Special solid-waste-based micro-expansion aggregate for anti-shrinkage concrete and preparation method of special solid-waste-based micro-expansion aggregate

Abstract

The invention discloses a special solid waste micro-expansion aggregate for anti-shrinkage concrete and a preparation method thereof, and relates to the technical field of building materials. The aggregate is prepared from the following components in parts by mass: 40 to 50 parts of washed sand mud, 8 to 15 parts of expanding agent, 7 to 12 parts of low-heat cement, 1 to 4 parts of exciting agent, 0.5 to 1.5 parts of fiber, 15 to 25 parts of tailings, 3 to 8 parts of slag, 0.1 to 0.5 part of water reducing agent, 1.3 to 4.8 parts of sulphoaluminate cement and 1 to 3 parts of building gypsum. The preparation method comprises the steps of segmented mixing, jet shaping and surface coating maintenance. According to the invention, a dual expansion compensation system and the closest packing design are innovatively adopted, and a solid waste synergistic utilization scheme is matched, so that the defects of large shrinkage, weak interface and low strength of the traditional recycled aggregate are overcome. The 28d dry shrinkage value of the product is only 348-463 * 10 <-6 >, the compressive strength reaches 43.6-51.1 MPa, and the product has excellent volume stability, mechanical properties and environmental protection benefits and is wide in application range.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and more specifically to a special solid waste-based micro-expansion aggregate for anti-shrinkage concrete and its preparation method. Background Technology

[0002] Concrete, as the world's most widely used and consumed building material, has aggregates (including coarse and fine aggregates) comprising approximately 70%-80% of its total volume. These aggregates form the skeleton of concrete and play a decisive role in its mechanical properties, durability, and volumetric stability. With the continuous development of global infrastructure construction, the demand for natural sand and gravel aggregates is growing exponentially. For a long time, humans have primarily relied on quarrying and sand mining to obtain concrete aggregates. This predatory exploitation of natural resources has led to serious environmental and social problems, including mountain destruction, riverbed erosion, soil erosion, and a sharp decline in biodiversity. Meanwhile, China and many other countries have successively introduced stringent policies to restrict or prohibit the mining of natural sand and gravel. This has resulted in the depletion of natural aggregate resources and soaring prices, severely hindering the sustainable development of the construction industry. Therefore, finding and developing new, stable, and economical alternative aggregates has become a pressing and critical issue in the building materials sector.

[0003] Faced with the dual pressures of resource conservation and environmental protection, the recycling of construction waste into recycled aggregates has become an industry consensus and a development direction. Utilizing waste concrete, bricks, tiles, and other construction solid waste to prepare recycled aggregates has the following significant advantages: —Environmental benefits: It has achieved the reduction, recycling and harmless treatment of solid waste, reduced the pressure on landfills, and reduced the damage to the natural environment; —Economic benefits: It reduces the cost of construction waste disposal and provides a relatively inexpensive source of aggregates, which is especially advantageous in areas where natural aggregate resources are scarce; —Policy guidance: It aligns with the national strategy of vigorously developing a circular economy and enjoys relevant tax incentives and policy support.

[0004] However, traditional recycled aggregates (mainly referring to recycled construction waste aggregates) have a series of inherent defects that are difficult to overcome, limiting their application in high-performance concrete. High porosity and high water absorption: The surface of recycled aggregates is covered with a large amount of old cement mortar, resulting in a porosity far higher than that of natural aggregates. This not only increases the water demand of concrete, affecting workability, but also reduces the strength, impermeability, and freeze-thaw resistance of the concrete. Weak interface transition zone: The complex interface formed between the old and new cement mortar is a weak point in the concrete structure, easily becoming a source of crack initiation and propagation, affecting the long-term durability of the concrete. Large volume shrinkage: This is a key bottleneck restricting the application of recycled aggregates in high-performance, high-volume-stability concrete. Recycled aggregates themselves have lower strength and are prone to creep under load; at the same time, their high water absorption exacerbates internal drying, leading to a significant increase in the drying shrinkage and autogenous shrinkage of the concrete. Under constrained conditions, excessive shrinkage can easily cause cracking, seriously threatening the safety and service life of the structure.

