Road base material using pyrite tailings and method for preparing the same

Abstract

This invention discloses a road base material using pyrite tailings. The road base material comprises: 10-40 parts by weight of a novel non-fired low-carbon cementitious material curing agent, 60-90 parts by weight of the stabilized material, and water. The novel non-fired low-carbon cementitious material curing agent comprises: 15%-40% steel slag powder, 40%-70% slag powder, 5%-30% by-product gypsum, and a special activator. The special activator comprises sodium carbonate, sodium sulfate, and / or sodium stearate. The stabilized material is pyrite tailings. A method for preparing the road base material using pyrite tailings is also disclosed. The beneficial effects of this invention are: utilizing the dual theories of alkali activation and sulfate activation, fully leveraging the synergistic coupling activation effect between solid wastes, achieving the formation of a hydration and hardening community between the curing agent and pyrite tailings, resulting in a road base material with excellent performance, and realizing the high-volume, high-value utilization of pyrite tailings.

Description

Technical Field

[0001] This invention relates to the fields of comprehensive utilization of solid waste and building materials technology, and more specifically, to a road base material using pyrite tailings and its preparation method. Background Technology

[0002] Pyrite tailings are solid wastes discharged during the ore beneficiation processes of pyrite mines, including grinding, classification, and flotation. They often occupy land resources in the form of tailings ponds, impacting the surrounding ecological environment. Because pyrite tailings contain unstable pyrite (FeS2) and pyrrhotite (Fe...), they are particularly problematic. 1～x Sulfide compounds such as iron sulfide (S) slowly decompose into sulfates and hydroxides under oxidizing conditions. Sulfides exposed to the atmosphere, under the combined action of oxygen, water, and microorganisms, produce sulfuric acid, forming acidic mine wastewater. This increases the solubility and reactivity of heavy metals, leading to the dissolution of solid solutions containing heavy metals such as Cd, Hg, and Pb, and the release of heavy metal ions, causing continuous pollution to the ecological environment.

[0003] Currently, there is a severe lack of comprehensive utilization technologies for pyrite tailings. Research mainly focuses on recovering sulfur concentrate and metallic elements, as well as preparing building materials and mine backfill materials. Although there has been some research on preparing road base mixtures from tailings, the overall strength of the mixtures is low due to the inert chemical properties and weak interparticle adsorption of pyrite tailings. This prevents the large-scale application of tailings in road construction, resulting in a low utilization rate of pyrite tailings.

[0004] In addition, the most commonly used road base stabilization materials are cement, lime, or lime-fly ash stabilized materials. Cement stabilized materials can meet the strength requirements of various engineering grades, but they are prone to drying shrinkage cracks, and cement production involves high energy consumption, significant natural resource depletion, and carbon dioxide emissions. Lime stabilized materials are low in cost, but have low early strength, are subject to seasonal limitations in construction, and exhibit significant drying shrinkage, easily leading to road base cracking. Lime-fly ash stabilized materials have low early strength but relatively high later strength, but they have high construction requirements and are prone to surface peeling, springiness, and cracking. Using traditional cementitious materials such as cement, lime, or lime-fly ash as curing agents and using recyclable tailings such as iron tailings and lead-zinc tailings as stabilized materials presents problems such as high processing costs for preparing road base mixtures from tailings and the inability to achieve large-scale application. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a road base material using pyrite tailings, enabling the large-scale and high-value utilization of pyrite tailings, resulting in a road base material with high early strength, short setting time, low hydration heat release, good volume stability, strong resistance to sulfate erosion, continuous strength growth in the later stages, and no drying shrinkage cracking.

[0006] This invention provides a road base material using pyrite tailings, the road base material comprising the following raw materials in parts by weight: 10-40 parts by weight of a novel non-fired low-carbon cementitious material curing agent, 60-90 parts by weight of stabilized material, and additionally added water;

[0007] The components of the novel non-fired low-carbon cementitious material curing agent include: steel slag powder, slag powder, by-product gypsum, and a special activator. The mass percentages of each component are as follows: steel slag powder 15%–40%, slag powder 40%–70%, and by-product gypsum 5%–30%. The special activator is added based on the mass of the novel non-fired low-carbon cementitious material curing agent. The components of the special activator include sodium carbonate, sodium sulfate, and / or sodium stearate.

[0008] The material being stabilized is pyrite tailings.

[0009] As a further improvement of the present invention, the components of the pyrite tailings include: quartz, pyrite compound, hemihydrate gypsum, mica and calcite, and the mass percentage of each component is: quartz 60% to 80%, pyrite compound 3% to 15%, hemihydrate gypsum 0% to 5%, mica 0% to 10%, and calcite 0% to 10%.

[0010] As a further improvement of the present invention, the sodium carbonate content is 0% to 1% of the mass of the curing agent of the novel non-fired low-carbon cementitious material, the sodium sulfate content is 0% to 2% of the mass of the curing agent of the novel non-fired low-carbon cementitious material, and the sodium stearate content is 0% to 1% of the mass of the curing agent of the novel non-fired low-carbon cementitious material.

[0011] As a further improvement of the present invention, the median particle size of the pyrite tailings is 20μm to 50μm, and the volume average diameter of the pyrite tailings is 40μm to 70μm.

[0012] As a further improvement of the present invention, the powder fineness of the novel non-fired low-carbon cementitious material curing agent meets the following condition: specific surface area ≥ 400 m². 2 / kg, and the residue on a 45μm square mesh sieve is ≤12%.

[0013] As a further improvement of the present invention, the amount of water added is such that the moisture content of the road base material using pyrite tailings is 9% to 15%.

