Method and system for evaluating the degree of fusion of recycled asphalt mixture during hot mix process

Abstract

This invention relates to the field of asphalt pavement regeneration technology, and more particularly to a method and system for evaluating the degree of fusion of regenerated asphalt mixtures during hot mix. The system uses infrared spectroscopy to acquire spectral data of the mixed asphalt, calculates the carbonyl index, and establishes a relationship between the proportion of old asphalt and the carbonyl index. The system also measures the old asphalt content through extraction. Infrared thermal imaging is used to acquire a cross-sectional temperature map of the mixture, analyzes the temperature distribution to calculate the proportion of low-temperature areas, and combines mathematical models to assess the degree of fusion. Through real-time data acquisition and analysis, the system achieves rapid and accurate assessment of the degree of fusion between new and old asphalt, optimizes the production process of regenerated asphalt mixtures, and improves the material's performance and quality control efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of asphalt pavement regeneration, and in particular to a method and system for evaluating the degree of fusion of regenerated asphalt mixtures during hot mixing. Background Art

[0002] Asphalt pavement occupies an important position in modern transportation infrastructure, especially in high-grade pavement, which accounts for more than 90%. However, after long-term use, the performance of asphalt pavement deteriorates and diseases appear, affecting driving safety and comfort, so it needs to be maintained and renovated. With the improvement of environmental protection requirements, the maintenance of asphalt pavement gradually tends to adopt asphalt pavement regeneration technology. The core of regeneration technology lies in the effective utilization of waste asphalt mixture to reduce resource waste and environmental pollution. The existing technology (Chinese invention patent, publication number: CN114324983B, name: Quantification method and system for the degree of fusion of new and old asphalt in hot-regenerated asphalt mixture) quantitatively evaluates the degree of fusion of new and old asphalt by testing the micro-scale modulus of recycled asphalt and nano-tracing methods. Although these methods can reflect the fusion situation, they rely on indoor tests and cannot be evaluated in real time and quickly at the production site, which limits the process optimization and quality control of recycled asphalt mixture in actual engineering. Summary of the Invention

[0003] In response to the many problems existing in the above-mentioned prior art, the present invention provides a method and system for evaluating the degree of fusion of recycled asphalt mixtures during hot mixing. The present invention determines the carbonyl index of completely mixed asphalt through infrared spectroscopy technology, thereby constructing a relationship model between the proportion of old asphalt and the carbonyl index. The cross-sectional temperature data of the recycled asphalt mixture is collected in combination with thermal imaging technology. By calculating the area ratio of the low-temperature area, the degree of fusion of the new and old asphalt is finally evaluated. The present invention can not only obtain the temperature distribution of the mixture and the fusion of the new and old asphalt in real time, but also construct a mathematical model based on the data to realize automated quantitative analysis. The implementation of the present invention helps to optimize the production process of the recycled asphalt mixture and improve the overall performance stability of the mixture.

[0004] like Figure 1 As shown, the method for evaluating the degree of fusion of recycled asphalt mixture in the hot mix process includes the following steps:

[0005] The infrared spectra of completely mixed asphalt with different ratios of new and old asphalt were obtained by infrared spectrometer, the carbonyl index was calculated, and a linear relationship equation between the ratio of old asphalt and the carbonyl index was constructed;

[0006] The old asphalt content in the waste asphalt mixture is tested by extraction method, and the mass proportion of the old asphalt in the recycled asphalt mixture is calculated;

[0007] An infrared thermal imager is used to collect cross-sectional temperature images of the recycled asphalt mixture after hot mixing to obtain temperature distribution data;

[0008] The mixed asphalt on the surface of the cubic tracer aggregate was recovered by extraction and rotary evaporation. The carbonyl index was calculated using infrared spectroscopy, and the proportion of old asphalt in the mixed asphalt was calculated based on a linear relationship equation.

[0009] According to the heat transfer model between materials, the theoretical temperature values ​​reached by different materials during the hot mixing process are calculated as the temperature threshold;

[0010] Taking the temperature threshold as the standard, calculate the proportion of pixels below the threshold in the temperature image of the recycled asphalt mixture cross section, and obtain the area proportion of the low-temperature area;

[0011] Based on the dataset of the degree of fusion between new and old asphalt and the area ratio of low-temperature areas in thermal images, a relationship model between the two was constructed and linear regression analysis was performed.

[0012] Based on the thermal image acquisition results and the low-temperature area ratio relationship model, the degree of fusion of new and old asphalt in the recycled asphalt mixture is calculated and evaluated.

