Low-carbon flow-state solidified soil for seasonal frozen regions and preparation method of low-carbon flow-state solidified soil

Abstract

The invention discloses low-carbon flow-state solidified soil for a seasonal frozen region. The low-carbon flow-state solidified soil comprises soil, a curing agent and water, the dosage of the curing agent is 15-20% of the mass of the dry soil; the water content is 40-60% of the dry mass of the soil and the curing agent; the soil comprises sludge and building residue soil, and the sludge accounts for 20-40 parts by weight, and the building residue soil accounts for 60-80 parts by weight; the curing agent is prepared from the following components in parts by weight: 40 to 60 parts of phosphogypsum, 10 to 15 parts of mixing plant waste slurry, 20 to 40 parts of steel slag, 5 to 10 parts of quick lime, 0.5 to 1.2 parts of glycerol, 0.2 to 0.6 part of hydroxypropyl methyl cellulose and 1 to 1.5 parts of water reducing agent; according to the invention, various technical problems of insufficient anti-freezing performance, unstable fluidity, long setting time, insufficient early strength, large shrinkage deformation, easy generation of segregation and bleeding and the like of the existing fluid-state solidified soil are solved, and meanwhile, more low-carbon environment-friendly raw materials are introduced, so that multi-aspect improvement of the performance of the fluid-state solidified soil and maximization of environment-friendly benefits are realized; and a more reliable and efficient solution is provided for earthwork such as foundation pit backfilling.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and in particular relates to a low-carbon fluidized solidified soil for seasonally frozen areas and a preparation method thereof. Background Art

[0002] In the process of modern urban construction and infrastructure construction, foundation pit backfilling is an important part of earthwork engineering, and its efficiency and quality are directly related to the overall progress and safety of the project. However, due to the complexity and space limitations of the construction site, traditional backfilling materials and methods are often difficult to meet construction needs efficiently and flexibly. As an innovative backfill material, fluidized solidified soil, due to its good fluidity and plasticity, effectively solves the problem of spatial limitations in foundation pit backfilling, and provides a new solution for backfilling operations in complex environments. More importantly, fluidized solidified soil can make full use of waste such as construction debris and silt excavated on site as raw materials, realize the recycling of resources, and reduce the treatment cost and environmental burden of construction waste. However, the fluidized solidified soil widely used in the current market still has environmental shortcomings in the selection of curing agents. Most curing agents are based on traditional materials such as cement and fly ash. These materials will produce certain carbon emissions during production, transportation and use, which is contrary to the low-carbon and environmentally friendly concept advocated globally. With the continuous improvement of social awareness of environmental protection, the development of low-carbon and environmentally friendly fluidized solidified soil has become an inevitable trend in the development of the industry.

[0003] Although fluidized solidified soil has shown many advantages in terms of environmental protection and construction convenience, the existing fluidized solidified soil also has many shortcomings in performance. For example, its fluidity is unstable, and the loss during the flow process is large, resulting in reduced construction efficiency; the setting time is too long, which is difficult to meet the needs of rapid construction; the early strength is insufficient, which affects the early bearing capacity of the backfill body; at the same time, the shrinkage deformation is large and segregation and bleeding are prone to occur, which also affects the integrity and durability of the material. More importantly, under cold climate conditions such as seasonal freezing areas, the anti-freeze performance of the existing fluidized solidified soil is significantly reduced, and its fluidity and long-term stability in low temperature environments cannot be guaranteed, thus limiting its application in a wider range of regions.

[0004] In view of the above-mentioned technical bottlenecks and environmental challenges, it is urgent to explore a low-carbon fluidized solidified soil and its preparation method for use in seasonally frozen areas. Summary of the invention

[0005] The present invention provides a low-carbon fluidized solidified soil for seasonally frozen areas and a preparation method thereof. One purpose is to consume sludge and construction waste at the same time, and its solidifying agent also uses a large amount of solid waste to make it cheaper and more environmentally friendly; the second purpose is to solve the various technical problems of the existing fluidized solidified soil, such as insufficient antifreeze performance, unstable fluidity, long setting time, insufficient early strength, large shrinkage deformation, and easy occurrence of segregation and bleeding. By optimizing the formula of the solidifying agent and introducing more low-carbon and environmentally friendly raw materials, the multi-faceted improvement of the performance of the fluidized solidified soil and the maximization of the environmental benefits can be achieved, providing a more reliable and efficient solution for earthwork projects such as foundation pit backfilling, while ensuring good fluidity, reducing flow losses, shortening setting time, improving early strength, and having excellent anti-segregation and bleeding and antifreeze performance.

