Modified phosphogypsum cement stabilizing material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of inorganic building materials, in particular to a modified phosphogypsum cement stabilizing material as well as a preparation method and application thereof. The modified ardealite cement stabilizing material comprises ardealite, cement, sodium silicate, slaked lime and water, the mass ratio of the ardealite to the cement is (85-95): (5-15). The invention provides a modified ardealite cement stabilizing material and a preparation method and application thereof. The mechanical property of the material can be improved, the comprehensive utilization level and efficiency of ardealite resources in the highway field are improved, the road environment quality is improved, and green, efficient, high-value and large-scale utilization of ardealite is achieved. The problem of large-scale use of the ardealite can be solved, and the problem of material shortage of road construction sites can also be solved; secondary pollution can be reduced, a large amount of energy and cost are saved, and the method has important significance on large-scale low-cost harmless utilization of phosphogypsum.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic building materials, and in particular to a modified phosphogypsum cement stabilizing material and a preparation method and application thereof. Background Art

[0002] Phosphorus chemical production generates a large amount of industrial solid waste such as phosphorus tailings, phosphogypsum, and phosphorus slag. The increasing output and accumulation have seriously restricted the development of phosphorus chemical enterprises. Phosphogypsum is the industrial waste discharged by phosphorus chemical enterprises during the sulfuric acid extraction of phosphoric acid. Phosphogypsum is produced when sulfuric acid and phosphate rock react to generate phosphoric acid.

[0003] In recent years, the development and utilization technology of phosphogypsum resources has made certain research progress, mainly including the following aspects: First, in terms of gypsum building materials, phosphogypsum is used to prepare various gypsum products such as building gypsum; second, in terms of chemical industry, phosphogypsum is used to prepare sulfuric acid co-production cement, and phosphogypsum is used to prepare potassium sulfate, ammonium sulfate, and potassium ammonium sulfate compound fertilizers; third, in terms of agriculture, phosphogypsum can provide phosphorus, sulfur, calcium, magnesium, silicon, etc. required by agricultural crops; fourth, in terms of greenhouse gas solidification, phosphogypsum can be used to solidify carbon dioxide to achieve the purpose of carbon neutrality and carbon emission reduction; fifth, in terms of the preparation of environmental functional materials, phosphogypsum is used to prepare adsorption materials such as nano-hydroxyapatite; sixth, in terms of filling materials, phosphogypsum is used to fill roadbeds and mine goafs. However, the large-scale consumption technology of phosphogypsum is far from meeting the new production and accumulation of phosphogypsum. Therefore, it is very important and urgent to solve the large-scale accumulation and environmental problems of phosphogypsum, optimize the consumption of phosphogypsum in product applications, and further expand the scope of application.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The present invention provides a modified phosphogypsum cement stabilized material and a preparation method and application thereof, which are used to solve the above-mentioned problems, improve the mechanical properties of the material, improve the comprehensive utilization level and efficiency of phosphogypsum resources in the highway field, improve the road environmental quality, and realize the green, efficient, high-value and large-scale utilization of phosphogypsum; not only can the problem of large-scale use of phosphogypsum be solved, but also the problem of material shortage in highway construction sites can be solved; it can reduce secondary pollution and save a lot of energy and cost, which is of great significance for large-scale, low-cost and harmless utilization of phosphogypsum.

[0006] The specific technical solutions of the present invention are as follows: In a first aspect, the present invention first provides a modified phosphogypsum cement stabilization material, comprising: phosphogypsum, cement, sodium silicate, slaked lime and water; the mass ratio of the phosphogypsum to cement is 85~95:5~15.

[0007] The present invention finds that when the amount relationship of phosphogypsum and cement in the modified phosphogypsum cement stabilized material is controlled to be within the above range, the synergy of the CSH gel generated by the cement hydration reaction, the AFt hydration product and the hardening effect of the phosphogypsum itself can improve the mechanical properties of the material. Furthermore, after adding sodium silicate and slaked lime modifiers, the strength of the material is improved by promoting the hydration reaction to produce more hydration products, wherein sodium silicate mainly improves the early strength of the material, and slaked lime mainly improves the later strength of the material. The two reagents can play a synergistic role after compounding, which is beneficial to the improvement of the mechanical properties of the material.

