. 2006-182583

[0006] CO that can be absorbed by materials such as concrete ２ The amount of CO2 that can be absorbed by the material varies greatly depending on the composition of the material and the conditions of carbonation curing. ２ The maximum amount of CO absorbed by the material ２ The amount does not necessarily correspond to the amount of

[0007] As a result of intensive research, the present inventors have found that CO ２ How much CO2 can be absorbed? ２ CO2 is absorbed. ２ The index of fixation rate and the CO ２ CO ２ Using the index of fixation rate, the CO after carbonation curing under specific conditions is calculated. ２ CO fixation rate within a predetermined range ２ The immobilization material ２ The inventors have found that the fixation rate can be increased while the strength development is improved, and have arrived at the present invention.

[0008] [1] Temperature 40°C, humidity 40% RH, and CO ２ CO in carbonation curing at a concentration of 20% ２ The fixation rate is 40 to 80%. ２ [2] The CO2 immobilization material according to [1] above, wherein the bound water content during carbonation curing under the above conditions is 1 to 30 mass%. ２ [3] The CO2 fixation material according to [1] or [2] above, which has a flow value ratio of 75 to 120% as measured by the method specified in JIS A 6206:2013 "Ground granulated blast furnace slag for concrete" Appendix A "Test method for activity index and flow value ratio of mortar made of ground granulated blast furnace slag." ２ [4] The CO according to any one of [1] to [3] above. ２ CO containing immobilizing material ２[5] The CO according to [4] above. ２ CO containing an immobilizing material-containing composition ２ [6] The CO2 immobilizing agent-containing cement concrete according to [5] above. ２ A CO2-containing hardened cement concrete product containing a fixing agent. ２ Fixed hardened body.

[0009] According to the present invention, CO ２ CO that improves fixation rate and strength development ２ An immobilizing material can be provided.

[0010] Hereinafter, one embodiment of the present invention (the present embodiment) will be described in detail, but the present invention is not limited to this embodiment. In addition, "%" and "parts" in this specification are based on mass unless otherwise specified.

[0011] Furthermore, the term "cement concrete" as used herein is a general term for cement paste, cement mortar, and concrete.

[0012] [CO ２ Immobilization material] ２ The immobilization material was stored at a temperature of 40°C, humidity of 40% RH, and CO ２ CO in carbonation curing at a concentration of 20% ２ The fixation rate is 40 to 80%. ２ The CO2 immobilization material was subjected to carbonation curing under the above conditions (hereinafter, simply referred to as curing conditions). ２ CO with a fixation rate of 40-80% ２ By using immobilization materials, CO ２ In the present invention, the temperature, relative humidity, and CO ２ The concentrations are meant to be maintained within the ranges of ±3°C, ±5%, and ±3%, respectively.

[0013] (CO ２ Fixation rate) CO in the present invention ２ The immobilization rate is calculated by the following formula (1).

[0014]

[0015] CO in the above formula (1) ２ The immobilization amount can be calculated by the following formula (2).

[0016]

[0017] In the above formula (2), the CO in the test specimens after and before curing ２ The amount can be measured by differential thermogravimetry or coulometric titration, but from the viewpoint of accuracy, it is preferable to measure by coulometric titration.

[0018] In the differential thermogravimetric analysis, a differential thermogravimetric analyzer (TG-DTA) was used, and the temperature was raised to 1,000°C at a rate of 10°C / min in a nitrogen atmosphere (gas flow rate 70 ml / min). Based on the obtained TG-DTA curve, the mass loss in the range of 550°C to 850°C was calculated as the CO content of each specimen. ２ It can be a quantity.

[0019] In the coulometric titration method, a coulometer is used. Each crushed specimen is placed in an Erlenmeyer flask, 3 mol / L hydrochloric acid is added, and the mixture is stirred with a stirrer. ２ The gas is introduced into the absorption solution with nitrogen, and the amount of carbon is calculated from the amount of electricity required to maintain the transmittance of the absorption solution at a constant level. ２ It can be converted into a quantity.

