A synergistic analysis method for aging state of SBS modified asphalt based on phase structure-mechanical properties

Abstract

A kind of SBS modified asphalt aging state synergistic analysis method based on phase structure-mechanical property, it is related to a kind of SBS modified asphalt aging state analysis method.The present application is to solve the technical problem that the parameter characterization ability of SBS modified asphalt aging state is weak at present.The present application introduces polymer mechanical state analysis, and proposes six different ductility, strength, toughness of mechanical type for SBS modified asphalt, so that the classification of SBS modified asphalt aging degree is more intuitive, and has more physical meaning;The present application combines the data of the fluorescence image of aging SBS modified asphalt calculated by Image-Pro Plus software, and synergistically analyzes with the data of toughness test, to clearly define the different modified states of aging SBS modified asphalt.

Description

Technical Field

[0001] This invention relates to a method for analyzing the aging state of SBS modified asphalt. Background Technology

[0002] Asphalt binders play a crucial role in the performance of asphalt mixtures. The process of adding polymers to the base asphalt has been extensively studied, as it can improve the physical and rheological properties of asphalt binders. Styrene-butadiene-styrene block copolymer (SBS) modified asphalt exhibits excellent high and low temperature performance and superior road performance, and is widely used. However, aging inevitably occurs after a period of use. For SBS modified asphalt, aging includes the aging of the SBS polymer and the aging of the base asphalt itself. As a waste pavement construction material, aged SBS modified asphalt still has high recycling value. When designing for the recycling of waste SBS modified asphalt mixtures, it is essential to understand the degree of aging of the SBS modified asphalt.

[0003] The most direct method for observing the phase structure of SBS-modified asphalt is fluorescence microscopy, which can reveal a single-phase continuous structure with SBS as the dispersed phase and asphalt as the continuous phase, as well as the network structure of the polymer system. With increasing aging time, the polymer degrades, and the network structure gradually breaks down and is lost. Although many researchers have used fluorescence microscopy to observe the phase structure of SBS-modified asphalt, its effective parameter characterization ability is weak, and it has not been used to quantitatively characterize the modification state of time-aged SBS-modified asphalt.

[0004] SBS modified asphalt is a typical multi-component, multiphase polymer system. When the polymer undergoes stress-strain curve testing, it exhibits several different mechanical types: soft and weak, soft and tough, hard and brittle, hard and strong, hard and tough, etc., encompassing properties such as hardness, toughness, and strength. Aging of SBS modified asphalt leads to different mechanical types at different aging stages. Load-deformation curves obtained from visco-toughness tests on SBS modified asphalt at different aging degrees will result in different mechanical types depending on the curve type. Therefore, it is essential to conduct a synergistic analysis of the phase structure and mechanical properties of time-aged SBS modified asphalt to determine the residual modification effect at different aging stages. Summary of the Invention

[0005] The present invention aims to address the technical problem of the weak parameter characterization ability of SBS modified asphalt aging state in current technology, and provides a collaborative analysis method for SBS modified asphalt aging state based on phase structure and mechanical properties.

[0006] The present invention provides a synergistic analysis method for the aging state of SBS-modified asphalt based on phase structure and mechanical properties, which is carried out according to the following steps:

[0007] First, the fluorescence microscopic images of SBS modified bitumen acquired by the standard method were binarized. Image-Pro Plus software was used to calculate the range and proportion of particle size in each fluorescence image, and a particle size-distribution percentage diagram was plotted to quantitatively analyze the relationship between the particle size and distribution of fluorescence images and aging time.

[0008] II. Six mechanical state judgment parameters are proposed for different states of the load-deformation curve of SBS modified asphalt, namely:

[0009] a) Low ductility, low strength, brittle and weak;

[0010] b) Low modulus, low strength, soft and weak;

[0011] c) Low strength, high ductility, soft yet tough;

[0012] d) Low ductility, high modulus, brittle and hard;

[0013] e) High strength, high modulus, strong and hard;

[0014] f) High ductility, high modulus, tough and hard;

[0015] III. By comparing the fluorescence images of SBS modified asphalt at different aging degrees, and adapting to different mechanical types, we can conduct a collaborative analysis of the aging residue modification effect of time-aged SBS modified asphalt.

