Sandwich-structure roadbed filler as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of waste utilization, and particularly relates to a sandwich structure roadbed filler as well as a preparation method and application thereof. According to the sandwich structure roadbed filler provided by the invention, the economical efficiency and environmental protection property of the muck and the water resistance and high strength of the waste concrete recycled aggregate are fully utilized, and the muck and the reinforced waste concrete recycled aggregate are arranged in a layered manner, so that a brand new sandwich structure is obtained; the construction waste is converted into a structural material with certain strength and stability, the strength of the roadbed filler is improved, meanwhile, the water resistance of the overall structure can be improved, the durability and reliability of road engineering are improved, resource utilization of the construction waste such as muck is achieved, the utilization rate of the construction material is increased, and the cost is reduced. And the cost of engineering construction is reduced, and the application of the construction waste in the fully-distributed grade road engineering is effectively promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of waste utilization, and in particular relates to a sandwich structure roadbed filler and a preparation method and application thereof. Background Art

[0002] With the development of urbanization, my country's infrastructure construction has flourished, and the demand for roadbed fillers has increased rapidly. At present, my country mainly relies on natural resources such as stone and river sand to produce roadbed fillers. Long-term mining has led to resource shortages, and the contradiction between municipal engineering and stone resources has become increasingly acute. In order to reduce the consumption of natural stones and mitigate the impact of construction waste on the environment, people have begun to use construction waste for roadbed backfill.

[0003] Common construction waste includes waste concrete, waste bricks, slag and miscellaneous gravel. Among them, waste concrete will produce a large number of micro cracks during the processing into recycled aggregate, and will be attached with impurities such as mortar and cement, resulting in low strength and easy to break. Slag has a large output, is economical and environmentally friendly, and is easy to obtain, but its composition is relatively complex, usually containing a variety of construction waste, with great heterogeneity, resulting in low strength and easy deformation and damage. Summary of the invention

[0004] The purpose of the present invention is to provide a sandwich structure roadbed filler and a preparation method and application thereof. The sandwich structure roadbed filler provided by the present invention has high strength.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The invention provides a sandwich structure roadbed filler, comprising a first construction waste soil layer, a first recycled aggregate layer, a geogrid, a second recycled aggregate layer and a second construction waste soil layer which are arranged in sequence.

[0007] Preferably, the grading of the construction waste in the first construction waste layer and the second construction waste layer is: the pass rate of the standard sieve hole 10 mm is 100%; the pass rate of the standard sieve hole 5 mm is 96.8%; the pass rate of the standard sieve hole 1 mm is 70%; the pass rate of the standard sieve hole 0.5 mm is 55.2%; the pass rate of the standard sieve hole 0.1 mm is 40.2%; the pass rate of the standard sieve hole 0.075 mm is 34.3%.

[0008] Preferably, the thickness of the first construction waste soil layer is 10 to 40 mm; the thickness of the first recycled aggregate layer is 20 to 50 mm; the thickness of the geogrid is 1 to 4 mm, and the aperture size is 25 mm×25 mm; the thickness of the second recycled aggregate layer is 20 to 50 mm; and the thickness of the second construction waste soil layer is 10 to 40 mm.

[0009] Preferably, the recycled aggregate is waste concrete recycled aggregate or improved recycled aggregate; the improved recycled aggregate comprises 100 parts of waste concrete and 1 to 2 parts of nano-silicon dioxide by mass.

[0010] Preferably, the gradation of the recycled aggregate in the first recycled aggregate layer and the second recycled aggregate layer is: the pass rate of the standard sieve hole 20 mm is 100%; the pass rate of the standard sieve hole 16 mm is 95%; the pass rate of the standard sieve hole 14 mm is 80.3%; the pass rate of the standard sieve hole 11 mm is 60.5%; the pass rate of the standard sieve hole 9 mm is 40%; the pass rate of the standard sieve hole 7 mm is 20.2%; the pass rate of the standard sieve hole 4.75 mm is 11.7%; the pass rate of the standard sieve hole 0.6 mm is 0.8%.

[0011] Preferably, the sandwich structure roadbed filler also includes a metal mesh arranged between the first building debris layer and the second recycled aggregate layer and / or a high-strength glass fiber mesh arranged between the second recycled aggregate layer and the second building debris layer; the performance parameters of the high-strength glass fiber mesh are: radial breaking strength ≥50kN / m, transverse breaking elongation ≤4%, latitudinal breaking strength ≥50kN / m, latitudinal breaking elongation ≤4%.

[0012] The present invention also provides a method for preparing the sandwich structure roadbed filler described in the above scheme, comprising the following steps:

[0013] On the roadbed surface, from bottom to top, construction waste is laid in sequence to form a first construction waste layer, recycled aggregate is laid to form a first recycled aggregate layer, geogrid is laid, recycled aggregate is laid to form a second recycled aggregate layer, and construction waste is laid to form a second construction waste layer, so as to obtain a sandwich structure roadbed filling material on the roadbed surface.

[0014] Preferably, the laying method of the metal mesh is: laying the metal mesh on the first construction waste soil layer, laying it longitudinally along the route, tightening and leveling it, and arranging fixing nails.

[0015] Preferably, the method for laying the high-strength glass fiber mesh is: laying the high-strength glass fiber mesh on the second recycled aggregate layer, tightening and leveling it, and arranging fixing nails on the high-strength glass fiber mesh.

[0016] The present invention also provides the use of the sandwich structure roadbed filler described in the above scheme or the sandwich structure roadbed filler obtained by the preparation method described in the above scheme in road engineering.

[0017] The present invention provides a sandwich structure roadbed filler. Traditional construction waste treatment methods often lead to a large amount of resource waste and environmental pollution. The sandwich structure roadbed filler provided by the present invention fully utilizes the economy and environmental protection of slag, as well as the water resistance and high strength of waste concrete recycled aggregate. By arranging slag and reinforced waste concrete recycled aggregate in layers, a new sandwich structure is obtained, which converts construction waste into a structural material with certain strength and stability. While improving the strength of the roadbed filler, the water resistance of the overall structure can be improved, the durability and reliability of the road project are increased, and the resource utilization of construction waste such as slag is realized, the utilization rate of building materials is improved, the cost of engineering construction is reduced, and the application of construction waste in full-distribution grade road projects is effectively promoted. By adding waste concrete recycled aggregate into the structure, the present invention reduces the demand for original resources, is economical and environmentally friendly, and also helps to protect natural resources, reduce carbon emissions and energy consumption, and reduce damage to the natural environment, reflecting the concept of resource recycling and environmental protection.

