JP2001146444A - Method for producing artificial lightweight aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing artificial lightweight aggregate capable of effectively utilizing industrial waste such as coal ash and stably producing the artificial lightweight aggregate having small absolute specific gravity by a method excellent in moldability. SOLUTION: This method for producing artificial lightweight aggregate comprises granulating a mixed raw material of sewage sludge burned ash with coal ash obtained by pulverizing at least either one of sewage sludge burned ash and coal ash and then compounding both raw materials or a mixed raw material obtained by further compounding the above mixed raw material with shale and then burning the resultant granulated material.

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 an artificial lightweight aggregate, and more particularly to a method for producing an artificial lightweight aggregate capable of effectively utilizing industrial waste.

[0002]

2. Description of the Related Art In recent years, as an aggregate for lightweight concrete,
Artificial lightweight aggregates mainly produced by firing expansive shale are used. The lightweight concrete using the above-mentioned artificial lightweight aggregate is used as a concrete for construction and a concrete for civil engineering.

FIG. 3 shows a process of manufacturing a conventional artificial lightweight aggregate. The gemstone (expandable shale) is first crushed and sieved to obtain a shale having a particle size of 20 to 5 mm (hereinafter referred to as coarse stone), a shale having a particle size of 5 to 3 mm (hereinafter referred to as medium stone), and Shale having a particle size of 3 mm or less (hereinafter referred to as fine stone) is obtained. Next, the obtained coarse crushed stone, medium crushed stone, and fine crushed stone are each baked and sieved to obtain coarse aggregate (particle diameter: 20 to 5 mm, absolute dry specific gravity: 1.29 ± 0.05), Aggregate (particle diameter: 5 to 3 mm, absolute dry gravity: 1.45 ± 0.05), fine aggregate (particle diameter: -3 mm, absolute dry specific gravity:
1.65 ± 0.05).

[0004] Coarse aggregate is used as a natural gravel, and fine aggregate is used as a concrete material corresponding to natural sand. Also, among the artificial lightweight aggregates manufactured by the above manufacturing method,
Coarse aggregate is mainly used as an aggregate of various types of concrete for civil engineering, such as a roadbed material or a lightweight backing material covering ground strength.

[0005] Lightweight concrete using the above-mentioned aggregate is 20 to 30% lighter than ordinary concrete, and has performance equivalent to that of ordinary concrete. Meanwhile, in recent years,
The treatment of industrial waste has become a problem, and the development of a treatment method that enables the recycling of industrial waste is desired. Coal ash (fly ash) generated from the combustion of coal in boilers at thermal power plants The technology of using as a raw material of artificial lightweight aggregate is being developed.

However, when producing artificial lightweight aggregates using industrial waste such as fly ash as a raw material, there are the following problems (1) to (3). (1): The artificial lightweight aggregate obtained has a large absolute specific gravity. (2): Poor moldability when granulating and molding the raw material. (3): Absolute dry specific gravity of the obtained artificial lightweight aggregate fluctuates depending on the quality of the raw material.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, effectively utilizes industrial waste such as coal ash, and produces an artificial lightweight aggregate having a small absolute specific gravity. It is an object of the present invention to provide a method for producing an artificial lightweight aggregate that can be stably produced by a method excellent in quality.

[0008]

SUMMARY OF THE INVENTION The present invention provides a method of granulating and then firing a mixed raw material of sewage sludge incineration ash and coal ash obtained by crushing and blending at least one of sewage sludge incineration ash and coal ash. This is a method for producing an artificial lightweight aggregate, which is a feature. In the present invention described above, the mixed raw material includes:
Further, it is preferable to add a binder (first of the present invention).
Preferred embodiment).

In the present invention and the first preferred embodiment of the present invention, it is preferable that shale is further added to the mixed raw material (second preferred embodiment and third preferred embodiment of the present invention). . Further, in the present invention and the first to third preferred embodiments of the present invention, it is preferable to mix 40 to 185 parts by weight of coal ash with respect to 100 parts by weight of the sewage sludge incineration ash.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present inventors have developed an artificial lightweight aggregate capable of effectively utilizing industrial waste as a raw material, and capable of stably producing an artificial lightweight aggregate having a small absolute specific gravity by a method excellent in moldability. As a result of intensive studies on the manufacturing method, the following findings
(1) to (5) have been found, and the present invention has been achieved.

