Phosphogypsum lightweight artificial aggregate, preparation method thereof and all-solid-waste lightweight concrete

Abstract

The invention provides a phosphogypsum lightweight artificial aggregate, a preparation method thereof and all-solid-waste lightweight concrete. The phosphogypsum light artificial aggregate is prepared from the following components in parts by mass: 70 parts of phosphogypsum, 4 to 13 parts of granulated blast furnace slag, 13 to 22 parts of waste incineration ash, 2 parts of lignocellulose, 2 to 4 parts of MgO and 15 to 20 parts of water. The phosphogypsum is used as a main component, other solid waste materials are used as a binder, resource utilization of the phosphogypsum can be achieved, and the prepared phosphogypsum light artificial aggregate is small in stacking density and high in single-particle compressive strength, has the 24-hour water absorption rate smaller than 20% and has the advantages of being light and high in strength. Meanwhile, when the phosphogypsum light artificial aggregate is applied to lightweight aggregate concrete, performance requirements can be met, the phosphogypsum light artificial aggregate can be used as a raw material of the lightweight aggregate concrete, and excessive dependence of the concrete field on natural aggregate can be effectively relieved. The invention also provides the phosphogypsum lightweight artificial aggregate and a preparation method thereof, and the all-solid waste lightweight concrete.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a phosphogypsum lightweight artificial aggregate and its preparation method, and all-solid-waste lightweight concrete. Background Technology

[0002] Phosphogypsum is a large-scale solid waste generated in the wet process of phosphoric acid production. Its main component is calcium sulfate dihydrate, and it also contains impurities such as phosphorus, fluorine, organic matter, and heavy metals. It is generally acidic (pH value typically between 1.9 and 5.9). Approximately 4-5 tons of phosphogypsum are produced for every ton of wet-process phosphoric acid produced. Currently, the comprehensive utilization rate of phosphogypsum is low, with most of it being disposed of through open-air stockpiling. Long-term, large-scale stockpiling not only occupies valuable land resources but also easily triggers safety accidents such as landslides and mudslides. Furthermore, soluble impurities can seep into and pollute soil, surface water, and groundwater, posing a serious threat to the ecological environment. How to achieve large-scale resource utilization of phosphogypsum has become a key issue restricting the sustainable development of the phosphoric acid chemical industry. Although phosphogypsum can be used to prepare building materials such as gypsum blocks, cement retarders, and sintered bricks, its strong acidity, high impurity content, and poor stability limit its use to fillers or some reaction raw materials, making it difficult to overcome the bottleneck of large-scale application.

[0003] Concrete, as the most widely used material in the construction industry, consumes a large amount of natural aggregates during its production process (coarse aggregates account for 60%-70% of the volume of concrete). Excessive mining of natural aggregates damages the ecological environment and contradicts the concept of green building development. With the rapid development of prefabricated buildings, large-span buildings, and high-rise buildings, lightweight aggregate concrete is experiencing increasing market demand due to its ability to reduce structural weight while maintaining structural load-bearing capacity. Converting solid waste into lightweight aggregates can not only replace natural aggregates and alleviate resource pressure but also achieve value-added utilization of solid waste, aligning with the requirements of a circular economy. Currently, the mainstream methods for producing lightweight aggregates include sintering and cold bonding. Sintering has disadvantages such as high energy consumption, easy generation of gas pollution, and limitations in the chemical composition of raw materials. Cold bonding, on the other hand, is gradually becoming a research hotspot due to its good economic efficiency, superior environmental performance, and wide adaptability of raw materials.

[0004] Existing technologies related to phosphogypsum-based lightweight aggregates still have significant shortcomings. For example, the method for preparing all-solid-waste lightweight phosphogypsum artificial aggregate disclosed in CN119841567A requires mixing and grinding phosphogypsum with blast furnace slag and activating it by heating at 110-120℃, and also requires a large amount of spraying with organosilicon water-repellent agent. This not only increases production costs and energy consumption, but also significantly reduces the strength of the untreated aggregate, making it highly sensitive to process changes. The method for preparing non-fired γ-C2S phosphogypsum lightweight aggregate disclosed in CN117142782B requires step-by-step vibration pressing (precisely controlling three levels of pressure, vibration frequency, and holding time), followed by crushing, rounding, and sieving after pressing. Compared with disc granulation technology, the process complexity is greatly increased, which is not conducive to industrialization.

[0005] In summary, existing technologies suffer from low resource utilization rates of phosphogypsum, high density and poor water resistance in phosphogypsum-based artificial aggregates, and the related preparation processes are either energy-intensive and costly, or complex and difficult to operate, making it difficult to meet the demand for lightweight high-strength aggregates in lightweight aggregate concrete. Therefore, there is an urgent need to develop a technology for lightweight artificial aggregates of phosphogypsum that can achieve efficient resource utilization of phosphogypsum, excellent aggregate performance, and a simple and environmentally friendly preparation process. Summary of the Invention

[0006] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides a phosphogypsum lightweight artificial aggregate, which realizes the efficient resource utilization of phosphogypsum and simultaneously meets the demand for lightweight high-strength aggregates in lightweight aggregate concrete.

[0007] The present invention also provides a method for preparing phosphogypsum lightweight artificial aggregate.

[0008] The present invention also provides a lightweight concrete made entirely from solid waste.

[0009] The present invention also provides a method for preparing lightweight concrete made entirely from solid waste.

[0010] A first aspect of the present invention provides a phosphogypsum lightweight artificial aggregate, comprising, by weight: 70 parts of phosphogypsum Granulated blast furnace slag, 4-13 parts 13-22 portions of waste incineration ash. Two parts lignocellulose, MgO 2-4 parts, 15-20 parts water.

