Low-carbon low-shrinkage high-ductility solid waste concrete and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and discloses low-carbon low-shrinkage high-ductility solid waste concrete and a preparation method thereof. The low-carbon low-shrinkage high-ductility solid waste concrete is prepared from the following raw materials in parts by weight: 690 to 710 parts of cement, 140 to 160 parts of silica fume, 140 to 160 parts of fly ash microspheres, 1080 to 1090 parts of quartz sand, 5 to 15 parts of a defoaming agent, 5 to 15 parts of a water reducing agent, 150 to 170 parts of water, 110 to 165 parts of steel fibers and 0 to 18 parts of basalt fibers. The low-carbon low-shrinkage high-ductility solid waste concrete provided by the invention is a low-carbon concrete material with a high solid waste mixing amount, and can realize low shrinkage, high compressive strength and high ductility without a large amount of additives, so that the problems of insufficient strength and high shrinkage control dependence in the prior art are solved.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a low-carbon, low-shrinkage, high-ductility solid waste concrete and its preparation method. Background Technology

[0002] As a key sector for carbon emissions and resource consumption, the construction industry urgently needs to develop a green and low-carbon building materials system. Traditional concrete, due to its large cement consumption, poor ductility, and prominent self-shrinkage cracking problems, can no longer meet the current dual requirements of sustainable development and engineering performance. Meanwhile, the large-scale accumulation of industrial solid waste not only occupies land resources but also causes environmental pollution, making its resource utilization a crucial issue that urgently needs to be addressed. High-ductility concrete, as a new type of material with excellent tensile deformation capacity and crack control capabilities, has significant advantages in structural seismic resistance, durability improvement, and prefabricated building connection parts. However, currently, high-ductility concrete generally suffers from high preparation costs, large carbon footprints, and significant early shrinkage, severely limiting its large-scale application in practical engineering. Therefore, developing a new type of ultra-high-performance concrete material from solid waste that combines low carbon emissions, low shrinkage performance, and high ductility can not only effectively improve the service performance and durability of building structures but also promote the large-scale resource utilization of industrial solid waste, achieving a balance of economic, environmental, and engineering benefits. This has significant practical implications and broad application prospects.

[0003] Currently, high-ductility solid waste concrete materials prepared using low-carbon cementitious material systems composed of solid waste as composite aggregates suffer from low compressive strength, making it difficult to simultaneously achieve low shrinkage, high tensile strength, and high compressive strength. Furthermore, low-shrinkage high-performance concrete often achieves its low-shrinkage performance by adding shrinkage-reducing agents, failing to utilize the inherent properties of solid waste materials to reduce shrinkage, which is a major challenge in the preparation of low-shrinkage high-ductility solid waste concrete. Current technologies focus on the mix design and development of low-carbon, low-shrinkage, high-ductility solid waste concrete. While this has achieved some degree of solid waste resource utilization and improved concrete ductility, most low-shrinkage high-ductility concretes rely on shrinkage-reducing agents and expansion agents to control shrinkage deformation, failing to fully utilize the inherent properties of solid waste materials to naturally reduce auto-shrinkage, thus posing a risk to the long-term stability of the concrete material. Moreover, the compressive strength of existing solid waste high-ductility concrete is generally low, making it difficult to meet the high-strength requirements of bridge pavement layers and large-span components, and thus unable to produce high-performance low-shrinkage high-ductility solid waste concrete.

[0004] Therefore, it is necessary to develop a low-carbon concrete material with high solid waste content that can achieve low shrinkage without the need for large amounts of admixtures, while also maintaining high compressive strength and high ductility, thereby solving the problems of insufficient strength and strong dependence on shrinkage control in existing technologies. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one objective of this invention is to provide a low-carbon, low-shrinkage, high-ductility solid waste concrete and its preparation method. The low-carbon, low-shrinkage, high-ductility solid waste concrete provided by this invention is a high-solid-waste-content, low-carbon, low-shrinkage, high-ductility solid waste concrete material that achieves low shrinkage without requiring large amounts of admixtures, while maintaining high compressive strength and high ductility, thereby solving the problems of insufficient strength and strong dependence on shrinkage control in existing technologies.

[0006] In a first aspect, the present invention provides a low-carbon, low-shrinkage, high-ductility solid waste concrete, wherein the low-carbon, low-shrinkage, high-ductility solid waste concrete comprises the following raw materials by weight: 690-710 parts cement, 140-160 parts silica fume, 140-160 parts fly ash microspheres, 1080-1090 parts quartz sand, 5-15 parts defoamer, 5-15 parts water-reducing agent, 150-170 parts water, 110-165 parts steel fiber, and 0-18 parts basalt fiber.

