JP2005042497A - Roadbed material and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roadbed material and its manufacturing method for effectively using powdery slag at low processing cost. <P>SOLUTION: This roadbed material 1 is arranged in a thickness of about 50 mm between road surface pavement 2 such as a parking garage and a road and the surface of soil 3. Asphalt and concrete are used as a material of the road surface pavement 2. The roadbed material 1 occupies 95 wt.% or more in a rate of a particle size of 450 μm or less, and is formed by mixing the powdery slag 4 including a calcium content by 35 wt.% or more, and massive slag 5 having the maximum particle size of 40 mm or less. A mixing rate of the powdery slag 4 to the roadbed material 1 is set in a range of 25 wt.% to 70 wt.%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a roadbed material using powdered slag generated in a steelmaking factory and the like, and a method for manufacturing the same.

Conventionally, in steel material factories such as steelworks and steelworks, a large amount of slag is produced as a by-product when molten steel is produced by melting ore and the like. Slag consists of silica contained in ore and coke, that is, silicon dioxide (SiO ₂ ), alumina, that is, aluminum oxide (Al ₂ O ₃ ), sulfide, etc., and limestone as a solvent react in the furnace. It becomes a melt and is taken out of the furnace and solidified. Since the slag contains metal, the metal is collected as much as possible in order to make effective use of resources.

The blast furnace slag and the like separated from the hot metal at the time of brewing from the blast furnace become a vitreous state that does not crystallize when quenched and pulverized with water, and become hydraulic when Portland cement or the like is added. Due to such latent hydraulic properties, blast furnace cement in which Portland cement is added to blast furnace slag has characteristics superior to Portland cement and is widely used. As the blast furnace slag, the basicity shown by dividing the sum of the contents of calcium oxide (CaO), aluminum oxide and magnesium oxide (MgO) by the content of silicon dioxide ((CaO% + Al ₂ O ₃ % + MgO%) When the value of ÷ SiO ₂ %) is 1.4 or more, it is considered preferable as a raw material for blast furnace cement. When the blast furnace slag is gradually cooled, it becomes a lump. Since the bulk slag has already been crystallized, it does not harden even if the bulk slag is collected. For this reason, it is pulverized and used as roadbed gravel or as aggregate for mixing with cement to obtain concrete.

  Slag obtained from a steelmaking converter is rich in iron oxide and free lime and is not usually used as a raw material for cement. When a material having a large amount of alloy components such as stainless steel is manufactured, the slag contains a relatively expensive alloy component, and thus is recovered as a bare metal. When processing for recovering metal from the slag is performed, fine powdery slag is also generated. Fine powdered slag is difficult to use effectively and is disposed of as industrial waste.

  The use of blast furnace slag and steelmaking slag in roadbeds and asphalt mixtures is also stipulated in Japanese Industrial Standards (for example, see Non-Patent Document 1). It has also been proposed that powdered slag is mixed with a silica source and a cement-based solidified material and granulated into a spherical shape and used as an alternative to sand or ballast (see, for example, Patent Document 1).

JP 2002-265246 A JIS A 5015 “Steel Slag for Roads”

  If the proposal of patent document 1 is followed, a fine powdery slag can also be effectively utilized as a civil engineering construction material as a part of concrete, without disposing as industrial waste. However, since the granulated product loses curability, it can be used only with a material having curability such as concrete. In addition, since it is necessary to granulate the entire amount of slag to be used, the processing cost is high, and it is not always economically sufficient to process a large amount of powdered slag.

  An object of the present invention is to provide a roadbed material capable of effectively using powdered slag at a low processing cost and a method for manufacturing the same.

In the present invention, a powder slag containing 95% by weight or more of a particle size of 450 μm or less and containing 35% by weight or more of calcium content;
A roadbed material formed by mixing massive slag having a maximum particle size of 40 mm or less,
A roadbed material characterized in that the mixing ratio of powdered slag is in the range of 25 wt% to 70 wt%.

