Building waste-based permeable pavement structure and construction method and application thereof

Abstract

This invention discloses a permeable pavement structure based on construction waste, its construction method, and its application, relating to the technical field of construction waste recycling. A permeable pavement structure, from top to bottom, includes a permeable surface layer, a leveling layer, a permeable base layer, and a filter layer. The leveling layer and permeable base layer are both constructed using modified recycled aggregates, and the filter layer is also constructed using recycled aggregates. The recycled aggregates are obtained from construction waste through crushing, washing, impurity removal, and screening. The modified recycled aggregates are obtained by first impregnating the recycled aggregates with an impregnation slurry and then coating them with a composite cement slurry. The permeable pavement structure formed by this invention not only has good permeability and long-term stability but also consumes a large amount of construction waste, achieving on-site resource utilization and effectively solving the problem of construction waste disposal in the renovation of existing old residential areas.

Description

Technical Field

[0001] This invention relates to the technical field of construction waste recycling applications, and in particular to a permeable pavement structure based on construction waste, its construction method, and its application. Background Technology

[0002] With the continuous advancement of urbanization, the renovation of old residential communities has become an important project in urban renewal. These projects often generate large amounts of construction waste such as concrete blocks, brick rubble, and ceramic fragments. The most common method for handling this waste is off-site removal and landfilling; however, this method is not only costly but also prone to dust pollution. Furthermore, due to the generally high rate of surface hardening in old residential communities, the runoff coefficient can reach 0.7 to 0.9, leading to severe flooding on community roads during the rainy season and rapid rainwater runoff. These two major problems have become significant challenges for old residential community renovation projects in recent years.

[0003] Permeable pavement, as an important technical means of sponge city construction, can effectively reduce the road surface runoff coefficient and alleviate urban flooding. Since most permeable pavements currently use natural sand and gravel as paving aggregate, using construction waste generated during the renovation process as paving aggregate for permeable pavements in residential areas can solve the problem of waste removal on-site, achieving resource reuse of construction waste. It can also reduce the demand for natural sand and gravel in permeable pavement renovations and simultaneously achieve the renovation and improvement of old residential area roads.

[0004] However, due to the complex sources and numerous impurities of construction waste, when used directly as paving aggregate without treatment, it differs significantly from natural aggregate in terms of water absorption, porosity, and mechanical properties. Furthermore, its compatibility with cementitious materials varies considerably, leading to problems such as insufficient strength, cracking, and excessive harmful large pores in permeable pavements. This results in a rapid decline in permeability and affects the service life of the permeable pavement. In addition, existing construction waste recycling technologies focus only on pavement aggregates, neglecting the stability and support strength of construction waste as base course aggregates. They also fail to effectively address the issues of graded utilization and overall synergy of construction waste within the permeable pavement structure. Therefore, developing a permeable pavement structure that can fully utilize existing construction waste, has a reasonable structure, stable permeability, and is suitable for the renovation of old residential area roads has significant practical significance and application value for the recycling of construction waste and the renovation of old residential areas. Summary of the Invention

[0005] To address the issues of high transportation costs and severe dust pollution associated with the disposal of construction waste during the renovation of existing old residential communities, and to simultaneously improve the severe waterlogging and rapid rainwater runoff caused by the high hardening rate and high runoff coefficient of old residential community pavements, this application provides a permeable pavement structure based on construction waste, its construction method, and its application.

[0006] Firstly, the permeable pavement structure provided in this application adopts the following technical solution: A permeable pavement structure, comprising, from top to bottom: The permeable surface layer is made of permeable paving bricks or permeable asphalt mixture, and has an effective porosity of 18-25%. The leveling layer is composed of modified recycled aggregate and natural sand and gravel, and has an effective porosity of 20-25%. The permeable base course is composed of cement, modified recycled aggregate, and natural sand and gravel, and has an effective porosity of 15-20%. A filter layer, wherein the filter layer is composed of recycled aggregate and natural sand and gravel, and has an effective porosity of 20-35%; The recycled aggregate is obtained by crushing, washing, removing impurities and screening construction waste; the modified recycled aggregate is obtained by first impregnating the recycled aggregate with an impregnation slurry, drying it and then coating it with a composite cement slurry; the impregnation slurry includes an alkali activator, phosphogypsum and steel slag powder; the composite cement slurry includes ordinary silicate cement, silica fume, redispersible latex powder and retarder.