[0018] The present invention also provides a method for preparing the sandwich structure roadbed filler described in the above scheme. The sandwich structure roadbed filler prepared by the present invention not only provides a theoretical basis for the application of construction waste in road engineering, but also provides technical support for resource conservation, waste utilization and cost reduction, and more effectively solves the problem of construction waste treatment and reuse.

[0019] The present invention also provides the use of the sandwich structure roadbed filler described in the above scheme or the sandwich structure roadbed filler obtained by the preparation method described in the above scheme in road engineering. The sandwich structure roadbed filler provided by the present invention conforms to the concept of sustainable development and helps to promote the construction industry to develop in a green and sustainable direction. In addition, the promotion and application of this structure can also promote the development of related industries, create jobs, and bring positive impacts to the social economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a side view of the sandwich structure roadbed filling material of Examples 1 to 4;

[0022] Figure 2 It is an elevation view of the sandwich structure roadbed filler of Examples 1 to 4 used for roadbed filling;

[0023] Figure 3It is a schematic diagram of part of the process flow of sandwich structure roadbed fillers of Examples 1 to 4;

[0024] Figure 4 Schematic diagram of the structure of the dynamic direct shear apparatus used in Examples 1 to 4;

[0025] Figure 5 Schematic diagram of direct shear specimens and shear paths of sandwich structure roadbed fillers of Examples 1 to 4;

[0026] Figure 6 is the monotonic shear stress-shear displacement relationship curve of Example 1 when the vertical stress is 30 kPa;

[0027] Figure 7 1 is the cyclic shear stress-shear displacement relationship curve of Example 1 when the vertical stress is 60 kPa and the shear amplitude is 3 mm;

[0028] Figure 8 is the monotonic shear stress-shear displacement relationship curve of Example 2 when the vertical stress is 30 kPa;

[0029] Fig. 9 cyclic shear stress-shear displacement relationship curve of Example 2 at a vertical stress of 60 kPa and a shear amplitude of 3 mm;

[0030] Fig.10 This is the monotonic shear stress-shear displacement relationship curve of Example 3 when the vertical stress is 30 kPa;

[0031] Fig.11 This is the cyclic shear stress-shear displacement relationship curve of Example 3 when the vertical stress is 60 kPa and the shear amplitude is 3 mm;

[0032] Fig.12 is the monotonic shear stress-shear displacement relationship curve of Example 4 when the vertical stress is 30 kPa;

[0033] Fig.13 4 is the cyclic shear stress-shear displacement relationship curve of Example 4 when the vertical stress is 60 kPa and the shear amplitude is 3 mm;

[0034] Fig.14 This is a schematic diagram of the process flow of improving recycled aggregate 7 in Example 6;

[0035] Fig.15 It is a side view of the bottom sandwich structure roadbed filling material of Example 7;

[0036] Fig.16 It is a side view of the top sandwich structure roadbed filler of Example 7;

[0037] Fig.17It is an elevation view of the sandwich structure roadbed filling material used for roadbed filling in Example 7;

[0038] Fig.18 The monotonic shear test result diagram of the construction waste / improved recycled aggregate, construction waste / metal mesh / improved recycled aggregate, and construction waste / high-strength glass fiber mesh / improved recycled aggregate in Example 7;

[0039] Figure numerals: 1 is construction waste, 2 is recycled aggregate, 3 is geogrid, 4 is roadbed, 5 is pavement, 6 is concrete block, 7 is hammer crusher, 8 is jaw crusher, 9 is crushed concrete block, 10 is vibrating screen, 11 is gradation curve (specific values ​​are shown in Table 1 and Table 2), 12 is indoor large direct shear instrument, 13 is horizontal displacement sensor, 14 is vertical displacement sensor, 15 is clamping block, 16 is linear guide rail, 17 is lower shear box, 18 is upper shear box, 19 is nano silicon dioxide, 20 is polyethylene glycol particles, 21 is nano silicon dioxide suspension, 22 is ultrasonic dispersion, 23 is large-size recycled aggregate spraying, 24 is small-size recycled aggregate soaking, 25 is metal mesh, 26 is improved recycled aggregate, and 27 is high-strength glass fiber mesh. DETAILED DESCRIPTION

[0040] The invention provides a sandwich structure roadbed filler, comprising a first construction waste soil layer, a first recycled aggregate layer, a geogrid, a second recycled aggregate layer and a second construction waste soil layer which are arranged in sequence.

[0041] The sandwich structure roadbed filler provided by the present invention includes a first construction debris layer; the first construction debris layer is construction debris; the construction debris preferably includes construction debris A, construction debris B, construction debris C, construction debris D, construction debris E and construction debris F.

[0042] In the present invention, the particle size of the construction waste A is preferably 5 to 10 mm, specifically 6 mm, 7 mm, 8 mm or 9 mm.

[0043] In the present invention, the particle size of the construction waste B is preferably 1 to 5 mm (excluding 5 mm), specifically 2 mm, 3 mm or 4 mm.

[0044] In the present invention, the particle size of the construction waste C is preferably 0.5-1 mm (excluding 1 mm), and specifically may be 0.6 mm, 0.7 mm, 0.8 mm or 0.9 mm.

[0045] In the present invention, the particle size of the construction waste soil D is preferably 0.1-0.5 mm (excluding 0.5 mm), and specifically may be 0.2 mm, 0.3 mm or 0.4 mm.

[0046] In the present invention, the particle size of the construction waste E is preferably 0.075-0.1 mm (excluding 0.1 mm), and specifically may be 0.080 mm, 0.085 mm, 0.090 mm or 0.095 mm.

[0047] In the present invention, the particle size of the construction waste F is preferably 0 to 0.075 mm (excluding 0.075 mm), and specifically may be 0.07 mm, 0.05 mm, 0.03 mm or 0.01 mm.

[0048] In the present invention, the grading of the construction waste in the first construction waste layer is preferably: the pass rate of the standard sieve hole 10 mm is 100%; the pass rate of the standard sieve hole 5 mm is 96.8%; the pass rate of the standard sieve hole 1 mm is 70%; the pass rate of the standard sieve hole 0.5 mm is 55.2%; the pass rate of the standard sieve hole 0.1 mm is 40.2%; the pass rate of the standard sieve hole 0.075 mm is 34.3%.

[0049] In the present invention, the method for preparing the construction waste in the first construction waste layer is preferably: the construction waste sampled on site is sieved using a vibrating screen to obtain 6 particle groups of construction waste, and the grading is performed according to the target gradation.

[0050] In the present invention, the performance parameters of the construction waste in the first construction waste layer are preferably: natural moisture content is 19%, natural density is 1.81 g / cm 3 , dry density is 1.74g / cm 3 , liquid limit is 29.5%, plastic limit is 21.3%, plasticity index is 8.2, optimum moisture content is 15%, maximum dry density is 1.83g / cm 3 , the CBR value is 51.2%.

