A method for quantitatively evaluating the degree of fusion between new and old asphalt based on recycled asphalt mortar

Abstract

This invention proposes a method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar. The method determines the linear viscoelastic region of the recycled asphalt mortar through strain scanning testing, obtains the rheological parameters of the recycled asphalt mortar based on frequency scanning, and compares the differences in rheological parameters between fully fused recycled asphalt mortar and actually fused recycled asphalt mortar. The complex modulus shift rate and the degree of fusion between new and old asphalt are calculated according to a formula at key frequencies. This invention is the first to evaluate the degree of fusion between new and old asphalt at the asphalt mortar scale, overcoming the limitations of traditional techniques in terms of realism, accuracy, and practicality.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, and in particular to a method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar. Background Technology

[0002] In recycled asphalt mixtures, the degree of integration between new and old asphalt is one of the core factors affecting the recovery of material properties. Insufficient integration between new and old asphalt will lead to weak interfaces and structural dispersion, thereby weakening the overall mechanical properties and long-term service capacity of the mixture. Current engineering practice relies heavily on indirect methods such as macroscopic performance indicators of the mixture, including rutting tests, low-temperature bending tests, or water stability tests. While these methods have some reference value, they cannot reveal the actual integration state of new and old asphalt at the microscopic level.

[0003] Against this backdrop, developing an assessment method for the degree of integration between new and old asphalt in recycled asphalt mortar is particularly necessary. On the one hand, mortar is a key bonding structure connecting asphalt and fine aggregates, and can sensitively reflect the internal integration behavior of the asphalt phase. On the other hand, focusing on the mortar stage can effectively shield the influence of the aggregate skeleton structure, making the observation of the integration characteristics of the asphalt phase more direct and clear. Quantitative analysis of the diffusion, cross-linking, and interfacial transition characteristics of new and old asphalt in mortar can provide microscopic evidence for assessing the activity of recycling agents, optimizing heating and mixing processes, and serve as a preliminary indicator for predicting the overall performance of the mixture.

[0004] Current research has attempted to characterize the asphalt phase fusion process using methods such as fluorescence microscopy, Fourier transform infrared spectroscopy (FTIR), and elemental analysis, but there is still a lack of standardized, engineered, and low-cost quantitative analysis systems.

[0005] Therefore, there is an urgent need to develop a method for evaluating the degree of integration between new and old asphalt based on recycled asphalt mortar systems, so as to achieve effective linkage from microstructure to macro performance, provide scientific support for the research and development and application of recycled asphalt materials, and promote the development of sustainable road engineering. Summary of the Invention

[0006] In view of this, the present invention proposes a method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar, which breaks through the limitations of traditional technical means in terms of authenticity, accuracy and practicality.

[0007] The technical solution of the present invention is achieved as follows:

[0008] In a first aspect, the present invention provides a method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar, comprising the following steps:

[0009] Step S1: Determine the amounts of recycled asphalt mixture (RAP), new aggregate, new mineral powder, and new asphalt, as well as the content of old aggregate, old mineral powder, and old asphalt in the RAP.

[0010] Based on the amounts of RAP, new aggregate, new mineral powder, and new asphalt, as well as the contents of old RAP aggregate, old RAP mineral powder, and old asphalt in RAP, recycled asphalt mortar with complete fusion of new and old asphalt and recycled asphalt mortar with actual fusion of new and old asphalt are prepared.

[0011] Step S2: Test the linear viscoelastic region of the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused.

[0012] Step S3: Based on the linear viscoelastic region in step S2, test the viscoelastic parameters of the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused.

[0013] Step S4: Based on the viscoelastic parameters in Step S3, fit the complex modulus master curves of the fully fused recycled asphalt mortar and the actually fused recycled asphalt mortar, and calculate the complex modulus.

[0014] Step S5: According to the formula , Calculate the complex modulus offset rate and the degree of fusion between new and old asphalt at the key frequency;

[0015] Where, The offset rate is the complex modulus. To determine the degree of integration between the old and new asphalt, The number of parallel trials, The complex modulus of the recycled asphalt mortar formed by the actual fusion of the old and new asphalt is given. The complex modulus of the recycled asphalt mortar where the old and new asphalt are fully integrated.

