A test method for evaluating the rheological properties of asphalt mixtures

Abstract

The present application belongs to the technical field of road surface performance detection and evaluation, and relates to a testing device and method for evaluating rheological properties of asphalt mixture, which comprises the following steps: S1, fixing a test sample formed by asphalt mixture on a sample loading rotating table of the testing device; S2, setting required load level, maximum deformation and test temperature according to test requirements; S3, controlling the environmental temperature to reach the test temperature and keeping it through the testing device; S4, adjusting the weight of the load, driving the test sample to rotate, rolling the test sample on the surface of the test sample according to the circular ring track line to roll and knead the test sample, and performing multiple load cycles until the deformation result reaches the set maximum deformation under the action of the nth load cycle; and S5, calculating the load resistance rheological index of the test sample. The present application can accurately and quantitatively characterize the rheological properties of asphalt mixture, accurately reflect the real deformation of the road surface structure, and improve the scientificity and rationality of the rheological property evaluation.

Description

Technical Field

[0001] This invention belongs to the field of pavement performance testing and evaluation technology, and relates to a testing device and method for evaluating the rheological properties of asphalt mixtures. Background Technology

[0002] Rheological properties refer to the quantitative relationship between strain and stress in an object under external force. Asphalt mixtures, as a typical viscoelastic material, exhibit significant temperature sensitivity, and their rheological properties reflect their deformation characteristics under specific environmental and load conditions. Under load, asphalt mixtures first undergo viscoelastic deformation, accompanied by a certain amount of viscous rheological deformation. When the load is removed, the elastic deformation recovers instantaneously, while the viscoelastic deformation recovers gradually over time. However, the viscous rheological deformation cannot be recovered, resulting in "permanent deformation." The rheological properties of asphalt mixtures depend on the properties of the asphalt material, the bond strength between the asphalt and aggregates, the gradation type, and the homogeneity of the asphalt mixture. Asphalt mixtures with high rheological properties are more prone to plastic deformation such as rutting, affecting pavement smoothness and driving safety. Furthermore, severe deformation can easily cause the loosening and detachment of surface aggregates, compromising pavement integrity. Therefore, accurately evaluating the rheological properties of asphalt mixtures is of significant guiding importance for maximizing the long-term service performance of asphalt pavements.

[0003] Currently, there are two main methods for evaluating the rheological properties of asphalt mixtures: modulus and deformation.

[0004] The creep modulus method primarily utilizes static creep tests. These tests measure and record the deformation of the specimen over time during the entire loading process, allowing for the calculation of the material's creep stiffness modulus. This stress-strain relationship under specific temperature and time conditions reflects the material's rheological properties under unconfined stress. A higher stiffness modulus indicates better deformation capacity and greater structural stability in the asphalt mixture. However, static creep tests often use beam or cylindrical specimens, which are unconfined and differ from the service environment of actual slab-type, confined pavement structures. Furthermore, static creep tests typically involve monotonic loading, significantly different from the cyclic dynamic load of tire rolling in actual use. Static loading also fails to account for loading and unloading intervals, leaving the pavement material in a constant load state and lacking a brief elastic deformation recovery phase. Due to the significant differences between the static creep test process and the actual service conditions of asphalt pavement, the test results cannot accurately reflect the true deformation characteristics of the pavement structure.

[0005] Currently, the evaluation method for deformation is mainly based on indoor rutting tests. This involves repeatedly rolling a test wheel over the surface of the test specimen, causing the flow deformation to accumulate and eventually form rutting-like plastic deformation. The number of wheel rolls per unit deformation is used as the evaluation index, reflecting the dynamic stability of the asphalt mixture's resistance to wheel-load rheological characteristics. In rutting tests, the test wheel is driven by a crank-connecting rod to perform reciprocating linear motion. First, the test wheel's motion within this straight segment is non-uniform; it maintains a higher speed in the middle of the specimen, while the speed is lower at the start and end points, and there are starting and braking phenomena, making it difficult to simulate the entire process of stable wheel load action. Furthermore, frequent stopping and starting make it difficult to achieve high-speed, continuous loading, reducing test efficiency. Secondly, the reciprocating motion of the test wheel represents a change in the direction of the force exerted by the test wheel on the specimen surface within one test cycle, while in actual road conditions, traffic is directional, which does not match the actual usage conditions of the road surface. Finally, the evaluation index is the deformation during the second half of the loading stage (45-60 min) or the number of load applications required to reach the specified deformation (25 mm), and is expressed as the number of test wheel compactions required to achieve a unit deformation. This evaluation index can only reflect the rheological resistance of the specimen through the final load deformation result, but cannot reflect the process of load deformation, nor can it accurately characterize the rheological behavior characteristics of each stage or period.

[0006] In summary, existing indoor rheological simulation testing methods and result evaluations suffer from technical shortcomings, failing to accurately characterize and reflect the true deformation of pavement structures, thus not meeting the current technical needs of asphalt pavement material design and performance evaluation. Therefore, it is necessary to develop novel indoor simulation testing devices and methods for the rheological properties of asphalt mixtures, tailored to specific practical requirements. Summary of the Invention

[0007] In view of the significant shortcomings of existing rheological evaluation methods for asphalt mixtures mentioned above, this invention provides a testing device and method for evaluating the rheological properties of asphalt mixtures.

