Asphalt mixture evaluation method and paving method

Abstract

To provide a new evaluation method for an asphalt mixture, and a paving method using the same.SOLUTION: An evaluation method for an asphalt mixture is an evaluation method for characteristics of an asphalt mixture includes: an installation step of installing a specimen 3 of a recycled asphalt mixture between a substrate 1 and an action body 2; a loading step of moving the action body 2 to the side of the substrate 1, and measuring a displacement value x of the action body 2 to the substrate 1, and a load value F(x) at the displacement value x; a breaking energy calculation step of calculating breaking energy E represented by expression (1); and an evaluation step of evaluating physical properties of the asphalt mixture on the basis of the breaking energy E. In the expression (1), x1 represents a displacement value x with a load of 0.1 kN after the specimen 3 has been broken.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an asphalt mixture evaluation method and a paving method. [Background technology]

[0002] Asphalt mixtures are produced by mixing asphalt and aggregate in specific ratios while heating, and are used for asphalt pavements. When asphalt pavement is damaged and needs to be repaired, it is demolished. Instead of being discarded, the demolished asphalt pavement is crushed, classified, and reused as recycled aggregate or roadbed material. Asphalt mixtures that use this recycled aggregate are sometimes referred to as recycled asphalt mixtures.

[0003] The classified recycled aggregate contains old asphalt components, which usually have poorer properties than new asphalt.

[0004] Using recycled aggregate in asphalt mixtures can reduce the amount of new aggregate and new asphalt used. However, recycled aggregate still contains old asphalt that has deteriorated in quality, so the quality of recycled asphalt mixtures differs from that of new asphalt mixtures made using new aggregate and new asphalt. Repeated reuse of recycled aggregate tends to harden, lose elasticity, and become brittle.

[0005] Therefore, when producing recycled asphalt mixtures, they must be modified by adding recycling additives or soft asphalt, and the recycled asphalt mixture must be evaluated for suitability for paving before being used.

[0006] One method for evaluating the physical properties of asphalt mixtures is the "Standard Test Method for Determining the Fracture Potential of Asphalt Mixtures by Flexibility Index Test" prescribed by the U.S. Association of State Highway and Transportation Officials. This test method evaluates the flexibility index (hereinafter sometimes referred to as "FI") obtained from a semi-circular bending test (hereinafter sometimes referred to as "SCB test").

[0007] In the state of Illinois, the physical properties of asphalt mixtures are evaluated using a matrix of this FI and the rut depth measured by the Hamburg Wheel Tracking Test. Specifically, an asphalt mixture with an FI of 8 or greater and a rut depth of less than 12.5 mm is rated as good (rigid and flexible), an FI of 8 or greater and a rut depth of 12.5 mm or greater is rated as soft and flexible, an FI of less than 8 and a rut depth of less than 12.5 mm is rated as hard and brittle, and an FI of less than 8 and a rut depth of 12.5 mm or greater is rated as soft and unstable.

[0008] Known methods for evaluating the physical properties of asphalt include, for example, a method for evaluating hardness using numerical values ​​of penetration or softening point, and a method for evaluating elongation using numerical values ​​of elongation.

[0009] Known methods for evaluating the physical properties of asphalt mixtures include, for example, static bending tests, bending fatigue tests (repeated bending tests), and compression tests.

[0010] As a method for evaluating the flow resistance and crack properties of asphalt mixtures using splitting strength, Non-Patent Document 1 describes a method for splitting tests. This test involves applying loads from above and below a cylindrical specimen of asphalt mixture in the diameter direction, and measuring the load and displacement on the specimen.

