KR950010000B1 - Manufacturing method of activated slag fine powder used for unsepared cement composition for underwater construction - Google Patents

Abstract

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Description

Manufacturing method of activated slag fine powder used for unsepared cement composition for underwater construction

FIG. 1A is a photograph (magnification of 3,000 times) of a paste cured product obtained by hydrated cement alone using a scanning microscope,

FIG. 1B is a photograph (magnification of 3,000 times) of a paste cured product hydrated by adding fine activated slag powder to cement according to the present invention.

2 is a graph measuring pores by the mercury intrusion method for the cured product of FIG.

The present invention relates to a method for preparing activated slag fine powder used in fire-dissolving cement composition for underwater construction.

In recent years, the demand and construction of underwater concrete structures have increased rapidly in the developed countries according to the trend of marine development.In addition, the domestic conditions are surrounded by the sea on three sides, and there are many projects related to the sea such as harbors, marine civil engineering, and pedestrian bridges. Most are for civil engineering. Currently, underwater concrete construction in Korea is mostly carried out by the bottom box and the bagging method, the bagging concrete method, the bucket method, the pumping method and the treme tube method, and the preliminary compact method by the high flow mortar injection method. . Underlay boxes, bags and buckets, which are most commonly used in Korea, are relatively easy to construct, and may be suitable for small-scale construction. However, the cement, sand, and aggregate separations are severe in the water, resulting in high precision and low strength. This is difficult, and there is a problem that the water pollution caused by the separation of the concrete is greatly caused.

Although the method of pumping and tremi pipe construction can reduce the separation of cement, sand, aggregates, etc., compared to the lower box or bucket method, the separation of cement cannot be avoided. It is difficult to move, and the equipment is expensive.

The pre-filled method developed in 1947 in the United States is a method of pouring the mortar into the void after filling it with coarse aggregate, and it is suitable for mass casting and continuous injection. However, this method also cannot prevent the separation shape completely. However, it is difficult to use for thin slab structures or small constructions. As such, the necessity of the development of a new underwater concrete pouring method has emerged to solve problems such as separation of cement and aggregate generated in the conventional construction method and cost increase due to the advancement of construction technology and equipment.

In 1974, a method was developed in Germany for the first time using a cement composition containing a highly viscous water-soluble polymer to prevent the separation of cement in water (West German Patent No. 2,326,647). Research on the development and construction technology of underwater disintegrating concrete using the disintegrating admixture is actively underway. For example, Japanese Patent Laid-Open Nos. 57-3,921, 58,69,760, 58-115,051, 58-18,1754, 60-251,159, 61-21,949, 62-1000,468, and Pyeong 2- 271,947 discloses cellulose ether-based and acrylic-based water-soluble polymer admixtures which are used as an indeterminate admixture in water.

The cellulose ether-based non-isolating admixtures known to date are nonionic methyl cellulose (MC), ethyl cellulose (EC), hydroxyethyl cellulose (HEC), hydroxy propyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC). ), Hydroxyethyl methyl cellulose (HEMC), hydroxy ethyl cellulose (HEEC) and ionic carboxy meth cellulose (CMC).

Examples of the acrylic disintegrating admixture include polyacrylamide (PAA), sodium acrylate, polyacrylamide partial hydrolyzate, and the like, and polyethylene oxide (PEO) and polyvinyl alcohol (PVA).

Currently, the cellulose ester-based non-isolated admixture described in the Japanese Patent Laid-Open is a small amount of antifoaming agent for suppressing air generation to a thickener having a viscosity of 2,000 to 100,000 cps (Japanese Patent Laid-Open No. 58-69,760), or a metal as a curing accelerator. Method of adding sulfate or metal chloride (JP-A-58-115,051), using anhydrous or calcined alum to increase strength (JP-A-60-65,755), Cellulose etler system to improve separation resistance And acrylic polymer or polyethylene oxide in a weight ratio (Japanese Laid-Open Patent Application No. 60-260, 453, 60-251,159, 63-206,344), and the like to prevent cellulose from curing of underwater concrete. There is a method in which part of the ether is partially substituted with a sulfonic acid base (JP-A 61-21,949).

