A gypsum composite admixture and its application in the preparation of α-type high-strength gypsum

Abstract

The present invention belongs to the technical field of high-strength gypsum, and provides a gypsum composite admixture and its application in the preparation of α-type high-strength gypsum. The gypsum composite admixture comprises the following raw material components in parts by mass: 30-50 parts of crystal morphology regulator, 25-45 parts of crystal growth inhibitor, 10-30 parts of dispersant, and 0.1-2.0 parts of emulsifier; the dispersant is selected from at least one of C1-C4 alkyl mono- or polyhydric alcohols, polyethylene glycol or polyvinyl alcohol, and the emulsifier is selected from at least one of anionic surfactants or non-ionic surfactants. Using the gypsum composite admixture of the present invention for the preparation of α-type high-strength gypsum, a gypsum product with uniform particle size, small size and dry compressive strength reaching 50 MPa can be obtained; and it is less affected by external working condition fluctuations during the product preparation process, and the product performance can be kept stable during continuous operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-strength gypsum preparation, and particularly relates to a gypsum composite admixture and its application in the preparation of α-type high-strength gypsum. Background Art

[0002] According to the industry standard JC / T 2038-2010 "α-Type High-Strength Gypsum", α-type high-strength gypsum refers to a powdery gelling material mainly in the crystal form of α-type hemihydrate calcium sulfate obtained by dihydrate calcium sulfate in a saturated water vapor medium or a liquid aqueous solution under certain temperature, pressure or crystal conversion agent conditions, and its dried compressive strength is above 25.0 MPa. Currently, the synthesis methods of α-type hemihydrate gypsum mainly include the autoclave method, the pressurized hydrothermal method, the atmospheric pressure salt solution method, etc. Among them, the pressurized hydrothermal method has high use efficiency of the admixture, good performance of the obtained α-type hemihydrate gypsum, and has great market potential. The main mechanism of the pressurized hydrothermal method is the dissolution and recrystallization of dihydrate gypsum in the solution. The key is to control the composition of the solution system and the reaction conditions to regulate the crystal nucleation and growth process, so as to obtain hemihydrate gypsum crystals with the required morphology and size.

[0003] Currently, the admixtures added during the preparation of α-type hemihydrate gypsum by pressurized hydrothermal method mainly include organic carboxylic acids (salts), high-valence cation inorganic salts, surfactants and macromolecular substances. Because the carboxyl group in the organic carboxylic acid (salt) combines with the calcium ions on the end face of dihydrate gypsum to form calcium carboxylate and coat the end face, the growth of the c-axis of the gypsum is inhibited, and the aspect ratio gradually decreases, and short-columnar hemihydrate gypsum crystals with a lower aspect ratio can be obtained. Currently, organic carboxylic acids (salts) are mainly used to regulate the crystal conversion of α-type hemihydrate gypsum. However, the effect of a single crystal conversion agent is limited, and it is difficult to obtain the α-type hemihydrate gypsum crystal form required for high-strength gypsum. Therefore, the composite crystal conversion agent technology has emerged. Currently, it is found that when the two types of crystal conversion agents, carboxylate and inorganic salt, act in combination, the best effect on regulating the crystal growth habit can be obtained, and crystals with uniform size and good morphology can be obtained. Different compounding methods have obvious differences in their effects, and appropriate compounding can produce a superposition effect. Due to the complexity of the composite crystal conversion agent system, the absolute dry compressive strength of the α-type hemihydrate gypsum prepared by the current composite crystal conversion agent technology is mostly lower than 50 MPa.