[0016] Based on the above technical solution, furthermore, the RAP in the recycled asphalt mortar that actually blends the new and old asphalt is added in the form of RAP mortar composed of old RAP aggregate, old asphalt and old RAP mineral powder, and the RAP mortar is obtained by fine screening of RAP with a particle size of less than 2.36mm.

[0017] Based on the above technical solutions, further, in step S1, the method for preparing recycled asphalt mortar with complete fusion of new and old asphalt includes the following steps:

[0018] Step A1: Mix the old asphalt and new asphalt in the recycled asphalt mixture (RAP) to obtain fully blended recycled asphalt;

[0019] Step A2: Heat the fully fused recycled asphalt from step A1 at 160°C for 1 hour, and heat the new aggregate, RAP old aggregate, RAP old mineral powder and new mineral powder at 170°C for 3 hours.

[0020] Step A3: Stir the new aggregate and RAP old aggregate from step A2 at 160°C for 30 seconds, add the fully fused recycled asphalt and stir for 60 seconds, add the RAP old mineral powder and new mineral powder and stir for 120 seconds. The stirring rate is 800 r / min.

[0021] Based on the above technical solutions, further, in step A1, the method for preparing old asphalt in the recycled asphalt mixture includes recovery through an asphalt mixture analyzer and a rotary evaporator.

[0022] Based on the above technical solution, further, in step S1, the method for preparing recycled asphalt mortar by actual fusion of new and old asphalt includes the following steps:

[0023] Step a1: Heat the new aggregate at 170°C for 3 hours, the RAP mortar at 110°C for 1 hour, and the new asphalt at 160°C until it reaches a fluid state.

[0024] Step a2: Mix the new aggregate and RAP mortar from step a1 for 30 seconds, add the new asphalt from step a1 and mix for 60 seconds, add the new mineral powder and mix for 120 seconds, and the mixing speed is 800 r / min.

[0025] Based on the above technical solution, step S2 further includes: using strain scanning to test the linear viscoelastic region of the fully fused recycled asphalt mortar and the actually fused recycled asphalt mortar, and selecting the complex shear modulus. The strain corresponding to the initial value decreasing to 95% is used as the critical point for determining the linear viscoelastic region. This is used to determine the strain level in the linear viscoelastic region. The strain scan range increases from 0.0001% logarithmically to 0.1%, the scan frequency is 10Hz, and the temperature is 20℃.

[0026] Asphalt mortar is a typical viscoelastic material. When the strain or stress applied to a sample is within a certain range, the sample's structure undergoes elastic deformation. This deformation is fully recoverable and does not damage the material structure, exhibiting a linear viscoelastic response. The corresponding stress or strain range constitutes the linear viscoelastic region (LVE). However, when the applied stress or strain exceeds this threshold, the sample will undergo irreversible structural changes, thus exhibiting nonlinear viscoelastic (NLVE) behavior. Typically, the boundary of the linear viscoelastic region is determined by the complex shear modulus (…). The stress or strain corresponding to a decrease to 90%~97% of its initial value is defined. This invention uses strain scanning testing to determine the linear viscoelastic region of recycled asphalt mortar, selecting... The strain corresponding to the initial value decreasing to 95% is taken as the key critical point for determining the linear viscoelastic region.

[0027] Based on the above technical solution, further, step S3 includes: selecting the corresponding strain amplitude based on the linear viscoelastic region of the fully fused new and old asphalt recycled asphalt mortar and the actually fused new and old asphalt recycled asphalt mortar tested in step S2, loading the frequency from 0.1Hz to 10Hz logarithmically, and testing the viscoelastic characteristic parameters of the actually fused new and old asphalt recycled asphalt mortar at 10℃, 20℃, 30℃ and 40℃ respectively.

[0028] The purpose of setting the frequency range (0.1Hz~10Hz) and temperature range (10℃, 20℃, 30℃, 40℃) is to comprehensively capture the viscoelastic behavior characteristics of recycled asphalt mortar under different working conditions. It is to systematically analyze the influence of the degree of fusion between new and old asphalt on the viscoelastic properties of recycled asphalt mortar in a multi-scale loading environment under simulated real driving conditions, and to build a performance identification model and fusion degree index basis under a wide frequency / wide temperature range.

