Lightweight thermal insulation foamed concrete and preparation method and application thereof

Abstract

This invention discloses a lightweight, thermally insulating foamed concrete, its preparation method, and its application. By weight, it comprises 100 parts of cementitious material, 40-55 parts of mixing water, 0.2-0.5 parts of polycarboxylate-based water-reducing agent, 3-15 vol% of composite modified EPS particles, and 0.5-2 parts of modified protein-based foaming agent. The EPS is modified through three steps: plasma activation, sulfonate silane grafting, and homologous protein coating. The foaming agent is prepared by grafting N-vinylpyrrolidone and hydroxyethyl methacrylate onto hydrolyzed animal protein. The product has high closed-cell rate, low thermal conductivity, high strength, is Class A non-combustible, and is resistant to temperature, acids, and alkalis, making it suitable for exterior walls, roofs, prefabricated walls, and underfloor heating insulation layers. This invention solves the problems of poor interfacial compatibility, insufficient foaming agent stability, and uneven pore structure, achieving a synergistic improvement in lightweight, high strength, thermal insulation, and durability.

Description

Technical Field

[0001] This invention belongs to the field of lightweight thermal insulation materials technology, specifically relating to a lightweight thermal insulation foamed concrete, its preparation method, and its application. Background Technology

[0002] With the acceleration of urbanization and the continuous development of building technology, high-rise residential buildings have gradually become the main form of urban living. Improving the fire safety level of high-rise buildings has become an urgent need to protect the lives and property of urban residents. One of the important contributing factors to the fire risk in high-rise buildings lies in the organic insulation materials widely used in the walls. Organic insulation materials, represented by expanded polystyrene and polyurethane, have advantages such as low thermal conductivity, low cost, and convenient construction, but they are highly flammable and can easily accelerate the spread of fire. Although in recent years, by incorporating components such as graphite, their combustion performance can be improved to B1 level, it is still difficult to reach the A-level non-combustible standard due to the inherent characteristics of the materials, and there is a risk of melting and dripping and releasing toxic fumes at high temperatures.

[0003] In contrast, inorganic insulation materials can reliably achieve Class A non-combustibility. However, some new materials, such as aerogel and vacuum insulation panels, while having low thermal conductivity, face challenges such as high cost, complex construction, and easy performance degradation, making large-scale promotion difficult. Therefore, there is an urgent need to develop insulation materials that combine low thermal conductivity with Class A non-combustibility to effectively improve the fire safety level of high-rise buildings.

[0004] Cement-based insulation materials are a type of building material made by creating pores in cement paste through physical or chemical foaming techniques. They offer advantages such as low cost and non-combustibility. However, their thermal conductivity is typically 0.08-0.22 W / (m·K), significantly higher than the 0.025-0.042 W / (m·K) of organic insulation materials. This difference mainly stems from the difference in porosity. Foamed concrete typically has a total porosity of 70%-80%, while organic insulation materials such as polystyrene foam boards can have a closed-cell air content exceeding 98%. Therefore, increasing the porosity of foamed concrete is an important way to reduce its thermal conductivity.

[0005] In existing technologies, the addition of polymer particles to optimize the pore structure of concrete improves its thermal insulation and frost resistance. However, this strategy still has the following core drawbacks: poor compatibility between polymer particles and the cement matrix interface, which easily leads to uneven pore structure and a significant decrease in strength; and the inability to achieve multi-level precise control of the pore structure of foamed concrete by simply adjusting the pore structure with polymer particles, resulting in limited improvement in the proportion of harmless pores and a still relatively high proportion of severely harmful pores, leaving considerable room for improvement in balancing thermal insulation and mechanical properties. Furthermore, the performance of foamed concrete is highly dependent on the performance of the foaming agent. Protein-based foaming agents are the mainstream foaming agents for foamed concrete due to their advantages such as high foaming ratio, fine foam, high closed-cell rate, and non-toxicity and environmental friendliness. However, traditional protein-based foaming agents have a fatal flaw: their core component is hydrolyzed animal protein peptides, and the peptide bonds in the molecules are highly sensitive to temperature and pH. In low-temperature, high-temperature, or extreme pH environments, the peptide bonds are prone to breakage, resulting in a significant decrease in foaming ratio, a significant shortening of foam stabilization time, and poor foam stability. Ultimately, this leads to poor uniformity of the pore structure of the foamed concrete, large performance fluctuations, and an inability to adapt to complex construction environments such as low temperatures in winter and high temperatures in summer, as well as the requirements of extreme pH service environments such as coastal areas and saline-alkali lands.

[0006] Therefore, existing technologies have not yet found a solution that can simultaneously address the three core issues of poor interfacial bonding between organic polymer particles and cement matrix, temperature / pH sensitivity of traditional protein-based foaming agents, and the inability to control the pore structure of foamed concrete at multiple levels. This makes it difficult for foamed concrete to simultaneously achieve the comprehensive properties of lightweight, high strength, ultra-low thermal conductivity, and high durability, which severely restricts its engineering applications in harsh environments. Summary of the Invention

[0007] In view of the above-mentioned technical defects of existing foamed concrete, the core objective of this invention is to provide a lightweight thermal insulation foamed concrete and its preparation method. Through multi-dimensional material modification and structural design, it breaks through the performance bottleneck of existing technology, and achieves simultaneous improvement in the thermal insulation performance, mechanical properties, durability and construction adaptability of foamed concrete, while meeting fire safety requirements and adapting to the engineering application needs of high-rise buildings.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A lightweight thermal insulation foamed concrete, by weight, comprises 100 parts of cementitious material, 40-55 parts of mixing water, 0.2-0.5 parts of polycarboxylate superplasticizer, and 3-15% of composite modified EPS particles and 0.5-2 parts of modified protein foaming agent by absolute volume relative to 100 parts of cementitious material; the modified protein foaming agent, by weight, comprises 30-45 parts of hydrolyzed animal protein base, 8-15 parts of modified graft monomer, 5-10 parts of amphoteric surfactant, 3-6 parts of silane coupling agent, 2-5 parts of polyol foam stabilizer, and 0.5-2 parts of pH adjuster, with a total formulation weight of 100 parts, the remainder being made up by deionized water; the modified graft monomer is a mixture of N-vinylpyrrolidone and hydroxyethyl methacrylate in a mass ratio of 2-3:1. "The absolute volume content is 3-15% relative to 100 parts by weight of cementitious material." Here, "absolute volume content" refers to the percentage of the actual volume of EPS particles to the absolute volume of cementitious material. For example, taking 100 parts of cementitious material (approximately 30-35L of the total slurry volume) as an example, 10% of the absolute volume of EPS particles (approximately 3-3.5L) can be added.

