KR102422247B1 - Low carbon and rapid hardening cement composition using ladle furnace slag - Google Patents

Abstract

A rapid hardening cement composition according to an embodiment of the present invention includes CA-based ladle furnace slag fine powder containing a lower content of Fe than the standard content and having smaller particle sizes than the sorting standard particle size; 0.2 to 2.0% of a setting retardant; and one or more selected from dihydrate gypsum and hemihydrate gypsum, wherein the CA-based ladle furnace slag fine powder includes CA-based minerals which are 40 to 60% of the CA-based ladle furnace slag fine powder, and the powder degree of the CA-based ladle furnace slag fine powder is from 5,000 to 7,000 cm^2/g. According to the present invention, the high early and long-term strength and volume stability of the low carbon and rapid hardening cement composition can be ensured.

Description

Low-carbon super-velocity cement composition using refining slag

The present invention relates to a low-carbon super-velocity cement composition using refining slag.

As a result of the present invention, the task information is as follows.

1. Assignment information: 10414841

2, Department name: Small and Medium Venture Business Corporation

3. Task management agency: Small and Medium Venture Business Corporation

4. Research project name: Startup success package commercialization support project

5. Research project name: Slag-based carbon-reducing ultra-velocity eco-cement

6. Name of project performing organization: CM Tech

7. Research period: 2021.03.23 ~ 2021.11.30

Looking at the amount of domestic steel slag generation and utilization, more than 26 million tons of slag is generated annually, and blast furnace slag, which accounts for 15 million tons, is used as cement admixture for more than 90%. Most of the 10 million tons of oxidized slag for converters and electric furnaces is used as aggregate for roads and fills, and both slags have a recycling rate of more than 99%.

However, it is estimated that about 1 million tons of secondary refining slag (or reduced slag) generated from converters and electric furnaces is generated per year, but most of them are not utilized, and steel companies are having difficulties in their treatment. (See Fig. 2a. Photo of discharging molten slag to the yard)

Refining slag contains 10~65% of C2S (2CaO·SiO2) in the process, and when discharged in a molten state of about 1,600°C, C2S existing in the α phase is gradually cooled and transitions to the γ phase at around 830°C. In this process, it undergoes a self-differentiation process for several hours to several days by volume expansion of 1.1 times and is powdered. For this reason, it cannot be used as aggregate, and water is continuously sprayed on the yard due to scattering dust, and alkaline leachate is generated in the process, causing environmental problems. This is pointed out as the main cause of environmental pollution at outdoor sites of steel companies. (See Fig. 2d. Photo of alkaline leachate generation)

Refining slag uses Si or Al as a deoxidizer along with quicklime (CaO) for desulfurization due to the nature of the process. CA-based refining slag contains 40-50% CaO, 20-30% Al2O3, and 5-15% SiO2 as main oxides. It contains about 40-55% of γ-C2S and contains 10-30% of γ-C2S. Even in the annealed refining slag, γ-C2S has low reactivity, but shows rapid hydration by C12A7.

Although CA-based slag contains a large amount of quick-setting minerals, currently, it is mixed with CS-based slag and discharged, which reduces the value of CA-based slag and causes severe fluctuations in the quality of the discharged slag. Furthermore, in most steel mills, by mixing and discharging refining slag with oxide slag and converter slag (see Fig. 2b. Photo of oxidized slag mixed and discharged), the value of oxidized slag and converter slag as an aggregate is reduced and refined slag is simultaneously discharged. It is a situation that nullifies the use value of In addition, as described above, most of the steel yarns lose their value as a raw material for cement compositions by spraying water in the cooling process after discharge. (See Fig. 2c. Photo of watering when slag is treated)

On the other hand, the cement industry is facing an unprecedented crisis in order to achieve the carbon emission target compared to 2030 at the level of 11% of the industry's total emission as a high greenhouse gas emission industry. The main raw material for cement is limestone, which is It emits 82.3% of the total emissions of the cement industry, and 0.83 CO2·ton.eq. discharge

Accordingly, as technical means and methods for carbon neutrality in the cement industry, the use of decarbonated raw materials, the use of alternative fuels, improvement of equipment and process efficiency, CCUS, etc. have been suggested, but among them, the most efficient and fastest approach is It was confirmed that the use of alternative raw materials with low emission). Therefore, it is time to develop various alternative low-carbon raw materials for the cement industry.

