A silicate cement admixture and a method for preparing the same
Patent Information
- Application Number
- CN202610780885.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-02
- Publication Date
- 2026-08-18
AI Technical Summary
从微观角度来看，粗糙且多孔的再生骨料表面，难以与水泥基体实现紧密且均匀地结合，导致在受力时，界面处极易形成应力集中点，进而引发裂缝的产生和扩展，严重影响材料的力学性能和耐久性
1.本发明制备的硅酸盐水泥掺合料，通过自合成的改性煤矸石纳米片、铜钙纳米针复合改性鳞片和改性粘结剂作为填料的一部分，改性粘结剂的存在能够显著增加硅酸盐水泥掺合料与水泥基体和再生骨料的界面结合力，提升整体性能，改性煤矸石纳米片和铜钙纳米针复合改性鳞片同时作为增强相能够赋予硅酸盐水泥掺合料整体足够的力学强度，并且两者同为片状结构，两者会通过相互滑移从而分散应力。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of recycled concrete technology, specifically a silicate cement admixture and its preparation method. Background Technology
[0002] With economic and social development and urban construction, the surface of modern cities is gradually covered by reinforced concrete buildings and impermeable pavements. Impermeable pavements hinder rainwater infiltration during rainy weather, preventing rainwater from effectively replenishing groundwater. Coupled with excessive groundwater extraction, urban pavements are prone to subsidence. Furthermore, rainwater flows through drainage ditches, and during heavy rain or storms, rainwater accumulates on the road surface, concentrating in large quantities in motor vehicle and bicycle lanes, causing widespread flooding. In addition, existing concrete pavements are generally dense in structure, resulting in loud tire noise. When vehicles travel at high speeds, the tires compress air between the tire and the road surface as they roll, and the air expands rapidly after the tire passes, producing noise. This noise is particularly noticeable on rainy days, affecting residents' lives and work.
[0003] In existing technologies, recycled coarse aggregate is commonly used to fill concrete. In traditional silicate cement applications, especially when recycled aggregate is involved, the interface between the cement matrix and the recycled aggregate has always been a key factor restricting the overall performance of the material. Recycled aggregate is derived from the recycling and reuse of waste concrete, and its surface is covered with a large amount of old cement paste, often exhibiting a porous structure. When recycled aggregate is mixed with new cement matrix, an interface transition zone is formed between the two. In this transition zone, due to differences in the cement hydration process, directional growth of calcium hydroxide crystals occurs. This directional growth significantly increases the porosity of this region, reaching 25-30%, while the interfacial bond strength is only 60-70% of the strength of the cement matrix itself. From a microscopic perspective, the rough and porous surface of recycled aggregate makes it difficult to achieve a tight and uniform bond with the cement matrix. This leads to stress concentration points easily forming at the interface under stress, which in turn causes cracks to form and propagate, severely affecting the mechanical properties and durability of the material. For example, in some building structures exposed to harsh environments for extended periods, the weak interfacial transition zone causes premature degradation of recycled aggregate concrete structures. Summary of the Invention
[0004] The purpose of this invention is to provide a silicate cement admixture and its preparation method. The admixture uses self-synthesized modified coal gangue nanosheets, copper-calcium nanoneedles composite modified flakes, and a modified binder as part of the filler. The presence of the modified binder significantly increases the interfacial bonding force between the silicate cement admixture and the cement matrix and recycled aggregate, improving overall performance. The modified coal gangue nanosheets and copper-calcium nanoneedles composite modified flakes simultaneously act as reinforcing phases, providing the silicate cement admixture with sufficient overall mechanical strength. Furthermore, both are plate-like structures, and they can disperse stress through mutual sliding, preventing stress concentration points at the interface.
[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a silicate cement admixture includes the following steps: Step 1: Hydrothermal coal gangue was prepared by methanol hydrothermal activation, and then hexadecyltrimethylammonium bromide was used as an intercalating agent for further hydrothermal exfoliation to obtain modified coal gangue nanosheets.
