Anti-bleeding ardealite-based filling material and preparation method thereof

Abstract

The invention discloses an anti-bleeding ardealite-based filling material and a preparation method thereof, the anti-bleeding ardealite-based filling material is prepared from a binding material, an aggregate, water and an additive, the binding material is wet-process phosphoric acid byproduct semi-hydrated ardealite, the aggregate is composed of dihydrate ardealite and quick lime, and the additive is water. The admixture is superfine active micro powder formed by mixing 32.5 cement, phosphogypsum, fly ash and limestone, and has gelling activity and pozzolanic effect. Aiming at the semi-hydrated phosphogypsum with high bleeding performance, the admixture with gelling activity and pozzolanic effect is used, the bleeding performance of the existing phosphogypsum-based filling slurry is improved, the compressive strength of a filling body is improved, and the filling cost is reduced while the environmental protection performance is ensured.

Description

Technical Field

[0001] This invention belongs to the technical field of mine backfill materials, specifically relating to a water-resistant phosphogypsum-based backfill material and its preparation method. Background Technology

[0002] Cement-bonded backfilling is currently the most common method for treating goaf areas both domestically and internationally. Cement, as the backfill binder, accounts for approximately 70% of the backfilling cost, resulting in persistently high costs. Meanwhile, phosphate rock is inexpensive, making it unaffordable for most mines to afford the high backfilling costs.

[0003] Hemihydrate phosphogypsum possesses excellent cementitious activity, making it a potential substitute for cement and a breakthrough point for the transformation and upgrading of phosphate chemical enterprises. Existing phosphogypsum backfilling technology relies on its cementitious properties and long setting time, significantly reducing costs compared to cement-based backfilling. However, due to the need to ensure transportation, storage, and conveying requirements, and the relatively large bleeding rate deviation of hemihydrate phosphogypsum, high bleeding rates result in lower compressive strength. Maintaining both low bleeding and high strength increases mine backfilling costs. Therefore, existing phosphogypsum-based backfill slurries suffer from excessive bleeding, low compressive strength, and high costs associated with adding admixtures. Furthermore, the unstable properties of hemihydrate phosphogypsum and the complex environment of backfilling stations lead to unstable slurry performance. Traditional backfill slurries have poor anti-interference capabilities, easily resulting in high slurry settling rates, poor pumping capacity, and potentially leading to pipe blockage accidents, making it difficult to meet the stable backfilling needs of modern mines. Therefore, there is an urgent need for a phosphogypsum-based mine backfill material that can achieve strong resistance to bleeding and interference, stable slurry properties, and high strength of the backfill body.

[0004] This invention targets hemihydrate phosphogypsum with high water seepage performance. It combines the cementing properties of hemihydrate phosphogypsum with paste backfilling mining technology. Using hemihydrate phosphogypsum as a backfill cementing material and making full use of other solid wastes as aggregates, it prepares a harmless all-solid waste paste that is non-stratified, non-segregated, non-dehydrated, and has good water seepage resistance. This allows for safe and efficient mining of phosphate mines, while simultaneously achieving the harmless large-scale utilization and disposal of phosphogypsum. Summary of the Invention

[0005] The purpose of this invention is to provide a phosphogypsum-based filler material with high bleeding resistance and its preparation method. This invention targets hemihydrate phosphogypsum with high bleeding resistance, and uses additives with gelling activity and pozzolanic effect to improve the bleeding resistance of existing phosphogypsum-based filler slurries and enhance the compressive strength of the filler, while reducing the filling cost while ensuring environmental performance.

[0006] The technical solution of this invention: A water-resistant phosphogypsum-based filler material, wherein the water-resistant phosphogypsum-based filler material is prepared from cementing materials, aggregates, water and additives; The cementitious materials, aggregates, and water are calculated as follows by mass percentage: cementitious materials account for 20-60% of the total, aggregates account for 60-20% of the total, and water accounts for 20-26% of the total. The amount of the admixture added is 6-8% of the mass of the cementitious material; The cementing material is hemihydrate phosphogypsum, a byproduct of wet-process phosphoric acid production, and the amount of quicklime in the aggregate is 3-5% of the mass of dihydrate gypsum. The aggregate is composed of dihydrate phosphogypsum and quicklime; The admixture is composed of 32.5 cement, phosphogypsum, fly ash and limestone mixed in a mass ratio of 55-65:2.8-3.2:20-22:15-17 to form an ultrafine active powder.