[0008] This invention improves the way wheel loads are applied and uses the load-resistance rheological index as an evaluation index, which can accurately and quantitatively characterize the rheological properties of asphalt mixtures, accurately reflect the true deformation of the pavement structure, and improve the scientificity and rationality of rheological performance evaluation.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for evaluating the rheological properties of asphalt mixtures includes the following steps:

[0011] S1, Fixation of the test sample

[0012] The asphalt mixture test sample is fixed on the sample rotating platform of the testing device;

[0013] S2, Parameter Setting

[0014] Based on the testing requirements, set the required load level P, maximum deformation L, and test temperature T;

[0015] S3. Test sample isothermal treatment

[0016] The ambient temperature is controlled by the temperature control device of the testing device to reach the test temperature T, and maintained at this temperature for 3 to 6 hours;

[0017] S4, Performance Testing

[0018] The testing device is activated, and a horizontal load P is applied to the test specimen. Simultaneously, the specimen is rotated, and the test wheel on the device rolls along a circular wheel track, crushing and rubbing the specimen on its surface. Multiple load cycles are performed along this circular wheel track. The load deformation of the test specimen at each time point is recorded, ultimately obtaining the deformation result l of the test specimen up to the nth load cycle. n The maximum deformation L is reached;

[0019] S5, Performance Evaluation

[0020] Calculate the load rheological index LRI of the test sample at the test temperature T. T The calculation formula is as follows:

[0021]

[0022] In the formula, LRI T The rheological index for load resistance is expressed in J / mm.

[0023] N represents the total number of cycles of rolling and kneading applied during the test;

[0024] l n The deformation result under the nth load cycle is in mm;

[0025] L is the maximum deformation, i.e., the deformation result under the Nth load cycle, in mm;

[0026] P represents the set load level, in kN;

[0027] T represents the set test temperature, in °C.

[0028] Further specifying, in step S2, the maximum deformation L is 30mm to 40mm, and the load level P is 50kN.

[0029] Further specifying, the specific process of step S4 is as follows:

[0030] Start the testing device, adjust the weight of the load in the loading device to P, and the sample rotation table drives the test sample to rotate. The test wheel at the bottom of the loading device is used to crush and rub the test sample. Record the expansion and contraction of the loading device at each moment during one rotation of the sample rotation table, that is, the load deformation of the test sample, and calculate the deformation result l of the test sample under the load during one rotation. n ;

[0031] One rotation of the sample rotation table constitutes one load cycle, until the deformation result of the test sample under the nth load cycle is obtained. n The maximum deformation L is reached.

[0032] Further specifying, in step S4, the deformation result of the test sample under load during one rotation is l n , is the average value of the deformation at each time point.

[0033] Further specifying, step S5 also includes calculating the load rheological rate LRR and the load-resistance rheological energy LRE;

[0034] The calculation methods for the load rheological rate LRR and the load-resistance rheological energy LRE are as follows:

[0035] Plotting the number of load cycles on the x-axis, the deformation result of the test specimen under each load cycle is l. n Plot the deformation-load cycle curve with the vertical axis as the ordinate. The load rheological rate LRR is the slope at each point on the deformation-load cycle curve. The load rheological energy LRE is the total area under the deformation-load cycle curve.

[0036] Furthermore, the smaller the load rheological rate LRR, the larger the load rheological energy LRE, indicating that the asphalt mixture of the test sample has a stronger load rheological resistance.

[0037] A testing apparatus for implementing the method for evaluating the rheological properties of asphalt mixtures, the testing apparatus comprising a constant temperature test chamber and a sample rotating stage, a loading device, a driving mechanism, and a computer processor respectively placed inside the constant temperature test chamber;

[0038] The constant temperature test chamber is equipped with a temperature control device to control the ambient temperature inside the constant temperature test chamber to reach the test temperature T, and to transmit the test temperature data to the computer processor.

[0039] The sample rotation stage is used to place the test sample;

[0040] The loading device has a load at the top and a test wheel at the bottom. The loading device is placed above the sample rotating table and applies a constant load to the test sample. The test wheel contacts the surface of the test sample and is used to crush and rub the test sample.

[0041] A displacement sensor is also provided on the side of the loading device. The displacement sensor is located between the test wheel and the load and is used to obtain the amount of expansion and contraction of the loading device in the vertical direction and transmit the amount of expansion and contraction to the computer processor.

[0042] The drive mechanism is connected to the sample rotating stage and is used to drive the sample rotating stage to rotate the test sample.

[0043] The drive mechanism is equipped with a rotation counter to record the number of load cycles and transmit the recorded data to the computer processor.

[0044] The computer processor is connected to the temperature control device, the speed counter, and the displacement sensor, respectively, to receive various data during the test and calculate the load rheological index LRI. T Load rheological rate (LRR) and load rheological energy (LRE).