[0051] In the present invention, the thickness of the first construction waste soil layer is preferably 10-40 mm, specifically 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm or 40 mm.

[0052] The sandwich structure roadbed filler provided by the present invention comprises a first recycled aggregate layer; the first recycled aggregate layer is recycled aggregate; the recycled aggregate is preferably waste concrete recycled aggregate or improved recycled aggregate; the improved recycled aggregate preferably comprises 100 parts of waste concrete and 1 to 2 parts of nano silicon dioxide in terms of mass; the particle size of the nano silicon dioxide is preferably 20 to 50 nm, specifically 30 nm or 40 nm.

[0053] In the present invention, the preparation method of the improved recycled aggregate is preferably: nano-silicon dioxide, a dispersant and water are mixed to obtain a nano-silicon dioxide suspension, the nano-silicon dioxide suspension is ultrasonically dispersed and then mixed with waste concrete, and then naturally air-dried.

[0054] In the present invention, the dispersant is preferably polyethylene glycol; the concentration of nano-silicon dioxide in the nano-silicon dioxide suspension is preferably 1-5wt%, specifically 3wt%, and the concentration of the dispersant is preferably 0.1-0.5wt%, specifically 0.3wt%.

[0055] In the present invention, the dispersion time of the ultrasonic dispersion is preferably 15 to 30 minutes, specifically 20 minutes or 25 minutes.

[0056] In the present invention, the waste concrete is preferably cleaned, dried and crushed before use; the drying is preferably air-drying.

[0057] In the present invention, when the particle size of the improved recycled aggregate is 14 to 20 mm, the mixing of the nano-silicon dioxide suspension and the waste concrete is preferably: spraying the nano-silicon dioxide suspension on the surface of the waste concrete; when the particle size of the improved recycled aggregate is less than 14 mm, the mixing of the nano-silicon dioxide suspension and the waste concrete is preferably: immersing the waste concrete in the nano-silicon dioxide suspension.

[0058] In the present invention, the soaking time is preferably 10 to 30 minutes, specifically 20 minutes. Through the above improvement, the present invention promotes the production of CSH gel between nano-silicon dioxide and concrete, and nano-silicon dioxide fills the surface pores, internal pores and micro-cracks of the recycled aggregate, making the contact between particles closer, improving its compression resistance, and significantly improving the CBR value of the improved recycled aggregate.

[0059] In the present invention, the recycled aggregate in the first recycled aggregate layer preferably includes recycled aggregate A, recycled aggregate B, recycled aggregate C, recycled aggregate D, recycled aggregate E, recycled aggregate F, recycled aggregate G and recycled aggregate H.

[0060] In the present invention, the particle size of the recycled aggregate A is preferably 16-20 mm, specifically 17 mm, 18 mm or 19 mm.

[0061] In the present invention, the particle size of the recycled aggregate B is preferably 14 to 16 mm (excluding 16 mm), and specifically may be 15 mm.

[0062] In the present invention, the particle size of the recycled aggregate C is preferably 11 to 14 mm (excluding 14 mm), specifically 12 mm or 13 mm.

[0063] In the present invention, the particle size of the recycled aggregate D is preferably 9 to 11 mm (excluding 11 mm), and specifically may be 10 mm.

[0064] In the present invention, the particle size of the recycled aggregate E is preferably 7 to 9 mm (excluding 9 mm), and specifically may be 8 mm.

[0065] In the present invention, the particle size of the recycled aggregate F is preferably 4.75 to 7 mm (excluding 7 mm), and specifically may be 5 mm or 6 mm.

[0066] In the present invention, the particle size of the recycled aggregate G is preferably 0.6-4.75 mm (excluding 4.75 mm), and specifically can be 0.8 mm, 1 mm, 2 mm, 3 mm, 4 mm or 4.5 mm.

[0067] In the present invention, the particle size of the recycled aggregate H is preferably 0-0.6 mm (excluding 0.6 mm), and specifically can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm or 0.5 mm.

[0068] In the present invention, the gradation of the recycled aggregate in the first recycled aggregate layer is preferably: the pass rate of the standard sieve hole 20 mm is 100%; the pass rate of the standard sieve hole 16 mm is 95%; the pass rate of the standard sieve hole 14 mm is 80.3%; the pass rate of the standard sieve hole 11 mm is 60.5%; the pass rate of the standard sieve hole 9 mm is 40%; the pass rate of the standard sieve hole 7 mm is 20.2%; the pass rate of the standard sieve hole 4.75 mm is 11.7%; the pass rate of the standard sieve hole 0.6 mm is 0.8%.

[0069] In the present invention, the preparation method of the recycled aggregate in the first recycled aggregate layer is preferably: the discarded concrete blocks are preliminarily manually screened to remove impurities, and then washed and air-dried in sequence, and then crushed with a hammer crusher and a jaw crusher in sequence to obtain crushed concrete blocks, and the crushed concrete blocks are sieved using a vibrating screen to obtain recycled aggregates of 8 particle groups, which are graded according to the target gradation.

[0070] In the present invention, the target particle size of the crushed particles is preferably not greater than 30 mm.

[0071] In the present invention, the performance parameters of the recycled aggregate in the first recycled aggregate layer are preferably: the crushing value of coarse particles is 13%, the Los Angeles abrasion rate is 20.5%, the optimal moisture content is 5%, and the maximum dry density is 1.76 g / cm 3 , the CBR value is 51.2%.

[0072] In the present invention, the thickness of the first recycled aggregate layer is preferably 20-50 mm, specifically 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm or 50 mm.

[0073] The sandwich structure roadbed filler provided by the present invention comprises a geogrid; the geogrid is preferably a bidirectional geogrid; the material of the geogrid is preferably polypropylene; and the aperture size of the geogrid is preferably 25×25 mm.

[0074] In the present invention, the performance parameters of the geogrid are preferably: transverse ultimate elongation of 13%, transverse ultimate tensile strength of 20 kN / m, longitudinal ultimate elongation of 15%, and transverse ultimate tensile strength of 20 kN / m.

[0075] In the present invention, the thickness of the geogrid is preferably 1-4 mm, specifically 1 mm, 2 mm, 3 mm or 4 mm, and the aperture size is preferably 25 mm×25 mm.

[0076] The sandwich structure roadbed filler provided by the present invention comprises a second recycled aggregate layer; the second recycled aggregate layer is recycled aggregate; the particle size and gradation of the recycled aggregate in the second recycled aggregate layer are preferably the same as those in the first recycled aggregate layer, which will not be repeated here.

[0077] In the present invention, the thickness of the second recycled aggregate layer is preferably 20-50 mm, specifically 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm or 50 mm.