[0008] In the present invention, the plasticity index of the phosphogypsum is 17.8.

[0009] Preferably, the moisture content of the attached water of the phosphogypsum is 8.5-10wt%; and the particle size of the phosphogypsum is ≤1.18mm.

[0010] In the present invention, the moisture content of the attached water of the phosphogypsum is controlled by drying. Preferably, when the drying temperature is 55-65°C, the moisture content of the phosphogypsum can be effectively controlled while avoiding damage to the internal structure of the phosphogypsum itself.

[0011] Further preferably, the pass rate of the phosphogypsum with a particle size of 1.18 mm to 0.6 mm is 96 to 99%, the pass rate of the particle size between 0.6 mm and 0.3 mm is 95 to 97%, the pass rate of the particle size between 0.3 mm and 0.15 mm is 93 to 96%, and the pass rate of the particle size between 0.15 mm and 0.075 mm is 86 to 90%.

[0012] Preferably, the modified phosphogypsum cement stabilizing material also includes an impurity remover.

[0013] In the present invention, the main chemical substances present in phosphogypsum are calcium sulfate dihydrate (CaSO4·2H2O) and silicon dioxide (SiO2), and contain a small amount of other impurity elements such as phosphorus and fluorine.

[0014] In the present invention, those skilled in the art can select conventional commercially available impurity removers as needed, which are not limited here. The aluminum salt in the impurity remover reacts with fluoride ions to form insoluble fluoride precipitates. This precipitation can fix the fluoride ions in the phosphogypsum in the sediment, reduce their migration and release, and thus reduce pollution to the surrounding environment.

[0015] Preferably, the modified phosphogypsum cement stabilized material comprises the following components in parts by weight: 85-95 parts of phosphogypsum, 5-15 parts of cement, 1-3 parts of sodium silicate, 1-3 parts of slaked lime, and 10-20 parts of water.

[0016] Further preferably, the modified phosphogypsum cement stabilized material comprises the following components in parts by weight: 85-95 parts of phosphogypsum, 5-15 parts of cement, 1-3 parts of sodium silicate, 1-3 parts of slaked lime, 10-20 parts of water; and 1-3 parts of an impurity remover.

[0017] Preferably, the specific surface area of ​​the cement is ≥380m2 / kg.

[0018] Preferably, the initial setting time of the cement is ≥210 min, and the final setting time is ≤270 min.

[0019] Preferably, the cement has a 3d compressive strength of ≥35Mpa, and a 28d compressive strength of ≥60Mpa.

[0020] Preferably, the cement has a 3d flexural strength of ≥6Mpa, and a 28d flexural strength of ≥9Mpa.

[0021] In a second aspect, the present invention provides a method for preparing the modified phosphogypsum cement stabilized material, comprising: S1: mixing sodium silicate, slaked lime and water to obtain a first mixture; S2: mixing the first mixture and the phosphogypsum to obtain a second mixture; S3: infiltrating the second mixture in a closed container, and mixing the infiltrated second mixture with cement and water to obtain a third mixture; S4: filling and statically pressing the third mixture to obtain a modified phosphogypsum cement stabilized test block; and then demolding the modified phosphogypsum cement stabilized test block after standing, and then putting it in for curing.

[0022] Preferably, in S1, the amount of water used accounts for 90-95 wt % of the total amount of water used; in S3, the amount of water used accounts for 5-10 wt % of the total amount of water used.

[0023] Preferably, the mixture in S1 is stirred for 3 to 5 minutes during mixing; the mixture in S2 is stirred for 5 to 8 minutes during mixing; and the soaking time in S3 is 12 to 24 hours, and the mixture is stirred for 5 to 8 minutes during mixing.

[0024] In a third aspect, the present invention provides the use of the modified phosphogypsum cement stabilized material in the base and subbase construction materials of expressways and / or first-class highways.