[0013] Preferably, the method for calculating the carbonyl index includes:

[0014] Obtain the infrared spectrum of the fully mixed asphalt through an infrared spectrometer;

[0015] Carbonyl Index I C＝O The calculation is as follows:

[0016]

[0017] Among them, A C＝O is the area of ​​the carbonyl functional group region; A Referance is the area of ​​the reference functional group region.

[0018] Preferably, the mass ratio of old asphalt in the recycled asphalt mixture is calculated by the following formula:

[0019]

[0020] Among them, x RAP is the mass ratio of old asphalt to total asphalt; C RHMA is the designed asphalt content of recycled asphalt mixture; P RAPi is the usage ratio of waste asphalt mixture of size i; C RAPi is the old asphalt content in the waste asphalt mixture of size i.

[0021] Preferably, the old asphalt ratio of the asphalt mixed on the surface of the cubic tracer aggregate is x iThe calculation is based on the carbonyl index I C＝O , determined by the following relational expression:

[0022] I C＝O =a×x i +b

[0023] Among them, x i is the proportion of old asphalt in the fully mixed asphalt; a and b are the specific values ​​of the constant terms in the linear regression model.

[0024] Preferably, the theoretical temperature value T f Calculated by the following formula:

[0025]

[0026] Among them, T f C is the theoretical temperature that can be reached after the materials in the recycled asphalt mixture are mixed with each other; i is the specific heat capacity of the i-th material; m i is the quality of the i-th material; T i is the initial mixing temperature of the i-th material.

[0027] Preferably, the low temperature area accounts for P T Calculated by the following formula:

[0028]

[0029] Among them, P T T is the area ratio of low temperature area in the thermal imaging image of the recycled asphalt mixture cross section; min T is the lowest temperature in the thermal imaging image of the recycled asphalt mixture cross section; f T is the theoretical temperature that can be reached after mixing different materials in the recycled asphalt mixture; max The highest temperature in the thermal imaging image of the recycled asphalt mixture cross section; N i is the number of pixels corresponding to temperature i in the thermal imaging image of the recycled asphalt mixture cross section.

[0030] Preferably, the degree of fusion of new and old asphalt is Y BD The proportion of low temperature area x PT The relationship model is expressed by the following linear regression equation:

[0031] Y BD =d×x PT +e

[0032] Among them, Y BD is the calculated value of the mixing degree in the recycled asphalt mixture; x PTis the area ratio of the low-temperature area in the cross-sectional temperature image obtained by the infrared thermal imager during the mixing process of the recycled asphalt mixture; d and e are the specific values ​​of the constant terms in the linear regression model.

[0033] Preferably, the test environment conditions of the infrared spectrum tester include: the test environment temperature is 25℃±0.5℃, the test resolution is 4cm -1 , the number of background and sample scans was 32 times, and the wave number range was 4000 cm -1 Up to 400cm -1 .

[0034] Preferably, the infrared thermal imager is used to collect cross-sectional temperature images of the recycled asphalt mixture in real time, and process the images through a thermal image data analysis module to determine the area ratio of the low-temperature area.

[0035] like Figure 2 As shown, a system for implementing the method for evaluating the degree of fusion of recycled asphalt mixture in a hot mix process comprises:

[0036] The infrared spectrum testing module is used to obtain infrared spectra of fully mixed asphalt with different ratios of new and old asphalt, calculate the carbonyl index, and construct a linear relationship equation between the ratio of old asphalt and the carbonyl index;

[0037] The extraction analysis module is used to test the old asphalt content in the waste asphalt mixture by extraction method and calculate the mass ratio of the old asphalt in the recycled asphalt mixture;

[0038] Infrared thermal imaging module, used to collect cross-sectional temperature images of recycled asphalt mixture after hot mixing to obtain temperature distribution data;

[0039] The tracer recovery module recovers the mixed asphalt from the surface of the cubic tracer aggregate through extraction and rotary evaporation, calculates the carbonyl index using infrared spectroscopy, and calculates the proportion of old asphalt in the mixed asphalt based on a linear relationship equation;

[0040] The temperature calculation module calculates the theoretical temperature value reached by different materials during the hot mixing process as the temperature threshold based on the heat transfer model between the materials;

[0041] The area analysis module uses the temperature threshold as a standard to calculate the proportion of pixels below the threshold in the temperature image of the recycled asphalt mixture cross section, and obtains the area proportion of the low-temperature area;

[0042] The relationship modeling module builds a relationship model based on the data set of the degree of fusion between new and old asphalt and the area ratio of low-temperature areas in thermal images, and performs linear regression analysis;

[0043] The fusion degree evaluation module calculates and evaluates the fusion degree of new and old asphalt in the recycled asphalt mixture based on the thermal image acquisition results and the low-temperature area ratio relationship model.

