Preparation process of green energy-saving light-weight high-strength castable

Abstract

The application discloses a kind of preparation processes of green energy-saving light high-strength castable, it is related to castable technical field, the process includes raw material pretreatment, composite batching mixing, gradient foaming forming, low temperature curing and high temperature sintering step, with building solid waste as main renewable raw material, combined with raw material composite modification, gradient foaming forming and other core technologies;The application realizes the resource utilization of building solid waste, reduces the dependence on natural aggregate, solves the problem that traditional castable light and high-strength are difficult to consider, the volume density of the prepared castable is ≤1.2g / cm³, the compressive strength is ≥30MPa, the thermal conductivity is ≤0.12W / (m·K), environmentally friendly and energy-saving and excellent comprehensive performance, wide application range, with significant economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of castable technology, and in particular to a preparation process for a green, energy-saving, lightweight, and high-strength castable. Background Technology

[0002] Castable refractories are widely used in construction, metallurgy, and chemical industries. However, with the increasing demands for energy conservation, environmental protection, and lightweighting, traditional castable refractories are gradually revealing their performance shortcomings: most products rely on natural aggregates, resulting in high resource consumption and poor environmental performance; lightweight and high-strength properties are difficult to balance, with conventional lightweight castable refractories generally having a compressive strength below 25 MPa, while high-strength castable refractories have high bulk density, high thermal conductivity, and poor energy-saving effects. Furthermore, existing processes suffer from insufficient raw material modification and uneven foaming, further hindering the improvement of overall product performance. In addition, the low utilization rate of construction solid waste resources and its large-scale accumulation create environmental pressure. Therefore, developing a castable refractories preparation process that uses recycled resources as raw materials, achieves a synergistic effect of lightweight and high strength, and combines environmental protection and energy-saving advantages has become an urgent need in this field. Summary of the Invention

[0003] To address the technical problems existing in the background art, this invention proposes a preparation process for green, energy-saving, lightweight, and high-strength castables.

[0004] The present invention proposes a preparation process for a green, energy-saving, lightweight, and high-strength castable, comprising the following steps: S1. Raw material pretreatment: After crushing, screening and magnetic separation to remove impurities from construction solid waste, green recycled aggregate is obtained through high-temperature roasting activation and surface modification. S2. Composite Ingredient Mixing: Green recycled aggregate, lightweight thermal insulation components, high-performance cementitious materials, environmentally friendly modifiers and water are mixed and stirred in a specific ratio to obtain a uniform base material; S3, Gradient foaming molding: A composite foaming agent is added to the base material, and after gradient heating and stirring, it is injected into the mold and molded using a vibration and negative pressure combined process. S4. Low-temperature curing: The molded blank is cured at constant temperature and humidity, supplemented by ultrasonic vibration treatment, and pre-dried after curing. S5. High-temperature sintering: The pre-dried green body is sintered using a gradient heating sintering process. Inert gas is introduced for protection during the sintering process, and the finished product is obtained by cooling after sintering. The raw materials include green recycled aggregate, lightweight insulation components, high-performance cementitious materials, environmentally friendly modifiers, composite foaming agents, and water.

[0005] Furthermore, the raw material pretreatment includes: crushing, screening, and magnetically separating the construction solid waste for impurity removal, followed by high-temperature roasting activation treatment. The roasting temperature is controlled at 650-800℃, and the holding time is 2-3 hours to obtain green recycled aggregate with a particle size of 0.15-5mm. During the high-temperature roasting activation process, oxygen-enriched gas with an oxygen mass fraction of 8-12% is introduced, and 0.5-1.2% of a silane coupling agent by mass of the construction solid waste is added simultaneously for surface modification to improve the interfacial bonding strength between the recycled aggregate and the cementitious material. The silane coupling agent is a compound of γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane, with a mass ratio of 1:0.6-1.2.

[0006] Furthermore, in the composite ingredient mixing step, the mass ratio of each component of the raw materials is as follows: 40-60 parts of green recycled aggregate, 15-25 parts of lightweight thermal insulation component, 20-30 parts of high-performance cementitious material, 2-5 parts of environmentally friendly modifier, and 8-12 parts of water; wherein, the lightweight thermal insulation component is a compound of hollow glass microspheres and cenospheres, the hollow glass microspheres have a particle size of 20-80μm and a bulk density of 0.18-0.25g / cm³, the cenospheres have a particle size of 50-150μm and a bulk density of 0.22-0.30g / cm³, and the mass ratio of the two is 1:0.8-1.5, and the hollow glass microspheres are pretreated with a titanate coupling agent with a mass fraction of 1-3%, and the cenospheres are pretreated with an aluminate coupling agent with a mass fraction of 0.8-2%, the pretreatment temperature is 60-80℃, and the treatment time is 30-60min.

