Photocatalytic-high-permeability environment-friendly asphalt mixture and preparation method thereof

Abstract

The invention relates to the technical field of asphalt mixtures, in particular to a preparation method of a photocatalytic-high-permeability environment-friendly asphalt mixture, which comprises the following steps: (1) preparing raw materials including aggregate, asphalt, mineral powder and composite modified TiO2; (2) gradation design: selecting proper mixture gradation as a research object, and taking the passing rate of 2.36 mm sieve pores as a key index; and (3) designing the optimal asphalt dosage according to the mixing ratio: determining the optimal asphalt dosage through an indirect tensile test (IDT) and a semicircular bending test (DIC technology). According to the method, an indirect tensile test and a semicircular bending test are carried out by controlling different temperatures and loading rates on the basis of a traditional optimal asphalt dosage determination method; analyzing the correlation between the IDT strength representing the cohesive force of the asphalt mixture and the freeze-thaw splitting strength ratio under each condition, and the correlation between the horizontal strain density reflecting the crack resistance and the damage strain of a small beam bending test, and determining the conditions of an indirect tensile test and a semicircular bending test according to the optimal correlation; and determining the optimal asphalt consumption of the mixture according to the average value of the asphalt consumption corresponding to the maximum value of the IDT strength and the horizontal strain density.

Description

Technical Field

[0001] This invention relates to the field of asphalt mixture technology, specifically to a photocatalytic-high-permeability environmentally friendly asphalt mixture and its preparation method. Background Technology

[0002] Large-particle-size permeable asphalt mixtures are exposed to heavy rainfall for extended periods, making them highly susceptible to erosion and causing significant damage to their water stability. Furthermore, to achieve a higher porosity, large-particle-size permeable asphalt mixtures are typically designed with fewer fine particles, leading to a loss of strength and poor crack resistance. Simply optimizing the material cannot guarantee the water stability and strength requirements of large-particle-size asphalt pavements under long-term rain erosion. Therefore, selecting the optimal asphalt content plays a crucial role in the water stability of large-particle-size permeable asphalt mixtures, directly affecting their strength and durability. Insufficient asphalt content leads to pavement loosening and water damage; excessive asphalt content results in rutting and segregation. Determining the appropriate asphalt content is paramount in asphalt mixture design to better ensure its water stability and crack resistance. Currently, the most common methods in my country, such as the fly-scattering test and segregation test, are somewhat arbitrary in determining the optimal asphalt content and cannot guarantee that the optimal asphalt content designed using these methods will meet the requirements for water stability and crack resistance under long-term heavy rainfall conditions.

[0003] Based on the above issues, many scholars have found through extensive research that there is a strong correlation between indirect tensile (IDT) strength and asphalt mixture cohesion: the greater the IDT strength, the greater the cohesion and the higher the water stability of the asphalt mixture; at the same time, the semi-circular bending test based on DIC technology can accurately reflect the crack resistance of asphalt mixtures. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the purpose of this invention is to provide a photocatalytic-high-permeability environmentally friendly asphalt mixture and its preparation method, so as to solve the problems mentioned in the background art.

[0005] The present invention solves the technical problem by adopting the following technical solution: This invention provides a method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture, comprising the following steps: First, the optimal asphalt content for permeable asphalt mixtures was determined through indirect tensile testing (IDT) and semicircular bending tests based on digital image correlation (DIC) technology. Based on this, composite modified nano-TiO2 was added to the permeable asphalt mixture at a ratio of 30%-60% to replace mineral powder. Based on the aforementioned optimal asphalt content and composite modified nano-TiO2 content, permeable asphalt mixtures were prepared. Finally, the exhaust gas degradation effect and mechanical properties of the mixture were verified through exhaust gas degradation tests and road performance tests. (1) Raw material preparation Including aggregates, asphalt, mineral powder, and composite modified TiO2; (2) Grading design A suitable mixture gradation was selected as the research object, and the passing rate of the 2.36 mm sieve was taken as the key indicator. (3) Mix design Optimal asphalt content: The asphalt-aggregate ratio was determined by indirect tensile testing (IDT) and semicircular bending testing (DIC technique).

[0006] Preferably, indirect tensile tests are performed on different samples. Based on the optimal asphalt-aggregate ratio range determined by traditional methods, Marshall specimens are formed with the ratio increasing by 0.3% sequentially for freeze-thaw splitting tests. The indirect tensile test conditions are set according to the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40—2004): test temperatures of 10℃, 20℃, 30℃ and 40℃, and loading rates of 5mm / min, 20mm / min and 50mm / min.