[0045] Further defined, the loading device includes a pressure rod, a force transmission column, and a gantry loading frame, which are placed inside the constant temperature test chamber and connected sequentially from top to bottom; the pressure rod is placed horizontally, the force transmission column is placed vertically, the test wheel is placed at the bottom of the gantry loading frame, one end of the pressure rod is movably connected to the bottom surface inside the constant temperature test chamber, the load is placed on the other end of the pressure rod, and the displacement sensor is placed on the force transmission column.

[0046] Further specifying, the gantry loading frame is a gantry structure formed by connecting a crossbar and two support rods. Each of the two support rods is provided with a steering bearing at its bottom end. There are two test wheels, with one test wheel corresponding to the bottom of each steering bearing and the test wheel connected to the steering bearing. The force transmission column is connected to the crossbar.

[0047] Further specifying, the testing device also includes a support device placed inside a constant temperature test chamber, the support device including a first support frame, a second support frame, and a crossbeam respectively located below the pressure rod; the displacement sensor is placed on the crossbeam and located beside the force transmission column;

[0048] Both the first and second support frames are placed vertically, and the sample rotating stage is located between the first and second support frames. One end of the pressure rod is connected to the bottom surface of the constant temperature test chamber through the first support frame. The bottom end of the second support frame is connected to the bottom surface of the constant temperature test chamber, and the top end of the second support frame is connected to the first support frame through a horizontally placed crossbeam. A force transmission hole is provided on the crossbeam, and the force transmission column passes through the force transmission hole and is connected to the gantry loading frame.

[0049] Compared with the prior art, the beneficial effects of the present invention are:

[0050] 1. The present invention discloses a testing device and method for evaluating the rheological properties of asphalt mixtures, which can accurately simulate the rolling and kneading action of traffic loads under indoor conditions, and realize the quantitative and accurate evaluation of the rheological properties of asphalt pavement materials.

[0051] 2. This invention achieves continuous, unidirectional rolling and kneading action of the test wheel on the test sample by using a sample rotating platform to drive the test sample to rotate. This can simulate the real load environment of asphalt mixture pavement materials during vehicle driving, ensuring the scientific and reasonable effect of the rolling and kneading action. At the same time, the design of the sample rotating platform and loading device can meet the needs of high-speed operation of the equipment, ensuring the continuity of the rolling and kneading load action and greatly improving the efficiency of the rheological action on the test sample.

[0052] 3. This invention is based on the proposed load-resistance rheological index LRI T Evaluation indicators enable the scientific characterization and evaluation of the load-bearing rheological properties of asphalt mixture materials and structures, making the evaluation results of the rheological properties of pavement materials and structures more accurate and reliable, and better serving the design and performance evaluation of asphalt pavement materials.

[0053] 4. The testing device provided by this invention is simple in structure, scientifically reasonable, easy to implement, and can be standardized for production and use. It has extremely important practical engineering significance for studying the load-bearing rheological properties of asphalt pavement materials and structures. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the test device of the present invention.

[0055] Figure 2 This is a schematic diagram of the loading device structure of the present invention;

[0056] Figure 3 This is a schematic diagram of the support device structure of the present invention;

[0057] Figure 4 This is a schematic diagram of the support frame structure of the present invention;

[0058] Figure 5 This is a schematic diagram of the wheel track position according to the present invention;

[0059] Figures 1-5The components are as follows: 1. Constant temperature test chamber; 11. Base; 111. Raised platform; 12. Temperature control device; 13. Sample rack; 2. Sample rotating stage; 21. Thrust bearing; 3. Support device; 31. First support frame; 311. Support column; 312. Fixing pin; 32. Second support frame; 33. Crossbeam; 331. Positioning end plate; 332. Square force transmission hole; 4. Loading device; 41. Pressure rod; 411. Load; 412. Rubber pad; 42. Gantry loading frame; 421. Force transmission column; 422. Steering bearing; 423. Fork frame; 43. Test wheel; 431. Rolling friction device; 5. Test sample; 51. Wheel track; 6. Computer processor; 61. Motor; 611. Rotating shaft; 612. Rotation counter; 62. Speed ​​controller; 63. Displacement sensor. Detailed Implementation

[0060] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0061] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0062] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0063] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0064] Example 1

[0065] See Figure 1 This embodiment provides a testing device for evaluating the rheological properties of asphalt mixtures. The testing device includes a constant temperature test chamber 1 and a sample rotating stage 2, a loading device 4, a driving mechanism, and a computer processor 6, which are respectively placed in the constant temperature test chamber 1.

[0066] In this embodiment, a temperature control device 12 is installed inside the constant temperature test chamber 1 to control the ambient temperature inside the constant temperature test chamber 1 to reach the test temperature T, and to transmit the test temperature data to the computer processor 6.

[0067] In this embodiment, the sample rotating stage 2 is used to place the test sample 5.

