Low-carbon concrete based on waste lithium slag and lithium slag resource utilization method

Abstract

The invention discloses low-carbon concrete based on waste lithium slag. The low-carbon concrete is characterized by comprising the following components in parts by weight: 100-150 parts of cement, 50-80 parts of fly ash, 130-150 parts of modified lithium slag composite powder, 900-950 parts of fine aggregate, 1050-1150 parts of coarse aggregate, 6-10 parts of a water reducing agent and 160-180 parts of water, the modified lithium slag composite powder is prepared from the following components in parts by weight: 75 to 80 parts of lithium slag, 8 to 12 parts of mineral powder, 5 to 10 parts of light calcined magnesia, 2 to 4 parts of limestone powder, 0.1 to 0.2 part of nano SiO2 powder and 0.1 to 0.2 part of gamma-phase nano aluminum oxide; by improving the activity, dispersion and apparent morphology of the lithium slag, the harm of the lithium slag to the durability of the concrete is reduced, and the proportion of the lithium slag in a cementing material is increased, so that the cement consumption is reduced, and the effects of concrete production cost, energy conservation and emission reduction are achieved.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and specifically relates to a low-carbon concrete. Background Technology

[0002] my country has abundant lithium ore resources, mainly spodumene and lepidolite. However, the extraction of lithium from these ores generates a large amount of lithium slag. Therefore, it is crucial to achieve comprehensive utilization of this lithium slag.

[0003] Currently, lithium slag has the following problems in its application: (1) The irregular surface structure of lithium slag leads to poor dispersion in concrete, rapid loss of concrete workability, and large amount of admixtures. (2) Literature shows that lithium slag has high active components, but its hydration activity cannot be fully utilized when it is directly used as an admixture in concrete. (3) The SO3 content in lithium slag (in the form of gypsum) is higher than 6%, and a high amount may cause poor stability.

[0004] There have been attempts to add lithium slag into concrete building materials for resource utilization: CN112079589 A discloses a modified lithium slag composite mineral admixture, comprising 40-70 parts of acid-process lithium slag, 20-55 parts of limestone powder, 5-10 parts of active calcium salt modifier, and 0.1-0.2 parts of reinforcing activator. This method increases the activity of the lithium slag by providing an active calcium salt modifier, but it does not solve the problem of high SO3 content in the lithium slag and insufficient durability when used in large-scale applications.

[0005] CN112374838 A discloses a lithium slag concrete and its preparation method, comprising 40-70 parts cement, 10-20 parts fly ash, 30-50 parts water, 170-230 parts sand, and 240-300 parts gravel. The concrete raw materials also include admixtures and modified lithium slag material. The admixtures include the following raw materials by weight: 1.5-3 parts water-reducing agent and 1.2-3 parts polyvinyl alcohol fiber. The modified lithium slag material is mainly made from the following raw materials by weight: 10-20 parts lithium slag powder, 0.2-1 parts cyclohexylaminomethyltriethoxysilane, and 0.1-0.4 parts ethyl cellulose. This method focuses on improving the flexural and crack resistance of lithium slag concrete, but it still does not solve the problem of high SO3 content in lithium slag, which prevents its large-scale application. Summary of the Invention

[0006] To address the problem of insufficient durability when lithium slag is applied to concrete at high concentrations due to its high SO3 content, this invention provides a low-carbon concrete based on waste lithium slag. By improving the activity, dispersion, and appearance morphology of lithium slag, the harmful effects of lithium slag on concrete durability are reduced, and the proportion of lithium slag in cementitious materials is increased, thereby reducing cement usage and achieving concrete production cost reduction and energy conservation and emission reduction effects.

[0007] A low-carbon concrete based on waste lithium slag, the composition of which is as follows by weight: 100-150 parts cement, 50-80 parts fly ash, 130-150 parts modified lithium slag composite powder, 900-950 parts fine aggregate, 1050-1150 parts coarse aggregate, 6-10 parts water-reducing agent, and 160-180 parts water. The modified lithium slag composite powder is composed of the following parts by weight: 75-80 parts lithium slag, 8-12 parts mineral powder, 5-10 parts lightly calcined magnesium oxide, 2-4 parts limestone powder, 0.1-0.2 parts nano-SiO2 powder, and 0.1-0.2 parts γ-phase nano-alumina.