[0025] Based on the above technical solution, the beneficial effects of the present invention are: 1) The large-volume modified phosphogypsum cement stabilizing material of the present invention makes use of phosphogypsum as a resource, thereby protecting the ecological environment, saving natural resources, developing a low-carbon economy and achieving sustainable development.

[0026] 2) The large-volume modified phosphogypsum cement stabilization material of the present invention greatly solves the problem of large-scale use of phosphogypsum and the problem of material shortage in highway construction, realizes the recycling of solid waste, and reduces the amount of cement used in road construction, thereby reducing construction costs.

[0027] 3) The optimal 7d unconfined compressive strength of the high-volume modified phosphogypsum cement stabilized material of the present invention has reached 5Mpa, and can be applied to the base and subbase construction of expressways and first-class highways, and has strong market competitiveness. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Unless otherwise specified, the various raw materials used in the examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art. In the following examples, the plasticity index of the phosphogypsum in Examples 1 to 5 is 17.8, the moisture content of the attached water of the phosphogypsum is 9.81wt%, and the particle size of the phosphogypsum is ≤1.18mm.

[0030] In the following examples, the impurity remover is a WDCF type impurity remover.

[0031] Example 1

[0032] This embodiment first provides a large amount of modified phosphogypsum cement stabilized material, which is prepared from the following components in parts by weight: 90 parts of phosphogypsum, 10 parts of cement, 1 part of sodium silicate, 1 part of slaked lime, and 12 parts of water.

[0033] The preparation method thereof comprises the following steps: (1) First, mix 1 part of sodium silicate, 1 part of slaked lime and 11 parts of water and stir thoroughly for 3 to 5 minutes to obtain a mixture 1.

[0034] (2) Mixture 1 and 90 parts of phosphogypsum are then mixed and stirred for 5 to 8 minutes to obtain mixture 2.

[0035] (3) Place mixture 2 in a sealed container and soak for 12 to 24 hours before use.

[0036] (4) Mix the mixture 2 after the impregnation is completed with 10 parts of cement and 1 part of water and stir thoroughly for 5 to 8 minutes to obtain mixture 3.

[0037] (5) Mixture 3 is filled and statically pressed within 1 hour after the mixing is completed to obtain a stabilized test block of modified phosphogypsum cement with a large amount of modified phosphogypsum.

[0038] (6) The stabilized test blocks of modified phosphogypsum cement with a large amount of admixture obtained after static pressing were left to stand for 1 to 2 hours before demoulding and then placed in a curing box for curing for 7 days, 14 days, and 28 days.

[0039] Example 2

[0040] This embodiment first provides a large amount of modified phosphogypsum cement stabilized material, which is prepared from the following components in parts by weight: 90 parts of phosphogypsum, 10 parts of cement, 3 parts of sodium silicate, 1 part of slaked lime, and 12 parts of water.

[0041] The preparation method thereof comprises the following steps: (1) First, mix 3 parts of sodium silicate, 1 part of slaked lime and 11 parts of water and stir thoroughly for 3 to 5 minutes to obtain a mixture 1.

[0042] (2) Mixture 1 and 90 parts of phosphogypsum are then mixed and stirred for 5 to 8 minutes to obtain mixture 2.

[0043] (3) Place mixture 2 in a sealed container and soak for 12 to 24 hours before use.

[0044] (4) Mix the mixture 2 after the impregnation is completed with 10 parts of cement and 1 part of water and stir thoroughly for 5 to 8 minutes to obtain mixture 3.

[0045] (5) Mixture 3 is filled and statically pressed within 1 hour after the mixing is completed to obtain a stabilized test block of modified phosphogypsum cement with a large amount of modified phosphogypsum.

[0046] (6) The stabilized test blocks of modified phosphogypsum cement with a large amount of admixture obtained after static pressing were left to stand for 1 to 2 hours before demoulding and then placed in a curing box for curing for 7 days, 14 days, and 28 days.

