KR20200076566A - Fine aggregate and concrete composition comprising the same - Google Patents

Abstract

The present invention relates to fine aggregate for concrete, including mixed slag in which ferronickel slag and blast furnace slag are mixed to compensate for the defects of ferronickel slag and blast furnace slag. According to the present invention, provided is fine aggregate for concrete, comprising mixed slag in which ferronickel slag and blast furnace slag are mixed. The mixed slag fine aggregate according to the present invention exhibits improved fluidity and/or strength when applied to concrete and/or mortar as a sand substitute. In addition, the mixed slag fine aggregate of the present invention exhibits improved shrinkage. In addition, the problem of unbalanced supply and demand of natural aggregate can be solved, and the effect can be expected as a method of recycling slag as valuable resources.

Description

Fine aggregate for concrete and composition for building material containing same{FINE AGGREGATE AND CONCRETE COMPOSITION COMPRISING THE SAME}

The present invention relates to a fine aggregate for concrete and a composition for a building material including the same, and more specifically, by using a mixture of ferronickel slag and blast furnace slag, a fine aggregate for concrete that can exhibit superior strength compared to natural sand aggregate and the same It relates to a composition for a building material.

Aggregate is a major component of concrete or mortar or concrete in the manufacture of concrete. Gravel, crushed stone, crushed sand, natural sand, etc. are commonly used. However, recently, natural aggregates for concrete have been exhausted and insufficient, and in the future, natural aggregate shortages for concrete due to strict regulations, such as river maintenance management, environmental conservation, and protection measures for masonry development according to the establishment of military protection zones It is expected to get worse. Therefore, there is an urgent need to develop an aggregate replacement material used as a main component of concrete.

The blast furnace slag is obtained by quenching molten blast furnace slag generated simultaneously with pig iron in a furnace (hereinafter also referred to as'blast furnace') in water, and is generated in the process shown in FIG. Particularly, as the slag is discharged from the blast furnace, high-pressure water is sprinkled as in the photo of FIG. 2, so that a crystalline phase is not provided and is produced as amorphous sand-like particles.

Currently, in Korea, the blast furnace slag is dried and finely pulverized to be used as a cement raw material or concrete admixture. Concrete manufactured using blast furnace slag powder has the following excellent properties. That is, (1) it has the effect of reducing the rate of heat of hydration and suppressing the temperature rise of concrete. (2) Long-term strength is improved. (3) Water tightness is improved. (4) It has the effect of inhibiting the generation (rust) of reinforcing bars by the inhibitory effect of chloride ion penetration. (5) Chemical resistance to sulfate is improved. (6) It has the effect of suppressing the alkali silica reaction. (7) Little bleeding and excellent fluidity. (8) High strength concrete can be obtained.

As blast furnace slag is used as a raw material for cement, it has a hardening property, so there is a fear that it will harden when aggregated for a long time. In Japan, sodium gluconate or sodium polyacrylate-based condensation retardants are being used to prevent the blast furnace slag from curing, but these components are expensive and sometimes cause side effects such as condensation delay in the manufacture of concrete. In addition, the fine glassy bed of the coagulation retarder may remain in the concrete to deteriorate the concrete fluidity, and there is a possibility of reducing the workability of the worker by the deterioration of the fluidity. In addition, the blast furnace slag is linked to the domestic construction industry, which may cause surpluses of by-products when the construction industry is stagnant. Therefore, a new resource recycling plan for blast furnace slag is required. As a conventional technique using blast furnace slag, there is Korean Patent No. 1560893.

On the other hand, in order to stably supply Ferronickel, which is used as a raw material in the manufacture of stainless steel among steel products, a ferronickel smelter has recently been established in Korea and has a production system of 300,000 tons per year (60,000 tons of pure nickel). Ferronickel is produced by reducing nickel (Ni) ore with coke or the like in an electric furnace type furnace. The slag generated at this time is a ferronickel slag. The generation amount of ferronickel slag is about 2 million tons per year, and the generation amount is enormous, and it is discharged by hydrocracking and slow cooling. Existing steel slag, that is, blast furnace slag and steel slag are mainly composed of calcium oxide (CaO) and silicon dioxide (SiO ₂ ) components, but the main component of ferronickel slag is 25 to 40% by weight of magnesium oxide (MgO) and It is composed of 45 to 60% by weight of silicon dioxide (SiO ₂ ). Such ferro nickel slag is characterized in that crystallization onto the other Enschede tight (Enstatite) (MgOSiO ₂₎ onto the forsterite (Forsterite) (2MgOSiO ₂₎ depending on the cooling method. The ferronickel slag is in the form of granules whose particle size is less than 10 mm. Here, "particle size" means the diameter of a sphere when the spectroscopy is a sphere shape, and means the average value of a number of diameters measured in a certain direction when the spectroscopy is made of a complex shape. Is used as

Table 1 below shows the content of the main components of the ferronickel slag. Since the content of SiO _{2 in} the ferronickel slag component is high, the viscosity of the ferronickel slag is high, and because of the high MgO content, the melting point is also higher than 1500°C.

ingredient SiO ₂ CaO T-Fe Al ₂ O ₃ MgO S Content (wt%) 53 One 5 2 34 0.04

As described above, the ferronickel slag is firmly composed of MgO-SiO ₂ -based compound crystals, but there is a risk of expansion when continuously exposed to high temperature and high alkali environments. More specifically, SiO ₂ is dissolved by high alkali, and the residual MgO is converted into magnesium hydroxide (Mg(OH) ₂ ), which may cause about twice the volume expansion. A technique using such ferronickel slag as fine aggregate is disclosed in Korean Patent Publication No. 10-2012-0066765. However, when only ferronickel slag is used as a fine aggregate as in the prior art, there is a possibility that an expansion phenomenon may occur.

