Baking-free and steaming-free full solid waste type iron tailing artificial fine aggregate and preparation method thereof

Abstract

The application relates to the technical field of building materials, and discloses a full-solid-waste type iron tailing artificial fine aggregate without baking and without steam curing and a preparation method thereof, which comprises the following steps: drying and screening an iron tailing to obtain an iron tailing powder with a particle size less than 0.3 mm; mixing, stirring and uniformly mixing a pozzolanic material, an activator, an expansive agent and a reinforcing agent to obtain a full-solid-waste cementing material; mixing the iron tailing powder and part of the full-solid-waste cementing material, and uniformly rolling and pressing and stirring to obtain a mixture; rolling and spraying water on the mixture to obtain iron tailing microspheres with a diameter of 1-4 mm; adding the remaining full-solid-waste cementing material into the iron tailing microspheres for rolling treatment, so that the full-solid-waste cementing material is wrapped on the surface of the iron tailing microspheres to obtain composite particles with a core-shell structure; and carrying out curing treatment on the composite particles with the core-shell structure to obtain the iron tailing artificial fine aggregate. The energy consumption, carbon emission and production cost can be reduced, the high-value utilization of multiple solid wastes is realized, and the shortage of natural sand and stone aggregate is relieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and relates to a full-solid-waste type iron tailing artificial fine aggregate free of baking and steam curing and a preparation method thereof. BACKGROUND

[0002] Converting industrial solid wastes such as iron tailings into sand aggregate not only effectively solves the problem of solid waste disposal, but also relieves the shortage of natural building material resources, and has environmental and economic benefits, so it has become a research hotspot and important development direction in the field of building materials.

[0003] In order to realize the resource utilization of industrial solid wastes, many explorations have been made by those skilled in the art. CN111116070A proposes a method for preparing a baked aggregate using iron tailings, which mainly mixes materials such as iron tailings with a particle size less than 150 μm, cement and silica fume, etc., granulates, then cures at room temperature, and finally screens to obtain a baked aggregate. The innovation of this scheme is to avoid high-temperature sintering and steam curing treatment, in order to reduce the production energy consumption.

[0004] Although the above-mentioned prior art scheme promotes the process of resource utilization of industrial solid wastes to a certain extent, its inherent technical principles and material selection strategies gradually reveal deep-seated limitations in realizing large-scale, economic and sustainable application, thereby causing more complex systemic contradictions. The aforementioned sintering method and hydrothermal synthesis method can effectively impart the mechanical properties required by artificial aggregate, but the core process of high-temperature sintering and steam curing is essentially a high-energy consumption treatment link.

[0005] High-temperature sintering requires heating the material to thousands of degrees Celsius, and steam curing also consumes a large amount of heat energy to maintain a high-temperature and high-humidity environment, which undoubtedly increases the production cost and to some extent offsets the environmental protection intention of using solid waste.

[0006] The more deep-seated contradiction is that even in the attempt of the baking-free process, as described in CN111116070A, cement is introduced as the main cementitious material to avoid high-temperature treatment. Although the energy consumption of direct sintering or steam curing is avoided, a new environmental and economic challenge is introduced. The production process of cement itself is an energy-intensive industry, accompanied by a large amount of carbon dioxide emissions, and its manufacturing cost and carbon footprint are relatively high.

[0007] Although the aggregate production process is exempted from burning, the overall energy consumption and carbon emissions in its life cycle are not fundamentally optimized, but may transfer environmental load to the production link of cement. More than that, excessive dependence on commercial cement as a cementing agent limits the possibility of other potentially active industrial solid wastes, such as iron tailings, alkali residues, red mud, etc., as core cementing components to replace cement. This not only reduces the comprehensive utilization rate of various bulk industrial solid wastes, so that they cannot fully exert their potential cementing or activation activity, but also makes the product still bear the high material cost brought by traditional cement, which is not conducive to the widespread promotion and market competitiveness of artificial aggregate in engineering application. The exploitation of natural sand and gravel aggregate also leads to the present situation of ecological destruction and resource shortage.

[0008] In other words, while trying to solve one problem (solid waste disposal), the prior art attempts to convert industrial solid waste into sand and gravel aggregate, which often accompanies another problem, a high-temperature sintering, steam curing or excessive dependence on the production mode of cement, and fails to achieve the synergistic optimization of low energy consumption, low cost, low carbon emission and high value utilization of multiple solid wastes from a system level. Especially in how to get rid of the high-energy mode of high-temperature sintering and steam curing, while avoiding excessive dependence on traditional high-carbon footprint cementitious materials (such as cement), and maximizing the use of diversified low-value industrial solid wastes as active components, to build a truly environmentally friendly, economically sustainable and reliable performance artificial fine aggregate production system.

[0009] Therefore, how to realize a low-energy, low-cost preparation process under the premise of exempting from burning and steam curing, and fully utilize multiple industrial solid wastes as core cementing components and functional components to build an environmentally friendly, economically feasible and reliable performance artificial fine aggregate production system has become a key challenge and technical problem to be solved for those skilled in the art. SUMMARY

[0010] Therefore, how to realize a low-energy, low-cost preparation process under the premise of exempting from burning and steam curing, and fully utilize multiple industrial solid wastes as core cementing components and functional components to build an environmentally friendly, economically feasible and reliable performance artificial fine aggregate production system has become a key challenge and technical problem to be solved for those skilled in the art.

[0011] In one aspect, the present application provides a preparation method of a full-solid waste type iron tailings artificial fine aggregate exempted from burning and steam curing, comprising the following steps:

[0012] S1, drying and screening the iron tailings to obtain iron tailings powder with a particle size less than 0.3 mm;

[0013] S2, mixing the pozzolanic material, the activator, the expansive agent and the reinforcing agent, stirring uniformly to obtain a full solid waste cementitious material; wherein the pozzolanic material is S95 grade mineral powder and II grade fly ash, the activator is alkali residue, carbide slag and red mud, the expansive agent is steel slag, and the reinforcing agent is desulfurization gypsum;

[0014] S3, mixing the iron tailings powder and part of the full solid waste cementitious material, and rolling and stirring uniformly to obtain a mixture;

[0015] S4, rolling and watering the mixture to obtain iron tailings microspheres with a diameter of 1-4mm;

[0016] S5, adding the remaining full solid waste cementitious material into the iron tailings microspheres for rolling treatment, so that the full solid waste cementitious material is wrapped on the surface of the iron tailings microspheres to obtain composite particles with core-shell structure;

[0017] S6, curing the composite particles with core-shell structure to obtain iron tailings artificial fine aggregate.