[0005] Those skilled in the art have explored numerous methods for preparing aggregates from solid waste, but existing technologies mostly focus on improving aggregate strength or simple substitution, failing to fundamentally solve the shrinkage problem caused by solid waste. While existing technologies have made progress in the resource utilization of solid waste, their approaches are largely limited to physical strengthening or simple sintering, failing to endow aggregates with the function of actively compensating for shrinkage. How to develop an aggregate from solid waste that possesses both excellent physical properties and micro-expansion capabilities, fundamentally improving the volume stability of concrete, remains a pressing technical challenge. Summary of the Invention

[0006] In order to overcome the defects and deficiencies in the existing technology, the present invention provides a special solid waste micro-expansion aggregate for anti-shrinkage concrete and its preparation method. The purpose of the invention is to solve the problems of weak interface transition zone connection, poor volume stability, low strength and high production cost in the existing recycled aggregate technology.

[0007] To address the problems existing in the prior art, the present invention is achieved through the following technical solution: The first aspect of this invention provides a micro-expansion aggregate made from solid waste for anti-shrinkage concrete, comprising the following components by mass parts: 40-50 parts washed sand and mud; 8-15 parts of expanding agent; 7-12 parts low-heat cement; 1-4 parts activator; 0.5-1.5 parts fiber; 15-25 portions of tailings; 3-8 parts slag; 0.1-0.5 parts water-reducing agent; 1.3-4.8 parts sulfoaluminate cement; 1-3 parts building plaster.

[0008] More preferably, the washed sand and mud is waste mud precipitated from the wastewater during the washing process of manufactured sand to remove fine powder, and its specific surface area is 300-350 m². 2 / kg, moisture content <30%.

[0009] Furthermore, limestone is preferred as the raw material for manufactured sand.

[0010] More preferably, the expansive agent is a calcium oxide-calcium sulfoaluminate composite expansive agent conforming to GB / T23439-2017 "Concrete Expansive Agents", with a calcium oxide content >20% and a specific surface area of ​​400-450 m². 2 / kg.

[0011] More preferably, the low-heat cement is a low-heat silicate cement conforming to the GB / T200-2017 standard "Medium-heat Silicate Cement, Low-heat Silicate Cement"; its dicalcium silicate content is >45%, its 3-day compressive strength is >15MPa, its 3-day heat of hydration is <230kJ / kg, and its specific surface area is 320-380m². 2 / kg.

[0012] More preferably, the activator is a composite activator made by compounding sodium hydroxide and water glass in a mass ratio of 1:5; the water glass has a modulus of 3.2-3.5, a solid content of 50%-60%, and a Na2O content of 15%-25%.

[0013] More preferably, the fiber is a hydrophilic polypropylene fiber.

[0014] More preferably, the fiber has a length of 6-19 mm, a diameter of 20-50 mm, and a tensile strength greater than 3.5 GPa.

[0015] More preferably, the tailings are non-ferrous metal ore flotation tailings with a fineness modulus of 2.3-2.8 and a particle content of less than 5% on a 0.075mm sieve.

[0016] More preferably, the slag is waste residue generated during the smelting of non-ferrous metal ore concentrate, with a specific surface area of ​​280-330 m². 2 / kg, with an activity greater than 10⁵ after 28 days.

[0017] More preferably, the non-ferrous metal ore is pyrite or chalcopyrite.

[0018] More preferably, the water-reducing agent is a polycarboxylate-based high-performance water-reducing agent that conforms to the JG / T223-2017 standard "Polycarboxylate-based high-performance water-reducing agent" and has a water reduction rate of more than 30%.

[0019] The sulfoaluminate cement is a rapid-hardening sulfoaluminate cement conforming to the GB / T20472-2006 standard for sulfoaluminate cement, and the calcium sulfoaluminate content of the sulfoaluminate cement is greater than 65%, with a specific surface area of ​​450-500 m². 2 / kg.

[0020] The building gypsum is a superior-grade natural building gypsum that conforms to the GB / T9776-2022 standard for building gypsum, and has a hemihydrate gypsum content of more than 90%.

