A full-depth phosphogypsum-based multi-source solid waste composite roadbed pavement structure

Abstract

The application discloses a full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure. The roadbed and pavement structure comprises, from bottom to top, a roadbed, a cushion layer, a bottom base layer, a base layer and a surface layer. The roadbed is a phosphogypsum-based multi-source solid waste composite roadbed with a thickness of 30-50 cm. The cushion layer is a phosphogypsum-based multi-source solid waste cushion layer with a thickness of 15-30 cm. The bottom base layer is a phosphogypsum-based multi-source solid waste composite bottom base layer with a thickness of 15-40 cm. The base layer is a phosphogypsum-based multi-source solid waste composite base layer with a thickness of 20-40 cm. The application can realize full-depth replacement of conventional roadbed and pavement structures by phosphogypsum, slag and steel slag composite materials, significantly reduces the dependence of highway and municipal road construction on natural resources, is beneficial to ecological environment protection and green traffic transformation, and has remarkable economic and social benefits.

Description

Technical Field

[0001] This invention relates to the intersection of road engineering structural materials and comprehensive utilization of solid waste, specifically to a full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure. Background Technology

[0002] The traditional roadbed and pavement structures of highways of all grades in my country, from bottom to top, are as follows: a roadbed composed of undisturbed soil or soil that has been replaced and compacted; a subbase made of permeable materials such as sand, gravel, and crushed stone; a sub-base or base course composed of materials such as cement-stabilized soil, lime-stabilized soil, lime-fly ash-stabilized soil (two-lime stabilized soil), graded crushed stone or cement-stabilized crushed stone, lime-fly ash-stabilized crushed stone (two-lime stabilized crushed stone), and asphalt-stabilized crushed stone; and a surface course made of asphalt concrete or cement concrete. It is evident that the various structural layers of highways have a huge demand for cementitious materials and a high dependence on natural sand and gravel aggregates. Under the current overall background of energy conservation and carbon reduction in the transportation industry, the transformation of roadbed and pavement structures and materials for all grades of highways from traditional materials to emerging low-carbon recycled materials is an important path for the green transportation transformation.

[0003] The industry standards such as "Modified Phosphogypsum for Road Use" issued by the Ministry of Transport will come into effect in July 2025. The co-utilization of phosphogypsum with solid wastes such as slag and steel slag in highway construction will inevitably become one of the largest scenarios for large-scale solid waste disposal. However, the lack of suitable utilization methods has resulted in the application scale and effectiveness of bulk solid wastes such as phosphogypsum, slag and steel slag in highway engineering falling short of expectations.

[0004] The reasons for the above situation are as follows: First, existing solid waste utilization technologies are mostly designed for a single structural layer in highways, which neither maximizes the utilization of solid waste nor achieves optimal compatibility with other structural layers. Second, most solid waste utilization scenarios only use one or a few types of solid waste as stabilized materials in highway structural layers, failing to fully realize their potential. Third, they place high demands on construction personnel, equipment, and processes, or require special designs, making it difficult to guarantee the stability of construction quality. Taking the utilization of phosphogypsum-based materials in highway engineering as an example, existing technologies mostly use cement or curing agents to mix with phosphogypsum and compact it to form a (sub)base. This all-powder system has high requirements for the construction process, which is significantly different from the standards for traditional highway base design, construction, and acceptance, and its compatibility with the structures above and below it cannot be guaranteed. Summary of the Invention

[0005] In view of the above-mentioned shortcomings in the existing technology, the technical problem to be solved by the present invention is to provide a full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure.

[0006] The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure provided by this invention comprises, from bottom to top, a roadbed, a subbase, a composite subbase, a composite base, and a surface layer. The roadbed is a phosphogypsum-based multi-source solid waste composite roadbed with a thickness of 30–50 cm, and its constituent materials include phosphogypsum-based multi-source solid waste cementitious materials and soil. The subbase is a phosphogypsum-based multi-source solid waste subbase with a thickness of 15–30 cm, and its constituent materials include phosphogypsum-based multi-source solid waste recycled aggregate and geotextile. The subbase is a phosphogypsum-based multi-source solid waste composite subbase with a thickness of 15–40 cm, and its constituent materials include phosphogypsum-based multi-source solid waste cementitious materials and phosphogypsum-based multi-source solid waste recycled aggregate. The base is a phosphogypsum-based multi-source solid waste composite base with a thickness of 20–40 cm, and its constituent materials include cement and phosphogypsum-based multi-source solid waste cementitious materials, as well as phosphogypsum-based multi-source solid waste recycled aggregate.