[0007] The low-carbon, low-shrinkage, high-ductility solid waste concrete of the present invention, compared with the prior art's method of controlling shrinkage with shrinkage-reducing agents or expanding agents, constructs an internally self-compacting, highly filled cementitious system using fly ash microspheres. This significantly reduces self-shrinkage without adding shrinkage-reducing agents or expanding agents, fundamentally solving the problems of strong shrinkage dependence and poor long-term stability of traditional high-performance concrete, and improving the structural safety and service life of the material. By using active industrial solid waste (fly ash microspheres, silica fume) to synergistically replace part of the cement, the replacement rate reaches more than 30%, effectively reducing self-shrinkage while taking into account both early strength and later durability. The cement dosage and overall carbon content; this raw material system not only fully taps the potential activity of solid waste, but also improves the density of the paste through particle size distribution optimization, effectively enhancing mechanical properties and shrinkage control capabilities, achieving a synergistic unity of low carbon and high performance; addressing the problems of poor fiber dispersion and unstable interfacial bonding performance in traditional high-ductility concrete, this invention selects steel fibers with good mechanical properties and interfacial anchoring effects, and adopts a step-by-step mixing process with multiple low-speed uniform additions, effectively improving the fiber dispersion uniformity and reinforcement efficiency; this measure significantly improves the later-stage ductility and crack resistance of concrete, effectively solving the engineering problem of the difficulty in achieving both strength and ductility.

[0008] In addition, the low-carbon, low-shrinkage, high-ductility solid waste concrete according to the above embodiments of the present invention may also have the following additional technical features: In some embodiments of the present invention, the cement comprises P·O 52.5 grade silicate cement; and / or, based on the total mass of the cement, the mass percentage of CaO is 55%~57%; and / or, the specific surface area of ​​the cement is 410 m². 2 / kg~430m2 / kg. Therefore, it is possible to achieve both strength and ductility in low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0009] In some embodiments of the present invention, the specific surface area of ​​the silica fume is 1.8 × 10⁻⁶. 4 m 2 / kg~1.9×10 4 m 2 / kg; and / or, based on the total mass of the silica fume, the mass percentage of SiO2 is 93%~94%. This allows for a balance between the strength and ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0010] In some embodiments of the present invention, the specific surface area of ​​the fly ash microspheres is ≥1200 m². 2 / kg; and / or, the volume average particle size d50 of the fly ash microspheres is ≤3μm. Thus, the strength and ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete can be balanced.

[0011] In some embodiments of the present invention, the particle size of the quartz sand is 20 mesh to 40 mesh. This allows for a balance between the strength and ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0012] In some embodiments of the present invention, the steel fibers include copper-plated steel fibers; and / or, the steel fibers are hook-shaped; and / or, the length of the steel fibers is 11.7 mm to 14.3 mm; and / or, the effective diameter of the steel fibers is 180 μm to 220 μm; and / or, the tensile strength of the steel fibers is ≥2850 MPa. Thus, both strength and ductility can be achieved in low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0013] In some embodiments of the present invention, the length of the basalt fiber is 11 mm to 13 mm; and / or, the effective diameter of the basalt fiber is 13 μm to 20 μm; and / or, the tensile strength of the basalt fiber is ≥1250 MPa; and / or, the elastic modulus of the basalt fiber is ≥30 GPa. Thus, both strength and ductility can be achieved in low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0014] In some embodiments of the present invention, the defoamer is a mixture of liquid hydrocarbons and polyglycerols with an inorganic carrier as the base; and / or, the water-reducing agent comprises modified polycarboxylic acid; and / or, the water-reducing agent has a density of 0.40 g / cm³. 3 ~0.55g / cm 3 Therefore, it is possible to achieve both strength and ductility in low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0015] In a second aspect of the present invention, a method for preparing the low-carbon, low-shrinkage, high-ductility solid waste concrete described in the first aspect is proposed, comprising: mixing cement, silica fume, fly ash microspheres and defoamer evenly; adding a pre-mixed water-reducing agent and water mixture solution; stirring for 3 min to 4 min to form a homogeneous slurry; adjusting the stirring speed to 275 r / min to 295 r / min; adding quartz sand to the homogeneous slurry; stirring for 2 min to 3 min to form a homogeneous mortar; reducing the stirring speed to 135 r / min to 145 r / min; and repeatedly and evenly adding steel fibers and basalt fibers and stirring for 8 min to 10 min to form a fiber mixture; filling the fiber mixture into a mold whose inner wall has been coated with a thin layer of mineral oil; allowing it to stand for 20 h to 25 h; removing the mold; and curing to obtain low-carbon, low-shrinkage, high-ductility solid waste concrete.

[0016] Therefore, the preparation method of low-carbon, low-shrinkage, and high-ductility solid waste concrete proposed in this invention, compared with the existing technology which requires complex chemical foaming and air entrainment processes to reduce the density of low-carbon, low-shrinkage, and high-ductility solid waste concrete, resulting in uneven pore structure and unstable product performance, adopts conventional mechanical mixing and step-by-step feeding processes, combined with multiple low-speed fiber dispersion methods, to ensure uniform material distribution and fiber dispersion effect. The process is simple and controllable, easy to standardize and promote, and is particularly suitable for the factory-based and large-scale production of precast components, significantly improving the engineering applicability and universality of the new material.

