Foamed asphalt adhesion characteristic testing method for cold recycled mixture

Abstract

The invention belongs to the technical field of road engineering material detection and evaluation, and provides a foamed asphalt adhesion characteristic testing method for a cold recycled mixture. The method comprises the following steps: applying short-time uniform thermal excitation to a loose sample of the foamed asphalt cold recycled mixture; a temperature monitoring device is used for collecting temperature-time data in the sample cooling process; according to the method, a'unit mass thermal power-time 'curve at different measuring points of foamed asphalt components is extracted through thermal inversion, integration is carried out on the curve in a preset 60s time window, a median of an integral value is taken as an adhesion index'thermal release energy index M', and the larger the value is, the better the adhesion characteristic is. The method has the advantages of no damage, objectiveness and high efficiency, and can provide reliable technical support for performance evaluation of the foamed asphalt cold recycled mixture and road construction quality control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of road engineering material detection and evaluation, and specifically provides a method for testing the adhesion properties of foamed asphalt in cold recycling mixture. The method follows the technical route of "short-time uniform thermal excitation-temperature monitoring-thermal inversion-energy integration", utilizes the difference in thermal diffusion performance between foamed asphalt and old aggregate and new aggregate, converts the temperature response in the cooling process into the heat release energy index M (the integral median of the unit mass heat power curve in the 60s window, the larger the value, the better the adhesion), so as to realize the accurate quantitative evaluation of the adhesion properties of the interface between foamed asphalt and aggregate. BACKGROUND

[0002] Foamed asphalt cold recycling mixture refers to a recycling asphalt mixture formed by mixing foamed asphalt as a binder, recycled old aggregate of milled old asphalt pavement, and appropriate amounts of new aggregate, cement and other admixtures at room temperature, which can be directly used for road subbase or subbase construction. This technology has the advantages of saving materials, reducing energy consumption and environmental protection, and has been increasingly applied in the field of road maintenance. Foamed asphalt is produced by instantaneously contacting high-temperature asphalt with a small amount of water to generate a large amount of asphalt foam, which instantaneously expands the volume of asphalt by several tens of times, forming an asphalt film containing uniform and tiny bubbles, thereby improving its wrapping capacity on the surface of cold aggregate.

[0003] In foamed asphalt cold recycling mixture, asphalt is "spot-welded" to the surface of recycled aggregate and new aggregate in the form of foamed droplets. The adhesion of foamed asphalt to the surface of aggregate in cold recycling mixture has a key influence on the mechanical strength, durability and water damage resistance of the mixture. If foamed asphalt does not adhere well to the surface of aggregate, it is easy to peel off under the action of vehicle load and water, reducing the strength and water stability of the mixture. Therefore, it is necessary to evaluate the adhesion properties of foamed asphalt in the design of cold recycling mixture and the quality control of construction.

[0004] However, there is currently a lack of intuitive quantitative test methods for the above-mentioned adhesion behavior of foamed asphalt in cold recycled mixtures in the industry, and it is usually evaluated only by indirect indicators or subjective experience. For example, during laboratory mixing sample preparation, technicians often observe the wrapping condition of asphalt on the surface of aggregates in the mixture by naked eye to judge the mixing uniformity and adhesion state, but the accuracy of this visual method is limited, and it cannot provide quantitative data. In addition, commonly used mechanical performance tests (such as Marshall stability, splitting strength, and immersion residual stability) mainly reflect the overall performance of the mixture and cannot distinguish the contribution of asphalt adhesion effect. Some researchers try to observe the asphalt distribution inside the mixture by visible light image analysis or CT scanning technology, but there are problems such as complex operation, high cost, and insufficient recognition accuracy, and a practical testing method has not yet been formed. Therefore, there is an urgent need for a fast and objective technology to identify and quantify the interfacial adhesion characteristics of foamed asphalt in cold recycled mixtures to guide the optimization of mix proportion and engineering quality evaluation. SUMMARY

[0005] OBJECTIVE

[0006] The present application relates to the field of road engineering material detection and evaluation technology, and specifically provides a foamed asphalt adhesion characteristic test method for cold recycled mixtures. The method follows the technical route of "short-time uniform thermal excitation-temperature monitoring-thermal inversion-energy integration", utilizes the difference in thermal diffusion performance between foamed asphalt and old aggregates and new aggregates, converts the temperature response during cooling into the heat release energy index M (the integral median of the unit mass heat power curve in the 60s window, the larger the value, the better the adhesion), thereby realizing precise quantitative evaluation of the adhesion characteristics of foamed asphalt and aggregate interface.

