KR20100035257A - Lyocell fibers for reinforcing concrete - Google Patents

Abstract

PURPOSE: Lyocell fiber for reinforcing concrete is provided to improve cohesion property and dispersibility of the concrete with hydrophilic property of fiber, and to improve structural performance of the concrete by improving tensile strength and abrasion resistance etc. CONSTITUTION: Lyocell fiber for reinforcing concrete has elongation of 6% - 15% and intensity of 7.0 g/d or more measured by 5 mm gauge length. The lyocell fiber has the alpha-Cellulose content of 90% or greater. The length of the lyocell fiber is 5 ~ 19 mm. The fineness of the lyocell fiber is 1.5 - 5.0 denier. The lyocell fiber has the optimized property to be used as a concrete reinforcing material.

Description

Lyocell Fiber for Concrete Reinforcement {LYOCELL FIBERS FOR REINFORCING CONCRETE}

The present invention relates to a lyocell fiber for concrete reinforcement, and more specifically, for concrete reinforcement to improve crack resistance, tensile strength and compressive strength due to excellent dispersibility in concrete, adhesion to concrete and mechanical properties. It relates to a lyocell fiber.

Cement hardener of concrete or mortar (hereinafter abbreviated as "concrete") is widely used as an economical construction material, but has a weak point in tensile strength and toughness.

Reinforcing bars have been used as a reinforcing material for improving the toughness of concrete for more than 100 years, and recently, steel system reinforcing materials such as steel plates, pipe steel fibers, and reinforcing bars are widely used instead of reinforcing bars.

Steel fiber, such as reinforcing bar, has a thickness of 0.5 mm and a length of 30 mm, and has good adhesion to concrete and high breaking strength compared to conventional reinforcing bars, and is used in tunnel and dam construction sites where reinforcing bars and mesh are difficult to install. This has the advantage of easy, but when used in the construction site, such as a tunnel in which a large amount of moisture, steel fibers are easily corroded, expensive, high specific gravity, there is a problem in the dispersibility in concrete, increasing the load of the concrete.

In order to solve the conventional problems as described above, in recent years, the use of synthetic fibers instead of steel reinforcing materials such as steel fibers as a concrete reinforcing material, such as US Patent No. 5,749,961 and Taiwan Patent Publication No. 2003-47669 Is being studied.

Specifically, synthetic fibers have a smaller specific gravity than steel fibers, and are excellent in corrosion resistance, but may also reinforce concrete crack resistance, tensile strength, and compressive strength than steel fibers.

However, it is known that synthetic fibers do not improve basic structural performances such as flexural strength and flexural performance of concrete, but express only the effect of preventing cracking of concrete.

When synthetic fiber is intended to improve the basic structural performance of concrete, the amount of synthetic fiber should be increased.However, if the amount is increased, it becomes difficult to disperse in concrete, resulting in deterioration of properties such as compressive strength and flexural strength of concrete. Degrades.

Meanwhile, some methods of using synthetic fibers having high strength such as carbon fiber, aramid fiber, and high strength polyolefin fiber as concrete reinforcing materials have been carried out. However, in this case, the effect of improving the basic structural performance of concrete is unknown but only expensive. There was a problem.

Therefore, until recently, although the basic structural performance of concrete is not improved, polypropylene fiber, which is inexpensive and effective in preventing cracking of concrete, has been most widely used as a reinforcing material of concrete.

However, polypropylene fiber has good tensile strength of the fiber itself, but due to its hydrophobicity, adhesion property with concrete is poor, and thus the tensile strength of the fiber itself is not sufficiently exerted, thereby improving crack resistance, tensile strength and compressive strength of concrete. There was a problem that the effect was greatly lacking.

In addition, polypropylene fibers have a good reinforcing effect when the amount of fibers used is high, but the dispersibility is poor and a uniform mixture is not obtained, workability is bad. In addition, the polypropylene fiber has a problem that the specific gravity is small and floated on the surface of the cement mortar to remove it later and a special mixing device is required in order not to bundle the fibers.

