Lightweight fireproof concrete and its preparation method and construction method

Abstract

The application relates to a light-weight fireproof concrete and a preparation method and a construction method thereof, and relates to the technical field of building materials.The light-weight fireproof concrete is composed of the following components in mass parts: Portland cement, fly ash, expanded perlite, silane coupling agent modified aerogel, steel fiber, polypropylene fiber, expandable graphite, polycarboxylate superplasticizer and water; the length of the steel fiber is 10-14 mm, and the diameter is 0.18-0.22 mm; the length of the polypropylene fiber is 5-7 mm, and the diameter is 16-20 microns; the preparation method comprises the following steps: dry powder mixing, water adding and stirring, stirring, and adding expandable graphite; the construction method comprises the following steps: erecting a scaffold, applying glue, hanging net construction, light-weight fireproof concrete spraying, applying sealant, spraying finish paint, removing fireproof materials and the scaffold; under the premise of ultralow thermal conductivity, the light-weight fireproof concrete reduces the risk of explosion caused by steam accumulation in the concrete in a high-temperature environment, and has excellent and durable heat insulation performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a lightweight fireproof concrete and a preparation method and construction method thereof. BACKGROUND

[0002] With the development of modern buildings towards high-rise and large-scale, the fire resistance of concrete structures has become the core problem of fire prevention. Lightweight fireproof concrete has become the focus of building material fireproof application because it can effectively reduce the self-weight of the structure, improve the space utilization rate, and has good fireproof performance.

[0003] A kind of fire-retardant green concrete added with expandable graphite and a preparation method thereof are disclosed in Chinese patent application with publication number CN120271303A and publication date July 8, 2025, wherein the concrete components include cement, aggregate, expandable graphite and water. The use of this special material, expandable graphite, can significantly improve the fireproof performance and thermal insulation performance of concrete. In a high-temperature environment, expandable graphite forms a thermal insulation layer by expanding, thereby effectively preventing concrete from cracking or structural damage caused by fire, significantly improving the fire resistance and safety of building structures.

[0004] For the above technical solution, the inventors found that the lightweight aggregate added in the lightweight fireproof concrete described above, while imparting lightweight properties to the concrete, can easily retain moisture in its porous structure. In a high-temperature fire environment, the internal moisture in the concrete vaporizes rapidly to produce high-pressure steam, and the fireproof components such as expandable graphite expand rapidly. The steam inside the concrete is difficult to discharge, which can easily lead to a sharp increase in internal pressure, causing an explosion, and thus causing the concrete to fall off and lose its fireproof performance. SUMMARY

[0005] To solve the problem of explosion of concrete materials caused by internal pressure accumulation and disordered expansion of fireproof components at high temperatures, the present application provides a lightweight fireproof concrete and a preparation method and construction method thereof.

[0006] In a first aspect, the present application provides a lightweight fireproof concrete, which adopts the following technical solution:

[0007] A lightweight fireproof concrete, the mass fraction of its components includes: 700-850 parts of Portland cement, 150-300 parts of fly ash, 200-300 parts of expanded perlite, 20-50 parts of silane coupling agent modified aerogel, 30-60 parts of steel fiber, 2-4 parts of polypropylene fiber, 80-120 parts of expandable graphite, 40-60 parts of polycarboxylate superplasticizer, and 350-390 parts of water. The length of the steel fiber is 10-14 mm, and the diameter is 0.18-0.22 mm. The length of the polypropylene fiber is 5-7 mm, and the diameter is 16-20 μm.

[0008] By adopting the above technical scheme, the expandable graphite can expand rapidly at high temperature of 350℃, forming a dense porous carbon layer covering the surface of the material, effectively isolating oxygen and heat radiation, and improving the fire resistance limit of the material; when a fire occurs, the polypropylene fiber melts at a lower temperature of 200-250℃, forming uniformly distributed microporous channels, which provides a directional space for the expansion of the expandable graphite, enabling the graphite to expand in an orderly manner rather than violently and disorderly, thereby reducing the risk of explosion caused by the accumulation of steam pressure in the concrete under high temperature environment; the steel fiber maintains the skeleton support under high temperature, and the efficient toughening effect and the filling effect of fly ash are synergistic, giving the material excellent tensile, bending and fracture toughness; the aerogel is modified by the silane coupling agent, improving the easy agglomeration and uneven dispersion of the nanomaterial in the cement matrix, ensuring that the material has excellent and durable thermal insulation performance under the premise of ultra-low thermal conductivity.

[0009] Optionally, the expanded perlite is pretreated expanded perlite.

[0010] The pretreatment method of the expanded perlite is as follows: the expanded perlite is soaked in a 5% polyvinyl alcohol solution for 24 hours, and then dried to obtain the pretreated expanded perlite.

[0011] By adopting the above technical scheme, after the pretreatment of the polyvinyl alcohol solution, the hydroxyl groups on the polyvinyl alcohol molecular chain form strong hydrogen bonds with the hydroxyl groups on the surface of the expanded perlite, so that the polyvinyl alcohol molecules are firmly attached to the surface of the aggregate, forming a uniform coating layer and improving the surface hydrophilicity; at the same time, the micropores of the expanded perlite absorb the polyvinyl alcohol into the internal pores through capillary action, making up for the strength loss caused by the lightweight aggregate, so that the lightweight aggregate has higher strength while maintaining light weight.