[0007] Preferably, through the correlation linear fitting data analysis of IDT strength and freeze-thaw splitting strength ratio in indirect tensile tests under different test conditions, the correlation between the two is the highest, reaching above 0.92, when the test conditions are a temperature of 40℃ and a loading rate of 20mm / min. Under these test conditions, the two have a positive correlation, and the splitting strength ratio of permeable asphalt mixture increases continuously with the increase of IDT strength. Under these conditions, the greater the IDT strength, the higher the cohesion of the mixture and the stronger its resistance to water damage. Under the above conditions, it is sufficient to determine that the IDT strength of permeable asphalt mixture in the indirect tensile test is sufficiently sensitive to changes in asphalt content, and has a good correlation with the splitting strength ratio of the freeze-thaw splitting test. Under these conditions, setting the IDT strength of permeable asphalt mixture as the mechanical parameter of asphalt mixture effectively ensures the excellent water stability of permeable asphalt mixture, optimizes the comprehensive performance of asphalt mixture, provides a scientific basis and quality assurance for pavement construction, and extends the service life of pavement.

[0008] Preferably, the asphalt mixture is a multiphase composite material, and its cracking characteristics differ from those of homogeneous materials. Further quantitative analysis is conducted on the differences in crack resistance of exhaust gas-degradable permeable asphalt mixtures under different external influencing factors. Horizontal strain density (HSD) is selected as the research object to analyze the crack resistance of exhaust gas-degradable permeable asphalt mixtures under external influencing factors from the perspective of the microscopic strain field. The formula for calculating horizontal strain density is: D—represents the horizontal strain at the i-th control point at time t; E t —This represents the horizontal strain in the region surrounding the crack initiation point at time t; t0—the time corresponding to the maximum horizontal strain; The failure characteristics of the crack initiation point are evaluated based on the full-field horizontal strain acquired by DIC, which effectively analyzes the location of the crack initiation point of the specimen and the displacement and strain data of the crack initiation point and its surroundings.

[0009] The semi-circular bending test conditions based on DIC technology are: test temperatures of -10℃, 0℃, 10℃ and 20℃, and loading rates of 5mm / min, 20mm / min and 50mm / min.

[0010] Preferably, the correlation study between the horizontal strain density of the semicircular bending test and the failure strain of the small beam bending test based on DIC technology shows that the horizontal strain density of the mixture reaches the optimum and the crack resistance is the strongest at a temperature of -10℃ and a loading rate of 20mm / min.

[0011] Preferably, nano-TiO2 is subjected to metal ions (Fe) 3+ The modification enhances the photocatalytic effect and improves the degradation rate of exhaust gas. Furthermore, the Al2O3 loading effectively reduces the aggregation of modified TiO2, improving the dispersion effect and stability.

[0012] Preferably, the specific preparation method of composite modified TiO2 is as follows: S1: Preheat nano-TiO2 at 55-60℃ for 1 hour, then add it to a sufficient amount of modification solution and stir for 1-2 hours at a stirring speed of 350-400 r / min. After stirring, filter and dry to obtain modified nano-TiO2. S2: Mix 4-7 parts of modified nano-TiO2, 2-3 parts of 5% ferric chloride solution and 1-3 parts of alumina and ball mill thoroughly at a speed of 1000-1500 r / min for 2 hours. After ball milling, filter and dry to obtain composite modified TiO2.

[0013] Preferably, the modified liquid is prepared by mixing 3-5 parts of bentonite, 2-4 parts of boron nitride, 2-4 parts of calcium sulfate whiskers and 3-5 parts of sodium lignosulfonate solution evenly to obtain the modified liquid.

[0014] By employing the lamellar interlayer structure of bentonite, combined with lamellar boron nitride and whisker structures, and through efficient load-bearing and intercalation into the system, the system performance stability of the product is optimized and the contact area is increased. This better complements the load-bearing capacity of nano-titanium dioxide and the modification of nano-TiO2 by loading on aluminum oxide (Al2O3) carrier. It can effectively inhibit the aggregation of nanoparticles, significantly increase their specific surface area and interfacial contact efficiency, effectively improve the degradation efficiency of automobile exhaust, and reduce environmental pollution.

[0015] Preferably, the sodium lignosulfonate solution has a mass fraction of 2-5%.

