A method for resource utilization of waste asphalt powder in road subgrade paving

Abstract

The present invention relates to a method for resource utilization of waste asphalt powder in road subgrade paving, and belongs to the field of waste recycling technology. In the present invention, the mixture of waste asphalt powder and slag or slag and fly ash is evenly placed, and the bags are manually broken before paving, and the mixture is evenly mixed with the soil using a road mixer. A rubber tube is used to fill the alkali activator, and the open end is wrapped with polyethylene plastic. After wrapping, the polyethylene plastic is heated to melt it and tightly cover the rubber tube to prevent liquid leakage. According to the calculated placement interval, the points are marked with lime in advance, and then the rubber tube is placed using a traffic cone placement device. After the placement is completed, a layer of soil is laid on the curing agent. After the operation is completed, the rubber tube is rolled with a roller to make the alkali activator flow out, and a chemical reaction occurs with the soil through seepage to produce a gelling substance, which fills the pores between the soil bodies and improves the mechanical properties of the soil bodies, thereby achieving the purpose of improving the soil bodies.

Description

Technical Field

[0001] The present invention relates to the technical field of waste recycling, and in particular to a method for resource utilization of waste asphalt powder in road subgrade paving. Background Art

[0002] Currently, there are two widely used methods for roadbed reinforcement: mechanical reinforcement and non-mechanical reinforcement. Mechanical reinforcement uses external forces to change the structural characteristics of the soil, making it meet the various technical requirements of the highway base. However, this method requires large construction equipment, strict construction conditions, and consumes a lot of manpower and material resources, resulting in high costs. Non-mechanical reinforcement, also known as chemical improvement, involves adding soft soil solidifiers to react with existing substances in the soil, thereby improving its properties. This method has good improvement effects and high economic benefits, and is currently the mainstream method for reinforcing soft soil.

[0003] Currently, commonly used curing agents can be divided into three categories: inorganic curing agents, organic curing agents, and bio-enzyme curing agents. Inorganic curing agents, which primarily include powdered materials such as cement, lime, fly ash, and slag powder, are currently the most widely used. Organic curing agents are usually liquid and primarily include sulfonated oil, modified water glass, and epoxy resin. Bio-enzyme curing agents are multi-enzyme complex structures produced by the mineralization and humification of hydrocarbons.

[0004] Cement is the most common material used in soft soil consolidation, offering advantages such as easy availability, reliable technology, and excellent improvement effects. However, cement solids have disadvantages such as high permeability, high concentrations of heavy metal precipitation, and high cost. Furthermore, cement production emits large amounts of CO2, causing environmental pollution. Geopolymer, a type of alkali-activated cementitious material proposed by French materials scientist Davidovits, is made from aluminosilicates, to which an appropriate amount of alkaline material is added as an activator, through a series of complex physical and chemical reactions. Geopolymer cementitious materials offer advantages such as low energy consumption, high strength, high temperature resistance, acid corrosion resistance, and low pollution during production and use, and have broad application prospects. The large-scale application of geopolymer materials can also effectively improve the comprehensive utilization rate of industrial waste pollutants such as fly ash and slag. Traditional geopolymerization reactions often use slag and fly ash as raw materials and alkaline solutions as activators. With the widespread use of slag, the cost is increasing.

[0005] Currently, commonly used forms of curing agent spraying include spray trucks and manual spraying. When manual spraying is used, the sprayer needs to carry a barrel of curing agent and spray the soil. The manual labor intensity is high, the spraying efficiency is low, and it is easy to spray unevenly or leak, affecting the overall soil improvement effect. When spraying with a spray truck, a certain proportion of curing agent needs to be added to the water tank of the sprinkler truck, but this method usually acts on the surface of the soil and requires further turning and stirring of the soil. The curing agent cannot be quickly and evenly mixed with the soil. Traditional geopolymer material construction mostly uses manual spraying of alkali activators. Due to the strong corrosiveness of alkali activators, manual spraying has certain safety hazards.

