A phosphogypsum road base material and its preparation method

Abstract

This application relates to the field of road base materials, and specifically discloses a phosphogypsum road base material and a preparation method thereof. The phosphogypsum road base material is prepared from raw materials including the following parts by weight: 100 parts of phosphogypsum mixture, 0.2 - 0.4 part of binder, and 0.2 - 0.4 part of curing agent; wherein, the phosphogypsum mixture is prepared by mixing phosphogypsum lightweight aggregate and phosphogypsum powder in a weight ratio of (35 - 80):(65 - 20), and the phosphogypsum lightweight aggregate is obtained by mixing large-sized phosphogypsum particles with a particle size of 19 - 31.5 mm, medium-sized phosphogypsum particles with a particle size of 9.5 - 19 mm, and small-sized phosphogypsum particles with a particle size of 4.75 - 9.5 mm in a weight ratio of (3 - 4):2:(2 - 3). The phosphogypsum road base material provided by this application has good compressive, crack-resistant, frost-resistant, and water-resistant properties. Since the content of phosphogypsum in the road base material is higher than 90%, phosphogypsum is easy to recycle and reuse.

Description

Technical Field

[0001] This application relates to the field of road base materials, and particularly to a phosphogypsum road base material and a preparation method thereof. Background Art

[0002] Phosphogypsum is a solid waste generated in the wet-process phosphoric acid process. Its main component is calcium sulfate dihydrate, and it also contains incompletely decomposed phosphate rock, residual phosphoric acid, fluorides, organic matter, etc. The presence of fluorine and organic matter has the greatest impact on the resource utilization of phosphogypsum. The random discharge and accumulation of phosphogypsum seriously damage the ecological environment, not only polluting the groundwater resources but also causing waste of land resources.

[0003] The Chinese patent with the authorization announcement number CN102690098B proposes a road subgrade filler and a preparation method thereof, which is prepared from raw materials such as lime, fly ash, phosphogypsum and a stabilizer; the weight percentages of each raw material in lime, fly ash and phosphogypsum are: lime 4 - 15%, fly ash 30 - 50%, phosphogypsum 35 - 60%. While ensuring that the road subgrade filler has relatively high strength, the utilization of phosphogypsum is also realized.

[0004] Under normal circumstances, in order to save resources and protect the environment, the waste road base materials will be recycled after the road is damaged. The above-mentioned related technology uses lime as a cementitious material, and the phosphogypsum content in the road base material is less than 60%, which is not convenient for recycling phosphogypsum. If the phosphogypsum content in the road base material is increased to improve the recycling efficiency, the mechanical properties of the road base material are usually poor due to the relatively brittle texture of phosphogypsum itself. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the first object of this application is to provide a phosphogypsum road base material, which uses phosphogypsum itself as a cementitious material and has good compressive, crack-resistant, frost-resistant and water-resistant properties when used in road engineering; and the content of phosphogypsum in the road base material reaches more than 90%, which is easy to recycle.

[0006] The second object of this application is to provide a preparation method of a phosphogypsum road base material, the process of which is simple and easy to implement.

[0007] To achieve the above first object, this application provides the following technical solutions:

[0008] A phosphogypsum road base material, which is prepared from raw materials including the following parts by weight: 100 parts of phosphogypsum mixture, 0.2 - 0.4 parts of binder, and 0.2 - 0.4 parts of curing agent; wherein, the phosphogypsum mixture is prepared by mixing phosphogypsum lightweight aggregate and phosphogypsum powder in a weight ratio of (35 - 80):(65 - 20), and the phosphogypsum lightweight aggregate is obtained by mixing large-size phosphogypsum particles with a particle size of 19 - 31.5 mm, medium-size phosphogypsum particles with a particle size of 9.5 - 19 mm, and small-size phosphogypsum particles with a particle size of 4.75 - 9.5 mm in a weight ratio of (3 - 4):2:(2 - 3).

[0009] Further, the binder is water-based epoxy resin, and the curing agent is selected from one or more of polyetheramine, polyamide, and polyamine.

