Anhydrous gypsum-based self-leveling mortar with high-temperature phase change regulation and control function and preparation method of anhydrous gypsum-based self-leveling mortar

Abstract

The invention discloses high-temperature phase change regulation and control anhydrite-based self-leveling mortar and a preparation method thereof. The self-leveling mortar is prepared from Portland cement, sulfur aluminum cement, modified fine sand, modified coarse sand, modified heavy calcium carbonate, ash calcium, anhydrite, cellulose, a water reducing agent, a defoaming agent, rubber powder and lithium sulfate. The preparation method comprises the following steps: S1, carrying out solid phase change on calcined phosphogypsum to prepare anhydrous gypsum, S2, preparing modified fine sand and modified coarse sand, S3, preparing modified coarse calcium carbonate, and S4, mixing all the components to obtain the anhydrous gypsum-based self-leveling mortar. Through the synergistic effect of all the raw materials, the modified fine sand, the modified coarse sand and the modified coarse calcium carbonate form a tight filling structure, the structural strength of the dried mortar is enhanced, in the alkaline environment of the self-leveling mortar, polyethylene glycol monomethyl ether on the surface of the modified coarse calcium carbonate reacts with silane coupling agents on the surfaces of the modified fine sand and the modified coarse sand to form a cross-linked structure, and the self-leveling mortar has the advantages that the self-leveling effect is good; the structural strength and the stability of the self-leveling mortar are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of self-leveling mortar, and particularly relates to a high-temperature phase change-regulated anhydrous gypsum-based self-leveling mortar and a preparation method thereof. Background Art

[0002] As a new type of building cementitious material, anhydrous gypsum-based materials have many unique advantages. Compared with traditional cement self-leveling mortar, anhydrous gypsum has a faster hydration rate and can form higher strength in a short time, which helps to shorten the construction period and improve construction efficiency. At the same time, anhydrous gypsum-based materials have a lower shrinkage rate, which can effectively reduce the crack problems caused by material shrinkage and improve the overall quality and service life of the ground.

[0003] Based on the above situation, in the prior art, the patent with the patent number CN202010698520.X discloses a sand-free gypsum-based self-leveling mortar, which includes water and the following components in parts by weight: 80-97 parts of hemihydrate phosphogypsum; 3-20 parts of alkaline substances; 0.1-2 parts of activator; 0.35-0.95 parts of admixture. The present invention uses hemihydrate phosphogypsum produced as a by-product of the hemihydrate phosphoric acid process to prepare gypsum-based self-leveling mortar. Only by drying the hemihydrate gypsum and removing free water and a small amount of crystal water can the energy consumption be greatly reduced, and it has a strong cost advantage. The present invention mixes hemihydrate phosphogypsum with cement, activator, and admixture in a certain proportion to obtain a self-leveling gypsum product with good water resistance and fluidity. Therefore, there is no need to add aggregate to further improve the strength and fluidity of the product.

[0004] Although the above self-leveling mortar obtains good water resistance and fluidity through the cooperation of hemihydrate phosphogypsum and other components, it still has deficiencies. Specifically, the above self-leveling mortar uses hemihydrate phosphogypsum as the main material, and lacks fillers to increase the structural strength and compressive strength in the composition components, resulting in problems such as insufficient structural strength and poor pressure resistance after drying in use of the above self-leveling mortar. Summary of the Invention

[0005] Aiming at the technical defects in the background art, the present invention provides a high-temperature phase change-regulated anhydrous gypsum-based self-leveling mortar and a preparation method thereof, which solve the above technical problems and meet the actual needs. The specific technical solutions are as follows:

[0006] A high-temperature phase-change regulated anhydrite-based self-leveling mortar, by weight, comprises the following raw materials: 1-5 parts of portland cement, 1-5 parts of sulfoaluminate cement, 2-6 parts of modified fine sand, 5-10 parts of modified coarse sand, 2-6 parts of modified heavy calcium, 1-5 parts of grey calcium, 100-150 parts of anhydrite, 0.01-0.15 parts of cellulose, 0.1-0.3 parts of water reducer, 0.05-0.1 parts of defoamer, 0.05-0.2 parts of rubber powder, and 0.1-1 part of lithium sulfate.

[0007] As a further technical solution of the present invention, the particle size of the modified fine sand is 0.15-0.25 mm, the particle size of the modified coarse sand is 0.25-0.5 mm, the particle size of the modified heavy calcium is 0.15-0.25 mm. Both the modified fine sand and the modified coarse sand are obtained by modifying quartz sand with a silane coupling agent containing chlorine atoms, and the modified heavy calcium is obtained by coating heavy calcium particles with methoxypolyethylene glycol.

[0008] As a further technical solution of the present invention, the cellulose is selected from any one of hydroxypropyl methylcellulose or hydroxyethyl methylcellulose, and the molecular weight of the cellulose is greater than 50,000 Da.

