Composite water reducing agent for lithium slag concrete, preparation method and application thereof

Abstract

The present application relates to a kind of lithium residue concrete with composite water-reducing agent, preparation method and its application, composite water-reducing agent includes the following weight parts of raw materials: 40-60 parts siloxane modified polycarboxylic acid polymer solution, 25-40 parts POSS base silane coupling agent, 3-5 parts polyethylene glycol, 20-25 parts alkali excitation agent, POSS base silane coupling agent is made by acryloyloxy silane, aminopropyl heptyl-cage polysilsesquioxane occurs Michael addition reaction at molar ratio 1:1-1.03;Siloxane modified polycarboxylic acid polymer solution is made by polymerization monomer monoalkenyl polyether monomer, acrylic monomer, monoalkenyl dibasic acid, unsaturated siloxane in solution at molar ratio 1:2-3:2-3:0.1-0.3 polymerization, and the solid content of polycarboxylic acid polymer solution is 40-50wt%.Under the synergistic and balanced effect of each component of composite water-reducing agent, the workability of lithium residue concrete can be significantly improved, and the water-reducing effect of water-reducing agent is fully played.

Description

Technical Field

[0001] This invention belongs to the technical field of polycarboxylate superplasticizers, specifically relating to a composite superplasticizer for lithium slag concrete, its preparation method, and its application. Background Technology

[0002] Lithium slag (lithium carbonate slag) is an industrial waste residue produced during the sulfuric acid process for lithium carbonate production. It has a yellowish-brown appearance, a large internal surface area, and a porous structure, mostly in a glassy state and lacking hydraulic properties. The chemical composition of lithium slag is similar to that of clay, mainly consisting of SiO2, Al2O3, and Fe2O3. The SiO2 and Al2O3 in lithium slag are mostly in amorphous form, exhibiting high pozzolanic activity; therefore, lithium slag can be used as an admixture in concrete. Using lithium slag as an admixture in concrete preparation not only disposes of industrial solid waste lithium slag, but also reduces energy consumption and pollution emissions during cement production. It is an important way to achieve energy conservation, emission reduction, green and low-carbon development, and sustainable development, and has become a research hotspot in the concrete field. For example, patent CN110981322B discloses a nickel-iron slag aggregate concrete, which is composed of the following raw materials in parts by weight: 100-150 parts cement, 100-200 parts lithium slag powder, 1500-1800 parts nickel-iron slag aggregate, 100-300 parts nickel-iron slag powder, 5-20 parts water-reducing agent, 30-50 parts polymer emulsion, and 120-150 parts mixing water. Patent CN106316248B discloses a low-auto-shrinkage high-strength concrete prepared using waste slurry from a concrete mixing plant. By weight, it is composed of 300-340 parts cement, 90-130 parts lithium slag, 70-110 parts waste slurry from a concrete mixing plant, 696-739 parts river sand, 1044-1109 parts crushed stone, 8.5-10 parts shrinkage reducing agent, 4-6 parts water reducing agent, and 80-92 parts water.

[0003] The above examples illustrate the application of lithium slag as an admixture to replace cement in concrete preparation. This approach fully utilizes the pozzolanic activity of lithium slag while reducing cement usage to some extent, achieving efficient resource utilization and effective cost control. However, lithium slag has a large internal surface area and a porous structure, making it prone to adsorbing commonly used high-molecular-weight water-reducing agents, especially comb-type polycarboxylate superplasticizers. This reduces the effective water-reducing agent content in the concrete, resulting in lower slump, reduced fluidity, and poorer workability. In this scenario, increasing the water-cement ratio is necessary to reduce construction difficulty, but this can lead to bleeding, negatively impacting the durability of the concrete.

[0004] Therefore, it is necessary to develop a water-reducing agent for lithium slag concrete to improve the workability and durability of concrete using lithium slag as an admixture. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a composite water-reducing agent for lithium slag concrete, its preparation method, and its application. The composite water-reducing agent comprises a siloxane-modified polycarboxylate polymer solution, a POSS-based silane coupling agent, polyethylene glycol, and an alkali activator. The POSS-based silane coupling agent acts as a sacrificial agent, preferentially covering / filling the porous structure of the lithium slag surface under the action of polyethylene glycol, thus hindering the adsorption of siloxane-modified polycarboxylate polymer molecules by the lithium slag. The siloxane-modified polycarboxylate polymer ensures that it can both adsorb and encapsulate other cementitious particles in the concrete and easily adsorb onto lithium slag particles to exert its water-reducing effect. The alkali activator compensates for the decrease in lithium slag activity caused by the coverage of the POSS-based silane coupling agent. Through the synergistic and balanced effects of the above components, the workability of lithium slag concrete can be significantly improved, fully utilizing the water-reducing effect of the water-reducing agent.

