Method for constructing road base and mixture therefor

Abstract

The objective of this invention is to provide a method for constructing a road base course that does not require a compaction process using a roller and does not require adjusting the moisture content of the mixture to an optimal moisture content, and a mixture for achieving the same. This is achieved by providing a rollerless construction method for a road base course that includes a process of mixing aggregates, asphalt emulsion, and cement to form a mixture with a high moisture content exceeding the optimal moisture content of the granular materials, and a process of leveling the mixture, without employing a compaction process using a roller. Furthermore, this invention provides a mixture for a road base course containing aggregates, asphalt emulsion, and cement with a high moisture content exceeding the optimal moisture content of the aggregates, thereby solving the aforementioned objective.

Description

Technical Field

[0001] The present invention relates to a method for constructing a roadbed and a mixture for use in the roadbed for the method of construction. Background Technology

[0002] The subgrade, together with the surface and base layers, forms the pavement cross section, playing a crucial role in distributing traffic loads and transferring them to the subgrade. When pavement damage occurs at the surface or base layer level, it can be addressed through surface treatment and covering. However, if the damage is caused by defects in the subgrade due to aging or other reasons, replacement of the pavement up to the base layer is necessary. However, pavement replacement is costly and generates a large amount of waste material from removing the existing pavement.

[0003] In response, a roadbed recycling construction method was proposed, which involves excavating and crushing the existing pavement at the current location without replacing it, mixing asphalt emulsion, cement and other additives into the crushed material at the current location and compacting it to construct a recycled road base (for example, see Patent Documents 1 to 3).

[0004] The above construction method reuses most of the existing paving directly in the current location. Therefore, it has the advantages of less material transportation in and out, less waste, energy saving, and more efficient use of resources and reduction of CO2 emissions. It also has the advantage of being cheaper to carry out construction compared to changing construction methods.

[0005] However, regardless of whether the construction method is changed or a new subgrade is constructed, the process of compacting the subgrade material spread evenly on the construction surface through rolling is indispensable in the previous methods of constructing the subgrade, including the construction of a new subgrade. However, for compaction using rolling, the strength of the constructed subgrade varies depending on the degree of rolling, thus requiring careful attention and caution. In addition, compaction using rolling usually uses large rollers such as road rollers and pneumatic tire rollers, resulting in large-scale construction and the need for a great deal of energy.

[0006] Furthermore, it is generally believed that the degree of compaction achieved by rolling varies significantly depending on the moisture content of the mixture being rolled. That is, when the moisture content of the mixture being rolled is its optimum moisture content, rolling can compact the mixture to its highest density, achieving the desired strength. However, if the moisture content deviates from the optimum moisture content, ideal compaction cannot be achieved, and the density and strength of the compacted mixture are significantly reduced. Therefore, during construction, there is a limitation that the moisture content of the mixture used must be adjusted to the optimum moisture content. If the moisture content of the mixture is too low, adjustments can be made, for example, by adding or distributing water. However, if the moisture content of the mixture is excessively high, adjustments are extremely difficult, often necessitating changes to the construction date.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 59-224705

[0010] Patent Document 2: Japanese Patent Application Publication No. 60-144402

[0011] Patent Document 3: Japanese Patent Application Publication No. 61-221404 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] The present invention was made to eliminate the shortcomings of the above-mentioned conventional roadbed construction methods. Its objective is to provide a roadbed construction method without compaction that does not require rolling and does not require adjusting the moisture content of the mixture to the optimal moisture content, and a roadbed mixture for achieving the same.

[0014] Methods for solving problems

[0015] To solve the above problems, repeated in-depth research and trial and error were conducted. As a result, the inventors discovered that when a mixture containing aggregates, asphalt emulsion and cement used as subgrade materials is spread evenly on the construction surface in a high moisture content state with a moisture content exceeding the optimum moisture content of the contained aggregates, unexpectedly, contrary to conventional technical common sense, a subgrade with practical strength can be constructed without the use of a compaction process.

[0016] That is, the present invention solves the above-mentioned problems by providing a method for constructing a road base course without rolling. The construction method includes: a step of mixing aggregates, asphalt emulsion and cement to form a mixture in a high moisture content state with a moisture content exceeding the optimum moisture content of the aggregates, and a step of leveling the mixture; excluding the compaction step of rolling.

[0017] Furthermore, the present invention solves the above-mentioned problems by providing a mixture for road base courses comprising aggregates, asphalt emulsions, and cement, in a high moisture content state exceeding the optimal moisture content of the aggregates.

[0018] In the non-compaction construction method for the road base of the present invention, the mixture comprising aggregate, asphalt emulsion, and cement is essentially only required to be in a high-moisture state where its moisture content exceeds the optimum moisture content of the aggregate. From the viewpoint of constructing a road base with more stable strength, it is preferable that the total mass of the evaporation residue in the asphalt emulsion and the mass of the cement in the mixture is 10% by mass or more of the total mass of the dry solids components contained in the mixture. Incidentally, the total mass of the dry solids components contained in the mixture refers to the total dry mass of the aggregate, the mass of the evaporation residue in the asphalt emulsion, and the mass of the cement when the mixture contains only aggregate, asphalt emulsion, and cement. When the total mass of the evaporation residue in the asphalt emulsion and the mass of the cement is 10% by mass or more of the total mass of the dry solids components contained in the mixture, this, combined with the high moisture content of the mixture, provides the advantage of being able to construct a recycled road base with more stable strength without the use of a compaction process involving rolling.