[0006] Waste asphalt powder, the waste generated during the asphalt concrete mixing process, mostly consists of fine dust particles with a particle size of 0.075mm or less. This not only occupies land but also constitutes a major source of air, water, and soil pollution, presenting a significant challenge for road and bridge construction companies. Current research focuses on the use of recycled powder in asphalt mixtures, concrete, road base materials, and grouting materials. Research on its use in soil reinforcement, such as foundations and roadbeds, where strength requirements are relatively low, is limited. Furthermore, research on the use of recycled asphalt powder in construction materials under an activated state is rare. Summary of the Invention

[0007] To address the above-mentioned technical problems, the present invention provides a roadbed paving method using waste asphalt powder. This method addresses the problems of uneven spraying, resulting in poor curing effectiveness, and the increasing cost of using alkali residue as raw material for geopolymerization. The present invention uses waste asphalt powder and fly ash as raw materials, which react with an alkaline activator to produce a gel. This gel strengthens the bond between the soil skeleton and improves the compressive strength of the soil.

[0008] The present invention is achieved through the following solutions:

[0009] The first object of the present invention is to provide a method for paving a roadbed based on waste asphalt powder, comprising the following steps:

[0010] (1) Remove debris from the construction section, loosen the soil, break up oversized soil clods, and make the maximum diameter of the soil clods no larger than 15 mm, so that the soil clods are evenly broken, and mark and stake out;

[0011] (2) Spreading a mixture of waste asphalt powder and auxiliary materials, and mixing it with the soil obtained in step (1) to obtain a mixed soil; the auxiliary materials include slag or slag plus fly ash;

[0012] (3) placing a rubber tube filled with alkaline activator on the surface of the mixed soil after mixing in step (2) according to the placement interval, and spreading the soil on the roadbed after the placement is completed;

[0013] (4) The roadbed after paving the soil is rolled from both sides to the center and from low to high. During the rolling process, the alkaline activator reacts chemically with the soil through seepage, producing a gelling substance that fills the pores between the soil. Among them, the rubber tube can play a reinforcing role in the soil, effectively improving the compressive strength, stiffness, plasticity and flexibility of the mixed filler, and effectively limiting the deformation of the soil and the expansion of microcracks.

[0014] In one embodiment of the present invention, the waste asphalt powder is waste generated during the asphalt concrete mixing process; the particle size of the waste asphalt powder is ≤0.075 mm.

[0015] In one embodiment of the present invention, in step (2), the mass ratio of the waste asphalt powder to the auxiliary material is 1:3 to 1:1, and the auxiliary material includes slag or slag plus fly ash.

[0016] In one embodiment of the present invention, in step (2), the mass of the mixture of the waste asphalt powder and auxiliary materials is 5%-20% of the mass of the soil, and the auxiliary materials include slag or slag plus fly ash.

[0017] In one embodiment of the present invention, in step (3), the alkaline activator is selected from one or more of sodium hydroxide water glass solution, activated magnesium oxide and anhydrous sodium metasilicate (ASM).

[0018] In one embodiment of the present invention, the modulus of the water glass solution in the sodium hydroxide water glass solution is 2.31 (i.e., the ratio of the molar number of SiO2 to Na2O, the lower the modulus, the stronger the alkalinity of the solution), and the pH value is 12.5.

[0019] In one embodiment of the present invention, the content of magnesium oxide in the active magnesium oxide is 74.8%, and the modulus reaches 1.2 by adjusting the mixing ratio of magnesium oxide to water glass.

[0020] In one embodiment of the present invention, in step (3), the open end of the rubber tube is wrapped with polyethylene plastic, and after wrapping, the polyethylene plastic is heated to melt it and tightly wrap the rubber tube to prevent liquid leakage; the heating temperature is 110°C-130°C.

[0021] In one embodiment of the present invention, in step (3), the mass ratio of the alkaline activator to the mixed soil is 2.5%-7.5%:1, the amount of the alkaline activator is obtained by calculation, and the number of rubber tubes is calculated based on the amount and added.

[0022] In one embodiment of the present invention, in step (3), the thickness of the paved soil is 30 cm-50 cm.

