Preparation of Conductive Asphalt Concrete Based on the Action Mechanism of Conductive Phase Materials

: Carbon fiber powder (CFP) was first applied to conductive asphalt concrete as a conductive phase material, but its action mechanism has not been clarified. In this paper, atomic force microscopy (AFM) and molecular dynamics (MDs) simulation are used to study the carbon fiber powder mechanism of action, guide the preparation of conductive asphalt concrete, and study the electrothermal properties of conductive asphalt concrete. The results show that carbon fiber powder weakens the adhesion property of asphalt mastic, and this weakening further strengthens in the water–temperature coupling, so water stability and conductivity are used as evaluation indicators to determine that the optimal content of carbon fiber powder is 2.0% and that the optimal content of carbon fibers (CFs) is 0.4%. Carbon fiber–carbon fiber powder conductive asphalt concrete with a resistivity of 0.98 Ω · m was finally prepared. In the temperature rise test of the Marshall specimen and rutting slab, its warming effect is obvious, and the heat transformation rate is more than 75%, so it has a very good ability to melt snow and ice.


Introduction
Under icy and snowy weather conditions, the driving environment on all grades of highways is significantly reduced due to the accumulation of snow and ice on the pavement.And the adhesion coefficient of the pavement is reduced to less than 0.35, which is only 12%~54% of the adhesion coefficient of normal temperature, dry, and clean pavement [1].This means that it is extremely easy to lose control of vehicles when driving, braking, and turning.According to statistics, the traffic accident rate in icy and snowy weather is about five times that of non-icy weather, which is significantly higher than the average level of the whole year [2].The above fully proves that the accumulation of snow and ice on the pavement seriously threatens the safety of road traffic as well as the safety of human life and property.To address the problem of snow and ice on the pavement, the snow removal methods of manual, mechanical, and spreading of snowmelt salt were adopted mainly.However, the road service level is affected by all of the above snow removal methods to varying degrees [3].In this context, conductive asphalt concrete pavement has received extensive attention from scholars because of its advantages of high efficiency of snow and ice melting, an environmentally friendly deicing process, convenient and quick use, low labor demand, and no mechanical maintenance [4].Conductive asphalt concrete pavement means that conductive phase materials are incorporated into the pavement surface structure.And electro-thermal conversion is achieved in energized conditions to melt snow and ice [5][6][7].
Common conductive phase materials mainly include graphite, steel slag, carbon black, steel fiber, and carbon fiber [3,8,9].Yang et al. [10] prepared steel fiber conductive Coatings 2024, 14, 512 3 of 18 by determining the resistivity and thermal conductivity of the concrete.This paper clarifies the carbon fiber dispersion and carbon fiber powder action mechanism and combines the conductive properties to determine the content of conductive phase materials to prepare a strong conductive carbon fiber-carbon fiber powder conductive asphalt concrete, and the temperature rise test was conducted to clarify its heat transformation rate and thus guide construction.

Raw Materials
In this paper, 70# asphalt produced by Sinopec, Beijing, China was used (Table 1).The aggregates were sourced from Jiaxing City, Zhejiang Province (Tables 2 and 3).The T700-12K-type glue-free 9 mm polyacrylonitrile-based carbon fiber and T700-type polyacrylonitrile-based carbon fiber powder produced by Toray, Japan, are used, and the main performance indexes of both are shown in Table 4.

Test Methods
This study is based on the Atomic Force Microscope (AFM) (Bruker Dimension Icon, Munich, Germany.)analysis of carbon fiber powder asphalt mastic adhesion, with the help of molecular dynamics (MDs) simulation, from the point of view of the molecular interlayer action to verify the carbon-fiber-powder-asphalt-mastic-related mechanisms.The carbon fiber powder action mechanism, carbon fiber dispersion, and conductive asphalt concrete conductive properties are used to determine the optimal mixing amount of the conductive phase materials in order to prepare a conductive asphalt concrete with excellent electrical and thermal properties.
Atomic force microscopy test asphalt film specimen preparation: An appropriate amount of asphalt mastic is dropped onto the slide and placed in the oven at 150 • C for 15 min so that it flows into a smooth plane, but the slide needs to be kept at a certain angle so that the asphalt can flow down naturally [23].
In this study, AFM scans of carbon fiber powder asphalt mastic and carbon fiber powder asphalt mastic immersed in water at 60 • C for 48 h were performed, and the microscopic experimental data were processed using Gwyddion software (Gwyddion-2.43.win64.) to investigate the effect of water-temperature coupling on the microscopic phase.
The molecular dynamics simulation test was modeled based on the results of the fourcomponent test, and dynamics simulation was carried out using the Dynamics sub-module of the Forcite module to obtain the total energy of each molecular model, and the interlayer force was calculated by combining with the interfacial bonding energy formula, which was used to form a comparison with the AFM test and validate the test.
Conductive asphalt concrete preparation was performed using <Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering> (JTG E20-2011) [24] using the asphalt mixture specimen production method (compacting method), and the concrete was ultimately made into a standard Marshall specimen.
The two-electrode method was used to perform electrical resistance tests on standard Marshall specimens at a room temperature of 25 • C (Figure 1), and the resistance measurement was performed with a Drexel 0801B multimeter.
The T700-12K-type glue-free 9 mm polyacrylonitrile-based carbon fiber and T700type polyacrylonitrile-based carbon fiber powder produced by Toray, Japan, are used, and the main performance indexes of both are shown in Table 4.

