A preparation method for multi-active-center synergistic fluidized solidified soil

Abstract

The present invention relates to the field of construction engineering materials, and particularly to a preparation method of multi-active center collaborative fluidized solidified soil. By precisely controlling the particle size of construction waste and the proportion of high-temperature treated silt, the material is ensured to be uniform and stable. The use of a mixture of construction waste and high-temperature sterilized silt improves the fluidity and self-compacting property of the solidified soil, shortens the construction period, reduces costs, and reduces environmental pollution. The FAU / carbon composite material enhances the early strength and bearing capacity of the solidified soil, reduces the solidification time, and enhances the anti-seepage performance. Montmorillonite improves the workability and environmental adaptability of the solidified soil, absorbs excess moisture, reduces shrinkage and cracking, and enhances the freeze-thaw resistance. The synergistic effect of the two promotes stress transfer and dispersion, improves the effective transfer of heat, enhances the mechanical properties and thermal conductivity of the fluidized solidified soil, improves the engineering efficiency and environmental adaptability, and provides an economical and practical solution for the engineering environment.

Description

Technical Field

[0001] The present invention relates to the field of construction engineering materials, and particularly relates to a preparation method of multi-active center collaborative fluidized solidified soil. Background Art

[0002] Backfilling operation is an important link in the process of engineering construction, and it is a technical measure to ensure the safety of the main structure and achieve functions such as anti-seepage and anti-settlement of surrounding structural parts. The backfilling of foundation pits in construction projects, the backfilling of urban utility tunnels or municipal pipelines / culverts, the "three backs" backfilling in traffic engineering, and the gob filling in mining engineering are the most typical. Traditional backfilling mainly achieves the specified compaction degree and strength through layered rolling or ramming. For backfilling areas with certain requirements for bearing capacity, well-graded sandy soil or gravel needs to be used to obtain a higher dry density and better mechanical properties. Lime-soil or lime-fly ash-soil is also a commonly used traditional backfilling material. However, the backfilling method of layered rolling or ramming has disadvantages such as cumbersome construction technology, low efficiency, and unstable compaction quality of backfill soil. In the case of working conditions such as narrow, irregular, and large backfilling depth that are not conducive to rolling and ramming, it is more difficult to ensure the quality of the backfilling project. Engineering accidents such as urban ground settlement or underground gob collapse caused by non-compact backfilling, and even building inclination, occur from time to time. In order to improve the backfilling quality, low-grade concrete or cement-based grouting materials are sometimes used as backfilling materials in narrow spaces in engineering, but it is difficult to be widely used due to high material costs; at the same time, since the strength of concrete and grouting materials is relatively high after hardening, it not only causes waste, but also creates new difficulties for the backfilling parts that need to be excavated again.

[0003] As a new type of building material and construction technology, fluidized solidified soil backfilling has been promoted and applied to a certain extent in China in recent years. The following is the development status and problems faced by fluidized solidified soil backfilling. The development of fluidized solidified soil backfilling technology in China began with the backfilling project of the foundation trench of the comprehensive utility tunnel in the Beijing Sub-center in 2017, which is the first case of large-scale application in domestic municipal engineering. Since then, the technology has been promoted on different scales in Chengdu, Shenzhen, Xiongan and other places. Fluidized solidified soil is a green building material that can co-dispose of various waste materials, 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-compacting properties, which is poured through transportation equipment such as pump trucks and chutes, and then cured to form an engineering material with strength. The strength of fluidized solidified soil after hardening is 0.5 - 10 MPa, and the mix ratio can be adjusted according to the use requirements to adjust its strength and fluidity.

