Anti-ion permeation modified composite silicon powder, and preparation method and application thereof

Abstract

The application discloses a kind of anti-ion permeation modified composite silicon powder, its preparation method includes the following steps: 1) sequentially using macroporous weak acid acrylic cation exchange resin and polyvinyl alcohol solution to modify silicon powder, and obtain modified silicon powder;2) silicon acid, alcohol solvent and water are mixed uniformly, then drop titanium source solution, stirring reaction is carried out under room temperature condition, and obtain nano TiO2 sol;3) adding modified silicon powder to the obtained nano TiO2 sol, mix uniformly, and dry, namely the anti-ion permeation modified composite silicon powder of the present application can effectively overcome the inherent problems such as high water demand and high viscosity of traditional silicon powder applied in concrete under the premise of reducing the cost of silicon powder, and effectively improve the ion adsorption performance and overall durability of concrete etc.;Realize the efficient application of low-quality, low-cost silicon powder in the field of concrete anti-ion permeation, and it is suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to ion penetration-resistant modified composite silicon powder, a preparation method and application thereof. Background Art

[0002] During the operation of subway projects, a small amount of current (stray current) inevitably escapes into the reinforced concrete structures that support them. Long-term effects on the steel reinforcement within the underground concrete can cause severe corrosion of the reinforcement, thereby damaging the concrete structure. Due to the special nature of subway construction, subway projects are generally located in underground soil environments with high water content, and most groundwater is rich in corrosive media such as chloride ions and sulfate ions. Furthermore, subway concrete is also subjected to the alternating fatigue loads brought about by subway operation. Therefore, subway concrete is primarily subject to the coupled erosion effects of stray currents, corrosive ions, and fatigue loads in a complex environment. Under the influence of these three factors, the concrete of the subway floor structure can rust the internal reinforcement, leading to structural collapse and premature repair. This seriously affects the long-term durability of the building structure, poses a safety hazard, and results in a significant waste of resources and property.

[0003] Currently, some experts and scholars have conducted research on the corrosion resistance of high-performance subway concrete and have achieved some results. For example, patent CN107304118A discloses a method for preparing C40 special concrete that inhibits chloride ion diffusion for subway projects; patent CN109095858A discloses a high-impedance concrete, its preparation method, and use; and patent CN107304111A discloses an organic corrosion inhibitor for concrete in sulfate-chloride environments. However, the service performance of long-term subway concrete needs to be improved. Some experts and scholars have also conducted research on introducing polymer materials to achieve composite impedance functions. For example, patent CN108529980A discloses a high-impedance concrete and concrete. Utilizing the ion adsorption properties of mineral admixtures, shale sand, and latex materials, it can effectively improve the ionic corrosion resistance of subway concrete. However, the resulting concrete has limitations such as large performance fluctuations and limited environmental adaptability. In addition, considering the good performance of silica fume in improving the overall density of concrete, some studies have designed to introduce modified silica fume into the subway concrete system to improve the performance of concrete through both physical and chemical aspects. While improving the density, it also plays a role in adsorbing harmful corrosive ions. For example, the literature "Research on High-Temperature Performance of Silica Fume / SBS Composite Modified Asphalt Concrete" does not involve the field of concrete's resistance to ion penetration and there are few related studies. Further exploration of the efficient application of modified silica fume in highly resistant to ion penetration concrete has important research and application significance. Summary of the Invention

[0004] The main purpose of the present invention is to address the shortcomings of the existing technology and provide a modified composite silica powder that is resistant to ion penetration. While reducing the cost of silica powder, the surface strength of silica powder particles is improved, the water demand is effectively reduced, and the ion adsorption capacity is enhanced. This can achieve the efficient application of low-quality, low-cost silica powder in the field of concrete resistance to ion penetration, and is suitable for promotion and application.

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

[0006] A method for preparing ion-resistant modified composite silicon powder comprises the following steps:

[0007] 1) adding a macroporous acrylic acid cation exchange resin to silicon powder and stirring the mixture, then adding the resulting mixture to a polyvinyl alcohol solution and stirring the mixture a second time, filtering out the silicon powder, drying it, and cooling it to obtain modified silicon powder;

[0008] 2) uniformly dispersing a titanium source in an alcohol solvent to obtain a titanium source solution; uniformly mixing silicic acid, an alcohol solvent, and water, then dropwise adding the titanium source solution thereto under stirring conditions, and reacting with stirring at room temperature to obtain a light yellow nano-TiO2 sol;

[0009] 3) Adding modified silicon powder to the obtained nano-TiO2 sol, mixing evenly, and drying to obtain the ion penetration-resistant modified composite silicon powder.

[0010] In the above scheme, the specific surface area of ​​the (low-quality) silicon powder is 15,000 to 18,000 m 2 / kg, the activity index is 80-90% at 3d, 85-95% at 7d, 95-105% at 28d, the silicon dioxide content is 85-90%, and the water requirement ratio is 115-120%; compared with conventional silica fume, its silicon dioxide content is lower (5-10% lower on average), the activity at different ages is lower (5-10% lower on average), the cost is about 100-200 yuan / ton lower, and the conventional silica fume is usually about 1000-1800 yuan / ton.