[0006] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0007] A low-carbon fluidized solidified soil for seasonally frozen areas, comprising soil, a solidifying agent, and water; the amount of the solidifying agent is 15% to 20% of the dry soil mass; the water content is 40% to 60% of the dry mass of the soil and the solidifying agent;

[0008] The soil comprises silt and construction waste, with 20-40 parts by weight of silt and 60-80 parts by weight of construction waste;

[0009] The composition of the curing agent is as follows by weight: 40-60 parts of phosphogypsum, 10-15 parts of waste slurry from a mixing station, 20-40 parts of steel slag, 5-10 parts of quicklime, 0.5-1.2 parts of glycerol, 0.2-0.6 parts of hydroxypropyl methylcellulose, and 1-1.5 parts of a water reducer.

[0010] According to the above scheme, the sludge comes from a construction site or a drainage project, and has a moisture content between 30wt% and 80wt%; after removing the moisture, clay minerals, sand particles, and powder particles account for more than 80wt%.

[0011] According to the above scheme, the construction waste soil comes from the construction site, and the moisture content does not exceed 20wt%; after removing the moisture, the silicate minerals and oxides account for more than 90wt%.

[0012] According to the above scheme, the phosphogypsum is original phosphogypsum with a specific surface area of ​​150m 2 / kg, pH value is 2.4-4.5.

[0013] According to the above scheme, the waste slurry of the mixing station is recycled concrete waste slurry residue, and its water content is 20-35wt%. In the optimized scheme, the recycled concrete waste slurry residue is a mixture of recycled concrete waste slurry residues with grades of C30, C40, C50, etc.

[0014] According to the above scheme, the steel slag is powder, with a specific surface area of ​​300m 2 / kg.

[0015] According to the above scheme, the quicklime is industrial quicklime with a specific surface area of ​​250m 2 / kg.

[0016] According to the above scheme, the hydroxypropyl methylcellulose has a content of ≥99wt% and a water content of ≤0.10wt%.

[0017] According to the above scheme, the water reducer is a polycarboxylate water reducer, specifically one of a standard polycarboxylate water reducer, an early strength polycarboxylate water reducer, and a shrinkage-reducing polycarboxylate water reducer, and the water reduction rate is ≥26%.

[0018] The method for preparing the low-carbon fluidized solidified soil for seasonally frozen areas comprises the following steps:

[0019] S1: Detect the moisture content of sludge and construction waste to determine the dosage of curing agent and total water consumption;

[0020] S2: Detect the moisture content of phosphogypsum, waste slurry from mixing stations, steel slag, and quicklime to determine the amount of water to be added;

[0021] S3: Put the silt and construction waste soil into a mixer successively, add water to make its water content 60-80% of the total water consumption, add curing agent and remaining water after stirring for 10-20 seconds, and stir for 40-60 seconds to obtain low-carbon fluidized solidified soil for seasonally frozen areas.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention can effectively solve the problems of weak construction performance and poor antifreeze performance of fluidized solidified soil in seasonally frozen areas. Glycerol is added to the curing agent, and through its unique molecular structure, an effective microporous structure network is formed in the fluidized solidified soil, which improves the interfacial adhesion between particles in the fluidized solidified soil and makes the particles more closely combined. This network structure not only enhances the compactness of the soil, but also effectively slows down the freezing speed of water at low temperatures by adsorbing and fixing water molecules, thereby significantly improving the antifreeze performance of the fluidized solidified soil. Under the frequent temperature changes in seasonally frozen areas, the introduction of glycerol enables the solidified soil to resist ice expansion pressure, maintain structural stability, and extend its service life.

