Preparation method of anhydrous gypsum lightweight self-leveling mortar

Abstract

The application provides a preparation method of anhydrite light self-leveling mortar. The anhydrite self-leveling mortar is prepared by mixing and stirring desulfurization gypsum, lime cement, self-made light gypsum sand, type II anhydrite and an additive in a specific ratio, and the volume density of the anhydrite self-leveling mortar is between 800 Kg / m 3 1000 Kg / m 3 , the 28d absolute dry compressive strength is 31MPa-40MPa, which is far greater than the 28d absolute dry compressive strength (20MPa) of the existing self-leveling mortar, wherein the light gypsum sand with high strength, water resistance, environmental protection and low cost is used in the formula, and the cost of the self-leveling mortar is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of building materials, and more particularly to a method for preparing anhydrous hard gypsum lightweight self-leveling mortar. Background Technology

[0002] Desulfurized building gypsum is an industrial by-product obtained from flue gas desulfurization technology in thermal power plants. After calcination and aging, it can be used as a cementing material. It also has advantages such as lightweight sound insulation, fireproofing and heat insulation, and volume stability. It is one of the green cementing materials that are currently promoted and developed internationally.

[0003] In recent years, the country has attached increasing importance to green building materials, and there has been a growing number of projects using gypsum-based self-leveling mortar for indoor floor leveling. Compared with cement-based self-leveling mortar, which is more prone to cracking, gypsum-based self-leveling mortar is less expensive, thus reducing costs. Furthermore, it produces less pollution during production compared to cement, posing less harm to the environment and making it a green building material.

[0004] CN 110482940 A discloses a sand-free lightweight self-leveling dry powder mortar. This gypsum-based self-leveling mortar, by weight percentage, comprises: 70-75% cement, 5-10% fly ash, 5-10% heavy calcium carbonate, 8-12% perlite, 1.5-3% redispersible latex powder, 0.3-0.5% methyl cellulose ether, 0.4-0.6% air-entraining agent, and 0.5-1% water-reducing agent. This gypsum-based self-leveling mortar exhibits good fluidity, low bulk density, and good sound insulation; however, its tensile bond strength is >0.3 MPa. Although this meets relevant standard requirements, the tensile bond strength may decrease during actual construction.

[0005] CN 108129122 A discloses a method for preparing a phosphorus-based lightweight self-leveling mortar. The composition and mass percentage of this self-leveling mortar are as follows: phosphorus-based building gypsum 70%–90%, dried sand 0%–20%, cement 0%–20%, fly ash 0%–5%, lightweight aggregate 5%–20%, active activator 0%–15%, water repellent 0%–3%, high-performance plasticizer 0.1%–1%, anti-settling agent 0%–0.2%, flocculant 0%–0.2%, gypsum retarder 0.01%–0.4%, polymer 0%–3%, and high-performance defoamer 0.05%–0.3%. The lightweight self-leveling mortar prepared by this technology has a bulk density ≤1000 kg / m³. 3With a compressive strength ≥10MPa, it is suitable for indoor thick-layer leveling projects, and has certain thermal insulation, heat insulation, and sound insulation functions. Furthermore, this product has the advantages of lower price, increased economic benefits, and reduced material energy consumption. However, currently available phosphogypsum self-leveling compounds on the market often experience large-area hollowing and cracking after leveling, which is a very serious problem that urgently needs to be solved.

[0006] CN109503088A discloses a gypsum-based self-leveling mortar, which, by weight, comprises or is composed of the following components: 480-520 parts iron tailings sand, 420-470 parts α-high-strength microcrystalline gypsum, 40-60 parts white cement, 1-4 parts water-reducing agent, 5-10 parts dispersible latex powder, 1-2 parts defoamer, 1-3 parts stabilizer, and 230-260 parts water. This product uses α-high-strength microcrystalline gypsum and iron tailings sand as the main raw materials. Based on implementation examples 1-4, the 28-day compressive strength is just over 20 MPa. During mass production, there is a reduction in strength, and the 28-day compressive strength margin is insufficient, which may not guarantee sufficient strength. Furthermore, the use of α-high-strength microcrystalline gypsum, a relatively expensive raw material, further complicates the situation.

[0007] The existing technologies for gypsum-based self-leveling mortars generally suffer from low tensile bond strength or compressive strength, making them prone to large-area hollowing and cracking during construction. Therefore, developing a method for preparing a gypsum-based self-leveling mortar with low density, good fluidity, high strength, and low cost is an urgent problem to be solved. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for preparing anhydrous hard gypsum lightweight self-leveling mortar. By mixing building gypsum, cementitious material, self-made lightweight gypsum sand, Type II anhydrous hard gypsum, and additives in specific proportions, the resulting anhydrous hard gypsum self-leveling mortar has a bulk density of 800 kg / m³. 3 -1000Kg / m 3 Between these values, the 28-day oven-dry compressive strength is 31-40 MPa, which is far greater than the 28-day oven-dry compressive strength (20 MPa) of existing self-leveling mortar. This is achieved by incorporating a high-strength, water-resistant, environmentally friendly, and low-cost lightweight gypsum sand into the formula, which greatly reduces the cost of self-leveling mortar.

[0009] The technical solution of the present invention is as follows:

[0010] This invention provides a method for preparing anhydrous gypsum lightweight self-leveling mortar, wherein the raw materials of the anhydrous gypsum lightweight self-leveling mortar comprise the following components by weight:

[0011] Building plaster: 30-80 parts;

[0012] 42.5 gray cement: 1 part - 5 parts;

[0013] Type II anhydrous gypsum: 10-50 parts;

[0014] Lightweight gypsum sand: 10-30 parts;

[0015] Activator: 0.1-1 part;

[0016] Water-reducing agent: 0.1-0.3 parts;

[0017] Defoamer: 0.05-0.1 parts;

[0018] Water-retaining and thickening agent: 0.05 parts - 0.1 parts;

[0019] Suspension stabilizer: 0.01-0.1 parts;

[0020] Redispersible latex powder: 0.1-0.5 parts;

[0021] Retarder: 0.01-0.03 parts.

[0022] Furthermore, the building gypsum meets the following mass percentage requirements: hemihydrate phase ≥ 80%, dihydrate phase ≤ 4%, anhydrous phase ≤ 5%; 2h flexural strength ≥ 3.5 MPa, 2h compressive strength ≥ 10.0 MPa, oven-dry flexural strength ≥ 5.0 MPa, oven-dry compressive strength ≥ 20.0 MPa, and chloride ion content ≤ 600 mg / Kg.

[0023] Furthermore, the type II anhydrous gypsum is required to meet the following requirements: a mass percentage of type II anhydrous gypsum ≥ 96%, a softening coefficient between 0.6 and 0.7, and a pH value between 12 and 13.

[0024] Further, the 42.5 lime cement comprises the following components by weight percentage: cement chemical composition CaO 60%-65%, SiO2 18%-19%, Al2O3 4%-5%, Fe2O3 2%-3%, MgO 2%-3%, and SO3 3%-4%, based on the total weight of the 42.5 lime cement. The 42.5 lime cement has a calcination vector ≤3%, NaOequi (this symbol represents alkaline oxides) ≤1%, 3-day compressive strength ≥3.5 MPa, 3-day compressive strength ≥17 MPa, 28-day flexural strength ≥6.5 MPa, and 28-day compressive strength ≥42.5 MPa.

[0025] Furthermore, the particle size of the lightweight gypsum sand is 40-140 mesh, and the CaSO4 content is ≥90%.

[0026] Furthermore, the activator is one or a combination of potassium sulfate, KAl(SO4)2, calcined alum, and sodium bisulfate.

[0027] Furthermore, the water-reducing agent is at least one of polycarboxylate-based water-reducing agents, naphthalene-based water-reducing agents, and melamine-based water-reducing agents.

[0028] Furthermore, the defoamer is at least one of the following: high carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether, and polydimethylsiloxane.

