A preparation method of surface modified composite micro-nano ultrafine powder and ultra-high performance concrete thereof

Abstract

The present invention relates to the technical field of ultra-high performance concrete preparation, and specifically discloses a preparation method of a surface-modified composite micro-nano ultrafine powder and ultra-high performance concrete thereof. The preparation method comprises the following steps: (1) dissolving isobutyl triethoxysilane and polyacrylate in acetone or ethyl acetate to obtain a surface modifier solution. (2) adding industrial solid waste micro-nano ultrafine powder having gelling activity to anhydrous ethanol dissolved with hexadecyl trimethyl ammonium bromide for reaction. After completion, a solid product is separated, washed, and dried to obtain a pre-treated micro-nano ultrafine powder. (3) adding the pre-treated micro-nano ultrafine powder to the surface modifier solution, then adding a pH regulator to adjust the reaction system to acidity, separating the solid product after the reaction, washing, and drying to obtain a surface-modified composite micro-nano ultrafine powder. The present invention uses modified micro-nano ultrafine powder to not only improve the dispersibility in concrete, but also significantly improve the mechanical properties of concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high performance concrete preparation, and in particular to a preparation method of surface-modified composite micro-nano ultrafine powder and ultra-high performance concrete 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] The field of concrete materials needs to vigorously develop various high-performance and ultra-high-performance special cement concretes, special functional mortar material systems and their supporting admixture systems. Ultra-high performance concrete (UHPC) is a new type of cement-based engineering material that has developed rapidly in recent years. It has ultra-high mechanical properties and good durability, and its main properties are about 5 to 100 times that of ordinary concrete. It has been proven to be a promising material for construction, structural repair and bridge engineering. However, the high cost of UHPC and its relatively large early shrinkage limit the application of UHPC.

[0004] Ultrafine mineral admixture is an ultrafine powder with high volcanic ash activity, such as slag. After ultrafine treatment, it not only has a high specific surface area, but also has a high volcanic ash activity. The application of this ultrafine powder in ultra-high performance concrete can help reduce the amount of cement used and the cost of ultra-high performance concrete. It can also help reduce the mining of cement raw material limestone, effectively reduce the consumption rate of limited natural resources, and reduce the emission of carbon dioxide in the cement production process, reducing damage to the ecological environment. However, due to the small particle size and high surface energy of ultrafine powder, it is easy to agglomerate to form secondary particles after being added to concrete, so that its micro-aggregate effect and morphological effect cannot be fully exerted, limiting the improvement of concrete performance. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing a surface-modified composite micro-nano ultrafine powder and an ultra-high performance concrete thereof, wherein the modified micro-nano ultrafine powder not only improves the dispersibility in concrete, but also significantly improves the mechanical properties of concrete. Specifically, the technical solution of the present invention is as follows.

[0006] First, the present invention provides a method for preparing a surface-modified composite micro-nano ultrafine powder, comprising the following steps:

[0007] (1) Dissolve isobutyltriethoxysilane and polyacrylate in acetone or ethyl acetate to obtain a surface modifier solution for later use.

[0008] (2) Add the industrial solid waste micro-nano ultrafine powder with gelling activity to anhydrous ethanol dissolved with hexadecyltrimethylammonium bromide for reaction. After completion, separate the solid product, wash it and dry it to obtain the pretreated micro-nano ultrafine powder for later use.

[0009] (3) adding the pretreated micro-nano ultrafine powder to the surface modifier solution, then adding a pH adjuster to adjust the reaction system to acidity, and performing ultrasonic treatment. After completion, separating the solid product, washing it and drying it to obtain the surface modified composite micro-nano ultrafine powder.

[0010] Furthermore, in step (1), the mass fractions of isobutyltriethoxysilane and polyacrylate in the surface modifier solution are both 3-5%. Optionally, the mass fraction of acetone or ethyl acetate is 1-2%.

[0011] Furthermore, in step (2), the solid-liquid ratio of the industrial solid waste micro-nano ultrafine powder to the anhydrous ethanol containing hexadecyltrimethylammonium bromide is 1 g: 10-30 ml. Optionally, the mass fraction of hexadecyltrimethylammonium bromide in the anhydrous ethanol is 0.5-1%.

[0012] Furthermore, in step (2), the reaction temperature is 50-70°C, the reaction time is 50-80 min, and the drying temperature is 100-120°C, and the mixture is dried to a constant weight at this temperature.