[0016] The present invention also provides an asphalt mixture prepared by a method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention builds upon traditional methods for determining optimal asphalt content by conducting indirect tensile tests at controlled temperatures and loading rates to analyze the IDT strength of asphalt mixture cohesion under various conditions. Furthermore, a semi-circular bending test combined with DIC (Digital Image Speckling) technology is used to examine the full-field strain of the test specimen from a microscopic perspective, studying the horizontal strain density under different temperatures and loading rates. Finally, the IDT strength from the indirect tensile test and the horizontal strain density from the semi-circular bending test using DIC technology are combined to determine the optimal asphalt content, thereby optimizing the design method for asphalt mixtures and meeting the long-term road performance requirements of asphalt pavements in areas with high rainfall. Attached Figure Description

[0018] Figure 1 IDT strength performance test diagram of the optimal asphalt content in Example 1 of this invention; Figure 2 Horizontal strain density performance test diagram of the optimal asphalt content in Example 1 of this invention; Figure 3 Graph showing the concentration change of HC in the exhaust gas degradation performance of Example 1 of the present invention; Figure 4 A graph showing the change in NO concentration in the exhaust gas degradation performance of Example 1 of this invention; Figure 5 Graph showing the concentration change of HC in the exhaust gas degradation performance of Example 2 of the present invention; Figure 6 The graph showing the change in NO concentration in the exhaust gas degradation performance of Example 2 of this invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. 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.

[0020] This embodiment describes a method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture, comprising the following steps: First, the optimal asphalt content for permeable asphalt mixtures was determined through indirect tensile testing (IDT) and semicircular bending tests based on digital image correlation (DIC) technology. Based on this, composite modified nano-TiO2 was added to the permeable asphalt mixture at a ratio of 30%-60% to replace mineral powder. Based on the aforementioned optimal asphalt content and composite modified nano-TiO2 content, permeable asphalt mixtures were prepared. Finally, the exhaust gas degradation effect and mechanical properties of the mixture were verified through exhaust gas degradation tests and road performance tests. (1) Raw material preparation Including aggregates, asphalt, mineral powder, and composite modified TiO2; (2) Grading design A suitable mixture gradation was selected as the research object, and the passing rate of the 2.36 mm sieve was taken as the key indicator. (3) Mix design Optimal asphalt content: The asphalt-aggregate ratio was determined by indirect tensile testing (IDT) and semicircular bending testing (DIC technique).

[0021] Preferably, indirect tensile tests are performed on different samples. Based on the optimal asphalt-aggregate ratio range determined by traditional methods, Marshall specimens are formed with the ratio increasing by 0.3% sequentially for freeze-thaw splitting tests. The indirect tensile test conditions are set according to the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40—2004): test temperatures of 10℃, 20℃, 30℃ and 40℃, and loading rates of 5mm / min, 20mm / min and 50mm / min.

[0022] This embodiment analyzes the correlation linear fitting data of IDT strength and freeze-thaw splitting strength ratio in indirect tensile tests under different test conditions. The correlation between the two is the highest, reaching over 0.92, when the test conditions are 40℃ and the loading rate is 20mm / min. Under these test conditions, the two are positively correlated. The splitting strength of permeable asphalt mixture increases continuously with the increase of IDT strength. Under these conditions, the greater the IDT strength, the higher the cohesion of the mixture and the stronger its resistance to water damage. Under the above conditions, it is sufficient to determine that the IDT strength of permeable asphalt mixture in the indirect tensile test is sufficiently sensitive to changes in asphalt content, and has a good correlation with the splitting strength ratio in the freeze-thaw splitting test. Under these conditions, setting the IDT strength of permeable asphalt mixture as the mechanical parameter of asphalt mixture effectively ensures the excellent water stability of permeable asphalt mixture, optimizes the comprehensive performance of asphalt mixture, provides a scientific basis and quality assurance for pavement construction, and extends the service life of pavement.

[0023] The asphalt mixture in this embodiment is a multiphase composite material, and its cracking characteristics differ from those of homogeneous materials. Further quantitative analysis was conducted on the differences in crack resistance of the exhaust gas-degradable permeable asphalt mixture under different external influencing factors. Horizontal strain density (HSD) was selected as the research object to analyze the crack resistance of the exhaust gas-degradable permeable asphalt mixture under external influencing factors from the perspective of the microscopic strain field. The formula for calculating horizontal strain density is: D—represents the horizontal strain at the i-th control point at time t; E t —This represents the horizontal strain in the region surrounding the crack initiation point at time t; t0—the time corresponding to the maximum horizontal strain; The failure characteristics of the crack initiation point are evaluated based on the full-field horizontal strain acquired by DIC, which effectively analyzes the location of the crack initiation point of the specimen and the displacement and strain data of the crack initiation point and its surroundings.

[0024] The semi-circular bending test conditions based on DIC technology are: test temperatures of -10℃, 0℃, 10℃ and 20℃, and loading rates of 5mm / min, 20mm / min and 50mm / min.

