Modified phosphogypsum roadbed filler and application method thereof

Abstract

This invention relates to a modified phosphogypsum roadbed filler and its application method. The modified phosphogypsum roadbed filler comprises, by weight: 40-60 parts wet-discharged phosphogypsum, 40-60 parts washed sand filter cake, 8-20 parts slag powder, 0.5-1 parts silica fume, 3-6 parts cement, and 0.2-0.6 parts water-absorbing resin. This method allows for the direct use of wet-discharged phosphogypsum in the preparation of roadbed filler, resulting in a large processing capacity and a simple and convenient process.

Description

Technical Field

[0001] This invention relates to the field of building materials, and in particular to a modified phosphogypsum roadbed filler and its application method. Background Technology

[0002] Phosphogypsum is an acidic solid waste produced in the wet process of phosphoric acid production. Typically, about 5 tons of phosphogypsum are produced for every ton of phosphoric acid produced. It is grayish-white or grayish-black in color and its main component is calcium sulfate dihydrate. The impurities contained in it, such as fluoride and free phosphoric acid, can easily pollute water, air and soil.

[0003] Phosphogypsum is mainly used as a cement retarder and in the production of building materials such as gypsum board, gypsum blocks, high-strength gypsum powder, and dry-mixed mortar. A small portion is used as a cementitious material to replace cement in road construction (water-stabilized layers) and mine filling. Although phosphogypsum has many uses, it generally requires washing, sedimentation, dehydration, or years of aging before use, which reduces the moisture content and impurities such as phosphorus and fluorine in wet-discharged phosphogypsum. This has prevented the widespread adoption of these methods. Except in areas lacking natural gypsum, where phosphogypsum is a relatively good substitute, the utilization rate of phosphogypsum, an industrial byproduct of most phosphate chemical companies, is very low.

[0004] Currently, highway construction consumes a large amount of materials. Using phosphogypsum as a road construction material can, to some extent, absorb the stock of phosphogypsum and achieve certain economic benefits. It also aligns with the national economic development direction of energy conservation, emission reduction, and consumption reduction, and is of great significance for the rational utilization of resources and the sustainable development of the phosphate industry. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a modified phosphogypsum roadbed filler and its application method, addressing the shortcomings of existing technologies. This method can directly utilize wet-discharged phosphogypsum to prepare roadbed filler, which not only allows for large-scale disposal but also features a simple and convenient process.

[0006] The objective of this invention is achieved by at least one of the following technical solutions.

[0007] A modified phosphogypsum roadbed filler, wherein the modified phosphogypsum roadbed filler comprises, by weight: 40-60 parts wet-discharged phosphogypsum, 40-60 parts washed sand filter cake, 8-20 parts slag powder, 0.5-1 parts silica fume, 3-6 parts cement, and 0.2-0.6 parts water-absorbing resin.

[0008] Preferably, the moisture content of the wet-discharged phosphogypsum is 5%-35%.

[0009] Preferably, the washed sand filter cake is the residual waste residue precipitated by flocculant during the crushing process of manufactured sand or coarse aggregate.

[0010] Preferably, the flocculant is cationic polyacrylamide.

[0011] Preferably, the slag powder has an activity index of ≥95% after 28 days.

[0012] Preferably, the cement is P·O 42.5 cement.

[0013] Preferably, the specific surface area of ​​the silica fume is ≥1.2 m2 / g.

[0014] Preferably, the absorbent resin is an acrylic absorbent resin.

[0015] The application method of the modified phosphogypsum roadbed filler includes the following steps:

[0016] After thoroughly mixing wet phosphogypsum with washed sand filter cake, add water-absorbing resin, stir again, and let stand to obtain modified phosphogypsum.

[0017] Modified phosphogypsum is mixed with slag powder, silica fume and cement to obtain modified phosphogypsum roadbed filler.

[0018] The maximum dry density and corresponding optimum moisture content of the modified phosphogypsum roadbed filler were determined based on the compaction curve.

[0019] The modified phosphogypsum roadbed filler is spread and then compacted according to the maximum dry density.

[0020] Preferably, the delayed construction time of the modified phosphogypsum roadbed filler is ≤2h; the compaction degree of the modified phosphogypsum roadbed filler is 91-93%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) This invention co-processes wet-discharged phosphogypsum with washed sand filter cake. Since the washed sand filter cake carries more negative charge, it is easier to form hydrogen bonds to bridge water molecules, which can improve the hydrophilicity of phosphogypsum. On the other hand, the polyacrylamide in the washed sand filter cake will agglomerate the particles and make them settle quickly, and will also adsorb free inorganic phosphorus, thus solving the problem that wet-discharged phosphogypsum must be washed or stored for a long time before reuse.

