A test method for determining the mixing state of new and recycled materials in recycled porous asphalt mixtures

Abstract

This invention discloses a test method for determining the mixing state of new and old aggregates in recycled porous asphalt mixtures. The method uses long-afterglow material as the new aggregate, which is mixed with new asphalt and RAP in a predetermined ratio to form a recycled porous asphalt mixture as the test group. The RAP is extracted and recovered to obtain old asphalt and old aggregate. New and old asphalt are then mixed in a predetermined ratio, and the old and new aggregates are added to form a recycled porous asphalt mixture as the control group. Marshall specimens are formed from the mixtures of the test and control groups, and the specimens are horizontally cut to obtain horizontal cross-sections. The horizontal cross-sections of the test and control groups are illuminated with a light source, and luminescent photographs of the horizontal cross-sections are taken in a dark environment. The mixing state of the new and old aggregates in the recycled porous asphalt mixture is calculated by comparing the test and control groups. This invention can accurately determine the mixing state of new and old aggregates in recycled porous asphalt mixtures.

Description

Technical Field

[0001] This invention belongs to the field of thermally recycled asphalt pavement technology, specifically relating to a test method for determining the mixing state of new and old materials in recycled porous asphalt mixtures. Background Technology

[0002] In the production and application of hot recycled asphalt mixtures, recycled asphalt pavement material (RAP) is mixed, paved, and compacted with new asphalt and new aggregates under certain high-temperature conditions. The blending behavior of RAP, as the old material, with the new asphalt and new aggregates, significantly impacts the pavement performance of the mixture. Applying RAP to the preparation of recycled porous asphalt mixtures represents a new approach and direction for the recycling of old materials. However, the extent to which RAP can be fully incorporated into the recycled porous asphalt mixture significantly affects its weather resistance, flowability, and resistance to plastic deformation. Therefore, accurately determining the blending state of the old and new materials in recycled porous asphalt mixtures has attracted considerable attention from researchers both domestically and internationally.

[0003] Chinese Patent CN111474157B discloses a method and system for determining the degree of fusion in recycled asphalt mixtures. It analyzes the fusion of new and old asphalt in recycled asphalt mixtures by combining fluorescence microscopy and layer-by-layer stripping methods. However, its drawback is that the observed asphalt state is detached from the mixture, and the test results cannot represent the asphalt distribution on the mixture surface, nor can they characterize the distribution of new and old aggregates. Chinese Patent CN104406993B discloses a method for detecting the degree of fusion of new and old asphalt in hot recycled asphalt mixtures. It uses industrial computed tomography (CT) technology and image analysis software to quantitatively detect the fusion of new and old asphalt. However, its drawback is that the poor bonding between iron powder and asphalt prevents it from reflecting the true asphalt distribution and cannot characterize the distribution of new and old aggregates. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a test method for determining the mixing state of new and old materials in recycled porous asphalt mixtures. This method can accurately determine the mixing state of new and old materials in recycled porous asphalt mixtures, thereby guiding the composition design of recycled porous asphalt mixtures and determining production process parameters based on the test results, so as to improve the performance and service life of recycled porous asphalt pavements.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] A test method for determining the mixing state of recycled porous asphalt mixtures, comprising:

[0007] Long afterglow material was used as a new aggregate, and recycled porous asphalt mixture was prepared by mixing it with new asphalt and RAP in a set ratio as a test group.

[0008] RAP is extracted and recycled to obtain old asphalt and old aggregate. Then, the new asphalt and the old asphalt are mixed according to the set ratio, and the old aggregate and the new aggregate are added to prepare a recycled porous asphalt mixture as a control group.

[0009] Marshall specimens were formed from the mixtures of the experimental group and the control group, respectively, and the Marshall specimens were horizontally cut to obtain the horizontal cross-sections of the specimens of the experimental group and the control group.

[0010] Illuminate the horizontal cross-sections of the test and control groups with a light source, and after the long afterglow material absorbs the light, take luminescent photographs of the horizontal cross-sections of the test and control groups in a dark environment.

[0011] By comparing the luminescent photographs of the horizontal cross-sections of the specimens from the experimental group and the control group, the mixing state of the new and old materials in the recycled porous asphalt mixture was calculated.

[0012] Furthermore, the experimental group, which uses long-afterglow materials as new aggregates and mixes them with new asphalt and RAP in a set ratio to prepare recycled porous asphalt mixtures, includes:

[0013] The new asphalt is heated to 170°C to 180°C;

[0014] The long afterglow material is heated to 15°C above the mixing temperature;

[0015] The RAP is heated to 110℃~120℃;

[0016] After the heated long afterglow material and the RAP were mixed evenly, the heated new asphalt was added and mixed until uniform, resulting in a recycled porous asphalt mixture as the test group.