[0006] Step 2: Copper powder flakes and glass flakes are mechanically mixed, and then the pH is adjusted with hydrochloric acid to promote the hydrolysis of γ-methacryloxypropyltrimethoxysilane to generate silanol groups, which condense with the hydroxyl groups on the flake surface to form covalent bonds, thus obtaining modified flakes.
[0007] Step 3: The modified flakes are oxidized in a mixture of ammonium persulfate and sodium hydroxide, and then immersed in a calcium chloride solution. Calcium ions combine with silanol groups through electrostatic adsorption, and then are reduced by electrochemical means to obtain copper-calcium nanoneedle composite modified flakes.
[0008] Step 4: Using potassium persulfate as an initiator, initiate the free radical polymerization of vinyl acetate and polyvinyl alcohol to obtain the modified binder.
[0009] Step 5: Mix P.O42.5 silicate cement, Class I fly ash (F grade), recycled concrete aggregate, modified coal gangue nanosheets, copper-calcium nanoneedle composite modified flakes, modified binder, and polycarboxylate superplasticizer to obtain silicate cement admixture.
[0010] Furthermore, the dosage ratio of silicate cement, fly ash, recycled concrete aggregate, modified coal gangue nanosheets, copper-calcium nanoneedle composite modified flakes, modified binder and polycarboxylate superplasticizer is 2.6-2.8kg: 3-4g: 11-12kg: 2-3kg: 4-5kg: 300-400g: 1.5-1.8kg.
[0011] Furthermore, the specific preparation steps of the modified coal gangue nanosheets are as follows: Coal gangue and methanol were added to a polytetrafluoroethylene hydrothermal reactor at a ratio of 3.5-3.7 kg: 10-20 L. The reactor was hydrothermally reacted at 100-110 °C and 500-600 r / min for 24-26 h. After filtration, the filter cake was washed 2-4 times with anhydrous ethanol and deionized water and dried under vacuum at 60-80 °C for 1-2 h to obtain hydrothermal coal gangue. The hydrothermal coal gangue, hexadecyltrimethylammonium bromide, and methanol were added to the polytetrafluoroethylene hydrothermal reactor and stirred at 100-110 °C and 500-600 r / min for 24-26 h. After natural cooling to room temperature, the mixture was centrifuged at 10000-12000 r / min for 3-4 min, filtered, and the filter cake was washed 2-4 times with methanol and deionized water and dried under vacuum at 60-80 °C for 1-2 h to obtain modified coal gangue nanosheets.
[0012] Furthermore, the ratio of hydrothermal coal gangue, hexadecyltrimethylammonium bromide, and methanol is 3.0-3.2 kg: 100-110 g: 10-20 L.
[0013] Furthermore, the specific preparation steps for the modified flakes are as follows: Copper powder flakes and glass flakes were mixed at a mass ratio of 5.0-6.0:8.0-9.0 to obtain mixed flakes. The mixed flakes, γ-methacryloyloxypropyltrimethoxysilane, anhydrous ethanol and deionized water were added to a reaction vessel, and the pH value was adjusted to 3-4 with hydrochloric acid solution. The mixture was stirred for 24-26 h at 20-25℃ and 500-600 r / min. After filtration, the precipitate was washed 2-4 times with deionized water and anhydrous ethanol and dried under vacuum at 60-80℃ for 1-2 h to obtain modified flakes.
[0014] Furthermore, the ratio of mixed scales, γ-methacryloyloxypropyltrimethoxysilane, anhydrous ethanol, and deionized water is 9-10 kg: 560-575 mL: 9700-9800 mL: 5200-6300 mL.
