Phosphogypsum-based self-healing temperature-sensitive building material and use method thereof

Abstract

The invention discloses an ardealite-based self-healing temperature-sensitive building material which comprises the following components in percentage by mass: 45-65% of ardealite, 25-35% of industrial solid waste powder, 5-10% of temperature-sensitive hydrogel and 2-10% of self-healing microcapsules, and light reinforced aggregate can also be added into the material. According to the material, ardealite is used as a main gelling component, alkaline industrial solid wastes such as carbide slag, red mud and slag are cooperatively introduced, a hydration reaction is promoted by adjusting the pH value, a stable and compact gelling structure is formed, and meanwhile, a temperature-sensitive hydrogel material is introduced, so that the material generates reversible volume response under the environment temperature change condition and has a certain degree of crack closing capacity; a microcapsule type self-healing component is further introduced, when the material is subjected to stress or structural micro-cracks, microcapsules are broken to release a repairing agent, the cracks are effectively sealed, and the structural integrity is improved; the method is wide in raw material source, remarkable in environmental protection benefit, suitable for large-scale popularization and application and good in industrial conversion prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials and industrial solid waste resource utilization, and specifically relates to a method for preparing a self-healing temperature-sensitive multifunctional building material based on phosphogypsum and industrial solid waste. Background Art

[0002] Phosphogypsum is a byproduct of phosphate fertilizer production, with huge annual production. If improperly stored and handled, it can easily cause land and water pollution. Existing research has primarily used phosphogypsum in combination with solid wastes such as fly ash and slag to create building materials, but these materials generally suffer from low strength, cracking, and poor durability.

[0003] On the other hand, building materials are easily affected by temperature and humidity fluctuations, structural stress, etc. during use, which can easily produce microcracks, leading to hidden dangers such as leakage, corrosion, and intrusion of pollutants. It is necessary to develop new functional building materials with self-repair and environmental response capabilities. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a method for preparing a self-healing temperature-sensitive multifunctional building material based on phosphogypsum and industrial solid waste, aiming to solve the problems of traditional phosphogypsum building materials such as easy generation of microcracks, difficulty in repair, poor sealing, and short service life during use, while improving the resource utilization rate of phosphogypsum and industrial solid waste.

[0005] The composition and weight percentage of the phosphogypsum-based self-healing thermosensitive building material of the present invention are 45-65% of phosphogypsum, 25-35% of industrial solid waste powder, 5-10% of thermosensitive hydrogel and 2-10% of self-healing microcapsule.

[0006] Or the composition and mass percentage are 45-55% of phosphogypsum, 25-30% of industrial solid waste powder, 5-6% of thermosensitive hydrogel, 2-4% of self-healing microcapsule, and 5-10% of lightweight reinforcing aggregate.

[0007] The phosphogypsum is a by-product gypsum of wet-process phosphoric acid, which is dried to a moisture content of less than 10% and crushed to a particle size of ≤100 mesh; the industrial solid waste is one or more of calcium carbide slag, red mud, slag, and steel slag.

[0008] The lightweight reinforcing aggregate is one or more of ceramsite, pumice powder, and expanded perlite, and has a particle size of 0.5-5 mm.

[0009] The thermosensitive hydrogel is poly (N-isopropylacrylamide) and has LCST thermosensitive properties.

[0010] When the above-mentioned phosphogypsum-based self-healing thermosensitive building material is used, the components are mixed, water is added, and the solid-liquid ratio g:mL is 1:0.4-0.6. After stirring and mixing, it is molded or extruded, and cured at 20-40°C and 85%-95% humidity for 7-28 days to obtain a building structure with self-healing and thermosensitive adjustment capabilities.

[0011] The self-healing microcapsules are prepared as follows: (1) Heat 5-10g of epoxy resin to 30-40℃ while stirring; (2) Add 1-2 g of urea and 2-3 mL of formaldehyde to a 1-2% mass volume concentration of polyvinyl alcohol (PVA) aqueous solution, and adjust the pH of the solution to 2.5-3.5 with citric acid; (3) adding the epoxy resin liquid from step (1) to the solution from step (2) and emulsifying the mixture using a high-speed shearing device at 500-1000 rpm; (4) The emulsion prepared in step (3) was heated to 55-60°C in a constant temperature water bath and reacted for 2-4 hours, then naturally cooled, allowed to settle, and the microcapsule solids were collected by vacuum filtration. After washing with deionized water, the microcapsules were dried at 40°C to obtain self-healing microcapsules.