  According to the present invention, the powdered slag is a fine powder in which the ratio of the particle size of 450 μm or less occupies 95% by weight or more and contains 35% by weight or more of calcium, so that it contains moderate moisture. When mixed with massive slag having a maximum particle size of 40 mm or less as a roadbed material, the powdery slag fills and cures a gap between relatively large massive slags, and can be effectively used as an appropriate roadbed material. Since the fine powdery slag may be mixed with the massive slag as it is in a state containing appropriate moisture, the processing cost can be reduced. A roadbed material using steel slag is defined in Japanese Industrial Standard (JIS A 5015). In the hydraulic particle size-adjusted steel slag HMS-25 for upper layer roadbed material, the particle size range is defined as 25 to 0 mm. In the crusher run steel slag CS-40 for the lower roadbed material, the particle size range is defined as 40 to 0 mm. Thus, the particle size of steel slag is regulated to a particle size of 25 to 40 mm at the maximum, and when the particle size is 40 mm or more, it becomes difficult to mix the entire material uniformly, and only bulk slag of 40 mm or more is used. Is unevenly distributed, which is a serious problem in construction. In this invention, since the particle size of the block slag mixed with powdered slag is 40 mm or less, a good roadbed material can be obtained.

  In the present invention, the massive slag is a granulated product in which the powdered slag, coal ash, and cement are mixed.

  According to the present invention, a granulated product obtained by mixing coal ash and cement with a fine powdery slag is used as the massive slag. The part can be granulated and changed into a block slag, and can be effectively used as a roadbed material.

In the present invention, a powder slag having a particle size of 450 μm or less occupies 95% by weight or more and contains calcium content of 35% by weight or more is mixed with coal ash and cement and granulated, and the maximum particle size is 40 mm. Form a massive slag granulation that becomes the following:
The slag granulated product and the powdered slag are mixed so that the mixing ratio of the powdered slag is in the range of 25% by weight to 70% by weight.

  According to the present invention, a powdery slag having a particle size of 450 μm or less occupies 95% by weight or more and 35% by weight or more of calcium content is mixed with coal ash and cement and granulated. It is used to form a massive slag granulated product of 40 mm or less, and even in the powdered slag itself, the mixing ratio of the formed slag granulated product and the powdered slag is 25% by weight or more and 70% by weight or less. It can be effectively used as a raw material for producing a roadbed material by mixing so as to be in the range. Since it is used as the raw material of the roadbed material even in the state of powdered slag, the processing cost can be reduced.

  In the present invention, the bulk slag granulated product is obtained by mixing the powdered slag with coal ash and cement and granulating, and then crushing the granulated product so that the maximum particle size is 40 mm or less. Features.

  According to the present invention, when granulated slag is granulated, the maximum particle size is reduced to 40 mm or less by crushing even if a particle size exceeding 40 mm is produced. Can do.

  As described above, according to the present invention, when fine powdery slag is mixed with massive slag having a maximum particle size of 40 mm or less in a state containing appropriate moisture, a gap between relatively large massive slags is powdered. Slag is buried and hardened, and can be effectively used as an appropriate roadbed material. Since the fine powdery slag may be mixed with the bulk slag as it is, the processing cost can be reduced. Since the particle size of the massive slag mixed with the powdered slag is 40 mm or less, a good roadbed material can be obtained.

  Further, according to the present invention, a granulated product obtained by mixing coal ash and cement with fine powdered slag is also used as a bulk slag mixed with powdered slag, so that powdered slag is effective as a roadbed material. Can be used.

  Furthermore, according to the present invention, a powder slag containing 95% by weight or more of particles having a particle size of 450 μm or less and containing 35% by weight or more of calcium is mixed with a slag granule formed using the powdered slag. In addition, it can be effectively used as a raw material for producing a roadbed material. Since it is used as the raw material of the roadbed material even in the state of powdered slag, the processing cost can be reduced.