[0025] The correlation study of horizontal strain density in the semi-circular bending test and failure strain in the small beam bending test based on DIC technology in this embodiment shows that the horizontal strain density of the mixture reaches the optimum and the crack resistance is the strongest at a temperature of -10℃ and a loading rate of 20mm / min.

[0026] In this embodiment, the nano-TiO2 is processed by metal ions (Fe) 3+ The modification enhances the photocatalytic effect and improves the degradation rate of exhaust gas. Furthermore, the Al2O3 loading effectively reduces the aggregation of modified TiO2, improving the dispersion effect and stability.

[0027] The specific preparation method of the composite modified TiO2 in this embodiment is as follows: S1: Preheat nano-TiO2 at 55-60℃ for 1 hour, then add it to a sufficient amount of modification solution and stir for 1-2 hours at a stirring speed of 350-400 r / min. After stirring, filter and dry to obtain modified nano-TiO2. S2: Mix 4-7 parts of modified nano-TiO2, 2-3 parts of 5% ferric chloride solution and 1-3 parts of alumina and ball mill thoroughly at a speed of 1000-1500 r / min for 2 hours. After ball milling, filter and dry to obtain composite modified TiO2.

[0028] The modified liquid in this embodiment is prepared by mixing 3-5 parts of bentonite, 2-4 parts of boron nitride, 2-4 parts of calcium sulfate whiskers and 3-5 parts of sodium lignosulfonate solution evenly to obtain the modified liquid.

[0029] By employing the lamellar interlayer structure of bentonite, combined with lamellar boron nitride and whisker structures, and through efficient load-bearing and intercalation into the system, the system performance stability of the product is optimized and the contact area is increased. This better complements the load-bearing capacity of nano-titanium dioxide and the modification of nano-TiO2 by loading on aluminum oxide (Al2O3) carrier. It can effectively inhibit the aggregation of nanoparticles, significantly increase their specific surface area and interfacial contact efficiency, effectively improve the degradation efficiency of automobile exhaust, and reduce environmental pollution.

[0030] The sodium lignosulfonate solution in this embodiment has a mass fraction of 2-5%.

[0031] This embodiment describes an asphalt mixture prepared by a method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture.

[0032] (1) Raw material preparation Aggregates: All aggregates of various sizes are made of limestone.

[0033] Asphalt: 70# SBS modified asphalt was used, and its performance indicators all met the specifications.

[0034] Mineral powder: The apparent density of mineral powder at 20℃ is 2.771 g / cm³. 3 It meets the relevant regulatory requirements.

[0035] Composite modified TiO2: This involves metal ion doping and loading onto suitable supports (e.g., Fe). 3+ Doping, Al2O3 loading treatment) (2) Grading design Taking the aggregate gradation design of OGFC-13 mixture as the research object, the passing rate of 2.36 mm sieve is used as the key indicator. The design is carried out according to the OGFC-13 gradation range recommended in the "Technical Specification for Construction of Asphalt Pavement of Highway" (JTG F40-2003) to ensure that the void ratio meets the standard.

[0036] (3) Mix design Optimal asphalt content: The asphalt-aggregate ratio was determined by indirect tensile testing (IDT) and semicircular flexural testing (DIC technique). The specific steps are as follows: Traditional methods determine the optimal asphalt content for permeable asphalt mixtures to be 4.75%, but these methods are easily affected by environmental factors and differences in specimen preparation, leading to test deviations.

[0037] Marshall specimens were molded with an oilstone ratio of 4.2% to 5.4% (in increments of 0.3%) and subjected to indirect tensile (IDT) tests at different temperatures (10℃, 20℃, 30℃, 40℃) and loading rates (5mm / min, 20mm / min, 50mm / min).

[0038] Indirect tensile tests showed that at 40℃ and 20mm / min, the correlation between IDT strength and freeze-thaw splitting strength ratio was the highest (>0.92). The greater the IDT strength, the stronger the cohesion and water damage resistance of the mixture. Therefore, using IDT strength as a mechanical parameter can optimize water stability and overall performance.

[0039] The semi-circular bending test was conducted with different temperatures (-10℃, 0℃, 10℃, 20℃) and loading rates (5mm / min, 20mm / min, 50mm / min). The results showed that at -10℃ and 20mm / min, the horizontal strain density had the highest correlation with the flexural strength ratio (>0.98). At low temperatures, the mixture becomes brittle and hard, leading to single crack propagation. A moderate loading rate ensures uniform stress distribution and improves crack resistance. Therefore, using horizontal strain density as a mechanical parameter can optimize performance.

[0040] Ultimately, the optimal asphalt content for the mixture was determined to be the average of the asphalt content corresponding to the best IDT strength from the indirect tensile test and the maximum horizontal strain density from the semicircular bending test.

