Multifunctional additive for self-leveling cement mortar as well as preparation method and application of multifunctional additive

Abstract

The invention discloses a self-leveling cement mortar multifunctional auxiliary agent and a preparation method and application thereof, and belongs to the technical field of cement-based material admixtures, and the preparation method comprises the following steps: copolymerizing polyether, acrylic acid, sodium methallyl sulfonate and an initiator, adjusting the pH to be neutral to prepare a first polyacrylic resin component, and adding diethylene glycol monovinyl ether, vinyl pyrrolidone and N, N-dimethylformamide into the first polyacrylic resin component to prepare a second polyacrylic resin component; copolymerizing N, N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt and hydroxyethyl acrylate, and adjusting the pH value to be neutral, so as to prepare a second polyacrylic resin component; performing ultrasonic dispersion on the sulfonic cellulose nanocrystal, the carboxyl cellulose nanocrystal and sulfoalanine to form a third cellulose nanocrystal dispersion liquid component; after the three components are mixed, through the synergistic effect of intermolecular hydrogen bonds and a three-dimensional network structure, the fluidity and bleeding and segregation resistance of the mortar are improved, and cement hydration products are induced to be densified. The preparation process is simple and environment-friendly, and the problems of insufficient flow, easy layering and cracking and the like of the traditional self-leveling mortar are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of cement-based material admixtures, and in particular relates to a multifunctional additive for self-leveling cement mortar, a preparation method and application thereof. Background Art

[0002] Self-leveling cement is actually a cement mortar that can flow freely and cover the entire construction surface under the action of its own weight in the initial state of mixing. The advantages of self-leveling cement are good fluidity, no leveling is required, and it can automatically form a flat and smooth surface structure on the surface of the building, which plays a role in replacing floor tiles and decorations. Its performance requirements are good fluidity, forming a flat covering layer, beautiful, wear-resistant, strong, and crack-free. Self-leveling cement mortar is similar to general cement-based materials in composition and preparation process. It is generally composed of cement, fine sand and various admixtures. The role of admixtures is particularly important. Self-leveling cement mortar needs to have sufficient fluidity and cohesion during the mixing construction stage to ensure the automatic formation of a flat surface layer; during the curing and solidification stage, mixing needs to prevent segregation and water seepage, and the hardening speed is fast. The surface layer construction can be carried out after 1 day. After hardening, the structure should be uniform and dense, with good mechanics and durability. Self-leveling cement mortar has the advantages of fast, safe and pollution-free construction. Therefore, self-leveling cement mortar has a wide range of uses and can be used for floor paving in factories, workshops, warehouses, shopping malls, exhibition halls, gymnasiums, hospitals, various open spaces, offices, homes, etc.

[0003] At present, self-leveling mortar is a solid material made of fine aggregate, cementitious material, water-retaining thickening material, functional admixture, mineral admixture or other components mixed in a certain proportion, and mixed with water before use for construction. The technical indicators for evaluating self-leveling cement mortar include fluidity, strength, setting time, water retention rate, wear resistance, dimensional stability, impact resistance, no dusting and cracking after solidification, and economy. The problem with self-leveling cement mortar is that there are still deficiencies in fluidity, surface flatness, strength, and crack resistance, which affects the practical application of self-leveling cement mortar.

[0004] In view of the problems of insufficient fluidity, water seepage, segregation and poor curing performance of the current self-leveling cement mortar, it is urgent to find a preparation method of a multifunctional additive for self-leveling cement mortar to achieve a comprehensive improvement in the performance of the self-leveling cement mortar. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a multifunctional additive for self-leveling cement mortar and its preparation method and application, so as to solve the technical problems of insufficient fluidity, water seepage, segregation and poor curing performance of self-leveling cement mortar.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The invention discloses a method for preparing a multifunctional additive for self-leveling cement mortar, comprising the following steps: Step 1, polyether, the first part of acrylic acid and the first part of water are stirred evenly, after the first heating, the second part of acrylic acid, sodium methacrylic acid, the first part of ammonium persulfate and the second part of water are slowly added dropwise, mixed evenly, after the first heat preservation and stirring reaction and the first cooling, the pH value is adjusted to 7.0-7.5 to obtain a first polyacrylic acid resin component; Step 2, diethylene glycol monovinyl ether, vinyl pyrrolidone, the third part of acrylic acid and the third part of water are stirred evenly, and after heating for the second time; the fourth part of acrylic acid, N, N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, hydroxyethyl acrylate, the second part of ammonium persulfate and the fourth part of water are slowly added, and the mixture is mixed evenly, and after the reaction is stirred and cooled for the second time, the pH value is adjusted to 7.0-7.5 to obtain a second polyacrylic acid resin component; Step 3, adding sulfoalanine to the fifth portion of water, stirring evenly, then adding sulfonic acid cellulose nanocrystals and carboxy cellulose nanocrystals, stirring and ultrasonically dispersing evenly, to obtain a third cellulose nanocrystal dispersion component; Step 4: Mix the first polyacrylic resin component, the second polyacrylic resin component and the third cellulose nanocrystal dispersion component, stir evenly, and prepare a multifunctional additive for self-leveling cement mortar.

[0007] Preferably, in step 1, the mass ratio of polyether, the first part of acrylic acid, the first part of water, the second part of acrylic acid, sodium methacrylic acid, the first part of ammonium persulfate and the second part of water is (63-70): (2-4): (75-85): (9-11): (2.5-3.5): (0.2-0.3): (40-50); The polyether is prepared from allyl alcohol polyoxyethylene ether with molecular weights of 800, 1200 and 2000 in a mass ratio of 1:2:3; the purity of allyl alcohol polyoxyethylene ether with molecular weights of 800, 1200 and 2000 is greater than 99%; The purity of the first part of acrylic acid, the second part of acrylic acid, sodium methacrylic sulfonate and the first part of ammonium persulfate is greater than 99%.

