Environment-friendly lightweight thermal-insulation fire-retardant concrete and preparation method thereof

Abstract

This application relates to the field of building materials, specifically disclosing an environmentally friendly lightweight thermal insulation and fire-retardant concrete and its preparation method. The environmentally friendly lightweight thermal insulation and fire-retardant concrete is made from the following raw materials in parts by weight: 300-400 parts of cementitious material, 450-550 parts of silicate insulating aggregate, 50-100 parts of high-temperature stabilizing material, 1-3 parts of composite fiber, 6-10 parts of state conditioner, and 80-100 parts of water; the silicate insulating aggregate is prepared by using waste aerated concrete particles as the core, coating them with an outer shell material, and curing them to form a hard silicate-calcium stone insulating material. The concrete of this application not only saves energy, is low-carbon and environmentally friendly, and has a simple preparation process, but also possesses good mechanical strength, volume stability, and low thermal conductivity.

Description

Technical Field

[0001] This application relates to the field of building materials, and more specifically, to an environmentally friendly lightweight thermal insulation and flame-retardant concrete and its preparation method. Background Technology

[0002] Organic insulation materials have become the mainstream wall insulation materials due to their low thermal conductivity and ease of processing. However, their flammability, poor aging resistance, short service life, and tendency to generate thermal bridges also limit their application in special situations. In particular, in terms of fire safety, there have been many serious fires caused by the combustion of organic insulation wall panels. Among them, organic insulation materials such as polystyrene, polystyrene board, and polyurethane have been banned by the state.

[0003] Inorganic thermal insulation materials are gaining increasing market favor due to their Class A fire resistance. To improve the mechanical properties and volume stability of inorganic insulation materials (such as foamed concrete), appropriate lightweight aggregates are typically added during their preparation. The introduction of lightweight aggregates provides a skeletal structure without affecting their insulation performance, effectively improving their overall service durability. Currently, lightweight aggregates are mainly man-made, such as clay ceramsite, shale ceramsite, expanded perlite, and vitrified microspheres. These materials not only consume limited arable land resources, but their calcination temperatures are typically above 1000℃, requiring significant energy consumption and being extremely environmentally unfriendly. Furthermore, common man-made lightweight aggregates suffer from low strength and high water absorption, severely limiting their application in the building materials field.

[0004] Chinese patent CN105645901 discloses a method for preparing lightweight thermal insulation boards using recycled fine powder from construction waste. This method achieves the reuse of construction waste while simultaneously producing a lightweight, low thermal conductivity thermal insulation wall panel material. However, because it employs a foamed concrete technology, it lacks aggregate as a rigid matrix, inevitably leading to problems such as large shrinkage and poor volume stability in the later stages. Chinese patent CN103601434, on the other hand, uses shale ceramsite and ceramsite to prepare a lightweight insulating concrete. This all-lightweight concrete can meet... Integrated insulation eliminates the need for a separate insulation layer, but requires a large amount of artificial calcined lightweight aggregate, resulting in high overall costs and environmental concerns. Chinese patent CN107512924 introduces modified high-strength wood particles into lightweight building concrete design, retaining the lightweight, insulating, and flame-retardant properties while replacing conventional artificial lightweight aggregates. However, because the density of the modified wood particles is still lower than that of cement-based paste, problems such as wood particle floating and concrete inhomogeneity are difficult to avoid during preparation, affecting the final design performance indicators. Meanwhile, aerated concrete accumulates a large amount of solid waste during the molding process (cutting the preform), transportation (damage), and demolition. Current practices mainly involve simple stockpiling and filling, which not only wastes significant land resources but also poses environmental safety hazards.

[0005] In view of this, the present invention makes full use of waste aerated concrete to prepare an environmentally friendly lightweight thermal insulation and flame retardant concrete with widely available materials and a simple preparation process. Summary of the Invention

[0006] This application provides an environmentally friendly lightweight thermal insulation and flame-retardant concrete and its preparation method. The concrete of this application not only saves energy, is low-carbon and environmentally friendly, and has a simple preparation process, but also possesses good mechanical strength, volume stability, and low thermal conductivity.

[0007] In the first aspect, this application provides an environmentally friendly lightweight thermal insulation and flame-retardant concrete, which adopts the following technical solution:

[0008] An environmentally friendly lightweight thermal insulation and flame-retardant concrete is made from the following raw materials in parts by weight: 300-400 parts of cementitious material, 450-550 parts of silicate insulating aggregate, 50-100 parts of high-temperature stabilizing material, 1-3 parts of composite fiber, 6-10 parts of state conditioner, and 80-100 parts of water; wherein the silicate insulating aggregate is made by using waste aerated concrete particles as the core, coating them with an outer shell material, and curing them to form a hard silicate calcium stone insulating material.

[0009] By adopting the above technical solutions, this application fully utilizes the lightweight, heat-insulating, and fire-resistant characteristics of waste aerated concrete to prepare non-calcined lightweight aggregate particles, avoiding the need for high-temperature calcination of artificial lightweight aggregates. This saves a significant amount of energy and also avoids the consumption of natural resources such as clay, shale, and perlite. Furthermore, this application coats and cures the surface of waste aerated concrete to form a hard silicate-calcium stone insulation material, endowing it with advantages such as high strength, low water absorption, and strong interlocking. Silicate insulating aggregates possess extremely high mechanical properties and extremely low thermal conductivity, reducing the problem of high water absorption when using waste aerated concrete as aggregate. In addition, hard silicate-calcium stone can be used at temperatures up to 1000℃. Compared to conventional high-temperature calcined artificial lightweight aggregates, this silicate insulating aggregate can impart excellent high-temperature stability to the aggregate simply through a suitable autoclaving process, saving a significant amount of energy. Therefore, the concrete of this application is not only energy-saving and low-carbon environmentally friendly, but also possesses good mechanical strength, volume stability, and low thermal conductivity.