[0021] A second aspect of the present invention provides a method for preparing the anti-shrinkage concrete-specific solid waste micro-expansion aggregate described in the first aspect above, comprising the following steps: S1. Weigh out the expansion agent, low-heat cement, fiber, tailings and slag according to the mass fractions, mix them thoroughly and evenly and set aside. S2. Weigh out the sulfoaluminate cement and building gypsum by mass, mix them thoroughly and evenly, and set aside. S3. Weigh out the washed sand, activator, and water-reducing agent according to the specified mass ratios, and place them in a high-speed mixer. Mix at low speed until homogeneous and achieving the set flowability. Then, add the mixture from step S1 to the high-speed mixer and mix thoroughly. Finally, use a spraying device to spray the mixture into particles 0.5-10 cm in size. 3 The blocky material is fed into a shaping machine for shaping. During the shaping process, the mixture obtained in step S2 is added. After the aggregate surface solidifies, it is removed and continuously cured to obtain the anti-shrinkage concrete special solid waste micro-expansion aggregate.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. The aggregate of this invention exhibits excellent volume stability, suppressing shrinkage cracking at its source. This invention uses tailings as the core skeleton, combined with washed sand and mud to construct the basic framework, and then fills the pores with powders such as expanding agents, low-heat cement, and slag. The particle size of each component is strictly controlled and the closest packing is achieved according to the Fuller curve, significantly reducing pore water content and suppressing auto-shrinkage during hydration from the source. An innovative "dual expansion compensation system" is adopted: the internal calcium oxide-calcium sulfoaluminate composite expanding agent continuously generates micro-expansion throughout the hydration process, precisely compensating for overall shrinkage; the surface sulfoaluminate cement reacts rapidly with building gypsum to generate ettringite, specifically compensating for localized shrinkage caused by rapid surface moisture evaporation, effectively reducing the stress difference between the internal and external aggregates. Ultimately, the aggregate maintains volume stability throughout its entire life cycle; after application to concrete, the 28-day drying shrinkage value is only 348-463 × 10⁻⁶. -6 It is far superior to traditional fully recycled aggregates, with the average width of the interface transition zone (ITZ) narrowed to 39-51μm, completely solving the core pain points of traditional recycled aggregates such as "large volume shrinkage and easy cracking".

[0023] 2. The aggregate of this invention exhibits high early strength and rapid setting, significantly improving production efficiency. The aggregate system of this invention contains an expansion agent rich in calcium sulfoaluminate, which rapidly hydrates to form early strength. The sodium silicate in the composite activator also has an early strength effect, accelerating the hydration reaction of the expansion agent, calcium sulfoaluminate, tricalcium silicate, and dicalcium silicate in the low-heat cement, further enhancing early mechanical properties. The polycarboxylate superplasticizer and calcium carbonate powder in the washed sand and mud produce a synergistic water-reducing effect, further improving early strength while reducing water consumption. The lower water consumption, combined with the rapid water absorption characteristics of building gypsum, significantly shortens the aggregate setting time. Actual measurements show a 1-day crushing index of only 16.1-22.3% (compared to 62.2% for traditional fully recycled aggregate), and a 3-day crushing index reduced to 10.0-12.3%, significantly improving production turnover efficiency and reducing production costs.

[0024] 3. The aggregate of this invention exhibits sustained strength growth in the later stages and stable and reliable mechanical properties. In the aggregate system of this invention, sodium silicate in the composite activator can efficiently activate the potential activity of slag and some washed sand and mud, promoting the formation of C-(A)-SH gel in the later stages, providing continuous impetus for strength growth; the dense structure formed by the most compact packing lays the physical basis for stable strength improvement. At the same time, the synergistic effect of the water-reducing agent and calcium carbonate powder in the washed sand and mud continuously reduces the water demand of the system, ensuring long-term strength development. After being applied to concrete, the 28-day compressive strength reaches 43.6-51.1 MPa, approaching the level of natural aggregate concrete, and far superior to traditional fully recycled aggregate concrete, solving the problem of "later-stage strength decay and insufficient mechanical properties" of traditional recycled aggregates.

[0025] 4. The aggregate system of this invention exhibits a tight and robust interfacial bond, significantly enhancing durability. This invention utilizes hydrophilic-treated polypropylene fibers, which effectively strengthen the bond strength within the aggregate and in the interfacial transition zone between the aggregate and the concrete matrix, inhibiting crack initiation and propagation. Unhydrated cement particles pre-retained on the aggregate surface continue to hydrate after concrete molding, further reinforcing the interfacial bond. Furthermore, the micro-expansion generated by the hydration of surface sulfoaluminate cement and building gypsum to produce ettringite compensates for any small voids that may form in the interfacial zone. Combined with the aggregate's dense structure and low surface porosity, this reduces the water demand of the concrete during application, ensuring overall strength and durability. Measured 28-day splitting tensile strength of the concrete is 3.5-4.2 MPa, with an electrical flux of only 1168-1438 C. Its resistance to ion intrusion is significantly superior to traditional recycled aggregate concrete, overcoming the shortcomings of traditional recycled aggregates, namely "weak interfacial transition zone and poor durability."