[0012] Optionally, the pretreatment method of the expanded perlite further comprises uniformly spraying a silane coupling agent with a concentration of 1-2% on the surface of the expanded perlite soaked in the 5% polyvinyl alcohol solution, and then drying to obtain the pretreated expanded perlite; the mass of the silane coupling agent accounts for 0.5-1.5wt% of the mass of the expanded perlite.

[0013] By adopting the above technical scheme, the siloxane groups in the silane first undergo hydrolysis in water to form silanol groups, and the silanol groups undergo condensation reaction with the hydroxyl groups of the expanded perlite to form stable covalent bonds; in addition, the amino groups at the ends of the silane molecules remain in a free state with strong reactivity, which can be combined with the cement paste to improve the interfacial bonding strength.

[0014] Optionally, the expandable graphite has a particle size of 80-120 mesh.

[0015] By adopting the above technical scheme, the mesh number is matched with the pore-forming mechanism of the polypropylene fiber, the particle size of the 80-120 mesh graphite in the concrete formula is about 150 mu m, which is matched with the micro-pore channel formed after the polypropylene fiber is melted, when heated, the graphite particles can effectively expand near the preset and distributed micro-pores, instead of blind and disordered expansion to generate internal stress; if the graphite particles are too thick, the pores formed by the polypropylene fiber cannot provide effective expansion space guidance for the graphite particles; if the graphite particles are too thin, the fireproof efficiency is reduced, and the synergistic effect is not good; the appropriate particle size mesh number needs to have a large enough particle size to ensure high expansibility, and also needs to have good suspensibility in the viscous concrete slurry to realize uniform distribution.

[0016] In the second aspect, the application provides a preparation method of the light-weight fireproof concrete, which adopts the following technical scheme:

[0017] The preparation method of the light-weight fireproof concrete comprises the following steps:

[0018] a. mixing silicate cement, fly ash, silane coupling agent modified aerogel and polycarboxylate superplasticizer dry powder, and stirring uniformly;

[0019] b. adding water, stirring to form a uniform slurry, and the water-binder ratio is 0.35-0.40;

[0020] c. adding expanded perlite, steel fiber and polypropylene fiber, and stirring until uniform;

[0021] d. adding expandable graphite, and stirring until dispersed uniformly;

[0022] The preparation method of the silane coupling agent modified aerogel is as follows:

[0023] The silane coupling agent is dissolved in a mixed solvent of ethanol and water in a volume ratio of 9:1, the pH is adjusted to 3-5, and the hydrolysis is stirred for 30-60 minutes; the hydrolyzed silane coupling agent solution is added to the aerogel sol system, the temperature is controlled at 40-60 DEG C, and the reaction is stirred for 1-2 hours; the modified aerogel is aged for 6-10 hours, washed with ethanol, and dried and solidified.

[0024] By adopting the above technical scheme, when there is no liquid phase interference, dry mixing can break the powder agglomeration through mechanical shearing force, so that the aerogel particles are embedded in the dry state particle gap of the cementitious material such as silicate cement, and the subsequent water is added, the aerogel directly floats due to the density far lower than the cementitious material; at the same time, the water reducing agent dry powder is mixed with the cementitious material in advance, which can be quickly adsorbed on the surface of the cement particles after water is added, to avoid local water reducing agent concentration being too high or too low;

[0025] After adding water, a hydration film forms on the surface of the cementitious material particles. The water-reducing agent reduces the high viscosity of the slurry due to interparticle attraction through adsorption and dispersion. At this point, the slurry has sufficient viscosity, and the high shear force generated by rapid stirring can break up the slight agglomeration of expanded perlite. If the fibers and cementitious materials are dry-mixed at the same time, the fibers are prone to tangling and clumping, which is difficult to untangle after adding water. However, when dispersed in the slurry, the viscosity of the slurry can reduce the friction between the fibers and prevent tangling. At the same time, the porous structure of perlite can adsorb the water in the slurry, further enhancing the interfacial bonding with the slurry. Finally, expandable graphite is added to prevent it from mixing with hard components such as steel fibers and expanded perlite for a long time, thus reducing collision damage.

[0026] Optionally, in step b, a 4-6% polyvinyl alcohol solution is added, wherein the solid mass of polyvinyl alcohol accounts for 0.2%-0.4 wt% of the total mass of cement and fly ash.

[0027] By adopting the above technical solution, polyvinyl alcohol is a water-soluble polymer. The polymer chains in the polyvinyl alcohol solution can be adsorbed on the surface of cement particles and lightweight aggregates simultaneously: on the one hand, it combines with cement hydration products through hydrogen bonds and chemical adsorption to form stable chemical bonds; on the other hand, polyvinyl alcohol molecules can penetrate into the surface pores of lightweight aggregates, avoiding the decrease in strength or the peeling of the fireproof layer caused by the separation of aggregates from the paste after hardening; and in synergy with water-reducing agents, it further improves the fluidity of the paste.

[0028] Optionally, in step d, the stirring speed is 60-120 r / min, stirring for 30 seconds and stopping for 10 seconds, and repeating 2-3 times.

[0029] The above technical solution employs low-speed, gentle stirring because the slurry is already fully formed at this point, allowing graphite particles to quickly embed into the slurry gaps without the need for high shear force to assist in dispersion. The structural integrity of expandable graphite is crucial for its functionality. If stirred at high intensity, the mechanical shear force will damage its layered crystal structure, leading to a decrease in the expansion ratio and reducing the active expansion fireproof and heat insulation effect under high-temperature conditions.

