JP2010189940A - Method for selecting material with no suitability of base course material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately and simply select a material with no suitability of a base course material having the risk of causing the upheaval of a paved surface by expansion, as a material for a pavement base course. <P>SOLUTION: This method is used to select the material with no suitability of the base course material, which has the risk of causing the upheaval of the paved surface by the expansion when the material is applied as the base course material, from among materials partially or wholly made of steel slag. In the method, the material, which satisfies at least both the following conditions, is selected as the material with no suitability of the base course material. The conditions include: (a) pH measured by an elution test based on a tank leaching test method predetermined by JIS-K0058-1 is 9.5 or less; and (b) the Fe content of a metal is 6 mass% or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, when a material containing steelmaking slag is used as a roadbed material for roads, parking lots, sidewalks, etc., the pavement surface may be raised due to expansion in order to prevent the pavement surface from rising due to expansion of the roadbed. It is related with the method for selecting the material which does not have a certain roadbed material suitability.

In asphalt concrete pavements such as roads and parking lots, the pavement surface may suddenly rise due to the expansion of the roadbed. In this way, the main cause of the expansion of the roadbed, especially when steel slag is used as the roadbed material, volumetric expansion or solidified steel slag when f-CaO in the slag is hydrated It has been thought that this is because ettringite is generated in the roadbed material and causes volume expansion.
Conventionally, as a steel slag roadbed material, various steel slags having different component compositions (for example, steel slag such as converter slag, blast furnace slow-cooled slag, etc.) have been used.

However, as a result of the investigation by the present inventors, even when the asphalt concrete pavement has a very small amount of f-CaO and ettringite in the roadbed (content rate), the pavement surface is raised due to the expansion of the roadbed. Turned out to be. It is clear that such roadbed expansion is not caused by f-CaO hydration or ettringite formation, and elucidation of the cause and appropriate countermeasures are desired. In particular, such expansion may occur. It was hoped that the criteria for selecting a certain roadbed material would be clear.
Accordingly, an object of the present invention is to provide a selection method that can accurately and easily select a material for roadbed that does not have a suitable roadbed material that may cause the pavement surface to rise due to the expansion of the roadbed as described above. It is to provide.
In addition, another object of the present invention is to predict the possibility of the pavement surface rising due to the roadbed expansion as described above for the existing pavement, and to accurately repair the roadbed to prevent such pavement surface protrusion. It is in providing the repair method of a roadbed which can be implemented in.

  As a result of investigation and examination on the existing asphalt concrete pavement by the present inventors, the above-mentioned uplift of the pavement surface due to the expansion of the roadbed occurs in the pavement using steel slag as the roadbed material, and the roadbed of the pavement in which the uplift has occurred Was found to contain a lot of iron rust. As a result of further investigation and examination based on these facts, when a material having a relatively low pH and containing a considerable amount of metal Fe derived from steelmaking slag is used as a roadbed material, the metal Fe in the roadbed material is oxidized. As a result, it was found that the roadbed expands due to the volume expansion, and the pavement surface is raised. Therefore, from these facts, if a material having a relatively low pH and containing a considerable amount of metal Fe derived from steelmaking slag is selected as a material having no roadbed material suitability, the roadbed expansion caused by the above causes and the paved surface caused thereby It was found that the uplift can be prevented appropriately.

The present invention has been made on the basis of such findings and has the following gist.
[1] A method for selecting materials that are not suitable for roadbed materials that may cause the pavement surface to rise due to expansion when constructed as roadbed materials among materials that are partly or entirely made of steel slag. There,
A method for selecting a material having no roadbed material suitability, wherein a material satisfying both of the following conditions (a) and (b) is selected as a material having no roadbed material suitability.
(A) pH measured by elution test by tank leaching test method specified in JIS-K0058-1 is 9.5 or less (b) Metal Fe content is 6 mass% or more

[2] When selecting a material that does not have roadbed material suitability for permeable pavement in the selection method of [1] above, a material that satisfies at least the following conditions (a) and (b) must be selected A method for selecting a material that does not have suitability for roadbed materials, wherein the material is selected as a material that does not have a road.
(A) pH measured by an elution test by the tank leaching test method specified in JIS-K0058-1 is 10.5 or less (b) Metal Fe content is 6 mass% or more

[3] The roadbed material is sampled from the existing pavement where the roadbed material, part or all of which is made of steel slag, is collected, and the collected roadbed material is subjected to an elution test by the tank leaching test method specified in JIS-K0058-1. A roadbed repair method characterized by measuring a pH and performing roadbed repair to prevent the pavement surface from rising due to roadbed expansion when the pH is equal to or lower than a threshold value.
[4] A repair method of a roadbed according to the repair method of [3], wherein the pH threshold is set in a pH region of 9.5 or more.

