Gluing agent for cemented filling of argillaceous tailings and use method of cementing agent

Abstract

The invention relates to the technical field of tailing treatment, in particular to a cementing agent for cemented filling of argillaceous tailings and a use method of the cementing agent. Comprising the following components in parts by weight: 20-35 parts of quick-hardening sulphoaluminate cement, 8-15 parts of silica fume, 30-60 parts of activated slag powder, 10-20 parts of limestone powder, 5-15 parts of desulfurized gypsum, 6-10 parts of nano SiO2 / Al2O3 composite sol and 30-40 parts of magnesium phosphate-red mud activated microspheres. Ions released by the magnesium phosphate-red mud activated microspheres destroy hydrogen bonds among kaolinite layers, so that the adsorption of clay to free water is reduced, and a framework is quickly formed in cooperation with the quick-hardening sulphoaluminate cement, so that the problem of insufficient hydration of a cementing material caused by imbalance of a water-binder ratio is solved; meanwhile, the nano-scale size and the positive charge characteristic of the nano SiO2 / Al2O3 composite sol penetrate through gaps of the clay, silica fume and slag powder are combined to generate gel on the surface of the clay in situ, a cross-scale bonding network is constructed, effective bonding of a cementing material and tailings particles is achieved, efficient cementing of the high-clay tailings is achieved, and the performance of a filling body is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tailings treatment, and particularly to a cementing agent for clay tailings cemented filling and a using method thereof. Background Art

[0002] With the expansion of the scale of mine exploitation, the treatment of high-content kaolinite tailings has become a difficult problem in the industry. In the prior art, when using ordinary Portland cement to treat such tailings, there are significant defects: the water demand is large, the dosage of the cementitious material is high, but even so, the strength after 28 days of curing can only reach 1.5 - 2.1 MPa, which is difficult to meet the strength requirements of the mine filling body. The specific problems are as follows:

[0003] Firstly, clay particles adsorb free water, resulting in the dilution of the cementitious material. Kaolinite has a unique layered structure and is rich in a large number of hydroxyl groups on its surface, with a strong adsorption capacity for free water. When using ordinary Portland cement for cementing, a large amount of free water is adsorbed by kaolinite, causing the actual water-cement ratio of the cement to be unbalanced, the cement hydration reaction to be insufficient, and a dense cementitious structure cannot be formed. The cement hydration products cannot effectively wrap and bond the tailings particles, resulting in low strength of the cemented filling body. At the same time, problems such as bleeding and segregation of the slurry will also occur, affecting the construction performance and the stability of the filling body.

[0004] Secondly, conventional materials cannot penetrate the clay to form an effective hydration network. The particle sizes of ordinary Portland cement and common auxiliary cementitious materials such as silica fume and slag powder are mostly in the micron range, while there are a large number of nanoscale gaps between the clay particles in kaolinite tailings. Conventional materials are difficult to penetrate these gaps and cannot come into sufficient contact with the clay particles to undergo a hydration reaction. Therefore, only a loose coating layer can be formed outside the clay aggregates, and a continuous and effective hydration network cannot be constructed, resulting in a weak bonding force between the tailings particles and the cementitious material, severely restricting the improvement of the overall strength and durability of the filling body.

[0005] The information disclosed in this background art section is only intended to deepen the understanding of the overall background art of the present invention, and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a cementing agent for clayey tailings cemented filling and its use method. The ions released by magnesium phosphate - red mud activated microspheres destroy the interlayer hydrogen bonds of kaolinite, reduce the adsorption of free water by clay, and cooperate with rapid hardening sulphoaluminate cement to quickly form a skeleton, solving the problem of insufficient hydration caused by the imbalance of water - binder ratio in the cementitious material. At the same time, the nano - scale size and positive charge characteristics of the nano - SiO2 / Al2O3 composite sol penetrate the clay gaps, and in combination with silica fume and slag powder, gels are in - situ generated on the clay surface and a cross - scale bonding network is constructed, realizing the effective bonding of the cementitious material and tailings particles, achieving efficient cementing of high - clay tailings and improving the performance of the filling body.

[0007] The first object of the present invention is to provide a cementing agent for clayey tailings cemented filling, which includes, by weight parts: 20 - 35 parts of rapid hardening sulphoaluminate cement, 8 - 15 parts of silica fume, 30 - 60 parts of activated slag powder, 10 - 20 parts of limestone powder, 5 - 15 parts of desulphurized gypsum, 6 - 10 parts of nano - SiO2 / Al2O3 composite sol, and 30 - 40 parts of magnesium phosphate - red mud activated microspheres;

