阅读说明：本技术 基于温度-频率等效模型的沥青混合料质量评价方法 (Asphalt mixture quality evaluation method based on temperature-frequency equivalent model ) 是由 罗蓉 于晓贺 王锦腾 于 2020-11-17 设计创作，主要内容包括：本发明公开了一种基于温度-频率等效模型的沥青混合料质量评价方法,其步骤包括：备样,介电常数测定,建立介电理论模型,建立温度-频率转换模型,验证温度-频率转换模型以及质量评价；建立温度-频率转换模型步骤具体包括：基于介电理论模型建立关于温度、频率之间的量化关系,得到温度-频率转换模型；质量评价步骤具体包括：根据介电理论模型和温度-频率转换模型,计算电导活化能值,用于评价沥青混合料的质量。本发明通过构建温度-频率等效转换模型,实现了无损检测设备在不同温度、频率条件下检测结果的统一,为无损检测设备的应用推广奠定了基础,并提高了对沥青混合料质量评价的准确度。(The invention discloses an asphalt mixture quality evaluation method based on a temperature-frequency equivalent model, which comprises the following steps: preparing a sample, measuring a dielectric constant, establishing a dielectric theoretical model, establishing a temperature-frequency conversion model, verifying the temperature-frequency conversion model and evaluating the quality; the step of establishing the temperature-frequency conversion model specifically comprises the following steps: establishing a quantitative relation between temperature and frequency based on a dielectric theoretical model to obtain a temperature-frequency conversion model; the quality evaluation step specifically comprises: and calculating the conductivity activation energy value according to the dielectric theory model and the temperature-frequency conversion model, and evaluating the quality of the asphalt mixture. According to the invention, by constructing the temperature-frequency equivalent conversion model, the unification of detection results of the nondestructive testing equipment under different temperature and frequency conditions is realized, a foundation is laid for the application and popularization of the nondestructive testing equipment, and the accuracy of the quality evaluation of the asphalt mixture is improved.)

1. A method for evaluating the quality of an asphalt mixture based on a temperature-frequency equivalent model is characterized by comprising the following steps of: preparing a sample, measuring a dielectric constant, establishing a dielectric theoretical model, establishing a temperature-frequency conversion model, verifying the temperature-frequency conversion model and evaluating the quality;

the step of establishing the temperature-frequency conversion model specifically comprises the following steps: establishing a quantitative relation between temperature and frequency based on a dielectric theoretical model to obtain a temperature-frequency conversion model;

the quality evaluation step specifically comprises: and calculating the conductivity activation energy value according to the dielectric theoretical model and the temperature-frequency conversion model, and evaluating the quality of the asphalt mixture.

2. The asphalt mixture quality evaluation method based on the temperature-frequency equivalent model according to claim 1, wherein the step of establishing the dielectric theory model specifically comprises the steps of: quantifying temperature and frequency influence factors, and establishing a dielectric theoretical model;

the dielectric theoretical model has the expression:

in the formula, epsilon is the dielectric constant of the asphalt mixture₀For the vacuum dielectric constant, d is the thickness of the test sample, tan delta is the loss tangent, E_iIs the conductivity activation energy of a certain component in the asphalt mixture, A_iThe' is the product of a certain conductivity proportionality coefficient and a conductivity constant in the asphalt mixture, n is the total number of single components in the asphalt mixture, f is the testing frequency, r is the radius of a testing sample, K is a Boltzmann constant, and T is the temperature difference in Kelvin; a. the_i'＝γ_i·A_iAnd γ_iIs the conductivity proportionality coefficient of a certain component in the mixture.

3. The asphalt mixture quality evaluation method based on the temperature-frequency equivalent model according to claim 2, wherein the step of establishing the temperature-frequency conversion model specifically comprises the following steps:

based on the dielectric theoretical model, the temperature is set as a constant value, the frequency is set as a variable value, and a first change value delta epsilon related to the dielectric constant is obtained₁；

Based on the dielectric theoretical model, the frequency is a fixed value, the temperature is a variable value, and a second change value delta epsilon related to the dielectric constant is obtained₂；

Matching the first change value Δ ε₁And a second change value delta epsilon₂Satisfy Δ ε₁＝Δε₂Obtaining a temperature-frequency conversion model related to the dielectric constant of the asphalt mixture;

the expression of the temperature-frequency conversion model is as follows:

in the formula, E is the conductive activation energy, K is the Boltzmann constant, and T is₀Is the Kelvin temperature at the initial moment, T₁Is the Kelvin temperature at a certain moment, f₀Frequency of detection for initial time, f₁Is the detection frequency at a certain moment.

