Asphalt mixture design method based on horizon function

Abstract

The invention provides a hierarchical mixture design index and optimization method according to functional requirements of different pavement layers (a surface layer, a middle surface layer and a lower surface layer) in combination with climate zoning and traffic load characteristics. According to the method, key mechanical parameters (the dynamic stability of a surface layer is greater than or equal to 6000 times / mm, and the low-temperature bending strain of a lower surface layer is greater than or equal to 2500 mu epsilon) are determined according to the horizon function, and then the mineral aggregate gradation and the special asphalt dosage are optimized through coupling analysis of volume parameters (the void ratio is 3%-5%, and the mineral aggregate void ratio is greater than or equal to 17%) and mechanical properties. And meanwhile, a bonding layer interface shear strength test (greater than or equal to 1.2 MPa) is introduced, so that the structural integrity is ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of road engineering, and particularly relates to a special asphalt mixture mixing ratio design method for different structural layer function requirements of expressways, which realizes long service life and high performance of pavements. BACKGROUND

[0002] The traditional design method of asphalt mixture in China adopts a unified performance standard, which cannot take into account the function differences of each layer (such as the surface layer needs to resist rutting and the lower layer needs to resist fatigue cracking); the interlayer bonding strength is insufficient (the conventional direct shear strength is less than or equal to 0.8 MPa), which leads to interlayer peeling and causes water damage; the mineral aggregate gradation and the asphalt content are not optimized in combination with the stress characteristics of the layer position, and high-temperature rutting and low-temperature cracking coexist. In the existing scheme, the Superpave method only controls the volume parameters and is not related to the function targets of the layer position; the Bailey method focuses on the skeleton structure, but is not linked with the material performance indicators. SUMMARY

[0003] The purpose of the application is to provide a special asphalt mixture mixing ratio design method for different structural layer function requirements of expressways, which realizes long service life and high performance of pavements.

[0004] An asphalt mixture design method based on layer position functions, characterized in that it comprises the following steps: 1. An asphalt mixture design method based on layer position functions, characterized in that it comprises:

[0005] (1) The function targets of dynamic stability ≥ 6000 times / mm, freeze-thaw splitting strength ratio ≥ 85%, and bending strain ≥ 2800 με are set for the surface layer, the middle layer, and the lower layer respectively;

[0006] (2) Mineral aggregate gradation optimization: the Bailey method is combined with the Superpave gradation range, the AC-13 type gradation (nominal maximum particle size 13.2 mm) is selected for the surface layer, and the AC-25 type gradation (nominal maximum particle size 26.5 mm) is selected for the lower layer, and the skeleton density of the gradation is verified through discrete element simulation;

[0007] (3) Special asphalt content determination: the best adhesion of asphalt binder and mineral aggregate is determined based on dynamic shear rheological test, the asphalt content of the surface layer is 4.5%-5.0%, and the asphalt content of the lower layer is 4.0%-4.5%, and the best oil-stone ratio is determined through rotary compaction test (rotary times 100);

[0008] (4) Interface performance optimization: special tack coat oil (amount 0.3-0.5 L / m 2 ) is sprayed between the layers, and the interlayer shear strength is ensured to be greater than or equal to 1.2 MPa through direct shear test.

[0009] Further, the method according to claim 1, wherein in step (2) is characterized by:

[0010] The surface layer adopts AC-13 gradation, CA ratio = 0.4-0.6, 4.75mm sieve hole passing rate 45-55%;

[0011] The lower layer adopts AC-25 gradation, CA ratio = 0.7-0.9, 2.36mm sieve hole passing rate 28-35%.

[0012] Further, the method according to claim 1, wherein in step (3) is characterized by DSR adhesion work test conditions:

[0013] Temperature: 25℃;

[0014] Frequency: 10 rad / s;

[0015] Target adhesion work ≥120mJ / m 2 .

[0016] Further, the method according to claim 1, wherein the tack coat oil comprises the following components:

[0017] SBS modified emulsified asphalt: 98wt%;

[0018] Styrene-acrylate copolymer: 2wt% (molecular weight 80000-150000).

[0019] Further, an asphalt pavement structure designed according to claims 1-4, characterized by comprising:

[0020] Surface layer: AC-13 mixture (oil stone ratio 4.6-4.9%);

[0021] Middle layer: AC-20 mixture (frozen splitting strength ratio ≥85%);

[0022] Lower layer: AC-25 mixture (bending strain ≥2800με);

[0023] Interlayer interface: copolymer reinforced bonding layer with direct shear strength ≥1.3MPa.