Therefore, although only a single component of ferronickel slag or blast furnace slag is unsuitable for use as a fine aggregate, it is expected that it can be widely applied in related fields as a fine aggregate replacement agent when it is possible to obtain suitable properties for the fine aggregate by mixing them.

One aspect of the present invention is to provide a fine aggregate for concrete comprising a mixed slag of ferronickel slag and blast furnace slag.

Another aspect of the present invention is to provide a composition for a building material comprising a fine aggregate for concrete of the present invention.

According to an embodiment of the present invention, there is provided a fine aggregate for concrete comprising a mixed slag in which ferronickel slag and blast furnace slag are mixed in a weight ratio of 7:3 to 2:8.

According to an embodiment of the present invention, a composition for a building material comprising the fine aggregate for concrete, coarse aggregate and cement is provided.

The fine aggregate for concrete (hereinafter, also referred to as'mixed slag fine aggregate') containing the mixed slag in which the ferronickel slag and blast furnace slag according to the present invention are mixed may be used for concrete and/or mortar as a sand substitute. The mixed slag fine aggregate according to the present invention shows improved fluidity and/or strength when applied to concrete and/or mortar as a sand substitute. In addition, the mixed slag fine aggregate of the present invention exhibits improved shrinkage. In addition, the problem of imbalance in supply and demand of natural aggregates can be solved, and the effect can be expected as a method of recycling slag as a valuable resource.

1 is a schematic view of a process in which blast furnace slag is obtained.
Figure 2 is a photograph showing a process of quench by sprinkling blast furnace slag.
Figure 3 is a schematic view showing the crushing process of ferronickel slag and blast furnace slag.
Figure 4 shows the particle size distribution according to the mixing ratio of the ferronickel slag and blast furnace slag.
5A and 5B are photographs showing the material separation phenomenon of the mixed slag in which the ferronickel slag and the blast furnace slag are mixed in a weight ratio of 8:2 and 9:1.
FIG. 6 is a photograph showing a slump flow of a test body including a mixed slag in which a ferronickel slag and a blast furnace slag are mixed in a 4:6 weight ratio.
7 is a graph showing unit quantity and slump flow according to the type and mixing ratio of aggregate.
8 is a photograph showing the slump flow according to the mixing ratio of the test body.
9 is a photograph showing the slump flow according to the mixing ratio of the comparative body and the reference body.
10 is a graph showing the compressive strength of a test body, a reference body and a comparative body.
11 is a graph showing the dry shrinkage of the test body, reference body and comparative body.
Figure 12 shows the results of the compressive strength test of the concrete test body.
13 shows the experimental results of the length change of the concrete test body. The number after "mixing" in FIG. 13 represents the weight percent of the mixing slag based on the weight of fine aggregate.
14 is a graph showing the intensity prediction values obtained through regression analysis. The number after "mixing" in FIG. 14 represents the weight percentage of the mixing slag based on the weight of fine aggregate.
15 shows a change in compressive strength according to the mixing ratio of ferronickel slag and blast furnace slag.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

According to the present invention, overcoming the disadvantages of ferronickel slag and blast furnace slag and providing a fine aggregate for concrete based on mutual synergy. In the present invention, a fine aggregate for concrete means an aggregate that passes through a 10 mm sieve and almost passes through a 5 mm sieve, and almost all remains in a 0.08 mm sieve, and a coarse aggregate for concrete means an aggregate that almost remains in a 5 mm sieve. (KS F 2525).

More specifically, the fine aggregate for concrete of the present invention is a mixture of ferronickel slag and blast furnace slag.

In order to use blast furnace slag, especially blast furnace slag as a sand substitute, two problems must be solved. First, because the blast furnace slag contains about 30 to 40% by weight of SiO ₂ , when it is subjected to high-pressure sprinkling treatment in a hot melt state, it is not only produced as amorphous (glassy), but also long and thin at a level of 2 to 7 mm. Needle-shaped needle-like glassy substances are also produced. When using blast furnace slag as a concrete or mortar aggregate, the fluidity of concrete or mortar is reduced by such needle-like glass material, and there is a problem in that it is difficult to use due to quality degradation such as material separation. Moreover, when aggregates containing a large amount of acicular glass are piled up, there is concern about the hazard to the human body of the worker. Therefore, in order to utilize the blast furnace slag as a valuable resource, it is necessary to solve the problem caused by needle-like glass.