[0008] Preferably, in step 1, the first heating temperature is 70-80° C.; the slow dripping time is 40-50 min; the first insulation stirring reaction time is 2-2.5 h; the first cooling is to 25-30° C.; and the pH value is adjusted to 7.0-7.5 using 40% sodium hydroxide solution.

[0009] Preferably, in step 2, the mass ratio of diethylene glycol monovinyl ether, vinyl pyrrolidone, the third part of acrylic acid and the third part of water, the fourth part of acrylic acid, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, hydroxyethyl acrylate, the second part of ammonium persulfate and the fourth part of water is (25-30): (15-20): (3-4): (55-68): (8-10): (6-8): (4-5): (0.1-0.2): (29-48); The purity of diethylene glycol monovinyl ether, vinyl pyrrolidone, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt and hydroxyethyl acrylate is greater than 99%.

[0010] Preferably, in step 2, the second heating temperature is 70-80°C; the slow dripping time is 40-50 min; the second heat preservation and stirring reaction time is 2-2.5 h; the second temperature is lowered to 25-30°C; and the pH value is adjusted to 7.0-7.5 using 40% sodium hydroxide solution.

[0011] Preferably, in step 3, the mass ratio of sulfalanine, the fifth part of water, sulfonate cellulose nanocrystals and carboxy cellulose nanocrystals is (5-10): (170-220): (20-25): (15-20); The purity of cysteic acid is greater than 99%; The ultrasonic dispersion time is 30~40min.

[0012] Preferably, in step 3, the fiber diameter of the sulfonate cellulose nanocrystals is 5-10 nm, and the fiber length is 100-500 nm; the fiber diameter of the carboxyl cellulose nanocrystals is 15-40 nm, and the fiber length is 100-400 nm; the sulfur content in the sulfonate cellulose nanocrystals is 20%-24%, and the degree of carboxyl substitution in the carboxyl cellulose nanocrystals is 0.3.

[0013] Preferably, in step 4, the mass ratio of the first polyacrylic resin component, the second polyacrylic resin component and the third cellulose nanocrystal dispersion component is 100:50:50.

[0014] The invention also discloses a multifunctional self-leveling cement mortar additive, which is prepared by adopting the preparation method of the multifunctional self-leveling cement mortar additive.

[0015] The present invention also discloses the use of the multifunctional additive for self-leveling cement mortar prepared by the preparation method in self-leveling cement. When the amount of the multifunctional additive for self-leveling cement mortar added is 2% to 3% of the mass of the self-leveling cement mortar, the 28-day compressive strength of the self-leveling cement mortar is 28.6 to 34.5 MPa; the 28-day flexural strength is 7.3 to 8.7 MPa; the 28-day dimensional change rate is 0.04 to 0.1%; the 28-day tensile strength is 1.5 to 1.8 MPa; the wear resistance is 526 to 638 mm 3 .

[0016] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a preparation method of a multifunctional additive for self-leveling cement mortar, wherein a first polyacrylic resin component is polymerized from a composite polyether macromonomer, acrylic acid, and sodium methacrylic acid, aiming to improve the fluidity, dispersibility, and cohesiveness of the self-leveling cement mortar, and has the effects of resisting water bleeding and segregation; a second polyacrylic resin component is polymerized from diethylene glycol monovinyl ether, vinyl pyrrolidone, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, hydroxyethyl acrylate, etc., and has the effects of improving the dispersion, suspension, cohesiveness, and uniform dispersion of the self-leveling cement mortar; and a third cellulose nanocrystal dispersion component is formed by nano-enhanced toughening of sulfonic acid cellulose nanocrystals and carboxyl cellulose nanocrystals. The synergistic effect of multiple functions of the three components improves the fluidity, dispersibility, cohesiveness, strength, toughness, and durability of the self-leveling cement mortar, overcomes the problems of insufficient fluidity, water bleeding, segregation, cracking, etc. of the existing self-leveling cement mortar, and improves the properties of wear resistance, impact resistance, crack resistance, etc. The self-leveling cement mortar multifunctional additive prepared by the present invention can form a three-dimensional network structure in cement mortar by relying on hydrogen bonds and intermolecular forces between linear molecules of the additive and active groups on the surface of cellulose nanocrystals, and has the effects of dispersion, suspension and cohesion. The high hydrophilicity on the surface of sulfonic acid cellulose nanocrystals and carboxyl cellulose nanocrystals and the abundant sulfonic acid groups, carboxylic acid groups and hydroxyl groups on the surface can rely on strong interactions between molecules in the solution, including hydrogen bonds, electrostatic attraction and van der Waals forces, to combine with each other in the solution to form an interwoven and cross-linked three-dimensional network structure. The three-dimensional structure restricts the free movement of water molecules and other components in the solution, and shows the effect of dispersing and suspending cement particles and sand and gravel.

[0017] Furthermore, the large and stable surface of sulfonate cellulose nanocrystals and carboxyl cellulose nanocrystals also has a very strong effect of dispersing, suspending and regulating the morphology and structure of cement hydration products. The high specific surface area (150-250 m 2 / g) can enhance the interaction between molecules and form a tighter structural network. The surface of carboxyl nanocellulose can play an inducing and template role in the formation of cement hydration products, promote the formation of more cement hydration products with regular morphology and dense structure, and promote the formation of a uniform and dense structure of cement-based materials. Sulfonic acid and carboxyl modified nanocellulose have unique physical and chemical properties, such as high strength, high modulus, low density and good compatibility. Its tensile strength can reach 1.5~3 GPa, its elastic modulus is about 150 GPa, and its density is only 1.5g / cm 3 , making it an ideal choice for lightweight composite materials. As a green, renewable material, it has significant advantages and application potential. With the development of research and technology, its application areas will continue to expand and deepen.

