Gypsum-based self-leveling mortar and preparation process thereof

Abstract

The invention relates to the technical field of building materials, and particularly discloses gypsum-based self-leveling mortar and a preparation process thereof. The gypsum-based self-leveling mortar is prepared from the following raw material components in parts by weight: 650 to 750 parts of gypsum, 10 to 20 parts of cement, 270 to 290 parts of ground calcium carbonate, 20 to 30 parts of river sand, 5 to 10 parts of fly ash, 0.2 to 0.6 part of a water-retaining agent, 1.5 to 2.5 parts of a water reducing agent, 0.5 to 1 part of a stabilizer, 0.2 to 0.3 part of a retarder and 0.5 to 0.7 part of a de-foaming agent. The preparation process of the gypsum-based self-leveling mortar comprises the following steps: grinding river sand to obtain river sand powder; the gypsum, the ground calcium carbonate and the fly ash are dried in advance and then stirred with the cement, then the water-retaining agent, the water reducing agent, the stabilizer, the retarder and the defoaming agent are added and stirred continuously, finally the river sand powder is added and stirred, and the gypsum-based self-leveling mortar is obtained.

Description

Technical Field

[0001] This application relates to the technical field of building materials, and in particular to a gypsum-based self-leveling mortar and its preparation process. Background Technology

[0002] Gypsum self-leveling mortar is a widely used material in building construction, primarily for leveling and improving the smoothness of floors. In recent years, with the rapid development of the construction industry, the demand for self-leveling mortar has been continuously increasing. High water retention gypsum self-leveling mortar, due to its excellent fluidity and hardened strength, has been widely used in building decoration and repair projects. This material not only improves construction efficiency but also effectively reduces labor costs and enhances the overall quality of buildings. However, commonly used gypsum self-leveling mortars need further improvement in water retention; they often struggle to retain moisture for extended periods, leading to cracking in dry environments and affecting construction quality and service life. Summary of the Invention

[0003] To improve the water retention performance of mortar, this application provides a gypsum-based self-leveling mortar and its preparation process.

[0004] Firstly, this application provides a gypsum-based self-leveling mortar, which adopts the following technical solution: A gypsum-based self-leveling mortar, the raw materials of which include the following components in parts by weight: 650-750 parts gypsum, 10-20 parts cement, 270-290 parts heavy calcium carbonate, 20-30 parts river sand, 5-10 parts fly ash, 0.2-0.6 parts water-retaining agent, 1.5-2.5 parts water-reducing agent, 0.5-1 part stabilizer, 0.2-0.3 parts retarder, and 0.5-0.7 parts defoamer; wherein the water-retaining agent includes cellulose ether, starch ether, sodium polyacrylate, and modified bentonite.

[0005] By adopting the above technical solutions, cellulose ether provides long-term water retention and viscosity stability, starch ether enhances initial water retention and thickening effects, sodium polyacrylate, as a highly absorbent polymer, can absorb and slowly release water, and modified bentonite physically adsorbs and binds water through its large specific surface area and three-dimensional network. The combined use of these components gives the mortar good water retention performance. The addition of heavy calcium carbonate and fly ash improves particle size distribution and reduces interconnected pores, thereby reducing the water migration path and binding with river sand, improving the density of the mortar, and indirectly enhancing water retention performance.

[0006] In one specific implementation, the method for preparing the modified bentonite includes the following steps: Preparation of bentonite slurry: Add sodium pyrophosphate to water and stir until dissolved. Then slowly add sodium-based bentonite, stir to disperse, let stand, and take the upper colloidal slurry to obtain bentonite slurry. Modification: Dissolve hexadecyltrimethylammonium bromide in deionized water at 60°C and stir until homogeneous to obtain a modified solution; heat the bentonite slurry to 55-65°C and stir at a constant temperature. During this process, slowly add the modified solution dropwise. After the addition is complete, stir at a constant temperature of 55-65°C for 2 hours to obtain the reaction mixture. Post-processing: The reaction material was filtered, and then the filter cake was washed, dried, and crushed to obtain modified bentonite.

