Green cast-in-situ high-strength light-weight foam concrete

Abstract

The application discloses green cast-in-situ high-strength light-weight foam concrete and belongs to the technical field of new materials. The concrete comprises cement 30-50 parts by weight, light-weight foam aggregate 20-40 parts by weight, fine aggregate 15-30 parts by weight, water 15-25 parts by weight, foaming agent 0.1-1.0 parts by weight, mineral admixture 5-15 parts by weight and chemical additive 0.1-2 parts by weight. The chemical additive contains high-efficiency water-reducing agent, modified retarder and air entraining agent, and the weight ratio is (5-7):(2-3):(1-2). The mechanical properties (compressive strength 20.5-24.5 MPa), durability (water absorption 3.4-4.0%) and construction performance (slump 162-175 mm) are remarkably improved by virtue of the modified retarder, nano-modified light-weight foam aggregate and fine aggregate, and the optimization of mixing proportion and preparation process. The carbon footprint is reduced by using industrial by-products, and the green environmental protection and economy are realized. The application is suitable for cast-in-situ high-strength light-weight structure, and has the advantages of light weight, high strength, durability and construction convenience, and provides a sustainable solution for modern engineering.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically, it relates to a green cast-in-place high-strength lightweight foamed concrete. Background Technology

[0002] Concrete, as the most widely used basic building material in contemporary civil engineering, occupies an irreplaceable position in infrastructure construction such as housing, roads and bridges, and water conservancy and hydropower projects due to its numerous advantages, including abundant raw material sources, relatively simple production processes, excellent mechanical properties, and good durability. While traditional ordinary Portland cement concrete boasts excellent comprehensive performance, its apparent density is relatively high (typically 2300-2500 kg / m³). 3 Self-weight load accounts for an important proportion in structural design, especially in high-rise buildings, large-span structures, and projects with special requirements for foundation bearing capacity. The self-weight of ordinary concrete not only increases the structural burden and limits the innovation of structural forms, but also leads to an increase in material consumption and transportation costs.

[0003] To overcome the heavy weight of traditional concrete and meet the demands of modern engineering structures for lightweight, high-rise, large-span, energy-saving, and environmentally friendly construction, lightweight concrete has emerged and developed rapidly. Lightweight concrete typically refers to concrete with an apparent density below 1950 kg / m³. 3 Lightweight concrete achieves its weight reduction goals by using lightweight aggregates, introducing numerous pores, or a combination of both. Depending on the type of aggregate and the pore formation method, lightweight concrete can be divided into lightweight aggregate concrete and porous concrete (such as foamed concrete and aerated concrete). Lightweight concrete not only effectively reduces structural self-weight, decreases foundation load, and saves material usage, but also, due to its porous structure, often possesses excellent thermal insulation, sound absorption, and noise reduction properties, showing broad application prospects in wall materials, roof insulation, and roadbed filling.

[0004] Foamed concrete, also known as aerated concrete or lightweight porous concrete, is a porous lightweight building material formed by introducing a large number of stable, uniform, and closed air bubbles into a cementitious slurry through physical or chemical methods, followed by mixing, pouring, and curing. Its main components include cementitious materials (cement, lime, etc.), water, and foaming agents, and fine aggregates, lightweight aggregates, mineral admixtures, and chemical additives can be added according to performance requirements. The apparent density of foamed concrete typically ranges from 300 to 1800 kg / m³. 3Adjustable within a certain range, it has a series of advantages such as lightweight and high fluidity, low elastic modulus, good thermal insulation performance, excellent sound absorption and sound insulation effect, good impermeability, fire resistance and convenient construction. It is widely used in self-insulating wall blocks, cast-in-place walls, roof insulation layers, underfloor heating underlayment, soft soil filling in road expansion, bridge abutment backfill, pipeline backfill and landscaping.

[0005] However, traditional foamed concrete still faces many challenges in practical applications, which to some extent limit its promotion in the fields of high-strength, high-durability structural load-bearing and enclosure structures: The contradiction between strength and density: The strength of foamed concrete is closely related to its apparent density. Typically, to obtain lower density and achieve better lightweight and thermal insulation effects, more pores need to be introduced. However, this leads to thinner pore walls and more pore structure defects, significantly reducing the material's mechanical properties, especially compressive and flexural strength. Traditional foamed concrete often struggles to simultaneously meet the requirement of low density (e.g., 10 MPa), limiting its application to non-load-bearing or low-strength applications. Poor pore structure stability and uniformity: The introduction and stabilization of foam are crucial for foamed concrete preparation. Improper selection of foaming agents, insufficient foam stabilization measures, or imprecise construction process control can easily lead to bubble coalescence, coarsening, or even rupture during mixing, pumping, or pouring, resulting in uneven pore size distribution, excessively large pores, and an increase in interconnected pores. An undesirable pore structure deteriorates the mechanical properties and durability of foamed concrete. High water absorption and durability issues: Due to its numerous pores, some of which may be open or interconnected, traditional foamed concrete generally has a high water absorption rate. This high absorption rate not only reduces its thermal insulation performance but also leads to a series of durability problems, such as poor freeze-thaw resistance (repeated freeze-thaw cycles in the pores generate expansion stress that damages the structure), easy carbonization (CO2 intrudes through the pores and reacts with Ca(OH)2), and susceptibility to chemical corrosion (harmful ions penetrate through the water), affecting its long-term service performance and lifespan. Poor volume stability and prone to cracking: Foamed concrete, especially formulations with high cement content, is prone to significant shrinkage during hydration, hardening, and drying, including chemical shrinkage, autogenous shrinkage, and drying shrinkage. High porosity weakens its resistance to deformation, making it difficult to effectively release shrinkage stress, resulting in surface and internal cracks, affecting the structural integrity and aesthetics, and even reducing thermal and sound insulation effects. Poor aggregate-matrix interface performance: In foamed concrete that partially uses lightweight aggregates (such as expanded clay aggregate, expanded perlite, etc.), the lightweight aggregates themselves have low strength, surface inertness, and high water absorption, easily forming a weak interfacial transition zone (ITZ) with the cement matrix. This region has high porosity, loose structure, and poor crystal orientation, resulting in low bond strength between the aggregate and the matrix. Under external forces, it easily becomes a path for crack propagation, limiting the improvement of the overall mechanical properties of foamed concrete. The degree of greening needs improvement: The preparation of traditional foamed concrete still uses ordinary Portland cement as the main cementing material, while the cement production process involves a large amount of energy consumption and CO2 emissions. How to make greater use of industrial waste (such as fly ash, slag powder, silica fume, desulfurized gypsum, waste glass powder, etc.) as alternative cementing materials or functional admixtures, reduce cement usage, and reduce environmental impact, is an important direction for achieving green and sustainable development of foamed concrete.

[0006] To address the aforementioned issues, researchers both domestically and internationally have conducted extensive research. For example, they have improved the uniformity and stability of pore structures by optimizing the types of foaming agents and foam-stabilizing techniques; introduced high-efficiency water-reducing agents to improve the rheological properties of slurries and reduce the water-cement ratio to increase matrix strength; added active mineral admixtures such as silica fume and fly ash to utilize their pozzolanic effect and micro-filling effect to improve pore structure, increase matrix density and strength, and reduce cement usage; used fibers (such as polypropylene fibers, steel fibers, and glass fibers) for reinforcement and toughening to inhibit shrinkage cracking; performed surface modification or pretreatment on lightweight aggregates to enhance their interfacial bonding with the cement matrix; and developed composite foaming technologies and special curing processes.

[0007] Despite some progress, existing technologies still fall short in systematically addressing the multiple challenges of achieving a balance between low density, high strength, excellent durability, good workability, and environmental friendliness in foamed concrete. Particularly in the field of cast-in-place high-strength lightweight foamed concrete, the challenge lies in how to optimize material composition design, achieve high-performance preparation of key raw materials (such as lightweight aggregates and fine aggregates), and synergistically regulate admixtures to maintain a low apparent density (e.g., 1500-1600 kg / m³). 3 Achieving high compressive strength (e.g., >20MPa) and significantly improving its durability properties such as crack resistance, impermeability, and freeze-thaw resistance, while also considering ease of construction and environmental friendliness, remains a pressing technical challenge in this field. Developing a high-strength, lightweight foamed concrete with scientifically formulated components, superior performance, environmental friendliness, and the ability to meet the requirements of cast-in-place construction is of significant theoretical and practical value for promoting its application in a wider range of engineering fields, especially in structural components with higher material performance requirements. Summary of the Invention

[0008] 1. The problem to be solved

[0009] To address the aforementioned issues, this invention innovatively designs modified retarders, develops high-performance lightweight foamed aggregates and functionalized fine aggregates, and optimizes mix design and preparation processes. The aim is to obtain a green cast-in-place foamed concrete that combines high strength, lightweight, excellent durability, good workability, and environmental friendliness, providing technical support for promoting the widespread application of foamed concrete in demanding engineering structures.

