A crumb rubber devulcanization degree test characterization method for rubber asphalt

Abstract

The application relates to the technical field of road engineering material detection, and discloses a crumb rubber desulfurization degree test characterization method for rubber asphalt, which comprises the following steps: constructing an equivalent thermal history sample system containing to-be-detected rubber asphalt and benchmark asphalt; collecting multi-temperature gradient frequency scanning and constant-temperature large-amplitude strain scanning data through a dynamic shear rheometer; calculating apparent flow activation energy thermodynamic parameters for characterizing structure unit slip characteristics and critical strain energy density structure mechanical parameters for reflecting microscopic network strength according to the data; and finally constructing a thermal-structure coupling factor by using the two parameters, and accurately obtaining a crumb rubber desulfurization degree index through decoupling calculation. The application constructs a thermal-structure coupling factor based on apparent flow activation energy and critical strain energy density, uses a mathematical decoupling algorithm to separate physical swelling interference, outputs a chemical desulfurization index with extremely high specificity, and realizes quantitative grading of the degradation degree of crumb rubber.

Description

Technical Field

[0001] This invention relates to the field of road engineering material testing technology, specifically a method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt. Background Technology

[0002] Rubber powder processed from waste tires is widely used in road engineering to prepare rubberized asphalt, serving as a high-quality modified material. This technology not only effectively utilizes solid waste but also significantly improves the crack resistance and durability of road surfaces. During the production of rubberized asphalt, the rubber powder undergoes a complex desulfurization degradation reaction within the high-temperature asphalt matrix. This evolution of the microscopic network structure directly determines the final performance of the modified asphalt. To ensure the quality of road construction, a method that can accurately quantify the degree of desulfurization of the rubber powder is urgently needed in production control to determine whether the reaction between the rubber powder and asphalt has reached the expected modified state.

[0003] Currently, the industry's evaluation of rubber asphalt mainly relies on the traditional three major indicators and viscosity testing. By measuring Brinell viscosity, softening point, and penetration, macroscopic consistency and temperature-sensitive performance data of the material can be quickly obtained, thus ensuring the operability of the construction process. To analyze changes in chemical composition, technicians also use the Soxhlet extraction method, using chemical solvents to dissolve and separate asphalt components, thereby determining the gel content of the residue. In addition, standard rheological testing based on dynamic shear rheometer (DSR) is also used to obtain the complex modulus and phase angle of the material, providing macroscopic mechanical parameter support for pavement structure design.

[0004] However, existing testing systems have significant logical flaws in distinguishing the true reaction state of rubber powder. Increased conventional physical indicators often confuse the physical swelling caused by oil absorption with the chemical modification resulting from bond breaking and desulfurization, failing to eliminate the rheological illusions caused by simple volume expansion, leading to misjudgments of the modification mechanism. While the mechanism of chemical extraction is clear, it involves toxic solvents and is too time-consuming, failing to meet the need for rapid feedback in engineering projects. In rheological evaluation, existing methods often directly use the original matrix asphalt as a reference, ignoring the thermal aging and hardening of the matrix caused by high-temperature shearing during preparation. This increase in matrix modulus masks the true modification contribution of the rubber powder. Furthermore, the parallel plate gaps set in conventional rheological tests are usually small, making it difficult to accommodate large-sized rubber powder particles. Particles easily form rigid bridging and mechanical friction between the fixtures, resulting in large data dispersion and difficulty in capturing stable microstructural features. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for testing and characterizing the degree of desulfurization of rubber powder in rubber asphalt. This method solves the problems in existing technologies, such as the inability to distinguish between physical swelling and chemical desulfurization, neglect of matrix aging interference, and data distortion and ambiguous index evaluation caused by the mismatch between large particles and small gaps.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt, comprising the following steps: A test sample system was constructed to obtain the rubber asphalt samples to be tested that underwent consistent thermal history treatment and the reference asphalt samples used to provide comparative data. Rheological tests were performed on both the rubber asphalt sample to be tested and the reference asphalt sample using a dynamic shear rheometer. Multi-temperature gradient frequency scanning data covering a preset temperature range were collected, and isothermal large-amplitude strain scanning data at a fixed temperature were also collected. Based on the multi-temperature gradient frequency scanning data, the apparent flow activation energy, which reflects the ease of slippage of the internal structural units of the material, is calculated as a thermodynamic parameter. The critical strain energy density, which reflects the strength of the material's micro-network structure, is calculated based on the isothermal large-amplitude strain scanning data and used as a structural mechanical parameter. A thermal-structural coupling factor is constructed using the aforementioned thermodynamic parameters and structural mechanical parameters, and the desulfurization degree index is obtained by decoupling based on the aforementioned thermal-structural coupling factor.

[0007] Preferably, the construction of the test sample system includes: Homologous matrix asphalt was selected as the raw material for preparing the rubber asphalt sample to be tested and the reference asphalt sample, respectively; Record the temperature parameters, shear duration, and stirring speed parameters set throughout the entire process of preparing the rubber asphalt sample to be tested; The homologous matrix asphalt used to prepare the reference asphalt sample is placed in a container free of rubber powder particles. The same temperature parameters, shear duration, and stirring speed parameters as those of the rubber asphalt sample to be tested are applied, so that the asphalt matrix of the reference asphalt sample undergoes a component volatilization and thermo-oxidative aging process equivalent to that of the asphalt matrix of the rubber asphalt sample to be tested.

[0008] Preferably, the step of performing rheological tests on both the rubber asphalt sample to be tested and the reference asphalt sample using a dynamic shear rheometer includes: Determine the maximum nominal particle size of the rubber powder particles contained in the rubber asphalt sample to be tested; Set the parallel plate test gap of the dynamic shear rheometer so that the value of the parallel plate test gap is at least four times the value of the maximum nominal particle size; Under the parallel plate test gap, isothermal frequency scanning is performed on the rubber asphalt sample to be tested and the reference asphalt sample respectively to obtain data on the change of complex modulus with angular frequency, which is used as the multi-temperature gradient frequency scanning data. Under the parallel plate test gap, logarithmic incremental shear strain scanning was performed on the rubber asphalt sample to be tested and the reference asphalt sample respectively to obtain data on the monotonically decreasing complex shear modulus with shear strain, which was used as the isothermal large amplitude strain scanning data.

