Method and application for preparing hydrophobic micropowder by using solid waste

Abstract

The present invention relates to the technical field of the preparation of concrete water repellents, and specifically discloses a method for preparing hydrophobic fine powder using solid waste and its application. The method comprises the following steps: (1) Mix a solid waste mainly composed of silicon dioxide, a surface modifier and water, and carry out a stirring reaction under heating conditions to obtain a reaction system containing modified solid waste, wherein the surface modifier is an alkaline substance. (2) Add a water repellent, a silicon-rich hydroxyl substance and a catalyst to the reaction system and carry out a stirring reaction. After the reaction is completed, separate the solid phase product, wash it to remove the reaction liquid remaining on the surface, dry it and grind it finely to obtain the hydrophobic fine powder. The method of the present invention prepares the solid waste into a concrete additive with stable hydrophobicity, which can not only prepare hydrophobic concrete, but also serve as a filler and improve the mechanical properties of concrete.

Description

Technical Field

[0001] The invention relates to the technical field of concrete hydrophobic agent preparation, and in particular to a method for preparing hydrophobic micropowder by utilizing solid waste and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Bulk solid waste is a core area of ​​comprehensive resource utilization, with large volume and wide coverage, prominent environmental impact and broad prospects for utilization. Bulk industrial solid waste refers to solid waste with an annual production volume of more than 10 million tons in various industrial fields in my country and a great impact on the environment and safety. It mainly includes tailings, fly ash, coal gangue, smelting waste, slag, desulfurized gypsum, phosphogypsum, red mud and sludge. In order to reduce the discharge of waste residues and recycle them, in addition to recycling them with expensive equipment, it is more important to increase the added value of bulk solid waste and improve the utilization rate of bulk solid waste. At present, the most direct and simplest method is to add solid waste to concrete to reduce costs. However, due to the very low hydration activity of these wastes, they can basically only play a physical filling role in concrete, and this method has a low utilization value for solid wastes. Solid wastes have failed to play their due potential and have limited improvement on the performance of concrete. Summary of the invention

[0004] The present invention provides a method for preparing hydrophobic micropowder using solid waste and its application, wherein the solid waste is prepared into a concrete additive with stable hydrophobicity, which can not only prepare hydrophobic concrete, but also has the functions of filler and improving the mechanical properties of concrete. To achieve the above purpose, the present invention provides the following technical solution.

[0005] First, the present invention discloses a method for preparing hydrophobic micropowder using solid waste, comprising the following steps:

[0006] (1) Solid waste mainly composed of silicon dioxide, a surface modifier and water are mixed and stirred for reaction under heating conditions to obtain a reaction system containing modified solid waste, wherein the surface modifier is an alkaline substance.

[0007] (2) adding a hydrophobic agent, a silanol-rich substance and a catalyst to the reaction system and stirring the reaction, separating the solid phase product after the reaction is completed, washing the solid phase product to remove the residual reaction liquid on the surface, drying the solid phase product and grinding the solid phase product to obtain a hydrophobic micropowder.

[0008] Further, in step (1), the ratio of the solid waste, the surface modifier, and water is 5 to 15 parts by weight: 13 to 25 parts by weight: 20 to 50 parts by weight.

[0009] Further, in step (1), the solid waste includes at least one of slag powder, ceramic sawdust, marble sawdust, fly ash, tailings, coal gangue, construction waste, etc. The main component of these solid wastes is silicon dioxide, and the hydration products formed after modification by the surface modifier expose a large number of hydroxyl groups on the surface of the solid waste particles, facilitating further modification treatment.

[0010] Further, in step (1), the surface modifier includes at least one of sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, sodium carbonate, etc.

[0011] Further, in step (1), the heating temperature range is 45 to 75 °C, the stirring rate of the stirring reaction is 600 to 1500 rpm, and the reaction time is 24 to 48 h.

[0012] Further, in step (2), the ratio of the hydrophobic agent, the silicon-rich hydroxyl substance, and the catalyst is 3 to 8 parts by weight: 0.3 to 0.5 parts by weight: 0.03 to 0.05 parts by weight.

[0013] Further, in step (2), the hydrophobic agent includes at least one of hydroxyl-terminated polydimethylsiloxane, isobutyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, hexamethyldisiloxane, hexamethyldisilazane, room temperature vulcanized silicone rubber, etc. In the present invention, the main function of the hydrophobic agent is to react with the hydroxyl groups exposed on the surface of the solid waste particles under the action of the catalyst to achieve the grafting of the hydrophobic agent.