[0018] Preferably, the weight ratio of the iron tailings powder to the full solid waste cementitious material is 1:0.2-0.5.

[0019] Preferably, in the step S1:

[0020] The iron tailings are silicon dioxide, diiron trioxide and aluminum trioxide; and / or

[0021] When the iron tailings are subjected to drying treatment, the water content of the iron tailings is less than 0.5wt%, the drying temperature is 80-120℃, and the drying time is 1-2 hours.

[0022] Preferably, in the step S2:

[0023] The weight ratio of the pozzolanic material, the activator, the expansive agent and the reinforcing agent is 1:0.5-1.0:0.1-0.2:0.05-0.1; and / or

[0024] The S95 grade mineral powder is amorphous or microcrystalline silicate and aluminate; and / or

[0025] The II grade fly ash is amorphous silicon dioxide and aluminum trioxide; and / or

[0026] The weight ratio of the S95 grade mineral powder to the II grade fly ash is 1:0.2-0.4; and / or

[0027] The alkali residue is calcium oxide, sodium oxide and potassium oxide; and / or

[0028] The carbide slag is calcium hydroxide; and / or

[0029] the red mud is diiron trioxide, di aluminum trioxide, silicon dioxide and sodium oxide; and / or

[0030] the weight ratio of the alkali residue, the carbide slag and the red mud is 1:0.8-1.2:0.1-0.5; and / or

[0031] the steel slag is free calcium oxide and free magnesium oxide; and / or

[0032] the specific surface area of the steel slag is greater than or equal to 400m 2 / kg.

[0033] Preferably, in the step S2:

[0034] the pozzolanic material, the activator, the expanding agent and the reinforcing agent are put into a planetary stirring pot for stirring treatment, the planetary stirring pot performs multi-dimensional and all-around shearing, mixing and diffusion on the materials through the revolution and rotation of the stirrer, and the stirring time is 2-4 min.

[0035] Preferably, in the step S3:

[0036] the added amount of the total solid waste cementitious material is 70-85wt% of the total weight of the total solid waste cementitious material; and / or

[0037] the iron tailings powder and 70-85wt% of the total solid waste cementitious material are put into a roller mill stirrer for roller pressing and stirring treatment, and the roller pressing and stirring time is 4-6 min.

[0038] Preferably, in the step S4:

[0039] the mixture is poured into a disc balling machine, the inclination and rotating speed of the disc balling machine are adjusted for rolling treatment, and 2-6% of water based on the total mass of the mixture is uniformly sprayed through a precision spraying system for watering treatment, which lasts for 3-6 min, to obtain the iron tailings microspheres with a diameter of 1-4 mm;

[0040] Preferably, in the step S5:

[0041] the remaining total solid waste cementitious material is added to the disc balling machine for rolling treatment, and the rolling continues for 2-5 min, so that the total solid waste cementitious material is wrapped on the surface of the iron tailings microspheres, to obtain the composite particles with core-shell structure.

[0042] Preferably, in the step S6:

[0043] The core-shell structure composite particles are placed in an environment with a temperature of 15-30 DEG C and a relative humidity maintained at 90% or more for curing treatment for 28 days to obtain the iron tailing artificial fine aggregate.

[0044] Another aspect of the present application provides a non-burning non-steaming curing full solid waste type iron tailing artificial fine aggregate, which is prepared by the preparation method of the non-burning non-steaming curing full solid waste type iron tailing artificial fine aggregate.

[0045] Compared with the prior art, the present application has the following beneficial effects:

[0046] The present application provides a preparation method of a non-burning non-steaming curing full solid waste type iron tailing artificial fine aggregate, and constructs a new type of artificial fine aggregate production system which completely relies on multiple industrial solid wastes as raw materials and realizes performance development through normal temperature and humidity curing. This system abandons the high energy consumption links of high temperature sintering and steam curing, greatly reduces the production cost and carbon emission. At the same time, by accurately regulating the ratio of various solid waste materials and the synergistic mechanism thereof in the preparation process, the full activation of pozzolanic materials is realized, the shrinkage is compensated, the strength is enhanced, and the artificial fine aggregate is ensured to have excellent mechanical properties and durability. The present application has environmental, economic and social benefits in solving the disposal problem of bulk industrial solid waste, alleviating the shortage of natural sand aggregate resources, and promoting the green and sustainable development of the building material industry. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0048] Figure 1 The flow chart of the preparation method of the non-burning non-steaming curing full solid waste type iron tailing artificial fine aggregate in the embodiments of the present application.

[0049] Figure 2 The raw material diagram of the iron tailing artificial fine aggregate of the present application.

[0050] Figure 3 The first stage diagram of the iron tailing artificial fine aggregate prepared in the present application.

[0051] Figure 4 The second stage diagram of the iron tailing artificial fine aggregate prepared in the present application.

[0052] Figure 5 The finished product diagram of the iron tailing artificial fine aggregate prepared in the present application. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0054] Please refer to, Figures 1 to 5 , Figure 2 The present application is an iron tailings artificial fine aggregate raw material diagram, and the present application provides a kind of full solid waste type iron tailings artificial fine aggregate of baking-free and steam-free curing and its preparation method, the iron tailings artificial fine aggregate prepared includes five major components of iron tailings powder, pozzolanic material, activator, expanding agent and reinforcing agent, these components are all derived from industrial solid waste, and through accurate mass ratio configuration and synergistic effect, the structure and function system of artificial fine aggregate is jointly built. For the integration and use of systematic engineering design and material science principles, change the production paradigm of traditional sand aggregate, especially focus on the high value of bulk industrial solid waste, low-carbon utilization. The unique feature of this artificial fine aggregate is that its main skeleton is composed of iron tailings powder particles with precise particle size control, these particles are uniformly wrapped by a layer of full solid waste cementing material generated by the synergistic reaction of multiple industrial solid wastes, forming a composite particle with typical core-shell structure. The generation and strength development of the full solid waste cementing material completely depend on the curing conditions of normal temperature and humidity, and abandon the huge energy consumption and carbon emissions brought by traditional high-temperature sintering or steam curing process.

