Multi-solid waste modified lithium slag powder low-carbon concrete and preparation method thereof

Abstract

The application provides a kind of multi-solid waste modified lithium slag powder low-carbon concrete and preparation method thereof, belongs to green low-carbon concrete technical field.The concrete includes raw materials: cement 180-200 parts, fly ash 40-60 parts, granulated blast furnace slag powder 20-30 parts, modified lithium slag powder 40-60 parts, hydroxyapatite powder 2-4 parts, machine-made sand 860-880 parts, gravel 1030-1060 parts, beta-cyclodextrin 0.05-0.2 parts, polycarboxylic acid water reducing agent 6-8 parts, water 150-160 parts.The application utilizes waste slurry of mixing station and corn deep processing leaching waste liquid, modifies lithium slag powder by mechanical force-chemical modification and in-situ organic-inorganic hybrid coating, simultaneously combines multi-component synergistic optimization of concrete formulation system, significantly improves the comprehensive performance of concrete, solves the problems of poor workability of lithium slag concrete, large loss of slump over time, weak interface and unstable late strength development and the like.

Description

Technical Field

[0001] This invention relates to the field of green and low-carbon concrete technology, specifically to a low-carbon concrete made from lithium slag powder modified with multiple solid wastes and its preparation method. Background Technology

[0002] Concrete, as the most widely used building material, relies heavily on cement for its production. The cement industry is a major source of carbon dioxide and a major consumer of natural resources. Under the macro-requirements of green development, utilizing industrial solid waste as mineral admixtures or aggregates to partially replace cement and natural sand and gravel has become a key technological path for the concrete industry to achieve low-carbon development.

[0003] Lithium slag is a major industrial solid waste generated during the production of lithium salts (such as lithium carbonate and lithium hydroxide). As the world's largest lithium salt producer, my country generates several to tens of tons of lithium slag for every ton of lithium salt produced, posing a severe environmental challenge due to its storage and disposal. Lithium slag is primarily glassy, ​​rich in SiO2 and Al2O3, and exhibits some pozzolanic activity, but it also possesses the "double high" characteristics of high porosity and high water absorption. Directly incorporating lithium slag into concrete can easily lead to poor flowability, rapid slump loss, unstable strength development, and even shrinkage in fresh concrete. Furthermore, it may introduce the risk of heavy metal leaching, thus limiting the large-scale, high-value utilization of lithium slag.

[0004] The application of lithium slag in concrete in the existing technology still has the following problems: (1) The workability of fresh concrete deteriorates rapidly: The porous structure of lithium slag quickly adsorbs a large amount of free water during the mixing process, resulting in poor initial fluidity of concrete and significant loss of slump over time, making it difficult to meet the requirements of pumping and construction; (2) Unstable development of mechanical properties: The original lithium slag has extremely low early activity. In the alkaline environment provided by conventional cement hydration, its volcanic ash reaction starts slowly and to a low degree. Moreover, the later strength development is prone to stagnation or even shrinkage, which increases the structural safety risk; (3) Weak interface transition zone and durability hazards: High water absorption lithium slag is prone to form a porous and loose structure in the cement stone-aggregate interface area due to uneven internal curing, resulting in poor density of the interface transition zone; At the same time, some lithium slag may be accompanied by heavy metals, which pose an environmental risk of excessive leaching in the pore liquid; (4) Low stability of existing coating modification technology: Existing coated admixtures have the core defect of insufficient shell mechanical and chemical stability. They are prone to premature cracking during mixing shearing or early hydration, leading to functional failure.

[0005] In summary, existing "single-factor modification" or simple coating technologies are insufficient to systematically address the complex problems of poor flowability, low strength, and high risk associated with lithium slag, failing to meet the synergistic requirements of high-performance concrete for high admixture volume, high workability, high durability, and environmental safety. Therefore, there is an urgent need to develop a novel multi-element solid waste synergistic lithium slag modification technology and concrete formulation system to fundamentally solve the problems of poor flowability and significant slump loss in lithium slag concrete, synergistically enhance the interface transition zone and density, achieve full-process control of environmental risks, and prepare high-performance concrete with excellent workability, mechanical properties, durability, and environmental friendliness. This has significant practical implications and broad industrial prospects for promoting the leap from "disposal" to "value creation" in the resource utilization of lithium slag, and for facilitating the synergistic green upgrading of the new energy industry and the construction industry. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a low-carbon concrete made from lithium slag powder modified with multiple solid wastes and its preparation method. This invention utilizes the synergistic utilization of multiple solid wastes, mechanical-chemical modification, and in-situ organic-inorganic hybrid coating technology, combined with multi-component synergistic optimization of the concrete formulation system. This solves the technical bottlenecks caused by the high porosity and high water absorption of lithium slag, such as poor workability of fresh concrete, significant slump loss over time, weak interfaces, and unstable later-stage strength development. It achieves synergistic benefits of efficient and high-value utilization of bulk solid wastes and improved concrete performance.

[0007] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0008] This invention provides a low-carbon concrete using modified lithium slag powder derived from multiple solid wastes, comprising the following raw materials in parts by weight: 180-200 parts cement, 40-60 parts fly ash, 20-30 parts granulated blast furnace slag powder, 40-60 parts modified lithium slag powder, 2-4 parts hydroxyapatite powder, 860-880 parts manufactured sand, 1030-1060 parts crushed stone, 0.05-0.2 parts β-cyclodextrin, 6-8 parts polycarboxylate superplasticizer, and 150-160 parts water;

[0009] The method for preparing the modified lithium slag powder includes the following steps:

[0010] Lithium slag powder is mixed with waste slurry from a mixing plant and activated by semi-dry ball milling at 50-60 ℃ to obtain pre-activated lithium slag powder. Subsequently, the pre-activated lithium slag powder is coated with corn deep processing leaching waste liquid at 55-70 ℃, and after aging and drying, modified lithium slag powder is obtained.

