Underwater non-dispersive flow-state solidified tailing sand and preparation method thereof

Abstract

The invention relates to underwater non-dispersible flow-state cured tailing sand and a preparation method thereof. The flow-state cured tailing sand comprises 500-550 kg / m < 3 > of a cementing material, 1300-1500 kg / m < 3 > of iron tailing sand, 2.5-5 kg / m < 3 > of an additive and water, wherein the mass ratio of the water to the cementing material is 0.45-0.55. According to the underwater non-dispersed flow-state solidified tailing sand, the mineral admixture in a used cementing material system can reach 80%, the tailing sand does not need to be subjected to particle size level division and can be used in a whole-size level mode, and by means of the synergistic adaptation mechanism of the ether admixture and the superfine tailing sand, the good workability of the flow-state solidified tailing sand is effectively maintained, and meanwhile the utilization rate of the mineral admixture is increased. The dispersion resistance and the mechanical strength of the material are remarkably enhanced, the technical standard of underwater construction is met, large-scale consumption of solid waste is realized, the material is endowed with double values of technical application and ecological environmental protection, and a new path is provided for research and development of green building materials of underwater engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of green building materials and bulk solid waste application, and particularly relates to underwater non-dispersive flow state solidified tailings sand and a preparation method thereof. BACKGROUND

[0002] With the continuous development of the steel industry, the discharge of tailings sand solid waste produced after the extraction of concentrate by beneficiation process increases year by year. Long-term large-scale stacking of iron tailings not only occupies high-quality land resources, but also easily seeps into the surrounding soil and groundwater system under the leaching of rainwater, causing regional water and soil pollution; the iron tailings sand particles in dry state are easy to produce dust, aggravate air pollution and damage the surrounding ecological environment; in addition, if there are design defects or improper maintenance, etc., the tailings pond commonly used for stacking iron tailings also causes serious safety hazards.

[0003] In recent years, the use of iron tailings and other industrial waste to prepare flow state solidified soil and apply it to goaf backfill, foundation treatment, water curtain, etc. has become one of the important technical directions of green engineering material low-carbon development, because of its high flowability, self-compacting, low cost, environmental protection, etc. It can not only adapt to complex spatial form well and effectively eliminate the safety hazards of backfill structure, but also realize the resource utilization of iron tailings through "waste instead of use", which has economic and ecological benefits. However, the existing flow state solidified soil is easy to bleed and separate in the environment with rich water, which leads to the decrease of strength and durability, and even causes the failure of material function, which seriously restricts its actual application. Therefore, it is of great significance to develop underwater non-dispersive flow state solidified tailings sand with anti-dispersion and mechanical properties.

[0004] In the field of underwater concrete, polyacrylamide (PAM) flocculants are commonly used additives to improve the anti-segregation and anti-dispersion performance of materials. Its mechanism can be divided into three stages: first, the polar groups (amide groups, carboxyl groups) on the PAM molecular chain preferentially adsorb on the surface of solid particles through electrostatic attraction or hydrogen bonds, realizing the stable combination of molecules and particles; second, the free chains of PAM adsorbed on different particles stretch and entangle with each other, forming a "particle-PAM-particle" cross-particle bridging connection, which connects the dispersed particles into flocculation, resisting the segregation caused by water flow impact; finally, a large number of flocculation further interweaves to form a continuous three-dimensional network structure, which wraps the free water and fine particles, reduces bleeding and slurry loss, and finally ensures the uniformity of components and the integrity of structure of concrete in underwater environment.

[0005] However, the special properties of tailings sand can significantly constrain the effect of PAM-based flocculants. On the one hand, the particle size of iron tailings sand is much smaller than that of natural river sand or machine-made sand, and the specific surface area is significantly increased, resulting in excessive dispersion and adsorption of flocculant molecules (i.e. a single PAM molecule chain only binds a single fine particle), which cannot form a "bridge" structure across the particles. Moreover, the residual reagents in the surface during the beneficiation process hinder the direct contact between the flocculant and the particles, further reducing the adsorption efficiency. On the other hand, the high alkaline environment of the composite material system can cause the PAM (especially anionic) molecule chain to easily hydrolyze and break, resulting in a decrease in molecular weight and a decrease in "bridge" capability. At the same time, the release of Fe 2+ 、Fe 3+ and other multivalent metal ions from iron tailings sand can form stable complexes with PAM molecule chains, making the molecule chains lose activity and unable to connect tailings sand particles through stretching, directly blocking the flocculation process.

