Roadbed material and method for manufacturing roadbed material

Abstract

Provided are a roadbed material containing, without clumping, granular carbonated steelmaking slag and a raw material having carbon fixation ability; and a method for manufacturing the roadbed material.　In the roadbed material, the content of at least one of carbonated steelmaking slag, a wood material, a synthetic resin, or a natural fiber is 1-90 mass%.

Description

Roadbed material and method for manufacturing roadbed material

[0001] The present invention relates to a roadbed material and a method for manufacturing the roadbed material.

[0002] Various decarbonization technologies are being considered to achieve carbon neutrality. ２ Carbonates and concrete-related technologies using other CO ２ It is easier to put into practical use than CO ２ Patent Document 1 discloses a roadbed material in which slag is solidified and agglomerated using calcium carbonate or magnesium carbonate, which is produced by a carbonation reaction of slag, as a binder.

[0003] Japanese Patent Application Publication No. 11-21153

[0004] In the roadbed material disclosed in Patent Document 1, carbon dioxide gas or a gas containing carbon dioxide gas is blown into a slag pile or packed bed to solidify and agglomerate the granular slag, and the agglomerates are then crushed, sieved, etc. to adjust the particle size, thereby producing the roadbed material. In this way, Patent Document 1 agglomerates granular slag and then crushes the agglomerates to produce the roadbed material, which poses a problem of a very large production load.

[0005] The present invention has been made in consideration of the problems of the conventional technology, and its purpose is to provide a roadbed material containing granular carbonated steelmaking slag and raw materials with carbon fixation capacity without agglomerating these raw materials, and a method for manufacturing the roadbed material.

[0006] The means for solving the above problems are as follows. [1] A roadbed material, the content of at least one of oxidized steelmaking slag, wood material, synthetic resin, and natural fiber being 1% by mass or more and 90% by mass or less. [2] The roadbed material according to [1], wherein the carbonated steelmaking slag is finely divided carbonized steelmaking slag powder having a particle size of 1 mm or less, and the content of carbonates contained in the finely divided carbonized steelmaking slag powder is 1% by mass or more. [3] The roadbed material according to [1] or [2], wherein the wood material is at least one of wood flour, wood chips, wood wool, wood fiber, pulp, semi-carbonized material, carbide, cellulose nanofiber, carbon nanofiber, and carbon fiber. [4] The roadbed material according to any one of [1] to [3], wherein the synthetic resin is at least one of synthetic rubber scraps, waste tires, polyvinyl chloride scraps, polyethylene scraps, and synthetic fiber scraps, which are synthetic polymer compounds. [5] The roadbed material according to any one of [1] to [4], wherein the natural fiber is at least one of plant fiber and animal fiber. [6] The roadbed material according to any one of [1] to [5], wherein the carbonated steelmaking slag is at least one of carbonated converter slag, carbonated secondary refining slag, carbonated hot metal pretreatment slag, and carbonated electric furnace slag. [7] The roadbed material according to any one of [1] to [6], wherein the carbonated steelmaking slag is slag obtained by carbonating ground steelmaking slag having a particle size of 1 mm or less. [8] A method for manufacturing a roadbed material, comprising a mixing step of mixing steelmaking slag with at least one of carbonated steelmaking slag, wood material, synthetic resin, and natural fiber, wherein the mixing step is performed so that the content of the at least one of carbonated steelmaking slag, wood material, synthetic resin, and natural fiber is 1% by mass or more and 90% by mass or less. [9] The roadbed material according to [8], wherein the carbonated steelmaking slag is ground carbonized steelmaking slag produced by carbonating ground steelmaking slag having a particle size of 1 mm or less.

[0007] According to the present invention, raw materials with carbon fixation capacity can be mixed without agglomeration to produce a roadbed material. Therefore, the roadbed material according to the present invention is a roadbed material that can be easily manufactured with a low production load. Furthermore, by using this roadbed material, CO２ This will make it easier to manufacture roadbed materials with fixed carbon, thereby contributing to the realization of carbon neutrality.

