A modified steel slag-bentonite-based premixed fluid soil and its preparation method

Abstract

This invention relates to the field of building materials technology, and more particularly to a modified steel slag-bentonite-based premixed fluid soil and its preparation method. The modified steel slag-bentonite-based premixed fluid soil comprises 30-50 parts steel slag, 30-50 parts bentonite, 5-15 parts fly ash, 5-15 parts blast furnace slag, 90-100 parts recycled medium sand, 2-5 parts fiber toughening material, 1-3 parts modifier, and 50-70 parts soil. The modifier is pyrophosphate, and the soil is riverbed sediment and / or lakebed sediment with a moisture content of 80%-90%. The strong water absorption of bentonite makes it a highly efficient thickening and water-retaining agent, effectively preventing bleeding and segregation. Pyrophosphate is used, which is a highly efficient dispersant that can be adsorbed on the surface of bentonite particles. Through electrostatic repulsion or steric hindrance, the fluidity of the slurry is greatly restored. This achieves both water retention and thickening while ensuring fluidity, thus solving the problem of insufficient performance of premixed fluid soil caused by high bottom mud moisture content and low early hydration activity of steel slag in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a modified steel slag-bentonite-based premixed fluid soil and its preparation method. Background Technology

[0002] Premixed fluidized bed (CLSM) is a new type of flowable, self-compacting backfill and reinforcement material that is now widely used with technological advancements. Traditional CLSM often uses large amounts of cement as a binder, resulting in high costs and significant carbon emissions. On the other hand, with rapid urbanization, river dredging projects generate large amounts of riverbed sediment. This sediment typically has extremely high water content (usually above 80%), high porosity, and low bearing capacity; direct landfilling of such sediment not only occupies significant land resources but also easily causes secondary environmental pollution. Furthermore, the steel, metallurgical, and power industries generate large quantities of industrial solid waste annually, including steel slag, blast furnace slag, and fly ash. Combining industrial solid waste with high-water-content riverbed sediment to prepare fluidized bed is an effective way to achieve the resource utilization of large quantities of solid waste.

[0003] However, in practical applications, the following technical bottlenecks are encountered: First, the early hydration activity of steel slag is low, which leads to slow early strength development of fluid soil and the potential for poor volume stability; Second, due to the extremely high water content of the bottom mud, the prepared fluid soil is prone to bleeding and segregation, resulting in poor solidification effect; Third, in order to improve water retention and stability, bentonite is usually introduced, but the strong water absorption of bentonite often leads to a significant decrease in the fluidity of the slurry, affecting the actual pumping and pouring construction. Summary of the Invention

[0004] In view of this, the present invention provides a modified steel slag-bentonite-based premixed fluid soil to solve the problem of insufficient performance of premixed fluid soil caused by high bottom mud moisture content and low early hydration activity of steel slag in the prior art; the present invention also provides a method for preparing modified steel slag-bentonite-based premixed fluid soil to solve the above-mentioned technical problems.

[0005] A modified steel slag-bentonite-based premixed fluid soil comprises 30-50 parts steel slag, 30-50 parts bentonite, 5-15 parts fly ash, 5-15 parts blast furnace slag, 90-100 parts recycled medium sand, 2-5 parts fiber toughening material, 1-3 parts modifier, and 50-70 parts soil. The modifier is pyrophosphate, and the soil is riverbed sediment and / or lakebed sediment with a moisture content of 80%-90%.

[0006] Furthermore, the fiber toughening material is waste glass fiber.

[0007] Furthermore, the specific surface area of ​​the steel slag is 400-600 m².2 / kg.

[0008] Furthermore, the blast furnace slag is grade S95 with a specific surface area of ​​400-500 m². 2 / kg, with an activity index of 98% after 28 days.

[0009] Furthermore, the bentonite is sodium-based bentonite.

[0010] Furthermore, the fly ash is Class II, Category C.

[0011] Furthermore, the fineness modulus of the recycled medium sand is between 2.3 and 3.0.

[0012] Furthermore, the pyrophosphate includes sodium pyrophosphate and / or potassium pyrophosphate.

