A kind of cinder-based non-fired core-shell structure ceramsite and its preparation method and application

Abstract

This invention discloses a volcanic slag-based non-fired core-shell structure ceramsite, its preparation method, and lightweight insulating concrete. The preparation of the non-fired core-shell structure ceramsite includes mixing volcanic slag powder, volcanic slag particles, waste EPS insulation board particles, electrolytic manganese slag, modified sludge powder, and water, and adding the mixture to a disc granulator to granulate core raw material balls with a particle size of 3-8 mm. The mixture is then fed into the disc granulator and coated with a mixture of the outer shell slurry and aluminum powder until the ball size reaches 5-10 mm. CO2 gas is introduced for curing to obtain volcanic slag-based non-fired core-shell structure ceramsite. This invention achieves functional zoning utilization of solid waste by preparing non-fired "core-shell structure" ceramsite, and, in conjunction with a special all-solid waste cementitious material, constructs a multi-scale, gradient porosity and functional system in concrete consisting of "lightweight core pores - dense outer shell layer - fine aggregate gradation pores - matrix micropores," thereby simultaneously addressing multiple objectives such as solid waste disposal, building energy conservation, and synergistic improvement of material performance.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a core-shell structured ceramic particle, its preparation method, and its application. Background Technology

[0002] With the rapid development of industrialization and urbanization, multi-source solid waste, represented by volcanic slag, municipal sludge, waste EPS boards, and various industrial waste, is facing severe challenges such as difficult disposal, low utilization rate, and high environmental risks. Traditional landfill or dumping methods occupy land and are prone to secondary pollution, while simple resource utilization is difficult to coordinate the treatment of various solid wastes with different compositions and properties, especially complex solid wastes containing organic matter and heavy metals, and cannot meet the needs of large-scale, high-value utilization.

[0003] Meanwhile, as a major national strategy, building energy conservation has created an increasingly urgent demand for self-insulating wall materials. However, existing lightweight insulation materials generally suffer from performance contradictions: organic insulation materials (such as EPS boards) are flammable and have poor durability; inorganic lightweight aggregate concrete often suffers from weak interfacial bonding between aggregate and cement matrix and a simple pore structure, making it difficult to balance insulation and strength, and also exhibiting thermal bridging effects. Even when using natural porous volcanic slag as aggregate, its random structure and undifferentiated functions make it difficult to systematically optimize overall performance. Although existing technologies attempt to utilize solid waste to prepare insulation materials, they often have limitations: first, the types of solid waste utilized are limited, lacking co-processing solutions for difficult-to-treat solid wastes such as sludge; second, the material structure design is crude, often employing homogeneous mixing, failing to build a systematic functional and pore gradient to coordinate the contradiction between insulation and load-bearing capacity; and third, traditional processes are energy-intensive or rely on cement and other cementing materials, resulting in insufficient green and low-carbon benefits.

[0004] Therefore, there is an urgent need for an innovative solution that can both synergistically absorb solid waste from multiple sources and produce high-performance thermal insulation building materials through refined structural design. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a systematic solution that enables the functional zoning of solid waste through the preparation of non-fired "core-shell structure" ceramsite. Furthermore, in conjunction with specialized all-solid-waste cementitious materials, a multi-scale, gradient porosity and functional system is constructed in concrete, consisting of a "lightweight core pore - dense outer shell layer - fine aggregate gradation pores - matrix micropores." This approach simultaneously tackles multiple objectives, including solid waste disposal, building energy conservation, and synergistic improvement of material performance, and can play a crucial role in urban construction and renewal.

[0006] To achieve the above objectives, the following technical solution is adopted: A method for preparing volcanic slag-based non-fired core-shell structured ceramsite includes the following steps: S1. Core preparation: Volcanic slag powder, volcanic slag granules, waste EPS insulation board granules, electrolytic manganese slag, modified sludge powder and water are mixed and added to a disc granulator to granulate and obtain core raw material balls with a particle size of 3~8mm. The balls are then cured under standard curing conditions for 8~12 hours. S2. Preparation of outer shell slurry: Volcanic slag powder, rice husk ash, phosphogypsum, carbide slag and water are mixed and wet-milled for more than 1 hour to obtain outer shell slurry; S3. Core-shell structure forming: The core raw material ball is put into a disc granulator and wrapped with a mixture of the outer shell slurry and aluminum powder until the ball size is 5~10mm. S4. CO2 Co-curing Enhancement: Place the coated aggregate in a carbonization curing box, introduce CO2 gas with a concentration of not less than 25%, maintain the pressure at 0.3~0.5MPa and the temperature at 50-70℃ for 4-8 hours, and then standard cure for more than 48 hours to obtain volcanic slag-based non-fired core-shell structure ceramsite.