[0008] Mg released by magnesium phosphate - red mud activated microspheres 2+ 、Fe 3+ coordinate with the surface hydroxyl groups of kaolinite, destroy the interlayer hydrogen bonds and promote the disassembly of the crystal lattice. While reducing the adsorption of free water by clay, the released active SiO2 and Al2O3 provide raw materials for the cementitious reaction. Among them, Fe 3+ catalyzes the breakage of Al - O - Si bonds in the activated slag powder, and synergistically with the Si 3 + 、Al 3+ ions carried by the nano - SiO2 / Al2O3 composite sol, accelerates the dissolution of active components of the slag powder in a weakly acidic micro - environment. And the nano - SiO2 / Al2O3 composite sol, relying on its nano - scale size and positive charge characteristics, overcomes the negative charge repulsion on the clay surface, penetrates into the nano - scale gaps of clay aggregates, and in - situ generates C - S - H and C - A - S - H gels on the surface of the activated kaolinite, realizing chemical bonding through Si - O - Al bonds. At the same time, Mg 2+ in the magnesium phosphate - red mud activated microspheres synergizes with the SO4 2- of desulphurized gypsum to accelerate the hydration of rapid hardening sulphoaluminate cement to generate ettringite skeletons, which support each other with the "nano - bridging - micron filling" cross - scale bonding network induced by the nano - sol. It not only weakens the water absorption ability of clay from the source, but also constructs a strong chemical - bonding cementitious system that penetrates inside and outside clay particles, upgrading the interface between the cementitious material and clay from physical adsorption to molecular - level bonding, significantly improving the depth of the hydration reaction and the density of the filling body, and systematically solving the problems of interface bonding and hydration efficiency in the cementing of high - clay tailings;

[0009] Mg 2+The ionic radius is relatively large (Fe 3+ The ionic radius is about Mg 2+ The ionic radius is about ). Without Fe 3+ previously destroying the tight interlayer structure of kaolinite, Mg 2+ is difficult to directly enter. Fe 3+ , relying on the high charge density of +3 and the relatively small ionic radius, can form strong coordination bonds (such as inner-sphere coordination) with the surface hydroxyl groups of kaolinite. Through strong electrostatic interaction and polarization effect, it can break the interlayer hydrogen bonds and cause lattice distortion. The initial cracks formed by Fe 3+ breaking the hydrogen bonds provide channels for the entry of Mg 2+ . After Mg 2+ expands the interlayer structure, more Fe 3+ action sites are exposed. Through the "destruction - expansion - re - destruction" cycle mechanism, the rate of lattice disintegration is greatly enhanced compared with the action of a single ion, and the dissolution amount of interlayer active SiO2 increases significantly, providing sufficient raw materials for the subsequent gelling reaction;

[0010] Limestone powder mainly plays a role in filling and assisting gelling. It can improve the particle size distribution of the gelling material, fill the voids between tailings particles, improve the density of the slurry. At the same time, it may participate in some hydration reactions to assist in enhancing the bonding strength. As the main source of sulfate ions, desulfurized gypsum synergizes with Mg 2+ released by magnesium phosphate - red mud activated microspheres to accelerate the hydration of rapid - hardening sulphoaluminate cement, promote the formation of ettringite skeleton, reduce the segregation and bleeding of the slurry, and enhance the density and early strength of the gelling structure.

[0011] As a preferred embodiment of the present invention, the preparation method of the nano - SiO2 / Al2O3 composite sol includes:

[0012] Dissolve tetraethyl orthosilicate in absolute ethanol, then dropwise add deionized water and hydrochloric acid, and stir at room temperature to obtain a silicon precursor solution containing silanol intermediates. More specifically, dissolve tetraethyl orthosilicate (TEOS) in absolute ethanol and dropwise add hydrochloric acid and deionized water. Through acid catalysis (pH≈2 - 3), TEOS is hydrolyzed to form silanol intermediates (Si - OH), while inhibiting the excessive polycondensation of silanol to form oligomer solutions, ensuring uniform mixing with the aluminum source in the subsequent process. The ethanol solvent prevents local high concentration from causing agglomeration and provides a stably dispersed active silicon source for constructing the silicon - aluminum composite network;

[0013] Dissolve aluminum isopropoxide in absolute ethanol, heat and stir until completely dissolved to form an aluminum source solution; more specifically, aluminum isopropoxide undergoes alcoholysis reaction in absolute ethanol under heating (60 - 80 °C) to generate a soluble aluminum alkoxide intermediate, avoiding direct hydrolysis to form Al(OH)3 precipitate. Heating enhances the coordination between the solvent and the aluminum alkoxide, regulates the chemical environment of aluminum species, and lays a foundation for the subsequent formation of Si - O - Al bonds through condensation reaction with the silicon precursor;

[0014] Slowly add the aluminum source solution to the silicon precursor solution to form a silicon - aluminum composite precursor solution; more specifically, slowly drip the aluminum source solution into the silicon precursor solution, and form Si - O - Al bonds through the co - condensation reaction of silanol and aluminum alkoxide to achieve uniform mixing of silicon and aluminum components at the nanoscale;

[0015] Add a cationic surfactant to the silicon - aluminum composite precursor solution, stir to dissolve, adjust the pH to 8 - 9 with ammonia water, and then perform ultrasonic dispersion to obtain a nano - SiO2 / Al2O3 composite sol; more specifically, the cation of the cationic surfactant adsorbs on the surface of the sol particles, imparting a positive charge. Through electrostatic attraction, it overcomes the negative charge repulsion on the clay surface and promotes the penetration of the sol into the nanoscale gaps; ammonia water provides an alkaline environment to accelerate the condensation reaction of silanol and aluminum alcohol groups.

