An ultra-low density lightweight concrete based on BiM hollow silica beads and its preparation method

Abstract

This invention relates to an ultra-low density lightweight concrete based on BiM hollow silica beads, characterized by comprising BiM hollow silica beads and a cement-based paste, wherein the cement-based paste coats the surface of the BiM hollow silica beads. Compared with the prior art, the beneficial effects of this invention are: this invention uses BiM hollow silica beads as ultra-lightweight aggregate, whose bulk density is significantly lower than that of traditional quartz sand aggregate, which can greatly reduce the apparent density of concrete and the self-weight of components, enabling the material to achieve an ultra-low density level.

Description

Technical Field

[0001] This invention belongs to the technical field of lightweight concrete and cement-based composite materials, specifically ultra-low density lightweight concrete based on BiM hollow silica beads and its preparation method. Background Technology

[0002] Ultra-high performance concrete is typically composed of materials such as cement, silica fume, fly ash, quartz sand, water, water-reducing agents, and steel fibers. It has high compressive strength, flexural strength, and durability, and is widely used in bridge engineering, marine engineering, protective structures, precast components, and prefabricated buildings.

[0003] Traditional ultra-high performance concrete typically uses quartz sand as the main fine aggregate. Quartz sand has a high density, which improves the compactness and mechanical properties of concrete, but it also results in a high overall apparent density; the apparent density of ordinary quartz sand-based ultra-high performance concrete typically reaches 2.3–2.5 g / cm³. This significant self-weight limits its application in lightweight building components, floating platforms, floating structures, low-load enclosure components, and other applications sensitive to material self-weight.

[0004] To reduce the self-weight of concrete, existing technologies often employ expanded clay aggregates, expanded perlite, vitrified microspheres, foaming agents, or foaming processes to prepare lightweight concrete. While these methods can reduce material density, they often suffer from significant strength reduction, high porosity, high water absorption, and insufficient molding stability. Especially in aquatic environments or for floating components, the increased mass after water absorption can lead to an increase in apparent density, thus affecting its buoyancy stability. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one and another objective of the present invention is to provide an ultra-low density lightweight concrete based on BiM hollow silica beads.

[0006] The third objective of this invention is to provide a method for preparing ultra-low density lightweight concrete based on BiM hollow silica beads.

[0007] The fourth objective of this invention is to provide the application of this ultra-low density lightweight concrete based on BiM hollow silica beads.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an ultra-low density lightweight concrete based on BiM hollow silica beads, comprising multiple BiM hollow silica beads and cement-based slurry, wherein the multiple BiM hollow silica beads are dispersed inside the cement-based slurry, and the cement-based slurry coats the surface of the BiM hollow silica beads and fills the interparticle gaps.

[0009] In some embodiments of the present invention, the BiM hollow silica beads are near-spherical hollow silica lightweight particles with a continuous silica shell and an internal closed cavity. The shell surface is smooth to rough and has micropores. The cavity reduces the particle's own density, the continuous shell provides compressive support, and the surface micropores and rough structure are beneficial for cement-based slurry adhesion and mechanical interlocking.

[0010] like Figure 6 As shown, the BiM hollow silica beads used in this invention are nearly spherical in shape, with continuous rough texture on the particle surface and locally visible micro-openings or depressions. This surface morphology increases the contact area between the BiM hollow silica beads and the cementitious slurry, which is beneficial for the adhesion of the cementitious slurry to the particle surface and enhances the mechanical interlocking between the particles and the cement matrix.

[0011] In some embodiments of the present invention, B03, B05, and B10 are all spherical lightweight particles. Specifically, B03 has a bulk density of 400±50 kg / m³, a compressive strength of 4.0 MPa, and a volumetric water absorption rate of less than 30%; B05 has a bulk density of 370±30 kg / m³, a compressive strength of 3.5 MPa, and a volumetric water absorption rate of less than 20%; and B10 has a bulk density of 340±30 kg / m³, a compressive strength of 3.2 MPa, and a volumetric water absorption rate of less than 15%. All three particle sizes possess material characteristics including a moisture content of no more than 0.5%, a softening point above 700 °C, and a thermal conductivity of 0.04–0.06 W / (m·K).

[0012] Secondly, the present invention provides an ultra-low density lightweight concrete based on BiM hollow silica beads, which, based on a total mass of 100 parts of cementitious materials, includes: 69-73 parts of cement, 12-16 parts of fly ash, 14-16 parts of silica fume, and 30-150 parts of BiM hollow silica beads.

[0013] In some embodiments of the present invention, the components include, by weight, 71 parts cement, 14 parts fly ash, 15 parts silica fume, and 90 parts BiM hollow silica beads.

