JP2019137584A - Method for manufacturing steelmaking slag roadbed material - Google Patents

Abstract

To provide a method for manufacturing a steelmaking slag roadbed material that has an extremely low expansibility, with high productivity.SOLUTION: Concerning a steelmaking slag a crushed to a grain-size in which the percentage of a grain size of 40 mm or less is 80 mass% or more and followed by applying steam aging at an ordinary pressure, by increasing/decreasing the fine-grain and fine-powder portions under a condition in which (i) concerning a portion of the steelmaking slag a, it is classified with a sieve x having a mesh size of 10 mm or less to reduce the fine-grain and fine-powder portions, followed by mixing with the remainder of the steelmaking slag a, or, (ii) fine-grain and fine-powder portions previously obtained by classifying a steelmaking slag crushed to a grain-size in which the percentage of a grain size of 40 mm or less is 80 mass% or more and following said crushing followed by applying steam aging, with a sieve x having a mesh size of 10 mm or less, are added to steelmaking slag a and mixed, the grain-size distribution of steelmaking slag a is adjusted so as the Fuller index satisfies 0.4 to 0.6 when the grain-size distribution of steelmaking slag a is approximated by Andreazen's curve formula.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a method for producing a steelmaking slag roadbed material produced by steam aging steelmaking slag.

  In the steelmaking slag, some of the lime source and magnesia source added by refining remain unmelted or free without forming a compound with other components. When such free CaO or free MgO hydrates with water, the volume expands more than twice and destroys surrounding structures. Therefore, before using steelmaking slag as a stone or roadbed material, It is necessary to promote hydration and calm down at this stage.

  In order to rapidly react free CaO and free MgO in steelmaking slag with moisture, reaction promotion (steam aging) with steam that simultaneously raises temperature and supplies moisture is generally performed. There are two types of steam aging: normal pressure and pressurized pressure (pressurized steam aging). Normal pressure steam aging has a lower processing speed than pressurized steam aging, but is simple. There is an advantage that a large amount of processing is possible with simple equipment (for example, Patent Document 1).

JP-A-63-260842

  When steam aging steelmaking slag, some of the slag particles collapse due to expansion reaction, so the particle size distribution changes to the fine side. If the time of steam aging at normal pressure is lengthened in an attempt to suppress the expansion, the atomization progresses but the expansion stability is slowed down. Thus, the productivity of the aging process for producing a stable roadbed material that satisfies the expansion standard of the roadbed material product is lowered.

  Accordingly, an object of the present invention is to provide a production method capable of producing a steelmaking slag roadbed material having extremely low expansibility with high productivity in a method for producing a steelmaking slag roadbed material by steam aging steelmaking slag at normal pressure. There is to do.

The gist of the present invention for solving the above problems is as follows.
[1] For steelmaking slag (a) that has been crushed to a particle size with a particle size of 40 mm or less of 80 mass% or more and then subjected to steam aging at normal pressure, fine granules and fine powder under the following conditions (i) or (ii) Adjust the particle size distribution of steelmaking slag (a) so that the Fuller index is 0.4 to 0.6 when the particle size distribution of steelmaking slag (a) is approximated by Andreazen's curve formula A method for producing a steelmaking slag roadbed material characterized by comprising:
(I) A part of the steelmaking slag (a) is classified with a sieve (x) having a sieve mesh of 10 mm or less to reduce fine particles and fine powder, and then mixed with the remainder of the steelmaking slag (a).
(Ii) By classifying steelmaking slag that has been previously crushed to a particle size in which the ratio of particle size of 40 mm or less is 80 mass% or more and steam-aged after the crushing, is classified with a sieve (x) having a mesh size of 10 mm or less. The fine particles and fine powder obtained are added to the steelmaking slag (a) and mixed.

[2] In the production method of [1], at least a part of the steelmaking slag (a) is a steelmaking slag having a basicity (however, a mass ratio of CaO / SiO ₂ ) of 3.3 or more. A method for manufacturing steelmaking slag roadbed material.
[3] In the production method of [1] or [2] above, the steelmaking slag (a) is decarburized slag generated in the same refining equipment on the same day, and a part of the steelmaking slag (a) has a mesh size of 10 mm. Fine particles and fines are reduced by classification with the following sieve (x), and then mixed with the remainder of the steelmaking slag (a) to reduce the fines and fines of the steelmaking slag (a). The manufacturing method of the steel-making slag roadbed material characterized by adjusting distribution.

