KR20170036584A - Lightweight geopolymer using fly ash highly containing unburned carbon contents and red mud and manufacturing method for the same - Google Patents

Abstract

The present invention relates to a hardened lightweight geopolymer and a method for manufacturing the same, provided with fly ash of high unburned carbon content, red mud, geopolymer slurry including an alkali activator polymerizing with the fly ash of high unburned carbon content and the red mud, and foam bubbles formed by a foaming agent. The fly ash of high unburned carbon content contains 6% to 21% of porous unburned carbon, the alkali activator is formed by mixing of sodium hydroxide and sodium silicate aqueous solutions at a weight ratio of 1 : 1 and polymerizes with the fly ash of high unburned carbon content and the red mud, and the foaming agent is configured as an animal surfactant-based foaming agent. According to the present invention, the fly ash of high unburned carbon content that has not been usable as a cement and concrete admixture can be used in geopolymer binder manufacturing, and thus thermal power plant byproducts can be disposed of at reduced costs and environmental problems related thereto can be dealt with. In addition, a decrease in volume and an increase in density attributable to microbubbles of bubbles, which occur during lightweight hardened body manufacturing, can be prevented by the use of the red mud while a high-pressure foaming technique is used that is suitable for the hardened body using the fly ash of high unburned carbon content. The present invention leads to better dry shrinkage effects than those of existing lightweight cement concrete. It is capable of reducing costs for the disposal of the red mud, which is an industrial byproduct, dealing with environmental problems related thereto, and reducing carbon dioxide during cement manufacturing.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight geopolymer cured product obtained by using red mud and unburned carbon high fly ash and a method of manufacturing the lightweight geopolymer cured product using the red mud and unburned carbon high fly ash,

The present invention relates to a lightweight geopolymer curing agent and a method for producing the same. More particularly, the present invention relates to a lightweight geopolymer curing agent and a method for producing the same. More particularly, And to solve the problem of the volume reduction of the lightweight concrete, and a method of manufacturing the lightweight geopolymer cured body.

In recent years, various measures have been sought to realize low carbon green growth and low carbon society, which are moving away from the existing carbon-dependent economic paradigm. One of the detailed measures is the regulation on coal-fired power plants, And the burner replacement and the boiler combustion temperature reduction to reduce SO _x and NO _x emissions. This change in coal-fired power generation method directly affects the quality of fly ash, and it is expected that a large amount of fly ash having a high unburned carbon content (hereinafter referred to as "unburned carbon high fly ash") is expected to be discharged compared with the conventional fly ash .

At present, about 65% of fly ash recycled is used as cement and concrete admixture, but it can not be used as a cement concrete admixture because of low strength of unburned carbon high fly ash. Therefore, most of the unburned carbon high fly ash is landfilled, and a method for utilizing such unburned carbon high fly ash is urgently required.

Recently, cement consumption has been continuously increasing, cement production has increased by about 3% every year in the world, and Portland cement is used in most construction sites in Korea. Portland cement produces a large amount of carbon dioxide, which accounts for about 5% of the world's total carbon dioxide emissions. Carbon dioxide is one of the main causes of global warming and is making efforts to reduce carbon dioxide emissions worldwide.

One of these efforts is to find binders that can replace Portland cement, and geopolymers that have been actively researched since the 1970s.

Geopolymers mix amorphous aluminosilicate materials with water-soluble alkali activators to induce polymerization (geopolymerization) and re-align the molecules to develop strength.

The strength of the geopolymer product is greatly influenced by the type of binder, the presence of the precured curing, the curing condition, and the kind of alkali activator.

Technological developments in geopolymers have been mainly focused on metakaolin, unburned carbon low fly ash, and blast furnace slag.

On the other hand, Redmud is a residue that is produced by taking alumina through the Bayer process (sodium hydroxide is dissolved and alumina fraction is extracted) using the bauxite as a raw material. Through this process, about 2 tons of red mud are produced to produce 1 ton of aluminum hydroxide, and about 120 million tons are generated annually around the world.