[0068] In this embodiment, a load 411 is provided on the top of the loading device 4, and a test wheel 43 is provided on the bottom of the loading device 4. The loading device 4 is placed above the sample rotating table 2, and a constant load is applied to the test sample 5 through the load 411. The test wheel 43 contacts the surface of the test sample 5 and is used to crush and rub the test sample 5.

[0069] In this embodiment, a displacement sensor 63 is also provided on the loading device 4. The displacement sensor 63 is located between the test wheel 43 and the load 411 and is used to obtain the amount of extension and retraction of the loading device 4 in the vertical direction and transmit the amount of extension and retraction to the computer processor 6.

[0070] In this embodiment, the driving mechanism is connected to the sample rotating stage 2 and is used to drive the sample rotating stage 2 to rotate the test sample 5.

[0071] In this embodiment, the drive mechanism is equipped with a rotation counter 612, which is used to record the number of load cycles and transmit the recorded data to the computer processor 6.

[0072] In this embodiment, the computer processor 6 is connected to the temperature control device 12, the speed counter 612, and the displacement sensor 63, respectively, to receive various data during the test and calculate the load rheological index LRI. T Load rheological rate (LRR) and load rheological energy (LRE).

[0073] See Figure 1 In this embodiment, the constant temperature test chamber 1 is a rectangular box, and a temperature control device 12 is installed inside the constant temperature test chamber 1. The temperature control device 12 is connected to the computer processor 6 and can realize automatic control of the temperature inside the constant temperature test chamber 1. It should be noted that the temperature control device 12 is a conventional temperature control device already available in the industry, preferably a blower type, to ensure the uniformity of temperature distribution inside the constant temperature test chamber 1.

[0074] In this embodiment, the bottom of the constant temperature test chamber 1 is provided with a base 11, and a raised platform 111 is provided on the base 11. The sample rotating stage 2 is placed on the raised platform 111 through a thrust bearing 21. The thrust bearing 21 plays the role of supporting the sample rotating stage 2 and ensuring the free rotation of the sample rotating stage 2.

[0075] In this embodiment, the constant temperature test chamber 1 is also provided with a sample rack 13, which is used to store the test specimens.

[0076] See Figure 1A sample rotating platform 2 is mounted on the base 11 of the constant temperature test chamber 1. Support devices 3 are located on both sides of the base 11. The test sample 5 is placed above the sample rotating platform 2, and a loading device 4 passes through the support devices 3 and contacts the upper surface of the test sample 5. Two test wheels 43 are located at the bottom of the loading device 4. The loading device 4 applies a constant load to the test sample 5 using the test wheels 43. A drive mechanism is located on the side of the sample rotating platform 2. Preferably, the drive mechanism is a motor 61, which drives the sample rotating platform 2 to rotate the test sample 5, thereby achieving continuous rolling of the test wheels 43 on the upper surface of the test sample 5. A rolling friction device 431 is provided on the test wheels 43 to achieve a crushing and kneading effect on the test sample 5 when the test wheels 43 roll on the surface of the test sample 5. A displacement sensor 63 is provided on the support device 3 to monitor the displacement change of the loading device 4 over the test time. A rotation counter 612 is provided on the motor 61. Deformation data and rotation data are transmitted to a computer processor 6 for storage via a connecting cable. During implementation, the rotating motion of the test sample 5 driven by the sample rotating table 2 enables the continuous and unidirectional rolling and kneading action of the test wheel 43 on the test sample 5. This can simulate the real load environment of asphalt mixture pavement material during vehicle driving, ensuring the scientific and reasonable effect of the rolling and kneading action. At the same time, the design of the sample rotating table 2 and the loading device 4 can meet the needs of high-speed operation of the equipment, ensuring the continuity of the rolling and kneading load action and greatly improving the efficiency of the rheological action on the test sample 5.

[0077] In this embodiment, the sample rotating stage 2 is a disc structure with a square groove inside, the size of which matches the size of the test sample 5. The bottom edge of the sample rotating stage 2 is connected to the rotating shaft 611 of the motor 61.

[0078] The computer processor 6 controls the speed of the motor 61 through the speed controller 62, and the rotating shaft 611 of the motor 61 drives the sample rotating table 2 to rotate through the gear teeth.

[0079] In this embodiment, a rotation counter 612 is also provided on the rotating shaft 611 of the motor 61, and the rotation counter 612 is connected to the computer processor 6. The computer processor 6 calculates the number of rotations of the sample rotating stage 2 by counting the number of teeth between the rotating shaft 611 and the sample rotating stage 2, and feeds back the rotation number information of the sample rotating stage 2 to the computer processor 6 for storage.

[0080] See also Figure 1In this embodiment, the loading device 4 includes a pressure rod 41, a force transmission column 421, and a gantry loading frame 42, which are placed inside the constant temperature test chamber 1 and connected sequentially from top to bottom. The pressure rod 41 is placed horizontally, the force transmission column 421 is placed vertically, the test wheel 43 is placed at the bottom of the gantry loading frame 42, one end of the pressure rod 41 is movably connected to the bottom surface inside the constant temperature test chamber 1, the load 411 is placed on the other end of the pressure rod 41, and the displacement sensor 63 is placed on the force transmission column 421.