In addition, as described above, the blast furnace slag is powdered and used as a cement raw material. In normal blast furnace slag powder, an amorphous glassy film coating the particle surface under a high pH environment is destroyed, and thus ions such as Ca ²⁺ , Al ^3+, etc. Elution of is facilitated. At this time, the eluted ions produce CaO-SiO ₂ -H ₂ O-based hydrate, and the cement is cured. This hydraulic response is called latent hydraulic. Due to this latent hydraulicity, consolidation (hardening) may occur in the process of storing or blasting blast furnace slag for use as aggregate for concrete, and if consolidation occurs, it cannot be used as aggregate for concrete. Therefore, the problem due to latent hydraulicity of blast furnace slag should be solved.

In the present invention, in order to use the blast furnace slag as a concrete or mortar aggregate, that is, as a sand substitute, the blast furnace slag may be crushed using a cone crusher, an impact crusher, or a roll crusher to improve the vitreous bed of the blast furnace slag and the angled grain shape. . In addition, by mixing homogeneously the ferronickel slag without hydraulicity with the blast furnace slag (pre-mixing, pre-mixing), the problem of consolidation due to latent hydraulicity is solved.

Meanwhile, in the present invention, the ferronickel slag may be cooled by air or water. The ferronickel slag comprises crystalline 2MgO·SiO ₂ and MgO·SiO ₂ crystal phases, or 2MgO·SiO ₂ and MgO·SiO ₂ crystal phases. When such a crystal phase is included, there is no hydraulic property, that is, there is no curing property, so pre-mixing with the blast furnace slag prevents hardening during storage and storage.

In addition, since the ferronickel slag has a spherical vertical shape, it can improve the fluidity of concrete when used as an aggregate for concrete (ball bearing effect). In addition, when ferronickel slag and blast furnace slag are mixed, it is possible to compensate for the decrease in fluidity due to the fine glassy bed of the blast furnace slag. That is, since the ferronickel slag is scattered and cooled by high-pressure sprinkling, it has the advantage of improving the fluidity of concrete because it can secure a spherical shape.

When ferronickel slag is used as a fine aggregate for concrete, it is possible to reduce the amount of water used in the manufacture of concrete, thereby increasing the strength of concrete and reducing shrinkage stress.

On the other hand, when the blast furnace slag is used as a fine aggregate for concrete, the long-term compression strength of the concrete can be improved by the long-term hydration reaction of the blast furnace slag. The glassy SiO ₂ present on the surface of the blast furnace slag can stabilize the reactivity through fixing of alkali (Na ₂ ⁺ , K ₂ ⁺ ) in a high temperature and high alkali environment, and prevent expansion reaction of the ferronickel slag. That is, Na ₂ ⁺ and K ₂ ⁺ destroy the Si-O-Si chain, which is a network structure of glassy SiO ₂ , and enter into it and immobilize alkali with Si-Na-O-Si and Si-KO-Si by polymerization. You can do it.

The fine aggregate for concrete of the present invention may include a mixed slag in which ferronickel slag and blast furnace slag are mixed in a weight ratio of 7:3 to 2:8. When the blast furnace slag is included in an amount exceeding the above range, physical properties such as strength are vulnerable due to the porous structure of the blast furnace slag, and there is a problem that fluidity is reduced due to excessive viscosity of the mixed slag. On the other hand, when the blast furnace slag is included below the above range, the phenomenon of separating the ferronickel slag and the blast furnace slag from the mixed slag may occur, and the long-term compressive strength of the entire concrete is improved by improving the adhesion properties of the cement paste and the blast furnace slag surface. The probability that the advantages to be exerted can be realized becomes lower. Particularly, since the ferronickel slag (density: 2.9~3.1cm ³ /g) has a higher weight than the blast furnace slag (density: 2.65~2.78cm ³ /g), if a relatively large amount of ferronickel slag is included, sagging during concrete application may occur. Occurrence may increase the number of application times and the working time. Therefore, when considering the aspect of finish and formability when applying concrete, it is preferable that the mixed slag is mixed with ferronickel slag and blast furnace slag in a weight ratio of 4:6 to 2:8.

Meanwhile, in order to be used as a sand substitute, the particle size of the sand substitute should be 5 mm or less (excluding 0). More precisely, sand substitutes containing particles having a particle size of 5 mm or less and containing 95% by weight or more and particles having a particle size of 5-10 mm or less can be used as a fine aggregate for concrete. The fine aggregate for concrete of the present invention may include ferronickel slag and blast furnace slag particles having a particle size of 5 mm or less at least 95% by weight.

Since ferronickel slag is generally in the form of granules having a particle size of 10 mm or less, it is difficult to use it as a substitute for sand. Therefore, the particle size of 5 mm or less (excluding 0) and the particle size of 5 to 10 mm formed by crushing a particle having a particle size of 5 mm or less can be combined and used as a fine aggregate for concrete. The ferronickel slag can be crushed by any method known in the art, but it is not limited to one or more means selected from the group consisting of cone crusher, impact crusher, and roll crusher.

In particular, the ferronickel slag has the advantage of a spherical shape as described above, because it does not crush all the amount at the time of manufacture, and does not crush particles having a particle size of 5 mm or less (excluding 0) and crushing only those having a particle size of 5 mm or more. .

On the other hand, the blast furnace slag may be an amorphous blast furnace slag improved in grain shape by processing and crushing by one or more means selected from the group consisting of cone crusher, impact crusher, and roll crusher.