[0013] Furthermore, in step (3), the solid-liquid ratio of the pretreated micro-nano ultrafine powder to the surface modifier solution is 1 g: 10-30 ml.

[0014] Furthermore, in step (2), the industrial solid waste micro-nano ultrafine powder includes at least one of fly ash, slag powder, coal gangue powder, clay brick powder, red mud powder, etc. Optionally, the particle size of the industrial solid waste micro-nano ultrafine powder is not greater than 10 μm.

[0015] Furthermore, in step (3), the pH of the reaction system is adjusted to 5-6. The acidic condition can promote the leaching of aluminum ions, iron ions, etc. in the micro-nano ultrafine powder, corrode the surface structure of the ultrafine powder, enhance the adsorption performance of the micro-nano ultrafine powder, promote the reaction, and ensure that the surface modifier is fully coated on the surface of the pretreated micro-nano ultrafine powder. Optionally, the pH adjuster includes at least one of hydrochloric acid, oxalic acid, etc.

[0016] Furthermore, in step (3), the ultrasonic treatment time is 1 to 2 hours, and the ultrasonic power is 200 to 500 W.

[0017] Secondly, the present invention provides an ultra-high performance concrete, comprising the following raw material components: 400-600 parts by weight of cement, 60-100 parts by weight of silica fume, 300-500 parts by weight of the surface-modified composite micro-nano ultrafine powder of the present invention, 500-600 parts by weight of No. 1 quartz sand, 400-500 parts by weight of No. 2 quartz sand, 126-200 parts by weight of steel fiber, 8-12 parts by weight of water reducer, and 180-200 parts by weight of water, wherein the particle size of the No. 2 quartz sand is smaller than that of the No. 1 quartz sand.

[0018] Furthermore, the steel fiber is a copper-plated steel fiber, which has the function of improving the strength, durability and deformation performance of ultra-high performance concrete. Optionally, the length of the steel fiber is not less than 10 mm and the diameter is 0.2-0.5 mm.

[0019] Furthermore, the water reducer includes at least one of a polycarboxylate water reducer, a naphthalene-based water reducer, a wood sulfonate water reducer, and the like.

[0020] Optionally, the fineness of the No. 1 quartz sand is 20-80 mesh, and the fineness of the No. 2 quartz sand is 90-200 mesh. In the present invention, the combination of two quartz sands with different particle sizes helps the particles to be more densely packed, thereby improving the density and strength of the concrete matrix.

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

[0022] In view of the fact that ultrafine powders are prone to agglomeration to form secondary particles, which limits their proper micro-aggregate effect and morphological effect in concrete, the present invention uses anhydrous ethanol dissolved with hexadecyltrimethylammonium bromide, isobutyltriethoxysilane and a surface modifier formed by polyacrylate to jointly modify the surface of industrial solid waste micro-nano ultrafine powder with gelling activity to form a surface-modified composite micro-nano ultrafine powder, which not only well avoids the problem of easy agglomeration of powder particles, but also improves the fluidity of ultra-high performance concrete slurry, significantly improves the workability and mechanical properties of ultra-high performance concrete, and also improves the internal microstructure of ultra-high performance concrete, overcoming the problem of easy cracking caused by early self-shrinkage, resulting in reduced bearing capacity and durability. This is due to:

[0023] First, the hexadecyl trimethyl ammonium bromide molecules adsorbed on the surface of the ultrafine powder particles help open the closed pores in the particles, increase the specific surface area, and significantly enhance the adsorption performance of the ultrafine powder particles, so that it can more effectively adsorb harmful substances (such as free calcium hydroxide, etc.) in ultra-high performance concrete, thereby improving the durability of the concrete. At the same time, the ultrafine powder particles after the above treatment also have better lubrication, thereby improving the fluidity and pumpability of the concrete.

[0024] Second, when the isobutyl triethoxysilane contacts the surface of the ultrafine powder, the ethoxy group (-OCH 2 CH 3 ) will react with the hydroxyl groups (-OH) on the surface of the ultrafine powder particles, removing the ethanol molecules to form Si-O- groups. These Si-O- groups will then further condense with the Si-OH bonds on the surface of the ultrafine powder particles to form a Si-O-Si bond network structure, significantly improving its compatibility and adhesion with the ultra-high performance concrete matrix.

