A Low-Temperature Crack-Resistant Composite Modified Asphalt Pavement Structure

Abstract

This invention discloses a low-temperature crack-resistant composite modified asphalt pavement structure, relating to the field of asphalt concrete pavement technology. It solves the technical problem of lacking an asphalt pavement structure that can reduce thermal shrinkage cracking in low-temperature environments without affecting the bonding effect between the base course and the asphalt surface layer and with low construction difficulty. The invention comprises, from top to bottom, a dense composite modified asphalt concrete top layer, a dense-graded composite modified asphalt concrete intermediate layer, a dense-graded modified asphalt concrete fatigue-resistant bottom layer, a modified asphalt synchronous chip seal, a crack-resistant cement-stabilized crushed stone base course, a crack-resistant cement-stabilized crushed stone subbase course, and a subbase. A modified emulsified asphalt bonding layer is provided between the top layer, intermediate layer, and bottom layer. A common emulsified asphalt tack coat is provided between the synchronous chip seal and the base course. The purpose is to enhance the bonding between the various structural layers of the pavement and ensure the shear resistance of the pavement structural layers.

Description

Technical Field

[0001] This invention belongs to the field of asphalt concrete pavement technology, specifically relating to a low-temperature crack-resistant composite modified asphalt pavement structure. Background Technology

[0002] Due to their high altitude, plateau regions have a climate characterized by low temperatures year-round, large diurnal temperature range, rapid cooling, and frequent extreme low temperatures. This makes asphalt pavements in plateau regions more prone to thermal shrinkage and cracking. Conventional asphalt materials are difficult to meet the application conditions in cold plateau regions, resulting in frequent pavement defects, affecting the service life of asphalt pavements, and increasing pavement maintenance costs.

[0003] Semi-rigid base asphalt pavements are widely used in my country due to their good load-bearing capacity, making them a major pavement structure type. Among semi-rigid base types, cement-stabilized crushed stone has a relatively large application rate. After compaction, as the cement hydration reaction proceeds, the cement gradually hardens, but this is accompanied by shrinkage of the base material, making it prone to drying shrinkage cracks. During pavement service, due to traffic loads and ambient temperature, the base layer is also prone to thermal shrinkage cracking, which gradually reflects to the asphalt surface layer, forming pavement distress.

[0004] To improve the crack resistance of asphalt pavements in cold regions, current technical solutions include setting a fatigue-resistant crack-resistant layer between the base course and the asphalt surface course to enhance the crack resistance of the pavement structure. This fatigue-resistant crack-resistant layer is made of materials such as rubber asphalt stress-absorbing layers and polypropylene nonwoven geotextiles, thereby reducing the occurrence of reflective cracking. However, polypropylene nonwoven geotextiles may affect the bonding effect between the base course and the asphalt surface course, reducing the interlayer shear strength of the pavement. Another method to improve the crack resistance of the pavement structure is to incorporate several pre-cracks in the base course. These pre-cracks include pre-cut joints, joint filling materials, and joint sealing materials. By actively controlling cracks that occur during the construction curing period and the operation period, the damage caused by crack reflection to the asphalt pavement is reduced. However, this technical solution requires a large number of pre-cut joints in the base course, making construction difficult. Furthermore, during the operation period, the location of cracks in the base course may not perfectly coincide with the pre-cut joints, leading to the failure of the measure.

[0005] Therefore, in response to the frequent occurrence of road surface cracks in cold plateau regions, there is a lack of asphalt pavement structures that can reduce thermal shrinkage cracking of asphalt pavement under extreme low-temperature environments without affecting the bonding effect between the base layer and the asphalt pavement layer and with low construction difficulty. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a low-temperature crack-resistant composite modified asphalt pavement structure. By combining a crack-resistant cement-stabilized crushed stone base course with a composite modified asphalt surface course exhibiting excellent low-temperature crack resistance, the overall low-temperature crack resistance of the pavement structure is improved. This results in an asphalt pavement structure that can reduce thermal shrinkage cracking of asphalt pavement under extreme low-temperature conditions without affecting the bonding effect between the base course and the asphalt pavement layer and with low construction difficulty.