[0018] The present invention also discloses a multifunctional additive for self-leveling cement mortar prepared by the above-mentioned preparation method. Through the synergistic effect of the three components, the fluidity, dispersibility and cohesiveness of the mortar are significantly improved, and the problems of insufficient fluidity, easy water seepage, segregation and sand and gravel sedimentation of traditional materials are overcome. Sulfonic acid groups and carboxylated cellulose nanocrystals are used to form a three-dimensional network structure, which restricts the free movement of water, enhances the suspension ability, and induces the densification of cement hydration products to form a uniform and high-strength solidified structure. After solidification, the surface is smooth and flat, the generation of microcracks is reduced, and the durability and resistance to environmental erosion are significantly improved. It has the functions of dispersion, suspension, flow increase, enhancement and toughening, and is suitable for high-precision self-leveling construction scenes, meeting the comprehensive demand for high-performance cement-based materials in the construction field.

[0019] The present invention also discloses the application of the multifunctional additive for self-leveling cement mortar prepared by the above-mentioned preparation method in self-leveling cement. Through the dispersing and water-reducing effect of the first polyacrylic resin component, the fluidity of the cement paste is significantly improved, high fluidity under low water consumption is achieved, the mortar is ensured to be quickly and evenly leveled, and the unevenness caused by manual paving is avoided. The second polyacrylic resin component and the third cellulose nanocrystal dispersion liquid component form a three-dimensional network structure in coordination, which inhibits the floating of water and the sedimentation of sand and gravel, ensures the homogeneity and stability of the slurry, and has no stratification and water bleeding defects after hardening. The specific surface area of ​​the sulfonic acid / carboxylated cellulose nanocrystals is 150~250 m² / g, and the cement matrix is ​​strengthened by hydrogen bonding and electrostatic action, and the wear resistance and impact resistance are significantly better than those of traditional materials. The densification induction effect of nanocellulose reduces microscopic pores and inhibits shrinkage cracking. At the same time, the high hydrophilic group delays environmental erosion, so that the mortar has improved resistance to freeze-thaw cycles and chloride ion penetration, and the service life is extended. It promotes the uniform growth of hydration products, and the hardened surface is smooth and flat, which can be directly used as a finishing layer, eliminating the need for secondary plastering. It does not release harmful substances such as formaldehyde, and is suitable for indoor and outdoor projects; the components work together to adapt to different temperature and humidity conditions, and have a wide range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention discloses a schematic diagram of the preparation process of a multifunctional additive for self-leveling cement mortar: wherein (a) is a schematic diagram of the chemical reaction of the preparation process of the first polyacrylic resin component; (b) is a schematic diagram of the chemical reaction of the preparation process of the second polyacrylic resin component; and (c) is a schematic diagram of the chemical reaction of the preparation process of the third cellulose nanocrystal dispersion component. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0023] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0024] In the present invention, unless otherwise specified, percentage (%) or part refers to the weight percentage or weight part relative to the composition.

[0025] In the present invention, unless otherwise specified, the components or preferred components involved can be combined with each other to form a new technical solution.

[0026] In the present invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is just an abbreviation of these numerical combinations.

[0027] The “range” disclosed in the present invention is in the form of a lower limit and an upper limit, which can be one or more lower limits, and one or more upper limits, respectively.

[0028] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0029] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the sequence. Preferably, the reaction method herein is carried out sequentially.

[0030] Unless otherwise specified, the professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present invention.

[0031] The present invention provides a preparation method and application of a multifunctional additive for self-leveling cement mortar, comprising the following steps: Step 1, according to the mass parts, 63-70 parts of polyether, 2-4 parts of acrylic acid and 75-85 parts of water are put into a reactor, stirred evenly to obtain a mixed solution, and heated to 70-80°C; 9-11 parts of acrylic acid, 2.5-3.5 parts of sodium methyl propylene sulfonate, 0.2-0.3 parts of ammonium persulfate and 40-50 parts of water are added dropwise and mixed evenly to obtain a monomer mixed solution, the dropping time is 40-50 minutes, after the dropping is completed, the reaction is stirred and kept warm for 2-2.5 hours, the temperature is lowered to 25°C-30°C, the pH value of the reactant is adjusted to 7.0-7.5 with 40% sodium hydroxide solution, the total mass percentage of non-aqueous matter in the obtained product solution is controlled to be 40%, and the first polyacrylic resin component is obtained.

[0032] Step 2, according to the mass parts, 25-30 parts of diethylene glycol monovinyl ether, 15-20 parts of vinyl pyrrolidone, 3-4 parts of acrylic acid and 55-68 parts of water are put into a reactor, stirred evenly to obtain a mixed solution, and heated to 70-80°C; 8-10 parts of acrylic acid, 6-8 parts of N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, 4-5 parts of hydroxyethyl acrylate, 0.1-0.2 parts of ammonium persulfate and 29-48 parts of water are added dropwise and mixed evenly to obtain a monomer mixed solution, the dropping time is 40-50min, after the dropping is completed, the reaction is stirred and kept warm for 2-2.5h, the temperature is lowered to 25°C-30°C, the pH value of the reactant is adjusted to 7.0-7.5 using 40% sodium hydroxide solution, and the total mass percentage of non-aqueous matter in the obtained product solution is controlled to be 40%, and the second polyacrylic acid resin component is obtained.

[0033] Step 3: Add 5 to 10 parts of sulfoalanine to 170 to 220 parts of water and stir evenly, then add 20 to 25 parts of sulfonate cellulose nanocrystals and 15 to 20 parts of carboxyl cellulose nanocrystals, stir and ultrasonically disperse for 30 to 40 minutes, dissolve and stir evenly, control the mass percentage of cellulose nanocrystals to 17%, and obtain a third cellulose nanocrystal dispersion component.

[0034] Step 4: Mix 100 parts of the first polyacrylic resin component, 50 parts of the second polyacrylic resin component and 50 parts of the third cellulose nanocrystal dispersion component, stir evenly, and obtain a multifunctional additive for self-leveling cement mortar.