[4] In the manufacturing method of [1] or [2] above, the steelmaking slag (a) comprises two or more types of steelmaking slag, and all or a part of one type of steelmaking slag (a1) is sieved. Is reduced with a sieve (x) of 10 mm or less to reduce fines and fines, then the remaining one or more types of steelmaking slag (a2) and the remainder of the steelmaking slag (a1) (however, steelmaking slag (a1) The method for producing a steelmaking slag roadbed material is characterized by adjusting the particle size distribution by reducing the fine and fine powder content of the steelmaking slag (a) by mixing with the above.
[5] In the production method of [4], the steelmaking slag (a1) is a decarburized slag generated in the same refining facility on the same day, and the steelmaking slag (a2) is a steelmaking slag other than the decarburized slag. A method for producing steelmaking slag roadbed material.

[6] The method for producing a steelmaking slag roadbed material according to any one of the above [1] to [5], wherein the sieve (x) has a mesh size of 4 mm or more and 6 mm or less.
[7] In the production method according to any one of the above [1] to [6], the particle size range of the steelmaking slag (a) after adjusting the particle size distribution is defined in JIS A5015 (2013). 40, CS-30, CS-20, MS-25, HMS-25 any particle size range is satisfied, The manufacturing method of the steel-making slag roadbed material characterized by the above-mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, the steel-making slag roadbed material which reduced the expansibility to the lowest level which can be reached | attained on the applied aging conditions can be manufactured with high productivity. For this reason, even when expandable steelmaking slag is steam-aged under the same aging conditions and steam intensity as before, more expansion rate acceptable products (roadbed material products) can be obtained. Moreover, the steel-making slag roadbed material manufactured by the method of the present invention has not only extremely low expansibility but also excellent compactability because of its high density.

Each tamping of steelmaking slag was performed by changing the standard 92 times / layer × 3 layers tamping to 46 times / layer × 3 layers, 92 times / layers × 3 layers, and 184 times / layers × 3 layers. Graph showing the dry density of the specimen FIG. 1 is a graph showing the transition of the expansion coefficient in a water immersion test immersed in a water tank maintained at 80 ° C. for each specimen shown in FIG. A graph showing the particle size distribution of a sample collected at the time when only one layer was tamped in the tamping of the three layers from which the specimens of FIGS. 1 and 2 were obtained. Graph showing the relationship between dry density and water immersion expansion rate of specimens (steel slag) subjected to steam aging at normal pressure Graph showing Andreasen's curve (cumulative distribution) Fuller index q in the case of approximating the particle size distribution of various steelmaking slag samples subjected to steam aging at normal pressure by Andreasen's curve formula and the dry density at the time of tamping each sample (specified in JIS A1210 (2009)) Graph showing the relationship with the standard (dry density obtained by tamping 92 times / layer × 3 layers) according to the method of Eb) Graph showing the relationship between the water immersion expansion rate (expansion rate after 4 days at 80 ° C.) and the Fuller index q of steel slag that has been steam-aged at normal pressure Graph showing changes in particle size distribution (changes in particle size distribution before and after steam aging) when steel slag having a basicity of 3.3 to 3.9 is steam-aged at normal pressure Graph showing an example of the result of obtaining Fuller index q for steelmaking slag after steam aging at normal pressure by approximating its particle size distribution with Andreazen's curve formula

In the following description, in addition to the case of "normal pressure steam aging", the case of simply "steam aging" means steam aging performed at normal pressure (atmospheric pressure) unless otherwise specified. To do.
The inventor conducted the following experiment.
In the tamping test used for the expansibility evaluation of the roadbed material, the number of tamping is determined depending on the conditions. In the E-b method defined in JIS A1210 (2009), a 4.5 kg rammer is dropped 92 times into a cylindrical container (CBR test form) with an inner diameter of 150 mm, and this is thrust into three layers. To a height of 125mm. If the mass of the solidified specimen is known, the specimen mass and density at the time of drying can be determined based on the moisture content adjusted in advance.

  The standard 92 times / layer x 3 layers tamping is changed to 46 times / layers x 3 layers, 92 times / layers x 3 layers, 184 times / layers x 3 layers, and the steelmaking slag is tamped and tamped. The dry density of each specimen was measured. The results are shown in FIG. 1, and the dry density increases as the number of tamping increases. On the other hand, the tamped specimen was immersed in a water tank maintained at 80 ° C., and the transition of expansion was measured. FIG. 2 shows the transition of the expansion coefficient of each specimen in this water immersion test. The expansion coefficient increases in the order of decreasing density. That is, the expansion coefficient is 46 times / layer> 92 times / layer> 184 times / layer. In the tamping of the three layers, a sample at the time of tamping only one layer was collected, and the result of the particle size distribution measurement is shown in FIG. 3, and it can be seen that the coarse particles slightly collapsed when the number of tamping times was 184.

