JP2014177795A - Roadbed material for asphalt pavement including granulation object of gypsum board waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roadbed material for asphalt pavement including recycling concrete (RC) 40 of 80-90 wt.% and a granulation object manufactured from gypsum board waste of 10-20 wt.%.SOLUTION: The granulation object 24 of the roadbed material is manufactured by a process of providing a crushed material by crushing the gypsum board waste, a process of removing a paper component from the crushed material, a mixing process of forming a mixture by adding a blast furnace cement B kind, water and a predetermined additive to the crushed material of removing the paper component and a granulation process of forming the granulation object 24 by granulating-processing the mixture, and in its mixing process, alkali for setting pH to 8 or more and ferrous iron being the iron content having reduction performance, are added as the predetermined additive, and are mixed under an environment in which oxidation-reduction potential is negative electric potential (a reduction atmosphere).

Description

  The present invention relates to a roadbed material for asphalt pavement including a granulated product of gypsum board waste material.

  Conventionally, newly constructed gypsum board waste material that is generated when building a new house is separated into gypsum and paper, for example, as raw material for gypsum board, gypsum for cement addition, or soil (ground) Some of them are recycled as improvement materials and solidification materials. However, the recycling rate of gypsum board waste material in the dismantling system that occurs during the dismantling of houses and the like is in a very low state. One of the reasons includes problems such as elution of harmful heavy metals (arsenic, cadmium, fluorine) and generation of hydrogen sulfide.

  In order to prevent the elution of harmful heavy metals, there is a method in which gypsum recovered from dismantled gypsum board waste is solidified and contained with cement material. However, there is another problem such as elution of hexavalent chromium derived from the cement material. As a countermeasure for suppressing the elution of hexavalent chromium, the addition of a reducing agent such as ferrous sulfate has been conventionally known.

  Japanese Laid-Open Patent Publication No. 2005-225742 or Japanese Laid-Open Patent Publication No. 2011-235242 discloses a method for producing a soil (ground) improving material using a gypsum board waste material together with a cement material. In these conventional soil (ground) improving materials, the above-described measures for suppressing elution of heavy metals or hexavalent chromium are taken. However, sufficient measures have not been taken to suppress the generation of hydrogen sulfide.

JP 2005-225742 A JP 2011-235242 A

  The present invention aims to eliminate / reduce the problems in reusing the above-mentioned conventional gypsum board waste material, and more specifically, gypsum that can sufficiently reduce / eliminate the generation of hydrogen sulfide. An object of the present invention is to provide a roadbed material for asphalt pavement including a granulated material of board waste.

  The present invention provides a roadbed material for asphalt pavement comprising 80 to 90% by weight of recycled concrete (RC) 40 and granulated material produced from 10 to 20% by weight of gypsum board waste. In the roadbed material, the granulated material is obtained by crushing gypsum board waste material to obtain a crushed material, the step of removing the paper component from the crushed material, the crushed material from which the paper component has been removed, And a mixing step of adding water and a predetermined additive to produce a mixture, and a granulation step of granulating the mixture to produce a granulated product. In the mixing step, the predetermined additive is produced. As described above, an alkali for adjusting the pH to 8 or more and ferrous iron, which is a reducing iron component, are added and mixed in an environment where the redox potential is a negative potential (reducing atmosphere).

According to the present invention, in the mixing step of the granulated material constituting the roadbed material for asphalt pavement, the granulation treatment is performed by mixing in an environment where the pH is 8 or more and the redox potential is a negative potential (reducing atmosphere). Suppresses the generation of hydrogen sulfide (H ₂ S) due to the reduction of the sulfuric acid component in the granulated product produced by the reaction, and reacts the generated hydrogen sulfide with the iron content in the granulated product to produce iron sulfide (FeS), etc. By confining, hydrogen sulfide can be prevented from being released from the roadbed material to the environment. Furthermore, according to the present invention, the elution of harmful heavy metals (arsenic, cadmium, fluorine) and hexavalent chromium can be suppressed by the blast furnace cement type B and the iron content in the granulated product.

  In one aspect of the present invention, in the mixing step of the granulated material constituting the roadbed material for asphalt pavement, the alkali includes an alkali metal or alkaline earth metal hydroxide, and the iron content is supplied by ferrous sulfate. Is done.

