A viscosity reducer for iron tailings sand with a gelled outer shell, its preparation method and application

Abstract

This invention belongs to the technical field of solid waste resource utilization and building materials. Specifically, it discloses a viscosity reducer for iron tailings sand with a cementitious outer shell, its preparation method, and its application. The preparation method includes the following steps: S1, grinding and sieving the iron tailings sand, acid washing, and heat treatment under a reducing atmosphere; S2, mixing and reacting the iron tailings sand with an alkaline activator solution; S3, drying and grinding to obtain a viscosity reducer with iron tailings sand as the core and a cementitious substance as the shell. This invention, using the above-mentioned viscosity reducer for iron tailings sand with a cementitious outer shell, its preparation method, and its application, transforms inert iron tailings sand into a high-performance material that combines the activity of mineral admixtures and the function of micro-aggregates. It solves the technical problem of weak interfacial bonding and poor adhesion when iron tailings sand is used as a building material, realizing high added value and large-scale resource utilization of iron tailings sand, with significant environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and building materials technology, and in particular to a viscosity reducer for iron tailings sand with a gelled shell, its preparation method and application. Background Technology

[0002] Iron tailings are a major solid waste generated during iron ore beneficiation, and their emissions have been increasing year by year with the development of the steel industry. Large stockpiles of iron tailings not only occupy land resources but also pose environmental pollution and safety hazards. From a materials science perspective, iron tailings are characterized by uniform particle size (mainly 0.075~0.6mm), smooth surface, and high chemical inertness. These characteristics lead to significant drawbacks when used directly as building materials: poor interparticle bonding, weak interfacial bonding with cementitious materials, and insufficient water stability, making it difficult to meet engineering application requirements.

[0003] In existing technologies, the utilization of iron tailings sand mainly adopts physical mixing methods, which simply involve mixing it as aggregate with cement, lime, and other cementing materials. Alternatively, modification methods such as activation are used to increase the cementitious activity of the iron tailings sand. Physical mixing methods require large amounts of cement, resulting in high costs and significant carbon emissions. The amount of iron tailings sand added is generally no more than 30%, leading to low resource utilization rates. Furthermore, although some studies have attempted modification, these methods are complex, costly, and have limited modification effects, making large-scale application difficult.

[0004] Therefore, developing an economical, efficient, simple, and industrially suitable surface modification technology for iron tailings has become a key technical challenge for promoting its large-scale resource utilization. Summary of the Invention

[0005] The purpose of this invention is to provide a viscosity reducer for iron tailings sand with a cementitious outer shell, its preparation method, and its application. This transforms inert iron tailings sand into a high-performance material that combines the activity of mineral admixtures and the function of micro-aggregates. The material is then used to prepare low-viscosity, ultra-high-performance concrete using iron tailings sand core-shell materials. This solves the technical problems of weak interfacial bonding and poor adhesion when iron tailings sand is used as a building material, and realizes high added value and large-scale resource utilization of iron tailings sand, resulting in significant environmental and economic benefits.

[0006] To achieve the above objectives, the present invention provides a method for preparing a viscosity reducer for iron tailings sand coated with a gelled shell, comprising the following steps: S1. Pretreatment and iron component activation: The iron tailings sand is ground and sieved to obtain raw materials with uniform particle size. It is then acid-washed to remove surface impurities and increase its specific surface area. It is then heat-treated in a reducing atmosphere to reduce the iron oxides in the iron tailings sand to catalytically active elemental iron nanoparticles, thus obtaining iron tailings sand with activated iron components. S2, gelling coating: The iron tailings sand obtained in S1 is mixed with an alkaline activator solution in proportion, stirred evenly, and reacted to obtain a gelled shell; after stirring evenly, a slurry is formed, and the slurry is reacted under certain temperature and pressure conditions to oxidize the elemental iron nanoparticles and participate in the reaction, generating a gelled shell mainly composed of amorphous iron-containing aluminosilicate gel on the surface of the iron tailings sand. S3. Curing and post-treatment: After the reaction is completed, the product is dried and ground to obtain a viscosity reducer with iron tailings sand as the core and cementing material as the shell.

[0007] Preferably, in S1, the proportion of 0.075~0.6mm particles in the iron tailings sand is not less than 50%, and the chemical composition of the iron tailings sand contains 30~50% SiO2 and 10~35% Fe2O3.

[0008] Preferably, in S1, the pickling process specifically includes: The acid washing reagent with a concentration of 0.5~1.5mol / L was used, the acid washing temperature was 50~80℃, the treatment time was 2~8h, and the solid-liquid ratio was 1:(3~10). The pickling reagent is one or more of hydrochloric acid, nitric acid, or sulfuric acid.

