Method for determining suitable phase change temperature of phase change material for asphalt pavement crack prevention

Abstract

This invention discloses a method for determining the suitable phase change temperature of phase change materials for crack prevention in asphalt pavements, relating to the field of road engineering technology. First, a TSRST test is conducted on the target asphalt mixture. The low-temperature cracking characteristic temperature is determined as a threshold based on the inflection point of the temperature-stress curve. Dates with a daily minimum temperature below this threshold are defined as high-risk days for low-temperature cracking. Multi-year meteorological data is collected, and representative values ​​of high-risk day temperatures are determined using statistical methods, and typical representative days are selected. A pavement temperature field model for representative days is established, and the hourly temperature of key control layers is calculated. Based on the hourly temperature distribution, a phase change matching degree evaluation index is constructed, and the suitable phase change temperature is optimized using the maximization of the matching degree as the criterion. This invention achieves precise matching between the phase change temperature and the pavement temperature field, improves the latent heat utilization efficiency of the phase change material, and is suitable for low-temperature crack-resistant design of asphalt pavements in cold regions.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, and in particular to a method for determining the suitable phase change temperature of a phase change material for crack prevention of asphalt pavement. Background Technology

[0002] my country has a vast cold region, accounting for about two-thirds of the land area. Low-temperature cracking is a typical disease that occurs widely on pavements in cold regions. Moisture intrusion into cracks will accelerate the softening of the structural layer and the reduction of load-bearing capacity, causing structural damage to the pavement and subgrade.

[0003] Phase change temperature control technology can actively and precisely regulate road surface temperature, weakening the temperature-induced factors of low-temperature cracking at the source and effectively reducing temperature stress. It is an important technical approach for low-temperature crack prevention of pavements in cold regions. The phase change temperature is the core parameter that determines the phase change temperature control effect and latent heat utilization rate: if the phase change temperature is too high, there will be insufficient heat storage during the heating stage; if the phase change temperature is too low, there will be insufficient heat release during the cooling stage, both of which will lead to insufficient temperature control and reduced crack prevention effect.

[0004] Existing methods for selecting phase change temperature generally suffer from the following defects: phase change temperature mostly relies on empirical values ​​and does not take into account the actual climate characteristics of the engineering area and the actual temperature field distribution characteristics of the pavement; high-risk meteorological conditions for low-temperature cracking are not quantitatively identified, and the selected working conditions do not match the actual cracking risk; a matching evaluation mechanism between phase change temperature and pavement temperature history has not been established, resulting in low latent heat utilization efficiency; and a threshold has not been determined for the actual low-temperature cracking characteristics of asphalt mixtures, resulting in insufficient pertinence and reliability of the methods.

[0005] Therefore, there is an urgent need to establish a scientific, quantitative, working-condition-appropriate, and engineering-applicable method for determining the phase transition temperature of asphalt pavement anti-cracking phase change materials. Summary of the Invention

[0006] This invention provides a method for determining the suitable phase change temperature of phase change materials for crack prevention in asphalt pavements, which solves the problems of lack of quantitative basis for phase change temperature selection and mismatch with actual pavement conditions in the prior art, and realizes the scientific determination of phase change temperature and the maximization of latent heat utilization efficiency.

[0007] This invention provides a method for determining the suitable phase transition temperature of a phase change material for crack prevention in asphalt pavement, comprising: The target asphalt mixture was subjected to a TSRST test to obtain a temperature-stress curve. The low-temperature cracking characteristic temperature was determined based on the inflection point of the temperature-stress curve, and the low-temperature cracking characteristic temperature was used as the threshold for judging the risk of low-temperature cracking of asphalt pavement. Dates with a minimum daily temperature lower than the low-temperature cracking characteristic temperature are defined as high-risk days for low-temperature cracking. Meteorological data of the engineering area over many years are collected, and statistical methods are used to determine the representative temperature values ​​of the high-risk days for low-temperature cracking. Typical representative days for high-risk days for low-temperature cracking are selected based on environmental conditions. A temperature field model of the asphalt pavement structure for a typical high-risk day of low-temperature cracking was established, and the hourly temperature of the key control layer of the pavement was calculated. An evaluation index for phase change matching degree is constructed based on the hourly temperature distribution of the key control layer of the road surface. The optimal phase change temperature for the crack-resistant phase change material is determined with the maximization of the phase change matching degree as the optimization objective.