[0017] Further, the step of extracting and recovering RAP to obtain old asphalt and old aggregate, then mixing the new asphalt and the old asphalt according to the set ratio, and then adding the old aggregate and the new aggregate to prepare a recycled porous asphalt mixture as a control group, includes:

[0018] The old asphalt and the new asphalt are mixed evenly to form a mixed asphalt, and then heated to 170℃~180℃.

[0019] The long afterglow material is heated to 15°C above the mixing temperature;

[0020] After the heated long afterglow material and the old mineral aggregate are mixed evenly, the heated mixed asphalt is added and mixed until uniform, resulting in a recycled porous asphalt mixture as a control group. The quality of the mixed asphalt is consistent with the quality of the new asphalt in the test group.

[0021] Further, the step of illuminating the horizontal cross-sections of the test and control groups with a light source, causing the long-afterglow material to absorb light, and then taking luminescent photographs of the horizontal cross-sections of the test and control groups in a dark environment includes:

[0022] The horizontal cross-sections of the test specimens from both the experimental and control groups were simultaneously placed in an ultraviolet analyzer. The specimens were excited and irradiated with 300nm-400nm ultraviolet light for 5-10 minutes, and then the excitation light source was turned off. The luminescence photographs of the two specimens were taken at a fixed angle in a dark environment.

[0023] Further, the comparison of the horizontal cross-sectional luminescence photographs of the specimens from the experimental group and the control group, and the calculation of the mixing state of the new and old materials in the recycled porous asphalt mixture, includes:

[0024] The coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photographs of the specimens in the experimental group and the control group were calculated respectively.

[0025] The mixing state of new and old materials in recycled porous asphalt mixtures was calculated using the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photographs of the test group specimens and the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photographs of the control group specimens. The calculation formula is as follows:

[0026]

[0027] In the formula, β is the degree of mixing between the old and new ore, %; CV1 is the coefficient of variation of the fluorescent dot area in the horizontal cross-section luminescent photograph of the test specimen, %; and CV2 is the coefficient of variation of the fluorescent dot area in the horizontal cross-section luminescent photograph of the control specimen, %.

[0028] Furthermore, the method for calculating the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photograph of the specimen in the experimental group includes:

[0029] The image processing software Image-Pro Plus was used to divide the horizontal cross-sectional luminescent photographs of the specimens in the experimental group into several equal parts.

[0030] The area of ​​each equally divided fluorescent dot region in the horizontal cross-sectional luminescent photograph of the test specimen was calculated using Image-Pro Plus image processing software. The standard deviation and average value of the fluorescent dot region area of ​​the test group were then calculated based on the area of ​​each equally divided fluorescent dot region.

[0031] Using the standard deviation and mean value of the fluorescent dot area in the experimental group, the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photographs of the specimens in the experimental group was calculated using the following formula:

[0032]

[0033] In the formula, σ1 is the standard deviation of the area of ​​the fluorescent spot region in the experimental group; μ1 is the average area of ​​the fluorescent spot region in the experimental group.

[0034] Furthermore, the method for calculating the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photograph of the control group specimen includes:

[0035] The horizontal cross-sectional luminescent photographs of the control group specimens were divided into several equal parts using Image-Pro Plus image processing software.

[0036] The area of ​​each equally divided fluorescent dot region in the horizontal cross-sectional luminescent photograph of the control group specimen was calculated using Image-Pro Plus image processing software. The standard deviation and average value of the fluorescent dot region area of ​​the control group were then calculated based on the area of ​​each equally divided fluorescent dot region.

[0037] Using the standard deviation and mean value of the fluorescent dot area in the control group, the coefficient of variation of the fluorescent dot area in the horizontal cross-section luminescent photograph of the control group specimen was calculated. The calculation formula is as follows:

[0038]

[0039] In the formula, σ2 is the standard deviation of the fluorescent spot area in the control group; μ2 is the average area of ​​the fluorescent spot area in the control group.

[0040] Furthermore, the long afterglow material is a photoluminescent material based on silicate.

[0041] Furthermore, the particle size range of the long afterglow material is 0–16 mm.