[0029] The reasons for setting the frequency range include: (1) Loading frequency changes, simulating the frequency changes of traffic load. The lower the frequency, the more it simulates the slow passage of vehicles or long-term loading (such as high temperature slow lane, traffic congestion); the higher the frequency, the more it simulates the fast load (such as vehicles passing by quickly); the frequency change can reveal the stress relaxation ability, modulus response and rheological characteristics of asphalt mortar under different stresses.

[0030] The reasons for setting the temperature range include: setting four temperatures—10℃, 20℃, 30℃, and 40℃—combined with the loading frequency range (0.1–10Hz), to enable multi-temperature, multi-frequency data to cover the time-temperature space. This design lays the foundation for applying the Time-Temperature Equivalence Principle (TTSP) to achieve the translational superposition of multi-condition data and the construction of complex modulus master curves, which helps to expand the frequency and temperature range and provides support for modeling the mechanical behavior and performance prediction of materials under actual service conditions.

[0031] Based on the above technical solution, step S4 further includes: calculating the complex modulus of the fully fused recycled asphalt mortar and the actually fused recycled asphalt mortar at frequencies of 0.001Hz, 1.0Hz, and 1000Hz.

[0032] Based on the above technical solution, step S5 further includes: calculating the complex modulus offset rate and the degree of fusion between the new and old asphalt at 0.001Hz, 1.0Hz, and 1000Hz for the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused.

[0033] Based on the above technical solution, step S5 further includes: calculating the complex modulus offset rate and the degree of fusion of the new and old asphalt at 0.001Hz for the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused.

[0034] At 0.001Hz (high temperature), the complex modulus offset rate (MDI) changes most significantly, indicating that this condition best "amplifies" the performance differences caused by insufficient fusion. The mid-frequency 1Hz is more suitable as a "benchmark" for performance evaluation. The MDI change at the high-frequency 1000Hz mainly reflects low-temperature rigidity and cracking risk.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) This invention provides a simpler and more reliable method to quantitatively assess the degree of fusion between new and old asphalt. This test method is highly practical and can quickly and accurately determine the degree of fusion between new and old asphalt in recycled asphalt mixtures under different production conditions, so as to improve production conditions. It has high practical value.

[0037] (2) This invention determines the linear viscoelastic region of recycled asphalt mortar by strain scanning test, obtains the rheological index of asphalt mortar based on frequency scanning, compares the difference in rheological index between recycled asphalt mortar with complete fusion of new and old asphalt and recycled asphalt mortar with actual fusion, and proposes complex modulus offset rate and fusion degree index of new and old asphalt to characterize the fusion degree of new and old asphalt in recycled asphalt mortar.

[0038] (3) This invention evaluates the degree of fusion between new and old asphalt at the asphalt mortar scale for the first time, breaking through the limitations of traditional technical methods in terms of authenticity, accuracy and practicality. By preserving the original state of RAP and incorporating key mineral powder factors, this method constructs a performance bridge between asphalt and mixture, providing a more reliable and sensitive scientific basis for the design and quality control of recycled asphalt mixtures. It is especially suitable for optimizing recycling processes and evaluating the fusion effectiveness under different RAP dosages. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This refers to the linear viscoelastic region of recycled asphalt mortar.

[0041] Figure 2 The complex modulus master curves are for different RAP dosages and degrees of fusion between new and old asphalt. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] In this invention, RAP stands for Reclaimed Asphalt Pavement.

[0044] In this invention, the stirring and dry mixing rate is 800 r / min.

[0045] In this invention, "25%RAP" and "50%RAP" refer to the addition of 25% or 50% RAP by mass fraction.

[0046] In the following specific implementation, among the recycled asphalt mortar types, the base asphalt mortar is 0RM, the 25% RAP recycled asphalt mortar with actual fusion of new and old asphalt is 25RBM, the 25% RAP recycled asphalt mortar with complete fusion of new and old asphalt is 25FBM, the 50% RAP recycled asphalt mortar with actual fusion of new and old asphalt is 50RBM, and the 50% RAP recycled asphalt mortar with complete fusion of new and old asphalt is 50FBM.