[0011] One of the technical solutions of the present invention concerning phosphogypsum lightweight artificial aggregate has at least the following beneficial effects: I. This invention achieves efficient resource utilization of bulk solid waste, possessing both environmental and economic value. It uses 70 parts phosphogypsum as the core raw material, combined with 4-13 parts granulated blast furnace slag and 13-22 parts waste incineration ash, constructing a raw material system of "main solid waste + auxiliary solid waste." As the background technology shows, phosphogypsum is a bulk waste product of wet-process phosphoric acid production (4-5 tons of phosphogypsum are generated for every 1 ton of phosphoric acid produced). Long-term stockpiling can easily lead to land occupation, environmental pollution, and safety accidents. Furthermore, in existing technologies, phosphogypsum is mostly used as a filler, making large-scale utilization difficult. Granulated blast furnace slag and waste incineration ash are also typical solid wastes from the steel industry and waste treatment sectors, with high disposal costs.

[0012] This invention, through its raw material formulation, achieves a solid waste content of 96% in the aggregate (70 parts phosphogypsum + 4-13 parts granulated blast furnace slag + 13-22 parts incineration ash, with a total solid waste content of 70+4+22=96 / 70+13+13=96 parts; combined with a total formula of 2 parts lignocellulose, 2-4 parts MgO, and 15-20 parts water, the solid waste content is significantly increased). This not only solves the industry problem of large-scale resource utilization of phosphogypsum but also simultaneously disposes of solid waste such as granulated blast furnace slag and incineration ash, reducing the environmental pressure caused by solid waste accumulation. At the same time, by replacing traditional natural raw materials with solid waste, it significantly reduces aggregate production costs, resulting in both significant environmental and economic benefits.

[0013] Second, it endows the aggregate with the core properties of "lightweight, high strength, and water resistance," meeting the needs of construction applications. The formulation combination of this invention (especially the ratio of phosphogypsum to cementitious auxiliary components) enables the aggregate to possess the key properties of "lightweight, high strength, and low water absorption." The bulk density of the aggregates in this invention is all less than 1000 kg / m³. 3 (e.g., Example 1 is 960 kg / m³) 3 Example 4: 945 kg / m 3 The strength of this lightweight aggregate is significantly lower than that of traditional natural aggregates and some phosphogypsum-based aggregates, meeting the core requirement of "reducing structural self-weight" in lightweight aggregate concrete and making it suitable for prefabricated buildings, large-span buildings, and other applications. Thanks to the synergistic effect of 4-13 parts granulated blast furnace slag and 2-4 parts MgO (MgO reacts with water to generate magnesium hydroxide, increasing the alkalinity of the system to activate the activity of the granulated blast furnace slag, generating hydration products such as calcium vanadate and CSH gel), the compressive strength of a single aggregate particle can reach over 3 MPa (4.54 MPa in Example 1 and 3.50 MPa in Example 4), and the cylinder compressive strength is consistently above 2.76 MPa, solving the problems of low strength and easy breakage of traditional phosphogypsum products. The aforementioned hydration products can fill and encapsulate the dihydrate gypsum phase in phosphogypsum, reducing the water absorption rate of aggregates and increasing the softening coefficient. In Examples 1-4, the lowest 24-hour water absorption rate of aggregates was only 9.52% (Example 4), and the highest softening coefficient was 0.74 (Example 1). This effectively improves the defect of poor water resistance of phosphogypsum itself, providing a guarantee for its stable application in concrete.

[0014] Third, the performance of each component is optimized through synergistic effects, taking into account both stability and process adaptability. The proportions of each component in this invention are not simply superimposed, but rather further optimized through synergistic effects. Specifically, 2-4 parts of MgO, as an alkaline activator, solve the problem of low hydration activity of granulated blast furnace slag in non-alkaline environments, promoting its full participation in the reaction to generate water-resistant and tough hydration products, which not only improves aggregate strength but also enhances water resistance, avoiding the problem of a sharp drop in strength (single particle compressive strength of only 2.83 MPa) in Comparative Example 4 (using steel slag instead of MgO). Although 13-22 parts of waste incineration ash have low activity, they can assist in the pozzolanic reaction under the activation of MgO, and at the same time, they act as fillers to fill the internal pores of the aggregate, optimizing the aggregate density. Compared with Comparative Example 3 (using stone powder instead of waste incineration ash), the aggregate strength and water resistance of the formulation of this invention are better (single particle compressive strength of Example 1: 4.54 MPa vs. 3.22 MPa of Comparative Example 3). Two parts of lignocellulose, with their flexibility and dispersibility, can improve the uniformity of powder mixing, reduce the risk of cracking of aggregate embryos during granulation and curing, and enhance the structural stability of aggregates, ensuring that aggregates are not easily damaged during transportation and mixing. It is suitable for the simple process of disc granulation and natural curing, without the need for complex pressing or high-temperature treatment.

[0015] According to some embodiments of the present invention, the average particle size D50 of the phosphogypsum is 60~70μm.

[0016] According to some embodiments of the present invention, the average particle size D50 of the phosphogypsum is any value among 60μm, 61μm, 62μm, 63μm, 64μm, 65μm, 65.65μm, 66μm, 67μm, 68μm, 69μm, and 70μm, such as 65.65μm, or any range formed by both, such as 64μm to 67μm.

[0017] According to some embodiments of the present invention, the average particle size D50 of the granulated blast furnace slag is 8~15μm.

[0018] According to some embodiments of the present invention, the average particle size D50 of the granulated blast furnace slag is any value among 8μm, 9μm, 10μm, 11μm, 11.13μm, 12μm, 13μm, 14μm, and 15μm, such as 11.13μm, or any range formed by both, such as 10μm to 12μm.

[0019] According to some embodiments of the present invention, the average particle size D50 of the waste incineration ash is 12~17μm.

[0020] According to some embodiments of the present invention, the average particle size D50 of the waste incineration ash is any value among 12μm, 13μm, 14μm, 15μm, 15.74μm, 16μm, and 17μm, such as 15.74μm, or any range formed by both, such as 14μm to 16μm.

[0021] According to some embodiments of the present invention, the particle size of the phosphogypsum lightweight artificial aggregate is 5~20mm.

