Construction method for semi-flexible pavement

Abstract

The present invention provides a method for constructing semi-flexible pavement that can provide semi-flexible pavement with excellent appearance even when constructed over a wide area. [Solution] The present invention provides a method for constructing a semi-flexible pavement, comprising a first step of impregnating cement milk into the voids of the asphalt pavement in a first area (11), and a second step of impregnating cement milk into the voids of the asphalt pavement in a second area (12) adjacent to the first area (11), wherein in the second step, a columnar member (2) is placed on the second area (12) side of the boundary (21) between the first area (11) and the second area (12).

Description

Technical Field

[0001] The present invention relates to a construction method for semi-flexible pavement. In particular, the present invention relates to a construction method for semi-flexible pavement that can provide semi-flexible pavement with excellent appearance even when constructed over a wide area.

Background Art

[0002] Asphalt pavement can be constructed at low cost and in a short construction period. However, when heavy vehicles frequently pass, rutting may occur. Concrete pavement is less likely to rut and has high durability and load-bearing capacity. On the other hand, due to its high cost and long curing period, it may require long-term traffic stoppage.

[0003] In contrast, semi-flexible pavement is a pavement in which cement milk is infiltrated into the voids of an open-graded semi-flexible pavement asphalt mixture layer with a large void ratio and cured. It is known as a pavement that combines the merits of flexible asphalt pavement and rigid concrete pavement. That is, semi-flexible pavement has durability and load-bearing capacity like concrete pavement and can be constructed in a relatively short construction period.

[0004] Patent Documents 1 and 2 disclose such semi-flexible pavement and construction methods.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] When constructing semi-flexible pavement, cement milk is poured onto the asphalt pavement from a mixer using a hose or similar device. The poured cement milk is then spread across the asphalt pavement using a rubber rake, and a vibratory roller is used to allow the cement milk to permeate into the voids in the asphalt. However, preparing the cement milk requires a large amount of water, and securing a water supply is crucial when constructing semi-flexible pavement. Thus, the process of permeating the cement milk into the voids of the asphalt pavement requires a certain number of workers, and there are limits to the availability of materials. Therefore, constructing semi-flexible pavement over a large area in a single operation is difficult.

[0007] Therefore, when constructing semi-flexible pavement over a wide area, it is common practice to partially construct the semi-flexible pavement by dividing the process of impregnating the voids in the asphalt pavement with cement grout into several stages for each area.

[0008] However, when semi-flexible pavement is installed area by area, even if the same material is used, the color will inevitably vary slightly from area to area. In this case, if the boundaries between areas are straight lines, the overall appearance will not be bad, but if the boundaries are wavy or jagged, the overall appearance will be very poor.

[0009] Therefore, the present invention provides a method for constructing a semi-flexible pavement that can provide a semi-flexible pavement with an excellent appearance even when constructed over a wide area. [Means for solving the problem]

[0010] The present inventors have found that a construction method for semi-flexible pavement having the following characteristics can solve the above problem.

[0011] 《Aspect 1》 In the first area, the first step is to impregnate the voids in the asphalt pavement with cement milk, and The second step involves impregnating the voids in the asphalt pavement with cement milk in the second area adjacent to the first area. A construction method for semi-flexible pavement, in which, in the second step, columnar members are placed on the second area side of the boundary between the first area and the second area.

[0012] When constructing semi-flexible pavement area by area, once the first area is completed and construction begins on the second area, the completed first area can be protected with a sheet-like material such as masking tape to prevent the cement grout used in the second area from flowing out.

[0013] However, even if an attempt is made to protect the first area by securing the sheet-like material with adhesive tape, the adhesive strength of the tape is lower on semi-flexible pavement than on asphalt pavement, causing cement grout to leak out from the underside of the sheet-like material. If cement grout leaks from the underside of the sheet-like material into the first area, it is possible to wipe it away immediately, but since the first area is hidden by the sheet-like material, it is impossible to notice that cement grout has leaked out. As a result, the boundary between the first and second areas becomes wavy or jagged, resulting in a very poor appearance.

