Super-lightweight concrete with high fire resistance and method for preparing same

Abstract

The application belongs to the technical field of building materials, and particularly relates to a super-light concrete with high fireproof performance, which is a multi-component composite system and is prepared by compounding a base cementing material, a light functional filler, a super-fine reinforcing component and a special-purpose composite additive according to a specific mass ratio; the base cementing material is ordinary Portland cement with a strength grade of 42.5 or above, the light functional filler is polyphenyl granules subjected to surface modification treatment, the super-fine reinforcing component is a compound of silica fume and super-fine powder, and the special-purpose composite additive contains a water reducing agent, a retarder, a water retaining agent and a crack resistance agent, and does not contain magnesium oxide. The application provides the super-light concrete with low apparent density, good interface adhesion, excellent strength and fireproof performance, and provides a preparation method which is controllable in process and simple in operation, and ensures stable product performance and is suitable for application in key parts such as building floor and floor.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to an ultra-lightweight concrete with high fire resistance and its preparation method. Background Technology

[0002] As the construction industry moves towards lightweight, green, and high-performance construction, ultralight concrete, with its low apparent density, excellent thermal insulation properties, and convenient construction, is widely used in the enclosure structures and non-load-bearing components of energy-efficient buildings. However, existing ultralight concrete often uses polystyrene particles and ceramsite as lightweight aggregates, which generally suffer from low strength, poor interfacial adhesion with cementitious substrates, and insufficient fire resistance, limiting its application in building floors and slabs where structural safety and fire resistance requirements are high.

[0003] Polystyrene particles, as a commonly used lightweight filler, have the advantages of extremely low density and good thermal insulation. However, due to their strong surface inertness and poor compatibility with cementitious materials, their low interfacial bond strength easily leads to the formation of weak interfaces within the concrete. This not only affects the structural strength and durability but also causes structural damage under extreme conditions such as fires due to interfacial peeling and particle shrinkage during combustion. Furthermore, existing ultra-lightweight concrete often uses silica fume or fly ash as the reinforcing components, failing to fully utilize their micro-aggregate filling effect and pozzolanic activity. This makes it difficult to effectively optimize the internal microstructure of the concrete, resulting in high porosity and further affecting strength and fire resistance.

[0004] Furthermore, existing ultralight concrete preparation processes suffer from problems such as unreasonable mixing techniques and inadequate raw material pretreatment, which easily lead to the agglomeration of lightweight particles and poor slurry homogeneity, resulting in internal defects in components. The selection and proportioning of specialized additives lack specificity, and some additives contain components such as magnesium oxide that can easily cause later volume expansion, affecting the long-term stability of the concrete. Therefore, developing an ultralight concrete with low apparent density, meeting strength standards, excellent fire resistance, and a stable and controllable preparation process has become an urgent need in the current building materials field.

[0005] To address the shortcomings of the existing technologies, this invention provides a high-fire-resistant ultralight concrete and its preparation method by optimizing component design, improving raw material pretreatment processes and preparation procedures. The aim is to solve the problems of poor interfacial bonding, low strength, insufficient fire resistance and unstable preparation process of existing ultralight concrete. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of existing ultralight concrete, such as low interfacial bond strength, insufficient strength, poor fire resistance, and unstable preparation process, and to provide an ultralight concrete with low apparent density, good interfacial bond, and excellent strength and fire resistance. At the same time, it provides a preparation method with controllable process and simple operation to ensure stable product performance and suitability for application in key parts of building floors and slabs.

[0007] The specific technical solution adopted by this invention is as follows: A high-fire-resistant ultralight concrete is a multi-component composite system, composed of basic cementitious materials, lightweight functional fillers, ultrafine reinforcing components, and special composite additives in a specific mass ratio. The basic cementitious material is ordinary Portland cement with a strength grade of 42.5 or higher; the lightweight functional filler is surface-modified polystyrene particles; the ultrafine reinforcing component is a mixture of silica fume and ultrafine powder; and the special composite additives include water-reducing agents, retarders, water-retaining agents, and crack-resistant agents, and explicitly do not contain magnesium oxide. The apparent density of the ultralight concrete is 300-400 kg / m³.