[0022] According to some embodiments of the present invention, the particle size of the phosphogypsum lightweight artificial aggregate is any value among 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, and 20mm, such as 12mm, or any range formed by both, such as 8mm to 15mm.

[0023] A second aspect of the present invention provides a method for preparing the phosphogypsum lightweight artificial aggregate of the first aspect of the present invention, comprising the following steps: (1) According to the proportion, phosphogypsum, granulated blast furnace slag, waste incineration, lignocellulose and MgO are mixed to obtain powder; (2) The powder is sprayed into water and nucleated by a disc granulator to form an artificial aggregate blank; (3) Curing the artificial aggregate blank to obtain the phosphogypsum lightweight artificial aggregate.

[0024] The present invention provides a method for preparing phosphogypsum lightweight artificial aggregate that does not require expensive equipment or complex process control, has undemanding reaction conditions, readily available raw materials, low production costs, and is easy to industrialize.

[0025] According to some embodiments of the present invention, the method further includes removing impurities from the phosphogypsum before step (1). The impurities removed from the undisturbed phosphogypsum by washing with water and ball milling include phosphorus, fluorine, organic impurities and heavy metals, and then drying is performed at a temperature of 60°C.

[0026] According to some embodiments of the present invention, the tilt angle of the disc granulation is 40~50°.

[0027] According to some embodiments of the present invention, the tilt angle of the disc granulation is any value among 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 499°, and 50°, such as 45°, or a range of any two, such as 44° to 46°.

[0028] According to some embodiments of the present invention, the diameter of the disc granulator is 0.4~0.6m.

[0029] According to some embodiments of the present invention, the diameter of the disc granulator is any value among 0.4m, 0.41m, 0.42m, 0.43m, 0.44m, 0.45m, 0.46m, 0.47m, 0.48m, 0.49m, 0.5m, 0.51m, 0.52m, 0.53m, 0.54m, 0.55m, 0.56m, 0.57m, 0.58m, 0.59m, and 0.6m, such as 0.5m, or a range formed by any two, such as 0.45m to 0.55m.

[0030] According to some embodiments of the present invention, the rotational speed of the disc granulator is 30~50 rpm.

[0031] According to some embodiments of the present invention, the rotational speed of the disc granulator is any value among 30 rpm, 31 rpm, 32 rpm, 33 rpm, 34 rpm, 35 rpm, 36 rpm, 37 rpm, 38 rpm, 39 rpm, 40 rpm, 41 rpm, 42 rpm, 43 rpm, 44 rpm, 45 rpm, 46 rpm, 47 rpm, 48 rpm, 49 rpm, and 50 rpm, such as 40 rpm, or any range formed by both, such as 38 rpm to 42 rpm.

[0032] According to some embodiments of the present invention, the disc granulation time is 8~12 min / kg.

[0033] According to some embodiments of the present invention, the disc granulation time is any value among 8 min / kg, 8.5 min / kg, 9 min / kg, 9.5 min / kg, 10 min / kg, 10.5 min / kg, 11 min / kg, 11.5 min / kg, and 12 min / kg, such as 10 min / kg, or any range formed by both, such as 9 min / kg to 11 min / kg.

[0034] According to some embodiments of the present invention, in step (3), the curing time can be 28 days.

[0035] According to some embodiments of the present invention, in step (3), the curing temperature can be 20-30°C.

[0036] According to some embodiments of the present invention, in step (3), the humidity for curing can be 50%-60%.

[0037] A third aspect of the present invention provides a lightweight concrete made entirely from solid waste, comprising phosphogypsum lightweight artificial aggregate of the first aspect of the present invention or phosphogypsum lightweight artificial aggregate prepared by the method of the second aspect of the present invention.

[0038] According to some embodiments of the present invention, by weight, it comprises: 55-60 parts of phosphogypsum lightweight artificial aggregate, 20 portions of granulated blast furnace slag 12 parts fly ash 3 parts of carbide slag 5-10 parts of waste rubber powder 40 parts water.

[0039] One of the technical solutions of the present invention concerning lightweight concrete made entirely from solid waste has at least the following beneficial effects: I. Through the design of all solid waste components, the synergistic utilization of multiple solid wastes is achieved, resulting in significant environmental and economic value. The all-solid-waste lightweight concrete of this invention uses the phosphogypsum lightweight artificial aggregate of this invention as the core, combined with 20 parts of granulated blast furnace slag, 12 parts of fly ash, 3 parts of carbide slag, and 5-10 parts of waste rubber powder, to construct an all-solid-waste raw material system of "artificial solid waste aggregate + industrial solid waste auxiliary materials", completely eliminating the dependence on non-renewable resources such as natural aggregates and traditional cement.

[0040] Phosphogypsum, granulated blast furnace slag, fly ash, carbide slag, and waste rubber powder are typical solid wastes from the phosphate chemical, steel, thermal power, chemical, and rubber product industries, respectively. Phosphogypsum stockpiling pollutes the environment, and waste rubber powder (such as 45-90 mesh waste tire rubber granules) is difficult to degrade naturally. Traditional disposal methods mainly involve landfilling or incineration, which both occupy land and cause secondary pollution. This invention uses a ratio of 55-60 parts phosphogypsum lightweight artificial aggregate (containing 70% phosphogypsum + 4-13% granulated blast furnace slag + 13-22% waste incineration ash) with 20 parts granulated blast furnace slag, 12 parts fly ash, 3 parts carbide slag, and 5-10 parts waste rubber powder. This ratio results in a very high proportion of solid waste in concrete, achieving a "waste-to-waste" recycling model. It simultaneously absorbs solid waste from multiple industries, reducing the environmental pressure of solid waste stockpiling, and replaces natural aggregates and some cementitious materials with low-cost solid waste, significantly reducing the raw material cost of concrete production. This invention possesses both significant environmental benefits and economic value.

