Lightweight soundproofing gypsum-based self-leveling mortar and method for preparing same

Abstract

This invention discloses a lightweight, sound-insulating gypsum-based self-leveling mortar and its preparation method, belonging to the field of building materials. Addressing the problems of weak interfacial bonding between rubber particles and the inorganic matrix, narrow sound insulation spectrum, and difficulty in synergistic enhancement of organic and inorganic networks in existing gypsum-based self-leveling mortars, this invention provides a mortar comprising 100 parts gypsum, 5-15 parts sulfoaluminate cement, 8-18 parts modified recycled rubber particles, 5-20 parts closed-cell vitrified microspheres, and 0.08-0.3 parts modified polyacrylamide. The rubber particles are coated with a polymethyl methacrylate reactive layer, the vitrified microspheres are activated by alkali etching and silane, and the polyacrylamide crosslinking lags the cement hydration acceleration period by 10-30 minutes. This invention achieves a unified performance of lightweight, sound insulation, high strength, and low shrinkage through chemically bridging interfaces, gradient impedance matching structures, and time-controlled interpenetrating networks.

Description

Technical Field

[0001] This application belongs to the field of building materials technology, specifically relating to a lightweight sound-insulating gypsum-based self-leveling mortar and its preparation method. Background Technology

[0002] Gypsum-based self-leveling mortar is widely used for indoor floor leveling due to its convenient construction and fast hardening. However, traditional products have high density and insufficient sound insulation, making it difficult to meet the building's requirements for floor comfort.

[0003] Existing technologies, which reduce density by incorporating lightweight aggregates and improve sound insulation by incorporating elastic aggregates, face multiple technical drawbacks. Firstly, the interfacial compatibility between recycled rubber particles and inorganic cementitious materials such as gypsum is poor. The rubber surface is hydrophobic while the gypsum matrix is ​​hydrophilic, making it difficult for them to form an effective bond. This leads to a significant decrease in mortar strength after the addition of rubber particles, and even interfacial debonding and delamination. Secondly, simple mixing of lightweight and elastic aggregates in the slurry results in a narrow and uneven sound insulation spectrum, failing to meet broadband sound insulation requirements. Thirdly, the hydration processes of organic polymer modifiers and inorganic cementitious materials are not synchronized, preventing the organic and inorganic networks from forming a synergistic reinforcing structure, thus limiting the improvement of mortar toughness, crack resistance, and dimensional stability. Finally, it is difficult to simultaneously achieve lightweight, sound insulation, high strength, and low shrinkage performance. Reducing density often sacrifices strength, while improving sound insulation exacerbates shrinkage and cracking. Existing technologies cannot simultaneously meet the comprehensive performance requirements of modern building floor materials.

[0004] Therefore, there is an urgent need for a lightweight sound-insulating gypsum-based self-leveling mortar and its preparation method that can improve interfacial bonding performance and take into account the comprehensive technical indicators of lightweight, high strength and low shrinkage. Summary of the Invention

[0005] In view of this, this application provides a lightweight sound-insulating gypsum-based self-leveling mortar and its preparation method to solve the problems of weak bonding between rubber particles and inorganic matrix and narrow sound insulation spectrum in existing gypsum-based self-leveling mortars.

[0006] To solve the above problems, the technical solution adopted in this application is as follows:

[0007] In one aspect, this application proposes a lightweight sound-insulating gypsum-based self-leveling mortar, comprising the following components by weight: 100 parts gypsum; 5-15 parts sulfoaluminate cement; 8-18 parts modified recycled rubber particles; 5-20 parts vitrified microspheres; and 0.08-0.3 parts modified polyacrylamide. The modified recycled rubber particles are coated with a polymethyl methacrylate reaction layer, and the calcium ions in the polymethyl methacrylate reaction layer participate in the hydration reaction of the gypsum / sulfoaluminate cement. The vitrified microspheres are closed-cell vitrified microspheres that have undergone alkali etching-silane composite activation treatment. The crosslinking reaction initiation time of the modified polyacrylamide lags behind the hydration acceleration period of the sulfoaluminate cement by 10-30 minutes. The mass ratio of the modified recycled rubber particles to the surface-activated closed-cell vitrified microspheres is 0.8:1-1.2:1, and the density difference between the two is ≥0.8 g / cm³. 3 The mass ratio of the sulfoaluminate cement to the modified polyacrylamide is 60-150:1.

[0008] Preferably, the thickness of the polymethyl methacrylate reaction layer on the surface of the modified recycled rubber particles is 50-200 nm.

[0009] Preferably, the alkaline etching depth of the vitrified microspheres is 0.5-2.0 μm, and the surface roughness Ra is 2-5 μm.

[0010] Preferably, it further includes 0.1-1.0 parts of polypropylene fiber, and at least one of the following: 0.1-0.3 parts of polyether-type polymer shrinkage reducer, 0.1-0.3 parts of cellulose ether, 0.1-0.5 parts of water-reducing agent, 0.05-0.2 parts of defoamer, and 0.05-0.2 parts of retarder.

[0011] Preferably, the crosslinking reaction of the modified polyacrylamide is delayed by 15-25 minutes from the start of the accelerated hydration period of the sulfoaluminate cement, and its degree of crosslinking is 60-80%.

[0012] Preferably, the mixture further comprises 0.5-2.0 parts of nano-calcium sulfoaluminate seed crystals, wherein the nano-calcium sulfoaluminate seed crystals have a particle size of 10-50 nm and a specific surface area ≥80 m². 2 / g.

[0013] Preferably, it further includes 0.02-0.1 parts of a redox delayed initiation system; the redox delayed initiation system includes a water-soluble persulfate initiator, a sulfite reducing agent, and a thiourea-based delaying agent; the mass ratio of the water-soluble persulfate initiator, the sulfite reducing agent, and the thiourea-based delaying agent is 1:0.8-1.2:0.3-0.8.

[0014] Secondly, this application also proposes a method for preparing the lightweight sound-insulating gypsum-based self-leveling mortar described in the first aspect, comprising the following steps: Step 1: Surface-reactively modifying recycled rubber particles to coat their surface with a calcium polymethacrylate reactive layer, thereby obtaining modified rubber particles; Step 2: Surface-activating closed-cell vitrified microspheres to obtain surface-activated closed-cell vitrified microspheres; Step 3: Pre-hydrolyzing and delayed crosslinking modifying modified polyacrylamide to obtain a modified polyacrylamide solution; Step 4: Surface-activating the modified rubber particles with the activated vitrified... Step 5: Mix microspheres and add some gypsum for pre-dispersion treatment to obtain a pre-dispersion lightweight aggregate mixture; Step 6: Dry mix sulfoaluminate cement, remaining gypsum, polypropylene fiber and admixture evenly to obtain inorganic cementitious base material; Step 7: Add the pre-dispersion lightweight aggregate mixture to the inorganic cementitious base material, continue dry mixing, add water and stir, then add modified polyacrylamide solution and continue stirring to form a fluid slurry; Step 8: Pour the fluid slurry onto the base surface, let it stand to form a gradient distribution structure in which rubber particles sink and vitrified microspheres float, and cure to obtain the final product.

[0015] Preferably, in step one, the reclaimed rubber particles are added to an ethanol-water solution containing γ-methacryloyloxypropyltrimethoxysilane, ultrasonically dispersed at 50-60°C for 40-60 min, filtered and dried, and then added to a calcium methacrylate monomer solution. In the presence of potassium persulfate initiator, the mixture is polymerized in situ at 60-70°C for 2-3 hours, washed and dried to obtain modified rubber particles with a surface coated with a calcium methacrylate reaction layer.

[0016] Preferably, in step two, the closed-cell vitrified microspheres are immersed in a 0.5-1.5 mol / L sodium hydroxide solution, subjected to alkaline etching at 40-50°C for 15-25 min, washed and dried, and then sprayed with an atomized ethanol solution containing γ-aminopropyltriethoxysilane. The mixture is then mixed at high speed at 80-90°C for 10-15 min to obtain surface-activated closed-cell vitrified microspheres.

[0017] Preferably, in step three, the modified polyacrylamide is added to warm water at 50-60°C for hydrolysis treatment for 30 minutes, cooled to room temperature, and then an ammonium persulfate / sodium bisulfite redox initiation system and a thiourea delay agent are added and stirred evenly to obtain a modified polyacrylamide solution.

[0018] Preferably, in step four, 0.5-1.0% of nano-calcium sulfoaluminate seed crystals are added, and the pre-dispersion treatment is a low-speed premixing at 80-120 rpm for 5-8 minutes.

[0019] Preferably, in step six, the water temperature is 18-22℃, the mixture is stirred at low speed for 1-2 minutes, then the modified polyacrylamide solution is added and stirred at high speed for 2-3 minutes. The amount of water added is 28-32% of the total mass of the dry powder mixture.