[0007] By adopting the above technical solution, the sodium ions between the layers of bentonite can be replaced by the cations in hexadecyltrimethylammonium bromide, which can enhance the dispersibility and thixotropy of bentonite in the aqueous phase of mortar. The resulting three-dimensional network structure can more effectively bind water, thereby producing a strong synergistic water retention effect with cellulose ether.

[0008] In one specific implementation, in the bentonite slurry preparation step, the weight ratio of water, sodium pyrophosphate, and sodium-based bentonite is 100:0.5:10; in the modification step, the weight ratio of hexadecyltrimethylammonium bromide and deionized water is 2:20; and the weight ratio of hexadecyltrimethylammonium bromide and sodium-based bentonite is (1.8-2.2):10.

[0009] By adopting the above technical solution, the ratio of hexadecyltrimethylammonium bromide and sodium bentonite was further limited, thereby improving the performance of the modified bentonite.

[0010] In one specific implementation scheme, the weight ratio of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite in the water-retaining agent is 1:(0.5-1):(0.25-0.5):(0.5-1).

[0011] By adopting the above technical solution, the proportions of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite are further defined, thereby improving the water retention performance of the mortar.

[0012] In one specific implementation, the water-reducing agent includes a polycarboxylate-based water-reducing agent.

[0013] In one specific implementation, the stabilizer includes one or more of polyvinyl alcohol, hydroxyethyl methylcellulose, and hydroxyethyl cellulose.

[0014] In one specific implementation, the retarder comprises a mixture of citric acid and tartaric acid.

[0015] By adopting the above technical solution and using citric acid and tartaric acid in combination, the hydration rate of gypsum is controlled, rapid water consumption is avoided, and a longer working time is provided for the water-retaining agent.

[0016] In one specific implementation, the defoamer includes a silicone defoamer.

[0017] Secondly, the preparation process of gypsum-based self-leveling mortar provided in this application adopts the following technical solution: A preparation process of gypsum-based self-leveling mortar includes the following steps: River sand is washed and then ground into fine powder with a particle size of 80-150μm to obtain river sand powder; Gypsum, heavy calcium carbonate, and fly ash are pre-dried to a moisture content of less than 1%, then mixed evenly with cement. Next, water-retaining agent, water-reducing agent, stabilizer, retarder, and defoamer are added, and mixing continues. Finally, river sand powder is added and mixed evenly to obtain gypsum-based self-leveling mortar.

[0018] By adopting the above technical solution, river sand is first ground to obtain river sand powder. Then, gypsum, heavy calcium carbonate and fly ash are pre-dried and mixed with cement. Then, water-retaining agent, water-reducing agent, stabilizer, retarder and defoamer are added. Finally, river sand powder is added and stirred to obtain gypsum-based self-leveling mortar with good water retention performance.

[0019] In summary, this application includes at least one of the following beneficial technical effects: 1. In this application, cellulose ether provides long-term water retention and viscosity stability, starch ether enhances initial water retention and thickening effects, sodium polyacrylate, as a highly absorbent polymer, can absorb and slowly release water, and modified bentonite physically adsorbs and binds water through its large specific surface area and three-dimensional network. The combined use of these ingredients gives the mortar good water retention performance. The addition of heavy calcium carbonate and fly ash improves particle size distribution and reduces interconnected pores, thereby reducing the water migration path and binding with river sand, improving the density of the mortar, and indirectly enhancing water retention performance. 2. In this application, the cations in hexadecyltrimethylammonium bromide replace sodium ions between bentonite layers, which can enhance the dispersibility and thixotropy of bentonite in the aqueous phase of mortar. The resulting three-dimensional network structure can more effectively bind water, thereby producing a strong synergistic water retention effect with cellulose ether. 3. The method in this application involves first grinding river sand to obtain river sand powder, then pre-drying gypsum, heavy calcium carbonate, and fly ash, then mixing them with cement, then adding water-retaining agent, water-reducing agent, stabilizer, retarder, and defoamer, and finally adding river sand powder and stirring to obtain gypsum-based self-leveling mortar with good water retention properties. Detailed Implementation

[0020] The present application will be further described in detail below with reference to the embodiments.