[0008] In a preferred embodiment, the lightweight functional filler polystyrene particles have a particle size range of 3-5 mm, a particle size distribution uniformity ≥90%, a bulk density ≤15 kg / m³, and a particle moisture content ≤0.5%. The polystyrene particles undergo surface modification treatment using a silane coupling agent. The specific parameters of the modification treatment are as follows: γ-aminopropyltriethoxysilane is selected as the modifier; a 2%-3% (w / w) aqueous solution of the silane coupling agent is prepared; this aqueous solution is uniformly sprayed onto the surface of the polystyrene particles using a mist spray method, with a spray volume of 1%-1.5% of the polystyrene particle mass. After spraying, the polystyrene particles are placed in a ventilated environment to air dry naturally for 4-6 hours to ensure complete curing of the modifier. After the above modification treatment, the interfacial bonding strength between the polystyrene particles and the cementitious substrate is increased by ≥30% compared to unmodified polystyrene particles.

[0009] In a preferred embodiment, the ultrafine reinforcing component has a fineness ≥800 mesh, a specific surface area ≥500 m² / kg, and its mass percentage in the ultralight concrete is 5%-8%; the ultrafine powder is a compound of silica fume and ultrafine powder in a mass ratio of 1:2-1:3, wherein the silica fume has a SiO2 content ≥90% and a loss on ignition ≤6%, and the ultrafine powder has a fineness ≥1200 mesh, a water requirement ratio ≤95%, and a loss on ignition ≤5%; this compounded ultrafine reinforcing component utilizes the micro-aggregate filling effect and pozzolanic activation... The superfine powder has a chemical effect, filling the pores between cement hydration products, optimizing the internal microstructure of concrete, reducing porosity, and undergoing a secondary hydration reaction with Ca(OH)2 produced by cement hydration to generate hydrated calcium silicate gel, thereby improving the strength, density, and durability of ultralight concrete. The superfine powder needs to be pretreated before use. The pretreatment method is to place the superfine powder in a drying oven at 105±5℃ for 1-2 hours to remove free moisture and ensure that the moisture content of the dried superfine powder is ≤0.3%.

[0010] In a preferred embodiment, a method for preparing ultra-lightweight concrete with high fire resistance is characterized by: the preparation method employing a process route of staged orderly mixing, precise temperature control, and pre-curing treatment, specifically including the following steps: Step 1: Raw material pretreatment: Polystyrene particle pretreatment: Place polystyrene particles with a particle size of 3-5mm in a constant temperature drying oven at 60-70℃ and dry for 2-3 hours to remove free moisture inside the particles. After drying, remove and cool to room temperature. Then, place the cooled polystyrene particles in a continuous spray modification equipment and use a 2%-3% silane coupling agent aqueous solution for surface spray modification. During the spraying process, control the equipment speed at 15-20r / min to ensure uniform spraying. After spraying, transport the polystyrene particles to a ventilated drying area and air dry naturally for 4-6 hours until the modifier is completely cured. Set aside for later use. Ultrafine powder pretreatment: Place the silica fume and ultrafine powder compound mixed evenly in a mass ratio of 1:2-1:3 in a drying oven at 105±5℃ and dry for 1-2 hours. Stir once every 30 minutes during the drying process to ensure uniform drying. After drying, remove and cool to room temperature. Check the moisture content and set aside for later use. Step 2: Preparation of premixed substrate: Weigh out ordinary Portland cement of grade 42.5 or above and pretreated special composite additive according to the mass ratio, wherein the mass ratio of special composite additive to cement is 1:15-1:20; put both into a twin-shaft paddle mixer, adjust the mixer speed to 120-150 r / min, mix for 6-8 min, control the mixing gap to 2-3 mm during the mixing process, the ambient temperature to 15-30℃, and the ambient humidity to ≤60%, to ensure that the cement and composite additive are fully and evenly mixed to form a premixed substrate with consistent color and no lumps; Step 3: Lightweight filler mixing: Add pretreated polystyrene particles to the premixed substrate prepared in Step 2. The amount of polystyrene particles added is 20%-30% of the mass of the premixed substrate. Adjust the speed of the twin-shaft paddle mixer to 90-120 r / min and stir for 4-5 min. During the stirring process, use an infrared thermometer to monitor the temperature of the stirring system in real time to ensure that the system temperature does not exceed 40℃, so as to avoid the polystyrene particles softening and deforming due to high temperature. At the same time, the mixing state can be observed in real time through the observation window during the stirring process to ensure that the polystyrene particles are uniformly dispersed in the premixed substrate without agglomeration. Step 4: Compounding of ultrafine reinforcing components: Add the pretreated ultrafine powder to the mixture obtained in Step 3 in 3-4 batches, with each batch accounting for 25%-33% of the total mass of the ultrafine powder; after adding the first batch of ultrafine powder, stir at a speed of 90 r / min for 2-3 minutes until it is completely dispersed before adding the second batch, and so on, until all the ultrafine powder has been added and completely dispersed, at which point the mixture forms a uniform slurry state; Step 5: Slurry maturation treatment: Transfer the ultralight concrete slurry obtained in Step 4 to a maturation tank and let it stand for 10-15 minutes. During the maturation process, stir it at 50 r / min for 1 minute every 5 minutes to eliminate air bubbles inside the slurry and ensure the homogeneity of the slurry. After maturation, test the fluidity and air content of the slurry. If it meets the requirements, it can be used for on-site pouring construction. If the test fails, it can be fine-tuned by adjusting the amount of water-reducing agent or extending the maturation time until the construction requirements are met.