[0020] Preferably, in step seven, the settling time after pouring is 8-12 minutes, and the yield stress τ0 of the fluidized slurry is 18-25 Pa. An interface agent is pre-coated onto the surface of the base layer. The interface agent is an acrylic emulsion containing 1-3% nano-silica, with a solid content of 18-22%, and a coating amount of 0.25-0.3 kg / m². 2 The curing process involves covering the product with a film for 72 hours at 20±2℃ and relative humidity ≥90%, followed by natural curing for 28 days.

[0021] Preferably, in step seven, the gradient distribution structure, from bottom to top, consists of: a rubber particle enrichment layer, a transition layer, and a vitrified microsphere enrichment layer, wherein the thickness of the rubber particle enrichment layer is 3-5 mm and the thickness of the vitrified microsphere enrichment layer is 2-4 mm.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of this application are:

[0023] This application first coats the surface of rubber particles with a calcium polymethacrylate reactive layer, transforming them from inert to reactive aggregates. Calcium ions participate in hydration, and carboxyl groups coordinate with delayed crosslinking polyacrylamide, establishing a chemically bridging interface between the organic elastomer and the inorganic matrix, replacing traditional physical adsorption. Second, this application further utilizes closed-cell vitrified microspheres activated by alkaline etching and silane, roughening the surface and grafting active groups, achieving both lightweight properties and slurry wetting and interlocking. Finally, this application utilizes modified rubber (high density) and activated microspheres (low density) ≥0.8 g / cm³. 3 The density difference allows for one-time casting and settling, achieving an impedance-matched gradient structure with a bottom layer of rubber sound absorption, a top layer of microspheres sound insulation, and an intermediate transition layer for sound scattering. Simultaneously, the polyacrylamide crosslinking initiation time is precisely delayed by 10-30 minutes after the cement hydration acceleration period, ensuring the inorganic skeleton forms first, followed by in-situ interpenetration of the organic network, constructing an interpenetrating polymer network. Chemical bridging ensures long-term stability of the gradient interface, the gradient structure broadens the sound insulation spectrum, and the interpenetrating network enhances toughness and shrinkage resistance. These three elements are mutually supportive, resulting in a synergistic unity of lightweight, sound insulation, high strength, and low shrinkage. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0025] Figure 1 This is a schematic flowchart of the method for preparing lightweight sound-insulating gypsum-based self-leveling mortar provided in the embodiments of this application;

[0026] Figure 2 The bar chart shows the comparison of four key performance parameters (compression resistance / adhesion / sound insulation / shrinkage) for each embodiment and comparative example of this application;

[0027] Subfigure (a) shows the comparison between 28-day compressive strength and wet density; the left Y-axis (bars) represents the 28-day compressive strength (MPa); the right Y-axis (dots) represents the wet density (kg·m³). -3 );

[0028] Subgraph (b) is a comparison of tensile bond strength; the Y-axis represents tensile bond strength (MPa).

[0029] Subgraph (c) is a comparison chart of airborne sound insulation; the Y-axis represents airborne sound insulation (dB).

[0030] Subplot (d) is a comparison of the improvement in impact sound versus the drying shrinkage rate; the left Y-axis (bars) represents the improvement in impact sound (dB); the right Y-axis (dots) represents the drying shrinkage rate (mm·m). -1 ). Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The components of the embodiments of this application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0035] In this application, unless otherwise expressly specified and limited, "above" or "below" a second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of a second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" a second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and do not limit the number of objects; for example, a first object can be one or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0036] Existing gypsum-based self-leveling mortars are widely used for indoor floor leveling due to their convenient construction and rapid hardening. However, traditional products have high density and insufficient sound insulation, making it difficult to meet the comfort requirements of buildings. Current technologies reduce density by incorporating lightweight aggregates and improve sound insulation by incorporating elastic aggregates, but they face several technical drawbacks. First, the interfacial compatibility between recycled rubber particles and inorganic cementitious materials such as gypsum is poor. The rubber surface is hydrophobic while the gypsum matrix is ​​hydrophilic, making it difficult for the two to form an effective bond. This leads to a significant decrease in mortar strength after the addition of rubber particles, and even interfacial debonding and hollowing. Second, the simple mixing of lightweight and elastic aggregates in the slurry results in a narrow and uneven sound insulation spectrum, which is difficult to meet broadband sound insulation requirements. Third, the hydration processes of organic polymer modifiers and inorganic cementitious materials are not synchronized, and the organic and inorganic networks cannot form a synergistic reinforcing structure, which limits the improvement of the mortar's toughness, crack resistance, and dimensional stability. Finally, it is difficult to simultaneously achieve lightweight, sound insulation, high strength, and low shrinkage performance. Reducing density often sacrifices strength, while improving sound insulation exacerbates shrinkage and cracking. Existing technologies cannot simultaneously meet the comprehensive performance requirements of modern building floor materials.

[0037] The core of this application lies in transforming recycled rubber particles, which are originally chemically inert to inorganic cementitious materials, into reactive aggregates by coating their surface with a calcium polymethyl methacrylate reactive layer. This allows calcium ions on the rubber surface to participate in the hydration reaction of gypsum and sulfoaluminate cement, while carboxylic acid groups form coordination bonds with delayed crosslinking modified polyacrylamide. This establishes a chemically bridging interface transition zone between the organic elastomer and the inorganic hydration products, completely changing the weak bonding state of the physical adsorption interface in traditional rubber-modified mortar. Simultaneously, closed-cell vitrified microspheres undergo alkali etching and silane composite activation treatment, transforming their surface from a smooth vitreous state to a rough state grafted with organic active groups. This maintains the lightweight characteristics of closed-cell low density while achieving good wettability and mechanical interlocking ability with the mortar. Based on this, a bond strength of not less than 0.8 g / cm³ is achieved between the modified rubber particles and the activated vitrified microspheres. 3 The density difference creates a bottom-up gradient distribution in the self-leveling slurry during static settling, based on the Stokes sedimentation principle: denser rubber particles sink to form a bottom high-damping sound-absorbing layer, while less dense vitrified microspheres float to form a top high-reflectivity sound-insulating layer. A naturally transitioning sound wave scattering and dissipation zone forms in the middle, achieving an impedance-matched gradient structure formed in a single pour. Furthermore, by controlling the timing of delayed crosslinking modified polyacrylamide, the crosslinking reaction initiation time is precisely delayed by 10-30 minutes beyond the accelerated hydration period of sulfoaluminate cement. This ensures that the inorganic framework is formed first during cement hydration, followed by the in-situ growth and interpenetration of the organic polymer network within the framework pores, constructing a true organic-inorganic interpenetrating polymer network.

[0038] The chemical bridging interface provides mechanical stability for the gradient structure: if there is only damping sound absorption from the rubber particles without chemical bonding, the rubber-enriched layer will become a weak area for interface debonding, resulting in hollowing under load or deformation, and the sound insulation performance will deteriorate accordingly. It is the dual chemical connection between the polymethyl methacrylate reactive layer and the inorganic hydration products and organic polymer network that allows the rubber particles to remain highly elastic while firmly anchored in the matrix, ensuring that the bottom sound-absorbing layer does not peel off or collapse during long-term use. The gradient impedance matching structure broadens the sound insulation spectrum and improves efficiency across the entire frequency band: the viscoelastic deformation of the bottom rubber particles absorbs low- and mid-frequency impact sound, the closed-cell structure of the surface vitrified microspheres reflects high-frequency airborne sound, and the gradual impedance change of the intermediate transition layer avoids sound energy transmission caused by abrupt changes between layers. The three work together to form a continuous dissipation chain of absorption, scattering, and reflection. The time-controlled interpenetrating network simultaneously enhances structural toughness and dimensional stability: if polyacrylamide crosslinks in the early stages of hydration, it will encapsulate hydration products and hinder cement hydration, leading to a sharp drop in strength; while the delayed crosslinking strategy allows the inorganic network to form a load-bearing skeleton first, followed by the organic network filling and bridging, with the two interpenetrating at the molecular level rather than being simply blended. This allows polymer segments to effectively bridge inorganic microcracks, improving fracture toughness and suppressing drying shrinkage. The composite cementitious system of sulfoaluminate cement and gypsum provides a time window and strength basis for the above synergy: the rapid hydration acceleration period of sulfoaluminate cement provides 10-30 minutes for delayed crosslinking, and the early-formed ettringite needle-like crystals and gypsum hydration products together constitute a dense skeleton. It is evident that the chemical bridging interface is the common bonding basis for the gradient structure and the interpenetrating network. The gradient structure is the spatial carrier of the sound insulation function, and the time-controlled interpenetrating network is the intrinsic guarantee of mechanical properties and durability. The three support each other and are indispensable. Together, they break through the technical bottleneck of traditional lightweight sound insulation materials, where lightweight materials inevitably sacrifice strength and sound insulation inevitably aggravates shrinkage. This achieves the synergistic unity of four properties: lightweight, sound insulation, high strength, and low shrinkage.