[0004] In addition, most of the current research mainly focuses on the regulation of the crystal morphology of α-type hemihydrate gypsum, while less attention is paid to the instability of different batches during the synthesis of hemihydrate gypsum and the problem of crystal agglomeration in the actual engineering project implementation process. Therefore, it is urgent to develop a new type of composite admixture to improve the crystal dispersibility and uniformity, improve the stability of the synthesis process, and ensure the stable quality of high-strength gypsum products during the continuous operation of the engineering project. Summary of the Invention

[0005] To solve the above problems, the present invention provides a gypsum composite admixture. Using this gypsum composite admixture to prepare α-type high-strength gypsum, hemihydrate gypsum with excellent crystallinity, dispersibility and uniformity can be obtained, and at the same time, the quality of the continuously produced high-strength gypsum is ensured to be stable.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A gypsum composite admixture, comprising the following raw material components in parts by mass: 30-50 parts of crystal morphology regulator, 25-45 parts of crystal growth inhibitor, 10-30 parts of dispersant and 0.1-2.0 parts of emulsifier; wherein, the crystal morphology regulator is selected from at least one of organic acids or organic acid salts, the crystal growth inhibitor is selected from at least one of inorganic metal salts of potassium, aluminum or iron, the dispersant is selected from at least one of C1-C4 alkyl mono- or polyhydric alcohols, polyethylene glycol or polyvinyl alcohol, and the emulsifier is selected from at least one of anionic surfactants or nonionic surfactants.

[0008] The present invention is further configured such that the crystal morphology regulator is selected from one or more of succinic acid, citric acid, ethylenediaminetetraacetic acid, potassium sodium tartrate, potassium oxalate or sodium citrate.

[0009] The present invention is further configured such that the crystal growth inhibitor is selected from one or more of aluminum sulfate, ferric sulfate, potassium alum, aluminum chloride, ferric chloride, ferric nitrate or aluminum nitrate.

[0010] The present invention is further configured such that the dispersant is selected from one or more of ethanol, glycerol, 1,4-butanediol, polyethylene glycol or polyvinyl alcohol; wherein, the molecular weight of the polyethylene glycol is 500-4000, and the molecular weight of the polyvinyl alcohol is 30,000-150,000.

[0011] The present invention is further configured such that the emulsifier is selected from one or more of sodium dodecyl sulfate, gum arabic, C 12 -C 18 potassium fatty acid, Tween 80 or sodium alginate.

[0012] The present invention provides a preparation method of the gypsum composite admixture, comprising the following process: mixing the required parts by mass of the crystal morphology regulator and the crystal growth inhibitor solids, adding deionized water and dissolving uniformly to obtain a mixed solution with a mixed solid concentration of 15-25%; then adding the required parts by mass of the dispersant and the emulsifier to the obtained mixed solution, homogenizing and emulsifying to form a nano-emulsion type composite solution; finally, using spray drying technology to process at 70-90 °C, preparing and forming a solid nano-composite additive and storing it sealed for standby.

[0013] The present invention also provides an α-type high-strength gypsum, the raw material components of which include dihydrate gypsum and the above-mentioned gypsum composite admixture, and the addition amount of the gypsum composite admixture is 0.5-2.0% of the mass of calcium sulfate dihydrate in the dihydrate gypsum.

[0014] The present invention is further configured such that the aspect ratio of the α-type high-strength gypsum is 1-3, and the absolute dry compressive strength ≥ 50 MPa.

[0015] The present invention also provides a preparation method of an α-type high-strength gypsum, which includes the following steps:

[0016] (1) Take industrial by-product gypsum with a calcium sulfate dihydrate content ≥ 90%, and wash it with water until the pH is approximately neutral;

[0017] (2) Mix and stir the washed dihydrate gypsum with water to prepare a gypsum slurry with a solid content of 15-25%, and add the above-prepared gypsum composite admixture in an amount of 0.5-2.0% of the mass of calcium sulfate dihydrate, and mix it evenly with the gypsum slurry;

[0018] (3) Add the above gypsum slurry into a hydrothermal reaction kettle, and react at a hydrothermal temperature of 125-135 °C and a hydrothermal time of 3-5 h;

[0019] (4) After the reaction is completed, perform solid-liquid separation and drying to obtain a high-strength gypsum product.