[0015] Furthermore, the specific preparation steps of the copper-calcium nanoneedle composite modified flakes are as follows: The modified flakes were oxidized in a 1:1 (v / v) mixture of 0.2 mol / L ammonium persulfate and 2 mol / L sodium hydroxide for 1-1.2 h. After filtration, the product was washed 2-3 times with deionized water and transferred to a 5 mmol / L calcium chloride solution. The mixture was stirred at 20-25 °C and 500-600 rpm for 20-40 min, then vacuum dried at 60-80 °C for 1-2 h. Finally, the product was placed in a 0.1 mol / L potassium bicarbonate solution and dried under a constant current of 100 mA / cm². -2Reduced under the specified conditions for 5-6 hours, filtered, the product was washed 2-3 times with deionized water, and vacuum dried at 60-80℃ for 1-2 hours to obtain copper-calcium nanoneedle composite modified flakes.
[0016] Furthermore, the ratio of modified flakes, mixed solution, calcium chloride solution, and potassium bicarbonate solution is 7-8 kg: 500-600 mL: 300-400 mL: 500-600 mL.
[0017] Furthermore, the specific preparation steps of the modified binder are as follows: Polyvinyl alcohol and deionized water are added to a reaction vessel and stirred for 1-2 hours at 80-90℃ and 500-600 r / min until the materials are completely dissolved. Then, the temperature is lowered to 40-50℃, octylphenol polyoxyethylene ether is added, and the reaction is continued to be stirred for 30-40 minutes. Then, vinyl acetate and potassium persulfate are added, and the mixture is heated to 50-65℃ and kept at this temperature for 1-2 hours. Sodium bicarbonate is added to adjust the pH value to 5-6, and then dibutyl phthalate is added. The mixture is stirred for 40-50 minutes, cooled naturally, and discharged to obtain the modified binder.
[0018] Furthermore, the ratio of polyvinyl alcohol, deionized water, octylphenol polyoxyethylene ether, vinyl acetate, potassium persulfate, and dibutyl phthalate is 500-600mL: 1000-1200mL: 10-20g: 200-300mL: 10-20g: 10-20g.
[0019] The beneficial effects of this invention are: 1. The silicate cement admixture prepared by this invention uses self-synthesized modified coal gangue nanosheets, copper-calcium nanoneedle composite modified flakes, and modified binder as part of the filler. The presence of the modified binder can significantly increase the interfacial bonding force between the silicate cement admixture and the cement matrix and recycled aggregate, thereby improving the overall performance. The modified coal gangue nanosheets and copper-calcium nanoneedle composite modified flakes also serve as reinforcing phases, which can give the silicate cement admixture sufficient overall mechanical strength. Furthermore, since both are plate-like structures, they can disperse stress through mutual slippage.
[0020] 2. The copper-calcium nanoneedle composite modified flakes of the present invention have nanoneedle-like structures grown on their surface, which can further increase the contact area with the modified binder, modified coal gangue nanosheets and other materials through mechanical interlocking effect, thereby improving the bonding strength. Furthermore, the presence of the nanoneedle-like structure allows for gaps between the flakes and other materials, especially the modified coal gangue nanosheets, thereby increasing porosity and improving water permeability.
[0021] 3. The copper-calcium nanoneedles in the copper-calcium nanoneedle composite modified flakes of the present invention contain calcium carbonate. During the stirring process, calcium ions will adhere to the surface of the modified flakes after oxidation treatment through electrostatic adsorption. At this time, calcium is adsorbed in a free form and undergoes constant current reduction with the subsequent potassium bicarbonate solution. Because elemental calcium is active, it exists mostly as calcium ions, which react with bicarbonate ions to generate calcium carbonate. In the absence of water, there are no free calcium ions. However, when in contact with water or when silicate cement admixtures encounter rainwater, some calcium ions will become free. The free calcium ions can act as crosslinking agents for polyvinyl alcohol in the modified binder, further improving the overall strength.