[0078] The sandwich structure roadbed filler provided by the present invention comprises a second construction waste soil layer; the second construction waste soil layer is construction waste soil; the particle size and gradation of the construction waste soil in the second construction waste soil layer are preferably the same as those in the first construction waste soil layer, which will not be repeated here.

[0079] In the present invention, the thickness of the second construction waste soil layer is preferably 10-40 mm, specifically 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm or 40 mm.

[0080] The sandwich structure roadbed filler provided by the present invention preferably also includes a metal mesh; the metal mesh is preferably a low-carbon steel galvanized mesh or a stainless steel mesh, and the thickness is preferably 2 to 6 mm, specifically 2 mm, 3 mm, 4 mm, 5 mm or 6 mm; the metal mesh is preferably arranged between the first building debris layer and the first recycled aggregate layer; when the sandwich structure roadbed filler includes a metal mesh, the sandwich structure roadbed filler containing the metal mesh is placed sideways for construction. The present invention arranges the metal mesh, and its main function is to enhance the stability, tensile strength and bearing capacity of the roadbed.

[0081] In the present invention, the laying method of the metal mesh is preferably: laying the metal mesh on construction waste, laying it longitudinally along the route, tightening and leveling it, and arranging fixing nails; the overlap of the metal mesh is preferably horizontally overlapped by 20 to 30 cm, specifically 25 cm, and preferably vertically overlapped by 15 to 25 cm, specifically 20 cm.

[0082] The sandwich structure roadbed filler provided by the present invention preferably also includes a high-strength glass fiber mesh; the thickness of the high-strength glass fiber mesh is preferably 0.5 to 2 mm, specifically 0.5 mm, 1 mm, 1.5 mm or 2 mm; the high-strength glass fiber mesh is preferably arranged between the second recycled aggregate layer and the second building debris layer; when the sandwich structure roadbed filler includes a high-strength glass fiber mesh, the sandwich structure roadbed filler containing the high-strength glass fiber mesh is placed against the road surface for construction. The present invention mainly enhances the stability of the roadbed on some soft foundations such as soft soil foundations, improves the tensile strength, reduces the expansion of cracks, and prevents deformation of the roadbed by arranging a high-strength glass fiber mesh.

[0083] In the present invention, the pore size of the high-strength glass fiber mesh is preferably 19×19 mm; the performance parameters of the high-strength glass fiber mesh are preferably: radial breaking strength ≥50 kN / m, transverse breaking elongation ≤4%, latitudinal breaking strength ≥50 kN / m, latitudinal breaking elongation ≤4%.

[0084] In the present invention, the overlapping size of the high-strength glass fiber mesh at the overlapping portion is preferably 20 to 30 cm, and specifically may be 25 cm.

[0085] In the present invention, the laying method of the high-strength glass fiber mesh is preferably: laying the high-strength glass fiber mesh on the second recycled aggregate layer, tightening and leveling it, and arranging fixing nails on the high-strength glass fiber mesh.

[0086] In the present invention, the high-strength glass fiber mesh and the metal mesh are preferably not provided at the same time.

[0087] The present invention also provides a method for preparing the sandwich structure roadbed filler described in the above scheme, comprising the following steps:

[0088] On the roadbed surface, from bottom to top, construction waste is laid in sequence to form a first construction waste layer, recycled aggregate is laid to form a first recycled aggregate layer, geogrid is laid, recycled aggregate is laid to form a second recycled aggregate layer, and construction waste is laid to form a second construction waste layer, so as to obtain a sandwich structure roadbed filling material on the roadbed surface.

[0089] In the present invention, the roadbed is preferably pretreated before use; the pretreatment is preferably: surveying the construction site, removing the original surface debris, leveling the foundation, and reinforcing the foundation when necessary according to conventional standards.

[0090] In the present invention, the laying method of the first construction waste soil layer is preferably: the construction waste soil is evenly laid on the roadbed surface to ensure that there is no obvious unevenness, watering or drying the construction waste soil appropriately according to site conditions to achieve the optimal moisture content of the construction waste soil, and the construction waste soil is compacted with a road roller to meet the conventional requirements for roadbed filling.

[0091] In the present invention, the paving equipment for the first construction waste layer is preferably a paver; the compacting equipment is preferably a roller; and the specification of the roller is preferably 36 tons or 32 tons.

[0092] In the present invention, the laying method of the first recycled aggregate layer is preferably: laying recycled aggregate on construction waste, stirring and mixing the recycled aggregate, and compacting at an optimal moisture content of the recycled aggregate. The present invention prevents the separation of coarse and fine aggregates by stirring and mixing.

[0093] In the present invention, the compacting equipment is preferably a road roller; the specification of the road roller is preferably 36 tons or 32 tons.

[0094] In the present invention, the laying method of the geogrid is preferably: the geogrid is flattened on the recycled aggregate, the ends are fixed with U-shaped nails and tightened in sequence, and the U-shaped nails are fixed with increasing density at the overlap of the geogrid.

[0095] In the present invention, the overlap width of the geogrid is preferably 20 to 35 cm, specifically 22 mm, 24 mm, 26 mm, 28 mm, 30 mm, 32 mm or 35 mm.

[0096] In the present invention, the laying method of the second recycled aggregate layer is preferably the same as that of the first recycled aggregate layer, which will not be described in detail herein.

[0097] In the present invention, the laying method of the second construction waste soil layer is preferably the same as that of the first construction waste soil layer, which will not be described in detail herein.

[0098] The present invention also provides the use of the sandwich structure roadbed filler described in the above scheme or the sandwich structure roadbed filler obtained by the preparation method described in the above scheme in road engineering.

[0099] In the present invention, the application preferably includes the following steps: laying the sandwich structure roadbed filler according to the preparation method of the sandwich structure roadbed filler, and repeatedly laying the sandwich structure roadbed filler until the target roadbed height is reached.

[0100] In order to further illustrate the present invention, the scheme of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be understood as limiting the protection scope of the present invention.

[0101] Example 1

[0102] A sandwich structure roadbed filler, the structure is as follows Figure 1 As shown, it is used for roadbed filling. The roadbed and filler structure is as follows Figure 2 As shown, it includes construction waste 1, recycled aggregate 2, geogrid 3, roadbed 4 and pavement 5 which are arranged in sequence.

[0103] The construction debris 1 is made from primary screening samples of construction waste, and the construction debris 1 is specifically divided into 6 groups: construction debris with a particle size of 5 to 10 mm, construction debris with a particle size of 1 to 5 mm (excluding 5 mm), construction debris with a particle size of 0.5 to 1 mm (excluding 1 mm), construction debris with a particle size of 0.1 to 0.5 mm (excluding 0.5 mm), construction debris with a particle size of 0.075 to 0.1 mm (excluding 0.1 mm), and construction debris with a particle size of 0 to 0.075 mm (excluding 0.075 mm).