[0007] By adopting the above technical solutions, the resulting permeable pavement structure not only possesses excellent permeability and long-term stability, but also effectively consumes a large amount of construction waste generated during the renovation of old residential areas. Furthermore, the recycling and modification of construction waste can be carried out on-site using small-scale equipment, achieving local resource utilization and effectively solving the problem of construction waste disposal in the renovation of existing old residential areas. In addition, by designing a gradient porosity for each layer of the permeable pavement structure, the overall structure possesses highly efficient and stable permeability and a certain water storage capacity, effectively reducing the runoff coefficient of hardened surfaces in old residential areas and helping to alleviate problems such as waterlogging and rapid rainwater runoff within the communities.

[0008] Optionally, the method for preparing the modified recycled aggregate includes the following steps: A1. Mix the alkali activator, phosphogypsum, steel slag powder and water and stir evenly to obtain an impregnation slurry; then mix the recycled aggregate and the impregnation slurry evenly, and add an appropriate amount of water to ensure that the impregnation slurry can fully soak the recycled aggregate. Adjust the pH value to 11-13, stir intermittently and continue soaking for 2-4 hours. After soaking, drain the surface liquid, spread the recycled aggregate and place it in a drying oven, heat it to 60-75℃ and dry it for 6-12 hours to obtain primary recycled aggregate. A2. Mix ordinary silicate cement, silica fume, redispersible latex powder, retarder and water and stir evenly to obtain composite cement slurry. Use a spraying device to evenly spray the composite cement slurry onto the surface of the primary recycled aggregate while stirring to ensure even coating. After coating, air dry with hot air to obtain the modified recycled aggregate.

[0009] By adopting the above technical solutions, impregnation treatment can effectively reduce the crushing value and water absorption rate of recycled aggregates, thereby reducing the generation of endogenous blockages in permeable pavement structures and improving the rigidity and strength of recycled aggregates. The composite cement slurry coating forms an incompletely hydrated cement shell on the surface of the primary recycled aggregates. This not only prevents the adhesion of exogenous blockages and alleviates the decline in permeability efficiency, but also allows for secondary hydration reactions during subsequent applications or long-term maintenance. This enhances the bonding performance between the modified recycled aggregates and the concrete system of the permeable base layer, continuously densifies the overall permeable pavement structure, and stabilizes the pore morphology, thus ensuring the long-term permeability and structural stability of the permeable pavement structure. Furthermore, the two-step modification process is simple, requiring minimal complexities and large equipment, and can be carried out in situ on vacant land near old residential areas. This helps solve problems such as high costs and severe dust pollution associated with off-site removal of construction waste from existing residential areas.

[0010] Optionally, the impregnation slurry comprises, by weight percentage of the recycled aggregate, 0.5-1% alkali activator, 2-4% phosphogypsum, and 3-6% steel slag powder; The alkaline activator is a sodium silicate solution, and the modulus of the sodium silicate solution is adjusted to 1.5-1.8 by sodium hydroxide.

[0011] By adopting the above technical solution, the alkali activator can activate the activity of steel slag powder and phosphogypsum, thereby generating filler materials such as CSH gel and ettringite, which can then penetrate and repair the microcracks and pores inside the recycled aggregate, reduce the crushing value and water absorption rate of the aggregate, and provide a solid core foundation for subsequent secondary coating of composite cement slurry.

[0012] Optionally, in the composite cement slurry, the amount of ordinary Portland cement added is 0.5-2% of the mass of the primary recycled aggregate, and the mass ratio of the ordinary Portland cement, the silica fume, the redispersible latex powder, and the retarder is 10:(1-3):(1-2):(0.02-0.025), with a water-cement ratio of 0.32-0.36. The water-cement ratio is the ratio of water to the total mass of the ordinary Portland cement, the silica fume, and the redispersible latex powder.

[0013] By adopting the above technical solution, a uniform, dense, and incompletely hydrated active shell can be formed on the surface of the primary recycled aggregate. This shell can not only further hydrate with the concrete system in the permeable base course, improving the adhesion and compatibility between the modified recycled aggregate and the concrete system of the permeable base course, and further improving the compressive strength of the permeable base course, but also continuously undergo a secondary hydration reaction in the leveling layer, continuously strengthening the adhesion and pore stability between structural layers. This helps prevent the reduction of effective pores caused by structural damage and ensures the overall effective porosity.