[0011] Furthermore, one way to evaluate the deterioration of the old asphalt content in recycled aggregate is to determine the spalling coefficient from data obtained by the aforementioned test method (Non-Patent Document 1), as described in Non-Patent Document 2. Non-Patent Document 2 describes how to determine the spalling coefficient of recycled asphalt mixtures. The spalling coefficient is the value obtained by dividing the maximum load by the amount of displacement, and the standard value for the spalling coefficient is 1.70 (MPa / mm) or less for recycled aggregate, 0.60 to 0.90 (MPa / mm) for general-purpose recycled asphalt mixtures, and 0.40 to 0.60 (MPa / mm) for use in snowy and cold regions. [Prior art documents] [Non-patent literature]

[0012] [Non-Patent Document 1] "Pavement Survey and Testing Method Handbook", Japan Road Association, March 2019, pp. 87-94 of Volume 3 [Non-patent document 2] "Pavement Regeneration Handbook," Japan Road Association, November 2010, pp. 152-166 Summary of the Invention [Problem to be solved by the invention]

[0013] The aforementioned method of evaluating asphalt mixtures in Illinois, USA, using FI and rutting volume, requires an FI of 8 or more. This is thought to be based on data from actual roads over three winter seasons, and is chosen to be an FI that can suppress the amount of cracking that occurs. However, when this evaluation method was applied to the evaluation of recycled asphalt mixtures, there was no consistent trend in the FI as the recycled aggregate content increased.

[0014] Generally, the higher the recycled aggregate content in a recycled asphalt mixture, the greater the impact on the properties of the recycled asphalt mixture. However, as mentioned above, this trend does not appear to be the case with FI, making it difficult to determine the appropriate recycled aggregate content.

[0015] Furthermore, when examining the relationship between the recycled aggregate content and the splitting coefficient measured using the splitting test method described in Non-Patent Document 2, a consistent trend was not always obtained, making it difficult to determine the change in the recycled aggregate content using the splitting coefficient.

[0016] Furthermore, theoretically, it is thought that an asphalt mixture with a high penetration of recycled aggregate will have a low spalling coefficient. However, when examining the relationship between the penetration of recycled aggregate and spalling coefficient measured using the spalling test method described in Non-Patent Document 2, results that differ from this trend were obtained, and therefore the degree of deterioration of recycled aggregate could not be evaluated using the spalling coefficient.

[0017] The present invention has been made in view of the above circumstances, and has an object to provide a new method for evaluating asphalt mixtures and a paving method using the same. [Means for solving the problem]

[0018] In order to achieve the above object, the method for evaluating an asphalt mixture according to the first aspect of the present invention comprises: A method for evaluating properties of an asphalt mixture, comprising: An installation step of placing the asphalt mixture specimen between a base body and an operating body so as to sandwich the specimen; a loading step of moving the acting body toward the base body and measuring a displacement value x of the acting body relative to the base body and a load value F(x) at the displacement value x; A fracture energy calculation step of calculating fracture energy E shown in the following formula (1);

number

[0021] Preferably, the penetration is 20.

[0022] In the installation step, a semi-cylindrical specimen made of the asphalt mixture having a diameter of 150 mm and a thickness of 49 mm to 51 mm, with a notch having a length of 14 mm to 16 mm and a width of 1.0 mm to 2.0 mm formed radially from the center of the circle, is used as the specimen, As the substrate, two rollers with a diameter of 25 mm were used, spaced 120 mm apart. The working body has a semi-cylindrical portion having a curvature radius of 12.45 mm to 12.55 mm as a contact surface with the test piece, The specimen is placed on the roller of the base so that the straight side of the specimen is in contact with the roller, and the working body is placed so that the curved side of the specimen can apply a load at the contact surface of the working body; In the loading step, it is preferable that the working body is moved toward the base body at a displacement speed of 50 mm / min to deform the specimen.

[0023] In this specification, the expression "A to B" means a range of A or more and B or less.

[0024] In the installation step, a cylindrical sample of the asphalt mixture having a diameter of 101.4 mm to 101.8 mm and a thickness of 62.2 mm to 64.8 mm is used as the test piece, and the test piece is arranged so that the circumferential portion is in contact with the base body and the acting body so that a load can be applied in the diameter direction of the test piece, In the loading step, it is preferable that the working body is moved toward the base body at a displacement speed of 50 mm / min to deform the specimen.