[0010] Furthermore, the waste aerated concrete particles, by mass percentage, include particles of the following sizes:

[0011] Waste aerated concrete particles with a particle size of 0.15–1.18 mm: 25–50%;

[0012] Waste aerated concrete particles with a particle size of 1.18–4.75 mm: 10–50%;

[0013] Waste aerated concrete particles with a particle size of 4.75–10.0 mm: 0–60%.

[0014] Furthermore, the raw materials for the outer shell material include siliceous materials and calcareous materials, wherein the molar ratio of silicon to calcium is 1.0 to 1.2. Even further, the raw materials for the silicate insulating aggregate also include mullite whiskers. The mullite whiskers, the outer shell material, and water constitute the outer shell material coating solution, wherein the mass ratio of water to the outer shell material is (10 to 20): 1, and the mullite whiskers constitute 10 to 20% of the mass of the outer shell material.

[0015] Furthermore, the siliceous material comprises one or more combinations of quartz sand powder, diatomaceous earth, rice husk ash, silica, silica sol, and silica micropowder, wherein the particle size of the siliceous material is less than 400 mesh. The calcareous material comprises one or more combinations of finely ground lime powder, calcium hydroxylite, and carbide slag; wherein the particle size of the calcareous material is less than 400 mesh. The mullite whiskers have a length of 60–200 μm and a diameter of 0.2–3.0 μm.

[0016] Furthermore, the preparation method of the silicate insulating aggregate includes the following steps:

[0017] (1) Spray the outer shell material coating liquid onto the waste aerated concrete, and then pre-cur it for 0 to 48 hours, controlling the ambient humidity ≥95% and the ambient temperature 20 to 25℃;

[0018] (2) The waste aerated concrete after pre-curing is autoclaved, and the curing temperature is controlled at 150-300℃, the pressure is 1.0-2.0MPa, and the heat preservation time is 4-8h.

[0019] Furthermore, the coating thickness of the material on the waste aerated concrete is 60–120 μm, specifically the thickness after drying.

[0020] By adopting the above technical solution, this application utilizes the high water absorption rate of aerated concrete to allow it to fully absorb the coating liquid on its outer surface. Under suitable autoclaving conditions, the calcium and silicon materials in the coating liquid will readily generate a hard calcium silicate insulation material with high crystallinity. The preparation process is simple and more environmentally friendly. Simultaneously, mullite whiskers mixed in the coating liquid are randomly distributed on the surface of the waste aerated concrete particles. After hardening, they form a "micro-protrusion" structure on the surface of the waste aerated concrete particles, strengthening the connection between the aggregate and the paste. This solves the problem that conventional coating materials, while improving the strength of lightweight aggregates, weaken the mechanical properties of the interface transition zone between the aggregate and the paste. Furthermore, the excellent high-temperature resistance of mullite whiskers enhances the interfacial stability of this silicate insulating aggregate with the paste material at high temperatures. Moreover, the coating liquid of this application forms Tober mullite in a high-temperature environment, exhibiting good compatibility with mullite whiskers, which can further improve the performance of concrete.

[0021] Furthermore, the high-temperature stable material comprises metakaolin and glass powder in a weight ratio of 2:(1-2); the metakaolin contains not less than 40% alumina and has a fineness of 1-10 μm; the glass powder has a fineness of 10-100 μm.

[0022] By adopting the above technical solutions, high-temperature stable materials can ensure that concrete retains its integrity and certain mechanical properties under fire conditions. Metakaolin effectively supplements the active alumina content in the system. Unlike cement hydration products or secondary hydration products of other mineral admixtures, which are mainly composed of van der Waals bonds and hydrogen bonds, the conventional hydration product of metakaolin, calcium aluminum feldspar, is an aluminosilicate phase product mainly composed of ionic and covalent bonds, exhibiting greater high-temperature stability. In addition, glass powder can play the following roles under fire conditions: 1. Network stabilization: Softened glass powder can flow into the channels formed by the melting of polypropylene fibers, connecting the various matrix phases and ensuring the high-temperature stability of the concrete structure; 2. Fluxing and mineralization: The suitable softening temperature of glass (around 600℃) provides the liquid environment required for the ceramization of various phases, accelerating the ceramization reaction between the calcium aluminum feldspar phase and the calcium and silicon phases, allowing the concrete to maintain its integrity and certain mechanical strength at high temperatures; 3. Thermal shock resistance. The initial temperature of a fire can reach over 1200℃. At this temperature, the rapidly melting glass powder can react with metakaolin to form mullite, which has high temperature resistance, high strength, and low thermal conductivity to resist thermal shock.

[0023] Furthermore, the composite fiber is composed of polypropylene fiber and basalt fiber in a weight ratio of 1:(0.2-1); the polypropylene fiber has a length of 6-19 mm and a diameter of 30-50 μm; the basalt fiber has a length of 6-19 mm and a diameter of 30-100 μm.

