Durable structure of low-carbon economical semi-rigid base asphalt pavement

Abstract

The invention discloses a low-carbon economical semi-rigid base asphalt pavement durable structure which comprises four semi-rigid bases, a modified asphalt waterproof bonding layer I, an asphalt concrete lower surface layer, a modified asphalt waterproof bonding layer II and an asphalt concrete upper surface layer which are arranged layer by layer from bottom to top, the four semi-rigid base layers comprise a semi-rigid material lower subbase layer, a semi-rigid material upper subbase layer, a semi-rigid material lower base layer and a semi-rigid material upper base layer from bottom to top, and the overall structure thickness is 84-92 cm. The whole structure adopts a form of'thin asphalt layer + high-quality semi-rigid base layer ', the total thickness of the asphalt surface layer is 12cm which is reduced by 30% compared with the thickness of the asphalt surface layer which is more than 18cm and is generally adopted by the existing domestic structure, and the base layer is increased by one layer compared with the traditional structure layer, so that the bearing capacity of the pavement can be obviously improved, and the strength of the pavement is enough to bear the repeated action of heavy traffic; and the double waterproof bonding layers are arranged in the structure, so that the problem of water damage is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of road engineering technology, and in particular to a low-carbon, economical, semi-rigid base asphalt pavement durability structure. Background Technology

[0002] Semi-rigid base asphalt pavement is one of the main forms of pavement structure for high-grade highways. However, with the increasing weight and frequency of traffic loads and the long-term erosion of pavement structures by extreme weather, the durability problems exposed by asphalt pavement during its service life not only affect the quality and safety of road traffic, but also significantly increase the cost of later maintenance and repair, which is inconsistent with the current development concept of "low-carbon and environmentally friendly, quality-improving and efficiency-enhancing" transportation construction.

[0003] Traditional semi-rigid base asphalt pavement structures suffer from the following drawbacks: First, the currently used cement-stabilized semi-rigid base is prone to drying shrinkage cracks and thermal shrinkage cracks, which gradually reflect upwards to the asphalt surface layer, forming reflective cracks. This allows rainwater to seep into the base layer, exacerbating the softening and strength reduction of the base material, leading to early-stage defects such as pumping, potholes, and network cracking, severely shortening the pavement's service life. Second, existing technologies often improve pavement performance by increasing the asphalt layer thickness and using large amounts of modified asphalt or additives, but these solutions often significantly increase project costs and fail to adequately consider life-cycle cost control. Furthermore, while some low-cost pavement structure designs have lower short-term construction costs, they significantly increase maintenance frequency and repair costs during service, resulting in poor life-cycle economics and failing to meet the actual needs of highway engineering for "long life, low cost, and low emissions." Therefore, this invention proposes a low-carbon, economical semi-rigid base asphalt pavement durability structure. Addressing the problems of severe cracking and insufficient durability in existing semi-rigid base asphalt pavements, developing a semi-rigid base asphalt pavement structure that improves pavement durability while maintaining good economic efficiency is of significant practical importance. Summary of the Invention

[0004] The purpose of this invention is to provide a low-carbon, economical, semi-rigid base asphalt pavement durability structure.

[0005] To achieve the above objectives, the present invention is implemented according to the following technical solution: A low-carbon, economical, semi-rigid base asphalt pavement durability structure includes four layers of semi-rigid base, modified asphalt waterproof bonding layer I, asphalt concrete lower layer, modified asphalt waterproof upper bonding layer II, and asphalt concrete upper layer arranged layer by layer from bottom to top, with an overall structural thickness of 84~92cm. The four-layer semi-rigid base course, from bottom to top, includes a semi-rigid material lower base course, a semi-rigid material upper base course, a semi-rigid material lower base course, and a semi-rigid material upper base course. The semi-rigid material lower base course and the semi-rigid material upper base course are 18-20cm thick cement-stabilized graded crushed stone with a 7-day compressive strength of 3-5 MPa. The semi-rigid material lower base course is 18-20cm thick cement-stabilized graded crushed stone with a 7-day compressive strength of 5-6 MPa. The semi-rigid material upper base course is 18-20cm thick cement-stabilized graded crushed stone with a 7-day compressive strength of 6-7 MPa. The thickness of the lower layer of asphalt concrete is 8cm; The thickness of the asphalt concrete surface layer is 4 cm; The asphalt mixture of the lower and upper layers of the asphalt concrete adopts a coarse aggregate gradation form, with the content of coarse aggregate with a thickness of 4.75cm or more being 65% to 70%.