[0010] 2. Technical Solution

[0011] To solve the above problems, the present invention adopts the following technical solution.

[0012] A green cast-in-place high-strength lightweight foamed concrete, comprising, by weight, the following components: cement: 30-50 parts, lightweight foamed aggregate: 20-40 parts, fine aggregate: 15-30 parts, water: 15-25 parts, foaming agent: 0.1-1.0 parts, mineral admixtures: 5-15 parts, chemical admixtures: 0.1-2 parts. The chemical admixtures include a high-efficiency water-reducing agent, a modified retarder, and an air-entraining agent, wherein the weight ratio of the high-efficiency water-reducing agent, the modified retarder, and the air-entraining agent is (5-7):(2-3):(1-2). The modified retarder is prepared as follows: sodium lignosulfonate (purity > 80%), an industrial byproduct, is selected and prepared at pH 10. Under -12°C conditions, the product was reacted with chloroacetic acid (CAS No. 79-11-8) at a molar ratio of 1:(2-6) and stirred in a water bath at 70-80°C for 4 hours to obtain a carboxylated product. The product was then dispersed in anhydrous ethanol at 10-20 times its mass of the carboxylated product, and 3-aminopropyltriethoxysilane (CAS No. 919-30-2) at 2-3 times its mass of the carboxylated product was added. The mixture was refluxed at 75-80°C for 6-8 hours to obtain a reflux product. The reflux product was then mixed with 4-vinylphenylboronic acid (CAS No. 2156-04-9) and azobisisobutyronitrile (CAS No. 78-67-1) at a mass ratio of 1:(2-4):0.5 and reacted at 65-75°C for 6-8 hours. The mixture was then freeze-dried under vacuum to obtain the final product. For the preparation method of the modified retarder, the following steps are taken: Carboxylation reaction (nucleophilic substitution-esterification reaction): Sodium lignosulfonate undergoes a nucleophilic substitution reaction between its phenolic hydroxyl group (-OH) and the α-chloro group of chloroacetic acid under alkaline conditions of pH 10-12 to generate a carboxymethylated product. Silanization reaction (sol-gel condensation): The carboxylated product is dispersed in ethanol and reacts with 3-aminopropyltriethoxysilane (APTES) through a hydrolysis-condensation reaction to generate a siloxane network. Free radical grafting reaction (boronic acid functionalization): Vinylphenylboronic acid is grafted onto the silanized product via free radical polymerization under the initiation of azobisisobutyronitrile (AIBN). Through the above multi-scale modification, this retarder achieves a synergistic improvement in retarding effect, dispersibility, and durability while maintaining its green and environmentally friendly nature (utilization of industrial by-products), providing key technical support for the cast-in-place construction of high-strength lightweight foamed concrete.

[0013] Preferably, the green cast-in-place high-strength lightweight foamed concrete comprises, by weight, the following components: cement: 35-45 parts, lightweight foamed aggregate: 25-32 parts, fine aggregate: 18-25 parts, water: 18-22 parts, foaming agent: 0.1-1.0 parts, mineral admixture: 8-12 parts, and chemical admixture: 0.8-1.5 parts.

[0014] Preferably, the green cast-in-place high-strength lightweight foamed concrete comprises the following components by weight: cement: 40 parts, lightweight foamed aggregate: 28 parts, fine aggregate: 22 parts, water: 20 parts, foaming agent: 0.7 parts, mineral admixture: 10 parts, and chemical admixture: 1.2 parts.

[0015] Preferably, the cement used is CEMI42.5 ordinary Portland cement, which meets the requirements of European standard EN197-1. It is mainly composed of clinker, with a clinker content between 95% and 100%. Chemical composition: by weight percentage, the main components are calcium oxide (60%-67%), silicon dioxide (17%-25%), aluminum oxide (3%-8%), and ferric oxide (0.5%-6%), with an alkali content (sodium oxide + potassium oxide) ≤0.6%.

[0016] Preferably, the preparation method of the lightweight foam aggregate is as follows: Raw material pretreatment: using waste glass or virgin glass as the substrate, crushing it to a particle size ≤90μm to obtain raw material particles; Nano-modifier preparation: mixing nano-alumina with a particle size of 10-50nm and nano-silica with a particle size of 20-60nm at a mass ratio of 1:(2-10), adding anhydrous ethanol at 30-50 times the mass of nano-alumina, ultrasonically dispersing for 30min to form a uniform suspension, and obtaining the nano-modifier; Functional doping: adding nano-titanium dioxide with a particle size of 100-200nm and magnesium chloride with a particle size of 50-100nm to the nano-modifier, wherein nano-titanium dioxide accounts for a certain percentage of the total mass of the nano-modifier. Add 5-15% of the raw material particles to silicon carbide (CAS No. 409-21-2) with a particle size ≤1μm at a mass ratio of (100-120):1, add 2-5 times the mass of deionized water of the raw material particles, and use a disc granulator to form wet particles with a diameter of 2-4mm; Pre-sintering: Under an argon atmosphere, heat the wet particles to 700±50℃ at 5℃ / min and hold for 30min to form a dense shell, obtaining pre-sintered particles; Sol-gel impregnation: Immerse the pre-sintered particles in the functionalized nano suspension. The mass ratio between the two is (2-3):(5-8). The mixture is subjected to a vacuum of -0.08 MPa for 20 min, then heated to 800℃ in argon at 10℃ / min and held for 20 min. The atmosphere is then switched to nitrogen, and the temperature is increased to 850-880℃ at 2℃ / min and held for 15 min. Finally, it is slowly cooled to 600℃ at 2℃ / min and allowed to cool naturally to form surface-modified aggregate particles. Chemical vapor deposition: Tetraethoxysilane (CAS No. 78-10-4) vapor is introduced at 300℃, maintaining the reaction chamber pressure within the range of 0.1-0.5 kPa, and controlling the tetraethoxysilane vapor flow rate to 0.5-1.0 g / min. The film thickness is controlled at ≤50nm, the deposition time is controlled at 30-60min, and the deposition rate is 0.8-1.5nm / min. Through real-time monitoring, a silica nanofilm with a thickness of ≤50nm is regenerated on the surface of the aggregate particles. Hot pressing densification: hot pressing is performed at 5MPa pressure and 400℃ for 10min, increasing the closed-cell rate to ≥85%. It should be noted that the temperature is increased from room temperature to 400℃ at a rate of 5-8℃ / min before hot pressing to ensure uniform release of internal stress in the particles and prevent microcracks caused by thermal shock. Particle size classification: particles with a gradation of 0.4-10mm are obtained by vibrating sieving, and the water absorption rate is ≤8% after 24h to obtain the product. The preparation method of lightweight foamed aggregate described in this invention significantly improves the mechanical properties and durability of the aggregate through a multi-scale modification process.Its mechanisms include: synergistic enhancement by nanoparticles – a highly active suspension is formed by nano-alumina (10-50nm) and silicon dioxide (20-60nm) at a mass ratio of 1:(2-10), which is then uniformly coated on the surface of glass particles by ultrasonic dispersion, enhancing interfacial bonding; functionalized doping control – the addition of nano-titanium dioxide (100-200nm) and magnesium chloride (50-100nm) exerts photocatalytic and grain boundary strengthening effects, respectively, reducing the sintering temperature and optimizing the pore structure; gradient sintering densification – after pre-sintering (700±50℃) to form a dense shell, sol-gel impregnation under vacuum negative pressure allows the nano-suspension to deeply penetrate. The process involves a step-by-step heating under an argon / nitrogen atmosphere (800℃→880℃) to promote solid-phase diffusion between nanoparticles and the matrix; chemical vapor deposition (CVD) sealing – tetraethoxysilane is pyrolyzed at 300℃ to generate a 50nm thick silica nanofilm, effectively sealing surface pores (deposition rate 0.8-1.5nm / min), combined with 5MPa hot pressing to achieve a closed-pore rate ≥85%; stress control process – the hot pressing stage uses a gradient heating of 5-8℃ / min to avoid thermal shock cracks, ultimately obtaining 0.4-10mm graded particles with a 24h water absorption rate ≤8%, and a strength improvement of more than 40% compared to traditional lightweight aggregates.