[0041] Second, it achieves a balance between lightweight and strength, adapting to the needs of various building scenarios and outperforming traditional concrete. This invention's all-solid-waste lightweight concrete possesses the core properties of "lightweight and low-density" and "sufficient strength," perfectly meeting the requirements of prefabricated buildings, large-span buildings, and high-rise buildings for lightweight aggregate concrete. Specifically, the density of this concrete is all below 2000 kg / m³. 3 (Application Example 1 is 1952 kg / m³) 3 Application Example 3 is 1935 kg / m 3 This is far lower than that of ordinary concrete (density approximately 2400 kg / m³).3 This method can significantly reduce the self-weight of the building structure, reduce the load on the main structure (such as beams, columns, and foundations), thereby reducing the amount of steel and cement used and lowering the overall construction cost. Furthermore, despite using all solid waste components, through the synergistic effect of 5-10 parts low-strength waste rubber powder, 55-60 parts phosphogypsum lightweight artificial aggregate (single particle compressive strength above 3MPa), 20 parts granulated blast furnace slag, 12 parts fly ash, and 3 parts carbide slag, the concrete still maintains a high compressive strength. The compressive strength of application example 1 reaches 28.39MPa, and even in application example 3 (10 parts waste rubber powder), the compressive strength is still 23.38MPa, meeting the requirements of the "Technical Specification for Lightweight Aggregate Concrete Structures" for lightweight aggregate concrete for structural use (strength grade LC20 and above). It can be used as a structural component, breaking through the limitation that "solid waste concrete can only be used for non-load-bearing components". Application tests show that the lowest 24-hour water absorption rate of the concrete was only 4.03% (Application Example 1), and the highest was 4.81% (Application Example 3), which is far lower than that of traditional lightweight aggregate concrete (usually with a water absorption rate of over 8%). This is due to the low water absorption rate of the phosphogypsum lightweight artificial aggregate itself (24-hour water absorption rate <20%), and the filling effect of the CSH gel generated by the hydration of granulated blast furnace slag and carbide slag on the pores, which can reduce problems such as freeze-thaw damage to concrete and corrosion of steel bars caused by water penetration, and improve the durability of buildings.

[0042] Third, the components synergistically optimize performance, balancing toughness and process adaptability. In this invention, the components are not simply mixed, but rather work synergistically to compensate for the deficiencies of individual components, further optimizing the overall performance of concrete. Specifically, 5-10 parts of waste rubber powder (45-90 mesh waste tire rubber particles) possess elastic properties, improving the brittleness of concrete. Compared to traditional concrete without rubber powder, this formulation significantly enhances the crack resistance and impact resistance of the concrete, better adapting to minor deformations during the building's service life (such as temperature changes and load fluctuations), reducing crack formation. Simultaneously, the addition of rubber powder lowers the elastic modulus of the concrete, preventing interfacial cracking caused by excessive differences in the elastic moduli between aggregates and the cementitious matrix, thus improving the overall integrity of the concrete. Three parts of calcium carbide slag are alkaline and can act as an activator to activate the pozzolanic activity of 20 parts of granulated blast furnace slag and 12 parts of fly ash, promoting the formation of a large amount of CSH gel, calcium vanadate and other hydration products. These products not only replace the cementitious function of traditional cement, but also fill the internal pores of concrete and optimize the density. The aggregate strength of Comparative Example 1 (with fly ash replacing granulated blast furnace slag) decreased, which proves that the cementitious combination of "granulated blast furnace slag + fly ash + calcium carbide slag" in this formula is better and can ensure the strength of concrete. 55-60 parts of phosphogypsum lightweight artificial aggregate should be in a "saturated surface-dry state" (step 2 in the application example) to avoid excessive water absorption by the aggregate during mixing, which can lead to slurry segregation and slump loss, ensuring stable concrete construction performance. At the same time, the aggregate particle size of 5-20mm forms a reasonable gradation with granulated blast furnace slag, fly ash (fine powder), and waste rubber powder (45-90 mesh), further optimizing the density and mechanical properties of concrete. It is suitable for the simple process of "mixing, vibration molding, and standard curing", which does not require complex equipment and is conducive to industrial production.

[0043] In concrete production, coarse aggregate accounts for 60%-70% of the volume. Over-exploitation of natural aggregates damages the ecological environment of mountains and rivers. This invention completely replaces natural coarse aggregates with 55-60 parts of phosphogypsum lightweight artificial aggregate, combined with 20 parts of granulated blast furnace slag and 12 parts of fly ash to replace part of the cement. This reduces the consumption of natural resources from the source of raw materials. Based on the formula in Application Example 1, for every 1m³ of concrete prepared... 3 This concrete can absorb approximately 0.33 m³ of phosphogypsum (through artificial aggregate). 3 Approximately 0.03m³ of waste tire rubber. 3 At the same time, the amount of natural aggregate used is reduced by approximately 0.3m³. 3 This effectively alleviates the excessive reliance on natural aggregates in the concrete industry.

[0044] In addition, this concrete does not require high-temperature sintering or complex pressing processes (curing temperature is only 20~30℃, relative humidity 50%~60%). Compared with traditional lightweight aggregate concrete, it has lower energy consumption and no gaseous pollution emissions, which is in line with the concept of green building development. It provides a feasible technical path for the concrete industry to transform from "high consumption and high pollution" to "circular and low carbon".

[0045] According to some embodiments of the present invention, the waste rubber powder is 45-90 mesh waste tire rubber particles.

[0046] A fourth aspect of the present invention provides a method for preparing lightweight concrete made entirely from solid waste, as described in the third aspect of the present invention, comprising the following steps: S1: Under stirring conditions, water is added to the mixed powder formed by phosphogypsum lightweight artificial aggregate, granulated blast furnace slag, fly ash, carbide slag and waste rubber powder to obtain all-solid waste lightweight aggregate concrete slurry. S2: Pour the all-solid-waste lightweight aggregate concrete slurry into a mold, and after vibration and curing, obtain the all-solid-waste lightweight concrete.

[0047] According to some embodiments of the present invention, the duration of the vibration is 30-60 seconds.

[0048] According to some embodiments of the present invention, the amplitude of the vibration is 0.1-0.5 mm.