[0026] 5. The aggregate of this invention exhibits excellent electrical conductivity, effectively extending its service life. The aggregate system of this invention extensively utilizes components with conductive properties, such as tailings and slag, combined with hydrophilically treated polypropylene fibers to construct an effective conductive network, thereby improving the overall conductivity of the aggregate. Electron migration replaces ion migration, which easily leads to structural damage, reducing the erosion of the aggregate and concrete structure by harmful substances. Combined with the dense structure's barrier effect against external ions, this further enhances the long-term durability of the concrete and extends the structural service life.

[0027] 6. The aggregate system of this invention has a high solid waste utilization rate and outstanding energy-saving and environmental protection advantages. In this invention's aggregate system, washed sand and mud, tailings, slag, and other solid wastes account for over 60%, achieving efficient resource utilization of solid waste. Among them, the washed sand and mud does not require traditional high-cost dewatering treatment and can be used directly. The polyacrylamide flocculant it contains slowly releases water during the preparation process, requiring no additional maintenance. This reduces maintenance costs and provides a feasible path for the environmentally friendly disposal of washed sand and mud, aligning with the national circular economy strategy and possessing significant environmental and economic benefits.

[0028] 7. The aggregate of this invention has strong adaptability and a wide range of applications. The aggregate exhibits balanced performance indicators, with an apparent density of 2442-2591 kg / m³, a bulk density of 1401-1488 kg / m³, and a water absorption rate of 4.3-6.8%, meeting the requirements of GB / T25177-2010 "Recycled Coarse Aggregate for Concrete". It can not only replace natural aggregates in ordinary concrete but also meet the needs of high-performance, high-volume-stability concrete. It is suitable for various scenarios such as building structures, road engineering, and underground engineering, solving the problem of "limited application range" of traditional recycled aggregates. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the aggregate used in this invention. Detailed Implementation

[0030] The present invention is further described below with reference to embodiments, but the embodiments are only for illustrating the present invention and not for limiting the present invention.

[0031] As specific embodiments of the present invention, the raw materials used in each embodiment are as follows: Washed sand and mud are waste mud precipitated from the wastewater during the washing process of manufactured sand to remove fine powder. Their specific surface area is 300-350 m². 2 / kg, moisture content <30%; in this embodiment, the raw material for manufactured sand is limestone; The expansive agent is a calcium oxide-calcium sulfoaluminate composite expansive agent conforming to the GB / T23439-2017 standard for concrete expansive agents, with a calcium oxide content >20% and a specific surface area of ​​400-450 m². 2 / kg; Low-heat cement is a type of low-heat silicate cement that conforms to the GB / T200-2017 standard "Medium-heat Silicate Cement and Low-heat Silicate Cement"; its dicalcium silicate content is >45%, its 3-day compressive strength is >15MPa, its 3-day heat of hydration is <230kJ / kg, and its specific surface area is 320-380m². 2 / kg; The activator is a composite activator prepared by mixing sodium hydroxide and water glass in a mass ratio of 1:5; the water glass has a modulus of 3.2-3.5, a solid content of 50%-60%, and a Na2O content of 15%-25%. The fiber is a hydrophilic polypropylene fiber, specifically, the fiber length is 6-19mm, the diameter is 20-50mm, and the tensile strength is greater than 3.5GPa; The tailings are pyrite flotation tailings with a fineness modulus of 2.3-2.8; the content of particles under a 0.075mm sieve is less than 5%. Slag is a waste residue generated during the smelting of chalcopyrite, with a specific surface area of ​​280-330 m². 2 / kg, with an activity greater than 10⁵ after 28 days; The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent that conforms to the JG / T223-2017 standard "Polycarboxylate-based High-Performance Water-Reducing Agents" and has a water reduction rate of more than 30%. Sulfoaluminate cement is a rapid-hardening sulfoaluminate cement that conforms to the GB / T20472-2006 standard for sulfoaluminate cement, and has a calcium sulfoaluminate content greater than 65% and a specific surface area of ​​450-500 m². 2 / kg; The building gypsum is a superior-grade natural building gypsum that meets the GB / T9776-2022 standard for building gypsum, and has a hemihydrate gypsum content of more than 90%.