On the other hand, as another conventional technique, Japanese Laid-Open Patent Publication No. 2002-137942 proposes a polyamide fiber having a release cross section as a concrete reinforcing material in order to improve the above problems caused when using polypropylene fiber as a reinforcing material.

However, the polyamide fiber has a problem of low strength and wear resistance of the fiber itself, lack of dispersibility in concrete, and insufficient effect of improving the crack resistance, tensile strength and compressive strength of the concrete.

Therefore, it is possible to improve the basic structural performance of concrete and to improve physical properties such as tensile strength and toughness, and research on the development of synthetic fiber as a reinforcing material having excellent dispersibility and adhesion with concrete is necessary.

The present invention is to provide a lyocell fiber for concrete reinforcement excellent in the strength and wear resistance of the fiber itself, excellent dispersibility in concrete and excellent adhesion to concrete.

The present invention provides a lyocell fiber for concrete reinforcement having a strength of 7.0 g / d or more and an elongation of 6% to 15% as measured by a gauge length of 5 mm.

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

The lyocell fiber to be developed in the present invention has the optimum physical properties for use as concrete reinforcement, and in particular, has the characteristics of improved strength and elongation.

In particular, the lyocell fiber of the present invention is characterized in that the strength measured by a gauge length of 5 mm (7.0 g / d or more or 7.0 to 9.0 g / d, preferably 7.5 to 8.5 g / d) do. In addition, the lyocell fibers of the present invention may have an elongation of 6% to 15%, preferably 8% to 12%, as measured by a gauge length of 5 mm.

The strength and elongation of the lyocell fiber for concrete reinforcement according to the present invention is a value measured under the following measurement conditions.

[Strength measurement conditions]

After grasping the lyocell fiber for concrete reinforcement with a gauge length of 5 mm in a universal fiber tension tester, 20 times of strength and elongation were obtained with a tension weight of 300 mg and a head speed of 50 mm / min. Measure it as these average values.

In the present invention, when the strength of the lyocell fiber is out of the above range, the reinforcing effect of the concrete worsens, and when the elongation is out of the above range, the dispersibility effect may deteriorate.

In addition, the polyamide fiber for concrete reinforcement according to the present invention has a relative viscosity (RV) of at least 2.9, more preferably at least 3.2.

If the relative viscosity (RV) is lower than the above range, the strength and abrasion resistance of the fiber itself is lowered, and if the strength and elongation of the fiber itself is outside the above range, the effect of improving the crack resistance of the concrete is weakened.

In addition, it is preferable that the lyocell fiber for concrete reinforcement according to the present invention has a length of 5 to 19 mm and a fineness of 1.5 to 5.0 denier.

If the length is less than 5 mm, the area where the concrete and the fiber is in contact with the narrower can be reduced effect of improving the tensile strength and compressive strength of the concrete, if the length exceeds 19 mm, the fibers in the concrete is less dispersed, the fibers are mutually The entanglement may occur and the concrete properties may be lowered.

When the fineness is less than 1.5 denier, there is an advantage that the surface area of the fiber is increased to increase the contact area with the concrete, but the strength of the fiber itself may be lowered and the dispersibility of the fiber in the concrete may be reduced.

If the fineness exceeds 5 denier, the number of fibers per unit area of concrete decreases, which creates the risk of forming relatively weak areas in concrete.

In addition, the present invention further improves various physical properties of concrete by providing alkali resistance, hydrophilicity, vibration damping resistance, and the like, which are inherent in polyamide fibers.

The lyocell fiber for concrete reinforcement according to the present invention is suitable to use 0.25 to 1 kg per 1 m 3 of concrete.

If less than 0.25 kg per 1 m 3 of concrete, the concrete reinforcing effect is lowered. If it is used more than 1 kg, the dispersibility of the fibers in the concrete is lowered, thereby reducing the tensile strength and slump of the concrete.

