KR20030016891A - Slag as substitute for aggregate of concrete and concrete composition comprising the slag and having a superior durability - Google Patents

Abstract

The present invention relates to a crushed slag for replacing concrete fine aggregates and a concrete composition, wherein a unit weight of 1.45 to 1.70 g replaced with a crushed slag having a unit weight of 1.45 to 1.70 g / l used as a substitute for fine aggregates is used. Concrete composition, including the hydrolysis slag / l is excellent in strength and durability such as watertightness.

Description

Slag as substitute for aggregate of concrete and concrete composition comprising the slag and having a superior durability}

The present invention relates to a concrete slab for replacing aggregate aggregates and a concrete composition having excellent durability, and more particularly to a specific unit weight slag used as a concrete aggregate substitute and a durable concrete composition comprising the same.

Aggregate is a major component of mortar or concrete together with cement, such as gravel, crushed stone, crushed stone, crushed sand, and natural sand. However, in recent years, not only is there a lack of natural aggregates for concrete, but in the future, it is expected that strict regulations such as river aggregate collection and quarrying restrictions will be followed according to river maintenance management, environmental preservation and military protection zone setting.

Therefore, there is an urgent need for the development of substitutes for aggregates that are used as the main components in concrete production.

In general, sand used as fine aggregates for concrete has a unit weight of 1.60Kg / L and a very dense structure. However, the crushed slag produced in the blast furnace of the steel mill is in the form of fine granules. It has a very soft structure with a unit weight of 1.0 to 1.1 Kg / L having a large amount of pores in the particles due to the expansion of the various gases such as sulfur remaining in the molten molten slag and the expansion of foam due to the generation of steam.

Therefore, in order to use the crushed slag as a substitute for sand, which is a fine aggregate for concrete, it is necessary to improve the unit weight and the properties of the soft tissue.

As a method for reforming physical properties of crushed slag, a method of reducing the cooling effect by adding dust and sludge to the molten slag to lower the slag temperature (Japanese Patent Application No. 53-123394), and designing a large number of nozzle diameters for slag cooling through each nozzle There have been proposed methods of modifying the properties of slag by using slag dropping methods.

In addition, a method of reducing the water cement ratio as a method of improving the durability of the concrete (Japanese Patent Laid-Open Patent Publication No. 1999-343159), a method of mixing short fibers as concrete as expansion inhibitors and expansion industrial by-products such as coal ash and converter slag (Japanese Laid-Open Patent Publication) Patent 1999-228803) has been proposed.

As described above, the methods proposed to improve the durability of the concrete are to reduce the water cement ratio, which mainly serves as a binder, or to add a reinforcing material so that the structure of the concrete can be more precisely formed.

However, it is also very difficult and uneconomical to modify the blast furnace slag to have properties that can replace the sand used as the fine aggregate for concrete.

Accordingly, an object of the present invention is to provide a crushed slag having a unit weight of 1.45 ~ 1.70g / ℓ used as a substitute for concrete aggregate aggregate.

It is another object of the present invention to provide a concrete composition comprising a hydrated slag having a unit weight of 1.45 to 1.70 g / l.

1 is a photograph showing the particle surface of the hydrated slag having a fibrous needle,

Fig. 2 is a photograph showing the particle surface of the hydrobroken slag with the fibrous needles removed and the unit weight increased.

According to one aspect of the invention,

There is provided a crushed slag having a unit weight of 1.45 to 1.70 g / l, which is used as a substitute for fine aggregate for concrete.

According to another aspect of the present invention,

A durable concrete composition is provided that comprises a hydrated slag having a unit weight of 1.45 to 1.70g / l so that up to 30% by weight of the fine aggregate is replaced by hydrated slag having a unit weight of 1.45 to 1.70 g / l.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present inventors have found that the soft slag can be used as a substitute for the fine aggregate for concrete by increasing the compact structure and increasing the low unit weight.

The blast furnace slag produced by the quenching process of the blast furnace pig iron manufacturing process as a by-product of ironworks is not only chemically unstable and highly reactive as an amorphous structure, but also has a latent hydraulic property that causes a hydration reaction when alkali components coexist. Attention is drawn to strength development due to such physical properties of slag.

Fig. 1 is a photograph showing the particle surface of hydroslag slag on which fibrous needles are formed. As shown in FIG. 1, the hydroslag slag has a fibrous needle formed on the surface of the particle, and may be damaged by vitreous needles when contacted with the human body. In particular, the particles contain a large amount of pores in the particles due to the escape of the gas by contact with the cooling water during the slag production, and because a large number of cracks on the surface does not form a compact structure can be used as a substitute for structural fine aggregates Could not.