[0055] The specific scheme of the present application is as follows:

[0056] Figure 1 It is a flow chart of the preparation method of the baking-free and steam-free curing full solid waste type iron tailings artificial fine aggregate in the embodiments of the present application, and a series of accurately controlled physical and chemical process steps are used to convert multiple solid wastes into high value-added artificial fine aggregate.

[0057] The embodiment of the present application provides a preparation method of baking-free and steam-free curing full solid waste type iron tailings artificial fine aggregate, as shown in Figure 1 , including the following steps:

[0058] S1, the iron tailings are dried, screened and treated to obtain iron tailings powder with a particle size of less than 0.3mm.

[0059] In this step, the main chemical components of the iron tailings usually include, but are not limited to, oxides such as silicon dioxide, diiron trioxide, and aluminum trioxide. The particle morphology and specific surface area of the iron tailings are optimized through pretreatment to ensure that their physical properties meet the needs of subsequent fine production, thereby further enhancing their ability to form a stable and dense interface structure with the subsequent cementitious components.

[0060] Preferably, when the iron tailings are subjected to drying treatment, the free water in the iron tailings is removed, and the moisture content of the iron tailings is controlled to be less than 0.5wt%. The drying operation is usually carried out in a dedicated rotary dryer or fluidized bed dryer, and the drying temperature is 80-120℃. The specific drying time is set according to the initial moisture content and the efficiency of the selected equipment, and is usually 1-2 hours.

[0061] The dried iron tailings are then subjected to precise particle size control through advanced screening equipment to ensure that all particles have a particle size of less than 0.3mm. The setting of the particle size range has multiple considerations: first, the relatively fine particle size gives the iron tailings powder a large specific surface area, providing a broad reaction interface for subsequent full-solid-waste cementitious material contact and interface cementation, which is beneficial to improving their interface bonding capacity with full-solid-waste cementitious material; second, appropriate fineness also ensures the packing density between particles in the subsequent balling process. This particle size range helps to achieve close packing and filling between particles during the balling process, forming a dense ball core structure, which lays a solid foundation for the mechanical strength and durability of the final artificial aggregate; third, it avoids the agglomeration effect that may be caused by excessively fine particles during mixing and balling, as well as the problem of uneven full-solid-waste cementitious material wrapping or insufficient interface bonding force that may be caused by excessively coarse particles.

[0062] S2, mixing the pozzolanic material, activator, expansive agent, and reinforcing agent to obtain a full-solid-waste cementitious material.

[0063] In this step, the pozzolanic material is the key active component of the cementitious system in the embodiments of the present application, which is S95 grade mineral powder and II grade fly ash. The activator is alkali residue, carbide slag, and red mud. The expansive agent is steel slag. The reinforcing agent is desulfurization gypsum.

[0064] Preferably, the weight ratio of the pozzolanic material, activator, expansive agent, and reinforcing agent is 1:0.5-1.0:0.1-0.2:0.05-0.1.

[0065] Preferably, in the pozzolanic material, the S95 grade mineral powder has excellent potential hydraulicity and is rich in amorphous or microcrystalline silicates and aluminates. The II grade fly ash has good pozzolanic activity and is composed of amorphous silicon dioxide and aluminum trioxide. The weight ratio of S95 grade mineral powder to II grade fly ash is 1:0.2-0.4.

[0066] Specifically, S95 grade mineral powder and II grade fly ash are the main contributors to the strength and density of the cementitious system.

[0067] S95 grade mineral powder, i.e. blast furnace slag powder, its S95 grade indicates that it has excellent potential hydraulicity, and its key performance indicators such as fineness, activity index and fluidity all meet or exceed the high activity requirements in the national standard. S95 grade mineral powder is rich in amorphous or microcrystalline silicates and aluminates, and under suitable alkaline activation conditions, these active components can react with water to generate calcium silicate hydrates, calcium aluminate hydrates and other cementitious materials.

[0068] II grade fly ash, its II grade quality indicates that its indicators such as loss on ignition, water demand ratio and fineness all meet the national standard, and it has good pozzolanic activity. The main chemical composition of fly ash is amorphous silicon dioxide and aluminum trioxide, and its particles are usually spherical in shape, which is beneficial to improve the rheological properties of the mixture and the density of the final aggregate.

[0069] In an alkaline environment, the active silicon dioxide and aluminum trioxide in fly ash can react with the calcium ions provided in the system to generate gels and calcium aluminate silicate hydrates, which interpenetrate and interweave with the mineral powder hydration products, further enhancing the strength and long-term stability of the cementitious system.

[0070] The weight ratio of S95 grade mineral powder to II grade fly ash is controlled in the range of 1:0.2-0.4, through their respective unique potential hydraulicity and pozzolanic effect, a high-efficiency synergistic cementitious mechanism is formed, which jointly builds the basis of the cement-free cementitious system in the embodiment, thereby optimizing the pozzolanic activity and particle size distribution of the two, achieving the best cementitious effect, pore structure filling and overall density improvement.

[0071] Preferably, in the activator, the alkali residue contains a high proportion of calcium oxide, sodium oxide and potassium oxide, the carbide slag is composed of calcium hydroxide, and the red mud contains iron trioxide, aluminum trioxide, silicon dioxide and sodium oxide; the activator is used to activate the potential activity of pozzolanic materials and promote them to efficiently undergo hydration reaction under normal temperature and humidity conditions; the activator is compounded by alkali residue, carbide slag and red mud in a specific ratio, and is controlled in the range of 1:0.8-1.2:0.1-0.5 to provide sufficient alkalinity and calcium source, ensuring that pozzolanic materials can be fully activated, while balancing the cost, performance contribution and possible negative effects of different activators, realizing the synergistic activation effect of multiple industrial solid wastes.