[0012] The building material of the present invention is suitable for the preparation of non-load-bearing walls, interior partition walls, lightweight bricks, filling plates, anti-seepage pads in underground projects, side wall sealing layers, culvert closing panels or contaminated site closing structures of prefabricated buildings.

[0013] The building structure made of the material of the present invention has the following properties: 28-day compressive strength ≥4.0 MPa; can automatically heal cracks with a width of ≤0.3 mm, with a healing rate of ≥70%; thermal conductivity ≤0.25 W / (m·K); permeability coefficient ≤1.0×10 -9 m / s; it has temperature-responsive contraction or expansion behavior, and can achieve seam closing function in a temperature environment of 60℃-80℃, with a closure rate ≥85%.

[0014] Advantages and technical effects of the present invention: 1. The building material of the present invention uses phosphogypsum and industrial solid waste in a coordinated manner, achieving "waste treatment with waste" and reducing dependence on natural mineral cementitious materials; 2. Self-healing function: Construct materials with microcapsule self-repairing structures. Repair is achieved by releasing secondary hydration products or polymer network structures through microcapsule rupture. When cracks appear, the repair slurry can be released to automatically seal the cracks. 3. Thermosensitive response: The introduction of thermosensitive hydrogel components causes the material to change volume with temperature, automatically compensating for shrinkage and cracking; 4. Environmental protection and strong sealing: forming a dense structure, effectively blocking the diffusion of moisture and harmful ions, reducing permeability and environmental risks; 5. Wide application: The material produced has moderate strength and low density, and can be used in lightweight blocks, non-load-bearing walls, prefabricated filling components and other fields. DETAILED DESCRIPTION

[0015] The present invention will be further described below with reference to the examples. However, the scope of the present invention is not limited to the following examples. Those skilled in the art will appreciate that various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. The instruments, reagents, and materials involved in the following examples, unless otherwise specified, are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through regular commercial channels. The experimental methods, detection methods, etc. involved in the following examples, unless otherwise specified, are all conventional experimental methods and detection methods already available in the prior art; The self-healing microcapsules in the embodiment are prepared by the following method: (1) Preparation of dispersed phase Add 8 g of epoxy resin to a beaker and heat it to 40°C using a magnetic stirrer. (2) Preparation of continuous phase In a 250 mL three-necked flask, add 100 mL of deionized water and 1.5 g of PVA (dispersant). Heat and stir until completely dissolved. Then add 1.5 g of urea and 2.5 mL of formaldehyde. Adjust the pH of the solution to 3.0 with citric acid. (3) Emulsion dispersion reaction The epoxy resin from step (1) was added dropwise into the continuous phase and emulsified using a high-speed shear (1000 rpm); (4) Polymerization coating reaction The mixture was heated to 55°C in a constant temperature water bath for 3 hours to condense urea and formaldehyde to form urea-formaldehyde resin, which coated the core material at the interface to form microcapsules. (5) Cooling and solid-liquid separation After the reaction is completed, the mixture is naturally cooled and allowed to settle. The microcapsule solids are collected by vacuum filtration and washed three times with deionized water. The microcapsules are placed in a vacuum drying oven and dried at 40°C for 12 hours to obtain self-healing microcapsules with a shell-core structure and an average particle size of about 100μm. These self-healing microcapsules have the function of breaking and releasing repair agents under the action of crack stress, and can react with Ca²⁺ and OH⁻ in building materials to form a closed structure, thereby improving the self-healing ability of the material.

[0016] Example 1: Phosphogypsum-based self-healing thermosensitive building material for the preparation of building blocks 1. The composition and mass percentage of this embodiment are 55% phosphogypsum, 25% carbide slag, 6% poly (N-isopropylacrylamide), 4% self-healing microcapsules, and 10% ceramsite; The phosphogypsum is a by-product of wet-process phosphoric acid, which is dried to a moisture content of 5% and crushed to a particle size of ≤100 mesh; the ceramsite particle size is 0.5-2 mm; the calcium carbide slag is dried and ground to a fineness of less than 75 μm; 2. When using, first mix phosphogypsum and carbide slag, then add poly (N-isopropylacrylamide), self-healing microcapsules, and ceramsite; add industrial water at a solid-liquid ratio of 1:0.5 (g:mL), stir for 15 minutes until uniform, inject the mixture into a standard brick mold, vibrate and compact; cure at room temperature and relative humidity of 90% for 28 days; 3. Performance testing 3.1 Self-Healing Test: Using a standard crack simulation method, a 0.2 mm crack was created in the center of the prepared blocks. The blocks were placed in an environment with a temperature of 25°C and a humidity of 90% and the crack changes were observed. The results showed that the crack closure rate was 83% within 72 hours, indicating that the material has excellent self-healing capabilities.

