KR20070102296A - The admixture for preventing the spalling of concrete and the concrete composition that the admixture is included - Google Patents

Abstract

An admixture for preventing the spalling of concrete is provided to have an excellent spalling-resistant effect and prevent workability deterioration and flowability reduction of concrete. An admixture for preventing the spalling of concrete includes a spalling-resistant fiber which forms a continuous particle size distribution, and glass powder. In a disk type grinder, the spalling-resistant fiber and broken glass are simultaneously ground in a weight ratio of 1:5-1:15 to obtain a continuous particle size distribution and form glass powder. The spalling-resistant fiber is one, two or more selected from polypropylene fiber, nylon fiber, and polyvinylalcohol fiber.

Description

The admixture for preventing the spalling of concrete and the concrete composition that the admixture is included}

The present invention relates to a concrete anti-expandable admixture and a concrete composition containing the admixture, and in detail, prevents deterioration of workability and fluidity of the concrete and includes a concrete anti-expansion admixture and its admixture capable of preventing thermal expansion in a fire. It relates to a concrete composition.

In general, the most widely used concrete is in the range of 21 to 24 Mpa of reference strength at 28 days of age. However, with the advent of ultra high-rise buildings and the development of concrete manufacturing technology, high-performance concrete having high strength and high flow characteristics has emerged. Such high-performance concrete is being used intensively in the lower floors of high-rise buildings. The classification of such high-performance concrete depends on the standard or classification agency, but usually refers to the case where the reference strength of 28 days is over 40 ~ 45Mpa. Such high-performance concrete is used in a very important part as a structural material in the pillars and beams of the lower floor of a high-rise building, although the ratio of the total ready-mixed concrete usage is small.

In order for concrete to exhibit high strength, its density must be large and its internal structure must be tight. However, in this case, if the concrete structure is directly heated in a fire, water vapor pressure is generated inside the concrete. Due to the dense and dense internal structure, water vapor is not naturally released to the outside of the concrete, and eventually the water vapor pressure exceeds the stress limit of the concrete, resulting in severe binge drinking. In addition, a thermal expansion phenomenon occurs in which the surface peels and falls off. This phenomenon occurs as the strength of concrete increases with high strength, and is reported as a more serious problem, especially in concrete of 40 ~ 45Mpa strength or more.

Once the part is dropped by the high heat caused by the fire, the part is continuously exposed to the possibility of peeling and dropping of the concrete, and eventually, the reinforcing bar inside the concrete is exposed to the outside, which causes a high temperature. As is known, the reinforcing bar is a material with severe degradation of stiffness due to heat, and thus, the stiffness of the reinforcing bar and the loss of the concrete cross section due to heat eventually lead to the collapse of the structure.

It is understood that concrete has already been recognized as a fireproof structure under the building code, so that no special fire-resistance measures are required. However, the thermal explosion phenomenon of the high-performance concrete described above may occur within 30 minutes as soon as the concrete is subjected to high heat, and thus may not have enough time for the user inside the concrete structure to evacuate. Therefore, the countermeasure against the thermal explosion phenomenon of the high-performance concrete has become an important solution for the related industry.

As a countermeasure against the heat-expanding phenomenon of high-performance concrete, a method of mixing a certain amount of synthetic fiber such as polypropylene, which has low heat resistance, as an anti-expanding fiber, has been proposed. In case of fire, the synthetic fiber reaches the melting point before the thermal explosion occurs and exists in the liquid state, but is absorbed by most of the surrounding matrix tissue to create an empty space. The pressure of the pressure decreases, and as a result, an anti-thermal effect is obtained. That is, the site where the mixed synthetic fibers are melted serves as a path for releasing internal water vapor to the outside.

However, this method is a general countermeasure that has already been applied to a number of practical applications, but it is difficult to homogeneously disperse the fibers inside the concrete, the workability of the concrete is deteriorated even if it is dispersed homogeneously, and the fluidity decreases quickly. There is this.

SUMMARY OF THE INVENTION An object of the present invention is to provide a concrete anti-expandable admixture and a concrete composition including the admixture having excellent anti-expanding effect and which do not result in reduced workability and reduced fluidity of concrete due to the mixing of the anti-expandable admixture of concrete.