[0019] Furthermore, in the non-compaction construction method of the present invention, when the mass of the evaporation residue in the asphalt emulsion is set as A and the mass of the cement is set as B, it is preferable to combine the asphalt emulsion and cement contained in the mixture in a ratio of A / B of 0.7 or more and 1.2 or less. When the asphalt emulsion and cement are used in the above-mentioned range, the asphalt moderately mitigates the hardness caused by the cement, enabling the construction of a road base with stable strength and moderate hardness, thus effectively preventing cracking of the road base. Furthermore, since a moderate amount of asphalt is included in the road base, the affinity between the road base and the asphalt mixture layer laid thereon is improved, and the adhesion between the two layers is enhanced.

[0020] Furthermore, in the non-compacting construction method of the present invention, in addition to aggregates, asphalt emulsions, and cement, fiber materials may also be mixed into the above-mentioned mixture. When fiber materials are included in the mixture, they complement the inclusion of asphalt, enabling a higher crack-inhibiting effect on the road base.

[0021] It should be noted that the mixture used in the non-compacting construction method of the present invention can be prepared by factory mixing, in which the materials are pre-mixed in a factory, or by mixing the materials at the construction site. Alternatively, when using pulverized material from the existing paved base course as aggregate, the mixture can be prepared by on-site mixing, in which the pulverized material, asphalt emulsion, cement, and any desired fiber material are mixed at the current location where the existing paved base course is excavated and pulverized. Alternatively, the pulverized material obtained from excavation and pulverization can be transported to a factory, mixed with other materials at the factory, and then transported to the construction site. In either case, the aggregate, asphalt emulsion, cement, and any desired fiber material can be mixed in virtually any order, but when using the above-described on-site mixing method, it is preferable to mix the aggregate with at least a pre-mixed asphalt emulsion and cement. When mixing the aggregate with a pre-mixed asphalt emulsion and cement, in addition to simplifying the mixing operation at the current location, it also has the convenience of not needing to pre-spread cement on the construction surface.

[0022] The roadbed constructed by the non-compacted roadbed construction method of the present invention can be a new roadbed constructed during the construction of new pavement, or a roadbed constructed by a replacement construction method, or a roadbed constructed by a roadbed recycling construction method such as a roadbed recycling construction method.

[0023] The effects of the invention

[0024] The non-compacting construction method for road base courses and the mixture for road base courses according to the present invention offer the following advantages: a road base course with stable strength and, depending on the situation, appropriate hardness can be constructed without the need for a compaction process requiring significant energy. Furthermore, according to the non-compacting construction method for road base courses and the mixture for road base courses according to the present invention, the mixture formed by mixing aggregates, asphalt emulsion, and cement only needs to be in a high-moisture state where its moisture content exceeds the optimum moisture content of the aggregates, rather than strictly adhering to the optimum moisture content. Therefore, it offers the advantage of significantly simplified construction conditions and greater flexibility in construction. Attached Figure Description

[0025] Figure 1 It is a graph showing the relationship between moisture content and dry density.

[0026] Figure 2 This is a graph showing the relationship between moisture content and uniaxial compressive strength.

[0027] Figure 3 It is a graph showing the relationship between moisture content and primary displacement.

[0028] Figure 4It is a graph showing the relationship between moisture content and residual strength rate.

[0029] Figure 5 This is a graph showing the relationship between the amount of cement + evaporation residue and the dry density.

[0030] Figure 6 This is a graph showing the relationship between the amount of cement + evaporation residue and uniaxial compressive strength.

[0031] Figure 7 This is a graph showing the relationship between the amount of cement + evaporation residue and the amount of primary displacement.

[0032] Figure 8 This is a graph showing the relationship between the amount of cement + evaporation residue and the residual strength rate. Detailed Implementation

[0033] As described above, the non-compacted construction method for road base courses according to the present invention includes the steps of mixing aggregates, asphalt emulsion, and cement to form a mixture in a high-moisture state with a moisture content exceeding the optimum moisture content of the aggregates, and the step of leveling the mixture. This method does not include a compaction step involving rolling. Each step will be described sequentially below.

[0034] The process of mixing aggregates, asphalt emulsion, and cement to produce a mixture in a high-moisture state with a moisture content exceeding the optimum moisture content of the aggregates, as described in the text, involves mixing aggregates, asphalt emulsion, and cement to produce a mixture in a high-moisture state with a moisture content exceeding the optimum moisture content of the aggregates. In this process, it is sufficient to mix at least the aggregates, asphalt emulsion, and cement to obtain a mixture containing aggregates, asphalt emulsion, and cement in a high-moisture state with a moisture content exceeding the optimum moisture content of the aggregates. Alternatively, other materials besides aggregates, asphalt emulsion, and cement can also be mixed together.

[0035] As aggregate, newly prepared crushed stone or other aggregates can be used as subgrade material, or the pulverized material of existing paving subgrade material can be reused as part or all of the aggregate. The pulverized material of existing paving subgrade material can be obtained by excavating and pulverizing the existing paving to a depth of at least part of the subgrade at the current location of the construction site where the subgrade is to be constructed using the construction method involved in this invention, or it can be the pulverized material of a subgrade excavated and pulverized at other construction sites.