  Moreover, according to this invention, the particle size of massive slag can be made into a suitable range as a roadbed material so that the maximum particle size may be 40 mm or less.

  FIG. 1 shows a schematic configuration of a roadbed material according to an embodiment of the present invention. The roadbed material 1 is provided with a thickness of about 50 mm between a road surface pavement 2 such as a parking lot or a road and the surface of the soil 3. As a material for the road pavement 2, asphalt or concrete is used. The roadbed material 1 of the present embodiment comprises a powdered slag 4 having a particle size of 450 μm or less occupying 95% by weight or more and containing 35% by weight or more of calcium, and a massive slag 5 having a maximum particle size of 40 mm or less. It is formed by mixing. The mixing ratio of the powdered slag 4 to the roadbed material 1 is in the range of 25% by weight to 70% by weight. The roadbed material 1 is used in two layers of an upper layer roadbed material 6 and a lower layer roadbed material 7.

  FIG. 2 shows a schematic manufacturing process of the roadbed material 1 of FIG. In step s1, a slag treatment process is performed in which steelmaking slag or blast furnace slag is used as a raw material and the metal is recovered as metal. Table 1 below shows examples of typical compositions for steelmaking slag and blast furnace slag. The numerical value in a table | surface shows the percentage (weight%) about a weight.

  As the steelmaking slag, slag discharged from a stainless steel electric furnace and a smelting furnace into a slag pan can be used. After cooling the slag with air cooling and water cooling, when the slag pan is turned over to the slag yard and the solidified slag is spread on the ground surface, the metal is solidified in a lump and can be recovered as a large bullion. Next, the slag is crushed.

  In the blast furnace slag, the slag separated from the hot metal when leaving the blast furnace is stored in a slag pan, and the slag discharged from the slag pan in a molten state in the slag yard is naturally cooled and then further cooled with water and solidified. The cooled slag is applied to a beneficiator, and the metal is separated by magnetic beneficiation and then crushed.

  In step s2 of FIG. 2, the classification process which divides the slag crushed after a slag processing process into powdery slag and block slag according to a magnitude | size is performed.

The powdery slag is a fine powder in which the ratio of the particle size of 450 μm or less occupies 95% by weight or more, and contains 35% by weight or more of calcium. Powdered slag contains a large amount of calcium oxide (CaO) and silica (SiO ₂ ), and therefore has a hydraulic property that reacts with water and hardens over time in the presence of moisture. That is, this powdery slag is a hydraulic slag.

  A part of the powdery slag divided in step s2 in FIG. 2 is mixed with coal ash and cement in the granulation process of step s3, and agglomerated slag is formed by granulation. As the granulation method, basically, the method described in Patent Document 1 described above can be used. In this embodiment, an Eirich mixer and a rotating cylinder mixer are used as a granulating apparatus. For example, about 15% by weight of coal ash and about 10% by weight of cement are added to the powdered slag, mixed and kneaded in a mixer, and granulated while adding water.

  Table 2 below shows the mixing ratio of slag, cement, coal ash, and water during granulation. As the slag, fine slag obtained by executing dry crushing, wet pulverization treatment and mineral processing in step s1 is used as slag generated in stainless steel. As the cement, a blast furnace cement type B standard product is used. Fly ash is used as the coal ash. However, it is an external number about a water | moisture content, and shows it by the ratio with respect to this as slag + cement + coal ash as 100%.

  Of the powdered steelmaking slag classified in the classification step of step s2, those having a particle size of 1 μm to 450 μm or less are put into the granulation step of step s3. The finer the powder, the better the homogeneity of mixing and the reactivity during the solidification reaction with cement and coal ash. As a result, the quality of the granulated product (strength, disintegration, etc.) also improves. Is desirable. However, most of the steelmaking slag is generated in a large lump, and processing this into a fine powder means that a large amount of energy is required for pulverization and the like. In this embodiment, in consideration of the cost and the necessity of powdered slag, a processing method that achieves an optimum particle size is determined, and a processing method that combines dry and wet crushing and grinding processes is used. The particle size of the finely pulverized steel slag is 450 μm or less.