[0007] Furthermore, the gradient foaming molding step specifically involves: first, adding green recycled aggregate, high-performance cementitious materials, and environmentally friendly modifiers to a planetary mixer and dry-mixing at 150-200 r / min for 10-15 min; then adding pretreated lightweight insulating components and 70% water and wet-mixing at 250-300 r / min for 20-30 min to obtain the base material; subsequently, adding 1.5-3% of the composite foaming agent by weight of the base material, while simultaneously adding the remaining 30% water. Stir at 300-350 r / min for 5-8 min, using a gradient heating method during stirring, gradually increasing the temperature from room temperature to 40-50℃ at a rate of 2-3℃ / min; inject the stirred foamed slurry into the mold, and use a vibration and negative pressure co-molding process, with a vibration frequency of 50-80 Hz and a vibration time of 3-5 min, a negative pressure of -0.03~-0.05 MPa, and a negative pressure holding time of 2-4 min, to achieve uniform foaming and dense stacking of the slurry.

[0008] Furthermore, the composite foaming agent is a mixture of hydrogen peroxide and ammonium bicarbonate, with a mass ratio of 1:0.5-0.8, and a foaming stabilizer is added at 0.2-0.5% of the composite foaming agent's mass. The foaming stabilizer is a mixture of gelatin and xanthan gum, with a mass ratio of 1:0.3-0.6. The high-performance cementitious material is a mixture of sulfoaluminate cement, metakaolin, and slag powder, with a mass ratio of sulfoaluminate cement, metakaolin, and slag powder of 1:0.3-0.6:0.2-0.4. The slag powder has a specific surface area of ​​400-500 m² / kg and is pretreated with an activator at a mass fraction of 2-4%. The activator is a mixture of sodium hydroxide and water glass, with a mass ratio of 1:1.2-1.8.

[0009] Furthermore, the low-temperature curing step is as follows: the formed green body is placed in a constant temperature and humidity curing chamber, the curing temperature is controlled at 20-30℃, the relative humidity is 85-95%, and the curing time is 24-48h; during the curing process, ultrasonic vibration treatment is performed every 8h, the ultrasonic frequency is 20-40kHz, and the treatment time is 5-10min, so as to promote the uniform diffusion of moisture and the full hydration reaction; after the low-temperature curing is completed, the green body is pre-dried, the drying temperature is 60-80℃, the drying time is 8-12h, and the drying rate is controlled at 5-8℃ / h to avoid cracks in the green body due to rapid drying.

[0010] Furthermore, the high-temperature sintering step adopts a gradient heating sintering process. The specific heating program is as follows: heating from room temperature to 200℃ at a heating rate of 5-8℃ / min, holding for 1-2 hours; then heating to 600-700℃ at a heating rate of 3-5℃ / min, holding for 2-3 hours; finally heating to 1000-1100℃ at a heating rate of 2-3℃ / min, holding for 3-5 hours. During the sintering process, an inert gas is introduced for protection. The inert gas is a mixture of nitrogen and argon with a volume ratio of 1:0.5-0.8 and a gas flow rate of 0.5-1.0 L / min. After sintering, the temperature is lowered by a combination of natural cooling and forced cooling, with the cooling rate controlled at 10-15℃ / min. After cooling to room temperature, a green, energy-saving, lightweight, and high-strength castable is obtained.

[0011] Furthermore, the environmentally friendly modifier includes a water-reducing agent, a retarder, and a reinforcing agent, with a mass ratio of 1:0.2-0.4:0.3-0.5; wherein, the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent with a solid content of 40-50% and a water reduction rate ≥30%; the retarder is a compound of citric acid and sodium gluconate with a mass ratio of 1:0.6-1.0; the reinforcing agent is a compound of nano-silica and nano-alumina with a nanoparticle size of 20-50nm and a specific surface area of ​​150-200m² / g, and is surface-modified with a silane coupling agent at a mass fraction of 1-2%.

[0012] Furthermore, in the raw material pretreatment process, after the construction solid waste is crushed, a three-stage screening process is adopted to obtain recycled aggregates with particle sizes of 3-5mm, 1-3mm, and 0.15-1mm, respectively. The mass ratio of the three particle sizes of recycled aggregates is 1:1.5-2.0:2.5-3.0, so as to achieve continuous gradation of aggregates and improve the bulk density and strength properties of castables. After the three-stage screening, water washing treatment is required, and the water washing time is 15-20 minutes. The mud content of the recycled aggregates after water washing is ≤1.0%.

[0013] Furthermore, in the gradient foaming molding step, the mold is a heat-insulating mold, and the inner wall of the mold is coated with a release agent with a thickness of 0.5-1.0 mm. The release agent is a water-based release agent, which is made by mixing polyvinyl alcohol, glycerin and water in a mass ratio of 1:0.5-0.8:10-15. After the foaming slurry is injected into the mold, a secondary material replenishment process is required. The replenishment time is 10-15 minutes after the start of foaming, and the replenishment amount is 3-5% of the mold volume to compensate for the volume shrinkage during the foaming process and ensure the dimensional accuracy of the casting. After the high-temperature sintering is completed, the casting is surface polished with a polishing accuracy of Ra≤0.8μm. At the same time, an environmentally friendly anti-corrosion coating with a thickness of 1-2 mm is coated on the surface. The coating material is a compound of water-based acrylic resin and nano titanium dioxide in a mass ratio of 1:0.1-0.2.

