KR20060086110A - Cement member with reinforcing fibers of different kind and composition thereof - Google Patents

Abstract

An object of the present invention is to simultaneously increase the structural performance, durability and fire resistance of cement materials. To this end, the present invention is a cement material selected from the group consisting of mortar, concrete and shotcrete, comprising steel fibers and organic fibers different in length and diameter from at least one of the steel fibers, the compression of up to 100MPa A cement material having strength and flexural strength of up to 10 MPa is provided. In addition, the present invention is a cement material composition selected from the group consisting of mortar, concrete and shotcrete, cement, aggregate particles, at least one dispersant, water, steel fibers, the length and diameter of the steel fibers Provided is a cement material composition comprising at least one different organic fiber and comprising steel fibers and organic fibers at 0.05 to 5% by volume relative to the cement material composition.

Mortar, Concrete, Shotcrete, Structural Performance, Crack Inhibition, Durability, Fire Resistance, Steel Fiber, Organic Fiber

Description

Cement material and its composition comprising heterogeneous reinforcing fibers {CEMENT MEMBER WITH REINFORCING FIBERS OF DIFFERENT KIND AND COMPOSITION THEREOF}

1 is a schematic diagram of steel fibers and organic fibers having different lengths contained in the cement material of the present invention.

2 is a schematic view of steel fibers and organic fibers having different diameters included in the cement material of the present invention.

3 is a schematic view of steel fibers and organic fibers having different lengths and diameters included in the cement material of the present invention.

4 is a schematic diagram of a plastic shrinkage crack control test facility of cement material.

5A and 5B are side cross-sectional views and plan views, respectively, for a fire resistance test for testing fire resistance performance of cement materials.

6 is a graph showing the temperature curve used in the fire resistance performance test.

The present invention relates to a cement material, and more particularly, has a compressive strength of 100 MPa or less and a bending strength of 10 MPa or less, and in order to secure structural performance, durability, and fire resistance at the same time, heterogeneous reinforcing fibers are used. It relates to a cement material and cement material composition included.

In general, when cement materials such as mortar, concrete and shotcrete are used in the construction of tunnels and underground structures subjected to flexural loads, their toughness is required to increase. At present, concrete reinforced with steel fiber is effective in increasing flexural toughness and is widely used in the field. However, steel fiber reinforced concrete is not satisfactory in suppressing fine cracks, which are a major cause of deterioration in durability.

Early microcracks do not significantly affect structural performance, but increase permeability, causing corrosion of steel fibers, and causing breakage of structures when freezing and thawing are repeated. In order to suppress the initial microcracks in the steel fiber reinforced concrete, the incorporation rate of the steel fiber must be increased considerably, which leads to a large increase in manufacturing cost.

In addition, in order to minimize the damage caused in the event of a fire in a tunnel or underground space, a cement material having a certain fire resistance is required.

As such, cement materials used in tunnels and underground spaces should increase the durability by suppressing fine cracks while securing structural performance (bending toughness) required for the structure, and exhibit sufficient fire resistance in the event of fire.

In the related art, US Patent No. 5,749,961 discloses a method of increasing fire resistance by mixing organic fibers with concrete having a compressive strength of about 90 to 105 MPa. However, since the registered patent uses only organic fibers, structural performance required for the structure cannot be secured, and since only a single shape of organic fibers is used, it is difficult to expect a great effect on improving durability through crack suppression.

International publication WO 99/28267 discloses ultra high performance concrete containing metal fibers. Metal fiber has a great effect on improving structural performance, but high electrical conductivity, etc., adversely affects the fire resistance, causing a thermal explosion in the event of fire. Also, in order to suppress cracking of concrete, a larger amount of metal fibers is required.

International Publication No. WO 99/58468 discloses a mixture of structural organic fibers in ultra-high performance concrete to increase the ductility of concrete. Structural organic fibers have a larger diameter and higher modulus of elasticity than ordinary organic fibers. Although this patent discloses general fire resistance performance due to the use of organic fibers, sufficient crack suppression performance cannot be realized, and thus the effect is weak in improving durability.