[0042] Furthermore, the new asphalt is a high-viscosity modified asphalt, in which the modifiers can be observed by a fluorescence microscope.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] This invention provides a test method for determining the mixing state of new and old aggregates in recycled porous asphalt mixtures. The method uses long-afterglow material as the new aggregate, which is mixed with new asphalt and RAP in a predetermined ratio to form a recycled porous asphalt mixture as the test group. The RAP is extracted and recovered to obtain old asphalt and old aggregate. New asphalt and old asphalt are then mixed in a predetermined ratio, and the old and new aggregates are added to form a recycled porous asphalt mixture as the control group. Marshall specimens are formed from the mixtures of the test group and the control group, and the Marshall specimens are horizontally cut to obtain horizontal cross-sections of the specimens. The horizontal cross-sections of the specimens of the test group and the control group are illuminated with a light source, allowing the long-afterglow material to absorb light. Luminous photographs of the horizontal cross-sections of the specimens of the test group and the control group are then taken in a dark environment. By comparing the luminous photographs of the horizontal cross-sections of the specimens of the test group and the control group, the mixing state of the new and old aggregates in the recycled porous asphalt mixture is calculated. A higher value indicates a better mixing state of the new and old aggregates and superior uniformity of the mixture. By applying this test method, the mixing state of new and old materials in recycled porous asphalt mixtures can be accurately determined, and the distribution state of new and old materials in recycled porous asphalt mixtures can be clarified. Based on the test results, the composition design of recycled porous asphalt mixtures and the determination of production process parameters can be guided to improve the performance and service life of recycled porous asphalt pavements.

[0045] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 This is a flowchart of a test method for determining the mixing state of new and old materials in recycled porous asphalt mixtures according to the present invention;

[0048] Figure 2 Images showing the luminescence effects of the experimental and control groups in Example 1 of this invention;

[0049] Figure 3 Images showing the luminescence effects of the experimental and control groups in Example 1 of this invention;

[0050] Figure 4 These are images showing the luminescence effects of the experimental group and the control group in Example 1 of this invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] As a specific embodiment of the present invention, such as Figure 1 As shown, a test method for determining the mixing state of new and recycled porous asphalt mixtures includes the following steps:

[0053] S1. Using long afterglow material as new aggregate, and mixing it with new asphalt and RAP in a set ratio to prepare recycled porous asphalt mixture as the test group;

[0054] S2. Extract and recycle RAP to obtain old asphalt and old aggregate. Then, mix new asphalt and old asphalt thoroughly according to the above-mentioned set ratio, and mix them together with old aggregate and new aggregate to prepare recycled porous asphalt mixture as a control group.

[0055] S3. The mixtures of the experimental group and the control group were molded into Marshall specimens, and the Marshall specimens were horizontally cut to obtain the horizontal cross sections of the specimens of the experimental group and the control group.

[0056] S4. Illuminate the horizontal cross-sections of the test and control groups with a light source to make the long-afterglow material absorb light, and then take luminescent photographs of the horizontal cross-sections of the test and control groups in a dark environment.

[0057] S5. Compare the horizontal cross-sectional luminescent photographs of the specimens from the test group and the control group, and calculate the mixing state of the new and old materials in the recycled porous asphalt mixture.

[0058] In one embodiment, the experiment was conducted in the following manner:

[0059] (1) Experimental preparation

[0060] ① The RAP is extracted and recovered to obtain old asphalt and old aggregate, and the gradation and asphalt content of the RAP are obtained;

[0061] ② The test group placed the new asphalt in an oven and heated it to 170-180℃; the control group mixed the old asphalt and new asphalt in a certain proportion to form a mixed asphalt, and then heated it in an oven to 170-180℃.

[0062] ③ The experimental group weighed out long afterglow materials of various specifications as new ore according to the mix design results, and heated them in an oven to 15°C above the mixing temperature for later use. The required amount of RAP was weighed out and heated in an oven to 110-120°C. The control group weighed out long afterglow materials of various specifications as new ore according to the same mix design, and weighed out the same mass of old ore as the experimental group, and heated them in an oven to 15°C above the mixing temperature for later use.

[0063] (2) Mixing and shaping

[0064] ① In the test group, the heated new aggregate and the required amount of RAP were poured into a preheated mixing pot, mixed evenly, and then new asphalt was added and mixed for an appropriate time. Then mineral powder was added and mixed until uniform. In the control group, the heated new aggregate and old aggregate were poured into a mixing pot, mixed evenly, and then preheated quantitative mixed asphalt was added according to the mix design results. The mass of the mixed asphalt was consistent with the asphalt content of the test group. After mixing for an appropriate time, mineral powder was added and mixed until uniform.

