KR20130075334A

KR20130075334A - Amorphous steel fiber cement composites and mortar products using the same

Info

Publication number: KR20130075334A
Application number: KR1020110143666A
Authority: KR
Inventors: 윤상훈; 김상원; 박언병; 최완철; 박홍근; 김화중; 조창근
Original assignee: 재단법인 포항산업과학연구원
Priority date: 2011-12-27
Filing date: 2011-12-27
Publication date: 2013-07-05

Abstract

The present invention relates to an amorphous steel fiber cement composite and concrete, comprising a cement binder (B) comprising cement and fine aggregate (S), matrix (M) comprising amorphous steel fiber (F), water (W), admixture (A) By providing an amorphous steel fiber cement composite and concrete prepared thereby, the amorphous steel fiber cement composite and the amorphous steel fibers of the concrete is thinner than the conventional steel fibers and the specific gravity is smaller, so more fibers are mixed for the same volume ratio, so that the dry shrinkage of the concrete Can be greatly reduced.
In addition, the amorphous steel fiber cement composite and concrete of the embodiment according to the present invention is excellent in the crack control effect can improve the resistance to structural cracking of the concrete structure.

Description

Amorphous Steel Fiber Cement Composites and Concrete Using Them {AMORPHOUS STEEL FIBER CEMENT COMPOSITES AND MORTAR PRODUCTS USING THE SAME}

The present invention relates to an amorphous steel fiber cement composite and concrete using the same, and more particularly, to a cement composite compounded by mixing a flexible amorphous steel fiber into a cement binder, water, and concrete using the same.

In general, concrete is widely used in construction structures together with steel as an economical and durable construction material, but has a small tensile strength, flexural strength and shear strength, and is easily cracked. In order to compensate for such defects in concrete, high toughness cement composites (ECC) using steel fibers reinforced concrete and synthetic fibers such as PVA, which are reinforced by adding steel fibers, are manufactured.

Conventional concrete reinforcement includes steel fibers and polymer fibers, most of which are used for tunnel slopes, shotcrete, and some floor crack control. However, in the case of steel fiber concrete, tensile strength, flexural strength and shear strength are improved compared to general concrete, but when a large amount of steel fiber is added, there is a problem of brittle fracture and durability degradation due to fiber aggregation.

The present invention is to provide a cement composite and concrete in which the mechanical properties are greatly improved by adding amorphous steel fibers to the cement binder.

In one or more embodiments of the invention includes a cement (B) comprising cement and fine aggregates (S), amorphous steel fibers (F), water (W), matrix (M) comprising admixture (A) An amorphous steel fiber cement composite can be provided.

The cement composite of one or more embodiments of the present invention has a cement binder / matrix (B / M) of 0.3 to 0.8, microfibers / matrix (F / M) of 0.001 to 0.03 in weight percent (%) ratio, and water / Cement binder (W / B) is 0.2 ~ 0.9, fine aggregate / cement binder (S / B) is 0.1 ~ 0.5, admixture / cement binder (A / B) is characterized in that 0.005 ~ 0.4.

The fine aggregate of one or more embodiments of the present invention comprises sand or silica sand, characterized in that the diameter is 2.5 mm or less, and the admixture is characterized in that at least one of a high performance water reducing agent, methyl cellulose thickener, air entrainer.

Amorphous steel fibers of one or more embodiments of the present invention are characterized by having a width of 1 to 3 mm, a thickness of 10 to 50 μm, and a length of 5 to 50 mm.

In one or more embodiments of the present invention, concrete prepared from the amorphous steel fiber cement composite of any one of the cement composites may be provided.

One or a plurality of embodiments of the present invention is characterized in that the concrete is prepared by installing the formwork directly on-site, manufactured in a precast in the factory, prepared for pouring concrete, or manufactured for spraying.

Embodiments of the present invention, the amorphous steel fiber cement composite and the amorphous steel fiber of the concrete is thinner than the conventional steel fiber and the specific gravity is smaller, so that more fibers can be mixed for the same volume ratio can significantly reduce the dry shrinkage of the concrete.

In addition, the amorphous steel fiber cement composite and concrete of the embodiment according to the present invention is excellent in the crack control effect can improve the resistance to structural cracking of the concrete structure.

In addition, the amorphous steel fiber cement composite and concrete of the embodiment according to the present invention improves the brittleness after tensile cracking and induces multiple microcracks and strain hardening characteristics after the initial cracking to improve tensile and flexural behavior. Can be.