International Publication No. WO2001 / 58826 discloses a content of metal fiber contained in ultra-high performance concrete having a compressive strength of 120 MPa or more and a flexural strength of 20 MPa or more to improve the structural performance and to increase the fire resistance performance by containing the organic fiber. However, this publication also uses a single shape of metal fibers and organic fibers, it is difficult to expect a sufficient durability performance improvement due to the lack of crack suppression function of various sizes, there is a problem that the economic deterioration to obtain structural performance.

As such, the conventional cement material has a disadvantage in that it is not possible to secure both structural performance, durability performance, and fire resistance performance using reinforcing fibers.

 Accordingly, the present invention is to solve the above problems, the object of the present invention is to use the heterogeneous reinforcing fibers to ensure the structural performance (bending toughness) required for the structure, to suppress both micro and large cracks It is to provide a cement material that can increase the durability performance and secure excellent fire performance.

In order to achieve the above object, the present invention is a cement material selected from the group consisting of mortar, concrete and shotcrete, comprising steel fibers and organic fibers different in length and diameter from the steel fibers The present invention provides a cement material having a compressive strength of up to 100 MPa and a bending strength of up to 10 MPa.

In addition, the present invention is a cement material composition selected from the group consisting of mortar, concrete and shotcrete, cement, aggregate particles, at least one dispersant, water, steel fibers and the length and diameter of the steel fibers Provided is a cement material composition comprising at least one of different organic fibers, wherein the steel fibers and the organic fibers comprise 0.05 to 5% by volume relative to the cement material composition.

Hereinafter, the present invention will be described in detail.

The present invention relates to cement materials used in construction and civil engineering structures, where the cement materials include mortar, concrete and shotcrete. The cement material according to the invention comprises steel fibers and organic fibers of different lengths, or steel fibers and organic fibers of different diameters, or steel fibers and organic fibers of different lengths and diameters.

FIG. 1 schematically shows steel fibers 1 and organic fibers 2 having different lengths included in the cement material of the present invention, and in FIG. 2, steel fibers 3 having different diameters included in the cement material of the present invention. ) And the organic fiber 4 are shown schematically. And in FIG. 3, the steel fiber 5 and the organic fiber 6 which differ in both length and diameter contained in the cement material of this invention are shown in outline. 1 to 3 illustrate hooked steel fibers as an example.

The steel fibers increase the structural strength by increasing the flexural strength and flexural toughness of the structure. Steel fibers may be formed in a form in which both ends are bent in the same direction or in different directions.

The organic fibers are all organic fibers having a melting point of 300 ° C. or lower, preferably olefin fibers including polyethylene, polyamide fibers including nylon, polyacrylic fibers, polyester fibers, polypropylene fibers and polyvinyl alcohol fibers. Made of either fiber.

These organic fibers have their own fire resistance because they have no thermal conductivity, and when the cement material rises above 300 ° C. by fire, it melts and forms voids in the cement material. This prevents heat and gas from moving through the air gap and causing the cement material to burst due to fire.

Among the steel fibers and the organic fibers, fibers having a large length or diameter suppress macro cracks occurring in cement material, and small fibers of small length or diameter generate micro cracks in cement material. Suppress Thus, steel fibers and organic fibers suppress both large and small cracks, increasing durability.

The steel fibers and organic fibers preferably have a length of 1 to 100 mm and a diameter of 0.01 to 25 mm.

As described above, the mortar, concrete, and shotcrete according to the present invention have the effect of simultaneously securing structural performance, durability, and fire resistance by including steel fibers and organic fibers having different lengths and diameters.

In addition, the cement material composition according to the present invention comprises cement, aggregate particles, at least one dispersant, steel fibers, organic fibers and water different from at least one of the length and diameter of the steel fibers, The organic fibers are contained in an amount of 0.05 to 5% by volume based on the cement material composition.

If the total mixing ratio of the steel fibers and the organic fibers is less than 0.05% by volume, the difference in effect is insignificant when compared with the cement material containing the steel fibers and without adding the organic fibers. And when the total content of steel fibers and organic fibers exceeds 5% by volume, the steel fibers and organic fibers are not uniformly dispersed in the cement material, but rather increase the voids in the concrete and shotcrete, which is a structural performance and crack suppression performance And fireproofing performance is reduced.