[0065] ②The following operations were performed on both the test group and the control group: the well-mixed hot recycled asphalt mixture was molded into Marshall specimens, and after demolding, it was cut along the horizontal plane to obtain the horizontal cross section of the specimen;

[0066] (3) Observation of mixing effect

[0067] The horizontal cross-sections of the test and control specimens were placed in an ultraviolet analyzer simultaneously. The specimens were excited and irradiated with 300nm-400nm ultraviolet light for 5min-10min, and then the excitation light source was turned off. The luminescence effect images of the two specimens were taken at a fixed angle in a completely dark environment.

[0068] (4) Calculation of degree of mixing

[0069] Image-Pro Plus image processing software was used to calculate the coefficient of variation (CV) of the fluorescent dot area in the cross-sectional images of the specimens from the experimental and control groups. The β of the mixed state of new and old materials in the recycled porous asphalt mixture is the ratio of (1-CV) between the experimental and control groups, as shown in the following formula:

[0070]

[0071] Where: β is the degree of mixing between new and old ore, %; CV1 is the coefficient of variation of the fluorescent dot area in the horizontal cross-section luminescent photograph of the test specimen, %; CV2 is the coefficient of variation of the fluorescent dot area in the horizontal cross-section luminescent photograph of the control specimen, %;

[0072] In this embodiment, the coefficient of variation for the area of ​​the fluorescent dot region is calculated by dividing the cross-sectional area of ​​the circular specimen into eight equal sectors, using Image-Pro Plus image processing software to calculate the fluorescent area of ​​each sector, and then calculating the standard deviation (σ) and mean (μ) of the fluorescent area of ​​each sector to obtain the coefficient of variation, as shown in the following formula:

[0073]

[0074] Where: CV is the coefficient of variation of the fluorescent dot area in the luminescent photograph of the horizontal cross-section of the specimen, %; σ is the standard deviation of the fluorescent dot area in the luminescent photograph of the horizontal cross-section of the specimen; μ is the average fluorescent dot area in the luminescent photograph of the horizontal cross-section of the specimen.

[0075] Preferably, the long afterglow material is a photoluminescent material based on silicate, which absorbs energy under excitation light and can continue to emit light in the dark after excitation stops. The particle size range is 0-16mm, and the technical specifications are consistent with those of commonly used mineral materials, meeting the requirements of the national ministerial technical standard JTG F40-2004.

[0076] Preferably, the new asphalt is a high-viscosity modified asphalt, in which the modifiers can be observed by a fluorescence microscope.

[0077] It should be noted that the mix proportions and materials of the experimental group and the control group are completely identical. The experimental group represents the actual mixing state of the hot recycled asphalt mixture, while the control group represents the fully mixed state of the hot recycled asphalt mixture.

[0078] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0079] Example 1

[0080] According to the technical solution of the present invention, this embodiment provides a test method for determining the mixing state of new and old aggregates in recycled porous asphalt mixture. Taking PAC-16 type recycled porous asphalt mixture as an example, the RAP content is 10%, the RAP asphalt content after RAP extraction and recovery is 3.7%, the old aggregate proportion is shown in Table 1, and after mix design, the total asphalt content of the recycled mixture is 4.9%, and the new aggregate proportion is shown in Table 1.

[0081] Table 1. Proportioning of New and Old Mineral Materials

[0082]

[0083] The specific implementation steps of the above embodiments are as follows:

[0084] (1) Experimental preparation

[0085] ① The RAP was extracted and recovered to obtain old asphalt and old aggregate. The proportion of old aggregate is shown in Table 1. The RAP asphalt content is 3.7%.

[0086] ② The test group prepared high-viscosity asphalt as new asphalt and heated it to 170°C in an oven; the control group mixed old asphalt and new asphalt in a ratio of 11.5:142.1 to form a mixed asphalt and heated it to 170°C in an oven.

[0087] ③ The experimental group weighed out long afterglow materials of various specifications as new ore according to the mix design results, with a total mass of 2700g. It was placed in an oven and heated to 170℃ for later use. 300g of RAP was weighed out and placed in an oven and heated to 110℃. The control group weighed out long afterglow materials of various specifications as new ore according to the same mix design, and weighed out old ore of the same mass as the experimental group. It was placed in an oven and heated to 170℃ for later use.