[0014] In some embodiments of the present invention, based on a total mass of 100 parts of cementitious material, the mixture further includes 18-23 parts of water and 1.5-2.5 parts of UHPC-specific polycarboxylate high-performance water-reducing agent by mass. The water-reducing agent is a DFTR-PCE type polycarboxylate high-performance water-reducing agent with a solid content of 25.2%, a pH value of 6.8, a density of 1.025 g / cm³, a water reduction rate of 47%, a chloride ion content of 0.03%, a total alkali content of 1.8%, and an air content of 2.0%. The manufacturer recommends a dosage of 2.0%-3.0% of the cementitious material mass; in the embodiments of the present invention, 2 parts are used.

[0015] In some embodiments of the present invention, based on a total mass of 100 parts of cementitious material, the material further includes 0 to 17.3 parts of steel fiber by mass; preferably, the steel fiber is 8.7 parts or 17.3 parts.

[0016] In some embodiments of the present invention, the BiM hollow silicon beads are composed of three particle sizes: B10, B05, and B03, with a mass ratio of 1:0.48:0.26. B10 forms a coarse-grained, lightweight framework, B05 fills the larger gaps between B10 particles, and B03 further fills the remaining fine gaps. The combination of these three particles can form a more continuous particle size distribution, reducing localized large pores and particle agglomeration caused by single particle sizes.

[0017] In some embodiments of the present invention, the BiM hollow silica beads are composed of three particle sizes: B10, B05, and B03, with a mass ratio of 1:0.48:0.26. The B10 particle size ranges from 0.70 to 1.50 mm, serving as a coarse particle to form a lightweight aggregate skeleton; the B05 particle size ranges from 0.50 to 0.75 mm, serving as an intermediate particle to fill the larger gaps between the B10 particles; and the B03 particle size ranges from 0.10 to 0.50 mm, serving as a fine particle to further fill the remaining small gaps, thereby forming a three-particle-size composite gradation structure with coarse, medium, and fine particle sizes complementing each other. This reduces the problems of uneven particle distribution, localized large pores, and particle agglomeration that are easily caused when using BiM hollow silica beads of a single particle size.

[0018] Three particle sizes of BiM hollow silica beads—B10, B05, and B03—form a composite distribution structure in cement-based lightweight concrete. The larger B10 particles serve as the main lightweight aggregate, forming the lightweight skeleton within the concrete. The medium-sized B05 particles are distributed between adjacent B10 particles, filling the larger inter-particle gaps. The smaller B03 particles are further distributed in the remaining fine gaps between B10 and B05. The three particle sizes interlock, and the cementitious paste fills the remaining spaces between the particles, connecting them into a cohesive whole. This achieves a balance between lightweight skeleton formation, inter-particle gap filling, and the stability of the mixture during molding.

[0019] Thirdly, the present invention provides a method for preparing ultra-low density lightweight concrete based on BiM hollow silica beads, comprising the following steps: S1. Dry mix cement, silica fume and fly ash at low speed for 2 minutes; S2. Add polycarboxylate-based high-performance water-reducing agent to water and stir for 60 seconds to obtain a uniform water-reducing agent solution; S3. Add the water-reducing agent solution to the cementitious material, stir at low speed for 120 seconds, stop the machine and scrape the wall for 30 seconds, then stir for another 120 seconds to form a uniform cement-based slurry. S4. Weigh three sizes of BiM hollow silicon beads according to B10∶B05∶B03=1∶0.48∶0.26 and dry mix them at low speed for 60 s. S5. Divide the mixed BiM hollow silica beads into three equal batches according to the total mass, and add them to the cement-based slurry in sequence. Stir at low speed for 60 seconds after each batch is added, and add the next batch only after the surface of the particles is evenly wetted and coated by the slurry.

[0020] In some embodiments of the present invention, when it is necessary to improve the flexural strength and crack resistance of the material, the steel fibers are divided into two batches according to the total mass and added to the mixture in a slow spreading manner. After each batch is added, the mixture is stirred at low speed for 60 seconds, and after all the batches are added, the mixture is stirred for another 120 seconds to ensure that the steel fibers are evenly dispersed.

[0021] The resulting mixture is poured into the mold in two layers, with each layer filling to approximately half the height of the mold. Each layer is gently inserted 10 times with a scraper or tamping rod, and the sides of the mold are tapped 5 times each. When there are still obvious air bubbles on the surface, short-term vibration of 1-3 seconds is applied, with no more than 2 vibrations and a total vibration time not exceeding 6 seconds, to reduce the floating of BiM hollow silica beads and the settling of the slurry.

