Application of tensile test method for semi-flexible pavement material

Abstract

The invention discloses application of a tensile test method of a semi-flexible pavement material, belongs to the technical field of traffic transportation, and is applied to tensile performance testing of a cement-asphalt interface of the semi-flexible pavement material.The tensile test method comprises the steps that a tested basalt base material is prepared; pouring asphalt which is heated in advance on the surface of the prepared basalt stone; wrapping the basalt stone coated with the asphalt by using a wood block to manufacture a cement grouting material pouring mold; pouring a cement grouting material on the mold; curing, demolding and forming; and carrying out a tensile test on the prepared sample. By adopting the method, a special cement-asphalt interface tensile test method is provided for the semi-flexible pavement material.

Description

Technical Field

[0001] The invention relates to the technical field of transportation, and in particular to an application of a tensile test method for semi-flexible pavement materials. Background Art

[0002] Semi-flexible pavement materials (SFPM) are composed of large-void asphalt concrete structures and cement-based grouting materials. They have both the flexibility of asphalt concrete pavement and the rigidity of cement concrete pavement. They are a kind of rigid and flexible pavement material with good resistance to permanent deformation. Due to its high bearing capacity and good high and low temperature stability, setting it as a surface layer can well solve the problems such as rutting, pushing, and congestion caused by insufficient temperature stability of asphalt mixtures. And thanks to its greatly improved low-temperature performance compared to cement pavement, the pavement can improve its driving comfort without temperature shrinkage joints.

[0003] On the other hand, SFPM itself is a three-phase heterogeneous material, in which the interface transition zone between the organic material of the asphalt phase and the inorganic binder of the cement phase is an excessively weak layer. The material properties on both sides of the interface are very different, and it is difficult to form a good connection effect between the materials. In addition, the deformation characteristics of its different rigid and flexible components will also cause additional stress inside the material. That is, when the deformation of the parent asphalt mixture and cement grouting material cannot be coordinated and exceeds a certain magnitude, cracks will appear inside the SFPM due to stress concentration, which will lead to the formation of a weak interface layer between the asphalt and cement grouting materials. These characteristics affect the development of semi-flexible pavement materials. Therefore, improving the tensile properties of the cement-asphalt interface is of great significance to ensure the crack resistance of semi-flexible pavements.

[0004] At present, analysis of existing specifications, standards, and literature has not found a tensile test method specifically for the cement-asphalt interface of semi-flexible pavement materials, which affects the actual application of semi-flexible pavement materials. Summary of the invention

[0005] The purpose of the present invention is to provide an application of a tensile test method for semi-flexible pavement materials, which has solved the problems mentioned in the background technology.

[0006] To achieve the above object, the present invention provides an application of a tensile test method for semi-flexible pavement materials, which is applied to the tensile performance test of cement-asphalt interface of semi-flexible pavement materials. The tensile test method includes:

[0007] S1. Prepare test basalt matrix material;

[0008] S2, pouring the pre-heated asphalt onto the surface of the prepared basalt stone;

[0009] S3. After the asphalt film is cooled, a cement grouting casting mold is prepared by wrapping the asphalt-coated basalt stone with a wooden block;

[0010] S4, pouring cement grouting material on the mold to make the cement grouting material bond with the asphalt membrane;

[0011] S5, curing, demoulding and molding;

[0012] S6. Perform a tensile test on the prepared specimens.

[0013] Preferably, in step S1, the size of the basalt block specimen is 40 mm in height, 40 mm in length, and 20 mm in width.

[0014] Preferably, in step S2, the asphalt poured on the surface of the prepared basalt block is controlled in thickness by volume method, and the thickness is 200 μm. The volume method formula is:

[0015] m 沥青 =S×d×ρ;

[0016] Where m is the asphalt mass, g; S is the specimen area, cm 2 ; d is the thickness of the asphalt film, cm; ρ is the density of asphalt, g / cm 3 .

[0017] Preferably, step S3 specifically includes:

[0018] Put the basalt blocks coated with asphalt into an oven at the temperature required for heating the asphalt, and keep it warm for 30 minutes until the asphalt film is spread smoothly, then take it out and let it cool to room temperature;

[0019] The cooled basalt blocks were tightly wrapped with small wooden boards of 40 mm and 20 mm in width and fixed with adhesive tape to make a cement grouting casting mold.

