JP2009179490A - Heavy weight aggregate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide heavy weight aggregate which has a particle diameter and density suitable as those of the fine aggregate of heavy weight concrete and heavy weight mortar, particularly, to provide heavy weight aggregate which can be produced with recycled resources for which a sufficient feed amount can be secured as raw materials, is hardly separated from cement paste, and can obtain high fluidity. <P>SOLUTION: Disclosed is heavy weight aggregate in which the ratio of spherical particles in which the following strain ruggedness is ≤3.3 among all the particles with the particle diameter of 50 μm to 5 mm is ≥20%, and the mass percentage of all the particles among the particles passing through a sifter with a nominal size of 0.15 mm is 10 to 20%. The heavy weight aggregate comprises mill scales generated in the rolling stage of steelmaking and an inorganic material having density in a saturated surface-dry condition of ≤4g/cm<SP>3</SP>, and in which the ratio of spherical particles with strain ruggedness of ≤3.3 is ≥50% among all the particles with the particle diameter of 50 μm to 5 mm: [strain ruggedness]=[the length of the periphery of a particle contour]/[the diameter of a round circle with an area same as the area of a particle contour]. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heavy aggregate used for heavy concrete such as a wave-dissipating block and a radiation shielding wall, and heavy mortar.

Heavy concrete is concrete whose unit volume weight is larger than usual, and is used for wave-dissipating blocks, concrete for revetments, radiation shielding walls, bridge weights, and the like. As heavy aggregates used for heavy concrete, iron ores such as magnetite and hematite have been used in many cases, but it has become difficult to obtain high quality heavy aggregates. It is not preferable from the viewpoint of economy and environmental consideration. As an alternative to iron ore aggregate, slag with high iron content such as electric furnace oxidation slag is also used, but many have a density of less than 4 g / cm ³ and it is difficult to obtain a heavy aggregate with sufficient density. It is. In addition, heavy concrete has been proposed in which cement is mixed with coarse particles obtained by separating steelmaking converter dust with a sieve (see, for example, Patent Document 1). However, the amount of coarse particles in the steelmaking converter dust generated as a recycled material is small, and a sufficient supply amount as a raw material for heavy aggregate cannot be secured.
JP-A-5-31880

Among the recycled materials with high surface dry density generated in the steelmaking process, the recycled material with a large amount generated is a mill scale generated in the rolling process, but it has a flat shape and has extremely low fluidity. Could not be used. The inventors appropriately mixed mill scale and hot scarf generated in the cutting process of the steel slab surface, coarse particles of converter dust for steel making, and granular pig iron separated from blast furnace granulated slag. By mixing in a ratio, it was found that a good heavy aggregate that has high surface dry density, is difficult to separate from cement paste, and can impart high fluidity to heavy concrete and heavy mortar, and filed a patent separately. . However, the hot scarf, the coarse fraction of the converter dust, and the granular pig iron are all not generated as a recycled material. Therefore, there has been a demand for a heavy aggregate that can be produced using a large amount of recycled resources as a material, is difficult to separate from cement paste, and has high fluidity.

  The present invention provides, at a low cost, a heavy aggregate having a suitable particle size and density as a fine aggregate of heavy concrete or heavy mortar. In particular, the present invention provides a heavy aggregate that can be manufactured using recycled resources capable of securing a sufficient supply amount, is difficult to separate from cement paste, and has high fluidity.

The present inventors pay attention to the fact that the mill scale of the recycled material generated in the steelmaking rolling process has iron oxide as a main component and a high surface dry density of about 5 g / cm ³ , and the surface dry density is 4 g. / Cm ³ or less, including 50% or more spherical particles, a large amount of recycled material mixed in the mill scale, and by adjusting the particle size distribution appropriately, as a fine aggregate of heavy concrete or heavy mortar It has been found that when used, a heavy aggregate that is difficult to separate from cement paste and can impart high fluidity can be produced.

Therefore, in the present invention, of all the particles having a particle size of 50 μm or more and 5 mm or less, the following spherical particles having a strain unevenness degree of 3.3 or less are 20% or more, and all particles passing through a sieve having a nominal size of 0.15 mm are all. It is a heavy aggregate having a mass percentage of 10% to 20% of the particles, the mill scale generated in the steelmaking rolling process, the surface dry density is 4 g / cm ³ or less, and the strain unevenness is 3. The present invention provides a heavy aggregate characterized in that 3 or less spherical particles include an inorganic material that is 50% or more of all particles having a particle size of 50 μm or more and 5 mm or less.
[Strain unevenness] = [Perimeter of particle outline] / [Diameter of a perfect circle having the same area as the particle outline area]

  Further, the heavy aggregate of the present invention comprises 20% or more of spherical particles having a strain unevenness of 3.3 or less among all particles having a particle size of 50 μm or more and 5 mm or less, and particles passing through a sieve having a nominal size of 0.15 mm. Is a heavy aggregate having a mass percentage of 10% to 20% of the total particle, and is characterized by including a mill scale generated in a steelmaking rolling process and an electric furnace oxidation slag.