[0025] Third, the steric hindrance effect of the polyacrylate helps prevent the agglomeration of the ultrafine powder particles. At the same time, the polyacrylate effectively improves the stability of the ultrafine powder particles, because the anchoring groups (such as -COOH, -COO-, etc.) in the polyacrylate can be tightly adsorbed on the surface of the ultrafine powder particles to form a stable adsorption layer. This strong anchoring effect improves the stability of the ultrafine powder particles in the dispersion system and reduces agglomeration.

[0026] Fourth, the active group ethoxy of the isobutyltriethoxysilane on the surface of the ultrafine powder particles reacts with the hydroxyl group in the concrete to construct a layered hydrophobic structure, thereby reducing the surface tension of water, thereby slowing down the seepage and loss of water inside the ultra-high performance concrete, ensuring the internal relative humidity, and reducing the tendency of the ultra-high performance concrete to produce cracks due to early self-shrinkage.

[0027] Fifth, the carboxyl groups generated by the hydrolysis of the polyacrylate can also chelate with the hydration product calcium hydroxide to generate [Ca(HCOO) 2 ], thus forming an interlaced spatial network structure, blocking the pores in the concrete, reducing the rate and amount of water evaporation, filling the pores in the concrete to play a bridging role, and thus limiting the shrinkage of UHPC. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which constitute a part of the present invention, are used to provide further understanding of the present invention and shall not constitute improper limitation of the present invention.

[0029] Figure 1 This is a SEM image of the ultra-high performance concrete prepared in Example 1 below.

[0030] Figure 2 This is a SEM image of the ultra-high performance concrete prepared in the following Example 2.

[0031] Figure 3 The XRD patterns of the ultra-high performance concrete specimens prepared in the following Examples 1 to 4 are shown below. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Unless otherwise defined, all professional and scientific terms used in the present invention have the same meanings as those familiar to those skilled in the art. The preferred implementation methods and materials described in the present invention are only for demonstration purposes. Now the technical solution of the present invention is further described in conjunction with specific embodiments.

[0033] In the following examples, the silica ash is from Shandong Boken Silicon Materials Co., Ltd., and the SiO 2 The content is 96.7% and the specific surface area is 20318m 2 / kg.

[0034] In the following examples, the No. 1 quartz sand and the No. 2 quartz sand are both from Henan Minghai Environmental Protection Technology Co., Ltd. The fineness of the No. 1 quartz sand is continuously graded between 20 and 80 meshes, and the fineness of the No. 2 quartz sand is continuously graded between 90 and 200 meshes.

[0035] In the following examples, the steel fiber is copper-plated steel fiber from Hengshui Fanhai Metal Products Co., Ltd.

[0036] Example 1

[0037] 1. A method for preparing surface-modified composite micro-nano ultrafine powder, comprising the steps of:

[0038] (1) The slag powder is dried and then ground to a particle size of less than 10 μm to obtain an initial ultrafine powder.

[0039] (2) Dissolving isobutyl triethoxy silane and polyacrylate in 2% by mass acetone to obtain a surface modifier solution, wherein the mass fractions of the isobutyl triethoxy silane and the polyacrylate are both 4.5%.

[0040] (3) Add the initial ultrafine powder of step (1) to anhydrous ethanol with a mass fraction of 0.8% hexadecyltrimethylammonium bromide in a solid-liquid ratio of 1g:15ml, and then react at 65°C for 60 minutes. After completion, cool to room temperature and filter under reduced pressure. Wash the obtained solid product with distilled water and dry it at 105°C to constant weight to obtain pretreated micro-nano ultrafine powder for later use.

[0041] (4) Add the pretreated micro-nano ultrafine powder to the surface modifier solution of step (2) at a solid-liquid ratio of 1 g:15 ml. Then add hydrochloric acid to adjust the pH of the reaction system to 5.5, and then perform ultrasonic treatment for 1.5 hours at an ultrasonic power of 500 W. After completion, filter out the solid product, wash it with distilled water, and dry it at 105°C to constant weight to obtain surface-modified composite micro-nano ultrafine powder.

[0042] 2. A method for preparing ultra-high performance concrete, comprising the following steps:

[0043] (1) Take the following raw materials in the following proportions: 600 parts by weight of 42.5 ordinary Portland cement, 100 parts by weight of silica fume, 300 parts by weight of the surface-modified composite micro-nano ultrafine powder prepared in this embodiment, 600 parts by weight of No. 1 quartz sand, 400 parts by weight of No. 2 quartz sand, 126 parts by weight of steel fiber, 10 parts by weight of water reducer, and 180 parts by weight of water. The diameter of the steel fiber is 0.3 mm and the length is 14 mm. The water reducer is a polycarboxylate high-efficiency water reducer (purchased from BASF China Co., Ltd., model MELFLUX4930F).