Test Methods
This study is based on the Atomic Force Microscope (AFM) (Bruker Dimension Icon, Munich, Germany.)analysis of carbon fiber powder asphalt mastic adhesion, with the help of molecular dynamics (MDs) simulation, from the point of view of the molecular interlayer action to verify the carbon-fiber-powder-asphalt-mastic-related mechanisms.The carbon fiber powder action mechanism, carbon fiber dispersion, and conductive asphalt concrete conductive properties are used to determine the optimal mixing amount of the conductive phase materials in order to prepare a conductive asphalt concrete with excellent electrical and thermal properties.
Atomic force microscopy test asphalt film specimen preparation: An appropriate amount of asphalt mastic is dropped onto the slide and placed in the oven at 150 °C for 15 min so that it flows into a smooth plane, but the slide needs to be kept at a certain angle so that the asphalt can flow down naturally [23].
In this study, AFM scans of carbon fiber powder asphalt mastic and carbon fiber powder asphalt mastic immersed in water at 60 °C for 48 h were performed, and the microscopic experimental data were processed using Gwyddion software (Gwyddion-2.43.win64.) to investigate the effect of water-temperature coupling on the microscopic phase.
The molecular dynamics simulation test was modeled based on the results of the four-component test, and dynamics simulation was carried out using the Dynamics submodule of the Forcite module to obtain the total energy of each molecular model, and the interlayer force was calculated by combining with the interfacial bonding energy formula, which was used to form a comparison with the AFM test and validate the test.
Conductive asphalt concrete preparation was performed using <Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering> (JTG E20-2011) [24] using the asphalt mixture specimen production method (compacting method), and the concrete was ultimately made into a standard Marshall specimen.
The two-electrode method was used to perform electrical resistance tests on standard Marshall specimens at a room temperature of 25 °C (Figure 1), and the resistance measurement was performed with a Drexel 0801B multimeter.The resistivity is calculated by the following formula: where R is the volume resistance of the test specimen, Ω; S is the effective area of the test specimen in contact with the electrode, m 2 ; and H is the height of the test specimen, m.

Molecular Modeling of Asphalt
In this study, Sinopec 70# asphalt was selected, and according to the results of the four-component analysis of crude oil [25], the four-component twelve-molecule model of asphalt was established [26], which more accurately reflects the real characteristics of asphalt molecules.According to the results of the four-component analysis, a programming solution method was used to calculate the number of four-component twelve molecules, and the solving results and test results are shown in Table 5.The Amorphous cell module of Materials Studio 2019 was used to establish the molecular model of asphalt, and the Geometry Optimization in the Forcite module was used to optimize the molecular model of asphalt.Because of the choice to use the NPT system (453.15K, 101.3 kPa), and the optimized density being 0.866 g/cm 3 , the model is reasonable.The Graphite cell model extracted from the Materials Studio structure library was utilized, and it was cut and then periodically enlarged to obtain the carbon fiber powder molecular model, which was optimized with a density of 1.68 g/cm 3 and a reasonable model.The water molecule model with a density of 0.98 g/cm 3 and a temperature of 333.15K was created and optimized using Construction in the Amorphous Cell module.The optimized carbon fiber powder molecular model, asphalt molecular model, and water molecular model were used to establish the asphalt-water, asphalt-carbon fiber powder, and asphalt-water-carbon fiber powder interface models through the Build Layers command in the Build menu (Figure 2), which were optimized, respectively.The microscopic test data were processed by Gwyddion software to investigate the

