Method for evaluating stability and sensitivity of recycled asphalt based on secondary aging

Abstract

The invention relates to the technical field of asphalt pavement construction and maintenance, in particular to a method for evaluating the stability and sensitivity of recycled asphalt based on secondary aging. The invention aims to evaluate the performance of the regenerated asphalt through the two aging processes of the asphalt, can effectively evaluate the aging resistance, stability and temperature sensitivity of the regenerated asphalt, and can be used for comparing the regeneration effect of the regenerant, selecting the mixing amount of the regenerant, selecting the regeneration process and the like. According to the evaluation mode, a proper regenerant can be selected according to different pavement environments. The method specifically comprises the following steps: preparing an asphalt sample; carrying out a rheological test; calculating data; and analyzing data. According to the evaluation method, the stability and the temperature sensitivity of the asphalt in the aging process can be evaluated at the same time, the property is defined as the stability sensitivity, the stability sensitivity of the recycled asphalt is evaluated through comparison of the two aging processes of the asphalt according to the property, and the stability and sensitivity improvement amplitude of the regenerant on the aged asphalt can be quantitatively evaluated.

Description

Technical Field

[0001] The invention relates to the technical field of asphalt pavement construction and maintenance, and in particular to a method for evaluating the stability sensitivity of recycled asphalt based on secondary aging. Background Art

[0002] During the long-term use of asphalt pavement, the quality of its constituent materials will change and decay under the influence of vehicle loads and climatic factors, which is mainly manifested in the degradation of mineral aggregate grading and the aging of asphalt. The regeneration technology of asphalt is the reverse process of aging. Regeneration agents can usually be added. Regeneration agents are additives that act on aged asphalt to restore the performance of asphalt. After adding regeneration agents, the relative content of asphaltene can be reduced, and the solubility of soft asphaltene in asphaltene can be increased, the compatibility of asphalt can be improved, and the penetration and ductility of asphalt can be increased, so that it can be restored to or close to its original performance. The methods for evaluating the performance of recycled asphalt are mainly conventional physical performance tests, such as the three major indicators and rheological tests. These tests are also applicable to the evaluation of the re-aging performance of recycled asphalt.

[0003] At present, some scholars have studied the performance changes of recycled asphalt after re-aging to compare the durability of regeneration agents on recycled asphalt. However, scholars' research on the re-aging of recycled asphalt often ignores the detailed changes from the asphalt aging and regeneration process to the re-aging process. In particular, the difference between the re-aging process and the first aging process. The changes in various performance parameters during the aging process of recycled asphalt are different from those during the aging process of the original asphalt, but how to compare the advantages and disadvantages of the two aging processes is still controversial. The field of recycled asphalt lacks a comparative evaluation method that combines the re-aging of recycled asphalt with the first aging performance of original asphalt.

[0004] In view of the above problems, the present invention proposes the concept of stability and sensitivity based on the two aging processes of asphalt. According to the changing process of asphalt aging, regeneration and re-aging, the concept reflects the changes in stability and temperature sensitivity between the second aging process and the first aging process. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for evaluating the stability and sensitivity of regenerated asphalt based on secondary aging. The performance of regenerated asphalt can be evaluated through two aging processes of asphalt. The aging resistance, stability and temperature sensitivity of regenerated asphalt during the aging process can be effectively evaluated, and it can be used to compare the regeneration effect of regeneration agents.

[0006] The second purpose of the present invention is to provide the application of the evaluation method in the fields of selection of regeneration agent, selection of regeneration agent dosage, selection of regeneration process, etc., which can be used to select suitable regeneration agent for different road surface environments.

