Asphalt mixture, method for producing same, and paving method using same

Abstract

Provided is an asphalt mixture obtained by mixing an aggregate, asphalt, a mineral oil and / or a vegetable oil having a flash point of not lower than 70°C, a lubricative solidifying material, and an alkaline additive material.

Description

Asphalt mixture, method for producing the same, and paving method using the same

[0001] This invention relates to an asphalt mixture used for road paving and the like, a method for producing the same, and a paving method using the same.

[0002] Typically, heated asphalt mixtures are compacted at an initial temperature of 110 to 140°C, as indicated in paving construction manuals. However, while heated asphalt mixtures provide high strength immediately after paving, their pot life is limited to the time it takes for the mixture's temperature to drop. Therefore, their application becomes difficult when using small amounts of mixture in several stages, when transporting the mixture for long periods, or when using thin-layer overlay methods where the construction thickness is thin and a significant temperature drop occurs immediately after leveling.

[0003] Therefore, heated asphalt mixtures using medium-temperature technology and room-temperature application type asphalt mixtures are being considered. Heated asphalt mixtures using medium-temperature technology, i.e., medium-temperature asphalt mixtures, are generally said to be able to extend the potable temperature range of heated asphalt mixtures by about 30°C to the lower limit. Room-temperature application type asphalt mixtures are asphalt mixtures that can be applied at room temperature (below 100°C).

[0004] In contrast, Patent Document 1 describes a room-temperature application type asphalt mixture that can be applied at room temperature. This mixture uses tall oil fatty acid as a cutback agent, and the action of the tall oil fatty acid reduces the viscosity of the asphalt mixture, thereby enabling application at room temperature. Furthermore, in the technology of Patent Document 1, after application, the tall oil fatty acid, acting as a cutback agent, reacts with the cement to act as a hardening agent, thereby achieving sufficient strength.

[0005] On the other hand, while the asphalt mixture obtained by the technology described in Patent Document 1 can provide a pavement with sufficient strength after construction, its workability when constructed in low-temperature ranges is not always sufficient, and there has been a need for an asphalt mixture that offers excellent workability when constructed in low-temperature ranges.

[0006] Patent No. 5583978

[0007] The present invention has been proposed in view of the above, and aims to provide an asphalt mixture that exhibits excellent workability during construction in low temperature ranges to room temperature ranges and that can provide a pavement with excellent flexibility.

[0008] The present inventors conducted diligent research to solve the above problems and have found that an asphalt mixture obtained by mixing aggregate and asphalt with mineral oil and / or vegetable oil having a flash point of 70°C or higher, a lubricating solidifying agent, and an alkaline additive offers excellent workability during construction in the low temperature range to room temperature range (for example, -10°C to 40°C, preferably -5°C to 25°C). Furthermore, by supplying a hardening accelerator to the mixture during construction, the added lubricating solidifying agent and alkaline component undergo a saponification or neutralization reaction, increasing viscosity and providing an asphalt mixture that can develop strength in a relatively short time. This led to the completion of the present invention.

[0009] [1] According to embodiment 1 of the present invention, an asphalt mixture is provided which is obtained by mixing aggregate, asphalt, mineral oil and / or vegetable oil having a flash point of 70°C or higher, a lubricating solidifying agent, and an alkaline additive.

[0010] [2] According to embodiment 2 of the present invention, an asphalt mixture of embodiment 1 is provided, wherein the content of the mineral oil and / or vegetable oil is 0.1 to 30% by weight relative to 100% by weight of the total amount of the asphalt and the mineral oil and / or vegetable oil.

[0011] [3] According to embodiment 3 of the present invention, an asphalt mixture of embodiment 1 or 2 is provided, wherein the content of the lubricating solidifying agent is 1 to 80% by weight relative to 100% by weight of the total amount of the asphalt and the lubricating solidifying agent.

[0012] [4] According to aspect 4 of the present invention, a paving method is provided characterized by adding a hardening accelerator to any asphalt mixture of aspects 1 to 3 and causing a saponification or neutralization reaction between the lubricating solidifying agent and the alkaline additive to improve strength.