[0017] In some embodiments of the present invention, the settling temperature is 18°C ​​to 22°C; and / or, the relative humidity of the environment during settling is 50%RH to 70%RH; and / or, the curing temperature is 18°C ​​to 22°C; and / or, the relative humidity of the curing environment is ≥95%RH. Thus, the resulting low-carbon, low-shrinkage, high-ductility solid waste concrete can balance the strength and ductility of low-carbon, low-shrinkage, high-ductility solid waste concrete.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 The diagram shows a flow chart of a method for preparing low-carbon, low-shrinkage, and high-ductility solid waste concrete according to an embodiment of the present invention. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] In a first aspect, the present invention provides a low-carbon, low-shrinkage, high-ductility solid waste concrete, wherein the low-carbon, low-shrinkage, high-ductility solid waste concrete comprises the following raw materials by weight: 690-710 parts cement, 140-160 parts silica fume, 140-160 parts fly ash microspheres, 1080-1090 parts quartz sand, 5-15 parts defoamer, 5-15 parts water-reducing agent, 150-170 parts water, 110-165 parts steel fiber, and 0-18 parts basalt fiber.

[0022] For example, the weight percentages of cement can be 690 parts, 695 parts, 700 parts, 705 parts, 710 parts, etc.; the weight percentages of silica fume can be 140 parts, 145 parts, 150 parts, 155 parts, 160 parts, etc.; the weight percentages of fly ash microspheres can be 140 parts, 145 parts, 150 parts, 155 parts, 160 parts, etc.; the weight percentages of quartz sand can be 1080 parts, 1082 parts, 1085 parts, 1087 parts, 1090 parts, etc.; and the weight percentage of defoamer can be 5 parts. The weight percentages of water-reducing agent can be 5 parts, 8 parts, 10 parts, 14 parts, 15 parts, etc.; the weight percentages of water can be 150 parts, 155 parts, 160 parts, 165 parts, 170 parts, etc.; the weight percentages of steel fiber can be 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, 160 parts, 165 parts, etc.; and the weight percentages of basalt fiber can be 0 parts, 2 parts, 5 parts, 8 parts, 10 parts, 13 parts, 15 parts, 18 parts, etc.

[0023] The low-carbon, low-shrinkage, high-ductility solid waste concrete of the present invention, through the use of fly ash microspheres, constructs an internally self-compacting, highly filled cementitious system, achieving a significant reduction in autogenous shrinkage without the addition of shrinkage-reducing agents or expansion agents. This fundamentally solves the problems of strong shrinkage dependence and poor long-term stability of traditional high-performance concrete, improving the structural safety and service life of the concrete. By using a composite of active industrial solid waste (fly ash microspheres and silica fume) to synergistically replace part of the cement, with a replacement rate of over 30%, it effectively reduces cement usage and overall carbon content while maintaining both early strength and later durability. The material system not only fully taps the potential activity of solid waste, but also improves the density of the slurry through particle size distribution optimization, effectively enhancing mechanical properties and shrinkage control capabilities, achieving a synergistic unity of low carbon and high performance. Addressing the problems of poor fiber dispersion and unstable interfacial bonding in traditional high-ductility concrete, this invention selects steel fibers with good mechanical properties and interfacial anchoring effects, and employs a step-by-step mixing process with multiple low-speed uniform additions, effectively improving fiber dispersion uniformity and reinforcement efficiency. This measure significantly enhances the later-stage ductility and crack resistance of concrete, effectively solving the engineering problem of achieving both strength and ductility.

[0024] According to an embodiment of the present invention, the cement comprises P·O 52.5 grade Portland cement, wherein P·O represents "Portland Ordinary cement"; 52.5 indicates that the cement has a compressive strength of not less than 52.5 MPa after 28 days under standard curing conditions. Thus, by using the above-mentioned Portland cement, the strength and long-term stability of low-carbon, low-shrinkage, and high-ductility solid waste concrete can be improved, resulting in high-performance low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0025] According to an embodiment of the present invention, the mass percentage of CaO based on the total mass of the cement is 55% to 57%. For example, it can be 55%, 55.5%, 56%, 56.5%, 57%, etc. Thus, by controlling the calcium oxide content in the cement within the above range, the strength and safety of low-carbon, low-shrinkage, and high-ductility solid waste concrete can be improved.

[0026] According to an embodiment of the present invention, the specific surface area of ​​the cement is 410 m². 2 / kg~430m 2 / kg. For example, it could be 410m 2 / kg, 415m 2 / kg, 420m 2 / kg, 425m 2 / kg, 430m 2By controlling the specific surface area of ​​cement within the above range, such as / kg, the density of the paste is optimized and improved, effectively enhancing mechanical properties and shrinkage control capabilities. This constructs an internally self-compacting, highly filled cementitious system, achieving a significant reduction in auto-shrinkage without the addition of shrinkage-reducing agents or expansion agents. This addresses the root cause of the problems of strong shrinkage dependence and poor long-term stability in traditional high-performance, low-carbon, low-shrinkage, and high-ductility solid waste concrete, thereby improving the structural safety and service life of the material.