[0009] Preferably, in S1, the heat treatment under a reducing atmosphere specifically involves: The reducing atmosphere consists of hydrogen and an inert gas, with hydrogen accounting for 8-15% of the volume and argon as the inert gas. The gas flow rate is 100-500 mL / min, the heat treatment temperature is 450-550℃, and the holding time is 1-2 h.

[0010] Preferably, in S2, the alkaline activator is one or more of sodium hydroxide, sodium silicate, calcium hydroxide or sodium carbonate, the concentration of the alkaline activator solution is 1~10 mol / L, and the solid-liquid ratio of iron tailings sand to alkaline activator solution is 1:(2~6).

[0011] Preferably, in S2, the reaction is as follows: The reaction temperature is 60~120℃, the reaction pressure is atmospheric pressure to 1.0MPa, and the reaction time is 4~24h.

[0012] The present invention also provides a viscosity reducer for iron tailings sand coated with a cementitious shell, wherein the viscosity reducer is a core-shell material with iron tailings sand particles as the core and cementitious material as the shell; The gelling material is an amorphous iron-containing aluminosilicate gel, and its mass percentage is 10-35%.

[0013] The present invention also provides the application of a viscosity reducer for iron tailings sand coated with a gelled shell in concrete preparation.

[0014] Preferably, the concrete comprises the following components: Cementitious materials, aggregates, water-reducing agents, water, and the aforementioned viscosity reducer; The viscosity reducer is added at a rate of 1-10% based on the total mass of the cementitious materials (100%).

[0015] Preferably, the concrete preparation includes the following steps: The cementitious materials, aggregates, and the aforementioned viscosity reducer are mixed, and then water and water-reducing agent are added and stirred to obtain concrete.

[0016] Therefore, the present invention employs the above-mentioned viscosity reducer for coating iron tailings sand with a gelled shell, its preparation method, and its application, with the following beneficial effects: To address the problems of poor interparticle adhesion and weak interfacial bonding with cementing materials caused by the strong inertness of iron tailings sand, this invention first performs acid washing activation and hydrogen reduction on the iron tailings sand, converting the iron oxides into highly reactive elemental iron nanoparticles. Subsequently, under alkaline hydrothermal conditions, active iron participates in the reaction, and a cementing shell mainly composed of amorphous iron-containing aluminosilicate gel grows in situ on the surface of the iron tailings sand particles, ultimately forming a core-shell structure material with iron tailings sand as the core and cementing material as the shell, thus transforming inert tailings into a high-performance core-shell material.

[0017] The core-shell structure material of this invention combines the activity of mineral admixtures with the function of micro-aggregates, which can significantly improve the strength of composite materials and the amount of iron tailings sand, realize the high-value resource utilization of solid waste, and at the same time greatly reduce cement usage and carbon emissions. It provides an economical and effective solution to the environmental problems caused by iron tailings accumulation, and has significant technological advancement, environmental benefits and industrialization potential.

[0018] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0019] The technical solution of the present invention will be further described below through embodiments.

[0020] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0021] Example 1 A low-viscosity, ultra-high-performance concrete uses a viscosity-reducing agent coated with iron tailings sand as a cementitious outer shell, and employs cement, silica fume, fly ash, and limestone powder as cementing materials. The aggregate is quartz sand. The raw materials include the following parts by weight: 585 parts cement, 130 parts silica fume, 245 parts fly ash, 95 parts limestone powder, 950 parts quartz sand, 34.6 parts commercially available ultra-high performance concrete water-reducing agent, 180 parts water, 95 parts viscosity reducer, and 160 parts steel fiber.

[0022] In this embodiment, the 95 parts of viscosity reducer replaced 95 parts of inert limestone powder, and due to its micro-aggregate effect, the amount of quartz sand was reduced by 50 parts.

[0023] The viscosity reducer for the cementitious outer shell coating of iron tailings sand is prepared by the following steps: S1. Pretreatment and Iron Component Activation: Iron tailings sand with SiO2 content of 45% and Fe2O3 content of 25% was ground and passed through an 80-mesh sieve to obtain raw materials with a particle size of 0.075~0.6mm accounting for no less than 50%. Then, it was acid-washed with 1.0mol / L hydrochloric acid at a solid-liquid ratio of 1:5 at 65℃ for 4h to remove surface impurities and increase its specific surface area. Then, it was heat-treated for 1.5h in a mixed atmosphere of hydrogen (hydrogen volume percentage of 10%) and argon at a gas flow rate of 300mL / min and 500℃ to reduce the iron oxides in the iron tailings sand to catalytically active elemental iron nanoparticles, thus obtaining iron component activated iron tailings sand.

