Asphalt mixture, its manufacturing method, and asphalt paving method

Abstract

To provide an asphalt mixture that allows reuse of polyolefin-based films and makes it possible to manufacture an asphalt pavement that is excellent in water resistance and durability, and a manufacturing method thereof.SOLUTION: An asphalt mixture manufacturing method has: a process A of stirring and mixing aggregates and polyolefin film crushed matters while melting the polyolefin film crushed matters; and a process B of stirring and mixing the mixture obtained in the process A with heated asphalt.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an asphalt mixture, a method for producing the same, and an asphalt paving method. [Background technology]

[0002] Roads are paved using asphalt mixtures, which are mixtures of aggregate and asphalt. The materials and formulations of asphalt mixtures are being studied to improve the durability of asphalt pavements.

[0003] For example, Patent Document 1 discloses a method of thermally decomposing plastic to produce a paraffin wax-like melt, which is then used as a modifier. Patent Document 2 discloses a method of substituting plastic as part of an aggregate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-7317 [Patent Document 2] Japanese Patent Application Publication No. 10-88001 Summary of the Invention [Problem to be solved by the invention]

[0005] Asphalt is basically a mixture of components that are soluble and insoluble in hydrocarbon solvents. On the other hand, polyolefins, such as polyethylene (PE) and polypropylene (PP), are compatible with the hydrocarbon solvent-soluble components of asphalt but incompatible with the hydrocarbon solvent-insoluble components. It is generally known that mixing polyolefins into heated asphalt causes the asphalt to lose its stability, phase separation occurs, and the asphalt becomes less uniform and its properties deteriorate. Therefore, mixing polyolefins into asphalt is generally not recommended, and even when mixed, the proportion is very small. Patent Document 1 suggests that compatibility is improved by burning the polyolefin to produce a low-molecular-weight waxy melt. However, the polyolefin is not used as is.

[0006] In most cases where polyolefins are used as they are, they are added to aggregates and used as part of the aggregate, as in Patent Document 2. However, in order to use them as aggregates, it was necessary to make the size uniform and to carefully control the temperature so that the polyolefins would not melt. On the other hand, in order to use them as aggregates, the polyolefins also needed to be heat resistant enough not to melt at the temperatures used in asphalt production and paving.

[0007] Furthermore, from the perspective of environmental conservation, there is an increasing need to recycle plastic waste. Polyolefin, a type of plastic, is widely used in agricultural and packaging applications, resulting in the generation of polyolefin waste every day. A simple method for recycling this waste and circulating resources is needed. However, much of this waste is contaminated, and cleaning is essential for recycling, which requires a lot of energy and costs, posing a challenge. In particular, agricultural film waste is known to be contaminated by soil contamination, which is difficult to remove.

[0008] Under these circumstances, the present invention aims to provide an asphalt mixture and a method for producing the same that enable the reuse of polyolefin-based films and the production of asphalt pavement that has excellent water resistance and durability, as well as an asphalt pavement method using the asphalt mixture. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems and have found that the following inventions meet the above objectives, thereby completing the present invention. <1> A method for producing an asphalt mixture, comprising: step A of stirring and mixing aggregate and crushed polyolefin film material while melting the crushed polyolefin film material; and step B of stirring and mixing the mixture obtained in step A with heated asphalt. <2> The polyolefin film crushed material contains polyethylene. <1> A method for producing an asphalt mixture according to claim 1. <3> The crushed polyolefin film has a size that can pass through a screen with a mesh diameter of 10 to 50 mm. <1> or <2> A method for producing an asphalt mixture according to claim 1. <4> The crushed polyolefin film is a crushed polyolefin film waste material. <1> from <3> 1. A method for producing an asphalt mixture according to any one of the preceding claims. <5> The polyolefin film waste is an agricultural film waste, and the crushed polyolefin film contains a component derived from soil attached to the agricultural film waste. <4> A method for producing an asphalt mixture according to claim 1. <6> In the step A, the temperature for stirring and mixing the aggregate and the crushed polyolefin film is 160°C to 180°C, and the time for stirring and mixing in the step A is 10 seconds to 30 seconds. <1> from <5> A method for producing an asphalt mixture according to claim 1. <7> In the step B, the temperature of stirring and mixing the mixture obtained in the step A and the asphalt is 160°C to 180°C, and the stirring and mixing time in the step B is 40 seconds to 80 seconds. <1> from <6> 1. A method for producing an asphalt mixture according to any one of the preceding claims. <8> The asphalt mixture is mixed so that the content of the asphalt in the asphalt mixture is 3% by mass or more and 8% by mass or less, and the ratio of the crushed polyolefin film material to the total of the asphalt and the crushed polyolefin film material is 1% by mass or more and 10% by mass or less. <1> from <7> 1. A method for producing an asphalt mixture according to any one of the preceding claims. <9> An asphalt mixture comprising aggregate, asphalt, and a polyolefin, wherein the polyolefin is present at the interface between the aggregate and the asphalt, and the surface of the aggregate has a portion coated with the polyolefin. <10> The aforementioned <1> from <8> 1. An asphalt paving method comprising the steps of: obtaining an asphalt mixture by the asphalt mixture manufacturing method described in any one of the above; and spreading and compacting the asphalt mixture. [Effects of the Invention]