[0104] The grading of the construction waste 1 is as follows: the passing rate of the standard sieve hole 10 mm is 100%; the passing rate of the standard sieve hole 5 mm is 96.8%; the passing rate of the standard sieve hole 1 mm is 70%; the passing rate of the standard sieve hole 0.5 mm is 55.2%; the passing rate of the standard sieve hole 0.1 mm is 40.2%; the passing rate of the standard sieve hole 0.075 mm is 34.3%, as shown in Table 1.

[0105] Table 1 Grading of construction waste 1

[0106] Screen size (mm) 10 5 1 0.5 0.1 0.075 Grading 100.0 96.8 70.0 55.2 40.2 34.3

[0107] The recycled aggregate 2 is made by cleaning, air-drying and crushing waste concrete blocks. The recycled aggregate 2 is specifically divided into 8 groups: recycled aggregate with a particle size of 16 to 20 mm, recycled aggregate with a particle size of 14 to 16 mm (excluding 16 mm), recycled aggregate with a particle size of 11 to 14 mm (excluding 14 mm), recycled aggregate with a particle size of 9 to 11 mm (excluding 11 mm), recycled aggregate with a particle size of 7 to 9 mm (excluding 9 mm), recycled aggregate with a particle size of 4.75 to 7 mm (excluding 7 mm), recycled aggregate with a particle size of 0.6 to 4.75 mm (excluding 4.75 mm) and recycled aggregate with a particle size of 0 to 0.6 mm (excluding 0.6 mm).

[0108] The grading of the recycled aggregate 2 is as follows: the pass rate of the standard sieve hole 20 mm is 100%; the pass rate of the standard sieve hole 16 mm is 95%; the pass rate of the standard sieve hole 14 mm is 80.3%; the pass rate of the standard sieve hole 11 mm is 60.5%; the pass rate of the standard sieve hole 9 mm is 40%; the pass rate of the standard sieve hole 7 mm is 20.2%; the pass rate of the standard sieve hole 4.75 mm is 11.7%; the pass rate of the standard sieve hole 0.6 mm is 0.8%, as shown in Table 2.

[0109] Table 2 Grading of recycled aggregate 2

[0110] Screen size (mm) 20 16 14 11 9 7 4.75 0.6 Grading 100.0 95.0 80.3 60.5 40.0 20.2 11.7 0.8

[0111] The preparation method of construction waste 1 and recycled aggregate 2 in this embodiment comprises the following specific steps (eg Figure 3 As shown): the construction waste and waste concrete blocks 6 are taken from a construction waste dump; the waste concrete blocks 6 sampled on site are preliminarily screened manually to remove impurities such as steel bars, and then washed and air-dried, and then crushed into small concrete blocks 9 (with a particle size not greater than 30 mm) using a hammer crusher and a jaw crusher in turn; the small concrete blocks 9 and the construction waste 1 sampled on site are sieved using a vibrating screen 10, respectively, to obtain 6 particle groups of construction waste and 8 particle groups of recycled aggregate, which are graded according to their respective grading curves 11 (see Tables 1 and 2 for specific gradations) to obtain construction waste 1 and recycled aggregate 2.

[0112] The natural moisture content of the construction waste 1 is 19%, and the natural density is 1.81 g / cm 3 , dry density is 1.74g / cm 3 , liquid limit is 29.5%, plastic limit is 21.3%, plasticity index is 8.2, optimum moisture content is 15%, maximum dry density is 1.83g / cm 3 , the CBR value is 51.2%, as shown in Table 3.

[0113] Table 3 Basic performance parameters of construction waste 1

[0114] Natural density ρ <![CDATA[Dry density ρ d > Maximum dry density <![CDATA[1.81g / cm 3 ]]> <![CDATA[1.74g / cm 3 ]]> <![CDATA[1.83g / cm 3 ]]> Natural moisture contentω Optimum moisture content CBR 19％ 15％ 51.2％ <![CDATA[Liquid limit ω L > <![CDATA[Plastic limit ω p > <![CDATA[Plasticity index I p > 29.5％ 21.3％ 8.2

[0115] The crushing value of the coarse particles of the recycled aggregate 2 (particle size of 4.75 mm or more) is 13%, the Los Angeles abrasion rate is 20.5%, the optimal moisture content is 5%, and the maximum dry density is 1.76 g / cm 3 , the CBR value is 51.2%.

[0116] The geogrid 3 is a bidirectional polypropylene geogrid with a pore size of 25×25 mm, a transverse ultimate elongation of 13%, a transverse ultimate tensile strength of 20 kN / m, a longitudinal ultimate elongation of 15%, and a transverse ultimate tensile strength of 20 kN / m.

[0117] In the order of construction waste, recycled aggregate, geogrid, recycled aggregate and construction waste, the roadbed surface is filled in turn to obtain a sandwich structure roadbed filler. In the sandwich structure roadbed filler of this embodiment, the thickness of construction waste 1 (the first construction waste layer or the second construction waste layer) is 40 mm, the thickness of recycled aggregate 2 (the first recycled aggregate layer or the second recycled aggregate layer) is 20 mm, and the thickness of the geogrid is 3 mm.

[0118] The sandwich structure roadbed filler of this embodiment was subjected to monotonic shear test and cyclic shear test to test the interface shear characteristics of the sandwich structure roadbed filler under different conditions. The shear test was conducted using an indoor large direct shear apparatus 12 (RAW-60 / 2 microcomputer-controlled electro-hydraulic servo dynamic direct shear apparatus, Hangzhou Bangwei Electromechanical Control Engineering Co., Ltd.), the specific structure of which is as follows: Figure 4 As shown, it includes a horizontal displacement sensor 13, a vertical displacement sensor 14, a clamping block 15, a horizontal moving seat 16 and a linear guide 17; the horizontal displacement sensor 13 is fixed on the base through a support and is connected to the horizontal moving seat 16 installed on the linear guide 17; the vertical displacement sensor 14 is fixed on the vertical brake and is arranged perpendicular to the loading plate; a lower side limit frame is installed on the horizontal moving seat 16, and a linear guide 17 is provided below, a spring is installed between the horizontal moving seat 16 and the lower side limit frame, and the weight of the lower side limit frame is completely supported by the spring; the relevant technical parameters and indicators of the indoor large direct shear instrument 12 are shown in Table 4.