[0008] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention utilizes the TSRST test on target asphalt mixtures to obtain temperature-stress curves. The inflection point of the temperature-stress curve is used to determine the characteristic temperature of low-temperature cracking, which is then used as the threshold for assessing the risk of low-temperature cracking in asphalt pavements. The beneficial effects of this step are: directly obtaining the characteristic temperature of low-temperature cracking of the material itself through the TSRST test avoids the bias of empirical formulas, providing an accurate and targeted threshold for subsequent risk assessment, and truly reflecting the crack resistance performance of a specific asphalt mixture, thereby improving the reliability of low-temperature cracking assessment. Dates where the daily minimum temperature is lower than the characteristic temperature of low-temperature cracking are defined as high-risk days for low-temperature cracking. Meteorological data from the engineering area over many years is collected, and statistical methods are used to determine the representative temperature values ​​for high-risk days for low-temperature cracking. Typical representative high-risk days for low-temperature cracking are then selected based on environmental conditions. The beneficial effects of this step are: based on the statistical screening of historical meteorological data, extreme weather days with typical low-temperature characteristics can be identified, making subsequent analysis more representative and practical for engineering, avoiding interference from random weather fluctuations, and improving the targeting and stability of low-temperature cracking risk assessment. A temperature field model of the asphalt pavement structure was established for a typical high-risk day for low-temperature cracking, and the hourly temperature and temperature variation range of the key control layers of the pavement were calculated. The benefits of this step are: by accurately simulating the temperature distribution and variation patterns within the pavement structure under typical day conditions using the temperature field model, the influence of temperature gradients on the constraint stress within the asphalt layer was revealed, providing crucial hourly temperature data for the matching design of phase change materials (PCMs), compensating for the shortcomings of considering only ambient temperature, and thus supporting more refined low-temperature crack-resistant design. Based on the hourly temperature distribution of the key control layers of the pavement, a phase change matching degree evaluation index was constructed. With maximizing the phase change matching degree as the optimization objective, the appropriate phase change temperature for crack-resistant PCMs was determined. The benefits of this step are: by introducing the phase change matching degree evaluation index, the phase change temperature of the PCMs was optimally matched with the actual temperature variation range of the pavement, enabling the PCMs to exert maximum heat absorption or temperature regulation during the high-risk period for low-temperature cracking, thereby effectively delaying or avoiding low-temperature cracking of asphalt pavements and improving the scientific and economic aspects of crack-resistant design. Attached Figure Description

[0009] Figure 1A flowchart illustrating the steps of determining the suitable phase change temperature for phase change materials used in asphalt pavement crack prevention, as provided in an embodiment of the present invention. Figure 2 The TSRST temperature-stress curve and linear cumulative temperature temperature diagram of asphalt mixture provided in the embodiments of the present invention; Figure 3 This is a schematic diagram of the road surface structure temperature field and the median temperature of the control layer on a representative day of low temperature and high risk, provided for an embodiment of the present invention. Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0011] This invention provides a method for determining the suitable phase transition temperature of phase change materials for crack prevention in asphalt pavements, see [link to relevant documentation]. Figure 1 The method includes the following steps S101 to S104.

[0012] S101. Conduct TSRST (Thermal Stress Restrained Specimen Test) on the target asphalt mixture to obtain the temperature-stress curve. Determine the low-temperature cracking characteristic temperature based on the inflection point of the temperature-stress curve and use the low-temperature cracking characteristic temperature as the threshold for judging the risk of low-temperature cracking of asphalt pavement. Specifically, in step S101, the target asphalt mixture includes: fresh asphalt mixture and asphalt mixture whose performance has degraded after different service cycles. The characteristic temperature of low-temperature cracking is determined according to the actual service condition of the target asphalt mixture to meet different needs such as short-term crack prevention, long-term crack prevention, or a combination of both.