[0047] In this invention, the asphalt content in the recycled asphalt mortar is calculated based on the reclaimed asphalt mixture (RAP). The asphalt content in the recycled asphalt mortar is calculated using 0 RAP, 25% RAP, and 50% RAP dosages. Using the optimal asphalt content commonly used in asphalt mixtures, expressed as a mass fraction of 4.4%, the asphalt content in the recycled asphalt mortar is measured to be 8.7% by mass fraction. When the RAP dosage is 25% and 50%, the total asphalt content in the recycled asphalt mortar remains constant at 8.7%.

[0048] When preparing recycled asphalt mortar that actually blends old and new asphalt, the asphalt content in the RAP mortar is 9.0% by mass. Based on the ratio of old to new asphalt in the RAP mortar, the amount of new asphalt to be added to 25% RAP recycled asphalt mortar is 6.4% by mass, and the amount of new asphalt to be added to 50% RAP recycled asphalt mortar is 4.2% by mass.

[0049] This invention provides a method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar, comprising the following steps:

[0050] Step S1: Determine the dosage of RAP, new aggregate, new mineral powder, and new asphalt, as well as the content of RAP old aggregate, RAP old mineral powder, and old asphalt in the RAP.

[0051] Based on the amounts of RAP, new aggregate, new mineral powder, and new asphalt, as well as the contents of old RAP aggregate, old RAP mineral powder, and old asphalt in RAP, recycled asphalt mortar with complete fusion of new and old asphalt and recycled asphalt mortar with actual fusion of new and old asphalt are prepared.

[0052] Step S2: Test the linear viscoelastic region of the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused.

[0053] Step S3: Based on the linear viscoelastic region in step S2, test the viscoelastic properties of the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused.

[0054] Step S4: Based on the viscoelastic property parameters in Step S3, fit the complex modulus master curves of the fully fused new and old asphalt recycled asphalt mortar and the actually fused new and old asphalt recycled asphalt mortar, and calculate the complex modulus.

[0055] Step S5: According to the formula , The degree of fusion between the old and new asphalt is obtained;

[0056] Where, The offset rate is the complex modulus. To determine the degree of integration between the old and new asphalt, The number of parallel trials, The complex modulus of the recycled asphalt mortar formed by the actual fusion of the old and new asphalt is given. The complex modulus of the recycled asphalt mortar where the old and new asphalt are fully integrated.

[0057] For example, at a frequency of 0.001 Hz (high temperature), the average complex modulus of 25 RBM is 2.91E+07 Pa, and the average complex modulus of 25 FBM is 2.33E+07 Pa. Then, according to the formula... , ,

[0058] Calculated , .

[0059] In step S4, the complex modulus is calculated at different RAP doping levels and key frequencies.

[0060] Increased RAP content means reduced actual fusion. High RAP content implies a higher proportion of old asphalt in the system, but in actual construction, this old asphalt often fails to fully activate and fuse with the new asphalt. This leads to incomplete fusion, a decrease in the effective asphalt content within the system, and an uneven structure, manifested as a complex modulus. As the complex modulus offset (MDI) increases, the ratio of complex modulus offset to the fully fused system also increases.

[0061] The key frequency is used to simulate the response under different service environments. Different frequencies simulate different operating conditions, and different frequencies reflect the influence of the degree of integration.

[0062] 0.001Hz (low frequency / high temperature): This corresponds to the working conditions of rutting and slow loading, and is the range where the material's viscosity behavior is most sensitive. Insufficient fusion at this time will significantly increase the viscosity of the system, resulting in a significantly higher MDI index, which keenly reflects the amplification effect of insufficient macroscopic deformation potential and fusion quality.

[0063] 1Hz (medium frequency / medium temperature): This corresponds to normal driving conditions and is a frequency range where material performance is relatively balanced. At this frequency, MDI mainly reflects the consistency and uniformity of the fusion of new and old asphalt, and has a strong indicative significance for the overall structural coordination of the material.

[0064] 1000Hz (High Frequency / Low Temperature): This corresponds to impact loading or low-temperature cracking conditions, where the material response is predominantly rigid. In this frequency band, insufficient fusion can lead to a significant increase in the complex modulus, resulting in abnormal structural rigidity and making the structure prone to brittle failure.