[0044] (2) The 42.5% ordinary Portland cement, silica fume and surface-modified composite micro-nano ultrafine powder are placed in a standard cement mortar planetary mixer and stirred for 2 minutes to obtain a mixed cementitious material for later use.

[0045] (3) Add the No. 1 quartz sand and the No. 2 quartz sand to the mixed cementitious material, stir for 1 minute, then add the pre-mixed water reducer and water, first slowly stir at a rate of 65 r / min for 3 minutes, and then quickly stir at a rate of 125 r / min for 1 minute. After completion, add the steel fiber, and then slowly stir at a rate of 65 r / min for 2 minutes to obtain an ultra-high performance concrete mortar.

[0046] Performance Test:

[0047] (1) Fluidity test: According to the "Method for Determination of Fluidity of Cement Mortar" (GB / T 2419-2005), the fluidity of the ultra-high performance concrete mortar prepared in this embodiment was tested using a cement mortar fluidity tester.

[0048] (2) Mechanical properties test: The ultra-high performance concrete mortar prepared in this example was poured into a test mold, demolded after hardening, and then the obtained specimen was cured for 28 days. The flexural strength and compressive strength of the obtained specimen were then tested according to the "Test Method for Cement Mortar Strength" (GB / T17671-1999). The SEM of the specimen was as follows: Figure 1 As shown, it can be seen that the steel fibers are tightly connected to the concrete matrix, and a large amount of hydration products are attached to the surface of the steel fibers.

[0049] (3) Autogenous shrinkage test: The autogenous shrinkage of the specimens prepared from the ultra-high performance concrete mortar of this embodiment is measured by combining a bellows with a non-contact probe. Specifically, the instrument mainly includes a non-contact probe, which can measure the distance between it and the stainless steel head (the measurement accuracy is 0.0001mm), and a polyethylene bellows (the inner diameter at the thinnest point is 80mm). The data recording interval is 5 minutes and the measurement time is 72 hours. The autogenous shrinkage value of each group of specimens is the arithmetic mean of the autogenous shrinkage values ​​of the two bellows specimens, and the calculation is accurate to 1×l0 -6 If one of the two autogenous shrinkage values ​​exceeds ±10% of the average value, the test is invalid and the test is repeated. The test results of the above performance indicators are shown in the following table.

[0050]

[0051] Example 2

[0052] 1. A method for preparing surface-modified composite micro-nano ultrafine powder, comprising the steps of:

[0053] (1) The fly ash is dried and then ground to a particle size of less than 10 μm to obtain initial ultrafine powder.

[0054] (2) Dissolving isobutyl triethoxy silane and polyacrylate in 1% by mass ethyl acetate to obtain a surface modifier solution, wherein the mass fractions of the isobutyl triethoxy silane and the polyacrylate are both 3% by mass.

[0055] (3) Add the initial ultrafine powder of step (1) to anhydrous ethanol with a mass fraction of 0.5% hexadecyltrimethylammonium bromide in a solid-liquid ratio of 1g:30ml, and then react at 50°C for 80 minutes. After completion, cool to room temperature and filter under reduced pressure. Wash the obtained solid product with distilled water and dry it at 120°C to constant weight to obtain pretreated micro-nano ultrafine powder for later use.

[0056] (4) Add the pretreated micro-nano ultrafine powder to the surface modifier solution of step (2) at a solid-liquid ratio of 1 g:30 ml. Then add hydrochloric acid to adjust the pH of the reaction system to 5, and then perform ultrasonic treatment for 1 hour at an ultrasonic power of 400 W. After completion, filter out the solid product, wash it with distilled water, and dry it at 105°C to constant weight to obtain surface-modified composite micro-nano ultrafine powder.

[0057] 2. A method for preparing ultra-high performance concrete, comprising the following steps:

[0058] (1) Take the following raw materials in the following proportions: 500 parts by weight of 42.5 ordinary Portland cement, 75 parts by weight of silica fume, 440 parts by weight of the surface modified composite micro-nano ultrafine powder prepared in this embodiment, 550 parts by weight of No. 1 quartz sand, 450 parts by weight of No. 2 quartz sand, 180 parts by weight of steel fiber, 12 parts by weight of water reducer, and 191 parts by weight of water. The steel fiber has a diameter of 0.2 mm and a length of 10 mm. The water reducer is a sodium wood sulfonate water reducer.