However, by modifying the surface by removing the fibrous needles of the crushed slag, and modifying the soft tissue into a dense tissue, and can be used as an aggregate substitute for concrete.

That is, by grinding the crushed slag by using a crusher, the needle bed is removed from the particle surface of the crushed slag and the particle size is adjusted to increase the unit weight of the crushed slag, so that the crushed slag has sufficient strength to be used as a substitute for concrete aggregate.

The unit weight of the aggregate may be expressed as a unit volume weight (T), and means the weight occupied by the aggregate in the container of the unit volume (1 L) as shown in Equation 1 below.

[Equation 1]

T = W / V

(Wherein, W is the weight of the sample in the container (kg) and V is the volume of the container (L).)

Figure 2 is a view showing a tissue photograph of the hydroslag slag according to the unit weight size from which the fibrous saliva is removed. As shown in FIG. 2, the crushed slag pulverized in the crusher is removed into fibrous needles and adjusted to a finer particle size according to the size of the unit weight, thereby changing to a very dense structure without pores and cracks. Accordingly, the crushed slag has a unit weight increase, and the crushed crushed slag having a dense structure can be used as a substitute for the concrete fine aggregate. Hydrolyzed slag has sufficient strength to be used as a substitute for concrete fine aggregates and has a unit weight of 1.45 g / l to 1.70 g / l.

As can be seen in Figure 2, there are almost no fines in the hydrolyzed slag unit weight of 1.1kg / l, 1.3kg / l, but the fine particles are present in the hydrolyzed slag of unit weight 1.47kg / l, 1.52kg / l It can be confirmed.

That is, when the cumulative passage content of the fine particles having a particle size of 0.3 mm or less is 24% or more, the slag exhibits a unit weight of 1.47 kg / L or more. In the case of containing excessive finely divided slag particles, there is a possibility that material separation between coarse aggregate and fine aggregate occurs.

As a pulverizer, generally commercially available pulverizers such as ball mills, rod mills, roller mills, edge runners, and cone crushers may be used.

Table 1 shows the physical properties of the slag and natural sand according to the unit weight.

TABLE 1

Slag Slag Slag Slag Natural sand Unit weight (kg / l) 1.1 1.3 1.47 1.52 1.67 Particle size distribution -10mm 100 100 100 100 100 -5mm 99.8 100 100 100 98 -2.5mm 90 100 100 100 93.7 -1.2mm 51.6 90 98.6 95.6 82.6 -0.6mm 19.2 45 57.7 53.2 59.1 -0.3mm 6 14.8 24.7 24.0 19.1 -0.15mm 2.4 6 11.2 14.0 3.4 Assembly rate 1.82 1.97 2.07 2.13 2.44 importance 2.12 2.23 2.67 2.67 2.59 Water absorption 0.21 0.24 0.13 0.13 0.9

As shown in Table 1, the crushed slag having a unit weight of about 1.45-1.70kg / L has a suitable assembly rate and specific gravity for use as concrete aggregates, and is used as a substitute for concrete aggregates.

In the case of using the hydraulic slag having a unit weight of 1.45Kg / L or less, the required strength of the concrete based on the design strength cannot be obtained, and the concrete durability can not be expected because the concrete of the compact structure cannot be manufactured. If the unit weight is over 1.70Kg / L, the material is separated from the coarse aggregate, gravel and fine aggregate slag due to the excess of fine powder, so the coarse aggregate is at the bottom of the concrete, and the fine aggregate slag is at the top of the concrete. Due to the bias phenomenon, it is impossible to produce concrete of uniform structure.

Durability of concrete refers to the ability of concrete to resist physical and chemical effects from the outside over a long period of time. Durability may be degraded by the surrounding environment surrounding the concrete structure or by internal causes of the concrete itself. The degradation of the durability of concrete structures is rarely caused by a single cause and is mostly caused by a combination of effects.

In particular, in the selection and mixing of materials during concrete mixing, the quantity or structure of aggregate used is an important variable for the durability of concrete.

By removing the fibrous needle-like structure of the present invention by mixing the granulated slag of the unit weight of 1.45-1.70kg / L adjusted to an appropriate ratio instead of the aggregate aggregate, by mixing the concrete, durability, such as strength and water tightness of the concrete is improved.

The crushed slag having a unit weight of 1.45-1.70 kg / L at the time of concrete compounding is compounded by substituting the amount of the fine aggregate to be mixed with concrete in an amount of up to 30% by weight, preferably 10-30% by weight. When the replacement ratio of the fine aggregate of slag exceeds 30% by weight, the watertightness is increased, but the material between the coarse aggregate and the fine aggregate is separated and the strength is lowered. When the fine aggregate is replaced with the slag in the above range, not only the material is not separated during the concrete mixing, but also the concrete of the denser structure can be produced by the slag fine powder.

