Alpha-like fresh semi-hydrated phosphogypsum retarder

Abstract

The invention relates to the technical field of ardealite retarders, in particular to an alpha-like fresh semi-hydrated ardealite retarder, which is prepared from the following raw materials in percentage by mass: 96 to 98 percent of fresh semi-hydrated ardealite and 2 to 4 percent of functional additive, the preparation method comprises the step of uniformly mixing the fresh semi-hydrated phosphogypsum and the functional additive. The alpha-type fresh semi-hydrated phosphogypsum is used as a main raw material, the retarding time is controlled by adjusting the mixing amount of sodium phosphate and tartaric acid, the retarding requirements of different types of cement can be met, and the application is wide; moreover, the retarder also has the characteristics of wide source, small additive dosage, simple preparation process, reinforcement modification on cement in the aspects of freezing resistance, water resistance and moisture resistance, and the like, and is beneficial to reducing the production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphogypsum retarders, and particularly to a pseudo-α type fresh hemihydrate phosphogypsum retarder. Background Art

[0002] A cement retarder is an admixture that can delay the hydration reaction of cement clinker, extend the setting time of cement building materials, keep the freshly mixed concrete plastic for a long time, facilitate pouring, and improve construction efficiency. Natural gypsum and desulfurized gypsum can be directly used as cement retarders. However, natural gypsum has been restrictively mined by the state, and its output cannot meet the demand of the cement industry. Desulfurized gypsum cannot meet the demand for retarders, and the cost of desulfurized gypsum is high. Therefore, it is necessary to develop a cement retarder with wide raw material sources and low production costs to meet the market demand.

[0003] Phosphogypsum is the fresh hemihydrate phosphogypsum waste residue discharged during the production of wet-process phosphoric acid by the dihydrate-hemihydrate process or the hemihydrate process. In recent years, the annual average discharge of phosphogypsum in China has exceeded 80 million tons. Due to insufficient comprehensive utilization of resources, a large amount of phosphogypsum is stacked, which not only occupies land resources but also poses potential ecological and environmental safety hazards. When directly using fresh hemihydrate phosphogypsum as a retarder, the cement has problems such as short initial setting time and long final setting time as well as low strength. Based on this, a pseudo-α type fresh hemihydrate phosphogypsum retarder is proposed. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a pseudo-α type fresh hemihydrate phosphogypsum retarder, which uses α type fresh hemihydrate phosphogypsum as the main raw material and controls the setting time by adjusting the dosages of sodium phosphate and tartaric acid, and can meet the retardation requirements of different types of cement.

[0005] To achieve the above object, the present invention provides the following technical solution: A pseudo-α type fresh hemihydrate phosphogypsum retarder, by mass percentage, comprises the following raw materials: 96-98% of fresh hemihydrate phosphogypsum and 2-4% of functional auxiliaries.

[0006] Preferably, the crystal of the fresh hemihydrate phosphogypsum is pseudo-α type.

[0007] Preferably, the functional auxiliaries are composed of sodium phosphate and tartaric acid.

[0008] Preferably, the mass ratio of sodium phosphate to tartaric acid is 1:(10-15).

[0009] Preferably, the functional additive is nano-silica coated with copolymer, and its preparation method is as follows: S1. Ultrasonically disperse nano-silica in deionized water to obtain a dispersion; S2. Add acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid to the dispersion, and stir and dissolve at 65 °C to obtain a solution; S3. Add ammonium persulfate to the solution, keep the temperature for 4 h, adjust the pH to neutral with 30 wt% sodium hydroxide solution, and then filter and freeze-dry to obtain the functional additive.

[0010] Preferably, in step S1, in the dispersion, the mass fraction of nano-silica is 5%.

[0011] Preferably, in step S2, in the solution, the total mass fraction of acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid is 3%; the mass ratio of acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid is 1:1.5:6.

[0012] Preferably, in step S3, the addition amount of ammonium persulfate is 2% of the total mass of acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid.

[0013] The present invention also provides a preparation method of a pseudo-α type fresh hemihydrate phosphogypsum retarder. The fresh hemihydrate phosphogypsum and the functional additive are uniformly mixed to obtain the pseudo-α type fresh hemihydrate phosphogypsum retarder.

[0014] The present invention provides a pseudo-α type fresh hemihydrate phosphogypsum retarder, which has the following beneficial effects compared with the prior art:

[0015] The present invention uses α type fresh hemihydrate phosphogypsum as the main raw material, and controls the setting time by adjusting the dosages of sodium phosphate and tartaric acid, which can meet the setting time requirements of different types of cement and has a wide application; moreover, the retarder also has the characteristics of wide source, less additive dosage and simple preparation process, which is beneficial to reducing production costs.