[0049] According to some embodiments of the present invention, the vibration frequency of the vibration is 30-50Hz.

[0050] According to some embodiments of the present invention, the curing includes pre-demolding curing and post-demolding curing.

[0051] According to some embodiments of the present invention, the pre-demolding curing conditions include placing the concrete before demolding in an environment with a temperature of 20-30°C and a relative humidity of 50%-60% for 24 hours before demolding.

[0052] According to some embodiments of the present invention, the post-demolding curing conditions include curing the demolded concrete for 28 days at a temperature of 20±2℃ and a relative humidity of >95% to obtain the all-solid-waste lightweight concrete.

[0053] According to some embodiments of the present invention, in step S1, the phosphogypsum lightweight artificial aggregate is in a saturated surface-dry state.

[0054] According to some embodiments of the present invention, in step S1, the stirring speed is 120-150 r / min before and after adding water.

[0055] In step S2, before pouring the all-solid-waste lightweight aggregate concrete slurry into the mold, the inside of the 70.7mm×70.7mm×70.7mm mold is cleaned and lubricated. Attached Figure Description

[0056] Figure 1 This is a process flow diagram of phosphogypsum lightweight artificial aggregate and lightweight aggregate concrete according to an embodiment of the present invention.

[0057] Figure 2 This is a photograph of the phosphogypsum lightweight artificial aggregate prepared according to an embodiment of the present invention.

[0058] Figure 3 This is a cross-sectional view of the compressive failure of lightweight aggregate concrete prepared for an application example of the present invention. Detailed Implementation

[0059] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0060] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the 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.

[0061] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0062] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0063] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0064] Phosphogypsum: After washing and ball milling, the particle size is 1-1000μm. It is mainly composed of CaSO4•2H2O and has poor water resistance.

[0065] Slag powder: Suitable for grades S95 and above. It has a high pozzolanic effect and can undergo a pozzolanic reaction to form CSH gel under the activation of MgO. It can also react with SO4 in phosphogypsum. 2- The reaction produces calcium vanadate.

[0066] Waste incineration ash: After being washed, dried and ground, the particle size is 1-500μm. It has low activity and is mostly used as a filler component.

[0067] Lignocellulose: After being crushed and sieved, it has good flexibility and dispersibility, which can improve the stability, strength, density and uniformity of the system.

[0068] MgO: The MgO content is greater than 99%, which can provide a high alkalinity to the system.

[0069] In this invention, the conditions for natural curing are: curing temperature of 20-30℃ and curing humidity of 50%-60%; the conditions for standard curing are: curing temperature of 20±2℃ and relative humidity of >90%.

[0070] Example 1 The phosphogypsum lightweight artificial aggregate provided in this embodiment consists of the following components by weight: 70 parts phosphogypsum, 13 parts granulated blast furnace slag, 13 parts waste incineration ash, 2 parts lignocellulose, 2 parts MgO, and 15 parts water.

[0071] Its preparation method includes the following steps: Step (1) involves washing and ball milling the raw phosphogypsum to remove impurities, including phosphorus, fluorine, organic impurities and heavy metals.

[0072] Step (2): Dry the phosphogypsum obtained in step (1) at a temperature of 60°C.

[0073] Step (3): Weigh 70 parts of phosphogypsum, 13 parts of granulated blast furnace slag, 13 parts of waste incineration ash, 2 parts of lignocellulose and 2 parts of MgO obtained in step (2), and put them into a mixer to mix evenly to obtain powder components.

[0074] Step (4): Add the powder components to the disc granulator. The disc granulator has a disc inclination angle of 45°, a disc diameter of 0.5m, a rotation speed of 40rpm, and a granulation time of 10min / kg. Spray water evenly into the powder, causing the powder to nucleate and form artificial aggregate embryos.

[0075] Step (5): The artificial aggregate obtained in step (4) is piled up and cured under natural conditions for 28 days to obtain phosphogypsum lightweight artificial aggregate.

[0076] Example 2 The phosphogypsum lightweight artificial aggregate provided in this embodiment differs from that in Embodiment 1 in that the granulated blast furnace slag in the composition is 10 parts.

[0077] Example 3 The phosphogypsum lightweight artificial aggregate provided in this embodiment differs from that in Embodiment 1 in that the granulated blast furnace slag in the composition is 7 parts.

[0078] Example 4 The phosphogypsum lightweight artificial aggregate provided in this embodiment differs from that in Embodiment 1 in that the granulated blast furnace slag in the composition is 4 parts.

[0079] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that granulated blast furnace slag is replaced with an equal amount of fly ash, while the composition of other raw materials remains unchanged.

[0080] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the granulated blast furnace slag is replaced with waste incineration ash, while the other components remain unchanged.

[0081] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the waste incineration ash is replaced with an equal amount of stone powder, while the other components remain unchanged.

[0082] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that MgO is replaced with steel slag in equal amounts, while other components remain unchanged.

[0083] Performance testing The apparent density, compressive strength, single-layer strength, water absorption and softening coefficient of the phosphogypsum lightweight artificial aggregates provided in Examples 1-4 and Comparative Examples 1-4 were tested, and the results are shown in Table 1 below.

[0084] Table 1

[0085] According to the data in Table 1: Single aggregate compressive strength: As the content of granulated blast furnace slag increased from 4 parts to 13 parts, the strength gradually increased from 3.50 MPa to 4.54 MPa, an increase of 30%, indicating that granulated blast furnace slag is a key raw material for improving the strength of individual aggregate particles. The CSH gel, calcium vanadate, and other hydration products generated by granulated blast furnace slag under MgO activation can fill the internal pores of the aggregate and enhance its structural integrity. The higher the content, the more hydration products are produced, and the stronger the resistance of individual aggregate particles to damage.

[0086] Compressive strength of the cylinder: Since compressive strength of the cylinder reflects the compressive strength of the aggregate, it is affected not only by the strength of individual aggregates, but also by the aggregate particle size distribution and packing density. In the example, the amount of waste incineration ash increases as the granulated blast furnace slag decreases (from 13 parts to 22 parts). As a low-activity filler, waste incineration ash may change the aggregate packing state, resulting in fluctuations in compressive strength of the cylinder.