[0011] In a preferred embodiment, the preparation process of the silane coupling agent aqueous solution in step 1 is as follows: first, deionized water is heated to 30-40℃, and then γ-aminopropyltriethoxysilane is slowly added while stirring. The stirring speed is 80-100 r / min, and the stirring time is 15-20 min to ensure that the silane coupling agent is completely dissolved and a uniform aqueous solution is formed. The moisture content of the polystyrene particles after drying and modification is ≤0.3%, and the thickness of the surface modification layer is 5-10 μm. The drying treatment of the ultrafine powder in step 1 needs to be carried out under negative pressure, with a negative pressure of -0.05--0.03 MPa, to accelerate the evaporation rate of moisture and improve the drying efficiency. After drying, the ultrafine powder is sealed and stored to avoid reabsorbing moisture from the air. The relative humidity of the storage environment is ≤50%, and the temperature is ≤30℃.

[0012] In a preferred embodiment, the blades of the twin-shaft paddle mixer in step 2 are made of wear-resistant stainless steel, and the blade angle adjustment range is 30°-60°. By adjusting the blade angle, it can adapt to the mixing requirements of different stages. During the mixing process, if a small amount of lumps are found in the premixed substrate, they are screened in real time using the mixer's built-in screening device. The screen mesh size is 1.2mm. The screened lumps need to be broken up and put back into the mixer for mixing. The water-reducing agent in the special composite additive in step 2 is a polycarboxylate-based high-efficiency water-reducing agent with a water reduction rate ≥25%; the retarder is trisodium citrate, with a dosage of 0.05%-0.1% of the cement mass; the water-retaining agent is hydroxypropyl methylcellulose ether with a molecular weight of 200,000-300,000, with a dosage of 0.1%-0.2% of the cement mass; and the crack-resistant agent is polypropylene fiber with a length of 6-12mm, with a dosage of 0.08%-0.15% of the cement mass.

[0013] In a preferred embodiment, the construction process of the application includes construction preparation, formwork erection, rebar tying, grout pouring, natural curing, and formwork removal.

[0014] In a preferred embodiment, the construction preparation includes: cleaning the construction site before construction to ensure that the site is flat and free of debris; re-inspecting the performance of the ultra-lightweight concrete slurry to ensure that the slurry's fluidity and air content meet the construction requirements; and preparing conventional building formwork, reinforcing bars, vibration equipment, and curing materials.

[0015] In a preferred embodiment, the formwork is erected using ordinary steel or wooden formwork. The inside of the formwork is coated with a release agent, preferably a water-based one, which is applied evenly to avoid any missed spots. The joints between the formwork panels are sealed to prevent grout leakage during the pouring process.

[0016] In a preferred embodiment, the natural curing process involves covering the slurry surface with geotextile or plastic film for moisture retention within 12 hours after pouring, maintaining an ambient temperature of 5-35℃ and a humidity of ≥70%. During curing, regular watering is required to ensure the surface remains moist, with a curing time of ≥7 days. If the ambient temperature is below 5℃, insulation measures must be taken to prevent the slurry from freezing. If the ambient temperature is above 35℃, the frequency of watering must be increased to prevent excessive surface water loss and cracking.

