Semi-hydrated-original phosphogypsum-based concrete composite material and preparation method thereof

Abstract

The present invention relates to the technical field of large-scale utilization of phosphogypsum resources, and in particular to a semi-hydrated, undisturbed phosphogypsum-based concrete composite material and a preparation method thereof. The present invention provides a semi-hydrated, undisturbed phosphogypsum-based concrete composite material and a preparation method thereof. The composite material comprises main raw materials, admixtures, and additives; the main raw materials include undisturbed phosphogypsum, semi-hydrated phosphogypsum, machine-made sand, gravel, cement, and water; the admixtures include quicklime and silica fume; and the admixtures include a retarder and a water reducer. The composite material has the characteristics of high comprehensive utilization rate of phosphogypsum, excellent material properties, simple production process, and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of large-volume utilization in resource utilization of phosphogypsum, and in particular to a semi-hydrated-original phosphogypsum-based concrete composite material and a preparation method thereof. Background Art

[0002] Phosphogypsum is a major byproduct of phosphoric acid and phosphate fertilizer production. Annual production in China and globally is enormous, yet its comprehensive utilization rate is low. This results in significant stockpiles, occupies significant land resources, and causes environmental pollution, harming ecosystems. Therefore, effectively utilizing phosphogypsum, a solid waste from the phosphorus industry, and achieving its comprehensive resource utilization has become a critical issue that needs to be addressed.

[0003] Raw phosphogypsum, primarily composed of calcium sulfate dihydrate (CaSO4·2H2O), lacks inherent gelling properties and contains significant amounts of impurities such as fluoride, eutectic phosphorus, and organic matter, further impacting the performance of phosphogypsum-based composites. This is the primary reason for its limited utilization. However, by modifying raw phosphogypsum, such as by high-temperature dehydration to form hemihydrate phosphogypsum (CaSO4·0.5H2O), its gelling properties can be significantly enhanced, thereby improving the overall performance of the composite material.

[0004] In recent years, experts and scholars have achieved numerous research results in the comprehensive resource utilization of phosphogypsum. These include phosphogypsum-based cementitious materials and phosphogypsum-based concrete. However, most studies still face challenges such as low phosphogypsum utilization rates and complex preparation processes, making it difficult to meet the needs of large-scale, high-value-added resource utilization of phosphogypsum.

[0005] Therefore, providing a phosphogypsum-based concrete composite material that is simple to prepare, has excellent performance, and is low in cost is of great significance for reducing environmental pollution and realizing the resource utilization of original phosphogypsum. Summary of the Invention

[0006] The purpose of the present invention is to provide a semi-hydrated-original phosphogypsum-based concrete composite material and a preparation method thereof, so as to solve the technical problems in the prior art of low comprehensive utilization rate of phosphogypsum, complex preparation process and poor environmental friendliness.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a semi-hydrated-original phosphogypsum-based concrete composite material, comprising a main raw material, an admixture and an additive;

[0009] The main raw materials include original phosphogypsum, hemihydrate phosphogypsum, machine-made sand, crushed stone, cement and water;

[0010] The external admixtures include quicklime and silica fume;

[0011] The admixtures include a retarder and a water reducer.

[0012] Furthermore, the mass ratio of water, cementitious material, machine-made sand and crushed stone is 1:2-3:4.5-5:6-7;

[0013] The cementitious material comprises original phosphogypsum, hemihydrated phosphogypsum and cement, and the mass ratio of the sum of the mass of the original phosphogypsum and the hemihydrated phosphogypsum to the mass of the cement is 80-95:5-20.

[0014] Furthermore, the mass ratio of original phosphogypsum to hemihydrate phosphogypsum in the concrete composite material is 0.1-20:80-100.

[0015] Furthermore, the mass of quicklime is 2-8% of the total mass of the original phosphogypsum and hemihydrate phosphogypsum, and the mass of silica fume is 6-10% of the total mass of the original phosphogypsum, hemihydrate phosphogypsum and cement.

[0016] Furthermore, the water reducer is a melamine water reducer, and the retarder is a powdered gypsum retarder.

[0017] Furthermore, the mass of the water reducer is 1-7% of the total mass of the cementitious material, and the mass of the retarder is 0.1-3% of the mass of the hemihydrate phosphogypsum.