[0025] A paving method according to a second aspect of the present invention uses, as a paving material, the recycled asphalt mixture that satisfies the criteria of formula (3) in the asphalt mixture evaluation method. [Effects of the Invention]

[0026] According to the present invention, it is possible to provide a new method for evaluating asphalt mixtures and a paving method using the same. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a conceptual diagram of an apparatus used in one embodiment of the evaluation method of the present invention, as viewed from the side. [Figure 2] 1A and 1B are conceptual diagrams of a specimen used in one embodiment of the evaluation method of the present invention, in which (A) is a view from the side, and (B) is a view from below. [Figure 3] 1A and 1B are conceptual diagrams of an apparatus used in another embodiment of the evaluation method of the present invention, where (A) is a view from the side and (B) is a view from diagonally above. [Figure 4] This is a conceptual diagram of the displacement-load curve and the compression coefficient. [Figure 5] This is a conceptual diagram of the displacement-load curve and fracture energy E. [Figure 6] 1 is a graph showing the relationship between the flexibility index and the recycled aggregate content of asphalt mixture samples 1 to 10. [Figure 7] 1 is a graph showing the relationship between the fracture energy and the recycled aggregate mix ratio for asphalt mixture samples 1 to 10. [Figure 8] 1 is a graph showing the fracture energy equivalent to that of a sample showing a penetration of 20 derived from the fracture energy and recycled aggregate blend ratio of asphalt mixture samples 1 to 10. [Figure 9] 1 is a graph showing fracture energy values ​​for evaluating the physical properties of asphalt mixtures. [Figure 10] 1 is a graph evaluating the physical properties of asphalt mixtures based on fracture energy. DETAILED DESCRIPTION OF THE INVENTION

[0028] While the present invention will be described with reference to figures, the invention is not limited thereto.

[0029] The asphalt mixture evaluation method of the present invention is a method for evaluating the properties of an asphalt mixture containing asphalt and aggregate, and includes an installation step, a loading step, a fracture energy calculation step, and an evaluation step.

[0030] (Asphalt mixture) The asphalt mixture is a mixture containing at least aggregate, filler, and asphalt.

[0031] Aggregates include coarse aggregates that pass through a 2.36 mm sieve, such as crushed stone, pebbles, gravel, and steel slag, and fine aggregates that pass through a 2.36 mm sieve but pass through a 0.075 mm sieve, such as natural sand, artificial sand, and screenings. The aggregate content in the asphalt mixture is, for example, 90% by mass. In this specification, the term "aggregate" includes new aggregate (new aggregate) and recycled aggregate, which will be described later.

[0032] The filler is a mineral powder that passes through a 0.075 mm sieve, such as powdered limestone. The content of the filler in the asphalt mixture is, for example, 5% by mass.

[0033] Asphalt is a polymeric material produced from petroleum, such as petroleum asphalt for paving (straight asphalt), polymer-modified asphalt, Trinidad asphalt (natural asphalt), and petroleum asphalt emulsion. The content in an asphalt mixture is, for example, 5% by mass. In this specification, the term "asphalt" includes new asphalt (new asphalt) and the old asphalt component described below.

[0034] Other components can be added to the asphalt mixture as needed. Examples of other components include additives such as recycling additives that can adjust the penetration of recycled aggregate, and supplementary materials. When the other component is a recycling additive, the content of the other component in the asphalt mixture is, for example, 5 to 20 mass% relative to the old asphalt content. In this specification, the term "asphalt mixture" includes new asphalt mixtures and recycled asphalt mixtures described below.

[0035] (Recycled asphalt mixture) Recycled asphalt mix is ​​an asphalt mix that contains recycled aggregate.