Although the blending ratio of fine steel slag is better from the viewpoint of effective use of waste, it is determined in consideration of the quality (strength, disintegration) and manufacturability of the granulated product. The content of 60 to 85% by weight varies depending on the type of coal ash to be mixed, depending on the content of silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), and calcium oxide (CaO) in the coal ash. Because.

For coal ash, its primary blending purpose is to use it as a source of silicon dioxide (SiO ₂ ) and aluminum oxide (Al ₂ O ₃ ) balanced with slag components, especially calcium oxide (CaO). Therefore, the blending ratio is determined by the type of coal ash, and is in the range of 10 to 35% by weight in consideration of the component ratio from general combustion ash to special pressurized fluidized bed combustion ash. If it is less than the lower limit of 10% by weight, no matter how much the slag ratio is decreased and the cement ratio is increased, the collapse cannot be prevented. Further, the upper limit is a sufficient amount for preventing the collapse of the normal component range of slag, and an increase exceeding the upper limit causes deterioration of the granulation property. In other words, compared to slag, coal ash has a very poor granulation property due to its particle shape and physical properties such as specific gravity, and at the same time, it causes the wear of the granulation plant to be accelerated. An unnecessary increase in the blending ratio is not preferable.

  Moisture is necessary to develop strength by blending three raw materials of fine steel slag, cement, and coal ash. At the same time, the granulation property (particle size control) at the time of granulation is greatly affected, so that it is necessary to add an optimal amount of water. The lower limit is a minimum amount of water necessary for the cement solidification reaction and for growing the raw material powder into a granular form. The upper limit is a value that, if added more than that, will result in excessive moisture, making the granulation operation impossible, and making the clay itself or a bowl-like massive lump, making the grain itself impossible. . Therefore, in order to obtain the optimum moisture, it is set to 15 to 25% by weight based on experience with respect to the raw material (slag + cement + coal ash).

  In addition, since slag may be generated in a state containing moisture depending on the processing method, it is necessary to consider that the moisture brought in by the slag is also included in the blending ratio of moisture. Therefore, when steelmaking slag with a high water content is used, there is a case where water addition is unnecessary, and there are cases where the water content becomes excessive and adjustment is made so as to reduce the blending ratio of the slag.

  Table 3 below shows examples of typical coal ash components for pulverized coal combustion ash and pressurized fluidized bed combustion ash. The pressurized fluidized bed is used in coal-fired power generation, and the combustion ash is called fly ash.

As shown in Table 1, although slag also contains calcium oxide (CaO), silicon dioxide (SiO ₂ ), and aluminum oxide (Al ₂ O ₃ ), these components are prepared by mixing with water. During the curing period after granulation, the solidification reaction proceeds with the cement. When the solidification reaction is completed, if a component that causes expansion and disintegration due to hydration reaction such as unreacted calcium oxide remains, disintegration occurs, which causes a problem in the quality of the granulated product. Therefore, it is necessary to optimize the ratio of the calcium oxide content to the silicon dioxide and aluminum oxide content so that the unreacted calcium oxide content does not remain so that the disintegration does not occur.

  The upper limit of 85% by weight of the slag blending ratio is that if it is added more than that, the blending amount of coal ash and cement will decrease, and excessive calcium oxide content in the slag will remain, causing disintegration. Because it becomes. In order to prevent disintegration from occurring with the balance of 15% by weight or less, it is necessary to increase the blend of coal ash compared to cement. This is because, as shown in Table 2, coal ash contains the most silicon dioxide in the raw material for granulation. However, since the blending ratio of cement becomes small, the strength of the granulated product itself also decreases. The reason why the lower limit of the blending ratio is 60% by weight is that the cost increases as the blending ratio of coal ash and cement increases. In order to prevent collapse and develop strength, it is sufficient to add up to 40% by weight of coal ash and cement.

