Lightweight aggregate based on industrial solid waste and method for preparing the same

Abstract

The application discloses a kind of light aggregate based on industrial solid waste and its preparation method, belong to the technical field of comprehensive recovery and resource utilization of arsenic-containing building (structure) waste materials.The light aggregate is made of building (structure) waste materials as main raw material, which is made by specific raw material formula and preparation process.The preparation method includes the steps of pretreatment, batching mixing, granulation, curing and the like of building (structure) waste materials.The light aggregate prepared by the application has excellent performance, can effectively solve the problem of arsenic-containing building (structure) waste material treatment, realize resource recycling, and has significant environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of comprehensive recycling and resource utilization technology of arsenic-containing building (structure) waste, specifically to a lightweight aggregate based on industrial solid waste and its preparation method. Background Technology

[0002] Industrial solid waste refers to solid waste generated during industrial production activities. Common industrial solid waste is construction waste, mainly composed of crushed concrete stones, broken bricks, and mortar fragments. Landfilling or stockpiling not only occupies landfill space but also easily wastes resources. Heavy metals such as antimony, lead, and arsenic in industrial solid waste can also be released and migrate into soil and rivers, causing heavy metal pollution of soil and water. Currently, building resource recovery products are mainly used in highway subgrade paving and sponge city construction. During highway subgrade construction, buildings are crushed and screened to be used as concrete aggregate. Concrete made from the aggregate of demolished buildings can be used as a road subbase material. In sponge city construction, aggregates from buildings can be used as a permeable layer to improve the city's water absorption and purification capacity. In addition, buildings can be used to produce concrete paving bricks, wall bricks, and other building materials. In recent years, the market for building materials and auxiliary materials has developed rapidly, especially with the increased demand for infrastructure such as roads and bridges.

[0003] Utilizing industrial solid waste to prepare lightweight aggregates can effectively solve the problem of industrial solid waste treatment, achieve resource recycling, and reduce dependence on natural mineral resources, resulting in significant environmental and economic benefits. However, current technologies for preparing lightweight aggregates from industrial solid waste still have some shortcomings. For example, some preparation methods are complex and costly, limiting their large-scale application. Lightweight aggregates prepared by some processes have unstable properties, such as low strength and high water absorption, failing to meet the high-quality requirements of construction projects. Therefore, developing a simple, low-cost method for preparing high-performance lightweight aggregates is of great significance. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a lightweight aggregate based on industrial solid waste and its preparation method. Through reasonable raw material ratio and unique preparation process, it makes full use of building waste to prepare high-performance lightweight aggregate, solves the problems of difficult treatment of existing building waste and unsatisfactory strength improvement effect, and realizes the resource utilization of industrial solid waste and green production of building materials.

[0005] The technical solution of this invention is as follows:

[0006] A lightweight aggregate based on industrial solid waste, comprising the following raw materials by weight:

[0007] 60 parts of industrial solid waste, 5-6 parts of nano titanium dioxide, 10-12 parts of metakaolin, 5-6 parts of polybutylene succinate oxalate, 9-10.9 parts of silica fume, 3-3.6 parts of hydroxypropyl methylcellulose, 2-2.4 parts of hydrogen peroxide, and 1-1.2 parts of sodium dodecyl sulfate.

[0008] In this formulation, industrial solid waste (including waste concrete, waste bricks, and waste stone) is used as the main raw material to achieve resource utilization of waste. Nano-titanium dioxide, metakaolin, and polybutylene succinate (POS) are used as modifiers, working synergistically to modify the industrial solid waste. POS has good film-forming and adhesive properties. During the raw material mixing stage, it can be uniformly dispersed in the material, coating other raw material particles and enhancing the adhesion between particles, making the material easier to form during granulation. Furthermore, under heating and stirring, and in the presence of hydrogen peroxide and sodium dodecyl sulfate, POS partially decomposes and acts on the solid waste, improving its microstructure. The generated gas helps form a more uniform pore structure, further optimizing the microstructure of the lightweight aggregate and improving its overall performance. Silica fume and hydroxypropyl methylcellulose act as binders and reinforcing agents, effectively improving the bonding strength of the lightweight aggregate and enhancing the overall structural stability.