[0011] The waste slurry from the mixing plant used in this invention to modify lithium slag powder is filter press waste slurry generated during the concrete production process of the mixing plant. Its solid content is 15%-20%, pH value is 12-12.5, and the proportion of unhydrated cement particles in the solid phase is ≥40%, while the proportion of calcium carbonate and calcium hydroxide is ≥30%. The corn deep processing leachate used in the modification of lithium slag powder is a by-product of corn deep processing (wet starch extraction), with a pH value of 3.0-4.0. It contains natural phytic acid (inositol hexaphosphate, mass fraction of 5%-8%), small molecule organic acid (lactic acid, mass fraction of 3%-5%), and residual starch polysaccharides and other effective components.

[0012] The lithium slag powder is in a glassy state, containing a large amount of alumina (Al2O3) and silicon dioxide (SiO2), but it suffers from physical defects such as high porosity and high water absorption. This invention uses a combination of mixing plant waste slurry and corn deep-processing leaching waste liquid to modify it, making it suitable for use in low-carbon cement-based materials. Specifically, the mixing plant waste slurry is rich in highly active unhydrated cement particles and calcium hydroxide (Ca(OH)2), providing strong alkalinity and free calcium; the corn deep-processing leaching waste liquid is rich in natural phytic acid, phosphate groups, and residual starch polysaccharides, providing organophosphate chelating groups with extremely strong metal coordination ability. During the modification treatment of the lithium slag powder, the high concentration of hydroxide ions (OH-) in the mixing plant waste slurry... - With the assistance of mechanical force, the glassy network structure (Si-O, Al-O bonds) on the surface of lithium slag powder can be broken, roughening and activating the surface of the lithium slag powder; at the same time, the ultrafine calcium carbonate (CaCO3) particles and hydrated calcium silicate crystal nuclei in the waste slurry of the mixing station are mechanically embedded into the micropores on the surface of the lithium slag powder, completing the pore sealing at the microscopic physical level. After the atomized corn deep processing leaching waste liquid is sprayed in, the corn deep processing leaching waste liquid encounters a strongly alkaline environment, and the organic acids (such as phytic acid, C6H) in it (C6H) 18 O 24 P6 (possessing six highly reactive phosphate groups) can react with calcium ions (Ca) provided by the waste slurry from the mixing plant. 2+ ) and aluminum ions (Al) released from the surface of lithium slag powder 3+ Metal cations such as metal cations undergo polydentate coordination reactions, which then crosslink in situ on the outer layer of lithium slag particles to form a dense "inorganic-organic hybrid thin shell layer", thereby effectively sealing the pores inside the lithium slag.

[0013] When the modified lithium slag powder described in this invention is added to concrete, in the early stages, because the lithium slag powder is wrapped by an inorganic-organic hybrid thin shell layer, its original strong water absorption is shielded, reducing the rate at which mixing water enters the internal pores of the lithium slag. This reduces the effective water loss caused by the rapid adsorption of mixing water by the lithium slag pores, solving the technical problem of poor fluidity and rapid slump loss in fresh concrete caused by undisturbed lithium slag. In the middle and later stages, as the cement continues to hydrate, the alkalinity of the concrete pore liquid increases significantly (pH > 13). Under continuous high-alkaline erosion, the inorganic-organic hybrid thin shell layer wrapped on the surface of the lithium slag gradually undergoes alkaline decomposition (i.e., the Al bonding points...). 3+ (Due to the extensive dissolution of the lithium slag, the inorganic-organic cross-linked network loses its skeletal support, resulting in structural collapse and alkaline lysis). After the shell ruptures, the highly active depolymerized SiO2 and Al2O3 pre-activated by the waste slurry from the mixing plant are released. These react rapidly with Ca(OH)2 produced during cement hydration to form a secondary pozzolanic reaction, generating a large amount of hydrated calcium silicate (CSH) gel. This compensates for the volume shrinkage of the concrete in the later stages and solves the problem of insufficient strength in the later stages of concrete caused by the addition of original lithium slag. In other words, if the lithium slag powder is not pre-activated by the waste slurry from the mixing plant, when the alkalinity of the concrete increases in the middle and later stages and the shell ruptures to release the lithium slag, the alkalinity of the interface transition zone is consumed, making it take a long time for the lithium slag to be activated by the concrete alkali, which may lead to missing the "time window" for compensating for concrete shrinkage.

[0014] Traditional coated admixtures are prone to premature shell cracking and failure during the intense shear mixing and early hydration stages of concrete. This invention introduces hydroxyapatite powder into the concrete formulation. Hydroxyapatite powder is rich in Ca... 2+ PO4 3- Plasma, based on the common ion effect, enhances the stability of the "inorganic-organic hybrid thin shell" on the surface of modified lithium slag powder in the early stages. This helps resist the mechanical wear of the modified lithium slag powder caused by strong early shear stirring and prevents abnormal leakage of its internal organic retarding components. In the later stages of concrete hydration, the organic-inorganic hybrid network of the modified lithium slag powder is dissolved by alkali, and the hydroxyapatite powder dispersed in the slurry and interface regions can act as a rigid nucleation template, inducing the highly active SiO2 and Al2O3 released from the internal lithium slag to undergo secondary pozzolanic reactions along their crystal planes, achieving "directional mineralization" growth of CSH gel and strengthening the interface transition zone. Furthermore, in the later stages of concrete hydration, the modified lithium slag powder participates in the reaction, and its residual heavy metal ions migrate into the pore fluid, while the PO4 released by the hydroxyapatite powder... 3- It can capture and fix free heavy metal ions, generating extremely insoluble phosphate precipitates, thus effectively solidifying the heavy metal ions while filling the pores of concrete.

