Semi-flexural pavement and construction method thereof

Abstract

To provide a semi-flexural pavement on which visibility of road white lines is high, and of which temperature in summer is suppressed from rising on road surface, and to provide a construction method thereof.SOLUTION: In a semi-flexural pavement according to the present invention a cement material is impregnated into an asphalt pavement whose surface layer contains asphalt and aggregates, and the cement material contains an infrared-reflective dark coloring material. A semi-flexural pavement construction method according to the present invention includes a process of forming an asphalt pavement using an asphalt mixture containing asphalt and aggregates, and a process of impregnating the asphalt pavement with cement milk and allowing it to harden, and the cement milk contains an infrared-reflective dark coloring material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a semi-flexible pavement and a method for constructing the same. [Background technology]

[0002] Asphalt pavement is low cost and can be constructed in a short construction period, but rutting can occur when heavy vehicles frequently pass through. Concrete pavement is less prone to rutting and has high durability and load-bearing capacity, but is expensive and requires a long curing period, which can result in long-term road closures.

[0003] In contrast, semi-flexible pavement is a road in which cement milk is infiltrated into the voids in open-graded asphalt pavement, and is known as a road that combines the benefits of asphalt pavement and concrete pavement. In other words, semi-flexible pavement has the durability and load-bearing capacity of concrete pavement, and can be constructed in a relatively short period of time.

[0004] Patent Documents 1 and 2 disclose such semi-flexible pavements. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 43-004695 [Patent Document 2] Japanese Patent Application Publication No. 3-259505 Summary of the Invention [Problem to be solved by the invention]

[0006] Semi-flexible pavements are essentially light in colour, the colour of cement milk, and may be coloured with colour pigments to obscure the white lines on the road.

[0007] However, when coloring the cement milk for semi-flexible pavement with a dark color like that of asphalt pavement, it was found that the temperature of the road surface would become very high in the summer, just like that of asphalt pavement.

[0008] Therefore, an object of the present invention is to provide a semi-flexible pavement that provides high visibility of road white lines and prevents the road surface from heating up in the summer, and a construction method for the same. [Means for solving the problem]

[0009] The present inventors have discovered that the above problems can be solved by the present invention having the following aspects: Ta. <<Aspect 1>> A semi-flexible pavement in which a cement material is impregnated into an asphalt pavement whose surface layer contains asphalt and aggregate, wherein the cement material contains an infrared-reflective dark coloring material. <<Aspect 2>> 2. The semi-flexible pavement of claim 1, wherein the dark colorant is a black pigment. Aspect 3 2. A semi-flexible pavement according to aspect 1, wherein the coating film containing the black pigment has an average reflectance of 60% or more in a wavelength range of 800 nm to 1200 nm. Aspect 4 2. A semi-flexible pavement according to aspect 1, wherein the coating film containing the black pigment has an average reflectance of 30% or less in a wavelength range of 400 nm to 700 nm. Aspect 5 2. The semi-flexible pavement of claim 1, wherein the cement material is composed of a cement milk containing Portland cement, a filler, a resin-based emulsion, and water. Aspect 6 A method for constructing a semi-flexible pavement, comprising the steps of forming an asphalt pavement using an asphalt mixture containing asphalt and aggregate, and permeating the asphalt pavement with cement milk and allowing it to harden, wherein the cement milk contains an infrared-reflective dark coloring material. [Effects of the Invention]

[0010] The present invention can provide a semi-flexible pavement that provides high visibility of road white lines and prevents the road surface from heating up in the summer, and a construction method for the same. DETAILED DESCRIPTION OF THE INVENTION

[0011] The semi-flexible pavement of the present invention is a semi-flexible pavement having a surface layer in which a cement material is impregnated into an asphalt pavement containing asphalt and aggregate, and the cement material contains an infrared-reflective dark color material. In this specification, "pavement" refers to the structure of a paved road.