Most of the main types of fire separation admixtures for water construction shown up to this time are contacted with nonionic cellulose ethers, and the improvement of the separation properties through their modification or mixed use with acrylics is expected. Underwater concrete pouring method using the disintegrating admixture, which has been increasing in recent years, is more economical because it is easier to install and shortens the air compared to the existing method, and it is possible to obtain high-quality concrete, but there are some disadvantages. It is becoming.

Construction problems caused by the use of non-isolated admixtures based on cellulose ether-based or acrylic thickeners include large amounts of air, delayed condensation and initial strength, and poor workability due to high viscosity. There are some limitations to the solution through the reform of the bay. In particular, considering the application to reinforced concrete and prestressed concrete in marine structures where they are mainly used, the reinforcement of concrete and securing fluidity are important.

However, when the amount of unit cement is increased to increase the strength of the structure, the erosion of the structure may be caused by the diffusion of chlorine ions contained in the seawater, and a problem of raising the insulation temperature in the mass concrete may be raised. Therefore, it is desirable to secure the required strength and workability while reducing the amount of cement and admixture used.

Therefore, in the present invention, in order to solve the problems of construction, such as the condensation delay phenomenon of concrete, early strength expression, difficulty in securing workability, intrusion resistance to chlorine ions, increase in heat insulation temperature of concrete, etc. In general, portland cement was mixed with an appropriate amount of glass blast furnace slag with anhydrous gypsum and sodium hydroxide to increase its activity, and a water-soluble cellulose ether-based polymer and an antifoaming agent were appropriately mixed to prepare an inert cement composition for underwater construction.

That is, the present invention improves the strength and workability in the early and late stages compared to the concrete using the existing underwater fire-dissolving admixtures, and is capable of producing durable concrete for underwater construction that can be used in marine environments. It is an object of the present invention to provide a method for preparing activated slag fine powder for use in a composition.

Hereinafter, the present invention will be described in detail.

The present invention mixes 4 to 10 parts by weight of sodium hydroxide with 3 to 7 parts by weight of Ⅲ anhydrous gypsum and dissolves 30 to 40 parts by weight with respect to 100 parts by weight of granular blast furnace slag before grinding. By stirring, aging, and drying, the powder is also 4,000 to 5,000 cm ² / g, which is a method for producing activated slag fine powders used in the separation of cement composition for underwater construction.

Referring to the present invention in more detail as follows.

The fire-resistant cement composition for underwater construction using the active and slag fine powder of the present invention is composed of cement, activated slag fine powder, nonionic cellulose ether thickener, high-melting agent and antifoaming agent of melaminesulfonic acid or triasine compound.

As the cement in the present invention, various portland cements such as crude steel, steam for heating, and sulfates may be used.

In the present invention, when placing in water to suppress the increase in the concrete insulation temperature according to a large amount of concrete pouring, and in order to increase the erosion resistance by chlorine ions in the acid or sea water, a fine glass blast furnace slag powder is used in place of cement. At this time, when the slag is pulverized and used at the specific surface area level of the cement (3,000 to 4,000 cm ² / g), the coagulation delay and the decrease in strength expression rate at the initial stage of the use of the slag appear, and when used with thickeners Has a problem that it occurs more largely, Japanese Laid-Open Patent Publication No. 63-11,553 used high-purity blast furnace slag of 6,000 to 14,000 cm ² / g to improve the initial strength reduction and separation resistance. Although described, in reality, when pulverized blast furnace slag poorly pulverized to a level of 6,000 to 14,000 cm ² / g, there is a disadvantage that it is not economical due to the increase in manufacturing cost.

In the present invention, using a stimulant that promotes hydration of slag without high-micronized slag, the hydration activity is better than that of conventional glass blast furnace slag, and then used in cement to express strength and durability at early and late stages. This makes excellent cement.

The method for producing the activated glass blast furnace slag in the present invention is as follows. First, 4 to 10 parts by weight of sodium hydroxide and 3 to 7 parts by weight of soluble type III anhydrous gypsum were mixed with 100 parts by weight of water to prepare an aqueous solution.

An aqueous solution of sodium hydroxide and anhydrous gypsum is then mixed with 30 to 40 parts by weight with respect to 100 parts by weight of granular glass gora slag having a size of 0.2 to 0.3 mm. Then, after sufficiently stirring for 20 to 30 minutes using a mixer, the slag particle supernatant in a wet state is separated using a 150 µm sieve. The slag particles filtered through the 150 μm sieve are aged in the atmosphere for 40 to 80 minutes and then completely dried in a drier at 110 ± 10 ° C.