. Carbon Fiber Powder Asphalt Mastic Microscopic Test Analysis
The microscopic test data were processed by Gwyddion software to investigate the effect of water on the microscopic phase of carbon fiber powder asphalt mastic through the microscopic morphology and micromechanical properties [27].
From Figure 3, it can be seen that there is a large number of "Bee structures" distributed on the surface of the carbon fiber powder asphalt mastic and that the surface is uneven.The absolute height of the maximum peaks and maximum valleys is 36.6 nm.The "Bee structures" in the carbon fiber powder asphalt mastic disappeared after watertemperature coupling, while the surface bumps and depressions were more obvious.The number of peaks and valleys in the three-dimensional view is reduced significantly, and the absolute height of the maximum peaks and maximum valleys is 53.4 nm, which is an increase of 45.9% compared to the pre-water-temperature coupling.It is shown that the roughness of the carbon fiber powder asphalt mastic will be reduced under the effect of water-temperature coupling, which leads to a decrease in the adhesion of the carbon fiber powder asphalt mastic.

Carbon Fiber Powder Asphalt Mastic Microscopic Test Analysis
The microscopic test data were processed by Gwyddion software to investigate the effect of water on the microscopic phase of carbon fiber powder asphalt mastic through the microscopic morphology and micromechanical properties [27].
From Figure 3, it can be seen that there is a large number of "Bee structures" distributed on the surface of the carbon fiber powder asphalt mastic and that the surface is uneven.The absolute height of the maximum peaks and maximum valleys is 36.6 nm.The "Bee structures" in the carbon fiber powder asphalt mastic disappeared after water-temperature coupling, while the surface bumps and depressions were more obvious.The number of peaks and valleys in the three-dimensional view is reduced significantly, and the absolute height of the maximum peaks and maximum valleys is 53.4 nm, which is an increase of 45.9% compared to the pre-water-temperature coupling.It is shown that the roughness of the carbon fiber powder asphalt mastic will be reduced under the effect of water-temperature coupling, which leads to a decrease in the adhesion of the carbon fiber powder asphalt mastic.The microscopic morphology, adhesion, and DMT modulus of the carbon fiber powder asphalt mastic before and after water-temperature coupling action were analyzed by comparison (Figure 4).It can be found that the increase in the number of "concave structures" after water-temperature coupling could be due to the formation of capillary channels by water diffusion.The increase in the modulus of elasticity is due to the increase in stiffness caused by the aging of the asphalt under water-temperature coupling conditions.Combined with the disappearance of the "bee structures" under water-temperature coupling in Figure 3, it is proved that the "bee structures" are related to the asphaltene content The microscopic morphology, adhesion, and DMT modulus of the carbon fiber powder asphalt mastic before and after water-temperature coupling action were analyzed by comparison (Figure 4).It can be found that the increase in the number of "concave structures" after water-temperature coupling could be due to the formation of capillary Coatings 2024, 14, 512 7 of 18 channels by water diffusion.The increase in the modulus of elasticity is due to the increase in stiffness caused by the aging of the asphalt under water-temperature coupling conditions.Combined with the disappearance of the "bee structures" under water-temperature coupling in Figure 3, it is proved that the "bee structures" are related to the asphaltene content according to the change in the asphalt aging components [28].Under the condition of water-temperature coupling, strongly polar water molecules are adsorbed on the surface of asphaltenes and resins.Asphaltene acid and asphaltene anhydride providing polarity to the asphaltene and resins are oxidized and neutralized.The weakening of asphaltene and resins polarity leads to a decrease in adhesion.
The microscopic morphology, adhesion, and DMT modulus of the carbon fiber powder asphalt mastic before and after water-temperature coupling action were analyzed by comparison (Figure 4).It can be found that the increase in the number of "concave structures" after water-temperature coupling could be due to the formation of capillary channels by water diffusion.The increase in the modulus of elasticity is due to the increase in stiffness caused by the aging of the asphalt under water-temperature coupling conditions.Combined with the disappearance of the "bee structures" under water-temperature coupling in Figure 3, it is proved that the "bee structures" are related to the asphaltene content according to the change in the asphalt aging components [28].Under the condition of water-temperature coupling, strongly polar water molecules are adsorbed on the surface of asphaltenes and resins.Asphaltene acid and asphaltene anhydride providing polarity to the asphaltene and resins are oxidized and neutralized.The weakening of asphaltene and resins polarity leads to a decrease in adhesion.