[0039] The following is in conjunction with the appendix Figure 1 The technical solutions provided in this application will be described in detail through specific embodiments and application scenarios.

[0040] In one aspect, this application proposes a lightweight sound-insulating gypsum-based self-leveling mortar, comprising the following components by weight: 100 parts gypsum; 5-15 parts sulfoaluminate cement; 8-18 parts modified recycled rubber particles; 5-20 parts vitrified microspheres; and 0.08-0.3 parts modified polyacrylamide. The modified recycled rubber particles are coated with a polymethyl methacrylate reaction layer, and the calcium ions in the polymethyl methacrylate reaction layer participate in the hydration reaction of the gypsum / sulfoaluminate cement. The vitrified microspheres are closed-cell vitrified microspheres that have undergone alkali etching-silane composite activation treatment. The crosslinking reaction initiation time of the modified polyacrylamide lags behind the hydration acceleration period of the sulfoaluminate cement by 10-30 minutes. The mass ratio of the modified recycled rubber particles to the surface-activated closed-cell vitrified microspheres is 0.8:1-1.2:1, and the density difference between the two is ≥0.8 g / cm³. 3 The mass ratio of the sulfoaluminate cement to the modified polyacrylamide is 60-150:1.

[0041] Specifically, gypsum is used as the matrix material, with a dosage set at 100 parts, forming the basic framework of the entire mortar system. It can be hemihydrate gypsum such as building gypsum, high-strength gypsum, or desulfurized gypsum, or it can be a pre-treated product of industrial by-product gypsum such as phosphogypsum. Its fineness is typically controlled between 200-400 mesh, and its specific surface area is greater than 300 m². 2 / kg. When gypsum comes into contact with water, it undergoes a hydration reaction to form dihydrate gypsum crystals. These crystals interweave to form an initial framework, giving the material basic strength and hardening properties. At the same time, the gypsum system has micro-expansion properties, which can compensate for some shrinkage and ensure the volume stability after hardening.

[0042] The admixture of sulfoaluminate cement is set at 5-15 parts to form a composite cementitious system with gypsum. Specifically, rapid-hardening sulfoaluminate cement or low-alkalinity sulfoaluminate cement can be used, and its specific surface area should be controlled at 350-450 m². 2 / kg, with a low tricalcium aluminate content and a moderate iron phase content. The anhydrous calcium sulfoaluminate in sulfoaluminate cement reacts with gypsum to generate a large number of ettringite needle-like crystals. These crystals rapidly form a dense network in the early stages of hardening, significantly improving early strength and water resistance. At the same time, the alkaline environment of sulfoaluminate cement is lower than that of silicate cement, which can reduce the corrosive effect on gypsum and has better compatibility with the gypsum matrix. Its hydration acceleration period usually occurs 30-90 minutes after water addition, providing a time window for the delayed cross-linking of the subsequent organic network.

[0043] The modified recycled rubber granules are added at a dosage of 8-18 parts, with a particle size typically controlled at 1-3 mm and a density of approximately 1.1-1.2 g / cm³. 3The core of this particle design lies in the surface coating of a poly(calcium methacrylate) reactive layer. The preparation process involves first surface anchoring the rubber particles with γ-methacryloyloxypropyltrimethoxysilane, then immersing them in a calcium methacrylate monomer solution. In situ polymerization at 60-70℃ for 2-3 hours is initiated by potassium persulfate, forming a coating layer with a thickness of 50-200 nm. The mechanism of action lies in the dual reactivity of calcium ions and carboxylic acid groups in the poly(calcium methacrylate) layer. Calcium ions can chemically bond with gypsum hydration products and ettringite generated from the hydration of sulfoaluminate cement, while carboxylic acid groups can form coordination bonds with the amide groups of modified polyacrylamide. This creates a chemically bridging interface transition zone between the rubber particles and the inorganic matrix, replacing the traditional physical adsorption interface. The resulting effect is that the rubber particles transform from inert fillers into reactive aggregates, effectively improving interfacial bonding strength while retaining the high damping characteristics of the rubber particles, effectively absorbing mid-to-low frequency sound wave energy.

[0044] The dosage of vitrified microspheres is 5-20 parts, and closed-cell vitrified microspheres are selected. The particle size is usually controlled at 0.5-2 mm, and the density is about 0.15-0.25 g / cm³. 3 The specific setup requires a combination of alkaline etching and silane activation treatment. First, alkali etching with a 0.5-1.5 mol / L sodium hydroxide solution at 40-50℃ for 15-25 minutes results in an alkali etching depth of 0.5-2 μm and a surface roughness of 2-5 μm. Then, a γ-aminopropyltriethoxysilane atomized ethanol solution is sprayed in and mixed at high speed at 80-90℃ to graft aminosilane active groups onto the surface. The mechanism is that the alkaline etching removes the smooth, glassy layer from the surface, forming a micro-uneven structure that increases the mechanical interlocking area with the slurry. The silane coupling agent introduces organic functional groups onto the surface of the vitrified microspheres, improving the interfacial wettability with organic polymers and gypsum slurry. The resulting effect is that the vitrified microspheres are uniformly dispersed in the slurry, preventing them from floating and agglomerating, while maintaining the integrity of the closed-cell structure, ensuring low thermal conductivity and lightweight properties. After surface activation, the interfacial bonding strength is improved, forming a stable, high-reflectivity sound-insulating layer within the gradient structure.

[0045] The modified polyacrylamide dosage is 0.08-0.3 parts, and its specific setting requires pre-hydrolysis and delayed crosslinking modification. Pre-hydrolysis involves treatment in warm water at 50-60℃ for 30 minutes, converting some amide groups into carboxylic acid groups. Delayed crosslinking modification is achieved by introducing a redox delayed initiation system, such as the redox pair of ammonium persulfate and sodium bisulfite, with thiourea added as a delaying agent, controlling the thiourea mass to be 30-80% of the ammonium persulfate mass. The mechanism of action lies in precisely controlling the crosslinking initiation time of polyacrylamide to lag behind the hydration acceleration period of sulfoaluminate cement by 10 to 30 minutes, preferably 15-25 minutes, through redox reaction kinetics and the complexation effect of the delaying agent. This means that within the first 30 minutes after water addition, sulfoaluminate cement rapidly hydrates to form ettringite and a gel skeleton, constructing the basic framework of the inorganic network; subsequently, polyacrylamide begins crosslinking, its molecular chains growing in situ and entangled in the pores of the inorganic skeleton, forming an organic three-dimensional network. The result is the construction of a true interpenetrating polymer network structure rather than a simple physical blend. The organic network effectively bridges inorganic microcracks, improving the fracture toughness of the mortar, reducing the drying shrinkage rate, and significantly improving water retention and workability.

[0046] The mass ratio of modified recycled rubber granules to vitrified microspheres is set at 0.8-1.2:1, and the density difference between the two is not less than 0.8 g / cm³. 3 The specific setting of this ratio and density difference is to create a controllable gradient in the self-leveling slurry using the Stokes sedimentation principle. Rubber particles, with their higher density, gradually sink after standing; vitrified microspheres, with their lower density, gradually float. When the slurry yield stress is controlled between 18-25 Pa, after standing for 5-15 minutes, a gradient distribution naturally forms from bottom to top in the slurry: a rubber particle enrichment layer, a transition layer, and a vitrified microsphere enrichment layer. The mechanism involves the incident sound wave being absorbed and attenuated by viscoelastic deformation in the bottom high-damping rubber enrichment layer. The residual sound wave is scattered and dissipated in the middle transition zone. Upon reaching the surface layer, it encounters the high-porosity vitrified microsphere enrichment layer, resulting in impedance mismatch reflection. The reflected wave then re-enters the middle and bottom layers and is repeatedly dissipated. This synergistic absorption and reflection mechanism replaces the traditional single dissipation mode of homogeneous materials. The resulting effect is a significantly broadened sound insulation spectrum, and no additional molds or layered construction are required; the gradient structure is formed in a single pour using the self-leveling properties.

[0047] The mass ratio of sulfoaluminate cement to modified polyacrylamide is set at 60-150:1. This ratio must ensure sufficient inorganic cementitious material to form a complete hydration skeleton, while the organic polymer content is sufficient to construct a continuous network within the pores without excessively encapsulating hydration products and hindering the hydration reaction. When the ratio is below 60:1, the polymer content is relatively excessive, leading to a sharp increase in slurry viscosity, loss of self-leveling properties, and an encapsulation effect that inhibits cement hydration. When the ratio is above 150:1, the polymer content is insufficient, failing to form a continuous interpenetrating network, resulting in limited toughening and crack resistance. The mechanism lies in this ratio range ensuring a match between the inorganic and organic networks in terms of volume fraction and spatial distribution, allowing the organic network to precisely fill the pores of the inorganic skeleton without disrupting its continuity. This achieves a unified approach of lightweight, high strength, and synergistic toughening of the organic and inorganic components.