[0007] The technical solution adopted in this invention is as follows:

[0008] A low-temperature crack-resistant composite modified asphalt pavement structure includes, from top to bottom, a dense-graded composite modified asphalt concrete top layer, a dense-graded composite modified asphalt concrete intermediate layer, a dense-graded modified asphalt concrete fatigue-resistant bottom layer, a modified asphalt synchronous chip seal, a crack-resistant cement-stabilized crushed stone base course, a crack-resistant cement-stabilized crushed stone subbase course, and a subbase course. A modified emulsified asphalt bonding layer is provided between the dense-graded composite modified asphalt concrete top layer, the dense-graded composite modified asphalt concrete intermediate layer, and the dense-graded modified asphalt concrete fatigue-resistant bottom layer. A common emulsified asphalt tack coat is provided between the modified asphalt synchronous chip seal and the crack-resistant cement-stabilized crushed stone base course.

[0009] Preferably, the mixture of the dense composite modified asphalt concrete surface layer is either SMA-13 ​​or AC-13 according to the material composition and structural gradation, and the thickness is 4-5 cm. The binder of the dense composite modified asphalt concrete surface layer is composite modified asphalt.

[0010] Preferably, the surface layer of the dense-graded composite modified asphalt concrete has a gradation of either AC-20 or AC-16, a thickness of 5-8 cm, and the binder of the surface layer is composite modified asphalt.

[0011] Preferably, the composite modified asphalt comprises, by weight, 100 parts of base asphalt, 0.5-4 parts of SBS modifier, 2-8 parts of SBR modifier, 2-8 parts of butadiene rubber, 6-20 parts of rubber oil, 0.02-0.2 parts of stabilizer, 0.2-1.0 parts of antioxidant, and 0.2-1.0 parts of UV stabilizer.

[0012] The above-mentioned technical solution uses asphalt modified with SBS, SBR, and butadiene rubber as the binder for the asphalt intermediate and surface layers. While commonly used SBS-modified asphalt typically exhibits good high-temperature performance, its low-temperature performance is often poorly adaptable in high-altitude regions. This technical solution fully utilizes the excellent low-temperature ductility of SBR and butadiene rubber, combined with the good high-temperature performance of SBS modifiers, to achieve excellent low-temperature performance while maintaining good high-temperature performance. Furthermore, the addition of antioxidants and UV stabilizers enhances the modified asphalt's resistance to thermo-oxidative and photo-oxidative aging, thereby reducing the aging rate of the modified asphalt during pavement service, lowering its brittleness, and effectively improving the low-temperature crack resistance of the composite modified asphalt and its mixture.

[0013] Preferably, the nominal particle size of the fatigue-resistant lower layer of the dense-graded modified asphalt concrete is ≤13.2mm, wherein the passing rate of 0.075mm is 6-8%, the passing rate of 2.36mm is 28-43%, the passing rate of 4.75mm is 41-64%, the passing rate of 9.5mm is 66-82%, the passing rate of 13.2mm is 80-100%, and the passing rate of 16mm is 100%; the asphalt-aggregate ratio is 5.5%-8.5%, the porosity of the asphalt concrete is 1.5%-3.0%, and the thickness is 3.5-5.0cm.

[0014] Using the above technical solution, the fatigue-resistant lower layer of dense-graded modified asphalt concrete has the characteristics of high asphalt-aggregate ratio and low porosity, which can improve the flexibility of asphalt mixture and increase the density of asphalt layer, reduce the probability of air and water entering the interior of asphalt layer, reduce the aging rate of asphalt, thereby improving the fatigue resistance and low-temperature cracking resistance of asphalt lower layer, and delaying the reflection of base layer cracks to asphalt surface layer.