[0044] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0045] By introducing infrared spectroscopy and thermal imaging technology, the present invention realizes real-time and accurate evaluation of the degree of integration of new and old asphalt in recycled asphalt mixtures;

[0046] Compared with the existing technology that relies on indoor experiments, the present invention can directly analyze the recycled asphalt mixture production site and quickly provide quantitative results of the degree of fusion;

[0047] By combining infrared spectrum testing with thermal image analysis, the shortcomings of existing technologies in terms of real-time performance and convenience are effectively addressed.

[0048] The present invention also uses a linear regression model to construct a relationship model between the degree of fusion of new and old asphalt and the area ratio of low-temperature areas in thermal imaging images, thereby improving the accuracy and operability of the assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Schematic diagram of the process of the present invention;

[0050] Figure 2 It is a structural block diagram of the system of the present invention;

[0051] Figure 3 The infrared spectrum test results of the old asphalt and SBS modified asphalt used in the embodiment of the present invention;

[0052] Figure 4 Four design gradations of recycled asphalt mixtures used in the embodiments of the present invention;

[0053] Figure 5 This is a thermal image of the cross section of the recycled asphalt mixture after mixing in Solution 1 adopted in the embodiment of the present invention;

[0054] Figure 6 This is a schematic diagram of the statistical results of the temperature distribution in the cross-section thermal image after the mixing of the regenerated asphalt mixture in Solution 1 adopted in the embodiment of the present invention;

[0055] Figure 7 This is a graph showing the degree of fusion of new and old asphalt in the recycled asphalt mixture and the changing trend of the area ratio of the low-temperature area in the thermal image obtained by in-situ measurement in an embodiment of the present invention. DETAILED DESCRIPTION

[0056] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0057] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0058] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0059] The present invention provides a method and system for evaluating the degree of fusion of recycled asphalt mixture during hot mixing, comprising the following steps:

[0060] Step S01: The waste asphalt mixtures used in the present invention have specifications of 0-8 mm, 8-12 mm, and 12-20 mm. The three types of waste asphalt mixtures are dried in an electric blast drying oven at 40°C until the quality remains unchanged, so as to completely remove the moisture in the three types of waste asphalt mixtures.

[0061] 2000 g of the three types of waste asphalt mixtures after drying were weighed respectively, and the old asphalt in the waste asphalt mixtures was recovered by extraction and rotary evaporation.

[0062] The new asphalt in the recycled asphalt mixture is SBS modified asphalt.

[0063] New asphalt and old asphalt are sampled in the ratio of 100%:0%, 70%:30%, 50%:50%, 30%:70% and 0%:100% respectively. The total mass of the new and old asphalts that are completely fused is designed to be 50g. The new asphalt and old asphalt sampled according to the designed ratio are added to a mixing mold. The new and old asphalt in the mold are stirred by a mixer at a speed of 500rpm for no less than 15min to obtain completely fused asphalt.

[0064] The new and old asphalts that are completely fused are sampled according to the test requirements of infrared spectroscopy test. The infrared spectrometer is used. The test environment temperature is 25℃±0.5℃, the test resolution is 4cm-1, the background and sample scan times are 32 times, and the test wave number range is 4000cm-1~400cm-1. According to the above parameter requirements, the infrared spectra of the completely fused asphalt with different ratios of new asphalt and old asphalt are tested respectively. The infrared spectra test results of the old asphalt and SBS modified asphalt are as follows: Figure 4 shown.

[0065] According to formula 1 and combined with the infrared spectrum test results, the carbonyl index of the fully fused asphalt at different fusion ratios of new asphalt and old asphalt was calculated. The results are shown in Table 1.