[0024] The present invention adds hydroxypropyl methylcellulose to the curing agent and mixes it with a polycarboxylate water-reducing agent, which can significantly improve the rheological properties of the fluidized solidified soil. Through the adsorption and bridging effect of the polymer chain, it can adsorb and retain moisture, effectively reduce the loss of fluidity over time, and maintain the stability of fluidity. This stability is particularly important during long-term transportation and construction, ensuring the uniformity and consistency of the solidified soil performance. At the same time, hydroxypropyl methylcellulose can also significantly reduce segregation and bleeding, further improving the overall quality of the solidified soil.

[0025] The present invention effectively prepares the curing agent by adding a low-carbon curing agent to sludge and construction waste soil, and utilizes industrial waste phosphogypsum, mixing station waste slurry and steel slag, which not only effectively reduces the pollution of these wastes to the environment, but also realizes the maximum utilization of resources, significantly reduces carbon emissions, and meets the requirements of green and low-carbon sustainable development. At the same time, the calcium aluminate generated by the reaction of phosphogypsum and quicklime can effectively enhance the strength of the solidified soil, and also compensates for the shrinkage of the solidified soil in the low temperature environment of the seasonally frozen zone through its slight expansion, thereby improving the structural stability. The recycled mixing station waste slurry and quicklime are used as alkali activators to accelerate the hydration of phosphogypsum and steel slag. Compounds such as iron oxide in steel slag can accelerate the hydration of other components in the curing agent, improve the initial strength of the fluidized solidified soil, and thus significantly shorten the setting time. Under construction conditions in seasonally frozen areas, this feature is particularly important because it allows the project to reach the design strength faster and reduces the risk of construction delays caused by cold weather. In addition, the mineral components in the steel slag also have a certain micro-expansion, which can compensate for the shrinkage and deformation of the solidified soil to a certain extent, thereby improving the stability and durability of the structure. DETAILED DESCRIPTION

[0026] The following examples further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0027] The specific implementation method provides a method for preparing low-carbon fluidized solidified soil for seasonally frozen areas, comprising the following steps:

[0028] S1: Remove foreign matter and contaminated and deteriorated parts from sludge and construction waste, and test their moisture content to determine the amount of curing agent and total water consumption.

[0029] S2: Testing the moisture content of phosphogypsum, mixing station waste slurry, steel slag and quicklime can determine the amount of water to be added to the low-carbon fluidized solidified soil used in seasonally frozen areas.

[0030] S3: Put the silt and construction waste soil into a mixer successively, add water to make its water content 60-80% of the total water consumption, add curing agent and remaining water after stirring for 10-20 seconds, and stir for 40-60 seconds to obtain low-carbon fluidized solidified soil for seasonally frozen areas.

[0031] Specifically, the amount of the curing agent is 15% to 20% of the dry soil mass; the water content is 40% to 60% of the dry mass of the soil and the curing agent;

[0032] The soil comprises silt and construction waste, with 20-40 parts by weight of silt and 60-80 parts by weight of construction waste;

[0033] The composition of the curing agent is as follows by weight: 40-60 parts of phosphogypsum, 10-15 parts of waste slurry from a mixing station, 20-40 parts of steel slag, 5-10 parts of quicklime, 0.5-1.2 parts of glycerol, 0.2-0.6 parts of hydroxypropyl methylcellulose, and 1-1.5 parts of a water reducer.

[0034] In a specific implementation manner, the silt used is excavated from a construction site, has a water content of 60%, and contains more than 80% clay minerals, sand particles, powder particles and the like.

[0035] Construction waste is excavated from construction sites, with a moisture content of 1% and silicate minerals and oxides accounting for more than 90%.

[0036] Mixing station waste slurry is a mixture of C30-C50 grade concrete waste slag and water produced by the concrete mixing station, with a moisture content not exceeding 20%.

[0037] Steel slag is waste slag produced during steelmaking, with a moisture content of less than 5%, and is dry-ground to a specific surface area of ​​300m 2 / kg.

[0038] Unless otherwise specified, the raw materials used in the specific implementation methods are all commercially available.

