Multifunctional autoclaved aerated concrete composite additive and application thereof

Abstract

The invention discloses a multifunctional autoclaved aerated concrete composite additive and application thereof, and belongs to the technical field of building materials. The additive is prepared from the following components in percentage by weight: 5%-15% of tannic acid modified cellulose nanocrystals (TA (at) CNCs), 0.5%-5% of a triethanolamine-citric acid compound, 0.2%-7.5% of tea saponin nano microcapsules (TS-NPs), 8%-22% of a silane / siloxane composite emulsion and a solvent: 2.5%-30% of deionized water and 7.5%-35% of glycerol. Through the synergistic effect of nanometer enhancement, environment-friendly excitation, slow-release foam stabilization and gradient hydrophobicity, the mechanical property, corrosion resistance and foam stabilization efficiency of a product can be remarkably improved, the water absorption rate can be remarkably reduced, the comprehensive performance of the autoclaved aerated concrete product is remarkably improved, and the environment-friendly foam stabilizer is suitable for the fields of prefabricated buildings and green building materials and has environment friendliness, economical efficiency and high performance.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a multifunctional autoclaved aerated concrete composite additive and application thereof. Background Art

[0002] Autoclaved aerated concrete (AAC), a green and environmentally friendly building material, has been widely used in the construction industry due to its lightweight, thermally insulating, soundproofing, and fire-resistant properties. However, in actual production, several issues remain unresolved. Traditional AAC relies on high-alkali activators (such as NaOH), which can lead to steel corrosion risks and environmental pollution (patent CN85105004A). Foam stabilizers are often chemically synthesized (such as sodium lauryl sulfate), which can easily cause pore coarsening and mold collapse (patent CN105110675B). Nano-enhancers (such as carbon nanotubes) are expensive and have poor compatibility with the matrix, limiting their industrial application. Traditional hydrophobic agents (such as paraffin wax) are prone to migration and failure, making water absorption difficult to stably control. Current technological advancements: Patent CN103466984A utilizes a saponin-based air-entraining agent, but this fails to address the issues of high water absorption and corrosiveness. Patent CN119100648A proposes a fly ash activator, but this relies on traditional triethanolamine and lacks environmental friendliness. Existing research on the synergistic effects of nano-enhancers and environmentally friendly activators is limited, making it difficult to achieve breakthroughs in overall performance. Summary of the Invention

[0003] The present invention aims to address the problems of poor mechanical properties, poor corrosion resistance, insufficient foam stabilization efficiency, and high water absorption encountered in the traditional autoclaved aerated concrete (AAC) production process. This invention provides a multifunctional autoclaved aerated concrete composite additive. By adding this additive during the material mixing and preparation stage, the additive significantly enhances the mechanical properties, corrosion resistance, and foam stabilization efficiency of the product, reduces water absorption, and significantly improves the overall performance of autoclaved aerated concrete (AAC) products through the synergistic effects of nanomaterial reinforcement, environmental stimulation, slow-release foam stabilization, and gradient hydrophobicity.

[0004] To this end, the present invention provides the following technical solutions:

[0005] A multifunctional autoclaved aerated concrete composite additive comprising the following components (by weight percentage):

[0006] a. Nano-enhancer: 5%-15% tannic acid-modified cellulose nanocrystals (TA@CNCs);

[0007] b. Compound stimulant: triethanolamine-citric acid complex 0.5%-5%;

[0008] c. Plant-based foam stabilizer and air-entraining agent: tea saponin nanocapsules (TS-NPs) 0.2%-7.5%;

[0009] d. Water repellent: silane / siloxane composite emulsion 8%-22%;

[0010] e. Solvent: deionized water 2.5%-30%, glycerol 7.5%-35%;

[0011] The preparation method and steps of the multifunctional autoclaved aerated concrete composite additive are as follows:

[0012] Step 1: grinding the solid phase material of tannic acid modified cellulose nanocrystals (TA@CNCs) by ball milling and sieving to obtain uniform powder particles;

