KR20240014425A - Eco-frienddly light-burned Magnesia Binder composition and Binder thereof - Google Patents

Abstract

The invention is a composition and manufacturing method of an eco-friendly light-fired magnesia binder for eco-friendly concrete that absorbs carbon dioxide and generates carbonate under curing conditions of 20% CO ₂ to produce a hardened body. The main material is Hydrated Magnesium Carbonates (magnesium carbonate hydrate) (xMgCO ₃ yMg ( OH) ₂ zH ₂ O) calcination method,
Sodium Hexametaphosphate (NaHMP), Magnesium acetate (Mg(CH ₃ COO) ₂ ), Hydrated magnesium carbonates and Sodium that increase dispersibility, initial hydration rate and carbonation. It relates to a composition in which hydrogen carbonate (sodium bicarbonate) (NaHCO ₃ ) is additionally mixed.

Description

Eco-friendly light-burned magnesia binder composition that induces increased dispersibility, hydration rate, and carbonation, and binder manufactured therefrom {Eco-friendly light-burned Magnesia Binder composition and Binder thereof}

The present invention is a composition and manufacturing method of an eco-friendly light-fired magnesia binder for eco-friendly concrete that absorbs carbon dioxide and generates carbonate under curing conditions of 20% CO ₂ to produce a hardened body, and the main material, Hydrated Magnesium Carbonates (xMgCO ₃ yMg) (OH) ₂ zH ₂ O) calcination method,

Sodium Hexametaphosphate (NaHMP), Magnesium acetate (Mg(CH ₃ COO) ₂ ), Hydrated magnesium carbonates and Sodium that increase dispersibility, initial hydration rate and carbonation. It relates to a composition in which hydrogen carbonate (sodium bicarbonate) (NaHCO ₃ ) is additionally mixed.

After the Kyoto Protocol (1997), which first introduced greenhouse gas reduction obligations in the UN Framework Convention on Climate Change (UNFCCC), Paris Climate, which contains responses to climate change after 2020, was launched in Paris, France in December 2015. A change agreement was adopted. Major emitting countries, including China, the United States, India, Russia, Japan, and the European Union, have pledged to reduce greenhouse gas emissions by 25-85% by 2030, and have presented figures higher than the previous target every five years starting from 2020. Greenhouse gas reduction goals must be submitted.

Accordingly, various CCS (Carbon dioxide Capture and Storage) technologies for CO ₂ reduction are attracting attention, and recently, the cement industry in developed countries has fixed alkaline earth metals with CO ₂ to form carbonates in a thermodynamically stable state. By doing so, attention is being paid to 'mineral carbonation' technology that can be stored permanently.

Mineral carbonation was first mentioned in 1990 by Seifritz (1990) [2] as the concept of “CO ₂ binding”, and the concept of CO ₂ binding in Ca-carbonate minerals and Mg-carbonate minerals was studied by Dunsmore (1992). It has been done.

Since then, research on mineral carbonation has advanced rapidly, and various CO ₂ fixation methods have been developed, including direct carbonation (carbonation of minerals that occurs in a single process), indirect carbonation (carbonation after extracting Ca or Mg from minerals), and other process methods. .

In particular, various studies have begun to develop carbon-free cement by forming a wide range of carbonates and hydroxycarbonates using magnesium using an indirect carbonation method that can be applied on a large scale. Research on light-burning magnesia cement, which is low in CO ₂ and can absorb and harden to produce carbonate minerals, has begun to attract attention.

Lightly burned magnesia, which is being developed as a substitute for Portland cement, generally undergoes a strong chemical reaction with water to produce Mg(OH) ₂ (magnesium hydroxide), and simply hardens with unreacted MgO residue mixed in. ₂ In environmental conditions of 20% (compared to about 0.3% of CO ₂ in general atmospheric conditions) and relative humidity of about 90% or more (compared to 50% relative humidity in general atmospheric conditions),

CO ₂ dissolved in water creates bicarbonate (HCl ^aq- ), which penetrates into the intermediate product Mg(OH) ₂ capillary and reacts to form carbonates such as Hydromagnesite, which is the final hydrate and hardens.