[0023] 2) Wet phosphogypsum and washed sand filter cake are used together as roadbed filler. The washed sand filter cake has finer particles, higher viscosity and stronger adsorption, which not only improves the cohesiveness of modified phosphogypsum, but also has better water retention. This solves the problems of phosphogypsum roadbed filler being easily pushed away during compaction and water easily leaking out during over-compaction.

[0024] 3) The present invention also uses water-absorbing resin to quickly absorb excess water from modified phosphogypsum, thus avoiding environmental pollution. This water can provide internal curing for the hydration and hardening of slag powder, solving the problem of drying and cracking caused by the later shrinkage of roadbed filler. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below.

[0026] Example 1

[0027] This embodiment provides a modified phosphogypsum roadbed filler, which comprises, by weight: 40 parts wet-discharged phosphogypsum, 60 parts washed sand filter cake, 8 parts slag powder, 0.5 parts silica fume, 3 parts cement, and 0.2 parts water-absorbing resin.

[0028] The wet-discharged phosphogypsum has a water content of 25%.

[0029] The activity index of the slag powder after 28 days was 98%.

[0030] The specific surface area of ​​the silica ash is 1.2 m². 2 / g.

[0031] Among them, the sand filter cake is the residual mud left after the natural rock is crushed, the manufactured sand and stone are separated by washing and screening, the mud is settled by flocculant and then compressed by plate and frame filter press.

[0032] This embodiment also provides a method for applying the modified phosphogypsum roadbed filler, including the following steps:

[0033] S101. After thoroughly mixing wet phosphogypsum and washed sand filter cake, add water-absorbing resin and stir again for 5 minutes, then let stand for 1 hour to obtain modified phosphogypsum.

[0034] S102 is a modified phosphogypsum roadbed filler obtained by mixing modified phosphogypsum with slag powder, silica fume and cement.

[0035] S103, based on the compaction curve, the optimum moisture content and maximum dry density of the phosphogypsum-based roadbed filler were determined to be 14.5% and 1.89 g / cm³, respectively. 3 ;

[0036] S104, after the phosphogypsum-based roadbed filler is laid, it is compacted to a compaction degree of 92%.

[0037] Example 2

[0038] This embodiment provides a modified phosphogypsum roadbed filler, which comprises, by weight: 60 parts wet-discharged phosphogypsum, 40 parts washed sand filter cake, 20 parts slag powder, 1 part silica fume, 6 parts cement, and 0.6 parts water-absorbing resin.

[0039] The wet-discharged phosphogypsum has a water content of 25%.

[0040] The activity index of the slag powder after 28 days was 98%.

[0041] The specific surface area of ​​the silica ash is 1.2 m². 2 / g.

[0042] This embodiment also provides a method for applying the modified phosphogypsum roadbed filler, including the following steps:

[0043] S101. After thoroughly mixing wet phosphogypsum and washed sand filter cake, add water-absorbing resin and stir again for 5 minutes, then let stand for 1 hour to obtain modified phosphogypsum.

[0044] S102 is obtained by mixing modified phosphogypsum, slag powder, silica fume and cement to obtain phosphogypsum-based roadbed filler.

[0045] S103, the optimum moisture content and maximum dry density of the phosphogypsum-based roadbed filler were determined to be 13.2% and 1.74 g / cm³, respectively, based on the compaction curve. 3 ;

[0046] S104, after the phosphogypsum-based roadbed filler is laid, it is compacted to a compaction degree of 92%.

[0047] Example 3

[0048] This embodiment provides a modified phosphogypsum roadbed filler, which comprises, by weight: 50 parts wet-discharged phosphogypsum, 50 parts washed sand filter cake, 15 parts slag powder, 0.8 parts silica fume, 5 parts cement, and 0.4 parts water-absorbing resin.

[0049] The wet-discharged phosphogypsum has a water content of 25%.

[0050] The activity index of the slag powder after 28 days was 98%.

[0051] The specific surface area of ​​the silica ash is 1.2 m². 2 / g.

[0052] This embodiment also provides a method for applying the modified phosphogypsum roadbed filler, including the following steps:

[0053] S101. After thoroughly mixing wet phosphogypsum and washed sand filter cake, add water-absorbing resin and stir again for 5 minutes, then let stand for 1 hour to obtain modified phosphogypsum.