[0008] According to the above scheme, the coarse aggregate is crushed stone or pebble crushed stone with a continuous gradation of 5-25mm and a needle-like and flaky content of less than 6%.

[0009] According to the above scheme, the fine aggregate fineness modulus is 2.5 to 2.8, and it is medium sand in zone two.

[0010] According to the above scheme, the water-reducing agent is a polycarboxylate water-reducing agent.

[0011] According to the above scheme, the cement is PO42.5 cement.

[0012] According to the above scheme, the fly ash is one or both of Grade I fly ash and Grade II fly ash.

[0013] According to the above scheme, the lithium slag powder is a by-product of the spodumene process for lithium extraction, with a moisture content of 10-20% and an apparent density of 2.4-2.5 g / cm³. 3 Specific surface area is 600 m² 2 / kg~900 m 2 / kg.

[0014] According to the above scheme, the mineral powder is S95 mineral powder.

[0015] According to the above scheme, the lightly calcined magnesium oxide has a density of 3.0~3.2 g / cm³. 3 The active magnesium oxide (α-MgO) content is ≥63%.

[0016] According to the above scheme, the specific surface area of ​​the limestone powder is ≥400 m². 2 / kg, with a fineness of 6%~8%.

[0017] According to the above scheme, the particle size of the nano-SiO2 is 20~50nm, and the specific surface area is 200~250m². 2 / g.

[0018] According to the above scheme, the γ-phase nano-alumina particles have a particle size of 40~60nm and a specific surface area of ​​100~150m².2 / g.

[0019] Another objective of this invention is to provide a method for the resource utilization of lithium slag.

[0020] A method for the resource utilization of lithium slag includes the following steps: (1) Process lithium slag, mineral powder, and limestone powder in a grinding mill for 8-10 minutes; (2) Add lightly calcined magnesium oxide, nano-SiO2 powder, and γ-phase nano-alumina, and continue processing for 5-7 minutes to obtain modified lithium slag composite powder; (3) The modified lithium slag composite powder is mixed with cement, fly ash, fine aggregate, coarse aggregate, water-reducing agent and water to prepare low-carbon concrete.

[0021] According to the above scheme, the grinding mill is a stirred mill with a stirring speed of 800~1000 rpm.

[0022] According to the above scheme, the dosage of each component should refer to the above-mentioned low-carbon concrete based on waste lithium slag.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention improves the activity and dispersibility of lithium slag through grinding, and modifies the lithium slag by introducing mineral powder, lightly calcined magnesium oxide, nano-SiO2 powder, γ-phase nano-alumina, and limestone powder. During the grinding process, the lightly calcined magnesium oxide first dissolves in the moisture brought in by the lithium slag, creating a strongly alkaline environment that causes the glassy structure in the lithium slag and mineral powder to dissociate and release Mg. 2+ , Ca 2+ And Al 3+ Layered bimetallic hydroxides were generated under the facilitation of γ-phase nano-alumina and limestone powder. At the same time, the reaction also removes impurities from the surface of lithium slag and improves the surface morphology.

[0024] The modified lithium slag composite powder is added to concrete, forming a layered bimetallic hydroxide. The structure can capture SO4 2- And generate stable Reduce SO4 in concrete 2- Concentration. On the other hand, γ-phase nano-alumina can also participate in CSH structural recombination by delaying the formation of ettringite and in conjunction with the action of nano-SiO2 powder, thereby improving its degree of polymerization and calcium retention capacity, and thus enhancing the durability of lithium slag concrete.

[0025] This invention modifies lithium slag to improve its activity, dispersion, and appearance, reduces the harmful effects of SO3 in lithium slag on concrete durability, and increases the proportion of lithium slag in cementitious materials, thereby reducing cement usage and achieving concrete production cost reduction and energy conservation and emission reduction effects. Attached Figure Description

[0026] Figure 1 Scanning electron microscope image of unmodified lithium slag.

[0027] Figure 2 Scanning electron microscope image of modified lithium slag. Detailed Implementation

[0028] The principles and features of the present invention are described below with reference to specific embodiments. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that in the description of the embodiments in this application, the term "some specific embodiments" means that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same implementation or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0029] A specific embodiment provides a low-carbon concrete based on waste lithium slag, the composition of which is as follows by weight: 100-150 parts cement, 50-80 parts fly ash, 130-150 parts modified lithium slag composite powder, 900-950 parts fine aggregate, 1050-1150 parts coarse aggregate, 6-10 parts water-reducing agent, and 160-180 parts water. The modified lithium slag composite powder is composed of the following parts by weight: 75-80 parts lithium slag, 8-12 parts mineral powder, 5-10 parts lightly calcined magnesium oxide, 2-4 parts limestone powder, 0.1-0.2 parts nano-SiO2 powder, and 0.1-0.2 parts γ-phase nano-alumina.

