KR101608841B1 - Steel scraps reinforced cement composite material and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a method for producing a steel scrap reinforced cement composite material having excellent workability, high strength, high toughness and high durability, and a cement composite material produced by such a method.
When a steel scrap reinforced cement composite material having high strength, high toughness and high durability according to the present invention is applied to a concrete structure such as a bridge, a building or a harbor structure, the mechanical strength such as strength and toughness is remarkably improved Steel scrap is a byproduct of the steel industry and is cheaper than steel fibers used in conventional steel fiber reinforced cement composites and uses steel scrap instead of steel fiber to suppress CO ₂ emissions from steel fiber production There is an eco-friendly effect.

Description

TECHNICAL FIELD The present invention relates to a steel scrap reinforced cement composite material and a manufacturing method thereof,

The present invention relates to a method for manufacturing a steel scrap reinforced cement composite material having high strength, high toughness and high durability, and a cement composite material produced by such a method.

Concrete is used to make various structures by mixing aggregate with cement, and cement plays a role of combining aggregate and aggregate. Cement has various characteristics depending on various materials to be mixed together as a generally basic material in the construction of roads, bridges, and buildings. That is, the compression strength can be increased, the tensile strength or the bending strength can be increased according to the material to be added, and the characteristics such as water resistance and fire resistance can be improved.

In addition, concrete is a construction material having excellent economy and durability, and is widely used for construction of steel structures and concrete structures.

Concrete, on the other hand, is excellent in compressive strength, durability, economic efficiency, material compatibility, fire resistance and low maintenance cost. However, tensile strength is low as about 10% of compressive strength, So that it is liable to corrode the reinforcing steel, and brittle fracture tends to occur.

In addition, concrete has a lower toughness than steel, and its energy absorption capability is significantly lowered, which is disadvantageous to natural disasters such as earthquakes. When the concrete is hydrated, it takes a long time for the strength development, and the weak brittle property and drying shrinkage are large in the tensile force. When the concrete is condensed immediately after casting with plasticity, tensile stress acts on the surface, And the like.

Therefore, researches on the development of concrete and cement composite materials mixed with various fibers have been actively carried out in order to enhance the tensile strength of concrete and to secure long - term durability through crack control.

Fiber reinforced concrete or fiber reinforced cement composite material, which is produced by mixing about 1% of steel fiber and organic fiber into a mixture of ordinary concrete to prevent brittle fracture of concrete, It is used in concrete structures.

Since fiber-reinforced concrete injects fiber into the blend of ordinary concrete, it can not satisfy satisfactory toughness due to insufficient amount of fiber due to lack of viscosity of concrete, and fiber ball phenomenon occurs, and consequently, There is also a case where it is lowered. In addition, fiber content of about 1% can not completely prevent the brittle fracture of high strength concrete. Therefore, it is vulnerable that structure is destroyed immediately when earthquake, repetitive and impact load of vehicle, fire and natural deterioration occurs.

Among various fibers, steel fiber is the most commonly used fiber in the construction industry, which reduces the fluidity of concrete but is very effective in improving tensile strength and ductility. However, since steel fibers are expensive, there is an urgent need to develop fibers that can replace steel fibers in order to economically develop fiber-reinforced concrete or cement composite materials.

Korean Patent No. 10-1190282

It is an object of the present invention to provide a steel scrap reinforced cement composite material having high strength, high toughness and high durability and capable of overcoming the problems of the conventional concrete and fiber reinforced concrete mentioned above, and a method of manufacturing the same.

In order to accomplish the above-mentioned technical object, the present invention provides a cement paste composition comprising 100 parts by weight of cement, 50 to 150 parts by weight of fine aggregate, 30 to 40 parts by weight of water, and 2 vol.% Or less of steel scrap This paper proposes a steel scrap reinforced cement composite material.

Also, the steel scrap has a length of 10 to 30 mm, a thickness of 0.3 to 0.5 mm, a width of 1 to 2 mm, and a density of 7.0 to 8.0 g / cm ³ .

The fine aggregate is sand having a density of 2.0 to 3.0 g / cm ³ , a unit volume of 1,400 to 1,800 kg / m ³ , a water absorption of 1 to 3% and a particle size of 5 mm or less. We suggest a composite material.

