A method for obtaining strength and dynamic modulus of existing asphalt pavement materials

Abstract

The invention discloses a method for obtaining the strength and dynamic modulus of existing asphalt pavement materials, including making asphalt mixture specimens of different thicknesses; obtaining the uniaxial compression and indirect tensile strength and dynamic modulus of the specimens of different thicknesses, and obtaining the variation law of the uniaxial compression and indirect tensile strength and dynamic modulus with thickness, and obtaining the mapping relationship between uniaxial compression and indirect tensile strength and dynamic modulus, and performing uniaxial compression and indirect tensile tests by drilling core samples of existing asphalt pavement, and then obtaining the uniaxial compression strength and dynamic modulus values ​​of strength and dynamic modulus under corresponding standard sizes according to the conversion relationship. The invention aims to make the measured data more accurate, and then obtain the existing asphalt pavement life extension design parameters that are more in line with the actual pavement state.

Description

Technical Field

[0001] The invention relates to the technical field of highway design and construction, and in particular to a method for obtaining the strength and dynamic modulus of an existing asphalt pavement material. Background Art

[0002] At present, asphalt pavements will develop certain pavement diseases after a long period of service under the influence of vehicles and the natural environment. With the continuous increase in traffic volume, the sustainable use of existing asphalt pavements will become more important. Therefore, in order to effectively increase the service life of asphalt pavements, it is necessary to repair and maintain the asphalt pavements, and reasonable life extension design can effectively extend the service life of existing asphalt pavements.

[0003] At present, one of the key issues in the life extension design of existing asphalt pavements is to accurately obtain the strength and dynamic modulus parameters of each structural layer of the existing asphalt pavement. These data are crucial for establishing a reliable life extension design model and formulating a reasonable maintenance plan. Existing technicians mainly use high-precision pavement non-destructive testing instruments to qualitatively and quantitatively evaluate the remaining life of the existing pavement structure and obtain the structural parameters of the existing asphalt pavement from the two aspects of structural integrity and modulus attenuation. However, what is obtained is the overall mechanical parameters of the pavement structure, and the parameters of each structural layer of the pavement cannot be accurately obtained. Furthermore, in terms of evaluating the mechanical properties of existing asphalt pavements and testing the conformity of the modulus and strength of the pavement structure layers, coring from the actual pavement is the most effective method to obtain test specimens. However, the thickness of most asphalt pavement surface layers is generally determined based on the principle of 2.5 to 3 times the maximum particle size. The core thickness of the current conventional asphalt surface layer is far from reaching the height of 100mm for the uniaxial compression strength test and the height of 150mm for the uniaxial compression dynamic modulus test specified in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), making it difficult to directly use the uniaxial compression test method to test the modulus and strength of the asphalt mixture in the actual pavement structure.

[0004] The invention patent with the existing patent publication number CN106483011A discloses a dynamic detection method and a fastening device for each layer of an asphalt pavement, which includes: detecting the dynamic modulus of the upper layer, middle layer and lower layer of the original pavement. It adopts a simple performance tester SPT or a loading device that can apply a load in the form of an offset sine wave or a half-positive wave, with a frequency range of 0.1 to 25Hz, and the maximum stress level should reach 2800KPa, and the loading resolution can reach 5N. Apply an offset sine wave or a half-positive wave axial compressive stress to each layer of the core sample, measure the axial strain that can be recovered by the test piece, and calculate the uniaxial compression dynamic modulus of each layer of the in-service asphalt pavement within the range of linear viscoelasticity. The strict requirements of the existing dynamic modulus detection equipment on the size of the core sample are solved. The measurable thickness range of the core sample is 3cm to 15cm, and the material parameters of each layer of the existing asphalt pavement can be calculated, and it is used to evaluate the current status of each layer of the in-service asphalt pavement and predict the remaining life of the old road. It can be seen that the Velcro device is used to simulate the stress on the core sample of the asphalt pavement and obtain the uniaxial compression dynamic modulus of the core sample. However, a large number of existing research results show that there are significant differences and correlations between the indirect tensile and uniaxial compression strengths of asphalt mixtures, and the indirect tensile and uniaxial compression dynamic moduli. Furthermore, there are discrepancies between the data measured in the prior art and the actual data. Therefore, in order to accurately obtain the design parameters of the existing pavement structure layer - strength and modulus, it is urgent to propose a new method for obtaining the strength and dynamic modulus parameters of existing asphalt pavement materials. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for obtaining the strength and dynamic modulus of existing asphalt pavement materials, aiming to solve the technical problem of inaccurate determination of the existing strength and dynamic modulus parameters of existing asphalt pavement materials.

[0006] To achieve the above object, the present invention provides a method for obtaining the strength and dynamic modulus of an existing asphalt pavement material, the method comprising the following steps:

[0007] Step 1, preparing upper layer, middle layer and lower layer asphalt mixture specimens corresponding to asphalt pavements of different thicknesses;

[0008] Step 2, respectively performing an indirect tensile strength test, an indirect tensile dynamic modulus test, a uniaxial compression strength test, and a uniaxial compression dynamic modulus test on the mixture specimens of each surface layer at different thicknesses, to obtain the indirect tensile strength, indirect tensile dynamic modulus, uniaxial compression strength, and uniaxial compression dynamic modulus of the mixture specimens of each surface layer at different thicknesses;

[0009] Step 3, according to the uniaxial compressive strength of the mixture specimens at different thicknesses of each surface layer, a conversion ratio fitting formula 1 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of the corresponding surface layer at different thicknesses is obtained;