[0021] All raw materials used in the embodiments are commercially available. The gypsum is α-hemihydrate gypsum with a purity of 95% and a fineness of 300 mesh; the cement is provided by Wuhan Jiyesheng Chemical Co., Ltd., item number A00238; the heavy calcium carbonate CAS number is 471-34-1; the fly ash is provided by Wuhan Jiyesheng Chemical Co., Ltd., item number A01085; the cellulose ether is hydroxypropyl methylcellulose; the starch ether is provided by Shenzhen Boshun Chemical Co., Ltd.; the sodium bentonite CAS number is 85049-30-5; the water-reducing agent is polycarboxylate high-efficiency water-reducing agent powder, provided by Luoyang Tongrun Nanotechnology Co., Ltd.; the defoamer is an organosilicon defoamer, CAS number 151-21-3; the stabilizer includes, but is not limited to, one or more of polyvinyl alcohol, hydroxyethyl methylcellulose, and hydroxyethyl cellulose, with polyvinyl alcohol being preferred in this application.

[0022] Preparation Example Preparation Example 1 Preparation Example 1 provides a method for preparing modified bentonite, comprising the following steps: Preparation of bentonite slurry: Sodium pyrophosphate was added to water and stirred at 250 rpm until dissolved. Then, sodium-based bentonite ore powder was slowly added and stirred and dispersed at 3000 rpm for 30 min. After standing for 3 h, the upper colloidal slurry was taken to obtain bentonite slurry. The weight ratio of water, sodium pyrophosphate and sodium-based bentonite ore powder was 100:0.5:10. Modification: Hexadecyltrimethylammonium bromide was dissolved in deionized water at 60°C and stirred until homogeneous to obtain a modified solution; the bentonite slurry was heated to 60°C and stirred at a constant temperature of 150 rpm. During this process, the modified solution was slowly added dropwise. After the addition was complete, the mixture was stirred at 60°C for 2 hours to obtain a reaction mixture; the weight ratio of hexadecyltrimethylammonium bromide to deionized water was 2:20; the weight ratio of hexadecyltrimethylammonium bromide to sodium bentonite ore powder was 1.8:10; Post-treatment: the reaction mixture was filtered, the filter cake was washed, dried at 105°C for 10 hours, then pulverized and passed through a 200-mesh sieve to obtain modified bentonite.

[0023] Preparation Example 2 Preparation Example 2 provides a method for preparing modified bentonite, comprising the following steps: Preparation of bentonite slurry: Sodium pyrophosphate was added to water and stirred at 250 rpm until dissolved. Then, sodium-based bentonite ore powder was slowly added and stirred and dispersed at 3000 rpm for 30 min. After standing for 3 h, the upper colloidal slurry was taken to obtain bentonite slurry. The weight ratio of water, sodium pyrophosphate and sodium-based bentonite ore powder was 100:0.5:10. Modification: Hexadecyltrimethylammonium bromide was dissolved in deionized water at 60°C and stirred until homogeneous to obtain a modified solution; the bentonite slurry was heated to 60°C and stirred at a constant temperature of 150 rpm. During this process, the modified solution was slowly added dropwise. After the addition was complete, the mixture was stirred at 60°C for 2 hours to obtain a reaction mixture; the weight ratio of hexadecyltrimethylammonium bromide to deionized water was 2:20; the weight ratio of hexadecyltrimethylammonium bromide to sodium-based bentonite ore powder was 2:10; Post-treatment: the reaction mixture was filtered, the filter cake was washed, dried at 105°C for 10 hours, then pulverized and passed through a 200-mesh sieve to obtain modified bentonite.