In other words, under normal atmospheric conditions (approximately 0.3% CO ₂ 0.3%), light-fired magnesia does not produce carbonate and simply hardens, but under conditions of 20% CO ₂ or higher, it absorbs CO ₂ during the hydration process and hardens to form carbonate, thereby reducing greenhouse gas emissions. It is attracting attention as a next-generation cement.

However, light burnt magnesia, which is highly reactive, undergoes a strong chemical reaction with water when used in mortar and concrete, quickly producing Mg(OH) ₂ only on the surface, stabilizing in the form of a film, and remaining unreacted MgO remains inside, resulting in The reality is that the amount of hydration product (carbonate) is small compared to the amount of raw materials, so the strength development of the final cured body is low, and the CO ₂ absorption is low, making it difficult to expect its use.

The present invention is to compensate for the disadvantages of existing light burned magnesia as described above, and is a light burned magnesia manufactured by sintering the main raw material, Hydrated magnesium carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O), at an optimal temperature and time. We propose an eco-friendly light-burning magnesia binder that improves _CO2 absorption rate and strength by increasing dispersibility, initial hydration rate, and carbonation by using additional mixing materials.

The present invention involves calcining Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O, magnesium carbonate hydrate) at 850-950°C (preferably 900°C) for 30-1 hour (60 minutes) (preferably 30 minutes). In addition to 80 to 90% by weight of light burned magnesia with a crystal size of 46 to 47 nm, four additional materials were added, namely, Sodium hydrogen carbonate (NaHCO ₃ ) (sodium bicarbonate), Magnesium acetate (Mg(CH ₃ COO) ₂ ) (Magnesium Acetate), Sodium Hexametaphosphate(NaHMP) (Sodium Hexametaphosphate)

Contains 10 to 20% by weight of Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O).

Here, the Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O) is used as a raw material by sintering, but the state before sintering improves the reactivity of light-fired magnesium when used as a raw material. It is used as a raw material for interest.

The present invention improves dispersibility, initial hydration rate, and carbonation by using light-burned magnesia manufactured by firing the main raw material, Hydrated magnesium carbonates, at an optimal temperature and time to compensate for the shortcomings of existing light-burned magnesia, and additional admixtures. It is possible to provide an eco-friendly light-burning magnesia binder that improves CO ₂ absorption rate and strength by inducing .

Figures 1a and 1b show TEM images of light-calcined magnesia according to calcination temperature conditions and crystal size according to calcination time and temperature;
Figure 2 is a diagram showing the heat of hydration state of light-calcined magnesia paste according to calcination temperature conditions.
Figure 3 is a diagram showing the amount of self-contraction of light-calcined magnesia according to calcination temperature conditions.
Figure 4a is a diagram showing the results of material separation according to the incorporation of less than 0.2% of sodium hexametaphosphate
Figure 4b is a diagram showing the material separation results according to the incorporation of 0.2-0.6% of sodium hexametaphosphate
Figure 4c is a view showing the result of no concrete slump value due to an excessive increase in viscosity when sodium hexametaphosphate is added in excess of 0.6% of the total composition.
Figure 5 is a graph showing the degree of activation when magnesium acetate is added to MgO (magnesium oxide).
Figure 6 shows comparison of mortar compressive strength and wall surface of Examples (1 to 4).
Figure 7 compares the mortar compressive strength of Comparative Example 1 and Examples (5 to 7)
Figure 8 schematically shows the results of a 28-day strength test of a mortar cured under CO ₂ 20% conditions of existing light burned magnesium (comparative example) and some examples of the invention embodiment.
Figure 9 is an XRD showing the hydration products of comparative examples and examples.
Figure 10 is a diagram showing TG/DSC results showing CO2 absorption rates of comparative examples and examples.

Hereinafter, the present invention will be described in more detail by way of example embodiments. Of course, the scope of the present invention is not limited to the following examples, and is within the scope of the present invention without departing from the technical gist of the present invention. Various modifications can be made by those with ordinary knowledge.

First, if there is no other definition in the terms used herein, they have the meaning commonly understood by those skilled in the art in the technical field to which this invention belongs.

The conditions (temperature, time, etc.) shown in the present invention are not only preferred conditions, but also the ranges described in the examples (invention) fall within the scope of the present invention.