[0015] During the alkaline hydrolysis and shell-breaking process, the modified lithium slag powder described in this invention releases trace amounts of residual plant proteins, lipids, and other surface-active substances (containing hydrophobic carbon chains) from corn deep-processing leaching wastewater into the concrete. The hydrophobic groups of these macromolecules easily trigger uncontrolled air-entraining effects, leading to deterioration of the concrete's pore structure. This invention introduces β-cyclodextrin into the concrete formulation as a free supramolecular acceptor. Utilizing its "externally hydrophilic and internally hydrophobic" truncated cone-shaped cavity, it captures and encapsulates the hydrophobic surface-active components released from the modified lithium slag powder through a host-guest recognition effect, forming stable supramolecular inclusion complexes. This reduces the risk of abnormal air entrainment and pore structure deterioration caused by hydrophobic organic components. Furthermore, to address the technical drawback of residual lactic acid and starch polysaccharides in corn deep-processing leachate leading to cement retardation, β-cyclodextrin and polycarboxylate superplasticizer complement each other. The densely packed, highly active hydroxyl (-OH) groups on the outer edge of β-cyclodextrin anchor the exudated polysaccharide components and organic acid macromolecules through multiple non-covalent hydrogen bonds, inhibiting their competitive adsorption on the cement particle surface. This not only effectively alleviates the "excessive retardation" side effect of organic matter, but its abundant surface hydroxyl groups also improve the rheology of the paste and enhance the slump retention of concrete.

[0016] Furthermore, the modified lithium slag powder has a Blaine specific surface area of ​​350-450 m². 2 / kg.

[0017] Furthermore, the mass ratio of the lithium slag powder, the waste slurry from the mixing plant (based on wet slurry), and the leaching waste liquid from corn deep processing is 100:(12-18):(4-7).

[0018] Furthermore, the lithium slag powder is lithium slag powder obtained by drying, crushing and pre-grinding raw lithium slag, with a Blaine specific surface area of ​​200-300 m². 2 / kg, moisture content ≤ 1.0%, its effective components include SiO2 50%-60%, Al2O3 20%-25%, CaO 4%-6%, SO3 6%-10%.

[0019] Furthermore, the ball-to-material mass ratio in the ball mill is (3-5):1, the ball mill rotation speed is 250-350 r / min, and the ball milling time is 15-20 min.

[0020] Further, the coating process is as follows: the pre-activated lithium slag powder is placed in a low-speed roller coating device, and the corn deep processing leaching waste liquid is atomized into micron-sized droplets with a particle size of 10-50 μm at 55-70 ℃. The atomized droplets are then continuously sprayed into the pre-activated lithium slag powder within 5-15 min, and the corn deep processing leaching waste liquid is coated onto the surface of the pre-activated lithium slag powder under low-speed rolling conditions.

[0021] Furthermore, the aging treatment is carried out at a temperature of 50-60 ℃ for a time of 20-40 min.

[0022] Furthermore, the drying is carried out by hot air drying at 60-80 ℃ until the moisture content of the modified lithium slag powder is ≤1.0%.

[0023] Specifically, the preparation method of the modified lithium slag powder is as follows:

[0024] S1: Add 100 parts of lithium slag powder and 12-18 parts of waste slurry from the mixing plant to a ball mill with temperature control, and control the ball-to-material mass ratio to be (3-5):1. Under the condition of 50-60 ℃, allow the material to be ball-milled and activated at a speed of 250-350 r / min for 15-20 min in a "semi-dry" state to obtain pre-activated lithium slag powder.

[0025] S2: The pre-activated lithium slag powder is placed in a low-speed roller coating device. Under the condition of 55-70 ℃, 4-7 parts of corn deep processing leaching waste liquid are atomized into micron-sized droplets with a particle size of 10-50 μm using an ultrasonic atomization device, and continuously sprayed into the pre-activated lithium slag powder within 5-15 min. Spray coating treatment is carried out under low-speed rolling conditions.

[0026] S3: The lithium slag powder obtained in step S2 is aged at 50-60 ℃ for 20-40 min, and then dried with hot air at 60-80 ℃ until the moisture content of the modified lithium slag powder is ≤ 1.0%, thus obtaining modified lithium slag powder.

[0027] Furthermore, the purity of the hydroxyapatite powder (HAP) is ≥ 96%, wherein the molar ratio of Ca / P is 1.60-1.67.

[0028] Furthermore, the particle size distribution of the hydroxyapatite powder is: D 50 The range is 0.5-2.0 μm.

[0029] Furthermore, the β-cyclodextrin is a white crystalline powder with a purity ≥ 98%; fineness: the residue passing through a 100-mesh sieve is ≤ 5%.

[0030] This invention also provides a method for preparing low-carbon concrete using the multi-solid waste modified lithium slag powder, comprising the following steps:

[0031] M1: Add cement, fly ash, granulated blast furnace slag powder, modified lithium slag powder and hydroxyapatite powder to a forced concrete mixer and dry mix for 30-60 seconds to ensure that the powders are evenly dispersed; then add manufactured sand and crushed stone and continue to dry mix for 30-60 seconds until the aggregates and cementitious materials are evenly mixed.