[0024] By adopting the above technical solutions, under normal service conditions of concrete, the two types of fibers can each play a toughening and crack-resistant role, reducing the risk of cracking of lightweight aggregate concrete due to its low elastic modulus and effectively improving its durability. Under fire conditions, the polypropylene fibers, which are three-dimensionally randomly distributed inside the concrete, melt rapidly due to their low melting point (160-165℃). The pressure-relieving network formed by them can effectively reduce the risk of high-temperature cracking of concrete when it encounters rapid temperature rise. Basalt fibers, due to their high-temperature stability, can still play a crack-resistant role under fire conditions, maintaining the overall safety of the concrete.

[0025] Furthermore, the conditioner comprises a water-reducing agent, an air-entraining agent, and a viscosity modifier in a weight ratio of 200:(0.5-1):(0.5-1).

[0026] By adopting the above technical solutions, the state regulator has the functions of water reduction, air entrainment and viscosity adjustment. The water-reducing agent improves the mechanical properties of lightweight fireproof concrete by reducing the amount of water used; the air entraining agent further optimizes the workability of concrete while also improving its thermal resistance effect; the viscosity adjuster overcomes the defect of lightweight aggregates floating in concrete paste by changing the rheological properties of concrete, making the lightweight aggregates more uniformly distributed in the concrete and the overall performance more excellent.

[0027] Furthermore, the cementitious material comprises silicate cement, fly ash, and mineral powder in a weight ratio of (2-3):(0.5-1):(0.5-1).

[0028] Secondly, this application provides a method for preparing environmentally friendly lightweight thermal insulation and flame-retardant concrete, using the following technical solution:

[0029] A method for preparing environmentally friendly lightweight thermal insulation and fire-retardant concrete includes the following steps:

[0030] Pre-wet the silicate insulating aggregate to a saturated surface-dry state for later use; dry-mix the cementitious material, high-temperature stabilizing material, and composite fiber, then add some water and state conditioner and mix; add the pre-wetted silicate insulating aggregate and stir, then add the remaining water and continue stirring until homogeneous to obtain the final product.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. This application utilizes waste aerated concrete to prepare an environmentally friendly, lightweight, fire-retardant concrete. A hard silica-calcium stone thermal insulation material is formed by coating and curing the surface of the waste aerated concrete, giving it advantages such as high strength, low water absorption, and strong interlocking. This avoids the need for high-temperature calcination of artificial lightweight aggregates, saving significant energy and also avoiding the consumption of natural resources such as clay, shale, and perlite. Compared to conventional recycled concrete research focusing on improving mechanical properties and activating potential activity, this invention focuses on the reuse of the thermal resistance effect of aerated concrete, increasing the ways to reuse waste aerated concrete.

[0033] 2. This application utilizes the characteristics of metakaolin and glass powder in that they can act as a bonding matrix, ceramicization and thermal shock resistance in concrete when it is exposed to fire conditions, which effectively improves the mechanical property stability of concrete in high-temperature environments.

[0034] 3. The composite fibers of this application can play different roles under normal and fire conditions. Among them, polypropylene fibers have both room temperature crack resistance and high temperature pressure relief effects, while basalt fibers can continue to play a crack resistance role under fire conditions, maintaining the overall integrity of concrete.

[0035] 4. The preparation process of this application is simple and easy to promote. It can be applied to occasions that require multiple aspects such as heat preservation, fire prevention, and lightweight, and has broad application prospects. Attached Figure Description

[0036] Figure 1 These are morphological photographs of the sample after the high-temperature test in Example 1.

[0037] Figure 2These are morphological photographs of the sample after the high-temperature test in Example 7.

[0038] Figure 3 This is a photograph of the morphology of sample 1 after high-temperature testing. Detailed Implementation

[0039] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0040] Example

[0041] An environmentally friendly lightweight thermal insulation and flame-retardant concrete is made from the following raw materials in parts by weight: 300-400 parts of cementitious material, 450-550 parts of silicate thermal insulation aggregate, 50-100 parts of high-temperature stabilizing material, 1-3 parts of composite fiber, 6-10 parts of condition modifier, and 80-100 parts of water.

[0042] Among them, silicate insulating aggregate is made by using waste aerated concrete particles as the core, coating them with an outer shell material, and curing them to form hard silica-calcium stone insulating material.

[0043] Furthermore, the waste aerated concrete particles, calculated by mass percentage, include particles of the following sizes:

[0044] Waste aerated concrete particles with a particle size of 0.15–1.18 mm: 25–50%;

[0045] Waste aerated concrete particles with a particle size of 1.18–4.75 mm: 10–50%;

[0046] Waste aerated concrete particles with a particle size of 4.75–10.0 mm: 0–60%.

[0047] The waste aerated concrete comes from the demolition site of the construction site.

[0048] Furthermore, the raw materials for the outer shell material include siliceous and calcareous materials, with a silicon to calcium molar ratio of 1.0 to 1.2. Even further, the raw materials for the silicate insulating aggregate also include mullite whiskers. The mullite whiskers, the outer shell material, and water constitute the outer shell material coating solution, with a water to outer shell material mass ratio of (10-20):1, and the mullite whiskers comprising 10-20% of the outer shell material mass.

[0049] Furthermore, the siliceous materials include one or more combinations of quartz sand powder, diatomaceous earth, rice husk ash, silica, silica sol, and silica micropowder, and the particle size of the siliceous materials is less than 400 mesh.