[0048] In summary, gypsum and sulfoaluminate cement constitute a composite inorganic cementitious system, providing the strength foundation and hardening framework for the entire material. Modified rubber particles and activated vitrified microspheres form a gradient impedance matching structure through density difference and proportion control, endowing the material with broadband sound insulation capabilities. Modified polyacrylamide constructs an interpenetrating network through time-controlled crosslinking, enhancing toughness and crack resistance. The polymethyl methacrylate reactive layer on the surface of the rubber particles acts as a chemical bridge, firmly anchoring the elastic aggregate to the inorganic matrix, avoiding the strength loss problem commonly found in traditional lightweight sound insulation materials. These characteristics work together to overcome the technical bottleneck of simultaneously achieving lightweight, sound insulation, high strength, and low shrinkage.

[0049] Secondly, this application also proposes a method for preparing the lightweight sound-insulating gypsum-based self-leveling mortar described in the first aspect, comprising the following steps: Step 1: Surface-reactively modifying recycled rubber particles to coat their surface with a calcium polymethacrylate reactive layer, thereby obtaining modified rubber particles; Step 2: Surface-activating closed-cell vitrified microspheres to obtain surface-activated closed-cell vitrified microspheres; Step 3: Pre-hydrolyzing and delayed crosslinking modifying modified polyacrylamide to obtain a modified polyacrylamide solution; Step 4: Surface-activating the modified rubber particles with the activated vitrified... Step 5: Mix microspheres and add some gypsum for pre-dispersion treatment to obtain a pre-dispersion lightweight aggregate mixture; Step 6: Dry mix sulfoaluminate cement, remaining gypsum, polypropylene fiber and admixture evenly to obtain inorganic cementitious base material; Step 7: Add the pre-dispersion lightweight aggregate mixture to the inorganic cementitious base material, continue dry mixing, add water and stir, then add modified polyacrylamide solution and continue stirring to form a fluid slurry; Step 8: Pour the fluid slurry onto the base surface, let it stand to form a gradient distribution structure in which rubber particles sink and vitrified microspheres float, and cure to obtain the final product.

[0050] In terms of specific setup, the recycled rubber granules are first subjected to surface reactive modification. Through silane coupling agent anchoring and in-situ polymerization, a polymethyl methacrylate reactive layer is coated onto the surface of the rubber granules, giving the originally hydrophobic and inert rubber surface calcium ion active sites that can participate in inorganic hydration reactions. Simultaneously, closed-cell vitrified microspheres undergo alkali etching and silane composite activation treatment, transforming their surface from a smooth, glassy state to a rough, activated state grafted with organic active groups. Subsequently, modified polyacrylamide undergoes pre-hydrolysis and delayed crosslinking modification. By introducing a redox delayed initiation system, the start time of the polymer crosslinking reaction is precisely delayed compared to the hydration acceleration period of sulfoaluminate cement. After the aggregate and polymer have been modified separately, the modified rubber granules and activated vitrified microspheres are mixed, and 5-8% (by weight of the total cementitious material) of gypsum is added for pre-dispersion treatment, allowing some gypsum particles to pre-attach to the surface of the lightweight aggregate, forming a pre-dispersed lightweight aggregate mixture. On the other hand, sulfoaluminate cement, remaining gypsum, polypropylene fibers, admixtures, and other components are dry-mixed uniformly to form an inorganic cementitious base material. Then, the pre-dispersed lightweight aggregate mixture is added to the inorganic cementitious base and dry-mixed. Water is then added and stirred, and finally, a modified polyacrylamide solution is added and stirred to form a fluid slurry. The fluid slurry is then poured onto the surface of the base layer and allowed to stand to form a gradient distribution structure where rubber particles sink and vitrified microspheres float. After curing, the finished product is obtained.

[0051] The core of this method lies in achieving precise control of the reactivity of each component through stepwise modification, synergistic construction of organic-inorganic networks through time-series control, and self-forming of gradient structures through rheological design. Surface reactive modification of rubber particles transforms them from inert fillers into reactive aggregates. Calcium ions in the polymethyl methacrylate layer on their surface can form chemical bonds with the hydration products of gypsum and sulfoaluminate cement during subsequent hydration, while carboxylic acid groups form coordination bonds with modified polyacrylamide, thus constructing a chemically bridging interface. Surface activation treatment of vitrified microspheres enhances mechanical interlocking and chemical wettability with the slurry through the synergistic effect of alkaline etching roughening and silane grafting, while maintaining the integrity of the closed-cell structure. Delayed crosslinking modification of the modified polyacrylamide, through the synergistic effect of the redox initiation system and the delay agent, lags the crosslinking reaction initiation time by 10-30 minutes after the cement hydration acceleration period, ensuring that the inorganic hydration skeleton forms first, followed by the in-situ growth of the organic network. The addition of gypsum during pre-dispersion treatment forms a preliminary cementitious material coating layer on the surface of lightweight aggregates, preventing electrostatic agglomeration and density segregation during subsequent dry mixing. In controlled mixing, inorganic cementitious base materials are first dry-mixed to ensure uniform dispersion of the cementitious materials, then water is added to initiate hydration of gypsum and cement. Finally, a delayed cross-linking polymer solution is added to prevent the polymer from being damaged by high shear in the initial water addition stage or inhibiting hydration due to early high concentrations of hydration products. During the static molding stage, the density difference between rubber particles and vitrified microspheres, along with the specific yield stress of the slurry, allows the slurry to naturally form a bottom-up gradient distribution under gravity without the need for vibration or layered construction.

[0052] The mortar prepared by this method achieves a synergistic improvement in comprehensive performance, including lightweight, sound insulation, high strength, and low shrinkage. High-strength bonding is achieved between the rubber particles and the inorganic matrix through a chemically bridged interfacial transition zone, significantly increasing tensile bond strength and overcoming the sharp drop in strength characteristic of traditional rubber-modified mortars. The organic-inorganic interpenetrating polymer network structure enhances the mortar's fracture toughness and reduces drying shrinkage. The entire preparation process requires no additional molds or layered casting equipment; the self-leveling properties allow for the formation of a gradient structure in a single application, achieving construction efficiency comparable to conventional self-leveling mortars.

[0053] In some embodiments, in step one, the reclaimed rubber particles are added to an ethanol-water solution containing γ-methacryloyloxypropyltrimethoxysilane, ultrasonically dispersed at 50-60°C for 40-60 min, filtered and dried, and then added to a calcium methacrylate monomer solution. In the presence of potassium persulfate initiator, the particles are polymerized in situ at 60-70°C for 2-3 hours, washed and dried to obtain modified rubber particles with a surface coated with a calcium methacrylate reaction layer.

[0054] The silane coupling agent is dispersed in a mixed solvent of ethanol and water, with the volume ratio of ethanol to water typically controlled between 4-9:1. This ratio ensures that silane molecules are fully hydrolyzed to generate silanol active groups while inhibiting the self-condensation precipitation of hydrolysis products in excess water. Reclaimed rubber particles are ultrasonically dispersed in this ethanol-water solution at 50-60°C for 40-60 minutes. The localized microjets generated by ultrasonic cavitation, combined with mechanical vibration, allow silane molecules to penetrate into the micropores on the surface of the rubber particles, promoting the dehydration condensation anchoring of silanol groups with the active sites on the rubber surface. After treatment, the particles are filtered and dried to remove unreacted free silane and solvent, preventing residual silane from interfering with subsequent in-situ polymerization. After the in-situ polymerization reaction is complete, the particles are repeatedly washed with deionized water to remove residual calcium methacrylate monomer and homopolymer byproducts, and then vacuum dried at 60°C to constant weight to ensure that the polymethyl methacrylate reaction layer firmly adheres to the surface of the rubber particles. Silane coupling agents hydrolyze in an ethanol-water system to generate silanol groups, which form a siloxane-silicon anchoring layer on the rubber surface through dehydration condensation, simultaneously introducing reactive double bonds. Calcium methacrylate monomers polymerize in situ on this anchoring layer, forming a 50-200 nm thick poly(calcium methacrylate) coating layer. The calcium ions in this coating layer exhibit inorganic reactivity, while the carboxylic acid groups possess organic coordination activity, achieving dual-reactivity modification of the rubber particle surface. The resulting effect is a transformation of the rubber particle surface from hydrophobic and nonpolar to hydrophilic and reactive, reducing the wetting angle with the gypsum slurry and laying the foundation for the subsequent formation of a chemically bridged interface.

[0055] In some embodiments, in step two, the closed-cell vitrified microspheres are immersed in a 0.5-1.5 mol / L sodium hydroxide solution, etched at 40-50°C for 15-25 min, washed and dried, and then sprayed with an atomized ethanol solution containing γ-aminopropyltriethoxysilane. The mixture is then mixed at 80-90°C at high speed for 10-15 min to obtain surface-activated closed-cell vitrified microspheres.