[0072] Specifically, the alkali residue mainly contains a high proportion of calcium oxide, sodium oxide and potassium oxide. These strong alkaline oxides hydrate in water to form strong alkaline hydroxides, providing a strong alkaline environment for the system, which can effectively promote the depolymerization and dissolution of the silicate-aluminate network in S95 grade mineral powder and II grade fly ash, thereby accelerating the hydration reaction.

[0073] Calcium hydroxide, the main chemical component of carbide slag, is a highly alkaline material and an important calcium source. Its hydration products not only provide a continuous supply of calcium ions for pozzolanic materials, but also further strengthen the alkalinity of the system, thereby promoting the rapid formation and accumulation of gel.

[0074] Red mud, as a complex industrial solid waste, contains various oxides such as diiron trioxide, aluminum trioxide, silicon dioxide and sodium oxide. The high-alkalinity sodium oxide component of red mud makes it an effective alkaline activator, while the presence of potential aluminate activity within it allows it to participate in the reaction as an auxiliary cementitious material, providing additional active components for the formation of hydration products in the system. The introduction of red mud not only further strengthens the alkaline activation intensity of the system, but also improves the diversity of components and the structure of reaction products of the cementitious system to some extent.

[0075] Preferably, the addition of an expansive agent effectively compensates for the self-shrinkage and drying shrinkage that may occur during the hydration and hardening process of the artificial fine aggregate, thereby improving the volume stability and crack resistance of the aggregate. The expansive agent is selected to have a specific surface area of 400 m 2 / kg or more. Steel slag with a high specific surface area has high chemical activity, and its main chemical components typically include calcium oxide, magnesium oxide, silicon dioxide, aluminum trioxide, and iron oxide.

[0076] Specifically, free calcium oxide (f-CaO) and free magnesium oxide (f-MgO) are the main expansion sources. During hydration, f-CaO reacts rapidly with water to form calcium hydroxide, while f-MgO hydrates relatively slowly to form magnesium hydroxide. These hydration reactions are accompanied by crystal growth and volume expansion, which can effectively offset early drying shrinkage and later self-shrinkage, thereby reducing the generation of microcracks caused by shrinkage stress concentration within the aggregate, and further improving its overall durability and long-term stability.

[0077] The amount of steel slag needs to be accurately controlled to achieve a moderate expansion compensation effect. Too low an amount may not be sufficient to offset shrinkage, while too high an amount may lead to excessive expansion, which may in turn cause cracking problems, affecting the structural integrity and mechanical properties of the aggregate.

[0078] Preferably, the introduction of the reinforcing agent is to optimize the hydration product structure of the cementitious system, increase the amount of hydration product, and ultimately enhance the density of the artificial fine aggregate, reduce the porosity, and finally enhance the mechanical strength. The reinforcing agent is desulfurized gypsum, whose main chemical component is calcium sulfate dihydrate. In the alkaline activation system constructed by the alkaline activator, desulfurized gypsum, as a kind of sulfate activator, can react with the active aluminum in the pozzolanic material to generate hydrated calcium aluminate with a unique crystal morphology, i.e., ettringite or monosulfate type hydrated calcium aluminate.

[0079] Specifically, ettringite is a needle-like or rod-like crystal, and its unique crystal morphology enables it to form a network structure that is interlaced and overlapped in the cementitious system. This network structure not only effectively fills the micropores in the cementitious system, improving the density of the cementitious layer, but also contributes to the strength development of the cementitious material through mechanical interlocking and physical overlapping between the crystals, similar to the effect of fiber reinforcement.

[0080] In addition, the addition of desulfurized gypsum can also adjust the hydration reaction rate to some extent, promote the dissolution and polymerization of active silicon and aluminum components, and optimize the gel structure to make it more dense and uniform.

[0081] The amount of desulfurized gypsum is precisely adjusted to ensure that ettringite is generated in an appropriate amount in the system. Too little desulfurized gypsum cannot fully exert its reinforcing effect, while too much desulfurized gypsum may cause unnecessary volume expansion or durability problems.

[0082] Preferably, the pozzolanic material, the activator, the expanding agent, and the reinforcing agent are placed in a planetary mixer for stirring treatment. The planetary mixer realizes multi-dimensional and all-around shearing, mixing, and diffusion of the materials through the rotation and revolution of the stirrer. The stirring process lasts for 2-4 min to ensure that the pozzolanic material, the activator, the expanding agent, and the reinforcing agent form a uniformly dispersed full-solid-waste cementitious material.

[0083] Specifically, the stirring time is set to 2-4 min. The purpose is to fully pre-mix all industrial solid waste materials as cementitious components and functional components to form a highly uniform full-solid-waste cementitious material composite powder. This time range is sufficient to ensure that various fine powders are fully mixed and uniform, and that the subsequent hydration reaction can proceed synchronously and efficiently. Too short a time may result in uneven mixing, while too long a time will increase unnecessary energy consumption without obvious benefits. In this stage, the particles of various solid waste materials achieve sufficient physical contact and dispersion, creating ideal initial conditions for subsequent chemical reactions in the presence of water.

[0084] S3, mixing the iron tailings powder and part of the full-solid-waste cementitious material, and uniformly rolling and stirring to obtain a mixture, please refer to Figure 3 ,Figure 3 The first stage diagram of the iron tailings artificial fine aggregate prepared in the present application.

[0085] The weight ratio of the iron tailings powder and the total solid waste cementitious material (i.e. the sum of the pozzolanic material, the activator, the expansive agent and the reinforcing agent) is controlled in the range of 1:0.2-0.5, which ensures that the iron tailings powder can be fully wrapped and cemented by sufficient cementitious components to form the artificial aggregate meeting the requirements of the final strength and durability for engineering applications.

[0086] In this step, the iron tailings powder obtained in step S1 is put into a roller mixer in a preset proportion with 70-85wt% of the total amount of the total solid waste cementitious material prepared in step S2 for roller compaction and stirring to obtain a uniform mixture. The roller compaction and stirring process lasts for 4-6min. This step is a key link for the preliminary mixing before balling, and the core lies in realizing the homogenization and pre-compaction of the material through mechanical action.