[0050] Furthermore, the calcareous material includes one or more combinations of finely ground lime powder, calcium hydroxide, and carbide slag; the particle size of the calcareous material is less than 400 mesh.

[0051] Furthermore, the mullite whiskers have a length of 60–200 μm and a diameter of 0.2–3.0 μm.

[0052] Furthermore, the preparation method of silicate insulating aggregate includes the following steps:

[0053] (1) Place the waste aerated concrete into a disc granulator, control the tilt angle of the granulator to be 40-60°, the rotation speed to be 10-40 r / min, and continuously spray the outer shell material coating liquid during the process, control the coating thickness to be 60-120 μm, and then move it to the curing room for pre-curing for 0-48 hours, control the ambient humidity to be ≥95%, and the ambient temperature to be 20-25℃;

[0054] (2) The waste aerated concrete after pre-curing is autoclaved, and the curing temperature is controlled at 150-300℃, the pressure is 1.0-2.0MPa, and the heat preservation time is 4-8h; further, the coating thickness on the waste aerated concrete is 60-120μm.

[0055] Furthermore, the high-temperature stable material comprises metakaolin and glass powder in a weight ratio of 2:(1-2); the metakaolin contains no less than 40% alumina and has a fineness of 1-10 μm; the glass powder has a fineness of 10-100 μm. The glass powder can be obtained from waste glass through washing and grinding, with an average fineness of 30 μm. Specifically, the metakaolin is provided by Zhenjiang Bote New Materials Co., Ltd., with an average fineness of 1.5 μm and an alumina content of 41.2%.

[0056] Furthermore, the composite fiber is composed of polypropylene fiber and basalt fiber in a weight ratio of 1:1; the polypropylene fiber has a length of 6–19 mm and a diameter of 30–50 μm; the basalt fiber has a length of 6–19 mm and a diameter of 30–100 μm.

[0057] Furthermore, the conditioner includes a water-reducing agent, an air-entraining agent, and a viscosity modifier in a weight ratio of 200:(0.5-1):(0.5-1). The water-reducing agent is one or more combinations of melamine-based, aminosulfonate-based, and polycarboxylate-based water-reducing agents; the air-entraining agent includes one or more combinations of alkylbenzene sulfonates, saponins, and fatty alcohol sulfonates; and the viscosity modifier includes one or more combinations of cellulose ethers, redispersible latex powder, and polyvinyl alcohol.

[0058] Furthermore, the cementitious materials include silicate cement, fly ash, and mineral powder in a weight ratio of (2-3):(0.5-1):(0.5-1). The silicate cement used is P·O 42.5, the fly ash is grade II, and the mineral powder is grade S95.

[0059] This application also provides a method for preparing environmentally friendly lightweight thermal insulation and flame-retardant concrete, including the following steps:

[0060] (1) Pre-wet the silicate insulating aggregate to a saturated surface-dry state for later use;

[0061] (2) Dry mix the cementitious material, high temperature stabilizing material and composite fiber for 30-60 seconds, then add 2 / 3 water and state conditioner and continue stirring for 1 minute.

[0062] (3) Add the pre-wetted silicate insulating aggregate and stir, then add the remaining water and continue stirring for 2-3 minutes to obtain the final product.

[0063] The following explanation is provided through specific examples.

[0064] Example 1

[0065] This embodiment provides an environmentally friendly, lightweight, heat-insulating, and flame-retardant concrete, the raw materials of which include the following components:

[0066] The mixture consists of 300 parts cementitious material, 500 parts silicate insulating aggregate, 100 parts high-temperature stabilizing material, 2 parts composite fiber, 10 parts conditioner, and 80 parts water.

[0067] The cementing materials include silicate cement, fly ash, and mineral powder in a weight ratio of 2:0.5:0.5.

[0068] The high-temperature stable material consists of metakaolin and waste glass powder in a weight ratio of 2:1.

[0069] The composite fiber consists of polypropylene fiber and basalt fiber in a 1:1 weight ratio. The polypropylene fiber has a diameter of 39.4 μm and a length of 12 mm, while the basalt fiber has a diameter of 40 μm and a length of 6 mm.

[0070] The conditioner includes a melamine-based water-reducing agent in a weight ratio of 200:1:1, sodium dodecylbenzenesulfonate, and hydroxypropyl methylcellulose ether with a viscosity of 20w.

[0071] The preparation of silicate insulating aggregate is as follows:

[0072] (1) Raw material preparation:

[0073] Waste aerated concrete particles: Calculated by mass percentage, including particles of the following sizes:

[0074] Waste aerated concrete particles with a particle size of 0.15–1.18 mm: 25%;

[0075] Waste aerated concrete particles with a particle size of 1.18–4.75 mm: 25%;

[0076] Waste aerated concrete particles with a particle size of 4.75–10.0 mm: 50%.

[0077] The outer shell material coating liquid is composed of 500-mesh quartz sand powder and 500-mesh lime powder, combined with a silicon to calcium molar ratio of 1.0 and a water-to-material ratio of 10:1, and mixed with 10% mullite whiskers with a length of 100μm and a diameter of 2μm by mass of the outer shell material.

[0078] (2) Place the waste aerated concrete into a disc granulator, control the tilt angle of the granulator to be 40°, the rotation speed to be 20r / min, and continuously spray the outer shell material coating liquid during the process, control the coating thickness to be 70μm, and then move it to the curing room for pre-curing for 24 hours, controlling the ambient humidity to be ≥95% and the ambient temperature to be 20~25℃.