[0065] At 0.001 Hz and high temperature, the complex modulus offset (MDI) changes most significantly, indicating that this condition best amplifies the performance differences caused by insufficient fusion. The mid-frequency 1 Hz is more suitable as a "benchmark" for performance evaluation. The MDI change at the high-frequency 1000 Hz mainly reflects low-temperature rigidity and cracking risk.

[0066] Example 1

[0067] This embodiment provides a method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar, including the following steps:

[0068] Step S1: Prepare asphalt mortar with 25% RAP content. The asphalt is 90# base asphalt. Based on the 25% RAP content, calculate the amount of RAP old aggregate, old asphalt, RAP old mineral powder, new asphalt, new aggregate, and new mineral powder.

[0069] The fully blended recycled asphalt mortar consists of fully blended recycled asphalt, RAP old aggregate, new aggregate, RAP old mineral powder, and new mineral powder. The recycled asphalt content, by mass fraction, is 8.7%. The mass fractions of RAP old aggregate, new aggregate, RAP old mineral powder, and new mineral powder are 21.9%, 64.9%, 0.9%, and 3.7%, respectively.

[0070] The recycled asphalt mortar, a mixture of old and new asphalt, consists of new aggregates, RAP mortar, new asphalt, and new mineral powder. Based on the ratio of old to new asphalt in the RAP mortar, the amount of new asphalt required for 25% RAP recycled asphalt mortar is 6.4% by mass. The amounts of new aggregates and new mineral powder are 64.9% and 3.7% by mass, respectively.

[0071] Methods for preparing recycled asphalt mortar that fully integrates old and new asphalt include:

[0072] Step A1: In advance, the old asphalt (recovered through an asphalt mixture analyzer and a rotary evaporator) from the recycled asphalt pavement material is mixed with new asphalt in a certain proportion to produce a homogeneous "fully fused recycled asphalt".

[0073] Step A2: During preparation, the "fully fused recycled asphalt" is first heated at 160°C for 1 hour, while the new aggregate, old RAP mineral powder and new mineral powder are heated at 170°C for 3 hours.

[0074] Step A3: Then, at a mixing temperature of 160℃, first dry mix the preheated new aggregate and RAP old aggregate for 30 seconds, then add the preheated "fully fused recycled asphalt" and mix for 60 seconds, and finally add the RAP old mineral powder and new mineral powder and mix for 120 seconds to finally obtain recycled asphalt mortar with fully fused new and old asphalt.

[0075] The preparation method of recycled asphalt mortar that actually blends new and old asphalt includes the following steps:

[0076] Step a1: Heat the new aggregate at 170℃ for 3 hours, the RAP mortar at 110℃ for 1 hour, and the new asphalt at 160℃ until it reaches a fluid state.

[0077] Step a2: Then, at a mixing temperature of 160℃, first dry mix the preheated new aggregate and RAP mortar for 30 seconds, then add the flowing new asphalt and mix for 60 seconds, and finally add the new mineral powder and mix for 120 seconds to obtain recycled asphalt mortar with actual fusion of new and old asphalt.

[0078] The gradation design of recycled asphalt mortar with actual fusion of new and old asphalt is shown in Table 1 below.

[0079] Table 1. Gradation Design of Recycled Asphalt Mortar Based on Actual Fusion of New and Old Asphalt

[0080]

[0081] Step S2: Use strain scanning tests to determine the linear viscoelastic region of the recycled asphalt mortar (e.g., Figure 1 As shown), select complex shear modulus. The strain corresponding to a decrease in the initial value to 95% is used as the key critical point for determining the linear viscoelastic region and to define the strain level within that region. The strain scan range increases from 0.0001% logarithmically to 0.1%, the scan frequency is 10 Hz, and the temperature is set to 20 °C.

[0082] Step S3: Based on the range of the linear viscoelastic region of the recycled asphalt mortar determined by strain scanning, select a strain amplitude of 0.001% and a loading frequency that increases logarithmically from 0.1Hz to 10Hz. Test the viscoelastic parameters of the asphalt mortar at 10℃, 20℃, 30℃ and 40℃ respectively.