[0007] Furthermore, the phosphogypsum-based multi-source solid waste composite roadbed is made by mixing 10%–100% phosphogypsum-based multi-source solid waste cementitious material and 0%–90% soil, with 0%–15% mixing water added (i.e., the weight of the mixing water accounts for 0%–15% of the sum of the weight of the phosphogypsum-based multi-source solid waste cementitious material and the soil), and then mixing and compacting it. The compaction degree is greater than 96%, and the California bearing capacity is greater than 8%.

[0008] Furthermore, the phosphogypsum-based multi-source solid waste cushion layer is formed by spreading and compacting phosphogypsum-based multi-source solid waste recycled aggregates, with a compaction degree greater than 96%, and geotextile is laid on the surface after compaction.

[0009] Furthermore, the phosphogypsum-based multi-source solid waste composite subbase consists of 60%–90% phosphogypsum-based multi-source solid waste cementitious material and 10%–40% phosphogypsum-based multi-source solid waste recycled aggregate, with 6%–40% mixing water added (i.e., the weight of mixing water accounts for 6%–40% of the sum of the weights of the phosphogypsum-based multi-source solid waste cementitious material and the phosphogypsum-based multi-source solid waste recycled aggregate), which is mixed, spread, and compacted, with a compaction degree greater than 96%.

[0010] Furthermore, the phosphogypsum-based multi-source solid waste composite base course is composed of 4%–6% cement or 6%–15% phosphogypsum-based multi-source solid waste cementitious material and 85%–96% phosphogypsum-based multi-source solid waste recycled aggregate, with 1.4%–10% mixing water added (i.e., the weight of mixing water accounts for 1.4%–10% of the sum of the weights of cement or phosphogypsum-based multi-source solid waste cementitious material and phosphogypsum-based multi-source solid waste recycled aggregate), which is mixed, spread and compacted, with a compaction degree greater than 98%.

[0011] Furthermore, the cement is ordinary Portland cement with a strength grade of 32.5 or 42.5.

[0012] Furthermore, the mixing water is ordinary tap water.

[0013] Furthermore, the tensile strength of the geotextile is ≥8 kN / m.

[0014] Furthermore, the phosphogypsum-based multi-source solid waste cementitious material is a mixture of phosphogypsum, slag, and steel slag in a mass ratio of (30–65):(30–55):(5–15).

[0015] Furthermore, the phosphogypsum-based multi-source solid waste recycled aggregate is made by mixing and granulating phosphogypsum, slag, and steel slag in a mass ratio of (30–65):(30–55):(5–15) with 7%–15% mixing water. The particle composition meets the gradation requirements of the "Technical Specifications for Construction of Highway Pavement Base Course" (JTG / T F20), and the crushing value is less than 26%.

[0016] Furthermore, the phosphogypsum has a particle size of 200–250 mesh, the slag is water-quenched granulated blast furnace slag produced in ironmaking, with a grade of S95, and the steel slag is alkaline oxygen converter steel slag produced in the converter steelmaking process, with a particle size of 200–300 mesh.

[0017] Compared with the prior art, the beneficial effects of the present invention include: (1) The solid waste content is nearly 100% from the roadbed to the base layer, which can maximize the absorption of bulk solid waste such as phosphogypsum, slag, and steel slag, and reduce the environmental pollution risk caused by the large-scale stockpiling of solid waste. At the same time, it saves a lot of traditional building materials such as cement and sand and reduces the exploitation of natural resources.

[0018] (2) The base course and subgrade, except for the surface course, are replaced in a full-depth manner in the traditional roadbed and pavement structure, so that the adaptation effect between each structural layer is optimal.