[0013] The beneficial effects of the modified steel slag-bentonite-based premixed fluid soil in this invention are as follows: This invention uses steel slag and soil composed of riverbed sediment and / or lakebed sediment to produce premixed fluid soil, facilitating the use of riverbed and construction waste, thus utilizing a large amount of existing waste and inexpensive materials. Addressing the problem of high water content, fine particles, and high organic matter content in the sediment, leading to poor stability of the freshly mixed slurry and easy separation of water, mud, and aggregates, bentonite is introduced. Bentonite's strong water absorption makes it a highly efficient thickening and water-retaining agent, effectively preventing bleeding and segregation. Simultaneously, fiber-reinforcing materials form a three-dimensional network structure in the slurry, physically intercepting and supporting solid particles, further stabilizing the system and preventing settling. Furthermore, fine particles such as fly ash and blast furnace slag fill the gaps between sediment particles, improving particle size distribution, making the slurry denser and more stable, and reducing free water. Since the introduction of bentonite leads to a decrease in fluidity, pyrophosphate is also used. Pyrophosphate is a highly efficient... The dispersant can be adsorbed on the surface of bentonite particles and effectively "deflocculates" through electrostatic repulsion or steric hindrance, thereby significantly restoring the fluidity of the slurry. This achieves both water retention and thickening while maintaining flowability. Furthermore, the spherical particles of fly ash act as "ball bearings" in the slurry, effectively reducing inter-particle friction, improving the rheological properties of the slurry, and further enhancing fluidity. In addition, pyrophosphate can promote the depolymerization of calcium silicate gel on the surface of steel slag under alkaline conditions, chemically stimulating the early activity of steel slag, promoting the carbonization reaction between steel slag and CO2, and improving strength. By utilizing the micro-expansion characteristics of steel slag and the physical toughening effect of waste glass fiber, a dual crack-resistant system of "microscopic chemical compensation + macroscopic physical toughening" is constructed. This allows the slag to maintain good performance even after using steel slag, riverbed sediment, and lakebed sediment, thus solving the problem of insufficient performance of premixed fluid soil caused by high water content of sediment and low early hydration activity of steel slag in existing technologies.

[0014] A method for preparing modified steel slag-bentonite-based premixed fluid soil is disclosed. The method utilizes the aforementioned components of the modified steel slag-bentonite-based premixed fluid soil. First, the soil and bentonite are mixed and stirred in a specific ratio to allow the bentonite to fully absorb water and expand, forming a stable base mud. Simultaneously, fly ash, blast furnace slag, steel slag, fiber toughening material, and pyrophosphate modifier are premixed uniformly to obtain a composite cementitious material. Then, recycled medium sand and the composite gel material are added to the base mud and stirred at high speed until a uniform fluid slurry is formed.

[0015] This invention utilizes steel slag and soil composed of riverbed sediment and / or lakebed sediment to produce premixed fluid soil, making it convenient to use riverbed and construction waste, thus leveraging a large amount of existing waste and inexpensive materials. Addressing the problem of high water content, fine particles, and high organic matter content in the riverbed sediment, leading to poor stability of the freshly mixed slurry and easy separation of water, mud, and aggregates, bentonite is introduced. Bentonite's strong water absorption makes it a highly efficient thickening and water-retaining agent, effectively preventing bleeding and segregation. Simultaneously, fiber-reinforcing materials form a three-dimensional network structure in the slurry, physically intercepting and supporting solid particles, further stabilizing the system and preventing settling. Additionally, fine particles such as fly ash and blast furnace slag fill the gaps between riverbed sediment particles, improving particle size distribution, making the slurry denser and more stable, and reducing free water. Since the introduction of bentonite reduces fluidity, pyrophosphate is also used. Pyrophosphate is a highly efficient dispersant that can adsorb onto bentonite particles. On the surface, through electrostatic repulsion or steric hindrance effect, effective "deflocculation" is achieved, thereby significantly restoring the fluidity of the slurry. This achieves both water retention and thickening while ensuring flowability. Furthermore, the spherical particles of fly ash act as "ball bearings" in the slurry, effectively reducing interparticle friction, improving the rheological properties of the slurry, and further enhancing fluidity. In addition, pyrophosphate can promote the depolymerization of calcium silicate gel on the surface of steel slag under alkaline conditions, chemically stimulating the early activity of steel slag, promoting the carbonization reaction between steel slag and CO2, and improving strength. Utilizing the micro-expansion characteristics of steel slag and the physical toughening effect of waste glass fiber, a dual crack-resistant system of "microscopic chemical compensation + macroscopic physical toughening" is constructed. This allows the slag to maintain good performance even after using steel slag, riverbed sediment, and lakebed sediment, thus solving the problem of insufficient performance of premixed fluid soil caused by high sediment moisture content and low early hydration activity of steel slag in existing technologies. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below through specific embodiments. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0017] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0018] To better understand the technical solution of the present invention, the present invention will be described in detail below.