In explaining the embodiments of the present invention, the description is based on weight%, but the range by weight part also falls within the scope of the present invention, and the content explained in weight% is applied and explained in correspondence to the weight part. You just need to understand.

Hereinafter, the present invention will be described with reference to each drawing, test results, etc.

First, the ingredients and contents of the embodiments of the present invention are as follows.

Crystal size of 46-47㎚ obtained by calcining Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O, magnesium carbonate hydrate) at 850-950 ℃ for 30-60 minutes (preferably 30 minutes). Magnesia 80-90% by weight; and

Sodium hydrogen carbonate(NaHCO ₃ ) (Sodium bicarbonate), Magnesium acetate(Mg(CH ₃ COO) ₂ ) (Magnesium acetate), Sodium Hexametaphosphate(NaHMP) (Sodium hexametaphosphate), Hydrated Magnesium Carbonates (xMgCO) 10 to 20% by weight of ₃ yMg(OH) ₂ zH ₂ O) mixed; containing It is a light burned magnesia binder composition,

In the above, hexametaphosphoric acid 0.2-0.6%, magnesium acetate 2-6%, sodium bicarbonate and magnesium carbonate hydrate mixture 7-16%; It consists of

Meanwhile, the present invention is a light-burned magnesia with a crystal size of 46-47 nm obtained by calcining Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O, magnesium carbonate hydrate) at 850-950 ° C. for 30-60 minutes. For 100 parts by weight,

Sodium hydrogen carbonate(NaHCO ₃ ) (Sodium bicarbonate), Magnesium acetate(Mg(CH ₃ COO) ₂ ) (Magnesium acetate), Sodium Hexametaphosphate(NaHMP) (Sodium hexametaphosphate), Hydrated Magnesium Carbonates (xMgCO) It is a light burned magnesia binder composition characterized in that it contains 11-25 parts by weight of four components ( ₃ yMg(OH) ₂ zH ₂ O) mixed together.

In addition, embodiments of the present invention,

About 100 parts by weight of light burnt magnesia with a crystal size of 46-47㎚ obtained by calcining Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O, magnesium carbonate hydrate) at 850-950 ℃ for 30-60 minutes. , 0.2-0.8 parts by weight of hexametaphosphoric acid, 2-8 parts by weight of magnesium acetate, 9-23 parts by weight of a mixture of sodium bicarbonate and magnesium carbonate hydrate; It is a light burned magnesia binder composition characterized by consisting of.

Prepare the above ingredients and contents and stir in a general manner to prepare a binder. That is, it is a binder manufactured by stirring the above ingredients and the contents of each ingredient.

1. Crystal size 46~47㎚ light calcined magnesia calcination temperature condition range

In general, the calcination temperature for light fired magnesia is defined as 1000°C or lower, but since the final product varies greatly depending on temperature conditions, it is essential to set more specific calcination temperature conditions.

Figure 1 shows TEM images (Transmission electron microscopy images) observed with a transmission electron microscope of light-burned magnesia produced after calcining the raw material, Hydrated magnesium carbonates, at various temperature ranges.

(A) in Figure 1 is MgO calcined at 700 ℃. The crystal grain size is about 5 to 30 nm and is composed of very small grains. However, as the calcination temperature increases, the grain growth is completed in the sintered area. It can be seen that a region in an amorphous state partially exists.

(B), (C), and (D) in Figure 1a are pictures of light-calcined magnesia calcined at 800 ℃, 900 ℃, and 1000 ℃, respectively. As the calcination temperature increases, the grains gradually grow and the size of the crystal increases. I was able to confirm that

Magnesia calcined at 900 ℃ has already been sintered with a crystal size of 46-47 nm, and it was confirmed that further sintering does not significantly affect the particle size or specific surface area. In the present invention, energy saving and grain growth experiment results Based on this, calcination conditions of 900°C for 30 minutes were selected as the range for manufacturing light-fired magnesia, the main material of the present invention, to produce a crystal size of 46-47 nm.

Additionally, Figure 1b shows crystal size according to calcination time and temperature.

It can be seen that the crystal size of MgO increases as calcination time and temperature increase. In particular, the effect of time was relatively small compared to the calcination temperature, and proportional crystal growth (independent aggregates) occurred up to 900 ℃, and then rapid crystal growth (neck formation between aggregates) occurred at 1000 ℃.