  Of the blending ratio of cement, the target strength cannot be obtained at the lower limit of 5% by weight or less. If the upper limit is 20% by weight or more, the cost increases, even if the strength is sufficient. In particular, the proportion of coal ash decreases, leading to deterioration of disintegration. The roadbed material is a civil engineering construction material, and depending on the application and construction method, it is necessary to consider the soil environmental standards for harmful substances. When cement is used, it is hexavalent chromium (Cr) that becomes a problem with the components contained therein, and therefore blast furnace cement with a low chromium content is used. Moreover, since the strength of the product as the roadbed material is also important as the quality, the type B of the blast furnace cement is selected as the type in which the strength is most easily developed by curing for several weeks to several months.

  When the granulated product generated in the granulating process of step s4 in FIG. 2 is discharged from the mixer, it is carried to the indoor curing pit by a conveyor and is allowed to rest for about 2 days. After standing and curing, it is taken out to the outdoor yard and cured for about 1 month outdoors, and then mixed with finely pulverized steel slag as massive slag.

  When fine steelmaking slag is mixed with massive slag having a maximum particle size of 40 mm or less as a roadbed material in a state containing moderate moisture, the powdered slag fills the gaps between relatively large massive slags and hardens. It can be used effectively as a roadbed material. Since the fine powdery steelmaking slag may be mixed with the massive slag as it is, the processing cost can be reduced.

  Japanese Industrial Standard JIS A 5015 describes provisions for roadbed materials using steel slag such as blast furnace slag and steelmaking slag. In the hydraulic particle size-adjusted steel slag HMS-25 for upper layer roadbed material, the particle size range is defined as 25 to 0 mm. In the crusher run steel slag CS-40 for the lower layer roadbed material, the particle size range is defined as 40 to 0 mm. In this way, the particle size of steel slag is regulated to a particle size of 25 to 40 mm at the maximum. If the particle size exceeds 40 mm, it becomes difficult to mix the entire material uniformly, and only bulk slag exceeding 40 mm is obtained. Is unevenly distributed, which is a serious problem in construction. When the construction thickness as the roadbed material 1 is thin, for example, when the thickness is 50 mm or less, a massive slag exceeding 40 mm protrudes from the surface, and the unevenness of the surface of the roadbed material 1 after construction becomes large, resulting in a poor finish. Because it ends up. In this embodiment, since the maximum particle size of the massive slag mixed with the fine steel slag is 40 mm or less, a good roadbed material can be obtained.

  In addition, when a granulated product having a particle size exceeding 40 mm is generated in the granulating step of step s3, a crushing step of step s4 is provided, and the granulated product is set so that the maximum particle size does not exceed 40 mm. Crush. The size of the massive slag is optimal from several mm to 40 mm, but it is necessary that it is at least 450 μm or more. This is because, in the present invention, massive slag and finely pulverized steel slag are mixed to form the roadbed material 1 which is a material for civil engineering construction. Here, since the particle size of the fine steel slag is several μm to several thousand μm (for example, 1 μm to 450 μm), it is desirable that the particle size distribution of the mixed material is smoothly connected as a whole.

  The smoother the particle size distribution, the better the tightening of the obtained roadbed material 1. The tightening degree of the roadbed material 1 is evaluated by, for example, a modified CBR (California Bearing Ratio) value defined in JIS A 1211 in the Japanese Industrial Standard. For example, if the particle size distribution is not smooth due to the absence of an intermediate particle size, for example, when the material is compacted, the tightening of the entire material is deteriorated and the corrected CBR value is lowered.