[0013] Specifically, in step S101, the low-temperature cracking characteristic temperature is determined based on the inflection point of the temperature-stress curve, including the following steps S1011 to S1012.

[0014] S1011, starting from the end point of the temperature-stress curve, gradually expands the temperature range in the direction of increasing temperature, and continuously calculates the squared value of the Pearson correlation coefficient between temperature and stress. S1012, the temperature at which the squared value of the Pearson correlation coefficient reaches 0.99 is the linear cumulative temperature of temperature stress. Subtracting 10℃ from the linear cumulative temperature of temperature stress is taken as the characteristic temperature of low-temperature cracking.

[0015] For example, see Figure 2 The target asphalt mixture for this road section was selected, fresh mixture samples were prepared, and TSRST tests were conducted to obtain temperature-stress curves. Taking the termination point of the TSRST test temperature-stress curve as the starting point, the temperature range was gradually expanded in the direction of increasing temperature, and the Pearson correlation coefficient r was continuously calculated. 2 until r 2 The temperature at the point where the coefficient of thermal stress (Ct) = 0.99 is the linear cumulative temperature of thermal stress. The linear cumulative temperature of thermal stress -10℃ is the characteristic temperature of low-temperature cracking, and it is used as the threshold for judging the risk of low-temperature cracking.

[0016] Taking a high-altitude expressway project in Shaanxi Province as an example, this section is located in a mountainous area at an altitude of over 1500 meters. The extreme minimum temperature in winter can reach -35℃, and the temperature difference between day and night exceeds 20℃, resulting in frequent low-temperature cracking of the asphalt pavement. AC-16 modified asphalt mixture actually used in this section was selected as the target material. Considering the natural degradation of the mixture's performance during pavement service, two types of specimens were prepared: one group consisted of fresh asphalt mixture specimens, and the other group consisted of specimens prepared using a long-term aging treatment procedure (referring to the AASHTO R30 standard, where the compacted fresh asphalt mixture specimens were continuously aged in an 85℃ oven for 120 hours to simulate the performance degradation after 5-8 years of service).

[0017] The TSRST test method in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" was used, employing a high-precision temperature stress constraint test system. The specimens were 250mm × 50mm × 50mm prisms. Three high-precision platinum resistance temperature sensors were attached to the sides of each specimen, located at both ends and the middle. The average value of these three sensors was taken as the real-time temperature of the specimen, with a measurement accuracy of ±0.1℃. Before the test, the specimens were kept at a constant temperature of 10℃ in the test chamber for 60 minutes to ensure uniform internal temperature distribution. After the test started, the temperature was linearly reduced from 10℃ to -30℃ at a constant cooling rate of 10℃ / h. Simultaneously, the displacement constraint servo system was activated, adjusting the constraint displacement in real time at a rate of 0.01mm / min to ensure the specimen length remained constant in the constraint direction. During the test, temperature and axial stress data were continuously acquired at a frequency of once per second until brittle fracture occurred, at which point the test automatically terminated, yielding a complete temperature-stress curve.

[0018] The experimental data processing was performed as follows: First, the final temperature corresponding to the fracture point in the temperature-stress curve was denoted as T_end, which corresponds to the instantaneous temperature at which the specimen experienced low-temperature cracking. Starting from T_end, the temperature interval was expanded point by point in the direction of temperature increase, with an expansion step size of 0.5℃. For each expanded temperature interval, the temperature values ​​and corresponding stress values ​​at all acquisition times within that interval were extracted, and the Pearson correlation coefficient r between these two variables was calculated. Furthermore, its squared value r² was obtained. The formula for calculating the Pearson correlation coefficient is... ,in, The covariance of temperature and stress, and These represent the standard deviations of temperature and stress, respectively. The temperature range is expanded further in the direction of increasing temperature, with r² recalculated each time, until r² first reaches 0.99. At this point, the expansion stops, and the upper limit of the temperature range is recorded. This temperature is the linear cumulative temperature of temperature stress, denoted as T_linear. Actual measurements show that the T_linear temperature for freshly mixed asphalt specimens is -10℃, and the linear cumulative temperature of temperature stress (-10℃) is the characteristic temperature for low-temperature cracking. For specimens after long-term aging, the T_linear temperature is -4℃, and the linear cumulative temperature of temperature stress (-10℃) is also the characteristic temperature for low-temperature cracking. These two characteristic temperatures correspond to the low-temperature cracking risk assessment thresholds for the early and late stages of pavement service, respectively. In practical applications, the appropriate threshold can be selected based on the actual service life of the pavement or the designed crack prevention target to achieve short-term crack prevention, long-term crack prevention, or a comprehensive crack prevention design that considers both.

