Regeneration construction method of pavement layer and regenerated pavement layer obtained by adopting regeneration construction method

Abstract

The present invention addresses the problem of providing a method for regenerating a pavement layer and a regenerated pavement layer, which are capable of ensuring sufficient compaction and heavy machine travability even when an original pavement to be constructed is in a state in which water is considered to be excessive, and which are capable of constructing a regenerated pavement layer, by providing a method for regenerating a pavement layer and a regenerated pavement layer obtained thereby, in order to solve the above-mentioned problem, this method for regenerating a pavement layer comprises a step for adding a water-absorbing material when the water content ratio of a recycled aggregate used exceeds a target water content ratio, and matching the apparent water content ratio of the recycled aggregate, which is obtained by removing the mass of water absorbed by the water-absorbing material, with the target water content ratio.

Description

Technical Field

[0001] The present invention relates to a method for recycling a pavement layer and a recycled pavement layer obtained by using the same. Background Art

[0002] A method of excavating and crushing a roadbed of an aged asphalt pavement, including an asphalt mixture layer thereon, and mixing and spreading an asphalt emulsion or foamed asphalt, and further an additive such as cement, and compacting them in place to construct a recycled road base layer, as shown in Patent Documents 1 and 2, for example, is a method that has been carried out in the past.

[0003] Since most of the original pavement is directly utilized in place in the above method, there is less material handling in and out, energy saving, and it has the advantages of contributing to the effective utilization of resources and the reduction of CO2 emissions. In addition, it is also an advantage that it can be constructed at a lower cost compared to the replacement method.

[0004] However, since most of the original pavement is directly utilized in place in the above method, there is a problem that the workability and the physical properties of the constructed recycled road base layer are greatly influenced by the state of the original pavement during construction.

[0005] For example, when it rains just before construction, the original pavement becomes a state containing a large amount of moisture. If the original pavement is excavated and crushed in this state, crushed materials containing a large amount of moisture are obtained. Therefore, if the crushed materials are used as recycled aggregates and an asphalt emulsion, cement, etc. are mixed therein, it is expected that the water content ratio of the mixture will greatly exceed the optimum water content ratio.

[0006] Incidentally, the optimum water content ratio is the water content ratio at which the dry density of the mixture reaches the maximum when it is compacted. If the water content ratio of the mixture exceeds the optimum water content ratio, the mixture cannot be compacted sufficiently at a high density, and it is difficult to construct a recycled road base layer, a recycled surface layer, etc. having the expected strength. Furthermore, if the water content ratio of the mixture is too large, the fluidity of the mixture increases, and construction heavy machinery such as a stabilizer and a roller cannot travel on the mixture, and there is also an inconvenience that construction cannot be carried out using heavy machinery.

[0007] The original pavement is in a dry state. When the water content is too low, it is easy to adjust the water content by sprinkling water or the like, and it is relatively easy to handle. However, when the original pavement contains a large amount of water and the water content ratio of the mixture of its crushed materials and asphalt emulsion, cement, etc. exceeds the optimum water content ratio, it is generally difficult to adjust the water content ratio of the original pavement or its crushed materials, that is, the recycled aggregate, in the direction of reduction. As a method for reducing the water content ratio of the original pavement or its crushed materials, for example, there are methods such as staggering the construction days and waiting for the water in the original pavement to naturally decrease, or removing the subgrade materials containing a large amount of water, replacing them with dry subgrade materials, or degassing by mixing the crushed subgrade materials with a stabilizer, etc. However, all of these methods require a large amount of labor and time, and it is inevitable that the construction efficiency is significantly reduced at present.

[0008] Prior art documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Laid-Open No. 2000-314105

[0011] Patent Document 2: Japanese Patent Laid-Open No. 2002-69922 Summary of the invention

[0012] Problems to be solved by the invention

[0013] The present invention has been completed to solve the problems of the above-mentioned conventional pavement layer recycling method. The problem is to provide a pavement layer recycling method that can ensure sufficient compaction and heavy machinery drivability even when the original pavement to be constructed is in a state where it is considered that the water is excessive, and can construct a recycled pavement layer, and a recycled pavement layer obtained thereby.

[0014] Means for solving the problems

[0015] The present inventors have conducted various studies and as a result, it is considered that it is usually difficult to adjust the water content ratio of the recycled aggregate, which is the original pavement or its crushed materials, in the direction of reduction. This may be because all of the conventional corresponding methods focus on removing the water contained in the recycled aggregate, which is the original pavement or its crushed materials, to the outside of the system by drying or the like. Therefore, compared with the conventional corresponding methods, the concept was reversed 180 degrees, and a method was studied to achieve the same compaction and workability as those obtained when the water content was reduced, in a state where the water contained in the original pavement or its crushed materials, that is, the recycled aggregate, is left in the system. As a result, it was surprisingly found that if a water-absorbing material in an amount sufficient to absorb the excess water is added, it is not necessary to remove the water contained in the recycled aggregate, which is the original pavement or its crushed materials, to the outside of the system, and a recycled pavement layer having physical properties at an expected level can be constructed in the same way as the workability obtained when using recycled aggregate containing an appropriate amount of water.

[0016] That is, the present invention provides a method for recycling a paving layer that uses a part of the original paving as recycled aggregate, which includes the following steps: when the water content ratio of the recycled aggregate used exceeds the target water content ratio, a water-absorbing material is added so that the apparent water content ratio of the recycled aggregate obtained by removing the mass of water absorbed by the water-absorbing material from the mass of water contained in the recycled aggregate is consistent with the target water content ratio; a recycled paving layer obtained by using this method, thereby solving the above problems.

[0017] In the method for recycling a paving layer according to the present invention, when the water content ratio of the recycled aggregate used exceeds the target water content ratio, instead of drying the recycled aggregate or the like to remove the excessively contained water out of the system, a water-absorbing material is added. Moreover, by making the apparent water content ratio of the recycled aggregate obtained by removing the mass of water absorbed by the water-absorbing material consistent with the target water content ratio, the same workability as when the water content ratio of the recycled aggregate used is the target water content ratio is achieved while leaving the excessively contained water in the system.

[0018] In a preferred embodiment, the target water content ratio is the water content ratio of the recycled aggregate when the water content ratio of the mixture formed by mixing aggregate containing at least a part of the recycled aggregate and additive materials such as asphalt emulsion and cement according to the designed mixing ratio becomes the optimum water content ratio. Additionally, in another preferred embodiment, the target water content ratio is the water content ratio of the recycled aggregate when the mixture formed by mixing aggregate containing at least a part of the recycled aggregate and additive materials such as asphalt emulsion and cement according to the designed mixing ratio becomes a mixture that can be compacted with a sufficient compaction rate by roller compaction. In any case, the recycled aggregate can be contained as at least a part of the aggregate used, and the total amount of the aggregate used can also be the recycled aggregate.

[0019] The optimum water content ratio of the mixture obtained by mixing various materials according to the designed mixing ratio generally coincides with the water content ratio of the mixture when the mixture obtained by mixing various materials according to the designed mixing ratio becomes a mixture that can be compacted with a sufficient compaction rate by roller compaction. If they are different, it is preferable to make the latter water content ratio the target water content ratio. Furthermore, the target water content ratio can also be a numerical range with a width.

[0020] In a preferred embodiment, the method for recycling a paving layer according to the present invention includes a compaction step using roller compaction. In the case where the method for recycling according to the present invention includes a compaction step using roller compaction, the advantage of being able to efficiently construct a recycled paving layer with expected physical properties using heavy machinery such as a roller can be obtained.

[0021] As the water-absorbing material, an inorganic granular material having water absorbency, an organic material having water absorbency, or both can be used. In a preferred embodiment, the inorganic granular material having water absorbency is porous ceramics. For example, one or more granular materials selected from calcined diatomaceous earth ceramics, zeolite, mesolite, perlite, glass foamed lightweight material, calcined fly ash, etc. can be used.