[0019] (3) The construction technology and equipment are no different from those of traditional roadbed and pavement construction, and the acceptance standards are also the same, which is conducive to promotion and application. Attached Figure Description

[0020] Figure 1 This is a structural diagram of the full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement of the present invention.

[0021] Figure 2 This is a diagram of a traditional roadbed and pavement structure. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides a full-depth phosphogypsum-based multi-source solid waste composite roadbed pavement structure, which is composed of a phosphogypsum-based multi-source solid waste composite roadbed, a phosphogypsum-based multi-source solid waste subbase, a phosphogypsum-based multi-source solid waste composite base course, a phosphogypsum-based multi-source solid waste composite base course, and a surface course laid in layers according to the designed thickness. From bottom to top, the components are as follows: a 30–50 cm thick phosphogypsum-based multi-source solid waste composite subgrade, mainly composed of 10%–100% phosphogypsum-based multi-source solid waste cementitious material and 0%–90% soil; a 15–30 cm thick phosphogypsum-based multi-source solid waste subbase, mainly composed of phosphogypsum-based multi-source solid waste recycled aggregate and geotextile; a 15–40 cm thick phosphogypsum-based multi-source solid waste composite base course, mainly composed of 60%–90% phosphogypsum-based multi-source solid waste cementitious material and 10%–40% phosphogypsum-based multi-source solid waste recycled aggregate; a 20–40 cm thick phosphogypsum-based multi-source solid waste composite base course, mainly composed of 4%–6% cement or 6%–15% phosphogypsum-based multi-source solid waste cementitious material and 85%–96% phosphogypsum-based multi-source solid waste recycled aggregate, and a conventional surface course. That is, both the roadbed and pavement structure of this invention and the traditional roadbed and pavement structure are five layers, but the composition of the five layers is different except for the surface layer (see...). Figure 1 and Figure 2 ).

[0024] Based on the physicochemical properties of industrial solid wastes such as phosphogypsum, slag, and steel slag, this invention designs a reasonable compounding scheme. This scheme not only utilizes the interactions between industrial solid wastes to increase recycling rates but also improves cementing efficiency to enhance the performance of subgrade and pavement materials. This invention combines different materials prepared from phosphogypsum-based multi-source solid waste cementitious materials and recycled aggregates into subgrade and base layers, fully leveraging the synergistic effect of similar materials to achieve superior overall structural mechanical properties. Therefore, the full-depth subgrade and pavement structure proposed in this invention, while ensuring the overall quality of the subgrade and pavement, significantly reduces the amount of cement and natural aggregates used in highway construction, saving costs, and is also beneficial to ecological environmental protection, resulting in outstanding social and economic benefits.

[0025] Unless otherwise specified, in the following examples and comparative examples, the phosphogypsum-based multi-source solid waste composite roadbed is made by mixing phosphogypsum-based multi-source solid waste cementitious material and soil, with 0%–15% mixing water added (i.e., the weight of the mixing water accounts for 0%–15% of the sum of the weights of the phosphogypsum-based multi-source solid waste cementitious material and soil), and then mixing and compacting it to achieve a compaction degree greater than 96% and a California bearing capacity greater than 8%. The phosphogypsum-based multi-source solid waste cushion layer is made by spreading and compacting phosphogypsum-based multi-source solid waste recycled aggregate to achieve a compaction degree greater than 96%, and then covering the surface with geotextile after compaction. The phosphogypsum-based multi-source solid waste composite subbase is composed of phosphogypsum-based multi-source solid waste cementitious materials and phosphogypsum-based multi-source solid waste recycled aggregates, with an external addition of 6%–40% mixing water (i.e., the weight of the mixing water accounts for 6%–40% of the sum of the weights of the phosphogypsum-based multi-source solid waste cementitious materials and phosphogypsum-based multi-source solid waste recycled aggregates). It is formed by mixing, spreading, and compacting, with a compaction degree greater than 96%. The phosphogypsum-based multi-source solid waste composite base course is composed of cement or phosphogypsum-based multi-source solid waste cementitious materials and phosphogypsum-based multi-source solid waste recycled aggregates, with an external addition of 1.4%–10% mixing water (i.e., the weight of the mixing water accounts for 1.4%–10% of the sum of the weights of the cement or phosphogypsum-based multi-source solid waste cementitious materials and phosphogypsum-based multi-source solid waste recycled aggregates). It is formed by mixing, spreading, and compacting, with a compaction degree greater than 98%. The cement is ordinary Portland cement with a strength grade of 32.5 or 42.5. The mixing water is ordinary tap water. The tensile strength of the geotextile is ≥8 kN / m. The phosphogypsum-based multi-source solid waste cementitious material is a mixture of phosphogypsum, slag, and steel slag in a mass ratio of 50:40:10. The phosphogypsum-based multi-source solid waste recycled aggregate is a mixture of phosphogypsum, slag, and steel slag in a mass ratio of 50:40:10, with 10% mixing water added, and then stirred and granulated. The particle composition meets the gradation requirements, and the crushing value is less than 26%. The particle size of the phosphogypsum is 200–250 mesh, the slag is water-quenched granulated blast furnace slag produced by ironmaking, grade S95, and the particle size of the steel slag is 200–300 mesh.