[0016] As a preferred embodiment of the present invention, the Zeta potential of the nano - SiO2 / Al2O3 composite sol is +35 ± 5 mV; due to the hydroxyl - rich surface of kaolinite particles with a layered structure, they are easily dissociated to form a negatively charged surface (the Zeta potential is usually -20 to -40 mV) in an aqueous medium, resulting in strong adsorption of free water and repulsion of external gelling components. However, through the modification of the nano - SiO2 / Al2O3 composite sol with a cationic surfactant (such as cetyltrimethylammonium bromide), the particles' surface carries a stable positive charge. This potential can not only overcome the negative charge repulsion on the kaolinite surface through the electrostatic attraction effect, promoting the active adsorption and penetration of the sol particles into the nanoscale gaps between kaolinite tailing particles, but also avoid the particle aggregation that may be caused by an overly high positive potential, ensuring good dispersion of the sol in the tailing slurry.

[0017] As a preferred embodiment of the present invention, the cationic surfactant is one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, dodecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide; the above substances all contain trimethylammonium cations, which can be firmly adsorbed on the surface of nano-SiO2 / Al2O3 composite sol particles under alkaline conditions, endowing them with significant positive charges; and the long-chain alkyl groups (dodecyl, cetyl, octadecyl) possessed by the above substances form a hydrophobic bridging effect between the sol particles and the clay surface. On the one hand, it reduces the surface energy of the particles, inhibits the aggregation of the sol, and ensures nano-scale dispersibility; on the other hand, the steric hindrance effect of the alkyl chain can stabilize the sol particles, enabling them to maintain a uniform distribution in the tailings slurry, enhancing the contact probability with the hydroxyl groups on the kaolinite surface, and promoting the subsequent chemical bonding of the Si-O-Al bond with the active sites of the clay.

[0018] As a preferred embodiment of the present invention, a method for preparing magnesium phosphate - red mud activated microspheres includes:

[0019] Weigh magnesium oxide and potassium dihydrogen phosphate according to a molar ratio of Mg 2+ ∶H2PO4 - =1∶1.2 - 1.5, add deionized water, and stir evenly at 50 - 60 °C to form a magnesium phosphate slurry; more specifically, potassium dihydrogen phosphate (KH2PO4) dissociates H + in water, undergoes a neutralization reaction with magnesium oxide (MgO) to generate Mg 2+ and HPO4 2- , forming a magnesium phosphate precursor solution. In this ratio, the phosphorus source is in excess, which promotes the stable dissolution of Mg 2+ and inhibits the formation of Mg(OH)2 precipitation;

[0020] According to a mass ratio of activated red mud ∶ magnesium phosphate slurry = 3 - 5 ∶ 5 - 7, slowly add the activated red mud to the magnesium phosphate slurry and mix evenly to form a mixed material; uniformly mixing the two can make the activated red mud particles fully dispersed and evenly wrapped by the magnesium phosphate slurry, ensuring that the two form nascent microspheres with a uniform composition distribution during the subsequent atomization and drying processes, laying a foundation for the release of Mg 2+ , Fe 3+ and components such as active SiO2 and Al2O3 in the gelling agent and playing a synergistic gelling role;

[0021] Atomize the mixed material to form droplets, and dry it in hot air to form nascent microspheres; atomizing the mixed material to form droplets and drying it in hot air can make the mixture of activated red mud and magnesium phosphate slurry uniformly disperse into fine droplets during the atomization process, use hot air to quickly evaporate water, and prompt the material to shrink into spherical particles under the action of surface tension, forming nascent microspheres with a porous structure, laying a foundation for the uniform release of components and the stability of the microsphere structure during the subsequent curing process;

[0022] Place the nascent microspheres in a curing box with a humidity ≥ 90% and a temperature of 25 ± 5 °C for 24 - 48 h to obtain magnesium phosphate - red mud activated microspheres; more specifically, during the curing process, the mineral phases in the red mud (such as Fe2O3) form complexes with magnesium phosphate to regulate the release rates of Mg 2+ and Fe 3+ so that they continuously play an activation role within 7 - 14 days, matching the cement hydration process and avoiding flash setting caused by excessive early ion concentration.

[0023] As a preferred embodiment of the present invention, the preparation method of activated red mud includes:

[0024] Calcine the red mud and then cool it, add sulfuric acid for etching, filter and dry it, and then mix it with 0.5 - 1.3% by mass of CaF2, and grind it to a particle size ≤ 75 μm;

[0025] After the red mud is calcined, the lattice structures of its internal inert mineral phases (such as aluminosilicates, iron - titanium oxides) are destroyed, and active components such as active SiO2 and Al2O3 are exposed. These active components can directly combine with the hydroxyl groups on the surface of kaolinite through hydrogen bonding or condensation reactions, reducing the adsorption sites of free water by the hydroxyl groups on the surface of kaolinite;

[0026] Sulfuric acid etching can dissolve some metal oxides in the red mud, forming a porous and rough structure on the particle surface, significantly increasing the specific surface area. The porous structure enables the red mud particles to more tightly embed into the nanoscale gaps between kaolinite tailing particles, breaking through the limitations of conventional micron - scale materials, directly contacting the surface of clay particles, and providing more active sites for subsequent cementitious reactions;