[0047] Example 3

[0048] This embodiment first provides a large amount of modified phosphogypsum cement stabilized material, which is prepared from the following components in parts by weight: 90 parts of phosphogypsum, 10 parts of cement, 1 part of sodium silicate, 3 parts of slaked lime, and 12 parts of water.

[0049] The preparation method thereof comprises the following steps: (1) First, mix 1 part of sodium silicate, 3 parts of slaked lime and 11 parts of water and stir thoroughly for 3 to 5 minutes to obtain mixture 1.

[0050] (2) Mixture 1 and 90 parts of phosphogypsum are then mixed and stirred for 5 to 8 minutes to obtain mixture 2.

[0051] (3) Place mixture 2 in a sealed container and soak for 12 to 24 hours before use.

[0052] (4) Mix the mixture 2 after the impregnation is completed with 10 parts of cement and 1 part of water and stir thoroughly for 5 to 8 minutes to obtain mixture 3.

[0053] (5) Mixture 3 is filled and statically pressed within 1 hour after the mixing is completed to obtain a stabilized test block of modified phosphogypsum cement with a large amount of modified phosphogypsum.

[0054] (6) The stabilized test blocks of modified phosphogypsum cement with a large amount of admixture obtained after static pressing were left to stand for 1 to 2 hours before demoulding and then placed in a curing box for curing for 7 days, 14 days, and 28 days.

[0055] Example 4

[0056] This embodiment first provides a large amount of modified phosphogypsum cement stabilized material, which is prepared from the following components in parts by weight: 90 parts of phosphogypsum, 10 parts of cement, 2 parts of sodium silicate, 3 parts of slaked lime, and 12 parts of water.

[0057] The preparation method thereof comprises the following steps: (1) First, mix 2 parts of sodium silicate, 3 parts of slaked lime and 11 parts of water and stir thoroughly for 3 to 5 minutes to obtain mixture 1.

[0058] (2) Mixture 1 and 90 parts of phosphogypsum are then mixed and stirred for 5 to 8 minutes to obtain mixture 2.

[0059] (3) Place mixture 2 in a sealed container and soak for 12 to 24 hours before use.

[0060] (4) Mix the mixture 2 after the impregnation is completed with 10 parts of cement and 1 part of water and stir thoroughly for 5 to 8 minutes to obtain mixture 3.

[0061] (5) Mixture 3 is filled and statically pressed within 1 hour after the mixing is completed to obtain a stabilized test block of modified phosphogypsum cement with a large amount of modified phosphogypsum.

[0062] (6) The stabilized test blocks of modified phosphogypsum cement with a large amount of admixture obtained after static pressing were left to stand for 1 to 2 hours before demoulding and then placed in a curing box for curing for 7 days, 14 days, and 28 days.

[0063] Example 5

[0064] This embodiment first provides a large amount of modified phosphogypsum cement stabilized material, which is prepared from the following components in parts by weight: 90 parts of phosphogypsum, 10 parts of cement, 2 parts of sodium silicate, 3 parts of slaked lime, 1 part of impurity remover, and 12 parts of water.

[0065] The preparation method thereof comprises the following steps: (1) First, mix 2 parts of sodium silicate, 3 parts of slaked lime, 1 part of impurity remover and 11 parts of water and stir thoroughly for 3 to 5 minutes to obtain a mixture 1.

[0066] (2) Mixture 1 and 90 parts of phosphogypsum are then mixed and stirred for 5 to 8 minutes to obtain mixture 2.

[0067] (3) Place mixture 2 in a sealed container and soak for 12 to 24 hours before use.

[0068] (4) Mix the mixture 2 after the impregnation is completed with 10 parts of cement and 1 part of water and stir thoroughly for 5 to 8 minutes to obtain mixture 3.

[0069] (5) Mixture 3 is filled and statically pressed within 1 hour after the mixing is completed to obtain a stabilized test block of modified phosphogypsum cement with a large amount of modified phosphogypsum.

[0070] (6) The stabilized test blocks of modified phosphogypsum cement with a large amount of admixture obtained after static pressing were left to stand for 1 to 2 hours before demoulding and then placed in a curing box for curing for 7 days, 14 days, and 28 days.

