A method for testing the precise mechanical parameters of new and old regions of recycled aggregate composite materials

Abstract

The present invention belongs to the field of recycled aggregate pavement composite materials, and specifically relates to a method for testing the precise mechanical parameters of new and old areas of recycled aggregate composite materials. The method performs probe scanning tests on the attached mortar-asphalt area (new area) and the attached mortar-aggregate area (old area), respectively, measures the modulus parameters of each scanning point, and statistically draws the Young's modulus-displacement relationship diagram of the new and old areas in the scanning direction, and analyzes its distribution characteristics, thereby determining the discrimination boundary and modulus interval of the new and old areas. The present invention uses microscopic testing technology to detect micro-nanomechanical changes in different regional positions, and obtains the discrimination boundary and modulus interval of the new and old areas of the recycled aggregate pavement composite material through the Young's modulus-displacement relationship diagram, providing precise micromechanical parameters for the mechanical property analysis of the recycled aggregate pavement composite material.

Description

Technical Field

[0001] The invention belongs to the field of recycled aggregate pavement composite materials, and in particular relates to a method for testing accurate mechanical parameters of new and old regions of recycled aggregate composite materials. Background Art

[0002] Recycled aggregate pavement composites are typical composite materials composed of recycled aggregate, asphalt, mineral powder, etc. Due to the cement mortar attached to the surface of the recycled aggregate, there are multiple regions on the contact surface - the attached mortar layer-asphalt region and the aggregate-attached mortar region, which are weak regions of the mechanical properties of the recycled aggregate pavement composites and key factors affecting their macroscopic performance variation. According to composite material theory, the load borne by the recycled aggregate pavement composite is jointly borne by the aggregate support and regional bonding. Therefore, its bearing capacity is not only related to the constituent materials, but also affected by the regional interaction of the constituent materials. The size of the Young's modulus determines the deformation capacity of the material. The higher the mean value of the Young's modulus, the better it is at improving the indirect tensile strength of the pavement composite and improving its crack resistance. Therefore, the mean value of the Young's modulus is very important. The region has a huge impact on the firmness of the connection between the aggregate material and the asphalt cement material. The regional interaction of multiple materials has an important impact on the working state and failure mode of the pavement composite.

[0003] However, the macro-performance experimental methods commonly used in existing research cannot characterize the micro-level areas and their material-related properties. In addition, due to the complexity of the surface connection areas, the similar material composition and micromorphology, and the uneven thickness distribution, various microscopy techniques are unable to accurately test the regional mechanical parameters, which seriously hinders the characterization of the surface connection areas of recycled aggregate pavement composites and the exploration of recycled aggregate applications.

[0004] In summary, the existing methods have the following problems: Traditional test methods cannot accurately characterize regional mechanical parameters. Probe scanning test, as a microscopic mechanical property test technology suitable for multi-material composite materials, can identify qualitative and quantitative regional mechanical property changes of multiple materials. However, the application of probe scanning test technology in the field of viscoelastic materials is not yet mature, and the test results of mechanical parameters in complex regions are not accurate enough. Summary of the invention

[0005] The purpose of the present invention is to provide a method for testing the precise mechanical parameters of new and old regions of a recycled aggregate composite material.

[0006] The technical solution to achieve the purpose of the present invention is: a method for accurately testing the mechanical parameters of new and old areas of recycled aggregate composite materials, characterized in that it includes the following steps:

[0007] Step (1): obtaining a recycled aggregate pavement composite material specimen by compaction, cutting and curing;

[0008] Step (2): Under a probe scanning test microscope, select an area including clear and flat asphalt (1), aggregate (2), and attached mortar (3) as a test area (4); set scanning points (5) in the attached mortar-aggregate area (old area) (4-1) and the attached mortar-asphalt area (new area) (4-2), perform a probe scanning test in a continuous stiffness measurement mode, record the pressure-indentation depth curve of each scanning point, and use the deformation energy method to obtain the modulus parameters of each scanning point;

[0009] Step (3): Performing data statistics on the modulus parameters of each scanning point, using the calculated statistics to draw a Young's modulus-displacement relationship diagram of the new and old test areas in the scanning direction, and analyzing the change amplitude and trend of the Young's modulus distribution in the scanning direction;

[0010] Step (4): The slope of the curve in the Young's modulus-displacement relationship diagram is defined as the modulus variation coefficient K, and the modulus interval is between the measured Young's moduli of asphalt (1)-adhesion mortar (3) and adhesion mortar (3)-aggregate (2), and the area where the modulus variation coefficient suddenly increases is defined as the new and old area, thereby determining the judgment boundary and modulus interval of the new and old areas.