[0017] The technical effects achieved by this invention are as follows: This invention uses γ-aminopropyltriethoxysilane to modify the surface of polystyrene particles. The modifier is uniformly covered by mist spraying, which significantly improves the interfacial bonding strength between polystyrene particles and cementitious substrate. This effectively solves the problems of poor compatibility and interfacial delamination between lightweight particles and cementitious substrate in traditional ultra-lightweight concrete, laying the foundation for high strength and high durability of concrete.

[0018] By compounding silica fume with ultrafine powder to form an ultrafine reinforcing component, the micro-aggregate filling effect and pozzolanic activity effect are utilized to optimize the internal microstructure of concrete and reduce porosity. At the same time, it undergoes a secondary hydration reaction with cement hydration products to generate hydrated calcium silicate gel, which significantly improves the strength, density and durability of ultralight concrete. The final product has an apparent density of only 300-400 kg / m³, achieving lightweight while meeting the strength requirements of building structures.

[0019] The special composite additive does not contain magnesium oxide or other components that easily cause volume expansion. By rationally combining water-reducing agents, retarders, water-retaining agents and crack-resistant agents, it effectively controls internal defects in concrete. Combined with optimized microstructure and excellent interfacial bonding performance, it can avoid structural damage caused by particle burning shrinkage and interfacial peeling under fire conditions, significantly improving fire resistance performance. It is suitable for building parts with high fire resistance requirements.

[0020] The process adopts a phased and orderly stirring, precise temperature control and pre-cooking treatment. The raw material pretreatment removes free moisture and ensures the modification effect. The batch addition of ultrafine reinforcing components and the control of stirring speed and temperature ensure the homogeneity of the slurry. Intermittent stirring during the cooking process eliminates air bubbles and further improves the stability of product performance. The whole process is simple to operate and the parameters are easy to control, making it suitable for industrial production.

[0021] The ultralight concrete of this invention can be directly applied to building floors, slabs and other parts. The construction process is simple and the curing conditions are easy to meet. The product has lightweight, high strength, high fire resistance and good durability. It can adapt to the building needs in different environments and has significant economic and social benefits. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a method for preparing ultra-lightweight concrete with high fire resistance according to the present invention. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] Example 1

[0025] A high-fire-resistant ultra-lightweight concrete is composed of the following components in the following mass ratio: 100 parts of 42.5 grade ordinary Portland cement, 25 parts of modified polystyrene particles, 6 parts of ultrafine reinforcing component (silica fume: ultrafine powder = 1:2), and 5 parts of special composite additive (the mass ratio of special composite additive to cement is 1:20).

[0026] in: - Modified polystyrene particles: particle size 3-5mm, particle size distribution uniformity 92%, bulk density 12kg / m³, moisture content 0.4%; modified by spraying with 2% γ-aminopropyltriethoxysilane aqueous solution, the spraying amount is 1% of the mass of polystyrene particles, and ventilated and dried for 4 hours; the interfacial bonding strength after modification is 32% higher than that of unmodified particles.

[0027] - Ultrafine reinforcing component: fineness 800 mesh, specific surface area 520m² / kg; silica fume SiO2 content 92%, loss on ignition 5%; ultrafine powder fineness 1200 mesh, water requirement ratio 93%, loss on ignition 4%; pretreatment conditions are drying at 105℃ for 1.5h, negative pressure -0.04MPa, and moisture content after drying is 0.2%.

[0028] - Special composite additives: polycarboxylate-based high-efficiency water-reducing agent (water reduction rate 26%), trisodium citrate retarder (dosage is 0.08% of cement mass), hydroxypropyl methylcellulose ether water-retaining agent (molecular weight 250,000, dosage is 0.15% of cement mass), polypropylene fiber crack-resistant agent (length 8mm, dosage is 0.12% of cement mass).

[0029] The above-mentioned method for preparing ultralight concrete includes the following steps: 1. Raw material pretreatment: (1) Polystyrene particles: Dry at 65℃ for 2.5h, cool to room temperature and then put into a continuous spray modification equipment, spray 2% silane coupling agent aqueous solution at 18r / min speed, and air dry for 5h for later use. (2) Ultrafine powder: Mix silica fume and ultrafine powder at a ratio of 1:2, dry at 105℃ and -0.04MPa negative pressure for 1.5h, stir once every 30min, cool and seal for later use; (3) Silane coupling agent aqueous solution: Add γ-aminopropyltriethoxysilane to deionized water at 35℃ and stir at 90r / min for 18min to form a uniform aqueous solution.