[0010] By adopting the above technical solution, a good gradation is achieved by combining phosphogypsum lightweight aggregate and phosphogypsum powder, and then the phosphogypsum particles are bonded by the binder and the curing agent. The obtained road base material has good mechanical properties, can meet the use requirements, and realizes the comprehensive utilization of phosphogypsum; in this application, phosphogypsum is used as a cementitious material, and the weight ratio of phosphogypsum in the road base material is higher than 90%, making phosphogypsum easy to recycle.

[0011] Further, the phosphogypsum powder is obtained by grinding modified phosphogypsum; the phosphogypsum lightweight aggregate is obtained by granulating and screening a mixture of modified phosphogypsum, water, and retarder in a weight ratio of 100:(25 - 40):(0.1 - 0.5); the modified phosphogypsum is obtained by calcining industrial phosphogypsum.

[0012] Further, the retarder is selected from one or more of sodium citrate, sodium polyphosphate, potassium tartrate, sodium acrylate, and borax.

[0013] By adopting the above technical solution, the modified phosphogypsum combines with water and hardens to form phosphogypsum lightweight aggregate, which serves as the aggregate of the phosphogypsum road base material; the retarder helps to slow down the hardening speed of phosphogypsum in water and avoid solidifying and forming in a short time.

[0014] Further, the raw materials for preparing the phosphogypsum road base material further include 1 - 2 parts by weight of fiber.

[0015] Further, the fiber is selected from one or more of mineral fiber, glass fiber, polyvinyl alcohol fiber, polypropylene fiber, and wood fiber.

[0016] By adopting the above technical solution, the fiber plays a restraining role on the components in the phosphogypsum road base material, which helps to improve the compressive, crack-resistant, frost-resistant, and water-resistant properties of the phosphogypsum road base material.

[0017] Furthermore, the raw materials for preparing the phosphogypsum road base material further include 1.8 - 2.2 parts by weight of sawdust mud, and the specific surface area of the sawdust mud is 300 - 700 ㎡ / kg.

[0018] By adopting the above technical solution, the sawdust mud fills the voids in the phosphogypsum road base material, improving the compactness of the phosphogypsum road base material and contributing to the improvement of the mechanical properties of the phosphogypsum road base material; at the same time, the sawdust mud is turned from waste into treasure, effectively utilizing the sawdust mud resources.

[0019] Furthermore, the raw materials for preparing the phosphogypsum road base material further include 0.18 - 0.22 parts by weight of chitosan.

[0020] By adopting the above technical solution, the combination of chitosan and sawdust mud forms a good grading with the phosphogypsum lightweight aggregate and the phosphogypsum powder, contributing to the improvement of the mechanical properties of the phosphogypsum road base material.

[0021] To achieve the above second object, the present application provides the following technical solution:

[0022] A preparation method of a phosphogypsum road base material, comprising the following steps:

[0023] S1. Prepare modified phosphogypsum: Calcinate industrial phosphogypsum at a temperature not lower than 120 °C for at least 10 min to obtain modified phosphogypsum;

[0024] S2. Prepare phosphogypsum lightweight aggregate: Mix the modified phosphogypsum obtained in step S1, water, and a retarder in a weight ratio of 100:(25 - 40):(0.1 - 0.5), granulate, and screen to obtain large-sized phosphogypsum particles with a particle size of 19 - 31.5 mm, medium-sized phosphogypsum particles with a particle size of 9.5 - 19 mm, and small-sized phosphogypsum particles with a particle size of 4.75 - 9.5 mm. Mix the large-sized phosphogypsum particles, the medium-sized phosphogypsum particles, and the small-sized phosphogypsum particles to obtain phosphogypsum lightweight aggregate;

[0025] S3. Prepare phosphogypsum powder: Grind the modified phosphogypsum obtained in step S1 to obtain phosphogypsum powder;

[0026] S4. Prepare phosphogypsum road base material: Mix the phosphogypsum lightweight aggregate obtained in step S2, the phosphogypsum powder obtained in step S3, and other raw materials evenly to obtain phosphogypsum road base material.