At this time, the remaining aqueous solution can be recovered through a 150 μm sieve and recycled by replenishing an appropriate amount of sodium hydroxide and type III anhydrous gypsum. The slag dried in a slag dryer is ground in a mill to a specific surface area of 4,000 to 5,000 cm ² / g to prepare the activated slag powder.

When the activated slag fine powder prepared in this way is used, unlike the conventional fine powder slag, the following actions can be expected.

The blast furnace slag, a waste by-product of the steel mill, is mostly in the glass phase during quenching with water. When glass blast furnace slag powder is mixed with water, no reaction occurs. This is because when CnO-rich glass powder such as slag comes into contact with water, Ca ²⁺ ions are eluted and H from water This is because ions are taken in to form a metastable thin film on the particle surface to stop melting of the slag. However, when an alkaline solution is added thereto, the hydration reaction proceeds because alumina is dissolved (breaking of the coating) in the coating. In particular, sodium hydroxide solution is the most effective material to destroy the impermeable film of the slag, like the coexisting sulfate ions (SO ₄ ^2- ) to increase the internal energy of the surface of the slag to make a very unstable state.

In addition, Na remaining in the slag grinding process , OH , Ca ₂ , SO ₄ ^2- ions are adsorbed evenly on the surface of slag powder to increase the activity of slag. As such, the prepared slag powders act to facilitate the elution of a significant amount of Ca ²⁺ , Mg ²⁺ , AlO ₄ ^4- , SiO ₄ ^4- ions contained in the glass of the slag, either mutually or When mixed with cement, the hydrate reaction is promoted by actively generating calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH) through the reaction with cement hydrate. In particular, the sulfate ions adsorbed on the slag powder cause the ethrinzite formation reaction with aluminum hydroxide [Al (OH) ₃ ], calcium hydroxide [Ca (OH) ₂ ] as follows.

2Al (OH) ₃ + 3Ca (OH) ₂ + 3CaSO ₄ 2H ₂ O + 19H ₂ O

→ 3CaOAl ₂ O ₃ + 3CaSO ₄ · 31H ₂ O (ethrinzite)

The resulting ethrinzite has a high bonding strength, good water resistance, and develops into a fibrous shape, which favors strength development.

Conventionally, there is a method of using an alkali-based slag stimulant to increase the hydration activity of the slag, but this technique is a method in which calcium hydroxide or sodium hydroxide aqueous solution is directly mixed with the fine slag powder, when calcium hydroxide is slag when stimulated by calcium hydroxide Although it is thought that it will react easily with alumina and aluminum hydroxide in water, in fact, the hydration reaction rate becomes insignificant in a stable state where the free energy (ΔG) is only -0.2 Kcal / mol.

_{2Al (OH) 3 + 3Ca (} OH) 2 → 3CaO · Al 2 O 3 · 6H 2 O

ΔH = −1.2 Kcal / mol, ΔG = −0.2 Kcal / mol

A high-temperature steam, and the curing process is necessary, reacted with the alumina component in the slag at a high temperature steam curing process, a stable hydrochloride Garnet _{(3CaO · Al 2 O 3 ·} SiO 4 · 4H 2 O) in order to facilitate the hydration of the slag by the calcium hydroxide By producing it, a phenomenon in which the strength expression is lowered appears.

Although there is a method of directly using sodium hydroxide, sodium carbonate aqueous solution or powder, when such a method is added to the slag alone system, the hydration activity of the slag itself is excellent, but when used directly in the system where the cement-slag co-exists, The added sodium hydroxide preferentially acts on the coexisting cement rather than reacts with slag, causing problems such as rapid hydration of cement, rapid hydration at the initial stage due to abnormal heat generation, and poor strength expression. The method of addition has not been put to practical use.

Therefore, the method of pre-activating the glass blast furnace slag itself in advance as in the present invention was not seen in the prior art, and the prior art simply makes the specific surface area of the slag 6,000 cm ² / g or more, In the present invention, the granular slag is treated with a stimulus solution, aged for a certain time, and then dried and pulverized to prepare high powder slag. Excellent slag can be produced, and in particular, by activating only the slag powder itself, even when mixed with cement, there is no problem appearing in the prior art.