Since red mud is generated by using strong basic sodium hydroxide in the refining process of bauxite, landfill landfill is limited since 2001 because it is discharged as a slurry type material with strong basicity of about 10-13. In Korea, since 1993, when aluminum smelting began, the amount of red mud increased gradually, resulting in an annual production of about 200,000 tons. However, the recycling rate is less than 15%, which is an industrial by-product with a low recycling rate. Due to this low recycling rate and harmfulness, there are many problems in loading red mud, and without the ultimate treatment of red mud, we do not know when an environmental disaster will happen due to red mud.

Therefore, it is imperative to develop economical and efficient recycling technology to solve the increase of by-products every year due to industrial development.

Korean Patent No. 10-1337759 (inorganic binder composition)

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a method of recycling an unburned carbon high fly ash which is gradually increased in amount without using a cement binder To provide a lightweight geopolymer cured body.

Another object of the present invention is to provide a method for producing a lightweight cured product which can prevent the volume reduction and the density increase due to the bubble of the bubble, And has a low shrinkage of drying, and a process for producing the same.

In order to accomplish the above object, the lightweight geopolymer cured product according to the present invention comprises a unburned carbon high-content fly ash, a red mud, an unburned carbon high-content fly ash, and an alkali activator polymerizing with the red mud And a foaming foam formed by a foaming agent, wherein the unburned carbon high content fly ash contains 6 to 21% of the porous unburned carbon, and the red mud contains the unburned carbon high fly ash And the alkali activator is formed by mixing an aqueous solution of sodium hydroxide and an aqueous solution of sodium silicate in a weight ratio of 1: 1 and is polymerized with the unburned carbon high content fly ash and the red mud, and the foaming agent is an animal surfactant Based foaming agent.

Here, the foaming foam is formed by foaming an animal surfactant foaming agent at 0.7 MPa, and the volume after high-pressure foaming has a volume ratio of 0.5: 1 with respect to the volume of the geopolymer slurry.

Here, the molar ratio (Si / Al molar ratio) of silicon to aluminum contained in the geopolymer slurry is in the range of 0.98 to 1.59.

The red mud is 10 to 40% by weight of the geopolymer slurry.

Here, the concentration of the surfactant-based foaming agent is 0.5 to 2.0%.

The method for producing a lightweight geopolymer cured product according to the present invention comprises the steps of mixing a unburned carbon high fly ash containing 6 to 21% of a porous unburned carbon with a red mud followed by dry beaming, And sodium silicate in a weight ratio of 1: 1 is added to the mixture of the unburned carbon high-content flyash and the red mud to cause a polymerization reaction to prepare a geopolymer slurry, and an animal surfactant- Mixing the foamed foam formed by foaming at 0.7 MPa with the geopolymer slurry; and pre-curing the geopolymer slurry containing the foamed foam at room temperature for 24 hours and then curing in a drying oven for 48 hours .

According to the lightweight geopolymer cured product of the present invention having the above-mentioned constitution and the method for producing the same, it is possible to utilize the unburned carbon high fly ash which can not be used as cement and concrete admixture in the production of the geopolymer binder, It is possible to reduce the cost and improve the environmental problem.

In addition, while utilizing a high-pressure foaming technique suitable for a cured product using a high unburned carbon content fly ash, it is possible to prevent the volume reduction and the density increase due to bubble vesicle, which is a disadvantage that occurs when a lightweight cured product is produced, And it is possible to obtain excellent effect on the drying shrinkage surface as compared with the conventional lightweight cement concrete.

In addition, it is possible to reduce the cost of processing the industrial by-product Red Mud, thereby to improve the environmental problems, and to alleviate the carbon dioxide generated in the production of cement.

1 is a view showing a particle size distribution curve of fly ash,
2 is a SEM photograph of the fly ash,
3 is a view for explaining the polymerization reaction of the alkali activating agent of the present invention,
4 is a view showing a method for producing a lightweight geopolymer cured product according to the present invention,
5 is a graph showing the compressive strength of the geopolymer composition according to Si / Al (molar ratio) of the geopolymer slurry of the present invention,
6 is a graph showing the compressive strength of the geopolymer composition according to the red mud concentration of the present invention,
7 is a graph showing the compressive strength and density of the lightweight geopolymer composition according to the red mud content of the present invention,
8 is a diagram showing the volume change of the lightweight geopolymer composition according to the red mud content of the present invention,
9 is a graph showing the compressive strength and density of a lightweight geopolymer composition according to the blowing agent concentration of the present invention.