[0007] According to the above scheme, the specific surface area of ​​the volcanic slag powder is >200m². 2 / kg, the volcanic slag particles have a particle size of 1.18mm~2.36mm and are all prepared by crushing or grinding the original volcanic slag.

[0008] According to the above scheme, the preparation method of the modified sludge powder includes the following steps: adding 0.1~0.3% of its mass of lysozyme to municipal sludge, stirring and enzymatically hydrolyzing for 1 hour; then adding 0.2~0.4% of its mass of alkaline protease, stirring and enzymatically hydrolyzing for 2 hours; then adding 20% ​​of its mass of carbide slag and drying at 80℃ until the moisture content is ≤3% to obtain modified sludge powder.

[0009] According to the above scheme, the waste EPS insulation board particles are obtained by crushing waste EPS insulation boards, with a particle size of 1-3mm.

[0010] According to the above scheme, the specific surface area of ​​the electrolytic manganese slag particles is >150m². 2 / kg, moisture content <5%.

[0011] According to the above scheme, the specific surface area of ​​the rice husk ash is >400 m². 2 / kg.

[0012] According to the above scheme, the phosphogypsum has a moisture content of less than 10 wt% and a specific surface area of ​​>100 m². 2 / kg.

[0013] According to the above scheme, the dried carbide slag has a CaO content > 60 wt% and a specific surface area > 200 m². 2 / kg.

[0014] According to the above scheme, in step S1, the raw materials of the core raw material ball are as follows by weight: 100-160 parts of volcanic slag powder, 80-120 parts of volcanic slag particles, 60-75 parts of waste EPS insulation board particles, 65-105 parts of modified sludge powder, 15-45 parts of electrolytic manganese slag, and 35-50 parts of water.

[0015] According to the above scheme, in step S2, the raw materials of the outer shell slurry are as follows by weight: 60-80 parts of volcanic slag powder, 15-30 parts of rice husk ash, 20-40 parts of phosphogypsum, 10-20 parts of carbide slag, and 15-25 parts of water.

[0016] According to the above scheme, in step S3, the outer shell slurry comprises 120-200 parts by weight, and the aluminum powder comprises 1-2 parts. The aluminum powder reacts in the outer shell slurry to generate bubbles, forming pores.

[0017] The present invention also provides a volcanic slag-based non-fired core-shell structured ceramic particle, which is prepared by the above-mentioned method.

[0018] The present invention also provides a lightweight thermal insulation concrete, the composition of which is as follows by weight: 270-360 parts of the above-mentioned volcanic slag-based non-fired core-shell structure ceramsite, 210-280 parts of volcanic slag particles, 100-140 parts of volcanic ash slag powder, 40-80 parts of phosphogypsum, 30-40 parts of red mud, 70-100 parts of steel slag powder, 1-3 parts of foaming agent, 0.5-1 part of foam stabilizer, 3-5 parts of water-reducing agent, and 80-100 parts of water.

[0019] In the raw materials for preparing the above-mentioned lightweight thermal insulation concrete, the volcanic slag powder has a specific surface area > 200 m². 2 / kg, the volcanic slag particles have a particle size of 1.18mm~2.36mm and are all prepared by crushing or grinding undisturbed volcanic slag. The phosphogypsum has a moisture content of less than 10wt% and a specific surface area >100m². 2 / kg. Red mud is a strongly alkaline solid waste residue produced after alumina extraction from bauxite, which is dried and ground to a specific surface area >100m². 2 / kg. Steel slag powder is made from molten steel slag produced during the steelmaking process in steel plants, through cooling, crushing, and grinding, with a specific surface area >400m². 2 / kg. The foaming agent is hydrogen peroxide, the foam stabilizer is calcium stearate, and the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0020] The present invention also provides a method for preparing the aforementioned lightweight thermal insulation concrete, comprising the following steps: First, mix the volcanic ash powder, phosphogypsum, red mud, and steel slag powder for more than 2 minutes; then add volcanic ash-based non-fired core-shell structure ceramsite and volcanic slag particles and mix for more than 1 minute; finally, add water, foaming agent, foam stabilizer, and water-reducing agent and mix for more than 3 minutes to obtain lightweight thermal insulation concrete.