[0006] In summary, conventional polyacrylamide flocculants cannot effectively cooperate with iron tailings sand, and cannot meet the anti-dispersion performance requirements of underwater non-dispersive flow state solidified tailings sand. SUMMARY

[0007] To solve the above technical problems, the present application replaces the coarse and fine aggregates in the commonly used flow state solidified soil with fine particle size iron tailings sand, the mineral admixture in the used cementitious material system can reach 80%, and the cellulose ether additive is used instead of the conventional flocculant. Through the synergistic mechanism of cellulose ether and tailings sand, a kind of underwater non-dispersive flow state solidified tailings sand is developed. This scheme effectively maintains the good workability of the flow state solidified material, significantly enhances the anti-dispersion performance and mechanical strength of the material, meets the technical standards of underwater construction, realizes the large-scale disposal of solid waste, and gives the material double values of technical application and ecological environmental protection, providing a new path for the research and development of green building materials for underwater engineering.

[0008] The technical scheme of the present application is as follows:

[0009] An underwater non-dispersive flow state solidified tailings sand, the content of each component is: cementitious material 500-550 kg / m 3 , iron tailings sand 1300-1500 kg / m 3 , additive 2.5-5 kg / m 3 , water; wherein the mass ratio of water to cementitious material is 0.45~0.55.

[0010] The cementitious material is a mixture of cement and fly ash, the cement uses P.O42.5R ordinary portland cement, and the fly ash uses first-grade fly ash.

[0011] The iron tailing sand has a particle size mainly distributed in the range of 0.6mm-0.01mm, and the particles in the particle size range account for more than 80% of the total mass of the iron tailing sand.

[0012] The additive is a cellulose ether material with a viscosity of 400 MPa·s.

[0013] Further, the mass ratio of cement to fly ash in the cementing material is 1:4-3:7.

[0014] Further, the iron tailing sand is in a natural state and has not been treated, and has a water content of 10%-13%.

[0015] In addition, the application discloses a preparation method of the underwater non-dispersed flow state solidified tailing sand.

[0016] First, the iron tailing sand is added into a mixer, 1 / 3 of water is added and stirred for 30-60s, then the cementing material and the additive are sequentially added into the mixer, stirred for 1-2min, then the remaining 2 / 3 of water is added into the mixer, stirred for 3-5min, and the underwater non-dispersed flow state solidified tailing sand is obtained.

[0017] Further, the stirring for 30-60s is to make the iron tailing sand reach a fully wetted saturated state, the stirring for 1-2min is to make the iron tailing sand, the cementing material and the additive be fully and uniformly dispersed in the mixer, and the stirring for 3-5min is to make the cementing material and the additive fully react.

[0018] The application prepares underwater non-dispersive fluidized solidified tailings sand by replacing traditional coarse and fine aggregates with iron tailings sand and using cellulose ether as an additive. The core mechanism is as follows: 1) The viscous colloid formed after the dissolution of cellulose ether can uniformly wrap the cementitious material and iron tailings sand particles, promoting the formation of a close cohesive structure between the particles. Compared with ordinary sand and stone, iron tailings sand has smaller particle size, larger specific surface area and higher surface energy characteristics. The surface active sites can form stronger physical adsorption and hydrogen bonding with the hydroxyl (-OH) and ether (-O-) groups on the cellulose ether molecular chain. At the same time, the thickening effect of cellulose ether can significantly increase the yield stress of concrete slurry, enhance the slurry's resistance to water flow scouring, and effectively reduce the dissolution and loss of material particles. 2) The three-dimensional colloid network of cellulose ether can stably wrap the free water inside the concrete, preventing it from being replaced by external water due to osmotic pressure and water flow scouring, and providing a stable water environment for the continuous hydration of cementitious materials. In addition, part of the cellulose ether molecules will form a dense polymer film at the interface between the mixture and the external water, slowing down the excessive penetration of external water into the concrete, preventing slurry dilution and internal hydration product dissolution and loss, and cutting off the "dispersion-loss" path. 3) The cellulose ether molecular chain adsorbed on the surface of the iron tailings sand particles forms a lubricating layer, reducing the frictional resistance between the particles and giving the mixture good flowability, meeting the long-distance pumping construction requirements in engineering. When the slurry comes into contact with old concrete structures (such as underwater repair, pile pouring) or rock base bonding layers, the polar groups on the cellulose ether molecular chain can form multiple hydrogen bonds and van der Waals forces with the active sites on the base surface, strengthening the physical anchoring effect of the interface and preventing the interface from failing to bond during underwater construction. 4) During the hydration process, cellulose ether can regulate the water release rate to ensure full hydration of cementitious materials, promote the uniform generation of hydration products (mainly C-S-H gel), effectively fill the capillary pores and harmful pores inside the fluidized solidified soil, and reduce the penetration channels for water and aggressive ions. At the same time, the segregation resistance of cellulose ether can significantly reduce the defects in the interfacial transition zone (ITZ) between the aggregate and the slurry, build a dense ITZ structure, and synergistically improve the impermeability and long-term corrosion resistance of the fluidized solidified soil through microstructure optimization, prolonging the service life of underwater structures.