Hereinafter, a lightweight geopolymer cured product and a method of producing the same according to the present invention will be described in detail with reference to the accompanying drawings.

The lightweight geopolymer cured product according to the present invention comprises a geopolymer slurry comprising unburned carbon high content fly ash, red mud and an alkali activator, wherein the geopolymer slurry is mixed with separately formed high pressure foamed foamed foam .

The geopolymer is formed by reaction of an aluminosilicate mineral with an alkali activator to form a three-dimensional structure of polysialate (Si-O-Al), polysialate-siloxo (Si-O-Al-O -Si-O, and polysialate-disiloxo (Si-O-Al-O-Si-O-Si-O).

As shown in Fig. 3, the geopolymer can be divided into two steps, which occur substantially simultaneously, not sequentially. 1) the dissolution and rearrangement of aluminosilicate minerals; and 2) the dissolved aluminosilicate minerals are cured by polymerization in a highly alkaline solution.

The unburned carbon high-content fly ash is a by-product produced by burning bituminous coal in a coal-fired power plant at a coal-fired power plant. The average particle size (D ₅₀ ) Amorphous aluminosilicate having a size of 20 탆 or less and a cenosphere.

In the geopolymer slurry of the present invention, it is exemplified that the fly ash contains a large amount of porous unburned carbon having a particle size of about 50 탆. Also, the fly ash contains fly ash in an amount of about 6% to 21%, which is a fly ash that can not be used as a cement concrete admixture according to the ASTM C618 standard.

The chemical composition of the unburned carbon high fly ash is shown in Table 1.

chemistry
ingredient SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO Na ₂ O K ₂ O SO ₃ MgO P ₂ O ₅ TiO ₂ L.O.I weight% 42.05 20.06 7.27 4.73 1.52 1.13 0.53 1.17 0.60 1.27 19.20

In addition, the alkali activator can be prepared by preparing sodium hydroxide (NaOH) at a proper molar concentration 24 hours prior to use in the polymerization reaction, adding sodium silicate (9-10% Na ₂ O, 28-30 SiO ₂ ) Mix 1: 1 and use after sufficient cooling.

In this embodiment, in order to form bubbles in the lightweight geopolymer cured product, a pre-foaming method is used in which the surfactant-based foaming agent is foamed at a high pressure and the foam is mixed with the geopolymer slurry.

The surfactant type foaming agent used in the present invention is an animal foaming agent, and the foaming pressure is 0.7 MPa when the foam is discharged.

In general, the selection method is used because of convenience of work and distribution of bubbles in the cured body relatively. However, when the curing concrete such as cement concrete and geopolymer is lightened by using the preliminary foaming method, the probability of the vesicle increases. In order to overcome such disadvantages, high-pressure steam curing is used in the manufacture of the product, and an additional amount of the volume reduced by the volume of the parasites is applied in the field.

In the present invention, red mud is added to compensate for these drawbacks in order to prevent volume reduction and density increase due to vesicles.

As shown in Table 2, red mud is mainly composed of ferric oxide (Fe ₂ O ₃ ) and has a pH of 10.97 and is a strongly basic substance.

chemistry
ingredient SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO Na ₂ O K ₂ O SO ₃ MgO P ₂ O ₅ TiO ₂ L.O.I weight% 18.3 21.6 29.45 2.76 12.02 0.03 - - 0.13 6.26 9.1

In addition, the addition of the red mud is performed by dry-blasting the fly ash and red mud before adding the alkali activating agent.

On the other hand, FIG. 4 is a view showing a method of producing the lightweight geopolymer cured product according to the present invention. As shown in Fig. 4, in the method for producing a lightweight geopolymer cured product of the present invention, a geopolymer slurry is first prepared. Mixing the unburned carbon high-content fly ash with the red mud followed by dry-blending, adding the alkali activator to the mixture of the unburned carbon high-content fly ash and the red mud to cause a polymerization reaction, To prepare a slurry.

Then, an animal surfactant based foaming agent is foamed at 0.7 MPa in the above-mentioned geopolymer slurry to form a foamed foam in the slurry.

Then, the above-mentioned geopolymer slurry containing the foamed foam is pre-cured at room temperature and then cured in a drying oven for 48 hours to complete the lightweight geopolymer cured product.