[0021] This invention uses multi-source solid waste such as volcanic slag, municipal sludge, waste EPS insulation board particles, electrolytic manganese slag, and calcium carbide slag as raw materials to prepare volcanic slag-based non-fired core-shell structured ceramsite. Inside the core, the naturally porous volcanic slag particles (particle size 1.18mm~2.36mm) provide abundant micron-sized mesopores, which intertwine with the millimeter-sized macropores introduced by the waste EPS insulation board particles and the micron-sized auxiliary pores formed by the modified municipal sludge, forming a core-level pore network. Through the encapsulation and densification of the highly active outer shell slurry doped with aluminum powder, a hundred-micron-sized transition layer is formed. Combined with a CO2 synergistic curing process, a robust carbonate structure rich in submicron-sized micropores is generated in the shell layer. This continuous gradient pore system, ranging from millimeter-level macropores to micrometer-level mesopores and auxiliary pores to a hundred-micrometer-level transition layer to submicrometer-level micropores, significantly increases the tortuosity of the heat flow path and interface reflection, thereby significantly improving the overall thermal insulation performance of the ceramsite without relying on high-temperature sintering. Simultaneously, its dense outer shell and carbonization-reinforced network ensure high compressive strength. Furthermore, this invention utilizes the strongly alkaline environment provided by carbide slag to chemically solidify harmful components in electrolytic manganese slag and municipal sludge, and employs a dense outer shell formed by CO2 curing to physically encapsulate them, constructing a dual safety mechanism. This core-shell structure and the chemical affinity between components also effectively optimize the interfacial bonding performance between the aggregate and the all-solid-waste concrete matrix, improving the long-term durability and volume stability of the concrete.

[0022] This invention employs a unique all-solid-waste cementitious system and graded aggregate design in lightweight insulating concrete: Volcanic slag-based non-fired core-shell structured ceramsite is used as coarse aggregate, providing the main lightweight and insulating functions; volcanic slag particles of a specific size (1.18mm~2.36mm) are used as fine aggregate. Their natural porous structure not only optimizes gradation and reduces paste requirements, but also forms a crucial "interfacial mesoporous" layer in the concrete, working synergistically with the ceramsite shell and matrix micropores to construct a complete gradient pore network, effectively suppressing thermal bridging effects. The cementitious material is a compound of volcanic ash slag powder, phosphogypsum, red mud, and steel slag powder. This combination can undergo a synergistic reaction of alkali-activated and sulfate-activated reactions at room temperature, forming a high-strength, stable geopolymer network, which is key to achieving cement-free construction. Furthermore, this invention introduces hydrogen peroxide and calcium stearate as a foam stabilizer during concrete mixing. This combination generates a large number of uniform, closed micron-sized bubbles in situ within the cementitious matrix. This not only further reduces the dry density and thermal conductivity of the concrete, enhancing its insulation effect, but also effectively buffers internal stress caused by temperature changes or loads, improving the material's frost resistance and durability. The addition of a polycarboxylate superplasticizer ensures that the mixture maintains excellent workability and encapsulation even under low water-cement ratio conditions, allowing the porous aggregate to bond tightly with the foamed matrix. This preparation method employs a process of first dry-mixing the powder and aggregate, then adding the liquid component and rapidly stirring. This effectively controls the initiation time and process of the foaming reaction, preventing premature foam rupture or uneven distribution, ensuring the uniformity of the concrete's pore structure and performance, and ultimately obtaining a lightweight, high-strength, heat-insulating, and durable new type of wall insulation material.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The volcanic slag-based non-fired core-shell structure ceramsite prepared by this invention has a precise core-shell and pore gradient structure, realizing the systematic optimization of thermal and mechanical properties. The core of the ceramsite is constructed by the synergy of porous volcanic slag particles, waste EPS insulation board particles and modified municipal sludge, forming a lightweight insulation core with millimeter-level macropores as the main component and micron-level pores as the auxiliary component. At the same time, the introduced electrolytic manganese slag is effectively solidified in the strongly alkaline environment provided by carbide slag, and its fine particles fill the above-mentioned pore network as functional micro-aggregates, which not only optimizes the gradation and density of the core, but also contributes to the auxiliary cementing potential of its silicon-aluminum components. The outer shell is wrapped by a highly active slurry made by wet grinding of volcanic slag powder, rice husk ash, phosphogypsum and carbide slag, and then strengthened by CO2 synergistic curing. The "micron-nano" gradation of volcanic slag powder and rice husk ash not only provides the core silicon-aluminum source, but the dense micro-framework it forms also stabilizes the microporous structure in the inner layer of the outer shell. The composite activation system composed of carbide slag and phosphogypsum is efficiently coupled with the above-mentioned framework, driving the reaction to rapidly generate a high-strength gel phase. After curing, the inner layer of the outer shell forms a transitional structure rich in submicron-level micropores due to aluminum powder foaming and early hydration, while the outer surface forms a dense and high-strength carbonate crystal protective layer under the dominance of CO2 permeation and carbonization reaction. The gradient transition between the two achieves synergistic effects of heat preservation and strengthening. This gradient system of "core macropores - outer shell micropores and dense layer" greatly increases the tortuosity of the heat flow path and the reflection interface, significantly improving the heat preservation efficiency of the ceramsite. At the same time, the carbonization network of the outer shell ensures that the ceramsite has high cylinder compressive strength. The alkaline environment provided by the carbide slag also enables the simultaneous chemical solidification of electrolytic manganese slag and sludge organic matter in the core, and the dense outer shell completes the physical encapsulation, forming a double safety barrier.

