Asphalt pavement structures and asphalt reinforcement materials

Abstract

To provide an asphalt pavement structure and asphalt reinforcement capable of increasing resistance to peeling of an asphalt layer from a crushed stone layer, preventing cracks from occurring on the lower surface of the asphalt layer, and suppressing deformation of the crushed stone layer due to wetting.SOLUTION: An asphalt pavement structure 2 comprises: a crushed stone layer 6 constructed above a roadbed 4; an asphalt layer 8 constructed above the crushed stone layer 6; and an asphalt reinforcement 10 embedded between the crushed stone layer 6 and the asphalt layer 8. The asphalt reinforcement 10 comprises: a sheet 20 having a thickness that absorbs and holds an asphalt emulsion E dispersed between the crushed stone layer 6 and the asphalt layer 8, and follows the unevenness of the upper surface of the crushed stone layer 6; and a geogrid 22 stacked on the sheet 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an asphalt pavement structure and an asphalt reinforcing material for reinforcing an asphalt pavement structure. [Background technology]

[0002] Generally, an asphalt pavement structure includes a crushed stone layer constructed above a roadbed, and an asphalt layer constructed above the crushed stone layer.

[0003] Immediately after construction of an asphalt pavement structure, the top surface of the crushed stone layer and the bottom surface of the asphalt layer are in close contact with each other, but the asphalt layer may peel off from the crushed stone layer. In such cases, the load of the asphalt pavement structure is mainly borne by the asphalt layer alone, so the thickness of the asphalt pavement structure decreases and the strength of the asphalt pavement structure decreases. In addition, the peeling of the asphalt layer from the crushed stone layer can cause the asphalt layer to turn into soil. Therefore, the peeling of the asphalt layer from the crushed stone layer is considered to be one of the factors that shorten the lifespan of asphalt pavement structures.

[0004] If the asphalt layer peels off from the crushed stone layer and the strength of the asphalt pavement structure is reduced, cracks are likely to occur on the underside of the asphalt layer due to loads acting on the upper surface of the asphalt layer (for example, wheel loads when vehicles pass by).

[0005] When cracks occur on the underside of the asphalt layer, groundwater in the crushed stone layer seeps into the cracks, causing the fine particles in the asphalt layer to flow out. This causes the cracks in the asphalt layer to extend further toward the top of the asphalt layer. These cracks in the asphalt layer are also considered to be a factor in shortening the lifespan of asphalt pavement structures.

[0006] In addition, rainwater and other water that seeps in through the joints in the asphalt layer can reach the crushed stone layer, causing the layer to become wet and deform, which can shorten the lifespan of asphalt pavement structures.

[0007] Therefore, various techniques have been put into practice to extend the lifespan of asphalt pavement structures. For example, the following Patent Document 1 discloses a technique for reinforcing asphalt pavement structures by laying a sheet-like reinforcing material in the asphalt layer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 6-248609 Summary of the Invention [Problem to be solved by the invention]

[0009] However, conventional reinforcement techniques are not sufficient to extend the service life of asphalt pavement structures, and there is a demand for further extending the service life of asphalt pavement structures.

[0010] In view of the above, an object of the present invention is to provide an asphalt pavement structure and asphalt reinforcement material that can increase the resistance of the asphalt layer to peeling from the crushed stone layer, prevent cracks from occurring on the underside of the asphalt layer, and suppress deformation of the crushed stone layer due to wetting. [Means for solving the problem]

[0011] According to the present invention, the following asphalt pavement structure that solves the above problems is provided. That is, the structure comprises a crushed stone layer constructed above a roadbed, an asphalt layer constructed above the crushed stone layer, and an asphalt reinforcing material embedded between the crushed stone layer and the asphalt layer, the asphalt reinforcing material absorbing and retaining an asphalt emulsion dispersed between the crushed stone layer and the asphalt layer, and comprising a sheet having a thickness that follows the unevenness of the upper surface of the crushed stone layer, and a geogrid superimposed on the sheet. See, the sheet and the geogrid are adhesively bonded or welded to each other in advance An asphalt pavement structure is provided.

