Tailing sand self-reinforced filling material based on high-temperature calcination activation as well as preparation method and application of tailing sand self-reinforced filling material

Abstract

The invention provides a tailings self-reinforced filling material based on high-temperature calcination activation. The filling material is prepared by mixing the following components in parts by weight: 100 parts of tailings subjected to high-temperature calcination activation, 5-15 parts of cement and 20-35 parts of water, wherein the tailings subjected to high-temperature calcination activation are prepared as follows: original tailings are dried until the water content is less than 5%, then the temperature is increased to 700-1400 DEG C at the rate of 4-7 DEG C / min, and heat preservation is performed for 1.8-2.2 h; and cooling to room temperature. The preparation process is simple and comprises the following steps: mixing the high-temperature calcined and activated tailings, the cement and the water, uniformly stirring, then pouring the mixed material into a mold, vibrating and exhausting, and finally curing and demolding. The prepared filling material is high in strength, good in slurry fluidity and suitable for being used in mine goaf backfilling and building production.

Description

Technical Field

[0001] This invention belongs to the field of mining tailings resource recycling technology, specifically relating to a self-reinforcing backfill material for tailings based on high-temperature calcination activation, its preparation method, and its application. Background Technology

[0002] Tailings are fine-grained solid waste generated during mineral mining (especially metal and non-metal mining) after mineral processing. Their annual output is enormous, and large-scale stockpiling not only occupies valuable land resources but also easily triggers ecological and environmental problems such as landslides and heavy metal leakage, becoming a key bottleneck restricting the green development of mines. Currently, the most important resource utilization method for tailings is as backfill aggregate, mixed with cementing materials (such as cement) and water to prepare cemented backfill bodies for use in backfilling mined-out areas. This achieves both "waste treatment" and ensures safe mine production.

[0003] In traditional tailings cemented backfilling technology, the means to improve the strength of the backfill are extremely limited, relying mainly on two directions: first, increasing the concentration of the backfill slurry (i.e., reducing the water content) to reduce the damage of free water to the compactness of the backfill structure; second, increasing the ratio of cementitious materials to tailings (i.e., increasing the cement-sand ratio) to form strength support through the hydration reaction of more cement. However, both methods have insurmountable drawbacks: increasing the concentration will cause a sharp decrease in slurry fluidity, increase the transport resistance, and easily cause pipeline blockage, which not only increases the energy consumption and maintenance costs of the transport equipment, but may also lead to safety risks such as construction interruption; increasing the cement-sand ratio will significantly increase the amount of cement used, resulting in a significant increase in backfilling costs (cement costs account for more than 80% of the total backfilling cost), which is inconsistent with the industrial policy of low-carbon energy conservation and efficient resource utilization. More importantly, the main components of natural tailings are silicate minerals such as quartz and feldspar. The silicon-oxygen bond (Si-O) bond energy in its crystal structure is as high as 460kJ / mol. It is structurally stable and chemically inert. It can only play a physical filling role as an "inert aggregate". It cannot react effectively with cement hydration products (such as Ca(OH)2), resulting in limited room for strength improvement of the filling body and insufficient long-term stability (it is prone to strength decay due to changes in environmental humidity).

[0004] Furthermore, there is an upper limit to the amount of tailings that can be disposed of in underground mining areas, making it impossible to fully absorb the large amount of tailings added each year. The remaining tailings still need to be stockpiled, making it difficult to achieve the goal of "tailings-free mines." The environmental risks and land occupation problems caused by tailings stockpiling remain unresolved. While existing technologies exist for the activation treatment of industrial solid wastes such as fly ash and slag (e.g., mechanical activation and chemical activation), these technologies are difficult to apply to tailings: mechanical activation (e.g., ball milling) can only change the morphology and specific surface area of ​​tailings particles, but cannot destroy the stable silicon-oxygen bond structure, resulting in a weak effect on activity enhancement; chemical activation (e.g., adding alkaline activators) introduces additional chemical agents, increasing costs and potentially causing secondary pollution, while also making it difficult to achieve "self-reinforcement" of tailings (relying on external agents rather than changes in their own properties). More importantly, existing technologies have not solved the core problems of limited tailings resource utilization pathways and limited disposal capacity, making it impossible to achieve full utilization of tailings.