[0036] Recycled aggregate is recycled from asphalt pavement and the like. Recycled aggregate is obtained, for example, by demolishing asphalt pavement that has been paved with an asphalt mixture containing aggregate and asphalt, crushing the demolished asphalt pavement, and classifying it. Recycled aggregate usually contains old asphalt, which is asphalt derived from the recycled asphalt pavement. The content of the old asphalt in the recycled aggregate is, for example, about 1 to 10% by mass. The properties of the old asphalt are usually worse than those of new asphalt.

[0037] The recycled aggregate content of the recycled asphalt mixture is selected appropriately based on the characteristics of the recycled aggregate used and the performance required of the recycled asphalt mixture, and is the ratio of recycled aggregate (including the attached old asphalt) to the total aggregate, and is more than 0% by mass and 100% by mass or less.

[0038] (Installation process) In the installation step, a test piece 3 of asphalt mixture is placed between the base body 1 and the working body 2 so as to be sandwiched therebetween (see FIG. 1).

[0039] Fig. 1 is a schematic diagram of an apparatus used in one embodiment of the evaluation method of the present invention, as viewed from the side. Fig. 2 is a schematic diagram of a specimen used in one embodiment of the evaluation method of the present invention, where (A) is a diagram viewed from the side and (B) is a diagram viewed from below.

[0040] The specimen 3 and the device may be the same as those used in the SCB test method, for example.

[0041] The specimen 3 used in the SCB test method is a semi-cylinder made of asphalt mixture with a diameter of 149 to 151 mm and a thickness of 49 to 51 mm, and has a notch 4 formed radially from the center of the circle, measuring 14 to 16 mm in length and 1.0 to 2.0 mm in width (see Figure 2). The semi-cylinder can be obtained, for example, by placing the asphalt mixture in a mold and compacting it into a semi-cylinder, or by cutting the compacted asphalt mixture into a semi-cylinder with a cutter.

[0042] The device used for the SCB test method includes a base body 1 on which two rollers 5, each 25 mm in diameter, are arranged at an interval of 119.9 to 120.1 mm, and an acting body 2 having a semi-cylindrical portion 6 with a curvature radius of 12.45 mm to 12.55 mm as a contact surface with the test piece 3 (see Figure 1).

[0043] When using an apparatus similar to that used in the SCB test method, specifically, as shown in Figure 1, in the installation step, the specimen 3 is placed with the curved surface of the semi-cylindrical specimen 3 facing upward so that the straight side of the specimen 3 comes into contact with the two rollers 5 of the base 1, and the acting body 2 is placed so that a load can be applied to the curved side of the specimen 3 at the contact surface of the acting body 2.

[0044] As the test specimen 3 and the equipment, instead of those used in the SCB test method, for example, those similar to those used in the Marshall stability test can also be used (see Figure 3).

[0045] FIG. 3 is a conceptual diagram of the device used in the Marshall stability test, where (A) in FIG. 3 is a view of the device from the side, and (B) in FIG. 3 is a view of the device from diagonally above.

[0046] The specimen 3 used in the Marshall stability test is, for example, a sample obtained by compacting an asphalt mixture into a cylindrical shape. The size of the cylinder of the specimen 3 is, for example, 101.4 mm to 101.8 mm in diameter and 62.2 mm to 64.8 mm in thickness. The specimen 3 can be obtained, for example, by putting the asphalt mixture into a mold and compacting it into a cylindrical shape, or by cutting the compacted asphalt mixture into a cylindrical shape with a cutter.

[0047] In FIG. 3, the specimen 3 is arranged so that the circumferential portion of the specimen 3 is in contact with the base body 1 and the working body 2 so that a load can be applied in the diameter direction of the cylinder of the specimen 3.

[0048] (Loading process) In the loading step, the acting body 2 is moved toward the base body 1, and the displacement value x of the acting body 2 relative to the base body 1 and the load value F(x) at the displacement value x are measured. For example, the load value F(x) at the displacement value x can be measured using an apparatus similar to that used in the SCB test method (see Figures 1 and 3).