[0017] Preferably, the preparation method of the fine aggregate is as follows: Raw material screening: Industrial silicon-based solid waste and natural quartz sand are mixed at a mass ratio of 2:1, and then pulverized by airflow to a D90 particle size ≤30μm and a specific surface area ≥2.0m². 2 / g, to obtain the crushed raw material; Preparation of composite nanopowder A: Nano-silica with a particle size of 5-20nm and nano-titanium dioxide with a particle size of 10-30nm and deionized water are mixed at a mass ratio of (3-5):1:(15-25), and 0.3% of polycarboxylate dispersant (sodium polycarboxylate, CAS No. 62601-60-9) is added. After ultrasonic dispersion for 50min, composite nanopowder A is obtained by centrifugation washing and vacuum drying at 70℃; Preparation of nano-carbon suspension B: Graphene oxide (CAS No. 1034343-98-0) with a thickness <3nm and a sheet diameter of 0.3-1.5μm is mixed with direct Single-walled carbon nanotubes (CAS No. 308068-56-6) with a diameter of 1-2 nm and a length of 5-20 μm were mixed at a mass ratio of 1:(2-6) and transferred to N,N-dimethylformamide (CAS No. 68-12-2) solvent, which was 20-30 times the mass of graphene oxide. The mixture was then subjected to high-speed shear emulsification (controlled at a speed of 8000-12000 rpm) for 80 min to form a nano-carbon suspension B. The crushed raw material was then placed in a low-temperature plasma reactor, using argon / oxygen at a volume ratio of 5:1 as the working gas, with a total gas flow rate controlled at 50-100 sccm and a power of 400W for 10 m. Using a radio frequency (RF) power supply (13.56MHz), a silica nanofilm with a thickness of 15-30nm was deposited by chemical vapor deposition at 150℃ with tetramethoxysilane vapor introduced. The reaction chamber pressure was maintained within the range of 0.5-1.0kPa, the tetramethoxysilane vapor flow rate was controlled at 0.3-0.8g / min, and the deposition rate was 0.75-1.5nm / min. The thickness accuracy was ensured by real-time monitoring to obtain coated raw material particles. The coated raw material particles were then added to a mixture of composite nanopowder A, nano-carbon suspension B, aqueous epoxy emulsion (CAS No. 1675-54-3), and a deionized raw material. The preparation method of the composite slurry composed of deionized water is simple (all components need to be stirred and mixed for 20 minutes). The mass ratio of the coated raw material particles, composite nanopowder A, nano-carbon suspension B, and deionized water is (20-40):(1-3):(0.2-0.7):(50-70). The mixture is stirred at 1500 rpm for 30 minutes and then granulated using spray fluidized bed technology. The spray pressure is set at 0.2-0.5 MPa, the spray rate is controlled at 50-100 mL / min, the inlet temperature is 170-210℃, and the outlet temperature is 85-105℃. The average particle size is 0.2-1 mm.0mm core-shell structured microspheres; Low-temperature pre-sintering: Under nitrogen protection, the above-mentioned core-shell structured microspheres are heated by microwave at 12-18℃ / min to 520-580℃ and held for 40min to form a microporous structure; High-temperature main sintering: Under nitrogen atmosphere, the temperature is further increased to 900-960℃ at 8-12℃ / min and held for 50-70min to form a macroporous structure; Pulsed inert gas rapid cooling: After sintering, pulsed argon purging and vacuum suction are alternated. Rapidly cool to below 200℃ at a rate ≥35℃ / min to construct a gradient pore structure with a dense outer layer and a sparse inner layer, wherein the outer layer pore size is <30μm and the inner layer pore size is 30-150μm, to obtain preliminary fine aggregate; double chemical grafting: first, the preliminary fine aggregate is impregnated in an ethanol solution containing 1.5wt% vinyltrimethoxysilane and stirred at 65-75℃ for 2.5h; then impregnated in an aqueous solution containing 0.8wt% polyamide and cured at 75-80℃ for 1.5h to obtain modified fine aggregate. The fine aggregate preparation mechanism of this invention achieves performance optimization through multi-scale synergistic effects: Nanocomposite reinforcement - nano-silica (5-20nm) and titanium dioxide (10-30nm) are mixed in a 3-5:1 ratio to form a highly active composite powder, which is uniformly distributed by sodium polycarboxylate dispersant (0.3wt%), enhancing the density and chemical stability of the aggregate matrix; Carbon nanostructure regulation - graphene oxide (<3nm thickness) and single-walled carbon nanotubes (1-2nm diameter) are emulsified in DMF at a mass ratio of 1:2-6 through high-speed shearing (8000-12000rpm) to form a three-dimensional network, improving the toughness and conductivity of the aggregate; Surface nanocoating - low-temperature plasma treatment (Ar / O2=5:1, 400W) combined with chemical vapor deposition to generate A 15-30 nm thick silica film reduces surface energy and enhances interfacial bonding with cement. Gradient pore construction—microwave pre-sintering (520-580℃) forms micropores, high-temperature main sintering (900-960℃) constructs macropores, and alternating pulsed argon purging (200-300 sccm, 10-15 times / min) and vacuum suction (≤0.1 Pa) rapid cooling (≥35℃ / min) creates an outer dense, inner sparse structure (outer layer <30μm, inner layer 30-150μm). Chemical grafting reinforcement—dual grafting of vinyltrimethoxysilane (1.5wt%) and polyamide (0.8wt%) introduces active groups onto the aggregate surface, forming covalent bonds with cement hydration products, increasing interfacial bond strength to 1.80-2.00 MPa. This process results in a fine aggregate water absorption rate ≤4.0%, porosity of 3.6-4.1%, and a strength increase of over 40% compared to traditional aggregates.

[0018] The details of the rapid cooling method after sintering using alternating pulsed argon purging and vacuum suction are as follows: Recommended equipment is a tube furnace or box furnace with a rapid cooling module (such as the Nabertherm RHTH series or Carbolite Gero HTRH series), capable of withstanding high temperatures (≥1000℃) and supporting rapid atmosphere switching. The pulsed argon purging system includes a high-purity argon (Ar, purity ≥99.999%) gas source, a precision flow controller (MFC, flow range 0-500 sccm), an electromagnetic pulse valve (response time ≤0.1s), and high-temperature resistant stainless steel nozzles (nozzle orifice diameter 1-2mm, distributed on the top and side walls of the furnace to ensure uniform gas coverage). The pulse valve is controlled by a PLC (Programmable Logic Controller) to achieve periodic gas injection. Vacuum suction system: Equipped with a rotary vane vacuum pump (ultimate vacuum ≤0.1Pa, pumping speed ≥10L / s, such as Edwards RV series) or a turbomolecular pump (suitable for higher vacuum requirements), connected to high-temperature resistant vacuum tubing (material 316L stainless steel or quartz, temperature resistance ≥800℃) and a quick-switching valve (switching time ≤0.5s) to ensure rapid removal of hot gases and residual atmosphere from the furnace. Furnace design: The inner wall of the furnace is made of high-purity alumina ceramic or mullite material, which is high-temperature resistant and has low thermal conductivity, reducing heat loss; the furnace volume is adapted to the sample volume (recommended processing volume 0.5-2kg per batch), equipped with a porous ceramic tray (pore diameter 1-2mm) to place particles, ensuring gas flow and uniform cooling. Temperature monitoring system: Equipped with K-type or S-type thermocouples (accuracy ±1℃, response time ≤1s) to monitor the furnace and particle surface temperature in real time. The data is fed back to the control unit through a data acquisition system (such as NIDAQ) to automatically adjust cooling parameters. Safety and Exhaust Gas Treatment: The furnace body is equipped with over-temperature protection and pressure monitoring devices (pressure range -0.1 to 0.5 MPa) to prevent overpressure or vacuum failure; exhaust gas is treated by activated carbon adsorption and condenser (temperature -10℃) to recover trace volatiles, meeting environmental protection requirements. Operating Parameters and Procedures: Cooling Target: Rapidly cool from the high-temperature main sintering temperature (900-960℃) to below 200℃, with a cooling rate ≥35℃ / min, ensuring the formation of a gradient pore structure with a dense outer layer and a loose inner layer, avoiding particle cracking due to thermal stress. Pulse Argon Purging Parameters: Gas Flow Rate: The argon flow rate for each pulse is controlled at 200-300 sccm, with a duration of 1-2 seconds, precisely adjusted by MFC to ensure rapid removal of heat from the particle surface. Pulse Frequency: 10-15 pulses per minute (i.e., once every 4-6 seconds), set by PLC to avoid excessive cooling or particle scattering due to continuous purging. Purging pressure: Controlled at 0.2-0.4 MPa to ensure that the gas impact force is sufficient to disturb the thermal boundary layer on the particle surface without damaging the particle structure.Vacuum suction parameters: Suction time: Each vacuum suction lasts 3-5 seconds, alternating with argon purging. After suction, the furnace pressure drops to 0.5-1.0 Pa, quickly removing hot gas and residual moisture. Suction frequency: Synchronized with argon purging, alternating 10-15 times per minute to ensure efficient heat and atmosphere exchange. Vacuum pump power: Adjust the pump power according to the furnace volume, with a target pumping speed ≥10L / s to ensure rapid attainment of the target pressure. Alternation cycle: The alternation cycle between argon purging and vacuum suction is 6-8 seconds (1-2 seconds of purging + 3-5 seconds of suction), continuing until the particle temperature drops below 200℃ (15-25 minutes, depending on the initial temperature and particle quantity). Particle placement method: Particles are placed on a porous ceramic tray, spread in a single layer with a thickness ≤2cm and a particle spacing ≥1mm to ensure uniform gas and vacuum action. The tray can be slightly agitated using a low-frequency vibration device (frequency 5-10Hz) to prevent particle adhesion or uneven cooling. Operating Procedures: Sintering Completion: After high-temperature main sintering (900-960℃, holding for 50-70 min), turn off the heating power, keep the furnace door sealed, and prepare for rapid cooling. Initial Vacuuming: Start the vacuum pump and remove the residual atmosphere in the furnace until the pressure is ≤0.1 Pa, continue for 1-2 min to remove high-temperature volatiles and oxidizing gases. Alternating Cooling: Start the alternating pulsed argon purging and vacuum suction program, set the purging flow rate (200-300 sccm), pulse frequency (10-15 times / min), and suction time (3-5 s / time), and monitor the particle temperature in real time. Cooling Monitoring: Monitor the particle temperature through thermocouples to ensure a cooling rate ≥35℃ / min. When the temperature drops below 200℃, reduce the alternating frequency (to 5-8 times / min) or stop the operation, and allow it to cool naturally to room temperature. Particle Removal: After cooling to room temperature, restore atmospheric pressure, remove the particles, visually inspect the particle integrity, and discard any broken or adhered particles.