According to the selection method of the present invention, a material that is not suitable for a roadbed material that may cause a pavement bulge due to roadbed expansion caused by oxidation of metal Fe among materials that are partly or entirely made of iron slag. Can be selected easily and accurately.
Further, according to the repair method of the roadbed of the present invention, it is predicted that the existing pavement may be raised due to the expansion of the roadbed due to the oxidation of metal Fe, and such a pavement is prevented from being raised. For this reason, it is possible to accurately carry out roadbed repair.

The result of examining the occurrence of iron rust in the roadbed and the presence or absence of bumps on the pavement surface due to the expansion of the roadbed. Graph showing

  In asphalt concrete pavement, when a material having a relatively low pH and containing a considerable amount of metal Fe is used as the roadbed material, the roadbed material expands due to oxidation of the metal Fe in the roadbed material and the pavement surface. Cause a bump. Therefore, if a material having a relatively low pH and containing a considerable amount of metal Fe is selected as a material that does not have roadbed material suitability, roadbed expansion due to the above causes and pavement surface bulging caused thereby can be appropriately prevented. . Here, the material (roadbed material) that causes the above problems is a material that is partly or entirely steel-manufactured slag. Therefore, in the present invention, part or all of the material to be selected is steel-manufactured slag. It is a certain material. This invention selects the material which does not have the roadbed material suitability which may produce the protrusion of the pavement surface by expansion | swelling, when it constructs as a roadbed material among such materials.

Steelmaking slag is slag generated in the steelmaking process of the steel manufacturing process, and includes hot metal pretreatment slag (for example, dephosphorization slag, desiliconization slag, etc.), converter slag (decarburization slag), etc. One or more types can be used.
In the case of materials that are partly made of steel slag, the remainder of the material includes concrete waste, waste roadbed material, brick waste, steel slag other than steel slag (for example, blast furnace slow-cooled slag, etc.), slag other than steel slag One or more types (such as waste molten slag) and crushed stone can be used.

In the present invention, a material satisfying both of the following conditions (a) and (b) is selected as a material having no roadbed material suitability (hereinafter, this material may be referred to as “unsuitable material”). In addition, the particle size of the material used as the specimen for pH measurement in the following (a) is naturally that of the particle size applied as the roadbed material.
(A) pH measured by elution test by tank leaching test method specified in JIS-K0058-1 is 9.5 or less (b) Metal Fe content is 6 mass% or more

  Fig. 1 shows a part or all of steel slag, which has various pH values, and is constructed as a roadbed material for asphalt concrete pavement. The result of examining the presence or absence is shown. The material is a steelmaking slag alone or a mixture of steelmaking slag and one or more types of blast furnace chilled slag and waste concrete, and the metal Fe content is 6 to 12 mass%. The pH of the material before construction was measured by an elution test using a tank leaching test method defined in JIS-K0058-1.

About asphalt concrete pavement two years after construction, the presence or absence of bumps on the pavement surface due to roadbed expansion was examined. In this investigation, when the pavement surface length was 20 cm and there was a height difference of 2 cm or more, it was judged as “uplift of the pavement surface”. In addition, a roadbed material was collected from the roadbed of the asphalt concrete pavement, and the rusting state of the roadbed material sample was visually observed, and evaluated according to the following criteria and indexed.
Rust index 1: Gray Rust index 2: Light brown Rust index 3: Brown Rust index 4: Dark brown to reddish brown

According to FIG. 1, among materials having a metal Fe content of 6 mass% or more, a material having a pH of 9.5 or less has a high rust index (rust index 3 to 4), and the pavement surface is raised due to roadbed expansion. ing. On the other hand, even if the metal Fe content is 6 mass% or more, the material having a pH of more than 9.5 has a low rust index (rust index 1 to 2), and does not cause the pavement surface to rise due to roadbed expansion .
From the above results, in the present invention, a material satisfying both the above conditions (a) and (b) is selected as a material having no roadbed material suitability (unsuitable material).

  Moreover, it is preferable to set the upper limit value of the pH of the unsuitable material specified as the above (a) higher. Specifically, it is preferable that the upper limit value is preferably pH 10.5, more preferably pH 11.5, and particularly preferably pH 12.5. For the same reason, it is preferable to set the lower limit of the metal Fe content of the unsuitable material specified as (b) above to be lower. Specifically, the lower limit is preferably 4 mass%, more preferably 2 mass%, and particularly preferably 1 mass%.

