Phosphorus building gypsum-based heavy plastering gypsum

Abstract

The invention provides phosphorus building gypsum based heavy plastering gypsum. The plastering gypsum is prepared from the following components in parts by mass: 450 to 475 parts of phosphorus building gypsum, 25 to 50 parts of cement, 20 to 30 parts of mineral admixture, 70 to 100 parts of filler, 380 to 400 parts of aggregate, 2 to 3 parts of cellulose ether, 1.5 parts of retarder, 5 to 7 parts of thixotropic agent and 0.5 to 1 part of plastic retaining agent. The phosphogypsum-based heavy plastering gypsum disclosed by the invention is long in operable time, high in strength after setting and hardening, and uniform in surface color.

Description

Technical Field

[0001] The present invention relates to the field of building materials, and particularly to a heavy plastering gypsum based on phosphogypsum. Background Art

[0002] Phosphogypsum is a by-product generated in the wet-process phosphoric acid industry. For every 1 ton of phosphoric acid produced, approximately 4 - 6 tons of phosphogypsum will be generated. The large-scale stacking of industrial by-product gypsum will bring a heavy burden to the environment and enterprises. At present, the annual output of phosphogypsum in China is huge, about 75 million tons, but the utilization rate is only 40%, far lower than 80% of desulfurized gypsum. Among them, the main reason is that phosphogypsum contains more impurities, resulting in relatively poor performance of calcined phosphogypsum, and its application and promotion are limited.

[0003] Phosphogypsum has strong acidity. When applied to gypsum mortar, alkaline materials must be added to adjust the system to alkaline, otherwise the functions of the added admixtures cannot be normally exerted, and mildew is likely to occur after setting and hardening. After adding alkaline materials such as cement and hydrated lime, the consistency of gypsum mortar will gradually increase, and the workability will become worse. The main reason is that the calcination of phosphogypsum is more difficult and the residual dihydrate phase is relatively high. The residual dihydrate phase will cause the setting speed of gypsum to accelerate and the slurry to thicken rapidly. Therefore, phosphogypsum-based mortar generally shows a relatively short workable time. Phosphogypsum also shows low strength, which is mainly related to the residual phosphoric acid, phosphates and fluorides in it.

[0004] Plastering gypsum is one of the most important application fields of building gypsum. Due to a series of disadvantages of phosphogypsum, its usage rate in plastering gypsum is not high. The present invention optimizes the proportion of plastering gypsum in response to the disadvantages of phosphogypsum, and significantly improves its performance. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a heavy plastering gypsum based on phosphogypsum, which has the characteristics of long workable time, high strength and no mildew phenomenon.

[0006] Specifically, the present invention is achieved through the following technical solutions:

[0007] A heavy plastering gypsum based on phosphogypsum, the plastering gypsum comprises the following components in parts by mass: 450 - 475 parts of phosphogypsum, 25 - 50 parts of cement, 20 - 30 parts of mineral admixture, 70 - 100 parts of filler, 380 - 400 parts of aggregate, 2 - 3 parts of cellulose ether, 1.5 parts of retarder, 5 - 7 parts of thixotropic agent, 0.5 - 1 part of plasticizer;

[0008] The retarder is a mixture of amino acid-based gypsum retarder, tartaric acid and sodium gluconate.

[0009] Furthermore, the mass ratio of the amino acid-based gypsum retarder, tartaric acid, and sodium gluconate is 5:2:3.

[0010] Furthermore, the amino acid-based gypsum retarder is of the wide pH applicability type, the tartaric acid is of the DL-type, with a fineness of 200 mesh, and the fineness of the sodium gluconate is 200 mesh.

[0011] Furthermore, the physical and mechanical properties of the phosphorus building gypsum meet the requirements of GB / T 9776-2008, and its strength grade is 3.0.

[0012] Furthermore, the cement is 42.5-grade or 52.5-grade portland cement;

[0013] The mineral admixture is ultrafine mineral powder with an activity grade of S105 and a specific surface area ≥ 600 m 2 / kg.

[0014] Furthermore, the filler is glass microspheres with a particle size range of 0.1 - 0.5 mm.

[0015] Furthermore, the aggregate is 40 - 140 mesh washed river sand with a mud content ≤ 3% and no flocculant.

[0016] Furthermore, the cellulose ether is instant hydroxypropyl methyl cellulose ether with a viscosity of 40000 - 100000 mPa.s.

[0017] Furthermore, the thixotropic agent is sodium polyacrylate with a molecular weight range of 2000 - 5000 and a fineness of 100 mesh.

[0018] Furthermore, the slump loss reducer is a slow-release polycarboxylate superplasticizer powder.