The lyocell fiber for concrete reinforcement according to the present invention may be used alone in concrete reinforcement, or may be mixed with other synthetic fibers known to be usable as other existing concrete reinforcement materials, that is, polyamide fibers and the like.

In addition, the lyocell fiber of the present invention can be prepared by a process comprising a conventional spinning, coagulation, washing, drying step, wherein the spinning dope is cellulose (pores), pore-forming material, N-methylmorpholine N-methylmorpholine-N-oxide (NMMO) and water.

The cellulose may be conventional in the art to which the present invention pertains, but in order to improve the physical properties of the fiber, the content of alpha-cellulose (α-cellulose) may be 90% or more. In particular, southern pine pulp containing 96% alpha-cellulose can be used.

The lyocell spinning dope of the present invention may include 5 to 35% by weight of cellulose in consideration of spinning properties, and may also be included to 7 to 18% by weight.

In the present invention, matters other than those described above can be added or subtracted as required, and therefore, the present invention is not particularly limited thereto.

In the present invention, the fibers themselves have hydrophilicity, excellent dispersibility in concrete, and excellent adhesion to concrete. In addition, the present invention is also excellent in the strength and wear resistance of the fiber itself.

Therefore, the lyocell fiber of the present invention can greatly improve the crack resistance, tensile strength, and compressive strength of concrete.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Example 1

162 kg of water, 330 kg of cement, 868 kg of sand and 964 kg of aggregates are used to produce concrete having a unit area of 1 m3. The method described above with a gauge length of 5 mm as a reinforcing material. 0.6 kg of lyocell fibers having a strength of 7.5 g / d and an elongation of 8% were measured.

The lyocell fibers have a length of 6 mm and a fineness of 2.0 denier, as shown in Table 1 below.

 The results of evaluating various physical properties of the concrete prepared as described above are as shown in Table 2 below.

Examples 2-4

Concrete was prepared in the same process and conditions as in Example 1 except that the addition of lyocell fiber, which is a concrete reinforcing material, and the length, fineness, strength, and elongation of the fiber were changed as shown in Table 1 below.

The results of evaluating various physical properties of the concrete prepared as described above are as shown in Table 2 below.

division Strength (g / d) Elongation (%) Addition amount (㎏ / ㎥) Length (mm) Fine island (denier) Example 1 7.5 8 0.6 6 2.0 Example 2 7.3 12 0.3 12 3.0 Example 3 8.1 7 0.6 12 1.5 Example 4 7.4 11 0.9 8 3.5

Comparative Example 1

Concrete was prepared in the same process and conditions as in Example 1 except that no lyocell fiber was added as a reinforcing material.

The results of evaluating various physical properties of the concrete prepared as described above are as shown in Table 2 below.

Comparative Example 2

As a reinforcing material in concrete production, 0.6 kg of polypropylene fiber having a strength of 6.39 g / d, 60% elongation, 12 mm in length, and 6.0 denier fineness was measured using a gauge length of 5 mm. Except one, concrete was prepared in the same process and conditions as in Example 1.

The results of evaluating various physical properties of the concrete prepared as described above are as shown in Table 2 below.

Comparative Example 3

0.3 kg of nylon 6 fiber with a strength of 7.8 g / d, 56% elongation, 12 mm in length and 4.5 denier is measured as a reinforcing material when measuring concrete with a gauge length of 5 mm. Except one, concrete was prepared in the same process and conditions as in Example 1.

The results of evaluating various physical properties of the concrete prepared as described above are as shown in Table 2 below.

Comparative Example 4

As a reinforcing material for concrete production, 0.6 kg of lyocell fiber with a strength of 5.8 g / d, elongation of 4%, length of 19 mm, and fineness of 1.5 denier was measured using a gauge length of 5 mm. Except one, concrete was prepared in the same process and conditions as in Example 1.

The results of evaluating various physical properties of the concrete prepared as described above are as shown in Table 2 below.