[0027] Preferably, in step S4, first mix the binder and the curing agent evenly, and then add the phosphogypsum lightweight aggregate obtained in step S2, the phosphogypsum powder obtained in step S3, and other raw materials, and mix evenly to obtain phosphogypsum road base material.

[0028] By adopting the above technical solution, first mix the binder and the curing agent evenly, and then add the phosphogypsum lightweight aggregate, phosphogypsum powder and other raw materials, which helps to make the bonding effect between phosphogypsum particles better, thereby improving the performance of the phosphogypsum road base material.

[0029] In summary, the present application includes the following beneficial technical effects:

[0030] 1. The present application provides a phosphogypsum road base material, which uses phosphogypsum as a cementitious material, combines phosphogypsum powder and phosphogypsum lightweight aggregates with different particle sizes to form a good gradation, and obtains a phosphogypsum road base material with good performance, realizing the comprehensive utilization of phosphogypsum; since the weight ratio of phosphogypsum in the phosphogypsum road base material is higher than 90%, phosphogypsum is easy to recycle;

[0031] 2. After adding fibers, sawdust mud, and chitosan, the components cooperate with each other to form a good gradation, which helps to improve the mechanical properties of the phosphogypsum road base material;

[0032] 3. The present application provides a preparation method of a phosphogypsum road base material, the steps are simple and easy to implement, and the prepared phosphogypsum road base material has good compressive, crack-resistant, freeze-resistant, and water-resistant properties. The unconfined compressive strength at 7 days reaches more than 13 MPa, and the dry shrinkage coefficient reaches 120×10 -6 Hereinafter, the compressive strength loss after 5 freeze-thaw cycles reaches less than 1%, the scouring mass loss reaches less than 1%, and the softening coefficient reaches 0.85; Specific Embodiments

[0033] The following further describes the present application in detail with reference to embodiments. The following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the following embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. The methods used, unless otherwise specified, are all conventional methods well known in the art. The consumables and reagents used, unless otherwise specified, are all commercially available. Unless otherwise stated, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0034] Examples 1-6

[0035] Examples 1-6 respectively provide a phosphogypsum road base material.

[0036] The differences between Examples 1-6 are as follows: the weight parts of the components in the phosphogypsum road base material are different, as shown in Table 1 specifically.

[0037] The preparation method of the phosphogypsum road base material is as follows:

[0038] 1) Preparation of modified phosphogypsum: Calcinate industrial phosphogypsum at 140 °C for 0.5 h to obtain modified phosphogypsum;

[0039] 2) Preparation of phosphogypsum lightweight aggregate: Mix the modified phosphogypsum obtained in step 1), water, and retarder in a weight ratio of 100:35:0.3, granulate, and screen to obtain large-sized phosphogypsum particles with a particle size of 19 - 31.5 mm, medium-sized phosphogypsum particles with a particle size of 9.5 - 19 mm, and small-sized phosphogypsum particles with a particle size of 4.75 - 9.5 mm. Mix the large-sized phosphogypsum particles, medium-sized phosphogypsum particles, and small-sized phosphogypsum particles in a weight ratio of 3.5:2:2.5 to obtain phosphogypsum lightweight aggregate;

[0040] 3) Preparation of phosphogypsum powder: Grind the modified phosphogypsum obtained in step 1) to obtain phosphogypsum powder;

[0041] 4) Preparation of phosphogypsum road base material: Mix the binder and curing agent, add the phosphogypsum lightweight aggregate obtained in step 2) and the phosphogypsum powder obtained in step 3), and mix evenly to obtain phosphogypsum road base material.

[0042] Among them, the binder is water-based epoxy resin, the curing agent is polyetheramine, and the retarder is sodium citrate.

[0043] The industrial phosphogypsum comes from the Huangmailing Phosphogypsum Yard in Dawu, Hubei.

[0044] Table 1 Weight parts of each component in the phosphogypsum road base material provided in Examples 1 - 6

[0045]

[0046] Examples 7 - 8

[0047] Examples 7 - 8 respectively provide a phosphogypsum road base material. The raw materials and preparation method refer to Example 3. The differences between Examples 7 - 8 and Example 3 are that in step 4), the weight parts of the binder and the curing agent are different, as shown in Table 2 specifically.