4. The asphalt mixture quality evaluation method based on the temperature-frequency equivalent model according to claim 3, characterized in that the expression of the first variation value is as follows:

in the formula, f₀Frequency of the initial moment, f₁Frequency at a certain time, tan delta₀Tan delta as initial loss tangent₁Is the loss tangent, epsilon, of a certain moment₀Is the vacuum dielectric constant, d is the thickness of the test sample, E is the asphaltThe conductivity activation energy of the mixture, A is the conductivity proportionality coefficient of the asphalt mixture, r is the radius of a test sample, K is the Boltzmann constant, and T is the conductivity proportionality coefficient of the asphalt mixture₀Is the kelvin temperature difference.

5. The asphalt mixture quality evaluation method based on the temperature-frequency equivalent model according to claim 3, characterized in that the expression of the second variation value is as follows:

in the formula, T₀Is the Kelvin temperature at the initial moment, T₁Is the Kelvin temperature at a certain moment, tan delta₀Tan delta as initial loss tangent₁Is the loss tangent, epsilon, of a certain moment₀Is the vacuum dielectric constant, d is the thickness of the tested sample, E is the conductivity activation energy of the asphalt mixture, A is the conductivity proportionality coefficient of the asphalt mixture, r is the radius of the tested sample, K is the Boltzmann constant, f₀Is the frequency of the initial time instant.

6. The asphalt mixture quality evaluation method based on the temperature-frequency equivalent model according to claim 1, characterized in that the sample preparation step specifically comprises: selecting asphalt and aggregate to mix to prepare a mixture, compacting, cutting and processing the mixture to prepare samples, wherein each group of the mixture comprises at least 5 parallel samples;

in the sample preparation step, the asphalt is selected from any one of 70# base asphalt and SBS modified asphalt, and the aggregate is selected from limestone;

the sample is a thin sheet with a central opening.

7. The asphalt mixture quality evaluation method based on the temperature-frequency equivalent model according to claim 1, wherein the dielectric constant determination step specifically comprises: the dielectric constant and the loss tangent of the sample were measured at different temperatures and frequencies.

8. The asphalt mixture quality evaluation method based on the temperature-frequency equivalent model according to claim 7, wherein the test platform in the dielectric constant determination step is a dielectric constant test platform, and the parameters of the dielectric constant test are as follows: the heating rate is 0.4K/min, the actual temperature deviation is +/-273.45K, the temperature range is 30-60 ℃, the set value of the test voltage is 2V, and the test frequency range is 1-500 KHz.

9. The asphalt mixture quality evaluation method based on the temperature-frequency equivalent model according to claim 1, wherein the step of verifying the temperature-frequency conversion model specifically comprises:

drawing an actually measured curve about the temperature-dielectric constant based on the dielectric constant and the loss tangent value under different temperature and frequency conditions actually measured in the dielectric constant measuring step;

drawing a model curve of the transformation with respect to the temperature-dielectric constant based on the temperature-frequency equivalent transformation model;

and when the fitting degree of the model curve and the actually measured curve is larger than a preset value, judging that the temperature-frequency equivalent conversion method is effective.

Technical Field

The invention relates to the field of road engineering, in particular to an asphalt mixture quality evaluation method based on a temperature-frequency equivalent model.

Background

When nondestructive detection equipment such as a ground penetrating radar is adopted to carry out nondestructive detection on the asphalt pavement, quality evaluation is carried out based on the difference of dielectric constant values of asphalt pavement materials at different positions of a certain road section. The dielectric constant value of the asphalt pavement material is usually related to engineering indexes such as density, compactness and the like, and the pavement diseases can be diagnosed according to the difference of the dielectric constant values at different positions. Therefore, it is important to realize accurate measurement of the dielectric constant of the asphalt pavement material for the quality evaluation of asphalt pavement.