[0008] [Embodiment 1] Hereinafter, the present invention will be described through an embodiment of the present invention. In the roadbed material according to this embodiment, a part of the amount of admixture mixed into the roadbed material is CO ２ The CO ２ As a first embodiment, a roadbed material containing carbonated steelmaking slag will be described.

[0009] The roadbed material according to embodiment 1 includes carbonated steelmaking slag. The roadbed material according to embodiment 1 includes carbonated steelmaking slag. A mixing step is carried out in which the carbonated steelmaking slag is mixed with at least one of non-carbonated steelmaking slag, blast furnace slag, and electric furnace slag. These are then crushed and blended to satisfy the particle size composition of CS-40 specified in JIS A 5015:2018 "Iron and steel slag for roads." This can be produced.

[0010] For the carbonated steelmaking slag, it is preferable to use carbonated ground steelmaking slag having a particle size of 1 mm or less, which is produced by carbonating ground steelmaking slag having a particle size of 1 mm or less. That is, it is preferable that the carbonated steelmaking slag is a slag obtained by carbonating ground steelmaking slag having a particle size of 1 mm or less. A particle size of 1 mm or less means a particle size that can be sieved through a sieve with a mesh size of 1 mm. By using ground steelmaking slag having a particle size of 1 mm or less, a reaction accelerating effect can be obtained by increasing the reaction interface area during the carbonation treatment, and the CO of the carbonated steelmaking slag can be increased. ２ The fixed amount increases.

[0011] Carbonated steelmaking slag is produced by adding steam to steelmaking slag and then adding CO ２ Instead of adding steam to the steelmaking slag, the steelmaking slag is kept in water and CO ２ Carbonated steelmaking slag may be produced by introducing a gas containing the steelmaking slag and carrying out a carbonation treatment for one day. ２Carbonated steelmaking slag may be produced by introducing a CO containing gas and carrying out the carbonation treatment for one day. ２ CO contained in gas ２ The concentration should be 1% by volume or more. ２ CO emitted from manufacturing process equipment in steelworks as a contained gas ２ An exhaust gas having a concentration of 10% by volume or more may be used. The steelmaking slag used to produce the carbonated steelmaking slag is at least one of converter slag, secondary refining slag, hot metal pretreatment slag, and electric furnace slag.

[0012] Carbonated steelmaking slag contains carbonates introduced by the carbonation treatment described above. The carbonates are, for example, any of calcium carbonate, calcium carbonate hydrate, magnesium carbonate, and magnesium carbonate hydrate. It is preferable to perform the carbonation treatment of steelmaking slag so that the carbonate content in the carbonated steelmaking slag is 1 mass % or more. Carbonates include CO ２ Therefore, the fact that carbonated steel slag contains a large amount of carbonates means that CO is fixed in the roadbed material. ２ Therefore, it is preferable to use carbonated steelmaking slag with a carbonate content of 1 mass % or more as a raw material for roadbed material, and this will increase the CO ２ The higher the content of carbonates in the carbonated steel slag, the more CO2 is fixed in the roadbed material. ２ Since the amount increases, there is no need to set an upper limit for the carbonate content.

[0013] Carbonated steel slag is mixed into the roadbed material so that the content of carbonated steel slag is 1 mass % or more. ２ This can fix carbon dioxide and contribute to the realization of carbon neutrality. Carbonated steelmaking slag is mixed into the roadbed material so that its content is 90% by mass or less. By keeping the content of carbonated steelmaking slag at 90% by mass or less, the bearing capacity of the roadbed material is improved, and the modified CBR of the roadbed material can be made 60 or more. Here, the modified CBR test is the CBR of roadbed material compacted to 95% of its maximum dry density.

[0014] In this way, the roadbed material containing carbonated steelmaking slag according to the first embodiment has a high carbon dioxide content. ２ The carbon dioxide is fixed in the base course material, so using this material can contribute to achieving carbon neutrality. Furthermore, a modified CBR of 60 or more can be secured, resulting in a base course material with high bearing capacity, and because carbonated steel slag contains calcium carbonate, etc., it also has the effect of suppressing alkali elution.

[0015] [Embodiment 2] Next, a roadbed material containing a wood material will be described as embodiment 2. By using a wood material as a raw material for the roadbed material, CO ２ The wood material is, for example, at least one of wood flour, wood chips, wood wool, wood fiber, pulp, semi-carbonized material, carbonized material, cellulose nanofiber, carbon nanofiber, and carbon fiber.