[0006] To achieve the above objectives, the present invention adopts the following solution:

[0007] A composite water-reducing agent for lithium slag concrete comprises the following raw materials in parts by weight: 40-60 parts of siloxane-modified polycarboxylate polymer solution, 25-40 parts of POSS-based silane coupling agent, 3-5 parts of polyethylene glycol, and 20-25 parts of alkali activator. The POSS-based silane coupling agent is prepared by a Michael addition reaction of acryloyloxysilane and aminopropylheptyl-cage polysilsesquioxane at a molar ratio of 1:1-1.03. The siloxane-modified polycarboxylate polymer solution is prepared by polymerizing monoalkenyl polyether monomers, acrylic monomers, monoalkenyl diacids, and unsaturated siloxanes in solution at a molar ratio of 1:2-3:2-3:0.1-0.3. The solid content of the polycarboxylate polymer solution is 40-50 wt%.

[0008] The acryloyloxysilane is selected from one or more combinations of (3-acryloyloxypropyl)trimethoxysilane, 3-acryloyloxypropylmethyldimethoxysilane, (methacryloyloxymethyl)triethoxysilane, (methacryloyloxymethyl)methyldiethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, methacryloyloxypropylmethyldiethoxysilane, acryloyloxypropyltrimethoxysilane, methacryloyloxymethyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-trimethoxysilane propylene acrylate, and 3-(triethoxysilyl)propyl methacrylate.

[0009] The POSS-based silane coupling agent is prepared by a method comprising the following steps:

[0010] Under an inert atmosphere, acryloyloxysilane and aminopropylheptyl-cage polysilsesquioxane were added to an organic solvent, a catalyst was added, and the reaction was carried out under controlled temperature. After the reaction was completed, the mixture was distilled under reduced pressure to obtain a POSS-based silane coupling agent.

[0011] The organic solvent is selected from one or more combinations of benzene, toluene, acetone, tetrahydrofuran, and chloroform. The temperature is controlled at 30-60℃, and the reaction time is 3-8 hours. The catalyst is selected from one or more combinations of triethylamine, tetramethylbutanediamine, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, and N-ethylmorpholine. The amount of catalyst used is 1-2% of the combined molar amounts of acryloyloxysilane and aminopropylheptyl-cage polysilsesquioxane.

[0012] The monoalkenyl polyether monomers have a weight-average molecular weight of 2400-3000 and are selected from one or a combination of two of allyl polyoxyethylene ether and allyl polyoxypropylene ether; the acrylic monomers are selected from one or a combination of two of acrylic acid and methacrylic acid; the monoalkenyl dicarboxylic acid is selected from one or a combination of two of itaconic acid, maleic acid, fumaric acid, and citraconic acid; the unsaturated siloxane is selected from one or a combination of two or more of allyltrimethoxysilane, allyltriethoxysilane, 3-butenetriethoxysilane, vinyltrimethylsilane, vinyltriethoxysilane, vinyldimethoxysilane, and vinylmethyldimethoxysilane.

[0013] The siloxane-modified polycarboxylate polymer solution is prepared by a method comprising the following steps:

[0014] Under an inert atmosphere, monoalkenyl polyether monomers, acrylic monomers, monoalkenyl dicarboxylic acids, unsaturated siloxanes, and molecular weight regulators are added to water and mixed evenly. The mixture is heated, and an initiator solution is added dropwise. The mixture is then reacted at a constant temperature. After the reaction is complete, the pH and solid content are adjusted to obtain a siloxane-modified polycarboxylic acid polymer solution.

[0015] The molecular weight regulator is selected from one or more combinations of mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, and isopropanol. The amount of the molecular weight regulator is 0.8-1.5 wt% of the total amount of polymeric monomers. The temperature is raised to 80-100℃, and the isothermal reaction time is 3-8 hours. The initiator solution concentration is 5-10 wt%, and the solvent is water. The initiator is selected from one or more combinations of ammonium persulfate, potassium persulfate, and sodium persulfate, and the amount of initiator is 1-3 wt% of the total amount of polymeric monomers. The initiator solution is added dropwise over 0.5-1 hour. The pH is adjusted to 7-9 using a 30-40 wt% alkaline solution, which is selected from one or more combinations of sodium hydroxide solution and potassium hydroxide solution. The solid content is adjusted to 40-50 wt% of the polycarboxylic acid polymer solution by adding water or distillation.