[0007] The first aspect of the present invention discloses a method for evaluating the stability sensitivity of regenerated asphalt based on secondary aging, comprising the following steps: Preparation of asphalt samples: Select original asphalt to obtain original asphalt sample, perform aging treatment on the original asphalt to obtain primary aged asphalt sample, perform regeneration treatment on the primary aged asphalt to obtain regenerated asphalt sample, perform aging treatment on the regenerated asphalt to obtain secondary aged asphalt sample, wherein the aging treatment and regeneration treatment test process shall be subject to the specification; Conduct rheological tests: Rheological tests were performed on original asphalt samples, primary aged asphalt samples, recycled asphalt samples, and secondary aged asphalt samples, and the test parameters at different temperatures were recorded; Data calculation: Calculate the change rate of the corresponding parameters after two aging processes. The specific process is as follows: Calculate the parameter change rate of the first aging process of asphalt samples; in, Represents the parameters of the once aged asphalt sample, represents the original asphalt sample parameters, Indicates the rate of change of the first aging process; Calculate the rate of change of the second aging process of the asphalt sample; in, represents the secondary aged asphalt sample parameters, Represents the recycled asphalt sample parameters, Indicates the rate of change of the second aging process; Data Analysis: Draw the obtained , The scatter plots at different temperatures are linearly fitted with a linear function, and the slope and variance of the linear function are recorded; Define asphalt stability-sensitivity ratio; C = variance / |slope| Among them, C represents the stability-sensitivity ratio of asphalt, which is used to evaluate the stability and sensitivity of asphalt affected by temperature changes during aging; the slope reflects the sensitivity of the parameter change rate to temperature changes during aging, and the variance reflects the stability of the parameter change rate to temperature changes; Calculate the stability and sensitivity change rate of asphalt during two aging processes; in, It represents the stability-sensitivity ratio of the original asphalt aging process. Indicates the stability-sensitivity ratio of the recycled asphalt aging process, It represents the rate of change of stability and sensitivity during two aging processes.

[0008] Furthermore, when <0, indicating that the stability and sensitivity of asphalt in the secondary aging process is lower than that in the primary aging process, the stability and sensitivity are judged as poor, and the asphalt regeneration effect is poor; when =0, indicating that the stability and sensitivity of the secondary aging process of asphalt is the same as that of the primary aging process, the stability and sensitivity are judged as medium, and the asphalt regeneration effect is medium; when >0, indicating that the stability and sensitivity of asphalt in the secondary aging process is higher than that in the primary aging process. The stability and sensitivity are judged to be excellent, and the asphalt regeneration effect is excellent.

[0009] Furthermore, the rheological test specifically includes: performing a temperature scanning test and a low-temperature bending beam rheological test by a dynamic shear rheometer and a low-temperature bending beam rheometer.

[0010] Furthermore, the test parameters specifically include: recording rutting factor parameters, fatigue factor parameters and low temperature rheological parameters at different temperatures.

[0011] Furthermore, the above-mentioned rheological test can be switched to other rheological evaluation indicators, such as multiple stress creep and recovery tests, etc.; the corresponding test parameters can be switched to other rheological evaluation indicators, such as recording complex modulus, phase angle, recovery rate, irrecoverable creep compliance and other data at different temperatures.

[0012] The second aspect of the present invention discloses the application of the regenerated asphalt stability sensitivity evaluation method based on secondary aging in the fields of selection of regeneration agent, selection of regeneration agent dosage, selection of regeneration process, etc.

[0013] Specifically, when When <0, it means that the corresponding regeneration agent cannot restore the stability of the regenerated asphalt to the level of the original asphalt. The smaller the value, the worse the stability and sensitivity of the regenerated asphalt, and the worse the corresponding regeneration agent effect; =0, it means that the corresponding regeneration agent can restore the stability of the regenerated asphalt to the level of the original asphalt; When >0, it indicates that the corresponding regeneration agent can restore the stability of the regenerated asphalt to a level better than that of the original asphalt. The larger it is, the better the stability and sensitivity of the recycled asphalt will be, and the better the corresponding regeneration agent will be.

[0014] The stability and sensitivity evaluation method of regenerated asphalt based on secondary aging provided by the present invention evaluates the stability and temperature sensitivity of regenerated asphalt by comparing the two aging processes of asphalt. First, the evaluation method can simultaneously evaluate the stability and temperature sensitivity of asphalt during the aging process. Based on this characteristic, the patent of the present invention combines the aging of the original asphalt with the fluctuation amplitude of the aging parameters of the regenerated asphalt, defines this property as stability and sensitivity, and quantitatively evaluates the stability and sensitivity improvement of the regenerator on the aged asphalt. The method is simple to operate and convenient to experiment; secondly, the method used in the patent of the present invention is innovative based on stress sensitivity, which can reflect the sensitivity parameters of asphalt before and after two agings with temperature changes, and the regenerator can be selected for road sections under different temperature environments according to this parameter; finally, the evaluation method can realize the quick and clear determination of the stability and temperature sensitivity of the regenerated asphalt, with accurate determination, clear data, concise process and simple operation.