[0010] The present invention provides an asphalt mixture and a method for producing the same that allows the reuse of polyolefin films and produces an asphalt pavement that is excellent in water resistance and durability. It also provides an asphalt pavement method using the asphalt mixture. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an example of a manufacturing plant in which the manufacturing method of the present invention can be implemented. [Figure 2] These are DSC curves for crushed film A (unused agricultural polyethylene) and crushed film B (used discarded agricultural polyethylene). [Figure 3]These are the results of GPC measurements of crushed film A (unused agricultural polyethylene) and crushed film B (used discarded agricultural polyethylene). [Figure 4] These are images of an asphalt mixture mixed with crushed film A, observed using SEM-EDS (scanning electron microscope). (a) is an image near the interface between the crushed stone and asphalt, and (b) is an image of the area avoiding the crushed stone. [Figure 5] These are images of the asphalt mixture without film fragment A observed using SEM-EDS (scanning electron microscope). (a) is an image near the interface between the crushed stone and asphalt, and (b) is an image of the area avoiding the crushed stone. [Figure 6] This is the result of FT-IR measurement of the interface of the crushed stone of the test specimen. [Figure 7] These are enlarged views of specific regions of the FT-IR spectrum in Figure 6. (a) is an enlarged view of the 1420 cm-1 to 1500 cm-1 region, and (b) is an enlarged view of the 2600 cm-1 to 3200 cm-1 region. [Figure 8] This is the measurement result of the contact angle of water. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes in detail an embodiment of the present invention, but the following description of the constituent elements is one example (typical example) of an embodiment of the present invention, and the present invention is not limited to the following content unless the gist of the present invention is changed. Note that when the expression "to" is used in this specification, it is used as an expression including the numerical values ​​or physical property values ​​before and after it.

[0013] <Asphalt mixture manufacturing method> The present invention relates to a method for producing an asphalt mixture (hereinafter sometimes referred to as the "production method of the present invention"), which includes step A of stirring and mixing aggregate and crushed polyolefin film material while melting the crushed polyolefin film material, and step B of stirring and mixing the mixture obtained in step A with heated asphalt.

[0014] One of the features of the present invention is the use of crushed polyolefin film (hereinafter sometimes simply referred to as "crushed film") as one of the raw materials. This material is prone to melting and therefore difficult to use as part of aggregate. As mentioned above, in the past, mixing polyolefins and other materials into asphalt has generally not been recommended, and they have mostly been used as part of aggregate. However, the inventors surprisingly discovered that adding crushed film to aggregate, stirring and mixing the crushed film while melting it, and then stirring and mixing it with heated asphalt produces an asphalt mixture that can produce an asphalt pavement with excellent water resistance and durability. Furthermore, it was previously thought that using films would cause them to fuse together, forming clumps, making uniform mixing difficult. However, the method of the present invention has been found to prevent the crushed film from fusing together and forming clumps, enabling uniform mixing.