[0027] CaF2 can significantly reduce the hardness and agglomeration of the material during the grinding process after the red mud is calcined. And the F - ions in CaF2 can chemically react with components such as aluminum and calcium in the red mud to form highly active sites on the surface of the red mud particles. These active sites can accelerate the hydration reaction of the cementitious material, especially promoting the dissolution and recombination of the aluminate phase and the silicate phase, generating more cementitious products such as C - S - H gel and C - A - S - H gel. For the hydroxyl groups on the surface of kaolinite, the active sites can reduce their adsorption of free water through chemical bonding or physical adsorption, alleviating the problem of water - cement ratio imbalance, making the cement hydration more complete and forming a denser cementitious structure.

[0028] As a preferred embodiment of the present invention, the specific surface area of the rapid - hardening sulphoaluminate cement ≥ 400 m 2 / kg, the content of tricalcium aluminate is 10 - 20 wt%, and the content of dicalcium silicate is 40 - 60 wt%;

[0029] The high specific surface area enables cement particles to have a larger reaction interface, accelerates early hydration, rapidly consumes free water, reduces the ineffective adsorption of water by kaolinite, alleviates the imbalance of water-binder ratio and the segregation of slurry; tricalcium aluminate and desulfurized gypsum synergistically generate a large number of ettringite acicular crystals, forming a rigid framework to maintain the stability of the slurry structure and resist clay expansion; the nano-scale C-S-H gel formed by the hydration of dicalcium silicate can penetrate the nano-scale gaps between kaolinite particles and enhance the interfacial bonding between tailings and cementitious materials through chemical bonding.

[0030] As a preferred embodiment of the present invention, the preparation method of activated slag powder includes:

[0031] Introduce CO2 microbubbles into the slag powder at a pressure of 0.3 - 0.5 MPa for 15 - 20 min to form a surface carbonated layer;

[0032] CO2 reacts with components such as CaO and Al2O3 on the surface of the slag powder under pressure to form a micro-layer of calcium carbonate and bicarbonate. These polar groups can directly bind to the hydroxyl groups on the surface of kaolinite through hydrogen bonding or ionic bonding, reducing the adsorption sites of hydroxyl groups on free water;

[0033] The carbonated layer changes the Zeta potential of the slag powder surface from negative to weakly positive, forming a gradient charge distribution with the strong positive charge of the nano-SiO2 / Al2O3 composite sol. Through the electrostatic synergistic effect, the adsorption on the negatively charged surface of kaolinite is enhanced, further weakening the competitive adsorption ability of clay for water.

[0034] The second object of the present invention is to provide a method for using the cementing agent for clay tailings cemented filling, including:

[0035] Mix the rapid hardening sulphoaluminate cement, activated slag powder, limestone powder, magnesium phosphate - red mud activated microspheres and desulfurized gypsum to form a basic cementitious material;

[0036] Mix the nano-SiO2 / Al2O3 composite sol with silica fume, and then add anhydrous ethanol accounting for 5 - 10% of the mass of the nano-SiO2 / Al2O3 composite sol, and ultrasonically disperse to form a pretreated sol; more specifically, when the nano-SiO2 / Al2O3 composite sol is directly added to dry powder, local agglomeration is likely to occur due to surface tension. By premixing with silica fume and adding a small amount of ethanol, a stable dispersion system of "solid carrier - liquid sol" is formed, which is convenient for uniformly adhering to the surfaces of particles such as cement and slag powder during the dry mixing stage, avoiding the "agglomeration" problem caused by traditional direct addition. And ethanol, as a dispersion medium, volatilizes during the wet mixing process. The remaining small amount of ethanol does not participate in the cementing reaction and only plays a temporary dispersion role, meeting the safety requirements of building material preparation;

[0037] Spray the pretreated sol onto the basic cementitious material and mix to form a cementing agent;

[0038] Mix the tailings, solidifying agent, water and water reducer, and then cure.

[0039] The usage method of the present invention forms a basic cementitious material through multi-component dry mixing, enabling the fast-hardening hydration components, long-acting activated microspheres and filling materials to be evenly coordinated, suppressing the water absorption of kaolinite and activating the interlayer activity from the source; the nano-sol and silica fume are dispersed in ethanol to form a stable system, avoiding agglomeration and uniformly coating the cementitious material particles with the help of a solid carrier. Its positive charge characteristics enhance the interfacial bonding activity, and without pre-treating the tailings, directly adjust the fluidity of the slurry with a water reducer, prompting the ionic de-bonding, nano-bridging and micro-filling functions in the solidifying agent to act synergistically during mixing and curing, forming a dense cementitious network that penetrates inside and outside the clay, significantly improving the strength of the filling body and the construction convenience, and efficiently solving the problems of weak interfacial bonding and insufficient hydration in the traditional cementing process.