[0081] See Figure 2 In this embodiment, the gantry loading frame 42 is a gantry structure consisting of a crossbar and two support rods connected together. Each of the two support rods is provided with a steering bearing 422 at its bottom end. There are two test wheels 43, with one test wheel 43 corresponding to the bottom of each steering bearing 422 and the test wheel 43 being connected to the steering bearing 422. The force transmission column 421 is connected to the crossbar.

[0082] In this embodiment, the pressure rod 41 is located above the loading device 4. One end of the pressure rod 41 is hinged to the support column 311 via a fixing pin 312, allowing the pressure rod 41 to rotate around the support column 311. The other end of the pressure rod 41 is connected to a load 411. Specifically, the load 411 consists of a number of counterweights.

[0083] In this embodiment, a rubber pad 412 is provided in the middle of the pressure rod 41, and the rubber pad 412 contacts the force transmission column 421. Specifically, the rubber pad 412 is made of hard rubber to reduce vibration of the loading device 4 during the test and ensure the stability of the test system.

[0084] Preferably, the pressure rod 41 is a lever system, with the fixed pin 312 as the fulcrum, the load 411 end as the force application point, and the rubber pad 412 as the resistance point. Based on the lever principle, the load applied by the loading device 4 is increased.

[0085] In this embodiment, the upper part of the gantry loading frame 42 is provided with a force transmission column 421, and the ends of the two lower support rods are provided with steering bearings 422. Test wheels 43 are installed on the steering bearings 422. The test wheels 43 are connected to the steering bearings 422 through a fork 423. The lower support rod of the gantry loading frame 42 is connected to the inner ring of the steering bearings 422, and the fork 423 is connected to the outer ring of the steering bearings 422.

[0086] Preferably, the steering bearing 422 is a thrust roller bearing, which can withstand axial load as the main load and combined axial and radial loads, so as to enable the test wheel 43 to rotate freely in the horizontal direction.

[0087] Preferably, in this embodiment, a rolling friction device 431 is provided on the fork 423 that fixes the test wheel 43 to reduce the degree of free rotation of the test wheel 43 during the test, so as to realize the crushing and kneading effect of the test wheel 43 on the test sample 5 when it rolls on the surface of the test sample 5.

[0088] Preferably, in this embodiment, the test wheel 43 is preferably a rubber pneumatic tire, and the rubber hardness is preferably 70-80 IRHD.

[0089] See Figure 5 In this embodiment, the wheel track 51 of the test wheel 43 when it rolls on the surface of the test sample 5 is a circular shape.

[0090] See Figure 1 The testing device provided in this embodiment also includes a support device 3 placed inside the constant temperature test chamber 1. The support device 3 includes a first support frame 31, a second support frame 32 and a crossbeam 33 located below the pressure rod 41 respectively; the displacement sensor 63 is placed on the crossbeam 33 and located next to the force transmission column 421.

[0091] In this embodiment, both the first support frame 31 and the second support frame 32 are placed vertically. The sample rotating stage 2 is located between the first support frame 31 and the second support frame 32. One end of the pressure rod 41 is connected to the bottom surface of the constant temperature test chamber 1 through the first support frame 31. The bottom end of the second support frame 32 is connected to the bottom surface of the constant temperature test chamber 1, and the top end of the second support frame 32 is connected to the first support frame 31 through a horizontally placed crossbeam 33. A force transmission hole 332 is provided on the crossbeam 33, and the force transmission column 421 passes through the force transmission hole 332 and is connected to the gantry loading frame 42.

[0092] See Figure 3 The crossbeam 33 consists of two parallel beams connected by a positioning end plate 331. The positioning end plate 331 has a square force transmission hole 332 in the center. The square force transmission hole 332 allows the force transmission column 421 of the loading device 4 to pass through. The size of the square force transmission hole 332 matches the cross-section of the force transmission column 421, ensuring that the force transmission column 421 can move vertically but cannot rotate horizontally, thus achieving the positioning function of the support device 3 for the loading device 4 during the test.

[0093] See Figure 4 Specifically, both the first support frame 31 and the second support frame 32 are portal-shaped brackets. The first support frame 31 and the second support frame 32 are located on both sides of the base 11, and a sample rotating stage 2 is placed in the space between the first support frame 31 and the second support frame 32. A support column 311 is provided at the center of the top of the first support frame 31, and a fixing pin 312 is provided at the end of the support column 311.

[0094] In this embodiment, the displacement sensor 63 measures the load deformation of the test sample 5 by monitoring the expansion and contraction of the force transmission column 421.

[0095] In this embodiment, the computer processor 6 stores the data information of the rotation counter 612 and the data information of the displacement sensor 63 monitored at each time point during the test, which are used to plot the deformation-load number change curve.

[0096] Preferably, the test wheel 43 completes one rotation around the test sample 5, and each point on the wheel track 51 is subjected to two rolling and kneading actions by the test wheel 43. During this period, the deformation result of the test sample 5 is represented by the average value of the deformation at each time point monitored in this cycle.