[0026] The present invention will be further described in detail below through specific embodiments.

[0027] Example 1: The roadbed and pavement structure, from bottom to top, consists of: a 30cm thick phosphogypsum-based multi-source solid waste composite roadbed (10% phosphogypsum-based multi-source solid waste cementitious material and 90% soil); an 18cm thick phosphogypsum-based multi-source solid waste subbase, with geotextile laid on the surface after compaction of phosphogypsum-based multi-source solid waste recycled aggregate); a 20cm thick phosphogypsum-based multi-source solid waste composite subbase (70% phosphogypsum-based multi-source solid waste cementitious material and 30% phosphogypsum-based multi-source solid waste recycled aggregate, with 28% mixing water added); and a 30cm thick phosphogypsum-based multi-source solid waste composite base course (5% cement and 95% phosphogypsum-based multi-source solid waste recycled aggregate, with 1.6% water added).

[0028] Example 2: The roadbed and pavement structure, from bottom to top, consists of: a 30cm thick phosphogypsum-based multi-source solid waste composite roadbed (50% phosphogypsum-based multi-source solid waste cementitious material and 50% soil, with 10% mixing water added); a 20cm thick phosphogypsum-based multi-source solid waste subbase, with geotextile laid on the surface after the phosphogypsum-based multi-source solid waste recycled aggregate is compacted; a 20cm thick phosphogypsum-based multi-source solid waste composite subbase (90% phosphogypsum-based multi-source solid waste cementitious material and 10% phosphogypsum-based multi-source solid waste recycled aggregate, with 35% mixing water added); and a 20cm thick phosphogypsum-based multi-source solid waste composite base course (10% phosphogypsum-based multi-source solid waste cementitious material and 90% phosphogypsum-based multi-source solid waste recycled aggregate, with 5% water added).

[0029] Example 3: The roadbed and pavement structure, from bottom to top, consists of: a 50cm thick phosphogypsum-based multi-source solid waste composite roadbed (90% phosphogypsum-based multi-source solid waste cementitious material and 10% soil, with 15% mixing water added); a 25cm thick phosphogypsum-based multi-source solid waste subbase, with geotextile laid on the surface after the phosphogypsum-based multi-source solid waste recycled aggregate is compacted; a 40cm thick phosphogypsum-based multi-source solid waste composite subbase (80% phosphogypsum-based multi-source solid waste cementitious material and 20% phosphogypsum-based multi-source solid waste recycled aggregate, with 25% mixing water added); and a 20cm thick phosphogypsum-based multi-source solid waste composite base course (15% phosphogypsum-based multi-source solid waste cementitious material and 85% phosphogypsum-based multi-source solid waste recycled aggregate, with 10% water added).

[0030] Example 4: The roadbed and pavement structure, from bottom to top, consists of: a 50cm thick phosphogypsum-based multi-source solid waste composite roadbed (80% phosphogypsum-based multi-source solid waste cementitious material and 20% soil, with 10% mixing water added); a 30cm thick phosphogypsum-based multi-source solid waste subbase, with geotextile laid on the surface after the phosphogypsum-based multi-source solid waste recycled aggregate is compacted; a 15cm thick phosphogypsum-based multi-source solid waste composite subbase (60% phosphogypsum-based multi-source solid waste cementitious material and 40% phosphogypsum-based multi-source solid waste recycled aggregate, with 18% mixing water added); and a 40cm thick phosphogypsum-based multi-source solid waste composite base course (15% phosphogypsum-based multi-source solid waste cementitious material and 85% phosphogypsum-based multi-source solid waste recycled aggregate, with 5% water added).