[0015] Preferably, the modified asphalt synchronous chip seal is one of SBS modified asphalt synchronous chip seal or rubber modified asphalt synchronous chip seal.

[0016] Using the above technical solutions, modified asphalt synchronous chip seal mainly plays the roles of bonding, waterproofing, and resisting reflective cracking in pavement structure design.

[0017] Preferably, the gradation range of the crack-resistant cement-stabilized crushed stone base course and the crack-resistant cement-stabilized crushed stone subbase course is as follows: 0.075mm passing rate is 0-5%, 0.6mm passing rate is 8-15%, 2.36mm passing rate is 17-27%, 4.75mm passing rate is 29-39%, 9.5mm passing rate is 47-57%, 19mm passing rate is 72-89%, and 26.5mm passing rate is 100%.

[0018] Using the above technical solution, since the on-site compaction situation needs to be considered, if the thickness of the cement-stabilized crushed stone layer is too large, it is impossible to compact it to the full thickness. Therefore, this application needs to set up two layers for compaction, dividing the base road surface into a crack-resistant cement-stabilized crushed stone base course and a crack-resistant cement-stabilized crushed stone subbase course.

[0019] The gradation of crack-resistant cement-stabilized crushed stone base course and crack-resistant cement-stabilized crushed stone subbase course has a significant impact on their crack resistance performance. When the gradation is fine, the mixture is easy to compact, but because fine aggregates, especially powders, have a higher specific surface area, they have a stronger ability to absorb moisture. Excessive fine aggregate content can easily lead to a "dry" phenomenon in the mixture, resulting in drying shrinkage cracks and thermal shrinkage cracks. When the gradation is coarse, the mixture is prone to segregation, making it difficult to compact, which in turn leads to poor compaction of the base course and reduces the overall structural bearing capacity of the pavement. By optimizing the gradation range of crack-resistant cement-stabilized crushed stone base course and crack-resistant cement-stabilized crushed stone subbase course, the content of fine aggregate in the mixture is effectively controlled, resulting in better overall uniformity of the mixture gradation.

[0020] Preferably, the proportion of cement in the crack-resistant cement-stabilized crushed stone base course is 3.0% to 4.5%, and polyurethane fiber with a proportion of 0.6% to 1.2% is added; the thickness is 16 to 25 cm.

[0021] By adopting the above technical solution, the cement dosage in the mixture is optimized to ensure the strength of the structural layer while controlling the strength value to be too high. Due to the excellent toughness and elasticity of polyurethane fiber, polyurethane fiber is applied to cement-stabilized crushed stone mixture. Through the "reinforcing" effect of polyurethane fiber in the mixture, the toughness of the mixture is enhanced, and the risk of thermal shrinkage cracks and drying shrinkage cracks in the crack-resistant cement-stabilized crushed stone base layer is reduced.

[0022] The crack-resistant cement-stabilized crushed stone base course is located at a higher level and is the main load-bearing layer. Therefore, the strength requirement of the crack-resistant cement-stabilized crushed stone base course mixture is higher than that of the crack-resistant cement-stabilized crushed stone subbase course. Therefore, this application proposes a stabilization cement dosage ratio that can be obtained by combining two different base course load levels.

[0023] The crack-resistant cement-stabilized crushed stone subbase layer is located at a lower level, and its layer temperature is less affected by changes in air temperature. Therefore, temperature changes have a smaller impact on the cracking of the crack-resistant cement-stabilized crushed stone subbase mixture. Thus, this application proposes a method to determine the most reasonable polyurethane fiber content by combining the temperature field changes of the two different base layers.

[0024] Preferably, the proportion of cement in the crack-resistant cement-stabilized crushed stone subbase is 3.0% to 4.0%, and polyurethane fiber with a proportion of 0.3% to 0.9% is added; the thickness is 16 to 25 cm.

