Cementing material and cemented filling material for filling mining

Abstract

The invention provides a cementing material and a cemented filling material for filling mining, and relates to the technical field of recycling of industrial building materials. The cementing material comprises cement, superfine slag powder, steel slag and fly ash, the cemented filling material comprises aggregate, a cementing material and water; the aggregate is modified phosphogypsum. Solid wastes such as slag, steel slag and fly ash are used for replacing part of cement to modify the ardealite filling body, so that the popularization and application of the ardealite cemented filling technology can be improved, the cost of part of materials can be reduced, and meanwhile, the problems of poor pollution element curing effect, high cost and the like when the cement is used as a cementing agent can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of industrial building material recycling technology, specifically to a cementing material and cemented backfill material used for filling mining materials. Background Technology

[0002] Phosphogypsum is an industrial byproduct generated during the wet process of phosphoric acid production in phosphate chemical enterprises. The presence of pollutants such as phosphorus (P) and phosphorus (F) limits its recycling and utilization, leading to safety and environmental problems such as land occupation and pollution. Cemented backfilling technology can not only alleviate a series of safety issues caused by phosphogypsum storage, but also provide effective support for the roof of the mining area, mitigate surface subsidence, and achieve safe and efficient mining of phosphorus resources. However, using cement as a binder has problems such as poor solidification of pollutants and high cost, which limits the widespread application of phosphogypsum cemented backfilling technology.

[0003] Therefore, there is an urgent need to provide a new technology that, based on the physicochemical properties of phosphogypsum backfill materials, can achieve the harmless reduction of large quantities of phosphogypsum, reduce the risk of geological disasters such as phosphogypsum dam failures caused by large-scale phosphogypsum stockpiles, provide a scientific theoretical basis for the scientific and effective prevention, control and management of the impact of phosphogypsum backfill bodies in mining areas on the groundwater environment, and have important theoretical significance and application value for the large-scale disposal of solid waste in mining areas and the protection of groundwater environment. Summary of the Invention

[0004] To overcome the shortcomings of the above-mentioned technologies, the purpose of this invention is to provide a cementing material and a cemented backfill material for backfilling mining, which solves the environmental pollution problems caused by phosphogypsum stockpiling, and while achieving the harmless reduction of phosphogypsum, provides effective support for the mining roof, alleviates surface subsidence, and realizes the safe and efficient mining and utilization of phosphorus resources.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A cementitious material for backfilling mining, characterized in that it comprises one or more of cement, slag powder, steel slag, and fly ash.

[0006] As a preferred embodiment, the cementitious material comprises the following components by mass percentage: 14-42% cement, 10-25% slag powder, 17-25% steel slag, and 30-40% fly ash.

[0007] As a preferred option, the cement is 32.5M ordinary Portland cement.

[0008] As a preferred embodiment, the slag powder is a grayish-white powder containing a large amount of amorphous glassy phase mainly composed of CaO, Al2O3, and SiO2, and a small amount of weak crystals. The slag powder has high hydration activity, and its fine particles can fill the gaps between phosphogypsum crystals, reduce the porosity of the cement, and make the microstructure more compact. It can also interweave with phosphogypsum hydration products to form a "crystal-particle" composite skeleton, reduce structural defects caused by the directional growth of phosphogypsum crystals, and improve the overall integrity of the cement.

[0009] As a preferred embodiment, the steel slag is solidified carbon steel slag powder, which is prepared by the following steps: drying the solidified carbon steel slag, grinding it, and then sieving it to remove particles, thereby obtaining solidified carbon steel slag powder; in the solidified carbon steel slag powder, the proportion of particles <45μm is ≥7%. This can maximize the cementitious activity of the steel slag powder and meet the fineness requirements of the filling cementitious material. Through the synergistic effect of "alkali activation-skeleton reinforcement-expansion regulation" in the phosphogypsum binder, the early strength, crack resistance, and environmental performance of the material can be significantly improved.