[0009] Preferably, the apparent flow activation energy, which reflects the ease of slippage of internal structural units of the material, is calculated based on the multi-temperature gradient frequency scanning data, including: By utilizing the time-temperature equivalence principle and selecting a reference temperature, the multi-temperature gradient frequency scanning data at different test temperatures are shifted along the frequency axis to construct a dynamic modulus master curve in the wide frequency domain. Extract the shift factor of different test temperatures relative to the reference temperature; Establish a linear regression model between the natural logarithm of the shift factor and the reciprocal of the absolute thermodynamic temperature; The slope value is extracted from the linear regression model, and the apparent flow activation energy is calculated using the slope value according to the Arrhenius equation.

[0010] Preferably, the calculation of the critical strain energy density reflecting the strength of the material's micro-network structure based on the isothermal large-amplitude strain scanning data includes: Establish a linear viscoelastic interval and calculate the arithmetic mean of the complex shear moduli within the linear viscoelastic interval as the initial linear modulus; Monitor the rate of change of the complex shear modulus relative to the initial linear modulus, and determine the shear strain value corresponding to the decay of the complex shear modulus to a preset linearity threshold, which is taken as the critical strain of linear viscoelasticity. The product of the initial linear modulus and the square of the linear viscoelastic critical strain is calculated, and the product is weighted according to the linearity threshold coefficient to obtain the critical strain energy density.

[0011] Preferably, the step of constructing the thermal-structural coupling factor using the thermodynamic parameters and the structural mechanical parameters includes: Calculate the absolute value of the difference between the apparent flow activation energy of the rubber asphalt sample to be tested and the apparent flow activation energy of the reference asphalt sample, and divide the absolute value of the difference by the apparent flow activation energy of the reference asphalt sample to obtain the thermodynamic normalized parameter. Calculate the difference between the critical strain energy density of the rubber asphalt sample to be tested and the critical strain energy density of the reference asphalt sample, and divide the difference by the critical strain energy density of the reference asphalt sample to obtain the structural mechanics normalized parameters. Using the structural mechanics normalized parameters as the basic quantity, an exponential decay function is constructed using the thermodynamic normalized parameters to correct the basic quantity. The thermal structure coupling factor is obtained by multiplying the structural mechanics normalized parameters by the exponential decay function.

[0012] Preferably, the step of selecting homologous matrix asphalt as the raw material for preparing the rubber asphalt sample to be tested and the reference asphalt sample includes: Verify that the base asphalt used to prepare the rubber asphalt sample to be tested and the base asphalt used to prepare the reference asphalt sample are from the same production batch from the same manufacturer; The matrix bitumen is extracted from the same storage container at the same time point to eliminate the initial deviations in saturated content, aromatic content, gum content, and asphaltenes content caused by differences in crude oil origin or refining process.

[0013] Preferably, setting the parallel plate test gap of the dynamic shear rheometer includes: The maximum nominal particle size of the rubber powder particles in the rubber asphalt sample to be tested is determined by standard sieving or laser particle size analysis. The physical test gap value is obtained by multiplying the maximum nominal particle size by the preset structural tolerance coefficient. The physical test gap value is input into the control software of the dynamic shear rheometer to update the shear strain constant and shear stress constant.

[0014] Preferably, constructing the exponential decay function using the thermodynamic normalization parameter includes: A compatibility penalty coefficient is introduced to adjust the weights of the thermodynamic normalization parameter; Calculate the negative value of the product of the thermodynamic normalized parameter and the compatibility penalty coefficient; Using the natural constant as the base, the exponent of the negative value of the product is calculated and used as the exponential decay function. The exponential decay function is then used to filter out the interference of the physical filling effect on the characterization of the desulfurization degree of the rubber powder.

[0015] Preferably, the desulfurization degree index obtained by decoupling based on the thermal structure coupling factor includes: Construct an S-shaped growth model; The thermal structure coupling factor is input into the S-shaped growth model and mapped to a standardized score within a numerical range. The standardized score is output as the desulfurization degree index. Based on the numerical range of the desulfurization degree index, the modification state of the rubber asphalt sample to be tested is determined to be either a physical swelling-dominated state of low-degree desulfurization, a transitional state of medium-degree desulfurization, or a chemical modification-dominated state of high-degree desulfurization.

[0016] This invention provides a method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt. It has the following beneficial effects: 1. This invention constructs a thermo-structural coupling factor based on apparent flow activation energy and critical strain energy density, and uses a mathematical decoupling algorithm to remove physical swelling interference, outputting a highly specific chemical desulfurization index, thereby realizing the quantitative classification of the degradation degree of rubber powder. Compared with the existing technology that relies on Soxhlet extraction or fuzzy evaluation of a single viscosity index, this invention solves the defect of unclear confusion between physical swelling and the rheological contribution of chemical reaction, and can quickly determine the modification quality without chemical reagents.

[0017] 2. This invention sets up a benchmark asphalt control group that has undergone equivalent shear heat history, and removes the aging and hardening effect of the matrix throughout the preparation cycle from the test data. It establishes an evaluation benchmark that purely reflects the modification behavior of the rubber powder, ensuring that the test results are not affected by the volatilization of the matrix asphalt components. Compared with the baseline drift caused by direct comparison of the original asphalt in the existing technology, this invention solves the problem of artificially high evaluation error caused by ignoring the contribution of matrix aging, and improves the reliability of cross-comparison of data from different batches.

[0018] 3. This invention implements a large-gap rheological testing strategy based on dynamic adjustment of particle size, combined with nonlinear viscoelastic critical scanning, to construct a stable mechanical testing field adapted to heterogeneous systems. This effectively avoids mechanical friction and rigid bridging effects between rubber particles and fixtures. Compared with existing general rheological gap testing schemes, it solves the problems of large data dispersion and microstructure response distortion in high solid content samples, and significantly improves the reproducibility and signal-to-noise ratio of test results. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the system structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the method flow according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the process for decoupling the thermal-structural coupling factor and outputting the desulfurization index in an embodiment of the present invention.