[0014] In contrast, if a columnar member is placed on the second area side of the boundary between the first and second areas, any leakage of cement grout into the first area can be immediately noticed. In this case, it would seem that the cement grout would not penetrate into the voids in the asphalt pavement below the columnar member in the second area. However, the inventors' research has shown that even if the columnar member is placed on the second area, the cement grout will still penetrate firmly into the area below the columnar member.

[0015] This is thought to be because, when attempting to infiltrate cement grout near the boundary between the first and second areas, the cement grout has already penetrated to a certain depth in the first area and begun to harden. Therefore, it is difficult for the cement grout to penetrate laterally from the second area to the first area, and instead, the cement grout tries to spread within the second area, penetrating all the way to the bottom of the columnar members. As a result, this construction method makes it possible to create an almost straight boundary between the first and second areas, providing a semi-flexible pavement with an excellent appearance.

[0016] 《Aspect 2》 The method for constructing a semi-flexible pavement according to Embodiment 1, wherein in the second step, a sheet-like member is placed on the third area side of the boundary between the second area and the third area adjacent to the second area.

[0017] When constructing the second area, it is preferable to protect the third area, which is adjacent to the second area and where cement grout has not yet permeated, with a sheet-like member rather than placing a columnar member on the boundary of the second area with the second area. This is because if a columnar member is placed on the second area at the boundary with the third area where cement grout has not yet permeated, and the cement grout is to permeate into the second area, the cement grout will flow into the third area, making it difficult for the cement grout to permeate into the second area below the columnar member.

[0018] 《Aspect 3》 The method for constructing a semi-flexible pavement according to Embodiment 1, wherein the height of the columnar member is 3 cm or more and 30 cm or less.

[0019] When the height of the columnar member is within this range, it is preferable because, in the second step, when the cement grout is permeated into the asphalt pavement using a vibratory roller or the like, the columnar member can catch the splashing of cement grout toward the first area, and because the height of the columnar member is not too large, it is easy to handle.

[0020] Appearance 4 The construction method of the semi-flexible pavement according to Embodiment 3, wherein the width of the columnar member is 3 cm or more and 10 cm or less.

[0021] When the width of the columnar member is within such a range, in the second step, it is preferable because the cement milk easily penetrates to the lower part of the columnar member.

[0022] 《Embodiment 5》 The construction method of the semi-flexible pavement according to Embodiment 1, wherein the columnar member is a formwork for pavement.

[0023] When the columnar member is a formwork for pavement, it is preferable because the height and width are appropriate and it is very easy to obtain at the construction site.

Advantages of the Invention

[0024] According to the construction method of the semi-flexible pavement of the present invention, even when constructing over a wide area, a semi-flexible pavement with excellent appearance can be provided.

Brief Description of the Drawings

[0025] [Figure 1] FIG. 1 is a conceptual diagram for explaining the construction method of the present invention. [Figure 2] FIG. 2 is a conceptual diagram for explaining a comparative construction method. [Figure 3] FIG. 3 is a conceptual diagram of the appearance of a semi-flexible pavement constructed by a comparative construction method.

Modes for Carrying Out the Invention

[0026] The present invention will be specifically described below by taking the following embodiments as examples, but the present invention is not limited thereto. When there is no particularly detailed mention of the configuration of each embodiment, those skilled in the art can use well-known configurations for these.

[0027] In this specification, the height direction refers to the direction of gravity, which is the z direction in the drawing; the length direction refers to the direction in which the boundary between the first area and the second area extends, which is the y direction in the drawing; and the width direction refers to the direction perpendicular to the height direction and the length direction, which is the x direction in the drawing.

[0028] Figure 1 is a conceptual diagram illustrating the construction method of the present invention. Figure 1(a) shows the first step of impregnating cement milk into the voids of the asphalt pavement in the first area 11, and Figure 1(b) shows the second step of impregnating cement milk into the voids of the asphalt pavement in the second area 12 adjacent to the first area 11. In Figure 1(b), the columnar member 2 is placed on the second area side.

[0029] Figure 2 is a conceptual diagram illustrating the comparative construction method. In Figure 2, the difference from Figure 1 is that in Figure 2(b), the columnar member 2 is not placed on the second area side as in Figure 1(b), but rather the sheet-like member 1 is placed on top of the first area 11.