[0036] When the aggregate is pulverized material obtained by excavating and crushing the existing pavement at the current location where the roadbed is to be constructed to a depth that includes at least a portion of the roadbed, the non-compacted roadbed construction method of the present invention includes the step of excavating and crushing the existing pavement at the current location where the roadbed is to be constructed to a depth that includes at least a portion of the roadbed to produce aggregate. In this case, it is preferable to also perform the step of mixing the aforementioned pulverized material used as aggregate with asphalt emulsion and cement at the current location to produce a mixture. Incidentally, the step of excavating and crushing the existing pavement to a depth that includes at least a portion of the roadbed to produce aggregate is essentially no different from the traditional methods for constructing recycled roadbeds. The above steps can be performed using virtually any tools or machinery, but typically, road-mixed stabilizers or load stabilizers are used.

[0037] Furthermore, if the aggregate is shredded material obtained by excavating and crushing the existing pavement at the current location where the roadbed is to be constructed, down to a depth that includes at least a portion of the roadbed, the excavation and crushing of the existing pavement only needs to reach a depth sufficient to cover at least a portion of the roadbed, specifically the thickness of the roadbed to be stabilized and used to create the recycled roadbed. It should be noted that, if the complexity of the process is not a concern, a portion or all of the amount of cement required per unit area can be spread on the construction surface before excavating and crushing the existing pavement, and the existing pavement can be excavated and crushed together with the spread cement.

[0038] There are no particular restrictions on the type of asphalt emulsion mixed with aggregates. Asphalt included in asphalt emulsions can be straight-run asphalt, blown asphalt, semi-blown asphalt, natural asphalt, deoiled asphalt, etc., or modified asphalt obtained by mixing these with the following substances: 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. It should be noted that aromatic hydrocarbons and fatty acid hydrocarbons can be listed as oils, and C9 resins and terpene phenols can be listed as resins. Furthermore, rubber latex, synthetic polymer emulsions, and water-soluble polymers, alone or in combination, can be added as modifiers to the emulsifier, or added after the emulsion is manufactured.

[0039] Furthermore, the emulsifier used in the emulsification of asphalt emulsions can be any of cationic, nonionic, or anionic systems. Particularly when good mixability with the pulverized subgrade material is required, nonionic emulsions using nonionic surfactants as emulsifiers are preferred. Conversely, when early strength development is required, cationic emulsions using cationic surfactants as emulsifiers are recommended.

[0040] There are no particular restrictions on the type of cement used. For example, various Portland cements such as ordinary Portland cement, early-strength Portland cement, ultra-fast-hardening Portland cement, medium-heat Portland cement, and low-heat Portland cement, as well as blast furnace cement, silica cement, fly ash cement, jet cement, and high-alumina cement can be used. Among these, ultra-fast-hardening Portland cement or early-strength Portland cement is preferred from the viewpoint of early strength development when shorter construction time is required. Furthermore, medium-heat Portland cement and low-heat Portland cement are recommended when there are concerns about cracking during curing. Moreover, quicklime and hydrated lime can also be used as cement. The scope of cement used in the construction methods and mixtures involved in this invention also includes quicklime and hydrated lime.

[0041] The aforementioned materials can be mixed in any order, using any machine and materials. For example, the mixing can be carried out using the factory mixing method described above, or a suitable mixer can be brought to the construction site and mixed there. Furthermore, as mentioned above, when the existing pavement to be constructed is excavated and crushed to a depth that includes at least a portion of the roadbed, and the crushed material is used as aggregate, it can also be done by mixing the crushed material as aggregate, asphalt emulsion, and cement at the current location of excavation and crushing in a road mixing method. The aforementioned load stabilizer typically has the function of spraying and distributing asphalt emulsion and other additives in addition to excavation and crushing. Therefore, by utilizing its function, while continuously excavating and crushing, it is possible to mix the crushed material as aggregate and the asphalt emulsion.

[0042] It should be noted that when using a road mixing method, regarding cement, a portion or all of the amount of cement required per unit area can be pre-spread on the existing pavement surface. Then, the existing pavement can be excavated and crushed to mix with the crushed material as aggregate. Alternatively, cement can be spread on the crushed material simultaneously and / or before and after the asphalt emulsion is spread onto it to mix with the crushed material. Furthermore, both of these spreading and mixing methods can be used together. Of these, pre-mixing the asphalt emulsion and cement in a given ratio, and then spreading the asphalt emulsion and cement together from a nozzle that sprays and spreads the asphalt emulsion onto the crushed material to mix with it as aggregate, is the simplest operation and is therefore preferred.

[0043] It should be noted that, in addition to the aggregates, asphalt emulsion, and cement mentioned above, fiber materials can also be mixed into the above mixture to improve the crack resistance of the constructed road base. As the mixed fiber materials, for example, mineral fibers such as basalt fibers, glass fibers, carbon fibers, organic fibers such as vinylon or cellulose, and steel fibers can be used. Regarding the size of the mixed fibers, fibers with a diameter of approximately 5 to 100 μm and a fiber length of approximately 5 to 40 mm are preferred. Preferably, the fiber material is mixed in a range of 0.1% to 5.0% by mass relative to the aggregates used.

[0044] In the above mixture, water-reducing agents, expansive admixtures, shrinkage-reducing agents, etc., commonly used in concrete, may also be added. As water-reducing agents, one or more may be selected from high-performance water-reducing agents, water-reducing agents, AE water-reducing agents, and high-performance AE water-reducing agents as specified in JIS A 6204 "Chemical Admixtures for Concrete". As the main components of these water-reducing agents, one or more may be selected from condensates of naphthalene sulfonic acid, lignin sulfonic acid, or melamine sulfonic acid with formaldehyde, polycarboxylic acids, and their sodium, potassium, or calcium salts. The amount of these water-reducing agents added relative to the cement mass is typically in the range of 0 to 3.0% by mass.