[0059] (2) The 42.5% ordinary Portland cement, silica fume and surface-modified composite micro-nano ultrafine powder are placed in a standard cement mortar planetary mixer and stirred for 2 minutes to obtain a mixed cementitious material for later use.

[0060] (3) Add the No. 1 quartz sand and the No. 2 quartz sand to the mixed cementitious material, stir for 1 minute, then add the pre-mixed water reducer and water, first slowly stir at a rate of 65 r / min for 3 minutes, and then quickly stir at a rate of 125 r / min for 1 minute. After completion, add the steel fiber, and then slowly stir at a rate of 65 r / min for 2 minutes to obtain an ultra-high performance concrete mortar.

[0061] Performance test: The same method as in Example 1 was used to test the fluidity of the ultra-high performance concrete mortar prepared in this example and the flexural strength, compressive strength and self-shrinkage of the specimens prepared by the mortar. The SEM of the specimens is as follows: Figure 2 As shown, it can be seen that the interface transition zone between quartz sand and hydration products is not obvious, and the two are closely connected. The test results of the above indicators are shown in the following table.

[0062]

[0063] Example 3

[0064] 1. A method for preparing surface-modified composite micro-nano ultrafine powder, comprising the steps of:

[0065] (1) Slag powder and coal gangue powder (mass ratio of 4:1) are dried and ground to a particle size of less than 10 μm to obtain initial ultrafine powder.

[0066] (2) Dissolving isobutyl triethoxy silane and polyacrylate in 2% by mass acetone to obtain a surface modifier solution, wherein the mass fractions of the isobutyl triethoxy silane and the polyacrylate are both 5% by mass.

[0067] (3) Add the initial ultrafine powder of step (1) to anhydrous ethanol with a mass fraction of 1.0% hexadecyltrimethylammonium bromide according to a solid-liquid ratio of 1g:10ml, and then react at 70°C for 50 minutes. After completion, cool to room temperature and filter under reduced pressure. Wash the obtained solid product with distilled water and dry it at 100°C to constant weight to obtain pretreated micro-nano ultrafine powder for later use.

[0068] (4) Add the pretreated micro-nano ultrafine powder to the surface modifier solution of step (2) at a solid-liquid ratio of 1 g:10 ml. Then add oxalic acid to adjust the pH of the reaction system to 6, and then perform ultrasonic treatment for 2 hours at an ultrasonic power of 200 W. After completion, filter out the solid product, wash it with distilled water, and dry it at 105°C to constant weight to obtain surface-modified composite micro-nano ultrafine powder.

[0069] 2. A method for preparing ultra-high performance concrete, comprising the following steps:

[0070] (1) Take the following raw materials in the following proportions: 400 parts by weight of 42.5 ordinary Portland cement, 60 parts by weight of silica fume, 500 parts by weight of the surface-modified composite micro-nano ultrafine powder prepared in this embodiment, 500 parts by weight of No. 1 quartz sand, 500 parts by weight of No. 2 quartz sand, 200 parts by weight of steel fiber, 8 parts by weight of water reducer, and 200 parts by weight of water. The steel fiber has a diameter of 0.5 mm and a length of 14 mm. The water reducer is a polycarboxylate high-efficiency water reducer (purchased from BASF China Ltd., model MELFLUX4930F).

[0071] (2) The 42.5% ordinary Portland cement, silica fume and surface-modified composite micro-nano ultrafine powder are placed in a standard cement mortar planetary mixer and stirred for 2 minutes to obtain a mixed cementitious material for later use.

[0072] (3) Add the No. 1 quartz sand and the No. 2 quartz sand to the mixed cementitious material, stir for 1 minute, then add the pre-mixed water reducer and water, first slowly stir at a rate of 65 r / min for 3 minutes, and then quickly stir at a rate of 125 r / min for 1 minute. After completion, add the steel fiber, and then slowly stir at a rate of 65 r / min for 2 minutes to obtain an ultra-high performance concrete mortar.

[0073] Performance test: The same method as in Example 1 was used to test the fluidity of the ultra-high performance concrete mortar prepared in this example and the flexural strength, compressive strength and self-shrinkage of the test piece prepared from the mortar. It can be seen that the interface transition zone between the quartz sand and the hydration product is not obvious, and the two are tightly connected. The test results of the above indicators are shown in the following table.