[0011] In the above scheme, the macroporous acrylic acid cation exchange resin is weakly acidic, has a pH value of 5-6, a hydrogen form rate of ≥98%, a water content of 45-48%, and a wet true density of 1.16-1.18 g / ml.

[0012] In the above solution, the amount of the macroporous acrylic acid cation exchange resin used accounts for 3-4% of the mass of the silicon powder.

[0013] In the above scheme, the stirring treatment time in step 1) is 25 to 35 minutes.

[0014] In the above scheme, the concentration of the polyvinyl alcohol solution is 6-8wt%; the polymerization degree of the polyvinyl alcohol is 1700-1800, and the alcoholysis degree is ≥99%.

[0015] In the above scheme, the mass ratio of polyvinyl alcohol solution to silicon powder is 4 to 6:1.

[0016] In the above scheme, the secondary stirring treatment time in the polyvinyl alcohol solution is 10 to 12 hours.

[0017] Furthermore, during the secondary stirring treatment, stirring is performed for 10 to 15 minutes every hour.

[0018] In the above scheme, the drying temperature in step 1) is 145-155° C. and the drying time is 30-40 minutes.

[0019] In the above solution, the titanium source can be selected from butyl titanate and the like.

[0020] In the above scheme, the alcohol solvent can be selected from anhydrous ethanol or the like.

[0021] In the above scheme, the preparation method of the titanium source solution includes: mixing the titanium source and the alcohol solvent, and vigorously stirring at a stirring rate of 3500 to 4000 r / min for 15 to 20 minutes.

[0022] In the above solution, the concentration of the titanium source solution is 35-40 wt%.

[0023] In the above scheme, the mass ratio of the titanium source introduced in step 2), the total alcohol solvent (the total amount of the alcohol solvent in step 2)), silicic acid and water is 1:(3.5-4.5):(1-2):(0.1-0.3).

[0024] In the above scheme, the stirring reaction in step 2) is carried out at a speed of 550 to 650 r / min and for a time of 20 to 24 hours.

[0025] In the above solution, the mass ratio of the nano-TiO2 sol to the modified silicon powder is 100:30-35.

[0026] In the above scheme, after the modified silicon powder is added in step 3), stirring is performed once, ultrasonic dispersion is performed, stirring is performed twice, filtration is performed, and drying is performed to obtain the ion penetration-resistant modified composite silicon powder.

[0027] Preferably, in step 3), PVA redispersible latex powder is added at the same time as the modified silica powder is added, and then the mixture is stirred once, ultrasonically dispersed, stirred twice, filtered, and dried to obtain an ion-penetration-resistant modified composite microsilica powder based on nano-TiO2 and redispersible latex powder.

[0028] In the above scheme, the redispersible latex powder is in the form of white powder with a density of 0.55 to 0.75 g / cm 3 , fineness is 0.15~0.20mm, and the sieve residue is less than 1%.

[0029] In the above scheme, the first stirring time in step 3) is 15 to 25 minutes, and the ultrasonic dispersion time is 10 to 20 minutes; the second stirring time is 1.5 to 2.5 hours, filtered, and dried in a vacuum drying oven at 100 to 110°C to obtain modified microsilica powder of composite nano-TiO2 and redispersible latex powder.

[0030] In the above scheme, the mass ratio of nano-TiO2 sol to PVA redispersible latex powder is 100:50-55.

[0031] The ion permeation-resistant modified composite silicon powder prepared according to the above scheme has a specific surface area of ​​10,000 to 12,000 m 2 / kg, the activity index was 85-95% at 3d, 90-100% at 7d, and 100-110% at 28d, the silicon dioxide content was 85-90%, and the water requirement ratio was 105-110%. The activity and water requirement at different ages were significantly improved compared with those before modification.

[0032] The ion penetration-resistant modified composite silica powder described in the above scheme is used to prepare concrete, with the addition amount being 1-1.5% of the mass of the cementitious material.

[0033] Furthermore, the present invention also specifically provides a subway concrete prepared by using the above-mentioned anti-ion penetration modified composite silica fume, the components and their contents include: cement 220-230 kg / m 3 , fly ash 85~95kg / m 3 , mineral powder 75~85kg / m 3 , anti-ion penetration modified composite silicon powder 4~6kg / m 3 , sand 710~730kg / m 3 , stone 1110~1140kg / m 3 , water 150~160g / m 3 , polycarboxylate water reducer 8.0~9.0kg / m 3 .

[0034] By using the above-mentioned formula system of the present invention, the water reducing agent dosage can be reduced by 0.6-1.0 kg / m compared with the silica fume system before modification. 3 .