[0054] S102 is obtained by mixing modified phosphogypsum, slag powder, silica fume and cement to obtain phosphogypsum-based roadbed filler.

[0055] S103, the optimum moisture content and maximum dry density of the phosphogypsum-based roadbed filler were determined to be 13.8% and 1.82 g / cm³, respectively, based on the compaction curve. 3 ;

[0056] S104, after the phosphogypsum-based roadbed filler is laid, it is compacted to a compaction degree of 92%.

[0057] Comparative Example 1

[0058] This comparative example provides a modified phosphogypsum roadbed filler, which comprises, by weight, 100 parts wet-discharged phosphogypsum, 15 parts slag powder, 0.8 parts silica fume, 5 parts cement, and 0.4 parts water-absorbing resin.

[0059] The wet-discharged phosphogypsum has a water content of 25%.

[0060] The activity index of the slag powder after 28 days was 98%.

[0061] The specific surface area of ​​the silica ash is 1.2 m². 2 / g.

[0062] This comparative example also provides a method for applying the modified phosphogypsum roadbed filler, including the following steps:

[0063] S101, phosphogypsum-based roadbed filler is obtained by mixing phosphogypsum with slag powder, silica fume and cement.

[0064] S102, the optimum moisture content and maximum dry density of the phosphogypsum-based roadbed filler were determined to be 12.8% and 1.64 g / cm³, respectively, based on the compaction curve. 3 ;

[0065] S103, after the phosphogypsum-based roadbed filler is laid, it is compacted to a compaction degree of 92%.

[0066] In accordance with the relevant provisions of JTG E51-2009 "Test Procedures for Inorganic Binder Stabilized Materials in Highway Engineering", core samples were taken and subjected to 7-day unconfined compressive strength tests. The results are shown in Table 1.

[0067] Table 17d Unconfined compressive strength test results

[0068]

[0069]

[0070] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A modified phosphogypsum road base filler, characterized in that, The modified phosphogypsum roadbed filler comprises, by weight: 40-60 parts wet-discharged phosphogypsum, 40-60 parts washed sand filter cake, 8-20 parts slag powder, 0.5-1 parts silica fume, 3-6 parts cement, and 0.2-0.6 parts water-absorbing resin. The washed sand filter cake is the residual waste residue precipitated by flocculant during the crushing process of manufactured sand or coarse aggregate. The preparation method of the modified phosphogypsum roadbed filler is as follows: after thoroughly mixing the wet-discharged phosphogypsum and the washed sand filter cake, water-absorbing resin is added and stirred again, and then allowed to stand to obtain modified phosphogypsum; the modified phosphogypsum is then mixed with slag powder, silica fume, and cement to obtain the modified phosphogypsum roadbed filler.

2. The modified phosphogypsum roadbed filler as described in claim 1, characterized in that, The moisture content of the wet-extracted phosphogypsum is 5%-35%.

3. The modified phosphogypsum roadbed filler as described in claim 1, characterized in that, The flocculant is cationic polyacrylamide.

4. The modified phosphogypsum roadbed filler as described in claim 1, characterized in that, The activity index of the slag powder is ≥95% after 28 days.

5. The modified phosphogypsum roadbed filler as described in claim 1, characterized in that, The cement is P·O 42.5 cement.

6. The modified phosphogypsum roadbed filler as described in claim 1, characterized in that, The silica ash specific surface area is > 1.2 m 2 / g.

7. The modified phosphogypsum roadbed filler as described in claim 1, characterized in that, The absorbent resin is an acrylic absorbent resin.

8. The method of applying the modified phosphogypsum roadbed filler as described in any one of claims 1 to 7, characterized in that, Includes the following steps: After thoroughly mixing wet phosphogypsum with washed sand filter cake, add water-absorbing resin, stir again, and let stand to obtain modified phosphogypsum. Modified phosphogypsum is mixed with slag powder, silica fume and cement to obtain modified phosphogypsum roadbed filler. The maximum dry density and corresponding optimum moisture content of the modified phosphogypsum roadbed filler were determined based on the compaction curve. The modified phosphogypsum roadbed filler is spread and then compacted according to the maximum dry density.

9. The application method as described in claim 8, characterized in that, The construction delay time of the modified phosphogypsum subgrade filler is ≤2h; the compaction degree of the modified phosphogypsum subgrade filler is 91-93%.