[0009] Preferably, the cementitious material, by weight, comprises 70-85 parts of P·O42.5 grade silicate cement, 10-20 parts of fly ash, 3-8 parts of silica fume, and 2-5 parts of nano-calcium carbonate. In this compound cementitious system, the pozzolanic activity of fly ash and silica fume can enhance the degree of cement hydration and optimize the structure of the interfacial transition zone. Nano-calcium carbonate can fill the pores of cement hydration products and, at the same time, act as crystal nuclei to promote hydration, thereby achieving a simultaneous improvement in matrix strength and density.

[0010] Furthermore, the composite modified EPS particles have a particle size of 0.5-3 mm and a bulk density of 15-25 kg / m³. 3 The three-step modification method is as follows: (1) Low-temperature plasma surface activation: EPS particles are placed in a low-temperature plasma reaction chamber, argon gas is introduced, the vacuum degree is controlled at 20-30 Pa, the power is 80-120 W, and the processing time is 5-10 min to obtain activated EPS particles with active hydroxyl groups and peroxy free radicals on the surface. This step breaks the CC bond on the surface of EPS particles by dry plasma bombardment, introduces active reaction sites, avoids environmental pollution and particle structure damage caused by wet roughening, and is green and efficient.

[0011] (2) Sulfonate silane copolymerization grafting: Activated EPS particles are added to a dispersion prepared by anhydrous ethanol and deionized water at a volume ratio of 9:1 and a solid-liquid ratio of 1:10. Nitrogen gas is introduced to remove oxygen. Vinyltriethoxysilane, sodium methacrylate sulfonate and initiator azobisisobutyronitrile are added, wherein the mass ratio of vinyltriethoxysilane to sodium methacrylate sulfonate is 3:1. The total amount of monomers added is 3-5% of the mass of EPS particles, and the amount of initiator added is 0.3-0.5% of the total mass of monomers. The temperature is raised to 60-65℃ and the reaction is stirred at a constant temperature for 3-4 hours. After filtration, the particles are washed three times with anhydrous ethanol and dried to obtain grafted modified EPS particles. This step grafts a large number of sulfonic acid groups and siloxane groups onto the surface of EPS particles through free radical copolymerization. The sulfonic acid groups greatly improve the hydrophilicity and dispersibility of the particles, and the siloxane groups can form chemical bonds with cement hydration products, fundamentally solving the interfacial bonding problem between EPS particles and cement matrix.

[0012] (3) Homologous protein pre-coating: The grafted modified EPS particles are immersed in an aqueous solution of hydrolyzed animal protein base material with a mass concentration of 2-4%. The hydrolyzed animal protein base material is the same material used in the modified protein foaming agent. The mixture is stirred for 15-20 minutes, filtered, and then vacuum dried at 40-50℃ to obtain composite modified EPS particles. This step is one of the core innovations of this invention. Through homologous protein pre-coating, a protein film completely homologous to the foaming agent base material is formed on the surface of the EPS particles. During the subsequent foaming and mixing process, the foam of the protein foaming agent can be homologously anchored on the surface of the EPS particles, forming a continuous and uniform foam coating layer. On the one hand, this completely avoids direct contact between the EPS particles and the cement paste, eliminating interface defects; on the other hand, it achieves precise control of the multi-level closed-cell structure of "large closed cells of EPS particles - micro pores of foam", which significantly reduces the thermal conductivity while avoiding strength loss caused by interconnected pore structures.

[0013] Furthermore, in the modified protein foaming agent, the hydrolyzed animal protein base is a hydrolysate obtained by protease hydrolysis of bovine bone waste; the amphoteric surfactant is one or both of dodecyl dimethyl betaine or cocamidopropyl hydroxysulfonate betaine; the silane coupling agent is KH550 or KH560; the polyol foam stabilizer is one or more of glycerol, butanediol or sorbitol; and the pH adjuster is citric acid or triethanolamine.

[0014] Furthermore, the preparation method of the modified protein-based foaming agent includes the following steps: S1: Base material dissolution: After crushing the bovine bone waste, it is hydrolyzed by compound protease, enzyme inactivation, filtration and concentration to obtain hydrolyzed animal protein base material with a solid content of 15-20%; the compound protease is a mixture of alkaline protease and neutral protease in a mass ratio of 1-3:1, and the enzyme activity of each enzyme is 100,000-200,000 U / g.

[0015] S2: Heat deionized water to 45-50℃, add hydrolyzed animal protein base, stir evenly, raise the temperature to 40-45℃, adjust the pH of the system to 7.5-8.5, and obtain the base premix solution; S3: Grafting modification: Nitrogen gas is introduced into the base material premix to remove oxygen, and the formulated amount of modified grafting monomer and initiator ammonium persulfate is added. The amount of initiator added is 0.4-0.6% of the total mass of the modified grafting monomer. The temperature is raised to 65-70℃ and the reaction is stirred at a constant temperature for 4-6 hours to complete the free radical grafting modification of the polypeptide molecules and obtain the grafting modified solution. S4: Compound homogenization: Cool the grafted modified liquid to 40-45℃, add the amphoteric surfactant, silane coupling agent and polyol foam stabilizer in sequence according to the formula, stir at constant temperature for 30-45 minutes to obtain homogenized liquid. S5: Post-treatment: Cool the homogenized liquid to room temperature, adjust the pH of the system to 6.5-7.5 with a pH adjuster, filter to remove insoluble matter, and obtain the modified protein foaming agent.

[0016] A method for preparing lightweight thermal insulation foamed concrete includes the following steps: (1) Powder premixing: Add each component of the gelling material into the mixer according to the formula, dry mix for 3-5 minutes, and mix evenly to obtain dry powder mixture; (2) Pre-foaming with foaming agent: Dilute the modified protein foaming agent with water at a mass ratio of 1:20-1:40, add it to the foaming machine, and prepare uniform and fine foam for later use; (3) Slurry mixing: Add the specified amount of mixing water and polycarboxylate superplasticizer to the dry powder mixture, stir for 3-5 minutes to obtain a uniform cement slurry; then add the composite modified EPS particles, stir for 2-3 minutes to ensure that the EPS particles are evenly dispersed in the slurry; finally add the foam prepared in step (2), stir for 2-4 minutes to obtain a uniform foamed concrete mixture. (4) Pouring and curing: The mixture is poured into the mold, allowed to stand at room temperature for foaming and initial setting, then covered with a film for curing for 24 hours before demolding, and then cured under standard curing conditions for 28 days to obtain the lightweight thermal insulation foamed concrete.

[0017] Furthermore, in step (3), the stirring speed is 60-90 r / min.