[0079] (3) The waste aerated concrete after pre-curing is autoclaved, and the curing temperature is controlled at 200℃, the pressure is 1.5MPa, and the heat preservation time is 6h.

[0080] This application also provides a method for preparing environmentally friendly lightweight thermal insulation and flame-retardant concrete, including the following steps:

[0081] (1) Pre-wet the silicate insulating aggregate to a saturated surface-dry state for later use;

[0082] (2) Dry mix the cementitious material, high temperature stabilizing material and composite fiber for 30 seconds, then add 2 / 3 water and state conditioner and continue stirring for 1 minute.

[0083] (3) Add the pre-wetted silicate insulating aggregate and stir, then add the remaining water and continue stirring for 3 minutes to obtain the final product.

[0084] Example 2

[0085] This embodiment provides an environmentally friendly, lightweight, heat-insulating, and flame-retardant concrete, the raw materials of which include the following components:

[0086] 400 parts of cementitious material, 450 parts of silicate insulating aggregate, 50 parts of high-temperature stabilizing material, 3 parts of composite fiber, 8 parts of conditioner, and 90 parts of water.

[0087] The cementing materials include silicate cement, fly ash, and mineral powder in a weight ratio of 2:0.5:0.5.

[0088] The high-temperature stable material consists of metakaolin and waste glass powder in a weight ratio of 2:1.

[0089] The composite fiber consists of polypropylene fiber and basalt fiber in a 1:1 weight ratio. The polypropylene fiber has a diameter of 39.4 μm and a length of 12 mm, while the basalt fiber has a diameter of 40 μm and a length of 6 mm.

[0090] The conditioners include a melamine-based water-reducing agent in a weight ratio of 200:0.5:0.5, sodium dodecylbenzenesulfonate, and hydroxypropyl methylcellulose ether with a viscosity of 20w.

[0091] The preparation of silicate insulating aggregate is as follows:

[0092] (1) Raw material preparation:

[0093] Waste aerated concrete particles: Calculated by mass percentage, including particles of the following sizes:

[0094] Waste aerated concrete particles with a particle size of 0.15–1.18 mm: 50%;

[0095] Waste aerated concrete particles with a particle size of 1.18–4.75 mm: 50%;

[0096] Waste aerated concrete particles with a particle size of 4.75–10.0 mm: 0%.

[0097] The outer shell material coating liquid consists of 100nm silica and 1000-mesh lime powder, combined with a silicon to calcium molar ratio of 1.0 and a water-to-material ratio of 10:1, and incorporates 10% by mass of mullite whiskers with a length of 110μm and a diameter of 2μm.

[0098] (2) Place the waste aerated concrete into a disc granulator, control the tilt angle of the granulator to be 40°, the rotation speed to be 40r / min, and continuously spray the outer shell material coating liquid during the process, control the coating thickness to be 120μm, and then move it to the curing room for pre-curing for 24 hours, controlling the ambient humidity to be ≥95% and the ambient temperature to be 20~25℃.

[0099] (3) The waste aerated concrete that has completed pre-curing is subjected to autoclaving, with the curing temperature controlled at 200℃, the pressure at 2.0MPa, and the heat preservation time at 6h.

[0100] This application also provides a method for preparing environmentally friendly lightweight thermal insulation and flame-retardant concrete, including the following steps:

[0101] (1) Pre-wet the silicate insulating aggregate to a saturated surface-dry state for later use;

[0102] (2) Dry mix the cementitious material, high temperature stabilizing material and composite fiber for 60 seconds, then add 2 / 3 water and state conditioner and continue stirring for 1 minute.

[0103] (3) Add the pre-wetted silicate insulating aggregate and stir, then add the remaining water and continue stirring for 3 minutes to obtain the final product.

[0104] Example 3

[0105] This embodiment provides an environmentally friendly, lightweight, heat-insulating, and flame-retardant concrete, the raw materials of which include the following components:

[0106] The mixture consists of 350 parts cementitious material, 550 parts silicate insulating aggregate, 75 parts high-temperature stabilizing material, 1 part composite fiber, 9 parts conditioner, and 100 parts water.

[0107] The cementing materials include silicate cement, fly ash, and mineral powder in a weight ratio of 2:0.5:0.5.

[0108] The high-temperature stable material consists of metakaolin and waste glass powder in a weight ratio of 2:1.

[0109] The composite fiber consists of polypropylene fiber and basalt fiber in a 1:1 weight ratio. The polypropylene fiber has a diameter of 39.4 μm and a length of 12 mm, while the basalt fiber has a diameter of 40 μm and a length of 6 mm.

[0110] The conditioner includes a melamine-based water-reducing agent in a weight ratio of 200:1:0.75, sodium dodecylbenzenesulfonate, and hydroxypropyl methylcellulose ether with a viscosity of 20w.

[0111] The preparation of silicate insulating aggregate is as follows:

[0112] (1) Raw material preparation:

[0113] Waste aerated concrete particles: Calculated by mass percentage, including particles of the following sizes:

[0114] Waste aerated concrete particles with a particle size of 0.15–1.18 mm: 30%;

[0115] Waste aerated concrete particles with a particle size of 1.18–4.75 mm: 10%;

[0116] Waste aerated concrete particles with a particle size of 4.75–10.0 mm: 60%.