[0020] in: 10. Sample preparation module; 20. Data acquisition module; 30. Thermodynamic calculation module; 40. Mechanical calculation module; 50. Coupled characterization module. Detailed Implementation

[0021] The technical solutions in 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.

[0022] See attached document Figure 1 , Figure 1 This is a structural block diagram of a rubber asphalt powder desulfurization degree testing and characterization system according to an embodiment of the present invention. The present invention provides a rubber asphalt powder desulfurization degree testing and characterization system, including a sample preparation module 10, a data acquisition module 20, a thermodynamic calculation module 30, a mechanical calculation module 40, and a coupled characterization module 50.

[0023] The sample preparation module 10 is used to construct a control group, including preparing the rubber asphalt sample to be tested and a reference asphalt sample. The sample preparation module 10 applies the same thermal history treatment to the reference asphalt sample as to the rubber asphalt sample to be tested.

[0024] The data acquisition module 20 is used to acquire rheological data, and it is equipped with a dynamic shear rheometer. The programs executed by the data acquisition module 20 include a multi-temperature gradient frequency scanning program and a constant-temperature large-amplitude strain scanning program.

[0025] The thermodynamic calculation module 30 is used to calculate the apparent flow activation energy. Based on data from a multi-temperature gradient frequency scanning program, the thermodynamic calculation module 30 constructs a master curve and extracts the shift factor. The thermodynamic calculation module 30 uses the Arrhenius equation to calculate the apparent flow activation energy of the tested rubber asphalt sample and the reference asphalt sample.

[0026] The mechanical calculation module 40 is used to calculate the linear viscoelastic critical strain. Based on data from an isothermal large-amplitude strain scanning program, the mechanical calculation module 40 determines the boundary of the linear viscoelastic region. The mechanical calculation module 40 outputs the linear viscoelastic critical strain of the rubber asphalt sample to be tested and the reference asphalt sample.

[0027] The coupling characterization module 50 is used to output the desulfurization degree index. The coupling characterization module 50 receives the apparent flow activation energy and the linear viscoelastic critical strain. The coupling characterization module 50 calculates the thermodynamic normalized parameters and the structural mechanics normalized parameters. The coupling characterization module 50 constructs the thermo-structural coupling factor and calculates the relative desulfurization degree index.

[0028] See attached document Figure 2 , Figure 2 This is a flowchart of a method for testing and characterizing the desulfurization degree of rubber asphalt powder according to an embodiment of the present invention. The present invention provides a method for testing and characterizing the desulfurization degree of rubber asphalt powder, comprising the following steps: S100, construct the test sample system using sample preparation module 10; select the rubber asphalt sample to be tested and the reference asphalt sample. Perform a dry-burning treatment on the reference asphalt sample to ensure that the temperature history and stirring shear history experienced by the reference asphalt sample are consistent with those of the rubber asphalt sample to be tested. The reference asphalt sample does not contain rubber powder particles.

[0029] S200: Data acquisition module 20 is used to acquire rheological response data. The rubber asphalt sample to be tested or the reference asphalt sample is placed in the parallel plate fixture of the dynamic shear rheometer. The fixture gap is set. A multi-temperature gradient frequency scanning program is executed to acquire complex modulus data. A constant-temperature large-amplitude strain scanning program is executed to acquire nonlinear decay data of storage modulus as a function of shear strain.

[0030] S300 uses the thermodynamic calculation module 30 to calculate thermodynamic parameters; based on the time-temperature equivalence principle, it processes the data from the multi-temperature gradient frequency scanning program to obtain the shift factor. Based on the relationship between the shift factor and temperature, it calculates the apparent flow activation energy of the rubber asphalt sample to be tested and the apparent flow activation energy of the reference asphalt sample.

[0031] S400 uses the mechanical calculation module 40 to calculate the structural mechanical parameters; based on the data from the isothermal large amplitude strain scanning program, it determines the strain value corresponding to the decay of the storage modulus to a preset linearity threshold. It then determines the linear viscoelastic critical strain of the rubber asphalt sample to be tested and the linear viscoelastic critical strain of the reference asphalt sample.

[0032] S500 utilizes the coupling characterization module 50 to decouple and calculate the desulfurization degree index. The apparent flow activation energy of the tested rubber asphalt sample is divided by the apparent flow activation energy of the reference asphalt sample to obtain the thermodynamic normalized parameter. The logarithm of the linear viscoelastic critical strain of the tested rubber asphalt sample is divided by the logarithm of the linear viscoelastic critical strain of the reference asphalt sample to obtain the structural mechanics normalized parameter. The thermodynamic normalized parameter is multiplied by the structural mechanics normalized parameter to obtain the thermo-structural coupling factor. Using the thermo-structural coupling factor in conjunction with the preset physical swelling reference value and the complete desulfurization reference value, the relative desulfurization degree index is calculated and output.

[0033] In this invention, the step of constructing the test sample system (S100) performed by the sample preparation module 10 specifically includes the following sub-steps for eliminating the interference of asphalt matrix aging through physical preparation methods: S110, Selection of Base Asphalt. The base asphalt used to prepare rubberized asphalt is selected as the raw material. Specific types of base asphalt include, but are not limited to, road petroleum asphalt No. 70, No. 90, or No. 110. To ensure consistency in chemical composition, the base asphalt used to prepare the rubberized asphalt sample and the base asphalt used to prepare the reference asphalt sample must be taken from the same production batch from the same manufacturer and sampled from the same storage container. This operation aims to eliminate initial differences in the content of the four components of asphalt—saturated components, aromatic components, resins, and asphaltenes—due to differences in crude oil origin or refining process.