[0032] M2: Dissolve β-cyclodextrin and polycarboxylate superplasticizer in water to form a homogeneous solution, add it to a mixer and mix evenly to obtain low-carbon concrete made from lithium slag powder modified with solid waste.

[0033] Furthermore, the homogeneous solution is added to the mixer in two batches. The first batch consists of 70% of the solution, and the mixture is stirred for 30-40 seconds. The remaining solution is added in the second batch, and the mixture is stirred for another 90-120 seconds to obtain low-carbon concrete made from lithium slag powder modified with solid waste.

[0034] Compared with the prior art, the advantages of the present invention are:

[0035] (1) This invention utilizes waste slurry from mixing plants (providing an alkaline environment and crystal nuclei) and leaching waste liquid from corn deep processing (providing organic phosphate groups such as phytic acid) to modify lithium slag powder through a combination of mechanical force and in-situ coordination reaction. An "inorganic-organic hybrid thin shell layer" is constructed on the surface of lithium slag, which effectively seals the micropores of lithium slag, shields the early strong water absorption, significantly reduces water consumption, and improves the fluidity and slump retention of fresh concrete. In the middle and later stages, the shell layer can be controlled to lyse and break down in the high-alkali environment of concrete, releasing highly active SiO2 and Al2O3, which quickly undergo a secondary pozzolanic reaction to generate CSH gel, filling the pores, increasing the density of the matrix, and improving the later strength development ability of concrete.

[0036] (2) In this invention, hydroxyapatite powder is introduced into the concrete formulation. Based on the common ion effect, it is beneficial to enhance the stability of the "inorganic-organic hybrid thin shell layer" on the surface of the modified lithium slag powder in the early stage, effectively resisting strong shear stirring and early hydration wear, and improving the stability of the shell structure of the modified lithium slag powder. After the shell layer is alkalily hydrolyzed in the middle and late stages of hydration, hydroxyapatite powder acts as a rigid nucleation template, inducing SiO2 and Al2O3 to form CSH gel in a directional manner, strengthening the interfacial transition zone; at the same time, the released PO4 3- It captures heavy metal ions and forms insoluble phosphate precipitates, thereby achieving heavy metal solidification and pore filling.

[0037] (3) In this invention, β-cyclodextrin is introduced into the concrete formula as a supramolecular acceptor. Through the host-guest recognition effect, it captures the hydrophobic surface active substances released by the alkaline decomposition of modified lithium slag powder, forming a stable inclusion complex, reducing the risk of abnormal air entrainment and pore structure deterioration. At the same time, its abundant outer hydroxyl groups anchor the exudated polysaccharides and organic acids through hydrogen bonds, inhibiting the side effects of retarding and improving the rheology of the slurry, thus enhancing the slump retention performance of concrete. Detailed Implementation

[0038] To enable those skilled in the art to clearly and completely understand the technical solution of the present invention, the present invention will be further described in detail below with reference to embodiments. Obviously, the embodiments described herein are only for explaining the present invention and are not intended to limit the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the raw materials, methods and equipment used in this invention are conventional raw materials, methods and equipment in the art.

[0040] This invention provides a low-carbon concrete using modified lithium slag powder derived from multiple solid wastes, comprising the following raw materials in parts by weight: 180-200 parts cement, 40-60 parts fly ash, 20-30 parts granulated blast furnace slag powder, 40-60 parts modified lithium slag powder, 2-4 parts hydroxyapatite powder, 860-880 parts manufactured sand, 1030-1060 parts crushed stone, 0.05-0.2 parts β-cyclodextrin, 6-8 parts polycarboxylate superplasticizer, and 150-160 parts water; wherein the preparation method of the modified lithium slag powder includes the following steps:

[0041] Lithium slag powder is mixed with waste slurry from a mixing plant and activated by semi-dry ball milling at 50-60 ℃ to obtain pre-activated lithium slag powder. Subsequently, the pre-activated lithium slag powder is coated with corn deep processing leaching waste liquid at 55-70 ℃, and after aging and drying, modified lithium slag powder is obtained.

[0042] The waste slurry from the mixing plant used in this invention to modify lithium slag powder is filter press waste slurry generated during the concrete production process of the mixing plant. Its solid content is 15%-20%, pH value is 12-12.5, and the proportion of unhydrated cement particles in the solid phase is ≥40%, while the proportion of calcium carbonate and calcium hydroxide is ≥30%. The corn deep processing leachate used in the modification of lithium slag powder is a by-product of corn deep processing (wet starch extraction). Its pH value is 3.0-4.0, and it contains natural phytic acid (inositol hexaphosphate, mass fraction of 5%-8%), small molecule organic acid (lactic acid, mass fraction of 3%-5%), and residual starch polysaccharides and other effective components.

[0043] In some examples, the modified lithium slag powder has a Blaine specific surface area of ​​350-450 m². 2 / kg.

[0044] In some examples, the mass ratio of the lithium slag powder, the mixing plant waste slurry (as wet slurry), and the corn deep processing leaching waste liquid is 100:(12-18):(4-7).

[0045] In some examples, the lithium slag powder is lithium slag powder obtained by drying, crushing and pre-grinding raw lithium slag, with a Blaine surface area of ​​200-300 m². 2 / kg, moisture content ≤ 1.0%, its effective components include SiO2 50%-60%, Al2O3 20%-25%, CaO 4%-6%, SO3 6%-10%.

[0046] In some examples, the ball-to-material mass ratio of the ball mill is (3-5):1, the ball mill rotation speed is 250-350 r / min, and the ball milling time is 15-20 min.