[0074]

[0075] Example 4

[0076] A method for preparing ultra-high performance concrete comprises the following steps:

[0077] (1) The slag powder is dried and then ground to a particle size of less than 10 μm to obtain an initial ultrafine powder.

[0078] (2) Take the following raw materials in the following proportions: 600 parts by weight of 42.5 ordinary Portland cement, 100 parts by weight of silica fume, 300 parts by weight of the initial ultrafine powder prepared in this example, 600 parts by weight of No. 1 quartz sand, 400 parts by weight of No. 2 quartz sand, 126 parts by weight of steel fiber, 10 parts by weight of water reducer, and 180 parts by weight of water. The steel fiber has a diameter of 0.3 mm and a length of 14 mm. The water reducer is a polycarboxylate high-efficiency water reducer (purchased from BASF China Ltd., model MELFLUX 4930F).

[0079] (3) The 42.5% ordinary Portland cement, silica fume and surface-modified composite micro-nano ultrafine powder are placed in a standard cement mortar planetary mixer and stirred for 2 minutes to obtain a mixed cementitious material for later use.

[0080] (4) Add the No. 1 quartz sand and the No. 2 quartz sand to the mixed cementitious material, stir for 1 minute, then add the pre-mixed water reducer and water, first slowly stir at a rate of 65 r / min for 3 minutes, and then quickly stir at a rate of 125 r / min for 1 minute. After completion, add the steel fiber, and then slowly stir at a rate of 65 r / min for 2 minutes to obtain an ultra-high performance concrete mortar.

[0081] Performance test: The fluidity of the ultra-high performance concrete mortar prepared in this embodiment and the flexural strength, compressive strength and self-shrinkage of the test piece prepared by the mortar were tested by the same method as in the above embodiment 1. The test results of the above indicators are shown in the following table.

[0082]

[0083] Example 5

[0084] A method for preparing ultra-high performance concrete is the same as the above-mentioned embodiment 3, except that the surface-modified composite micro-nano ultrafine powder of this embodiment is prepared by the following method:

[0085] (1) Slag powder and coal gangue powder (mass ratio of 4:1) are dried and ground to a particle size of less than 10 μm to obtain initial ultrafine powder.

[0086] (2) Dissolving polyacrylate in 2% by mass acetone to obtain a surface modifier solution, wherein the mass fraction of the polyacrylate is 5%.

[0087] (3) Add the initial ultrafine powder of step (1) to anhydrous ethanol with a mass fraction of 1.0% hexadecyltrimethylammonium bromide according to a solid-liquid ratio of 1g:10ml, and then react at 70°C for 50 minutes. After completion, cool to room temperature and filter under reduced pressure. Wash the obtained solid product with distilled water and dry it at 100°C to constant weight to obtain pretreated micro-nano ultrafine powder for later use.

[0088] (4) Add the pretreated micro-nano ultrafine powder to the surface modifier solution of step (2) at a solid-liquid ratio of 1 g:10 ml. Then add oxalic acid to adjust the pH of the reaction system to 6, and then perform ultrasonic treatment for 2 hours at an ultrasonic power of 200 W. After completion, filter out the solid product, wash it with distilled water, and dry it at 105°C to constant weight to obtain surface-modified composite micro-nano ultrafine powder.

[0089] Performance test: The same method as in Example 1 was used to test the fluidity of the ultra-high performance concrete mortar prepared in this example and the flexural strength, compressive strength and self-shrinkage of the specimens prepared from the mortar. The results are shown in the following table.

[0090]

[0091] Example 6

[0092] A method for preparing ultra-high performance concrete is the same as the above-mentioned embodiment 2, except that the surface-modified composite micro-nano ultrafine powder of this embodiment is prepared by the following method:

[0093] (1) The fly ash is dried and then ground to a particle size of less than 10 μm to obtain initial ultrafine powder.

[0094] (2) Dissolving isobutyltriethoxysilane in 1% by mass ethyl acetate to obtain a surface modifier solution, wherein the mass fraction of isobutyltriethoxysilane is 3%.

[0095] (3) Add the initial ultrafine powder of step (1) to anhydrous ethanol with a mass fraction of 0.5% hexadecyltrimethylammonium bromide in a solid-liquid ratio of 1g:30ml, and then react at 50°C for 80 minutes. After completion, cool to room temperature and filter under reduced pressure. Wash the obtained solid product with distilled water and dry it at 120°C to constant weight to obtain pretreated micro-nano ultrafine powder for later use.