[0013] Step 2: triethanolamine and citric acid are mixed in proportion, a solvent is added, and the mixture is reacted at 60° C. for 2 hours to obtain a composite activator;

[0014] Step 3, adding the nano-enhancer, the composite stimulator, the plant-based foam stabilizer and air-entraining agent and the water repellent to the solvent in sequence, stirring until uniform, to obtain a multifunctional autoclaved aerated concrete composite additive;

[0015] Step 4: Add the multifunctional autoclaved aerated concrete composite additive together with the dry material or slurry into a mixing tank, mix them evenly and use them for the production of autoclaved aerated concrete.

[0016] Preferably, the mass ratio of tannic acid to cellulose nanocrystals in the tannic acid modified cellulose nanocrystals (TA@CNCs) is 0.3:1-0.6:1.

[0017] Preferably, the molar ratio of triethanolamine to citric acid in the triethanolamine-citric acid complex is 2:1.

[0018] Preferably, the wall material of the tea saponin nanocapsules (TS-NPs) is polylactic acid, and the core material coverage is ≥90%.

[0019] Preferably, the multifunctional autoclaved aerated concrete composite additive in step 4 is used in the production of autoclaved aerated concrete, and the water-to-material ratio is ≤0.65.

[0020] Preferably, the multifunctional autoclaved aerated concrete composite additive is used in the production of autoclaved aerated concrete, which can significantly improve the compressive strength, corrosion resistance, foaming efficiency, and improve the overall performance of the product.

[0021] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0022] 1. Improved mechanical properties: Tannic acid cross-links with cellulose nanocrystals (CNCs) and lignin residues through phenolic hydroxyl groups to form a three-dimensional network of "cellulose-tannic acid-lignin", significantly improving flexural strength;

[0023] 2. Improve corrosion resistance: By chelating the free alkali metal ions in triethanolamine with citric acid, the pH of the system is reduced to 8.0-8.5 (the pH of traditional activators is greater than 12), thereby reducing the corrosion current density of steel bars;

[0024] 3. Optimize the foaming process: Use polylactic acid (PLA) as the wall material to cover tea saponin, which gradually degrades under a steaming environment and prolongs the foaming time;

[0025] 4. Reduce water absorption: Compound silane (KH570) with siloxane (polydimethylsiloxane) to form a gradient hydrophobic layer on the pore wall, making the water absorption rate ≤5%;

[0026] 5. The multifunctional autoclaved aerated concrete composite additive prepared by the present invention is used in the production of autoclaved aerated concrete, which can significantly improve the mechanical properties, corrosion resistance, foam stabilization efficiency and reduce water absorption of the products, significantly improve the comprehensive performance of autoclaved aerated concrete (AAC) products, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of a method for preparing a multifunctional autoclaved aerated concrete composite additive. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] In order to enable those skilled in the art to fully understand how to implement the present invention, this section provides an explanatory embodiment that expands on the technical solutions of the claims.

[0030] like Figure 1 As shown, the method for preparing the additive used in the production process of autoclaved aerated concrete of the present invention comprises the following steps:

[0031] S101, grinding the solid phase material of tannic acid modified cellulose nanocrystals (TA@CNCs) by ball milling and sieving to obtain uniform powder particles;

[0032] S102, triethanolamine and citric acid are mixed in proportion, a solvent is added, and the mixture is reacted at 60° C. for 2 hours to obtain a composite activator;

[0033] S103, sequentially adding a nano-enhancer, a composite stimulator, a plant-based foam stabilizer and air-entraining agent, and a hydrophobic agent to the solvent, stirring until uniform, to obtain a multifunctional autoclaved aerated concrete composite additive;

[0034] S104, adding the multifunctional autoclaved aerated concrete composite additive together with the dry material or slurry into a mixing tank, mixing them evenly for use in the production of autoclaved aerated concrete.

[0035] Furthermore, the solid material in S101 is ground and sieved to obtain a uniform powder with a particle size of 200-2000 nm, wherein the optimal particle size is 500 nm.