[0013] [5] According to aspect 5 of the present invention, a method for producing an asphalt mixture according to aspects 1 to 3 is provided, comprising: a first step of mixing aggregate heated to 100 to 170°C and asphalt heated to 130 to 170°C in a mixing device; a second step of adding and mixing the mineral oil and / or the vegetable oil and the lubricating solidifier to the mixture obtained in the first step; and a third step of adding and mixing the alkaline additive to the mixture obtained in the second step.

[0014] According to the present invention, it is possible to obtain a pavement that exhibits excellent workability during construction in the low temperature range to the room temperature range (for example, -10°C to 40°C, preferably -5°C to 25°C) and also has excellent flexibility.

[0015] Figure 1 is a diagram illustrating the disintegration test method. Figure 2 is a graph showing the relationship between the loading time and the displacement of the height position of the pressing member when a disintegration test was performed on a specimen made of the asphalt mixture of Comparative Example 1.

[0016] The asphalt mixture of the present invention is an asphalt mixture obtained by mixing aggregate, asphalt, mineral oil and / or vegetable oil having a flash point of 70°C or higher, a lubricating solidifying agent, and an alkaline additive. The strength of the asphalt mixture of the present invention is improved when a hardening accelerator is added during construction, as the lubricating solidifying agent undergoes a saponification or neutralization reaction with the alkaline components derived from the alkaline additive. In the present invention, the hardening accelerator can be, for example, water.

[0017] In this invention, the saponification or neutralization reaction can be any reaction that produces an alkali salt of a fatty acid. Examples include a saponification method in which alkaline water is added to a fatty acid ester to produce an alkali salt of a fatty acid (soap) and glycerin, and a neutralization method in which higher fatty acids are neutralized with alkaline water. In a saponification reaction, if an alkaline additive is added in a solid state, the reaction generally does not start if a solvent such as water is not present. On the other hand, if a solvent such as water is present, the reaction "fatty acids and resin acids in the lubricating solidifying agent + alkaline additive + water = soap (solid)" (saponification or neutralization reaction) occurs, producing soap, which in turn provides strength.

[0018] Here, the asphalt mixture of the present invention contains aggregate, asphalt, mineral oil and / or vegetable oil with a flash point of 70°C or higher, a lubricating solidifying agent, and an alkaline additive, and its microstructure is thought to be as follows: A lubricating film composed of low-viscosity mineral oil and / or vegetable oil, a lubricating solidifying agent, and an alkaline additive is interposed between the aggregates on which the asphalt film is formed, and this is thought to exert a lubricating effect. As a result, the pavement is kept in a low viscosity state before the saponification or neutralization reaction. In other words, in the present invention, the lubricating solidifying agent acts as a cutback agent that reduces the viscosity of the asphalt mixture before construction, and the mineral oil and / or vegetable oil further enhance the effect of the lubricating solidifying agent as a cutback agent, especially in the low-temperature range (for example, -10°C to 15°C). The asphalt mixture of the present invention, having such a composition, can achieve excellent workability in the low temperature range to the room temperature range (for example, -10°C to 40°C, preferably -5°C to 25°C).

[0019] After applying the asphalt mixture according to the present invention, a hardening accelerator (for example, water) is sprayed on it, and it is compacted with a plate or roller. Alternatively, after compaction with a plate or roller, a hardening accelerator (for example, water) is sprayed on it. As a result, the lubricating solidifying agent and the alkaline additive contained in the asphalt mixture undergo a saponification or neutralization reaction with the hardening accelerator (for example, water), causing it to solidify and thus improving its strength. When paving using the asphalt mixture according to the present invention, the compaction method is not limited to plate compaction or roller compaction, and can be appropriately selected according to the purpose of the pavement. Depending on the purpose of the pavement, for example, a method such as treading may be adopted.

[0020] Next, the materials constituting the asphalt mixture of the present invention will be described. The asphalt mixture of the present invention contains aggregate, asphalt, mineral oil and / or vegetable oil having a flash point of 70°C or higher, a lubricating solidifying agent, and an alkaline additive.