[0096] (4) Add the pretreated micro-nano ultrafine powder to the surface modifier solution of step (2) at a solid-liquid ratio of 1 g:30 ml. Then add hydrochloric acid to adjust the pH of the reaction system to 5, and then perform ultrasonic treatment for 1 hour at an ultrasonic power of 400 W. After completion, filter out the solid product, wash it with distilled water, and dry it at 105°C to constant weight to obtain surface-modified composite micro-nano ultrafine powder.

[0097] Performance test: The same method as in Example 1 was used to test the fluidity of the ultra-high performance concrete mortar prepared in this example and the flexural strength, compressive strength and self-shrinkage of the specimens prepared from the mortar. The results are shown in the following table.

[0098]

[0099] Example 7

[0100] A method for preparing ultra-high performance concrete is the same as the above-mentioned embodiment 1, except that the surface-modified composite micro-nano ultrafine powder of this embodiment is prepared by the following method:

[0101] (1) The slag powder is dried and then ground to a particle size of less than 10 μm to obtain an initial ultrafine powder.

[0102] (2) Dissolving isobutyl triethoxy silane and polyacrylate in 2% by mass acetone to obtain a surface modifier solution, wherein the mass fractions of the isobutyl triethoxy silane and the polyacrylate are both 4.5%.

[0103] (3) Add the initial ultrafine powder of step (1) to anhydrous ethanol with a mass fraction of 0.8% hexadecyltrimethylammonium bromide in a solid-liquid ratio of 1g:15ml, and then react at 65°C for 60 minutes. After completion, cool to room temperature and filter under reduced pressure. Wash the obtained solid product with distilled water and dry it at 105°C to constant weight to obtain pretreated micro-nano ultrafine powder for later use.

[0104] (4) Add the pretreated micro-nano ultrafine powder to the surface modifier solution of step (2) at a solid-liquid ratio of 1 g:15 ml, and then perform ultrasonic treatment for 1.5 hours at an ultrasonic power of 500 W. After completion, filter out the solid product, wash it with distilled water, and dry it at 105° C. to constant weight to obtain surface-modified composite micro-nano ultrafine powder.

[0105] Performance test: The same method as in Example 1 was used to test the fluidity of the ultra-high performance concrete mortar prepared in this example and the flexural strength, compressive strength and self-shrinkage of the specimens prepared from the mortar. The results are shown in the following table.

[0106]

[0107] Example 8

[0108] A method for preparing ultra-high performance concrete is the same as the above-mentioned embodiment 2, except that the surface-modified composite micro-nano ultrafine powder of this embodiment is prepared by the following method:

[0109] (1) The fly ash is dried and then ground to a particle size of less than 10 μm to obtain initial ultrafine powder.

[0110] (2) Dissolving isobutyl triethoxy silane and polyacrylate in 1% by mass ethyl acetate to obtain a surface modifier solution, wherein the mass fractions of the isobutyl triethoxy silane and the polyacrylate are both 3% by mass.

[0111] (3) Add the initial ultrafine powder of step (1) to the surface modifier solution of step (2) at a solid-liquid ratio of 1 g:30 ml. Then add hydrochloric acid to adjust the pH of the reaction system to 5, and then perform ultrasonic treatment for 1 hour at an ultrasonic power of 400 W. After completion, filter out the solid product, wash it with distilled water, and dry it at 105°C to constant weight to obtain surface-modified composite micro-nano ultrafine powder.

[0112] Performance test: The same method as in Example 1 was used to test the fluidity of the ultra-high performance concrete mortar prepared in this example and the flexural strength, compressive strength and self-shrinkage of the specimens prepared from the mortar. The results are shown in the following table.

[0113]

[0114] Figure 3 The XRD diagram of the ultra-high performance concrete specimens (aged 28 days) prepared in Examples 1 to 4 above shows that the hydration product contains ettringite cementitious components and calcium hydroxide (Ca(OH) 2 ) etc. In addition, the ultra-high performance concrete specimen also contains calcium silicate hydrate (CSH) gel component. The active silica and alumina in the surface-modified composite micro-nano ultrafine powder react with cement to produce Ca(OH) 2 The secondary hydration reaction occurs to generate more CSH gel, which is beneficial to improving the mechanical strength of concrete.