[0022] Fourthly, the present invention provides the application of the ultra-low density lightweight concrete based on BiM hollow silicon beads described above in lightweight wall panels, prefabricated lightweight high-strength wall or ground components, non-load-bearing infill core material for floating platforms, floating landscape components, and low-load enclosure components.

[0023] in: a. The cement is grade 52.5 silicate cement with a density of approximately 3.1 g / cm³ and a 28-day compressive strength of not less than 52.5 MPa; b. The fly ash is a powdery, non-caking material with a loss on ignition of no more than 5% and a density of approximately 2.1 g / cm³. c, The silica fume is a fine powder with a high silica content. The content is not less than 85%, and the specific surface area is not less than 15 m² / g; d, the BiM hollow silicon beads are near-spherical hollow silicon particles with a continuous shell and an internal cavity, a bulk density of 220-450 kg / m³, and a cylinder compressive strength of not less than 3.2 MPa; e. The steel fiber is a copper-plated microfiber steel fiber with a diameter of 0.22±0.02 mm, a length of 13±1.3 mm, an aspect ratio of approximately 59, a density of approximately 7.85 g / cm³, and a tensile strength of not less than 2000 MPa.

[0024] f. The water-reducing agent is a DFTR-PCE type UHPC-specific polycarboxylate high-performance water-reducing agent with a solid content of 25.2%, a pH value of 6.8, a density of 1.025 g / cm³, a water reduction rate of 47%, a chloride ion content of 0.03%, a total alkali content of 1.8%, and an air content of 2.0%. The manufacturer recommends a dosage of 2.0% to 3.0% of the mass of the cementitious material.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses BiM hollow silica beads as ultra-lightweight aggregate, which has a significantly lower bulk density than traditional quartz sand aggregate. This can greatly reduce the apparent density of concrete and the self-weight of components, enabling the material to reach an ultra-low density level. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] In the attached diagram: Figure 1 This is a graph showing the density variation of lightweight concrete in the embodiments and comparative examples of the present invention; Figure 2 The diagram shows the variation of the spread of lightweight concrete in the embodiments and comparative examples of the present invention. Figure 3 This is a graph showing the variation of compressive strength of lightweight concrete in embodiments and comparative examples of the present invention; Figure 4 The graph shows the variation of flexural strength of lightweight concrete in the embodiments and comparative examples of the present invention. Figure 5 This is a diagram showing the floating state of the ultra-low density lightweight concrete specimen obtained in Example 8 of the present invention in water.

[0029] Figure 6 Electron microscopy image of the surface morphology of BiM hollow silicon beads.

[0030] Figure 7 Electron micrographs showing the distribution and interfacial encapsulation state of BiM hollow silica beads in a cement matrix.

[0031] Figure 8 A schematic diagram showing the composite relationship of three-sized BiM hollow silicon beads: B10, B05, and B03. Detailed Implementation

[0032] The embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the testing or experimental methods are conventional methods in the art.

[0033] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with an embodiment or example that are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0034] A method for preparing ultra-low density lightweight concrete based on BiM hollow silica beads includes the following steps: S1. Cement, silica fume, fly ash, BiM hollow silica beads, water, water-reducing agent, and steel fiber are accurately weighed using an electronic balance with an accuracy of 0.1 g. This embodiment uses a QJ-20 mixer, an NLD-3 cement mortar flowability tester, a vibration table with a vibration frequency of approximately 50 Hz, and a 40 mm × 40 mm × 160 mm triple mold.

[0035] S2. Add cement, silica fume and fly ash to a QJ-20 mixer and dry mix at low speed for 2 minutes to ensure the cementitious materials are mixed evenly.

[0036] S3. Add polycarboxylate-based high-performance water-reducing agent to water and stir for 60 seconds to obtain a uniform water-reducing agent solution; S4. Add the water-reducing agent solution to the cementitious material in the QJ-20 mixer, stir at low speed for 120 seconds, stop the machine and scrape off the dry powder on the mixing bowl wall and blades for 30 seconds, then continue stirring at low speed for another 120 seconds to form a uniform cement-based slurry.

[0037] S5. Weigh three sizes of BiM hollow silicon beads according to the mass ratio of B10∶B05∶B03=1∶0.48∶0.26, and dry mix them at low speed for 60 s to make the coarse, medium and fine particles uniformly dispersed without obvious agglomeration and classification. S6. Divide the mixed BiM hollow silica beads into three equal batches according to the total mass and add them to the cement-based slurry in sequence. After each batch is added, stir at low speed for 60 seconds. After the particle surface is evenly wetted and coated by the slurry, add the next batch. After all three batches are added, continue to stir at low speed for 120 seconds to reduce the agglomeration, floating and settling of lightweight particles and slurry. like Figure 7 As shown, after being added in batches and stirred at low speed, BiM hollow silica beads are embedded in the cement matrix in a near-spherical particle state. The outer surface of the particles is in contact with the surrounding cement-based slurry, and a slurry coating layer and interface region can be observed around the particles. This microstructure indicates that the above preparation method can coat the surface of BiM hollow silica beads with cement-based slurry, which is beneficial to improving the distribution stability of lightweight particles inside concrete and their interfacial bonding with the cement matrix.