[0029] Further, the water-retaining thickener is a low-viscosity water-retaining thickener with a viscosity of 400-600 mps. More preferably, the water-retaining thickener is at least one selected from methyl cellulose ether with a viscosity of 400-600 mps, hydroxypropyl methyl cellulose ether with a viscosity of 400-600 mps, and methyl hydroxyethyl cellulose ether with a viscosity of 400-600 mps.

[0030] Furthermore, the redispersible latex powder is at least one of ethylene / vinyl acetate copolymer, vinyl acetate / ethylene tert-carbonate copolymer, and styrene / acrylic acid copolymer.

[0031] Furthermore, the retarder is a protein-based gypsum retarder.

[0032] Furthermore, the preparation method of the anhydrous gypsum lightweight self-leveling mortar includes the following steps:

[0033] Step 1: Add building gypsum, anhydrous gypsum II, cement and lightweight gypsum sand to the mixing tank, and mix them together for 3-5 minutes to obtain a mixture of adhesive and aggregate.

[0034] Step 2: Pre-disperse the activator, water-reducing agent, defoamer, water-retaining thickener, suspension stabilizer, redispersible latex powder, retarder and heavy calcium carbonate to obtain an additive mixture;

[0035] Step 3: Add the additive mixture to the mixing tank and mix it with the adhesive and aggregate mixture for 3-5 minutes to obtain the anhydrous hard gypsum lightweight self-leveling mortar.

[0036] Furthermore, in step 2, the amount of added heavy calcium carbonate is 2 kg.

[0037] The early strength of the anhydrous gypsum lightweight self-leveling mortar of the present invention is provided by desulfurized gypsum during construction, and the later strength is provided by Type II anhydrous gypsum. The reaction mechanism is as follows:

[0038] Reaction 1: CaSO4·0.5H2O + 1.5H2O → CaSO4·2H2O + Q (19.2 J / g SO3)

[0039] Reaction 2: mCaSO4 (type II anhydrous gypsum) + salt (activator) + 2H2O → salt.mCaSO4.nH2O (double salt)

[0040] Salt.mCaSO4.nH2O + 2mH2O → m(CaSO4.2H2O) + Salt.nH2O

[0041] Reaction 1 involves the reaction of building gypsum with water to produce gypsum dihydrate. Reaction 2 involves the reaction of type II anhydrous gypsum with an activator to generate unstable mCaSO4·nH2O (double salt), which then decomposes into gypsum dihydrate. This process is repeated through the intermediate hydrate (mCaSO4·nH2O) to transform back into gypsum dihydrate, thereby accelerating the dissolution of type II anhydrous gypsum.

[0042] In this invention, the lightweight gypsum sand serves as aggregate, acting as a skeleton and filler in the anhydrous gypsum lightweight self-leveling mortar.

[0043] In this invention, the activator plays a role in activating the early strength of anhydrous gypsum II.

[0044] In this invention, the water-reducing agent can reduce the amount of water added to the product and improve the fluidity of the slurry.

[0045] In this invention, the defoamer serves to reduce or eliminate air bubbles.

[0046] In this invention, the water-retaining and thickening agent mainly functions to retain water and increase viscosity.

[0047] In this invention, the suspension stabilizer can prevent stratification, bleeding, and sedimentation in the slurry.

[0048] In this invention, the redispersible latex powder increases the cohesion of the mortar, and in wet mortar, it can improve workability, improve flowability, increase thixotropy and anti-sagging properties, and improve cohesion.

[0049] In this invention, the mechanism of action of the protein-based retarder is mainly to inhibit the rate of crystallization and reduce the solubility of hemihydrate gypsum, thereby slowing down the crystallization process of hemihydrate gypsum to dihydrate gypsum and delaying the setting time of gypsum.

[0050] Furthermore, the method for preparing the lightweight gypsum sand includes:

[0051] Based on the total mass of raw materials, the percentage content of the raw materials in the lightweight gypsum sand is as follows: 5-10 parts of parent material particles, 65-80 parts of main material 1, 10-15 parts of main material 2, 2-5 parts of auxiliary materials, 3-5 parts of pelletizing material, and the remainder is dispersant.

[0052] Parent material particles: perlite filter aid with a particle size ≤ 0.102 mm;

[0053] Main material 1: Any one or a mixture of any two or more of the following: natural gypsum, desulfurized gypsum, phosphogypsum, fluorogypsum, titanium gypsum, or other industrial by-product gypsum;

[0054] Main material 2: Any one or a mixture of any two or more of the following: aluminate compounds, siliceous aluminate minerals, kaolin minerals, dolomite, soluble oxides, and aluminum oxide;

[0055] Auxiliary materials: any one or a mixture of two of activated calcium and slaked lime;

[0056] Pelletizing material: any one or a mixture of two or more of clay, lignin cellulose or bentonite, with a particle size ≤0.048mm;

[0057] Dispersant: Sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, or any one or a mixture of two of polycarboxylate;

[0058] Preparation methods include:

[0059] (1) Grinding: Main material 1, main material 2, auxiliary material and pelletizing material are ground to 0.037±0.005mm respectively;

[0060] (2) Mud reaction: Add appropriate amount of water to the main material 1, main material 2, auxiliary material and pelletizing material and stir thoroughly in the mixing tank. The speed is 50-300 r / min and the stirring time is 5-10 min. At this time, the various materials are fully dispersed in the water to form mud liquid, and the various materials can fully contact and mix evenly.

[0061] (3) Dehydration: The mud slurry after the mud reaction is dehydrated by centrifugation, adsorption, and extrusion, and then dried at 150-250℃ to control the water content of the mud slurry to be below 3% by mass, so as to obtain block material.

[0062] (4) Grinding: The block material is ground by a high-speed grinding mill at a speed of 3000-6000 r / min to a powder size of 0.037±0.005 mm;

[0063] (5) Formation of mother ball: The mother ball is poured into a round pot granulator, and water is sprayed through the water spraying component of the granulator to form particles A. 1 / 3 to 1 / 2 of the total weight of the powder is added to particles A, and the mother ball is formed by continuing to rotate rapidly in the ball mill.

[0064] (6) Spherical formation: While the mother ball is being sprayed with water mist in the granulator, the remaining powder is added while spraying. As the ball mill rotates rapidly, the mother ball gradually grows to form the first sphere. At this point, no more water spraying is needed. Then, the dispersant is added to form the second spherical particles.

[0065] (7) Sieving: Remove the coarse particles from the second spherical particles obtained in step (6), leaving particles of 40-140 mesh for later use;

[0066] (8) Spherical shaping: The 40-140 mesh particles obtained in step (7) are spherical shaped again to form more rounded spheres. The sphericity of the rounded spheres after the shaping operation reaches more than 98%.

[0067] (9) Curing: Send the round sphere obtained in step (8) to the curing chamber for curing. The curing is carried out in two stages: water mist curing and dry curing.

[0068] (10) The spherical particles obtained in step (9) are sieved to obtain lightweight gypsum sand, wherein the lightweight gypsum sand has a size of 0.106mm-0.425mm and an internal bulk density of 600kg / m³. 3 -700kg / m 3 All other indicators meet the requirements of GB / T 14684-2022 "Construction Sand".

[0069] Furthermore, in step (6), the particle size of the first sphere is 40-140 mesh.

[0070] Furthermore, in step (6), particles with a diameter ≥ 0.425 mm are removed.

[0071] Further, the curing in step (9) is as follows: water mist curing lasts for 4-7 days, each water spray lasts for 4 hours, spraying once a day, and the temperature of the curing chamber is 15-25 degrees Celsius; then it is transferred to the next curing chamber for dry curing, and the room temperature is maintained for dry curing for 11-14 days. The principle of the curing stage is: to make the gypsum in the raw material react with the gypsum reactant (main material 2) to form ceramic spheres, thereby giving the product high strength and water resistance, for example, the cylinder compressive strength is 4-6MPa, the mass loss rate of the ceramic spheres is less than 5% (high strength), which meets the requirements of GB / T 14684-2022 "Construction Sand" Class I standard, the water absorption rate is 6-7%, and the softening coefficient is 0.76.

