KR20100069881A - Wave type steel fiber and ultra-high performance fiber reinforced cementitious composites using the steel fiber - Google Patents

Abstract

PURPOSE: A manufacturing method of a steel fiber for an ultra high performance fiber reinforced concrete and a concrete using the same are provided to increase the mechanical performance such as compressive strength and flexural strength. CONSTITUTION: A steel fiber for an ultra high performance fiber reinforced concrete is mixed in a cement complex and improves the tensile strength of the composite. The steel fiber is formed with a wave shape. The wave number of the steel fiber is 4~8. The wave depth of the steel fiber is 0.12~0.35mm. The wave length of the steel fiber is 1.86~3.82mm. The diameter of the steel fiber is 0.15~0.35mm. The length of the steel fiber is 10~30mm. The tensile strength of the steel fiber is 2000~4000MPa.

Description

WAVE TYPE STEEL FIBER AND ULTRA--HIGH PERFORMANCE FIBER REINFORCED CEMENTITIOUS COMPOSITES USING THE STEEL FIBER}

The present invention relates to a steel fiber for ultra-high performance fiber reinforced concrete and a method for producing concrete using the same, more similarly, the steel fiber and mechanically improve the adhesion performance of the fiber and cement composite (concrete) by processing in a wave shape using the same It relates to a method for producing an ultra-high performance fiber reinforced cement composite.

Concrete is widely used in the construction of concrete structures together with steel as an economical and durable construction material. However, concrete has an inherent bond with low tensile strength and flexural strength, and is easily cracked, and brittle failure of concrete has been a problem due to an increase in compressive strength due to the practical use of high strength concrete.

Meanwhile, in order to prevent brittle fracture of concrete, fiber reinforced concrete (Fiber Reinforced Concrete) manufactured by mixing steel fiber in volume of 1% (75kg / ㎥) or less in general concrete is applied to some concrete structures. It is used. Most of these steel fibers use straight steel fibers with a circular cross section and hook-type steel fibers with bent ends. In general, the steel fibers are those having a tensile strength of 1,500 MPa or less, lengths of about 10 mm to 30 mm, and diameters of about 0.45 mm to 1.0 mm.

However, the 1% fiber mixing does not sufficiently prevent brittle fracture of high-strength concrete, and thus, the structure is immediately destroyed when an earthquake or repetitive and impact load of a vehicle, fire, and natural degradation occur.

In addition, in the case of using the conventional circular fiber for ultra-high strength concrete that is more than 180MPa conventionally (Patent No. 10-0620866; steel fiber reinforced cement composite and its manufacturing method), the fiber is broken before the cement composite is broken due to the lack of tensile strength of the fiber. Reaching the yield strength has a problem that does not help to improve the bending or tensile strength.

As shown in FIG. 1, even when steel fibers having a tensile strength of 2,000 MPa or more are used, when circular fibers are used, steel fibers are first pulled out of concrete before bending and tensile failure to reach yield strength and fracture (Debonding). ), There was a problem in that the steel fiber reinforcing effect is poor and does not contribute significantly to toughness improvement.

Accordingly, the present inventors have repeatedly conducted research and experiments to overcome the problems of the conventional general concrete, fiber reinforced concrete and ultra high strength fiber reinforced concrete mentioned above. It was found that the cement composite having a better tensile strength can be obtained by having a shape capable of improving the present invention, and the present invention has been proposed, and the present invention can exhibit high mechanical performance by making the shape wavy. To provide an ultra-high performance steel fiber and a method for producing concrete using the same, the purpose is.

Steel fiber of the present invention for achieving the above object is characterized in that the steel fiber in the form of a wave (shape, wave type) in the steel fiber incorporating the cement composite to increase the tensile strength of the composite.

In addition, the concrete manufacturing method of the present invention for achieving the above object is characterized by producing a high-performance fiber-reinforced concrete by including 1 to 5vol% of the wavy steel fibers with respect to 100vol% of concrete.

Hereinafter, the present invention will be described more specifically.