Figure 1a is a photograph of the concrete made of amorphous steel fiber cement composite according to an embodiment of the present invention, Figure 1b is a photograph of the concrete specimen is not mixed with amorphous steel fibers as a comparative example.
2A and 2B are graphs showing the behavior characteristics of tensile strength and tensile strain of concrete specimens prepared in Examples and Comparative Examples according to FIG. 1.
3a and 3b are graphs showing the tensile strength of the concrete specimens prepared in Examples and Comparative Examples according to FIG.
4A is a one-side shear test scene photo of a concrete shear specimen according to an embodiment of the present invention, and FIG. 4B is a one-side shear test scene photo of a concrete shear specimen of a comparative example prepared without incorporating amorphous steel fibers.
5A and 5B are photographs showing cracking patterns after testing of the examples and comparative examples of FIGS. 4A and 4B.
6a and 6b are graphs showing the one-side shear strength of the concrete shear specimens of the examples and comparative examples of FIGS. 4a and 4b.
7 is a photograph showing a broken cross section of a specimen prepared according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention, and are not intended to limit the scope of the inventions. I will do it.

Embodiment according to the present invention relates to an amorphous steel fiber cement composite and an concrete prepared by using the amorphous steel fiber (F) to the cement binder (B), water (W), admixture (A). In particular, it relates to high-performance amorphous steel fiber cement composites and concretes that maintain tensile strength and greatly improve tensile strength since tensile stress does not immediately become zero after tensile cracking. That is, the concrete constructed of the cement composite of the embodiment according to the present invention has excellent characteristics such as improved tensile and bending behavior ability, excellent crack control effect, and improved durability.

High-performance amorphous steel fiber cement composite and concrete of the embodiment according to the present invention is a cement (B) containing cement, blast furnace slag and fly ash, matrix (M) comprising micro-sized amorphous steel fibers (F), water (W) It comprises a, wherein the amorphous steel fiber is a thin cross section of micro units extending in the longitudinal direction means a steel fiber (Steel Fiber) having a constant width and length.

Amorphous steel fiber used in the embodiment according to the present invention, for example, can be produced by the molten iron production process, such as the molten iron through a Finex (FINEX) process, the aspect ratio (Aspect Ratio) of about 60 ~ 200 It may be used, but may be used by appropriate modification depending on the purpose and purpose.

The ratio (B / M) of the weight percent (%) of the cement binder and the matrix is preferably 0.3 to 0.8, which is in the range as described above because it is an addition range to allow sufficient hydration reaction to occur with water and miscible materials. It is limited.

In order to ensure sufficient fiber dispersibility of the amorphous steel fiber (F) of the embodiment according to the present invention, the weight percent ratio (F / M) of the amorphous steel fiber and the matrix is preferably 0.001 to 0.03. When a large amount of the amorphous steel fiber is used in mixing the concrete, various properties are improved, but when the excessive amount is mixed, a fiber ball phenomenon occurs, so that the mixing amount is limited. If the ratio (F / M) is less than 0.001, it is not easy to secure tensile strength and tensile strain, and even if it exceeds 0.03, the tensile strength and tensile strain do not increase significantly.

At this time, the length of the amorphous steel fiber is 5 ~ 50mm, the width is 1 ~ 3mm, the thickness is 10 ~ 50㎛, the aspect ratio is used 60 ~ 200. The length and incorporation rate of the amorphous steel fiber is an important factor that can improve the tensile strength and tensile strain in the fiber blending range, in the embodiment according to the present invention the material of the amorphous steel fiber in the numerical range to improve the tensile strength and tensile strain It is limited to. The longer the length of the amorphous steel fibers can control the macrocrack (macrocrack) inside the concrete, but the fiber ball phenomenon occurs when blending, and the number of amorphous steel fibers that can enter when compared to the short amorphous steel fibers. On the other hand, when the length of amorphous steel fiber is small, it controls microcrack in concrete and does not generate fiber ball when mixing, so it can be uniformly distributed in concrete, thereby increasing the strength and ductility of the concrete. The length of the steel fiber is limited to 5-50mm.

In addition, the thickness of the amorphous steel fiber, the thicker the thickness of the amorphous steel fiber manufacturing, the amorphous fraction is reduced to crystallize easily broken (brittle) or less flexibility (flexibility). In the case of amorphous steel fibers of 50 µm or less, an amorphous fraction of 100% can be obtained, so it is limited to the above range.

In addition, the amorphous steel fiber of the embodiment according to the present invention uses a tensile strength of 500 ~ 2000MPa, it can be made to have a tensile strength in the above range when manufacturing the amorphous steel fiber having the thickness, width and length of the concrete using amorphous steel fiber The structure crack control effect of the structure is to be fully exhibited.