Molecular Interlayer Interaction
Dynamics simulation was carried out using the Dynamics sub-module of the Forcite module, using the isothermal and isovolumetric systematic (NVT), setting the total time duration to 100 ps, the time step to 1 fs, and the simulation temperature to 333.15 K (60 °C).The whole simulation process uses the COMPASS II force field, Andersen method for temperature control, Berendsen method for pressure control, Ewald algorithm for electrostatic force calculation, and Atom-based method for the Van der Waals force.The calculation results of each model are shown in Table 6.

Molecular Interlayer Interaction
Dynamics simulation was carried out using the Dynamics sub-module of the Forcite module, using the isothermal and isovolumetric systematic (NVT), setting the total time duration to 100 ps, the time step to 1 fs, and the simulation temperature to 333.15 K (60 • C).The whole simulation process uses the COMPASS II force field, Andersen method for temperature control, Berendsen method for pressure control, Ewald algorithm for electrostatic force calculation, and Atom-based method for the Van der Waals force.The calculation results of each model are shown in Table 6.The stability of individual interfaces can be measured and compared by the interfacial binding energy (IBE) [29].Based on the date in Table 6, the interfacial binding energy of asphalt-carbon fiber powder and asphalt-water-carbon fiber powder (See Table 7) was calculated by Equation ( 2): where E bind is the interfacial binding energy, kcal/mol; E inter is the interaction energy of the molecular model, with negative values indicating gravitational forces and positive values indicating repulsive forces, kcal/mol; E total is the total free energy of the molecular model after complete relaxation, kcal/mol; E 1 is the free energy of model 1 after complete relaxation, kcal/mol; and E 2 is the free energy of model 2 after complete relaxation, kcal/mol.As can be seen from Table 7, the Asphalt-CFP molecular model interaction force is 162,636.943kcal/mol, the interfacial binding energy is −162,636.943kcal/mol, and the interlayer force shows repulsive force.The Asphalt-H 2 O-CFP molecular model interaction force is 360,361.861kcal/mol, the interfacial binding energy is −360,361.861kcal/mol.The interlayer repulsion of the Asphalt-H 2 O-CFP molecular model increased by 121.6% compared to the Asphalt-CFP molecular model.This indicates that the molecules' interlayer repulsion between the asphalt and carbon fiber powder is enhanced due to the action of water, leading to a decrease in the adhesion between the asphalt and the carbon fibers.

Mixing Process
The mixing process of carbon fiber-carbon fiber powder conductive asphalt concrete needs to be optimized because carbon fibers are prone to being agglomerated.In this study, two different processes were developed based on existing research [13] (Figure 5).The optimal mixing process was selected by testing the resistance and calculating the resistivity.
Four specimens were molded for each of the two processes.The specimens were compacted 75 times on each side, while the molding temperature was 155 • C. The mixing homogeneity of the two mixing processes is shown in Figure 6, and the resistivity of the specimens obtained by the two mixing processes is shown in Table 8.
From Figure 6, it was found that the carbon fibers in Process I were heavily agglomerated.The carbon fibers are more homogeneous in Process II, which is beneficial to the formation of a conductive network in carbon fiber-carbon fiber powder conductive asphalt concrete.
From Table 8, it can be seen that the overall resistivity and variability of the Marshall specimens molded by Process II were better than Process I.It was further demonstrated that Process II facilitates the homogeneity of carbon fiber dispersion.Process II will be adopted in a subsequent study.

sistivity.
Four specimens were molded for each of the two processes.The specimens were com pacted 75 times on each side, while the molding temperature was 155 °C.The mixing h mogeneity of the two mixing processes is shown in Figure 6, and the resistivity of th specimens obtained by the two mixing processes is shown in Table 8.From Figure 6, it was found that the carbon fibers in Process I were heavily agglomerated.The carbon fibers are more homogeneous in Process II, which is beneficial to the formation of a conductive network in carbon fiber-carbon fiber powder conductive asphalt concrete.
From Table 8, it can be seen that the overall resistivity and variability of the Marshall specimens molded by Process II were better than Process I.It was further demonstrated that Process II facilitates the homogeneity of carbon fiber dispersion.Process II will be adopted in a subsequent study.

Grading Selection
In this study, AC grading was used for asphalt concrete mix design.AC-13 grading and AC-16 grading (Table 9) were selected initially, combined with the requirements for the use of the upper surface layer of the pavement.The Marshall specimens of AC-13 grading and AC-16 grading were molded, while the carbon fiber content was 0.4%, the carbon fiber powder content was 2.0%, and the oilstone ratio was 5.0%.Resistivity is used as a measure of which grading is more suitable for conductive asphalt concrete and more beneficial for carbon fibers to build three-dimensional conductive networks.Specific data are shown in Table 10.It can be found that the resistivity of AC-16 is 44% lower than AC-13, which is more beneficial for carbon fibers to build three-dimensional conductive networks.Therefore, AC-16 grading was used in this study.