[0010] According to the uniaxial compression dynamic modulus of the mixture specimens at different thicknesses of each surface layer, a conversion ratio fitting formula 2 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of the corresponding surface layer at different thicknesses is obtained;

[0011] Step 4, according to the uniaxial compressive strength of the first standard size specimens of each surface layer and the indirect tensile strength of the mixture specimens of each surface layer at different thicknesses, obtain the conversion ratio fitting formula 3 between the uniaxial compressive strength of the first standard size specimens of each surface layer and the indirect tensile strength of the corresponding surface layer at different thicknesses;

[0012] According to the uniaxial compression dynamic modulus of the second standard size specimens of each surface layer and the indirect tensile dynamic modulus of the mixture specimens of each surface layer at different thicknesses, the conversion ratio fitting formula 4 between the uniaxial compression dynamic modulus of the second standard size specimens of each surface layer and the indirect tensile dynamic modulus of the corresponding surface layer at different thicknesses is obtained;

[0013] Step 5, obtaining specimens of different thicknesses of each surface layer of the existing asphalt pavement on site, and conducting indirect tensile strength test, indirect tensile dynamic modulus test, uniaxial compression strength test and uniaxial compression dynamic modulus test, to obtain the indirect tensile strength, indirect tensile dynamic modulus, uniaxial compression strength and uniaxial compression dynamic modulus corresponding to different thickness sizes of each surface layer;

[0014] Step 6, obtaining the uniaxial compressive strength of the first standard size of each surface layer based on the indirect tensile strength test according to the indirect tensile strength corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 3 in step 4, and obtaining the uniaxial compressive strength of the first standard size of each surface layer based on the uniaxial compressive strength test according to the uniaxial compressive strength corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 1 in step 3, and calculating the mean of the uniaxial compressive strength of the first standard size of each surface layer based on the indirect tensile strength test and the uniaxial compressive strength of the first standard size of each surface layer based on the uniaxial compressive strength test, to obtain the uniaxial compressive strength of the first standard size of each surface layer;

[0015] According to the indirect tensile dynamic modulus corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 4 in step 4, the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the indirect tensile dynamic modulus test is obtained, and according to the uniaxial compression dynamic modulus corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 2 in step 3, the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the uniaxial compression dynamic modulus test is obtained, and the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the indirect tensile dynamic modulus test and the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the uniaxial compression strength test are averaged to obtain the uniaxial compression dynamic modulus of the second standard size of each surface layer.

[0016] Optionally, in step 3, the step of obtaining a conversion ratio fitting formula 1 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of the corresponding surface layer at different thicknesses according to the uniaxial compressive strength of the mixture specimens of each surface layer at different thicknesses includes:

[0017] The uniaxial compressive strength of the first standard size specimen of each surface layer is divided by the uniaxial compressive strength of different thicknesses to obtain the conversion ratio between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of different thicknesses;

[0018] The conversion ratio between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of different thicknesses is fitted to obtain the conversion ratio fitting formula 1 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of any thickness.

[0019] Optionally, in step 3, the step of obtaining a conversion ratio fitting formula 2 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of the corresponding surface layer of different thicknesses according to the uniaxial compression dynamic modulus of the mixture specimens of each surface layer at different thicknesses includes:

[0020] The uniaxial compression dynamic modulus of the second standard size specimen of each surface layer is divided by the uniaxial compression dynamic modulus of different thicknesses to obtain the conversion ratio between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of different thicknesses;

[0021] The conversion ratio between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of different thicknesses is fitted to obtain the conversion ratio fitting formula 2 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of any thickness.

[0022] Optionally, in step 4, the step of obtaining a conversion ratio fitting formula 3 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength of the corresponding surface layer at different thicknesses according to the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength of the mixture specimen of each surface layer at different thicknesses includes:

[0023] The uniaxial compressive strength of the first standard size specimen of each surface layer is divided by the indirect tensile strength of the corresponding surface layer with different thicknesses to obtain the conversion ratio between the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength with different thicknesses;

[0024] The conversion ratio between the uniaxial compressive strength of each surface layer of the standard size specimen and the indirect tensile strength of different thicknesses is fitted to obtain the conversion ratio fitting formula 3 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength of any thickness.

[0025] Optionally, in step 4, the step of obtaining a conversion ratio fitting formula 4 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the indirect tensile dynamic modulus of the corresponding surface layer at different thicknesses according to the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the indirect tensile dynamic modulus of the mixture specimen of each surface layer at different thicknesses includes:

[0026] The uniaxial compression dynamic modulus of the second standard size specimen of each surface layer is divided by the indirect tensile dynamic modulus of the corresponding surface layer with different thicknesses to obtain the conversion ratio between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the indirect tensile dynamic modulus of different thicknesses;

[0027] The conversion ratio between the uniaxial compression dynamic modulus of each surface layer of the standard-sized specimen and the indirect tensile dynamic modulus of different thicknesses is fitted to obtain the conversion ratio fitting formula 4 between the uniaxial compression dynamic modulus of each surface layer of the standard-sized specimen and the indirect tensile dynamic modulus of any thickness.

[0028] Optionally, in step 1, the asphalt mixture specimen is a cylinder with a thickness of 30 to 150 mm and a diameter of 100 mm.

[0029] Optionally, the indirect tensile strength test, indirect tensile dynamic modulus test, uniaxial compression strength test and uniaxial compression dynamic modulus test in step 2 are all measured using a multifunctional material testing machine MTS-Landmark.