[0027] According to an embodiment of the present invention, the specific surface area of ​​the silica fume is 1.8 × 10⁻⁶. 4 m 2 / kg~1.9×10 4 m 2 / kg, for example, could be 1.8 × 10 4 m 2 / kg, 1.82×10 4 m 2 / kg, 1.84×10 4 m 2 / kg, 1.86×10 4 m 2 / kg, 1.88×10 4 m 2 / kg, 1.9×10 4 m 2 By controlling the specific surface area of ​​silica fume within the specified range (e.g., / kg), and optimizing particle size distribution, the slurry density was improved, effectively enhancing mechanical properties and shrinkage control, thus achieving a synergistic balance between low carbon footprint and high performance. According to an embodiment of the present invention, based on the total mass of the silica fume, the mass percentage of SiO2 is 93% to 94%, for example, it can be 93%, 93.2%, 93.5%, 93.7%, 93.9%, 94%, etc. By controlling the mass percentage of SiO2 in the silica fume within the above range, a high degree of compatibility between silica fume and water-reducing agent can be achieved, resulting in high strength and high durability of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0028] According to an embodiment of the present invention, the specific surface area of ​​the fly ash microspheres is ≥1200 m². 2 / kg, for example, could be 1200m 2 / kg, 1300m 2 / kg, 1400m 2 / kg, 1500m 2 / kg, 1600m 2 / kg, 1700m 2 / kg, 1800m 2 / kg, 1900m 2 / kg, 2000m 2 / kg, etc., control the specific surface area of ​​fly ash microspheres within the above range, so that the particle size of fly ash microspheres is small, which is conducive to building an internally self-compacting and highly filled cementitious system. It can significantly reduce self-shrinkage without adding shrinkage-reducing agents or expansion agents, and solve the problem of strong shrinkage dependence and poor long-term stability of traditional high-performance low-carbon low-shrinkage high-ductility solid waste concrete from the source. It improves the structural safety and service life of low-carbon low-shrinkage high-ductility solid waste concrete.

[0029] According to an embodiment of the present invention, the volume average particle size d50 of the fly ash microspheres is ≤3μm. For example, it can be 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, etc. Controlling the volume average particle size d50 of the fly ash microspheres within the above range further facilitates the construction of an internally self-compacting, highly filled cementitious system. This significantly reduces self-shrinkage without adding shrinkage-reducing agents or expansion agents, fundamentally solving the problems of strong shrinkage dependence and poor long-term stability of traditional high-performance, low-carbon, low-shrinkage, and high-ductility solid waste concrete. This further improves the structural safety and service life of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0030] It is understood that volume average particle size is a well-known term in the field, also known as median particle size or average particle size d50, used to represent the average particle size of powder. Physically, it means that particles smaller than this size account for 50% of the total particle volume, and particles larger than this size also account for 50% of the total particle volume. Volume average particle size can be conveniently determined using a laser particle size analyzer, such as GB / T19077-2016 "Particle Size Distribution - Laser Diffraction Method", using the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0031] According to an embodiment of the present invention, the particle size of the quartz sand is 20 mesh to 40 mesh, for example, it can be 20 mesh, 25 mesh, 30 mesh, 35 mesh, 40 mesh, etc. Controlling the particle size of the quartz sand within the above range is beneficial to the particle size matching with other components of low-carbon, low-shrinkage, high-ductility solid waste concrete, optimizes and improves the density of the paste, effectively improves the mechanical properties and shrinkage control ability of low-carbon, low-shrinkage, high-ductility solid waste concrete, and achieves the synergistic unity of low carbon and high performance in low-carbon, low-shrinkage, high-ductility solid waste concrete.

[0032] According to an embodiment of the present invention, the steel fiber includes copper-plated steel fiber, which has good mechanical properties and interfacial anchoring effect. It has good dispersibility and stable interfacial bonding performance in low-carbon, low-shrinkage, and high-ductility solid waste concrete, and has high reinforcing efficiency. It can further improve the later-stage ductility and crack resistance of low-carbon, low-shrinkage, and high-ductility solid waste concrete, and effectively solve the engineering problem of difficulty in achieving both strength and ductility.

[0033] According to an embodiment of the present invention, the steel fiber is hooked at the end. The hook structure of the steel fiber further increases the mechanical interlocking force between the steel fiber and the low-carbon, low-shrinkage, high-ductility solid waste concrete. It forms a three-dimensional mesh support uniformly distributed in the low-carbon, low-shrinkage, high-ductility solid waste concrete, which inhibits crack propagation. In addition, it can further enhance its dispersion and interfacial bonding performance in the low-carbon, low-shrinkage, high-ductility solid waste concrete, and further improve the later-stage ductility and crack resistance of the low-carbon, low-shrinkage, high-ductility solid waste concrete.