[0022] In addition, in another preferred embodiment, the organic material having water absorbency is a synthetic polymer or natural polymer having water absorbency. Examples of the synthetic polymer that can be used include synthetic polymers of polyacrylate series, polysulfonate series, maleic anhydride salt series, polyacrylamide series, polyvinyl alcohol series, polyethylene oxide series, or polyamine series. In addition, examples of the natural polymer that can be used include natural polymers of polyaspartate series, polyglutamate series, polyalgalate series, starch series, cellulose series, or polyglycol series. These organic materials can be used alone or in combination of two or more.

[0023] In the first aspect of the present invention, it is the above-described regeneration method of the paving layer. By adding a water-absorbing material, the apparent water content ratio of the aggregate used is adjusted to a preferred water content ratio. Therefore, from another aspect, the present invention provides a method for improving the physical properties of the aggregate depending on the water content ratio, which is characterized in that the aggregate and the water-absorbing material are mixed to reduce the apparent water content ratio of the aggregate obtained by removing the mass of the water absorbed by the water-absorbing material.

[0024] Effects of the Invention

[0025] According to the regeneration method of the paving layer of the present invention, even when the water content ratio of the recycled aggregate used is larger than the target water content ratio, it is not necessary to remove the excess water outside the system, and the same workability as in the case of the target water content ratio can be achieved, and the advantage of being able to construct a recycled paving layer with high efficiency can be obtained. In addition, according to the method for improving the physical properties of the aggregate depending on the water content ratio of the present invention, the physical properties of the aggregate depending on the water content ratio can be improved without spending time removing the water outside the system, and thus the advantage of being able to improve the construction efficiency in various constructions using the aggregate can be obtained. Detailed Description of the Invention

[0026] Hereinafter, the present invention will be described in detail mainly taking the roadbed regeneration method as an example, but the regeneration method of the paving layer related to the present invention is of course not limited to the roadbed regeneration method.

[0027] 1. Regeneration Method of Paving Layer

[0028] As a representative method of the recycling method for the paving layer, the roadbed recycling method for recycling the original roadbed of the paving at the current location can be cited. The roadbed recycling method is a construction method for excavating and crushing the original paving to a depth of at least including a part of the road base course, using the crushed material as recycled aggregate, adding additive materials such as asphalt emulsion, foamed asphalt, and cement thereto and mixing them, and then leveling and compacting them to form a recycled road base course.

[0029] When the recycling method for the paving layer according to the present invention is the roadbed recycling method, its operation process is basically no different from the roadbed recycling method carried out in the past. The processes of excavating and crushing the original paving and mixing the crushed material with the additive materials can basically be carried out using any equipment or machinery, but typically a road mixer stabilizer or a load stabilizer is used.

[0030] In addition, the depth of excavating and crushing the original paving only needs to be the depth of excavating and crushing at least a part of the road base course, and only needs to be the depth of covering the road base course thickness where the predetermined stabilization treatment is to be carried out to form a recycled road base course. Further, if the operation is not troublesome, a part or all of the cement required per unit area can also be scattered on the construction surface before excavating and crushing the original paving, and the original paving can be excavated and crushed together with the scattered cement.

[0031] Next, the crushed material obtained by excavating and crushing is used as recycled aggregate, and asphalt emulsion and cement are mixed therein. Foamed asphalt can also be mixed instead of asphalt emulsion. This mixing is carried out at the current location where the original road base course has been excavated and crushed. The above-mentioned load stabilizer usually has, in addition to the excavating and crushing functions, functions of spraying and scattering asphalt emulsion and other additive materials. Therefore, by using this function, while scattering asphalt emulsion on the crushed material, the crushed material and asphalt emulsion can be mixed by continuously excavating and crushing.

[0032] Regarding cement, as described above, a part or all of the cement required per unit area can also be pre-scattered on the construction surface of the original paving, and then, by excavating and crushing the original paving, it can be mixed into the recycled aggregate as the crushed material. Or, cement can be scattered on the crushed material and mixed with the crushed material simultaneously and / or before and after scattering the asphalt emulsion. In addition, these two scattering and mixing routes can also be used in combination. However, it is most convenient in operation to pre-mix asphalt emulsion and cement in a predetermined ratio and scatter and mix asphalt emulsion and cement together on the crushed material from the nozzle for spraying and scattering asphalt emulsion, so this is preferred.

[0033] There is no particular limitation on the type of asphalt contained in the added mixed asphalt emulsion. Straight-run asphalt, blown asphalt, semi-blown asphalt, natural asphalt, solvent-deasphalted asphalt, etc. can be used, and it is also possible to use modified asphalt in which styrene-butadiene block copolymer (SBS), styrene-isoprene block copolymer (SIS), styrene-butadiene random copolymer (SBR), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), polystyrene-polyethylene-butene block copolymer (SEBS), natural rubber (NR), chloroprene rubber (CR), isoprene rubber (IR), petroleum resin, oil, etc. are mixed. Further, as the oil, aromatic hydrocarbons, fatty acid hydrocarbons, etc. can be cited, and as the resin, C9, terpene phenol, etc. can be cited. Furthermore, a product obtained by mixing a rubber latex, a synthetic polymer emulsion, and a water-soluble polymer as monomers or in combination can also be added to the emulsifier as a modifier, or added after the emulsion is manufactured.

[0034] As the emulsifier for emulsifying the asphalt emulsion, any of cationic, nonionic, and anionic types can be used. Among them, especially when good mixability with the crushed subgrade material is required, a nonionic emulsion using a nonionic surfactant as the emulsifier is preferably used. In addition, when early strength development is required, a cationic emulsion using a cationic surfactant as the emulsifier is recommended.

[0035] There is no particular limitation on the cement used. For example, various Portland cements such as ordinary Portland cement, early-strength Portland cement, super-rapid-hardening Portland cement, medium-heat Portland cement, and low-heat Portland cement, blast-furnace cement, silica cement, fly-ash cement, shotcrete cement, alumina cement, etc. can be used. Among them, when shortening the construction time is required, from the viewpoint of early strength development, super-rapid-hardening Portland cement or early-strength Portland cement is preferably used. In addition, when cracking due to curing is a concern, medium-heat Portland cement, low-heat Portland cement, etc. are recommended. Furthermore, slaked lime, quicklime, etc. can also be used instead of cement.

[0036] Furthermore, for the crushed material, in addition to the above-mentioned asphalt emulsion and cement, fibers can be mixed to improve the crack resistance of the constructed recycled road base course. As the mixed fibers, for example, mineral fibers such as basalt fibers, inorganic fibers such as glass fibers and steel fibers, organic fibers such as carbon fibers, vinylon, or cellulose can be used. The size of the mixed fibers is preferably a diameter of 5 to 100 μm and a fiber length of about 5 to 40 mm. The fiber material is preferably mixed in an amount of 0.1% to 5.0% by mass with respect to the crushed material.

[0037] 2. Recycled Aggregate and Water Content Ratio

[0038] The recycling method of the paving layer of the present invention includes the following steps in addition to the above-mentioned steps carried out in the past: when the water content ratio of the crushed material obtained by crushing the original paving, that is, the recycled aggregate used as aggregate, exceeds the target water content ratio, a water-absorbing material is mixed into the recycled aggregate so that the apparent water content ratio of the recycled aggregate obtained by removing the mass of water absorbed by the mixed water-absorbing material is consistent with the target water content ratio.

[0039] The water content ratio of the recycled aggregate is a value expressed as the ratio (percentage) of the mass of water contained in the recycled aggregate to the dry mass of the recycled aggregate, and is a value obtained by the following formula (1).

[0040] Rw = (Ww / Ws) × 100 [%] (1)

[0041] In formula (1),

[0042] Rw: water content ratio (%)

[0043] Ww: mass of water contained in the recycled aggregate

[0044] Ws: dry mass of the recycled aggregate.

[0045] The water content ratio of the recycled aggregate can be obtained by taking a part of the original paving to be constructed, excavating and crushing it to sample the crushed material, measuring the mass of water contained in the crushed material and the dry mass of the crushed material, and based on the measured values, using formula (1).