[0030] In some specific embodiments, the coarse aggregate is crushed stone or pebble crushed stone with a continuous gradation of 5-25mm and a needle-like and flaky content of less than 6%.

[0031] In some specific embodiments, the fine aggregate has a fineness modulus of 2.5 to 2.8 and is medium sand in zone two.

[0032] In some specific embodiments, the water-reducing agent is a polycarboxylate water-reducing agent.

[0033] In some specific embodiments, the cement is PO42.5 cement.

[0034] In some specific embodiments, the fly ash is one or both of Class I fly ash and Class II fly ash.

[0035] In some specific embodiments, the lithium slag powder is a by-product of the spodumene acid process for lithium extraction, with a moisture content of 10-20% and an apparent density of 2.4-2.5 g / cm³. 3 Specific surface area is 600 m²2 / kg~900 m 2 / kg.

[0036] In some specific embodiments, the mineral powder is S95 mineral powder.

[0037] In some specific embodiments, the lightly calcined magnesium oxide has a density of 3.0~3.2 g / cm³. 3 The active magnesium oxide (α−MgO) content is ≥63%.

[0038] In some specific embodiments, the limestone powder has a specific surface area ≥ 400 m². 2 / kg, with a fineness of 6%~8%.

[0039] In some specific embodiments, the nano-SiO2 has a particle size of 20-50 nm and a specific surface area of ​​200-250 m². 2 / g.

[0040] In some specific embodiments, the γ-phase nano-alumina particles have a particle size of 40-60 nm and a specific surface area of ​​100-150 m². 2 / g.

[0041] A specific implementation also provides a method for the resource utilization of lithium slag, including the following steps: (1) Process lithium slag, mineral powder, and limestone powder in a grinding mill for 3-5 minutes; (2) Add lightly calcined magnesium oxide, nano-SiO2 powder, and γ-phase nano-alumina, and continue stirring for 2-3 minutes to obtain modified lithium slag composite powder; (3) The modified lithium slag composite powder is mixed with cement, fly ash, fine aggregate, coarse aggregate, water-reducing agent, and water to prepare low-carbon concrete. In some specific embodiments, the dosage of each component is the same as that of the low-carbon concrete based on waste lithium slag described above.

[0042] In the following specific embodiments, lithium slag powder is used as a by-product of the spodumene process for lithium extraction, with a moisture content of 15% and an apparent density of 2.42 g / cm³. 3 Specific surface area is 680m² 2 / kg. Its scanning electron microscope image is attached. Figure 1 As shown.

[0043] Example 1 This embodiment provides a low-carbon concrete based on waste lithium slag: 120 parts cement, 50 parts fly ash, 130 parts modified lithium slag composite powder, 920 parts fine aggregate, 1080 parts coarse aggregate, 6 parts water-reducing agent, and 160 parts water.

[0044] A modified lithium slag composite powder, the preparation method of which is as follows: S1. Weigh out 80 parts of lithium slag, 10 parts of mineral powder, 6 parts of MgO, 4 parts of limestone powder, 0.1 parts of nano-SiO2, and 0.1 parts of γ-phase nano-alumina.

[0045] S2. First, put lithium slag, mineral powder and limestone powder into a mixing mill and stir for 800~1000 rpm for 8 minutes.

[0046] S3. Add the stated weight proportions of MgO, nano-SiO2, and γ-phase nano-alumina Al2O3, and continue stirring for 5 minutes.

[0047] The scanning electron microscope image of the modified lithium slag is attached. Figure 2 As shown. From the appendix Figure 1 and attached Figure 2 The comparison shows that the impurities on the surface of the modified lithium slag have been removed, and the surface morphology has become more compact.

[0048] Example 2 This embodiment provides a low-carbon concrete based on waste lithium slag: 100 parts cement, 50 parts fly ash, 150 parts modified lithium slag composite powder, 950 parts fine aggregate, 1100 parts coarse aggregate, 6 parts water-reducing agent, and 165 parts water.