[0020] Preferably, the height of the wooden boards around the cement slurry casting mold is 40 mm ± 1 mm higher than the test piece.

[0021] Preferably, in step S5, the mold is removed after being placed in a natural environment for 1 day, and the curing is continued until the age of 7 days. The cured specimen is placed in a thermal insulation environment box and the temperature is set to be kept warm for 3 hours.

[0022] Preferably, in step S6, an indirect bending-pull method is used to perform a tensile test on the interface. The specimen is placed on a three-point bending support for SCB testing, and the support span is adjusted to be set to 0.8 times the total length of the specimen. The test is performed using a UTM universal testing machine at -10°C to calculate the tensile strength. The tensile strength is expressed as:

[0023]

[0024] Where, T is the tensile strength, MPa; F t is the tensile failure load, N; S t is the stress-bearing area of ​​the specimen, m 2 .

[0025] Therefore, the present invention adopts the above-mentioned tensile test method for semi-flexible pavement materials and applies it to the cement-asphalt interface of semi-flexible pavement materials, providing a basis for calculating the tensile strength of the cement-asphalt interface of semi-flexible pavement materials in practice.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of preparing cement-asphalt interface tensile test pieces according to an embodiment of the present invention;

[0028] Figure 2 A cement-asphalt structure diagram of an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of loading for a cement-asphalt interface tensile test according to an embodiment of the present invention;

[0030] Reference numerals

[0031] 1. Basalt blocks; 2. Asphalt membrane; 3. Cement-based grouting material. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] Example

[0034] The present invention provides an application of a tensile test method for semi-flexible pavement materials, which is applied to the tensile performance test of cement-asphalt interface of semi-flexible pavement materials. Figure 1 , tensile test methods include:

[0035] S1. Select basalt stone 1 as the test matrix material, and use a high-precision cutting machine to form a basalt stone 1 specimen. The specimen size is 40 mm high, 40 mm long, and 20 mm wide.

[0036] S2. Pour the pre-heated asphalt onto the surface of the prepared basalt stone 1.

[0037] It should be noted that before paving asphalt, the surface of the basalt stone 1 specimen must be cleaned with an ultrasonic cleaner, and then the basalt stone 1 specimen is placed in an oven at the temperature required for heating the corresponding asphalt. The asphalt can only be paved after it is taken out of the oven.

[0038] Prepare the 70# matrix asphalt, SBS modified asphalt and high viscosity modified asphalt used in the test in the oven for use, take out the rock specimen and place it on an electronic scale, pour the pre-heated asphalt on the basalt specimen, use the volume method to control the thickness of the asphalt film 2 to 200μm, and calculate the required asphalt mass according to the asphalt density as follows;

[0039] m 70#基质沥青 =S×d×ρ=4×4×0.02×1.038=0.332(g);

[0040] m SBS沥青 =S×d×ρ=4×4×0.02×1.034=0.331(g);

[0041] m 高黏沥青 =S×d×ρ=4×4×0.02×1.044=0.334(g);

[0042] Where: m is the asphalt mass, g; S is the specimen area, cm 2 ; d is the thickness of the asphalt film, cm; ρ is the density of asphalt, g / cm 3 .

[0043] S3. After the asphalt film 2 cools down, a wooden block is used to wrap the asphalt coated basalt stone block 1 to make a cement grouting material casting mold. Specifically:

[0044] Put the basalt block 1 coated with asphalt into an oven at the temperature required for heating the corresponding asphalt, and keep it warm for 30 minutes until the asphalt film 2 is spread smoothly, then take it out and let it cool to room temperature;

[0045] Small wooden boards with widths of 40 mm and 20 mm were used to tightly wrap the cooled basalt block 1 and fixed with adhesive tape to make a cement grouting material casting mold. The height of the wooden boards around the cement slurry casting mold was 40 mm ± 1 mm higher than the test piece.

[0046] S4, pouring the pre-mixed cement-based grouting material 3 into the groove of the mold to bond the cement-based grouting material to the asphalt membrane 2. The cement-based grouting material 3 can be ordinary cement type, styrene acrylic emulsion type, emulsified asphalt type and polyvinyl alcohol fiber type.