[0016] The roadbed material containing the wood material according to the second embodiment is produced by carrying out a mixing step in which the wood material is mixed with uncarbonated steel slag. Then, these are crushed and blended to satisfy the particle size composition of CS-40 specified in JIS A 5015:2018 "Iron and steel slag for roads." The wood material is mixed so that the content of the wood material in the roadbed material is 1% by mass or more and 90% by mass or less. This allows CO2 to be added to the roadbed material. ２ The modified CBR of the roadbed material can be increased to 60 or more.

[0017] By using wood materials as the raw material for roadbed materials, it is possible to adjust the specific gravity of the roadbed material to be manufactured. Roadbed materials with a high specific gravity and a low content of wood materials are suitable for use as roadbed materials for parking lots, for example. On the other hand, roadbed materials with a low specific gravity and a high content of wood materials are suitable for use as paving materials for solar power generation facilities, for example. Using roadbed materials with a low specific gravity and a high content of wood materials makes construction easier, and therefore can shorten the construction period.

[0018] Wood materials have high water absorption, and this high water absorption can suppress the separation of fine powder raw materials in the roadbed material during construction. Therefore, roadbed materials containing wood materials have a high filling rate during construction, resulting in roadbed materials with high bearing capacity. Furthermore, roadbed materials containing wood materials can absorb the expansion of the roadbed material with the wood material, resulting in roadbed materials with excellent elasticity. As the elastic modulus of the roadbed material increases, the modified CBR of the roadbed material improves, so roadbed materials containing wood materials have a higher modified CBR than roadbed materials that do not contain wood materials.

[0019] Due to its high water absorption, roadbed materials that do not contain wood have a natural moisture content of 2 to 3% by mass when piled up, while roadbed materials that contain wood have a natural moisture content of 6 to 7% by mass when piled up. Due to this difference in natural moisture content, roadbed materials that contain wood produce less dust and other particles when piled up than roadbed materials that do not contain wood.

[0020] Furthermore, it is preferable that the wood material contains at least one of semi-carbonized materials and carbides. Semi-carbonized materials and carbides contain many pores, which further increases the water absorption of the wood material. Therefore, roadbed materials containing wood materials containing at least one of semi-carbonized materials and carbides have a higher filling rate during construction and become roadbed materials with higher bearing capacity. Semi-carbonized materials can be produced by heating wood materials in an oxygen-free or low-oxygen reducing atmosphere at a temperature of 200°C or higher but lower than 300°C. Carbonized materials can be produced by heating wood materials in an oxygen-free or low-oxygen reducing atmosphere at a temperature of 300°C or higher but lower than 1000°C.

[0021] [Embodiment 3] Next, a roadbed material containing a synthetic resin will be described as embodiment 3. By using a synthetic resin as a raw material for the roadbed material, ２ The synthetic resin is, for example, at least one of synthetic rubber scraps, which are synthetic polymer compounds, waste tires, polyvinyl chloride scraps, polyethylene scraps, and synthetic fiber scraps. The synthetic fiber scraps include, for example, polyester-based, polyurethane-based, polyvinyl alcohol-based, polyacrylonitrile-based, and polypropylene-based synthetic fiber scraps, but does not include nylon resin fiber scraps, which are polyamide-based.

[0022] The roadbed material containing synthetic resin according to the third embodiment is produced by carrying out a mixing step in which synthetic resin is mixed with uncarbonated steelmaking slag. Then, these are crushed and blended so as to satisfy the particle size composition of CS-40 specified in JIS A 5015:2018 "Iron and steel slag for roads." The synthetic resin is mixed so that the content of synthetic resin in the roadbed material is 1% by mass or more and 90% by mass or less. This allows CO2 to be added to the roadbed material. ２ The modified CBR of the roadbed material can be increased to 60 or more.