[0016] The present invention also formulates nano-silica coated with copolymer as the functional additive. The introduction of sulfonic acid groups and carboxyl groups on the surface of the nanoparticles delays the normal growth of Ca(OH)2 crystal nuclei and crystals through adsorption and complexation inhibition, and prolongs the cement hydration time; moreover, the nanoparticles are uniformly dispersed in the cement matrix, which can also improve the strength of cement products. Specific Embodiments

[0017] The following examples are used to illustrate the implementation manners of the present application in detail, so as to fully understand how the present application uses technical means to solve technical problems and achieve the realization process of technical effects and implement accordingly.

[0018] Example 1

[0019] A kind of α-type fresh hemihydrate phosphogypsum retarder, calculated by mass percentage, includes the following raw materials: 96% of fresh hemihydrate phosphogypsum with α-type crystals and 2% of functional additives.

[0020] Among them, the functional additives are composed of sodium phosphate and tartaric acid; and the mass ratio of sodium phosphate to tartaric acid is 1:10.

[0021] The preparation method of the above-mentioned α-type fresh hemihydrate phosphogypsum retarder: uniformly mix the fresh hemihydrate phosphogypsum and the functional additives, and you will get it.

[0022] Example 2

[0023] A kind of α-type fresh hemihydrate phosphogypsum retarder, calculated by mass percentage, includes the following raw materials: 98% of fresh hemihydrate phosphogypsum with α-type crystals and 2% of functional additives.

[0024] Among them, the functional additives are composed of sodium phosphate and tartaric acid; and the mass ratio of sodium phosphate to tartaric acid is 1:12.

[0025] The preparation method of the above-mentioned α-type fresh hemihydrate phosphogypsum retarder: uniformly mix the fresh hemihydrate phosphogypsum and the functional additives, and you will get it.

[0026] Example 3

[0027] A kind of α-type fresh hemihydrate phosphogypsum retarder, calculated by mass percentage, includes the following raw materials: 97% of fresh hemihydrate phosphogypsum with α-type crystals and 3% of functional additives.

[0028] Among them, the functional additives are composed of sodium phosphate and tartaric acid; and the mass ratio of sodium phosphate to tartaric acid is 1:15.

[0029] The preparation method of the above-mentioned α-type fresh hemihydrate phosphogypsum retarder: uniformly mix the fresh hemihydrate phosphogypsum and the functional additives, and you will get it.

[0030] Example 4

[0031] A kind of α-type fresh hemihydrate phosphogypsum retarder is basically the same as that in Example 3, the difference is that: the functional additive is nano-silica coated with copolymer, and its preparation method is as follows,

[0032] S1. Ultrasonically disperse the nano-silica in deionized water to obtain a dispersion; in the dispersion, the mass fraction of nano-silica is 5%.

[0033] S2. Add acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid to the dispersion according to the mass ratio of 1:1.5:6, and stir and dissolve at 65°C to obtain a solution; in the solution, the total mass fraction of acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid is 3%.

[0034] S3. Add ammonium persulfate to the dissolution solution, keep it warm for 4 h, adjust the pH to neutral with 30 wt% sodium hydroxide solution, and then obtain the functional auxiliary agent through filtration and freeze-drying. Among them, the addition amount of ammonium persulfate is 2% of the total mass of acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid.

[0035] Comparative Example 1

[0036] A kind of pseudo-α type fresh hemihydrate phosphogypsum retarder, calculated by mass percentage, includes the following raw materials: 97% of fresh hemihydrate phosphogypsum with pseudo-α type crystal and 3% of functional auxiliary agent.

[0037] Among them, the functional auxiliary agent is sodium phosphate.

[0038] The preparation method of the above-mentioned pseudo-α type fresh hemihydrate phosphogypsum retarder: uniformly mix fresh hemihydrate phosphogypsum and functional auxiliary agent, then it can be obtained.

[0039] Comparative Example 2

[0040] A kind of pseudo-α type fresh hemihydrate phosphogypsum retarder, calculated by mass percentage, includes the following raw materials: 97% of fresh hemihydrate phosphogypsum with pseudo-α type crystal and 3% of functional auxiliary agent.

[0041] Among them, the functional auxiliary agent is tartaric acid.

[0042] The preparation method of the above-mentioned pseudo-α type fresh hemihydrate phosphogypsum retarder: uniformly mix fresh hemihydrate phosphogypsum and functional auxiliary agent, then it can be obtained.

[0043] Comparative Example 3

[0044] A kind of pseudo-α type fresh hemihydrate phosphogypsum retarder, calculated by mass percentage, includes the following raw materials: 97% of fresh hemihydrate phosphogypsum with pseudo-α type crystal and 3% of functional auxiliary agent.

[0045] Among them, the functional auxiliary agent is composed of sodium phosphate and tartaric acid; and the mass ratio of sodium phosphate to tartaric acid is 1:5.

[0046] The preparation method of the above-mentioned pseudo-α type fresh hemihydrate phosphogypsum retarder: uniformly mix fresh hemihydrate phosphogypsum and functional auxiliary agent, then it can be obtained.