[0021] There are no particular restrictions on the aggregates used; crushed stone, sand, stone powder, and other materials commonly used in paving asphalt can be used as appropriate, and aggregates of any particle size range, such as dense-graded or open-graded, can be used without restriction. For example, aggregates containing 25-75% by weight of crushed stone, 24-60% by weight of sand, and 1-15% by weight of stone powder can be used.

[0022] Furthermore, there are no particular restrictions on the asphalt used, and straight asphalt and modified asphalt can be used without limitation. The asphalt content in the asphalt mixture of the present invention is preferably 1 to 7 parts by weight, more preferably 2 to 5 parts by weight, and even more preferably 3 to 3.5 parts by weight, per 100 parts by weight of aggregate.

[0023] In this invention, recycled aggregate may be used as the aggregate and asphalt in place of or in combination with conventional aggregate. When recycled aggregate is used, new asphalt may be used in combination with asphalt derived from recycled aggregate.

[0024] The asphalt mixture of the present invention contains mineral oil and / or vegetable oil having a flash point of 70°C or higher. In the present invention, by using mineral oil and / or vegetable oil having a flash point of 70°C or higher, the asphalt mixture can be made to have excellent workability during construction in the low temperature range to the room temperature range, and in particular, excellent workability during construction in the low temperature range. More specifically, by using mineral oil and / or vegetable oil having a flash point of 70°C or higher, the effect of the lubricating solidifying agent as a cutback agent that reduces the viscosity of the asphalt mixture, particularly the effect in the low temperature range, can be further enhanced, thereby making the asphalt mixture to have excellent workability during construction in the low temperature range to the room temperature range. Furthermore, in the present invention, by using mineral oil and / or vegetable oil having a flash point of 70°C or higher, the pavement obtained by solidifying the asphalt mixture can also be made to have excellent flexibility.

[0025] Mineral oils and / or vegetable oils are not particularly limited as long as they have a flash point of 70°C or higher, but examples of mineral oils include aromatic mineral oils, paraffinic mineral oils, and naphthenic mineral oils. Generally, paraffinic mineral oils are distinguished as those in which the number of carbon atoms in the paraffin chain accounts for 50% or more of the total number of carbon atoms, naphthenic mineral oils are distinguished as those in which the number of carbon atoms in the naphthenic ring accounts for 35-45% of the total number of carbon atoms, and aromatic mineral oils are distinguished as those in which the number of carbon atoms in the aromatic chain accounts for 30% or more of the total number of carbon atoms. As for mineral oils, paraffinic mineral oils are preferred from the viewpoint that they can provide excellent workability during construction in the low temperature range to the room temperature range, while further improving the flexibility of the resulting pavement. Examples of vegetable oils include linseed oil, camellia oil, macadamia nut oil, corn oil, mink oil, olive oil, avocado oil, sasanqua oil, castor oil, safflower oil, jojoba oil, sunflower oil, almond oil, rapeseed oil, sesame oil, soybean oil, peanut oil, cottonseed oil, coconut oil, palm kernel oil, rice bran oil, and fatty acid esters thereof. As for vegetable oils, vegetable fatty acid esters such as fatty acid esters of the above oils are preferred from the viewpoint of providing excellent workability during construction in low to normal temperature ranges, while further improving the flexibility of the resulting pavement. Mineral oils and vegetable oils may be used individually or in combination of multiple types. In addition, multiple types of mineral oils may be used in combination, multiple types of vegetable oils may be used in combination, or one or more types of mineral oils may be used in combination with one or more types of vegetable oils.

[0026] In the present invention, the flash point of the mineral oil and / or vegetable oil may be 70°C or higher, but from the viewpoint of improving workability during construction in the low temperature range to room temperature range, and further improving the flexibility of the resulting pavement, the flash point is preferably 120°C or higher, and more preferably 180°C or higher. The upper limit of the flash point is not particularly limited, but for example, it is 350°C or lower.

[0027] Furthermore, from the viewpoint of improving workability during construction in low-temperature to room-temperature ranges while further improving the flexibility of the resulting pavement, the rate of change in mass of the thin film when heated is preferably 5% or less, preferably 3% or less, and more preferably 0.5% or less.