[0041] (4) Preparation of mixture Studies have shown that modifying nano-TiO2 with an alumina (Al2O3) support can effectively suppress the aggregation of nanoparticles and significantly increase their specific surface area and interfacial contact efficiency. This effectively improves the degradation efficiency of automobile exhaust and reduces environmental pollution. The composite modified TiO2 can be used to replace mineral powder in the mixing process.

[0042] Based on the determined asphalt-aggregate ratio, asphalt, aggregates, and mineral powder are mixed. Composite modified TiO2 is then used to replace 30%-60% of the mineral powder, uniformly incorporated into the mixture using a dry-mixing method, and then molded into standard specimens according to specifications.

[0043] Example 1: Preparation of photocatalytic-high-permeability environmentally friendly asphalt mixture (1) Raw material preparation Aggregates: All aggregates of various sizes are made of limestone.

[0044] Asphalt: 70# SBS modified asphalt was used, and its performance indicators all met the specifications.

[0045] Mineral powder: The apparent density of the mineral powder at 20℃ is 2.771 g / cm3, which meets the relevant specifications.

[0046] Composite modified TiO2: This involves metal ion doping and loading onto suitable supports (e.g., Fe3+ doping, Al2O3 loading). The specific preparation method of composite modified TiO2 is as follows: S1: Preheat nano-TiO2 at 58℃ for 1 hour, then add it to a sufficient amount of modification solution and stir for 1.5 hours at a stirring speed of 375 r / min. After stirring, filter and dry to obtain modified nano-TiO2. S2: 5.5 parts of modified nano-TiO2, 2.5 parts of 5% ferric chloride solution and 2 parts of alumina were mixed and ball-milled thoroughly at a speed of 1250 r / min for 2 h. After ball milling, the mixture was filtered and dried to obtain composite modified TiO2.

[0047] The modified liquid in this embodiment is prepared by mixing 4 parts bentonite, 3 parts boron nitride, 3 parts calcium sulfate whiskers and 4 parts sodium lignosulfonate solution evenly to obtain the modified liquid.

[0048] (2) Grading design Taking the aggregate gradation design of OGFC-13 mixture as the research object, the passing rate of 2.36 mm sieve is used as the key indicator. The design is carried out according to the OGFC-13 gradation range recommended in the "Technical Specification for Construction of Asphalt Pavement of Highway" (JTG F40-2003) to ensure that the void ratio is 21.37%.

[0049] (3) Mix design Optimal asphalt content: The asphalt-aggregate ratio was determined to be 4.79% by indirect tensile testing (IDT) and semicircular bending testing (DIC technique).

[0050] The specific steps are as follows: Firstly, the optimal asphalt content was determined to be 4.75% based on traditional methods of leakage and scattering tests. However, the traditional methods for determining permeable asphalt mixtures are easily affected by environmental conditions such as temperature and humidity. Furthermore, the differences in the preparation and curing processes of the same specimens can lead to deviations in the test results.

[0051] To more clearly and effectively reflect the impact of different asphalt-aggregate ratios on the test, the asphalt-aggregate ratio was redefined. Based on this, Marshall specimens with asphalt-aggregate ratios of 4.2%, 4.5%, 4.8%, 5.1%, and 5.4% were prepared in increments of 0.3% for indirect tensile testing. The indirect tensile test conditions were set according to the "Technical Specification for Construction of Asphalt Pavement on Highways" (JTG F40—2004): test temperatures of 10℃, 20℃, 30℃, and 40℃, and loading rates of 5mm / min, 20mm / min, and 50mm / min.

[0052] Analysis of the correlation linear fitting data between IDT strength and freeze-thaw splitting strength ratio from indirect tensile tests under different test conditions revealed the highest correlation (above 0.92) under the test conditions of 40℃ temperature and 20mm / min loading rate. This indicates a positive correlation between the two under these test conditions: the splitting strength of permeable asphalt mixtures increases with increasing IDT strength; furthermore, under these conditions, higher IDT strength correlates with higher cohesion and stronger resistance to water damage.

[0053] Under the experimental conditions of 40℃ and a loading rate of 20mm / min, it is sufficient to determine that the IDT strength of permeable asphalt mixtures in the indirect tensile test is sufficiently sensitive to changes in asphalt content, and shows a good correlation with the splitting strength ratio in the freeze-thaw splitting test. Therefore, setting the IDT strength of permeable asphalt mixtures as a mechanical parameter under these conditions can effectively ensure the excellent water stability of permeable asphalt mixtures and optimize their overall performance. Simultaneously, it provides a scientific basis and quality assurance for pavement construction, extending the service life of the pavement.