[0049] The movement of the working body 2 toward the base body 1 can be carried out at a displacement speed of, for example, 50 mm / min. The specimen 3 gradually deforms and breaks. The load value F(x) gradually increases after the start of measurement, reaches a maximum value when the specimen 3 breaks, and then decreases to 0.1 kN. Measurement of the displacement value x and the load value F(x) is continued until the load value F(x) reaches at least 0.1 kN.

[0050] (Fracture energy calculation process) In the fracture energy calculation step, fracture energy E shown in the following formula (1) is calculated.

number

[0051] In the compression test method described in Non-Patent Document 1, the displacement value x and the load value F(x) are measured, and as shown in Figure 4, the compression coefficient is calculated from the maximum load at the time of failure of the test specimen 3 and the displacement value x at that time, and the physical properties are evaluated based on the compression coefficient.

[0052] In contrast, in the present invention, in the fracture energy calculation step, the area of ​​the range shown in gray between the axis of displacement and the load curve in the graph of FIG. 5, i.e., the fracture energy E shown in formula (1), is calculated, and evaluation is performed based on that fracture energy E in the evaluation step described below.

[0053] The fracture energy E can also be calculated in the same way as in the SCB test.

[0054] (Evaluation process) In the evaluation process, the physical properties of the asphalt mixture are evaluated based on the fracture energy E.

[0055] In the aforementioned "Standard Test Method for Determining the Fracture Potential of Asphalt Mixtures by Flexibility Index Testing," the flexibility index (FI) is calculated by dividing the fracture energy E calculated in the SCB test by the post-peak slope of the load curve, and the physical properties of the asphalt mixture are evaluated based on whether or not the FI is equal to or greater than a specific value. In contrast, in the evaluation process according to the present invention, the physical properties of the asphalt mixture are evaluated based on whether or not the fracture energy E of the asphalt mixture being evaluated itself satisfies specific conditions.

[0056] The evaluation can be carried out based on, for example, the recycled aggregate content m and the fracture energy E of the asphalt mixture.

[0057] More specifically, the evaluation is carried out in the following manner.

[0058] 1) First, determine the evaluation criteria in advance using the following procedure. (i) In advance, an additive capable of adjusting the penetration is added to the recycled aggregate to be used in the recycled asphalt mixture to be evaluated, thereby producing recycled aggregate with a penetration adjusted to a specific value. (b) Multiple recycled asphalt mixtures are produced by mixing new aggregate and new asphalt with recycled aggregate adjusted to the specific penetration described above at multiple levels of recycled aggregate mixing ratio m. c) Measure the fracture energy E for each asphalt mixture. d) The fracture energy E is calculated as a function of the recycled aggregate mixing ratio m as a variable using the following equation (2): E=am+b (2) By approximating the function to a linear function shown below, we can find the constant slope a and the constant intercept b. 2) In the evaluation process, the fracture energy E of the recycled asphalt mixture to be evaluated is measured, and the fracture energy E is calculated using the following equation (3), which is expressed by the slope a and intercept b mentioned above. E≧am+b (3) (m is the recycled aggregate mix ratio m of the recycled asphalt mixture being evaluated.) Recycled asphalt mixtures are evaluated based on this standard.

[0059] The conventional pavement recycling handbook states that recycled aggregate with a penetration of 20 or higher can be used in recycled asphalt mixtures. This standard prohibits the use of recycled aggregate with a penetration of less than 20. However, when focusing on the fracture energy E of the asphalt mixture, even if recycled aggregate with a penetration of less than 20 is used, if it is modified, it is possible to obtain an asphalt mixture of the same quality as one using recycled aggregate with a penetration of 20 or higher. Therefore, by evaluating an asphalt mixture based on the fracture energy E, it is possible to evaluate a recycled asphalt mixture of the same quality as a conventional recycled asphalt mixture, even if it uses non-standard recycled aggregate with a penetration of less than 20, which was previously not permitted for use.