[0019] Compared with the related technologies, the phosphorus building gypsum-based heavy plastering gypsum provided by the present invention has the following beneficial effects:

[0020] In the present invention, the components of the phosphorus building gypsum-based heavy plastering gypsum are scientifically formulated and act synergistically. Among them, the three retarders are used in combination to delay the thickening phenomenon of the gypsum. Using low-molecular-weight sodium polyacrylate as the thixotropic agent, its thickening effect gradually weakens over time. The slow-release polycarboxylate superplasticizer plays a good role in controlling the thickening of the plastering gypsum. The selection and combination of the cementitious material, mineral admixture, filler, and aggregate take into account the workable time, strength, and constructability of the plastering gypsum.

[0021] In the present invention, a broad pH-applicable amino acid-based gypsum retarder is selected. Its retardation performance is less affected by the dosage of alkaline substances in the formulation and the pH of the system, which is beneficial to improving the stability of the setting time of plastering gypsum. DL-tartaric acid is selected. Compared with the commonly used L(+)-tartaric acid, the DL-tartaric acid has slightly better retardation performance, stronger anti-moisture absorption and caking resistance, and is also cheaper. 200-mesh tartaric acid and sodium gluconate are selected, which are easily mixed evenly with other powder materials during the production of plastering gypsum. In addition, when adding water and stirring, it can quickly dissolve in water and play a role rapidly.

[0022] The heavy plastering gypsum based on phosphogypsum in the present invention effectively extends the operable time without affecting the workability and sagging. After setting and hardening, the plastering gypsum has high strength and uniform surface color. Detailed implementation modes

[0023] The following combines with the specific implementation modes of the present invention to clearly and completely describe the technical solutions in the embodiments of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] A heavy plastering gypsum based on phosphogypsum provided by the present invention comprises the following components in parts by mass: 450-475 parts of phosphogypsum, 25-50 parts of cement, 20-30 parts of mineral admixture, 70-100 parts of filler, 380-400 parts of aggregate, 2-3 parts of cellulose ether, 1-1.5 parts of retarder, 5-7 parts of thixotropic agent, and 0.5-1 part of plasticizer.

[0025] The physical and mechanical properties of the phosphogypsum meet the requirements of GB / T 9776-2008. Preferably, in the specific implementation mode of the present invention, the highest strength grade of 3.0 is selected.

[0026] The cement is 42.5-grade or 52.5-grade Portland cement, which can adjust the pH of the mortar to alkaline and give full play to the functions of various admixtures. Under the same setting time, the higher the cement dosage, the shorter the corresponding operable time. When phosphogypsum and cement are used in combination, when the cement dosage is 5-10% of the total mass of the two, the strength of the composite cementitious system is the highest. Preferably, in the specific implementation mode of the present invention, the cement dosage is 5-10% of the total mass of phosphogypsum and cement.

[0027] The mineral admixture is ultra-fine mineral powder with an activity grade of S105 and a specific surface area ≥ 600m 2 / kg. The mineral powder can react with cement and gypsum to improve the strength of the composite cementitious system. Due to the high activity, large specific surface area and appropriate dosage of the mineral powder, it can participate in chemical reactions faster, improve the strength of the composite cementitious system, and largely reduce the formation of delayed ettringite, reducing the negative impact on the later strength. In addition, the ultra-fine mineral powder also optimizes the particle size distribution of the plastering gypsum, can fill the internal and surface pores, and makes the structure more dense.

[0028] The filler is glass microspheres with a particle size range of 0.1 - 0.5 mm. The glass microspheres are hollow spheres with high hardness and low water absorption. Without affecting the strength, they reduce the bulk density of the plastering gypsum and improve the workability.

[0029] The aggregate is 40 - 140 mesh washed river sand with a mud content of ≤ 3%. Compared with other types of sand, the shape of river sand is approximately spherical, with high hardness and relatively lower water absorption, which is beneficial to improving the workability and strength of the plastering gypsum. If a flocculant is used during the processing of the sand, it will increase the viscosity of the plastering gypsum and also extend the setting time to a certain extent.

[0030] The cellulose ether is a fast-dissolving type of hydroxypropyl methyl cellulose ether with a viscosity of 40000 - 100000 mPa.s. The fast-dissolving cellulose ether can quickly play its corresponding role. After the plastering gypsum is stirred, there is little or almost no undissolved cellulose ether, and it is not easy to continue increasing the viscosity of the slurry.

