KR102435016B1 - Magnesium Oxychloride Cement And Method for Manufacturing the Same - Google Patents

Abstract

The present invention generates magnesium hydroxide (Mg(OH) ₂ ) from the inside by a chemical reaction, and the resulting magnesium hydroxide (Mg(OH) ₂ ) combines with carbon dioxide generated by the reaction of magnesium chloride and limestone to hydrate carbonization Disclosed is a magnesium oxide chloride cement capable of reducing water solubility and increasing strength by phase change to hydrated magnesium carbonate (HMC), wherein the magnesium oxide chloride cement according to the present invention includes magnesium oxide (MgO), chloride Magnesium hexahydrate (MgCl ₂ .6H ₂ O), limestone, silica fume, and water to produce magnesium hydroxide (Mg(OH) ₂ ) inside.

Description

Magnesium Oxychloride Cement And Method For Manufacturing the Same

The present invention relates to magnesium oxide chloride cement (Magnesium Oxychloride Cement) and a method for manufacturing the same, and more particularly, by mixing magnesium oxide (MgO) and magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O), limestone, and silica fume. By generating a large amount of magnesium hydroxide (Mg(OH) ₂ ) inside and securing a large amount of hydrated magnesium carbonate (HMC), which is generated by combining with carbon dioxide, eco-friendliness and water resistance are increased, and carbon fiber is added to prevent shrinkage. It relates to magnesium oxide chloride cement and a method for manufacturing the same.

Cement mixed with magnesium oxide (hereinafter referred to as 'magnesium oxide cement') has excellent initial strength, high heat resistance, low thermal conductivity, low coefficient of thermal expansion, and excellent abrasive resistance due to high heat of hydration. There are significant limitations. In addition, there is a drawback in that the cement shrinks to a rather large extent in the initial hydration process.

As mentioned above, the biggest factor in the limitation that magnesium oxide cement cannot be applied to various industries is because its resistance to water is very low, and when continuously exposed to water, the strength significantly lower than the expected strength (up to 50%) abnormal decrease) is expressed.

Republic of Korea Patent Publication No. 10-2015-0142769 Republic of Korea Patent No. 10-1783063 Republic of Korea Patent Registration No. 10-2089218

Magnesium oxide cement (MOC) is environmentally friendly because it can be viewed as carbon dioxide capture, that is, carbon dioxide bound to the HMC chemical structure as the residue Mg(OH) ₂ is expressed as HMC after generating phase 3 and phase 5, which are the main phases. It is known as a high cement material.

However, in the carbonation process of magnesium oxide cement, the amount of potential carbon dioxide capture is limited because the sufficiency for generating the HMC phase is entirely dependent on Mg(OH) ₂ , which has not changed to the main phase. Accordingly, in order to properly control the corresponding performance, a large amount of magnesium oxide (MgO) must be added at the initial material mixing ratio, but in this case, there is a problem that sufficient strength cannot be obtained.

In addition, the existing magnesium oxide cement has a limitation in being applied to large-scale building structures due to its rather high shrinkage rate.

The present invention is to solve the above problems, and an object of the present invention is magnesium oxide chloride that can be applied to various concrete structures by increasing environmental friendliness and water resistance while retaining the advantages of conventional magnesium oxide cement as it is. To provide cement and a method for manufacturing the same.

Another object of the present invention is to provide a magnesium oxide chloride cement and a method for manufacturing the same, which can be applied to large-scale building structures by suppressing the shrinkage of the cement during the initial hydration process.

Magnesium oxide chloride cement according to the present invention for achieving the above object, including magnesium oxide (MgO), magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O), limestone, silica fume, and water, hydroxyl in the interior Magnesium (Mg(OH) ₂ ) is produced.

The magnesium oxide chloride cement of the present invention may further include carbon fibers.

Magnesium oxide chloride cement of the present invention is 20 to 25% by weight of magnesium oxide (MgO), 5 to 12% by weight of magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O), 1 to 10% by weight of limestone, and 10 to 30% by weight of silica fume. %, 1 to 15% by weight of carbon fiber, and the balance may include water.

The magnesium hydroxide (Mg(OH) ₂ ) is combined with carbon dioxide generated by the reaction of magnesium chloride and limestone to form hydrated magnesium carbonate (HMC).