Various physical properties in the present invention were evaluated by the following method.

1) Slump: Measured by KS F 2402 method.

2) Air content (%): measured by KS F 2421 method.

3) Compressive strength (MPa): measured by KS F 2405 method.

4) Tensile strength (MPa): Measured by the KS F 2423 method.

5) Dispersibility:

In accordance with the test method of JCI-SF 7, the concrete mixture of unit area is washed again with water, filtered to collect reinforcing fibers contained therein, and dried to weigh. When the weight of the reinforcing fiber obtained as described above is within ± 10% of the input amount, it was divided into ◎, ○ within ± 20%, and Ⅹ when exceeding ± 20%.

6) Crack Resistance:

The cracking resistance is placed in a 1m × 1m × 10cm formwork with 5 cm in height and 10 cm smaller than the formwork. Laboratory average temperature is 30 ℃. The average humidity was measured at 35% after one week of curing. The crack resistance was expressed as the total crack length by the sum of the average crack width and the total crack length in the cracked area.

The results of evaluating various physical properties of the concrete prepared according to Examples 1 to 4 and Comparative Examples 1 to 4 are as shown in Table 2 below.

division Example Comparative example One 2 3 4 One 2 3 4 Slump (cm) 17.2 18.1 18.3 17.9 17.5 17.9 18.4 18.1 Air content rate (%) 4.2 4.3 4.1 4.6 4.9 4.7 4.8 4.7 Compressive strength (MPa) 15 hours 4.25 4.31 4.56 4.15 4.31 4.12 3.67 4.11 18 hours 6.81 6.74 6.91 6.35 6.15 6.21 6.23 6.31 1 day 13.62 13.74 13.89 12.97 12.43 12.45 12.37 13.02 3 days 29.47 28.97 29.64 30.13 25.96 26.35 26.47 27.02 7 days 36.47 37.11 35.47 38.26 32.18 33.64 34.15 33.76 Tensile strength (MPa) 1 day 1.57 1.61 1.64 1.59 1.34 1.46 1.48 1.43 3 days 2.84 2.67 2.61 2.59 2.31 2.34 2.26 2.60 7 days 3.67 3.58 3.63 3.61 2.58 3.15 3.24 3.31 Dispersibility ◎ ◎ ◎ ◎ - Ⅹ Ⅹ ○ Crack resistance Crack Initiation Width (mm) 0.04 0.03 0 (no crack) 0 (no crack) 0.09 0.06 0.06 0.07 Total crack length (cm) 10 12 14 12 110 60 58 75

As shown in Table 2, it can be seen that the concrete of Examples 1 to 4 to which the lyocell fibers were added as a reinforcing material according to the present invention has very excellent strength and crack resistance. On the other hand, in the case of Comparative Example 1, which does not add a separate fiber reinforcing material is not good in terms of tensile strength and crack resistance, Comparative Examples 2 ~ using the existing polypropylene fiber, nylon 6, and conventional lyocell fiber as a reinforcing material In case of 4, it can be seen that it is not good in terms of dispersibility and crack resistance.

The present invention by using the lyocell fiber excellent in strength and wear resistance of the fiber itself as a reinforcing material to improve the physical properties of the concrete, it is excellent in the dispersibility and adhesion in the concrete and excellent corrosion resistance, but also crack resistance, tensile strength and compressive strength of the concrete Can be effectively improved.

Claims (4)

A lyocell fiber for concrete reinforcement with a strength of at least 7.0 g / d and an elongation of 6% to 15%, as measured by a gauge length of 5 mm. The method of claim 1, The lyocell fiber is a lyocell fiber for concrete reinforcement having an alpha-cellulose content of 90% or more. The method of claim 1, The lyocell fiber is 5 to 19mm in length lyocell fiber for concrete reinforcement. The method of claim 1, The lyocell fiber is lyocell fiber for concrete reinforcement having a fineness of 1.5 to 5.0 denier.