Hardened fly ash

Abstract

In the cement sector, there is a need to reduce CO2 emissions, and the process does not involve CO2 emissions. There is a demand for high-quality building materials. [Solution] A dehydration condensation polymerization reaction hardened product of fly ash, alkali and carbon dioxide. It contains a dehydrated polymer of fly ash and alkali, sodium carbonate monohydrate, and trona. Furthermore, the bulk density is 1.30-1.70 g / cm³ 3 Fly ash hard, characterized by being A transformed form.

Description

[Technical Field]

[0001] This invention relates to a hardened fly ash body. [Background technology]

[0002] Ordinary Portland cement is basically a mixture of limestone and clay that is fired at high temperatures and then cooled. The clinker obtained from this process is used as the raw material. A large amount of CO2 is emitted during the production of this clinker. It will be released.

[0003] As for the blended cement, blast furnace cement using blast furnace slag and fly ash are used. Fly ash cement and silica cement made from silica-based raw materials are used. These blended cements can reduce the amount of cement used, but clinker cements It is not possible to suppress CO2 emissions during manufacturing (Non-Patent Documents 1 and 2). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Basic physical properties and CO2 reduction effects of cement-based mixed materials with various admixture substitutions. Concrete Engineering Vol. 32 No. 1 2010 [Non-Patent Document 2] Efforts to Reduce CO2 Emissions in the Cement Industry, Concrete Engineering Vol. 48 No. 9, September 2010. [Overview of the project] [Problems that the invention aims to solve]

[0005] From this perspective, the cement sector is required to reduce CO2 emissions, There is a need for building materials that do not involve waste. [Means for solving the problem]

[0006] Therefore, the inventors have developed a method for using fly ash, which is an industrial waste discharged from coal-fired power plants. Focusing on this, we conducted various studies to manufacture a hardened material with sufficient hardness without CO2 emissions. By reacting fly ash with alkali and carbon dioxide, a certain bulk density can be obtained. We found that a hardened fly ash body with sufficient compressive and flexural strength could be obtained.

[0007] In other words, the present invention provides the following [1] to [6]. [1] A dehydration condensation polymerization reaction hardened product of fly ash, alkali and carbon dioxide, It contains a dehydrated condensate polymer of ash and alkali, sodium carbonate monohydrate, and trona. Bulk density of 1.30-1.70 g / cm³ 3 A hardened fly ash body characterized by being . [2] The hardened fly ash described in [1], wherein the alkali is sodium hydroxide. [3] A dehydrated condensation polymer of fly ash and alkali is formed by the following formula

[0008] [ka] A hardened fly ash product according to [1] or [2], which is a dehydrated condensate polymer having [1] or [2]. [4] The total content of sodium carbonate monohydrate and trona is 1V in the hardened fly ash. A hardened fly ash product as described in any of [1] to [3], wherein the content is ol% or more. [5] The initial compressive strength is 2 MPa or more and the flexural strength is 1 MPa or more. [1]~[4] A hardened fly ash body according to claim 1, wherein any of the following applies: [6] React the fly ash and alkaline solution under a carbon dioxide atmosphere at a temperature of 25°C or higher. A method for producing a fly ash hardened body according to any one of [1] to [5], characterized by comprising .

Effects of the Invention

[0009] The fly ash hardened body of the present invention uses fly ash, which is industrial waste, as a main raw material, and C does not require high-temperature treatment that causes O₂ emission, can be obtained by a simple treatment, and has sufficient compressive strength and flexur al strength, and can be used for various architectural structures and building materials.

Brief Description of Drawings

[0010] [Figure 1] It is a figure showing infrared absorption spectra of the surface of a fly ash hardened body at different curing ages. [Figure 2] It is a figure showing strength test results of a fly ash hardened body cured in a 100% carbon dioxide atmosphere. [Figure 3] It is a figure showing strength test results of fly ash hardened bodies cured under various conditions. [Figure 4] It is a figure showing strength test results of fly ash hardened bodies cured under various atmospheres.

Mode for Carrying Out the Invention

[0011] Terms used in the present specification have meanings commonly used in the art, unless otherwise specifically mentioned. .