The present invention relates to a steel fiber incorporating the cement composite to increase the tensile strength of the composite, the shape of the steel fiber has a wave shape. That is, the steel fiber for concrete of the present invention is characterized in that it is formed in a wave shape, and the wave shape will be able to be modified and modified in various forms by those skilled in the art. Therefore, such improvements and modifications are obvious to those skilled in the art to be within the protection scope of the present invention.

The wave shape of the steel fiber can be modified in various ways depending on the wave number, length and depth of the steel fiber and the tensile strength of the steel fiber, among which the inventors found a more optimal shape through the experiment, described below. do. However, this is only an optimum form and the scope of protection of the present invention is not limited thereto.

Figure 2a is a longitudinal cross-sectional view of the steel fiber used in the prior art, Figure 2b is a longitudinal cross-sectional view of the wavy steel fiber according to the present invention. Steel fiber of such a shape can be manufactured by cutting, casting, etc. of carbon steel thinly, the aspect ratio (the ratio of the length to the cross-sectional dimension) may be used in the 30 ~ 100, but the purpose and purpose It can be used according to the appropriate modification, the length can also be manufactured by various lengths.

Preferably, the steel fiber according to the present invention preferably has a diameter of 0.15 to 0.35 mm, and a length of 10 to 30 mm, for the purpose of optimizing the ease of wave work of the steel fiber and the adhesion with the hardened cement body. When manufactured in such a diameter, length and wave form, the tensile strength of the steel fiber can be determined to be 2,000 ~ 4,000MPa, so that the effect can be sufficiently exhibited in the ultra-high performance fiber reinforced cement composite.

As can be seen in Figures 2a and 2b, the wavy steel fiber of the present invention has a geometrical shape compared to the steel fiber of the conventional circular cross-section, so that the mechanical adhesion is increased to improve the adhesion performance of the steel fiber and cement hardened body ultra-high performance fiber The ability of the reinforcement cement composite to be improved. In other words, the technical features of improving the adhesion performance with the cement hardened body by introducing the shape of the steel fiber in a wave form without changing the length, diameter and shape ratio of the steel fiber.

These corrugated steel fibers have different effects on the performance of ultra high-performance fiber-reinforced cement composites depending on the number, depth and length of the wave. Therefore, the corrugated steel fiber can be determined by appropriately determining the number, depth and length of the wave according to the formulation of the ultra-high performance fiber-reinforced cement composite and the material used.

Preferably, the corrugated steel fiber according to the present invention preferably has 4 to 8 wave numbers, 0.12 to 0.35 mm wave length, and 1.86 to 3.82 mm wave length in consideration of mechanical adhesiveness, filling rate of steel fiber, and fracture property of steel fiber. Do.

The manufacturing method of the wavy steel fiber as described above, unlike the circular fiber that takes the process of drawing-cutting work is going to take the process of drawing-shaped-cutting work. Here, the shape work is a work to make the steel fiber so that the fresh steel fiber circle line into the wavy frame to the required number, depth and length of the wave, and after this work is cut to a certain size to produce a wavy steel fiber. The manufactured corrugated steel fibers may be manufactured in a single type and bundle type (Buddle), which can improve the dispersibility of the fiber and ease of input into the cement composite, one by one as shown in FIG.

Corrugated steel fiber as described above is included 1 to 5vol% with respect to 100vol% of concrete when concrete mixing. If the content of the corrugated steel fiber is less than 1vol% with respect to concrete, the mixing effect is insignificant, and if it exceeds 5vol%, the strength decreases due to the aggregation of the fiber.

The present invention uses a corrugated steel fiber in order to improve the mechanical adhesion performance with the super high-performance cement hardened body by the shape of the steel fiber, and experiments with the wave number, length and depth of the steel fiber and the range of tensile strength of the steel fiber Finally, the mechanical performances such as flexural strength and tensile strength of the ultra-high-performance steel fiber reinforced cement composites were ultimately enhanced. That is, by improving the adhesion performance with the cement composite it is possible to greatly improve the mechanical performance, such as bending strength and tensile strength of 180MPa or more compressive strength.