[0036] Furthermore, the solvent in S102 is a mixture of deionized water and glycerol in a ratio of 1:1.5.

[0037] Furthermore, the stirring time in S103 is 0.2-1.5 h, wherein the optimal time is 0.5 h.

[0038] Furthermore, the mixing time in S104 is 0.5-2 h, with the optimal time being 0.8 h.

[0039] In order to make the disclosure of the present invention more complete, it is described below through more specific embodiments.

[0040] Example 1:

[0041] The functional autoclaved aerated concrete composite additive of the present invention mainly consists of the following components (by weight percentage): 5% of a tannic acid modified cellulose nanocrystal (TA@CNCs) enhancer, 0.5% of a triethanolamine-citric acid composite activator, 2% of a tea saponin nanocapsule (TS-NPs) plant-based foam stabilizer and air entrainer, 8% of a silane / siloxane composite emulsion hydrophobic agent, and a solvent of deionized water and glycerol: 2.5% of deionized water and 7.5% of glycerol. The preparation and application methods of the additive are as follows: (1) The solid phase material of the tannic acid modified cellulose nanocrystal (TA@CNCs) is ground by a ball milling process and sieved to obtain uniform powder particles of 200 nm. (2) Triethanolamine and citric acid are mixed in proportion, and a mixture solvent of deionized water and glycerol (ratio of 1:1.5) is added, and the mixture reacts at a certain temperature to obtain a composite activator. (3) Tannic acid modified cellulose nanocrystals (TA@CNCs), a composite activator, a plant-based foam stabilizer and air entraining agent, and a hydrophobic agent were sequentially added to the solvent and stirred for 0.2 h until uniform, thereby obtaining a multifunctional autoclaved aerated concrete composite additive. (4) The multifunctional autoclaved aerated concrete composite additive was added to a mixing tank along with dry materials or slurry, mixed for 0.5 h until uniform, and then used in the production of autoclaved aerated concrete.

[0042] Example 2:

[0043] The multifunctional autoclaved aerated concrete composite additive of the present invention mainly consists of the following components (by weight percentage): 10% of a tannic acid modified cellulose nanocrystal (TA@CNCs) enhancer, 2% of a triethanolamine-citric acid composite activator, 4% of a tea saponin nanocapsule (TS-NPs) plant-based foam stabilizer and air entrainer, 10% of a silane / siloxane composite emulsion hydrophobic agent, and a solvent of deionized water and glycerol: 7% of deionized water and 10% of glycerol. The preparation and application methods of the additive are as follows: (1) The solid phase material of the tannic acid modified cellulose nanocrystal (TA@CNCs) is ground by a ball milling process and sieved to obtain uniform powder particles of 500 nm. (2) Triethanolamine and citric acid are mixed in proportion, and a mixture solvent of deionized water and glycerol (ratio of 1:1) is added, and the mixture reacts at a certain temperature to obtain a composite activator. (3) Tannic acid modified cellulose nanocrystals (TA@CNCs), a composite activator, a plant-based foam stabilizer and air entraining agent, and a hydrophobic agent were sequentially added to the solvent and stirred for 0.5 h until uniform, thereby obtaining a multifunctional autoclaved aerated concrete composite additive. (4) The multifunctional autoclaved aerated concrete composite additive was added to a mixing tank along with dry materials or slurry, mixed for 0.8 h until uniform, and then used in the production of autoclaved aerated concrete.