Optimal Content of Carbon Fiber
In this paper, the optimal content of the carbon fiber is determined based on the control variate method.And the range of the carbon fiber content was initially determined to be 0.3%~0.7%based on the results of the previous test.The test results are shown in Figure 7.
In this paper, the optimal content of the carbon fiber is determined based on th trol variate method.And the range of the carbon fiber content was initially determ be 0.3%~0.7%based on the results of the previous test.The test results are shown in 7. From Figure 7, it can be seen that the resistivity of conductive asphalt concr creases with the increase in the carbon fiber content, and the resistivity changes le the carbon fiber content when the content reaches 0.4%.The reason for this is t three-dimensional conductive network constructed by carbon fibers in conductive a concrete is basically completed at this time.The optimal content of carbon fiber was determined to be 0.4%, combined with the microscopic dispersion of 0.4% carbon asphalt concrete (Figure 8).From Figure 7, it can be seen that the resistivity of conductive asphalt concrete decreases with the increase in the carbon fiber content, and the resistivity changes less with the carbon fiber content when the content reaches 0.4%.The reason for this is that the three-dimensional conductive network constructed by carbon fibers in conductive asphalt concrete is basically completed at this time.The optimal content of carbon fiber was finally determined to be 0.4%, combined with the microscopic dispersion of 0.4% carbon fiber in asphalt concrete (Figure 8).

Optimal Content of Carbon Fiber Powder
Due to carbon fiber powder adversely affecting the adhesion of the asphalt ma especially in water-temperature coupling conditions, this will make its adhesion fu reduced and will affect the water stability of conductive asphalt concrete.Therefore water stability and electrical conductivity of conductive asphalt concrete need to be sidered together while determining the optimum content of carbon fiber powder.In study, the freeze-thaw splitting strength ratio, residual stability, and resistivity are as evaluation indexes to determine the optimal content of carbon fiber powder; the results are shown in Figure 9.

Optimal Content of Carbon Fiber Powder
Due to carbon fiber powder adversely affecting the adhesion of the asphalt mastic, especially in water-temperature coupling conditions, this will make its adhesion further reduced and will affect the water stability of conductive asphalt concrete.Therefore, the water stability and electrical conductivity of conductive asphalt concrete need to be considered together while determining the optimum content of carbon fiber powder.In this study, the freeze-thaw splitting strength ratio, residual stability, and resistivity are used as evaluation indexes to determine the optimal content of carbon fiber powder; the test results are shown in Figure 9.
especially in water-temperature coupling conditions, this will make its adhesion fu reduced and will affect the water stability of conductive asphalt concrete.Therefor water stability and electrical conductivity of conductive asphalt concrete need to b sidered together while determining the optimum content of carbon fiber powder.I study, the freeze-thaw splitting strength ratio, residual stability, and resistivity are as evaluation indexes to determine the optimal content of carbon fiber powder; th results are shown in Figure 9.In Figure 9, with the increase in the carbon fiber powder content, the residual sta and freeze-thaw splitting strength ratio decreases, and the resistivity decreases and increases.However, the freeze-thaw splitting strength ratio does not meet the re ments when the content of carbon fiber powder reaches 2.5% according to the Spe tions for the Design of High-Asphalt Pavement.And a large number of agglome phenomenon will occur when the carbon fiber powder is doped too much, which beneficial to the formation of a conductive pathway.
The basic properties of the asphalt mastic with 2.0% carbon fiber powder were to measure the effect of adding carbon fiber powder on asphalt mastic properties.Th results are shown in Table 11.In Figure 9, with the increase in the carbon fiber powder content, the residual stability and freeze-thaw splitting strength ratio decreases, and the resistivity decreases and then increases.However, the freeze-thaw splitting strength ratio does not meet the requirements when the content of carbon fiber powder reaches 2.5% according to the Specifications for the Design of High-Asphalt Pavement.And a large number of agglomeration phenomenon will occur when the carbon fiber powder is doped too much, which is not beneficial to the formation of a conductive pathway.
The basic properties of the asphalt mastic with 2.0% carbon fiber powder were tested to measure the effect of adding carbon fiber powder on asphalt mastic properties.The test results are shown in Table 11.From Table 11, the three major indexes of asphalt mastic with 2.0% carbon fiber powder are close to the matrix asphalt.It is shown that the addition of 2% carbon fiber powder has less effect on the properties of asphalt.