The above results show that the expansion is smaller when the particles are packed so as to have a higher density even if the particles are broken to some extent and broken to some extent.
In addition, the dry density and the water expansion coefficient (here, 80%) of the water expansion test specimen (steel slag) which has been tested under various conditions where the treatment time of the normal pressure steam aging was changed from 48 hours to 96 hours. As a result of investigating the expansion rate after 4 days at a constant temperature, the specimen having a lower dry density tended to have a higher expansibility.

FIG. 4 shows the dry density of a specimen (steel slag) subjected to steam aging (treatment time: 72 ± 24 hours) (standard 92 times / layer × 3 according to the method of Eb defined in JIS A1210 (2009)). Although the relationship between the dry density obtained by tamping the layer) and the water expansion coefficient is shown, the same tendency as described above is observed.
When focusing on one slag particle, if the filling property is high and the constraint from surrounding particles is large, the expansion source in the crack of the particle reacts and expands, and even if it tries to expand the particle itself, it is restrained. The reaction does not proceed freely. If the particle is further destroyed by the expansion reaction and the crack is advanced, the space in which moisture reaches the expansion source during the reaction and the unreacted expansion source at the advanced crack tip is expanded. However, if the constraint around the particles is strong, the space for supplying moisture to the expansion source cannot be easily expanded, and as a result, the expansion reaction is suppressed.

  In order to increase the density of the steelmaking slag, it is desirable to arrange the coarse particles densely, fill the voids formed between the coarse particles with fine particles, and further fill the voids where fine powder remains between the fine particles. However, if there are more fine particles or fine powder than necessary to fill the voids, the fine particles come into contact with each other to form a large number of small voids. Even if the steam aging is lengthened, if the fine particles increase more than necessary, the packing of the slag particles is deteriorated and the reduction of the expansion rate is hindered.

When the particle size distribution of various steelmaking slags subjected to steam aging was examined, it was found that there was a considerable difference in the particle size distribution.
There is Andreasen's curve formula for the expression of the continuous particle size distribution, and the passing mass fraction at each intermediate diameter (Dp) with respect to the maximum particle diameter (Dpmax) is expressed as the following formula (1) using the Fuller index q. .
U (Dp) = (Dp / Dpmax) ^q (1)
Here, Dp is the particle size, Dpmax is the maximum particle size, and U (Dp) is the passing mass fraction up to the particle size Dp. (Source: For example, “Shigeo Miwa, Powder Engineering, Nikkan Kogyo Shimbun, 1981, p. 42”)
This Andreasen curve has an integrated distribution as shown in FIG. 5, and the smaller the number of fine particles, the smaller the Fuller index q. Experimentally, q = 1/2 for sparse filling and q = 1/3 for dense filling, and the density is highest.

  Using the maximum particle size Dpmax and the Fuller index q as variables, the particle size distribution of various steelmaking slag samples subjected to steam aging was approximated by Andreasen's curve formula. The dry density at the time of tamping each sample (dry density obtained by tamping of 92 times / layer × 3 layers in accordance with the method of Eb defined in JIS A1210 (2009)) and the Fuller index q The relationship is shown in FIG. According to FIG. 6, the dry density has a maximum when q is 0.4 to 0.6, and tends to be small before and after that. When fine particles and fine powder increase, q falls below 0.4 and the dry density decreases. On the other hand, q exceeds 0.6 at a level where the fine particles and fine powder were experimentally reduced, but the dry density is still small. This means that q has an optimum range for filling, and is consistent with the tendency of Andreasen's curve formula.

In an actual crushing plant for steelmaking slag, products that have undergone crushing process and re-crushing coarse particles that have been classified should have less fines and fines than necessary in light of the JIS standard for steel slag roadbed materials (JIS A5015). There are not so many, and it is thought that there are many cases where it is crushed finely.
In FIG. 4 mentioned above, the level at which the dry density is small and the expansion is large is that q is less than 0.4. Incidentally, the relationship between the water immersion expansion rate (expansion rate after 4 days at 80 ° C.) and the Fuller index q of steelmaking slag subjected to steam aging at normal pressure is q = 0.5 as shown in FIG. The water immersion expansion rate is decreasing toward.