According to the shape and mixing ratio of the amorphous steel fibers used as described above, the viscosity, flowability, workability and compressive strength, tensile strength and multi-microcracks behavior characteristics of the mortar can be appropriately adjusted.

In addition, the weight percent ratio (W / B) of the water and cement binder is to satisfy 0.2 ~ 0.9 to ensure the workability and the required strength.

In the embodiment according to the present invention by further comprising at least one of the fine aggregate (S) and admixture (A) in the matrix to improve the properties of the matrix, the weight percent ratio (S / B) of the fine aggregate and cement binder is 0.1 It is limited to ˜0.5, and the weight percent ratio (A / B) of the admixture and the cement binder is limited to 0.005 to 0.4. At this time, the mixing range of the fine aggregate is to consider the compression and secure the tensile strength, the admixture is to consider the workability (workability), high toughness, fluidity, viscosity and dry shrinkage control in the embodiment according to the present invention the fine aggregate, admixture and The mixing range of the cement binder is limited to the above range.

The fine aggregate is used as silica sand or sand having a diameter of 2.5 mm or less, and the admixture may include one or more of a high performance sensitizer, a methyl cellulose thickener, and an air entrainer, and a high performance sensitizer is used to secure fluidity. Cellulose thickeners and air entrainers can be used to prevent agglomeration of the fibers. In other words, in the case of steel fiber mixed concrete, the specific gravity of steel fiber and the aspect ratio are different from the particles of the material constituting the cement matrix. It may not exhibit the original performance of concrete or may cause brittle fracture and deterioration of durability. In the embodiment according to the present invention, fiber dispersibility is secured by the use of the above-described high-performance sensitizer, methyl cellulose thickener, and air entrainer. This can prevent fiber agglomeration.

In addition, the high-performance amorphous steel fiber cement composite and concrete according to the embodiment of the present invention is not only applicable to the sidewalk block and revetment block, high-performance cement wall and building interior and exterior materials, it is also applicable to the structural material. Therefore, the concrete produced by the mortar composite of the embodiment according to the present invention has a wide range of application, not only has excellent characteristics, but also manufactured by installing the site directly by installing the formwork, manufactured by precast in the factory, or ready-mixed concrete It can be made or made for blowing.

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

[Example]

First, high performance amorphous steel fiber cement composite and concrete were prepared according to the mixing ratio of Table 1 below.

Cement, blast furnace slag, silica sand, and a high performance water-reducing agent were added and dried for 1 minute or more. Thereafter, the amorphous steel fibers were mixed with a mixer until well mixed. The high-performance sensitizer was administered half the time of dry bibim, and after adding water and bibim, the state of fluidization was administered and the other half was administered. At this time, the target slump flow was set to be in the range of 300 to 700 mm.

combination W / B (%) S / A (%) Component Weight (kg / m3) Fiber Incorporation Rate (Vf) (%) cement water Silica sand Example Amorphous
Steel fiber
incorporation 76 1.17 660 500 528 0.75
~
1.50 Comparative example No fiber mixing 0

[Experimental Example 1]

The high-performance amorphous steel fiber cement composite prepared in Example and the mortar of the comparative example were poured to prepare concrete specimens, and cured for 28 days to carry out a high toughness direct tensile test, and the results are shown in FIGS. 2A and 2B, respectively.

Figure 2a and 2b is a graph showing the behavior of the tensile strength and tensile strain of the direct tensile test specimen prepared in Examples and Comparative Examples, referring to Figure 2a and 2b, high performance amorphous steel fiber cement of the present invention The concrete specimens made of composites had improved tensile strength and tensile strain than those made with the mortars of the comparative example, in which fibers were not mixed, and the specimens made of the mortars of the comparative example did not exhibit tensile strain immediately after the occurrence of local tensile cracks. It can be confirmed that the tensile failure.

In the drawings of the embodiment according to the present invention, L represents the length of amorphous steel fiber, Vf represents the mixing ratio (volume fraction) of amorphous steel fiber, and FIGS. 2A and 2B show the mixing ratios of 0, 0.75, 1.00, 1.25, and 1.50, respectively. The results of two experiments are shown. That is, FIG. 2A illustrates a case where the length of the amorphous steel fiber is 15 mm, FIG. 2B illustrates a case where the length of the amorphous steel fiber is 30 mm, and the remaining experimental conditions are the same. In FIG. 2A and FIG. 2B, when the mixing ratio (Vf) of the amorphous steel fiber is 0, that is, in the comparative example in which the amorphous steel fiber is not mixed, the tensile strain breaks within 0.05%, but as shown in FIGS. 2A and 2B, When the length is 15mm, the tensile strain can withstand up to about 1%, and when the length of the amorphous steel fiber is 30mm, it can be seen that the tensile strain is not broken even when the tensile strain is 2%.