The present invention relates to a concrete anti-expandable admixture and a concrete composition containing the admixture, and more particularly, to a concrete anti-expandable admixture including a heat-resistant fiber and a glass powder to form a continuous particle size and a concrete composition including the same when mixing concrete. .

If the anti-expandable fiber forms a continuous particle size rather than a single particle size, the slump reduction is reduced, and the anti-explosion effect is also excellent. If the heat-resistant fiber forms a single particle size, the longer the fiber is, the better the formation of a passage through which water vapor escapes, but it is difficult to disperse. The better anti-explosion effect is shown. In the case of the glass powder serves to facilitate the dispersion of the fiber in the concrete, and plays an additional role in preventing the heat of the concrete due to the endothermic effect at high temperatures in the event of fire.

Concrete anti-expandable admixture is selected from polypropylene fiber, nylon fiber, polyvinyl alcohol fiber, etc. and one or more anti-explosion fibers, mixed with glass shreds in a weight ratio of 1: 5 ~ 1: 15 By doing so, the fibers can be formed to form a continuous particle size. In the case of the weight ratio of 1: 5 or less, the effect due to the glass shredding is reduced. In the case of the weight ratio of 1:15 or more, the strength of the concrete decreases as the ratio of the glass shredding increases. When pulverizing synthetic fibers alone, the fibers are not pulverized well and continuous particle size is not formed. However, when the fiber is crushed together with glass crushed particles, it is effective to obtain continuous particle size.

At this time, the particle size can be controlled to the desired degree by adjusting the interval, grinding time, and grinding speed in the grinding process. When the 5mm and 20mm synthetic fibers are ground together with the glass crushed material, a continuous particle size of 0.05 ~ 20mm can be obtained.

Thus, the anti-expandable admixture obtained by simultaneously crushing the synthetic fiber and glass shreds is used in the range of 5 ~ 40kg / m ³ in concrete. In 5kg / m ³ or less and effect a reduction in the 40kg / m ³ or more, there is a problem that affects the performance of the original, such as concrete strength. At this time, preferably used in the range of 20 ~ 30kg / m ³ .

Hereinafter, with reference to the experimental example of the present invention will be described in detail.

1. Preparation of anti-expansion admixture

The manufacture of the heat-expandable admixture used for the experiment was performed as follows.

<Table 1> Preparation of anti-heating admixture

Raw material ratio (wt%)  Grinding method Polypropylene fiber Glass shreds 5 mm 10 mm 3mm or less 5 5 90 Disk type grinder

The anti-expansion admixture is prepared by mixing and grinding 5 mm and 10 mm polypropylene fibers according to the ratio of the glass crushed product to the <Table 1>.

The anti-expansion admixture prepared in this way forms a continuous particle size of 0.05 ~ 10mm.

2. Mixing of Concrete

The mix of concrete for the experiment was based on the following mix, which can represent a base strength of 40 Mpa for 28 days.

<Table 2> Concrete Mixing Standards

Concrete mix (kg / m ³ )  cement  Blast furnace slag  Fly ash  Unit quantity  Coarse aggregate  Fine aggregate Naphthalene AE water reducing agent 262 140 66 185 819 753 2.34

In the experiment, Portland cement, blast furnace slag powder, and fly ash, which are used in Remicon, Korea, were used as binders.

<Table 3> Properties of the binder used in the experiment

  division Physical properties Chemical composition (%)  importance Powder level (cm ² / g) SiO ₂ Al ₂ O ₃ Fe ₂ O ₃  CaO  MgO SO ₃ K ₂ O Na ₂ O Ig- loss  Portland cement  3.14  3250  20.48  4.88  3.04  63.47  3.56  2.40  1.13  0.11  1.85  Blast furnace slag powder  2.89  3850  33.81  15.23  0.47  41.25  8.02  -  0.38  0.31  0.42 Fly ash 2.23 3650 61.02 19.41 6.32 5.08 - - 2.34 - 0.84

3. The mixing amount of the anti-expandable fiber and the anti-expandable admixture

Meanwhile, the mixing amount of the anti-explosion fiber and the anti-explosion admixture to confirm the anti-explosion effect was planned and tested as follows.

