Prefabricated building wallboard and manufacturing method thereof

Abstract

This invention relates to a prefabricated building wall panel and its manufacturing method, belonging to the technical field of prefabricated building new wall material manufacturing. The panel body is manufactured through mixing, pouring, and curing. The raw materials, by weight, include: 360-400 parts cement, 70-90 parts fly ash, 110-130 parts modified lightweight aggregate, 530-570 parts manufactured sand, 1.0-1.5 parts polypropylene fiber, 3.5-4.5 parts polycarboxylate superplasticizer, and 150-170 parts water. The aggregate surface is coated with an interface layer formed by crosslinking of amphiphilic hyperbranched polysiloxanes containing C12-C18 long-chain alkyl groups, alkoxysilanes, and flexible amino segments containing hydroxyl groups. Through the reaction of alkoxysilanes with cement hydration products, a Si-O-Si-Ca covalent bond network is constructed internally for connection. This invention effectively solves the technical problem of low strength and easy cracking in the interface transition zone, significantly improving the compressive strength and structural integrity of the wall panel.

Description

Technical Field

[0001] This invention relates to the field of manufacturing new wall materials for prefabricated buildings, specifically a prefabricated building wall panel and its manufacturing method. Background Technology

[0002] Prefabricated building wall panels are core components for realizing building industrialization and improving construction efficiency. Their physical and mechanical properties and durability directly determine the service life and safety of buildings. Wall panels are usually made by mixing and curing cementitious materials, lightweight aggregates, and reinforcing materials. The introduction of lightweight aggregates aims to reduce the self-weight of the wall panels and improve thermal insulation. However, commonly used porous lightweight aggregates have high water absorption characteristics, which easily attract mixing water, leading to poor rheological properties and shrinkage cracking after hardening. Although existing technologies mostly use hydrophobic materials to coat the surface of the aggregates, traditional inert hydrophobic films are still effective in blocking moisture. While penetrating, it also blocks the chemical bonding between aggregates and cement hydration products, forming a physical barrier layer. This hinders the direct chemical bonding between cement hydration products and the aggregate surface, resulting in a significant decrease in the bond strength of the interfacial transition zone and creating a weak mechanical link. Furthermore, simple surface physical coating lacks a buffering and dissipation mechanism for interfacial micro-stress, and conventional impregnation processes cannot achieve three-dimensional protection of the deep pores of aggregates. Once the surface is worn, the waterproof function is lost, and it is impossible to maintain high-strength interfacial bonding while ensuring low water absorption. Therefore, a solution is urgently needed to address the problems existing in the current technology.

[0003] The information disclosed in the background section above is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a prefabricated building wall panel and its manufacturing method to solve the problems mentioned in the background art.

[0005] The technical solution of the present invention includes: a wall panel body, wherein the wall panel body is made by mixing, pouring and curing cementitious materials, reinforcing fibers, modified lightweight aggregates, manufactured sand, water reducing agent and water;

[0006] The wall panel body is prepared from the following components in parts by weight: 360-400 parts cement, 70-90 parts fly ash, 110-130 parts modified lightweight aggregate, 530-570 parts manufactured sand, 1.0-1.5 parts polypropylene fiber, 3.5-4.5 parts polycarboxylate superplasticizer and 150-170 parts water;

[0007] The modified lightweight aggregate includes a porous mineral core and an interface modification layer covering the surface of the porous mineral core.

[0008] The interface modification layer is formed by in-situ crosslinking and curing of amphiphilic hyperbranched polysiloxane. The molecular structure of the amphiphilic hyperbranched polysiloxane simultaneously contains C12-C18 long-chain alkyl groups, unhydrolyzed alkoxysilyl groups, and flexible segments derived from the ring-opening addition reaction of long-chain aliphatic amines. The interior of the wall panel body is connected by a Si-O-Si-Ca covalent bond network formed by the reaction of the alkoxysilyl groups with cement hydration products.

[0009] Preferably, the preparation method of the amphiphilic hyperbranched polysiloxane includes the following steps:

[0010] Step 1: Tetraethoxysilane and an epoxy-containing silane coupling agent are dissolved in anhydrous ethanol solvent. Under the presence of an acidic catalyst, the mixture is subjected to a reflux condensation reaction at 60-65°C to carry out controlled hydrolysis and condensation, thereby obtaining a hyperbranched polysiloxane intermediate containing surface epoxy groups.

[0011] Step 2: Raise the temperature of the reaction system to 70-80°C, and slowly add an ethanol solution of a long-chain fatty amine to the hyperbranched polysiloxane intermediate to carry out a ring-opening addition reaction under heat preservation until the characteristic peak of the epoxy group disappears as shown by infrared spectroscopy.

[0012] Step 3: After the reaction is complete, the reaction solution is subjected to vacuum distillation to remove part of the solvent, and the amphiphilic hyperbranched polysiloxane stock solution is obtained.

[0013] Preferably, in step one, the molar ratio of the tetraethoxysilane to the epoxy-containing silane coupling agent is 1:2; the epoxy-containing silane coupling agent is γ-glycidoxypropyltrimethoxysilane; and the acidic catalyst is an aqueous hydrochloric acid solution with pH=3, and its addition amount is 0.5% to 1.5% of the total mass of the tetraethoxysilane and the epoxy-containing silane coupling agent.

