Salinized soil curing agent, preparation method and application of salinized soil curing agent on roadbed

Abstract

The invention relates to the technical field of special low-carbon building materials, in particular to a salinized soil curing agent, a preparation method and application of the salinized soil curing agent to a roadbed, specifically, air-cooled high-carbon ferrochrome slag powder is adopted as a main raw material, and active micro powder is prepared by treating red mud, phosphorus slag powder and magnesite tailing powder; and reinforcing waste gypsum and steel slag powder are added as main active substances, and a large amount of stone powder is added, so that the salinized soil curing agent with excellent mechanical properties, good seawater resistance and high solid waste utilization rate is prepared.

Description

Technical Field

[0001] This invention relates to the field of special low-carbon building materials technology, and in particular to a saline soil solidifier, its preparation method, and its application in roadbeds. Background Technology

[0002] Foundation reinforcement in buildings and transportation engineering is an important aspect of improving construction quality. Soil stabilizers are commonly used building materials for reinforcing soft foundations. Traditional soil stabilizers mainly use cement and lime as raw materials. In recent years, the reuse of industrial solid waste has become a research hotspot in the building materials industry. Fly ash and mineral powder have become very mature active admixtures, and their prices are gradually rising. The efficient utilization of other types of industrial solid waste, such as ferrochrome slag, red mud, and steel slag, has also become a research topic for solid waste disposal.

[0003] Saline soil exists in coastal and inland areas. Unlike ordinary soil, it contains high levels of chloride and sulfate ions, which can erode and severely damage cement-based hardeners, affecting the service life of projects. Therefore, developing special hardeners for saline soil is of great significance.

[0004] The inventors researched solidifying agents for saline soils, using ferrochrome slag, slag, gypsum, and lime as main raw materials to prepare the solidifying agent. This agent demonstrated good solidification effects on chloride-containing saline soils and on harmful ions. In subsequent research, to utilize the less active dry ferrochrome slag, the inventors applied for patent CN120519169A, using air-cooled high-carbon ferrochrome slag powder as the main raw material, combined with mineral powder and fly ash, and adding Bayer process red mud and sulfide sintering process red mud to prepare a coastal saline soil solidifying agent that meets engineering requirements. While fly ash and mineral powder disposal technologies are mature, the application of steel slag, phosphorus slag, and tailings in saline soil solidifying agents is not yet widespread. Stone powder is commonly used as an inert filler, but increasing its dosage reduces the mechanical properties of cement-based materials. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a saline soil solidification agent. Specifically, this invention uses air-cooled high-carbon ferrochrome slag powder as the main raw material, and prepares active micro powder by processing red mud, phosphorus slag powder and magnesite tailings powder. Solid waste gypsum and steel slag powder are added as the main active substances, and a large amount of stone powder is added to prepare a saline soil solidification agent with excellent mechanical properties, good seawater resistance, and high solid waste utilization rate.

[0006] Specifically, the saline soil solidification agent of the present invention is composed of the following raw materials in parts by weight: 45-55 parts of air-cooled high-carbon ferrochrome slag powder, 30-40 parts of stone powder, 8-12 parts of activated micro powder, 10-15 parts of solid waste gypsum, and 6-9 parts of steel slag powder.

[0007] The active micro powder is prepared by mixing, thermally activating, cooling, and grinding red mud, phosphorus slag powder, and magnesite tailings powder in a mass ratio of 1:(0.6-0.8):(0.1-0.3).

[0008] Based on previous research, this invention continues to use air-cooled high-carbon ferrochrome slag powder as the base material, and utilizes red mud, phosphorus slag powder, and magnesite tailings powder to prepare a highly active micro-powder. Solid waste gypsum is used as a sulfate activator. Since steel slag powder has high alkalinity and a composition similar to cement clinker, the cementitious material system of this invention does not require the addition of an alkaline activator, fully utilizing the activating effect of steel slag and exhibiting high mechanical properties. Therefore, a large amount of stone powder can be added, which can exert a filling effect. After mixing with soil particles, it can form a compacted embedding, improving the volume stability during the hydration process of the solidifying agent, and significantly reducing production costs while still meeting the mechanical performance requirements of the solidified soil.