  The heavy aggregate of the present invention contains spherical particles in a moderate amount and has a particle size distribution that is moderately shifted to the finer particle side as compared with a normal fine aggregate, thereby providing a fine aggregate of heavy concrete or heavy mortar. When used as, it is possible to provide high fluidity while suppressing the separation of the cement paste and the aggregate, which has been conventionally considered difficult without adding a large amount of thickener. Furthermore, since it is obtained by mixing recycled materials with abundant generation amount, it is effective as an alternative to iron ore aggregate, which is an expensive natural resource that is feared to be exhausted.

Hereinafter, the heavy aggregate of the present invention will be described in more detail. In the present invention, the heavy aggregate refers to an aggregate having a surface dry density of 4 g / cm ³ or more. Further, unless otherwise mentioned, it refers to a heavy fine aggregate having a particle size of 5 mm or less.

  The heavy aggregate of the present invention comprises 20% or more of spherical particles having a strain unevenness degree of 3.3 or less, out of all particles having a particle size of 50 μm or more and 5 mm or less, and particles passing through a sieve having a nominal size of 0.15 mm. Is characterized in that it is 10% to 20% in terms of mass percentage of all particles. When the spherical particles are less than 20%, the fluidity of concrete and mortar when used as a fine aggregate is not sufficiently obtained, and the aggregate and the cement paste may be separated, which is not preferable. When particles passing through a sieve with a nominal size of 0.15 mm are less than 10% by mass or more than 20%, the fluidity of concrete and mortar when used as fine aggregate is not sufficiently obtained. The aggregate and the cement paste may be separated, which is not preferable.

Here, the “spherical particle” refers to a particle having a strain irregularity defined by the following formula of 3.3 or less.
[Strain unevenness] = [Perimeter of particle outline] / [Diameter of a perfect circle having the same area as the particle outline area]
That is, by visually observing a scanning electron microscope (SEM) image, particles that can be judged to be discoid or hemispherical from the shadow are excluded, and particles that are clearly close to a sphere are image-processed and analyzed. Image processing may be performed using general image processing software (for example, Adobe Photoshop). First, a contour-only figure is created by removing shadows from an image of particles close to a sphere, and the area of the figure and the perimeter of the outline are obtained. The figure is approximated to a circle (assuming a circle having the same area as the figure), the radius r is obtained from the area πr ^{2 of} the circle, and the diameter is obtained by doubling the radius r. The ratio of the circumference length to the diameter becomes smaller as the contour is closer to a circle, that is, as the particle is closer to a sphere, and becomes a value closer to the circumference ratio π.

The mill scale of the iron oxide film generated in the steel rolling process is a recycled material with a large amount of generation among the recycled materials with high surface dry density generated in the steelmaking process, but it has a flat shape and is fluid. Is extremely low, and the mill scale cannot be used alone as an aggregate. The weight aggregate of the present invention has a mill scale with a surface dry density of 4 g / cm ³ or less, and 50% of all spherical particles having a strain unevenness of 3.3 or less and a particle size of 50 μm or more and 5 mm or less. It can be obtained by mixing the above inorganic materials.

Considering that the surface dry density of the mill scale is about 5 g / cm ³ , the mixing ratio of the mill scale and the inorganic material is preferably 30:70 to 70:30 in volume ratio, and 40:60 Or more preferably 60:40. The surface dry density of the inorganic material is preferably 3.5 g / cm ³ to 4 g / cm ³ . When the mixing volume ratio of the mill scale is less than 30%, the surface dry density of the heavy aggregate may be less than 4 g / cm ^3, and when the mixing volume ratio of the mill scale exceeds 60%, the spherical particles Is less than 20%, which is not preferable. However, when the ratio of the spherical particles in the inorganic material is 67% or more, the volume ratio of the mill scale can be mixed up to 70%. Further, even when the mixing volume ratio is 30:70 to 70:30, the particle size distribution of the inorganic material to be mixed is uneven, and the particles passing through the sieve having a nominal size of 0.15 mm among the heavy aggregate after mixing However, when the mass percentage does not satisfy the condition of 10% to 20%, the fluidity of concrete or mortar may not be sufficiently obtained, or the material may be separated, which is not preferable.