[0066] Formula 1:

[0067]

[0068] Where, I C＝O is the carbonyl index of the fully fused asphalt; A C＝O A is the area of ​​the carbonyl functional group region, which is the area of ​​the closed region formed by connecting the upper wavelength limit (1722 cm-1) and the lower wavelength limit (1672 cm-1) of the functional group; Referance is the area of ​​the reference functional group region, which is the area of ​​the closed region formed by connecting the upper limit of the reference functional group (3026 cm-1) and the lower limit of the wavelength (2766 cm-1);

[0069] Ratio of old asphalt / % 0 30 50 70 100 Carbonyl index 0.00008853 0.00456 0.00764 0.00938 0.0149

[0070] Table 1 Calculation results of carbonyl index of fully fused asphalt at different fusion ratios of new asphalt and old asphalt

[0071] According to Formula 2, the relationship equation between the proportion of old asphalt in the fully mixed asphalt and the carbonyl index IC=0 with different ratios of new asphalt to old asphalt is constructed:

[0072] Formula 2:

[0073] I C＝O =a×x i +b

[0074] Where x i is the proportion of old asphalt in the fully mixed asphalt; a, b are the specific values ​​of the constant terms in the linear regression model;

[0075] Using the data in Table 1 and formula 2, the mathematical relationship between the old asphalt ratio and the carbonyl index is obtained as follows:

[0076] I C＝O =1.4307×10 -4 ×xi +8.8980×10 -5

[0077] Step S02: 1200g of each of the dried waste asphalt mixtures with sizes of 0-8mm, 8-12mm, and 12-20mm were weighed. Using the extraction method, the extracted aggregate masses of the different sizes of waste asphalt mixtures were measured to be 1133.64g, 1160.28g, and 1159.08g, respectively. The calculated asphalt masses were 66.36g, 39.72g, and 40.92g, respectively. Using Formula 3, the asphalt contents of the 0-8mm, 8-12mm, and 12-20mm waste asphalt mixtures were calculated to be 5.53%, 3.31%, and 3.41%, respectively.

[0078] Formula 3:

[0079]

[0080] Where C RAP is the content of old asphalt in waste asphalt mixture; m1 is the mass of old asphalt in waste asphalt mixture obtained by extraction test; m RAP The total mass of waste asphalt mixture used for the extraction test;

[0081] The proportion of waste asphalt mixture added to the recycled asphalt mixture is designed to be 40%, of which the proportions of 0-8mm, 8-12mm, and 12-20mm waste asphalt mixtures are 13%, 13%, and 14% respectively. Considering four factors that affect the fusion of new and old asphalt in the recycled asphalt mixture, namely gradation type, asphalt content, mixing time, and RAP preheating temperature, the material composition and mixing process parameters of the recycled asphalt mixture are designed. The composition of each parameter is shown in Table 2. The four gradation types in Table 2 are as follows: Figure 4 shown.

[0082]

[0083] Table 2 Design material composition and mixing process parameters of recycled asphalt mixture

[0084] According to the design scheme in Table 2, using Formula 4, it is calculated that the mass proportion of old asphalt contained in the waste asphalt mixture in the recycled asphalt mixture at asphalt contents of 3.7%, 4.0%, 4.3% and 4.6% is 44.3%, 40.8%, 37.9% and 35.3% of the total asphalt respectively.

[0085] Formula 4:

[0086]

[0087] Where x RAPis the mass ratio of old asphalt to total asphalt in recycled asphalt mixture; C RHMA is the designed asphalt content of recycled asphalt mixture; P RAPi is the proportion of waste asphalt mixture of size i in recycled asphalt mixture; C RAPi is the content of old asphalt in the waste asphalt mixture of size i; n is the number of sizes of waste asphalt mixture in the recycled asphalt mixture;

[0088] Step S03: Three types of cubic artificial aggregates are used in the mixing process of the recycled asphalt mixture. The cubic artificial aggregate is limestone, and the limestone aggregates with cube sizes of 13.2±0.5 mm, 16.0±0.5 mm, and 19.0±0.5 mm are obtained by cutting;

[0089] The recycled asphalt mixture consists of waste asphalt mixture, new aggregate, SBS modified asphalt, and mineral powder. These four materials must be heated to the designed preheating temperature before mixing. The preheating temperature for the waste asphalt mixture is shown in Table 2. The preheating temperatures for the new aggregate, SBS modified asphalt, and mineral powder are 195°C, 170°C, and 170°C, respectively. After the various materials have been heated to the designed preheating temperature, the recycled asphalt mixture is mixed. The recycled asphalt mixture mixing process involves first mixing the waste asphalt mixture, then adding new aggregate and new asphalt, and finally adding mineral powder to produce the recycled asphalt mixture. The mixing time for each of the three stages is the same, and the total mixing time is controlled according to the design. In this example, the total mixing times used are 60s, 120s, 150s, and 180s, respectively, corresponding to mixing times of 20s, 40s, 50s, and 60s for each stage, respectively.

[0090] The designed total mixing mass of the recycled asphalt mixture is 5000g. In each scheme of this embodiment, 100g±10g of the three types of cubic limestone artificial aggregates are used, and the total added mass of the cubic limestone artificial aggregates is 300g±30g.