[0007] The aforementioned cementitious materials, aggregates, and water are calculated as a percentage by mass: cementitious materials account for 25-50% of the total, aggregates account for 50-25% of the total, and water accounts for 20-25% of the total.

[0008] The aforementioned hemihydrate phosphogypsum has a free water content of 20-25% and a crystal water content of 6.5-8%.

[0009] The amount of quicklime used in the aforementioned aggregate is 4% of the mass of dihydrate gypsum.

[0010] The aforementioned admixture is added at 7% of the mass of the cementitious material. The mass ratio of 32.5 cement, phosphogypsum, fly ash, and limestone in the admixture is 60:3:21:16, and the particle size of the admixture is <38μm.

[0011] The concentration of the aforementioned anti-bleeding phosphogypsum-based filler material is 70-80%.

[0012] The aforementioned method for preparing the anti-bleeding phosphogypsum-based filling material is carried out according to the following steps; (1) Take 32.5 cement, phosphogypsum, fly ash and limestone mixed and ground into powder, pass through a 350-450 mesh sieve to obtain an admixture, and set aside for later use; (2) Mix the cementitious material, aggregate and admixture for 20-35 seconds, then slowly add water for 20-35 seconds, and then stir for 160-200 seconds to obtain the anti-bleeding phosphogypsum-based filling material.

[0013] In step (1) above, 32.5 cement, phosphogypsum, fly ash and limestone are mixed and ground into particles, which are then passed through a 400-mesh sieve to obtain an admixture for later use.

[0014] In step (2) above, the cementitious material, aggregate and admixture are mixed and stirred for 30 seconds, and then water is slowly added for 20 to 30 seconds. After stirring for 175 to 185 seconds, the water-resistant phosphogypsum-based filling material is obtained.

[0015] Specifically, in step (2) above, the cementitious material, aggregate and additive are mixed and stirred for 30 seconds, then water is slowly added for 25 seconds, and then stirred for 180 seconds to obtain the anti-bleeding phosphogypsum-based filling material.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention targets hemihydrate phosphogypsum with high water seepage performance. It combines the cementing properties of hemihydrate phosphogypsum with paste backfilling mining technology. Hemihydrate phosphogypsum is used as the backfill cementing material, and dihydrate phosphogypsum and quicklime are used as aggregates. An ultrafine powder additive with pozzolanic effect is added as aggregate to prepare a harmless solid waste paste that does not separate, does not dehydrate, and has good water seepage resistance. This paste is used for safe and efficient mining of phosphate mines, while realizing the harmless large-scale utilization and disposal of phosphogypsum. The water seepage rate can be reduced from 10.35% to 0.95%.

[0017] 2. The gelling material used in this invention is hemihydrate phosphogypsum, a byproduct of wet-process phosphoric acid. Although it has gelling activity, it has a long setting time, a high bleeding rate, and unstable slurry performance. By adding a small amount of ultrafine powder additive with pozzolanic effect, the bleeding rate of the filling slurry can be reduced while the compressive strength can be improved. Compared with suspending agents and pumping agents with the same effect on the market, the cost is significantly reduced. Attached Figure Description

[0018] Figure 1 : Particle size distribution diagram of active fine powder; Figure 2 XRD pattern of active fine powder; Figure 3 XRD pattern of hemihydrate phosphogypsum. Detailed Implementation

[0019] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention.

[0020] Example 1 Formula: Cementitious materials, aggregates, and water are calculated by mass percentage: cementitious materials account for 25% of the total, aggregates account for 50% of the total, and water accounts for 25% of the total; the amount of admixture added is 7% of the mass of cementitious materials. The cementing material is hemihydrate phosphogypsum, a byproduct of wet-process phosphoric acid production. The free water content of hemihydrate phosphogypsum is 20-25%, and the crystal water content is 6.5-8%. It has cementing activity, but the setting time is long, the bleeding rate is high, and the slurry performance is unstable. The aggregate consists of dihydrate phosphogypsum and quicklime, with the amount of quicklime being 4% of the mass of dihydrate phosphogypsum. The admixture is an ultrafine active powder composed of 32.5 cement, phosphogypsum, fly ash and limestone in a mass ratio of 60:3:21:16, which has cementitious activity and pozzolanic effect.

[0021] Preparation process: (1) Take 32.5 cement, phosphogypsum, fly ash and limestone mixed grinding particles with a mass ratio of 60:3:21:16, pass them through a 400-mesh sieve to obtain an admixture with a particle size <38μm, and set it aside; (2) Mix the cementitious material, aggregate and admixture for 30 seconds, then slowly add water for 25 seconds, and then stir for 180 seconds to obtain the anti-bleeding phosphogypsum-based filling material.