At present, the research on the dielectric property of the asphalt mixture mainly focuses on a composite material dielectric model and the application thereof, and the influence of external factors on the dielectric property of the asphalt mixture is not fully considered. In the actual detection process, the main factors disturbing the detection precision of the nondestructive detection equipment are the detection frequency and the temperature. Different nondestructive testing equipment needs to adopt different testing frequencies due to different requirements on testing depth in the testing process, and the dielectric properties of the asphalt mixture under different frequencies are different, so that the testing results of a plurality of nondestructive testing equipment lack uniformity and cannot form effective reference. In addition, the temperature of the asphalt pavement is not a constant value due to dynamic change, and the dielectric properties of the asphalt mixture are greatly different at different temperatures, so that the detection results cannot be unified. In summary, how to determine the influence of frequency and temperature factors on the dielectric properties of the asphalt mixture so that nondestructive testing data under different frequency and temperature conditions can be unified is a key for improving the detection precision of nondestructive testing equipment and the result uniformity of the nondestructive testing equipment.

Therefore, a new evaluation scheme for the quality of the asphalt mixture needs to be provided to solve the above problems in the prior art.

Disclosure of Invention

The invention aims to provide an asphalt mixture quality evaluation method based on a temperature-frequency equivalent model, which is used for solving the problem that detection results of nondestructive detection equipment under different frequencies and different temperatures are difficult to unify in the prior art.

In order to solve the technical problems, the invention provides an asphalt mixture quality evaluation method based on a temperature-frequency equivalent model, which comprises the following steps: preparing a sample, measuring a dielectric constant, establishing a dielectric theoretical model, establishing a temperature-frequency conversion model, verifying the temperature-frequency conversion model and evaluating the quality; the step of establishing the temperature-frequency conversion model specifically comprises the following steps: establishing a quantitative relation between temperature and frequency based on a dielectric theory model to obtain a temperature-frequency conversion model; the quality evaluation step specifically comprises: and calculating the conductivity activation energy value according to the dielectric theory model and the temperature-frequency conversion model, and evaluating the quality of the asphalt mixture.

The dielectric theoretical model establishing method specifically comprises the following steps: quantifying temperature and frequency influence factors, and establishing a dielectric theoretical model; the expression of the dielectric theoretical model is:

in the formula, epsilon is the dielectric constant of the asphalt mixture₀For the vacuum dielectric constant, d is the test sample thickness, tan delta is the loss tangent, E_iIs the conductivity activation energy of a certain component in the asphalt mixture, A_iThe' is the product of a certain conductivity proportionality coefficient and a conductivity constant in the asphalt mixture, n is the total number of single components in the asphalt mixture, f is the testing frequency, r is the radius of a testing sample, K is a Boltzmann constant, and T is the temperature difference in Kelvin; a. the_i'＝γ_i·A_iAnd γ_iElectricity for a component of the mixA conductivity proportionality coefficient.

The step of establishing the temperature-frequency conversion model specifically comprises the following steps: based on the dielectric theoretical model, the temperature is set as a constant value, the frequency is set as a variable value, and a first change value delta epsilon related to the dielectric constant is obtained₁(ii) a Based on the dielectric theoretical model, the frequency is a fixed value, the temperature is a variable, and a second change value delta epsilon related to the dielectric constant is obtained₂(ii) a Matching the first change value delta epsilon₁And a second change value delta epsilon₂Satisfy Δ ε₁＝Δε₂Obtaining a temperature-frequency conversion model related to the dielectric constant of the asphalt mixture; the expression of the temperature-frequency conversion model is:

in the formula, E is the conductive activation energy, K is the Boltzmann constant, and T is₀Is the Kelvin temperature at the initial moment, T₁Is the Kelvin temperature at a certain moment, f₀Frequency of detection for initial time, f₁Is the detection frequency at a certain moment.

Wherein the expression of the first variation value is:

in the formula, f₀Frequency of the initial moment, f₁Frequency at a certain time, tan delta₀Tan delta as initial loss tangent₁Is the loss tangent, epsilon, of a certain moment₀Is the vacuum dielectric constant, d is the thickness of the tested sample, E is the conductivity activation energy of the asphalt mixture, A is the conductivity proportionality coefficient of the asphalt mixture, r is the radius of the tested sample, K is the Boltzmann constant, T₀Is the kelvin temperature difference.

Wherein the expression of the second variation value is:

in the formula, T₀Is the Kelvin temperature at the initial moment, T₁Is the Kelvin temperature at a certain moment, tan delta₀Tan delta as initial loss tangent₁Is the loss tangent, epsilon, of a certain moment₀Is the vacuum dielectric constant, d is the thickness of the tested sample, E is the conductivity activation energy of the asphalt mixture, A is the conductivity proportionality coefficient of the asphalt mixture, r is the radius of the tested sample, K is the Boltzmann constant, f₀Is the frequency of the initial time instant.