[0005] Therefore, research on targeted activation technology for tailings is still lacking. There is an urgent need to develop a technology that can change the properties of tailings, stimulate their intrinsic activity, expand resource utilization pathways, and achieve 100% full utilization of tailings. This technology should break through the bottleneck of backfill strength without increasing the concentration and ash-sand ratio, and completely solve the problem of tailings storage, thus achieving the goal of "tailings-free mines". Summary of the Invention

[0006] In view of this, the present invention provides a self-reinforcing tailings backfill material based on high-temperature calcination activation and its preparation method: by precisely controlling the high-temperature calcination process, the silicon-oxygen bonds in the tailings are broken and their stable crystal structure is destroyed, giving the tailings chemical activity; the activated tailings can undergo a secondary hydration reaction with cement hydration products to generate high-strength cementitious substances, thereby achieving a significant increase in the strength of the backfill body under the same concentration and ash-sand ratio, truly achieving the goal of "self-reinforcing" tailings; at the same time, the highly active tailings can be extended to diversified resource utilization fields such as building materials, achieving 100% full utilization of tailings, completely eliminating tailings stockpiling, and helping mines achieve "tailings-free" green development.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A self-reinforced backfill material based on high-temperature calcined and activated tailings, wherein the backfill material is prepared by mixing the following components in parts by weight: 100 parts of high-temperature calcined and activated tailings, 5-15 parts of cement, and 20-35 parts of water. The high-temperature calcination activated tailings are prepared as follows: the original tailings are dried to a moisture content of <5%, and then heated to 700℃~1400℃ at a rate of 4~7℃ / min and kept at that temperature for 1.8~2.2h; then cooled to room temperature to obtain the tailings.

[0008] In some specific embodiments, preferably, the filling material is prepared by mixing the following components in parts by weight: 100 parts of high-temperature calcined and activated tailings, 10 parts of cement, and 28 parts of water; The high-temperature calcination activated tailings are prepared as follows: the original tailings are dried to a moisture content of 4.2%, then heated to 900℃ at a rate of 5℃ / min and kept at that temperature for 2 hours; then cooled to room temperature to obtain the tailings.

[0009] In some specific embodiments, preferably, the cement is silicate cement.

[0010] The preparation method of the above-mentioned filling material includes the following steps: mixing high-temperature calcined and activated tailings, cement, and water, stirring evenly, then pouring the mixture into a mold, vibrating to remove air, and finally curing and demolding to obtain the final product.

[0011] Furthermore, the stirring conditions are: 250~350 rpm for 3~5 min.

[0012] Furthermore, the vibration conditions are: amplitude 0.3~0.5mm, duration 25~35s.

[0013] Further maintenance conditions: temperature 20±2℃, relative humidity ≥95%, time 28~30 days.

[0014] The above-mentioned filling materials are used in backfilling and construction of mining goaf areas.

[0015] The technical principles of this solution are as follows: The inertness of natural tailings stems from its complete silicon-oxygen tetrahedral (SiO4) structure, where tightly connected silicon-oxygen bonds form a stable crystal framework. This invention provides energy through high-temperature calcination. When the temperature reaches above 700℃, the silicon-oxygen bonds absorb energy and break, resulting in lattice distortion in the crystal structure. This creates numerous "active sites" (such as ≡Si-O- and ≡Al-O-) with unsaturated valence bonds on the surface of the tailings particles. During the curing process of the backfill, these active sites can undergo a secondary hydration reaction with Ca(OH)2 produced by cement hydration: ≡Si-O- + Ca(OH)2 + H2O → CaO・SiO2・nH2O (CSH gel). CSH gel is the core source of strength for cement-based materials. Therefore, activated tailings are no longer "inert aggregates" but rather "active reinforcing components" that participate in strength formation, ultimately achieving self-reinforcing properties of the backfill.