[0018] Furthermore, in step (4), the standard maintenance conditions are a temperature of 20±2℃ and a relative humidity of ≥95%.

[0019] Application of a lightweight insulating foamed concrete in building exterior wall insulation, roof insulation, prefabricated building wall filling, and underfloor heating insulation layer.

[0020] Beneficial effects: 1. This invention pioneers a three-step composite modification technology for EPS particles, fundamentally solving the industry problem of poor interfacial compatibility between organic particles and cement matrix. Active sites are introduced through low-temperature plasma activation, and a hydrophilic reactive interface is constructed through sulfonate-silane copolymerization grafting. In particular, the innovative design of pre-coating with homologous proteins achieves homologous bridging between EPS particles and protein foaming agents. This not only eliminates interfacial defects between EPS particles and cement paste but also achieves uniform anchoring of foam on the surface of EPS particles, avoiding problems such as particle agglomeration, paste stratification, and foam collapse, laying the foundation for multi-level pore structure control.

[0021] 2. This invention employs N-vinylpyrrolidone and hydroxyethyl methacrylate to graft and modify hydrolyzed animal protein, introducing a temperature- and hydrolysis-resistant rigid five-membered ring structure and hydrophilic hydroxyethyl side chains, significantly enhancing the stability of the protein molecule backbone. Simultaneously, a dense interfacial film is constructed by combining an amphoteric surfactant and a silane coupling agent. The foaming agent of this invention exhibits a low foaming ratio decay rate and low bleeding rate over a wide temperature range of 5-45℃ and a wide pH range of 4-10, far superior to traditional protein foaming agents, and can adapt to harsh construction and service environments such as low winter temperatures, high summer temperatures, and coastal and saline-alkali land.

[0022] 3. This invention achieves a multi-level porous structure through the combination of "composite modified EPS particles" and "highly stable modified protein foaming agent". More importantly, because both have a "homogeneous protein" layer on their surface, the foam and EPS particles can spontaneously and uniformly distribute and anchor themselves in the cement paste, avoiding the agglomeration and co-location phenomena caused by interfacial energy differences in traditional technologies. The resulting concrete exhibits uniform internal pore distribution, nested pores of varying sizes, and an extremely high closed-cell rate, achieving a perfect balance between ultra-low thermal conductivity and excellent mechanical properties, with overall performance far exceeding existing technologies.

[0023] 4. The technical solution of this invention possesses excellent engineering adaptability and environmental friendliness. The preparation process is simple and controllable, requiring no complex equipment, and is compatible with existing foamed concrete construction processes and equipment, making it easy to scale up and promote. Raw materials are widely available and costs are controllable. Using bovine bone waste as the protein base material, solid waste resource utilization is achieved, with no toxic or harmful substances added and no waste emissions during the preparation process. The product can stably achieve Class A non-combustible properties, with no high-temperature melting drips or toxic fumes released. It also possesses excellent freeze-thaw resistance, impermeability, and shrinkage resistance, making it perfectly suitable for various applications such as high-rise building exterior wall insulation, roof insulation, and prefabricated building filling, possessing extremely high economic and engineering application value. Attached Figure Description

[0024] Figure 1The images shown are SEM microstructure images of lightweight thermal insulation foamed concrete in the embodiments and comparative examples of the present invention; wherein, ad represents the microstructure of comparative examples 1-4 in sequence, and e represents the microstructure of example 1. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto. All raw materials used in the embodiments are commercially available analytical grade or industrial grade products; those not specifying their source are conventional commercially available products.

[0026] Example 1 Step 1: Preparation of composite modified EPS particles A three-step modification process is adopted, with the following specific parameters: (1) Low-temperature plasma surface activation: Take 1 kg of dry native EPS particles, spread them evenly on the quartz tray of the low-temperature plasma reaction chamber, seal the chamber and evacuate to 25 Pa, introduce high-purity argon gas to maintain the vacuum degree of the chamber at 25 Pa, set the discharge power to 100 W and the processing time to 8 min; after the processing is completed, introduce air to break the vacuum and take out activated EPS particles with active hydroxyl groups and peroxy free radicals on the surface. (2) Silane sulfonate copolymerization grafting: Add 9L of anhydrous ethanol and 1L of deionized water to a 20L reactor to prepare a dispersion with a volume ratio of 9:1. Add 1kg of activated EPS particles prepared in step (1), control the solid-liquid ratio at 1:10, turn on the stirring speed at 120r / min, and purge the system with high-purity nitrogen for 30min to remove oxygen. Then add 30g of vinyltriethoxysilane and 10g of sodium methacrylate sulfonate (mass ratio of the two is 3:1, and the total amount of monomer added is 4% of the mass of EPS particles). After stirring evenly, add 0.16g of initiator AIBN (0.4% of the total mass of monomers), heat to 62℃, and stir at a constant temperature for 3.5h. After the reaction is completed, filter and wash the filter cake 3 times with anhydrous ethanol, each time using 5L of anhydrous ethanol. After washing, place in a 60℃ forced-air drying oven and dry to constant weight to obtain silane sulfonate grafted modified EPS particles. (3) Homologous protein pre-coating: Prepare 10L of 3% hydrolyzed animal protein base water solution (the hydrolyzed animal protein base used is the same batch of material used in the subsequent foaming agent preparation), add 1kg of grafted modified EPS particles prepared in step (2), stir at 80r / min for 18min at room temperature; after stirring, filter with a 100-mesh sieve, place the filter cake in a vacuum drying oven at 45℃ and 0.09MPa and dry to constant weight to obtain composite modified EPS particles, and seal for later use.