The method for producing magnesium oxide chloride cement according to the present invention comprises:

(S1) mixing magnesium chloride hexahydrate (MgCl ₂ ·6H ₂ O) in water; and,

(S2) mixing magnesium oxide (MgO), limestone, and silica fume in the mixture mixed in step (S1);

(S3) curing the mixture made in step (S2) by pouring it into a mold;

may include.

In the process of performing the step (S2), carbon fibers may be additionally mixed.

In addition, in the step (S3), it is preferable to cure while maintaining the temperature range of 20 ~ 50 ℃.

Magnesium oxide chloride cement of the present invention produces magnesium hydroxide (Mg(OH) ₂ ) inside by a chemical reaction, and the produced magnesium hydroxide (Mg(OH) ₂ ) is carbon dioxide generated by the reaction of magnesium chloride and limestone. It is combined with hydrated magnesium carbonate (HMC) to change the phase to hydrated magnesium carbonate (HMC), thereby reducing water solubility and increasing strength.

In other words, the magnesium oxide chloride cement of the present invention has increased durability and reactivity by adding limestone and silica fume that increase hydroxide ions during the reaction for capturing carbon dioxide. It has the effect of maximizing and preventing soil and sewage contamination around the ground with M-S-H phase generated by oxidation by-products using silica fume.

1 shows the results of X-ray diffraction analysis for Comparative Example of magnesium oxide cement (MOC) and Example of magnesium oxide chloride cement of the present invention.

Hereinafter, magnesium oxide chloride cement and a method for manufacturing the same according to the present invention will be described in detail.

Magnesium oxide chloride cement according to the present invention contains magnesium oxide (MgO), magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O), limestone, silica fume, carbon fiber, and water, and magnesium hydroxide from the inside by a chemical reaction. (Mg(OH) ₂ ) is formed, and the generated magnesium hydroxide (Mg(OH) ₂ ) is combined with carbon dioxide generated by the reaction of magnesium chloride and limestone to form hydrated magnesium carbonate (HMC). This reduces water solubility and increases strength.

Magnesium oxide chloride cement of the present invention is 20 to 25% by weight of magnesium oxide (MgO), 5 to 12% by weight of magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O), 1 to 10% by weight of limestone, and 10 to 30% by weight of silica fume. %, 1 to 15% by weight of carbon fiber, and the balance may include water.

Magnesium oxide (MgO) is preferably used in a molar ratio (MgO/MgCl ₂ ) of 5 to 15 with respect to magnesium chloride (MgCl ₂ ). Magnesium oxide (MgO) can secure better performance when it is a high-purity product, but it satisfies the requirements in terms of performance even if it is only about 98% pure.

Water (H ₂ O) is preferably used in a molar ratio (H ₂ O/MgCl ₂ ) to magnesium chloride (MgCl ₂ ) of 10 to 13. Since the compounding ratio calculation process is derived according to the molar ratio, it is preferable to use water in which only H ₂ O is present, such as ultrapure water or distilled water. H ₂ O left unattended for a long time reacts with carbon dioxide in the atmosphere and has weak acidity, so magnesium oxide (MgO) is mass-crystallized due to a rapid reaction, so it can be expected to use in a state close to neutral for the most efficient performance.

Magnesium chloride hexahydrate (MgCl ₂ ·6H ₂ O) can show improved results when it is a high-purity product, but it was confirmed that it showed satisfactory results in terms of performance even when only about 98% purity was secured.

For limestone, Ca(CO) ₃ with a purity of about 98% is most suitable, and it is added together with MgO in the order of mixing. Limestone is a mixture that can be extracted in a natural state and has the advantage of excellent economical efficiency.

Carbon fiber serves to suppress the shrinkage of cement in the initial hydration process and to increase overall strength at the same time, providing a more advantageous advantage in the manufacture of large-capacity cement structures. It is appropriate that the length of the carbon fiber is 3 to 15 mm. Since carbon fiber is a material added to prevent volume reduction, it is preferable that the mixing order be placed at a lower priority.