[0035] Furthermore, the polyether is prepared by allyl alcohol polyoxyethylene ether with molecular weights of 800, 1200 and 2000 respectively in a mass ratio of 1:2:3, and the purity of the allyl alcohol polyoxyethylene ether is greater than 99%.

[0036] Furthermore, the purity of acrylic acid, sodium methacrylic acid sulfonate, ammonium persulfate, diethylene glycol monovinyl ether, vinyl pyrrolidone, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, hydroxyethyl acrylate and cysteic acid is greater than 99%.

[0037] Furthermore, the modified cellulose nanocrystals are sulfonate cellulose nanocrystals or carboxyl cellulose nanocrystals, wherein the fiber diameter of the sulfonate cellulose nanocrystals is 5~10nm, and the fiber length is 100~500nm, the fiber diameter of the carboxyl cellulose nanocrystals is 15~40nm, and the fiber length is 100~400nm, the sulfur content in the sulfonate cellulose nanocrystals is 20%~24%, and the carboxyl substitution degree in the carboxyl cellulose nanocrystals is 0.3.

[0038] The multifunctional additive for self-leveling cement mortar prepared by the invention is added into the self-leveling cement mortar at a weight of 2% to 3%, thereby increasing fluidity, improving suspension effect, increasing strength, and making the surface smooth, flat, dense and crack-free.

[0039] Figure 1The present invention discloses a schematic diagram of the preparation process of a multifunctional additive for self-leveling cement mortar: (a) is a schematic diagram of the chemical reaction of the preparation process of the first polyacrylic resin component; (b) is a schematic diagram of the chemical reaction of the preparation process of the second polyacrylic resin component; (c) is a schematic diagram of the preparation process of the third cellulose nanocrystal dispersion component. As can be seen from Figure (a), the first polyacrylic resin component is a multi-branched molecular structure composed of three branched polyethers of different lengths, acrylic acid and sodium methacrylic acid sulfonate. The lengths of the three branches are relatively short chain, medium chain and long chain, and the number of the three branches is relatively balanced. The length of the branches and multiple ether bonds make it easy for cement particles and sand particles in the system to form a stable coating and winding layer structure, which prevents them from agglomerating and condensing, and improves the fluidity, dispersibility and cohesion of cement mortar. The side carboxyl group increases the hydrophilicity of the system, coordinates the compatibility of the system with water and retains water, and the side sulfonic acid group plays a role in foaming, entraining air and improving the dispersion effect and flow effect. As can be seen from Figure (b), the second polyacrylic resin component is a molecular structure containing five different side groups formed by the polymerization of diethylene glycol monovinyl ether, vinyl pyrrolidone, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid salt, hydroxyethyl acrylate and acrylic acid. The molecules containing ethanol ether side groups, pyrrole side groups, aminopropyl sulfonic acid salt side groups, hydroxyethyl side groups and carboxyl side groups have a dispersing effect and the coating and entanglement layer formed in the system by the first component acrylic resin component forms a stable three-dimensional network structure through hydrogen bonds, intermolecular forces, etc., which inhibits the floating of water and the sedimentation of sand and gravel, and ensures the homogeneity and stability of the slurry. As can be seen from Figure (c), the third cellulose nanocrystal dispersion component is uniformly dispersed sulfonic acid cellulose nanocrystals and carboxyl cellulose nanocrystals, which rely on the large and stable surface of the nanocrystals to disperse, suspend and regulate the morphology and structure of cement hydration products. The nanocellulose surface formation plays an induction and template role in the morphology and structure formation of the hydration products. The high strength, high modulus and good compatibility of the nanocellulose crystals improve the tensile strength and elastic modulus of the cement mortar.

[0040] The present invention provides a method for preparing a multifunctional additive for self-leveling cement mortar, which can solve the problems existing in the current self-leveling cement mortar by compounding with the self-leveling cement mortar. The uniqueness of the present invention lies in that the theoretical roots and technical solutions for solving the existing problems are found from the theoretical and technical roots of the existing problems, and the molecular structure and performance of the multifunctional additive are adjusted through monomer selection and preparation process to solve the existing problems. The multifunctional admixture is compounded by hydrophilic linear macromolecules with flow-increasing, dispersing and suspending effects and nano-reinforced materials. It has the functions of dispersing, suspending, cohesion, promoting fluidity and promoting uniform dispersion in the mixing stage, which can make the cement-based materials in the mixing stage form a uniform, stable and self-leveling state, and there is no segregation, no water seepage, and no sedimentation of sand and gravel in the mixing stage. In the curing stage, it can promote the cement mortar to form a uniform, wear-resistant, impact-resistant, high-strength, non-cracking, smooth and beautiful structure. To this end, the additive of the present invention selects components for improving fluidity and dispersibility by using polyether macromonomer, acrylic acid, and sodium methacrylic acid; selects diethylene glycol monovinyl ether, vinyl pyrrolidone, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, hydroxyethyl acrylate, etc. to prepare components for improving dispersion, suspension, cohesion, and uniform dispersion; and selects reinforcing and toughening components formed by sulfonic acid cellulose nanocrystals and carboxyl cellulose nanocrystals. The multifunctionality of the additive of the present invention is reflected in the ability to improve fluidity, dispersibility, cohesion, reinforcement, toughening, etc., overcome the problems of insufficient fluidity, water seepage, segregation, cracking, etc., and improve the properties of wear resistance, impact resistance, crack resistance, etc.

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] The polyethers used in Examples 1 to 5 are allyl alcohol polyoxyethylene ethers with molecular weights of 800, 1200, and 2000, respectively, prepared in a mass ratio of 1:2:3, and the purity of the allyl alcohol polyoxyethylene ether is greater than 99%.

[0043] The purity of acrylic acid, sodium methacrylic acid sulfonate, ammonium persulfate, diethylene glycol monovinyl ether, vinyl pyrrolidone, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, hydroxyethyl acrylate and cysteic acid selected in Examples 1 to 5 is greater than 99%.