[0117] The outer shell material coating liquid is composed of 500-mesh silica powder and 500-mesh lime powder, combined with a silicon to calcium molar ratio of 1.2 and a water-to-material ratio of 20:1, and mixed with 20% by mass of mullite whiskers with a length of 100μm and a diameter of 2μm.

[0118] (2) Place the waste aerated concrete into a disc granulator, control the tilt angle of the granulator to be 40°, the rotation speed to be 10r / min, and continuously spray the outer shell material coating liquid during the process, control the coating thickness to be 60μm, and then move it to the curing room for pre-curing for 24 hours, controlling the ambient humidity to be ≥95% and the ambient temperature to be 20~25℃.

[0119] (3) The waste aerated concrete after pre-curing is autoclaved, and the curing temperature is controlled at 200℃, the pressure is 1.0MPa, and the heat preservation time is 6h.

[0120] This application also provides a method for preparing environmentally friendly lightweight thermal insulation and fire-retardant concrete. The method includes the following steps:

[0121] (1) Pre-wet the silicate insulating aggregate to a saturated surface-dry state for later use;

[0122] (2) Dry mix the cementitious material, high temperature stabilizing material and composite fiber for 30-60 seconds, then add 2 / 3 water and state conditioner and continue stirring for 1 minute.

[0123] (3) Add the pre-wetted silicate insulating aggregate and stir, then add the remaining water and continue stirring for 2-3 minutes to obtain the final product.

[0124] Example 4

[0125] This embodiment provides an environmentally friendly, lightweight, heat-insulating, and flame-retardant concrete, the raw materials of which include the following components:

[0126] The mixture contains 350 parts of cementitious material, 550 parts of silicate insulating aggregate, 100 parts of high-temperature stabilizing material, 2 parts of composite fiber, 6 parts of conditioner, and 90 parts of water.

[0127] The cementing materials include silicate cement, fly ash, and mineral powder in a weight ratio of 3:1:1.

[0128] The high-temperature stable material consists of metakaolin and waste glass powder in a weight ratio of 2:2.

[0129] The composite fiber consists of polypropylene fiber and basalt fiber in a weight ratio of 0.2:1. The polypropylene fiber has a diameter of 39.4 μm and a length of 12 mm, while the basalt fiber has a diameter of 40 μm and a length of 6 mm.

[0130] The conditioner includes a melamine-based water-reducing agent in a weight ratio of 200:1:0.75, sodium dodecylbenzenesulfonate, and hydroxypropyl methylcellulose ether with a viscosity of 20w.

[0131] The preparation of silicate insulating aggregate is as follows:

[0132] (1) Raw material preparation:

[0133] Waste aerated concrete particles: Calculated by mass percentage, including particles of the following sizes:

[0134] Waste aerated concrete particles with a particle size of 0.15–1.18 mm: 30%;

[0135] Waste aerated concrete particles with a particle size of 1.18–4.75 mm: 30%;

[0136] Waste aerated concrete particles with a particle size of 4.75–10.0 mm: 40%.

[0137] The outer shell material coating liquid is composed of rice husk ash of 1000 mesh and lime powder of 500 mesh, combined with a silicon to calcium molar ratio of 1.1 and a water-to-material ratio of 10:1, and mixed with 15% mullite whiskers of 100 μm length and 2 μm diameter by mass of the outer shell material.

[0138] (2) Place the waste aerated concrete into a disc granulator, control the tilt angle of the granulator to be 40°, the rotation speed to be 25r / min, and continuously spray the outer shell material coating liquid during the process, control the coating thickness to be 90μm, and then move it to the curing room for pre-curing for 24 hours, controlling the ambient humidity to be ≥95% and the ambient temperature to be 20~25℃.

[0139] (3) The waste aerated concrete after pre-curing is autoclaved, and the curing temperature is controlled at 200℃, the pressure is 1.2MPa, and the heat preservation time is 6h.

[0140] This application also provides a method for preparing environmentally friendly lightweight thermal insulation and flame-retardant concrete, including the following steps:

[0141] (1) Pre-wet the silicate insulating aggregate to a saturated surface-dry state for later use;

[0142] (2) Dry mix the cementitious material, high temperature stabilizing material and composite fiber for 30-60 seconds, then add 2 / 3 water and state conditioner and continue stirring for 1 minute.

[0143] (3) Add the pre-wetted silicate insulating aggregate and stir, then add the remaining water and continue stirring for 2-3 minutes to obtain the final product.

[0144] Example 5

[0145] The difference between Example 5 and Example 1 is that the waste aerated concrete particles, calculated by mass percentage, include particles of the following sizes:

[0146] Waste aerated concrete particles with a particle size of 0.15–1.18 mm: 40%;

[0147] Waste aerated concrete particles with a particle size of 1.18–4.75 mm: 60%;

[0148] Waste aerated concrete particles with a particle size of 4.75–10.0 mm: 0%.

[0149] Example 6

[0150] The difference between Example 6 and Example 1 is that the outer shell covering material does not contain mullite whiskers.

[0151] Example 7

[0152] The difference between Example 7 and Example 1 is that the mullite whiskers constitute 50% of the mass of the shell material.