[0046] 3. Target water content ratio

[0047] In a preferred example, the target water content ratio is the water content ratio of the recycled aggregate when the water content ratio of the mixture becomes the optimum water content ratio when at least a part of the aggregate containing the recycled aggregate is mixed with additive materials such as asphalt emulsion and cement according to the designed mixing ratio. The mixing ratio of the recycled aggregate and additive materials such as asphalt emulsion and cement, together with the types of additive materials such as asphalt emulsion and cement used, is generally determined in advance according to the strength requirements of the constructed recycled paving layer. When using the predetermined types of additive materials and mixing the recycled aggregate and other additive materials according to the designed mixing ratio, the water content ratio of the recycled aggregate when the water content ratio of the mixture becomes the optimum water content ratio is the target water content ratio. Furthermore, as the aggregate, not only the recycled aggregate is used, but also when new aggregate is used, of course, the target water content ratio of the recycled aggregate is obtained on the basis of considering the water content ratio and mixing amount of the new aggregate used.

[0048] Incidentally, the optimum water content ratio is described in "Method of Compaction Test for Soil by Tamping" (JIS A1210) 8(c) as follows: "Plot the measured values with the dry density on the vertical axis and the water content ratio on the horizontal axis, connect them with a smooth curve to form a dry density - water content ratio curve. Set the maximum dry density of this curve as the maximum dry density ρ dmax (g / cm 3 ), and set the water content ratio corresponding to it as the optimum water content ratio w opt (%).", which is the water content ratio when the dry density is maximized by compaction.

[0049] Therefore, when the water content ratio of the recycled aggregate is the same as the target water content ratio, the water content ratio of the mixture prepared with this recycled aggregate according to the design ratio is the same as the optimum water content ratio. When this mixture is compacted using a roller or the like, the maximum compaction density can be obtained. In addition, for the constructed recycled road base course, it is possible to expect to exhibit the expected level of strength. Furthermore, the method for obtaining the optimum water content ratio is described in detail, for example, in "Guidelines for Mix Design of In - situ Recycling Cement - Asphalt Emulsion Stabilization Treatment" (Guidelines for Mix Design of In - situ Recycling Cement - Asphalt Emulsion Stabilization Treatment), Japan Asphalt Emulsion Association, 2003, pages 1 - 4.

[0050] Since the optimum water content ratio is obtained as the value of the water content ratio that gives the maximum dry density in the dry density - water content ratio curve, it is usually a single point. When setting the water content ratio of the recycled aggregate that makes the water content ratio of the mixture the optimum water content ratio as the target water content ratio, the target water content ratio is also a single point. However, since the multiple mixtures used as test specimens when obtaining the optimum water content ratio are mixtures each having its own water content ratio, it is also possible to set the optimum water content ratio as a numerical range based on the water content ratios of the top two mixtures that give a larger compaction density. For example, set the water content ratio of one as the upper limit and the water content ratio of the other as the lower limit. In this case, the target water content ratio is also set as a numerical range with a width.

[0051] In another preferred example, when a mixture is made by mixing an aggregate containing recycled aggregate in at least a part thereof with additive materials such as asphalt emulsion and cement according to a designed mixing ratio, it is also possible to use the water content ratio of the recycled aggregate when the mixture can be compacted with a sufficient compaction rate by roller compaction as the target water content ratio.

[0052] Whether the obtained mixture is a mixture that can be compacted by roller compaction at a sufficient compaction rate can be determined based on the compaction rate and fluidity of the mixture. The compaction rate of the mixture can be obtained according to the method described in "Technical Guidelines for Roller-Compacted Concrete Pavement (Draft)" by the Japan Road Association, October 1990, pages 76 - 77, "Appendix 3 Marshall Compaction Test Method". Generally, a mixture with a compaction rate of 96.0% or more is considered a mixture that can be sufficiently compacted.

[0053] On the other hand, the fluidity of the mixture can be determined based on, for example, the slump value. That is, the slump value of the mixture is measured. When this value is below a certain value, the mixture is difficult to flow, and it can be judged as a mixture on which heavy machinery such as a roller compactor can travel. Incidentally, in the experimental examples described later, when the slump value is 0 cm, the fluidity is small enough, and it is judged as a mixture that can be compacted by roller compaction. However, this reference value of 0 cm for the slump value is not absolute and can be appropriately changed according to the mix composition of the mixture that becomes the recycled pavement layer, the construction site conditions, etc. Also, regarding the method for measuring the slump value, it is described in JIS A1101 "Slump Test Method for Concrete".

[0054] As described above, the recycled aggregate and additives such as asphalt emulsion and cement are mixed in the designed mixing ratio to make a mixture, and its compaction rate and slump value are measured. If the compaction rate is above a certain value and the slump value is below a certain value, it can be judged that this mixture is a mixture that can be sufficiently compacted using a roller compaction heavy machine. As long as the water content ratio of the recycled aggregate that can become such a mixture is used as the target water content ratio.

[0055] The water content ratio of the recycled aggregate for which the compaction rate of the mixture is above a certain value and the slump value becomes below a certain value is sometimes a single point and sometimes a numerical range with a width. Therefore, when setting the water content ratio of the recycled aggregate that can be made into a mixture that can be sufficiently compacted by roller compaction as the target water content ratio, the target water content ratio can be set as a single point value or a numerical range with a width.

[0056] Both the target water content ratio determined based on the optimum water content ratio of the mixture and the target water content ratio determined based on whether it can become a mixture that can be sufficiently compacted by roller compaction can be used. However, the latter target water content ratio can more flexibly respond to the construction site conditions, the mix composition of the mixture, etc. by changing the compaction rate and slump value used as the reference, so it is more preferable.

[0057] 4. Water Absorbent Material

[0058] In the recycling method of the paving layer according to the present invention, when the water content ratio of the recycled aggregate used exceeds the target water content ratio, a water-absorbing material is mixed into the recycled aggregate. Further, when the water content ratio of the recycled aggregate used is lower than the target water content ratio, the original paving to be constructed is sprinkled with water or the like to increase the water content ratio of the recycled aggregate.

[0059] As the water-absorbing material to be mixed, any material that can absorb water can be used, and an inorganic or organic water-absorbing material or both can be used. As the inorganic water-absorbing material, porous ceramics are preferred. As the porous ceramics, for example, diatomaceous earth fired ceramics, zeolites, meso-zeolites, perlite, glass foam lightweight materials, fired fly ash, etc. are used, and among them, diatomaceous earth fired ceramics or zeolites are preferred, and diatomaceous earth fired ceramics are most preferred. Two or more of these inorganic water-absorbing materials can also be used in combination. In addition, these inorganic water-absorbing materials are preferably granular. Further, there is no particular limitation on the water absorption rate of the inorganic water-absorbing material used, but when the water absorption rate is too small, the usage amount increases, so it is not preferred. Usually, the water absorption rate is preferably 20% by mass or more, and more preferably 40% by mass or more.

[0060] On the other hand, as the organic water-absorbing material, a synthetic or natural polymer having water absorption is used. As the synthetic polymer, for example, a synthetic polymer of polyacrylate-based, polysulfonate-based, maleic anhydride salt-based, polyacrylamide-based, polyvinyl alcohol-based, polyethylene oxide-based or polyamine-based can be used. As the natural polymer, for example, a natural polymer of polyaspartate-based, polyglutamate-based, polyalgalate-based, starch-based, cellulose-based or polyglycol-based can be used, and a synthetic polymer of polyacrylate-based is preferably used. They can be used alone or in combination of two or more.

[0061] 5. Apparent water content ratio

[0062] The above-mentioned water-absorbing material is mixed with the recycled aggregate in an amount such that the apparent water content ratio of the above-mentioned recycled aggregate, which is obtained by adding only the mass obtained by removing the water absorbed by the water-absorbing material, is sufficient to be consistent with the target water content ratio.

[0063] The apparent water content ratio of the recycled aggregate is the water content ratio of the recycled aggregate obtained by removing the mass of the water absorbed by the mixed water-absorbing material. When the water-absorbing material is an inorganic material, the mass of the water-absorbing material is counted as the mass of the aggregate, and it is calculated by the following formula (2).

[0064] Rwf = {(Ww - Wa) / (Ws + A)} × 100 [%] (2)

[0065] In formula (2),

[0066] Rwf: Apparent water content ratio (%)

[0067] Ww: Mass of water contained in recycled aggregate

[0068] Wa: Mass of water absorbed by water-absorbing material

[0069] Ws: Dry mass of recycled aggregate

[0070] A: Mass of water-absorbing material.

