Service asphalt pavement hardening low-loss evaluation method based on structure-activity relationship

Abstract

The invention discloses a service asphalt pavement hardening low-loss evaluation method based on a structure-activity relationship. At present, a quantitative evaluation method for the performance of the modified asphalt in the mixture is lacked on the premise of not damaging the pavement structure; after the type of the modified asphalt on the old pavement is obtained, at least three types of homologous modified asphalt are correspondingly configured according to the type of the modified asphalt on the old pavement, a modulus change index MCI is obtained through related experimental testing and calculation, and a functional group change index FCI is obtained after the type of the modified asphalt on the old pavement is subjected to related analysis calculation. An MCI-FCI correlation equation is constructed according to MCI and FCI data, and the MCI-FCI correlation equation and FTIR analysis are combined to complete the quantitative analysis and evaluation process of the service performance of the old modified asphalt pavement.

Description

Technical Field

[0001] Specifically, this invention is a method for evaluating the hardening and low-loss of in-service asphalt pavement based on structure-property relationships. Background Technology

[0002] Modified asphalt, with its excellent high and low temperature stability, fatigue resistance, and rutting resistance, has been widely used in important transportation infrastructure such as highways and urban arterial roads. However, with the increase of service time, the performance of modified asphalt gradually deteriorates under the combined effects of multiple factors, including vehicle loads, solar radiation, rain erosion, temperature fluctuations, and changes in its own chemical properties. The internal modifiers may degrade, segregate, or decrease their compatibility with the asphalt matrix, resulting in a significant reduction in its original excellent performance. This makes the pavement prone to cracks, potholes, and other defects, directly affecting the service life of the road and driving safety. Therefore, in order to accurately assess the actual condition of old modified asphalt pavements, scientifically formulate maintenance strategies, and avoid the waste of resources caused by blind renovation, systematic performance testing of old modified asphalt is particularly important. However, current methods for testing the performance of modified asphalt pavements that have been in service for many years require obtaining large quantities of pavement material and separating the modified asphalt from the mixture. This not only damages the pavement and causes significant economic losses, but also, over time, some polymer modifiers degrade or become difficult to dissolve in solvents during the aging process. Furthermore, commonly used reagents for separating modified asphalt and determining its performance are mostly harmful solvents such as trichloroethylene, toluene, and gasoline, which greatly increases the difficulty of separating the modified asphalt from the mixture. Current research is still exploring methods to easily measure the performance of modified asphalt in the mixture without damaging the pavement structure, in order to meet the needs of different road engineering projects.

[0003] The core reasons and technical challenges that make it difficult to accurately quantify and evaluate modified asphalt in actual road surfaces are mainly threefold:

[0004] First: The service performance of asphalt pavement is affected by multiple factors such as load, environment, asphalt grade or aggregate gradation, etc. These factors are coupled with each other, and it is difficult to separate the influence weight of a single factor.

[0005] Second: Road surface performance degradation is a dynamic process. For example, the degree of wear and damage varies greatly between different road sections such as intersections, ramps, and straight sections. Single-point detection data cannot represent the overall level of the road section, and the cost and technical threshold for long-term continuous monitoring are high.

[0006] Third: the limitations of testing technology. For example, some performance indicators such as road fatigue performance and water stability cannot be obtained through simple on-site rapid testing. They need to be combined with indoor tests and on-site data for fitting and extrapolation. At the same time, the accuracy of the testing equipment and the standardization of operation will directly affect the accuracy of the quantitative data, and the test results of different equipment will also differ.

[0007] In summary, there is currently a lack of quantitative evaluation methods for the performance of modified asphalt in asphalt mixtures without compromising the pavement structure. Summary of the Invention

[0008] This invention provides a method for evaluating the hardening and low-loss of in-service asphalt pavement based on structure-property relationship, in order to solve the above-mentioned problems.

[0009] A method for evaluating the hardening and low-loss performance of in-service asphalt pavement based on structure-property relationship is proposed. After obtaining the type of modified asphalt for the old pavement, at least three types of homologous modified asphalt are prepared according to the type of modified asphalt for the old pavement. The modulus change index (MCI) is obtained through relevant tests and calculations. The functional group change index (FCI) is obtained by performing correlation analysis on the type of modified asphalt for the old pavement. The MCI-FCI correlation equation is constructed based on the MCI and FCI data. The MCI-FCI correlation equation is combined with FTIR analysis to complete the quantitative analysis and evaluation process of the service performance of the old modified asphalt pavement.

[0010] As a preferred option: After obtaining the type of modified asphalt for the old road surface, at least three types of homologous modified asphalt should be prepared according to the type of modified asphalt for the old road surface, and the difference in the percentage of aging degree between two adjacent homologous modified asphalts should be in the range of 1% to 1.5%.