Optimal Oil-Stone Ratio
The optimal oil-stone ratio was determined by the performance test of conductive asphalt concrete specimens molded in accordance with the specifications.Based on the experience of previous tests, 4.0%, 4.5%, 5.0%, 5.5%, and 6.0% were selected as the test oil-stone ratios.And four specimens were molded for each group of tests.The Marshall stability, flow value, gross bulk density, and maximum relative density of each Marshall specimen were tested, respectively, and the theoretical maximum density, air voids (VVs), asphalt saturation (VFA), and voids in the mineral aggregate (VMA) of each specimen were calculated.The test results are shown in Table 12.It was found that there is a slight variation in resistivity when the oil-stone ratio is in the range of 4.5%-6.0%.Therefore, the optimal oil-stone ratio should be determined by combining with the Marshall mix design.The relationship between the gross bulk density, air voids (VVs), asphalt saturation (VFA), voids in mineral aggregate (VMA), Marshall stability, flow value, and oil-stone ratio is shown in Figure 10.
From Figure 10, it can be seen that oil-stone ratios of 4.6%, 4.5%, 4.8%, and 5.1%, respectively, correspond to the maximum gross bulk density, the maximum Marshall stability, the median air voids (VVs), and the median asphalt saturation (VFA), then OAC1 = (4.6%+ 4.5% + 4.8% + 5.1%)/4 = 4.75% (3) The range of the oil-stone ratio that satisfies all the performance indicators at the same time is 4.6%-5.5%,then OAC2 = (4.6%+ 5.5%)/2 = 5.05% Thus, the calculation shows that OAC3 = (OAC1 + OAC2)/2 = (4.75%+ 5.05%)/2 = 4.9% The optimal oil-stone ratio was determined to be 4.9% based on the Marshall specimen performance test.The basic performance parameters of the carbon fiber-carbon fiber powder conductive asphalt concrete molded with an oil-stone ratio of 4.9% are shown in Table 13.The resistivity of carbon fiber-carbon fiber powder conductive asphalt concrete with a 4.9% oil-stone ratio is 0.98 Ω•m.The electrical conductivity was better than that of the previous tests, and the 4.9% oil-stone ratio was used in all the subsequent tests.

Content (%)
(KN) ( ∕  ) 4.9 0.4 2.0 7.7 0.98 12.10 3.95 2.400 The resistivity of carbon fiber-carbon fiber powder conductive asphalt concrete with a 4.9% oil-stone ratio is 0.98 Ω • m.The electrical conductivity was better than that of the previous tests, and the 4.9% oil-stone ratio was used in all the subsequent tests.To assure that the internal and external temperatures of the Marshall specimens were consistent, the Marshall specimens were placed in a refrigerator at a temperature of 0 • C for 16 h.Copper electrodes were attached to the upper and lower ends of the specimen while connecting the transformer.The 36v DC voltage was selected to ensure the safety of the energization.The test is shown in Figure 11.The UNI-TREND Uti120S infrared thermal imager was used to test the temperature of the specimens.And the temperature was tested and recorded in one-minute intervals after the power was switched on.The whole process was carried out in a refrigerator at a temperature of 0 • C to simulate the real situation.The temperature variation with time is shown in Figure 12.