[0004] Although the fluid-state solidified soil backfilling technology has many advantages, it also faces some challenges and problems. First, due to the complex diversity of soil in different regions, extensive research is needed to determine the appropriate mix design to ensure that the fluidity and strength of the fluid-state solidified soil meet the engineering requirements. Second, for low-strength fluid-state filling materials, more extensive and in-depth research is required for different engineering needs, including systematic research in multiple aspects such as material systems, performance requirements, construction operations, and quality control. Special attention should be paid to the impact of the relatively high pH value of the material system and possible heavy metal leachates on underground water and soil when used for underground backfilling; it should also be noted that the material system previously used for underground filling will face challenges such as drying shrinkage, carbonation (which may affect the stability of hydration products), wet-dry cycles, and freeze-thaw cycles when used in semi-exposed or exposed atmospheric environments. During the construction process, environmental protection and waste treatment issues also need to be considered to ensure that the construction process does not cause pollution to the surrounding environment and at the same time achieve the effective utilization of waste. In addition, the durability of the fluid-state solidified soil, including its impermeability, freeze-thaw resistance, and long-term stability, etc., directly affects the quality and service life of the backfilling project. These challenges need to be overcome through technological innovation, process improvement, and strict quality control to promote the wide application of the fluid-state solidified soil backfilling technology. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of fluid-state solidified soil with multi-active center synergy. This fluid-state solidified soil technology shows extremely strong fluidity and self-compaction in construction, can be constructed by pumping, ensures controllable construction quality, reduces the impact on the main structure, and does not damage the waterproof layer. In addition, the fluid-state 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. This technology is also remarkable in terms of environmental protection and economic benefits. It can effectively consume the waste soil at the construction site, reduce land occupation, save material costs, and avoid secondary treatment. The method of centralized mixing and on-site pouring enables the materials to be constructed in a liquid state, reducing dust pollution and conforming to the concept of green environmental protection. At the same time, the cost of the fluid-state solidified soil is lower than that of traditional concrete backfilling, has good economic benefits, and can flexibly adjust the mix ratio according to design requirements to achieve the effective utilization of industrial waste and resource recycling.

[0006] To solve the above technical problems, the present invention provides a preparation method of fluid-state solidified soil with multi-active center synergy.

[0007] To achieve the above object, the present invention provides the following technical solution: A preparation method of fluid-state solidified soil with multi-active center synergy, characterized by comprising the following steps:

[0008] Step 1: Mix the calcined kaolin powder and waste coal cinder powder in a stirrer at 400 - 800 r / min for 0.5 - 2 hours until evenly mixed. Then add water and continue stirring for 0.5 - 1 hour. Place the mixture in an industrial hydrothermal reaction kettle and crystallize it at 70 - 105°C for 6 - 20 hours. Wash it with water and dry it to obtain the FAU / carbon composite material. The mass ratio of the above raw materials is: calcined kaolin powder : waste coal cinder powder : water = 1 : 0.5 - 1.5 : 8 - 50;

[0009] Step 2: Stir the recycled crushed construction waste and the FAU / carbon composite material in a stirrer for 0.5 - 2 hours until evenly mixed. Add the washing water from Step 1 and continue stirring for 1 hour to obtain the pretreated solidified soil product. The mass ratio of the above raw materials is: recycled crushed construction waste : FAU / carbon composite material : washing water = 1 : 0.05 - 0.12 : 0.1 - 0.15;

[0010] Step 3: Add industrial zeolite A to the pretreated solidified soil product and stir at 400 - 800 r / min for 20 - 40 minutes. Then add montmorillonite clay and stir at 40 - 60°C and 400 - 800 r / min for 0.5 - 2 hours until evenly mixed to obtain the multi-active center synergistic fluidized solidified soil. The mass ratio of the above raw materials is: pretreated solidified soil product : industrial zeolite A : montmorillonite clay = 1 : 0.01 - 0.05 : 0.05 - 0.1.

[0011] Further, the calcined kaolin powder includes the following steps: crush and screen the kaolin to ensure uniform particle size, with 90% of the particle size being ≥10 μm. Calcinate it at 500 - 650°C for 4 - 8 hours to obtain the calcined kaolin powder.

[0012] Further, the recycled crushed construction waste is obtained by crushing and screening the construction waste so that its particle diameter does not exceed 15 mm, and then mixing it with the sludge treated at high temperature and stirring evenly. The mass fraction of the sludge is 8% - 15%.

[0013] Further, the sludge treated at high temperature is the sludge from rivers, lakes, and the sludge caused by reservoir construction, waterway construction, and mineral mining. After treating it at 200 - 500°C for 4 - 6 hours, crush it to a particle size less than 5 mm to obtain the sludge treated at high temperature.

[0014] Further, the multi-active center synergistic fluidized solidified soil is transported through pipelines or pumped, and has the characteristics of self-compacting and self-hardening.