[0031] Comparative Example 1: The roadbed and pavement structure, from bottom to top, consists of: a 30cm thick roadbed (lime-soil); a 20cm thick lime-fly ash stabilized subbase; a 20cm thick cement-stabilized crushed stone lower base; and a 20cm thick cement-stabilized crushed stone upper base.

[0032] Comparative Example 2: The roadbed and pavement structure, from bottom to top, consists of: a 30cm thick phosphogypsum-based multi-source solid waste composite roadbed (10% phosphogypsum-based multi-source solid waste cementitious material and 90% soil); an 18cm thick phosphogypsum-based multi-source solid waste subbase (without geotextile); a 20cm thick phosphogypsum-based multi-source solid waste composite subbase (70% phosphogypsum-based multi-source solid waste cementitious material and 30% phosphogypsum-based multi-source solid waste recycled aggregate, with 28% mixing water added); and a 30cm thick phosphogypsum-based multi-source solid waste composite base course (5% cement and 95% phosphogypsum-based multi-source solid waste recycled aggregate, with 1.6% water added).

[0033] Comparative Example 3: The roadbed and pavement structure, from bottom to top, consists of: a 30cm thick roadbed (lime-soil); an 18cm thick phosphogypsum-based multi-source solid waste subbase, with geotextile laid on the surface after compaction; a 20cm thick phosphogypsum-based multi-source solid waste composite base course (70% phosphogypsum-based multi-source solid waste cementitious material and 30% phosphogypsum-based multi-source solid waste recycled aggregate, with 28% mixing water added); and a 30cm thick phosphogypsum-based multi-source solid waste composite base course (5% cement and 95% phosphogypsum-based multi-source solid waste recycled aggregate, with 1.6% water added).

[0034] Comparative Example 4: The roadbed and pavement structure, from bottom to top, consists of: a 30cm thick phosphogypsum-based multi-source solid waste composite roadbed (50% phosphogypsum-based multi-source solid waste cementitious material and 50% soil, with 10% mixing water added); a 20cm thick lime-fly ash stabilized soil subbase; a 20cm thick phosphogypsum-based multi-source solid waste composite subbase (90% phosphogypsum-based multi-source solid waste cementitious material and 10% phosphogypsum-based multi-source solid waste recycled aggregate, with 35% mixing water added); and a 20cm thick phosphogypsum-based multi-source solid waste composite base course (10% phosphogypsum-based multi-source solid waste cementitious material and 90% phosphogypsum-based multi-source solid waste recycled aggregate, with 5% water added).

[0035] Comparative Example 5: The roadbed and pavement structure, from bottom to top, consists of: a 50cm thick phosphogypsum-based multi-source solid waste composite roadbed (90% phosphogypsum-based multi-source solid waste cementitious material and 10% soil, with 15% mixing water added); a 25cm thick phosphogypsum-based multi-source solid waste subbase, with geotextile laid on the surface after compaction; a 40cm thick cement-stabilized crushed stone subbase; and a 20cm thick phosphogypsum-based multi-source solid waste composite base course (15% phosphogypsum-based multi-source solid waste cementitious material and 85% phosphogypsum-based multi-source solid waste recycled aggregate, with 10% water added).

[0036] Comparative Example 6: The roadbed and pavement structure, from bottom to top, consists of: a 50cm thick phosphogypsum-based multi-source solid waste composite roadbed (80% phosphogypsum-based multi-source solid waste cementitious material and 20% soil, with 10% mixing water added); a 30cm thick phosphogypsum-based multi-source solid waste subbase, with geotextile laid on the surface after compaction; a 15cm thick phosphogypsum-based multi-source solid waste composite subbase (60% phosphogypsum-based multi-source solid waste cementitious material and 40% phosphogypsum-based multi-source solid waste recycled aggregate, with 18% mixing water added); and a 40cm thick cement-stabilized crushed stone base course.