[0091] After three stages of mixing, the recycled asphalt mixture is obtained. The cross-sectional thermal imaging of the recycled asphalt mixture with different design schemes is collected using an infrared thermal imager. Taking the implementation scheme 1 in Table 2 as an example, the thermal imaging results are as follows: Figure 5 shown.

[0092] After the thermal images were collected, cubic tracer aggregates of mixed asphalt formed by mixing new asphalt and old asphalt in recycled asphalt mixtures of different design schemes were obtained in situ by manual selection.

[0093] Step S04: Use extraction and rotary evaporation to recover the mixed asphalt on the surface of the asphalt-coated cubic tracer aggregate of different designs. Use the same infrared spectroscopy test conditions as in step S01 to obtain the infrared spectrum of the mixed asphalt at 4000-400 cm-1. Use formula 1 in step S01 to calculate the carbonyl index I of the mixed asphalt on the surface of the tracer aggregate. C＝O , and adopt the relationship equation between the old asphalt ratio and carbonyl index obtained in step S01 (I C＝O =1.4307×10 -4 ×x i +8.8980×10 -5 ), calculate the proportion of old asphalt in the mixed asphalt, and obtain the mixed asphalt proportion results of 16 design schemes, see Table 3.

[0094] Trial plan Carbonyl index Ratio of old asphalt / % Trial plan Carbonyl index Ratio of old asphalt / % 1 0.00314 21.33 9 0.00439 30.04 2 0.00428 29.27 10 0.00436 29.82 3 0.00389 26.54 11 0.00416 28.48 4 0.00441 30.20 12 0.00417 28.55 5 0.00436 29.87 13 0.00467 32.03 6 0.00385 26.32 14 0.00498 34.21 7 0.00456 31.25 15 0.00366 24.98 8 0.00458 31.42 16 0.00537 36.93

[0095] Table 3 Calculation results of the proportion of mixed asphalt on the surface of tracer aggregate

[0096] According to the calculation results of the mixed asphalt ratio on the surface of the tracer aggregate obtained in Table 3, combined with the mass ratio of old asphalt to total asphalt in the recycled asphalt mixture x RAP Formula 5 is used to calculate the fusion degree BD of new and old asphalt in the recycled asphalt mixture after the hot mixing process. The results are shown in Table 4.

[0097] Formula 5:

[0098]

[0099] Where x a is the calculated value of the proportion of old asphalt in the mixed asphalt; x RAP The calculated value of the mass ratio of old asphalt to total asphalt in the recycled asphalt mixture;

[0100]

[0101] Table 4 Calculation results of the fusion degree of new and old asphalt in recycled asphalt mixture after hot mixing under different test schemes

[0102] Step S05: Analyze the infrared thermal imager data to analyze the temperature distribution characteristics of the recycled asphalt mixture cross section in the 16 test schemes in Table 2. Taking test scheme 1 in Table 2 as an example, the data from the infrared thermal imager are analyzed to obtain the statistical results of the temperature distribution of the recycled asphalt mixture cross section in test scheme 1. Figure 6 shown.

[0103] Testing the specific heat capacities of the SBS modified asphalt and aggregate used in this solution revealed a specific heat capacity of 1.763 kJ / kg·°C for SBS modified asphalt and 0.92 kJ / kg·°C for limestone aggregate. The heating temperatures for the waste asphalt mixture in the recycled asphalt mixture are shown in Table 2. The preheating temperatures for the new aggregate, SBS modified asphalt, and mineral powder were 195°C, 170°C, and 170°C, respectively.

[0104] According to the ratio of waste asphalt mixture, new aggregate and SBS modified asphalt in the recycled asphalt mixture, taking the mixing mass of 5000g recycled asphalt mixture as an example, the theoretical temperature T that different materials in the recycled asphalt mixture can reach when in contact with each other is calculated using Formula 6. f , which is the temperature threshold. The temperature threshold calculation results for the 16 test schemes are shown in Table 5. During the calculation process, the waste asphalt mixture is a mixture of old asphalt and aggregate. The mass ratios of old asphalt and aggregate are considered separately in the calculation of the temperature threshold.