[0017] 3.2 Referring to the "Test Method for Strength of Cement Mortar (ISO Method) GB / T 17671-2021", the compressive strength after 28 days of curing was tested and the result was 6.2MPa.

[0018] 3.3 Leakage performance: refer to "Solid Waste Leaching Toxicity - Leaching Method (HJ / T 299-2007)", test the F - PO4 3- The results showed that all indicators were lower than the hazardous waste judgment standard, and the permeability coefficient was 2.4×10 -9 m / s.

[0019] 3.4 Thermal conductivity test: The laser thermal conductivity analyzer (LFA) test showed that the thermal conductivity was 0.21 W / (m·K), which meets the thermal performance requirements of lightweight insulation materials.

[0020] 3.5 Temperature Sensitivity: After being stored at 60°C for 4 hours, the block's volume shrinkage was approximately 1.3%. After cooling to room temperature, it recovered to over 95% of its initial volume, demonstrating excellent temperature responsiveness and joint sealing. These results demonstrate that the block is suitable for use in prefabricated buildings, partition walls, and non-load-bearing walls, combining lightweight, thermal insulation, and self-healing properties.

[0021] Example 2: Phosphogypsum-based self-healing temperature-sensitive building materials for the preparation of interior wall panels 1. The composition and mass percentage of this embodiment are 50% phosphogypsum, 30% slag, 6% poly (N-isopropylacrylamide), 4% self-healing microcapsules, and 10% pumice powder; The phosphogypsum is a by-product of wet-process phosphoric acid, which is dried to a moisture content of 3% and crushed to a particle size of ≤100 mesh; the pumice powder has a particle size of 2-4 mm; the slag is pretreated to a specific surface area of ​​>400 m 2 / kg; 2. When using, first mix phosphogypsum and carbide slag, then add poly (N-isopropylacrylamide), self-healing microcapsules, and pumice powder; add industrial water at a solid-liquid ratio of 1:0.55 (g:mL), stir for 15 minutes until uniform, and mold the mixture into 10-12 mm boards; cure at room temperature and relative humidity of 95% for 28 days; 3. Performance testing 3.1 Crack resistance test: The test was conducted with reference to the "Test Method for Crack Resistance of Building Wall Materials". The traditional phosphogypsum-based board material was used as a comparison sample (with a crack resistance index of 0.50). The crack resistance index of the board material of this embodiment was 0.64. The results showed that the crack resistance index of the board material of this embodiment was increased by 28%, significantly improving the crack resistance under thermal expansion and contraction and dry-wet cycles.

[0022] 3.2 Temperature Responsiveness: The prepared sheet was heated at 60°C for 2 hours, and its volume shrinkage was measured using image recognition. The results showed a volume shrinkage of 1.1%. After cooling to room temperature, it rebounded to 96% of its original size, demonstrating excellent temperature-responsive reversible deformation properties. After further cycling 10 times at 60°C / 20°C, the sheet showed no structural cracking or deformation, remaining intact.

[0023] 3.3 Thermal conductivity: Using the Laser Flash Analysis (LFA) method, in accordance with the standard GB / T10294-2008 “Determination of steady-state thermal resistance and related properties of thermal insulation materials,” the samples after 28 days of curing were cut into standard discs of Φ50 mm × 10 mm. Transverse thermal conductivity tests were conducted at room temperature (approximately 25°C). The resulting thermal conductivity was 0.18 W / (m·K), indicating that the material has excellent thermal insulation properties.

[0024] 3.4 Moisture Absorption Rebound Rate: Referring to the "Determination Method for Moisture Absorption Rebound Rate," the sample was first dried in a constant temperature drying oven (60°C, humidity <20%) for 24 hours and the dry weight was measured. The sample was then placed in a constant temperature and humidity chamber (25°C, 90% humidity) for 48 hours, removed, and weighed again. The dimensional change due to moisture absorption was calculated and found to be <0.3%, indicating that the material exhibits good dimensional stability in humid environments.

[0025] The results show that the above-mentioned panels are suitable for interior wall insulation panels, roof sandwich panels, etc., and have the advantages of heat insulation, self-adjustment of stress, and crack prevention.