[0025] By adopting the above technical solution, the cement dosage in the mixture is optimized to ensure the strength of the structural layer while controlling the strength value to be too high. Due to the excellent toughness and tensile properties of polyurethane fiber, polyurethane fiber is applied to cement-stabilized crushed stone mixture. Through the "reinforcing" effect of polyurethane fiber in the mixture, the toughness of the mixture is enhanced, and the risk of thermal shrinkage cracks and drying shrinkage cracks in the crack-resistant cement-stabilized crushed stone subbase is reduced.

[0026] Preferably, the subbase is graded gravel or graded crushed stone, with a thickness of 15-20 cm.

[0027] In summary, due to the adoption of the above technical solutions, the beneficial effects of this invention are as follows: the crack-resistant cement-stabilized crushed stone layer reinforced with polyurethane fibers improves the crack resistance of the base course and reduces the risk of drying shrinkage cracking and thermal shrinkage cracking of the base course; the use of SBS modified asphalt or rubber modified asphalt synchronous crushed stone seal layer as the bonding layer between the base course and the asphalt surface course enables the pavement structure layers to form a continuous whole, improving the overall structural stability; at the same time, the use of oil-rich and low-voidity fatigue-resistant asphalt mixture as the lower layer and composite modified asphalt mixture with excellent low-temperature performance as the middle and upper layers of asphalt improves the fatigue crack resistance and low-temperature crack resistance of the asphalt surface course; by improving the low-temperature crack resistance of each structural layer such as the pavement subbase, base course and asphalt surface course, the low-temperature crack resistance of the entire pavement structure layer can also be significantly improved, thereby enabling the pavement structure to have excellent crack resistance without increasing the construction difficulty of the pavement structure layer and without affecting the interlayer bonding effect of the pavement structure layer. Attached Figure Description

[0028] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0029] Figure 1 This is a schematic diagram of a low-temperature crack-resistant composite modified asphalt pavement structure according to the present invention.

[0030] Figure Labels

[0031] 1-Dense composite modified asphalt concrete surface layer, 2-Dense graded composite modified asphalt concrete intermediate layer, 3-Dense graded modified asphalt concrete fatigue-resistant lower layer, 4-Modified asphalt synchronous chip stone seal layer, 5-Crack-resistant cement-stabilized crushed stone base course, 6-Crack-resistant cement-stabilized crushed stone subbase course, 7-Subbase course. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and marked in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0033] In the description of the embodiments of this application, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] The following is combined Figure 1 The present invention will be described in detail below.

[0035] Example 1:

[0036] A low-temperature crack-resistant composite modified asphalt pavement structure includes, from top to bottom, a dense composite modified asphalt concrete surface layer, a dense-graded composite modified asphalt concrete intermediate layer, a dense-graded modified asphalt concrete fatigue-resistant bottom layer, a modified asphalt synchronous chip seal layer, a crack-resistant cement-stabilized crushed stone base course, a crack-resistant cement-stabilized crushed stone subbase course, and a subbase.

[0037] A modified emulsified asphalt bonding layer is provided between the dense composite modified asphalt concrete top layer, the dense graded composite modified asphalt concrete middle layer, and the dense graded modified asphalt concrete fatigue-resistant bottom layer.

[0038] A common emulsified asphalt tack coat is provided between the modified asphalt synchronous chip seal and the crack-resistant cement-stabilized chip base course.

[0039] In this embodiment, the mixture of the dense composite modified asphalt concrete surface layer is SMA-13 ​​according to the material composition and structural gradation, and the thickness is 4cm. The binder of the dense composite modified asphalt concrete surface layer is composite modified asphalt.

[0040] In this embodiment, the surface layer of the dense-graded composite modified asphalt concrete has an AC-16 gradation and a thickness of 5cm, and the binder of the surface layer of the dense-graded composite modified asphalt concrete is composite modified asphalt.

[0041] In this embodiment, the composite modified asphalt comprises, by weight, 100 parts of No. 70 base asphalt, 2 parts of SBS modifier, 4 parts of SBR modifier, 4 parts of butadiene rubber, 14 parts of rubber oil, 0.04 parts of stabilizer, 0.5 parts of antioxidant, and 0.4 parts of UV stabilizer.