[0012] Fly ash is ash collected by a dust collector from coal ash, having a particle diameter of about 0.1 to 300 μm and a particle diameter of that, and is a spherical hollow body mainly composed of silicon dioxide and alumina. Fly ash is discharged as industrial waste in an amount of about 8 to 9 million tons per year. Further, unlike cement, fly ash does not harden only by being mixed with water. Howeve Meanwhile, by adding an alkaline additive to the fly ash, the dehydration condensation polymerization reaction proceeds. It hardens, but the strength of the hardened material is not sufficient for use as a building material. The reaction products are thought to be the following structures.

[0013] [ka]

[0014] One aspect of the present invention relates to a dehydration condensation polymerization reaction cured product of fly ash, alkali, and carbon dioxide. and a dehydrated condensate polymer of fly ash and alkali, sodium carbonate monohydrate and Contains Rona and has a bulk density of 1.30-1.70 g / cm³ 3 A fly characterized by being It is a hardened ash material.

[0015] As mentioned above, fly ash is coal ash collected by a dust collector with a diameter of 0.1 to 30 It is an ash with a particle size of approximately 0 μm, consisting mainly of silicon dioxide and alumina, forming spherical hollow bodies. Yes, it is. Fly ash from various coal-fired power plants can be used, but JIS In accordance with A 6201, they are classified into types I to IV based on their chemical and physical properties. It is preferable that such a product be classified as Type II.

[0016] Examples of alkalis include alkali metal hydroxides, silicates, and carbonates. From the perspective of producing sodium carbonate monohydrate, trona, under mild conditions through reaction with carbon dioxide. Therefore, alkali metal hydroxides and alkali metal silicates are preferred. Examples include sodium hydroxide, potassium hydroxide, and lithium hydroxide, but water Sodium oxide is more preferred. Examples of alkali metal silicates include sodium silicate and ke Examples include potassium sulfate and lithium silicate.

[0017] The hardened fly ash material of the present invention is formed by the dehydration and shrinkage of fly ash, alkali, and carbon dioxide. A polymer reaction cured product, comprising a dehydrated condensation polymer of fly ash and alkali, and sodium carbonate. It contains monohydrate and trona, and has a bulk density of 1.30-1.70 g / cm³. 3 That is the case. Here, the dehydration condensation polymer of fly ash and alkali is contained in fly ash It is a reaction product of silicon dioxide and alumina with alkali, and the following formula

[0018] [ka]

[0019] This is a dehydrated condensation polymer represented by [formula]. Sodium carbonate monohydrate is a compound represented by the chemical formula Na2CO3·H2O, and It is a reaction product of sodium, a lucid metal, and carbon dioxide. Trona is a type of carbonate mineral, with the chemical formula Na3H(CO3)2·2H2O, Na3 (CO3)(HCO3)·2H2O, or Na2CO3·NaHCO3·2H2O (expressed as (CO3)(HCO3)·2H2O) It is also called sodium sesquicarbonate dihydrate. Trona is also an alkali metal. It is thought to be a reaction product of lium and carbon dioxide.

[0020] The total content of sodium carbonate monohydrate and trona is the pressure of the hardened fly ash body of the present invention. From the viewpoint of increasing shrinkage strength and flexural strength, a concentration of 1 Vol% or more in the hardened fly ash is preferred. Furthermore, it is more preferable that the concentration be between 1 Vol% and 23 Vol%. (Note: Fly ash) The sodium carbonate monohydrate and trona content (volume fraction) in the hardened body was determined by SEM observation. It can be calculated.

[0021] The bulk density of the hardened fly ash of the present invention is determined from the viewpoint of increasing compressive strength and flexural strength. , 1.30~1.70 g / cm³ 3 Preferably, it is 1.30 to 1.65 g / cm³. 3 but More preferably, 1.30 to 1.60 g / cm³ 3 That is even more preferable.

[0022] The hardened fly ash product of the present invention is a dehydrated condensation polymer of ordinary fly ash and alkali. Compared to the previous example, the initial compressive strength and flexural strength are significantly higher. The initial compressive strength is 1M It is preferable that the strength is Pa or higher, and more preferably 2 MPa or higher. Also, the bending strength is 0 It is preferable that the pressure be 0.5 MPa or higher, and more preferably 1 MPa or higher. Here, compressive strength is the strength measured by a universal testing machine, and flexural strength is measured by a universal testing machine. This is the strength measured by [method / method].

[0023] The hardened fly ash body of the present invention contains, in addition to the above components, cement, reinforcing fibers, etc. It may be present. The content of cement and other components is as described above for the hardened fly ash body of the present invention. The amount of the main component is preferably 10% by mass or less, and 8% by mass or less, of the total amount of the cured product. More preferably, and even more preferably 5% by mass or less.