[0023] In one embodiment of the present invention, in step (3), the rubber tube has a diameter of 4 mm to 8 mm and a length of 5 cm.

[0024] In one embodiment of the present invention, in step (4), the rolling conditions are: first use an 18-20 ton vibratory roller to roll 1-2 times at a speed less than or equal to 1.7 km / h, and then use a 12-16 ton heavy tire roller to roll 4-6 times at a speed less than or equal to 2.5 km / h.

[0025] Mechanism of the present invention:

[0026] Measurements of the elemental and material composition of asphalt waste powder revealed that CaO, SiO2, Al2O3, and Fe2O3 are predominant. The primary reaction product of asphalt waste powder, slag, and alkali-activated geopolymer-stabilized soil in the present invention is a gel, including calcium silicate hydrate gel (CSH), accompanied by the formation of calcium carbonate crystals. With increasing age, the pores between particles in both types of stabilized soil are filled with the generated gel. The gel's cementing action forms a highly compacted mass, significantly enhancing the sample's strength.

[0027] The present invention provides a method for paving a roadbed based on waste asphalt powder, the operation steps are as follows: Figure 1 As shown, the mixture of waste asphalt powder and fly ash is evenly distributed according to the calculated spacing. The bags are manually broken and then spread, and the mixture is evenly mixed with the soil using a road mixer. The alkali activator is filled using a rubber tube, and the open end is wrapped with polyethylene plastic. After wrapping, the polyethylene plastic is heated to melt and tightly wrap around the rubber tube to prevent leakage. The placement intervals are pre-marked with lime, and the rubber tubes are placed using a traffic cone placement device. After placement, a layer of soil is laid on top of the curing agent. After this operation, the rubber tubes are rolled with a road roller to release the alkali activator. Through seepage, it reacts chemically with the soil, producing a gelling agent that fills the pores between the soil and improves its mechanical properties, thereby achieving the goal of improving the soil. The remaining rubber tube acts as a reinforcement in the soil, effectively increasing the compressive strength, stiffness, plasticity, and flexibility of the mixed filler, while also effectively limiting soil deformation and the expansion of microcracks.

[0028] The above technical solution of the present invention has the following advantages over the prior art:

[0029] (1) The present invention provides a method for paving a roadbed using waste asphalt powder. Traditional geopolymerization reactions often use slag and fly ash as raw materials. With the widespread use of slag, the cost of use is increasing. However, the present invention uses waste asphalt powder and fly ash as raw materials for solidification, achieving the goal of "using waste to treat waste" and having high social and economic benefits.

[0030] (2) The present invention uses a rubber tube to wrap the alkali activator and then rolls it to react with the mixed soil. On the one hand, the alkali activator is packaged separately to avoid safety hazards when the alkali activator is manually sprayed. On the other hand, the residual rubber tube has a reinforcing effect on the soil, thereby improving the compressive strength, stiffness, plasticity and flexibility of the soil.

[0031] (3) The present invention uses a roller to roll the rubber tube, and the alkali activator reacts with the mixture immediately. Compared with the traditional method of first stirring the curing agent and then rolling it, the reaction rate is effectively controlled, the project progress is reasonably controlled, and the curing effect is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0033] Figure 1 These are the operating steps of the method for paving a roadbed based on waste asphalt powder of the present invention;

[0034] Figure 2 1 is an outline diagram of a rubber tube in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0036] Example 1

[0037] This embodiment provides a method for paving a roadbed using waste asphalt powder, and the specific steps are as follows:

[0038] (1) Loosen the silty soft clay on site, remove grass roots and tree roots, break up oversized soil blocks, make the soil particles uniform and fine, and ensure that the loosening depth reaches the designed bottom elevation of the solidified soil layer. According to the calculated spacing grid, evenly distribute the asphalt waste powder, slag, and fly ash mixture with a mass ratio of 1:3 to 1:1, manually break the bags and spread them, and use a road mixer for mixing. When mixing, mix from both sides to the center in sections until it reaches the bottom of the solidified soil layer. Mix at least three times until the color of the mixture is uniform; among them, the mass of the asphalt waste powder, slag, and fly ash mixture is 5%-20% of the mass of the silty soft clay.