[0038] S7. When it is necessary to improve the flexural strength and crack resistance of the material, the steel fibers are divided into two batches according to the total mass, and added in a uniform spreading manner under stirring. After each batch is added, stir at low speed for 60 seconds, and continue stirring for 120 seconds after all the batches are added. This step is omitted in the example without steel fibers. S8. Divide the obtained mixture into two layers and fill them into a 40 mm × 40 mm × 160 mm prism mold. The filling height of each layer is about half the height of the mold. For each layer, gently insert a scraper or tamping rod 10 times and tap each side of the mold 5 times. When there are still obvious air bubbles on the surface, use short-term spot vibration for 1 to 3 seconds at a time, not exceeding 2 times, and the cumulative vibration time should not exceed 6 seconds. Do not use long-term mechanical vibration to reduce stratification caused by the floating of BiM hollow silica beads and the settling of the slurry. S9. After molding, cover the surface of the specimen with a plastic film, let it stand in an environment of 20±2 ℃ for 24±2 h, then demold it, and then place it in a standard curing environment of 20±2 ℃ and relative humidity not less than 95% to cure it for the specified age to obtain ultra-low density lightweight concrete based on BiM hollow silica beads.

[0039] As an improvement to a specific embodiment, the lightweight concrete, with a total mass of cementitious materials of 100 parts, comprises 69-73 parts cement, 12-16 parts fly ash, 14-16 parts silica fume, 30-150 parts BiM hollow silica beads, 18-23 parts water, 1.5-2.5 parts polycarboxylate-based high-performance water-reducing agent, and 0-17.3 parts steel fiber.

[0040] As an improvement to a specific embodiment, the mass ratio of cement, fly ash, and silica fume is 0.71:0.14:0.15.

[0041] As an improvement to a specific embodiment, the mass ratio of the BiM hollow silica beads to the cementitious material is 0.3–1.3:1. Examples 5 and 6 selected 0.9:1 as the benchmark for steel fiber comparison because this ratio falls in the middle of the study range, offering a good balance between lightweighting, strength, and moldability. By adding 8.7 and 17.3 parts of steel fiber while keeping other components constant, the effects of steel fiber content on density, spread, and flexural strength can be evaluated independently.

[0042] As an improvement to a specific embodiment, the BiM hollow silicon beads are composed of three particle sizes: B10, B05, and B03, with a mass ratio of 1:0.48:0.26. During compounding, the three types of particles are weighed separately and then dry-mixed at low speed for 60 seconds. After mixing, B10 forms a coarse-grained, lightweight skeleton, B05 fills the larger gaps between B10 particles, and B03 further fills the remaining fine gaps, forming a composite gradation state where coarse, medium, and fine particles are intercalated and evenly distributed.

[0043] As an improvement in a specific embodiment, the particle size range of B10 is 0.70–1.50 mm, the particle size range of B05 is 0.50–0.75 mm, and the particle size range of B03 is 0.10–0.50 mm. These adjacent particle size ranges have a certain degree of continuity, which can reduce gradation gaps and take into account the lower bulk density of B10, the higher cylinder compressive strength of B03, and the intermediate transitional role of B05.

[0044] like Figure 8 As shown, the compounded B10, B05 and B03 form a distribution state of coarse-grained skeleton, medium-grained interstitial filling and fine-grained supplementary filling, respectively, so that BiM hollow silica beads of different particle sizes form a multi-scale synergistic distribution structure in cement-based paste.

[0045] As an improvement to a specific embodiment: a. The cement is grade 52.5 silicate cement with a density of approximately 3.1 g / cm³ and a 28-day compressive strength of not less than 52.5 MPa; b. Fly ash is a powdery, non-caking material with a loss on ignition of no more than 5% and a density of approximately 2.1 g / cm³. c. Silica ash is a fine powder with a high silica content. The content is not less than 85%, and the specific surface area is not less than 15 m² / g; d. BiM hollow silicon beads are near-spherical hollow silicon particles with a continuous shell and internal cavity, a bulk density of 220-450 kg / m³, and a cylinder compressive strength of not less than 3.2 MPa. e. The steel fiber is UHPC copper-plated microfiber steel fiber, formed in single loose form, with a diameter of 0.22±0.02 mm, a length of 13±1.3 mm, an aspect ratio of approximately 59, a density of approximately 7.85 g / cm³, and a tensile strength of not less than 2000 MPa.