[0014] The beneficial effects of this invention are as follows: Through the resource utilization of construction solid waste and the core processes such as raw material composite modification and gradient foaming molding, the dependence of castables on natural aggregates is effectively reduced, the utilization rate of construction solid waste is improved, the pollution from solid waste accumulation is reduced, and green and environmentally friendly production is achieved. It also synergistically improves the lightweight level and mechanical properties of castables, reduces the thermal conductivity, and solves the problem that traditional castables are difficult to balance in terms of lightweight and high strength and have poor energy-saving effects. The prepared castables have excellent comprehensive performance, wide applicability, and significant economic and social benefits. Detailed Implementation

[0015] Example 1

[0016] The present invention proposes a preparation process for a green, energy-saving, lightweight, and high-strength castable, the specific steps of which are as follows: S1. Raw material pretreatment: Construction solid waste (concrete waste blocks) is selected, crushed, screened in three stages (to obtain aggregates with particle sizes of 3-5mm, 1-3mm, and 0.15-1mm respectively, with a mass ratio of 1:1.5:2.5), and magnetically separated to remove impurities. After washing, the aggregates are washed for 15 minutes, and the mud content is controlled to be ≤1.0%. Then, high-temperature roasting activation treatment is carried out at a roasting temperature of 650℃ and a holding time of 2 hours. During the roasting process, oxygen-enriched gas with an oxygen mass fraction of 8% is introduced, and 0.5% of the mass of construction solid waste silane coupling agent (γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane in a mass ratio of 1:0.6) is added simultaneously for surface modification to obtain green recycled aggregates. S2. Composite Ingredient Mixing: Prepare raw materials according to the following mass ratio: 40 parts green recycled aggregate, 15 parts lightweight insulation component, 20 parts high-performance cementitious material, 2 parts environmentally friendly modifier, and 8 parts water; wherein, the lightweight insulation component is a mixture of hollow glass microspheres (particle size 20-80μm, bulk density 0.18g / cm³) and cenospheres (particle size 50-150μm, bulk density 0.22g / cm³), with a mass ratio of 1:0.8. The hollow glass microspheres are pretreated with 1% titanate coupling agent at 60℃ for 30min, and the cenospheres are pretreated with 0.8% aluminate coupling agent at 60℃ for 30min; the high-performance cementitious material is sulfur... A compound of aluminate cement, metakaolin, and slag powder (mass ratio 1:0.3:0.2), with a slag powder specific surface area of ​​400 m² / kg, is pretreated with 2% (mass fraction) activator (sodium hydroxide and water glass mass ratio 1:1.2). The environmentally friendly modifier is a compound of water-reducing agent, retarder, and reinforcing agent (mass ratio 1:0.2:0.3). The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent with a solid content of 40%. The retarder is a compound of citric acid and sodium gluconate mass ratio 1:0.6. The reinforcing agent is a compound of nano-silica and nano-alumina with a particle size of 20-50 nm and a specific surface area of ​​150 m² / g, which is surface modified with 1% (mass fraction) silane coupling agent. Green recycled aggregate, high-performance cementitious materials and environmentally friendly modifiers are added to a planetary mixer and dry-mixed at 150 r / min for 10 min. Then, pretreated lightweight insulation components and 70% water are added and wet-mixed at 250 r / min for 20 min to obtain a uniform base material. S3. Gradient Foaming Molding: Add 1.5% (by weight of the base material) of a composite foaming agent (hydrogen peroxide to ammonium bicarbonate in a mass ratio of 1:0.5) to the base material, and simultaneously add the remaining 30% water. Add 0.2% (by weight of the composite foaming agent) of a foaming stabilizer (gelatin to xanthan gum in a mass ratio of 1:0.3). Stir at 300 rpm for 5 minutes, using a gradient heating method during stirring, gradually increasing the temperature from room temperature to 40°C at a rate of 2°C / min. Inject the stirred foamed slurry into a thermal insulation mold (with a 0.5 mm thick water-based release agent coated on the inner wall, the release agent being a mixture of polyvinyl alcohol, glycerin, and water in a mass ratio of 1:0.5:10). Use a vibration and negative pressure co-molding process, with a vibration frequency of 50 Hz, a vibration time of 3 minutes, a negative pressure of -0.03 MPa, and a negative pressure holding time of 2 minutes. After foaming begins, perform a second material replenishment 10 minutes later, with the replenishment amount being 3% of the mold volume. S4. Low-temperature curing: Place the formed blank in a constant temperature and humidity curing chamber at a curing temperature of 20℃ and a relative humidity of 85% for 24 hours. During the curing process, perform ultrasonic vibration treatment at 20kHz every 8 hours for 5 minutes each time. After the low-temperature curing is completed, perform pre-drying treatment at a drying temperature of 60℃ for 8 hours and a drying rate of 5℃ / h. S5. High-temperature sintering: A gradient heating sintering process is adopted, with the following specific procedure: the temperature is raised from room temperature to 200℃ at a rate of 5℃ / min and held for 1 hour; then raised to 600℃ at a rate of 3℃ / min and held for 2 hours; finally raised to 1000℃ at a rate of 2℃ / min and held for 3 hours. During the sintering process, an inert gas with a nitrogen to argon volume ratio of 1:0.5 and a gas flow rate of 0.5L / min is introduced. After sintering, a combination of natural cooling and forced cooling is used to control the cooling rate at 10℃ / min. After cooling to room temperature, the surface of the casting is polished (polishing accuracy Ra≤0.8μm) and coated with a 1mm thick environmentally friendly anti-corrosion coating (water-based acrylic resin to nano titanium dioxide mass ratio of 1:0.1) to obtain the finished product.

