Composite fault layer for inverted semi-rigid base asphalt pavement structural layer combination

Abstract

The present invention relates to a composite intermittent layer for use in an inverted semi-rigid base asphalt pavement structural layer combination, belonging to the technical field of road engineering. The composite intermittent layer comprises the following components by weight: 50-70 parts crushed stone with a particle size of 4-6 cm, 5-20 parts sand, and 20-40 parts cement emulsified asphalt sand concrete. This composite intermittent layer blocks upward reflection of cracks in the semi-rigid base, preventing the formation of reflective cracks in the asphalt pavement. It also improves the compressive rebound modulus of the intermittent layer, resulting in an asphalt pavement with comparable rutting resistance to that of an asphalt pavement in a continuous structural layer combination with a semi-rigid base asphalt pavement.

Description

Technical Field

[0001] The invention belongs to the technical field of road engineering, and in particular relates to a composite fault layer for an inverted semi-rigid base asphalt pavement structural layer combination. Background Art

[0002] As the asphalt pavement structure layer combination of inorganic binder semi-rigid base (semi-rigid base for short) has strong bearing capacity and low cost, it has made great contributions to my country's road engineering construction and has been widely used for a long time. To this day, most of my country's road engineering construction still and will continue to use this pavement structure layer combination.

[0003] In the semi-rigid base asphalt pavement structure layer combination, the semi-rigid base has strong bearing capacity and is the main load-bearing layer, and the thickness of the asphalt pavement is relatively thin. Therefore, this pavement structure layer combination is called a strong base and thin surface pavement structure layer combination.

[0004] The combination of semi-rigid base asphalt pavement structural layers is a multi-layer elastic continuous system. Therefore, a penetration layer of asphalt is poured on the upper part of the semi-rigid base to increase the bonding force between the semi-rigid base and the asphalt pavement surface layer.

[0005] Problems with semi-rigid base asphalt pavement structural layer combinations include: The semi-rigid base is prone to cracking (these cracks are prone to cracking early, typically within a year, and they are more frequent). This in turn can lead to reflective cracking in the asphalt pavement (although some asphalt gravel stress absorption layers are used, their effectiveness is limited and the results are less than ideal). Furthermore, asphalt pavements can also develop cold shrinkage cracks. These reflective and cold shrinkage cracks act as channels for water to penetrate the pavement structure, making it difficult for water to escape. This results in premature road damage (manifested by reduced base strength and bearing capacity, mud pumping, block cracking, potholes, etc.) and accelerated structural failure, often failing to meet the designed service life (10-15 years). This is a common problem with semi-rigid base asphalt pavement structural layer combinations in my country.

[0006] Asphalt pavement structures with a semi-rigid base are multi-layered, elastic, and continuous systems. This requires strong bonding between the layers, otherwise the bearing capacity will be severely reduced. However, semi-rigid bases are prone to cracking (an inherent property), which in turn drives cracks in the asphalt pavement, leading to early damage to the entire pavement. Strong interlayer bonding can produce reflective cracks, while weak interlayer bonding can severely reduce the bearing capacity, creating a paradox.

[0007] To resolve this paradox, the inverted semi-rigid base asphalt pavement structural layer combination was developed. This involves placing a graded crushed stone layer (with a maximum crushed stone particle size of no more than 30 mm) between the semi-rigid base and the asphalt pavement. Because the loose (unbound) granular material does not transmit tensile stress and strain, it prevents cracks in the semi-rigid base from reflecting back into the asphalt pavement. The graded crushed stone layer acts as a discontinuous layer, making this pavement structural layer a discontinuous system. However, the loose, graded crushed stone layer has a low compressive rebound modulus (200-450 MPa) and exhibits significant plastic deformation, making rutting a common problem in asphalt pavement. Summary of the Invention

[0008] The purpose of the present invention is to provide a composite fault layer for an inverted semi-rigid base asphalt pavement structural layer combination, which blocks the upward reflection of cracks in the semi-rigid base and does not produce reflective cracks in the asphalt pavement. At the same time, it improves the compressive rebound modulus of the fault layer, so that the anti-rutting performance of the asphalt pavement is equivalent to that of the asphalt pavement in the continuous system structural layer combination of the semi-rigid base asphalt pavement.