[0119] Table 4 Relevant technical parameters and indicators of indoor large direct shear apparatus 12

[0120] Serial number Project Name Technical specifications 1 Vertical maximum output test force 60kN 2 Maximum lateral output test force 35kN 3 Test force accuracy ＜±1％ 4 Maximum stroke of vertical actuator 150mm 5 Maximum stroke of horizontal actuator 150mm 6 Displacement measurement resolution 0.01mm

[0121] according to Figure 5 As shown, the sandwich structure roadbed filler is loaded in layers into the upper and lower shear boxes: before loading, the upper shear box 18 and the lower shear box 17 are first pushed out along the linear guide rail 16, and the upper shear box 18 is removed, and vaseline is applied around the box wall; the construction waste 1 is loaded into the lower shear box 17 and compacted, and then the recycled aggregate 2 is loaded until the lower shear box 17 is full, leveled, and compacted; secondly, the geogrid 3 is placed between the upper shear box 18 and the lower shear box 17, and the geogrid 3 is fixed to the front and rear ends of the lower shear box 17 with the clamping block 15, so that the geogrid 3 and the lower shear box 17 do not move relative to each other during the shearing process, ensuring that the sample is sheared along the shear surface; then the upper shear box 18 is placed at a specific position on the lower shear box 17, and the upper shear box 18 is filled with recycled aggregate 2 and construction waste 1 and compacted like the lower shear box 17. Finally, the upper and lower shear boxes are connected to the vertical loading plate and the horizontal brake with screws respectively. The internal dimensions of the upper shear box 18 are 600×200×50mm, and the internal dimensions of the lower shear box 17 are 800×200×50mm. The shear path of the monotonic shear test starts from the equilibrium position and proceeds along path ① until it reaches the set displacement, and the vertical stress is 30kPa. The path of the cyclic shear test also starts from the equilibrium position and proceeds along path ①-②-③-④-① until it reaches the equilibrium position. The cyclic shear test adopts a sinusoidal loading waveform, the vertical stress is 60kPa, and the shear amplitude is 3mm. The results are as follows: Figures 6-7 shown.

[0122] according to Figure 6 and Figure 7 It can be seen that Figure 6 The relationship between shear stress and shear displacement at the reinforcement-soil interface is shown. As the shear displacement increases, the shear stress first shows an increasing trend until it reaches a peak value. Subsequently, the shear stress decreases and stabilizes after dropping to a certain value, showing typical shear softening behavior. The maximum shear stress in this process is 33 kPa; Figure 7 It describes the change of the maximum shear stress in each hysteresis loop. In the early stage of cyclic shearing, the maximum shear stress increases significantly, while the change of the minimum shear stress is relatively stable. As the number of cycles increases, the hysteresis loops gradually tend to overlap, and the maximum shear stress is 69.34 kPa. The sandwich structure roadbed filler of the present invention has strong shear resistance and high strength.

[0123] Example 2

[0124] The preparation method of this embodiment is the same as that of embodiment 1, except that the thickness of the construction waste in the sandwich structure roadbed filler is 30 mm, and the thickness of the recycled aggregate is 30 mm. The results of the monotonic shear test and the cyclic shear test in this embodiment are shown in FIG. Figures 8-9 shown.

[0125] according to Figure 8 and Fig. 9 It can be seen that Figure 8 The relationship between shear stress and shear displacement at the reinforcement-soil interface is shown. In the early stage of shear displacement, the shear stress shows an increasing trend, and then decreases after reaching the peak value, and then gradually decreases to a certain level and tends to be stable, showing typical shear softening characteristics. The maximum shear stress in this process is 35kPa; Fig. 9 The shear stress changes of each hysteresis loop are described. In the early stage of cyclic shearing, the maximum shear stress increases significantly, while the minimum shear stress changes more slowly. As the number of cycles increases, the hysteresis loops gradually tend to overlap, with the maximum shear stress being 82.28 kPa. The sandwich structure roadbed filler of the present invention has strong shear resistance and high strength.

[0126] Example 3

[0127] The preparation method of this embodiment is the same as that of embodiment 1, except that the thickness of the construction waste in the sandwich structure roadbed filler is 20 mm, and the thickness of the recycled aggregate is 40 mm. The results of the monotonic shear test and the cyclic shear test in this embodiment are shown in FIG. Figures 10-11 shown.

[0128] according to Fig.10 and Fig.11 It can be seen that Fig.10The trend of shear stress at the reinforcement-soil interface changing with shear displacement is presented. As the shear displacement increases, the shear stress first increases, and then begins to decrease after reaching a peak value, and then decreases to a certain value and tends to be stable, reflecting the characteristics of shear softening. In this process, the maximum shear stress is 37.5 kPa; Fig.11 The variation law of shear stress in each hysteresis loop is shown. In the early stage of cyclic shearing, the maximum shear stress increases significantly, while the change of the minimum shear stress is relatively stable. As the number of cycles increases, the hysteresis loops gradually tend to overlap, and the maximum shear stress is 95.4 kPa. The sandwich structure roadbed filler of the present invention has strong shear resistance and high strength.

[0129] Example 4

[0130] The preparation method of this embodiment is the same as that of embodiment 1, except that the thickness of the construction waste in the sandwich structure roadbed filler is 10 mm, and the thickness of the recycled aggregate is 50 mm. The results of the monotonic shear test and the cyclic shear test in this embodiment are shown in FIG. Figures 12-13 shown.

[0131] according to Fig.12 and Fig.13 It can be seen that Fig.12 The law of shear stress at the reinforcement-soil interface changing with shear displacement is shown. In the early stage of shear displacement, the shear stress gradually increases, and begins to decrease after reaching the peak value, and then decreases to a certain level and tends to be stable, showing the characteristics of shear softening. During this process, the maximum shear stress is 35kPa; Fig.13 The shear stress variation trend of each hysteresis loop is shown. In the early stage of cyclic shearing, the maximum shear stress increases significantly, while the change of the minimum shear stress is relatively gentle. As the number of cycles increases, the hysteresis loops gradually tend to overlap, and the maximum shear stress is 81.7 kPa. The sandwich structure roadbed filler of the present invention has strong shear resistance and high strength.

[0132] Example 5

[0133] The construction method of the sandwich structure roadbed filler in this embodiment includes the following steps:

[0134] (1) Survey the construction site, remove the original surface debris, level the foundation, and reinforce the foundation if necessary.

[0135] (2) According to the design requirements, first lay construction waste 1 on the foundation surface; use a paver to evenly lay the construction waste 1 in the construction area to ensure that there is no obvious unevenness; sprinkle water or dry it according to the site conditions to achieve the optimal moisture content of the construction waste 1, and use a roller (36-ton roller) to compact the construction waste 1 to meet the roadbed filling requirements: the lower embankment (h>1.5m) meets the compaction degree ≥93%, and is compacted in layers to prevent uneven settlement.