[0035] In the above scheme, the cement can be silicate cement with PO 42.5 grade or above; the fly ash can be F·III or F·II fly ash with a fineness of 32-38%; the mineral powder can be mineral powder with S75 grade or above and a specific surface area of ​​380-400m 2 / kg; the sand is coarse sand with a fineness modulus of 3.2-3.5, a moisture content of 2.2-2.6%, and a mud content of 1.0-1.2%; the stone is 5-20 mm crushed stone with a mud content of 0.4-0.6%, a crushing index of 2-4%, and an apparent density of 2650-2700 kg / m 3 ; The solid content of polycarboxylic acid water reducer is 12.00~13.00%, and the water reduction rate is 26~28%.

[0036] The present invention aims at achieving high resistivity and high resistance to ion penetration, and adopts a modified silica powder polymerization method. First, the silica powder is preliminarily modified by using ion exchange resin and polyvinyl alcohol solution, so that it has the functions of improving the durability of concrete and ion adsorption performance while reducing water demand. Then, butyl titanate and silicic acid are used as main raw materials, and a sol-gel method is adopted to prepare a nano-TiO2 solution. Finally, modified silica powder and redispersible latex powder are added for further mixing and modification to obtain the ion penetration-resistant modified composite silica powder. The composite silica powder is introduced into concrete to prepare high ion penetration-resistant concrete, which can effectively achieve excellent properties such as high compactness and high ion penetration resistance. At the same time, it can effectively reduce the water consumption of concrete, improve the working performance of concrete mixtures, and enhance the mechanical properties and durability of hardened concrete.

[0037] The principle of the present invention is:

[0038] The present invention firstly adopts a macroporous weakly acidic acrylic acid cation exchange resin and a polyvinyl alcohol solution to mix and modify silicon powder, and utilizes the unique strong adhesiveness and membrane flexibility of the polyvinyl alcohol solution to overcome the problem of the difficulty of the ion exchange resin adhering to the surface of the silicon powder particles; secondly, the macroporous characteristics of the ion exchange resin are utilized to provide good attachment sites for the polyvinyl alcohol solution on its surface and internal structure, thereby increasing the attachment efficiency; finally, the surface modification of the silicon powder particles by the ion exchange resin and the polyvinyl alcohol solution can reduce the overall specific surface area of ​​the particles, thereby reducing the water demand of the modified silicon powder particles, while utilizing the characteristics that both the ion exchange resin and the polyvinyl alcohol solution have ion adsorption capacity to comprehensively improve the ion adsorption capacity of the modified silicon powder; then, a hydrolyzable titanium source, an alcohol solvent, silicic acid and water are used to prepare the silicon powder. Nano-TiO2 solution is used to further modify silica powder. The resulting nano-TiO2 solution can improve the overall dispersibility of the particles during the modification process and increase the surface strength of the silica powder particles. The introduced silicic acid can provide a weakly acidic environment, which can be further combined with the acidic environment provided by the acrylic acid cation exchange resin to effectively promote the preparation process of the nano-TiO2 solution. In addition, the polyvinyl alcohol solution introduced into the modified silica powder can produce a certain chemical reaction with the silicic acid, chemically modifying the surface of the modified silica powder particles, reducing the hydrophilicity and thus reducing the water demand of the silica powder particles, reducing the viscosity of the concrete slurry, etc., while ensuring good ion adsorption. It can effectively reduce the migration rate and migration amount of corrosion ions under the coupling of multiple factors, and improve the problem of subway project concrete being eroded by multiple factors such as stray current and corrosion ions.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1) The present invention uses a weakly acidic acrylic cation exchange resin and a polyvinyl alcohol solution to modify silica fume, and further combines it with nano-TiO2 after optimizing the hydrolysis conditions. This can overcome the inherent problems of silica fume in concrete, such as high water demand and high viscosity, while effectively improving the ion adsorption performance and overall durability.

[0041] 2) The present invention proposes for the first time the introduction of silicic acid and other means to regulate the hydrolysis process of the titanium source. The resulting nano-TiO2 has strong dispersibility, a certain ion adsorption capacity, and is beneficial to improving the surface strength of the silica fume particles. It can also further react with modified silica fume to comprehensively improve the modification efficiency, effectively reduce water demand, and at the same time improve the weather resistance of concrete in underground environments.

[0042] 3) On the basis of modified silica fume, further combining with redispersible latex powder can effectively improve the dispersion performance of the anti-ion penetration modified composite silica fume, and further effectively enhance its contribution to the anti-ion penetration ability of concrete;

[0043] 4) The present invention can realize the efficient application of low-quality, low-cost silica fume in the field of concrete anti-ion penetration, and is suitable for promotion and application. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] In the following examples, the cement used is Qingsong PO 42.5R cement; the fly ash is F·III fly ash from Honger Power Plant with a fineness of 35%; the mineral powder is Baoxin Shengyuan S75 mineral powder with a specific surface area of ​​395m 2 / kg; the sand is coarse sand provided by Xinjiang Hetongyuan Building Materials Co., Ltd., with a fineness modulus of 3.4, a moisture content of 2.5%, and a mud content of 1.1%; the stone is crushed stone with a particle size of 5-20 mm, a mud content of 0.4%, a crushing index of 3%, and an apparent density of 2670 kg / m 3 The water reducer is a polycarboxylic acid high-performance water reducer provided by Kehuida Chemical Building Materials Co., Ltd., with a solid content of 12.15% and a water reduction rate of 27%.