[0044] The modified cellulose nanocrystals selected in Examples 1 to 5 are sulfonate cellulose nanocrystals or carboxyl cellulose nanocrystals, wherein the fiber diameter of the sulfonate cellulose nanocrystals is 5 to 10 nm, and the fiber length is 100 to 500 nm, the fiber diameter of the carboxyl cellulose nanocrystals is 15 to 40 nm, and the fiber length is 100 to 400 nm, the sulfur content in the sulfonate cellulose nanocrystals is 20% to 24%, and the degree of carboxyl substitution in the carboxyl cellulose nanocrystals is 0.3.

[0045] The multifunctional additives for self-leveling cement mortar prepared in Examples 1 to 5 are added at 2% to 3% by weight of the self-leveling cement mortar to increase fluidity, improve suspension effect, increase strength, and make the surface smooth, flat, dense, and crack-free.

[0046] Example 1 A method for preparing a multifunctional additive for self-leveling cement mortar comprises the following steps: Step 1, 63 parts of polyether, 2 parts of acrylic acid and 75 parts of water are put into a reactor by mass, and the mixed solution obtained by stirring is heated to 70°C; 9 parts of acrylic acid, 2.5 parts of sodium methyl acrylate sulfonate, 0.2 parts of ammonium persulfate and 40 parts of water are added dropwise and mixed to obtain a monomer mixed solution, the dropping time is 40 minutes, and after the dropping is completed, the mixture is stirred and reacted for 2 hours at a temperature of 25°C, and the pH value of the reactant is adjusted to 7.0 with a 40% sodium hydroxide solution, and the content is controlled to be 40%, to obtain a first polyacrylic resin component.

[0047] Step 2, 25 parts of diethylene glycol monovinyl ether, 15 parts of vinyl pyrrolidone, 3 parts of acrylic acid and 55 parts of water are put into a reactor by mass, and the mixed solution obtained by stirring is heated to 70°C; 8 parts of acrylic acid, 6 parts of N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, 4 parts of hydroxyethyl acrylate, 0.1 parts of ammonium persulfate and 29 parts of water are added dropwise and mixed to obtain a monomer mixed solution, the dropping time is 40 minutes, and after the dropping is completed, the reaction is stirred and kept warm for 2 hours, and the temperature is lowered to 25°C, and the pH value of the reactant is adjusted to 7.0 with 40% sodium hydroxide solution, and the content is controlled to 40%, to obtain a second polyacrylic resin component.

[0048] Step 3, add 5 parts of sulfoalanine to 170 parts of water and stir evenly, then add 20 parts of sulfonate cellulose nanocrystals and 15 parts of carboxyl cellulose nanocrystals, stir and ultrasonically disperse for 30 minutes, dissolve and stir evenly; the fiber diameter of the sulfonate cellulose nanocrystals is 5nm, the fiber length is 100nm, and the sulfur content in the sulfonate cellulose nanocrystals is 20%; the fiber diameter of the carboxyl cellulose nanocrystals is 15nm, the fiber length is 100nm, and the carboxyl substitution degree in the carboxyl cellulose nanocrystals is 0.3; control the cellulose nanocrystal content to 17% to obtain a third cellulose nanocrystal dispersion component.

[0049] Step 4: 100 parts of the first polyacrylic resin component, 50 parts of the second polyacrylic resin component and 50 parts of the third cellulose nanocrystal dispersion component are mixed and stirred evenly to obtain a multifunctional additive for self-leveling cement mortar. The additive is added at 2% by weight of the self-leveling cement mortar to measure the additive and its application performance.

[0050] Example 2 A method for preparing a multifunctional additive for self-leveling cement mortar comprises the following steps: Step 1, 65 parts of polyether, 2.5 parts of acrylic acid and 80 parts of water are put into a reactor by mass, and the mixed solution obtained by stirring is heated to 72°C; 9.5 parts of acrylic acid, 2.7 parts of sodium methyl propylene sulfonate, 0.25 parts of ammonium persulfate and 42 parts of water are added dropwise and mixed to obtain a monomer mixed solution, the dropping time is 42 minutes, and after the dropping is completed, the mixture is stirred and reacted for 2.2 hours at a temperature of 27°C, and the pH value of the reactant is adjusted to 7.1 with a 40% sodium hydroxide solution, and the content is controlled to be 40%, to obtain a first polyacrylic acid resin component.

[0051] Step 2, 26 parts of diethylene glycol monovinyl ether, 16 parts of vinyl pyrrolidone, 3.2 parts of acrylic acid and 58 parts of water are put into a reactor by mass, and the mixed solution obtained by stirring is heated to 72°C; 8.5 parts of acrylic acid, 6.5 parts of N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, 4.2 parts of hydroxyethyl acrylate, 0.12 parts of ammonium persulfate and 35 parts of water are added dropwise and mixed to obtain a monomer mixed solution, the dropping time is 42 minutes, and after the dropping is completed, the reaction is stirred and kept warm for 2.1 hours, and the temperature is lowered to 26°C, and the pH value of the reactant is adjusted to 7.1 with 40% sodium hydroxide solution, and the content is controlled to 40%, to obtain a second polyacrylic resin component.

[0052] Step 3, add 6 parts of sulfoalanine to 180 parts of water and stir evenly, then add 21 parts of sulfonate cellulose nanocrystals and 16 parts of carboxyl cellulose nanocrystals, stir and ultrasonically disperse for 32 minutes, dissolve and stir evenly; the fiber diameter of the sulfonate cellulose nanocrystals is 6nm, the fiber length is 200nm, and the sulfur content in the sulfonate cellulose nanocrystals is 21%; the fiber diameter of the carboxyl cellulose nanocrystals is 16nm, the fiber length is 200nm, and the carboxyl substitution degree in the carboxyl cellulose nanocrystals is 0.3; control the cellulose nanocrystal content to 17% to obtain a third cellulose nanocrystal dispersion component.