[0042] The rubber oil is furfural extract oil, the stabilizer is elemental sulfur, the antioxidant is Irganox L 101, and the UV stabilizer is UV-531.

[0043] In this embodiment, the gradation rates of each sieve aperture in the fatigue-resistant lower layer of the dense-graded modified asphalt concrete are as follows: 0.075mm passing rate is 7.5%, 2.36mm passing rate is 34.4%, 4.75mm passing rate is 49.5%, 9.5mm passing rate is 74.0%, 13.2mm passing rate is 96.8%, and 16mm passing rate is 100%; the asphalt-aggregate ratio is 5.8%, the asphalt concrete porosity is 2.5%, and the thickness is 4cm.

[0044] In this embodiment, the modified asphalt synchronous chip seal is an SBS modified asphalt synchronous chip seal; the asphalt spreading rate is 1.6 kg / m³. 2 The crushed stone used is 4.75–9.5 mm single-particle size crushed stone, and the crushed stone spreading rate is 6.5 kg / m³. 2 .

[0045] In this embodiment, the sieve gradation passing rates of the crack-resistant cement-stabilized crushed stone base course and the crack-resistant cement-stabilized crushed stone subbase course are as follows: 0.075mm passing rate is 2.2%, 0.6mm passing rate is 12.1%, 2.36mm passing rate is 22.4%, 4.75mm passing rate is 35.7%, 9.5mm passing rate is 53.1%, 19mm passing rate is 82.3%, and 26.5mm passing rate is 100%.

[0046] In this embodiment, the proportion of cement in the crack-resistant cement-stabilized crushed stone base course is 4.0%, and 0.7% of polyurethane fiber is added; the thickness is 20cm.

[0047] In this embodiment, the proportion of the crack-resistant cement-stabilized crushed stone base course cement is 3.0%, and 0.4% of polyurethane fiber is added; the thickness is 20cm.

[0048] In this embodiment, the cushion layer is graded gravel or graded crushed stone, with a thickness of 15cm.

[0049] Example 2:

[0050] A low-temperature crack-resistant composite modified asphalt pavement structure includes, from top to bottom, a dense composite modified asphalt concrete surface layer, a dense-graded composite modified asphalt concrete intermediate layer, a dense-graded modified asphalt concrete fatigue-resistant bottom layer, a modified asphalt synchronous chip seal layer, a crack-resistant cement-stabilized crushed stone base course, a crack-resistant cement-stabilized crushed stone subbase course, and a subbase.

[0051] A modified emulsified asphalt bonding layer is provided between the dense composite modified asphalt concrete top layer, the dense graded composite modified asphalt concrete middle layer, and the dense graded modified asphalt concrete fatigue-resistant bottom layer.

[0052] A common emulsified asphalt tack coat is provided between the modified asphalt synchronous chip seal and the crack-resistant cement-stabilized chip base course.

[0053] In this embodiment, the mixture of the dense composite modified asphalt concrete surface layer is AC-13C according to the material composition and structural gradation, and the thickness is 4cm. The binder of the dense composite modified asphalt concrete surface layer is composite modified asphalt.

[0054] In this embodiment, the surface layer of the dense-graded composite modified asphalt concrete has an AC-20 gradation and a thickness of 6cm, and the binder of the surface layer of the dense-graded composite modified asphalt concrete is composite modified asphalt.

[0055] In this embodiment, the composite modified asphalt comprises, by weight, 100 parts of No. 70 base asphalt, 0.5-4 parts of SBS modifier, 4 parts of SBR modifier, 6 parts of butadiene rubber, 16 parts of rubber oil, 0.02 parts of stabilizer, 0.3 parts of antioxidant, and 0.3 parts of UV stabilizer.