(1): Blowing action of sewage sludge incineration ash; sewage sludge incineration ash, which is incineration ash of sewage sludge, has a composition close to that of shale, furthermore has a foaming action, and is useful as a raw material for artificial lightweight aggregate. It is. (2): Effect of preventing coalescence of particles during firing by blending of coal ash; fusion of particles during burning of granulated raw material by blending coal ash as a raw material of artificial lightweight aggregate This makes it possible to produce an artificial lightweight aggregate having a predetermined particle size range by a method excellent in yield.

(3): Complementary effect by blending both sewage sludge incineration ash and coal ash; By blending both sewage sludge incineration ash and coal ash as raw materials for artificial lightweight aggregate, the characteristics of both are incompatible. As a result, it is possible to prevent the fusion of the granulated particles at the time of firing and to produce an artificial lightweight aggregate having a low absolute dry specific gravity and a low water absorption.

(4): Improvement of formability by pulverizing sewage sludge incineration ash and coal ash: pulverizing at least one of sewage sludge incineration ash and coal ash to convert both sewage sludge incineration ash and coal ash into artificial lightweight bone When used as a raw material for a material, moldability is improved, the amount of binder (hereinafter also referred to as a binder) and the amount of water added can be reduced, and resource saving and energy saving can be achieved.

(5): Variation in quality of artificial lightweight aggregate due to difference in lots of sewage sludge incineration ash and coal ash and its prevention method: Raw material is obtained by pulverizing at least one of sewage sludge incineration ash and coal ash. The physical properties of the resulting artificial lightweight aggregate are improved, but the quality of the artificial lightweight aggregate varies due to the difference in the chemical composition of each sewage sludge incineration ash and coal ash lot due to pulverization. It is amplified and the foaming property is reduced depending on the lot, and the absolute specific gravity of the obtained artificial lightweight aggregate is increased.

That is, when the present inventors manufacture artificial lightweight aggregates using sewage sludge incineration ash as a raw material, the foaming property of the kneaded material during firing of the kneaded material differs between the rainy season and the drought season when the sewage sludge is collected. I found that new. [Incineration ash of sewer sludge collected during the drought period:]
Since the inflow of natural mud outdoors into the sewer is small, the organic components in the sewer drainage are large, the sewer sludge incineration ash has good foaming properties, and the production of artificial lightweight aggregate having a small absolute dry specific gravity is facilitated.

[Incineration ash of sewer sludge collected in the rainy season:]
During the rainy season, outdoor natural muddy water flows into the sewage system much, so the organic components in the sewage sewage system are low, the effervescence of sewage sludge incineration ash is inferior, and it is difficult to manufacture artificial lightweight aggregates with a small absolute density. Become. The present inventors have conducted intensive studies to solve the above-described problems, and as a result, inferior sewer sludge incineration ash having poor foamability, such as when using coal ash, pulverize at least one of sewer sludge incineration ash and coal ash. At the same time, by blending shale with a raw material containing both sewage sludge incineration ash and coal ash, good moldability and foaming properties are ensured, excellent physical properties, and a small absolute dry specific gravity of artificial lightweight aggregate. Was obtained.

FIG. 1 shows an example of a process chart of the method for producing an artificial lightweight aggregate of the present invention. The production method shown in FIG. 1 (a) is an artificial lightweight method in which both coal ash and sewage sludge incineration ash are pulverized, a binder (binder) and water are added to the pulverized product, kneaded, granulated, and fired. This is a method for producing an aggregate. In addition, the production method shown in FIG. 1 (b) crushes sewage sludge incineration ash,
This is a method for producing an artificial lightweight aggregate in which a binder (: binder) and water are added to a raw material composed of a pulverized product and coal ash, kneaded, granulated, and fired.

In the production method shown in FIG. 1 (c), coal ash is pulverized, a binder (binder) and water are added to a raw material composed of the pulverized product and sewage sludge incineration ash, and the mixture is kneaded and formed. This is a method for producing an artificial lightweight aggregate that is granulated and fired. According to the above-described method for producing an artificial lightweight aggregate of the present invention, it is possible to produce a target artificial lightweight aggregate having a small absolute dry specific gravity by a method excellent in moldability.

