JP2010229707A - Permeable pavement structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a permeable pavement structure which makes a construction period short, does not cause a problem of dust generation, has inexpensively water permeability as well as water retentivity, and can suppress a rise in the temperature of a paved surface over a long period of time as a result. <P>SOLUTION: This permeable pavement structure 1 formed on a subgrade layer 2 is characterized in that a filter layer 3, a water-retentive subgrade layer 4 composed of a water-retentive subgrade material obtained by mixing a coal-ash granulated material 21 as a supplementary material into a subgrade material 22, and a surface layer 5 with the water permeability are sequentially superposed on one another. The mixing ratio of the supplementary material 21 to the subgrade material 22 is set to, supplementary material:subgrade material=10:90 to 50:50 (weight ratio). The coal-ash granulated material 21 is obtained by granulating coal ash or a mixture containing at least the coal ash and cement. Preferably, fly ash is used as the coal ash. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water-permeable pavement structure having water retention.

In recent years, urban warming has become a problem. As a main factor of this urban warming,
(1) A large amount of energy is consumed in urban areas than in the suburbs, and artificial exhaust heat has increased significantly.
(2) In urban areas, facilities with large heat capacity such as concrete and asphalt occupy most of the ground surface, and because the heat absorbed during the day is released slowly at night, the temperature in urban areas is raised at night. (Heat storage effect), and (3) As the ground surface is covered with concrete and other structures due to urbanization, the surface area of the groundwater, such as rainwater, penetrates into the ground, which is due to the evaporation of moisture from the ground surface. The point where the dissipation of latent heat is suppressed and the surface temperature rises compared to the suburbs (suppression of evaporation),
Is listed.

  For each of these factors, many countermeasure technologies are currently being put into practical use. In particular, as a countermeasure for factor (3), in order to promote the diffusion of latent heat of evaporation from urban areas, it is proactive. In addition, it has been promoted to increase water permeability by installing green spaces and hydrophilic spaces in urban areas.

  In recent years, various techniques related to water-permeable pavement have been proposed as one technique for increasing the water-permeable surface. Generally, a road pavement has a structure in which a roadbed layer and a surface layer are sequentially laminated on a roadbed layer. This water-permeable pavement has a porous porous asphalt mixture or cement on a granular roadbed layer. A surface layer made of concrete is paved to improve the water permeability between the surface layer and the roadbed. With this structure, in the case of permeable pavement, rainwater penetrates from the pavement surface to the roadbed during rain and temporarily stores water in the pavement structure. By evaporating up to the vicinity of the pavement surface and evaporating, the heat of vaporization can be taken away and the temperature increase of the pavement surface can be mitigated.

  However, in this permeable pavement, the temperature rise of the pavement surface can be kept low until about one day after the rain compared with normal non-permeable pavement and drainage pavement, but the subsequent temperature rise is not permeable pavement. As a result, there was a problem that the effect of suppressing the temperature rise of the pavement surface was lost.

  In order to solve the problem of this water-permeable pavement, a water-retaining pavement structure (water-retaining water-permeable pavement) in which this pavement structure also has water retention has been recently proposed. This water-retaining pavement has a relatively small gap between the surface layer and the roadbed layer to enable gap water retention, and has an increased amount of water retention inside than the water-permeable pavement structure.

As such a water-retaining pavement structure, for example, a roadbed formed by placing a mixture of soil, cement-based solidified material, aggregated material, and coal ash on a roadbed that is impermeable. A structure composed of a water-retaining pavement layer has been proposed (see Patent Document 1). However, this pavement structure requires construction for making the roadbed impermeable, which is expensive and time consuming, and the mixture is laid on the roadbed thus formed impermeable. There is a problem of dust generation during uniform rolling.
JP 2006-37571 A

  In view of the above circumstances, the present invention has a short period of construction, does not cause dusting problems, and is provided with water permeability and water retention at low cost, and as a result, the water permeability that can suppress the temperature rise of the pavement surface over a long period of time. An object is to provide a pavement structure.

