JPH08157244A - Production of artificial lightweight aggregate - Google Patents

Abstract

PURPOSE: To obtain an artificial lightweight aggregate having a desired specific gravity by using a specific silicon carbide powder as a foaming agent to make the specific gravity low and to control the fluctuation of the specific gravity without changing the firing temp. and the quantity of the foaming agent to be added. CONSTITUTION: An acidic volcanic rock such as rhyolite, perlite, an acidic volcanic ejecta such as rhyolite-dacite volcanic ash, a tuff such as rhyolite-dacite tuff or the like of main raw materials are pulverized into <=30μm in particle diameter to use and 1-7wt.% binder is added to the main raw materials. As the foaming agent, the silicon carbide powder having 5-60wt.% particle <=1μm in particle diameter is used by 0.1-0.5wt.% per the main raw materials and the artificial lightweight aggregate having the desired specific gravity is obtained by controlling the ratio of the particle having <=1μm particle diameter by y=a-bx ((a) and (b) are constants corresponding to the main raw materials to be used) when the content of the particle <=1μm in particle diameter is (x) (wt.%) and the specific gravity of the artificial lightweight aggregate is (y) (wt.%). These are mixed, granulated and fired at 1000-1300 deg.C.

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 a calcinable artificial lightweight aggregate.

[0002]

2. Description of the Related Art Conventionally, a method for producing artificial lightweight aggregate by using powders of acidic volcanic rocks, acidic volcanic ejecta and tuff as raw materials, adding a foaming agent made of silicon carbide powder and firing at 1000 to 1300 ° C. Are known. The artificial lightweight aggregate thus obtained has a relatively high strength and a low water absorption rate despite its small specific gravity, but it has a drawback that it is difficult to obtain a desired specific gravity.

Therefore, in order to obtain a desired specific gravity, the firing temperature is controlled and the amount of the foaming agent added is adjusted. However, in the former case, it is necessary to raise the firing temperature in order to reduce the specific gravity.
There is a problem that the aggregates are fused together during firing. In the latter case, in order to reduce the specific gravity, it is sufficient to increase the amount of the foaming agent added, but this has the disadvantage that the foaming becomes heterogeneous and the strength of the artificial lightweight aggregate is reduced.

The average particle size and the like are also known as a standard for the foaming agent. However, even if an artificial lightweight aggregate is manufactured using a foaming agent judged to be the same according to these criteria, the specific gravity varies, and a preliminary experiment must be conducted every time the foaming agent is obtained from a different source. There was a flaw.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a manufacturing method for manufacturing an artificial lightweight aggregate having a low specific gravity without changing the firing temperature and the amount of the foaming agent added. A further object of the present invention is to provide a method for producing an artificial lightweight aggregate having a desired specific gravity by controlling the variation of the specific gravity of the artificial lightweight aggregate due to the variation of the foaming agent.

[0006]

Under these circumstances, the inventors of the present invention have conducted extensive studies and as a result, have found that the silicon carbide powder used as a foaming agent for producing artificial lightweight aggregates has a particle size of 1 μm.
The inventors have found that by setting the content of the following particles, it is possible to produce an artificial lightweight aggregate having a desired specific gravity without changing the firing temperature or the amount of the foaming agent added, and completed the present invention.

That is, the present invention is characterized in that an artificial lightweight aggregate having a desired specific gravity is produced by using silicon carbide powder having a controlled content of particles having a particle size of 1 μm or less as a foaming agent. .

Among the main raw materials used in the present invention, examples of acidic volcanic rocks include rhyolite, pearlite and quartz andesite, and acidic volcanic products include rhyolite-quartz andesite volcanic ash, Examples include volcanic pumice, and examples of tuff include rhyolite-quartz andesite tuff. Since all of these are rich in glass, they are materials that are easily fired because the decrease in viscosity with increasing temperature is slow.

It is preferable to sinter these main raw materials densely and to pulverize them so as to form fine bubbles so that the average particle diameter is 30 μm or less. More preferably, they are pulverized to 20 μm or less before use. good.

As the binder, bentonite, chlorite,
Examples include clay minerals such as sericite, but bentonite is particularly preferable. The amount of the binder added may vary depending on the average particle size of the main raw material and the like, but it is preferably 1 to 7% by weight with respect to the main raw material so that powdering of the raw material does not occur during firing.