[0026] Example 3: Phosphogypsum-based self-healing temperature-sensitive building materials prepared from closed anti-seepage pads for underground facilities 1. The composition and mass percentage of this embodiment are 45% phosphogypsum, 35% red mud, 10% poly (N-isopropylacrylamide), and 10% self-healing microcapsules; The phosphogypsum is a by-product of wet-process phosphoric acid, which is dried to a moisture content of 6% and crushed to a particle size of ≤80 mesh; the red mud is crushed to a particle size of ≤80 mesh; 2. When using, first mix phosphogypsum and carbide slag, then add poly (N-isopropylacrylamide) and self-healing microcapsules; add industrial water at a solid-liquid ratio of 1:0.6 (g:mL), stir for 15 minutes until uniform, and mold the mixture into plate or block components. The thickness can be set according to the project (usually 30-50mm); cure at room temperature and relative humidity of 85% for 21 days; 3. Performance testing 3.1 The test was carried out in accordance with the "Test Procedure for the Impermeability of Hydraulic Concrete" (SL / T 352-2020). The molded sample was placed in a permeability test device with a water pressure of 2.0 MPa for 72 hours and then the permeability was measured. The results showed that the material permeability coefficient was less than 1×10 -9 m / s, meeting the requirements of waterproof and anti-seepage performance of underground structures.

[0027] 3.2 A 0.3 mm crack was artificially cut in the center of the specimen. The specimen was placed in an environment with a relative humidity of 90% and then cured for 24 hours to observe the crack closure. The results showed that the crack closure rate exceeded 90%, demonstrating that the material has a rapid self-healing response capability in a room temperature and humid environment.

[0028] 3.3 According to the "Test Method for Strength of Cement Mortar (ISO Method) GB / T 17671-2021", the compressive strength after 21 days of curing was tested, and the result was 3.9 MPa, which can meet the structural pressure requirements of underground closed projects.

[0029] The results show that this material is suitable for high-sealing scenarios such as underground waterproofing, structural joint linings, and linings of sewage treatment facilities, and is suitable for projects such as underground garages and drainage ditches.

Claims

1. A phosphogypsum-based self-healing temperature-sensitive building material, characterized by: The composition and mass percentage are 45-65% of phosphogypsum, 25-35% of industrial solid waste powder, 5-10% of thermosensitive hydrogel, and 2-10% of self-healing microcapsule.

2. A phosphogypsum-based self-healing temperature-sensitive building material, characterized by: The composition and mass percentage are 45-55% of phosphogypsum, 25-30% of industrial solid waste powder, 5-6% of thermosensitive hydrogel, 2-4% of self-healing microcapsule, and 5-10% of lightweight reinforcing aggregate.

3. The phosphogypsum-based self-healing thermosensitive building material according to claim 1 or 2, characterized in that: Industrial solid waste is one or more of carbide slag, red mud, slag, and steel slag.

4. The phosphogypsum-based self-healing thermosensitive building material according to claim 2, characterized in that: The lightweight reinforcing aggregate is one or more of ceramsite, pumice powder, and expanded perlite, with a particle size of 0.5-5 mm.

5. The phosphogypsum-based self-healing thermosensitive building material according to claim 1 or 2, characterized in that: Phosphogypsum is a by-product gypsum of wet-process phosphoric acid, which is dried to a moisture content of less than 10% and crushed to a particle size of ≤100 mesh.

6. The phosphogypsum-based self-healing thermosensitive building material according to claim 1 or 2, characterized in that: The thermosensitive hydrogel is poly (N-isopropylacrylamide).

7. The phosphogypsum-based self-healing thermosensitive building material according to claim 1 or 2, characterized in that: Self-healing microcapsules were prepared as follows: (1) Heat 5-10g of epoxy resin to 30-40℃ while stirring; (2) Add 1-2 g of urea and 2-3 mL of formaldehyde to a 1-2% mass volume concentration of polyvinyl alcohol aqueous solution, and adjust the pH of the solution to 2.5-3.5 with citric acid; (3) adding the epoxy resin liquid from step (1) to the solution from step (2) and emulsifying the mixture using a high-speed shearing device at 500-1000 rpm; (4) The emulsion prepared in step (3) was heated to 55-60°C in a constant temperature water bath and reacted for 2-4 hours, then naturally cooled, allowed to settle, and the microcapsule solids were collected by vacuum filtration, washed with deionized water, and dried to obtain self-healing microcapsules.

8. The method for using the phosphogypsum-based self-healing temperature-sensitive building material according to claim 1 or 2, characterized in that: After the components are mixed, water is added to a solid-liquid ratio of 1:0.4-0.6 (g:mL). After stirring and mixing, the components are molded or extruded, and cured at 20-40°C and 85%-95% humidity for 7-28 days to obtain a building structure with self-healing and temperature-sensitive adjustment capabilities.