Further, the present invention further provides a steel scrap reinforced cement composite material characterized by further containing 1 part by weight or less of a high-performance water reducing agent.

The high-performance water reducing agent is at least one selected from the group consisting of a polycarboxylic acid-based water reducing agent having a solid content of 15 to 25% by weight, a naphthalene-based water reducing agent, a melamine-based water reducing agent and a lignin-based water reducing agent. I suggest.

Also, the steel scrap reinforced cement composite material has a 28-day compressive strength of 50 to 70 MPa and a flexural strength of 8.5 to 10.5 MPa.

(A) mixing 50 to 150 parts by weight of a fine aggregate with 100 parts by weight of cement, (b) mixing 30 to 40 parts by weight of water with respect to 100 parts by weight of the cement to the mixture prepared in the step (a) And (c) mixing the mixture prepared in the step (b) with steel scrap of 2 vol.% Or less based on the volume of the mixture and curing the mixed steel scrap. I suggest.

The steel scrap has a length of 10 to 30 mm, a thickness of 0.3 to 0.5 mm, a width of 1 to 2 mm, and a density of 7.0 to 8.0 g / cm ³ . .

Also, in the step (b), 1 part by weight or less of a high-performance water reducing agent is further mixed, thereby producing a steel scrap-reinforced cement composite material.

In the step (a), 50 to 150 parts by weight of the fine aggregate is mixed with 100 parts by weight of cement for 1 to 2 minutes using a pan mixer or a similar mixer, and in step (b) 30 to 40 parts by weight of water based on 100 parts by weight of cement is mixed with a pan mixer or a similar mixer for 2 to 3 minutes to obtain a predetermined fluidity. In the step (c) And mixing the steel scrap with 2 vol.% Or less of the volume of the mixture to the mixture with a pan mixer or a similar mixer for 3 to 5 minutes.

When a steel scrap reinforced cement composite material having high strength, high toughness and high durability according to the present invention is applied to a concrete structure such as a bridge, a building or a harbor structure, the mechanical strength such as strength and toughness is remarkably improved .

In the steel scrap reinforced cement composite material according to the present invention, the steel scrap is a by-product of the steel industry, and thus the steel scrap is less expensive than the steel fiber used in the conventional steel fiber reinforced cement composite, CO ₂ emissions from production cutbacks are suppressed, which is environmentally friendly.

1 is a graph showing the density of steel scrap according to the type.
FIG. 2 is a graph showing a flow value of a cement composite material incorporating shelf scrap when the weight ratio of water to cement is 30%. FIG.
3 is a graph showing a flow value of a cement composite material incorporating shelf scrap when the weight ratio of water to cement is 40%.
4 is a graph showing the compressive strength of a cement composite material incorporating shelf scrap when the weight ratio of water to cement is 30%.
5 is a graph showing the compressive strength of a cement composite material incorporating shelf scrap when the weight ratio of water to cement is 40%.
6 is a graph showing the flexural strength of a cement composite material incorporating shelf scrap when the weight ratio of water to cement is 30%.
7 is a graph showing the flexural strength of a cement composite material incorporating shelf scrap when the water to cement ratio is 40%.

Hereinafter, the present invention will be described in more detail.

The steel scrap reinforced cement composite material according to the present invention comprises a mixture comprising 100 parts by weight of cement, 50 to 150 parts by weight of fine aggregate and 30 to 40 parts by weight of water and 2 vol.% Or less of steel scrap with respect to the mixture volume .

The cement is mainly pulverized by mixing the calcareous raw material and the clay raw material at an appropriate ratio (the siliceous raw material and the iron oxide raw material are added to adjust the component), and then the calcined product is fired until a part thereof is melted (about 1,450 ° C.) However, the present invention is not limited to the ordinary portland cement obtained by adding fine gypsum to the resulting clinker as a coagulation controlling agent.

The steel scrap is used to impart high toughness to cement composites having high strength and high durability. It serves to hold concrete by bonding with concrete inside of concrete and has a length of 10 to 30 mm and a thickness of 0.3 A width of 1 to 2 mm, and a density of 7.0 to 8.0 g / cm < ³ >.