[0034] S120, Obtain the preparation process parameters of the sample to be tested. During the preparation of the rubber powder modified rubber asphalt, i.e., the rubber asphalt sample to be tested, record the thermodynamic and kinetic parameters of the entire reaction process. These parameters include: the isothermal temperature value during the shearing phase. Shear duration Speed ​​of shear mixer and the temperature for heat preservation during the developmental stage and development time Simultaneously, record the mass or volume of the matrix asphalt added during the preparation of the rubber asphalt sample to be tested, as well as the geometric dimensions of the reaction vessel. For the preparation equipment and conventional operating procedures of rubber powder modified asphalt, those skilled in the art can use a high-shear emulsifier with a heating jacket, which will not be elaborated here.

[0035] S130, Perform the thermal history simulation procedure for the reference sample. The base asphalt selected in S110 is placed in a mixing vessel and subjected to an unloaded heat treatment without rubber powder particles to prepare the reference asphalt sample. This step aims to subject the reference asphalt sample to a component volatilization and thermo-oxidative aging process equivalent to that of the rubber asphalt sample to be tested.

[0036] In practice, a reaction vessel of the same specifications as in S120 is selected, and pure asphalt raw material with a mass equal to that of the base asphalt in the rubber asphalt sample to be tested is added. The heating device is controlled to maintain the real-time temperature of the reference asphalt sample. The following relationship must be satisfied: ; in, For the reference asphalt sample in Temperature at any moment During the preparation of the rubber asphalt sample to be tested Real-time temperature recording The allowable temperature control error is set to ±2℃.

[0037] Simultaneously, mechanical stirring was applied to the reference asphalt sample. The stirring speed and stirring duration were controlled in accordance with those recorded in S120. and Consistency. By using the same container specifications, the same liquid level, and the same mixing parameters, it is ensured that the reference asphalt sample and the rubber asphalt sample to be tested have the same air contact surface area and liquid surface renewal rate. Throughout step S130, the mixing container contains only base asphalt (if the sample to be tested contains non-volatile liquid additives, the reference sample should be added in proportion), but no rubber powder particles or other solid modifiers are added.

[0038] Through the S130 process described above, the volatile proportion of light components and the formation proportion of asphalt in the reference asphalt sample are matched with the asphalt matrix in the rubber asphalt sample to be tested. The instruction manual clearly states that this step is thermal history normalization, used to eliminate aging interference caused by thermal history. By reproducing the temperature field, shear field, and gas-liquid interface exchange conditions, it ensures that the asphalt matrix in the reference sample and the sample to be tested has consistent carbonyl index and viscosity increments, thereby limiting the modulus difference in subsequent rheological tests to be solely due to the physical swelling and chemical desulfurization effects of the rubber powder particles.

[0039] S140, Sample Molding and Preservation. The prepared rubber asphalt samples to be tested and the reference asphalt samples are poured into molds suitable for demolding and cooled to a solid state at room temperature. To prevent secondary oxidation or physical hardening after cooling, the samples must be stored in a dark, constant-temperature, and oxygen-free environment, and subsequent rheological tests must be completed within 24 hours.

[0040] In this invention, the step of acquiring rheological response data (S200) performed by the data acquisition module 20 specifically includes the following sub-steps for constructing the test environment: S210, configure the geometric and physical boundaries of the test terminal. A dynamic shear rheometer (DSR) is selected as the measurement host. A 25mm diameter metal parallel plate is installed as a loading fixture. This fixture includes an upper parallel plate connected to the motor shaft and a lower parallel plate fixed to the temperature control base. The 25mm diameter parallel plate is chosen to provide sufficient contact area within the test temperature range of 30°C to 80°C, ensuring a torque signal with a signal-to-noise ratio meeting preset requirements when testing high-viscosity rubber asphalt. For the motor drive principle and temperature control system structure of the dynamic shear rheometer, those skilled in the art can refer to the relevant equipment manuals, which will not be elaborated here.

[0041] S220, Obtain the size distribution characteristics of the rubber powder particles. Before conducting rheological testing, obtain the particle size parameters of the rubber powder particles contained in the rubber asphalt sample to be tested. Determine the maximum nominal particle size of the rubber powder particles using standard sieve analysis or laser particle size analysis. Record this maximum nominal particle size as... For rubber powder particles defined by mesh size, convert them to particle size values ​​in millimeters. For example, if all the rubber powder raw materials pass through a 30-mesh sieve, then... The value is 0.6mm.

[0042] S230, Set the test gap to eliminate particle size effects. Establish and set the test gap between the upper and lower parallel plates. This step aims to dynamically adjust the distance between plates based on the particle size of the adhesive powder, in order to eliminate the particle size effect and prevent the adhesive powder particles from forming rigid bridging in narrow spaces.

[0043] Set physical test interval The following inequality conditions must be met: ; in, The structural tolerance coefficient is a dimensionless factor, which is set in this embodiment. That is, the test gap value should be at least four times the maximum nominal particle size value. At the same time, this set value should be... The numerical values ​​are input into the control software of the dynamic shear rheometer to update the shear strain constant. and shear stress constant This ensures that the rheological data output by the instrument is calculated based on the actual thickness of the medium.

[0044] When the test gap meets the above conditions, the sample within the fixture is considered a uniform, continuous medium and its representative volume unit. This setting avoids the following two nonlinear errors: first, the mechanical friction generated by large particles of rubber powder directly contacting the upper and lower plate surfaces; and second, the rigid contact formed by the mutual compression between particles interfering with the viscoelastic signal of the asphalt mastic itself. For example, for rubber powder with a maximum particle size of 0.425 mm (40 mesh), the test gap is set to 1.7 mm or 2.0 mm.

[0045] S240, Sample Loading and Geometric Trimming. Using a scraper or sampling spoon, place the heated and softened rubber asphalt sample or reference asphalt sample at the center of the lower parallel plate. Control the upper parallel plate to descend to the preset trimming height, which is the set test gap. Add a margin of 0.05mm.