[0014] In step two, the long-chain fatty amine is dodecylamine, and the molar ratio of the long-chain fatty amine to the tetraethoxysilane is 1:1; the time for the heat-preserving ring-opening addition reaction is 5 to 7 hours.

[0015] Preferably, the method for preparing the modified lightweight aggregate includes the following steps:

[0016] Step A: Dilute the amphiphilic hyperbranched polysiloxane stock solution with water to prepare a modified solution with a concentration of 1.5% to 2.5%;

[0017] Step B: Place expanded perlite with a particle size of 3-5mm in a vacuum impregnation tank, evacuate to a negative pressure state and maintain it for 3-8 minutes to remove the air from the pores of the expanded perlite;

[0018] Step C: Under negative pressure, draw in the modified liquid until the expanded perlite is submerged, then restore normal pressure for permeation impregnation, and filter out excess liquid;

[0019] Step D: Place the impregnated expanded perlite in an oven and dry and solidify it at 110-130°C to obtain the modified lightweight aggregate.

[0020] Preferably, in step B, the vacuum level of the vacuuming is -0.08 MPa to -0.1 MPa; in step C, the permeation and impregnation time is 8 to 15 minutes.

[0021] A method for manufacturing prefabricated building wall panels includes the following steps:

[0022] S1. Dry material mixing: Cement, fly ash, modified lightweight aggregate, manufactured sand and polypropylene fiber are put into a forced mixer for dry mixing and dispersion to obtain uniform dry material;

[0023] S2, Wet mixing and molding: Add water and polycarboxylate superplasticizer to the uniform dry material, wet mix and stir, then pour into a mold for vibration molding, and let stand still;

[0024] S3. Reactive curing: The mold after settling is sent into a steam curing kiln for steam curing. The steam curing includes a gradient heating stage, a constant temperature and high humidity stage, and a cooling stage. In the constant temperature and high humidity stage, the alkoxysilane groups on the surface of the interface modified layer undergo a chemical condensation reaction with calcium hydroxide in the cement paste.

[0025] S4. Demolding: After curing, demold to obtain the prefabricated building wall panel.

[0026] Preferably, in step S3, the gradient heating stage involves raising the temperature from room temperature to 60-80°C within 1.5-2.5 hours; the constant temperature and high humidity stage involves maintaining the temperature at 60-80°C and relative humidity greater than 90% for 5-7 hours.

[0027] This invention provides an improved prefabricated building wall panel and its manufacturing method, which has the following improvements and advantages compared with the prior art:

[0028] 1. This invention coats the surface of modified lightweight aggregate with an interface modification layer formed by amphiphilic hyperbranched polysiloxane. The unhydrolyzed alkoxysilane groups in the molecular structure undergo a chemical condensation reaction with cement hydration products under humid and hot curing conditions, establishing a Si-O-Si-Ca covalent bond network between the aggregate and the cement matrix. This chemical bonding mechanism replaces the weak physical-mechanical interlocking between the aggregate and the matrix in traditional lightweight wall panels, effectively solving the technical problems of low strength and easy cracking in the interface transition zone, and significantly improving the compressive strength and structural integrity of the wall panel.

[0029] 2. This invention utilizes the long-chain alkyl groups in the amphiphilic hyperbranched polysiloxane molecular structure to impart excellent hydrophobic properties to the aggregate surface, effectively sealing the surface openings of porous mineral cores, significantly reducing the water absorption rate of lightweight aggregates, and avoiding the problem of loss of slurry fluidity or subsequent water return caused by excessive water absorption of aggregates during mixing; at the same time, the amphiphilic characteristics of the hyperbranched polymer improve the compatibility between lightweight aggregates and cement slurry, preventing lightweight aggregates from floating or delaminating during vibration molding, and ensuring the internal density and uniform material distribution of the wall panel;

[0030] 3. This invention introduces hydroxyl-containing flexible amino segments into the molecular structure of the interface modification layer. This flexible structure can act as a stress buffer between the rigid cement matrix and the porous aggregate, absorbing and dissipating the internal stress caused by temperature difference or drying shrinkage. Combined with the vacuum impregnation process, the modification liquid deeply fills the internal pores of the aggregate and cross-links and cures in situ, which not only strengthens the particle strength of the aggregate itself, but also works synergistically with the reinforcing fiber, effectively inhibiting the expansion of microcracks in prefabricated building wall panels and improving the crack resistance and durability of the wall panels. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] Example 1:

[0033] A prefabricated building wall panel includes: a wall panel body, which is made of cement-based cementitious materials, reinforcing fibers, modified lightweight aggregates, manufactured sand, water-reducing agents and water through mixing, pouring and curing;

[0034] The wall panel body is made of the following components in parts by weight: 360 parts cement, 70 parts fly ash, 110 parts modified lightweight aggregate, 530 parts manufactured sand, 1.0 part polypropylene fiber, 3.5 parts polycarboxylate superplasticizer and 150 parts water.