[0087] Preferably, the pretreated iron tailings powder and most of the cementitious material are accurately weighed and then put into the roller mixer for mixing. The working principle of the roller mixer combines the effects of roller compaction, shearing and stirring, and is particularly suitable for the mixing of semi-dry materials. The huge pressure exerted by the heavy roller on the material can effectively destroy the agglomeration, promote the close contact of particles of different particle sizes and different properties, and form a high-density mixture. This strong mechanical action is important for the subsequent balling process, which can improve the strength and compactness of the green balls and reduce the dependence on moisture during the balling process.

[0088] Specifically, the roller compaction and stirring time is controlled in the range of 4-6min to ensure that the material is fully mixed and uniform to obtain a uniform mixture with high density and stable quality, and to achieve the required initial humidity and compaction degree to provide stable and uniform raw materials for the next stage of balling operation.

[0089] S4, rolling and watering treatment is performed on the mixture to obtain iron tailings microspheres with a diameter of 1-4mm, please refer to Figure 4 , Figure 4 The second stage diagram of the iron tailings artificial fine aggregate prepared in the present application.

[0090] In this step, the uniform mixture is poured into a disc balling machine, and under the synergistic action of the inclination angle and rotational speed of the device, the material begins to form a rolling bed layer in the disc, and the particles roll, collide and coalesce under the action of gravity and centrifugal force.

[0091] Preferably, 2-6% of the total mass of the mixture is sprayed evenly by a high-precision spraying system for 3-6 minutes until the iron tailings microspheres with a diameter of 1-4 mm are formed. The sprayed water is the key medium in the balling process, which serves as the carrier for the formation of liquid bridge force to bond fine powder particles into larger pellets.

[0092] Specifically, the amount of water needs to be controlled at 2-6% of the total mass of the mixture: too little amount will result in insufficient liquid bridge force, making it difficult to effectively ball; while too much amount will result in over-wet pellets, insufficient strength and easy to stick to each other. The rolling time lasts for 3-6 minutes to ensure that the pellet core can grow uniformly to the target diameter in the range of 1-4 mm, which is highly matched with the particle size distribution of natural fine aggregate, thus ensuring its good applicability in concrete or mortar applications.

[0093] S5, the remaining full solid waste cementitious material is added to the iron tailings microspheres for rolling treatment, so that the full solid waste cementitious material is wrapped on the surface of the iron tailings microspheres, to obtain core-shell structure composite particles.

[0094] In this step, after the formation of the iron tailings microspheres, the remaining 15-30wt% of the cementitious material is directly added to the disc balling machine without interrupting the balling process, and the rolling continues for 2-5 minutes. The purpose is to perform secondary wrapping on the formed iron tailings microspheres to enhance their surface properties and density. The remaining cementitious material adheres and is compacted by rolling on the wet surface of the iron tailings microspheres, forming a dense, smooth and uniform outer shell. This wrapping layer not only can further improve the compressive strength and wear resistance of the artificial fine aggregate, but also can effectively avoid the adhesion of aggregate particles due to mutual friction or humid environment during subsequent storage and transportation, ensuring good dispersibility and flowability of the final product. The continued rolling time of 2-5 minutes is used to ensure that the wrapping layer can be uniformly and completely formed, and reach the ideal state of smooth outer shell without adhesion, which is of great significance to improve the appearance quality of the product, reduce the construction difficulty and ensure the engineering performance.

[0095] S6, the core-shell structure composite particles are cured to obtain the iron tailings artificial fine aggregate, please refer to Figure 5 , Figure 5 is the finished product diagram of the iron tailings artificial fine aggregate prepared in the present application.

[0096] In this step, the obtained core-shell structure composite particles are taken out from the disc pelletizer, placed in an environment with a temperature of 15-30°C and a relative humidity maintained at above 90% for maintenance for 28 days, to obtain the iron tailings artificial fine aggregate. This step is the final embodiment of the core technology of the present application. The maintenance is carried out in a normal temperature and high humidity environment, avoiding the high temperature and high energy consumption required by the traditional sintering process, as well as the expensive equipment investment and high operating cost required by the steam maintenance. Under this specific maintenance condition, the multi-solid waste cementitious system composed of pozzolanic materials and activators will continuously carry out complex hydration reactions and pozzolanic reactions.

[0097] Preferably, the high humidity environment ensures the continuous supply of water required for the reaction, effectively preventing self-drying and reaction interruption caused by too fast internal water evaporation, thereby ensuring the full progress of the hydration reaction. The temperature is controlled in the range of 15-30°C, providing suitable kinetic conditions for the cementitious reaction, neither too fast to cause early cracks, nor too slow to affect the efficiency of strength development.

[0098] Preferably, the 28-day maintenance period, during which a large amount of calcium silicate hydrate, calcium alumino-silicate hydrate, sodium alumino-silicate hydrate gel and ettringite and other hydration products will be continuously generated in the system. These nanoscale and microscale products interweave and fill the pores, gradually increasing the density, hardness and compressive strength of the artificial fine aggregate, and finally forming high-quality artificial fine aggregate with stable performance and meeting the requirements of various engineering applications.

[0099] In order to more fully reveal the superiority and feasibility of the full-solid waste type iron tailings artificial fine aggregate and its preparation method of the present application, the following will be described in detail through specific examples and comparative examples, and quantitative experimental data will be provided.

[0100] Example 1

[0101] The present embodiment provides a preparation method of a full-solid waste type iron tailings artificial fine aggregate, comprising the following steps:

[0102] 1) Prepare raw materials: the weight ratio of iron tailings powder and full-solid waste cementitious material is 1:0.3.

[0103] In the full-solid waste cementitious material, the weight ratio of pozzolanic material, activator, expansive agent and reinforcing agent is 1:0.7:0.15:0.08. Among them, the weight ratio of S95 grade mineral powder and II grade fly ash in the pozzolanic material is 1:0.3; the weight ratio of alkali residue, carbide slag and red mud in the activator is 1:1.0:0.3; the specific surface area of steel slag in the expansive agent is 420 m 2 / kg.