[0024] Preparation Example 3 Preparation Example 3 provides a method for preparing modified bentonite, comprising the following steps: Preparation of bentonite slurry: Sodium pyrophosphate was added to water and stirred at 250 rpm until dissolved. Then, sodium-based bentonite ore powder was slowly added and stirred and dispersed at 3000 rpm for 30 min. After standing for 3 h, the upper colloidal slurry was taken to obtain bentonite slurry. The weight ratio of water, sodium pyrophosphate and sodium-based bentonite ore powder was 100:0.5:10. Modification: Hexadecyltrimethylammonium bromide was dissolved in deionized water at 60°C and stirred until homogeneous to obtain a modified solution; the bentonite slurry was heated to 60°C and stirred at a constant temperature of 150 rpm. During this process, the modified solution was slowly added dropwise. After the addition was complete, the mixture was stirred at 60°C for 2 hours to obtain a reaction mixture; the weight ratio of hexadecyltrimethylammonium bromide to deionized water was 2:20; the weight ratio of hexadecyltrimethylammonium bromide to sodium bentonite ore powder was 2.2:10; Post-treatment: the reaction mixture was filtered, the filter cake was washed, dried at 105°C for 10 hours, then pulverized and passed through a 200-mesh sieve to obtain modified bentonite. Example

[0025] Example 1 Example 1 provides a preparation process for gypsum-based self-leveling mortar, including the following steps: 20 kg of river sand was washed and ground into fine powder with a particle size of 80-150 μm to obtain river sand powder; 650 kg of gypsum, 270 kg of heavy calcium carbonate, and 5 kg of fly ash were pre-dried to a moisture content of <1%. They were then mixed with 10 kg of cement for 3 minutes. Next, 0.2 kg of water-retaining agent, 1.5 kg of water-reducing agent, 0.5 kg of stabilizer, 0.2 kg of retarder, and 0.5 kg of defoamer were added, and mixing continued for 5 minutes. Finally, river sand powder was added, and mixing was continued for 5 minutes to obtain gypsum-based self-leveling mortar. The water-retaining agent was a mixture of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite from Preparation Example 1, with a weight ratio of 1:0.5:0.25:0.5. The water-reducing agent was polycarboxylate high-efficiency water-reducing agent powder. The stabilizer was polyvinyl alcohol. The retarder was a mixture of citric acid and tartaric acid, with a weight ratio of 1:1. The defoamer was an organosilicon defoamer.

[0026] Example 2 Example 2 provides a preparation process for gypsum-based self-leveling mortar, including the following steps: 25 kg of river sand was washed and then ground into fine powder with a particle size of 80-150 μm to obtain river sand powder. 700 kg of gypsum, 280 kg of heavy calcium carbonate, and 7.5 kg of fly ash were pre-dried to a moisture content of <1%. Then, they were mixed with 15 kg of cement for 3 minutes. Next, 0.4 kg of water-retaining agent, 2 kg of water-reducing agent, 0.75 kg of stabilizer, 0.25 kg of retarder, and 0.6 kg of defoamer were added, and mixing continued for 5 minutes. Finally, river sand powder was added, and mixing was continued for 5 minutes to obtain gypsum-based self-leveling mortar. The water-retaining agent was a mixture of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite from Preparation Example 1, with a weight ratio of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite of 1:0.5:0.25:0.5. The water-reducing agent was polycarboxylate high-efficiency water-reducing agent powder. The stabilizer was polyvinyl alcohol. The retarder was a mixture of citric acid and tartaric acid, with a weight ratio of citric acid to tartaric acid of 1:1. The defoamer was an organosilicon defoamer.

[0027] Example 3 Example 3 provides a preparation process for gypsum-based self-leveling mortar, including the following steps: 30 kg of river sand was washed and ground into fine powder with a particle size of 80-150 μm to obtain river sand powder; 750 kg of gypsum, 290 kg of heavy calcium carbonate, and 10 kg of fly ash were pre-dried to a moisture content of <1%. Then, they were mixed with 20 kg of cement for 3 minutes. Next, 0.6 kg of water-retaining agent, 2.5 kg of water-reducing agent, 1 kg of stabilizer, 0.3 kg of retarder, and 0.7 kg of defoamer were added, and mixing continued for 5 minutes. Finally, river sand powder was added, and mixing was continued for 5 minutes to obtain gypsum-based self-leveling mortar. The water-retaining agent was a mixture of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite from Preparation Example 1, with a weight ratio of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite of 1:0.5:0.25:0.5. The water-reducing agent was polycarboxylate high-efficiency water-reducing agent powder. The stabilizer was polyvinyl alcohol. The retarder was a mixture of citric acid and tartaric acid, with a weight ratio of citric acid to tartaric acid of 1:1. The defoamer was an organosilicon defoamer.