[0016] The number average molecular weight of the polyethylene glycol is 600-1000.

[0017] The activator is selected from one or a combination of two or more of sodium hydroxide, sodium sulfate, gypsum, sodium carbonate, and sodium silicate.

[0018] The present invention also provides a method for preparing the above-mentioned composite water-reducing agent for lithium slag concrete, comprising the following steps: taking a siloxane-modified polycarboxylic acid polymer solution, a POSS-based silane coupling agent, polyethylene glycol, and an alkali activator and mixing them evenly to obtain the composite water-reducing agent for lithium slag concrete.

[0019] The present invention also provides a lithium slag concrete, comprising the following raw materials in parts by weight: 200-250 parts cement, 50-80 parts lithium slag, 20-40 parts fly ash, 1-2 parts early strength agent, 650-800 parts sand, 850-1000 parts crushed stone, and 8-10 parts of the above-mentioned composite water-reducing agent.

[0020] The lithium slag concrete also includes water, and the mass ratio of the total mass of cement, lithium slag, and fly ash to water is 1:0.3-0.35.

[0021] The present invention also provides a method for preparing the above-mentioned lithium slag concrete, comprising the following steps:

[0022] The composite water-reducing agent and water are mixed evenly, lithium slag is added and mixed evenly, cement, fly ash, early strength agent, sand and crushed stone are added and mixed evenly to obtain lithium slag concrete.

[0023] The lithium slag has a median particle size of 15-20 μm and a specific surface area of ​​500-800 m². 2 / kg, of which by mass percentage CaO content is 5-9%, SiO2 content is 56-64%, Al2O3 content is 17-24%, MgO content is 0.4-1.2%, SO3 content is 6-8%, and other properties meet the requirements of YB / T 4230-2010 "Lithium Slag Powder for Cement and Concrete".

[0024] The cement is silicate cement with a strength grade of 42.5-52.5.

[0025] The fly ash is selected from one or more of Grade I fly ash and Grade II fly ash.

[0026] The fineness modulus of the sand is 2.3-3.0.

[0027] The crushed stone is a 5-25mm continuous particle size distribution crushed stone.

[0028] The early strength agent is selected from one or more of triethanolamine, triisopropanolamine, diethanolamine, and urea.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] The composite water-reducing agent comprises a siloxane-modified polycarboxylate polymer solution, a POSS-based silane coupling agent, polyethylene glycol, and an alkali activator. The POSS-based silane coupling agent acts as a sacrificial agent, preferentially covering and filling the porous structure of the lithium slag surface under the action of polyethylene glycol, thus hindering the adsorption of siloxane-modified polycarboxylate polymer molecules by the lithium slag. The siloxane-modified polycarboxylate polymer ensures that it can both adsorb and encapsulate other cementitious particles in the concrete and easily adsorb onto lithium slag particles to exert its water-reducing effect. The alkali activator compensates for the decrease in lithium slag activity caused by the coverage of the POSS-based silane coupling agent. Through the synergistic and balanced effects of these components, the workability of lithium slag concrete can be significantly improved, fully leveraging the water-reducing effect of the water-reducing agent. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.

[0032] Allyl polyoxyethylene ethers with a weight average molecular weight of 2400 and 3000 were purchased from Jinjinle Chemical Co., Ltd.

[0033] The median particle size of lithium slag is 16.5 μm, and the specific surface area is 714.4 m². 2 / kg, of which by mass percentage CaO content is 8.8%, SiO2 content is 61%, Al2O3 content is 20%, MgO content is 0.8%, SO3 content is 6%, and other properties meet the requirements of YB / T 4230-2010 "Lithium Slag Powder for Cement and Concrete", purchased from Sichuan Green Ruisang Renewable Resources Utilization Co., Ltd.

[0034] The aminopropylheptyl-cage polysilsesquioxane (CAS No. 444315-15-5) was purchased from Henan Weitixi Chemical Technology Co., Ltd.

[0035] The fineness modulus of the quartz sand is 2.3, and it was purchased from Fengyang Jihui Quartz Sand Co., Ltd.

[0036] 5-25mm continuous gradation crushed stone, purchased from Huzhou Xinkaiyuan Crushed Stone Co., Ltd.