[0060] Furthermore, if recycled asphalt mixtures with fracture energy E that satisfies formula (3) are used as paving materials, it is possible to produce pavements that meet the quality standards of conventional pavements that use recycled aggregate with a penetration of 20 or more.

[0061] Here, when calculating the constant slope a and constant intercept b in equation (2), the penetration for adjusting the recycled aggregate can be set to 20, but the penetration can be changed depending on the quality required for the recycled asphalt mixture being evaluated.

[0062] (Example) The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0063] (Production of recycled aggregate) An asphalt mixture was prepared using aggregate with the properties shown in Table 1 and asphalt (Polymer Modified Type II As; Nichireki Corporation, Polyphalt SS, hereafter sometimes referred to as "Modified Type II") with the properties shown in Table 2. The aggregate blend ratio and composite gradation of the aggregate are shown in Table 3.

[0064] [Table 1]

[0065] No. 6 crushed stone; manufactured by Tokyo Lime Industry Co., Ltd. No. 7 crushed stone; manufactured by Tokyo Lime Industry Co., Ltd. Coarse sand; manufactured by Seibu Construction Materials Co., Ltd. Stone powder; manufactured by Okutama Kogyo Co., Ltd. Polymer Modified Type II As; Nichireki Co., Ltd., Polyphalt SS To reduce variations in quality due to sampling errors, No. 6 crushed stone was divided into two classes (13-10 mm, 10-5 mm). No. 6 crushed stone with sizes of 13.2 mm or larger and 4.75 mm or smaller, No. 7 crushed stone with sizes of 4.75 mm or larger and 2.36 mm or smaller, and coarse sand with sizes of 2.36 mm or larger were removed.

[0066] [Table 2]

[0067] [Table 3]

[0068] Next, recycled aggregate was produced from the prepared asphalt mixture. 7.5 kg of the asphalt mixture was spread evenly in a 36 cm x 24 cm bat and cured in a drying oven at 110°C for a specified time to deteriorate the asphalt mixture and produce recycled aggregate. As shown in Table 4, recycled aggregate with penetrations of 14, 20, and 27 was produced by changing the curing time.

[0069] [Table 4]

[0070] (Preparation of asphalt mixture samples) Next, the new aggregate was mixed with the recycled aggregate with penetrations of 14, 20, and 27 at recycled aggregate mixing ratios of 30%, 50%, or 70% to produce aggregate samples (Aggregate Samples 1 to 9). Table 5 shows the ratio of the new aggregate, the ratio of recycled aggregate with penetrations of 14, 20, and 27, and the composite grading for each aggregate sample.

[0071] [Table 5]

[0072] Next, straight asphalt as new asphalt and RDEX (manufactured by ENEOS Corporation) as a reclamation additive were added to the produced aggregate samples (aggregate samples 1-9) so that the total amount (total asphalt) of the old asphalt, reclamation additive, and straight asphalt was 5% to 7% by mass, to produce asphalt mixture samples (asphalt mixture samples 1-9). Additionally, an asphalt mixture sample was produced by adding 60 / 80 straight asphalt to the new aggregate at a ratio of 5% to 7% by mass (asphalt mixture sample 10). Table 6 shows the amount of new asphalt added (optimal asphalt amount) and Marshall property values ​​for asphalt mixture samples 1-10. Table 7 shows the property values ​​of straight asphalt (60 / 80). Table 8 shows the property values ​​of the reclamation additive RDEX.

[0073] [Table 6]

[0074] [Table 7]

[0075] [Table 8]

[0076] (Asphalt Mixture Flexibility Index (FI) Evaluation) Specimens 3 for SCB tests were prepared using the manufactured asphalt mixture samples (asphalt mixture samples 1–10), and SCB tests were performed to calculate the flexibility index (FI). The test conditions were a test temperature of 25°C, a loading rate of 50 mm / min, a span length of 120 mm, a specimen diameter of 150 mm, a specimen thickness of 50 mm, a notch depth of 15 mm, and a notch width of 1.5 mm. Figure 6 shows a graph of the flexibility index (FI) versus recycled aggregate mix ratio. Figure 6 reveals that as the recycled aggregate mix ratio increased from 0% to 30%, 50%, and 70%, the flexibility index (FI) increased and decreased without any consistent trend. Therefore, it was difficult to determine the appropriate recycled aggregate mix ratio using an evaluation method based on the flexibility index (FI).