[0046] The silicon powder used was provided by Xinjiang East Hope Group Co., Ltd. (Wucaiwan) and its specific surface area is 16000m 2 / kg, the activity index is 83% at 3 days, 86% at 7 days, 98% at 28 days, the silicon dioxide content is 88.6%, and the water requirement ratio is 118%.

[0047] The macroporous weakly acidic acrylic acid cation exchange resin used was provided by Beijing Jinlijiang Biotechnology Development Co., Ltd., and had a pH value of 5, a hydrogen form rate of 98%, a water content of 46%, and a wet true density of 1.16 g / ml.

[0048] Example 1

[0049] A method for preparing a composite silicon powder modified to resist ion penetration comprises the following steps:

[0050] 1) 3 parts (by weight, the same below) of macroporous acrylic acid cation exchange resin (parameters as described above) were added to 100 parts of silicon powder (parameters as described above), and the mixture was uniformly stirred for 30 minutes. The resulting mixture was then added to 500 parts of polyvinyl alcohol solution (concentration of 6wt%, degree of polymerization of 1700, and degree of alcoholysis of 99%), and stirred for 10 minutes every hour. After 12 hours, the silicon powder was removed by filtration (qualitative slow filter paper), dried at 150°C for 35 minutes, and cooled to obtain modified silicon powder;

[0051] 2) 20 parts of butyl titanate (analytical grade, molecular weight 340.3, density 0.966 g / cm3 ) was uniformly dispersed in 40 parts of anhydrous ethanol solvent, and vigorously stirred at a speed of 3500 r / min for 20 minutes to obtain a titanium source solution; 40 parts of anhydrous ethanol, 25 parts of silicic acid (density 2.2 g / ml) and 4 parts of distilled water were added to a beaker and vigorously stirred for 15 minutes, and then the titanium source solution was added dropwise thereto at a speed of 600 r / min. The reaction was stirred at room temperature for 24 hours to obtain a light yellow nano-TiO2 sol;

[0052] 3) Add 30 g of modified silicon powder to 100 parts of the obtained nano-TiO2 dispersion, stir for 20 minutes, ultrasonically disperse for 15 minutes, continue stirring for 2 hours, filter, and dry in a vacuum drying oven at 105°C to obtain the ion penetration-resistant modified composite silicon powder (denoted as Modification 1).

[0053] The test showed that the anti-ion penetration modified composite silicon powder prepared in this embodiment has a specific surface area of ​​11000m 2 / kg, the activity index was 91% at 3d, 96% at 7d, and 105% at 28d, the silicon dioxide content was 88.6%, and the water requirement ratio was 106%. The activity and water requirement at different ages were significantly improved compared with those before modification.

[0054] Application Example 1

[0055] The ion permeation-resistant modified composite silicon powder obtained in Example 1 was used to prepare subway concrete (grade C40), and the specific steps included:

[0056] First, add coarse and fine aggregates into the mixer and mix them evenly for 20 seconds. Then add the cementitious material (total design amount is 400kg / m 3 ) Dry mix in a mixer for 30 seconds, and finally pour water into the mixer and mix thoroughly for 5 minutes. The slump of the concrete is controlled at (180±20) mm by adjusting the amount of water reducer. The specific mix ratio is shown in Table 1, and the performance test results of the obtained concrete are shown in Table 2.

[0057] Table 1 Concrete mix ratio (kg / m 3 )

[0058]

[0059]

[0060] Table 2 Performance test results of concrete obtained in Application Example 1

[0061]

[0062] The above results show that the modified composite silica fume concrete obtained in this application example can simultaneously improve the mechanical properties, impedance properties and ion penetration resistance of concrete compared with the silica fume baseline group concrete before modification. Specifically, in terms of mechanical properties, the 28d compressive strength is improved by 13% compared with the baseline group. In terms of impedance properties, the 28d resistivity is improved by 14KΩ·cm compared with the baseline group. In terms of ion penetration resistance, the 56d electric flux is reduced by 421C, and the chloride ion migration coefficient is reduced by 45%.

[0063] Example 2

[0064] A method for preparing a composite silicon powder modified to resist ion penetration comprises the following steps:

[0065] 1) 4 parts of a macroporous acrylic cation exchange resin (parameters as described above) were added to 100 parts of silicon powder (parameters as described above), and the mixture was uniformly stirred for 35 minutes. The resulting mixture was then added to 500 parts of a polyvinyl alcohol solution (concentration of 6 wt%, degree of polymerization of 1700, and degree of alcoholysis of 99%), and stirred for 15 minutes every hour. After 10 hours, the silicon powder was removed by filtration (qualitative slow filter paper), dried at 150° C. for 40 minutes, and cooled to obtain modified silicon powder;