[0054] Furthermore, since the semi-circular bending test can directly evaluate the crack resistance macroscopic mechanical properties of asphalt mixtures, by measuring the crack propagation state and fracture energy changes of the specimens through bending loading, its crack resistance and crack propagation resistance can be determined.

[0055] Therefore, Marshall specimens with asphalt-aggregate ratios of 4.2%, 4.5%, 4.8%, 5.1%, and 5.4% were molded for semi-circular bending tests. Based on the "Technical Specification for Construction of Asphalt Pavement on Highways" (JTG F40—2004), the test conditions were set as follows: test temperatures of -10℃, 0℃, 10℃, and 20℃, and loading rates of 5mm / min, 20mm / min, and 50mm / min.

[0056] Experimental results show that the correlation between the horizontal strain density and the flexural strength ratio of permeable asphalt mixtures varies significantly under different test conditions. Linear fitting analysis of DIC data under different temperatures and loading rates revealed the highest correlation (correlation coefficient exceeding 0.98) at a test temperature of -10℃ and a loading rate of 20 mm / min. This specific test condition indicates that permeable asphalt mixtures become more sensitive to the fracture process at lower temperatures. Permeable asphalt mixtures become more brittle and hard at low temperatures, resulting in more singular crack formation and propagation without redundant microcracks, which improves the correlation between horizontal strain density and flexural strength ratio. Simultaneously, at moderate loading rates, the stress distribution within the mixture is more uniform, and crack formation and propagation are more stable, significantly improving the crack resistance of the mixture. Under these conditions, the correlation between horizontal strain density and flexural strength ratio is also higher. This suggests that under specific conditions, the crack resistance of permeable asphalt mixtures increases with increasing horizontal strain density, particularly demonstrating outstanding crack resistance.

[0057] The horizontal strain density of permeable asphalt mixtures in the semi-circular bending test is sufficiently sensitive to changes in asphalt content and exhibits a good correlation with the splitting strength ratio in the freeze-thaw splitting test. Therefore, setting the horizontal strain density of permeable asphalt mixtures as a mechanical parameter under these conditions can effectively ensure the excellent water stability of permeable asphalt mixtures and optimize their overall performance. Simultaneously, it provides a scientific basis and quality assurance for pavement construction, extending the service life of the pavement.

[0058] This result indicates that the average asphalt content corresponding to the optimal IDT strength under indirect tensile conditions and the maximum horizontal strain density under semi-circular bending can be used as the optimal asphalt content for the mixture.

[0059] The experimental data are shown in the table below:

[0060] To further determine the optimal asphalt content, the above data was processed as follows: Figure 1-2 The optimal asphalt content corresponding to the optimal IDT strength under indirect tension conditions and the maximum horizontal strain density based on semi-circular bending are 4.86 and 4.72, respectively. Calculation of the average of these two values ​​reveals that the optimal asphalt-aggregate ratio is 4.79.

[0061] (4) Preparation of mixture Based on the determined asphalt-aggregate ratio, asphalt, aggregates, and mineral powder are mixed. Composite modified TiO2 is used to replace 50% of the mineral powder, and is uniformly incorporated into the mixture using a dry-mixing method. Then, it is molded into Marshall specimens and rutted surface specimens according to specifications.

[0062] II. Performance Verification Exhaust gas degradation performance: The concentration changes of pollutants such as NO and HC were measured in real time using an exhaust gas analyzer. A blank control group was set up. The exhaust gas analyzer parameters were set, and the total duration was 120 minutes. The initial HC concentration was controlled at 55-60 ppm. Because NO is easily oxidized slowly in air, the initial NO concentration was controlled at 195-200 ppm for easier testing. Concentration measurements were taken every 20 minutes. Specific experimental data are as follows: Figure 3-4 As shown: Road performance: Asphalt mixtures were prepared by replacing mineral powder with composite modified nano-TiO2 at a 50% substitution rate, and Marshall specimens were formed for a series of performance tests, including: dynamic water scouring test, indirect tensile test, rutting test, and fatigue test, which tested its water stability, low temperature crack resistance, high temperature stability, and fatigue performance.

[0063] The specific experimental results of the effect of composite modified nano-TiO2 replacing mineral powder on the performance of OGFC-13 mixture are shown in the table below:

[0064] This embodiment optimizes the asphalt content and the amount of composite modified TiO2, enabling it to not only possess excellent exhaust gas degradation capabilities but also superior water stability, low-temperature crack resistance, high-temperature stability, and fatigue performance. It is suitable for road paving in areas with high rainfall and high pollution. This achieves a synergistic improvement in the mechanical properties and environmental functions of permeable asphalt mixtures.