[0011] After sequentially subjecting each type of modified asphalt from the same source as the old pavement to rotating thin film oven tests, pressure aging tests, and rheological tests, each asphalt sample, after rheological testing and calculation, corresponds to a modulus change index (MCI). The calculation process is as follows:

[0012] Temperature-frequency scanning was performed on each asphalt sample, and [the following was selected]. and 10 4 Using the Hz reduction frequency as the integration limit, and based on the complex modulus master curve in a double logarithmic coordinate system, the modulus change index (MCI) of the modified asphalt sample is calculated. The MCI calculation formula is as follows:

[0013]

[0014] In the above formula, The reduction frequency is the logarithm of the unaged asphalt.

[0015] The reduction frequency after taking the logarithm of aged asphalt;

[0016] This refers to the dynamic shear modulus.

[0017] As a preferred approach: Obtain actual old pavement modified asphalt samples, with a mass of less than or equal to 1 gram. Use the attenuated total reflectance (ATR) mode of Fourier transform infrared spectroscopy (FTIR) to obtain the infrared spectral bands of the actual old pavement modified asphalt. After peak fitting processing of the spectral aging fingerprints of the amide band a and sulfoxide b functional groups of the actual old pavement modified asphalt, obtain the peak areas of the corresponding absorption peaks, and then use the Gaussian-Lorentzian function... The FTIR spectra within the specified range are analyzed, and the functional group variation index (FCI) is quantitatively calculated using the following formula:

[0018]

[0019] In the above formula, FCI is the functional group change index; FI is the aging index.

[0020] As a preferred approach: After performing peak fitting on the spectral aging fingerprints of the amide band a and sulfoxide b functional groups of the modified asphalt from actual old pavements, the peak areas of the corresponding absorption peaks are obtained, and then the Gaussian-Lorentzian function is used to... During the analysis of the FTIR spectra within the range, the absorption peak areas corresponding to a(i), a(ii), and b are first obtained, and carbonyl AI is then performed. a And sulfoxide AI b The formula for calculating the index is as follows:

[0021]

[0022]

[0023]

[0024] In the above formula, A 1700 for Absorption peak area at position; A 1650 for Absorption peak area at position; A 1030 for Absorption peak area at position; A ref2 For reference absorption peak area.

[0025] As a preferred approach: calculate the carbonyl and sulfoxide indices of the RTFO and PAV-aged asphalt samples and divide them by the indices of the unaged asphalt samples to obtain the corresponding characteristic functional groups. The change index is used to analyze the functional groups that affect asphalt aging by plotting a bar chart of functional group change indexes. The calculation formula is as follows:

[0026]

[0027]

[0028]

[0029] AI in the above formula a (i), unaged AI is the a(i) index of unaged asphalt. a (ii), unaged For unaged asphalt a(ii) index; AI b,unaged The β-index of unaged asphalt; AI a (i), aged AI is the a(i) index of aged asphalt. a (ii), aged For aged asphalt a(ii) index; AI b , aged For aged asphalt, the b-index is used; FI a (i) Let a(i) be the aging index; FI a (ii) a(ii) aging index; FI b b represents the aging index.

[0030] As a preferred approach: Fit the obtained MCI and FCI data to establish an MCI-FCI correlation equation. Plot a scatter plot with the MCI values ​​as the ordinate and the corresponding FCI values ​​as the abscissa. Observe the fitting results and determine the correlation index of the fitted equation to verify the correlation between MCI and FCI. When the correlation index of the fitted equation is greater than 85%, it indicates that there is a correlation between MCI and FCI, which corresponds to the excellent service performance of the modified asphalt in the actual old pavement. When the correlation index of the fitted equation is less than 85%, it indicates that there is no correlation between MCI and FCI, which corresponds to the deterioration of the service performance of the modified asphalt in the actual old pavement.

[0031] Compared with the prior art, the present invention provides a method for evaluating the hardening and low loss of in-service asphalt pavement based on structure-property relationship, which has the following beneficial effects:

[0032] This invention, a structure-property relationship-based low-destructive testing method for the hardening of service-grade asphalt pavement, is essentially a structure-property relationship-based non-destructive testing method for the hardening of service-grade asphalt pavement that minimizes damage to the pavement. This method avoids the cumbersome extraction steps and damage to the modified asphalt pavement caused by sampling and testing in previous methods for testing old modified asphalt pavement. The process is scientifically sound, reasonable, and easy to implement. It can quantitatively test and evaluate the service performance of asphalt, and the evaluation results provide accurate guidance for the subsequent maintenance of asphalt pavement. Specific advantages include:

[0033] 1. By setting different modifier dosages for pavement homogeneous asphalt, rotating thin film oven aging test (RTFO) and pressure aging test (PAV) are conducted on the old pavement homogeneous modified asphalt to simulate short-term and long-term asphalt aging, thereby achieving the purpose of controlling different aging degrees of pavement homogeneous asphalt.