Steel scrap is generated in the process of steel production or processing of the steel industry or inability to use steel products. It generates about 23,000 tons per year (2010, Korea Iron & Steel Association standard), and the generated steel scrap .

The classification methods of steel scrap include classification by source, classification by composition and form, classification by purchase type, and classification criteria by source are as follows.

The sources are classified into self-generated scrap, processed scrap, and scrap scrap. The self-generated scrap is generated during the manufacturing process of steel products by steel companies and is recovered and used without any separate processing or distribution transactions. Scrap refers to scrap generated during processing steel products in the steel industry, such as machinery and automobiles, and scrap scrap refers to steel scrap that is processed into steel waste due to the loss of usefulness of the final product.

Steel scrap is classified into steel scrap, scrap, scrap, and scrap according to the steel scrap classification standard (KSD 2101). The steel scrap has a density of 7.0 to 8.0 g / cm ^{3 and} a density of 7.7 g / cm < ³ >, steel scrap may be used as the alternative fiber of the steel fiber, and lathe scrap may be most preferably used as the steel fiber alternative fiber in manufacturing the steel scrap reinforced cement composite material of the present invention.

Domestic steel scrap accounts for about 75% of scrap and about 25% of self-generated scrap. Unlike other materials that do their utilities once they have been used once, their lifetime is recovered as iron scrap, and more than 90% of steel is produced again. The production of 1 ton of iron is about 40 reprocessing processes, so the cumulative usage is over 10 tons. Recycling iron can reduce carbon dioxide by 82%, nitrogen oxides by 88.9%, and sulfur oxides by 94.7% compared with iron production directly from iron ore.

The fine aggregate may be sand having a density of 2.0 to 3.0 g / cm ³ , a unit volume of 1,400 to 1,800 kg / m ³ , a water absorption of 1 to 3% and a particle size of 5 mm or less, but is not limited thereto.

The fine aggregate is used for securing the homogeneity of the cement composite material to improve its strength. According to one embodiment of the present invention, 50 to 150 parts by weight of sand may be included based on 100 parts by weight of cement.

Further, if necessary, 1 part by weight or less of a high-performance water reducing agent based on 100 parts by weight of cement may be further included.

Specifically, the high performance water reducing agent may be at least one selected from the group consisting of a polycarboxylic acid type water reducing agent having a solid content of 15 to 25% by weight, a naphthalene type water reducing agent, a melamine water reducing agent and a lignin water reducing agent.

The high performance water reducing agent activates and disperses the cement particles in the concrete electrostatically to disperse the cement particles so that the cement particles repel each other to improve the workability and reduce the unit amount and the unit cement amount to obtain a predetermined consistency and strength . Typical high-performance water reducing agents include naphthalene sulfonic acid condensate, melamine resin sulfonate condensate, and polycarboxylic acid.

The conventional high performance water reducing agent may be added with an amine compound, a gluconate compound and a nitrite compound to maximize the compressive strength of the concrete at the initial stage and at the age of 28 days.

Also, the steel scrap reinforced cement composite material according to the present invention has a 28-day compressive strength of 50 to 70 MPa and a flexural strength of 8.5 to 10.5 MPa.

(A) mixing 50 to 150 parts by weight of a fine aggregate with 100 parts by weight of cement; (b) mixing 100 parts by weight of cement into the mixture prepared in step (a) (C) mixing the mixture prepared in the step (b) with steel scrap of 2 vol.% Or less based on the volume of the mixture and curing the mixture. have.

In addition, the present invention steel scrap reinforced cement composite material characterized in that the steel scrap length of 10 ~ 30 mm, a thickness of 0.3 ~ 0.5 mm, a width of 1 ~ 2 mm, a density of 7.0 ~ 8.0 g / cm ³ Which is characterized in that it is a production method of the present invention.

Further, in the step (b) of the present invention, 1 part by weight or less of a high-performance water reducing agent may be further mixed as necessary.