[0011] Furthermore, in step (1), the recycled aggregate pavement composite material specimen is a cylindrical specimen with a diameter of 20 mm in which a small block (7) of the recycled aggregate pavement composite material is wrapped with a curing agent (6).

[0012] Furthermore, in step (2), a surface roughness test is performed on the surface of the specimen to be tested before the probe scanning test is performed.

[0013] Furthermore, in step (2), the spacing between the scanning points (5) is set to be equidistant 10 μm, and the scanning range is 100 μm*100 μm.

[0014] Furthermore, in step (2), before performing a probe scanning test on the new and old areas (4-1) (4-2), a probe scanning test is performed on each material of the asphalt (1), aggregate (2), and adhesion mortar (3) to measure the modulus parameters of each material.

[0015] Furthermore, in step (4), the criterion for determining whether the modulus coefficient increases suddenly is set to K ≥ 0.8.

[0016] Compared with the prior art materials, the present invention has the following significant advantages:

[0017] (1) The present invention uses probe scanning to test the mechanical properties of each material at the microscopic level of the recycled aggregate pavement composite material. The probe scanning test technology is selected to detect the micro-nanomechanical changes at the connection area. The range of the new and old areas is obtained through the Young's modulus-displacement relationship diagram to avoid the shortcomings of the microscopic image being difficult to distinguish and unable to be intuitively characterized. It is a practical and feasible test method for accurately characterizing the mechanical parameters of the new and old areas of the recycled aggregate pavement composite material;

[0018] (2) The present invention identifies the boundary between the new and old regions of the recycled aggregate pavement composite material and accurately quantifies the micro-nano mechanical parameters of the new and old regions of the recycled aggregate pavement composite material, which helps to improve the indirect tensile strength of the pavement composite material and improve its crack resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of recycled aggregate pavement composite specimen and probe scanning test domain.

[0020] Figure 2 Intended arrangement of old and new areas and scanning points under the microscopic microscope.

[0021] Figure 3 Young's modulus-displacement relationship diagram of the old area of ​​recycled aggregate pavement composite material.

[0022] Description of reference numerals:

[0023] 1—asphalt material, 2—aggregate material, 3—adhesion mortar material, 4—test area of ​​aggregate-adhesion mortar-asphalt, 4-1—aggregate-adhesion mortar area (old area), 4-2—adhesion mortar-asphalt area (new area), 5—scanning point, 6—curing agent, 7—small piece of recycled aggregate pavement composite material. DETAILED DESCRIPTION

[0024] The present invention is further described below with reference to the accompanying drawings and embodiments.

[0025] The probe scanning test technology in the present invention is a test method for measuring the micro-nano mechanical properties of materials. By recording the pressure applied to the indenter during loading and the remaining indentation depth after the external load is removed when the maximum pressure is reached, the pressure-indentation depth curve of each scanning point is recorded, and the mechanical parameters of each scanning point are obtained using the deformation energy method. By drawing a more intuitive Young's modulus-displacement relationship diagram, the Young's modulus distribution in the scanning direction is analyzed to determine the new and old area discrimination boundary and modulus range. Recycled aggregate pavement composite materials are complex due to their multiple material composite conditions, forming new and old areas that affect the strength of recycled aggregate pavement composite materials. The probe scanning test technology can identify the differences in mechanical parameters of each material in the pavement composite material and the changes in mechanical parameters of the new and old connection areas, thereby realizing accurate identification of mechanical parameters of new and old areas. Example

[0026] like Figure 1-3 As shown, this embodiment adopts the following steps to measure the mechanical parameters of the new and old areas of the recycled aggregate pavement composite material:

[0027] Preparation of specimens: Use standard compaction method to form cylindrical recycled aggregate asphalt concrete. Use a cutter to cut a specimen with a length and width of about 1-1.5 cm and a height of about 1 cm, including a uniform and flat test area of ​​recycled aggregate-adhesive mortar-asphalt, such as Figure 1 ; Pour the curing agent into the cylindrical mold to cure the cut small specimens to form a cylindrical specimen with a diameter of 2 cm. The small pieces of recycled aggregate pavement composite material are required to be completely wrapped by the ring curing agent and demoulded after curing is completed;