[0047] S5, curing and demoulding, specifically: demoulding after placing in the natural environment for 1 day, and continuing to cure until the age of 7 days, placing the cured specimens in a heat preservation environment box, set to 10℃ and keep warm for 3 hours.

[0048] S6. Perform a tensile test on the prepared sample. The overall structure of the sample is as follows: Figure 2 As shown in the figure, the indirect bending and pulling method is used to carry out the tensile test on the interface. The specimen is placed on the three-point bending support for SCB test, as shown in the figure. Figure 3 As shown, adjust the support span to 0.8 times the total length of the specimen, and use the UTM universal testing machine to test at -10℃ to calculate the tensile strength. The tensile strength formula is:

[0049]

[0050] Where, T is the tensile strength, MPa; F t is the tensile failure load, N; S t is the stress-bearing area of ​​the specimen, m 2 .

[0051] The tensile strength of different cement types and interfaces calculated by the tensile strength formula is shown in Table 1.

[0052] Table 1 Interface strength of different cement types with asphalt at -10℃

[0053]

[0054] Therefore, the present invention adopts the above-mentioned tensile test method and applies it to the tensile performance test of the cement-asphalt interface of semi-flexible pavement materials, providing a basis for calculating the tensile strength of the cement-asphalt interface of semi-flexible pavement materials in practice.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. Application of a tensile test method for semi-flexible pavement materials, characterized in that: Applied to the tensile performance test of cement-asphalt interface of semi-flexible pavement materials. The tensile test methods include: S1. Prepare test basalt matrix material; S2, pouring the pre-heated asphalt onto the surface of the prepared basalt stone; S3. After the asphalt film is cooled, a cement grouting casting mold is prepared by wrapping the asphalt-coated basalt stone with a wooden block; S4, pouring cement grouting material on the mold to make the cement grouting material bond with the asphalt membrane; S5, curing, demoulding and molding; S6. Perform a tensile test on the prepared specimens.

2. The application of the tensile test method for semi-flexible pavement materials according to claim 1 is characterized in that: In step S1, the dimensions of the basalt block specimen are 40 mm in height, 40 mm in length, and 20 mm in width.

3. The application of the tensile test method for semi-flexible pavement materials according to claim 1, characterized in that: In step S2, the asphalt poured on the surface of the prepared basalt block is controlled by volume method, and the thickness is 200 μm. The volume method formula is: m 沥青 =S×d×ρ; Where m is the asphalt mass, g; S is the specimen area, cm 2 ; d is the thickness of the asphalt film, cm; ρ is the density of asphalt, g / cm 3 .

4. The application of the tensile test method for semi-flexible pavement materials according to claim 1 is characterized in that: Step S3 specifically includes: Put the basalt blocks coated with asphalt into an oven at the temperature required for heating the asphalt, and keep it warm for 30 minutes until the asphalt film is spread smoothly, then take it out and let it cool to room temperature; The cooled basalt blocks were tightly wrapped with small wooden boards of 40 mm and 20 mm in width and fixed with adhesive tape to make a cement grouting casting mold.

5. The application of the tensile test method for semi-flexible pavement materials according to claim 4 is characterized in that: The height of the wooden boards around the cement slurry casting mold is 40mm±1mm higher than the basalt stone specimen.

6. The application of the tensile test method for semi-flexible pavement materials according to claim 1, characterized in that: In step S5, the samples are placed in a natural environment for 1 day before demoulding and continued to be cured until the age of 7 days. The cured samples are placed in a heat preservation environment box and the temperature is set to be kept warm for 3 hours.

7. The application of the tensile test method for semi-flexible pavement materials according to claim 1, characterized in that: In step S6, the tensile test of the interface is carried out by the indirect bending and pulling method. The specimen is placed on the three-point bending support for the SCB test, and the support span is adjusted to be set to 0.8 times the total length of the specimen. The test is carried out using a UTM universal testing machine at -10°C to calculate the tensile strength. The tensile strength is expressed as: Where, T is the tensile strength, MPa; F t is the tensile failure load, N; S t is the stress-bearing area of ​​the specimen, m 2 .

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