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

≪ Example 1 >

This embodiment is to analyze the effect of the shape of the corrugated steel fiber according to the present invention on the adhesion performance with ultra-high performance cement hardened body having more than 180MPa.

First, a specimen as shown in FIG. 4 was prepared, wherein the steel fibers used were 0.2 mm in fiber diameter and 2800 MPa in fiber tensile strength, respectively, as shown in FIGS. 5A to 5C (wave depth, wave length, wave). Molded).

At this time, the cement composite of the specimen used was prepared by selecting a formulation that can secure a compressive strength of 180MPa or more among the formulations proposed in Patent No. 10-0620866 (steel fiber reinforced cement composite and its manufacturing method), the formulation used was water -binder ratio of 20%, silica fume (SiO ₂ 96%, density of 2.10g / ㎤, a specific surface area 200,000㎠ / g) was 30% of the cement mass, sand (density 2.62g / ㎤, average particle size of 0.5mm or less) is 110% of the cement mass and 30% of the filler (SiO ₂ 99.3, average particle diameter of less than 10㎛) were used for the cement mass, and the polycarboxylic acid-based high-performance reducing agent (35% of the solid component) was used for the cement mass to ensure fluidity. 1.8% was used.

In the mixing operation, the cement, silica fume, sand and fillers constituting the cement composite are added to a mixer and mixed at a speed of 30 rpm for about 10 minutes, and then mixed with water and a high performance water reducer for 10 minutes at a speed of 100 rpm, and then mixed again. Mixing is carried out for 5 minutes at a speed of 40 rpm. In addition, the curing operation was performed after the specimens were wet cured for 2 days, and then steam cured at 90 ^° C. for 2 days, and then exposed to air condition until the 28th day, and then tested.

The compressive strength of the cement composite thus produced showed an ultra high strength of about 203 MPa.

Using the specimen prepared by the above method, the drawing test of the fibers was carried out in the same manner as in FIG. 4, and the results are shown in 5a, 5b, and 5c according to the number of waves, wave depth, and wave length of the wavy steel fibers. It was. In the drawing test, the steel fiber according to the present invention is buried first so that the neck is led upward from the neck surface in the specimen of the extended length bottom.

In such a state that the specimen is fixed by the specimen grip system, the steel fibers are fixed by the steel fiber grip system. At this time, the strain gauge is attached to the steel fiber grip system to measure the strain, the steel fiber grip system in contact with the load gauge is to generate a tensile force on the steel fiber of the specimen.

At this time, the test apparatus used was UTM of 1tonf capacity that can adjust the load and displacement, and the load-slim curve was measured until the load gauge loading speed reached 0.35mm / min and the slim amount reached 15mm.

As can be seen from the test results of Figures 5a, 5b, 5c, the corrugated steel fiber according to the present invention showed a higher maximum load than the conventional circular cross-section of the steel fiber is excellent in adhesion performance with the cement hardened body of the parent and its bending It was confirmed that the tensile strength can be improved.

In the steel fiber according to the present invention, the number of waves is up to 6, the number of waves is larger, the depth of wave is 0.24mm, the length of wave length is 1.86mm, the adhesion is excellent, and the adhesion performance is deteriorated thereafter. This is due to the fact that the wave shape improves the mechanical adhesion performance to some extent, but if the wave is made more than necessary, the hardened cement hardly fills every corner of the fiber, and the fiber is easily broken before the hardened cement is destroyed. to be.

Thus, in the present invention, it is understood that the wavy steel fiber is more preferably about 6 waves, 0.24 to 0.3 mm wave depth, and 1.86 to 2.78 mm wave length.

< Example  2>

This embodiment is to analyze the effect of the corrugated steel fiber according to the present invention on the performance of ultra-high performance fiber reinforced cement composite, the slump flow, fiber dispersibility, compressive strength, flexural strength test of the ultra-high performance fiber reinforced cement composite Was carried out.