On the other hand, super-velocity cement started with Regulated Set Cement (RSC), developed by the Portland Cement Association (PCA) research institute of the United States, and it is possible to secure the required strength at an early stage. , it plays a very important role as a high-performance concrete in the civil engineering field.

In Korea, C ₄ A ₃ S (3CaO·3Al ₂ O ₃ ·CaSO ₄ , Hauyne) and CA (Calcium Aluminate) such as C12A7 and C3A are mainly used to manufacture super-fast cement.

Although the use of ultra-fast cement is increasing due to the high speed, urbanization, and density of structures, which are characteristics of modern society, the market is limited due to the price more than 10 times higher than that of general cement.

The Al ₂ O ₃ source of super-velocity cement mainly uses bauxite as a raw material, and it is also an expensive raw material that is mostly imported from Korea, and has a limit on the lowest unit price.

Korean Patent Publication No. 10-2017-0122919 (published on November 7, 2017) Republic of Korea Patent Publication No. 10-1333084 (Registered on November 20, 2013)

An object of the present invention is to provide a low-carbon super-velocity cement composition having high ultra/long-term strength and volume stability.

The task of the present application is not limited to the task mentioned above, and another task that is not mentioned will be clearly understood by those skilled in the art from the following description.

The cement composition for super-velocity cement according to one aspect of the present invention includes a fine powder of CA-based refining slag that contains Fe in an amount lower than the reference content, and is smaller than the selection standard particle size; 0.2% to 2.0% of a setting retardant; and at least one selected from dihydrate gypsum and hemihydrate gypsum, wherein the CA-based fine powder of refined slag contains 40% to 60% of the fine powder of CA-based refining slag, CA-based minerals, and the fineness of the CA-based refined slag fine powder is 5,000 cm ² /g to 7,000 cm ² /g.

When hemihydrate gypsum is selected among the dihydrate gypsum and hemihydrate gypsum, the fineness of the hemihydrate gypsum is 2,500 cm ² /g to 6,500 cm ² /g, the CA-based refined slag fine powder is 100 parts by weight, and the hemihydrate gypsum is It may be 10 parts by weight to 30 parts by weight.

When dihydrate gypsum is selected among the dihydrate gypsum and hemihydrate gypsum, the fineness of the dihydrate gypsum is 2,500 cm ² /g to 6,500 cm ² /g, the CA-based refined slag fine powder is 100 parts by weight, and the dihydrate gypsum is 20 parts by weight parts to 40 parts by weight.

When the dihydrate gypsum and the hemihydrate gypsum are selected, the CA-based refined slag fine powder is 100 parts by weight, the hemihydrate gypsum is 10 parts by weight to 30 parts by weight, and the dihydrate gypsum may be 20 parts by weight to 40 parts by weight.

The selection criterion particle size may be 0.6mm to 10mm.

The CA-based refining slag fine powder may be formed by cooling slag in a molten state without contact with water.

The setting delay agent may be made of at least one selected from the tartaric acid, sodium citrate, gluconic acid and citric anhydride.

The present invention is to improve low ultra-long-term strength development and high volume change rate in order to utilize a low-carbon quick-setting cement composition using dry slow cooling refining slag (or reduced slag) as a substitute for super-velocity cement. Two types of gypsum It is possible to provide a low-carbon, super-velocity cement composition with high ultra-long-term strength and volume stability by using the optimal mixture.