[0019] In this embodiment, by establishing a quantitative criterion of r²=0.99, the traditional empirical identification of curve "inflection points" is transformed into an objective and reproducible statistical calculation process. S102 defines days when the daily minimum temperature is lower than the characteristic temperature of low-temperature cracking as high-risk days for low-temperature cracking. Meteorological data of the engineering area over many years are collected, and statistical methods are used to determine the representative temperature values ​​of high-risk days for low-temperature cracking. Typical representative days for high-risk days for low-temperature cracking are selected based on environmental conditions. Specifically, in step S102, a statistical method is used to determine the representative temperature value of the day with a high risk of low temperature cracking, including the following steps S1021 to S1024.

[0020] S1021, collect daily meteorological data for the project area over multiple consecutive winter cycles; the daily meteorological data shall include at least: daily minimum temperature, daily maximum temperature, solar radiation intensity, wind speed and weather type; S1022, select all days from the daily meteorological data where the daily minimum temperature is lower than the low temperature cracking characteristic temperature, and use the meteorological data corresponding to the selected dates as the dataset of high-risk days for low temperature cracking; S1023, a nonparametric statistical method based on probability density estimation is used to statistically fit the temperature data in the dataset of days with high risk of low temperature cracking, and the probability density distribution of the temperature on days with high risk of low temperature cracking is obtained. S1024. Based on the probability density distribution, calculate the temperature interval quantiles under the pre-set confidence level, and use the temperature interval quantiles as the representative values ​​of the temperature on days with high risk of low temperature cracking.

[0021] For example, dates with a daily minimum temperature below the aforementioned low-temperature cracking characteristic temperature (-10℃) are defined as high-risk days for low-temperature cracking. Daily meteorological data for the past 5 years from meteorological stations along the road section are collected, including indicators such as daily minimum temperature, daily maximum temperature, solar radiation, wind speed, and weather type.

[0022] The kernel density estimation method was used to statistically analyze the temperature data of days with high risk of low temperature cracking, and the representative values ​​of the lowest and highest temperatures of days with high risk of low temperature cracking were calculated at a 70% confidence level.

[0023] Representative days were selected based on the principle of typicality. The representative days were required to be sunny with no precipitation, and the daily minimum and maximum temperatures were close to the representative values ​​with a 70% confidence level. The representative days with typical low-temperature cracking high risk were finally determined.

[0024] For the aforementioned highway section in the same cold region, after determining the characteristic temperature for low-temperature cracking, the next step was to identify and select representative days for high-risk low-temperature cracking days. First, using the characteristic temperature of -10°C for low-temperature cracking of freshly mixed asphalt as the threshold, daily meteorological data for nearly five consecutive winter cycles (November to March of the following year) were obtained from meteorological stations along the road section. Each data record included the daily minimum temperature, daily maximum temperature, daily cumulative solar radiation, daily average wind speed, and weather type (sunny, cloudy, overcast, rainy, snowy, etc.). From this dataset, all days with a minimum temperature below -10°C were selected, totaling 47 days, constituting the high-risk low-temperature cracking day dataset. Statistical analysis was then performed on the daily minimum and maximum temperatures within these 47 days.