[0153] Comparative Example

[0154] Comparative Example 1

[0155] The difference between Comparative Example 1 and Example 1 is that the outer shell material coating liquid in Comparative Example 1 is composed of 500-mesh silica powder and 500-mesh lime powder, combined with a silicon to calcium molar ratio of 0.8 and a water-to-material ratio of 10:1, and incorporates 10% by mass of mullite whiskers with a length of 100 μm and a diameter of 2 μm. All other aspects remain unchanged.

[0156] Comparative Example 2

[0157] The difference between Comparative Example 2 and Example 1 is that shale ceramsite of equal mass is used instead of silicate insulating aggregate in this invention. Specifically, 250 parts of 0-5mm shale ceramsite sand and 250 parts of 5-10mm shale ceramsite are used. The shale ceramsite used is provided by Hunan Huaxin Ceramsite Factory.

[0158] Comparative Example 3

[0159] The difference between Comparative Example 3 and Example 1 is that an equal mass of fly ash was used to replace the high-temperature stabilizing material. The fly ash used was provided by Zhenjiang Jiangsu Bote New Material Co., Ltd., and was Class I fly ash.

[0160] Performance testing:

[0161] After mixing, the concrete samples from the examples and comparative examples were cured for 28 days according to standard. Their dry density and softening coefficient were tested according to standard JGJ / T12-2019 (Technical Standard for Application of Lightweight Aggregate Concrete), their compressive strength according to standard GB / T50081-2019 (Standard for Test Methods of Physical and Mechanical Properties of Concrete), their drying shrinkage according to standard GB / T50082-2009 (Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete), and their thermal conductivity according to standard GB / T10294-2008 (Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials—Protective Hot Plate Method). The high-temperature stability of the concrete was tested according to the following procedure: First, the concrete specimens after 28 days of standard curing were dried to equilibrium moisture content. Then, they were placed in a high-temperature furnace, and a fire simulation test was conducted according to the ISO 834 heating curve to evaluate their high-temperature stability. The test data are shown in Table 1. Meanwhile, the morphological photographs of Examples 1, 7, and Comparative Example 1 after high-temperature testing are shown in Table 1. Figure 1-3 As shown.

[0162] Table 1 Performance test results of each embodiment and comparative example

[0163]

[0164] As demonstrated by the performance tests in Examples 1-4, the concrete of this application exhibits excellent mechanical strength, volume stability, and low thermal conductivity. This is because this application uses silicate insulating aggregate with waste aerated concrete particles as the core, coated with an outer shell material, and cured to form a hard calcium silicate insulating material. This not only endows waste aerated concrete with advantages such as high strength, low water absorption, and strong interlocking, but also gives the silicate insulating aggregate extremely high mechanical properties and extremely low thermal conductivity, reducing the problem of high water absorption when using waste aerated concrete as aggregate. Furthermore, the hard calcium silicate formed can be used at temperatures up to 1000℃. Compared to conventional high-temperature calcined artificial lightweight aggregates, this silicate insulating aggregate can impart excellent high-temperature stability simply through a suitable autoclaving process. In addition, the concrete of this embodiment is not only energy-saving and low-carbon environmentally friendly, but also has a simple preparation process.

[0165] Regarding the selection of waste aerated concrete, the performance test of Example 5 revealed that the strength and softening coefficient of Example 5 were lower than those of Examples 1-4. This indicates that the selection of waste aerated concrete particles, as the core of silicate insulating aggregate, has a significant impact on the performance of silicate insulating aggregate. This may be because waste aerated concrete particles can affect the gradation and interfacial contact between components, thereby affecting the uniformity of hard silicate formation.

[0166] Combining the embodiments without adding mullite whiskers, it can be found that the performance of Example 6 still has good strength and low thermal conductivity. This indicates that the addition of mullite whiskers does not affect the formation of hard calcium silicate. However, since mullite whiskers optimize the strength of the interfacial transition zone between aggregate and paste, the overall performance of Examples 1-4 is better than that of Example 6. However, further analysis of the performance of Example 7 reveals that although the addition of mullite whiskers is beneficial to the strength and other properties of concrete, excessive addition of mullite whiskers actually reduces the performance of concrete. This is because although the preparation process of this application is simple, there are still complex coordination relationships between the components. Excessive mullite whiskers may cause agglomeration, which is not conducive to the reinforcement of the aggregate-matrix interfacial transition zone, ultimately resulting in a decrease in strength; moreover, excessive mullite whiskers also increase costs.

[0167] Further analysis of the performance data of the comparative examples revealed that changes in the silicon and calcium molar ratio in Comparative Example 1 resulted in a certain degree of decrease in its strength and high-temperature resistance. This may be because the scheme in Comparative Example 1 is not conducive to the formation of a hard calcium silicate coating material or cannot form high-performance hard calcium silicate. This also proves that the silicate insulating aggregate used in this application, which uses waste aerated concrete particles as the core, coats them with an outer shell material, and cures them to form a hard calcium silicate insulating material, can indeed endow waste aerated concrete with advantages such as high strength, low water absorption, strong interlocking, extremely high mechanical properties, and extremely low thermal conductivity. Further analysis of the performance of Comparative Example 2 shows that without the silicate insulating aggregate of this application, the performance of concrete in all aspects decreased significantly. On the one hand, the waste aerated concrete particles modified by the outer shell coating liquid have higher compressive strength and lower water absorption than shale ceramsite under similar bulk density conditions. Moreover, the randomly distributed mullite whiskers on the surface of the silicate insulating aggregate further enhance the connection between the aggregate and the paste, effectively improve the strength of the interface transition zone, and ultimately improve the mechanical properties of the concrete. Comparative Example 2 illustrates that the good high-temperature resistance and other properties of the concrete in this application are largely due to the silicate insulating aggregate in this application.