The crushing of the ferronickel slag and the crushing of the blast furnace slag can be performed separately or by mixing them together.

The blast furnace slag contains 30 to 40% by weight of SiO ₂ , which causes needles and granules to form when cooling the sprinkler in a high-temperature melting state. If the blast furnace slag containing needles is used as a fine aggregate for concrete, there is a concern about the decrease in fluidity, and in particular, the safety of workers. In addition, when the granules form, the ball bearing effect decreases and the fluidity of concrete decreases.

The blast furnace slag can be increased in spherical shape by crushing the bed into a single phase, a powder phase, and cutting the angular granules using one or more means selected from the group consisting of a cone crusher, an impact crusher, and a roll crusher.

The ferronickel slag and the blast furnace slag may have an average particle size of greater than 0 and less than or equal to 5 mm. Preferably, the average particle size of the ferronickel slag and the blast furnace slag may range from 1.5 mm to 3.0 mm, and more preferably from 2.0 mm to 2.5 mm. If the average particle size is less than 2 mm, the fineness of the concrete is increased due to excessive fine particles, and the amount of cement and the number of units added during the production of concrete increases, so the fluidity decreases and the strength decreases. In addition, concrete shrinkage cracking may occur due to an increase in capillary tension in the micropores as the amount of fine particles increases. On the other hand, if the average particle size exceeds 3 mm, on the contrary, the fine powder is excessively insufficient and the viscosity is excessively lost. When concrete is poured, a bleeding phenomenon (cement paste and aggregate separation due to weakening of viscosity) may occur.

Meanwhile, the blast furnace slag may be crushed to have an average particle size of 2 mm or less, and preferably may be crushed to have an average particle size in the range of 0.03 mm to 2 mm.

The mixed slag according to the present invention may have an assembly rate of 2.55 to 2.90, preferably an assembly rate of 2.58 to 2.79, more preferably about 2.7. When the assembly rate is less than 2.55, the contact area between cement and aggregate is increased due to excessive fine-graining of fine aggregates, and accordingly, a large amount of water is required when forming concrete, so the strength tends to be low. On the other hand, when the granulation rate exceeds 2.9, concrete with insufficient viscosity may be manufactured due to excessive granulation of fine aggregate, which may deteriorate workability. On the other hand, when the assembly rate of the mixed slag is 2.58 ~ 2.79 range, excellent strength improvement effect can be obtained.

At this time, the mixed slag can be adjusted by setting the granulation rate after crushing the mixed slag, respectively, or by crushing the mixed slag by mixing the two slags.

In the present invention, the fluidity of fine aggregate is usually measured and expected by a mortar slump flow. The target slump flow is set to 200 to 210 mm in consideration of workability in the field. If the slump flow is less than 200 mm, the fluidity of concrete does not meet the standard, and if it exceeds 210 mm, there is a fear of material separation.

The particle size distribution of the mixed slag in which the ferronickel slag and the blast furnace slag are mixed at 7:3 to 2:8 corresponds to a fine aggregate that can be used for concrete or mortar, and more specifically, it can be used as a fine aggregate replacement material. Outside the above range, when mixing the mixed slag with cement and sand, there is a problem that fluidity standards are not satisfied and/or materials are separated.

As described above, the mixed slag according to the present invention may be used alone as a fine aggregate for concrete, or the fine aggregate for concrete may further include sand.

The sand may be added in an amount of more than 0 to 75% by weight based on the total fine aggregate weight, and preferably 25 to 50% by weight based on the total fine aggregate weight. When the sand is added in excess of 75% by weight, the effect of increasing strength tends to decrease.

Furthermore, according to another aspect of the present invention, a mortar comprising the fine aggregate for concrete and water of the present invention is provided.

According to another aspect of the present invention, there is provided a composition for a building material comprising the fine aggregate for concrete, coarse aggregate and cement of the present invention. The composition for building materials may further include water. At this time, as the coarse aggregate, natural gravel or artificial crushed stone may be used, but is not particularly limited.

For example, the composition for building materials may include 2 to 6 parts by weight of fine aggregate based on 1 weight of cement.

Meanwhile, the cement includes cement such as super hard cement, general Portland cement, crude steel cement, and ultra-hard steel cement, but is not limited thereto, and other types of cement widely used in the art may be used.

Example

Hereinafter, embodiments of the present invention will be described in detail. The following examples are only for understanding the present invention and are not intended to limit the present invention.

Example 1: Preparation of fine aggregate of mixed slag according to the mixing ratio of ferronickel slag and blast furnace slag

Fig. 3 schematically shows the crushing process of ferronickel slag and blast furnace slag. As shown in FIG. 3, the ferronickel slag and the blast furnace slag were each processed and crushed by an impact crushing process. The ferronickel slag was crushed to pass more than 95% by weight of a molecular sieve having a size of 5 mm. The blast furnace slag was processed and crushed to a particle size of 2 mm or less.

The crushed ferronickel slag and blast furnace slag in a weight ratio of 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2 and 9:1, respectively. After mixing, the particle size distribution of the mixed slag was measured and shown in Tables 2 and 4 below. The black dotted line in FIG. 4 represents a range of particle size distribution of sand usable as a fine aggregate for concrete. When the mixed slag has a particle size distribution falling between two black dotted lines, it can be used as a fine aggregate for concrete, that is, as a sand substitute.