This is because as the temperature increases, the mobility of molecules increases and bonding with other crystals progresses rapidly, and the temperature at which the mobility of this crystal increases rapidly is 900°C.

However, at 1000°C, the crystal size more than doubles and a condensation of aggregates is formed, which reduces the specific surface area and lowers the mechanical properties, making it unusable.

On the other hand, MgO produced at a calcination temperature of 900°C or lower has incomplete crystal growth, has a very large specific surface area, and is highly reactive, so it quickly solidifies and generates heat of hydration, making it difficult to use. Therefore, MgO calcined at 900℃ is the temperature at which optimally grown independent aggregates (crystal size 46-47nm) can be produced.

In addition, in the table of Figure 1b, the calcination times of 30 minutes, 60 minutes, and 120 minutes were determined to be preferably 30 minutes in consideration of economics related to the calcination time as a result of having a minor effect on crystal size generation, but 30 minutes - 60 minutes are also used according to the present invention. falls within the range of

Figure 2 is a graph showing the heat of hydration of light fired magnesia paste made at each firing temperature measured through an embedded temperature sensor.

The forms of light burnt magnesia that react with water are brucite (Mg(OH) ₂ ), hydromagnesite (Mg ₅ (CO ₃ ) ₄ ·(OH) ₂ ·4H ₂ O), which is produced by absorbing CO ₂ , and dyspingite (Mg ₅ (CO ₃ ) ₄ (OH) ₂ ·5H ₂ O), Nesquehonite (MgCO ₃ ·3H ₂ O), etc.

In particular, the formation of magnesium carbonate tends to form various metastable carbonates due to the high heat of hydration of Mg ²⁺ , and it is known that the most advantageous carbonate mineral in terms of compressive strength is Nesquehonite.

However, since nesquehonite is created at a low temperature between 0 and 50 ℃ during the hydration process with water, nesquehonite is not produced in lightly burned magnesia that generates a high heat of hydration above 50 ℃.

As a result of the experiment, light calcined magnesia calcined at 700 ℃ generated very large heat and the internal temperature was measured at 120 ℃, light calcined magnesia calcined at 800 ℃ was approximately 50 ℃, light calcined magnesia calcined at 900 ℃ was approximately 40 ℃, and 1000 ℃. The light calcined magnesia was less than 30°C.

Therefore, in the present invention, in order to form Nesquehonite carbonate with excellent strength development, calcination conditions of 850 ~ 950 ℃ (preferably 900 ℃) 30 minutes to 1 hour (preferably 30 minutes) are used based on the paste experiment results. It is selected based on the scope of manufacturing light fired magnesia, which is a material.

Figure 3 is a graph showing the amount of self-contraction of light-calcined magnesia according to calcination temperature conditions.

Light-burned magnesia calcined at a calcination temperature of 700 ℃ showed self-contraction between immediately after curing and 6 hours of curing, showing an amount of self-contraction of -27187.9 με, and light-burned magnesia calcined at 800 ℃ self-contracted between 2 and 14 hours of curing. This progressed and showed an amount of self-contraction of -26356.8 με.

Light-burned magnesia calcined at 900 ℃ also underwent self-contraction between 2 and 22 hours of curing, but self-contraction occurred very slowly in the early stages of curing for light-calcined magnesia calcined at 1000 ℃, and light-calcined magnesia calcined at 700 ℃ and 800 ℃ Compared to magnesia, the shrinkage amount was also about 1/3, showing lower reactivity and shrinkage than the low-temperature calcined specimen.

As a result of evaluating the amount of self-shrinkage according to calcination conditions, in the case of magnesia calcined at 1000 ℃, the sintering of magnesia reaches the completion stage and is converted to hard burnt MgO with low hydration reactivity, and the calcination temperature of about 1000 ℃ is excluded from the scope of the invention. .

In summary, the light burnt magnesia used in the present invention refers to light burnt magnesia with a crystal size of 46 to 47 nm, which is produced when hydrated magnesium carbonates are preferably fired at about 900 ° C. for 30 minutes. The firing method and crystal size are Set the optimal invention scope.