[0032] The specific proportions of each embodiment by weight are shown in Table 1 below: Table 1 shows the raw materials for micro-expansion aggregates made from solid waste specifically for anti-shrinkage concrete (unit: kg).

[0033] All the above embodiments use the following unified preparation process, the specific preparation process is as follows: S1. Weigh out the expansion agent, low-heat cement, fiber, tailings and slag according to the dosage shown in Table 1, put them into the mixer and stir them thoroughly until uniform to obtain mixture S1 for later use. S2. Weigh out sulfoaluminate cement and building gypsum according to the dosage shown in Table 1, mix and stir until uniform to obtain mixture S2. S3. Weigh the washed sand, activator, and water-reducing agent according to the dosage shown in Table 1, and put them into a high-speed mixer. Mix them evenly at low speed (250-350 r / min) until the mixture returns to the set fluidity (flowability 220-280 mm). Then add the prepared mixture S1 to the high-speed mixer, adjust the speed to 800-1000 r / min, and mix at high speed for 3-5 minutes until evenly mixed. Use a spraying device to spray the above-mentioned evenly mixed material into blocks of 0.5-10 cm³. Immediately put the blocks into a shaping machine, and at the same time, evenly sprinkle the prepared mixture S2 according to the mass fraction. Shape the blocks for 2-3 minutes at a speed of 100-160 r / min to evenly coat the surface of the blocks with S2. After the aggregate surface has solidified (4-6 hours at room temperature), take it out and place it in a natural environment for continuous curing for 7-14 days. No additional water is needed during this period to obtain anti-shrinkage concrete special solid waste-based micro-expansion aggregate.

[0034] Referring to GB / T25177-2010 "Recycled Coarse Aggregate for Concrete" standard, the aggregates prepared in the above embodiments were subjected to routine performance tests. The apparent density, bulk density, water absorption, crushing index, soundness, and fine powder content of the recycled aggregates prepared in the above embodiments were tested after 28 days, and compared with natural aggregates and fully recycled aggregates. The test results are shown in Table 2 below: Table 2 shows the performance indicators of recycled aggregates.

[0035] Referring to GB / T25177-2010 "Recycled Coarse Aggregate for Concrete", the 1-day and 3-day crushing index and soundness index of the recycled aggregate prepared in the above examples were tested and compared with natural aggregate and fully recycled aggregate. The test results are shown in Table 3 below: Table 3 shows the early strength performance indicators of recycled aggregates.

[0036] The recycled aggregates from Examples 1-5 were molded into concrete according to the mass fractions and preparation steps. The drying shrinkage and electrical flux were tested according to GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The compressive strength and splitting tensile strength were tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The average width of the interface transition zone (ITZ) was detected using SEM. The test results are shown in Table 4.

[0037] Table 4 shows the performance indicators of recycled aggregate concrete.

[0038] As shown in Tables 2 and 3 above, the apparent density of the aggregates prepared in each embodiment is 2442-2591 kg / m³, and the bulk density is 1401-1488 kg / m³, which are significantly higher than those of traditional fully recycled aggregates (apparent density 2312 kg / m³, bulk density 1258 kg / m³) and close to the level of natural aggregates (apparent density 2653 kg / m³, bulk density 1522 kg / m³). This indicates that the internal structure of the aggregates is dense, solving the defects of "high porosity and loose structure" of traditional recycled aggregates. The water absorption rate is controlled at 4.3%-6.8%, which is much lower than the 10.2% of fully recycled aggregates, effectively reducing the water demand of concrete and laying the foundation for improving the workability and durability of concrete.

[0039] In terms of early strength, the 1-day crushing index is only 16.1%-22.3% (62.2% for all recycled aggregate), and the 3-day crushing index drops to 10.0%-12.3% (39.7% for all recycled aggregate), demonstrating the advantage of "early strength and rapid setting" and meeting the needs of rapid construction in engineering projects. The 28-day crushing index is 9.8%-13.7%, and the soundness is 6.6%-9.2%, both of which are better than all recycled aggregate (crushing index 26.5%, soundness 9.8%). Moreover, the micro powder content is only 1.1%-2.7% (4.5% for all recycled aggregate), indicating that the aggregate particles have good integrity, low impurity content, and excellent mechanical stability.

