JP2002160952A - Artificial lightweight aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide artificial lightweight aggregate which is manufactured by using incinerator ash of sludge, etc., and treating at a low temperature about 100 deg.C to suppress the elution of hazardous substances. SOLUTION: An inorganic powder mix comprising calcium silicate and incinerator ash of 100 pts.wt. and lightweight aggregate or synthetic resin powder of 5-50 pts.wt. are mixed, agglomerated and carbonated to give the lightweight aggregate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight artificial lightweight aggregate capable of mixing incinerated ash as an aggregate into cement and concrete materials.

[0002]

2. Description of the Related Art At present, volume reduction by incineration is adopted for disposal of general garbage and sewage sludge. These wastes are greatly reduced in volume by incineration, and can also solve problems such as putrefaction odor. However, such waste treatment by incineration also causes problems such as generation of harmful substances by incineration and harmful heavy metals remaining.
On the other hand, a method of directly treating incinerated ash or waste at a high temperature, vitrifying it and treating it in a slag state has been studied (for example, a technology for manufacturing a permeable block using sewage sludge; monthly sewerage). Vol.17 No.4,
1994). Such a slag-forming method is an effective method of treating harmful organic substances because harmful organic substances are thermally decomposed and the diffusion rate of heavy metals is extremely low. However, there is a problem that it is very large and requires large-scale equipment.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is possible to perform a treatment for suppressing the elution of harmful substances from incinerated ash such as sludge at a low temperature of about 100 ° C. It is an object of the present invention to provide an artificial lightweight aggregate that can utilize incinerated ash that can also be expected to be lightweight.

[0004]

According to the present invention, a lightweight aggregate or a synthetic resin powder is mixed with 5 to 50 parts by weight with respect to 100 parts by weight of an inorganic mixed powder comprising calcium silicate and incinerated ash. An artificial lightweight aggregate characterized by being carbonized after being granulated.

[0005] The incinerated ash is not particularly limited as long as it is in the form of powder, and includes, for example, general refuse incinerated ash and sludge incinerated ash. is there.

[0006] The calcium silicate material is an inorganic material in which calcium and silica are combined, and examples thereof include natural minerals such as cement and wollastonite; and slag generated in steel works. Among the above calcium silicate materials, cement is particularly preferable because it is inexpensive and easy to granulate.

[0007] The cement is not particularly limited as long as calcium hydroxide is produced with hydration. For example, ordinary Portland cement, special Portland cement, alumina cement and the like can be used. However, Portland cement is preferred in that the effect of densification during the carbonation treatment is large.

The above Portland cement is a cement mainly composed of an unhydrated calcium silicate compound called alite (C3S: 3CaO.SiO ₂ ) or belite (C2S: 2CaO.SiO ₂ ).
Mixed cements such as ordinary Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, sulfate-resistant Portland cement, various low-alkali type Portland cements, blast furnace cement, silica cement, fly ash cement, etc. And white cement.

The mixing ratio of incinerated ash in the inorganic mixed powder comprising calcium silicate and incinerated ash is 1
The range of 0 to 80 wt% is preferable. 80 wt% incinerated ash
If it is larger, the effect of suppressing the elution of harmful substances will not be sufficiently exhibited,
If it is less than 10 wt%, there is no problem in controlling harmful substances, but the effectiveness is low from the viewpoint of effective utilization of incinerated ash. More preferably, it is 25 to 65 wt%.

The compounding amount of the above-mentioned lightweight aggregate or synthetic resin powder is 5 to 50 parts by weight based on 100 parts by weight of the inorganic mixed powder comprising calcium silicate and incinerated ash.
If the amount is less than 5 parts by weight, the effect of reducing the weight is reduced. Further, the water absorption of the obtained artificial lightweight aggregate also increases. More preferably, it is 10 to 35 parts by weight.

The above-mentioned lightweight aggregate is not particularly limited. For example, inorganic lightweight aggregates such as pearlite, shirasu balloon, fly ash balloon and glass balloon; organic lightweight aggregates such as styrene beads and polyethylene beads are used. Among these lightweight aggregates, inorganic lightweight aggregates that undergo little dimensional change due to changes in moisture and temperature are preferable.

Although the above synthetic resin powder is not particularly limited,
The lower the specific gravity, the greater the weight reduction effect even if the amount added is small. The particle size is preferably 2 mm or less because granulation is easy. In addition, industrial waste such as pulverized waste plastic and processing waste in the manufacturing process can be effectively reused as the synthetic resin powder. As the resin constituting the synthetic resin powder, for example, vinyl chloride resin,
Examples include polyethylene and FRP.

The method of mixing and granulating according to the present invention is not limited, but since the materials can be uniformly dispersed, calcium silicate, incinerated ash, and artificial lightweight aggregate / synthetic resin powder are once mixed in a dry manner. A method of adding water and mixing after homogenization is preferable. These mixing and granulating methods include, for example, tumbling, extrusion, tableting, uniaxial stirring, and a mixer (Henschel mixer).