[0024] (2) This invention employs a full solid waste cementitious system and multi-grade aggregate synergistic design in lightweight thermal insulation concrete, achieving complementary and enhanced performance. The core-shell ceramsite serves as the core coarse aggregate, providing the main lightweight and thermal insulation functions; volcanic slag particles of a specific size serve as fine aggregate, their natural pores forming a crucial "interfacial mesoporous" layer in the concrete, synergistically optimizing the gradation and blocking thermal bridges; the cementitious material is a compound of volcanic ash slag powder, phosphogypsum, red mud, and steel slag powder, undergoing an alkali-sulfate composite activation reaction at room temperature to form a high-strength and stable geopolymer network. The introduction of hydrogen peroxide and calcium stearate generates a large number of uniform, closed micron-sized bubbles in situ within the cementitious matrix, further reducing the density and thermal conductivity of the concrete and buffering internal stress. The polycarboxylate superplasticizer ensures excellent workability of the mixture at a low water-cement ratio, allowing the porous aggregate to bond tightly with the foamed matrix.

[0025] (3) This invention constructs a multi-level functional and porosity gradient through a holistic design from aggregate to matrix. At the macroscopic level, volcanic slag-based non-fired core-shell structure ceramsite serves as a functional integration unit, integrating lightweight insulation, high-strength protection, and consolidation of harmful substances. At the mesoscopic level, the natural pores of volcanic slag fine aggregate serve as a transition zone, optimizing the interface and suppressing thermal bridges. At the microscopic level, the geopolymerization reaction and foaming micropores of multi-solid waste cementitious materials provide the matrix strength and insulation foundation. This multi-scale synergy from "ceramsite macropores - fine aggregate mesopores - cementitious material micropores" enables concrete to achieve excellent thermal insulation performance while also possessing good mechanical strength, interfacial adhesion, and long-term durability, realizing the unity of lightweight, high strength, thermal insulation, waste utilization, and safety, and providing a systematic solution for solid waste resource utilization and building energy conservation. Detailed Implementation

[0026] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0027] The raw materials used in the specific implementation are as follows: Volcanic slag is obtained from porous glassy lava formed by natural volcanic eruptions, which is mined, crushed, and screened. Its main components are SiO2, Al2O3, and a small amount of alkali metal oxides, and it has a natural microporous structure and certain volcanic ash activity.

[0028] Municipal sludge is dewatered sludge produced by urban wastewater treatment plants. It has a water content of about 80% and contains organic matter, nitrogen, phosphorus and trace heavy metals.

[0029] Waste EPS insulation boards are made from polystyrene foam insulation boards discarded during building demolition or packaging. They are lightweight, closed-cell organic polymer materials.

[0030] Electrolytic manganese slag is an acidic filter residue produced during the electrolytic production of metallic manganese. Its main components are SiO2, Al2O3, CaO, and soluble manganese and ammonium salts.

[0031] Calcium carbide slag is a waste residue produced after acetylene gas production in chemical plants. After drying, it has a CaO content >60%, is strongly alkaline, and has a specific surface area >200 m². 2 / kg.

[0032] Rice husk ash is the ash obtained by burning rice husks under controlled conditions. It has a high SiO2 content (>85%) and a high specific surface area (>400m²). 2 / kg) and volcanic ash activity.

[0033] Phosphogypsum is an industrial byproduct of wet-process phosphoric acid production. It is in its original form, with a moisture content of less than 10% and a specific surface area greater than 100 m². 2 / kg.

[0034] Red mud is a highly alkaline solid waste residue produced after alumina extraction from bauxite, which is dried and ground to a specific surface area >100m². 2 / kg, rich in Fe2O3, Al2O3 and SiO2.

[0035] Steel slag powder is made from molten steel slag produced during the steelmaking process in steel plants, through cooling, crushing, and grinding, with a specific surface area > 400 m². 2 / kg, containing minerals such as calcium silicate and calcium aluminoferrite. Unless otherwise specified, all other raw materials and equipment were obtained commercially.