Temperature Rise Test of Marshall Specimens
To assure that the internal and external temperatures of the Marshall specimens were consistent, the Marshall specimens were placed in a refrigerator at a temperature of 0 °C for 16 h.Copper electrodes were attached to the upper and lower ends of the specimen while connecting the transformer.The 36v DC voltage was selected to ensure the safety of the energization.The test is shown in Figure 11.The UNI-TREND Uti120S infrared thermal imager was used to test the temperature of the specimens.And the temperature was tested and recorded in one-minute intervals after the power was switched on.The whole process was carried out in a refrigerator at a temperature of 0 °C to simulate the real situation.The temperature variation with time is shown in Figure 12.The temperature of the Marshall specimens shows a nonlinear increase with the time of the energization.The reason for this is that when the temperature difference between the Marshall specimen and the test environment becomes larger, the rate of heat loss becomes faster, resulting in a slower rise in the specimen's temperature per unit of time.The voltage was kept constant throughout the test, and the current did not vary, reflecting the stabilization of the energy transformation in conductive asphalt concrete Marshall specimens.The heat transformation rate was calculated according to the relevant parameters of the existing relevant research results [11,30,31].As shown in Table 14, the conductive asphalt concrete Marshall specimens have a high heat transformation rate of 83.09%.consistent, the Marshall specimens were placed in a refrigerator at a temperature of for 16 h.Copper electrodes were attached to the upper and lower ends of the spec while connecting the transformer.The 36v DC voltage was selected to ensure the safe the energization.The test is shown in Figure 11.The UNI-TREND Uti120S infrared mal imager was used to test the temperature of the specimens.And the temperature tested and recorded in one-minute intervals after the power was switched on.The w process was carried out in a refrigerator at a temperature of 0 °C to simulate the real ation.The temperature variation with time is shown in Figure 12.The temperature of the Marshall specimens shows a nonlinear increase with the of the energization.The reason for this is that when the temperature difference bet the Marshall specimen and the test environment becomes larger, the rate of heat los comes faster, resulting in a slower rise in the specimen's temperature per unit of time voltage was kept constant throughout the test, and the current did not vary, reflectin stabilization of the energy transformation in conductive asphalt concrete Marshall s mens.The heat transformation rate was calculated according to the relevant param of the existing relevant research results [11,30,31].As shown in Table 14, the condu asphalt concrete Marshall specimens have a high heat transformation rate of 83.09%The temperature of the Marshall specimens shows a nonlinear increase with the time of the energization.The reason for this is that when the temperature difference between the Marshall specimen and the test environment becomes larger, the rate of heat loss becomes faster, resulting in a slower rise in the specimen's temperature per unit of time.The voltage was kept constant throughout the test, and the current did not vary, reflecting the stabilization of the energy transformation in conductive asphalt concrete Marshall specimens.The heat transformation rate was calculated according to the relevant parameters of the existing relevant research results [11,30,31].As shown in Table 14, the conductive asphalt concrete Marshall specimens have a high heat transformation rate of 83.09%.Firstly, a 300 mm × 300 mm × 50 mm carbon fiber-carbon fiber powder conductive asphalt concrete rutting slab was prepared.Then, the surface of the rutting slab was divided into five points, A, B, C, D, and E, and copper electrodes were attached on both sides of the rutting slab (as shown in Figure 13).To assure that the internal and external temperatures of the rutting slabs were consistent, the rutting slabs were placed in a refrigerator at a temperature of 0 • C for 16 h.The temperatures of the five points were tested at 10 min intervals after being connected to a 36V DC voltage.The temperature variation with time is shown in Figure 14.Firstly, a 300 mm × 300 mm × 50 mm carbon fiber-carbon fiber powder asphalt concrete rutting slab was prepared.Then, the surface of the rutting s vided into five points, A, B, C, D, and E, and copper electrodes were attached o of the rutting slab (as shown in Figure 13).To assure that the internal and ex peratures of the rutting slabs were consistent, the rutting slabs were placed in tor at a temperature of 0 °C for 16 h.The temperatures of the five points were min intervals after being connected to a 36V DC voltage.The temperature va time is shown in Figure 14.As can be seen from Figure 14, the surface temperature of the rutting slab after 30 min of heating, and the whole warming process shows a nonlinear va reason for this is that when the temperature difference between the rutting large surface area and the test environment becomes larger, the rate of heat lo faster.The heat transformation rate of the rutting slab was calculated and i Table 15.Firstly, a 300 mm × 300 mm × 50 mm carbon fiber-carbon fiber powder asphalt concrete rutting slab was prepared.Then, the surface of the rutting sl vided into five points, A, B, C, D, and E, and copper electrodes were attached on of the rutting slab (as shown in Figure 13).To assure that the internal and ex peratures of the rutting slabs were consistent, the rutting slabs were placed in tor at a temperature of 0 °C for 16 h.The temperatures of the five points were t min intervals after being connected to a 36V DC voltage.The temperature var time is shown in Figure 14.As can be seen from Figure 14, the surface temperature of the rutting slab r after 30 min of heating, and the whole warming process shows a nonlinear var reason for this is that when the temperature difference between the rutting s large surface area and the test environment becomes larger, the rate of heat los faster.The heat transformation rate of the rutting slab was calculated and is Table 15.As can be seen from Figure 14, the surface temperature of the rutting slab rises slowly after 30 min of heating, and the whole warming process shows a nonlinear variation.The reason for this is that when the temperature difference between the rutting slab with a large surface area and the test environment becomes larger, the rate of heat loss becomes faster.The heat transformation rate of the rutting slab was calculated and is shown in Table 15.