[0017] Example 2

[0018] The present invention proposes a preparation process for a green, energy-saving, lightweight, and high-strength castable, the specific steps of which are as follows: S1. Raw material pretreatment: Construction solid waste (waste mortar blocks) is selected, crushed, screened in three stages (to obtain aggregates with particle sizes of 3-5mm, 1-3mm, and 0.15-1mm respectively, with a mass ratio of 1:1.8:2.8), and magnetically separated to remove impurities. After washing, the aggregates are washed for 18 minutes, and the mud content is controlled to be ≤1.0%. Then, high-temperature roasting activation treatment is carried out at a roasting temperature of 720℃ and a holding time of 2.5h. During the roasting process, oxygen-enriched gas with an oxygen mass fraction of 10% is introduced, and silane coupling agent (γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane in a mass ratio of 1:0.9) is added simultaneously, accounting for 0.8% of the mass of construction solid waste, to modify the surface and obtain green recycled aggregates. S2. Composite Ingredient Mixing: Prepare raw materials according to the following mass ratio: 50 parts green recycled aggregate, 20 parts lightweight insulation component, 25 parts high-performance cementitious material, 3.5 parts environmentally friendly modifier, and 10 parts water; wherein, the lightweight insulation component is a mixture of hollow glass microspheres (particle size 20-80μm, bulk density 0.22g / cm³) and cenospheres (particle size 50-150μm, bulk density 0.26g / cm³), with a mass ratio of 1:1.2. The hollow glass microspheres are pretreated with 2% titanate coupling agent at 70℃ for 45min, and the cenospheres are pretreated with 1.4% aluminate coupling agent at 70℃ for 45min; the high-performance cementitious material is sulfur... The compound of aluminate cement, metakaolin, and slag powder (mass ratio 1:0.45:0.3), with a slag powder specific surface area of ​​450 m² / kg, is pretreated with 3% (mass fraction) activator (sodium hydroxide and water glass mass ratio 1:1.5). The environmentally friendly modifier is a compound of water-reducing agent, retarder, and reinforcing agent (mass ratio 1:0.3:0.4). The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent with a solid content of 45%. The retarder is a compound of citric acid and sodium gluconate mass ratio 1:0.8. The reinforcing agent is a compound of nano-silica and nano-alumina with a particle size of 20-50 nm and a specific surface area of ​​180 m² / g, which is surface modified with 1.5% (mass fraction) silane coupling agent. Green recycled aggregate, high-performance cementitious materials and environmentally friendly modifiers are added to a planetary mixer and dry-mixed at 180 r / min for 12 min. Then, pretreated lightweight insulation components and 70% water are added and wet-mixed at 280 r / min for 25 min to obtain a uniform base material. S3. Gradient Foaming Molding: Add 2.2% (by weight of the base material) of a composite foaming agent (hydrogen peroxide to ammonium bicarbonate in a mass ratio of 1:0.65) to the base material, and simultaneously add the remaining 30% water. Add 0.35% (by weight of the composite foaming agent) of a foaming stabilizer (gelatin to xanthan gum in a mass ratio of 1:0.45). Stir at 320 r / min for 6.5 min, using a gradient heating method during stirring, gradually increasing the temperature from room temperature to 45℃ at a rate of 2.5℃ / min. Inject the stirred foamed slurry into a heat-insulating mold (with a 0.8 mm thick water-based release agent coated on the inner wall, the release agent being a mixture of polyvinyl alcohol, glycerin, and water in a mass ratio of 1:0.65:12). Use a vibration and negative pressure co-molding process, with a vibration frequency of 65 Hz, a vibration time of 4 min, a negative pressure of -0.04 MPa, and a negative pressure holding time of 3 min. After 12 min of foaming, perform a second material replenishment, with the replenishment amount being 4% of the mold volume.

[0019] S4. Low-temperature curing: Place the formed blank in a constant temperature and humidity curing chamber at a curing temperature of 25℃ and a relative humidity of 90% for 36 hours. During the curing process, perform ultrasonic vibration treatment at 30kHz every 8 hours for 8 minutes each time. After the low-temperature curing is completed, perform pre-drying treatment at a drying temperature of 70℃ for 10 hours and a drying rate of 6.5℃ / h.

[0020] S5. High-Temperature Sintering: A gradient heating sintering process is adopted, with the following specific steps: heating from room temperature to 200℃ at a rate of 6.5℃ / min and holding for 1.5h; then heating to 650℃ at a rate of 4℃ / min and holding for 2.5h; finally heating to 1050℃ at a rate of 2.5℃ / min and holding for 4h; during the sintering process, an inert gas with a nitrogen to argon volume ratio of 1:0.65 is introduced at a flow rate of 0.75L / min; after sintering, a combination of natural and forced cooling is used to control the cooling rate at 12℃ / min. After cooling to room temperature, the surface of the casting is polished (polishing accuracy Ra≤0.8μm) and coated with a 1.5mm thick environmentally friendly anti-corrosion coating (water-based acrylic resin to nano titanium dioxide mass ratio of 1:0.15) to obtain the finished product.