[0072] The beneficial effects of this invention are as follows:

[0073] (1) In the prior art, the coating rate of gypsum-based self-leveling mortar is mainly provided by lightweight aggregates, and it follows the rule that the higher the coating rate, the lower the flexural and compressive strength. This is because a higher coating rate will generate a large number of pores in the gypsum-based self-leveling mortar, causing its strength to decrease with the increase of coating rate. However, the coating rate in this invention is provided by a small amount of lightweight gypsum sand. Since the CaSO4 content of gypsum sand is ≥90%, the addition of lightweight gypsum sand will reduce the amount of desulfurized gypsum added, and the density of gypsum sand is 600 kg / m³. 3 This results in the anhydrous gypsum lightweight self-leveling mortar of the present invention having a bulk density of approximately 800 kg / m³. 3 -1000Kg / m 3 between.

[0074] (2) The present invention incorporates II anhydrous gypsum and adds an activator, which ensures the high mechanical strength of the lightweight self-leveling mortar of anhydrous gypsum in the later stage. On the other hand, the incorporation of II anhydrous gypsum and gypsum sand can improve the water resistance and mildew resistance of the product.

[0075] (3) The anhydrous gypsum lightweight self-leveling mortar uses a type of gypsum sand, which has the characteristics of being non-fired, high-strength, water-resistant, energy-saving and environmentally friendly, and reducing energy consumption; the gypsum sand is prepared by one or any two of desulfurized gypsum, natural gypsum, fluorogypsum, phosphogypsum, titanium gypsum or other industrial by-product gypsum.

[0076] (4) This invention uses self-developed gypsum sand, combined with anhydrous gypsum (II type), to produce anhydrous gypsum lightweight self-leveling mortar, which has the characteristics of high strength, lightweight, and environmentally friendly and pollution-free. The anhydrous gypsum lightweight self-leveling mortar exhibits excellent performance in terms of mechanical strength, fluidity, bulk density, and impact resistance; for example, its bulk density is 800 kg / m³. 3 -1000Kg / m 3 Between these values, the 28-day oven-dry compressive strength is 31-40 MPa, and the 28-day oven-dry flexural strength is 8-10 MPa, both of which are significantly improved compared to the performance standards of the gypsum-based self-leveling compound industry (as shown in Table 2).

[0077] (5) This invention utilizes industrial waste to produce anhydrous hard gypsum lightweight self-leveling mortar, turning waste into treasure. Moreover, it uses gypsum sand to replace building sand, thus solving the problem of sand resource shortage. The cost is reduced by about half compared to building sand, resulting in higher economic benefits. Attached Figure Description

[0078] Figure 1 This is a flow chart of the preparation process of the anhydrous hard gypsum lightweight self-leveling mortar of the present invention. Detailed Implementation

[0079] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0080] Example 1

[0081] A method for preparing anhydrous gypsum lightweight self-leveling mortar includes the following steps:

[0082] Step 1: Add building gypsum, anhydrous gypsum II, 42.5 lime cement and lightweight gypsum sand to the mixing tank, and mix them together for 3-5 minutes to obtain a mixture of adhesive and aggregate.

[0083] Step 2: Pre-disperse the activator, water-reducing agent, defoamer, water-retaining thickener, suspension stabilizer, redispersible latex powder, retarder and heavy calcium carbonate to obtain an additive mixture;

[0084] Step 3: Add the additive mixture to the mixing tank and mix it with the adhesive and aggregate mixture for 3-5 minutes to obtain the anhydrous hard gypsum lightweight self-leveling mortar.

[0085] The weight proportions of each material are as follows:

[0086] 45 parts building gypsum, 40 parts type II anhydrous gypsum, 2 parts cement, 13 parts lightweight gypsum sand, 0.25 parts water-reducing agent, 0.1 parts defoamer, 0.03 parts suspension stabilizer, 0.5 parts activator, 0.3 parts redispersible latex powder, 0.05 parts water-retaining thickener, and 0.015 parts retarder;

[0087] The following additives are used:

[0088] Activator: One or more of potassium sulfate, KAl(SO4)2, calcined alum, and sodium bisulfate are used in combination;

[0089] Water-reducing agent: at least one of polycarboxylate-based water-reducing agent, naphthalene-based water-reducing agent, and melamine-based water-reducing agent;

[0090] Defoamer: at least one of the following: high carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether, and polydimethylsiloxane;

[0091] Water-retaining thickener: is a low-viscosity water-retaining thickener with a viscosity of 400-600 mps, preferably at least one of methyl cellulose ether with a viscosity of 400-600 mps, hydroxypropyl methyl cellulose ether with a viscosity of 400-600 mps, and methyl hydroxyethyl cellulose ether with a viscosity of 400-600 mps.

[0092] Suspension stabilizers: one or more combinations of polyacrylamide, SBR latex, and cellulose ether;

[0093] Redispersible latex powder: is at least one of ethylene / vinyl acetate copolymer, vinyl acetate / ethylene tert-carbonate copolymer and styrene / acrylic acid copolymer;

[0094] Retarder: Protein-based gypsum retarder.

[0095] The specific properties of the gypsum-based self-leveling mortar in Example 1 are shown in Table 2.

[0096] The lightweight gypsum sand used in the anhydrous gypsum lightweight self-leveling mortar of Example 1 is prepared as follows:

[0097] Based on the total mass of raw materials, the percentage content of raw materials in lightweight gypsum sand is as follows:

[0098] Parent material: Perlite filter aid with a particle size ≤ 0.102 mm, 5 parts;

[0099] Main ingredient 1: 35 parts desulfurized gypsum, 30 parts natural gypsum, and 5 parts fluorogypsum;

[0100] Main ingredient 2: 5 parts aluminate compound and 5 parts kaolin mineral;

[0101] Auxiliary materials: 3 parts quicklime and 2 parts activated calcium;

[0102] pelletizing materials: 1 part clay, 2 parts bentonite and 1 part lignin cellulose;

[0103] Dispersant: 3 parts sodium pyrophosphate, 3 parts polycarboxylate, 3 parts sodium tripolyphosphate;

[0104] Preparation methods include:

[0105] (1) Grinding: Main material 1, main material 2, auxiliary material, and pelletizing material are ground to 0.038mm respectively;

[0106] (2) Mud reaction: Add appropriate amount of water to the main material 1, main material 2, auxiliary material and pelletizing material and stir thoroughly in the mixing tank at a speed of 250 r / min for 5 min. At this time, the various materials are fully dispersed in the water to form mud liquid, and the various materials can fully contact and mix evenly.

[0107] (3) Dehydration: The mud slurry after the mud reaction is dehydrated by centrifugation, adsorption, and extrusion, and then dried at 250℃ to control the water content of the mud slurry to below 3% by mass, so as to obtain block material.

[0108] (4) Grinding: Grind the lumpy material into powder using a high-speed grinding mill at a speed of 3000 r / min to a particle size of 0.038 mm;

[0109] (5) Formation of mother ball: Pour the mother ball into the round pot granulator, and spray water to form granules A through the water spraying component of the granulator. Add 1 / 3 of the total weight of powder to granules A, and continue to form mother balls under the rapid rotation in the ball mill.

[0110] (6) Spherical formation: While the mother ball is being sprayed with water mist in the granulator, the remaining powder is added while spraying. As the ball mill rotates rapidly, the mother ball gradually grows larger to form the first spherical. At this point, no more water spraying is needed. Then, a dispersant is added to form the second spherical particles.

[0111] (7) Sieving: Remove the coarse particles from the second spherical particles obtained in step (6), leaving particles of 40-140 mesh for later use;

[0112] (8) Spherical shaping: The 40-140 mesh particles obtained in step (7) are spherically shaped again to form more rounded spheres. The sphericity of the rounded spheres after the shaping operation reaches more than 98%.