[0012] In the asphalt pavement structure of the present invention, it is preferable that the geogrid is a mesh having a plurality of openings, the sheet is disposed on the crushed stone layer side, and the geogrid is disposed on the asphalt layer side. It is preferable that the sheet or the geogrid is formed from a material that softens or melts at the material temperature of the asphalt layer when the asphalt layer is constructed. It is preferable that the sheet is formed from a nonwoven fabric.

[0013] The present invention also provides the following asphalt reinforcing material that solves the above problems. That is, the asphalt reinforcing material reinforces an asphalt pavement structure that includes a crushed stone layer constructed above a roadbed and an asphalt layer constructed above the crushed stone layer, and includes a sheet that absorbs and retains asphalt emulsion that is spread between the crushed stone layer and the asphalt layer and has a thickness that follows the unevenness of the upper surface of the crushed stone layer, and a geogrid that is overlaid on the sheet, and the sheet and the geogrid are are adhesively bonded or welded to each other, An asphalt reinforcement is provided that is embedded between the crushed stone layer and the asphalt layer.

[0014] In the asphalt reinforcement material of the present invention, it is preferable that the geogrid is a mesh having a plurality of openings, the sheet is disposed on the crushed stone layer side, and the geogrid is disposed on the asphalt layer side. It is preferable that the sheet or the geogrid is formed from a material that softens or melts at the material temperature of the asphalt layer when the asphalt layer is constructed. It is preferable that the sheet is formed from a nonwoven fabric. Effect of the Invention

[0015] According to the present invention, the sheet absorbs and retains the asphalt emulsion, so that the crushed stone layer and the asphalt layer are strongly bonded by the sheet retaining the asphalt emulsion, and the peeling resistance of the asphalt layer from the crushed stone layer can be increased. Furthermore, since the sheet has a thickness that follows the unevenness of the upper surface of the crushed stone layer, when the sheet is laid on the upper surface of the crushed stone layer, the lower surface of the sheet deforms along the unevenness of the upper surface of the crushed stone layer. Therefore, the contact area between the lower surface of the sheet that absorbs and retains the asphalt emulsion and the upper surface of the crushed stone layer is increased. Therefore, according to the present invention, the adhesion between the crushed stone layer and the asphalt layer can be increased, and the peeling resistance of the asphalt layer from the crushed stone layer can be further increased.

[0016] In the present invention, the resistance of the asphalt layer to peeling off from the crushed stone layer can be increased, suppressing the reduction in thickness (reduction in strength) of the asphalt pavement structure, and dispersing the load acting on the asphalt pavement structure (for example, the wheel load when vehicles pass by) by the geogrid. Therefore, according to the present invention, it is possible to prevent cracks from occurring on the underside of the asphalt layer.

[0017] In the present invention, the sheet absorbs and retains the asphalt emulsion, so that the sheet retaining the asphalt emulsion exerts a waterproofing function and suppresses the flow of water between the crushed stone layer and the asphalt layer. Therefore, rainwater and the like that has infiltrated through the joints of the asphalt layer is prevented from reaching the crushed stone layer, and deformation of the crushed stone layer due to wetting is suppressed. Furthermore, the nonwoven fabric retaining the asphalt emulsion also prevents groundwater present in the crushed stone layer from infiltrating into the asphalt layer (capillary water rise), so the outflow of fine particles from the asphalt layer is suppressed. [Brief description of the drawings]

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0019] Hereinafter, preferred embodiments of the asphalt pavement structure and asphalt reinforcing material of the present invention will be described with reference to the drawings.

[0020] Referring to FIG. 1, an asphalt pavement structure 2 comprises a crushed stone layer 6 constructed above a roadbed 4, an asphalt layer 8 constructed above the crushed stone layer 6, and an asphalt reinforcement material 10 embedded between the crushed stone layer 6 and the asphalt layer 8.

[0021] The crushed stone layer 6 shown in Fig. 1 is mainly composed of a sub-base course 12. The sub-base course 12 is made of crushed run, crushed run steel slag, recycled crushed run, cut gravel, mountain gravel, sand, or the like.

[0022] The asphalt layer 8 shown in FIG. 1 includes a supersubgrade 14 constructed above a subgrade 12, a base course 16 constructed above the supersubgrade 14, and a top course 18 constructed above the base course 16.