[0027] Step 2: Preparation of modified protein-based foaming agents The formula, based on a total mass of 100 parts, consists of: 38 parts hydrolyzed animal protein base, 12 parts modified graft monomer (N-vinylpyrrolidone NVP: hydroxyethyl methacrylate HEMA = 2.5:1), 8 parts cocamidopropyl hydroxysulfonate betaine (CHSB), 4 parts KH550, 3 parts glycerol, 1 part triethanolamine, and 34 parts deionized water; the specific preparation steps are as follows: S1 base material preparation: Take 10kg of bovine bone waste, crush it to 20 mesh, add 50L of deionized water, heat to 80℃ for 30min for defatting, skim off the upper layer of floating oil, cool to 55℃, adjust the pH of the system to 8.0 with triethanolamine, add 100g of compound protease, the compound protease is a mixture of alkaline protease (150,000 U / g) and neutral protease (150,000 U / g) in a mass ratio of 2:1, and hydrolyze at a constant temperature for 6h with stirring; after hydrolysis, heat to 95℃, stir at a constant temperature for 10min to inactivate the enzyme, then filter through a plate and frame filter to remove insoluble bone residue, transfer the filtrate to a vacuum concentrator, concentrate to a solid content of 18% at 60℃ and 0.08MPa to obtain hydrolyzed animal protein base material, cool to room temperature and seal for later use; S2 base material premix: Add the prescribed amount of deionized water to a 100L reactor, turn on the stirring speed to 100r / min, heat to 48℃, add the prescribed amount of hydrolyzed animal protein base material, stir for 20min until completely homogeneous; then cool to 42℃, adjust the pH of the system to 8.0 with triethanolamine to obtain the base material premix solution; S3 Grafting Modification: High-purity nitrogen gas was continuously introduced into the base material premix for 30 minutes to completely remove oxygen from the system. Under nitrogen atmosphere, the formulated amounts of NVP and HEMA monomers were added. After stirring for 10 minutes to homogenize, 0.06 parts of initiator ammonium persulfate (0.5% of the total mass of the modified grafting monomers) were added. The temperature was raised to 68℃ and the reaction was carried out at a constant temperature with stirring for 5 hours to complete the free radical grafting modification of the peptide molecules and obtain the grafting modified solution. S4 compound homogenization: Cool the grafted modified liquid to 42℃, keep the stirring speed at 100r / min, and add CHSB, KH550 and glycerol in sequence according to the formula. Stir at constant temperature for 10min after each addition of one component. After all the components are added, continue to stir at constant temperature for 30min to obtain the homogenized liquid. S5 post-treatment: Cool the homogenized liquid naturally to room temperature, adjust the pH of the system to 7.0 with citric acid or triethanolamine, filter with a 200-mesh filter cloth to remove trace amounts of insoluble matter, and obtain the modified protein foaming agent. Store in a sealed, light-proof container for later use.

[0028] Step 3: Preparation of lightweight thermal insulation foamed concrete The formula, by weight, is as follows: 100 parts cementitious material, 45 parts mixing water, 0.3 parts polycarboxylate superplasticizer, 8% absolute volume content of composite modified EPS particles (relative to cementitious material), and 1.0 part modified protein foaming agent; wherein the cementitious material formula is: 80 parts P·O42.5 silicate cement, 12 parts fly ash, 5 parts silica fume, and 3 parts nano calcium carbonate, totaling 100 parts; The specific preparation steps are as follows: (1) Powder premixing: Cement, fly ash, silica fume and nano calcium carbonate are put into a forced mixer according to the formula, dry mix for 4 minutes, the mixing speed is 140 r / min, and the dry powder mixture is obtained evenly. (2) Pre-foaming with foaming agent: The modified protein foaming agent is diluted with water at a mass ratio of 1:30, added to a physical foaming machine, and the air pressure is adjusted to 0.4MPa to prepare uniform and fine foam, which is used immediately after preparation. (3) Slurry mixing: Keep the mixer speed at 140 r / min, add the amount of mixing water and polycarboxylate superplasticizer to the dry powder mixture, and stir for 4 min to obtain a uniform cement slurry without lumps; then reduce the mixer speed to 80 r / min, add the amount of composite modified EPS particles, and stir at low speed for 2 min to ensure that the EPS particles are uniformly dispersed in the slurry without agglomeration or floating; finally, keep the speed at 80 r / min, add the foam prepared in step (2), and stir at low speed for 3 min to obtain a uniform foamed concrete mixture without bleeding or broken bubbles; (4) Pouring and curing: Slowly pour the mixture into the mold. After pouring, gently vibrate the mold to remove surface air bubbles. Let it stand at room temperature for 6 hours until it foams and sets. Then cover it with polyethylene film for 24 hours to keep it moist and cure before demolding. After demolding, transfer the specimen to the standard curing room and cure it for 28 days at a temperature of 20±2℃ and a relative humidity of ≥95% to obtain the foamed concrete sample to be tested.

[0029] Example 2 The method for preparing lightweight thermal insulation foamed concrete described in this embodiment differs from that in Embodiment 1 only in that: Adjustment of foamed concrete formula: By weight, 100 parts cementitious materials, 40 parts mixing water, 0.2 parts polycarboxylate superplasticizer, 3% absolute volume of composite modified EPS particles (relative to cementitious materials), and 0.5 parts modified protein foaming agent. Adjustment of cementitious material formula: 85 parts of P·O42.5 silicate cement, 10 parts of fly ash, 3 parts of silica fume, and 2 parts of nano calcium carbonate, totaling 100 parts; Adjusted formulation of modified protein foaming agent (total mass 100 parts): 45 parts hydrolyzed animal protein base, 8 parts modified graft monomer (NVP:HEMA=2:1), 5 parts CHSB, 3 parts KH550, 2 parts glycerol, 0.5 parts triethanolamine, and 36.5 parts deionized water; The specifications of the remaining raw materials, preparation process parameters, and curing conditions are completely consistent with those in Example 1.

[0030] Example 3 The method for preparing lightweight thermal insulation foamed concrete described in this embodiment differs from that in Embodiment 1 only in that: Adjustment of foamed concrete formula: by weight, 100 parts cementitious materials, 55 parts mixing water, 0.5 parts polycarboxylate superplasticizer, 15% absolute volume of composite modified EPS particles (relative to cementitious materials), and 2.0 parts modified protein foaming agent. Adjustment of cementitious material formula: 70 parts P·O42.5 silicate cement, 20 parts fly ash, 5 parts silica fume, 5 parts nano calcium carbonate, totaling 100 parts; Adjusted formulation of modified protein foaming agent (total mass 100 parts): 30 parts hydrolyzed animal protein base, 15 parts modified graft monomer (NVP:HEMA=3:1), 10 parts CHSB, 6 parts KH550, 5 parts glycerol, 2 parts triethanolamine, and 32 parts deionized water. Adjustment of parameters for preparing composite modified EPS particles: particle size 0.5-1mm, plasma treatment power 120W, time 5min, copolymerization reaction temperature 65℃, time 3h, homologous protein coating concentration 4%, time 15min; Adjustment of preparation parameters for modified protein-based foaming agents: grafting reaction temperature 70℃, time 4h; The specifications of the remaining raw materials, preparation process parameters, and curing conditions are completely consistent with those in Example 1.