[0022] 4. In the process of preparing copper-calcium nanoneedle composite modified scales by modifying scales, ammonium persulfate is used as an oxidant to oxidize copper to copper oxide. At this time, the surface of the modified scales contains double bond sites. Ammonium persulfate also acts as an initiator to attack the unsaturated bonds of the double bonds, causing the C=C bond to break and generating oxygen-containing functional groups such as hydroxyl, carbonyl or carboxyl groups. Oxygen-containing functional groups can enhance the adsorption capacity of the scale surface for calcium ions and improve the subsequent calcium salt deposition efficiency. Detailed Implementation
[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0024] Example 1: A method for preparing a silicate cement admixture, comprising the following steps: S1: 3.5 kg of coal gangue and 10 L of methanol were added to a polytetrafluoroethylene hydrothermal reactor and hydrothermally reacted at 100 °C and 500 r / min for 24 h. After filtration, the filter cake was washed twice with anhydrous ethanol and deionized water and dried under vacuum at 60 °C for 1 h to obtain hydrothermal coal gangue. 3.0 kg of hydrothermal coal gangue, 100 g of hexadecyltrimethylammonium bromide and 10 L of methanol were added to a polytetrafluoroethylene hydrothermal reactor and stirred at 100 °C and 500 r / min for 24 h. After natural cooling to room temperature, the mixture was centrifuged at 10000 r / min for 3 min, filtered, and the filter cake was washed twice with methanol and deionized water and dried under vacuum at 60 °C for 1 h to obtain modified coal gangue nanosheets.
[0025] S2: Mix 5.0 kg of copper powder flakes and 8.0 kg of glass flakes to obtain mixed flakes; add 9 kg of mixed flakes, 560 mL of γ-methacryloxypropyltrimethoxysilane, 9700 mL of anhydrous ethanol and 5200 mL of deionized water into a reaction vessel, adjust the pH value to 3 with hydrochloric acid solution, stir for 24 h at 20 °C and 500 r / min, filter, wash the precipitate twice with deionized water and anhydrous ethanol, and vacuum dry at 60 °C for 1 h to obtain modified flakes.
[0026] S3: 7 kg of modified flakes were placed in a 1:1 mixture of 0.2 mol / L ammonium persulfate and 2 mol / L sodium hydroxide solution for oxidization treatment for 1 h. After filtration, the product was washed twice with deionized water and transferred to 300 mL of 5 mmol / L calcium chloride solution. The mixture was stirred at 20 °C and 500 r / min for 20 min and then vacuum dried at 60 °C for 1 h. The product was then placed in 500 mL of 0.1 mol / L potassium bicarbonate solution and reduced at a constant current of 100 mA cm⁻² for 5 h. After filtration, the product was washed twice with deionized water and vacuum dried at 60 °C for 1 h to obtain copper-calcium nanoneedle composite modified flakes.
[0027] S4: Add 500 mL of polyvinyl alcohol and 1000 mL of deionized water to a reactor and stir for 1 hour at 80 °C and 500 r / min until the materials are completely dissolved. Then, cool down to 40 °C and add 10 g of octylphenol polyoxyethylene ether as an emulsifier. Continue stirring for 30 min. Then, add 200 mL of vinyl acetate and 10 g of potassium persulfate as an initiator. Heat to 50 °C and keep warm for 1 hour. Add sodium bicarbonate to adjust the pH to 5. Then, add 10 g of dibutyl phthalate as a plasticizer and continue stirring for 40 min. Allow to cool naturally and discharge to obtain the modified binder.
[0028] S5: Mix 2.6 kg of P.O42.5 silicate cement, 3 g of Class I fly ash (F type), 11 kg of recycled concrete aggregate, 2 kg of modified coal gangue nanosheets, 4 kg of copper-calcium nanoneedle composite modified flakes, 300 g of modified binder, and 1.5 kg of polycarboxylate superplasticizer to obtain silicate cement admixture.