<Table 3> Mixing amount of anti-expandable fiber and anti-expandable admixture by compound

 division Mixing amount of anti-expandable fiber and anti-expandable admixture (kg / m ³ ) PP fiber (5mm) PP fiber (10 mm) Anti-expansion admixture    Comparative example Control A-1 1.0 A-2 2.5 A-3 4.0 B-1 1.0 B-2 2.5 B-3 4.0  Example C-1 10.0 C-2 20.0 C-3 30.0

In this case, the comparative example used 5 mm and 10 mm of polypropylene fiber among the anti-expansion fibers currently being used for the case of not using the fiber and to prevent the thermal expansion. An anti-expanding admixture obtained by mixing and pulverizing fibers and glass shreds was used.

4. Experimental Results

The experimental results are as follows.

<Table 5> Experimental Results

division slump Air volume Compressive strength (MPa) Concrete thermal rating cm % 3 days 7 days 28 days One 2 3 4 5    Comparative example Control 17.0 4.7 27.0 36.4 56.7 ○ A-1 16.5 4.4 25.4 29.4 48.6 ○ A-2 16.0 4.2 23.8 27.7 44.5 ○ A-3 14.0 4.5 24.1 28.3 43.2 ○ B-1 15.5 4.4 25.9 28.4 46.4 ○ B-2 15.5 4.6 24.4 28.1 44.3 ○ B-3 13.5 4.2 23.9 26.3 42.3 ○  Example C-1 16.5 4.4 26.2 28.3 45.6 ○ C-2 16.5 4.7 24.8 27.8 46.2 ○ C-3 16.0 4.3 23.5 26.9 43.4 ○

Here, the concrete thermal test was conducted for 30 minutes according to the standard heating curve of the circular specimen of 15cm * 30cm in the fireproof test furnace, and the anti-expansion effect was expressed as 1 to 5 grades. In this case, the grade 1 represents a very good case where there is almost no damage of the test specimen due to the explosion. In the case of the grade 5, the grade was selected based on the case where the bursting phenomenon occurred so severely that the shape of the specimen was hardly maintained.

As shown in the experimental results, the control group showed a slump of 17.0 cm, an air content of 4.7%, and a compressive strength of 56.7 Mpa at 28 days of age. Showed a tendency to. However, the result of using the anti-expansion admixture showed a tendency to decrease slightly in the slump and the air amount compared to the control formulation, but the decrease in the slump was slightly reduced than the comparative examples of the A or B series containing the fiber. This indicates that when the anti-expansion admixture is used, the workability decreases and the fluidity decrease of the concrete due to the blending of fibers is reduced, unlike in the other comparative examples.

In addition, the results of the thermal test showed that after the heating, the appearance and shape of the test body were observed, and in the case of the control group, there was a severe rupture and no shape remained.In the test sample containing the fiber, part of the test sample was dropped due to some explosion. In the case of the test specimen containing the anti-expansion admixture, the anti-expansion effect was superior to that of the fiber in the comparatively maintained original shape.

As described above, according to the present invention, it is possible to provide a concrete anti-expandable admixture and a concrete composition including the admixture, which is excellent in anti-expanding effect and does not reduce workability and decrease fluidity of concrete due to the mixing of the anti-expandable admixture of concrete. Will be.

Claims (5)

In concrete heat-resistant admixture, Concrete anti-expandable admixture comprising a heat-resistant fiber and a glass powder to form a continuous particle size. In claim 1, In the disk-type grinder crushing the anti-explosion fibers and glass shreds at a weight ratio of 1: 5 to 1:15 at the same time to form a continuous particle size and concrete powder preventing admixture, characterized in that the glass powder is formed. In claim 2, The heat-resistant fiber is selected from one of the heat-resistant fiber of length 5mm or more and 20mm or by selecting two or more heat-resistant fiber of different length within the particle size of the heat-resistant fiber itself within the range of 0.05mm or more and 20mm or less. Concrete anti-expansion admixture, characterized in that to form a continuous particle size. In claim 3, The anti-expandable fiber is a concrete anti-expandable admixture, characterized in that at least one selected from polypropylene fiber, nylon fiber, polyvinyl alcohol fiber. A concrete composition comprising the concrete anti-expandable admixture of any one of claims 1 to 4, characterized in that the compound is mixed using 5 to 40kg / m ³ when concrete mixing.