[0071] Comparative Example 1

[0072] This embodiment provides a high-dosage phosphogypsum cement stabilized material, which differs from Embodiment 1 only in that the sodium silicate is replaced by an equal amount of cement, and the slaked lime is replaced by an equal amount of water.

[0073] Comparative Example 2

[0074] This embodiment provides a large amount of modified phosphogypsum cement stabilized material, which is different from Embodiment 1 only in that the sodium silicate is replaced by an equal amount of cement.

[0075] Comparative Example 3

[0076] This embodiment provides a large amount of modified phosphogypsum cement stabilized material, which is different from Embodiment 1 only in that the slaked lime is replaced by an equal amount of cement.

[0077] Test example

[0078] The present invention detects the mechanical properties of the modified phosphogypsum cement stabilized materials prepared in the above embodiments and comparative examples, and the detection process is carried out in accordance with the requirements of the unconfined compressive strength test of T0805-2024 in the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" (JTG 3441-2024).

[0079] Table 1 Unconfined compressive strength test results of the examples and comparative examples

[0080] As can be seen from Table 1, the high-volume modified phosphogypsum cement stabilized material provided by the present invention has an enhanced unconfined compressive strength as the curing period increases, and the differences between different mix ratios will also decrease as the curing period increases.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modified phosphogypsum cement stabilized material, characterized in that: include: Phosphogypsum, cement, sodium silicate, slaked lime and water; The mass ratio of the phosphogypsum to cement is 85-95:5-15.

2. The modified phosphogypsum cement stabilized material according to claim 1, characterized in that: The plasticity index of the phosphogypsum is ≥12.

3. The modified phosphogypsum cement stabilized material according to claim 1 or 2, characterized in that: The attached water content of the phosphogypsum is 8.5-10wt%; the particle size of the phosphogypsum is ≤1.18mm.

4. The modified phosphogypsum cement stabilized material according to claim 3, characterized in that: The moisture content of the attached water of the phosphogypsum is controlled by drying, and the drying temperature is 55-65°C.

5. The modified phosphogypsum cement stabilized material according to any one of claims 1 to 4, characterized in that: The modified phosphogypsum cement stabilizing material also includes an impurity remover.

6. The modified phosphogypsum cement stabilized material according to any one of claims 1 to 5, characterized in that: The invention comprises the following components in parts by weight: 5-95 parts of phosphogypsum, 5-15 parts of cement, 1-3 parts of sodium silicate, 1-3 parts of slaked lime, and 10-20 parts of water; Preferably, the modified phosphogypsum cement stabilized material comprises the following components in parts by weight: 85-95 parts of phosphogypsum, 5-15 parts of cement, 1-3 parts of sodium silicate, 1-3 parts of slaked lime, 10-20 parts of water; and 1-3 parts of an impurity remover.

7. The modified phosphogypsum cement stabilized material according to any one of claims 1 to 6, characterized in that: The specific surface area of ​​the cement is ≥380m 2 / kg.

8. The method for preparing the modified phosphogypsum cement stabilized material according to any one of claims 1 to 7, characterized in that: include: S1: Mix sodium silicate, slaked lime and water to obtain a first mixture; S2: Mix the first mixture and the phosphogypsum to obtain a second mixture; S3: Infiltrate the second mixture in a sealed container, and mix the infiltrated second mixture with cement and water to obtain a third mixture; S4: Fill and statically press the third mixture to obtain a modified phosphogypsum cement stabilized test block; then let the modified phosphogypsum cement stabilized test block stand for demoulding, and then put it in for curing.

9. The method for preparing the modified phosphogypsum cement stabilized material according to claim 8, characterized in that: In S1, the amount of water used accounts for 90~95wt% of the total water used; in S3, the amount of water used accounts for 5~10wt% of the total water used.

10. Use of the modified phosphogypsum cement stabilized material according to any one of claims 1 to 7 or the modified phosphogypsum cement stabilized material prepared by the preparation method according to claim 8 or 9 in the base and subbase construction materials of expressways and / or first-class highways.

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