[0088] (2) Mixing and shaping

[0089] ① In the experimental group, heated new aggregate and RAP were poured into a preheated mixing pot, mixed evenly, and then 142.1g of new asphalt was added and mixed for an appropriate time. Then, mineral powder was added and the mixture was continued until it was uniform. In the control group, heated new aggregate and old aggregate were poured into a mixing pot, mixed evenly, and then 153.6g of preheated mixed asphalt was added according to the mix design. After mixing for an appropriate time, mineral powder was added and the mixture was continued until it was uniform.

[0090] ②The following operations were performed on both the test group and the control group: the well-mixed hot recycled asphalt mixture was molded into two Marshall specimens, and after demolding, it was cut along the horizontal plane to obtain the horizontal cross section of the specimen;

[0091] (3) Observation of mixing effect

[0092] The horizontal cross-sections of the test and control specimens were simultaneously placed in a UV analyzer. The specimens were irradiated with 300mm UV light for 5 minutes, after which the excitation source was turned off. The luminescence effect images of the two specimens were taken at a fixed angle in complete darkness. The luminescence effect images of the test and control groups are shown below. Figure 2 As shown in the figure, the white particles represent the distribution of the new ore in the horizontal section of the Marshall specimen.

[0093] (4) Calculation of degree of mixing

[0094] The cross-sectional area of ​​the circular specimen was divided into eight equal sectors, forming eight sectors of equal area. The fluorescence area of ​​each sector was calculated using Image-Pro Plus image processing software. Subsequently, the standard deviation (σ) and mean (μ) of the fluorescence area of ​​each sector were calculated. The coefficient of variation (CV) of the fluorescence area of ​​the cross-section images of the specimens in the experimental and control groups was calculated, as shown in the following formula:

[0095]

[0096] In the formula:

[0097] CV1—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photograph of the specimen in the experimental group, %;

[0098] σ1—Standard deviation of the area of ​​fluorescent spots in the experimental group;

[0099] μ1 — Average area of ​​fluorescent spot region in the experimental group;

[0100]

[0101] In the formula:

[0102] CV2—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photographs of the specimens in the experimental group, %;

[0103] σ² — Standard deviation of the area of ​​fluorescent spot region in the experimental group;

[0104] μ2 — ​​Average area of ​​fluorescent spot region in the experimental group.

[0105] The mixing state β of new and recycled materials in recycled porous asphalt mixtures is the ratio of (1-Cv) between the experimental group and the control group, as shown in the following formula:

[0106]

[0107] In the formula:

[0108] β—Degree of mixing between new and old ore, %;

[0109] CV1—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photograph of the specimen in the experimental group, %;

[0110] CV2—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photographs of the specimens in the experimental group, %;

[0111] Calculations show that the fusion state of recycled porous asphalt mixtures is β = 77.0% for both new and old materials.

[0112] Example 2

[0113] According to the technical solution of the present invention, this embodiment provides a test method for determining the mixing state of new and old aggregates in recycled porous asphalt mixtures. Taking PAC-16 type recycled porous asphalt mixture as an example, the RAP content is 20%, the RAP asphalt content after RAP extraction and recovery is 3.7%, the old aggregate proportion is shown in Table 1, and after mix design, the total asphalt content of the recycled mixture is 5.0%, and the new aggregate proportion is shown in Table 2.

[0114] Table 2. Proportioning of New and Old Mineral Materials

[0115]

[0116] The specific implementation steps of the above embodiments are as follows:

[0117] (1) Experimental preparation

[0118] ① The RAP was extracted and recovered to obtain old asphalt and old aggregate. The proportion of old aggregate is shown in Table 1. The RAP asphalt content is 3.7%.

[0119] ② The test group prepared high-viscosity asphalt as new asphalt and heated it to 180°C in an oven; the control group mixed old asphalt and new asphalt in a ratio of 23.0:134.9 to form a mixed asphalt and heated it to 180°C in an oven.

[0120] ③ The experimental group weighed out 2400g of long afterglow material of each specification as new ore according to the mix design results. It was placed in an oven and heated to 180℃ for later use. 600g of RAP was weighed out and heated to 120℃ in an oven. The control group weighed out 2400g of long afterglow material of each specification as new ore according to the same mix design. It also weighed out the same mass of old ore as the experimental group and heated to 180℃ in an oven for later use.

[0121] (2) Mixing and shaping

[0122] ① In the experimental group, heated new aggregate and RAP were poured into a preheated mixing pot, mixed evenly, and then 134.9g of new asphalt was added and mixed for an appropriate time. Then, mineral powder was added and the mixture was continued until it was uniform. In the control group, heated new aggregate and old aggregate were poured into a mixing pot, mixed evenly, and then 157.9g of preheated mixed asphalt was added according to the mix design. After mixing for an appropriate time, mineral powder was added and the mixture was continued until it was uniform.