[0022] Example 2 Formula: Cementitious materials, aggregates, and water are calculated by mass percentage: cementitious materials account for 50% of the total, aggregates account for 25% of the total, and water accounts for 25% of the total; the amount of admixture added is 7% of the mass of cementitious materials. The cementing material is hemihydrate phosphogypsum, a byproduct of wet-process phosphoric acid production, with a free water content of 20-25% and a crystal water content of 6.5-8%. It has cementing activity, but the setting time is long, the bleeding rate is high, and the slurry properties are unstable. The aggregate consists of dihydrate phosphogypsum and quicklime, with the amount of quicklime being 4% of the mass of dihydrate phosphogypsum. The admixture is an ultrafine active powder composed of 32.5 cement, phosphogypsum, fly ash and limestone in a mass ratio of 60:3:21:16, which has cementitious activity and pozzolanic effect.

[0023] Preparation process: (1) Take 32.5 cement, phosphogypsum, fly ash and limestone mixed grinding particles with a mass ratio of 60:3:21:16, pass them through a 400-mesh sieve to obtain an admixture with a particle size <38μm, and set it aside; (2) Take the cementitious material, aggregate and admixture, mix and stir for 30s, then slowly add water for 30s, and stir for 180s to obtain the anti-bleeding phosphogypsum-based filling material.

[0024] Example 3 Formula: Cementitious materials, aggregates, and water are calculated by mass percentage: cementitious materials account for 20% of the total, aggregates account for 60% of the total, and water accounts for 20% of the total; the amount of admixture added is 6% of the mass of cementitious materials. The cementing material is hemihydrate phosphogypsum, a byproduct of wet-process phosphoric acid production. The free water content of hemihydrate phosphogypsum is 20-25%, and the crystal water content is 6.5-8%. It has cementing activity, but the setting time is long, the bleeding rate is high, and the slurry performance is unstable. The aggregate consists of dihydrate phosphogypsum and quicklime, with the amount of quicklime being 4% of the mass of dihydrate phosphogypsum. The admixture is an ultrafine active powder composed of 32.5 cement, phosphogypsum, fly ash and limestone in a mass ratio of 55:3.2:22:17, which has cementitious activity and pozzolanic effect.

[0025] Preparation process: (1) Take 32.5 cement, phosphogypsum, fly ash and limestone mixed grinding particles with a mass ratio of 60:3:21:16, pass them through a 450 mesh sieve to obtain an admixture with a particle size <38μm, and set it aside; (2) Take the cementitious material, aggregate and admixture, mix and stir for 35s, then slowly add water for 20s, and stir for 200s to obtain the anti-bleeding phosphogypsum-based filling material.

[0026] Example 4 Formula: Cementitious materials, aggregates, and water are calculated by mass percentage: cementitious materials account for 60% of the total, aggregates account for 20% of the total, and water accounts for 20% of the total; the amount of admixture added is 8% of the mass of cementitious materials. The cementing material is hemihydrate phosphogypsum, a byproduct of wet-process phosphoric acid production. The free water content of hemihydrate phosphogypsum is 20-25%, and the crystal water content is 6.5-8%. It has cementing activity, but the setting time is long, the bleeding rate is high, and the slurry performance is unstable. The aggregate consists of dihydrate phosphogypsum and quicklime, with the amount of quicklime being 4% of the mass of dihydrate phosphogypsum. The admixture is an ultrafine active powder composed of 32.5 cement, phosphogypsum, fly ash and limestone in a mass ratio of 65:2.8:20:15, which has cementitious activity and pozzolanic effect.

[0027] Preparation process: (1) Take 32.5 cement, phosphogypsum, fly ash and limestone mixed grinding particles, pass them through a 400-mesh sieve to obtain an admixture with a particle size <38μm, and set it aside; (2) Take the cementitious material, aggregate and admixture, mix and stir for 25s, then slowly add water for 35s, and stir for 160s to obtain the anti-bleeding phosphogypsum-based filling material.