[0056] Sodium hydroxide selectively dissolves the vitreous layer on the surface of vitrified microspheres, forming a rough structure and increasing the mechanical interlocking area with the slurry. Atomized silane solution spreads uniformly on the rough surface in droplet form, undergoing hydrolysis and condensation under the combined action of heat and mechanical shear, grafting aminosilane active groups. While maintaining the integrity of the closed-cell structure and without increasing density, the surface wettability and interfacial adhesion strength of the vitrified microspheres are significantly improved, resulting in better dispersion uniformity in the slurry and reducing the likelihood of flotation and aggregation.

[0057] In some embodiments, in step three, the modified polyacrylamide is added to warm water at 50-60°C for hydrolysis treatment for 30 minutes, cooled to room temperature, and then an ammonium persulfate / sodium bisulfite redox initiation system and a thiourea delay agent are added and stirred evenly to obtain a modified polyacrylamide solution.

[0058] Modified polyacrylamide was hydrolyzed in 50-60°C water for 30 minutes, converting some amide groups into carboxylic acid groups. After cooling to room temperature, a redox initiation system consisting of ammonium persulfate and sodium bisulfite, along with a thiourea-based delaying agent, was added and stirred until a homogeneous solution was obtained. The working principle is that the warm water hydrolysis partially breaks the polyacrylamide molecular chains and introduces carboxylic acid groups, enhancing its reactivity and dispersibility. In the redox initiation system, persulfate and sulfite generate free radicals through electron transfer reactions, initiating the crosslinking reaction of the polyacrylamide. The thiourea delaying agent controls the reaction triggering timing by complexing free radical precursors or consuming primary free radicals, ensuring that the crosslinking initiation time is precisely delayed by 10-30 minutes from the start of the accelerated hydration period of sulfoaluminate cement. The resulting effect is that the polyacrylamide solution maintains a low-viscosity linear state in the initial stage after being added to the slurry, not interfering with the early process of gypsum dissolution and cement hydration. Crosslinking begins to construct a three-dimensional network only after the inorganic framework has initially formed, thus achieving time-controlled interpenetration of the organic and inorganic dual networks.

[0059] In some embodiments, in step four, 0.5-1.0% of nano-calcium sulfoaluminate seed crystals are added, and the pre-dispersion treatment is a low-speed premixing at 80-120 rpm for 5-8 minutes.

[0060] Some gypsum particles are pre-adhered to the surface of lightweight aggregate through physical adsorption and electrostatic interaction, forming a preliminary cementitious material coating layer. This coating layer hydrates rapidly upon subsequent water addition, generating early bonding force and preventing segregation or agglomeration of lightweight aggregate in the slurry due to density differences. Nano-calcium sulfoaluminate seed crystals selectively adsorb onto the polymethyl methacrylate layer on the surface of rubber particles via electrostatic adsorption, serving as heterogeneous nucleation sites during subsequent hydration to induce the directional growth of ettringite. The resulting effect is a significant improvement in the dispersion stability of lightweight aggregate during the dry mixing stage. The pre-positioning of the seed crystals on the surface of rubber particles densifies the interfacial transition zone, providing a prerequisite for the uniform formation of the gradient structure. The nano-calcium sulfoaluminate seed crystals are added to the pre-dispersion system at a ratio of 0.5-1.0% of the total mass of the cementitious material. This mass percentage corresponds to the part limit in the product formulation, facilitating quick conversion based on the total amount of cementitious material used on-site. The pre-dispersion treatment uses a low-speed premixing of 80-120 rpm for 5-8 minutes. This speed is significantly lower than the mixing speed of conventional dry powder mortar. This is intended to avoid high-speed shearing from damaging the nanoparticle morphology of the seed crystals and the integrity of the polymethyl methacrylate coating layer on the surface of the rubber particles, while ensuring that the seed crystals are uniformly adsorbed on the surface of the lightweight aggregate without agglomeration.

[0061] In some embodiments, in step six, the temperature of the water added is 18-22°C, and the mixture is first stirred at low speed for 1-2 minutes, then the modified polyacrylamide solution is added and stirred at high speed for 2-3 minutes. The amount of water added is 28-32% of the total mass of the dry powder mixture.

[0062] The water temperature is strictly controlled between 18-22℃. This temperature range is below the sensitive temperature threshold for rapid hydration of sulfoaluminate cement, avoiding excessively high water temperatures that could cause instantaneous hydration heat release and shorten the workable time of the slurry. Simultaneously, excessively low water temperatures could delay the dissolution rate of gypsum and the development of early strength. Mixing is performed initially at low speed for 1-2 minutes to preliminarily wet and disperse the dry powder, followed by the addition of modified polyacrylamide solution and high-speed mixing for 2-3 minutes. The low-speed stage prevents excessively high local concentrations of the polymer solution, which could lead to gel agglomeration. The high-speed stage ensures homogenization of the slurry and introduces a moderate shear thinning effect to optimize leveling properties. The total amount of water added is 28-32% of the total mass of the dry powder mixture. This water-to-slurry ratio is precisely matched to the rheological requirement of the slurry yield stress of 18-25 Pa. Too little water results in a viscous slurry with insufficient self-leveling properties, while too much water leads to bleeding and uncontrolled aggregate buoyancy. The slurry exhibits good workability and sufficient workable time, maintaining its flow dynamics within a certain settling window after pouring, providing time for gradient self-forming.

[0063] In some embodiments, in step seven, the settling time after pouring is 8-12 minutes, and the yield stress τ0 of the fluidized slurry is 18-25 Pa. An interface agent is pre-coated onto the base surface; the interface agent is an acrylic emulsion containing 1-3% nano-silica, with a solid content of 18-22%, and a coating amount of 0.25-0.3 kg / m². 2 The curing process involves covering the product with a film for 72 hours at 20±2℃ and relative humidity ≥90%, followed by natural curing for 28 days.

[0064] Nano-silica forms a nanoscale filling network in the emulsion, enhancing the penetration and sealing ability of the interface agent into the capillary pores of the substrate. The acrylic polymer provides a flexible transition layer, mitigating the difference in elastic modulus between the gypsum-based mortar and the concrete substrate. The coating amount is less than 0.25 kg / m². 2 Incomplete film formation at the interface, exceeding 0.3 kg / m 2 Excessive residual liquid film can weaken the direct bond between the mortar layer and the substrate. The curing regime involves covering the mortar with a film for 72 hours after pouring, at 20±2℃ and relative humidity not less than 90%, to allow the gypsum and sulfoaluminate cement to fully hydrate and prevent early moisture evaporation that could lead to surface powdering and shrinkage cracking. Subsequently, the material is allowed to cure naturally for 28 days until it reaches the design strength and sound insulation performance of the material.

[0065] In some embodiments, in step seven, the gradient distribution structure, from bottom to top, consists of: a rubber particle enrichment layer, a transition layer, and a vitrified microsphere enrichment layer, wherein the thickness of the rubber particle enrichment layer is 3-5 mm and the thickness of the vitrified microsphere enrichment layer is 2-4 mm.

[0066] After the slurry settles, it forms a rubber particle enrichment layer, a transition layer, and a vitrified microsphere enrichment layer sequentially from bottom to top. The thickness of the rubber particle enrichment layer corresponds to the main absorption zone in the initial stage of sound wave incidence, where the volume fraction of rubber particles reaches its peak, and its viscoelastic deformation can fully dissipate mid-to-low frequency sound energy. The vitrified microsphere enrichment layer is located on the surface layer; its high porosity and low impedance characteristics cause strong sound wave reflection, and its thickness is sufficient to form a continuous reflection interface without sound energy transmission loss due to excessive thinness. The thickness of the transition layer is adaptively adjusted with the total casting thickness, achieving a continuous gradient change in acoustic impedance from the bottom layer to the surface layer, avoiding the enhanced sound wave transmission and the sound insulation trough caused by abrupt changes in interlayer impedance.

[0067] Example 1

[0068] This embodiment provides a lightweight sound-insulating gypsum-based self-leveling mortar, the components and dosages of which are as follows: 100 parts building gypsum, 10 parts rapid-hardening sulfoaluminate cement, 13 parts surface-reactive modified recycled rubber particles, 12 parts surface-activated closed-cell vitrified microspheres, 0.15 parts delayed crosslinking modified polyacrylamide, 1.0 part nano-calcium sulfoaluminate seed crystals, 0.5 parts polypropylene fiber, 0.05 parts redox delayed initiation system, 0.2 parts polyether-type polymer shrinkage reducer, 0.2 parts hydroxypropyl methylcellulose ether, 0.3 parts polycarboxylate superplasticizer, 0.1 parts organosilicon defoamer, 0.1 parts tartaric acid retarder, and appropriate amount of mixing water. The mass ratio of surface reactive modified recycled rubber particles to surface activated closed-cell vitrified microspheres is approximately 1.08:1, the mass ratio of sulfoaluminate cement to delayed crosslinking modified polyacrylamide is approximately 66.7:1, and the mass ratio of ammonium persulfate, sodium bisulfite, and thiourea in the redox delayed initiation system is 1:1:0.5.