  According to the present invention, the above object is a pavement structure built on a road bed layer, comprising a filter layer and a water retention roadbed material obtained by mixing coal ash granulated material as a supplement to the roadbed material. This is achieved by a water-permeable pavement structure in which a permeable roadbed layer and a surface layer having water permeability are sequentially laminated.

  According to the present invention, since the coal ash granulated material is mixed as a supplement to the road bed layer constituting a part of the permeable pavement structure, not only the pore water retention of the road bed layer but also the coal ash granulation. As a result, the water retention of the object itself can be effectively utilized, and as a result, the temperature rise of the pavement surface in the daytime can be suppressed for a longer period than the conventional water-permeable pavement. In addition, since coal ash granulated material is mixed as a supplement to the roadbed material, it can be paved inexpensively in a short construction period, and a pavement structure can be obtained without causing the problem of dust generation.

It is a figure which shows an example of the water-permeable pavement structure which is embodiment of this invention. It is a graph which shows the particle size distribution of the coal ash granulated material as a supplementary material, a roadbed material, and these mixtures. It is a graph which shows the temperature measurement result of a pavement. It is a graph which shows the temperature measurement result in the pavement surface and the said pavement surface vicinity.

  Hereinafter, the water-permeable pavement structure of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1: has shown the vertical sectional view of the water-permeable pavement structure which is embodiment of this invention. As shown in this figure, the water-permeable pavement structure 1 of the present invention comprises a filter layer 3, a roadbed layer 4 and a surface layer 5 having water permeability that are sequentially laminated on a roadbed layer (ground) 2. The roadbed layer 2 can be constructed by using a known ground method (roadbed work) or the like. Specific examples of the roadbed include a cut method, a banking method, a stable treatment method, a replacement method, and the like. In the present invention, the roadbed layer 2 can be formed by any of these roadbed methods. Here, the cut method is a method that uses the conventional ground as a roadbed by leveling or cutting down to a predetermined depth, and the embankment method is a method that builds up the roadbed by raising good quality soil on the conventional ground. It is. The stable treatment method is a method of improving the bearing capacity of the roadbed by mixing the roadbed soil and a stabilizing material such as cement or lime in situ. Usually, as the stabilizer, cement is used when the roadbed soil is sandy soil, and lime is used when the subgrade soil is viscous soil, but a cement-based or lime-based solidified material can also be used. The replacement method is a method of excavating part or all of the road bed and replacing it with high quality soil when there is a soft road bed soil at the cut portion. These construction methods can be applied alone or in combination of two or more. For example, after the cut method, a stabilization method can be combined to improve the CBR of the paved area.

  The filter layer 3 formed on the road bed layer 2 allows the rainwater that has passed through the water-permeable surface layer 5 and the road bed layer 4 to permeate into the road bed layer 2 at the time of raining, etc. It is provided to prevent softening and destruction of the pavement structure. The filter layer 3 is usually formed by spreading fine aggregate such as sand to a predetermined thickness. The fine aggregate is preferably free of dust, mud, organic matter and the like. In particular, when sand is used as the fine aggregate, any of natural sand, crushed sand, and crushed stone dust can be used, and the particle size should satisfy the specified values in each of the JIS standards that define these, but preferably pass through a 75 μm sieve. It is preferable to use a particle having an amount of 6% or less. The finished layer thickness of the filter layer is usually 30 to 100 mm, preferably 40 to 80 mm, and more preferably 40 to 60 mm in the case of paving bodies such as parks and parking lots. In the case of a sidewalk pavement, the length is set to 50 to 100 mm. The layer thickness may be set to such an extent that the roadbed layer can be prevented from being weakened, and does not need to be excessively thick. However, if the thickness is less than the above range, the softening cannot be effectively prevented.

  A water retaining roadbed layer 4 is formed on the filter layer 3. The water retaining roadbed layer 4 is a layer provided to further disperse the traffic load transmitted from the surface layer 5 and transmit the traffic load to the roadbed layer 2 and to retain moisture passing in the layer thickness direction. In the pavement structure 1 of the present invention, the roadbed layer 4 is composed of a water-retaining roadbed material in which coal ash granulated material 41 is mixed as a supplementary material with the roadbed material 42.