[0097] In this embodiment, the computer processor 6 is equipped with data receiving and processing software, which can automatically calculate the deformation value under a single cyclic load for evaluating and analyzing the load rheological performance of the test sample 5. Specifically, the computer processor 6 can receive the collected data on the number of cycles, test temperature, and expansion / contraction of the displacement sensor 63, calculate the deformation value under a single cyclic load, calculate the load rheological index using a calculation model, plot the deformation-load cycle change curve, and calculate the load rheological rate LRR and load rheological energy LRE.

[0098] Preferably, in this embodiment, test sample 5 can be prepared by indoor molding or by on-site sampling and cutting at newly built or existing roads. The test surface of test sample 5 should be the upper surface of the molded or sampled sample, and the upper surface should be clean and flat.

[0099] Preferably, during the test, the weight of the load 411 can be adjusted according to the required load level.

[0100] Preferably, the termination condition for the test operation in this embodiment is reaching the specified maximum deformation.

[0101] Example 2

[0102] This embodiment provides a method for evaluating the rheological properties of asphalt mixtures, comprising the following steps:

[0103] S1, Fixation of test sample 5

[0104] The asphalt mixture test sample 5 is fixed on the sample rotating table 2 of the testing device;

[0105] S2, Parameter Setting

[0106] According to the test requirements, set the required load level P, maximum deformation L and test temperature T; in step S2, the maximum deformation L is 30mm to 40mm, and the standard value of the load level P is preferably 50kN.

[0107] S3, Test Sample 5 is kept at a constant temperature

[0108] The ambient temperature is controlled by the temperature control device 12 of the testing device to reach the test temperature T, and maintained at this temperature for 3 to 6 hours;

[0109] S4, Performance Testing

[0110] The testing device is activated, and a horizontal load P is applied to the test specimen 5. Simultaneously, the test specimen 5 is driven to rotate. The test wheel 43 on the testing device rolls along a circular wheel track on the surface of the test specimen 5, crushing and rubbing it. Multiple load cycles are performed along the circular wheel track. The load deformation of the test specimen 5 at each time point is recorded, ultimately obtaining the deformation result l of the test specimen 5 up to the nth load cycle. n The maximum deformation L is reached. In this embodiment, during the test, the test wheel 43 is static and the test sample 5 is dynamic. The test wheel 43 contacts the upper surface of the test sample 5, so that the static test wheel 43 moves in a circular trajectory on the rotating test sample 5, thereby accurately simulating the rolling and kneading effect of the traffic load and ensuring the accuracy of the evaluation results.

[0111] Specifically, the testing device is started, and the weight of the load 411 in the loading device 4 is adjusted to P. The sample rotation table 2 drives the test sample 5 to rotate, and the test wheel 43 at the bottom of the loading device 4 is used to crush and rub the test sample 5. The amount of expansion and contraction of the loading device 4 at each moment during one rotation of the sample rotation table 2 is recorded, that is, the load deformation of the test sample 5. The deformation result l of the test sample 5 under the load during one rotation is calculated. n One rotation of the sample rotation table 2 constitutes one load cycle, until the deformation result of the test sample 5 under the nth load cycle is obtained. n The maximum deformation L is reached.

[0112] In this embodiment, the deformation result of test specimen 5 under load during one rotation is shown in Figure 1. n , is the average value of the deformation at each time point. The wheel track 51 of the test wheel 43 rolling on the surface of the test sample 5 is circular. In this embodiment, the placement, fixing and rotation of the test sample 5 on the sample rotating table 2, the connection between the loading device 4 and the support device 3, and the operation of the loading device 4 are all in accordance with Embodiment 1.

[0113] S5, Performance Evaluation

[0114] Calculate the load rheological index LRI of test sample 5 at test temperature T. T The calculation formula is as follows:

[0115]

[0116] In the formula, LRI T The rheological index for load resistance is expressed in J / mm.

[0117] N represents the total number of cycles of rolling and kneading applied during the test;

[0118] l n The deformation result under the nth load cycle is in mm;

[0119] L is the maximum deformation, i.e., the deformation result under the Nth load cycle, in mm;

[0120] P represents the set load level, in kN;

[0121] T represents the set test temperature, in °C.

[0122] Further specifying, step S5 also includes calculating the load rheological rate LRR and the load rheological energy LRE; the calculation methods for the load rheological rate LRR and the load rheological energy LRE are as follows:

[0123] Plotting the number of load cycles on the x-axis, the deformation result of test sample 5 under each load cycle is shown. n Plot the deformation-load cycle curve with the vertical axis as the ordinate. The load rheological rate LRR is the slope at each point on the deformation-load cycle curve. The load rheological energy LRE is the total area under the deformation-load cycle curve.

[0124] Specifically, in this embodiment, the method for evaluating the rheological properties of asphalt mixtures includes the following steps:

[0125] 1) Test sample 5 molding. Prepare a square plate specimen indoors according to the square groove size of the sample rotating table 2; or cut the road surface on site, and then cut the sample according to the square groove size of the sample rotating table 2. Ensure that the surface of test sample 5 is flat and free of loose sand.