3A and 3B are graphs showing the tensile strengths of the specimens of FIGS. 2A and 2B, respectively. The tensile strength of the concrete specimens in which the amorphous steel fibers are not mixed is a little more than 1 MPa, but the amorphous steel fibers are mixed. Tensile strength of concrete specimens may exceed 5 MPa at maximum, and at least 2.5 MPa. In this case, PIBM refers to a micro amorphous steel fiber based on molten iron as Pig Iron Based Micro.

[Experimental Example 2]

The one-side shear strength test of the one-piece shear strength test specimens of 150 mm x 120 mm x 240 mm (Lx Bx H) (shear area 120 mm x 60 mm) of the concrete produced in the Examples and Comparative Examples was conducted. Performed as in the photo of Figure 4b, the results are shown in Figures 5a and 5b. 5A and 5B, it can be seen that in FIG. 5A, the edge of the specimen is broken but the central portion of the specimen is not completely broken, which is due to amorphous steel fibers. However, when the amorphous steel fibers are not mixed as shown in Figure 5b it can be seen that after the occurrence of cracking completely.

That is, the concrete specimen in the embodiment according to the present invention can control the crack by the amorphous steel fiber, it can be seen that the brittleness properties after the crack is improved.

6A and 6B are graphs showing the shear strength test of the specimens of the Examples and Comparative Examples. Referring to FIGS. 6A and 6B, the shear strength of concrete prepared from a high performance amorphous steel fiber cement composite as a result of the one-sided shear strength test. It can be seen that greatly improved. FIG. 6A illustrates a case in which the length of the amorphous steel fiber is 15 mm, and FIG. 6B illustrates a case in which the length of the amorphous steel fiber is 30 mm, and shows the results of two experiments while varying the mixing ratio of the amorphous steel fiber for the same specimen.

The shear strength of the concrete specimens of the embodiment according to the present invention may exceed 12 MPa and sometimes exceed at least 6 MPa, whereas in the comparative example, the shear strength of 5 to 8 MPa was improved when the amorphous steel fibers were incorporated. .

[Experimental Example 3]

After fracture of the specimen prepared in the embodiment according to the present invention and observed its cross section, the resulting photograph is shown in FIG. Referring to FIG. 7, it can be predicted that amorphous steel fibers are mixed in the concrete so that they will not be easily broken even if a stress is applied from the outside.

The above test results clearly show that the high performance amorphous steel fiber cement composite mortar and concrete of the present invention improve the tensile strength, shear strength and tensile strain after cracking. Therefore, the concrete constructed of the cement composite of the embodiment according to the present invention shows excellent characteristics such as improved tensile and bending behavior ability, excellent crack control effect, and improved durability.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, And all changes to the scope that are deemed to be valid.

Claims

An amorphous steel fiber cement composite comprising a cement binder (B) comprising cement and fine aggregate (S), an amorphous steel fiber (F), a water (W), and a matrix (M) comprising a miscible material (A).

The method of claim 1,
The cement composite has a weight percent (%) ratio of cement binder / matrix (B / M) of 0.3 to 0.8, micro fiber / matrix (F / M) of 0.001 to 0.03, and water / cement binder (W / B). Is 0.2 to 0.9, fine aggregate / cement binder (S / B) is 0.1 to 0.5, admixture / cement binder (A / B) is amorphous steel fiber cement composite, characterized in that 0.005 ~ 0.4.

The method of claim 2,
The fine aggregate comprises sand or silica sand, amorphous steel fiber cement composite, characterized in that less than 2.5mm in diameter.

The method of claim 2,
The admixture is an amorphous steel fiber cement composite, characterized in that at least one of a high performance sensitizer, methyl cellulose thickener, air entrainer.

The method of claim 1,
The amorphous steel fiber is an amorphous steel fiber cement composite, characterized in that the width: 1 ~ 3mm, thickness: 10 ~ 50㎛, length: 5 ~ 50mm.

Concrete prepared from the amorphous steel fiber cement composite according to any one of claims 1 to 5.

The method according to claim 6,
The concrete is prepared by installing the formwork directly on-site casting, manufactured in the factory precast, ready for concrete laying, or characterized in that it is manufactured for spraying.