[0046] After reaching the trimming height, use a heated scraper to remove excess asphalt along the edge of the parallel plate to ensure a smooth, vertical cylindrical surface on the sample edge. Then, lower the upper parallel plate to the final test gap. This operation creates a slightly convex meniscus at the sample edge, compensating for volume shrinkage caused by temperature changes. Before formal data acquisition, the sample is kept at the test temperature for at least 10 minutes to ensure a uniform internal temperature field and eliminate residual normal stress generated during loading.

[0047] In this invention, the thermodynamic characteristic acquisition step (S300) executed by the thermodynamic calculation module 30 utilizes temperature frequency scanning testing and the time-temperature equivalence principle to analyze the viscoelastic property parameters of the sample, specifically including the following sub-steps: S310, perform isothermal frequency scanning test. For the rubber asphalt sample to be tested and the reference asphalt sample prepared in S100, the test program of the dynamic shear rheometer is set separately. The test mode is set to isothermal frequency scanning. The temperature scanning range is set to cover the service temperature of the rubber asphalt pavement, specifically from 30°C to 80°C. Within this range, the temperature interval is set to 10°C, and a total of 6 characteristic temperature points are selected (30°C, 40°C, 50°C, 60°C, 70°C, 80°C).

[0048] At each characteristic temperature point, the sample was kept at a constant temperature, and an angular frequency was applied. Dynamic shear loads ranging from 0.1 rad / s to 100 rad / s were applied. To ensure that the test data reflected the linear viscoelastic properties of the material, the sample underwent an amplitude scan beforehand to determine the linear viscoelastic range where the complex modulus attenuation was less than 5%. In this embodiment, the shear strain was controlled within the range of 0.1% to 1.0%, and it was ensured that the feedback torque value remained higher than the instrument's minimum torque resolution even under high-temperature, high-frequency loading at 80 degrees Celsius.

[0049] S320, constructing the dynamic modulus master curve. Based on the complex modulus acquired by the instrument. With phase angle The data was normalized using the Time-Temperature Equivalence Principle (TTSP). 60 degrees Celsius was selected as the reference temperature. This reference temperature corresponds to the highest surface temperature of asphalt pavement in summer and is a key temperature range for evaluating high-temperature rutting resistance.

[0050] Using a translation algorithm, the curve at the reference temperature is kept stationary, while the logarithmic curves of the complex modulus at other test temperatures are horizontally translated along the frequency axis. During the translation process, the sum of squared residuals in the overlapping regions of the curves at different temperatures is calculated using the least squares method. The horizontal displacement that minimizes the sum of squared residuals is then iteratively solved; this displacement is the shift factor at that temperature. Ultimately, this forms a wide-bandwidth spectrum (equivalent frequency range covering 10...). 3 rad / s to 10 4 A continuous master curve within rad / s.

[0051] S330: An Arrhenius thermodynamic model was established. The shift factor extracted from S320 was used to quantitatively characterize the temperature sensitivity of the material's viscoelastic behavior. For the rubber-asphalt system, its rheological behavior approximately follows the Arrhenius equation within the test temperature range of 30°C to 80°C. The natural logarithm of the shift factor was then used. As the dependent variable, the reciprocal of the absolute thermodynamic temperature Using these variables as independent variables, a linear regression model is constructed.

[0052] The specific mathematical relationships are as follows: ; in, For temperature The horizontal shift factor below, Apparent activation energy (unit: J / mol). This is the universal gas constant (valued at 8.314 J / (mol·K)). The absolute temperature at the test point (unit: K). The absolute temperature (unit: K) is the reference temperature.

[0053] S340 analyzes the apparent flow activation energy parameters. Linear fitting is performed on the data points constructed in S330, and the coefficient of determination of the linear fit is calculated. .like If the value is greater than a preset threshold (e.g., 0.95), the sample is determined to conform to the Arrhenius model assumptions, and the slope of the fitted line is then extracted. Calculate the apparent flow activation energy based on the differential form of the Arrhenius equation. : ; Following the steps described above, the activation energy values ​​of the rubber asphalt samples to be tested were calculated. Activation energy values ​​compared to reference asphalt samples .

[0054] The above apparent flow activation energy The calculation of this is the specific implementation of obtaining the thermodynamic parameters described in this invention. Physically, The numerical values ​​reflect the energy barrier that the internal structural units of a material need to overcome when they undergo relative slippage or rearrangement under shearing.

[0055] In rubber asphalt systems, the swelling and desulfurization of rubber particles directly alter the free volume and intermolecular forces of the asphalt matrix, thus causing changes in the flow activation energy. By obtaining the activation energies of the test sample and the reference sample separately, and performing subsequent differential calculations, the influence of the thermal sensitivity of the base asphalt itself can be eliminated, thereby independently characterizing the thermodynamic state evolution caused by the modification behavior of rubber particles.

[0056] In this invention, the structural stability assessment step (S400) executed by the structural mechanics calculation module 40 aims to quantitatively characterize the micro-network strength of the asphalt-rubber powder composite system through destructive testing, specifically including the following sub-steps: S410, large amplitude strain scanning test was performed. After sample preparation, the dynamic shear rheometer was set to perform large amplitude oscillating shear (LAOS) test. The test temperature was kept constant at 25 degrees Celsius. Given that rubber asphalt has a high complex modulus at 25 degrees Celsius, and the test requires large strain to destroy the material structure, to prevent instrument overload and reduce instrument compliance error, the loading fixture was replaced with a metal parallel plate with a diameter of 8 mm, and the test gap was adjusted to 2.0 mm.

[0057] Set the loading angular frequency to a fixed value (e.g., 10 rad / s). Set the shear strain. The loading mode was logarithmic incremental scanning, with the scan range set from 0.1% to 30%. During the scan, the data sampling density was set to at least 10 data points per decibel to ensure sufficient data resolution in the modulus attenuation region. The instrument recorded the shear stress as strain increased. Complex shear modulus and phase angle data.

[0058] S420 identifies the linear viscoelastic limit and modulus decay characteristics. Based on the test data obtained from S410, a complex shear modulus is constructed. With shear strain The changing rheological spectrum. In the low strain region (e.g.) The complex modulus remains stable. The arithmetic mean of the moduli at all sampling points within the linear viscoelastic interval (LVE) is calculated and defined as the initial linear modulus. .