[0021] Example 3

[0022] The present invention proposes a preparation process for a green, energy-saving, lightweight, and high-strength castable, the specific steps of which are as follows: S1. Raw material pretreatment: Construction solid waste (brick and concrete waste blocks) is selected, crushed, screened in three stages (to obtain aggregates with particle sizes of 3-5mm, 1-3mm, and 0.15-1mm respectively, with a mass ratio of 1:2.0:3.0), and magnetically separated to remove impurities. After washing with water for 20 minutes, the mud content of the aggregate after washing is controlled to be ≤1.0%. Then, high-temperature roasting activation treatment is carried out at a roasting temperature of 800℃ and a holding time of 3 hours. During the roasting process, oxygen-enriched gas with an oxygen mass fraction of 12% is introduced, and silane coupling agent (γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane in a mass ratio of 1:1.2) is added simultaneously to modify the surface and obtain green recycled aggregate.

[0023] S2. Composite Ingredient Mixing: Prepare raw materials according to the following mass ratio: 60 parts green recycled aggregate, 25 parts lightweight insulation component, 30 parts high-performance cementitious material, 5 parts environmentally friendly modifier, and 12 parts water; wherein, the lightweight insulation component is a mixture of hollow glass microspheres (particle size 20-80μm, bulk density 0.25g / cm³) and cenospheres (particle size 50-150μm, bulk density 0.30g / cm³), with a mass ratio of 1:1.5. The hollow glass microspheres are pretreated with 3% titanate coupling agent at 80℃ for 60min, and the cenospheres are pretreated with 2% aluminate coupling agent at 80℃ for 60min; the high-performance cementitious material is sulfur... The compound of aluminate cement, metakaolin, and slag powder (mass ratio 1:0.6:0.4), with a slag powder specific surface area of ​​500 m² / kg, is pretreated with 4% by mass of an activator (sodium hydroxide and water glass mass ratio 1:1.8). The environmentally friendly modifier is a compound of water-reducing agent, retarder, and reinforcing agent (mass ratio 1:0.4:0.5). The water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent with a solid content of 50%. The retarder is a compound of citric acid and sodium gluconate in a mass ratio of 1:1.0. The reinforcing agent is a compound of nano-silica and nano-alumina with a particle size of 20-50 nm and a specific surface area of ​​200 m² / g, which is surface modified with 2% by mass of a silane coupling agent. Green recycled aggregate, high-performance cementitious materials and environmentally friendly modifiers are added to a planetary mixer and dry-mixed at 200 r / min for 15 min. Then, pretreated lightweight heat insulation components and 70% water are added and wet-mixed at 300 r / min for 30 min to obtain a uniform base material.

[0024] S3. Gradient Foaming Molding: Add 3% (by weight of the base material) of composite foaming agent (hydrogen peroxide to ammonium bicarbonate in a mass ratio of 1:0.8) to the base material, and simultaneously add the remaining 30% of water. Add 0.5% (by weight of the composite foaming agent) of foaming stabilizer (gelatin to xanthan gum in a mass ratio of 1:0.6). Stir at 350 r / min for 8 min, using a gradient heating method during stirring, gradually increasing the temperature from room temperature to 50℃ at a rate of 3℃ / min. Inject the stirred foamed slurry into a heat-insulating mold (with a 1.0 mm thick water-based release agent coated on the inner wall, the release agent being a mixture of polyvinyl alcohol, glycerin, and water in a mass ratio of 1:0.8:15). Use a vibration and negative pressure co-molding process, with a vibration frequency of 80 Hz, a vibration time of 5 min, a negative pressure of -0.05 MPa, and a negative pressure holding time of 4 min. After foaming begins, perform a second material replenishment 15 min later, with the replenishment amount being 5% of the mold volume.

[0025] S4. Low-temperature curing: Place the formed blank in a constant temperature and humidity curing chamber at a curing temperature of 30℃ and a relative humidity of 95% for 48 hours. During the curing process, perform ultrasonic vibration treatment at 40kHz every 8 hours for 10 minutes each time. After the low-temperature curing is completed, perform pre-drying treatment at a drying temperature of 80℃ for 12 hours and a drying rate of 8℃ / h.

[0026] S5. High-Temperature Sintering: A gradient heating sintering process is adopted, with the following specific procedure: the temperature is raised from room temperature to 200℃ at a rate of 8℃ / min and held for 2 hours; then raised to 700℃ at a rate of 5℃ / min and held for 3 hours; finally, the temperature is raised to 1100℃ at a rate of 3℃ / min and held for 5 hours. During the sintering process, an inert gas with a nitrogen to argon volume ratio of 1:0.8 is introduced at a flow rate of 1.0 L / min. After sintering, a combination of natural and forced cooling is used to control the cooling rate at 15℃ / min. After cooling to room temperature, the surface of the casting is polished (polishing accuracy Ra≤0.8μm) and coated with a 2mm thick environmentally friendly anti-corrosion coating (water-based acrylic resin to nano titanium dioxide mass ratio of 1:0.2) to obtain the finished product.

[0027] Experimental Section I. Experimental Objective The feasibility and superiority of the green, energy-saving, lightweight, and high-strength castable preparation process were verified.