[0015] A method for preparing multi-active center synergistic fluidized solidified soil provided by the present invention ensures the uniformity and stability of materials through fine-tuning the mass ratio of the particle size of construction waste and the mass of silt treated at high temperature. This technology uses construction waste after crushing and screening and silt that has been sterilized at high temperature and has improved performance, endowing the solidified soil with excellent fluidity and self-compacting properties, facilitating pipeline transportation or pumping, and significantly improving construction efficiency. At the same time, the self-hardening property shortens the compaction and curing cycles and speeds up the project progress. In addition, this technology is outstanding in environmental protection and economic benefits. By recycling construction waste and silt, it reduces environmental pollution and material costs, while reducing the dependence on natural resources, providing an economical and practical solution for various engineering environments.

[0016] The FAU / carbon composite material, montmorillonite soil, and their synergistic effect play a key role. The FAU / carbon composite material is prepared from calcined kaolin powder and waste coal slag powder at high temperature, and has high strength and stability. It can significantly improve the early strength and bearing capacity of the solidified soil, reduce the solidification time, enhance the impermeability performance, reduce the erosion of groundwater on the solidified soil, and adsorb possible heavy metal leachates and other harmful substances, reducing the impact on underground water and soil. The addition of montmorillonite soil improves the workability and environmental adaptability of the solidified soil. Its high cation exchange capacity and adsorption capacity can absorb excess water, reduce shrinkage and cracking, and at the same time improve the freeze-thaw resistance performance and enhance the stability in cold environments. The FAU / carbon composite material and montmorillonite have a good synergistic effect. First, the carbon material in the FAU / carbon composite material 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 the montmorillonite soil, enhancing the interfacial bonding between the montmorillonite soil and the FAU / carbon composite material. 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 the fluidized solidified soil. Second, the layered structure of montmorillonite soil provides a template for biomass pyrolysis. The carbonized products generated by the polymerization after the biomass pyrolysis breaks the bonds activate the surface of the montmorillonite crystal layer, promoting the decomposition of the montmorillonite crystal structure and changing the layered stacking structure morphology of the montmorillonite mineral. This structural change reduces the distribution of surface functional groups on 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 an obvious impact on the carbonization of associated organic biomass and the prepared biomass carbon composite. This impact enhances the pore structure and adsorption performance of the composite, making the composite show more excellent adsorption capacity in environmental applications. In summary, the combination of the FAU / carbon composite material and montmorillonite soil not only improves the mechanical properties and durability of the fluidized solidified soil but also improves its construction performance, solving multiple challenges in the fluidized solidified soil backfilling technology. Description of the Drawings

[0017] Figure 1 This is the flow chart of the preparation method of multi-active center synergistic fluidized solidified soil provided by the present invention. Specific embodiments

[0018] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0019] See Figure 1 , the flow chart of the preparation method of multi-active center synergistic fluidized solidified soil provided by the embodiments of the present invention.

[0020] The following specifically describes a preparation method of multi-active center synergistic fluidized solidified soil provided by the present invention through embodiments. Example 1

[0021] Step 1: Mix the kaolin powder calcined at 600 °C for 6 hours and the waste coal slag powder in a stirrer at 800 r / min for 1 hour, stir and mix evenly, add water and continue to stir for 0.5 hour, place it in an industrial hydrothermal reaction kettle and crystallize at 90 °C for 12 hours, wash it with water, and dry it to obtain the FAU / carbon composite material. The mass ratio of the above raw materials is: kaolin powder after high-temperature calcination: waste coal slag powder: water = 1:0.8:20;

[0022] Step 2: Stir the recycled crushed construction waste (the sludge from mineral mining is calcined at 500 °C for 5 hours, and the mass fraction of the sludge is 12%) and the FAU / carbon composite material in a stirrer for 1 hour, mix evenly, add the washing water in Step 1, and continue to stir for 1 hour to obtain the solidified soil pretreatment product. The mass ratio of the above raw materials is: recycled crushed construction waste: FAU / carbon composite material: washing water = 1:0.1:0.12;

[0023] Step 3: Add industrial A-type zeolite to the solidified soil pretreatment product, stir at 800 r / min for 30 minutes, then add montmorillonite soil and stir at 50 °C and 800 r / min for 0.5 hour. After stirring evenly, obtain the multi-active center synergistic fluidized solidified soil. The mass ratio of the above raw materials is: solidified soil pretreatment product: industrial A-type zeolite: montmorillonite soil = 1:0.03:0.1. Example 2