[0009] Red mud is a solid waste from the aluminum smelting industry, mainly composed of siliceous aluminum raw materials, and has high alkalinity, but relatively low gelling activity. Phosphorus slag is waste residue discharged during the extraction of yellow phosphorus, containing some calcium silicate minerals and glass, with low early hydration activity, and containing impurities such as phosphorus and fluorine, which delays cement hydration. Magnesite tailings are generated during the mining process, and their chemical composition contains a large amount of magnesium carbonate, resulting in low resource utilization. This invention utilizes the composition and characteristics of various industrial solid wastes, and thoroughly mixes red mud, phosphorus slag powder, and magnesite tailings powder, followed by high-temperature thermal activation. During the thermal activation process, the glass phases of red mud and phosphorus slag powder undergo deconstruction and recombination of Si-O and Al-O structures. Magnesite tailings powder contains a large amount of magnesium carbonate, which partially decomposes during high-temperature processes to produce MgO and a small amount of CaO, as well as some amorphous magnesium carbonate. MgO and CaO can accelerate the deconstruction of the Si-O structure, and the deconstruction of Al-O will also change the coordination state at high temperatures, ultimately significantly improving the hydration activity of the active micropowder. Soluble phosphates react with MgO and CaO to reduce solubility, thereby avoiding any impact on the setting time of the curing agent.

[0010] This invention utilizes air-cooled high-carbon ferrochrome slag powder, activated micro-powder, and steel slag powder, which contain a large amount of active aluminate components, supplemented by active silicates and calcium sources. Being alkaline, these components, when activated by solid waste gypsum, can hydrate to produce a large amount of AFt and CSH, CAH, and CASH gels. The hydration products solidify chloride ions in saline soil to form Friedel salts. Simultaneously, the desulfurized gypsum provides a sufficient sulfate environment, further hydrating sulfate ions in the saline soil to produce Kuzel salts, thus achieving stable solidification of the saline soil. The MgO contained in the activated micro-powder also plays a partial activating role, supplementing the strength of the solidified soil. The cementitious material of this invention has high activity, thus absorbing more stone powder. The addition of stone powder forms a compact structure, reducing volume deformation during hydration, improving the stability of the solidified soil, exhibiting a certain degree of resistance to seawater erosion, and meeting the requirements for construction mechanical properties.

[0011] Preferably, the air-cooled high-carbon ferrochrome slag powder is obtained by grinding air-cooled high-carbon ferrochrome slag, and has a specific surface area ≥ 600 m². 2 / kg.

[0012] Preferably, the stone powder is at least one of manufactured sand powder and stone cutting powder, with a particle size ≤75μm.

[0013] Preferably, the red mud is at least one of Bayer process red mud, sintered process red mud, and combined process red mud. More preferably, the red mud is Bayer process red mud or sintered process red mud.

[0014] Preferably, the chemical composition of the Bayer process red mud includes 20-25% SiO2, 20-30% Al2O3, 10-20% CaO, 5-10% Fe2O3, 5-10% Na2O, and the balance being impurities.

[0015] Preferably, the chemical composition of the sintering red mud includes 10-25% SiO2, 5-10% Al2O3, 35-45% CaO, 5-10% Fe2O3, 0-5% Na2O, with the balance being impurities.

[0016] Preferably, during the preparation of the active micro powder, the thermal activation temperature is 800-900℃, the thermal activation time is 1-3h, and the powder is ground to a particle size ≤45μm.

[0017] Preferably, the solid waste gypsum is at least one of desulfurized gypsum, phosphogypsum, and fluorogypsum.

[0018] Preferably, the steel slag powder has a particle size ≤ 60 μm.

[0019] This invention also relates to a method for preparing the above-mentioned saline soil stabilizer, specifically comprising the following steps:

[0020] 1) Weigh each raw material according to its weight.

[0021] 2) Mix all the ingredients evenly to obtain the final product.

[0022] This invention also relates to the application of the above-mentioned saline soil solidifier in the solidification of coastal saline soil.

[0023] Preferably, the amount of the curing agent added is 5-25% of the dry mass of the coastal saline soil.