[0066] 2) 25 parts of butyl titanate (analytical grade, molecular weight 340.3, density 0.966 g / cm 3 ) was uniformly dispersed in 40 parts of anhydrous ethanol solvent, and vigorously stirred at a speed of 4000 r / min for 15 minutes to obtain a titanium source solution; 40 parts of anhydrous ethanol, 30 parts of silicic acid (density 2.2 g / ml) and 4 parts of distilled water were added to a beaker and vigorously stirred for 10 minutes, and then the titanium source solution was added dropwise thereto at a stirring speed of 600 r / min. The reaction was stirred at room temperature for 24 hours to obtain a light yellow nano-TiO2 sol;

[0067] 3) Add 35 g of modified silicon powder to 100 parts of the obtained nano-TiO2 dispersion, stir for 20 minutes, ultrasonically disperse for 15 minutes, continue stirring for 2 hours, filter, and dry in a vacuum drying oven at 105°C to obtain the ion-resistant modified composite silicon powder (denoted as Modification 2).

[0068] The test showed that the anti-ion penetration modified composite silicon powder prepared in this embodiment has a specific surface area of ​​11500m 2 / kg, the activity index was 94% at 3d, 99% at 7d, and 107% at 28d, the silicon dioxide content was 88.8%, and the water requirement ratio was 105%. The activity and water requirement at different ages were significantly improved compared with those before modification.

[0069] Application Example 2

[0070] The ion permeation-resistant modified composite silicon powder obtained in Example 2 was used to prepare subway concrete (grade C40), and the specific steps included:

[0071] First, add coarse and fine aggregates into the mixer and mix them evenly for 20 seconds. Then add the cementitious material (total design amount is 400kg / m 3 ) were dry-mixed in a mixer for 30 seconds, and finally water was poured into the mixer and fully stirred for 5 minutes. The slump of the concrete was controlled at (180±20) mm by adjusting the amount of water reducer. The specific mix ratio is shown in Table 3, and the performance test results of the obtained concrete are shown in Table 4.

[0072] Table 3 Concrete mix ratio (kg / m 3 )

[0073] Group cement fly ash Mineral powder sand stone water water reducer Silicon powder Benchmark 230 85 80 720 1125 155 8.5 5 (before modification) Application Example 2 230 85 80 720 1125 155 8.5 5 (Modification 2)

[0074] Table 4 Performance test results of concrete obtained in Application Example 2

[0075]

[0076] The above results show that the modified composite silica fume concrete obtained in this application example can simultaneously improve the mechanical properties, impedance properties and ion penetration resistance of concrete compared with the silica fume baseline group concrete before modification. Specifically, in terms of mechanical properties, the 28d compressive strength is improved by 15% compared with the baseline group. In terms of impedance performance, the 28d resistivity is improved by 13KΩ·cm compared with the baseline group. In terms of ion penetration resistance, the 56d electric flux is reduced by 433C, and the chloride ion migration coefficient is reduced by 47%.

[0077] Example 3

[0078] A method for preparing a composite silicon powder modified to resist ion penetration comprises the following steps:

[0079] 1) 3 parts of a macroporous acrylic acid cation exchange resin (parameters as described above) were added to 100 parts of silicon powder (parameters as described above), and the mixture was uniformly stirred for 30 minutes. The resulting mixture was then added to 500 parts of a polyvinyl alcohol solution (concentration of 6 wt%, degree of polymerization of 1700, and degree of alcoholysis of 99%), and stirred for 10 minutes every hour. After 12 hours, the silicon powder was removed by filtration (qualitative slow filter paper), dried at 150° C. for 35 minutes, and cooled to obtain modified silicon powder;

[0080] 2) 20 parts of butyl titanate (analytical grade, molecular weight 340.3, density 0.966 g / cm 3) was uniformly dispersed in 40 parts of anhydrous ethanol solvent, and vigorously stirred at a speed of 3500 r / min for 20 minutes to obtain a titanium source solution; 40 parts of anhydrous ethanol, 25 parts of silicic acid (density 2.2 g / ml) and 4 parts of distilled water were added to a beaker and vigorously stirred for 15 minutes, and then the titanium source solution was added dropwise thereto at a speed of 600 r / min. The reaction was stirred at room temperature for 24 hours to obtain a light yellow nano-TiO2 sol;

[0081] 3) Add 30g of modified silicon powder to 100 parts of the obtained nano-TiO2 dispersion, stir for 15 minutes, and then add 50g of PVA renewable dispersible latex powder (white powder, solid content 99%, density 0.60g / cm 3 , fineness is 0.18mm, resistivity is 3.3×10 4 kΩ·cm), stirred for 20 minutes, ultrasonically dispersed for 15 minutes, continued stirring for 2 hours, filtered, and dried in a vacuum drying oven at 105° C. to obtain the ion penetration-resistant modified composite silicon powder (denoted as modification 3).

[0082] The test showed that the anti-ion penetration modified composite silicon powder prepared in this embodiment has a specific surface area of ​​11000m 2 / kg, the activity index was 92% at 3d, 97% at 7d, and 106% at 28d, the silicon dioxide content was 88.6%, and the water requirement ratio was 105%. The activity and water requirement at different ages were significantly improved compared with those before modification.