[0024] Step 1: Mix the kaolin powder calcined at 550°C for 5 hours with the waste coal cinder powder in a stirrer at 800 r / min for 1 hour. Stir and mix evenly, add water and continue stirring for 0.5 hour. Place it in an industrial hydrothermal reaction kettle and crystallize at 100°C for 8 hours. Wash it with water and dry it to obtain the FAU / carbon composite material. The mass ratio of the above raw materials is: kaolin powder after high-temperature calcination: waste coal cinder powder: water = 1:1.2:25;

[0025] Step 2: Mix the recycled and crushed construction waste (the silt in the river is calcined at 500°C for 6 hours, and the mass fraction of the silt is 14%) with the FAU / carbon composite material in a stirrer for 1 hour. Mix evenly, add the washing water in Step 1, and continue stirring for 1 hour to obtain the solidified soil pretreatment product. The mass ratio of the above raw materials is: recycled and crushed construction waste: FAU / carbon composite material: washing water = 1:0.08:0.1;

[0026] Step 3: Add industrial zeolite A to the solidified soil pretreatment product and stir at 800 r / min for 30 minutes. Then add montmorillonite clay and stir at 50°C and 800 r / min for 0.5 hour. Stir evenly to obtain the multi-active center synergistic fluidized solidified soil. The mass ratio of the above raw materials is: solidified soil pretreatment product: industrial zeolite A: montmorillonite clay = 1:0.05:0.08. Example 3

[0027] Step 1: Mix the kaolin powder calcined at 650°C for 8 hours with the waste coal cinder powder in a stirrer at 800 r / min for 1 hour. Stir and mix evenly, add water and continue stirring for 0.5 hour. Place it in an industrial hydrothermal reaction kettle and crystallize at 110°C for 10 hours. Wash it with water and dry it to obtain the FAU / carbon composite material. The mass ratio of the above raw materials is: kaolin powder after high-temperature calcination: waste coal cinder powder: water = 1:0.6:18;

[0028] Step 2: Mix the recycled and crushed construction waste (the silt in the river is calcined at 500°C for 6 hours, and the mass fraction of the silt is 15%) with the FAU / carbon composite material in a stirrer for 1 hour. Mix evenly, add the washing water in Step 1, and continue stirring for 1 hour to obtain the solidified soil pretreatment product. The mass ratio of the above raw materials is: recycled and crushed construction waste: FAU / carbon composite material: washing water = 1:0.12:0.1;

[0029] Step 3: Add industrial zeolite A to the pre-treated solidified soil product, stir at 800 r / min for 30 minutes, then add montmorillonite soil and stir at 50 °C and 800 r / min for 0.5 hours. After stirring evenly, a multi-active center synergistic fluidized solidified soil is prepared. The mass ratio of the above raw materials is: pre-treated solidified soil product: industrial zeolite A: montmorillonite soil = 1:0.05:0.1.

[0030] Experiments show 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.

[0031] The multi-active center synergistic fluidized solidified soil obtained in Examples 1 to 3 of this example was subjected to a compressive strength test with reference to T / BGEA 001—2019 "Technical Standard for the Filling Project of Premixed Fluidized Solidified Soil" to obtain the data shown in Table 1.

[0032] Test method for the volume shrinkage rate of premixed fluidized solidified soil: Use a vernier caliper to measure the length, width, and height of the test block at 28 d, and calculate its volume. The difference between the volume of the test mold 4 cm × 4 cm × 16 cm = 256 cm3 and the measured value of the test block volume divided by the volume of the test mold is defined as the volume shrinkage rate.

[0033] Table 1 Compressive strength test of the multi-active center synergistic fluidized solidified soil in Examples 1 to 3

[0034] Test items Example 1 Example 2 Example 3 Compressive strength (28d) / Mpa 5.8 6.2 6.8 Volume shrinkage rate / % 0.2 0.18 0.13

[0035] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by 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, and after stirring evenly, obtain multi-active center synergistic fluidized solidified soil, 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; The construction waste recycled crushed material is obtained by crushing the construction waste, screening it so that its particle size does not exceed 15 mm, mixing it with the high-temperature treated sludge, and stirring it evenly to obtain the construction waste recycled crushed material, wherein the mass fraction of the sludge is 8% to 15%; The high temperature treated sludge is sludge in rivers and lakes and sludge caused by reservoir construction, waterway construction, and mineral mining. 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.

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 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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