Under the above manufacturing conditions, the moldability is improved by the action and mechanism of the following (1) to (3),
This is considered to be because an artificial lightweight aggregate having a small absolute dry specific gravity is formed without causing fusion of the particles of the granulated material during firing. (1): Foaming action of sewage sludge incineration ash; sewage sludge incineration ash has a loss on ignition (JIS R 5202) of about 0.1 to 3.0% [mass percentage (hereinafter referred to as mass%)]. When baking the granulated material of the raw material containing the compound, the granulated material particles expand due to the generation of gas from inside the granulated material particles corresponding to the ignition loss of the sewage sludge incineration ash in a high temperature range.

As a result, according to the present invention, an artificial lightweight aggregate having a small absolute density and having a large number of air bubbles inside the particles can be manufactured. (2) Effect of preventing coalescence of particles during firing by blending of coal ash; fusion of particles during burning when using sewer sludge incineration ash can be prevented by blending of coal ash.

It is considered that this is because the melting point of the raw material increases due to alumina in the coal ash. (3): Improvement of formability by pulverizing coal ash and sewage sludge incineration ash: By crushing at least one of sewage sludge incineration ash and coal ash, the number of contact points between particles increases, and kneading and mixing of raw materials The formability at the time of granulation is improved, the amount of binder added, the amount of water added can be reduced, and resources can be saved, and the latent heat of evaporation during firing decreases, so that energy can be saved. .

Next, FIG. 2 shows another example of a process chart of the method for producing an artificial lightweight aggregate of the present invention. The production method shown in FIG. 2 (a) crushes both sewage sludge incineration ash and coal ash,
This is a method for producing an artificial lightweight aggregate in which shale, a binder (: binder) and water are added to a ground product, kneaded, granulated, and fired. 2 (b) and 2 (c), the sewage sludge incineration ash and coal ash are pulverized, and the shale, binder (binder) and water Is added, kneaded, granulated, and then fired to produce an artificial lightweight aggregate.

As described above, the present inventors use the incinerated ash of sewage sludge discharged in the rainy season as a raw material for artificial lightweight aggregates. It was found that the amount of organic components in the sewage drainage was low due to the large amount of ash, and that the sewage sludge incineration ash was inferior in foamability.
On the other hand, according to the present invention, when sewage sludge incineration ash and coal ash having inferior foaming properties are used, sewage sludge incineration ash and coal ash are pulverized, and by adding shale to the raw material, good shaping is achieved. This makes it possible to obtain an artificial lightweight aggregate having sufficient properties and foaming properties, excellent physical properties, and a small absolute specific gravity.

In the present invention, even when sewage sludge incineration ash or coal ash having no foaming problem is used, at least one of the sewage sludge incineration ash and coal ash is pulverized, and the sewage sludge incineration ash and coal ash are used. By further blending shale with the raw material containing the coal ash, it is possible to obtain an artificial lightweight aggregate having more excellent moldability and foaming properties, excellent physical properties, and low absolute dry specific gravity.

In the present invention, the sewage sludge incineration ash 100
It is preferable to mix 40 to 185 parts by weight of coal ash with respect to parts by weight. When the blending amount of the coal ash is less than 40 parts by weight, the effect of preventing the fusion of the particles of the granulated material due to the blending of the coal ash is small, and the artificial lightweight aggregate having a predetermined particle size range can be produced by a method excellent in yield. It is difficult to manufacture.

Conversely, if the amount of coal ash exceeds 185 parts by weight, the specific gravity of the dry bone becomes large, making it difficult to obtain a lightweight aggregate. Also, if the blended amount of coal ash exceeds 185 parts by weight, the obtained artificial lightweight aggregate will have a large increase in water absorption for 24 hours, and it will be necessary to cope with the pumping of ready-mixed concrete containing artificial lightweight aggregate. It becomes necessary to absorb water sufficiently by presoaking, and the productivity in the production and shipping of artificial lightweight aggregates is reduced.