[0059] As shear strain increases, the microstructure within the sample (including the physical cross-linking network formed by asphaltene micelles and resin particles) undergoes orientation changes or deentanglement, manifested as a monotonically decreasing complex modulus with increasing strain. Monitoring... Relative to the initial linear modulus The rate of change is used as the basis for obtaining the structural yield characteristics and judging the integrity state of the internal structure of the material.

[0060] S430, calculate the critical strain point for structural failure. Based on modulus decay data, determine the critical point at which the material exits the linear region and the structure yields. This embodiment adopts the definition in the SHRP (Strategic Highway Research Program) specification, defining the shear strain value corresponding to the decrease of the complex modulus to 95% of the initial linear modulus as the critical strain. .

[0061] The specific calculation follows these criteria: ; in, To measure the shear strain, This is the complex modulus under corresponding strain. If there is no point in the measured data that is exactly equal to the 95% attenuation rate, then a two-point logarithmic linear interpolation method is used to accurately calculate the modulus based on two adjacent data points. x-coordinate value at time .

[0062] S440, calculate the critical strain energy density parameter. To comprehensively characterize a material's resistance to deformation and failure, the accumulated strain energy density at the critical point is calculated. This critical strain energy density... This is a structural mechanics parameter characterizing the strength of the network. It represents the maximum deformation energy that a material can store per unit volume while maintaining the integrity of its microstructure.

[0063] The calculation formula is as follows: ; in, The unit is joules per cubic meter (J / m³). 3 ) or Pascal (Pa). The product of coefficients 0.5 and 0.95.

[0064] Calculate the critical strain energy density of the rubber asphalt samples to be tested. Critical strain energy density compared to the reference asphalt sample Compared to a single modulus index, At the same time, the stiffness of the material was weighted (from (embodied) and maximum linear deformation capacity (by This allows for a more comprehensive evaluation of the crack initiation resistance of modified asphalt.

[0065] S450 is used to extract the micro-network enhancement factor. Based on the calculation results of S440, the structural gain brought about by rubber powder modification is quantified. Because rubber powder absorbs oil and swells in asphalt to establish a three-dimensional elastic network structure, it typically... Significantly greater than Define the structural enhancement factor. : ; Should The value is a quantitative index of the modification mechanism based on the critical state. Its physical meaning is: the percentage increase in the ability of the asphalt matrix to accommodate elastic-plastic deformation energy after the introduction of rubber powder particles.

[0066] See attached document Figure 3 , Figure 3This is a schematic diagram of the process for decoupling the thermal-structural coupling factor and outputting the desulfurization index according to an embodiment of the present invention.

[0067] In this invention, the index calculation and rating step (S500) performed by the comprehensive analysis module 50 aims to comprehensively calculate the independently acquired thermodynamic parameters and structural mechanical parameters, and eliminate the performance increment brought by pure mechanical filling by constructing a decoupling algorithm, thereby independently quantifying the contribution of the desulfurization reaction of the rubber powder to the material performance. Specifically, it includes the following sub-steps: S510, parameter normalization preprocessing. This involves calling upon the four key physical quantities obtained from the above steps: the apparent flow activation energy of the rubber asphalt to be tested and the reference asphalt (…). , ), and the critical strain energy density of the rubber asphalt to be tested and the reference asphalt ( , ).

[0068] To eliminate the impact of dimensional differences in physical quantities on the comprehensive evaluation, a dimensionless comparison operator was constructed to calculate the thermodynamic sensitivity difference ratio. Ratio of structural strength increment The calculation formula is as follows: ; ; in, The magnitude of the value reflects the degree of deviation between the modified asphalt and the base asphalt in terms of rheological properties, that is, the degree of incompatibility. The magnitude of this value reflects the extent to which the rubber network enhances the resistance of the asphalt matrix to damage. Under ideal chemical modification conditions, the material should possess high... That is, a significant enhancement effect while maintaining a low level. That is, good compatibility and processing stability.

[0069] S520, construct the thermal-structural coupling factor. Based on the normalized data from S510, construct the thermal-structural coupling factor. The decoupling calculations using this factor are used to distinguish between two different modification mechanisms: physical swelling and filling, and chemical desulfurization and crosslinking.

[0070] Physical swelling-dominated rubber asphalt typically exhibits the following characteristics: Limited increase accompanied by The concentration of [something] increased significantly; while rubber asphalt that underwent deep desulfurization showed improved interfacial compatibility. It is suppressed, while the polymer chain entanglement it releases makes promote.

[0071] Based on this, the coupling factor is defined. The calculation model is as follows: ; in, For the natural constant An exponential function with base 0; This is the compatibility penalty coefficient (or sensitivity coefficient), used to adjust the weighting of thermodynamic differences on the final score. In this embodiment, for the calibration of a specific base asphalt, it is set as follows: In other embodiments, this coefficient can be adjusted within the range of 1.0 to 5.0 depending on the colloidal type (sol or gel) of the base bitumen. The physical meaning of this formula is: taking the structural reinforcement ratio as a base quantity, it is exponentially corrected using thermodynamic differences. When When it is large, the coupling factor It will be rapidly attenuated, thus filtering out the false enhancements brought about by physical fill alone.

[0072] S530, calculate the desulfurization index. Use the coupling factor obtained from S520... Mapped to a standardized desulfurization index .Should The value is a quantitative indicator of the degree of desulfurization. To facilitate engineering-level evaluation, a sigmoid function growth model is used. Convert the value to a score within a numerical range (e.g., 10 to 100): ; in, and The shape parameters of the model determine the initial threshold and growth rate of the scoring curve. In this embodiment, we take... , This model ensures The value increases nonlinearly with the increase of the coupling factor, which is consistent with the evolution law of the polymer modification effect from quantitative change to qualitative change.