[0030] Thirdly, the present invention provides a construction method for lightweight fireproof concrete, which adopts the following technical solution:

[0031] A construction method for lightweight fire-resistant concrete includes the following steps:

[0032] S1: Erect scaffolding: Erect scaffolding around the steel components to be constructed. The scaffolding must not be connected to the fireproof structure.

[0033] S2: Apply adhesive: Apply adhesive to the surface of the steel structure;

[0034] S3: net construction: the precast wire mesh, with the net nail fixed to the steel structure, the gap between the wire mesh and the steel structure surface is 11-13mm;

[0035] S4: lightweight fireproof concrete spraying: the prepared lightweight fireproof concrete is sprayed on the fireproof component, and is sprayed twice, the thickness of the first layer is controlled to be 13-17mm, after spraying, it is solidified for 11-13 hours, then the second layer of lightweight fireproof concrete is constructed, the spraying thickness is controlled to be 30-40mm, after completion, maintenance is carried out, water is sprayed 2 times a day, and the maintenance is carried out for 4 days;

[0036] S5: daub sealing glue: after the lightweight fireproof concrete is completely solidified, the joint is daubed with fireproof sealing glue, and is solidified;

[0037] S6: face paint spraying: spraying is carried out twice, the first layer of paint film thickness is 0.07-0.08mm, and the second layer of paint film thickness is 0.12-0.13mm;

[0038] S7: remove the fireproof material and the scaffold.

[0039] By adopting the above technical scheme: the lightweight fireproof concrete is sprayed twice, the problems that the internal water of the concrete cannot be volatilized and the surface layer is cracked caused by single thick coating can be avoided, the concrete of each layer can be fully solidified, and a dense fireproof barrier is formed; the lightweight fireproof concrete can not only reduce the load of the steel structure by utilizing the lightweight property, but also delay the high temperature from being transmitted to the steel material by the heat insulation and non-combustibility of the material, so that the requirement of the steel structure on the fire resistance limit of the building is met;

[0040] The cementing agent can fill the small gaps on the surface of the steel structure, improve the surface roughness, make the connection between the subsequent wire mesh and the steel structure more firm, provide a bonding basis for the lightweight fireproof concrete, and prevent the fireproof layer from being separated from the steel structure under high temperature in a fire; the net construction can increase the firmness of the concrete; the fireproof sealing glue can block the gaps at the joint of the fireproof layer and the corners of the concrete and the steel structure, and prevent smoke from entering from the gaps in a fire; the double-layer face paint can not only protect the surface layer of the fireproof concrete from dust erosion, but also further reduce the loss caused by direct burning of the concrete by the flame.

[0041] In summary, the present application has at least one of the following beneficial technical effects:

[0042] 1. The polypropylene fiber provides a directional space for the expansion of the expandable graphite in advance, so that the graphite can expand in an orderly manner instead of violently and disorderly, and the risk of explosion caused by the accumulation of internal steam pressure of the concrete in a high temperature environment is reduced; the steel fiber maintains the skeleton support in a high temperature environment, and excellent tensile strength, bending strength and crack toughness are obtained; the whole system composition ensures that the lightweight concrete material has excellent and durable thermal insulation performance under the premise of ultra-low thermal conductivity.

[0043] 2. By pretreating with polyvinyl alcohol solution, polyvinyl alcohol molecules are firmly attached to the surface of the aggregate to form a uniform coating layer; at the same time, the expanded perlite absorbs polyvinyl alcohol into the internal pores, making up for the strength loss caused by lightweight aggregate, so that the lightweight aggregate has higher strength while maintaining light weight; spraying silane coupling agent can improve the interfacial bonding strength.

[0044] 3. By mixing in stages, it can ensure uniform dispersion of each component, avoid breaking and floating of lightweight aggregate, and ensure the structural integrity of expandable graphite, significantly improving the uniformity and workability of lightweight fireproof concrete mixture.

[0045] 4. By spraying lightweight fireproof concrete twice, problems such as internal moisture in concrete unable to evaporate and surface cracking caused by single thick coating can be avoided, ensuring that each layer of concrete can be fully cured to form a dense fireproof barrier. DETAILED DESCRIPTION

[0046] The application will be further described in conjunction with the following examples.

[0047] Example 1: This example discloses a lightweight fireproof concrete and its preparation method and construction method.

[0048] A lightweight fireproof concrete, the mass fraction of its composition includes: 700 parts of Portland cement, 300 parts of fly ash, 200 parts of expanded perlite, 20 parts of silane coupling agent modified aerogel, 30 parts of steel fiber, 2 parts of polypropylene fiber, 80 parts of expandable graphite, 40 parts of polycarboxylate superplasticizer, and 350 parts of water; the length of the steel fiber is 12 mm and the diameter is 0.20 mm; the length of the polypropylene fiber is 6 mm and the diameter is 18 μm, and the particle size of the expandable graphite is 40-80 mesh.

[0049] The fly ash can be selected from one or a combination of grade I fly ash and grade II fly ash, and grade II fly ash is selected in this example; the aerogel can be selected from one or a combination of silica aerogel and alumina aerogel, and silica aerogel is selected in this example; the silane coupling agent can be selected from one or a combination of γ-aminopropyl triethoxysilane, γ-aminopropyl trimethoxysilane, and N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane, and γ-aminopropyl triethoxysilane is selected in this example; the polycarboxylate superplasticizer can be selected from one or a combination of methoxy polyethylene glycol methacrylate copolymer, olefin and unsaturated carboxylic acid and ester copolymer, and acrylic acid-hydroxyethyl acrylate copolymer, and methoxy polyethylene glycol methacrylate copolymer is selected in this example.