[0018] Furthermore, the particle size of the original phosphogypsum is ≤0.15 mm;

[0019] The preparation method of the hemihydrate phosphogypsum comprises: sequentially crushing, calcining and aging the original phosphogypsum to obtain the hemihydrate phosphogypsum;

[0020] The calcination temperature is 155-165° C., the calcination time is 1.5-2.5 hours, the aging time is 5-10 days, and the particle size of the hemihydrate phosphogypsum is ≤0.15 mm.

[0021] The present invention provides a method for preparing a semi-hydrated-original phosphogypsum-based concrete composite material, comprising the following steps:

[0022] Step 1) mixing raw phosphogypsum, hemihydrate phosphogypsum, machine-made sand, crushed stone, cement, quicklime, silica fume, a water reducer, a retarder and water to obtain a composite slurry;

[0023] Step 2) curing the composite slurry to obtain a semi-hydrated-original phosphogypsum-based concrete composite material.

[0024] Furthermore, in step 1), the mixing speed is 30 to 50 r / min, and the mixing time is 3 to 6 minutes.

[0025] Furthermore, in the composite slurry of step 2), the water-binder ratio is 0.33 to 0.5.

[0026] The beneficial effects of the present invention are as follows:

[0027] (1) The present invention utilizes the superior gelling properties of hemihydrate phosphogypsum obtained after high-temperature pretreatment to prepare a phosphogypsum-based concrete composite material, which has high later strength and excellent performance.

[0028] (2) The present invention uses quicklime as a neutralizing agent, which has outstanding effects and simple processes; a small amount of silica fume is used as an external admixture to prepare phosphogypsum-based concrete composite materials, and the mechanical performance indicators are significantly improved.

[0029] (3) The water-reducing agent used in the present invention effectively reduces the water-cement ratio of the slurry, thereby improving the mechanical performance index of the matrix and improving the fluidity of the slurry; the retarder delays the setting time of the slurry, so that the slurry has certain working performance.

[0030] (4) The present invention utilizes semi-hydrated-original phosphogypsum to prepare phosphogypsum-based concrete composite materials, thereby realizing the utilization of a large amount of phosphogypsum, effectively alleviating the pressure on the resource utilization of phosphogypsum, and having significant environmental value.

[0031] (5) The semi-hydrated-original phosphogypsum-based concrete composite material provided by the present invention only requires natural curing, and no secondary pollutants are discharged during the entire process, which saves energy and reduces emissions. The production process is simple and has high green production value. DETAILED DESCRIPTION

[0032] The present invention provides a semi-hydrated-original phosphogypsum-based concrete composite material, comprising a main raw material, an admixture and an additive;

[0033] The main raw materials include original phosphogypsum, hemihydrate phosphogypsum, machine-made sand, crushed stone, cement and water;

[0034] The external admixtures include quicklime and silica fume;

[0035] The admixtures include a retarder and a water reducer.

[0036] In the present invention, the mass ratio of water, cementitious material, machine-made sand and crushed stone is 1:2-3:4.5-5:6-7, preferably 1:2.78:4.85:6.97;

[0037] The cementitious material includes original phosphogypsum, hemihydrate phosphogypsum and cement. The mass ratio of the sum of the mass of the original phosphogypsum and hemihydrate phosphogypsum to the mass of the cement is 80-95:5-20, preferably 82-90:10-18, and more preferably 85:15.

[0038] In the present invention, the mass ratio of original phosphogypsum to hemihydrate phosphogypsum in the concrete composite material is 0.1-20:80-100, preferably 15:85.

[0039] In the present invention, the mass of quicklime is 2-8% of the total mass of original phosphogypsum and hemihydrate phosphogypsum, preferably 4%, and the mass of silica fume is 6-10% of the total mass of original phosphogypsum, hemihydrate phosphogypsum and cement, preferably 7%.

[0040] In the present invention, the quicklime is commercially available common quicklime, which is in the form of a white powder. The quicklime can neutralize the acidic soluble impurities in phosphogypsum, improving the hydration properties of the phosphogypsum cementitious material. The silica fume is commercially available common silica fume, which is in the form of a gray powder. Silica fume has excellent micro-aggregate filling and pozzolanic effects, effectively improving the matrix strength of phosphogypsum-based concrete composites.