[0015] Although the reason for this is unclear, by using polyolefin as the film fragments, the film is heated by heat such as frictional heat generated when crushed by a crusher, and some of the film fragments shrink or fuse while being crushed. Therefore, when the film fragments are mixed with aggregate, the film fragments are less likely to shrink or fuse and form clumps. Furthermore, by melting the film fragments when mixed with aggregate, the molten film fragments easily coat the aggregate, and the aggregate and asphalt are bonded via the molten film fragments, which is thought to improve adhesion and reduce volumetric shrinkage of the asphalt. When the resulting asphalt mixture is used to pave asphalt, the adhesion between the aggregate and asphalt is improved, making it less likely for cracks to occur due to volumetric shrinkage of the asphalt, resulting in an asphalt pavement with excellent water resistance and durability. Using the asphalt mixture obtained by the manufacturing method of the present invention, it is possible to produce an asphalt pavement with water resistance and durability equivalent to or greater than that of a conventional asphalt mixture without the addition of film fragments.

[0016] Furthermore, the mixing time for aggregate and asphalt in current asphalt mixture manufacturing plants is approximately one minute. It was previously thought that it would be difficult to mix polyolefins, which have poor compatibility with asphalt, with aggregate and asphalt in such a limited time to obtain a high-quality asphalt mixture. However, it has been found that the manufacturing method of the present invention makes it possible to obtain a high-quality asphalt mixture without significantly extending the mixing time. Therefore, the manufacturing method of the present invention can be implemented without significantly changing the configuration of conventional asphalt mixture manufacturing plants, making it easy to put into practical use.

[0017] Furthermore, as will be described later, the manufacturing method of the present invention is also excellent from the viewpoint of recycling waste polyolefin film, since the quality of the resulting asphalt mixture can be ensured even when using film crushed material obtained by crushing waste polyolefin film without washing it, etc.

[0018] (aggregate) The type of aggregate is not particularly limited, and known aggregates can be used. Aggregates are classified by size into coarse aggregates that are retained on a 2.36 mm sieve, fine aggregates that pass through a 2.36 mm sieve and a 0.075 mm sieve, and fillers that pass through a 0.075 mm sieve. Any of these can be used as aggregates in step A. Aggregates can be used alone or in combinations of two or more types, but typically multiple aggregates are combined to achieve the desired particle size. Examples of aggregates include coarse aggregates such as No. 7 crushed stone, No. 6 crushed stone, No. 5 crushed stone, and No. 4 crushed stone; fine aggregates such as gravel, coarse sand, fine sand, screenings, steel slag, ceramics, and recycled aggregate; and fillers such as stone powder, fly ash, slaked lime, and cement.

[0019] (asphalt) The type of asphalt is not particularly limited, and known asphalts can be used. For example, asphalt includes straight asphalt, solvent deasphalted asphalt, petroleum asphalt such as cutback asphalt, natural asphalt, modified asphalt, etc., and straight asphalt is preferred. These may be used alone or in combination of two or more.

[0020] (Crushed polyolefin film) Crushed polyolefin film (crushed film) is a fluff-like material obtained by crushing polyolefin film with a crusher. Crushed film usually contains additives such as weathering agents, antioxidants, UV absorbers, light stabilizers, matting agents, antiblocking agents, antifogging agents, and antistatic agents in addition to polyolefin, the main component of the film. Crushed film may be crushed from one type of polyolefin film or a mixture of crushed polyolefin films.

[0021] Examples of polyolefins contained in the crushed film include polyethylene, polypropylene, and ethylene-vinyl acetate copolymer. Among polyolefins, polyethylene is particularly preferred because it has a melting point near the processing temperature of Step A described below, and it is therefore preferable that the crushed film contain polyethylene. Examples of polyethylene include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE). Low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) are commonly used in agricultural films.

[0022] The method for producing the crushed film material is not particularly limited, and it can be obtained by crushing a polyolefin film using a general crusher such as a uniaxial crusher, a biaxial crusher, etc. The crushed film material obtained is usually irregular in shape.