Wherein, the sample preparation step specifically comprises: selecting asphalt and aggregate to mix to prepare a mixture, compacting, cutting and processing the mixture to prepare samples, wherein each group of the mixture comprises at least 5 parallel samples; in the sample preparation step, the asphalt is selected from any one of 70# base asphalt and SBS modified asphalt, and the aggregate is selected from limestone; the test specimens were thin sheets with a central opening.

The dielectric constant measuring method specifically comprises the following steps: the dielectric constant and the loss tangent of the sample were measured at different temperatures and frequencies.

Wherein, the test platform in the dielectric constant determination step is a dielectric constant test platform, and the parameters of the dielectric constant test are as follows: the heating rate is 0.4K/min, the actual temperature deviation is +/-273.45K, the temperature range is 30-60 ℃, the set value of the test voltage is 2V, and the test frequency range is 1-500 KHz.

The step of verifying the temperature-frequency conversion model specifically comprises the following steps: drawing an actual measurement curve about the temperature-dielectric constant based on the dielectric constant and the loss tangent value under different temperature and frequency conditions actually measured in the dielectric constant measurement step; drawing a model curve of the conversion with respect to the temperature-dielectric constant based on the temperature-frequency equivalent conversion model; and when the fitting degree of the comparison model curve and the actual measurement curve is greater than a preset value, judging that the temperature-frequency equivalent conversion method is effective.

The invention has the beneficial effects that: the invention provides an asphalt mixture quality evaluation method based on a temperature-frequency equivalent model, which is different from the prior art, realizes the unification of detection results of nondestructive detection equipment under different temperature and frequency conditions by constructing a temperature-frequency equivalent conversion model, lays a foundation for the application and popularization of the nondestructive detection equipment, and improves the accuracy of asphalt mixture quality evaluation.

Drawings

FIG. 1 is a flow chart of an embodiment of the method for evaluating the quality of an asphalt mixture based on a temperature-frequency equivalent model according to the present invention;

FIG. 2 is a flow chart of the sample preparation step in example 1 of the present invention: a is a rotary compaction test piece, b is a standard test piece, c is a thin slice, d is a test piece, e is the test piece diameter measurement, and f is the test piece thickness measurement;

FIG. 3 is a graph comparing the degree of matching of the dielectric constants of two asphalt mixtures according to example 1 of the present invention: a is a comparison graph of the fitting degree of the 70# matrix asphalt and the limestone sample relative to the dielectric constant, and b is a comparison graph of the fitting degree of the SBS modified asphalt and the limestone sample relative to the dielectric constant.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Referring to fig. 1, fig. 1 is a flow chart illustrating an embodiment of a method for evaluating quality of asphalt mixture based on a temperature-frequency equivalent model according to the present invention. The invention relates to an asphalt mixture quality evaluation method based on a temperature-frequency equivalent model, which comprises the following steps:

and S1, preparing samples. In the step, asphalt and aggregate are selected and mixed to prepare a mixture, the mixture is compacted, cut and processed to prepare samples, and each group of the mixture comprises at least 5 parallel samples; in the embodiment, the asphalt is selected from any one of 70# base asphalt and SBS modified asphalt, the aggregate is selected from limestone, and the sample is a thin slice with a middle opening hole; in other embodiments, the material and the preparation of the sample may be adaptively selected according to actual requirements, and are not limited herein.

S2, measuring the dielectric constant. In this step, specifically, the dielectric constant and the loss tangent of the sample at different temperatures and frequencies are measured, and the conductivity activation energy is calculated. In this embodiment, the test platform in the dielectric constant measuring step is a dielectric constant test platform, and the parameters of the dielectric constant test are as follows: the heating rate is 0.4K/min, the actual temperature deviation is +/-273.45K, the temperature range is 30-60 ℃, the set value of the test voltage is 2V, the test frequency range is 1-500 KHz, and the specific test frequencies are 1KHz, 10KHz, 50KHz, 100KHz and 500 KHz.