[0023] By using synthetic resin as a raw material for roadbed material, it is possible to produce roadbed material with high thermal insulation properties. Furthermore, by using synthetic resin as a raw material for roadbed material, it is possible to produce lightweight roadbed material and roadbed material with a high elastic modulus. As the elastic modulus of the roadbed material increases, the modified CBR of the roadbed material improves, so roadbed material containing synthetic resin has a higher modified CBR than roadbed material that does not contain synthetic resin.

[0024] [Embodiment 4] Next, a roadbed material containing natural fibers will be described as embodiment 4. By using natural fibers as a raw material for the roadbed material, ２ The natural fiber is at least one of plant fibers such as cotton, hemp, linen, rice husk, palm kernel shell, and banana peel, and animal fibers such as wool, cashmere, and silk.

[0025] The roadbed material containing natural fibers according to the fourth embodiment is produced by carrying out a mixing step in which natural fibers are mixed with uncarbonated steelmaking slag. Then, these are crushed and blended so as to satisfy the particle size composition of CS-40 specified in JIS A 5015:2018 "Iron and steel slag for roads." The natural fibers are mixed so that the content of natural fibers in the roadbed material is 1% by mass or more and 90% by mass or less. This allows CO2 to be added to the roadbed material. ２ The modified CBR of the roadbed material can be increased to 60 or more.

[0026] By using natural fibers as the raw material for roadbed material, it is possible to produce roadbed material with high strength. Furthermore, by using natural fibers as the raw material for roadbed material, it is possible to produce lightweight roadbed material and roadbed material with a high elastic modulus. As the elastic modulus of the roadbed material increases, the modified CBR of the roadbed material improves, so roadbed material containing natural fibers has a higher modified CBR than roadbed material that does not contain natural fibers.

[0027] In the first to fourth embodiments, the roadbed material has been described using an example of a roadbed material containing carbonated steelmaking slag, a wood material, a synthetic resin, or natural fibers, but the present invention is not limited to this. Roadbed material may be manufactured using a wood material together with carbonated steelmaking slag, a synthetic resin together with carbonated steelmaking slag, or natural fibers together with carbonated steelmaking slag. Furthermore, roadbed material may be manufactured using a synthetic resin together with wood material, a natural fiber together with wood material, or natural fibers together with synthetic resin.

[0028] The roadbed material according to this embodiment contains at least one of carbonated steelmaking slag, wood material, synthetic resin, and natural fibers, and the content of at least one of the carbonated steelmaking slag, wood material, synthetic resin, and natural fibers is 1% by mass or more and 90% by mass or less. As such, the roadbed material according to this embodiment can be produced by mixing the carbonated steelmaking slag, wood material, synthetic resin, and natural fibers without agglomerating these raw materials and adjusting them to a predetermined particle size, resulting in a roadbed material that is easier to manufacture and requires less production load than conventional roadbed materials.

[0029] Next, CO ２ This example describes the production of roadbed material that satisfies the CS-40 particle size structure by adjusting the mixing ratio of the mixed raw materials, using carbonated steel slag, wood material, synthetic resin, and natural fiber as mixed raw materials with fixed carbon dioxide. The type of mixed raw materials, mixing ratio, maximum particle size, natural moisture content of the roadbed material, corrected CBR of the roadbed material, strength evaluation results, and CO of the roadbed material are shown in Table 1. ２ The fixed amounts are shown in Table 1 below. The component compositions of the steelmaking slags used in the examples are shown in Table 2 below.

[0030]

[0031]

[0032] In Table 1 above, "mixing ratio" is the content ratio (mass%) of the mixed raw material contained in the roadbed material. "Maximum particle size of the mixed raw material" means that the entire amount passed through a sieve with a nominal opening specified in JIS Z 8801-1:2019 corresponding to the maximum particle size (mm).

[0033] "Modified CBR" is CBR at a maximum dry density of 95%, and CBR is the load when a 5.0 cm diameter piston is penetrated 2.5 mm or 5.0 mm into the surface of the roadbed material, expressed as a percentage of the standard load. The standard load is 13.4 kN for 2.5 mm penetration and 19.9 kN for 5.0 mm penetration. For "strength judgment," if the modified CBR is 60 or more, the material is judged to have sufficient bearing capacity as a roadbed material and is rated as "Good," and if the modified CBR is less than 60, the material is judged to have insufficient bearing capacity as a roadbed material and is rated as "Poor."