[0136] (3) Spreading recycled aggregate 2 on construction waste 1, stirring the recycled aggregate 2 evenly to avoid separation of coarse and fine aggregates, and compacting the recycled aggregate 2 at an optimal moisture content.

[0137] (4) After the recycled aggregate 2 is laid, prepare the bidirectional geogrid 3, flatten the geogrid 3 on the recycled aggregate 2, fix the ends with U-shaped nails and tighten them in sequence, and use U-shaped nails to fix them evenly. The overlap width of the geogrid 3 is 20 to 35 cm, and the U-shaped nails are densely fixed at the overlap.

[0138] (5) Prepare recycled aggregate 2 and lay it symmetrically on the geogrid 3. The laying method is the same as step (3).

[0139] (6) Prepare construction waste 1 and lay it symmetrically on the recycled aggregate 2. The laying method is the same as step (2).

[0140] (7) Repeat steps (1) to (6) to lay the sandwich structure roadbed filler until the target roadbed height is reached; when laying upward, compact the construction waste 1 to the compaction degree required by the roadbed: the upper roadbed (h = 0 ~ 80m) meets the compaction degree ≥ 96%, and the upper embankment (h = 0.8 ~ 1.5m) meets the compaction degree ≥ 94%.

[0141] Example 6

[0142] The preparation method of this embodiment is the same as that of embodiment 3, except that: the sandwich structure roadbed filler is used to fill the soft soil roadbed, such as Fig.16 As shown; the sandwich structure roadbed filler includes construction waste 1, improved recycled aggregate 26, geogrid 3, roadbed 4, pavement 5, metal mesh 25 and high-strength glass fiber mesh 27; the thickness of the construction waste 1 is 30 mm, and the thickness of the improved recycled aggregate 26 is 40 mm; the construction waste 1 is obtained by manually screening and sampling construction waste, and the specific components of the construction waste 1 are the same as those in Example 3.

[0143] The gradation of the improved recycled aggregate 26 is the same as that of Example 1. The raw material formula of the improved recycled aggregate 26 is as follows: 100 parts of component A, of which nano-silicon dioxide accounts for 1-2% of component A; the particle size of the nano-silicon dioxide 19 is 20-50 nm; and component A is waste concrete blocks.

[0144] The preparation method of the improved recycled aggregate 26 is as follows (the specific process is as follows Fig.14 As shown in the figure): nano-silicon dioxide 19 particles and dispersant particles (polyethylene glycol) 20 are mixed in water to obtain a nano-silicon dioxide suspension 21, and the nano-silicon dioxide suspension 21 is placed in an ultrasonic disperser 22 to ensure that the particles are evenly dispersed, and the dispersion time is 15 to 30 minutes; the surface of the discarded concrete block is cleaned, air-dried and crushed, and the crushed concrete blocks are divided into groups and added with nano-silicon dioxide suspensions in different treatment methods: the improved recycled aggregate 26 with a particle size of 16 to 20 mm and the improved recycled aggregate 26 with a particle size of 14 to 16 mm belong to the recycled aggregates with larger particle sizes, and the nano-silicon dioxide suspension is evenly sprayed onto the surface of the improved recycled aggregate 26 through a spraying device 23; the other 6 groups of improved recycled aggregate 26 belong to smaller aggregates, which are respectively immersed in the nano-silicon dioxide suspension 21 for a soaking time of 10 to 30 minutes, fully ensuring that the suspension penetrates the surface and pores of the improved recycled aggregate 26, and the excess liquid is discharged after the soaking is completed, and the treated improved recycled aggregate 26 is naturally dried in a well-ventilated environment.

[0145] The high-strength glass fiber mesh 27 has an aperture size of 19×19 mm, a radial breaking strength of ≥50 kN / m, a transverse breaking elongation of ≤4%, a latitudinal breaking strength of ≥50 kN / m, and a latitudinal breaking elongation of ≤4%.

[0146] The recycled aggregates of Example 3 and Example 6 were subjected to compaction tests and bearing ratio CBR tests in accordance with the Technical Specifications for Highway Roadbed Construction (JTG / T3610-2019). The test results are shown in Table 5.

[0147] Table 5 Basic properties of recycled aggregate

[0148]

[0149] According to Table 5, in the compaction test, the maximum dry density and the optimum moisture content of Example 3 are 1.76 g / cm 3 and 5%, the CBR value is 51.2%, and the maximum dry density and the optimum moisture content of Example 6 are 1.82 g / cm 3 and 3%, the CBR value is 64.2%; it can be seen that nano-silica fills the pores on the surface of the recycled aggregate, makes the contact between the particles closer, improves its compressive resistance, and the CBR value of the improved recycled aggregate is significantly improved.

[0150] Example 7

[0151] The construction method of the sandwich structure roadbed filler in this embodiment is applicable to soft soil roadbed or road sections with poor original foundation conditions, and includes the following steps:

[0152] (1) Survey the construction site, remove the original surface debris, level the foundation, and reinforce the foundation if necessary.

[0153] (2) According to the design requirements, first lay the construction waste 1 on the foundation surface, and use a paver to evenly spread the construction waste 1 in the construction area to ensure that there is no obvious unevenness; according to the site conditions, sprinkle water or turn it over to achieve the best moisture content of the construction waste 1, and use a roller (32-ton roller) to compact the construction waste 1 to meet the roadbed filling requirements: the lower embankment (h>1.5m) meets the compaction degree ≥93%, and is compacted in layers to prevent uneven settlement.

[0154] (3) Lay a layer of metal mesh 25 on the construction waste 1, lay it longitudinally along the route, tighten and level it, overlap it horizontally by 30 cm and longitudinally by 25 cm, and evenly arrange fixing nails on the metal mesh 25.

[0155] (4) Laying improved recycled aggregate 26 on the metal mesh 25. During laying, the improved recycled aggregate 26 is stirred evenly to promote the nano-silica and concrete blocks to produce CSH gel to fill the internal pores and micro-cracks. The laying thickness of the improved recycled aggregate 26 is 20 mm, and compaction is carried out at an optimal moisture content according to conventional methods.

[0156] (5) After the improved recycled aggregate 26 is laid, prepare the bidirectional geogrid 3. First, ensure that the geogrid 3 is flattened on the recycled aggregate layer 26. The ends are fixed with U-shaped nails and tightened in sequence. The U-shaped nails are used to fix the geogrid evenly. The overlap width of the geogrid is 20 to 35 cm, and the U-shaped nails are fixed densely at the overlap.

[0157] (6) Prepare improved recycled aggregate 26 and lay it symmetrically on the geogrid 3. The laying method and details are the same as step (4).