[0029] Example 2: A method for preparing a silicate cement admixture, comprising the following steps: S1: 3.6 kg of coal gangue and 15 L of methanol were added to a polytetrafluoroethylene hydrothermal reactor and hydrothermally reacted at 105 °C and 550 r / min for 25 h. After filtration, the filter cake was washed three times with anhydrous ethanol and deionized water and dried under vacuum at 70 °C for 1.5 h to obtain hydrothermal coal gangue. 3.1 kg of hydrothermal coal gangue, 105 g of hexadecyltrimethylammonium bromide and 15 L of methanol were added to a polytetrafluoroethylene hydrothermal reactor and stirred at 105 °C and 550 r / min for 25 h. After natural cooling to room temperature, the mixture was centrifuged at 11000 r / min for 3.5 min, filtered, and the filter cake was washed three times with methanol and deionized water and dried under vacuum at 70 °C for 1.5 h to obtain modified coal gangue nanosheets.
[0030] S2: Mix 5.5 kg of copper powder flakes and 8.5 kg of glass flakes to obtain mixed flakes; add 9.5 kg of mixed flakes, 567.5 mL of γ-methacryloyloxypropyltrimethoxysilane, 9750 mL of anhydrous ethanol and 5750 mL of deionized water to a reaction vessel, adjust the pH value to 3.5 with hydrochloric acid solution, stir for 25 h at 22.5 ℃ and 550 r / min, filter, wash the precipitate three times with deionized water and anhydrous ethanol, and vacuum dry at 70 ℃ for 1.5 h to obtain modified flakes.
[0031] S3: 7.5 kg of modified flakes were placed in a 1:1 mixture of 0.2 mol / L ammonium persulfate and 2 mol / L sodium hydroxide solution in 550 mL and oxidized for 1.1 h. After filtration, the product was washed 2.5 times with deionized water and transferred to 350 mL of 5 mmol / L calcium chloride solution. The mixture was stirred at 22.5 °C and 550 r / min for 30 min and then vacuum dried at 70 °C for 1.5 h. The product was then placed in 550 mL of 0.1 mol / L potassium bicarbonate solution and reduced at a constant current of 100 mA cm⁻² for 5.5 h. After filtration, the product was washed 2.5 times with deionized water and vacuum dried at 70 °C for 1.5 h to obtain copper-calcium nanoneedle composite modified flakes.
[0032] S4: Add 550 mL of polyvinyl alcohol and 1100 mL of deionized water to a reactor and stir for 1.5 h at 85 °C and 550 r / min until the materials are completely dissolved. Then cool to 45 °C, add 15 g of octylphenol polyoxyethylene ether as an emulsifier, and continue stirring for 35 min. Then add 250 mL of vinyl acetate and 15 g of potassium persulfate as an initiator, heat to 57.5 °C, and keep warm for 1.5 h. Add sodium bicarbonate to adjust the pH to 5.5, then add 15 g of dibutyl phthalate as a plasticizer, and continue stirring for 45 min. Allow to cool naturally and discharge to obtain the modified binder.
[0033] S5: Mix 2.7 kg of P.O42.5 silicate cement, 3.5 g of Class I fly ash (F grade), 11.5 kg of recycled concrete aggregate, 2.5 kg of modified coal gangue nanosheets, 4.5 kg of copper-calcium nanoneedle composite modified flakes, 350 g of modified binder, and 1.65 kg of polycarboxylate superplasticizer to obtain silicate cement admixture.
[0034] Example 3: A method for preparing a silicate cement admixture, comprising the following steps: S1: 3.7 kg of coal gangue and 20 L of methanol were added to a polytetrafluoroethylene hydrothermal reactor and hydrothermally reacted at 110 °C and 600 r / min for 26 h. After filtration, the filter cake was washed four times with anhydrous ethanol and deionized water and dried under vacuum at 80 °C for 2 h to obtain hydrothermal coal gangue. 3.2 kg of hydrothermal coal gangue, 110 g of hexadecyltrimethylammonium bromide and 20 L of methanol were added to a polytetrafluoroethylene hydrothermal reactor and stirred at 110 °C and 600 r / min for 26 h. After natural cooling to room temperature, the mixture was centrifuged at 12000 r / min for 4 min, filtered, and the filter cake was washed four times with methanol and deionized water and dried under vacuum at 80 °C for 2 h to obtain modified coal gangue nanosheets.