Recycled material with abundant amount of generation, inorganic material that can be used in the present invention, wherein spherical particles having a strain unevenness degree of 3.3 or less are 50% or more of all particles having a particle size of 50 μm or more and 5 mm or less As an example, an electric furnace oxidation slag can be mentioned. In particular, pulverized granulated slag is preferable because the content ratio of spherical particles is high. Since the electric furnace oxidation slag has a high calcium content, the surface dry density is low among the recycled materials generated in the steelmaking process, but the main component is iron oxide, so 3.5 to 4 g / cm ³ The surface dry density can be secured. However, when mill scale and electric furnace oxidation slag are mixed, there may be a shortage of particles passing through a sieve having a nominal size of 0.15 mm. In that case, it is preferable to supplement the fine particles by mixing steelmaking converter dust and the like. When mixing coarse particles obtained by separating mill scale, electric furnace oxidation slag, and converter dust with 50 μm sieve, the mass percentage may be 50-70%, 20-30%, and 10-20%, respectively. preferable.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

Example 1
(Test method)
(1) Mill scale shown in Table 1 for surface dry density, spherical ratio (spherical particle ratio), particle size distribution (sieving passage rate), electric furnace oxidation slag (pulverized granulated slag), converter dust (50 μm sieve) The divided coarse powder) was mixed at a mixing ratio shown in Table 2 to prepare mixed sands 1 to 6. Table 2 shows the surface dry density, spherical ratio, and 0.15 mm sieve passing rate of each mixed sand.
(2) (1) ordinary Portland cement mixed sand was adjusted by mixing with sand cement volume ratio 2.97, the cement 570 kg / ^{m 3} per, 6.27 kg / ^{m 3} of a polycarboxylic acid ether high AE water reducing The agent and 256 kg / m ³ water (water cement ratio 45.0%) containing 0.23 kg / m ³ defoamer were added and kneaded.
(3) Using the flow cone of the physical test method of JIS R 5201 cement, the flow cone with a diameter of 100 mm and a height of 40 mm was filled with the mortar prepared in (2), the cone was pulled out, and the mortar flow was measured. Further, the state of separation between the cement paste and the aggregate was visually judged.

(Test results)
Table 3 shows the measurement results of the mortar flow and the determination results of the material separation state. The determination of the mortar flow was good at 130 mm or more.

As shown in Table 2 and Table 3, in the mixed sand 1 and the mixed sand 2 having a 0.15 mm sieve passage rate of less than 10%, the separation of the cement paste and the aggregate was remarkable. In the mixed sand 3 in which the ratio of the spherical particles was less than 20%, the mortar flow was 105 mm and hardly flowed. On the other hand, in the mixed sand 4 to 6 having a spherical particle ratio of 20% or more and a 0.15 mm sieve passage rate of 10% to 20%, a high mortar flow was obtained without separation of the cement paste and the aggregate. . Therefore, it is shown that by mixing electric furnace oxidation slag as a material that gives fluidity to the mill scale and further adjusting the particle size, a heavy aggregate that is difficult to separate from cement paste and has high fluidity can be obtained. It was. In order to adjust the particle size, mixing of the coarse particles of the converter dust is effective, and the mixing ratio of the mill scale, the electric furnace oxidation slag, and the converter dust coarse particles is 50 to 70 in terms of mass percentage, respectively. %, 20-30%, and 10-20%.

  The heavy aggregate of the present invention can be widely used as a fine aggregate for heavy concrete that requires a unit volume mass higher than that of ordinary concrete, and is particularly useful in applications requiring high workability such as pumping.

Claims (2)

Among all the particles having a particle size of 50 μm or more and 5 mm or less, the spherical particles having a strain unevenness degree of 3.3 or less described below are 20% or more, and the particles passing through a sieve having a nominal size of 0.15 mm are expressed by mass percentage of the total particles A heavy aggregate of 10% to 20%, a spherical scale having a mill scale generated in a steelmaking rolling process, a surface dry density of 4 g / cm ³ or less, and a strain unevenness of 3.3 or less. A heavy aggregate comprising an inorganic material that is 50% or more of all particles having a particle diameter of 50 μm or more and 5 mm or less.
[Strain unevenness] = [Perimeter of particle outline] / [Diameter of a perfect circle having the same area as the particle outline area]   Spherical particles having a strain irregularity of 3.3 or less are 20% or more of all particles having a particle size of 50 μm or more and 5 mm or less, and particles passing through a sieve having a nominal size of 0.15 mm are 10% by mass of all particles. A heavy aggregate that is 20% or more, comprising a mill scale generated in a steelmaking rolling process and an electric furnace oxidation slag.