The blending ratios of the unburned carbon high fly ash, sodium hydroxide, sodium silicate, red mud, and water generated in the geopolymer slurry for producing the lightweight geopolymer cured product are shown in [Table 3] to [Table 6] The preparation of the geopolymer was carried out while varying as shown.

As described above, fly ash is a by-product of thermal power plants and has different chemical composition depending on the type of coal used in the process, the temperature of the burner, the environment, the power plant, and the date of occurrence. Red mud also contains aluminum And the purity of the bauxite used as a by-product, and the pH of the process, etc., and have different chemical compositions depending on the smelter, the date of occurrence, and the like.

The fly ash and red mud and sodium hydroxide in accordance with (NaOH) and sodium silicate (Na ₂ SiO ₃₎ mixture of the geo-polymer slurry are all different intensity, depending on purity or chemical composition of the material (raw material) used, even if the weight ratio is constant in And characteristics.

division Geopolymer composition and blending ratio (% by weight) according to Si / Al (molar ratio) Fly ash (wt%) Red mud (% by weight) Si / Al (molar ratio) Example 1 90 10 0.98 Example 2 90 10 1.08 Example 3 90 10 1.19 Example 4 90 10 1.32 Example 5 90 10 1.45 Example 6 90 10 1.59

Table 3 is an example of a fly ash geopolymer composition in which the red mud according to the present invention is mixed to grasp the strength of the geopolymer product according to the Si / Al (molar ratio) of the slurry. The weight ratio of fly ash and red mud was fixed at 90:10 and the concentration of the alkali activator was changed to prepare a geopolymer slurry. The slurry was injected into a 50 ㅧ 50 ㅧ 50 mm cube mold, and the temperature was changed to room temperature (T = 23.0 3.0 3.0 ㅀ C, RH = 50 ㅁ 10%) for 24 hours and cured in a 60 ㅀ C drying furnace for 48 hours.

As a result of the measurement, the molar ratio of silicon / aluminum (Si / Al) contained in the geopolymer slurry gradually increased from 0.98 as shown in FIG. 5, and the effect of increasing the strength was remarkably in the range of 1.32 to 1.59. It can be seen that the maximum strength is 1.45 to 29.6 MPa.

division The composition of the geopolymer and the mixing ratio Fly ash
(weight %) Red mud (% by weight) Si / Al (molar ratio) Example 1 100 0 1.52 Example 2 90 10 1.45 Example 3 80 20 1.38 Example 4 60 40 1.36

Table 4 is an example of a fly ash geopolymer composition in which the red mud according to the present invention is mixed at different weight ratios in order to grasp the strength of the geopolymer product according to the red mud content.

As shown in Table 3, the same amount of the alkali activating agent having the same molar concentration as in Example 5 showing the highest strength was blended, cured in the same manner as described above, and the strength was measured for 3 days. Respectively.

As shown in FIG. 6, the maximum intensity of the red mud content was 0% (Si / Al molar ratio is about 1.5). As the red mud content was increased, the Si / Al molar ratio decreased and the red mud content 40 And decreased by about 55% at 15.6 MPa.

division Lightweight Geopolymer Composition and Mixing Ratio According to Red Mud Content Fly ash
(weight %) Red mud (% by weight) Blowing agent concentration
(weight %) Example 1 100 0 2.0 Example 2 90 10 2.0 Example 3 80 20 2.0 Example 4 60 40 2.0

Table 5 shows an example in which the red muds were mixed at different weight ratios in order to grasp the strength of the lightweight geopolymer product according to the content of the red mud.

Here, the concentration of the foaming agent was 2.0%, and the ratio of the above-mentioned geopolymer slurry to the high-pressure foamed foaming foam was fixed at a volume ratio of 1: 0.5. The experimental procedure was the same as the above- .

As shown in FIG. 7, in the case of the lightweight geopolymer composition to which the red mud is not added, the volume reduction is about 33%, whereas when the red mud is added, about 2% (40%) and 3% (10% red mud content).