  When the Fuller index q is larger than 0.6, the frequency with which the coarse particles come into contact with each other increases, and the fine particles that fill the gaps between the coarse particles are insufficient, thereby reducing the filling property. Also in this case, the constraint between the particles becomes low, and an environment in which expansion and collapse can be promoted more freely. Furthermore, in the case of only coarse particles, the probability that the coarse particles are directly subjected to the impact of the Ranma increases when the sample particles are solidified in the mold by the water immersion expansion test specified in JIS A5015. Since there are few particles in contact with the filler, the stress cannot be dispersed to the surroundings, and the impacted coarse particles are frequently broken down. As a result, an unreacted expansion source appears on the new fracture surface.Despite steam aging, many unreacted expansion sources are likely to react before the water immersion expansion test. Will be raised. Therefore, it is not necessary to simply coarsen the particle size.

From the above, the inventor of the present invention, the water immersion expansion of the steel slag subjected to steam aging is also affected by the particle size distribution, and when the filling property of the slag particles is reduced because the particle size distribution is inappropriate, It was found that the water immersion expansion was increased. Therefore, even if the desired steam aging is performed, it is considered that a considerable number of cases where the expansibility is determined to be unacceptable due to an inappropriate particle size distribution. Further, in the case of steelmaking slag having a high basicity, since free CaO as an expansion source is widely distributed in the slag, the expansion source appears on any fracture surface, and the expansion / collapse chain is further strengthened. Such a phenomenon becomes prominent particularly in steelmaking slag having a basicity (however, the mass ratio of CaO / SiO ₂ , the same applies hereinafter) of 3.3 or more. This is because 3CaO.SiO ₂ (tricalcium silicate) appears in the mineral phase at a high temperature stage where slag is condensed, but when it falls below 1250 ° C., it decomposes into CaO and 2CaO.SiO ₂ to produce free CaO. For this reason, the expansion source is widely dispersed in the slag structure.

  As a result of further investigation based on the above knowledge, the present inventor can reach the applied aging condition by increasing / decreasing the fine particle / fine powder content under a predetermined condition with respect to the steel slag subjected to steam aging. It was found that a roadbed material with the smallest expansion rate can be obtained. In addition, in the case of steelmaking slag having a particularly high basicity, the slag particle size becomes finer when steam aging is performed, but even in such steelmaking slag after steam aging, fine particles are formed under predetermined conditions as described above.・ It has been found that by increasing or decreasing the fine powder content, a roadbed material with the smallest expansion rate can be obtained. Specifically, it has been found desirable to adjust the particle size distribution so that the Fuller index q is 0.4 to 0.6. According to this method, it is only necessary to increase / decrease the fine particles / fine powder content of the steelmaking slag after steam aging, so that it is possible to produce a steelmaking slag roadbed material with extremely low expansibility with high productivity. The steelmaking slag roadbed material has a high density and is excellent in compaction.

For this reason, in the present invention, the steelmaking slag (hereinafter referred to as “steelmaking slag a” for convenience of explanation) subjected to steam aging at normal pressure after being crushed to a particle size with a particle size of 40 mm or less being 80 mass% or more is described below ( When the particle size distribution of steelmaking slag a is approximated by Andreazen's curve formula by increasing or decreasing the fine grain / fine powder content under the conditions of i) or (ii), the Fuller index is 0.4 to 0.6. The particle size distribution of the steelmaking slag a is adjusted. The particle size of 40 mm or less is a particle size that passes through a sieve having a sieve mesh of 40 mm (nominal diameter).
(I) A part of the steelmaking slag a is classified by a sieve having a sieve mesh of 10 mm or less (hereinafter referred to as “sieve x” for convenience of explanation) to reduce fine particles and fine powder, and then the remainder of the steelmaking slag a ( Mix with solid grain steelmaking slag a).
(Ii) A steelmaking slag that has been previously crushed to a particle size with a particle size of 40 mm or less of 80 mass% or more and that has been subjected to steam aging (steam aging at normal pressure or pressurized steam aging) is sieved. Is added to steelmaking slag a (solid steelmaking slag a) and mixed.

The “previously obtained fine particles / fine powder” in (ii) above refers to the fine particles / fine particles obtained and classified in the previous classification.
Steelmaking slag is slag generated in the steelmaking process of the steel manufacturing process, including decarburization slag (converter decarburization slag), hot metal pretreatment slag (desiliconization slag, dephosphorization slag, etc.), ingot slag, smelting reduction slag There are electric furnace slags, and one or more of these can be used. Especially, since decarburization slag is generally high in basicity, it can be said that the usefulness of the present invention is particularly high when part or all of the steelmaking slag a is decarburization slag.