The carbonation treatment of the present invention means a treatment for promoting a carbonation reaction of a calcium component in the calcium silicate material. As a method of the carbonation treatment, carbon dioxide gas having an arbitrary concentration or carbon dioxide in a supercritical state can be used.

The carbonation temperature is 30 to 20.
Preferably it is 0 ° C. If the temperature is lower than 30 ° C., it takes a long time for the carbonation reaction to take place sufficiently,
If the temperature is higher than 00 ° C., the carbonation reaction becomes quick, but large energy is required, and the equipment becomes large-scale. When the organic reinforcing fiber or the like is contained in the aggregate, the fiber or the like may cause thermal deterioration.

The pressure of the carbonation treatment is 0.1 M
The range of Pa to 15 MPa is preferable, and particularly when the treatment is performed in the initial stage of hydration, if the pressure is lower than 0.1 MPa, the carbonation reaction may be insufficient or a sufficient carbonation reaction may require a long time. . On the other hand, even if the pressurizing pressure is higher than 15 MPa, the rate of the carbonation reaction does not change much. Conversely, only a large amount of energy is required, and rationality is inevitable from the viewpoint of industrial productivity and enlargement of equipment. Appropriate.

The time for the carbonation treatment depends on the particle size of the cement or granulated material to be used, but is preferably within 24 hours when the treatment is performed within the above-mentioned preferred temperature and pressure ranges. More preferably, it is 5 to 60 minutes.
If the treatment time is shorter than 5 minutes, the carbonation reaction is unlikely to occur sufficiently. On the other hand, if the treatment time is longer than 24 hours, the carbonation reaction does not proceed any more, and the carbonation effect is not easily improved anymore, and conversely, it is not reasonable in terms of energy consumption and equipment.

It is preferable that the calcium silicate is a cement, since granulation is facilitated by adding water. In this case, the amount of water is preferably from 10 to 300 parts by weight based on 100 parts by weight of the inorganic mixed powder composed of calcium silicate and incinerated ash. If it exceeds this range, granulation becomes difficult.

In the case of granulating a mixture comprising the cement, incinerated ash and water, an aggregate having good physical properties is obtained by granulating with a uniaxial stirrer (eg, "Henschel mixer" manufactured by Mitsui Mining Co., Ltd.). This is preferable in that it can be performed.

The carbonation treatment is performed after the stage in which the final shape is obtained by the granulation step. Preferably, the hydration ratio of the calcium silicate compound contained in the cement is preferably at the initial stage of hydration of the cement. % (Substantially immediately after granulation) to 30%.

The hydration rate of the calcium silicate compound is as follows:
Assuming that the amount of the unhydrated calcium silicate compound contained in the cement raw material is A and the amount of the remaining unhydrated calcium silicate compound at the time of measuring the hydration ratio is B, a value represented by [(AB) / A] × 100 Say. As a method for measuring the amount of unhydrated calcium silicate compound (alite and belite) in cement, an X-ray diffractometer or a nuclear magnetic resonance apparatus (29Si-N
A known method utilizing MR) can be used (N
References for methods utilizing MR: Parry-Jo
nes, Cementand Concrete Re
search, Vol. 19, p228-234,19
89).

In addition, at the time of the carbonation treatment, the water / cement ratio of the granulated material to be subjected to the carbonation treatment is 0.075 to
It is preferably in the range of 0.5. The water / cement ratio of the granulated product is a value obtained by dividing the weight of water contained in the granulated product by the weight of the cement component.
When it is lower than 5, the reaction with carbon dioxide does not sufficiently occur, and the efficiency of the carbonation reaction decreases. Conversely, if the water / cement ratio is higher than 0.5, the excess water existing between the cement particles hinders the diffusion of carbon dioxide, and the carbonation reaction in the initial stage of the hydration reaction does not sufficiently occur. If the water / cement ratio of the granulated material is lower than 0.075, newly add water, and if it is higher than 0.5, remove excess water by suction or the like. , Finally 0.075-0.5
Should be within the range.

Further, even when the water / cement ratio is more than 0.5, by delaying the carbonation treatment, part of the excess water that inhibits diffusion is used for the hydration reaction, Although the carbonation reaction may proceed by evaporating from the water, it is more effective to prepare an appropriate amount of water and carbonate at the beginning of the hydration reaction. The optimum water / cement ratio varies depending on the amount of cement and aggregate used, but the water / cement ratio is most preferably 0.1 to 0.4.
By providing a layer of only a calcium silicate material on the surface of the granulated material, the harmful substance control effect can be further enhanced.