[0030] To achieve the above-mentioned objectives, the present invention also provides a system for obtaining the strength and dynamic modulus of existing asphalt pavement materials, including a memory, a processor, and a program for obtaining the strength and dynamic modulus of existing asphalt pavement materials stored in the memory and executable on the processor. When the program for obtaining the strength and dynamic modulus of existing asphalt pavement materials is executed by the processor, the steps of the method for obtaining the strength and dynamic modulus of existing asphalt pavement materials as described above are implemented.

[0031] To achieve the above-mentioned purpose, the present invention also provides a storage medium, on which is stored a program for obtaining the strength and dynamic modulus of existing asphalt pavement materials. When the program for obtaining the strength and dynamic modulus of existing asphalt pavement materials is executed by a processor, the steps of the method for obtaining the strength and dynamic modulus of existing asphalt pavement materials as described above are implemented.

[0032] Beneficial effects:

[0033] (1) The present invention prepares asphalt mixture specimens of different thicknesses of each surface layer, and successively conducts uniaxial compression and indirect tensile strength and dynamic modulus tests, thereby obtaining the variation law of uniaxial compression and indirect tensile strength and dynamic modulus with the thickness of the specimen, and obtains the conversion ratio fitting formula 1 between the uniaxial compression strength of the first standard size specimen of each surface layer and the uniaxial compression strength of the corresponding surface layer with different thicknesses, the conversion ratio fitting formula 2 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of the corresponding surface layer with different thicknesses, the conversion ratio fitting formula 3 between the uniaxial compression strength of the first standard size specimen of each surface layer and the indirect tensile strength of the corresponding surface layer with different thicknesses, and the conversion ratio fitting formula 4 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the indirect tensile dynamic modulus of the corresponding surface layer with different thicknesses, and obtains core samples of each surface layer of the existing asphalt pavement for uniaxial compression and indirect tensile tests, and then obtains the strength and dynamic modulus design parameters of each surface layer of the existing asphalt pavement under standard size according to the conversion ratio fitting formula. This method effectively combines uniaxial compression and indirect tensile strength and dynamic modulus tests, avoiding large deviations in the results of a single test, making the final data more consistent with the actual pavement stress state, and making the measured uniaxial compression strength and uniaxial compression dynamic modulus data of existing asphalt pavements more accurate, ultimately making the basis for pavement design clearer and the design effect better.

[0034] (2) By conducting on-site core sampling tests and testing of existing asphalt pavements, the structural design parameters of existing asphalt pavement materials can be obtained, which can provide a scientific basis for evaluating the remaining life of the pavement and formulating maintenance and repair plans, thereby extending the service life of the pavement. Furthermore, this method can be widely used in various road engineering maintenance, renovation and expansion projects, and can be used for the maintenance of existing asphalt pavements that are approaching or have exceeded their design service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of a system for acquiring strength and dynamic modulus of existing asphalt pavement materials involved in an embodiment of the present invention;

[0036] Figure 2 It is a flow chart of the first embodiment of the method for obtaining the strength and dynamic modulus of existing asphalt pavement materials of the present invention;

[0037] Figure 3 is the fitted linear graph of the uniaxial compressive strength of AC-13 versus thickness;

[0038] Figure 4 is the fitted linear graph of the uniaxial compressive strength of SMA-13 ​​versus thickness;

[0039] Figure 5 is the fitted linear graph of the indirect tensile strength of AC-13 versus thickness;

[0040] Figure 6 is the fitted linear graph of the indirect tensile strength of SMA-13 ​​versus thickness;

[0041] Figure 7 is the fitted linear graph of the uniaxial compression dynamic modulus of AC-13 versus thickness;

[0042] Figure 8 It is the fitted linear graph of uniaxial compression dynamic modulus of SMA-13 ​​versus thickness;

[0043] Fig. 9 is the fitted linear graph of the indirect tensile dynamic modulus of AC-13 versus thickness;

[0044] Fig.10 is the fitted linear graph of the indirect tensile dynamic modulus of SMA-13 ​​versus thickness;

[0045] Fig.11 Schematic diagram of the method for obtaining the strength and dynamic modulus parameters of existing asphalt pavement materials.

[0046] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0047] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0048] like Figure 1 As shown, Figure 1 It is a structural schematic diagram of a system for acquiring strength and dynamic modulus of existing asphalt pavement materials involved in an embodiment of the present invention.

[0049] like Figure 1 As shown, the system may include: a processor 1001, such as a CPU, a communication bus 1002, a user interface 1003, a network interface 1004, and a memory 1005. Among them, the communication bus 1002 is used to realize the connection and communication between these components. The user interface 1003 can be an infrared receiving module for receiving control instructions triggered by a user through a remote control. The optional user interface 1003 can also include a standard wired interface and a wireless interface. The network interface 1004 can optionally include a standard wired interface and a wireless interface (such as a WI-FI interface). The memory 1005 can be a high-speed RAM memory, or a stable memory (non-volatile memory), such as a disk memory. The memory 1005 can also be a storage device independent of the aforementioned processor 1001.

[0050] Those skilled in the art will understand that Figure 1 The structure of the system for obtaining the strength and dynamic modulus of existing asphalt pavement materials shown in the figure does not constitute a limitation of the system for obtaining the strength and dynamic modulus of existing asphalt pavement materials, and may include more or fewer components than shown in the figure, or a combination of certain components, or a different arrangement of components.