[0115] In addition, since Example 4 uses unmodified ultrafine powder instead of surface-modified composite micro-nano ultrafine powder, the ultrafine powder is prone to agglomeration to form secondary particles, which limits the improvement of concrete performance, which is consistent with the above-mentioned strength test results. The mechanical properties and autogenous shrinkage of the ultra-high performance concrete prepared in Examples 5, 6, 7, and 8 also decreased compared with the comparative examples, indicating that the ultrafine powder treated in Examples 1 to 3 can better improve the strength of concrete and reduce autogenous shrinkage.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made shall be included in the protection scope of the present invention.

Claims

1. A method for preparing surface-modified composite micro-nano ultrafine powder, characterized in that: The steps include: (1) dissolving isobutyl triethoxysilane and polyacrylate in acetone or ethyl acetate to obtain a surface modifier solution for later use; (2) adding the industrial solid waste micro-nano ultrafine powder with gelling activity to anhydrous ethanol dissolved with hexadecyltrimethylammonium bromide for reaction, separating the solid product after completion, washing it and drying it to obtain the pretreated micro-nano ultrafine powder for standby use; (3) adding the pretreated micro-nano ultrafine powder to the surface modifier solution, then adding a pH adjuster to adjust the reaction system to acidity, and performing ultrasonic treatment. After completion, separating the solid product, washing it and drying it to obtain the surface modified composite micro-nano ultrafine powder.

2. The method for preparing the surface-modified composite micro-nano ultrafine powder according to claim 1, characterized in that: In step (1), the mass fractions of isobutyltriethoxysilane and polyacrylate in the surface modifier solution are both 3-5%; Alternatively, in step (1), the mass fraction of acetone or ethyl acetate is 1-2%.

3. The method for preparing the surface-modified composite micro-nano ultrafine powder according to claim 1, characterized in that: In step (2), the solid-to-liquid ratio of the industrial solid waste micro-nano ultrafine powder to anhydrous ethanol dissolved with hexadecyltrimethylammonium bromide is 1 g: 10-30 ml.

4. The method for preparing the surface-modified composite micro-nano ultrafine powder according to claim 1, characterized in that: In step (2), the mass fraction of hexadecyltrimethylammonium bromide in the anhydrous ethanol is 0.5-1%; Alternatively, in step (2), the reaction temperature is 50-70°C and the reaction time is 50-80 min; Alternatively, in step (2), the drying temperature is 100-120° C., and the mixture is dried to a constant weight at this temperature.

5. The method for preparing the surface-modified composite micro-nano ultrafine powder according to claim 1, characterized in that: In step (3), the solid-to-liquid ratio of the pretreated micro-nano ultrafine powder to the surface modifier solution is 1 g: 10-30 ml.

6. The method for preparing the surface-modified composite micro-nano ultrafine powder according to claim 1, characterized in that: In step (2), the industrial solid waste micro-nano ultrafine powder includes at least one of fly ash, slag powder, coal gangue powder, clay brick powder, and red mud powder; Alternatively, in step (2), the particle size of the industrial solid waste micro-nano ultrafine powder is not greater than 10 μm.

7. The method for preparing the surface-modified composite micro-nano ultrafine powder according to any one of claims 1 to 6, characterized in that: In step (3), the pH of the reaction system is adjusted to 5-6; Alternatively, in step (3), the pH adjuster includes at least one of hydrochloric acid and oxalic acid; Alternatively, in step (3), the ultrasonic treatment time is 1 to 2 hours, and the ultrasonic power is 200 to 500 W.

8. An ultra-high performance concrete, characterized in that: The invention comprises the following raw material components: 400-600 parts by weight of cement, 60-100 parts by weight of silica fume, 300-500 parts by weight of the surface-modified composite micro-nano ultrafine powder obtained by the preparation method according to any one of claims 1 to 7, 500-600 parts by weight of No. 1 quartz sand, 400-500 parts by weight of No. 2 quartz sand, 126-200 parts by weight of steel fiber, 8-12 parts by weight of water reducer, and 180-200 parts by weight of water, wherein the particle size of the No. 2 quartz sand is smaller than that of the No. 1 quartz sand.

9. The ultra-high performance concrete according to claim 8, characterized in that: The steel fiber is a copper-plated steel fiber; or, the length of the steel fiber is not less than 10 mm and the diameter is 0.2-0.5 mm.

10. The ultra-high performance concrete according to claim 8 or 9, characterized in that: The fineness of the No. 1 quartz sand is 20-80 mesh, and the fineness of the No. 2 quartz sand is 90-200 mesh; Alternatively, the water reducer includes at least one of a polycarboxylate water reducer, a naphthalene-based water reducer, and a wood sulfonate water reducer.

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