[0016] Compared with existing technologies, this method has the following advantages:

[0017] I. This invention introduces polymer mechanical state analysis and proposes six different mechanical types of SBS modified asphalt with different ductility, strength, and toughness, making the classification of the aging degree of SBS modified asphalt more intuitive and physically meaningful.

[0018] Second, this invention combines the data of fluorescence images of aged SBS modified asphalt calculated by Image-Pro Plus software with the data of viscosity and toughness test to clarify the different modification states of aged SBS modified asphalt. Attached Figure Description

[0019] Figure 1 The image shows the fluorescence binarized image of SBS modified asphalt after 0 hours of RTFOT aging in Experiment 2.

[0020] Figure 2 This is a fluorescence binarized image of SBS modified asphalt after 2 hours of RTFOT aging in Experiment 2.

[0021] Figure 3 The image shows the fluorescence binarized image of SBS modified asphalt after 4 hours of RTFOT aging in Experiment 2.

[0022] Figure 4 The image shows the fluorescence binarized image of SBS modified asphalt after 6 hours of RTFOT aging in Experiment 2.

[0023] Figure 5 The image shows the fluorescence binarized image of SBS modified asphalt after 8 hours of RTFOT aging in Experiment 2.

[0024] Figure 6 This is a fluorescence binarized image of the unaged matrix asphalt in Experiment 2;

[0025] Figure 7 This is a particle size distribution percentage graph of SBS modified asphalt after RTFOT aging for 0 hours in Experiment 2;

[0026] Figure 8 The particle size distribution percentage of SBS modified asphalt after 2 hours of RTFOT aging in Experiment 2 is shown.

[0027] Figure 9 The particle size distribution percentage of SBS modified asphalt after 4 hours of RTFOT aging in Experiment 2 is shown.

[0028] Figure 10 The particle size distribution percentage of SBS modified asphalt after 6 hours of RTFOT aging in Experiment 2 is shown.

[0029] Figure 11 The particle size distribution percentage of SBS modified asphalt after 8 hours of RTFOT aging in Experiment 2 is shown.

[0030] Figure 12 This is a particle size distribution percentage diagram of the unaged matrix asphalt in Experiment 2;

[0031] Figure 13 This is a schematic diagram of type a of the mechanics in Experiment 3;

[0032] Figure 14 This is a schematic diagram of type b of the mechanical type in Experiment 3;

[0033] Figure 15 This is a schematic diagram of type c of the mechanical types in Experiment 3;

[0034] Figure 16 This is a schematic diagram of type d of the mechanics in Experiment 3;

[0035] Figure 17 This is a schematic diagram of type e of the mechanical types in Experiment 3;

[0036] Figure 18 This is a schematic diagram of type f of the mechanics type in Experiment 3;

[0037] Figure 19 This is the load-deformation curve from Experiment 3;

[0038] Figure 20 The figure shows the viscosity and toughness test results of the modified asphalt in Experiment 3;

[0039] Figure 21 The figure shows the viscosity and toughness test results of the base asphalt in Experiment 3. Detailed Implementation

[0040] Specific Implementation Method 1: This implementation method is a synergistic analysis method for the aging state of SBS modified asphalt based on phase structure and mechanical properties, specifically carried out according to the following steps:

[0041] First, the fluorescence microscopic images of SBS modified asphalt with different aging times acquired by the standard method were binarized. The Image-Pro Plus software was used to calculate the range and proportion of particle size in each fluorescence image, and a particle size-distribution percentage diagram was drawn to quantitatively analyze the relationship between the particle size and distribution of fluorescence images and aging time.