[0083] Application Example 3

[0084] The ion permeation-resistant modified composite silicon powder obtained in Example 3 was used to prepare subway concrete (grade C40), and the specific steps included:

[0085] First, add coarse and fine aggregates into the mixer and mix them evenly for 20 seconds. Then add the cementitious material (total design amount is 400kg / m 3 ) Dry mix in a mixer for 30 seconds, and finally pour water into the mixer and mix thoroughly for 5 minutes. The slump of the concrete is controlled at (180±20) mm by adjusting the amount of water reducer. The specific mix ratio is shown in Table 5, and the performance test results of the obtained concrete are shown in Table 6.

[0086] Table 5 Concrete mix ratio (kg / m 3 )

[0087] Group cement fly ash Mineral powder sand stone water water reducer Silicon powder Benchmark 225 90 80 720 1125 155 8.5 5 (before modification) Application Example 3 225 90 80 720 1125 155 8.5 5 (modification 3)

[0088] Table 6 Performance test results of concrete obtained in Application Example 3

[0089]

[0090] The above results show that the modified composite silica fume concrete obtained in this application example can simultaneously improve the mechanical properties, impedance properties and ion penetration resistance of concrete compared with the silica fume baseline group concrete before modification. Specifically, in terms of mechanical properties, the 28d compressive strength is improved by 15% compared with the baseline group. In terms of impedance properties, the 28d resistivity is improved by 17KΩ·cm compared with the baseline group. In terms of ion penetration resistance, the 56d electric flux is reduced by 436C, and the chloride ion migration coefficient is reduced by 45%.

[0091] Comparative Example 1

[0092] A method for preparing a composite silicon powder modified to resist ion penetration comprises the following steps:

[0093] 1) 3 parts of a strongly basic styrene anion exchange resin (pH 10, effective particle size 0.05 mm, water content 55%, wet true density 1.10 g / ml) were added to 100 parts of silicon powder and stirred uniformly for 30 minutes. The resulting mixture was then added to 500 parts of a polyvinyl alcohol solution (concentration 6 wt%, degree of polymerization 1700, degree of alcoholysis 99%) and stirred for 10 minutes every hour. After 12 hours, the silicon powder was removed by filtration (qualitative slow filter paper), dried at 150° C. for 35 minutes, and cooled to obtain modified silicon powder;

[0094] 2) 20 parts of butyl titanate (analytical grade, molecular weight 340.3, density 0.966 g / cm 3 ) was uniformly dispersed in 40 parts of anhydrous ethanol solvent, and vigorously stirred at a speed of 3500 r / min for 20 minutes to obtain a titanium source solution; 40 parts of anhydrous ethanol, 25 parts of silicic acid (density 2.2 g / ml) and 4 parts of distilled water were added to a beaker and vigorously stirred for 15 minutes, and then the titanium source solution was added dropwise thereto at a speed of 600 r / min. The reaction was stirred at room temperature for 24 hours to obtain a light yellow nano-TiO2 sol;

[0095] 3) Add 30 g of modified silicon powder to 100 parts of the obtained nano-TiO2 dispersion, stir for 20 minutes, ultrasonically disperse for 15 minutes, continue stirring for 2 hours, filter, and dry in a vacuum drying oven at 105°C to obtain the ion penetration-resistant modified composite silicon powder (denoted as Modification 4).

[0096] After testing, the prepared ion penetration-resistant modified composite silicon powder has a specific surface area of ​​14800m 2 / kg, the activity index is 85% at 3d, 85% at 7d, 98% at 28d, the silicon dioxide content is 88.6%, the water requirement ratio is 117%, and the activity and water requirement at different ages have no obvious changes compared with those before modification. Compared with the modified silicon powder obtained in Examples 1, 2, and 3, the performance of various aspects has been significantly reduced.

[0097] The anti-ion penetration modified composite silica fume obtained in this comparative example was used to prepare subway concrete (C40 grade). The specific steps included: first, adding coarse and fine aggregates into a mixer and stirring evenly for 20 seconds; then, adding cementitious materials (total design amount of 400 kg / m 3 ) Dry mix in a mixer for 30 seconds, then pour water into the mixer and mix thoroughly for 5 minutes. The slump of the concrete is controlled at (180±20) mm by adjusting the amount of water reducer. The specific mix ratio is shown in Table 7, and the performance test results of the obtained concrete are shown in Table 8.

[0098] Table 7 Concrete mix ratio (kg / m 3 )

[0099] Group cement fly ash Mineral powder sand stone water water reducer Silicon powder Benchmark 225 90 80 720 1125 155 8.5 5 (before modification) Comparative Example 1 225 90 80 720 1125 155 8.5 5 (modified 4)

[0100] Table 8 Performance test results of concrete obtained in Comparative Example 1

[0101]

[0102] The above results show that the modified composite silica fume concrete obtained in this comparative example has no significant changes in various properties compared with the silica fume benchmark group concrete before modification. Compared with Application Example 1, the mechanical properties, impedance properties and ion penetration resistance are significantly reduced. Specifically, the 28d compressive strength is reduced by 13%, the 28d resistivity is reduced by 14KΩ·cm, the 56d electric flux is increased by 417C, and the chloride ion migration coefficient is increased by 78%.