[0046] f, The water-reducing agent is a DFTR-PCE type UHPC-specific polycarboxylate high-performance water-reducing agent with a solid content of 25.2%, a pH value of 6.8, a density of 1.025 g / cm³, a water reduction rate of 47%, a chloride ion content of 0.03%, a total alkali content of 1.8%, and an air content of 2.0%.

[0047] BiM (bi-methyl) hollow silica beads possess a hollow structure and ultra-low bulk density, significantly lower than that of traditional silica sand aggregate. They can be used to completely or partially replace traditional high-density fine aggregates and reduce the apparent density of concrete. The resulting lightweight concrete has an apparent density of 0.91–1.5768 g / cm³, a spread of 515–605 mm, a 3-day compressive strength of 12.5–42 MPa, a 3-day flexural strength of 2.4–8.2 MPa, a 28-day compressive strength of 24.7–62 MPa, and a 28-day flexural strength of 3.8–11 MPa. When the mass ratio of BiM hollow silica beads to cementitious materials is 1.3:1, the resulting lightweight concrete has an apparent density of 0.91 g / cm³, a spread of 515 mm, a 3-day compressive strength of 12.5 MPa, a 3-day flexural strength of 2.4 MPa, a 28-day compressive strength of 24.7 MPa, and a 28-day flexural strength of 3.8 MPa. When steel fibers are added, the steel fiber content is 8.7–17.3 parts per 100 parts of total cementitious materials, which improves the flexural strength, crack resistance, and failure toughness of the lightweight concrete. The resulting lightweight concrete can be used for lightweight building components, infill materials for floating platforms, floating components, low-load enclosure components, or other cement-based composite materials sensitive to self-weight.

[0048] Ultra-high performance concrete is typically composed of materials such as cement, silica fume, fly ash, quartz sand, water, water-reducing agents, and steel fibers. It has high compressive strength, flexural strength, and durability, and is widely used in bridge engineering, marine engineering, protective structures, precast components, and prefabricated buildings.

[0049] Traditional ultra-high performance concrete typically uses quartz sand as the main fine aggregate. Quartz sand has a high density, which improves the compactness and mechanical properties of concrete, but it also results in a high overall apparent density; the apparent density of ordinary quartz sand-based ultra-high performance concrete typically reaches 2.3–2.5 g / cm³. This significant self-weight limits its application in lightweight building components, floating platforms, floating structures, low-load enclosure components, and other applications sensitive to material self-weight.

[0050] To reduce the self-weight of concrete, existing technologies often employ expanded clay aggregates, expanded perlite, vitrified microspheres, foaming agents, or foaming processes to prepare lightweight concrete. While these methods can reduce material density, they often suffer from significant strength reduction, high porosity, high water absorption, and insufficient molding stability. Especially in aquatic environments or for floating components, the increased mass after water absorption can lead to an increase in apparent density, thus affecting its buoyancy stability.

[0051] BiM hollow silica beads are a type of near-spherical hollow silica lightweight granular material with a continuous shell and an internal closed cavity. Their outer surface can be smooth or rough and has micropores, while the cross-section exhibits a porous shell surrounding the internal cavity. The internal cavity allows the particles to occupy a large volume with a relatively small mass, while the continuous shell provides necessary compressive support. The surface micropores and rough structure facilitate the adhesion of cement hydration products, creating an encapsulating and mechanically interlocking interface between the particles and the slurry.

[0052] However, because the density of BiM hollow silica beads is much lower than that of cement-based paste, if they are prepared directly using the mixing and vibration methods of ordinary concrete or ordinary ultra-high performance concrete, problems such as lightweight particles floating, paste settling, local segregation, increased porosity, and uneven molding are likely to occur. Therefore, it is necessary to rationally design the composition of cementitious materials, the gradation of BiM hollow silica beads, the dosage range, and the molding method to ensure that while reducing the density of concrete, it still maintains certain mechanical properties and molding stability.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the present invention uses BiM hollow silica beads as ultra-lightweight aggregate, which has a significantly lower bulk density than traditional quartz sand aggregate, thus greatly reducing the apparent density of concrete and the self-weight of components, enabling the material to reach an ultra-low density level.

[0054] Secondly, this invention uses a blend of three particle sizes of BiM hollow silica beads: B10, B05, and B03. During blending, the beads are weighed at a ratio of 1:0.48:0.26 and dry-mixed at a low speed. After mixing, B10 forms a coarse-grained lightweight skeleton, B05 fills the larger gaps, and B03 fills the remaining small gaps, forming a composite gradation structure with interlocking coarse, medium, and fine particles. This improves the uneven particle distribution and localized pore concentration problems caused by single-size lightweight aggregates.