[0031] Comparative Example 1 This comparative example serves as a blank control of conventional foamed concrete using existing technology, with the following adjustments: 1. Add ordinary EPS granules to the formula, with a particle size of 0.5-3mm; 2. The modified protein foaming agent was replaced with a commercially available ordinary animal protein foaming agent (industrial grade, solid content 18%), purchased from Henan Luoyang Haiping Foaming Agent Co., Ltd. 3. The dosages of other cementitious materials, mixing water, water-reducing agent, preparation processes, and curing conditions are all the same as in Example 1. That is: The formula, by weight, is as follows: 100 parts cementitious material, 45 parts mixing water, 0.3 parts polycarboxylate superplasticizer, 8% absolute volume content of EPS particles (relative to cementitious material), and 1.0 part protein foaming agent; wherein the cementitious material formula is: 80 parts P·O42.5 silicate cement, 12 parts fly ash, 5 parts silica fume, and 3 parts nano calcium carbonate, totaling 100 parts; The specific preparation steps are as follows: (1) Powder premixing: Cement, fly ash, silica fume and nano calcium carbonate are put into a forced mixer according to the formula, dry mix for 4 minutes, the mixing speed is 140 r / min, and the dry powder mixture is obtained evenly. (2) Pre-foaming with foaming agent: Dilute protein foaming agent with water at a mass ratio of 1:30, add it to a physical foaming machine, adjust the air pressure to 0.4MPa, and prepare uniform and fine foam, which is used immediately after preparation; (3) Slurry mixing: Keep the mixer speed at 140 r / min, add the amount of mixing water and polycarboxylate superplasticizer to the dry powder mixture, and stir for 4 min to obtain a uniform cement slurry without lumps; then reduce the mixer speed to 80 r / min, add the amount of EPS particles according to the formula, and stir at low speed for 2 min to ensure that the EPS particles are evenly dispersed in the slurry without agglomeration or floating; finally, keep the speed at 80 r / min, add the foam prepared in step (2), and stir at low speed for 3 min to obtain a uniform foamed concrete mixture without bleeding or broken bubbles; (4) Pouring and curing: Slowly pour the mixture into the mold. After pouring, gently vibrate the mold to remove surface air bubbles. Let it stand at room temperature for 6 hours until it foams and sets. Then cover it with polyethylene film for 24 hours to keep it moist and cure before demolding. After demolding, transfer the specimen to the standard curing room and cure it for 28 days at a temperature of 20±2℃ and a relative humidity of ≥95% to obtain the foamed concrete sample to be tested.

[0032] Comparative Example 2 In this comparative example, except that the modified protein-based foaming agent from Example 1 was used, and the composite modified EPS particles were replaced with an equal volume of virgin unmodified EPS particles (particle size 0.5~3mm), and no surface modification treatment was performed, the remaining cementitious materials, mixing water, water-reducing agent dosages, preparation processes, and curing conditions were all the same as in Example 1. That is: Preparation of lightweight thermal insulation foamed concrete The formula, by weight, is as follows: 100 parts cementitious material, 45 parts mixing water, 0.3 parts polycarboxylate superplasticizer, 8% absolute volume content of EPS particles (relative to cementitious material), and 1.0 part modified protein foaming agent; wherein the cementitious material formula is: 80 parts P·O42.5 silicate cement, 12 parts fly ash, 5 parts silica fume, and 3 parts nano calcium carbonate, totaling 100 parts; The specific preparation steps are as follows: (1) Powder premixing: Cement, fly ash, silica fume and nano calcium carbonate are put into a forced mixer according to the formula, dry mix for 4 minutes, the mixing speed is 140 r / min, and the dry powder mixture is obtained evenly. (2) Pre-foaming with foaming agent: The modified protein foaming agent is diluted with water at a mass ratio of 1:30, added to a physical foaming machine, and the air pressure is adjusted to 0.4MPa to prepare a uniform and fine foam with a bubble diameter of 50-200μm and a closed-cell rate of ≥96%, which is used immediately after preparation. (3) Slurry mixing: Keep the mixer speed at 140 r / min, add the amount of mixing water and polycarboxylate superplasticizer to the dry powder mixture, and stir for 4 min to obtain a uniform cement slurry without lumps; then reduce the mixer speed to 80 r / min, add the amount of EPS particles according to the formula, and stir at low speed for 2 min to ensure that the EPS particles are evenly dispersed in the slurry without agglomeration or floating; finally, keep the speed at 80 r / min, add the foam prepared in step (2), and stir at low speed for 3 min to obtain a uniform foamed concrete mixture without bleeding or broken bubbles; (4) Pouring and curing: Slowly pour the mixture into the mold. After pouring, gently vibrate the mold to remove surface air bubbles. Let it stand at room temperature for 6 hours until it foams and sets. Then cover it with polyethylene film for 24 hours to keep it moist and cure before demolding. After demolding, transfer the specimen to the standard curing room and cure it for 28 days at a temperature of 20±2℃ and a relative humidity of ≥95% to obtain the foamed concrete sample to be tested.

[0033] Comparative Example 3 In this comparative example, except that the composite modified EPS particles from Example 1 were used, and the modified protein foaming agent was replaced with a commercially available ordinary animal protein foaming agent (industrial grade, 18% solid content, purchased from Henan Luoyang Haiping Foaming Agent Co., Ltd.), the remaining cementitious materials, mixing water, water-reducing agent dosages, preparation processes, and curing conditions were all the same as in Example 1. That is: Preparation of lightweight thermal insulation foamed concrete The formula, by weight, is as follows: 100 parts cementitious material, 45 parts mixing water, 0.3 parts polycarboxylate superplasticizer, 8% absolute volume content of composite modified EPS particles (relative to cementitious material), and 1.0 part protein foaming agent; wherein the cementitious material formula is: 80 parts P·O42.5 silicate cement, 12 parts fly ash, 5 parts silica fume, and 3 parts nano calcium carbonate, totaling 100 parts; The specific preparation steps are as follows: (1) Powder premixing: Cement, fly ash, silica fume and nano calcium carbonate are put into a forced mixer according to the formula, dry mix for 4 minutes, the mixing speed is 140 r / min, and the dry powder mixture is obtained evenly. (2) Pre-foaming with foaming agent: Dilute protein foaming agent with water at a mass ratio of 1:30, add it to a physical foaming machine, adjust the air pressure to 0.4MPa, and prepare uniform and fine foam, which is used immediately after preparation; (3) Slurry mixing: Keep the mixer speed at 140 r / min, add the amount of mixing water and polycarboxylate superplasticizer to the dry powder mixture, and stir for 4 min to obtain a uniform cement slurry without lumps; then reduce the mixer speed to 80 r / min, add the amount of composite modified EPS particles, and stir at low speed for 2 min to ensure that the EPS particles are uniformly dispersed in the slurry without agglomeration or floating; finally, keep the speed at 80 r / min, add the foam prepared in step (2), and stir at low speed for 3 min to obtain a uniform foamed concrete mixture without bleeding or broken bubbles; (4) Pouring and curing: Slowly pour the mixture into the mold. After pouring, gently vibrate the mold to remove surface air bubbles. Let it stand at room temperature for 6 hours until it foams and sets. Then cover it with polyethylene film for 24 hours to keep it moist and cure before demolding. After demolding, transfer the specimen to the standard curing room and cure it for 28 days at a temperature of 20±2℃ and a relative humidity of ≥95% to obtain the foamed concrete sample to be tested.