[0113] (9) Curing: Send the round sphere obtained in step (8) to the curing chamber for curing. The curing is carried out in two stages: water mist curing and dry curing.

[0114] (10) The spherical particles obtained in step (9) are sieved to obtain lightweight gypsum sand sample 1. The lightweight gypsum sand has a size of 0.106mm-0.425mm and an internal bulk density of 600kg / m³. 3 -700kg / m 3 All other indicators meet the requirements of GB / T 14684-2022 "Construction Sand".

[0115] The curing process in step (9) involves water mist curing for 7 days, with each water mist spraying lasting 4 hours, once a day, and the curing chamber temperature maintained at 25 degrees Celsius. Then, the product is moved to the next curing chamber for dry curing, maintaining dry curing at room temperature for 14 days. The principle of the curing stage is to cause the gypsum in the raw materials to undergo a ceramicization reaction with the gypsum reactant (main material 2) to form ceramic spherical particles, thereby giving the product higher strength and water resistance. Specific properties are shown in Table 1.

[0116] Example 2

[0117] A method for preparing anhydrous gypsum lightweight self-leveling mortar includes the following steps:

[0118] Step 1: Add building gypsum, anhydrous gypsum II, 42.5 lime cement and lightweight gypsum sand to the mixing tank, and mix them together for 3-5 minutes to obtain a mixture of adhesive and aggregate.

[0119] Step 2: Pre-disperse the activator, water-reducing agent, defoamer, water-retaining thickener, suspension stabilizer, redispersible latex powder, retarder and heavy calcium carbonate to obtain an additive mixture;

[0120] Step 3: Add the additive mixture to the mixing tank and mix it with the adhesive and aggregate mixture for 3-5 minutes to obtain the anhydrous hard gypsum lightweight self-leveling mortar.

[0121] The weight proportions of each material are as follows:

[0122] 50 parts building gypsum, 20 parts type II anhydrous gypsum, 1.5 parts cement, 23.5 parts lightweight gypsum sand, 0.3 parts water-reducing agent, 0.09 parts defoamer, 0.02 parts suspension stabilizer, 0.3 parts activator, 0.5 parts redispersible latex powder, 0.03 parts water-retaining thickener, and 0.02 parts retarder;

[0123] The following additives are used:

[0124] Activator: One or more of potassium sulfate, KAl(SO4)2, calcined alum, and sodium bisulfate are used in combination;

[0125] Water-reducing agent: at least one of polycarboxylate-based water-reducing agent, naphthalene-based water-reducing agent, and melamine-based water-reducing agent;

[0126] Defoamer: at least one of the following: high carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether, and polydimethylsiloxane;

[0127] Water-retaining thickener: is a low-viscosity water-retaining thickener with a viscosity of 400-600 mps, preferably at least one of methyl cellulose ether with a viscosity of 400-600 mps, hydroxypropyl methyl cellulose ether with a viscosity of 400-600 mps, and methyl hydroxyethyl cellulose ether with a viscosity of 400-600 mps.

[0128] Suspension stabilizers: one or more combinations of polyacrylamide, SBR latex, and cellulose ether;

[0129] Redispersible latex powder: is at least one of ethylene / vinyl acetate copolymer, vinyl acetate / ethylene tert-carbonate copolymer and styrene / acrylic acid copolymer;

[0130] Retarder: Protein-based gypsum retarder.

[0131] The specific properties of the anhydrous gypsum lightweight self-leveling mortar in Example 2 are shown in Table 2.

[0132] The lightweight gypsum sand used in the anhydrous gypsum lightweight self-leveling mortar of Example 2 is prepared as follows:

[0133] Based on the total mass of raw materials, the percentage content of raw materials in lightweight gypsum sand is as follows:

[0134] Parent material: Perlite filter aid with a particle size ≤ 0.102 mm, 8 parts;

[0135] Main ingredient 1: 32 parts desulfurized gypsum, 21 parts natural gypsum, 2 parts titanium gypsum and 3 parts phosphogypsum;

[0136] Main material 2: 5 parts soluble oxide, 10 parts aluminum oxide and 1 part dolomite;

[0137] Auxiliary materials: 3 parts quicklime;

[0138] pelletizing materials: 1 part clay, 1 part bentonite and 2 parts lignin cellulose;

[0139] Dispersant: 2 parts sodium pyrophosphate, 3 parts sodium hexametaphosphate and 5 parts sodium tripolyphosphate;

[0140] Preparation methods include:

[0141] (1) Grinding: Main material 1, main material 2, auxiliary material and pelletizing material are ground to 0.039mm respectively;

[0142] (2) Mud reaction: Add appropriate amount of water to the main material 1, main material 2, auxiliary material and pelletizing material and stir thoroughly in the mixing tank at a speed of 250 r / min for 8 min. At this time, the various materials are fully dispersed in the water to form mud liquid, and the various materials can fully contact and mix evenly.

[0143] (3) Dehydration: The mud slurry after the mud reaction is dehydrated by centrifugation, adsorption, and extrusion, and then dried at 200℃ to control the water content of the mud slurry to below 3% by mass, so as to obtain block material.

[0144] (4) Grinding: Grind the lumpy material into powder using a high-speed grinding mill at a speed of 3500 r / min to a particle size of 0.039 mm;

[0145] (5) Formation of mother ball: Pour the mother ball into the round pot granulator, and spray water to form granules A through the water spraying component of the granulator. Add 1 / 2 of the total weight of powder to granules A, and continue to form mother balls under the rapid rotation in the ball mill.

[0146] (6) Spherical formation: While the mother ball is being sprayed with water mist in the granulator, the remaining powder is added while spraying. As the ball mill rotates rapidly, the mother ball gradually grows larger to form the first spherical. At this point, no more water spraying is needed. Then, a dispersant is added to form the second spherical particles.

[0147] (7) Sieving: Remove the coarse particles from the second spherical particles obtained in step (6), leaving particles of 40-140 mesh for later use;

[0148] (8) Spherical shaping: The 40-140 mesh particles obtained in step (7) are spherically shaped again to form more rounded spheres. The sphericity of the rounded spheres after the shaping operation reaches more than 98%.

[0149] (9) Curing: Send the round sphere obtained in step (8) to the curing chamber for curing. The curing is carried out in two stages: water mist curing and dry curing.

[0150] (10) The spherical particles obtained in step (9) are sieved to obtain lightweight gypsum sand sample 2. The lightweight gypsum sand has a size of 0.106mm-0.425mm and an internal bulk density of 600kg / m³. 3 -700kg / m 3 All other indicators meet the requirements of GB / T 14684-2022 "Construction Sand".

[0151] The curing process in step (9) involves water mist curing for 6 days, with each water mist spraying lasting 4 hours, once a day, and the curing chamber temperature maintained at 205 degrees Celsius. The product is then moved to the next curing chamber for dry curing, with the room temperature maintained for 12 days. The principle of the curing stage is to cause the gypsum in the raw materials to undergo a ceramicization reaction with the gypsum reactant (main material 2) to form ceramic spherical particles, thereby giving the product higher strength and water resistance. Specific performance details are shown in Table 1.

[0152] Example 3

[0153] A method for preparing anhydrous gypsum lightweight self-leveling mortar includes the following steps:

[0154] Step 1: Add desulfurized gypsum, anhydrous gypsum II, 42.5 lime cement and lightweight gypsum sand to the mixing tank, and mix them together for 3-5 minutes to obtain a mixture of adhesive and aggregate.

[0155] Step 2: Pre-disperse the activator, water-reducing agent, defoamer, water-retaining thickener, suspension stabilizer, redispersible latex powder, retarder and heavy calcium carbonate to obtain an additive mixture;

[0156] Step 3: Add the additive mixture to the mixing tank and mix it with the adhesive and aggregate mixture for 3-5 minutes to obtain the anhydrous hard gypsum lightweight self-leveling mortar.