[0023] If the size of the crushed film material is too small, it becomes difficult to handle; if it is too large, it takes a long time to melt in step A, making it difficult to coat the surfaces of the aggregate and filler during production. Therefore, it is preferable to use a crusher equipped with a screen at the discharge section of the crushed material to crush it to a predetermined size. The mesh diameter of the screen (hole diameter in the case of punched metal, opening size in the case of lattice mesh) is preferably 10 mm to 50 mm, more preferably 15 mm to 40 mm, and even more preferably 20 mm to 30 mm. That is, the crushed film material is preferably of a size that can pass through a screen with a mesh diameter of 10 mm to 50 mm, more preferably a size that can pass through a screen with a mesh diameter of 15 mm to 40 mm, and even more preferably a size that can pass through a screen with a mesh diameter of 20 mm to 30 mm.

[0024] Examples of polyolefin-based films include polyethylene films, polypropylene films, and ethylene-vinyl acetate copolymer films, with polyethylene films being particularly preferred. These films may be used for any purpose, such as agricultural films, packaging films, or bag films. The polyolefin-based film may be a single-layer film or a laminate film, and may be a laminate film with a layer other than a polyolefin, as long as it contains a layer formed of polyolefin. Furthermore, the polyolefin-based film may be transparent or translucent, and may have an embossed surface.

[0025] In particular, polyolefin films are preferred for agricultural use. Specific examples of agricultural films include greenhouse film, mulch film, and tunnel film. Examples of polyolefin films for agricultural use include agricultural polyethylene film, agricultural ethylene-vinyl acetate copolymer, and agricultural polyolefin specialty film.

[0026] From the viewpoint of recycling, the crushed film is preferably crushed waste polyolefin film. The waste polyolefin film includes not only used polyolefin film but also scraps generated during the molding of polyolefin film and defective products that do not satisfy the quality of the product. In particular, crushed waste agricultural film is more preferable.

[0027] Since used polyolefin film waste is contaminated with foreign matter such as dust and debris, when recycling the waste, it is common to thoroughly wash the waste to remove the foreign matter and use it to prevent the foreign matter from affecting the performance of the recycled product. In particular, agricultural film waste often contains foreign matter, such as soil-derived components, and if it is crushed without thorough washing, the crushed film will be contaminated with the foreign matter. However, by using the manufacturing method of the present invention, it has been found that even if agricultural film waste is crushed without excessive washing, the quality of the asphalt mixture is not reduced and good asphalt paving can be achieved using this. For example, agricultural film waste can be shaken and washed in a dry state, and then crushed without washing to obtain crushed film. This crushed film can be used in step A.

[0028] The manufacturing method of the present invention can also utilize crushed agricultural film waste containing soil-derived components attached to the waste. Soil-derived components include elements such as Si, Al, Fe, Ca, K, Na, and Mg. For example, Si is a component found in large amounts in soil, and crushed agricultural film waste with soil-derived components still attached may contain Si. The use of such crushed film is also acceptable. Using crushed agricultural film waste in the manufacturing method of the present invention reduces the energy required for cleaning the agricultural film, which is environmentally beneficial.

[0029] (Asphalt Mixture Manufacturing) The manufacturing method of the present invention can be implemented in a general asphalt mixture manufacturing plant or a plant that partially recovers such a mixture. Figure 1 shows an example of a manufacturing plant in which the manufacturing method of the present invention can be implemented. The manufacturing plant 100 shown in Figure 1 includes a hopper 10 for receiving various aggregates, a dryer 11 for heating the aggregates, a bag filter 12 for passing exhaust gas generated in the dryer 11 and capturing dust, an elevator 13 for sending the heated aggregate to a hot bin 14, the hot bin 14 for storing the aggregates, an aggregate measuring tank 15 for measuring the aggregate stored in the hot bin 14, a stone powder storage bin 20 for storing stone powder, a stone powder measuring tank 21 for measuring the stone powder, an asphalt tank 30 for storing asphalt, an asphalt measuring tank 31 for measuring the asphalt, a storage unit 40 for crushed film material, and a mixer 50 for mixing various materials. Mixer 50 is equipped with aggregate inlet 51 for feeding weighed aggregate into mixer 50, stone powder inlet 52 for feeding weighed stone powder into mixer 50, asphalt inlet 53 for feeding weighed asphalt into mixer 50, and crushed material inlet 54 for feeding crushed film material into mixer 50. The asphalt mixture produced by mixing in mixer 50 is loaded onto dump truck 60 and transported to the paving site.