[0103] Comparative Example 2

[0104] A method for preparing a composite silicon powder modified to resist ion penetration comprises the following steps:

[0105] 1) 3 parts of a macroporous acrylic acid cation exchange resin (parameters as described above) were added to 100 parts of silicon powder (parameters as described above), and the mixture was uniformly stirred for 30 minutes. The resulting mixture was then added to 500 parts of a polyvinyl alcohol solution (concentration of 6 wt%, degree of polymerization of 1700, and degree of alcoholysis of 99%), and stirred for 10 minutes every hour. After 12 hours, the silicon powder was removed by filtration (qualitative slow filter paper), dried at 150° C. for 35 minutes, and cooled to obtain modified silicon powder;

[0106] 2) 20 parts of butyl titanate (analytical grade, molecular weight 340.3, density 0.966 g / cm 3) was uniformly dispersed in 40 parts of anhydrous ethanol solvent, and vigorously stirred at a speed of 3500 r / min for 20 minutes to obtain a titanium source solution; 40 parts of anhydrous ethanol, 20 parts of glacial acetic acid (density 1.06 g / ml) and 4 parts of distilled water were added to a beaker and vigorously stirred for 15 minutes, and then the titanium source solution was added dropwise thereto at a speed of 600 r / min. The reaction was stirred at room temperature for 24 hours to obtain a light yellow nano-TiO2 sol;

[0107] 3) Add 30 g of modified silicon powder to 100 parts of the obtained nano-TiO2 dispersion, stir for 20 minutes, ultrasonically disperse for 15 minutes, continue stirring for 2 hours, filter, and dry in a vacuum drying oven at 105°C to obtain the ion penetration-resistant modified composite silicon powder (denoted as Modification 5).

[0108] After testing, the prepared ion penetration-resistant modified composite silicon powder has a specific surface area of ​​12500m 2 / kg, the activity index was 86% at 3d, 88% at 7d, and 100% at 28d, the silica content was 88.6%, the water requirement ratio was 111%, the water requirement was slightly lower than that before modification, and there was no obvious change in activity at different ages.

[0109] The anti-ion penetration modified composite silica powder obtained in this comparative example is used to prepare subway concrete (C40 grade), and the specific steps include:

[0110] First, add coarse and fine aggregates into the mixer and mix them evenly for 20 seconds. Then add the cementitious material (total design amount is 400kg / m 3 ) Dry mix in a mixer for 30 seconds, then pour water into the mixer and mix thoroughly for 5 minutes. The slump of the concrete is controlled at (180±20) mm by adjusting the amount of water reducer. The specific mix ratio is shown in Table 9, and the performance test results of the obtained concrete are shown in Table 10.

[0111] Table 9 Concrete mix ratio (kg / m 3 )

[0112] Group cement fly ash Mineral powder sand stone water water reducer Silicon powder Benchmark 225 90 80 720 1125 155 8.5 5 (before modification) Comparative Example 2 225 90 80 720 1125 155 8.5 5 (Modified 5)

[0113] Table 10 Performance test results of concrete obtained in Comparative Example 2

[0114]

[0115] The above results show that the modified composite silica fume concrete obtained in this comparative example has no significant change in mechanical properties compared with the silica fume benchmark group concrete before modification, and the impedance performance and ion penetration resistance are improved to a certain extent. Compared with Application Example 1, the mechanical properties, impedance performance and ion penetration resistance are all significantly reduced, among which the mechanical properties are the most obvious, as follows: the 28d compressive strength is reduced by 10%, the 28d resistivity is reduced by 8KΩ·cm, the 56d electric flux is increased by 27C, and the chloride ion migration coefficient is increased by 22%.

[0116] Comparative Example 3

[0117] A method for preparing a composite silicon powder modified to resist ion penetration comprises the following steps:

[0118] 1) Add 3 parts of macroporous acrylic acid cation exchange resin (parameters as described above) to 100 parts of silicon powder and stir evenly for 30 minutes. After 12 hours, remove the silicon powder by filtration (qualitative slow filter paper), dry it at 150°C for 35 minutes, and cool it to obtain modified silicon powder;

[0119] 2) 20 parts of butyl titanate (analytical grade, molecular weight 340.3, density 0.966 g / cm 3 ) was uniformly dispersed in 40 parts of anhydrous ethanol solvent, and vigorously stirred at a speed of 3500 r / min for 20 minutes to obtain a titanium source solution; 40 parts of anhydrous ethanol, 25 parts of silicic acid (density 2.2 g / ml) and 4 parts of distilled water were added to a beaker and vigorously stirred for 15 minutes, and then the titanium source solution was added dropwise thereto at a speed of 600 r / min. The reaction was stirred at room temperature for 24 hours to obtain a light yellow nano-TiO2 sol;

[0120] 3) Add 30 g of modified silicon powder to 100 parts of the obtained nano-TiO2 dispersion, stir for 20 minutes, ultrasonically disperse for 15 minutes, continue stirring for 2 hours, filter, and dry in a vacuum drying oven at 105°C to obtain the ion penetration-resistant modified composite silicon powder (denoted as Modification 6).