[0020] CO in the above formula (1) ２ The immobilization capacity can be calculated by the following formula (3).

[0021]

[0022] The apparent density of the specimen before curing in the above formula (3) is the density of the specimen 1 m including the internal voids. ３ It can be calculated, for example, by Archimedes' method, from the dry weight obtained by drying and weighing at 105°C, the weight obtained by immersing in a solvent such as ethanol and weighing, and the density of the solvent. ２ The immobilization ability is a parameter that can be calculated by the following formula (4).

[0023]

[0024] CaO and CaCO in the above formula (4) ３ , S.O. ３ , MgO, Na ２ O and K ２ O represents the amount of each chemical component in the material. If known, the value can be used. However, CaO, SO ３ , MgO, Na ２ O and K ２ The CaCO 2 content was measured in accordance with the method specified in JIS R 5202:2015 "Methods for Chemical Analysis of Cement." ３ can also be measured by differential thermogravimetry or powder X-ray diffraction.

[0025] In the differential thermogravimetric analysis, a differential thermogravimetric analyzer (TG-DTA) was used, and the temperature was raised to 1,000°C at a temperature increase rate of 10°C / min in a nitrogen atmosphere (gas flow rate 70 ml / min). Based on the obtained TG-DTA curve, the mass loss in the range of 550°C to 850°C was calculated as CaCO ３ CO derived from ２ As equivalent to CO ２ Molecular weight and CaCO ３ It can be calculated from the molecular weight.

[0026] In the powder X-ray diffraction method, CaCO is determined based on the diffraction pattern obtained from the powder X-ray diffraction analysis. ３ From the Rietveld analysis using the crystal structure data of CaCO ３ can be calculated.

[0027] In addition, CO ２ The immobilization ability may be calculated by the following formula (5) or (6) by simplifying the above formula (4) as needed.

[0028]

[0029]

[0030] CO ２ The CaO content in the immobilizing material is preferably 15% or more, more preferably 50% or more, and even more preferably 20% or more. When the CaO content is within the above range, CO ２ The immobilization rate can be easily adjusted within a predetermined range.

[0031] CO ２ Immobilization material CO ２ The immobilization capacity is preferably 40 to 60, more preferably 45 to 58, and even more preferably 48 to 55. ２ By having the fixing ability within the above range, CO ２ The immobilization rate can be easily adjusted within a predetermined range.

[0032] CO ２ The apparent density of the immobilizing material is 1,500 to 5,000 kg / m ３ It is preferable that the density is 2,000 to 4,500 kg / m ３ More preferably, it is 2,500 to 4,000 kg / m ３ It is more preferable that the apparent density is within the above range. ２ The immobilization rate can be easily adjusted within a predetermined range.

[0033] CO ２ The Blaine specific surface area (also called the Blaine value) of the immobilization material is 1,200 to 9,000 cm ２ / g, and 1,500 to 8,000 cm ２ / g, and more preferably 1,750 to 6,500 cm ２ / g. When the Blaine specific surface area is within the above range, CO ２ The fixation rate can be easily adjusted within a predetermined range. The Blaine specific surface area can be determined in accordance with the method specified in JIS R 5201:2015 "Physical testing methods for cement."

[0034] CO in the carbonation curing under the above curing conditions according to this embodiment ２ The fixation rate is preferably 45 to 75%, and more preferably 50 to 70%. ２ The fixation rate is ２ This can be adjusted by adjusting the composition and particle size of the immobilizing material.

[0035] The bound water content in the carbonation curing under the above curing conditions according to this embodiment is preferably 1 to 30%, and more preferably 3 to 25%. ２ The bound water ratio in the present invention can be calculated by measuring the mass after drying at 105°C and the mass after ignition at 1,050°C, and then using the following formula:

[0036]

[0037] CO according to this embodiment ２ The flow value ratio when a fixing material is used is preferably 75 to 120%, and more preferably 80 to 110%. In the present invention, the flow value ratio can be measured in accordance with the method specified in JIS A 6206:2013 "Ground granulated blast furnace slag for concrete" Appendix A "Test method for activity index and flow value ratio of mortar made of ground granulated blast furnace slag." That is, a standard mortar and a test mortar are prepared according to the formulations shown in Table 1 below, and the flow value is measured and calculated by the flow test specified in JIS R 5201:2015 "Physical testing methods for cement." When the flow value ratio is within the above range, CO ２ It is easier to achieve a better fixation rate.