[0044] Example 3:

[0045] The multifunctional autoclaved aerated concrete composite additive of the present invention mainly consists of the following components (by weight percentage): 12% of a tannic acid modified cellulose nanocrystal (TA@CNCs) enhancer, 2% of a triethanolamine-citric acid composite activator, 5.5% of a tea saponin nanocapsule (TS-NPs) plant-based foam stabilizer and air entrainer, 12.5% ​​of a silane / siloxane composite emulsion hydrophobic agent, and 13% of deionized water and 16% of glycerol as solvents. The preparation and application methods of the additive are as follows: (1) The solid phase material of the tannic acid modified cellulose nanocrystal (TA@CNCs) is ground by a ball milling process and sieved to obtain uniform powder particles of 1000 nm. (2) Triethanolamine and citric acid are mixed in proportion, and a mixture solvent of deionized water and glycerol (ratio of 1:1) is added, and the mixture reacts at a certain temperature to obtain the composite activator. (3) Tannic acid modified cellulose nanocrystals (TA@CNCs), a composite activator, a plant-based foam stabilizer and air-entraining agent, and a hydrophobic agent were sequentially added to the solvent and stirred for 1.2 hours until uniform, thereby obtaining a multifunctional autoclaved aerated concrete composite additive. (4) The multifunctional composite additive was added to a mixing tank along with dry materials or slurry, mixed for 0.9 hours until uniform, and then used in the production of autoclaved aerated concrete.

[0046] Example 4:

[0047] The multifunctional autoclaved aerated concrete composite additive of the present invention mainly consists of the following components (by weight percentage): 12.5% ​​of a tannic acid modified cellulose nanocrystal (TA@CNCs) enhancer, 4% of a triethanolamine-citric acid composite activator, 5.5% of a tea saponin nanocapsule (TS-NPs) plant-based foam stabilizer and air entrainer, 18% of a silane / siloxane composite emulsion hydrophobic agent, and 20.5% of deionized water and 21% of glycerol as solvents. The preparation and application methods of the additive are as follows: (1) The solid phase material of the tannic acid modified cellulose nanocrystal (TA@CNCs) is ground by ball milling and sieved to obtain uniform powder particles of 1200 nm. (2) Triethanolamine and citric acid are mixed in proportion, and a mixture solvent of deionized water and glycerol (ratio of 1:1) is added, and the mixture reacts at a certain temperature to obtain the composite activator. (3) Tannic acid modified cellulose nanocrystals (TA@CNCs), a composite activator, a plant-based foam stabilizer and air entraining agent, and a hydrophobic agent were sequentially added to the solvent and stirred for 1.1 hours until uniform, thereby obtaining a multifunctional autoclaved aerated concrete composite additive. (4) The multifunctional autoclaved aerated concrete composite additive was added to a mixing tank along with dry materials or slurry, mixed for 1.7 hours until uniform, and then used in the production of autoclaved aerated concrete.

[0048] Example 5:

[0049] The multifunctional autoclaved aerated concrete composite additive of the present invention mainly consists of the following components (by weight percentage): 15% of a tannic acid modified cellulose nanocrystal (TA@CNCs) enhancer, 5% of a triethanolamine-citric acid composite activator, 7.5% of a tea saponin nanocapsule (TS-NPs) plant-based foam stabilizer and air entrainer, 22% of a silane / siloxane composite emulsion hydrophobic agent, and a solvent of deionized water and glycerol: 30% of deionized water and 35% of glycerol. The preparation and application methods of the additive are as follows: (1) The solid phase material of the tannic acid modified cellulose nanocrystal (TA@CNCs) is ground by a ball milling process and sieved to obtain uniform powder particles of 2000 nm. (2) Triethanolamine and citric acid are mixed in proportion, and a mixture solvent of water and glycerol (ratio of 1:1) is added, and the mixture reacts at a certain temperature to obtain the composite activator. (3) Tannic acid modified cellulose nanocrystals (TA@CNCs), a composite activator, a plant-based foam stabilizer and air entraining agent, and a hydrophobic agent were sequentially added to the solvent and stirred for 1.5 hours until uniform, thereby obtaining a multifunctional autoclaved aerated concrete composite additive. (4) The multifunctional autoclaved aerated concrete composite additive was added to a mixing tank along with dry materials or slurry, mixed for 2 hours until uniform, and then used in the production of autoclaved aerated concrete.