[0035] Modified lightweight aggregates include porous mineral cores and an interface modification layer coating the surface of the porous mineral cores;

[0036] The interface modification layer is formed by in-situ crosslinking and curing of amphiphilic hyperbranched polysiloxane. The molecular structure of the amphiphilic hyperbranched polysiloxane simultaneously contains C12 long-chain alkyl groups, unhydrolyzed alkoxysilyl groups, and flexible segments derived from the ring-opening addition reaction of long-chain aliphatic amines.

[0037] The interior of the wall panel is connected by a Si-O-Si-Ca covalent network formed by the reaction of alkoxysilane groups with cement hydration products;

[0038] This embodiment selects a cementitious system of 360 parts cement and 70 parts fly ash, aiming to improve the rheological properties of the mixture by utilizing the morphological effect of fly ash, and at the same time to provide strength gain in the later stage by utilizing its pozzolanic activity; the introduction of 110 parts modified lightweight aggregate significantly reduces the bulk density of the wall panel, and the interface modification layer on its surface is the core of the invention; among them, the C12 long-chain alkyl in the amphiphilic hyperbranched polysiloxane forms micro-hydrophobic protrusions on the aggregate surface similar to the lotus leaf effect, effectively blocking the capillary penetration of liquid water;

[0039] Unhydrolyzed alkoxysilyl groups act as chemical anchors, activated in the subsequent alkaline environment of cement hydration, and interact with the cement paste. Chemical bonding occurs, forming a Si-O-Si-Ca covalent bond network; the flexible amino segments containing hydroxyl groups act as molecular springs, dissipating the micro-stress caused by drying shrinkage and wet expansion at the interface and preventing the propagation of interfacial microcracks.

[0040] The preparation method of amphiphilic hyperbranched polysiloxane includes the following steps:

[0041] Step 1: Tetraethoxysilane and epoxy-containing silane coupling agent are dissolved in anhydrous ethanol solvent. Under the condition of acidic catalyst, the mixture is refluxed and condensed at 60°C to carry out controlled hydrolysis and condensation, thereby obtaining a hyperbranched polysiloxane intermediate containing surface epoxy groups.

[0042] Step 2: Raise the temperature of the reaction system to 70°C, slowly add an ethanol solution of a long-chain fatty amine to the hyperbranched polysiloxane intermediate, and carry out a ring-opening addition reaction under heat preservation until the characteristic peak of the epoxy group disappears as monitored by infrared spectroscopy.

[0043] Step 3: After the reaction is complete, the reaction solution is subjected to vacuum distillation to remove part of the solvent, and an amphiphilic hyperbranched polysiloxane stock solution is obtained.

[0044] In this preparation process, step one adopts a quasi-one-pot synthesis strategy; in order to achieve the controlled hydrolysis and condensation as described in the instructions, the specific technical means adopted in this embodiment is as follows: at a constant stirring rate of 500-600 rpm, an ethanol solution containing silane monomers is added dropwise to a bottom liquid containing an acidic catalyst at a rate of 3-5 mL / min, and the viscosity of the system is monitored in real time. When the viscosity increases to 12-15 mPa·s, the reaction is stopped, thereby constructing a hyperbranched core with a three-dimensional spherical topology.

[0045] In step two, the temperature is raised to 70°C to overcome the steric hindrance of the long-chain aliphatic amine and promote an efficient ring-opening addition reaction between its amino group and the epoxy group on the surface of the intermediate. This reaction not only introduces hydrophobic long chains but also generates secondary hydroxyl groups at the reduction site. These hydroxyl groups further enhance the wettability of the molecule with the inorganic substrate. The stock solution obtained in step three was measured to have a solid content of 40% ± 1% and a viscosity of 45-55 mPa·s, which provides a metering standard for the subsequent preparation of modified solutions with accurate concentrations.

[0046] Step 1: The molar ratio of tetraethoxysilane to the epoxy-containing silane coupling agent is 1:2; the epoxy-containing silane coupling agent is γ-glycidoxypropyltrimethoxysilane; the acidic catalyst is an aqueous hydrochloric acid solution with pH=3, and its addition amount is 0.5% to 1.5% of the total mass of tetraethoxysilane and the epoxy-containing silane coupling agent; Step 2: The long-chain aliphatic amine is dodecylamine, and the molar ratio of the long-chain aliphatic amine to tetraethoxysilane is 1:1; the time for the ring-opening addition reaction is 5 hours.

[0047] In this embodiment, the molar ratio of tetraethoxysilane to epoxy-containing silane coupling agent is set to 1:2, which is based on a preferred range. The determined experimental optimization value. If the proportion is lower than... Insufficient branching leads to a reduction in reaction sites; if it is higher than... Early gelation is likely to occur; this embodiment selects The aim is to precisely control the crosslinking density of the hyperbranched core, avoid the formation of over-crosslinked gel networks while ensuring sufficient branching; the acidic catalyst pH=3 is selected from the effective range of pH 2.5 to 3.5, providing a suitable proton concentration, which both catalyzes the hydrolysis reaction and inhibits the rapid condensation of silanols, ensuring the controllable growth of the intermediate molecular weight.