[0073] S540 generates a modified quality rating conclusion. Based on the calculated... The numerical values ​​are used to classify the samples under test into different desulfurization modification levels. The classification logic in this embodiment is set as follows: like The conclusion is that the low degree of desulfurization / physical swelling is dominant, indicating that the sample mainly exhibits physical blending characteristics and has low high-temperature stability. like The conclusion is that the desulfurization is moderate / transitional, indicating that a partial decrosslinking reaction has occurred on the surface of the rubber powder. like The conclusion is that the process is dominated by high desulfurization / chemical modification, indicating that the rubber powder and asphalt have gradually formed a stable interpenetrating network structure.

[0074] Through the above steps, microrheological data are transformed into a single quantitative indicator. This indicator can be directly used as a feedback basis for optimizing rubber asphalt production process parameters (such as development time, shear temperature, and shear rate).

[0075] To further clarify the collaborative working process of the technical solution described in this invention, a specific working scenario example will be used below. This example demonstrates how to optimize and screen the development time parameters in the rubber asphalt production process using the aforementioned thermo-structural coupling evaluation method.

[0076] In a typical rubber asphalt production control scenario, technicians need to determine the optimal reaction time for rubber asphalt prepared via a wet process. The base asphalt was selected as No. 70 road petroleum asphalt, and the modifier was 40-mesh waste tire rubber powder, with an internal admixture dosage set at 20%. To evaluate the microscopic modification mechanism at different reaction stages, three groups of rubber asphalt samples were prepared and matured at 180 degrees Celsius for 45 minutes (sample A), 90 minutes (sample B), and 240 minutes (sample C), respectively. Unmodified base asphalt was retained as a control benchmark.

[0077] For reference asphalt, its apparent flow activation energy was calculated by testing with a dynamic shear rheometer. The critical strain energy density is 85 kJ / mol. 150J / m 3 This baseline data serves as the normalization origin for subsequent evaluation models.

[0078] Next, sample A (developed for 45 minutes) was tested. During this stage, the rubber particles mainly underwent volume swelling, adsorbing light oils from the asphalt. Test data showed its flow activation energy... The critical strain energy density increases significantly to 120 kJ / mol because the swollen particles, acting as elastic inclusions, impede the flow of the medium, leading to increased fluid sensitivity to temperature changes. Simultaneously, the enhanced physical contact between particles increases the critical strain energy density. Increased to 450J / m 3 .

[0079] According to the computational logic of this invention, normalization is first performed: Thermodynamic sensitivity difference ratio ; Structural strength increment ratio .

[0080] Substitute into the thermal-structural coupling factor formula (assuming...) ): .

[0081] Further mapping to the desulfurization index (assuming...) ): .

[0082] The result was low (less than 40), which quantitatively determined that sample A was in the physical swelling stage. This indicates that although the material hardened (modulus increased), it was mainly due to the particle filling effect and had not yet formed a stable chemical network, posing a compatibility risk to its road performance.

[0083] Subsequently, sample B (developed for 90 minutes) was tested. During this stage, partial desulfurization and degradation occurred on the surface of the rubber powder, releasing polymer segments that grafted or interpenetrated with the asphalt components. Test data showed its flow activation energy... The temperature dropped to 95 kJ / mol, indicating that the system tended towards homogenization and improved compatibility. Simultaneously, due to the formation of an effective elastic network, the critical strain energy density... It further jumped to 900J / m 3 .

[0084] The calculation process is as follows: ; ; ; .

[0085] The result is high (greater than 70), indicating that sample B is in the stage dominated by high-level desulfurization / chemical modification. The values ​​confirm that the sample achieves the optimal balance between a strong structural network and high compatibility, that is, it maximizes structural strength while suppressing thermal sensitivity fluctuations.

[0086] Finally, sample C (developed for 240 minutes) was tested. Due to the excessively long reaction time, the rubber powder particles underwent deep degradation and even carbonization, leading to the collapse of the network structure. Test data showed that although the flow activation energy... Further reduced to 88 kJ / mol (close to the base asphalt), but the critical strain energy density Significantly reduced to 300 J / m 3 .

[0087] Calculations show: (Excellent compatibility); (Structural reinforcement is weak).

[0088] .

[0089] .

[0090] Although sample C exhibits excellent compatibility, its desulfurization index is low due to the lack of structural enhancement factors. Instead, it decreased significantly. This result accurately identified the overreaction phenomenon, avoiding misjudgments that might occur based solely on conventional viscosity indicators. In conventional testing, a decrease in viscosity is often mistakenly considered an indication of good compatibility, when in fact it indicates modification failure.

[0091] As can be seen from the above comparative scenarios, the technical solution provided by this invention can penetrate macroscopic indicators such as viscosity and accurately locate the modified state of rubber asphalt through decoupled analysis of thermodynamics and structural mechanics. Production units can then use this... The peak position of the index (around 90 minutes in this example) can be used to determine the optimal production process parameters, thereby enabling digital closed-loop control of quality in industrial production.

[0092] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for testing and characterizing the desulfurization degree of rubber powder used in rubber asphalt, characterized in that, Includes the following steps: A test sample system was constructed to obtain the rubber asphalt samples to be tested that underwent consistent thermal history treatment and the reference asphalt samples used to provide comparative data. Rheological tests were performed on both the rubber asphalt sample to be tested and the reference asphalt sample using a dynamic shear rheometer. Multi-temperature gradient frequency scanning data covering a preset temperature range were collected, and isothermal large-amplitude strain scanning data at a fixed temperature were also collected. Based on the multi-temperature gradient frequency scanning data, the apparent flow activation energy, which reflects the ease of slippage of the internal structural units of the material, is calculated as a thermodynamic parameter. The critical strain energy density, which reflects the strength of the material's micro-network structure, is calculated based on the isothermal large-amplitude strain scanning data and used as a structural mechanical parameter. A thermal-structural coupling factor is constructed using the aforementioned thermodynamic parameters and structural mechanical parameters, and the desulfurization degree index is obtained by decoupling based on the aforementioned thermal-structural coupling factor.