[0104] 2) Preparation of all-solid-waste cementitious material: put the pozzolanic material, activator, expanding agent and reinforcing agent into the planetary stirring pot and stir for 3 min, and stir uniformly to obtain the all-solid-waste cementitious material.

[0105] 3) Preparation of mixture: put the iron tailings powder and 80wt% of the total amount of all-solid-waste cementitious material into the wheel mill stirring machine and roll and stir for 5 min to obtain the mixture.

[0106] 4) Preparation of iron tailings microspheres: pour the mixture into the disc balling machine, spray water while rolling, the amount of water sprayed accounts for 4% of the total mass of the mixture, stir for 4.5 min, until the iron tailings microspheres with a diameter of 1-4 mm are formed.

[0107] 5) Preparation of composite particles with core-shell structure: add the remaining all-solid-waste cementitious material into the disc balling machine, continue to roll for 3.5 min, until the surface of the iron tailings microspheres is completely wrapped by the all-solid-waste cementitious material to form the composite particles with core-shell structure with smooth outer shell and no adhesion.

[0108] 6) Obtain iron tailings artificial fine aggregate: place the composite particles with core-shell structure in an environment with a temperature of 20℃ and a relative humidity of 95% for 28 days to obtain the iron tailings artificial fine aggregate.

[0109] The iron tailings artificial fine aggregate prepared in this embodiment is tested, and the test results are shown in Table 1, the 28-day compressive strength is 6.2MPa, the bulk density is 1450kg / m 3 , the water absorption is 6.8%, and the volume shrinkage is 0.32%.

[0110] Example 2

[0111] The difference between this embodiment and Example 1 is only that:

[0112] In step 1), the weight ratio of the iron tailings powder and the all-solid-waste cementitious material is 1:0.2.

[0113] In the all-solid-waste cementitious material, the weight ratio of the pozzolanic material, the activator, the expanding agent and the reinforcing agent is 1:0.5:0.1:0.05. Among them, the weight ratio of the S95 grade mineral powder and the II grade fly ash in the pozzolanic material is 1:0.2; the weight ratio of the alkali residue, carbide slag and red mud in the activator is 1:0.8:0.1.

[0114] In step 2), the pozzolanic material, the activator, the expanding agent and the reinforcing agent are put into the planetary stirring pot and stirred for 2 min.

[0115] In step 3), the iron tailings powder and 75wt% of the total amount of all-solid-waste cementitious material are put into the wheel mill stirring machine and roll and stir for 4 min.

[0116] In step 4, the amount of water sprayed accounts for 2% of the total mass of the mixture, and stirring is performed for 3.5 min.

[0117] In step 5, rolling is continued for 2.5 min.

[0118] In step 6, the core-shell structure composite particles are placed in an environment with a temperature of 15°C and a relative humidity of 90% for 28 days.

[0119] The iron tailings artificial fine aggregate prepared in this example is tested, and the test results are shown in Table 1. The 28-day compressive strength is 5.5 MPa, the bulk density is 1380 kg / m 3 , the water absorption is 8.2%, and the volume shrinkage is 0.45%.

[0120] Example 3

[0121] The difference between this example and Example 1 is only that:

[0122] In step 1, the weight ratio of iron tailings powder to total solid waste cementitious material is 1:0.5.

[0123] In the total solid waste cementitious material, the weight ratio of pozzolanic material, activator, expansive agent and reinforcing agent is 1:1.0:0.2:0.1. Among them, the weight ratio of S95 grade mineral powder and II grade fly ash in the pozzolanic material is 1:0.4; the weight ratio of alkali residue, carbide slag and red mud in the activator is 1:1.2:0.5.

[0124] In step 2, the pozzolanic material, activator, expansive agent and reinforcing agent are placed in a planetary stirring pot and stirred for 4 min.

[0125] In step 3, 85wt% of the total amount of iron tailings powder and total solid waste cementitious material is placed in a wheel roller mixer and rolled and stirred for 6 min.

[0126] In step 4, the amount of water sprayed accounts for 6% of the total mass of the mixture, and stirring is performed for 6 min.

[0127] In step 5, rolling is continued for 5 min.

[0128] In step 6, the core-shell structure composite particles are placed in an environment with a temperature of 30°C and a relative humidity of 98% for 28 days.

[0129] The iron tailings artificial fine aggregate prepared in this example is tested, and the test results are shown in Table 1. The 28-day compressive strength is 7.1 MPa, the bulk density is 1520 kg / m 3 , the water absorption is 5.3%, and the volume shrinkage is 0.25%.

[0130] Example 4

[0131] The difference between this embodiment and embodiment 1 is only that:

[0132] In step 1), the weight ratio of iron tailings powder and total solid waste cementitious material is 1:0.4.

[0133] In the total solid waste cementitious material, the weight ratio of pozzolanic material, activator, expansive agent and reinforcing agent is 1:0.8:0.18:0.09. Among them, the weight ratio of alkali residue, carbide slag and red mud in the activator is 1:1.1:0.4.

[0134] In step 3), 82wt% of the total amount of iron tailings powder and total solid waste cementitious material is put into the roller mill mixer for 5.5min.

[0135] In step 4), the water spraying amount is 5% of the total mass of the mixture, and the stirring time is 5min.

[0136] In step 5), continue to roll for 4min.

[0137] In step 6), the core-shell structure composite particles are placed in an environment with a temperature of 25℃ and a relative humidity of 96% for 28 days.

[0138] The iron tailings artificial fine aggregate prepared in this embodiment is tested, and the test results are shown in Table 1. The 28-day compressive strength is 6.8MPa, the bulk density is 1480kg / m 3 , the water absorption is 5.9%, and the volume shrinkage rate is 0.28%.

[0139] Embodiment 5

[0140] The difference between this embodiment and embodiment 1 is only that:

[0141] In step 1), the weight ratio of iron tailings powder and total solid waste cementitious material is 1:0.35.