[0007] TECHNICAL SCHEME

[0008] The present application provides a foamed asphalt adhesion characteristic test method for cold recycled mixtures, which can objectively evaluate the adhesion characteristics of foamed asphalt. The method of the present application realizes the test of the adhesion characteristics of foamed asphalt by the following steps:

[0009] S01, sample preparation: preparing a foamed asphalt cold recycled mixture loose sample and laying it flat;

[0010] S02, constant temperature curing: placing the loose sample in a 60℃ oven for constant temperature curing for 4h, and after taking it out, placing it on the test platform for not less than 30min to balance the temperature field and eliminate the interference of surface moisture;

[0011] S03, short-time uniform thermal excitation: applying short-time uniform thermal excitation to the cured loose sample to instantaneously increase the temperature of the loose sample;

[0012] S04, temperature data collection: immediately after the end of the short-time uniform thermal excitation, the temperature monitoring device is used to collect the "temperature-time" data during the cooling process of the loose sample;

[0013] S05, data preprocessing and normalization: the collected "temperature-time" data is preprocessed for ambient temperature correction and noise reduction, and the temperature data is normalized to eliminate initial state differences;

[0014] S06, clustering division: fitting the preprocessed and normalized "temperature-time" data, obtaining the "temperature-time" cooling curve, analyzing it, extracting the thermal response characteristic parameters of the "temperature-time" curve: initial cooling rate k, initial temperature (temperature at 0s), and based on the initial cooling rate k, performing unsupervised clustering to automatically classify each measuring point in the sample into three components: foam asphalt, old aggregate and new aggregate;

[0015] S07, thermal power function construction: for the foam asphalt component area identified by clustering, according to the "temperature-time" curve collected at each measuring point position in the area and the specific heat capacity c of the foam asphalt, the unit mass thermal power function of each measuring point foam asphalt is calculated Convert temperature to unit mass thermal power, and then convert "temperature-time" curve to "unit mass thermal power-time" curve;

[0016] S08, thermal inversion adhesion characteristics: integrating the above "unit mass thermal power-time" curve, calculating the heat release energy index M as the energy characterization index of the adhesion characteristics of the foam asphalt on the thermal conductivity capacity, realizing the thermal characterization inversion analysis of the foam asphalt interface thermal conductivity and its adhesion characteristics.

[0017] Further, the short-time uniform thermal excitation is realized by uniformly radiating the whole loose sample by the matrix-arranged infrared heating lamp group for 5s, which provides the same heat to the three components of foam asphalt, old aggregate and new aggregate.

[0018] Further, the initial cooling rate k is the average speed of temperature drop per unit time in the initial stage (0-2s) after the thermal excitation stops, and its calculation formula is as follows:

[0019]

[0020] In the formula: T0-0s at the end of the short-time uniform thermal excitation, the corresponding temperature, ℃;

[0021] T2-2s at the end of the short-time uniform thermal excitation, the corresponding temperature, ℃.

[0022] Further, the clustering division divides the necessary parameters (initial cooling rate k) according to the thermal property differences of the three types of materials (foamed asphalt, old aggregate, and new aggregate), and the divided necessary parameter intervals are: initial cooling rate k < 0.5 for foamed asphalt, initial cooling rate 0.5 ≤ k ≤ 1.2 for old aggregate, and initial cooling rate k > 1.2 for new aggregate.