[0071] On the other hand, when the water-absorbing material is an organic material, the apparent water content ratio of the recycled aggregate is calculated not by including the mass of the water-absorbing material in the mass of the aggregate, but by the following formula (3).

[0072] Rwf = {(Ww - Wa) / Ws} × 100 [%] (3)

[0073] Furthermore, when the water-absorbing material is an organic material, the mass of the water-absorbing material is not included in the mass of the aggregate because the water absorption rate of the organic water-absorbing material is generally extremely high, so the mass of the water-absorbing material mixed with the recycled aggregate is usually extremely small. When the water-absorbing material is an organic material, of course, the mass of the water-absorbing material can also be included in the mass of the aggregate to calculate the apparent water content ratio of the recycled aggregate.

[0074] Furthermore, the mass Wa of water absorbed by the water-absorbing material can be obtained, for example, by the following formula (4).

[0075] Wa = A × (a / 100) (4)

[0076] In formula (4),

[0077] A: Mass of water-absorbing material

[0078] a: Water absorption rate of water-absorbing material [%].

[0079] The water absorption rate of the water-absorbing material can be obtained by the method described in "Manual of Pavement Investigation and Test Methods" (2019 Edition, Volume 2), Japan Road Association, March 2019, pages 11 - 13, "A002 Test Method for Density and Water Absorption Rate of Fine Aggregate" or a corresponding method.

[0080] The regeneration method of the present invention includes the following steps: when the water content ratio of the recycled aggregate used exceeds the target water content ratio, a water-absorbing material is mixed into the recycled aggregate to make the apparent water content ratio of the recycled aggregate consistent with the target water content ratio. By "consistent" is meant making the apparent water content ratio of the recycled aggregate numerically consistent with the target water content ratio, or when the target water content ratio is a numerical range with a width, setting the apparent water content ratio of the recycled aggregate to a value within this numerical range. In order to make the apparent water content ratio of the recycled aggregate used consistent with the target water content ratio, it is only necessary to mix a water-absorbing material in an amount sufficient for the apparent water content ratio Rwf(%) calculated by formula (2) or formula (3) to be consistent with the target water content ratio.

[0081] Furthermore, the amount of the water-absorbing material sufficient to make the water content ratio of the recycled aggregate consistent with the target water content ratio can be obtained based on the above formula (2) or formula (3) when the water absorption rate of the water-absorbing material used is known. However, when the water absorption rate of the water-absorbing material used is unknown or it requires a great deal of labor to obtain, the amount of the water-absorbing material mixed with the recycled aggregate can also be obtained through experiments.

[0082] That is, it is also possible to prepare a mixture in which recycled aggregate, asphalt emulsion, cement and other additive materials are mixed in accordance with a designed mixing ratio, add the predetermined water-absorbing material in varying amounts thereto, measure the dry density of the obtained mixture, and set the addition amount of the water-absorbing material when the dry density is maximized as the addition amount for making the apparent water content ratio of the recycled aggregate consistent with the target water content ratio. Alternatively, it is also possible to prepare a mixture in which recycled aggregate, asphalt emulsion, cement and other additive materials are mixed in accordance with a designed mixing ratio, add the predetermined water-absorbing material in varying amounts thereto, measure the compaction rate and slump value of the obtained mixture, and set the addition amount of the water-absorbing material when the compaction rate is above a certain value and the slump value is below a certain value as the addition amount for making the apparent water content ratio of the recycled aggregate consistent with the target water content ratio.

[0083] As described above, by adding a water-absorbing material, if the apparent water content ratio of the recycled aggregate is made consistent with the target water content ratio, unexpectedly, although the water is not removed from the system, the same workability as when constructing with recycled aggregate having a water content ratio of the target water content ratio is obtained. That is, if a water-absorbing material is added to make the apparent water content ratio of the recycled aggregate consistent with the target water content ratio, not only can compaction be carried out at a high compaction rate, but also the fluidity of the mixture is reduced, and construction heavy machinery such as a stabilizer and a roller can travel on the mixture. Therefore, the mixture can be mixed with high construction efficiency and sufficiently compacted by roller rolling, and as a result, a recycled road base layer with an expected level of strength can be constructed.

[0084] Furthermore, in the above description, it is mainly described that the recycling method of the paving layer involved in the present invention is the roadbed recycling method for recycling the road base layer at the current position. However, the paving layer recycled by the recycling method of the paving layer involved in the present invention is not limited to the road base layer. In addition to this, it can also be the surface layer or the base layer. In addition, in the recycling method of the paving layer involved in the present invention, the total amount of aggregate used can be recycled aggregate obtained by crushing the original paving, or it can contain new aggregate on the basis of recycled aggregate.

[0085] The present invention will be described in more detail based on experiments below.

[0086] <Experiment 1: Determination of target water content ratio>

[0087] For a mixture with a supposed composition, its target water content ratio was obtained through experiments. As the target water content ratio, the compaction rate and slump value were used as indicators to determine whether it was a mixture that could be sufficiently compacted by roller compaction. The water content ratio of the aggregate when it was determined that the mixture could be sufficiently compacted by roller compaction was used as the target water content ratio.

[0088] The materials used in the experiment and the mixture proportions are shown in Table 1 below. Furthermore, in this experiment, as the aggregate, graded crushed stone often used as a roadbed material was used. However, if possible, it was also possible to excavate and crush the original paving from a predetermined construction site, obtain the crushed material, and use it as the aggregate for the experiment.

[0089]

Table 1

[0090]

[0091] Five kinds of aggregates with different water content ratios of 1 mass%, 2 mass%, 3 mass%, 4 mass%, or 5 mass% were prepared. The five kinds of prepared aggregates were mixed with cement and asphalt emulsion respectively according to the mixture proportions shown in Table 1 above to prepare five kinds of mixtures with different water content ratios of the aggregate. The compaction rate and slump value were measured using the prepared mixtures. The results are shown in Table 2.

[0092] <Compaction rate>

[0093] The compaction rate was measured according to the measurement method described in the "Roller Compacted Concrete Pavement Technical Guidelines (Draft)", Japan Road Association, October 1990, pages 76 - 77, "Appendix 3 Marshall Compaction Test Method". That is, the test specimen mixture was filled into the test mold, tamped 50 times with a Marshall compaction hammer, the depth from the upper end of the mold to the upper surface of the test specimen was measured, the height of the test specimen was obtained from the difference from the depth to the bottom surface of the mold, and the volume V of the test specimen was calculated. Dividing this by the mass of the specimen measured in advance, the density of the test specimen (g / cm 3)。Divide the density of the test specimen by the theoretical maximum density of the test specimen to obtain the compaction rate (%). That is,

[0094] Compaction rate (%) = {[Density of test specimen (g / cm 3 )] / [Theoretical maximum density (g / cm 3 )]} × 100 [%] (5)

[0095] Furthermore, the theoretical maximum density of the test specimen is obtained by the following formula (6).

[0096] Theoretical maximum density (g / cm 3 ) = (Total mass of each material contained in the test specimen (g)) / (Total volume of each material contained in the test specimen (cm 3 )) (6)

[0097] When the compaction rate is 96.0% or more, it is judged that sufficient compaction can be carried out.

[0098] <Slump value>

[0099] Based on the test method described in JIS A1101 "Test Method for Slump of Concrete", the slump values were measured using the above 5 mixtures as specimens. When the slump value is 0 cm, it is judged that construction heavy machinery such as stabilizers and roller compactors can travel.

[0100]

Table 2

[0101]

[0102] *Judging that 96.0% or more can be fully compacted.

[0103] **Judging that 0 cm or less can be compacted by roller rolling.

[0104] As shown in Table 2, when preparing mixtures using aggregates with a water content ratio of 2% by mass or 1% by mass, the slump values of the obtained mixtures are both 0 cm, meeting the reference value. However, the compaction rates are as low as 95.5% or 93.8%, and cannot reach 96.0% or more of the reference. Therefore, it is judged that when the water content ratio of the aggregate is 2% by mass or less, a mixture that can be fully compacted by roller rolling cannot be prepared.