[0040] As a preferred embodiment of the present invention, the mass ratio of the tailings to the solidifying agent is 5-8:1. At this ratio, the dosages of the nano-SiO2 / Al2O3 composite sol and the magnesium phosphate - red mud activated microspheres in the solidifying agent are sufficient to cover the surfaces and nano-gaps of the kaolinite particles in the tailings, weaken the adsorption of free water by the clay through electrostatic attraction, interlayer de-bonding and other effects, and form a cementitious network such as C-S-H gel and ettringite skeleton inside and outside the tailings particles, avoiding the problem of weak interfacial bonding caused by insufficient solidifying agent.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Mg 2+ , Fe 3+ released from the magnesium phosphate - red mud activated microspheres in the solidifying agent coordinate with the surface hydroxyl groups of kaolinite, break the interlayer hydrogen bonds and promote the disassembly of the crystal lattice, reducing the adsorption of free water by the clay and alleviating the problem of water-cement ratio imbalance from the source; the released active SiO2 and Al2O3 provide raw materials for the cementitious reaction, and Fe 3+ catalyzes the breakage of the Al-O-Si bond in the slag powder, and synergistically with the Si 3+ , Al 3+ ions carried by the nano-SiO2 / Al2O3 composite sol accelerate the dissolution of the active components in the slag powder. The nano-composite sol, with its +35±5mV positive charge characteristics and nano-scale size, overcomes the negative charge repulsion on the clay surface, penetrates into the nano-scale gaps and in-situ generates C-S-H and C-A-S-H gels on the surface of kaolinite, and realizes chemical bonding through the Si-O-Al bond, upgrading the interfacial bonding between the cementitious material and the clay from physical adsorption to molecular-level bonding, significantly improving the depth of the hydration reaction and the density of the filling body;

[0042] 2) After the activated red mud is calcined, acid-etched with sulfuric acid and modified with CaF2, its lattice structure is damaged and a porous and rough surface is formed, exposing the active SiO2 and Al2O3 components. With a particle size ≤ 75 μm, it can be embedded in the nano-gaps of kaolinite, providing more gelation reaction sites; CaF2 promotes the formation of highly active sites on the surface of red mud, accelerating the dissolution and recombination of aluminates and silicate phases, generating more gelation products. The magnesium phosphate-activated red mud microspheres form a porous structure through atomization drying, and through wet and heat curing, the release of Mg 2+ and Fe 3+ is continuously released within 7 - 14 days, matching the cement hydration process; the activated slag powder forms a surface carbonated layer through CO2 microbubble treatment, enhancing its adsorption capacity on the clay surface, and synergistically with the rapid hardening sulfoaluminate cement and desulfurized gypsum to generate ettringite skeletons, improving the 28-day strength of the filling body. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a schematic flow chart of the usage method of the cementing agent for clay tailings cemented filling of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0044] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings of the specification.

[0045] The raw materials in the specific embodiments are all purchased from the market;

[0046] Example 1:

[0047] A cementing agent for clay tailings cemented filling, by weight, includes:

[0048] Rapid hardening sulfoaluminate cement: 25 parts (specific surface area 420 m 2 / kg, tricalcium aluminate content 12 wt%, dicalcium silicate content 55 wt%)

[0049] Silica fume: 12 parts (average particle size 1.5 μm, SiO2 content ≥ 96%)

[0050] Activated slag powder: 40 parts

[0051] Limestone powder: 18 parts (particle size ≤ 40 μm, CaCO3 content ≥ 92%)

[0052] Desulfurized gypsum: 8 parts (CaSO4·2H2O content ≥ 93%)

[0053] Nano-SiO2 / Al2O3 composite sol: 7 parts

[0054] Magnesium phosphate-activated red mud microspheres: 32 parts;

[0055] Among them, the preparation method of the activated slag powder is as follows:

[0056] Put the slag powder into a pressure reactor, and introduce CO2 microbubbles under a pressure of 0.35 MPa, and continuously ventilate for 18 min to obtain the surface-carbonated activated slag powder.

[0057] The preparation method of the magnesium phosphate - red mud activated microspheres is as follows:

[0058] According to the molar ratio of Mg 2 +∶H2PO4 - = 1∶1.3, weigh magnesium oxide and potassium dihydrogen phosphate, add deionized water, and stir at 55 °C for 60 min to dissociate H + in the water from potassium dihydrogen phosphate, and react with magnesium oxide to generate Mg 2+ and HPO4 2- , forming a uniform and stable magnesium phosphate slurry;

[0059] According to the mass ratio of activated red mud∶magnesium phosphate slurry = 4∶6, slowly add the prepared activated red mud into the magnesium phosphate slurry, and stir at a speed of 200 r / min for 30 min to fully disperse the activated red mud particles and be uniformly wrapped by the magnesium phosphate slurry, forming a mixed material;

[0060] Atomize the mixed material through a pressure atomizer to form droplets, and the droplets enter a hot air drying tower and are dried in hot air. The hot air temperature is set at 120 °C, and the droplets quickly evaporate water in the hot air and shrink into spherical particles under the action of surface tension, forming nascent microspheres with a porous structure;

[0061] Place the nascent microspheres in a curing box with a humidity of 95% and a temperature of 25 °C for 36 h, so that the mineral phases (such as Fe2O3) in the red mud form complexes with magnesium phosphate, and regulate the release rates of Mg 2+ and Fe 3+ to obtain the magnesium phosphate - red mud activated microspheres.