Silicon carbide powder is used as the foaming agent. The amount of the foaming agent added is preferably 0.1 to 1.5% by weight based on the main raw material. If the addition amount is less than 0.1% by weight, only a product having a large specific gravity can be obtained, and if the addition amount exceeds 1.5% by weight, the cells are coarse and non-uniformly dispersed, resulting in a decrease in aggregate strength. Further, the proportion of particles of 1 μm or less in the foaming agent is preferably 5 to 60% by weight. If it is less than 5% by weight, a large amount of unreacted foaming agent is scattered in the product aggregate, resulting in a decrease in aggregate strength. On the other hand, when the content is 60% by weight or more, over-foaming occurs and the strength is lowered. An artificial lightweight aggregate having a desired specific gravity can be obtained by controlling the proportion of particles of 1 μm or less in the foaming agent.

That is, as shown in the embodiments described later,
Assuming that the specific gravity y of the artificial lightweight aggregate and the content x (% by weight) of particles of the silicon carbide powder having a particle size of 1 μm or less are the following y-x relational expressions (where a and b are constants corresponding to the main raw materials used) As shown in, the specific gravity y of the aggregate is 1 μm of the particle size of the silicon carbide powder.
It has a proportional relationship with the content of particles of m or less, and based on this relational expression, an artificial lightweight aggregate having a desired specific gravity can be obtained.

Y = a-bx

Next, the above raw materials and additives are mixed, granulated and fired. Granulation can be carried out using a rolling granulator typified by a pan type pelletizer, a pressure molding machine such as a briquette machine, or various molding machines such as an extrusion molding machine, and pelletizing a few mm to a dozen mm. Grain. A rotary furnace, a vertical furnace, a moving grate furnace, or the like is preferably used for firing the granulated material, and the firing temperature is preferably a temperature higher than the softening point of the main raw material and the foaming temperature of the foaming agent. The specific firing temperature varies depending on the type of main raw material used, components, etc., but is 1000 to 13
The temperature is preferably 00 ° C.

[0015]

The foaming action of the foaming agent is due to the redox reaction of the main raw material silica and silicon carbide. In the firing step, the granulated pellets are sintered and densified as the temperature rises. When the temperature further rises, the pellets start to soften, the foaming agent reacts with the raw material to generate gas, and foaming starts.

At this time, the foaming agent starts to react from the one having a small particle size and completely reacts to the particles having a particle size of about 1 μm. Therefore, fine and uniform bubbles are formed by the reaction of particles having a particle size of 1 μm or less in the foaming agent, and the artificial lightweight aggregate is lightened. When the firing temperature is further increased, the foaming agent particles with a particle size of 1 μm or more also react and participate in foaming, but in this temperature range, the softening of the main raw material progresses further and the air bubbles collapse, resulting in coarse and non-uniform foaming. Strength is reduced. According to the present invention, an artificial lightweight aggregate having a desired specific gravity can be preferably produced by using a silicon carbide powder having a controlled content of particles having a particle size of 1 μm or less as a foaming agent.

[0017]

The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

<Main raw materials and additives> Rhyolite (an anti-firestone from Niijima, Tokyo), which is a type of acidic volcanic rocks, volcanic pumice (quartz andesite pumice tuff from Fukushima Prefecture), which is a type of acidic volcanic ejecta, Shirasu (produced in Kushira, Kagoshima Prefecture) was crushed with a ball mill and used as the main raw material. Table 1 shows the average particle size.

[0019]

[Table 1]

Bentonite (manufactured by Wyoming, USA) was used as the binder, and 3% by weight was added to the main raw material. As the foaming agent, seven kinds of silicon carbide having different average particle sizes shown in Table 2 and particle contents of 1 μm or less were used, and 0.3% by weight was added to the main raw material.

[0021]

[Table 2]

<Granulation Method> The mixed powder of the main raw material, the binder and the foaming agent was well stirred, an appropriate amount of water was added thereto and kneaded well, and then about 1 g was weighed and granulated. This was dried and made into pellets. Average dry weight of pellets is 0.8 ± 0.05
g, average diameter was 8 ± 0.2 mm.

<Baking conditions> The above pellets were heated from room temperature to a baking temperature at 20 ° C / min in an electric furnace, held at the baking temperature for 5 minutes, and then cooled to 1000 ° C at 20 ° C / min. After that, the electric furnace was turned off and naturally cooled in the furnace.
The firing temperature is 1240 for pellets composed mainly of rhyolite.
~ 1300 ℃, since the softening temperature of pellets mainly composed of volcanic pumice and shirasu is lower than that of rhyolite,
It was set to a range of ˜1240 ° C.

<Physical Properties of Fired Product> The specific gravity of the fired product was measured. The following Tables 3 (A) and (B) show the average particle diameters of the artificial lightweight aggregates produced by the above-mentioned procedure, in which the main raw materials shown in NO 1 and NO 2 of Table 1 are anti-fire stones. And specific densities of the aggregates when the foaming agents having different particle contents of 1 μm or less and the firing temperature are changed.
Similarly, the main raw materials are NO3, NO4 volcanic pumice, and NO
5, various characteristics of the artificial lightweight aggregate in the case of Shirasu of NO6 are shown in Tables 4 (A) and (B) and Tables 5 (A) and (B).