[0047] In some examples, the coating process is performed as follows: the pre-activated lithium slag powder is placed in a low-speed roller coating device, and the corn deep-processing leaching waste liquid is atomized into micron-sized droplets with a particle size of 10-50 μm at 55-70 ℃. The atomized droplets are then continuously sprayed into the pre-activated lithium slag powder within 5-15 min, and the corn deep-processing leaching waste liquid coats the surface of the pre-activated lithium slag powder under low-speed rolling conditions.

[0048] In some examples, the aging process is carried out at a temperature of 50-60 °C for 20-40 min.

[0049] In some examples, the drying is performed by hot air drying at 60-80 °C until the moisture content of the modified lithium slag powder is ≤ 1.0%.

[0050] In some examples, the hydroxyapatite powder (HAP) has a purity ≥ 96%, wherein the Ca / P molar ratio is 1.60-1.67; the particle size distribution of the hydroxyapatite powder is: D 50 The range is 0.5-2.0 μm.

[0051] In some examples, the β-cyclodextrin is a white crystalline powder with a purity ≥ 98%; fineness: ≤ 5% residue passing through a 100-mesh sieve.

[0052] The specifications and sources of the raw materials used in the following specific implementation cases are shown in Table 1 below.

[0053] Table 1: Specifications and sources of raw materials used in the examples

[0054]

[0055] Example 1

[0056] A low-carbon concrete made from modified lithium slag powder containing multiple solid wastes comprises the following raw materials in parts by weight: 190 parts cement, 50 parts fly ash, 25 parts granulated blast furnace slag powder, 50 parts modified lithium slag powder, 3 parts hydroxyapatite powder, 870 parts manufactured sand, 1040 parts crushed stone, 0.13 parts β-cyclodextrin, 7 parts polycarboxylate superplasticizer, and 155 parts water.

[0057] The modified lithium slag powder is prepared as follows:

[0058] S1: Add 100 parts of lithium slag powder and 18 parts of waste slurry from the mixing plant to a ball mill with temperature control, control the ball-to-material mass ratio to be 4:1, the ball mill speed to be 300 r / min, and ball mill the material in a semi-dry state for 15 min at 55 ℃ to obtain pre-activated lithium slag powder.

[0059] S2: Transfer the pre-activated lithium slag powder obtained in step S1 into a low-speed drum coating device. Control the drum speed at 60 r / min. Under the condition of 60 ℃, use an ultrasonic atomizing device to atomize 5 parts of corn deep processing leaching waste liquid into micron-sized droplets with a particle size of 10-50 μm, and continuously spray them into the pre-activated lithium slag powder within 10 min, so that the corn deep processing leaching waste liquid coats the surface of the pre-activated lithium slag powder. After the spraying is completed, continue low-speed rolling and mixing for 8 min to obtain wet coated lithium slag powder.

[0060] S3: The wet-coated lithium slag powder obtained in step S2 is aged at 55 ℃ for 30 min, then dried with hot air at 70 ℃ until the moisture content is ≤ 1.0%. After depolymerization using a low-speed depolymerizer at 200-300 r / min for 3-6 min, the powder is sieved to obtain a Blaine surface area of ​​350-450 m². 2 / kg of modified lithium slag powder.

[0061] The preparation method of the low-carbon concrete using multi-solid waste modified lithium slag powder includes the following steps:

[0062] M1: Add cement, fly ash, granulated blast furnace slag powder, modified lithium slag powder and hydroxyapatite powder to a forced concrete mixer and dry mix for 45 seconds to ensure that the powders are evenly dispersed; then add manufactured sand and crushed stone and continue to dry mix for 45 seconds until the aggregates and cementitious materials are evenly mixed.

[0063] M2: Dissolve β-cyclodextrin and polycarboxylate superplasticizer in water to form a homogeneous solution, and add it to the mixer in two batches. The first batch is 70% of the solution, and the mixture is stirred for 35 seconds. The second batch is the remaining solution, and the mixture is stirred for another 120 seconds to obtain low-carbon concrete made from lithium slag powder modified with solid waste.

[0064] Example 2

[0065] A low-carbon concrete made from modified lithium slag powder containing multiple solid wastes comprises the following raw materials in parts by weight: 200 parts cement, 40 parts fly ash, 30 parts granulated blast furnace slag powder, 60 parts modified lithium slag powder, 4 parts hydroxyapatite powder, 860 parts manufactured sand, 1030 parts crushed stone, 0.2 parts β-cyclodextrin, 6 parts polycarboxylate superplasticizer, and 160 parts water.

[0066] The modified lithium slag powder is prepared as follows:

[0067] S1: Add 100 parts of lithium slag powder and 15 parts of waste slurry from the mixing plant to a ball mill with temperature control, control the ball-to-material mass ratio to be 3:1, the ball mill speed to be 280 r / min, and ball mill the material in a semi-dry state for 15 min at 55 ℃ to obtain pre-activated lithium slag powder.

[0068] S2: Transfer the pre-activated lithium slag powder obtained in step S1 into a low-speed drum coating device. Control the drum speed at 50 r / min. Under the condition of 55 ℃, use an ultrasonic atomizing device to atomize 4 portions of corn deep processing leaching waste liquid into micron-sized droplets with a particle size of 10-50 μm, and continuously spray them into the pre-activated lithium slag powder within 8 min, so that the corn deep processing leaching waste liquid coats the surface of the pre-activated lithium slag powder. After the spraying is completed, continue low-speed rolling and mixing for 5 min to obtain wet coated lithium slag powder.

[0069] S3: The wet-coated lithium slag powder obtained in step S2 is aged at 50 ℃ for 20 min, then dried with hot air at 60 ℃ until the moisture content is ≤ 1.0%. After depolymerization using a low-speed depolymerization machine at 200-300 r / min for 3-6 min, the powder is sieved to obtain a Blaine surface area of ​​350-450 m². 2 / kg of modified lithium slag powder.