[0065] Example 2: Preparation of photocatalytic-high-permeability environmentally friendly asphalt mixture (1) Raw material preparation Aggregates: All aggregates of various sizes are made of limestone.

[0066] Asphalt: 70# SBS modified asphalt was used, and its performance indicators all met the specifications.

[0067] Mineral powder: The apparent density of mineral powder at 20℃ is 2.771 g / cm³. 3 It meets the relevant regulatory requirements.

[0068] Composite modified TiO2: This involves metal ion doping and loading onto suitable supports (e.g., Fe3+ doping, Al2O3 loading). The specific preparation method of composite modified TiO2 is as follows: S1: Preheat nano-TiO2 at 58℃ for 1 hour, then add it to a sufficient amount of modification solution and stir for 1.5 hours at a stirring speed of 375 r / min. After stirring, filter and dry to obtain modified nano-TiO2. S2: 5.5 parts of modified nano-TiO2, 2.5 parts of 5% ferric chloride solution and 2 parts of alumina are mixed and ball-milled thoroughly at a speed of 1000-1500 r / min for 2 hours. After ball milling, the mixture is filtered and dried to obtain composite modified TiO2.

[0069] The modified liquid in this embodiment is prepared by mixing 4 parts bentonite, 3 parts boron nitride, 3 parts calcium sulfate whiskers and 4 parts sodium lignosulfonate solution evenly to obtain the modified liquid.

[0070] (2) Grading design Taking the aggregate gradation design of OGFC-16 mixture as the research object, the passing rate of 2.36 mm sieve is used as the key indicator. The design is carried out according to the OGFC-16 gradation range recommended in the "Technical Specification for Construction of Asphalt Pavement of Highway" (JTG F40-2003) to ensure that the void ratio is 20.43%.

[0071] (3) Mix design Optimal asphalt content: The optimal asphalt-aggregate ratio for asphalt mixtures was determined to be 4.46% by indirect tensile testing (IDT) and semicircular bending testing (DIC technique).

[0072] (4) Preparation of mixture Based on the determined asphalt-aggregate ratio, asphalt, aggregates, and mineral powder are mixed. Composite modified TiO2 is used to replace 50% of the mineral powder, and is uniformly incorporated into the mixture using a dry-mixing method. Then, it is molded into Marshall specimens and rutted surface specimens according to specifications.

[0073] II. Performance Verification Exhaust gas degradation performance: The concentrations of HC and NO were measured using an exhaust gas analyzer. Specific experimental data are as follows: Figure 5-6 As shown: Road performance: Asphalt mixtures were prepared by replacing mineral powder with composite modified nano-TiO2 at a 50% substitution rate, and Marshall specimens were formed for a series of performance tests, including: dynamic water scouring test, indirect tensile test, rutting test, and fatigue test, which tested its water stability, low temperature crack resistance, high temperature stability, and fatigue performance.

[0074] The specific experimental results of the effect of composite modified nano-TiO2 replacing mineral powder on the performance of OGFC-16 mixture are shown in the table below:

[0075] This embodiment optimizes the asphalt content and the amount of composite modified TiO2, enabling it to not only possess excellent exhaust gas degradation capabilities but also superior water stability, low-temperature crack resistance, high-temperature stability, and fatigue performance. It is suitable for road paving in areas with high rainfall and high pollution. This achieves a synergistic improvement in the mechanical properties and environmental functions of permeable asphalt mixtures.

[0076] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0077] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture, characterized in that, Includes the following steps: First, the optimal asphalt content for permeable asphalt mixtures was determined through indirect tensile testing (IDT) and semicircular bending tests based on digital image correlation (DIC) technology. Based on this, composite modified nano-TiO2 was added to the permeable asphalt mixture at a ratio of 30%-60% to replace mineral powder. Based on the aforementioned optimal asphalt content and composite modified nano-TiO2 content, permeable asphalt mixtures were prepared. Finally, the exhaust gas degradation effect and mechanical properties of the mixture were verified through exhaust gas degradation tests and road performance tests. (1) Raw material preparation Including aggregates, asphalt, mineral powder, and composite modified TiO2; (2) Grading design A suitable mixture gradation was selected as the research object, and the passing rate of the 2.36 mm sieve was taken as the key indicator. (3) Mix design Optimal asphalt content: The asphalt-aggregate ratio was determined by indirect tensile test (IDT) and semicircular flexural test (DIC technique), and the optimal asphalt content of the mixture was determined by the average asphalt content corresponding to the maximum values ​​of IDT strength and horizontal strain density.