[0014] Optionally, the thickness of the permeable surface layer is 50-80mm, the thickness of the leveling layer is 80-100mm, the thickness of the permeable base layer is 150-200mm, and the thickness of the filter layer is 100-150mm.

[0015] Optionally, in the leveling layer, the modified recycled aggregate has a particle size of 20-40 mm, the natural sand and gravel has a particle size of 16-31.5 mm, and the mass ratio of the modified recycled aggregate to the natural sand and gravel is (7-9):(1-3).

[0016] By adopting the above technical solution, and mixing an appropriate amount of natural sand and gravel into the modified recycled aggregate of the leveling layer, the aggregate gradation of the leveling layer can be adjusted and the compaction density of the leveling layer can be optimized. This can effectively provide a flat and solid supporting foundation for the permeable surface layer, which is beneficial to preventing surface cracking and damage caused by local interlayer or aggregate loosening in the leveling layer.

[0017] Optionally, the permeable base layer comprises the following raw materials in parts by weight: 250-320 parts of ordinary Portland cement, 800-1000 parts of modified recycled aggregate, 100-200 parts of natural sand and gravel, 20-40 parts of fly ash, 15-30 parts of silica fume, 2-10 parts of reinforcing fiber, 1.5-3 parts of water-reducing agent, and 80-120 parts of water. The modified recycled aggregate includes large modified recycled aggregate with a particle size of 50-100mm, medium modified recycled aggregate with a particle size of 20-40mm, and small modified recycled aggregate with a particle size of 5-20mm. The mass ratio of the large modified recycled aggregate, the medium modified recycled aggregate, and the small modified recycled aggregate is (6-8):(2-4):(0-1). The particle size of the natural sand and gravel is 50-100mm.

[0018] By adopting the above technical solution, by mixing and stacking modified recycled aggregates of multi-sized particle sizes with a small amount of natural sand and gravel, a permeable structure with good skeleton support and interconnected pores can be formed in the concrete system of the permeable base layer. Combined with the 15-20% effective porosity of the permeable base layer, it can ensure that the permeable base layer has both good permeability and a certain water storage capacity, thereby reducing the instantaneous drainage pressure of the drainage pipe.

[0019] Optionally, the filter layer comprises a first filter layer, a second filter layer and a third filter layer from top to bottom, and the thickness ratio of the first filter layer, the second filter layer and the third filter layer is 5:(3-4):(1-2). The first filter layer is made of recycled aggregate with a particle size of 10-20mm and natural sand and gravel, and the mass ratio of the recycled aggregate to the natural sand and gravel is (5-7):(3-5). The second filter layer is made of recycled aggregate with a particle size of 5-10 mm and natural sand and gravel, and the mass ratio of the recycled aggregate to the natural sand and gravel is (2-4):(6-8). The third filter layer is made of natural sand and gravel with a particle size of 0-5mm.

[0020] By adopting the above technical solution, a filter layer with a gradient particle size structure from coarse to fine is laid from top to bottom. This not only enables rapid water infiltration through the gradual change in pore size, but also works synergistically with the geotextile on the bottom side of the filter layer to prevent the loss of fine particles from the roadbed and prevent siltation in both directions. Simultaneously, it allows for a smooth and gradual change in the overall structural stiffness of the filter layer, reducing interlayer stress concentration, improving the load-bearing stability of the filter layer, and ensuring the long-term service life of the drainage pavement structure. Furthermore, the filter layer consumes a large amount of unmodified recycled aggregate, which helps reduce the additional costs associated with modifying the recycled aggregate and further improves the utilization rate of construction waste in the overall structure.