[0016] Meanwhile, the activated tailings, due to their chemical activity, have a significantly expanded range of applications. Besides being used for backfilling mining subsidence areas, they can also serve as raw materials for building materials such as cement retarders, gypsum board aggregates, and road base admixtures. Their high activity allows for synergistic reactions with other building material components, enhancing product performance and achieving 100% utilization of tailings. This completely solves the problem of tailings disposal in mines, achieving the goal of "tailings-free mines."

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a self-reinforced backfill material prepared from high-temperature calcined and activated tailings, achieving a compressive strength of 8.5~11.2 MPa, which meets the GB / T 2542-2012 standard "Test Methods for Masonry Bricks". Besides its use in backfilling mining goaf areas, it can also be prepared into non-fired bricks for construction. Furthermore, the grout prepared from this material has a flowability of 265~280 mm, exhibiting good construction fluidity and facilitating production. Attached Figure Description

[0018] Figure 1 This is a flowchart of the technical process in Embodiment 1 of the present invention.

[0019] Figure 2 The images shown are SEM images of tailings particles before and after calcination in Example 1 of this invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art, and all reagents and consumables are commercially available products.

[0021] Example 1 This embodiment provides a self-reinforced backfill material for tailings based on high-temperature calcination activation, which is prepared as follows: (1) Preparation of activated tailings: First, put the original tailings into a 70℃ forced-air oven and dry it until the moisture content is 4.2%; then put the pretreated tailings into a corundum crucible and put it into a box-type resistance furnace and calcine it at a heating rate of 5℃ / min to 700℃. After reaching the target temperature, keep it at that temperature for 2 hours; then turn off the heating device and cool it to room temperature with the furnace (to avoid rapid cooling that could cause the tailings particles to break). Finally, take it out to obtain activated tailings.

[0022] (2) Take 100 kg of activated tailings, 10 kg of silicate cement (PO 42.5) and 28 kg of tap water by weight. Mix the materials and stir at 300 rpm for 3 min to ensure that the materials are mixed evenly to obtain filling slurry. Slowly pour the filling slurry into a standard concrete mold of 50 mm × 100 mm and place it on a vibrating table to vibrate for 30 seconds (amplitude 0.5 mm) to remove air bubbles in the slurry. Then place the mold in a standard curing box (temperature 20 ± 2℃, relative humidity ≥ 95%) and cure for 3 days, 7 days and 28 days respectively. After curing, demold to obtain tailings self-reinforced filling body.

[0023] Example 2 This embodiment provides a tailings self-reinforced filling material based on high-temperature calcination activation. Its preparation is basically the same as that in Example 1, except that the calcination temperature during tailings activation is 900℃, while the rest remain unchanged.

[0024] Example 3 This embodiment provides a tailings self-reinforced filling material based on high-temperature calcination activation. Its preparation is basically the same as that in Example 1, except that the calcination temperature during tailings activation is 1100℃, while the rest remain unchanged.

[0025] Example 4 This embodiment provides a tailings self-reinforced filling material based on high-temperature calcination activation. Its preparation is basically the same as that in Example 1, except that the calcination temperature during tailings activation is 1400℃, while the rest remain unchanged.

[0026] Comparative Example 1 This comparative example provides a tailings self-reinforced filling material, which is prepared in the same way as in Example 2, except that the tailings are not calcined and activated, and the original tailings are used directly, while the rest remain unchanged.

[0027] Comparative Example 2 This comparative example provides a tailings self-reinforced filling material, which is prepared in basically the same way as in Example 2, except that the heating rate during calcination of activated tailings is 15℃ / min, while the rest remain unchanged.

[0028] Furthermore, in order to understand the performance of the filling materials prepared in the above embodiments and comparative examples, relevant tests were also conducted, and the specific test results are shown in Table 1.