[0023] Further, the heat release energy index M is obtained by integrating the "unit mass heat power-time" curve in a preset temperature collection time window and taking the median of the integral value, wherein the temperature collection time window is 60s, and the greater the value of the heat release energy index M, the better the adhesion property, and the calculation formula of the heat release energy index M is as follows:

[0024]

[0025] In the formula: - the integral value of the "unit mass heat power-time" curve of the bulk sample at the (x, y) point in the temperature collection time window of 60s, that is, the heat release energy of unit mass foamed asphalt at the (x, y) measurement point;

[0026] t0- initial time, that is, the 0s time after the end of short-term uniform heat excitation;

[0027] t ω - temperature collection time window, 60s;

[0028] c- specific heat capacity of foamed asphalt;

[0029] Ω- coordinate system where the bulk sample is located.

[0030] In addition, the application also provides a foamed asphalt adhesion property testing device for performing the above-mentioned testing method, which comprises: a heating unit for applying short-term uniform heat excitation to the sample; a temperature monitoring device for collecting "temperature-time" data during the cooling process of the sample after being heated; a data processing unit for forming a fitting curve according to the "temperature-time" data, extracting a thermal response characteristic parameter, performing clustering analysis to identify the distribution of each component in the mixture, and calculating a heat release energy index M representing the adhesion property of the foamed asphalt and aggregate interface.

[0031] Further, the temperature monitoring device is a temperature sensor array, which is composed of one or more of infrared thermal imaging equipment, thermocouples, thermistors or MEMS temperature sensors, which converts the reading of a certain physical quantity that changes monotonically and predictably with temperature into a temperature value through a calibration curve or a physical formula, to realize the collection of temperature time series data of the sample surface area and quasi-surface area, wherein: the infrared thermal imaging equipment detects the infrared radiation intensity of the target surface through each photosensitive pixel on its focal plane array, and converts the radiation intensity data of each pixel point into a temperature value based on Planck's radiation law, thereby generating a surface temperature distribution map; the thermocouple measures the Seebeck voltage (i.e. thermoelectric power) generated between its measurement end and reference end due to temperature difference, and converts the voltage signal into a temperature value; the thermistor measures the resistance value that changes due to its temperature change under constant excitation, and converts the resistance value into a temperature value through a pre-marked "resistance-temperature" curve; the MEMS temperature sensor measures the forward voltage drop of its internal PN junction under constant bias current, and converts the voltage signal into a digital temperature reading.

[0032] Further, in order to facilitate the understanding of the cooperative working relationship of each unit of the device, the functional correspondence is further described as follows:

[0033] A. Heating unit (input end): responsible for applying short-term uniform thermal excitation to the loose sample of cold recycled mixture, and its output is the transient change signal of the sample surface temperature field. This signal serves as the input heat source of the entire test system, providing initial conditions for subsequent temperature monitoring and data processing.

[0034] B. Temperature monitoring device (intermediate detection end): real-time collection of "temperature-time" time series data of the cooling process of the sample after the action of the heating unit. This device converts physical temperature changes into voltage, resistance or radiation intensity electrical signals, and outputs digitized temperature data streams. Its output results serve as input signals for the data processing unit.

[0035] C. Data processing unit (output calculation end): receives the temperature time series data collected by the temperature monitoring device, and after pre-processing, curve fitting, cluster recognition and heat power calculation, outputs the heat release energy index M as a representation of the adhesion characteristics of the "foamed asphalt-aggregate" interface. This index is the final output result of the device, which is used to quantitatively evaluate the thermal conductivity and adhesion characteristics of the material interface.