  The powdery slag separated in the classification process of step s2 is mixed with the massive slag separated in the classification process in the mixing process of step s5, and the roadbed material 1 shown in FIG. 1 is generated. In addition, as the bulk slag to be mixed with the powdered slag, the granulated product in the granulation process of step s3 is used, or the granulated product is crushed in the crushing process of step s4 and mixed in the mixing process of step s6. A roadbed material 1 is generated. The mixing ratio in each mixing step is 75 to 25% by weight of finely pulverized steel slag, and the bulk slag is 25 to 75% by weight of the balance so that the whole is 100% by weight.

  The following Table 4 shows the evaluation test results for roadbed materials generated at various blending ratios including the blending ratio of the present embodiment. In the test according to the JIS standard method, the sample using the slag granulated material as the massive slag in the mixing process of step s6 in FIG. 2 is much better than the sample using the massive slag such as blast furnace slag in step s5. It turns out that it is suitable for roadbed materials. Since cement is blended in the granulated product, solidification reaction between the slag and cement occurs even in the granulated product surface layer by mixing with the powder of fine steel slag having hydraulic properties, and the entire material is firmly compacted This is probably because of this. Of the samples shown in Table 4, No. 1-No. No. 11 gives a good evaluation, so these are examples of the present invention. 12-No. Since No. 17 is poor in evaluation, it is a comparative example that deviates from the examples. That is, the blending ratio of the present invention is determined so that the examples in Table 4 are within the range and the comparative examples are out of the range.

The acceptance criteria for each evaluation test result are 130% or more for the corrected CBR value, 1.2 N / mm ² or more for the uniaxial compression strength, 1.5% or less for the water immersion expansion ratio, and 1 for the unit volume mass. .5 kg / L or more, and comprehensive evaluation was added. The circle mark is acceptable, the double circle mark is judged to be particularly excellent, and the cross mark indicates that there is an evaluation that does not reach the standard. That is, No. which is a comparative example. 12-No. In 17 samples, the standard was not reached in the corrected CBR value or uniaxial compressive strength.

  Table 5 below shows No. 1 in Table 4. 6-No. The manufacturing conditions of the slag granulated material used for 17 samples are shown. The ash type indicates the use of pressurized fluidized bed combustion ash, ie fly ash, in a “fluidized bed”. As the mixer type, “Eirich” indicates an Eirich mixer, and “rotary cylinder type” indicates a rotary cylinder mixer. As in Table 2, the sum of powdered steel slag, coal ash, and cement is 100% by weight, and the water content is the outer number, that is, the ratio to the sum.

It is typical sectional drawing which shows the use condition of the roadbed material 1 which is one Embodiment of this invention. It is a schematic manufacturing-process figure of the roadbed material 1 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Roadbed material 2 Road surface pavement 3 Soil 4 Powdery slag 5 Bulk slag 6 Upper layer roadbed material 7 Lower layer roadbed material

Claims (4)

A powder slag containing a particle size of 450 μm or less occupying 95% by weight or more and containing 35% by weight or more of calcium;
A roadbed material formed by mixing massive slag having a maximum particle size of 40 mm or less,
A roadbed material characterized in that the mixing ratio of powdered slag is in the range of 25 wt% to 70 wt%.   The roadbed material according to claim 1, wherein the massive slag is a granulated material in which the powdery slag, coal ash, and cement are mixed. A powdery slag having a particle size of 450 μm or less occupies 95% by weight or more, and a powdered slag containing 35% by weight or more of calcium is mixed with coal ash and cement and granulated to obtain a lump-like shape having a maximum particle size of 40 mm or less Forming slag granulate,
A method for producing a roadbed material, comprising mixing the slag granulated material and the powdered slag so that the mixing ratio of the powdered slag is in the range of 25 wt% to 70 wt%.   The aggregated slag granulated product is characterized in that the powdered slag is granulated by mixing with coal ash and cement, and then the granulated product is crushed to a maximum particle size of 40 mm or less. 3. A method for producing a roadbed material according to 3.

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