[0034] Comparative Example 4 In this comparative example, except for the absence of homologous protein pre-coating in the preparation of the modified EPS particles, the dosage of all other gelling materials, mixing water, water-reducing agent, preparation process, and curing conditions are the same as in Example 1. That is: Step 1: Preparation of composite modified EPS particles A three-step modification process is adopted, with the following specific parameters: (1) Low-temperature plasma surface activation: Take 1 kg of dry native EPS particles, spread them evenly on the quartz tray of the low-temperature plasma reaction chamber, seal the chamber and evacuate to 25 Pa, introduce high-purity argon gas to maintain the vacuum degree of the chamber at 25 Pa, set the discharge power to 100 W and the processing time to 8 min; after the processing is completed, introduce air to break the vacuum and take out activated EPS particles with active hydroxyl groups and peroxy free radicals on the surface. (2) Grafting of sulfonate silane copolymer: Add 9L of anhydrous ethanol and 1L of deionized water to a 20L reactor to prepare a dispersion with a volume ratio of 9:1. Add 1kg of activated EPS particles prepared in step (1), control the solid-liquid ratio at 1:10, turn on the stirring speed at 120r / min, and purge the system with high-purity nitrogen for 30min to remove oxygen. Then add 30g of vinyltriethoxysilane and 10g of sodium methacrylate sulfonate (mass ratio of the two is 3:1, and the total amount of monomer added is 4% of the mass of EPS particles). After stirring evenly, add 0.16g of initiator AIBN (0.4% of the total mass of monomers), raise the temperature to 62℃, and stir at a constant temperature for 3.5h. After the reaction is completed, filter and wash the filter cake 3 times with anhydrous ethanol, each time using 5L of anhydrous ethanol. After washing, place it in a 60℃ forced-air drying oven and dry to constant weight to obtain grafted modified EPS particles, which are then sealed for later use.

[0035] Step 2: Preparation of modified protein-based foaming agents This is completely consistent with step 2 of Example 1.

[0036] Step 3: Preparation of lightweight thermal insulation foamed concrete (1) The formula by weight is as follows: 100 parts of cementitious material, 45 parts of mixing water, 0.3 parts of polycarboxylate superplasticizer, 8% absolute volume of the above two-step modified EPS particles (relative to the cementitious material), and 1.0 part of modified protein foaming agent; wherein the formula of the cementitious material is completely consistent with that of Example 1; (2) The specific preparation steps and pouring and curing conditions are completely consistent with those in Example 1.

[0037] Performance testing 1. Test Samples and Test Environment 1.1 Test Sample The test samples included lightweight thermal insulation foamed concrete specimens prepared in Examples 1-3 and Comparative Examples 1-4. All concrete specimens were cured under standard conditions for 28 days before performance testing. Three parallel specimens were set up for each test group, and the final result was the arithmetic mean.

[0038] 1.2 Test Environment The test environment temperature was controlled at 23±2℃ and the relative humidity was controlled at 50±5%; the standard curing room environment for the specimens was 20±2℃ and the relative humidity was ≥95%, which met the relevant requirements of GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0039] 2. Test items, execution standards, and test methods 2.1 Performance Testing of Foaming Agent This section of the test is divided into two categories: basic performance test of the foaming agent and environmental adaptability test, as detailed below: Foaming ratio and 1-hour bleeding rate: The test was conducted according to GB / T 7462-1994 "Determination of foaming power of surfactants - Modified Ross-Miles method". The test was carried out at room temperature of 25℃. The foaming agent to be tested was diluted with water at a mass ratio of 1:30. The initial foaming volume was measured and the foaming ratio was calculated. After the prepared foam was allowed to stand for 1 hour, the mass of the precipitated liquid was measured and the 1-hour bleeding rate was calculated.

[0040] Temperature stability: The core test method of GB / T 7462-1994 was used for verification. The foaming agent dilution was left to stand for 2 hours in a constant temperature environment of 5℃ and 45℃ respectively. The foaming ratio was measured according to the above unified method, and the foaming ratio decay rate relative to the normal temperature condition of 25℃ was calculated.

[0041] pH stability: The core test method of GB / T 7462-1994 was used for verification. Citric acid and triethanolamine were used to adjust the pH value of the foaming agent dilution to 4.0 and 10.0 respectively. After standing in a constant temperature environment of 25℃ for 2 hours, the foaming ratio was measured according to the above unified method, and the foaming ratio decay rate under the relative pH=7.0 neutral condition was calculated.

[0042] The foaming agent used in Example 1 and the commercially available common animal protein foaming agent (industrial grade, solid content 18%) used in Comparative Example 1 were purchased from Henan Luoyang Haiping Foaming Agent Co., Ltd. and Chiping Zetai Building Materials Co., Ltd. Three parallel specimens were set up for each test group, and the final result was the arithmetic mean.

[0043] 2.2 Testing of Physical and Mechanical Properties of Concrete Dry density: The test method for the performance of autoclaved aerated concrete was carried out in accordance with GB / T 11969-2020. A cubic specimen of 100mm×100mm×100mm was used. After the specimen was dried to constant weight, the absolute mass and volume of the specimen were measured and the dry density was calculated.

[0044] Cube compressive strength: The test was conducted according to GB / T 11969-2020 "Test Method for Performance of Autoclaved Aerated Concrete". 100mm×100mm×100mm cube specimens were used. A universal pressure testing machine was used to load the specimens at a constant loading rate of 2mm / min. The ultimate failure load of the specimens was recorded, and the cube compressive strength was calculated.

[0045] 2.3 Performance Testing of Concrete Insulation and Pore Structure Thermal conductivity: The test was conducted according to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method". A 300mm×300mm×30mm flat plate specimen was used. The average test temperature was set to 25℃, and the temperature difference between the hot and cold plates was controlled at 15℃. After the system reached thermal steady state, the thermal conductivity of the specimen was measured and calculated.

[0046] Closed-cell ratio: The closed-cell ratio of rigid foamed plastics was determined by following GB / T 10799-2008 "Determination of open-cell and closed-cell volume percentage". A cubic specimen of 100mm×100mm×100mm was used. The closed-cell volume of the specimen was determined by gas displacement method and the closed-cell ratio of the specimen was calculated.