[0123] ②The following operations were performed on both the test group and the control group: the well-mixed hot recycled asphalt mixture was molded into two Marshall specimens, and after demolding, it was cut along the horizontal plane to obtain the horizontal cross section of the specimen;

[0124] (3) Observation of mixing effect

[0125] The horizontal cross-sections of the test and control specimens were simultaneously placed in a UV analyzer. The specimens were irradiated with 400mm UV light for 10 minutes, after which the excitation source was turned off. The luminescence effect images of the two specimens were taken at a fixed angle in complete darkness. The luminescence effect images of the test and control groups are shown below. Figure 3 As shown in the figure, the white particles represent the distribution of the new ore in the horizontal section of the Marshall specimen.

[0126] (4) Calculation of degree of mixing

[0127] The cross-sectional area of ​​the circular specimen was divided into eight equal sectors, forming eight sectors of equal area. The fluorescence area of ​​each sector was calculated using Image-Pro Plus image processing software. Subsequently, the standard deviation (σ) and mean (μ) of the fluorescence area of ​​each sector were calculated. The coefficient of variation (CV) of the fluorescence area of ​​the cross-section images of the specimens in the experimental and control groups was calculated, as shown in the following formula:

[0128]

[0129] In the formula:

[0130] CV1—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photograph of the specimen in the experimental group, %;

[0131] σ1—Standard deviation of the area of ​​fluorescent spots in the experimental group;

[0132] μ1 — Average area of ​​fluorescent spot region in the experimental group;

[0133]

[0134] In the formula:

[0135] CV2—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photographs of the specimens in the experimental group, %;

[0136] σ² — Standard deviation of the area of ​​fluorescent spot region in the experimental group;

[0137] μ2 — ​​Average area of ​​fluorescent spot region in the experimental group;

[0138] The mixing state β of new and recycled materials in recycled porous asphalt mixtures is the ratio of (1-Cv) between the experimental group and the control group, as shown in the following formula:

[0139]

[0140] In the formula:

[0141] β—Degree of mixing between new and old ore, %;

[0142] CV1—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photograph of the specimen in the experimental group, %;

[0143] CV2—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photographs of the specimens in the experimental group, %;

[0144] Calculations show that the fusion state of recycled porous asphalt mixtures is β = 67.6%.

[0145] Example 3

[0146] According to the technical solution of the present invention, this embodiment provides a test method for determining the mixing state of new and old aggregates in recycled porous asphalt mixtures. Taking PAC-16 type recycled porous asphalt mixture as an example, the RAP content is 30%, the RAP asphalt content after RAP extraction and recovery is 3.7%, the old aggregate proportion is shown in Table 3, and after mix design, the total asphalt content of the recycled mixture is 5.2%, and the new aggregate proportion is shown in Table 3.

[0147] Table 3. Proportioning of New and Old Mineral Materials

[0148]

[0149]

[0150] The specific implementation steps of the above embodiments are as follows:

[0151] (1) Experimental preparation

[0152] ① The RAP was extracted and recovered to obtain old asphalt and old aggregate. The proportion of old aggregate is shown in Table 1. The RAP asphalt content is 3.7%.

[0153] ② The test group prepared high-viscosity asphalt as new asphalt and heated it to 175°C in an oven; the control group mixed old asphalt and new asphalt in a ratio of 34.6:130.0 to form a mixed asphalt and heated it to 175°C in an oven.

[0154] ③ The experimental group weighed out 2100g of long afterglow material of each specification as new ore according to the mix design results. It was placed in an oven and heated to 175℃ for later use. 900g of RAP was weighed out and heated to 120℃ in an oven. The control group weighed out 2100g of long afterglow material of each specification as new ore according to the same mix design. It also weighed out the same mass of old ore as the experimental group and heated to 175℃ in an oven for later use.

[0155] (2) Mixing and shaping

[0156] ① In the experimental group, heated new aggregate and RAP were poured into a preheated mixing pot, mixed evenly, and then 130.0g of new asphalt was added and mixed for an appropriate time. Then, mineral powder was added and the mixture was continued until it was uniform. In the control group, heated new aggregate and old aggregate were poured into a mixing pot, mixed evenly, and then 164.6g of preheated mixed asphalt was added according to the mix design. After mixing for an appropriate time, mineral powder was added and the mixture was continued until it was uniform.