In preparing the cement material composition, a simplex lattice design may be used to determine a mixing ratio of steel fibers and organic fibers having different lengths and diameters.

Equation 1 shows a mixture ratio of steel fibers and organic fibers included in the cement material composition.

(X _{steel fiber 1} + X _{steel fiber 2} + ... + X _{steel fiber n} ) + (Y _{organic fiber 1} + Y _{organic fiber 2} + ... + Y _{organic fiber n} ) = 0.05 ~ 5% by volume

At this time, (X _{steel fiber} )> 0% by volume, (Y _{organic fiber} )> 0% by volume

The present invention will be described in more detail with reference to the following examples. However, the Examples are provided to illustrate the present invention and the present invention is not limited to these.

EXAMPLE

Examples 1 to 13, Comparative Examples 1 to 5

Table 1 below shows the optimum mixing ratio of the steel fibers and the organic fibers determined using the Simplex lattice arrangement so that the total mixing ratio of the steel fibers and the organic fibers is 0.7% by volume with respect to the cement material composition. The steel fiber used at this time is a hook type bent at both ends, the length is 30mm and 50mm, respectively, the diameter is the same 0.5mm. The organic fibers are polypropylene fibers, 10 mm long and 19 mm long, with the same diameter of 0.09 mm.

Kind of combination Fiber blend rate (%) Steel fiber 1 (length 30mm) Steel fiber 2 (length 50mm) Organic Fiber 1 (length 10mm) Organic Fiber 2 (length 19mm) A 0.3500 - 0.3500 - B 0.3500 - - 0.3500 C - 0.3500 0.3500 - D - 0.3500 - 0.3500 E 0.4380 0.0875 0.0875 0.0875 F 0.0875 0.4380 0.0875 0.0875 G 0.0875 0.0875 0.4380 0.0875 H 0.0875 0.0875 0.0875 0.4380 I 0.1750 0.1750 0.1750 0.1750 J 0.3500 - 0.1750 0.1750 K 0.1750 0.1750 0.3500 -

Table 2 below shows three examples included in the actual cement material composition among the formulations described in Table 1 to be considered in order to evaluate the structural performance, durability performance, and fire resistance performance of the cement material.

Fiber blend rate (%) Steel fiber 1 (length 30mm) Steel fiber 2 (length 50mm) Organic Fiber 1 (length 10mm) Organic Fiber 2 (length 19mm) Example 1 0.3500 - 0.3500 - Example 2 0.4380 0.0875 0.0875 0.0875 Example 3 0.1750 0.1750 0.1750 0.1750 Example 4 0.3500 - 0.1750 0.1750 Example 5 0.1750 0.1750 0.3500 -

Table 3 below shows the optimum mixing ratio of the steel fibers and the organic fibers determined using the Simplex lattice arrangement method such that the total mixing ratio of the steel fibers and the organic fibers is 0.7% by volume with respect to the cement material composition. The steel fiber used at this time is a hook type bent at both ends, the diameter is 0.5mm and 0.7mm, respectively, the length is equal to 30mm. The organic fibers are polypropylene fibers, diameters of 0.02 mm and 0.09 mm, respectively, and the length is equal to 19 mm.

Kind of combination Fiber blend rate (%) Steel fiber 1 (0.5mm in diameter) Steel fiber 2 (0.7mm in diameter) Organic Fiber 1 (diameter 0.02mm) Organic Fiber 2 (0.09mm in diameter) A 0.3500 - 0.3500 - B 0.3500 - - 0.3500 C - 0.3500 0.3500 - D - 0.3500 - 0.3500 E 0.4380 0.0875 0.0875 0.0875 F 0.0875 0.4380 0.0875 0.0875 G 0.0875 0.0875 0.4380 0.0875 H 0.0875 0.0875 0.0875 0.4380 I 0.1750 0.1750 0.1750 0.1750 J 0.3500 - 0.1750 0.1750 K 0.1750 0.1750 0.3500 -

Table 4 below shows three examples included in the actual cement material composition among the formulations described in Table 3 to be considered in order to evaluate the structural performance, durability performance, and fire resistance performance of the cement material.