2. Range of addition of active ingredients

Securing physical properties (strength) and CO ₂ absorption rate of lightly burned magnesia are determined by the type and amount of the final carbonate product.

However, when using only light-fired magnesia made using a generally defined manufacturing method, only the outer part of the raw material reacts quickly due to a violent reaction with water, resulting in a low production of Mg(OH) ₂ (magnesium hydroxide), an intermediate product that creates carbonate, and the product cannot react. The reality is that residual MgO (magnesium oxide) remains inside, resulting in less hydration products (carbonate) compared to the input amount of raw materials, which reduces the strength development of the final hardened body and low CO ₂ absorption, making it difficult to expect its use.

Therefore, in the present invention, in order to compensate for the above shortcomings, the following additional mixed composition is used as an additive to increase the physical properties.

- Sodium Hexametaphosphate (NaHMP, sodium hexametaphosphate) has a dispersing effect on the powder mixture and alleviates the cohesion caused by the strong reactivity of light burnt magnesia with water, thereby increasing the possibility of hydration of the remaining unreacted MgO (magnesium oxide), which is an intermediate product. Induces the production of large quantities of Mg(OH) ₂ (magnesium hydroxide).

In order to obtain the dispersion effect of Sodium Hexametaphosphate, the addition of a small amount can lead to a large change in physical properties. Therefore, the appropriate amount of Sodium Hexametaphosphate is 0.2 to 0.6% by weight of the total composition. Do this.

Figure 4 shows the results of material separation according to the degree of incorporation of sodium hexametaphosphate.

In the case of Figure 4a, where less than 0.2% of sodium hexametaphosphate was mixed, material separation phenomenon (agglomeration of aggregates, gap of more than 3 cm between coarse aggregates) that occurs in general concrete occurred significantly. On the other hand, in Figure 4b, a test specimen containing sodium hexametaphosphate at a weight ratio of 0.2-0.6% of the total composition, it was confirmed that material separation did not occur due to the dispersion effect.

However, when sodium hexametaphosphate is added in excess of 0.6% of the total composition, the concrete slump value does not appear due to an excessive increase in viscosity, and the result is shown in Figure 4c.

- Magnesium acetate (Mg(CH ₃ COO) ₂ , magnesium acetate improves the initial hydration rate when light-burning magnesia reacts with water, leading to the production of a large amount of intermediate product Mg(OH) ₂ .

Figure 5 is a graph showing the degree of activation when magnesium acetate (magnesium acetate) is added to MgO (magnesium oxide).

According to Figure 5, it can be confirmed that it follows a linear equation graph in which the activation level increases as the amount of magnesium acetate added increases.

This high activation degree is due to the addition of Magnesium acetate (magnesium acetate), which has a relatively fast hydration rate compared to MgO (magnesium oxide), which reduces the amount of water ions dissociated into hydrogen and hydroxide ions due to ionization of magnesium dissolved in the aqueous solution. It can be confirmed that it increases and MgO (magnesium oxide) is also activated accordingly.

However, as Magnesium acetate dissociates, the remaining acetate combines with hydrogen ions before magnesium hydroxide to form acetic acid, which lowers the pH of the entire aqueous solution. Therefore, adding a large amount may inhibit the reaction with other activators. Also, the total amount of magnesium, which is a key ion in adsorbing carbonic acid, is reduced, so an appropriate amount must be added.

As a result of the activation experiment, the red line shown in Figure 5 represents an input amount of about 6%. When added more than that, the increase in activation is small, but it has a large effect on increasing the acidity of the aqueous solution, so it was selected as the maximum input amount, and the lowest amount was selected. When less than 2% of magnesium acetate was added, the activation level did not even reach 30%, so it was selected as the minimum input amount.

Therefore, the appropriate amount suggested in the present invention is about 2 to 6% by weight of the total composition for the purpose of advancing the time of initial hydration.

When Magnesium acetate (Magnesium acetate) was added to MgO (Magnesium oxide) and MgO (Magnesium oxide) and Magnesium acetate (Magnesium acetate) were added in a 2:1 mol ratio, the initial hydration rate was found to increase by about 2 times. Accordingly, the initial hydration is faster, but when excessive addition of Magnesium acetate (Magnesium acetate) is added, the total amount of MgO (Magnesium oxide) that can be carbonated decreases. Therefore, Magnesium acetate should be used at 20-30% of the active composition by weight, which is 2% of the total composition. It is set at ~6% by weight.