[0024] This invention has the following technical advantages:

[0025] 1. This invention uses solid waste materials to prepare the solidifying agent, without using fly ash or mineral powder, thus enabling the disposal of more difficult-to-treat low-grade industrial solid waste and achieving high-value utilization of low-grade solid waste.

[0026] 2. This invention prepares highly active micro-powder, which, when combined with solid waste gypsum and steel slag powder, forms a hydration activation environment, eliminating the need for additional alkaline activators.

[0027] 3. The curing agent of this invention has high mechanical properties and a certain resistance to seawater erosion. It can solidify chloride and sulfate ions in saline soil, and the hydration products have a stable structure, making it suitable for consolidation of coastal saline soil. Detailed Implementation

[0028] To characterize the technical effect of this invention, a curing agent was prepared and the saline soil was cured before performance testing. During the testing process, the saline soil used was the Lianyungang saline soil described in the paper "Research on the Reaction Mechanism of Chloride-Constrained Ferrochrome Slag-Slag Base Polymer Solidification of Chloride-Constrained Saline Soil". The air-cooled high-carbon ferrochrome slag powder was obtained by grinding air-cooled high-carbon ferrochrome slag in an ultrafine grinding mill for 10 minutes, resulting in a specific surface area of ​​644.7 m². 2 / kg, stone powder is manufactured sand and gravel powder with a particle size ≤75μm, red mud is Bayer process red mud, steel slag powder with a particle size ≤60μm, the amount of solidifying agent added is 15% of the dry weight of saline soil, and the amount of water is the optimum moisture content of 24.58%.

[0029] Example 1

[0030] The curing agent is composed of the following raw materials in parts by weight: 52 parts air-cooled high-carbon ferrochrome slag powder, 40 parts stone powder, 10 parts activated micro powder, 13 parts desulfurized gypsum, and 9 parts steel slag powder. The activated micro powder is prepared by mixing red mud, phosphorus slag powder, and magnesite tailings powder in a mass ratio of 1:0.6:0.2, thermally activating at 850℃ for 1.5h, cooling, and grinding to a particle size ≤45μm.

[0031] Tests showed that the compressive strength of the solidified soil after 28 days of standard curing was 8.5 MPa, and the compressive strength after 27 days of standard curing plus 1 day of seawater immersion curing was 8.2 MPa.

[0032] Example 2

[0033] The curing agent is composed of the following raw materials in parts by weight: 50 parts air-cooled high-carbon ferrochrome slag powder, 38 parts stone powder, 12 parts activated micro powder, 15 parts desulfurized gypsum, and 8 parts steel slag powder. The activated micro powder is prepared by mixing red mud, phosphorus slag powder, and magnesite tailings powder in a mass ratio of 1:0.7:0.2, thermally activating at 850℃ for 1.5 hours, cooling, and grinding to a particle size ≤45μm.

[0034] Tests showed that the compressive strength of the solidified soil after 28 days of standard curing was 8.7 MPa, and the compressive strength after 27 days of standard curing plus 1 day of seawater immersion curing was 8.3 MPa.

[0035] Comparative Example 1

[0036] The curing agent is composed of the following raw materials in parts by weight: 50 parts air-cooled high-carbon ferrochrome slag powder, 38 parts stone powder, 12 parts silica fume, 15 parts desulfurized gypsum, and 8 parts steel slag powder.

[0037] Tests showed that the compressive strength of the solidified soil after 28 days of standard curing was 2.4 MPa, and the compressive strength after 27 days of standard curing plus 1 day of seawater immersion curing was 1.8 MPa.

[0038] Comparative Example 2

[0039] The curing agent is composed of the following raw materials in parts by weight: 50 parts of air-cooled high-carbon ferrochrome slag powder, 38 parts of stone powder, 12 parts of active micro powder, 15 parts of desulfurized gypsum, and 8 parts of steel slag powder. The active micro powder is prepared by mixing red mud and phosphorus slag powder in a mass ratio of 1:0.7, thermally activating at 850℃ for 1.5h, cooling, and grinding to a particle size ≤45μm.

[0040] Tests showed that the compressive strength of the solidified soil after 28 days of standard curing was 4.6 MPa, and the compressive strength after 27 days of standard curing plus 1 day of seawater immersion curing was 4.0 MPa.