[0053] Step 4: 100 parts of the first polyacrylic resin component, 50 parts of the second polyacrylic resin component and 50 parts of the third cellulose nanocrystal dispersion component are mixed and stirred evenly to obtain a multifunctional additive for self-leveling cement mortar. The additive is added at 2.5% by weight of the self-leveling cement mortar to measure the additive and its application performance.

[0054] Example 3 A method for preparing a multifunctional additive for self-leveling cement mortar comprises the following steps: Step 1, 66 parts of polyether, 3 parts of acrylic acid and 80 parts of water are put into a reactor by mass, and the mixed solution obtained by stirring is heated to 75°C; 10 parts of acrylic acid, 3.0 parts of sodium methyl acrylate sulfonate, 0.25 parts of ammonium persulfate and 45 parts of water are added dropwise and mixed to obtain a monomer mixed solution, the dropping time is 45 minutes, and after the dropping is completed, the mixture is stirred and reacted for 2.3 hours at a temperature of 28°C, and the pH value of the reactant is adjusted to 7.3 with a 40% sodium hydroxide solution, and the content is controlled to be 40%, to obtain a first polyacrylic resin component.

[0055] Step 2, according to mass parts, put 27 parts of diethylene glycol monovinyl ether, 17 parts of vinyl pyrrolidone, 3.5 parts of acrylic acid and 60 parts of water into a reactor, stir and evenly obtain a mixed solution, and heat it to 75°C; add dropwise 9.5 parts of acrylic acid, 7.0 parts of N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, 4.5 parts of hydroxyethyl acrylate, 0.5 parts of ammonium persulfate and 40 parts of water to mix evenly to obtain a monomer mixed solution, the dropping time is 45 minutes, after the dropping is completed, the reaction is stirred and kept warm for 2.2 hours, the temperature is lowered to 28°C, and the pH value of the reactant is adjusted to 7.3 with 40% sodium hydroxide solution, and the content is controlled to 40%, to obtain a second polyacrylic resin component.

[0056] Step 3, add 8 parts of sulfoalanine to 190 parts of water and stir evenly, then add 23 parts of sulfonate cellulose nanocrystals and 18 parts of carboxyl cellulose nanocrystals, stir and ultrasonically disperse for 36 minutes, dissolve and stir evenly; the fiber diameter of the sulfonate cellulose nanocrystals is 7nm, the fiber length is 300nm, and the sulfur content in the sulfonate cellulose nanocrystals is 22%; the fiber diameter of the carboxyl cellulose nanocrystals is 17nm, the fiber length is 300nm, and the carboxyl substitution degree in the carboxyl cellulose nanocrystals is 0.3; control the cellulose nanocrystal content to 17% to obtain a third cellulose nanocrystal dispersion component.

[0057] Step 4: 100 parts of the first polyacrylic resin component, 50 parts of the second polyacrylic resin component and 50 parts of the third cellulose nanocrystal dispersion component are mixed and stirred evenly to obtain a multifunctional additive for self-leveling cement mortar. The additive is added at 3% by weight of the self-leveling cement mortar to measure the additive and its application performance.

[0058] Example 4 A method for preparing a multifunctional additive for self-leveling cement mortar comprises the following steps: Step 1, 68 parts of polyether, 3.5 parts of acrylic acid and 82 parts of water are put into a reactor by mass, and the mixed solution obtained by stirring is heated to 78°C; 10 parts of acrylic acid, 3.0 parts of sodium methyl acrylate sulfonate, 0.28 parts of ammonium persulfate and 48 parts of water are added dropwise and mixed to obtain a monomer mixed solution, the dropping time is 48 minutes, and after the dropping is completed, the mixture is stirred and reacted for 2.4 hours at a temperature of 28°C, and the pH value of the reactant is adjusted to 7.5 with a 40% sodium hydroxide solution, and the content is controlled to be 40%, to obtain a first polyacrylic resin component.

[0059] Step 2, 28 parts of diethylene glycol monovinyl ether, 18 parts of vinyl pyrrolidone, 3.8 parts of acrylic acid and 62 parts of water are put into a reactor by mass, and the mixed solution obtained by stirring is heated to 80°C; 9.5 parts of acrylic acid, 6.8 parts of N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, 4.8 parts of hydroxyethyl acrylate, 0.18 parts of ammonium persulfate and 43 parts of water are added dropwise and mixed to obtain a monomer mixed solution, the dropping time is 48 minutes, and after the dropping is completed, the reaction is stirred and kept warm for 2.5 hours, the temperature is lowered to 30°C, and the pH value of the reactant is adjusted to 7.0 with 40% sodium hydroxide solution, and the content is controlled to 40%, to obtain a second polyacrylic resin component.

[0060] Step 3, add 8 parts of sulfoalanine to 210 parts of water and stir evenly, then add 23 parts of sulfonate cellulose nanocrystals and 18 parts of carboxyl cellulose nanocrystals, stir and ultrasonically disperse for 38 minutes, dissolve and stir evenly; the fiber diameter of the sulfonate cellulose nanocrystals is 8nm, the fiber length is 400nm, and the sulfur content in the sulfonate cellulose nanocrystals is 23%; the fiber diameter of the carboxyl cellulose nanocrystals is 18nm, the fiber length is 350nm, and the carboxyl substitution degree in the carboxyl cellulose nanocrystals is 0.3; control the cellulose nanocrystal content to 17% to obtain a third cellulose nanocrystal dispersion component.

[0061] Step 4: 100 parts of the first polyacrylic resin component, 50 parts of the second polyacrylic resin component and 50 parts of the third cellulose nanocrystal dispersion component are mixed and stirred evenly to obtain a multifunctional additive for self-leveling cement mortar. The additive is added at 2.3% by weight of the self-leveling cement mortar to measure the additive and its application performance.

