Preparation method of multi-active-center synergistic flow-state solidified soil

Abstract

The invention relates to the field of constructional engineering materials, in particular to a preparation method of multi-active-center synergistic flow-state solidified soil, which ensures the uniformity and stability of materials by accurately controlling the particle size of construction waste and the proportion of high-temperature treated sludge. The construction waste is mixed with the high-temperature sterilized sludge, so that the fluidity and self-compaction of the solidified soil are improved, the construction period is shortened, the cost is reduced, and the environmental pollution is reduced. The FAU / carbon composite material enhances the early strength and bearing capacity of the solidified soil, shortens the solidification time and enhances the impermeability. The montmorillonite soil improves the workability and environmental adaptability of the solidified soil, absorbs excessive moisture, reduces shrinkage and cracking, and improves the freeze-thaw resistance. Through the synergistic effect of the two components, stress transmission and dispersion are promoted, effective transmission of heat is improved, the mechanical property and the heat-conducting property of the fluid-state solidified soil are enhanced, the engineering efficiency and the environmental adaptability are improved, and an economical and practical solution is provided for the engineering environment.

Description

Technical Field

[0001] The invention relates to the field of building engineering materials, and in particular to a method for preparing multi-active center collaborative fluidized solidified soil. Background Art

[0002] Backfilling (backfilling) operations are an important part of the engineering construction process. They are technical measures to ensure the safety of the main structure and to achieve the functions of anti-seepage and anti-settlement of the surrounding structural parts. The most typical examples are the backfilling of foundation pits in construction projects, the backfilling of urban integrated pipe corridors or municipal pipelines / culverts, the backfilling of "three backs" in transportation projects, and the backfilling of goafs in mining projects. Traditional backfilling mainly achieves the specified compaction and strength through layered rolling or tamping. For backfill areas with certain requirements for bearing capacity, well-graded sandy soil or crushed stone are required to obtain higher dry density and better mechanical properties. 28-ash soil or 37-ash soil are also traditional commonly used backfill materials. However, the layered rolling or tamping filling method has the disadvantages of cumbersome construction process, low efficiency, and unstable backfill soil tamping quality. If narrow, irregular, and deep backfilling conditions are encountered that are not conducive to rolling and tamping, the quality of the backfill project will be even more difficult to guarantee. Engineering accidents such as urban ground subsidence or underground goaf collapse, or even building tilting, due to loose backfill, often occur. In order to improve the quality of backfill, low-grade concrete or cement-based grouting materials are sometimes used as filling materials for narrow spaces, but they are difficult to be widely used due to the high cost of materials. At the same time, since the strength of concrete and grouting materials is high after hardening, it not only causes waste, but also creates new difficulties for the backfill parts that need secondary excavation.

[0003] As a new type of building material and construction technology, fluidized solidified soil backfill has been promoted and applied to a certain extent in China in recent years. The following is the development status and problems of fluidized solidified soil backfill. The development of fluidized solidified soil backfill technology in China began with the Beijing Urban Sub-Center Comprehensive Pipeline Corridor Foundation Trench Backfill Project in 2017. This is the first case of large-scale application in domestic municipal engineering. Since then, the technology has been promoted in Chengdu, Shenzhen, Xiong'an and other places on different scales. Fluidized solidified soil is a green building material that can synergistically dispose of a variety of wastes, including fluidity and strength. This technology uses solid waste on site or nearby to prepare a special high-efficiency curing agent to form a mixture with strong fluidity, uniform particles and strong self-compactness. It is poured through transportation equipment such as pump trucks and chutes, and then maintained to form a strong engineering material. The strength of fluidized solidified soil after hardening is 0.5~10MPa, and the mix ratio can be adjusted according to the use requirements to adjust its strength and fluidity.