[0012] Semi-flexible pavements have traditionally been constructed in locations where road renewal work is difficult, and construction has been common in tunnels, so road surface temperatures in the summer have rarely been a concern. In recent years, semi-flexible pavements have been constructed in a variety of locations, but because they are essentially light-colored and light-reflective, the problem of high road surface temperatures in the summer was not anticipated. The inventors, however, discovered that even semi-flexible pavements colored to highlight white road lines outdoors can cause significant increases in road surface temperature in the summer, leading to the development of the semi-flexible pavement of the present invention.

[0013] Furthermore, in the semi-flexible pavement of the present invention, the cement material that permeates the asphalt pavement contains an infrared-reflective coloring material, so that the effect of reducing road surface temperature can be sustained even if the surface of the pavement is slightly worn away. It has been known for some time to apply a heat-shielding coating to the surface of asphalt roads, but if the heat-shielding coating peels off, it must be reapplied. This reapplication can be problematic in places where construction is difficult, such as where semi-flexible pavements are installed, so the semi-flexible pavement of the present invention is extremely advantageous.

[0014] <Cement materials> Semi-flexible pavement includes cementitious materials that permeate the asphalt pavement. By allowing the cementitious materials to permeate the voids in the asphalt pavement and hardening, semi-flexible pavement can have the durability and load-bearing properties of concrete pavement.

[0015] <Cement materials - dark color materials> The cement material used in the present invention includes an infrared-reflective dark coloring material. The dark coloring material is not particularly limited as long as it can make the white lines stand out when contained in the semi-flexible pavement. Furthermore, while the dark coloring materials used in conventional technology are infrared-absorbing, the coloring material used in the present invention is infrared-reflective, thereby preventing the semi-flexible pavement from absorbing the heat rays of sunlight and causing a temperature rise.

[0016] For example, a coating film containing a dark colorant may have an average reflectance in the wavelength range of 800 nm to 1200 nm of 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more, or may be 95% or less, 90% or less, 80% or less, or 70% or less.

[0017] Furthermore, the average reflectance of a coating film containing a dark colorant in the wavelength range of 400 nm to 700 nm may be 0% or more, 3% or more, 5% or more, 10% or more, or 20% or more, or may be 40% or less, 30% or less, 20% or less, or 10% or less.

[0018] In this specification, the average reflectance of a coating film is measured as follows. First, 1.5 parts by weight of colorant, 8.5 parts by weight of butylated melamine resin (Super Beckamine J-820, manufactured by Dainippon Ink and Chemicals, Inc.), 17.0 parts by weight of coconut oil-based short-oil alkyd resin (Phtalquid 133-60, manufactured by Hitachi Chemical Co., Ltd.), and 5.0 parts by weight of a xylene / 1-butanol (2 / 1 (by weight)) mixed solvent are mixed and dispersed for 90 minutes using a paint conditioner to prepare a coating. Next, the prepared coating is applied to a drawing paper using an applicator (3 mils) and baked at 140°C for 30 minutes to form a coating film. The visible-infrared absorption spectrum of the coating film is then measured using a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Corporation). The reflectance measured in this manner is calculated as the average reflectance across each wavelength.

[0019] Such dark colorants include pigments, particularly black pigments. The pigments may be organic or inorganic. The dark colorants may also be a combination of multiple colorants.

[0020] Specific examples of black pigments include inorganic black pigments such as Dipyroxide Color Black 9590, Dipyroxide Color Brown 9290, and Dipyroxide Color Brown 9211 (all manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), Black 411 (manufactured by The Shepherd Color Company), and Black 6350 (manufactured by Asahi Kasei Kogyo Co., Ltd.), and organic black pigments such as Chromofine Black A-1103 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), Fastogen Super Black MX (manufactured by DIC Corporation), Paliogen Black S0084, and Paliotol Black L0080 (all manufactured by BASF), and Hoster Palm Brown HFR-01 (manufactured by Clariant Japan KK).