[0036] Example 1 S1. Core Material Preparation: The undisturbed volcanic slag is crushed and sieved to obtain volcanic slag particles (particle size 1.18mm~2.36mm). The remaining volcanic slag particles are ground to a specific surface area >200m². 2 / kg, to obtain volcanic slag powder; to modify municipal sludge: add 0.1% of its mass of lysozyme to municipal sludge, stir and enzymatically hydrolyze for 1 hour; then add 0.2% of its mass of alkaline protease, stir and enzymatically hydrolyze for 2 hours, then add 20% of its mass of carbide slag and dry at 80℃ until the moisture content is ≤3%, to obtain modified sludge powder; crush waste EPS insulation boards into waste EPS insulation board particles with a particle size of 1-3mm. S2. Core Preparation: The volcanic slag powder, volcanic slag particles (particle size 1.18mm~2.36mm), waste EPS insulation board particles, electrolytic manganese slag, the modified sludge powder and carbide slag mixture obtained in step S1, and water are added to a disc granulator for granulation to obtain core raw material balls with a particle size of 3~8mm, and cured under standard curing conditions for 8~12h. The composition includes 120 parts volcanic slag powder, 100 parts volcanic slag particles (particle size 1.18mm~2.36mm), 60 parts waste EPS insulation board particles, 85 parts modified sludge powder, 15 parts electrolytic manganese slag, and 35 parts water.

[0037] S3. Preparation of the outer shell slurry: Volcanic slag powder, rice husk ash, phosphogypsum, carbide slag and water are mixed and wet-milled for 1 hour to obtain the outer shell slurry. The slurry consists of 60 parts volcanic slag powder, 15 parts rice husk ash, 20 parts phosphogypsum, 10 parts carbide slag and 15 parts water.

[0038] S4. Core-shell structure forming: The core obtained in step S2 is put into a disc granulator. After spraying water on the surface, the shell slurry obtained in step S3 is mixed evenly with aluminum powder and put into the disc granulator to wrap the core. The wrapping continues until the size of the pellet is 5~10mm. The aluminum powder is 1 part.

[0039] S5. CO2 Co-curing Enhancement: The coated aggregate is placed in a carbonization curing box, and CO2 gas with a concentration of 30% is introduced. The pressure is maintained at 0.5MPa and the temperature is 50-70℃ for 6 hours, followed by standard curing for 48 hours, to obtain the volcanic slag-based non-fired core-shell structure ceramsite.

[0040] Example 2 The preparation method of Example 1 is repeated, except that the raw materials used are as follows by weight: Core components: 160 parts volcanic slag powder, 80 parts volcanic slag granules (particle size 1.18mm~2.36mm), 75 parts waste EPS insulation board granules, 105 parts modified sludge powder, 40 parts electrolytic manganese slag, and 50 parts water.

[0041] The outer shell slurry consists of 80 parts volcanic slag powder, 25 parts rice husk ash, 40 parts phosphogypsum, 20 parts carbide slag, and 20 parts water.

[0042] Comparative Example 1 The preparation method of Example 1 was repeated, except that the volcanic slag powder in the core and shell was replaced with fly ash of the same particle size, and the volcanic slag particles were replaced with crushed stone of the same particle size.

[0043] Comparative Example 2 The preparation method of Example 1 was repeated, except that the outer shell was removed. All the raw materials of the core and the outer shell in Example 1 were mixed at one time, and the total amount of water was added. The raw material balls of 5-10 mm were granulated and CO2 synergistic curing was carried out to obtain volcanic slag-based non-fired ceramsite.

[0044] Comparative Example 3 The preparation method of Example 1 was repeated, except that no waste EPS insulation board particles were added during the core preparation process, and the remaining core raw materials were increased proportionally to keep the total dry material amount unchanged.

[0045] Comparative Example 4 The preparation method of Example 1 was repeated, except that CO2 synergistic curing was not performed, and the encapsulated aggregate balls were directly cured under standard curing conditions for 54 hours.

[0046] Referring to GB / T 17431.1-2010 "Lightweight Aggregates and Their Test Methods Part 1: Lightweight Aggregates" and GB / T 17431.2-2010 "Lightweight Aggregates and Their Test Methods Part 2: Lightweight Aggregates Test Methods", the apparent density, 1-hour water absorption rate, and cylinder compressive strength of the volcanic slag-based non-fired core-shell structure ceramsite in Examples 1-2 and Comparative Examples 1-4 were tested. Referring to GB 6566-2010 "Limits of Radionuclides in Building Materials", the internal and external exposure indices of the ceramsite in Examples 1-2 and Comparative Examples 1-4 were tested. The test results are shown in Table 1.