[0009] As a further technical solution of the present invention, the water reducer is selected as a polycarboxylate water reducer, the defoamer is selected as polydimethylsiloxane, and the rubber powder is selected from any one of vinyl acetate-ethylene copolymer rubber powder or styrene-butadiene-styrene copolymer rubber powder.

[0010] A preparation method of a high-temperature phase-change regulated anhydrite-based self-leveling mortar comprises the following steps:

[0011] S1. Prepare anhydrite. First, calcine phosphogypsum to obtain hemihydrate gypsum, and then perform pickling and a second calcination on the hemihydrate gypsum to obtain anhydrite.

[0012] S2. Prepare the modified fine sand and the modified coarse sand. Stir and dissolve the silane coupling agent in an ethanol solution to obtain a silane coupling agent-ethanol solution. Put a certain amount of fine quartz sand and coarse quartz sand into two stirrers respectively, react for a period of time under stirring, filter and separate, and dry to obtain the modified fine sand and the modified coarse sand respectively.

[0013] S3. Prepare the modified heavy calcium. Dissolve methoxypolyethylene glycol in deionized water to obtain a methoxypolyethylene glycol aqueous solution. Put a certain amount of heavy calcium particles into the methoxypolyethylene glycol aqueous solution, impregnate for a period of time under stirring, filter, and dry to obtain the modified heavy calcium.

[0014] S4. Prepare self-leveling mortar. Add cement, sulfoaluminate cement, modified fine sand, modified coarse sand, modified heavy calcium, hydrated lime, anhydrous gypsum, cellulose, water reducer, defoamer, rubber powder, and lithium sulfate into a mixer and stir evenly to obtain a powder material. Then add water to the powder material in the mixer and stir evenly to obtain anhydrous gypsum-based self-leveling mortar.

[0015] As a further technical solution of the present invention, in step S1, calcine phosphogypsum at 160 °C for 3 h to obtain hemihydrate gypsum. Mix the hemihydrate gypsum with sulfuric acid having a mass concentration of 10%. The mass-volume ratio of the hemihydrate gypsum to the sulfuric acid is 1:10 g / mL. Perform acid leaching for 1 h under stirring, then filter and separate, wash the solid with deionized water more than 5 times, and dry at 90 °C for 5 h. Calcinate the dried hemihydrate gypsum at 800 °C for 2 h to obtain anhydrous gypsum.

[0016] As a further technical solution of the present invention, in step S2, stir and dissolve the silane coupling agent in an ethanol solution to obtain a silane coupling agent-ethanol solution. The mass percentage of the silane coupling agent in the ethanol solution of the silane coupling agent and the ethanol solution is 5:95. The ethanol solution is a 90% ethanol aqueous solution. The silane coupling agent is selected from any one of chloropropyltrimethoxysilane or chloromethyltrimethoxysilane.

[0017] As a further technical solution of the present invention, in step S2, put a certain amount of fine quartz sand and the silane coupling agent-ethanol solution into a stirrer respectively, react for 20 min under stirring, then filter the solid and dry to obtain modified fine sand. The mass ratio of the fine quartz sand to the silane coupling agent-ethanol solution is 1:100. Put a certain amount of coarse quartz sand and the silane coupling agent-ethanol solution into another stirrer respectively, react for 20 min under stirring, then filter the solid and dry to obtain modified coarse sand. The mass ratio of the coarse quartz sand to the silane coupling agent-ethanol solution is 1:100.

[0018] As a further technical solution of the present invention, in step S3, dissolve polyethylene glycol monomethyl ether in deionized water to prepare a 5% polyethylene glycol monomethyl ether aqueous solution. Put a certain amount of heavy calcium particles into the polyethylene glycol monomethyl ether aqueous solution, impregnate for 2 h under stirring, filter and dry to obtain modified heavy calcium. The mass ratio of the heavy calcium particles to the polyethylene glycol monomethyl ether aqueous solution is 1:10.

[0019] As a further technical solution of the present invention, in step S4, the mass ratio of the powder material to water is 1:0.2 - 0.4.

[0020] The beneficial effects of the present invention are as follows:

[0021] Through the synergistic effect of raw materials such as anhydrite, modified fine sand, modified coarse sand, and modified heavy calcium, the modified fine sand, modified coarse sand, and modified heavy calcium form a tightly packed structure, increasing the structural strength of the mortar after drying. In the alkaline self-leveling mortar environment, the polyethylene glycol monomethyl ether on the surface of the modified heavy calcium can undergo a substitution reaction with the chlorine atoms in the silane coupling agent on the surfaces of the modified fine sand and modified coarse sand at room temperature, forming a cross-linked structure between the modified heavy calcium and the modified fine sand and modified coarse sand, further enhancing the structural strength and stability of the mortar. The added components such as cellulose, water reducer, defoamer, and rubber powder can improve the mortar performance in terms of water retention, fluidity, defoaming property, and adhesion. Specific Embodiments

[0022] The following describes the embodiments of the present invention in conjunction with relevant embodiments. The embodiments of the present invention are not limited to the following examples, and the necessary components related to the technical field of the present invention should be regarded as well-known technologies in the technical field, which can be known and mastered by those skilled in the technical field.