[0019] In Example 1 of the preparation method of modified steel slag-bentonite-based premixed fluid soil in this invention (hereinafter referred to as the fluid soil preparation method): In this embodiment, the preparation method of fluidized soil first determines the components of the foundation, selecting 30-50 parts steel slag, 30-50 parts bentonite, 5-15 parts fly ash, 5-15 parts blast furnace slag, 90-100 parts recycled medium sand, 2-5 parts fiber toughening material, 1-3 parts modifier, and 50-70 parts soil, wherein the specific surface area of ​​the steel slag is 400-600 m². 2 / kg, preferably 500m in this embodiment. 2 / kg; the bentonite is sodium-based bentonite, and the fly ash is Class II C fly ash; the blast furnace slag is S95 grade, with a specific surface area of ​​400-500 m². 2 / kg, with an activity index of 98% after 28 days, and a preferred specific surface area of ​​450m². 2 / kg; the fineness modulus of the recycled medium sand is between 2.3 and 3.0, the fiber toughening material is waste glass fiber; the modifier is phosphate, specifically sodium pyrophosphate and / or potassium pyrophosphate, and of course other pyrophosphates can also be used; the soil is riverbed mud or lakebed mud with a water content of 80%-95%.

[0020] After selecting the above materials, the fluidized soil needs to be prepared. First, the mud is pretreated by mixing riverbed sediment and bentonite in a specific ratio, allowing the bentonite to fully absorb water and expand, forming a stable base mud. Simultaneously, dry powder mixing is performed, premixing fly ash, blast furnace slag, steel slag, waste glass fiber, and pyrophosphate modifier to obtain a composite cementitious material. Finally, recycled medium sand and the composite cementitious material are added to the base mud and stirred at high speed for 3-5 minutes to form a uniform fluidized slurry. Pumping, pouring, and natural curing are then carried out according to the construction plan. It is worth noting that the preparation of the base mud and the composite cementitious material does not have a specific order; they can be carried out simultaneously, or the other material can be prepared after one has been completed.

[0021] Compared with existing technologies, the above-mentioned proportions have the following advantages: 1. Synergistic viscosity reduction and activation: Pyrophosphate not only acts as a modifier to disperse bentonite particles and reduce the yield shear stress of the slurry, but also promotes the depolymerization of calcium silicate gel on the surface of steel slag in an alkaline environment, thereby activating the early activity of steel slag from a chemical perspective, promoting the carbonization reaction between steel slag and CO2, and improving strength.

[0022] 2. Volume Compensation and Crack Resistance: To address the common problem of large shrinkage in the later stage of fluid soil, a dual crack prevention system of "microscopic chemical compensation + macroscopic physical toughening" was constructed by utilizing the micro-expansion characteristics of steel slag and the physical toughening effect of waste glass fiber.

[0023] 3. Environmental and cost benefits: It greatly increases the amount of industrial solid waste (steel slag, slag, fly ash, waste glass) added, completely replaces the use of traditional silicate cement, and disposes of high-moisture-content bottom mud and construction waste on a large scale.

[0024] The following experiments were conducted using specific proportions to determine the performance of this component: Example 1: 40 parts steel slag, 40 parts bentonite, 10 parts fly ash, 10 parts blast furnace slag, 100 parts recycled medium sand, 5 parts fiber toughening material, 3 parts modifier, and 70 parts soil.

[0025] Example 2: 30 parts steel slag, 40 parts bentonite, 15 parts fly ash, 15 parts blast furnace slag, 100 parts recycled medium sand, 5 parts fiber toughening material, 3 parts modifier, and 70 parts soil.

[0026] Comparative Example 1: 60 parts cement, 40 parts bentonite, 100 parts recycled medium sand, 5 parts fiber toughening material, 3 parts modifier, and 70 parts soil.

[0027] Comparative Example 2: 60 parts steel slag, 40 parts bentonite, 100 parts recycled medium sand, 5 parts fiber toughening material, 3 parts modifier, and 70 parts soil.

[0028] Comparative Example 3: 40 parts steel slag, 40 parts bentonite, 10 parts fly ash, 10 parts blast furnace slag, 100 parts recycled medium sand, 5 parts fiber toughening material, 5 parts modifier, and 70 parts soil.

[0029] Comparative Example 4: 40 parts steel slag, 40 parts bentonite, 10 parts fly ash, 10 parts blast furnace slag, 100 parts recycled medium sand, 10 parts fiber toughening material, 3 parts modifier, and 70 parts soil.