[0048] In step two, the molar ratio of long-chain aliphatic amine to tetraethoxysilane is 1:1. This parameter can be finely adjusted within the range of 0.9:1 to 1.1:1 to accommodate the reactivity of different amines and ensure the stoichiometric balance between amino and epoxy groups. Dodecylamine is selected as the hydrophobic modifier, as its C12 chain length provides sufficient hydrophobicity while maintaining good solubility of the molecule in ethanol solvent, thus avoiding phase separation. The optimal reaction time of 5 hours is determined based on infrared spectroscopy monitoring, at which point the conversion rate of epoxy groups reaches over 98%.

[0049] The preparation method of modified lightweight aggregate includes the following steps:

[0050] Step A: Dilute the prepared amphiphilic hyperbranched polysiloxane stock solution with water to prepare a modified solution with a concentration of 1.5%;

[0051] Step B: Place expanded perlite with a particle size of 3-5mm in a vacuum impregnation tank, evacuate to a negative pressure state and maintain it for 3 minutes to remove the air from the pores of the expanded perlite;

[0052] Step C: While maintaining negative pressure, draw in the modified liquid until the expanded perlite is submerged, then restore normal pressure for permeation impregnation and filter out excess liquid;

[0053] Step D: Place the impregnated expanded perlite in an oven and dry it at 110°C to obtain modified lightweight aggregate;

[0054] In step A, the consistency of intermediate product names is strictly adhered to, and the amphiphilic hyperbranched polysiloxane stock solution obtained in step three is explicitly used as the dilution target, rather than the pure polymer without solvent treatment. During the preparation process, the mass fraction of the active ingredient amphiphilic hyperbranched polysiloxane in the modified solution is adjusted to 1.5% by precisely adding solvent based on the measured solid content of the amphiphilic hyperbranched polysiloxane stock solution. Here, the technical name "amphiphilic hyperbranched polysiloxane stock solution" is fully retained, clearly defining the conversion logic from stock solution to active ingredient concentration.

[0055] This low-concentration design is to reduce the surface tension and viscosity of the modified liquid, making it easier to penetrate into the micropores; steps B and C constitute a vacuum-pressure cyclic impregnation method, in which maintaining a negative pressure state for 3 minutes is to completely remove the trapped air in the honeycomb pores of the expanded perlite and eliminate the air resistance effect; then the pressure difference generated by restoring normal pressure drives the modified liquid to instantly fill the depth of the pores, achieving three-dimensional modification from the inside out; the drying temperature of 110°C in step D is not only used to remove the solvent, but also triggers the self-crosslinking reaction between polysiloxane molecules, solidifying on the aggregate surface to form a water-resistant crosslinked network film;

[0056] In step B, the vacuum level is -0.08 MPa; in step C, the impregnation time is 8 minutes.

[0057] This vacuum level is an optimized value that balances equipment energy consumption and exhaust efficiency, and is sufficient to overcome capillary pressure; the 8-minute penetration time ensures that the modified liquid undergoes sufficient physical adsorption and preliminary chemical bonding with the hydroxyl groups on the surface of the mineral substrate, laying the foundation for subsequent thermosetting.

[0058] A method for manufacturing prefabricated building wall panels includes the following steps:

[0059] S1. Dry material mixing: Cement, fly ash, modified lightweight aggregate, manufactured sand and polypropylene fiber are put into a forced mixer for dry mixing and dispersion to obtain uniform dry material;

[0060] S2. Wet mixing molding: Add water and polycarboxylate superplasticizer to the uniform dry material, wet mix and stir, then pour into the mold for vibration molding, and let stand still;

[0061] S3. Reactive curing: The mold after standing is sent into the steam curing kiln for steam curing. Steam curing includes a gradient heating stage, a constant temperature and high humidity stage, and a cooling stage. In the constant temperature and high humidity stage, the alkoxysilane groups on the surface of the interface modified layer undergo a chemical condensation reaction with the calcium hydroxide in the cement paste.

[0062] S4. Demolding: After curing, demold to obtain prefabricated building wall panels;

[0063] The dry mixing and dispersion in step S1 is to prevent lightweight aggregates from floating and separating, and to ensure uniform fiber dispersion. The reactive curing in step S3 is the key process of this invention. Unlike traditional physical heating curing, this step uses a constant temperature and high humidity environment as a chemical reactor. In this stage, the high temperature accelerates the release of CaOH2 from cement hydration, and the high humidity environment maintains the water activity at the interface, which promotes the hydrolysis of the alkoxysilane groups reserved in the modified layer to generate silanol, which then undergoes a condensation reaction with CaOH2 and CSH gel. This in-situ chemical bonding mechanism completely solves the problem of weak interface caused by traditional physical encapsulation.

[0064] In step S3, the gradient heating stage involves raising the temperature from room temperature to 60°C within 1.5 hours; the constant temperature and high humidity stage involves maintaining the temperature at 60°C and relative humidity greater than 90% for 5 hours.

[0065] The gradient heating strategy is to avoid thermal stress cracks inside the wall panel caused by drastic temperature changes; the constant temperature condition of 60℃ is the economical temperature point that balances the reaction rate and energy consumption. At this temperature, the reactivity of alkoxysilanes is significantly activated, while the cement hydration rate is moderate, avoiding thermal damage effects.