[0004] Although fluidized solidified soil backfill technology has many advantages, it also faces some challenges and problems. First, due to the complexity and diversity of soil bodies in various regions, extensive research is needed to determine the appropriate mix design to ensure that the fluidity and strength of fluidized solidified soil meet the engineering requirements. Secondly, low-strength fluidized filling materials need to be studied more extensively and in-depth according to different engineering needs, and systematic research should be conducted from multiple aspects such as material system, performance requirements, construction operations, and quality control. Special attention should be paid to the impact of the high pH value of the material system and the possible presence of heavy metal leaching on groundwater and soil when used for underground backfill; it should also be noted that the material system previously used for underground backfill will face challenges such as drying shrinkage, carbonization (which may affect the stability of hydration products), dry-wet cycles, and freeze-thaw cycles when used in semi-exposed or exposed atmospheric environments. During the construction process, environmental protection and waste disposal issues need to be considered to ensure that no pollution is caused to the surrounding environment during the construction process, while achieving effective utilization of waste. In addition, the durability of fluidized solidified soil is also an issue that needs attention, including its impermeability, freeze-thaw resistance, and long-term stability, which directly affect the quality and service life of the backfill project. These challenges need to be overcome through technological innovation, process improvement and strict quality control to promote the widespread application of fluidized soil backfill technology. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a multi-active center collaborative fluidized solidified soil, which exhibits extremely strong fluidity and self-compactness during construction, can be constructed by pumping, ensures that the construction quality is controllable, reduces the impact on the main structure, and does not damage the waterproof layer. In addition, the fluidized solidified soil has good impermeability, can effectively prevent surface water from infiltrating along the interface between the structure and the backfill soil, thereby improving the safety and durability of the project. The technology is also significant in terms of environmental protection and economic benefits, can effectively consume waste soil at the construction site, reduce land occupation, save material costs, and avoid secondary treatment. The centralized mixing and on-site pouring methods allow the material to be constructed in a liquid state, reducing dust pollution, in line with the concept of green environmental protection. At the same time, the cost of fluidized solidified soil is lower than that of traditional concrete backfill, has good economic benefits, and can flexibly adjust the mix ratio according to design requirements to achieve effective utilization and resource recycling of industrial waste.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing multi-active center collaborative fluidized solidified soil.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for preparing multi-active center synergistic fluidized solidified soil, characterized in that it comprises the following steps: Step 1: Stir the high-temperature calcined kaolin powder and waste coal slag powder in a stirrer at 400-800 r / min for 0.5-2 hours, stir and mix evenly, add water and continue stirring for 0.5-1 hour, place it in an industrial hydrothermal reactor at 70-105° C. for crystallization for 6-20 hours, wash it with water, and obtain FAU / carbon composite material after drying, wherein the mass ratio of the above raw materials is kaolin powder after high-temperature calcination: waste coal slag powder: water = 1:0.5-1.5:8-50; Step 2: Stir the construction waste recycled and crushed materials and the FAU / carbon composite material in a stirrer for 0.5 to 2 hours to mix them evenly, add the washing water in step 1, and continue stirring for 1 hour to obtain a solidified soil pretreatment product, wherein the above raw materials are calculated by mass ratio: construction waste recycled and crushed materials: FAU / carbon composite material: washing water = 1:0.05~0.12:0.1~0.15; Step 3: Add industrial A-type zeolite to the solidified soil pretreatment product, stir at 400-800 r / min for 20-40 minutes, then add montmorillonite soil and stir at 40-60°C and 400-800 r / min for 0.5-2 hours. After stirring evenly, a multi-active center synergistic fluidized solidified soil is obtained, wherein the mass ratio of the above raw materials is solidified soil pretreatment product: industrial A-type zeolite: montmorillonite soil = 1:0.01-0.05:0.05-0.1.

[0008] Furthermore, the high-temperature calcined kaolin powder includes the following steps: kaolin is crushed and sieved to ensure uniform particle size, and its particle size is 10μm≥90%, and it is calcined at 500~650℃ for 4~8 hours to obtain high-temperature calcined kaolin powder.

[0009] Furthermore, the construction waste recycled and crushed material is obtained by crushing and screening the construction waste so that its particle size does not exceed 15 mm, mixing it with high-temperature treated sludge, and stirring it evenly to obtain the construction waste recycled and crushed material, wherein the mass fraction of the sludge is 8% to 15%.