[0069] The preparation process of the above-mentioned surface reactive modified recycled rubber particles is as follows: waste tire recycled rubber particles with a particle size of 2-3 mm are selected and immersed in an ethanol aqueous solution containing 2.5% γ-methacryloyloxypropyltrimethoxysilane. The volume ratio of ethanol to water is 8:2. Under the action of ultrasonic waves with a frequency of 40 kHz and a power of 300 W, the particles are dispersed at a constant temperature of 55 °C for 50 min. Then, they are vacuum filtered and vacuum dried at 60 °C for 4 h to obtain silane anchored rubber particles. The above-mentioned silane-anchored rubber particles were added to an 8% aqueous solution of calcium methacrylate monomer, nitrogen gas was introduced to remove oxygen, and potassium persulfate (0.8% by mass of monomer) was added as an initiator. The in-situ polymerization reaction was carried out in a constant temperature water bath at 65°C with a stirring rate of 150 r / min for 2.5 h. After the reaction, the particles were washed three times with deionized water to remove unreacted monomers and homopolymers. The particles were then dried to constant weight in a vacuum drying oven at 60°C to obtain modified rubber particles with a surface coating of calcium methacrylate reaction layer. The thickness of the coating layer was measured to be approximately 120 nm by transmission electron microscopy.

[0070] The preparation process of the above-mentioned surface-activated closed-cell vitrified microspheres is as follows: Particles with a diameter of 0.5-1 mm and a bulk density of 120 kg / m³ are selected. 3 Closed-cell vitrified microspheres were immersed in a 1 mol / L sodium hydroxide solution and etched in a constant temperature water bath at 45°C for 20 min with slow stirring at 60 r / min. The microspheres were then washed with deionized water until the filtrate was neutral and dried in an oven at 80°C for 3 h to obtain alkali-etched vitrified microspheres. These microspheres were then placed in a high-speed mixer, preheated to 85°C, and sprayed with an ethanol solution containing 3% γ-aminopropyltriethoxysilane at a mist pressure of 0.3 MPa and a droplet size of 20-40 μm. The mixture was stirred at 1500 r / min for 12 min at 85°C, then discharged and cooled to obtain surface-activated closed-cell vitrified microspheres. The surface roughness Ra, measured by laser confocal microscopy, was approximately 3.5 μm.

[0071] The preparation process of the above-mentioned delayed crosslinking modified polyacrylamide solution is as follows: Anionic polyacrylamide powder is added to warm water at 55°C to prepare a 2% (w / w) solution. The solution is then hydrolyzed by stirring at 300 r / min for 30 min to convert some amide groups into carboxylic acid groups. The solution is then cooled to 20°C. 0.02 parts of ammonium persulfate, 0.02 parts of sodium bisulfite, and 0.01 parts of thiourea are added to the pre-hydrolyzed solution. The solution is stirred at 200 r / min for 10 min to ensure complete dissolution and uniform mixing, resulting in a delayed crosslinking modified polyacrylamide solution. The apparent viscosity of this solution at 25°C is 300 mPa·s, and the crosslinking initiation time is approximately 45 min after the addition of water.

[0072] The aforementioned nano-calcium sulfoaluminate seed crystals are commercially available products, modified with citric acid, with a particle size of 20-30 nm and a specific surface area of ​​120 m². 2 / g, Zeta potential -30mV.

[0073] The preparation method of the above-mentioned lightweight sound-insulating gypsum-based self-leveling mortar is carried out according to the following steps. Step 1, preparation of pre-dispersed lightweight aggregate mixture: 13 parts of surface-reactive modified recycled rubber particles and 12 parts of surface-activated closed-cell vitrified microspheres are put into a biaxial paddle mixer, 6.4 parts of building gypsum and 1.0 parts of nano-calcium sulfoaluminate seed crystals are added, and the mixture is premixed at a low speed of 100 r / min for 6 min, so that the nano-crystals are selectively adsorbed on the polymethyl methacrylate layer on the surface of the rubber particles, while the gypsum particles uniformly coat the surface of the lightweight aggregate, thus obtaining the pre-dispersed lightweight aggregate mixture. Step 2, Preparation of inorganic cementitious base material: 10 parts of rapid-hardening sulfoaluminate cement, the remaining 93.6 parts of building gypsum, 0.5 parts of polypropylene fiber, 0.2 parts of polyether-type polymer shrinkage reducer, 0.2 parts of hydroxypropyl methylcellulose ether, 0.3 parts of polycarboxylate superplasticizer, 0.1 parts of organosilicon defoamer and 0.1 parts of tartaric acid retarder are put into another mixer and dry-mixed for 10 minutes until uniform to obtain inorganic cementitious base material. Step 3, Time-controlled mixing: Add the pre-dispersed lightweight aggregate mixture to the inorganic cementitious base material and continue dry mixing for 5 minutes. Then add mixing water at 20℃, with the water volume being 30% of the total mass of the dry powder mixture. First, stir at a low speed of 60 r / min for 1.5 minutes to initially wet the dry powder, then stir at a high speed of 300 r / min for 2.5 minutes. Finally, add the above-mentioned delayed crosslinking modified polyacrylamide solution and continue high-speed stirring for 1 minute to form a uniform fluid slurry. The yield stress τ0 of this slurry at 25℃ is approximately 20 Pa, and the flowability is 145 mm. Step 4, Base layer pretreatment and pouring: Pre-apply an interface agent to the concrete base surface. The interface agent is an acrylic emulsion containing 2% nano-silica, with a solid content of 20%. Apply using a roller, with a coating amount of 0.27 kg / m². 2 Wait until the interface agent is surface dry but not sticky before pouring. Pour the above-mentioned fluid slurry onto the base surface, using a scraper to assist in spreading, controlling the thickness of each pour to 15mm. The slurry will self-level under its own weight and stand for 10 minutes, during which time the rubber particles gradually sink and the vitrified microspheres gradually float, forming a gradient distribution structure from bottom to top. Step 5, curing: After pouring, cover the surface of the slurry with a plastic film and place it in an environment of 20℃ and 95% relative humidity for 72 hours of curing. Then remove the film and allow it to cure naturally at room temperature for 28 days.

[0074] Example 2

[0075] The only difference between this embodiment and Embodiment 1 is that the amount of surface reactive modified recycled rubber particles is 8 parts, the amount of surface activated closed-cell vitrified microspheres is 10 parts, the mass ratio of the two is 0.8:1, and the corresponding adjustment in step four is to mix 8 parts of modified rubber particles with 10 parts of activated vitrified microspheres, and add 6.4 parts of building gypsum and 1.0 parts of nano calcium sulfoaluminate seed crystals for pre-dispersion treatment.

[0076] Example 3

[0077] The only difference between this embodiment and Embodiment 1 is that the amount of surface reactive modified recycled rubber particles is 18 parts, the amount of surface activated closed-cell vitrified microspheres is 15 parts, the mass ratio of the two is 1.2:1, and the corresponding adjustment in step four is to mix 18 parts of modified rubber particles with 15 parts of activated vitrified microspheres, and add 6.4 parts of building gypsum and 1.0 parts of nano calcium sulfoaluminate seed crystals for pre-dispersion treatment.

[0078] Example 4

[0079] The only difference between this embodiment and Embodiment 1 is that the amount of surface-activated closed-cell vitrified microspheres is 5 parts, the amount of surface-reactive modified recycled rubber particles is 6 parts, the mass ratio of the two is 1.2:1, and the corresponding adjustment in step four is to mix 6 parts of modified rubber particles with 5 parts of activated vitrified microspheres, and add 6.4 parts of building gypsum and 1.0 parts of nano calcium sulfoaluminate seed crystals for pre-dispersion treatment.

[0080] Example 5

[0081] The only difference between this embodiment and Embodiment 1 is that the amount of surface-activated closed-cell vitrified microspheres is 20 parts, the amount of surface-reactive modified recycled rubber particles is 16 parts, the mass ratio of the two is 0.8:1, and the corresponding adjustment in step four is to mix 16 parts of modified rubber particles with 20 parts of activated vitrified microspheres, and add 6.4 parts of building gypsum and 1.0 parts of nano calcium sulfoaluminate seed crystals for pre-dispersion treatment.

[0082] Example 6

[0083] The only difference between this embodiment and Embodiment 1 is that the amount of delayed crosslinking modified polyacrylamide is 0.08 parts, the amount of sulfoaluminate cement is 10 parts, the mass ratio of the two is 125:1, the corresponding adjustment in step three is to pre-hydrolyze and delay crosslinking modify 0.08 parts of modified polyacrylamide, and the corresponding addition of 0.08 parts of modified polyacrylamide solution in step six.

