JP3402001B2 - Manufacturing method of artificial lightweight aggregate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial lightweight that uses a coal ash and has a low water absorption under pressure, which can industrially easily manufacture an artificial lightweight aggregate having high strength and low water absorption under pressure. The present invention relates to an aggregate manufacturing method.

[0002]

2. Description of the Related Art In recent years, in order to save energy, save resources, save labor, and improve earthquake resistance, structures such as buildings are required to be made lighter and have heat insulation materials such as wall materials, interior materials and structural materials. This is being promoted, and a large amount of artificial lightweight aggregate is used as aggregate for lightweight concrete. However, since the conventional artificial lightweight aggregate has a very high water absorption rate, it cannot be pumped as it is as concrete. Therefore, although it is used in such a manner that it can be pre-etched to absorb water sufficiently and pumped, concrete using aggregate that absorbs a large amount of water has extremely low durability. That is, the conventional artificial lightweight aggregates have a major drawback that not only pre-etching is required before use, but also highly durable concrete cannot be obtained. Further, if water absorption during pumping is predicted in advance and the amount of kneading water is excessive, pumping may be possible, but concrete using a large amount of kneading water has low strength and is not practical. . For lightweight aggregates that have extremely low water absorption under pressure such as pumping, pre-etching is unnecessary, the amount of kneading water can be reduced, and the lightweight aggregates hardly absorb water. It has high durability and excellent durability. Therefore,
In order to efficiently and inexpensively manufacture high-strength lightweight concrete, it is strongly desired to develop an artificial lightweight aggregate having a low water absorption rate under pressure.

Conventionally, expanded shale artificial lightweight aggregates have been mainly used as artificial lightweight aggregates. Expanded shale artificial lightweight aggregate has the advantage that it can be manufactured at low cost, but cutting of shale is often restricted due to resource depletion, protection of the natural environment, and the like. Therefore, there is a demand for the development of artificial lightweight aggregate that replaces the expansive shale artificial lightweight aggregate, including the redevelopment of unused resources and the use of industrial waste. A technique for producing an artificial lightweight aggregate by effectively utilizing the coal ash that is discharged in large quantities during the combustion of is attracting attention and many proposals have been made.

However, in reality, artificial lightweight aggregates containing coal ash as a main raw material have not been commercialized yet. The main reason for this is that the conventionally proposed method can produce a reasonable amount of lightweight aggregate when it is manufactured in a small amount such as in a laboratory scale. No artificial lightweight aggregates with the desired shape can be obtained due to the collapse of the granules, or the granules fuse together during firing, and only those with low strength or high water absorption can be obtained. It is considered that there is a large variation in quality, or an alkaline-aggregate reaction is likely to occur, resulting in an increase in manufacturing cost and a quality problem.

Regarding the artificial lightweight aggregate mainly composed of coal ash, for example, Japanese Patent Publication No. 38-25820 and Japanese Patent Publication No.
0-16270, JP-B-54-64680, JP-A-59-39757, and JP-B-6-116.
59, JP-A-3-88749, JP-A-4-119952, JP-A-5-170567,
Many proposals have already been made such as JP-A-7-41343. The method of blending shale with coal ash described in JP-A-3-88749, and granulating and firing is likely to cause many open pores on the surface of the fired product, and tends to be a fired product having high water absorption, and crushing strength. Is also low. The mixture of natural glass, water glass and a foaming agent described in JP-A-4-119952 increases the alkali content, so that a large amount of melt is generated during firing and the particles are easily fused to each other, and a lightweight aggregate. As a result, the risk of alkali-aggregate reaction is high, and the crush strength is low. Further, the coal ash described in JP-A No. 5-170567, which is mixed with clay and feldspar, is likely to cause fusion of particles during firing, not only the strength of the fired product is low and the water absorption is high, but also alkali-aggregate reaction Is also very dangerous. The coal ash described in JP-A-7-41343, which contains fine glass powder, silicon carbide and clay, also has a large amount of alkali and has the same drawbacks as the method described in the above publication.