[0041] In the present invention, the water reducer is BASF F10 melamine water reducer, which is in the form of white crystalline particles; the retarder is a powdered gypsum retarder, which is in the form of white powder.

[0042] In the present invention, the mass of the water reducer is 1-7% of the total mass of the cementitious material, preferably 2-5%, more preferably 3%, and the mass of the retarder is 0.1-3% of the mass of the hemihydrate phosphogypsum, preferably 0.3-2%, more preferably 0.5%.

[0043] In the present invention, the particle size of the original phosphogypsum is ≤0.15 mm, preferably obtained by crushing and naturally air-drying to remove free water and then passing through a 0.15 mm sieve;

[0044] The preparation method of the hemihydrate phosphogypsum comprises: crushing, calcining and aging the original phosphogypsum in sequence to obtain the hemihydrate phosphogypsum;

[0045] The calcination temperature is 155-165° C., preferably 160° C., the calcination time is 1.5-2.5 hours, preferably 2 hours, the aging time is 5-10 days, preferably 7 days, and the particle size of the hemihydrate phosphogypsum is ≤0.15 mm.

[0046] The present invention provides a method for preparing a semi-hydrated-original phosphogypsum-based concrete composite material, comprising the following steps:

[0047] Step 1) mixing raw phosphogypsum, hemihydrate phosphogypsum, machine-made sand, crushed stone, cement, quicklime, silica fume, a water reducer, a retarder and water to obtain a composite slurry;

[0048] Step 2) curing the composite slurry to obtain a semi-hydrated-original phosphogypsum-based concrete composite material.

[0049] In the present invention, the mixing speed in step 1) is 30 to 50 r / min, preferably 45 r / min, and the mixing time is 3 to 6 min, preferably 4 to 5 min, and more preferably 4.5 min.

[0050] In the present invention, in the composite slurry of step 2), the water-binder ratio is 0.33 to 0.5, preferably 0.36.

[0051] In the present invention, the composite slurry is molded, vibrated, and surface-smoothed, and then demolded after being cured for 72 hours. The composite slurry is then placed under natural conditions for curing. After curing for 28 days, a semi-hydrated-original phosphogypsum-based concrete composite material is obtained.

[0052] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] In an embodiment of the present invention:

[0054] The machine-made sand was taken from the material yard of Guizhou Industrial Investment High-tech Co., Ltd. in Huaxi District, and its fineness modulus was 3.69.

[0055] The crushed stone was taken from the crushed stone particles in the material yard of Guizhou Industrial Investment High-tech Co., Ltd. in Huaxi District, with a particle size range of 2.36 to 26.5 mm.

[0056] The quicklime used was produced by Sichuan Yibin Chuanshi Trading Co., Ltd.

[0057] The silica fume is made of high-quality microsilica powder produced by Baichuan Environmental Protection Engineering Co., Ltd. in Gongyi City, Henan Province.

[0058] The water reducer used is BASF F10 melamine water reducer produced by Shanghai Chenqi Chemical Technology Co., Ltd.

[0059] The retarder used is a protein gypsum retarder produced by Shanghai Chenqi Chemical Technology Co., Ltd.

[0060] The water used was tap water from the Civil Engineering Laboratory of Guizhou University.

[0061] In the composite slurry, the water-binder ratio is 0.36.

[0062] Example 1

[0063] A semi-hydrated-original phosphogypsum-based concrete composite material, comprising a main raw material, an admixture and an additive;

[0064] The main raw materials include original phosphogypsum, hemihydrate phosphogypsum, machine-made sand, crushed stone, cement and water;

[0065] The external admixtures include quicklime and silica fume;

[0066] Admixtures include retarders and water reducers.

[0067] The mass ratio of water, cementitious materials, machine-made sand and gravel is 1:2.78:4.85:6.97; the cementitious materials include original phosphogypsum, hemihydrated phosphogypsum and cement. The mass ratio of the sum of the mass of original phosphogypsum and hemihydrated phosphogypsum to cement is 95:5, and the mass ratio of original phosphogypsum and hemihydrated phosphogypsum is 15:85.