[0024] Another aspect of the present invention involves preparing fly ash and an alkaline solution under a carbon dioxide atmosphere, 25 A method for producing the aforementioned hardened fly ash, characterized by reacting at a temperature of °C or higher. ru. The alkaline solution is an aqueous solution of alkali metal hydroxide or alkali metal silicate. Any solution would suffice, but an aqueous sodium hydroxide solution is more preferable. The concentration of alkali metal hydroxide in the alkaline aqueous solution is preferably 2.5 to 10 mol / L. 5-9 mol / L is more preferable. The amount of fly ash used is 1.4 to 2.3 times the amount of alkali metal oxides. This is preferable, and it is even more preferable that the amount is twice the amount. Under a carbon dioxide atmosphere, the reaction between fly ash and an alkaline solution contains 5% or more carbon dioxide. All that is required is to allow carbon to be involved, even if more than 5% carbon dioxide comes into contact with the interface of the reaction solution. Alternatively, you may bubble 5% or more carbon dioxide into the reaction mixture. Preferably, the carbon dioxide concentration is 5% or higher, and more preferably 10% or higher. It is even preferable if it is 20% or more.

[0025] The reaction temperature can be 25°C or higher, but 28°C or higher is more preferable. The upper limit is 100°C or lower, but from the perspective of CO2 reduction, 50°C or lower is preferable. A temperature of 40°C or lower is preferable. Furthermore, a reaction time (curing time) of 5 to 10 days is sufficient. Furthermore, the reaction may take place under high humidity conditions. In the reaction solution, components such as cement may be added, for example, in an amount of 10% by mass or less.

[0026] The hardened fly ash body of the present invention uses fly ash, which is an industrial waste, as its main raw material, C This material achieves sufficient compressive strength and bending strength through a simple process without high-temperature treatment that causes O2 emissions. It is a hardened material with high strength and can be used in various building structures and building materials. As a building material that can be used for the hardened fly ash of the present invention, concrete is used. examples include substitutes for building materials (such as blocks), and the like.

Examples

[0027] Next, the present invention will be described in further detail with reference to examples, but the present invention is not limited in any way to these examples.

[0028] Comparative Production Example 4 to 40 g of sodium hydroxide was added to 80 cm 3 of pure water to prepare a 1.2 to 12 mol·dm -3 aqueous sodium hydroxide solution. 200 g of fly ash was added thereto, and after stirring for 3 minutes with a stirring rod, the mixture was placed in a mold and cured at 38°C for 3 to 28 days in an air atmosphere.

[0029] Production Example 16 g or 24 g of sodium hydroxide was added to 80 cm 3 of pure water to prepare a 4.75 to 7.13 m ol·dm -3 aqueous sodium hydroxide solution. 200 g of fly ash was added thereto , and after stirring with a stirring rod for 3 minutes, the mixture was placed in a mold. The mold was placed in a desiccator, and 100% carbon dioxide gas was introduced into the desiccator at a flow rate of 500 mL or more for 3 minutes to create a 100% carbon dioxide atmosphere. The desiccator was placed in a 38°C constant temperature tank and cured for 3 days or 7 days. 100% carbon dioxide gas was replenished twice a day.

[0030] Test Example 1 Fig. 1 shows the results of infrared absorption spectra of the surface of a fly ash cured body at a curing temperature of 38°C with an addition amount of 24 g of sodium hydroxide at different curing days. 1440 cm -1 for carbonate ions and 1000 cm -1 for orthosilicate ions absorption peaks By using this ratio, the carbonation rate of the hardened fly ash was calculated for each curing period. As a result, the carbonation rate of the hardened fly ash tended to decrease with increasing curing time. Therefore, the shorter the curing period for hardened fly ash, the more it reacts with carbon dioxide. It is thought that... Also, the 1060 cm³ observed in the fly ash sample... -1 Nearby Metas The absorption of acid ions shifts, reaching 990cm -1 It changed to absorption. This means that In the presence of sodium hydroxide, the SiO4 tetrahedron of metasilicic acid in ash decomposes, It is thought that this was converted to rutosilicic acid, and trona was produced. Based on these measurement results, the hardened fly ash material of the present invention is made of fly ash and alkali. In addition to the dehydrated polymer, this novel cured product contains sodium carbonate monohydrate and trona. It was discovered that...