[0019] Preferably, the foaming agent is sodium bicarbonate (CAS No. 144-55-8), sodium dodecyl sulfate (CAS No. 151-21-3), or sodium fatty alcohol polyoxyethylene ether sulfate (CAS No. 68585-34-2).

[0020] Preferably, the mineral admixture is silica fume (CAS No. 69012-64-2), fly ash (CAS No. 68131-74-8), or slag powder (CAS No. 65996-69-2).

[0021] Preferably, the high-efficiency water-reducing agent is polycarboxylate ether (CAS No. 62601-60-9), sodium naphthalene sulfonic acid formaldehyde condensate (CAS No. 9084-06-4), or sodium acetone sulfonate (CAS No. 5324-84-5); the air-entraining agent is rosin soap (CAS No. 61790-51-0) or sodium lignosulfonate (CAS No. 8061-51-6).

[0022] The preparation method of green cast-in-place high-strength lightweight foamed concrete is as follows: Cement, mineral admixtures, lightweight foamed aggregate, and fine aggregate are uniformly mixed in a dry state for 3-5 minutes to obtain a dry mix. A foaming agent is dissolved in one-third of its mass of water and stirred thoroughly to generate stable foam, resulting in precast foam. The remaining water and chemical admixtures are added to the dry mix and stirred evenly to form a slurry. The precast foam is slowly added to the slurry and stirred evenly to prevent foam breakage and ensure uniform foam distribution, resulting in a foamed concrete slurry. The uniformly mixed foamed concrete slurry is poured into the formwork, and slight vibration is used to vent air and ensure compaction. Initial curing: Cover with plastic film and maintain a high humidity (ambient humidity 85%) environment for 24 hours to prevent early moisture evaporation. Standard curing: After 24 hours, the formwork is removed, and the concrete is transferred to a curing environment of 20±2℃ and humidity ≥95% for 28 days.

[0023] 3. Beneficial effects

[0024] Compared to existing technologies, the beneficial effects of this invention are as follows: Significantly improved mechanical properties: This invention, through innovative design of the preparation process for modified retarder, lightweight foamed aggregate, and fine aggregate, significantly improves the compressive strength and flexural strength of green cast-in-place high-strength lightweight foamed concrete. Test results show that the compressive strength of Examples 1-18 reaches 20.5-24.5 MPa, and the flexural strength is 3.8-4.5 MPa, far exceeding the 11.5-16.0 MPa and 2.2-2.9 MPa of the comparative examples. The mechanism is as follows: the modified retarder, through carboxylation, silanization, and grafting reactions, forms modified particles with excellent dispersibility and retarding effect, which can effectively regulate the cement hydration rate, optimize the structure of hydration products, and reduce the generation of early microcracks; the lightweight foamed aggregate is modified with nano-alumina, silica, and functionalized dopants, and through sol-gel impregnation and chemical vapor deposition processes, forms an aggregate structure with high closed-cell rate (≥85%) and low water absorption rate (≤8%), significantly enhancing the strength of the aggregate itself and the interfacial bonding with the matrix; the fine aggregate, through composite nanoparticles, nano-carbon suspension, and dual chemical grafting processes, constructs a gradient pore structure with a dense outer layer and a sparse inner layer, improving the bond strength between the aggregate and the cement matrix (1.80-2.00MPa) and effectively reducing the thickness of the interfacial transition zone (ITZ) (4.5-4.9μm). These comprehensive measures work together to enable the foamed concrete of this invention to maintain its lightweight properties (apparent density 1550-1620kg / m³). 3This invention achieves high strength while overcoming the traditional contradiction between strength and density in foamed concrete. Excellent durability: The foamed concrete of this invention exhibits significant advantages in durability, with an alkali-aggregate reaction (ASR) expansion rate of only 0.040-0.047%, a strength loss rate of 7.5-8.8% after freeze-thaw cycles, and a water absorption rate of 3.4-4.0%, far superior to the comparative examples of 0.075-0.105%, 12.0-16.5%, and 5.3-7.2%. The mechanism lies in the following: the silica nanofilm generated on the surface of the lightweight foamed aggregate and the gradient pore structure of the fine aggregate effectively reduce the permeability of the material, reducing the intrusion of moisture and harmful ions, thereby inhibiting ASR and freeze-thaw damage; mineral admixtures (such as silica fume and fly ash) generate more CSH gel through the pozzolanic effect, filling the matrix pores, increasing the Ca(OH)2 fixation rate (0.90-0.95 mg / mg), enhancing the matrix density, and reducing the risk of carbonation and chemical erosion. Furthermore, the nano-modification process controls the porosity to 3.6-4.1%, and the pore structure is more uniform and closed, reducing the proportion of interconnected pores and further improving impermeability and freeze-thaw resistance. Improved interfacial bonding performance: This invention significantly improves the interfacial properties between the aggregate and the cement matrix through nano-modification and surface functionalization of lightweight foamed aggregate and fine aggregate. Test results show that the ITZ thickness of the embodiment is 4.5-4.9 μm, and the bond strength is 1.80-2.00 MPa, which is superior to the 7.8-10.5 μm and 0.95-1.25 MPa of the comparative examples. The mechanism lies in the following: lightweight foamed aggregates, through functional doping with nano-alumina, silica, and titanium dioxide, form a dense nanofilm on their surface, enhancing the chemical bonding and mechanical intercalation with the cement matrix. Fine aggregates undergo low-temperature plasma treatment and chemical vapor deposition to deposit a 15-30 nm thick silica nanofilm on their surface. Furthermore, through dual chemical grafting, vinyltrimethoxysilane and polyamide active groups are introduced, significantly improving surface roughness and chemical activity, resulting in a stronger interfacial bond with cement hydration products. This interface optimization effectively reduces stress concentration, inhibits crack propagation, and improves overall mechanical properties. Superior workability: The foamed concrete of this invention exhibits excellent workability, with a slump of 162-175 mm, an initial setting time of 2.6-2.9 h, and a bubble loss rate of 7.0-7.9%, superior to the comparative examples of 135-152 mm, 3.4-4.0 h, and 9.8-12.5%.The mechanism is as follows: the modified retarder, through carboxylation and silanization modification of sodium lignosulfonate, introduces multifunctional groups, which can form steric hindrance and electrostatic repulsion in the cement paste, significantly improving the paste fluidity. Simultaneously, it precisely controls the setting time, avoiding construction problems caused by premature setting or excessively long retarding. The synergistic effect of the high-efficiency water-reducing agent and air-entraining agent further optimizes the rheological properties of the paste, ensuring uniform distribution of foam during mixing and casting. The selection of foaming agents (such as sodium bicarbonate and sodium dodecyl sulfate) and the pre-foaming process effectively improve foam stability and reduce the risk of bubble breakage and coalescence. These characteristics make the foamed concrete of this invention particularly suitable for cast-in-place construction, meeting the operational requirements of complex engineering environments. Green and economical: This invention fully utilizes industrial by-products (such as waste glass and silicon-based solid waste) and mineral admixtures (such as fly ash and slag powder), significantly reducing cement usage and environmental impact. Test results show that the carbon footprint of the embodiment is 110-123 kg CO2 / m³. 3 The production cost is 210-228 yuan / m². 3 Comparison ratio (138-160 kg CO2 / m³) 3 238-260 yuan / m 3 Compared to traditional lightweight concrete, this invention reduces costs by approximately 25-35% and 10-15%, respectively. The mechanism lies in the following: lightweight foamed aggregate uses waste glass as a base material, achieving resource recycling through nano-modification, reducing the mining of virgin materials and energy consumption; fine aggregate is prepared by combining industrial silicon-based solid waste with natural quartz sand, reducing raw material costs; the pozzolanic effect and micro-filling effect of mineral admixtures not only improve material performance but also further reduce cement usage and CO2 emissions. This green design enables the invention to achieve a win-win situation of environmental friendliness and economic benefits while meeting high-performance requirements. Pore structure optimization and functional improvement: This invention optimizes the pore structure of foamed concrete through the gradient pore design of nano-modified foaming agents and fine aggregates, controlling the porosity at 3.6-4.1%, resulting in more uniform pore distribution, smaller pore size, and denser bubble walls, a significant improvement over the comparative example's 5.8-7.2%. The mechanism lies in the following: fine aggregates are rapidly cooled using a pulsed inert airflow process to form a gradient pore structure with a dense outer layer and a sparse inner layer (outer layer pore size <30μm, inner layer pore size 30-150μm), effectively balancing the requirements of lightweight and strength. The synergistic effect of nano-modified aggregates and foaming agents improves the rigidity of the liquid film and the stability of the foam, delays foam discharge and aggregation, and reduces bubble size. This optimized pore structure not only enhances compressive strength and durability but also strengthens functional properties such as thermal insulation and sound absorption, giving the foamed concrete of this invention greater potential in multifunctional application scenarios.