[0168] Analysis of the performance of Comparative Example 3 revealed that the final performance decreased because no high-temperature stabilizing material was added. This indicates that in this application, the use of metakaolin and glass powder as high-temperature stabilizing materials not only provides high-temperature stability to concrete by metakaolin forming calcium aluminum feldspar, but also allows the combination of metakaolin and waste glass to generate mullite, which combines high temperature resistance, high strength, and low thermal conductivity to resist thermal shock.

[0169] In summary, the environmentally friendly lightweight thermal insulation and flame-retardant concrete provided by this invention can comprehensively utilize solid waste such as waste aerated concrete and waste glass without reducing or even improving the overall performance of lightweight aggregate concrete. In particular, it breaks the inherent concept that artificial aggregates that have undergone high-temperature calcination are required to prepare lightweight fire-retardant concrete, saving a lot of energy, and is economical and environmentally friendly, with broad application prospects.

[0170] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An environmentally friendly lightweight thermal insulation fire resistant concrete, characterized in that, It is made from the following raw materials in parts by weight: 300-400 parts of cementitious material, 450-550 parts of silicate insulating aggregate, 50-100 parts of high-temperature stabilizing material, 1-3 parts of composite fiber, 6-10 parts of state conditioner, and 80-100 parts of water; wherein the silicate insulating aggregate is made by using waste aerated concrete particles as the core, coating them with an outer shell material, and curing them to form a hard silicate calcium stone insulating material; The waste aerated concrete particles, by mass percentage, include particles of the following sizes: Waste aerated concrete particles with a particle size of 0.15–1.18 mm: 25-50%; 1. Waste aerated concrete particles with a particle size of 1.18–4.75 mm: 10–50%; Waste aerated concrete particles with a particle size of 4.75–10.0 mm: 0–60%; The raw materials for the outer shell material include siliceous materials and calcareous materials, wherein the molar ratio of silicon to calcium is 1.0 to 1.2; The raw materials of the silicate insulating aggregate also include mullite whiskers. The mullite whiskers, shell material and water constitute the shell material coating liquid. The mass ratio of water to shell material is (10-20):

1. The mullite whiskers account for 10-20% of the mass of the shell material. The high-temperature stable material comprises metakaolin and glass powder in a weight ratio of 2:(1-2); the metakaolin contains no less than 40% alumina and has a fineness of 1-10 μm; the glass powder has a fineness of 10-100 μm; the composite fiber is composed of polypropylene fiber and basalt fiber in a weight ratio of 1:(0.2-1); the polypropylene fiber has a length of 6-19 mm and a diameter of 30-50 μm; the basalt fiber has a length of 6-19 mm and a diameter of 30-100 μm; the state conditioner comprises a water-reducing agent, an air-entraining agent, and a viscosity modifier in a weight ratio of 200:(0.5-1):(0.5-1).

2. The environment-friendly lightweight thermal-insulation fire-retardant concrete according to claim 1, characterized in that, The siliceous material includes one or more combinations of quartz sand powder, diatomaceous earth, rice husk ash, silica, silica sol, and silica micropowder, and the particle size of the siliceous material is less than 400 mesh.

3. The environment-friendly lightweight thermal-insulation fire-retardant concrete according to claim 1, characterized in that, The calcareous material includes one or more combinations of finely ground lime powder, calcium hydroxide, and carbide slag; the particle size of the calcareous material is less than 400 mesh.

4. The environment-friendly lightweight thermal-insulation fire-retardant concrete according to claim 1, characterized in that, The mullite whiskers are 60–200 μm in length and 0.2–3.0 μm in diameter.

5. The environment-friendly lightweight thermal-insulation fire-retardant concrete according to claim 1, wherein the lightweight aggregate is a porous aggregate having a bulk density of 0.5 to 1.5 g / cm3. The preparation method of the silicate insulating aggregate includes the following steps: (1) Spray the outer shell material coating liquid onto the waste aerated concrete, and then pre-cur it for 0 to 48 hours, controlling the ambient humidity ≥95% and the ambient temperature 20 to 25℃; (2) The waste aerated concrete after pre-curing is autoclaved, and the curing temperature is controlled at 150-300℃, the pressure is 1.0-2.0MPa, and the heat preservation time is 4-8h.

6. The environmentally friendly lightweight thermal insulation and fire resistant concrete according to claim 5, wherein, The coating thickness of the material on the waste aerated concrete is 60–120 μm.

7. The environmentally friendly lightweight thermal insulation and flame-retardant concrete according to claim 1, characterized in that, The cementitious material includes silicate cement, fly ash and mineral powder in a weight ratio of (2-3):(0.5-1):(0.5-1).

8. A method for preparing environmentally friendly lightweight thermal insulation and flame-retardant concrete as described in any one of claims 1-7, characterized in that, Includes the following steps: Pre-wet the silicate insulating aggregate to a saturated surface-dry state for later use; dry-mix the cementitious material, high-temperature stabilizing material, and composite fiber, then add some water and state conditioner and mix; add the pre-wetted silicate insulating aggregate and stir, then add the remaining water and continue stirring until homogeneous to obtain the final product.

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