[0041] Comparative Example 3

[0042] The curing agent is composed of the following raw materials in parts by weight: 50 parts of air-cooled high-carbon ferrochrome slag powder, 38 parts of stone powder, 12 parts of active micro powder, 15 parts of desulfurized gypsum, and 8 parts of steel slag powder. The active micro powder is prepared by mixing red mud and magnesite tailings powder at a mass ratio of 1:0.2, thermally activating at 850℃ for 1.5h, cooling, and grinding to a particle size ≤45μm.

[0043] Tests showed that the compressive strength of the solidified soil after 28 days of standard curing was 3.4 MPa, and the compressive strength after 27 days of standard curing plus 1 day of seawater immersion curing was 2.8 MPa.

[0044] Comparative Example 4

[0045] The curing agent is composed of the following raw materials in parts by weight: 50 parts of air-cooled high-carbon ferrochrome slag powder, 38 parts of fly ash, 12 parts of active micro powder, 15 parts of desulfurized gypsum, and 8 parts of steel slag powder. The active micro powder is prepared by mixing and grinding red mud, phosphorus slag powder, and magnesite tailings powder in a mass ratio of 1:0.7:0.2 to a particle size ≤45μm.

[0046] Tests showed that the compressive strength of the solidified soil after 28 days of standard curing was 2.8 MPa, and the compressive strength after 27 days of standard curing plus 1 day of seawater immersion curing was 2.1 MPa.

[0047] Comparative Example 5

[0048] The curing agent is composed of the following raw materials in parts by weight: 50 parts air-cooled high-carbon ferrochrome slag powder, 38 parts stone powder, 12 parts activated micro powder, 15 parts desulfurized gypsum, and 8 parts carbide slag. The activated micro powder is prepared by mixing red mud, phosphorus slag powder, and magnesite tailings powder in a mass ratio of 1:0.7:0.2, thermally activating at 850℃ for 1.5h, cooling, and grinding to a particle size ≤45μm.

[0049] The test results showed that the compressive strength of the solidified soil after 28 days of standard curing was 6.8 MPa, and the compressive strength after 27 days of standard curing plus 1 day of seawater immersion curing was 6.2 MPa.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A soil stabilizer, characterized in that, Composed of the following raw materials in parts by weight: 45-55 parts air-cooled high-carbon ferrochrome slag powder, 30-40 parts stone powder, 8-12 parts activated micro powder, 10-15 parts solid waste gypsum, and 6-9 parts steel slag powder. The active micro powder is prepared by mixing, thermally activating, cooling, and grinding red mud, phosphorus slag powder, and magnesite tailings powder in a mass ratio of 1:(0.6-0.8):(0.1-0.3).

2. The saline soil stabilizer according to claim 1, characterized in that, The air-cooled high-carbon ferrochrome slag powder is obtained by grinding air-cooled high-carbon ferrochrome slag, with a specific surface area ≥600 m². 2 / kg.

3. The saline soil stabilizer according to claim 1, characterized in that, The stone powder is at least one of manufactured sand powder and stone cutting powder, with a particle size ≤75μm.

4. The saline soil stabilizer according to claim 1, characterized in that, The red mud is at least one of Bayer process red mud, sintering process red mud, and combined process red mud.

5. The saline soil stabilizer according to claim 1, characterized in that, During the preparation of the active micro powder, the thermal activation temperature is 800-900℃, the thermal activation time is 1-3h, and the powder is ground to a particle size ≤45μm.

6. The saline soil stabilizer according to claim 1, characterized in that, The solid waste gypsum is at least one of desulfurization gypsum, phosphogypsum, and fluorogypsum.

7. The saline soil stabilizer according to claim 1, characterized in that, The particle size of the steel slag powder is ≤60μm.

8. The method for preparing the saline soil stabilizing agent according to claim 1, characterized in that, Includes the following steps: 1) Weigh each raw material according to its weight. 2) Mix all the ingredients evenly to obtain the final product.

9. The application of the saline soil stabilizer according to any one of claims 1-7 on roadbeds.

10. The application according to claim 9, characterized in that, The amount of the curing agent added is 5-25% of the dry mass of the coastal saline soil.