JP6041006B2 - Reduction material for civil engineering materials - Google Patents

Description

  The present invention relates to a material (reducing material) for improving environmental characteristics of a civil engineering material in which a small amount of hexavalent chromium or the like may be eluted, and particularly suitable for civil engineering materials mainly composed of concrete waste materials. Regarding materials.

  2. Description of the Related Art Conventionally, concrete waste generated as construction waste has been widely used as civil engineering materials such as roadbed materials, recycled sand, earthwork materials (for example, backfill materials), and the like. By the way, it is known that cement produced in a high growth period or the like may contain a trace amount of hexavalent chromium derived from chromium mixed in the manufacturing process. Once the cement has solidified as concrete, there is little risk of elution of hexavalent chromium from the cement. However, it has been pointed out that hexavalent chromium that exceeds soil environmental standards may be eluted when concrete that has been neutralized (deteriorated) is finely crushed.

Moreover, even in general soil, it may be contaminated by harmful substances due to the environment in which it is placed, the surrounding drainage, or natural origin, and it may exceed the environmental standard value. Heavy metals such as arsenic and organic compounds such as trichlorethylene and dioxin have upper limits set by soil environmental standards.
Since hexavalent chromium can be reduced to trivalent to significantly reduce solubility and ensure safety, a method for suppressing elution by mixing a reducing material is well known as a reducing material. A method using ferrous sulfate (for example, Patent Document 1), a method using a sulfur-based reducing material (for example, Patent Document 2), a method using iron powder (for example, Patent Document 3), and the like are known. ing.

  However, although ferrous sulfate has a rapid effect, there is a drawback that the effect is lost immediately. In addition, it has been pointed out that the sulfur-based reducing material maintains a relatively long-term reduction performance, but it is desirable to determine the particle size and characteristics of the material within a specific range in order to ensure quick action. In addition, iron powder can be expected to have a long-term reduction effect compared to ferrous sulfate, which is the same iron-based reducing material, but in fact, it has been pointed out that the ground is softened by mixing in a slurry state. Has been. This is because homogeneous mixing is difficult unless sufficient attention is paid to the mixing conditions of the iron powder and the target material.

  As techniques for dealing with such problems, Patent Documents 4 to 6 show techniques for suppressing a small amount of chromium elution by mixing blast furnace slow-cooled slag with limited particle size and mixing conditions into concrete waste. It has been confirmed that the elution characteristics of hexavalent chromium are greatly reduced by this technique. However, as a result of a more detailed investigation, when concrete waste was processed, the surrounding soil was brought together and processed together with the concrete waste, or the local civil engineering materials were used together. It has been found that various materials (such as soil) may be mixed with the waste material, and in such a case, the reduction performance may be reduced depending on conditions.

  On the other hand, Patent Documents 7 to 9 show techniques for using steelmaking slag for soil improvement. Among these, the method of Patent Document 7 uses desulfurized slag and is expected to have a reducing ability with sulfur, but the effects of iron oxide and iron powder are unclear. Patent Document 8 discloses a method for treating harmful substances using a collecting material composed of steelmaking slag and alkanolamine. In this document, when only steelmaking slag is used, various disturbing anions are used. It is said that the effect cannot be expected in a high concentration environment. Patent Document 9 discloses a method of stabilizing waste containing heavy metals using steelmaking slag such as converter slag. However, this method requires a special treatment field and a temperature field such as coexistence in a hot water environment, and the possibility of elution suppression by a simple method such as mixing with civil engineering materials is not clear.