[0083] Step S4: Fit the master curves of the complex modulus of fully fused and actually fused 25% RAP recycled asphalt mortar (e.g., ...). Figure 2 As shown in the figure, calculate its complex modulus at the key frequencies of 0.001Hz (high temperature), 1.0Hz (medium temperature), and 1000Hz (low temperature).

[0084] Based on the formula, the complex modulus offset ratio (MDI) and the degree of fusion between new and old asphalt (DOB) at the critical frequency are calculated to quantitatively describe the degree of fusion between new and old asphalt in the matrix asphalt mortar.

[0085] Example 2

[0086] This embodiment provides a method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar. The difference between this embodiment and Embodiment 1 is that:

[0087] Step S1: Prepare asphalt mortar with 50% RAP content. The asphalt is 90# base asphalt. Based on the 50% RAP content, calculate the amount of RAP old aggregate, old asphalt, RAP old mineral powder, new asphalt, new aggregate, and new mineral powder.

[0088] The fully blended recycled asphalt mortar consists of fully blended recycled asphalt, RAP old aggregate, new aggregate, RAP old mineral powder, and new mineral powder. The recycled asphalt content, by mass fraction, is 8.7%. The contents of RAP old aggregate, new aggregate, RAP old mineral powder, and new mineral powder are 37.4%, 45.8%, 8.2%, and 0%, respectively.

[0089] The recycled asphalt mortar, which is actually a blend of old and new asphalt, consists of new aggregates, RAP mortar, new asphalt, and new mineral powder. Based on the ratio of old to new asphalt in the RAP mortar, the amount of new asphalt required to make 50% RAP recycled asphalt mortar is 4.2% by mass. The amounts of new aggregates and new mineral powder are 45.8% and 0%, respectively.

[0090] The gradation design of recycled asphalt mortar with actual fusion of new and old asphalt is shown in Table 2 below.

[0091] Table 2. Gradation Design of Recycled Asphalt Mortar Based on Actual Fusion of New and Old Asphalt

[0092]

[0093] Comparative Example 1

[0094] This comparative example provides a method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar, including the following steps:

[0095] The base asphalt mortar is mainly composed of 70# base asphalt, new aggregate, and new mineral powder. The asphalt selected is 70# base asphalt, and the asphalt content is 8.7% by mass fraction. The content of new aggregate is 84%, and the content of new mineral powder is 7.3%. The asphalt mortar gradation design is shown in Table 3.

[0096] Table 3 Asphalt Mortar Gradation Design

[0097]

[0098] The preparation method of matrix asphalt mortar includes the following steps:

[0099] Step a1: Heat the new aggregate at 170℃ for 3 hours and the base asphalt at 160℃ until it reaches a fluid state.

[0100] Step a2: Then, at a mixing temperature of 160℃, first add the flowing base asphalt and stir for 60 seconds, then add the new mineral powder and stir for 120 seconds to finally obtain the base asphalt mortar.

[0101] The linear viscoelastic region of the matrix asphalt mortar was determined using strain scanning testing (e.g., Figure 1 As shown), select complex shear modulus. The strain corresponding to a decrease in the initial value to 95% is used as the key critical point for determining the linear viscoelastic region and to define the strain level within that region. The strain scan range increases from 0.0001% logarithmically to 0.1%, the scan frequency is 10 Hz, and the temperature is set to 20 °C.

[0102] The rheological properties of the base asphalt mortar were obtained by frequency scanning. Based on the linear viscoelastic region of the recycled asphalt mortar determined by strain scanning, a strain amplitude of 0.001% was selected, and the loading frequency was increased logarithmically from 0.1Hz to 10Hz. The viscoelastic parameters of the base asphalt mortar were tested at 10℃, 20℃, 30℃ and 40℃ respectively.

[0103] The master curve of the complex modulus of the fitted matrix asphalt mortar (e.g.) Figure 2 As shown in the figure, calculate its complex modulus at the key frequencies of 0.001Hz (high temperature), 1.0Hz (medium temperature), and 1000Hz (low temperature).