[0037] Polyethylene glycol with a number average molecular weight of 600 and 1000 was purchased from Jiangsu Haian Petrochemical Plant.

[0038] Example 1

[0039] 1) Under a nitrogen atmosphere, 1 mol of (3-acryloyloxypropyl)trimethoxysilane and 1 mol of aminopropylheptyl-cage polysilsesquioxane were added to 9.2 mol of chloroform, and 11.1 g of triethylamine was added. The reaction was carried out at 60 °C for 3 h. After the reaction was completed, chloroform and triethylamine were removed by vacuum distillation to obtain POSS-based silane coupling agent.

[0040] 2) Under a nitrogen atmosphere, 1 mol of allyl polyoxyethylene ether (weight-average molecular weight 3000), 2 mol of acrylic acid, 3 mol of maleic acid, 0.3 mol of allyl trimethoxysilane, and 1 wt% mercaptoacetic acid (based on the total mass of monomers) were added to 4000 g of water and mixed thoroughly. The mixture was heated to 80°C, and a 10 wt% ammonium persulfate solution (water as solvent, ammonium persulfate accounting for 1.5 wt% of the total mass of monomers) was added dropwise over 1 hour. The reaction was then carried out at a constant temperature. After the reaction was completed, the pH was adjusted to 7 with a 40 wt% sodium hydroxide solution, and the solid content was adjusted by distillation to obtain a siloxane-modified polycarboxylic acid polymer solution with a solid content of 50 wt%. The weight-average molecular weight M was determined by GPC. w It is 68,000.

[0041] 3) Take 60 kg of siloxane-modified polycarboxylic acid polymer solution, 40 kg of POSS-based silane coupling agent, 5 kg of polyethylene glycol with a number average molecular weight of 600, and 25 kg of sodium hydroxide and mix them evenly to obtain a composite water-reducing agent for lithium slag concrete.

[0042] 4) Mix 1kg of the above-mentioned composite water-reducing agent and 10.5kg of water (adhesive / water ratio is 1:0.35) evenly, add 8kg of lithium slag and mix evenly, add 20kg of cement, 2kg of Grade I fly ash, 0.2kg of triethanolamine, 65kg of quartz sand and 85kg of continuously graded crushed stone and mix evenly to obtain lithium slag concrete.

[0043] Example 2

[0044] The rest is the same as in Example 1, except that in step 3), the amount of siloxane-modified polycarboxylic acid polymer solution used is 40 kg.

[0045] Example 3

[0046] The rest is the same as in Example 1, except that in step 3), the amount of POSS-based silane coupling agent used is 25 kg.

[0047] Example 4

[0048] The rest is the same as in Example 1, except that in step 3), the amount of polyethylene glycol with a number average molecular weight of 600 is 3 kg.

[0049] Example 5

[0050] The rest is the same as in Example 1, except that in step 3), the amount of sodium hydroxide used is 20 kg.

[0051] Example 6

[0052] The rest is the same as in Example 1, except that in step 2), the amount of allyltrimethoxysilane used is 0.1 mol. w It is 65,000.

[0053] Example 7

[0054] The rest is the same as in Example 1, except that in step 3), polyethylene glycol with a number average molecular weight of 1000 is replaced with polyethylene glycol with a number average molecular weight of 600.

[0055] Example 8

[0056] The rest is the same as in Example 1, except that in step 4), the amount of composite water-reducing agent used is 800g.

[0057] Example 9

[0058] 1) Under a nitrogen atmosphere, 1 mol of (3-acryloyloxypropyl)trimethoxysilane and 1 mol of aminopropylheptyl-cage polysilsesquioxane were added to 9.2 mol of chloroform, and 11.1 g of triethylamine was added. The reaction was carried out at 60 °C for 3 h. After the reaction was completed, chloroform and triethylamine were removed by vacuum distillation to obtain POSS-based silane coupling agent.

[0059] 2) Under a nitrogen atmosphere, 1 mol of allyl polyoxyethylene ether (weight-average molecular weight 2400), 3 mol of acrylic acid, 2 mol of maleic acid, 0.3 mol of allyl trimethoxysilane, and 1 wt% mercaptoacetic acid (based on the total mass of monomers) were added to 4000 g of water and mixed thoroughly. The mixture was heated to 80°C, and a 10 wt% ammonium persulfate solution (water as solvent, ammonium persulfate accounting for 1.5 wt% of the total mass of monomers) was added dropwise over 1 hour. The reaction was then carried out at a constant temperature. After the reaction was completed, the pH was adjusted to 7 with a 40 wt% sodium hydroxide solution, and the solid content was adjusted by distillation to obtain a siloxane-modified polycarboxylic acid polymer solution with a solid content of 50 wt%. w It is 71,000.