[0047] Comparative Example 4

[0048] A kind of pseudo-α type fresh hemihydrate phosphogypsum retarder, calculated by mass percentage, includes the following raw materials: 97% of fresh hemihydrate phosphogypsum with pseudo-α type crystal and 3% of functional auxiliary agent.

[0049] Among them, the functional auxiliary agent is composed of sodium phosphate and tartaric acid; and the mass ratio of sodium phosphate to tartaric acid is 1:20.

[0050] The preparation method of the above-mentioned α-type fresh hemihydrate phosphogypsum retarder: uniformly mix fresh hemihydrate phosphogypsum and functional additives, and that's it.

[0051] Performance testing

[0052] 1. Prepare Portland cement with the α-type fresh hemihydrate phosphogypsum retarder and fresh hemihydrate phosphogypsum in Examples 1-4 and Comparative Examples 1-4, where the dosage of the α-type fresh hemihydrate phosphogypsum retarder is 3% of the mass of Portland cement. Refer to the quality standard GB / T 21371-2019 "Industrial by-product gypsum used in cement" to detect the setting time and compressive strength of the above Portland cements. The specific results are shown in the following table.

[0053] Table 1 Performance of Portland cement

[0054]

[0055]

[0056] 2. Based on the α-type fresh hemihydrate phosphogypsum retarder in Example 3, control 97% of α-type fresh hemihydrate phosphogypsum and 3% of functional additives. By adjusting the proportion of sodium phosphate and tartaric acid in the functional additives and preparing the corresponding ordinary Portland cement, where the dosage of the α-type fresh hemihydrate phosphogypsum retarder is 3% of the mass of ordinary Portland cement, detect the setting time of each ordinary Portland cement. The specific results are shown in the following table.

[0057] Table 2 Setting time of ordinary Portland cement

[0058] Category Initial setting time Final setting time Cement type and retarding index Whether it meets the requirements Sodium phosphate : tartaric acid = 1:10 175 300 Ordinary Portland cement Meets the requirements Sodium phosphate : tartaric acid = 1:11 200 320 Ordinary Portland cement Meets the requirements Sodium phosphate : tartaric acid = 1:12 220 350 Ordinary Portland cement Meets the requirements Sodium phosphate : tartaric acid = 1:13 250 380 Ordinary Portland cement Meets the requirements Sodium phosphate : tartaric acid = 1:14 260 400 Ordinary Portland cement Meets the requirements Sodium phosphate : tartaric acid = 1:15 280 420 Ordinary Portland cement Meets the requirements

[0059] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A kind of α-type fresh hemihydrate phosphogypsum retarder, characterized in that, Comprising the following raw materials by mass percentage: 96 - 98% of fresh hemihydrate phosphogypsum, 2 - 4% of functional auxiliary agent.

2. The α-type fresh hemihydrate phosphogypsum retarder according to claim 1, characterized in that, The crystal of the fresh hemihydrate phosphogypsum is of the pseudo-α type.

3. The retarding agent for fresh hemihydrate phosphogypsum of the α-type according to claim 1, wherein The functional auxiliary agent is composed of sodium phosphate and tartaric acid.

4. The retarding agent for fresh hemihydrate phosphogypsum of the α-type according to claim 3, characterized in that, The mass ratio of the sodium phosphate to the tartaric acid is 1:(10 - 15).

5. The retarding agent for fresh hemihydrate phosphogypsum of the α-type according to claim 1, characterized in that, The functional auxiliary agent is nano-silica coated with copolymer, and its preparation method is as follows: S1. Ultrasonically disperse nano-silica in deionized water to obtain a dispersion liquid; S2. Add acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid to the dispersion liquid, and stir and dissolve at 65 °C to obtain a dissolved liquid; S3. Add ammonium persulfate to the dissolved liquid, keep warm for 4 h, adjust the pH to neutral with 30 wt% sodium hydroxide solution, and then obtain the functional auxiliary agent through filtration and freeze-drying.

6. The retarding agent for fresh hemihydrate phosphogypsum of the α-type according to claim 1, characterized in that, In step S1, in the dispersion liquid, the mass fraction of nano-silica is 5%.

7. The retarding agent for fresh hemihydrate phosphogypsum of the α-type class according to claim 1, wherein In step S2, in the dissolved liquid, the total mass fraction of acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid is 3%; the mass ratio of acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid is 1:1.5:

6.

8. The retarding agent for fresh hemihydrate phosphogypsum of the α-type according to claim 1, characterized in that, In step S3, the addition amount of ammonium persulfate is 2% of the total mass of acrylic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid.

9. The preparation method of the α-type fresh hemihydrate phosphogypsum retarder according to any one of claims 1-8, characterized in that, Uniformly mix the fresh hemihydrate phosphogypsum and the functional auxiliary agent to prepare a pseudo-α type fresh hemihydrate phosphogypsum retarder.

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