[0157] The weight proportions of each material are as follows:

[0158] 48 parts building gypsum, 25 parts type II anhydrous gypsum, 2 parts cement, 25 parts lightweight gypsum sand, 0.35 parts water-reducing agent, 0.08 parts defoamer, 0.04 parts suspension stabilizer, 0.05 parts water-retaining thickener, 0.5 parts activator, 0.35 parts redispersible latex powder, and 0.025 parts retarder;

[0159] The following additives are used:

[0160] Activator: One or more of potassium sulfate, KAl(SO4)2, calcined alum, and sodium bisulfate are used in combination;

[0161] Water-reducing agent: at least one of polycarboxylate-based water-reducing agent, naphthalene-based water-reducing agent, and melamine-based water-reducing agent;

[0162] Defoamer: at least one of the following: high carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether, and polydimethylsiloxane;

[0163] Water-retaining thickener: is a low-viscosity water-retaining thickener with a viscosity of 400-600 mps, preferably at least one of methyl cellulose ether with a viscosity of 400-600 mps, hydroxypropyl methyl cellulose ether with a viscosity of 400-600 mps, and methyl hydroxyethyl cellulose ether with a viscosity of 400-600 mps.

[0164] Suspension stabilizers: one or more combinations of polyacrylamide, SBR latex, and cellulose ether;

[0165] Redispersible latex powder: is at least one of ethylene / vinyl acetate copolymer, vinyl acetate / ethylene tert-carbonate copolymer and styrene / acrylic acid copolymer;

[0166] Retarder: Protein-based gypsum retarder.

[0167] The specific properties of the anhydrous gypsum lightweight self-leveling mortar in Example 3 are shown in Table 2.

[0168] The lightweight gypsum sand used in the anhydrous gypsum lightweight self-leveling mortar of Example 3 is prepared as follows:

[0169] Based on the total mass of raw materials, the percentage content of raw materials in lightweight gypsum sand is as follows:

[0170] Parent material: Perlite filter aid with a particle size ≤ 0.102 mm, 9 parts;

[0171] Main material 1: 31 parts desulfurized gypsum, 24 parts natural gypsum, 10 parts fluorogypsum and 5 parts phosphogypsum;

[0172] Main material 2: 5 parts of silica-alumina minerals, 3 parts of kaolin minerals, 2 parts of aluminum oxide, and 1 part of dolomite;

[0173] Auxiliary materials: 2 parts quicklime;

[0174] pelletizing materials: 1 part clay, 2 parts bentonite, 2 parts lignin cellulose;

[0175] Dispersant: 2 parts sodium pyrophosphate, 1 part sodium hexametaphosphate;

[0176] Preparation methods include:

[0177] (1) Grinding: Main material 1, main material 2, auxiliary material and pelletizing material are ground to 0.040mm respectively;

[0178] (2) Mud reaction: Add appropriate amount of water to the main material 1, main material 2, auxiliary material and pelletizing material and stir thoroughly in the mixing tank at a speed of 300 r / min for 10 min. At this time, the various materials are fully dispersed in the water to form mud liquid, and the various materials can fully contact and mix evenly.

[0179] (3) Dehydration: The mud slurry after the mud reaction is dehydrated by centrifugation, adsorption, and extrusion, and then dried at 250℃ to control the water content of the mud slurry to below 3% by mass, so as to obtain block material.

[0180] (4) Grinding: Grind the lumpy material into powder using a high-speed grinding mill at a speed of 4000 r / min to a particle size of 0.040 mm;

[0181] (5) Formation of mother ball: Pour the mother ball into the round pot granulator, and spray water to form granules A through the water spraying component of the granulator. Add 1 / 2 of the total weight of powder to granules A, and continue to form mother balls under the rapid rotation in the ball mill.

[0182] (6) Spherical formation: While the mother ball is being sprayed with water mist in the granulator, the remaining powder is added while spraying. As the ball mill rotates rapidly, the mother ball gradually grows larger to form the first spherical. At this point, no more water spraying is needed. Then, a dispersant is added to form the second spherical particles.

[0183] (7) Sieving: Remove the coarse particles from the second spherical particles obtained in step (6), leaving particles of 40-140 mesh for later use;

[0184] (8) Spherical shaping: The 40-140 mesh particles obtained in step (7) are spherically shaped again to form more rounded spheres. The sphericity of the rounded spheres after the shaping operation reaches more than 98%.

[0185] (9) Curing: Send the round sphere obtained in step (8) to the curing chamber for curing. The curing is carried out in two stages: water mist curing and dry curing.

[0186] (10) The spherical particles obtained in step (9) are sieved to obtain lightweight gypsum sand sample 3. The lightweight gypsum sand has a size of 0.106mm-0.425mm and an internal bulk density of 600kg / m³. 3 -700kg / m 3 All other indicators meet the requirements of GB / T 14684-2022 "Construction Sand".

[0187] The curing process in step (9) involves water mist curing for 5 days, with each water mist spraying lasting 4 hours, once a day, and the curing chamber temperature maintained at 20 degrees Celsius. Then, the product is moved to the next curing chamber for dry curing, which is maintained at room temperature for 14 days. The principle of the curing stage is to cause the gypsum in the raw materials to undergo a ceramicization reaction with the gypsum reactant (main material 2) to form ceramic spherical particles, thereby giving the product higher strength and water resistance. Specific performance details are shown in Table 1.

[0188] Example 4

[0189] A method for preparing anhydrous gypsum lightweight self-leveling mortar includes the following steps:

[0190] Step 1: Add desulfurized gypsum, anhydrous gypsum II, 42.5 lime cement and lightweight gypsum sand to the mixing tank, and mix them together for 3-5 minutes to obtain a mixture of adhesive and aggregate.

[0191] Step 2: Pre-disperse the activator, water-reducing agent, defoamer, water-retaining thickener, suspension stabilizer, redispersible latex powder, retarder and heavy calcium carbonate to obtain an additive mixture;

[0192] Step 3: Add the additive mixture to the mixing tank and mix it with the adhesive and aggregate mixture for 3-5 minutes to obtain the anhydrous hard gypsum lightweight self-leveling mortar.

[0193] The weight proportions of each material are as follows:

[0194] 40 parts building gypsum, 38 parts type II anhydrous gypsum, 3 parts cement, 19 parts lightweight gypsum sand, 0.3 parts water-reducing agent, 0.09 parts defoamer, 0.02 parts suspension stabilizer, 0.2 parts redispersible latex powder, 0.7 parts activator, 0.03 parts water-retaining thickener, and 0.03 parts retarder;

[0195] The following additives are used:

[0196] Activator: One or more of potassium sulfate, KAl(SO4)2, calcined alum, and sodium bisulfate are used in combination;

[0197] Water-reducing agent: at least one of polycarboxylate-based water-reducing agent, naphthalene-based water-reducing agent, and melamine-based water-reducing agent;

[0198] Defoamer: at least one of the following: high carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether, and polydimethylsiloxane;

[0199] Water-retaining thickener: is a low-viscosity water-retaining thickener with a viscosity of 400-600 mps, preferably at least one of methyl cellulose ether with a viscosity of 400-600 mps, hydroxypropyl methyl cellulose ether with a viscosity of 400-600 mps, and methyl hydroxyethyl cellulose ether with a viscosity of 400-600 mps.

[0200] Suspension stabilizers: one or more combinations of polyacrylamide, SBR latex, and cellulose ether;

[0201] Redispersible latex powder: is at least one of ethylene / vinyl acetate copolymer, vinyl acetate / ethylene tert-carbonate copolymer and styrene / acrylic acid copolymer;

[0202] Retarder: Protein-based gypsum retarder.

[0203] The specific properties of the anhydrous gypsum lightweight self-leveling mortar in Example 4 are shown in Table 2.