[0028] The rate of change in mass when a thin film is heated can be determined as follows. First, approximately 50 g of mineral oil or vegetable oil is placed in a container to form a thin film of approximately 3 mm, and the weight of the mineral oil or vegetable oil (initial weight of mineral oil or vegetable oil) is weighed. Then, the mineral oil or vegetable oil is left at 35°C for 5 hours. The weight of the mineral oil or vegetable oil after standing is weighed, and the rate of change in mass when a thin film is heated (%) is calculated based on the following formula (1). Rate of change in mass when a thin film is heated (%) = ([Initial weight of mineral oil or vegetable oil] - [Weight of mineral oil or vegetable oil after standing]) / [Initial weight of mineral oil or vegetable oil] × 100 (1)

[0029] The content of mineral oil and / or vegetable oil is not particularly limited, but from the viewpoint of further improving the workability of the asphalt mixture during construction in the low temperature range to the room temperature range, and further improving the flexibility of the resulting pavement, it is preferably 0.1 to 30% by weight, more preferably 1 to 15% by weight, and even more preferably 2.5 to 10% by weight, based on 100% by weight of the total amount of asphalt and mineral oil and / or vegetable oil.

[0030] A lubricating solidifying agent acts as a cutback agent that reduces the viscosity of the asphalt mixture before application, while during application, by adding a hardening accelerator, it undergoes a saponification or neutralization reaction with the alkaline components derived from the alkaline additive. The lubricating solidifying agent is not particularly limited, but it is preferable to use oils and / or fatty acids. Examples of oils and fatty acids include tall oil fatty acids, dimer acid, abietic acid, dehydroabietic acid, neoabietic acid, pimaric acid, isopimaric acid, palastric acid, oleic acid, palmitic acid, stearic acid, myristic acid, myristoleic acid, linoleic acid, linolenic acid, isoheptanoic acid, octic acid, isononanoic acid, isodecylic acid, isotridecylic acid, isopalmitic acid, isostearic acid, isomistyric acid, palmitoleic acid, caproic acid, caprylic acid, capric acid, lauric acid, and behenic acid. Among these, tall oil fatty acids are preferred because they can further improve the workability of the asphalt mixture during construction in the low-temperature to room-temperature range, and also improve the flexibility of the resulting pavement. The lubricating solidifying agent may be used alone or in combination of multiple types.

[0031] The content of the lubricating solidifying agent in the asphalt mixture of the present invention is preferably 1 to 80% by weight, more preferably 20 to 65% by weight, and more preferably 40 to 55% by weight, based on 100% by weight of the total amount of asphalt and lubricating solidifying agent. By setting the content of the lubricating solidifying agent within the above range, it is possible to further improve workability during construction in the low temperature range to the room temperature range, while appropriately increasing the strength, rutting resistance, and deflection of the resulting pavement. The content of the lubricating solidifying agent per 100 parts by weight of aggregate is not particularly limited, but is preferably 0.6 to 5 parts by weight, more preferably 1 to 4 parts by weight, and even more preferably 2.5 to 3.0 parts by weight.

[0032] Furthermore, in the asphalt mixture of the present invention, the content ratio of mineral oil and / or vegetable oil to the lubricating solidifying material can further improve workability during construction of the asphalt mixture from low temperature to normal temperature ranges, and can also further improve the flexibility of the obtained pavement. From the above viewpoints, the weight ratio of "mineral oil and / or vegetable oil: lubricating solidifying material" is preferably within the range of 1:3 to 1:50, more preferably within the range of 1:5 to 1:40, still more preferably within the range of 1:7 to 1:30, and particularly preferably within the range of 1:11 to 1:17.

[0033] Furthermore, the acid value of the lubricating solidifying material used in the present invention is not particularly limited, but is preferably 130 to 380 mgKOH / g, more preferably 150 to 320 mgKOH / g, and still more preferably 160 to 280 mgKOH / g.