[0060] 3) Take 60 kg of siloxane-modified polycarboxylic acid polymer solution, 40 kg of POSS-based silane coupling agent, 5 kg of polyethylene glycol with a number average molecular weight of 600, and 25 kg of sodium hydroxide and mix them evenly to obtain a composite water-reducing agent for lithium slag concrete.

[0061] 4) Mix 1 kg of the above-mentioned composite water-reducing agent and 11.2 kg of water (adhesive / water ratio of 1:0.35) evenly, add 5 kg of lithium slag and mix evenly, add 25 kg of cement, 2 kg of Grade I fly ash, 0.2 kg of triethanolamine, 80 kg of quartz sand and 100 kg of continuously graded crushed stone and mix evenly to obtain lithium slag concrete.

[0062] Comparative Example 1

[0063] Compared with Example 1, the difference is that in steps 1) and 3), the POSS-based silane coupling agent is replaced with an equal mass of aminopropylheptyl-cage polysilsesquioxane.

[0064] Comparative Example 2

[0065] The rest is the same as in Example 1, except that in step 3), polyethylene glycol with a number average molecular weight of 600 is not added.

[0066] Comparative Example 3

[0067] The rest is the same as in Example 1, except that in step 3), the amount of sodium hydroxide is changed to 15 kg.

[0068] Comparative Example 4

[0069] The rest is the same as in Example 1, except that in step 3), an equal mass of Subote PCA®-10 series polycarboxylate superplasticizer is used instead of the siloxane-modified polycarboxylate polymer solution.

[0070] The lithium slag concrete prepared in the above embodiments and comparative examples was subjected to the following performance tests:

[0071] Strength test: Refer to GB / T 50081-2002 Standard for Test Methods of Mechanical Properties of Ordinary Concrete, standard curing, test 7-day compressive strength and 28-day compressive strength.

[0072] Chloride ion penetration resistance: The test was conducted using the Rapid Chloride Ion Migration Coefficient (RCM) method as specified in GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete," with the Chloride Ion Migration Coefficient (DRCM) value as the standard (the lower the better).

[0073] Slump / spread: Tested in accordance with GB / T 50080-2016 Standard for Test Methods of Performance of Ordinary Concrete Mixtures.

[0074] Table 1 Performance Test Results

[0075]

[0076] As can be seen from the examples and comparative examples in Table 1, the workability of the concrete fluctuates significantly with the changes in the components of the composite water-reducing agent for lithium slag concrete. Under the synergistic effect of the components of the composite water-reducing agent, the workability of the concrete prepared by this invention is significantly improved, giving full play to the role of the water-reducing agent in improving the workability of concrete.

[0077] As can be seen from Table 1, Examples 1 and 5, and Comparative Example 3, a smaller amount of alkali activator is beneficial to improving the workability of concrete. It is speculated that the alkali activator has the effect of destroying the local POSS-based silane coupling agent covering / filling layer, penetrating, and activating. The smaller the amount, the less damage is done to the POSS-based silane coupling agent covering / filling on the lithium slag, the worse the water absorption of the lithium slag, and the better the workability of the concrete. However, a smaller amount of alkali activator will lead to a slower or even incomplete hydration reaction, resulting in poor interfacial bonding of the concrete, slow strength development, and low strength.

[0078] As can be seen from the test results of chloride ion penetration resistance in Table 1, the microstructure of the concrete is improved and the density is increased under the synergistic effect of the components of the composite water-reducing agent for lithium slag concrete of this invention, and the chloride ion penetration capacity is reduced.

[0079] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A composite water-reducing agent for lithium slag concrete, characterized in that, The raw materials comprise the following parts by weight: 40-60 parts of siloxane-modified polycarboxylate polymer solution, 25-40 parts of POSS-based silane coupling agent, 3-5 parts of polyethylene glycol, and 20-25 parts of alkali activator. The POSS-based silane coupling agent is prepared by a Michael addition reaction of acryloyloxysilane and aminopropylheptyl-cage polysilsesquioxane at a molar ratio of 1:1-1.