[0036] Invention principle

[0037] The present application is based on the technical route of "short-time uniform thermal excitation-temperature monitoring-thermal inversion-energy integration", which excites the response characteristics of the sample temperature field by the way of short-time uniform thermal excitation, and realizes the component phase identification of foamed asphalt, old aggregate and new aggregate by taking the thermal conductivity, specific heat capacity and thermal capacity rate difference between different components as the physical basis. The short-time uniform thermal excitation provides the same heat input for each component of the bulk sample, but due to the different thermal diffusion characteristics of the three components, the cooling curves of each component appear significant differences during the cooling process, and this difference is the basis for adhesion evaluation. Through real-time acquisition of "temperature-time" data, it is converted into "unit mass heat power-time" curve, the integral value of the curve is calculated, and the median of the integral value of all measuring points of the foamed asphalt component is taken, the temperature change in the cooling process is converted into "heat release energy index M" representing the adhesion characteristics of the interface by thermal inversion, and then the macro temperature response and the adhesion characteristics of the foamed asphalt are corresponded, so as to realize the rapid, non-destructive and accurate characterization of the adhesion of the foamed asphalt.

[0038] (1) Three-component phase separation mechanism of bulk material: in the cooling process, different components of bulk material show significant temperature response difference due to the difference in thermal properties. By taking advantage of the difference in thermal properties and microstructure of the three components, the present application applies the same thermal energy to the bulk material by "short-time uniform thermal excitation", so that the three components show different characteristics in thermal aspect, so as to realize multi-dimensional thermal phase separation identification of the three components. The mechanism is as follows: the thermal conductivity of foamed asphalt is low (about 0.2-0.4 W / m·K), and the cooling curve shows fast initial attenuation and slow later tail; the overall thermal conductivity of old aggregate is between that of foamed asphalt and new aggregate (the thermal conductivity of old aggregate is 1.0-1.5 W / m·K) due to the presence of aged asphalt film and aggregate composite structure, and the cooling curve has a certain hysteresis; the thermal conductivity of new aggregate is high (about 2.0-3.5 W / m·K), which can quickly release heat, and its temperature curve drops the fastest. By extracting and classifying the key characteristic quantities such as initial cooling rate k and initial temperature of "temperature-time" curve, automatic phase separation identification of foamed asphalt, old aggregate and new aggregate can be realized. This phase separation mechanism provides a reliable thermal basis for the subsequent establishment of adhesion evaluation index. In the extraction of characteristics, the initial cooling rate k is the necessary judgment characteristic, supplemented by optional initial temperature, etc., for robustness enhancement, but does not change the necessary characteristics defined in the claims.

[0039] (2) The relationship between interface heat transfer and adhesion: The foamed asphalt adheres to the aggregate surface in a "spot welding" manner, which can be regarded as a thin film heat capacity attached to a rigid substrate. Its cooling process is affected by two main heat dissipation channels: one is the conduction of heat through the "asphalt-aggregate" interface to the inside of the aggregate (this channel is controlled by the interface contact heat conduction ability), and the other is the convection and radiation heat dissipation between the asphalt surface and the surrounding air. The adhesion property directly affects the efficiency of the first heat dissipation channel. When the adhesion is good, the asphalt is in close contact with the aggregate, the interface contact area is large, the thermal contact heat conduction coefficient is high, the interface thermal resistance is small, and the heat can quickly transfer into the aggregate substrate, which shows that the heat release Q * of unit mass of foamed asphalt is high. On the contrary, when the adhesion is poor, there are gaps or micro peeling phenomena between the asphalt and the aggregate interface, the conduction of heat flow through the interface is blocked, more heat is retained in the asphalt film, the equivalent interface thermal resistance increases, resulting in less heat energy transferred from the foamed asphalt to the aggregate in the same time, and the heat release Q * of unit mass of foamed asphalt is low.

[0040] (3) Definition of heat release energy index M: In order to quantitatively characterize the difference in interface heat transfer ability, the "unit mass heat power-time" curve of foamed asphalt components is integrated within the time window of 0-60s after the heat excitation stops, and the integral value Q * of each measuring point is obtained, and the median value is defined as the heat release energy index M; the larger the index value, the more sufficient the interface heat conduction, and the better the adhesion property. The integral value Q * represents the total heat released by each unit mass of foamed asphalt in the entire cooling process, which has a clear thermal physical meaning and can truly reflect the complete energy output ability of the interface heat conduction process of foamed asphalt. Selecting the median value as the core statistical quantity can stably reflect the heat attenuation ability of the whole foamed asphalt components, avoid the excessive deviation caused by individual abnormal measuring points or local heat reflux phenomenon, and thus ensure the stability and repeatability of the evaluation results. The larger the heat release energy index value, the more sufficient the interface heat conduction, and the better the adhesion property of foamed asphalt. Correspondingly, a small index indicates that the interface heat conduction is blocked and the adhesion effect is poor.