[0157] ②The following operations were performed on both the test group and the control group: the well-mixed hot recycled asphalt mixture was molded into two Marshall specimens, and after demolding, it was cut along the horizontal plane to obtain the horizontal cross section of the specimen;

[0158] (3) Observation of mixing effect

[0159] The horizontal cross-sections of the test and control specimens were simultaneously placed in a UV analyzer. The specimens were irradiated with 365 nm UV light for 5 minutes, after which the excitation source was turned off. The luminescence effect images of the two specimens were taken at a fixed angle in a completely dark environment. The luminescence effect images of the test and control groups are shown below. Figure 4 As shown in the figure, the white particles represent the distribution of the new ore in the horizontal section of the Marshall specimen.

[0160] (4) Calculation of degree of mixing

[0161] The cross-sectional area of ​​the circular specimen was divided into eight equal sectors, forming eight sectors of equal area. The fluorescence area of ​​each sector was calculated using Image-Pro Plus image processing software. Subsequently, the standard deviation (σ) and mean (μ) of the fluorescence area of ​​each sector were calculated. The coefficient of variation (CV) of the fluorescence area of ​​the cross-section images of the specimens in the experimental and control groups was calculated, as shown in the following formula:

[0162]

[0163] In the formula:

[0164] CV1—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photograph of the specimen in the experimental group, %;

[0165] σ1—Standard deviation of the area of ​​fluorescent spots in the experimental group;

[0166] μ1 — Average area of ​​fluorescent spot region in the experimental group;

[0167]

[0168] In the formula:

[0169] CV2—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photographs of the specimens in the experimental group, %;

[0170] σ² — Standard deviation of the area of ​​fluorescent spot region in the experimental group;

[0171] μ2 — ​​Average area of ​​fluorescent spot region in the experimental group;

[0172] The mixing state β of new and recycled materials in recycled porous asphalt mixtures is the ratio of (1-Cv) between the experimental group and the control group, as shown in the following formula:

[0173]

[0174] In the formula:

[0175] β—Degree of mixing between new and old ore, %;

[0176] CV1—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photograph of the specimen in the experimental group, %;

[0177] CV2—Coefficient of variation of the area of ​​fluorescent spot regions in the horizontal cross-section luminescent photographs of the specimens in the experimental group, %;

[0178] Calculations show that the fusion state of recycled porous asphalt mixtures is β = 57.0%.

[0179] The above test results show that when the RAP content is 10% to 30%, the new and old materials of the recycled porous asphalt mixture are mixed during the mixing and compaction process, and the degree of mixing is about 60% to 80%. The mixing state of the new and old materials decreases with the increase of RAP content. The test method of the present invention realizes in-situ measurement in the mixture, the results are reliable, and it can accurately determine the mixing state of the new and old materials of the recycled porous asphalt mixture under various production conditions.

[0180] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A test method for determining the mixing state of new and recycled materials in recycled porous asphalt mixtures, characterized in that, include: Long afterglow material was used as a new aggregate, and recycled porous asphalt mixture was prepared by mixing it with new asphalt and RAP in a set ratio as a test group. RAP is extracted and recycled to obtain old asphalt and old aggregate. Then, the new asphalt and the old asphalt are mixed according to the set ratio, and the old aggregate and the new aggregate are added to prepare a recycled porous asphalt mixture as a control group. Marshall specimens were formed from the mixtures of the experimental group and the control group, respectively, and the Marshall specimens were horizontally cut to obtain the horizontal cross-sections of the specimens of the experimental group and the control group. Illuminate the horizontal cross-sections of the test and control groups with a light source, and after the long afterglow material absorbs the light, take luminescent photographs of the horizontal cross-sections of the test and control groups in a dark environment. By comparing the luminescent photographs of the horizontal cross-sections of the specimens from the experimental group and the control group, the mixing state of the new and old materials in the recycled porous asphalt mixture was calculated. The comparison of the horizontal cross-sectional luminescence photographs of the specimens from the experimental group and the control group, and the calculation of the mixing state of the new and old materials in the recycled porous asphalt mixture, include: The coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photographs of the specimens in the experimental group and the control group were calculated respectively. The mixing state of new and old materials in recycled porous asphalt mixtures was calculated using the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photographs of the test group specimens and the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photographs of the control group specimens. The calculation formula is as follows: In the formula, β The degree of mixing between new and old ore, % CV 1 represents the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photograph of the specimen in the experimental group, % . CV 2 represents the coefficient of variation of the fluorescent dot area in the horizontal cross-section luminescent photograph of the control group specimen, %.