[0204] The lightweight gypsum sand used in the anhydrous gypsum lightweight self-leveling mortar of Example 4 is prepared as follows:

[0205] Based on the total mass of raw materials, the percentage content of raw materials in lightweight gypsum sand is as follows:

[0206] Parent material: Perlite filter aid with a particle size ≤ 0.102 mm, 6 parts;

[0207] Main material 1: 30 parts desulfurized gypsum, 28 parts natural gypsum, 10 parts fluorogypsum, and 5 parts phosphogypsum;

[0208] Main material 2: 6 parts of silica-alumina minerals, 3 parts of kaolin minerals, 3 parts of aluminum oxide, and 1 part of dolomite;

[0209] Auxiliary materials: 2 parts quicklime;

[0210] pelletizing materials: 1 part clay, 2 parts bentonite, 1 part lignin cellulose;

[0211] Dispersant: 1 part sodium pyrophosphate, 1 part sodium hexametaphosphate;

[0212] Preparation methods include:

[0213] (1) Grinding: Main material 1, main material 2, auxiliary material and pelletizing material are ground to 0.041mm respectively;

[0214] (2) Mud reaction: Add appropriate amount of water to the main material 1, main material 2, auxiliary material and pelletizing material and stir thoroughly in the mixing tank at a speed of 300 r / min for 7 min. At this time, the various materials are fully dispersed in the water to form mud liquid, and the various materials can fully contact and mix evenly.

[0215] (3) Dehydration: The mud slurry after the mud reaction is dehydrated by centrifugation, adsorption, and extrusion, and then dried at 180℃ to control the water content of the mud slurry to be below 3% by mass, so as to obtain block material.

[0216] (4) Grinding: Grind the lumpy material into powder using a high-speed grinding mill at a speed of 4500 r / min to a particle size of 0.041 mm.

[0217] (5) Formation of mother ball: Pour the mother ball into the round pot granulator, and spray water to form granules A through the water spraying component of the granulator. Add 1 / 3 of the total weight of powder to granules A, and continue to form mother balls under the rapid rotation in the ball mill.

[0218] (6) Spherical formation: While the mother ball is being sprayed with water mist in the granulator, the remaining powder is added while spraying. As the ball mill rotates rapidly, the mother ball gradually grows larger to form the first spherical. At this point, no more water spraying is needed. Then, a dispersant is added to form the second spherical particles.

[0219] (7) Sieving: Remove the coarse particles from the second spherical particles obtained in step (6), leaving particles of 40-140 mesh for later use;

[0220] (8) Spherical shaping: The 40-140 mesh particles obtained in step (7) are spherically shaped again to form more rounded spheres. The sphericity of the rounded spheres after the shaping operation reaches more than 98%.

[0221] (9) Curing: Send the round sphere obtained in step (8) to the curing chamber for curing. The curing is carried out in two stages: water mist curing and dry curing.

[0222] (10) The spherical particles obtained in step (9) are sieved to obtain lightweight gypsum sand sample 4. The lightweight gypsum sand has a size of 0.106mm-0.425mm and an internal bulk density of 600kg / m³. 3 -700kg / m 3 All other indicators meet the requirements of GB / T 14684-2022 "Construction Sand".

[0223] The curing process in step (9) involves water mist curing for 6 days, with each water mist spraying lasting 4 hours, once a day, and the curing chamber temperature maintained at 25 degrees Celsius. Then, the product is moved to the next curing chamber for dry curing, maintaining dry curing at room temperature for 12 days. The principle of the curing stage is to cause the gypsum in the raw materials to undergo a ceramicization reaction with the gypsum reactant (main material 2) to form ceramic spherical particles, thereby giving the product higher strength and water resistance. Specific performance details are shown in Table 1.

[0224] Example 5

[0225] A method for preparing anhydrous gypsum lightweight self-leveling mortar includes the following steps:

[0226] Step 1: Add building gypsum, anhydrous gypsum II, 42.5 lime cement and lightweight gypsum sand to the mixing tank, and mix them together for 3-5 minutes to obtain a mixture of adhesive and aggregate.

[0227] Step 2: Pre-disperse the activator, water-reducing agent, defoamer, water-retaining thickener, suspension stabilizer, redispersible latex powder, retarder and heavy calcium carbonate to obtain an additive mixture;

[0228] Step 3: Add the additive mixture to the mixing tank and mix it with the adhesive and aggregate mixture for 3-5 minutes to obtain the anhydrous hard gypsum lightweight self-leveling mortar.

[0229] The weight proportions of each material are as follows:

[0230] 40 parts building gypsum, 40 parts type II anhydrous gypsum, 2 parts cement, 18 parts lightweight gypsum sand, 0.3 parts water-reducing agent, 0.7 parts defoamer, 0.02 parts suspension stabilizer, 0.4 parts redispersible latex powder, 0.9 parts activator, 0.02 parts water-retaining thickener, and 0.035 parts retarder;

[0231] The following additives are used:

[0232] Activator: One or more of potassium sulfate, KAl(SO4)2, calcined alum, and sodium bisulfate are used in combination;

[0233] Water-reducing agent: at least one of polycarboxylate-based water-reducing agent, naphthalene-based water-reducing agent, and melamine-based water-reducing agent;

[0234] Defoamer: at least one of the following: high carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether, and polydimethylsiloxane;

[0235] Water-retaining thickener: is a low-viscosity water-retaining thickener with a viscosity of 400-600 mps, preferably at least one of methyl cellulose ether with a viscosity of 400-600 mps, hydroxypropyl methyl cellulose ether with a viscosity of 400-600 mps, and methyl hydroxyethyl cellulose ether with a viscosity of 400-600 mps.

[0236] Suspension stabilizers: one or more combinations of polyacrylamide, SBR latex, and cellulose ether;

[0237] Redispersible latex powder: is at least one of ethylene / vinyl acetate copolymer, vinyl acetate / ethylene tert-carbonate copolymer and styrene / acrylic acid copolymer;

[0238] Retarder: Protein-based gypsum retarder.

[0239] The specific properties of the anhydrous gypsum lightweight self-leveling mortar in Example 5 are shown in Table 2.

[0240] The lightweight gypsum sand used in the anhydrous gypsum lightweight self-leveling mortar of Example 5 is prepared as follows:

[0241] Based on the total mass of raw materials, the percentage content of raw materials in lightweight gypsum sand is as follows:

[0242] Parent material: Perlite filter aid with a particle size ≤ 0.102 mm, 9 parts;

[0243] Main material 1: 21 parts desulfurized gypsum, 34 parts natural gypsum, 10 parts fluorogypsum, and 5 parts phosphogypsum;

[0244] Main material 2: 6 parts of silica-alumina minerals, 3 parts of kaolin minerals, 3 parts of aluminum oxide, and 1 part of dolomite;

[0245] Auxiliary materials: 2 parts quicklime;

[0246] pelletizing materials: 1 part clay, 2 parts bentonite, 1 part lignin cellulose;

[0247] Dispersant: 1 part sodium pyrophosphate, 1 part sodium hexametaphosphate;

[0248] Preparation methods include:

[0249] (1) Grinding: Main material 1, main material 2, auxiliary material, and pelletizing material are ground to 0.038mm respectively;

[0250] (2) Mud reaction: Add appropriate amount of water to the main material 1, main material 2, auxiliary material and pelletizing material and stir thoroughly in the mixing tank at a speed of 300 r / min for 5 min. At this time, the various materials are fully dispersed in the water to form mud liquid, and the various materials can fully contact and mix evenly.

[0251] (3) Dehydration: The mud slurry after the mud reaction is dehydrated by centrifugation, adsorption, and extrusion, and then dried at 150℃ to control the water content of the mud slurry to below 3% by mass, so as to obtain block material.

[0252] (4) Grinding: Grind the lumpy material into powder using a high-speed grinding mill at a speed of 3000 r / min to a particle size of 0.038 mm;

[0253] (5) Formation of mother ball: Pour the mother ball into the round pot granulator, and spray water to form granules A through the water spraying component of the granulator. Add 1 / 2 of the total weight of powder to granules A, and continue to form mother balls under the rapid rotation in the ball mill.