[0020] The present invention has the following beneficial effects: Using the gypsum composite admixture described in the present invention to prepare high-strength gypsum promotes the growth of high-strength gypsum crystal particles in the form of single crystals, avoids cross-growth between crystals, and obtains a high-strength gypsum product with good development and smooth morphology. The prepared high-strength gypsum product has uniform particle size, small size, and absolute dry compressive strength ≥ 50 MPa; and by using the gypsum composite admixture described in the present invention, the preparation process of high-strength gypsum is less affected by external working conditions fluctuations, and the product performance can be kept stable during continuous operation. Description of the Drawings

[0021] Figure 1 It is a scanning electron micrograph of the high-strength gypsum prepared in Example 1.

[0022] Figure 2 It is a scanning electron micrograph of the high-strength gypsum prepared in Comparative Example 1.

[0023] Figure 3 It is a scanning electron micrograph of the high-strength gypsum prepared in Comparative Example 3. Detailed Embodiments

[0024] Next, the present invention will be further described in conjunction with the accompanying drawings and embodiments. It is necessary to point out here that the following embodiments are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0025] Embodiment 1

[0026] (I) Preparation of gypsum composite admixture

[0027] In this embodiment, the raw material components of the gypsum composite admixture, in parts by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of ferric chloride solid, 30 parts of 1,4-butanediol, and 0.1 part of sodium dodecyl sulfonate. The preparation of the gypsum composite admixture includes the following steps:

[0028] (1) Mix the given parts by mass of ethylenediaminetetraacetic acid, citric acid, and ferric chloride solid, add deionized water and dissolve uniformly to obtain a mixed solution with a mixed solid concentration of 20%;

[0029] (2) Add the given parts by mass of 1,4-butanediol and sodium dodecyl sulfonate to the mixed solution prepared in step (1), and perform homogeneous emulsification with a high-speed stirrer at 2500 r / min to form a nano-emulsion type composite solution;

[0030] (3) Treat the obtained nano-emulsion type composite solution using spray drying technology at 80°C to prepare and form a solid nano-composite additive, which is sealed and stored for later use.

[0031] (II) Preparation of α-type high-strength gypsum

[0032] It includes the following steps:

[0033] (1) Take industrial by-product gypsum with a calcium sulfate dihydrate content greater than 90%, and wash it until the pH is approximately neutral;

[0034] (2) Mix the washed calcium sulfate dihydrate with water and stir to prepare a gypsum slurry with a solid content of 20%. At the same time, add the above-prepared gypsum composite admixture according to 1.0% of the mass of calcium sulfate dihydrate, and mix it uniformly with the gypsum slurry;

[0035] (3) Add the gypsum slurry with the gypsum composite admixture in step (2) to a hydrothermal reaction kettle, and control the stirring speed to be 400 r / min, the hydrothermal temperature to be 135°C, and the hydrothermal time to be 3 h.

[0036] (4) After the reaction is completed, perform solid-liquid separation and drying to obtain a high-strength gypsum product.

[0037] The prepared high-strength gypsum product was characterized by SEM, and the results Figure 1 are shown as follows. The prepared α-type high-strength gypsum product has a small degree of agglomeration between crystals, good dispersibility, a narrow range of aspect ratios (1 - 2) for single crystal particles, and good uniformity. The dry compressive strength of the prepared high-strength gypsum product was detected. Referring to JC / T 2038-2010 "α-Type High-Strength Gypsum", the testing process is as follows: First, prepare the test specimens. The preparation process of the test specimens is as follows: Add the prepared high-strength gypsum powder to an appropriate amount of water for hydration, with a consistency of 30% - 40%, stir for about 15 - 30 s, pour the fluid with appropriate consistency into a cement test mold (specification: 10*10*40 mm - six-piece), so that the fluid slightly overflows the test mold, and then lift the left and right ends by 1 - 2 cm respectively, let the test mold fall freely to remove air bubbles, repeat this 10 - 15 times until there are no obvious air bubbles, then gently scrape off the overflowing slurry on the surface with a scraping board, let it stand for 2 - 4 h, remove the mold to take out the specimens, place them at room temperature for 24 h, then place them in an oven at 40 ± 5 °C for 24 - 48 h, take out the specimens, and store them after drying; then use a CTM9100 universal testing machine to detect the compressive strength of the test specimens to obtain the dry compressive strength value. In this example, the dry compressive strength of the high-strength gypsum prepared in this step is 57 MPa.