[0031] [Measurement of bulk density] After drying at 60°C for 24 hours, the external dimensions were measured with calipers to determine the volume, and the mass was also measured. The bulk density was measured and calculated using the following formula. Bulk density (g / cm³) 3 ) = Mass (g) / Volume (cm³) 3 )

[0032] [Measurement of compressive strength] Using a strength testing machine, the maximum load is measured, and the maximum load is divided by the cross-sectional area of ​​the center of the test specimen to determine the pressure. The shrinkage strength (N / mm2) was determined. The test conditions were 20mm wide x 20mm long x 20mm high. The test specimen was pressurized from above at a rate of 0.5 mm / min.

[0033] [Measurement of bending strength] The maximum load was measured using a strength testing machine, and the bending strength was determined using the following formula. Bending strength (N / mm²) = 1.5 × Maximum load (N) × Distance between supports (mm) × 10 6 / width (mm) / Thickness 2 (m) The test conditions were a distance of 60 mm between supports, and a test sample measuring 20 mm wide x 80 mm long x 20 mm high. The test specimen was pressurized from above at a rate of 0.5 mm / min.

[0034] Test Example 2 The samples were cured at a curing temperature of 38°C for 3 days under a 100% carbon dioxide atmosphere. Figure 2 shows the strength test results for the hardened lyash material. As shown in Figure 2, the hardened fly ash treated under an air atmosphere is treated with sodium hydroxide. With increasing weight, neither compressive nor flexural strength increased, but in a 100% carbon dioxide atmosphere... The hardened fly ash body, cured under air pressure, compresses as the amount of sodium hydroxide added increases. Both strength and bending strength increased. Therefore, curing was carried out in a 100% carbon dioxide atmosphere. This is thought to have accelerated the reaction between sodium hydroxide and carbon dioxide, leading to the early development of strength. It can be obtained.

[0035] Under the following conditions, with a curing temperature of 38°C, a total curing period of 3 days, and a sodium hydroxide addition amount of 24g: Figure 3 shows the results of the strength test on the cured fly ash hardened material. As shown in Figure 3, all hardened fly ash was cured for a total of 3 days, but some of the curing time was 1 The product was cured in a 00% carbon dioxide atmosphere, then moved to an air atmosphere and cured again. Under these conditions, compressive strength and flexural strength increase with increasing curing time in a 100% carbon dioxide atmosphere. The hardness increased. This suggests that the hardness of the fly ash hardened material is accelerated by carbon dioxide. It is thought that this was done.

[0036] Each atmosphere under curing temperature of 38°C, total curing period of 3 days, and sodium hydroxide addition amount of 24g Figure 4 shows the strength test results of hardened fly ash treated under specific conditions. Figure 4 shows the results of curing under a 30% carbon dioxide atmosphere and a 100% carbon dioxide atmosphere. In addition, the compressive strength and flexural strength of the hardened fly ash increased.

[0037] Curing temperature 38°C, total curing days 3 days, 100% with sodium hydroxide added at 24g Strength test results and bulk density of hardened fly ash cured under carbon dioxide atmosphere conditions The relationship is shown in Table 1. From Table 1, when the bulk density is 1.30 to 1.70, the compressive strength of the hardened fly ash is It can be seen that the bending strength increases.

[0038] [Table 1]

Claims

1. A hardened product of a dehydration condensation polymerization reaction of fly ash, alkali, and carbon dioxide, wherein the fly ash It contains a dehydrated polymer of ash and alkali, sodium carbonate monohydrate and trona, and is bulky. The concentration is 1.30 to 1.70 g / cm³. ３ A hardened fly ash body characterized by the following:

2. The hardened fly ash according to claim 1, wherein the alkali is sodium hydroxide.

3. The dehydration condensation polymer of fly ash and alkali is produced by the following formula: 【Chemistry 1】 The fly ash cured body according to claim 1, which is a dehydrated condensed polymer represented by the formula.

4. The content of sodium carbonate monohydrate and trona is 1 vol% or less in the hardened fly ash. The hardened fly ash according to claim 1.

5. The initial compressive strength is 1 MPa or more, and the bending strength is 0.5 MPa or more, according to claim 1. Hardened fly ash.

6. Fly ash and alkaline solution are subjected to a high concentration of carbon dioxide at a temperature of 25°C or higher. A hardened fly ash according to any one of claims 1 to 5, characterized by being reacted Manufacturing method.

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