[0048] Table 2 Weight parts of each component in the phosphogypsum road base material provided in Examples 7 - 8

[0049]

[0050]

[0051] Examples 9 - 10

[0052] Examples 9 - 10 respectively provide a phosphogypsum road base material. The raw materials and preparation method refer to Example 3. The differences between Examples 9 - 10 and Example 3 are that in step 2), the weight fraction ratios of large - sized, medium - sized, and small - sized phosphogypsum particles in the phosphogypsum lightweight aggregate are different, as shown in Table 3 specifically.

[0053] Table 3 Weight fraction ratios of large - sized, medium - sized, and small - sized phosphogypsum particles in the phosphogypsum lightweight aggregate provided in Examples 9 - 10

[0054]

[0055] Examples 11 - 12

[0056] Examples 11 - 12 respectively provide a phosphogypsum road base material. The raw materials and preparation method refer to Example 3. The only difference between Examples 11 - 12 and Example 3 is that in step 2), among the raw materials for preparing the phosphogypsum lightweight aggregate, the weight fraction ratios of modified phosphogypsum, water, and retarder are different, as shown in Table 4 specifically.

[0057] Table 4 Weight fraction ratios of modified phosphogypsum, water, and retarder in the phosphogypsum lightweight aggregate provided in Examples 11 - 12

[0058] Embodiment Weight portion ratio of modified phosphogypsum, water and retarder in phosphogypsum lightweight aggregate 11 100:25:0.5 12 100:40:0.1

[0059] Example 13

[0060] Example 13 provides a phosphogypsum road base material. The raw materials and preparation method refer to Example 3. The only difference between Example 13 and Example 3 is that in step 4), 1.5 parts by weight of mineral fiber is further added.

[0061] Examples 14 - 16

[0062] Examples 14 - 16 respectively provide a phosphogypsum road base material. The raw materials and preparation method refer to Example 13. The differences between Examples 14 - 16 and Example 13 are that in step 4), one or both of sawdust mud and chitosan are further added, and the specific surface area of the sawdust mud is 500 ㎡ / kg, as shown in Table 5 specifically.

[0063] Table 5 Weight parts of each component in the phosphogypsum road base materials provided in Example 13, Examples 14 - 16

[0064]

[0065]

[0066] Example 17

[0067] Example 17 provides a phosphogypsum road base material. The raw materials and preparation method refer to Example 16. The difference between Example 17 and Example 16 is only that in step 4), the specific surface area of the sawdust is 300 ㎡ / kg.

[0068] Example 18

[0069] Example 18 provides a phosphogypsum road base material. The raw materials and preparation method refer to Example 16. The difference between Example 18 and Example 16 is only that in step 4), the specific surface area of the sawdust is 700 ㎡ / kg.

[0070] Comparative Example 1

[0071] Comparative Example 1 provides a phosphogypsum road base material. The raw materials and preparation method refer to Example 3. The difference between Comparative Example 1 and Example 3 is only that in step 4), the weight ratio of the phosphogypsum lightweight aggregate to the phosphogypsum powder is 30:70.

[0072] Comparative Example 2

[0073] Comparative Example 2 provides a phosphogypsum road base material. The raw materials and preparation method refer to Example 3. The difference between Comparative Example 2 and Example 3 is only that in step 3), the weight ratio of the large-sized phosphogypsum particles, medium-sized phosphogypsum particles, and small-sized phosphogypsum particles is 2:2:4.

[0074] Performance Testing

[0075] For the phosphogypsum road base materials provided in Examples 1 to 18 and Comparative Examples 1-2 of this application, the following performance tests were carried out according to the test methods in JTG E51-2009 "Test Procedures for Inorganic Binder Stabilized Materials in Highway Engineering":

[0076] Unconfined compressive strength: Tested according to T 0805-1994 "Test Method for Unconfined Compressive Strength of Inorganic Binder Stabilized Materials"; Dry shrinkage coefficient: Tested according to T 0854-2009 "Dry Shrinkage Test Method for Inorganic Binder Stabilized Materials";

[0077] Compressive strength loss after freeze-thaw: Tested according to T 0858-2009 "Freeze-Thaw Test Method for Inorganic Binder Stabilized Materials";

[0078] Scouring mass loss: Tested according to T 0860-2009 "Scouring Resistance Test Method for Inorganic Binder Stabilized Materials".