[0034] The semi-carbonized wood material was produced by treating wood flour with a particle size of 1 mm or less with superheated steam at 250°C for 10 minutes. The carbonized wood material was produced by treating wood flour with an average particle size of 300 μm or less with superheated steam at 300°C for 20 minutes.

[0035] As shown in Table 1, examples 1 to 23 of the present invention, the roadbed materials containing 1% by mass or more and 90% by mass or less of at least one of carbonated steelmaking slag, wood material, synthetic resin, and natural fiber had a good balance of coarse particles and fine particles within the range of the particle size composition of CS-40, and the packing density of the roadbed material was high, resulting in a high corrected CBR. ２ It was confirmed that this roadbed material can fix the soil and has a high bearing capacity with a modified CBR of 60 or more. Furthermore, the use of this roadbed material can contribute to the realization of carbon neutrality.

[0036] On the other hand, the roadbed material (Comparative Example 5) that did not contain carbonated steel slag, wood material, synthetic resin or natural fiber had a corrected CBR value of 60 or more, but CO ２The roadbed materials containing 95% by mass, which is more than 90% by mass, of carbonated steelmaking slag, wood material, synthetic resin or natural fiber had a high blending ratio of the mixed raw materials, and the ratio of fine particles increased within the range that satisfied the CS-40 particle size, resulting in a decrease in the filling rate of the roadbed material and a decrease in the corrected CBR to less than 60%. From these results, it can be seen that the roadbed materials according to Comparative Examples 1 to 4, which contained more than 90% by mass of carbonated steelmaking slag, wood material, synthetic resin or natural fiber, had a high CO ２ Although it was possible to fix the foundation, the corrected CBR was less than 60, and it was confirmed that the bearing capacity of the roadbed material was low.

[0037] It has been confirmed that roadbed materials mixed with wood materials have a higher natural moisture content than other roadbed materials, resulting in roadbed materials with a higher modified CBR. Furthermore, because the higher natural moisture content allows fine powder to be adsorbed, when roadbed materials containing wood materials are stored in piles, the generation of dust and other particles can be suppressed more than with other roadbed materials.

Claims

1. A roadbed material having a content of at least one of carbonated steelmaking slag, wood material, synthetic resin, and natural fiber of 1% by mass or more and 90% by mass or less.

2. The carbonated steelmaking slag is finely powdered carbonated steelmaking slag having a particle size of 1 mm or less, 2. The roadbed material according to claim 1, wherein the content of carbonates contained in the carbonated ground steelmaking slag is 1% by mass or more.

3. The roadbed material according to claim 1 or 2, wherein the wood material is at least one of wood flour, wood chips, wood wool, wood fiber, pulp, semi-carbonized material, carbonized material, cellulose nanofiber, carbon nanofiber, and carbon fiber.

4. The roadbed material according to claim 1 or 2, wherein the synthetic resin is at least one of synthetic rubber scraps, waste tires, polyvinyl chloride scraps, polyethylene scraps, and synthetic fiber scraps, which are synthetic polymer compounds.

5. The roadbed material according to claim 1 or 2, wherein the natural fibers are at least one of plant fibers and animal fibers.

6. 3. The roadbed material according to claim 1 or 2, wherein the carbonated steelmaking slag is at least one of carbonated converter slag, carbonated secondary refining slag, carbonated hot metal pretreatment slag, and carbonated electric furnace slag.

7. 3. The roadbed material according to claim 1, wherein the carbonated steelmaking slag is slag obtained by carbonating finely powdered steelmaking slag having a particle size of 1 mm or less.

8. A method for manufacturing a roadbed material, A method for producing a mixture of carbonated steelmaking slag, wood material, synthetic resin, and natural fiber with steelmaking slag, A method for manufacturing roadbed material, wherein in the mixing step, the carbonated steelmaking slag, wood material, synthetic resin, and natural fiber are mixed so that the content of at least one of them is 1% by mass or more and 90% by mass or less.

9. The method for manufacturing a roadbed material according to claim 8, wherein the carbonated steelmaking slag is produced by carbonating ground steelmaking slag having a particle size of 1 mm or less.