According to the present invention, when gypsum is properly mixed and used in the cement composition using refining slag (or reduced slag), it can be utilized as a low-carbon cement composition that exhibits performance equal to or higher than that of super-velocity cement.

The present invention can provide price competitiveness by significantly reducing the amount of natural raw materials used and omitting the firing process, thereby reducing the production cost through energy consumption reduction.

The present invention emits 0.92 tons of CO2 per ton of cement per ton, but the developed product can reduce the carbon footprint by significantly reducing CO2 emissions of 0.16 tons.

The effect of the present application is not limited to the above-mentioned effects, and another effect not mentioned will be clearly understood by those skilled in the art from the following description.

1 shows a process for preparing an annealed drying slag fine powder.
2A to 2D are photographs of a conventional refining slag treatment method.
3A to 3D are photographs of the results of the particle size selection step in the process of FIG. 1 .
4 is a table showing an example of the particle size distribution of slag after the dry slow cooling step.
5A to 5C are photographs of results of the magnetic screening step.
6 shows a photograph of the binder used in the present invention.
7 shows the result of setting gypsum mixture according to the present invention.
8 shows the strength results according to the mixing rate of hemihydrate gypsum.
9 shows the strength results according to the mixing rate of dihydrate gypsum.
10 shows the length change according to the mixing of hemihydrate gypsum and dihydrate gypsum.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the accompanying drawings are only described in order to more easily disclose the contents of the present invention, and those of ordinary skill in the art can easily understand that the scope of the present invention is not limited to the scope of the accompanying drawings. you will know

In addition, the terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that this does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

The present invention utilizes a fast-hardening cement composition using dry slow cooling refining slag. In other words, CA-based refining slag (or reduced slag) is dry annealed through process separation, and magnetically selected slag of 5 mm under size (size less than 5 mm) through particle size screening to exclude samples with high Fe content. As a raw material, it is a fine powder having a powder of 5,000 cm ² /g to 7,000 cm ² /g with a CA mineral content of 40% to 60%, and at least one selected from tartaric acid, sodium citrate, gluconic acid and citric anhydride. A fast-setting cement composition containing 0.2% to 2.0% of a setting retardant of the hard cement composition is provided.

If the CS mineral content in the refining slag is less than 40%, the initial and long-term strength is low. .

Unlike the present invention, if the fineness is less than 5,000cm ² /g, the hydration reaction rate may be reduced. In addition, unlike the present invention, when the fineness is greater than 7,000cm ² /g, the mixing number is increased, so that the fluidity is deteriorated and the grinding cost may increase in order to produce a high fineness.

1 shows a process for producing a fine powder from the selected raw material. As shown in FIG. 1 , the manufacturing process includes a process separation step, dry slow cooling step, particle size screening step, coarse crushing step, magnetic screening step and fine pulverization step.

1) Process separation step

This step is a step to secure and prepare CA-based slag in a molten state that is not mixed with CS-based slag among refining slag. Separate ports are provided so that oxidation, converter slag and refining slag are separately discharged in the discharge process, and are discharged to each port. .

In other words, in order to utilize CA-based slag for low-carbon quick-setting cement, when discharged from the melting stage, it is collected in a separate port and stored separately for the slow cooling process.

Table 1 below describes the oxide composition ratios according to the CS-based and CA-based slags. CS-based slag and CA-based slag show a large difference in oxide composition, and in particular, a large difference in SiO ₂ and Al ₂ O ₃ content due to process characteristics depending on the type of reducing agent used. Referring to Table 1, the Al ₂ O ₃ content of the CS system is 5-15% and the CA system is 25-35%. The currently secured slag is slag in a mixed state, and Table 1 below shows that there is a slight deviation in the composition ratio of components as self-separated.