[0045] In the non-compacted construction method of the road base layer of the present invention, aggregates, asphalt emulsion, cement, and additives such as fiber materials and water-reducing agents as required are mixed as described above, and water is added as required to prepare a mixture in a high moisture content state where the moisture content exceeds the optimal moisture content of the aggregates used.

[0046] Incidentally, the so-called moisture content (w(%)) is the value of the mass (Ww) of water contained in the mixture as a percentage relative to the dry mass (Ws) of the mixture, and is calculated by the following formula 1.

[0047] w = (Ww / Ws) × 100 [%] Equation 1

[0048] Furthermore, the so-called optimum moisture content, as specified in "Compaction Test Method for Soil Using Tamping" (JIS A1210), is defined as "the measured values ​​are recorded with dry density as the vertical axis and moisture content as the horizontal axis, and these values ​​are connected by a smooth curve to form a dry density-moisture content curve. The maximum dry density of this curve is set as the maximum dry density ρ". dmax (g / cm 3 Set the corresponding moisture content as the optimum moisture content w. opt "(%)" refers to the moisture content of soil, roadbed materials, etc., when the dry density is maximized through compaction.

[0049] The optimum moisture content of aggregates in a mixture can be determined by the method specified in the "Compaction Test Method for Compacted Soil" (JIS A1210) or by methods thereof. Alternatively, when the existing pavement is excavated and pulverized to a depth that includes at least a portion of the subgrade, and the resulting pulverized material is used as aggregate, and mixed with other materials at the current excavation and pulverization location, a sample of the existing pavement to be constructed is taken to the same depth as the construction depth, pulverized until it reaches the particle size intended for construction, and used as a sample. A compaction test is then conducted while varying the moisture content, thereby determining the optimum moisture content.

[0050] On the other hand, as mentioned above, the moisture content *w* of the mixture obtained by mixing aggregate, asphalt emulsion, and cement is the ratio of the mass of water contained in the mixture (Ww) to the dry mass of the mixture (Ws). Therefore, it can be calculated based on the moisture content of the aggregate used, the moisture content of the asphalt emulsion used, and the mixing ratio of aggregate, asphalt emulsion, and cement. It should be noted that in the case of mixed fiber materials, the mixing ratio of the fiber materials must obviously be considered. Incidentally, the moisture content of the aggregate can be determined by measuring the mass of the aggregate before and after drying. Furthermore, when the existing pavement is excavated and pulverized to a depth that includes at least a portion of the roadbed, and the resulting pulverized material is used as aggregate and mixed with other materials at the current excavation and pulverization location, the moisture content can be determined by sampling a portion of the existing pavement constituting the road surface to be constructed, as is done when determining the optimum moisture content.

[0051] If the moisture content of the mixture obtained in this way exceeds the optimum moisture content, the mixture can be prepared by mixing aggregate, asphalt emulsion, cement, and the required fiber material in the same proportions as when the moisture content was determined. On the other hand, if the moisture content of the mixture obtained as described above is the same as or lower than the optimum moisture content, an appropriate amount of water can be added to the mixture. Furthermore, when excavating and pulverizing the existing pavement to a depth that includes at least a portion of the roadbed, and using the resulting pulverized material as aggregate, and mixing it with other materials at the current excavation and pulverization site, an appropriate amount of water can be spread on the construction surface before excavating and pulverizing the existing pavement, or an appropriate amount of water can be added during the pulverization process and / or the process of preparing the mixture, to adjust the mixture to a high moisture content state where the moisture content exceeds the optimum moisture content.

[0052] In the non-compacted construction method of the road base course involved in this invention, the mixture used for the road base course only needs to substantially contain aggregate, asphalt emulsion and cement, and be in a high moisture content state where its moisture content exceeds the optimal moisture content of the aggregate used. However, from the viewpoint of enabling the constructed road base course to exhibit stable strength, it is preferable to include asphalt emulsion and cement in a proportion of at least 10% by mass of the total mass of the dry solids contained in the mixture, which is the total mass of the residual evaporates in the asphalt emulsion and the mass of cement.

[0053] Regarding the ratio of asphalt emulsion to cement in the mixture, in principle, any amount is acceptable. However, generally, if the amount of cement increases relative to the amount of asphalt in the asphalt emulsion, there is a tendency for the hardness of the recycled road base to increase. Conversely, if the amount of asphalt in the asphalt emulsion increases relative to the amount of cement, there is a tendency for the softness of the recycled road base to increase. Therefore, depending on the desired characteristics of the recycled road base to be constructed, when the mass of the evaporation residue in the asphalt emulsion is set as A and the mass of cement as B, it is preferable to mix the asphalt emulsion and cement in the above mixture with a ratio of A / B of 0.7 or more and 1.2 or less.

[0054] As described above, the mixture produced by mixing aggregates, asphalt emulsion, and cement to create a mixture with a high moisture content exceeding the optimum moisture content of the granular materials is spread evenly on the construction surface during the spreading process. Because the mixture is in a high moisture content state, exceeding the optimum moisture content of the aggregates contained within it, it has relatively high self-flowability and can be tightly filled simply by spreading it evenly on the construction surface, allowing the road base course to be constructed without a compaction process. It should be noted that if voids may remain internally when simply spreading the mixture evenly on the construction surface, appropriate vibration can be applied using push rods or a vibrator to reduce these voids. The spread mixture cures over time, thus constructing the road base course.