[0105] On the other hand, in the case of preparing a mixture using aggregate with a water content ratio of 4% by mass or 5% by mass, the compaction rate of the resulting mixture is as high as 98.0% or 97.8%, both of which meet the requirement of being above 96.0% as the reference value. However, the slump value is as large as 8 cm or 15 cm, indicating a mixture with high fluidity, which is judged to be a mixture on which heavy machinery cannot travel. Therefore, it is judged that when the water content ratio of the aggregate is 4% by mass or more, a mixture that can be compacted by roller compaction cannot be prepared.

[0106] In the case of preparing a mixture using aggregate with a water content ratio of 3% by mass, the compaction rate of the resulting mixture is as high as 97.8%, exceeding the reference value of 96.0%. In addition, the slump value is 0 cm, still meeting the requirement of being 0 cm or less of the reference. Therefore, when the water content ratio of the aggregate is 3% by mass, it is judged that a mixture can be prepared on which heavy machinery can travel and can be sufficiently compacted by roller compaction. From the above results, for the mixtures with the mix compositions tested, the target water content ratio is determined to be 3% by mass.

[0107] Furthermore, in the above experiment, the water content ratio of the aggregate was varied at intervals of 1% by mass from 1% by mass to 5% by mass. As a result, it was found that the reference was not met when the water content ratio was below 2% by mass and above 4% by mass, and a mixture that could be sufficiently compacted by roller compaction was judged when the water content ratio was 3% by mass. Based on this, the target water content ratio was determined to be 3% by mass. However, assuming that the water content ratio of the aggregate was varied at intervals of 0.5% by mass from 1% by mass to 5% by mass and the same experiment was carried out, the reference was not met when the water content ratio of the aggregate was below 2% by mass and above 4% by mass, but when the water content ratio was 2.5% by mass, 3.0% by mass, and 3.5% by mass, both the compaction rate and the slump value met the reference values, and in the case of obtaining a mixture that could be sufficiently compacted by roller compaction, a water content ratio with a numerical width from 2.5% by mass to 3.5% by mass could also be determined as the target water content ratio.

[0108] Furthermore, if the mix composition of the mixture changes including the types of materials used, it is fully expected that the target water content ratio will also change. Therefore, the above target water content ratio of 3% by mass is for the mixtures with the mix compositions shown in Table 1. The target water content ratio is of course not limited to the above 3% by mass or from 2.5% by mass to 3.5% by mass.

[0109] <Experiment 2: Influence of water content ratio on the physical properties of the mixture>

[0110] Using the same materials as in Experiment 1 and with the same composition as shown in Table 1, three mixtures 1, 2, and 3 were prepared with only the water content ratio of the aggregate different, which were 3 mass%, 5 mass%, or 7 mass%. The compaction rate and slump value of the obtained mixtures 1, 2, and 3 were measured. And, three specimens were made using each of these three mixtures, and their flexural strengths were measured by the method shown below. The results are shown in Table 3. Further, the details of the water contained in the mixtures are also shown in Table 3.

[0111] <Method for measuring flexural strength>

[0112] According to the method specified in "JIS A 1106 Test Method for Flexural Strength of Concrete", the flexural strength was measured by the three-point loading method. Further, for the mixture with a slump value of 0 cm, the mixture was put into a mold frame (15×15×53 cm), carefully compacted with a vibrating rammer to cure it, and cured for 7 days to make a specimen. On the other hand, for the mixture with a slump value exceeding 0 cm, the mixture was put into a mold frame (15×15×53 cm), an internal vibrator was inserted into the mixture, and it was compacted and cured until no large bubbles were generated from the mixture, and cured for 7 days to make a specimen. Three specimens were made for each mixture, and the average value of the flexural strength obtained by the flexural test was taken as the flexural strength of the mixture.

[0113]

Table 3

[0114]

[0115] As shown in Table 3, mixture 1 using the aggregate with a water content ratio of 3 mass% which is the same as the target water content ratio, similarly to that shown in Table 2 before, showed a high compaction rate of 97.8%. In addition, the slump value was also 0 cm, and it was a mixture on which heavy machinery could travel and could be sufficiently compacted by rolling with a roller compactor. In addition, the specimen obtained by putting mixture 1 into a mold frame and compacting and curing it showed a high flexural strength of 1.15 (N / mm 2 ).

[0116] For mixture 2 using the aggregate with a water content ratio exceeding the target water content ratio by 3 mass% and being 5 mass%, and mixture 3 using the aggregate with an even greater water content ratio of 7 mass%, although both showed a high compaction rate exceeding 96.0%, the slump values were as large as 15 cm and 25 cm respectively, showing high fluidity. Therefore, mixture 2 and mixture 3 were judged to be mixtures on which heavy machinery could not travel and could not be rolled with a roller compactor. In addition, the flexural strengths of the specimens obtained by putting mixture 2 and mixture 3 into a mold frame and curing them were as low as 0.75 (N / mm 2 ) and 0.66 (N / mm2 ) is a value of flexural strength lower than 1.0 (N / mm 2 ).

[0117] As described above, when the water content ratio of the aggregate used exceeds the target water content ratio, the resulting mixture has a high compaction rate but high fluidity and cannot be compacted by roller compaction. In addition, the flexural strength of the resulting solidified body is also low, and it is judged that it is difficult to construct a recycled road base layer with the expected strength.

[0118] <Experiment 3: Influence of addition of water-absorbing material on physical properties of mixture - Part 1 - >

[0119] To the mixtures 1, 2, and 3 prepared in Experiment 2, 0 part by mass, 2.58 parts by mass, and 5.0 parts by mass of water-absorbing material were added respectively, and the amount of aggregate was reduced only by the amount of the added water-absorbing material. Except for this, mixtures 1a, 2a, and 3a were prepared in the same manner as in Experiment 2.

[0120] The water-absorbing material used is as described below.

[0121] Water-absorbing material: Ceramic porous body (trade name "IsoLite CG1", prepared by IsoLite Industries Co., Ltd. [fired diatomaceous earth content: 45 - 75% by mass], granular [diameter: 0.3 - 2 mm], water absorption rate: 61% by mass)

[0122] The addition amount of the water-absorbing material was determined by calculating A (mass of the water-absorbing material) according to Equation (2).

[0123] Rwf = {(Ww - Wa) / (Ws + A)} × 100 [%] (2)

[0124] In Equation (2), it is assumed that

[0125] Rwf (%) (apparent water content ratio) = 3% by mass (target water content ratio)

[0126] Ww (mass of water contained in the aggregate) = (85.0 - A) × water content ratio of the aggregate

[0127] Wa (mass of water absorbed by the water-absorbing material) = A × water absorption rate of the water-absorbing material Ws (dry mass of the aggregate) = 85.0 - A

[0128] , and A was determined. Furthermore, in this experiment, since an inorganic material was used as the water-absorbing material, the mass A of the water-absorbing material was counted as the mass of the aggregate, on the premise that (mass A of the water-absorbing material + dry mass Ws of the aggregate) = 85.0 parts by mass.

[0129] For the prepared mixtures 1a, 2a, and 3a, in the same manner as in Experiment 2, the compaction rate and slump value were measured, and furthermore, the flexural strength was measured. The results are shown in Table 4. Additionally, the results of mixture 1a are the same as those of mixture 1 and are transcribed from Table 3.

[0130]

Table 4

[0131]

[0132] As shown in Table 4, the water content ratio of the aggregate used in mixture 2a was 5.0 mass%, exceeding the target water content ratio of 3 mass%. However, by adding 2.58 mass parts of the water-absorbing material, the apparent water content ratio of the aggregate was made consistent with the target water content ratio of 3 mass%, resulting in a high compaction rate of 97.6%, and the slump value was also 0 cm. That is, mixture 2a is a mixture that can allow heavy machinery to travel and can be sufficiently rolled by roller compaction. Additionally, the flexural strength was also as high as 1.05 (N / mm 2 ), having excellent physical properties. This result is an excellent result compared to the result of mixture 2 that also uses an aggregate with a water content ratio of 5 mass% and does not add a water-absorbing material. Additionally, compared to mixture 1a that uses an aggregate with a water content ratio consistent with the target water content ratio, both the workability of the mixture and the strength of the solidified body are not inferior.