[0050] The preparation method is as follows:

[0051] a. Mix the dry powders of Portland cement, fly ash, silane coupling agent modified aerogel, polycarboxylate superplasticizer, and stir until uniform;

[0052] b. Add water and stir to form a uniform slurry, with a water-binder ratio of 0.35-0.40;

[0053] c. Add expanded perlite, steel fiber, and polypropylene fiber, and stir until uniform;

[0054] d. Add expandable graphite and stir until uniformly dispersed;

[0055] The preparation method of the silane coupling agent modified aerogel is as follows:

[0056] Dissolve the silane coupling agent in a mixture of ethanol and water with a volume ratio of 9:1, add 1 mol / L hydrochloric acid dropwise to adjust the pH to 4, and stir for 45 minutes for hydrolysis. Add the hydrolyzed silane coupling agent solution to the aerogel sol system, control the temperature at 50°C, and stir for 1.5 hours for reaction. Let it stand for 8 hours at 25±2°C, wash the modified aerogel with ethanol to ensure that the pH of the washing liquid is stable at 6.8±0.2, and place it in a vacuum drying oven set at a temperature of 40°C and a vacuum degree of 0.08 MPa for drying for 4 hours.

[0057] The prepared lightweight fireproof concrete has the following construction method:

[0058] S1: Set up scaffolding: Set up scaffolding around the steel member to be constructed, and the scaffolding cannot be connected to the fireproof structure;

[0059] S2: Apply adhesive: Apply the adhesive to the surface of the steel structure;

[0060] S3: Netting construction: Fix the pre-prepared wire mesh to the steel structure using netting nails, with a gap of 11-13 mm between the wire mesh and the steel structure surface;

[0061] S4: Lightweight fireproof concrete spraying: Spray the prepared lightweight fireproof concrete onto the fireproof member, in two layers, with the first layer thickness controlled at 13-17 mm, and after solidification for 11-13 hours, perform the second layer of lightweight fireproof concrete construction, with the spraying thickness controlled at 30-40 mm. After completion, perform curing, with water spraying twice a day for 4 days;

[0062] S5: Apply sealant: After the lightweight fireproof concrete is completely solidified, apply fireproof sealant to the joints and solidify;

[0063] S6: Spray finish: Spray in two layers, with the first layer of paint film thickness of 0.07-0.08 mm, and the second layer of paint film thickness of 0.12-0.13 mm;

[0064] S7: Remove the fireproof material and scaffolding.

[0065] The detection mainly detects the initial fluidity, the bending strength, the compressive strength, the fire resistance limit, the thermal conductivity, and the crack number per unit area;

[0066] The specific detection method is as follows:

[0067] The initial fluidity: the diffusion diameter of the concrete slurry is measured by a "flowing cone" to reflect the fluidity of the concrete; the mixed slurry is poured into the flowing cone at one time to avoid overflow, and the surface is scraped flat with a scraper to remove air bubbles; the valve is quickly opened to allow the slurry to flow freely into the center of the glass flat, and at the same time, the stopwatch is started; when the slurry completely stops flowing, there is no obvious diffusion, and the timing is stopped; the diameters of the two perpendicular directions of the slurry diffusion circle are measured on the flat, and the average value is taken as the "initial fluidity".

[0068] The bending strength and the compressive strength:

[0069] a. The slurry is poured into the bending test mold and the compression test mold respectively, and the air bubbles are removed. After the surface is scraped flat, it is placed in a curing box with a temperature of 20±2℃ and a relative humidity of ≥90%; after 24h of curing, it is demolded and continues to be cured in the curing box until the 28d age; after demolding, the actual size of the sample is measured with a vernier caliper for correction of the strength calculation results;

[0070] b. Bending strength detection: the 28d age bending sample is placed on the bending support, ensuring that the sample axis is aligned with the center of the support span, and the loading point is located at the midpoint of the span; the pressure testing machine is started, and the speed is uniformly loaded at 5mm / min until the sample is broken, and the maximum load Fbreak at the time of fracture is recorded. The bending strength is calculated according to the formula: bending strength (MPa) = 3xFbreakxL / (bxh2) (wherein: L is the span, b is the sample cross-sectional width, and h is the sample cross-sectional height);

[0071] c. Compressive strength detection: the separately prepared compression sample is placed in the center of the pressure testing machine pressure plate, ensuring that the upper and lower surfaces of the sample are in full contact with the pressure plate. If the surface is uneven, it needs to be leveled with plaster; the speed is uniformly loaded at 2.4kN / s until the sample is crushed, and the maximum load Fpress at the time of crushing is recorded; the compressive strength is calculated according to the formula: compressive strength (MPa) = Fpress / A

[0072] (wherein: A is the sample compression area, i.e. the square of the cross-sectional length).

[0073] Fire resistance limit: make 100mm×100mm×50mm cubic test piece, standard curing 28d, fix the test piece on the test piece frame of the fire test furnace, control the temperature of the test furnace according to the standard temperature curve: time-temperature curve: T=345lg(8t+1)+20, t is time, unit min, continuously observe the state of the test piece, stop the test when any of the following conditions occurs: ① the temperature of the back surface of the test piece rises to 220℃ or the average temperature rises to 180℃; ② the test piece appears penetrating cracks; ③ the test piece collapses, record the time from the start of the test to the stop of the test, which is the fire resistance limit of the test piece.