  The coal ash granule 41 is granulated with coal ash as a main component. As the coal ash, fly ash and clinker ash generated from various boiler facilities such as a pulverized coal fired boiler, an oil fired boiler, a fluidized bed boiler, and a pressurized fluidized bed boiler can be used. Clinker ash is porous in itself and has water retention, but since a pulverization step is required, it is preferable to use fly ash that can be granulated relatively inexpensively. For example, when using fly ash from a pressurized fluidized bed boiler, this fly ash is self-hardening, and since sufficient strength characteristics can be obtained by curing, it can be granulated alone and other coal ash When used, in order to obtain a predetermined strength characteristic, the other components can be mixed and granulated within a range of a predetermined mixing ratio.

  As the other powder component, various binders and additives can be used. Examples of the binder include hydraulic binders such as cement, gypsum, and lime, as well as various slags such as steelmaking slag, and can also include known organic binders. These binders can be used alone or in combination of two or more.

  Further, as the additive, in addition to a material that itself has water absorption, moisture absorption, and water retention, an organic binder material that enhances the binding force of the powder material can be used. Examples of the former include clay minerals such as zeolite, bentonite, kaolinite, and montmorillonite, as well as known solid organic water-absorbing materials. The latter binder material does not matter if it is solid and liquid. These additives can be used singly or in combination of two or more.

  When a binder, or a binder and an additive are mixed with coal ash, the mixing ratio can be appropriately set in consideration of the curing conditions and strength characteristics (mainly crushing strength) of the resulting granulated product. Usually, the total amount of the powder mixture is 100% by weight, and the range is 0 to 20% by weight of the binder and 0 to 5% by weight of the additive (the remainder is coal ash).

  The powder mixture is granulated after being hydro-kneaded. The amount of kneading water is 10 to 40 parts by weight, preferably 12 to 30 parts by weight, with respect to 100 parts by weight of the powder component, taking into consideration the moisture adhering to the powder component and the target strength of the granulated product It can be set as appropriate within the range of parts by weight. Kneading can be performed using a known kneader such as a mortar mixer. When the liquid organic binder material is used, a predetermined amount can be added in advance to the kneaded water.

  The granulation can be performed using a known granulator such as a rotating dish granulator (rolling granulation) or a roll press (compression granulation). For example, in the case of the former granulator, the powder mixture is charged while rotating the rotating dish, and kneading and granulation can be performed simultaneously by adding kneading water by a method such as spraying. . The obtained granulated product is then cured under natural curing or under a temperature condition of 30 to 70 ° C. The curing period can be appropriately set so that the obtained granulated product has a predetermined strength characteristic.

The properties of the coal ash granule obtained in this way are usually formed from an almost spherical shape to an almond shape, with a crushing strength of 1 to 10 MN / m ² , an average particle size of 10 to 20 mm, and a maximum particle size of 40 mm or less. The water absorption rate is about 20-30%, and the water retention rate after standing in the air for 10 days is 20% or more. By using coal ash as the main component in this way, a granulated product that is relatively light compared to natural crushed stone and is excellent in water retention and water absorption can be obtained.

  As the roadbed material 42, natural crushed stone, steel slag, asphalt, concrete recycled aggregate (hereinafter referred to as RC material), or the like can be suitably used. Any of these may be used alone or in combinations of two or more. In particular, among these, the use of RC materials is becoming mainstream due to the recent increase in the effective use of recycled aggregates, and RC materials usually show a water absorption rate of 4 to 8% by weight. Since the effect of suppressing the temperature rise of the pavement surface to some extent can be expected as compared with the above, it is preferable to use the RC material alone or to use this as a main material and other natural crushed stones.