[0024] S2. Gelation Coating: Iron tailings sand is mixed with a 5 mol / L sodium hydroxide solution at a solid-liquid ratio of 1:4 and stirred evenly to form a slurry. The slurry is reacted at 90℃ and atmospheric pressure to 1.0 MPa for 1.5 h. The slurry reacts under certain temperature and pressure conditions, causing the elemental iron nanoparticles to oxidize and participate in the reaction, forming a gelled shell mainly composed of amorphous iron-containing aluminosilicate gel on the surface of the iron tailings sand.

[0025] S3. Curing and post-treatment: After the reaction is completed, dry at 105℃ for 6 hours, grind, and pass through a 120-mesh sieve to obtain a viscosity reducer with iron tailings sand as the core and cementing material as the shell.

[0026] This low-viscosity, ultra-high-performance concrete is prepared using the following steps: a. Weigh out the cement, silica fume, fly ash, limestone powder, quartz sand and viscosity reducer according to the mass fraction, put them into the mixer and mix evenly; b. Add water and water-reducing agent according to the mass ratio to form a composite admixture, and stir until the powder material is completely fluidized into a plastic concrete. c. Add steel fiber according to the mass ratio and stir for 5 minutes to obtain ultra-high performance concrete mixture, pour into shape, and cure according to standard for 28 days as specified age.

[0027] Example 2 A low-viscosity, ultra-high-performance concrete uses a viscosity-reducing agent coated with iron tailings sand as a cementitious outer shell, and employs cement, silica fume, fly ash, and limestone powder as cementing materials. The aggregate is quartz sand. The raw materials include the following parts by weight: 585 parts cement, 130 parts silica fume, 245 parts fly ash, 95 parts limestone powder, 950 parts quartz sand, 28 parts commercially available ultra-high performance concrete water-reducing agent, 195.5 parts water, 95 parts viscosity reducer, and 160 parts steel fiber.

[0028] The viscosity reducer used to coat the iron tailings sand with the cementitious outer shell and the preparation method of the low-viscosity ultra-high performance concrete are the same as in Example 1.

[0029] Example 3 A low-viscosity, ultra-high-performance concrete uses a viscosity-reducing agent coated with iron tailings sand as a cementitious outer shell, and employs cement, silica fume, fly ash, and limestone powder as cementing materials. The aggregate is quartz sand. The raw materials include the following parts by weight: 585 parts cement, 130 parts silica fume, 245 parts fly ash, 95 parts limestone powder, 950 parts quartz sand, 22 parts commercially available ultra-high performance concrete water-reducing agent, 230 parts water, 95 parts viscosity reducer, and 160 parts steel fiber.

[0030] The viscosity reducer used to coat the iron tailings sand with the cementitious outer shell and the preparation method of the low-viscosity ultra-high performance concrete are the same as in Example 1.

[0031] Comparative Example 1 A type of ordinary ultra-high performance concrete comprises the following raw materials in parts by weight: 585 parts cement, 130 parts silica fume, 245 parts fly ash, 190 parts limestone powder, 1000 parts quartz sand, 34.6 parts commercially available ultra-high performance concrete water-reducing agent, 180 parts water, and 160 parts steel fiber.

[0032] The difference between its preparation method and that of Example 1 is that no viscosity reducer was added.

[0033] Comparative Example 2 A type of ordinary ultra-high performance concrete comprises the following raw materials in parts by weight: 585 parts cement, 130 parts silica fume, 245 parts fly ash, 190 parts limestone powder, 1000 parts quartz sand, 34.6 parts commercially available ultra-high performance concrete water-reducing agent, 195.5 parts water, and 160 parts steel fiber.

[0034] The difference between its preparation method and that of Example 1 is that no viscosity reducer was added.

[0035] Comparative Example 3 A type of ordinary ultra-high performance concrete comprises the following raw materials in parts by weight: 585 parts cement, 130 parts silica fume, 245 parts fly ash, 190 parts limestone powder, 1000 parts quartz sand, 34.6 parts commercially available ultra-high performance concrete water-reducing agent, 230 parts water, and 160 parts steel fiber.

[0036] The difference between its preparation method and that of Example 1 is that no viscosity reducer was added.

[0037] Test The products prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing, and the testing methods are as follows: The expansion and T500 were tested according to GB / T 31387-2015 "Test Methods for Basic Properties of Ultra-High Performance Concrete"; the viscosity was tested according to GB / T 2794-2013 "Determination of Viscosity of Adhesives"; the 28-day compressive strength and flexural strength were tested according to GB / T 31387-2015, after 28 days of standard curing. The test results are shown in Table 1.