[0126] 2) Installation of test sample 5. Place test sample 5 in the square groove of the sample rotating stage 2. Fill the four sides of test sample 5 with elastic filler to ensure the stability of test sample 5.

[0127] 3) Equipment debugging. Adjust the weight P of load 411 according to the required load level; turn on the computer processor 6 and set the speed of motor 61; clear the reading of displacement sensor 63; set the test termination condition: maximum deformation L.

[0128] 4) Temperature control treatment of test sample 5. Turn on the temperature control device 12, set the test temperature T, and keep test sample 5 at the set ambient temperature for 3 to 6 hours.

[0129] 5) Rheological property testing.

[0130] The automatic operation programs of displacement sensor 63 and rotation counter 612 are activated, the equipment is started, and rheological performance testing and real-time information acquisition are performed. The computer processor 6 records the number of cycles n of the rolling and kneading action of the test wheel 43, as well as the load deformation of the test sample 5 at each time point. Furthermore, the computer processor 6 calculates the deformation result l of the test sample 5 under the load of that cycle. n The loading cycle is repeated until the set maximum deformation L is reached. The deformation result l under each loading cycle is recorded and stored by the computer processor 6. n And plot the deformation-load cycle variation curve.

[0131] 6) Results processing: Calculate the load rheological index LRI of test sample 5 at ambient temperature T. T As an evaluation index characterizing the load-resistance rheological properties of asphalt mixture materials.

[0132] In this embodiment, it is specifically noted that the maximum deformation parameter L is preferably 30-40 mm.

[0133] In this embodiment, it is specifically noted that the standard value of the load level P is preferably 50kN.

[0134] In this embodiment, it is specifically noted that the load-resistance rheological index LRI T LRI characterizes the ability of test sample 5 to resist load deformation at a specified ambient temperature T, expressed as the work required to produce a unit deformation. T The larger the value, the stronger the ability of the pavement material to resist load deformation. Under the action of rolling and kneading, the pavement material is less likely to undergo load rheological deformation.

[0135] In this embodiment, it is specifically noted that, for the same material, the load-resistance rheological index LRI T It should be a fixed value to facilitate comparative analysis of the load-resistance rheological properties of various materials.

[0136] In this embodiment, the slope of the deformation-load cycle variation curve at each point represents the load rheological rate (LRR) of test sample 5, which represents its rheological properties under rolling and kneading loads, expressed as the rheological deformation variable under a single rolling and kneading load, in J / mm. A higher load rheological rate (LRR) indicates a poorer resistance to load rheology. The load rheological rate (LRR) can be used to analyze the load rheological performance of materials at different loading stages.

[0137] In this embodiment, in the deformation-load cycle change curve, the deformation value l nIt increases with the number of load cycles n. The total area under the deformation-load cycle curve represents the load rheological energy LRE of the material when the maximum deformation L is reached. The larger the load rheological energy LRE, the stronger the material's resistance to load rheology.

[0138] It should be noted that the measurement of the load rheological index is automatically completed through the programming control software of the central computer, which reduces human operation error.

[0139] In particular, based on the device of the present invention, the ambient temperature can be adjusted in real time according to actual needs to simulate the load-bearing rheological level of asphalt mixture materials under real conditions.

[0140] It should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for evaluating the rheological properties of asphalt mixtures, characterized in that, Includes the following steps: S1, Fixation of test sample (5) The test sample (5) formed from asphalt mixture is fixed on the sample rotating table (2) of the testing device; S2, Parameter Setting Based on the testing requirements, set the required load level P, maximum deformation L, and test temperature T; S3, Test sample (5) isothermal treatment The ambient temperature is controlled by the temperature control device (12) of the test device to reach the test temperature T, and is maintained at this temperature for 3 to 6 hours; S4, Performance Testing The testing device is started, and a load level P is applied to the test specimen (5). At the same time, the test specimen (5) is driven to rotate. The test wheel (43) on the testing device rolls on the surface of the test specimen (5) along a circular wheel track to crush and rub the test specimen (5), and performs multiple load cycles along the circular wheel track. The load deformation of the test specimen (5) at each time point is recorded, and the deformation result of the test specimen (5) up to the nth load cycle is finally obtained. n The maximum deformation L is reached; S5, Performance Evaluation Calculate the load rheological index LRI of test sample (5) at test temperature T. T The calculation formula is as follows: In the formula, LRI T The rheological index for load resistance is expressed in J / mm. N represents the total number of cycles of rolling and kneading applied during the test; l n The deformation result under the nth load cycle is in mm; L is the maximum deformation, i.e., the deformation result under the Nth load cycle, in mm; P represents the set load level, in kN; T represents the set test temperature, in °C; The testing device includes a constant temperature test chamber (1) and a sample rotating stage (2), a loading device (4), a driving mechanism and a computer processor (6) respectively placed in the constant temperature test chamber (1); The constant temperature test chamber (1) is equipped with a temperature control device (12) to control the ambient temperature inside the constant temperature test chamber (1) to reach the test temperature T, and transmit the test temperature data to the computer processor (6). The sample rotating stage (2) is used to place the test sample (5); The loading device (4) has a load (411) on top and a test wheel (43) on the bottom. The loading device (4) is placed above the sample rotating table (2) and applies a constant load to the test sample (5) through the load (411). The test wheel (43) contacts the surface of the test sample (5) and is used to crush and rub the test sample (5). A displacement sensor (63) is also provided on the side of the loading device (4) to obtain the amount of extension and retraction of the loading device (4) in the vertical direction and transmit the amount of extension and retraction to the computer processor (6); The drive mechanism is connected to the sample rotating stage (2) and is used to drive the sample rotating stage (2) to rotate the test sample (5); The drive mechanism is equipped with a rotation counter (612) to record the number of load cycles and transmit the recorded data to the computer processor (6); The computer processor (6) is connected to the temperature control device (12), the speed counter (612), and the displacement sensor (63) respectively, and is used to receive various data during the test process and calculate the load rheological index LRI. T Load rheological rate (LRR) and load rheological energy (LRE); The loading device (4) includes a pressure rod (41), a force transmission column (421), and a gantry loading frame (42) that are placed inside the constant temperature test chamber (1) and connected sequentially from top to bottom. The pressure rod (41) is placed horizontally, the force transmission column (421) is placed vertically, the test wheel (43) is placed at the bottom of the gantry loading frame (42), one end of the pressure rod (41) is movably connected to the bottom surface inside the constant temperature test chamber (1), the load (411) is placed on the other end of the pressure rod (41), and the displacement sensor (63) is placed on the force transmission column (421).