[0030] The manufacturing method of the present invention can also be carried out in an existing asphalt mixture manufacturing plant equipped with a dryer, bag filter, elevator, hot bin, aggregate measuring bin, stone powder storage bin, stone powder measuring bin, asphalt tank, asphalt metering bin, and mixer, by utilizing openings such as the aggregate inlet and asphalt inlet of the mixer as crushed material inlet. Also, an existing asphalt mixture manufacturing plant can be partially renovated to add a measuring device for crushed film material, a crushed material inlet, etc., to create a manufacturing plant for carrying out the manufacturing method of the present invention.

[0031] (Process A) Step A is a step of stirring and mixing aggregate and crushed polyolefin film material while melting the crushed polyolefin film material. Specifically, step A can be performed by adding aggregate (coarse aggregate, fine aggregate, and filler) to a mixer (e.g., a pugmill mixer), then adding the crushed polyolefin film material to the mixer and stirring in a heated state. The aggregate may be added to the mixer at room temperature or in a heated state, but the aggregate is generally added to the mixer in a heated state. In the mixer, the aggregate is mixed in a heated state, and the crushed film material is added to the mixer. Because the crushed film material is difficult to handle in a heated state, it is usually added to the mixer at room temperature. The crushed film material may be added to the mixer as is, or may be added to the mixer in a state where it is contained in a thermoplastic resin container or the like, taking into account ease of addition. For example, a predetermined amount of crushed film material may be packed into a thermoplastic resin bag and then the bag may be placed into the mixer. By dividing the crushed film material into small containers, the container becomes less bulky and the amount to be added is easier to calculate.

[0032] The temperature and time in step A are set to melt the crushed film material. The mixing temperature and time in step A are preferably set higher than the standard mixing temperature and longer than the standard mixing time to promote melting of the crushed film material and ensure uniformity of the mixture. For example, after adding the crushed film material, mixing is preferably performed at 160°C to 180°C for 10 to 30 seconds, and more preferably at 165°C to 175°C for 15 to 25 seconds.

[0033] (Process B) Step B is a step of stirring and mixing the mixture obtained in Step A with heated asphalt. Step B is the step performed after Step A, and specifically, asphalt heated to the mixing temperature is added to the mixture where the aggregate and crushed film material are being mixed. The asphalt is added while the asphalt is heated. In order to ensure the homogeneity of the mixture, the mixing temperature and mixing time in Step B are preferably set higher than the standard mixing temperature and longer than the standard mixing time. For example, after adding the asphalt, mixing is preferably performed at 160°C to 180°C for 40 to 80 seconds, and more preferably at 165°C to 175°C for 45 to 70 seconds.

[0034] The temperature and time during mixing may be set appropriately depending on the type and size of the crushed film material, but if the total mixing time, which includes the mixing time in step A and the mixing time in step B, is too long, productivity will decrease. Therefore, the total mixing time is preferably 50 to 120 seconds, more preferably 55 to 100 seconds, and even more preferably 60 to 80 seconds. In the manufacturing method of the present invention, a high-quality asphalt mixture can be obtained with such a total mixing time, even at a manufacturing scale like a manufacturing plant (for example, a mixer capacity of 0.5 to 2 tons).

[0035] The asphalt blending ratio in an asphalt mixture is generally designed by a Marshall stability test in accordance with the "Pavement Construction Handbook (2006 Edition)." The asphalt blending ratio can also be designed in a similar manner in the manufacturing method of the present invention. In the manufacturing method of the present invention, it is preferable to design the blending ratio so that a portion of the asphalt in the asphalt mixture is replaced with crushed polyolefin film. The asphalt content in the asphalt mixture is preferably 3% by mass to 8% by mass, more preferably 4% by mass to 6% by mass. Furthermore, the ratio of crushed film to the total of asphalt and crushed film is preferably 1% by mass to 10% by mass, more preferably 2% by mass to 8% by mass. As the ratio of crushed film increases, the workability of the asphalt pavement tends to decrease.