[0047] 2.4 Concrete Durability Test Freeze-thaw resistance: The test method for autoclaved aerated concrete was carried out in accordance with GB / T 11969-2020. A prism specimen with a diameter of 100mm×100mm×400mm was used. 100 freeze-thaw cycles were carried out using the rapid freezing method. After the cycle, the mass loss rate and relative dynamic modulus of elasticity of the specimen were measured.

[0048] Drying shrinkage value: GB / T 11969-2020 "Test Method for Performance of Autoclaved Aerated Concrete" was followed. A prism specimen of 100mm×100mm×400mm was used. The length change of the specimen after drying to constant weight was measured in a standard test environment of 20±2℃ and 43±2% relative humidity. The drying shrinkage value was calculated.

[0049] 2.5 Fire safety performance test of concrete Combustion performance: The combustion performance rating of the test specimens was determined by systematic testing using the large plate combustion method and cone calorimeter method in accordance with GB 8624-2012 "Classification of Combustion Performance of Building Materials and Products".

[0050] Table 1. Performance Test Results of Foaming Agent

[0051] As can be seen from the data in Table 1, the modified protein foaming agents prepared in Examples 1-3 of this invention have a comprehensive performance that is far superior to the two mainstream commercially available foaming agents.

[0052] The foaming agent of this invention maintains a stable foaming ratio of 26-30 times at room temperature, and the water bleeding rate is less than 10% after 1 hour. In a wide temperature range of 5-45℃ and a wide range of acid and alkaline environments with pH=4-10, the foaming ratio decay rate is less than 8%, which fully realizes the wide adaptability of temperature and pH resistance claimed in this invention and meets the design goals for the performance of the foaming agent in the invention.

[0053] Comparing two commercially available products, the pure animal protein-based foaming agent exhibited a foaming ratio attenuation rate exceeding 35% under high and low temperatures and extreme pH conditions, and a water bleeding rate exceeding 30% within 1 hour. Even the animal-plant composite foaming agent FP-50, which boasts superior overall performance, still showed an attenuation rate exceeding 20% ​​under high and low temperatures, exceeding 25% under extreme pH conditions, and a water bleeding rate exceeding 24%. The core reason lies in this invention: through free radical grafting modification of polypeptide molecules with N-vinylpyrrolidone and hydroxyethyl methacrylate, a rigid five-membered ring structure with temperature and hydrolysis resistance and a hydrophilic hydroxyethyl side chain are introduced, significantly enhancing the stability of the protein molecule backbone. This fundamentally solves the industry pain points of traditional protein-based foaming agents, such as temperature sensitivity, pH sensitivity, and poor foam stability, making it suitable for complex construction and service environments such as low winter temperatures, high summer temperatures, and coastal saline-alkali land.

[0054] Table 2. Comprehensive performance test results of lightweight thermal insulation foamed concrete at 28 days.

[0055] As can be seen from the data in Table 2, Comparative Example 2, which used virgin unmodified EPS particles but only replaced them with the modified foaming agent of this invention, showed a 51.8% drop in 28-day compressive strength, a 39.6% increase in thermal conductivity, and an 11.0% decrease in closed-cell rate compared to Example 1. After freeze-thaw cycles, its performance was severely degraded, and its flammability dropped to B1 grade. This directly proves that virgin EPS particles have extremely poor interfacial compatibility with the cement matrix, easily leading to particle agglomeration, interfacial peeling, and pore structure collapse. It also poses a safety risk of molten dripping in a fire. Optimization with foaming agents alone cannot compensate for this core defect.

[0056] Comparative Example 4 lacked only the homologous protein pre-coating step; the remaining modification processes, foaming agents, and concrete formulations were completely identical to Example 1. Compared to Example 1, the compressive strength decreased by 28.4%, the thermal conductivity increased by 18.8%, and the closed-cell rate and freeze-thaw resistance both declined significantly. This fully verifies that the original homologous protein pre-coating technology of this invention is the core key to achieving homologous bridging between EPS particles and protein foaming agents, uniform foam anchoring, and the construction of a multi-level closed-cell structure of "EPS large closed cells - foam micropores." It fundamentally eliminates interface defects and achieves a synergistic improvement in thermal insulation and mechanical properties, providing direct data support for the core innovation of this invention.

[0057] Comparative Examples 2 and 3, using the modified foaming agent and the composite modified EPS particles of this invention separately, respectively, showed significantly lower overall performance than Example 1. Example 1, through the synergistic design of the two, relied on the interfacial bridging effect of the homologous protein layer to achieve spontaneous and uniform distribution and mutual anchoring of foam and EPS particles in the cement paste. This avoided the agglomeration and co-location problems caused by interfacial energy differences in traditional technologies, increasing the closed-cell rate to over 92% and reducing the thermal conductivity to a minimum of 0.040 W / (m·K), while maintaining excellent compressive strength. This breakthrough overcomes the technical bottleneck of existing foamed concrete where "lightweight, high strength, and thermal insulation" are mutually exclusive.

[0058] Comparative Example 1 serves as a blank control in the prior art. It uses both commercially available common foaming agent and virgin EPS particles. Its performance is the worst among all samples, further proving that the present invention comprehensively solves the three core problems in the prior art—poor interface bonding, insufficient foaming agent stability, and inability to precisely control pore structure—through the synergistic design of dual-material modification.

[0059] Scanning electron microscopy (SEM) images of 28-day-old foamed concrete were used. Sample 1 (Figure e) exhibited the most optimized microstructure, with uniform particle spacing, a transition zone width controlled within 2 μm, and reduced matrix porosity and crack count, displaying typical "dense filling" characteristics and fully utilizing the particle filling effect. Figures a and b, corresponding to the SEM images of samples 1-4, show severe separation between EPS and the matrix interface, large and interconnected pores, particle agglomeration, and a loose structure. Comparative Example 2 still showed obvious interface gaps and an uneven pore structure. Comparative Example 3 showed improved interface, but poor foam stability resulted in numerous co-occurring and open pores, and many matrix cracks. Comparative Example 4 lacked homologous protein coating, still had micro-cracks at the interface, and an insufficiently uniform pore structure.

[0060] The foamed concrete in Examples 1-3 can achieve a strength of 265-385 kg / m³. 3 Within a wide range of dry density, it stably achieves compressive strength of 1.42~3.05MPa and thermal conductivity of 0.040~0.059W / (m・K). Its combustion performance consistently reaches Class A non-combustible, with no high-temperature melting drips or toxic gas release. Its freeze-thaw resistance and shrinkage resistance durability far exceed those of conventional foamed concrete. It fully meets the engineering application requirements of building exterior wall insulation, roof insulation, prefabricated building wall filling, and underfloor heating insulation layers, and has excellent engineering adaptability and promotion value.