[0038] (III) Stability tests under different working conditions

[0039] The dry compressive strength of the high-strength gypsum products prepared under different working conditions was detected. The preparation method and strength detection method of high-strength gypsum are the same as the content in the above (II) Preparation of high-strength gypsum. Set 5 parallel experiments, control the working conditions of the hydrothermal reaction to fluctuate within a certain range, and investigate the influence on the product quality and stability. Among them, the reaction temperature fluctuates at 130 ± 5 °C, and the reaction time fluctuates within 3 - 5 h. The hydrothermal reaction conditions and the strength values of the high-strength gypsum products in the 5 parallel experiments are statistically shown in Table 1.

[0040] Table 1 Strength of high-strength gypsum products obtained under the working condition fluctuations in Example 1

[0041]

[0042] As shown in Table 1, under the fluctuating working conditions, the average dry compressive strength of the high-strength gypsum products prepared in this example is 59.2 MPa, and the mean square deviation of the dry compressive strength data of the high-strength gypsum products obtained in each group is 2.71, indicating that the product quality of high-strength gypsum produced by using the gypsum composite admixture prepared in this example is relatively stable under fluctuating working conditions.

[0043] Example 2

[0044] (I) Preparation of gypsum composite admixture

[0045] Compared with Example 1, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, in parts by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of ferric chloride solid, 30 parts of 1,4-butanediol, and 1.0 part of sodium dodecylsulfonate.

[0046] (II) Preparation of α-type high-strength gypsum

[0047] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared in Example 2. The obtained α-type high-strength gypsum product has a smaller degree of agglomeration between crystals, better dispersibility, a narrower distribution range of the aspect ratio of single crystal particles, an aspect ratio of 1 - 2, better uniformity, and the absolute dry compressive strength of the prepared high-strength gypsum product is 56 MPa.

[0048] (III) Stability test under different working conditions

[0049] The test method is the same as that in Example 1. In this example, the average strength of the high-strength gypsum products obtained from 5 groups of parallel experiments is 57 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained in each group is 3.69.

[0050] In this example, the strength test method of the high-strength gypsum in the above (II) and (III) processes is the same as that in Example 1.

[0051] Example 3

[0052] (I) Preparation of gypsum composite admixture

[0053] Compared with Example 1, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, in parts by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of ferric chloride solid, 30 parts of 1,4-butanediol, and 0.05 part of sodium dodecylsulfonate.

[0054] (II) Preparation of α-type high-strength gypsum

[0055] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared above in this example. The obtained α-type high-strength gypsum product has slightly worse crystal dispersibility and aspect ratio uniformity of single crystal particles than those in Example 1 and Example 2, the aspect ratio is 1 - 4, and the absolute dry compressive strength of the prepared high-strength gypsum product is 53 MPa.

[0056] (III) Stability test under different working conditions

[0057] The test method is the same as that in Example 1. In this example, the average strength of the high-strength gypsum products obtained by 5 groups of parallel experiments is 51.4 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained between the groups is 6.28.

[0058] In this embodiment, the strength test method of high-strength gypsum in the above processes (ii) and (iii) is the same as that in Example 1.

[0059] Example 4

[0060] 1. Preparation of gypsum composite admixture

[0061] Compared with Example 1, the only difference is that the raw material components for preparing the gypsum composite admixture are different. In this embodiment, the raw material components of the gypsum composite admixture, by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of solid ferric chloride, 30 parts of 1,4-butanediol and 1.0 part of sodium alginate.