[0055] Third, by increasing the amount of BiM hollow silica beads in the cementitious material system, the present invention enables the dispersed lightweight particles to gradually form a lightweight aggregate skeleton, thereby effectively reducing the material density.

[0056] Fourth, by adding BiM hollow silicon beads in batches, stirring at low speed, layering and molding, and lightly compacting, this invention can reduce the stratification caused by the floating of lightweight particles and the sinking of slurry, thereby improving the stability of material molding.

[0057] Fifth, the ultra-low density lightweight concrete obtained by this invention still maintains certain mechanical strength and workability under the condition of low apparent density, and can be used for lightweight building components, infill materials for floating platforms, floating components, low-load enclosure components and other cement-based composite materials that are sensitive to self-weight.

[0058] The following are specific embodiments. In all embodiments, cement, fly ash, and silica fume are used as cementitious materials, with a mass ratio of 0.71:0.14:0.15. BiM hollow silica beads are made of three particle sizes: B10, B05, and B03, with a mass ratio of 1:0.48:0.26. These three particle sizes are chosen to form a continuous coarse, medium, and fine gradation: B10 forms the lightweight skeleton, while B05 and B03 sequentially fill the interparticle gaps. During preparation, the three types of BiM particles are first dry-mixed at low speed for 60 seconds until uniformly distributed. Then, the cementitious materials are dry-mixed, and water and a water-reducing agent are added to form a slurry. Subsequently, BiM is added to the slurry in three batches and stirred at low speed to form the final product. Example 1

[0059] In this embodiment, based on a total cementitious material mass of 100 parts, BiM hollow silica beads comprised 30 parts, water 19 parts, and water-reducing agent 2 parts, with no steel fibers added. The resulting lightweight concrete had an apparent density of 1.5768 g / cm³, a spread of 605 mm, a 3-day compressive strength of 42 MPa, a 3-day flexural strength of 4.0 MPa, a 28-day compressive strength of 62 MPa, and a 28-day flexural strength of 6.5 MPa. Example 2

[0060] In this embodiment, based on a total cementitious material mass of 100 parts, BiM hollow silica beads comprised 50 parts, water 19 parts, and water-reducing agent 2 parts, with no steel fibers added. The resulting lightweight concrete had an apparent density of 1.3269 g / cm³, a spread of 590 mm, a 3-day compressive strength of 33 MPa, a 3-day flexural strength of 3.5 MPa, a 28-day compressive strength of 48 MPa, and a 28-day flexural strength of 5.3 MPa. Example 3

[0061] In this embodiment, based on a total mass of 100 parts cementitious materials, 70 parts BiM hollow silica beads, 19 parts water, and 2 parts water-reducing agent were used, with no steel fibers added. The resulting lightweight concrete had an apparent density of 1.1710 g / cm³, a spread of 575 mm, a 3-day compressive strength of 25 MPa, a 3-day flexural strength of 3.1 MPa, a 28-day compressive strength of 38 MPa, and a 28-day flexural strength of 4.8 MPa. Example 4

[0062] In this embodiment, based on a total cementitious material mass of 100 parts, BiM hollow silica beads comprised 90 parts, water 19 parts, and water-reducing agent 2 parts, with no steel fibers added. The resulting lightweight concrete had an apparent density of 1.0379 g / cm³, a spread of 560 mm, a 3-day compressive strength of 18 MPa, a 3-day flexural strength of 3.0 MPa, a 28-day compressive strength of 28 MPa, and a 28-day flexural strength of 4.6 MPa. Example 5

[0063] In this embodiment, based on a total mass of 100 parts cementitious materials, 90 parts are BiM hollow silica beads, 19 parts are water, 2 parts are water-reducing agent, and 8.7 parts are steel fibers. The resulting lightweight concrete has an apparent density of 1.1969 g / cm³, a spread of 535 mm, a 3-day compressive strength of 20 MPa, a 3-day flexural strength of 6.8 MPa, a 28-day compressive strength of 32 MPa, and a 28-day flexural strength of 9.5 MPa. Example 6

[0064] In this embodiment, based on a total mass of 100 parts cementitious materials, 90 parts are BiM hollow silica beads, 19 parts are water, 2 parts are water-reducing agent, and 17.3 parts are steel fibers. The resulting lightweight concrete has an apparent density of 1.2636 g / cm³, a spread of 515 mm, a 3-day compressive strength of 22 MPa, a 3-day flexural strength of 8.2 MPa, a 28-day compressive strength of 36 MPa, and a 28-day flexural strength of 11 MPa. Example 7