The effect of the activated slag fine powder prepared by the present invention is to reduce the heat of hydration of the cement as the slag is partially substituted into the cement, the slag is adsorbed calcium hydroxide which is a hydration product of the cement is consumed in the process of hydration of slag Chlorine ions in seawater ) And the production of soluble calcium chloride produced by the reaction of calcium hydroxide is reduced, thereby increasing the resistance to seawater. In addition, in the present invention, when the slag is finely pulverized to 4,000 ~ 5,000cm ² / g powder also used in cement, the slag fine powder plays a role of filler to fill the pores of the cement particles, thereby improving the workability of concrete at the same work volume Effect.

In particular, the mixed use of activated slag powder exhibits excellent characteristics in which the initial and late strength development properties of mortar and concrete are higher than the conditions of using cement alone, despite the relative decrease in the amount of cement. The amount of activated blast furnace slag fine powder is good in the range of 25 to 67 parts by weight with respect to 100 parts by weight of cement. If it is used in an amount of more than 67 parts by weight, the effect of strength expression at the initial stage is less. , The heat of hydration is increased.

In the present invention, the thickener used to impart separation resistance in water includes hydroxy propyl methyl cellulose (HPMC), hydroxy ethyl cellulose (HEC), hydroxy ethyl methyl cellulose (HEMC), and hydroxy ethyl cellulose (HEEC). Non-ionic cellulose ethers can be used in water solubility, such as ethyl cellulose (EC) and methyl cellulose (HC). In this case, the cellulose ether-based thickeners used may have the same properties depending on the molecular weight, degree of substitution, etc. of the thickener, and in particular, the amount of the cellulose ether-based thickener used varies depending on the concrete mix. The viscosity measured after that) is in the range of 50,000 cps to 8,000 cps or more. If the viscosity of the thickener is less than 8,000 cps, the molecular resistance effect is insufficient. If the viscosity of the thickener is more than 50,000 cps, the workability is poor due to the high viscosity of the thickener, air volume increases, condensation delay occurs, and the thickener is expensive. The relationship has an adverse effect such as an increase in the cost of manufacturing concrete. In the present invention, the amount of the thickener is 0.5 to 2.5 parts by weight with respect to 100 parts by weight of cement, and if the amount is less than 0.5 parts by weight, when the concrete is placed in water, a large amount of cement is leaked into the water, and thus, it is impossible to confirm the disintegration effect. When used in excess of 2.5 parts by weight, the fluidity becomes difficult to work.

In the present invention, a small amount of antifoam is used to reduce the amount of air generated by using the thickener, and to maintain the amount of entrained air of the concrete at a level of 3 to 5%. Examples of the antifoaming agent used include silicone, alcohol, nonionic, aliphatic and phosphate ethers. Although the usage-amount of an antifoamer does not need to restrict | limit in particular, It is appropriate to use 0.04-0.5 weight part with respect to 100 weight part of cement. If less than 0.04 parts by weight, the effect of the antifoaming agent appears small, and when used in excess of 0.5 parts by weight no further defoamer effect is exhibited.

In the present invention, a high fluidizing agent or a high performance water reducing agent is used to impart excellent fluidity and magnetic flatness while preventing separation in water. These components currently used include lignin sulfonates, oxycarboxylic acids, polyols, naphthalin sulfonates, melamine sulfonates, and highly condensed triasin compounds, among which melamine sulfonates and triasins are used in the amount of entrained air. The best effect without increase.

The amount of the fluidizing agent used in the present invention is 0.6 to 5.0 parts by weight with respect to 100 parts by weight of cement, when used in more than 5.0 parts by weight, no further flow effect is exerted, rather the adverse effect of reducing the separation resistance appears. In addition, an AE agent, a cement coagulation hardening regulator, etc. can be used together as needed in the range which does not reduce the effect of this invention.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[Examples 1 to 4]

[Comparative Examples 1 to 4]

100 parts by weight of general ordinary Portland cement was prepared by adding activated glass blast furnace slag fine powder (Examples 1 to 4) and ordinary blast furnace slag fine powder (Comparative Examples 1 to 4), respectively, according to the present invention in the same amount as in Table 1 below. The compressive strength and heat of hydration of the cement were measured.

Here, the amount of the slag used in Example 4 to 100 parts by weight is to determine whether the range of the amount of use according to the present invention is appropriate.

The progress of this is shown in Table 1 below, and the test method was performed according to Korean Industrial Standards (KSL 5105 and KSL 5121).