[0105] Formula 6:

[0106]

[0107] Where, T f C is the theoretical temperature that can be reached after different materials in the recycled asphalt mixture are mixed with each other; i is the specific heat capacity of material i in the recycled asphalt mixture; m i is the quality of material i in recycled asphalt mixture; T i is the initial mixing temperature of material i in the recycled asphalt mixture;

[0108]

[0109]

[0110] Table 5 Temperature threshold calculation results

[0111] According to the temperature threshold calculation results in Table 5, combined with the temperature distribution statistics of the cross-section temperature image of the recycled asphalt mixture after hot mixing obtained by the infrared thermal imager, the temperature distribution of the cross-section temperature image below the temperature threshold T is calculated using Formula 7. f The proportion of the number of pixels, that is, the area proportion of the low temperature area in the thermal image P T , the results are shown in Table 6.

[0112] Formula 7:

[0113]

[0114] Where, P T T is the area ratio of low temperature area in the thermal imaging image of the recycled asphalt mixture cross section;min T is the lowest temperature in the thermal imaging image of the recycled asphalt mixture cross section; f T is the theoretical temperature that can be reached after mixing different materials in the recycled asphalt mixture; max The highest temperature in the thermal imaging image of the recycled asphalt mixture cross section; N i is the number of pixels corresponding to temperature i in the thermal imaging image of the recycled asphalt mixture cross section;

[0115]

[0116]

[0117] Table 6 Area ratio of low temperature areas in thermal imaging images

[0118] Step S06: In this embodiment, 16 test schemes are designed as shown in Table 2. The cubic aggregate tracing method is used to obtain mixed asphalt of different schemes and infrared thermal images of in-situ tests. The degree of fusion of the new and old asphalt and the area ratio of the low-temperature area in the thermal image are calculated. The results are shown in Tables 4 and 6, respectively. A data set of the degree of fusion of the new and old asphalt and the area ratio of the low-temperature area in the thermal image is constructed.

[0119] Step S07: Based on the data sets of the degree of fusion of new and old asphalt and the area ratio of low-temperature areas in the thermal image obtained by in-situ measurement in Table 4 and Table 6, the trend of the degree of fusion of new and old asphalt and the area ratio of low-temperature areas in the thermal image obtained by in-situ measurement is as follows: Figure 7 As shown in Figure 2, it can be seen that there is a significant correlation between the degree of fusion between the new and old asphalt and the area ratio of the low-temperature area in the thermal image obtained by in-situ measurement.

[0120] Using the relational modeling module, taking the linear model as an example, a linear model is constructed to determine the proportion of low-temperature areas and the degree of integration between new and old asphalt:

[0121] Y BD =-15.033x PT +152.58

[0122] Where Y BD is the degree of fusion of new and old asphalt in recycled asphalt mixture; x PT The area ratio of low temperature area in the thermal image of the recycled asphalt mixture cross section;

[0123] The goodness of fit of the linear model is 0.88, indicating that there is a significant linear relationship between the proportion of the low-temperature area and the degree of fusion of the new and old asphalt. The linear model can be used to characterize the relationship between the proportion of the low-temperature area and the degree of fusion of the new and old asphalt.

[0124] Step S08: Using the waste asphalt mixture, SBS modified asphalt, new aggregate, and tracer artificial aggregate used in the present invention, six experimental schemes (see Table 7) were designed to verify the accuracy of the linear model in predicting the degree of integration of new and old asphalt in the recycled asphalt mixture. In each of the six experimental schemes, the preheating temperatures of the waste asphalt mixture, SBS modified asphalt, new aggregate (tracer artificial aggregate), and mineral powder were 130°C, 195°C, 170°C, and 170°C, respectively. 5000g of recycled asphalt mixture was prepared. Thermal images of the recycled asphalt mixture cross-sections were collected for each of the six experimental schemes, and in situ samples of artificial aggregate coated with new and old asphalt were obtained.

[0125] Trial plan Grading type Asphalt content / % Mixing time / s 1 Grading I 4.0 60 2 Grading ⅠⅠ 4.0 120 3 Grading ⅠⅠⅠ 4.0 150 4 Grading IV 4.0 180 5 Grading ⅠⅠ 4.3 150 6 Grading ⅠⅠ 4.3 150

[0126] Table 7 Test plan for recycled asphalt mixture

[0127] According to the composition of recycled asphalt mixture in the six test schemes, the ideal temperature threshold of the recycled asphalt mixture section was calculated, and the area ratio of the low-temperature area below the temperature threshold in the thermal imaging image was calculated.

[0128] According to the area ratio of the low-temperature area below the temperature threshold in the thermal imaging image, the relationship model (Y BD =-15.033x PT +152.58), and the predicted values ​​of the fusion degree of new and old asphalt in the recycled asphalt mixture during the hot mix process of the six test schemes were obtained. The results are shown in Table 7.