[0010] Furthermore, the high-temperature treated sludge is sludge in rivers and lakes and sludge caused by reservoir construction, waterway construction, mineral mining, etc. After being treated at 200-500°C for 4-6 hours, it is crushed to a particle size of less than 5 mm to obtain the high-temperature treated sludge.

[0011] Furthermore, the multi-active center synergistic fluidized solidified soil is transported through pipelines or pumped, and has the characteristics of self-compacting and self-hardening.

[0012] The present invention provides a method for preparing multi-active center synergistic fluidized solidified soil. By finely controlling the mass ratio of construction waste particle size and high-temperature treated sludge, the fluidized solidified soil backfill technology ensures the uniformity and stability of the material. This technology uses crushed and screened construction waste mixed with high-temperature sterilized and performance-enhanced sludge to give the solidified soil excellent fluidity and self-compactness, which is convenient for pipeline transportation or pumping, and significantly improves construction efficiency. At the same time, the self-hardening characteristics shorten the compaction and maintenance cycle and speed up the progress of the project. In addition, the technology has outstanding performance in environmental protection and economic benefits. By recycling construction waste and sludge, it reduces environmental pollution and material costs, while reducing dependence on natural resources, providing an economical and practical solution for a variety of engineering environments.

[0013] FAU / carbon composites and montmorillonite soil and their synergistic effect play a key role. FAU / carbon composites are made of high-temperature calcined kaolin powder and waste coal slag powder. They have high strength and stability, can significantly improve the early strength and bearing capacity of solidified soil, reduce solidification time, enhance impermeability, reduce groundwater erosion of solidified soil, and adsorb possible heavy metal leaching and other harmful substances to reduce the impact on groundwater and soil. The addition of montmorillonite soil improves the workability and environmental adaptability of solidified soil. Its high cation exchange capacity and adsorption capacity can absorb excess water, reduce shrinkage and cracking, while improving freeze-thaw resistance and enhancing stability in cold environments. FAU / carbon composites and montmorillonite have good synergistic effects. First, the carbon material in the FAU / carbon composite contains organic functional groups such as C=O, O—H and C—N. These functional groups can form chemical bonds with the silicon-oxygen tetrahedron and aluminum-oxygen octahedron crystal layers or surfaces in montmorillonite soil, enhancing the interface bonding between montmorillonite soil and FAU / carbon composites. This chemical bonding not only promotes the transfer and dispersion of stress, but also improves the effective transfer of heat, thereby enhancing the mechanical properties and thermal conductivity of fluidized solidified soil. Secondly, the layered structure of montmorillonite soil provides a template for biomass pyrolysis. The carbonized products generated by the polymerization after the biomass pyrolysis and bond breaking activate the surface of the montmorillonite crystal layer, promote the decomposition of the montmorillonite crystal structure, and change the layered stacking structure morphology of the montmorillonite mineral. This structural change reduces the distribution of functional groups on the surface of the composite, increases the particle size of the composite, and thus enhances the pore structure and adsorption performance of the composite. Finally, the surface effect of FAU has a significant effect on the carbonization of the associated organic biomass and the obtained biomass carbon composite. This effect enhances the pore structure and adsorption performance of the composite, making the composite material show better adsorption capacity in environmental applications. In summary, the combination of FAU / carbon composites and montmorillonite soil not only improves the mechanical properties and durability of fluidized solidified soil, but also improves its construction performance, solving many challenges in the backfill technology of fluidized solidified soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a flow chart of the method for preparing multi-active center collaborative fluidized solidified soil provided by the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0016] See also Figure 1 , a flow chart of the method for preparing multi-active center collaborative fluidized solidified soil provided by an embodiment of the present invention.