2. The test method for determining the mixing state of new and old materials in recycled porous asphalt mixture according to claim 1, characterized in that, The experimental group uses long-afterglow materials as new aggregates, and mixes them with new asphalt and RAP in a set ratio to prepare recycled porous asphalt mixtures, including: The new asphalt is heated to 170℃~180℃; The long afterglow material is heated to 15°C above the mixing temperature; The RAP is heated to 110℃~120℃; After the heated long afterglow material and the RAP were mixed evenly, the heated new asphalt was added and mixed until uniform, resulting in a recycled porous asphalt mixture as the test group.

3. The test method for determining the mixing state of new and old materials in recycled porous asphalt mixture according to claim 1, characterized in that, The process involves extracting and recovering RAP to obtain old asphalt and old aggregate, then mixing the new asphalt and old asphalt according to the predetermined ratio, and finally adding the old aggregate and new aggregate to prepare a recycled porous asphalt mixture as a control group. This includes: The old asphalt and the new asphalt are mixed evenly to form a mixed asphalt, and then heated to 170℃~180℃. The long afterglow material is heated to 15°C above the mixing temperature; After the heated long afterglow material and the old mineral aggregate are mixed evenly, the heated mixed asphalt is added and mixed until uniform, resulting in a recycled porous asphalt mixture as a control group. The quality of the mixed asphalt is consistent with the quality of the new asphalt in the test group.

4. The test method for determining the mixing state of new and old materials in recycled porous asphalt mixture according to claim 1, characterized in that, The step of illuminating the horizontal cross-sections of the test specimens in the experimental and control groups with a light source, causing the long-afterglow material to absorb light, and then taking luminescent photographs of the horizontal cross-sections of the test specimens in a dark environment includes: The horizontal cross-sections of the test specimens from both the experimental and control groups were simultaneously placed in an ultraviolet analyzer. The specimens were excited and irradiated with 300nm~400nm ultraviolet light for 5min~10min, and then the excitation light source was turned off. The luminescence photographs of the two specimens were taken at a fixed angle in a dark environment.

5. The test method for determining the mixing state of new and old materials in recycled porous asphalt mixture according to claim 1, characterized in that, The method for calculating the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photographs of the specimens in the experimental group includes: The image processing software Image-Pro Plus was used to divide the horizontal cross-sectional luminescent photographs of the specimens in the experimental group into several equal parts. The area of ​​each equally divided fluorescent dot region in the horizontal cross-sectional luminescent photograph of the test specimen was calculated using Image-Pro Plus image processing software. The standard deviation and average value of the fluorescent dot region area of ​​the test group were then calculated based on the area of ​​each equally divided fluorescent dot region. Using the standard deviation and mean value of the fluorescent dot area in the experimental group, the coefficient of variation of the fluorescent dot area in the horizontal cross-sectional luminescent photographs of the specimens in the experimental group was calculated using the following formula: In the formula, σ 1 represents the standard deviation of the area of ​​the fluorescent spot region in the experimental group; μ 1 represents the average area of ​​the fluorescent spot region in the experimental group.

6. The test method for determining the mixing state of new and old materials in recycled porous asphalt mixture according to claim 1, characterized in that, The method for calculating the coefficient of variation of the fluorescence dot area in the horizontal cross-sectional luminescent photograph of the control group specimen includes: The horizontal cross-sectional luminescent photographs of the control group specimens were divided into several equal parts using Image-Pro Plus image processing software. The area of ​​each equally divided fluorescent dot region in the horizontal cross-sectional luminescent photograph of the control group specimen was calculated using Image-Pro Plus image processing software. The standard deviation and average value of the fluorescent dot region area of ​​the control group were then calculated based on the area of ​​each equally divided fluorescent dot region. Using the standard deviation and mean value of the fluorescent dot area in the control group, the coefficient of variation of the fluorescent dot area in the horizontal cross-section luminescent photograph of the control group specimen was calculated. The calculation formula is as follows: In the formula, σ 2 represents the standard deviation of the fluorescent dot area in the control group; μ 2 represents the average area of ​​the fluorescent spot region in the control group.

7. The test method for determining the mixing state of new and old materials in recycled porous asphalt mixture according to claim 1, characterized in that, The long afterglow material is a photoluminescent material based on silicate.

8. The test method for determining the mixing state of new and old materials in recycled porous asphalt mixture according to claim 7, characterized in that, The particle size range of the long afterglow material is 0~16mm.

9. The test method for determining the mixing state of new and old materials in recycled porous asphalt mixture according to claim 1, characterized in that, The new asphalt is a high-viscosity modified asphalt.

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