[0042] II. Six mechanical state judgment parameters are proposed for different states of the load-deformation curve of SBS modified asphalt, namely:

[0043] a) Low ductility, low strength, brittle and weak;

[0044] b) Low modulus, low strength, soft and weak;

[0045] c) Low strength, high ductility, soft yet tough;

[0046] d) Low ductility, high modulus, brittle and hard;

[0047] e) High strength, high modulus, strong and hard;

[0048] f) High ductility, high modulus, tough and hard;

[0049] III. By comparing the fluorescence images of SBS modified asphalt at different aging degrees, and adapting to different mechanical types, we can conduct a collaborative analysis of the aging residue modification effect of time-aged SBS modified asphalt.

[0050] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the specific method for step one is as follows:

[0051] I. The phase structure morphology of SBS modified asphalt was characterized and analyzed by fluorescence microscopy. Fluorescence microscopic images of SBS modified asphalt were collected at RTFOT0h, 2h, 4h, 6h and 8h, and their binarized images were used as the research object.

[0052] 2. Use Image-Pro Plus software to calculate the range and proportion of particle size in each fluorescence image and draw a particle size-distribution percentage map;

[0053] 3. The abscissa of the particle size-distribution percentage graph is divided into blocks with 5μm as the reference, and the interval where the peak value is located is found;

[0054] 4. Observe the fluorescence images of the time-division aged SBS modified asphalt to determine the modification state of the aged asphalt based on the above-mentioned block division. Everything else is the same as in Specific Implementation Method 1.

[0055] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the specific method for step two is as follows:

[0056] I. Load-deformation curves of time-aged SBS modified asphalt were plotted by collecting data through asphalt viscosity-toughness tests.

[0057] II. Two parameters for obtaining the area of ​​the region in the load-deformation curve: visco-ductility and toughness parameters;

[0058] III. Based on the factors of fracture strength, yield strength, and ductility, SBS modified asphalt with different aging degrees is classified into mechanical types.

[0059] 4. Observe the fluorescence images of the time-division aged SBS modified asphalt to determine the modification state of the aged asphalt based on the above-mentioned mechanical types. Other aspects are the same as in specific implementation method one or two.

[0060] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Three in that: the extension ε B A value less than 0.02m is considered low-longitude, while a value greater than or equal to 0.085m is considered high-longitude. Values ​​between 0.02m and 0.085m are not relevant. Everything else is the same as in Specific Implementation Method Three.

[0061] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Three in that: Intensity σ B Strength less than 300 kPa is considered low strength, and strength greater than or equal to 300 kPa is considered high strength. Other aspects are the same as in Specific Implementation Method Three.

[0062] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Three in that a modulus E less than 120 kPa is considered a low modulus, and a modulus greater than or equal to 120 kPa is considered a high modulus. Everything else is the same as in Specific Implementation Method Three.

[0063] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the preparation method of SBS modified asphalt with different aging times is as follows:

[0064] 1. The base bitumen and SBS are sheared at high temperature;

[0065] 2. Mechanically stir the materials at high temperature;

[0066] 3. Add stabilizer and stir continuously at high temperature;

[0067] IV. Place the samples in a high-temperature rolling film oven and keep them at that temperature for different times to prepare SBS modified asphalt with different aging times; this process is carried out in air at an airflow rate of 5000 mL / min ± 200 mL / min. Other procedures are the same as in Specific Implementation Method VI.

[0068] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the stabilizer used is elemental sulfur. Everything else is the same as in Specific Implementation Method Seven.

[0069] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Seven in that the high temperature is 180°C. Everything else is the same as in Specific Implementation Method Seven.

[0070] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Three in that the SBS described is a linear SBS1301. Everything else is the same as in Specific Implementation Method Three.