[0035] S2: Mix 6.0 kg of copper powder flakes and 9.0 kg of glass flakes to obtain mixed flakes; add 10 kg of mixed flakes, 575 mL of γ-methacryloyloxypropyltrimethoxysilane, 9800 mL of anhydrous ethanol and 6300 mL of deionized water to a reaction vessel, adjust the pH value to 4 with hydrochloric acid solution, stir for 26 h at 25 °C and 600 r / min, filter, wash the precipitate 4 times with deionized water and anhydrous ethanol, and vacuum dry at 80 °C for 2 h to obtain modified flakes.
[0036] S3: 8 kg of modified flakes were placed in a 1:1 mixture of 0.2 mol / L ammonium persulfate and 2 mol / L sodium hydroxide solution for oxidization treatment for 1.2 h. After filtration, the product was washed three times with deionized water and transferred to 400 mL of 5 mmol / L calcium chloride solution. The mixture was stirred at 25 °C and 600 r / min for 40 min and then vacuum dried at 80 °C for 2 h. The product was then placed in 600 mL of 0.1 mol / L potassium bicarbonate solution and reduced at a constant current of 100 mA cm⁻² for 6 h. After filtration, the product was washed three times with deionized water and vacuum dried at 80 °C for 2 h to obtain copper-calcium nanoneedle composite modified flakes.
[0037] S4: Add 600 mL of polyvinyl alcohol and 1200 mL of deionized water to a reactor and stir for 2 hours at 90 °C and 600 r / min until the materials are completely dissolved. Then, cool to 50 °C and add 20 g of octylphenol polyoxyethylene ether as an emulsifier. Continue stirring for 40 min. Then, add 300 mL of vinyl acetate and 20 g of potassium persulfate as an initiator. Heat to 65 °C and keep warm for 2 hours. Add sodium bicarbonate to adjust the pH to 6. Then, add 20 g of dibutyl phthalate as a plasticizer and continue stirring for 50 min. Allow to cool naturally and discharge to obtain the modified binder.
[0038] S5: Mix 2.8 kg of P.O42.5 silicate cement, 4 g of Class I fly ash (F grade), 12 kg of recycled concrete aggregate, 3 kg of modified coal gangue nanosheets, 5 kg of copper-calcium nanoneedle composite modified flakes, 400 g of modified binder, and 1.8 kg of polycarboxylate superplasticizer to obtain silicate cement admixture.
[0039] Comparative Example 1: Based on Example 3, the modified coal gangue nanosheets in step S5 were replaced with the raw coal gangue in step S1.
[0040] Comparative Example 2: Based on Example 3, the copper-calcium nanoneedle composite modified scales in step S5 were replaced with the modified scales prepared in step S2.
[0041] Comparative Example 3: Based on Example 3, the modified binder in step S5 was omitted.
[0042] The performance of the silicate cement admixtures prepared in Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in Table 1: 1. Permeability coefficient: Tested according to GB / T 50082-2009 and JTJ 275-2000 "Technical Specification for Corrosion Protection of Concrete Structures in Harbor Engineering".
[0043] 2. Compressive strength test: Tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".
[0044] 3. Flexural strength test: Tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".
[0045] 4. Porosity test: Tested according to CJJ / T 135-2019 "Technical Specification for Permeable Cement Concrete Pavement".
[0046] Table 1 As shown in Table 1, in Comparative Example 1, the modified coal gangue nanosheets in step S5 were replaced with the raw coal gangue in step S1. The raw coal gangue had not undergone methanol hydrothermal activation and hexadecyltrimethylammonium bromide intercalation modification, and was still a blocky / coarse-grained structure. Its specific surface area decreased, and it had very few surface active sites, which could not fill the internal pores and interface transition zone defects of cement stone. The raw coal gangue did not have the sheet-like structure of nanosheets, so it could not form a layered stack with copper-calcium nanoneedles composite scales, nor could it disperse stress through mutual sliding of the sheets. Under stress, stress concentration was easily formed in the interparticle gaps, resulting in poor crack resistance and increased brittleness of the material. The raw coal gangue particles were coarse and could not accurately fill the microscopic gaps between copper-calcium scales, resulting in a decrease in effective porosity and poor pore connectivity, and a decrease in water permeability.