03. The siloxane-modified polycarboxylate polymer solution is prepared by polymerizing monomers monoalkenyl polyether monomers, acrylic monomers, monoalkenyl diacids, and unsaturated siloxanes in solution at a molar ratio of 1:2-3:2-3:0.1-0.

3. The solid content of the polycarboxylate polymer solution is 40-50 wt%.

2. The composite water-reducing agent for lithium slag concrete according to claim 1, characterized in that, The acryloyloxysilane is selected from one or more combinations of (3-acryloyloxypropyl)trimethoxysilane, 3-acryloyloxypropylmethyldimethoxysilane, (methacryloyloxymethyl)triethoxysilane, (methacryloyloxymethyl)methyldiethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, methacryloyloxypropylmethyldiethoxysilane, acryloyloxypropyltrimethoxysilane, methacryloyloxymethyltrimethoxysilane, 3-(methacryloyloxy)propyltrimethoxysilane, 3-trimethoxysilane propylene acrylate, and 3-(triethoxysilyl)propyl methacrylate.

3. The composite water-reducing agent for lithium slag concrete according to claim 1, characterized in that, The POSS-based silane coupling agent is prepared by a method comprising the following steps: Under an inert atmosphere, acryloyloxysilane and aminopropylheptyl-cage polysilsesquioxane were added to an organic solvent, a catalyst was added, and the reaction was carried out under controlled temperature. After the reaction was completed, the mixture was distilled under reduced pressure to obtain a POSS-based silane coupling agent.

4. The composite water-reducing agent for lithium slag concrete according to claim 1, characterized in that, The monoalkenyl polyether monomers have a weight-average molecular weight of 2400-3000 and are selected from one or a combination of two of allyl polyoxyethylene ether and allyl polyoxypropylene ether; the acrylic monomers are selected from one or a combination of two of acrylic acid and methacrylic acid; the monoalkenyl dicarboxylic acid is selected from one or a combination of two of itaconic acid, maleic acid, fumaric acid, and citraconic acid; the unsaturated siloxane is selected from one or a combination of two or more of allyltrimethoxysilane, allyltriethoxysilane, 3-butenetriethoxysilane, vinyltrimethylsilane, vinyltriethoxysilane, vinyldimethoxysilane, and vinylmethyldimethoxysilane.

5. The composite water-reducing agent for lithium slag concrete according to claim 1, characterized in that, The siloxane-modified polycarboxylate polymer solution is prepared by a method comprising the following steps: Under an inert atmosphere, monoalkenyl polyether monomers, acrylic monomers, monoalkenyl dicarboxylic acids, unsaturated siloxanes, and molecular weight regulators are added to water and mixed evenly. The mixture is heated, and an initiator solution is added dropwise. The mixture is then reacted at a constant temperature. After the reaction is complete, the pH and solid content are adjusted to obtain a siloxane-modified polycarboxylic acid polymer solution.

6. The composite water-reducing agent for lithium slag concrete according to claim 1, characterized in that, The number average molecular weight of the polyethylene glycol is 600-1000; the activator is selected from one or more of sodium hydroxide, sodium sulfate, gypsum, sodium carbonate, and sodium silicate.

7. The preparation method of the composite water-reducing agent for lithium slag concrete according to any one of claims 1-6, characterized in that, The process includes the following steps: take a siloxane-modified polycarboxylic acid polymer solution, POSS-based silane coupling agent, polyethylene glycol, and alkali activator, mix them evenly, and the resulting composite water-reducing agent for lithium slag concrete is obtained.

8. A lithium slag concrete, characterized in that, The raw materials include the following parts by weight: 200-250 parts cement, 50-80 parts lithium slag, 20-40 parts fly ash, 1-2 parts early strength agent, 650-800 parts sand, 850-1000 parts crushed stone, and 8-10 parts of the composite water-reducing agent as described in any one of claims 1-6 or 7.

9. The lithium slag concrete according to claim 8, characterized in that, The lithium slag has a median particle size of 15-20 μm and a specific surface area of ​​500-800 m². 2 / kg, of which, by mass percentage, CaO content is 5-9%, SiO2 content is 56-64%, Al2O3 content is 17-24%, MgO content is 0.4-1.2%, and SO3 content is 6-8%.

10. The method for preparing lithium slag concrete according to claim 8, characterized in that, Includes the following steps: The composite water-reducing agent and water are mixed evenly, lithium slag is added and mixed evenly, cement, fly ash, early strength agent, sand and crushed stone are added and mixed evenly to obtain lithium slag concrete.

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