Fiber blend rate (%) Steel fiber 1 (0.5mm in diameter) Steel fiber 2 (0.7mm in diameter) Organic Fiber 1 (diameter 0.02mm) Organic Fiber 2 (0.09mm in diameter) Example 6 0.3500 - 0.3500 - Example 7 0.4380 0.0875 0.0875 0.0875 Example 8 0.1750 0.1750 0.1750 0.1750 Example 9 0.3500 - 0.1750 0.1750 Example 10 0.1750 0.1750 0.3500 -

Table 5 shows the optimum mixing ratio of the organic fibers determined using the Simplex lattice arrangement method so that the total mixing ratio of the steel fibers and the organic fibers having different lengths and diameters is 0.35% by volume with respect to the cement material composition. Three examples are considered to evaluate the durability and fire resistance performance. The steel fiber used at this time is a hook type steel fiber bent at both ends, and the organic fiber is a polypropylene fiber.

Fiber blend rate (%) Steel fiber 1 (length 30mm, diameter 0.5mm) Steel fiber 2 (length 50mm, diameter 0.7mm) Organic Fiber 1 (length 10mm, diameter 0.02mm) Organic Fiber 2 (length 19mm, diameter 0.09mm) Example 11 0.17500 - 0.17500 - Example 12 0.04375 0.04375 0.21900 0.04375 Example 13 0.08750 0.08750 0.08750 0.08750

On the other hand, five comparative examples considered in order to evaluate the structural performance, durability performance and fire resistance performance of the cement material is as follows.

In Comparative Example 1, the steel fibers having a single shape having a length of 30 mm and a diameter of 0.5 mm were included in the volume of the cement material composition. In Comparative Example 2, the organic fiber having a single shape having a length of 19 mm and a diameter of 0.09 mm (polypropylene fiber) ) Is included in the volume of the cement material composition 0.7% by volume. In Comparative Example 3, 1 vol% of the structural organic fibers having a length of 50 mm and a diameter of 1 mm single shape having the strength and elastic modulus of the fiber improved by using the polyolefin-based synthetic fibers were included in the cement material composition.

Comparative Example 4 includes steel fibers and organic fibers of different lengths and diameters, but includes 0.04% by volume of the fibers in the cement composition, and Comparative Example 5 includes steel fibers and organic fibers of different lengths and diameters. These fibers are included in the volume of the cement material 5.6% by volume. Table 6 below shows the fiber mixing ratios of Comparative Example 4 and Comparative Example 5.

Total Incorporation Rate (%) Fiber blend rate (%) Steel fiber 1 (length 30mm, diameter 0.5mm) Steel fiber 2 (length 50mm, diameter 0.7mm) Organic Fiber 1 (length 10mm, diameter 0.02mm) Organic Fiber 2 (length 19mm, diameter 0.09mm) Comparative Example 4 0.04 0.01 0.01 0.01 0.01 Comparative Example 5 5.6 1.4 1.4 1.4 1.4

Table 7 is a composition table of the cement material used for the performance evaluation.

(kg / mm ³ ) water cement Fine aggregate Coarse aggregate High fluidizing agent (% of C) Examples 1-13 211 480 1,110 483 1.35 Comparative Examples 1 to 5

(Structural performance test)

Table 8 below shows the flexural strength and flexural toughness test results of cement materials.

Flexural strength (MPa) Flexural Toughness (Nm) Example 1 6.3 100.5 Example 2 6.2 101.5 Example 3 6.4 103.7 Example 4 6.5 102.8 Example 5 6.7 104.3 Example 6 6.1 98.5 Example 7 6.5 97.7 Example 8 6.8 98.8 Example 9 6.5 96.5 Example 10 6.7 98.4 Example 11 6.5 101.5 Example 12 6.7 108.7 Example 13 6.9 109.8 Comparative Example 1 5.1 83.5 Comparative Example 2 3.5 25.2 Comparative Example 3 4.3 55.6 Comparative Example 4 4.0 48.4 Comparative Example 5 4.3 60.2

From the above results, in the embodiments of the present invention in which at least one of length and diameter is mixed with different steel fibers and organic fibers, the flexural strength and the flexural toughness are superior to those of Comparative Example 1 in which the single-shaped steel fibers are mixed, and the single shape It can be seen that they show superior advantages over Comparative Example 2 and Comparative Example 3 in which the organic fibers and the structural organic fibers were mixed.