Patent Document 10 discloses a harmful substance reducing material composed of a blast furnace slow cooling slag and a steelmaking slag. This technique exhibits a reduction effect by the blast furnace slow cooling slag, and Fe ₂ O _{3 of the} steelmaking slag. And Al ₂ O ₃ insolubilize harmful substances. With this technology, it is thought that reduction and insolubilization of heavy metals can be realized, but oxidizing slag with high concentrations of Fe ₂ O ₃ and Al ₂ O ₃ , which is said to be steelmaking slag in the same document, It differs greatly from the composition of steelmaking slag generated in the steelmaking process (integrated blast furnace ironmaking). For reference, the composition of typical converter slag shown in the Steel Slag Association HP (FeO: Fe ₂ O _{3 in} T-Fe is 1: 1 to 2: 1) and the composition of electric furnace slag Table 1 shows. Even in Patent Document 10, the steelmaking slag to be used contains 20% or more of calcium ferrite or calcium aluminoferrite, and calcium ferrite is a mixture of a raw material containing a CaO source and a raw material containing a Fe ₂ O ₃ source, It describes that it is a general term for substances obtained by heat treatment in a kiln or an electric furnace (paragraph 0016), and the steelmaking slag used in Patent Document 10 is an electric furnace system oxidation slag or a general steel manufacturing process. It is considered that the steelmaking slag generated in (Blast Furnace Integrated Steelmaking) is a component adjusted and heat-treated using raw material. Moreover, the technique of patent document 10 does not utilize effectively reaction of metal Fe and FeO which steelmaking slag has, as evident from the reaction mechanism by said substance.

On the other hand, Patent Document 11 proposes a soil improvement material made of steelmaking slag having a specific composition, focusing on the reducing function of metal Fe and FeO in steelmaking slag. This soil improvement material is made of steelmaking slag having a T-Fe content of 15% by mass or more, an FeO content of 10% by mass or more, and CaO / SiO ₂ of 2 or more and less than 5, and has a reducing effect on the soil. The Further, the same document shows that it is effective to mix unaged blast furnace chilled slag with steelmaking slag when the characteristics of the soil fluctuate.

JP 09-85224 A Japanese Patent No. 3299174 JP 2001-198567 A Japanese Patent No. 4692064 Japanese Patent No. 4972242 Japanese Patent No. 4972243 JP 2003-206172 A Japanese Patent Laid-Open No. 2005-74280 JP 2000-37676 A Japanese Patent No. 4264523 JP 2011-93946 A

  Concrete waste materials are often applied to roadbed materials and backfill materials. In this case, volume stability is required at the same time as compared to general soil. This is because the roadbed material and backfill material need to be maintained in a state in which the load capacity and flatness are ensured by compaction or the like. Therefore, it is necessary to apply a reducing material having a reduction characteristic while ensuring volume stability to a civil engineering material mainly composed of concrete waste material. However, in the soil improvement material disclosed in Patent Document 11, an appropriate volume stability is required. It was found that sex cannot be secured.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and has an excellent reduction performance capable of reducing hexavalent chromium and the like contained in a trace amount in a civil engineering material such as concrete waste material. An object of the present invention is to provide a reducing material for civil engineering materials that can effectively suppress elution of valence chromium and the like and can ensure appropriate volume stability of the civil engineering materials.

As a result of repeated studies to find an optimum reducing material that can solve the above-mentioned problems, the present inventors have found that (i) when civil engineering materials mainly composed of concrete waste materials are used, CaO / SiO ₂ is relatively it can exert a desired reduction performance at low steelmaking slag, in one (ii), from the viewpoint of the volume stability of civil engineering materials, requires the CaO / SiO ₂ as a reducing agent using a relatively low and low expansion of steel slag (Iii) Facts such as (iii) Mixing steelmaking slag with unaged blast furnace slow-cooled slag and providing multiple reduction routes can suppress fluctuations in the elution suppression effect due to changes in the target material I found.

The present invention has been made on the basis of the above-described findings and has the following gist.
[1] FeO amount is 8% by mass or more, T-Fe amount is 10% by mass or more, the total of Al ₂ O ₃ amount and Fe ₂ O ₃ amount is less than 20% by mass, and CaO / SiO ₂ (mass ratio) is 1. A steelmaking slag (A) of 0.0 or more and less than 2.0 and an unaged blast furnace slow cooling slag (B), and the steelmaking slag (A) has an expansion coefficient of 1 when immersed in hot water at 80 ° C. for 10 days. A reducing material for civil engineering materials, characterized in that the mass ratio of steelmaking slag (A) and blast furnace slow-cooled slag (B) is 20:80 to 80:20.