[0066] Example 2:

[0067] This embodiment provides a prefabricated building wall panel, the wall panel body being prepared from the following components by weight: 380 parts cement, 80 parts fly ash, 120 parts modified lightweight aggregate, 550 parts manufactured sand, 1.2 parts polypropylene fiber, 4.0 parts polycarboxylate superplasticizer and 160 parts water.

[0068] This embodiment appropriately increases the amount of cement and fly ash to prepare wall panels with higher strength; at the same time, it increases the proportion of water-reducing agent to accommodate the increase in cementitious materials and maintain a low water-cement ratio.

[0069] In the preparation method of amphiphilic hyperbranched polysiloxane: the reaction temperature in step one is 62℃; the reaction system temperature in step two is 75℃, and the time for the ring-opening addition reaction is 6 hours; the long-chain fatty amine is dodecylamine; the other raw materials and molar ratios are the same as in Example 1.

[0070] Fine-tuning of the reaction temperature and extension of the reaction time aim to improve the reaction conversion rate, so that the product has a higher degree of branching and a more perfect end-capping rate;

[0071] In the preparation method of modified lightweight aggregate: the concentration of the modifying liquid in step A is 2.0%; the vacuum degree in step B is -0.09MPa and the holding time is 5 minutes; the penetration and impregnation time in step C is 12 minutes; and the drying and curing temperature in step D is 120℃.

[0072] In step A, the intermediate product morphology is strictly distinguished, and the amphiphilic hyperbranched polysiloxane stock solution is directly used for dilution. Based on the solid content calibration of the stock solution, the concentration of the effective component amphiphilic hyperbranched polysiloxane is precisely adjusted to 2.0%, and with a higher vacuum degree, the amount of active material adhering to the surface of aggregate per unit area is significantly increased, making the hydrophobic layer more dense. The drying temperature of 120℃ promotes the depth of cross-linking reaction.

[0073] In the manufacturing method of prefabricated building wall panels: the gradient heating stage in step S3 is to raise the temperature from room temperature to 70℃ in 2.0 hours; the constant temperature and high humidity stage is to maintain the temperature at 70℃ and relative humidity greater than 90% for 6 hours.

[0074] The curing temperature of 70℃ further accelerated the formation rate of interfacial chemical bonds, and the 6-hour constant temperature maintenance period ensured the full progress of the hydration reaction. Through comprehensive optimization of parameters, this embodiment improved the mechanical properties of the wall panel while ensuring excellent waterproof performance, demonstrating the reliability of the technical solution in pursuing high strength indicators.

[0075] Example 3:

[0076] This embodiment provides a prefabricated building wall panel, the wall panel body being prepared from the following components by weight: 400 parts cement, 90 parts fly ash, 130 parts modified lightweight aggregate, 570 parts manufactured sand, 1.5 parts polypropylene fiber, 4.5 parts polycarboxylate superplasticizer and 170 parts water.

[0077] This embodiment uses a high proportion of cementitious materials and the highest proportion of modified aggregate to test the interfacial bonding ability under high filling amount.

[0078] In the preparation method of amphiphilic hyperbranched polysiloxane: the reaction temperature in step one is 65℃; the reaction system temperature in step two is 80℃, and the holding time for the ring-opening addition reaction is 7 hours; the long-chain aliphatic amine is octadecylamine C18;

[0079] The use of octadecylamine introduces a longer hydrophobic carbon chain. Compared with C12, the C18 segment can provide a stronger hydrophobic shielding effect and greater steric hindrance. The higher reaction temperature and longer reaction time are to overcome the steric hindrance effect brought about by the long C18 chain and ensure the smooth progress of the grafting reaction.

[0080] In the preparation method of modified lightweight aggregate: the concentration of the modifying liquid in step A is 2.5%; the vacuum degree in step B is -0.1MPa and the holding time is 8 minutes; the penetration and impregnation time in step C is 15 minutes; and the drying and curing temperature in step D is 130℃.

[0081] In step A, the amphiphilic hyperbranched polysiloxane stock solution is continued to be used as the operating standard to prevent confusion of the feeding object due to similar names; based on the solid content calibration of the stock solution, the ultimate vacuum degree and high effective concentration of the modified liquid are used, combined with immersion for up to 15 minutes, to achieve full-depth saturation modification of aggregate pores; high-temperature curing at 130℃ ensures complete cross-linking of the thick coating.

[0082] In the manufacturing method of prefabricated building wall panels: the gradient heating stage in step S3 is to raise the temperature from room temperature to 80℃ within 2.5 hours; the constant temperature and high humidity stage is to maintain the temperature at 80℃ and relative humidity greater than 90% for 7 hours.

[0083] The high-temperature curing conditions of 80°C stimulated the thermal motion of the C18 segments, causing them to rearrange their orientation at the interface and form a more ordered hydrophobic array. This embodiment demonstrates that by adjusting the alkyl chain length and process parameters, extreme waterproof performance can be obtained, which is suitable for basements or coastal building wall panels with extremely high moisture-proof requirements.

[0084] Example 4:

[0085] This embodiment provides a prefabricated building wall panel, the wall panel body being prepared from the following components by weight: 370 parts cement, 75 parts fly ash, 115 parts modified lightweight aggregate, 540 parts manufactured sand, 1.1 parts polypropylene fiber, 3.8 parts polycarboxylate superplasticizer and 155 parts water.