[0038] Table 1. Concrete performance test results

[0039] As shown in Table 1, the core-shell structure viscosity reducer prepared in this invention has an amorphous iron-containing aluminosilicate gel shell with active effect generated in situ on its surface, which can participate in the hydration reaction of the cementitious system, densify the interface structure, improve the integrity of the matrix, and make the 28-day compressive and flexural strength of the concrete significantly higher than that of the control proportion without viscosity reducer. Its uniform and regular core-shell particles exert the micro-aggregate ball effect in the concrete mixture, effectively reducing the friction in the system, improving the slurry encapsulation, and making the mixture more extensible, with a shorter T500 time and lower apparent viscosity.

[0040] Therefore, this invention employs the aforementioned viscosity reducer for coating iron tailings with a gelled shell, its preparation method, and its application. This transforms inert iron tailings into a high-performance material that combines the activity of mineral admixtures and the function of micro-aggregates. The material is then used to prepare low-viscosity, ultra-high-performance concrete from iron tailings core-shell materials. This solves the technical problems of weak interfacial bonding and poor adhesion when iron tailings are used as building materials. It achieves high added value and large-scale resource utilization of iron tailings, resulting in significant environmental and economic benefits.

[0041] 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a viscosity reducer for iron tailings sand with a gelled outer shell, characterized in that, Includes the following steps: S1. Pretreatment and iron component activation: The iron tailings sand is ground and screened to obtain raw materials with uniform particle size. It is then acid washed and heat-treated in a reducing atmosphere to obtain iron tailings sand with activated iron components. S2, gelling coating: The iron tailings sand obtained in S1 is mixed with an alkaline activator solution in proportion, stirred evenly, and reacted to obtain a gelled outer shell; S3. Curing and post-treatment: After the reaction is completed, the product is dried and ground to obtain a viscosity reducer with iron tailings sand as the core and cementing material as the shell.

2. The method for preparing a viscosity reducer for iron tailings sand with a gelled outer shell according to claim 1, characterized in that, In S1, the proportion of 0.075~0.6mm particles in the iron tailings sand is not less than 50%, and the chemical composition of the iron tailings sand contains 30~50% SiO2 and 10~35% Fe2O3.

3. The method for preparing a viscosity reducer for iron tailings sand with a gelled outer shell according to claim 1, characterized in that, In S1, the pickling process specifically involves: The acid washing reagent with a concentration of 0.5~1.5mol / L was used, the acid washing temperature was 50~80℃, the treatment time was 2~8h, and the solid-liquid ratio was 1:(3~10). The pickling reagent is one or more of hydrochloric acid, nitric acid, or sulfuric acid.

4. The method for preparing a viscosity reducer for iron tailings sand with a gelled outer shell according to claim 1, characterized in that, In S1, the heat treatment under a reducing atmosphere specifically involves: The reducing atmosphere consists of hydrogen and an inert gas, with hydrogen accounting for 8-15% of the volume and argon as the inert gas. The gas flow rate is 100-500 mL / min, the heat treatment temperature is 450-550℃, and the holding time is 1-2 h.

5. The method for preparing a viscosity reducer for iron tailings sand with a gelled outer shell according to claim 1, characterized in that, In S2, the alkaline activator is one or more of sodium hydroxide, sodium silicate, calcium hydroxide or sodium carbonate, the concentration of the alkaline activator solution is 1~10 mol / L, and the solid-liquid ratio of iron tailings sand to alkaline activator solution is 1:(2~6).

6. The method for preparing a viscosity reducer for iron tailings sand with a gelled outer shell according to claim 1, characterized in that, In S2, the reaction is specifically as follows: The reaction temperature is 60~120℃, the reaction pressure is atmospheric pressure to 1.0MPa, and the reaction time is 4~24h.

7. A viscosity reducer for iron tailings sand with a gelled shell, prepared by the method of preparing the viscosity reducer for iron tailings sand with a gelled shell as described in any one of claims 1 to 6, characterized in that: The viscosity reducer is a core-shell material with iron tailings sand particles as the core and cementing substances as the outer shell; The gelling material is an amorphous iron-containing aluminosilicate gel, and its mass percentage is 10-35%.

8. The application of a viscosity reducer for iron tailings sand with a gelled outer shell as described in claim 7 in concrete preparation.

9. The application according to claim 8, characterized in that, The concrete comprises the following components: Cementitious materials, aggregates, water-reducing agents, water, and the aforementioned viscosity reducer; The viscosity reducer is added at a rate of 1-10% based on the total mass of the cementitious materials (100%).

10. The application according to claim 8, characterized in that, The concrete preparation includes the following steps: The cementitious materials, aggregates, and the aforementioned viscosity reducer are mixed, and then water and water-reducing agent are added and stirred to obtain concrete.

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