(Operation) In the artificial lightweight aggregate of the present invention, the incinerated ash is dispersed in the carbonated dense calcium silicate tissue, so that the diffusion and movement of harmful substances are suppressed. Further, since the waste is used as the main material of the aggregate, it is very useful from the viewpoint of effective use of the waste. Further, by mixing a synthetic resin powder or a fine lightweight aggregate, the specific gravity of the aggregate is reduced, so that it can be used as a lightweight aggregate.

[0025]

(Examples 1 and 2) According to the composition shown in Table 1, ordinary Portland cement, sludge incineration ash and fly ash balloon were uniformly mixed with a Henschel mixer (Mitsui Mining Co., Ltd.). Water 3 in the above mixture
5 parts by weight were added, and granulation was subsequently performed with a Henschel mixer to obtain a granulated product having a diameter of about 10 mm. The granulated product was taken out of the mixer, cured at room temperature for 6 hours, placed in an autoclave, and subjected to carbon dioxide treatment at a temperature of 100 ° C. and a pressure of 8 MPa for 30 minutes to obtain an artificial lightweight aggregate.

(Examples 3 and 4) According to the composition shown in Table 1, ordinary Portland cement, sludge incineration ash, and vinyl chloride resin powder were mixed with a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.).
And mixed uniformly. 35 parts by weight of water was added thereto, and the mixture was granulated with a Henschel mixer, and the diameter was 10 mm.
Granules of a degree were obtained. The granulated product was taken out of the mixer, cured at room temperature for 6 hours, placed in an autoclave, and subjected to carbon dioxide treatment at a temperature of 100 ° C. and a pressure of 8 MPa for 30 minutes to obtain an artificial lightweight aggregate. In addition, the cutting powder generated at the time of processing a vinyl chloride resin pipe was used for the above-mentioned vinyl chloride resin powder.

(Comparative Example) According to the composition shown in Table 1, except that fly ash balloon and vinyl chloride resin powder were not blended, a granulated product was obtained in the same manner as in the above example, and carbonation was performed. It was cured at room temperature for one week without treatment to obtain an artificial lightweight aggregate.

[Aggregate Dissolution Test] The Aggregate obtained in the above Examples and Comparative Examples was used and evaluated without pulverization. Prepare a test solution for a heavy metal elution test in accordance with the method shown in "Environmental Standards for Soil Contamination", and quantify Cd, Pb, Se, As, and T-Cr (total chromium) by ICP emission analysis. Was done. The results and test data of the sludge incineration ash are shown in Table 1.

[Aggregate Compressive Strength Test] Using the aggregates obtained in Examples and Comparative Examples, the maximum strength of the aggregate at the time of compressive fracture was measured at a test speed of 5 mm / min. The strength was calculated by dividing the maximum load by the cross-sectional area of the aggregate. Table 2 shows the results of specific gravity, water absorption and compressive strength of these aggregates.

As can be seen from Table 2, no harmful heavy metals are eluted from the incinerated ash aggregate produced in the examples. On the other hand, in the comparative example, elution of Cr is observed. Also,
As can be seen from Table 3, the artificial lightweight aggregates of Examples 1 to 4 are superior in both mechanical strength and denseness (water absorption) to those of Comparative Example.
In addition, the weight can be reduced by adding the lightweight aggregate, and the result is suitable as a lightweight aggregate for concrete.

[0031]

[Table 1]

[Table 2]

[Table 3]

[0032]

The artificial lightweight aggregate of the present invention can be used for cement and concrete as well as general aggregate. Normally, when incinerated ash is used as a civil engineering material, it is in powder form and is poorly handled, and harmful heavy metal components may be eluted.
However, in the artificial lightweight aggregate of the present invention, the incineration ash is dispersed in the carbonated dense calcium silicate tissue, so that elution of harmful substances is suppressed.
In addition, the artificial lightweight aggregate of the present invention can be easily and simply manufactured by performing a low-temperature carbonation treatment, and can provide an artificial aggregate at low cost because it is a low-energy treatment. Also, by adding a lightweight aggregate having a low specific gravity or a synthetic resin powder, the above-mentioned aggregate can be given lightness, and can be used as a lightweight aggregate. Furthermore, waste plastics such as incinerated ash and vinyl chloride resin, which are generally difficult to treat as waste, can be effectively used as raw materials, which is significant for recyclability.

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Claims (3)

[Claims] 1. After mixing and granulating 5 to 50 parts by weight of a lightweight aggregate or a synthetic resin powder with respect to 100 parts by weight of an inorganic mixed powder composed of calcium silicate and incinerated ash,
An artificial lightweight aggregate characterized by being carbonated. 2. The artificial lightweight aggregate according to claim 1, wherein the calcium silicate is cement. 3. The artificial lightweight aggregate according to claim 1, wherein the content of the incinerated ash in the inorganic mixed powder is 10 to 80 wt%.