[0036] The asphalt mixture obtained by the production method of the present invention (hereinafter sometimes referred to as the "asphalt mixture of the present invention") contains aggregate, polyolefin, and asphalt. The polyolefin in the asphalt mixture of the present invention is derived from the crushed film material, and is not scattered in clumps like the aggregate, but rather most of it is present at the interface between the aggregate and asphalt, and the asphalt mixture of the present invention has portions where the surface of the aggregate is coated with polyolefin. When crushed waste polyolefin film is used, the asphalt mixture of the present invention may contain, in addition to aggregate, polyolefin, and asphalt, components derived from foreign matter in the crushed film material (for example, components derived from soil).

[0037] Furthermore, the asphalt mixture of the present invention can be made more hydrophobic than general asphalt mixtures produced without using crushed film material. The production method of the present invention can produce an asphalt mixture with a contact angle with water of 70° or more.

[0038] <Asphalt paving method> Asphalt pavement can be carried out using the asphalt mixture obtained by the manufacturing method of the present invention. That is, the asphalt pavement method of the present invention comprises the steps of obtaining an asphalt mixture by the asphalt mixture manufacturing method of the present invention and spreading and compacting the asphalt mixture. Asphalt pavement can be carried out in the same manner as conventional asphalt pavement methods. Specifically, after producing an asphalt mixture by the manufacturing method of the present invention at a manufacturing plant, the asphalt mixture is loaded into a dump truck or the like while still warm and transported to the construction site. At the construction site, the asphalt mixture is spread and leveled to a predetermined width and thickness on a paving surface (such as a roadbed or base course) that has been pretreated by cleaning or other methods, using heavy machinery such as an asphalt finisher. It is then compacted using a rolling machine such as a road roller or tire roller. The pavement formed from the asphalt mixture of the present invention is suitable for use as an asphalt base course or surface course. It is preferable to control the temperature during spreading and initial compaction (rolling) so that it is higher than the melting point of polyolefin, and the initial compaction temperature (rolling temperature) is preferably 130°C to 180°C, 140°C to 170°C, or 150°C to 160°C.

[0039] The asphalt pavement formed by the asphalt paving method of the present invention contains aggregate, asphalt, and polyolefin, with the polyolefin present at the interface between the aggregate and asphalt, and portions of the aggregate surface being coated with the polyolefin. In this asphalt pavement, the majority of the polyolefin is present at the interface between the aggregate and asphalt, contributing to improved adhesion between the aggregate and asphalt. The asphalt pavement can also have a Marshall stability of 9.0 kN or more and a dynamic stability of 1,000 times / mm or more. [Example]

[0040] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not changed.

[0041] (Crushed film) For the asphalt mixture test, the following crushed film A or crushed film B was used.

[0042] Film fragments A: Unused agricultural polyethylene (LDPE, mulch sheet) was crushed in a uniaxial crusher (punched metal hole diameter 20 mm) and used as crushed film A.

[0043] Film fragments B: Used agricultural waste polyethylene (LDPE, mulch sheet) was collected, crushed, and used. After the soil adhering to the surface of the crushed agricultural polyethylene was easily removed, the crushed film was crushed in a uniaxial crusher (punched metal hole diameter 20 mm). This was used as crushed film B.

[0044] Physical property evaluation of crushed film: Crushed film A and crushed film B were each vacuum-dried at 100°C for 24 hours, then sandwiched between fluororesin release resins and processed into films and tablets at 210°C and 30 MPa. The resulting films and tablets were used to measure their melting points using DSC, observe them using SEM-EDS (scanning electron microscope), and evaluate their molecular weights using high-temperature GPC.

[0045] Figure 2 shows the DSC curves of crushed film A (unused agricultural polyethylene) and crushed film B (used discarded agricultural polyethylene). As shown in Figure 2, crushed film B has more peaks than crushed film A, indicating that it contains miscellaneous components.

[0046] When crushed film A (unused agricultural polyethylene) and crushed film B (used discarded agricultural polyethylene) were observed using a SEM-EDS (scanning electron microscope), a large amount of foreign matter was confirmed in crushed film B. Elemental analysis of crushed film B using EDS detected elements such as Si, Na, and F that were not observed in crushed film A. These elements are found in soil, so it is thought that crushed film B contains elements that are thought to be derived from the soil.