As can be seen in Figure 4, when the ferronickel slag and blast furnace slag according to the present invention are mixed in a weight ratio of 2:8 to 7:3, the particle size distribution of the mixed slag is in the particle size distribution between the two black dotted lines. As it belongs, it can be used as a sand substitute in concrete.

On the other hand, the results of measuring the particle size distribution by passing the mixed slag ferronickel slag and blast furnace slag mixed in a weight ratio of 1:9 to 9:1 through a sieve is shown in Table 2 below.

Particle size distribution according to the mixing ratio of ferronickel slag and blast furnace slag With ferronickel slag
Mixing ratio of blast furnace slag
(Weight ratio) Checker (mm) pan 0.15 0.3 0.6 1.2 2.5 5 10 1:9 0 8.1 27.4 52.3 89.7 97.6 99.8 100.0 2:8 0 7.4 24.9 47.1 82.2 95.2 99.5 100.0 3:7 0 6.6 22.3 42.0 74.8 92.7 99.3 100.0 4:6 0 5.9 19.7 36.8 67.3 90.3 99.0 100.0 5:5 0 5.2 17.2 31.6 59.9 87.9 98.8 99.9 6:4 0 4.5 14.6 26.5 52.4 85.5 98.5 99.9 7:3 0 3.7 12.0 21.3 45.0 83.0 98.3 99.9 8:2 0 3.0 9.4 16.1 37.5 80.6 98.0 99.9 9:1 0 2.3 6.9 10.9 30.1 78.2 97.8 99.9

Example 2: Evaluation of mixed slag containing ferronickel slag and blast furnace slag as a sand substitute for mortar

As in Example 1, a mortar test body was prepared using a mixed slag fine aggregate containing ferronickel slag and blast furnace slag. When preparing a mortar test body, the weight ratio of cement:mixed slag:water was 1:1.1:5. As the mixed slag, a mixture of ferronickel slag and blast furnace slag of Example 1 in a weight ratio of 2:8, 3:7, 4:6, 5:5, 6:4 and 7:3 was used.

In addition, sand mortar (crushed sand, particle size range: 1.5 to 5 mm) and seaweed (particle size range: 0.3 to 1.5 mm), which are commonly used as aggregates, were used as a mortar comparator in combination with cement and water. The comparator was composed of a mixture of cement: crushed sand and seawater:water in a weight ratio of 1:1.1:5. The shredded sand and seaweed were mixed in a weight ratio of 2:8, 3:7, 4:6, 5:5, 6:4, and 7:3.

As shown in FIGS. 5A and 5B, the mortar test body prepared from the mixed slag in which the ferronickel slag and the blast furnace slag were mixed in a weight ratio of 8:2 and 9:1 was not usable due to material separation. Figure 5a is a case of mixing the ferronickel slag and blast furnace slag in a weight ratio of 8:2, Figure 5b is a case of mixing the ferronickel slag and blast furnace slag in a weight ratio of 9:1.

Mortar test specimens prepared from mixed slag in which the ferronickel slag and the blast furnace slag were mixed at a weight ratio of 4:6 were evaluated for slump flow values of 140 mm, as shown in FIG. 6. That is, the mortar test body prepared from the mixed slag in which the ferronickel slag and the blast furnace slag were mixed at a weight ratio of 4:6 did not satisfy the target slump flow of 200 to 210 mm. From this, it can be seen that the degree of good workability is not preferable. The slump flow was evaluated by KS L 5111, a slump flow evaluation method of cement mortar.

As described above, when the target slump flow is not satisfied, in order to satisfy the target slump flow, water must be additionally added to increase the unit quantity. However, when additional water is added, defects such as cracks due to a decrease in compressive strength of concrete and an increase in drying shrinkage may occur.

When producing concrete or mortar using mixed slag in which the ferronickel slag and blast furnace slag are mixed in a weight ratio of 2:8 to 7:3, when preparing concrete or mortar using commonly used ground and seaweed aggregates, Even if the same amount of water is used, it satisfies the target slump flow (200 to 210 mm). From this, it exhibited fluidity suitable for use as a sand substitute for concrete.

Example 3: Change in unit quantity when a mixed slag of ferronickel slag and blast furnace slag is used

The target slump flow was set to 200 to 210 mm, and the amount of water blended during the preparation of the test body and the comparative body was adjusted to satisfy the target slump flow. In Example 3, 600 g of cement and 3,000 g of sand substitute were mixed in Test Nos. 1 to 12 of Table 3, respectively. On the other hand, in the case of Test No. 11, 650 g of water was added and blended, and the amount of water in this case was set to 100% (satisfying the slump flow of 200 to 210 mm), and the relative amounts thereof were used in Test Nos. 1 to 10, and 12. The amount of water (by weight) was adjusted. As the ferronickel slag and the blast furnace slag, the same one as in Example 1 was used, and the yarn and seaweed were the same as in Example 2. When mixing according to each test number, water was added so that the flow of the concrete composition satisfies the range of 200 to 210 mm, and the amount of water added was more or less than the reference body.