[0040] From the performance of each component in the dosage range, when the core components such as washed sand and mud and expanding agent are at the extreme values ​​of the dosage range (e.g., Example 3: 50 parts of washed sand and mud and 8 parts of expanding agent; Example 2: 40 parts of washed sand and mud and 15 parts of expanding agent), the aggregate performance remains stable. The 28-day crushing index under extreme conditions is 11.7% and 11.3%, respectively, and the water absorption rate is 6.8% and 4.3%, respectively. No sudden change or deterioration in performance has occurred, which verifies the scientific nature and adaptability of the dosage range of the formulation of this invention.

[0041] As shown in Table 4 above, the 28-day drying shrinkage value of the aggregates in each embodiment after application to concrete is 348-463×10⁻⁶. -6 Only traditional all-recycled aggregate concrete (906×10 -6 The shrinkage value of Example 2 was 348 × 10⁻⁶, which was 38%-51% of the total shrinkage value of Example 2. -6 It is even superior to natural aggregate concrete (438×10). -6 The average width of the interface transition zone (ITZ) is 39-51 μm, narrower than the 68 μm of fully recycled aggregate concrete and close to the 36 μm of natural aggregate concrete. This result fully demonstrates that the "dual expansion compensation system + densest packing design" of this invention has successfully achieved "active shrinkage compensation", fundamentally solving the core pain points of traditional recycled aggregate concrete, namely "large volume shrinkage and weak interface that is prone to cracking".

[0042] The 28-day concrete compressive strength reached 43.6-51.1 MPa, and the splitting tensile strength reached 3.5-4.2 MPa, which not only far exceeded that of fully recycled aggregate concrete (compressive strength 39.6 MPa, splitting tensile strength 2.9 MPa), but also approached the level of natural aggregate concrete (compressive strength 52.0 MPa, splitting tensile strength 3.9 MPa), meeting the requirements of high-performance concrete for aggregate strength. The electrical flux was 1168-1438 C, far lower than that of fully recycled aggregate concrete (3656 C), and better than that of natural aggregate concrete (1503 C), indicating that the dense aggregate structure and conductive network worked together to effectively block the intrusion of external ions, significantly improving the durability properties of concrete such as impermeability and corrosion resistance, and extending the service life of the structure.

[0043] Based on the above performance test results, this invention successfully prepared solid waste-based micro-expanding aggregate with excellent volume stability, high strength, and high durability by optimizing the component ratio (40-50 parts of washed sand and mud, 8-15 parts of expanding agent, etc.), innovating the "dual expansion compensation system," and using the "segmented mixing-jet shaping" preparation process. This comprehensively solves the inherent defects of traditional recycled aggregates, such as "high porosity, large shrinkage, weak interface, and low strength." The aggregate and concrete performance corresponding to each embodiment remained stable and excellent, with no performance degradation. This fully verifies the scientific, rational, and reliable nature of the formulation dosage range, raw material selection standards, and preparation process of this invention. The product has a solid waste utilization rate of over 60%, and the washed sand and mud do not require dehydration or additional water replenishment during curing. This balances environmental benefits with production cost control, aligns with the development direction of the circular economy, and has broad engineering application prospects and promotional value.

Claims

1. A micro-expansion aggregate made from solid waste specifically for anti-shrinkage concrete, characterized in that: By mass parts, it includes the following components: 40-50 parts washed sand and mud; 8-15 parts of expanding agent; 7-12 parts low-heat cement; 1-4 parts activator; 0.5-1.5 parts fiber; 15-25 portions of tailings; 3-8 parts slag; 0.1-0.5 parts water-reducing agent; 1.3-4.8 parts sulfoaluminate cement; 1-3 parts building plaster.

2. The anti-shrinkage concrete-specific solid waste micro-expansion aggregate as described in claim 1, characterized in that: The washed sand and mud mentioned above are waste mud precipitated from the wastewater during the washing process of manufactured sand to remove fine powder, and their specific surface area is 300-350 m². 2 / kg, moisture content <30%.