[0014] This invention also provides a method for preparing road base material using pyrite tailings, the method comprising the following steps:

[0015] Weigh out steel slag, mineral slag, by-product gypsum and special activator according to the proportions to obtain each raw material;

[0016] The raw materials are processed to obtain a novel non-fired low-carbon cementitious material curing agent, wherein the processing includes at least: crushing, drying, grinding and magnetic separation.

[0017] Prepare pyrite tailings according to the proportion, and mix the pyrite tailings and the new non-fired low-carbon cementitious material curing agent evenly to obtain pyrite tailings road base mixture.

[0018] Water is added to the pyrite tailings road base mixture and mixed evenly to obtain a road base material using pyrite tailings.

[0019] As a further improvement of the present invention, the symmetrically selected raw materials are processed to obtain a novel non-fired low-carbon cementitious material curing agent, comprising:

[0020] The symmetrically selected steel slag is crushed to ensure that its particle size meets the requirements.

[0021] The slag powder, by-product gypsum, and steel slag obtained from the symmetrical extraction process are dried separately, and the steel slag powder is subjected to magnetic separation.

[0022] The dried slag, by-product gypsum and crushed steel slag were separately ground to obtain the corresponding powders.

[0023] The weighed special activator is mixed with the corresponding powder to obtain the powder, which is the curing agent of the new type of non-fired low-carbon cementitious material.

[0024] As a further improvement of the present invention, the symmetrically selected powders are processed to obtain a novel non-fired low-carbon cementitious material curing agent, comprising:

[0025] The symmetrically selected steel slag is crushed to ensure that its particle size meets the requirements.

[0026] The slag, by-product gypsum, and steel slag obtained from symmetrical extraction and crushing were dried separately.

[0027] The special activator obtained by symmetry is mixed with the dried slag, by-product gypsum and crushed steel slag, then ground and magnetically separated. The resulting powder is the curing agent of the novel non-fired low-carbon cementitious material.

[0028] As a further improvement of this invention, the steel slag is crushed to obtain a particle size of no more than 4.75 mm. The slag is then ground to a specific surface area of ​​no less than 400 m². 2 / kg, by-product gypsum powder ground to a specific surface area of ​​not less than 400m² 2 / kg, steel slag ground to a specific surface area of ​​not less than 350m² 2 / kg, and the residue on a 45μm square mesh sieve is ≤12%.

[0029] As a further improvement of the present invention, the moisture content of the pyrite tailings road base mixture is 9% to 15%.

[0030] The beneficial effects of this invention are as follows: by optimizing the types and dosages of industrial solid waste, utilizing the dual theories of alkali activation and sulfate activation, the synergistic coupling activation effect between solid wastes is fully utilized, effectively utilizing pyrite compounds and gypsum in pyrite tailings, and preparing a curing agent based on a ternary system of steel slag-slag-gypsum, and combining it with a special activator, the early strength of the curing agent is effectively improved.

[0031] By utilizing the curing agent to form a hydration-hardening community with the stabilized material, the mechanical properties and durability of road base mixtures are effectively improved. This produces road base materials with high early strength, short setting time, low hydration heat release, good volume stability, strong resistance to sulfate attack, continuous strength growth in the later stage, and no drying shrinkage cracking. These materials can meet the strength requirements of cement-stabilized materials for expressways and first-class highways, and enable large-scale utilization of pyrite tailings.

[0032] By utilizing the synergistic effect of solid waste, sulfates produced by the oxidation and decomposition of pyrite compounds in pyrite tailings are actively consumed, thereby accelerating the oxidation of pyrite compounds in pyrite tailings. This reduces the harm caused by poor volume stability due to passive oxidation of pyrite tailings, effectively solves the problem of poor stability in the process of using pyrite tailings as building materials, and realizes the resource utilization and high-value utilization of pyrite tailings. Attached Figure Description

[0033] Figure 1 This is a schematic flowchart illustrating a method for preparing road base material using pyrite tailings according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic flowchart illustrating another method for preparing road base material using pyrite tailings according to an embodiment of the present invention;

[0035] Figure 3 This is a schematic flowchart illustrating the preparation method of road base material using pyrite tailings according to an embodiment of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0037] It should be noted that the terminology used in the description of this invention is for illustrative purposes only and is not intended to limit the scope of this disclosure. Terms such as "having," "comprising," and "including" as used in this invention do not exclude the presence or addition of one or more other materials, steps, operations, and / or combinations. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in the embodiments of this invention are commercially available or can be prepared by existing methods.

[0038] This invention discloses a road base material using pyrite tailings. The raw materials for preparing this road base material include: a novel non-fired low-carbon cementitious material curing agent (10-40 parts by weight), a stabilized material (60-90 parts by weight), and additionally added water. The novel non-fired low-carbon cementitious material curing agent comprises: steel slag powder, slag powder, by-product gypsum, and a special activator. The mass percentages of each component are: steel slag powder 15%-40%, slag powder 40%-70%, and by-product gypsum 5%-30%. The special activator is added based on the mass of the novel non-fired low-carbon cementitious material curing agent, and its components include sodium carbonate, sodium sulfate, and / or sodium stearate.