[0009] To achieve the above object, the technical solution adopted by the present invention is:

[0010] A composite fault layer for an inverted semi-rigid base asphalt pavement structural layer combination, comprising the following components in parts by weight: 50-70 parts of crushed stone with a particle size of 4-6 cm, 5-20 parts of sand, and 20-40 parts of cement emulsified asphalt sand-type concrete.

[0011] Furthermore, the thickness h of the composite fault layer is 6 cm.

[0012] Furthermore, the content of crushed stones with a particle size of 6 cm in the crushed stones with a particle size of 4 cm to 6 cm is ≥50%.

[0013] Further, the sand is used for the lower part of the composite fault layer. s = 2cm~3cm, the cement emulsified asphalt sand concrete is used for the upper part of the composite fault layer h AC =3cm~4cm.

[0014] Furthermore, the cement-emulsified asphalt sand concrete includes the following components and parts by weight: 100 parts of mineral material, 6-9 parts of emulsified asphalt, and 2-4 parts of cement, wherein the mineral material gradation meets the requirements of sand AC-5 in (JTG F40-2004) "Technical Specifications for Highway Asphalt Pavement Construction".

[0015] Furthermore, the type and quality of the emulsified asphalt meet the requirements of (JTG F40-2004) "Technical Specifications for Highway Asphalt Pavement Construction".

[0016] Furthermore, the type and quality of the cement meet the requirements of (JTG F40-2004) "Technical Specifications for Highway Asphalt Pavement Construction".

[0017] Furthermore, the compressive rebound modulus of the composite fault layer is ≥700 MPa.

[0018] Research shows that in the inverted semi-rigid base asphalt pavement structural layer combination, except for the addition of the composite fault layer, when the other structural layers are the same as the semi-rigid base asphalt pavement continuous system structure layer combination, the compressive rebound modulus of the composite fault layer ≥ 700MPa can ensure that the rutting resistance of the asphalt pavement in the inverted semi-rigid base asphalt pavement structural layer combination is better than that of the asphalt pavement in the semi-rigid base asphalt pavement continuous system structure layer combination.

[0019] The quality of the materials used in the composite fault layer of the present invention complies with the relevant provisions of (JTG F40-2004) "Technical Specifications for Highway Asphalt Pavement Construction".

[0020] A construction method for a composite fault layer for an inverted semi-rigid base asphalt pavement structural layer combination comprises the following steps:

[0021] 1. Spread 4cm to 6cm gravel

[0022] Spread 4cm~6cm crushed stone according to the designed amount per unit area;

[0023] 2. Paving sand

[0024] Spread sand according to the designed amount per unit area;

[0025] 3. Compacted sand

[0026] Compact the sand using water ballast method;

[0027] 4. Mixing, transportation and paving of cement emulsified asphalt sand concrete mixture

[0028] Use a cement concrete mixing station to mix cement emulsified asphalt sand concrete mixture. After the mineral material and cement are evenly mixed, add emulsified asphalt and continue mixing until uniform.

[0029] Use dump trucks to transport cement emulsion asphalt sand concrete mixture to the construction site;

[0030] Spread cement emulsified asphalt sand concrete mixture according to the designed dosage per unit area;

[0031] 5. Crushing

[0032] Use a 16t rubber-wheel roller to roll 5-6 times until the cement emulsified asphalt sand concrete is dense;

[0033] 6. Maintenance

[0034] The composite fault layer will be maintained for 7 days after construction is completed, and heavy vehicles are prohibited from passing through.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The present invention can not only block the upward reflection of cracks in the semi-rigid base layer, but also improve the integrity and continuity of the pavement structure.

[0037] Although the semi-rigid base has a high modulus and strong bearing capacity, it is easy to crack as its inherent characteristic, and it drives the asphalt pavement to produce cracks, namely reflection cracks. These cracks are continuous from top to bottom, destroying the integrity of the pavement structure. Figure 1 As shown, the composite fault layer of the present invention uses large-particle crushed stone to form a skeleton. The gaps in the skeleton are filled with sand at the bottom and cement emulsified asphalt sand concrete at the top. Because interlayer sliding is permitted, and the stress generated by the upward reflection of cracks in the semi-rigid base is far less than the tensile strength of the crushed stone, the cracks are not pulled apart at the crushed stone. Furthermore, sand does not transmit tensile stress and strain, thus blocking the upward reflection of cracks in the semi-rigid base. Furthermore, the large-particle crushed stone placed above the cracks in the base acts like a bridge spanning the cracks between two base layers (i.e., a bridging effect), significantly improving the longitudinal integrity and continuity of the pavement. Existing graded crushed stone, with a maximum crushed stone particle size of ≤3 cm, does not provide a bridging effect, resulting in poor longitudinal integrity and continuity of the pavement.