[0031] The retarder is a mixture of an amino acid-based gypsum retarder, tartaric acid and sodium gluconate, and the mass ratio of the three is 5:2:3. Among the three retarders, the amino acid-based gypsum retarder has the strongest retardation effect. Sodium gluconate can limit the nucleation effect of the residual dihydrate gypsum in the phosphorus building gypsum, weaken its accelerating effect, and prevent the slurry from thickening too quickly. The incorporated portland cement contains dihydrate gypsum, which has an accelerating and thickening effect on the phosphorus building gypsum, while tartaric acid has a relatively more significant restrictive effect on the externally added dihydrate gypsum. Therefore, in order to ensure that the plastering gypsum has sufficient workable time, three retarders are used simultaneously. Preferably, the amino acid-based gypsum retarder is a broad pH applicable type of amino acid-based gypsum retarder, and its retardation performance is less affected by the cement in the ratio. The manufacturer and model of the amino acid-based gypsum retarder used in the present invention are: ZJ-AG36 of Jiangsu Zhaojia Building Materials Technology Co., Ltd. Tartaric acid is of the DL-type with a fineness of 200 mesh, and the fineness of sodium gluconate is 200 mesh. Compared with the commonly used L+ type of tartaric acid, the DL-tartaric acid has slightly better retardation performance, stronger anti-moisture absorption and caking resistance, and a lower price. The 200-mesh tartaric acid and sodium gluconate are selected, which are easy to be mixed evenly with other powders during the production of the plastering gypsum. In addition, when adding water and stirring, they can quickly dissolve in water and play a role rapidly.

[0032] The thixotropic agent is sodium polyacrylate with a molecular weight range of 2000 - 5000 and a fineness of 100 mesh. Sodium polyacrylate within this molecular weight range, when applied to plastering gypsum, can play a role in thickening and thixotropy. However, the thickening effect gradually weakens over time, which is beneficial to improving the continuous thickening phenomenon after the plastering gypsum is stirred.

[0033] The plasticizer is a slow - release type polycarboxylate water - reducing agent powder. During the stirring process of plastering gypsum, a small part of the performance of the slow - release type polycarboxylate water - reducing agent is released, improving the dispersibility and uniformity of the plastering gypsum paste. Over time, the performance of the remaining polycarboxylate water - reducing agent is gradually released, causing free water to be continuously released from the plastering gypsum, thereby reducing the consistency of the paste and extending the workable time. Since the dosage of cement in the formulation is not high and the plastering gypsum paste is not strongly alkaline, during the stirring process, the slow - release type polycarboxylate water - reducing agent does not release much and will not affect the sagging of the plastering gypsum.

[0034] The following further illustrates the above - mentioned specific embodiments through examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions indicated in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product instructions. Reagents, raw materials, and instrument equipment without special instructions can be directly purchased through commercial channels.

[0035] Example 1:

[0036] A phosphorus - based building gypsum heavy - duty plastering gypsum, which includes the following components in parts by mass: 470 parts of phosphorus - based building gypsum, 30 parts of 42.5 cement, 20 parts of ultra - fine mineral powder, 100 parts of glass microspheres, 380 parts of river sand, 2.5 parts of 40,000 - viscosity cellulose ether, 0.5 part of amino - acid - type gypsum retarder, 0.2 part of DL - tartaric acid, 0.3 part of sodium gluconate, 5 parts of sodium polyacrylate with a molecular weight of 5000, and 0.7 part of slow - release type polycarboxylate water - reducing agent.

[0037] Example 2:

[0038] A phosphorus - based building gypsum heavy - duty plastering gypsum, which includes the following components in parts by mass: 450 parts of phosphorus - based building gypsum, 50 parts of 42.5 cement, 30 parts of ultra - fine mineral powder, 70 parts of glass microspheres, 400 parts of river sand, 2 parts of 100,000 - viscosity cellulose ether, 0.75 part of amino - acid - type gypsum retarder, 0.3 part of DL - tartaric acid, 0.45 part of sodium gluconate, 5 parts of sodium polyacrylate with a molecular weight of 5000, and 1 part of slow - release type polycarboxylate water - reducing agent.

[0039] Example 3:

[0040] A heavy plaster for rendering based on phosphogypsum, which includes the following components in parts by mass: 475 parts of phosphogypsum, 25 parts of 52.5 cement, 20 parts of ultrafine mineral powder, 80 parts of glass microspheres, 400 parts of river sand, 3 parts of 40,000 viscosity cellulose ether, 0.6 part of amino acid gypsum retarder, 0.24 part of DL-tartaric acid, 0.36 part of sodium gluconate, 7 parts of polyacrylate sodium with a molecular weight of 2000, and 0.5 part of slow-release polycarboxylate water reducer.