[0025] In summary, this invention, through innovative design and optimized preparation process of modified retarders, lightweight foamed aggregates, fine aggregates, and overall mix proportions, systematically addresses the shortcomings of traditional foamed concrete in terms of strength, durability, workability, and environmental friendliness. Test data and mechanistic analysis demonstrate that this invention significantly outperforms existing technologies in terms of mechanical properties, durability, interfacial bonding, workability, and environmental and economic efficiency. It particularly exhibits excellent application prospects in the field of cast-in-place high-strength lightweight foamed concrete, providing an effective technical solution to the demands of modern engineering structures for lightweight, high-performance, and green sustainable development. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of the modified retarder prepared in Example 1.

[0027] Figure 2 This is a photograph of the lightweight foamed aggregate prepared in Example 1.

[0028] Figure 3 This is a photograph of the fine aggregate prepared in Example 1.

[0029] Figure 4 This is a scanning electron microscope image of the foamed concrete prepared in Example 1. Detailed Implementation

[0030] The present invention will now be described in detail through specific embodiments. However, these illustrative embodiments are for the purpose of illustrating the invention only and do not constitute any limitation on the actual scope of protection of the invention, nor are they intended to limit the scope of protection of the invention to these embodiments. For parameter ranges not mentioned, intermediate values ​​are selected. Furthermore, for mass percentages or weight percentages not explicitly stated or mentioned, they generally refer to the final concentration after addition. Additionally, for percentages mentioned, they generally refer to mass percentages or weight percentages, unless it is an industry-standard convention.

[0031] Example 1

[0032] Formula (unit: g): Cement (CEMI42.5 ordinary Portland cement, clinker content 95%-100%, calcium oxide 60%-67%, silicon dioxide 17%-25%, aluminum oxide 3%-8%, ferric oxide 0.5%-6%, alkali content ≤0.6%): 3000g; Lightweight foamed aggregate: 4000g; Fine aggregate: 1500g; Water: 2500g; Foaming agent (sodium bicarbonate, CAS No. 144-55-8): 10g; Mineral admixture (silica fume, CAS No. 69012-64-2): 1500g; Chemical admixture: 100g (High-efficiency water-reducing agent: polycarboxylate ether, CAS No. 62601-60-9, 62.5g; Modified retarder: 25g; Air-entraining agent: rosin soap, CAS No. 61790-51-0, 12.5g).

[0033] Preparation of modified retarder: 100g of sodium lignosulfonate (purity > 80%), an industrial byproduct, was mixed with 200g of chloroacetic acid (CAS No. 79-11-8) (molar ratio 1:2) at pH 10 and stirred in a water bath at 70℃ for 4h to obtain a carboxylated product. This carboxylated product was dispersed in 1000g of anhydrous ethanol, and 200g of 3-aminopropyltriethoxysilane (CAS No. 919-30-2) was added. The mixture was refluxed at 75℃ for 6h to obtain a reflux product. 100g of the reflux product was mixed with 200g of 4-vinylphenylboronic acid (CAS No. 2156-04-9) and 50g of azobisisobutyronitrile (CAS No. 78-67-1) (mass ratio 1:2:0.5), reacted at 65℃ for 6h, and then freeze-dried under vacuum to obtain the modified retarder. Its scanning electron microscope image is shown below. Figure 1 As shown.

[0034] Lightweight foam aggregate preparation: Raw material pretreatment: Using waste glass as the substrate, crush it to a particle size ≤90μm to obtain 1000g of raw material particles. Nanomodifier preparation: Mix 100g of nano-alumina (particle size 10nm) and 200g of nano-silica (particle size 20nm) (mass ratio 1:2), add 3000g of anhydrous ethanol, and ultrasonically disperse for 30min to obtain the nanomodifier. Functional doping: Add 15g of nano-titanium dioxide (particle size 100nm) (5% of the total mass of the nanomodifier) ​​and 6g of magnesium chloride (particle size 50nm) (2%) to the nanomodifier, and ultrasonically treat for 15min to obtain a functionalized nano suspension. Mixing and granulation: Mix 1000g of raw material particles with 10g of silicon carbide (particle size ≤1μm, CAS No. 409-21-2) (mass ratio 100:1), add 2000g of deionized water, and granulate into wet particles with a diameter of 2mm using a disc granulator. Pre-sintering: Under an argon atmosphere, heat to 650℃ at 5℃ / min and hold for 30min to form a dense shell, obtaining pre-sintered particles. Sol-gel impregnation: Immerse 200g of pre-sintered particles in 500g of functionalized nano-suspension (mass ratio 2:5), treat under -0.08MPa vacuum for 20min, heat to 800℃ at 10℃ / min in an argon atmosphere and hold for 20min, switch to a nitrogen atmosphere, heat to 850℃ at 2℃ / min and hold for 15min, slowly cool to 600℃ and then allow to cool naturally to obtain surface nano-modified aggregate particles. Chemical vapor deposition: Tetraethoxysilane (CAS No. 78-10-4) vapor is introduced at 300℃, with a reaction chamber pressure of 0.1 kPa, a vapor flow rate of 0.5 g / min, a deposition time of 30 min, and a deposition rate of 0.8 nm / min, to generate a silica nanofilm with a thickness ≤50 nm. Hot pressing densification: Hot pressing is performed at 5 MPa and 400℃ (heating at 5℃ / min) for 10 min, resulting in a closed-cell rate ≥85%. Particle size classification: Vibration sieving is used to obtain particles with a 0.4-10 mm particle size distribution. The water absorption rate after 24 h is ≤8%, yielding the product, such as... Figure 2 As shown.