[0023] The upper subgrade 14 shown in Fig. 1 is made of a stabilized subgrade material. When the upper subgrade 14 is made of a stabilized subgrade material, the upper subgrade 14 is included in the asphalt layer 8. On the other hand, when the upper subgrade 14 is not made of a stabilized subgrade material, the upper subgrade 14 is included in the crushed stone layer 6, and the asphalt layer 8 is mainly composed of a base layer 16 and a surface layer 18 (see Fig. 2).

[0024] The stabilized roadbed material may be, for example, one produced by adding bituminous materials such as straight asphalt to suitable aggregates and mixing them by a hot mixing method. The aggregates may be a mixture of single-grained crushed stone, sand, etc., or crushed run or locally produced materials to which supplementary materials such as crushed stone, gravel, steel slag, sand, etc. are added as necessary. The stabilized roadbed material may also be one produced by adding cement, lime, or cement and bituminous materials to aggregates.

[0025] The upper roadbed 14 (see FIG. 2) when included in the crushed stone layer 6 can be formed from graded crushed stone, graded steel slag, recycled graded crushed stone, hydraulic graded steel slag, or the like.

[0026] Both the base layer 16 and the surface layer 18 may be composed of an asphalt mixture. However, the aggregate used in the base layer 16 may have a different particle size from that used in the surface layer 18. The asphalt mixture used to make up the base layer 16 and the surface layer 18 may be a cold asphalt mixture, but is preferably a heated asphalt mixture, which has better durability than a cold asphalt mixture.

[0027] Continuing the explanation with reference to Figure 1, the asphalt reinforcement material 10 includes a sheet 20 that absorbs and retains asphalt emulsion E sprayed between the crushed stone layer 6 and the asphalt layer 8 and has a thickness that follows the irregularities of the upper surface of the crushed stone layer 6, and a geogrid 22 overlaid on the sheet 20.

[0028] The sheet 20 and the geogrid 22 are embedded between the crushed stone layer 6 and the asphalt layer 8. Specifically, when the upper roadbed 14 is formed from a stabilized roadbed material, the upper roadbed 14 is included in the asphalt layer 8, and therefore the sheet 20 and the geogrid 22 are embedded between the upper surface of the lower roadbed 12 and the lower surface of the upper roadbed 14, as shown in Fig. 1. On the other hand, when the upper roadbed 14 is not formed from a stabilized roadbed material, the upper roadbed 14 is included in the crushed stone layer 6, and therefore the sheet 20 and the geogrid 22 are embedded between the upper surface of the upper roadbed 14 and the lower surface of the base layer 16, as shown in Fig. 2.

[0029] 1, the sheet 20 is arranged on the crushed stone layer 6 side (lower side), and the geogrid 22 is arranged on the asphalt layer 8 side (upper side), but the geogrid 22 may be arranged on the crushed stone layer 6 side (lower side), and the sheet 20 may be arranged on the asphalt layer 8 side (upper side). In addition, the sheet 20 and the geogrid 22 may each be one layer, but as shown in FIG. 2, the sheets 20 may be arranged above and below the geogrid 22.

[0030] The sheet 20 is preferably made of a nonwoven fabric. The sheet 20 may be made of either short or long fibers, but is preferably made of short fibers that can absorb and hold more asphalt emulsion E than long fibers. The sheet 20 that absorbs and holds more asphalt emulsion E will increase the adhesion between the crushed stone layer 6 and the asphalt layer 8 and will exhibit a better waterproof function.

[0031] Since the sheet 20 has a thickness that conforms to the unevenness of the upper surface of the crushed stone layer 6, when the sheet 20 is laid on the upper surface of the crushed stone layer 6, the lower surface of the sheet 20 deforms to conform to the unevenness of the upper surface of the crushed stone layer 6. This increases the contact area between the lower surface of the sheet 20, which has absorbed and retained the asphalt emulsion E, and the upper surface of the crushed stone layer 6.

[0032] The sheet 20 may be made of an appropriate synthetic resin such as polypropylene, polyethylene, acrylic, etc. Of the synthetic resins, it is preferable that the sheet 20 is made of a thermoplastic synthetic resin that softens or melts at the material temperature of the asphalt layer 8 when the asphalt layer 8 is constructed.