[0039] The stabilized material is pyrite tailings, a high-sulfur type of tailings. The sulfur in the tailings mainly exists in three mineral forms: pyrite, pyrrhotite, and gypsum. When pyrite tailings are incorporated into cement and concrete, the pyrite, pyrrhotite, and other pyrite compounds in the tailings will slowly oxidize within the cement and concrete, with a reaction period that can last from several years to decades. The resulting sulfates react with the calcium in the matrix. 2+ Secondary reactions involving substances such as CAH can generate minerals like ettringite, leading to volume expansion and potential stability risks in cement concrete. In this invention, pyrite tailings are used as a stabilized material. This not only provides skeletal reinforcement to the matrix but also participates in the hydration reaction, providing sulfates to stimulate later-stage strength growth in the matrix. This solves the problem of poor stability, turning the disadvantages of pyrite tailings into advantages and achieving high-value, resource-efficient utilization.

[0040] The granulated blast furnace slag (i.e., slag powder) in the curing agent of the novel non-fired low-carbon cementitious material is mainly composed of aluminosilicate minerals. After processing and grinding, it has certain hydration activity and can undergo hydration under alkaline conditions, exhibiting a structure and properties similar to cement stone. The synergistic activation technology between solid wastes can be used to prepare novel non-fired low-carbon cementitious materials to replace or partially replace cement in engineering construction. In the industrial solid waste synergistic activation system, steel slag powder can increase the alkalinity of the pore solution and promote the hydration of aluminosilicate minerals. Granulated blast furnace slag (slag powder) has a pozzolanic effect, which can stably provide active components such as silica and alumina. Desulfurized gypsum (by-product gypsum) can activate the activity of steel slag powder and slag powder, accelerating the formation of hydration products AFt and CSH gel in the cementitious material. The ternary system of steel slag-slag-gypsum has a synergistic promoting effect during hydration. The amount of hydration products increases rapidly in the later stage of the reaction. The needle-like AFt crystals interpenetrate in the CSH gel, making the structure of the hardened paste more compact and improving the stability of the entire concrete system.

[0041] The special activator in this invention can be, for example, a mixture of sodium carbonate, sodium sulfate, and sodium stearate, or a mixture of sodium carbonate and sodium sulfate. Sodium carbonate and sodium sulfate provide alkali and sulfate, respectively, and are incorporated to adjust performance fluctuations in steel slag powder, blast furnace slag powder, and by-product gypsum. Sodium stearate can improve the water repellency and resistance to sulfate and chloride ion corrosion of the base mixture; it can be omitted from projects without these requirements.

[0042] This invention employs a novel non-fired low-carbon cementitious material curing agent, combined with a special activator, to achieve the formation of a hydration hardening community between the curing agent and the stabilized material. This significantly improves the mechanical properties and durability of road base mixtures. Furthermore, during the hydration process, it actively consumes sulfates in pyrite tailings, promotes the accelerated oxidation of pyrite compounds, reduces the harm caused by the passive oxidation of pyrite tailings leading to poor volume stability, and enables the large-scale utilization of pyrite tailings.

[0043] Optionally, the steel slag powder, blast furnace slag powder, and by-product gypsum components in the novel non-fired low-carbon cementitious material curing agent may include, for example, the following composition (by mass percentage):

[0044] Component 1: 15% steel slag powder, 70% blast furnace slag powder, and 15% by-product gypsum;

[0045] Component 2: 20% steel slag powder, 60% blast furnace slag powder, and 20% by-product gypsum;

[0046] Component 3: 25% steel slag powder, 50% blast furnace slag powder, and 25% by-product gypsum;

[0047] Component 4: 30% steel slag powder, 40% blast furnace slag powder, and 30% by-product gypsum;

[0048] Component 5: 35% steel slag powder, 55% blast furnace slag powder, and 10% by-product gypsum;

[0049] Component 6: 40% steel slag powder, 55% blast furnace slag powder, and 5% by-product gypsum.

[0050] It is understood that the mineral composition of the steel slag powder, slag powder and by-product gypsum in the novel non-fired low-carbon cementitious material curing agent listed above is only for illustrative purposes and is not intended to limit the composition of the steel slag powder, slag powder and by-product gypsum in the novel non-fired low-carbon cementitious material curing agent.

[0051] In one optional embodiment, the pyrite tailings comprises: quartz, pyrite compound, hemihydrate gypsum, mica, and calcite, with the following mass percentages: quartz 60%–80%, pyrite compound 3%–15%, hemihydrate gypsum 0%–5%, mica 0%–10%, and calcite 0%–10%. The pyrite compound may be pyrite, pyrrhotite, or a mixture of pyrite and pyrrhotite.

[0052] Pyrite tailings may include, for example, the following components (by mass percentage):

[0053] Component 1: Quartz 60%, pyrite 15%, hemihydrate gypsum 5%, mica 10%, calcite 10%;

[0054] Component 2: Quartz 65%, pyrite compound (pyrrhotite) 15%, hemihydrate gypsum 2%, mica 10%, calcite 8%;

[0055] Component 3: Quartz 70%, pyrite 10%, mica 10%, calcite 10%;

[0056] Component 4: Quartz 75%, pyrite compound (pyrrhotite) 6%, hemihydrate gypsum 4%, mica 7%, calcite 8%;

[0057] Component 5: Quartz 78%, pyrite compounds (pyrrhotite, pyrite) 12%, hemihydrate gypsum 5%, mica 5%;

[0058] Component 6: Quartz 80%, pyrite compounds (pyrrhotite, pyrite) 8%, hemihydrate gypsum 4%, calcite 8%;

[0059] Component 7: Quartz 80%, pyrite compound (pyrrhotite) 3%, hemihydrate gypsum 5%, mica 8%, calcite 4%;

[0060] Component 8: Quartz 80%, pyrite 15%, hemihydrate gypsum 5%.

[0061] It is understood that the mineral composition of the pyrite tailings listed above is only used as an example to illustrate the mineral composition of different pyrite tailings and is not a limitation on the composition of pyrite tailings.