[0037] Comparative Example 7: The roadbed and pavement structure, from bottom to top, consists of: a 50cm thick phosphogypsum-based multi-source solid waste composite roadbed (80% phosphogypsum-based multi-source solid waste cementitious material and 20% soil, with 10% mixing water added); a 30cm thick phosphogypsum-based multi-source solid waste subbase, with geotextile laid on the surface after compaction; and a 55cm thick phosphogypsum-based multi-source solid waste composite base course (60% phosphogypsum-based multi-source solid waste cementitious material and 40% phosphogypsum-based multi-source solid waste recycled aggregate, with 18% mixing water added).

[0038] Comparative Example 8 The roadbed and pavement structure, from bottom to top, consists of: a 50cm thick phosphogypsum-based multi-source solid waste composite roadbed (90% phosphogypsum-based multi-source solid waste cementitious material and 10% soil, with 15% mixing water added); a 25cm thick phosphogypsum-based multi-source solid waste subbase, with geotextile laid on the surface after the phosphogypsum-based multi-source solid waste recycled aggregate is compacted; a 40cm thick phosphogypsum-based multi-source solid waste composite subbase (30% phosphogypsum-based multi-source solid waste cementitious material and 70% phosphogypsum-based multi-source solid waste recycled aggregate, with 25% mixing water added); and a 20cm thick phosphogypsum-based multi-source solid waste composite base course (15% phosphogypsum-based multi-source solid waste cementitious material and 85% phosphogypsum-based multi-source solid waste recycled aggregate, with 10% water added).

[0039] To verify the effectiveness of this invention, the mechanical response of asphalt pavement structures (with the same surface layers: a 4cm thick AC-13 top layer, a 6cm thick AC-20 middle layer, and an 8cm thick AC-25 bottom layer) using the above embodiments and comparative examples was calculated according to the "Specifications for Design of Asphalt Pavement of Highways" (JTG D50). The materials listed in this invention meet the requirements of the "Technical Specifications for Construction of Asphalt Pavement of Highways" (JTG F40) and the "Detailed Technical Specifications for Construction of Base Course of Highway Pavement" (JTG / T F20). The results are shown in Table 1.

[0040] Table 1 Calculation results of mechanical properties of different asphalt pavement structures As shown in Table 1, firstly, compared with the comparative examples, the asphalt pavement structures using Examples 1 to 4 all exhibited lower vertical compressive strain on the top surface of the subgrade. This indicates that the subgrades composed of different proportions of phosphogypsum-based multi-source solid waste cementitious materials and soil in the examples demonstrated excellent deformation resistance, and the superstructure layer composed of phosphogypsum-based multi-source solid waste cushion layer, composite subbase layer, and foundation also had good load diffusion effect.

[0041] Secondly, thanks to the suitable and continuously varying stiffness of the phosphogypsum-based multi-source solid waste cushion layer, the phosphogypsum-based multi-source solid waste composite subbase layer, and the phosphogypsum-based multi-source solid waste composite base layer, the combined effect results in a significantly lower tensile stress at the bottom of the asphalt pavement base layer using Examples 1-4, which is beneficial for improving the fatigue life of the asphalt pavement.

[0042] Third, the permanent deformation and tensile strain at the bottom of the asphalt mixture layer are similar to those of the traditional pavement structure asphalt pavement (Comparative Example 1), and significantly lower than those of other comparative examples. This indicates that the structural layer composed of the phosphogypsum-based multi-source solid waste subbase, composite subbase, and foundation provides sufficient support for the asphalt surface layer.