TABLE 1

Note) Slag powder degree: 4500 ± 150cm ² / g

When using the fine powder slag activated in the same slag powder as the measurement results of Table 1, the initial strength of the 1st and 3rd days and the later 28th day strength are usually higher than the mortar rolling stress of the cement alone (plane), the heat of hydration It shows a good characteristic that the heat is generated as low as 5 to 6 kcal / g. In particular, the conditions (Examples 1-3) which mix 25-67 weight part of slags are shown to be more favorable than the conditions (Example 4) which mix 100 weight part of slags from the strength and the heat of hydration.

On the other hand, in order to compare the hydrated tissue properties of the paste cured product obtained by adding activated slag fine powder to the cement and the paste cured product prepared from the cement alone, the SEM and pores were observed through a porosimeter. The attached drawings are shown in FIGS. 1 and 2, respectively.

In the cement paste used in the experiment, a cured product hydrated for 7 days in an intake box kept at 20 ° C. with a water / bonding material (cement, activated slag powder) ratio of 0.5 was used for the measurement. Scanning electron micrographs showed that a large amount of calcium hydroxide was observed around the unhydrated allite (C ₃ S) particles in the paste cured body made of cement alone, and the calcium silicate hydrate (CSH) Whereas capillary pores are visible (Fig. 1a), calcium hydroxide is not produced in the cement to which the activated slag is added, and plate and gel silicate hydrates (CSH) are mixed, and calcium aluminate hydrates (CAH) and ethane Hydrates such as linzite also show complex forms that are produced in large quantities. The active formation reaction of the hydrate acts to densify the tissue by filling the capillary pores and pores in the cement paste, and the formation of calcium hydroxide, which is soluble in water and highly corrosive to salts, has not been observed (Fig. 1b).

2 shows the pore of the cement paste cured product, the microporous structure of the paste cured product prepared by adding the activated slag fine powder is distributed in the vicinity of 0.1 to 0.01 μm. It is shown that it is mainly distributed around 0.8-0.05 micrometers. The difference in pore size distribution is due to the active hydration reaction between cement and slag particles, and the production of a large amount of hydrates such as CSH, CAH, ethrinzite, etc., according to the use of activated slag fine powder, and the resulting hydrate is supplied to the capillary between hydrate tissues. This is because the hydrate was moved from the larger side to the smaller side by filling the pores. In other words, the structure of the cured body was found to increase in strength due to the densification effect.

[Examples 5 to 10]

[Comparative Examples 5 and 6]

After the slag prepared by the present invention and the normal slag is mixed with cement with a thickener, an antifoaming agent, and a high oiling agent at a compounding ratio as shown in the following Table 2 to prepare a non-separable cement in water, concrete is prepared at the compounding ratio as shown in Table 3 below. Inconsistent characteristics of concrete, fluidity (workability), compressive strength of airborne and underwater specimens were measured. The measured results are shown in Table 4 below.

In Table 3, hydroxypropyl methylcellulose (HPMC) of Nippon Shinwol Chemical, having a viscosity of 30,000pcs, was used as a thickener, and Atantan P 803, a Japanese product of Sannobko, was used as an antifoaming agent. As the high fluidizing agent, Melment F-101, a Japanese fire extinguishing product, which is a melamine sulfonic acid formalin condensate, was used.

Here, the method for evaluating concrete properties by cement composition for underwater construction has not been defined in Korea until now, but the Japanese Society of Civil Engineers only proposed "Underwater Uncontained Concrete Design and Construction Guidelines in 1991". The experimental method suggested by the Korean Society of Civil Engineers was used.

The main experimental method used in the present invention is as follows.

Slump flow:

Fill the concrete slump cone with compacted concrete and remove the slump cone. After leaving for 5 minutes, measure the spread diameter of the concrete and average the two points.

Compressive strength:

-Fabrication of aerial specimens: A mold of diameter 10cm x height 20cm was used, and the manufacturing method is the same as the existing method of producing concrete strength (KSL 2405).

-Underwater specimens: immerse the mold for strength measurement in a 30 cm deep water bath. The distance between the center of the mold and the water surface is always kept 20 cm.

The concrete is divided into 10 equal parts on the surface of the water and allowed to stand for 15 minutes to be filled by self-weight without any commitment. After 15 minutes, remove the mold and pat the sinus side with a rubber mallet two or three times. The curing method is the same as the existing concrete curing method.