[0041] Advantages

[0042] (1) Without relying on manual visual observation or visible light images, the distribution of different components (foamed asphalt, old aggregate, and new aggregate) in the mixture can be automatically identified through temperature monitoring by utilizing the differences in thermal properties of different components, overcoming the difficulty in distinguishing similar colors in conventional image recognition, realizing objective and intelligent three-component phase separation analysis, and effectively avoiding the interference of human subjective factors.

[0043] (2) The present application constructs a special quantitative index of the interface adhesion characteristics of foamed asphalt, namely the heat release energy index M (the integral median of the unit mass heat power curve in the 60s window, the larger the value, the better the adhesion), which can directly reflect the adhesion of foamed asphalt and aggregate interface, solve the technical problem that the adhesion of foamed asphalt can only be inferred indirectly by the overall performance of the mixture in the past, and it is difficult to distinguish the adhesion contribution of asphalt, and provide intuitive and clear quantitative basis for the research and evaluation of the adhesion characteristics of foamed asphalt in cold recycled mixture.

[0044] (3) The test process is fast and efficient and does not damage the sample, the required equipment is simple and easy to obtain, the thermal excitation and data acquisition can be completed in a few minutes, and it can be used for laboratory analysis, and is expected to be expanded as a field evaluation method, thereby improving the timeliness and convenience of the quality control of cold regeneration construction;

[0045] (4) The core innovation of the present application is to use the dynamic thermal response characteristics of the temperature field with time to invert the interface adhesion state of foamed asphalt in bulk material, which breaks through the limitation of traditional evaluation methods that can only rely on visual observation or post-interface mechanical test, making the evaluation of the adhesion characteristics of foamed asphalt more intuitive and accurate, and providing a new technical means for the evaluation of the adhesion characteristics of foamed asphalt. DETAILED DESCRIPTION

[0046] In order to better understand the present application, the present application will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present application is not limited to these embodiments.

[0047] Example 1

[0048] Take A item 70# base asphalt to prepare foamed asphalt cold regeneration mixture bulk sample with a total mass of about 10 kg, spread the bulk material after mixing evenly in a shallow tray to form a thin layer of sample. After placing the sample in a 60℃ oven for 4 hours, take it out and place it in a windproof room temperature environment for 30 minutes to make the temperature field of the sample balanced and the surface free of excess moisture. Then, turn on the matrix heating unit composed of 16 infrared heating lamps to uniformly radiate and heat the entire sample surface for 5s, and apply a short and uniform thermal excitation to the sample to provide instantaneous and uniform heat to the foamed asphalt, old aggregate and new aggregate. After 5s of heating, turn off the heating unit.

[0049] At the moment when the heating stops, the temperature data of the cooling process of the sample is recorded by using the temperature monitoring device. In this embodiment, the temperature monitoring device is an infrared thermal imaging device arranged above the sample, which obtains the temperature field of the surface area in real time. The data acquisition and recording time is 90 s (the monitoring time is extended to ensure that complete data of the 60 s temperature acquisition time window is obtained), so as to obtain complete temperature time sequence records from the moment when the heating ends to the moment when the sample cools to near ambient temperature. During the acquisition process, each sensor continuously outputs the temperature reading of the corresponding position, so as to obtain the “temperature-time” data of different points of the foamed asphalt.