[0021] Secondly, the construction method for a permeable pavement structure provided in this application adopts the following technical solution: A construction method for a permeable pavement structure includes the following steps: S1. The subgrade soil is leveled and compacted in advance to form a roadbed, and the subgrade soil on both sides of the roadbed is compacted to form a subgrade soil cross-section, so that the subgrade soil cross-section is perpendicular to the roadbed. A layer of geotextile is laid on the surface of the roadbed and the subgrade soil cross-section, and then a filter layer is laid from bottom to top. Drainage blind pipes are buried in the filter layer. After the laying is completed, static pressure is used to compact it. S2. Lay a permeable base layer on the top side of the filter layer. During the laying process, local vibration is carried out. After the laying is completed, static pressure is used to compact it and it is cured for 1-2 days. S3. Lay a leveling layer on the top side of the permeable base layer, and control the surface flatness deviation to be ≤5mm / 2m. After laying, statically compact the layer. S4. Lay a permeable surface layer on the top side of the leveling layer. After laying, spray water for 1-3 days to cure, and the construction of the permeable pavement structure is completed.

[0022] By adopting the above technical solutions, the construction method is simple to operate and has a short maintenance period, making it suitable for application in old residential areas with narrow spaces, short construction periods, and complex construction conditions.

[0023] Thirdly, the application of the permeable pavement structure provided in this application adopts the following technical solution: An application of a permeable pavement structure in the road renovation project of an old residential area.

[0024] By adopting the above technical solution and applying the permeable pavement structure to road renovation projects in old residential areas, it can effectively handle construction waste such as concrete blocks, brick rubble, and ceramic fragments generated during the renovation process. Furthermore, the crushing, screening, and modification of construction waste can all be carried out on open land near the residential area. After processing, the waste can be used as aggregates at various levels in the permeable pavement structure, perfectly solving the problems of high costs and severe dust pollution associated with off-site removal of construction waste from existing residential areas. Simultaneously, because the permeable pavement structure has a gradient effective porosity of 18-35%, it can significantly reduce the runoff coefficient of hardened pavements in old residential areas from the original 0.7-0.9, which helps alleviate the problems of severe flooding and rapid rainwater runoff loss in old residential areas.

[0025] In summary, the technical solution of this application has at least one of the following beneficial effects: 1. By designing a permeable pavement structure with gradient porosity and using a large amount of modified recycled aggregate and recycled aggregate as filler aggregate, on the one hand, it can consume a large amount of construction waste generated in the renovation of old residential areas, realizing on-site resource utilization and effectively solving the problem of disposal of construction waste in the renovation of existing old residential areas. On the other hand, the structure can have efficient and stable permeability and a certain water storage capacity, thereby effectively reducing the runoff coefficient of hardened ground in old residential areas, which is conducive to alleviating problems such as waterlogging on roads and excessive rainwater loss in the community.

[0026] 2. By impregnating recycled aggregates and coating them with composite cement slurry, not only can the micro-cracks and pore defects inside the recycled aggregates made from construction waste be repaired, reducing their water absorption and crushing value, but a dense shell with secondary hydration activity can also be formed on the surface of the recycled aggregates. Through secondary hydration, the overall compressive strength and permeability efficiency attenuation rate of the permeable pavement structure can be improved, which is beneficial to solving various problems caused by the uneven quality of existing recycled aggregates when directly paving pavement structures. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of a permeable pavement structure according to Embodiment 1 of this application.

[0028] Explanation of reference numerals in the attached figures: 1. Permeable surface layer; 2. Leveling layer; 3. Permeable base layer; 4. Filter layer; 41. First filter layer; 42. Second filter layer; 43. Third filter layer. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings, preparation examples, embodiments and comparative examples.

[0030] For ordinary silicate cement, PO.42.5 grade silicate cement is specifically selected.

[0031] The sodium silicate solution was purchased from Kening New Materials, specifically the industrial grade sodium silicate solution-4. The mass fraction of Na2O in this grade of sodium silicate solution is 12.8%, and the initial modulus is 2.2 (the modulus is the molar ratio of SiO2 to Na2O).

[0032] The redispersible latex powder was purchased from Wacker Chemie, brand name ETONIS 7550A.

[0033] The retarder was purchased from Jiangsu Subote New Materials, brand name SBT-SR(Ⅰ) concrete retarder.

[0034] The water-reducing agent was purchased from Jiangsu Subote New Materials Co., Ltd., and its brand name is PCA-I, a polycarboxylate-based water-reducing agent. Preparation Example

[0035]

Preparation Example 1

[0036]

Preparation Example 2-1

[0037] In this preparation example, the recycled aggregate was prepared according to [Preparation Example 1], the alkali activator was sodium silicate solution, and the modulus of sodium silicate solution was adjusted to 1.5 using sodium hydroxide.