[0009] Preferably, the lightweight aggregate based on industrial solid waste comprises, by weight, the following raw materials: 60 parts industrial solid waste, 5 parts nano titanium dioxide, 10 parts metakaolin, 5 parts polybutylene succinate, 9 parts silica fume, 3 parts hydroxypropyl methylcellulose, 2 parts hydrogen peroxide, and 1 part sodium dodecyl sulfate.

[0010] Preferably, the industrial solid waste mentioned in this invention refers to general industrial solid waste. The industrial solid waste includes building waste or structure waste.

[0011] Preferably, the main components of the building waste or structure waste are SiO2, CaO, Al2O3 and Fe2O3.

[0012] Preferably, the lightweight aggregate based on industrial solid waste contains 53.9%–57.7% SiO2 by weight, from the building waste or structural waste. 、 CaO 17.1~18.6%, Al2O3 9.8~10.1%, Fe2O3 7.4~8.2%, MgO 1.1~1.2%, K2O 1.5~1.6%.

[0013] Preferably, the industrial solid waste contains arsenic.

[0014] Furthermore, the present invention provides a method for preparing lightweight aggregate based on industrial solid waste, comprising the following steps:

[0015] (1) Crush and grind industrial solid waste, and then sieve it;

[0016] (2) Weigh the solid waste, nano titanium dioxide, metakaolin, polybutylene succinate oxalate, silica fume, hydroxypropyl methylcellulose, hydrogen peroxide, and sodium dodecyl sulfate after the treatment in step (1).

[0017] (3) Preparation of modifier: Nano titanium dioxide, metakaolin and polybutylene succinate are mixed to obtain a mixture, water is added and stirred to obtain modifier slurry;

[0018] (4) First, mix the solid waste with silica fume and hydroxypropyl methylcellulose, then add hydrogen peroxide, sodium dodecyl sulfate and modifier slurry and stir.

[0019] (5) Granulation and molding to produce particles with a particle size of 2.5 to 4.75 mm. The mixed material is granulated by a disc granulator with a rotation speed of 40 to 60 r / min. Under these conditions, the material can roll and agglomerate fully to form particles with regular shape and uniform particle size, which meets the molding requirements of lightweight aggregate.

[0020] (6) Curing to further stabilize the internal structure of lightweight aggregate.

[0021] Preferably, in step (3), the mass ratio of the mixture to water is 1:3.

[0022] Preferably, in step (3), the mixture is stirred at 300-400 r / min for 15-25 minutes.

[0023] Preferably, the maintenance period is at least 3 days.

[0024] Preferably, the maintenance environment conditions are a temperature of 30–35℃ and a relative humidity of 60–70%.

[0025] Preferably, in step (4), the stirring temperature is 60-65℃.

[0026] Compared with the prior art, the beneficial results of the present invention are as follows:

[0027] This invention uses construction waste as the main raw material, realizing the large-scale and efficient utilization of industrial solid waste, reducing the pollution of construction waste to the environment, protecting the soil, water and atmospheric environment, and having good environmental benefits. At the same time, it alleviates the dependence of traditional lightweight aggregate production on natural mineral resources. The lightweight aggregate produced by this invention can also significantly improve the strength of concrete, which meets the requirements of sustainable development.

[0028] When the curing time reaches 28 days, the arsenic content in the concrete test blocks produced with the lightweight aggregate of this invention is low, which can achieve the harmless treatment of arsenic and reduce environmental risks.

[0029] By using waste building materials as raw materials, the cost of raw materials is greatly reduced. At the same time, the preparation process is relatively simple and the production efficiency is high, which further reduces the production cost and improves the market competitiveness of the product. Detailed Implementation

[0030] To better understand the technical content of this invention, the invention will be further described below with reference to specific embodiments.

[0031] Example 1: Lightweight aggregate based on industrial solid waste and its preparation method

[0032] (1) Crushing of building waste: Select the demolished wall bricks and wall brick coating mixtures (buildings or structures left over from the relocation of the old factory area, containing arsenic 0.191~0.213mg / L), remove metal products, wood chips, plastics and other debris to obtain industrial solid waste, whose main components are SiO2, CaO, Al2O3 and Fe2O3, with the main component accounting for 53.9~57.7% of SiO2. 、 CaO 17.1–18.6%, Al2O3 9.8–10.1%, Fe2O3 7.4–8.2%, MgO 1.1–1.2%, K2O 1.5–1.6%. The sample was crushed and ground to reduce particle size; the pulverized sample was then sieved (10 mesh) to maintain uniform sample size.