[0051] The specific embodiments of the system for obtaining the strength and dynamic modulus of existing asphalt pavement materials of the present invention are basically the same as the embodiments of the method for obtaining the strength and dynamic modulus of existing asphalt pavement materials described below, and are not described in detail here.

[0052] Reference Figure 2 , is a flow chart of a first embodiment of an improved method for obtaining strength and dynamic modulus of an existing asphalt pavement material according to the present invention, the method comprising the following steps:

[0053] Step 1, make asphalt mixture specimens of different thicknesses, specifically, use the same asphalt type, aggregate type, mineral powder type, gradation curve, asphalt dosage, aggregate dosage, and mineral powder dosage as the asphalt layer of the existing asphalt pavement, generally use rotary compaction to form a cylindrical specimen with a diameter of 100mm, and then cut it into asphalt mixture specimens with a thickness of 30 to 150mm according to the thickness of the upper layer, middle layer, and lower layer corresponding to the preset asphalt pavement of different thicknesses. Preferably, cylindrical specimens with thicknesses of 30, 40, 70, 100, 130, and 150mm are selected, and the void ratio of specimens of different thicknesses is measured to ensure that the deviation between the void ratio of the formal specimen and the target void ratio is controlled within the range of ±0.50%, and five parallel tests are set under each size condition.

[0054] Step 2, conducting indirect tensile strength test, indirect tensile dynamic modulus test, uniaxial compression strength test and uniaxial compression dynamic modulus test on the mixture specimens of each surface layer at different thicknesses, to obtain the indirect tensile strength, indirect tensile dynamic modulus, uniaxial compression strength and uniaxial compression dynamic modulus of the mixture specimens of each surface layer at different thicknesses.

[0055] Specifically, the uniaxial compression strength test, uniaxial compression dynamic modulus test, indirect tensile strength test, and indirect tensile dynamic modulus test were all measured using the multifunctional material testing machine MTS-Landmark. Before the test, the specimen was kept at a constant temperature of 20°C for 5 hours. The test temperature was controlled at 20°C, the loading rate of the uniaxial compression strength test was controlled at 2mm / min, and the frequency of the uniaxial compression dynamic modulus test was controlled at 10Hz. The stress control mode was used during the loading process, and a sine wave was applied to the specimen. The displacement of the specimen during the test loading process was measured using an external extensometer displacement sensor. In the uniaxial compression strength test, in order to reduce the influence of the end effect between the specimen surface and the upper and lower loading plates, a layer of polytetrafluoroethylene film with a thickness of 0.3mm±0.5mm was placed between the upper and lower surfaces of the specimen and the loading plates. And before the uniaxial compression dynamic modulus test, the specimen was first subjected to loading pretreatment. The pretreatment method was to apply a sine wave axial compressive stress test load to the specimen at a frequency of 25Hz for 200 cycles. At the same time, the indirect tensile test operation of asphalt mixture is basically the same as the uniaxial compression test, the difference is the force mode of the specimen. The loading rate of the indirect tensile strength test is controlled at 50mm / min, and the dynamic modulus test is considered to be a non-destructive test.

[0056] The uniaxial compressive strength calculation formula is as follows:

[0057]

[0058] Where: R c is the uniaxial compressive strength, MPa; P is the maximum load when the specimen is destroyed, N; D is the diameter of the specimen, mm.

[0059] The calculation formula of uniaxial compression dynamic modulus is as follows:

[0060]

[0061] Where: |E * | is the uniaxial compression dynamic modulus, MPa; σ0 is the axial stress amplitude, MPa; ε0 is the axial strain amplitude, mm / mm; P i is the average amplitude of the axial test load in the last five loading cycles, N; l0 is the measurement spacing of the displacement sensor on the specimen, mm; A is the radial cross-sectional area of ​​the specimen, mm 2 ; Δ iis the average amplitude of recoverable axial deformation in the last five loading cycles, mm.

[0062] The indirect tensile strength calculation formula is as follows (3) (the negative sign represents the tensile force):

[0063]

[0064] Where: t is the indirect tensile strength, MPa; P t is the maximum load when the specimen is destroyed, N; L is the specimen thickness, mm; D is the specimen diameter, mm.

[0065] And the indirect tensile dynamic modulus calculation formula is as follows:

[0066]

[0067] Where: E t is the indirect tensile dynamic modulus, MPa; P is the average amplitude of the test load in the last five loading cycles, N; μ is the Poisson's ratio; L' is the length between the two blades of the extensometer, mm; is the average amplitude of the recoverable axial strain (microstrain 10 -6 ).

[0068] The uniaxial compression strength test and the indirect tensile strength test are carried out to obtain the uniaxial compression strength and the indirect tensile strength corresponding to the asphalt mixture at different thicknesses, and then the mapping relationship between the uniaxial compression strength and the indirect tensile strength and the different thicknesses is obtained. In this embodiment, the uniaxial compression strength test and the indirect tensile strength test of different thicknesses are carried out by taking AC-13 and SMA-13 ​​as examples, and then the change of the uniaxial compression strength and the indirect tensile strength with the thickness of the specimen is obtained, wherein, Figure 3 The uniaxial compressive strength of AC-13 varies with specimen thickness, and Figure 4 The figure shows the variation of uniaxial compressive strength of SMA-13 ​​with specimen thickness. Figure 5 The figure shows the variation of indirect tensile strength of AC-13 with specimen thickness. Figure 6 The indirect tensile strength of SMA-13 ​​varies with the thickness of the specimen.