[0038]

Preparation Example 2-2

[0039] In this preparation example, the recycled aggregate was prepared according to [Preparation Example 1], the alkali activator was sodium silicate solution, and the modulus of sodium silicate solution was adjusted to 1.8 using sodium hydroxide.

[0040]

Preparation Examples 2-3

[0041]

Preparation Examples 2-4

[0042]

Example 1

[0043] In this embodiment, the permeable surface layer 1 is made of permeable asphalt mixture with a thickness of 50 mm and an effective porosity of 18-25%.

[0044] In this embodiment, the leveling layer 2 is composed of modified recycled aggregate and natural sand and gravel, with a thickness of 100 mm and an effective porosity controlled at 20-25%. The modified recycled aggregate has a particle size of 20-40 mm and is prepared according to [Preparation Example 2-1]. The natural sand and gravel has a particle size of 16-31.5 mm, and the mass ratio of modified recycled aggregate to natural sand and gravel is 7:3.

[0045] In this embodiment, the permeable base layer 3 has a thickness of 150 mm and an effective porosity controlled at 15-20%. The permeable base layer 3 is composed of the following raw materials: 300 kg of ordinary silicate cement, 1000 kg of modified recycled aggregate, 100 kg of natural sand and gravel, 20 kg of fly ash, 30 kg of silica fume, 5 kg of reinforcing fiber, 1.8 kg of water-reducing agent, and 100 kg of water.

[0046] The modified recycled aggregate includes 800 kg of large modified recycled aggregate with a particle size of 50-100 mm and 200 kg of medium modified recycled aggregate with a particle size of 20-40 mm, both prepared according to [Preparation Example 2-1]. The natural sand and gravel have a particle size of 50-100 mm. The reinforcing fiber is basalt fiber with a length of 6 mm.

[0047] In this embodiment, the thickness of the filter layer 4 is 100mm, and the effective porosity is controlled to be 20-35%. The filter layer 4 includes, from top to bottom, a first filter layer 41, a second filter layer 42, a third filter layer 43, and a drainage blind pipe buried in the third filter layer 43.

[0048] The first filter layer 41 is composed of recycled aggregate with a particle size of 10-20 mm and natural sand and gravel, with a thickness of 50 mm and a mass ratio of recycled aggregate to natural sand and gravel of 7:3. The second filter layer 42 is composed of recycled aggregate with a particle size of 5-10 mm and natural sand and gravel, with a thickness of 30 mm and a mass ratio of recycled aggregate to natural sand and gravel of 4:6. The third filter layer 43 is composed of natural sand and gravel with a particle size of 0-5 mm. Specifically, the recycled aggregate is prepared according to [Preparation Example 1].

[0049] A construction method for a permeable pavement structure includes the following steps: S1. The subgrade soil is leveled and compacted in advance to form a roadbed, and the subgrade soil on both sides of the roadbed is compacted to form a subgrade soil cross-section, so that the subgrade soil cross-section is perpendicular to the roadbed. A layer of geotextile is laid on the surface of the roadbed and the subgrade soil cross-section, and then the filter layer 4 is laid from bottom to top. Drainage blind pipes are buried in the filter layer 4. After the laying is completed, static pressure compaction is performed. S2. Lay a permeable base layer 3 on the top side of the filter layer 4. During the laying process, local vibration is carried out. After the laying is completed, static pressure is used to compact it and it is cured for 1 day. S3. Lay a leveling layer 2 on the top side of the permeable base layer 3, and control the surface flatness deviation to be ≤5mm / 2m. After laying, static pressure compaction is performed. S4. Lay a permeable surface layer 1 on the top side of the leveling layer 2. After laying, spray water for 2 days to cure, and the construction of the permeable pavement structure is completed.

[0050] An application of a permeable pavement structure in the renovation project of hardened pavement in old residential areas.

[0051]

Example 2

[0052] In this embodiment, the permeable surface layer 1 is paved with permeable paving bricks, with a thickness of 80mm, and the effective porosity is controlled to be 18-25%.