[0070] The preparation method of the low-carbon concrete using multi-solid waste modified lithium slag powder includes the following steps:

[0071] M1: Add cement, fly ash, granulated blast furnace slag powder, modified lithium slag powder and hydroxyapatite powder to a forced concrete mixer and dry mix for 45 seconds to ensure that the powders are evenly dispersed; then add manufactured sand and crushed stone and continue to dry mix for 45 seconds until the aggregates and cementitious materials are evenly mixed.

[0072] M2: Dissolve β-cyclodextrin and polycarboxylate superplasticizer in water to form a homogeneous solution, and add it to the mixer in two batches. The first batch is 70% of the solution, and the mixture is stirred for 35 seconds. The second batch is the remaining solution, and the mixture is stirred for another 120 seconds to obtain low-carbon concrete made from lithium slag powder modified with solid waste.

[0073] Example 3

[0074] A low-carbon concrete made from modified lithium slag powder containing multiple solid wastes comprises the following raw materials in parts by weight: 180 parts cement, 60 parts fly ash, 20 parts granulated blast furnace slag powder, 40 parts modified lithium slag powder, 2 parts hydroxyapatite powder, 880 parts manufactured sand, 1060 parts crushed stone, 0.05 parts β-cyclodextrin, 8 parts polycarboxylate superplasticizer, and 150 parts water.

[0075] The modified lithium slag powder is prepared as follows:

[0076] S1: Add 100 parts of lithium slag powder and 12 parts of waste slurry from the mixing plant to a ball mill with temperature control, control the ball-to-material mass ratio to be 5:1, the ball mill speed to be 350 r / min, and ball mill the material in a semi-dry state for 20 min at 60 ℃ to obtain pre-activated lithium slag powder.

[0077] S2: Transfer the pre-activated lithium slag powder obtained in step S1 into a low-speed drum coating device. Control the drum speed to 80 r / min. Under the condition of 70 ℃, use an ultrasonic atomizing device to atomize 7 parts of corn deep processing leaching waste liquid into micron-sized droplets with a particle size of 10-50 μm, and continuously spray them into the pre-activated lithium slag powder within 15 min, so that the corn deep processing leaching waste liquid coats the surface of the pre-activated lithium slag powder. After the spraying is completed, continue low-speed rolling and mixing for 10 min to obtain wet coated lithium slag powder.

[0078] S3: The wet-coated lithium slag powder obtained in step S2 is aged at 60 ℃ for 40 min, then dried with hot air at 80 ℃ until the moisture content is ≤ 1.0%. After depolymerization using a low-speed depolymerizer at 200-300 r / min for 3-6 min, the powder is sieved to obtain a Blaine surface area of ​​350-450 m². 2 / kg of modified lithium slag powder.

[0079] The preparation method of the low-carbon concrete using multi-solid waste modified lithium slag powder includes the following steps:

[0080] M1: Add cement, fly ash, granulated blast furnace slag powder, modified lithium slag powder and hydroxyapatite powder to a forced concrete mixer and dry mix for 45 seconds to ensure that the powders are evenly dispersed; then add manufactured sand and crushed stone and continue to dry mix for 45 seconds until the aggregates and cementitious materials are evenly mixed.

[0081] M2: Dissolve β-cyclodextrin and polycarboxylate superplasticizer in water to form a homogeneous solution, and add it to the mixer in two batches. The first batch is 70% of the solution, and the mixture is stirred for 35 seconds. The second batch is the remaining solution, and the mixture is stirred for another 120 seconds to obtain low-carbon concrete made from lithium slag powder modified with solid waste.

[0082] Comparative Example 1

[0083] A type of concrete, differing from Example 1 in that the lithium slag in this comparative example is not modified. That is, the concrete in this comparative example comprises the following raw materials in parts by weight: 190 parts cement, 50 parts fly ash, 25 parts granulated blast furnace slag powder, 50 parts lithium slag powder, 3 parts hydroxyapatite powder, 870 parts manufactured sand, 1040 parts crushed stone, 0.13 parts β-cyclodextrin, 7 parts polycarboxylate superplasticizer, and 155 parts water.

[0084] Comparative Example 2

[0085] A type of concrete, differing from Example 1 in that this comparative example uses an equal mass of water instead of corn deep-processing leaching waste liquid, while the types, amounts, and preparation parameters of other raw materials are the same as in Example 1. That is, the preparation steps of the modified lithium slag in this comparative example are as follows:

[0086] S1: Same as Example 1;

[0087] S2: Transfer the pre-activated lithium slag powder obtained in step S1 into a low-speed drum coating device, control the drum speed to 60 r / min, and use an ultrasonic atomizing device to atomize 5 parts of water into micron-sized droplets with a particle size of 10-50 μm at 60 ℃, and continuously spray them into the pre-activated lithium slag powder within 10 min; after spraying, continue low-speed rolling and mixing for 8 min to obtain wet coated lithium slag powder;

[0088] S3: Same as Example 1.

[0089] Comparative Example 3

[0090] A type of concrete, differing from Example 1 in that this comparative example uses an equal mass of water to replace the waste slurry from the mixing plant; the other raw material types, amounts, and preparation parameters are the same as in Example 1. That is, the preparation steps of the modified lithium slag in this comparative example are as follows:

[0091] S1 is: 100 parts of lithium slag powder and 18 parts of water are added to a ball mill with temperature control, the ball-to-material mass ratio is controlled at 4:1, the ball milling speed is 300 r / min, and the ball milling is carried out at 55 ℃ for 15 min to obtain pretreated lithium slag powder.