Among the above-mentioned proposals, as a method for producing an artificial lightweight aggregate on an industrial scale, Japanese Patent Publication No. 6-11659 is available.
There is a method proposed in the publication. In this method, coal ash having a standard mesh screen of 297 μm and a residue of 1% by weight or less is used.
After curing a granulated material obtained by granulating a powder raw material containing 1 to 20 parts by weight of a hydraulic material in the presence of water with respect to 00 parts by weight for 20 hours or more, 1000 to 1500 ° C According to this method, the 24-hour water absorption is about 1.2 to 3.6% and the crushing strength is about 15 to
At about 50 kgf, an artificial lightweight aggregate with low water absorption and high strength can be manufactured on an industrial scale. However,
Furthermore, in order to easily pump fresh concrete with high strength without the pre-etching of the artificial lightweight aggregate, in addition to the 24-hour water absorption rate as the artificial lightweight aggregate, it is necessary to consider the pressurized water absorption rate and the crush strength. , Tokuhei 6-11659
There is still room for improvement in the method proposed in the publication.

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to make an artificial lightweight aggregate which has coal ash as a main raw material and has particularly high strength and excellent pressure-absorption-resistant property easily on an industrial scale. An object is to provide a method for manufacturing aggregate. An object of the present invention is to provide an industrial production method of an artificial lightweight aggregate that can further improve the properties of the artificial lightweight aggregate by a conventionally known method using coal ash as a main raw material. The present invention provides a method for producing an artificial lightweight aggregate that can be used as an aggregate for building structures and civil engineering structures, which has been conventionally used as an aggregate for secondary products. And

[0008]

The present invention granulates a powder raw material in which 30 to 120 parts by weight of activated siliceous powder are mixed with 100 parts by weight of coal ash having an unburned carbon content of 1 to 15% by weight. The present invention relates to a method for producing an artificial lightweight aggregate, which comprises firing at a temperature of 1150 to 1350 ° C after molding.

In the present invention, as coal ash, coal ash generated when coal is burned in a combustion furnace of a thermal power plant or various factories, such as fly ash, cinder ash, bottom ash and clinker ash, is required. The coal ash has an unburned carbon content of 1 to 15% by weight, preferably 2 to 10% by weight. When the amount of unburned carbon in the coal ash is too small, the fired product with high crush strength and low water absorption (foam) has a closed spherical shape with fine pores and uniform size inside the fired product.
Is not obtained, and when it is too large, foaming becomes remarkable, and for example, a foamed product having a hollow inside and a specific gravity of about 0.5 is obtained, which is too light for use in pumping concrete.

The coal ash used preferably has a Blaine specific surface area of 2000 cm ² / g or more, more preferably 3000 cm ² / g or more, 3000-14000 c.
Those of m ² / g are particularly suitable. When the Blaine specific surface area is less than 2000 cm ² / g, granulation and molding tends to be difficult, and a Blaine ratio is required to obtain a low water-absorption product having a high crush strength and a closed spherical shape with fine internal pores and uniform dimensions. The surface area is preferably 2000 cm ² / g or more. On the other hand, in order to make the Blaine specific surface area larger than 14000 cm ² / g, a special crushing device is required, so that it is not economical and even if the size is increased, the result is not particularly good.

In the present invention, the active siliceous powder is S
It is preferable that the content of iO ₂ is 60% by weight or more, preferably 70% by weight or more, and the vitreous content is 70% by weight or more. Activated siliceous powder usually contains Al ₂ O ₃ component, CaO component, alkali component and the like in addition to SiO ₂ component. If the content of the SiO ₂ component of the activated siliceous powder is too small, in other words, the Al ₂ O ₃ component, the CaO component,
If the content of alkali components etc. is too high, the viscosity will decrease sharply during the firing process, and the bubbles during foaming will break and become coarse air holes, and open pores due to gas escape, No artificial lightweight aggregate can be obtained. Further, if the amount of glassy material is small, foaming failure tends to occur. Activated siliceous powder is
The Blaine specific surface area is 2000 to 14000 cm ² /
g, preferably 2000 to 10000 cm ² / g is suitable from the viewpoints of obtaining a fired product having fine internal pores and a uniform size and economical efficiency. Typical examples of the activated siliceous powder include quartz trachyte, obsidian, and pearlite.