[0068] The mass of quicklime is 4% of the total mass of original phosphogypsum and hemihydrate phosphogypsum, and the mass of silica fume is 7% of the total mass of original phosphogypsum, hemihydrate phosphogypsum and cement.

[0069] The mass of the water reducer is 3% of the total mass of the cementitious material.

[0070] The mass of the retarder is 0.5% of the total mass of the hemihydrate phosphogypsum.

[0071] The original phosphogypsum is obtained by crushing and naturally air-drying to remove free water and then passing through a 0.15 mm diameter sieve. The main component is calcium sulfate dihydrate (CaSO4·2H2O).

[0072] Hemihydrate phosphogypsum is obtained by calcining original phosphogypsum at 160℃ for 2h and then aging it in natural state for 7d. Its main component is CaSO4·0.5H2O.

[0073] The original phosphogypsum, hemihydrated phosphogypsum, machine-made sand, crushed stone, quicklime, silica fume, water reducer and retarder were mixed at a rotation speed of 45 r / min for 1 min, and then water was added and mixed for 3.5 min to obtain a composite slurry; the composite slurry was molded and vibrated, and the surface was leveled. After being cured in the mold for 72 hours, the mold was removed and placed under natural conditions for curing at a natural curing temperature of 23°C and a humidity of 80%. The semi-hydrated-original phosphogypsum-based concrete composite material was obtained after curing for 28 days.

[0074] Example 2

[0075] Different from Example 1, in this embodiment, the mass ratio of the sum of the mass of the original phosphogypsum and the hemihydrate phosphogypsum to the mass of the cement is 90:10.

[0076] Example 3

[0077] Different from Example 1, in this embodiment, the mass ratio of the sum of the mass of the original phosphogypsum and the hemihydrate phosphogypsum to the mass of the cement is 85:15.

[0078] Example 4

[0079] Different from Example 1, in this embodiment, the mass ratio of the sum of the mass of the original phosphogypsum and the hemihydrate phosphogypsum to the mass of the cement is 80:20.

[0080] Example 5

[0081] Different from Example 1, in this embodiment, the mass ratio of the sum of the mass of original phosphogypsum and hemihydrate phosphogypsum to cement is 85:15, and the mass ratio of original phosphogypsum to hemihydrate phosphogypsum is 20:80.

[0082] Example 6

[0083] Different from Example 1, in this embodiment, the mass ratio of the sum of the mass of original phosphogypsum and hemihydrate phosphogypsum to cement is 85:15, and the mass ratio of original phosphogypsum to hemihydrate phosphogypsum is 10:90.

[0084] Example 7

[0085] Different from Example 1, in this embodiment, the mass ratio of the sum of the mass of original phosphogypsum and hemihydrate phosphogypsum to cement is 85:15, and the mass ratio of original phosphogypsum to hemihydrate phosphogypsum is 5:95.

[0086] Comparative Example 1

[0087] Different from Example 1, in this comparative example, the mass ratio of the sum of the mass of original phosphogypsum and hemihydrate phosphogypsum to cement is 85:15, and the mass ratio of original phosphogypsum to hemihydrate phosphogypsum is 0:100.

[0088] Comparative Example 2

[0089] Different from Example 1, in this comparative example, the mass ratio of water, cementitious material, machine-made sand and gravel is 1:2.78:4.10:6.97.

[0090] Comparative Example 3

[0091] Different from Example 1, in this comparative example, the mass ratio of water, cementitious material, machine-made sand and gravel is 1:2.78:3.88:5.58.

[0092] Comparative Example 4

[0093] Different from Example 1, in this comparative example, the mass ratio of water, cementitious material, machine-made sand and gravel is 1:2.78:3.28:5.58.

[0094] The performance indicators of the phosphogypsum-based concrete in Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table 1.