In the method of manufacturing a steel-scrap reinforced cement composite material according to the present invention, 50 to 150 parts by weight of the fine aggregate is mixed with 100 parts by weight of cement for 1 to 2 minutes with a pan mixer or a similar mixer, (b), 30 to 40 parts by weight of water is mixed with the mixture prepared in step (a) on the basis of 100 parts by weight of cement for 2 to 3 minutes with a pan mixer or a similar mixer to obtain a predetermined fluidity, c) mixing the mixture produced in step (b) with steel scrap of 2 vol.% or less by volume of the mixture in a pan mixer or a similar mixer for 3 to 5 minutes.

In order to produce the steel scrap reinforced cement composite material according to the present invention, the final mixture is subjected to wet curing for 1 to 3 days, and then steam curing is carried out at a high temperature of 60 to 120 DEG C to activate the hydration reaction of the cement. To 4 days.

By using steel scrap instead of steel fiber in the production of steel fiber reinforced cement composites, the flexural strength can be improved by about 10% compared to ordinary concrete without steel scrap. By using steel scrap instead of steel fiber, manufacturing cost is reduced In addition, carbon emissions due to the reduction of steel fiber production, which is a steel product, are suppressed, which is environmentally friendly.

Hereinafter, embodiments for explaining the present invention in more detail will be presented.

However, the following examples are provided to more easily illustrate the present invention, and the present invention is not limited by the examples.

< Examples >

In this example, the workability, compressive strength and bending strength characteristics of steel scrap reinforced cement composites according to the present invention were analyzed as follows.

1) Materials used

Cement is usually Portland cement (Hanil cement) which can be easily purchased in the market, and its physical properties are shown in Table 1.

 [Table 1]

The chemical admixture for improving the flowability of the mortar was a polycarboxylic acid high performance water reducing agent of S Company which is used for high strength and fluidized concrete. The physical properties of these materials are as follows: Table 2 and 3 show the results.

 [Table 2]

 [Table 3]

In order to utilize steel scrap as a substitute for steel fiber in fiber - reinforced cement composites, a scrap of steel scrap was collected in the densely - machined area of Dormero, Yeongdeungpo - gu, Seoul and Seongseo Industrial Complex, Daegu Metropolitan City. Shelf scrap is a scrap generated during metal working or milling work. Most of the steel scrap is scrap close to steel fiber because it has a small diameter and is formed in a vine shape. Depending on the work type The thickness and length of scrap have different characteristics. Fig. 1 shows the density of each type of lathe scrap. The density of all the scrap except aluminum shelf scrap was about 7.5 ~ 8.0 g / cm ^{3, which} was similar to the density (7.70 g / cm ³ ) of a commercially available steel fiber. The shelf scrap used in this experiment was a short scrap having an average length of 20 mm, an average thickness of 0.4 mm, an average width of 1.5 mm and a density of 7.53 g / cm ³ .

2) Mixing experiment of cement composites incorporating shelf scrap

In order to fabricate specimens of cement composites incorporating shelf scrap, the mixing ratio by unit mass was determined as shown in Table 4. The ratio of water to cement was set at 30% and 40%, and the mixing ratio of steel scrap was varied from 0 to 2.0% of the mortar volume by 0.5% based on the steel fiber content. The target flow value was set at 210 ± 20 mm Respectively. A cylindrical specimen (Ø100 × 200 mm) and a rectangular specimen (40 × 40 × 160 mm) were fabricated in accordance with KS F 2403 and KS L ISO 679. The mold was removed after 24 hours after molding, Curing was carried out at a temperature of 20 ± 3 ° C until the test.

[Table 4]

3) Compressive strength and flexural strength test

In order to evaluate the compressive strength and flexural strength characteristics of the cement composites incorporating shelf scrap, the compressive strength and the 28th day bending strength test were carried out according to KS F 2405 and KS L ISO 679 Respectively.

4) Steel scrap  Characteristics of mixed cement composites

(1) Workability

FIG. 2 and FIG. 3 show the flow values for evaluating the workability of the cement composite material incorporating the lathe scrap. When the water ratio to the cement is 30% and the addition amount of the high performance water reducing agent is 0.5% Since the flow rate of the cement composites decreases slightly as the mixing ratio of the lathe scrap increases, the workability of the cement composite incorporating the lathe scrap decreases slightly as the water ratio to the cement is small There was no aggregation of steel scrap. On the other hand, when the ratio of water to cement is 40%, the target flow value (210 ± 20 mm) is satisfied even without the addition of high-performance water reducing agent, and the flow value is not decreased even if the mixing ratio of the scrap is increased. When the ratio of water to cement is rather large, the workability of cement composites incorporating shelf scrap is similar to that of ordinary concrete without lath scrap.