[0039] Example 1

[0040] The low-carbon fluidized solidified soil for seasonally frozen areas provided in this embodiment has a solidifying agent dosage of 15% of the dry soil mass and a water content of 50wt% of the dry soil mass and the solidifying agent mass.

[0041] Among them, the composition of the soil by weight is 240 parts of silt and 360 parts of construction waste.

[0042] The ingredients of the curing agent are calculated by weight: 50 parts of phosphogypsum, 10 parts of waste slurry from a mixing station, 20 parts of steel slag, 5 parts of quicklime, 0.5 parts of glycerol, 0.3 parts of hydroxypropyl methylcellulose, and 1.2 parts of a water reducer.

[0043] Example 2

[0044] The low-carbon fluidized solidified soil for seasonally frozen areas provided in this embodiment has a solidifying agent dosage of 15% of the dry soil mass and a water content of 60wt% of the dry soil mass and the solidifying agent mass.

[0045] Among them, the composition of the soil by weight is 200 parts of silt and 460 parts of construction waste.

[0046] The ingredients of the curing agent are 60 parts of phosphogypsum, 15 parts of waste slurry from a mixing station, 25 parts of steel slag, 5 parts of quicklime, 0.8 parts of glycerol, 0.5 parts of hydroxypropyl methylcellulose, and 1.3 parts of a water reducer in parts by weight.

[0047] Example 3

[0048] The low-carbon fluidized solidified soil for seasonally frozen areas provided in this embodiment has a solidifying agent dosage of 15% of the dry soil mass and a water content of 40wt% of the dry soil mass and the solidifying agent mass.

[0049] Among them, the composition of the soil by weight is 120 parts of silt and 480 parts of construction waste.

[0050] The ingredients of the curing agent are calculated by weight: 40 parts of phosphogypsum, 12 parts of waste slurry from a mixing station, 30 parts of steel slag, 10 parts of quicklime, 1.0 part of glycerol, 0.6 part of hydroxypropyl methylcellulose, and 1.0 part of a water reducer.

[0051] Example 4

[0052] The low-carbon fluidized solidified soil for seasonally frozen areas provided in this embodiment has a solidifying agent dosage of 15% of the dry soil mass and a water content of 55wt% of the dry soil mass and the solidifying agent mass.

[0053] Among them, the composition of the soil by weight is 160 parts of silt and 500 parts of construction waste.

[0054] The ingredients of the curing agent are 55 parts of phosphogypsum, 15 parts of waste slurry from a mixing station, 20 parts of steel slag, 8 parts of quicklime, 1.2 parts of glycerol, 0.2 parts of hydroxypropyl methylcellulose, and 1.5 parts of a water reducer in parts by weight.

[0055] Example 5

[0056] The low-carbon fluidized solidified soil for seasonally frozen areas provided in this embodiment has a solidifying agent dosage of 15% of the dry soil mass and a water content of 45wt% of the dry soil mass and the solidifying agent mass.

[0057] Among them, the composition of the soil by weight is 160 parts of silt and 500 parts of construction waste.

[0058] The ingredients of the curing agent are 45 parts of phosphogypsum, 14 parts of waste slurry from a mixing station, 35 parts of steel slag, 10 parts of quicklime, 0.8 parts of glycerol, 0.4 parts of hydroxypropyl methylcellulose, and 1.1 parts of a water reducer in parts by weight.

[0059] Comparative Example 1

[0060] The fluidized solidified soil provided in this comparative example has a solidifying agent dosage of 15% of the dry soil mass, wherein the soil comprises 200 parts of silt and 400 parts of construction waste soil by weight.

[0061] The curing agent is prepared from cement, fly ash and quicklime, wherein the cement, fly ash and quicklime are 180 parts, 300 parts and 120 parts respectively by weight.

[0062] The water content is 50% of the dry mass of soil and curing agent.

[0063] Comparative Example 2

[0064] The low-carbon fluidized solidified soil for seasonally frozen areas provided in this comparative example has a solidifying agent dosage of 15% of the dry soil mass and a water content of 50wt% of the dry soil mass and the solidifying agent mass.

[0065] Among them, the composition of the soil by weight is 240 parts of silt and 360 parts of construction waste.

