JPH05194007A - Production of amorphous silica fine powder and concrete blended with amorphous silica fine powder - Google Patents

Abstract

PURPOSE:To inexpensively produce amorphous silica fine powder from chaff as a raw material and to provide a high-strength concrete product blended with the amorphous silica fine powder. CONSTITUTION:Chaff immersed in a solution of hydrochloric acid is burnt, the ash is ground into fine powder to characteristically produce amorphous silica fine powder and the chaff immersed in a solution of hydrochloric acid is burnt, the ash is ground into fine powder and the fine powder is added to cement to characteristically provide a concrete product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing amorphous silica fine powder using rice husks as a raw material, and a high-strength concrete product containing the amorphous silica fine powder.

[0002]

2. Description of the Related Art Conventionally, this type of amorphous silica fine powder is a dust collector as a by-product contained in exhaust gas when refining silicon alloys such as metallic silicon and ferrosilicon alloys by an arc type electric furnace. It is collected by the company and is generally called silica fume.

[0003]

However, the conventional silica fume is obtained as a by-product,
There are various drawbacks such as high price because the quality varies greatly and it is difficult to control the production volume. Therefore, when this silica fume is mixed into concrete, there are various problems that the strength of the concrete product is not constant and the cost is increased.

[0004]

The present invention has been made in order to solve the above-mentioned conventional problems, and is rarely used industrially. It is intended to provide amorphous silica fine powder made from rice husk as a raw material, which can be easily obtained in the rice-growing area where it was burned or incinerated, and its gist is to soak it in a hydrochloric acid solution. When burning rice husks, the method for producing amorphous silica fine powder characterized by crushing the baked ash into fine powder, and burning rice husks dipped in hydrochloric acid solution also A concrete product characterized in that a fine powder of amorphous silica obtained by crushing the fired ash is mixed in cement.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments of FIGS. 1 is a block diagram showing a manufacturing process according to the present invention, FIG. 2 is an X-ray diffraction spectrum diagram of a crystal lattice depending on a combustion temperature and a burning time, and FIGS. 3 and 4 are particle size distributions obtained by crushing in the crushing process. Show.

In the figure, reference numeral 1 denotes a rice husk as a raw material. In the pretreatment step 2, this rice husk is immersed in a hydrochloric acid solution (HCl) of about 10% for a short time. This makes it possible to melt an alkaline organic component such as potassium, which accounts for about 80% of the rice husk 1. The reason why the hydrochloric acid solution is used in this pretreatment step 2 is that, as shown in Table 1, the content of silica contained in the treated rice husk 1 is higher than that in other treatment methods.

[0007]

[Table 1]

Reference numeral 3 is a firing step, in which the rice husk 1 treated in the pretreatment step 2 is fired in a calcination device such as a rotary kiln, a shaft kiln or a fluidized bed furnace to obtain a calcined ash of the rice husk 1. The firing temperature of the rice husks in step 3 is preferably 600 to 700 ° C., and the firing time is preferably 1 to 2 hours. The burning temperature and the burning time are determined by the experimental results. As an experimental example, as shown in FIG. 2, for example, when the burning temperature is too high, the calcined ash is transformed into crystals called cristobalite (quartz crystal). And the pozzolanic activity becomes smaller.

That is, in FIG. 2 showing the relationship between the X-ray diffraction and the crystal lattice, the case A (firing temperature 600 ° C., burning time 8 hr) and the case B (firing temperature 700 ° C., firing time 8 hr) are used. In the case of C, which is amorphous and has pozzolanic activity, but has a higher firing temperature (firing temperature 800 ° C., burning time 4 hr), the X-ray reflection line at the diffraction angle of 21 to 22 degrees (see the figure As is clear in (K portion), the cristobalite phenomenon occurs and the pozzolanic activity becomes small. Further, as shown in Table 2, if the firing time is too long, the surface area tends to be small, and the activity index tends to decrease. Here, the pozzolanic activity means that the stable silicic acid such as silicon dioxide and alumina is gradually combined with the cement under normal temperature and calcium hydroxide generated when the cement is hydrated, and the stability of the inertness. It has the property of forming calcium silicate and the like, and as a result, the cement paste hardened body becomes dense and the concrete strength is improved.