[0028] II. Experimental Materials 1. Experimental Samples: Castable finished products prepared according to the corresponding preparation processes of Examples 1, 2, and 3, with 3 parallel samples prepared for each group; Comparative Examples 1 and 2 are based on the raw material ratio of Example 3, but lack the corresponding innovative process to prepare the castable finished product, with 3 parallel samples prepared for each group as well.

[0029] 2. Source of raw materials: Construction solid waste (waste concrete blocks, waste mortar blocks, and waste brick-concrete blocks) was taken from a construction demolition site; hollow glass microspheres and cenospheres were purchased from a new material technology company; sulfoaluminate cement, metakaolin, and slag powder were qualified industrial-grade products; silane coupling agent, titanate coupling agent, and other additives were all analytical grade reagents; and the experimental water was deionized water.

[0030] 3. Testing instruments: Electronic universal testing machine (model: WDW-100), fully automatic density tester (model: MDJ-300A), thermal conductivity meter (model: DRM-III), constant temperature and humidity curing chamber (model: YH-40B), high temperature sintering furnace (model: SX2-12-16), etc. All instruments have been metrologically calibrated and qualified.

[0031] III. Experimental Testing Standards 1. Bulk density: According to Clause 5.2 of "Test Methods for Lightweight Castables" (GB / T50726-2011), the water displacement method was used for determination, and the average value of 3 parallel samples was taken as the final result.

[0032] 2. Compressive strength: In accordance with Clause 6.3 of "Test Methods for Refractory Castables" (GB / T30873-2014), the samples were processed into 40mm×40mm×40mm test blocks. After standard curing, the compressive strength test was carried out using an electronic universal testing machine with a loading rate of 0.5MPa / s. The average value of 3 parallel samples was taken.

[0033] 3. Thermal conductivity: According to the "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method" (GB / T10294-2008), the value was measured at an average temperature of 25℃, and the average value of 3 parallel samples was taken.

[0034] 4. Environmental performance: The utilization rate of construction solid waste is calculated as the ratio of the actual amount added to the total mass of raw materials; the emission of harmful gases is measured using a gas detector during the sintering process, in accordance with the "Integrated Emission Standard of Air Pollutants" (GB16297-1996). , Concentration of harmful gases, etc.

[0035] IV. Comparison Settings 1. Comparative Example 1 (lacking gradient foaming molding process): The raw material ratio is completely the same as in Example 3, except that gradient heating and stirring are cancelled (stirring is done at room temperature of 25°C), vibration-negative pressure co-molding is cancelled (normal casting and natural molding is done), and the remaining process steps (raw material pretreatment, batching and mixing, low temperature curing, and high temperature sintering) are the same as in Example 3.

[0036] 2. Comparative Example 2 (Missing Raw Material Composite Modification Process): The raw material ratio is completely consistent with Example 3. The construction solid waste is only crushed, screened, and impurity removed. High-temperature roasting activation and silane coupling agent surface modification are omitted. The lightweight thermal insulation component (insulating glass microspheres + cenospheres) is not pretreated with coupling agent. The slag powder in the high-performance cementitious material is exempt from activator pretreatment. All other process steps are the same as in Example 3.

[0037] V. Experimental Data Results The core performance test results of each experimental group and the comparative sample are shown in the table below (all data are the average of 3 parallel samples):

[0038] VI. Experimental Analysis 1. Performance Analysis of Examples: The castables prepared in Examples 1, 2, and 3 all meet the core requirements of "lightweight, high-strength, and energy-saving". Their bulk density is ≤1.2 g / cm³, compressive strength is ≥32 MPa, thermal conductivity is ≤0.11 W / (m·K), and the utilization rate of construction solid waste is ≥78%, with no harmful gas emissions. Example 3 exhibits the best overall performance, with a compressive strength of 38.6 MPa and a thermal conductivity as low as 0.09 W / (m·K). This is because Example 3 uses a better raw material gradation (three-stage sieved aggregate mass ratio of 1:2.0:3.0), more thorough raw material modification treatment (high-dose coupling agent, high-temperature long-time calcination), and more reasonable process parameters (high-frequency vibration, strong negative pressure molding, long-time high-temperature sintering). The synergistic effect of each process step maximizes the improvement of the castable performance.

[0039] 2. Analysis of the Impact of Innovative Processes: Comparing Example 3 and Comparative Example 1, it can be seen that without the gradient foaming molding process, the bulk density of Comparative Example 1 increased by 17.4%, the compressive strength decreased by 37.3%, and the thermal conductivity increased by 88.9%. This is because gradient heating and stirring can cause the foaming agent to decompose evenly, generating fine bubbles, and vibration-negative pressure synergistic molding can remove air from the slurry and promote uniform bubble distribution. Without this process, the bubble size is uneven, and the slurry density decreases, leading to a simultaneous deterioration in both lightweight and high-strength properties. Comparing Example 3 and Comparative Example 2, it can be seen that without the raw material composite modification process, the compressive strength of Comparative Example 2 decreased by 44.3%, and the thermal conductivity increased by 77.8%. This is mainly because the unmodified construction solid waste resulted in weak interfacial bonding with the cementitious material, the lightweight insulation component lacked pretreatment leading to poor dispersibility, and the slag powder lacked activation, resulting in insufficient activity. Ultimately, these factors affected the mechanical and insulation properties of the castable.