[0030] 2. Preparation of premixed substrate: Cement and special composite additives are put into a twin-shaft paddle mixer and stirred at 130 r / min for 7 min with a stirring gap of 2.5 mm. The ambient temperature is 25℃ and the humidity is 55%. The mixture is then sieved to remove lumps and a uniform premixed substrate is obtained.

[0031] 3. Lightweight filler mixing: Add modified polystyrene particles to the premixed substrate, stir at 100 r / min for 4.5 min, and monitor the temperature in real time at 38℃ to ensure that the particles are uniformly dispersed and do not agglomerate.

[0032] 4. Blending of ultrafine reinforcing components: Add the ultrafine powder in 3 batches, 2 parts per batch. After adding the first batch, stir at 90 r / min for 3 min, and then add the subsequent batches in sequence, stirring until a uniform slurry is formed.

[0033] 5. Slurry maturation treatment: Transfer the slurry to a maturation tank, let it stand for 12 minutes, and stir it for 1 minute at 50 r / min every 5 minutes. After maturation, test the fluidity and air content to ensure they are qualified before using it for casting.

[0034] 6. Application and construction: Construction is carried out according to the process of construction preparation, formwork erection, rebar binding and grout pouring. After pouring, geotextile is covered for moist curing within 12 hours. The ambient temperature is 20℃ and the humidity is 75%. Curing is carried out for 8 days to obtain the building floor slab components.

[0035] The ultralight concrete prepared in this embodiment has an apparent density of 350 kg / m³, a compressive strength of 3.2 MPa, an interfacial bond strength of 1.8 MPa, and a fire resistance rating of Class A, meeting the requirements for use as a building floor slab.

[0036] Example 2

[0037] A high-fire-resistant ultra-lightweight concrete is composed of the following components in the following mass ratio: 100 parts of 42.5 grade ordinary Portland cement, 20 parts of modified polystyrene particles, 8 parts of ultrafine reinforcing component (silica fume: ultrafine powder = 1:3), and 6.7 parts of special composite additive (the mass ratio of special composite additive to cement is 1:15).

[0038] in: - Modified polystyrene particles: particle size 3-5mm, particle size distribution uniformity 93%, bulk density 10kg / m³, moisture content 0.3%; modified by spraying with 3% γ-aminopropyltriethoxysilane aqueous solution, the spraying amount is 1.5% of the mass of polystyrene particles, and ventilated and dried for 6 hours; the interfacial bonding strength after modification is 35% higher than that of unmodified particles.

[0039] - Ultrafine reinforcing component: fineness 900 mesh, specific surface area 550m² / kg; silica fume SiO2 content 93%, loss on ignition 4%; ultrafine powder fineness 1500 mesh, water requirement ratio 92%, loss on ignition 3%; pretreatment conditions are drying at 110℃ for 1h, negative pressure -0.05MPa, and moisture content after drying is 0.1%.

[0040] - Special composite additives: polycarboxylate-based high-efficiency water-reducing agent (water reduction rate 28%), trisodium citrate retarder (dosage is 0.1% of cement mass), hydroxypropyl methylcellulose ether water-retaining agent (molecular weight 300,000, dosage is 0.2% of cement mass), polypropylene fiber crack-resistant agent (length 12mm, dosage is 0.15% of cement mass).

[0041] The preparation and application process was the same as in Example 1, with the following parameters adjusted: polystyrene particles were dried at 70°C for 2 hours, modified by spraying at 20 rpm for 6 hours; ultrafine powder was dried at 110°C for 1 hour; premixed substrate was stirred at 150 rpm for 6 minutes; lightweight filler was mixed at 120 rpm for 4 minutes; ultrafine powder was added in 4 batches; curing time was 15 minutes; curing temperature was 25°C and humidity was 80% for 7 days.

[0042] The ultralight concrete prepared in this embodiment has an apparent density of 320 kg / m³, a compressive strength of 3.5 MPa, an interfacial bond strength of 2.0 MPa, and a fire resistance rating of Class A, making it suitable for building floor components.

[0043] Example 3

[0044] A high-fire-resistant ultra-lightweight concrete is composed of the following components in the following mass ratio: 100 parts of 42.5 grade ordinary Portland cement, 30 parts of modified polystyrene particles, 5 parts of ultra-fine reinforcing component (silica fume: ultra-fine powder = 1:2.5), and 5.5 parts of special composite additive (the mass ratio of special composite additive to cement is 1:18).