[0028] Probe scanning test: Under the probe scanning test microscope, select an area containing clear and flat aggregate, attached mortar, and asphalt as the test area; set scanning points in the attached mortar-natural aggregate area and the attached mortar-asphalt area, such as Figure 2 , perform probe scanning test in continuous stiffness measurement mode, record the pressure-indentation depth curve of each scanning point, and use deformation energy method to obtain the mechanical parameters of each scanning point. Control the full load time to about 2s, set the loading rate to complete the loading within 20s, and the unloading rate is the same as the loading rate. Execute scanning points such as Figure 2 (10μm in X direction, 10μm in Y direction), the total scanning test range is 100μm*100μm.

[0029] Mechanical parameter analysis of new and old areas; firstly, probe scanning tests were performed on each single material, namely asphalt, aggregate, and attached mortar. In this example, the data from different test areas showed that the Young's modulus of asphalt was in the range of 1.25GPa to 10.51GPa, and the average Young's modulus of attached mortar and aggregate were 20.96GPa and 39.65GPa, respectively. Then, appropriate new and old areas were selected for probe scanning, and the modulus parameters of each scanning point were statistically analyzed. The calculated statistics were used to draw the Young's modulus-displacement relationship diagram of the new and old test areas in the scanning direction, as shown in the figure. Figure 3 , analyze the distribution of Young's modulus in the scanning direction, and determine the distinction boundary and modulus range of the new and old areas through the steep increase area of ​​the relationship curve between the modulus difference between asphalt and attached mortar, and between attached mortar and aggregate. Figure 3 It can be obtained that according to the modulus difference between mortar and aggregate of 20.96 GPa-39.65 GPa, the steep increase area of ​​the relationship curve is selected within this modulus difference range. It can be obtained that the area of ​​68-86 μm on the grid distance in this example is the old area, the range is 18 μm, and the modulus interval is 21.70-37.76 GPa.

Claims

1. A method for testing the precise mechanical parameters of new and old regions of recycled aggregate composite materials, characterized in that: The steps include: Step (1): obtaining a recycled aggregate pavement composite material specimen by compaction, cutting and curing; Step (2): Under a probe scanning test microscope, an area including clear and flat asphalt (1), aggregate (2), and attached mortar (3) is selected as a test area (4); scanning points (5) are set in the attached mortar-aggregate area, i.e., the old area (4-1), and the attached mortar-asphalt area, i.e., the new area (4-2), and a probe scanning test is performed in a continuous stiffness measurement mode, and a pressure-indentation depth curve of each scanning point is recorded, and the modulus parameters of each scanning point are obtained using a deformation energy method; Step (3): Performing data statistics on the modulus parameters of each scanning point, using the calculated statistics to draw a Young's modulus-displacement relationship diagram of the new and old test areas in the scanning direction, and analyzing the change amplitude and trend of the Young's modulus distribution in the scanning direction; Step (4): define the slope of the curve in the Young's modulus-displacement relationship diagram as the modulus variation coefficient K, define the modulus interval between the measured Young's moduli of asphalt (1)-attached mortar (3) and attached mortar (3)-aggregate (2), and the area where the modulus variation coefficient suddenly increases as the new and old area, thereby determining the judgment boundary and modulus interval of the new and old areas; In step (4), the criterion for determining a sudden increase in the modulus coefficient is set to K ≥ 0.

8.

2. The method according to claim 1, characterized in that In step (1), the recycled aggregate pavement composite material specimen is a cylindrical specimen with a diameter of 20 mm in which a small block (7) of the recycled aggregate pavement composite material is wrapped with a curing agent (6).

3. The method according to claim 1, characterized in that In step (2), the surface roughness of the test piece is tested before the probe scanning test.

4. The method according to claim 1, characterized in that: In step (2), the spacing between the scanning points (5) is set to be 10 μm, and the scanning range is 100 μm*100 μm.

5. The method according to claim 1, characterized in that In step (2), before the probe scanning test is performed on the new and old areas (4-1) (4-2), the asphalt (1), aggregate (2), and adhesion mortar (3) are subjected to a probe scanning test to measure the modulus parameters of each material.

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