[0039] (2) The alkali activator is filled with a rubber tube, and the open end is wrapped with polyethylene plastic. After wrapping, the polyethylene plastic is heated to melt it and tightly wrap the rubber tube to prevent liquid leakage. Figure 2As shown. The alkaline activator is sodium hydroxide solution with a modulus of 2.31 and a pH value of 12.5. According to the calculated interval for placing the rubber tube, the points are marked with lime in advance, and then the rubber tube is placed on the surface of the mixed soil after mixing in step (1) using a traffic cone placement device. After the placement is completed, the loader is driven to unload the silty soft clay soil, and finally the roadbed is leveled using a bulldozer, with a paving thickness of about 50 cm. When the bulldozer is driven, the straight section is scraped from both sides to the center of the road, and the flat curve section is scraped from the inside to the outside. The excess material is directly scraped out of the road to ensure the smoothness of the joints.

[0040] (3) After leveling, use a roller to compact the roadbed. According to the road width and roller wheelbase, formulate a corresponding compaction plan. First, use an 18-ton vibratory roller to compact the roadbed twice at a speed not exceeding 1.5 km / h, and then use a 12-ton heavy tire roller to compact the roadbed six times at a speed not exceeding 2 km / h. The compaction direction is from both sides to the center, and from low to high. When compacting, the overlapping part should be 1 / 2 to 1 / 3 of the wheel width to ensure the joint connection and ensure that there are no obvious wheel marks on the surface of the soil layer. During the compaction process, the alkali activator flows out and reacts chemically with the soil through seepage to produce gelling substances to fill the pores between the soil bodies. After the operation is completed, the soil layer is quality tested to ensure the solidification effect.

[0041] (4) The above operations can be repeated to treat each soil layer until the design elevation is reached, and the roadbed quality can be tested and confirmed.

[0042] Example 2

[0043] This embodiment provides a method for paving a roadbed using waste asphalt powder, and the specific steps are as follows:

[0044] (1) Loosen the silty soft clay on site, remove grass roots and tree roots, break up oversized soil blocks, make the soil particles uniform and fine, and ensure that the loosening depth reaches the designed bottom elevation of the solidified soil layer. According to the calculated spacing grid, manually break the bags of asphalt waste powder and slag mixture with a mass ratio of 1:3 to 1:1 and spread them, and use a road mixer for mixing. When mixing, mix from both sides to the center in sections until it reaches the bottom of the solidified soil layer. Mix at least three times until the color of the mixture is uniform; among them, the mass of the asphalt waste powder and slag mixture is 5%-20% of the mass of the silty soft clay.

[0045] (2) Use a rubber tube to fill the alkali activator, and wrap the open end with polyethylene plastic. After wrapping, heat the polyethylene plastic to melt it and tightly cover the rubber tube to prevent liquid leakage. The alkali activator is activated magnesium oxide with a concentration of 74.8%. According to the calculation, the rubber tube placement interval is obtained, and the points are marked with lime in advance. Then, use a traffic cone placement device to place the rubber tube on the surface of the mixed soil after step (1). After the placement is completed, the loader is driven to unload the soil. Finally, the roadbed is leveled using a bulldozer. The paving thickness is about 50 cm. When the bulldozer is driven, it is scraped from both sides to the center of the road in the straight section, and from the inside to the outside in the flat curve section. The excess material is directly scraped out of the road to ensure the smoothness of the joints.

[0046] (3) After leveling, use a roller to compact the roadbed. According to the road width and roller wheelbase, formulate a corresponding compaction plan. First, use an 18-ton vibratory roller to compact the roadbed twice at a speed not exceeding 1.5 km / h, and then use a 12-ton heavy tire roller to compact the roadbed six times at a speed not exceeding 2 km / h. The compaction direction is from both sides to the center, and from low to high. When compacting, the overlapping part should be 1 / 2 to 1 / 3 of the wheel width to ensure the joint connection and ensure that there are no obvious wheel marks on the surface of the soil layer. During the compaction process, the alkali activator flows out and reacts chemically with the soil through seepage to produce gelling substances to fill the pores between the soil bodies. After the operation is completed, the soil layer is quality tested to ensure the solidification effect.