[0133] Similarly, the water content ratio of the aggregate used in mixture 3a was 7.0 mass%, exceeding the target water content ratio of 3 mass%. However, by adding 5.0 mass parts of the water-absorbing material, the apparent water content ratio was made consistent with the target water content ratio of 3 mass%, and as a result, a high compaction rate of 97.8% was obtained. The slump value was also 0 cm. Mixture 3a is a mixture that can allow heavy machinery to travel and can be sufficiently rolled by roller compaction. Additionally, the flexural strength was also as high as 1.08 (N / mm 2 ), having excellent physical properties. This result is an excellent result compared to the result of mixture 3 that also uses an aggregate with a water content ratio of 7 mass% and does not add a water-absorbing material. Additionally, compared to the result of mixture 1a that uses an aggregate with a water content ratio consistent with the target water content ratio, both the workability of the mixture and the strength of the solidified body are not inferior.

[0134] As described above, when the water content ratio of the aggregate used exceeds the target water content ratio, by mixing a water-absorbing material and making the apparent water content ratio of the aggregate obtained by removing the mass of water absorbed by the water-absorbing material consistent with the target water content ratio, a mixture having the same compactability and workability as the mixture obtained using an aggregate with a water content ratio the same as the target water content ratio can be obtained. Additionally, the solidified body of this mixture has the expected strength.

[0135] From the perspective of the aggregate, when the water content ratio of the aggregate used exceeds the target water content ratio, by mixing a water-absorbing material, the apparent water content ratio of the aggregate obtained by removing the mass of water absorbed by the water-absorbing material is made to coincide with the target water content ratio, and it can be considered that the physical properties of the aggregate depending on the water content ratio are improved. The addition of such a water-absorbing material is also useful as a method for improving the physical properties of the aggregate depending on the water content ratio.

[0136] Furthermore, although the above experiments were not conducted using recycled aggregates obtained by excavating and crushing a part of the existing pavement, since graded crushed stone, which is frequently used as a subgrade material, was used as the aggregate, it is reasonable to judge that the same results can be obtained when using recycled aggregates.

[0137] Incidentally, the mixture composition used in this experiment contains 5.8 parts by mass of cement and 9.2 parts by mass of asphalt emulsion with respect to 85 parts by mass of the aggregate. Compared with the mixture composition commonly used in the in-situ subgrade recycling method, the mixing amounts of cement and asphalt emulsion with respect to the aggregate are large. With such a mixture composition, since the mixing ratio of cement with respect to the aggregate is large, it is possible to expect to construct a recycled pavement layer with high strength. However, on the other hand, since the amount of asphalt emulsion is also large, at a large number of construction sites, the water content ratio of the recycled aggregates obtained by crushing the original pavement becomes too large. As long as the water content ratio of the recycled aggregates is not reduced, it is expected that the fluidity of the mixture is large and compaction cannot be carried out using a roller compactor or the like. However, according to the recycling method of the present invention, when the water content ratio of the recycled aggregates obtained at the construction site is too large and exceeds the target water content ratio, by appropriately adding a water-absorbing material, the same workability as in the case where the water content ratio of the recycled aggregates is the target water content ratio can be achieved. As described above, according to the recycling method of the present invention, even for a mixture design in which the mixing amounts of cement and asphalt emulsion with respect to the aggregate are relatively large, it is possible to carry out the compaction process using roller rolling without being affected by the water content ratio of the recycled aggregates and without an excessive work burden, and obtain the advantage of being able to construct a recycled pavement layer with high strength.

[0138] <Experiment 4: Influence of addition of water-absorbing material on physical properties of mixture - Part II ->

[0139] The water-absorbing material was changed to the following water-absorbing material. In the mixtures 1, 2, and 3 prepared in Experiment 2, 0 part by mass, 3.21 parts by mass, and 6.18 parts by mass of the water-absorbing material were added respectively, and the aggregate mixing amount was reduced only by the amount of the added water-absorbing material. Except for this, mixtures 4a, 5a, and 6a were prepared in the same manner as in Experiment 2.

[0140] The water-absorbing material used is as follows.

[0141] Water-absorbing material: Ceramic porous body (trade name "Zeofil 1424#", manufactured by Shin-Tohoku Chemical Industry Co., Ltd. [natural zeolite (mordenite-type zeolite)], granular [diameter: 1.0 - 2.0 mm], water absorption rate: 48% by mass)

[0142] The addition amount of the water-absorbing material is obtained by calculating A (mass of the water-absorbing material) according to formula (2).

[0143] Rwf = {(Ww - Wa) / (Ws + A)} × 100 [%] (2)

[0144] In formula (2), let

[0145] Rwf (%) (apparent water content ratio) = 3% by mass (target water content ratio)

[0146] Ww (mass of water contained in the aggregate) = (85.0 - A) × water content ratio of the aggregate

[0147] Wa (mass of water absorbed by the water-absorbing material) = A × water absorption rate of the water-absorbing material Ws (dry mass of the aggregate) = 85.0 - A

[0148] . Further, in this experiment, since an inorganic material is used as the water-absorbing material, the mass A of the water-absorbing material is counted as the mass of the aggregate, on the premise that (mass A of the water-absorbing material + dry mass Ws of the aggregate) = 85.0 parts by mass.

[0149] For the prepared mixtures 4a, 5a, and 6a, in the same manner as in Experiment 2, the compaction rate and slump value were measured, and further the flexural strength was measured. The results are shown in Table 5. Further, the results of mixture 4a are the same as those of mixture 1 and are transcribed from Table 3.

[0150]

Table 5

[0151]

[0152] As shown in Table 5, the water content ratio of the aggregate used in mixture 5a is 5.0% by mass, exceeding 3% by mass as the target water content ratio. However, by adding 3.21 parts by mass of the water-absorbing material, the apparent water content ratio of the aggregate is made to coincide with the target water content ratio of 3% by mass, and a high compaction rate of 97.5% is obtained, and the slump value is also 0 cm. That is, mixture 5a is a mixture that can allow heavy machinery to travel and is a mixture that can be sufficiently rolled by roller compaction. In addition, the flexural strength is also high, being 0.95 (N / mm 2 ), and it has excellent physical properties. This result is an excellent result compared with the result of mixture 2 that uses an aggregate with a water content ratio of 5% by mass and does not add a water-absorbing material.

[0153] Similarly, the moisture content of the aggregate used in mixture 6a was 7.0% by mass, exceeding the target moisture content of 3% by mass. However, by adding 6.18 parts by mass of a water-absorbing material, the apparent moisture content was made consistent with the target moisture content, i.e., 3% by mass, thereby obtaining a high compaction rate of 97.6%. The slump value was also 0 cm. Mixture 6a was a mixture that could be driven by heavy machinery and was a mixture that could be fully rolled by roller compaction. In addition, the flexural strength was also high, at 0.80 (N / mm 2 ), and has excellent physical properties. This result is an excellent result compared with the result of Mixture 3 which also uses aggregates with a water content of 7 mass % and does not add water-absorbing materials.

[0154] As described above, even when the water-absorbing material used is changed from calcined diatomaceous earth as a ceramic porous body to natural zeolite as a ceramic porous body, by adding a water-absorbing material in an amount sufficient to make the apparent water content ratio of the aggregates coincide with the target water content ratio, it is possible to achieve workability as high as when the water content ratio of the aggregates used coincides with the target water content ratio. In addition, the strength of the obtained solidified body is also excellent.

[0155] <Experiment 5: Effect of adding water-absorbing materials on the physical properties of the mixture - Part 3 ->

[0156] The water-absorbing material was replaced with the following organic water-absorbing material, and the effect of the addition of the water-absorbing material on the physical properties of the mixture was studied.

[0157] The water-absorbent materials used are as follows.