In the present invention, the maximum particle size of the slag occupying 80 mass% or more of the steelmaking slag a before steam aging is set to 40 mm. This is because even if applied, the variation in the water immersion expansion rate becomes large, and the expansibility is not stabilized.
It is considered that the curve under the integrated sieve greatly changes in Andreazen's curve formula in a region where the particle size is 20% or less of the maximum particle size in the region where the Fuller index q is smaller than 1. If the particle size distribution passes 80 mass% or more at a mesh size of 40 mm, the particle size of 20% of the maximum particle size is substantially 10 mm, and it is desirable to adjust the amount of fine particles and fine powder below that. For this reason, in the present invention, as in (i) and (ii) above, the fine particle / fine powder content is increased / decreased through classification with a sieve x having a sieve mesh of 10 mm or less, and the particle size distribution is adjusted.

  In addition, in the vicinity of half of the desired Fuller index q, the change in the total sieve (passing mass fraction up to the particle size Dp) is large because the particle size is about 10% or less of the maximum particle size (that is, about 4 to It is easy to manipulate the particle size distribution by directly increasing or decreasing the particles of 4 to 6 mm or less. For this reason, in this invention, the screen of the sieve x of said (i) and (ii) shall be 4-6 mm, and the increase / decrease of the fine particle and fine powder of the particle size of 4-6 mm or less which pass the screen will be performed. preferable. For example, the screen size of the sieve x is set to 5 mm (nominal diameter), and the fine particle / fine powder component having a particle size of 5 mm or less passing through the sieve screen is increased / decreased (in the following description, “particle size of 5 mm or less) “,“ −5 mm ”means a particle diameter passing through a mesh size of 5 mm (nominal diameter)). That is, in the case of reducing the fine particle / fine powder content as in (i) above, for example, a pile of target steelmaking slag a (generated in the same refining equipment on the same day, the ratio of particle size of 40 mm or less is 80 mass% or more (Part of the steelmaking slag that has been crushed to a particle size and then steam-aged) is separated by a sieve x having a mesh size of 5 mm (nominal diameter) to separate particles with a particle size of 5 mm or less, and the remaining peak portion (The remainder of the steelmaking slag a) is left in the solid particle size without classification, and the classified steelmaking slag a and the steelmaking slag a in the solid particle size not classified are mixed. In this case, by changing the ratio of the steelmaking slag a classified by the sieve x having a sieve mesh of 5 mm, the ratio of fine particles / fine powder having a particle diameter of 5 mm or less as a whole can be adjusted. On the other hand, when there are insufficient particles of 5 mm or less and the amount of fine particles and fines to be insufficient is increased as in (ii) above, -5 mm of the stock screened by the previous classification (ratio of particle size of 40 mm or less) Steelmaking slag that has been crushed to a particle size of 80 mass% or more and that has been subjected to steam aging (steam aging at normal pressure or pressurized steam aging) is classified with sieve x having a mesh size of 5 mm (nominal diameter). Add as much fine particles and fine powder as possible) and mix. Then, by adjusting the particle size distribution as described above, the Fuller index q is set to 0.4 to 0.6.

  Two or more kinds of steelmaking slag can be mixed and used for the steelmaking slag roadbed material. Thus, when steelmaking slag a consists of two or more types of steelmaking slag, steam aging was performed after crushing to one of these types of steelmaking slag a1 (the ratio of particle size of 40 mm or less is 80 mass% or more) The whole or part of the steelmaking slag) is classified with a sieve x having a mesh size of 10 mm or less (for example, a sieve x having a nominal diameter of 5 mm), and the fine particle / fine powder content is reduced. Remaining one or more types of steelmaking slag a2 (steelmaking slag that has been subjected to steam aging after being crushed to a particle size with a particle size of 40 mm or less being 80 mass%) and the remainder of steelmaking slag a1 (however, steelmaking slag a1 The particle size distribution may be adjusted by mixing with the above). In this case, (1) changing the ratio of the steelmaking slag a1 classified by a sieve x having a sieve mesh of 10 mm or less (for example, a sieve x having a nominal diameter of 5 mm), (2) the steelmaking slag a1 and the steelmaking slag a2 The ratio of fine particles / fine powder having a particle size of 5 mm or less as a whole can be adjusted by either or both of changing the quantitative ratio. Then, by adjusting the particle size distribution as described above, the Fuller index q is set to 0.4 to 0.6.

  A typical example of using two or more types of steelmaking slag mixed with steelmaking slag roadbed material as described above is decarburization slag generated in the same refining equipment on the same day, and steelmaking slag a2 is decarburized. This is the case of steelmaking slag other than slag. The decarburized slag, which is steelmaking slag a1, generally has a high basicity, and the basicity is often 3.3 or more. On the other hand, steelmaking slag other than decarburized slag, which is steelmaking slag a2, has various basicities depending on its type.