The water mixing amount and the slump flow according to the mixing ratio of the ferronickel slag and the blast furnace slag and the mixing ratio of the abrasive sand and the sea are shown in the graphs of Table 3 and FIG.

Test number Sand substitute Water mixing ratio compared to the reference body (wt%) Slump flow
(mm) One (Test body) ferronickel slag: blast furnace slag 2: 8 weight ratio mixed 98 200 2 (Test body) ferronickel slag: blast furnace slag 3: 7 weight ratio mixed 92 200 3 (Test body) ferronickel slag: blast furnace slag 4:6 weight ratio mixed 82 200 4 (Test body) ferronickel slag: blast furnace slag 5: 5 weight ratio mixed 78 200 5 (Test body) ferronickel slag: blast furnace slag 6:4 weight ratio mixed 69 200 6 (Test body) ferronickel slag: blast furnace slag 7: 3 weight ratio mixed 67 205 8 (Comparison) Ferronickel slag: blast furnace slag 8: 2 weight ratio mixed 62 205 9 (Comparison) Ferronickel slag: blast furnace slag 9: 1 weight ratio mixing 61 210 10 (Comparison) Shredding: Mixing of 7:3 weight ratio 92 210 11 (Reference body) Shredding: Mixing of 6:4 weight ratio 100 210 12 (Comparative) Printing: mixing of 5:5 weight ratio 112 205

As can be seen from Table 3 and FIG. 7, when the mixed slag in which ferronickel slag and blast furnace slag is mixed is used as a fine aggregate for concrete, a phenomenon in which the unit quantity is reduced compared to the case of using natural aggregate mixed with sand and seaweed is observed. Became. Accordingly, it is possible to exert advantages such as an improvement in compressive strength and a reduction in drying shrinkage due to a decrease in the unit quantity.

As shown in Fig. 8, the ferronickel slag and the blast furnace slag were mixed in the case of a test specimen using a mixed slag in a weight ratio of 2:8, 3:7, 4:6, 5:5, 6:4 and 7:3. It can be seen that the amount of water to be reduced is reduced, but the slump flow satisfies the range of 200 to 210 mm. As shown in Fig. 9, the slump flow satisfies the range of 200-210 mm, as compared to and the reference body prepared by mixing the shredded sand and seaweed in a weight ratio of 5:5, 6:4, and 7:3. This means that even when the mixed slag of the present invention is used as a fine aggregate for concrete, good fluidity can be secured during concrete construction.

In addition, compressive strength and dry shrinkage of test specimens, reference bodies, and comparative bodies according to Test Nos. 4 to 6 and 10 to 12 in Table 3 were measured, and the results are shown in FIGS. 10 and 11, respectively. The compressive strength was KS L ISO 679, which is a method for evaluating the compressive strength of cement mortar, and the shrinkage was evaluated in accordance with KS F 2586, a self-contraction test method for cement, mortar, and concrete.

Referring to FIG. 10, the compressive strength of the test specimens of Test Nos. 4 to 6 is slightly larger than the compressive strength of the comparative and reference bodies of Test Nos. 10 to 12 on the 7th day, and is significantly increased on the 28th day, of 56 days. It can be seen that the long-term compressive strength increases significantly.

In addition, referring to FIG. 11, the dry shrinkage rate up to 66 days of age (aging) was found to be that the dry shrinkage rate of the test specimens of Test Nos. 4 to 6 was absolutely smaller than that of the comparative and reference bodies of Test Nos. 10 to 12. In Fig. 11, the unit of the dry shrinkage rate corresponds to 10 ^-3 mm/mm. The smaller the shrinkage rate of drying, the better the crack reduction effect of the manufactured concrete, and can replace or reduce the shrinkage reduction material used as an expensive mixed material according to the recent high performance of the structure, which can have an effective economic effect in the construction industry.

Example 4: Preparation of fine aggregate for concrete

A representative granularity index for fine aggregates for concrete has an assembly rate. The assembly modulus (Fine modulus, FM) is based on KS F 2502, and the sieve size is 80 mm, 40 mm, 20 mm, 10 mm, 5 mm, 2.5 mm, 1.2 mm, 0.6 mm, 0.3 mm, 0.15 mm. Is the sum of the remaining cumulative percentages divided by 100. It means that the larger the assembly rate value, the finer the assembly.

A small impact crusher was used to adjust the degree of crushing while mixing the ferronickel slag and the blast furnace slag at a ratio of 5:5 to prepare fine aggregates for concrete with 3 levels of assembly rates of 2.58, 2.69, and 2.79. The fine aggregate thus prepared is hereinafter referred to as a mixed slag fine aggregate.

To evaluate the strength of the mixed slag fine aggregate for 28 days, the ratio of cement: fine aggregate: water was set to 1:4:0.8 to prepare a compressive strength mortar test sample with the composition shown in Table 4 below. At this time, the sand used was a mixture of sand and sea sand in half using natural sand, and the mixing ratio of the mortar test body was also set to cement: fine aggregate: water = 1:4:0.8 in the same manner to prepare the test body.

After preparing a mortar test specimen using a mortar composition having such a composition, it was cured in water at a temperature condition of 20±2°C, and taken out of the water prior to the strength measurement to measure the compressive strength after removing water and passing for 1 hour.