[0086] This embodiment adopts a medium-to-low formulation design, focusing on the balance between economy and performance;

[0087] In the preparation method of amphiphilic hyperbranched polysiloxane: the reaction temperature in step one is 61℃; the reaction system temperature in step two is 72℃, and the holding time for the ring-opening addition reaction is 5.5 hours; the long-chain aliphatic amine is tetradecylamine C14;

[0088] Tetradecylamine was chosen as the equilibrium point because it is more hydrophobic than C12 and more reactive than C18; the mild adjustment of reaction conditions was aimed at reducing energy consumption.

[0089] In the preparation method of modified lightweight aggregate: the concentration of the modifying liquid in step A is 1.8%; the vacuum degree in step B is -0.085MPa and the holding time is 4 minutes; the penetration and impregnation time in step C is 10 minutes; and the drying and curing temperature in step D is 115℃.

[0090] Fine-tuning of process parameters reflects considerations for production efficiency; moderate vacuum level and time are sufficient to meet the needs of most conventional building environments.

[0091] In the manufacturing method of prefabricated building wall panels: the gradient heating stage in step S3 is to raise the temperature from room temperature to 65℃ within 1.8 hours; the constant temperature and high humidity stage is to maintain the temperature at 65℃ and relative humidity greater than 90% for 5.5 hours.

[0092] This embodiment demonstrates the flexibility of the process window, showing that even at slightly lower curing temperatures, good interfacial bonding can still be achieved by relying on the reactivity of the molecular structure, thus verifying the potential of the technical solution in energy conservation and emission reduction.

[0093] Example 5:

[0094] This embodiment provides a prefabricated building wall panel, the wall panel body being prepared from the following components by weight: 390 parts cement, 85 parts fly ash, 125 parts modified lightweight aggregate, 560 parts manufactured sand, 1.4 parts polypropylene fiber, 4.2 parts polycarboxylate superplasticizer and 165 parts water.

[0095] This embodiment further verifies the stability of the formulation under fluctuations in different components;

[0096] In the preparation method of amphiphilic hyperbranched polysiloxane: the reaction temperature in step one is 64℃; the reaction system temperature in step two is 78℃, and the holding time for the ring-opening addition reaction is 6.5 hours; the long-chain aliphatic amine is hexadecylamine C16;

[0097] The use of hexadecylamine further enriches the range of alkyl chain lengths, and the specific reaction temperature profile ensures the uniformity of the product.

[0098] In the preparation method of modified lightweight aggregate: the concentration of the modifying liquid in step A is 2.2%; the vacuum degree in step B is -0.095MPa and the holding time is 6 minutes; the penetration and impregnation time in step C is 14 minutes; and the drying and curing temperature in step D is 125℃.

[0099] The higher modification parameter setting ensures that each aggregate can still obtain sufficient coating even when the amount of aggregate is increased;

[0100] In the manufacturing method of prefabricated building wall panels: the gradient heating stage in step S3 is to raise the temperature from room temperature to 75℃ in 2.2 hours; the constant temperature and high humidity stage is to maintain the temperature at 75℃ and relative humidity greater than 90% for 6.5 hours.

[0101] The results of this embodiment show that by introducing the C16 segment and combining it with high-temperature curing, the wall panel exhibits excellent overall durability, verifying the robustness of the technical solution of this invention in adapting to the diversity of raw materials.

[0102] Comparative Example 1:

[0103] This comparative example provides a prefabricated building wall panel, which differs from Example 2 only in that the modified lightweight aggregate is replaced with an equal volume of unmodified expanded perlite, i.e., the preparation and coating steps of the interface modification layer are omitted; this comparative example is intended as a blank control to verify the basic impact of the high water absorption of expanded perlite itself on the performance of the wall panel, as well as the natural bonding state of cement paste and aggregate in the absence of interface modification.

[0104] Comparative Example 2:

[0105] This comparative example provides a prefabricated building wall panel, which differs from Example 2 only in that: in the preparation process of the modified lightweight aggregate, the modifying liquid used is a traditional methyl silicone oil emulsion. This emulsion does not contain an amphiphilic hyperbranched polysiloxane structure, nor does it have alkoxysilane groups or flexible amino segments containing hydroxyl groups. This comparative example aims to verify that although traditional inert hydrophobic films can reduce water absorption, they will cause an oil film effect due to the blockage of chemical bonds, thereby severely weakening the interfacial bonding strength.

[0106] Comparative Example 3:

[0107] This comparative example provides a prefabricated building wall panel, which differs from Example 2 only in that the amphiphilic hyperbranched polysiloxane is replaced with a long-chain alkyltrimethoxysilane, which lacks the multidimensional anchoring points provided by the hyperbranched spherical structure and the toughening effect provided by the hydroxyl-containing flexible amino segments. This comparative example aims to verify the specific contribution of the hyperbranched topology and flexible segments in relieving interfacial stress and providing multi-site bonding.

[0108] Comparative Example 4:

[0109] This comparative example provides a prefabricated building wall panel, which differs from Example 2 only in that the vacuuming process in step B is omitted in the preparation of the modified lightweight aggregate. Instead, the expanded perlite is directly immersed in the modification liquid and adsorbed solely by natural capillary action. This comparative example aims to verify the necessity of the vacuum impregnation process for achieving deep modification and preventing water absorption failure after surface wear.