[2] In the reducing material for civil engineering materials according to [1] above, the blast furnace slow-cooled slag (B) is mixed with water at a mass part ratio of water: slag = 10: 1, shaken at 200 rpm for 6 hours, and then filtered. A reducing material for civil engineering materials, characterized in that it is a blast furnace slow-cooled slag in which the leaching amount of thiosulfate ions is 30 mg / L or more.
[3] In the above-mentioned [1] or [2] reducing material for civil engineering materials, the steelmaking slag (A) has a total amount of Si ₂ O and Al ₂ O ₃ of 40% by mass or less. Reducing material for materials.
[4] The civil engineering material reducing material according to any one of the above [1] to [3], wherein the steelmaking slag (A) and the blast furnace annealed slag (B) have a particle size of 10 mm or less. Reducing material for materials.

[5] A method for modifying a civil engineering material, wherein the reducing material for civil engineering material according to any one of the above [1] to [4] is mixed with a civil engineering material partially or entirely made of concrete waste.
[6] A method for modifying a civil engineering material with a reducing material for civil engineering materials according to any one of the above [1] to [4], wherein the steelmaking slag (A) and the blast furnace annealed slag to constitute the reducing material for civil engineering material A method for modifying a civil engineering material, characterized in that (B) is added to a civil engineering material partially or wholly made of waste concrete material and then mixed.

  The reducing material for civil engineering materials of the present invention has an excellent reducing performance capable of reducing hexavalent chromium and the like contained in a small amount in a civil engineering material such as concrete waste, and effectively dissolves hexavalent chromium from the civil engineering material. While being able to suppress, appropriate volume stability of civil engineering material can be ensured. For this reason, it is particularly useful when concrete waste is used for roadbed materials and the like.

A graph showing the relationship between the mixing ratio (mass ratio) of steelmaking slag of reducing material and blast furnace annealing slag, and the elution ratio of hexavalent chromium in civil engineering materials (concrete waste material + soil, etc.) to which the reducing material is added

The reducing material for civil engineering materials of the present invention comprises steel slag (A) and unaged blast furnace slow-cooled slag (B), and the mass ratio of steel-making slag (A) and blast furnace slow-cooled slag (B) is 20:80. ~ 80: 20. The steelmaking slag (A) has an FeO amount of 8% by mass or more, a T-Fe amount of 10% by mass or more, a total of Al ₂ O ₃ amount and Fe ₂ O ₃ amount of less than 20% by mass, CaO / SiO _2. While having a composition whose (mass ratio) is 1.0 or more and less than 2.0, the expansion rate when immersed in warm water at 80 ° C. for 10 days is 1.5% or less.

  Steelmaking slag (A) can be reduced by hexavalent chromium or the like by FeO or metal Fe contained therein. Steelmaking slag (A) includes converter decarburization slag, hot metal pretreatment slag (eg, dephosphorization slag, desiliconization slag), electric furnace slag, secondary refining slag, ingot slag, etc. Species or two or more can be used. Among the steelmaking slags, hot metal pretreatment slag is preferable, and among them, slag generated in the dephosphorization process (generally, dephosphorization slag) is particularly preferable from the viewpoint of the abundance ratio of Fe and volume stability.

  The steelmaking slag (A) has an FeO amount of 8 mass% or more, preferably 10 mass% or more, and a T-Fe amount (total iron element amount) of 10 mass% or more, preferably 15 mass% or more. When the amount of FeO is less than 8% by mass and the amount of T—Fe is less than 10% by mass, sufficient reduction performance cannot be obtained. The iron content in the steelmaking slag may be present in addition to FeO, such as metallic iron, iron hydroxide, and trivalent iron oxide. From the viewpoint of reducing action, it is desirable that the iron content is 1% by mass or more. More preferably, the content is 2% by mass or more.