[0104] Based on a custom formula, the complex modulus offset ratio (MDI) and the degree of fusion between new and old asphalt (DOB) at key frequencies are calculated to quantitatively describe the degree of fusion between new and old asphalt in the matrix asphalt mortar.

[0105] Performance testing

[0106] 1. The extreme values ​​of linear viscoelastic strain in the recycled asphalt mortar, the recycled asphalt mortar, and the matrix asphalt mortar with actual fusion of new and old asphalt in Examples 1-2 and Comparative Example 1 are as follows: Figure 1 As shown in Table 4.

[0107] Table 4. Extreme values ​​of strain in the linear viscoelastic region of recycled asphalt mortar

[0108]

[0109] Depend on Figure 1 As shown in Table 4, the initial complex modulus of recycled asphalt increases with the increase of RAP mortar content. There is also a noticeable difference in modulus between recycled asphalt mortar where new and old asphalt are fully fused and recycled asphalt mortar that is actually fused. The linear viscoelastic region generally decreases with the increase of RAP mortar content. To satisfy the linear viscoelastic region of all tested mortars, a strain level of 0.001% should be selected for subsequent tests.

[0110] 2. The complex moduli of recycled asphalt mortar with actual fusion of new and old asphalt in Examples 1-2 and Comparative Example 1, and recycled asphalt mortar with complete fusion of new and old asphalt, under different RAP dosages and frequencies are shown in Table 5. The master curve of the complex modulus is shown in... Figure 2 As shown.

[0111] Table 5 Complex modulus of recycled asphalt mortar at different frequencies

[0112]

[0113] Table 5 shows the average complex modulus of each recycled asphalt mortar at key frequencies. At 0.001Hz, 1.0Hz, and 1000Hz, corresponding to high temperature, medium temperature, and low temperature conditions, the complex modulus of recycled asphalt mortar that is actually fused with old and new asphalt is compared with that of fully fused recycled asphalt mortar.

[0114] 3. Table 6 shows the MDI and DOB of recycled asphalt mortar with actual fusion of new and old asphalt in Examples 1-2 and Comparative Example 1, and recycled asphalt mortar with complete fusion of new and old asphalt at different frequencies.

[0115] Table 6. MDI and DOB of recycled asphalt mortar at different frequencies

[0116]

[0117] As shown in Table 6, the complex modulus deviation rates of 25% RAP recycled asphalt mortar and 50% RAP recycled asphalt mortar are the largest at 0.001 Hz (high temperature), which are 24.8% and 61.3% respectively, and the corresponding fusion degrees are 75.2% and 38.7% respectively.

[0118] At 1.0 Hz (medium temperature), the elastic components of asphalt dominate its mechanical behavior. If the old and new asphalt do not fully integrate, the brittleness of the old asphalt will form microcracks under cyclic loading, which will then propagate along the weak interface, accelerating fatigue failure. Medium-temperature fatigue failure requires the accumulation of multiple loads, while high-temperature rutting can manifest under short-term heavy loads.

[0119] At 1000Hz (low temperature), the complex modulus of recycled asphalt mortar is mainly determined by the elastic modulus of the old RAP asphalt and the skeleton structure of the aggregate. The degree of fusion between the old and new asphalt has little effect on the low-temperature crack resistance. That is, although the complex modulus deviation rate of the 25% RAP recycled asphalt mortar and the 50% RAP recycled asphalt mortar with actual fusion of old and new asphalt is the smallest at 1000Hz, the degree of fusion between the old and new asphalt is no longer the main influencing factor at this time.