[0006] Furthermore, cement slurry is poured between the four semi-rigid base layers, and cement slurry is poured between the semi-rigid material underbase and the soil base.

[0007] Furthermore, the cement-stabilized graded crushed stone is designed using a cement-stabilized crushed stone design method based on multi-dimensional performance balance.

[0008] Furthermore, the asphalt mixtures of both the lower and upper layers of the asphalt concrete are designed using the asphalt mixture equilibrium design method based on the densest state.

[0009] Furthermore, the modified asphalt waterproof bonding layer I is disposed between the semi-rigid material upper base layer and the asphalt concrete lower layer, using SBS modified asphalt or rubber asphalt, with a dosage of 2.2±0.2 kg / m³. 2 The modified asphalt waterproof bonding layer I is covered with 13.2~19mm or 19~26.5mm crushed stone. When the crushed stone is 13.2~19mm, the amount of crushed stone used is 60~70% of the full coverage. When the crushed stone is 19~26.5mm, the amount of crushed stone used is 55~65% of the full coverage.

[0010] Furthermore, the modified asphalt waterproof bonding layer II is disposed between the lower and upper layers of the asphalt concrete, using SBS modified asphalt or rubber asphalt, at a dosage of 2.0 ± 0.2 kg / m³. 2 The modified asphalt waterproof bonding layer II is spread with 13.2~19mm crushed stone, and the amount of crushed stone is 60~70% of the full coverage.

[0011] Furthermore, both the modified asphalt waterproof bonding layer I and the modified asphalt waterproof bonding layer II adopt a separate construction process; the specific steps of the separate construction process are as follows: first, a layer of asphalt is spread on the underlying layer according to the specified amount to form an asphalt film, and then crushed stone of specified specifications and quality is spread on the asphalt film.

[0012] The beneficial effects of this invention are: This invention is a low-carbon, economical, semi-rigid base asphalt pavement durability structure. Compared with existing technologies, this invention has the following technical advantages: The road surface has a strong load-bearing capacity, and the structural safety life can be increased from the current 15 years to more than 30 years: The road base layer of this invention has an additional layer of thickness compared with the traditional structural layer, and adopts a cement-stabilized crushed stone design method based on the balance of multiple performances for the mixture design. This allows the cement-stabilized crushed stone base layer to achieve the same strength as the traditional base layer while reducing the amount of cement by 10% and the coefficient of thermal shrinkage by 30%. It can effectively solve the engineering problem of easy cracking of semi-rigid base layers, and the strength is sufficient to withstand the repeated action of heavy traffic, which can guarantee a structural safety life of more than 30 years.

[0013] With strong rutting resistance, the functional life of the road surface can be increased from the current 5-8 years to more than 15 years: The coarse aggregate gradation used in the surface layer of this invention has the ability to resist high temperature permanent deformation, which can ensure that the rutting depth of the asphalt surface layer is less than 15mm within 15 years, and no maintenance is required; The asphalt mixture of the surface layer of this invention is designed using the asphalt mixture equilibrium design method based on the most compact state, which is not prone to significant water damage, while ensuring that the surface has excellent anti-skid performance.

[0014] A double-layer waterproof system solves the chronic problem of water damage: The present invention sets a double-layer waterproof adhesive layer inside the road structure to prevent surface water from penetrating into the structure, effectively solving the chronic problem of water damage to the road surface.

[0015] Cost-saving and environmentally friendly: This invention adopts a durable structure of "thin asphalt layer + high-quality semi-rigid base". The total thickness of the asphalt surface layer is 12cm, which is 30% less than the thickness of the asphalt surface layer of more than 18cm commonly used in the existing domestic structure. This greatly saves the cost of the project. Its structural safety life and road surface functional life are twice that of the existing design specifications, which greatly saves maintenance costs and reduces resource extraction and consumption during the maintenance process. Attached Figure Description

[0016] Figure 1 This is a design drawing of a low-carbon, economical, semi-rigid base asphalt pavement durability structure according to the present invention. Figure 2 The above are the rebound deflection test results of each layer of the semi-rigid base asphalt pavement structure in the example section. In the diagram: Subgrade-1; Semi-rigid material lower base course-2; Semi-rigid material upper base course-3; Semi-rigid material lower base course-4; Semi-rigid material upper base course-5; Cement slurry-6; Modified asphalt waterproof bonding layer I-7; Asphalt concrete lower layer-8; Modified asphalt waterproof bonding layer II-9; Asphalt concrete upper layer-10. Detailed Implementation