Figure 3 .
Figure 3. Morphology of carbon fiber powder asphalt mastic before and after water-temperature coupling: (a) plan of carbon fiber powder asphalt mastic; (b) three-dimensional view of carbon fiber powder asphalt mastic; (c) plan of water-temperature coupled carbon fiber powder asphalt mastic; (d) three-dimensional view of water-temperature coupled carbon fiber powder asphalt mastic.

Figure 3 .
Figure 3. Morphology of carbon fiber powder asphalt mastic before and after water-temperature coupling: (a) plan of carbon fiber powder asphalt mastic; (b) three-dimensional view of carbon fiber powder asphalt mastic; (c) plan of water-temperature coupled carbon fiber powder asphalt mastic; (d) three-dimensional view of water-temperature coupled carbon fiber powder asphalt mastic.

Figure 4 .
Figure 4. Micromechanics of carbon fiber powder asphalt mastic before and after water-temperature coupling: (a) adhesion of carbon fiber powder asphalt mastic; (b) adhesion of water-temperature coupled carbon fiber powder asphalt mastic; (c) DMT modulus of carbon fiber powder asphalt mastic; (d) DMT modulus of water-temperature coupled carbon fiber powder asphalt mastic.

Figure 4 .
Figure 4. Micromechanics of carbon fiber powder asphalt mastic before and after water-temperature coupling: (a) adhesion of carbon fiber powder asphalt mastic; (b) adhesion of water-temperature coupled carbon fiber powder asphalt mastic; (c) DMT modulus of carbon fiber powder asphalt mastic; (d) DMT modulus of water-temperature coupled carbon fiber powder asphalt mastic.

Figure 5 .
Figure 5. Two mixing processes for carbon fiber-carbon fiber powder conductive asphalt concret (a) Process I; (b) Process II.

Figure 6 .
Figure 6.The mixing homogeneity of the two mixing processes: (a) Process I; (b) Process II.

Figure 7 .
Figure 7. Relation between resistivity and carbon fiber content.

Figure 7 .
Figure 7. Relation between resistivity and carbon fiber content.

Figure 9 .
Figure 9. Relationship curve between carbon fiber powder content and evaluation indexes.

Figure 9 .
Figure 9. Relationship curve between carbon fiber powder content and evaluation indexes.

Figure 10 .Figure 10 .
Figure 10.(a) Relationship between gross bulk density and oil-stone ratio; (b) relationship between air voids (VVs) and oil-stone ratio; (c) relationship between voids in mineral aggregate (VMA) and oil-stone ratio; (d) relationship between asphalt saturation (VFA) and oil-stone ratio; (e) relationshipFigure 10.(a) Relationship between gross bulk density and oil-stone ratio; (b) relationship between air voids (VVs) and oil-stone ratio; (c) relationship between voids in mineral aggregate (VMA) and oil-stone ratio; (d) relationship between asphalt saturation (VFA) and oil-stone ratio; (e) relationship between Marshall stability and oil-stone ratio; (f) relationship between flow value and oil-stone ratio.

Figure 12 .
Figure 12.Temperature variation in Marshall specimens with time.

Figure 12 .
Figure 12.Temperature variation in Marshall specimens with time.

Figure 12 .
Figure 12.Temperature variation in Marshall specimens with time.

Figure 14 .
Figure 14.Temperature variation in rutting slab with time.

Figure 14 .
Figure 14.Temperature variation in rutting slab with time.

Figure 14 .
Figure 14.Temperature variation in rutting slab with time.

Table 1 .
Basic properties of asphalt.

Table 4 .
Basic parameters of carbon fiber and carbon fiber powder.

Table 4 .
Basic parameters of carbon fiber and carbon fiber powder.

Table 5 .
Calculation and test results of the planning solution method.

Table 6 .
Total energy of dynamic relaxation for molecular modeling.

Table 6 .
Total energy of dynamic relaxation for molecular modeling.

Table 7 .
Asphalt-carbon fiber powder and asphalt-water-carbon fiber powder interfacial binding energy.

Table 8 .
The resistivity of specimens obtained by the two mixing processes.

Table 11 .
Properties of asphalt mastic with 2% carbon fiber powder.

Table 12 .
Basic properties for carbon fiber-carbon fiber powder conductive asphalt concrete with different oil-stone ratio.

Table 13 .
Basic performance parameters of carbon fiber-carbon fiber powder conductive asphalt concrete with 4.9% oil-stone ratio.

Table 14 .
The heat transformation rate of Marshall specimens.

Table 15 .
The heat transformation rate of rutting slab.