[0033] When constructing the asphalt layer 8, the temperature of the stabilized roadbed material (material of the upper roadbed 14) produced by the hot mixing method and the temperature of the heated asphalt mixture (material of the base layer 16 and surface layer 18) are high, for example, at about 110 to 170°C. To give a more specific example, the material temperature of the asphalt layer 8 when it arrives at the site is about 160 to 170°C, the material temperature of the asphalt layer 8 when it is laid is about 120 to 150°C, and the material temperature of the asphalt layer 8 during the primary compaction is about 110 to 140°C.

[0034] For this reason, if the sheet 20 is made of a thermoplastic synthetic resin (such as polypropylene) that softens or melts at such temperatures (for example, 110 to 170°C), then when constructing the asphalt layer 8, the sheet 20 will soften or melt due to the temperature of the material of the asphalt layer 8, and then the sheet 20 will cool and solidify. As a result, the effect of bonding the upper surface of the crushed stone layer 6 and the lower surface of the asphalt layer 8 is exerted not only by the asphalt emulsion E absorbed in the sheet 20, but also by the sheet 20 itself.

[0035] The geogrid 22 in the illustrated embodiment is in the form of a net having a plurality of openings 24, as shown in Fig. 3. Therefore, when the geogrid 22 is arranged on the asphalt layer 8 side (upper side) as in the form shown in Fig. 1, the aggregate of the asphalt layer 8 enters the openings 24 of the geogrid 22, thereby firmly connecting the geogrid 22 and the asphalt layer 8. Note that, although the shape of the openings 24 is quadrangular in the illustrated embodiment, it is not limited to a quadrangular shape, and various shapes (for example, a triangular shape as shown in Fig. 4, or a tortoiseshell shape or a circular shape, not shown) may be adopted.

[0036] The geogrid 22 may be made of an appropriate synthetic resin such as polyolefin (for example, polypropylene or polyethylene) similar to the sheet 20. However, it is not necessary for the geogrid 22 to be made of the same material as the sheet 20.

[0037] Like the sheet 20, the geogrid 22 is advantageously formed from a thermoplastic synthetic resin that softens or melts at the material temperature of the asphalt layer 8 when the asphalt layer 8 is constructed. In this case, the effect of bonding the upper surface of the crushed stone layer 6 and the lower surface of the asphalt layer 8 is also exerted by the geogrid 22.

[0038] Next, a construction method for the asphalt pavement structure 2 as described above will be described.

[0039] When constructing the asphalt pavement structure 2, first, the roadbed 4 and the crushed stone layer 6 are constructed. A known method can be used to construct the roadbed 4 and the crushed stone layer 6. For example, the roadbed 4 can be constructed by excavating the existing ground to a predetermined depth with an excavating machine such as a hydraulic excavator, leveling the top surface of the roadbed 4 with a ground leveling vehicle such as a bulldozer, and then compacting the surface of the roadbed 4 with a compacting vehicle such as a tire roller.

[0040] Once the roadbed 4 has been constructed, roadbed material brought in by a dump truck is laid on the top surface of the roadbed 4 using a ground-leveling vehicle such as a motor grader, and then compacted using a rolling vehicle to make the top surface of the crushed stone layer 6 flat.

[0041] As described above, the crushed stone layer 6 shown in Fig. 1 is mainly composed of the lower roadbed 12, so when constructing the crushed stone layer 6 shown in Fig. 1, a step of constructing the lower roadbed 12 is carried out. On the other hand, the crushed stone layer 6 shown in Fig. 2 includes the lower roadbed 12 and the upper roadbed 14, so when constructing the crushed stone layer 6 shown in Fig. 2, a step of constructing the lower roadbed 12 and a step of constructing the upper roadbed 14 are carried out.

[0042] After constructing the crushed stone layer 6, asphalt emulsion E is sprayed on the upper surface of the crushed stone layer 6 and asphalt reinforcement 10 is laid. Although Fig. 1 shows an example in which asphalt emulsion E is sprayed on the upper surface of the crushed stone layer 6 and then asphalt reinforcement 10 is laid, asphalt emulsion E may be sprayed after laying asphalt reinforcement 10. That is, asphalt emulsion E may be sprayed directly on the upper surface of the crushed stone layer 6, or asphalt emulsion E may be sprayed on the upper surface of the crushed stone layer 6 via asphalt reinforcement 10 that has been laid previously.