[0110] Verification experiment:

[0111] The prefabricated building wall panels prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to corresponding performance tests. The test results are shown in Table 1.

[0112] Testing standards:

[0113] Volumetric water absorption rate: determined according to GB / T11969-2008 "Test Method for Performance of Autoclaved Aerated Concrete", with specimen size of 100mm×100mm×100mm, 3 specimens tested in each group, and the average value was taken;

[0114] 28-day compressive strength and flexural strength: Standard specimens were prepared according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". After curing under standard curing conditions for 28 days, the specimens were tested. Three specimens were tested in each group, and the average value was taken.

[0115] Softening coefficient: The ratio of the compressive strength in a saturated state to the compressive strength in a dry state, which characterizes the water resistance of a material;

[0116] Interface feature evaluation: Scanning electron microscopy (SEM, model: Hitachi S-4800) was used in... Microscopic morphology of the aggregate-cement paste interface observed at magnification; interface density refers to the absence of particles larger than [a certain value] in the interface transition zone. Visible microcracks; chemically bonded regions were scanned using energy-dispersive X-ray spectroscopy. , The distribution density of overlapping areas of elements is used to determine this.

[0117] Specific testing process:

[0118] All specimens were cured in a standard curing room (temperature 20±2℃, relative humidity ≥95%) for 28 days after demolding. In the volume water absorption test, the specimens were dried to constant weight, cooled and then immersed in water with the water level 30mm above the specimen. After soaking for 24 hours, the specimens were removed, the surface moisture was wiped off and weighed. The strength test was performed using an electro-hydraulic servo universal testing machine, and the loading rate was strictly performed in accordance with the standard.

[0119] Data table

[0120] Table 1 Performance test data of Examples 1-5 and Comparative Examples 1-4

[0121] Group 28-day compressive strength (MPa) 28-day flexural strength (MPa) Volumetric water absorption rate (%) Softening coefficient Interface combined with feature description Example 1 19.5 4.3 2.3 0.90 The interface is dense, and a large amount of CSH gel is implanted into the surface of the aggregate. Example 2 20.8 4.6 2.1 0.92 The interface is crack-free, and chemically bonded regions are widely distributed. Example 3 21.5 4.8 1.9 0.94 Aggregate bulk failure, interfacial bonding force greater than aggregate strength Example 4 20.1 4.5 2.2 0.91 The interface is well integrated and has no obvious defects. Example 5 21.0 4.7 2.0 0.93 The interface is tightly integrated and the structure is uniform. Comparative Example 1 15.4 3.2 18.5 0.75 The interface shows obvious shrinkage cracks, and the aggregate softens due to water absorption. Comparative Example 2 14.8 3.0 2.8 0.72 The interface exhibits oil film separation and slurry peeling. Comparative Example 3 17.5 3.8 2.5 0.82 The interface has microcracks and lacks a flexible buffer layer. Comparative Example 4 18.2 4.0 5.6 0.85 Water absorption channels appear at the surface wear points, resulting in poor durability.

[0122] As shown by the test data and microstructure analysis in Table 1, the prefabricated building wall panels prepared in Examples 1-5 achieved an excellent balance between mechanical properties and waterproof performance; the specific analysis is as follows:

[0123] The effectiveness of the interfacial chemical bonding mechanism was confirmed. Compared with Comparative Example 2, although both used hydrophobic modifiers and had low water absorption rates of 2.1% and 2.8% respectively, their compressive strengths differed significantly. The conventional silicone oil used in Comparative Example 2 formed an inert isolation layer on the aggregate surface, blocking the adhesion of cement hydration products, which made the interface a mechanically weak area. In contrast, Example 2 achieved a hydrophobic but not slurry-repellent intelligent interface by generating Si-O-Si-Ca covalent bonds in situ during steam curing through the alkoxysilane groups in the amphiphilic hyperbranched polysiloxane, resulting in a softening coefficient as high as 0.92, far exceeding the 0.72 of Comparative Example 2.

[0124] The toughening effect of the hyperbranched structure and flexible segments is significant. Compared with Comparative Example 3, although Comparative Example 3, which uses linear silane, also has some chemical bonding, its flexural strength of 3.8 MPa is significantly lower than that of 4.6 MPa. This is attributed to the fact that the hyperbranched spherical structure designed in this invention provides a higher density of reaction sites, and the flexible amino segments in the molecule play a role in stress buffering and energy dissipation when subjected to interfacial forces, effectively inhibiting the propagation of microcracks.

[0125] Vacuum impregnation is crucial for improving durability. Comparing Example 2 and Comparative Example 4, Comparative Example 4, which omits the vacuum step, shows a water absorption rate of 5.6%. This is because atmospheric pressure impregnation only covers the outer surface of the aggregate. Once the aggregate surface is worn during construction or transportation, the internal porous structure is exposed and absorbs water. In contrast, the vacuum impregnation process of this invention introduces the modifier into the deep pores, constructing a three-dimensional protective network to ensure the performance stability of the wall panel during long-term use. In summary, this invention successfully solves the technical problem of the inverted relationship between water absorption rate and interfacial strength in lightweight aggregate concrete through the synergistic effect of molecular structure design and process optimization.