[0019] The beneficial effects of the present application are: 1) The present application uses solid waste iron tailings generated in the metallurgical industry to completely replace traditional coarse and fine aggregates, and adopts a large amount of industrial solid waste fly ash and a small amount of cement to construct a composite cementitious system to prepare underwater non-dispersive fluidized solidified tailings, which realizes the storage of more than 1700 kg of solid waste per cubic meter of material, and to a certain extent, it can alleviate the storage and disposal problems of iron tailings in the metallurgical industry, save a large amount of natural mineral raw materials, and reduce the mining and damage to mines and rivers. At the same time, the toxic and harmful ions in the iron tailings are stabilized and solidified by the physical encapsulation and chemical adsorption of the hydration products of the cementitious material, avoiding their migration and release into the environment, eliminating the potential environmental risk of solid waste storage, and meeting the strategic direction of national energy saving and carbon reduction and resource recycling. 2) The present application uses cellulose ether instead of conventional flocculants to prepare underwater non-dispersive fluidized solidified soil with iron tailings as full aggregate, which solves the two core problems that the conventional flocculants are not compatible with the surface properties of the iron tailings, resulting in the failure of the interface action, and within the dosage threshold, it is difficult to balance the contradiction between the anti-dispersion and workability. The cellulose ether and the iron tailings form a stable slurry system through molecular-particle level adsorption, thickening, water retention and other synergies, which fundamentally solves the problem of underwater slurry loss, and makes the fluidized solidified soil have the comprehensive performance of anti-dispersion, self-leveling and high density, and takes into account the cost and environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The XRD graph of the iron tailings used for preparing the underwater non-dispersive fluidized solidified tailings of the present application.

[0021] Figure 2 The grading curve graph of the iron tailings used for preparing the underwater non-dispersive fluidized solidified tailings of the present application. DETAILED DESCRIPTION

[0022] The present application will be further described below in conjunction with specific embodiments, but not as a limitation of the present application.

[0023] In the following examples, the raw materials used are: cementitious materials are cement and fly ash, cement uses P.O42.5R ordinary portland cement, fly ash uses first-grade fly ash; iron tailings have a particle size mainly distributed in the range of 0.6mm-0.01mm, and the particles in this particle size range account for more than 80% of the total amount of iron tailings, which are untreated iron tailings in a natural state, with a fineness modulus of 0.67, a non-uniformity coefficient Cu=10.13, and a curvature coefficient Cc=2; cellulose ether uses hydroxypropyl methyl cellulose ether with a viscosity of 400MPa·s.

[0024] In the following embodiment, the preparation method of underwater non-dispersive fluidized solidified tailings sand with iron tailings sand as full aggregate, comprising the following steps: first, the iron tailings sand is added into the mixer, 1 / 3 of the water is added and stirred for 30s, then the mixed cementing material and the additive are sequentially added into the mixer, stirred for 1min, then the remaining 2 / 3 of the water is added into the mixer, stirred for 3min, and finally the underwater non-dispersive fluidized solidified soil is obtained.

[0025] Example 1

[0026] A kind of underwater non-dispersive fluidized solidified tailings, the mixing ratio is shown in table 1.