[0029] Table 1. Performance details of the filling materials prepared in each example and comparative example. Table 1 shows that the strength of the filling materials prepared by this invention is significantly higher than that of Comparative Example 1, with a 28-day compressive strength increase of 60%-111%, proving that high-temperature calcination activation can effectively achieve self-reinforcement of tailings. Furthermore, the data shows that 900℃ is the optimal calcination temperature. At lower temperatures (700℃), the silicon-oxygen bonds are not sufficiently broken, resulting in fewer active sites; at higher temperatures (1400℃), tailings particles are prone to sintering and agglomeration, which reduces the exposure of active sites. At 900℃, the degree of silicon-oxygen bond breakage in the tailings is moderate, and the activity is highest, thus achieving the best strength improvement effect. In addition, the filling materials prepared from activated tailings not only have excellent strength but also good construction fluidity (flowability ≥265mm), and can be fully utilized through various means such as building materials, solving the problem of limited tailings disposal capacity in traditional technologies.

[0030] Comparative Example 2 data shows that with a rapid heating rate of 15℃ / min, the 28-day compressive strength is only 7.8MPa, with a strength increase of only 47%, far lower than the 111% increase in Example 2. The core reason for this difference is that the heating rate directly determines the uniformity of heat conduction inside and outside the tailings particles, which in turn affects the efficiency of silicon-oxygen bond breaking and the amount of active sites generated. When the heating rate is controlled within the range of 4~7℃ / min as defined in this invention (e.g., 5℃ / min in Example 2), heat gradually penetrates from the surface of the tailings particles to the interior, resulting in a small internal and external temperature gradient. Under sufficient and uniform energy conditions, the silicon-oxygen bonds can be fully broken, forming a large number of unsaturated valence bond active sites (≡Si-O-, ≡Al-O-), providing sufficient reaction sites for the secondary hydration reaction, ultimately promoting the large-scale generation of high-strength CSH gel. However, when the heating rate is too fast (e.g., 15℃ / min), the outer layer of the tailings particles absorbs a large amount of heat instantaneously, causing excessive breakage of silicon-oxygen bonds. At the same time, the temperature lag in the inner layer results in insufficient breakage of silicon-oxygen bonds, significantly reducing the total number of active sites. Furthermore, the temperature difference between the inside and outside of the particles caused by rapid heating generates internal stress, leading to microcracks in the particles and damaging the structural integrity of the filling body. Ultimately, this manifests as a significant decrease in the strength improvement and an increase in porosity.

[0031] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.

[0032] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tailings self-strengthening backfill material based on high-temperature calcination activation, characterized in that, The filling material is prepared by mixing the following components in parts by weight: high-temperature calcined and activated tailings 100 parts, cement 5-15 parts, and water 20-35 parts. The high-temperature calcined and activated tailings are prepared as follows: the original tailings are dried to a moisture content of <5%, then raised to 700-1400°C at a rate of 4-7°C / min, and kept at this temperature for 1.8-2.2 h; then cooled to room temperature.

2. The filling material according to claim 1, wherein The filling material is prepared by mixing the following components in parts by weight: high-temperature calcined and activated tailings 100 parts, cement 10 parts, and water 28 parts. The high-temperature calcined and activated tailings are prepared as follows: the original tailings are dried to a moisture content of 4.2%, then raised to 900°C at a rate of 5°C / min, and kept at this temperature for 2 h; then cooled to room temperature.

3. The proppant material of claim 1, wherein, The cement is Portland cement.

4. A method of producing the filling material according to claims 1 to 3, characterized in that, The method comprises the following steps: mixing the high-temperature calcined and activated tailings, cement, and water, stirring until uniform, then pouring the mixture into a mold, vibrating to remove air, and finally curing, demolding, and obtaining the product.

5. The preparation method according to claim 4, characterized in that, Stirring conditions: rotation speed 250-350 rpm, time 3-5 min.

6. The preparation method according to claim 4, characterized in that, Vibration conditions: amplitude 0.3-0.5 mm, time 25-35 s.

7. The preparation method according to claim 4, characterized in that, Curing conditions: temperature 20±2°C, relative humidity ≥95%, time 28-30 days.

8. Use of the filling material of claim 1 in backfilling of mined-out areas in mines and in construction.

Images