[0047] Table 1

[0048] As shown in Table 1, the performance of the ceramsite in Examples 1-2 of this invention is significantly better than that in Comparative Examples 1-4. This is due to the effective synergy between the components and the process. In the core, volcanic slag particles and waste EPS insulation board particles synergistically construct a lightweight porous skeleton (resulting in an apparent density as low as 800-850 kg / m³ in the examples). 3 The modified sludge powder and electrolytic manganese slag are solidified and filled with micro-aggregates under the alkaline activation of carbide slag. In the outer shell, volcanic slag powder, rice husk ash, and phosphogypsum are wet-milled to form a highly active slurry, which, after CO2 synergistic curing, forms a dense and high-strength carbonate protective layer, giving the ceramsite a compressive strength of 8.5-9.0 MPa (far higher than the comparative example). Moreover, the alkaline environment of carbide slag and the dense outer shell synergistically achieve chemical-physical dual solidification of harmful components in the core (radioactivity index meets the standard). This structure of "lightweight and porous core, dense and high-strength outer shell", combined with a moderate water absorption rate (13-14%), optimizes the interface between aggregate and concrete matrix, thus enabling the formulation of a bulk density of 1100-1300 kg / m³. 3 This laid the foundation for high-performance lightweight thermal insulation concrete.

[0049] As shown in Table 1, the volcanic slag-based non-fired core-shell structured ceramsite prepared in Examples 1-2 of this invention exhibits excellent comprehensive performance: apparent density of 800-850 kg / m³. 3 The compressive strength of the cylinder is as high as 8.5~9.0MPa, and the density is lower than that of ceramsite with the same strength level. The water absorption rate in 1 hour is as low as 7.5%~8.2%. The internal radiation index and external radiation index are 0.24-0.26 and 0.31-0.35 respectively, both of which meet the national standard limits. This excellent performance is due to the synergistic effect between the components. The natural porosity of the volcanic slag particles in the core and the macroporous characteristics of the waste EPS particles work together to construct a lightweight skeleton. The modified sludge powder is stably consolidated in the alkaline environment of carbide slag and is filled with electrolytic manganese slag to optimize the gradation. The outer shell is coupled with the highly active silicon-aluminum source of volcanic slag powder and rice husk ash and the phosphogypsum-carbide slag activation system through wet grinding, and then a dense carbonate protective layer is formed by CO2 synergistic curing, thus achieving the unity of lightweight and high strength. Compared to the comparative examples, the lack of this synergistic effect directly led to performance degradation: Comparative Example 1, which used fly ash and crushed stone to replace the volcanic slag system, completely destroyed the porous structure and chemical synergy of the material, resulting in a sharp increase in apparent density and a drastic drop in compressive strength; Comparative Example 2, by eliminating the core-shell structure, caused the material to lose its functional gradient, resulting in a water absorption rate as high as 15.1% and the lowest strength, proving that the core-shell design is crucial for reconciling performance contradictions; Comparative Example 3, lacking waste EPS particles, caused the density to rise to 1100 kg / m³. 3This lightweight component plays a crucial role in reducing density; in Comparative Example 4, the strength decreased to 5.0 MPa and the water absorption rate increased to 12.4% after CO2 curing was removed, indicating that carbonization curing can form a dense and high-strength outer shell. These comparative examples fully demonstrate that through the synergistic system of core-shell structure design, multi-source solid waste design, and enhanced CO2 curing, it is possible to achieve a balance between lightweight, high-strength, low-water-absorption, and environmentally friendly safety in non-fired ceramsite.

[0050] Example 3 The specific embodiment provides a lightweight thermal insulation concrete composition by weight as follows: 300 parts of volcanic slag-based non-fired core-shell structure ceramsite, 250 parts of volcanic slag particles (particle size 1.18mm~2.36mm), 120 parts of volcanic ash powder, 60 parts of phosphogypsum, 30 parts of red mud, 70 parts of steel slag powder, 1 part of foaming agent, 0.5 parts of foam stabilizer, 4 parts of water-reducing agent, and 90 parts of water. Among these, the volcanic slag-based non-fired core-shell structure ceramsite is the one obtained in Example 1, the foaming agent is hydrogen peroxide, the foam stabilizer is calcium stearate, and the water-reducing agent is a polycarboxylate-based water-reducing agent.

[0051] The preparation method includes the following steps: first, mix and stir the volcanic ash powder, phosphogypsum, red mud, and steel slag powder for 2 minutes to form mixture A; then add volcanic ash-based non-fired core-shell structure ceramsite and volcanic ash particles (particle size ≤ 2.36 mm) and stir for 1 minute; finally, add water, foaming agent, foam stabilizer, and water-reducing agent and stir for 3 minutes to obtain lightweight thermal insulation concrete.