[0028] Example 4 Example 4 provides a preparation process for gypsum-based self-leveling mortar, including the following steps: 25 kg of river sand was washed and then ground into fine powder with a particle size of 80-150 μm to obtain river sand powder. 700 kg of gypsum, 280 kg of heavy calcium carbonate, and 7.5 kg of fly ash were pre-dried to a moisture content of <1%. Then, they were mixed with 15 kg of cement for 3 minutes. Next, 0.4 kg of water-retaining agent, 2 kg of water-reducing agent, 0.75 kg of stabilizer, 0.25 kg of retarder, and 0.6 kg of defoamer were added, and mixing continued for 5 minutes. Finally, river sand powder was added, and mixing was continued for 5 minutes to obtain gypsum-based self-leveling mortar. The water-retaining agent was a mixture of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite (as in Preparation Example 2), with a weight ratio of 1:0.5:0.25:0.5. The water-reducing agent was polycarboxylate high-efficiency water-reducing agent powder. The stabilizer was polyvinyl alcohol. The retarder was a mixture of citric acid and tartaric acid, with a weight ratio of 1:1. The defoamer was an organosilicon defoamer.

[0029] Example 5 Example 5 provides a preparation process for gypsum-based self-leveling mortar, including the following steps: 25 kg of river sand was washed and then ground into fine powder with a particle size of 80-150 μm to obtain river sand powder. 700 kg of gypsum, 280 kg of heavy calcium carbonate, and 7.5 kg of fly ash were pre-dried to a moisture content of <1%, then mixed with 15 kg of cement for 3 minutes. Next, 0.4 kg of water-retaining agent, 2 kg of water-reducing agent, 0.75 kg of stabilizer, 0.25 kg of retarder, and 0.6 kg of defoamer were added, and mixing continued for 5 minutes. Finally, river sand powder was added, and mixing was continued for 5 minutes to obtain gypsum-based self-leveling mortar. The water-retaining agent was a mixture of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite (as in Preparation Example 3), with a weight ratio of 1:0.5:0.25:0.5. The water-reducing agent was polycarboxylate high-efficiency water-reducing agent powder. The stabilizer was polyvinyl alcohol. The retarder was a mixture of citric acid and tartaric acid, with a weight ratio of 1:1. The defoamer was an organosilicon defoamer.

[0030] Example 6 Example 6 provides a preparation process for gypsum-based self-leveling mortar, including the following steps: 25 kg of river sand was washed and then ground into fine powder with a particle size of 80-150 μm to obtain river sand powder. 700 kg of gypsum, 280 kg of heavy calcium carbonate, and 7.5 kg of fly ash were pre-dried to a moisture content of <1%. Then, they were mixed with 15 kg of cement for 3 minutes. Next, 0.4 kg of water-retaining agent, 2 kg of water-reducing agent, 0.75 kg of stabilizer, 0.25 kg of retarder, and 0.6 kg of defoamer were added, and mixing continued for 5 minutes. Finally, river sand powder was added, and mixing was continued for 5 minutes to obtain gypsum-based self-leveling mortar. The water-retaining agent was a mixture of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite (as in Preparation Example 2), with a weight ratio of 1:0.75:0.4:0.75. The water-reducing agent was polycarboxylate high-efficiency water-reducing agent powder. The stabilizer was polyvinyl alcohol. The retarder was a mixture of citric acid and tartaric acid, with a weight ratio of 1:1. The defoamer was an organosilicon defoamer.

[0031] Example 7 Example 7 provides a preparation process for gypsum-based self-leveling mortar, including the following steps: 25 kg of river sand was washed and then ground into fine powder with a particle size of 80-150 μm to obtain river sand powder. 700 kg of gypsum, 280 kg of heavy calcium carbonate, and 7.5 kg of fly ash were pre-dried to a moisture content of <1%. Then, they were mixed with 15 kg of cement for 3 minutes. Next, 0.4 kg of water-retaining agent, 2 kg of water-reducing agent, 0.75 kg of stabilizer, 0.25 kg of retarder, and 0.6 kg of defoamer were added, and mixing continued for 5 minutes. Finally, river sand powder was added, and mixing was continued for 5 minutes to obtain gypsum-based self-leveling mortar. The water-retaining agent was a mixture of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite (as in Preparation Example 2), with a weight ratio of 1:1:0.5:1. The water-reducing agent was polycarboxylate high-efficiency water-reducing agent powder. The stabilizer was polyvinyl alcohol. The retarder was a mixture of citric acid and tartaric acid, with a weight ratio of 1:1. The defoamer was an organosilicon defoamer.