[0040] 3. Environmental performance analysis: No harmful gas emissions were detected in any of the experimental groups and the comparative examples, and the utilization rate of construction solid waste was relatively high. This indicates that the process of the present invention achieves lightweight and high-strength performance while taking into account environmental protection. By utilizing construction solid waste resources, solid waste pollution is reduced, which meets the needs of green development.

[0041] VII. Experimental Conclusions 1. The green, energy-saving, lightweight, and high-strength castable preparation process proposed in this invention is feasible. The finished products prepared in Examples 1, 2, and 3 can all meet the requirements of bulk density ≤1.2g / cm³, compressive strength ≥30MPa, and thermal conductivity ≤0.12W / (m·K), and have excellent environmental performance.

[0042] 2. The gradient foaming molding process and the raw material composite modification process are the core innovations of this invention. The synergistic effect of the two can significantly improve the lightweight level, mechanical properties and thermal insulation properties of the castable. Their absence will lead to a significant drop in performance, proving that this innovative process is irreplaceable.

[0043] 3. The combination of process parameters in Example 3 (aggregate gradation 1:2.0:3.0, calcination at 800℃ for 3 hours, vibration molding at 80Hz, sintering at 1100℃ for 5 hours, etc.) is the optimal solution, and the castable prepared by it has the best comprehensive performance. It can be promoted and applied as a preferred process.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A preparation process for a green, energy-saving, lightweight, high-strength castable, characterized in that, Includes the following steps: S1. Raw material pretreatment: After crushing, screening and magnetic separation to remove impurities from construction solid waste, green recycled aggregate is obtained through high-temperature roasting activation and surface modification. S2. Composite Ingredient Mixing: Green recycled aggregate, lightweight thermal insulation components, high-performance cementitious materials, environmentally friendly modifiers and water are mixed and stirred in a specific ratio to obtain a uniform base material; S3, Gradient foaming molding: A composite foaming agent is added to the base material, and after gradient heating and stirring, it is injected into the mold and molded using a vibration and negative pressure combined process. S4. Low-temperature curing: The molded blank is cured at constant temperature and humidity, supplemented by ultrasonic vibration treatment, and pre-dried after curing. S5. High-temperature sintering: The pre-dried green body is sintered using a gradient heating sintering process. Inert gas is introduced for protection during the sintering process, and the finished product is obtained by cooling after sintering. The raw materials include green recycled aggregate, lightweight insulation components, high-performance cementitious materials, environmentally friendly modifiers, composite foaming agents, and water.

2. The preparation process of the green, energy-saving, lightweight, and high-strength castable according to claim 1, characterized in that, The raw material pretreatment includes: crushing, screening, and magnetic separation to remove impurities from construction solid waste, followed by high-temperature roasting activation treatment. The roasting temperature is controlled at 650-800℃, and the holding time is 2-3 hours to obtain green recycled aggregate with a particle size of 0.15-5mm. During the high-temperature roasting activation process, oxygen-enriched gas with an oxygen mass fraction of 8-12% is introduced, and 0.5-1.2% of a silane coupling agent by mass of construction solid waste is added simultaneously for surface modification to improve the interfacial bonding strength between the recycled aggregate and the cementitious material. The silane coupling agent is a compound of γ-aminopropyltriethoxysilane and γ-methacryloyloxypropyltrimethoxysilane, with a mass ratio of 1:0.6-1.

2.

3. The preparation process of the green, energy-saving, lightweight, and high-strength castable according to claim 1, characterized in that, In the compounding step, the mass ratio of each component of the raw materials is as follows: 40-60 parts of green recycled aggregate, 15-25 parts of lightweight thermal insulation component, 20-30 parts of high-performance cementitious material, 2-5 parts of environmentally friendly modifier, and 8-12 parts of water. The lightweight thermal insulation component is a compound of insulating glass microspheres and cenospheres. The insulating glass microspheres have a particle size of 20-80 μm and a bulk density of 0.18-0.25 g / cm³, while the cenospheres have a particle size of 50-150 μm and a bulk density of 0.22-0.30 g / cm³. The mass ratio of the two is 1:0.8-1.

5. The insulating glass microspheres are pretreated with 1-3% by mass of titanate coupling agent, and the cenospheres are pretreated with 0.8-2% by mass of aluminate coupling agent. The pretreatment temperature is 60-80℃, and the treatment time is 30-60 min.

4. The preparation process of the green, energy-saving, lightweight, and high-strength castable according to claim 1, characterized in that, The gradient foaming molding step is as follows: First, green recycled aggregate, high-performance cementitious materials, and environmentally friendly modifiers are added to a planetary mixer and dry-mixed at 150-200 r / min for 10-15 min. Then, pretreated lightweight insulation components and 70% water are added and wet-mixed at 250-300 r / min for 20-30 min to obtain the base material. Subsequently, 1.5-3% of a composite foaming agent by weight of the base material is added to the base material, while the remaining 30% water is added, and the mixture is stirred at 3... Stir at a speed of 00-350 r / min for 5-8 minutes, using a gradient heating method during the stirring process, gradually increasing the temperature from room temperature to 40-50℃ at a heating rate of 2-3℃ / min; inject the stirred foamed slurry into the mold, and use a vibration and negative pressure co-molding process, with a vibration frequency of 50-80Hz and a vibration time of 3-5 minutes, a negative pressure of -0.03~-0.05MPa, and a negative pressure holding time of 2-4 minutes to achieve uniform foaming and dense stacking of the slurry.