[0034] According to an embodiment of the present invention, the length of the steel fiber is 11.7mm to 14.3mm, for example, it can be 11.7mm, 12mm, 12.5mm, 12.9mm, 13mm, 13.5mm, 14mm, 14.3mm, etc. Controlling the length of the steel fiber within the above range can further enhance its dispersibility and interfacial bonding performance in low-carbon, low-shrinkage, and high-ductility solid waste concrete, and further improve the later-stage ductility and crack resistance of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0035] According to an embodiment of the present invention, the effective diameter of the steel fiber is 180μm~220μm, for example, it can be 180μm, 190μm, 200μm, 210μm, 220μm, etc. Controlling the effective diameter of the steel fiber within the above range can further enhance its dispersibility and interfacial bonding performance in low-carbon, low-shrinkage, and high-ductility solid waste concrete, and further improve the later-stage ductility and crack resistance of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0036] According to an embodiment of the present invention, the tensile strength of the steel fiber is ≥2850MPa. For example, it can be 2850MPa, 2900MPa, 3000MPa, 3100MPa, 3500MPa, 4000MPa, 5000MPa, etc. By controlling the tensile strength of the steel fiber within the above range, the high ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete can be achieved.

[0037] According to an embodiment of the present invention, the length of the basalt fiber is 11mm to 13mm, for example, it can be 11mm, 11.5mm, 12mm, 12.5mm, 13mm, etc. By controlling the length of the basalt fiber within the above range, the basalt fiber can be combined with steel fiber to improve the ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete. Through reasonable raw material ratio, low-shrinkage, high-compressive strength, and high-tensile strength of low-carbon, low-shrinkage, and high-ductility solid waste concrete can be achieved.

[0038] According to an embodiment of the present invention, the effective diameter of the basalt fiber is 13μm~20μm, for example, it can be 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc. Controlling the effective diameter of the basalt fiber within the above range can further improve the ductility of low-carbon, low-shrinkage, high-ductility solid waste concrete, and through reasonable raw material ratio, achieve low shrinkage, high compressive strength, and high tensile strength of low-carbon, low-shrinkage, high-ductility solid waste concrete.

[0039] It can be understood that the "effective diameter" (also known as the "equivalent diameter") is the calculated diameter obtained by converting a fiber of any cross-sectional shape into a circular cross-section according to the principle of equal cross-sectional area.

[0040] According to an embodiment of the present invention, the tensile strength of the basalt fiber is ≥1250MPa, for example, it can be 1250MPa, 1300MPa, 1400MPa, 1500MPa, 1600MPa, 1700MPa, 1800MPa, 1900MPa, 2000MPa, etc. By controlling the tensile strength of the basalt fiber within the above range, the high ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete can be further achieved.

[0041] According to an embodiment of the present invention, the elastic modulus of the basalt fiber is ≥30 GPa. For example, it can be 30 GPa, 40 GPa, 50 GPa, 60 GPa, 70 GPa, 80 GPa, 90 GPa, 100 GPa, 200 GPa, 500 GPa, etc. Controlling the elastic modulus of the basalt fiber within the above range can further achieve low shrinkage of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0042] According to an embodiment of the present invention, the defoamer is a mixture of an inorganic carrier as a base, a liquid hydrocarbon and a polyglycerol. This composite defoamer is highly compatible with cement-based materials and can achieve instantaneous defoaming and continuous foam suppression. It can achieve multiple goals of rapid defoaming, long-term foam suppression, convenient construction, cost optimization and green environmental protection while maintaining the mechanical properties and durability of low-carbon, low-shrinkage and high-ductility solid waste concrete.

[0043] It is understandable that inorganic carriers can include SiO2, Al2O3, bentonite, perlite, etc.; liquid hydrocarbons can include white oil, mineral oil, C12-C18 alkanes, etc.

[0044] According to an embodiment of the present invention, the water-reducing agent includes modified polycarboxylic acid. The water-reducing agent has a high compatibility with silica fume, which can further improve the strength and durability of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0045] According to an embodiment of the present invention, the density of the water-reducing agent is 0.40 g / cm³.3 ~0.55g / cm 3 For example, it could be 0.40 g / cm³. 3 0.42 g / cm 3 0.45g / cm 3 0.47 g / cm 3 0.5g / cm 3 0.52g / cm 3 0.54 g / cm 3 0.55g / cm 3 By controlling the density of the water-reducing agent within the above range, the stability of the strength of low-carbon, low-shrinkage, and high-ductility solid waste concrete can be further improved.

[0046] In a second aspect, the present invention provides a method for preparing low-carbon, low-shrinkage, high-ductility solid waste concrete as described in the first aspect. Please refer to [link to relevant documentation]. Figure 1 The method includes: S1. Mix cement, silica fume, fly ash microspheres, and defoamer evenly. Add a pre-mixed solution of water-reducing agent and water, and stir for 3-4 minutes (e.g., 3 minutes, 3.5 minutes, 4 minutes, etc.) to form a homogeneous slurry. Adjust the stirring speed to 275-295 r / min (e.g., 275 r / min, 280 r / min, 285 r / min, 290 r / min, 295 r / min, etc.). Add quartz sand to the homogeneous slurry and stir for 2-3 minutes (e.g., 2 minutes, 2.5 minutes, 3 minutes, etc.) to form a uniform mortar. Reduce the stirring speed to 135-145 r / min (e.g., 135 r / min, 140 r / min, 145 r / min, etc.). Add steel fibers and basalt fibers evenly multiple times and stir for 8-10 minutes (e.g., 8 minutes, 9 minutes, 10 minutes, etc.) until the mixture is homogeneous and a fiber mixture is formed.

