Lithium slag light aggregate foam concrete and preparation method thereof

Abstract

This invention belongs to the field of foamed concrete production technology, and particularly relates to a lithium slag lightweight aggregate foamed concrete and its preparation method. It is made by mixing lithium slag lightweight aggregate, foam, and cement-based slurry at a mass fraction of 180-350:40-50:300-500. The cement-based slurry is made by mixing cement, fly ash, slag powder, silica fume, lithium slag fine powder, polycarboxylate superplasticizer, waterproofing agent, anti-settling agent, and water at a mass fraction of 800-600:0-200:0-300:0-100:0-300:1-3:5-10:1-3:300-400. The lithium slag content in the lithium slag lightweight aggregate foamed concrete product is no more than 72%. The lithium slag lightweight aggregate foamed concrete mixture of this invention does not stratify or settle. The hardened lithium slag lightweight aggregate foamed concrete has low drying shrinkage, low water absorption, and high strength, resulting in significant environmental and economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of foamed concrete production technology, and particularly relates to a lithium slag lightweight aggregate foamed concrete and its preparation method. Background Technology

[0002] With the maturing supply of traditional energy sources such as oil and coal, new energy sources such as hydropower, geothermal energy, and wind power, due to their advantages of being clean, environmentally friendly, less polluting, and sustainable, have become the vanguard of the future new energy industry. This has led to a surge in market demand for new energy storage materials. With the strong rise of the new energy storage industry, represented by lithium batteries, China, as one of the major lithium battery producers, has seen significant development in its lithium salt industry, including lithium carbonate, lithium hydroxide, and lithium chloride. However, the corresponding industrial waste, lithium slag, is increasing year by year. Typically, producing one ton of lithium salt generates 8-10 tons of lithium slag. It is estimated that my country currently has tens of millions of tons of lithium slag stockpiles. The accumulation of lithium slag causes significant land waste and environmental pollution. How to rationally dispose of and utilize lithium slag is a major technical challenge facing industrial upgrading.

[0003] Currently, lithium slag is mainly used in the building materials industry. Lithium slag can be incorporated into cement-based materials (including mortar, concrete, and foamed concrete) at a rate of 20% to 30%, as illustrated by patents CN108609925A and CN114656280A. Given the current stockpile of lithium slag and the pressure of newly added lithium slag each year, new technologies are needed to further improve the utilization rate of lithium slag. Furthermore, current lightweight foamed concrete products suffer from problems such as low strength, high drying shrinkage, and high water absorption. Summary of the Invention

[0004] The purpose of this invention is to provide a lithium slag lightweight aggregate foamed concrete and its preparation method. This application achieves a comprehensive effect by incorporating lithium slag lightweight aggregate, which increases the strength of foamed concrete, reduces the drying shrinkage of foamed concrete, and reduces the water absorption rate. At the same time, it increases the lithium slag content in the product (i.e., the total lithium slag content in the product exceeds 70%), which has significant environmental and economic benefits.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A lithium slag lightweight aggregate foamed concrete, wherein 1 cubic meter of lithium slag lightweight aggregate foamed concrete is composed of lithium slag lightweight aggregate, foam, and cement-based slurry mixed in a mass fraction of 180~350:40~50:300~500; the cement-based slurry is composed of cement, fly ash, slag powder, silica fume, lithium slag fine powder, polycarboxylate superplasticizer, waterproofing agent, anti-settling agent, and water mixed in a mass fraction of 800~600:0~200:0~300:0~100:0~300:1~3:5~10:1~3:300~400, and mechanically stirred to form a uniform slurry; the lithium slag content in the lithium slag lightweight aggregate foamed concrete product of this invention is not higher than 72%, and the dry density of the product is ≤630kg / m³. 3 Compressive strength ≥ 3.0 MPa, thermal conductivity ≤ 0.14 W / (m˙K), volumetric water absorption ≤ 15%, drying shrinkage ≤ 2.0 (mm / m).