2. The method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture as described in claim 1, characterized in that, Indirect tensile tests were conducted on different specimens. Based on the optimal asphalt-aggregate ratio range determined by traditional methods, Marshall specimens were molded with the ratio increasing by 0.3% in sequence for freeze-thaw splitting tests. The indirect tensile test conditions were set according to the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40—2004): test temperatures of 10℃, 20℃, 30℃ and 40℃, and loading rates of 5mm / min, 20mm / min and 50mm / min.

3. The method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture as described in claim 1, characterized in that, Analysis of the correlation linear fitting data of IDT strength and freeze-thaw splitting strength ratio in indirect tensile tests under different test conditions showed that the correlation between the two was highest at a temperature of 40℃ and a loading rate of 20mm / min, reaching over 0.

92. Under these test conditions, the two showed a positive correlation, and the splitting strength of permeable asphalt mixtures increased continuously with the increase of IDT strength. Under these conditions, the greater the IDT strength, the higher the cohesion of the mixture and the stronger its resistance to water damage. Under the above conditions, it is sufficient to determine that the IDT strength of permeable asphalt mixture in the indirect tensile test is sufficiently sensitive to changes in asphalt content, and has a good correlation with the splitting strength ratio in the freeze-thaw splitting test. Under these conditions, setting the IDT strength of permeable asphalt mixture as the mechanical parameter of asphalt mixture effectively ensures the excellent water stability of permeable asphalt mixture, optimizes the comprehensive performance of asphalt mixture, provides a scientific basis and quality assurance for pavement construction, and extends the service life of pavement.

4. The method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture as described in claim 1, characterized in that, Asphalt mixture is a multiphase composite material, and its cracking characteristics differ from homogeneous materials. To further quantitatively analyze the differences in crack resistance of exhaust gas-degradable permeable asphalt mixtures under different external influencing factors, horizontal strain density (HSD) was selected as the research object. The crack resistance of exhaust gas-degradable permeable asphalt mixtures under external influencing factors was analyzed from the perspective of the microscopic strain field. The formula for calculating horizontal strain density is: D—represents the horizontal strain at the i-th control point at time t; E t —This represents the horizontal strain in the region surrounding the crack initiation point at time t; t0—the time corresponding to the maximum horizontal strain; The failure characteristics at the crack initiation point were evaluated based on the full-field horizontal strain acquired by DIC (Displacement Induction Capacity) data, effectively analyzing the location of the crack initiation point and the displacement and strain data of the crack initiation point and its surrounding area. The semi-circular bending test conditions based on DIC technology were: test temperatures of -10℃, 0℃, 10℃, and 20℃, and loading rates of 5mm / min, 20mm / min, and 50mm / min. Simultaneously, different small beam bending tests were conducted under the conditions of -10℃ and 50mm / min.

5. The method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture as described in claim 1, characterized in that, A correlation study based on DIC technology on the horizontal strain density of the semicircular bending test and the failure strain of the beam bending test shows that the horizontal strain density of the mixture reaches the optimum and the strongest crack resistance at a temperature of -10℃ and a loading rate of 20mm / min.

6. The method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture as described in claim 1, characterized in that, Nano TiO2 passes through metal ions (Fe) 3+ The modification enhances the photocatalytic effect and improves the degradation rate of exhaust gas. Furthermore, the Al2O3 loading effectively reduces the aggregation of modified TiO2, improving the dispersion effect and stability.

7. The method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture as described in claim 6, characterized in that, The specific preparation method of composite modified TiO2 is as follows: S1: Preheat nano-TiO2 at 55-60℃ for 1 hour, then add it to a sufficient amount of modification solution and stir for 1-2 hours at a stirring speed of 350-400 r / min. After stirring, filter and dry to obtain modified nano-TiO2. S2: Mix 4-7 parts of modified nano-TiO2, 2-3 parts of 5% ferric chloride solution and 1-3 parts of alumina and ball mill thoroughly at a speed of 1000-1500 r / min for 2 hours. After ball milling, filter and dry to obtain composite modified TiO2.

8. The method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture as described in claim 7, characterized in that, The modified solution is prepared by mixing 3-5 parts of bentonite, 2-4 parts of boron nitride, 2-4 parts of calcium sulfate whiskers and 3-5 parts of sodium lignosulfonate solution evenly to obtain the modified solution.

9. The method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture as described in claim 8, characterized in that, The mass fraction of sodium lignosulfonate solution is 2-5%.

10. An asphalt mixture prepared by the method for preparing a photocatalytic-high-permeability environmentally friendly asphalt mixture as described in any one of claims 1-9.

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