  In the present invention, the roadbed material 42 is mixed with the coal ash granulated material 41 as a supplementary material to prepare a water retaining roadbed material. The mixing ratio of the two can be set as appropriate. However, from the viewpoint of the water-absorbing and water-holding properties of the formed water-retaining roadbed layer, it is necessary to satisfy the standard of the walking road board material of corrected CBR of 30% or more. = 10: 90 to 50:50, preferably 10:90 to 30:70 (all are in a weight ratio). If the mixing ratio of the supplementary material is less than the above range, the water retention is insufficient and the temperature increase of the pavement surface cannot be effectively suppressed. Further, when the value is larger than the above range, it is necessary to perform a modified CBR test and confirm whether or not the modified CBR value satisfies the standard value.

  The water-retaining roadbed material is carried onto the filter layer 3 and spread uniformly so as to have a predetermined finished thickness. For leveling, asphalt finisher, bulldozer, motor grader, etc. are usually used, and leveling work is performed continuously. Thereafter, the surface of the water-retaining roadbed layer 4 that has been spread and leveled is usually further rolled and flattened by a tire roller, road roller, or the like of about 4 to 20 t until a predetermined degree of compaction is obtained. This rolling compaction crushes the coal ash granulated material in the water-retaining roadbed material, and the crushed product is filled in the gaps between the roadbed materials, which is denser and, if necessary, filled with a certain density. A structure can be formed. The finished layer thickness of the water-retaining roadbed layer thus formed is usually 100 to 200 cm, preferably 50 to 150 cm.

  A surface layer 5 having water permeability is formed on the water retaining roadbed layer 4. This surface layer 5 has water permeability, disperses the traffic load and transmits it to the lower layer, has resistance to surface wear and cracks, is flat and difficult to slip, and can be driven well by means of transportation. Is to provide. In this invention, if it has such a function, surface layer materials, such as various asphalt mixtures and water-permeable cement concrete, can be used, for example, Among them, an open-graded asphalt mixture is used suitably. This open-graded asphalt mixture is usually a heated asphalt mixture made of coarse aggregate, fine aggregate, filler, and asphalt, and has a 2.36 mm sieve passage in the synthetic particle size in the range of 15 to 30% by weight. The coarse aggregate blended in the asphalt mixture is an aggregate that is 85% by weight or more on a 5 mm sieve, and the fine aggregate is an aggregate that passes through the entire 10 mm sieve and passes through the 5 mm sieve by 85% by weight or more. The maximum particle size of the coarse aggregate 51 is 20 mm or less, preferably 13 mm or less. The filler is usually a mineral powder (for example, stone powder such as limestone or igneous rock) that passes through a 75 μm sieve, and is added to increase the apparent viscosity of asphalt.

  In the case of construction using an open-graded asphalt mixture, this is spread on the water-retaining roadbed layer 4 using an asphalt finisher and then compacted. This compacting operation is performed by a plurality of rotational pressures using a load roller, tire roller, vibration roller, or the like having a predetermined weight in accordance with a normal construction method. The weight of the tire roller or the like can be set as appropriate according to the construction situation. In the case of water-permeable cement concrete, it can be similarly constructed. In addition, the surface layer having water permeability can be constructed by being divided into two layers of a surface layer portion and a base layer portion located below the surface layer portion. In this case, the surface layer material having the same or different water permeability as described above can be used for each part of the base layer and the surface layer, and can be laid by the above-described method of leveling and compacting.

  Further, the surface layer material formed of the water-permeable asphalt mixture or cement concrete is further provided with water permeability, for example, a plate-like or block-like surface layer material (pavement material such as a pavement flat plate or an interlocking block). ) Can be laid. As such a pavement material, for example, composite particles obtained by mixing and granulating hard aggregate, coal ash, low refractory ceramic materials and water described in JP-A-7-315951 are formed into a predetermined shape and fired. And those obtained by mixing a thermoplastic resin, a thermosetting resin, and coal ash as described in JP-A-2004-52244, a mixture of melted and solidified crushed artificial crushed stones into a block shape with cement, and the like can be suitably used. . Moreover, when using a water-permeable flat plate or an interlocking block, according to a normal method, sand is spread on the water-retaining roadbed layer 4 to provide a cushion layer, and these are spread on it.