[0010] As a preferred embodiment, the fly ash is a grayish-black solid powder, with mullite and quartz as its main phases. The fly ash contains an amorphous aluminosilicate glassy structure, which can form CSH and CAH gels under alkaline activation conditions. Replacing part of silicate cement can not only save costs but also improve mechanical strength.

[0011] The present invention also provides a cemented backfill material, which is characterized in that it includes aggregate, cementing material and water; wherein the cementing material is the cementing material used for backfilling mining as described above.

[0012] As a preferred embodiment, the aggregate is modified phosphogypsum; the modified phosphogypsum is obtained by modifying phosphogypsum with a composite crystallization agent; the composite crystallization agent includes magnesium sulfate and ferric sulfate.

[0013] Further, the preparation process of the modified phosphogypsum includes the following steps: phosphogypsum is dried at 48-52℃ and then pulverized. The pH value is then adjusted to 6-7, followed by heating to 140-150℃ and holding for 25-35 minutes. After the holding period, a composite crystallizing agent accounting for 1-2% of the phosphogypsum weight is added for further treatment to obtain the modified phosphogypsum. The heating rate is 0.5-1.5℃ / min. The composite crystallizing agent can significantly optimize the mechanical properties and durability of phosphogypsum-based materials, providing an effective way to utilize phosphogypsum for high added value. The constant temperature and time are adjusted according to the crystal water content of the product, and the ratio and dosage of the composite crystallizing agent are adjusted according to the actual product morphology.

[0014] The preparation method of the above-mentioned cementitious filling material is characterized by including the following steps: 1) Weigh the cementitious materials and aggregates; 2) Mix and add water to prepare filling slurry with a slurry mass concentration of 68%; the slurry mortar ratio is 1:4.

[0015] The special feature of the above-mentioned cemented backfill material is that it is used for backfilling in mining.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a cementitious material and a cemented backfill material for backfilling mining, which can not only alleviate a series of safety problems caused by the stockpiling of phosphogypsum, but also provide effective support for the roof of the mining area, alleviate surface subsidence, and realize safe and efficient mining of phosphorus resources.

[0017] This invention utilizes solid wastes such as slag, steel slag, and fly ash to partially replace cement in the modification of phosphogypsum fillers. This not only promotes the application of phosphogypsum-bonded filler technology but also reduces material costs. Furthermore, it effectively addresses the problems of poor solidification of pollutants and high costs associated with using cement as a binder. This invention uses phosphogypsum as a raw material and solid wastes such as slag, steel slag, and fly ash as modifiers to prepare high-strength gypsum, which significantly improves the compressive strength of phosphogypsum fillers. Finally, this invention proposes a method for applying carbon-fixed steel slag powder, which can effectively promote steel slag carbon fixation technology. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1 A cementitious material for backfilling mining includes cement, slag powder, steel slag and fly ash; the components and their mass percentages are as follows: cement 42%, slag powder 10.5%, steel slag 17.5%, and fly ash 30%.

[0020] The cement is 32.5M ordinary Portland cement. The slag is a grayish-white powder. The slag powder contains a large amount of amorphous glassy phase mainly composed of CaO, Al2O3 and SiO2, and a small amount of weak crystals. The contents of CaO, Al2O3 and SiO2 in the slag powder are 39.99%, 0.74% and 7.50%, respectively.

[0021] The steel slag is carbon-fixed steel slag powder, and its preparation method includes the following steps: drying the carbon-fixed steel slag to constant weight and then grinding it, followed by sieving to remove particles, thereby obtaining carbon-fixed steel slag powder; in the carbon-fixed steel slag powder, the proportion of particles with a size <45μm is ≥7%.

[0022] Fly ash is a grayish-black solid powder, with mullite and quartz as its main phases.

[0023] A cementitious filler material includes aggregate and the aforementioned cementitious material, with mass percentages of 60% and 40%, respectively. The aggregate is modified phosphogypsum. The preparation process of the modified phosphogypsum includes the following steps: taking phosphogypsum, drying it at 50°C and then pulverizing it, then adjusting the pH value to 6-7, then heating it to 145°C and holding it for 30 minutes, then adding 0.5% ferric sulfate and 1% magnesium sulfate by weight of the phosphogypsum as a composite crystallizing agent and holding it for 30 minutes to obtain modified phosphogypsum; wherein, the heating rate is 1°C / min.