[0035] Fine aggregate preparation: Raw material screening: Industrial silicon-based solid waste and natural quartz sand are mixed at a mass ratio of 2:1 (2000g:1000g), and air-jet milled until the D90 particle size is ≤30μm and the specific surface area is ≥2.0m². 2 / g. Preparation of composite nanopowder A: 300g of nano-silica (5nm particle size), 100g of nano-titanium dioxide (10nm particle size), and 1500g of deionized water (mass ratio 3:1:15) were added, along with 12g of 0.3% sodium polycarboxylate (CAS No. 62601-60-9). The mixture was ultrasonically dispersed for 50min, centrifuged and washed, and vacuum dried at 70℃ to obtain composite nanopowder A. Preparation of nano-carbon suspension B: 100g of graphene oxide (thickness <3nm, sheet diameter 0.3μm, CAS No. 1034343-98-0) and 200g of single-walled carbon nanotubes (diameter 1nm, length 5μm, CAS No. 308068-56-6) (mass ratio 1:2) were mixed, and 2000g of N,N-dimethylformamide (CAS No. 68-12-2) was added. The mixture was emulsified by high-speed shearing (8000rpm) for 80min to obtain nano-carbon suspension B. Surface modification: 3000g of crushed raw material was placed in a low-temperature plasma reactor and treated with argon / oxygen (volume ratio 5:1, flow rate 50 sccm) at 400W for 10 min. Chemical vapor deposition was then performed at 150℃ with tetramethoxysilane vapor introduced at a pressure of 0.5 kPa, a flow rate of 0.3 g / min, and a deposition rate of 0.75 nm / min, generating a 15 nm silica nanofilm. Granulation: 3000g of the coated raw material was added to a composite slurry (100g of composite nanopowder A, 20g of nano-carbon suspension B, 50g of aqueous epoxy emulsion (CAS No. 1675-54-3), and 5000g of deionized water, mass ratio 20:1:0.2:50). The mixture was stirred at high speed at 1500 rpm for 30 min and then granulated in a spray fluidized bed (pressure 0.2 MPa, spray rate 50 mL / min, inlet temperature 170℃, outlet temperature 85℃) to prepare core-shell structured microspheres with a particle size of 0.2-1.0 mm. Sintering: Microwave heating (nitrogen protection, heating to 520℃ at 12℃ / min, holding for 40 min), then heating to 900℃ at 8℃ / min, holding for 50 min. Pulsed inert gas rapid cooling: Alternating pulsed argon purging (200 sccm, 1s, 10 times / min, pressure 0.2MPa) and vacuum suction (0.5Pa, 3s), cooling to below 200℃ at a rate ≥35℃ / min, outer layer pore size <30μm, inner layer pore size 30-150μm. Chemical grafting: Preliminary fine aggregate is impregnated in a 1.5wt% vinyltrimethoxysilane ethanol solution and reacted at 65℃ for 2.5h; then impregnated in a 0.8wt% polyamide aqueous solution and cured at 75℃ for 1.5h to obtain fine aggregate, such as... Figure 3 As shown.

[0036] Foamed concrete preparation: Dry mix 3000g cement, 1500g mineral admixtures, 4000g lightweight foamed aggregate, and 1500g fine aggregate for 3 minutes to obtain a dry mix. Dissolve 10g foaming agent in 833g water and stir to produce stable foam. Add the remaining 1667g water and 100g chemical admixture to the dry mix and stir to form a slurry. Slowly add precast foam, stirring evenly to prevent foam breakage. Pour into the formwork and gently vibrate to release air. Initial curing: Cover with plastic film and maintain high humidity (85%) for 24 hours. Standard curing: After demolding, cure at 20±2℃ and humidity ≥95% for 28 days. Figure 4 As shown.

[0037] Example 2-18

[0038] Examples 2-18 refer to the process flow of Example 1, but adjust the formulation and preparation parameters of key components, as shown in Table 1. The formulations and preparation parameters cover both endpoint and intermediate values ​​to ensure comprehensive verification of the feasibility of the formulation and process.

[0039] Table 1. Formulations and key preparation parameters for Examples 1-18 (unit: g)

[0040]

[0041]

[0042] Note: The weight ratio of high-efficiency water-reducing agent, modified retarder, and air-entraining agent in the chemical admixtures is 5:2:1 (Examples 1, 4, 7, 10, 13, 16), 6:2.5:1.5 (Examples 2, 5, 8, 11, 14, 17), and 7:3:2 (Examples 3, 6, 9, 12, 15, 18). The foaming agents are sodium bicarbonate (Examples 1-6), sodium dodecyl sulfate (Examples 7-12), and sodium fatty alcohol polyoxyethylene ether sulfate (Examples 13-18). The mineral admixtures are silica fume (Examples 1-6), fly ash (Examples 7-12), and slag powder (Examples 13-18). The high-efficiency water-reducing agents are polycarboxylate ether (Examples 1-6), sodium naphthalenesulfonic acid formaldehyde condensate (Examples 7-12), and sodium acetone sulfonate (Examples 13-18). The air-entraining agents are rosin soap (Examples 1-9) and sodium lignosulfonate (Examples 10-18).

[0043] Comparative Examples 1-16

[0044] To verify the necessity of key components and processes, the following comparative examples were designed, referring to the formulations and processes of Examples 1-18, and comparative experiments were conducted on the absence of modified retarder, lightweight foamed aggregate and fine aggregate.

[0045] Comparative Example 1 (based on Example 1) differs from Example 1 in that it does not use a modified retarder, but instead uses an equal amount of sodium lignosulfonate (purity > 80%). The chemical admixture formula is adjusted to: 62.5g of high-efficiency water-reducing agent, 25g of sodium lignosulfonate, and 12.5g of air-entraining agent.

[0046] Comparative Example 2 (based on Example 1) differs from Example 1 in that the carboxylation reaction of the modified retarder is not carried out. Instead, sodium lignosulfonate is directly blended with 3-aminopropyltriethoxysilane, and the chemical additive formulation is the same as in Example 1.

[0047] Comparative Example 3 (based on Example 2) differs from Example 2 in that the silanization reaction of the modified retarder is not carried out. Instead, the carboxylation product is directly blended with 4-vinylphenylboronic acid and azobisisobutyronitrile. The chemical additive formulation is the same as in Example 2.

[0048] Comparative Example 4 (based on Example 2) differs from Example 2 in that the grafting reaction of the modified retarder is not carried out, and the silanized product is used directly. The chemical admixture formulation is the same as that in Example 2.

[0049] Comparative Example 5 (based on Example 3) differs from Example 3 in that it does not use lightweight foamed aggregate, but instead uses an equal amount of ordinary lightweight aggregate (expanded perlite, particle size 0.4-10mm).

[0050] Comparative Example 6 (based on Example 3) differs from Example 3 in that no nano-modifiers or functional doping are prepared in the preparation of lightweight foam aggregate. The raw material particles are directly mixed with silicon carbide and granulated. The subsequent process is the same as in Example 3.

[0051] Comparative Example 7 (based on Example 4) differs from Example 4 in that the lightweight foam aggregate is not impregnated with sol-gel, but the pre-sintered particles are directly subjected to chemical vapor deposition, and the subsequent process is the same as in Example 4.

[0052] Comparative Example 8 (based on Example 4) differs from Example 4 in that chemical vapor deposition is not performed in the preparation of lightweight foam aggregate. Instead, the particles impregnated with sol-gel are directly densified by hot pressing, and the subsequent processes are the same as in Example 4.

[0053] Comparative Example 9 (based on Example 5) differs from Example 5 in that it does not use fine aggregate, but instead uses an equal amount of natural quartz sand (D90 particle size ≤ 30 μm).

[0054] Comparative Example 10 (based on Example 5) differs from Example 5 in that the preparation of composite nanopowder A is not carried out in the fine aggregate preparation. Instead, the crushed raw materials are directly surface modified, and the subsequent process is the same as in Example 5.

[0055] Comparative Example 11 (based on Example 6) differs from Example 6 in that the preparation of nano-carbon suspension B is not carried out in the fine aggregate preparation. Instead, composite nanopowder A is directly added to the composite slurry, and the subsequent process is the same as in Example 6.

[0056] Comparative Example 12 (based on Example 6) differs from Example 6 in that chemical vapor deposition is not performed in the preparation of fine aggregates. Instead, the plasma-treated raw material particles are directly added to the composite slurry, and the subsequent processes are the same as in Example 6.

[0057] Comparative Example 13 (based on Example 7) differs from Example 7 in that the fine aggregate preparation does not involve pulsed inert gas rapid cooling, but is naturally cooled to below 200°C, and the subsequent processes are the same as in Example 7.

[0058] Comparative Example 14 (based on Example 7) differs from Example 7 in that no chemical grafting is performed in the preparation of fine aggregates. The preliminary fine aggregates after sintering are used directly, and the subsequent processes are the same as in Example 7.

[0059] Comparative Example 15 (based on Example 8) differs from Example 8 in that it does not involve the preparation of lightweight foamed aggregate and fine aggregate, but instead uses equal amounts of expanded perlite and natural quartz sand.

[0060] Comparative Example 16 (based on Example 8) differs from Example 8 in that the modified retarder, lightweight foamed aggregate and fine aggregate were not prepared, and were replaced with equal amounts of sodium lignosulfonate, expanded perlite and natural quartz sand, respectively.

[0061] Table 2 Comparative Examples 1-16 Key Component Missing Settings

[0062]

[0063] Note: The formulations and non-missing process parameters of Comparative Examples 1-16 are consistent with those of the corresponding Examples, and the weight unit is grams (g). The comparative examples, by omitting key components or process steps, verify the contribution of modified retarders, lightweight foamed aggregates, and fine aggregates and their preparation processes to the performance of foamed concrete. The process flows of the Examples and Comparative Examples strictly follow the preparation method of Example 1, with adjustments only made to the specified parameters.