[0030] Comparative Example 5: 40 parts steel slag, 40 parts bentonite, 10 parts fly ash, 10 parts blast furnace slag, 100 parts recycled medium sand, 5 parts fiber toughening material, and 70 parts soil.

[0031] Comparative Example 6: 40 parts steel slag, 40 parts bentonite, 10 parts fly ash, 10 parts blast furnace slag, 100 parts recycled medium sand, 3 parts modifier, and 70 parts soil.

[0032] Samples were prepared using the same method, and the flowability, 28-day compressive strength, and 7-day shrinkage of the samples were tested to obtain the following performance parameters:

[0033] Comparing Example 1 and Comparative Example 5, it can be seen that the lack of pyrophosphate modifier leads to a sharp decrease in the fluidity of the system (from 235 mm to 145 mm), and the early strength (7 days) is significantly insufficient. This proves that the modifier has the core role of reducing viscosity and dispersing while activating the early activity of steel slag. Comparing Example 1 and Comparative Example 6, it can be seen that after removing waste glass fiber, the 28-day drying shrinkage rate of the fluid soil soared from 0.8% to 3.2%, verifying the necessity of fiber materials to inhibit soil shrinkage and cracking at the macroscopic physical level. As can be seen from Comparative Example 1, although the traditional pure cement curing system has high strength, its fluidity is extremely poor under high bentonite content, and the later drying shrinkage rate is as high as 4.5%, making it very easy to crack. Comparing Example 2 and Comparative Example 4 shows that excessive addition of modifier or fiber material will have negative effects: excessive modifier will lead to severe retardation and bleeding (significant decrease in strength); excessive fiber will lead to slurry agglomeration, loss of fluidity, and even affect the compaction and curing effect, thereby reducing strength.

[0034] In the embodiments of the modified steel slag-bentonite-based premixed fluid soil (hereinafter referred to as fluid soil) in this invention: The structure and composition of the fluid soil in this embodiment are the same as those in the above-mentioned embodiment of the preparation method of modified steel slag-bentonite-based premixed fluid soil, and will not be repeated here.

[0035] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A modified steel slag-bentonite-based premixed fluid soil, characterized in that: The mixture comprises 30-50 parts steel slag, 30-50 parts bentonite, 5-15 parts fly ash, 5-15 parts blast furnace slag, 90-100 parts recycled medium sand, 2-5 parts fiber toughening material, 1-3 parts modifier, and 50-70 parts soil. The modifier is pyrophosphate, and the soil is riverbed sediment and / or lakebed sediment with a moisture content of 80%-90%.

2. The modified steel slag-bentonite-based premixed fluid soil according to claim 1, characterized in that: The fiber toughening material is waste glass fiber.

3. The modified steel slag-bentonite-based premixed fluid soil according to claim 1 or 2, characterized in that: The specific surface area of ​​the steel slag is 400-600 m². 2 / kg.

4. The modified steel slag-bentonite-based premixed fluid soil according to claim 1 or 2, characterized in that: The blast furnace slag is grade S95, with a specific surface area of ​​400-500 m². 2 / kg, with an activity index of 98% after 28 days.

5. The modified steel slag-bentonite-based premixed fluid soil according to claim 1 or 2, characterized in that: The bentonite is sodium-based bentonite.

6. The modified steel slag-bentonite-based premixed fluid soil according to claim 1 or 2, characterized in that: The fly ash is classified as Class II, Category C.

7. The modified steel slag-bentonite-based premixed fluid soil according to claim 1 or 2, characterized in that: The fineness modulus of the recycled medium sand is between 2.3 and 3.

0.

8. The modified steel slag-bentonite-based premixed fluid soil according to claim 1 or 2, characterized in that: The pyrophosphate includes sodium pyrophosphate and / or potassium pyrophosphate.

9. A method for preparing modified steel slag-bentonite-based premixed fluid soil, characterized in that: Using the components of the modified steel slag-bentonite-based premixed fluid soil as described in any one of claims 1-8, the soil and bentonite are first mixed and stirred in proportion to allow the bentonite to fully absorb water and expand, forming a stable base mud; at the same time, fly ash, blast furnace slag, steel slag, fiber toughening material and pyrophosphate modifier are premixed evenly to obtain a composite cementitious material; then, recycled medium sand and composite gel material are added to the base mud and stirred at high speed until a uniform fluid slurry is formed.

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