[0158] (7) Prepare construction waste 1 and lay it symmetrically on the improved recycled aggregate layer 26. The laying method and details are the same as step (2). The resulting structure is as follows: Fig.15 shown.

[0159] (8) Repeat steps (2) to (7) to lay the sandwich structure roadbed filler. When filling upward, pay attention to compacting the construction waste soil 1 to the required compaction degree of the roadbed: the upper roadbed (h = 0 ~ 80m) meets the compaction degree ≥ 96%, and the upper embankment (h = 0.8 ~ 1.5m) meets the compaction degree ≥ 94%.

[0160] (9) Lay the top sandwich structure roadbed filler (i.e., construction waste 1-improved recycled aggregate 26-bidirectional geogrid 3-improved recycled aggregate 26), and then lay a layer of high-strength glass fiber mesh 27, ensuring that it is tightened and leveled, with an overlap of 20 to 30 cm at the joints, and evenly arrange fixing nails on the high-strength glass fiber mesh 27.

[0161] (10) Prepare construction waste 1 and lay it on the high-strength glass fiber mesh 27. The laying method and details are the same as step (2). The top structure obtained is as follows: Fig.16 As shown, the overall structure is Fig.17 shown.

[0162] The construction waste / improved recycled aggregate, construction waste / metal mesh / improved recycled aggregate, and construction waste / high-strength glass fiber mesh / improved recycled aggregate in this embodiment were subjected to direct monotonic shear tests at a vertical stress of 30 kPa to test the single-interface shear properties of the sandwich structure roadbed filler under different reinforcement conditions. The results are as follows: Fig.18 shown.

[0163] according to Fig.18 It can be seen that the maximum shear stresses of the three groups of construction waste / improved recycled aggregate, construction waste / metal mesh / improved recycled aggregate, and construction waste / high-strength glass fiber mesh / improved recycled aggregate are 43kPa, 88kPa, and 96kPa, respectively. The peak shear strength is high-strength glass fiber mesh>metal mesh>no reinforcement, and the shear force of the unreinforced soil drops rapidly after reaching the peak, showing a strong strain softening phenomenon. After adding metal mesh and high-strength glass fiber mesh, the downward trend of the curve becomes gentle, especially the high-strength glass fiber mesh, which keeps the bearing capacity at a high level in the later stage of shearing. The horizontal displacement position where the peak value appears (about 27-30mm) is consistent with the typical single shear test results. The reinforcement material can increase the displacement value at the peak position, giving it a greater deformation capacity.

[0164] It can be seen from the above embodiments that the sandwich structure roadbed filler provided by the present invention converts construction waste into structural materials with certain strength and stability, while improving the strength of the roadbed filler, the water resistance of the overall structure is improved, the durability and reliability of the road project are increased, and the resource utilization of construction waste such as slag is realized, thereby reducing the cost of project construction.

[0165] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A sandwich structure roadbed filler, characterized in that: It comprises a first construction waste soil layer, a first recycled aggregate layer, a geogrid, a second recycled aggregate layer and a second construction waste soil layer which are arranged in sequence.

2. The sandwich structure roadbed filler according to claim 1, characterized in that: The gradation of the construction waste in the first construction waste layer and the second construction waste layer is: The pass rate of the standard sieve hole of 10mm is 100%; the pass rate of the standard sieve hole of 5mm is 96.8%; the pass rate of the standard sieve hole of 1mm is 70%; the pass rate of the standard sieve hole of 0.5mm is 55.2%; the pass rate of the standard sieve hole of 0.1mm is 40.2%; the pass rate of the standard sieve hole of 0.075mm is 34.3%.

3. The sandwich structure roadbed filler according to claim 1, characterized in that: The thickness of the first construction waste soil layer is 10 to 40 mm; the thickness of the first recycled aggregate layer is 20 to 50 mm; the thickness of the geogrid is 1 to 4 mm, and the aperture size is 25 mm×25 mm; the thickness of the second recycled aggregate layer is 20 to 50 mm; the thickness of the second construction waste soil layer is 10 to 40 mm.

4. The sandwich structure roadbed filler according to any one of claims 1 to 3, characterized in that: The recycled aggregates in the first recycled aggregate layer and the second recycled aggregate layer are waste concrete recycled aggregates or improved recycled aggregates; The improved recycled aggregate comprises 100 parts of waste concrete and 1 to 2 parts of nano silicon dioxide by mass.

5. The sandwich structure roadbed filler according to claim 1 or 3, characterized in that: The gradation of the first recycled aggregate layer and the second recycled aggregate layer is: The pass rate of standard sieve hole 20mm is 100%; the pass rate of standard sieve hole 16mm is 95%; the pass rate of standard sieve hole 14mm is 80.3%; the pass rate of standard sieve hole 11mm is 60.5%; the pass rate of standard sieve hole 9mm is 40%; the pass rate of standard sieve hole 7mm is 20.2%; the pass rate of standard sieve hole 4.75mm is 11.7%; the pass rate of standard sieve hole 0.6mm is 0.8%.

6. The sandwich structure roadbed filler according to claim 1 or 2, characterized in that: It also includes a metal mesh arranged between the first construction waste soil layer and the second recycled aggregate layer and / or a high-strength glass fiber mesh arranged between the second recycled aggregate layer and the second construction waste soil layer; The performance parameters of the high-strength glass fiber mesh are: radial breaking strength ≥50 kN / m, transverse breaking elongation ≤4%, latitudinal breaking strength ≥50 kN / m, and latitudinal breaking elongation ≤4%.

7. The method for preparing the sandwich structure roadbed filler according to any one of claims 1 to 6, characterized in that: The following steps are involved: On the roadbed surface, from bottom to top, construction waste is laid in sequence to form a first construction waste layer, recycled aggregate is laid to form a first recycled aggregate layer, geogrid is laid, recycled aggregate is laid to form a second recycled aggregate layer, and construction waste is laid to form a second construction waste layer, so as to obtain a sandwich structure roadbed filling material on the roadbed surface.

8. The preparation method according to claim 7, characterized in that: When the sandwich structure roadbed filler includes a metal mesh, the laying method of the metal mesh is: laying the metal mesh on the first construction waste soil layer, laying it longitudinally along the route, tightening and leveling it, and arranging fixing nails.

9. The preparation method according to claim 7 or 8, characterized in that: When the sandwich structure roadbed filler includes high-strength glass fiber mesh, the laying method of the high-strength glass fiber mesh is: laying the high-strength glass fiber mesh on the second recycled aggregate layer, tightening and leveling it, and arranging fixing nails on the high-strength glass fiber mesh.

10. Use of the sandwich structure roadbed filler according to any one of claims 1 to 6 or the sandwich structure roadbed filler obtained by the preparation method according to any one of claims 7 to 9 in road engineering.

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