[0038]

[0039] (Carbonation Curing) ２ Carbonation curing for evaluating the immobilization material was performed at a temperature of 40°C, humidity of 40% RH, and CO ２ This is carried out at a concentration of 20%.

[0040] In the present invention, CO ２ Carbonation curing for evaluating immobilization materials is usually performed by adding water. ３ Styrofoam bottle of CO ２ 5 g of the immobilizing material and an equal amount of water are added, and the mixture is left to stand for 7 days under the above-mentioned curing conditions, during which time an equal amount of water is replenished every day.

[0041] [CO ２Immobilizing material-containing composition] ２ The immobilizing material-containing composition of the present invention ２ Contains immobilizing material.

[0042] CO ２ CO in the immobilizing material-containing composition ２ The content of the immobilizing material is preferably 1 to 100%, more preferably 3 to 70%, and even more preferably 5 to 50%.

[0043] CO ２ The immobilizing material-containing composition preferably contains cement. The cement is not particularly limited, and examples thereof include various portland cements such as normal, early strength, ultra-early strength, low heat, and medium heat, various mixed cements obtained by mixing these portland cements with blast furnace slag, fly ash, silica, silica fume, metakaolin, allophane, etc., environmentally friendly cements (ecocement) manufactured using municipal waste incineration ash and sewage sludge incineration ash as raw materials, commercially available fine particle cements, white cements, filler cements obtained by mixing limestone fine powder, etc., and various cements can also be used in a fine powder form. In addition, compared to conventional cements, CO ２ Low-emission geopolymer cement, sulfoaluminate cement, limestone-burned clay cement (LC3), CO ２ Examples include carbonated cement, which hardens by immobilizing . Also, cements prepared by increasing or decreasing the amount of components typically used in cement (e.g., gypsum) can be used. Furthermore, combinations of two or more of these can also be used.

[0044] From the viewpoint of manufacturing cost and strength development, the cement should have a Blaine specific surface area of ​​2,500 to 7,000 cm ２ / g, and 2,750 to 6,000 cm ２ / g, and more preferably 3,000 to 4,500 cm ２ It is more preferable that the SiO2 content is 1 / g.

[0045] The CO of the present invention ２The immobilizing material-containing composition may be, within a range that does not adversely affect performance, a water reducing agent, an air-entraining water reducing agent, a high-performance water reducing agent, a superplasticizer, an antifoaming agent, a thickener, an anticorrosive agent, an antifreeze agent, a polymer dispersion for cement admixture, a shrinkage reducing agent, granulated blast furnace slag powder, slowly cooled blast furnace slag powder, limestone powder, calcium hydroxide such as slaked lime, by-product slaked lime such as acetylene by-product slaked lime, fine powder generated from waste concrete blocks, artificial calcium carbonate obtained from raw materials such as paper sludge, calcium carbonate such as eggshells and seashells One or more of the known additives and admixtures used in ordinary cement materials, such as those produced by processing wastes whose main component is sewage sludge incineration ash or its molten slag, municipal waste incineration ash or its molten slag, and pulp sludge incineration ash, fibrous materials such as polymers, vinylon fiber, acrylic fiber, and carbon fiber, setting modifiers, clay minerals such as bentonite, and anion exchangers such as hydrotalcite, can be used within a range that does not substantially impair the objects of the present invention.

[0046] [CO ２ Fixing agent-containing cement concrete] ２ The immobilizing agent-containing cement concrete is ２ The cement concrete in the present invention includes a paste containing no aggregate, and a mortar or concrete containing aggregate.