[0062] The preparation method of the nano-SiO2 / Al2O3 composite sol is as follows:

[0063] Dissolve 40 g of tetraethyl orthosilicate in 180 mL of absolute ethanol, then add dropwise 45 mL of deionized water and 4 mL of hydrochloric acid (37%), and stir at a speed of 300 r / min at room temperature for 2.5 h. Through acid catalysis, tetraethyl orthosilicate is hydrolyzed to generate silanol intermediates (Si-OH), inhibiting the excessive polycondensation of silanol to form oligomer solutions, and obtaining a silicon precursor solution containing silanol intermediates;

[0064] Dissolve 25 g of aluminum isopropoxide in 120 mL of absolute ethanol, heat to 65 °C, and stir at a speed of 250 r / min until completely dissolved to cause the alcoholysis reaction of aluminum isopropoxide to generate a soluble aluminum alkoxide intermediate, avoiding the direct hydrolysis to form Al(OH)3 precipitate, thereby forming an aluminum source solution;

[0065] Slowly drop the aluminum source solution into the silicon precursor solution, control the dropping time within 30 min, and continue stirring for 4 h after the dropping is completed to cause the co - condensation reaction between silanol and aluminum alkoxide to form Si - O - Al bonds, realizing the uniform mixing of silicon and aluminum components at the nanoscale and forming a silicon - aluminum composite precursor solution;

[0066] Add 1.8 g of cetyltrimethylammonium chloride to the silicon - aluminum composite precursor solution, stir to dissolve, adjust the pH to 8.8 with ammonia water, and then perform ultrasonic dispersion at an ultrasonic frequency of 40 kHz for 18 min to obtain a nano - SiO2 / Al2O3 composite sol.

[0067] The preparation method of activated red mud is as follows:

[0068] Place the red mud in a muffle furnace, heat to 750 °C and calcine for 2 h, and then naturally cool to room temperature;

[0069] Add a sulfuric acid solution with a concentration of 12% to the cooled red mud, acid - etch at 50 °C for 3 h, continuously stir during the acid - etching process to dissolve some metal oxides in the red mud with sulfuric acid, filter after the reaction is completed, wash with deionized water until neutral, and then dry at 105 °C for 12 h;

[0070] Mix the dried red mud with 1.0% of its mass of CaF2, place it in a ball mill and grind, control the grinding time to make the particle size of the red mud ≤ 75 μm to obtain activated red mud.

[0071] The usage method of the above - mentioned cementing agent for clay - type tailings cemented backfill includes:

[0072] Put the rapid - hardening sulphoaluminate cement, activated slag powder, limestone powder, magnesium phosphate - red mud activated microspheres and desulfurized gypsum into a horizontal mixer, dry - mix at a speed of 280 r / min for 10 min to ensure the uniform dispersion of each component;

[0073] Mix the nano - SiO2 / Al2O3 composite sol with silica fume, add absolute ethanol accounting for 8% of the mass of the nano - SiO2 / Al2O3 composite sol, and perform ultrasonic dispersion for 12 min to form a pretreated sol;

[0074] Spray the pretreated sol evenly onto the basic cementitious materials, use a planetary mixer to stir at a speed of 220 r / min for 12 min to make the nano - SiO2 / Al2O3 composite sol evenly wrap the dry powder particles to form a cementing agent;

[0075] Take 560 parts of kaolinite tailings, 80 parts of the above-mentioned binder, 70 parts of water, and a water reducer (polycarboxylate series, dosage 0.6%), and put them into a double-shaft mixer and stir at 350 r / min for 6 min to form a uniform slurry. Pour the slurry into a mold and cure it in a curing box with a humidity of 92% and a temperature of 24 ± 1°C for 28 days.

[0076] Example 2:

[0077] A binder for clay tailings cemented filling, by weight, includes:

[0078] Rapid hardening sulphoaluminate cement: 32 parts (specific surface area 410 m 2 / kg, tricalcium aluminate content 18 wt%, dicalcium silicate content 48 wt%)

[0079] Silica fume: 14 parts (average particle size 1.5 μm, SiO2 content ≥ 96%)

[0080] Activated slag powder: 55 parts

[0081] Limestone powder: 13 parts (particle size ≤ 40 μm, CaCO3 content ≥ 92%)

[0082] Desulfurized gypsum: 12 parts (CaSO4·2H2O content ≥ 93%)

[0083] Nano-SiO2 / Al2O3 composite sol: 9 parts

[0084] Magnesium phosphate - red mud activated microspheres: 38 parts;

[0085] Among them, the preparation methods of the activated slag powder, magnesium phosphate - red mud activated microspheres, nano-SiO2 / Al2O3 composite sol and activated red mud are the same as those in Example 1;

[0086] The usage method of the above-mentioned binder for clay tailings cemented filling is the same as that in Example 1.