[0021] The dark colorant may be contained in the cement milk used to form the cement material in an amount of 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, or 3.0% by mass or more, or 10% by mass or less, 5.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, or 1.0% by mass or less.

[0022] <Cement materials - Other> The cement material is formed when cement milk hardens in the asphalt pavement. The cement milk contains at least cement and water, preferably a filler and a resin emulsion, in addition to a dark colorant. The cement milk can be prepared on the construction site by mixing water with a premix containing elements other than water.

[0023] The cement is not particularly limited, but any known Portland cement known as a cement source for semi-flexible paving cement milk can be used, such as ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, moderate-heat Portland cement, or low-heat Portland cement.

[0024] 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, or may be 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, or 560 parts by mass or less.

[0025] Examples of fillers include stone powder, slaked lime, cement, recovered dust, fly ash, etc. The content of filler in the semi-flexible paving 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, and may 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, per 100 parts by mass of cement.

[0026] The resin emulsion may be any known material used as a resin emulsion for semi-flexible paving cement milk, particularly a rubber emulsion, such as an acrylic, acrylic-Veova, EVA (ethylene-vinyl acetate copolymer), or SBR (styrene-butadiene rubber).The resin emulsion content of the semi-flexible paving 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, or 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, based on the resin solids content, per 100 parts by mass of cement.

[0027] The cement milk may also contain known setting retarders, water reducing agents, antifoaming agents, thickeners, air entraining agents, rust inhibitors, and the like.

[0028] <Asphalt pavement> The asphalt pavement in semi-flexible pavements can be formed from an asphalt mix containing asphalt and aggregate, typically a hot mix asphalt mix.

[0029] <Asphalt pavement - aggregate> The aggregate used in the asphalt pavement of semi-flexible pavement is not particularly limited, and those commonly used in this field can be used. Coarse aggregate and / or fine aggregate can be used as the 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 used by selecting the particle size, blending ratio, etc. from the viewpoint of interlocking of the aggregates and fluidity. The particle sizes of the coarse aggregate and fine aggregate refer to the values ​​specified in JIS A5001-2008.

[0030] Examples of coarse aggregate 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.

[0031] Examples of fine aggregates include fine aggregates of less than 2.36 mm, such as river sand, dune sand, mountain sand, sea sand, crushed sand, fine sand, screenings, crushed stone dust, silica sand, artificial sand, glass cullet, and foundry sand.

[0032] By selecting the type and mixing ratio of these aggregates, the resulting asphalt mixture can be made into an open-graded asphalt mixture that can create an asphalt pavement with many voids to allow the cement material to easily penetrate.

[0033] For example, an asphalt pavement (13) used in the surface course of a semi-flexible pavement and having a maximum aggregate particle size of 13 mm may contain 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more of aggregate having a particle size of 4.75 mm or more, and 95% by mass or less, 90% by mass or less, 80% by mass or less, or 70% by mass or less. Also, an asphalt pavement (13) used in the surface course of a semi-flexible pavement may contain 5% by mass or more, 10% by mass or more, 20% by mass or more, or 30% by mass or more of aggregate having a particle size of 4.75 mm or less, and 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less. For example, the asphalt pavement (13) used as the surface layer of a semi-flexible pavement contains 60% to 90% by mass of aggregate with a particle size of 4.75 mm or more, and 10% to 40% by mass of aggregate with a particle size of 4.75 mm or less.