[0028] In order to obtain the solution of this invention and verify its technical effects, the inventors conducted a large number of experimental studies, some of which are recorded below: 1. Raw material preparation 1.1 Admixture Investigation Take 32.5 cement, phosphogypsum, fly ash, and limestone in a mass ratio of 60:3:21:16, mix and finely grind them through a 400-mesh sieve to obtain active fine powder. The particle size distribution of the active fine powder is as follows: Figure 1 As shown, the particle size characteristic values ​​D10, D30, D50, D60, D90, and D97 of the active fine powder are 1.813 μm, 6.50 μm, 11.91 μm, 15.14 μm, 28.99 μm, and 37.45 μm, respectively, and the non-uniformity coefficient Cu and curvature coefficient Cc are 8.274 and 1.539, respectively.

[0029] XRD pattern of active fine powder as follows Figure 2 As shown, the mineral composition is mainly Ca3SiO5, with small amounts of CaSO4·2H2O and CaCO3 added.

[0030] 1.2 Cementitious Materials The cementing material is hemihydrate phosphogypsum, a byproduct of wet-process phosphoric acid production. The free water content of the hemihydrate phosphogypsum is 20-25%, and the crystal water content is 6.5-8%.

[0031] XRD pattern of hemihydrate gypsum as follows Figure 3 As shown, the mineral composition of hemihydrate gypsum is mainly CaSO4·0.5H2O, with small amounts of CaSO4·2H2O and SiO2.

[0032] 1.3 Aggregates The aggregate consists of dihydrate phosphogypsum and quicklime, with the amount of quicklime being 4% of the mass of dihydrate phosphogypsum.

[0033] 2. Preparation process Mix the cementitious material, aggregate and admixture for 30 seconds, then slowly add water for 20-30 seconds, and stir for another 180±5 seconds to obtain the anti-bleeding phosphogypsum-based filling material.

[0034] 3. Process Validation Experiment 3.1 Experimental Study Without Adding Aggregates and Admixtures The cementing material used was hemihydrate phosphogypsum (batch 1), a byproduct of wet-process phosphoric acid production. The hemihydrate phosphogypsum had a free water content of 20.5% and a crystal water content of 6.5%.

[0035] The performance of phosphogypsum-based fillers without the addition of aggregates and admixtures was investigated. Specific data are shown in Table 1. Table 1 Properties of phosphogypsum-based mine backfill materials As can be seen from Table 1, without the addition of aggregates and admixtures, the raw material has a maximum water bleeding rate of 10%, and the setting time is long, 3 days and 7 days, with low strength.

[0036] 3.2 Admixture Particle Size Investigation Experiment The cementing material used was hemihydrate phosphogypsum (batch 2), a byproduct of wet-process phosphoric acid production. The hemihydrate phosphogypsum had a free water content of 23.6% and a crystal water content of 7.8%.

[0037] The effects of additives with different particle sizes on the performance of phosphogypsum-based fillers were investigated. Specific data are shown in Table 2. Table 2. Effect of admixture particle size on the properties of phosphogypsum-based mine backfill materials As shown in Table 2, under the same standard fluidity, with the decrease of admixture particle size, the bleeding rate of phosphogypsum-based mine backfill material slurry gradually decreases, while the later compressive strength gradually increases. Reducing the admixture particle size has the effect of reducing bleeding and improving the strength of the backfill slurry. Reducing the admixture particle size has an optimizing effect on the particle size distribution of the material.

[0038] 3.3 Experiment on the Dosage of Admixtures The cementing material used was hemihydrate phosphogypsum (batch 3), a byproduct of wet-process phosphoric acid production. The hemihydrate phosphogypsum had a free water content of 21.3% and a crystal water content of 6.6%.

[0039] The effects of different amounts of admixtures on the performance of phosphogypsum-based fillers were investigated. Specific data are shown in Table 3. Table 3. Effect of admixture dosage on the performance of phosphogypsum-based mine backfill materials As shown in Table 3, under the same standard fluidity, with the increase of admixture dosage, the bleeding rate of phosphogypsum-based mine backfill material slurry also showed a decreasing trend, and the compressive strength also gradually increased. However, when the admixture dosage reached 7wt%, the effect of reducing bleeding rate and improving strength performance reached its peak, indicating that a small amount of admixture has the effect of resisting bleeding and improving strength, and its optimal dosage is 7wt%.

[0040] 3.4 Experiments to investigate different slurry ratios The cementing material used was hemihydrate phosphogypsum (batch 4), a byproduct of wet-process phosphoric acid production. The hemihydrate phosphogypsum had a free water content of 22.6% and a crystal water content of 7.3%.