oxide
composition ratio division
delivery date CS-based slag CA-based slag CaO Fe ₂ O ₃ Al ₂ O ₃ SiO ₂ MgO CaO Fe ₂ O ₃ Al ₂ O ₃ SiO ₂ MgO 2021. 1st 50.2 1.2 14.6 20.2 11.2 54.7 1.1 26.3 7.0 6.7 2021. 2nd 44.8 2.3 13.9 22.6 12.1 54.4 0.8 27.7 6.9 7.3 2021. 3rd 36.1 21.7 9.4 17.6 8.0 49.1 2.1 33.3 5.2 6.6 2021. 4th 40.3 6.2 12.3 23.2 11.9 51.3 1.2 29.0 6.3 6.7 2021. 5th 36.1 21.7 9.4 17.6 8.0 46.2 5.1 32.6 6.2 6.6

However, when the process is separated and only CA-based slag is used alone, the Al ₂ O ₃ content deviation range of the current mixed state refining slag can be easily controlled from 10-35% to 25-35%. 60%) of CA (Calcium aluminate)-based minerals (C12A7 (Mayenite) and C3A, etc.) content of slag raw materials can be secured.

2) Dry slow cooling step

In order to prevent the quick-setting minerals C12A7 and C3A from losing their cementitious properties through sprinkling treatment, the slag in the molten state is moved to a cooling place using a pot, and then completely undergoes the differentiation process without contact with water. That is, the slag discharged in the molten state is maintained and stored in the pot without contact with moisture until it is cooled to room temperature and moved to the sorting plant.

In order to dry refining slag, a closed space without separate moisture and contact is required. It is also possible to recover the heat of high-temperature hot air through an air circulator by using the waste heat generated in the process of cooling the high-temperature molten slag above 1600℃ in the enclosed space. And, as the differentiated fine powder exists as a fine powder of 25% or more and 150 μm or less as shown in FIG. 4, it is possible to secure a high fine powder of 150 μm or less through a dust collector without a grinding process.

Dry slow cooling refining slag cooled without contact with water can maintain its value as a raw material for quick-setting cement compositions as the minerals such as C12A7 and C3A contained therein maintain high reactivity.

3) Particle size selection step

3A to 3D are photographs of the results of the particle size selection step. 3a: slag resulting from the dry slow cooling step, 3b, 3c: a particle size exceeding 5 mm, 3d: a particle size of 5 mm or less. 4 is a table showing an example of the particle size distribution of slag after the dry slow cooling step.

The dry slow-cooled refining slag is moved to the particle size sorting plant and classified into ① 5mm over size and ② 5mm under size through particle size classification based on a 5mm sieve. Dry annealed refining slag shows a big difference in quick setting and initial exothermic properties depending on the particle size, so it is to classify the particle size and use it differently.

However, as the particle size of slag differs according to the composition and environmental changes at the time of discharge, the range of the particle size classification sieve is 0.6 mm to 10 mm depending on the design conditions, and there is a possibility of variation depending on the required product quantity. That is, the range of the sieve may vary depending on the selection standard particle size.

In other words, it includes using a combination of slags to match the properties of the slags classified according to the selection standard particle size. Thus, slags can be combined and used through the same property analysis. Therefore, it is natural that the present invention can also be applied by adopting a selection standard particle size within the range of 0.6mm to 10mm to fit the range of the fine aggregate standard particle size.

4) Crushing step

In the case of over size of 5mm, it exists in lumps of various sizes (5mm ~ tens of cm), and it is crushed to size under 5mm (under size) using a crusher. Depending on the design conditions, the selection standard particle size may vary.

5) Magnetic screening step

① 5mm under size slag obtained by rough crushing 5mm over size slag and ② 5mm under size slag are all sorted and moved to a magnetic separator for magnetic separation. 5A to 5C are photographs of results of the magnetic screening step. 5a, 5b: Examples of magnetic sorting, 5c: magnetically screened samples by particle size.

Dry slow cooling slag shows a maximum of 10% or more of Fe oxide when pulverized without a magnetic sorting step, which is a factor in reducing strength when used as a binder. In addition, high Fe content can decrease the efficiency of grinding due to ductility, so it is necessary to control it to within 2% through Gauss control of the sorter during magnetic sorting.