[0071] The invention was verified using the following experiments:

[0072] Experiment 1: This experiment used 70# base asphalt and SBS modified asphalt (ID). SBS modified asphalt (ID) was prepared using 70# base asphalt, linear SBS1301 modifier, and stabilizer. SBS1301, provided by Yanshan Petrochemical Company, is a linear copolymer with an average molecular weight of 100,000 g / mol and a styrene content of 30 wt%. Commercially available elemental sulfur was added to the SBS modified asphalt as a stabilizer to achieve chemical crosslinking. A 5% SBS content was used to match actual conditions, and the RTFOT delayed aging method was used to simulate the aging process. The specific steps for preparing time-aged SBS modified asphalt included:

[0073] 1. Add 5wt% linear SBS1301 to 70# base bitumen and shear at 4000rpm for 0.5h at 180℃;

[0074] 2. Mechanically stir the material at 180℃ and a stirring rate of 500 rpm for 1 hour;

[0075] 3. Add 0.15wt% stabilizer and stir continuously at 180℃ for 1.5h;

[0076] IV. Place the samples in a 180℃ rolling film oven and keep them at that temperature for 2h, 4h, 6h and 8h respectively to prepare specimens with different aging degrees; this process is carried out in air with an airflow of 5000mL / min±200mL / min.

[0077] Experiment 2: Fluorescence microscopy was performed on SBS modified asphalt with different aging degrees from Experiment 1. A CSM-900E series fluorescence microscope was used to observe the SBS modified asphalt under a 400× magnification microscope and collect its microscopic images. The color images were first converted to grayscale images, such as... Figures 1-6 As shown, Figures 1-5 The images shown are, in order, fluorescence binarized images of RTFOT aged for 0h, 2h, 4h, 6h, and 8h. Figure 6 These are fluorescence binarized images of unaged base asphalt. In the unaged modified asphalt, SBS polymer is distributed as spherical particles, forming a single-phase continuous structure with SBS as the dispersed phase and asphalt as the continuous phase. Before aging, the particle size of the SBS-modified asphalt is relatively large, but after aging, the particle size decreases significantly, and the particle uniformity improves. Image-Pro Plus software was used to calculate the range and proportion of particle size in each fluorescence image, such as... Figures 7-12 , Figures 7-11 The RTFOT aging times are 0h, 2h, 4h, 6h, and 8h in sequence. Figure 12 The matrix bitumen was not aged. The particle size and distribution of SBS polymers at different aging times are shown. It can be observed that the size of the SBS polymers continuously decreases during aging, starting from an initial maximum particle size of 50 μm and reaching 17 μm after 8 h of RTFOT. After 2 h of RTFOT, fluorescence images continue to show persistent filamentous structures that form the polymer network; these filamentous structures gradually dissipate at 6 h of RTFOT.

[0078] Combination Figures 1-12 Comparative analysis revealed that the abscissa of the particle size distribution percentage graph was segmented with a 5μm reference. It was found that significant dissipation of the SBS polymer network occurred starting from 6 hours of RTFOT. Correspondingly, the peak values ​​of the particle size distribution percentage graph from 6 hours onwards all fell on the 0-5μm abscissa. This indicates that as the SBS modified asphalt ages, the polymer network structure changes, and the polymer particle size and distribution also change. When the peak value of the curve falls within 0-5μm, the aged SBS modified asphalt loses its properties as a modified asphalt, and the residual modification effect after aging is consistent with that of the base asphalt.

[0079] Experiment 3: Six types of load-deformation curves for SBS-modified asphalt were defined according to polymer mechanics types, namely:

[0080] a) Low ductility, low strength, brittle and weak;

[0081] b) Low modulus, low strength, soft and weak;

[0082] c) Low strength, high ductility, soft yet tough;

[0083] d) Low ductility, high modulus, brittle and hard;

[0084] e) High strength, high modulus, strong and hard;

[0085] f) High ductility, high modulus, tough and hard, such as Figures 13-18 As shown.