[0033] (2) Raw material preparation: Weigh 60kg of solid waste treated in step (1), 5kg of nano titanium dioxide, 10kg of metakaolin, 5kg of polybutylene succinate, 9kg of silica fume, 3kg of hydroxypropyl methylcellulose, 2kg of hydrogen peroxide, and 1kg of sodium dodecyl sulfate.

[0034] (3) Modifier pretreatment: Mix nano-titanium dioxide, metakaolin, and polybutylene succinate, add 60 kg of water, and stir at 300-400 r / min for 15-25 minutes. This allows the components to fully swell and disperse, improving the modification effect.

[0035] (4) Mixing and stirring: First, mix industrial solid waste with silica fume and hydroxypropyl methylcellulose, stir at 60-65℃ for 10 minutes to form a preliminary bonding system, then add hydrogen peroxide, sodium dodecyl sulfate and modifier slurry, stir at 60-65℃ for 15-10 minutes to lay the foundation for subsequent molding and performance improvement.

[0036] (5) Granulation and molding: Granulation is carried out by a disc granulator at a speed of 40-60 r / min to produce particles with a diameter of 2.5-4.75 mm.

[0037] (6) Curing: Curing for 3 days in an environment with a temperature of 30-35℃ and a relative humidity of 60-70%.

[0038] Example 2: Lightweight aggregate based on industrial solid waste and its preparation method

[0039] (1) Crushing of building waste: Select the demolished wall bricks and wall brick coating mixtures (buildings or structures left over from the relocation of the old factory area, containing arsenic 0.191~0.213mg / L), remove metal products, wood chips, plastics and other debris to obtain industrial solid waste, whose main components are SiO2, CaO, Al2O3 and Fe2O3, with the main component accounting for 53.9~57.7% of SiO2. 、 CaO 17.1–18.6%, Al2O3 9.8–10.1%, Fe2O3 7.4–8.2%, MgO 1.1–1.2%, K2O 1.5–1.6%. The sample was crushed and ground to reduce particle size; the pulverized sample was then sieved (10 mesh) to maintain uniform sample size.

[0040] (2) Raw material preparation: Weigh 60kg of solid waste treated in step (1), 6kg of nano titanium dioxide, 12kg of metakaolin, 6kg of polybutylene succinate, 10.9kg of silica fume, 3.6kg of hydroxypropyl methylcellulose, 2.4kg of hydrogen peroxide, and 1.2kg of sodium dodecyl sulfate.

[0041] (3) Modifier pretreatment: Mix nano-titanium dioxide, metakaolin, and polybutylene succinate, add 72 kg of water, and stir at 300-400 r / min for 15-25 minutes. This allows the components to fully swell and disperse, improving the modification effect.

[0042] (4) Mixing and stirring: First, mix industrial solid waste with silica fume and hydroxypropyl methylcellulose, stir at 60-65℃ for 10 minutes to form a preliminary bonding system, then add hydrogen peroxide, sodium dodecyl sulfate and modifier slurry, stir at 60-65℃ for 15-10 minutes to lay the foundation for subsequent molding and performance improvement.

[0043] (5) Granulation and molding: Granulation is carried out by a disc granulator at a speed of 40-60 r / min to produce particles with a diameter of 2.5-4.75 mm.

[0044] (6) Curing: Curing for 3 days in an environment with a temperature of 30-35℃ and a relative humidity of 60-70%.

[0045] Comparative Example 1

[0046] In Example 1, polybutylene succinate was replaced with calcium lignosulfonate. The preparation steps of Example 1 were then attempted to produce lightweight aggregate.

[0047] Comparative Example 2

[0048] In Example 1, polybutylene succinate was replaced with polyethylene terephthalate. The preparation steps of Example 1 were then attempted to produce lightweight aggregate.

[0049] Comparative Example 3

[0050] The polybutylene succinate in Example 1 was replaced with metakaolin. The preparation steps of Example 1 were then attempted to produce lightweight aggregate.

[0051] Comparative Example 4

[0052] The modifier ratio in Example 1 was adjusted (i.e., 2 kg of nano titanium dioxide, 13 kg of metakaolin, 10 kg of polybutylene succinate, with other components remaining unchanged), and the preparation steps of Example 1 were used to produce lightweight aggregate.