[0047] In this step, multiple low-speed fiber dispersion methods are used to ensure the uniformity of material distribution and fiber dispersion effect, further enabling low-carbon, low-shrinkage, and high-ductility solid waste concrete to achieve both high compressive strength and high ductility.

[0048] S2. The fiber mixture is loaded into a mold whose inner wall has been coated with a thin layer of mineral oil, left to stand for 20-25 hours, then demolded and cured to obtain low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0049] For example, the settling time can be 20h, 21h, 22h, 23h, 24h, 25h, etc.

[0050] According to some embodiments of the present invention, the settling temperature is 18℃~22℃. For example, it can be 18℃, 19℃, 20℃, 21℃, 22℃, etc., which facilitates the uniform curing of low-carbon, low-shrinkage, and high-ductility solid waste concrete, ensuring uniformity and taking into account both the strength and ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0051] According to some embodiments of the present invention, the relative humidity of the environment during the static setting is 50%RH~70%RH. For example, it can be 50%RH, 55%RH, 60%RH, 65%RH, 70%RH, etc., which facilitates the uniform curing of low-carbon, low-shrinkage, and high-ductility solid waste concrete, ensures uniformity, and can take into account both the strength and ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0052] According to some embodiments of the present invention, the curing temperature is 18℃~22℃, for example, it can be 18℃, 19℃, 20℃, 21℃, 22℃, etc., which facilitates the uniform curing of low-carbon, low-shrinkage, and high-ductility solid waste concrete, ensures uniformity, and can take into account both the strength and ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0053] According to some embodiments of the present invention, the relative humidity of the curing environment is ≥95%RH. For example, it can be 95%RH, 96%RH, 97%RH, 98%RH, 99%RH, 100%RH, etc., thereby further balancing the strength and ductility of low-carbon, low-shrinkage, and high-ductility solid waste concrete.

[0054] In summary, the preparation method of low-carbon, low-shrinkage, and high-ductility solid waste concrete proposed in this invention addresses the problems of uneven pore structure and unstable product performance caused by some existing technologies that require complex chemical foaming and air entrainment processes to reduce the density of low-carbon, low-shrinkage, and high-ductility solid waste concrete. This method employs mechanical stirring and step-by-step feeding processes, combined with multiple low-speed fiber dispersion methods, ensuring uniform material distribution and fiber dispersion effects. The process is simple and controllable, easy to standardize and promote, and particularly suitable for the factory-based and large-scale production of precast components, significantly improving the engineering applicability and universality of the new material.

[0055] The present disclosure will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the disclosure. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0056] Example 1 This embodiment discloses a low-carbon, low-shrinkage, high-ductility solid waste concrete, the specific mass parts of which are: 700 parts cement, 150 parts silica fume, 150 parts fly ash microspheres, 1083 parts quartz sand, 10 parts defoamer, 10 parts water-reducing agent, 160 parts water, 165 parts steel fiber, and 0 parts basalt fiber.

[0057] Example 2 This embodiment discloses a low-carbon, low-shrinkage, high-ductility solid waste concrete, the specific mass parts of which are: 700 parts cement, 150 parts silica fume, 150 parts fly ash microspheres, 1083 parts quartz sand, 10 parts defoamer, 10 parts water-reducing agent, 160 parts water, 138 parts steel fiber, and 9 parts basalt fiber.

[0058] Example 3 This embodiment discloses a low-carbon, low-shrinkage, high-ductility solid waste concrete, the specific mass parts of which are: 700 parts cement, 150 parts silica fume, 150 parts fly ash microspheres, 1083 parts quartz sand, 10 parts defoamer, 10 parts water-reducing agent, 160 parts water, 110 parts steel fiber, and 18 parts basalt fiber.

[0059] In Examples 1-3 above, the cement was P·O 52.5 grade Portland cement with a CaO content of 55.95% and a specific surface area of ​​420 m². 2 / kg; Specific surface area of ​​silica fume 1.81×10 4 m 2 / kg, SiO2 content 93.77%; fly ash microspheres specific surface area ≥1200m² 2 / kg, fineness (d50) is 1.62μm; quartz sand particle size is 20~40 mesh; steel fiber is copper-plated steel fiber, hook-shaped, length 12.97mm, effective diameter 200μm, tensile strength 2961MPa; basalt fiber, length 12mm, effective diameter 17μm, tensile strength 1938MPa, elastic modulus 76.1GPa; defoamer is an inorganic carrier-based mixture of liquid hydrocarbons and polyglycerol; water-reducing agent is mainly composed of modified polycarboxylic acid, Sika ViscoCrete-540P powder water-reducing agent, density 0.40~0.55g / cm³. 3 .

[0060] The difference between Example 4 and Example 1 is that the steel fiber is in the shape of a straight rod.

[0061] The difference between Comparative Example 4 and Example 1 is that no steel fibers are added.