The sewage sludge incineration ash, coal ash, binder and a suitable production method used in the present invention will be described below. [Sewage sludge incineration ash:] Sewage sludge incineration ash as industrial waste has a composition similar to that of shale, which has been conventionally used as a raw material for artificial lightweight aggregates, and its main components are SiO ₂ , Al ₂ O ₃ and It is an oxide of iron and has a very small particle size.

The composition of the sewer sludge incineration ash used in the present invention is preferably the following composition as a sample composition after drying at 100 ° C. Preferred compositions of the Sewer sludge incineration ash; SiO _2: 20 to 80 wt%, Al ₂ O _3: 5~30 wt%, Fe ₂ O _3:
2 to 20% by mass Also, as sewage sludge incineration ash, JIS R 5202-1989
Loss on ignition by (chemical analysis method of Portland cement) is preferably 0.1 to 3.0% by mass, more preferably
It is preferable to use sewage sludge incineration ash of 0.2 to 2.0% by mass.

When the ignition loss is less than 0.1% by mass, the amount of gas generated is small and the weight reduction by foaming becomes insufficient. On the other hand, when the ignition loss exceeds 3.0% by mass, foaming becomes remarkable and obtained. This is because the strength of the artificial lightweight aggregate may be insufficient. Conventionally, disposal of sewage sludge incineration ash has been an important problem. According to the present invention, these problems can be largely solved.

[Coal ash:] Coal ash as industrial waste is mainly composed of oxides of SiO ₂ , Al ₂ O ₃ and iron, and has a composition close to that of shale. As the coal ash used in the present invention, it is preferable to use coal ash generated from the combustion of coal in a boiler of a thermal power plant from a quantitative point of view. There is no restriction.

The coal ash used in the present invention is preferably a coal ash having the following composition after drying at 100 ° C. Preferred compositions of coal ash; SiO _2: 50 to 75 wt%, Al ₂ O _3: 15~30 wt%, Fe ₂ O _3:
0.5 to 10% by mass [Binder:] In the present invention, it is preferable to add a binder to the compounding raw material.

The binder is not particularly limited in view of the above-mentioned gist of the present invention, but is preferably one selected from bentonite, lignin, pulp waste liquor, polyvinyl alcohol, styrene-butadiene latex, carboxymethyl cellulose and the like. Or two or more types are exemplified, and it is more preferable to use bentonite.

When bentonite is used, for example, the amount of the binder added is preferably 3 to 30% by mass based on the total raw materials (dry amount). [Manufacturing Method] As shown in FIGS. 1 and 2 described above, in the present invention, a raw material in which sewage sludge incineration ash and coal ash are blended is used.

That is, water is added to a mixed raw material of sewage sludge incineration ash and coal ash obtained by pulverizing and blending at least one of sewage sludge incineration ash and coal ash, granulating, firing, and then sieving. To produce artificial lightweight aggregate. The amount of water added to the raw material depends on the amount of water in the raw material during granulation.
The added amount is preferably 15 to 35% by mass.

In the present invention, as described above, it is more preferable to mix a binder (: binder) and shale with the raw material. As the granulation method, an extrusion molding machine (: an extrusion granulation machine), a pan-type pelletizer, and the like can be used, and the method of the granulation method is not particularly limited, but the obtained artificial lightweight aggregate is obtained. It is more preferable to use an extrusion molding machine from the viewpoint of strength.

In firing the granulated product, a rotary kiln, a great firing furnace, a fluidized roasting furnace, or the like can be used, and the firing method is not particularly limited. The sintering temperature is preferably 1000 to 1150 ° C., and more preferably 10 to 1150 ° C.
The temperature is more preferably from 00 to 1100 ° C. Firing temperature 1000
If the temperature is lower than ℃, the foaming in the granulated particles does not proceed sufficiently, and the absolute density of the obtained aggregate is large.On the contrary, if it exceeds 1150 ° C, gas is rapidly generated, and uniform and sufficient Foaming and expansion do not progress, and the absolute dry specific gravity increases as described above.

The method for producing an artificial lightweight aggregate according to the present invention has been described above. According to the present invention, industrial wastes such as sewage sludge incineration ash and coal ash are used to the maximum and an artificially dried specific gravity having a small absolute density is used. A lightweight aggregate can be manufactured by a method excellent in formability. In the present invention, in addition to sewage sludge incineration ash, coal ash, shale and the above-mentioned binder, unless otherwise detrimental to the purpose of the present invention, volcanic pebble (pumice) conventionally used in the production of artificial lightweight aggregates And additives such as silicon carbide (foaming aid).