[0062] (II) Preparation of α-type high-strength gypsum

[0063] Compared with Example 1, the only difference is that the gypsum composite admixture used is the gypsum composite admixture prepared as described above in this Example. The prepared α-type high-strength gypsum product has a small degree of agglomeration between crystals, good dispersibility, a narrow distribution range of the aspect ratio of single crystal particles, an aspect ratio of 1 to 2, good uniformity, and the prepared high-strength gypsum product has an absolute dry compressive strength of 61 MPa.

[0064] (III) Stability test under different working conditions

[0065] The test method is the same as that in Example 1. In this example, the average strength of the high-strength gypsum products obtained by 5 groups of parallel experiments is 60 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained between the groups is 2.83.

[0066] In this embodiment, the strength test method of high-strength gypsum in the above processes (ii) and (iii) is the same as that in Example 1.

[0067] Example 5

[0068] 1. Preparation of gypsum composite admixture

[0069] Compared with Example 1, the only difference is that the raw material components for preparing the gypsum composite admixture are different. In this embodiment, the raw material components of the gypsum composite admixture, by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of solid ferric chloride, 10 parts of 1,4-butanediol and 1.0 part of sodium alginate.

[0070] (II) Preparation of α-type high-strength gypsum

[0071] Compared with Example 1, the only difference is that the gypsum composite admixture used is the gypsum composite admixture prepared in this example above. The obtained α-type high-strength gypsum product has a smaller degree of agglomeration between crystals, better dispersibility, a narrower range of aspect ratios of single crystal particles, an aspect ratio of 1 to 2, better uniformity, and the absolute dry compressive strength of the prepared high-strength gypsum product is 57 MPa.

[0072] (III) Stability tests under different working conditions

[0073] The testing method is the same as that in Example 1. In this example, the average strength of the high-strength gypsum products prepared from 5 groups of parallel experiments is 59.2 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained between groups is 2.71.

[0074] In this example, the strength testing method of the high-strength gypsum in the above (II) and (III) processes is the same as that in Example 1.

[0075] Example 6

[0076] (I) Preparation of gypsum composite admixture

[0077] Compared with Example 1, the only difference is that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of ferric chloride solid, 40 parts of 1,4-butanediol, and 1.0 part of sodium alginate.

[0078] (II) Preparation of α-type high-strength gypsum

[0079] Compared with Example 1, the only difference is that the gypsum composite admixture used is the gypsum composite admixture prepared in this example above. For the obtained α-type high-strength gypsum product, since the slightly larger dosage of the dispersant weakens the contact effect between the dispersant and the crystals, the crystal particles are in an agglomerated state, with poor dispersibility, the aspect ratio range of single crystal particles is 1 to 6, and the uniformity decreases compared with Examples 4 and 5. The absolute dry compressive strength of the prepared high-strength gypsum product is 48 MPa.

[0080] (III) Stability tests under different working conditions

[0081] The testing method is the same as that in Example 1. In this example, the average strength of the high-strength gypsum products prepared from 5 groups of parallel experiments is 47.2 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained between groups is 4.31.

[0082] In this example, the strength testing method of the high-strength gypsum in the above (II) and (III) processes is the same as that in Example 1.

[0083] Example 7

[0084] (1) Preparation of gypsum composite admixture

[0085] Compared with Example 1, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of ferric chloride solid, 5 parts of 1,4-butanediol, and 1.0 part of sodium alginate.

[0086] (2) Preparation of α-type high-strength gypsum

[0087] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared in the above example of this example. The obtained α-type high-strength gypsum product has agglomerated particles and poor crystal dispersibility. The aspect ratio distribution range of single crystal particles is 1 - 7. Compared with Examples 4 and 5, the uniformity decreases, and the absolute dry compressive strength of the prepared high-strength gypsum product is 46 MPa.

[0088] (3) Stability test under different working conditions

[0089] The test method is the same as that in Example 1. In this example, the average strength of the high-strength gypsum products obtained from 5 groups of parallel experiments is 48.6 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained between groups is 5.78.

[0090] In this example, the strength test method of the high-strength gypsum in the above (2) and (3) processes is the same as that in Example 1.

[0091] Example 8

[0092] (1) Preparation of gypsum composite admixture

[0093] The same as Example 1.