3. The anti-shrinkage concrete-specific solid waste micro-expansion aggregate as described in claim 2, characterized in that: The raw material for manufactured sand is limestone.

4. A micro-expansion aggregate for anti-shrinkage concrete as described in any one of claims 1-3, characterized in that: The expansive agent is a calcium oxide-calcium sulfoaluminate composite expansive agent conforming to GB / T23439-2017 "Concrete Expansive Agents" standard, with a calcium oxide content >20% and a specific surface area of ​​400-450 m². 2 / kg.

5. A micro-expansion aggregate for anti-shrinkage concrete as described in any one of claims 1-3, characterized in that: The low-heat cement is a low-heat silicate cement conforming to the GB / T200-2017 standard "Medium-heat Silicate Cement and Low-heat Silicate Cement"; its dicalcium silicate content is >45%, its 3-day compressive strength is >15MPa, its 3-day heat of hydration is <230kJ / kg, and its specific surface area is 320-380m². 2 / kg.

6. A micro-expansion aggregate for anti-shrinkage concrete as described in any one of claims 1-3, characterized in that: The activator is a composite activator made by mixing sodium hydroxide and water glass in a mass ratio of 1:5; the water glass has a modulus of 3.2-3.5, a solid content of 50%-60%, and a Na2O content of 15%-25%.

7. A micro-expansion aggregate for anti-shrinkage concrete as described in any one of claims 1-3, characterized in that: The fiber is a hydrophilic polypropylene fiber.

8. The anti-shrinkage concrete special solid waste micro-expansion aggregate as described in claim 7, characterized in that: The fiber has a length of 6-19 mm, a diameter of 20-50 mm, and a tensile strength greater than 3.5 GPa.

9. A micro-expansion aggregate for anti-shrinkage concrete as described in any one of claims 1-3, characterized in that: The tailings are non-ferrous metal ore flotation tailings with a fineness modulus of 2.3-2.8 and a particle content of less than 5% on a 0.075mm sieve. The slag is waste residue generated during the smelting of non-ferrous metal ore concentrates, with a specific surface area of ​​280-330 m². 2 / kg, with an activity greater than 10⁵ after 28 days.

10. The anti-shrinkage concrete special solid waste micro-expansion aggregate as described in claim 9, characterized in that: The non-ferrous metal ore is pyrite or chalcopyrite.

11. A micro-expansion aggregate for anti-shrinkage concrete as described in any one of claims 1-3, characterized in that: The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent that conforms to the JG / T223-2017 standard "Polycarboxylate-based high-performance water-reducing agent" and has a water reduction rate of more than 30%.

12. A micro-expansion aggregate for anti-shrinkage concrete as described in any one of claims 1-3, characterized in that: The sulfoaluminate cement is a rapid-hardening sulfoaluminate cement conforming to the GB / T20472-2006 standard for sulfoaluminate cement, and the calcium sulfoaluminate content of the sulfoaluminate cement is greater than 65%, with a specific surface area of ​​450-500 m². 2 / kg.

13. A micro-expansion aggregate for anti-shrinkage concrete as described in any one of claims 1-3, characterized in that: The building gypsum is a superior-grade natural building gypsum that conforms to the GB / T9776-2022 standard for building gypsum, and has a hemihydrate gypsum content of more than 90%.

14. The method for preparing a special solid waste micro-expansion aggregate for anti-shrinkage concrete according to any one of claims 1-13, characterized in that: Includes the following steps, S1. Weigh out the expansion agent, low-heat cement, fiber, tailings and slag according to the mass fractions, mix them thoroughly and evenly and set aside. S2. Weigh out the sulfoaluminate cement and building gypsum by mass, mix them thoroughly and evenly, and set aside. S3. Weigh out the washed sand, activator, and water-reducing agent according to the specified mass ratios, and place them in a high-speed mixer. Mix thoroughly until homogeneous and achieving the desired fluidity. Then, add the mixture from step S1 to the high-speed mixer and mix thoroughly. Finally, use a spraying device to spray the mixture into particles 0.5-10 cm in size. 3 The blocky material is fed into a shaping machine for shaping. During the shaping process, the mixture obtained in step S2 is added. After the aggregate surface solidifies, it is removed and continuously cured to obtain the anti-shrinkage concrete special solid waste micro-expansion aggregate.

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