[0052] Example 4 The preparation process of Example 3 was repeated, except that the raw materials used were as follows by weight: 340 parts of volcanic slag-based non-fired core-shell structure ceramsite, 260 parts of volcanic slag particles (particle size 1.18mm~2.36mm), 110 parts of volcanic ash slag powder, 50 parts of phosphogypsum, 30 parts of red mud, 70 parts of steel slag powder, 2 parts of foaming agent, 1 part of foam stabilizer, 4 parts of water reducing agent, and 90 parts of water.

[0053] Comparative Example 5 The preparation process of Example 3 was repeated, except that the volcanic slag-based non-fired core-shell structure ceramsite of Comparative Example 1 was used instead of the volcanic slag-based non-fired core-shell structure ceramsite of Example 1.

[0054] Comparative Example 6 The preparation process of Example 3 was repeated, except that the volcanic slag-based non-fired core-shell structure ceramsite of Comparative Example 2 was used instead of the volcanic slag-based non-fired core-shell structure ceramsite of Example 1.

[0055] Comparative Example 7 The preparation process of Example 3 was repeated, except that ordinary sand of the same volume was used instead of volcanic slag particles (particle size 1.18mm~2.36mm).

[0056] Comparative Example 8 The preparation process of Example 3 was repeated, except that the same mass of PO42.5 cement was used instead of volcanic ash slag powder, phosphogypsum, red mud, and steel slag powder.

[0057] Comparative Example 9 The preparation process of Example 3 was repeated, except that the addition of volcanic ash slag powder was omitted, and the amount of other cementing materials was increased to the following weight parts: 100 parts phosphogypsum, 60 parts red mud, and 120 parts steel slag powder.

[0058] The mechanical and durability properties of concrete were tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" and GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete". The bond strength of concrete was tested according to JGJ / T 70-2009 "Standard for Test Methods of Basic Performance of Building Mortar". The results are shown in Table 2.

[0059] Table 2

[0060] Based on the test results in Table 2, the lightweight thermal insulation concrete prepared in Examples 3-4 of this invention exhibits excellent comprehensive performance. Its apparent density is 1210~1280 kg / m³. 3In its lightweight state, its 28-day compressive strength reaches 16.8 MPa and 19.5 MPa, respectively, and its bond strength is between 2.12 and 2.28 MPa. Compared with other lightweight thermal insulation materials, its mechanical properties are superior, while its thermal conductivity is only 0.26 to 0.28 W / (m·K), demonstrating excellent thermal insulation capabilities. Compared with the comparative examples, the embodiments of the present invention achieve a breakthrough balance in the contradictory performance system of "lightweight-high strength-low thermal conductivity," and the superior performance is attributed to the systematic and synergistic design of the technical solution of the present invention. In Comparative Examples 5 and 6, non-volcanic slag aggregate and core-shell-free aggregate were used respectively. The apparent density of the concrete increased to 1390~1530 kg / m3, the compressive strength decreased to below 11.2 MPa, and the thermal conductivity increased to 0.74~0.81 W / (m·K). This is because the "gradient porous core" in the expanded clay aggregate of this invention is the physical basis for achieving ultra-lightweight insulation, while the "dense and high-strength outer shell" is the key to contributing core mechanical properties and firmly bonding with the matrix. Comparative Example 7, using ordinary sand, resulted in the highest thermal conductivity, verifying the irreplaceable role of volcanic slag particles as fine aggregate in blocking thermal bridges and optimizing insulation. In Comparative Example 8, after using PO·42.5 cement as a cementing material, both the compressive strength and bond strength were reduced compared to the examples. The "volcanic ash slag powder-phosphogypsum-red mud-steel slag powder" all-solid waste cementing system in this invention has unique advantages as a highly efficient composite activation system. The geopolymer network it generates is denser and tougher in microstructure than traditional cement. In contrast, Comparative Example 9 omitted the addition of volcanic ash powder, resulting in a significant decrease in strength. This is because the lack of a substantial source of silicon and aluminum provided by the volcanic ash powder is detrimental to the strength development of the system. The material system of this invention achieves high-value-added resource utilization of various solid wastes while providing a lightweight, high-strength, and thermally insulating novel wall material solution for the field of building energy conservation.