[0034] 2. Rheological tests were conducted on the modified asphalt before and after aging, and the modulus change index (MCI) of the modified asphalt was quantitatively calculated.

[0035] 3. The sample size of the old modified asphalt pavement is small. Fourier transform infrared spectroscopy (FTIR) analysis is performed. The spectral aging fingerprint of the amide band C=O and sulfoxide S=O functional groups of the old pavement modified asphalt is peak-fitted by using the GL function to obtain the peak area of ​​the corresponding absorption peak and to quantitatively calculate the functional group change index (FCI).

[0036] IV. Fit the MCI and FCI data, propose the MCI-FCI correlation equation, and ensure that the correlation index of the fitted equation is greater than 85%;

[0037] 5. Substitute the modulus information of the modified asphalt of the old pavement into the MCI-FCI correlation equation to quantitatively determine the service performance of the old modified asphalt pavement.

[0038] This invention enables the measurement of the mechanical properties of modified asphalt in old pavements without affecting pavement use, causing minimal damage to the pavement and achieving non-destructive testing, thus reducing economic losses and saving at least 60% of testing costs. This invention avoids the cumbersome steps of separating modified asphalt from the original mixture, improving testing efficiency. This invention standardizes and effectively combines MCI and FCI, resulting in highly accurate results. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the principal curves of the complex modulus of the same modified asphalt pavement before and after aging with different modifier contents. The modifier content in the figure is 0%.

[0040] Figure 2 This is the first schematic diagram of the principal curves of the complex modulus of the same modified asphalt pavement before and after aging with different modifier contents. The modifier content in the figure is 1.5%.

[0041] Figure 3 This is the first schematic diagram of the principal curves of the complex modulus of the same modified asphalt pavement before and after aging with different modifier contents. The modifier content in the figure is 2.5%.

[0042] Figure 4 This is the first schematic diagram of the principal curves of the complex modulus of the same modified asphalt pavement before and after aging with different modifier contents. The modifier content in the figure is 4%.

[0043] Figure 5 This is a schematic diagram for calculating the Modulus Change Index (MCI).

[0044] Figure 6This diagram illustrates the change index of aging modulus of pavement modified asphalt with different modifier contents, where the modifier contents are 0%, 1.5%, 2.5%, and 4%.

[0045] Figure 7 The image shows the FTIR spectrum of modified asphalt for old road surfaces, with a modifier content of 0%.

[0046] Figure 8 The image shows the FTIR spectrum of modified asphalt for old road surfaces, with a modifier content of 1.5%.

[0047] Figure 9 The image shows the FTIR spectrum of modified asphalt for old road surfaces, with a modifier content of 2.5%.

[0048] Figure 10 The image shows the FTIR spectrum of modified asphalt for old road surfaces, with a modifier content of 4%.

[0049] Figure 11 When the wave number is at Analytical FTIR spectra of unaged asphalt and old pavement asphalt;

[0050] Figure 12 When the wave number is at Analytical FTIR spectra of unaged asphalt and old pavement asphalt;

[0051] Figure 13 This is a schematic diagram of the functional group change index of pavement homologous modified asphalt containing different modifiers, where the aging index is a(i).

[0052] Figure 14 This is a schematic diagram of the functional group change index of pavement homologous modified asphalt containing different modifiers. The aging index in the figure is a (ii).

[0053] Figure 15 This is a schematic diagram showing the functional group change index of pavement homologous modified asphalt containing different modifiers. The aging index in the figure is b.

[0054] Figure 16 This is a schematic diagram showing the functional group change index of pavement homologous modified asphalt containing different modifiers. The chemical aging index in the figure is FCI.

[0055] Figure 17 This is a schematic diagram showing the relationship between the modulus change index and the functional group change index.

[0056] Figure 18 This is a flowchart of the present invention. Detailed Implementation

[0057] The technical solutions of the embodiments 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, and 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.

[0058] Specific implementation method one: Combining Figures 1 to 18 This embodiment describes a method for evaluating the low-loss hardening of service-grade asphalt pavement based on structure-property relationships. The method involves obtaining the type of modified asphalt for the old pavement, configuring at least three types of homologous modified asphalt according to the type, and then obtaining the modulus change index (MCI) through relevant tests and calculations. The functional group change index (FCI) is then obtained by performing correlation analysis on the type of modified asphalt for the old pavement. An MCI-FCI correlation equation is constructed based on the MCI and FCI data. Finally, the MCI-FCI correlation equation is combined with FTIR analysis to complete the quantitative analysis and evaluation of the service performance of the old modified asphalt pavement.