[0077] (Evaluation based on fracture energy of asphalt mixture) In the following examples, in relation to the use of recycled aggregate, the fracture energy E, calculated from the integral of the displacement and load in the SCB test, is used to evaluate the physical properties of asphalt mixtures (containing asphalt and new aggregate and / or recycled aggregate). This fracture energy E is related to the flexural strength and tensile strength of the asphalt mixture, and is an index that can also be used to evaluate the retention of tensile strength after the yield point has been exceeded.

[0078] Figure 7 shows the relationship between the fracture energy E obtained from the data used to calculate the flexibility index (FI) described above and the recycled aggregate mixing ratio m.

[0079] Figure 7 clearly shows that the fracture energy E tends to decrease as the recycled aggregate mixing ratio m increases or the recycled aggregate penetration decreases. Therefore, by determining a threshold value for fracture energy E, it is possible to evaluate the appropriate values ​​for the recycled aggregate mixing ratio m and the recycled aggregate penetration.

[0080] Next, the threshold value of the fracture energy E is determined.

[0081] The Pavement Regeneration Handbook states that recycled aggregate with a penetration of 20 or higher can be used in recycled asphalt mixtures. This means that the recycled aggregate has the physical properties necessary for use in recycled asphalt mixtures. Therefore, if a recycled asphalt mixture maintains the fracture energy required for recycled aggregate with a penetration of 20, it can be interpreted as having properties that meet the existing standards. Figure 8 shows a graph of fracture energy E versus recycled aggregate penetration, plotted from the data in Figure 7. The fracture energy E for a penetration of 20 for each recycled aggregate mix ratio is 1860 when the recycled aggregate mix ratio is 30%, 1560 when the recycled aggregate mix ratio is 50%, and 1200 when the recycled aggregate mix ratio is 70%, as shown in Figure 8. Furthermore, the fracture energy E for a 0% recycled aggregate mix ratio is 2440, as calculated for asphalt mixture sample 10.

[0082] When the penetration is 20, the recycled aggregate mix ratio m and the four values ​​of fracture energy E (E, m) = (0, 2440), (30, 1860), (50, 1560) and (70, 1200) are approximated to a linear function to find the slope a and intercept b of Equation 2. The slope a is -17 and the intercept b = 2423. Each point and the linear function are shown in Figure 9. The grey part of Figure 9 is the following equation 4. E(m)≧-17m+2423 (4) It is a region that satisfies the following.

[0083] It can be estimated that an asphalt mixture that satisfies Equation 4 has physical properties equivalent to those of an asphalt mixture made with recycled aggregate with a penetration of 20 or more in terms of fracture energy E.

[0084] Next, using recycled aggregate equivalent to that used in producing asphalt mixture samples 1 to 9, a predetermined amount of recycled additive was added, new aggregate was mixed at a predetermined recycled aggregate mix ratio, and a predetermined amount of new asphalt was added to produce 30 types of recycled asphalt mixtures 1 to 30. Typical compositions of these recycled asphalt mixtures are shown in Tables 9 and 10. Asphalt mixture samples S1 to S10 in Table 10 are asphalt mixtures that used aggregate samples S1 to S10 in Table 9, respectively.

[0085] [Table 9]

[0086] [Table 10]

[0087] SCB tests were conducted on the manufactured recycled asphalt mixtures 1 to 30 to determine the fracture energy E. When the recycled aggregate mix ratio m and fracture energy E of each recycled asphalt mixture were plotted in Figure 9, the results were scattered across the graph, as shown in Figure 10. Therefore, by measuring and judging the fracture energy E of the recycled asphalt mixture, the quality of the mixture can be properly evaluated.