[0053] Comparative Example 5

[0054] The amounts of nano-titanium dioxide, metakaolin, silica fume, and polybutylene oxalate in the raw materials of Example 1 were increased by about 30%, i.e., the raw materials were: 60 kg of solid waste treated in step (1), 6.5 kg of nano-titanium dioxide, 1.3 kg of metakaolin, 6.5 kg of polybutylene oxalate, 11.7 kg of silica fume, 3.9 kg of hydroxypropyl methylcellulose, 2.6 kg of hydrogen peroxide, and 1.3 kg of sodium dodecyl sulfate. The preparation steps of Example 1 were then used to produce lightweight aggregate.

[0055] Comparative Example 5

[0056] The selected new construction waste mainly consists of SiO2, CaO, Al2O3, and Fe2O3, with SiO2 accounting for 48.6% to 51.5% of the total. 、 CaO 19.1–20.3%, Al2O3 13.8–14.2%, Fe2O3 3.2–3.8%, MgO 1.92–2.0%, K2O 2.3–2.9%. The preparation steps of Example 1 were also attempted to produce lightweight aggregate.

[0057] Experimental example:

[0058] Strength is a crucial performance indicator for concrete products made from recycled lightweight aggregate derived from building waste. This experiment tested the mechanical properties of concrete according to the methods in the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2019) to analyze the impact of the substitution of recycled lightweight aggregate on the mechanical properties of concrete. Specimens were cured in a standard curing room for 7, 14, and 28 days, respectively. Afterward, the specimens were immersed in a water tank within the curing room for 24 hours, and the surface moisture was wiped off. The parameters of the universal testing machine were then set. The compressive strength of the concrete was tested using non-standard cubic blocks (100mm×100mm×100mm) under standard curing conditions at 7, 14, and 28 days. The flexural strength of the concrete was tested using rectangular blocks (100mm×100mm×400mm) after curing under standard conditions for 7, 14, and 28 days. The test results were multiplied by a size conversion factor of 0.95. Adjust the height of the lifting platform, set the loading rate to 1 mm / min, and record the maximum destructive pressure.

[0059] The cement used in the experiment was 42.5R type ordinary Portland cement. The lightweight aggregates prepared in the aforementioned examples and comparative examples were applied to concrete, and the concrete strength was analyzed. The specific material proportions for the experiment are shown in Table 1.

[0060] The specific concrete mixing method refers to the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2019). Three parallel samples were made for each group of specimens. After the specimens were molded, they were demolded within 24h±45min. The demolded standard specimens were cured according to the "Test Method for Strength of Cement Mortar" (GB / T17671-2021). The specimens were immersed in water at a temperature of 20±3℃ for curing. The flexural and compressive strengths were tested after 7d, 14d, and 28d of curing, respectively.

[0061] Table 1

[0062]

[0063] Experimental results and analysis:

[0064] The strength of concrete specimens is an important technical indicator and a primary basis for evaluating the effectiveness of recycled aggregate resource utilization. Table 2 shows the test results of compressive and flexural strength at specific admixture dosages and different curing times.

[0065] Compressive strength: When the curing time was 7 days, 14 days, and 28 days, the compressive strength of the concrete specimens in this experiment showed an increasing trend with the increase of curing time. The compressive strength of the example specimens and the comparative specimens was significantly higher than that of the blank control specimens, and the compressive strength of the example specimens was significantly higher than that of the comparative specimens. Among them, the compressive strength of Example 1 increased by about 32% compared with the blank specimen after 28 days of curing.

[0066] Table 2

[0067]

[0068] Flexural strength: When the curing time was 7 days, 14 days, and 28 days, the flexural strength of the concrete specimens in this experiment showed an increasing trend with the increase of curing time. The flexural strength of the examples and comparative examples was significantly higher than that of the blank control specimens, and the flexural strength of the examples was significantly higher than that of the comparative examples. Among them, the flexural strength of Example 1 increased by about 21% compared with the blank specimen after 28 days of curing. It can be seen that when the recycled fine aggregate of the examples is added to prepare concrete specimens, the compressive strength of the concrete specimens can be well improved.

[0069] The above mechanical property test results show that when the lightweight aggregate in the example replaces 5% of the natural river sand, the compressive strength and flexural strength of the concrete specimen are significantly higher than those of the reference concrete.