(Durability test)

Plastic shrinkage crack control test was performed to evaluate the durability improvement through the crack control performance of cement materials. 4 is a schematic diagram of a plastic shrinkage crack control test facility. In the figure, reference numeral 7 denotes a mold and reference numeral 8 denotes metal fixing pieces fixed to the mold bottom surface. The mold 7 has an internal volume of 560 × 365 × 114 mm, and the distance between the centers of the metal fixing pieces 8 is set to 76 mm.

Oil the inside of the mold (7) so that the cement material can be easily separated from the mold (7), fill the mold (7) with the cement material composition having the composition shown in Table 7, and then the upper surface is horizontal Vibration compaction is performed for 30 seconds. Immediately after the vibration compaction, a temperature of 28 ± 3 ° C. and a relative humidity of 40 ± 5% were maintained, and a wind of 4.5-5 m / sec wind speed was applied to promote the evaporation of water in the cement material composition.

As the cement material composition filled in the mold (7) is dried over time shrinkage proceeds, the metal fixing pieces (8) restrain the cement material shrinking to cause a stress, and as a result the metal fixing pieces ( 8) Cracks occur in the vicinity.

Table 9 shows the results of measuring the crack width and crack length generated in the cement material, the crack area was obtained by multiplying the crack width and crack length.

Since cracks in cement materials increase permeability to promote structural destruction, suppressing cracks is an important factor in improving durability. From the above results, crack control superior to Comparative Examples 1 to 3 using single-shaped steel fibers, organic fibers and structural organic fibers in embodiments of the present invention in which at least one of length and diameter were mixed with different steel fibers and organic fibers. It can be seen that performance is exhibited.

In addition, the steel fibers and organic fibers of different lengths and diameters were mixed, but Comparative Example 4, in which the total content of the fibers was 0.04% by volume, did not show a sufficient effect of suppressing the occurrence of cracks. However, in Comparative Example 5, in which the total mixing ratio of the fibers was 5.6% by volume, the steel fibers and the organic fibers were not uniformly dispersed in the cement material, and it was found that the cracking inhibitory effect was not large due to agglomeration. .

(Fireproof performance test)

To evaluate the fire resistance, compressive and flexural strengths were measured after exposing cement specimens to fire.

The fire test was performed using the fire resistance test furnaces shown in FIGS. 5A and 5B, and was performed according to the RABT curve (see FIG. 6), which is a fire curve temperature defined by the Ministry of Transport, Road, and Construction. In FIG. 5A and FIG. 5B, the code | symbol 9 represents a cement material specimen and the code | symbol 10 shows a heating element. The compressive strength test was conducted according to KS F 2405, and the flexural strength test was performed according to JCI SF-4.

Table 10 below shows the results of observing the surface after the cement specimen was exposed to fire, and the compressive and flexural strength test results.

Surface observation Compressive strength (MPa) Flexural strength (MPa) Residual Compressive Strength (%) Residual flexural strength (%) crack Peeling Bomb Example 1 X X X 43.5 5.4 88.2 86.7 Example 2 X X X 42.4 5.3 87.3 85.9 Example 3 X X X 41.7 5.4 85.4 84.3 Example 4 X X X 40.9 5.5 86.1 85.1 Example 5 X X X 41.8 5.6 86.8 83.9 Example 6 X X X 43.2 5.3 86.5 84.3 Example 7 X X X 44.8 5.6 86.3 83.9 Example 8 X X X 45.4 5.8 86.0 82.3 Example 9 X X X 42.9 5.5 85.9 84.3 Example 10 X X X 43.3 5.5 86.7 82.9 Example 11 X X X 38.9 4.9 77.8 75.1 Example 12 X X X 40.0 4.9 80.1 73.8 Example 13 X X X 39.6 5.0 79.3 72.1 Comparative Example 1 O O O 21.1 2.1 42.2 41.7 Comparative Example 2 O X X 24.3 1.4 48.5 40.5 Comparative Example 3 O O O 22.6 1.8 45.2 40.9 Comparative Example 4 0 X 0 23.5 3.1 46.7 47.1 Comparative Example 5 O X X 25.7 3.6 46.8 51.5

