JPS6256097B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a hardened body using coal ash discharged during coal combustion as a main raw material, specifically, to coal ash, slaked lime or/and quicklime, and dihydrate gypsum, hemihydrate gypsum or/and type anhydrous gypsum are added. Knead the mixed powder with water,
The present invention relates to a method for producing a hydrated material with high mechanical strength by curing at room temperature. In recent years, the development of alternative energy sources for oil in order to reduce our dependence on oil has become a national issue in our country, and coal energy is attracting attention as one of the pillars of energy. One of the challenges in the practical application of coal utilization technology to cope with the large consumption of coal as a primary energy source is the disposal of large amounts of coal ash generated during coal combustion. When burning coal, usually almost 10 to 20 of the coal usage
% coal ash is generated. The so-called pulverized coal combustion ash generated from a typical pulverized coal combustion boiler is classified into bottom ash, cinder ash, and fly ash, depending on where it is generated, and of these, fly ash accounts for the majority of the amount generated. Traditionally in Japan, a portion of fly ash has been reused as cement admixtures, cement raw materials, etc.
The rest is disposed of in landfills. However, it is not possible to expect enough demand to meet the huge amount of coal ash that will be generated in the future through current recycling methods alone. With the tightening of environmental regulations, it is becoming increasingly difficult to secure land for coal ash disposal. It is expected that it will be difficult to dispose of this amount of coal ash. Furthermore, when considering mass processing technology for coal ash, it is necessary to aim for reuse as much as possible without causing environmental pollution. This is because in a country with limited domestic resources and limited land, it is important to reuse coal ash as a resource rather than simply dumping it. In view of the above points, the present invention utilizes coal ash in large quantities in the civil engineering sector, such as as a soil material for sea surface reclamation and land reclamation, as a soil improvement material for soft ground, and as a road base material for road construction. It was developed for the purpose of producing a hardened clay body with high compressive strength using coal ash as a raw material.
Weight%, preferably 60 to 80% by weight, slaked lime or/and quicklime (hereinafter abbreviated as slaked lime etc.) 5
~40% by weight, preferably 15-30% by weight, 1-40% by weight of dihydrate gypsum, hemihydrate gypsum or/and type anhydrous gypsum (hereinafter abbreviated as dihydrate gypsum etc.),
Preferably, when producing a cured product using a mixed powder containing 5 to 20% by weight as a raw material, it is preferable to add 10 to 60% by weight of water (weight% of water added to 100% by weight of powder). After kneading the raw material powder, the kneaded product is cured at room temperature in a predetermined shape using a mold or a molding container, or this kneaded product is directly poured into the area to be constructed. The present invention provides a method for manufacturing a hardened soil body with high compressive strength by curing at room temperature in a fixed shape. Hereinafter, the configuration of the present invention will be explained in detail. In general, the typical properties of coal ash, such as components, composition, and particle size distribution, greatly depend on the coal's production area and combustion history. First of all, it depends on where the coal comes from.
The proportions of ingredients such as SiO ₂ , Al ₂ O ₃ , CaO, Fe ₂ O ₃ , Na ₂ O, K ₂ O are different, and secondly, the coal ash currently generated in Japan is mainly pulverized coal combustion ash. Yes, the particle size distribution varies depending on the location and collection method. Therefore, when producing a hydrated hardened material with high compressive strength using coal ash as the main raw material and curing at room temperature, the appropriate manufacturing conditions for the hydrated hardened material may vary depending on the composition and particle size distribution of the coal ash. different. Factors that have a large contribution rate as manufacturing conditions are the mixing ratio of raw material powder, kneading time and kneading temperature, and room temperature curing time. The main component of the hydrated hardened material produced by curing at room _temperature is ettringite (3CaO・_Al2O3・_3CaSO4・
32H ₂ O) and various forms of calcium silicate hydrate (xCaO・ySiO ₂・zH ₂ O), but the one that contributes most to early strength development is ettringite.
For this reason, the appropriate mixing ratio of the raw material powder is the one most favorable for the production of ettringite, and the amount of slaked lime etc. to be added is 5 to 40% by weight, preferably 15 to 40% by weight.
30% by weight, and the amount of dihydrate gypsum added is limited to 1 to 40% by weight, preferably 5 to 20% by weight. Furthermore, the main factor in curing at room temperature is the processing time.
When cured at room temperature, it usually takes a few days to a week for Etrin guide to form and exhibit a compressive strength of several kg/cm ² or more, which is sufficient to withstand normal civil engineering work. The particle size distribution of coal ash also has a large effect on the properties of the hydrated hardened material. Generally, as the particle size of coal ash becomes smaller, that is, as the specific surface area becomes larger, the hydrated hardened material tends to exhibit a predetermined strength with a shorter curing time. This is because the formation reaction of ettringite is a through solution reaction, and the dissolution rate of alumina (Al ₂ O ₃ ) contained in coal ash is significantly lower than that of slaked lime and dihydrate gypsum. This is because it can be estimated that the production rate of ettringite depends on the dissolution rate of alumina. in this way,
The properties of the hydrated hardened product are determined by the components and composition of the coal ash,
It is greatly influenced by manufacturing conditions such as the amount of other raw material powders added, amount of water mixed, kneading method and kneading time, and room temperature curing period, and each manufacturing condition must be appropriately selected according to the required characteristics of the hydrated material. It is necessary. The present invention is capable of producing a hydrated material with high initial strength in a simple kneading process and in a short kneading time by simultaneously kneading a mixed powder consisting of an appropriate blending ratio of each raw material powder and water. It is intended to be manufactured by curing at room temperature. In the present invention, the amount of mixed water is 10 to 60% by weight, but if the amount of mixed water is reduced, the strength will increase, but the moldability will deteriorate, and if the amount of mixed water is less than about 10% by weight, molding will not be possible. In addition, when the amount of mixed water is increased, the fluidity increases and it becomes difficult to solidify, and the amount of mixed water is about 60% by weight as the limit. Therefore, in the present invention, the desirable amount of water to be mixed is 30 to 50% by weight. Next, Examples and Comparative Examples will be described.
The raw material coal ash in Examples and Comparative Examples is commercially available fly ash, and the composition and properties are shown in Table 1.