[0094] (2) Preparation of α-type high-strength gypsum

[0095] Compared with Example 1, the difference is only that the addition amount of the gypsum composite admixture is different. In this example, the prepared gypsum composite admixture is added according to 2.0% of the mass of calcium sulfate dihydrate. The obtained α-type high-strength gypsum product has good crystal dispersibility and good uniformity of the aspect ratio of single crystal particles, and there is no obvious difference compared with Example 1; the aspect ratio is 1 - 2, and the absolute dry compressive strength of the prepared high-strength gypsum product is 60 MPa.

[0096] (3) Stability test under different working conditions

[0097] The test method is the same as that in Example 1. In this example, the average strength of the high-strength gypsum products obtained from 5 groups of parallel experiments is 59 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained between groups is 2.61.

[0098] In this embodiment, the strength test method of the high-strength gypsum in the above (ii) and (iii) processes is the same as that in Example 1.

[0099] Example 9

[0100] (i) Preparation of gypsum composite admixture

[0101] The same as in Example 1.

[0102] (ii) Preparation of α-type high-strength gypsum

[0103] Compared with Example 1, the difference is only that the addition amount of the gypsum composite admixture is different. In this embodiment, the prepared gypsum composite admixture is added at 0.5% of the mass of calcium sulfate dihydrate. The prepared α-type high-strength gypsum product has good crystal dispersibility and uniformity of the aspect ratio of single crystal particles, and there is no obvious difference compared with Example 1; the aspect ratio is 1-2, and the absolute dry compressive strength of the prepared high-strength gypsum product is 59 MPa.

[0104] (iii) Stability test under different working conditions

[0105] The test method is the same as that in Example 1. In this embodiment, the average strength of the high-strength gypsum products prepared by 5 groups of parallel experiments is 57.4 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained between groups is 2.15.

[0106] In this embodiment, the strength test method of the high-strength gypsum in the above (ii) and (iii) processes is the same as that in Example 1.

[0107] Example 10

[0108] (i) Preparation of gypsum composite admixture

[0109] The same as in Example 1.

[0110] (ii) Preparation of α-type high-strength gypsum

[0111] Compared with Example 1, the difference is only that the addition amount of the gypsum composite admixture is different. In this embodiment, the prepared gypsum composite admixture is added at 0.2% of the mass of calcium sulfate dihydrate. The prepared α-type high-strength gypsum product has poorer crystal dispersibility and uniformity of the aspect ratio of single crystal particles than Example 9; the aspect ratio is 5-10, and the absolute dry compressive strength of the prepared high-strength gypsum product is 44 MPa.

[0112] (iii) Stability test under different working conditions

[0113] The testing method is the same as that in Example 1. In this example, the average strength of the high-strength gypsum products obtained from 5 groups of parallel experiments is 42.8 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained among the groups is 2.79.

[0114] In this example, the strength testing method of the high-strength gypsum in the above (ii) and (iii) processes is the same as that in Example 1.

[0115] Example 11

[0116] (i) Preparation of gypsum composite admixture

[0117] Compared with Example 1, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of ferric chloride solid, 20 parts of 1,4-butanediol, and 1.0 part of sodium alginate.

[0118] (ii) Preparation of α-type high-strength gypsum

[0119] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared in this example above. The obtained α-type high-strength gypsum product has good crystal dispersibility, good uniformity of the aspect ratio of single crystal particles, the aspect ratio is 1 - 2, and the absolute dry compressive strength of the prepared high-strength gypsum product is 59 MPa.

[0120] (iii) Stability testing under different working conditions

[0121] The testing method is the same as that in Example 1. In this example, the average strength of the high-strength gypsum products obtained from 5 groups of parallel experiments is 60 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained among the groups is 2.81.

[0122] In this example, the strength testing method of the high-strength gypsum in the above (ii) and (iii) processes is the same as that in Example 1.