Since silica fume itself has a purity of 85 to 98% of SiO ₂ , it is preferable to use silica fume having a high purity. When a large amount of magnesium hydroxide is produced inside the cement, the relative distribution of crystals for strength expression is lowered, so it is possible to secure initial strength by adding silica fume. In addition, when silica fume is mixed, the magnesium silica hydrate (MSH) phase is secured to prevent contamination by calcium ions in the nearby soil and groundwater by the CSH phase, which is mainly generated in general Portland cement (OPC), Since the finally manufactured product has a pH of about 8, it is possible to smoothly prevent soil and sewage contamination.

Therefore, the magnesium oxide chloride cement of the present invention has increased durability and reactivity by adding limestone and silica fume, which increase hydroxide ions during the reaction for capturing carbon dioxide. The M-S-H phase generated by oxidation by-products using silica fume has the effect of preventing soil and sewage contamination around the ground in advance.

Hereinafter, a method for producing the magnesium oxide chloride cement of the present invention will be described.

The order of mixing is very important because magnesium oxide chloride cement maximizes the strength improvement effect in a weakly acidic environment.

First, to make phase 3 and phase 5, which occupy most of the strength, magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O) is mixed with pure water by stirring at an appropriate speed.

Magnesium oxide (MgO), limestone, and silica fume are added in a predetermined mixing ratio to the homogeneously mixed mixture solution, and the mixture is stirred and mixed. After this, carbonic acid fibers are added thereto and stirred.

Since a chemical reaction occurs from the moment magnesium oxide (MgO) is added, the amount of heat generated increases and the chemical reaction is accelerated. Therefore, it is preferable not to exceed a maximum of 30 minutes agitation when the whole amount is added and mixed at a predetermined mixing ratio.

When the magnesium oxide chloride cement in the form of paste is made in this way, the cement paste is poured into the mold and cured. At this time, it is preferable to apply the surface of the poured cement with a lap to prevent moisture evaporation, penetration, and mixing with other materials.

After the magnesium oxide chloride cement is placed, it is desirable to maintain a temperature range of 20 to 50° C. for the curing temperature, but it is important to maintain the curing temperature because phase 3 and phase 5 are not generated when the temperature is out of the above temperature range.

The chemical reaction occurring inside the magnesium oxide chloride cement described above is as follows, and the subscripts x, y, and z are affected by temperature.

Example

In order to confirm the performance of magnesium oxide chloride cement, compressive strength and carbon dioxide capture performance were measured for the specimens of Comparative Examples in which magnesium oxide was not mixed with limestone and the specimens of Examples 1 and 2 in which magnesium oxide and limestone were mixed in a predetermined mixing ratio. measured.

In Comparative Example, after mixing 23 wt% of magnesium oxide, 11 wt% of magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O), 16 wt% of silica fume, and 50 wt% of water, the width, length, and height are each 50 mm × 50 Specimens were prepared by pouring them into a mold in the form of a cube block measuring ㎜ × 50㎜, and then curing them in air and in a carbonation chamber, respectively. Curing in the carbonation chamber was performed on the specimens after 14 days of age in air.

Example 1 is the same as in Comparative Example after mixing 22 wt% of magnesium oxide, 1 wt% of limestone, 11 wt% of magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O), 16 wt% of silica fume, and 50 wt% of water It is a specimen prepared by pouring and curing (in air and carbonation chamber) in a mold, Example 2 is 21 wt% of magnesium oxide, 2 wt% of limestone, 11 wt% of magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O), After mixing 16% by weight of silica fume and 50% by weight of water, it is a specimen prepared by pouring and curing in a mold in the same manner as in Comparative Example and Example 1.

Table 1 below shows the compressive strength measurement results according to the curing conditions of Comparative Examples and Examples 1 and 2, respectively.

Compressive strength (MPa) age curing in air Curing in carbonation chamber (concentration 3%) after 14 days of age in air comparative example Example 1 Example 2 comparative example Example 1 Example 2 One 41 37 32 - - - 4 47 45 45 - - - 7 50 52 58 52 55 59 14 55 58 61 - - - 28 57 63 69 61 66 72

As can be seen from Table 1 above, the initial compressive strength of the comparative example is greater than that of Examples 1 and 2, but the compressive strength after 7 days of age is significantly increased in Examples 1 and 2, which is larger than that of the comparative example. can be checked

1 shows the results of X-ray diffraction analysis for specimens of Comparative Examples and Example 2 exposed for 7 days in a carbonation chamber after 14 days of age in air.