[0023] A high-temperature phase-change-regulated anhydrite-based self-leveling mortar, by weight, comprises the following raw material components: 1-5 parts of portland cement, 1-5 parts of sulfoaluminate cement, 2-6 parts of modified fine sand, 5-10 parts of modified coarse sand, 2-6 parts of modified heavy calcium, 1-5 parts of hydrated lime, 100-150 parts of anhydrite, 0.01-0.15 parts of cellulose, 0.1-0.3 parts of water reducer, 0.05-0.1 parts of defoamer, 0.05-0.2 parts of rubber powder, and 0.1-1 part of lithium sulfate.

[0024] Specifically, the above self-leveling mortar contains the following raw materials in weight fractions: 5 parts of portland cement, 5 parts of sulfoaluminate cement, 2 parts of modified fine sand, 10 parts of modified coarse sand, 2 parts of modified heavy calcium, 1 part of hydrated lime, 150 parts of anhydrite, 0.1 part of cellulose, 0.2 parts of water reducer, 0.1 part of defoamer, 0.05 part of rubber powder, and 0.1 part of lithium sulfate.

[0025] The modified fine sand, modified coarse sand, and modified heavy calcium of the present invention form a tightly packed multi-level structure after self-leveling and drying through different particle size combinations. The modified fine sand fills the gaps between the modified coarse sand, and the modified heavy calcium further fills the micro-pores. The gradient filling method effectively reduces the internal void ratio of the mortar, and can effectively improve the structural density and strength after drying.

[0026] The modified fine sand and modified coarse sand are treated with a chlorine-containing silane coupling agent, and active chlorine atoms are introduced on the surface. The modified heavy calcium is coated with polyethylene glycol monomethyl ether, forming an organic hydrophilic layer on the surface. In the alkaline environment of the self-leveling mortar, the hydroxyl group of polyethylene glycol monomethyl ether reacts with the chlorine atoms of the silane coupling agent to form a chemical bond, forming a three-dimensional cross-linked network structure between the three aggregates and enhancing the overall structural stability.

[0027] In the present invention, portland cement and sulfoaluminate cement are used in combination. The portland cement provides early strength, and the sulfoaluminate cement rapidly hydrates to form ettringite, compensating for the late strength development. The double-cement system optimizes the heat release curve of hydration, reduces shrinkage cracks, and improves the early workability and late durability of the mortar. At the same time, in the self-leveling mortar system, anhydrite is used as the matrix material. Through a two-step calcination process and pickling treatment, impurities are removed and the crystal structure is optimized.

[0028] Cellulose forms a spatial network through the entanglement of long-chain molecules, effectively improving the water retention and thixotropy of the mortar. The polycarboxylate superplasticizer maintains fluidity while reducing the water-cement ratio through electrostatic repulsion and steric hindrance effects, enabling a self-leveling effect to be achieved even when the mass ratio of powder to water is (1:0.2 - 0.4). The defoamer rapidly breaks the bubbles generated during stirring by reducing the surface tension, avoiding honeycombing and pitting defects. The rubber powder forms a flexible interface layer during the curing process of the mortar, enhancing the bonding strength with the base layer and inhibiting the propagation of microcracks.

[0029] As a further technical solution of the present invention, the particle size of the modified fine sand is 0.15 - 0.25 mm, the particle size of the modified coarse sand is 0.25 - 0.5 mm, the particle size of the modified heavy calcium is 0.15 - 0.25 mm. Both the modified fine sand and the modified coarse sand are obtained by modifying quartz sand with a silane coupling agent containing chlorine atoms, and the modified heavy calcium is obtained by coating heavy calcium particles with methoxypolyethylene glycol.

[0030] Specifically, the particle size of the modified fine sand is 0.15 mm, the particle size of the modified coarse sand is 0.5 mm, the particle size of the modified heavy calcium is 0.15 mm. The modified fine sand and the modified heavy calcium together fill the gaps between the modified coarse sand, significantly reducing the porosity inside the self-leveling mortar, thereby enhancing the structural compactness and strength after drying.

[0031] Active chlorine atoms are introduced on the surface of the fine / coarse sand modified with the chlorine-containing silane coupling agent, and hydroxyl groups are present on the surface of the heavy calcium coated with methoxypolyethylene glycol. In an alkaline mortar environment, a nucleophilic substitution reaction occurs between the chlorine atoms and the hydroxyl groups, forming a C-O-Si covalent bond, resulting in the formation of a three-dimensional cross-linked network structure between the modified fine sand, the modified coarse sand, and the modified heavy calcium, improving the mechanical properties and durability of the self-leveling mortar through chemical bonding.