Moreover, since the roadbed material constructed on the water-permeable pavement is liable to lower the pH by contact with rainwater, when selecting a material that does not have suitability for the roadbed material for water-permeable pavement, the above (a) It is preferable to set the upper limit of the pH of the unsuitable material specified as Specifically, the upper limit is preferably set to pH 10.5, more preferably pH 11.5, and particularly preferably pH 12.5.
Here, the water-permeable pavement is a pavement having a function of infiltrating rainwater that has fallen on the road surface into the ground through the gap inside the pavement. It is constructed under the condition that the ratio of coarse aggregate is increased to increase the porosity. Generally, the permeability coefficient of water-permeable pavement is 1.0 × 10 ⁻² cm / sec or more.

In addition, as the degree of consolidation of the roadbed is more likely to be raised due to the expansion of the roadbed, the consolidation of the material should be added to the selection criteria in order to select materials that do not have suitable roadbed materials more strictly. It is preferable.
As mentioned above, when it is constructed as a roadbed material such as asphalt concrete pavement, a material that does not have roadbed material suitability that may cause the pavement surface to rise due to the expansion of the roadbed due to oxidation of metal Fe is selected easily and accurately. be able to.

Next, a method for repairing a roadbed using the principle of the selection method of the present invention described above will be described.
The oxidation of metallic Fe contained in the roadbed material gradually proceeds after construction, causing expansion of the roadbed and uplift of the pavement surface. Moreover, in that case, the pH of the material decreases due to contact with rainwater, and an environment in which metal Fe is more easily oxidized is obtained. Therefore, even for existing pavements such as asphalt concrete pavement, by measuring the pH of the roadbed material composing the roadbed, it is predicted with a certain degree of accuracy that roadbed expansion and pavement surface bulging due to metal Fe oxidation may occur. If a roadbed repair (roadbed repair to prevent the pavement from rising due to expansion of the roadbed material) is carried out based on the prediction, even if an inappropriate material is used for the roadbed, the pavement surface Can be prevented in advance.

That is, in the roadbed repair method of the present invention, a roadbed material is collected from existing pavements (such as asphalt concrete pavement) in which a roadbed material partially or entirely made of steel slag is constructed, and the JIS- The pH is measured by an elution test according to the tank leaching test method defined in K0058-1, and it is determined that there is a possibility of causing roadbed expansion and pavement surface uplift when the pH is below a specific threshold value. Implement roadbed repairs to prevent surface bumps.
The above-mentioned threshold value of the pH of the roadbed material can be set to an appropriate pH value. However, from the upper limit value of the pH of the unsuitable material in the selection method of the present invention described above, a pH range of 9.5 or more, preferably 10 It is appropriate to set in the above pH range.

The roadbed repair for preventing the pavement surface from rising due to the expansion of the roadbed can be implemented, for example, in any one of the following forms (A) and (B).
(A) After removing the asphalt concrete layer, a part of the roadbed layer is removed in the form of a groove in the almost entire layer thickness direction, and a granular material capable of absorbing the expansion of the roadbed layer is filled in the groove, and the upper layer is asphalt concrete. Re-install.
(B) After cutting the roadbed layer together with the asphalt concrete layer with a cutter to form a cutter groove, the cutter groove is filled with a filler capable of absorbing the expansion of the roadbed layer.

Claims (4)

It is a method for selecting a material that does not have roadbed material suitability that may cause the pavement surface to rise due to expansion when it is constructed as a roadbed material among materials that are partly or entirely steelmaking slag,
A method for selecting a material having no roadbed material suitability, wherein a material satisfying both of the following conditions (a) and (b) is selected as a material having no roadbed material suitability.
(A) pH measured by elution test by tank leaching test method specified in JIS-K0058-1 is 9.5 or less (b) Metal Fe content is 6 mass% or more When selecting materials that do not have roadbed material suitability for permeable pavement, a material that satisfies at least the following conditions (a) and (b) is selected as material that does not have roadbed material suitability: The method for selecting a material having no suitability for roadbed material according to claim 1.
(A) pH measured by an elution test by the tank leaching test method specified in JIS-K0058-1 is 10.5 or less (b) Metal Fe content is 6 mass% or more   The roadbed material is sampled from the existing pavement where the roadbed material, part or all of which is made of steel slag, is collected, and the pH of the collected roadbed material is measured by the elution test by the tank leaching test method specified in JIS-K0058-1. Then, when the pH is equal to or lower than the threshold value, a roadbed repairing method is carried out to perform roadbed repairing to prevent the pavement surface from being raised due to roadbed expansion.   4. The roadbed repair method according to claim 3, wherein the pH threshold is set in a pH range of 9.5 or more.

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