[0007] Furthermore, the lithium slag lightweight aggregate is formed directly from lithium ore through grinding, adding reagents, pelletizing, calcining at 900-1000℃, and then extracting lithium carbonate and lithium hydroxide through liquid leaching, or by further preparing powdered lithium slag into lightweight aggregate, with a bulk density of 500-700 kg / m³. 3 Porosity 38-42%, approximately spherical particles with diameter 6-8mm, and compressive strength 1-2MPa;

[0008] Furthermore, the foam is a nanoscale pore size foam produced by mixing a foaming agent, a foam stabilizer, and water in a mass fraction of 1~3:10~80:917~989 and mechanically stirring. The foaming agent is one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and fatty acid polyoxyethylene ether; the foam stabilizer is one or more of methylcellulose, hydroxypropyl cellulose ether, hydroxyethyl cellulose ether, nano-bentonite, nano-calcium carbonate, nano-silica, nano-alumina, nano-titanium dioxide, carbon-based materials (graphite, graphene, carbon nanotubes, etc.), micron-sized aluminosilicate mineral powder, and rare earth powder.

[0009] Furthermore, the cement is 52.5 grade ordinary Portland cement; the fly ash is grade 1 or grade 2 fly ash; the slag powder is grade 105 or grade 95; the silica fume has a silica content of ≥85%; the lithium slag fine powder is composed of fine particles (fine particles ≤5µm) ≥50% after ball milling of lithium slag; the waterproofing agent is one or more of emulsified paraffin wax, organosilicon waterproofing agent, and stearates (calcium, zinc, magnesium, etc.); the anti-settling agent is one or more of nano-bentonite, nano-calcium carbonate, and nano-silica.

[0010] A method for preparing lithium slag lightweight aggregate foamed concrete includes mixing foam and cement-based slurry to form a homogeneous foam mixture; then adding lithium slag lightweight aggregate to the foam mixture and stirring evenly to prepare a lithium slag lightweight aggregate foamed concrete mixture; after curing, hardened lithium slag lightweight aggregate foamed concrete is obtained; the lithium slag lightweight aggregate is required to be water-saturated and surface-dry before being added to the foam mixture; the curing of the lithium slag lightweight aggregate foamed concrete after molding includes: room temperature and moisturizing for more than 14 days; heating to 50℃~70℃ and moisturizing for more than 24 hours.

[0011] The optimal mix proportion of lithium slag lightweight aggregate foamed concrete provided by this invention (maximum lithium slag content, 72%) has a dry density of 616 kg / m³. 3 It has a compressive strength of 3.2 MPa, a thermal conductivity of 0.14 W / (m·K), a volumetric water absorption rate of 8.0%, and a drying shrinkage value of 1.5 (mm / m).

[0012] Mechanism: This invention analyzes the mechanism by which the lithium slag lightweight aggregate foamed concrete exhibits a significantly lower drying shrinkage value compared to ordinary foamed concrete. Foamed concrete is formed by adding foam to cement-based slurry. Since foam is formed by encapsulating air in a liquid film, the foam introduced into foamed concrete is essentially water introduced. The drying process of foamed concrete after setting and hardening is a water evaporation process, and the amount of water evaporation is positively correlated with the magnitude of the product's drying shrinkage. This explains the high drying shrinkage of foamed concrete. The lithium slag lightweight aggregate of this invention is directly formed during the process of grinding lithium ore, adding reagents, pelletizing, calcining at 900-1000℃, and then extracting lithium carbonate and lithium hydroxide through liquid leaching. Alternatively, it can be prepared from powdered lithium slag into lightweight aggregate, with a bulk density of 500-700 kg / m³. 3 The lithium slag lightweight aggregate consists of approximately spherical particles with a porosity of 38-42%, a diameter of 6-10 mm, and a compressive strength of 1-2 MPa. During the preparation of foamed concrete, the lithium slag lightweight aggregate is controlled to a saturated surface-dry state. This type of aggregate is volumetrically stable and does not absorb water from the foamed concrete. As the amount of lithium slag lightweight aggregate replacing foamed concrete increases, the foam content decreases, leading to reduced drying shrinkage. Furthermore, the lithium slag lightweight aggregate, being calcined or reshaped particles, is volumetrically stable and possesses a certain strength. During the drying shrinkage process of foamed concrete, the lithium slag lightweight aggregate can resist the stress generated by the drying shrinkage, resulting in a significant reduction in the drying shrinkage value of the lithium slag lightweight aggregate foamed concrete, thus preventing cracking during the drying process.