  According to one embodiment of the present invention, in the mixing step, alkali and iron can be added (supplied) as a powdery or solution-like additive that can easily be added.

  In one aspect of the present invention, 15-25% by weight of Blast Furnace Cement B is added to the crushed material in the step of mixing the granulated material constituting the roadbed material for asphalt pavement.

  According to one aspect of the present invention, in the mixing step, harmful heavy metals (arsenic) in the granulated product generated by the granulation treatment are added by adding 15 to 25% by weight of blast furnace cement B type to the crushed material. , Fluorine) can be suppressed below the environmental standard.

  In one aspect of the present invention, in the mixing step of the granulated material that constitutes the roadbed material for asphalt pavement, zero portion that is a fine particle component of RC40 is added to the crushed material at a predetermined weight%.

  According to one aspect of the present invention, in the mixing step, uniaxial compression of the granulated product generated by the granulation process is performed by adding a zero component that is a fine-grained component of RC40 to the crushed material at a predetermined weight%. The strength can be made equal to the uniaxial compressive strength of RC40.

  In one aspect of the present invention, the method further includes a step of curing the granulated material, which is generated by the granulation treatment and constitutes the roadbed material for asphalt pavement, for at least 4 days.

  According to one aspect of the present invention, the granulated product produced by the granulation treatment is cured for at least 4 days, so that harmful heavy metals (arsenic, fluorine) in the granulated product produced by the granulation treatment are removed. The amount of elution can be further reduced.

It is a schematic diagram which shows the structure of the roadbed material for asphalt pavement of one Embodiment of this invention. It is a figure which shows the characteristic of the roadbed material for asphalt pavement of one Embodiment of this invention. It is a figure which shows the process of the method of manufacturing the granulated material of the roadbed material for asphalt pavement of one Embodiment of this invention. It is a figure which shows the relationship between the addition amount of the cement of one Embodiment of this invention, and the elution amount of an arsenic and a fluorine. It is a figure which shows the relationship between the addition amount of the zero part of one Embodiment of this invention, and the compressive strength of a granulated material.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a roadbed material for asphalt pavement according to an embodiment of the present invention. The roadbed material for asphalt pavement referred to in the present invention means the roadbed material 20 disposed under the surface layer / base layer 10 containing asphalt in the asphalt pavement, and particularly means a material for the lower roadbed of the roadbed material. As shown in FIG. 1, the roadbed material 20 includes a granulate 24 made from gypsum board waste mixed to fill between recycled concrete 40 (RC40) 22. The granulated material 24 is mixed at a ratio of 10 to 20% by weight with respect to 80 to 90% by weight of RC40 (22). For example, when RC40 (22) is 80, 90% by weight, the granulated material 24 is added by 20, 10% by weight. The granulated product 24 needs to be used with an upper limit of about 20% by weight in order to suppress expansion due to water absorption or strength reduction.

  FIG. 2 is a diagram showing characteristics of a roadbed material for asphalt pavement according to an embodiment of the present invention. Sample B is a roadbed material for asphalt pavement according to an embodiment of the present invention. For reference, characteristics of RC40 simple substance (100%) of sample A and a granulated simple substance (100%) of waste gypsum board of sample C are used as a reference. Is also shown. The data shown in FIG. 2 is data obtained by inspecting about half a year after actually carrying out (embedding) a specimen (sample) as a field test. The modified CBR in FIG. 2 means a CBR test of the roadbed material obtained in consideration of the compacted state during construction (95% of the maximum dry density).

According to the quality (standard) required for the lower roadbed material (recycled crusher run RC40), for example,
Grinding loss: 50% or less Plasticity index: 6 or less Modified CBR: 20% or more

It is necessary to satisfy. The asphalt pavement roadbed material according to an embodiment of the present invention of sample B satisfies these conditions and has substantially the same characteristics as the RC40 single sample A. Therefore, it turns out that the roadbed material for asphalt pavement of one embodiment of the present invention can be used as a lower layer roadbed material. On the other hand, in the case of a single granulated product of gypsum board waste material of Sample C, the plasticity index is far from the standard and the water absorption rate is quite large. It turns out that it is difficult from the surface.

  Next, a granulated material of a roadbed material for asphalt pavement according to an embodiment of the present invention will be described with reference to FIGS. Drawing 3 is a figure showing a process of a method of manufacturing a granulated thing of a roadbed material for asphalt pavement of one embodiment of the present invention. The manufacturing process of FIG. 3 can be implemented using, for example, equipment of an intermediate processing facility (for example, “Zero Emi Plant” owned by the applicant) that recycles construction waste.