[0032] As a further technical solution of the present invention, the cellulose is selected from any one of hydroxypropyl methylcellulose or hydroxyethyl methylcellulose, and the molecular weight of the cellulose is greater than 50,000 Da.

[0033] Specifically, hydroxypropyl methylcellulose is selected as the cellulose. The hydroxypropyl groups in the molecular chain of hydroxypropyl methylcellulose have strong hydrophilicity, and its long-chain structure (molecular weight > 50,000 Da) can form a dense three-dimensional network structure in the mortar, effectively adsorbing and retaining water, ensuring that there is sufficient water for hydration reaction during the hardening process of the self-leveling mortar, avoiding early drying and cracking. The long-chain hydroxypropyl methylcellulose slowly releases water during the drying process of the self-leveling mortar, maintaining a moist environment for the matrix, promoting the full hydration of anhydrous gypsum and cement, and improving the late strength development.

[0034] As a further technical solution of the present invention, the water-reducing agent is selected as a polycarboxylate-based water-reducing agent, the defoaming agent is selected as polydimethylsiloxane, and the rubber powder is selected from any one of vinyl acetate-ethylene copolymer rubber powder or styrene-butadiene-styrene copolymer rubber powder.

[0035] Specifically, vinyl acetate-ethylene copolymer rubber powder is selected as the rubber powder. The ethylene groups in the molecular chain of vinyl acetate-ethylene copolymer rubber powder provide flexibility, and the vinyl acetate groups provide adhesiveness, enabling the rubber powder to adapt to the micro-deformation of the base layer in the mortar and form a strong adhesive force. The rubber powder particles are dispersed at the interface between the aggregate and the matrix during the stirring process of the self-leveling mortar, filling the micro-pores, reducing stress concentration, and forming chemical bonding with the hydration products of cement through its polar groups, optimizing the structure of the interfacial transition zone and improving the integrity of the mortar.

[0036] The polycarboxylate-based water-reducing agent efficiently disperses cement particles through electrostatic repulsion and steric hindrance effects, reduces the friction between particles, and can effectively reduce the water consumption. The polydimethylsiloxane defoaming agent quickly destroys the bubbles generated during the stirring process by reducing the surface tension of the liquid, avoiding defects such as honeycombing, pockmarks, and pinholes on the surface of the self-leveling mortar. At the same time, its low surface tension property enables the bubbles to be evenly eliminated inside the mortar, preventing local density unevenness.

[0037] A preparation method of a high-temperature phase-change regulated anhydrous gypsum-based self-leveling mortar includes the following steps:

[0038] S1. Prepare anhydrous gypsum. Calcinate phosphogypsum for the first time to obtain hemihydrate gypsum, and then pickle and calcinate the hemihydrate gypsum for the second time to obtain anhydrous gypsum.

[0039] S2. Prepare modified fine sand and modified coarse sand. Stir and dissolve the silane coupling agent in an ethanol solution to obtain a silane coupling agent-ethanol solution. Put a certain amount of fine quartz sand and coarse quartz sand into two stirrers respectively, react for a period of time under stirring, filter and separate, and dry to obtain modified fine sand and modified coarse sand respectively.

[0040] S3. Prepare modified heavy calcium carbonate. Dissolve polyethylene glycol monomethyl ether in deionized water to obtain an aqueous solution of polyethylene glycol monomethyl ether. Put a certain amount of heavy calcium carbonate particles into the aqueous solution of polyethylene glycol monomethyl ether, impregnate for a period of time under stirring, filter, and dry to obtain modified heavy calcium carbonate.

[0041] S4. Prepare self-leveling mortar. Add cement, sulfoaluminate cement, modified fine sand, modified coarse sand, modified heavy calcium carbonate, hydrated lime, anhydrous gypsum, cellulose, water reducing agent, defoamer, rubber powder, and lithium sulfate into a mixer and stir evenly to obtain a powder material. Add water to the powder material in the mixer and stir evenly to obtain anhydrous gypsum-based self-leveling mortar.

[0042] In the preparation method of the present invention, through two calcination and pickling processes, impurities in phosphogypsum are effectively removed, the purity of anhydrous gypsum is improved, thereby enhancing the strength and durability of the mortar. Through the method of high-temperature calcination, the conversion of hemihydrate gypsum and anhydrous gypsum is ensured. The process of calcining phosphogypsum into anhydrous gypsum belongs to solid-state phase transformation. Phosphogypsum (CaSO4·2H2O) loses crystal water during calcination and its crystal structure is reorganized from monoclinic system to orthorhombic system (such as type II anhydrous gypsum), forming a new cubic coordination structure.