[0013] The lithium slag lightweight aggregate foamed concrete provided by this invention has higher strength, lower drying shrinkage, and lower water absorption compared to ordinary foamed concrete because it is composed of a three-phase composite of lithium slag lightweight aggregate, foamed concrete, and their interface. The drying shrinkage and water absorption of lithium slag lightweight aggregate foamed concrete mainly originate from the cement foamed concrete. The lithium slag lightweight aggregate, due to high-temperature calcination, exhibits good volume stability. Although its inherent water absorption is relatively high, it is encapsulated by cement hydration products in the product, significantly reducing or eliminating water absorption. While the compressive strength of lithium slag lightweight aggregate is relatively low (1-2 MPa), its breaking strength in the product is approximately 5-12 MPa (5-6 times its compressive strength). Furthermore, lithium slag lightweight aggregate is a porous material with active silica, alumina, and gypsum on its surface, resulting in strong bonding strength with cement. Therefore, according to the basic theory of composite materials, in lithium slag lightweight aggregate foamed concrete, as the content of lithium slag lightweight aggregate increases while the content of cement paste remains constant and the content of foam decreases, the density and volume of the cement foamed concrete increase, resulting in increased product strength, decreased drying shrinkage, and reduced water absorption. Conversely, in lithium slag lightweight aggregate foamed concrete, as the content of lithium slag lightweight aggregate increases while the product density remains essentially constant, the content of cement paste and foam decreases, resulting in decreased drying shrinkage, unchanged strength, and reduced water absorption.

[0014] The advantages of this invention are:

[0015] 1. Lithium slag lightweight aggregate has good volume stability due to high-temperature calcination. It also has high resistance to damage and does not absorb water. As the amount of lithium slag lightweight aggregate in the product increases, the volume of cement foam concrete decreases, resulting in a decrease in product drying shrinkage, an increase in strength, and a decrease in water absorption.

[0016] 2. After high-temperature calcination and rapid cooling, the content of inert components such as spodumene in lithium slag and olivine in nickel slag is reduced and transformed into amorphous components such as silica and alumina, which improves the activity. After grinding, lithium slag can replace about 20-30% of cement without reducing strength. The lithium slag content in this product exceeds 70%, resulting in significant environmental and economic benefits.

[0017] 3. The foam in this invention is composed of a foaming agent, a foam stabilizer, and water, wherein the foam stabilizer is mainly composed of nanomaterials, which is beneficial to the stability of the bubbles. Detailed Implementation

[0018] Example 1

[0019] Example 1 serves as a blank control group. The lithium slag lightweight aggregate and the lithium slag fine powder in the cement-based slurry both contain zero content. Specifically, 1 cubic meter of foamed concrete is composed of foam and cement-based slurry mixed at a mass fraction of 55:700. The cement-based slurry is composed of cement, fly ash, slag powder, silica fume, lithium slag fine powder, polycarboxylate superplasticizer, waterproofing agent, anti-settling agent, and water mixed at a mass fraction of 800~600:0~200:0~300:0~100:0:1~3:5~10:1~3:300~400, and mechanically stirred to form a uniform slurry. The foam is composed of foaming agent, foam stabilizer, and water mixed at a mass fraction of 1~3:10~80:917~989, and mechanically stirred to produce nanoscale pores. The foaming agent is dodecylbenzene sulfonate. The foam is composed of one or more of sodium sulfate, sodium dodecyl sulfate, and fatty acid polyoxyethylene ether; the foam stabilizer is composed of one or more of methyl cellulose, hydroxypropyl cellulose ether, hydroxyethyl cellulose ether, nano-bentonite, nano-calcium carbonate, nano-silica, nano-alumina, nano-titanium dioxide, carbon-based materials (graphite, graphene, carbon nanotubes, etc.), micron-sized aluminosilicate mineral powder, and rare earth powder, and is a nano-sized foam produced by mechanical stirring; the cement is 52.5 grade ordinary Portland cement; the fly ash is grade I or II fly ash; the slag powder is grade 105 or 95; the silica fume has a silica content ≥85%; the waterproofing agent is composed of one or more of emulsified paraffin wax, organosilicon waterproofing agent, and stearates (calcium, zinc, magnesium, etc.); the anti-settling agent is composed of one or more of nano-bentonite, nano-calcium carbonate, and nano-silica.