- The raw material, Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O, magnesium carbonate hydrate) and

Sodium hydrogen carbonate (NaHCO ₃ , sodium bicarbonate) can be used as seeds for unbalanced nucleation to reduce the interfacial energy required for the creation of solidification nuclei on an already existing surface.

As the amount added increases, the nucleation of carbonate becomes more advantageous, which can increase the production of carbonate that was not generated in the existing hardened body using only light burnt magnesia.

However, adding more than 20% of MgO (magnesium oxide) leads to a rapid deterioration of physical properties, an increase in the amount required, and a decrease in the total amount of carbonation, so adding an appropriate amount is effective.

Therefore, the appropriate amount of Hydrated Magnesium Carbonates and Sodium hydrogen carbonate is 7 to 16% by weight of the total composition. However, since the performance of magnesium carbonate hydrate and sodium bicarbonate are similar, their ratios are not related.

The appropriate dosage of Hydrated Magnesium Carbonates and Sodium Hydrogen Carbonate is 70-80% of the active composition and 7-16% by weight of the total composition.

Components and contents of compositions according to Examples 1 to 4 Example 1 Example 2 Example 3 Example 4 Magnesium carbonate hydrate and sodium bicarbonate weight percent 0 5 10 15 MgO fired below 1000℃ 100 95 90 85

The compressive strength of the test specimen manufactured according to [Table 1] is shown in Figure 6a.

Hydrated Magnesium Carbonates (xMgCO3yMg(OH)2zH2O, magnesium carbonate hydrate) and Sodium hydrogen carbonate (NaHCO3, sodium bicarbonate) are used as seeds for unbalanced nucleation. When used as seeds for unbalanced nucleation, the strength development does not reach the maximum critical point when used at 10% or less, but at 15%, 5.8 It showed the highest strength in MPa, and there was no significant difference when mixed beyond that.

This is the seed of unbalanced nucleation. When a combination of hydrated magnesium carbonate (xMgCO3yMg(OH)2zH2O) and sodium bicarbonate (NaHCO3) is added to light burned MgO, the surface such as the Wall in Figure 6b increases, and the already existing surface ( When nuclei are generated on the surface, the interfacial energy required to generate solidification nuclei is reduced (see formula below).

Here, the angle between the Wall, which is a Seed, and the newly created (solidification nucleus) is called δ. Since the shape of the Seeds is spherical, the free energy of heterogeneous nucleation is smaller, so nuclei can be created more easily than uniform nucleation. You can know what you can do.

Therefore, as the amount of the mixture added increases, carbonate nucleation becomes more advantageous, and hydromagnesite, which was not formed with existing magnesium, is observed in the present invention.

However, as can be seen from the strength test results in Figure 7, the limit is 15%, where the maximum reactivity forms a hydration product, and it can be seen that there is no significant difference when mixed beyond that.

Components and contents of compositions according to Examples 5 to 7 and Comparative Example 1 Example 5 Example 6 Example 7 Comparative Example 1 S% T% S% T% S% T% S% T% article
castle
water bow
castle
issue Sodium Hexametaphosphate
(Sodium hexametaphosphate) 3 - 3 - 2 - - - Magnesium acetate
(Magnesium Acetate) 30 - 30 - 20 - - - Sodium hydrogen carbonate 30 - 20 - 20 - - - Hydrated Magnesium Carbonates 37 - 47 - 58 - - - subtotal 100 20 100 20 100 10 - - crystal size 45~60㎚ MgO - 80 - 80 - 90 - - MgO fired below 1000℃ - - - - - - - 100 total - 100 - 100 - 100 - 100 admixture AE agent or water reducing agent - 0.5 - 0.5 - 0.5 - 0.5

Figure 8 schematically shows the results of a 28-day strength test for mortar cured under CO ₂ 20% conditions of existing light burned magnesium (comparative example) and some examples of the invention.

The compressive strength test was conducted with reference to KS I 2218 compressive strength measurement method.

As shown in Figure 8, the 28-day compressive strength of the inventive example was significantly higher than that of the comparative example.