[0043] In the preparation method of the present invention, the surface of quartz sand is modified by silane coupling agent, which enhances the adhesion between sand particles and the matrix, improves the overall performance of the mortar. By controlling the concentration and reaction time of the silane coupling agent, uniform coating of the sand particle surface is achieved. Polyethylene glycol monomethyl ether is used to coat heavy calcium carbonate particles, which improves the dispersibility of heavy calcium carbonate particles. The tightly packed structure of modified fine sand, modified coarse sand and modified heavy calcium carbonate increases the structural strength of the mortar after drying, improves its load-bearing capacity and crack resistance. The formation of the crosslinked structure further enhances the internal adhesion of the mortar and improves its durability and anti-aging performance.

[0044] As one of the preferred embodiments of the present invention, in step S1, calcine phosphogypsum at 160°C for 3 h to obtain hemihydrate gypsum. Mix the hemihydrate gypsum with sulfuric acid with a mass concentration of 10%. The mass-volume ratio of the hemihydrate gypsum to the sulfuric acid is 1:10 g / mL. Acid leach for 1 h under stirring, then filter and separate, wash the solid with deionized water more than 5 times, and dry at 90°C for 5 h. The dried hemihydrate gypsum is calcined at 800°C for 2 h to obtain anhydrous gypsum.

[0045] The main component of phosphogypsum is calcium sulfate dihydrate (CaSO4·2H2O). When calcined at 160°C, it will lose part of its crystal water and be converted into calcium sulfate hemihydrate (CaSO4·0.5H2O), that is, hemihydrate gypsum. This process is the process of gypsum dehydration. By controlling the temperature and time, it can ensure that phosphogypsum is fully converted into hemihydrate gypsum, while avoiding overcalcination resulting in gypsum decomposition or performance degradation.

[0046] The hemihydrate gypsum may contain some impurities, such as soluble salts, unreacted dihydrate gypsum, etc. By mixing with sulfuric acid with a mass concentration of 10% and acid-leaching for 1 h under stirring, these impurities can be dissolved to improve the purity of the hemihydrate gypsum. After filtration and separation, the solid is washed with deionized water more than 5 times to remove the residual sulfuric acid and dissolved impurities.

[0047] After the acid-washed and washed hemihydrate gypsum is dried at 90 °C for 5 h, it is calcined again. This time, the calcination temperature is higher (800 °C). The purpose is to further dehydrate the hemihydrate gypsum and convert it into anhydrous calcium sulfate (CaSO4), that is, anhydrite. Anhydrite has higher hardness and stability and is a key raw material for preparing high-temperature phase change regulating anhydrite-based self-leveling mortar. By controlling the calcination temperature and time, it can be ensured that the hemihydrate gypsum is fully converted into anhydrite, while avoiding overcalcination resulting in a decline in the performance of the gypsum.

[0048] As one of the preferred embodiments of the present invention, in step S2, the silane coupling agent is stirred and dissolved in an ethanol solution to obtain a silane coupling agent-ethanol solution. The mass percentage of the silane coupling agent and the ethanol solution in the ethanol solution of the silane coupling agent is 5:95. The ethanol solution is a 90% ethanol aqueous solution. The silane coupling agent is selected from any one of chloropropyltrimethoxysilane or chloromethyltrimethoxysilane.

[0049] A certain amount of fine quartz sand and the silane coupling agent-ethanol solution are respectively put into a stirrer and reacted for 20 min under stirring, and then the solid is filtered and dried to obtain modified fine sand. The mass ratio of the fine quartz sand to the silane coupling agent-ethanol solution is 1:100. A certain amount of coarse quartz sand and the silane coupling agent-ethanol solution are respectively put into another stirrer and reacted for 20 min under stirring, and then the solid is filtered and dried to obtain modified coarse sand. The mass ratio of the coarse quartz sand to the silane coupling agent-ethanol solution is 1:100.

[0050] Specifically, the silane coupling agent is chloropropyltrimethoxysilane. The molecular structure of chloropropyltrimethoxysilane contains a chlorine atom and a hydrolyzable methoxy group. The chlorine atom can undergo a substitution reaction with polyethylene glycol monomethyl ether on the surface of the modified heavy calcium in subsequent reactions to form a crosslinked structure; while the methoxy group can be hydrolyzed in water to generate a silanol group, which further undergoes a condensation reaction with the hydroxyl group on the surface of the quartz sand to form a chemical bond.

[0051] When the silane coupling agent - ethanol solution contacts with quartz sand, the methoxy groups of the silane coupling agent are hydrolyzed under the action of water to generate silanol groups. These silanol groups then undergo a condensation reaction with the hydroxyl groups on the surfaces of fine quartz sand and coarse quartz sand, forming stable chemical bonds, enhancing the adhesion between the fine quartz sand and the coarse quartz sand and the matrix material, and also improving the dispersibility and wettability of the fine quartz sand and the coarse quartz sand, enabling the silane coupling agent to uniformly coat the surfaces of the fine quartz sand and the coarse quartz sand, forming modified fine sand and modified coarse sand. The modified sand grains can form a tight filling structure with other raw materials during the subsequent preparation of self - leveling mortar, improving the structural strength and durability of the mortar.