[0014] Further, in step (2), the silicon-rich hydroxyl substance includes at least one of tetraethyl orthosilicate, silica sol, nano-silica dispersion liquid, etc. In the present invention, the silicon-rich hydroxyl substance serves as an intermediate for grafting the hydrophobic modifier to the pre-activated slag powder, improving the loading capacity of the hydrophobic modifier on the slag powder.

[0015] Further, in step (2), the catalyst includes dibutyltin dilaurate, etc. In the present invention, the main functions of the catalyst include improving the grafting efficiency of the hydrophobic modifier to the pre-activated slag powder.

[0016] Further, in step (2), the stirring rate of the stirring reaction is 300 to 700 rpm, and the reaction time is 20 to 28 hours.

[0017] Further, in step (2), any one of absolute ethanol, isopropanol, ethylene glycol, etc. is used to wash the solid-phase product. Optionally, the washing process is repeated 3 to 5 times to fully remove the reaction solution remaining on the surface of the solid-phase product.

[0018] Further, in step (2), the drying temperature is 100 to 110 °C, and the drying time is 22 to 25 hours.

[0019] Further, in step (2), the particle size range of the hydrophobic micropowder is 150 nm to 200 μm.

[0020] Secondly, the present invention discloses the application of the hydrophobic micropowder prepared by the method for preparing hydrophobic micropowder using solid waste in concrete materials. Preferably, the addition amount of the hydrophobic micropowder in the concrete is 5 to 60% of the mass of the concrete.

[0021] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0022] In the previous experiments of the present invention, in order to prepare hydrophobic micropowders from solid waste, the solid waste and a hydrophobizing agent were simply physically blended for physical adsorption modification. However, the present invention found that the results obtained by adding the hydrophobic micropowders prepared by this method to concrete were not satisfactory. Further research revealed that: under the action of external forces such as those brought about by the mixing of the concrete, the hydrophobizing agent adsorbed by this hydrophobic micropowder would fall off, resulting in poor hydrophobic stability and hydrophobic effect of this hydrophobic micropowder, and it could not play the due role of a hydrophobic powder. For this reason, the present invention proposes a method of pre-exciting the solid waste and grafting the hydrophobizing agent in-situ for modification. Not only is the obtained hydrophobic micropowder highly hydrophobic stable, but it can also actively participate in the hydration process of cement in concrete to form a gelling substance and play a seeding effect, promoting the early hydration of the cement-based material and improving the strength of the concrete. The reasons are as follows: First, the present invention uses the surface modifier to modify the surface of the solid waste particles, so that a large number of hydroxyl groups are exposed on the surface of the solid waste particles. These hydroxyl groups serve as grafting sites, and under the action of the silicon-rich hydroxyl substance and the catalyst, they complete bonding with the polycondensation terminal hydroxyl groups on the hydrophobizing agent, thereby firmly connecting the hydrophobizing agent to the surface of the solid waste particles, effectively overcoming the problem that the hydrophobizing agent adsorbed on the surface of the solid waste particles is prone to fall off in the above-mentioned physical adsorption method, and greatly improving the hydrophobic stability of the obtained hydrophobic micropowder. Second, due to the establishment of the grafting sites, it helps to improve the grafting success rate and uniformity of the hydrophobizing agent and improve the hydrophobic effect. In addition, the hydrophobic micropowders obtained by physically adsorbing the hydrophobizing agent on the surface of the solid waste mainly exhibit hydrophobic effects in addition to acting as fillers, and this hydrophobic effect further hinders the hydration of the solid waste and fails to utilize the potential of the solid waste in concrete. After being modified by the surface modifier of the present invention, the silicon-oxygen bonds on the surface of the solid waste are broken, so that the surface of the low-activity solid waste is converted into a high-activity surface, making the hydrophobic micropowder of the present invention have both stable high hydrophobicity and high activity. After entering the concrete, it can quickly and actively participate in hydration to form a gelling substance, improve the strength of the concrete, and not only play the role of a filler, thereby improving the utilization value of the solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings, wherein:

[0024] Figure 1 is a test diagram of the surface contact angle of the hydrophobic micro-nano powder prepared in Example 1 below.