[0047] In Comparative Example 2, the copper-calcium nanoneedle composite modified scales in step S5 were replaced with the modified scales prepared in step S2. The modified scales were only modified by silane grafting and had no nanoneedle structure on the surface. The contact area with the modified binder and coal gangue nanosheets was reduced compared with the copper-calcium nanoneedle composite scales. The lack of the mechanical interlocking effect of nanoneedles led to a decrease in interfacial bonding force, compressive strength, and flexural strength. The modified scales did not have the gap reservation function brought by the nanoneedle structure. The scales were tightly stacked, the effective interconnected pores were reduced, the porosity decreased, the water permeability coefficient decreased, and the high-efficiency water permeability function could not be achieved.
[0048] In Comparative Example 3, the modified binder in step S5 was removed, resulting in a breakdown of interfacial bonding and a sharp drop in mechanical strength. The modified binder is a flexible bridge connecting cement particles, recycled aggregates, modified nanosheets, and composite flakes. After its removal, the components are only rigidly bonded by cement hydration products. A large number of micropores and cracks exist in the interfacial transition zone, stress cannot be effectively transferred, compressive strength decreases, flexural strength decreases, and the material is prone to interfacial cracking due to wet-dry cycles and temperature shrinkage.
[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.
Claims
1. A method for preparing a silicate cement admixture, characterized in that, Includes the following steps: Step 1: Hydrothermal coal gangue was prepared by methanol hydrothermal activation, and then hexadecyltrimethylammonium bromide was used as an intercalating agent for further hydrothermal exfoliation to obtain modified coal gangue nanosheets. Step 2: Copper powder flakes and glass flakes are mechanically mixed, and then the pH is adjusted with hydrochloric acid to promote the hydrolysis of γ-methacryloxypropyltrimethoxysilane to generate silanol groups, which condense with the hydroxyl groups on the flake surface to form covalent bonds, thus obtaining modified flakes. Step 3: The modified flakes are oxidized in a mixture of ammonium persulfate and sodium hydroxide, and then immersed in a calcium chloride solution. Calcium ions combine with silanol groups through electrostatic adsorption, and then are reduced by electrochemical means to obtain copper-calcium nanoneedle composite modified flakes. Step 4: Using potassium persulfate as an initiator, initiate the free radical polymerization of vinyl acetate and polyvinyl alcohol to obtain the modified binder; Step 5: Mix silicate cement, fly ash, recycled concrete aggregate, modified coal gangue nanosheets, copper-calcium nanoneedle composite modified flakes, modified binder and polycarboxylate superplasticizer to obtain silicate cement admixture.
2. The method for preparing a silicate cement admixture according to claim 1, characterized in that, The ratio of silicate cement, fly ash, recycled concrete aggregate, modified coal gangue nanosheets, copper-calcium nanoneedle composite modified flakes, modified binder and polycarboxylate superplasticizer is 2.6-2.8kg: 3-4g: 11-12kg: 2-3kg: 4-5kg: 300-400g: 1.5-1.8kg.
3. The method for preparing a silicate cement admixture according to claim 1, characterized in that, The specific preparation steps of the modified coal gangue nanosheets are as follows: Coal gangue and methanol were added to a polytetrafluoroethylene hydrothermal reactor at a ratio of 3.5-3.7 kg: 10-20 L. The reactor was hydrothermally reacted at 100-110 °C and 500-600 r / min for 24-26 h. After filtration, the filter cake was washed 2-4 times with anhydrous ethanol and deionized water and dried under vacuum at 60-80 °C for 1-2 h to obtain hydrothermal coal gangue. The hydrothermal coal gangue, hexadecyltrimethylammonium bromide, and methanol were added to the polytetrafluoroethylene hydrothermal reactor and stirred at 100-110 °C and 500-600 r / min for 24-26 h. After natural cooling to room temperature, the mixture was centrifuged at 10000-12000 r / min for 3-4 min, filtered, and the filter cake was washed 2-4 times with methanol and deionized water and dried under vacuum at 60-80 °C for 1-2 h to obtain modified coal gangue nanosheets.