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

Example 1 Strength Measurement

(Invention Examples 1 to 4)

The crushed slag generated in the steelworks blast furnace process is passed through the slag by adjusting the distance between two helical-shaped friction plates, thereby producing slag with unit weight of 1.47kg / ℓ and slag with 1.52kg / ℓ. It was used instead of fine aggregate.

10% by weight and 30% by weight of the natural sand used as a fine aggregate was replaced by slag to prepare a concrete specimen for measuring the compressive strength (φ100XH200mm). The design reference strength of concrete based on 28 days of age was 233 Kg / cm ² .

In case of replacing 10% by weight of fine aggregate with slag, 18.65kg of coarse aggregate with particle size of 25mm, 3.5kg of water, 7.22kg of cement and 15.2kg of natural sand and 1.74kg of slag sand as fine aggregate are mixed Was prepared.

In the case of replacing 30% by weight of the fine aggregate with slag, a specimen was prepared by mixing in the same manner as in the case of 10% by weight replacement except 15.2kg of natural sand and 5.22kg of slag sand.

After fabrication of specimens, curing was carried out in water under 23 ± 1 ° C. and the compressive strength according to age was measured using a compressive strength tester. The results are shown in Table 2 below.

(Comparative Examples 1-7)

The slag with unit weight of 1.47Kg / L is replaced with 50%, 70% and 100% of the existing fine aggregate natural sand, while the slag with unit weight of 1.1Kg / L and 1.3Kg / L is 10% and 30%. Except that the concrete was prepared by mixing the replacement of the concrete specimen for measuring the compressive strength was prepared in the same manner as in the invention example, and the compressive strength was measured and shown in Table 2 below.

In case of replacing 50% by weight of fine aggregate with slag, 18.65kg of coarse aggregate with particle size of 25mm, 3.5kg of water, 7.22kg of cement and 8.45kg of natural sand and 8.7kg of slag sand as fine aggregate are mixed Was prepared.

When 70% by weight of the aggregate was replaced with slag, except that 12.2kg of slag sand was mixed with 5.07 kg of natural sand, 50% by weight was prepared in the same manner as in the case of replacement.

When 100% slag was used as fine aggregate, except that 17.4 kg of slag sand was used, other components were mixed in the same amount as the above amount to prepare a specimen.

(Conventional example 1)

As the fine aggregate, 16.89 kg of natural sand, 18.65 kg of coarse aggregate having a particle size of 25 mm, air volume of 3%, 7.22 kg of cement, and 3.5 kg of water were prepared. After the specimen was prepared, it was cured in water under the condition of 23 ± 1 ° C., and the compressive strength according to the age was measured by using a compressive strength and the results are shown in Table 2 below.

TABLE 2

Condition Concrete compressive strength (kg / ㎠) Fine aggregate Unit weight (Kg / L) Slag replacement ratio (%) 7 days 28 days 8 Weeks 12 Weeks 24 Weeks 36 Weeks Inventive Example One Slag 1.47 10 209 243 251 270 272 278 2 " 30 205 242 255 269 272 276 3 1.52 10 215 247 255 272 280 283 4 " 30 217 250 257 274 283 287 Comparative example One 1.47 50 184 235 247 258 262 266 2 " 70 180 235 246 255 260 264 3 " 100 171 234 244 253 260 262 4 1.1 10 120 126 128 128 130 132 5 " 30 124 126 126 128 131 134 6 1.3 10 154 161 169 178 190 199 7 " 30 157 166 170 177 194 201 Conventional example One Natural sand 1.67 - 213 242 250 262 266 275

As can be seen in Table 2, Inventive Examples (1-4) compared to Comparative Examples (1-7) showed excellent compressive strength characteristics under all age conditions, and exceeded all of the standard strength of 233 Kg / cm ² for 28 days. The value is shown.

In addition, compared to the case of using natural sand as the fine aggregate of the conventional example (1), only slightly lower value was obtained after the initial strength of 7 days, and in all the long-term ages, the slag of the present invention was used as the fine aggregate. It can be seen that excellent compressive strength characteristics.

As in the case of the present invention, the use of slag as fine aggregate shows higher strength characteristics than the case of using the existing natural sand is considered to be due to the latent hydraulic rigidity of the slag.

On the other hand, when the slag of unit weight less than 1.45Kg / L is used, the aggregate separation between the coarse aggregate and the slag used as the fine aggregate is considered to exhibit low compressive strength because it cannot form concrete of dense structure.