[0025] Figure 2It is a test diagram of the surface contact angle of the hydrophobic micro-nano powder prepared in Example 3 below.

[0026] Figure 3 It is a test diagram of the surface contact angle of the hydrophobic micro-nano powder prepared in Example 4 below. Detailed implementation manners

[0027] The present invention will be further described below in conjunction with specific embodiments. These embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The preferred implementation methods and materials described in the text are only for demonstration purposes. The present invention will be described in detail below in conjunction with the specific implementation manners.

[0028] Example 1

[0029] A method for preparing hydrophobic micro-powder using solid waste, comprising the following steps:

[0030] (1) Put 10 parts by weight of slag powder, 21 parts by weight of sodium hydroxide and 40 parts by weight of water into an oil bath stirring device, heat to 65 °C, and stir and react at a speed of 1000 rpm for 24 h. Complete the dropwise addition of 5 parts by weight of isobutyltriethoxysilane, 0.4 parts by weight of tetraethyl orthosilicate, and 0.04 parts by weight of dibutyltin dilaurate into the reaction system, and stir and react at a speed of 500 rpm for 24 h to obtain liquid material A.

[0031] (2) After taking out the liquid material A, cool it at room temperature for 10 min, and then centrifuge for 10 minutes at a speed of 16000 rpm for centrifugal separation. Wash the solid-phase product collected after the centrifugal separation with absolute ethanol, and repeat the above washing process 4 times. Then place the obtained solid-phase product in a vacuum drying oven and dry it at 105 °C for 24 h. After completion, take out the solid-phase product, mill it with a mill, and pass through a 200-mesh sieve to obtain the hydrophobic micro-powder.

[0032] Example 2

[0033] A method for preparing hydrophobic micro-powder using solid waste, comprising the following steps:

[0034] (1) Put 5 parts by weight of slag powder, 13 parts by weight of sodium silicate and 20 parts by weight of water into an oil bath stirring device, heat to 45 °C, and stir and react at a speed of 600 rpm for 48 h. Complete the dropwise addition of 3 parts by weight of isobutyltriethoxysilane, 0.3 parts by weight of tetraethyl orthosilicate, and 0.03 parts by weight of dibutyltin dilaurate into the reaction system, and stir and react at a speed of 700 rpm for 20 h to obtain liquid material A.

[0035] (2) After taking out the liquid material A, it is cooled at room temperature for 10 min, and then centrifuged for 10 minutes at a rotational speed of 16,000 rpm for centrifugal separation. The solid-phase product collected after the centrifugal separation is washed with absolute ethanol, and the above washing process is repeated 3 times. Then the obtained solid-phase product is placed in a vacuum drying oven and dried at 100 °C for 25 h. After completion, the solid-phase product is taken out, milled with a mill, and passed through a 200-mesh sieve to obtain the hydrophobic fine powder.

[0036] Example 3

[0037] A method for preparing hydrophobic fine powder from solid waste, comprising the following steps:

[0038] (1) 15 parts by weight of slag powder, 25 parts by weight of potassium hydroxide, and 20 parts by weight of water are placed in an oil bath stirring device and heated to 75 °C, and stirred and reacted at a rotational speed of 1500 rpm for 36 h. After completion, 8 parts by weight of hydroxyl-terminated polydimethylsiloxane, 0.5 part by weight of silica sol, and 0.05 part by weight of dibutyltin dilaurate are added dropwise to the reaction system, and stirred and reacted at a rotational speed of 300 rpm for 28 h to obtain liquid material A.

[0039] (2) After taking out the liquid material A, it is cooled at room temperature for 10 min, and then centrifuged for 10 minutes at a rotational speed of 16,000 rpm for centrifugal separation. The solid-phase product collected after the centrifugal separation is washed with absolute ethanol, and the above washing process is repeated 4 times. Then the obtained solid-phase product is placed in a vacuum drying oven and dried at 110 °C for 22 h. After completion, the solid-phase product is taken out, milled with a mill, and passed through a 200-mesh sieve to obtain the hydrophobic fine powder.

[0040] Example 4

[0041] A method for preparing hydrophobic fine powder from solid waste, comprising the following steps:

[0042] (1) 10 parts by weight of slag powder and 40 parts by weight of water are placed in an oil bath stirring device and heated to 65 °C, and stirred and reacted at a rotational speed of 1000 rpm for 24 h. After completion, 5 parts by weight of isobutyltriethoxysilane, 0.4 part by weight of tetraethyl orthosilicate, and 0.04 part by weight of dibutyltin dilaurate are added dropwise to the reaction system, and stirred and reacted at a rotational speed of 500 rpm for 24 h to obtain liquid material A.