Furthermore, the slag with a high Fe oxide content selected by magnetic force can be reintroduced as a process raw material for steel mills, and can also be used as an Fe source for cement companies.

Tables 2 and 3 below describe the oxide and mineral compositions after the magnetic separation step for each particle size.

CaO Al ₂ O ₃ SiO ₂ MgO SO ₃ Fe ₂ O ₃ Etc Sum 5mm over + crushing 48.6 30.3 5.74 10.7 3.66 0.62 0.38 100 5mm under size 47.1 30.4 8.29 7.67 3.4 2.14 One 100

granularity CaO Al ₂ O ₃ SiO ₂ MgO SO ₃ Fe ₂ O ₃ 5mm over
+ Crushing 48.6 30.3 5.74 10.7 3.6 0.6 2.5mm 47.3 26.3 6.9 8.0 3.2 2.2 1.2mm 49.1 27.7 7.1 10.0 3.9 0.8 0.6mm 49.2 29.0 7.6 8.2 4.1 0.6 0.3mm 49.1 30.5 7.0 6.6 3.3 2.0 0.15mm 49.3 31.5 6.2 6.5 3.3 1.6

6) pulverization step

① 5mm over size + coarse crushed slag and ② 5mm under size slag, excluding screening samples with high Fe content after magnetic screening, are each finely pulverized to produce fine powder with a fineness of 5,000~7,000cm ² /g.

① 5mm over size + coarse crushed slag and ② 5mm under size slag are different in shape depending on the degree of self-differentiation due to volume change in the C2S phase change process. ② The SiO ₂ content is relatively high at 5mm under size higher

(7) Preparation of fast-setting cement composition

There is provided a fast-setting cement composition containing the previously formed fine powder and at least one selected from tartaric acid, sodium citrate, gluconic acid and citric anhydride in an amount of 0.2% to 2.0% of a setting retarder.

The main mineral of the quick-hardening cement composition using the dry slow-cooling refining slag (or reduced slag) above is a CA-based mineral. The CA-based mineral ultimately produces a C3AH6 mineral when it reacts with water, but by mixing gypsum, the SO ₃ ^2- ion Through the reaction with dissolution, needle-like ettringite (3CaO·Al ₂ O ₃ ·3CaSO ₄ ·32H ₂ O) is generated on the surface, which induces continuous strength expression and can contribute to long-term strength expression. .

Etrinzite has a high binding water, so it has a low density, so it has a large occupied volume and is used as an intumescent material. It is possible.

However, since gypsum has different manufacturing conditions depending on the type, its solubility and its contribution to cement are different, and there is a potential risk of expansion and fracture due to the formation of ethrinzite due to excessive mixing, the appropriate type and mixing rate of gypsum are important. become the determinant

Accordingly, the present invention intends to propose a type and mixing rate of gypsum suitable for a low-carbon, super-fast cement composition using a fast-setting cement composition using dry slow-cooling refining slag (or reduced slag).

Example 1. High-quality low-carbon super-velocity cement composition using hemihydrate gypsum

Calcined gypsum (CaSO ₄ ·1/2H ₂ O) is artificially processed into hemihydrate by high-temperature treatment or high-temperature treatment and high-pressure treatment with gypsum dihydrate (CaSO ₄ ·2H ₂ O). It is sold at a high unit price in Korea by additional processing.

Since hemihydrate gypsum has a higher initial solubility than dihydrate gypsum, it contributes to a quick reaction during mixing and can greatly improve the initial strength. It was confirmed that expression is possible up to time intensity expression impossible).

In addition, by pouring the cement composition of the present invention after mixing and expressing 20 MPa or more within 1 hour, it can be utilized for shortening the production time of secondary concrete products.