[0024] Further, the pavement structure according to claim 5, wherein the function life of each structure layer is matched: surface layer: anti-rutting life ≥12 years; lower layer: anti-fatigue life ≥30 years.

[0025] In summary, the beneficial effects brought by the present application are as follows:

[0026] 1、The present application establishes a three-layer differentiated performance index system (surface layer anti-rutting → middle layer waterproofing → lower layer anti-cracking) through the correspondence of layer function-material performance.

[0027] 2、Coupling design of gradation-performance: fusion of Bailey method (CA ratio, FAc control) and Superpave gradation method, and verification of skeleton density by discrete element simulation.

[0028] 3、Interlayer interface molecular enhancement: special binder oil containing styrene-acrylate copolymer, which improves the interlayer shear strength by ≥40%. BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0029] The present application will be further described below in conjunction with specific examples:

[0030] Example 1: Surface layer AC-13 mixture design

[0031] Functional target: dynamic stability ≥6000 times / mm

[0032] Gradation optimization:

[0033] Bailey method CA=0.52, 1.18mm sieve passing rate 39.5%; discrete element simulation: skeleton contact point ratio 88.7%(target ≥85%). Asphalt content:

[0034] DSR adhesion work peak: 4.7% oil stone ratio (adhesion work 128mJ / m 2 ); Rotational compaction void ratio: 4.2%.

[0035] Performance verification:

[0036] Dynamic stability: 6230 times / mm;

[0037] Interlayer direct shear strength: 1.38MPa.

[0038] Example 2: Lower layer AC-25 mixture design

[0039] Parameter Design Value Test Result Bending Strain Goal ≥ 2800 με 3015 με Frost Heave Split Strength Ratio ≥85％ 87.3％ Interlaminar Direct Shear Strength ≥ 1.2 MPa 1.41 MPa

Claims

1. A layer function-based asphalt mixture design method, characterized in that Comprising: (1) Setting the functional targets of dynamic stability ≥ 6000 times / mm, freeze-thaw splitting strength ratio ≥ 85%, and bending strain ≥ 2800 με for the surface layer, middle layer, and lower layer, respectively; (2) Optimization of mineral aggregate gradation: using the combination of the Bailey method and the Superpave gradation range, the surface layer selects the AC-13 type gradation (nominal maximum particle size 13.2 mm), and the lower layer selects the AC-25 type gradation (nominal maximum particle size 26.5 mm), and the skeleton density of the gradation is verified by discrete element simulation; (3) Determination of the amount of special asphalt: based on dynamic shear rheological test to determine the best adhesion of asphalt binder and mineral aggregate, the asphalt content of the surface layer is 4.5%-5.0%, and the lower layer is 4.0%-4.5%, and the best oil aggregate ratio is determined by the rotary compaction test (rotary times 100 times); (4) Interface performance optimization: special adhesive oil is sprayed between layers (0.3-0.5 L / m 2 ), and the interlayer shear strength is ensured to be ≥1.2 MPa through direct shear test.

2. The method of claim 1, wherein: In the step (2): The surface layer uses AC-13 gradation, CA ratio = 0.4-0.6, 4.75 mm sieve hole passing rate 45-55%; The lower layer uses AC-25 gradation, CA ratio = 0.7-0.9, 2.36 mm sieve hole passing rate 28-35%.

3. The method of claim 1, wherein: The DSR adhesion test conditions in the step (3) are: Temperature: 25℃; Frequency: 10 rad / s; Target adhesion work ≥ 120 mJ / m 2 .

4. The method of claim 1, wherein: The tack coat oil comprises the following components: SBS modified emulsified asphalt: 98wt%; Styrene-acrylate copolymer: 2wt% (molecular weight 80000-150000).

5. An asphalt pavement structure designed according to claims 1 - 4, characterized in that Comprising: Surface layer: AC-13 mixture (oil aggregate ratio 4.6-4.9%); Middle layer: AC-20 mixture (freeze-thaw splitting strength ratio ≥ 85%); Lower layer: AC-25 mixture (bending strain ≥ 2800 με); Interlayer interface: copolymer reinforced bonding layer with direct shear strength ≥ 1.3 MPa.

6. The pavement structure of claim 5, wherein: The functional life of each structural layer is matched: Surface layer: anti-rutting life ≥ 12 years; lower layer: anti-fatigue life ≥ 30 years.