[0158] Water-absorbent material: Acrylate-based artificial polymer (trade name: "High-water-content soil improver MT-2" manufactured by Mori Environmental Research Laboratory Co., Ltd. [partial sodium salt cross-linked acrylic acid polymer], powder, water absorption rate: unknown)

[0159] Since the water absorption rate of the water-absorbing material used was unknown, the amount of the water-absorbing material added in the mixture 2 (water content of aggregate: 5 mass%) prepared in Experiment 2 was changed to 0, 0.04, 0.08, and 0.12 mass% relative to the mass% of the aggregate to prepare mixtures 7a, 7b, 7c, and 7d. Similarly, in the mixture 3 (water content of aggregate: 7 mass%) prepared in Experiment 2, the amount of the water-absorbing material added was changed to 0, 0.08, 0.16, and 0.24 mass% relative to the mass% of the aggregate to prepare mixtures 8a, 8b, 8c, and 8d.

[0160] For the prepared mixtures 7b to 7d and 8b to 8d, the compaction rate and slump value were measured in the same manner as in Experiment 2, and the flexural strength was further measured. The results are shown in Tables 6 and 7. Additionally, the formulation and physical property values of Mixture 1 were transcribed from Table 3. Also, since the formulations of Mixtures 7a and 8a are the same as those of Mixtures 2 and 3, respectively, the physical property values of Mixtures 7a and 8a were transcribed from the physical property values of Mixtures 2 and 3 in Table 3.

[0161]

Table 6

[0162]

[0163]

Table 7

[0164]

[0165] As shown in Table 6, in Mixtures 7a to 7d using aggregates with a water content ratio of 5% by mass, when the addition amount of the water-absorbing material is 0.04% by mass or less (Mixtures 7a and 7b), although the compaction rate exceeds 96.0%, the slump value is as large as 15 cm or 7 cm, and they are mixtures that cannot be compacted by roller compaction. However, when the addition amount of the water-absorbing material is increased to 0.08% by mass (Mixture 7c) and 0.12% by mass (Mixture 7d), the slump value becomes 0 cm, and the compaction rate also maintains a high value.

[0166] Judging from the above results, when the water content ratio of the aggregates used exceeds 3% by mass, which is the target water content ratio, and is 5% by mass, the addition amount of this organic water-absorbing material relative to the mass of the aggregates is preferably 0.08% by mass or more, at least 0.08 to 0.12% by mass, and thus a mixture that can be sufficiently compacted by roller compaction can be made. Therefore, it can be known that when the water content ratio of the aggregates used exceeds 3% by mass, which is the target water content ratio, and is 5% by mass, the addition amount of 0.08% by mass or more, preferably 0.08 to 0.12% by mass relative to the mass of the aggregates is the addition amount of this organic water-absorbing material that can make the apparent water content ratio of the aggregates used the target water content ratio. However, when using this organic water-absorbing material, no significant change in flexural strength was confirmed depending on the addition amount.

[0167] Similarly, as shown in Table 7, in Mixtures 8a to 8d using aggregates with a water content ratio of 7% by mass, if the addition amount of the water-absorbing material is 0.08% by mass or less (Mixtures 8a and 8b), although the compaction rate exceeds 96.0%, the slump value is as large as 25 cm or 11 cm, and they are mixtures that cannot be compacted by roller compaction. However, when the addition amount of the water-absorbing material is increased to 0.16% by mass (Mixture 8c) and 0.24% by mass (Mixture 8d), the slump value becomes 0 cm, and the compaction rate also maintains a high value.

[0168] Judging from the above results, when the water content ratio of the aggregate used exceeds 3% by mass, which is the target water content ratio, and is 7% by mass, the addition amount of the organic water-absorbing material is preferably 0.16% by mass or more, at least 0.16 to 0.24% by mass, relative to the mass of the aggregate. Thus, a mixture that can be sufficiently compacted by roller compaction can be made. Therefore, it can be seen that when the water content ratio of the aggregate used exceeds 3% by mass, which is the target water content ratio, and is 7% by mass, the addition amount of 0.16% by mass or more, preferably 0.16 to 0.24% by mass, relative to the mass of the aggregate is the addition amount of the organic water-absorbing material that can make the apparent water content ratio of the aggregate used the target water content ratio. However, even when the water content ratio of the aggregate used is 7% by mass, no large change in the flexural strength was confirmed depending on the addition amount of the organic water-absorbing material.

[0169] As described above, even when an organic water-absorbing material is used as the water-absorbing material, by adding the water-absorbing material and making the apparent water content ratio of the aggregate used consistent with the target water content ratio, a mixture that can be sufficiently compacted by roller compaction can be formed. In addition, when the water absorption rate of the water-absorbing material is unknown, specimens with different addition amounts of the water-absorbing material can be prepared in advance, and by measuring their compaction rates and slump values, the addition amount that makes the apparent water content ratio of the aggregate used consistent with the target water content ratio can be obtained. Furthermore, when the water absorption rate is known, of course, the addition amount of the water-absorbing material can be obtained according to the above formula (3).

[0170] <Experiment 6: Influence of Aggregate Water Content Ratio on Workability in High-Proportion Cement and Asphalt Emulsion Systems>

[0171] Regarding a mixture with a high-proportion design in which the cement amount and the asphalt emulsion amount are further increased compared to the mix designs in Experiments 1 to 5, an experiment was conducted to study the influence of the water content ratio of the aggregate used on workability. The materials used and their mixing ratios are shown in Table 8. Furthermore, through a preliminary experiment conducted in advance, it was confirmed that the water content ratio of the aggregate when the mixture with the mixing ratio shown in Table 8 becomes a mixture that can be sufficiently compacted by roller compaction is 1.5% by mass, so the target water content ratio was set to 1.5% by mass.

[0172]

Table 8

[0173]

[0174] Four different kinds of aggregates with water contents of 1.5 mass%, 3 mass%, 5 mass% or 7 mass% were prepared. The four prepared aggregates were mixed with cement and asphalt emulsion respectively at the mixing ratios shown in Table 8 above to prepare four mixtures 9, 10, 11, 12 with different water contents of the aggregates. Using the prepared mixtures 9 to 12, the compaction rate and slump value were measured. The results are shown in Table 9.

[0175]

Table 9

[0176]

[0177] As shown in Table 9, mixture 9 in which the water content of the used aggregate is consistent with the target water content shows a high compaction rate of 97.7%, and the slump value is also 0 cm, which is a mixture judged to be sufficiently compactable by roller compaction.

[0178] For mixtures 10, 11, 12 in which the water content of the used aggregate exceeds the target water content by as much as 3.0 mass%, 5 mass% or 7 mass%, although the compaction rate shows a high value exceeding 96.0%, the slump values are as large as 15 cm, 25 cm, 25 cm, showing high fluidity. As a result, mixtures 10, 11, 12 are mixtures judged to be unable to allow heavy machinery such as a roller to travel thereon for roller compaction.

[0179] <Experiment 7: Influence of addition of water-absorbing material on physical properties of mixture in high cement and asphalt emulsion mixing system>

[0180] As the water-absorbing material, the same one as used in Experiment 3 was used, that is, a ceramic porous body (trade name “IsoLite CG1” prepared by IsoLite Industry Co., Ltd. [fired diatomaceous earth content: 45 to 75 mass%], granular [diameter: 0.3 to 2 mm], water absorption rate: 61 mass%). In the mixtures 9, 10, 11, 12 prepared in Experiment 6, 0 part by mass, 1.8 part by mass, 4.2 part by mass and 6.5 part by mass of the above water-absorbing material were added respectively. Except that the aggregate mixing amount was only reduced by the amount of the added water-absorbing material, mixtures 9a, 10a, 11a and 12a were prepared in the same manner as in Experiment 3.

[0181] The above addition amounts of the water-absorbing material are values obtained by calculating A (mass of the water-absorbing material) according to Equation (2).