[0087] Bulk density: The bulk density of Examples 1-4 is all around 945 kg / m³. 3 -960kg / m 3 Between, all are less than 1000 kg / m 3 It meets the requirements for lightweight artificial aggregates; and with the reduction of granulated blast furnace slag content and the increase of waste incineration ash content, the bulk density only decreases slightly (960 kg / m³). 3 →945kg / m 3 This indicates that within the range of 4-13 parts granulated blast furnace slag content, the density difference between the two solid waste raw materials has minimal impact on the overall bulk density of the aggregate, and the "lightweight" characteristics of the aggregate remain stable.

[0088] Regarding water resistance, the 24-hour water absorption rate and softening coefficient showed no obvious pattern with the amount of granulated blast furnace slag added, and the overall performance met the requirements. Specifically, the 24-hour water absorption rate was lowest in Example 4 (4 parts granulated blast furnace slag, 9.52%) and highest in Example 3 (7 parts granulated blast furnace slag, 13.89%), showing no clear trend. It is speculated that while the increased amount of waste incineration ash (from 13 parts to 22 parts) may have introduced some porosity, the reduction in hydration products due to the decrease in granulated blast furnace slag offset the effect of these two factors on the water absorption rate, ultimately stabilizing it between 9.52% and 13.89%, both lower than the standard of <20% for 24-hour water absorption. Regarding the softening coefficient, Example 1 (13 parts of granulated blast furnace slag) had the highest (0.74), while Example 4 (4 parts of granulated blast furnace slag) had the lowest (0.4). This indicates that the higher the content of granulated blast furnace slag, the better the water resistance of the aggregate (the higher the softening coefficient, the stronger the water resistance). This is because a higher content of granulated blast furnace slag generates more hydration products, which can more fully coat the phosphogypsum phase, reduce the damage of water to the aggregate structure, and improve water resistance stability.

[0089] Comparative Examples 1-4, by replacing key raw materials (granulated blast furnace slag → fly ash / incineration ash, incineration ash → stone powder, MgO → steel slag), compared with Example 1 (baseline formula), verified the irreplaceability of the raw material combination of the present invention.

[0090] Comparative Example 1 (granulated blast furnace slag → fly ash): The compressive strength of a single particle (4.92 MPa) is slightly higher than that of Example 1, but the water absorption rate (18.03%) is significantly higher than that of Example 1 (12.81%). The softening coefficient (0.35) is only 47% of that of Example 1 (0.74). This indicates that although fly ash can improve strength, it cannot improve water resistance like granulated blast furnace slag. This is because the reaction product of fly ash and phosphogypsum has poor water resistance, resulting in a more severe strength reduction of the aggregate after water absorption.

[0091] Comparative Example 2 (granulated blast furnace slag → waste incineration ash): The single particle compressive strength (3.31 MPa) and cylinder compressive strength (1.52 MPa) were the lowest among all samples, only 73% and 51% of those in Example 1, respectively. This indicates that waste incineration ash cannot replace the "strength support" role of granulated blast furnace slag. Because the activity of waste incineration ash is much lower than that of granulated blast furnace slag, very few hydration products are generated under MgO activation, which cannot enhance the aggregate structure.

[0092] Comparative Example 3 (incineration ash → stone powder): The single particle compressive strength (3.22 MPa) and cylinder compressive strength (2.04 MPa) were both lower than those of Example 1, while the 24-hour water absorption rate (15.16%) was higher than that of Example 1. This indicates that the filling effect and activity of stone powder are not as good as those of incineration ash. Although incineration ash has low activity, it can still undergo a weak pozzolanic reaction under MgO activation, which helps to generate a small amount of hydration products. Stone powder, on the other hand, is an inert filler that can only fill pores and cannot improve strength and water resistance. This verifies the necessity of incineration ash in the formulation.

[0093] Comparative Example 4 (MgO → Steel Slag): The single-particle compressive strength (2.83 MPa) and cylinder compressive strength (0.74 MPa) were significantly lower than those of Example 1, only 62% and 25% of those of Example 1, respectively. This indicates that steel slag cannot replace the "alkaline activation" effect of MgO. MgO reacts with water to generate magnesium hydroxide, which can quickly increase the alkalinity of the system and activate the activity of granulated blast furnace slag. However, the alkali release rate of steel slag is slow and the alkalinity is insufficient, which cannot effectively activate the granulated blast furnace slag, resulting in a small amount of hydration products and a significant decrease in aggregate strength.

[0094] The test results of Examples 1-4 and Comparative Examples 1-4 show that, under the synergistic effect of phosphogypsum, granulated blast furnace slag, waste incineration ash, lignocellulose, and MgO, this combination can achieve a bulk density of less than 1000 kg / m³. 3 Lightweight artificial aggregate, while ensuring other physical properties of phosphogypsum lightweight artificial aggregate.

[0095] The process flow of phosphogypsum lightweight artificial aggregate and lightweight aggregate concrete in this invention is referenced in the embodiments. Figure 1 As shown.

[0096] Application Example 1 This application example provides a lightweight aggregate concrete, which, by mass parts, consists of: 60 parts of phosphogypsum lightweight artificial aggregate, 20 parts of granulated blast furnace slag, 12 parts of fly ash, 3 parts of carbide slag, 5 parts of waste rubber powder, and 40 parts of water. The phosphogypsum lightweight artificial aggregate has a particle size of 5-20 mm, and the waste rubber powder is 45-90 mesh waste tire rubber granules.

[0097] Its preparation method includes the following steps: Step (1): Clean the inside of the 70.7mm×70.7mm×70.7mm mold and apply lubricating oil.

[0098] Step (2): Place 60 parts of phosphogypsum lightweight artificial aggregate, 20 parts of granulated blast furnace slag, 12 parts of fly ash, 3 parts of carbide slag and 5 parts of waste rubber powder into a mixer and stir for 3 minutes. The speed of the mixer is 120-150 r / min. The phosphogypsum lightweight artificial aggregate is in a saturated surface-dry state.