[0053] In this embodiment, the leveling layer 2 is composed of modified recycled aggregate and natural sand and gravel, with a thickness of 80 mm and an effective porosity controlled at 20-25%. The modified recycled aggregate has a particle size of 20-40 mm and is prepared according to [Preparation Example 2-1]. The natural sand and gravel has a particle size of 16-31.5 mm, and the mass ratio of modified recycled aggregate to natural sand and gravel is 9:1.

[0054] In this embodiment, the permeable base layer 3 has a thickness of 200 mm and an effective porosity of 15-20%. The permeable base layer 3 is made of the following raw materials: 320 kg of ordinary silicate cement, 800 kg of modified recycled aggregate, 200 kg of natural sand and gravel, 40 kg of fly ash, 15 kg of silica fume, 8 kg of reinforcing fiber, 2 kg of water-reducing agent, and 120 kg of water.

[0055] The modified recycled aggregate includes 600 kg of large modified recycled aggregate with a particle size of 50-100 mm, 180 kg of medium modified recycled aggregate with a particle size of 20-40 mm, and 20 kg of small modified recycled aggregate with a particle size of 5-10 mm, all prepared according to [Preparation Example 2-1]. The natural sand and gravel have a particle size of 50-100 mm. The reinforcing fiber is basalt fiber with a length of 6 mm.

[0056] In this embodiment, the thickness of the filter layer 4 is 150 mm, and the effective porosity is controlled to be 20-35%.

[0057] The first filter layer 41 is composed of recycled aggregate with a particle size of 10-20 mm and natural sand and gravel, with a thickness of 75 mm and a mass ratio of recycled aggregate to natural sand and gravel of 1:1. The second filter layer 42 is composed of recycled aggregate with a particle size of 5-10 mm and natural sand and gravel, with a thickness of 60 mm and a mass ratio of recycled aggregate to natural sand and gravel of 1:4. The third filter layer 43 is composed of natural sand and gravel with a particle size of 0-5 mm and a thickness of 15 mm. Specifically, the recycled aggregate is prepared according to [Preparation Example 1]. Comparative Example

[0058] Comparative Example 1 A permeable pavement structure, which differs from [Example 1] in that it does not use modified recycled aggregate.

[0059] In this comparative example, unmodified recycled aggregates of the same particle size were used to replace the modified recycled aggregates in each layer of the structure in equal amounts. Specifically, the unmodified recycled aggregates were all prepared according to [Preparation Example 1]. The construction method remained the same as in [Example 1].

[0060] Comparative Example 2 A permeable pavement structure, which differs from [Example 1] in that it uses different modified recycled aggregates.

[0061] In this comparative example, the modified recycled aggregate used in each layer structure was prepared according to [Preparation Examples 2-3].

[0062] Comparative Example 3 A permeable pavement structure, which differs from [Example 1] in that it uses different modified recycled aggregates.

[0063] In this comparative example, the modified recycled aggregate used in each layer structure was prepared according to [Preparation Examples 2-4]. Performance testing

[0064] 1. Overall permeability and long-term effectiveness: Referring to the permeable pavement structures in the various embodiments and comparative examples, paving was carried out in 2m×5m areas as experimental zones, ensuring that each experimental zone did not permeate or interfere with the others. After construction, normal watering and curing were carried out for 5 days. Then, a water truck simulated rainfall of 30mm / h for 2 hours. After the rain stopped, the time for water to recede from the road surface was measured. If the water receding time was ≤10min, it was considered qualified. After the test, the permeable pavement structures in each experimental zone were put into normal use and opened to traffic. One year later, the pavement condition was compared, and the overall permeability efficiency was tested again.

[0065] 2. Compressive strength test of permeable base course 3: Referring to the formula and construction process of permeable base course 3 in each embodiment and comparative example, and in accordance with the requirements of Chapter 4 of "GB / T 50081-2020 Standard for Test Methods of Mechanical Properties of Ordinary Concrete", standard cubic specimens with a side length of 150mm*150mm*150mm were poured and cured for 28 days. Then, the test was carried out in accordance with Section 5 of "GB / T 50081-2002 Standard for Test Methods of Physical and Mechanical Properties of Concrete", and the compressive strength (MPa) of the permeable base course 3 prepared in each embodiment and comparative example was recorded.