[0087] Example 3:

[0088] A binder for clay tailings cemented filling, by weight, includes:

[0089] Rapid hardening sulphoaluminate cement: 20 parts (specific surface area 405 m 2 / kg, tricalcium aluminate content 10 wt%, dicalcium silicate content 60 wt%)

[0090] Silica fume: 8 parts (average particle size 1.5 μm, SiO2 content ≥ 96%)

[0091] Activated slag powder: 30 parts

[0092] Limestone powder: 20 parts (particle size ≤ 40μm, CaCO3 content ≥ 92%)

[0093] Desulfurized gypsum: 5 parts (CaSO4·2H2O content ≥ 93%)

[0094] Nano-SiO2 / Al2O3 composite sol: 6 parts

[0095] Magnesium phosphate - red mud activated microspheres: 30 parts;

[0096] Among them, the preparation methods of activated slag powder, magnesium phosphate - red mud activated microspheres, nano-SiO2 / Al2O3 composite sol and activated red mud are the same as those in Example 1;

[0097] The usage method of the above binder for clay tailings cemented filling is the same as that in Example 1.

[0098] Comparative Example 1: The difference from Example 1 is that nano-SiO2 / Al2O3 composite sol is not added.

[0099] Comparative Example 2: The difference from Example 1 is that magnesium phosphate - red mud activated microspheres are not added.

[0100] Comparative Example 3: The difference from Example 1 is that iron-containing mineral microspheres of equal weight are used instead of magnesium phosphate - red mud activated microspheres;

[0101] The preparation method of iron-containing mineral microspheres includes:

[0102] Mix Fe2O3 powder (particle size ≤ 45μm) and potassium dihydrogen phosphate in a mass ratio of 1:2, add water to make a slurry, atomize and dry, and then calcine at 600°C for 2h to form porous microspheres.

[0103] Comparative Example 4: The difference from Example 1 is that magnesium mineral microspheres of equal weight are used instead of magnesium phosphate - red mud activated microspheres;

[0104] The preparation method of magnesium mineral microspheres includes:

[0105] Mix MgO powder and potassium dihydrogen phosphate in a mass ratio of 1:1.5, atomize and dry, and then calcine at 500°C for 1.5h.

[0106] Test the tailings treated in the above Examples 1 - 3 and Comparative Examples 1 - 4. The test contents include:

[0107] Compressive strength, the test standard is: GB / T 17671;

[0108] Porosity, the test method uses the mercury intrusion method (ASTM C1723);

[0109] Slurry segregation rate: The test standard is: GB / T 50080;

[0110] After the above test, the data obtained are shown in Table 1;

[0111] Table 1 Test results of Examples 1-3 and Comparative Examples 1-4

[0112] Compressive strength (MPa) Porosity (%) Segregation rate of slurry (%) Example 1 4.8 26 8 Example 2 4.6 24 7 Example 3 4.7 28 9 Comparative example 1 2.5 38 18 Comparative example 2 2.2 42 28 Comparative example 3 2.4 32 12 Comparative example 4 2.7 30 10

[0113] In the above embodiment, the Mg released by magnesium phosphate-red mud activated microspheres 2+ , Fe 3+ Through the "strong bond destruction + interlayer expansion" cycle mechanism (Fe 3+ Strong coordination destroys the interlayer hydrogen bonds of kaolinite, Mg 2+ Hydrated ions support the interlayer structure), which greatly improves the lattice disintegration efficiency and greatly increases the amount of active SiO2 dissolved between the layers; the nano-SiO2 / Al2O3 composite sol, with its +35±5mV positive charge and nanoscale size, overcomes the negative charge repulsion on the clay surface, penetrates into the nanoscale gap to generate CSH and CASH gels in situ, realizes molecular-level bonding through Si-O-Al bonds, upgrades the interface bonding from physical adsorption to chemical bonding, and reduces the porosity to 24-28%.

[0114] Fe 3+ Catalytic activation of the Al-O-Si bond in the slag powder breaks and synergistically activates the Si 3+ 、Al 3+ Ions accelerate the dissolution of active components, forming a cross-scale network of "nano-bridge-micro-filling (activated slag / silica fume)-macro-skeleton (ettringite)", desulfurized gypsum and Mg 2+ Synergistically accelerate the hydration of fast-hardening sulphoaluminate cement, generate needle-shaped crystal skeleton of ettringite, and reduce slurry segregation;

[0115] In Comparative Example 1, due to the lack of composite sol with nano-scale size and +35±5mV positive charge, it is impossible to overcome the negative charge repulsion on the surface of kaolinite, and the cementitious material can only be physically adsorbed outside the clay aggregates, and cannot penetrate into the nano-scale gaps to in-situ generate CSH / CASH gel and Si-O-Al bonds, resulting in weak interfacial bonding, increased porosity, and aggravated slurry segregation;

[0116] Comparative Example 2: Mg deficiency 2+ , Fe 3+ The synergistic debonding effect did not destroy the hydrogen bonds between kaolinite layers, the free water adsorption rate of clay increased, the water-binder ratio was seriously unbalanced, and there was no release of active SiO2 / Al2O3 and Fe 3+ Catalytic slag activation, insufficient raw materials for gelling reaction, and inadequate hydration lead to a significant decrease in filling strength, an increase in porosity, and a significant increase in segregation rate;