[0059] Specific Implementation Method Two: This implementation method is a further limitation of Specific Implementation Method One. In this implementation method, after obtaining the type of modified asphalt for the old road surface, at least three types of homologous modified asphalt are configured according to the type of modified asphalt for the old road surface. The value range of the difference in the percentage of aging degree between two adjacent homologous modified asphalts is 1%~1.5%.

[0060] After sequentially subjecting each type of modified asphalt from the same source as the old pavement to rotating thin film oven tests, pressure aging tests, and rheological tests, each asphalt sample, after rheological testing and calculation, corresponds to a modulus change index (MCI). The calculation process is as follows:

[0061] Temperature-frequency scanning was performed on each asphalt sample, and [the following was selected]. and 10 4 Using the Hz reduction frequency as the integration limit, and based on the complex modulus master curve in a double logarithmic coordinate system, the modulus change index (MCI) of the modified asphalt sample is calculated. The MCI calculation formula is as follows:

[0062]

[0063] In the above formula, The reduction frequency after taking the logarithm of unaged asphalt

[0064] The reduction frequency after taking the logarithm of aged asphalt

[0065] This refers to the dynamic shear modulus.

[0066] In this embodiment, the thin-film oven test simulates the short-term aging of asphalt during hot mixing and paving, and evaluates its aging resistance by assessing the performance changes under the influence of heat and air. The principle and detailed process are as follows.

[0067] The principle of the thin film oven test is to make a uniform thin film of asphalt and heat it at a specified temperature, time and air flow rate to simulate the heat-oxygen aging during hot-mix construction. The degree of aging is quantified by changes in indicators such as mass change, penetration ratio, ductility and viscosity.

[0068] The experimental mechanism of the thin film oven test is that heat accelerates the volatilization and oxidative polymerization of lightweight components in asphalt, air enhances oxidation, and rotation makes the film heated evenly, which is closer to the real working conditions.

[0069] This invention can be adapted to common standards, specifically TFOT according to GB / T 5304, JTG E20 T0609; RTFO according to SH / T0736, ASTM D2872, AASHTO T240.

[0070] The specific process of the thin film drying oven test is as follows:

[0071] 1. Sample preparation: Heat the asphalt to a fluid state, take about 50g ± 0.5g and pour it into a sample dish to form a thin film about 3mm thick. After cooling, weigh the sample. Accurate to 0.01g.

[0072] 2. Equipment preparation: Preheat the oven to 163℃±1℃, turntable speed 5.5r / min±1r / min, tilt angle ≤3°, and place the thermometer at the center and edge of the turntable at equal distances.

[0073] 3. Sample loading and timing: Quickly place the sample dish, close the door and start the turntable; start timing when the temperature rises to 162℃, and keep it at a constant temperature for 5 hours (total time ≤ 5.25 hours).

[0074] 4. Post-processing and testing: Remove and cool, then weigh. ; Calculate the rate of change in mass Test penetration, ductility, viscosity, etc., and calculate penetration ratio and other indicators.

[0075] The experimental procedure is as follows:

[0076] 1. Sample preparation: Heat the asphalt to a fluid state (≤150℃), pour approximately 35g ± 0.5g into a bottle, cool horizontally for 60–180 min, and weigh. Accurate to 0.001g.

[0077] 2. Equipment preparation: Preheat to 163℃±0.5℃, air flow rate 4000mL / min±200mL / min, turntable speed 15r / min±0.2r / min.

[0078] 3. Sample loading and start-up: Place the sample vials evenly on the ring rack, ensuring the empty vials are balanced. Close the door and start the rotation and gas path. Within 10 minutes, the temperature will rise to 163℃±0.5℃ and be maintained for 85 minutes.

[0079] 4. Post-processing and testing: Remove, cool, and weigh. Calculate the quality changes; collect aged asphalt and test indicators such as penetration and viscosity.

[0080] In this embodiment, the pressure aging test is mainly used to simulate the long-term aging of asphalt during the service period of the road surface. It complements the short-term aging test of the thin film oven test to jointly evaluate the aging resistance performance of asphalt throughout its entire life cycle.

[0081] The principle of the pressure aging test is to apply high temperature and high pressure to asphalt that has undergone short-term aging and introduce air to accelerate the deep oxidation and condensation reaction of the asphalt, simulating the aging process of the road surface under long-term traffic load and environmental action. The long-term performance stability of the asphalt is evaluated by the changes in dynamic shear modulus, phase angle, ductility and other indicators after aging.