[0070] The main potential risk element in the buildings and structures involved in this project is arsenic. The following analysis examines the environmental impact by detecting changes in the leaching concentration of arsenic in concrete test blocks. The leaching toxicity (acid leaching) of the samples was determined according to the "Identification Standard for Hazardous Waste: Leaching Toxicity Identification" (GB5085.3). The leaching method used was "Leaching Toxicity of Solid Waste: Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJT299-20073).

[0071] The acid leaching results of arsenic in each embodiment and comparative sample are shown in Table 3. Table 3 shows that when the curing time reaches 28 days, the arsenic levels in the embodiment group (containing lightweight aggregate from building waste) are 0.0321–0.0337 mg / L, close to the blank specimens, indicating that the concrete prepared with lightweight aggregate from building waste in the embodiments does not affect the environment. The arsenic levels in comparative examples 1–3 are 0.0370–0.0383 mg / L, with the embodiment results being superior to the comparative examples. This result indirectly suggests that the process of this invention may have a certain complexing or adsorption effect on arsenic in industrial solid waste, effectively preventing the diffusion and leaching of arsenic.

[0072] Table 3. Acid Immersion Test Results of Concrete Products (n=10, average value)

[0073] Group Arsenic (mg / L) blank test specimens 0.0322 Example 1 0.0337 Example 2 0.0321 Comparative Example 1 0.0380 Comparative Example 2 0.0370 Comparative Example 3 0.0383 Comparative Example 4 0.0339 Comparative Example 5 0.0335 Comparative Example 6 0.0347

[0074] The above description is only a part of the embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall fall within the protection scope of the present invention.

Claims

1. A lightweight aggregate based on industrial solid waste, characterized in that, By weight, it includes the following ingredients: 60 parts of industrial solid waste, 5-6 parts of nano titanium dioxide, 10-12 parts of metakaolin, 5-6 parts of polybutylene succinate oxalate, 9-10.9 parts of silica fume, 3-3.6 parts of hydroxypropyl methylcellulose, 2-2.4 parts of hydrogen peroxide, and 1-1.2 parts of sodium dodecyl sulfate.

2. The lightweight aggregate based on industrial solid waste according to claim 1, characterized in that, By weight, it includes the following raw materials: 60 parts industrial solid waste, 5 parts nano titanium dioxide, 10 parts metakaolin, 5 parts polybutylene succinate oxalate, 9 parts silica fume, 3 parts hydroxypropyl methylcellulose, 2 parts hydrogen peroxide, and 1 part sodium dodecyl sulfate.

3. The lightweight aggregate based on industrial solid waste according to claim 1, characterized in that, The industrial solid waste includes building waste.

4. The lightweight aggregate based on industrial solid waste according to claim 3, characterized in that, The main components of the building waste are SiO2, CaO, Al2O3 and Fe2O3.

5. The lightweight aggregate based on industrial solid waste according to claim 4, characterized in that, The building waste contains, by mass percentage, 53.9-57.7% SiO2, 17.1-18.6% CaO, 9.8-10.1% Al2O3, 7.4-8.2% Fe2O3, 1.1-1.2% MgO, and 1.5-1.6% K2O.

6. The lightweight aggregate based on industrial solid waste according to claim 1, characterized in that, The industrial solid waste contains arsenic.

7. The method for preparing lightweight aggregate based on industrial solid waste according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Crush and grind industrial solid waste, and then sieve it; (2) Weigh the solid waste, nano titanium dioxide, metakaolin, polybutylene succinate oxalate, silica fume, hydroxypropyl methylcellulose, hydrogen peroxide, and sodium dodecyl sulfate after the treatment in step (1). (3) Preparation of modifier: Nano titanium dioxide, metakaolin and polybutylene succinate are mixed to obtain a mixture, water is added and stirred to obtain modifier slurry; (4) First, mix the solid waste with silica fume and hydroxypropyl methylcellulose, then add hydrogen peroxide, sodium dodecyl sulfate and modifier slurry and stir. (5) Granulation and molding to produce particles with a particle size of 2.5~4.75 mm; (6) Maintenance.

8. The preparation method according to claim 7, characterized in that, In step (3), the mass ratio of the mixture to water is 1:3, and the stirring conditions are 300~400r / min for 15~25 minutes.

9. The preparation method according to claim 7, characterized in that, The curing period is at least 3 days, and the curing environment conditions are a temperature of 30~35℃ and a relative humidity of 60~70%.

10. The preparation method according to claim 7, characterized in that, Step (4): The stirring temperature is 60~65℃.

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