[0055] Generally, compaction processes using rolling require a great deal of energy. Therefore, the ability to construct a road base without rolling is a significant advantage of the construction method involved in this invention. Furthermore, in conventional construction methods where rolling is essential, the strength of the constructed road base varies depending on the degree of compaction. Therefore, without uniform and constant-strength compaction, there is a problem of localized variations in the strength of the road base. However, in the rolling-free construction method of this invention, rolling is not required, thus eliminating such adverse effects on the localized strength of the constructed road base.

[0056] The present invention will now be described in more detail based on experiments.

[0057] <Experiment 1: Effect of Moisture Content on the Properties of the Mixture>

[0058] Using the materials described below and in accordance with the formulations shown in Table 1, samples 1, 2, 3, 4, and 5, each with a moisture content of 3.0 wt%, 5.0 wt%, 7.0 wt%, 9.0 wt%, or 11.0 wt%, were prepared. Samples 1–5 were divided into two systems and filled into a template. For one system, it was compacted by impacting both sides 50 times with a Marshall compactor to create a compacted mixture (hereinafter referred to as “compacted”). For the other system, after filling into the template, it was not impacted with a Marshall compactor; instead, it was left to stand and gently pushed with a pusher to remove voids as needed, creating a non-compacted mixture (hereinafter referred to as “non-compacted”).

[0059] The materials used are as described below.

[0060] • Aggregate: Size-adjusted crushed stone (maximum particle size 40mm) (drying complete)

[0061] • Asphalt emulsion: MN-1 (non-ionic asphalt emulsion for mixing) (solids concentration: 57% by mass)

[0062] • Cement: Ordinary Portland cement

[0063] It should be noted that the optimal moisture content of the above aggregate (size-adjusted crushed stone) was determined by compaction tests, and the result was 5.0% by mass. Furthermore, the aggregate was used for experiments after drying; therefore, all aggregate masses shown in the following table are dry masses.

[0064] [Table 1]

[0065]

[0066] After curing each mixture for 7 days, the dry density (g / cm³) was determined according to the method specified in "Guidelines for Mix Design of Road Recycled Cement and Asphalt Emulsion Stabilization Treatment 1996" (Japan Asphalt Emulsion Association). 3 ), uniaxial compressive strength (N / mm 2 The results are shown in Table 2 and 100cm. The displacement (1 / 100cm) and residual strength percentage are also included. Figures 1-4 .

[0067] [Table 2]

[0068]

[0069] *Dry density (g / cm³) 3 Uniaxial compressive strength (N / m)2 )

[0070] Single displacement (1 / 100cm) Residual strength rate (%)

[0071] As shown in Table 2 and Figure 1 , 2 As shown, under the condition of "with rolling", the dry density and uniaxial compressive strength of the mixture (cured body) filled into the template for curing and curing both showed the highest values ​​at 5.0% by mass of the optimal moisture content of the aggregate used (sample 2), and then decreased with increasing moisture content.

[0072] In contrast, under the "no rolling" condition, at a moisture content of 5.0% by mass (the same as the optimum moisture content), both the dry density and uniaxial compressive strength showed lower values ​​than under the "rolled" condition. However, if the moisture content exceeded 5.0% by mass (the optimum moisture content), the dry density and uniaxial compressive strength gradually increased. If the moisture content reached 7% by mass (1.4 times the optimum moisture content), both the dry density and uniaxial compressive strength increased sharply. It should be noted that the reason why the uniaxial compressive strength of sample 1 (without rolling) at a moisture content of 3.0% by mass (below the optimum moisture content) is "0" is that at a moisture content of 3.0% by mass, the mixture was completely dry and could not aggregate, making it impossible to form a test specimen for uniaxial compressive strength measurement without rolling. The same applies to the first displacement and residual strength rate.

[0073] If the moisture content is 9% by mass (sample 4), which is 1.8 times the optimum moisture content, the dry density and uniaxial compressive strength of the "unrolled" mixture (cured body) become values ​​that are roughly equivalent to those of the "rolled" cured body. Regarding the dry density, at a moisture content of 11.0% by mass (sample 5), the value of the "unrolled" cured body is higher than that of the "rolled" cured body.

[0074] On the other hand, regarding uniaxial compressive strength, a tendency to decrease is observed when the moisture content is 11.0% by mass (sample 5), but this tendency is also the same for cured bodies that have been "rolled". In the case of "unrolled", the moisture content may not be the optimal moisture content, and therefore it can be sufficiently improved by increasing the amount of mixed asphalt emulsion and cement or changing the type of mixed asphalt emulsion.

[0075] Additionally, as shown in Table 2 and Figure 3As shown, the primary displacement, an indicator of the softness of the cured body, exhibits the same tendency to increase with increasing moisture content in both the "with rolling" and "without rolling" conditions. However, in the "with rolling" condition, if the optimum moisture content is exceeded, the primary displacement increases sharply, reaching 38 (1 / 100 cm) at a moisture content of 7.0% by mass (sample 3), exceeding the upper limit of 5–30 (1 / 100 cm), which is generally considered the benchmark value. In contrast, in the "without rolling" condition, the primary displacement is 11 (1 / 100 cm) at a moisture content of 7.0% by mass (sample 3), still within the allowable range. When the moisture content reaches 9.0% by mass (sample 4), it exceeds 30 (1 / 100 cm) for the first time, reaching 36 (1 / 100 cm).