[0082] The mechanism of the pressure aging test is that the high pressure environment increases the solubility of oxygen in asphalt, and the high temperature accelerates the oxidative cross-linking of molecular chains, which leads to a further reduction in the lightweight components of asphalt and an increase in macromolecular polymers, resulting in increased hardness and reduced ductility, which is consistent with the performance degradation law of actual pavement after long-term use.

[0083] The experimental process consists of the following steps:

[0084] 1. Sample pretreatment: Take asphalt samples that have undergone short-term RTFO aging, heat them to a fluid state (the temperature of modified asphalt should not exceed 163℃), and pour them into a stainless steel pressure vessel sample dish for PAV. The sample thickness should be controlled at 3.2mm ± 0.2mm. After cooling to room temperature, they are ready for use.

[0085] 2. Equipment preparation and debugging: Put the sample dish containing the sample into the pressure vessel, seal the pressure vessel, and check the airtightness.

[0086] Test parameters were set as follows: temperature 100℃±0.5℃, pressure 2.1MPa±0.05MPa, and air flow rate 10L / h±0.5L / h for modified asphalt.

[0087] Start the equipment, first introduce air to purge inert gases such as nitrogen from the reactor, then increase the pressure and temperature to the set value.

[0088] 3. Constant temperature and pressure aging: Start timing when both temperature and pressure reach the set values, and continue aging for 20 hours ± 10 minutes. During the process, maintain stable temperature, pressure and air flow to ensure uniform oxidation reaction.

[0089] 4. Post-processing and performance testing: After aging, slowly release the pressure inside the vessel to atmospheric pressure, close the gas path and heating device, and open the pressure vessel after it has cooled to room temperature.

[0090] Remove the sample dish, collect the aged asphalt samples, and test their dynamic shear rheology (DSR), bending beam rheology (BBR), ductility, and other indicators to evaluate the long-term aging resistance of the asphalt.

[0091] In this embodiment, rheological tests are mainly conducted using a dynamic shear rheometer and a bending beam rheometer to evaluate the high-temperature and low-temperature rheological properties of asphalt, respectively. The core is to characterize the viscoelastic behavior based on the stress-strain-time relationship of the material after it is subjected to force.

[0092] The rheological testing principle is based on the dynamic shear rheometer principle, employing an oscillating shear mode. The asphalt sample is subjected to periodic alternating shear forces between two parallel plates, causing the asphalt to simultaneously exhibit viscous flow and elastic deformation. The dynamic shear modulus is calculated by measuring the phase difference δ between shear stress and strain. And the phase angle δ, further deriving the rutting factor. . The rutting factor reflects the total ability of asphalt to resist deformation. δ reflects the viscoelasticity ratio. The smaller the δ, the stronger the elasticity. The larger the rutting factor, the better the high-temperature rutting resistance of asphalt.

[0093] The principle of the bending beam rheometer is based on a low-temperature creep mode. Asphalt beam samples are placed in a constant low-temperature environment, and a constant load is applied to induce bending deformation. The creep compliance and stiffness modulus are measured at different time points. A smaller stiffness modulus and a larger creep rate indicate better low-temperature crack resistance of the asphalt, and better ability to adapt to low-temperature shrinkage deformation.

[0094] The dynamic shear rheometer (DSR) test process in this embodiment is as follows:

[0095] 1. Sample preparation: Take aged RTFO or PAV asphalt, heat it to a fluid state, pour it into a preheated mold, and after cooling, make a round cake sample with a diameter of 25mm and a thickness of 1mm. The diameter and thickness need to be selected according to the test temperature. Correspondingly, use a larger size for high temperature and a smaller size for medium and low temperature.

[0096] 2. Equipment debugging: Install the parallel plate rotor of the corresponding size, set the test temperature, preheat the instrument and sample to the target temperature and keep it at a constant temperature for at least 10 minutes.

[0097] 3. Test operation: Place the sample in the center of the lower plate, lower the upper plate to the set gap, and trim any excess sample; set the oscillation frequency and strain control range, start the oscillation shear, and record the stress, strain, and phase difference data.

[0098] 4. Data processing and calculation The asphalt high-temperature performance is judged by comparing the δ and rutting factor with the standard requirements.

[0099] In this embodiment, when the BBR (Bending Beam Rheometer) test is involved, the BBR test process is as follows:

[0100] 1. Sample preparation: PAV-aged asphalt is heated and poured into a metal mold, cooled and demolded to form a standard small beam sample of 127mm×12.7mm×6.35mm. The sample is then placed in a specified low-temperature environment (e.g., -12℃, -18℃) and kept at a constant temperature for at least 60 minutes.

[0101] 2. Equipment setup: Adjust the BBR support spacing to 102mm, set the test temperature to match the constant temperature of the sample, and install the load sensor, which typically has a load of 980mN.