[0025] Kernel density estimation was used as a nonparametric statistical method. A Gaussian kernel function was selected, and the bandwidth was automatically determined using the Silverman rule. Probability density was fitted to the daily minimum and maximum temperatures of high-risk days, resulting in two probability density distribution curves. With a confidence level of 70%, the temperature values ​​corresponding to the cumulative probability reaching 70% from negative infinity to a certain quantile under the probability density distribution curves for both the daily minimum and daily maximum temperatures were calculated. The results show that the representative value for the daily minimum temperature at a 70% confidence level is -14.9℃, and the representative value for the daily maximum temperature is -0.2℃. This means that on days with a 70% high risk of low-temperature cracking, the daily minimum temperature is no lower than -14.9℃, and the daily maximum temperature is no higher than -0.2℃.

[0026] Based on the above representative values, typical representative days were further selected from the 47 high-risk days. The selection criteria were as follows: weather type was sunny or partly cloudy (excluding the interference of cloudy days, snowfall, and strong winds on radiative and convective heat transfer), daily average wind speed ≤ level 2 (i.e., light wind or no wind), daily minimum temperature deviation from -14.8℃ within ±1.5℃, and daily maximum temperature deviation from -0.5℃ within ±1.5℃. A date that met the criteria was finally selected: December 22nd of a certain year. The weather on this day was sunny, with a daily average wind speed of 1.2 m / s, a daily minimum temperature of -14.6℃, and a daily maximum temperature of -0.4℃. This day was selected as a typical high-risk representative day for low-temperature cracking and used in subsequent pavement temperature field calculations.

[0027] If crack prevention design is to be carried out for long-term aging mixtures (characteristic temperature -4℃), then high-risk days with the lowest daily temperature below 4℃ are selected, and representative values ​​are recalculated and selected using the same statistical method.

[0028] S103, establish a temperature field model of asphalt pavement structure on a typical high-risk day for low-temperature cracking, and calculate the hourly temperature of key control layers of the pavement. S104. Based on the hourly temperature distribution of key control layers in the road surface, an evaluation index for phase change matching degree is constructed. With the maximization of phase change matching degree as the optimization objective, the appropriate phase change temperature for crack-resistant phase change materials is determined.

[0029] Specifically, in step S104, an evaluation index for phase change matching degree is constructed based on the hourly temperature distribution of the key control layer of the road surface, including the following steps S1041 to S1045.

[0030] S1045, determine the temperature range of candidate phase transition temperatures; wherein, the temperature range covers the daily temperature variation range of the key control layer of the road surface; S1042, For any candidate phase transition temperature in the temperature range, the similarity value between the candidate phase transition temperature and each hourly temperature of the key control layer of the road surface is calculated using a Gaussian matching degree function. Here, the expression for the matching degree function is: ; in, Phase transition temperature; For the first Hourly temperature of key road surface layers at each moment; The phase transition interval is half-width; This represents the total number of temperature points per hour. Here, the half-width of the phase change interval is determined based on the actual phase change temperature range of the phase change material, which is the temperature range between the start and end temperatures of the phase change process.

[0031] Here, the key control layer of the road surface is the position within the asphalt surface layer at a preset depth from the road surface. The preset depth is determined based on the road structure combination and the low-temperature cracking sensitive layer.

[0032] S1043, sum up all similarity values ​​corresponding to the candidate phase transition temperature and divide by the total number of temperature points per hour to obtain the phase transition matching degree corresponding to the candidate phase transition temperature. S1045 defines the phase change matching degree as a function of the candidate phase change temperature. The function is an evaluation index of the phase change matching degree and is used to characterize the overall matching degree between different candidate phase change temperatures and the hourly temperature distribution of the key control layer of the road surface.

[0033] Specifically, in step S104, with maximizing the phase transformation matching degree as the optimization objective, the suitable phase transformation temperature for the crack-resistant phase transformation material is determined, including: Using the median daily temperature variation of the key control layer of the road surface as the reference center, multiple candidate phase transition temperatures are selected within a preset neighborhood of the reference center. The phase transition matching degree corresponding to each candidate phase transition temperature is calculated, and the candidate phase transition temperature corresponding to the maximum value of the phase transition matching degree is determined as the suitable phase transition temperature.