Fine aggregate
Assembly rate Fine aggregate composition cement Fine aggregate water sand Mixed slag 2.76 sand 100 1100 4400 880 2.58 Mixed Slag 25+ Sand 75 1100 3300 1100 880 Mixed slag 50+sand 50 1100 2200 2200 880 Mixed Slag 75+ Sand 25 1100 1100 3300 880 Mixed slag 100 1100 4400 880 2.69 Mixed Slag 25+ Sand 75 1100 3300 1100 880 Mixed slag 50+sand 50 1100 2200 2200 880 Mixed Slag 75+ Sand 25 1100 1100 3300 880 Mixed slag 100 1100 4400 880 2.79 Mixed Slag 25+ Sand 75 1100 3300 1100 880 Mixed slag 50+sand 50 1100 2200 2200 880 Mixed Slag 75+ Sand 25 1100 1100 3300 880 Mixed slag 100 1100 4400 880

(Unit: g)

Example 5: Compressive strength experiment of mortar specimen prepared in Example 4

The compressive strength of the mortar test body prepared in Example 4 was measured using a universal test machine (UTM).

As a result of compressive strength measurement, as can be seen in FIG. 12, when the mixed slag of the present invention is used, it exhibits superior strength properties compared to the case of using natural aggregate sand. Particularly, it was confirmed that, when the mixed slag was used by replacing natural sand by 25% or more based on the total fine aggregate weight in the range of assembly ratio 2.58 to 2.79, it was confirmed that it shows excellent strength in all areas. 12 is a view showing the amount of shrinkage of the test sample in the 2.58 to 2.79 category.

When the aggregate slag aggregate level of 2.5 is used, 28 days of compressive strength of 25.7 MPa and 26.7 MPa, respectively, of 25% mixed + 75% natural, 50% mixed + 50% natural, 75% mixed + 25% natural, and 100% mixed , 26.9MPa, 24.8MPa, and 100% of natural sand compared to 27.1MPa. In addition, it was not possible to produce high-quality concrete due to the lack of viscosity when producing test specimens with fine aggregates of mixed slag with an assembly rate of 2.9.

Example 6: Experiment of changing the length of a concrete specimen

The length change test body was prepared in the same manner as the compressive strength test body of Example 5 in the state that the ratio of cement: fine aggregate: water presented in Example 4 was set equal to 1:4:0.8. The size of the length change specimen is 22.5 mm (height) x 22.5 mm (width) x 225 mm (length).

The change in the length of the test body was referred to as the stud gauge method, and the change was evaluated by measuring both lengths of the stud gauges previously embedded at both ends of the test body at the time of manufacturing the test body. The length change scale is measurable up to the 10 ^-3 mm category.

As a result, as shown in FIG. 13, when the mixed slag of the present invention was used, it was confirmed that the shrinkage reduction property is superior to that of natural aggregate sand. 13 is a view showing a change in the length of the test body in the range of assembly ratio 2.58 to 2.79. Referring to FIG. 13, when replacing the mixed slag of the present invention by 25 to 100% based on the amount of natural sand shrinkage (100%), it can be seen that the shrinkage amount can be reduced by 84 to 46%. Therefore, when the mixed slag of the present invention is used as a fine aggregate, it is judged that the effect is excellent in reducing the crack of concrete due to shrinkage.

Example 7: Derivation of natural aggregate replacement rate

Based on the evaluation results of the compressive strength of Example 5, the strength prediction equation could be derived as follows through a regression analysis using a statistical tool, and the results are shown graphically in FIG. 14.

-25% mixed slag + 75% natural sand: -56.71(FM) ² +299.29(FM)-366.29

-50% mixed slag + 50% natural sand: -122.51 (FM) ² +667.41 (FM) -876.827

-Mixed slag 75% + Natural sand 25%: -179.65(FM) ² +979.98(FM)-1303.1

-100% mixed slag: -73.16(FM) ² +393.82(FM)-499.88

In addition, by using this strength prediction formula, the optimal assembly degree according to the replacement rate of natural aggregate of the mixed slag fine aggregate could be derived as follows.

division Replacement rate of fine aggregate of mixed slag 25% 50% 75% 100% Optimum assembly 2.64 2.72 2.73 2.69 Maximum predicted value (MPa) 28.6 32.1 33.3 30.1

It was confirmed that the mixed slag fine aggregate of the blast furnace slag and ferronickel slag according to the present invention can exhibit an effect of enhancing strength compared to 100% of natural sand when mixed at least 25% with respect to sand, which is a natural aggregate. On the other hand, in order to reduce the natural resources by replacing natural sand, it is preferable to mix 50% or more of the mixed slag fine aggregate.

Therefore, when the mixed slag fine aggregate is mixed with 50% by weight or more and 100% by weight or less based on the total weight of the fine aggregate, the optimum assembly rate is predicted to fall into the category 2.69 to 2.72, and the average assembly rate of 2.71 provides significantly better results. Could be derived. In this category, the compressive strength was 30.1 to 33.3 MPa, which was confirmed to be significantly superior to 27.1 MPa, 100% of natural sand. Therefore, in manufacturing the mixed slag, among the mixed slags of the present invention, particularly, the fine aggregate of the granulated slag in the range of 2.58 to 2.79 can have a very effective effect. The optimum assembly rate through strength prediction was 2.71, which was included in the categories confirmed in the test, 2.58 to 2.79.