[0038] 2. Research shows that the performance of the traditional graded crushed stone layer and the composite fault layer in the present invention are completely different, as shown in the following aspects:

[0039] 1) The stress-strain relationship of a traditional graded crushed stone layer exhibits a significant nonlinear relationship, with the compressive resilient modulus varying with its thickness, load magnitude, layer location, and the thickness and stiffness of other layers. In a composite discontinuity layer, where the maximum crushed stone particle size is equal to its thickness, its stress-strain relationship approaches a linear relationship, and the compressive resilient modulus remains essentially unchanged by changes in load magnitude, layer location, and the thickness and stiffness of other layers.

[0040] 2) The compressive resilience modulus of a conventional graded crushed stone layer is 200 MPa to 450 MPa, while the compressive resilience modulus of the composite fault layer of the present invention is ≥700 MPa. Apart from the addition of the composite fault layer, the other structural layers are the same as the continuous structural layer combination of the semi-rigid base asphalt pavement. This is sufficient to ensure that the asphalt pavement in the inverted semi-rigid base asphalt pavement structural layer combination has better rutting resistance than the asphalt pavement in the continuous structural layer combination of the semi-rigid base asphalt pavement.

[0041] 3) If Figure 1As shown, in the composite fault layer of the present invention, the maximum particle size of the crushed stone is equal to the thickness of the composite fault layer, which "stands upright" in the composite fault layer, improving the compressive rebound modulus and shear strength of the layer and significantly reducing plastic deformation. In addition, the upper 3cm to 4cm thick portion of the composite fault layer uses cement-asphalt composite binder concrete, whose compressive rebound modulus and shear strength are much higher than those of conventional asphalt pavement. Moreover, since it is based on a large amount of large-size crushed stone, it will not cause rutting.

[0042] 4) The traditional graded crushed stone layer is an isotropic material; however, the composite fault layer of the present invention is not an isotropic material. It is isotropic in the circumferential direction on the road surface, but anisotropic in the vertical direction. Moreover, the vertical compressive modulus of resilience is much higher than that in the circumferential direction on the road surface.

[0043] It can be seen from this that the traditional graded crushed stone layer and the composite fault layer of the present invention are qualitatively different and are two completely different types of structural layers.

[0044] In summary, the composite fault layer of the present invention can block the upward reflection of cracks in the semi-rigid base layer, and will not produce reflective cracks in the asphalt pavement. It can also significantly improve the integrity and continuity of the pavement, while increasing the compressive rebound modulus of the fault layer, ensuring that the anti-rutting performance of the asphalt pavement in the inverted semi-rigid base asphalt pavement structural layer combination is not reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the internal structure of the composite fault layer and the semi-rigid base layer and its cracks;

[0046] In the figure, 1. Gravel with a particle size of 4cm to 6cm; 2. Sand; 3. Cement emulsified asphalt sand concrete; 4. Semi-rigid base; 5. Cracks in the semi-rigid base. DETAILED DESCRIPTION

[0047] The technical solutions and effects of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0048] Example 1

[0049] The material dosage design process for the composite fault layer of the inverted semi-rigid base asphalt pavement structure layer combination in this embodiment is as follows:

[0050] 1. Select h s

[0051] Select h s =2cm, then h AC =6cm-2cm=4cm.

[0052] 2. Material dosage design of cement emulsified asphalt sand concrete

[0053] Select cement emulsified asphalt sand concrete with a mineral content of 100 kg, an emulsified asphalt with an asphalt content of 60% and an ordinary Portland cement of 32.5 grade asphalt 3kg.

[0054] The compressive modulus of resilience (E) of the composite fault layer was tested. The test method for the compressive modulus of resilience of the composite fault layer was conducted in accordance with Appendix D, Test Method for Rebound Modulus of Aggregate Materials, in the "Highway Asphalt Pavement Design Specification" (JTG D50-2017), with the following differences: First, the specimen dimensions were diameter × height = 300 mm × 60 mm, equal to the thickness of the composite fault layer, to ensure consistency between the specimen and the composite fault layer; second, the specimen was placed indoors for at least 7 days after fabrication before the compressive modulus test was conducted; the test result in this example was E = 750 MPa.