  In step S1 of FIG. 3, the recovered gypsum board waste material is crushed by a crusher (pulverizer) to obtain a crushed material. The crushed material is crushed so as to have a predetermined size according to the intended use. The predetermined size is, for example, a size of 10 mm or less. In the crushing step S1, the crushed material previously crushed in another facility or the like is collected, crushed again to a predetermined size and adjusted, or inspection of the size of the collected crushed material is confirmed. You may make it use as it is after performing.

  In step S2, the paper component is removed from the obtained crushed material. The removal of the paper component can be carried out by selecting a light paper component in the crushed material with a wind vibration sorter, or by heat-treating the crushed material to ash and separate the paper component.

  In the mixing step of step S3, a blast furnace cement B type, water, and a predetermined additive are added to the crushed material from which the paper component has been removed to generate a mixture. Details of the mixing step S3 will be described later.

  In step S4, the mixture obtained in the mixing step S3 is granulated in a granulator to produce a granulated product. The particle size of the granulated product varies depending on the rotation speed and rotation time of the agitation blade of the granulator, and the proportion of the granulated product having a large particle size is increased by increasing the rotation time (ie granulation time). Can do.

  In experiments by the present inventors, when the granulation time is varied in the range of 1 to 10 minutes, when the granulation time is short (1 to 3 minutes), the ratio of the particle size of about 4.8 mm or less is high, It was found that when the time is long (5 to 10 minutes), the ratio of the particle size of about 4.8 mm or more becomes high. It was also found that the amount (%) of blast furnace cement B added has little effect on the particle size of the granulated product.

  In step S5, the granulated material is cured. Curing is important for improving the strength of the granulated product, and is also important for reducing the amount of arsenic and fluorine eluted. In the experiment by the present inventor, by securing a curing period of at least 4 days, for example, about 5 days, the elution amount of arsenic and fluorine is 0.01 mg / L or less, which is each designated standard (environmental standard), 0. It turned out that it can reduce to 8 mg / L or less. The curing period is not an essential requirement in the production method of the present invention, and can be arbitrarily selected according to the use of the granulated product.

  In step S6, quality control of the generated granulated material is performed. Quality control inspects / confirms whether the granulated product meets specifications (grain size, environmental standards, etc.) suitable for the application. The granulated product whose quality is confirmed is mixed with RC40 and used as a roadbed material (for example, a lower layer roadbed material).

  Here, the mixing step S3 will be further described. In mixing process S3, blast furnace cement B seed | species is added in 15-25 weight% with respect to a crushed material. FIG. 4 is a diagram showing the relationship between the added amount of blast furnace cement type B and the arsenic and fluorine elution amounts. FIG. 4 shows the result of an experiment by the present inventor. As is clear from FIG. 4, the elution amounts (mg / L) of arsenic (graph B) and fluorine (graph A) both decrease as the cement addition amount (%) increases. It can be seen that in the range C in which the cement addition amount is 15 to 25%, arsenic and fluorine are lower than the specified standards (environmental standards) of 0.01 mg / L and 0.8 mg / L. Therefore, leaching of harmful heavy metals (arsenic, fluorine) in the granulated product generated in the above-described granulation step S4 by adding blast furnace cement B in the range of 15 to 25% by weight to the crushed material. The amount can be suppressed below the environmental standard.

In the mixing step S3, as a predetermined additive, an alkali for adjusting the pH to 8 or more and iron are added and mixed in an environment where the redox potential is a negative potential (reducing atmosphere). The alkali includes an alkali metal or alkaline earth metal hydroxide, and the iron is supplied by ferrous sulfate (FeSO ₄ ). Thereby, in the mixing step S3, alkali and iron can be added (supplied) as a powdery or solution-like additive whose addition amount can be easily adjusted.

Adding an alkali to make the pH 8 or higher, and mixing in an environment where the oxidation-reduction potential is −100 mV or higher are both the sulfuric acid component (SO ₄ ) in the granulated product produced in step S6. This is to suppress the growth and activity of sulfate-reducing bacteria in the soil that acts to reduce and generate hydrogen sulfide (H ₂ S). For example, it has been found that sulfate-reducing bacteria grow exclusively in an environment with an oxidation-reduction potential of -100 mV or less, and an environment with a pH in the range of 6.5 to 8.0 is the optimal growth condition. Therefore, in the mixing step S3 of the present invention, as described above, the addition of an alkali to make the pH 8 or higher and the mixing in an environment where the oxidation-reduction potential is a negative potential (reducing atmosphere) are employed.