[0086] Ductility ε B A value less than 0.02m is considered low ductility, and a value greater than or equal to 0.085m is considered high ductility. Values ​​between 0.02m and 0.085m are not of reference value.

[0087] Strength σ B Strength less than 300 kPa is considered low strength, and strength greater than or equal to 300 kPa is considered high strength.

[0088] Modulus E: less than 120 kPa is considered low modulus, and greater than or equal to 120 kPa is considered high modulus.

[0089] Viscosity and toughness tests were conducted on time-aged SBS modified asphalt according to ASTM D5801 (ASTM 2017c). The specific procedures were as follows: Asphalt samples were treated in an oven at 80°C for 1 hour, and then 50 g ± 1 g of the sample was poured into a test container for preparation. The sample (using the test container) was placed in a water bath at 25°C for 1.5 hours. Afterwards, the sample was subjected to tensile testing at 25°C with a loading rate of 500 mm / min.

[0090] The area of ​​the region in the load-deformation curve yields two parameters: visco-ductility To and toughness Te. For example... Figure 19 As shown, viscoelasticity and toughness can be calculated using the following equations:

[0091] T o =SA + SB;

[0092] T e =SB.

[0093] Where To and Te are the viscosity-toughness and toughness of the asphalt binder, respectively, in N·m;

[0094] SA and SB are Figure 19 The corresponding areas of the white and shaded parts are shown in N·m.

[0095] Viscosity-toughness and toughness tests can describe the unique properties of SBS-modified asphalt, which also have a strong correlation with viscoelasticity. Viscosity-toughness characterizes the tensile strength and cohesive strength of asphalt binders, while toughness reflects the ability of asphalt binders to resist deformation and fracture. Generally, the viscosity-toughness curve of conventional asphalt is unimodal, while that of SBS-modified asphalt is bimodal. The most obvious difference between the two shapes is the presence or absence of delayed fracture and considerable deformation. Viscosity-toughness tests were conducted on SBS-modified asphalt after RTFOT aging for 0h, 2h, 4h, 6h, and 8h, and on base asphalt after RTFOT aging for 0h and 8h. The results are as follows: Figure 20 and 21 As shown.

[0096] Table 1. Data on the mechanical type classification of toughness curves

[0097]

[0098] Viscosity-toughness curves further confirmed that the aging residual modification effect of SBS modified asphalt after 6 hours of RTFOT was consistent with that of the base asphalt; both curves showed the same type, d) low ductility, high modulus, brittle and hard (see...). Figure 20 At this point, the asphalt is in the aged matrix stage, and its residual modification effect is consistent with that of the matrix asphalt. There is no need for regeneration, and the original asphalt should be added to restore the polymer.

[0099] Using 0.08m of ductility as the boundary, it was found that SBS modified asphalt aged for 0h and 2h by RTFOT belonged to b) low modulus, low strength, soft and weak. At this time, the asphalt is in the initial aging stage, and whether it should be recycled can be determined according to the requirements of road grade.

[0100] The SBS modified bitumen aged by RTFOT for 4 hours belongs to the category of e) high strength, high modulus, strong and hard, in the aging and hardening stage, with high modulus and high strength, and has a certain polymer and polymer network structure, which can be used to formulate and select recycling schemes as needed.

[0101] Based on the analysis and statistics of the experimental results, the three stages are divided as follows:

[0102] For the viscosity-toughness curves of SBS modified asphalt at different aging degrees, the aging matrix stage and the aging modification stage are first divided based on a ductility of 0.02m (greater than or equal to 0 and less than 0.02m, greater than or equal to 0.02m). Then, the initial aging stage and the aging hardening stage are divided based on a strength of 300 kPa (greater than or equal to 0 and less than 300 kPa, greater than or equal to 300 kPa).

[0103] This invention provides a synergistic analysis method for the aging state of SBS modified asphalt based on phase structure and mechanical properties. It combines the mechanical properties obtained by viscosity and toughness testing with the phase structure obtained by fluorescence microscopy testing to synergistically determine the aging state of SBS modified asphalt, with the two serving as mutual references.