[0043] (2) After taking out the liquid material A, cool it at room temperature for 10 min, and then centrifuge it at a speed of 16000 rpm for 10 minutes for centrifugal separation. Wash the solid-phase product collected after the centrifugal separation with absolute ethanol, and repeat the above washing process 4 times. Then place the obtained solid-phase product in a vacuum drying oven and dry it at 105 °C for 24 h. After completion, take out the solid-phase product, mill it with a mill, and pass it through a 200-mesh sieve to obtain the hydrophobic fine powder.

[0044] Example 5

[0045] A method for preparing hydrophobic fine powder from solid waste, comprising the following steps:

[0046] (1) Place 5 parts by weight of slag powder, 13 parts by weight of sodium silicate, and 20 parts by weight of water in an oil bath stirring device, heat it to 45 °C, and stir and react at a speed of 600 rpm for 48 h. After completion, add 3 parts by weight of isobutyltriethoxysilane and 0.03 parts by weight of dibutyltin dilaurate dropwise into the reaction system, and stir and react at a speed of 700 rpm for 20 h to obtain liquid material A.

[0047] (2) After taking out the liquid material A, cool it at room temperature for 10 min, and then centrifuge it at a speed of 16000 rpm for 10 minutes for centrifugal separation. Wash the solid-phase product collected after the centrifugal separation with absolute ethanol, and repeat the above washing process 3 times. Then place the obtained solid-phase product in a vacuum drying oven and dry it at 100 °C for 25 h. After completion, take out the solid-phase product, mill it with a mill, and pass it through a 200-mesh sieve to obtain the hydrophobic fine powder.

[0048] Example 6

[0049] A method for preparing hydrophobic fine powder from solid waste, comprising the following steps:

[0050] (1) Place 15 parts by weight of slag powder, 25 parts by weight of potassium hydroxide, and 20 parts by weight of water in an oil bath stirring device, heat it to 75 °C, and stir and react at a speed of 1500 rpm for 36 h. After completion, add 8 parts by weight of hydroxyl-terminated polydimethylsiloxane and 0.05 parts by weight of dibutyltin dilaurate dropwise into the reaction system, and stir and react at a speed of 300 rpm for 28 h to obtain liquid material A.

[0051] (2) After taking out the liquid material A, cool it at room temperature for 10 min, and then centrifuge it at a speed of 16000 rpm for 10 minutes for centrifugal separation. Wash the solid-phase product collected after the centrifugal separation with absolute ethanol, and repeat the above washing process 4 times. Then place the obtained solid-phase product in a vacuum drying oven and dry it at 110 °C for 22 h. After completion, take out the solid-phase product, mill it with a mill, and pass it through a 200-mesh sieve to obtain the hydrophobic fine powder.

[0052] Example 7

[0053] A method for preparing hydrophobic micropowder from solid waste, comprising the following steps:

[0054] (1) Mix 10 parts by weight of slag powder, 20 parts by weight of water, and 5 parts by weight of isobutyltriethoxysilane, and then stir and mix at a rotation speed of 500 rpm for 24 h to obtain liquid material A.

[0055] (2) After taking out the liquid material A, cool it at room temperature for 10 min, and then centrifuge it at a rotation speed of 16,000 rpm for 10 minutes for centrifugal separation. Wash the solid-phase product collected after the centrifugal separation with absolute ethanol, and repeat the above washing process 4 times. Then place the obtained solid-phase product in a vacuum drying oven and dry it at 105 °C for 24 h. After completion, take out the solid-phase product, mill it with a mill, and pass it through a 200-mesh sieve to obtain the hydrophobic micropowder.

[0056] Performance test: Test the contact angle of the hydrophobic powder prepared in each of the above embodiments. In addition, add the hydrophobic micropowder prepared in each of the above embodiments to the concrete material according to a mass percentage of 10%, and after molding, cure it to the set age (7 days, 28 days), and test the compressive strength and the impregnation water absorption of the obtained concrete specimens. The results are shown in Table 1 below.