The amount of the activated siliceous powder is 30 to 120 parts by weight, preferably 50 to 9 parts by weight based on 100 parts by weight of coal ash.
0 parts by weight. If the amount of activated siliceous powder is too small, the glass layer on the surface of the pores of the fired product becomes thin, and the pores are less likely to be a closed type and open pores due to gas escape, resulting in poor pressurized water absorption and crush strength. . On the other hand, if the amount of active silicic acid powder is too large, the foamability of the fired product is poor and the desired artificial lightweight aggregate cannot be obtained.

In the present invention, a predetermined amount of coal ash and activated siliceous powder are granulated and formed into granules. The coal ash and the activated siliceous powder may be mixed at the time of granulation molding or may be mixed in advance. It is usually convenient to perform granulation in the presence of water. In order to obtain a lightweight aggregate that has a closed spherical shape with fine pores and a uniform size inside the fired product, it is better to granulate and mold as little amount as possible. It is preferable to use the minimum amount necessary to maintain the self-morphology. When used, it is appropriately selected from the range of 15 parts by weight or less with respect to 100 parts by weight of the powder raw material. If the amount of water is large, the granulated product will explode during firing, and the pores will tend to be open type. For the granulation and molding, for example, a pan type granulator, a rotary cylinder granulator, a briquette machine, a compression roll machine, a tableting machine and the like are appropriately used. The size and shape of the granulated product is not particularly limited, and it is usually formed into a spherical or cylindrical shape having a particle size of 5 to 20 mm, depending on the use of the artificial lightweight aggregate, but particularly a rugby ball shape. Alternatively, almond shape is preferable. The crushing strength of the granulated product is preferably 1 kgf or more.

In the present invention, when the coal ash and the activated siliceous powder are granulated and molded, the use of a hydrophilic paste material can improve the crushing strength of the granulated product, and the use of water during granulation. Not only can the amount of the granulated product be prevented from exploding during firing, but also the pores tend to be uniform and the amount of heat required for evaporation of water can be reduced. When the amount of the hydrophilic paste material used is too large, it may be difficult to granulate and mold it into a desired shape. Therefore, it is usually 5 parts by weight or less, preferably 0.5 to 5 parts by weight based on 100 parts by weight of coal ash. Used in parts by weight. Typical examples of hydrophilic paste materials include polyvinyl alcohol, cellulose derivatives,
Examples thereof include polyacrylic acid salt, polyacrylamide, synthetic rubber latex, and epoxy polymer emulsion. Among them, polyvinyl alcohol is preferable.

In the present invention, the granulated product obtained by granulation molding may be immediately calcined or may be calcined after being cured to evaporate and condense water and the like in the granulated product. . Curing is generally 0.5-at a temperature of 100-700 ° C.
It will be held for 24 hours. When the granulated product is fired, coal ash particles and activated siliceous particles of the granulated product are combined in a semi-molten state, and moisture, carbon, sulfur and other components in the granulated product react or gas without reacting. As a result, air bubbles are generated inside the granulated product containing the particles in a semi-molten state, resulting in an artificial lightweight aggregate. That is, a viscous glass layer is formed inside the granulated product that has become a semi-molten state by firing, and the generated bubbles are mainly uniformly distributed as independent bubbles inside, and the internal pores of the fired product are fine. It is an artificial lightweight aggregate with a uniform spherical shape and low water absorption and high crush strength. Firing is 1150-
It is carried out in an oxygen-containing gas atmosphere at a temperature of 1350 ° C. If the firing temperature is too low, the air bubbles are insufficiently generated and the granules do not expand sufficiently, and if the firing temperature is too high, the granules are fused and become large lumps, which makes it difficult to operate the firing apparatus. Therefore, the firing temperature is preferably in the above range. For firing, a commonly used firing apparatus known per se, such as a rotary kiln or a sinter grade, can be used.

The artificial lightweight aggregate obtained by firing has 2
4 hours water absorption is 1 wt% or less, 40 kg / cm ² pressurized water absorption is 5 wt% or less, crush strength is 200 kgf or more, and absolute dry specific gravity is 0.8 to 1.5 with uniform closed spherical pores. is doing. The details of the mechanism for obtaining a fired product with such excellent properties are not fully clear, but it is presumed that it is related to the firing temperature, unburned carbon of coal ash, bound moisture of activated siliceous powder, etc. ing.