[0254] (6) Spherical formation: While the mother ball is being sprayed with water mist in the granulator, the remaining powder is added while spraying. As the ball mill rotates rapidly, the mother ball gradually grows larger to form the first spherical. At this point, no more water spraying is needed. Then, a dispersant is added to form the second spherical particles.

[0255] (7) Sieving: Remove the coarse particles from the second spherical particles obtained in step (6), leaving particles of 40-140 mesh for later use;

[0256] (8) Spherical shaping: The 40-140 mesh particles obtained in step (7) are spherically shaped again to form more rounded spheres. The sphericity of the rounded spheres after the shaping operation reaches more than 98%.

[0257] (9) Curing: Send the round sphere obtained in step (8) to the curing chamber for curing. The curing is carried out in two stages: water mist curing and dry curing.

[0258] (10) The spherical particles obtained in step (9) are sieved to obtain lightweight gypsum sand sample 4. The lightweight gypsum sand has a size of 0.106mm-0.425mm and an internal bulk density of 600kg / m³. 3 -700kg / m 3 All other indicators meet the requirements of GB / T 14684-2022 "Construction Sand".

[0259] The curing process in step (9) involves water mist curing for 6 days, with each water mist spraying lasting 4 hours, once a day, and the curing chamber temperature maintained at 15 degrees Celsius. Then, the product is moved to the next curing chamber for dry curing, which is maintained at room temperature for 13 days. The principle of the curing stage is to cause the gypsum in the raw material to undergo a ceramicization reaction with the gypsum reactant (main material 2) to form ceramic spherical particles, thereby giving the product higher strength and water resistance. Specific performance details are shown in Table 1.

[0260] Example 6

[0261] A method for preparing anhydrous gypsum lightweight self-leveling mortar includes the following steps:

[0262] Step 1: Add building gypsum, anhydrous gypsum II, 42.5 lime cement and lightweight gypsum sand to the mixing tank, and mix them together for 3 minutes to obtain a mixture of adhesive and aggregate.

[0263] Step 2: Pre-disperse the activator, water-reducing agent, defoamer, water-retaining thickener, suspension stabilizer, redispersible latex powder, retarder and heavy calcium carbonate to obtain an additive mixture;

[0264] Step 3: Add the additive mixture to the mixing tank and mix it with the adhesive and aggregate mixture for 3 minutes to obtain the anhydrous hard gypsum lightweight self-leveling mortar.

[0265] 41 parts building gypsum, 36 parts type II anhydrous gypsum, 3 parts cement, 20 parts lightweight gypsum sand, 0.35 parts water-reducing agent, 0.8 parts defoamer, 0.02 parts suspension stabilizer, 0.03 parts water-retaining thickener, 0.5 parts activator, 0.3 parts redispersible latex powder, and 0.03 parts retarder;

[0266] The following additives are used:

[0267] Activator: One or more of potassium sulfate, KAl(SO4)2, calcined alum, and sodium bisulfate are used in combination;

[0268] Water-reducing agent: at least one of polycarboxylate-based water-reducing agent, naphthalene-based water-reducing agent, and melamine-based water-reducing agent;

[0269] Defoamer: at least one of the following: high carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene alcohol amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether, and polydimethylsiloxane;

[0270] Water-retaining thickener: is a low-viscosity water-retaining thickener with a viscosity of 400-600 mps, preferably at least one of methyl cellulose ether with a viscosity of 400-600 mps, hydroxypropyl methyl cellulose ether with a viscosity of 400-600 mps, and methyl hydroxyethyl cellulose ether with a viscosity of 400-600 mps.

[0271] Suspension stabilizers: one or more combinations of polyacrylamide, SBR latex, and cellulose ether;

[0272] Redispersible latex powder: is at least one of ethylene / vinyl acetate copolymer, vinyl acetate / ethylene tert-carbonate copolymer and styrene / acrylic acid copolymer;

[0273] Retarder: Protein-based gypsum retarder.

[0274] The specific properties of the gypsum-based self-leveling mortar in Example 6 are shown in Table 2.

[0275] The preparation method of the lightweight gypsum sand used in the gypsum-based self-leveling mortar of Example 6 is as follows:

[0276] Based on the total mass of raw materials, the percentage content of raw materials in lightweight gypsum sand is as follows:

[0277] Parent material: 10 parts of perlite filter aid with a particle size ≤ 0.102 mm;

[0278] Main material 1: 30 parts desulfurized gypsum, 24 parts natural gypsum, 10 parts fluorogypsum, and 5 parts phosphogypsum;

[0279] Main material 2: 6 parts of silica-alumina minerals, 3 parts of kaolin minerals, 3 parts of aluminum oxide, and 1 part of dolomite;

[0280] Auxiliary materials: 2 parts quicklime;

[0281] pelletizing materials: 1 part clay, 2 parts bentonite, 1 part lignin cellulose;

[0282] Dispersant: 1 part sodium pyrophosphate, 1 part sodium hexametaphosphate;

[0283] Preparation methods include:

[0284] (1) Grinding: Main material 1, main material 2, auxiliary material and pelletizing material are ground to 0.041mm respectively;

[0285] (2) Mud reaction: Add appropriate amount of water to the main material 1, main material 2, auxiliary material and pelletizing material and stir thoroughly in the mixing tank at a speed of 280 r / min for 8 min. At this time, the various materials are fully dispersed in the water to form mud liquid, and the various materials can fully contact and mix evenly.

[0286] (3) Dehydration: The mud slurry after the mud reaction is dehydrated by centrifugation, adsorption, and extrusion, and then dried at 220℃ to control the water content of the mud slurry to below 3% by mass, so as to obtain block material.

[0287] (4) Grinding: Grind the lumpy material into powder using a high-speed grinding mill at a speed of 3400 r / min to a particle size of 0.041 mm.

[0288] (5) Formation of mother ball: Pour the mother ball into the round pot granulator, and spray water to form granules A through the water spraying component of the granulator. Add 1 / 2 of the total weight of powder to granules A, and continue to form mother balls under the rapid rotation in the ball mill.

[0289] (6) Spherical formation: While the mother ball is being sprayed with water mist in the granulator, the remaining powder is added while spraying. As the ball mill rotates rapidly, the mother ball gradually grows larger to form the first spherical. At this point, no more water spraying is needed. Then, a dispersant is added to form the second spherical particles.

[0290] (7) Sieving: Remove the coarse particles from the second spherical particles obtained in step (6), leaving particles of 40-140 mesh for later use;

[0291] (8) Spherical shaping: The 40-140 mesh particles obtained in step (7) are spherically shaped again to form more rounded spheres. The sphericity of the rounded spheres after the shaping operation reaches more than 98%.

[0292] (9) Curing: Send the round sphere obtained in step (8) to the curing chamber for curing. The curing is carried out in two stages: water mist curing and dry curing.

[0293] (10) The spherical particles obtained in step (9) are sieved to obtain lightweight gypsum sand sample 4. The lightweight gypsum sand has a size of 0.106mm-0.425mm and an internal bulk density of 600kg / m³. 3 -700kg / m 3 All other indicators meet the requirements of GB / T 14684-2022 "Construction Sand".

[0294] The curing process in step (9) involves water mist curing for 7 days, with each water mist spraying lasting 4 hours, once a day, and the curing chamber temperature maintained at 25 degrees Celsius. Then, the product is moved to the next curing chamber for dry curing, maintaining dry curing at room temperature for 14 days. The principle of the curing stage is to cause the gypsum in the raw materials to undergo a ceramicization reaction with the gypsum reactant (main material 2) to form ceramic spherical particles, thereby giving the product higher strength and water resistance. Specific properties are shown in Table 1.

[0295] Table 1 shows the performance test results of lightweight gypsum sand samples 1-4 according to GB / T 14684-2011 "Construction Sand".