[0020] Example 2

[0021] A lithium slag lightweight aggregate foamed concrete, wherein 1 cubic meter of lithium slag lightweight aggregate foamed concrete is composed of lithium slag lightweight aggregate, foam, and cement-based paste mixed in a mass fraction of 180:50:500; the lithium slag lightweight aggregate is formed directly from lithium ore through grinding, adding reagents, pelletizing, calcining at 900-1000℃, and then extracting lithium carbonate and lithium hydroxide through liquid leaching, or by further preparing powdered lithium slag into lightweight aggregate, with a bulk density of 500 kg / m³. 3The foam consists of approximately spherical particles with a porosity of 40%, a diameter of 8 mm, and a compressive strength of 1.5 MPa. The foam is produced by mechanically mixing a foaming agent, a foam stabilizer, and water in a mass ratio of 1:40:959, resulting in a nano-sized pore size. The cement-based slurry is composed of cement, fly ash, slag powder, silica fume, lithium slag fine powder, polycarboxylate superplasticizer, waterproofing agent, anti-settling agent, and water in a mass ratio of 600:0:0:0:300:1:10:3:400, and is mechanically stirred into a homogeneous slurry. The foaming agent is one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and fatty acid polyoxyethylene ether. The foam stabilizer is one of methylcellulose, hydroxypropyl cellulose ether, hydroxyethyl cellulose ether, nano-bentonite, nano-calcium carbonate, nano-silica, nano-alumina, nano-titanium dioxide, carbon-based materials (graphite, graphene, carbon nanotubes, etc.), micron-sized aluminosilicate mineral powder, and rare earth powder. One or more of the following: foam with nanoscale pores produced by mechanical stirring; cement is 52.5 grade ordinary Portland cement; fly ash is grade I or II fly ash; slag powder is grade 105 or 95; silica fume has a silica content ≥85%; lithium slag fine powder is composed of fine particles (≤5µm) ≥50% after ball milling of lithium slag; waterproofing agent is one or more of emulsified paraffin wax, organosilicon waterproofing agent, stearates (calcium, zinc, magnesium, etc.); anti-settling agent is one or more of nano-bentonite, nano-calcium carbonate, and nano-silica.

[0022] The preparation method of lithium slag lightweight aggregate foamed concrete in this embodiment is as follows: after mixing foam and cement-based slurry, stir to form a uniform foam mixture; then add lithium slag lightweight aggregate to the foam mixture and stir evenly to prepare lithium slag lightweight aggregate foamed concrete mixture; after curing, hardened lithium slag lightweight aggregate foamed concrete is obtained.

[0023] Example 3

[0024] The difference between Example 3 and Example 2 is that 1 cubic meter of lithium slag lightweight aggregate foamed concrete is made by mixing lithium slag lightweight aggregate, foam, and cement-based paste in a mass fraction of 250:46:420.

[0025] Example 4

[0026] The difference between Example 4 and Example 2 is that 1 cubic meter of lithium slag lightweight aggregate foamed concrete is made by mixing lithium slag lightweight aggregate, foam, and cement-based paste in a mass fraction of 300:43:370.

[0027] Example 5

[0028] The difference between Example 5 and Example 2 is that 1 cubic meter of lithium slag lightweight aggregate foamed concrete is made by mixing lithium slag lightweight aggregate, foam, and cement-based paste in a mass fraction of 350:40:300.

[0029] Performance testing

[0030] The products prepared according to the proportions and preparation methods of Examples 1-5 were subjected to performance tests according to the performance test conditions required by national standards. The specific test results are shown in Table 1:

[0031] Table 1 shows the raw material proportions and some product parameters for 1 cubic meter of lithium slag lightweight aggregate foamed concrete.