[0092] S2: Same as Example 1;

[0093] S3: Same as Example 1.

[0094] Comparative Example 4

[0095] A type of concrete, differing from Example 1 in that the concrete in this comparative example does not contain hydroxyapatite powder. That is, the concrete in this comparative example comprises the following raw materials in parts by weight: 190 parts cement, 50 parts fly ash, 25 parts granulated blast furnace slag powder, 50 parts modified lithium slag powder, 870 parts manufactured sand, 1040 parts crushed stone, 0.13 parts β-cyclodextrin, 7 parts polycarboxylate superplasticizer, and 155 parts water.

[0096] Comparative Example 5

[0097] A type of concrete, which differs from Example 1 in that the concrete in this comparative example does not contain β-cyclodextrin, that is, the concrete in this comparative example comprises the following raw materials in parts by weight: 190 parts cement, 50 parts fly ash, 25 parts granulated blast furnace slag powder, 50 parts modified lithium slag powder, 3 parts hydroxyapatite powder, 870 parts manufactured sand, 1040 parts crushed stone, 7 parts polycarboxylate superplasticizer, and 155 parts water.

[0098] Experimental examples: Performance testing of modified lithium slag powder and concrete.

[0099] The modified lithium slag powders obtained in Examples 1-3 were subjected to physical property and activity tests. The test items included Blaine surface area, 30 min water absorption rate, water demand ratio and 28 d activity index. The test results are shown in Table 2.

[0100] The workability and mechanical properties of the concrete prepared in Examples 1-3 and Comparative Examples 1-5 were tested. The slump, spread, and 2-hour slump loss of the concrete were tested according to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures"; the 7-day and 28-day compressive strengths of the concrete were tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test results are shown in Table 3.

[0101] To verify the solidification effect of hydroxyapatite powder on potential heavy metal ions in lithium slag, the leaching concentration of heavy metal elements was tested on the crushed hardened concrete samples of Example 1, Comparative Example 1, and Comparative Example 4. After 28 days of standard curing, the hardened concrete was crushed to the specified particle size and leached according to the solid waste leaching toxicity test method. The leaching concentrations of Pb, Cd, Cr, Ni, and Zn were determined using ICP-OES. The test results are shown in Table 4.

[0102] Table 2: Performance Test Results of Modified Lithium Slag Powder

[0103]

[0104] As shown in Table 2, compared with the original pre-ground lithium slag powder, the modified lithium slag powder prepared in Examples 1-3 showed significantly lower 30-minute water absorption rate and water demand ratio, and significantly higher 28-day activity index. Specifically, in Example 1, the modified lithium slag powder showed a decrease in 30-minute water absorption rate from 18.3% to 8.6%, a decrease in water demand ratio from 118% to 103%, and an increase in 28-day activity index from 72% to 88%. This indicates that the co-treatment of waste slurry from the mixing plant and leaching waste liquid from corn deep processing can effectively reduce the early water absorption of lithium slag powder and significantly improve its reactivity in cement-based systems.

[0105] Table 3: Concrete Performance Test Results

[0106]

[0107] As can be seen from the test results in Table 3, the low-carbon concrete prepared by multi-solid waste modified lithium slag powder in Examples 1-3 all have high initial slump and spread, and low slump loss after 2 hours. This indicates that the lithium slag powder modified by the waste slurry from the mixing plant and the leaching waste liquid from corn deep processing in this invention can effectively reduce the early water absorption of lithium slag powder and improve the fluidity and slump retention of the concrete mixture.

[0108] Compared with Example 1, Comparative Example 1 uses unmodified raw lithium slag powder, which has a slump of only 160 mm, a slump loss of 88 mm in 2 hours, and a compressive strength of only 33.2 MPa in 28 days. This shows that raw lithium slag powder has high porosity and strong water absorption, and its direct addition to concrete will significantly reduce the workability and strength development of concrete.

[0109] Comparative Example 2 used an equal mass of water to replace the corn deep processing leachate. Its slump, slump retention, and later strength were all lower than those of Example 1. This indicates that the phytic acid, organic acid, and polysaccharide components in the corn deep processing leachate are beneficial to forming an organic-inorganic composite coating layer on the surface of the pre-activated lithium slag powder, thereby reducing the early water absorption rate of the lithium slag powder and improving the workability of concrete.

[0110] Comparative Example 3 used an equal mass of water to replace the waste slurry from the mixing plant, and its 28-day compressive strength was significantly lower than that of Example 1. This indicates that the alkaline environment, calcareous components, and hydration nuclei provided by the waste slurry from the mixing plant play an important role in the surface activation, pore filling, and subsequent pozzolanic reaction of lithium slag powder.

[0111] Comparative Example 4, which did not incorporate hydroxyapatite powder, had a slump similar to that of Example 1, but its compressive strength was significantly reduced. This indicates that hydroxyapatite powder promotes interfacial nucleation, later-stage reaction, and interfacial transition zone strengthening of modified lithium slag powder in cement-based systems.

[0112] Comparative Example 5, which did not incorporate β-cyclodextrin, showed a slump loss of 70 mm after 2 hours. This indicates that the hydrophobic organic components remaining in the corn deep-processing leachate may cause abnormal air entrainment and flowability loss. β-cyclodextrin can reduce the adverse effects of such organic components through inclusion and hydrogen bonding, thereby improving the slump retention and pore structure stability of concrete.