Claims

1. A synergistic analysis method for the aging state of SBS-modified asphalt based on phase structure and mechanical properties, characterized in that... The synergistic analysis method for the aging state of SBS modified asphalt based on phase structure and mechanical properties is carried out according to the following steps: First, the fluorescence microscopic images of SBS modified asphalt with different aging times acquired by the standard method were binarized. The Image-Pro Plus software was used to calculate the range and proportion of particle size in each fluorescence image, and a particle size-distribution percentage diagram was plotted to quantitatively analyze the relationship between the particle size and distribution of fluorescence images and aging time. The specific method for step one is as follows: ① The phase structure of SBS modified asphalt was characterized and analyzed by fluorescence microscopy. Fluorescence microscopic images of SBS modified asphalt were collected at 0h, 2h, 4h, 6h and 8h in RTFOT, and their binarized images were used as the research object. ② Use Image-Pro Plus software to calculate the range and proportion of particle size in each fluorescence image, and plot a particle size-distribution percentage map; ③ Divide the x-axis of the particle size-distribution percentage graph into blocks with 5μm as the reference, and find the interval where the peak value is located; ④ Observe the fluorescence images of SBS modified asphalt aged at different times, and determine the modification state of the aged asphalt based on the above-mentioned blocks; II. Six mechanical state judgment parameters are proposed for different states of the load-deformation curve of SBS modified asphalt, namely: a) Low ductility, low strength, brittle and weak; b) Low modulus, low strength, soft and weak; c) Low strength, high ductility, soft yet tough; d) Low ductility, high modulus, brittle and hard; e) High strength, high modulus, strong and hard; f) High ductility, high modulus, tough and hard; Depth A value less than 0.02m is considered low ductility, and a value greater than or equal to 0.085m is considered high ductility. Values ​​between 0.02m and 0.085m are not of reference value. strength Strength less than 300 kPa is considered low strength, and strength greater than or equal to 300 kPa is considered high strength. A modulus E less than 120 kPa is considered a low modulus, and a modulus greater than or equal to 120 kPa is considered a high modulus. The specific method for step two is as follows: ① Load-deformation curves of time-aged SBS modified asphalt were plotted by collecting data through asphalt viscosity-toughness tests. ② Obtain two parameters for the area of ​​the region in the load-deformation curve: visco-ductility and toughness parameters; ③ Classify the mechanical types of SBS modified asphalt with different aging degrees based on factors such as fracture strength, yield strength, and ductility; ④ Observe the fluorescence images of SBS modified asphalt aged over time, and determine the modification state of the aged asphalt based on the above mechanical types; III. By comparing the fluorescence images of SBS modified asphalt at different aging degrees, and adapting to different mechanical types, we can conduct a collaborative analysis of the aging residual modification effect of time-aged SBS modified asphalt.

2. The method for synergistic analysis of the aging state of SBS-modified asphalt based on phase structure and mechanical properties as described in claim 1, characterized in that... The preparation method of SBS modified asphalt with different aging times is as follows:

1. The base bitumen and SBS are sheared at high temperature; 2. Mechanically stir the materials at high temperature; 3. Add stabilizer and stir continuously at high temperature; IV. The samples were placed in a high-temperature rolling film oven and kept at that temperature for different times to prepare SBS modified asphalt with different aging times. This process is carried out in air at a flow rate of 5000 mL / min ± 200 mL / min; The aforementioned high temperatures are all 180℃.

3. The method for synergistic analysis of the aging state of SBS-modified asphalt based on phase structure and mechanical properties according to claim 2, characterized in that... The stabilizer is elemental sulfur.

4. The method for synergistic analysis of the aging state of SBS-modified asphalt based on phase structure and mechanical properties according to claim 2, characterized in that... The SBS mentioned is a linear SBS1301.

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