In the present invention, it is the steelmaking slag a after steam aging that adjusts the particle size distribution so that the Fuller index q is 0.4 to 0.6. When steam aging is applied to steelmaking slag, the slag becomes finer, but steelmaking slag with a high basicity, especially steelmaking slag with a basicity of 3.3 or more, has a wide distribution of free CaO as the expansion source in the slag. Therefore, there is a strong tendency to generate a chain of expansion / disintegration, and fine particles and fine powder are easily generated by performing steam aging. FIG. 8 shows changes in particle size distribution (changes in particle size distribution before and after steam aging) when steelmaking slag having a basicity of 3.3 to 3.9 is steam-aged. As shown in FIG. 8, the higher the basicity of the steelmaking slag, the more fine particles and fine powders after steam aging increase, and the change in the particle size distribution becomes larger. In addition, the range of variation in the basicity itself of each refining charge is expanded, and it becomes difficult to predict the change in particle size after steam aging. Therefore, in order to adjust to the desired Fuller index q, it is preferable to adjust the particle size after measuring the particle size distribution after steam aging, thereby ensuring that the Fuller index q is in the range of 0.4 to 0.6. Can be put in.
From the above points, it can be said that the method of the present invention is particularly useful when a part or all of the steelmaking slag a is a steelmaking slag having a basicity of 3.3 or more.

  The treatment time for steam aging is suitably about 24 to 144 hours. Here, the processing time refers to the heat retention time at about 100 ° C. after the temperature rising period of the stacked slag beds (until the temperature measuring thermometer reaches about 100 ° C.) ends. The reason why the desirable upper limit of the processing time is set to 144 hours is that productivity is lowered when the processing time is too long. The reason why the desirable lower limit of the treatment time is set to 24 hours is that a minimum of 24 hours is required to accelerate the reaction by increasing the temperature of the piled slag into which steam has been blown.

In the method of the present invention, the particle size of the steelmaking slag after adjusting the particle size distribution is CS-40, CS-30, CS-20, MS-25, HMS-25 whose particle size ranges are defined in JIS A5015 (2013). It is preferable that any one of the particle size ranges is satisfied. These stipulate the physical properties including the grain size of steel slag for roads, and the numbers in the standard names indicate the approximate maximum grain size. In practice, those satisfying this granularity are used for road paving work, so it is necessary to pass this standard to sell roadbed materials.
The steelmaking slag roadbed material manufactured by the method of the present invention as described above preferably has a particle size distribution with a Fuller index of 0.4 to 0.6 when the particle size distribution is approximated by an Andreazen curve formula.
The steelmaking slag roadbed material manufactured according to the present invention may be used (constructed) alone, or used (constructed) by mixing with other roadbed materials (for example, other slag roadbed materials and crushed stones). Also good.

  Steelmaking slag used as a raw material is decarburized slag and ingot slag, both of which are crushed to a particle size of 40 mm or less (passed through a sieve having a sieve size of 40 mm (nominal diameter)). The decarburized slag has a free CaO content of 4.9 to 6.1 mass% and a basicity of 3.3 to 4.3, and the ingot slag has a free CaO content of 1.3 mass% and a basicity of It was 2.7 to 2.9. In Example 1 and Example 2, as decarburized slag, slag B (granularity 0-40 mm) obtained by steam aging slag A having an untreated solid particle size at normal pressure, and a mesh size of 5 mm from this slag B ( Slag C (particle size 5-40 mm) obtained by classifying and removing particles of -5 mm with a sieve having a nominal diameter was used. Slag B and slag C are slag generated in the same refining equipment on the same day. Moreover, in Example 2, the slag D (particle size 0-40 mm) which was the solid particle size which is not classified and was steam-aged at normal pressure was used as the ingot slag. Further, in Example 3, as decarburized slag, slag E (grain size 0-40 mm) having a solid particle size that is not classified and steam-aged at normal pressure, and previously crushed to a particle size of 40 mm or less and When decarburized slag that had been subjected to steam aging at normal pressure after crushing was classified with a sieve having a sieve mesh size of 5 mm (nominal diameter), slag F (particle size 0-5 mm) that had been stocked was used. The slag E has a particle size of 0 to 40 mm, but is a slag having a particle size distribution with a coarse particle size overall and a small fine particle content.