[0142] In the total solid waste cementitious material, the weight ratio of pozzolanic material, activator, expansive agent and reinforcing agent is 1:0.6:0.12:0.06. Among them, the weight ratio of S95 grade mineral powder and II grade fly ash in the pozzolanic material is 1:0.25; the weight ratio of alkali residue, carbide slag and red mud in the activator is 1:0.9:0.2.

[0143] In step 2), the pozzolanic material, activator, expansive agent and reinforcing agent are put into the planetary mixer pot and stirred for 2.5min.

[0144] In step 3), 70wt% of the total amount of iron tailings powder and total solid waste cementitious material is put into the roller mill mixer for 4.5min.

[0145] In step 4), the water spraying amount is 3% of the total mass of the mixture, and the stirring time is 4min.

[0146] In step 5), continue rolling for 3 min.

[0147] In step 6), the core-shell structure composite particles are placed in an environment with a temperature of 22°C and a relative humidity of 94% for 28 days.

[0148] The iron tailings artificial fine aggregate prepared in this example is tested, and the test results are shown in Table 1. The 28-day compressive strength is 6.0 MPa, the bulk density is 1420 kg / m 3 , the water absorption is 7.1%, and the volume shrinkage is 0.35%.

[0149] Example 6

[0150] The difference between this example and Example 1 is only that:

[0151] In step 1), the weight ratio of iron tailings powder to total solid waste cementitious material is 1:0.45.

[0152] In the total solid waste cementitious material, the weight ratio of pozzolanic material, activator, expansive agent and reinforcing agent is 1:0.9:0.16:0.07. Among them, the weight ratio of S95 grade mineral powder and II grade fly ash in the pozzolanic material is 1:0.35; the weight ratio of alkali residue, carbide slag and red mud in the activator is 1:1.0:0.4.

[0153] In step 2), the pozzolanic material, activator, expansive agent and reinforcing agent are put into the planetary stirring pot and stirred for 3.5 min.

[0154] In step 3), 83wt% of the total amount of iron tailings powder and total solid waste cementitious material is put into the wheel roller mixer and rolled and stirred for 5.5 min.

[0155] In step 4), the water spraying amount is 4.5% of the total mass of the mixture, and stirring is carried out for 5.5 min.

[0156] In step 5), continue rolling for 4.5 min.

[0157] In step 6), the core-shell structure composite particles are placed in an environment with a temperature of 28°C and a relative humidity of 97% for 28 days.

[0158] The iron tailings artificial fine aggregate prepared in this example is tested, and the test results are shown in Table 1. The 28-day compressive strength is 6.9 MPa, the bulk density is 1500 kg / m 3 , the water absorption is 6.2%, and the volume shrinkage is 0.30%.

[0159] Comparative Example 1

[0160] The difference between this comparative example and Example 1 is only that:

[0161] In step 1), the weight ratio of iron tailings powder and (total solid waste cementitious material + P.O42.5 cement) is 1:0.3, wherein P.O42.5 cement is introduced into the total solid waste cementitious material.

[0162] In the total solid waste cementitious material, the weight ratio of the pozzolanic material, the activator + P.O42.5 cement, the expansive agent and the reinforcing agent is 1:0.5:0.1:0.05. In the pozzolanic material, the weight ratio of S95 grade mineral powder and II grade fly ash is 1:0.2; in the activator, the weight ratio of alkali residue, carbide slag and red mud is 1:0.8:0.1.

[0163] The iron tailings artificial fine aggregate prepared in the present comparative example is tested, and the test results are shown in Table 1. The 28-day compressive strength is 5.0 MPa, the bulk density is 1400 kg / m 3 , the water absorption is 9.5%, and the volume shrinkage rate is 0.55%.

[0164] Comparative Example 2

[0165] The difference between the present comparative example and Example 1 is only that:

[0166] In step 1), the weight ratio of iron tailings powder and total solid waste cementitious material is 1:0.5, wherein no expansive agent is added in the total solid waste cementitious material.

[0167] In the total solid waste cementitious material, the weight ratio of the pozzolanic material, the activator and the reinforcing agent is 1:1.0:0.1. In the pozzolanic material, the weight ratio of S95 grade mineral powder and II grade fly ash is 1:0.4; in the activator, the weight ratio of alkali residue, carbide slag and red mud is 1:1.2:0.5.

[0168] In step 2), the pozzolanic material, the activator and the reinforcing agent are put into the planetary mixer and stirred for 4 min.

[0169] In step 3), 85wt% of the total amount of iron tailings powder and total solid waste cementitious material is put into the roller mill mixer and rolled and stirred for 6 min.

[0170] In step 4), the water spraying amount is 6% of the total mass of the mixture, and the stirring time is 6 min.

[0171] In step 5), the rolling is continued for 5 min.

[0172] In step 6), the core-shell structure composite particles are placed in an environment with a temperature of 30℃ and a relative humidity of 98% for 28 days.

[0173] The preparation parameters of steps 2) to 6) in the present comparative example are consistent with those of Example 3.

[0174] The iron tailings artificial fine aggregate prepared in the comparative example was tested, and the test results are shown in Table 1. The 28-day compressive strength is 5.2 MPa, the bulk density is 1480 kg / m 3 , the water absorption is 7.8%, and the volume shrinkage is 0.85%.

[0175] Table 1 Mechanical properties of iron tailings artificial fine aggregate

[0176]

[0177] The iron tailings artificial fine aggregate prepared in the comparative example was tested, and the test results are shown in Table 1. The 28-day compressive strength is 5.2 MPa, the bulk density is 1480 kg / m 3 , the water absorption is 7.8%, and the volume shrinkage is 0.85%. 3 , can be directly replaced by natural sand; the water absorption is 5.3-8.2%, which is lower than the durability threshold of ≤10% of artificial fine aggregate; the volume shrinkage is 0.25-0.45%, which reflects excellent volume stability and avoids later cracking. This shows that the technical route of full solid waste ratio + normal temperature and humidity curing in the patent can stably prepare high-performance artificial fine aggregate.