[0088] The quality of recycled asphalt mixtures 1 to 30 was evaluated based on whether they satisfied formula 4, which is calculated based on the fracture energy E and the recycled aggregate blend ratio m. Recycled asphalt mixtures that satisfy formula 4 were judged to have physical properties equivalent to those with a fracture energy E of 20 or more, even if the recycled aggregate used has a penetration of less than 20.

[0089] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, the above-described embodiments are intended to explain the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are considered to be within the scope of the present invention. [Explanation of symbols]

[0090] 1: Base 2:Agent 3: Specimen 4: Notch 5: Roller 6: Semi-cylindrical part

Claims

1. A method for evaluating properties of an asphalt mixture, comprising: An installation step of placing the asphalt mixture specimen between a base body and an operating body so as to sandwich the specimen; a loading step of moving the acting body toward the base body and measuring a displacement value x of the acting body relative to the base body and a load value F(x) at the displacement value x; A fracture energy calculation step of calculating fracture energy E represented by the following formula (1); [Equation 1] (Here, x1 represents the displacement value x at which the load becomes 0.1 kN after the specimen breaks.) An evaluation step of evaluating the physical properties of the asphalt mixture based on the fracture energy E; Including, In the evaluation step, the physical properties of the asphalt mixture are evaluated based on the recycled aggregate mix ratio m of the aggregate in the asphalt mixture and the fracture energy E, A plurality of asphalt mixtures are produced by adding an additive capable of adjusting the penetration to the recycled aggregate used in the recycled asphalt mixture to be evaluated, and mixing the recycled aggregate with the adjusted penetration at a plurality of levels of the recycled aggregate blending ratio m. The fracture energy E is measured for each of the asphalt mixtures, and the fracture energy E, which is a variable of the recycled aggregate blending ratio m, is calculated using the following formula (2): E=am+b...(2) The following equation (3) is expressed by a slope a and an intercept b of a constant obtained by approximating to a linear function represented by E≧am+b...(3) This is a method for evaluating an asphalt mixture, which evaluates whether the recycled asphalt mixture satisfies the same quality as the recycled asphalt mixture in terms of penetration, based on the above criteria.

2. The method for evaluating an asphalt mixture according to claim 1, wherein the penetration is 20.

3. In the installation step, a semi-cylindrical specimen made of the asphalt mixture having a diameter of 150 mm and a thickness of 49 mm to 51 mm, and having a notch formed radially from the center of the circle having a length of 14 mm to 16 mm and a width of 1.0 mm to 2.0 mm, is used as the specimen, As the substrate, two rollers with a diameter of 25 mm were used, spaced 120 mm apart. the working body has a semi-cylindrical portion having a radius of curvature of 12.45 mm to 12.55 mm as a contact surface with the test piece, The specimen is placed on the roller of the base so that the straight side of the specimen is in contact with the roller, and the working body is placed so that the curved side of the specimen can apply a load at the contact surface of the working body; 3. The method for evaluating an asphalt mixture according to claim 1, wherein in the loading step, the working body is moved toward the base body at a displacement rate of 50 mm / min to deform the specimen.

4. In the installation step, a cylindrically compacted sample of the asphalt mixture having a diameter of 101.4 mm to 101.8 mm and a thickness of 62.2 mm to 64.8 mm is used as the test piece, and the test piece is arranged so that the circumferential portion is in contact with the base body and the acting body so that a load can be applied in the diameter direction of the test piece; In the loading step, the working body is moved toward the base body at a displacement speed of 50 mm / min to deform the specimen. The method for evaluating an asphalt mixture according to claim 1 or 2.

5. A paving method in which the recycled asphalt mixture satisfying the criteria of formula (3) in the asphalt mixture evaluation method according to claim 1 or 2 is used as a paving material.

Images