[0034] The alkaline additive is not particularly limited as long as it is a compound that becomes an alkaline component under the action of a hardening accelerator (e.g., water). In order to neutralize saturated fatty acids, those exhibiting a low hydrogen ion concentration (i.e., a high pH) under the action of the hardening accelerator are desirable. In soap production, commonly used sodium hydroxide, potassium hydroxide, and the like can also be used; however, from an environmental perspective, ordinary cement (ordinary Portland cement), which exhibits a low hydrogen ion concentration under the action of a hardening accelerator among cements used as general civil engineering materials, is preferably used. As ordinary Portland cement, for example, tricalcium silicate (3CaO·SiO ２ ), dicalcium silicate (2CaO·SiO ２ ), calcium aluminate (3CaO·Al ２ O ３ ), calcium aluminoferrite (4CaO·Al ２ O ３ ·Fe ２ O ３ ), calcium sulfate (CaSO ４ ·2H ２O) or the like as a main component can be used. In addition, as the alkaline additive, there are also other than these: sodium ions (Na+), potassium ions (K+), magnesium ions (Mg ２＋ ), calcium ions (Ca ２＋ ), an aqueous solution containing metal ions such as the above, a powder containing a metal salt that decomposes into the above ions when water is added, or sodium bicarbonate (NaHCO ３ ), potassium bicarbonate (KHCO ３ ) and the like can be used. In the asphalt mixture of the present invention, the content ratio of the alkaline additive, in terms of the weight ratio of "lubricating solidified material: alkaline additive", is preferably within the range of 100:10 to 100:300, more preferably within the range of 100:15 to 100:40.

[0035] In the asphalt mixture of the present invention, the content of the alkaline additive, based on 100 parts by weight of aggregate, is preferably 0.05 to 5 parts by weight, more preferably 0.1 to 2 parts by weight, still more preferably 0.6 to 0.8 parts by weight.

[0036] In addition, to the asphalt mixture of the present invention, as long as the functions and effects of the present invention are not impaired, other additives commonly used in the field of asphalt pavement can be added in addition to the above. Such additives are not particularly limited, and examples thereof include fillers, plant fibers, pigments, antifreeze agents and the like.

[0037] Hereinafter, the method for producing the asphalt mixture of the present example will be described.

[0038] First, aggregate is charged into a mixing device, and dry mixing of the aggregate is performed. The dry mixing is carried out while the aggregate is heated to 100 to 170°C, preferably 100 to 140°C, more preferably 110 to 130°C. The temperature and time of dry mixing are not particularly limited, but the dry mixing temperature is usually 100 to 140°C, preferably 110 to 130°C, and the dry mixing time is usually about 1 second to 1 minute. In this example, by using the aggregate heated to the above temperature, the moisture content contained in the aggregate can be controlled, whereby the storage stability of the obtained asphalt mixture can be improved.

[0039] Next, asphalt is added to the mixing device, and the aggregate and asphalt are mixed. In this example, asphalt is heated to 130 to 170°C, preferably 140 to 160°C, added into the mixing device, and then the aggregate and asphalt are mixed. The mixing temperature and mixing time at this stage are not particularly limited as long as they are conditions that allow an asphalt layer to be uniformly formed on the surface of the aggregate, but the mixing temperature is usually 100 to 140°C, preferably 110 to 130°C, and the mixing time is usually about 1 second to 5 minutes.

[0040] Next, mineral oil and / or vegetable oil and a lubricating solidifying material are added to the mixing device, and the mixture obtained above, the mineral oil and / or vegetable oil, and the lubricating solidifying material are mixed. It is preferable to use the lubricating solidifying material at normal temperature or after heating to about 30 to 55°C. The mixing temperature and mixing time at this stage are not particularly limited, but the mixing temperature is usually 100 to 140°C, preferably 110 to 130°C, and the mixing time is usually about 1 second to 5 minutes.

[0041] Next, an alkaline additive is added to the mixing device, and the mixture obtained above and the alkaline additive are mixed. The mixing temperature and mixing time at this stage are not particularly limited, but the mixing temperature is usually 100 to 140°C, preferably 110 to 130°C, and the mixing time is usually about 1 second to 5 minutes.