[0182] Rwf = {(Ww - Wa) / (Ws + A)} × 100 [%] (2)

[0183] In Equation (2), it is assumed that

[0184] Rwf (%) (apparent water content) = 1.5 mass% (target water content)

[0185] Ww (mass of water contained in the aggregate) = (80.0 - A) × water content ratio of the aggregate

[0186] Wa (mass of water absorbed by the water-absorbing material) = A × water absorption rate of the water-absorbing material Ws (dry mass of the aggregate) = 80.0 - A

[0187] Furthermore, in this experiment, since an inorganic material is used as the water-absorbing material, the mass A of the water-absorbing material is counted as the mass of the aggregate, on the premise that (mass A of the water-absorbing material + dry mass Ws of the aggregate) = 80.0 parts by mass.

[0188] For the prepared mixtures 9a, 10a, 11a, and 12a, in the same manner as in Experiment 2, the compaction rate and slump value were measured, and furthermore, the flexural strength was measured. The results are shown in Table 10. Furthermore, the mixture 9a is the same as the mixture 9, and its compaction rate and slump value are transcribed from Table 9.

[0189]

Table 10

[0190]

[0191] As shown in Table 10, the water content ratio of the aggregate used in the mixture 10a is 3.0% by mass, exceeding the target water content ratio of 1.5% by mass. However, by adding 1.8 parts by mass of the water-absorbing material, the apparent water content ratio of the aggregate is made consistent with the target water content ratio of 1.5% by mass. As a result, a high compaction rate of 97.6% is obtained, and the slump value is also 0 cm. That is, the mixture 10a is a mixture that can allow heavy machinery to travel and is a mixture that can be sufficiently rolled by roller compaction. In addition, the flexural strength is also relatively high, being 2.2 (N / mm 2 ), and it has excellent physical properties.

[0192] Similarly, the water content ratios of the aggregates used in the mixtures 11a and 12a are 5.0% by mass and 7.0% by mass, respectively, both exceeding the target water content ratio of 1.5% by mass. However, by adding 4.2 parts by mass and 6.5 parts by mass of the water-absorbing material, respectively, the apparent water content ratio is made consistent with the target water content ratio of 1.5% by mass. As a result, high compaction rates of 97.7% and 97.4% are obtained, respectively. In addition, the slump values are both 0 cm. The mixtures 11a and 12a are mixtures that can allow heavy machinery to travel and are mixtures that can be sufficiently rolled by roller compaction. In addition, the flexural strength of both is as high as 2.0 (N / mm 2 ), and they have excellent physical properties.

[0193] As described above, even in the case of a mixture with a high content of additive materials of 20.0 parts by mass in total of cement and asphalt emulsion relative to 80 parts by mass of aggregate, by adding a water-absorbing material to make the apparent water content ratio of the used aggregate consistent with the target water content ratio, it is possible to obtain a mixture having the same workability as when using an aggregate with the water content ratio of the used aggregate being consistent with the target water content ratio.

[0194] Thus, the regeneration method for the pavement layer according to the present invention is useful regardless of the mixing composition of the mixture to be treated. However, it is particularly useful when constructing a regenerated pavement layer using a mixture with a relatively large designed mixing amount of cement and asphalt emulsion relative to the aggregate. As a mixture with a relatively large designed mixing amount of cement and asphalt emulsion relative to the aggregate, for example, a mixture can be cited in which the total mass of the evaporation residue in the asphalt emulsion and the mass of the cement is contained in a proportion of 10% by mass or more of the total mass of the dry solid components in the mixture. In such a mixture, it is preferable to mix the asphalt emulsion and the cement in a proportion such that the ratio of the mass of the evaporation residue in the asphalt emulsion to the mass of the cement is 0.7 or more and 1.2 or less.

[0195] As described above, the regenerated pavement layer constructed by mixing a water-absorbing material is a pavement layer characterized by containing regenerated aggregate and a water-absorbing material, and further is a regenerated pavement layer characterized by containing a solidified body of asphalt and cement. Therefore, the regenerated pavement layer obtained by performing the regeneration method for the pavement layer according to the present invention is a regenerated pavement layer containing regenerated aggregate and a water-absorbing material, and generally is a regenerated pavement layer further containing a solidified body of asphalt and cement.

[0196] Furthermore, as described above, it is known that by mixing a water-absorbing material to make the apparent water content ratio of the aggregate consistent with the target water content ratio, the physical properties depending on the water content ratio of the aggregate can be improved. Not limited to the regeneration method for the pavement layer, it also has a great effect in cases where the water content ratio of the used aggregate affects the physical properties of the mixture obtained by mixing the aggregate with other additive materials and the solidified body thereof. Therefore, the above method is not limited to regenerated aggregate, and is also a method of improving the physical properties of the aggregate depending on the water content ratio or the physical properties of the aggregate-containing mixture depending on the water content ratio of the aggregate by mixing a water-absorbing material in the aggregate and reducing the apparent water content ratio of the aggregate obtained by removing the mass of water absorbed by the water-absorbing material.

[0197] Industrial Applicability

[0198] As described above, according to the method for recycling a paving layer of the present invention, even when the original paving to be constructed contains a large amount of moisture, it is possible to reduce the apparent water content ratio by adding a water-absorbing material, thereby constructing a recycled paving layer with good workability. Therefore, there is no need to wait for the natural evaporation of moisture, nor to replace the subgrade material or the crushed material of the original paving, and the paving layer can be recycled and constructed quickly according to the plan. The industrial applicability of the present invention is very high.

Claims

1. The recycling method for a paving layer is a recycling method for a paving layer that uses a part of the original paving as recycled aggregate, and includes the following steps: when the water content ratio of the recycled aggregate used exceeds the target water content ratio, a water-absorbing material is added so that the apparent water content ratio of the recycled aggregate obtained by removing the mass of water absorbed by the water-absorbing material from the mass of water contained in the recycled aggregate is consistent with the target water content ratio.

2. The recycling method for a paving layer according to claim 1 includes a compaction step of rolling and compacting.

3. The recycling method for a paving layer according to claim 1 or 2, wherein the water-absorbing material is an inorganic granular material having water absorption and / or an organic material having water absorption.

4. The regeneration method of the paving layer according to claim 3, wherein, The inorganic granular material having water absorption is one or more granular materials selected from porous ceramics such as diatomite fired ceramics, zeolite, mesolite, perlite, glass foam lightweight material, and fired fly ash.

5. The regeneration method of the paving layer according to claim 3, wherein, The organic material having water absorption is one or more selected from artificial polymers such as polyacrylate-based, polysulfonate-based, maleic anhydride-based, polyacrylamide-based, polyvinyl alcohol-based, polyethylene oxide-based, or polyamine-based, or natural polymers such as polyaspartate-based, polyglutamate-based, polyalgalate-based, starch-based, cellulose-based, or polyglycol-based.

6. The regeneration method of the paving layer according to claim 1 or 2, wherein, The recycled paving layer is a surface layer, a base layer, or a subbase layer.

7. A recycled paving layer, which includes recycled aggregate and a water-absorbing material.

8. The regenerated paving layer according to claim 7, wherein, The water-absorbing material is one or more inorganic granular materials selected from porous ceramics such as diatomite fired ceramics, zeolite, mesolite, perlite, glass foam lightweight material, and fired fly ash; or one or more organic materials selected from artificial polymers such as polyacrylate-based, polysulfonate-based, maleic anhydride-based, polyacrylamide-based, polyvinyl alcohol-based, polyethylene oxide-based, or polyamine-based, or natural polymers such as polyaspartate-based, polyglutamate-based, polyalgalate-based, starch-based, cellulose-based, or polyglycol-based; or both of them.

9. A method for improving the physical properties of aggregates depending on the water content ratio, characterized in that, Mix the aggregate and the water-absorbing material to reduce the apparent water content ratio of the aggregate obtained by removing the mass of water absorbed by the water-absorbing material.

10. The improvement method according to claim 9, wherein, The material having water absorption is one or more inorganic granular materials selected from porous ceramics such as diatomite fired ceramics, zeolite, mesolite, perlite, glass foam lightweight material, and fired fly ash; or one or more organic materials selected from artificial polymers such as polyacrylate-based, polysulfonate-based, maleic anhydride-based, polyacrylamide-based, polyvinyl alcohol-based, polyethylene oxide-based, or polyamine-based, or natural polymers such as polyaspartate-based, polyglutamate-based, polyalgalate-based, starch-based, cellulose-based, or polyglycol-based; or both of them.

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