The ultra-high performance fiber reinforced cement composites used were prepared by selecting a formulation that can secure a compressive strength of 180 MPa or more among the formulations proposed in Patent No. 10-0620866 (Steel Fiber Reinforced Cement Composite and its Manufacturing Method) as in Example 1. The same applies to the materials used and curing procedures. Regardless of the shape, steel fibers were 0.2mm in diameter × 13mm in length and 2,800 MPa in tensile strength. The number of waves was 4, 6, and 8, respectively, and the wave depths were 0.12, 0.24, 0.30, and 0.35mm, respectively. The wave lengths were 0.93, 1.86, 2.78 and 3.72 mm, respectively.

Slump flow KS F 2594, fiber dispersion is classified as good, normal, poor by visual observation, and the results are shown in Table 1 below. Compressive strength and flexural strength were measured according to KS F 2405 and KS F 2566 at predetermined ages, and the results are shown in Table 1 below.

Type of fiber Slump Flow (mm) Dispersibility of the Fiber Compressive strength (MPa) Flexural strength (Mpa) Flexural toughness Conventional example (round section steel fiber) 630 Good 203 43 10.2 foot
persons
Yes Wave count 4 627 Good 207 57 15.5 6 620 Good 211 65 21.6 8 590 Good 206 59 17.8 Wave depth (mm) 0.12 625 Good 205 58 15.5 0.24 620 Good 211 65 21.6 0.30 618 Good 209 62 19.3 0.35 595 Good 201 57 15.3 Wave length (mm) 0.93 632 Good 205 58 16.3 1.86 628 Good 209 61 19.9 2.78 620 Good 211 65 21.6 3.72 585 Good 201 55 15.3

As can be seen in Table 1, the slump flow is a general slump flow of high-flow concrete that does not require compaction when constructing concrete with a slump flow of 600 mm or more, except for 8 waves, 0.35 mm wave depth, and 3.72 wave lengths. It appeared to be more than 600mm, and the dispersibility of the fiber was also found to be mostly good.

In addition, the compressive strength was found to be up to about 8MPa when using the steel fiber according to the present invention compared to the conventional circular section steel fiber. In addition, the steel fiber according to the present invention showed that the flexural strength was greatly improved by up to 1.5 times and the flexural toughness up to 2.1 times compared to the steel fiber of the conventional circular section. Such a large increase in bending behavior can be said to be due to the improved bridging effect of the fiber due to improved adhesion between the fiber and the cement hardened body.

According to the results of the present invention it was analyzed that the use of the wavy steel fiber consisting of a wave number of six, wave depth 0.24mm, wave length 2.78mm is the most excellent performance. And the wavy steel fiber composed of 8 wave number, wave depth 0.35mm, wave length 3.72mm or more showed the deterioration of workability and strength. This is because the cement hardened body is hard to fill up to every corner of the fiber, and the fiber is easily broken before the cement hardened body is destroyed.

< Example  3>

Slump flow of super high performance fiber reinforced cement composites incorporating wavy steel fibers according to the present invention to analyze the effects of tensile strength, diameter and length used on the steel fibers according to the present invention on the performance of ultra high performance fiber reinforced cement composites, Dispersibility, compressive strength and flexural strength test of the fibers were performed.

The blending and testing method of the ultra-high performance fiber reinforced cement composite is the same as in Examples 1 and 2, the steel fiber used has a tensile strength as shown in Table 2 in the case of the conventional example, a circular cross section having a fiber diameter of 0.2 × 13mm Steel fiber was used, in the case of the invention example a has a tensile strength as shown in Table 2 and the fiber diameter of 0.2 × 13mm was used, in the case of the invention example b has a fiber diameter as shown in Table 2 and the fiber tensile strength 2800MPa, A fiber length of 13 mm was used, and inventive example c had a fiber length as shown in Table 2 below, and used a fiber tensile strength of 2800 MPa and a fiber diameter of 0.2 mm. In addition, the invention examples a-c all used the wavy steel fiber shape | molded to six wave numbers, the wave depth 0.24mm, and the wave length 2.78mm.