The CaO / SiO ₂ (mass ratio) of the steelmaking slag (A) is 1.0 or more and less than 2.0, preferably 1.2 to 1.9, more preferably 1.2 to 1.7.
In the invention of Patent Document 11, CaO / SiO 2 _(weight ratio) as a reducing agent for soil is used is relatively high steel slag. On the other hand, in the present invention, as a result of examining reducing materials for civil engineering materials, particularly reducing materials for civil engineering materials mainly composed of concrete waste materials, steelmaking slag having a relatively low CaO / SiO ₂ (mass ratio) was used. Even in this case, it has been found that an effective reducing action can be obtained. The reason for this is not necessarily clear, but it is considered that Ca is supplied from the concrete waste that is the applied material, which compensates for the lack of dissolved Ca from the steelmaking slag, and as a result, an effective reducing action is obtained. On the other hand, from the viewpoint of volume stability of civil engineering materials, it is highly desirable that the steelmaking slag has a low CaO / SiO ₂ (mass ratio). When CaO / SiO ₂ (mass ratio) is 2.0 or more, CaO becomes excessive with respect to the mineral phase of 2CaO · SiO ₂ , and free CaO is easily expressed. Free CaO reacts easily with moisture and becomes Ca (OH) ₂ to cause volume expansion. In particular, civil engineering materials such as roadbed materials and recycled sand are often used after being compacted, and are more susceptible to expansion than normal soil. When the steelmaking slag (A) used in the reducing material has a CaO / SiO ₂ (mass ratio) of 2.0 or more, if the additional treatment such as steam aging is not performed, the roadbed surface is deformed or raised by volume expansion. It is easy to cause problems such as.
On the other hand, if the CaO / SiO ₂ (mass ratio) is less than 1.0, it is not preferable because it is likely to become amorphous when the steelmaking slag is cooled and the feed rate of Fe ²⁺ tends to decrease.

Steel slag (A) is the sum of the amount of _Al 2 _{O 3} and the amount of _Fe 2 _{O 3} and less than 20 wt%. When the ratio of the amount of Al ₂ O ₃ is too high, Al ₂ O ₃ forms a compound with FeO or the like, so that the effective supply rate of Fe ²⁺ decreases. In addition, Fe ₂ O ₃ is considered not to contribute to the reduction performance of the reducing material of the present invention. Rather, increasing Fe ₂ O ₃ in normal steelmaking slag also decreases FeO. Less is preferable. Therefore, the total amount of Al ₂ O ₃ and Fe ₂ O ₃ is less than 20% by mass.

Even when the amount of SiO ₂ is too high, SiO ₂ forms a compound with FeO or the like, so that the supply rate of Fe ²⁺ decreases. Therefore, the total amount of Si ₂ O and Al ₂ O ₃ is preferably 40% by mass or less.
The steelmaking slag (A) has an expansion rate of 1.5% or less, preferably 0.7% or less when immersed in warm water at 80 ° C. for 10 days. When the expansion rate of the steelmaking slag (A) exceeds 1.5%, the volume stability of the civil engineering material is lowered. In addition, the expansion rate here is based on the water immersion expansion test method described in the appendix of JIS-A-5015 “Steel Slag for Roads”.

In the unaged blast furnace slow-cooled slag (B), polysulfides and thiosulfuric acid supplied from this have a reducing action such as hexavalent chromium.
Aging of blast furnace slow-cooled slag is defined in JIS-A-5015 “Steel Slag Subbase Material”. Unaged blast furnace slow-cooled slag is one whose aging period after crushing is less than 6 months It is.
As described above, unaged blast furnace slag is used for blast furnace chilled slag that has been aged in the atmosphere while polysulfides and thiosulfate ions are leached from unaged blast furnace chilled slag. This is because in the slag, the oxidation of sulfide proceeds from the surface and changes to sulfate (SO ₄ ²⁻ ), and the reducing ability is greatly reduced.