[0034] For example, see Figure 3 The temperature field of asphalt pavement under representative daily working conditions was simulated using conventional unsteady heat conduction methods in this field to obtain the key control layer of the pavement. Here, the key control layer of the pavement is the hourly temperature change at a depth of 4 cm in the asphalt surface layer, and the daily maximum temperature, daily minimum temperature and median temperature of this layer were obtained.

[0035] Centered on the median temperature at a depth of 4 cm, candidate phase transition temperatures are selected within a range of ±2℃ from the median. The temperature interval is adaptively adjusted according to the engineering accuracy requirements; in this embodiment, it is set to 0.5℃.

[0036] Calculate the phase transition matching degree corresponding to each candidate phase transition temperature. The candidate phase transition temperatures can be -4.9, -4.4, -3.9, -3.4, -2.9, -2.4, -1.9, -1.4, or -0.9℃. The hourly temperature at a depth of 4 cm on the road surface is shown in Table 1. The half-width of the phase transition interval is 8.2℃; N is the total number of temperature points per hour, which is 24 here.

[0037] Table 1. Hourly Temperature at a 4cm Depth of Road Surface

[0038] The phase transition matching degree corresponding to different phase transition temperatures was calculated, and the results are shown in Table 2. The candidate temperature with the largest phase transition matching degree was selected as the most suitable phase transition temperature for the phase transition material used for crack prevention of asphalt pavement in this section, which is -3.9℃.

[0039] Table 2 Calculation results of phase transition matching degree at different phase transition temperatures

[0040] According to calculations in this embodiment, under typical high-risk low-temperature cracking conditions with a 70% confidence level, the median temperature change at a depth of 4cm in the pavement is -2.9℃. After optimization of the phase change matching degree, the suitable phase change temperature for the pavement section in this embodiment is determined to be -3.9℃. Using this phase change temperature allows for a high degree of matching between the phase change material and the pavement temperature history, fully utilizing latent heat, significantly reducing pavement temperature stress, and improving the low-temperature crack resistance of asphalt pavement.

[0041] The various embodiments described in this specification are presented in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. All or part of this invention can be used in numerous general-purpose or special-purpose computer system environments or configurations. Examples include: personal computers, server computers, handheld or portable devices, tablet devices, mobile communication terminals, multiprocessor systems, microprocessor-based systems, programmable electronic devices, network PCs, minicomputers, mainframe computers, and distributed computing environments including any of the above systems or devices, etc.

[0042] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for determining a suitable phase transition temperature of a phase change material for use in asphalt pavement crack prevention, characterized by, include: The target asphalt mixture was subjected to a TSRST test to obtain a temperature-stress curve. The low-temperature cracking characteristic temperature was determined based on the inflection point of the temperature-stress curve, and the low-temperature cracking characteristic temperature was used as the threshold for judging the risk of low-temperature cracking of asphalt pavement. Dates with a minimum daily temperature lower than the low-temperature cracking characteristic temperature are defined as high-risk days for low-temperature cracking. Meteorological data of the engineering area over many years are collected, and statistical methods are used to determine the representative temperature values ​​of the high-risk days for low-temperature cracking. Typical representative days for high-risk days for low-temperature cracking are selected based on environmental conditions. A temperature field model of the asphalt pavement structure for a typical high-risk day of low-temperature cracking was established, and the hourly temperature of the key control layer of the pavement was calculated. An evaluation index for phase change matching degree is constructed based on the hourly temperature distribution of the key control layer of the road surface. The optimal phase change temperature for the crack-resistant phase change material is determined with the maximization of the phase change matching degree as the optimization objective.

2. The method for determining the suitable phase transition temperature of the phase change material for asphalt pavement crack prevention according to claim 1, characterized in that, The target asphalt mixture includes: fresh asphalt mixture and asphalt mixture whose performance has degraded after different service cycles; The low-temperature cracking characteristic temperature is determined according to the actual service state of the target asphalt mixture to meet different needs such as short-term crack prevention, long-term crack prevention, or a combination of both.