Type of fiber Slump Flow (mm) Dispersibility of the Fiber Compressive strength (MPa) Flexural strength (MPa) Flexural toughness Conventional example a
(Round section steel fiber) The tensile strength
(MPa) 1500 630 Good 187 32 7.8 2000 630 Good 201 42 9.9 2800 630 Good 203 43 10.2 3800 630 Good 202 45 10.4 Inventive Example a The tensile strength
(MPa) 1500 623 Good 188 43 11.5 2000 620 Good 210 61 20.1 2800 620 Good 211 65 21.6 4000 620 Good 214 67 21.9 Inventive Example b Fiber diameter
(mm) 0.15 630 Good 197 58 20.5 0.20 620 Good 211 65 21.6 0.30 610 Good 209 62 19.7 0.35 590 Good 203 53 16.3 Inventive Example c Fiber length
(mm) 10 625 Good 208 62 20.3 13 620 Good 211 65 21.6 20 612 Good 208 61 20.7 30 602 Good 205 58 18.5

As can be seen in Table 2, the tensile strength of the steel fiber has a small effect on the workability of the ultra-high performance fiber reinforced cement composite regardless of the shape of the fiber, but the longer the diameter of the steel fiber, the longer the length of the steel fiber As the slump flow was lowered.

Compressive strength had a small effect on the tensile strength, diameter and length of steel fiber. In addition, the flexural behavior of the corrugated steel fiber according to the present invention was superior to the conventional round fiber regardless of tensile strength, fiber length and diameter.

Steel fiber according to the present invention has been shown that the tensile strength of 2000MPa or more, the diameter of the fiber 0.2mm, the length of the fiber consisting of 13mm is most advantageous for flexural strength and flexural toughness.

The present invention uses a corrugated steel fiber in order to improve the mechanical adhesion performance with the super high-performance cement hardened body by the shape of the steel fiber, and experiments with the wave number, length and depth of the steel fiber and the range of tensile strength of the steel fiber Finally, the mechanical performances such as flexural strength and tensile strength of the ultra-high-performance steel fiber reinforced cement composites were ultimately enhanced. That is, by improving the adhesion performance with the cement composite it is possible to greatly improve the mechanical performance, such as bending strength and tensile strength of 180MPa or more compressive strength.

1 is a real picture of the drawing conditions of steel fibers during bending failure of the ultra-high performance fiber reinforced cement composite.

Figure 2a is a longitudinal cross-sectional view of a steel fiber of a circular cross section conventionally used.

Figure 2b is a longitudinal cross-sectional view of the wavy steel fiber according to the present invention.

3 is an actual picture of the wavy steel fiber according to the present invention.

Figure 4 is a schematic diagram showing the state of the pull test in the steel fiber according to the present invention.

Figure 5a is a graph showing the pull test results (pulling load according to the number of water wave) in the steel fiber according to the present invention.

Figure 5b is a graph showing the pull test results (pulling load according to the water depth) in the steel fiber according to the present invention.

Figure 5c is a graph showing the pull test results (pulling load according to the wave length) in the steel fiber according to the present invention.

Claims (5)

In the steel fiber incorporating the cement composite to increase the tensile strength of the composite, Ultra high-performance fiber-reinforced concrete, characterized in that the steel fiber has a wave shape. The method of claim 1, The wave form of the steel fiber is 4 to 8 wave number, the depth of the wave 0.12 ~ 0.35mm, the ultra-high performance fiber reinforced concrete steel fiber, characterized in that the wave length 1.86 ~ 3.82mm. The method of claim 1, The steel fiber has a diameter of 0.15 ~ 0.35mm, ultra-high performance fiber reinforced concrete steel fiber, characterized in that the length of 10 ~ 30mm. The method according to any one of claims 1 to 3, The steel fiber is a high-performance fiber reinforced concrete steel fiber, characterized in that the tensile strength is 2000 ~ 4000MPa. When the concrete is blended, the method of producing ultra-high performance fiber reinforced concrete, characterized in that to include 1 to 5vol% of the steel fiber of any one of claims 1 to 4 with respect to 100vol% of concrete.

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