[0043] Alternatively, as shown in FIG. 2, half of the specified amount of asphalt emulsion E may be directly spread on the top surface of the crushed stone layer 6, and then the asphalt reinforcement material 10 may be laid in the order of sheet 20, geogrid 22, and sheet 20, and the remaining asphalt emulsion E may be spread on top of the asphalt reinforcement material 10.

[0044] It is preferable to bond or weld the sheet 20 and the geogrid 22 together before laying the asphalt reinforcing material 10, as this will facilitate construction.

[0045] After laying the asphalt reinforcement 10, the asphalt layer 8 is constructed. In the asphalt layer 8 shown in Fig. 1, the upper roadbed 14, the base layer 16, and the surface layer 18 are constructed in this order. On the other hand, in the asphalt layer 8 shown in Fig. 2, the base layer 16 and the surface layer 18 are constructed in this order.

[0046] The upper roadbed 14 can be constructed, for example, by spreading stabilized roadbed material heated to about 150 to 170°C and uniformly compacting it. The base layer 16 and the surface layer 18 are also constructed in a manner similar to the upper roadbed 14, for example, by spreading a heated asphalt mixture heated to about 150 to 170°C and uniformly compacting it. In this manner, the asphalt pavement structure 2 is constructed.

[0047] Incidentally, asphalt emulsion E is sprayed between each of the layers constituting the asphalt layer 8. Specifically, in the embodiment shown in Fig. 1, asphalt emulsion E is sprayed on the upper surface of the upper roadbed 14 and the upper surface of the base layer 16, and in the embodiment shown in Fig. 2, asphalt emulsion E is sprayed on the upper surface of the base layer 16.

[0048] As described above, in the illustrated embodiment, the sheet 20 absorbs and retains the asphalt emulsion E, so that the crushed stone layer 6 and the asphalt layer 8 are strongly bonded by the sheet 20 retaining the asphalt emulsion E, and the peeling resistance of the asphalt layer 8 from the crushed stone layer 6 can be increased. Furthermore, since the sheet 20 has a thickness that follows the unevenness of the upper surface of the crushed stone layer 6, when the sheet 20 is laid on the upper surface of the crushed stone layer 6, the lower surface of the sheet 20 deforms along the unevenness of the upper surface of the crushed stone layer 6. Therefore, the contact area between the lower surface of the sheet 20 that absorbs and retains the asphalt emulsion E and the upper surface of the crushed stone layer 6 is increased. Therefore, the adhesion between the crushed stone layer 6 and the asphalt layer 8 is increased, and the peeling resistance of the asphalt layer 8 from the crushed stone layer 6 is further increased.

[0049] In addition, since the asphalt emulsion is absorbed by the sheet 20, the uneven distribution of the asphalt emulsion E is reduced, and the evaporation of the water contained in the asphalt emulsion E is promoted, thereby shortening the construction time.

[0050] In the form shown in Figure 1, when laying the asphalt reinforcement material 10, the sheet 20 is placed on the crushed stone layer 6 side (lower side), and the geogrid 22 having multiple openings 24 is placed on the upper roadbed 14 side (upper side) of the asphalt layer 8. Therefore, when the upper roadbed 14 is constructed, the aggregate of the upper roadbed 14 enters the openings 24 of the geogrid 22, and the geogrid 22 and the upper roadbed 14 are firmly connected.

[0051] In addition, when at least one of sheet 20 and geogrid 22 is formed from a material that softens or melts at the material temperature of asphalt layer 8 when constructing asphalt layer 8, sheet 20 itself or geogrid 22 itself has the effect of bonding the upper surface of crushed stone layer 6 and the lower surface of asphalt layer 8.

[0052] In this manner, in the illustrated embodiment, the peeling resistance of the asphalt layer 8 from the crushed stone layer 6 can be increased, suppressing a decrease in the layer thickness (reduction in strength) of the asphalt pavement structure 2, and dispersing the load (for example, wheel load when vehicles pass) acting on the asphalt pavement structure 2 by the geogrid 22. Therefore, according to the illustrated embodiment, it is possible to prevent cracks from occurring on the lower surface of the asphalt layer 8.