[0079] For the phosphogypsum road base materials provided in Examples 1 to 18 and Comparative Examples 1-2 of this application, the softening coefficient was tested according to the test method in JC / T698-2010 "Gypsum Blocks".

[0080] The test data is shown in Table 6.

[0081] Table 6 Test result data sheet of the unconfined compressive strength, dry shrinkage coefficient, compressive strength after 5 freeze-thaw cycles, compressive strength loss after 5 freeze-thaw cycles, scouring mass loss, and softening coefficient of Examples 1-18 and Comparative Examples 1-2

[0082] The present application will be described in detail below in combination with the test data provided in Table 6.

[0083] Examples 1-6 investigated the influence of the weight ratio of phosphogypsum lightweight aggregate to phosphogypsum powder in the phosphogypsum road base material on the performance of the phosphogypsum road base material. The results showed that when the weight ratio of phosphogypsum lightweight aggregate to phosphogypsum powder varied within the range of (35-80):(65-20), it had a slight influence on the performance of the phosphogypsum road base material, and Example 3 was relatively superior.

[0084] Compared with Example 3, in Comparative Example 1, when the weight ratio of phosphogypsum lightweight aggregate to phosphogypsum powder was outside the range of (35-80):(65-20), the performance of the phosphogypsum road base material deteriorated.

[0085] Taking Example 3 as a control, Examples 7-8 investigated the influence of the addition amounts of the binder and curing agent in the phosphogypsum road base material on the performance of the phosphogypsum road base material. The results showed that the addition amounts of the binder and curing agent had a slight influence on the performance of the phosphogypsum road base material, and Example 3 was relatively superior.

[0086] Taking Example 3 as a control, Examples 9-10 investigated the influence of the weight ratio of large-sized, medium-sized, and small-sized phosphogypsum particles in the phosphogypsum lightweight aggregate on the performance of the phosphogypsum road base material. The results showed that when the weight ratio of large-sized, medium-sized, and small-sized phosphogypsum particles varied within the range of (3-4):2:(2-3), it had a slight influence on the performance of the phosphogypsum road base material, and Example 3 was relatively superior.

[0087] Compared with Example 3, the performance of the phosphogypsum road base material in Comparative Example 2 deteriorated significantly, indicating that when the weight ratio of large-sized, medium-sized, and small-sized phosphogypsum particles in the phosphogypsum lightweight aggregate was outside the range of (3-4):2:(2-3), the large-sized, medium-sized, and small-sized phosphogypsum particles could not form a good gradation, which was not conducive to improving the performance of the phosphogypsum road base material.

[0088] Taking Example 3 as a control, Examples 11-12 investigated the influence of the weight ratios of various components in the phosphogypsum lightweight aggregate on the properties of the phosphogypsum road base material. The results showed that when the weight ratios of the modified phosphogypsum, water, and retarder in the phosphogypsum lightweight aggregate had a certain influence on the properties of the phosphogypsum road base material, and Example 3 was relatively better.

[0089] Based on Example 3, Example 13 added fibers. The results showed that after adding fibers, the compressive, crack-resistant, frost-resistant, and water-resistant properties of the phosphogypsum road base material were all improved. This was because the fibers played a constraining role on the components in the phosphogypsum road base material, thereby improving the mechanical properties of the phosphogypsum road base material.

[0090] Based on Example 13, Examples 14-16 added one or both of sawdust sludge and chitosan. The results showed that when only sawdust sludge or only chitosan was added, the properties of the phosphogypsum road base material were slightly improved; when both sawdust sludge and chitosan were added, the compressive, crack-resistant, frost-resistant, and water-resistant properties of the phosphogypsum road base material were significantly enhanced. This indicated that sawdust sludge and chitosan synergistically formed a good gradation with the phosphogypsum lightweight aggregate and phosphogypsum powder, which helped to improve the mechanical properties of the phosphogypsum road base material.