[0017] The present invention will be further described below through specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0018] This invention discloses a low-carbon, economical, semi-rigid base asphalt pavement durability structure, comprising four layers arranged from bottom to top: a semi-rigid base layer, a modified asphalt waterproof bonding layer I, an asphalt concrete lower layer, a modified asphalt waterproof bonding layer II, and an asphalt concrete upper layer, with an overall structural thickness of 84~92cm. The four-layer semi-rigid base course, from bottom to top, includes a semi-rigid material lower base course, a semi-rigid material upper base course, a semi-rigid material lower base course, and a semi-rigid material upper base course. The semi-rigid material lower base course and the semi-rigid material upper base course are 18-20cm thick cement-stabilized graded crushed stone with a 7-day compressive strength of 3-5 MPa. The semi-rigid material lower base course is 18-20cm thick cement-stabilized graded crushed stone with a 7-day compressive strength of 5-6 MPa. The semi-rigid material upper base course is 18-20cm thick cement-stabilized graded crushed stone with a 7-day compressive strength of 6-7 MPa. The thickness of the lower layer of asphalt concrete is 8cm; The thickness of the asphalt concrete surface layer is 4 cm; The asphalt mixture of the lower and upper layers of the asphalt concrete adopts a coarse aggregate gradation form, with the content of coarse aggregate with a thickness of 4.75cm or more being 65% to 70%.

[0019] In practical application, for a coal transportation line located in Inner Mongolia, a two-way five-lane expressway standard was adopted, with a design speed of 80-100 km / h and a roadbed width of 27.75 m. Among them, the test section of durable asphalt concrete pavement is eleven kilometers long. Based on the conditions and characteristics of this project, the following design was carried out: (1) First, the structural design should be carried out based on the conditions and characteristics of the project: Table 1 below shows the structural design of the durable asphalt concrete pavement of the test section of this coal transport line located in Inner Mongolia. Table 1. Design of Durable Asphalt Concrete Pavement Structure for Test Section

[0020] (2) Further material design based on pavement structure design: For the SBS modified asphalt used in the surface layer of asphalt concrete and the Class A No. 20 road petroleum asphalt used in the bottom layer, the specific index requirements are shown in Tables 2 and 3. Table 2 Technical Requirements for the Upper Layer SBS Modified Asphalt

[0021] Table 3 Technical Requirements for Petroleum Asphalt Layer of Road No. 20 (Lower Layer)

[0022] Select cement with a strength standard of 32.5, and ensure that all performance indicators meet the relevant technical specifications of GB175 "General Portland Cement"; The surface and base course aggregates are single-sized crushed stone, with the content of oversized particles of various specifications not exceeding 10%. SAC-16 uses five types of aggregates: 13.2~19mm, 9.5~13.2mm, 4.75~9.5mm, 3~5mm, and 0~3mm. SAC-25 uses six types of aggregates: 19.0~26.5mm, 13.2~19mm, 9.5~13.2mm, 4.75~9.5mm, 3~5mm, and 0~3mm. CBG-25 base course uses six types of aggregates: 19.0~26.5mm, 13.2~19mm, 9.5~13.2mm, 4.75~9.5mm, 3~5mm, and 0~3mm. The asphalt mixture gradation of the lower and upper layers of asphalt concrete adopts coarse aggregate discontinuous gradation, and the design gradation is shown in Table 4. Table 4 Asphalt Mixture Design Gradation Table

[0023] The crushed stone mixture of the semi-rigid material lower base course and the semi-rigid material upper base course adopts coarse aggregate discontinuous gradation, and the design gradation is shown in Table 5. Table 5. Gradation Table for Base Mixture Design

[0024] The mix proportions of asphalt mixtures were designed using the asphalt mixture equilibrium design method based on the most compact state, determining the asphalt-aggregate ratio of AC16 asphalt mixture to be 4.9% and that of AC25 asphalt mixture to be 4.3%. The cement-stabilized graded crushed stone mixture was designed using a multi-dimensional performance balance-based cement-stabilized crushed stone mixture design method, determining the CBG25 cement dosage to be 6.5% and the cement dosage of the cement-stabilized crushed stone to be 3%. (3) Based on the material design results of the pavement structure, determine the material properties of each layer: The technical requirements for asphalt mixtures for the lower and upper layers of asphalt concrete are shown in Tables 6 and 7. Table 6 Design parameters for asphalt mixtures