[0047] CO ２ CO in cement concrete containing immobilizing agents ２ The content of the immobilizing material is 5 to 500 kg / m ３ is preferably 5 to 450 kg / m ３ More preferably, it is 10 to 400 kg / m ３ It is more preferable that:

[0048] CO ２ The aggregate used in the fixing agent-containing cement concrete is not particularly limited, and fine aggregates such as river sand, mountain sand, sea sand, lime sand, silica sand, and artificial calcium carbonate, and coarse aggregates such as river gravel, mountain gravel, and lime gravel can be used.

[0049] The aggregate content is 1,200 to 2,200 kg / m ３ It is preferable that the density is 1,500 to 2,000 kg / m ３ More preferably, it is 1,600 to 1,800 kg / m ３ When the content of the aggregate is within the above range, the fluidity retention and strength development can be improved.

[0050] CO ２ The cement concrete containing the fixing agent can be produced by mixing with water. The mixing ratio of water is 50 to 200 kg / m ３ is preferably 100 to 190 kg / m ３ More preferably, it is 120 to 185 kg / m ３ As the mixing device, any existing device can be used, for example, a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, a Nauta mixer, etc. The water is not particularly limited, and examples thereof include tap water, groundwater, recycled water from a ready-mix concrete plant, CO ２ Water containing the above may be used.

[0051] [CO ２ Fixed hardened body] ２ The immobilized hardened material is the CO ２ It consists of a hardened cement concrete containing a fixing agent. ２ It can be obtained by hardening the cement concrete containing the fixing agent by carbonation curing, and the CO after carbonation curing ２ The fixation rate is good.

[0052] The atmosphere for carbonation curing is 5 to 80°C, 20 to 80% RH, CO ２ It is preferable to carry out the process in an environment with a concentration of 0.04 to 99.5%, a temperature of 10 to 70°C, a humidity of 40 to 75% RH, and CO ２ It is more preferable to carry out the treatment in an environment with a concentration of 1 to 95%. The atmosphere may be atmospheric pressure, but may be pressurized as necessary.

[0053] CO ２ Fixed hardened CO２ The fixation rate is preferably 1.5% or more, more preferably 1.6% or more, and even more preferably 1.7% or more.

[0054] The present invention will be further explained below based on experimental examples, but the present invention is not limited to these.

[0055] <Experimental Example 1> The CO ２ The immobilization material is placed in a volume of 50 cm ３ A styrene bottle was filled with 5 g and an equal amount of water, and the temperature was 40°C, humidity was 40% RH, and CO ２ Carbonation curing was carried out for 7 days at a concentration of 20%, and CO ２ The immobilization material was evaluated. During this period, the temperature, relative humidity, and CO2 concentration were maintained within the ranges of ±3°C, ±5%, and ±3%, respectively, and an equal amount of water was replenished every day. The results are shown in Table 2 below.

[0056] (CO ２ Immobilization material) Material 1: Calcium carbonate (reagent grade 1) and silicon dioxide (reagent grade 1) were mixed in a molar ratio of 2:1, baked at 1,400 °C for 2 hours, then slowly cooled in the furnace to synthesize the material, and the particle size was adjusted. Blaine specific surface area: 4,000 cm ２ / g, specific gravity 3.00g / cm ３ Material 2: Material 1 and Material 4 mixed in a mass ratio of 1:2. Material 3: Research cement, Blaine specific surface area 3,390 cm ２ / g, specific gravity 3.16g / cm ３ Material 4: Limestone fine powder, Blaine specific surface area 4,000 cm ２ / g, specific gravity 2.70g / cm ３ .

[0057] (Evaluation item) CO ２ Fixation rate: CO based on the above-mentioned formulas (1) to (4) ２ The fixation rate was calculated. ２ The amount was measured by the coulometric drip method, and the amount of each chemical component in formula (4) was measured by the method specified in JIS R 5202:2015 "Methods for chemical analysis of cement" and differential thermogravimetric analysis.