[0047] Figure 3 shows the results of GPC measurements of crushed film A (unused agricultural polyethylene) and crushed film B (used waste agricultural polyethylene). Figure 3 shows that there is no significant change in Mw between crushed film A and crushed film B, which indicates that crushed film B has not undergone much chemical degradation.

[0048] [Example 1]: Blending test Mixing tests were conducted to determine the aggregate mix and the optimum amount of asphalt.

[0049] (Type of mixture) Dense grain size 13mm (straight asphalt 60 / 80, mixed with film fragments) Crushed film B was used to replace 2% by mass of the asphalt weight.

[0050] (Asphalt Mixture Manufacturing) The aggregate was placed in a 1 ton scale mixer, and then the crushed film was placed in the mixer and mixed for 20 seconds at 170°C ± 3°C. Asphalt was then placed in the mixer and mixed for 50 seconds.

[0051] (Other test conditions) Asphalt (As) content range: 4.0% to 6.0% by mass 50 tamping times Compaction temperature: 153°C ± 3°C

[0052] (Test results) The blending ratios and composite particle sizes are as shown in Tables 1 and 2.

[0053] [Table 1]

[0054] [Table 2]

[0055] The optimum amount of asphalt and Marshall test property values ​​are as shown in Table 3.

[0056] [Table 3]

[0057] [Examples 2A and 2B, Reference Example 2] The coarse aggregate and crushed film B were mixed at 170°C, and then 170°C straight asphalt was added to cover the coarse aggregate. The adhesion between the coarse aggregate and asphalt was evaluated in accordance with the static peeling test (Asphalt Pavement Guidelines). The results are shown in Table 4.

[0058] [Table 4]

[0059] [Examples 3A and 3B, Examples 4A and 4B, Reference Example 3, Reference Example 4] The crushed film material used was crushed film material B. Except for the type of mixture, amount of asphalt (ratio of asphalt to asphalt mixture), and amount of crushed film (ratio of crushed film to asphalt mixture) shown in Table 5, an asphalt mixture was obtained in the same manner as in the production of the asphalt mixture of Example 1.

[0060] [Table 5]

[0061] [evaluation] (Water immersion Marshall test) Evaluation was carried out in accordance with the Water Immersion Marshall Test (Asphalt Pavement Guidelines). Test specimens were prepared using the asphalt mixtures of Examples 3A and 3B, Reference Example 3, Examples 4A and 4B, and Reference Example 4. Pressure was then applied to the test specimens, and the maximum load (stability) until they broke was measured. The results are shown in Tables 6 and 7. As shown in Tables 6 and 7, the residual stability of the test specimens to which the film fragments had been added was equal to or greater than that of the test specimens to which the film fragments had not been added.

[0062] [Table 6]

[0063] [Table 7]

[0064] (Wheel tracking test) Evaluation was carried out according to the wheel tracking test described in the Pavement Survey and Testing Methods Handbook. Test specimens were prepared using the asphalt mixture of Example 3A or Reference Example 3. A wheel was then run back and forth on the test specimen, the amount of deformation of the test specimen was measured, and the dynamic stability (cycles / mm) was evaluated. The results are shown in Table 8. As shown in Table 8, the dynamic stability of the test specimen with the addition of crushed film was improved by 229.1% compared to the test specimen without the addition of crushed film.

[0065] [Table 8]

[0066] (Asphalt mixture property evaluation) Except for using crushed film A instead of crushed film B, the asphalt mixture was produced in the same manner as in Example 3A and Reference Example 3, and was evaluated using SEM-EDS (scanning electron microscope), Fourier transform infrared spectrophotometer (FT-IR), and water contact angle.

[0067] Figure 4 shows images of an asphalt mixture mixed with crushed film A, observed using an SEM-EDS (scanning electron microscope). (a) is an image near the interface between the crushed stone and asphalt, and (b) is an image of the area avoiding the crushed stone. Figure 5 shows images of an asphalt mixture without crushed film A, observed using an SEM-EDS (scanning electron microscope). (a) is an image near the interface between the crushed stone and asphalt, and (b) is an image of the area avoiding the crushed stone. Comparing Figures 4 and 5, distortion can be seen at the interface of the crushed stone in Figure 4, but in Figure 5 it can be seen that the crushed stone and the rest of the asphalt mixture are clearly separated. On the other hand, there was no significant difference between the two in the area avoiding the crushed stone.