[0024] The preparation method of this cementitious filling material includes the following steps: 1) Weigh the cementitious materials and aggregates; 2) Mix and add water to prepare filling slurry with a slurry mass concentration of 68% and a mortar-to-material ratio of 1:4.

[0025] Example 2 The difference between this embodiment and Embodiment 1 is that the components and their mass percentages in the cementitious material are as follows: cement 25.3%, slag powder 16.9%, steel slag 22.8%, and fly ash 35%.

[0026] Example 3 The difference between this embodiment and Embodiment 1 is that the components and their mass percentages in the cementitious material are as follows: cement 14.4%, slag powder 21.6%, steel slag 24%, and fly ash 40%.

[0027] Comparative Example 1 The difference between this comparative example and Example 1 is that the cementitious material contains only cement.

[0028] Performance Results After the cementitious filling material slurries of Examples 1-3 and Comparative Example 1 were prepared, they were poured evenly into a standard cylindrical mold of 50mm×100mm in 3-5 batches. To facilitate demolding, a layer of lubricating oil was evenly applied to the inside of the mold before pouring. After the slurry initially set, excess slurry on the upper surface of the sample was scraped off, so that the slurry inside the mold was flush with the mold. After curing in a natural environment for 3 days, the sample was demolded. The compressive strength of the cemented filling was tested, and the test results are shown in Table 1.

[0029] Table 1: Performance results of cementitious filling materials in Examples 1-3 and Comparative Example 1 As shown in Table 1, the compressive strength of the cemented backfill material using the present invention at 7 days and 28 days is increased by at least 80% and 114% respectively compared with the cemented backfill material using only cement as a cementing material. It has higher compressive strength than the traditional cemented backfill material and is suitable for the requirements of backfilling mining. In addition, the use of slag, steel slag and fly ash to replace cement effectively reduces costs.

[0030] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A cementitious material for backfilling in mining, characterized in that, It includes one or more of cement, slag powder, steel slag, and fly ash.

2. The cementitious material according to claim 1, characterized in that, The cementitious material comprises the following components by mass percentage: 14-42% cement, 10-25% slag powder, 17-25% steel slag, and 30-40% fly ash.

3. The cementitious material according to claim 1, characterized in that, The cement is 32.5M ordinary Portland cement.

4. The cementitious material according to any one of claims 1 to 3, characterized in that, The steel slag is solid carbon steel slag powder; the preparation method of the solid carbon steel slag powder includes the following steps: drying the solid carbon steel slag, grinding it, and then sieving it to remove particles, thereby obtaining solid carbon steel slag powder.

5. A cementitious filling material, characterized in that, It includes aggregates, cementitious materials and water; wherein the cementitious material is the cementitious material for backfilling mining as described in any one of claims 1 to 4.

6. The cemented filling material according to claim 5, characterized in that, The aggregate is modified phosphogypsum; the modified phosphogypsum is obtained by modifying phosphogypsum with a composite crystallization agent; the composite crystallization agent includes magnesium sulfate and ferric sulfate.

7. The cemented filling material according to claim 6, characterized in that, The preparation process of the modified phosphogypsum includes the following steps: take phosphogypsum, dry it at 48~52℃ and then pulverize it, then adjust the pH value to 6~7, then heat it to 140~150℃, add a composite crystallizing agent accounting for 1~2% of the weight of phosphogypsum for treatment, and obtain modified phosphogypsum; wherein, the heating rate is 0.5~1.5℃ / min.

8. A method for preparing the cemented filling material according to any one of claims 5 to 7, characterized in that, Includes the following steps: 1) Weigh the cementitious materials and aggregates; 2) Mix and add water to prepare filling slurry with a slurry mass concentration of 65~70%; the mortar-to-material ratio of the slurry is 1:3~5.

9. The application of the cementitious filling material according to any one of claims 5 to 7, characterized in that, Used for filling mining.

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