[0069] At the same time, for the uniaxial compression dynamic modulus test and the indirect tensile dynamic modulus test, AC-13 and SMA-13 ​​were used as examples to conduct uniaxial compression dynamic modulus tests and indirect tensile dynamic modulus tests of different thicknesses, and then the mapping relationship between the uniaxial compression dynamic modulus and the indirect tensile dynamic modulus and different thicknesses was obtained. Figure 7 The figure shows the variation of the uniaxial compression dynamic modulus of AC-13 with the thickness of the specimen. Figure 8The figure shows the variation of the uniaxial compression dynamic modulus of SMA-13 ​​with the thickness of the specimen. Fig. 9 The figure shows the variation of the indirect tensile dynamic modulus of AC-13 with the thickness of the specimen. Fig.10 Shown is the variation of the indirect tensile dynamic modulus of SMA-13 ​​with specimen thickness.

[0070] Preferably, in order to more accurately compare the correlation between the uniaxial compression and indirect tension dynamic moduli, the same asphalt mixture specimen is used to perform uniaxial compression and indirect tension dynamic modulus tests respectively.

[0071] Step 3, according to the uniaxial compressive strength of the mixture specimens at different thicknesses of each surface layer, the conversion ratio fitting formula 1 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of the corresponding surface layer at different thicknesses is obtained. Among them, the first standard size specimen for uniaxial compressive strength refers to a specimen with a specimen height of 100mm, and the second standard size specimen for uniaxial compression dynamic modulus refers to a specimen with a specimen height of 150mm. Then UCS 100 is the uniaxial compressive strength of the first standard size specimen, UCS x is the uniaxial compressive strength of the mixture specimens at different thicknesses, UCS 100 / UCS x is the conversion coefficient, as shown in Table 1.

[0072] Table 1 is UCS 100 / UCS x Conversion factor

[0073]

[0074] After fitting according to the conversion ratio coefficient in Table 1, the uniaxial compressive strength conversion ratio fitting formula 1 of AC-13 and SMA-13 ​​specimens is obtained, as shown in the following formula (5).

[0075]

[0076] According to the uniaxial compression dynamic modulus of the mixture specimens at different thicknesses of each surface layer, the conversion ratio fitting formula 2 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of the corresponding surface layer of different thicknesses is obtained.

[0077] Among them, UCM 150 is the uniaxial compression dynamic modulus of the second standard size specimen, UCM x is the uniaxial compression dynamic modulus of the mixture specimens at different thicknesses, UCM 150 / UCM x The conversion ratio coefficient is shown in Table 2.

[0078] Table 2 shows the UCM 150 / UCM x Conversion factor

[0079]

[0080] After fitting according to the conversion ratio coefficient in Table 2, the uniaxial compression dynamic modulus conversion ratio fitting formula 2 of the AC-13 and SMA-13 ​​specimens is obtained, as shown in the following formula (7).

[0081]

[0082] Step 4: According to the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength of the mixture specimen of each surface layer at different thicknesses, the conversion ratio fitting formula 3 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength of the corresponding surface layer at different thicknesses is obtained. Among them, the indirect tensile strength of the mixture specimen at different thicknesses is expressed by ITS x The proportionality coefficient between the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength of the corresponding surface layer of different thickness is expressed by UCS 100 / ITS x To express, as shown in the following Table 3:

[0083] Table 3 is UCS 100 / ITS x Conversion factor

[0084]

[0085] According to the proportional coefficient obtained in Table 3, the conversion ratio fitting formula 3 of AC-13 and SMA-13 ​​specimens is obtained after further fitting, as shown in the following formula (8).

[0086]

[0087] According to the uniaxial compression dynamic modulus of the second standard size specimens of each surface layer and the indirect tensile dynamic modulus of the mixed material specimens at different thicknesses of each surface layer, the conversion ratio fitting formula 4 between the uniaxial compression dynamic modulus of the second standard size specimens of each surface layer and the indirect tensile dynamic modulus of the corresponding surface layer with different thicknesses is obtained. Among them, the indirect tensile dynamic modulus of the mixed material specimens at different thicknesses is expressed by ITM x The proportionality coefficient between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the indirect tensile dynamic modulus of the corresponding surface layer of different thickness is expressed by UCM 150 / ITM x To express, as shown in Table 4.

[0088] Table 4 shows the UCM 150 / ITMx Conversion factor

[0089]

[0090] According to the proportional coefficient obtained in Table 4, the conversion ratio fitting formula 4 of AC-13 and SMA-13 ​​specimens is obtained after further fitting, as shown in the following formula (9).

[0091]

[0092] Step 5, obtain specimens of different thicknesses of each surface layer of the existing asphalt pavement, and conduct indirect tensile strength test, indirect tensile dynamic modulus test, uniaxial compression strength test and uniaxial compression dynamic modulus test to obtain the indirect tensile strength, indirect tensile dynamic modulus, uniaxial compression strength and uniaxial compression dynamic modulus corresponding to the different thickness sizes of each surface layer. Specifically, Fig.11 As shown, samples of each surface layer of the existing asphalt pavement were obtained on site and subjected to indirect tensile strength test, indirect tensile dynamic modulus test, uniaxial compression strength test and uniaxial compression dynamic modulus test. The tests were measured using the multifunctional material testing machine MTS-Landmark, and the basic operation was the same as that of the aforementioned mixture specimens.

[0093] Step 6, for obtaining the uniaxial compressive strength of the first standard size of each surface layer of the existing asphalt pavement, is obtained by respectively obtaining the uniaxial compressive strength of the first standard size of each surface layer based on the indirect tensile strength test and the uniaxial compressive strength of the first standard size of each surface layer based on the uniaxial compressive strength test, and then calculating the average.