[0066] Table 1 Performance test data of permeable pavement structure

[0067] Based on Examples 1-2 and the data in Table 1, it can be seen that the permeable pavement structure disclosed in this application has good permeability and long-term durability. Moreover, it can use a large amount of recycled aggregate in the structure, which can not only solve the problem of construction waste disposal in the renovation of existing old residential areas, but also be applied to the renovation of old residential area roads and solve the problems of severe waterlogging and excessive rainwater runoff in existing old residential area roads.

[0068] Based on Example 1 and Comparative Examples 1-3, and the data in Table 1, it can be seen that by performing a two-step modification treatment on the recycled aggregate, namely impregnation treatment and composite cement slurry coating, the modified recycled aggregate can significantly improve the compressive strength of the permeable base course 3. In addition, during daily use, the modified recycled aggregate can reduce the decay of the permeability efficiency of the overall permeable pavement structure, and can still maintain good permeability after long-term use. Moreover, the permeable surface layer 1 is not prone to cracking, subsidence, or other problems.

[0069] The above effects are likely due to the fact that during the two-step modification process, the impregnation treatment can effectively repair the internal defects of the recycled aggregate, improve its density, and reduce the water absorption and crushing value of the recycled aggregate. This not only reduces the tendency of the recycled aggregate to pulverize and reduces the endogenous blockages generated by the recycled aggregate itself, ensuring the effective porosity of the overall permeable pavement structure, but also significantly improves the strength and rigidity of the recycled aggregate itself. This provides uniform and solid support for the permeable base layer 3 and the leveling layer 2, reducing the possibility of the permeable surface layer 1 being crushed and structurally deformed due to insufficient strength of the underlying structure. The composite cement slurry coating can form a uniform and dense, incompletely hydrated cement shell on the surface of the aggregate. This not only makes it difficult for exogenous mud and sand to adhere to or remain in the gaps on the surface of the recycled aggregate, thus helping to solve the problems of exogenous blockage and reduced permeability, but also allows the incompletely hydrated cement in the shell to undergo a secondary hydration reaction when the modified recycled aggregate is filled into the concrete system of the permeable base layer 3 or during long-term use. This enhances the bonding performance between the modified recycled aggregate and the concrete system of the permeable base layer 3, which is beneficial to further improve the compressive strength of the permeable base layer 3. Furthermore, it continuously compacts the structure of the leveling layer 2 and stabilizes the pore morphology, which helps to prevent the reduction of effective pores caused by structural damage and ensures the overall effective porosity.

[0070] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A pervious pavement structure, characterized by, From top to bottom, they include: The permeable surface layer (1) is made of permeable paving bricks or permeable asphalt mixture and has an effective porosity of 18-25%. Leveling layer (2), the leveling layer (2) is made of modified recycled aggregate and natural sand and gravel, and has an effective porosity of 20-25%; The permeable base course (3) is made of cement, modified recycled aggregate and natural sand and gravel, and has an effective porosity of 15-20%. The filter layer (4) is composed of recycled aggregate and natural sand and gravel, and has an effective porosity of 20-35%. The recycled aggregate is obtained by crushing, washing, removing impurities and screening construction waste; the modified recycled aggregate is obtained by first impregnating the recycled aggregate with an impregnation slurry, drying it and then coating it with a composite cement slurry; the impregnation slurry includes an alkali activator, phosphogypsum and steel slag powder; the composite cement slurry includes ordinary silicate cement, silica fume, redispersible latex powder and retarder.

2. A pervious pavement structure according to claim 1, wherein: The method for preparing the modified recycled aggregate includes the following steps: A1. Mix the alkali activator, phosphogypsum, steel slag powder and water and stir evenly to obtain an impregnation slurry; then mix the recycled aggregate and the impregnation slurry evenly, and add an appropriate amount of water to ensure that the impregnation slurry can fully soak the recycled aggregate. Adjust the pH value to 11-13, stir intermittently and continue soaking for 2-4 hours. After soaking, drain the surface liquid, spread the recycled aggregate and place it in a drying oven, heat it to 60-75℃ and dry it for 6-12 hours to obtain primary recycled aggregate. A2. Mix ordinary silicate cement, silica fume, redispersible latex powder, retarder and water and stir evenly to obtain composite cement slurry. Use a spraying device to evenly spray the composite cement slurry onto the surface of the primary recycled aggregate while stirring to ensure even coating. After coating, air dry with hot air to obtain the modified recycled aggregate.