[0076] In addition, the residual strength rate, which serves as an indicator of the degree of strength retention after reaching maximum strength, is shown in Table 2 and... Figure 4 As shown, in regions where the moisture content exceeds the optimum moisture content, the "unrolled" cured body reaches a moisture content generally considered to be "above 65%" and exhibits a residual strength rate exceeding that of the "rolled" cured body. The fact that the "unrolled" cured body displays such a high residual strength rate in regions with moisture contents exceeding the optimum moisture content is an unexpected result. This indicates that the "unrolled" cured body, even after reaching maximum strength, possesses the characteristic of maintaining relatively high residual strength and being difficult to break in regions with moisture contents exceeding the optimum moisture content.

[0077] As described above, if the mixture is in a high moisture content state where the moisture content exceeds the optimum moisture content of the aggregate used, a solidified body with corresponding physical properties can be obtained even without "rolling". If the moisture content is more than 1.4 times the optimum moisture content, the physical properties of the solidified body are drastically improved. Therefore, it is concluded that it is sufficient to be in a high moisture content state where the moisture content of the mixture exceeds the optimum moisture content of the aggregate used, and more preferably more than 1.4 times the optimum moisture content.

[0078] <Experiment 2: The Effect of Asphalt Emulsion and Cement Content on the Physical Properties of the Mixture>

[0079] In Experiment 1, even with a moisture content exceeding the optimum moisture content, the dry density and uniaxial compressive strength were comparable to those obtained under "rolled" conditions, despite being "unrolled." Furthermore, good results were achieved in both primary displacement and residual strength rate, which are indicators of moderate hardness and resistance to breakage. Therefore, the effect of varying the amounts of mixed asphalt emulsion and cement on the physical properties of the mixture cured under "unrolled" conditions was investigated by fixing the moisture content at 9.0% by mass (1.8 times the optimum moisture content).

[0080] Samples 6, 7, 8, and 9 were prepared by mixing the same materials used in Experiment 1 with the proportions shown in Table 3 below, and by different amounts of asphalt emulsion and cement relative to the aggregate.

[0081] [Table 3]

[0082]

[0083] Similar to the "no compaction" in Experiment 1, the prepared samples were filled into the template without being impacted using a Marshall compactor. Instead, they were left to stand until voids were removed by gently pushing with a pusher as needed, creating a "no" compacted mixture. Next, as in Experiment 1, after curing each mixture for 7 days, the dry density (g / cm³) was determined according to the method specified in "Guidelines for Mix Design of Road Recycled Cement and Asphalt Emulsion Stabilization Treatment 2016" (Japan Asphalt Emulsion Association). 3 ), uniaxial compressive strength (N / mm 2 The results are shown in Table 4 and 100cm. The displacement (1 / 100cm) and residual strength rate (%) are also included. Figures 5-8 .

[0084] [Table 4]

[0085]

[0086] *Dry density (g / cm³) 3 Uniaxial compressive strength (N / m) 2 )

[0087] Single displacement (1 / 100cm) Residual strength rate (%)

[0088] As shown in Table 4 and Figure 5 As shown, although the dry density of the mixture (cured body) filled into the template and cured under "no rolling" conditions gradually decreases with increasing total mass of cement and evaporation residue in the asphalt emulsion ("(cement) + (evaporation residue in asphalt emulsion)"), as shown in Table 4 and Figure 6 As shown, the uniaxial compressive strength increases with the increase of "(cement) + (evaporation residue in asphalt emulsion)". If it becomes 11.2% by mass (sample 7) when it exceeds 10% by mass of the total mass of dry solids contained in the mixture (in this experiment, (aggregate + cement + evaporation residue in asphalt emulsion) is equivalent to dry solids), then it exceeds the lower limit of 1.5 N / mm² for the uniaxial compressive strength of cement- and asphalt-stabilized subgrades. 2 Subsequently, the concentration of "(cement) + (evaporation residue in asphalt emulsion)" stabilized at 1.5 N / mm until it reached 19.2% by mass of the total dry solids contained in the mixture (sample 9).2 above.

[0089] Additionally, as shown in Table 4 and Figure 7 As shown, the displacement of the first displacement, which is an indicator of the softness of the cured body, is 36 (1 / 100 cm) when the content of "(cement) + (evaporation residue in asphalt emulsion)" is as low as 5.5% by mass of the total mass of dry solids contained in the mixture (sample 6). This exceeds the upper limit of the generally regarded benchmark value of 5 to 30 (1 / 100 cm). However, if the content of "(cement) + (evaporation residue in asphalt emulsion)" increases to 11.2% by mass (sample 7), it becomes 10% by mass or more. This is below the upper limit of the above benchmark value and above the lower limit of the above benchmark value. The softness of the cured body is just right and reaches a satisfactory level.

[0090] Furthermore, regarding the residual strength rate, as shown in Table 4 and Figure 8 As shown, within the entire range of the test for "(cement) + (evaporation residue in asphalt emulsion)," which is generally considered to be "more than 65%", it can be seen that within the range of at least 5.5% to 20.0% by mass of the total mass of dry solids (aggregate + cement + evaporation residue in asphalt emulsion) contained in the mixture, the "uncompacted" cured body has the characteristics of maintaining relatively large residual strength and being difficult to break even after reaching maximum strength.