2. The method for evaluating the rheological properties of asphalt mixtures according to claim 1, characterized in that, In step S2, the maximum deformation L is 30mm to 40mm, and the load level P is 50kN.

3. The method for evaluating the rheological properties of asphalt mixtures according to claim 1, characterized in that, The specific process of step S4 is as follows: Start the testing device, adjust the weight of the load (411) in the loading device (4) to P, the sample rotation table (2) drives the test sample (5) to rotate, and use the test wheel (43) at the bottom of the loading device (4) to crush and rub the test sample (5). Record the amount of expansion and contraction of the loading device (4) at each moment during one rotation of the sample rotation table (2), that is, the load deformation of the test sample (5), and calculate the deformation result l of the test sample (5) under the load during one rotation. n One rotation of the sample rotation table (2) constitutes one load cycle, until the deformation result of the test sample (5) under the nth load cycle is obtained. n The maximum deformation L is reached.

4. The method for evaluating the rheological properties of asphalt mixtures according to claim 3, characterized in that, In step S4, the deformation result of the test specimen (5) under load during one rotation is... n , is the average value of the deformation at each time point.

5. The method for evaluating the rheological properties of asphalt mixtures according to claim 1, characterized in that, Step S5 also includes calculating the load rheological rate LRR and the load rheological energy LRE; The calculation methods for the load rheological rate LRR and the load-resistance rheological energy LRE are as follows: The deformation result of the test specimen (5) under each load cycle is shown on the x-axis as the number of load cycles. n Plot the deformation-load cycle curve with the vertical axis as the ordinate. The load rheological rate LRR is the slope at each point on the deformation-load cycle curve. The load rheological energy LRE is the total area under the deformation-load cycle curve.

6. The method for evaluating the rheological properties of asphalt mixtures according to claim 5, characterized in that, The smaller the load rheological rate LRR, the larger the load rheological energy LRE, indicating that the asphalt mixture of test sample (5) has a stronger load rheological resistance.

7. The method for evaluating the rheological properties of asphalt mixtures according to claim 6, characterized in that, The gantry loading frame (42) is a gantry structure consisting of a crossbar and two support rods connected together. Each of the two support rods is provided with a steering bearing (422) at its bottom end. There are two test wheels (43), with one test wheel (43) corresponding to the bottom of each steering bearing (422) and the test wheel (43) is connected to the steering bearing (422). The force transmission column (421) is connected to the crossbar.

8. The method for evaluating the rheological properties of asphalt mixtures according to claim 7, characterized in that, The testing device also includes a support device (3) placed inside the constant temperature test chamber (1). The support device (3) includes a first support frame (31), a second support frame (32), and a crossbeam (33) located below the pressure rod (41), respectively. The displacement sensor (63) is placed on the crossbeam (33) and located next to the force transmission column (421). The first support frame (31) and the second support frame (32) are both placed vertically. The sample rotating stage (2) is located between the first support frame (31) and the second support frame (32). One end of the pressure rod (41) is connected to the bottom surface of the constant temperature test chamber (1) through the first support frame (31). The bottom end of the second support frame (32) is connected to the bottom surface of the constant temperature test chamber (1). The top end of the second support frame (32) is connected to the first support frame (31) through a horizontally placed crossbeam (33). A force transmission hole (332) is provided on the crossbeam (33). The force transmission column (421) passes through the force transmission hole (332) and is connected to the gantry loading frame (42).

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