[0062] In one optional implementation, the special activator is added based on the mass of the novel non-fired low-carbon cementitious material curing agent ("novel non-fired low-carbon cementitious material curing agent" can be simply referred to as "curing agent"). The dosage of each component of the special activator includes: sodium carbonate at 0% to 1% of the mass of the novel non-fired low-carbon cementitious material curing agent, sodium sulfate at 0% to 2% of the mass of the novel non-fired low-carbon cementitious material curing agent, and sodium stearate at 0% to 1% of the mass of the novel non-fired low-carbon cementitious material curing agent. Each component of the special activator is added based on the curing agent and in a certain proportion. It is understood that when the special activator includes sodium carbonate, sodium sulfate, and sodium stearate, the amount of sodium carbonate is 0% to 1% of the mass of the curing agent, the amount of sodium sulfate is 0% to 2% of the mass of the curing agent, and the amount of sodium stearate is 0% to 1% of the mass of the curing agent; when the special activator includes sodium carbonate and sodium sulfate, the amount of sodium carbonate is 0% to 1% of the mass of the curing agent, and the amount of sodium sulfate is 0% to 2% of the mass of the curing agent.

[0063] The dosage of each component in a dedicated activator includes, for example, the following situations:

[0064] Special activator dosage 1: The dosage of special activator is 2% of the mass of curing agent, of which the dosage of sodium sulfate is 2% of the mass of curing agent;

[0065] Special activator dosage 2: The dosage of special activator is 2% of the mass of curing agent, of which the dosage of sodium carbonate is 1% of the mass of curing agent and the dosage of sodium sulfate is 1% of the mass of curing agent;

[0066] Special activator dosage 3: The dosage of special activator is 2% of the mass of curing agent, of which sodium carbonate is 0.5% of the mass of curing agent, sodium sulfate is 1% of the mass of curing agent, and sodium stearate is 0.5% of the mass of curing agent;

[0067] Special activator dosage 4: The dosage of special activator is 1% of the mass of curing agent, of which the dosage of sodium carbonate is 1% of the mass of curing agent;

[0068] Special activator dosage 5: The dosage of special activator is 1% of the mass of curing agent, of which the dosage of sodium carbonate is 0.5% of the mass of curing agent and the dosage of sodium stearate is 0.5% of the mass of curing agent.

[0069] Special activator dosage 6: The dosage of special activator is 1% of the mass of curing agent, of which sodium sulfate is 0.7% of the mass of curing agent and sodium stearate is 0.3% of the mass of curing agent.

[0070] It is understood that the above-listed dosage of special activator is only used as an example to illustrate different dosages of special activator, and is not a limitation on the components of special activator and the dosage of each component.

[0071] In one optional implementation, the median particle size of the pyrite tailings is 20 μm to 50 μm, and the volume average diameter of the pyrite tailings is 40 μm to 70 μm. This can fully leverage the synergistic effect between solid wastes, enabling the solidifying agent and the stabilized material to form a hydration-hardening community.

[0072] In one optional implementation, the powder fineness of the novel non-fired low-carbon cementitious material curing agent meets the following condition: specific surface area ≥ 400 m². 2 / kg, and the residue on a 45μm square-hole sieve is ≤12%. Steel slag powder needs to be magnetically separated before testing. Optionally, the specific surface area of ​​the slag powder should not be less than 400m². 2 / kg, or the specific surface area of ​​slag powder is not less than 420m². 2 / kg. Optional, the specific surface area of ​​the by-product gypsum is not less than 400m². 2 / kg, or the specific surface area of ​​by-product gypsum is not less than 450m². 2 / kg, or the specific surface area of ​​by-product gypsum is not less than 500m². 2 / kg. Optional, the specific surface area of ​​steel slag powder is not less than 400m². 2 / kg, or the specific surface area of ​​steel slag powder is not less than 380m². 2 / kg, or the specific surface area of ​​steel slag powder is not less than 350m². 2 / kg.

[0073] In one optional embodiment, road base material made from pyrite tailings is used, wherein the amount of water added is such that the moisture content of the road base material made from pyrite tailings is 9% to 15%, preferably 15% for the mixture (i.e., the mixture obtained by uniformly mixing pyrite tailings and a novel non-fired low-carbon cementitious material curing agent); more preferably, 13% for the mixture; and even more preferably, 11% for the mixture.

[0074] The present invention provides a method for preparing road base material using pyrite tailings, as described in the embodiments of the present invention. Figure 3 As shown, the method includes the following steps:

[0075] S1, according to the proportions, weigh out steel slag, ore slag, by-product gypsum and special activator to obtain each raw material;

[0076] S2, the symmetrically selected raw materials are processed to obtain a new type of non-fired low-carbon cementitious material curing agent, wherein the processing includes at least: crushing, drying, grinding and magnetic separation.

[0077] S3, prepare pyrite tailings according to the proportion, and mix the pyrite tailings and the new non-fired low-carbon cementitious material curing agent evenly to obtain pyrite tailings road base mixture;

[0078] S4, add water to the pyrite tailings road base mixture and mix and stir evenly to obtain the road base material using pyrite tailings.

[0079] It is understood that the proportions of each powder in S1 are determined according to the mass parts and mass percentages of each powder in the foregoing embodiments of the present invention, and the specific parameters will not be repeated here.

[0080] The pyrite tailings prepared in S3 are also weighed according to the mass proportions described in the foregoing embodiments of the present invention. This weighing process can also be completed in S1. Whether the weighing of the pyrite tailings is completed in S1 or in S3 does not affect the overall preparation method of the present invention. It should be noted that the median particle size and volume average diameter of the weighed pyrite tailings must meet the parameters described in the foregoing embodiments. The specific parameters will not be repeated here.