[0038]

EXAMPLES The present invention will be described below more specifically based on examples. [Example 1] (Examples 1 to 22 of the present invention and Comparative Examples 1 to 11) According to the above-described production process shown in Fig. 1, an artificial lightweight aggregate was produced using both sewage sludge incineration ash and coal ash as raw materials.

That is, as shown in Table 1, a predetermined amount (40 parts by weight: 60 parts by weight or 60 parts by weight: 40 parts by weight) of sewage sludge incineration ash and coal ash, at least one of which has been pulverized, is mixed. Was added with the amount of water shown in Table 1 and kneaded with a kneader. In addition, bentonite was added to the raw material before adding water in a blending amount shown in Table 1 as a binder.

The sewage sludge incineration ash and coal ash are pulverized by using a ball mill, and the 50% cumulative average particle diameter after pulverization is 5 to 10 μm [pulverized product for 4 hours (4h pulverized product),
8 hours pulverized product (8h pulverized product)]. In addition, a laser diffraction type particle size distribution measuring device was used as a particle size distribution measuring device.

As the sewage sludge incineration ash, sewage sludge incineration ash having the following particle size, composition and ignition loss was used, and as coal ash, coal ash having the following composition generated in a thermal power plant was used. (Sewage sludge incineration ash :) 50% cumulative average particle size: 20 μm Composition of sample after drying at 100 ° C .: SiO ₂ ; 35% by mass, Al ₂ O ₃ ;
18 mass%, Fe ₂ O ₃ ; 4 mass% Loss on ignition [JIS R 5202-1989]: 2.0 mass% (coal ash :) 50% cumulative average particle size: 15 to 25 μm SiO ₂ : 60 mass%, Al ₂ O ₃ : 22% by mass, Fe ₂ O ₃ : 4% by mass Next, a sample for a plastic limit test as an index of formability was collected from the obtained kneaded product.

Next, the kneaded material was granulated by using an extrusion molding machine (: an extrusion granulator), fired at 1080 ° C. by a rotary kiln, and then subjected to a 20 mm mesh sieve (mesh size: 19 m).
m) The mixture was sieved with a 5 mm mesh sieve (mesh size: 4.75 mm) to produce an artificial lightweight aggregate (coarse aggregate) having a particle size of 20 to 5 mm (Examples 1 to 22 of the present invention). In addition, a test was performed in the same manner as in Examples 1 to 22 of the present invention described above, using either unmilled sewage sludge incineration ash, unmilled coal ash, or both as raw materials (Comparative Examples 1 to 11). ).

Next, using the obtained sample for the plastic limit test, a plastic limit test of the kneaded material which is an index of the formability of the kneaded material is performed, and the artificial lightweight aggregate (coarse aggregate) is dried. Specific gravity, 24-hour water absorption (hereinafter also referred to as 24h water absorption) and crushing strength were measured. In addition, the absolute dry gravity, the measurement of 24 hours of water absorption, and the plastic limit test were performed based on the following test methods.

[Dry specific gravity, 24 hour water absorption:] JIS A 1135
It measured based on. [Plastic limit test:] Test based on JIS A 1205,
The moldability of the kneaded product was evaluated according to the following criteria. ：: A predetermined amount of water is added, and molding can be performed sufficiently to a diameter of about 3 mm.

：: A predetermined amount of water was added, and although there were some cracks, molding was possible up to a diameter of about 3 mm. ×: Molding to a diameter of about 3 mm is impossible even when a predetermined amount of water is added. Table 2 shows the obtained test results. As shown in Tables 1 and 2, it was found that the following effects (1) to (3) were obtained according to the present invention.

(1) By using both sewage sludge incineration ash and coal ash, it is possible to obtain the desired artificial lightweight aggregate having a small absolute specific gravity. (2) By grinding and using sewage sludge incineration ash and coal ash, it is possible to obtain an artificial lightweight aggregate having good formability as shown in the plastic limit test and excellent crushing strength.