5. The preparation process of the green, energy-saving, lightweight, and high-strength castable according to claim 4, characterized in that, The composite foaming agent is a mixture of hydrogen peroxide and ammonium bicarbonate, with a mass ratio of 1:0.5-0.

8. A foaming stabilizer, comprising 0.2-0.5% of the composite foaming agent's mass, is added. This foaming stabilizer is a mixture of gelatin and xanthan gum, with a mass ratio of 1:0.3-0.

6. The high-performance cementitious material is a mixture of sulfoaluminate cement, metakaolin, and slag powder, with a mass ratio of 1:0.3-0.6:0.2-0.

4. The slag powder has a specific surface area of ​​400-500 m² / kg and is pretreated with an activator comprising 2-4% by mass. This activator is a mixture of sodium hydroxide and water glass, with a mass ratio of 1:1.2-1.

8.

6. The preparation process of the green, energy-saving, lightweight, and high-strength castable according to claim 1, characterized in that, The low-temperature curing step is as follows: the formed green body is placed in a constant temperature and humidity curing chamber, the curing temperature is controlled at 20-30℃, the relative humidity is 85-95%, and the curing time is 24-48h; during the curing process, ultrasonic vibration treatment is performed every 8h, the ultrasonic frequency is 20-40kHz, and the treatment time is 5-10min, so as to promote the uniform diffusion of moisture and the full hydration reaction; after the low-temperature curing is completed, the green body is pre-dried, the drying temperature is 60-80℃, the drying time is 8-12h, and the drying rate is controlled at 5-8℃ / h to avoid cracks in the green body due to rapid drying.

7. The preparation process of the green, energy-saving, lightweight, and high-strength castable according to claim 1, characterized in that, The high-temperature sintering step adopts a gradient heating sintering process. The specific heating program is as follows: from room temperature to 200℃, the heating rate is 5-8℃ / min, and the temperature is held for 1-2 hours; then the temperature is raised to 600-700℃, the heating rate is 3-5℃ / min, and the temperature is held for 2-3 hours; finally, the temperature is raised to 1000-1100℃, the heating rate is 2-3℃ / min, and the temperature is held for 3-5 hours. During the sintering process, an inert gas is introduced for protection. The inert gas is a mixture of nitrogen and argon with a volume ratio of 1:0.5-0.8 and a gas flow rate of 0.5-1.0 L / min. After sintering, the temperature is lowered by a combination of natural cooling and forced cooling, with the cooling rate controlled at 10-15℃ / min. After cooling to room temperature, a green, energy-saving, lightweight, and high-strength castable is obtained.

8. The preparation process of the green, energy-saving, lightweight, and high-strength castable according to claim 1, characterized in that, The environmentally friendly modifier includes a water-reducing agent, a retarder, and a reinforcing agent, with a mass ratio of 1:0.2-0.4:0.3-0.

5. Among them, the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent with a solid content of 40-50% and a water reduction rate of ≥30%; the retarder is a compound of citric acid and sodium gluconate with a mass ratio of 1:0.6-1.0; the reinforcing agent is a compound of nano-silica and nano-alumina with a particle size of 20-50nm and a specific surface area of ​​150-200m² / g, and is surface-modified with a silane coupling agent at a mass fraction of 1-2%.

9. The preparation process of the green, energy-saving, lightweight, and high-strength castable according to claim 1, characterized in that, In the raw material pretreatment process, after the construction solid waste is crushed, a three-stage screening process is adopted to obtain recycled aggregates with particle sizes of 3-5mm, 1-3mm, and 0.15-1mm, respectively. The mass ratio of the three particle sizes of recycled aggregates is 1:1.5-2.0:2.5-3.0, so as to achieve continuous gradation of aggregates and improve the bulk density and strength properties of castables. After the three-stage screening, water washing is required, and the washing time is 15-20 minutes. The mud content of the recycled aggregates after washing is ≤1.0%.

10. The preparation process of the green, energy-saving, lightweight, and high-strength castable according to claim 1, characterized in that, In the gradient foaming molding step, the mold is a heat-insulating mold, and the inner wall of the mold is coated with a release agent with a thickness of 0.5-1.0 mm. The release agent is a water-based release agent, which is made by mixing polyvinyl alcohol, glycerin and water in a mass ratio of 1:0.5-0.8:10-15. After the foaming slurry is injected into the mold, a secondary material replenishment process is required. The replenishment time is 10-15 minutes after the start of foaming, and the replenishment amount is 3-5% of the mold volume to compensate for the volume shrinkage during the foaming process and ensure the dimensional accuracy of the casting. After the high-temperature sintering is completed, the casting is surface polished with a polishing accuracy of Ra≤0.8μm. At the same time, an environmentally friendly anti-corrosion coating with a thickness of 1-2 mm is coated on the surface. The coating material is a compound of water-based acrylic resin and nano titanium dioxide in a mass ratio of 1:0.1-0.2.

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