[0053] In the illustrated embodiment, the sheet 20 absorbs and retains the asphalt emulsion E, and the sheet 20 retaining the asphalt emulsion E exhibits a waterproof function and suppresses the flow of water between the crushed stone layer 6 and the asphalt layer 8. This prevents rainwater and the like that has seeped in through the joints of the asphalt layer 8 from reaching the crushed stone layer 6, suppressing deformation of the crushed stone layer 6 due to wetting. Furthermore, the sheet 20 retaining the asphalt emulsion E also prevents groundwater present in the crushed stone layer 6 from permeating the asphalt layer 8 (capillary water rise), suppressing the outflow of fine particles from the asphalt layer 8.

[0054] In the above explanation, examples have been given of the asphalt layer 8 having three layers, namely, the upper roadbed 14, the base layer 16, and the surface layer 18 (the form shown in Figure 1), and the asphalt layer 8 having two layers, namely, the base layer 16 and the surface layer 18 (the form shown in Figure 2), but the asphalt layer 8 may be a single layer rather than multiple layers.

[0055] For example, on general roads with low traffic volume, asphalt reinforcement material 10 may be buried between a crushed stone layer 6 including a lower roadbed 12 and an upper roadbed 14, and an asphalt layer 8 consisting of a single layer, as shown in Fig. 5. Also, on simple pavements, farm roads, etc., asphalt reinforcement material 10 may be buried between a crushed stone layer 6 consisting of a lower roadbed 12, and an asphalt layer 8 consisting of a single layer, as shown in Fig. 6. [Explanation of symbols]

[0056] 2: Asphalt pavement structures 4: Roadbed 6: Crushed stone layer 8: Asphalt layer 10: Asphalt reinforcement material 12: Lower roadbed 14: Upper roadbed 16: Base layer 18: Surface layer 20:Sheet 22: Geogrid 24:Aperture E: Asphalt emulsion

Claims

1. The roadbed comprises a crushed stone layer constructed above the roadbed, an asphalt layer constructed above the crushed stone layer, and an asphalt reinforcement material buried between the crushed stone layer and the asphalt layer; The asphalt reinforcement material comprises a sheet that absorbs and retains asphalt emulsion spread between the crushed stone layer and the asphalt layer and has a thickness that conforms to the unevenness of the upper surface of the crushed stone layer, and a geogrid overlaid on the sheet, wherein the sheet and the geogrid are previously bonded or welded to each other to form an asphalt pavement structure.

2. The geogrid is a mesh having a plurality of openings, The asphalt pavement structure according to claim 1 , wherein the sheet is disposed on the crushed stone layer side, and the geogrid is disposed on the asphalt layer side.

3. 3. The asphalt pavement structure according to claim 1 or 2, wherein the sheet or the geogrid is formed from a material that softens or melts at the material temperature of the asphalt layer when the asphalt layer is constructed.

4. 4. The asphalt pavement structure according to claim 1, wherein the sheet is formed from a nonwoven fabric.

5. An asphalt reinforcing material for reinforcing an asphalt pavement structure comprising a crushed stone layer constructed above a roadbed and an asphalt layer constructed above the crushed stone layer, The sheet absorbs and retains the asphalt emulsion spread between the crushed stone layer and the asphalt layer and has a thickness that follows the unevenness of the upper surface of the crushed stone layer, and a geogrid is superimposed on the sheet; The sheet and the geogrid are bonded or welded to each other, and are embedded between the crushed stone layer and the asphalt layer to form an asphalt reinforcement material.

6. The geogrid is a mesh having a plurality of openings, The asphalt reinforcement material according to claim 5 , wherein the sheet is placed on the crushed stone layer side and the geogrid is placed on the asphalt layer side.

7. The asphalt reinforcing material according to claim 5 or 6, wherein the sheet or the geogrid is formed from a material that softens or melts at the material temperature of the asphalt layer when the asphalt layer is constructed.

8. The asphalt reinforcement according to any one of claims 5 to 7, wherein the sheet is formed from a nonwoven fabric.

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