(3) By setting the blending amount of coal ash with the incineration ash of sewerage sludge in the preferred range of the present invention, fusion of particles at the time of firing the granulated product is prevented, and artificial light weight having a low water absorption rate for 24 hours is obtained. Aggregate can be obtained.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

[0051]

[Table 4]

[0052]

[Table 5]

[0053]

[Table 6]

Example 2 (Examples 27 to 32 of the present invention, Comparative Example 1)
2, 13) A test was conducted in the same manner as in Example 1 except that shale was further added to the raw material in Example 1 described above (Examples 27 to 32 of the present invention). In addition, a test was performed on the raw material containing no shale in the same manner as in Example 1 (Comparative Examples 12 and 13).

Table 3 shows the raw material composition. In this example, as the incineration ash of the sewage sludge, the ash of the sewage sludge discharged from the sewerage sludge discharged in the rainy season, having the following particle size, composition and loss on ignition, was used. (Sewage sludge incineration ash :) 50% cumulative average particle size: 20 μm Composition of sample after drying at 100 ° C .: SiO ₂ ; 33.4% by mass, Al
₂ O ₃ ; 16.5 mass%, Fe ₂ O ₃ ; 7.6 mass% Loss on ignition [JIS R 5202-1989]: 0.7 mass% The test results obtained are shown in Table 4.

The incineration ash of sewer sludge discharged in the rainy season is:
Low ignition loss and low organic components. As a result, Table 4
As shown in the figure, when sewer sludge incineration ash discharged in the rainy season is used, the foaming property at the time of firing is inferior, the absolute specific gravity is large (Comparative Example 12), and the sewer sludge incineration ash is not pulverized. , Poor formability shown in plastic limit test (Comparative Example
13).

On the other hand, as shown in Table 4, at least one of sewage sludge incineration ash and coal ash was pulverized, and shale was further blended as a raw material, whereby formability indicated in the plastic limit test was confirmed. And an artificial lightweight aggregate excellent in crushing strength and small in absolute dry weight was obtained.

[0058]

[Table 7]

[0059]

[Table 8]

[0060]

According to the present invention, the following excellent effects (1) to (4) can be obtained, industrial waste can be effectively used, and an artificial lightweight aggregate having a small absolute specific gravity can be manufactured. It has become possible. (1) By using both sewage sludge incineration ash and coal ash, it is possible to obtain the desired artificial lightweight aggregate having a small absolute dry specific gravity.

(2) By crushing and using sewage sludge incineration ash and coal ash, it is possible to obtain an artificial lightweight aggregate having good formability as shown in the plastic limit test and excellent crushing strength. Further, by crushing and using sewage sludge incineration ash and coal ash, the addition amount of bentonite as a binder can be significantly reduced, and the addition amount of water can be reduced, thereby achieving energy saving.

(3) By setting the blending amount of coal ash to incineration ash of sewerage sludge within the preferred range in the present invention, fusion of particles at the time of firing of granulated material is prevented, and artificial water having a low water absorption rate for 24 hours is prevented. A lightweight aggregate can be obtained. (4) In addition to pulverizing sewage sludge incineration ash and coal ash and further blending shale as a raw material, even when using a raw material with poor foamability, it is excellent in formability and an artificial light weight with a low absolute dry specific gravity. Aggregate can be manufactured.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of a method for producing an artificial lightweight aggregate of the present invention.

FIG. 2 is a process chart showing an example of a method for producing an artificial lightweight aggregate of the present invention.

FIG. 3 is a process chart showing a conventional method for producing an artificial lightweight aggregate.

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Claims (4)

[Claims] An artificial lightweight aggregate characterized in that a mixed raw material of sewage sludge incineration ash and coal ash obtained by pulverizing and blending at least one of sewage sludge incineration ash and coal ash is granulated and then fired. Production method. 2. The method for producing an artificial lightweight aggregate according to claim 1, wherein a binder is further added to the mixed raw material. 3. The method for producing an artificial lightweight aggregate according to claim 1, wherein shale is further added to the mixed raw material. 4. The method for producing an artificial lightweight aggregate according to claim 1, wherein 40 to 185 parts by weight of coal ash is mixed with 100 parts by weight of the sewage sludge incineration ash.