[0129]

[0130]

[0131] Table 7 Test plan for recycled asphalt mixture

[0132] To verify the accuracy of the prediction results, the artificial aggregate coated with new and old asphalt obtained in situ was subjected to extraction and rotary evaporation to obtain mixed asphalt. The same infrared spectroscopy test conditions as in step S01 were used to obtain the infrared spectrum of the mixed asphalt at 4000-400 cm-1. The carbonyl index I of the mixed asphalt on the surface of the tracer aggregate was calculated using formula 1 in step S01. C＝O , and adopt the relationship equation between the old asphalt ratio and carbonyl index obtained in step S01 (I C＝O =1.4307×10 -4 ×x i +8.8980×10 -5 ), calculate the proportion of old asphalt in the mixed asphalt, and use the BD calculation formula for the fusion degree of new and old asphalt in the recycled asphalt mixture in step S04 to obtain the actual values ​​of the fusion degree of new and old asphalt in the 6 groups of test schemes.

[0133] The actual values ​​of the degree of fusion between the new and old asphalt in the six test schemes were compared with the predicted values ​​in Table 7, and the comparison results are shown in Table 8. It can be seen that the difference between the predicted values ​​and the actual values ​​is small.

[0134] Trial plan Prediction of the degree of fusion between new and old asphalt / % Actual value of the degree of fusion between new and old asphalt / % 1 63.3 65.1 2 75.6 74.2 3 82.7 82.4 4 89.4 88.6 5 85.1 87.9 6 85.1 86.4

[0135] Table 8 Comparison of predicted and actual values ​​of fusion degree in the recycled asphalt mixture test scheme

[0136] The comparison between the predicted and actual fusion levels of the new and old asphalt in the recycled asphalt mixture (Table 8) indicates that the degree of fusion can be indirectly characterized by the proportion of low-temperature areas in the cross-sectional temperature distribution of the recycled asphalt mixture. By constructing a relationship model between the degree of fusion between the new and old asphalt and the proportion of low-temperature areas and collecting thermal images of the cross-sectional temperature of the recycled asphalt mixture, the degree of fusion can be predicted in real time, quantitatively characterizing the degree of fusion between the new and old asphalt.

[0137] By employing the proposed method and system for evaluating the degree of fusion of new and old asphalt in a recycled asphalt mixture during the hot mix process, the degree of fusion of new and old asphalt in the recycled asphalt mixture can be measured in real time during the production process. By capturing a cross-sectional thermal image of the recycled asphalt mixture using an infrared thermal imager and combining it with the proposed method and system, the degree of fusion of new and old asphalt in the recycled asphalt mixture can be predicted, providing a rapid decision-making basis for quality control and process parameter adjustment in the recycled asphalt mixture production.

[0138] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware.

[0139] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for evaluating the degree of fusion of recycled asphalt mixture during hot mix, characterized in that: The following steps are involved: The infrared spectra of completely mixed asphalt with different ratios of new and old asphalt were obtained by infrared spectrometer, the carbonyl index was calculated, and a linear relationship equation between the ratio of old asphalt and the carbonyl index was constructed; The old asphalt content in the waste asphalt mixture is tested by extraction method, and the mass proportion of the old asphalt in the recycled asphalt mixture is calculated; An infrared thermal imager is used to collect cross-sectional temperature images of the recycled asphalt mixture after hot mixing to obtain temperature distribution data; The mixed asphalt on the surface of the cubic tracer aggregate was recovered by extraction and rotary evaporation. The carbonyl index was calculated using infrared spectroscopy, and the proportion of old asphalt in the mixed asphalt was calculated based on a linear relationship equation. According to the heat transfer model between materials, the theoretical temperature values ​​reached by different materials during the hot mixing process are calculated as the temperature threshold; Taking the temperature threshold as the standard, calculate the proportion of pixels below the threshold in the temperature image of the recycled asphalt mixture cross section, and obtain the area proportion of the low-temperature area; Based on the dataset of the degree of fusion between new and old asphalt and the area ratio of low-temperature areas in thermal images, a relationship model between the two was constructed and linear regression analysis was performed. Based on the thermal image acquisition results and the low-temperature area ratio relationship model, the degree of fusion of new and old asphalt in the recycled asphalt mixture is calculated and evaluated.