[0042] In this example, the aggregate and asphalt are first mixed, and then mineral oil and / or vegetable oil, a lubricating solidifier, and an alkaline additive are added and mixed in that order to obtain an asphalt mixture in which an asphalt film is formed on the surface of the aggregate, a layer of mineral oil and / or vegetable oil and a lubricating solidifier is formed on the surface of this asphalt film, and furthermore, the surface of this layer of lubricating solidifier is covered with a solid alkaline additive. This increases the reaction efficiency between the alkaline additive and the hardening accelerator, and even when the amount of alkaline additive added is relatively small, the strength-enhancing effect when the hardening accelerator is added can be sufficiently expressed. In addition, by adding a relatively small amount of alkaline additive, the resulting asphalt mixture can be made to have excellent storage stability.

[0043] Next, the asphalt mixture of this example can be produced by removing the mixture obtained above from the mixing apparatus while maintaining a temperature of 100 to 130°C.

[0044] The present invention will be described below based on more detailed examples, but the present invention is not limited to these examples.

[0045] <Example 1> 93.4 parts by weight of aggregate, 3.0 parts by weight of straight asphalt (StAs60 / 80), 0.2 parts by weight of paraffinic mineral oil (product name "Shell Terrace Oil S2M22", manufactured by Shell Lubricants Japan Co., Ltd., flash point: 210°C), 2.7 parts by weight of lubricating solidifying agent (tall oil fatty acid, product name "Hartol FA-1", manufactured by Harima Chemicals Group Co., Ltd.), and 0.7 parts by weight of ordinary Portland cement were blended in this order in a twin-screw Pugmill type mixer (1 batch: 30-60 kg) and mixed to obtain an asphalt mixture. In this process, the heating temperature of the aggregate was 110-130°C, the heating temperature of the asphalt was 150-165°C, and the other components were kept at room temperature.

[0046] <Examples 2 and 3> An asphalt mixture was obtained in the same manner as in Example 1, except that 0.2 parts by weight of paraffinic mineral oil (product name "Shell Terrace Oil S2M22") was replaced with 0.2 parts by weight of paraffinic mineral oil (product name "Shell Molina S2B220", manufactured by Shell Lubricants Japan Co., Ltd., flash point: 288°C) and 0.2 parts by weight of butyl vegetable fatty acid (product name "DBE", manufactured by Sanwa Synthetic Chemicals Co., Ltd., flash point: 200°C) as a vegetable oil.

[0047] <Example 4> An asphalt mixture was obtained in the same manner as in Example 1, except that 0.1 parts by weight of paraffin-based mineral oil (product name "Shell Terrace Oil S2M68", manufactured by Shell Lubricants Japan Co., Ltd., flash point: 252°C) was used instead of 0.2 parts by weight of paraffin-based mineral oil (product name "Shell Terrace Oil S2M22"), and the amount of straight asphalt was changed from 3.0 parts by weight to 3.1 parts by weight.

[0048] <Example 5> An asphalt mixture was obtained in the same manner as in Example 4, except that the amount of paraffinic mineral oil (product name "Shell Terrace Oil S2M68") was changed from 0.1 parts by weight to 0.2 parts by weight, and the amount of straight asphalt was changed from 3.1 parts by weight to 3.0 parts by weight.

[0049] <Example 6> An asphalt mixture was obtained in the same manner as in Example 4, except that the amount of paraffinic mineral oil (product name "Shell Terrace Oil S2M68") was changed from 0.1 parts by weight to 0.3 parts by weight, and the amount of straight asphalt was changed from 3.1 parts by weight to 2.9 parts by weight.

[0050] <Comparative Example 1> An asphalt mixture was obtained in the same manner as in Example 1, except that paraffinic mineral oil (product name "Shell Terrace Oil S2M22") was not blended and the amount of straight asphalt was changed from 3.0 parts by weight to 3.2 parts by weight.

[0051] <Comparative Examples 2 and 3> Asphalt mixtures were obtained in the same manner as in Example 1, except that 0.2 parts by weight of kerosene (flash point: 43°C) and 0.2 parts by weight of aromatic mineral oil (product name "Mineral Spirit", manufactured by Kishida Chemical Co., Ltd., flash point: 43°C) were used instead of 0.2 parts by weight of paraffinic mineral oil (product name "Shell Terrace Oil S2M22").