[0056] The rubber oil is furfural extract oil, the stabilizer is elemental sulfur, the antioxidant is Irganox L 101, and the UV stabilizer is UV-531.

[0057] In this embodiment, the gradation passing rates of each sieve in the fatigue-resistant lower layer of the dense-graded modified asphalt concrete are as follows: 0.075mm passing rate is 7.2%, 2.36mm passing rate is 37.2%, 4.75mm passing rate is 53.4%, 9.5mm passing rate is 75.3%, 13.2mm passing rate is 97.2%, and 16mm passing rate is 100%; the asphalt-aggregate ratio is 6.0%, the asphalt concrete porosity is 2.5%, and the thickness is 4cm.

[0058] In this embodiment, the modified asphalt synchronous chip seal is a rubber-modified asphalt synchronous chip seal, and the asphalt spreading rate is 1.8 kg / m³. 2 The crushed stone used is 4.75–9.5 mm single-particle size crushed stone, and the crushed stone spreading rate is 6.5 kg / m³. 2 .

[0059] In this embodiment, the sieve gradation passing rates of the crack-resistant cement-stabilized crushed stone base course and the crack-resistant cement-stabilized crushed stone subbase course are as follows: 0.075mm passing rate is 1.7%, 0.6mm passing rate is 11.1%, 2.36mm passing rate is 21.1%, 4.75mm passing rate is 33.5%, 9.5mm passing rate is 51.7%, 19mm passing rate is 80.4%, and 26.5mm passing rate is 100%.

[0060] In this embodiment, the proportion of the crack-resistant cement-stabilized crushed stone base layer is 3.9%, and 0.9% of polyurethane fiber is added; the thickness is 18cm.

[0061] In this embodiment, the proportion of the crack-resistant cement-stabilized crushed stone subbase cement is 3.9%, and 0.9% of polyurethane fiber is added; the thickness is 18cm.

[0062] In this embodiment, the cushion layer is graded gravel or graded crushed stone, with a thickness of 15cm.

[0063] Comparative Example 1

[0064] To verify the effect of polyurethane fiber on improving the crack resistance of cement-stabilized crushed stone mixture, a comparative example of cement-stabilized crushed stone without polyurethane fiber was set up. Meanwhile, the other addition amounts and data were the same as in Example 1.

[0065] In this comparative example, the gradation passing rates of each sieve aperture of the cement-stabilized crushed stone base course and the cement-stabilized crushed stone subbase course are as follows: 0.075mm passing rate is 2.2%, 0.6mm passing rate is 12.1%, 2.36mm passing rate is 22.4%, 4.75mm passing rate is 35.7%, 9.5mm passing rate is 53.1%, 19mm passing rate is 82.3%, and 26.5mm passing rate is 100%.

[0066] In this comparative example, the cement content of the cement-stabilized crushed stone base course is 4.0%, and the cement content of the cement-stabilized crushed stone subbase course is 3.0%. Unlike Example 1, neither the crack-resistant cement-stabilized crushed stone base course nor the crack-resistant cement-stabilized crushed stone subbase course mixture contains polyurethane fiber.

[0067] Comparative Example 2

[0068] To verify the improvement in crack resistance performance of the cement-stabilized crushed stone mixture gradation in this technical solution, a set of comparative examples were set up with different gradation curves for the cement-stabilized crushed stone base course and the cement-stabilized crushed stone subbase course under the same conditions. At the same time, polyurethane fiber with the same dosage as in Example 1 was added to the cement-stabilized crushed stone mixture.

[0069] In this comparative example, the gradation curve of the cement-stabilized crushed stone mixture is based on the "Technical Specifications for Construction of Highway Pavement Base Course".

[0070] The gradation median of CB-1 in (JTG / F20-2015) is used for blending.

[0071] In this comparative example, the cement content of the cement-stabilized crushed stone base course is 4.0%, and 0.7% of polyurethane fiber is added; the cement content of the cement-stabilized crushed stone subbase course is 3.0%, and 0.4% of polyurethane fiber is added.