Also, when the high-pressure foamed foam was mixed, the strength decreased from 17.1 MPa (Redmud content 0%) to 0.4 MPa (Redmud content 40%) and the density decreased to 1.51 g / cm ³ Red mud content of 0%) to 1.05 g / cm ³ (Red mud content of 40%). If the red mud content is excessive, the use of the red mud is inadequate because of the large decrease in compressive strength. However, since volume reduction can be prevented even with mixing of about 10% of red mud, Red mud can be used by adjusting the amount of mixture.

division The lightweight geopolymer composition and blending ratio Fly ash
(weight %) Red Mud
(weight %) Blowing agent concentration
(weight %) Example 1 90 10 0.0 Example 2 90 10 0.5 Example 3 90 10 1.0 Example 4 90 10 2.0

Table 6 shows an example of a lightweight fly ash geopolymer composition in which high-pressure foamed foam produced by varying the concentration of the foaming agent according to the present invention is mixed to determine the strength of the lightweight geopolymer product according to the concentration of the foaming agent.

The experimental procedure is the same as that of the experiment described above, so duplicate explanation is omitted. The compressive strength according to the concentration of the foaming agent decreased as the foaming agent concentration increased from 0% to 0.5% and 1.0% as shown in FIG. 9, and then to 12.4 MPa which was increased by about 50% from 2.0%. The density was also similar, but increased from 2.0% to about 1.41 g / cm ³ by about 6%.

The lightweight geopolymer cured product using the red mud and the unburned carbon high fly ash according to the present invention complements the volume reduction and the density increase which are disadvantages of the conventional selective foaming method, and the high unburned carbon high fly ash and red This can contribute to increasing the recycling rate of the mud. In addition, it can be used as a substitute for cement that generates a large amount of carbon dioxide during production, and can be used for lightweight foam blocks, slabs, and the like.

In addition, lightweight geopolymers with high red mud content can be used for controlled low strength materials (CLSM) because of their low fluidity instead of low strength.

Although several embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various modifications may be made without departing from the principles and spirit of the invention . The scope of the invention will be determined by the appended claims and their equivalents.

Claims (6)

A geopolymer slurry comprising unburned carbon high fly ash, red mud, an unburned carbon high fly ash, and an alkali activator polymerized with the red mud,
And a foaming foam formed by the foaming agent,
The unburned carbon high-content fly ash contains 6 to 21% of the porous unburned carbon,
The red mud is gun beam-beamed with the unburned carbon high-content fly ash,
The alkali activator is formed by mixing an aqueous solution of sodium hydroxide and an aqueous solution of sodium silicate in a weight ratio of 1: 1, and is polymerized with the unburned carbon high-content fly ash and the red mud,
Wherein the foaming agent is an animal surfactant-based foaming agent, and a lightweight geopolymer cured body using red mud and unburned carbon high fly ash.
The method according to claim 1,
Wherein the foaming foam is formed by foaming an animal surfactant foaming agent at 0.7 MPa and a volume after high-pressure foaming has a volume ratio of 0.5: 1 with respect to the volume of the geopolymer slurry. Lightweight geopolymer cured with fly ash.
The method according to claim 1,
Wherein the molar ratio of silicon to aluminum contained in the geopolymer slurry (Si / Al molar ratio) is in the range of 0.98 to 1.59, and a lightweight geopolymer cured body using red mud and unburned carbon high fly ash.
4. The method according to any one of claims 1 to 3,
Wherein the red mud is 10 to 40 wt% based on the geopolymer slurry, and the lightweight geopolymer cured body using the red mud and the unburned carbon high fly ash.
5. The method of claim 4,
Wherein the concentration of the surfactant-based foaming agent is 0.5 to 2.0%. The lightweight geopolymer cured product is obtained by using red mud and high unburned carbon content fly ash.
Mixing the unburned carbon high-content flyash containing 6 to 21% of the porous unburned carbon with the red mud followed by dry bombarding,
Adding an alkali activator in a weight ratio of 1: 1 by weight of an aqueous sodium hydroxide solution and an aqueous sodium silicate solution to a mixture of the unburned carbon high-content flyash and the red mud to cause a polymerization reaction to prepare a geopolymer slurry;
Mixing the foaming foam formed by foaming an animal surfactant-based foaming agent with 0.7 MPa into the above-mentioned geopolymer slurry,
And curing the geopolymer slurry containing the foaming foam at a room temperature for 24 hours and then curing in a drying oven for 48 hours, characterized by comprising the step of curing the lightweight geopolymer cured product using red mud and unburned carbon high fly ash Gt;

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