[0061] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A lightweight, thermally insulating foamed concrete, characterized in that, The formula comprises, by weight, 100 parts of cementitious material, 40-55 parts of mixing water, 0.2-0.5 parts of polycarboxylate superplasticizer, and 3-15% of composite modified EPS particles (by absolute volume) relative to 100 parts of cementitious material, and 0.5-2 parts of modified protein foaming agent. The modified protein foaming agent, by weight, comprises 30-45 parts of hydrolyzed animal protein base, 8-15 parts of modified graft monomer, 5-10 parts of amphoteric surfactant, 3-6 parts of silane coupling agent, 2-5 parts of polyol foam stabilizer, and 0.5-2 parts of pH adjuster. The total mass of the formula is 100 parts, with any fraction less than 100 parts made up by deionized water. The modified graft monomer is a mixture of N-vinylpyrrolidone and hydroxyethyl methacrylate in a mass ratio of 2-3:

1.

2. The lightweight thermal insulation foamed concrete according to claim 1, characterized in that, The cementitious material, by weight, includes 70-85 parts of P·O42.5 grade silicate cement, 10-20 parts of fly ash, 3-8 parts of silica fume, and 2-5 parts of nano-calcium carbonate.

3. The lightweight thermal insulation foamed concrete according to claim 1, characterized in that, The composite modified EPS particles have a particle size of 0.5-3 mm, and the three-step modification method is as follows: (1) Low-temperature plasma surface activation: EPS particles are placed in a low-temperature plasma reaction chamber, argon gas is introduced, the vacuum degree is controlled at 20-30Pa, the power is 80-120W, and the processing time is 5-10min to obtain activated EPS particles with active hydroxyl groups and peroxy free radicals on the surface. (2) Silane sulfonate copolymerization grafting: Activated EPS particles are added to a dispersion prepared by anhydrous ethanol and deionized water at a volume ratio of 9:1 and a solid-liquid ratio of 1:

10. Nitrogen gas is introduced to remove oxygen. The monomers vinyltriethoxysilane and sodium methacrylate sulfonate and the initiator azobisisobutyronitrile are added. The mass ratio of vinyltriethoxysilane to sodium methacrylate sulfonate is 3:

1. The total amount of monomer added is 3-5% of the mass of EPS particles, and the amount of initiator added is 0.3-0.5% of the total mass of monomers. The temperature is raised to 60-65℃ and the reaction is stirred at a constant temperature for 3-4 hours. After filtration, the particles are washed 3 times with anhydrous ethanol and dried to obtain grafted modified EPS particles. (3) Homologous protein pre-coating: The grafted modified EPS particles are immersed in a hydrolyzed animal protein base water solution with a mass concentration of 2-4%. The hydrolyzed animal protein base water solution is the same material used in the modified protein foaming agent. The mixture is stirred for 15-20 minutes, filtered, and then vacuum dried at 40-50℃ to obtain composite modified EPS particles.

4. The lightweight thermal insulation foamed concrete according to claim 1, characterized in that, In the modified protein foaming agent, the hydrolyzed animal protein base is a hydrolysate obtained by protease hydrolysis of bovine bone waste; the amphoteric surfactant is one or both of dodecyl dimethyl betaine or cocamidopropyl hydroxysulfonate betaine; the silane coupling agent is KH550 or KH560; the polyol foam stabilizer is one or more of glycerol, butanediol or sorbitol; and the pH adjuster is citric acid or triethanolamine.

5. The lightweight thermal insulation foamed concrete according to claim 4, characterized in that, The preparation method of the modified protein-based foaming agent includes the following steps: S1: Base material dissolution: After crushing the bovine bone waste, it is hydrolyzed by protease, enzyme inactivation, filtration and concentration to obtain hydrolyzed animal protein base material with a solid content of 15-20%; S2: Heat deionized water to 45-50℃, add hydrolyzed animal protein base, stir evenly, raise the temperature to 40-45℃, adjust the pH of the system to 7.5-8.5, and obtain the base premix solution; S3: Grafting modification: Nitrogen gas is introduced into the base material premix to remove oxygen, and the formulated amount of modified grafting monomer and initiator ammonium persulfate is added. The amount of initiator added is 0.4-0.6% of the total mass of the modified grafting monomer. The temperature is raised to 65-70℃ and the reaction is stirred at a constant temperature for 4-6 hours to complete the free radical grafting modification of the polypeptide molecules and obtain the grafting modified solution. S4: Compound homogenization: Cool the grafted modified liquid to 40-45℃, add the amphoteric surfactant, silane coupling agent and polyol foam stabilizer in sequence according to the formula, stir at constant temperature for 30-45 minutes to obtain homogenized liquid. S5: Post-treatment: Cool the homogenized liquid to room temperature, adjust the pH of the system to 6.5-7.5 with a pH adjuster, filter to remove insoluble matter, and obtain the modified protein foaming agent.

6. A method for preparing lightweight thermal insulation foamed concrete according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Powder premixing: Add each component of the gelling material into the mixer according to the formula, dry mix for 3-5 minutes, and mix evenly to obtain dry powder mixture; (2) Pre-foaming with foaming agent: Dilute the modified protein foaming agent with water at a mass ratio of 1:20-1:40, add it to the foaming machine, and prepare uniform and fine foam for later use; (3) Slurry mixing: Add the specified amount of mixing water and polycarboxylate superplasticizer to the dry powder mixture, stir for 3-5 minutes to obtain a uniform cement slurry; then add the composite modified EPS particles, stir for 2-3 minutes to ensure that the EPS particles are evenly dispersed in the slurry; finally add the foam prepared in step (2), stir for 2-4 minutes to obtain a uniform foamed concrete mixture. (4) Pouring and curing: The mixture is poured into the mold, allowed to stand at room temperature for foaming and initial setting, then covered with a film for curing for 24 hours before demolding, and then cured under standard curing conditions for 28 days to obtain the lightweight thermal insulation foamed concrete.

7. The method for preparing lightweight thermal insulation foamed concrete according to claim 6, characterized in that, In step (3), the stirring speed is 60-90 r / min.

8. The method for preparing lightweight thermal insulation foamed concrete according to claim 6, characterized in that, In step (4), the standard curing conditions are a temperature of 20±2℃ and a relative humidity of ≥95%.

9. The application of the lightweight thermal insulation foamed concrete according to any one of claims 1-5 in building exterior wall insulation, roof insulation, prefabricated building wall filling, and underfloor heating insulation layer.

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