While measuring the particle size distribution of slags A to F, the Fuller index q in Andreasen's curve formula for slags A to E was determined using the regression function of the graph software. An example is shown in FIG. At that time, the passing mass fraction of 100 mass%, that is, the passing mass fraction of the entire mesh was not used as data, and only the passing mass fraction of the mesh with a passing mass fraction of less than 100 mass% was approximated as data. Moreover, the slags A to E were subjected to a water immersion expansion test as defined in JIS A5015 (2013) Annex 2, and the dry density and the water immersion expansion rate were measured.
When mixing two slags out of the slags B to F, a heavy machine such as a wheel loader was used for mixing the slags, and the mixing was made uniform by repeating the turnover several times.

37.5 mm (nominal diameter 40 mm), 31.5 mm, 26.5 mm, 19.0 mm, 13.0 mm, 9.5 mm (nominal diameter 10 mm), to measure the passing mass fraction (particle size distribution) of slag, The sieves of 4.75 mm (nominal diameter 5 mm), 2.36 mm, 1.18 mm, 0.6 mm, 0.425 mm, 0.3 mm, 0.15 mm, and 0.075 mm were used. This sieve series is a compromise between the sieve series for measuring the aggregate particle size and the sieve series for measuring the particle size of the slag roadbed material. This is in order to precisely measure the distribution on the finer grain side than the slag roadbed material sieve series. JIS A5015 (2013) The steel slag for roads has a water immersion expansion rate of 1.5% or less, but in actual operation, it is stabilized to a smaller expansion rate in consideration of variations in the product. It is often done. In this example, the standard was to reduce the water expansion coefficient to 0.5% or less with a simple slag after steam aging.
Steam aging was carried out under conditions where the temperature was maintained for 72 hours after reaching about 100 ° C. with an aging facility in which steam was blown from the bottom of the slag piled up with a thickness of 1.5 m to raise the temperature.

[Example 1]
Except for Comparative Example 3, slag C (decarburized slag, particle size 5-40 mm) in which -5 mm fine particles are classified and eliminated, and slag B having a solid particle size in which -5 mm fine particles are not classified and eliminated. (Decarburized slag, particle size 0-40 mm) were mixed to obtain slags (samples) of Invention Examples 1 to 3 and Comparative Examples 1 and 2 having a predetermined particle size distribution. In addition, the comparative example 3 is a slag (sample) which consists only of slag B of solid particle size (decarburization slag, particle size 0-40 mm). For each slag, the particle size distribution was measured and the Fuller index q was calculated by the method described above. Further, each slag was subjected to a water immersion expansion test as defined in JIS A5015 (2013) Annex 2 to measure the dry density and the water expansion coefficient.

  The results are shown in Tables 1 and 2 together with the particle size distribution of the slags A to C, the Fuller index q, the water immersion expansion rate, and the dry density. According to this, Invention Examples 1-3 in which the Fuller index q is in the range of 0.4 to 0.6 have a higher dry density and a lower water immersion expansion rate than the comparative example. On the other hand, in Comparative Examples 2 and 3 in which the Fuller index q is smaller than 0.4, and in Comparative Example 1 in which the Fuller index q is larger than 0.6, the slag is the same as that of the invention example. Low drying density and high water immersion expansion rate.

[Example 2]
Slag C (decarburized slag, particle size 5-40mm) that classifies and excludes -5mm fine particles, and slag D (agglomerated slag, particle size) that does not classify and exclude -5mm fine particles 0-40 mm) were mixed to obtain slags (samples) of Invention Example 4 and Comparative Example 4 having a predetermined particle size distribution. For each slag, the particle size distribution was measured and the Fuller index q was calculated by the method described above. Further, each slag was subjected to a water immersion expansion test as defined in JIS A5015 (2013) Annex 2 to measure the dry density and the water expansion coefficient.

  The results are shown in Tables 3 and 4 together with the particle size distribution of the slags C and D, the fuller index q, the water immersion expansion rate, and the dry density. According to this, the comparative example 4 which mixed slag C (decarburization slag, particle size 5-40mm) and slag D (ingot forming slag, particle size 0-40mm) in the ratio (mass ratio) of 0.75: 0.25. The Fuller index q is greater than 0.6. On the other hand, Invention Example 4 in which slag C and slag D are mixed at a ratio (mass ratio) of 0.4: 0.6 has a fuller index q in the range of 0.4 to 0.6. Here, when the cases where the slags C and D are respectively used are simple, the Fuller index q is both out of the range of 0.4 to 0.6, but the slag D which is an agglomerated slag is free CaO amount. Therefore, the expansion stabilization is prompt and the water expansion rate after steam aging is as low as 0.29%. On the other hand, slag C which is decarburized slag has a larger amount of free CaO than slag D, a low dry density, and a high water immersion expansion rate of 1.02%. In the case of Invention Example 4, the dry density is high, and the water expansion coefficient is lower than the weighted water expansion coefficient average of the slag C and slag D, and the effect of adjusting the particle size distribution appears.