[0052] As one of the preferred embodiments of the present invention, in step S3, polyethylene glycol monomethyl ether is dissolved in deionized water to prepare a 5% aqueous solution of polyethylene glycol monomethyl ether. A certain amount of heavy calcium particles are put into the aqueous solution of polyethylene glycol monomethyl ether and impregnated for 2 h under stirring, filtered, and dried to obtain modified heavy calcium. The mass ratio of the heavy calcium particles to the aqueous solution of polyethylene glycol monomethyl ether is 1:10.

[0053] The principle of step S3 is to improve the performance of heavy calcium particles through the surface coating effect of polyethylene glycol monomethyl ether and provide active sites for subsequent cross - linking reactions, thereby enhancing the overall performance of the self - leveling mortar. Polyethylene glycol monomethyl ether is a macromolecular compound with hydrophilicity and certain hydrophobicity, which can dissolve in deionized water to form a uniform aqueous solution. When the heavy calcium particles are put into the aqueous solution of polyethylene glycol monomethyl ether, due to the action of stirring, the molecules of polyethylene glycol monomethyl ether can uniformly adhere to the surfaces of the heavy calcium particles.

[0054] The polyethylene glycol monomethyl ether coating layer can improve the hydrophilicity and dispersibility of heavy calcium particles, making it easier to mix evenly with other raw materials during the subsequent preparation of self - leveling mortar. The coating layer can also serve as an active site for subsequent cross - linking reactions, undergoing a substitution reaction with the chlorine atoms in the silane coupling agent on the surfaces of the modified fine sand and the modified coarse sand to form a cross - linked structure, thereby enhancing the internal adhesion and overall performance of the mortar.

[0055] As one of the preferred embodiments of the present invention, in step S4, the mass ratio of the powder material to water is 1:0.2 - 0.4.

[0056] Specifically, in step S4, the mass ratio of the powder material to water is 1:0.3

[0057] In step S4, various raw materials such as portland cement, sulfoaluminate cement, modified fine sand, modified coarse sand, modified heavy calcium, hydrated lime, anhydrous gypsum, cellulose, water - reducing agent, defoaming agent, rubber powder, lithium sulfate, etc. are added to a mixer and stirred evenly to form a uniform powder mixture. Water is added to the powder in the mixer and stirred evenly again to obtain anhydrous gypsum - based self - leveling mortar.

[0058] It should be noted that although the direct formation of the cross-linked structure is not completed in step S4, step S4 provides conditions for the formation of the cross-linked structure. Since the polyethylene glycol monomethyl ether on the surface of the modified heavy calcium can react with the chlorine atoms in the silane coupling agent on the surfaces of the modified fine sand and modified coarse sand, a substitution reaction can occur at room temperature under the alkaline conditions of the self-leveling mortar. This reaction continues during the mixing and subsequent drying processes of the mortar, and finally a cross-linked structure is formed. The formation of the cross-linked structure enhances the internal cohesion of the mortar and improves its overall performance and durability.

[0059] Example 1

[0060] A preparation method of a high-temperature phase change-regulated anhydrous gypsum-based self-leveling mortar includes the following steps:

[0061] S1. Prepare anhydrous gypsum

[0062] First calcination: Place the phosphogypsum in a calcination furnace and calcine it at 160 °C for 3 hours to dehydrate and convert it into hemihydrate gypsum (CaSO4·0.5H2O).

[0063] Pickling treatment: Mix the hemihydrate gypsum with a 10% sulfuric acid solution by a mass-to-volume ratio of 1:10 (g / mL), stir and acid-leach for 1 hour, filter and separate the solid, wash it with deionized water more than 5 times to remove residual sulfuric acid and impurities, and dry it at 90 °C for 5 hours to obtain purified hemihydrate gypsum.

[0064] Second calcination: Calcinate the dried hemihydrate gypsum at 800 °C for 2 hours to completely dehydrate and convert it into type II anhydrous gypsum (CaSO4).

[0065] S2. Prepare modified fine sand and modified coarse sand

[0066] Dissolve chloropropyltrimethoxysilane in a 90% ethanol aqueous solution to prepare a silane coupling agent-ethanol solution with a mass ratio of 5:95. Put the fine quartz sand and the silane coupling agent-ethanol solution into a stirrer at a mass ratio of 1:100, stir and react for 20 minutes, filter and separate the solid, and obtain modified fine sand with chlorine-containing active groups on the surface after drying. Treat the coarse quartz sand in the same way as above to obtain modified coarse sand.