2. The method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt according to claim 1, characterized in that, The construction of the test sample system includes: Homologous matrix asphalt was selected as the raw material for preparing the rubber asphalt sample to be tested and the reference asphalt sample, respectively; Record the temperature parameters, shear duration, and stirring speed parameters set throughout the entire process of preparing the rubber asphalt sample to be tested; The homologous matrix asphalt used to prepare the reference asphalt sample is placed in a container free of rubber powder particles. The same temperature parameters, shear duration, and stirring speed parameters as those of the rubber asphalt sample to be tested are applied, so that the asphalt matrix of the reference asphalt sample undergoes a component volatilization and thermo-oxidative aging process equivalent to that of the asphalt matrix of the rubber asphalt sample to be tested.

3. The method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt according to claim 1, characterized in that, The rheological testing of both the rubber asphalt sample to be tested and the reference asphalt sample using a dynamic shear rheometer includes: Determine the maximum nominal particle size of the rubber powder particles contained in the rubber asphalt sample to be tested; Set the parallel plate test gap of the dynamic shear rheometer so that the value of the parallel plate test gap is at least four times the value of the maximum nominal particle size; Under the parallel plate test gap, isothermal frequency scanning is performed on the rubber asphalt sample to be tested and the reference asphalt sample respectively to obtain data on the change of complex modulus with angular frequency, which is used as the multi-temperature gradient frequency scanning data. Under the parallel plate test gap, logarithmic incremental shear strain scanning was performed on the rubber asphalt sample to be tested and the reference asphalt sample respectively to obtain data on the monotonically decreasing complex shear modulus with shear strain, which was used as the isothermal large amplitude strain scanning data.

4. The method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt according to claim 1, characterized in that, The apparent flow activation energy, which reflects the ease of slippage of internal structural units of the material, is calculated based on the aforementioned multi-temperature gradient frequency scanning data. By utilizing the time-temperature equivalence principle and selecting a reference temperature, the multi-temperature gradient frequency scanning data at different test temperatures are shifted along the frequency axis to construct a dynamic modulus master curve in the wide frequency domain. Extract the shift factor of different test temperatures relative to the reference temperature; Establish a linear regression model between the natural logarithm of the shift factor and the reciprocal of the absolute thermodynamic temperature; The slope value is extracted from the linear regression model, and the apparent flow activation energy is calculated using the slope value according to the Arrhenius equation.

5. The method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt according to claim 1, characterized in that, The critical strain energy density, which reflects the strength of the material's micro-network structure, calculated based on the isothermal large-amplitude strain scanning data, includes: Establish a linear viscoelastic interval and calculate the arithmetic mean of the complex shear moduli within the linear viscoelastic interval as the initial linear modulus; Monitor the rate of change of the complex shear modulus relative to the initial linear modulus, and determine the shear strain value corresponding to the decay of the complex shear modulus to a preset linearity threshold, which is taken as the critical strain of linear viscoelasticity. The product of the initial linear modulus and the square of the linear viscoelastic critical strain is calculated, and the product is weighted according to the linearity threshold coefficient to obtain the critical strain energy density.

6. The method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt according to claim 1, characterized in that, The method of constructing the thermal-structure coupling factor using the thermodynamic parameters and the structural mechanical parameters includes: Calculate the absolute value of the difference between the apparent flow activation energy of the rubber asphalt sample to be tested and the apparent flow activation energy of the reference asphalt sample, and divide the absolute value of the difference by the apparent flow activation energy of the reference asphalt sample to obtain the thermodynamic normalized parameter. Calculate the difference between the critical strain energy density of the rubber asphalt sample to be tested and the critical strain energy density of the reference asphalt sample, and divide the difference by the critical strain energy density of the reference asphalt sample to obtain the structural mechanics normalized parameters. Using the structural mechanics normalized parameters as the basic quantity, an exponential decay function is constructed using the thermodynamic normalized parameters to correct the basic quantity. The thermal structure coupling factor is obtained by multiplying the structural mechanics normalized parameters by the exponential decay function.

7. The method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt according to claim 2, characterized in that, The selection of homologous matrix asphalt as the raw material for preparing the rubber asphalt sample to be tested and the reference asphalt sample includes: Verify that the base asphalt used to prepare the rubber asphalt sample to be tested and the base asphalt used to prepare the reference asphalt sample are from the same production batch from the same manufacturer; The matrix bitumen is extracted from the same storage container at the same time point to eliminate the initial deviations in saturated content, aromatic content, gum content, and asphaltenes content caused by differences in crude oil origin or refining process.

8. The method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt according to claim 3, characterized in that, The setting of the parallel plate test gap of the dynamic shear rheometer includes: The maximum nominal particle size of the rubber powder particles in the rubber asphalt sample to be tested is determined by standard sieving or laser particle size analysis. The physical test gap value is obtained by multiplying the maximum nominal particle size by the preset structural tolerance coefficient. The physical test gap value is input into the control software of the dynamic shear rheometer to update the shear strain constant and shear stress constant.

9. The method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt according to claim 6, characterized in that, The construction of the exponential decay function using the thermodynamic normalized parameters includes: A compatibility penalty coefficient is introduced to adjust the weights of the thermodynamic normalization parameter; Calculate the negative value of the product of the thermodynamic normalized parameter and the compatibility penalty coefficient; Using the natural constant as the base, the exponent of the negative value of the product is calculated and used as the exponential decay function. The exponential decay function is then used to filter out the interference of the physical filling effect on the characterization of the desulfurization degree of the rubber powder.

10. The method for testing and characterizing the desulfurization degree of rubber powder in rubber asphalt according to claim 6, characterized in that, The desulfurization degree index obtained by decoupling calculation based on the thermal structure coupling factor includes: Construct an S-shaped growth model; The thermal structure coupling factor is input into the S-shaped growth model and mapped to a standardized score within a numerical range. The standardized score is output as the desulfurization degree index. Based on the numerical range of the desulfurization degree index, the modification state of the rubber asphalt sample to be tested is determined to be either a physical swelling-dominated state of low-degree desulfurization, a transitional state of medium-degree desulfurization, or a chemical modification-dominated state of high-degree desulfurization.

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