[0099] Step (3): Mix 40 parts of water and add them to a mixer. Mix for 3 minutes and the mixer speed is 120-150 r / min to obtain lightweight aggregate concrete slurry.

[0100] Step (4): Pour the lightweight aggregate concrete slurry from step (3) into the mold from step (1) and vibrate it for 30-60 seconds, with an amplitude of 0.1-0.5 mm and a vibration frequency of 30-50 Hz.

[0101] Step (5): Curing the lightweight aggregate concrete from step (4): Curing the lightweight aggregate concrete in an environment with a temperature of 20-30℃ and a relative humidity of 50%-60% for 24 hours, and then demolding to obtain demolded lightweight aggregate concrete. Curing the demolded lightweight aggregate concrete in an environment with a temperature of 20±2℃ and a relative humidity of >90% for 28 days to obtain lightweight aggregate concrete.

[0102] Application Example 2 This application example provides a lightweight aggregate concrete made entirely of solid waste, which differs from Application Example 1 only in that its composition is: 57 parts of phosphogypsum lightweight artificial aggregate and 8 parts of waste rubber powder, while the other raw material composition and steps remain unchanged.

[0103] Application Example 3 This application example provides a lightweight aggregate concrete made entirely of solid waste. The only difference between this example and application example 1 is that the composition is: 55 parts of phosphogypsum lightweight artificial aggregate and 10 parts of rubber powder. The composition and steps of other raw materials remain unchanged.

[0104] Figure 2 This is a photograph of the phosphogypsum lightweight artificial aggregate prepared according to an embodiment of the present invention. Figure 2Medium-phosphorus gypsum lightweight artificial aggregate is spherical or elliptical in shape, with high particle roundness and no obvious sharp edges, cracks, or defects. The regular spherical shape can improve the aggregate's bulk density, reduce porosity during subsequent preparation of lightweight aggregate concrete, and lower the breakage rate during transportation and mixing, providing a foundation for stable concrete performance and verifying the reliability of the disc granulation process. Figure 2 Visual comparison of the aggregates (such as differences in particle size) indicates that most aggregate particles are concentrated in the 5-20mm range, with no obviously coarse (>20mm) or ultrafine (<5mm) particles. This conforms to the technical characteristics of phosphogypsum lightweight artificial aggregate with a particle size of 5-20mm, and is also consistent with the design goal of controlling particle size through disc granulation in the embodiment. Uniform particle size distribution can optimize aggregate gradation, avoid segregation of concrete paste due to excessive particle size differences, and ensure the quality of concrete molding. Figure 2 The surface of the aggregate showed no large areas of looseness, powdering, or impurities, and was relatively dense. This indirectly reflects the uniformity of the raw material mixing and the rationality of the curing process. The process of uniform mixing of powder components (step 3) + natural curing for 28 days (temperature 20-30℃, humidity 50%-60%) ensures that components such as MgO and granulated blast furnace slag fully react to generate hydration products, which coat the phosphogypsum particles and fill the internal pores, forming a structurally complete aggregate surface. This provides direct evidence for the aggregate's low water absorption and high compressive strength (24h water absorption <20%, single particle compressive strength ≥3MPa in Table 1).

[0105] Figure 3 This is a cross-sectional view of the compressive failure of lightweight aggregate concrete prepared for an application example of the present invention. Figure 3 The compressive failure section of the concrete mainly showed cracking in the cementitious matrix, while the phosphogypsum lightweight artificial aggregate particles mostly maintained their intact shape, without any crushing. This indicates that during compressive failure, the stress was primarily borne by the cementitious matrix, and the interfacial bond strength between the aggregate and the cementitious matrix (granulated blast furnace slag, fly ash, and hydration products of carbide slag) was high, preventing aggregate-matrix separation failure. This phenomenon corroborates the high compressive strength (≥23.38 MPa) of the concrete in Table 2, proving that the interfacial compatibility of the phosphogypsum lightweight artificial aggregate + all-solid-waste cementitious system is good, meeting the mechanical performance requirements of structural concrete. Furthermore, Figure 3The concrete failure section exhibits a dense overall structure with no visible large pores (such as holes with a diameter > 5 mm), only a small number of micropores. This is related to the process design of vibration molding (vibration duration 30-60s, amplitude 0.1-0.5mm, frequency 30-50Hz) + cementitious system hydration filling. Vibration molding can remove air bubbles from the slurry, and the CSH gel generated by the hydration of granulated blast furnace slag, fly ash, and other cementitious components can fill the internal pores, ultimately forming a dense structure. This characteristic also explains the low water absorption rate (≤4.81%) of the concrete in Table 2; the dense structure reduces water penetration channels and improves the durability of the concrete. Figure 3 Fine, dark particles (corresponding to 45-90 mesh waste rubber powder) can be observed in the concrete cross-section. They are found to be evenly dispersed without obvious agglomerates. The evenly distributed waste rubber powder can exert its elastic advantage, forming elastic buffer points inside the concrete, improving the concrete's crack resistance and impact resistance, and avoiding the problem of localized weakness caused by rubber powder agglomeration. This further verifies the rationality of the preparation process.

[0106] Performance testing The density, water absorption rate, and compressive strength of the lightweight aggregate concrete provided in test cases 1-3 were tested, as shown in Table 2 below.

[0107] Table 2

[0108] As shown in Table 2, the all-solid-waste formula of this invention, consisting of 55-60 parts of phosphogypsum lightweight artificial aggregate, 20 parts of granulated blast furnace slag, 12 parts of fly ash, 3 parts of carbide slag, 5-10 parts of waste rubber powder, and 40 parts of water, can stably produce lightweight, high-strength, and low-water-absorption lightweight aggregate concrete—with a density ≤1952 kg / m³ in all application examples. 3 The compressive strength is ≥23.38MPa and the water absorption rate is ≤4.81%. All three indicators meet the core requirements of lightweight aggregate concrete for structural use, and the performance fluctuation is small, indicating that the formula parameters are reasonably designed and have the stability for industrial production.