[0015] The patent of the present invention can be evaluated according to a variety of performance indicators, such as complex modulus and rutting factor in temperature scanning tests, creep rate and creep stiffness under low-temperature bending beam rheological tests, etc. Specifically refer to the amplitude of change of parameters in the first aging process of asphalt. If the amplitude of change of performance parameters in the second aging process is smaller, the stability of the regenerated asphalt is better; if the amplitude of fluctuation of the second aging process of asphalt affected by temperature is close to or smaller than that of the first aging process, it can be considered that the temperature sensitivity of the regenerated asphalt in the aging process is better. The patent of the present invention can also compare the regeneration effects of different regeneration agents, different regeneration processes or different regeneration agent dosages through the changes in the two aging processes of asphalt, so as to select materials or processes in actual projects, evaluate the performance of different regeneration agents, and determine the best regeneration plan. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of scatter point fitting of high temperature rheological test in the present invention; Figure 2 It is a schematic diagram of scatter point fitting of the medium temperature rheological test in the present invention; Figure 3 It is a schematic diagram of scatter point fitting of the low temperature rheological test in the present invention; Figure 4 This is a schematic diagram of the polymer content in the fluorescence microscope test of the present invention; Figure 5 This is a schematic diagram of the fluorescence area ratio in the fluorescence microscope test of the present invention; Figure 6 It is a schematic diagram of the change of functional group area in the Fourier transform infrared spectroscopy test in the present invention.

[0017] Description of the accompanying drawings: The corresponding process of ① in the figure is: the primary aging process from original asphalt to primary aged asphalt; the corresponding process of ② in the figure is: the secondary aging process from regenerated asphalt 1 to secondary aged asphalt 1; the corresponding process of ③ in the figure is: the secondary aging process from regenerated asphalt 2 to secondary aged asphalt 2; the corresponding process of ④ in the figure is: the secondary aging process from regenerated asphalt 3 to secondary aged asphalt 3. DETAILED DESCRIPTION

[0018] The following embodiments and comparative examples are only used to more clearly illustrate the technical solution of the present invention so that those skilled in the art can understand and utilize the present invention well, but not to limit the protection scope of the present invention.

[0019] The names and abbreviations of the experimental methods, production processes, instruments and equipment involved in the embodiments and comparative examples of the present invention are conventional names in the field and are very clear and unambiguous in the relevant application fields. Technicians in the field can understand the conventional process steps and apply the corresponding equipment based on the names and implement them according to conventional conditions or conditions recommended by the manufacturer.

[0020] The various raw materials or reagents used in the embodiments of the present invention and the comparative examples are not particularly limited in terms of their sources, and are all conventional products that can be purchased commercially. The rheological tests involved in the embodiments of the present invention are conducted with reference to existing standards, and the test standards involved in this embodiment are implemented with reference to JTG E20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering".

[0021] In the embodiment of the present invention, ①, ②, ③, and ④ respectively correspond to the following processes: the primary aging process from original asphalt to primary aged asphalt, the secondary aging process from regenerated asphalt 1 to secondary aged asphalt 1, the secondary aging process from regenerated asphalt 2 to secondary aged asphalt 2, and the secondary aging process from regenerated asphalt 3 to secondary aged asphalt 3. The following examples will introduce in detail the application of the evaluation method provided by the present invention in comparing the regeneration effects of different regeneration agents.

[0022] Example 1 High temperature rheological test

[0023] Preparation of asphalt samples: SBS modified asphalt prepared by adding 4% styrene-butadiene-styrene (SBS) to base asphalt is defined as the original asphalt sample. The original asphalt sample is placed in a thin film oven for 5 hours and a pressure aging container for 20 hours to obtain a primary aged asphalt sample. Three commercially available regeneration agents are selected, and the primary aged asphalt sample is heated to 150°C, and the three regeneration agents are added respectively, and a mixer is used to fully stir and regenerate; the samples obtained after the primary aged asphalt sample is regenerated are defined as regenerated asphalt 1, 2, and 3 samples, and the regenerated asphalt 1, 2, and 3 samples are subjected to secondary aging treatment to obtain secondary aged asphalt 1, 2, and 3 samples. The above aging and regeneration test processes shall be subject to the specifications.