[0117] In Comparative Example 3, only Fe3+ The "destruction - expansion" synergistic mechanism cannot be achieved. Although it can destroy the surface hydrogen bonds, it lacks Mg 2+ to expand the interlayer structure. The lattice disintegration is limited to the surface, the dissolution amount of active SiO2 is insufficient, and there is no porous structure of activated red mud embedded in the clay interstices, resulting in a reduction in the gelling reaction sites, and the strength, density, and slurry stability are all lower than those in the examples;

[0118] In Comparative Example 4, only Mg 2+ lacks Fe 3+ 's strong coordination destruction effect, cannot effectively break the Si - O bond and trigger lattice distortion, the expansion of the interlayer spacing is limited, the agglomeration state of clay particles is not significantly improved, and there is no Fe 3+ to catalyze the activation of slag, the dissolution amount of active Al2O3 is insufficient, and the "nano - bridging - micro - filling" cross - scale network cannot be constructed, resulting in limited performance improvement.

[0119] It should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A cementing agent for clay tailings cemented filling, characterized in that, By weight parts, it includes: 20-35 parts of rapid hardening sulphoaluminate cement, 8-15 parts of silica fume, 30-60 parts of activated slag powder, 10-20 parts of limestone powder, 5-15 parts of desulphurized gypsum, 6-10 parts of nano-SiO2 / Al2O3 composite sol, and 30-40 parts of magnesium phosphate-red mud activated microspheres.

2. The cementing agent for clay tailings cemented filling according to claim 1, characterized in that, The preparation method of the nano-SiO2 / Al2O3 composite sol includes: Dissolve tetraethyl orthosilicate in absolute ethanol, then dropwise add deionized water and hydrochloric acid, and stir at room temperature to obtain a silicon precursor solution containing silanol intermediates; Dissolve aluminum isopropoxide in absolute ethanol, heat and stir until completely dissolved to form an aluminum source solution; Slowly add the aluminum source solution to the silicon precursor solution to form a silicon-aluminum composite precursor solution; Add a cationic surfactant to the silicon-aluminum composite precursor solution, stir to dissolve, adjust the pH to 8-9 with ammonia water, and then perform ultrasonic dispersion to obtain the nano-SiO2 / Al2O3 composite sol.

3. The consolidant for clay tailings cemented filling according to claim 2, wherein The Zeta potential of the nano-SiO2 / Al2O3 composite sol is +35±5mV.

4. The consolidant for clay tailings cemented filling according to claim 2, characterized in that, The cationic surfactant is one or more of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, dodecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.

5. The cementing agent for clay tailings cemented filling according to claim 1, characterized in that, The preparation method of the magnesium phosphate-red mud activated microspheres includes: By molar ratio of Mg 2+ ∶H2PO4 - = 1∶1.2 - 1.5, weigh magnesium oxide and potassium dihydrogen phosphate, add deionized water, and stir evenly at 50 - 60 °C to form a magnesium phosphate slurry; According to the mass ratio of activated red mud∶magnesium phosphate slurry = 3-5∶5-7, slowly add the activated red mud to the magnesium phosphate slurry, mix evenly to form a mixed material; Atomize the mixed material to form droplets, and dry in hot air to form primary microspheres; Place the primary microspheres in a curing box with a humidity ≥90% and a temperature of 25±5°C, and cure for 24-48h to obtain the magnesium phosphate-red mud activated microspheres.

6. The cementing agent for clay tailings cemented filling according to claim 5, characterized in that, The preparation method of the activated red mud includes: Calcine the red mud and then cool it, add sulfuric acid for acid etching, filter and dry it, and mix it with 0.5-1.3% of its mass of CaF2, and grind it to a particle size ≤75μm.

7. The cementing agent for clay tailings cemented filling according to claim 1, characterized in that, The specific surface area of the rapid hardening sulphoaluminate cement is ≥ 400 m 2 / kg, the content of tricalcium aluminate is 10 - 20 wt%, and the content of dicalcium silicate is 40 - 60 wt%.

8. The consolidant for clay tailings cemented filling according to claim 1, characterized in that, The preparation method of the activated slag powder includes: Pass CO2 microbubbles into the slag powder at a pressure of 0.3-0.5MPa for 15-20min to form a surface carbonation layer.

9. The method for using the cementing agent for clay tailings cemented filling according to any one of claims 1-8, characterized in that, It includes: Mix the rapid hardening sulphoaluminate cement, the activated slag powder, the limestone powder, the magnesium phosphate-red mud activated microspheres, and the desulphurized gypsum to form a basic cementitious material; Mix the nano-SiO2 / Al2O3 composite sol with the silica fume, then add absolute ethanol accounting for 5-10% of the mass of the nano-SiO2 / Al2O3 composite sol, and perform ultrasonic dispersion to form a pretreatment sol; Spray the pretreatment sol onto the basic cementitious material, and mix to form the cementing agent; Mix the tailings, the cementing agent, water, and water reducer, and then cure.

10. The method for using the cementing agent for clay tailings cemented filling according to claim 9, characterized in that, The mass ratio of the tailings to the cementing agent is 5-8:1.

Images