[0017]

According to the present invention, the main raw material is coal ash,
In particular, an artificial lightweight aggregate having high strength and excellent water absorbency under pressure can be easily produced on an industrial scale, and the characteristics of the artificial lightweight aggregate can be further improved by a conventionally known method. Further, since the artificial lightweight aggregate according to the present invention has high strength and low pressure absorption, it is easy to pump fresh concrete without pre-etching of the artificial lightweight aggregate, and the amount of kneading water can be reduced. The artificial lightweight aggregate that has been conventionally used as an aggregate for secondary products can also be used as an aggregate for high-strength lightweight concrete building structures and civil engineering structures.

[0018]

EXAMPLES In each example, the absolute dry specific gravity and the 24-hour water absorption (% by weight) were measured according to JIS A 1135 "Testing method for specific gravity and water absorption of lightweight structural aggregate". In addition, the amount of pressurized water absorption (% by weight) was measured by placing the foam (calcined product) in a 10 liter autoclave and using a pressure pump to measure the amount of pressurized water absorption at 40 kgf / cm ² . The crush strength (kgf) was measured by using a precision force measuring instrument manufactured by Maruhishi Kagaku Kikai Seisakusho Co., Ltd., in which a foam placed on a sample table is weighted from above to measure the weight when the foam collapses.

Further, the chemical composition (% by weight) of the coal ash and the activated siliceous powder used in each example is shown in Table 1, and the specific gravity, the Blaine specific surface area (cm ² / g), the average particle diameter (μm) and the glass. The mass is shown in Table 2. The glass mass is 297μ for the sample.
After being pulverized to m or less, it was floated and separated by an aqueous zinc bromide solution having a specific gravity of 2.40, and the float was regarded as volcanic glass, and the weight ratio to the whole was determined.

[0020]

[Table 1]

[0021]

[Table 2]

Example 1 5 parts by weight of water was added to 100 parts by weight of coal ash A and 100 parts by weight of quartz trachyte E, 5 parts by weight of water was added, and the mixture was mixed by a magnetic pot mill. A granulated product was obtained. The crushing strength of the granulated product was 2 kgf. Granules are heated in an electric furnace with a heating program at a heating rate of 20 °
The temperature was raised at C / min, and firing was performed at 1200 ° C for 30 minutes to obtain a foam. Physical properties such as absolute dry specific gravity, 24-hour water absorption, pressurized water absorption, and crush strength of the obtained foam were measured. The results are shown in Table 3.

Examples 2 to 3 Foams were obtained in the same manner as in Example 1 except that the amount of quartz trachyte E used in Example 1 was changed to the amount shown in Table 3. Table 3
The measurement results of physical properties of the obtained foam are shown below.

Example 4 A pan type granulator was used for the granulation of Example 1, and the firing temperature was set to 1
Example 1 except that the temperature was changed from 200 ° C to 1190 ° C
A foam was obtained in the same manner as. Table 3 shows the results of measuring the physical properties of the obtained foam.

Comparative Examples 1 to 3 Foams were obtained in the same manner as in Example 1 except that the amount of coal ash A or quartz trachyte E of Example 1 was changed to the amount shown in Table 3. When the amount of quartz trachyte E used is too large (Comparative Examples 1 and 2), the foaming is insufficient and the absolute dry specific gravity is large.
When the amount of the quartz trachyte E is out of the range of the coarse aggregate specified in A-5002 (Comparative Example 3)
Has a large water absorption capacity under pressure. Table 3 shows the results of measuring the physical properties of the obtained foam.

Comparative Examples 4 to 7 In Example 1, except that the firing temperature was changed to the temperature shown in Table 3 and the amount of quartz trachyte E shown in Table 3 was used,
A foam was obtained in the same manner as in Example 1. Firing temperature is 140
When the temperature is too high as 0 ° C (Comparative Example 7), fusion of the fired product is severe and when it is too low as 1000 ° C (Comparative Example 6).
Has a large water absorption capacity for 24 hours and has a very low crushing strength. Further, even when the firing temperature is within the range of the present invention, when the amount of the quartz trachyte E used is small (Comparative Examples 4 and 5), the pressurized water absorption amount is large. Table 3
The measurement results of physical properties of the obtained foam are shown below.