[0017] The following is a specific description of the method for preparing a multi-active center cooperative fluidized solidified soil provided by the present invention through examples. Example 1

[0018] Step 1: calcining kaolin powder and waste coal slag powder at 600°C for 6 hours in a stirrer at 800r / min for 1 hour, stirring and mixing evenly, adding water and continuing stirring for 0.5 hours, placing it in an industrial hydrothermal reactor at 90°C for crystallization for 12 hours, washing it with water, and drying it to obtain a FAU / carbon composite material, wherein the mass ratio of the above raw materials is calcined kaolin powder: waste coal slag powder: water = 1:0.8:20; Step 2: Stir the construction waste regeneration and crushing material (mineral mining sludge at 500°C, calcined for 5 hours, wherein the mass fraction of sludge is 12%) and FAU / carbon composite material in a stirrer for 1 hour, mix them evenly, add the washing water in step 1, and continue stirring for 1 hour to obtain a solidified soil pretreatment product, wherein the above raw materials are calculated by mass ratio: construction waste regeneration and crushing material: FAU / carbon composite material: washing water = 1:0.1:0.12; Step 3: Add industrial A-type zeolite to the solidified soil pretreatment product, stir at 800 r / min for 30 minutes, then add montmorillonite and stir at 50°C and 800 r / min for 0.5 hour. After stirring evenly, a multi-active center synergistic fluidized solidified soil is obtained, wherein the mass ratio of the above raw materials is solidified soil pretreatment product: industrial A-type zeolite: montmorillonite = 1:0.03:0.1. Example 2

[0019] Step 1: calcining kaolin powder and waste coal slag powder at 550°C for 5 hours in a stirrer at 800r / min for 1 hour, stirring and mixing evenly, adding water and continuing stirring for 0.5 hours, placing it in an industrial hydrothermal reactor at 100°C for crystallization for 8 hours, washing it with water, and drying it to obtain a FAU / carbon composite material, wherein the mass ratio of the above raw materials is calcined kaolin powder: waste coal slag powder: water = 1:1.2:25; Step 2: Stir the recycled and crushed construction waste (sludge in the river is calcined at 500°C for 6 hours, wherein the mass fraction of the sludge is 14%) and the FAU / carbon composite material in a stirrer for 1 hour, mix them evenly, add the washing water in step 1, and continue stirring for 1 hour to obtain a solidified soil pretreatment product, wherein the above raw materials are calculated by mass ratio: recycled and crushed construction waste: FAU / carbon composite material: washing water = 1:0.08:0.1; Step 3: Add industrial A-type zeolite to the solidified soil pretreatment product, stir at 800 r / min for 30 minutes, then add montmorillonite and stir at 50°C and 800 r / min for 0.5 hour. After stirring evenly, a multi-active center synergistic fluidized solidified soil is obtained, wherein the mass ratio of the above raw materials is solidified soil pretreatment product: industrial A-type zeolite: montmorillonite = 1:0.05:0.08. Example 3

[0020] Step 1: calcining kaolin powder and waste coal slag powder at 650°C for 8 hours in a stirrer at 800r / min for 1 hour, stirring and mixing evenly, adding water and continuing stirring for 0.5 hours, placing it in an industrial hydrothermal reactor at 110°C for crystallization for 10 hours, washing it with water, and drying it to obtain a FAU / carbon composite material, wherein the mass ratio of the above raw materials is calcined kaolin powder: waste coal slag powder: water = 1:0.6:18; Step 2: Stir the recycled and crushed construction waste (sludge in the river is calcined at 500°C for 6 hours, wherein the mass fraction of the sludge is 15%) and the FAU / carbon composite material in a stirrer for 1 hour, mix them evenly, add the washing water in step 1, and continue stirring for 1 hour to obtain a solidified soil pretreatment product, wherein the above raw materials are calculated by mass ratio: recycled and crushed construction waste: FAU / carbon composite material: washing water = 1:0.12:0.1; Step 3: Add industrial A-type zeolite to the solidified soil pretreatment product, stir at 800 r / min for 30 minutes, then add montmorillonite and stir at 50°C and 800 r / min for 0.5 hour. After stirring evenly, a multi-active center synergistic fluidized solidified soil is obtained, wherein the mass ratio of the above raw materials is solidified soil pretreatment product: industrial A-type zeolite: montmorillonite = 1:0.05:0.1.