And S3, establishing a dielectric theoretical model. In this step, specifically, the kelvin temperature is used for calculation, so the test temperature T is converted into the kelvin temperature T, and the conversion relation is shown as formula (1):

T＝t+273.15 (1)

when the temperature of the asphalt mixture is gradually increased, the polarization capability is gradually enhanced, namely, the state of weak electrolyte is presented, and the Arrhenius relation shown in the formula (2) can be adopted to construct the relation between the sample conductivity and the temperature:

wherein A is the conductance constant of the material in ohm^-1cm^-1(ii) a E is the electrical conductivity activation energy of the material, and the unit kcal/mol; k is Boltzmann constant and has a value of 1.3806505 (24). times.10^-23J/K; t is the temperature difference in Kelvin, in K.

Since the asphalt mixture is a three-phase mixture composed of aggregate, asphalt and air, a composite conductivity formula of the asphalt mixture can be constructed, as shown in formula (3):

wherein: sigma_aIs the conductivity of air, μ S/cm; sigma_asIs the conductivity of the asphalt, mu S/cm; sigma_aThe conductivity of the aggregate is [ mu ] S/cm; gamma ray_aIs the proportionality coefficient of aggregate conductivity; gamma ray_asIs the proportional coefficient of the conductivity of the asphalt; gamma ray_sIs the proportionality coefficient of aggregate conductivity; a. the_aIs the conductivity constant of the aggregate component; a. the_asIs the conductivity constant of the bitumen component; a. the_sIs the conductivity constant of the aggregate component; e_aThe conductivity activation energy of the aggregate; e_asIs the conductive activation energy of the asphalt; e_sIs the conductivity activation energy of the aggregate.

Since the conductivity of air is 0, equation (4) can be simplified as:

to simplify the formula and reduce the parameter variables, the conductivity proportionality coefficients and the conductivity constants of the components can be combined, i.e. processed as formula (5) and formula (6).

γ_asA_as＝A′_as (5)

γ_sA_s＝A′_s (6)

Wherein: a'_asIs the product of the conductivity proportionality coefficient and the conductivity constant of the asphalt; a'_sIs the product of the aggregate conductivity proportionality coefficient and the conductivity constant.

Through the simplified processing of the formula (5) and the formula (6), the following asphalt mixture composite conductivity formula (7) can be obtained:

if it is necessary to add other materials besides aggregate, asphalt and air to the asphalt mixture, the conductivity composite relationship can be further expanded as shown in formula (8):

wherein: a'_iIs the product of the conductivity proportionality coefficient and the conductivity constant of a certain material; e_iIs the conductive activation energy of a certain material; and n is the number of all materials in the asphalt mixture.

The relationship of the dielectric constant of the asphalt mixture with respect to the temperature can be simplified as shown in formula (9):

in the formula (9), ε represents the dielectric constant of the asphalt mixture₀For the vacuum dielectric constant, d is the test sample thickness, tan delta is the loss tangent, E_iThe conductivity activation energy of a certain component in the asphalt mixture is shown, n is the total number of single components in the asphalt mixture, f is the testing frequency, r is the radius of a testing sample, K is a Boltzmann constant, and T is the Kelvin temperature; wherein A is_i' is the product of a certain conductivity proportionality coefficient and a conductivity constant in the asphalt mixture, A_i'＝γ_i·A_i，γ_iIs the conductivity proportionality coefficient of a certain component in the mixture. .

S4, establishing a temperature-frequency conversion model

1) Based on the dielectric theoretical model, the temperature is set to be a constant value, and the frequency is set to be a variable value, so that a first change value related to the dielectric constant is obtained. In this step, the temperature T is calculated based on the dielectric theory model expression in the step S3₀At an initial temperature, at a frequency f₀At an initial frequency, a first change value delta epsilon of the dielectric constant of the asphalt mixture under the change of a single frequency factor₁Expressed as formula (10):

in the formula, f₀Frequency of the initial moment, f₁Frequency at a certain time, tan delta₀Tan delta as initial loss tangent₁Is the loss tangent value at a certain time,ε₀is the vacuum dielectric constant, d is the thickness of the tested sample, E is the conductivity activation energy of the asphalt mixture, A is the conductivity proportionality coefficient of the asphalt mixture, r is the radius of the tested sample, K is the Boltzmann constant, T₀Is the kelvin temperature difference.