[0123] Example 12

[0124] (i) Preparation of gypsum composite admixture

[0125] Compared with Example 1, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, by mass, include 20 parts of succinic acid, 20 parts of citric acid, 30 parts of aluminum sulfate solid, 10 parts of polyethylene glycol 1000, and 1.0 part of Tween 80.

[0126] (ii) Preparation of α-type high-strength gypsum

[0127] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared above in this example. The prepared α-type high-strength gypsum product has basically no agglomeration between crystal particles, good dispersibility, the aspect ratio distribution range of single crystal particles is 1-2, good uniformity, and the absolute dry compressive strength of the prepared high-strength gypsum product is 59 MPa.

[0128] In this example, the strength test method of high-strength gypsum is the same as that in Example 1.

[0129] Example 13

[0130] (I) Preparation of gypsum composite admixture

[0131] Compared with Example 1, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, by mass, include 10 parts of potassium sodium tartrate, 20 parts of potassium oxalate, 25 parts of potassium alum, 20 parts of glycerol and 0.5 part of arabic gum.

[0132] (II) Preparation of α-type high-strength gypsum

[0133] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared above in this example. The prepared α-type high-strength gypsum product has basically no agglomeration between crystal particles, good dispersibility, the aspect ratio distribution range of single crystal particles is 1-2, good uniformity, and the absolute dry compressive strength of the prepared high-strength gypsum product is 60 MPa.

[0134] In this example, the strength test method of high-strength gypsum is the same as that in Example 1.

[0135] Example 14

[0136] (I) Preparation of gypsum composite admixture

[0137] Compared with Example 1, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of ferric chloride solid, 15 parts of polyvinyl alcohol (molecular weight: 30,000) and 0.5 part of potassium palm oil fatty acid soap.

[0138] (II) Preparation of α-type high-strength gypsum

[0139] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared above in this example. The prepared α-type high-strength gypsum product has basically no agglomeration between crystal particles, good dispersibility, the aspect ratio distribution range of single crystal particles is 1-2, good uniformity, and the absolute dry compressive strength of the prepared high-strength gypsum product is 58 MPa.

[0140] In this embodiment, the strength test method of high-strength gypsum is the same as that in Example 1.

[0141] Comparative Example 1

[0142] (I) Preparation of gypsum composite admixture

[0143] Compared with Example 1, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this embodiment, the raw material components of the gypsum composite admixture, by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of ferric chloride solid, and 30 parts of 1,4-butanediol, and no emulsifier is added.

[0144] (II) Preparation of high-strength gypsum

[0145] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared above in this embodiment. The morphology of the obtained high-strength gypsum product is as Figure 2 shown. The crystal dispersibility is close to that in Example 3, the uniformity of the aspect ratio of single crystal particles is poor, the aspect ratio is 2 - 3, and the absolute dry compressive strength of the prepared high-strength gypsum product is 52 MPa.

[0146] (III) Stability test under different working conditions

[0147] The test method is the same as that in Example 1. In this embodiment, the hydrothermal reaction conditions and the strength values of the high-strength gypsum products in 5 parallel experiments are statistically shown in Table 2, and the average strength of the high-strength gypsum products prepared in 5 parallel experiments is 50.2 MPa.

[0148] Table 2 Strength of high-strength gypsum products obtained under working condition fluctuations in Comparative Example 1

[0149]

[0150] Although the strength value of the obtained high-strength gypsum product ≥ 50 MPa, the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained in each group is 6.43, indicating that the quality of the gypsum products produced under working condition fluctuations is unstable.

[0151] In this comparative example, the strength test method of high-strength gypsum in the above (II) and (III) processes is the same as that in Example 1.

[0152] Comparative Example 2

[0153] (I) Preparation of gypsum composite admixture

[0154] Compared with Example 4, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, 35 parts of ferric chloride solid, and 1.0 part of sodium alginate, and no dispersant is added.