4. The method for preparing a silicate cement admixture according to claim 3, characterized in that, The ratio of hydrothermal coal gangue, hexadecyltrimethylammonium bromide, and methanol is 3.0-3.2 kg: 100-110 g: 10-20 L.
5. The method for preparing a silicate cement admixture according to claim 1, characterized in that, The specific preparation steps for the modified flakes are as follows: Copper powder flakes and glass flakes were mixed at a mass ratio of 5.0-6.0:8.0-9.0 to obtain mixed flakes. The mixed flakes, γ-methacryloyloxypropyltrimethoxysilane, anhydrous ethanol and deionized water were added to a reaction vessel, and the pH value was adjusted to 3-4 with hydrochloric acid solution. The mixture was stirred for 24-26 h at 20-25℃ and 500-600 r / min. After filtration, the precipitate was washed 2-4 times with deionized water and anhydrous ethanol and dried under vacuum at 60-80℃ for 1-2 h to obtain modified flakes.
6. The method for preparing a silicate cement admixture according to claim 5, characterized in that, The ratio of the mixed flakes, γ-methacryloxypropyltrimethoxysilane, anhydrous ethanol and deionized water is 9-10 kg: 560-575 mL: 9700-9800 mL: 5200-6300 mL.
7. The method for preparing a silicate cement admixture according to claim 1, characterized in that, The specific preparation steps for the copper-calcium nanoneedle composite modified flakes are as follows: The modified flakes were oxidized in a 1:1 (v / v) mixture of 0.2 mol / L ammonium persulfate and 2 mol / L sodium hydroxide for 1-1.2 h. After filtration, the product was washed 2-3 times with deionized water and transferred to a 5 mmol / L calcium chloride solution. The mixture was stirred at 20-25 °C and 500-600 rpm for 20-40 min, then vacuum dried at 60-80 °C for 1-2 h. Finally, the product was placed in a 0.1 mol / L potassium bicarbonate solution and dried under a constant current of 100 mA / cm². -2 Reduced under the following conditions for 5-6 hours, filtered, the product was washed 2-3 times with deionized water, and vacuum dried at 60-80℃ for 1-2 hours to obtain copper-calcium nanoneedle composite modified flakes. The ratio of the modified flakes, mixed solution, calcium chloride solution, and potassium bicarbonate solution is 7-8 kg: 500-600 mL: 300-400 mL: 500-600 mL.
8. The method for preparing a silicate cement admixture according to claim 1, characterized in that, The specific preparation steps of the modified binder are as follows: Polyvinyl alcohol and deionized water are added to a reaction vessel and stirred for 1-2 hours at 80-90℃ and 500-600 r / min until the materials are completely dissolved. Then, the temperature is lowered to 40-50℃, octylphenol polyoxyethylene ether is added, and the reaction is continued to be stirred for 30-40 minutes. Then, vinyl acetate and potassium persulfate are added, and the mixture is heated to 50-65℃ and kept at this temperature for 1-2 hours. Sodium bicarbonate is added to adjust the pH value to 5-6, and then dibutyl phthalate is added. The mixture is stirred for 40-50 minutes, cooled naturally, and discharged to obtain the modified binder.
9. The method for preparing a silicate cement admixture according to claim 1, characterized in that, The ratio of polyvinyl alcohol, deionized water, octylphenol polyoxyethylene ether, vinyl acetate, potassium persulfate and dibutyl phthalate is 500-600mL: 1000-1200mL: 10-20g: 200-300mL: 10-20g: 10-20g.
10. A silicate cement admixture, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.