[0102] 3. Loading test: Place the small beam sample on the support, apply a constant load, automatically record the change in deflection at the midpoint of the beam during the loading time (usually 240s), and calculate the stiffness modulus and creep rate at different time points.

[0103] 4. Result determination: The stiffness modulus and creep rate at 60s loading are used as evaluation indicators. If they meet the standard limits, the low-temperature crack resistance is qualified.

[0104] Specific Implementation Method 3: This implementation method is a further limitation of Specific Implementation Method 1 or 2. In this implementation method, actual old pavement modified asphalt samples are obtained. The mass of the actual old pavement modified asphalt samples is less than or equal to 1 gram. The infrared spectral bands of the actual old pavement modified asphalt are obtained using the attenuated total reflection ATR mode of Fourier transform infrared spectroscopy (FTIR). After peak fitting processing of the spectral aging fingerprints of the amide band a and sulfoxide b functional groups of the actual old pavement modified asphalt, the peak areas of the corresponding absorption peaks are obtained, and the Gaussian-Lorentzian function is used to determine the peak areas. The FTIR spectra within the specified range are analyzed, and the functional group variation index (FCI) is quantitatively calculated using the following formula:

[0105]

[0106] In the above formula, FCI is the functional group change index.

[0107] Specific Implementation Method Four: This implementation method is a further limitation of Specific Implementation Methods One, Two, or Three. In this implementation method, after performing peak fitting processing on the spectral aging fingerprints of the amide band a and sulfoxide b functional groups of the modified asphalt of actual old pavement, the peak areas of the corresponding absorption peaks are obtained, and then the Gaussian-Lorentzian function is used to... During the analysis of the FTIR spectra within the range, the absorption peak areas corresponding to a(i), a(ii), and b are first obtained, and carbonyl AI is then performed. a And sulfoxide AI b The formula for calculating the index is as follows:

[0108]

[0109]

[0110]

[0111] In the above formula, A 1700 for Absorption peak area at position; A 1650 for Absorption peak area at position; A 1030 for Absorption peak area at position; A ref2 For reference absorption peak area.

[0112] Specific Implementation Method Five: This implementation method is a further limitation of Specific Implementation Methods One, Two, Three, or Four. In this implementation method, the carbonyl and sulfoxide indices of the RTFO and PAV aged asphalt samples are calculated and divided by the indices of the unaged asphalt samples to obtain the corresponding characteristic functional groups. The change index is used to analyze the functional groups that affect asphalt aging by plotting a bar chart of functional group change indexes. The calculation formula is as follows:

[0113]

[0114]

[0115]

[0116] AI in the above formula a (i), unaged AI is the a(i) index of unaged asphalt. a (ii), unaged For unaged asphalt a(ii) index; AI b,unaged The β-index of unaged asphalt; AI a (i), aged AI is the a(i) index of aged asphalt. a (ii), aged For aged asphalt a(ii) index; AI b , aged For aged asphalt, the b-index is used; FI a (i) Let a(i) be the aging index; FI a (ii) a(ii) aging index; FI b b represents the aging index.

[0117] Specific Implementation Method Six: This implementation method is a further limitation of Specific Implementation Methods One, Two, Three, Four, or Five. In this implementation method, the obtained MCI and FCI data are fitted to establish an MCI-FCI correlation equation. A scatter plot is drawn with the MCI value as the vertical axis and the corresponding FCI value as the horizontal axis. The fitting results are observed and the correlation index of the fitted equation is determined to verify the correlation between MCI and FCI. When the correlation index of the fitted equation is greater than 85%, it indicates that there is a correlation between MCI and FCI, which corresponds to the excellent service performance of the modified asphalt on the actual old pavement. When the correlation index of the fitted equation is less than 85%, it indicates that there is no correlation between MCI and FCI, which corresponds to the degradation of the service performance of the modified asphalt on the actual old pavement.

[0118] Specific Implementation Method Seven: This implementation method is a further limitation of Specific Implementation Methods One, Two, Three, Four, Five, or Six. This implementation method combines... Figures 1 to 18 As shown, the method for evaluating the hardening and low-loss of in-service asphalt pavement based on structure-property relationship, as described in this invention, involves selecting a batch of old pavement-derived asphalt and setting four different modifier contents to achieve four different aging degrees: 0%, 1.5%, 2.5%, and 4%. According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20–2011), a rotating thin-film aging oven (RTFO) test is conducted, heating the asphalt samples at 163°C and an air flow rate of 4000 ml / min. The pressure aging (PAV) testing system (Prentex Alloy Fabricators Inc.) is used to continuously control the temperature of the RTFO-aged asphalt samples at 100°C and 2.1 MPa to simulate the long-term aging state of asphalt.