[0296] project index Sample 1 Sample 2 Sample 3 Sample 4 <![CDATA[Bulk density kg / m 3 > ≤1000 620 635 680 650 Cylinder compressive strength / MPa ≥2 4.1 4.7 5.0 4.9 Breakage rate / 28MPa ≤5％ 4.1 4.3 4.5 4.2 Water absorption rate / % ≤8％ 6.0 6.3 6.4 6.1 Sphericity / % ≥98 98 99 99 99 Softening coefficient ≥0.5 0.76 0.75 0.76 0.74

[0297] Table 2 shows the performance test results of the anhydrous gypsum lightweight self-leveling mortars in Examples 1-6, based on the softening coefficients in JC / T 1023-2021 "Gypsum-based Self-leveling Mortar" (G25) and GBT 20473-2021 "Building Thermal Insulation Mortar".

[0298]

[0299] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A process for the preparation of anhydrite lightweight self-leveling mortar, characterized by, The raw materials of the anhydrous hard gypsum lightweight self-leveling mortar include the following components by weight: Building gypsum: 30-80 parts; 42.5 gray cement: 1-5 parts; Type II anhydrous hard gypsum: 10-50 parts; Lightweight gypsum sand: 10-30 parts; Activator: 0.1-1 part; Water reducing agent: 0.1-0.3 part; Defoaming agent: 0.05-0.1 part; Water retention thickening agent: 0.05-0.1 part; Suspension stabilizer: 0.01-0.1 part; Redispersible latex powder: 0.1-0.5 part; and Retarder: 0.01-0.03 part; The preparation method of the lightweight gypsum sand includes the following steps: The raw materials of the lightweight gypsum sand include the following components by weight: 5-10 parts of matrix particles, 65-80 parts of main material 1, 10-15 parts of main material 2, 2-5 parts of auxiliary material, 3-5 parts of ball-forming material, and 1-10 parts of dispersing agent; the total amount of the above raw materials is 100 parts; Matrix particles: perlite filter aid with a particle size of ≤0.102 mm; Main material 1: any one or a mixture of two or more of natural gypsum, desulfurization gypsum, phosphogypsum, fluorogypsum, titanium gypsum, or other industrial by-product gypsum; Main material 2: any one or a mixture of two or more of aluminate compound, silico-aluminate mineral, dolomite, soluble oxide, and aluminum oxide; Auxiliary material: any one or a mixture of two of active calcium and slaked lime; Ball-forming material: any one or a mixture of two or more of clay, lignin cellulose, or bentonite, all with a particle size of ≤0.048 mm; Dispersing agent: any one or a mixture of two of sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, and polycarboxylate; (1) Grinding: grinding main material 1, main material 2, auxiliary material, and ball-forming material to 0.037±0.005 mm respectively; (2) Mud reaction: adding an appropriate amount of water to main material 1, main material 2, auxiliary material, and ball-forming material in a stirring kettle to fully stir, at a speed of 50-300 r / min for 5-10 min, at which time the materials are fully dispersed in the water to form a mud liquid, and the materials can fully contact and mix uniformly; (3) Dewatering: after the mud reaction, the mud liquid is dewatered by centrifugation, adsorption, and extrusion, and then dried at 150-250°C to control the water content of the mud liquid to less than 3% by mass, to obtain a block material; (4) Powdering: grinding the block material through a high-speed grinding machine at a speed of 3000-6000 r / min to obtain a powder with a particle size of 0.037±0.005 mm; (5) Mother ball formation: pouring the matrix particles into a round pan granulator, spraying water through the water spraying assembly of the granulator to form particles A, adding 1 / 3-1 / 2 of the total weight of the powder to the particles A, and continuously rotating in the ball mill to form mother balls. (6) Spheroid formation: the mother spheres continue to be sprayed with water mist in the granulator while the remaining powder is added, and the mother spheres gradually grow into first spheroids under the rapid rotation of the ball mill, at which point water spraying is no longer needed, and then the dispersing agent is added to form second spheroid particles; (7) Screening: the second spheroid particles obtained in step (6) are screened to remove coarse particles, and particles with a size of 40-140 mesh are left for use; (8) Spheroid shaping: the particles with a size of 40-140 mesh obtained in step (7) are subjected to spheroid shaping again to form more rounded spheroids, and the roundness of the rounded spheroids after shaping reaches more than 98%; (9) Curing: the rounded spheroids obtained in step (8) are sent to a curing bin for curing, and curing is carried out in two stages of water mist curing and dry curing. (10) The spherical particles obtained in step (9) are sieved to obtain light gypsum sand, wherein the light gypsum sand has a size of 0.106 mm-0.425 mm, and an internal bulk density of 600 kg / m 3 -700 kg / m 3 .

2. The production method according to claim 1, characterized by, The building gypsum meets the quality percentage: hemihydrate phase ≥80%, dihydrate phase ≤4%, anhydrous phase ≤5%, 2h flexural strength ≥3.0MPa, 2h compressive strength ≥6.0MPa, and chloride ion content ≤600mg / kg.

3. The production method according to claim 1 or 2, characterized by, The II type anhydrous hard gypsum meets the quality percentage of type II anhydrous gypsum ≥96%, a softening coefficient between 0.6-0.7, and a pH value between 12-13.

4. The production method according to claim 1 or 2, characterized by, The 42.5 grey cement comprises the following ingredients in weight percentage: cement chemical components CaO 60%-65%, SiO2 18%-19%, Al2O3 4%-5%, Fe2O3 2%-3%, MgO 2%-3%, and SO3 3%-4%, based on the total weight of the 42.5 grey cement.

5. The production method according to claim 1 or 2, characterized by, The activator is one or a combination of more than one of KAl(SO4)2, potassium sulfate, calcined alum, and sodium bisulfate.

6. The production method according to claim 1 or 2, characterized by, The water reducing agent is at least one of a polycarboxylic acid type water reducing agent, a naphthalene type water reducing agent, and a melamine type water reducing agent.

7. The production method according to claim 1 or 2, characterized by, The defoaming agent is at least one of a high-carbon alcohol fatty acid ester complex, a polyoxyethylene polyoxypropylene pentaerythritol ether, a polyoxyethylene polyoxypropylamine ether, a polyoxypropylene glycerol ether, a polyoxypropylene polyoxyethylene glycerol ether, and a polydimethylsiloxane.

8. The production method according to claim 1 or 2, characterized by, The water-retention thickener is a low-viscosity water-retention thickener having a viscosity of 400-600 mPa s.

9. The production method according to claim 1 or 2, characterized by, The redispersible latex powder is at least one of an ethylene / vinyl acetate copolymer, a vinyl acetate / tertiary carbon acid ethylene copolymer, and a styrene / propylene acid copolymer.

10. The production method according to claim 1 or 2, characterized by, The retarder is a protein type gypsum retarder.

11. The production method according to claim 1 or 2, characterized by, The preparation method of the anhydrous hard gypsum lightweight self-leveling mortar comprises the following steps: Step 1: building gypsum, II anhydrous hard gypsum, cement, and lightweight gypsum sand are added to a stirring kettle and stirred and mixed together for 3-5 minutes to obtain a glue material and aggregate mixture; Step 2: an activator, a water reducing agent, a defoaming agent, a water-retaining thickening agent, a suspension stabilizer, a redispersible latex powder, and a retarder are pre-dispersed with heavy calcium to obtain an additive mixture; Step 3: the additive mixture is poured into the stirring kettle and mixed and stirred with the glue material and aggregate mixture for 3-5 minutes to obtain the anhydrous hard gypsum lightweight self-leveling mortar.

12. The method of claim 11, wherein, The maintenance in step (9) is that, the water spray maintenance lasts for 4-7 days, the water spraying lasts for 4 hours each time, the water spraying is carried out once a day, the temperature of the maintenance warehouse is 15-25 DEG C; the dry maintenance is carried out in the next maintenance warehouse, and the room temperature is maintained for 11-14 days.

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