[0050] The above demonstrates the creativity and technical value of the technical solution of the present invention. The multifunctional autoclaved aerated concrete composite additives prepared according to Examples 1-5 were used in the production of autoclaved aerated concrete. Among them, tannic acid-modified cellulose nanocrystals (TA@CNCs) form hydrogen bond bridges with cellulose nanocrystals (CNCs) and lignin residues through phenolic hydroxyl groups, constructing a cross-scale three-dimensional cross-linked network, significantly improving the matrix density (25%-30%). Triethanolamine-citric acid complex (TEA-CA) effectively reduces the system pH to 8.0-8.5 (traditional activator pH>12) through chelation. Tea saponin nanocapsules (TS-NPs) use polylactic acid (PLA) as the wall material to achieve slow-release gasification. Under steam curing conditions at 55°C, the degradation rate of the microcapsules matches the slurry thickening process, and the foam stabilization time is extended from 30 minutes in the traditional formula to 55-60 minutes. After silane (KH570) is compounded with siloxane (polydimethylsiloxane), a sol-gel reaction forms a gradient hydrophobic layer on the pore walls, reducing water absorption from 12% in a conventional formulation to below 4.5%. These examples demonstrate the significant advantages of the additive in improving mechanical properties, optimizing pore structure, enhancing durability, and reducing water absorption. This additive aligns with the development trend of green building materials technology and possesses potential for industrialization and promotion.

[0051] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A multifunctional autoclaved aerated concrete composite additive, characterized in that: Contains the following components (by weight percentage): a. Nano-enhancer: 5%-15% tannic acid-modified cellulose nanocrystals (TA@CNCs); b. Compound stimulant: triethanolamine-citric acid complex 0.5%-5%; c. Plant-based foam stabilizer and air-entraining agent: tea saponin nanocapsules (TS-NPs) 0.2%-7.5%; d. Water repellent: silane / siloxane composite emulsion 8%-22%; e. Solvent: deionized water 2.5%-30%, glycerol 7.5%-35%; The preparation method and steps of the multifunctional autoclaved aerated concrete composite additive are as follows: Step 1: grinding the solid phase material of tannic acid modified cellulose nanocrystals (TA@CNCs) by ball milling and sieving to obtain uniform powder particles; Step 2: triethanolamine and citric acid are mixed in proportion, a solvent is added, and the mixture is reacted at 60° C. for 2 hours to obtain a composite activator; Step 3, adding the nano-enhancer, the composite stimulator, the plant-based foam stabilizer and air-entraining agent and the water repellent to the solvent in sequence, stirring until uniform, to obtain a multifunctional autoclaved aerated concrete composite additive; Step 4: Add the multifunctional autoclaved aerated concrete composite additive together with the dry material or slurry into a mixing tank, mix them evenly and use them for the production of autoclaved aerated concrete.

2. The multifunctional autoclaved aerated concrete composite additive according to claim 1, characterized in that: The mass ratio of tannic acid to cellulose nanocrystals in the tannic acid modified cellulose nanocrystals (TA@CNCs) is 0.3:1-0.6:

1.

3. The multifunctional autoclaved aerated concrete composite additive according to claim 1, characterized in that: The molar ratio of triethanolamine to citric acid in the triethanolamine-citric acid complex is 2:

1.

4. The multifunctional autoclaved aerated concrete composite additive according to claim 1, characterized in that: The wall material of the tea saponin nano-microcapsules (TS-NPs) is polylactic acid, and the core material coverage rate is ≥90%.

5. The multifunctional autoclaved aerated concrete composite additive according to claim 1, characterized in that: The multifunctional autoclaved aerated concrete composite additive in step 4 is used for the production of autoclaved aerated concrete, and the water-to-material ratio is ≤0.

65.

6. The multifunctional autoclaved aerated concrete composite additive according to claim 1, characterized in that: The multifunctional autoclaved aerated concrete composite additive is used in the production of autoclaved aerated concrete, can significantly improve the compressive strength, corrosion resistance, foaming efficiency, and improve the comprehensive performance of the product.

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