In the present invention, only CA-based refining slag (or reduced slag) is subjected to dry slow cooling through process separation, and magnetically selected slag of 5 mm under size through particle size screening to exclude samples with high Fe content, 100 parts by weight of a fine powder having a fineness of 5,000cm ² /g to 7,000cm ² /g containing 40% to 60% or more of a CA (Calcium aluminate)-based mineral as a raw material, a fineness of 2,500 cm ² /g to 6,500cm ² / g Hemihydrate gypsum 10 to 30 parts by weight, the setting retardant is provided with a quick-setting cement composition containing 0.2% to 2.0% of at least one selected from tartaric acid, sodium citrate, gluconic acid and citric anhydride.

If the fineness of the hemihydrate gypsum is less than 2,500 cm ² /g, the reactivity is lowered, and if the fineness of the hemihydrate gypsum is greater than 6,500 cm ² /g, the grinding cost may excessively increase.

Example 2. Low-cost, low-carbon, super-velocity cement composition using dihydrate gypsum

Dihydrate gypsum is classified into natural dihydrate gypsum dissolved in seawater or existing in the earth's crust in its natural state, and chemical gypsum, which is a generic term for waste gypsum produced in the process of industrial development.

Natural gypsum has a higher purity than chemical gypsum, but its utilization rate is low due to its high unit price. In addition, chemical gypsum is produced by various processes such as phosphate gypsum, hydrofluoric acid gypsum, and desulfurized gypsum.

Dihydrate gypsum has lower initial solubility compared to hemihydrate gypsum, so the 3-hour strength (5-10 MPa) expression rate is low. However, from the age of 3 days, the strength is greater than that of semi-hydraulic gypsum, which has strengths in terms of unit cost for the production of super-fast cement compositions, and in terms of the environment in which 100% industrial by-products are used when chemical gypsum is used.

The present invention is a dry slow cooling treatment for only CA-based refining slag (or reduced slag) through process separation, and magnetic separation of 5mm under size slag through particle size screening, excluding samples with high Fe content, selected raw materials 100 parts by weight of a fine powder having a fineness of 5,000 cm ² /g to 7,000 cm ² /g containing 40% to 60% of a calcium aluminate (CA)-based mineral, a fineness of 2,500 cm ² /g to 6,500 cm ² /g Selectively from 20 parts by weight to 40 parts by weight of natural dihydrate gypsum or chemical gypsum having A composition is provided.

Example 3. Low-carbon ultra-rapid cement composition using a mixture of hemihydrate and dihydrate gypsum

In the case of using hemihydrate gypsum, the strength expression rate at the initial age (1 hour, 3 hours, and daily strength) is high, but as a problem of unit price increase occurs, a composition using hemihydrate gypsum and dihydrate gypsum appropriately mixed can also be used depending on the purpose. .

Only CA-based refining slag (or reduced slag) is dry annealed through process separation, and magnetically selected slag of 5mm under size through particle size screening to exclude samples with high Fe content, and CA ( Calcium aluminate) containing 40% to 60% of a fine powder having a fineness of 5,000cm ² /g to 7,000cm ² /g, 100 parts by weight, 10 parts by weight to 30 parts by weight of hemihydrate gypsum, natural dihydrate gypsum or chemical gypsum 20 to 40 parts by weight of the selected gypsum dihydrate, and the setting retarder is provided with a quick-setting cement composition containing 0.2% to 2.0% of at least one selected from tartaric acid, sodium citrate, gluconic acid and citric anhydride.

7 shows the result of setting gypsum mixture according to the present invention. In the case of Figure 7, 0.5% to 1.5% of the setting retarder is contained, OPC100 is 100% ordinary Portland cement, RSC100 is concrete using super-velocity cement 100%, SC-LFS is dry slow cooling refining slag, HG25 is The ratio of dry slow-cooled refining slag to hemihydrate gypsum is 75:25, and DG40 shows the ratio of dry slow-cooled refining slag to dihydrate gypsum is 60:40. .