[0074] Thermal conductivity: make 300mm×300mm×50mm flat plate-shaped test piece, after curing for 28d, place the pretreated test piece between the cold and hot plates of the thermal conductivity instrument, after the instrument heat flow and temperature are stable, record the heat flux density, cold and hot plate temperature difference and test piece thickness, according to the formula λ=Q×d / (A×ΔT) (λ is thermal conductivity, Q is heat flux density, d is test piece thickness, A is test piece area, ΔT is cold and hot plate temperature difference), calculate the thermal conductivity of the test piece, unit: W / (m·K).

[0075] Number of cracks per unit area: make 100mm×100mm×50mm cubic test piece, after curing for 28d, place the test piece in a muffle furnace, raise the temperature from room temperature to 800℃ at a rate of 5℃ / min, keep the temperature constant for 120min after reaching the set temperature, naturally cool to room temperature, use a crack observation instrument with magnification of 20-50 times to observe the 6 surfaces (top, bottom, front, back, left, right) of the test piece one by one, mark the cracks with a width of ≥0.02mm, measure the actual size of each surface of the test piece with a vernier caliper, calculate the total effective surface area (S) of the test piece, count the total number of cracks (N) that meet the requirements on all surfaces of the test piece; according to the formula n=N / S×100 (n is the number of cracks per unit area), calculate the number of cracks per unit area, unit: pieces / 100cm².

[0076] Initial fluidity reflects the fluidity and construction performance of the concrete slurry in the initial state, strong fluidity facilitates construction, poor fluidity may cause blockage of the machine nozzle pipeline.

[0077] Flexural strength and compressive strength reflect the strength of the concrete slurry, under the premise of meeting the requirements of other indicators of lightweight concrete materials, the higher the strength, the better.

[0078] Fire resistance limit is an index of building materials to maintain material integrity and bearing capacity under the action of standard fire temperature curve, under the premise of meeting the requirements of other indicators of lightweight concrete materials, the higher the fire resistance limit, the better.

[0079] The smaller the value of thermal conductivity, the stronger the heat insulation ability of the material.

[0080] The fewer the number of cracks per unit area, the better the volume stability, interfacial adhesion strength, and shrinkage resistance of the material, and thus the better the fireproof performance.

[0081] High-quality lightweight fireproof concrete needs to strike a balance among low thermal conductivity, few cracks, and high fire resistance limit.

[0082] Embodiment 2: The embodiment discloses a lightweight fireproof concrete and a preparation method and construction method thereof.

[0083] A lightweight fireproof concrete, which comprises, in mass fraction, 850 parts of Portland cement, 150 parts of fly ash, 300 parts of expanded perlite, 50 parts of silane coupling agent modified aerogel, 60 parts of steel fiber, 4 parts of polypropylene fiber, 120 parts of expandable graphite, 60 parts of polycarboxylate superplasticizer, and 390 parts of water; the steel fiber has a length of 12 mm and a diameter of 0.20 mm; the polypropylene fiber has a length of 6 mm and a diameter of 18 μm; and the expandable graphite has a particle size of 40-80 mesh.

[0084] The other parts are the same as those in Embodiment 1.

[0085] Embodiment 3: The embodiment discloses a lightweight fireproof concrete and a preparation method and construction method thereof.

[0086] A lightweight fireproof concrete, which comprises, in mass fraction, 775 parts of Portland cement, 225 parts of fly ash, 250 parts of expanded perlite, 35 parts of silane coupling agent modified aerogel, 45 parts of steel fiber, 3 parts of polypropylene fiber, 100 parts of expandable graphite, 50 parts of polycarboxylate superplasticizer, and 370 parts of water; the steel fiber has a length of 12 mm and a diameter of 0.20 mm; the polypropylene fiber has a length of 6 mm and a diameter of 18 μm; and the expandable graphite has a particle size of 40-80 mesh.

[0087] The other parts are the same as those in Embodiment 1.

[0088] The lightweight fireproof concrete prepared in Embodiment 1, Embodiment 2, and Embodiment 3 is detected, and the detection results are shown in Table 1.

[0089] Table 1:

[0090]

[0091] As can be seen from the data of Example 1, Example 2 and Example 3, Example 1 has the worst fluidity among the three examples, but still meets the spraying requirements; Example 2 has the best fluidity due to the high amount of cement and aggregate, has the highest amount of expandable graphite, fiber and aerogel, and has better fireproof performance, but has the worst strength among the three examples due to the less fly ash; Example 3 has balanced indexes, and the construction performance and fireproof performance meet the standards, and the synergistic effect of the components is the best, so it is the optimal scheme among the three examples; in general, the three examples can all meet the basic construction performance and fireproof requirements of lightweight concrete, and there is no risk of construction delay.

[0092] Example 4: The example discloses a lightweight fireproof concrete and a preparation method and a construction method thereof.