[0058] Bound water content: The mass after drying at 105°C and the mass after ignition at 1050°C were measured, and the bound water content was calculated based on the above-mentioned formula (7).

[0059] Flow value ratio: Measured in accordance with the method specified in JIS A6206:2013 "Ground granulated blast furnace slag for concrete" Appendix A "Test method for activity index and flow value ratio of mortar made from ground granulated blast furnace slag."

[0060]

[0061] Experimental Example 2: Prepared CO ２ The immobilization material and cement are mixed, and CO ２ The content of the immobilizing material was adjusted to 30%. ２ An immobilizing material-containing composition was prepared. ２ The immobilizing agent-containing composition was mixed with 300 parts by mass of fine aggregate per 100 parts by mass of cement, and water was added at a mixing ratio of 50%. The mixture was then kneaded to obtain a CO ２ A mortar containing a fixing material was prepared. ２ The mortar containing the fixing material was poured into a formwork (4 cm x 4 cm x 16 cm), and then removed from the formwork after one day. The mortar was then stored at a temperature of 40°C, humidity of 60% RH, and CO ２ Carbonation curing was carried out in an environment with a concentration of 20% for up to 28 days to harden the material. ２ A fixed hardened body was obtained. ２ The following measurements were carried out on the fixed and cured product, and the results are shown in Table 3 below.

[0062] (Materials used) Cement: Ordinary Portland cement (commercially available), Blaine specific surface area 3,300 cm ２ / g, specific gravity 3.15g / cm ３ Water: Tap water. Fine aggregate: Sand from the Himekawa River system in Itoigawa City, Niigata Prefecture, maximum size 5 mm or less, density 2.62 g / cm ３ .

[0063] (Measurement items) CO ２ Fixation rate: After demolding after 1 day, CO ２ The entire surface of the 4cm x 4cm container was covered with aluminum tape to allow the air to diffuse. The container was then stored at a temperature of 40°C, humidity of 60% RH, and CO ２The material was subjected to carbonation curing in an environment containing a 20% concentration of carbon dioxide for up to 7 days. After 7 days, the aluminum tape was removed and the specimen was cut, and a section 20 to 25 mm deep from the surface was sampled. The sampled section was pulverized, hydration was stopped using acetone, and then the specimen was dried under reduced pressure at 40°C until it reached a constant weight. The dried sample was analyzed for ignition loss and CO2 according to the method specified in JIS R 5202:2015 "Methods for Chemical Analysis of Cement." ２ The amount of CO was measured by the coulometric drip method and calculated based on the above-mentioned formula (2). ２ The fixed amount was calculated based on the following formula (8): ２ The fixation rate was calculated.

[0064]

[0065] Compressive strength: In accordance with the method specified in JIS R 5201:2015 "Physical testing methods for cement," the compressive strength was measured at ages of 3 days, 7 days, and 28 days, with the time of pouring being considered as age 0.

[0066]

[0067] The CO of the present invention ２ The immobilizing material can be suitably used particularly in the fields of civil engineering and construction.

Claims

1. Temperature 40°C, humidity 40% RH, and CO ２ CO in carbonation curing at a concentration of 20% ２ The fixation rate is 40 to 80%. ２ Immobilization material.

2. The CO2 according to claim 1, wherein the bound water content during carbonation curing under the above conditions is 1 to 30 mass%. ２ Immobilization material.

3. The CO2 composition according to claim 1 or 2, wherein the flow value ratio measured by the method specified in JIS A 6206:2013 "Ground granulated blast furnace slag for concrete" Appendix A "Test method for activity index and flow value ratio of mortar made from ground granulated blast furnace slag" is 75 to 120%. ２ Immobilization material.

4. CO according to claim 1 or 2 ２ CO containing immobilizing material ２ Immobilizing material-containing composition.

5. The CO according to claim 4 ２ CO containing an immobilizing material-containing composition ２ Cement concrete containing fixing material.

6. The CO according to claim 5 ２ A CO2-containing hardened cement concrete product containing a fixing agent. ２ Fixed hardened body.

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