[0119] Then perform a temperature-frequency scan, selecting... and 10 4 The Hz reduction frequency is used as the integration limit, based on the complex modulus master curve in a double log-log coordinate system. Taking modified asphalt with 2.5% modifier content as an example, the modulus change index (MCI) of the modified asphalt sample is calculated. The MCI calculation formula is as follows:

[0120]

[0121] In the above formula The reduction frequency after taking the logarithm of aged asphalt

[0122] The reduction frequency after taking the logarithm of aged asphalt

[0123] This refers to the dynamic shear modulus.

[0124] Infrared bands of trace samples from old asphalt pavement were acquired using a Thermo Scientific Nicolet iS50 Fourier transform infrared spectrometer in ATR mode. The aging fingerprints of the infrared spectra were analyzed and compared to determine the types of functional groups in the spectral aging fingerprints. After aging... and The nearby peak intensities increased significantly, attributed to carbonyl (a) and sulfoxide (b) compounds, respectively. Therefore, the evolution of the carbonyl and sulfoxide absorption bands can be used to assess the aging state of asphalt materials. Comparing the infrared spectra, in... The evolution of the absorption peaks at the position can be observed and can be used to represent the composition of amide compounds that play a key role.

[0125] The effects of thermo-oxidative aging on asphalt samples were quantified, and the absorption peak areas corresponding to a(i), a(ii), and b were obtained. Carbonyl (AI) assays were then performed. a ) and sulfoxide (AI) b The index is calculated using the following formula:

[0126]

[0127]

[0128]

[0129] In the above formula, A 1700 for The absorption peak area at the location is expressed in units of: ×Absorbance; A 1650 for The absorption peak area at the location is expressed in units of: ×Absorbance; A 1030 for The absorption peak area at the location is expressed in units of: ×Absorbance; A ref2 For reference absorption peak area, the unit is... ×Absorbance.

[0130] The carbonyl and sulfoxide indices of the RTFO and PAV aged asphalt samples were calculated and divided by the indices of the unaged asphalt samples to obtain the corresponding characteristic functional groups. The functional group change index was used to analyze the functional groups that affect asphalt aging, and a bar chart of the functional group change index was plotted. The calculation formula is as follows:

[0131]

[0132]

[0133]

[0134] In the above formula, AI a (i), unaged AI a (ii), unaged AI b, unaged The indices of unaged asphalt are a(i), a(ii), and b, respectively; AI a (i), aged AI a (ii), aged, AI b , aged The indices of aged asphalt are a(i), a(ii), and b, respectively; FI a (i) FI a (ii) FI b The aging indices are a(i), a(ii), and b, respectively.

[0135]

[0136] In the above formula, FCI is the functional group change index, and FI a(i) FI a(ii) FI b These are the characteristic functional group change indices.

[0137] After the calculation is completed, the relationship between MCI and FCI is described based on the calculation results. A scatter plot is drawn with the MCI value as the vertical axis and the corresponding FCI value as the horizontal axis. The MCI and FCI data are fitted with a logarithmic equation. The fitting result is 87%, which is greater than 85%, indicating that there is a correlation between MCI and FCI.

[0138] FTIR analysis was performed on trace samples (less than 1 gram) of the old modified asphalt pavement, and the FCI of the old pavement asphalt was obtained through step three. Based on the MCI-FCI correlation equation proposed in step four, the modulus information of the old pavement asphalt was obtained, and the service performance of the old pavement asphalt was determined.

[0139] Combination Figure 5 and Figure 6 It can be seen that as the degree of aging increases, the modulus change index (MCI) of asphalt gradually increases, indicating that the increase in thermo-oxidative aging significantly improves the aging degree of asphalt samples and has a significant impact on the rheological response of asphalt binder.

[0140] Combination Figure 13 , 14 As shown in 15 and 16, comparing the a(i) and a(ii) change indices of asphalt with different aging degrees, the functional group change index in asphalt increases significantly with the deepening of aging, indicating that the functional group change index can be used as a representative analytical index.

[0141] Combination Figure 17It can be seen that the correlation between MCI and FCI data is 87%, which is greater than 85%, indicating that MCI and FCI have a certain correlation. By obtaining the modulus information of old pavement asphalt, the service performance of old modified asphalt pavement can be determined.

Claims

1. A method for evaluating the low-loss hardening of in-service asphalt pavement based on structure-property relationship, characterized in that: After obtaining the type of modified asphalt for the old pavement, at least three types of homologous modified asphalt are prepared according to the type of modified asphalt for the old pavement. The modulus change index (MCI) is obtained through relevant tests and calculations. The functional group change index (FCI) is obtained by performing relevant analysis and calculation on the type of modified asphalt for the old pavement. Based on the MCI and FCI data, the MCI-FCI correlation equation is constructed. The MCI-FCI correlation equation and FTIR analysis are combined to complete the quantitative analysis and evaluation process of the service performance of the old modified asphalt pavement.