[0049] A modified lithium slag composite powder, the preparation method of which is as follows: S1. 75 parts lithium slag, 12 parts mineral powder, 10 parts MgO, 3 parts limestone powder, 0.1 parts nano SiO2, and 0.1 parts γ-phase nano alumina.

[0050] S2. First, put lithium slag, mineral powder and limestone powder into a mixing mill and stir for 800~1000 rpm for 8 minutes.

[0051] S3. Add the stated weight proportions of MgO, nano-SiO2, and γ-phase nano-alumina Al2O3, and continue stirring for 5 minutes.

[0052] Example 3 This embodiment provides a low-carbon concrete based on waste lithium slag: 100 parts cement, 50 parts fly ash, 150 parts modified lithium slag composite powder, 950 parts fine aggregate, 1100 parts coarse aggregate, 6 parts water-reducing agent, and 165 parts water.

[0053] A modified lithium slag composite powder, the preparation method of which is as follows: S1. 77 parts lithium slag, 10 parts mineral powder, 9 parts MgO, 4 parts limestone powder, 0.2 parts nano SiO2, and 0.1 parts γ-phase nano alumina.

[0054] S2. First, put lithium slag, mineral powder and limestone powder into a mixing mill and stir for 800~1000 rpm for 8 minutes.

[0055] S3. Add the stated weight proportions of MgO, nano-SiO2, and γ-phase nano-alumina Al2O3, and continue stirring for 5 minutes.

[0056] Example 4: This embodiment provides a low-carbon concrete based on waste lithium slag: 100 parts cement, 50 parts fly ash, 150 parts modified lithium slag composite powder, 950 parts fine aggregate, 1100 parts coarse aggregate, 6 parts water-reducing agent, and 165 parts water.

[0057] A modified lithium slag composite powder, the preparation method of which is as follows: S1. 77 parts lithium slag, 10 parts mineral powder, 9 parts MgO, 4 parts limestone powder, 0.2 parts nano SiO2, and 0.2 parts γ-phase nano alumina.

[0058] S2. First, put lithium slag, mineral powder and limestone powder into a mixing mill and stir for 9 minutes at a stirring speed of 800~1000 rpm.

[0059] S3. Add the stated weight proportions of MgO, nano-SiO2, and γ-phase nano-alumina Al2O3, and continue stirring for 7 minutes.

[0060] Comparative Example 1: Repeat Example 1, except that the amount of MgO added is 14 parts, and the rest remain the same.

[0061] Comparative Example 2: Repeat Example 1, but without adding limestone powder, and keep everything else the same.

[0062] Comparative Example 3: Repeat Example 1, except that the amount of γ-phase nano-alumina added is changed to 0.4 parts, and the rest remains unchanged.

[0063] Comparative Example 4: Repeat Example 1, but without adding γ-phase nano-alumina, and keep everything else the same.

[0064] Comparative Example 5: Repeat Example 1, except that the lithium slag composite powder is directly mixed without grinding, and the rest remains unchanged.

[0065] The mechanical and durability properties of the concrete obtained in the above embodiments and comparative examples were tested. The mechanical properties of the concrete were tested according to the "GB / T 50081-2019 Standard for Test Methods of Physical and Mechanical Properties of Concrete", and the sulfate resistance of the concrete was tested according to the "GB / T 50082-2009 Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The test results are shown in Table 1. Table 1

[0066] The test data show that the concrete in Examples 1-4 has good workability and its strength meets the standard requirements for concrete.

[0067] Comparative Example 1 used excessive MgO, resulting in poor concrete fluidity, high early strength, reduced later strength, and decreased durability. Its resistance to sulfate attack was slightly reduced, and its 28-day strength did not meet the requirements for C30 concrete.

[0068] In Comparative Example 2, CaCO3 was not used during the lithium slag modification treatment, resulting in insufficient amount of layered bimetallic hydroxides generated, reduced resistance to sulfate attack, and fewer sulfate attack cycles compared to the Example.

[0069] In Comparative Example 3, excessive γ-phase nano-alumina was added during the lithium slag modification process, which led to excessive reaction of the active substances. The activity of the modified lithium slag decreased, and the strength at 7 days and 28 days decreased, failing to meet the requirements of C30 concrete.