[0068] Figure 6 shows the results of FT-IR measurement of the interface between the crushed stone and the asphalt mixture. Figure 7 shows an enlarged view of a specific region of the FT-IR. At the interface between the crushed stone and the asphalt mixture mixed with crushed film A, the peak was 1460 cm -1 Near 2850cm -1 Near 2930cm -1 A peak thought to be derived from LDPE was confirmed in the vicinity.

[0069] Figure 8 shows the results of measuring the water contact angle. The water contact angle of the asphalt mixture mixed with crushed film A (the water contact angle 30 seconds after water was dropped) was larger than the water contact angle of the asphalt mixture without crushed film A, and the water contact angle of the asphalt part avoiding the crushed stone was particularly large. The addition of crushed film A improved hydrophobicity, which is thought to be one of the reasons for the improvement in properties such as water resistance.

[0070] From these evaluation results, it is believed that in the asphalt mixture of the present invention, polyethylene is present at the interface between the aggregate and the asphalt, coating the aggregate. [Explanation of symbols]

[0071] 10 Hopper 11 Dryer 12 Bag filter 13 Elevator 14 Hot Bottle 15 Aggregate measuring tank 20 Stone Powder Storage Bin 21 Stone powder measuring tank 30 Asphalt Tank 31 Asphalt measuring tank 40 Film crusher storage area 50 Mixer 51 Aggregate inlet 52 Stone powder inlet 53 Asphalt inlet 54 Crushed material inlet 60 Dump Truck 100 manufacturing plants

Claims

1. A method for producing an asphalt mixture comprising aggregate, asphalt, and a polyolefin, wherein the polyolefin is present at the interface between the aggregate and the asphalt, and the surface of the aggregate has a portion coated with the polyolefin, A step A of stirring and mixing the aggregate and the crushed polyolefin film while melting the crushed polyolefin film; and a step B of stirring and mixing the mixture obtained in the step A with the heated asphalt, The crushed polyolefin film contains polyethylene, The method for producing an asphalt mixture, wherein the temperature of stirring and mixing the aggregate and the crushed polyolefin film in the step A is 160 ° C to 180 ° C.

2. The method for producing an asphalt mixture according to claim 1, wherein the crushed polyolefin film is sized to pass through a screen having a mesh diameter of 10 to 50 mm.

3. The method for producing an asphalt mixture according to claim 1, wherein the crushed polyolefin film is crushed waste polyolefin film.

4. The waste polyolefin film is waste agricultural film, The method for producing an asphalt mixture according to claim 3, wherein the crushed polyolefin film contains components derived from soil attached to the agricultural film waste.

5. A method for producing an asphalt mixture as described in claim 1, wherein the stirring and mixing time in step A is 10 to 30 seconds.

6. The temperature of the stirring and mixing of the mixture obtained in the step A and the asphalt in the step B is 160 ° C. to 180 ° C., and the stirring and mixing time in the step B is 40 seconds to 80 seconds. The method for producing an asphalt mixture according to claim 1.

7. The asphalt mixture is mixed so that the content of the asphalt in the asphalt mixture is 3% by mass or more and 8% by mass or less, and the ratio of the polyolefin film crushed material to the total of the asphalt and the polyolefin film crushed material is 1% by mass or more and 10% by mass or less. A method for producing an asphalt mixture according to claim 1.

8. The present invention relates to a method for making a polyolefin film, a method for making a polyolefin film, and a method for making a polyolefin film. The polyolefin is present at the interface between the aggregate and the asphalt, and the surface of the aggregate has a portion coated with the polyolefin, The asphalt mixture, wherein the polyolefin comprises polyethylene.

9. A step of obtaining an asphalt mixture by the asphalt mixture manufacturing method according to any one of claims 1 to 7; A step of spreading and compacting the asphalt mixture; An asphalt paving method comprising:

Images