[0094] Specifically, according to the indirect tensile strength corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 3 in step 4, the uniaxial compressive strength of the first standard size of each surface layer based on the indirect tensile strength test is obtained, that is, the different thickness specimens of each surface layer of the existing asphalt pavement site obtained in step 5 are substituted into the conversion ratio fitting formula 3, and then the proportionality coefficient between the uniaxial compressive strength of the first standard size specimen based on the indirect tensile strength test and the indirect tensile strength of the specimens with different thicknesses is obtained, and the obtained proportionality coefficient is multiplied by the indirect tensile strength corresponding to the different thickness sizes of each surface layer obtained in step 5 to obtain the uniaxial compressive strength of the first standard size specimen of each surface layer of the existing asphalt pavement site based on the indirect tensile strength test.

[0095] And according to the uniaxial compressive strength corresponding to different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 1 in step 3, the uniaxial compressive strength of the first standard size of each surface layer based on the uniaxial compressive strength test is obtained, that is, the different thickness specimens of each surface layer obtained in step 5 are substituted into the conversion ratio fitting formula 1, and then the proportional coefficient between the uniaxial compressive strength of the first standard size specimens of each surface layer based on the single-pulling compression strength test and the uniaxial compressive strength of different thicknesses is obtained, and the obtained proportional coefficient is multiplied by the uniaxial compressive strength corresponding to different thickness sizes of each surface layer obtained in step 5 to obtain the uniaxial compressive strength of the first standard size specimens of each surface layer of the existing asphalt pavement on site based on the uniaxial compression strength test.

[0096] Furthermore, the uniaxial compressive strength of the first standard size of each surface layer based on the indirect tensile strength test and the uniaxial compressive strength of the first standard size of each surface layer based on the uniaxial compressive strength test are averaged to obtain the uniaxial compressive strength of the first standard size of each surface layer of the existing asphalt pavement.

[0097] Furthermore, for obtaining the uniaxial compression dynamic modulus of the second standard size of each surface layer, it is achieved by respectively obtaining the uniaxial compression dynamic modulus of the second standard size of each surface layer based on an indirect tensile dynamic modulus test and the uniaxial compression dynamic modulus of the second standard size of each surface layer based on a uniaxial compression dynamic modulus test, and then calculating the average.

[0098] Specifically, according to the indirect tensile dynamic modulus corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 4 in step 4, the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the indirect tensile dynamic modulus test is obtained, that is, the different thickness specimens of each surface layer of the existing asphalt pavement site obtained in step 5 are substituted into the conversion ratio fitting formula 4, and then the proportional coefficient of the uniaxial compression dynamic modulus of the second standard size specimen based on the indirect tensile dynamic modulus test and the indirect tensile dynamic modulus of the specimens with different thicknesses is obtained, and the obtained proportional coefficient is multiplied with the indirect tensile dynamic modulus corresponding to the different thickness sizes of each surface layer obtained in step 5 to obtain the uniaxial compression dynamic modulus of the second standard size of each surface layer of the existing asphalt pavement site based on the indirect tensile dynamic modulus test.

[0099] And according to the uniaxial compression dynamic modulus corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 2 in step 3, the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the uniaxial compression dynamic modulus test is obtained, that is, the different thickness specimens of each surface layer of the existing asphalt pavement site obtained in step 5 are substituted into the conversion ratio fitting formula 2, and then the proportional coefficient of the uniaxial compression dynamic modulus of the second standard size specimen based on the uniaxial compression dynamic modulus test and the uniaxial compression dynamic modulus of the specimens with different thicknesses is obtained, and the obtained proportional coefficient is multiplied with the uniaxial compression dynamic modulus corresponding to the different thickness sizes of each surface layer obtained in step 5 to obtain the uniaxial compression dynamic modulus of the second standard size of each surface layer of the existing asphalt pavement site based on the uniaxial compression dynamic modulus test.

[0100] Furthermore, the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the indirect tensile dynamic modulus test and the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the uniaxial compression strength test are averaged to obtain the uniaxial compression dynamic modulus of the second standard size of each surface layer.

[0101] In this embodiment, asphalt mixture specimens of different thicknesses of each surface layer are prepared, and uniaxial compression, indirect tensile strength and dynamic modulus tests are carried out successively; then the variation law of uniaxial compression, indirect tensile strength and dynamic modulus with specimen thickness is obtained, and the conversion ratio fitting formula 1 between the uniaxial compression strength of the first standard size specimen of each surface layer and the uniaxial compression strength of the corresponding surface layer with different thicknesses is obtained, the conversion ratio fitting formula 2 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of the corresponding surface layer with different thicknesses is obtained, the conversion ratio fitting formula 3 between the uniaxial compression strength of the first standard size specimen of each surface layer and the indirect tensile strength of the corresponding surface layer with different thicknesses is obtained, and the conversion ratio fitting formula 4 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the indirect tensile dynamic modulus of the corresponding surface layer with different thicknesses is obtained, and core sampling is performed to obtain asphalt mixture specimens of each surface layer of the existing asphalt pavement for uniaxial compression and indirect tensile tests, and then the strength and dynamic modulus design parameters of the existing asphalt pavement of each surface layer of the existing asphalt pavement under standard size are obtained according to the conversion ratio fitting formula. This method effectively combines uniaxial compression and indirect tensile strength and dynamic modulus tests, avoiding large deviations in the results of a single test, making the final data more consistent with the actual pavement stress state, and making the measured uniaxial compression strength and uniaxial compression dynamic modulus data of existing asphalt pavements more accurate, ultimately making the basis for pavement design clearer and the design effect better.