[0055] Verify the compressive resilience modulus E of the composite fault layer. The compressive resilience modulus E of the composite fault layer should be 750 MPa or greater than 700 MPa, meeting the design requirements. If not, use one or more of the following methods to increase the compressive resilience modulus of the composite fault layer until it meets the design requirements: increase the content of crushed stone with a particle size of 4 cm or greater, use manufactured sand, increase the softening point and viscosity of the emulsified asphalt evaporation residue, adjust the emulsified asphalt dosage, increase the cement dosage, or use more than one of the following methods.

[0056] Test the compaction density ρ of cement emulsified asphalt sand concrete AC The compaction density test of cement emulsified asphalt sand concrete was carried out in accordance with the method of (JTG E20-2011) "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering"; the test result of this embodiment is ρ AC =2.23g / cm 3 .

[0057] 3. Test the packed density of sand ρ s and the density of standard sand ρ 标准砂 Calculate the amount of 4cm to 6cm crushed stone, sand and cement emulsified asphalt sand concrete

[0058] Test sand's packed density ρ s and the density of standard sand ρ 标准砂 The test method of the packed density of sand and the density of standard sand is carried out in accordance with the method of (JTG E42-2005) "Highway Engineering Aggregate Test Procedure". The test results are: ρ s =1.70g / cm 3 , ρ 标准砂 =1.45g / cm 3 ;

[0059] Tightly cover a rectangular container (length × width × height = 100 cm × 100 cm × 6 cm) with a layer of 4 cm to 6 cm gravel, and fill the rectangular container with standard sand. The material consumption per square meter of composite fault layer is:

[0060] Weigh the amount of 4cm to 6cm gravel m ss =90kg;

[0061] Weigh the standard sand weight m 标准砂 =34.8kg;

[0062] Gravel gap volume V 间隙 =m 标准砂 ÷ρ 标准砂 =34.8kg÷1.45g / cm 3 =0.024m 3 ;

[0063] Amount of sand m s =V 间隙 ×h s ÷h×ρ s =0.024m 3 ×2cm÷6cm×1.70g / cm 3 =13.6kg;

[0064] Cement emulsified asphalt sand concrete dosage m AC =V 间隙 ×h AC ÷h×ρ AC =0.024m 3 ×4cm÷6cm×2.23g / cm 3 =35.86kg.

[0065] Therefore, the components of the composite fault layer per square meter in this embodiment are: 90 kg of crushed stone with a particle size of 4 cm to 6 cm, 13.6 kg of sand, and 35.86 kg of cement emulsified asphalt sand concrete, wherein the components of the cement emulsified asphalt sand concrete are: 100 kg of mineral material, 7 kg of emulsified asphalt with an asphalt content of 60%, and 3 kg of 32.5 grade ordinary Portland cement.

[0066] A construction method for a composite fault layer combined with an inverted semi-rigid base asphalt pavement structure layer is as follows:

[0067] 1. Spread 4cm to 6cm gravel

[0068] Spread 4cm to 6cm gravel evenly at a dosage of 90kg per square meter.

[0069] 2. Paving sand

[0070] Spread the sand evenly at a rate of 13.6 kg per square meter.

[0071] 3. Compacted sand

[0072] Compact the sand using water compaction method.

[0073] 4. Mixing, transportation and paving of cement emulsified asphalt sand concrete mixture

[0074] According to the mix ratio of cement emulsified asphalt sand concrete mixture: mineral aggregate: emulsified asphalt: cement = 100:7:3, use a cement concrete mixing station to mix the cement emulsified asphalt sand concrete mixture. After the mineral aggregate and cement are mixed evenly, add the emulsified asphalt and continue mixing until uniform.

[0075] Use dump trucks to transport cement emulsion asphalt sand concrete mixture to the construction site;

[0076] Evenly spread the cement emulsion asphalt sand concrete mixture at a dosage of 35.86 kg per square meter.

[0077] 5. Crushing

[0078] Use a ≥16t rubber-wheel roller to roll 5 to 6 times until the cement emulsion asphalt sand concrete is dense.

[0079] 6. Maintenance

[0080] The composite fault layer will be maintained for 7 days after construction is completed, and heavy vehicles are prohibited from passing through.