2) And on the basis of the dielectric theoretical model, the frequency is a fixed value, and the temperature is a variable, so that a second change value related to the dielectric constant is obtained. In this step, the temperature T is calculated based on the dielectric theory model expression in the step S3₀At an initial temperature, at a frequency f₀At an initial frequency, a second value of change of the dielectric constant of the asphalt mixture at a single factor of temperature, Δ ε₂Expressed by formula (11):

in the formula, T₀Is the Kelvin temperature at the initial moment, T₁Is the Kelvin temperature at a certain moment, tan delta₀Tan delta as initial loss tangent₁Is the loss tangent, epsilon, of a certain moment₀Is the vacuum dielectric constant, d is the thickness of the tested sample, E is the conductivity activation energy of the asphalt mixture, A is the conductivity proportionality coefficient of the asphalt mixture, r is the radius of the tested sample, K is the Boltzmann constant, f₀Is the frequency of the initial time instant.

3) And matching the first change value and the second change value to obtain a temperature-frequency conversion model related to the dielectric constant of the asphalt mixture. In this step, the first variation value Δ ε is matched₁And a second change value delta epsilon₂That is, the equation (10) and the equation (11) are combined to establish the equivalent relationship of temperature and frequency, and there is:

simplified to obtain formula (13):

the formula (13) is an expression of a temperature-frequency conversion model about the dielectric constant of the asphalt mixture, and it can be known from the formula (13) that if the conductivity activation energy E of the asphalt mixture is known, the equivalent relationship between the temperature and the frequency can be obtained, thereby providing clear theoretical support for the unification of the detection results of the nondestructive detection equipment under different temperature and frequency conditions. In the above formula, f is present₁≠f₀，T₁≠T₀The preconditions of (a).

And S5, verifying the temperature-frequency conversion model. In this step, based on the dielectric constant and the loss tangent value under different temperature and frequency conditions actually measured in step S2, an actually measured curve relating to the temperature-dielectric constant is drawn; drawing a model curve of the conversion with respect to the temperature-dielectric constant based on the temperature-frequency equivalent conversion model; and comparing the fitting degree of the model curve and the actually measured curve, and judging that the temperature-frequency equivalent conversion method has better applicability to the asphalt mixture when the fitting degree is greater than a preset value. In the present embodiment, the degree of fitting R is determined²The preset value of the reference to be compared is set to 0.90, and in other embodiments, the preset value of the reference may be adaptively adjusted according to actual needs, which is not limited herein.

And S6, evaluating the quality. In the step, the conductivity activation energy value is calculated according to the dielectric theory model and the temperature-frequency conversion model, and the conductivity activation energy value is used for evaluating the quality of the asphalt mixture. Because the existing quality evaluation mode only obtains the variation coefficients of asphalt and aggregate and the point-to-activation energy of each substance through the dielectric theory model solution and is used for evaluating the quality of the asphalt mixture, the prior art scheme does not limit the quantitative relation between temperature and frequency, and different detection frequencies and temperature environments can influence the dielectric property of the asphalt mixture, so that when the prior art is used for quality evaluation, nondestructive detection data cannot be unified due to the influence of different frequencies and temperature conditions, and the final quality evaluation result is influenced. The invention introduces a temperature-frequency conversion model, establishes a quantitative relation between temperature and frequency, and calculates the conductivity activation energy value by combining a dielectric theory model, thereby realizing the unification of detection results of nondestructive detection equipment under different temperature and frequency conditions and improving the accuracy of evaluating the quality of the asphalt mixture.

The application effect of the asphalt mixture quality evaluation method based on the temperature-frequency equivalent model is explained by the following specific examples.

Example 1

(1) The test samples were prepared.

The test aggregate adopts limestone from Hubei province in China, and asphalt adopts 70# matrix asphalt and SBS modified asphalt provided by Hubei China, and the performance of each material can meet the standard requirement.

The optimal gradation of the asphalt mixture is designed according to the standard requirements, and the specific gradation of mineral aggregates is shown in the following table 1. The Marshall test determines that the optimal oilstone ratio of the limestone and the basalt to the asphalt is 5.6%, and the porosity of the test piece is ensured to be controlled within the range of 4 +/-0.5%.

TABLE 1 limestone AC-20C asphalt mixture grading composition table

Referring to fig. 2, the specific sample preparation method is as follows:

(a) an initial sample was prepared. The method adopts 70# matrix asphalt and SBS modified asphalt from Hubei province of China, and adopts limestone aggregate from Hubei province of China. And respectively combining the two kinds of asphalt and aggregate to prepare six kinds of asphalt mixture rotary compaction test pieces.