[0064] Test methods

[0065] Mechanical property tests: Compressive strength: According to ISO22965-1:2007, 100mm×100mm×100mm cubic specimens were used. After 28 days of standard curing (20±2℃, humidity ≥95%), the compressive strength was tested using a 2000kN universal testing machine (MTSCMT5504) at a loading rate of 0.5MPa / s. The average value of three specimens was recorded, in MPa. Flexural strength: According to GB / T50081-2019, 150mm×150mm×550mm prismatic specimens were used. After 28 days of curing, the three-point bending method (loading rate 0.05MPa / s) was used. The average value of three specimens was recorded, in MPa. Apparent density: According to GB / T11969-2020, the mass of the specimen after 28 days of curing (dry state) was weighed, the volume was measured, and the apparent density was calculated, in kg / m³. 3 .

[0066] Durability Testing: Alkali-Aggregate Reaction (ASR) Expansion Rate: Referring to ASTM C1260-21, using the mortar bar method (40mm × 40mm × 160mm specimens), the specimens were immersed in 1 mol / L NaOH solution at 80℃ for 14 days. The length change rate (%) was measured, and the average value of 3 specimens was recorded. Ca(OH)₂ Fixation Rate: Thermogravimetric analysis (TGA, instrument: TAQ500) was used. Under a nitrogen atmosphere, the temperature was increased to 800℃ at 10℃ / min to determine the amount of Ca(OH)₂ decomposition, and the fixation rate (mg / mg) was calculated. Freeze-Thaw Cycling Performance: According to ASTM C666 / C666M-15, 100mm × 100mm × 400mm specimens were subjected to 25 freeze-thaw cycles (-18℃ to 5℃, 4 hours per cycle), and the compressive strength loss rate (%) was tested. Water absorption rate: According to GB / T11970-1997, after curing for 28 days, the specimens were dried to constant weight, immersed in water for 24 hours, and then weighed to calculate the water absorption rate (%).

[0067] Interface bonding performance testing: Interfacial transition zone (ITZ) thickness: The cross-section of the specimen was observed using a scanning electron microscope (SEM, instrument: FEI Quanta 450), and the ITZ thickness (μm) between the aggregate and the cement matrix was measured. The average value of 10 fields of view was taken. Bond strength: A pull-out test was conducted. A steel plate (50mm × 50mm) was adhered to the surface of the specimen and pulled out at a rate of 0.05MPa / s. The bond strength (MPa) was recorded. Porosity: The internal pore structure of the specimen was scanned using X-ray micro-CT (instrument: Zeiss Xradia 510 Versa), and the porosity (%) was calculated.

[0068] Construction performance test: Slump: The slump (mm) of fresh foamed concrete paste was tested in accordance with GB / T50080-2016.

[0069] Initial setting time: The initial setting time (h) of the slurry was recorded using a Vicat apparatus (refer to GB / T1346-2011). Air bubble loss rate: The air bubble loss rate (%) was calculated by measuring the density difference between the fresh slurry and the hardened specimen.

[0070] Environmental and Economic Analysis: Carbon Footprint: Using the Life Cycle Assessment (LCA) method (referencing ISO 14040:2006), the carbon footprint is calculated based on the carbon footprint of 1m³ of production. 3 Carbon emissions of foamed concrete (kgCO2 / m³) 3 Production cost: Estimated based on raw material, energy consumption, and process costs, in yuan / m³. 3 Compared with traditional lightweight concrete.

[0071] Test Results

[0072] Test results of Examples 1-18

[0073] Table 3 summarizes the test results of Examples 1-18, covering mechanical properties, durability, interfacial properties, workability, and environmental and economic benefits. The formulations and process parameters of Examples 1-18 are shown in Table 1, covering different component ratios and preparation conditions (such as parameter variations of modified retarders, lightweight foamed aggregates, and fine aggregates).

[0074] Table 3 Test results of Examples 1-18

[0075]

[0076] Note: Examples 3, 6, 9, 12, 15, and 18, employing a higher proportion of modified retarder (7:3:2) and optimized processes (such as nano-modification of lightweight foamed aggregate and pulse rapid cooling of fine aggregate), exhibit superior compressive strength (24.0-24.5 MPa), durability (ASR expansion rate ≤0.041%), and interfacial properties (ITZ thickness ≤4.6 μm). Apparent density remains at 1500-1620 kg / m³. 3 It meets the requirements for lightweight concrete. It exhibits good workability, with a slump of 160-175mm, an initial setting time of 2.6-2.9h, and an air bubble loss rate of ≤7.9%. Its carbon footprint and production cost are reduced by approximately 25-35% and 10-15% respectively compared to traditional lightweight concrete.

[0077] Comparative Examples 1-16 Test Results

[0078] Table 4 summarizes the test results of Comparative Examples 1-16, verifying the contribution of the modified retarder, lightweight foamed aggregate, and fine aggregate, as well as their processes, to the performance. The comparative examples are adjusted based on the implementation examples, and key components or processes are missing (see Table 2).

[0079] Table 4 Test results of Comparative Examples 1-16

[0080]

[0081] Notes: Comparative Examples 1-4 (Missing Modified Retarder or Simplified Process): The absence of a modified retarder or a simplified preparation process (e.g., omitting carboxylation, silanization, or grafting reactions) resulted in prolonged initial setting time (3.4-3.5 h), decreased compressive strength (15.0-16.0 MPa), increased ASR expansion rate (0.075-0.080%), and poorer interfacial bonding performance (ITZ thickness 7.8-8.0 μm). Comparative Examples 5-8 (Missing Lightweight Foamed Aggregate or Simplified Process): The use of ordinary expanded perlite or the omission of nano-modification, sol-gel impregnation, chemical vapor deposition, and other processes led to increased apparent density (1715-1750 kg / m³). 3 Increased water absorption (5.6-6.0%) and decreased compressive strength (13.5-14.8 MPa). Comparative Examples 9-14 (fine aggregate missing or process simplified): Using natural quartz sand or omitting composite nanopowder A, nano-carbon suspension B, chemical vapor deposition, or pulse rapid cooling processes resulted in increased porosity (6.4-6.8%), increased freeze-thaw strength loss (13.8-15.0%), and decreased bond strength (1.05-1.15 MPa).

[0082] Comparative Examples 15-16 (Multi-component deficiency): Simultaneous deficiency of modified retarder, lightweight foamed aggregate, and fine aggregate resulted in a comprehensive decline in performance, with compressive strength only 11.5-12.0 MPa, and a significant increase in carbon footprint and production cost (155-160 kg CO2 / m³). 3 255-260 yuan / m 3 ).

[0083] Results Analysis

[0084] Mechanical properties: The compressive strength (20.5-24.5 MPa) and flexural strength (3.8-4.5 MPa) of Examples 1-18 were significantly better than those of the comparative examples (11.5-16.0 MPa, 2.2-2.9 MPa), thanks to the modified retarder optimizing the setting time and the nano-modified aggregate enhancing the interfacial bonding. The optimized formulations of Examples 3 and 15 performed best, approaching the standard for high-strength lightweight concrete. Durability: The ASR expansion rate (0.040-0.047%) and freeze-thaw strength loss (7.5-8.8%) of the examples were much lower than those of the comparative examples (0.075-0.105%, 12.0-16.5%), indicating that nano-modification and chemical grafting processes effectively inhibited alkali-aggregate reaction and improved freeze-thaw resistance. Interface performance: The ITZ thickness (4.5-4.9 μm) and porosity (3.6-4.1%) of the examples were lower than those of the comparative examples (7.8-10.5 μm, 5.8-7.2%), with an increase in bond strength of about 180-200%, which is attributed to the surface nano-modification of the lightweight foam aggregate and fine aggregate and chemical vapor deposition.

[0085] Construction performance: The slump (162-175 mm) and bubble loss rate (7.0-7.9%) of the examples were superior to those of the comparative examples (135-152 mm, 9.8-12.5%), showing that the synergistic effect of the modified retarder and foaming agent improved the slurry fluidity and foam stability. Environmental and economic benefits: The examples utilized waste glass and industrial byproducts, with a carbon footprint (110-123 kg CO2 / m³). 3 ) and production costs (210-228 yuan / m 3 ) lower than the comparative ratio (138-160 kg CO2 / m 3 238-260 yuan / m 3 This demonstrates the advantages of green building materials. Tests in Examples 1-18 and Comparative Examples 1-16 verified the significant improvement in the performance of green cast-in-place high-strength lightweight foamed concrete achieved by the nano-modification process of modified retarders, lightweight foamed aggregates, and fine aggregates. The optimized formulations (such as Examples 3 and 15) met the standards for high-strength lightweight concrete in terms of mechanical properties, durability, interfacial bonding, and workability, while reducing carbon footprint and cost by approximately 25-35% and 10-15%, respectively, demonstrating excellent environmental and economic benefits. The performance decline in the comparative examples further proves the necessity of each key process.