[0065] In this embodiment, based on a total cementitious material mass of 100 parts, BiM hollow silica beads comprised 110 parts, water 19 parts, and water-reducing agent 2 parts, with no steel fibers added. The resulting lightweight concrete had an apparent density of 1.0158 g / cm³, a spread of 530 mm, a 3-day compressive strength of 15 MPa, a 3-day flexural strength of 2.8 MPa, a 28-day compressive strength of 26 MPa, and a 28-day flexural strength of 4.2 MPa. Example 8

[0066] In this embodiment, based on a total cementitious material mass of 100 parts, BiM hollow silica beads comprised 130 parts, water 19 parts, and water-reducing agent 2 parts, with no steel fibers added. The resulting lightweight concrete had an apparent density of 0.91 g / cm³, a spread of 515 mm, a 3-day compressive strength of 12.5 MPa, a 3-day flexural strength of 2.4 MPa, a 28-day compressive strength of 24.7 MPa, and a 28-day flexural strength of 3.8 MPa.

[0067] The formulations and performance results of Examples 1-8 are shown in Table 1.

[0068]

[0069] From Table 1 and Figure 1It can be seen that as the mass ratio of BiM hollow silica beads to cementitious materials increases from 0.3:1 to 1.3:1, the apparent density of lightweight concrete decreases from 1.5768 g / cm³ to 0.91 g / cm³, indicating that BiM hollow silica beads can significantly reduce the density of cement-based materials. Specifically, the apparent density of Example 8 is 0.91 g / cm³, which is less than the density of water, while the 28-day compressive strength still reaches 24.7 MPa and the 28-day flexural strength still reaches 3.8 MPa, demonstrating that the present invention achieves ultra-low density while maintaining certain mechanical properties.

[0070] From Table 1 and Figure 2 It can be seen that the expansion of Examples 1 to 8 is 515 to 605 mm, indicating that the present invention still has basic molding workability after introducing ultra-lightweight BiM hollow silicon beads. As the content of BiM hollow silicon beads increases, the overall expansion of the mixture decreases; under the same mass ratio of BiM hollow silicon beads to cementitious material, the addition of steel fibers will further reduce the expansion.

[0071] As shown in Examples 4, 5, and 6, under the same mass ratio of BiM hollow silica beads to cementitious materials, the flexural strength of lightweight concrete is significantly improved after the addition of steel fibers. In Example 4, the 28-day flexural strength without steel fibers was 4.6 MPa; in Example 5, the 28-day flexural strength increased to 9.5 MPa after the addition of 8.7 parts of steel fibers; and in Example 6, the 28-day flexural strength increased to 11.0 MPa after the addition of 17.3 parts of steel fibers. This indicates that steel fibers can effectively improve the flexural and crack resistance of BiM hollow silica bead lightweight concrete.

[0072] Comparative Example 1 Comparative Example 1 used ordinary quartz sand as aggregate, and the composition of the cementitious material was the same as in the Example. The performance results of UHPC using ordinary quartz sand are shown in Table 2.

[0073]

[0074] As shown in Table 2, compared with ordinary silica sand UHPC, the material density of Example 8, using BiM hollow silica beads as lightweight aggregate, decreased from 2.4375 g / cm³ to 0.91 g / cm³, a reduction of approximately 62.7%. This result demonstrates that BiM hollow silica beads can significantly reduce the density of cement-based composite materials, enabling lightweight concrete to achieve ultra-low density levels.

[0075] Compared with ordinary quartz sand UHPC, the compressive strength and flexural strength of Example 8 are reduced, but under the condition of significantly reduced apparent density, it can still achieve a 28-day compressive strength of 24.7 MPa and a 28-day flexural strength of 3.8 MPa, and maintain a spread of 515 mm. It can meet the comprehensive requirements of lightweight components, floating platform filling materials and floating components for low self-weight, certain strength and molding workability.

[0076] Data pattern description Based on Examples 1-8, it is evident that the content of BiM hollow silica beads is a crucial factor affecting the apparent density, spread, and mechanical properties of lightweight concrete. As the content of BiM hollow silica beads increases, the overall apparent density and spread of the lightweight concrete decrease. When the mass ratio of BiM hollow silica beads to cementitious materials reaches 1.3:1, the apparent density of the resulting lightweight concrete can be reduced to 0.91 g / cm³, which is less than the density of water.

[0077] During the density reduction process, the compressive and flexural strengths of lightweight concrete decrease with increasing BiM hollow silica bead content. However, through reasonable cementitious material composition, BiM hollow silica bead gradation, and steel fiber reinforcement, the resulting material can still maintain a certain strength. In this invention, the apparent density of ultra-low density lightweight concrete can reach 0.91–1.5768 g / cm³, the spread can reach 515–605 mm, the 28-day compressive strength can reach 24.7–62 MPa, and the 28-day flexural strength can reach 3.8–11 MPa.