[0081] The processing step S2 includes at least crushing, drying, grinding, and magnetic separation. It is understood that these four processes are not in a specific order; the order of one or more processes can be adjusted adaptively without affecting the final powder of the novel non-fired low-carbon cementitious material curing agent. It should be noted that the particle size of the steel slag powder and the fineness of the novel non-fired low-carbon cementitious material curing agent obtained in the processing step S2 must meet the parameters described in the aforementioned embodiments. Specific parameters will not be elaborated here.

[0082] The amount of water added in S4 must also meet the moisture content requirements of the aforementioned embodiments; the specific parameters will not be elaborated here.

[0083] It should also be noted that the processing in S2 includes the process of separately grinding the slag, by-product gypsum, and steel slag and then mixing them with the special activator, as well as the process of mixing and grinding the slag, by-product gypsum, steel slag, and special activator together. The detailed steps of the preparation method described in this invention will be explained below.

[0084] Preparation method 1, such as Figure 1 As shown in the embodiment of the present invention, a method for preparing road base material using pyrite tailings includes the following steps:

[0085] S101: Weigh the appropriate amounts of steel slag, mineral slag, and by-product gypsum according to the specified proportions. Various raw materials are precisely measured using a weighing scale.

[0086] S102: The steel slag weighed in S101 is crushed to ensure that its particle size meets the requirements: the particle size of the crushed steel slag is not greater than 4.75 mm.

[0087] S103: The slag and by-product gypsum weighed in S101 and the steel slag obtained from the crushing process in S102 are dried separately, and the steel slag is subjected to magnetic separation.

[0088] S104: The slag, by-product gypsum, and steel slag obtained from drying in S103 are ground separately to obtain the corresponding powders. Optionally, the slag, by-product gypsum, and steel slag can be added separately to a mill (such as a ball mill, vertical mill, or tube mill) for separate grinding until the specific surface area of ​​the slag powder is not less than 400 m². 2 / kg, the specific surface area of ​​by-product gypsum is not less than 400m² 2 The specific surface area of ​​ / kg steel slag powder is not less than 350m². 2 / kg, and the residue on a 45μm square hole sieve is no more than 12%, of which the steel slag powder is tested after magnetic separation.

[0089] S105: Weigh out the appropriate amount of special activator according to the formula, and mix the weighed special activator with the powders obtained in S104 to obtain a new type of non-fired low-carbon cementitious material curing agent. The mixing process may be, for example, homogenization in a pneumatic and mechanical composite mixer.

[0090] S106: Mix the pyrite tailings with the new non-fired low-carbon cementitious material curing agent obtained in S105 according to the specified ratio, and stir evenly to obtain the pyrite tailings road base mixture.

[0091] S107: Add water to the pyrite tailings road base mixture in S106, and mix and stir evenly to obtain the road base material using pyrite tailings.

[0092] Preparation method 2, such as Figure 2 As shown in the embodiment of the present invention, another method for preparing road base material using pyrite tailings includes the following steps:

[0093] S201: Prepare pyrite tailings and new non-fired low-carbon cementitious material curing agent according to the formula ratio. The new non-fired low-carbon cementitious material curing agent shall weigh out the corresponding amounts of steel slag, ore slag, by-product gypsum and special activator according to the formula ratio.

[0094] S202: The steel slag weighed in S201 is crushed to ensure that its particle size meets the requirements: the particle size of the crushed steel slag is not greater than 4.75 mm.

[0095] S203: The slag and by-product gypsum weighed in S201 and the steel slag obtained from the crushing process in S202 are dried separately.

[0096] S204: The special activator in S201 and the dried slag, by-product gypsum, and steel slag obtained in S203 are mixed, ground, and then magnetically separated. The resulting powder is the curing agent for the new type of non-fired low-carbon cementitious material. Optionally, the slag, by-product gypsum, and steel slag can be added separately to a mill (such as a ball mill, vertical mill, or tube mill) for individual grinding until the specific surface area of ​​the slag powder is not less than 400 m². 2 / kg, the specific surface area of ​​by-product gypsum is not less than 400m² 2 / kg and the specific surface area of ​​steel slag powder is not less than 400m² 2 / kg, and the residue on a 45μm square hole sieve is no more than 12%. The powder processed by grinding and magnetic separation is the curing agent for the new type of non-fired low-carbon cementitious material.

[0097] S205: Mix the pyrite tailings weighed in S201 with the new non-fired low-carbon cementitious material curing agent obtained in S204 until they are evenly stirred to obtain the pyrite tailings road base mixture.

[0098] S206: Add water to the pyrite tailings road base mixture in S205, and mix and stir evenly to obtain the road base material using pyrite tailings.

[0099] The road base material of this invention can be obtained through the two methods described above for preparing road base materials using pyrite tailings. The preparation process involves only crushing, drying, and grinding. Based on the grinding steps of the raw materials, it can be divided into two types: separate grinding and mixed grinding. Crushing and grinding the raw materials to reduce their particle size can accelerate the synergistic activation effect, promote the hydration process of aluminosilicate minerals, and produce a road base material with high early strength, short setting time, low hydration exothermic reaction, good volume stability, and strong resistance to sulfate attack.