[0093] The lightweight fireproof concrete comprises, in mass fraction, 775 parts of Portland cement, 225 parts of fly ash, 250 parts of expanded perlite, 35 parts of silane coupling agent modified aerogel, 45 parts of steel fiber, 3 parts of polypropylene fiber, 100 parts of expandable graphite, 50 parts of polycarboxylate superplasticizer and 370 parts of water; the steel fiber has a length of 12 mm and a diameter of 0.20 mm; the polypropylene fiber has a length of 6 mm and a diameter of 18 microns; and the expandable graphite has a particle size of 40-80 mesh.

[0094] The expanded perlite in the example is pretreated expanded perlite, and the pretreatment method is as follows: the expanded perlite is soaked in a 5% polyvinyl alcohol solution for 24 hours, and then dried for use.

[0095] The other components are the same as those in Example 3.

[0096] Example 5: The example discloses a lightweight fireproof concrete and a preparation method and a construction method thereof.

[0097] The lightweight fireproof concrete comprises, in mass fraction, 775 parts of Portland cement, 225 parts of fly ash, 250 parts of expanded perlite, 35 parts of silane coupling agent modified aerogel, 45 parts of steel fiber, 3 parts of polypropylene fiber, 100 parts of expandable graphite, 50 parts of polycarboxylate superplasticizer and 370 parts of water; the steel fiber has a length of 12 mm and a diameter of 0.20 mm; the polypropylene fiber has a length of 6 mm and a diameter of 18 microns; and the expandable graphite has a particle size of 40-80 mesh.

[0098] The pretreatment method of the expanded perlite in the example further comprises uniformly spraying a 1.5% concentration silane coupling agent on the surface of the expanded perlite soaked in the 5% polyvinyl alcohol solution, and then drying for use; the mass of the silane coupling agent accounts for 1.0% of the mass of the expanded perlite.

[0099] The other components are the same as those in Example 4.

[0100] Embodiment 6: The embodiment discloses a lightweight fireproof concrete and a preparation method and construction method thereof.

[0101] The lightweight fireproof concrete comprises, in mass fraction, 775 parts of Portland cement, 225 parts of fly ash, 250 parts of expanded perlite, 35 parts of silane coupling agent modified aerogel, 45 parts of steel fiber, 3 parts of polypropylene fiber, 100 parts of expandable graphite, 50 parts of polycarboxylate superplasticizer and 370 parts of water.

[0102] The expandable graphite in the embodiment has a particle size of 80-120 mesh.

[0103] The other parts are the same as those in Embodiment 5.

[0104] Embodiment 7: The embodiment discloses a lightweight fireproof concrete and a preparation method and construction method thereof.

[0105] The preparation method of the embodiment comprises the following steps:

[0106] a. mixing dry powders of Portland cement, fly ash, silane coupling agent modified aerogel and polycarboxylate superplasticizer, and stirring uniformly;

[0107] b. adding a polyvinyl alcohol solution with a concentration of 5%, wherein the solid mass of polyvinyl alcohol in the solution accounts for 0.3wt% of the total mass of cement and fly ash, stirring to disperse the solution, and then adding the remaining required water to form a uniform slurry, and the water-binder ratio is 0.35-0.40;

[0108] c. adding expanded perlite, steel fiber and polypropylene fiber, and stirring until uniform;

[0109] d. adding expandable graphite, and stirring until uniformly dispersed;

[0110] The other parts are the same as those in Embodiment 6.

[0111] Embodiment 8: The embodiment discloses a lightweight fireproof concrete and a preparation method and construction method thereof.

[0112] The preparation method of the embodiment comprises the following steps:

[0113] a. mixing dry powders of Portland cement, fly ash, silane coupling agent modified aerogel and polycarboxylate superplasticizer, and stirring uniformly;

[0114] b. adding water, and stirring to form a uniform slurry, and the water-binder ratio is 0.35-0.40;

[0115] c. Add expanded perlite, steel fiber, polypropylene fiber, and stir until uniform;

[0116] d. Add expandable graphite, stir at 60-120 r / min, stir for 30 seconds and stop for 10 seconds, repeat 2-3 times, and disperse uniformly.

[0117] The other aspects are exactly the same as example 7.

[0118] The lightweight fireproof concrete prepared in examples 4-8 is detected, and the detection results are shown in table 2:

[0119] Table 2:

[0120]

[0121] By comparing example 4 with example 3, the expanded perlite has a porous structure, and when not pretreated, the pores are mostly open pores, and the water in the cementitious system can easily penetrate into the pores, forming an "air-water vapor" convection channel after drying, increasing heat conduction. After pretreatment, a dense film-shaped coating is formed on the surface of the expanded perlite, effectively blocking the air convection in the pores, reducing the thermal conductivity, and in combination with the nano-porous structure of aerogel, better play the role of synergistic heat conduction blocking.

[0122] In addition, polyvinyl alcohol mainly improves the hydrophilicity of the surface of expanded perlite, reduces the frictional resistance between particles, and improves the fluidity, but the role of strengthening the interfacial bonding after pretreatment is weak, so the mechanical properties do not change significantly; in combination with polycarboxylic acid water reducing agent, the fluidity of the slurry is further improved, so the initial fluidity is greatly improved.

[0123] By comparing example 5 with example 4, the bridging effect of the silane coupling agent can make the expanded perlite more uniformly dispersed in the cementitious system, avoiding the increase of flow resistance caused by local agglomeration, and increasing the fluidity compared with example 4; the amino group of silane forms a stable covalent bond with the hydroxyl group in the cement hydration product, making the internal structure more dense, so the strength is improved compared with example 4.