[0095] Table 1 Performance indexes of phosphogypsum-based concrete in Examples 1 to 7 and Comparative Examples 1 to 4

[0096]

[0097] As can be seen from the above examples, the present invention provides a semi-hydrated-undeformulated phosphogypsum-based concrete composite material and its preparation method. As shown in Table 1, Examples 1-7 and Comparative Example 1 demonstrate the effects of changes in the cement content and the relative content of undeformulated phosphogypsum and semi-hydrated phosphogypsum on the mechanical properties of the resulting semi-hydrated-undeformulated phosphogypsum-based concrete composite material. With increasing cement content or increasing the specific gravity of semi-hydrated phosphogypsum, the mechanical properties of the semi-hydrated-undeformulated phosphogypsum-based concrete composite material significantly improve. However, cement is less economical than phosphogypsum, and secondary processing of semi-hydrated phosphogypsum also requires a certain amount of energy. Examples 1-7 and Comparative Examples 2-4 all demonstrate the effects of the mass ratio of water, cementitious material, manufactured sand, and crushed stone on the mechanical properties of the resulting semi-hydrated-undeformulated phosphogypsum-based concrete composite material. As the mass ratio of the components in the raw material system changes, the mechanical properties of the semi-hydrated-undeformulated phosphogypsum-based concrete composite material are also affected. Through a large number of creative experiments, the present invention has determined the optimal mass ratio of water, cementitious material, manufactured sand, and crushed stone. The semi-hydrated-original phosphogypsum-based concrete composite material provided by the present invention has excellent mechanical properties, a low-cost preparation method, realizes resource utilization of phosphogypsum, and is environmentally friendly.

[0098] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A semi-hydrated-original phosphogypsum-based concrete composite material, characterized in that: Including main raw materials, admixtures and additives; The main raw materials include original phosphogypsum, hemihydrate phosphogypsum, machine-made sand, crushed stone, cement and water; The external admixtures include quicklime and silica fume; The admixtures include retarders and water reducers; The mass ratio of water, cementitious material, machine-made sand and gravel is 1:2-3:4.5-5:6-7; The cementitious material comprises original phosphogypsum, hemihydrate phosphogypsum and cement, and the mass ratio of the sum of the mass of the original phosphogypsum and hemihydrate phosphogypsum to the mass of the cement is 80-95:5-20; The mass ratio of original phosphogypsum to hemihydrate phosphogypsum in the concrete composite material is 0.1-20:80-100.

2. The semi-hydrated-original phosphogypsum-based concrete composite material according to claim 1, characterized in that: The mass of quicklime is 2~8% of the total mass of original phosphogypsum and hemihydrate phosphogypsum, and the mass of silica fume is 6~10% of the total mass of original phosphogypsum, hemihydrate phosphogypsum and cement.

3. The semi-hydrated-original phosphogypsum-based concrete composite material according to claim 2, characterized in that: The water reducing agent is a melamine water reducing agent, and the retarder is a powdered gypsum retarder.

4. The semi-hydrated-original phosphogypsum-based concrete composite material according to claim 3, characterized in that: The mass of the water reducer is 1-7% of the total mass of the cementitious material, and the mass of the retarder is 0.1-3% of the mass of the hemihydrate phosphogypsum.

5. The semi-hydrated-original phosphogypsum-based concrete composite material according to claim 4, characterized in that: The particle size of the original phosphogypsum is ≤0.15 mm; The preparation method of the hemihydrate phosphogypsum comprises: crushing, calcining and aging the original phosphogypsum in sequence to obtain the hemihydrate phosphogypsum; The calcination temperature is 155-165° C., the calcination time is 1.5-2.5 hours, the aging time is 5-10 days, and the particle size of the hemihydrate phosphogypsum is ≤0.15 mm.

6. The method for preparing the semi-hydrated-original phosphogypsum-based concrete composite material according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1) mixing raw phosphogypsum, hemihydrate phosphogypsum, machine-made sand, crushed stone, cement, quicklime, silica fume, water reducer, retarder and water to obtain a composite slurry; Step 2) curing the composite slurry to obtain a semi-hydrated-original phosphogypsum-based concrete composite material.

7. The method for preparing a semi-hydrated-original phosphogypsum-based concrete composite material according to claim 6, characterized in that: In step 1), the mixing speed is 30-50 r / min, and the mixing time is 3-6 min.

8. The method for preparing a semi-hydrated-original phosphogypsum-based concrete composite material according to claim 7, characterized in that: In the composite slurry of step 2), the water-binder ratio is 0.33-0.5.

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