In the mixing step S3, iron is added as a predetermined additive because, when the sulfuric acid component in the granulated product is reduced and hydrogen sulfide is generated, it is reacted with the iron content in the granulated product and sulfided. This is to prevent hydrogen sulfide from being released to the environment by confining it as iron (FeS). When iron is supplied by the ferrous sulfate (FeSO ₄ ) described above, it is possible to reduce the hexavalent chromium in the blast furnace cement type B and suppress its elution as is conventionally known.

Furthermore, according to the experimental results obtained by the present inventor, when iron is supplied by the ferrous sulfate (FeSO ₄ ) described above, arsenic and fluorine elution of harmful heavy metals (arsenic, fluorine) in the granulated product It has been found that there is an effect of suppressing. Specifically, for example, when 0.5% by weight of ferrous sulfate (FeSO ₄ ) is added, the arsenic elution amount from the granulated product is 0.0065 mg / L on average, and the designated standard (environmental standard) It was found to be less than 0.01 mg / L. Under similar conditions, the fluorine elution amount averaged 0.46 mg / L, which was found to be lower than the designated standard (environmental standard) 0.8 mg / L.

In addition, in the mixing step S3, a zero component which is a fine grain component of the recycled concrete (RC) 40 is added to the crushed material at a predetermined weight%. FIG. 5 is a diagram showing the relationship between the addition amount (%) of zero and the uniaxial compressive strength (N / mm ² ) of the granulated product according to one embodiment of the present invention. The straight line A connecting the black circles in FIG. 5 is the case where the amount (ratio) of the blast furnace cement B type is 15%, and the straight line B connecting the white circles is the amount (ratio) of the blast furnace cement B type 20%. This is the case. The star in the figure indicates the uniaxial compressive strength of RC40. As is clear from FIG. 5, even if the amount (ratio) of the blast furnace cement type B is 15% or 20%, the zero component is increased and added at a rate of 25 to 50%, for example. The compressive strength of the granulated product produced by the granulation process can be made substantially equal to that of the existing RC40.

  The granulated product manufactured by the above manufacturing process is also used in the roadbed material for asphalt pavement of the embodiment of the present invention of the sample B of FIG. 2 described above. About half a year later, as a result of the dissolution test of chromium (Cr), arsenic (As), and fluorine (F), all were environmental standards (Cr: <0.05 mg / L, As: <0.01 mg / L, F: < 0.8 mg / L) was confirmed.

  Embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to these embodiments. The present invention can be implemented in variously modified, modified, and modified embodiments based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

10 Surface layer / base layer 20 containing asphalt
22 RC40
24 Granulated material

Claims (5)

A roadbed material for asphalt pavement comprising 80 to 90% by weight of recycled concrete (RC) 40 and a granulated material produced from 10 to 20% by weight of gypsum board waste material, ,
Crushing gypsum board waste material to obtain crushed material;
Removing paper components from the crushed material;
A mixing step of adding a blast furnace cement type B, water, and a predetermined additive to the crushed material from which the paper component has been removed, to generate a mixture;
Produced from the granulation step of granulating the mixture to produce a granulated product,
In the mixing step, as the predetermined additive, an alkali for adjusting the pH to 8 or more and ferrous iron which is a reducing iron component are added, and the oxidation-reduction potential is a negative potential (reducing atmosphere). Roadbed material characterized by mixing below.   The road base material according to claim 1, wherein the alkali includes a hydroxide of an alkali metal or an alkaline earth metal, and the iron is supplied by ferrous sulfate.   The roadbed material according to claim 1 or 2, wherein in the mixing step, 15 to 25 wt% of the blast furnace cement type B is added to the crushed material.   The roadbed material according to any one of claims 1 to 3, wherein in the mixing step, a zero component which is a fine-grain component of the RC40 is added to the crushed material at a predetermined weight%.   The roadbed material according to any one of claims 1 to 4, further comprising a step of curing the granulated material generated by the granulation treatment for at least 4 days.

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