[0124] The synergistic effect of the carbonized layer of polyvinyl alcohol and the hydrophobic layer of silane optimizes the thermal insulation performance, and further inhibits the expansion of cracks, and finally the number of cracks is 1.7.

[0125] By comparing Example 6 with Example 5, the 80-120 mesh graphite particles have a finer particle size and a larger specific surface area than the 40-80 mesh graphite particles, and are more uniformly dispersed when mixed with the cementitious system, and can fill the small gaps between the cement and the expanded perlite, and the unique lamellar structure of the graphite can reduce the sliding friction between the particles, so the initial fluidity of Example 6 is slightly higher; the 80-120 mesh graphite particles are more fully combined with the cement hydration products, reducing the interfacial gap and forming a dense graphite and cement composite structure, which improves the structural integrity, so the flexural and compressive strengths of Example 6 are improved compared to Example 5;

[0126] The 80-120 mesh fine particle size graphite particles are uniformly dispersed, making the heat radiation path longer inside the concrete, reducing heat transfer, and at the same time, the low thermal conductivity of graphite can further reduce the overall component heat conduction effect, which is reflected in the long fire resistance limit and low thermal conductivity of Example 6; when expanded at high temperature, the stress generated by the 80-120 mesh fine particle size graphite matches the micro-porous channels formed after the polypropylene fibers are melted, and when heated, the graphite particles can effectively expand in a specific direction, reducing the cracks caused by structural disintegration, and ultimately reducing the number of high-temperature cracks to 1.1 per 100 cm², which is 35% lower than Example 5.

[0127] By comparing Example 7 with Example 6, polyvinyl alcohol is a water-soluble polymer that can be adsorbed on the surface of silicate cement and fly ash particles, reducing inter-particle friction, reducing slurry flow resistance, reducing the adsorption of water by expanded perlite, and retaining more water for flow, so the initial fluidity of Example 7 is increased; at the same time, polyvinyl alcohol fills the small voids in the gel system, improving the strength through a micro-reinforcement mechanism;

[0128] Polyvinyl alcohol will dehydrate and carbonize at 200-300°C, converting into a rigid and brittle carbonized layer that loses stress buffering capacity, easily producing interfacial peeling stress and causing interfacial cracking, reducing the fire resistance limit compared to Example 6, and also being the main reason for the increase in cracks at 800°C compared to Example 6.

[0129] By comparing Example 8 with Example 7, low-speed stirring avoids excessive shearing of graphite lamellae, and the pause gap allows the agglomerated graphite particles to naturally disperse due to gravity, and further dispersing the remaining small agglomerates during re-stirring without significant flow resistance points; the complete fibers and expandable graphite form a three-dimensional support network, further improving the structural bearing capacity and improving the strength;

[0130] Gentle stirring reduces the mechanical shear force during stirring, preserving the layered crystal structure of the expandable graphite and the original expansion ratio, improving the active expansion fireproof and heat insulation effect in high temperature environments.

[0131] Comparative Example 1: This comparative example discloses a lightweight fireproof concrete and a preparation method and construction method thereof.

[0132] A lightweight fireproof concrete, the mass fraction of its composition includes: 775 parts of Portland cement, 225 parts of fly ash, 250 parts of expanded perlite, 35 parts of aerogel, 45 parts of steel fiber, 3 parts of polypropylene fiber, 100 parts of expandable graphite, 50 parts of polycarboxylate superplasticizer, and 370 parts of water; the length of the steel fiber is 12 mm, and the diameter is 0.20 mm; the length of the polypropylene fiber is 6 mm, and the diameter is 18 μm.

[0133] The preparation method is as follows:

[0134] a. dry powder mixing of Portland cement, fly ash, aerogel, and polycarboxylate superplasticizer, and stirring uniformly;

[0135] b. adding water, stirring to form a uniform slurry, and the water-binder ratio is 0.35-0.40;

[0136] c. adding expanded perlite, steel fiber, and polypropylene fiber, and stirring until uniform;

[0137] d. adding expandable graphite, and stirring until uniformly dispersed;

[0138] The use method of the lightweight fireproof concrete in the example is exactly the same as that in Example 3.

[0139] Comparative Example 2: The present comparative example discloses a lightweight fireproof concrete and a preparation method and construction method thereof.

[0140] A lightweight fireproof concrete, the mass fraction of its composition includes: 850 parts of Portland cement, 150 parts of fly ash, 300 parts of expanded perlite, 50 parts of silane coupling agent modified aerogel, 120 parts of expandable graphite, 60 parts of polycarboxylate superplasticizer, and 390 parts of water.

[0141] The preparation method is as follows:

[0142] a. dry powder mixing of Portland cement, fly ash, silane coupling agent modified aerogel, and polycarboxylate superplasticizer, and stirring uniformly;

[0143] b. adding water, stirring to form a uniform slurry, and the water-binder ratio is 0.35-0.40;

[0144] c. adding expanded perlite, and stirring until uniform;

[0145] d. adding expandable graphite, and stirring until uniformly dispersed;

[0146] The other aspects are exactly the same as those in Example 3.

[0147] The plastering gypsum prepared in Comparative Example 1 and Comparative Example 2 is detected, and the detection results are shown in Table 3:

[0148] Table 3:

[0149]

[0150] By comparing the comparative example 1 with the example 3, the aerogel surface is hydrophobic, and the compatibility with the gelling system is poor, and the initial fluidity is low; at the same time, the interface bonding force between the aerogel and the gelling component is insufficient, and the interface peeling is easy to occur, and the strength is low; due to the gap existing in the interface between the aerogel and the gelling component, the "interface thermal bridge" is formed, and the aerogel is easy to fall off at high temperature.