[0062] Example 5 A method for preparing a multifunctional additive for self-leveling cement mortar comprises the following steps: Step 1, 70 parts of polyether, 4 parts of acrylic acid and 85 parts of water are put into a reactor by mass, and the mixed solution obtained by stirring is heated to 80°C; 11 parts of acrylic acid, 3.5 parts of sodium methyl acrylate sulfonate, 0.3 parts of ammonium persulfate and 50 parts of water are added dropwise and mixed to obtain a monomer mixed solution, the dropping time is 50 minutes, and after the dropping is completed, the mixture is stirred and reacted for 2.5 hours at a temperature of 30°C, and the pH value of the reactant is adjusted to 7.5 with a 40% sodium hydroxide solution, and the content is controlled to be 40%, to obtain a first polyacrylic resin component.

[0063] Step 2, 30 parts of diethylene glycol monovinyl ether, 20 parts of vinyl pyrrolidone, 4 parts of acrylic acid and 68 parts of water are put into a reactor by mass, and the mixed solution obtained by stirring is heated to 80°C; 10 parts of acrylic acid, 8 parts of N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, 5 parts of hydroxyethyl acrylate, 0.2 parts of ammonium persulfate and 48 parts of water are added dropwise and mixed evenly to obtain a monomer mixed solution, the dropping time is 50 minutes, and after the dropping is completed, the reaction is stirred and kept warm for 2.5 hours, and the temperature is lowered to 30°C, and the pH value of the reactant is adjusted to 7.5 with 40% sodium hydroxide solution, and the content is controlled to 40%, to obtain a second polyacrylic resin component.

[0064] Step 3, adding 10 parts of sulfoalanine to 220 parts of water and stirring evenly, then adding 25 parts of sulfonate cellulose nanocrystals and 20 parts of carboxyl cellulose nanocrystals, stirring and ultrasonically dispersing for 40 minutes, dissolving and stirring evenly; the fiber diameter of the sulfonate cellulose nanocrystals is 10nm, the fiber length is 500nm, and the sulfur content in the sulfonate cellulose nanocrystals is 24%; the fiber diameter of the carboxyl cellulose nanocrystals is 20nm, the fiber length is 400nm, and the carboxyl substitution degree in the carboxyl cellulose nanocrystals is 0.3; controlling the cellulose nanocrystal content to 17%, to obtain a third cellulose nanocrystal dispersion component.

[0065] Step 4: 100 parts of the first polyacrylic resin component, 50 parts of the second polyacrylic resin component and 50 parts of the third cellulose nanocrystal dispersion component are mixed and stirred evenly to obtain a multifunctional additive for self-leveling cement mortar. The additive is added at 2.8% by weight of the self-leveling cement mortar to measure the additive and its application performance.

[0066] A multifunctional additive for self-leveling cement mortar prepared in Examples 1 to 5 was used for application test of self-leveling cement mortar.

[0067] In order to compare the performance of the samples prepared in different embodiments, the self-leveling cement mortar multifunctional additives prepared in Examples 1 to 5 were used for self-leveling cement mortar for testing and performance testing. 3 The amount of each component material of the mortar: 916 kg of machine-made sand, 538 kg of ultra-fine sand, 298 kg of cement, 293 kg of fly ash, 235 kg of water and 0.6 kg of solid polycarboxylate water reducer were used to prepare the sample. The sample was prepared and tested according to GB8077-2023 "Test method for homogeneity of concrete admixtures", JG / T230-2016 "Premixed mortar", JC / T985-2017 "Cement-based self-leveling mortar for floor use" and GB / T50082-2023 "Standard for test method for long-term performance and durability of ordinary concrete". The control sample refers to the sample prepared according to the above self-leveling mortar without adding the self-leveling cement mortar multifunctional additive of the present invention. The preparation method of the control sample and the ratio of machine-made sand, ultra-fine sand, cement, fly ash, water and solid polycarboxylate water reducer are the same as the preparation process and detection test method of the sample mixed with the self-leveling cement mortar multifunctional additive prepared in Examples 1 to 5. The test and application results are shown in Table 1.

[0068] Table 1 is a performance comparison of the self-leveling cement mortar multifunctional additives prepared in Examples 1 to 5 and applied to self-leveling cement mortar. It can be seen from Table 1 that the initial fluidity and 20min fluidity of the cement mortar using the additives in the examples are both greater than 130mm, meeting the technical requirements; the final setting time is 289 to 321min, the 24h compressive strength and flexural strength are 8.3 to 9.8MPa and 3.1 to 4.5MPa, respectively, and the 28-day compressive strength and flexural strength are 28.6 to 34.5MPa and 7.3 to 8.7MPa, respectively, which can meet the compressive strength and flexural strength of 1 day and 28 days, which can meet the requirements of technology and construction; the 28-day dimensional change rate, tensile strength, wear resistance, impact resistance, 30 freeze-thaw mass loss rate, surface cracks, etc. all meet the technical and construction requirements. The results show that the application performance of the self-leveling cement mortar multifunctional additives prepared in Examples 1 to 5 meets the technical requirements, and the application results are better than those of the comparative samples.

[0069] Table 1 Comparison of application performance of multifunctional additives for self-leveling cement mortar prepared in Examples 1 to 5