[0041] The effects of different cementitious materials and aggregate slurry ratios on the performance of phosphogypsum-based backfill materials were investigated. Specific data are shown in Table 4. Table 4. Effects of admixtures on the performance of phosphogypsum-based mine backfill materials with different slurry ratios As can be seen from Table 4, under the same standard fluidity, although reducing the amount of cementitious material will reduce the compressive strength to a certain extent, the addition of admixture can reduce the bleeding rate and maintain a high compressive strength. This indicates that the 7wt% admixture has the effect of anti-bleeding and improving strength for filling slurries with different proportions.

[0042] In summary, the phosphogypsum-based backfill material prepared by this invention comprises, by mass percentage: cementitious material accounts for 25-50% of the total, aggregate accounts for 50-25% of the total, water accounts for 26-25% of the total (slurry concentration 75-76%), and the amount of additive is 7% of the mass of cementitious material, with the additive having a particle size <38μm. This can improve the water bleeding performance of the backfill slurry, increase the compressive strength of the backfill, reduce the cost of backfill material, and improve environmental benefits.

Claims

1. A phosphogypsum-based filler material with anti-bleeding properties, characterized in that: The anti-bleeding phosphogypsum-based filling material is prepared from cementitious materials, aggregates, water, and additives; The cementitious materials, aggregates, and water are calculated as follows by mass percentage: cementitious materials account for 20-60% of the total, aggregates account for 60-20% of the total, and water accounts for 20-26% of the total. The amount of the admixture added is 6-8% of the mass of the cementitious material; The cementing material is hemihydrate phosphogypsum, a byproduct of wet-process phosphoric acid production, and the amount of quicklime in the aggregate is 3-5% of the mass of dihydrate gypsum. The aggregate is composed of dihydrate phosphogypsum and quicklime; The admixture is composed of 32.5 cement, phosphogypsum, fly ash and limestone mixed in a mass ratio of 55-65:2.8-3.2:20-22:15-17 to form an ultrafine active powder.

2. The anti-bleeding phosphogypsum-based filling material according to claim 1, characterized in that: The cementitious materials, aggregates, and water are calculated as follows by mass percentage: cementitious materials account for 25-50% of the total, aggregates account for 50-25% of the total, and water accounts for 20-25% of the total.

3. The anti-bleeding phosphogypsum-based filling material according to claim 1, characterized in that: The hemihydrate phosphogypsum has a free water content of 20-25% and a crystal water content of 6.5-8%.

4. The anti-bleeding phosphogypsum-based filling material according to claim 1, characterized in that: The amount of quicklime used in the aggregate is 4% of the mass of dihydrate gypsum.

5. The anti-bleeding phosphogypsum-based filling material according to claim 1, characterized in that: The amount of the admixture added is 7% of the mass of the cementitious material. The mass ratio of 32.5 cement, phosphogypsum, fly ash and limestone in the admixture is 60:3:21:16, and the particle size of the admixture is <38μm.

6. The anti-bleeding phosphogypsum-based filling material according to claim 1, characterized in that: The concentration of the anti-bleeding phosphogypsum-based filler material is 70-80%.

7. The method for preparing the anti-bleeding phosphogypsum-based filling material according to any one of claims 1 to 6, characterized in that: Follow these steps; (1) Take 32.5 cement, phosphogypsum, fly ash and limestone mixed and ground into powder, pass through a 350-450 mesh sieve to obtain an admixture, and set aside for later use; (2) Mix the cementitious material, aggregate and admixture for 20-35 seconds, then slowly add water for 20-35 seconds, and then stir for 160-200 seconds to obtain the anti-bleeding phosphogypsum-based filling material.

8. The anti-bleeding phosphogypsum-based filling material according to claim 7, characterized in that: In step (1), 32.5 cement, phosphogypsum, fly ash and limestone are mixed and ground into particles, which are then passed through a 400-mesh sieve to obtain an admixture for later use.

9. The anti-bleeding phosphogypsum-based filling material according to claim 7, characterized in that: In step (2), the cementitious material, aggregate and admixture are mixed and stirred for 30 seconds, and then water is slowly added for 20 to 30 seconds. After stirring for 175 to 185 seconds, the water-resistant phosphogypsum-based filling material is obtained.

10. The anti-bleeding phosphogypsum-based filling material according to claim 9, characterized in that: In step (2), the cementitious material, aggregate and admixture are mixed and stirred for 30 seconds, then water is slowly added for 25 seconds, and then stirred for 180 seconds to obtain the anti-bleeding phosphogypsum-based filling material.

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