[0121] After testing, the prepared ion penetration-resistant modified composite silicon powder has a specific surface area of ​​14000m 2 / kg, the activity index is 86% at 3d, 87% at 7d, and 99% at 28d, the silicon dioxide content is 88.6%, and the water requirement ratio is 115%. There is no significant change in the activity and water requirement at different ages compared with those before modification. Compared with the modified silicon powder obtained in Examples 1, 2, and 3, the performance in all aspects has been significantly reduced.

[0122] The anti-ion penetration modified composite silica fume obtained in this comparative example was used to prepare subway concrete (C40 grade). The specific steps included: first, adding coarse and fine aggregates into a mixer and stirring evenly for 20 seconds; then, adding cementitious materials (total design amount of 400 kg / m3 ) Dry mix in a mixer for 30 seconds, then pour water into the mixer and mix thoroughly for 5 minutes. The slump of the concrete is controlled at (180±20) mm by adjusting the amount of water reducer. The specific mix ratio is shown in Table 11, and the performance test results of the obtained concrete are shown in Table 12.

[0123] Table 11 Concrete mix ratio (kg / m 3 )

[0124] Group cement fly ash Mineral powder sand stone water water reducer Silicon powder Benchmark 225 90 80 720 1125 155 8.5 5 (before modification) Comparative Example 3 225 90 80 720 1125 155 8.5 5 (modified 6)

[0125] Table 12 Performance test results of concrete obtained in Comparative Example 1

[0126]

[0127] The above results show that the modified composite silica fume concrete obtained in this comparative example has no significant changes in various properties compared with the silica fume benchmark group concrete before modification. Compared with Application Example 1, the mechanical properties, impedance properties and ion penetration resistance are significantly reduced. Specifically, the 28d compressive strength is reduced by 12%, the 28d resistivity is reduced by 12KΩ·cm, the 56d electric flux is increased by 414C, and the chloride ion migration coefficient is increased by 78%.

[0128] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for preparing ion-resistant modified composite silicon powder, characterized in that: The following steps are involved: 1) adding a macroporous weakly acidic acrylic acid cation exchange resin to silicon powder and stirring the mixture, then adding the resulting mixture to a polyvinyl alcohol solution and stirring the mixture a second time, filtering out the treated silicon powder, drying it, and cooling it to obtain modified silicon powder; 2) uniformly dispersing a titanium source in an alcohol solvent to obtain a titanium source solution; uniformly mixing silicic acid, an alcohol solvent, and water, then dropwise adding the titanium source solution thereto under stirring conditions, and reacting with stirring at room temperature to obtain a nano-TiO2 sol; 3) Adding modified silicon powder to the obtained nano-TiO2 sol, mixing evenly, and drying to obtain the ion penetration-resistant modified composite silicon powder.

2. The preparation method according to claim 1, characterized in that The specific surface area of ​​the silicon powder is 15000~18000m 2 / kg, the activity index is 80-90% at 3 days, 85-95% at 7 days, 95-105% at 28 days, the silicon dioxide content is 85-90%, and the water requirement ratio is 115-120%.

3. The preparation method according to claim 1, characterized in that The pH value of the macroporous weakly acidic acrylic acid cation exchange resin is 5-6, the hydrogen form rate is ≥98%, the water content is 45-48%, and the wet true density is 1.16-1.18 g / ml.

4. The preparation method according to claim 1, characterized in that The amount of the macroporous weakly acidic acrylic acid cation exchange resin used in step 1) is 3-4% of the mass of the silicon powder.

5. The preparation method according to claim 1, characterized in that The mass ratio of the titanium source, the total alcohol solvent, the silicic acid and the water introduced in step 2) is 1:(3.5-4.5):(1-2):(0.1-0.3).

6. The preparation method according to claim 1, characterized in that The stirring reaction time in step 2) is 20 to 24 hours.

7. The preparation method according to claim 1, characterized in that The mass ratio of the nano-TiO2 sol to the modified silicon powder is 100:30-35.

8. The preparation method according to claim 1, characterized in that In step 3), PVA redispersible latex powder is added simultaneously.

9. The ion penetration-resistant modified composite silicon powder prepared by the preparation method according to any one of claims 1 to 8, characterized in that: Its specific surface area is 10000~12000m 2 / kg, the activity index is 85-95% at 3 days, 90-100% at 7 days, 100-110% at 28 days, the silicon dioxide content is 85-90%, and the water requirement ratio is 105-110%.

10. A concrete prepared using the anti-ion penetration modified composite silica fume according to claim 9, characterized in that: The addition amount of the anti-ion penetration modified composite silica powder is 1 to 1.5% of the mass of the cementitious material.

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