[0050] The multi-channel “temperature-time” data acquired by the temperature monitoring device is imported into the data processing unit of the computer, and is analyzed and processed according to the following steps: after the ambient baseline deduction and denoising of the “temperature-time” data within 60 s, the “temperature-time” curves of each measuring point are extracted; unsupervised clustering is performed based on the initial cooling rate k, and the foamed asphalt area is automatically identified; within the area, the “temperature-time” curves at different measuring points are converted into “unit mass heat power-time” curves in combination with the specific heat capacity, and the integrals within 0-60 s are taken, and the median of all integral values is defined as the heat release energy index M. In this embodiment, the calculated heat release energy index M is about 42018, which is a relatively large value, indicating that the heat conduction of the interface between the foamed asphalt and the aggregate is sufficient, and the adhesion characteristics are good. The test results also show that the standard deviation of the integral values of each measuring point is within a reasonable range, indicating that most of the foamed asphalt points in the sample have good adhesion.

[0051] Table 1 Test result table of Example 1

[0052]

[0053] Comparative Example 1

[0054] In order to verify the effectiveness of the method of the present application, the following comparative example is set: under the premise that the test equipment, operation process and the like remain unchanged, the B-grade 70# base asphalt is used instead of the A-grade 70# base asphalt in Example 1, and then the same short-time uniform thermal excitation and temperature monitoring test is carried out.

[0055] Compared with Example 1, the heat release energy index M of the sample of Comparative Example 1 is obviously smaller (41576 vs 42018), indicating that the interface heat conduction efficiency is low, and the adhesion of the foamed asphalt to the aggregate is insufficient. Although the dispersion coefficient is small (indicating that the overall state is consistent), the consistency is manifested as “overall poor adhesion”. This is consistent with the actual situation in the mixing process, that is, the asphalt is insufficiently wrapped, and the interface is loosely combined.

[0056] Table 2 Test result table of Comparative Example 1

[0057]

[0058] From the comparison between Example 1 and Comparative Example 1, it can be seen that the heat release energy index M measured by the method of the present application can effectively distinguish the samples with different adhesion states. When the interface adhesion property of the foamed asphalt is good, the heat release energy index M is higher (such as 42018 in Example 1); when the interface adhesion property of the foamed asphalt is insufficient, the heat release energy index M is lower (such as 41576 in Comparative Example 1). Therefore, the method can be used as a reliable quantitative index for objectively evaluating the interface adhesion property between the foamed asphalt and the aggregate.

[0059] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for testing the adhesion properties of foamed asphalt in cold recycled mixtures, characterized in that, Includes the following steps: S01. Sample preparation: Prepare loose samples of foamed asphalt cold recycled mixture and lay them flat. S02. Constant temperature curing: Place the loose sample in a 60℃ oven for constant temperature curing for 4 hours. After taking it out, let it stand on the test platform for no less than 30 minutes to equalize the temperature field and eliminate surface moisture interference. S03, Short-time uniform thermal excitation: Apply short-time uniform thermal excitation to the cured loose sample to cause the temperature of the loose sample to rise instantaneously; S04. Temperature data acquisition: After the short-term uniform thermal excitation ends, immediately use a temperature monitoring device to acquire the "temperature-time" data during the cooling process of the loose sample. S05. Data preprocessing and normalization: Perform environmental temperature correction and noise reduction preprocessing on the collected "temperature-time" data, and normalize the temperature data to eliminate initial state differences. S06. Clustering: Fit the preprocessed and normalized "temperature-time" data to obtain the "temperature-time" cooling curve. Analyze it and extract the thermal response characteristic parameters of the "temperature-time" curve: initial cooling rate k and initial temperature (temperature at 0s). Based on the initial cooling rate k, perform unsupervised clustering to automatically classify each measuring point in the sample into three components: foamed asphalt, old aggregate, and new aggregate. S07. Construction of Thermal Power Function: For the foamed asphalt component regions identified by clustering, based on the temperature-time curves collected at each measuring point within the region and the specific heat capacity c of the foamed asphalt, the thermal power function per unit mass of foamed asphalt at each measuring point is calculated. Temperature is converted into heat power per unit mass, and then the "temperature-time" curve is converted into a "heat power per unit mass-time" curve. S08. Thermal Inversion Adhesion Characteristics: Integrate the above "unit mass heat power-time" curve to calculate the heat release energy index M, which serves as the energy characterization index of the adhesion characteristics of foamed asphalt in terms of thermal conductivity, thereby realizing the thermal characterization and inversion analysis of the adhesion characteristics of foamed asphalt interface thermal conductivity.