[0067] S3. Prepare modified heavy calcium

[0068] Dissolve polyethylene glycol monomethyl ether in deionized water to prepare an aqueous solution with a mass concentration of 5%. Mix the heavy calcium particles and the polyethylene glycol monomethyl ether solution at a mass ratio of 1:10, stir and impregnate for 2 hours, filter and separate the solid, and obtain modified heavy calcium with hydroxyl groups on the surface after drying.

[0069] S4. Mix dry material components

[0070] Add the following raw materials by weight parts to a blender: 5 parts of portland cement, 5 parts of sulfoaluminate cement, 2 parts of modified fine sand, 10 parts of modified coarse sand, 2 parts of modified heavy calcium, 1 part of hydrated lime, 150 parts of anhydrous gypsum, 0.1 part of cellulose, 0.2 part of water reducing agent, 0.1 part of defoaming agent, 0.05 part of rubber powder, 0.1 part of lithium sulfate, and stir until the powder materials are uniformly mixed to form a powder. Add water to the dry-mixed mortar according to the mass ratio of powder to water of 1:0.3, and stir at high speed for 3 - 5 minutes to ensure uniform fluidity of the slurry without caking or air bubble aggregation.

[0071] Example 2

[0072] The difference between Example 2 and Example 1 is that in step S4, the dosage of anhydrous gypsum is reduced to 100 parts, the sulfoaluminate cement is reduced to 1 part, the modified fine sand is increased to 6 parts, and the modified coarse sand is reduced to 5 parts. In step S2, the silane coupling agent is changed to chloromethyltrimethoxysilane, and the rest is the same as in Example 1.

[0073] Comparative Example 1

[0074] The difference between Comparative Example 1 and Example 1 is that in step S4, unmodified fine sand (0.25mm), coarse sand (0.5mm), and ordinary heavy calcium (0.15mm) are used, and the rest is the same as in Example 1.

[0075] Comparative Example 2

[0076] The difference between Comparative Example 2 and Example 1 is that in step S4, the sulfoaluminate cement is replaced with an equal amount of portland cement (total cement 10 parts), and the rest is the same as in Example 1.

[0077] Comparative Example 3 (without chlorosilane coupling agent)

[0078] The difference between Comparative Example 3 and Example 1 is that in step S2, the silane coupling agent is changed to amino silane (without chlorine), and the rest is the same as in Example 1.

[0079] Comparative Example 4

[0080] The difference between Comparative Example 3 and Example 1 is that in step S1, the hemihydrate gypsum is calcined at 600°C for 2h after pickling, and the rest is the same as in Example 1.

[0081] Perform performance tests on Examples 1 - 2 and Comparative Examples 1 - 3. The test method is carried out according to JC / T 60021 - 2024, and the test results are shown in the following table:

[0082]

[0083] From the data in the above table, it can be seen that the modified fine sand, modified coarse sand, and modified heavy calcium carbonate effectively improve the compressive strength (by 48%) and bonding strength (by 61%) through chemical cross-linking (chlorine-hydroxy substitution reaction). The absence of chlorosilane coupling agent (Comparative Example 3) leads to cross-linking failure and performance degradation. By comparing Example 1 with Comparative Example 2, it can be proven that the formation of ettringite in sulfoaluminate cement compensates for the late strength, and the compressive strength increases by 32%. By comparing Example 1 with Comparative Example 4, it is obtained that Type II anhydrous gypsum is calcined at 800 °C, and the crystal structure is more stable. By comparing Example 1 with Comparative Example 1, it can be seen that the particle size gradient (0.15 - 0.5 mm) of the modified sand can effectively improve the high density of the self-leveling mortar.

[0084] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A high-temperature phase change-regulated anhydrite-based self-leveling mortar, characterized in that, Comprising the following raw materials by weight parts: Portland cement 1 - 5 parts, sulfoaluminate cement 1 - 5 parts, modified fine sand 2 - 6 parts, modified coarse sand 5 - 10 parts, modified heavy calcium 2 - 6 parts, grey calcium 1 - 5 parts, anhydrous gypsum 100 - 150 parts, cellulose 0.01 - 0.15 parts, water reducing agent 0.1 - 0.3 parts, defoaming agent 0.05 - 0.1 parts, rubber powder 0.05 - 0.2 parts, lithium sulfate 0.1 - 1 part.

2. The anhydrite-based self-leveling mortar with high-temperature phase change regulation according to claim 1, wherein The particle size of the modified fine sand is 0.15 - 0.25 mm, the particle size of the modified coarse sand is 0.25 - 0.5 mm, the particle size of the modified heavy calcium is 0.15 - 0.25 mm. Both the modified fine sand and the modified coarse sand are obtained by modifying quartz sand with a silane coupling agent containing chlorine atoms. The modified heavy calcium is obtained by coating heavy calcium particles with methoxypolyethylene glycol.