[0034] Furthermore, asphalt pavement (20) used in the surface course of semi-flexible pavement and having a maximum aggregate particle size of 20 mm can contain 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more of aggregate with a particle size of 13.2 mm or more, and can contain 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less.Asphalt pavement (20) used in the surface course of semi-flexible pavement can contain 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more of aggregate with a particle size of 4.75 mm or more and 13.2 mm or less, and can contain 60% by mass or less, 50% by mass or less, 40% by mass or less, or 30% by mass or less. The asphalt pavement (20) used in the surface course of a semi-flexible pavement may contain 5% by mass or more, 10% by mass or more, 20% by mass or more, or 30% by mass or more of aggregate with a particle size of 4.75 mm or less, and may contain 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less. For example, the asphalt pavement (20) used in the surface course of a semi-flexible pavement may contain 20% by mass or more and 50% by mass or less of aggregate with a particle size of 13.2 mm or more, 10% by mass or more and 40% by mass or less of aggregate with a particle size of 4.75 mm or more and 13.2 mm or less, and 10% by mass or more and 30% by mass or less of aggregate with a particle size of 4.75 mm or less.

[0035] For example, recycled aggregate may be used as the aggregate, which is obtained by crushing waste asphalt mixtures used in the surface and base layers of asphalt pavement.

[0036] These recycled aggregates may account for 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more of the total mass of the aggregate (and filler), and may be 100% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less. Substantially no recycled aggregates may be used, for example, less than 20% by mass, 10% by mass or less, 5% by mass or less, or none at all may be used in the asphalt pavement.

[0037] The aggregate content in the 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, or 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.

[0038] <Asphalt pavement - asphalt> Various types of asphalt can be used. Examples include straight asphalt, which is petroleum asphalt for paving, and modified asphalt. Modified asphalt includes blown asphalt and polymer-modified asphalt modified with polymeric materials such as thermoplastic elastomers and thermoplastic resins. The asphalt may be contained as an asphalt emulsion. Furthermore, the asphalt emulsion may contain polymer-modified asphalt.

[0039] The content of new asphalt used in the production of an asphalt mixture other than the old asphalt attached to the recycled aggregate may be 1.0 parts 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, and may be 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, per 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, and may be 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, per 100 parts by mass of the total mass of aggregate and filler.

[0040] <Asphalt pavement - Other> Asphalt pavement may contain other components than those commonly used in the art, such as fillers, such as stone powder, hydrated lime, cement, recycled dust, and fly ash.

[0041] The amount of filler may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts 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, relative to 100 parts by mass of the total of the aggregate and filler. The amount of filler may be, for example, 0.1 parts by mass or more and 10.0 parts by mass or more, or 1.0 parts by mass or more and 7.0 parts by mass or less.

[0042] <Each layer> A semi-flexible pavement may include a surface course of asphalt pavement impregnated with a cement material, and a base course underlying the surface course.

[0043] The thickness of the surface course may be, for example, 10 mm or more, 30 mm or more, or 50 mm or more, and may be 200 mm or less, 150 mm or less, 100 mm or less, or 50 mm or less. The total thickness of the surface course and base course can be changed depending on the traffic volume or traffic load of the semi-flexible pavement, and may be, for example, 50 mm or more, 100 mm or more, or 200 mm or more, and may be 500 mm or less, 300 mm or less, or 200 mm or less.

[0044] The base layer can be formed from an asphalt mixture, particularly a heated asphalt mixture, containing at least asphalt and aggregate, similar to the asphalt pavement used for the surface layer. The aggregate composition of the base layer may be different from that of the surface layer. However, it is preferable that the base layer be made of aggregate that constitutes an asphalt mixture that is difficult for cement milk to penetrate. In addition, the maximum particle size of the aggregate in the base layer is generally larger than that in the surface layer, but it may also be similar in size in the surface layer and base layer.

[0045] Semi-flexible pavements may also include a subbase layer below the base layer. The subbase layer may be made of granular materials such as crushed stone, gravel, slag, recycled aggregate, sand, crushed run, crushed run steel slag, recycled crushed run, or clinker ash, or these materials mixed with stabilizers such as cement, lime, or asphalt. The thickness of the subbase layer may be, for example, at least 10 cm, at least 20 cm, or at least 30 cm, or may be at most 100 cm, at most 80 cm, at most 60 cm, or at most 40 cm.