[0078] Figures 1-4 The variation patterns of density, scalability, compressive strength, and flexural strength of lightweight concrete in different groups are presented. Figure 1 and Figure 2 It is evident that increasing the BiM polyhollow silicon bead content is beneficial for reducing material density, but it also decreases the spread of the mixture; Figure 3 and Figure 4 It is evident that the 28-day intensity is higher than the 3-day intensity, indicating that the system has the ability to sustain intensity development.

[0079] The ultra-low density lightweight concrete obtained by this invention can be used for lightweight wall panels, precast lightweight high-strength wall or ground components, non-load-bearing infill core material for floating platforms, floating landscape components, lightweight infill layers inside buoy shells, and low-load enclosure components. Taking Example 8 as an example, the concrete can be made into non-load-bearing infill blocks inside a modular floating platform, with an external waterproof protective layer and connecting frame to reduce the platform's self-weight and provide buoyancy reserves. This application example is only for illustrating the material's uses and does not limit the scope of protection of this invention.

[0080] This invention utilizes the hollow structure and ultra-low bulk density of BiM (bimally soluble silica) beads to construct an ultra-lightweight aggregate skeleton in a cement-based system, achieving an ultra-low apparent density. In the embodiments, the apparent density of the material can reach 0.91 g / cm³, which is less than the density of water. Compared with traditional quartz sand UHPC, this material has significant advantages in terms of lightweighting, reducing the self-weight of components and providing a new technical path for floating cement-based materials.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultra-low density lightweight concrete based on BiM hollow silica beads, characterized in that, It includes BiM hollow silica beads and cement-based slurry, wherein the cement-based slurry coats the surface of the BiM hollow silica beads.

2. The ultra-low density lightweight concrete based on BiM hollow silica beads according to claim 1, characterized in that, The BiM hollow silica beads are hollow, lightweight silica particles with a bulk density of 220–450 kg / m³ and a compressive strength of not less than 3.2 MPa; the cement-based slurry is a mixture of cement, silica fume, and fly ash.

3. An ultra-low density lightweight concrete based on BiM hollow silica beads, characterized in that, The components, by weight, include: 69-73 parts cement, 12-16 parts fly ash, 14-16 parts silica fume, and 30-150 parts BiM hollow silica beads.

4. The ultra-low density lightweight concrete based on BiM hollow silica beads according to claim 3, characterized in that, The components, by weight, are: 71 parts cement, 15 parts silica fume, 14 parts fly ash, and 90 parts BiM polyhollow silica beads.

5. The ultra-low density lightweight concrete based on BiM hollow silica beads according to claim 3, characterized in that, The ingredients, by weight, also include: 18-23 parts water and 1.5-2.5 parts water-reducing agent.

6. The ultra-low density lightweight concrete based on BiM hollow silica beads according to claim 3, characterized in that, The product also includes, by weight, 0 to 17.3 parts of steel fiber.

7. The ultra-low density lightweight concrete based on BiM hollow silica beads according to claim 1 or 3, characterized in that, The BiM hollow silicon beads are composed of three particle sizes: B10, B05, and B03, with a mass ratio of 1:0.48:0.

26. The particle size range of B10 is 0.70–1.50 mm, the particle size range of B05 is 0.50–0.75 mm, and the particle size range of B03 is 0.10–0.50 mm.

8. A method for preparing ultra-low density lightweight concrete based on BiM hollow silica beads, characterized in that... Includes the following steps: S1. Dry mix cement, silica fume and fly ash; S2. Add the water-reducing agent to water and stir until homogeneous to obtain a water-reducing agent solution; S3. Add the water-reducing agent solution to the cementitious material and stir to form a cement-based slurry; S4. Mix BiM hollow silicon beads of different particle sizes; S5. Add the mixed BiM hollow silica beads to the cement-based slurry and stir to coat the surface of the BiM hollow silica beads with the cement-based slurry.

9. The method for preparing ultra-low density lightweight concrete based on BiM hollow silica beads according to claim 8, characterized in that, When it is necessary to improve the flexural and crack resistance of the material, steel fibers are added to the mixture in batches and stirring is continued. The resulting mixture is layered and placed into a mold, and then formed by manual light compaction or short-term vibration.

10. The application of the ultra-low density lightweight concrete based on BiM hollow silica beads according to claims 1-9 in lightweight building components, infill materials for floating platforms, floating components, low-load enclosure components, and cement-based composite materials sensitive to self-weight.

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