[0091] Taking Example 16 as a control, Examples 17-18 investigated the influence of the specific surface area of sawdust sludge on the properties of the phosphogypsum road base material. The results showed that changing the specific surface area of sawdust sludge had an impact on the properties of the phosphogypsum road base material. When the specific surface area of sawdust sludge was 500 ㎡ / kg, the synergistic effect between sawdust sludge and chitosan was better.

[0092] This specific embodiment is only an interpretation of the present application and is not a limitation thereof. Those skilled in the art can make modifications without creative contributions to this embodiment according to their needs after reading this specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A phosphogypsum road base material, characterized in that: The phosphogypsum road base material is prepared from the following raw materials by weight: 100 parts of phosphogypsum mixture, 0.2 - 0.4 parts of binder, 0.2 - 0.4 parts of curing agent; wherein, the phosphogypsum mixture is prepared by mixing phosphogypsum lightweight aggregate and phosphogypsum powder in a weight ratio of (35 - 80):(65 - 20), and the phosphogypsum lightweight aggregate is obtained by mixing large-size phosphogypsum particles with a particle size of 19 - 31.5 mm, medium-size phosphogypsum particles with a particle size of 9.5 - 19 mm, and small-size phosphogypsum particles with a particle size of 4.75 - 9.5 mm in a weight ratio of (3 - 4):2:(2 - 3), The raw materials for preparing the phosphogypsum road base material further include 1 - 2 parts by weight of fiber; The raw materials for preparing the phosphogypsum road base material further include 1.8 - 2.2 parts by weight of sawdust, and the specific surface area of the sawdust is 300 - 700 ㎡ / kg; The raw materials for preparing the phosphogypsum road base material further include 0.18 - 0.22 parts by weight of chitosan.

2. The phosphogypsum road base material according to claim 1, characterized in that: The phosphogypsum powder is obtained by grinding modified phosphogypsum; the phosphogypsum lightweight aggregate is obtained by mixing modified phosphogypsum, water, and retarder in a weight ratio of 100:(25 - 40):(0.1 - 0.5), followed by granulation and screening; the modified phosphogypsum is obtained by calcining industrial phosphogypsum.

3. The phosphogypsum road base material according to claim 1, characterized in that: The fiber is selected from one or more of mineral fiber, glass fiber, polyvinyl alcohol fiber, polypropylene fiber, and wood fiber.

4. The phosphogypsum road base material according to claim 2, characterized in that: The retarder is selected from one or more of sodium citrate, sodium polyphosphate, potassium tartrate, sodium acrylate, and borax.

5. The phosphogypsum road base material according to claim 1, characterized in that: The binder is water-based epoxy resin, and the curing agent is selected from one or more of polyetheramine, polyamide, and polyamine.

6. A preparation method of the phosphogypsum road base material according to any one of claims 1 - 5, characterized in that: It includes the following steps: S1. Prepare modified phosphogypsum: Calcinate industrial phosphogypsum at a temperature not lower than 120 °C for at least 10 min to obtain modified phosphogypsum; S2. Prepare phosphogypsum lightweight aggregate: Mix the modified phosphogypsum, water, and retarder obtained in step S1 in a weight ratio of 100:(25 - 40):(0.1 - 0.5), granulate, and screen to obtain large-size phosphogypsum particles with a particle size of 19 - 31.5 mm, medium-size phosphogypsum particles with a particle size of 9.5 - 19 mm, and small-size phosphogypsum particles with a particle size of 4.75 - 9.5 mm, and mix the large-size phosphogypsum particles, the medium-size phosphogypsum particles, and the small-size phosphogypsum particles to obtain phosphogypsum lightweight aggregate; S3. Prepare phosphogypsum powder: Grind the modified phosphogypsum obtained in step S1 to obtain phosphogypsum powder; S4. Preparation of phosphogypsum road base material: Mix the phosphogypsum lightweight aggregate obtained in step S2, the phosphogypsum powder obtained in step S3 and other raw materials to obtain the phosphogypsum road base material.

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