[0046] Semi-flexible pavements can include a subgrade layer below the roadbed layer, which is typically soil, but can also be made of concrete decks, steel decks, etc.

[0047] <Construction method> The method for constructing semi-flexible pavement of the present invention comprises the steps of forming an asphalt pavement using an asphalt mixture containing asphalt and aggregate, and infiltrating cement milk into the asphalt pavement and allowing it to harden, wherein the cement milk contains an infrared-reflective dark colorant.

[0048] The process can include a step of forming the base layer before the step of forming the asphalt pavement, and can also include a step of forming the roadbed layer and subgrade layer. The surface layer (and base layer) of the semi-flexible pavement can be formed by spreading a heated asphalt mixture heated to, for example, about 150 to 170°C using an asphalt finisher and then uniformly compacting it using a roller.

[0049] When infiltrating cement milk into the surface asphalt pavement, the amount of cement milk to be used can be calculated based on the area, thickness, porosity, etc. of the asphalt pavement. Cement milk can be prepared in a mixer at the construction site by adding water to a premix containing the elements necessary for preparing cement milk except for water. Furthermore, after the asphalt pavement formation process, the asphalt pavement is cooled to a temperature of 70°C or below, 50°C or below, and then the cement milk is spread evenly with a rake or other tool, and then infiltrated while vibrating with a vibrating roller or other tool. After this process, any excess cement milk that has not been infiltrated can be removed with a rake or other tool. This prevents a decrease in the skid resistance of the pavement.

[0050] Furthermore, the curing period can be set according to the hardening speed of the cement milk, allowing the cement milk to harden. [Example]

[0051] In a laboratory, a small area of ​​asphalt pavement was prepared using a heated asphalt mixture. As Comparative Example 1, a standard semi-flexible pavement was prepared using cement milk containing no colorant. As Comparative Example 2, a semi-flexible pavement was prepared containing 3 parts by mass of carbon black as a colorant per 100 parts by mass of cement in the cement milk. As Example 1, a semi-flexible pavement was prepared by replacing the carbon black in Comparative Example 2 with an infrared-reflective black pigment (Chromofine Black A1103, Dainichiseika Color & Chemicals Co., Ltd.).

[0052] A reflector lamp (150 W) was continuously irradiated onto these pavements, and the temperature at which the temperature stopped rising was taken as the maximum surface temperature. The maximum surface temperatures were about the same for Comparative Example 1 and Example 1, but the maximum surface temperatures for Comparative Example 2 were higher than those for Comparative Example 1 and Example 1.

[0053] This temperature difference is significantly greater than the temperature difference between asphalt pavement with a thermal barrier coating and asphalt pavement without a thermal barrier coating. This is thought to be because asphalt pavement without cement impregnated is a porous body, while semi-flexible pavement with cement impregnated is essentially a solid body.

Claims

1. A semi-flexible pavement in which a cement material is impregnated into an asphalt pavement whose surface layer contains asphalt and aggregate, wherein the cement material contains an infrared-reflective dark coloring material.

2. 2. The semi-flexible pavement according to claim 1, wherein the dark colorant is a black pigment.

3. The semi-flexible pavement according to claim 1, wherein the coating film containing the black pigment has an average reflectance of 60% or more in the wavelength range of 800 nm to 1200 nm.

4. The semi-flexible pavement according to claim 1, wherein the coating film containing the black pigment has an average reflectance of 30% or less in the wavelength range of 400 nm to 700 nm.

5. 2. The semi-flexible pavement of claim 1, wherein the cement material is composed of a cement milk containing Portland cement, a filler, a resin-based emulsion, and water.

6. A method for constructing a semi-flexible pavement, comprising the steps of forming an asphalt pavement using an asphalt mixture containing asphalt and aggregate, and permeating the asphalt pavement with cement milk and allowing it to harden, wherein the cement milk contains an infrared-reflective dark coloring material.