[0091] The results of Experiments 1 and 2 above show that, in a high-moisture state where the moisture content of the mixture of aggregate, asphalt emulsion, and cement exceeds the optimum moisture content of the aggregate, a road base course with both stable strength and resistance to cracking can be constructed without compaction after spreading. As a preferred high-moisture state, without adding the water-reducing agent described later, it is preferably 1.4 times or more of the optimum moisture content, and more preferably 1.6 times or more. Furthermore, regarding uniaxial compressive strength, it is known that if cement and asphalt emulsion are incorporated into the mixture in a proportion of 10% or more of the total mass of dry solids (in this experimental example, (aggregate + cement + evaporation residue in asphalt emulsion)) of the dry solids contained in the mixture, then a uniaxial compressive strength exceeding the lower limit of the benchmark for cement- and asphalt-stabilized road base courses can be obtained without compaction. 2 High uniaxial compressive strength roadbed.

[0092] The same applies to the displacement, which is an indicator of the softness of the solidified body, and the residual strength rate, which is an indicator of the degree of strength retention after reaching maximum strength. If cement and asphalt emulsion are mixed in a mixture in a proportion of 10% to 20% by mass of the total mass of dry solids contained in the mixture (in this experimental example, (aggregate + cement + evaporation residue in asphalt emulsion)) based on the total mass of cement and evaporation residue in asphalt emulsion, a road base course with high uniaxial compressive strength, moderate softness, and residual strength exceeding the benchmark value can be constructed.

[0093] It should be noted that in experiments 1 and 2 above, asphalt emulsion and cement were mixed in the aggregate at a ratio of 1.14:1 (mass of evaporation residue in the asphalt emulsion:mass of cement). However, the mixing ratio of evaporation residue in the asphalt emulsion to cement is not limited to this specific ratio. Generally, it is believed that if the amount of cement increases, the hardness of the solidified mixture increases; if the amount of asphalt increases, the hardness of the solidified mixture decreases and the softness increases. Therefore, the ratio of asphalt emulsion to cement mixed in the aggregate can be changed according to the required characteristics of the road base. From the perspective of constructing a road base that combines strength and crack resistance, the ratio of asphalt emulsion to cement mixed with the aggregate can be appropriately adjusted to a ratio of 0.7:1 to 1.2:1 (mass of evaporation residue in the asphalt emulsion:mass of evaporation residue in the cement).

[0094] <Experiment 3: The effect of adding water-reducing agent on the physical properties and suitable moisture content of the cured body>

[0095] Experiments were conducted to investigate how the physical properties of the cured mixture and the appropriate moisture content are affected when a water-reducing agent commonly used in concrete is added to a mixture containing aggregates, asphalt emulsions, and cement.

[0096] The materials used are as described below.

[0097] • Aggregate: Size-adjusted crushed stone (maximum particle size 40mm) (drying complete)

[0098] • Asphalt emulsion: MN-1 (non-ionic asphalt emulsion for mixing) (solids concentration 65% by mass)

[0099] • Cement: Ordinary Portland cement

[0100] It should be noted that the optimal moisture content of the above aggregate (size-adjusted crushed stone) was determined by compaction tests, and the result was 5.0% by mass. Furthermore, the aggregate was used for experiments after drying.

[0101] Aggregates, asphalt emulsion, and cement were mixed in the proportions shown in Table 5 below to prepare mixtures with various compositions and moisture contents. Samples 10–19 were prepared by adding 0.5%, 1.0%, or 1.5% by mass of a water-reducing agent (based on the mass of cement). The mass of the water-reducing agent is very small compared to the total mass of the mixture and is therefore not included in the calculation of the proportions. Incidentally, a high-performance polycarboxylate-based AE water-reducing agent (trade name "MIGHTY 3000S," manufactured by Kao Corporation) was used as the water-reducing agent.

[0102] Samples 10–19 were poured into 15cm × 15cm × 53cm molds. Similar to the "no-rolling" method in Experiment 1, no Marshall compaction was performed. The samples were left to stand, and gaps were gently removed using a push rod as needed. They were then cured at 20°C for 7 days. The cured samples were removed from the molds and made into 15cm × 15cm × 53cm test pieces for flexural strength testing. The flexural strength (N / mm²) was determined according to the flexural strength test method described in "Test Method for Flexural Strength of Concrete" (JIS A1106). 2 It should be noted that the application speed is set to 0.06 N / mm / s. 2 The results are shown in Table 5.

[0103] In addition, the value obtained by converting the flexural strength to uniaxial compressive strength based on the following Equation 2 described in the "Pavement Design and Construction Guide (Heisei 18 Edition)" (edited and published by the Japan Road Association, September 18, Reiwa 2, page 270, Appendix - 8.2.25 Relationship between flexural strength and other strengths of concrete for paving) is also recorded.

[0104] fc = (fb / 0.42) 1.5 [N / mm 2 Equation 2

[0105] fc: Uniaxial compressive strength [N / mm] 2 ]

[0106] fb: Bending strength [N / mm] 2 ]

[0107] [Table 5]

[0108]

[0109] As shown in Table 5, samples 10–19 all had a total mass of cement and evaporation residue in the asphalt emulsion that was more than 10% by mass of the total mass of the dry solids component of the aggregate, cement, and evaporation residue in the asphalt emulsion. This “uncompacted” cured body showed a mass of 1.52 N / mm. 2 The above-mentioned high flexural strength, when converted to uniaxial compressive strength, is equivalent to 6.88 N / mm². 2 Therefore, this exceeds the lower limit of 1.5 N / mm², which is the benchmark for uniaxial compressive strength used in cement and asphalt-stabilized roadbeds. 2 As the strength of the road base layer, it is sufficient to withstand practical use. The results of Experiment 3 confirm that it is preferable to combine the asphalt emulsion and cement in the mixture at a ratio where the total mass of the evaporation residue in the asphalt emulsion and the mass of the cement is at least 10% by mass of the total mass of the dry solids components contained in the mixture.