[Table] The test methods for coal ash and hydrated hardened bodies are shown below. The plain specific surface area measurement was performed using a powder specific surface area measuring instrument SS-100 manufactured by Shimadzu Corporation and by an air permeation method. Bending strength test uses 20×20 as a test piece
For the compressive strength test, a 20 x 20 x 20 (mm) test piece was used as the test piece, and a universal testing machine manufactured by Instron was used as the testing device. The test method was based on the constant deflection method. In Examples and Comparative Examples, curing at room temperature was carried out indoors without direct sunlight. Details of Examples and Comparative Examples are shown in Table 2. Example 1 88 parts of coal ash, 10 parts of slaked lime, 2 parts of dihydrate gypsum, water
40 parts were simultaneously kneaded to form a slurry, and this slurry was cured at room temperature for 7 days to obtain a hydrated hardened product.
The properties of the hydrated and cured product were as shown in Table 2. Example 2 85 parts of coal ash, 10 parts of slaked lime, 5 parts of dihydrate gypsum, water
40 parts were simultaneously kneaded to form a slurry, and this slurry was cured indoors at room temperature for 7 days to obtain a hydrated hardened product. The properties of the hydrated and cured product were as shown in Table 2. Example 3 90 parts of coal ash, 5 parts of slaked lime, 5 parts of dihydrate gypsum, water
40 parts were simultaneously kneaded to form a slurry, and this slurry was cured indoors at room temperature for 7 days to obtain a hydrated hardened product. The properties of the hydrated and cured product were as shown in Table 2. Example 4 80 parts of coal ash, 15 parts of slaked lime, 5 parts of dihydrate gypsum, water
40 parts were simultaneously kneaded to form a slurry, and this slurry was cured indoors at room temperature for 7 days to obtain a hydrated hardened product. The properties of the hydrated and cured product were as shown in Table 2. Comparative Example 1 90 parts of coal ash, 10 parts of slaked lime, and 40 parts of water were simultaneously kneaded to form a slurry, and this slurry was cured at room temperature for 7 days to obtain a hydrated hardened product. The properties of the hydrated and cured product were as shown in Table 2. Comparative Example 2 95 parts of coal ash, 5 parts of dihydric gypsum, and 40 parts of water were simultaneously kneaded to form a slurry, and this slurry was heated indoors for 7
A hydrated and cured product was obtained by curing at room temperature for several days. The properties of the hydrated and cured product were as shown in Table 2.

【table】

[Table] Table 2 shows that a hydrated hardened product with high initial strength can be produced by simultaneously kneading raw material powder and water and then curing at room temperature. As explained above, according to the present invention, coal ash, which is an exhaust product during coal combustion, slaked lime and/or quicklime, which is an inexpensive raw material, dihydrate gypsum, hemihydrate gypsum, and/or type anhydrous gypsum are used, By kneading in water and then curing at room temperature, it is possible to easily and inexpensively produce a hydrated material with high compressive strength. It is useful as a technology that contributes to the production of soil materials for land reclamation, land reclamation, road construction, etc. in the field. Furthermore, since the method of the present invention kneads the raw material powder and water at the same time, the process is extremely simplified and the kneading time is shortened.
This has the effect that a hydrated and cured product can be produced at a lower cost.

Claims (1)

[Claims] 1. 50-94% by weight of coal ash discharged during coal combustion, 5-40% by weight of slaked coal or/and quicklime,
When producing a hardened body using a mixed powder of 1 to 40% by weight of dihydrate gypsum, hemihydrate gypsum, or/and type anhydrous gypsum as a raw material, 10 to 60% by weight of water is added to the mixed powder. A method for producing a hardened product using coal ash as a main raw material, which comprises adding coal ash and sufficiently kneading it, molding the kneaded product using a mold or a molding container, and then curing it at room temperature. 2 50-94% by weight of coal ash discharged during coal combustion, 5-40% by weight of slaked coal or/and quicklime,
When producing a hardened body using a mixed powder of 1 to 40% by weight of dihydrate gypsum, hemihydrate gypsum, or/and type anhydrous gypsum as a raw material, 10 to 60% by weight of water is added to the mixed powder. A method for producing a hardened product using coal ash as a main raw material, which comprises adding coal ash, sufficiently kneading it, and curing the kneaded product at room temperature without molding the kneaded product into a specific shape.