[0070] In Comparative Example 4, no γ-phase nano-alumina was used during lithium slag modification treatment, resulting in insufficient amount of layered bimetallic hydroxides, reduced resistance to sulfate attack, and high calcium silicate content in the CSH gel generated after concrete hydration, leading to lower durability.

[0071] Comparative Example 5: The lithium slag composite powder was used directly after mixing without grinding. The lithium slag composite powder had low activity, and the concrete prepared from it had insufficient strength and poor workability.

[0072] The above description is only a preferred embodiment 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 should be included within the protection scope of the present invention.

Claims

1. A low-carbon concrete based on waste lithium slag, characterized in that... The composition by weight is as follows: 100-150 parts cement, 50-80 parts fly ash, 130-150 parts modified lithium slag composite powder, 900-950 parts fine aggregate, 1050-1150 parts coarse aggregate, 6-10 parts water-reducing agent, and 160-180 parts water. The modified lithium slag composite powder is composed of the following parts by weight: 75-80 parts lithium slag, 8-12 parts mineral powder, 5-10 parts lightly calcined magnesium oxide, 2-4 parts limestone powder, 0.1-0.2 parts nano-SiO2 powder, and 0.1-0.2 parts γ-phase nano-alumina.

2. The low-carbon concrete based on waste lithium slag as described in claim 1, characterized in that... The coarse aggregate is crushed stone or pebble crushed stone with a continuous gradation of 5-25mm and a needle-like and flaky content of less than 6%; the fine aggregate has a fineness modulus of 2.5-2.8 and is medium sand in Zone II; the water-reducing agent is a polycarboxylate water-reducing agent; the cement is PO42.5 cement; and the fly ash is one or both of Grade I and Grade II fly ash.

3. The low-carbon concrete based on waste lithium slag as described in claim 1, characterized in that... The lithium slag powder is a byproduct of the spodumene process for lithium extraction, with a moisture content of 10-20% and an apparent density of 2.4-2.5 g / cm³. 3 Specific surface area is 600 m² 2 / kg~900 m 2 / kg.

4. The low-carbon concrete based on waste lithium slag as described in claim 1, characterized in that... The mineral powder is S95 mineral powder.

5. The low-carbon concrete based on waste lithium slag as described in claim 1, characterized in that... The lightly calcined magnesium oxide has a density of 3.0~3.2 g / cm³. 3 The active magnesium oxide content is ≥63%.

6. The low-carbon concrete based on waste lithium slag as described in claim 1, characterized in that... The specific surface area of ​​the limestone powder is ≥400 m². 2 / kg, with a fineness of 6%~8%.

7. The low-carbon concrete based on waste lithium slag as described in claim 1, characterized in that... The nano-SiO2 has a particle size of 20-50 nm and a specific surface area of ​​200-250 m². 2 / g.

8. The low-carbon concrete based on waste lithium slag as described in claim 1, characterized in that... The γ-phase nano-alumina particles have a particle size of 40-60 nm and a specific surface area of ​​100-150 m². 2 / g.

9. A method for the resource utilization of lithium slag, characterized in that... Includes the following steps: (1) Process lithium slag, mineral powder, and limestone powder in a grinding mill for 8-10 minutes; (2) Add lightly calcined magnesium oxide, nano-SiO2 powder, and γ-phase nano-alumina, and continue processing for 5-7 minutes to obtain modified lithium slag composite powder; (3) The modified lithium slag composite powder is mixed with cement, fly ash, fine aggregate, coarse aggregate, water-reducing agent and water to prepare low-carbon concrete; The raw material composition of the low-carbon concrete is as follows by weight: 100-150 parts cement, 50-80 parts fly ash, 130-150 parts modified lithium slag composite powder, 900-950 parts fine aggregate, 1050-1150 parts coarse aggregate, 6-10 parts water-reducing agent, and 160-180 parts water. The raw material composition of the modified lithium slag composite powder is as follows by weight: 75-80 parts lithium slag, 8-12 parts mineral powder, 5-10 parts lightly calcined magnesium oxide, 2-4 parts limestone powder, 0.1-0.2 parts nano SiO2 powder, and 0.1-0.2 parts γ-phase nano alumina.

10. The method for resource utilization of lithium slag as described in claim 9, characterized in that... The grinding mill described in step 1 is a stirred mill with a stirring speed of 800~1000 rpm.

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