[0110] On the other hand, regarding moisture content, among samples 10-17 containing 0.5% by mass of water-reducing agent relative to the cement mass, sample 10, with a moisture content 1.15 times the optimum moisture content, yielded 1.52 N / mm. 2 (If converted to uniaxial compressive strength, it is 7.16 N / mm²) 2 The flexural strength reached a satisfactory level. Furthermore, in sample 19, which contained 1.5% by weight of water-reducing agent relative to the cement mass, a strength of 2.05 N / mm was obtained. 2 (If converted to uniaxial compressive strength, it is 10.78 N / mm²) 2 The sample 19 exhibited high flexural strength, with a moisture content 1.09 times the optimum moisture content. Based on these results, the following conclusions can be drawn: While the optimal moisture content / optimal moisture content also depends on the amount of water-reducing agent added, a more suitable range is one where the ratio is reduced by at least 1.05 times compared to the ratio without the water-reducing agent, even if it is more than 1.4 times.

[0111] <Experiment 4: The effect of adding fiber materials on the physical properties of the cured mixture>

[0112] Sample 20, a mixture of the formulations listed in Table 6 below, was prepared using the same materials and fiber materials as those used in Experiment 3, and its flexural strength was measured in the same manner as in Experiment 3. It should be noted that basalt fiber (fiber diameter: 15 μm, fiber length: 24 mm) was used as the fiber material. It should also be noted that in the formulation of Sample 20, the amount of fiber material, which is 1% by mass relative to the total mass of the mixture, is equivalent to approximately 1.3% by mass relative to the dry mass of the aggregate.

[0113] [Table 6]

[0114]

[0115] ※ Value obtained by converting bending strength to uniaxial compressive strength

[0116] The results are shown in Table 6. The flexural strength of the cured body of sample 20 containing fiber material is significantly increased compared with the flexural strength of the cured body of sample 18 (Table 5), which has a composition that is approximately the same except for the absence of fiber material. This confirms that the addition of fiber material is extremely effective in improving the strength of the constructed road base.

[0117] [Industrial Applicability]

[0118] As explained above, the non-compacting construction method for roadbeds and the mixture for roadbeds according to the present invention enable the construction of recycled roadbeds with stable strength without the need for a compaction process requiring significant energy and large operating machinery, and without the need to adjust the moisture content to the optimal level. The non-compacting construction method for roadbeds and the mixture for roadbeds of the present invention not only contribute to energy conservation but also reduce the burden on operators, enabling construction with high operational efficiency, and thus have great industrial applicability.

Claims

1. A method for constructing a road base course without rolling, comprising a step of mixing aggregates, asphalt emulsion and cement to form a mixture in a high moisture content state with a moisture content of more than 1.4 times and less than 2.2 times the optimum moisture content of the aggregates, and a step of paving the mixture; excluding a compaction step using rolling.

2. The method for constructing a road base without compaction according to claim 1, wherein, In the process of preparing the mixture, the asphalt emulsion and the cement are mixed with the aggregate in a proportion that is at least 10% by mass of the total mass of the dry solids contained in the mixture, based on the total mass of the evaporation residue in the asphalt emulsion and the mass of the cement.

3. The method for constructing a road base without compaction according to claim 1 or 2, wherein, In the process of preparing the mixture, the asphalt emulsion and the cement are mixed with the aggregate in a ratio of 0.7 or more and 1.2 or less of the mass of the evaporation residue in the asphalt emulsion to the mass of the cement.

4. The method for constructing a road base without compaction according to claim 1 or 2, wherein, The process of preparing the mixture also includes the process of mixing fibrous materials.

5. The method for constructing a road base without compaction according to claim 1 or 2, wherein, The mixture is prepared by a factory mixing process.

6. The method for constructing a roadbed without compaction according to claim 1 or 2, comprising the steps of excavating and crushing the existing pavement to a depth containing at least a portion of the roadbed to produce the aggregate, wherein the steps of producing the mixture and producing the aggregate are performed together at the current location of constructing the roadbed.

7. A mixture for road base course, comprising aggregate, asphalt emulsion and cement, in a high moisture content state of more than 1.4 times and less than 2.2 times the optimum moisture content of said aggregate.

8. The mixture for road base course according to claim 7, wherein the asphalt emulsion and the cement comprise at least 10% by mass of the total mass of the dry solids contained in the mixture, where the total mass of the evaporation residue in the asphalt emulsion and the mass of the cement constitutes at least 10% by mass of the total mass of the dry solids contained in the mixture.

9. The mixture for road base course according to claim 7 or 8, wherein the asphalt emulsion and the cement comprise a ratio of the mass of the evaporation residue in the asphalt emulsion to the mass of the cement of 0.7 or more and 1.2 or less.

10. The mixture for roadbed as claimed in claim 7 or 8, further comprising fibrous material.

11. The mixture for roadbed according to claim 7 or 8, wherein, The aggregate is part or all of the crushed material from the original roadbed.

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