  Unaged blast furnace slow-cooled slag is a reducing material that is particularly effective for waste concrete. Further, among the non-aged blast furnace chilled slag, one having a high reducing ability is more desirable. In particular, it is mixed with water at a mass part ratio of water: slag = 10: 1, shaken at 200 rpm for 6 hours, and then filtered. It is preferable to use a blast furnace slow cooling slag in which the leaching amount of thiosulfate ions is 30 mg / L or more, preferably 50 mg / L or more. The thiosulfate ion is an ion known as a reducing agent, and is eluted in a state in which the sulfur component contained in the blast furnace slow cooling slag is partially oxidized. Although the effect can be expected even with blast furnace slow cooling slag having a leaching amount of thiosulfate ions of less than 30 mg / L, in order to obtain a stable reduction effect against the influence of interfering anions, the leaching amount of thiosulfate ions is It is 30 mg / L or more, preferably 50 mg / L or more.

  Although there is no special restriction | limiting in the particle size of steelmaking slag (A) and blast furnace slow cooling slag (B), Since a reducing substance becomes easy to be supplied to civil engineering material, so that a surface area is large, a particle size is preferable 10 mm or less. For the same reason, it is more preferable that the ratio of the particle size of 5 mm or less has a particle size of 90% by mass or more, and it is particularly preferable that the ratio of the particle size of 2 mm or less has a particle size of 90% by mass or more. The particle diameter of slag means the particle diameter prescribed | regulated using the sieve which has the said mesh. As the size of the sieve, those represented by JIS1-Z-8801 and the like can be used.

The mixing ratio of the steelmaking slag (A) and the blast furnace slow-cooled slag (B) is 20:80 to 80:20 by mass ratio. Outside this range, the effect of combining the reducing action of both slags cannot be sufficiently obtained.
Steel slag (T-Fe amount: 16.7% by weight, FeO amount: 10 wt%, the metal Fe content: 4 wt%, _Al 2 _{O 3} amount: 5.5 wt%, _Fe 2 _{O 3} amount: 7% , SiO ₂ amount: 25% by mass, CaO / SiO _2: 1.2, expansion rate: 0.2%) and unaged blast furnace annealed slag (thiosulfate leaching amount 70 mg / L) Satisfactory reducing material (reducing material having a mass ratio of steelmaking slag and blast furnace slow cooling slag of three levels of 20:80, 50:50, 80:20), reducing material consisting of the above steelmaking slag alone, unaged blast furnace Reducing materials consisting of simple slow slag are used, and 5% by mass of these reducing materials are added to civil engineering materials (concrete waste materials: 96% by mass) mixed with concrete wastes. Dissolution test based on dissolution test method The elution amount of hexavalent chromium was measured. Construction waste soil collected at several locations was used as concrete waste and soil mixed with it, and tests were conducted on different types of civil engineering materials.

  Regarding the hexavalent chromium elution suppression effect in this test, the average value of the hexavalent chromium elution amount ratio (the hexavalent chromium elution amount when no reducing material is added is “1”, and the hexavalent chromium elution amount ratio is the same)) The degree of variation is shown in FIG. According to this, although the reducing material which consists of a steelmaking slag single-piece | unit has the elution inhibitory effect of hexavalent chromium, the grade is not so high. On the other hand, the reducing material composed of unaged blast furnace annealed slag alone has a high hexavalent chromium elution inhibitory effect, and the average value is low, but the hexavalent chromium elution inhibitory effect may be reduced depending on the case, The variation of the suppression effect is increasing. In contrast, a reducing material in which steelmaking slag and unaged blast furnace chilled slag are mixed (mass ratio of steelmaking slag and blast furnace chilled slag is three-level reducing material of 20:80, 50:50, 80:20) Compared to a reducing material made of unaged blast furnace chilled slag alone, the average value does not change much and the variation is small. In this way, the reducing material satisfying the conditions of the present invention in which steelmaking slag and unaged blast furnace slow-cooled slag are mixed has a wide range of conditions for reducing elution of hexavalent chromium by combining two reducing actions (target material) It can be seen that it can be obtained effectively.