[0100] This invention relates to the comprehensive utilization of various industrial solid wastes. By optimizing the types and amounts of industrial solid wastes and utilizing the dual theories of alkali activation and sulfate activation, it fully leverages the synergistic coupling activation effect between solid wastes. It actively consumes sulfates produced by the oxidation and decomposition of pyrite compounds in pyrite tailings, thereby accelerating the oxidation of pyrite compounds in pyrite tailings. This enables the solidifying agent and the stabilized material to form a hydration hardening community. Not only can it consume a large amount of industrial solid waste and realize the resource utilization of multiple solid wastes, but it can also ensure the bearing capacity and overall stability of the road structure and improve the service life of the road surface, resulting in significant economic, environmental, and social benefits.

[0101] To more clearly understand the purpose, technical solution, and advantages of this invention, the following detailed description is provided in conjunction with embodiments. The specific data used in the specific examples described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0102] The following examples use pyrite tailings from a city in southern my country, which were collected on-site and then sealed. The pyrite tailings have a sulfur trioxide content of 14.7%, an optimum moisture content of 13%, a median particle size D(50) of 45.5 μm, and a volume average diameter D(4,3) of 62.86 μm. Their mineral composition is shown in Table 1 (the numbers represent the mass percentage of each component):

[0103] Table 1. Mineral composition of pyrite tailings in a southern city

[0104] Pyrite mica hemihydrate gypsum quartz Feldspar chlorite calcite 7.4 6.7 2.5 70.3 3.9 4.7 4.5

[0105] Steel slag and ore slag are produced by Tangshan Iron and Steel Group and ground to 380m³ respectively. 2 / kg and 420m 2 / kg.

[0106] By-product gypsum ① is desulfurized gypsum produced by China Huadian Corporation, with a specific surface area of ​​450 m². 2 / kg, by-product gypsum ② is titanium gypsum provided by Yunnan Sulfur Mining Group Co., Ltd., with a specific surface area of ​​500m². 2 / kg.

[0107] The dosage of the special activator is 1% of the mass of the curing agent, of which the dosage of sodium carbonate is 0.4% of the mass of the curing agent, the dosage of sodium stearate is 0% of the mass of the curing agent, and the dosage of sodium sulfate is 0.6% of the mass of the curing agent.

[0108] It is understood that the components and dosages of pyrite tailings, novel non-fired low-carbon cementitious material curing agent, and special activator can be other embodiments included in the present invention, and are not limited to the methods selected in the following embodiments.

[0109] The experimental procedure was conducted according to the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" (JTG E51-2009). All strengths mentioned below refer to the 7-day unconfined compressive strength. Water stability indicators were expressed as the ratio of immersion strength to non-immersion strength, as specified in CJJ / T286-2018 "Technical Standard for Application of Soil Stabilizers". Immersion strength was determined by curing the specimens in a standard curing chamber for 6 days, with the last day being immersion curing; non-immersion strength was determined by curing in a standard curing room for 7 days. The ratio of the unconfined compressive strength of the first group to the second group was used as the water stability coefficient.

[0110] Example 1:

[0111] A road base material using pyrite tailings is composed of the following components in the indicated mass ratios: 20 parts slag powder, 10 parts by-product gypsum①, 10 parts steel slag powder, 60 parts pyrite tailings, 0.4 parts special activator, and 13 parts water content. The mass ratios of each component are shown in Table 2.

[0112] The specific steps of the above-mentioned method for preparing road base material using pyrite tailings are as follows:

[0113] The various raw materials are precisely measured using a weighing scale according to the formula ratio;

[0114] Mix 200g of slag powder, 100g of by-product gypsum powder, 100g of steel slag powder, and 8g of a special activator for 4 minutes to obtain a novel non-fired, low-carbon cementitious material curing agent. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0115] After mixing 130ml of water with the curing agent for 4 minutes, add 600g of pyrite tailings to the curing agent and continue mixing for 5 minutes to obtain the pyrite tailings road base material. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0116] Example 2: A road base material using pyrite tailings, composed of the following components in the indicated mass ratios: 14 parts slag powder, 10.5 parts by-product gypsum①, 10.5 parts steel slag powder, 65 parts pyrite tailings, 0.35 parts special activator, and 13 parts water content. The mass ratios of each component are shown in Table 2.

[0117] The specific steps of the above-mentioned method for preparing road base material using pyrite tailings are as follows:

[0118] The various raw materials are precisely measured using a weighing scale according to the formula ratio;

[0119] 140g of slag powder, 105g of by-product gypsum powder, 105g of steel slag powder, and 7g of special activator were stirred for 4 minutes to obtain a novel non-fired low-carbon cementitious material curing agent. The stirring speed was 140±2 r / min for rotation and 62±2 r / min for revolution.

[0120] After mixing 130ml of water with the curing agent for 4 minutes, add 650g of pyrite tailings to the curing agent and continue mixing for 5 minutes to obtain the pyrite tailings road base material. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0121] Example 3: A road base material using pyrite tailings, composed of the following components in the indicated mass ratios: 15 parts slag powder, 7.5 parts by-product gypsum①, 7.5 parts steel slag powder, 70 parts pyrite tailings, 0.3 parts special activator, and 13 parts water content. The mass ratios of each component are shown in Table 2.

[0122] The specific steps of the above-mentioned method for preparing road base material using pyrite tailings are as follows:

[0123] The various raw materials are precisely measured using a weighing scale according to the formula ratio;

[0124] Mix 150g of slag powder, 75g of by-product gypsum powder, 75g of steel slag powder, and 6g of a special activator for 4 minutes to obtain a novel non-fired, low-carbon cementitious material curing agent. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0125] After mixing 130ml of water with the curing agent for 4 minutes, add 700g of pyrite tailings to the curing agent and continue mixing for 5 minutes to obtain the pyrite tailings road base material. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0126] Example 4: A road base material using pyrite tailings, composed of the following components in the indicated mass ratios: 13.75 parts slag powder, 1.25 parts by-product gypsum①, 10 parts steel slag powder, 75 parts pyrite tailings, 0.25 parts special activator, and 13 parts water content. The mass ratios of each component are shown in Table 2.