-Strength measurement is measured as the ratio of compressive strength in water / air after measuring the 7.28 days compressive strength for each specimen manufactured in standard and in water.

Inseparability (turbidity):

Fill 800cc of water in 1000cc beaker (outer diameter of 100m, height of 150mm), divide the concrete into 500g more than 10 equal parts and leave for 3 minutes. Thereafter, 600 cc of beakers are collected using a dropper to measure suspended matter. At this time, the suspended substance is expressed as mg / l.

Air volume, condensation, slump: Perform according to KSFF 241, KSF 2436.

TABLE 2

※ The amount of thickener, antifoaming agent, and high fluidizing agent is based on 100 parts by weight of cement.

TABLE 3

TABLE 4

As a result of measuring the activated slag fine powder, the thickener and the antifoaming agent in Table 4, the results show excellent effects in the workability and strength characteristics of concrete as compared to the method of using ordinary Portland cement alone or using ordinary slag powder. In particular, when the activated slag fine powder is used, as the sulfate ions adsorbed in the slag particles act as an antifoaming agent, the amount of air generated in the concrete is reduced.

For reference, Table 5 shows the performance regulations of underwater unseparated concrete by the underwater inseparable admixture presented by the Japanese Society of Civil Engineers (1991 Concrete Library No. 67) and the cement composition for underwater construction of the present invention. This is a comparison between the quality of water-insoluble concrete and the quality of erucone (onoda cement product), which is a cellulose ester-based water-insulating admixture commercially available in Japan. Here, concrete mixing conditions as shown in Table 3 were used for quality comparison under the same experimental conditions, and the amount of erucone was added in an amount of 0.75 parts by weight based on 100 parts by weight of portland cement.

TABLE 5

Note) A is the performance of the segregation of concrete, B is the composition of Example 6 of the present invention, C is the composition of Example 9 of the present invention, D is a composition of Comparative Example 5. * Is not prescribed, and is the normal concrete workable range.

Looking at the measurement results of Table 5, as a result of comparing the overall characteristics of the concrete for underwater pouring with the cement composition for underwater construction of the present invention, all the evaluation items are showing a good result significantly exceeding the level prescribed by the Japanese Society of Civil Engineers, Compared with Japanese products, the concrete produced from the cement composition of the present invention appears to have excellent workability and strength expression characteristics. The contents of the present invention have not been known in the past, and the prior art mainly improves the non-separation performance by modifying or fixing the thickener, and using a mixed agent of an acrylic viscosity and a thickener, or for improving the early strength of the cement-type cement, The method of using hydration accelerators such as alumina-based cement and inorganic metal salts and other high-powder slag was used to prepare fire-separated cements in water. However, the poor early strength development rate, resistance to seawater, There are limitations to solve both the applicability of mass concrete due to hydration heating and the economic problem due to the rise of manufacturing cost.

In the present invention, instead of simply grinding the slag used for the improvement of resistance to seawater, reduction of heat of hydration and improvement of workability, it is not used in cement, but instead of sodium hydroxide and type III anhydrous gypsum for stimulation of slag during the slag powder manufacturing process. An appropriate amount of the mixed aqueous solution was added to the granular blast furnace slag, and the powder was also pulverized to a level of 4,000 to 50,000 cm ² / g by stirring, aging and drying, thereby increasing the hydration activity of the slag, and alkali and adsorbed to some slag particles. The action of sulfate ions promotes the hydration reaction between cement hydrate and slag to induce high strength.

In addition, by using a thickener, antifoaming agent, and a high fluidizing agent appropriately mixed with cement to which activated fine slag powder is added, an economical method is used for economically separating unsealed cement for underwater construction, which can expect excellent strength expression characteristics, seawater resistance, and reduction of hydration heat. Its feature is that it can be manufactured.

Claims (1)

4 to 10 parts by weight of sodium hydroxide and 3 to 7 parts by weight of Ⅲ anhydrous gypsum were dissolved and dissolved in an aqueous solution of 30 to 40 parts by weight with respect to 100 parts by weight of granular blast furnace slag before grinding, followed by stirring and aging. Process for producing activated fine slag powder used in the fire separation cement composition for underwater construction, which is dried and pulverized to 4,000 ~ 5,000cm ² / g.