[0025] Table 7 Technical Requirements for Asphalt Mixtures

[0026] The base course CBG-25 cement-stabilized crushed stone is required to have an unconfined compressive strength of not less than 5 MPa after 7 days, and the subbase course cement-stabilized gravel is required to have a molding compressive strength of not less than 3 MPa after 7 days. (4) Conduct engineering testing and experimental verification: Rebound deflection tests were conducted after each layer of construction was completed, and the results are shown below. Figure 2 As shown, the data shows that the representative value of the rebound deflection of the subgrade is 116, which decreases to 40 after laying a base course, reaches 6.4 after laying the top course, and increases slightly after laying the bottom and top courses, to 10.3 and 8.0 respectively. The test results confirm that the test road has excellent structural bearing capacity. The same structure was laid on a full-scale road test track in Beijing in 2015. After 130 million cumulative standard axle load tests (equivalent to 37 years of heavy traffic load in my country), no structural damage occurred. Various road surface performance indicators such as rutting and skid resistance were within the allowable range of the specifications. The structural safety life and road surface functional life were more than doubled compared with the current design specifications, which greatly saved maintenance costs and had significant economic benefits.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-carbon, economical, semi-rigid base asphalt pavement durability structure, characterized in that: It includes a four-layer semi-rigid base layer, modified asphalt waterproof bonding layer I, asphalt concrete lower layer, modified asphalt waterproof bonding layer II, and asphalt concrete upper layer, arranged layer by layer from bottom to top, with an overall structural thickness of 84~92cm. The four-layer semi-rigid base course, from bottom to top, includes a semi-rigid material lower base course, a semi-rigid material upper base course, a semi-rigid material lower base course, and a semi-rigid material upper base course. The semi-rigid material lower base course and the semi-rigid material upper base course are 18-20cm thick cement-stabilized graded crushed stone with a 7-day compressive strength of 3-5 MPa. The semi-rigid material lower base course is 18-20cm thick cement-stabilized graded crushed stone with a 7-day compressive strength of 5-6 MPa. The semi-rigid material upper base course is 18-20cm thick cement-stabilized graded crushed stone with a 7-day compressive strength of 6-7 MPa. The thickness of the lower layer of asphalt concrete is 8cm; The thickness of the asphalt concrete surface layer is 4 cm; The asphalt mixture of the lower and upper layers of the asphalt concrete adopts a coarse aggregate gradation form, with the content of coarse aggregate with a thickness of 4.75cm or more being 65% to 70%.

2. The low-carbon, economical, semi-rigid base asphalt pavement durability structure according to claim 1, characterized in that: Cement slurry is poured between the four semi-rigid base layers, and cement slurry is poured between the semi-rigid material underbase and the soil base.

3. The low-carbon, economical, semi-rigid base asphalt pavement durability structure according to claim 1, characterized in that: The cement-stabilized graded crushed stone is designed using a cement-stabilized crushed stone design method based on multi-dimensional performance balance.

4. The low-carbon, economical, semi-rigid base asphalt pavement durability structure according to claim 1, characterized in that: The asphalt mixtures for both the lower and upper layers of the asphalt concrete were designed using the asphalt mixture equilibrium design method based on the most compact state.

5. The low-carbon, economical, semi-rigid base asphalt pavement durability structure according to claim 1, characterized in that: The modified asphalt waterproof bonding layer I is disposed between the semi-rigid material upper base layer and the asphalt concrete lower layer, and uses SBS modified asphalt or rubber asphalt, with a dosage of 2.2±0.2 kg / m³. 2 The modified asphalt waterproof bonding layer I is covered with 13.2~19mm or 19~26.5mm crushed stone. When covering with 13.2~19mm crushed stone, the amount of crushed stone is 60~70% of the full coverage. When covering with 19~26.5mm crushed stone, the amount of crushed stone is 55~65% of the full coverage.

6. The low-carbon, economical, semi-rigid base asphalt pavement durability structure according to claim 1, characterized in that: The modified asphalt waterproof bonding layer II is disposed between the lower and upper layers of the asphalt concrete, and uses SBS modified asphalt or rubber asphalt at a dosage of 2.0 ± 0.2 kg / m³. 2 ; The modified bitumen waterproof bonding layer II is covered with 13.2~19mm crushed stone, and the amount of crushed stone is 60~70% of the full coverage.

7. The low-carbon, economical, semi-rigid base asphalt pavement durability structure according to claims 5-6, characterized in that: The modified asphalt waterproof bonding layer I and the modified asphalt waterproof bonding layer II are constructed using a separate construction process. The specific steps of the separate construction process are as follows: first, a layer of asphalt is spread on the underlying layer according to the specified amount to form an asphalt film, and then crushed stone of specified specifications and quality is spread on the asphalt film.

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