The composition conditions of the steelmaking slag defined in the present invention are, for example, CaO / SiO ₂ (mass ratio),
About the amount of Al ₂ O ₃ and SiO ₂ , by adjusting the auxiliary raw materials (lime, silica, etc.) during refining, etc., and about the amount of T—Fe, the amount of FeO, the amount of Fe ₂ O _{3 and the} amount of metallic Fe, It can be realized by adjusting the iron oxide addition conditions and oxygen blowing conditions during the ironmaking operation, adjusting the magnetic separation conditions, adjusting the cooling conditions, and the like. Further, the expansion rate of the slag can be realized by selecting the input raw material of the CaO component, adjusting the input amount and the input timing, and the like.

The civil engineering materials to which the reducing material of the present invention is applied are, for example, roadbed materials, recycled sand, earthwork materials (for example, backfill materials, hearth materials, laying materials other than roadbed materials, etc.). In particular, for the reasons described above, civil engineering materials that are partly or entirely made of concrete waste materials are suitable, and in particular, civil engineering materials mainly composed of concrete waste materials, generally more than 50% by mass, preferably 70% by mass or more, Particularly preferred is a civil engineering material comprising 90% by mass or more of a waste concrete material (however, a civil engineering material consisting only of a concrete waste material is included). The effect of the present invention can be expected sufficiently if the waste concrete material exceeds 50% by mass, but depending on the mineral phase of the soil, there may be an effect on the reaction, etc., and the variation in quality may increase. The civil engineering material is preferably composed of 70% by mass or more, particularly preferably 90% by mass or more of concrete waste.
As the concrete waste material, construction waste material is the most representative, but is not limited to this. Moreover, it does not prevent that waste materials other than concrete are mixed inevitably on the property of waste materials.

  Therefore, in a preferred embodiment in the case of modifying a civil engineering material using the reducing material for civil engineering material of the present invention as described above, the reducing material for civil engineering material is converted into a civil engineering material partially or entirely made of concrete waste material. Mix. More preferably, the reducing material for civil engineering material is mixed with a civil engineering material mainly composed of concrete waste (generally more than 50% by mass, preferably 70% by mass or more, particularly preferably 90% by mass or more consisting of concrete waste). To do.

As a method of mixing the reducing material for civil engineering material of the present invention with the civil engineering material, the reducing material for civil engineering material in a state where the steelmaking slag (A) and the blast furnace slow cooling slag (B) are mixed is added to the civil engineering material and mixed. Alternatively, the steelmaking slag (A) and the blast furnace slow-cooled slag (B) that constitute the reducing material for the civil engineering material may be added to the civil engineering material (separately) and then mixed. In the latter case, for example, the steelmaking slag (A) and the blast furnace slow cooling slag (B) may be weighed and added separately to the civil engineering material in one mixing line, and then the whole may be mixed. Moreover, after adding and mixing steelmaking slag (A) or blast furnace slow cooling slag (B) to a civil engineering material, the remaining blast furnace slow cooling slag (B) or steelmaking slag (A) is added and mixed. Also good.
There is no special limitation on the method of mixing the reducing material for civil engineering material with the civil engineering material (including the case where steelmaking slag (A) and blast furnace slow-cooled slag (B) are added to the civil engineering material and then mixed), for example Alternatively, the mixing may be performed batch-wise using a mixer, shooter, shovel, or the like, or may be continuously mixed by charging into a hopper or the like.