As a result of X-ray diffraction analysis, it was found that a larger amount of HMC was present in Example 2 in which limestone was added. However, since M-S-H is an amorphous crystal, it is difficult to measure it by X-ray diffraction analysis.

Table 2 below shows the measurement results of the carbon dioxide capture amount of Comparative Examples and Examples 1 and 2. In Table 2, the carbon dioxide capture amount is a theoretical calculation of the carbon dioxide reaction amount of HMC.

Carbon dioxide capture (kg/㎡) age curing in air Curing in carbonation chamber (concentration 3%) after 14 days of age in air comparative example Example 1 Example 2 comparative example Example 1 Example 2 One - - - - - - 4 0.01 0.01 0.01 - - - 7 0.01 0.02 0.02 0.095 0.106 0.132 14 0.029 0.031 0.031 - - - 28 0.057 0.061 0.058 0.298 0.311 0.326

As can be seen from Table 2 above, it can be confirmed that the carbon dioxide capture amount of Examples 1 and 2 in which limestone is mixed is significantly higher than that of Comparative Examples in which limestone is not mixed.

In the magnesium oxide chloride cement of the present invention, limestone (calcium carbonate) is added to increase the basicity of the cement paste, and silica fume is added to secure initial strength and M-S-H phase. The process of pre-treatment or post-treatment can be excluded, and the complicated mixing ratio and mixing method according to the addition of various heterogeneous materials can be eliminated, so that operator errors and risks can be reduced, and economic feasibility can be improved.

The above-described magnesium oxide chloride cement of the present invention generates a large amount of magnesium hydroxide from the inside through calcium carbonate of limestone and potentially secures a large amount of HMC generated by combining with carbon dioxide, thereby increasing environmental friendliness.

In addition, by adding silica fume to secure the M-S-H (magnesium silica hydrate) phase, it is possible to prevent contamination of the nearby soil and groundwater by the C-S-H phase, which is mainly generated in general Portland cement, in advance. Since it converges to about 8, it is possible to smoothly prevent ground and sewage pollution, thereby further improving eco-friendliness.

In addition, a small amount of carbon dioxide generated by the reaction of magnesium chloride and calcium carbonate is combined with magnesium hydroxide inside the cement to undergo phase transformation into HMC, which has the effect of expanding the range of cement application by improving water resistance. to provide.

The magnesium oxide chloride cement of the present invention can obtain very advantageous advantages when applied to heating materials and flooring materials, but can also be applied to various fields.

The above description is merely illustrative of the technical spirit of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of the present invention by those skilled in the art to which the present invention pertains. Accordingly, the embodiments described in the present invention are not intended to limit the technical spirit of the present invention, but to illustrate, and the technical spirit of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (7)

Magnesium oxide (MgO) 20-25 wt%, magnesium chloride hexahydrate (MgCl ₂ 6H ₂ O) 5-12 wt%, limestone 1-10 wt%, silica fume 10-30 wt%, carbon fiber 1-15 wt% %, and the balance water, magnesium oxide chloride cement to produce magnesium hydroxide (Mg(OH) ₂ ) therein. delete delete The magnesium oxide chloride cement of claim 1, wherein the magnesium hydroxide (Mg(OH) ₂ ) is combined with carbon dioxide generated by the reaction of magnesium chloride and limestone to form hydrated magnesium carbonate (HMC). A method for producing magnesium oxide chloride cement according to claim 1 or 4, comprising:
(S1) mixing magnesium chloride hexahydrate (MgCl ₂ ·6H ₂ O) in water; and,
(S2) mixing magnesium oxide (MgO), limestone, silica fume, and carbon fiber with the mixture mixed in step (S1);
(S3) curing the mixture made in step (S2) by pouring it into a mold;
A method for producing magnesium oxide chloride cement comprising a. delete [Claim 6] The method of claim 5, wherein in the step (S3), the magnesium oxide chloride cement is cured while maintaining a temperature range of 20 to 50°C.

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