[0062] The low-carbon, low-shrinkage, high-ductility solid waste concrete described in Examples 1-3 above was prepared through the following steps: (1) Mix cement, silica fume, fly ash microspheres and defoamer evenly, add water-reducing agent and water mixed solution that has been mixed evenly in advance, stir for 3 minutes to form a homogeneous slurry, adjust the stirring speed to 285±10r / min, add quartz sand to the homogeneous slurry, stir for 2 minutes to form a uniform mortar, reduce the stirring speed to 140±5r / min, and add steel fiber and basalt fiber evenly several times and stir for 8 minutes to form a fiber mixture. (2) Put the mixture from step (1) into a mold whose inner wall is already covered with a thin layer of mineral oil, and use a spatula to tamp along the mold wall to scrape off the excess mixture at the top of the mold. (3) After the mold containing the mixture in step (2) is left to stand for 24 hours at room temperature of 20℃±2℃ and relative humidity of 60±10%RH, it is removed and placed in a curing room of 20℃±2℃ and relative humidity of 95%RH or higher for 28 days.

[0063] Comparative Example 1 references Example 2 from the patent "All-solid waste high-ductility low-shrinkage geopolymer low-carbon low-shrinkage high-ductility solid waste concrete material and its preparation method" (application number 202411681377.8). Comparative Example 2 references Example 2 from the patent "An ecological high-ductility low-shrinkage cement-based composite material and method prepared using coal gangue as aggregate" (application number 202410907273.8). Comparative Example 3 uses low-carbon low-shrinkage high-ductility solid waste concrete with P·O 52.5 ordinary Portland cement as the cementing material. The mix proportions (parts by mass) of the three comparative examples are shown in Table 1.

[0064] Table 1

[0065] In Comparative Example 1, the water glass modulus is 1.8; the fineness modulus of the coal gangue fine aggregate is 1.39; the fiber is PVA fiber, 8 mm in length, with an elastic modulus of 35.4 GPa, a tensile strength of 1250 MPa, and an ultimate elongation of 9.5%. In Comparative Example 2, the cement is P·I cement, the coal gangue fine aggregate has a particle size of 0.06~1.18 mm, and a fineness modulus of 1.60; the coal gangue used has a sulfur content of 0.8%, belonging to low-sulfur coal gangue; the shrinkage-reducing admixture is a composite of ethylene glycol diethyl ether liquid shrinkage-reducing agent and superabsorbent resin; the fiber is polypropylene fiber, 10 mm in length, with an elastic modulus of 35 GPa and a tensile strength of 1200 MPa; the water-reducing agent is liquid polycarboxylate water-reducing agent. In Comparative Example 3, all fibers are steel fibers; other raw materials are consistent with those in the method of this invention.

[0066] The compressive strength test was conducted according to GB / T 17671-2021 "Test Method for Compressive Strength of Cement Mortar (ISO Method)", the tensile strength test was conducted according to JC / T 2461-2018 "Test Method for Mechanical Properties of High-Ductility Fiber Reinforced Cement-Based Composite Materials", and the autogenous shrinkage test was conducted according to GB / T 50082-2024 "Standard for Test Methods for Long-Term Performance and Durability of Concrete".

[0067] Mechanical property tests were conducted on the low-carbon, low-shrinkage, high-ductility solid waste concretes prepared in Examples 1-3 using the above steps. The results showed that their performance met the requirements of GB / T 51231-2016 "Technical Standard for Prefabricated Concrete Buildings" and JTG / T 3365-05—2022 "Design Specification for Prefabricated Concrete Bridges for Highways". The 28-day average compressive strength of the low-carbon, low-shrinkage, high-ductility solid waste concrete in Example 1 reached 109.1 MPa, the average tensile strength reached 9.5 MPa, and the maximum ultimate tensile strain was 1.63%. The 28-day average compressive strength of the low-carbon, low-shrinkage, high-ductility solid waste concrete in Example 2 reached 132.3 MPa, the highest average tensile strength reached 7.7 MPa, and the maximum ultimate tensile strain was 1.30%. The 28-day compressive strength of the low-carbon, low-shrinkage, high-ductility solid waste concrete in Example 3 reached a maximum of 125.4 MPa, the highest tensile strength reached 9.6 MPa, and the maximum ultimate tensile strain was 1.56%.

[0068] Table 2

[0069] Compared with Comparative Examples 1-3, the low-carbon, low-shrinkage, high-ductility solid waste concrete prepared according to the method of the present invention in Examples 1-4 showed that the maximum autogenous shrinkage of the low-carbon, low-shrinkage, high-ductility solid waste concrete in Examples 1-4 was -480 με after 7 days, which was 7.2% and 39.2% lower than that in Comparative Examples 1 and 3, respectively. The minimum compressive strength of the low-carbon, low-shrinkage, high-ductility solid waste concrete in Examples 1-3 was 109.1 MPa, which was 159.1% higher than that in Comparative Example 2. The minimum ultimate tensile strain of the low-carbon, low-shrinkage, high-ductility solid waste concrete in Examples 1-3 was 1.3%, which was 32.7% higher than that in Comparative Example 3, and the carbon emissions were reduced by at least 21.3%.