[0030] A method typically considered by those skilled in the art when constructing semi-flexible pavement area by area is the method shown in Figure 2, which involves laying a sheet-like member 1 over the completed area for protection. However, with this method, as shown in Figure 2(b), leakage of cement milk occurs on the underside of the first sheet-like member 1 in the first area 11 where cement milk has permeated. When leakage A exists in this way, as shown in Figure 3, the boundary 21 becomes wavy or jagged, resulting in a very poor appearance.

[0031] In contrast, according to the construction method of the present invention, semi-flexible pavement can be constructed in a straight line for each area on the boundary 21 as intended.

[0032] As shown in Figure 1(a), in the first step, when the cement grout is permeated into the first area 11, the sheet-like member 1 is placed on the second area 12 side of the boundary 21 between the first area 11 and the second area 12 adjacent to the first area 11. The sheet-like member 1 catches the cement grout that is scattered when the first area 11 is constructed, preventing the cement grout from adhering to the surface of the second area 12.

[0033] As shown in Figure 1(b), in the second step, the columnar member 2 is placed on the second area 12 side of the boundary 21 between the first area 11 and the second area 12. By placing the columnar member 2 on the second area side, even if cement grout leaks out into the first area 11 side, it can be easily seen and the leaked cement grout can be wiped away during construction.

[0034] Although cement grout cannot be directly applied to the lower part of the columnar member 2 in the second area 12, it was found that cement grout can be applied effectively to the lower part of the columnar member 2 even if the columnar member 2 is placed on top of the second area 12.

[0035] In the second step, the columnar member 2 may be positioned on the boundary 21 between the first area 11 and the second area 12, to the extent that the advantageous effects of the present invention can be obtained, but preferably, the entire width of the columnar member 2 is positioned on the second area 12 so that the leakage of cement grout into the first area 11 can be visually observed.

[0036] The columnar member 2 has a certain height, which allows it to catch the scattering of cement milk when the cement milk is permeated into the asphalt pavement with a vibratory roller or the like in the second step 12. From this viewpoint and from the viewpoint of ease of handling, the height of the columnar member 2 may be 3 cm or more, 5 cm or more, 8 cm or more, or 10 cm or more, and may be 50 cm or less, 30 cm or less, 20 cm or less, or 15 cm or less.

[0037] Furthermore, it is preferable that the columnar member 2 has a relatively small width, as this facilitates the penetration of cement grout into the lower part of the columnar member 2 during the second step. From this viewpoint and from the viewpoint of ease of handling, the width of the columnar member 2 may be 2 cm or more, 3 cm or more, 4 cm or more, or 5 cm or more, and may be 15 cm or less, 10 cm or less, 8 cm or less, or 6 cm or less.

[0038] The length of the columnar member 2 is not particularly limited, but may be, for example, 2m to 10m, or 3m to 5m. The material of the columnar member 2 is also not limited, but it is preferably made of wood due to its ease of handling.

[0039] Such columnar members 2 may be wooden paving formwork used in ordinary asphalt paving. Such paving formwork is well known in this field, has a height of 10 cm, a width of 3 cm to 5 cm, and a length of 4 m, and is standardized. Since road paving contractors usually have a large stock of paving formwork, it is preferable because it can be obtained very easily when constructing semi-flexible pavement.

[0040] In addition, in the second step, it is also possible to place the sheet-like member on the second area 12 at the boundary 21 between the first area 11 and the second area 12. However, in this case, it becomes necessary to adhere the tape used to adhere the sheet-like member to the asphalt pavement of the second area 12. In this case, the cement milk will not be able to cover the pavement surface where the adhesive tape is attached to the asphalt pavement, and after the adhesive tape is removed, a residue will remain, resulting in an unsightly appearance.