[0024] Conduct rheological tests: The original asphalt sample, the first aged asphalt sample, the recycled asphalt samples 1, 2, 3 and the second aged asphalt samples 1, 2, 3 were subjected to temperature scanning rheological tests, and the rutting factor parameters at different temperatures were recorded. The specific parameters are shown in Table 1;

[0025] Data calculation: The change rate of the rutting factor parameters after two aging processes is calculated as follows: Calculate the rate of change during the first aging process of asphalt: in, Represents the rutting factor parameter of a once aged asphalt sample, represents the rutting factor parameter of the original asphalt sample, Indicates the rate of change of the first aging process.

[0026] Calculate the rate of change during the second aging process of asphalt: in, Represents the rutting factor parameter of the secondary aged asphalt sample, Represents the rutting factor parameter of the recycled asphalt sample, Represents the rate of change of the second aging process.

[0027] See Table 2 for specific data parameters:

[0028] Data Analysis: Draw a scatter fit graph, such as Figure 1 As shown: Record the slope and variance of the linear function. The slope reflects the sensitivity of the rate of change parameter to temperature changes during the aging process, and the variance reflects the stability of the rate of change of the parameter to temperature changes. The definition formula is: C = variance / |slope| Among them, C represents the stability-sensitivity ratio of asphalt. The larger the C, the better the stability and temperature sensitivity of the asphalt itself. It is used to evaluate the stability and sensitivity of asphalt affected by temperature changes during the aging process of asphalt.

[0029] Calculate the difference between the secondary aging and primary aging processes and define the formula: in, It represents the stability-sensitivity ratio of the original asphalt aging process. Indicates the stability-sensitivity ratio of the recycled asphalt aging process, It represents the rate of change of stability and sensitivity during two aging processes.

[0030] See Table 3 for specific data parameters:

[0031] Analysis of the stability-sensitivity change rate: ②<0<③<④, indicating that under the high-temperature anti-rutting rheology test, based on the temperature range of 46℃~82℃, the stability-sensitivity change rate of the secondary aged asphalt 1 during the two aging processes is less than 0, indicating that the stability-sensitivity of the regenerated asphalt 1 during the secondary aging process is lower than that of the original asphalt during the first aging process, the stability-sensitivity is poor, and the asphalt regeneration effect is poor; it can also be explained that the regeneration agent 1 cannot restore the stability-sensitivity of the regenerated asphalt 1 to the level of the original asphalt. Compared with the three regeneration agents, the regeneration agent 1 has the poor effect.

[0032] The stability-sensitivity change rate of secondary aged asphalt 2 and secondary aged asphalt 3 during the two aging processes is greater than 0, indicating that the stability-sensitivity of regenerated asphalts 2 and 3 during the secondary aging process is higher than that of the original sample during the one aging process, the stability-sensitivity is excellent, and the asphalt regeneration effect is good; comparing asphalt groups ③ and ④, the stability-sensitivity change rate of secondary aged asphalt 3 during the two aging processes is greater than that of secondary aged asphalt 2 during the two aging processes, indicating that regenerated asphalt 3 has the best stability-sensitivity and the best asphalt regeneration effect, followed by regenerated asphalt 2; it can also be explained that regeneration agents 2 and 3 can restore the stability-sensitivity of regenerated asphalts 2 and 3 to a level better than that of the original asphalt, and the regeneration agent has a good effect, among which regeneration agent 3 has the best regeneration effect, followed by regeneration agent 2.

[0033] Example 2 Medium temperature rheological test The asphalt samples used in Example 2 and Example 1 are the same, and the data calculation method is the same; the difference is that the rheological test in Example 2 is specifically a temperature scanning test, and the selected test parameters are fatigue factor parameters at different temperatures.