[0043] Fourth, in Comparative Example 2, the absence of geotextile on the subbase resulted in significant vertical deformation of the subgrade top surface, as well as substantial permanent deformation and tensile strain at the bottom of the asphalt surface layer. Comparative Examples 2-6 employed various schemes, including a geotextile-free subbase, a lime-soil subbase, a lime-fly ash stabilized soil subbase, a cement-stabilized crushed stone subbase, and a cement-stabilized crushed stone base, respectively. Comparative Example 7 employed a phosphogypsum-based multi-source solid waste composite base scheme with a relatively large single-layer thickness. Mechanical calculations showed that the vertical deformation of the subgrade top surface, the tensile strain at the bottom of the asphalt mixture layer, and the tensile stress at the bottom of the layer were greater in these schemes than in the previous example, indicating poor structural coordination. Comparative Example 8 used a smaller amount of phosphogypsum multi-source solid waste cementitious material to prepare the subbase, which could not guarantee the mechanical strength of this layer, resulting in poor overall pavement structural mechanical performance.

[0044] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0045] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure, comprising, from bottom to top, a roadbed, a subbase, a base course, and a surface course, characterized in that, The roadbed is a 30–50 cm thick phosphogypsum-based multi-source solid waste composite roadbed, composed of 10%–100% phosphogypsum-based multi-source solid waste cementitious material and 0%–90% soil; the subbase is a 15–30 cm thick phosphogypsum-based multi-source solid waste subbase, composed of phosphogypsum-based multi-source solid waste recycled aggregate and geotextile; the subbase is a 15–40 cm thick phosphogypsum-based multi-source solid waste composite subbase, composed of 60%–90% phosphogypsum-based multi-source solid waste cementitious material and 10%–40% phosphogypsum-based multi-source solid waste recycled aggregate; the base course is a 20–40 cm thick phosphogypsum-based multi-source solid waste composite base course, composed of 4%–6% cement and one of 6%–15% phosphogypsum-based multi-source solid waste cementitious material and 85%–96% phosphogypsum-based multi-source solid waste recycled aggregate.

2. The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure according to claim 1, characterized in that, The phosphogypsum-based multi-source solid waste composite roadbed is made by mixing phosphogypsum-based multi-source solid waste cementitious material and soil, adding 0%–15% mixing water, and then mixing and compacting it. The compaction degree is greater than 96%, and the California bearing capacity is greater than 8%.

3. The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure according to claim 1 or 2, characterized in that, The phosphogypsum-based multi-source solid waste cushion layer is formed by spreading and compacting phosphogypsum-based multi-source solid waste recycled aggregates, with a compaction degree greater than 96%, and geotextile is laid on the surface after compaction.

4. The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure according to claim 1 or 2, characterized in that, The phosphogypsum-based multi-source solid waste composite subbase is made by mixing phosphogypsum-based multi-source solid waste cementitious material and phosphogypsum-based multi-source solid waste recycled aggregate, with 6%–40% mixing water added, and is formed by mixing, spreading and rolling, with a compaction degree greater than 96%.

5. The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure according to claim 1 or 2, characterized in that, The phosphogypsum-based multi-source solid waste composite base course is made by mixing cement or phosphogypsum-based multi-source solid waste cementitious material and phosphogypsum-based multi-source solid waste recycled aggregate, with 1.4%–10% mixing water added, and then mixing, spreading and compacting it, with a compaction degree greater than 98%.

6. The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure according to claim 1 or 2, characterized in that, The cement is ordinary Portland cement with a strength grade of 32.5 or 42.

5.

7. The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure according to claim 1 or 2, characterized in that, The tensile strength of the geotextile is ≥8 kN / m.

8. The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure according to claim 1, characterized in that, The phosphogypsum-based multi-source solid waste cementitious material is a mixture of phosphogypsum, slag, and steel slag in a mass ratio of (30–65):(30–55):(5–15).

9. The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure according to claim 1, characterized in that, The phosphogypsum-based multi-source solid waste recycled aggregate is made by mixing and granulating phosphogypsum, slag, and steel slag in a mass ratio of (30–65):(30–55):(5–15) with 7%–15% mixing water. The particle composition meets the gradation requirements and the crushing value is less than 26%.

10. The full-depth phosphogypsum-based multi-source solid waste composite roadbed and pavement structure according to claim 8 or 9, characterized in that, The phosphogypsum has a particle size of 200–250 mesh, the slag is water-quenched granulated blast furnace slag produced in ironmaking, grade S95, and the steel slag is alkaline oxygen converter steel slag produced in the converter steelmaking process, with a particle size of 200–300 mesh.

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