  The open particle size asphalt mixture or the like or a plate-like or block-like surface layer material may have water retention. Moreover, you may make it also have water retention property by making the material which has water retention property into the space | gap with which these surface layer materials are equipped by making it into a slurry form.

  In the water-permeable pavement structure of the present invention, rainwater permeates into the road bed layer over time at the time of rain, water is retained in the coal ash granule in the road bed layer, and with the temperature rise of the pavement surface at fine weather, The groundwater in the roadbed layer, the roadbed layer, and the ground below it rises toward the surface layer, where it evaporates to suppress the temperature rise of the pavement surface, and also when permeated water passes through the water-retaining roadbed layer The water is absorbed and retained in the coal ash granulation. As a result, in the conventional permeable pavement structure, if the clear weather continues for about 2 to 5 days after the rainy day, the pavement structure dries and the increase in pavement surface temperature cannot be suppressed. Since the granule releases its retained moisture over a long period of time, it is possible to suppress the temperature rise of the pavement surface for a long period of about 1 week to 10 days after the rainy day.

  The water-permeable pavement structure of the present invention can be applied to pavements such as roadways, sidewalks, open spaces, and general parking lots. By using for these pavements, it becomes possible to suppress effectively the temperature rise of a pavement surface in summer. In addition, about the roadway, it is preferable to apply the water-permeable pavement structure of this invention to the pavement of a roadway with a plan traffic volume relatively smaller than what is called a main road etc. in consideration of the temporal change of the intensity | strength.

[Materials used]
(1) Roadbed material (RC material) RC-30 (maximum particle size 30mm or less, concrete shell)
(2) Supplementary material Coal ash granulation (trade name “Hi beads”, manufactured by Energia Eco Materia Co., Ltd.)
(3) Surface layer material Permeable asphalt mixture-13 (maximum particle size of aggregate 13mm)

[Preparation of coal ash granules]
In the test, granulation is carried out while adding a powder mixture (100% by weight in total) consisting of 87% by weight of fly ash generated from a pulverized coal-fired boiler and 13% by weight of cement using a pan-type granulator. (The amount of kneading water was 23% by weight with respect to the powder mixture), and the one cured in air for 4 weeks was used. Table 1 shows the properties of the obtained coal ash granulate.

[Preparation of water-retaining roadbed material]
RC material and coal ash granulated material were mixed so that RC material: coal ash granulated material (supplementary material) = 80: 20, and a water retention roadbed material was prepared. The following physical property test was performed on this water-retaining roadbed material.
(1) Screening test (conforms to JIS A1102)
(2) Soil compaction test by tamping (conforms to JIS A1210)
(3) Modified CBR test (JIS A1211 compliant)

  The physical property test results are shown in Table 2. In Table 2, when the standard value about RC material (RC-30) is prescribed | regulated, the value is written together.

[Construction of pavement structure]
As part of the repair work for the sidewalks along the road, two work areas of a predetermined area (each 180 m ² ) are set in a part of the repair work area, and one of these work areas (hereinafter referred to as work area 1). The pavement structure of the present invention was constructed. First, sand was spread on a road bed layer having a flat surface, and a filter layer having a finished layer thickness of 50 mm was formed by rolling. On top of that, the above-mentioned water-retaining roadbed material was carried in, spread by a bulldozer, and then subjected to surface rolling (load 4t) using a biaxial tandem roller to form a water-retaining roadbed layer (finished layer thickness retention 100 mm) ). Furthermore, after carrying an open-graded asphalt mixture onto the roadbed layer, leveling, and rolling using a biaxial tandem roller to form a water-permeable surface layer (finished layer thickness 40 mm), the water-permeable pavement structure of the present invention A body was obtained (Example 1).

  In the pavement work in the remaining work zone (hereinafter referred to as “work zone 2”), a pavement structure was obtained using the same materials and methods as described above except that only RC-30 was used as the roadbed material (Comparative Example 1).