[Example 3]
Slag E (decarburized slag, particle size 0-40mm) of solid particle size that does not classify and exclude fine particles of -5mm and slag F (decarburized slag, particle size 0-5mm) under sieve with a mesh size of 5mm The slag (sample) of Invention Example 5 having a predetermined particle size distribution was mixed. About this slag, the particle size distribution measurement and the calculation of the Fuller index q were performed by the method described above. Further, the slag was subjected to a water immersion expansion test as defined in JIS A5015 (2013) Annex 2, and the dry density and the water expansion coefficient were measured.

  The results are shown in Tables 5 and 6 together with the particle size distribution of slag F alone, the particle size distribution of slag E alone, the Fuller index q, the water immersion expansion rate, and the dry density. According to this, the fuller index q of the slag E (decarburized slag, particle size 0-40 mm) having a solid particle size slightly less than the fine particles is larger than 0.6. On the other hand, in Example 5 in which fine slag F (decarburized slag, particle size 0-5 mm) was mixed at a ratio (mass ratio) of 86:14 to solid slag E, Fuller index q was 0. Within the range of 4-0.6. In addition, Invention Example 5 has a higher dry density than slag E, and the water immersion expansion rate is less than 0.5%.

Claims (7)

For steelmaking slag (a) that has been steam-aged at normal pressure after being crushed to a particle size with a particle size of 40 mm or less at 80 mass% or more, the fine and fine powder content is increased or decreased under the following conditions (i) or (ii) By adjusting the particle size distribution of the steelmaking slag (a) so that the Fuller index is 0.4 to 0.6 when the particle size distribution of the steelmaking slag (a) is approximated by the curve formula of Andreazen A method for producing a steelmaking slag roadbed material.
(I) A part of the steelmaking slag (a) is classified with a sieve (x) having a sieve mesh of 10 mm or less to reduce fine particles and fine powder, and then mixed with the remainder of the steelmaking slag (a).
(Ii) By classifying steelmaking slag that has been previously crushed to a particle size in which the ratio of particle size of 40 mm or less is 80 mass% or more and steam-aged after the crushing, is classified with a sieve (x) having a mesh size of 10 mm or less. The fine particles and fine powder obtained are added to the steelmaking slag (a) and mixed. _2. The steelmaking slag roadbed material according to claim 1, wherein at least a part of the steelmaking slag (a) is steelmaking slag having a basicity (however, a mass ratio of CaO / SiO ₂ ) of 3.3 or more. Production method.   Steelmaking slag (a) is decarburized slag generated in the same refining equipment on the same day, and a part of the steelmaking slag (a) is classified with a sieve (x) having a sieve mesh of 10 mm or less, so that fine particles and fine powder content 3. The particle size distribution is adjusted by reducing the fine particle / fine powder content of the steelmaking slag (a) by mixing with the remainder of the steelmaking slag (a) after reducing the amount of the steelmaking slag (a). Method for manufacturing steelmaking slag roadbed material.   Steelmaking slag (a) is composed of two or more types of steelmaking slag, and all or part of one type of steelmaking slag (a1) is classified with a sieve (x) having a mesh size of 10 mm or less. After reducing the fine powder content, it is mixed with the remaining one or more types of steelmaking slag (a2) and the remainder of the steelmaking slag (a1) (except when all of the steelmaking slag (a1) is classified above). The method for producing a steelmaking slag roadbed material according to claim 1 or 2, wherein the particle size distribution is adjusted by reducing the fine particles and fine powder content of the steelmaking slag (a).   The steelmaking slag roadbed material according to claim 4, wherein the steelmaking slag (a1) is decarburized slag generated in the same refining equipment on the same day, and the steelmaking slag (a2) is steelmaking slag other than decarburized slag. Manufacturing method.   The method for producing a steelmaking slag roadbed material according to any one of claims 1 to 5, wherein the sieve (x) has a mesh size of 4 mm or more and 6 mm or less.   The particle size of the steelmaking slag (a) after adjusting the particle size distribution is any of CS-40, CS-30, CS-20, MS-25, and HMS-25 whose particle size range is defined in JIS A5015 (2013). The method for producing a steelmaking slag roadbed material according to any one of claims 1 to 6, wherein the particle size range is satisfied.

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