3. The method for determining the suitable phase transition temperature of the phase change material for asphalt pavement crack prevention according to claim 1, characterized in that, The step of determining the low-temperature cracking characteristic temperature based on the inflection point of the temperature-stress curve includes: Starting from the end point of the temperature-stress curve, the temperature range is gradually expanded in the direction of increasing temperature, and the squared value of the Pearson correlation coefficient between temperature and stress is continuously calculated. The temperature at which the squared value of the Pearson correlation coefficient reaches 0.99 is the linear cumulative temperature of temperature stress. Subtracting 10°C from the linear cumulative temperature of temperature stress is taken as the characteristic temperature of low-temperature cracking.

4. The method for determining the suitable phase transition temperature of the phase change material for asphalt pavement crack prevention according to claim 1, characterized in that, The method of determining the representative temperature value for the high-risk day for low-temperature cracking using statistical methods includes: Collect daily meteorological data for the project area over multiple consecutive winter cycles; wherein the daily meteorological data includes at least: daily minimum temperature, daily maximum temperature, solar radiation intensity, wind speed, and weather type; From the daily meteorological data, select all days when the daily minimum temperature is lower than the low-temperature cracking characteristic temperature, and use the meteorological data corresponding to the selected dates as the dataset of high-risk days for low-temperature cracking. The temperature data in the dataset of days with high risk of low temperature cracking were statistically fitted using a nonparametric statistical method based on probability density estimation to obtain the probability density distribution of the temperature on the days with high risk of low temperature cracking. Based on the probability density distribution, calculate the temperature interval quantiles under the preset confidence level, and use the temperature interval quantiles as the representative values ​​of the temperature on the high-risk days for low-temperature cracking.

5. The method for determining the suitable phase transition temperature of the phase change material for crack prevention of asphalt pavement according to claim 1, characterized in that, The evaluation index for phase transition matching degree, constructed based on the hourly temperature distribution of the key control layers of the road surface, includes: Determine the temperature range of candidate phase transition temperatures; wherein the temperature range covers the daily temperature variation range of the key control layer of the road surface; For any candidate phase transition temperature within the temperature range, a Gaussian matching degree function is used to calculate the similarity value between the candidate phase transition temperature and each hourly temperature of the key control layer of the road surface. The phase transition matching degree corresponding to the candidate phase transition temperature is obtained by summing all the similarity values ​​corresponding to the candidate phase transition temperature and dividing by the total number of temperature points per hour. The phase transition matching degree is defined as a function of the candidate phase transition temperature. The function is an evaluation index of the phase transition matching degree and is used to characterize the overall matching degree between different candidate phase transition temperatures and the hourly temperature distribution of the key control layer of the road surface.

6. The method for determining the suitable phase transition temperature of the phase change material for crack prevention of asphalt pavement according to claim 5, characterized in that, The expression for the matching degree function is: ； in, The phase transition temperature; For the first Hourly temperature of key road surface layers at each moment; The phase transition interval is half-width; This represents the total number of temperature points per hour.

7. The method for determining the suitable phase transition temperature of the phase change material for asphalt pavement crack prevention according to claim 6, characterized in that, The half-width of the phase change interval is determined based on the actual phase change temperature range of the phase change material, which is the temperature range between the start temperature and the end temperature of the phase change process of the phase change material.

8. The method for determining the suitable phase transition temperature of the phase change material for crack prevention of asphalt pavement according to claim 1, characterized in that, The key control layer of the road surface is the location within the asphalt surface layer at a preset depth from the road surface. The preset depth is determined based on the road structure combination and the low-temperature cracking sensitive layer.

9. The method for determining the suitable phase transition temperature of the phase change material for crack prevention of asphalt pavement according to claim 1, characterized in that, The step of determining the suitable phase transition temperature of the crack-resistant phase transition material with maximizing the phase transition matching degree as the optimization objective includes: Using the median daily temperature variation of the key control layer of the road surface as the reference center, multiple candidate phase transition temperatures are selected within a preset neighborhood of the reference center. The phase transition matching degree corresponding to each candidate phase transition temperature is calculated, and the candidate phase transition temperature corresponding to the maximum value of the phase transition matching degree is determined as the suitable phase transition temperature.

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