[0102] Furthermore, in order to better illustrate the influence of the above-mentioned uniaxial compression size effect and indirect tension size effect on the asphalt pavement strength and dynamic modulus acquisition method, the following uses AC-13 and SMA-13 ​​asphalt mixtures as examples for explanation.

[0103] (1) Scope of application of the method for obtaining the strength and dynamic modulus of existing asphalt pavement based on uniaxial compression size effect:

[0104] like Figure 3-4 As shown in the figure, the trend of the uniaxial compressive strength of AC-13 and SMA-13 ​​asphalt mixtures with thickness shows that when the specimen thickness is small (specimen thickness < 70mm), the uniaxial compressive strength changes with thickness and the data is more discrete; when the specimen thickness is large (specimen thickness > 70mm), the uniaxial compressive strength changes with thickness and the data is less discrete. Figure 7-8 As shown in the figure, the trend of the dynamic modulus of AC-13 and SMA-13 ​​asphalt mixtures in uniaxial compression with thickness also shows that when the specimen thickness is small (specimen thickness < 70mm), the trend of the dynamic modulus of uniaxial compression with thickness is obvious, and the data discreteness is large; when the specimen thickness is large (specimen thickness > 70mm), the trend of the dynamic modulus of uniaxial compression with thickness tends to be stable, and the data discreteness is small. Therefore, the method for obtaining the strength and dynamic modulus of existing asphalt pavements based on the uniaxial compression size effect is suitable for existing asphalt pavements with asphalt layer thickness greater than 70mm.

[0105] (2) Scope of application of the method for obtaining the strength and dynamic modulus of existing asphalt pavement based on indirect tensile size effect:

[0106] like Figure 5-6 As shown in the figure, the trend of indirect tensile strength of AC-13 and SMA-13 ​​asphalt mixtures with thickness shows that within the studied thickness range of 30mm-150mm, the trend of indirect tensile strength with thickness tends to be stable, and the data discreteness is small. Figure 9-10 As shown in the figure, it can be seen from the trend diagram of the indirect tensile dynamic modulus of AC-13 and SMA-13 ​​asphalt mixtures with thickness that within the studied thickness range of 30mm-150mm, the trend of the indirect tensile dynamic modulus with thickness tends to be stable, and the data discreteness is small; therefore, the method for obtaining the strength and dynamic modulus of existing asphalt pavement based on the indirect tensile size effect is not limited by the thickness of the asphalt layer of the existing asphalt pavement, and the strength, dynamic modulus and thickness of asphalt mixtures of different gradations basically satisfy the two-variable first-order equation, that is, they are linearly distributed.

[0107] In addition, an embodiment of the present invention also proposes a storage medium, on which is stored a program for obtaining the strength and dynamic modulus of existing asphalt pavement materials. When the program for obtaining the strength and dynamic modulus of existing asphalt pavement materials is executed by a processor, the steps of the method for obtaining the strength and dynamic modulus of existing asphalt pavement materials as described above are implemented.

[0108] The specific embodiments of the readable storage medium of the present invention are basically the same as the embodiments of the above-mentioned existing asphalt pavement material strength and dynamic modulus acquisition method, and will not be described in detail here.