[0052] (Measurement of the rate of change in mass of mineral oil and vegetable oil when heated in a thin film) Approximately 50 g of mineral oil or vegetable oil was placed in a container and made into a thin film of approximately 3 mm, and the weight of the mineral oil or vegetable oil (initial weight of mineral oil or vegetable oil) was weighed. Then, the mineral oil or vegetable oil was left in an environment of 35°C for 5 hours. The weight of the mineral oil or vegetable oil after standing was weighed, and the rate of change in mass of the thin film when heated (%) was calculated based on the following formula (1). Rate of change in mass of thin film when heated (%) = ([Initial weight of mineral oil or vegetable oil] - [Weight of mineral oil or vegetable oil after standing]) / [Initial weight of mineral oil or vegetable oil] × 100 (1)

[0053] (Disintegration Test) The asphalt mixtures obtained in Examples 1-6 and Comparative Examples 1-3 were poured into molds at 20°C and compacted to a degree of compaction of 80% to obtain specimens with a diameter of 10.2 cm and a height of 7.8 cm. Disintegration tests were performed on the obtained specimens using the test apparatus shown in Figure 1 to evaluate the workability during construction in low-temperature ranges.

[0054] Specifically, as shown in Figure 1, first, the obtained specimen 10 was placed on the base 20, and then the pressing member 30 was placed on the specimen 10. After that, a load 40 was applied to the pressing member 30 so that the total weight of the pressing member 30 and the load 40 was 10 kg. The displacement of the height position of the pressing member 30 from the time the load 40 was applied until the specimen 10 collapsed was measured using a displacement meter (not shown), and the amount of displacement of the height position of the pressing member 30 was calculated. Then, as shown in Figure 2, in the curve showing the amount of displacement of the height position of the pressing member 30 with respect to the loading time of the load 40, the loading time at which the rate of increase of the displacement is maximum (i.e., the loading time at which the slope of the curve showing the amount of displacement is maximum) was considered as the time when the specimen 10 unravelled, and the time from the time the load 40 was applied until the specimen 10 unravelled was calculated. The unravelling test was conducted in an environment of 0°C. The shorter the time it takes for the specimen 10 to disintegrate, the easier the asphalt mixture disintegrates in low-temperature ranges, and the better the workability during construction in low-temperature ranges, which is desirable. The results are shown in Table 1.

[0055] (Bending Test) The asphalt mixtures obtained in Examples 1-6 and Comparative Examples 1-3 were poured into molds at 20°C, water was added, and the mixtures were compacted to a degree of compaction of 96%. The mixtures were then cured for 28 days at a temperature of 50°C and a humidity of 60% to obtain test specimens. Using the obtained test specimens, a bending test was performed at a test temperature of 20°C in accordance with the "Pavement Survey and Test Method Handbook B005" to determine the strain at fracture (×10 －３ The strain (mm / mm) was determined. In bending tests, a larger strain at fracture is desirable because it results in better deflection and reduces the occurrence of cracks. The results are shown in Table 1.

[0056] (Wheel Tracking Test) The asphalt mixtures obtained in Example 5 and Comparative Example 1 were poured into molds at 20°C, water was added, and the mixture was compacted to a degree of compaction of 100%. The mixtures were then cured for 7 days at a temperature of 20°C and a humidity of 60% to obtain test specimens. Using the obtained test specimens, a wheel tracking test was performed at a test temperature of 20°C in accordance with "3-7-1" and "3-7-3" of the "Pavement Testing Methods Handbook" (Japan Road Association, published November 1988) to determine the dynamic stability (cycles / mm). A higher value of dynamic stability (cycles / mm) is desirable because it indicates higher strength, reduced rutting, and superior rutting resistance. The results are shown in Table 2.