[0070] Based on the test results of the above embodiments and the comparison results with the comparative examples, the 28-day compressive strength of the low-carbon, low-shrinkage, high-ductility solid waste concrete in Examples 1-3 all reached the C100 standard, the tensile strength was greater than 7 MPa, the ultimate tensile strain was greater than 1.3%, and the use of industrial solid waste to replace cement reduced carbon emissions by 21.3%, with a maximum self-shrinkage of 190 μm. This is because Examples 1-3 of this invention utilize the physicochemical properties of industrial solid waste to construct a matrix with extremely low porosity, few defects, and extremely high strength, simultaneously achieving low carbon emissions in the production stage and low shrinkage in the use stage. Through the synergistic bridging effect of steel fibers and basalt fibers, the material is transformed into a pseudo-ductile "multi-crack" mode, ultimately achieving economic and environmental benefits while possessing good mechanical and workability properties.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," "some implementations," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is 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. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0072] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A low-carbon, low-shrinkage, high-ductility solid waste concrete, characterized in that, The low-carbon, low-shrinkage, high-ductility solid waste concrete comprises the following raw materials by weight: 690-710 parts cement, 140-160 parts silica fume, 140-160 parts fly ash microspheres, 1080-1090 parts quartz sand, 5-15 parts defoamer, 5-15 parts water-reducing agent, 150-170 parts water, 110-165 parts steel fiber, and 0-18 parts basalt fiber.

2. The low-carbon, low-shrinkage, high-ductility solid waste concrete according to claim 1, characterized in that, The cement includes P·O 52.5 grade Portland cement; and / or, Based on the total mass of the cement, the mass percentage of CaO is 55%~57%; and / or, The specific surface area of ​​the cement is 410 m². 2 / kg~430m 2 / kg.

3. The low-carbon, low-shrinkage, high-ductility solid waste concrete according to claim 1 or 2, characterized in that, The specific surface area of ​​the silica fume is 1.8 × 10⁻⁶. 4 m 2 / kg~1.9×10 4 m 2 / kg; and / or, Based on the total mass of the silica ash, the mass percentage of SiO2 is 93% to 94%.

4. The low-carbon, low-shrinkage, high-ductility solid waste concrete according to claim 1 or 2, characterized in that, The specific surface area of ​​the fly ash microspheres is ≥1200 m². 2 / kg; and / or, The volume average particle size d50 of the fly ash microspheres is ≤3μm.

5. The low-carbon, low-shrinkage, high-ductility solid waste concrete according to claim 1 or 2, characterized in that, The quartz sand has a particle size of 20-40 mesh.

6. The low-carbon, low-shrinkage, high-ductility solid waste concrete according to claim 1 or 2, characterized in that, The steel fibers include copper-plated steel fibers; and / or, The steel fiber is hook-shaped; and / or, The steel fibers have a length of 11.7 mm to 14.3 mm; and / or, The effective diameter of the steel fiber is 180μm~220μm; and / or, The tensile strength of the steel fiber is ≥2850MPa.

7. The low-carbon, low-shrinkage, high-ductility solid waste concrete according to claim 1 or 2, characterized in that, The basalt fibers are 11mm to 13mm in length; and / or, The effective diameter of the basalt fibers is 13μm~20μm; and / or, The basalt fiber has a tensile strength ≥1250MPa; and / or, The elastic modulus of the basalt fiber is ≥30 GPa.

8. The low-carbon, low-shrinkage, high-ductility solid waste concrete according to claim 7, characterized in that, The defoamer is a mixture of an inorganic carrier as a base, liquid hydrocarbons, and polyglycerol; and / or, The water-reducing agent includes modified polycarboxylic acid; and / or, The water-reducing agent has a density of 0.40 g / cm³. 3 ~0.55g / cm 3 .

9. A method for preparing low-carbon, low-shrinkage, high-ductility solid waste concrete according to any one of claims 1 to 8, characterized in that, include: Cement, silica fume, fly ash microspheres and defoamer are mixed evenly, and a pre-mixed water-reducing agent and water mixture is added. The mixture is stirred for 3 to 4 minutes to form a homogeneous slurry. The stirring speed is adjusted to 275 r / min to 295 r / min, and quartz sand is added to the homogeneous slurry. After stirring for 2 to 3 minutes to form a homogeneous mortar, the stirring speed is reduced to 135 r / min to 145 r / min. Steel fibers and basalt fibers are added evenly in multiple batches and stirred for 8 to 10 minutes. The mixture is stirred evenly to form a fiber mixture. The fiber mixture is placed into a mold whose inner wall has been coated with a thin layer of mineral oil, left to stand for 20-25 hours, then demolded and cured to obtain low-carbon, low-shrinkage, and high-ductility solid waste concrete.

10. The method according to claim 9, characterized in that, The settling temperature is 18℃~22℃; and / or, The relative humidity of the environment during the static placement period is 50%RH~70%RH; and / or, The curing temperature is 18℃~22℃; and / or, The relative humidity of the environment to be maintained is ≥95%RH.

Images