[0109] Application Example 1 (60 parts aggregate + 5 parts rubber powder) has the highest compressive strength (28.39 MPa) and the lowest water absorption (4.03%), making it the preferred option with balanced performance. The higher content of phosphogypsum lightweight artificial aggregate can maximize the strength support role of the aggregate, while the lower content of waste rubber powder can reduce the weakening of strength. At the same time, it maintains low water absorption and lightweight characteristics, making it suitable for building structure scenarios with high strength requirements (such as prefabricated components and frame beams).

[0110] If the building scenario has higher requirements for toughness (such as seismic components and ground subbase), you can choose to use Example 2 (8 parts of rubber powder) or Example 3 (10 parts of rubber powder). Although the compressive strength is slightly reduced, the elastic properties of the rubber powder can improve the crack resistance and impact resistance of concrete, and the density is further reduced, which can more accurately match the performance preferences of different scenarios, indicating that the formulation has good flexibility and adaptability.

[0111] Table 2 shows the performance data that verifies the feasibility of preparing high-performance concrete from all solid waste raw materials. This concrete uses solid waste from multiple industries, such as phosphogypsum, granulated blast furnace slag, fly ash, carbide slag, and waste rubber powder, as raw materials. It not only solves the environmental problem of solid waste storage, but also replaces natural aggregates and traditional cement, alleviating resource dependence. At the same time, its performance meets the structural use standards, achieving a dual unity of environmental benefits and technical performance.

[0112] This invention uses a cold bonding method to prepare artificial aggregates. Compared with the sintering method, which has disadvantages such as energy consumption, gas pollution, and limited chemical composition of raw materials, the cold bonding method is more economical and environmentally friendly, and can use materials from a variety of sources for production.

[0113] The phosphogypsum lightweight artificial aggregate prepared by this invention mainly uses industrial by-products (granulated blast furnace slag and waste incineration ash) as raw materials, with solid waste accounting for 94%-96%. This can effectively reduce costs and realize the resource utilization of phosphogypsum. Furthermore, the application of this artificial aggregate to lightweight concrete has good environmental and economic benefits.

[0114] In this invention, MgO can change the acidic environment caused by phosphogypsum in the system. Granulated blast furnace slag and a small amount of waste incineration ash undergo a pozzolanic reaction under the activation of MgO to generate CSH gel. In addition, granulated blast furnace slag reacts with SO42- in phosphogypsum to generate calcium vanadium. These hydration products improve the strength and water resistance of aggregates by filling and encapsulating the internal structure of the aggregates.

[0115] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A phosphogypsum lightweight artificial aggregate, characterized in that, By weight, it includes: 70 parts of phosphogypsum Granulated blast furnace slag, 4-13 parts 13-22 portions of waste incineration ash. Two parts lignocellulose, MgO 2-4 parts, 15-20 parts water.

2. The phosphogypsum lightweight artificial aggregate according to claim 1, characterized in that, The average particle size D50 of the phosphogypsum is 60~70μm; and / or, the average particle size D50 of the granulated blast furnace slag is 8~15μm; and / or, the average particle size D50 of the waste incineration ash is 12~17μm.

3. The phosphogypsum lightweight artificial aggregate according to claim 1, characterized in that, The particle size of the phosphogypsum lightweight artificial aggregate is 5~20mm.

4. A method for preparing phosphogypsum lightweight artificial aggregate as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) According to the proportion, phosphogypsum, granulated blast furnace slag, waste incineration, lignocellulose and MgO are mixed to obtain powder; (2) The powder is sprayed into water and nucleated by a disc granulator to form an artificial aggregate blank; (3) Curing the artificial aggregate blank to obtain the phosphogypsum lightweight artificial aggregate.

5. The method according to claim 4, characterized in that, The method further includes removing impurities from the phosphogypsum before step (1).

6. The method according to claim 4, characterized in that, The inclination angle of the disc granulator is 40~50°; and / or, the diameter of the disc granulator is 0.4~0.6m; and / or, the rotation speed of the disc granulator is 30~50rpm; and / or, the disc granulation time is 8~12min / kg.

7. A lightweight concrete made entirely from solid waste, characterized in that, The components include phosphogypsum lightweight artificial aggregate as described in any one of claims 1 to 3 or phosphogypsum lightweight artificial aggregate prepared by any one of claims 4 to 6.

8. The lightweight concrete made entirely from solid waste according to claim 7, characterized in that, By weight, it includes: 55-60 parts of phosphogypsum lightweight artificial aggregate, 20 portions of granulated blast furnace slag 12 parts fly ash 3 parts of calcium carbide slag 5-10 parts of waste rubber powder 40 parts water.

9. A method for preparing all-solid-waste lightweight concrete as described in claim 7 or 8, characterized in that, Includes the following steps: S1: Under stirring conditions, water is added to the mixed powder formed by phosphogypsum lightweight artificial aggregate, granulated blast furnace slag, fly ash, carbide slag and waste rubber powder to obtain all-solid waste lightweight aggregate concrete slurry. S2: Pour the all-solid-waste lightweight aggregate concrete slurry into a mold, and after vibration and curing, obtain the all-solid-waste lightweight concrete.

10. The method according to claim 9, characterized in that, The duration of the vibration is 30-60 seconds; and / or, the amplitude of the vibration is 0.1-0.5 mm; and / or, the vibration frequency is 30-50 Hz; and / or, the curing includes pre-demolding curing and post-demolding curing; and / or, the pre-demolding curing conditions include placing the concrete in an environment with a temperature of 20-30℃ and a relative humidity of 50%-60% for 24 hours before demolding; and / or, the post-demolding curing conditions include placing the demolded concrete in an environment with a temperature of 20±2℃ and a relative humidity of >95% for 28 days to obtain the all-solid-waste lightweight concrete.

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