[0072] The penetration at 25°C, ductility at 5°C, and softening point of the composite modified asphalt in Examples 1 and 2 were compared with those of commonly used SBS modified asphalt. The supplier of SBS modified asphalt was Sichuan Baoli Asphalt Co., Ltd. The specific test results are shown in Table 1.

[0073] Table 1: Comparison of Performance Test Results of Composite Modified Asphalt and SBS Modified Asphalt in Examples 1-2

[0074] 25℃ penetration / 0.1mm Ductility at 5℃ / cm Softening point / °C Example 1 77 ＞100 70.5 Example 2 87 ＞100 73.0 Commonly used SBS modified asphalt 54 30 81.0

[0075] It can be seen that the ductility of the composite modified asphalt at 5℃ is >100cm, which is much higher than that of the SBS modified asphalt. However, the softening point, which represents the high-temperature performance of asphalt, is lower than that of the SBS modified asphalt, but far exceeds the requirement of not less than 60℃ for the softening point of I-D modified asphalt in the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40-2004).

[0076] The composite modified asphalt prepared by the methods in Examples 1 and 2 was mixed with commonly used SBS modified asphalt under the same gradation ratio and mixture void ratio conditions and the specimens were molded. Low-temperature bending tests were carried out according to the method T0715 in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011). The test results are shown in Table 2.

[0077] Table 2: Low-temperature performance test results of composite modified asphalt and SBS modified asphalt mixtures in Examples 1-2

[0078] Mixture type Maximum bending tensile strain / με Example 1 AC-13C 3374 Example 2 AC-13C 3568 Commonly used SBS modified asphalt AC-13C 2658

[0079] It can be seen that the maximum flexural strain of the composite modified asphalt mixture is significantly higher than that of the SBS modified asphalt mixture. The test results of the composite modified asphalt mixture can meet the low-temperature bending technical requirements of asphalt mixture in the severe winter cold region in the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40-2004).

[0080] The cement-stabilized crushed stone mixture was mixed and shaped using the proportions of Examples 1-2 and Comparative Examples 1-2. Dry shrinkage test and thermal shrinkage test were carried out according to the methods of T0854 and T0855 in the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" (JTG E51-2009). The test results are shown in Table 3.

[0081] Table 3: Comparison of Dry Shrinkage and Thermal Shrinkage Test Data of Cement-Stabilized Crushed Stone Base Course and Cement-Stabilized Crushed Stone Subbase Course in Examples 1-2 and Comparative Examples 1-2

[0082]

[0083]

[0084] It can be seen that the drying shrinkage coefficient and thermal shrinkage coefficient of the crack-resistant cement-stabilized crushed stone base course and subbase course in Examples 1-2 are significantly smaller than those in Comparative Examples 1-2, indicating that the crack-resistant cement-stabilized crushed stone base course and subbase course in this example have better resistance to drying shrinkage and thermal shrinkage.

[0085] The synchronous chip seal layer in Examples 1 and 2 was used as the bonding layer between the base course and the asphalt surface course. The bonding performance was compared with that of the polymer nonwoven geotextile as the bonding layer between the base course and the asphalt surface course. The bonding performance of different bonding layers was tested according to the shear strength and bond strength test methods in "Waterproof Coatings for Roads and Bridges" (JC / T 975-2005). The test results are shown in Table 4.

[0086] Table 4: Comparison of bonding performance tests between synchronous chip seal and polymer nonwoven geotextile in Examples 1 and 2

[0087]

[0088] It can be seen that the shear strength and bond strength of the synchronous chip seal layer in Examples 1 and 2 as the bonding layer are significantly higher than the interlayer bond strength when the polymer nonwoven geotextile is placed between the base layer and the asphalt layer.