[0047] (4) The above operations can be repeated to treat each soil layer until the design elevation is reached, and the roadbed quality can be tested and confirmed.

[0048] The scheme situation table of Example 1 and Example 2 is shown in Table 1:

[0049] Table 1 Example Scheme Status Table

[0050]

[0051] According to the "Highway Geotechnical Test Code" (JTG E40-2007), unconfined compressive strength tests were performed on Example 1 and Example 2. The data obtained by the tests are shown in Table 2:

[0052] Table 2

[0053] project Example 1 Example 2 Compressive strength 1563kPa 1657kPa

[0054] As can be seen from Table 2, in Examples 1 and 2, asphalt waste powder, slag, fly ash mixture and alkali activator are mixed, and a road roller is used to roll the rubber tube to make the alkali activator flow out, and chemically react with the soil through seepage to produce a gelling substance to fill the pores between the soil bodies. At the same time, the rubber tube has a reinforcing effect on the soil, further improving the mechanical properties of the soil. Its solidification effect meets the requirements of relevant specifications, and at the same time realizes the resource utilization of asphalt waste powder, realizes "waste treatment with waste", and greatly reduces costs.

[0055] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for resource utilization of waste asphalt powder in road subgrade paving, characterized in that: The following steps are involved: (1) Remove debris from the construction section, loosen the soil, break up oversized soil clods, and make the maximum diameter of the soil clods no larger than 15 mm. Make the soil clods uniform and finely broken, and then mark and stake out the road; (2) Spreading a mixture of waste asphalt powder and auxiliary materials, and mixing it with the soil obtained in step (1) to obtain a mixed soil; the auxiliary materials include slag or slag plus fly ash; (3) placing a rubber tube filled with alkaline activator on the surface of the mixed soil after mixing in step (2) according to the placement interval, and spreading the soil on the roadbed after the placement is completed; (4) The roadbed after paving the soil is rolled from both sides to the center and from low to high. During the rolling process, the alkaline activator reacts chemically with the soil through seepage to produce gelling substances, which fill the pores between the soil.

2. The resource utilization method according to claim 1, characterized in that: The waste asphalt powder is waste generated during the asphalt concrete mixing process; the particle size of the waste asphalt powder is ≤0.075mm.

3. The resource utilization method according to claim 1, characterized in that: In step (2), the mass ratio of the waste asphalt powder to the auxiliary material is 1:3 to 1:

1.

4. The resource utilization method according to claim 1, characterized in that: In step (2), the mass of the mixture of the waste asphalt powder and the auxiliary materials is 5%-20% of the mass of the soil.

5. The resource utilization method according to claim 1, characterized in that: In step (3), the alkaline activator is selected from one or more of sodium hydroxide water glass solution, activated magnesium oxide and anhydrous sodium silicate.

6. The resource utilization method according to claim 1, characterized in that: In step (3), the open end of the rubber tube is wrapped with polyethylene plastic. After wrapping, the polyethylene plastic is heated to melt it and tightly wrap the rubber tube to prevent liquid leakage.

7. The resource utilization method according to claim 1, characterized in that: In step (3), the mass ratio of the alkaline activator to the mixed soil is 2.5%-7.5%:

1. The amount of the alkaline activator is obtained by calculation, and the number of rubber tubes is calculated based on the amount and then added.

8. The resource utilization method according to claim 1, characterized in that: In step (3), the thickness of the paved soil is 30 cm to 50 cm.

9. The resource utilization method according to claim 1, characterized in that: In step (3), the diameter of the rubber tube is 4 mm to 8 mm.

10. The resource utilization method according to claim 1, characterized in that: In step (4), the rolling conditions are: first use an 18-20 ton vibratory roller to roll 1-2 times at a speed of less than or equal to 1.7 km / h, and then use a 12-16 ton heavy tire roller to roll 4-6 times at a speed of less than or equal to 2.5 km / h.

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