[0066] The ingredients of the curing agent are calculated by weight: 50 parts of phosphogypsum, 10 parts of waste slurry from a mixing station, 20 parts of steel slag, 5 parts of quicklime, 1.0 part of glycerol, 0.3 parts of hydroxypropyl methylcellulose, and 1.2 parts of a water reducer.

[0067] Comparative Example 3

[0068] The low-carbon fluidized solidified soil for seasonally frozen areas provided in this comparative example has a solidifying agent dosage of 15% of the dry soil mass and a water content of 40wt% of the dry soil mass and the solidifying agent mass.

[0069] Among them, the composition of the soil by weight is 120 parts of silt and 480 parts of construction waste.

[0070] The ingredients of the curing agent are calculated by weight: 60 parts of phosphogypsum, 12 parts of waste slurry from a mixing station, 30 parts of steel slag, 10 parts of quicklime, 1.0 part of glycerol, 0.6 part of hydroxypropyl methylcellulose, and 1.0 part of a water reducer.

[0071] Comparative Example 4

[0072] The low-carbon fluidized solidified soil for seasonally frozen areas provided in this comparative example has a solidifying agent dosage of 15% of the dry soil mass and a water content of 60wt% of the dry soil mass and the solidifying agent mass.

[0073] Among them, the composition of the soil by weight is 200 parts of silt and 460 parts of construction waste.

[0074] The ingredients of the curing agent are 60 parts of phosphogypsum, 15 parts of waste slurry from a mixing station, 40 parts of steel slag, 5 parts of quicklime, 0.8 parts of glycerol, 0.5 parts of hydroxypropyl methylcellulose, and 1.3 parts of a water reducer by weight.

[0075] Comparative Example 5

[0076] The low-carbon fluidized solidified soil for seasonally frozen areas provided in this comparative example has a solidifying agent dosage of 15% of the dry soil mass and a water content of 55wt% of the dry soil mass and the solidifying agent mass.

[0077] Among them, the composition of the soil by weight is 160 parts of silt and 500 parts of construction waste.

[0078] The ingredients of the curing agent are 55 parts of phosphogypsum, 15 parts of waste slurry from a mixing station, 20 parts of steel slag, 8 parts of quicklime, 1.2 parts of glycerol, 0.6 parts of hydroxypropyl methylcellulose, and 1.5 parts of a water reducer by weight.

[0079] The above-mentioned Examples 1-5 and Comparative Examples 1-5 were used to prepare fluidized solidified soil, and the solidified soil was tested for 3d and 28d unconfined compressive strength, fluidity, 28d volume shrinkage, initial setting time, mass loss rate after 25 freeze-thaw cycles, and strength loss rate, wherein the strength and volume shrinkage were natural curing, and the freeze-thaw cycle test adopted air freezing and air thawing with slow freezing at -20°C for 3h and melting at 20°C for 3h, which was regarded as one cycle, and a total of 25 cycles were performed. The test results are shown in Table 1.

[0080] Table 1

[0081]

[0082] As shown in Table 1 above, Comparative Example 1 is a common fluidized solidified soil, and its construction performance and antifreeze performance cannot meet the requirements in seasonally frozen areas. Compared with Examples 1-5, all indicators are greatly reduced. Comparing the data of Examples 1-5, it can be seen that the working performance, strength, volume shrinkage, and antifreeze performance are all good, and it can be constructed and used in seasonally frozen areas. Comparing the data of Comparative Example 2 with that of Example 1, it can be seen that the glycerol in the curing agent has a greater impact on the antifreeze performance of the fluidized solidified soil. After increasing the glycerol content in the curing agent, the mass loss is reduced by 64.3%, and the strength loss is reduced by 49.0%, indicating that under the frequent temperature changes in seasonally frozen areas, the microporous structure formed by glycerol enables the fluidized solidified soil to resist ice expansion pressure. Comparing the data of Comparative Example 3 with that of Example 3, it can be seen that phosphogypsum has a greater impact on the unconfined compressive strength of the fluidized solidified soil. After increasing the amount of phosphogypsum, the unconfined compressive strength of 3d and 28d is increased by 12.5% ​​and 13.6%, respectively, indicating that phosphogypsum and hydration effectively improve the early and 28d strengths. Comparing the data of comparative example 4 with that of example 2, it can be seen that the steel slag in the curing agent has a greater effect on the volume shrinkage of the fluidized solidified soil. After increasing the amount of steel slag, the volume shrinkage rate is reduced by 24.8%, indicating that the micro-expansion of the steel slag after hydration reduces the effect of volume shrinkage. Comparing the data of comparative example 5 with that of example 4, it can be seen that the hydroxypropyl methylcellulose in the curing agent has a greater effect on the fluidity of the fluidized solidified soil. After adding hydroxypropyl methylcellulose, the fluidity of the fluidized solidified soil increases by 20.5%, indicating that the adsorption and bridging effect of the polymer chain can absorb and retain moisture and maintain the stability of the fluidity.