[0084] Example 7

[0085] The only difference between this embodiment and Example 1 is that the amount of delayed crosslinking modified polyacrylamide is 0.25 parts, the amount of sulfoaluminate cement is 15 parts, the mass ratio of the two is 60:1, step three is adjusted to pre-hydrolyze and delay crosslinking modification of 0.25 parts of modified polyacrylamide, step five is adjusted to dry mix 15 parts of sulfoaluminate cement, the remaining 93.6 parts of building gypsum and other components evenly, and step six is ​​adjusted to add 0.25 parts of modified polyacrylamide solution.

[0086] Example 8

[0087] The only difference between this embodiment and Embodiment 1 is that the amount of nano-calcium sulfoaluminate seed crystals used is 0.5 parts, and the corresponding adjustment in step four is to add 0.5 parts of nano-calcium sulfoaluminate seed crystals.

[0088] Example 9

[0089] The only difference between this embodiment and Embodiment 1 is that the amount of nano-calcium sulfoaluminate seed crystals used is 2.0 parts, and step four is adjusted accordingly to add 2.0 parts of nano-calcium sulfoaluminate seed crystals.

[0090] Comparative Example 1

[0091] The only difference between this comparative example and Example 1 is that no surface-reactive modified recycled rubber particles are added, nor are any other alternative aggregates added. In step one, the surface-reactive modification of the recycled rubber particles is no longer performed, and in step four, no modified rubber particles are added. Instead, 12 parts of surface-activated closed-cell vitrified microspheres are mixed with 6.4 parts of building gypsum and 1.0 parts of nano-calcium sulfoaluminate seed crystals for pre-dispersion treatment.

[0092] Comparative Example 2

[0093] The only difference between this comparative example and Example 1 is that no surface-activated closed-cell vitrified microspheres or other alternative lightweight aggregates are added. The surface activation treatment of the closed-cell vitrified microspheres is no longer performed in step two, and no activated vitrified microspheres are added in step four. Instead, 13 parts of surface-reactive modified recycled rubber particles are mixed with 6.4 parts of building gypsum and 1.0 parts of nano-calcium sulfoaluminate seed crystals for pre-dispersion treatment.

[0094] Comparative Example 3

[0095] The only difference between this comparative example and Example 1 is that the delayed crosslinking modified polyacrylamide and the redox delayed initiation system are not added, the delayed crosslinking modified polyacrylamide solution is no longer prepared in step three, and the modified polyacrylamide solution is no longer added in step six. Instead, an equal amount of ordinary unmodified polyacrylamide solution is directly added in step six.

[0096] Comparative Example 4

[0097] The only difference between this comparative example and Example 1 is that no nano-calcium sulfoaluminate seed crystals are added. In step four, no nano-calcium sulfoaluminate seed crystals are added. Instead, 13 parts of modified rubber particles, 12 parts of activated vitrified microspheres, and 6.4 parts of building gypsum are mixed and pre-dispersed.

[0098] Test method:

[0099] The wet density test uses the volumetric cylinder method. The freshly mixed slurry is loaded into a 5L standard volumetric cylinder, tamped and leveled in layers, and then weighed. The mass per unit volume is calculated, and the result is expressed in kilograms per cubic meter.

[0100] The 28-day compressive strength test was conducted using the method specified in JC / T 1023 "Gypsum-based Self-leveling Mortar". The specimen size was 40mm×40mm×160mm. The standard curing conditions were a temperature of 20±1℃ and a relative humidity of over 90%. After curing for 28 days, a universal testing machine was used to apply a load at a rate of 2.0±0.5kN / s. The failure load was recorded and the compressive strength was calculated.

[0101] The tensile bond strength test was conducted using the method specified in JC / T 985. Mortar was applied to a 70mm×70mm×20mm C30 concrete specimen, and an interface agent was applied as described in the example. The thickness of the specimen was 10mm. After standard curing for 28 days, a tensile testing machine was used to perform tensile testing at a rate of 5mm / min. The maximum tensile force at failure was recorded, and the bond strength was calculated.

[0102] The airborne sound insulation test adopts the small specimen impedance tube method GB / T 18696.2 (transfer function method). The mortar is poured into a test mold with a diameter of 100 mm and a thickness of 10 mm. After curing for 28 days, it is placed in the impedance tube test section. The vertical incident sound transmission loss in the frequency range of 100 to 5000 Hz is measured. The arithmetic mean of three frequencies of 500 Hz, 1000 Hz and 2000 Hz is used as the characterization value of airborne sound insulation. When reporting, it should be noted as the vertical incident sound insulation value of the impedance tube method.

[0103] The impact sound improvement test adopts the floating surface layer method, in which a 15mm thick mortar layer is poured on a 120mm thick standard concrete floor slab. The floor slab is impacted with a standard impactor according to the method specified in GB / T 19889.6, and the difference in standardized impact sound pressure level before and after the mortar layer is laid is measured as the impact sound pressure level improvement.

[0104] The drying shrinkage rate test was conducted using the method specified in JC / T 603. The slurry was poured into a 25mm×25mm×280mm mold with stainless steel probes embedded at both ends. After standard curing for 3 days, the mold was moved into a constant temperature and humidity chamber at 20±2℃ and 50±5% relative humidity. The length change was measured periodically using a length comparator, and the 28-day drying shrinkage rate was calculated. The results were expressed in millimeters per meter.

[0105] The relevant test data for the above embodiments and comparative examples are shown in Table 1.

[0106] Table 1. Relevant data and test data of Examples 1-9 and Comparative Examples 1-4

[0107] Example 1 13 12 1.08 66.7 1 1280 16.5 1.35 29 19 0.65 Example 2 8 10 0.8 66.7 1 1250 17.2 1.4 26 16 0.6 Example 3 18 15 1.2 66.7 1 1320 15.8 1.28 30 20 0.7 Example 4 6 5 1.2 66.7 1 1450 16.8 1.3 24 15 0.72 Example 5 16 20 0.8 66.7 1 1180 13.5 1.15 25 15 0.58 Example 6 13 12 1.08 125 1 1280 17 1.1 26 17 0.85 Example 7 13 12 1.08 60 1 1290 15.5 1.45 30 20 0.55 Example 8 13 12 1.08 66.7 0.5 1280 15.2 1.25 28.5 18.5 0.68 Example 9 13 12 1.08 66.7 2 1280 17 1.42 29.5 19.5 0.62 Comparative Example 1 0 12 — 66.7 1 1150 18.5 1.5 22 5 0.5 Comparative Example 2 13 0 — 66.7 1 1650 14 1.2 24 12 1.1 Comparative Example 3 13 12 1.08 66.7 1 1280 14.5 0.75 27 16 1.25 Comparative Example 4 13 12 1.08 66.7 0 1280 13.8 1.05 28 17.5 0.78

[0108] like Figure 2As shown in the test data, the synergistic effect of modified recycled rubber particles and activated vitrified microspheres within a specific ratio range is crucial for achieving lightweight sound insulation. In Examples 1 to 3, the mass ratio of the two components was between 0.8 and 1.2, and the wet density of the mortar was controlled between 1250 and 1320 kg / m³. 3 Within this range, the airborne sound insulation is no less than 26 dB, and the impact sound improvement is no less than 16 dB, indicating that this ratio range allows the damping sound absorption of rubber particles and the closed-cell reflection of vitrified microspheres to form an effective gradient impedance match. Comparative Example 1, which completely lacks modified rubber particles, has a lower density and higher strength, but its impact sound improvement is only 5 dB, almost completely losing its ability to isolate mid-to-low frequency impact sounds; Comparative Example 2, which completely lacks vitrified microspheres, has a wet density as high as 1650 kg / m³. 3 This exceeds the requirements for lightweight materials, and the improvement in impact sound is only 12dB, proving that a single aggregate cannot achieve both lightweight and sound insulation.

[0109] like Figure 2 As shown in the test data, the mass ratio of sulfoaluminate cement to delayed crosslinking modified polyacrylamide has a significant impact on interfacial bonding and shrinkage control. In Examples 1, 6, and 7, this ratio was 66.7, 125, and 60, respectively. When the ratio was 66.7, the tensile bond strength was 1.35 MPa and the drying shrinkage was 0.65 mm·m. -1 The overall performance is optimal. At a ratio of 125, although the compressive strength is high, the tensile bond strength drops to 1.10 MPa, indicating that a relative deficiency in the polymer leads to decreased interfacial bonding and toughness. At a ratio of 60, the tensile bond strength reaches a maximum of 1.45 MPa, and the shrinkage rate is the lowest at 0.55 mm·m. -1 However, the compressive strength decreased slightly to 15.5 MPa, proving that there is a reasonable optimization range for this ratio.