(2) Compressive strength of cement composites incorporating shelf scrap

Figs. 4 and 5 show the compressive strengths of the cement composites incorporating the lathe scrap at the ages of 7 days and 28 days. As the mixing ratio of the lath scrap increases, the compressive strength decreases somewhat regardless of the water ratio to the cement But it was not at the level to be noticed. In other words, the compressive strength of cement composites incorporating shelf scrap up to 40% of the cement ratio showed up to 93% of the ordinary concrete even when the shelf scrap was mixed up to 2.0%. When the water ratio to cement was 30% The compressive strength of cement composites incorporating shelf scrapings showed up to 92% of ordinary concrete even when mixed with shelf scrap 2.0%. Since the fiber reinforced cement composites are used for the purpose of improving the bending strength and toughness rather than improving the compressive strength, the compressive strength of the cement composite containing the shelf scrap is slightly reduced.

(3) Flexural strength of cement composites incorporating shelf scrap

Fig. 6 and Fig. 7 show the bending strength of the cement composites incorporating the lathe scrap at 28 days. The bending strength was improved up to 2.0%, which is the maximum range of the scrap inclusion ratio regardless of the water ratio to the cement. , And the bending strength is improved by about 10% compared with the ordinary concrete without the scrap.

Claims (10)

100 parts by weight of cement; 50 to 150 parts by weight of fine aggregate; 30 to 40 parts by weight of water; And a mixture containing an amine-based compound, a gluconate-based compound, and a nitrite-based compound, in an amount exceeding 1 part by weight and a lignin-based water-reducing agent in an amount of 0 to 2 vol.
Wherein the steel scrap has a length of 10 to 30 mm, a thickness of 0.3 to 0.5 mm, a width of 1 to 2 mm, and a density of 7.0 to 8.0 g / cm ³ . delete The fine aggregate according to claim 1, wherein the fine aggregate is sand having a density of 2.0 to 3.0 g / cm ³ , a unit volume of 1,400 to 1,800 kg / m ³ , a water absorption of 1 to 3%, and a particle size of 5 mm or less Steel scrap reinforced cement composites. delete delete The steel scrap reinforced cement composite material according to claim 1, wherein the steel scrap-reinforced cement composite material has a 28-day compressive strength of 50 to 70 MPa and a flexural strength of 8.5 to 10.5 MPa. (a) 100 parts by weight of cement and 50 to 150 parts by weight of fine aggregate;
(b) 30 to 40 parts by weight of water on the basis of 100 parts by weight of cement to the mixture prepared in the step (a); And not less than 1 part by weight of a lignin-based water reducing agent containing an amine compound, a gluconate compound and a nitrite compound; And
(c) mixing the mixture prepared in the step (b) with steel scrap in an amount of not less than 0 vol% and not more than 2 vol.% based on the volume of the mixture, followed by curing,
Wherein the steel scrap has a length of 10 to 30 mm, a thickness of 0.3 to 0.5 mm, a width of 1 to 2 mm, and a density of 7.0 to 8.0 g / cm ³ . delete delete 8. The method of claim 7,
In step (a), 50 to 150 parts by weight of the fine aggregate is mixed with 100 parts by weight of cement for 1 to 2 minutes with a pan mixer,
In the step (b), 30 to 40 parts by weight of water is added to the mixture prepared in step (a) on the basis of 100 parts by weight of cement; And 1 part by weight of a lignin-based water reducing agent containing an amine compound, a gluconate compound and a nitrite compound, were mixed for 2 to 3 minutes with a pan mixer,
Wherein in step (c), the steel scrap is mixed with the mixture prepared in step (b) in an amount of not less than 0 vol% and not more than 2 vol.% Based on the volume of the mixture with a fan mixer for 3 to 5 minutes. Gt;

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