[0086] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted herein.

Claims

1. A green, cast-in-place, high-strength, lightweight foamed concrete, characterized in that: The aforementioned green cast-in-place high-strength lightweight foamed concrete comprises, by weight, the following components: Cement: 30-50 parts, lightweight foamed aggregate: 20-40 parts, fine aggregate: 15-30 parts, water: 15-25 parts, foaming agent: 0.1-1.0 parts, mineral admixture: 5-15 parts, chemical admixture: 0.1-2 parts. The chemical admixture includes high-efficiency water-reducing agent, modified retarder, and air-entraining agent, wherein the weight ratio of high-efficiency water-reducing agent, modified retarder, and air-entraining agent is (5-7):(2-3):(1-2). The preparation method of the modified retarder is as follows: sodium lignosulfonate, an industrial by-product, is selected and reacted with chloroacetic acid at a ratio of 1:(2-6) under pH 10-12 conditions. The reaction was carried out by stirring in a water bath at 70-80℃ for 4 hours to obtain a carboxylated product. This product was then dispersed in anhydrous ethanol at 10-20 times its mass, and 3-aminopropyltriethoxysilane at 2-3 times its mass was added. The mixture was refluxed at 75-80℃ for 6-8 hours to obtain a reflux product. This reflux product was then mixed with 4-vinylphenylboronic acid and azobisisobutyronitrile at a mass ratio of 1:(2-4):0.5 and reacted at 65-75℃ for 6-8 hours. The mixture was then freeze-dried under vacuum to obtain the final product. The preparation method of the lightweight foam aggregate is as follows: Raw material pretreatment: Waste glass or virgin glass was used as the substrate and crushed to a particle size ≤9 mm. 0μm, to obtain raw material particles; preparation of nano-modifier: mix nano-alumina with a particle size of 10-50nm and nano-silica with a particle size of 20-60nm at a mass ratio of 1:(2-10), add anhydrous ethanol at 30-50 times the mass of nano-alumina and ultrasonically disperse for 30min to form a uniform suspension, to obtain nano-modifier; functionalization doping: add nano-titanium dioxide with a particle size of 100-200nm and magnesium chloride with a particle size of 50-100nm to the nano-modifier, wherein nano-titanium dioxide accounts for 5-15% of the total mass of the nano-modifier, and magnesium chloride accounts for 2- 6%, continue ultrasonic treatment for 15 min to obtain functionalized nano-suspension; Mixing and granulation: Mix raw material particles with silicon carbide with a particle size ≤1μm at a mass ratio of (100-120):1, add 2-5 times the mass of deionized water of raw material particles and make wet particles with a diameter of 2-4mm; Pre-sintering: Under an argon atmosphere, heat the wet particles to 700±50℃ at 5℃ / min and hold for 30 min to form a dense shell to obtain pre-sintered particles; Sol-gel impregnation: Immerse the pre-sintered particles in the functionalized nano-suspension, with a mass ratio of (2-3):(5-8), -0.The aggregate was subjected to a vacuum negative pressure treatment of 0.08 MPa for 20 min, followed by heating to 800°C in argon atmosphere at 10°C / min and holding for 20 min. Then, the atmosphere was switched to nitrogen, and the temperature was increased to 850-880°C at 2°C / min and held for 15 min. Finally, it was slowly cooled to 600°C at 2°C / min and then allowed to cool naturally to form surface-modified nano-aggregate particles. Chemical vapor deposition was then performed: tetraethoxysilane vapor was introduced at 300°C to regenerate a carbon dioxide layer with a thickness ≤50 nm on the surface of the aggregate particles. Silicon nanofilm; hot-pressing densification: hot-pressing at 5MPa pressure and 400℃ for 10min to increase the closed-pore rate to ≥85%; particle size classification: obtaining particles with a 0.4-10mm gradation by vibrating sieve, meeting the requirement of ≤8% water absorption rate in 24h, to obtain the product; the preparation method of the fine aggregate is as follows: raw material screening: industrial silicon-based solid waste and natural quartz sand are mixed at a mass ratio of 2:1, and then pulverized by airflow to a D90 particle size ≤30μm and a specific surface area ≥2.0m². 2 / g, to obtain the crushed raw material; Preparation of composite nanopowder A: Nano-silica with a particle size of 5-20nm, nano-titanium dioxide with a particle size of 10-30nm and deionized water are mixed at a mass ratio of (3-5):1:(15-25), and 0.3% polycarboxylic acid dispersant is added. After ultrasonic dispersion for 50min, composite nanopowder A is obtained by centrifugation washing and vacuum drying at 70℃; Preparation of nano-carbon suspension B: Graphene oxide with a thickness <3nm and a sheet diameter of 0.3-1.5μm is mixed with single-walled carbon nanotubes with a diameter of 1-2nm and a length of 5-20μm at a mass ratio of 1:(2-6) and transferred to N,N-dimethylformamide solvent with a mass ratio of 20-30 times that of graphene oxide. High-speed shear emulsification is performed for 80min to form nano-carbon suspension B; The crushed raw material is placed in a low-temperature plasma reactor, with argon / oxygen gas at a volume ratio of 5:1 as the working gas and a power of 400W for 10min. Subsequently, a silica nanofilm with a thickness of 15-30 nm was deposited by chemical vapor deposition at 150°C by introducing tetramethoxysilane vapor, resulting in coated raw material particles. The coated raw material particles were then added to a composite slurry composed of composite nanopowder A, nano-carbon suspension B, aqueous epoxy emulsion, and deionized water, wherein the mass ratio of the coated raw material particles, composite nanopowder A, nano-carbon suspension B, and deionized water was (20-40):(1-3):(0) .2-0.7): (50-70), mix at high speed 1500 rpm for 30 min, and use spray fluidized bed granulation technology with inlet temperature 170-210℃ and outlet temperature 85-105℃ to prepare core-shell structured microspheres with an average particle size of 0.2-1.0 mm; low temperature pre-sintering: under nitrogen protection, heat the microspheres to 520-580℃ at 12-18℃ / min by microwave heating, and hold for 40 min to form a microporous structure; High-temperature sintering: Continue heating to 900-960℃ at 8-12℃ / min under a nitrogen atmosphere, hold for 50-70min to form a macroporous structure; Pulsed inert gas rapid cooling: After sintering, rapidly cool to below 200℃ using alternating pulsed argon purging and vacuum suction at a rate ≥35℃ / min to construct a gradient pore structure with a dense outer layer and a sparse inner layer, where the outer pore diameter is <30μm and the inner pore diameter is 30-150μm, to obtain preliminary fine aggregate; Double chemical grafting: First, impregnate the preliminary fine aggregate in an ethanol solution containing 1.5wt% vinyltrimethoxysilane and stir at 65-75℃ for 2.5h; then impregnate it in an aqueous solution containing 0.8wt% polyamide and cure at 75-80℃ for 1.5h to obtain modified fine aggregate.

2. The green cast-in-place high-strength lightweight foamed concrete according to claim 1, characterized in that: The aforementioned green cast-in-place high-strength lightweight foamed concrete comprises, by weight, the following components: Cement: 35-45 parts, lightweight foamed aggregate: 25-32 parts, fine aggregate: 18-25 parts, water: 18-22 parts, foaming agent: 0.1-1.0 parts, mineral admixture: 8-12 parts, chemical admixture: 0.8-1.5 parts.

3. The green cast-in-place high-strength lightweight foamed concrete according to claim 2, characterized in that: The aforementioned green cast-in-place high-strength lightweight foamed concrete comprises, by weight, the following components: Cement: 40 parts, lightweight foamed aggregate: 28 parts, fine aggregate: 22 parts, water: 20 parts, foaming agent: 0.7 parts, mineral admixture: 10 parts, chemical admixture: 1.2 parts.

4. The green cast-in-place high-strength lightweight foamed concrete according to claim 1, characterized in that: The cement used is CEMI42.5 ordinary Portland cement.

5. The green cast-in-place high-strength lightweight foamed concrete according to claim 1, characterized in that: The foaming agent is sodium bicarbonate, sodium dodecyl sulfate, or sodium fatty alcohol polyoxyethylene ether sulfate.

6. The green cast-in-place high-strength lightweight foamed concrete according to claim 1, characterized in that: The mineral admixture is silica fume, fly ash, or slag powder.

7. The green cast-in-place high-strength lightweight foamed concrete according to claim 1, characterized in that: The high-efficiency water-reducing agent is polycarboxylic acid ether, sodium salt of naphthalene sulfonic acid formaldehyde condensate, or sodium acetone sulfonate; the air-entraining agent is rosin soap or sodium lignin sulfonate.

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