[0041] Example 4:

[0042] A heavy plaster for rendering based on phosphogypsum, which includes the following components in parts by mass: 460 parts of phosphogypsum, 40 parts of 52.5 cement, 30 parts of ultrafine mineral powder, 80 parts of glass microspheres, 390 parts of river sand, 2.5 parts of 40,000 viscosity cellulose ether, 0.75 part of amino acid gypsum retarder, 0.3 part of DL-tartaric acid, 0.45 part of sodium gluconate, 6 parts of polyacrylate sodium with a molecular weight of 3000, and 0.8 part of slow-release polycarboxylate water reducer.

[0043] Comparative Example 1:

[0044] A heavy plaster for rendering based on phosphogypsum, which includes the following components in parts by mass: 475 parts of phosphogypsum, 25 parts of 42.5 cement, 100 parts of heavy calcium carbonate, 400 parts of river sand, 2.5 parts of 40,000 viscosity cellulose ether, 0.8 part of amino acid gypsum retarder, and 0.5 part of starch ether.

[0045] Comparative Example 2:

[0046] A heavy plaster for rendering based on phosphogypsum, which includes the following components in parts by mass: 475 parts of phosphogypsum, 25 parts of 42.5 cement, 100 parts of heavy calcium carbonate, 400 parts of river sand, 3 parts of 40,000 viscosity cellulose ether, 0.8 part of amino acid gypsum retarder, 0.5 part of starch ether, and 0.5 part of polycarboxylate water reducer.

[0047] Comparative Example 3

[0048] In this example, L+ type tartaric acid is selected, and the rest is the same as Example 3.

[0049] For the performance test method of the plaster for rendering prepared in Comparative Examples 1 to 4 and Comparative Examples 1 to 3, refer to GB / T28627-2023 "Plaster for Rendering", and the specific results are shown in Table 1:

[0050] Table 1

[0051]

[0052] As can be seen from Table 1, compared with the comparative example, the phosphorus building gypsum-based plaster of the present invention effectively extends the operable time without affecting the workability. At the same time, the mechanical properties are improved to a certain extent.

[0053] The above are only the embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A phosphorus building gypsum-based heavy plaster gypsum, characterized in that: The plastering gypsum comprises the following components in parts by weight: 450-475 parts of phosphorus building gypsum, 25-50 parts of cement, 20-30 parts of mineral admixture, 70-100 parts of filler, 380-400 parts of aggregate, 2-3 parts of cellulose ether, 1.5 parts of retarder, 5-7 parts of thixotropic agent, and 0.5-1 part of plasticizer; The retarder is a mixture of an amino acid gypsum retarder, tartaric acid and sodium gluconate.

2. The phosphorus building gypsum-based heavy plastering gypsum according to claim 1, characterized in that: The mass ratio of the amino acid gypsum retarder, tartaric acid and sodium gluconate is 5:2:

3.

3. The phosphorus building gypsum-based heavy plastering gypsum according to claim 1, characterized in that: The amino acid gypsum retarder is of a broad pH applicable type, the tartaric acid is of DL-type with a fineness of 200 meshes, and the fineness of the sodium gluconate is 200 meshes.

4. The phosphorus building gypsum-based heavy plaster gypsum according to claim 1, characterized in that: The physical and mechanical properties of the phosphorus building gypsum meet the requirements of GB / T 9776-2008, wherein the strength grade is 3.

0.

5. The phosphorus building gypsum-based heavy plastering gypsum according to claim 1, characterized in that: The cement is 42.5 grade or 52.5 grade Portland cement; The mineral admixture is ultra-fine mineral powder with an activity grade of S105 and a specific surface area of ​​≥600m 2 / kg.

6. The phosphorus building gypsum-based heavy plastering gypsum according to claim 1, characterized in that: The filler is glass microbeads with a particle size ranging from 0.1 to 0.5 mm.

7. The phosphorus building gypsum-based heavy plastering gypsum according to claim 1, characterized in that: The aggregate is 40-140 mesh washed river sand with a mud content of ≤3% and does not contain flocculant.

8. The phosphorus building gypsum-based heavy plastering gypsum according to claim 1, characterized in that: The cellulose ether is instant hydroxypropyl methyl cellulose ether with a viscosity of 40000-100000 mPa.s.

9. The phosphorus building gypsum-based heavy plaster gypsum according to claim 1, characterized in that: The thixotropic agent is sodium polyacrylate with a molecular weight range of 2000-5000 and a fineness of 100 mesh.

10. The phosphorus building gypsum-based heavy plaster gypsum according to claim 1, characterized in that: The plasticizer is a slow-release polycarboxylate water-reducing agent powder.

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