[0045] The preparation and application process were the same as in Example 1, with the following parameters adjusted: polystyrene particles were dried at 60°C for 3 hours, modified by spraying at 15 r / min for 4 hours; ultrafine powder was dried at 100°C for 2 hours; premixed substrate was stirred at 120 r / min for 8 minutes; lightweight filler was mixed at 90 r / min for 5 minutes; ultrafine powder was added in 3 batches; curing time was 10 minutes; curing temperature was 10°C and humidity was 70% for 10 days.

[0046] The ultralight concrete prepared in this embodiment has an apparent density of 380 kg / m³, a compressive strength of 3.0 MPa, an interfacial bond strength of 1.7 MPa, and a fire resistance rating of Class A. It can be used for building floor slab construction in low ambient temperatures.

[0047] This invention employs γ-aminopropyltriethoxysilane to surface-modify polystyrene particles. A mist spray ensures uniform coverage of the modifier, significantly improving the interfacial bond strength between the polystyrene particles and the cementitious substrate. This effectively solves the problems of poor compatibility and interfacial delamination between lightweight particles and the cementitious substrate in traditional ultra-lightweight concrete, laying the foundation for high strength and durability of the concrete. By compounding silica fume with ultrafine powder to form an ultrafine reinforcing component, the micro-aggregate filling effect and pozzolanic activity effect are utilized to optimize the internal microstructure of the concrete and reduce porosity. Simultaneously, a secondary hydration reaction occurs with cement hydration products to generate hydrated calcium silicate gel, significantly improving the strength, density, and durability of the ultra-lightweight concrete. The final product has an apparent density of only 300-400 kg / m³, achieving lightweight while meeting the strength requirements of building structures. The special composite additive does not contain components such as magnesium oxide that easily cause volume expansion. Through reasonable proportioning of water-reducing agents, retarders, water-retaining agents, and crack-resistant agents… This agent effectively controls internal defects in concrete. Combined with optimized microstructure and excellent interfacial bonding performance, it avoids structural damage caused by particle shrinkage and interfacial peeling under fire conditions, significantly improving fire resistance. Suitable for building components with high fire resistance requirements, it employs a phased, orderly mixing, precise temperature control, and pre-curing process. Raw material pretreatment removes free moisture and ensures modification effects. Batch addition of ultrafine reinforcing components and control of mixing speed and temperature ensure slurry homogeneity. Intermittent mixing during curing eliminates air bubbles, further enhancing product performance stability. The entire process is simple to operate and parameters are easily controlled, making it suitable for industrial production. This ultralight concrete can be directly applied to building floors and slabs, with a simple construction process and easily met curing conditions. The product combines lightweight, high strength, high fire resistance, and good durability, adapting to building needs in different environments and offering significant economic and social benefits.

[0048] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A type of ultra-lightweight concrete with high fire resistance, characterized in that: The ultralight concrete is a multi-component composite system, which is composed of basic cementitious materials, lightweight functional fillers, ultrafine reinforcing components and special composite additives in a specific mass ratio. The basic cementitious material is ordinary Portland cement with a strength grade of 42.5 or above. The lightweight functional filler is polystyrene particles with surface modification treatment. The ultrafine reinforcing component is a compound of silica fume and ultrafine powder. The special composite additives include water-reducing agents, retarders, water-retaining agents and crack-resistant agents, and the special composite additives are explicitly free of magnesium oxide. The apparent density of the ultralight concrete is 300-400 kg / m³.

2. The ultra-lightweight concrete with high fire resistance according to claim 1, characterized in that: The lightweight functional filler polystyrene particles have a particle size range of 3-5 mm, a particle size distribution uniformity of ≥90%, a bulk density of ≤15 kg / m³, and a particle moisture content of ≤0.5%. The polystyrene particles undergo surface modification treatment using a silane coupling agent. The specific parameters of the modification treatment are as follows: γ-aminopropyltriethoxysilane is selected as the modifier; a 2%-3% (w / w) aqueous solution of the silane coupling agent is prepared; this aqueous solution is uniformly sprayed onto the surface of the polystyrene particles using a mist spray method, with a spray volume of 1%-1.5% of the polystyrene particle mass. After spraying, the polystyrene particles are placed in a ventilated environment to air dry naturally for 4-6 hours to ensure complete curing of the modifier. After the above modification treatment, the interfacial bonding strength between the polystyrene particles and the cementitious substrate is increased by ≥30% compared to unmodified polystyrene particles.