[Measurement of pavement temperature]
The pavement structure (Example 1) of the present invention in the construction zone 1 and the pavement structure (comparative example 1) in the construction zone 2 are each measured at one location, the temperature at the interface between the surface layer of the pavement structure and the roadbed layer. Attached to. The temperature sensor was installed in the pavement structure by cutting out the surface layer with a core cutter to make a hole, installing the temperature sensor in it, and backfilling with the same surface material. At the same time, a temperature sensor was installed at a height of 1 m above the ground surface in order to measure the ambient temperature around this area.

  The temperature of the pavement and the outside air temperature were measured for 10 days from July 19th to 29th in the summer. This period is a period in which clear days continued after July 10th to 11th rain (daily rainfall 47 mm). The measurement results are shown in Table 2 and FIG. Each data in Table 2 is obtained from the plot of FIG.

  From the data of Table 3, in Example 1, the maximum value of the pavement temperature was 57 ° C., and the average value was 39.8 ° C. On the other hand, in Comparative Example 1, the maximum value of the pavement temperature is 58.8 ° C., and the average value is 40.7 ° C., and the maximum value is 1.8 by using the water-permeable pavement structure of the present invention. Suppression of a temperature rise of 0.9 ° C. was observed at an average value of ° C.

  Moreover, the pavement temperature of Example 1 is lower than that of Comparative Example 1 in any time zone during this period, and by using the water-permeable pavement structure of the present invention, the temperature of the pavement rises over a long period of time. It was shown that can be suppressed.

[Measurement of temperature at and near the pavement surface]
The pavement (surface layer) surface temperature of the pavement structure of the present invention (Example 1) in the work zone 1 and the pavement structure (Comparative Example 1) in the work zone 2 and the temperature near the pavement surface at a height of 10 cm above the pavement surface. A non-contact type radiation thermometer was installed by a known method so that the temperature could be measured. Thereafter, water was sprayed around the place where the radiation thermometer was installed, and the pavement surface temperature and the temperature near the pavement surface were continuously measured for one week from that day. The results are shown in Table 4 and FIG. In these charts, the “maximum temperature” is a measured value in the area to which the work area 1 and the work area 2 belong.

  From the results shown in Table 4 and FIG. 4, the pavement structure of Example 1 has a lower surface temperature on the first day after watering by 6 ° C. than the pavement structure of Comparative Example 1, and is substantially equivalent after four days. Thus, it was shown that the former can suppress the surface temperature more than the latter during the measurement period. Further, the temperature at a height of 10 cm on the pavement surface is lower in the pavement structure of Example 1 than in Comparative Example 1.

  As described above, it is clear that the pavement structure of the present invention can suppress the temperature rise of the pavement inside and the pavement surface in the daytime for a longer period than the conventional water-permeable pavement. In addition, since coal ash granulated material is mixed as a supplement to the roadbed material, it can be paved inexpensively in a short construction period, and a pavement structure can be obtained without causing the problem of dust generation.

DESCRIPTION OF SYMBOLS 1 Water-permeable pavement structure 2 Road bed layer 3 Filter layer 4 Water retention roadbed layer 41 Supplementary material (coal ash granulated material)
42 Roadbed material 5 Surface layer 51 Aggregate

Claims (4)

  A pavement structure built on a roadbed layer, comprising a filter layer, a water-retaining roadbed layer composed of a water-retaining roadbed material mixed with coal ash granulated material as a supplement to the roadbed material, and water permeability A water-permeable pavement structure characterized by being sequentially laminated with a surface layer.   The water-permeable pavement structure according to claim 1, wherein a mixing ratio of the supplementary material to the roadbed material is supplementary material: roadbed material = 10: 90 to 50:50 (weight ratio).   The permeable pavement structure according to claim 1 or 2, wherein the coal ash granulated material is obtained by granulating coal ash or a mixture containing at least coal ash and cement.   The water-permeable pavement structure according to any one of claims 1 to 3, wherein the coal ash is fly ash.

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