8 shows the strength results according to the mixing rate of hemihydrate gypsum. 8 shows the changes in compressive strength and flexural strength after 3 hours, 1 day, 3 days, and 28 days. In FIG. 8, LFS+ represents the cement of the present invention including hemihydrate gypsum and dry slow cooling refining slag. In addition, HG20 to HG28 indicate that the ratio of dry slow cooling refining slag and hemihydrate gypsum is 80:20 to 72:28.

9 shows the strength results according to the mixing rate of dihydrate gypsum. FIG. 9 shows the compressive strength after 3 hours, 1 day, 3 days, and 28 days during air curing and water curing. In FIG. 9, LFS75HG25 represents cement in which the ratio of dry slow-cooled refining slag to hemihydrate gypsum is 75:25. LFS+ refers to the cement of the present invention comprising dihydrate gypsum and dry slow cooling refining slag. DG30 to DG 40 represent the case where the ratio of dry slow cooling refining slag and dihydrate gypsum is 70:30, 68:32, 66:34, 64:36, 62:38, and 60:40, respectively. AI is an abbreviation for Activity Index (hydration activity), and compares the intensity value of the OPC100 specimen to the comparison specimen in a ratio.

Figure 10 shows the length change in the water curing and air-dry curing of the specimen according to the mixing of hemihydrate gypsum and dihydrate gypsum. In Figure 10, SCLFS75HG25 shows a 75:25 ratio of dry slow cooling refining slag and hemihydrate gypsum. In SCLFS60DG40, the ratio of dry slow cooling refining slag to dihydrate gypsum is 60:40.

As described above, the embodiments according to the present invention have been reviewed, and the fact that the present invention can be embodied in other specific forms without departing from the spirit or scope of the present invention in addition to the above-described embodiments is recognized by those with ordinary skill in the art. It is self-evident to Therefore, the above-described embodiments are to be regarded as illustrative rather than restrictive, and accordingly, the present invention is not limited to the above description, but may be modified within the scope of the appended claims and their equivalents.

Claims (7)

The slag in the molten state is slowly cooled without contact with water, the particle size of the selection criterion is smaller than 0.6 to 10 mm, contains Fe lower than the reference content, contains 40 to 60% of CA-based minerals, and the fineness is 5,000 to 7,000 cm ² /g 100 parts by weight of CA-based refined slag fine powder prepared to satisfy the condition;
10 to 30 parts by weight of hemihydrate gypsum having a fineness of 2,500 to 6,500 cm ² /g; and
Containing 0.2 to 2.0% of the cement composition, a setting retardant comprising at least one selected from tartaric acid, sodium citrate, gluconic acid and citric anhydride; The slag in the molten state is slowly cooled without contact with water, the particle size of the selection criterion is smaller than 0.6 to 10 mm, contains Fe lower than the reference content, contains 40 to 60% of CA-based minerals, and the fineness is 5,000 to 7,000 cm ² /g 100 parts by weight of CA-based refined slag fine powder prepared to satisfy the condition;
20 to 40 parts by weight of dihydrate gypsum having a fineness of 2,500 to 6,500 cm ² /g; and
Containing 0.2 to 2.0% of the cement composition, a setting retardant comprising at least one selected from tartaric acid, sodium citrate, gluconic acid and citric anhydride; The slag in the molten state is slowly cooled without contact with water, the particle size of the selection criterion is smaller than 0.6 to 10 mm, contains Fe lower than the reference content, contains 40 to 60% of CA-based minerals, and the fineness is 5,000 to 7,000 cm ² /g 100 parts by weight of CA-based refined slag fine powder prepared to satisfy the condition;
10 to 30 parts by weight of hemihydrate gypsum having a fineness of 2,500 to 6,500 cm ² /g;
20 to 40 parts by weight of dihydrate gypsum having a fineness of 2,500 to 6,500 cm ² /g; and
Containing 0.2 to 2.0% of the cement composition, a setting retardant comprising at least one selected from tartaric acid, sodium citrate, gluconic acid and citric anhydride; delete delete delete delete

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