3. The ultra-lightweight concrete with high fire resistance according to claim 2, characterized in that: The ultrafine reinforcing component has a fineness ≥800 mesh, a specific surface area ≥500 m² / kg, and its mass percentage in ultralight concrete is 5%-8%. The ultrafine powder is a compound of silica fume and ultrafine powder in a mass ratio of 1:2-1:3, wherein the silica fume has a SiO2 content ≥90% and a loss on ignition ≤6%, and the ultrafine powder has a fineness ≥1200 mesh, a water requirement ratio ≤95%, and a loss on ignition ≤5%. This compounded ultrafine reinforcing component utilizes the micro-aggregate filling effect and the pozzolanic activity effect. It fills the pores between cement hydration products, optimizes the internal microstructure of concrete, reduces porosity, and undergoes a secondary hydration reaction with Ca(OH)2 produced by cement hydration to generate hydrated calcium silicate gel, thereby improving the strength, density, and durability of ultra-lightweight concrete. The ultra-fine powder needs to be pretreated before use. The pretreatment method is to place the ultra-fine powder in a drying oven at 105±5℃ for 1-2 hours to remove free moisture and ensure that the moisture content of the dried ultra-fine powder is ≤0.3%.

4. The method for preparing ultra-lightweight concrete with high fire resistance according to claim 3, characterized in that: The preparation method employs a process route of staged orderly stirring, precise temperature control, and pre-cooking treatment, specifically including the following steps: Step 1: Raw material pretreatment: Polystyrene particle pretreatment: Place polystyrene particles with a particle size of 3-5mm in a constant temperature drying oven at 60-70℃ and dry for 2-3 hours to remove free moisture inside the particles. After drying, remove and cool to room temperature. Then, place the cooled polystyrene particles in a continuous spray modification equipment and use a 2%-3% silane coupling agent aqueous solution for surface spray modification. During the spraying process, control the equipment speed at 15-20r / min to ensure uniform spraying. After spraying, transport the polystyrene particles to a ventilated drying area and air dry naturally for 4-6 hours until the modifier is completely cured. Set aside for later use. Ultrafine powder pretreatment: Place the silica fume and ultrafine powder compound mixed evenly in a mass ratio of 1:2-1:3 in a drying oven at 105±5℃ and dry for 1-2 hours. Stir once every 30 minutes during the drying process to ensure uniform drying. After drying, remove and cool to room temperature. Check the moisture content and set aside for later use. Step 2: Preparation of premixed substrate: Weigh out ordinary Portland cement of grade 42.5 or above and pretreated special composite additive according to the mass ratio, wherein the mass ratio of special composite additive to cement is 1:15-1:20; put both into a twin-shaft paddle mixer, adjust the mixer speed to 120-150 r / min, mix for 6-8 min, control the mixing gap to 2-3 mm during the mixing process, the ambient temperature to 15-30℃, and the ambient humidity to ≤60%, to ensure that the cement and composite additive are fully and evenly mixed to form a premixed substrate with consistent color and no lumps; Step 3: Lightweight filler mixing: Add pretreated polystyrene particles to the premixed substrate prepared in Step 2. The amount of polystyrene particles added is 20%-30% of the mass of the premixed substrate. Adjust the speed of the twin-shaft paddle mixer to 90-120 r / min and stir for 4-5 min. During the stirring process, use an infrared thermometer to monitor the temperature of the stirring system in real time to ensure that the system temperature does not exceed 40℃, so as to avoid the polystyrene particles softening and deforming due to high temperature. At the same time, the mixing state can be observed in real time through the observation window during the stirring process to ensure that the polystyrene particles are uniformly dispersed in the premixed substrate without agglomeration. Step 4: Compounding of ultrafine reinforcing components: Add the pretreated ultrafine powder to the mixture obtained in Step 3 in 3-4 batches, with each batch accounting for 25%-33% of the total mass of the ultrafine powder; after adding the first batch of ultrafine powder, stir at a speed of 90 r / min for 2-3 minutes until it is completely dispersed before adding the second batch, and so on, until all the ultrafine powder has been added and completely dispersed, at which point the mixture forms a uniform slurry state; Step 5: Slurry maturation treatment: Transfer the ultralight concrete slurry obtained in Step 4 to a maturation tank and let it stand for 10-15 minutes. During the maturation process, stir it at 50 r / min for 1 minute every 5 minutes to eliminate air bubbles inside the slurry and ensure the homogeneity of the slurry. After maturation, test the fluidity and air content of the slurry. If it meets the requirements, it can be used for on-site pouring construction. If the test fails, it can be fine-tuned by adjusting the amount of water-reducing agent or extending the maturation time until the construction requirements are met.