2. The method for evaluating the hardening and low loss of in-service asphalt pavement based on structure-property relationship according to claim 1, characterized in that: After obtaining the type of modified asphalt for the old road surface, at least three types of homologous modified asphalt should be prepared according to the type of modified asphalt for the old road surface. The difference in the percentage of aging degree between two adjacent homologous modified asphalts should range from 1% to 1.5%. After sequentially subjecting each type of modified asphalt from the same source as the old pavement to rotating thin film oven tests, pressure aging tests, and rheological tests, each asphalt sample, after rheological testing and calculation, corresponds to a modulus change index (MCI). The calculation process is as follows: Temperature-frequency scanning was performed on each asphalt sample, and [the following was selected]. and 10 4 Using the Hz reduction frequency as the integration limit, and based on the complex modulus master curve in a double logarithmic coordinate system, the modulus change index (MCI) of the modified asphalt sample is calculated. The MCI calculation formula is as follows: ； In the above formula, The reduction frequency is the logarithm of the unaged asphalt. The reduction frequency after taking the logarithm of aged asphalt; This refers to the dynamic shear modulus.

3. A method for evaluating the hardening and low-loss of in-service asphalt pavement based on structure-property relationship according to claim 1 or 2, characterized in that: Actual old pavement modified asphalt samples were obtained, with a mass of less than or equal to 1 gram. The infrared spectral bands of the modified asphalt were obtained using the attenuated total reflectance (ATR) mode of Fourier transform infrared spectroscopy (FTIR). The spectral aging fingerprints of the amide band a and sulfoxide b functional groups of the modified asphalt were obtained by peak fitting and the corresponding absorption peak areas were then calculated using the Gaussian-Lorentzian function. The FTIR spectra within the specified range are analyzed, and the functional group variation index (FCI) is quantitatively calculated using the following formula: ； In the above formula, FCI is the functional group change index; FI is the aging index.

4. The method for evaluating the hardening and low loss of in-service asphalt pavement based on structure-property relationship according to claim 3, characterized in that: After peak fitting of the spectral aging fingerprints of amide band a and sulfoxide b functional groups in modified asphalt from actual old pavements, the peak areas of the corresponding absorption peaks were obtained, and then analyzed using the Gaussian-Lorentzian function. During the analysis of the FTIR spectra within the range, the absorption peak areas corresponding to a(i), a(ii), and b are first obtained, and carbonyl AI is then performed. a And sulfoxide AI b The formula for calculating the index is as follows: ； ； ； In the above formula, A 1700 for Absorption peak area at position; A 1650 for Absorption peak area at position; A 1030 for Absorption peak area at position; A ref2 For reference absorption peak area.

5. The method for evaluating the hardening and low-loss of in-service asphalt pavement based on structure-property relationship according to claim 4, characterized in that: The carbonyl and sulfoxide indices of the RTFO and PAV aged asphalt samples were calculated and divided by the indices of the unaged asphalt samples to obtain the corresponding characteristic functional groups. The change index is used to analyze the functional groups that affect asphalt aging by plotting a bar chart of functional group change indexes. The calculation formula is as follows: ； ； ； AI in the above formula a (i), unaged AI is the a(i) index of unaged asphalt. a (ii), unaged For unaged asphalt a(ii) index; AI b,unaged The β-index of unaged asphalt; AI a (i), aged AI is the a(i) index of aged asphalt. a (ii), aged For aged asphalt a(ii) index; AI b , aged For aged asphalt, the b-index is used; FI a (i) Let a(i) be the aging index; FI a (ii) a(ii) aging index; FI b b represents the aging index.

6. The method for evaluating the low-loss hardening of in-service asphalt pavement based on structure-property relationship according to claim 5, characterized in that: The obtained MCI and FCI data were fitted to establish an MCI-FCI correlation equation. A scatter plot was drawn with the MCI values ​​as the ordinate and the corresponding FCI values ​​as the abscissa. The fitting results were observed and the correlation index of the fitted equation was determined to verify the correlation between MCI and FCI. When the correlation index of the fitted equation is greater than 85%, it indicates that there is a correlation between MCI and FCI, which corresponds to the excellent service performance of the modified asphalt in the actual old pavement. When the correlation index of the fitted equation is less than 85%, it indicates that there is no correlation between MCI and FCI, which corresponds to the degradation of the service performance of the modified asphalt in the actual old pavement.

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