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

[Table 5]

Specific gravity and average particle size of the foaming agent for artificial light-weight aggregates of different foaming agents made by using the main raw materials having an average particle size of 7.1 μm shown in Table 3 (A) and having a firing temperature of 1200 ° C. Figure 1 (A) shows the relationship between the diameter and the specific gravity and 1 μm in the foaming agent.
The following relationship with the particle content is shown in FIG. 1 (B), and the relationship between the specific gravity and the particle content of 2 μm or less in the foaming agent is shown in FIG. 1 (C). From FIG. 1 (B), it can be seen that the specific gravity decreases in proportion to the increase in the particle content of 1 μm or less in the foaming agent. However, it can be seen from FIGS. 1 (A) and 1 (C) that there is no correlation between the specific gravity, the average particle diameter of the foaming agent, and the particle content of 1 μm or more in the foaming agent. This means that particles of 1 μm or less play a central role in the particles of the foaming agent that foam the artificial lightweight aggregate.

The above-mentioned tendency is shown in Table 4 (A) and Table 5
It has been confirmed in the main raw material shown in (A), and the firing temperature of 1200 ° C. is shown in FIG.
(A), (B), (C) and FIGS. 3 (A), (B),
It shows in (C). Although not shown, the above tendency was confirmed even when the firing temperature was changed in each main raw material. The relationship between FIG. 1 (B), FIG. 2 (B) and FIG. 3 (B) is that the specific gravity is y and the content of particles of 1 μm or less in the foaming agent is x.
Then, each can be expressed by the following equations.

Y = 1.11-0.019x (1) y = 1.07-0.022x (2) y = 1.08-0.017x (3)

More generally, these equations can be expressed by the y-x relational expression given by y = a-bx. The constants a and b are 1.05 <a <1.15, 0.015 <b <in correspondence with the main raw materials used, the firing temperature, etc. from the above experimental results.
By appropriately setting in the range of 0.025, it becomes possible to calculate the particle content rate of 1 μm or less required according to the desired specific gravity of the aggregate. That is, by obtaining the y-x relational expression in advance, it becomes possible to control the content of particles of 1 μm or less in the foaming agent and extremely easily manufacture an artificial lightweight aggregate having a desired specific gravity. .

In this embodiment, 1 of the foaming agent is used.
We used particles with a particle size of less than μm up to 25.0% by weight.
Are preferably used.

[0033]

As described above, according to the present invention,
By setting the content of particles of silicon carbide powder of 1 μm or less, it is possible to manufacture an artificial lightweight aggregate having a desired specific gravity, and it is possible to meet various diversifying needs and applications very easily.

[Brief description of drawings]

FIG. 1 shows the specific gravity of an artificial lightweight aggregate using an anti-fire stone with an average particle size of 7.1 μm as the main raw material, the average particle size (A) of the foaming agent used, and the particle content of 1 μm or less in the foaming agent ( 2B is a graph showing the relationship between B) and the content of particles (C) of 2 μm or less in the foaming agent.

FIG. 2 is a graph corresponding to FIG. 1 in which volcanic pumice having an average particle size of 7.3 μm is used as a main raw material.

FIG. 3 is a graph corresponding to FIG. 1, using shirasu having an average particle size of 6.8 μm as the main raw material.

Claims (4)

[Claims] 1. A silicon carbide powder having a controlled content of particles having a particle size of 1 μm or less is used as a foaming agent,
A method for producing an artificial lightweight aggregate, which comprises producing an artificial lightweight aggregate having a desired specific gravity. 2. A powder of acidic volcanic rocks, acidic volcanic products or tuff is used as a main raw material, and the powder has a particle size of 1 μm.
The following content of silicon carbide powder was controlled to 0.1%
Add up to 1.5% by weight, mix the binder, and add 1000
A method for producing an artificial lightweight aggregate, which comprises firing at ˜1300 ° C. 3. The method for producing an artificial lightweight aggregate according to claim 2, wherein the acidic volcanic rocks, acidic volcanic ejecta or tuff are anti-firestones, rhyolite, volcanic pumice and shirasu. 4. As the specific gravity y of the artificial lightweight aggregate and the content x (% by weight) of particles of the silicon carbide powder having a particle size of 1 μm or less, the following y-x relational expression (where a and b are main raw materials used) The method for producing an artificial lightweight aggregate according to claim 1 or 2, wherein the content of particles having a particle diameter of 1 µm or less of the silicon carbide powder is controlled by a corresponding constant). y = a-bx