5. The method for preparing ultra-lightweight concrete with high fire resistance according to claim 4, characterized in that: The preparation process of the silane coupling agent aqueous solution in step 1 is as follows: first, deionized water is heated to 30-40℃, and then γ-aminopropyltriethoxysilane is slowly added while stirring. The stirring speed is 80-100 r / min, and the stirring time is 15-20 min to ensure that the silane coupling agent is completely dissolved and a uniform aqueous solution is formed. The moisture content of the polystyrene particles after drying and modification is ≤0.3%, and the thickness of the surface modification layer is 5-10 μm. The drying treatment of the ultrafine powder in step 1 needs to be carried out under negative pressure, with a negative pressure of -0.05--0.03 MPa, to accelerate the evaporation rate of water and improve the drying efficiency. After drying, the ultrafine powder is sealed and stored to avoid reabsorbing moisture from the air. The relative humidity of the storage environment is ≤50%, and the temperature is ≤30℃.

6. The method for preparing ultralight concrete with high fire resistance according to claim 4, characterized in that: The blades of the twin-shaft paddle mixer mentioned in step 2 are made of wear-resistant stainless steel, and the blade angle adjustment range is 30°-60°. By adjusting the blade angle, it can adapt to the mixing requirements of different stages. During the mixing process, if a small amount of lumps are found in the premixed substrate, they are screened in real time using the mixer's built-in screening device. The screen mesh size is 1.2mm. The screened lumps need to be broken up and put back into the mixer for mixing. The water-reducing agent in the special composite additive mentioned in step 2 is a polycarboxylate-based high-efficiency water-reducing agent with a water reduction rate ≥25%; the retarder is trisodium citrate, with a dosage of 0.05%-0.1% of the cement mass; the water-retaining agent is hydroxypropyl methylcellulose ether with a molecular weight of 200,000-300,000, with a dosage of 0.1%-0.2% of the cement mass; and the crack-resistant agent is polypropylene fiber with a length of 6-12mm, with a dosage of 0.08%-0.15% of the cement mass.

7. The application of the high fire-resistant ultralight concrete according to claim 6 in building floor slabs and floor coverings, characterized in that, The construction process of the application includes construction preparation, formwork erection, rebar tying, grout pouring, natural curing, and formwork removal.

8. The application of ultra-lightweight concrete with high fire resistance according to claim 7 in building floor slabs and floor coverings, characterized in that: Construction preparation: Before construction, the construction site needs to be cleaned to ensure that the site is flat and free of debris; at the same time, the performance of the ultra-light concrete slurry should be re-inspected to ensure that the slurry fluidity and air content meet the construction requirements; and conventional building formwork, steel bars, vibration equipment and curing materials should be prepared.

9. The application of a high-fire-resistant ultralight concrete according to claim 7 in building floor slabs and floor coverings, characterized in that: The formwork erection is carried out using ordinary steel or wooden formwork. The inside of the formwork must be coated with a release agent, preferably a water-based one, and the agent should be applied evenly to avoid any missed spots. The joints between the formwork sections must be sealed to prevent grout leakage during the pouring process.

10. The application of a high-fire-resistant ultralight concrete according to claim 4 in building floor slabs and floor coverings, characterized in that: Natural curing: Within 12 hours after pouring, cover the slurry surface with geotextile or plastic film for moisture retention and curing. The curing environment temperature should be controlled between 5-35℃, and the curing humidity ≥70%. During the curing period, water should be sprayed regularly to ensure that the surface is always moist. The curing time is ≥7 days. If the ambient temperature is below 5℃, insulation measures should be taken to prevent the slurry from freezing. If the ambient temperature is above 35℃, the frequency of watering should be increased to prevent the surface from losing water too quickly and causing cracks.

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