[0113] In summary, this invention modifies lithium slag powder by using waste slurry from mixing plants and leaching waste liquid from corn deep processing, and further combines it with hydroxyapatite powder and β-cyclodextrin. This achieves a reduction in early water absorption, an improvement in workability, and an increase in mid-to-late-stage strength of lithium slag powder, making it suitable for preparing low-carbon concrete with high solid waste utilization and good construction performance.

[0114] Table 4: Leaching concentration of heavy metal elements in concrete samples

[0115]

[0116] Table 4 shows that the leaching concentration of heavy metals in Comparative Example 1 is relatively high, indicating that there is a certain risk of heavy metal migration when unmodified lithium slag powder is directly used in concrete. Compared with Comparative Example 1, the leaching concentrations of Pb, Cd, total Cr, Ni, and Zn in Comparative Example 4 are all reduced, indicating that the coating structure formed by the synergistic modification of the mixing plant waste slurry and corn deep processing leaching waste liquid is beneficial to reducing the migration of potential heavy metals in lithium slag.

[0117] Compared with Comparative Example 4, the leaching concentrations of each heavy metal element in Example 1 were further reduced, with Pb decreasing from 0.045 mg / L to 0.017 mg / L, Ni from 0.071 mg / L to 0.030 mg / L, and Zn from 0.270 mg / L to 0.115 mg / L. This indicates that hydroxyapatite powder can form insoluble precipitates with heavy metal ions through phosphate groups, thereby further improving the concrete system's ability to solidify heavy metal ions. These results demonstrate that the present invention not only improves the workability and mechanical properties of lithium slag powder concrete but also reduces the environmental risks during the resource utilization of lithium slag.

[0118] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A low-carbon concrete made from lithium slag powder modified with multiple solid wastes, characterized in that, The raw materials include the following parts by weight: 180-200 parts cement, 40-60 parts fly ash, 20-30 parts granulated blast furnace slag powder, 40-60 parts modified lithium slag powder, 2-4 parts hydroxyapatite powder, 860-880 parts manufactured sand, 1030-1060 parts crushed stone, 0.05-0.2 parts β-cyclodextrin, 6-8 parts polycarboxylate superplasticizer, and 150-160 parts water; The method for preparing the modified lithium slag powder includes the following steps: Lithium slag powder is mixed with waste slurry from a mixing plant and activated by semi-dry ball milling at 50-60 ℃ to obtain pre-activated lithium slag powder. Subsequently, the pre-activated lithium slag powder is coated with corn deep processing leaching waste liquid at 55-70 ℃, and after aging and drying, modified lithium slag powder is obtained.

2. The low-carbon concrete made from modified lithium slag powder with multiple solid wastes according to claim 1, characterized in that, The mass ratio of lithium slag powder, mixing plant waste slurry and corn deep processing leaching waste liquid is 100:(12-18):(4-7), wherein the mixing plant waste slurry is calculated as wet slurry.

3. The low-carbon concrete made from modified lithium slag powder with multiple solid wastes according to claim 2, characterized in that, The lithium slag powder is a lithium slag powder obtained by drying, crushing and pre-grinding raw lithium slag. Its Blaine specific surface area is 200-300 m². 2 / kg, moisture content ≤ 1.0%, its effective components include SiO2 50%-60%, Al2O3 20%-25%, CaO 4%-6%, SO3 6%-10%.

4. The low-carbon concrete made from modified lithium slag powder with multiple solid wastes according to claim 1, characterized in that, The modified lithium slag powder has a Blaine specific surface area of ​​350-450 m². 2 / kg.

5. The low-carbon concrete made from modified lithium slag powder with multiple solid wastes according to claim 1, characterized in that, The ball-to-material mass ratio of the ball mill is (3-5):1, the ball mill rotation speed is 250-350 r / min, and the ball milling time is 15-20 min.

6. The low-carbon concrete made from modified lithium slag powder with multiple solid wastes according to claim 1, characterized in that, The coating process is as follows: the pre-activated lithium slag powder is placed in a low-speed roller coating device. Under the condition of 55-70 ℃, the corn deep processing leaching waste liquid is atomized into micron-sized droplets with a particle size of 10-50 μm and continuously sprayed into the pre-activated lithium slag powder within 5-15 min. Under the condition of low-speed rolling, the corn deep processing leaching waste liquid coats the surface of the pre-activated lithium slag powder.

7. The low-carbon concrete made from modified lithium slag powder with multiple solid wastes according to claim 1, characterized in that, The aging process is carried out at a temperature of 50-60 ℃ for 20-40 min.

8. The low-carbon concrete made from modified lithium slag powder with multiple solid wastes according to claim 1, characterized in that, The drying process involves hot air drying at 60-80 ℃ until the moisture content of the modified lithium slag powder is ≤ 1.0%.

9. The method for preparing low-carbon concrete using multi-solid waste modified lithium slag powder according to any one of claims 1-8, characterized in that, Includes the following steps: M1: Add cement, fly ash, granulated blast furnace slag powder, modified lithium slag powder and hydroxyapatite powder to the mixer and dry mix for 30-60 seconds; then add manufactured sand and crushed stone and continue to dry mix for 30-60 seconds. M2: Dissolve β-cyclodextrin and polycarboxylate superplasticizer in water to form a homogeneous solution, add it to a mixer and mix evenly to obtain low-carbon concrete made from lithium slag powder modified with solid waste.

10. The method for preparing low-carbon concrete using multi-solid waste modified lithium slag powder according to claim 9, characterized in that, The homogeneous solution was added to the mixer in two batches. The first batch consisted of 70% of the solution, and the mixture was stirred for 30-40 seconds. The remaining solution was added in the second batch, and the mixture was stirred for another 90-120 seconds to obtain low-carbon concrete made from lithium slag powder modified with solid waste.

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