[0057] Table 1

[0058]

[0059]

[0060] It can be seen from the above test results that: the micro-nano hydrophobic powder slag prepared in Examples 1 to 3 significantly has better hydrophobicity, and the compressive strength of the concrete prepared from these micro-nano hydrophobic powder slags is significantly better than that of other embodiments. This is mainly because, compared with other embodiments, Examples 1 to 3 adopt the method of pre-exciting solid waste and grafting a hydrophobic agent in situ for modification. Not only the hydrophobic stability of the obtained hydrophobic micropowder is high, but also it has high activity. In the concrete, it can not only fully play the crystal seed effect to improve the early hydration activity of the cement-based material, thereby improving the strength of the concrete, but also provide hydrophobic sites, reduce the capillary tension of the micro-nano pores of the cement-based material, reduce the water-salt transport caused by the capillary effect, reduce the water absorption rate, and improve the hydrophobicity.

[0061] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing hydrophobic micropowder using solid waste, characterized in that, Including the steps: (1) Mix a solid waste mainly composed of silica, a surface modifier, and water, and then carry out a stirring reaction to obtain a reaction system containing the modified solid waste. The surface modifier is an alkaline substance; (2) Add a water repellent, a silicon-rich hydroxyl substance, and a catalyst to the reaction system and stir to react. After the reaction is completed, separate the solid-phase product, wash it to remove the residual reaction liquid on the surface, dry it, and then grind it finely to obtain the hydrophobic micropowder. The silicon-rich hydroxyl substance includes at least one of tetraethyl orthosilicate, silica sol, and nano-silica dispersion; 2. The method for preparing hydrophobic micropowder from solid waste according to claim 1, characterized in that, In step (1), the ratio of the solid waste, the surface modifier, and water is 5-15 parts by weight: 13-25 parts by weight: 20-50 parts by weight.

3. The method for preparing hydrophobic fine powder using solid waste according to claim 1, wherein In step (1), the solid waste includes at least one of slag powder, ceramic sawdust, marble sawdust, fly ash, tailings, coal gangue, and construction waste.

4. The method for preparing hydrophobic fine powder from solid waste according to claim 1, characterized in that, The surface modifier includes at least one of sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, and sodium carbonate.

5. The method for preparing hydrophobic fine powder from solid waste according to claim 1, characterized in that, In step (1), the heating temperature range of the stirring reaction is 45-75°C, the stirring rate of the stirring reaction is 600-1500 rpm, and the reaction time is 24-48 h.

6. The method for preparing hydrophobic micropowder from solid waste according to claim 1, wherein In step (2), the ratio of the water repellent, the silicon-rich hydroxyl substance, and the catalyst is 3-8 parts by weight: 0.3-0.5 parts by weight: 0.03-0.05 parts by weight.

7. The method for preparing hydrophobic fine powder using solid waste according to claim 6, characterized in that, In step (2), the water repellent includes at least one of hydroxyl-terminated polydimethylsiloxane, isobutyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, hexamethyldisiloxane, hexamethyldisilazane, and room temperature vulcanized silicone rubber.

8. The method for preparing hydrophobic micropowder from solid waste according to claim 6, characterized in that, In step (2), the catalyst includes dibutyltin dilaurate.

9. The method for preparing hydrophobic micropowder from solid waste according to any one of claims 1-8, characterized in that, In step (2), the stirring rate of the stirring reaction is 300-700 rpm, and the reaction time is 20-28 hours.

10. The method for preparing hydrophobic fine powder from solid waste according to any one of claims 1-8, characterized in that, In step (2), any one of absolute ethanol, isopropyl alcohol, ether, and chloroform is used to wash the solid-phase product.

11. The method for preparing hydrophobic fine powder using solid waste according to any one of claims 1-8, characterized in that, In step (2), the washing process is repeated 3-5 times.

12. The method for preparing hydrophobic fine powder from solid waste according to any one of claims 1-8, characterized in that, In step (2), the drying temperature is 100-110°C, and the drying time is 22-25 hours.

13. The method for preparing hydrophobic fine powder using solid waste according to any one of claims 1-8, characterized in that, In step (2), the particle size range of the hydrophobic micropowder is 150 nm-200 µm.

14. Application of the hydrophobic micropowder prepared by the method for preparing hydrophobic micropowder using solid waste according to any one of claims 1-13 in concrete materials.

15. The application according to claim 14, characterized in that, The addition amount of the hydrophobic micropowder in the concrete is 5-60% of the mass of the concrete.

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