3. The permeable pavement structure according to claim 2, characterized in that: The impregnation slurry comprises, by weight percentage of the recycled aggregate, 0.5-1% alkali activator, 2-4% phosphogypsum, and 3-6% steel slag powder; The alkaline activator is a sodium silicate solution, and the modulus of the sodium silicate solution is adjusted to 1.5-1.8 by sodium hydroxide.

4. The permeable pavement structure according to claim 2, characterized in that: In the composite cement slurry, the amount of ordinary silicate cement added is 0.5-2% of the mass of the primary recycled aggregate, and the mass ratio of the ordinary silicate cement, the silica fume, the redispersible latex powder and the retarder is 10:(1-3):(1-2):(0.02-0.025), and the water-cement ratio is 0.32-0.

36.

5. The permeable pavement structure according to claim 1, characterized in that: The thickness of the permeable surface layer (1) is 50-80mm, the thickness of the leveling layer (2) is 80-100mm, the thickness of the permeable base layer (3) is 150-200mm, and the thickness of the filter layer (4) is 100-150mm.

6. A permeable pavement structure according to claim 5, characterized in that: In the leveling layer (2), the particle size of the modified recycled aggregate is 20-40 mm, the particle size of the natural sand and gravel is 16-31.5 mm, and the mass ratio of the modified recycled aggregate to the natural sand and gravel is (7-9):(1-3).

7. A permeable pavement structure according to claim 5, characterized in that: The permeable base layer (3) comprises the following raw materials in parts by weight: 250-320 parts of ordinary Portland cement, 800-1000 parts of modified recycled aggregate, 100-200 parts of natural sand and gravel, 20-40 parts of fly ash, 15-30 parts of silica fume, 2-10 parts of reinforcing fiber, 1.5-3 parts of water-reducing agent, and 80-120 parts of water. The modified recycled aggregate includes large modified recycled aggregate with a particle size of 50-100mm, medium modified recycled aggregate with a particle size of 20-40mm, and small modified recycled aggregate with a particle size of 5-20mm. The mass ratio of the large modified recycled aggregate, the medium modified recycled aggregate, and the small modified recycled aggregate is (6-8):(2-4):(0-1). The particle size of the natural sand and gravel is 50-100mm.

8. A permeable pavement structure according to claim 5, characterized in that: The filter layer (4) includes a first filter layer (41), a second filter layer (42) and a third filter layer (43) from top to bottom. The thickness ratio of the first filter layer (41), the second filter layer (42) and the third filter layer (43) is 5:(3-4):(1-2). The first filter layer (41) is made of recycled aggregate with a particle size of 10-20 mm and natural sand and gravel, and the mass ratio of the recycled aggregate to the natural sand and gravel is (5-7):(3-5). The second filter layer (42) is made of recycled aggregate with a particle size of 5-10 mm and natural sand and gravel, and the mass ratio of the recycled aggregate to the natural sand and gravel is (2-4):(6-8). The third filter layer (43) is made of natural sand and gravel with a particle size of 0-5 mm.

9. A construction method for a permeable pavement structure, used for constructing the permeable pavement structure as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. The subgrade soil is leveled and compacted in advance to form a roadbed, and the subgrade soil on both sides of the roadbed is compacted to form a subgrade soil cross-section, so that the subgrade soil cross-section is perpendicular to the roadbed. A layer of geotextile is laid on the surface of the roadbed and the subgrade soil cross-section, and then a filter layer (4) is laid from bottom to top. Drainage blind pipes are buried in the filter layer (4). After the laying is completed, static pressure compaction is performed. S2. Lay a permeable base layer (3) on the top side of the filter layer (4), and perform local vibration during the laying process. After the laying is completed, static pressure compaction is performed and the layer is cured for 1-2 days. S3. Lay a leveling layer (2) on the top side of the permeable base layer (3), control the surface flatness deviation to be ≤5mm / 2m, and compact it with static pressure after laying. S4. Lay a permeable surface layer (1) on the top side of the leveling layer (2). After laying, spray water for 1-3 days to cure, and the construction of the permeable pavement structure is completed.

10. An application of a permeable pavement structure, applicable to the permeable pavement structure as described in any one of claims 1-8, characterized in that: It is applied to road renovation projects in old residential areas.

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