Example 8: Derivation of mixing ratio of slag

The ferronickel slag: blast furnace slag=9:1, 8:2, 7:3, 6:4, 5:5, 4 by weight to calculate the mixing ratio of ferronickel slag and blast furnace slag included in the fine aggregate of mixed slag. A mixed slag of 6:6, 3:7, 2:8, and 1:9 was prepared at a granulation rate of 2.7.

As a result of the evaluation of compressive strength, ferronickel slag: blast furnace slag=7:3, 6:4, 5:5, 4:6, 3:7, 2:8 weight ratio category replaces more than 25% of mixed slag fine aggregate compared to natural sand. It was confirmed that the compressive strength was significantly higher than that of natural sand in all regions. The resulting graph is shown in FIG. 15.

As can be seen in Figure 15, the ferronickel slag: blast furnace slag = 9: 1, 2: 8 and 1: 9 weight ratio showed lower compressive strength compared to natural sand. This is because the final concrete is structurally vulnerable when the blast furnace slag exceeds the content range of the present invention due to the porous structure of the blast furnace slag.

The mixed slag fine aggregate in which the ferronickel slag and the blast furnace slag according to the present invention are mixed, or when used in combination with natural sand, exhibits high strength compared to natural sand and can reduce cracks in concrete due to shrinkage reduction characteristics. It has an effect.

Example 9: Preparation of dry mortar for plastering

A dry mortar for plastering was prepared comprising the mixed slag fine aggregate of the present invention. Dry mortar for plastering is mainly used for interior and exterior finishing construction, and the demand for dry mortar for plastering has increased rapidly in recent years as remodeling of aged concrete structures has increased.

To evaluate the finish of the prepared dry mortar for plastering, the number of coatings and the finish time were measured. In particular, when the dry mortar for plastering is applied to the wall surface, a sagging phenomenon occurs due to the weight of the mortar itself. When the sagging phenomenon occurs, the number of times the worker applies the mortar increases, so that the finishing time also increases.

The ferronickel slag and blast furnace slag are mixed in a weight ratio of 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9 to prepare a mixed slag, cement : Mixing slag: water = 1: 4: 1 and then mixed to prepare a dry mortar. The same worker applied the dried mortar prepared in a mold having a size of 1 m x 1 m x 5 cm, and the number of application and the finish time were measured. The number of times of application is a measure of the number of times the worker applied the dry mortar to all areas in the frame, and the finish time is the time taken from the start of application to completion of application.

Ferronickel slag: blast furnace slag
Mixing ratio (weight ratio) Number of times (times) Deadline (Min) 28-day compressive strength (Mpa) 8:2 62 24 21.7 7:3 50 14 21.2 6:4 48 14 20.7 5:5 48 14 20.4 4:6 45 12 19.6 3:7 47 12 19.5 2:8 45 11 18.7 1:9 45 11 17.2

The dry mortar's 28-day strength control criterion is 18 MPa.

According to Table 6, it can be seen that as the content of the ferronickel slag increased, a sagging phenomenon occurred and the number of coatings and the finishing time increased. This is because the ferronickel slag is relatively heavier than the blast furnace slag.

On the other hand, it can be seen that in the case of mixed slag mixed in a weight ratio of ferronickel slag: blast furnace slag = 1:9, it does not reach the standard compressive strength.

Although the embodiments of the present invention have been described in detail above, the scope of rights of the present invention is not limited to this, and various modifications and variations are possible without departing from the technical spirit of the present invention as set forth in the claims. It will be obvious to those of ordinary skill in the field.

Claims (11)

Fine aggregate for concrete comprising ferronickel slag and blast furnace slag mixed slag in a weight ratio of 7:3 to 2:8.
According to claim 1,
Fine aggregate for concrete comprising ferronickel slag and blast furnace slag mixed slag in a weight ratio of 7:3 to 5:5.
According to claim 1,
Fine aggregate for concrete comprising ferronickel slag and blast furnace slag mixed slag in a weight ratio of 4:6 to 2:8.
According to claim 1,
The fine aggregate for concrete with an assembly rate of mixed slag is 2.55 to 2.9.
According to claim 1,
The granularity of the mixed slag is 2.58 to 2.79.
According to claim 1,
The fine aggregate for concrete is a fine aggregate for concrete containing more than 95% by weight of ferronickel slag and blast furnace slag with a particle size of more than 0 and less than 5 mm.
According to claim 1,
Fine aggregate for concrete with average particle size of ferronickel slag and blast furnace slag from 1.5mm to 3.0mm.
According to claim 1,
The fine aggregate for concrete is a fine aggregate for concrete that further includes sand.
The method of claim 8,
The sand is a fine aggregate for concrete containing more than 0 to 75% by weight or less based on the total fine aggregate weight.
A composition for a building material comprising a fine aggregate for concrete according to any one of claims 1 to 9, a coarse aggregate and cement.
The composition for building materials according to claim 10, wherein the composition for building materials comprises 200 to 600 parts by weight of fine aggregate based on 100 parts by weight of cement.

Images