[0032] Example 8 Example 8 provides a preparation process for gypsum-based self-leveling mortar, including the following steps: 25 kg of river sand was washed and then ground into fine powder with a particle size of 80-150 μm to obtain river sand powder. 700 kg of gypsum, 280 kg of heavy calcium carbonate, and 7.5 kg of fly ash were pre-dried to a moisture content of <1%. Then, they were mixed with 15 kg of cement for 3 minutes. Next, 0.4 kg of water-retaining agent, 2 kg of water-reducing agent, 0.75 kg of stabilizer, 0.25 kg of retarder, and 0.6 kg of defoamer were added, and mixing continued for 5 minutes. Finally, river sand powder was added, and mixing was continued for 5 minutes to obtain gypsum-based self-leveling mortar. The water-retaining agent was a mixture of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite from Preparation Example 2, with a weight ratio of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite of 1:0.75:0.4:0.75. The water-reducing agent was polycarboxylate high-efficiency water-reducing agent powder; the stabilizer was polyvinyl alcohol; the retarder was citric acid; and the defoamer was an organosilicon defoamer.

[0033] Example 9 Example 9 provides a preparation process for gypsum-based self-leveling mortar, including the following steps: 25 kg of river sand was washed and then ground into fine powder with a particle size of 80-150 μm to obtain river sand powder. 700 kg of gypsum, 280 kg of heavy calcium carbonate, and 7.5 kg of fly ash were pre-dried to a moisture content of <1%. Then, they were mixed with 15 kg of cement for 3 minutes. Next, 0.4 kg of water-retaining agent, 2 kg of water-reducing agent, 0.75 kg of stabilizer, 0.25 kg of retarder, and 0.6 kg of defoamer were added, and mixing continued for 5 minutes. Finally, river sand powder was added, and mixing was continued for 5 minutes to obtain gypsum-based self-leveling mortar. The water-retaining agent was a mixture of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite from Preparation Example 2, with a weight ratio of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite of 1:0.75:0.4:0.75. The water-reducing agent was polycarboxylate high-efficiency water-reducing agent powder; the stabilizer was polyvinyl alcohol; the retarder was tartaric acid; and the defoamer was an organosilicon defoamer.

[0034] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the water-retaining agent is cellulose ether; the remaining steps are the same as in Example 1.

[0035] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the water-retaining agent is a mixture of cellulose ether, starch ether, and sodium polyacrylate, and the weight ratio of cellulose ether, starch ether, and sodium polyacrylate is 1:0.5:0.25; the remaining steps are the same as in Example 1.

[0036] Performance testing: Water retention performance was tested according to the vacuum filtration method in GB / T 28627-2012. The higher the water retention rate, the better the water retention performance of the mortar.

[0037] Table 1 Performance test results of mortar sample Water retention rate (%) Example 1 95.5 Example 2 95.9 Example 3 95.7 Example 4 96.5 Example 5 96.1 Example 6 97.5 Example 7 97.0 Example 8 96.8 Example 9 96.7 Comparative Example 1 91.0 Comparative Example 2 93.5 Combining Example 1 and Comparative Examples 1-2, the mortar in Example 1 exhibits the best water retention performance. This indicates that when preparing the mortar, the water-retaining agent is a compound of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite. Cellulose ether provides long-term water retention and viscosity stability, starch ether enhances initial water retention and thickening effects, sodium polyacrylate, as a highly absorbent polymer, can absorb and slowly release water, and modified bentonite physically adsorbs and binds water through its large specific surface area and three-dimensional network. Therefore, the compound use of these agents improves the water retention performance of the mortar.