2. The method for evaluating the degree of fusion of recycled asphalt mixture in hot mix process according to claim 1, characterized in that: The calculation method of the carbonyl index includes: Obtain the infrared spectrum of the fully mixed asphalt through an infrared spectrometer; Carbonyl Index I C＝O The calculation is as follows: Among them, A C＝O is the area of ​​the carbonyl functional group region; A Referance is the area of ​​the reference functional group region.

3. The method according to claim 1, characterized in that The mass ratio of old asphalt in recycled asphalt mixture is calculated by the following formula: Among them, x RAP is the mass ratio of old asphalt to total asphalt; C RHMA is the designed asphalt content of recycled asphalt mixture; P RAPi is the usage ratio of waste asphalt mixture of size i; C RAPi is the old asphalt content in the waste asphalt mixture of size i.

4. The method according to claim 2, characterized in that The old asphalt ratio of the asphalt mixed on the surface of the cube tracer aggregate is x i The calculation is based on the carbonyl index I C＝O , determined by the following relational expression: I C＝O =a×x i +b Among them, x i is the proportion of old asphalt in the fully mixed asphalt; a and b are the specific values ​​of the constant terms in the linear regression model.

5. The method according to claim 1, wherein The theoretical temperature value T f Calculated by the following formula: Among them, T f C is the theoretical temperature that can be reached after the materials in the recycled asphalt mixture are mixed with each other; i is the specific heat capacity of the i-th material; m i is the quality of the i-th material; T i is the initial mixing temperature of the i-th material.

6. The method according to claim 1, characterized in that The proportion of low temperature area P T Calculated by the following formula: Among them, P T T is the area ratio of low temperature area in the thermal imaging image of the recycled asphalt mixture cross section; min T is the lowest temperature in the thermal imaging image of the recycled asphalt mixture cross section; f T is the theoretical temperature that can be reached after mixing different materials in the recycled asphalt mixture; max The highest temperature in the thermal imaging image of the recycled asphalt mixture cross section; N i is the number of pixels corresponding to temperature i in the thermal imaging image of the recycled asphalt mixture cross section.

7. The method according to claim 1, characterized in that The degree of integration of new and old asphalt is Y BD The proportion of low temperature area x PT The relationship model is expressed by the following linear regression equation: AND BD =d×x PT +e Among them, Y BD is the calculated value of the mixing degree in the recycled asphalt mixture; x PT is the area ratio of the low-temperature area in the cross-sectional temperature image obtained by the infrared thermal imager during the mixing process of the recycled asphalt mixture; d and e are the specific values ​​of the constant terms in the linear regression model.

8. The method according to claim 1, characterized in that The test environment conditions of the infrared spectrum tester include: the test environment temperature is 25℃±0.5℃, the test resolution is 4cm -1 , the number of background and sample scans was 32 times, and the wave number range was 4000 cm -1 Up to 400cm -1 .

9. The method according to claim 1, characterized in that The infrared thermal imager is used to collect cross-sectional temperature images of the recycled asphalt mixture in real time, and process the images through a thermal image data analysis module to determine the area ratio of the low-temperature area.

10. A system for implementing the method for evaluating the degree of fusion of recycled asphalt mixture in a hot mix process according to any one of claims 1 to 9, characterized in that: include: The infrared spectrum testing module is used to obtain infrared spectra of fully mixed asphalt with different ratios of new and old asphalt, calculate the carbonyl index, and construct a linear relationship equation between the ratio of old asphalt and the carbonyl index; The extraction analysis module is used to test the old asphalt content in the waste asphalt mixture by extraction method and calculate the mass ratio of the old asphalt in the recycled asphalt mixture; Infrared thermal imaging module, used to collect cross-sectional temperature images of recycled asphalt mixture after hot mixing to obtain temperature distribution data; The tracer recovery module recovers the mixed asphalt from the surface of the cubic tracer aggregate through extraction and rotary evaporation, calculates the carbonyl index using infrared spectroscopy, and calculates the proportion of old asphalt in the mixed asphalt based on a linear relationship equation; The temperature calculation module calculates the theoretical temperature value reached by different materials during the hot mixing process as the temperature threshold based on the heat transfer model between the materials; The area analysis module uses the temperature threshold as a standard to calculate the proportion of pixels below the threshold in the temperature image of the recycled asphalt mixture cross section, and obtains the area proportion of the low-temperature area; The relationship modeling module builds a relationship model based on the data set of the degree of fusion between new and old asphalt and the area ratio of low-temperature areas in thermal images, and performs linear regression analysis; The fusion degree evaluation module calculates and evaluates the fusion degree of new and old asphalt in the recycled asphalt mixture based on the thermal image acquisition results and the low-temperature area ratio relationship model.

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