[0010]

[Table 2]

4 is a crushing step, which is a processing step in which the burned ash of the rice husks obtained in the above burning step 3 is crushed into fine powder by ball milling. The rotation speed N of the mill (rp.
m. ) Is based on a value calculated by 32 / root D (D is the inner diameter m of the cylinder of the ball mill). By controlling the rotation speed of the mill to this value, the largest amount of amorphous silica fine powder having a particle size of 1 to 5 μm can be obtained. That is, the rotation speed N of the mill at the time of crushing the calcined ash is determined by an experiment. As an example of this experiment, for example, when the rotation speed N of the mill is 32 / route D as shown in FIG. Is 50.7% with a particle size of 1-5 μm
(1% to 5 μm, occupying the most (weight percent)
The fine powder having a particle size of 10 is the best in the kneading performance when mixing it into concrete.

Further, the one shown in FIG. 4 shows the particle size distribution when the rotation speed N of the mill is 20 / route D. At this time, particles having a particle size of 1 μm or less account for 66.7%, which is the largest. The fine powder having this particle size has poor fluidity when it is mixed with concrete, resulting in poor kneading performance. Therefore, in ball milling, if the rotation speed of the mill is reduced, as shown in FIG. 4, the particles in the mill are crushed to increase the number of fine particles, and if the rotation speed is increased,
As shown in FIG. 3, it tends to be coarse particles. As a result of the experiment, in order to obtain many fine powders having a particle size in the range of 1 to 5 μm, the rotation speed N of the mill should be about 32 / route D. And fine powder with a particle size in this range is suitable for obtaining high-strength concrete, if the particle size is too fine than this, the fluidity during kneading and molding becomes poor, and if the particle size is too coarse, the filling effect Can not be expected and high strength concrete cannot be obtained.

Reference numeral 5 is a concrete mixing step, which is a step of mixing the amorphous silica fine powder obtained in the crushing step 4 into concrete. That is, when the concrete is mixed, the amorphous silica fine powder is added to the cement with water, aggregate,
It is formed by mixing with an admixture. The mixing ratio of the amorphous silica fine powder to the cement is preferably about 20% (weight ratio). Further, as shown in Table 3, it is possible to obtain high-strength concrete in which the compressive strength of the concrete containing the amorphous silica fine powder is comparable to the concrete containing the commercially available silica fume.

[0014]

[Table 3]

[0015]

EFFECTS OF THE INVENTION In the present invention, the raw material is rice husk which can be obtained in a large amount because of the above-mentioned constitution, and after the hydrochloric acid treatment as the pretreatment is performed, the calcination and pulverization thereof are relatively easy. Since it can be obtained by a treatment method, it can be manufactured at low cost, and it is possible to obtain an amorphous silica fine powder having a uniform quality and a rich pozzolanic activity. Also, it is possible to easily control to a particle size that is more suitable than a crushing device such as a commercially available ball mill, and by mixing this with concrete,
There are various effects that high strength concrete with constant strength can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a manufacturing process of amorphous silica fine powder according to the present invention.

FIG. 2 is an X-ray diffraction spectrum diagram of a crystal lattice according to combustion temperature and combustion time.

FIG. 3 is a distribution diagram of particle diameters at a rotation speed of the mill of 32 / route D (where D is the inner diameter m of the mill).

FIG. 4 is a distribution diagram of particle diameters at a rotation speed of the mill of 30 / route D (where D is the inner diameter m of the mill).

[Explanation of symbols]

 1 Rice husk 2 Pretreatment process 3 Firing process 4 Grinding process 5 Concrete mixing process

Claims (2)

[Claims] 1. A method for producing amorphous silica fine powder, characterized in that when the rice husk immersed in a hydrochloric acid solution is fired, the fired ash is crushed into fine powder. 2. A concrete characterized in that, when rice husks dipped in a hydrochloric acid solution are fired, amorphous silica fine powder obtained by crushing the fired ash is mixed in cement. Product.