[0110] like Figure 2 As shown in the test data, the time-controlled crosslinking characteristics of delayed crosslinking modified polyacrylamide are key to constructing organic-inorganic interpenetrating networks. Comparative Example 3 replaced the delayed crosslinking modified polyacrylamide with an equal amount of ordinary unmodified polyacrylamide; the remaining components were identical to those in Example 1. However, the tensile bond strength decreased sharply from 1.35 MPa to 0.75 MPa, and the drying shrinkage rate decreased from 0.65 mm·m. -1 Increased dramatically to 1.25 mm·m -1 Meanwhile, the improvement in impact sound decreased from 19 dB to 16 dB. This indicates that ordinary polyacrylamide forms a high-viscosity coating layer in the early stage of water addition, which hinders the hydration reaction and prevents it from interpenetrating with the inorganic network, resulting in weak interfacial adhesion and uncontrolled shrinkage. In contrast, delayed crosslinking modified polyacrylamide achieves synergistic enhancement of the organic and inorganic dual networks through time-series control.

[0111] like Figure 2As shown in the test data, nano-sized calcium sulfoaluminate seeds play an irreplaceable role in densifying the interfacial transition zone. In Examples 8 and 9, the seed amounts were 0.5 parts and 2.0 parts, respectively. With increasing amounts, the compressive strength increased from 15.2 MPa to 17.0 MPa, and the tensile bond strength increased from 1.25 MPa to 1.42 MPa. In Comparative Example 4, which completely lacked seeds, the compressive strength decreased to 13.8 MPa and the tensile bond strength decreased to 1.05 MPa after 28 days, while the other components were the same as in Example 1. These values ​​were significantly lower than the 16.5 MPa and 1.35 MPa of Example 1, demonstrating that the seeds act as heterogeneous nucleation sites, inducing the directional growth of ettringite and significantly densifying the interfacial transition zone between the rubber particles and the inorganic matrix.

[0112] In summary, Example 1 achieved optimal overall balance with a ratio of 13 parts modified rubber particles, 12 parts activated vitrified microspheres, a cement to PAM mass ratio of 66.7, and 1.0 part seed crystals, verifying the synergistic effect of each innovative component within a specific ratio range.

[0113] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0114] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0115] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0116] Furthermore, it should be noted that the scope of the methods and apparatus in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

Claims

1. A lightweight sound-insulating gypsum-based self-leveling mortar, characterized in that, The components include the following parts by weight: 100 parts gypsum; 5-15 parts sulfoaluminate cement; 8-18 parts modified recycled rubber granules; 5-20 parts vitrified microspheres; 0.08-0.3 parts modified polyacrylamide; The modified recycled rubber particles are coated with a polymethyl methacrylate reaction layer, and the calcium ions in the polymethyl methacrylate reaction layer participate in the hydration reaction of gypsum / sulfoaluminate cement. The vitrified microspheres are closed-cell vitrified microspheres that have undergone alkaline etching-silane composite activation treatment. The crosslinking reaction of the modified polyacrylamide is delayed by 10-30 min compared to the acceleration period of sulfoaluminate cement hydration. The mass ratio of the modified recycled rubber particles to the surface-activated closed-cell vitrified microspheres is 0.8:1-1.2:1, and the density difference between the two is ≥0.8 g / cm³. 3 ; The mass ratio of the sulfoaluminate cement to the modified polyacrylamide is 60-150:

1.

2. The lightweight sound-insulating gypsum-based self-leveling mortar according to claim 1, characterized in that, The thickness of the polymethyl methacrylate reaction layer on the surface of the modified recycled rubber particles is 50-200 nm. And / or, the alkaline etching depth of the vitrified microspheres is 0.5-2.0 μm, and the surface roughness Ra is 2-5 μm.

3. The lightweight sound-insulating gypsum-based self-leveling mortar according to claim 1, characterized in that, It also includes 0.1-1.0 parts of polypropylene fiber, and at least one of the following: 0.1-0.3 parts of polyether-type polymer shrinkage reducer, 0.1-0.3 parts of cellulose ether, 0.1-0.5 parts of water-reducing agent, 0.05-0.2 parts of defoamer, and 0.05-0.2 parts of retarder.

4. The lightweight sound-insulating gypsum-based self-leveling mortar according to claim 1, characterized in that, The crosslinking reaction of the modified polyacrylamide is delayed by 15-25 minutes compared to the hydration acceleration period of the sulfoaluminate cement, and its degree of crosslinking is 60-80%.

5. The lightweight sound-insulating gypsum-based self-leveling mortar according to claim 1, characterized in that, It also includes 0.5-2.0 parts of nano-calcium sulfoaluminate seed crystals, wherein the particle size of the nano-calcium sulfoaluminate seed crystals is 10-50 nm and the specific surface area is ≥80 m². 2 / g; And / or, it also includes 0.02-0.1 parts of a redox delayed initiation system; the redox delayed initiation system includes a water-soluble persulfate initiator, a sulfite reducing agent and a thiourea retarder; the mass ratio of the water-soluble persulfate initiator, the sulfite reducing agent and the thiourea retarder is 1:0.8-1.2:0.3-0.

8.

6. A method for preparing lightweight sound-insulating gypsum-based self-leveling mortar according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Surface reactive modification of recycled rubber granules is carried out to coat the surface with a polymethyl methacrylate reactive layer, thereby obtaining modified rubber granules; Step 2: Surface-activate the closed-cell vitrified microspheres to obtain surface-activated closed-cell vitrified microspheres; Step 3: The modified polyacrylamide is pre-hydrolyzed and subjected to delayed crosslinking modification to obtain a modified polyacrylamide solution; Step 4: Mix the modified rubber particles with activated vitrified microspheres, add some gypsum for pre-dispersion treatment, and obtain a pre-dispersion lightweight aggregate mixture; Step 5: Dry mix the sulfoaluminate cement, remaining gypsum, polypropylene fiber and admixtures evenly to obtain the inorganic cementitious base material; Step 6: Add the pre-dispersed lightweight aggregate mixture to the inorganic cementitious base, continue dry mixing, add water and stir, then add the modified polyacrylamide solution and continue stirring to form a fluid slurry; Step 7: Pour the fluidized slurry onto the base surface, let it stand to form a gradient distribution structure in which rubber particles sink and vitrified microspheres float, and then cure it.

7. The preparation method according to claim 6, characterized in that, In step one, the reclaimed rubber particles are added to an ethanol-water solution containing γ-methacryloyloxypropyltrimethoxysilane, ultrasonically dispersed at 50-60°C for 40-60 min, filtered and dried, and then added to a calcium methacrylate monomer solution. In the presence of potassium persulfate initiator, the particles are polymerized in situ at 60-70°C for 2-3 hours, washed and dried to obtain modified rubber particles with a surface coated with a calcium methacrylate reaction layer. And / or, in step two, the closed-cell vitrified microspheres are immersed in a 0.5-1.5 mol / L sodium hydroxide solution, treated with alkaline etching at 40-50°C for 15-25 min, washed and dried, and then sprayed with an atomized ethanol solution containing γ-aminopropyltriethoxysilane, and mixed at high speed at 80-90°C for 10-15 min to obtain surface-activated closed-cell vitrified microspheres; And / or, in step three, the modified polyacrylamide is added to warm water at 50-60℃ for hydrolysis treatment for 30 minutes, cooled to room temperature, and then an ammonium persulfate / sodium bisulfite redox initiation system and a thiourea delay agent are added and stirred evenly to obtain a modified polyacrylamide solution.

8. The preparation method according to claim 6, characterized in that, In step four, 0.5-1.0% of nano-calcium sulfoaluminate seed crystals are added, and the pre-dispersion treatment is a low-speed premixing at 80-120 rpm for 5-8 minutes.

9. The preparation method according to claim 6, characterized in that, In step six, the water temperature is 18-22℃. First, stir at low speed for 1-2 minutes, then add the modified polyacrylamide solution and stir at high speed for 2-3 minutes. The amount of water added is 28-32% of the total mass of the dry powder mixture.

10. The preparation method according to any one of claims 6-9, characterized in that, In step seven, the settling time after pouring is 8-12 minutes, and the yield stress τ0 of the fluidized slurry is 18-25 Pa. An interface agent is pre-coated onto the base surface; this interface agent is an acrylic emulsion containing 1-3% nano-silica, with a solid content of 18-22%, and a coating amount of 0.25-0.3 kg / m². 2 The curing process involves covering the product with a film for 72 hours at 20±2℃ and relative humidity ≥90%, followed by natural curing for 28 days. In step seven, the gradient distribution structure, from bottom to top, consists of: a rubber particle enrichment layer, a transition layer, and a vitrified microsphere enrichment layer. The thickness of the rubber particle enrichment layer is 3-5 mm, and the thickness of the vitrified microsphere enrichment layer is 2-4 mm.

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