[0089] It should be noted that:

[0090] Currently, there is no suitable evaluation method for the low-temperature crack resistance of the entire pavement structure layer. This patent does not include an invention of a complete pavement structure crack resistance evaluation method. It is generally believed that the improvement of the low-temperature crack resistance of each individual structural layer material will inevitably lead to the improvement of the crack resistance of the entire pavement structure layer.

[0091] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-temperature crack-resistant composite modified asphalt pavement structure, characterized in that: The system comprises, from top to bottom, a dense-graded composite modified asphalt concrete top layer, a dense-graded composite modified asphalt concrete intermediate layer, a dense-graded modified asphalt concrete fatigue-resistant bottom layer, a modified asphalt synchronous chip stone seal layer, a crack-resistant cement-stabilized crushed stone base layer, a crack-resistant cement-stabilized crushed stone subbase layer, and a subbase layer; a modified emulsified asphalt bonding layer is provided between the dense-graded composite modified asphalt concrete top layer, the dense-graded composite modified asphalt concrete intermediate layer, and the dense-graded modified asphalt concrete fatigue-resistant bottom layer; and an ordinary emulsified asphalt tack coat is provided between the modified asphalt synchronous chip stone seal layer and the crack-resistant cement-stabilized crushed stone base layer. The modified asphalt synchronous chip seal is one of SBS modified asphalt synchronous chip seal or rubber modified asphalt synchronous chip seal. The crack-resistant cement-stabilized crushed stone base course and crack-resistant cement-stabilized crushed stone subbase course have the following gradation ranges: 0.075mm passing rate is 0-5%, 0.6mm passing rate is 8-15%, 2.36mm passing rate is 17-27%, 4.75mm passing rate is 29-39%, 9.5mm passing rate is 47-57%, 19mm passing rate is 72-89%, and 26.5mm passing rate is 100%. The crack-resistant cement-stabilized crushed stone base course contains 3.0% to 4.5% cement and 0.6% to 1.2% polyurethane fiber; the thickness is 16 to 25 cm. The crack-resistant cement-stabilized crushed stone subbase has a cement content of 3.0% to 4.0% and contains 0.3% to 0.9% polyurethane fiber; its thickness is 16 to 25 cm. The composite modified asphalt comprises, by weight, 100 parts of base asphalt, 0.5-4 parts of SBS modifier, 2-8 parts of SBR modifier, 2-8 parts of butadiene rubber, 6-20 parts of rubber oil, 0.02-0.2 parts of stabilizer, 0.2-1.0 parts of antioxidant, and 0.2-1.0 parts of UV stabilizer.

2. The low-temperature crack-resistant composite modified asphalt pavement structure according to claim 1, characterized in that: The dense composite modified asphalt concrete surface layer mixture is of either SMA-13 ​​or AC-13 in terms of material composition and structural gradation, with a thickness of 4-5 cm. The binder of the dense composite modified asphalt concrete surface layer is composite modified asphalt.

3. The low-temperature crack-resistant composite modified asphalt pavement structure according to claim 1, characterized in that: The surface layer of the dense-graded composite modified asphalt concrete has a gradation of either AC-20 or AC-16, a thickness of 5-8 cm, and the binder of the surface layer is composite modified asphalt.

4. The low-temperature crack-resistant composite modified asphalt pavement structure according to claim 1, characterized in that: The nominal particle size of the fatigue-resistant lower layer of the dense-graded modified asphalt concrete is ≤13.2mm, wherein the passing rate of 0.075mm is 6-8%, the passing rate of 2.36mm is 28-43%, the passing rate of 4.75mm is 41-64%, the passing rate of 9.5mm is 66-82%, the passing rate of 13.2mm is 80-100%, and the passing rate of 16mm is 100%; the asphalt-aggregate ratio is 5.5%-8.5%, the porosity of the asphalt concrete is 1.5%-3.0%, and the thickness is 3.5-5.0cm.

5. The low-temperature crack-resistant composite modified asphalt pavement structure according to claim 1, characterized in that: The subbase is composed of graded gravel or graded crushed stone, with a thickness of 15–20 cm.

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