Claims

1. A low-carbon fluidized solidified soil for seasonally frozen areas, characterized in that It includes soil, curing agent and water; the amount of the curing agent is 15% to 20% of the dry soil mass; the water content is 40% to 60% of the dry mass of the soil and the curing agent; The soil comprises silt and construction waste, with 20-40 parts by weight of silt and 60-80 parts by weight of construction waste; The composition of the curing agent is as follows by weight: 40-60 parts of phosphogypsum, 10-15 parts of waste slurry from a mixing station, 20-40 parts of steel slag, 5-10 parts of quicklime, 0.5-1.2 parts of glycerol, 0.2-0.6 parts of hydroxypropyl methylcellulose, and 1-1.5 parts of a water reducer.

2. The low-carbon fluidized solidified soil for seasonally frozen areas as claimed in claim 1, characterized in that The sludge comes from a construction site or a drainage project, and has a moisture content between 30wt% and 80wt%. After removing the moisture, clay minerals, sand particles, and powder particles account for more than 80wt%.

3. The low-carbon fluidized solidified soil for seasonally frozen areas as claimed in claim 1, characterized in that The construction waste soil comes from a construction site, and has a moisture content of no more than 20wt%. After removing the moisture, silicate minerals and oxides account for more than 90wt%.

4. The low-carbon fluidized solidified soil for seasonally frozen areas as claimed in claim 1, characterized in that The phosphogypsum is original phosphogypsum with a specific surface area of ​​>150m 2 / kg, pH value is 2.4-4.

5.

5. The low-carbon fluidized solidified soil for seasonally frozen areas as claimed in claim 1, characterized in that The waste slurry from the mixing station is waste slurry residue recovered from concrete, and its water content is 20-35wt%.

6. The low-carbon fluidized solidified soil for seasonally frozen areas as claimed in claim 1, characterized in that The steel slag is powder with a specific surface area of ​​300m 2 / kg.

7. The low-carbon fluidized solidified soil for seasonally frozen areas as claimed in claim 1, characterized in that The quicklime is industrial quicklime with a specific surface area of ​​>250m 2 / kg.

8. The low-carbon fluidized solidified soil for seasonally frozen areas as claimed in claim 1, characterized in that The hydroxypropyl methylcellulose has a content of ≥99wt% and a water content of ≤0.10wt%.

9. The low-carbon fluidized solidified soil for seasonally frozen areas as claimed in claim 1, characterized in that The water reducer is a polycarboxylate water reducer, specifically one of a standard polycarboxylate water reducer, an early strength polycarboxylate water reducer, and a shrinkage-reducing polycarboxylate water reducer, and the water reduction rate is ≥26%.

10. The method for preparing the low-carbon fluidized solidified soil for seasonally frozen areas according to any one of claims 1 to 9, characterized in that The following steps are involved: S1: Detect the moisture content of sludge and construction waste to determine the dosage of curing agent and total water consumption; S2: Detect the moisture content of phosphogypsum, waste slurry from mixing stations, steel slag, and quicklime to determine the amount of water to be added; S3: Put the silt and construction waste soil into a mixer successively, add water to make its water content 60-80% of the total water consumption, add curing agent and remaining water after stirring for 10-20 seconds, and stir for 40-60 seconds to obtain low-carbon fluidized solidified soil for seasonally frozen areas.

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