Claims

1. A method for preparing volcanic slag-based non-fired core-shell structured ceramsite, characterized in that... Includes the following steps: S1. Core preparation: Volcanic slag powder, volcanic slag granules, waste EPS insulation board granules, electrolytic manganese slag, modified sludge powder and water are mixed and added to a disc granulator to granulate and obtain core raw material balls with a particle size of 3~8mm. The balls are then cured under standard curing conditions for 8~12 hours. S2. Preparation of outer shell slurry: Volcanic slag powder, rice husk ash, phosphogypsum, carbide slag and water are mixed and wet-milled for more than 1 hour to obtain outer shell slurry; S3. Core-shell structure forming: The core raw material ball is put into a disc granulator and wrapped with a mixture of the outer shell slurry and aluminum powder until the ball size is 5~10mm. S4. CO2 Co-curing Enhancement: Place the coated aggregate in a carbonization curing box, introduce CO2 gas with a concentration of not less than 25%, maintain the pressure at 0.3~0.5MPa and the temperature at 50-70℃ for 4-8 hours, and then standard cure for more than 48 hours to obtain volcanic slag-based non-fired core-shell structure ceramsite.

2. The preparation method of volcanic slag-based non-fired core-shell structured ceramsite as described in claim 1, characterized in that... The specific surface area of ​​the volcanic slag powder is >200 m². 2 / kg, the volcanic slag particles have a particle size of 1.18mm~2.36mm and are all prepared by crushing or grinding the original volcanic slag.

3. The preparation method of volcanic slag-based non-fired core-shell structured ceramsite as described in claim 1, characterized in that... The preparation method of the modified sludge powder includes the following steps: adding 0.1~0.3% of its mass of lysozyme to municipal sludge, stirring and enzymatically hydrolyzing for 1 hour; then adding 0.2~0.4% of its mass of alkaline protease, stirring and enzymatically hydrolyzing for 2 hours; then adding 20% ​​of its mass of carbide slag and drying at 80℃ until the moisture content is ≤3% to obtain modified sludge powder.

4. The preparation method of volcanic slag-based non-fired core-shell structured ceramsite as described in claim 1, characterized in that... The waste EPS insulation board particles are obtained by crushing waste EPS insulation boards, with a particle size of 1-3mm; the electrolytic manganese slag particles have a specific surface area >150m². 2 / kg, moisture content <5%; the specific surface area of ​​the rice husk ash >400m² 2 / kg; the phosphogypsum has a moisture content of less than 10wt% and a specific surface area >100m². 2 / kg; the dried calcium carbide slag has a CaO content >60wt% and a specific surface area >200m². 2 / kg.

5. The preparation method of volcanic slag-based non-fired core-shell structured ceramsite as described in claim 1, characterized in that... In step S1, the raw materials of the core raw material ball are as follows by weight: 100-160 parts of volcanic slag powder, 80-120 parts of volcanic slag granules, 60-75 parts of waste EPS insulation board granules, 65-105 parts of modified sludge powder, 15-45 parts of electrolytic manganese slag, and 35-50 parts of water.

6. The preparation method of volcanic slag-based non-fired core-shell structured ceramsite as described in claim 1, characterized in that... In step S2, the raw materials of the outer shell slurry are as follows by weight: 60-80 parts of volcanic slag powder, 15-30 parts of rice husk ash, 20-40 parts of phosphogypsum, 10-20 parts of carbide slag, and 15-25 parts of water.

7. The preparation method of volcanic slag-based non-fired core-shell structured ceramsite as described in claim 1, characterized in that... In step S3, the outer shell slurry is 120-200 parts by weight, and the aluminum powder is 1-2 parts.

8. A type of volcanic slag-based non-fired core-shell structured ceramsite, characterized in that... The volcanic slag-based non-fired core-shell structured ceramic particles according to any one of claims 1-7 are prepared.

9. A lightweight thermal insulation concrete, characterized in that... The composition by weight is as follows: 270-360 parts of volcanic slag-based non-fired core-shell structure ceramsite as described in claim 8, 210-280 parts of volcanic slag particles, 100-140 parts of volcanic ash slag powder, 40-80 parts of phosphogypsum, 30-40 parts of red mud, 70-100 parts of steel slag powder, 1-3 parts of foaming agent, 0.5-1 part of foam stabilizer, 3-5 parts of water-reducing agent, and 80-100 parts of water.

10. The method for preparing the lightweight thermal insulation concrete according to claim 9, characterized in that... Includes the following steps: First, mix the volcanic ash powder, phosphogypsum, red mud, and steel slag powder for more than 2 minutes; then add volcanic ash-based non-fired core-shell structure ceramsite and volcanic slag particles and mix for more than 1 minute; finally, add water, foaming agent, foam stabilizer, and water-reducing agent and mix for more than 3 minutes to obtain lightweight thermal insulation concrete.

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