[0127] The specific steps of the above-mentioned method for preparing road base material using pyrite tailings are as follows:

[0128] The various raw materials are precisely measured using a weighing scale according to the formula ratio;

[0129] 137.5g of slag powder, 12.5g of by-product gypsum powder, 100g of steel slag powder, and 5g of special activator were stirred for 4 minutes to obtain a novel non-fired low-carbon cementitious material curing agent. The stirring speed was 140±2 r / min for rotation and 62±2 r / min for revolution.

[0130] After mixing 130ml of water with the curing agent for 4 minutes, add 750g of pyrite tailings to the curing agent and continue mixing for 5 minutes to obtain the pyrite tailings road base material. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0131] Example 5: A road base material using pyrite tailings, composed of the following components in the indicated mass ratios: 10 parts slag powder, 5 parts by-product gypsum①, 5 parts steel slag powder, 80 parts pyrite tailings, 0.2 parts special activator, and 13 parts water content. The mass ratios of each component are shown in Table 2.

[0132] The specific steps of the above-mentioned method for preparing road base material using pyrite tailings are as follows:

[0133] The various raw materials are precisely measured using a weighing scale according to the formula ratio;

[0134] Mix 100g of slag powder, 50g of by-product gypsum powder, 50g of steel slag powder, and 4g of a special activator for 4 minutes to obtain a novel non-fired, low-carbon cementitious material curing agent. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0135] After mixing 130ml of water with the curing agent for 4 minutes, add 800g of pyrite tailings to the curing agent and continue mixing for 5 minutes to obtain the pyrite tailings road base material. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0136] Example 6: A road base material using pyrite tailings, composed of the following components in the indicated mass ratios: 20 parts slag powder, 10 parts by-product gypsum ②, 10 parts steel slag powder, 60 parts pyrite tailings, 0.4 parts special activator, and 13 parts water content. The mass ratios of each component are shown in Table 2.

[0137] The specific steps of the above-mentioned method for preparing road base material using pyrite tailings are as follows:

[0138] The various raw materials are precisely measured using a weighing scale according to the formula ratio;

[0139] Mix 200g of slag powder, 100g of by-product gypsum powder, 100g of steel slag powder, and 8g of a special activator for 4 minutes to obtain a novel non-fired, low-carbon cementitious material curing agent. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0140] After mixing 130ml of water with the curing agent for 4 minutes, add 600g of pyrite tailings to the curing agent and continue mixing for 5 minutes to obtain the pyrite tailings road base material. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0141] Example 7: A road base material using pyrite tailings, composed of the following components in the indicated mass ratios: 5 parts slag powder, 2.5 parts by-product gypsum ②, 2.5 parts steel slag powder, 90 parts pyrite tailings, 0.1 parts special activator, and 13 parts water content. The mass ratios of each component are shown in Table 2.

[0142] The specific steps of the above-mentioned method for preparing road base material using pyrite tailings are as follows:

[0143] The various raw materials are precisely measured using a weighing scale according to the formula ratio;

[0144] Mix 50g of slag powder, 25g of by-product gypsum powder, 25g of steel slag powder, and 1g of a special activator for 4 minutes to obtain a novel non-fired, low-carbon cementitious material curing agent. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0145] After mixing 130ml of water with the curing agent for 4 minutes, add 900g of pyrite tailings to the curing agent and continue mixing for 5 minutes to obtain the pyrite tailings road base material. The mixing speed is 140±2 r / min for rotation and 62±2 r / min for revolution.

[0146] The mass fractions of each component in Examples 1-7 are shown in Table 2 below:

[0147] Table 2. Mass proportions of road base materials made from pyrite tailings

[0148]

[0149] Performance tests were conducted on the road base materials of Examples 1-7 above, including 7-day unconfined compressive strength tests and water stability index calculations. The performance test results are shown in Table 3 below.

[0150] Table 3 Performance Tests of Road Base Materials Made from Pyrite Tailings

[0151] Serial Number 7d unconfined compressive strength / MPa Water stability index (%) 1 8.95 103 2 7.81 98 3 5.79 98 4 4.63 91 5 3.86 85 6 6.71 101 7 3.52 82

[0152] The experimental results show that:

[0153] In Example 1, when the content of pyrite tailings is 60%, the 7-day unconfined compressive strength of the road base mixture made from pyrite tailings can reach 8.95 MPa, which meets the strength requirements of cement-stabilized materials for expressways and first-class highways.

[0154] In Examples 1-6, the content of pyrite tailings is 60-80%. The 7-day unconfined compressive strength of the road base material using pyrite tailings is greater than 3.5 MPa, which meets the strength requirements of cement fly ash stabilized materials for heavy traffic on expressways and first-class highways in the "Technical Specifications for Construction of Highway Pavement Base" JTG / T F20-2015.

[0155] In Examples 1-3 and 6, when the content of pyrite tailings is 60-70%, the 7-day unconfined compressive strength of the road base material using pyrite tailings is greater than 5.0 MPa, which meets the strength requirements of cement-stabilized materials of various grades in the "Technical Specifications for Construction of Highway Pavement Base" JTG / T F20-2015.

[0156] In Example 4, when the content of pyrite tailings is 75%, the 7-day unconfined compressive strength of the road base mixture made from pyrite tailings is greater than 4.0 MPa, which meets the strength requirements of cement-stabilized materials for various traffic levels of Class II and below highways in the "Technical Specifications for Construction of Highway Pavement Base" JTG / T F20-2015.