[0109] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0110] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0111] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for obtaining the strength and dynamic modulus of an existing asphalt pavement material, characterized in that: The method comprises the following steps: Step 1, preparing upper layer, middle layer and lower layer asphalt mixture specimens corresponding to asphalt pavements of different thicknesses; Step 2, respectively performing an indirect tensile strength test, an indirect tensile dynamic modulus test, a uniaxial compression strength test, and a uniaxial compression dynamic modulus test on the mixture specimens of each surface layer at different thicknesses, to obtain the indirect tensile strength, indirect tensile dynamic modulus, uniaxial compression strength, and uniaxial compression dynamic modulus of the mixture specimens of each surface layer at different thicknesses; Step 3, according to the uniaxial compressive strength of the mixture specimens at different thicknesses of each surface layer, a conversion ratio fitting formula 1 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of the corresponding surface layer at different thicknesses is obtained; According to the uniaxial compression dynamic modulus of the mixture specimens at different thicknesses of each surface layer, a conversion ratio fitting formula 2 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of the corresponding surface layer at different thicknesses is obtained; Step 4, according to the uniaxial compressive strength of the first standard size specimens of each surface layer and the indirect tensile strength of the mixture specimens of each surface layer at different thicknesses, obtain the conversion ratio fitting formula 3 between the uniaxial compressive strength of the first standard size specimens of each surface layer and the indirect tensile strength of the corresponding surface layer at different thicknesses; According to the uniaxial compression dynamic modulus of the second standard size specimens of each surface layer and the indirect tensile dynamic modulus of the mixture specimens of each surface layer at different thicknesses, the conversion ratio fitting formula 4 between the uniaxial compression dynamic modulus of the second standard size specimens of each surface layer and the indirect tensile dynamic modulus of the corresponding surface layer at different thicknesses is obtained; Step 5, obtaining specimens of different thicknesses of each surface layer of the existing asphalt pavement on site, and conducting indirect tensile strength test, indirect tensile dynamic modulus test, uniaxial compression strength test and uniaxial compression dynamic modulus test, to obtain the indirect tensile strength, indirect tensile dynamic modulus, uniaxial compression strength and uniaxial compression dynamic modulus corresponding to different thickness sizes of each surface layer; Step 6, obtaining the uniaxial compressive strength of the first standard size of each surface layer based on the indirect tensile strength test according to the indirect tensile strength corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 3 in step 4, and obtaining the uniaxial compressive strength of the first standard size of each surface layer based on the uniaxial compressive strength test according to the uniaxial compressive strength corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 1 in step 3, and calculating the mean of the uniaxial compressive strength of the first standard size of each surface layer based on the indirect tensile strength test and the uniaxial compressive strength of the first standard size of each surface layer based on the uniaxial compressive strength test, to obtain the uniaxial compressive strength of the first standard size of each surface layer; According to the indirect tensile dynamic modulus corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 4 in step 4, the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the indirect tensile dynamic modulus test is obtained, and according to the uniaxial compression dynamic modulus corresponding to the different thickness sizes of each surface layer obtained in step 5 and the conversion ratio fitting formula 2 in step 3, the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the uniaxial compression dynamic modulus test is obtained, and the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the indirect tensile dynamic modulus test and the uniaxial compression dynamic modulus of the second standard size of each surface layer based on the uniaxial compression strength test are averaged to obtain the uniaxial compression dynamic modulus of the second standard size of each surface layer; Wherein in step 3, the step of obtaining the conversion ratio fitting formula 1 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of the corresponding surface layer with different thicknesses according to the uniaxial compressive strength of the mixture specimens of each surface layer at different thicknesses includes: The uniaxial compressive strength of the first standard size specimen of each surface layer is divided by the uniaxial compressive strength of different thicknesses to obtain the conversion ratio between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of different thicknesses; Fitting the conversion ratio between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of different thicknesses, to obtain the conversion ratio fitting formula 1 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the uniaxial compressive strength of any thickness; Wherein in step 3, the step of obtaining the conversion ratio fitting formula 2 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of the corresponding surface layer of different thicknesses according to the uniaxial compression dynamic modulus of the mixture specimens of each surface layer at different thicknesses includes: The uniaxial compression dynamic modulus of the second standard size specimen of each surface layer is divided by the uniaxial compression dynamic modulus of different thicknesses to obtain the conversion ratio between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of different thicknesses; Fitting the conversion ratio between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of different thicknesses, and obtaining the conversion ratio fitting formula 2 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the uniaxial compression dynamic modulus of any thickness; Wherein in step 4, the step of obtaining the conversion ratio fitting formula 3 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength of the corresponding surface layer at different thicknesses according to the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength of the mixture specimen of each surface layer at different thicknesses includes: The uniaxial compressive strength of the first standard size specimen of each surface layer is divided by the indirect tensile strength of the corresponding surface layer with different thicknesses to obtain the conversion ratio between the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength with different thicknesses; Fitting the conversion ratio between the uniaxial compressive strength of each surface layer of the standard size specimen and the indirect tensile strength of different thicknesses, to obtain the conversion ratio fitting formula 3 between the uniaxial compressive strength of the first standard size specimen of each surface layer and the indirect tensile strength of any thickness; Wherein in step 4, the step of obtaining the conversion ratio fitting formula 4 between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the indirect tensile dynamic modulus of the mixture specimen of each surface layer at different thicknesses according to the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the indirect tensile dynamic modulus of the mixture specimen of each surface layer at different thicknesses includes: The uniaxial compression dynamic modulus of the second standard size specimen of each surface layer is divided by the indirect tensile dynamic modulus of the corresponding surface layer with different thicknesses to obtain the conversion ratio between the uniaxial compression dynamic modulus of the second standard size specimen of each surface layer and the indirect tensile dynamic modulus of different thicknesses; The conversion ratio between the uniaxial compression dynamic modulus of each surface layer of the standard-sized specimen and the indirect tensile dynamic modulus of different thicknesses is fitted to obtain the conversion ratio fitting formula 4 between the uniaxial compression dynamic modulus of each surface layer of the standard-sized specimen and the indirect tensile dynamic modulus of any thickness.

2. The method for obtaining the strength and dynamic modulus of existing asphalt pavement materials according to claim 1, characterized in that: In step 1, the asphalt mixture specimen is a cylinder with a thickness of 30-150 mm and a diameter of 100 mm.

3. The method for obtaining the strength and dynamic modulus of existing asphalt pavement materials according to claim 1, characterized in that: The indirect tensile strength test, indirect tensile dynamic modulus test, uniaxial compression strength test and uniaxial compression dynamic modulus test in step 2 are all measured using a multifunctional material testing machine MTS-Landmark.

4. A system for obtaining the strength and dynamic modulus of existing asphalt pavement materials, characterized in that: It includes a memory, a processor, and a program for obtaining the strength and dynamic modulus of existing asphalt pavement materials, which is stored in the memory and can be run on the processor. When the program for obtaining the strength and dynamic modulus of existing asphalt pavement materials is executed by the processor, the steps of the method for obtaining the strength and dynamic modulus of existing asphalt pavement materials as described in any one of claims 1 to 3 are implemented.

5. A storage medium, characterized in that: The storage medium stores a program for obtaining the strength and dynamic modulus of existing asphalt pavement materials. When the program for obtaining the strength and dynamic modulus of existing asphalt pavement materials is executed by the processor, the steps of the method for obtaining the strength and dynamic modulus of existing asphalt pavement materials as described in any one of claims 1 to 3 are implemented.

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