[0081] like Figure 1 As shown, the composite fault layer of the present invention uses large-particle crushed stone (1) with a diameter of 4-6 cm to form a framework. The gaps between the frameworks are filled with sand (2) at the bottom and cement-emulsified asphalt sand-grain concrete (3) at the top. Because interlayer sliding is permitted, and the stress generated by the upward reflection of existing semi-rigid base cracks (5) in the semi-rigid base (4) is far less than the tensile strength of the crushed stone, the crushed stone is not pulled apart. Sand does not transmit tensile stress and strain, thus preventing the upward reflection of cracks in the semi-rigid base. Furthermore, the large-particle crushed stone placed above the base cracks acts like a bridge spanning the cracks between the two base layers (i.e., a bridging effect), significantly improving the longitudinal integrity and continuity of the road surface.

[0082] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A composite fault layer for an inverted semi-rigid base asphalt pavement structure layer combination, characterized in that: The composite fault layer comprises the following components in parts by weight: 50-70 parts of crushed stone with a particle size of 4cm-6cm, 5-20 parts of sand, and 20-40 parts of cement emulsified asphalt sand concrete; The thickness h of the composite fault layer is 6 cm; The content of 6cm crushed stones in the 4cm to 6cm crushed stones is ≥50%; The sand is used for the lower part of the composite fault s = 2cm~3cm, the cement emulsified asphalt sand concrete is used for the upper part of the composite fault layer h AC =3cm~4cm; The cement emulsified asphalt sand concrete comprises the following components in parts by weight: 100 parts of mineral material, 6-9 parts of emulsified asphalt, and 2-4 parts of cement, wherein the mineral material gradation conforms to the requirements of sand AC-5 in JTG F40-2004 Technical Specifications for Highway Asphalt Pavement Construction; The composite fault layer uses large-size crushed stones to form a skeleton, with sand filling the lower part of the skeleton gap and cement emulsified asphalt sand concrete filling the upper part. Since the interlayers allow sliding, and the stress generated by the upward reflection of the semi-rigid base cracks is much smaller than the tensile strength of the crushed stones, the semi-rigid base cracks will not be pulled apart. Moreover, the sand does not transmit tensile stress and strain, thereby preventing the upward reflection of the semi-rigid base cracks. The upper 3cm to 4cm thick part of the composite fault layer is made of cement-asphalt composite binder concrete, which has a compressive rebound modulus and shear strength much higher than that of commonly used asphalt pavement. Moreover, it is based on a large amount of large-particle gravel, so it will not produce rutting.

2. The composite fault layer for an inverted semi-rigid base asphalt pavement structure layer combination according to claim 1, characterized in that: The emulsified asphalt complies with the requirements of JTG F40-2004 Technical Specification for Highway Asphalt Pavement Construction.

3. The composite fault layer for an inverted semi-rigid base asphalt pavement structure layer combination according to claim 1, characterized in that: The cement meets the requirements of JTG F40-2004 Technical Specification for Highway Asphalt Pavement Construction.

4. The composite fault layer for inverted semi-rigid base asphalt pavement structure layer combination according to claim 1, characterized in that: The compressive rebound modulus of the composite fault layer is ≥700MPa.

5. The composite fault layer for an inverted semi-rigid base asphalt pavement structure layer combination according to claim 1, characterized in that: The construction method of the composite fault layer comprises the following steps:

1. Spread 4cm to 6cm gravel Spread 4cm~6cm crushed stone according to the designed amount per unit area; 2. Paving sand Spread sand according to the designed amount per unit area; 3. Compacted sand Compact the sand using water ballast method; 4. Mixing, transportation and paving of cement emulsified asphalt sand concrete mixture Use a cement concrete mixing station to mix cement emulsified asphalt sand concrete mixture. After the mineral material and cement are evenly mixed, add emulsified asphalt and continue mixing until uniform. Use dump trucks to transport cement emulsion asphalt sand concrete mixture to the construction site; Spread cement emulsified asphalt sand concrete mixture according to the designed dosage per unit area; 5. Crushing Use a 16t rubber-wheel roller to roll 5-6 times until the cement emulsified asphalt sand concrete is dense; 6. Maintenance The composite fault layer will be maintained for 7 days after construction is completed, and heavy vehicles are prohibited from passing through.

Images