3. The self-leveling mortar based on anhydrite with high-temperature phase change regulation according to claim 1, characterized in that The cellulose is selected from any one of hydroxypropyl methyl cellulose or hydroxyethyl methyl cellulose, and the molecular weight of the cellulose is greater than 50,000 Da.

4. A high-temperature phase-change regulated anhydrite-based self-leveling mortar according to claim 1, characterized in that The water reducing agent is selected as a polycarboxylate water reducing agent, the defoaming agent is selected as polydimethylsiloxane, and the rubber powder is selected from any one of vinyl acetate - ethylene copolymer rubber powder or styrene - butadiene - styrene copolymer rubber powder.

5. The preparation method of a high-temperature phase-change regulated anhydrite-based self-leveling mortar according to any one of claims 1-4, characterized in that, Including the following steps: S1. Prepare anhydrous gypsum. Calcine phosphogypsum for the first time to obtain hemihydrate gypsum, and then perform acid washing and the second calcination on the hemihydrate gypsum to obtain anhydrous gypsum. S2. Prepare modified fine sand and modified coarse sand. Stir and dissolve the silane coupling agent in an ethanol solution to obtain a silane coupling agent - ethanol solution. Put a certain amount of fine quartz sand and coarse quartz sand into two stirrers respectively, react for a period of time under stirring, filter and separate, and dry to obtain modified fine sand and modified coarse sand respectively. S3. Prepare modified heavy calcium. Dissolve methoxypolyethylene glycol in deionized water to obtain a methoxypolyethylene glycol aqueous solution. Put a certain amount of heavy calcium particles into the methoxypolyethylene glycol aqueous solution, impregnate for a period of time under stirring, filter, and dry to obtain modified heavy calcium. S4. Prepare self - leveling mortar. Add cement, sulfoaluminate cement, modified fine sand, modified coarse sand, modified heavy calcium, grey calcium, anhydrous gypsum, cellulose, water reducing agent, defoaming agent, rubber powder, and lithium sulfate into a mixer and stir evenly to obtain a powder material. Add water to the powder material in the mixer and stir evenly to obtain anhydrous gypsum - based self - leveling mortar.

6. The preparation method of a high-temperature phase-change regulated anhydrite-based self-leveling mortar according to claim 5, wherein, In step S1, calcine phosphogypsum at 160 °C for 3 h to obtain hemihydrate gypsum. Mix the hemihydrate gypsum with sulfuric acid with a mass concentration of 10%. The mass - to - volume ratio of the hemihydrate gypsum to the sulfuric acid is 1:10 g / mL. Acid - leach under stirring for 1 h, then filter and separate, wash the solid with deionized water more than 5 times, and dry at 90 °C for 5 h. The dried hemihydrate gypsum is calcined at 800 °C for 2 h to obtain anhydrous gypsum.

7. The preparation method of a high-temperature phase-change regulated anhydrite-based self-leveling mortar according to claim 5, characterized in that, In step S2, the silane coupling agent is stirred and dissolved in an ethanol solution to obtain a silane coupling agent-ethanol solution. The mass percentage of the silane coupling agent to the ethanol solution in the silane coupling agent-ethanol solution is 5:

95. The ethanol solution is a 90% ethanol aqueous solution. The silane coupling agent is selected from any one of chloropropyltrimethoxysilane or chloromethyltrimethoxysilane.

8. The preparation method of a high-temperature phase-change regulated anhydrite-based self-leveling mortar according to claim 5, characterized in that, In step S2, a certain amount of fine quartz sand and the silane coupling agent-ethanol solution are respectively put into a stirrer, and reacted for 20 min under stirring, then the solid is filtered and dried to obtain modified fine sand. The mass ratio of the fine quartz sand to the silane coupling agent-ethanol solution is 1:

100. A certain amount of coarse quartz sand and the silane coupling agent-ethanol solution are respectively put into another stirrer, and reacted for 20 min under stirring, then the solid is filtered and dried to obtain modified coarse sand. The mass ratio of the coarse quartz sand to the silane coupling agent-ethanol solution is 1:

100.

9. The preparation method of a high-temperature phase change-regulated anhydrite-based self-leveling mortar according to claim 5, characterized in that, In step S3, polyethylene glycol monomethyl ether is dissolved in deionized water to prepare a 5% polyethylene glycol monomethyl ether aqueous solution. A certain amount of heavy calcium particles are put into the polyethylene glycol monomethyl ether aqueous solution and impregnated for 2 h under stirring, then filtered and dried to obtain modified heavy calcium. The mass ratio of the heavy calcium particles to the polyethylene glycol monomethyl ether aqueous solution is 1:

10.

10. The preparation method of a high-temperature phase-change regulated anhydrite-based self-leveling mortar according to claim 5, characterized in that, In step S4, the mass ratio of the powder to water is 1:0.2 - 0.4.

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