[0157] In Example 7, when the content of pyrite tailings is 90%, the 7-day unconfined compressive strength of the road base mixture made from pyrite tailings is greater than 3.5 MPa, which meets the strength requirements of cement fly ash stabilized materials for heavy traffic on expressways and first-class highways in the "Technical Specifications for Construction of Highway Pavement Base" JTG / T F20-2015.

[0158] In Examples 1-7, the water stability coefficient of the pyrite tailings base course mixture was greater than 80%, which meets the requirements of the "Technical Standard for Application of Soil Stabilizers" CJJ / T286-2018 for the water stability coefficient.

[0159] Furthermore, this invention proposes using pyrite tailings to produce road base materials. Compared to existing road base materials made from ordinary iron tailings, this method allows for a larger dosage and yields road base materials with superior performance. The following description, in conjunction with comparative examples, illustrates this point.

[0160] Comparative Example 1:

[0161] A road base mixture made from iron tailings is composed of the following components in the indicated mass ratios: 20 parts slag powder, 10 parts by-product gypsum①, 10 parts steel slag powder, 60 parts iron tailings, 0.8 parts special activator, and 13 parts water content. The mass ratios of each component are shown in Table 4, and the preparation method is the same as in Example 1.

[0162] Comparative Example 2:

[0163] A road base mixture made from iron tailings is composed of the following components in the indicated mass ratios: 20 parts slag powder, 10 parts by-product gypsum, 10 parts steel slag powder, 60 parts iron tailings, 0.8 parts special activator, and 13 parts water content. The mass ratios of each component are shown in Table 4. The preparation method is the same as that used in Example 1.

[0164] Table 4. Mass proportions of road base materials made from iron tailings

[0165]

[0166] Performance tests were conducted on the road base materials of Comparative Examples 1 and 2 above, including 7-day unconfined compressive strength testing and water stability index calculation. The performance test results are shown in Table 5 below.

[0167] Table 5 Performance Tests of Road Base Materials Made from Iron Tailings

[0168] Serial Number 7d unconfined compressive strength / MPa Water stability index (%) 1 5.85 96 2 4.42 92

[0169] Comparative Examples 1 and 2 show that when iron tailings are used to replace pyrite tailings, the 7-day unconfined compressive strength of the road base mixture decreases by more than 30%. This indicates that pyrite tailings have a synergistic effect on the system. Using pyrite tailings to prepare road base materials effectively improves the mechanical properties of the road base mixture and significantly increases the matrix strength. The 7-day unconfined compressive strength of the pyrite tailings-based road base mixture can reach 8.95 MPa.

[0170] In this invention, pyrite tailings are used as the stabilized material. They not only provide skeletal reinforcement to the matrix but also participate in the hydration reaction, providing sulfates to stimulate the later-stage strength growth of the matrix. This solves the problem of poor stability, turning the disadvantages of pyrite tailings into advantages and achieving high-value and resource-based utilization. The preparation process involves only crushing, drying, and grinding, and involves the comprehensive utilization of various industrial solid wastes. This not only consumes a large amount of industrial solid waste, reduces land occupation for stockpiling, and achieves resource utilization of multiple solid wastes, but also ensures the load-bearing capacity and overall stability of the pavement structure, extends the service life of the pavement, has low manufacturing costs, is easy to promote, and has significant economic, environmental, and social benefits.

[0171] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0172] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0173] Those skilled in the art will understand that although the invention has been described with reference to exemplary embodiments, various changes may be made and its elements may be substituted with equivalents without departing from the scope of the invention. Furthermore, many modifications may be made to adapt particular situations or materials to the teachings of the invention without departing from the essential scope of the invention. Therefore, the invention is not limited to the specific embodiments disclosed, but rather the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A road base material using pyrite tailings, characterized in that, The road base material is made from the following raw materials by weight: 60 parts pyrite tailings, 20 parts slag, 10 parts steel slag powder, 10 parts by-product gypsum, 0.4 parts special activator, and 13 parts water. The mineral composition of the pyrite tailings, by mass percentage, consists of 7.4% pyrite, 6.7% mica, 2.5% hemihydrate gypsum, 70.3% quartz, 3.9% feldspar, 4.7% chlorite, and 4.5% calcite. The pyrite tailings contain 14.7% sulfur trioxide, have a median particle size (D50) of 45.5 μm, and a volume average particle size of 62.86 μm. The specific surface area of ​​the steel slag powder is 380 m². 2 / kg, the specific surface area of ​​slag powder is 420m². 2 / kg; The by-product gypsum is desulfurized gypsum with a specific surface area of ​​450 m². 2 / kg; The special activator is composed of sodium carbonate and sodium sulfate, wherein the sodium carbonate accounts for 40% of the mass of the special activator and the sodium sulfate accounts for 60% of the mass of the special activator.

2. The method for preparing road base material using pyrite tailings as described in claim 1, characterized in that, The preparation method includes the following steps: Weigh out steel slag, mineral slag, by-product gypsum and special activator according to the proportions to obtain each raw material; The raw materials are processed to obtain a novel non-fired low-carbon cementitious material curing agent, wherein the processing includes at least: crushing, drying, grinding and magnetic separation. Prepare pyrite tailings according to the proportion, and mix the pyrite tailings with the slag, steel slag powder, by-product gypsum and special activator evenly to obtain pyrite tailings road base mixture; Water is added to the pyrite tailings road base mixture and mixed evenly to obtain a road base material using pyrite tailings.

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