[0041] In the second step, the sheet-like member 1 can be placed on the third area 13 side of the boundary 22 between the second area 12 and the third area 13, which is adjacent to the second area and where cement grout has not yet permeated. Here, it is also possible to place the columnar member on the second area 12 side of the boundary 22 and construct the work, but since cement grout has not yet permeated the third area 13, it is difficult for cement grout to permeate the second area 12 directly beneath the columnar member. Furthermore, since cement grout has not yet permeated the third area 13, it is relatively easy to fix the sheet-like member 1 on the asphalt pavement of the third area using adhesive tape.

[0042] While masking tape, protective sheets, and the like can be used as sheet-like materials, they are not limited to these.

[0043] After the completion of the second step, the third step can be carried out in the third area 13, in which cement grout is infiltrated into the voids of the asphalt pavement. This can be done in the same manner as the second step described above. Further areas can also be treated in the same manner as the second step.

[0044] <others> A construction method for semi-flexible pavement may include the steps of forming an asphalt pavement using an asphalt mixture containing asphalt and aggregate, and the cement milk injection step of impregnating the asphalt pavement with cement milk and hardening it. Here, the cement milk injection step may include the first and second steps described above.

[0045] The construction method for semi-flexible pavement may further include a step of forming the base layer beneath the asphalt pavement before the step of forming the surface asphalt pavement, and may also include a step of forming the subbase layer and subgrade layer below the base layer. The surface layer (and base layer) of semi-flexible pavement can be formed, for example, by spreading a heated asphalt mixture heated to about 150-170°C with an asphalt finisher and compacting it uniformly with a compaction machine.

[0046] When infiltrating surface asphalt pavement with cement milk, the amount of cement milk to be used can be calculated based on the area, thickness, and void ratio of the asphalt pavement. Cement milk can be prepared at the construction site by adding water to a premix material containing all elements necessary for cement milk preparation except water, using a mixer. Furthermore, cement milk can be infiltrated after the asphalt pavement is formed, once it has cooled to a temperature of 70°C or below, 50°C or below, or 30°C or below, by spreading it uniformly with a rake or similar tool and applying vibration with a vibratory roller or similar tool. After this process, any excess cement milk that has not been fully infiltrated can be removed with a rake or similar tool.

[0047] Furthermore, in the cement grout injection process, the curing period can be set according to the hardening speed of the cement grout, allowing the cement grout to harden.

[0048] <Cement Milk> Semi-flexible pavement contains cement material that permeates the asphalt pavement, and the cement material is formed when cement milk hardens in the asphalt pavement. The cement milk contains at least cement and water, preferably further containing fillers and resin emulsions, and may further contain colorants for coloring the semi-flexible pavement. The cement milk can be prepared at the construction site by mixing water with a premix material containing elements other than water.

[0049] The cement contained in the cement grout is not particularly limited, but known Portland cements known for use in permeable cement grout can be used. Examples of Portland cements that can be used include ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, and ultra-fast-setting cement.

[0050] The amount of water contained in the cement milk may be 25 parts by mass or more, 30 parts by mass or more, 35 parts by mass or more, or 40 parts by mass or more per 100 parts by mass of cement, and may also be 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, or 50 parts by mass or less.

[0051] Examples of fillers include stone powder, slaked lime, cement, recovered dust, and fly ash. The filler content of the permeable cement milk may be 5 parts by mass or more, 10 parts by mass or more, 20 parts by mass or more, or 30 parts by mass or more per 100 parts by mass of cement, and may also be 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, or 40 parts by mass or less.

[0052] As the resin emulsion, known materials used as resin emulsions for impregnating cement milk, particularly rubber emulsions, such as acrylic, acrylic-beova, EVA (ethylene-vinyl acetate copolymer), and SBR (styrene-butadiene rubber), can be used. The resin emulsion content of the impregnating cement milk may be 0.5 parts by mass or more, 1 part by mass or more, 3 parts by mass or more, or 5 parts by mass or more per 100 parts by mass of cement, based on the resin solids content, and may also be 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less.

[0053] The cement milk may also contain other known setting retarders, water-reducing agents, defoaming agents, thickeners, air-entraining agents, rust inhibitors, and so on.

[0054] <Asphalt paving> Asphalt pavement in semi-flexible pavement can be formed from an asphalt mixture containing asphalt and aggregate. The asphalt mixture is usually a hot-mix asphalt mixture. For asphalt pavement in semi-flexible pavement, open-graded asphalt pavement is usually used to facilitate the penetration of cement grout.