[0120] In conclusion, it is more appropriate to define the effective fusion degree as the degree of fusion between new and old asphalt under high temperature conditions, i.e., 0.001Hz.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar, characterized in that, Includes the following steps: Step S1: Determine the amounts of recycled asphalt mixture (RAP), new aggregate, new mineral powder, and new asphalt, as well as the content of old aggregate, old mineral powder, and old asphalt in the RAP. Based on the amounts of RAP, new aggregate, new mineral powder, and new asphalt, as well as the contents of old RAP aggregate, old RAP mineral powder, and old asphalt in the RAP, recycled asphalt mortar with complete fusion of new and old asphalt and recycled asphalt mortar with actual fusion of new and old asphalt are prepared. Step S2: Test the linear viscoelastic region of the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused. Step S3: Based on the linear viscoelastic region in step S2, test the viscoelastic parameters of the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused. Step S4: Based on the viscoelastic parameters in Step S3, fit the complex modulus master curves of the fully fused recycled asphalt mortar and the actually fused recycled asphalt mortar, and calculate the complex modulus. Step S5: According to the formula , Calculate the complex modulus offset rate and the degree of fusion between new and old asphalt at the key frequency; Where, The offset rate is the complex modulus. To determine the degree of integration between the old and new asphalt, The number of parallel trials, The complex modulus of the recycled asphalt mortar formed by the actual fusion of the old and new asphalt is given. The complex modulus of the recycled asphalt mortar where the old and new asphalt are fully integrated; The RAP in the recycled asphalt mortar that is actually a blend of new and old asphalt is added in the form of RAP mortar composed of old RAP aggregate, old asphalt and old RAP mineral powder. The RAP mortar is obtained by fine screening of RAP material with a particle size of less than 2.36 mm. In step S1, the method for preparing recycled asphalt mortar with complete fusion of new and old asphalt includes the following steps: Step A1: Mix the old asphalt and new asphalt in the recycled asphalt mixture (RAP) to obtain fully blended recycled asphalt; Step A2: Heat the fully fused recycled asphalt from step A1 at 160°C for 1 hour, and heat the new aggregate, RAP old aggregate, RAP old mineral powder and new mineral powder at 170°C for 3 hours. Step A3: Stir the new aggregate and RAP old aggregate from Step A2 at 160°C for 30 seconds, add the fully fused recycled asphalt and stir for 60 seconds, add the RAP old mineral powder and new mineral powder and stir for 120 seconds. The stirring rate is 800 r / min. In step S1, the method for preparing recycled asphalt mortar by actual fusion of new and old asphalt includes the following steps: Step a1: Heat the new aggregate at 170°C for 3 hours, the RAP mortar at 110°C for 1 hour, and the new asphalt at 160°C until it reaches a fluid state. Step a2: Mix the new aggregate and RAP mortar from step a1 for 30 seconds, add the new asphalt from step a1 and mix for 60 seconds, add the new mineral powder and mix for 120 seconds, and the mixing speed is 800 r / min.

2. The method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar as described in claim 1, characterized in that, Step S2 includes: using strain scanning to test the linear viscoelastic region of the fully fused new and old asphalt recycled asphalt mortar and the actually fused new and old asphalt recycled asphalt mortar. The strain corresponding to the initial value of the complex shear modulus G* decreasing to 95% is selected as the critical point for determining the linear viscoelastic region, which is used to determine the strain level of the linear viscoelastic region. The strain scanning range increases from 0.0001% logarithmically to 0.1%, the scanning frequency is 10Hz, and the temperature is 20℃.

3. The method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar as described in claim 1, characterized in that, Step S3 includes: based on the linear viscoelastic region of the fully fused new and old asphalt recycled asphalt mortar and the actually fused new and old asphalt recycled asphalt mortar tested in step S2, selecting the corresponding strain amplitude, loading frequency from 0.1Hz logarithmically increasing to 10Hz, and testing the viscoelastic parameters of the actually fused new and old asphalt recycled asphalt mortar at 10℃, 20℃, 30℃ and 40℃ respectively.

4. The method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar as described in claim 1, characterized in that, Step S4 includes: calculating the complex modulus of the fully fused recycled asphalt mortar and the actually fused recycled asphalt mortar at frequencies of 0.001Hz, 1.0Hz, and 1000Hz.

5. The method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar as described in claim 1, characterized in that, Step S5 includes: calculating the complex modulus offset rate and the degree of fusion between the new and old asphalt at 0.001Hz, 1.0Hz, and 1000Hz for the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused.

6. The method for quantitatively assessing the degree of fusion between new and old asphalt based on recycled asphalt mortar as described in claim 5, characterized in that, Step S5 includes: calculating the complex modulus offset rate and the degree of fusion between the new and old asphalt at 0.001 Hz for the recycled asphalt mortar where the new and old asphalt are fully fused and the recycled asphalt mortar where the new and old asphalt are actually fused.

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