[0070] In summary, the present invention discloses a multifunctional additive for self-leveling cement mortar, and its preparation method and application. A flow-increasing dispersion component is prepared by polymerization of composite polyether, acrylic acid and sodium propylene sulfonate, a dispersion and suspension component is prepared by polymerization of diethylene glycol monovinyl ether, vinyl pyrrolidone, acrylic acid, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, and hydroxyethyl acrylate, and a strengthening and toughening component is prepared by polymerization of sulfoalanine, sulfonic cellulose nanocrystals and carboxyl cellulose crystals. The synergistic effect of the three components makes the additive have the significant effects of dispersion, suspension, flow-increasing and strengthening and toughening, and the cured surface is smooth and flat, high in strength, good in toughness, no cracks and good in durability. The preparation method of the present invention has the characteristics of cheap and easy-to-obtain raw materials, simple and feasible preparation process, green and pollution-free preparation method, simple and convenient application method, can significantly increase the mechanical properties, crack-proof ability and durability of self-leveling cement mortar, and has a significant application effect.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a multifunctional additive for self-leveling cement mortar, characterized in that: The steps include: Step 1, polyether, the first part of acrylic acid and the first part of water are stirred evenly, after the first heating, the second part of acrylic acid, sodium methacrylic acid, the first part of ammonium persulfate and the second part of water are slowly added dropwise, mixed evenly, after the first heat preservation and stirring reaction and the first cooling, the pH value is adjusted to 7.0-7.5 to obtain a first polyacrylic acid resin component; Step 2, diethylene glycol monovinyl ether, vinyl pyrrolidone, the third part of acrylic acid and the third part of water are stirred evenly, and after heating for the second time; the fourth part of acrylic acid, N, N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, hydroxyethyl acrylate, the second part of ammonium persulfate and the fourth part of water are slowly added, and the mixture is mixed evenly, and after the reaction is stirred and cooled for the second time, the pH value is adjusted to 7.0-7.5 to obtain a second polyacrylic acid resin component; Step 3, adding sulfoalanine to the fifth portion of water, stirring evenly, then adding sulfonic acid cellulose nanocrystals and carboxy cellulose nanocrystals, stirring and ultrasonically dispersing evenly, to obtain a third cellulose nanocrystal dispersion component; Step 4: Mix the first polyacrylic resin component, the second polyacrylic resin component and the third cellulose nanocrystal dispersion component, stir evenly, and prepare a multifunctional additive for self-leveling cement mortar.

2. The method for preparing the multifunctional additive for self-leveling cement mortar according to claim 1, characterized in that: In step 1, the mass ratio of the polyether, the first part of acrylic acid, the first part of water, the second part of acrylic acid, sodium methacrylic acid, the first part of ammonium persulfate and the second part of water is (63-70): (2-4): (75-85): (9-11): (2.5-3.5): (0.2-0.3): (40-50); The polyether is prepared from allyl alcohol polyoxyethylene ethers with molecular weights of 800, 1200 and 2000 in a mass ratio of 1:2:3; the purity of the allyl alcohol polyoxyethylene ethers with molecular weights of 800, 1200 and 2000 is greater than 99%; The purity of the first portion of acrylic acid, the second portion of acrylic acid, sodium methacrylic acid sulfonate and the first portion of ammonium persulfate is greater than 99%.

3. The method for preparing the multifunctional additive for self-leveling cement mortar according to claim 1, characterized in that: In step 1, the temperature of the first heating is 70-80° C.; the time of slow dripping is 40-50 min; the time of the first heat preservation and stirring reaction is 2-2.5 h; the first temperature is lowered to 25-30° C.; and the pH value is adjusted to 7.0-7.5 using 40% sodium hydroxide solution.

4. The method for preparing the multifunctional additive for self-leveling cement mortar according to claim 1, characterized in that: In step 2, the mass ratio of diethylene glycol monovinyl ether, vinyl pyrrolidone, the third part of acrylic acid and the third part of water, the fourth part of acrylic acid, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt, hydroxyethyl acrylate, the second part of ammonium persulfate and the fourth part of water is (25-30): (15-20): (3-4): (55-68): (8-10): (6-8): (4-5): (0.1-0.2): (29-48); The purity of the diethylene glycol monovinyl ether, vinyl pyrrolidone, N,N-dimethyl (methacryloyloxyethyl) aminopropyl sulfonic acid inner salt and hydroxyethyl acrylate is greater than 99%.

5. The method for preparing the multifunctional additive for self-leveling cement mortar according to claim 1, characterized in that: In step 2, the second heating temperature is 70-80° C.; the slow dripping time is 40-50 min; the second heat preservation and stirring reaction time is 2-2.5 h; the second temperature is lowered to 25-30° C.; and the pH value is adjusted to 7.0-7.5 using 40% sodium hydroxide solution.

6. The method for preparing the multifunctional additive for self-leveling cement mortar according to claim 1, characterized in that: In step 3, the mass ratio of sulfalanine, the fifth part of water, sulfonate cellulose nanocrystals and carboxy cellulose nanocrystals is (5-10): (170-220): (20-25): (15-20); The purity of the cysteic acid is greater than 99%; The ultrasonic dispersion time is 30 to 40 minutes.

7. The method for preparing the multifunctional additive for self-leveling cement mortar according to claim 1, characterized in that: In step 3, the fiber diameter of the sulfonate cellulose nanocrystals is 5-10 nm, and the fiber length is 100-500 nm; the fiber diameter of the carboxyl cellulose nanocrystals is 15-40 nm, and the fiber length is 100-400 nm; the sulfur content in the sulfonate cellulose nanocrystals is 20%-24%, and the degree of carboxyl substitution in the carboxyl cellulose nanocrystals is 0.

3.

8. The method for preparing the multifunctional additive for self-leveling cement mortar according to claim 1, characterized in that: In step 4, the mass ratio of the first polyacrylic resin component, the second polyacrylic resin component and the third cellulose nanocrystal dispersion liquid component is 100:50:

50.

9. A multifunctional additive for self-leveling cement mortar, characterized in that: The multifunctional additive for self-leveling cement mortar is prepared by the preparation method of any one of claims 1 to 8.

10. Application of the multifunctional additive for self-leveling cement mortar prepared by the preparation method according to any one of claims 1 to 8 in self-leveling cement, characterized in that: When the amount of multifunctional additives added to the self-leveling cement mortar is 2%~3% of the mass of the self-leveling cement mortar, the 28-day compressive strength of the self-leveling cement mortar is 28.6~34.5MPa; the 28-day flexural strength is 7.3~8.7MPa; the 28-day dimensional change rate is 0.04~0.1%; the 28-day tensile strength is 1.5~1.8MPa; the wear resistance is 526~638mm 3 .

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