[0057]

[0058]

[0059] The aggregates used in Examples 1-6 and Comparative Examples 1-3 have the following composition: Crushed stone No. 6: 30.2% by weight Crushed stone No. 7: 20.2% by weight Crushed sand: 19.2% by weight Coarse sand: 16.1% by weight Fine sand: 9.1% by weight Stone powder: 5.2% by weight

[0060] Furthermore, the mineral oils and vegetable oils used in each example and comparative example are as follows: • Shell Terrace Oil S2M22 (product name "Shell Terrace Oil S2M22", manufactured by Shell Lubricants Japan Co., Ltd., flash point: 210°C, thin film heating mass change rate: 0.1%) • Shell Molina S2B220 (product name "Shell Molina S2B220", manufactured by Shell Lubricants Japan Co., Ltd., flash point: 288°C, thin film heating mass change rate: 0.1%) • Vegetable fatty acid butyl (product name "DBE", manufactured by Sanwa Synthetic Chemicals Co., Ltd., flash point: 200°C, thin film heating mass change rate: 0.1%) • Shell Terrace Oil S2M68 (product name "Shell Terrace Oil S2M68", manufactured by Shell Lubricants Japan Co., Ltd., flash point: 252°C, thin film heating mass change rate: 0.0%) • Kerosene (flash point: 43°C, thin film heating mass change rate: 17.5%) - Mineral Spirit (product name "Mineral Spirit", manufactured by Kishida Chemical Co., Ltd., flash point: 43°C, thin film heating mass change rate: 27.9%)

[0061] Furthermore, the tall oil fatty acid (product name "Hartol FA-1", manufactured by Harima Chemicals Group Co., Ltd.) used in Examples 1-6 and Comparative Examples 1-3 has the following properties: Fatty acid: Resin acid = 98.5:1.5 (weight ratio) Unsaponifiable matter content: 2.0% by weight Fatty acid component ratio: Palmitic acid 1-3% by weight, stearic acid 1-3% by weight, oleic acid 40-50% by weight, linoleic acid 35-45% by weight Type of resin acid: Rosin acid value: 194 mg KOH / g

[0062] As shown in Table 1, when mineral oil or vegetable oil with a flash point of 70°C or higher was used, the resulting asphalt mixture was easily loosened at low temperatures (loosening test) and exhibited excellent workability during application at low temperatures (Examples 1-6). Furthermore, specimens obtained from such asphalt mixtures showed large strain at fracture (bending test) and excellent flexibility.

[0063] On the other hand, when mineral oil or vegetable oil was not used, the resulting asphalt mixture was difficult to break down at low temperatures and had poor workability during construction at low temperatures. In addition, the specimens obtained from such asphalt mixtures exhibited small strain at fracture and poor flexibility (Comparative Example 1). When mineral oil with a flash point of less than 70°C was used, the resulting asphalt mixture was easily broken down at low temperatures and had excellent workability during construction at low temperatures. However, the specimens obtained from such asphalt mixtures exhibited small strain at fracture and poor flexibility (Comparative Examples 2 and 3).

Claims

1. An asphalt mixture obtained by mixing aggregate, asphalt, mineral oil and / or vegetable oil having a flash point of 70°C or higher, a lubricating solidifying agent, and an alkaline additive.

2. The asphalt mixture according to claim 1, wherein the content of the mineral oil and / or vegetable oil is 0.1 to 30% by weight relative to 100% by weight of the total amount of the asphalt and the mineral oil and / or vegetable oil.

3. The asphalt mixture according to claim 1 or 2, wherein the content of the lubricating solidifying agent is 1 to 80% by weight relative to 100% by weight of the total amount of the asphalt and the lubricating solidifying agent.

4. A paving method characterized by improving strength by adding a hardening accelerator to the asphalt mixture according to any one of claims 1 to 3, and causing a saponification or neutralization reaction between the lubricating solidifying agent and the alkaline additive.

5. A method for producing an asphalt mixture according to any one of claims 1 to 3, comprising: a first step of mixing aggregate heated to 100 to 170°C and asphalt heated to 130 to 170°C in a mixing device; a second step of adding and mixing the mineral oil and / or vegetable oil and the lubricating solidifier to the mixture obtained in the first step; and a third step of adding and mixing the alkaline additive to the mixture obtained in the second step.

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