[0032]

[0033] The product of this invention was tested for various properties according to the Chinese standard JC / T 2459-2018 (ceramsite foamed concrete), as detailed in Table 2.

[0034] Table 2 Experimental Data Table

[0035]

[0036] The experimental data in Table 2 show that: when preparing products of the same dry density grade (e.g., 600 kg / m³), 3 Grade, according to national standards, dry density ≤630kg / m³ 3 When the lithium slag aggregate content in the product increases, the volume of cement-based foamed concrete decreases, meaning both the cement-based paste and the foam content decrease. Results: Compared to the control group, when the product's dry density remained essentially constant, the increase in lithium slag aggregate led to an increase in strength (but the decrease in cement-based paste also led to a decrease in strength). As a result, the product's strength increased, drying shrinkage decreased, and water absorption decreased. When the lithium slag content in the product reached its maximum (cement-based paste decreased significantly), the product's strength remained essentially constant, drying shrinkage further decreased, and water absorption further decreased.

Claims

1. A lithium slag lightweight aggregate foamed concrete, characterized in that: The product is made by mixing lithium slag lightweight aggregate, foam, and cement-based slurry in a mass fraction of 180-350:40-50:300-500. The cement-based slurry is prepared by mixing cement, fly ash, slag powder, silica fume, lithium slag fine powder, polycarboxylate superplasticizer, waterproofing agent, anti-settling agent, and water in a mass fraction of 800-600:0-200:0-300:0-100:0-300:1-3:5-10:1-3:300-400. The lithium slag content in the lithium slag lightweight aggregate foamed concrete product is no more than 72%, and the product dry density is ≤630 kg / m³. 3 The compressive strength is ≥3.0 MPa, thermal conductivity is ≤0.14 W / (m·K), volumetric water absorption is ≤15%, and drying shrinkage is ≤2.0 (mm / m). The lithium slag lightweight aggregate is either directly formed during the extraction of lithium carbonate and lithium hydroxide from lithium ore or prepared from powdered lithium slag, with a bulk density of 500~700 kg / m³. 3 Approximately spherical particles with a porosity of 38-42%, a diameter of 6-10 mm, and a cylinder compressive strength of 1-2 MPa.

2. The lithium slag lightweight aggregate foamed concrete as described in claim 1, characterized in that: The foam is a mixture of foaming agent, foam stabilizer, and water in a mass fraction of 1~3:10~80:917~989, and is produced by mechanical stirring to form a foam with nanoscale pores. The foaming agent is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and fatty acid polyoxyethylene ether. The foam stabilizer is at least one of methylcellulose, hydroxypropyl cellulose ether, hydroxyethyl cellulose ether, nano-bentonite, nano-calcium carbonate, nano-silica, nano-alumina, nano-titanium dioxide, carbon-based materials, micron-sized aluminosilicate mineral powder, and rare earth powder, and is produced by mechanical stirring to form a foam with nanoscale pores.

3. The lithium slag lightweight aggregate foamed concrete as described in claim 1, characterized in that: The cement is grade 42.5 or 52.5 ordinary Portland cement; the fly ash is grade 1 or 2 fly ash; the slag powder is grade 105 or 95; the silica fume has a silica content of ≥85%; the lithium slag fine powder is composed of fine particles of lithium slag after ball milling with ≥50%; the waterproofing agent is at least one of emulsified paraffin wax, organosilicon waterproofing agent, and stearate; the anti-settling agent is at least one of nano-bentonite, nano-calcium carbonate, and nano-silica.

4. The method for preparing lithium slag lightweight aggregate foamed concrete as described in any one of claims 1-3, characterized in that, Includes the following steps: After mixing foam and cement-based slurry, stir to form a uniform foam mixture; then add lithium slag lightweight aggregate to the foam mixture and stir evenly to prepare lithium slag lightweight aggregate foam concrete mixture; keep at room temperature and moist for more than 14 days; heat to 50℃~70℃ and keep moist for more than 24 hours to obtain hardened lithium slag lightweight aggregate foam concrete; wherein, the lithium slag lightweight aggregate is water-saturated and surface-dry before being added to the foam mixture.

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