[0034] Conduct rheological tests: The original asphalt sample, the first aged asphalt sample, the recycled asphalt samples 1, 2, 3 and the second aged asphalt samples 1, 2, 3 were subjected to temperature scanning rheological tests, and the fatigue factor parameters at different temperatures were recorded. The specific parameters are shown in Table 4;

[0035] Data calculation: Calculate the change rate of fatigue factor parameters after two aging processes. The specific process is as follows: Calculate the rate of change during the first aging process of asphalt: in, Represents the rutting factor parameter of a once aged asphalt sample, represents the rutting factor parameter of the original asphalt sample, Indicates the rate of change of the first aging process.

[0036] Calculate the rate of change during the second aging process of asphalt: in, Represents the rutting factor parameter of the secondary aged asphalt sample, Represents the rutting factor parameter of the recycled asphalt sample, Represents the rate of change of the second aging process.

[0037] See Table 5 for specific data parameters:

[0038] Data Analysis: Draw a scatter fit graph, such as Figure 2 As shown: The slope and variance of the linear function were recorded, and the difference between the secondary aging and primary aging processes was calculated. The stability and sensitivity change rate parameters of the two aging processes are shown in Table 6:

[0039] Analysis of the stability-sensitivity change rate: 0<②<③<④, indicating that under the medium-temperature fatigue rheological test, based on the temperature range of 16℃~40℃, the stability-sensitivity change rate of the secondary aged asphalts 1, 2, and 3 during the two aging processes is greater than 0, indicating that the stability-sensitivity of the regenerated asphalts 1, 2, and 3 during the secondary aging process is higher than that during the one aging process of the original asphalt, with excellent stability-sensitivity and good asphalt regeneration effect; comparing asphalt groups ②, ③, and ④, the stability-sensitivity change rate of the secondary aged asphalt 3 during the two aging processes is greater than that of the secondary aged asphalt 2 and greater than that of the secondary aged asphalt 1, indicating that the stability-sensitivity of the regenerated asphalt 3 is the best, and the asphalt regeneration effect is the best, the regenerated asphalt 2 is the second, and the regenerated asphalt 1 is the worst; it also shows that the three regeneration agents can restore the stability-sensitivity of the regenerated asphalt to a level better than that of the original asphalt, and the regeneration agent has a good effect. Compared with the three regeneration agents, the regeneration effect of the regeneration agent 3 is the best, the regeneration agent 2 is the second, and the regeneration agent 1 is the worst.

[0040] Example 3 Low temperature rheological test

[0041] The asphalt samples used in Example 3 and Example 1 are the same, and the data calculation method is the same; the difference is that the rheological test in Example 3 is specifically a bending beam rheological test, and the selected test parameter is the ratio of the creep rate m to the creep stiffness S at different temperatures, m / S, which is defined in this embodiment as the low-temperature rheological parameter m / S.

[0042] Conduct rheological tests: The original asphalt sample, the first aged asphalt sample, the recycled asphalt samples 1, 2, 3 and the second aged asphalt samples 1, 2, 3 were subjected to bending beam rheological tests, and the ratio m / S parameter of creep rate m to creep stiffness S at different temperatures was recorded. The specific parameters are shown in Table 7;

[0043] Data calculation: The change rate of low-temperature rheological parameters after two aging processes is calculated as follows: Calculate the rate of change during the first aging process of asphalt: in, Represents the rutting factor parameter of a once aged asphalt sample, represents the rutting factor parameter of the original asphalt sample, Indicates the rate of change of the first aging process.

[0044] Calculate the rate of change during the second aging process of asphalt: in, Represents the rutting factor parameter of the secondary aged asphalt sample, Represents the rutting factor parameter of the recycled asphalt sample, Represents the rate of change of the second aging process.

[0045] See Table 8 for specific data parameters:

[0046] Data Analysis: Draw a scatter fit graph, such as Figure 3 As shown: Record the slope and variance of the linear function, calculate the difference between the second aging process and the first aging process, and see Table 9 for the stability and sensitivity change rate parameters of the two aging processes:

[0047] Analysis of the stability-sensitivity change rate: ②<③<④<0, indicating that under the low-temperature anti-cracking rheological test, based on the temperature range of -6℃~-24℃, the stability-sensitivity change rate of the secondary aged asphalts 1, 2, and 3 during the two aging processes is less than 0, indicating that the stability-sensitivity of the regenerated asphalts 1, 2, and 3 during the secondary aging process is lower than that of the original asphalt during the one aging process, with poor stability-sensitivity and poor asphalt regeneration effect; comparing asphalt groups ②, ③, and ④, the stability-sensitivity change rate of the secondary aged asphalt 3 during the two aging processes is greater than that of the secondary aged asphalt 2 and greater than that of the secondary aged asphalt 1, indicating that the stability-sensitivity of the regenerated asphalt 3 is the best, the regenerated asphalt 2 is the second, and the regenerated asphalt 1 is the worst; it also shows that the three regeneration agents cannot restore the stability-sensitivity of the regenerated asphalt to the level of the original asphalt. Compared with the three regeneration agents, the regeneration effect of the regeneration agent 3 is the best, the regeneration agent 2 is the second, and the regeneration agent 1 is the worst.

[0048] Example 4 (Comparative Example 1): Stability

[0049] (1) Verification by fluorescence microscopy

[0050] The asphalt samples used in Example 4 are the same as those used in Example 1. The samples are subjected to stability tests with reference to existing standards. Based on the fact that the original asphalt sample in this application is SBS modified asphalt, a fluorescence microscope test can be carried out. The experiment indicates the SBS polymer content in the asphalt by the distribution area of ​​fluorescence. The polymer contained in this asphalt is the main source of asphalt performance. The higher the polymer content during the aging process, the better the corresponding asphalt performance. The polymer content will be degraded due to aging of the asphalt and regenerated and restored by the repair-type regeneration agent.

[0051] from Figure 4It can be seen that the fluorescent component content of the original asphalt is greatly reduced after the first aging. After adding the regeneration agent to regenerate the asphalt, the changes in the fluorescent component content in the regenerated asphalt 2 and regenerated asphalt 3 are significantly better than the first aging asphalt, and the regeneration effect is good; the fluorescent component content of the regenerated asphalt 1 does not change significantly, and is not much different from the first aging asphalt, and the regeneration effect is poor. After the second aging, the fluorescent component content in the second aging asphalt 2 and 3 is reduced compared with the regenerated asphalt 2 and 3, but is still better than the first aging asphalt, and the regeneration effect is stable; the fluorescent content of the second aging asphalt 1 does not change significantly compared with the regenerated asphalt 1, and the regeneration effect is poor.

[0052] The software was used to calculate the percentage of fluorescence area in each fluorescence image. Figure 5 From the results of fluorescence percentage, during the primary aging process, the fluorescence percentage content decreased by 86.24%; during the secondary aging process, the fluorescence percentage content of secondary aged asphalt 1 decreased by 43.67% compared with recycled asphalt 1, the fluorescence percentage content of secondary aged asphalt 2 decreased by 42.57% compared with recycled asphalt 2, and the fluorescence percentage content of secondary aged asphalt 3 decreased by 66.65% compared with recycled asphalt 3. Compared with the two aging processes, the fluorescence percentage content decrease rate of the secondary aging process is less than that of the primary aging process, indicating that the stability of the secondary aging process of recycled asphalt 1, 2, and 3 is higher than that of the original asphalt in the primary aging process, and the stability of recycled asphalt 1, 2, and 3 is better, which also shows that the three regeneration agents can improve the stability of recycled asphalt to the level of original asphalt. According to the verification of the fluorescence microscope test, it can be seen that the test results are consistent with the results of the evaluation method of this application, and the evaluation method in this application is more accurate and quick.

[0053] Compared with the first-aging asphalt, the fluorescence content of recycled asphalt 1 increased by 0.4%, the fluorescence content of recycled asphalt 2 increased by 145%, and the fluorescence content of recycled asphalt 3 increased by 384% compared with the first-aging asphalt; the fluorescence content of secondary aged asphalt 1 decreased by 43.43% compared with the first-aging asphalt, the fluorescence content of secondary aged asphalt 2 increased by 40.89% compared with the first-aging asphalt, and the fluorescence content of secondary aged asphalt 3 increased by 61.44% compared with the first-aging asphalt. It can be seen that the regeneration effect stability of recycled asphalt 1 is the worst, and there is no regeneration effect after secondary aging; the regeneration effect stability of recycled asphalt 2 and 3 is better, and after secondary aging, they still have stable regeneration effects compared with the first-aging asphalt. Among them, the regeneration effect stability of recycled asphalt 3 is the best, followed by recycled asphalt 2.