Figure 9 is an XRD result showing the hydration product of existing light burned magnesium (comparative example) and some examples of the invention.

In the comparative example, unreacted MgO and carbonate hydromagnesite were confirmed as hydration products, but in the example, Mg(OH) _{2 ,} an intermediate product for making carbonate, and Nesquehonite (MgCO ₃ ·3H ₂ O), a carbonate advantageous for developing compressive strength, were confirmed. .

Figure 10 is a graph showing the results of TGA/DSC analysis.

In the DSC results, an endothermic peak corresponding to decarbonation was observed, and the amount of CO₂ fixed in the specimen was analyzed through the weight loss rate in the corresponding section.

The formula is as below.

In Figure 10, the CO₂ adsorption amount of each combination is about 12% of CO₂ in the comparative example, but about 19% of CO₂ in the example.

As described above, the present invention is a method of manufacturing a light-fired magnesia binder for eco-friendly concrete that absorbs carbon dioxide and generates carbonate under curing conditions of 20% CO ₂ to create a hardened body. The main material, Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O) calcination method and dispersibility, initial hydration rate, and sodium hexametaphosphate (NaHMP), which induces increased carbonation, Magnesium acetate (Mg(CH ₃ COO)) ₂ ), Hydrated magnesium carbonates (magnesium carbonate hydrate), and Sodium hydrogen carbonate (NaHCO ₃ ).

Through the above examples and comparative examples, it can be seen that the critical meaning of the content/conditions of the scope of rights of the present invention has become clear.

The present invention as described above is a composition and method of manufacturing a light-fired magnesia binder for eco-friendly concrete that absorbs carbon dioxide and generates carbonate under a curing condition of 20% CO ₂ to produce a hardened body. The main material is Hydrated Magnesium Carbonates. (xMgCO ₃ yMg(OH) ₂ zH ₂ O) calcination method,

Sodium Hexametaphosphate (NaHMP), Magnesium acetate (Mg(CH ₃ COO) ₂ ), Hydrated magnesium carbonates and Sodium that increase dispersibility, initial hydration rate and carbonation. It relates to a binder composition produced by additional mixing of hydrogen carbonate (NaHCO ₃ ).

Claims (5)

80-90% by weight of light burnt magnesia with a crystal size of 46-47㎚ obtained by calcining Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O, magnesium carbonate hydrate) at 850-950 ℃ for 30-60 minutes. ;and
Sodium hydrogen carbonate(NaHCO ₃ ),
Magnesium acetate(Mg(CH ₃ COO) ₂ ) (magnesium acetate),
Sodium Hexametaphosphate (NaHMP) and
Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O) is 10 to 20% by weight; A light burned magnesia binder composition comprising a mixture.
The method of claim 1, comprising 0.2-0.6% of hexametaphosphoric acid, 2-6% of magnesium acetate, 7-16% of a mixture of sodium bicarbonate and magnesium carbonate hydrate; A light burned magnesia binder composition comprising:
About 100 parts by weight of light burnt magnesia with a crystal size of 46-47㎚ obtained by calcining Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O, magnesium carbonate hydrate) at 850-950 ℃ for 30-60 minutes. ,
Sodium hydrogen carbonate(NaHCO ₃ ) (Sodium bicarbonate), Magnesium acetate(Mg(CH ₃ COO) ₂ ) (Magnesium acetate), Sodium Hexametaphosphate(NaHMP) (Sodium hexametaphosphate), Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O) 11-25 parts by weight of the four components mixed; A light burned magnesia binder composition characterized in that.
About 100 parts by weight of light burnt magnesia with a crystal size of 46-47㎚ obtained by calcining Hydrated Magnesium Carbonates (xMgCO ₃ yMg(OH) ₂ zH ₂ O, magnesium carbonate hydrate) at 850-950 ℃ for 30-60 minutes. ,
0.2-0.8 parts by weight of hexametaphosphoric acid, 2-8 parts by weight of magnesium acetate, 9-23 parts by weight of sodium bicarbonate and magnesium carbonate hydrate; A lightly burned magnesia binder composition, characterized in that it is mixed.
The binder according to any one of claims 1 to 4, wherein the binder is prepared by stirring the ingredients and contents.