As shown in the table, in Comparative Example 1 containing a single-shaped steel fiber and Comparative Example 3 containing a single-shaped structural organic fiber, cracks, peeling, and thermal phenomena occurred in most of the specimens after the fire resistance test. In the case of Comparative Example 1, since the steel fibers are thermally conductive, there is little resistance to fire. And most of the compressive and flexural strengths were lost after the fire test.

In Comparative Example 2 including a single-shaped organic fiber, only a slight crack was generated but delamination and thermal expansion were hardly generated, but were greatly occurred in comparison with the embodiments of the present invention. In addition, the compressive and flexural strengths were greatly lost after the fire test, due to the formation of the same sized voids in the specimen as the organic fibers of the same shape melted by the fire.

In addition, in Comparative Example 4 containing 0.04% by volume of steel fibers and organic fibers having different lengths and diameters, the amount of fibers was not sufficient, resulting in a large drop in strength after fire, and cracking and thermal expansion. In Comparative Example 5, which contained 5.6% by volume of steel fibers and organic fibers having different lengths and diameters, the amount of fibers was excessive, and the fibers did not spread evenly.

On the other hand, in the embodiments of the present invention, after the fire resistance test, cracking, peeling, and thermal expansion did not occur in the specimen, and the decrease in the compressive strength and the flexural strength was less than that of the comparative examples. From the above results, it can be seen that the embodiments of the present invention exhibit better fire resistance than the comparative examples.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to

As described above, the mortar, concrete, and shotcrete according to the present invention increase the structural performance by increasing the flexural strength and the flexural toughness by mixing different types of steel fibers and organic fibers having different lengths and diameters, thereby improving both structural and large cracks and microcracks. By suppressing, durability performance is increased, and the use of organic fibers ensures excellent fire resistance. Therefore, mortar, concrete and shotcrete according to the present invention have the effect of securing both structural performance and durability and fire resistance at the same time.

Claims (11)

In any cement material selected from the group consisting of mortar, concrete and shotcrete, Wherein said cement material comprises steel fibers and organic fibers different in length and diameter from said steel fibers, said cement material having a compressive strength of up to 100 MPa and a flexural strength of up to 10 MPa. The method of claim 1, A cement material comprising the steel fibers differing in at least one of length and diameter. The method of claim 1, A cement material comprising the organic fibers differing in at least one of a length and a diameter. The method according to claim 1 or 3, Cement material having a melting point of the organic fibers below 300 ℃. The method of claim 3, Cement material consisting of any one of the fibers selected from the group consisting of olefin fiber comprising polyethylene, polyamide fiber including nylon, polyacrylic fiber, polyester fiber, polypropylene fiber and polyvinyl alcohol fiber . The method according to any one of claims 1 to 3, Concrete or shotcrete wherein the steel fibers and organic fibers have a length of 1 to 100 mm and a diameter of 0.01 to 25 mm. In any cement composition selected from the group consisting of mortar, concrete and shotcrete, The cement material composition includes cement, aggregate particles, at least one dispersant, water, steel fibers, and organic fibers different in length and diameter from the steel fibers, wherein the steel fibers and organic fibers A cement material composition comprising 0.05 to 5% by volume based on the cement material composition. The method of claim 7, wherein Wherein said steel fibers are comprised of steel fibers that differ in at least one of a length and a diameter. The method of claim 7, wherein A cement material composition, wherein the organic fibers are made of organic fibers different in at least one of a length and a diameter. The method according to claim 7 or 9, Cement material composition having a melting point of less than 300 ℃ the organic fibers. The method according to any one of claims 7 to 9, The steel fibers and organic fibers have a length of 1 to 100mm and a diameter of 0.01 to 25mm.

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