[0027] Table 1 Mixing ratio of underwater non-dispersive fluidized solidified tailings sand in example 1 (kg / m 3 )

[0028]

[0029] Wherein the cementing material is cement and fly ash mixed according to the mass ratio of 1:4, the mass ratio of water and cementing material is 0.45, the additive is hydroxypropyl methyl cellulose, and the water content of iron tailings sand is 10%.

[0030] Example 2

[0031] A kind of underwater non-dispersive fluidized solidified tailings, the mixing ratio is shown in table 2.

[0032] Table 2 Mixing ratio of underwater non-dispersive fluidized solidified tailings in example 2 (kg / m 3 )

[0033]

[0034] Wherein the cementing material is cement and fly ash mixed according to the mass ratio of 3:7, the mass ratio of water and cementing material is 0.45, the additive is hydroxypropyl methyl cellulose ether, and the water content of iron tailings sand is 11.7%.

[0035] Example 3

[0036] A kind of underwater non-dispersive fluidized solidified tailings, the mixing ratio is shown in table 3.

[0037] Table 3 Mixing ratio of underwater non-dispersive fluidized solidified tailings in example 3 (kg / m 3 )

[0038]

[0039] Wherein the cementing material is cement and fly ash mixed according to the mass ratio of 3:7, the mass ratio of water and cementing material is 0.52, the additive is hydroxypropyl methyl cellulose ether, and the water content of iron tailings sand is 13%.

[0040] Example 4

[0041] An underwater non-dispersive fluidized solidified tailings, the mix proportion of which is shown in Table 4.

[0042] Table 4 Mix proportion of underwater non-dispersive fluidized solidified tailings of Example 4 (kg / m 3 )

[0043]

[0044] The cementing material is cement mixed with fly ash at a mass ratio of 3:7, the mass ratio of water to cementing material is 0.55, the additive is hydroxypropyl methyl cellulose ether, and the water content of the iron tailings sand is 13%.

[0045] Comparative Example 1

[0046] An underwater non-dispersive fluidized solidified tailings, the mix proportion of which is shown in Table 6.

[0047] Table 5 Mix proportion of underwater non-dispersive fluidized solidified tailings of Comparative Example 1 (kg / m 3 )

[0048]

[0049] The cementing material is cement mixed with fly ash at a mass ratio of 3:7, the mass ratio of water to cementing material is 0.45, and the additive is polyacrylamide flocculant.

[0050] Comparative Example 2

[0051] A fluidized solidified soil suitable for underwater molding, which is prepared from the following raw materials in parts by weight: magnesium slag 3 parts, mineral powder 10 parts, calcium sulfate 0.8 parts, polyacrylic acid sodium salt 0.04 parts, phosphoric acid 0.01 parts, water 30 parts, and soil 50 parts. The preparation method comprises the following steps: Step 1, according to the design ratio of the target product fluidized solidified soil, the slag, mineral powder, calcium sulfate, polyacrylic acid sodium salt and soil are weighed and put into a mixer for low-speed stirring at 60 r / min for 30 s to mix uniformly, to obtain dry powder; Step 2, the mixed water prepared from the weighed phosphoric acid and water is added to the dry powder in Step 1 for low-speed stirring at 60 r / min for 120 s, to obtain the fluidized solidified soil suitable for underwater molding.

[0052] Comparative Example 3

[0053] A steel slag and mineral powder mixed solidified iron tailings, which is prepared from the following raw materials in parts by weight: ordinary Portland cement P·O42.5 8 parts, steel slag with a sieve hole size of less than 2 mm 6 parts, S95 finely ground blast furnace granulated slag powder 6 parts, iron tailings sand with a sieve hole size of less than 2 mm 80 parts, and the water amount is 14.04% of the total mass of the powder (cement + slag powder + tailings sand).

[0054] Performance test

[0055] The underwater non-dispersible flowable solidified tailings of Examples 1-4 were tested, and the specific performance test methods refer to the standards GB / T 37990-2019 “Underwater Non-dispersible Concrete Flocculant Technical Requirements” and GB / T 50081-2019 “Standard for Test Methods of Mechanical Properties of Concrete”.

[0056] The test results of Table 6 show that the Examples 1-4 do not disperse after being cast into water, and all harden and set on the second day of underwater curing. In Comparative Example 1, the flowable solidified tailings sand cannot be formed underwater when using polyvinyl amide flocculant; Comparative Example 2 is an underwater non-dispersible solid flowable soil, which is also based on the binding effect of sodium polyacrylate and soil, and the mechanism is completely different from that of the solidified tailings sand, and the 28-day land compressive strength is much lower than that of Example 2; Comparative Example 3 also cannot be formed underwater.