[0054] (2) Verification by Fourier transform infrared spectroscopy test

[0055] The stability test of the samples was carried out with reference to the existing standards. The changes of the functional groups in the asphalt before and after aging can be tested by Fourier transform infrared spectroscopy. The higher the area occupancy of the polybutadiene group, the better the performance of the asphalt. The area occupancy of the polybutadiene group in the asphalt sample used in the experiment can be calculated to intuitively prove the aging condition of the asphalt.

[0056] from Figure 6 It can be seen from the figure that the proportion of polybutadiene functional groups in each asphalt sample decreased by 23.92% during the first aging process; during the second aging process, the proportion of polybutadiene functional groups in the second aged asphalt 1 decreased by 20.02% compared with the recycled asphalt 1, the proportion of polybutadiene functional groups in the second aged asphalt 2 decreased by 15.18% compared with the recycled asphalt 2, and the proportion of polybutadiene functional groups in the second aged asphalt 3 decreased by 14.01% compared with the recycled asphalt 3. Compared with the two aging processes, the decrease rate of the proportion of polybutadiene functional groups in the second aging process was less than that in the first aging process, indicating that the stability of the second aging process of recycled asphalt 1, 2, and 3 was higher than that of the original asphalt in the first aging process, and the stability of recycled asphalt 1, 2, and 3 was better, which also showed that the three regeneration agents could improve the stability of the recycled asphalt to the level of the original asphalt. According to the Fourier transform infrared spectroscopy test verification, the test results are consistent with the results of the evaluation method of this application, and the evaluation method in this application is more accurate and quick.

[0057] Compared with the first-aging asphalt, the proportion of polybutadiene functional groups in recycled asphalt 1 was reduced by 4.24%, the proportion of polybutadiene functional groups in recycled asphalt 2 was reduced by 2.36%, and the proportion of polybutadiene functional groups in recycled asphalt 3 was increased by 2.28% compared with the first-aging asphalt; the proportion of polybutadiene functional groups in secondary-aging asphalt 1 was reduced by 23.41% compared with the first-aging asphalt, the proportion of polybutadiene functional groups in secondary-aging asphalt 2 was reduced by 17.18%, and the proportion of polybutadiene functional groups in secondary-aging asphalt 3 was reduced by 12.04% compared with the first-aging asphalt. It can be seen that among the three recycled asphalt samples, recycled asphalt 3 has the best stability, recycled asphalt 2 is the second, and recycled asphalt 1 is the worst.

[0058] Example 5 (Comparative Example 2): Sensitivity

[0059] The asphalt samples used in Example 5 are the same as those used in Example 1. By referring to the experiments for detecting asphalt sensitivity in the existing standards, it is found that the temperature sensitivity described in the present invention has not been discussed yet. The prior art usually uses stress sensitivity to evaluate asphalt sensitivity. The stress sensitivity experiment is conducted on asphalt samples with reference to the existing standards. The stress sensitivity parameter can be used to evaluate the sensitivity of asphalt under stress at different temperatures. As the temperature increases, each type of asphalt shows a law of weakening sensitivity. This stress sensitivity method can better reflect the sensitivity of aged and recycled asphalt. The recovery rate parameter R at 0.1kPa and 3.2kPa pressure levels in the multiple stress creep and recovery test is calculated as follows: {R}_{diff}=\frac {\left [ {\left ( {{R}_{0.1}-{R}_{3.2}} \right )*100} \right ]} {{R}_{0.1}} Among them, the relative difference in recovery rate Reflects the sensitivity of the viscoelastic properties of modified asphalt to stress changes. The larger it is, the more sensitive the asphalt viscoelastic properties are to stress changes. See Table 10 for specific parameters:

[0060] From Table 10, we can see the relative differences in the recovery rates of various asphalt samples at relative temperatures. diff It increases significantly, indicating that asphalt is more sensitive to stress after aging. Comparing the three types of regenerated asphalts, regenerated asphalt 3 has the lowest stress sensitivity, followed by regenerated asphalt 2, and regenerated asphalt 1 has the highest stress sensitivity and the worst regeneration effect; after secondary aging, the stress sensitivity of secondary aged asphalt 1 is higher than that of primary aged asphalt at each temperature, and the stress sensitivity of secondary aged asphalt 2 and secondary aged asphalt 3 is lower than that of primary aged asphalt and secondary aged asphalt 1, among which secondary aged asphalt 3 has the lowest sensitivity, followed by secondary aged asphalt 2, and secondary aged asphalt 1 has the highest stress sensitivity and the worst regeneration effect. The related experiments for detecting asphalt sensitivity in the prior art can only reflect the stress sensitivity of asphalt at a certain temperature, and cannot reflect the changes in sensitivity with temperature changes or asphalt aging process, and this stress sensitivity evaluation method is not regular and has poor practicality. According to the stress sensitivity test verification, the test results are consistent with the results of the evaluation method of this application, and the evaluation method in this application is more accurate, faster, and more regular.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. The stability and sensitivity evaluation method of recycled asphalt based on secondary aging includes the following steps: Preparation of asphalt samples: Select original asphalt to obtain original asphalt sample, perform aging treatment on the original asphalt to obtain primary aged asphalt sample, perform regeneration treatment on the primary aged asphalt to obtain regenerated asphalt sample, perform aging treatment on the regenerated asphalt to obtain secondary aged asphalt sample, and the aging treatment and regeneration treatment test process shall be subject to the specification; To perform rheological tests: Rheological tests were performed on original asphalt samples, primary aged asphalt samples, recycled asphalt samples, and secondary aged asphalt samples, and the test parameters at different temperatures were recorded; Data calculation: Calculate the change rate of the corresponding parameters after two aging processes. The specific process is as follows: Calculate the rate of change during the first aging process of the asphalt sample; in, Represents the parameters of the once aged asphalt sample, represents the original asphalt sample parameters, Indicates the rate of change of the first aging process; Calculate the rate of change of the second aging process of the asphalt sample; in, represents the secondary aged asphalt sample parameters, Represents the recycled asphalt sample parameters, Indicates the rate of change of the second aging process; Data Analysis: Draw the obtained , The scatter plots at different temperatures are linearly fitted with a linear function, and the slope and variance of the linear function are recorded; Define asphalt stability-sensitivity ratio; C = variance / |slope| Among them, C represents the stability-sensitivity ratio of asphalt, which is used to evaluate the stability and sensitivity of asphalt affected by temperature changes during aging; the slope reflects the sensitivity of the parameter change rate to temperature changes during aging, and the variance reflects the stability of the parameter change rate to temperature changes; Calculate the stability and sensitivity change rate of asphalt during two aging processes; in, It represents the stability-sensitivity ratio of the original asphalt aging process, Indicates the stability-sensitivity ratio of the recycled asphalt aging process, It represents the rate of change of stability and sensitivity during two aging processes.

2. The method for evaluating the stability sensitivity of regenerated asphalt based on secondary aging according to claim 1 is characterized in that: when <0, indicating that the stability and sensitivity of asphalt in the secondary aging process is lower than that in the primary aging process, and the stability and sensitivity is judged as poor; =0, indicating that the stability and sensitivity of the secondary aging process of asphalt is the same as that of the primary aging process, and the stability and sensitivity is judged as medium; >0, indicating that the stability sensitivity of asphalt in the secondary aging process is higher than that in the primary aging process, and the stability sensitivity is judged to be excellent.

3. The method for evaluating the stability and sensitivity of regenerated asphalt based on secondary aging according to claim 1, characterized in that: The rheological test specifically includes: performing a temperature scanning test and a low temperature bending beam rheological test by using a dynamic shear rheometer and a low temperature bending beam rheometer.

4. The method for evaluating the stability and sensitivity of regenerated asphalt based on secondary aging according to claim 1, characterized in that: The test parameters include: rutting factor parameters, fatigue factor parameters and low temperature rheological parameters at different temperatures.

5. The method for evaluating the stability sensitivity of regenerated asphalt based on secondary aging according to claim 3 or 4, characterized in that: The rheological test and test parameters can be switched to other rheological evaluation indicators.

6. Application of the regenerated asphalt stability sensitivity evaluation method based on secondary aging as described in claim 1 in the fields of selection of regeneration agent, selection of regeneration agent dosage, selection of regeneration process, etc.

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