[0055] <Asphalt pavement - aggregate> The aggregate used in asphalt pavement in semi-flexible pavement is not particularly limited, and aggregates commonly used in this field can be used. Coarse aggregate and / or fine aggregate can be used as aggregate. Coarse aggregate with a particle size of 2.36 mm or more and fine aggregate with a particle size of less than 2.36 mm can be selected based on particle size, mixing ratio, etc., from the viewpoint of interlocking between aggregates and fluidity. The particle sizes of coarse aggregate and fine aggregate refer to the values ​​specified in JIS A5001-2008.

[0056] Examples of coarse aggregates include No. 7 crushed stone with a particle size range of 2.36 mm or more and less than 4.75 mm, No. 6 crushed stone with a particle size range of 4.75 mm or more and less than 13.2 mm, No. 5 crushed stone with a particle size range of 13.2 mm or more and less than 19 mm, and No. 4 crushed stone with a particle size range of 19 mm or more and less than 31.5 mm.

[0057] Examples of fine aggregates include those less than 2.36 mm in size, such as river sand, hill sand, mountain sand, sea sand, crushed sand, fine sand, screenings, crushed stone dust, silica sand, artificial sand, glass cullet, and foundry sand.

[0058] By selecting the types and mixing ratios of these aggregates, the resulting asphalt mixture can be an open-graded asphalt mixture that can form an asphalt pavement with many voids, allowing cement material to penetrate easily.

[0059] For example, asphalt pavement (13) used for the surface layer of semi-flexible pavement, with a maximum aggregate particle size of 13 mm, may contain aggregate with a particle size of 13.2 mm or larger in amounts of 0% or more by mass, 1% or more by mass, or 3% or more by mass, and may contain 10% or less by mass, or 5% or less by mass, and aggregate with a particle size of 4.75 mm or larger in amounts of 65% or more by mass, 70% or more by mass, or 80% or more by mass, and may contain 90% or less by mass, 80% or less by mass, or 70% or less by mass. Furthermore, asphalt pavement (13) used for the surface layer of semi-flexible pavement may contain aggregate with a particle size of 4.75 mm or smaller in amounts of 10% or more by mass, 20% or more by mass, or 30% or more by mass, and may contain 35% or less by mass, 30% or less by mass, 20% or less by mass, or 10% or less by mass. For example, the asphalt pavement (13) used for the surface layer of a semi-flexible pavement contains aggregate with a particle size of 4.75 mm or larger in an amount of 65% to 90% by mass, and aggregate with a particle size of 4.75 mm or smaller in an amount of 10% to 35% by mass.

[0060] Furthermore, asphalt pavement (20) used for the surface layer of semi-flexible pavement, with a maximum aggregate particle size of 20 mm, may contain aggregate with a particle size of 19.0 mm or larger in amounts of 0% or more by mass, 1% or more by mass, or 3% or more by mass, and may contain 10% or less by mass, or 5% or less by mass, and aggregate with a particle size of 13.2 mm or larger in amounts of 30% or more by mass, 40% or more by mass, 50% or more by mass, or 60% or more by mass, and may contain 65% or less by mass, 60% or less by mass, 50% or less by mass, or 40% or less by mass. Asphalt pavement (20) used for the surface layer of semi-flexible pavement may contain aggregate with a particle size of 4.75 mm or larger and smaller in amounts of 10% or more by mass, 20% or more by mass, 30% or more by mass, or 40% or more by mass, and may contain 60% or less by mass, 50% or less by mass, 40% or less by mass, or 30% or less by mass. Asphalt pavement (20) used for the surface layer of semi-flexible pavement may contain aggregate with a particle size of 4.75 mm or less in amounts of 7% or more by mass, 10% or more by mass, 20% or more by mass, or 25% or more by mass, and may contain 30% or less by mass, 20% or less by mass, 15% or less by mass, or 10% or less by mass. For example, asphalt pavement (20) used for the surface layer of semi-flexible pavement may contain aggregate with a particle size of 13.2 mm or more in amounts of 20% or more by mass and 50% or less by mass, aggregate with a particle size of 4.75 mm or more and 13.2 mm or less in amounts of 10% or more by mass and 30% or less by mass.