[0178] In Comparative Example 1, the 28-day compressive strength decreased by 19.4% (6.2→5.0 MPa) compared with Example 1 due to the introduction of cement to replace part of the full solid waste, the water absorption increased by 39.7% (6.8→9.5%), and the volume shrinkage increased by 71.9% (0.32→0.55%). The reason is that the introduction of cement destroys the synergistic activation mechanism of multiple solid wastes, and the cement itself has large shrinkage, poor interface combination with solid waste, and increases carbon emissions (cement production carbon emissions about 800 kgCO2 / ton), which proves the rationality of abandoning cement dependence in the patent.

[0179] In Comparative Example 2, the volume shrinkage increased by 240% (0.25→0.85%) compared with Example 3 due to the absence of expanding agent, which is far beyond the engineering allowable range (≤0.5%), and the compressive strength decreased by 26.8% (7.1→5.2 MPa). This shows that the addition of steel slag expanding agent in the examples of the present application can effectively compensate for the hydration shrinkage, which is the key to ensuring the volume stability and mechanical properties of the aggregate.

[0180] It is to be understood that the terminology used herein such as first and second, and the like, is only used to distinguish one entity or action from another entity or action, and does not necessarily require or imply any such actual relationship or order between such entities or actions. Moreover, the terms includes and comprising, and any other variant thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0181] While embodiments of the application have been shown and described, it is to be understood that the application is not limited to the details of the embodiments described, since numerous modifications and changes can be made to the embodiments without departing from the spirit and scope of the application as defined by the appended claims.

Claims

1. A method for preparing a sinter-free and steam-free full solid waste type iron tailings artificial fine aggregate, characterized by, The method comprises the following steps: S1, drying and screening the iron tailings to obtain iron tailings powder with a particle size less than 0.3 mm; S2, mixing and uniformly stirring a pozzolanic material, an activator, an expansive agent and a reinforcing agent to obtain a full-solid waste cementing material; wherein the pozzolanic material is S95 grade ore powder and II grade fly ash, the activator is alkali residue, carbide slag and red mud, the expansive agent is steel slag, and the reinforcing agent is desulfurization gypsum; S3, mixing the iron tailings powder and part of the full-solid waste cementing material, and uniformly rolling and pressing to obtain a mixture; S4, rolling and watering the mixture to obtain iron tailings microspheres with a diameter of 1-4 mm; S5, adding the remaining full-solid waste cementing material into the iron tailings microspheres for rolling treatment, so that the full-solid waste cementing material is wrapped on the surface of the iron tailings microspheres to obtain composite particles with a core-shell structure; S6, curing the composite particles with the core-shell structure to obtain iron tailings artificial fine aggregate; The weight ratio of the iron tailings powder to the full-solid waste cementing material is 1:0.2-0.5; The weight ratio of the pozzolanic material, the activator, the expansive agent and the reinforcing agent is 1:0.5-1.0:0.1-0.2:0.05-0.

1.

2. The method according to claim 1, wherein the method is characterized by: In the step S1, The main chemical components of the iron tailings include silicon dioxide, diiron trioxide and di-aluminum trioxide; and / or When the iron tailings are subjected to drying treatment, the water content of the iron tailings is less than 0.5wt%, the drying temperature is 80-120℃, and the drying time is 1-2 hours.

3. The method according to claim 1, wherein the method is characterized by: In the step S2, The S95 grade ore powder contains amorphous or microcrystalline silicates and aluminates; and / or The main chemical components of the II grade fly ash are amorphous silicon dioxide and di-aluminum trioxide; and / or The weight ratio of the S95 grade ore powder to the II grade fly ash is 1:0.2-0.4; and / or The alkali residue contains a high proportion of calcium oxide, sodium oxide and potassium oxide; and / or The main chemical component of the carbide slag is calcium hydroxide; and / or The chemical composition of the red mud includes diiron trioxide, di-aluminum trioxide, silicon dioxide and sodium oxide; and / or The weight ratio of the alkali residue, the carbide slag and the red mud is 1:0.8-1.2:0.1-0.5; and / or The main chemical components of the steel slag include free calcium oxide and free magnesium oxide; and / or The specific surface area of the steel slag is greater than or equal to 400 m 2 / kg.

4. The method according to claim 1, wherein the method is characterized by: In the step S2, The pozzolanic material, the activator, the expansive agent and the reinforcing agent are put into a planetary stirring pot for stirring treatment, the planetary stirring pot performs multi-dimensional and all-around shearing, mixing and diffusion on the materials through the revolution and rotation of the stirrer, and the stirring time is 2-4 min.

5. The method according to claim 1, wherein the method is characterized by: In the step S3, The addition amount of part of the full-solid waste cementing material is 70-85wt% of the total weight of the full-solid waste cementing material; and / or The iron tailings powder and 70-85wt% of the full-solid waste cementing material are put into a wheel roller mixer for rolling and pressing stirring treatment, and the rolling and pressing stirring time is 4-6 min.

6. The method according to claim 1, wherein the method is characterized by: In the step S4, The mixture is poured into a disc pelletizer, the inclination and rotation speed of the disc pelletizer are adjusted for rolling treatment, and 2-6% of water based on the total mass of the mixture is uniformly sprayed through a precision spraying system for watering treatment, lasting for 3-6 min, to obtain the iron tailings microspheres with a diameter of 1-4 mm.

7. The method according to claim 6, wherein the method is characterized by, In the step S5: The remaining full-solid-waste cementitious material is added to the disc pelletizer for rolling treatment, and the rolling is continued for 2-5 min, so that the full-solid-waste cementitious material is wrapped on the surface of the iron tailings microspheres, to obtain the core-shell structure composite particles.

8. The method according to claim 1, wherein the method is characterized by: In the step S6: The core-shell structure composite particles are placed in an environment with a temperature of 15-30 ℃ and a relative humidity maintained at above 90% for curing treatment for 28 days, to obtain the iron tailings artificial fine aggregate.

9. A non-burned and non-autoclaved full-solid-waste type iron tailings artificial fine aggregate, characterized by, The iron tailings artificial fine aggregate is prepared by the preparation method of the non-burning and non-autoclaved full-solid-waste type iron tailings artificial fine aggregate according to any one of claims 1-8.

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