As the steelmaking slag for the reducing material, hot metal pretreatment slag (grain size 0-5 mm) generated in the dephosphorization process of the steel manufacturing process was used. Similarly, unaged blast furnace slow-cooled slag is slag (granularity 0-5mm) which is crushed after releasing and gradually cooling the slag generated from the blast furnace when producing pig iron, and re-crushing with a rod mill within one month from the release. ) Was used. In addition, each slag was crushed with a crusher after cooling, and used after adjusting the particle size according to the conditions. Among the compositions of the steel slag, the metal Fe content is adjusted by selecting the conditions of the magnetic separation, FeO amount, Fe ₂ O ₃ amount by selecting the adding conditions and oxygen-blown conditions iron oxide during steelmaking operations The amount of T-Fe was adjusted by selecting magnetic selection conditions (magnetic field strength, distance, etc.), and each was applied based on the analysis value. The amount of T-Fe is the total amount of Fe in the metals Fe, FeO, and Fe ₂ O ₃ . Further, the CaO / SiO ₂ (mass ratio), Al ₂ O ₃ amount, and SiO ₂ amount were adjusted by controlling the amount of auxiliary raw material added and selecting the obtained slag, and applied based on the analysis values. . Moreover, the expansion rate of steelmaking slag used what adjusted the input amount of CaO, and also confirmed by carrying out the expansion test of the obtained slag.
The civil engineering material was a mixture of concrete waste and soil, and the amount of reducing material added to the civil engineering material was 5% by mass. From the sieving, the concrete content in the mixture (target civil engineering material) was 90% by mass or more in Invention Examples 1 to 8 and Comparative Examples 1 to 8, and 70% by mass in Invention Example 9.

The expansion test of the civil engineering material to which the reducing material was added was measured by the method defined in Annex 2 of JIS-A-5015 “Steel Slag Roadbed Material”. However, the curing conditions were changed from the standard “10 days of heating-cooling” to “10 days of continuous heating at 80 ° C.”. In this case, the case where the final expansion amount was 0.5% or less was evaluated as “◯”, the case where it exceeded 0.5% and 1.0% or less was evaluated as “△”, and the case where it exceeded 1.0% was evaluated as “X” .
In addition, the dissolution test was performed by the dissolution test method according to the Environmental Agency Notification No. 46 method. The samples were piled up samples prepared under each condition, collected from five different places, and the average and width were confirmed. The numerical values in Table 2 are the ratio of the hexavalent chromium elution amount with respect to the hexavalent chromium elution amount without addition of the reducing material being “1”.
The test results are shown in Table 2 together with the configuration (composition, etc.) of the reducing material. According to this, in the reducing material of the present invention, the elution amount of hexavalent chromium from the civil engineering material is suppressed to a standard value (0.05 mg / L) or less with small variations, and the expansion of the civil engineering material is small. It can be seen that stability can also be maintained.

Claims (6)

FeO amount is 8% by mass or more, T-Fe amount is 10 mass% or more, _Al 2 _{O 3} amount and the amount of _Fe 2 _{O 3} total less than 20 wt% of, CaO / SiO ₂ (weight ratio) is 1.0 or more It consists of steelmaking slag (A) of less than 2.0 and unaged blast furnace slow-cooled slag (B),
Steelmaking slag (A) has an expansion coefficient of 1.5% or less when immersed in warm water at 80 ° C. for 10 days,
A reducing material for civil engineering materials, wherein the mass ratio of the steelmaking slag (A) and the blast furnace slow cooling slag (B) is 20:80 to 80:20.   The blast furnace slow-cooled slag (B) is mixed with water at a mass part ratio of water: slag = 10: 1, shaken at 200 rpm for 6 hours, and the leaching amount of thiosulfate ions when filtered is 30 mg / L or more. The reducing material for civil engineering materials according to claim 1, wherein The steelmaking slag (A) has a total amount of Si ₂ O and Al ₂ O ₃ of 40% by mass or less, and the reducing material for civil engineering materials according to claim 1 or 2.   The steelmaking slag (A) and the blast furnace slow-cooled slag (B) have a particle size of 10 mm or less, the reducing material for civil engineering materials according to any one of claims 1 to 3.   A method for modifying a civil engineering material, wherein the reducing material for civil engineering material according to any one of claims 1 to 4 is mixed with a civil engineering material partially or entirely made of concrete waste.   A method for modifying a civil engineering material with the reducing material for civil engineering material according to any one of claims 1 to 4, wherein the steelmaking slag (A) and the blast furnace slag (B) to constitute the reducing material for civil engineering material A method for modifying a civil engineering material, characterized in that a part or the whole is added to a civil engineering material made of concrete waste and then mixed.

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