[0061] For example, recycled aggregate may be used as aggregate. Recycled aggregate is obtained by crushing waste material from asphalt mixtures used in the surface and base layers of asphalt pavement.

[0062] These recycled aggregates may be 5% or more by mass, 10% or more by mass, 20% or more by mass, 30% or more by mass, or 40% or more by mass of the total mass of the aggregate (and filler), and may be 100% or less by mass, 90% or less by mass, 80% or less by mass, 70% or less by mass, 60% or less by mass, 50% or less by mass, or 40% or less by mass. These recycled aggregates may not be used substantially, for example, in asphalt pavement they may be less than 20% by mass, 10% or less by mass, 5% or less by mass, or not used at all.

[0063] The aggregate content in asphalt pavement may be 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, or 90% by mass or more, and may be 97% by mass or less, 95% by mass or less, 93% by mass or less, 90% by mass or less, or 85% by mass or less.

[0064] <Asphalt pavement - asphalt> Various types of asphalt can be used. Examples include straight asphalt, a type of petroleum asphalt used for paving, and modified asphalt. Modified asphalts include blown asphalt and polymer-modified asphalt, which is modified with polymer materials such as thermoplastic elastomers and thermoplastic resins. Asphalt may also be included as an asphalt emulsion. Furthermore, the asphalt emulsion may contain polymer-modified asphalt.

[0065] In addition to the old asphalt adhering to the recycled aggregate, the content of new asphalt newly used during the manufacture of the asphalt mixture may be 1.0 part by mass or more, 2.0 parts by mass or more, 3.0 parts by mass or more, or 4.0 parts by mass or more, or 6.0 parts by mass or less, 5.0 parts by mass or less, 4.0 parts by mass or less, or 3.0 parts by mass or less, based on 100 parts by mass of the total mass of aggregate and filler. The total content of old asphalt and new asphalt may be 3.0 parts by mass or more, 3.5 parts by mass or more, 3.0 parts by mass or more, or 4.0 parts by mass or more, or 6.0 parts by mass or less, 5.5 parts by mass or less, 5.0 parts by mass or less, or 4.5 parts by mass or less, based on 100 parts by mass of the total mass of aggregate and filler.

[0066] <Asphalt Paving - Others> Asphalt pavement may contain other components besides those commonly used in this field. For example, asphalt pavement may contain fillers. Examples of fillers include stone powder, slaked lime, cement, recycled dust, and fly ash.

[0067] For every 100 parts by mass of aggregate and filler combined, the amount of filler may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 part by mass or more, or 2.0 parts by mass or more, and may be 10.0 parts by mass or less, 7.0 parts by mass or less, 5.0 parts by mass or less, or 3.0 parts by mass or less. For example, the amount of filler can be 0.1 parts by mass or more and 10.0 parts by mass or less, or 1.0 part by mass or more and 7.0 parts by mass or less. [Explanation of Symbols]

[0068] 1…Sheet-like member 2…Columnar member 11, 12, 13… Areas 1-3 21,22...boundary

Claims

1. In the first area, the first step is to impregnate the voids in the asphalt pavement with cement milk, and The second step involves impregnating the voids in the asphalt pavement with cement milk in the second area adjacent to the first area. A construction method for semi-flexible pavement, in which, in the second step, columnar members are placed on the second area side of the boundary between the first area and the second area.

2. The method for constructing a semi-flexible pavement according to claim 1, wherein in the second step, a sheet-like member is placed on the third area side of the boundary between the second area and the third area adjacent to the second area.

3. The method for constructing a semi-flexible pavement according to claim 1, wherein the height of the columnar member is 3 cm or more and 30 cm or less.

4. The method for constructing a semi-flexible pavement according to claim 3, wherein the width of the columnar member is 3 cm or more and 10 cm or less.

5. The method for constructing a semi-flexible pavement according to claim 1, wherein the columnar member is a formwork for paving.

Images