[0057] Table 6 Performance test results of underwater non-dispersible concrete provided by Examples 1 and 2

[0058]

[0059] The experimental data of Table 6 shows that the reduction of cement content will directly lead to the decrease of the mechanical properties of the underwater non-dispersible flowable solidified soil, which is mainly due to two factors: first, in the existing cementitious system, cement as a high-activity component dominates the early hydration process, while fly ash as a pozzolanic material needs to rely on Ca(OH)2 generated by cement hydration to generate C-S-H gel for secondary activation. When the amount of cement is reduced and the amount of fly ash is increased, the proportion of high-activity mineral phases in the system is significantly reduced, causing significant changes in early hydration kinetics—hydration rate slows down and initial hydration product volume is greatly reduced, making it difficult to effectively fill the interstitial space of aggregates to form a dense cementitious structure, thus leading to significant deterioration of early strength. Although fly ash can supplement a small amount of C-S-H gel through secondary hydration later, its reaction process is slow and the amount of product is limited. External water continues to penetrate into the interior of the mixture, and the interfacial transition zone shows characteristics of increased porosity and weakened adhesion due to insufficient hydration products, ultimately causing synchronous attenuation of late strength; second, the retarding properties of cellulose ether have a synergistic negative effect in this system. With the reduction of cement content, the overall hydration activity of the system is already reduced, and the physical wrapping and chemical blocking effects of cellulose ether on trace amounts of cement particles are more pronounced, further delaying cement hydration and inhibiting early hydration. Since fly ash cannot provide effective hydration products in time, and cellulose ether hinders the hydration process of the remaining cement, it is difficult to build a stable skeletal structure during the initial setting stage, and the double effect exacerbates the strength degradation trend. Therefore, reasonable control of the ratio of “cement-fly ash” composite cementitious system is one of the keys to preparing the underwater non-dispersible flowable solidified tailings sand.

[0060] As shown by the above results in Table 6, the underwater non-dispersible flowable solidified tailings obtained in the present embodiment have good workability and mechanical properties, and at the same time have stable underwater anti-dispersive capacity, meeting the underwater construction requirements. The material system is in line with the development direction of green building and carbon neutralization, and through the solid waste resource utilization path, the effective synergy of engineering value and environmental protection benefit is realized.

Claims

1. An underwater non-dispersible, fluidized solidified tailings sand, characterized in that, The content of each component in the underwater non-dispersible fluidized solidified tailings sand is as follows: cementitious material 500-550 kg / m³ 3 Iron tailings sand 1300-1500 kg / m³ 3 Admixture 2.5-5 kg / m 3 Water; wherein the mass ratio of water to cementitious material is 0.45~0.

55.

2. The underwater non-dispersible fluid solidified tailings sand according to claim 1, characterized in that, The cementing material is a mixture of cement and fly ash. The cement used is P.O42.5R silicate cement, and the fly ash used is Grade I fly ash.

3. The underwater non-dispersible fluid solidified tailings sand according to claim 1, characterized in that, The iron tailings sand has particles with a diameter distribution in the range of 0.6mm-0.01mm accounting for more than 80% of the total mass of the iron tailings sand.

4. The underwater non-dispersible fluid solidified tailings sand according to claim 1, characterized in that, The additive is a cellulose ether material with a viscosity of 400 MPa·s.

5. The underwater non-dispersible fluidized solidified tailings sand according to claim 1, characterized in that, The mass ratio of cement to fly ash in cementitious materials is 1:4 to 3:

7.

6. The underwater non-dispersible fluid solidified tailings sand according to claim 1, characterized in that, The iron tailings sand is in its natural state and has not undergone any treatment, with a moisture content of 10% to 13%.

7. A method for preparing underwater non-dispersible fluidized solidified tailings sand according to any one of claims 1-6, characterized in that, Includes the following steps: First, add iron tailings sand to the mixer, add 1 / 3 of the water and stir for 30-60 seconds. Then, add the cementitious material and additives to the mixer in sequence and stir for 1-2 minutes. Then, add the remaining 2 / 3 of the water to the mixer and stir for 3-5 minutes to obtain underwater non-dispersed fluid solidified tailings sand.

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