[0151] By comparing the comparative example 2 with the example 3, after the steel fibers and the polypropylene fibers are missed, the sliding friction between the slurry particles is reduced, and the resistance formed by the fiber winding is also avoided, and the fluidity is increased, but the initial fluidity is improved, and the strength and the crack resistance are greatly reduced; after the steel fibers and the polypropylene fibers are missed, the concrete loses the crack blocking, the micro cracks are easy to develop into macro cracks, and the stress is transmitted without the fibers, the cracks directly penetrate the test piece when stressed, and the strength is significantly reduced; at high temperature, the stress generated by the expandable graphite when expanding and the micro-pore channels formed by the polypropylene fibers after melting are combined, so that the graphite particles can effectively expand in a direction, reduce the cracks, and better play the fireproof performance of the expandable graphite.

[0152] The above are preferred embodiments of the present application, and are not limited to the protection scope of the present application, so: any equivalent changes made according to the structure, shape, principle of the present application should be covered in the protection scope of the present application.

Claims

1. A lightweight fire-resistant concrete, characterized in that, The composition comprises, by weight, 700–850 parts silicate cement, 150–300 parts fly ash, 200–300 parts expanded perlite, 20–50 parts silane coupling agent modified aerogel, 30–60 parts steel fiber, 2–4 parts polypropylene fiber, 80–120 parts expandable graphite, 40–60 parts polycarboxylate superplasticizer, and 350–390 parts water; the steel fiber has a length of 10–14 mm and a diameter of 0.18–0.22 mm; the polypropylene fiber has a length of 5–7 mm and a diameter of 16–20 μm.

2. The lightweight fireproof concrete according to claim 1, characterized in that, The expanded perlite is pretreated expanded perlite; The pretreatment method for expanded perlite is as follows: the expanded perlite is soaked in a 5% polyvinyl alcohol solution for 24 hours and then dried.

3. The lightweight fireproof concrete according to claim 2, characterized in that, The pretreatment method for expanded perlite further includes uniformly spraying a 1-2% concentration of silane coupling agent onto the surface of expanded perlite soaked in a 5% polyvinyl alcohol solution, followed by drying; the silane coupling agent accounts for 0.5-1.5 wt% of the mass of the expanded perlite.

4. A lightweight fire-resistant concrete according to any one of claims 1-3, characterized in that, The expandable graphite is expandable graphite with a particle size of 80-120 mesh.

5. A method for preparing lightweight fire-resistant concrete according to any one of claims 1-4, characterized in that, Includes the following steps: a. Mix silicate cement, fly ash, silane coupling agent modified aerogel, and polycarboxylate superplasticizer dry powder, and stir evenly; b. Add water and stir to form a uniform slurry with a water-to-binder ratio of 0.35–0.40; c. Add expanded perlite, steel fiber, and polypropylene fiber, and stir until homogeneous; d. Add expandable graphite and stir until evenly dispersed; The method for preparing the silane coupling agent modified aerogel is as follows: Dissolve the silane coupling agent in a 9:1 volume ratio ethanol-water mixed solvent, adjust the pH to 3-5, and stir for 30-60 minutes to hydrolyze. Add the hydrolyzed silane coupling agent solution to the aerogel sol system, control the temperature at 40-60℃, and stir for 1-2 hours. Allow it to stand for 6-10 hours, wash the modified aerogel with ethanol, and dry and solidify.

6. The method for preparing lightweight fire-resistant concrete according to claim 5, characterized in that, In step b, a 4-6% polyvinyl alcohol solution is added, wherein the solid mass of polyvinyl alcohol accounts for 0.2%-0.4 wt% of the total mass of cement and fly ash.

7. A method for preparing lightweight fire-resistant concrete according to claim 5 or 6, characterized in that, In step d, the stirring speed is 60-120 r / min, stirring for 30 seconds and stopping for 10 seconds, and repeating 2-3 times.

8. A construction method for lightweight fire-resistant concrete according to any one of claims 1-4, or lightweight fire-resistant concrete prepared by the preparation method according to any one of claims 5-7, characterized in that, Includes the following steps: S1: Erect scaffolding: Erect scaffolding around the steel components to be constructed. The scaffolding must not be connected to the fireproof structure. S2: Apply adhesive: Apply adhesive to the surface of the steel structure; S3: Wire mesh installation: Fix the prefabricated wire mesh to the steel structure with wire mesh nails. The gap between the wire mesh and the surface of the steel structure is 11-13mm. S4: Lightweight fireproof concrete spraying: Spray the prepared lightweight fireproof concrete onto the fireproof components in two coats. The thickness of the first coat is controlled at 13-17mm. After spraying, allow it to cure for 11-13 hours before applying the second coat of lightweight fireproof concrete. The thickness of the second coat is controlled at 30-40mm. After completion, perform curing by watering twice a day for 4 days. S5: Apply sealant: After the lightweight fireproof concrete has fully cured, apply fireproof sealant to the joints and allow it to cure. S6: Topcoat: Two coats are applied. The first coat has a thickness of 0.07-0.08 mm, and the second coat has a thickness of 0.12-0.13 mm. S7: Remove fireproof materials and scaffolding.

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