In other words, coarse aggregates, fine aggregates and cement as binders are uniformly mixed so that there is no separation of aggregates to form dense concrete. Since it is biased on the upper side of concrete, it becomes difficult to form concrete of dense structure by uniform mixing of aggregate.

Example 2: Watertightness Measurement

Invention Examples 5 to 8

The crushed slag produced in the steelworks blast furnace process was crushed in a cone crusher to produce slag with a unit weight of 1.47Kg / L and slag with 1.52Kg / L, which was used as a fine aggregate for concrete. A concrete specimen (φ100XH200mm) for chlorine ion permeation test, which is a standard for watertightness by mixing with%, was prepared. The design reference strength of concrete based on 28 days of age was 233 Kg / cm ² .

In case of replacing 10% by weight of fine aggregate with slag, the coarse aggregate with 25mm particle size is 18.65kg, 3.5kg of water, 7.22kg of cement and 15.2kg of natural sand and 1.74kg of slag sand as fine aggregate. The specimen was prepared.

In the case of replacing 30% by weight of the fine aggregate with slag, the specimen was prepared in the same manner as in the case of replacing 10% by weight, except that 5.22kg of slag sand was mixed with 11.8kg of natural sand.

After the test specimens were cured in water under the condition of 23 ± 1 ° C., the chlorine ion permeation test was carried out according to the age and the results are shown in Table 3 below.

The chlorine ion permeation test was performed by measuring the amount of charge of chlorine ions passing through the concrete interior. If the measured amount of charge is high, it means that the concrete is not dense due to poor watertightness. If the amount of charge is small, it means that the structure is dense and the penetration of chlorine ions is difficult. The amount of chlorine ions passing through the specimen was cut to 10 cm in diameter and 5 cm in length, and the specimen was set in the center of the left cell filled with 0.1 N NaOH solution and the right cell filled with 3% NaCl solution. The amount of charge passing through the chloride ion after 6 hours was measured.

(Comparative Examples 8-9)

The slag having a unit weight of 1.3 Kg / L was replaced with 10% and 30% of the fine aggregate, and mixed in the same manner as in Examples 5 to 8 except that the concrete specimens were prepared. The results are shown in Table 3 below. It was.

(Conventional example 2)

After preparing the specimen as in the conventional example 1 and curing in water, the chlorine ion permeability according to the age was measured and the results are shown in Table 3 below.

TABLE 3

Condition Concrete Chlorine Ion Permeability (Coulomb) Fine aggregate Unit weight (Kg / L) Slag replacement rate (%) 28 days 8 Weeks 12 Weeks 24 Weeks 36 Weeks Inventive Example 5 Slag 1.47 10 4123 3882 3799 2215 2012 6 " " 30 3631 3140 2664 2138 1930 7 " 1.52 10 3938 3623 3424 2179 2009 8 " " 30 3421 3008 2429 2002 1783 Comparative example 8 " 1.3 10 7324 6980 6824 6534 6321 9 " " 30 6824 6634 6534 6321 6003 Conventional example 2 Natural sand 1.67 - 4782 4130 3433 2755 2366

As can be seen in Table 3, the chlorine ion permeability of concrete manufactured by using a unit weight of slag of 1.45Kg / L or more as a fine aggregate as the case of the present invention (5 to 8) using a replacement ratio of up to 30% The chlorine ion exhibited lower chlorine ion permeability than the conventional example (2) under all age conditions and showed a tendency to show better chlorine ion permeability with increasing age. On the other hand, as in the case of Comparative Examples (8-9), the chlorine ion permeability of concrete prepared using slag having a unit weight of less than 1.45 Kg / L showed superior characteristics compared with the case of using natural sand of the conventional example.

The low chlorine ion permeability means that the internal structure of the concrete is densely formed, which means that chlorine ions are difficult to penetrate the inside of the concrete.

If the internal structure of concrete is formed densely, it is highly resistant to environmental influences from the outside and thus durability is maintained for a long time.

As such, when slag manufactured from crushed slag manufactured in blast furnace process is replaced with less than 50% of fine aggregate, and mixed and used, it is possible to manufacture concrete of denser structure by latent hydraulic reaction of crushed slag. It seems to be very effective.

The slag with the fibrous needles of the present invention removed and the granular particle size of 1.47-1.70 Kg / L can be used as a substitute for the concrete aggregate, so that the concrete composition containing it is excellent in strength and watertightness.

Claims (2)

Slag with a unit weight of 1.47-1.70Kg / L used as a substitute for fine aggregates for concrete. In the concrete composition, excellent durability, characterized in that up to 30% by weight of the fine aggregate comprises a crushed slag with a unit weight of 1.45 ~ 1.7g / ℓ so that the crushing slag with a unit weight of 1.45 ~ 1.7g / ℓ Concrete composition