Examples 5-8 100 parts by weight of coal ash A of Example 1 and quartz trachyte E100
From parts by weight, only the kind of coal ash or the kind of activated siliceous powder was changed to the combination shown in Table 4, and the firing temperature was partially changed as shown in Table 4, except that the firing temperature was changed. A foam was obtained. Even if the type of coal ash, the type of activated silicic acid powder, and the firing temperature are different, good results are obtained with a small amount of pressurized water absorption within the scope of the present invention. Table 4 shows the results of measuring the physical properties of the obtained foam.

Examples 9 to 13 In place of 100 parts by weight of quartz trachyte E of Example 1, the type and amount of active siliceous powder were changed to the types and amounts shown in Table 4, except that A foam was obtained in the same manner as in 1. Even if the type and amount of the activated siliceous powder are different, the amount of pressurized water absorption is small and good results can be obtained within the scope of the present invention. Table 4 shows the results of measuring the physical properties of the obtained foam.

Comparative Example 8 A foam was prepared in the same manner as in Example 1 except that coal ash D having a large amount of unburned carbon was used in place of coal ash A and the firing temperature was changed to 1100 ° C. Got Table 4 shows the results of measuring the physical properties of the obtained foam. Comparative Examples 9 to 10 Similar to Example 1 except that the type and amount of the active siliceous powder were changed to the types and amounts shown in Table 4 in place of 100 parts by weight of the quartz trachyte E of Example 1. To obtain a foam. Table 4 shows the results of measuring the physical properties of the obtained foam. When the amount of active siliceous powder used is small regardless of the type (Comparative Examples 9 and 10), the amount of pressurized water absorption is large. Table 3 shows the results of measuring the physical properties of the obtained foam.

Example 14 In Example 1, 2% by weight of a hydrophilic sizing agent (polyvinyl alcohol) was added at the time of mixing the raw material powders in the magnetic pot mill, and pressure molding was performed, and the firing temperature was 1200 ° C. to 1180.
A foam was obtained in the same manner as in Example 1 except that the temperature was changed to ° C. Table 4 shows the results of measuring the physical properties of the obtained foam.

Comparative Example 11 The shale L was used in place of 100 parts by weight of the quartz trachyte E of Example 1.
A foam was obtained in the same manner as in Example 1 except that 100 parts by weight was used. Table 4 shows the results of measuring the physical properties of the obtained foam. It has a large amount of water absorption under pressure and low crush strength.

Example 15 To a raw material powder obtained by adding 100 parts by weight of quartz trachyte E to 100 parts by weight of coal ash A, 5% by weight of water was added and the mixture was molded by a briquette machine, and then a midget rotary kiln (Φ0.4) was used.
5 × 12 m) was used to obtain a foam by firing at a kiln residence time of 100 minutes, a kiln retention rate of 6%, and a firing temperature of 1180 ° C. Absolute dry specific gravity of the obtained foam, 24-hour water absorption,
Physical properties such as water absorption under pressure and crushing strength were measured. The results are shown in Table 4.

[0033]

[Table 3]

[0034]

[Table 4]

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-119952 (JP, A) JP-A-4-238842 (JP, A) JP-A-62-197343 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C04B 18/10

Claims (5)

(57) [Claims] 1. A coal ash 10 having an unburned carbon content of 1 to 15% by weight.
After granulating a powder raw material in which 30 to 120 parts by weight of active silicic acid powder is mixed with 0 part by weight, 1150 to 135
A method for producing an artificial lightweight aggregate, which comprises firing at a temperature of 0 ° C. 2. An activated siliceous powder containing 60% by weight or more of SiO ₂ component and 70% by weight or more of glassy material,
The method for producing an artificial lightweight aggregate according to claim 1, wherein the Blaine specific surface area is 2000 to 14000 cm ² / g. 3. The production of the artificial lightweight aggregate according to claim 1, wherein the activated siliceous powder is one or more kinds of powder selected from the group consisting of obsidian, quartz trachyte and pearlite. Law. 4. The powder raw material contains 1 to 15% by weight of unburned carbon.
30 parts by weight of activated siliceous powder to 100 parts by weight of coal ash
The method for producing an artificial lightweight aggregate according to claim 1, 2 or 3, wherein 20 parts by weight and 5% by weight or less of a hydrophilic paste material are mixed. 5. The method for producing an artificial lightweight aggregate according to claim 1, claim 2, claim 3 or claim 4, wherein the firing is performed in a rotary kiln.