(b) And cutting the standard test piece. As the obtained asphalt mixture is rotated and compacted to obtain a test piece with the diameter of 150mm and the height of 170mm, as shown in figure 2(a), a core drilling machine and a cutting machine are utilized to process the test piece into a standard test piece with the diameter of 100mm and the height of 170mm, as shown in figure 2 (b). Controlling the porosity of the obtained standard test piece within the range of 4 +/-0.5%.

(c) The measurement sample was cut. According to the size requirement of the high-temperature dielectric constant test platform for the tested object, the obtained standard test piece is processed into a sheet with the thickness of about 10mm, as shown in figure 2(c), core drilling is carried out on the sheet, the asphalt mixture test piece which is suitable for the high-temperature dielectric constant test platform and is suitable for being used in figure 2(d) and has the diameter of about 26mm as shown in figure 2(e) and the thickness of about 10mm as shown in figure 2(f) is obtained, and at least 5 intact parallel test samples are prepared for each type of aggregate and asphalt combination.

(2) And (4) measuring the dielectric constant.

The equipment adopted in the embodiment is mainly a dielectric constant high-temperature test platform which is usually used for testing the dielectric constant of an object to be tested, and the equipment mainly comprises a fixing device, an isolation layer, a measuring device, an environment box and a heating device. The device has the greatest advantage that the temperature can be uniformly changed according to the gradient, so that the dielectric constant and the loss tangent value of a measured object can be continuously measured under different temperature gradients, and specific test condition parameters are shown in table 2.

TABLE 2 parameters of the conditions in the dielectric constant test

Conditions of the experiment	Parameter(s)
		Setting temperature range (K)	303.15～333.15
Temperature rise rate (DEG C/min)	0.4
		Actual temperature deviation value (. degree. C.)	±0.3
Test voltage (V)	2
		Test frequency (kHz)	1、10、50、100、500、1000
Number of points of measured temperature	180
		Parallel test piece (piece)	5

After the measurement parameters are set, the manufactured sample is placed into the measuring device of the dielectric constant testing platform according to the display mode, so that two ends of the sample are attached to two-stage contact surfaces of the measuring device, and the measuring accuracy is ensured. After the sample is put into the measuring device according to the requirements, the measuring device can be put into an environmental box to formally start a measuring test.

(3) The steps for establishing the dielectric theory model and the temperature-frequency conversion model are described in detail above and will not be described herein.

(4) The temperature-frequency conversion model was verified.

For the two asphalt mixtures described above, the following expression can be obtained from the conversion principle formula of formula (13):

1) group 1: 70# matrix asphalt + limestone

2) Group 2: SBS modified asphalt and limestone

The frequency of 1MHz is used as the initial frequency, 302.85K is used as the initial temperature, the temperature corresponding to the two groups of asphalt mixtures under the frequency of 1KHz, 10KHz, 50KHz, 100KHz and 500KHz is respectively calculated by applying the temperature-frequency equivalent principle, and the calculation results are shown in the following table 3.

TABLE 3 corresponding temperatures based on temperature-frequency conversion model

The results of plotting the dielectric constant values of two groups of asphalt mixtures under the actual temperature condition and the transition temperature based on the temperature-frequency equivalent principle are shown in fig. 3 below. Wherein, fig. 3a is a comparison graph of the fitting degree of the 70# matrix asphalt + limestone sample with respect to dielectric constant, and fig. 3b is a comparison graph of the fitting degree of the SBS modified asphalt + limestone sample with respect to dielectric constant. As can be seen from FIG. 3, the dielectric constant value of the asphalt mixture under the actual temperature condition is substantially consistent with that of the asphalt mixture under the conversion temperature based on the temperature-frequency equivalent relationship, and the goodness of fit R²All of them are 0.90 or more, and it can be confirmed that the temperature-frequency equivalent relationship is effective for measuring the dielectric constant of the asphalt mixture.

The invention provides an asphalt mixture quality evaluation method based on a temperature-frequency equivalent model, which is different from the situation of the prior art, realizes the unification of detection results of nondestructive detection equipment under different temperature and frequency conditions by constructing a temperature-frequency equivalent conversion model, lays a foundation for the application and popularization of the nondestructive detection equipment, and improves the accuracy of asphalt mixture quality evaluation.

The above-mentioned embodiments only express the embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.