[0155] (II) Preparation of high-strength gypsum

[0156] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared above in this example. The obtained high-strength gypsum product has poor crystal dispersibility, the crystal particles are in an aggregated state, the uniformity of the aspect ratio of single crystal particles is average, the aspect ratio is 1-2, and the absolute dry compressive strength of the prepared high-strength gypsum product is 47 MPa.

[0157] (III) Stability test under different working conditions

[0158] The test method is the same as that in Example 1. In this example, the hydrothermal reaction conditions and the strength value statistics of the high-strength gypsum products in 5 parallel experiments are shown in Table 3. The average strength of the high-strength gypsum products prepared in 5 parallel experiments is 48.6 MPa, and the mean square deviation of the absolute dry compressive strength data of the high-strength gypsum products obtained in each group is 5.39. The absolute dry compressive strength of the prepared high-strength gypsum product < 50 MPa, which does not meet the requirements of the compressive strength of high-strength gypsum.

[0159] Table 3 Strength of high-strength gypsum products obtained under working condition fluctuations in Comparative Example 2

[0160]

[0161] In this comparative example, the strength test method of high-strength gypsum in the above (II) and (III) processes is the same as that in Example 1.

[0162] Comparative Example 3

[0163] (I) Preparation of gypsum composite admixture

[0164] Compared with Example 1, the difference is only that the raw material components for preparing the gypsum composite admixture are different. In this example, the raw material components of the gypsum composite admixture, by mass, include 30 parts of ethylenediaminetetraacetic acid, 10 parts of citric acid, and 35 parts of ferric chloride solid, and no emulsifier and dispersant are added.

[0165] (II) Preparation of high-strength gypsum

[0166] Compared with Example 1, the difference is only that the gypsum composite admixture used is the gypsum composite admixture prepared above in this example. The morphology of the obtained high-strength gypsum product is as Figure 3As shown, the crystal dispersion is poor, the particles are in an agglomerated state, the uniformity of the aspect ratio of single crystal particles is poor, the aspect ratio is 4 to 8, and the absolute dry compressive strength of the prepared high-strength gypsum product is 45.6 MPa. The absolute dry compressive strength < 50 MPa, which does not meet the requirements for the compressive strength of high-strength gypsum.

[0167] In this comparative example, the strength test method of high-strength gypsum is the same as that in Example 1.

[0168] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A gypsum composite admixture, characterized in that It comprises the following raw material components in parts by mass: 30-50 parts of crystal morphology regulator, 25-45 parts of crystal growth inhibitor, 10-30 parts of dispersant, and 0.1-2.0 parts of emulsifier; Among them, the crystal morphology regulator is selected from one or more of succinic acid, citric acid, ethylenediaminetetraacetic acid, potassium sodium tartrate, potassium oxalate or sodium citrate; the crystal growth inhibitor is selected from one or more of aluminum sulfate, iron sulfate, potassium alum, aluminum chloride, iron chloride, iron nitrate or aluminum nitrate; the dispersant is selected from one or more of glycerol, 1,4-butanediol, polyethylene glycol or polyvinyl alcohol, wherein the molecular weight of the polyethylene glycol is 500-4000, and the molecular weight of the polyvinyl alcohol is 30,000-150,000; the emulsifier is selected from one or more of sodium dodecyl sulfonate, gum arabic, C 12 -C 18 -fatty acid potassium, Tween 80 or sodium alginate.

2. An α-type high-strength gypsum, characterized in that, Its raw material components include gypsum dihydrate and the gypsum composite admixture described in Claim 1, and the addition amount of the gypsum composite admixture is 0.5-2.0% of the mass of calcium sulfate dihydrate in the gypsum dihydrate; by reacting a gypsum slurry with a solid content of calcium sulfate dihydrate of 15-25% and the gypsum composite admixture in a hydrothermal reaction kettle at a hydrothermal temperature of 125-135 °C and a hydrothermal time of 3-5 h, and then through solid-liquid separation and drying, a high-strength gypsum product is obtained.

3. The α-type high-strength gypsum according to claim 2, characterized in that, The aspect ratio is 1-3, and the absolute dry compressive strength ≥ 50 MPa.

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