2. The method according to claim 1, characterized in that, The short-term uniform thermal excitation is achieved by uniformly radiating the loose sample with infrared heating lamps arranged in a matrix for 5 seconds, providing equal heat to the three components: foamed asphalt, old aggregate, and new aggregate.

3. The method according to claim 1, characterized in that, The initial cooling rate k is the average rate of temperature decrease per unit time in the initial stage (0-2s) after the thermal excitation stops, and its calculation formula is as follows: Where: T0 - the temperature at time 0s after the end of the short-term uniform thermal excitation, in °C; T2 is the temperature at 2 seconds after the end of the short-term uniform thermal excitation, in °C.

4. The method according to claim 1, characterized in that, The clustering is based on the differences in the thermophysical properties of the three types of materials (foamed asphalt, old aggregate, and new aggregate) and distinguishes them by the necessary parameter (initial cooling rate k). The necessary parameter ranges are as follows: initial cooling rate k < 0.5 for foamed asphalt, initial cooling rate 0.5 ≤ k ≤ 1.2 for old aggregate, and initial cooling rate k > 1.2 for new aggregate.

5. The method according to claim 1, characterized in that, The heat release energy index M is obtained by integrating the "unit mass heat power - time" curve within a preset temperature acquisition time window and taking the median of the integral values. The temperature acquisition time window is 60 seconds. A larger value of the heat release energy index M indicates better adhesion properties. The formula for calculating the heat release energy index M is as follows: In the formula: - Within the temperature acquisition time window of 60s, the integral value of the "unit mass heat power-time" curve at the point (x, y) where the bulk sample is located, that is, the heat release energy of a unit mass of foamed asphalt at the (x, y) measuring point; t0 - Initial time, i.e., time 0s after the end of the short-term uniform thermal excitation; t ω -Temperature acquisition time window, 60s; c-Specific heat capacity of foamed asphalt; Ω - The coordinate system of the bulk sample.

6. A testing device for the adhesion properties of foamed asphalt in cold recycled mixtures, characterized in that, include: A heating unit is used to apply short-term uniform thermal excitation to the sample; A temperature monitoring device is used to collect "temperature-time" data during the cooling process of the sample after it has been heated. The data processing unit is used to form a fitting curve based on the "temperature-time" data, extract thermal response characteristic parameters, perform cluster analysis to identify the distribution of each component in the mixture, and calculate the heat release energy index M, which characterizes the adhesion properties between foamed asphalt and aggregate interface.

7. The apparatus according to claim 6, characterized in that, The temperature monitoring device is a temperature sensor array, which consists of one or more of the following: an infrared thermal imaging device, a thermocouple, a thermistor, or a MEMS temperature sensor. It measures a physical quantity that changes monotonically and predictably with temperature, and then converts the reading of this physical quantity into a temperature value using a calibration curve or physical formula. This enables the acquisition of time-series temperature data of the sample's surface and quasi-surface regions. Specifically, the infrared thermal imaging device detects the infrared radiation intensity of the target surface through each photosensitive pixel on its focal plane array, and, based on Planck's radiation law, maps each pixel... The radiation intensity data is converted into temperature values ​​to generate a surface temperature distribution map; the thermocouple measures the Seebeck voltage (i.e., thermoelectric electromotive force) generated by the temperature difference between its measuring end and reference end, and converts the voltage signal into a temperature value; the thermistor measures its resistance value as it changes due to its own temperature change under constant excitation, and converts the resistance value into a temperature value through a pre-calibrated "resistance-temperature" curve; the MEMS temperature sensor measures the forward voltage drop of its internal PN junction under constant bias current, and converts the voltage signal into a digital temperature reading.

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