[0021] Experiments have shown that the multi-active center synergistic fluidized solidified soil obtained in Examples 1 to 3 of the present invention can be transported through pipelines and has the characteristics of self-compacting and self-hardening.

[0022] The multi-active center collaborative fluidized solidified soil obtained in Examples 1 to 3 was subjected to a compressive strength test with reference to T / BGEA 001-2019 "Technical Standard for Premixed Fluidized Solidified Soil Filling Engineering" to obtain the data shown in Table 1.

[0023] Volume shrinkage test method for premixed fluidized solidified soil: Use a vernier caliper to measure the length, width and height of the test block at 28 days and calculate its volume. The difference between the test mold volume 4cm×4cm×16cm=256cm3 and the measured value of the test block volume divided by the test mold volume is defined as the volume shrinkage.

[0024] Table 1 Compressive strength test of multi-active center synergistic fluidized solidified soil in Examples 1 to 3 Test items Example 1 Example 2 Example 3 Compressive strength (28d) / Mpa 5.8 6.2 6.8 Volume shrinkage / % 0.2 0.18 0.13 Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing multi-active center collaborative fluidized solidified soil, characterized in that: The following steps are involved: Step 1: Stir the high-temperature calcined kaolin powder and waste coal slag powder in a stirrer at 400-800 r / min for 0.5-2 hours, stir and mix evenly, add water and continue stirring for 0.5-1 hour, place it in an industrial hydrothermal reactor at 70-105° C. for crystallization for 6-20 hours, wash it with water, and obtain FAU / carbon composite material after drying, wherein the mass ratio of the above raw materials is kaolin powder after high-temperature calcination: waste coal slag powder: water = 1:0.5-1.5:8-50; Step 2: Stir the construction waste recycled and crushed materials and the FAU / carbon composite material in a stirrer for 0.5 to 2 hours to mix them evenly, add the washing water in step 1, and continue stirring for 1 hour to obtain a solidified soil pretreatment product, wherein the above raw materials are calculated by mass ratio: construction waste recycled and crushed materials: FAU / carbon composite material: washing water = 1:0.05~0.12:0.1~0.15; Step 3: Add industrial A-type zeolite to the solidified soil pretreatment product, stir at 400-800 r / min for 20-40 minutes, then add montmorillonite soil and stir at 40-60°C and 400-800 r / min for 0.5-2 hours. After stirring evenly, a multi-active center synergistic fluidized solidified soil is obtained, wherein the mass ratio of the above raw materials is solidified soil pretreatment product: industrial A-type zeolite: montmorillonite soil = 1:0.01-0.05:0.05-0.

1.

2. The method for preparing multi-active center cooperative fluidized solidified soil according to claim 1, characterized in that: The high-temperature calcined kaolin powder comprises the following steps: kaolin is crushed and sieved to ensure uniform particle size, and the particle size is 10μm≥90%, and it is calcined at 500-650°C for 4-8 hours to obtain high-temperature calcined kaolin powder.

3. The method for preparing multi-active center cooperative fluidized solidified soil according to claim 1, characterized in that: The construction waste recycled and crushed material is obtained by crushing and screening construction waste so that its particle size does not exceed 15 mm, mixing it with high-temperature treated sludge, and stirring it evenly to obtain the construction waste recycled and crushed material, wherein the mass fraction of the sludge is 8% to 15%.

4. The method for preparing multi-active center cooperative fluidized solidified soil according to claim 3, characterized in that: The high temperature treated sludge is sludge in rivers and lakes and sludge caused by reservoir construction, waterway construction, mineral mining, etc. After being treated at 200-500° C. for 4-6 hours, it is crushed to a particle size of less than 5 mm to obtain the high temperature treated sludge.

5. The method for preparing multi-active center cooperative fluidized solidified soil according to claim 1, characterized in that: The multi-active center synergistic fluidized solidified soil is transported through pipelines or pumps and has the characteristics of self-compacting and self-hardening.

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