[0038] Based on Examples 1-3, the mortar in Examples 1-3 has good water retention performance. It can be seen that when preparing mortar, following the proportion of raw materials in Examples 1-3 will result in mortar with good water retention performance.

[0039] Combining Examples 2, 4, and 5, the mortar in Example 4 exhibits the best water retention performance. This indicates that the preparation conditions in Example 2 are optimal for preparing modified bentonite, resulting in the best performance of the modified bentonite.

[0040] Combining Examples 4, 6, and 7, the mortar in Example 6 exhibits the best water retention performance. This indicates that when preparing the mortar, the optimal ratio of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite in the water-retaining agent of Example 6 results in the mortar with the best water retention performance.

[0041] Combining Examples 6, 8, and 9, the mortar in Example 6 exhibits the best water retention performance. This indicates that when preparing mortar, the preferred retarder is a mixture of citric acid and tartaric acid, which results in mortar with better water retention performance.

[0042] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A gypsum-based self-leveling mortar, characterized in that: The mortar raw materials include the following components in parts by weight: 650-750 parts gypsum, 10-20 parts cement, 270-290 parts heavy calcium carbonate, 20-30 parts river sand, 5-10 parts fly ash, 0.2-0.6 parts water-retaining agent, 1.5-2.5 parts water-reducing agent, 0.5-1 part stabilizer, 0.2-0.3 parts retarder, and 0.5-0.7 parts defoamer; the water-retaining agent includes cellulose ether, starch ether, sodium polyacrylate, and modified bentonite.

2. The gypsum-based self-leveling mortar according to claim 1, characterized in that: The method for preparing the modified bentonite includes the following steps: Preparation of bentonite slurry: Add sodium pyrophosphate to water and stir until dissolved. Then slowly add sodium-based bentonite, stir to disperse, let stand, and take the upper colloidal slurry to obtain bentonite slurry. Modification: Dissolve hexadecyltrimethylammonium bromide in deionized water at 60°C and stir until homogeneous to obtain a modified solution; heat the bentonite slurry to 55-65°C and stir at a constant temperature. During this process, slowly add the modified solution dropwise. After the addition is complete, stir at a constant temperature of 55-65°C for 2 hours to obtain the reaction mixture. Post-processing: The reaction material was filtered, and then the filter cake was washed, dried, and crushed to obtain modified bentonite.

3. The gypsum-based self-leveling mortar according to claim 2, characterized in that: In the bentonite slurry preparation step, the weight ratio of water, sodium pyrophosphate, and sodium-based bentonite is 100:0.5:10; in the modification step, the weight ratio of hexadecyltrimethylammonium bromide and deionized water is 2:20; and the weight ratio of hexadecyltrimethylammonium bromide and sodium-based bentonite is (1.8-2.2):

10.

4. The gypsum-based self-leveling mortar according to claim 1, characterized in that: The weight ratio of cellulose ether, starch ether, sodium polyacrylate, and modified bentonite in the water-retaining agent is 1:(0.5-1):(0.25-0.5):(0.5-1).

5. The gypsum-based self-leveling mortar according to claim 1, characterized in that: The water-reducing agent includes a polycarboxylate-based water-reducing agent.

6. The gypsum-based self-leveling mortar according to claim 1, characterized in that: The stabilizer includes one or more of polyvinyl alcohol, hydroxyethyl methylcellulose, and hydroxyethyl cellulose.

7. The gypsum-based self-leveling mortar according to claim 1, characterized in that: The retarder comprises a mixture of citric acid and tartaric acid.

8. The gypsum-based self-leveling mortar according to claim 1, characterized in that: The defoamer includes silicone defoamers.

9. A preparation process for gypsum-based self-leveling mortar as described in any one of claims 1-8, characterized in that: Includes the following steps: River sand is washed and then ground into fine powder with a particle size of 80-150μm to obtain river sand powder; Gypsum, heavy calcium carbonate, and fly ash are pre-dried to a moisture content of less than 1%, then mixed evenly with cement. Next, water-retaining agent, water-reducing agent, stabilizer, retarder, and defoamer are added, and mixing continues. Finally, river sand powder is added and mixed evenly to obtain gypsum-based self-leveling mortar.