[0126] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A prefabricated building wall panel, characterized in that, The wall panel body is made of cement-based cementitious materials, reinforcing fibers, modified lightweight aggregates, manufactured sand, water-reducing agents and water through mixing, pouring and curing. The wall panel body is prepared from the following components in parts by weight: 360-400 parts cement, 70-90 parts fly ash, 110-130 parts modified lightweight aggregate, 530-570 parts manufactured sand, 1.0-1.5 parts polypropylene fiber, 3.5-4.5 parts polycarboxylate superplasticizer and 150-170 parts water; The modified lightweight aggregate includes a porous mineral core and an interface modification layer covering the surface of the porous mineral core. The interface modification layer is formed by in-situ crosslinking and curing of amphiphilic hyperbranched polysiloxane. The molecular structure of the amphiphilic hyperbranched polysiloxane simultaneously contains C12-C18 long-chain alkyl groups, unhydrolyzed alkoxysilyl groups, and flexible segments derived from the ring-opening addition reaction of long-chain aliphatic amines. The interior of the wall panel body is connected by a Si-O-Si-Ca covalent bond network formed by the reaction of the alkoxysilyl groups with cement hydration products.

2. The prefabricated building wall panel according to claim 1, characterized in that, The preparation method of the amphiphilic hyperbranched polysiloxane includes the following steps: Step 1: Tetraethoxysilane and an epoxy-containing silane coupling agent are dissolved in anhydrous ethanol solvent. Under the presence of an acidic catalyst, the mixture is subjected to a reflux condensation reaction at 60-65°C to carry out controlled hydrolysis and condensation, thereby obtaining a hyperbranched polysiloxane intermediate containing surface epoxy groups. Step 2: Raise the temperature of the reaction system to 70-80°C, and slowly add an ethanol solution of a long-chain fatty amine to the hyperbranched polysiloxane intermediate to carry out a ring-opening addition reaction under heat preservation until the characteristic peak of the epoxy group disappears as shown by infrared spectroscopy. Step 3: After the reaction is complete, the reaction solution is subjected to vacuum distillation to remove part of the solvent, and the amphiphilic hyperbranched polysiloxane stock solution is obtained.

3. A prefabricated building wall panel according to claim 2, characterized in that, Step 1: The molar ratio of the tetraethoxysilane to the epoxy-containing silane coupling agent is 1:2; the epoxy-containing silane coupling agent is γ-glycidoxypropyltrimethoxysilane; the acidic catalyst is an aqueous hydrochloric acid solution with pH=3, and its addition amount is 0.5% to 1.5% of the total mass of the tetraethoxysilane and the epoxy-containing silane coupling agent. In step two, the long-chain fatty amine is dodecylamine, and the molar ratio of the long-chain fatty amine to the tetraethoxysilane is 1:1; the time for the heat-preserving ring-opening addition reaction is 5 to 7 hours.

4. A prefabricated building wall panel according to claim 3, characterized in that, The method for preparing the modified lightweight aggregate includes the following steps: Step A: Dilute the amphiphilic hyperbranched polysiloxane stock solution with water to prepare a modified solution with a concentration of 1.5% to 2.5%; Step B: Place expanded perlite with a particle size of 3-5mm in a vacuum impregnation tank, evacuate to a negative pressure state and maintain it for 3-8 minutes to remove the air from the pores of the expanded perlite; Step C: Under negative pressure, draw in the modified liquid until the expanded perlite is submerged, then restore normal pressure for permeation impregnation, and filter out excess liquid; Step D: Place the impregnated expanded perlite in an oven and dry and solidify it at 110-130°C to obtain the modified lightweight aggregate.

5. A prefabricated building wall panel according to claim 4, characterized in that, In step B, the vacuum level of the vacuuming is -0.08MPa to -0.1MPa; in step C, the permeation and impregnation time is 8 to 15 minutes.

6. A method for manufacturing prefabricated building wall panels as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Dry material mixing: Cement, fly ash, modified lightweight aggregate, manufactured sand and polypropylene fiber are put into a forced mixer for dry mixing and dispersion to obtain uniform dry material; S2, Wet mixing and molding: Add water and polycarboxylate superplasticizer to the uniform dry material, wet mix and stir, then pour into a mold for vibration molding, and let stand still; S3. Reactive curing: The mold after settling is sent into a steam curing kiln for steam curing. The steam curing includes a gradient heating stage, a constant temperature and high humidity stage, and a cooling stage. In the constant temperature and high humidity stage, the alkoxysilane groups on the surface of the interface modified layer undergo a chemical condensation reaction with calcium hydroxide in the cement paste. S4. Demolding: After curing, demold to obtain the prefabricated building wall panel.

7. The method for manufacturing prefabricated building wall panels according to claim 6, characterized in that, In step S3, the gradient heating stage involves raising the temperature from room temperature to 60-80°C within 1.5-2.5 hours; the constant temperature and high humidity stage involves maintaining the temperature at 60-80°C and relative humidity greater than 90% for 5-7 hours.