Preparation method and application of cement-based silicon-aluminum micro-nano composite hydrophobic material

Abstract

The present invention relates to the technical field of cement hydrophobicity, and specifically discloses a preparation method and application of a cement-based silica-alumina micro-nano composite hydrophobic material. The preparation method of the composite hydrophobic material comprises the following steps: (1) mixing a cement-based cementitious material with mixing water and stirring evenly, then adding a hydrophobic agent A and stirring evenly to obtain a prehydrated hydrophobically modified cement slurry. (2) mixing an acid solution, a silica-alumina material and a hydrophobic agent B and grinding them to obtain silica-alumina hydrophobic modified powder. (3) mixing the prehydrated hydrophobically modified cement slurry with the silica-alumina hydrophobic modified powder and grinding them to obtain the cement-based silica-alumina micro-nano composite hydrophobic material. The method of the present invention not only does not hinder the full hydration of cement clinker, but also helps to promote the hydration reaction, and the obtained concrete has both long-lasting hydrophobicity and impermeability and excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of cement hydrophobicity, and in particular to a preparation method and application of a cement-based silicon-aluminum micro-nano composite hydrophobic material. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance 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 those skilled in the art.

[0003] Because cement hydration can cause a large amount of pores, defects and hydroxyl groups in concrete, cement concrete is usually a kind of internal loose and porous hydrophilic material, water migration and transportation in this hydrophilic porous structure is the main reason for the degradation of concrete durability, which causes concrete to be in a harsh marine environment, easily subject to the erosion of inorganic salts in the ocean, plus the effects such as wave scouring, freeze-thaw damage, concrete carbonization, very easily cause concrete to corrode and damage. At present, one of the ways to overcome the above problems is to carry out surface coating of hydrophobic coating on concrete. However, this type of method often has problems such as higher cost, complicated preparation method, weak bond strength between hydrophobic material and cement-based material. And the durability of hydrophobic coating is poor, and problems such as aging, cracking, peeling occur easily, causing it to be difficult to form long-term protection for concrete.

[0004] Therefore, researchers have proposed a method for modifying concrete to be hydrophobic overall. While this method offers superior long-term impermeability compared to surface hydrophobic modification, the modified concrete suffers from a significant loss of mechanical properties. This is primarily due to the hydrophobic material enveloping the cement clinker, preventing it from fully contacting the mixing water. This hinders the hydration reaction, leading to insufficient formation of the cementitious component and increased porosity in the concrete. Consequently, this method currently faces the challenge of achieving both long-term hydrophobicity and high mechanical properties. Summary of the Invention

[0005] The present invention provides a method for preparing a cement-based silica-alumina micro-nano composite hydrophobic material and its application. This method not only does not hinder the full hydration of cement but also helps promote the hydration reaction. The resulting concrete exhibits both long-lasting hydrophobicity and impermeability as well as excellent mechanical properties. Specifically, the present invention discloses the following technical solutions.

[0006] First, the present invention discloses a method for preparing a cement-based silica-alumina micro-nano composite hydrophobic material, comprising the following steps:

[0007] (1) Prepare the following raw materials: 50-80 parts by weight of cement-based gelling material, 20-50 parts by weight of silicon-aluminum material, 5-15 parts by weight of hydrophobic agent A, 5-15 parts by weight of hydrophobic agent B, 0.1-1 parts by weight of acid solution, and 40-50 parts by weight of mixing water.

[0008] (2) The cement-based cementitious material is mixed with mixing water and stirred evenly, and then the hydrophobic agent A is added and stirred evenly to obtain a prehydrated hydrophobically modified cement slurry for use.

[0009] (3) The acid solution, the silicon-aluminum material and the hydrophobic agent B are mixed and then ground to obtain silicon-aluminum hydrophobic modified powder for standby use.

[0010] (4) The prehydrated hydrophobically modified cement slurry is mixed with the silica-alumina hydrophobically modified powder and then ground to obtain the cement-based silica-alumina micro-nano composite hydrophobic material.

[0011] Furthermore, in step (1), the cement-based cementitious material includes any one of ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement, etc. Preferably, the cement-based cementitious material is a semi-finished product obtained from the cement clinker production stage without fine grinding, which can be fully ground in the subsequent step (4), thereby helping to reduce the cement production steps and energy consumption.

[0012] Furthermore, in step (1), the silicon-alumina material includes but is not limited to at least one of: mineral powder, fly ash, silica fume, metakaolin, waste glass, etc. These solid wastes can not only provide potentially active components such as calcium, silicon, and aluminum for the preparation of the cement-based silicon-alumina micro-nano composite hydrophobic material of the present invention, thereby increasing the content of silicon oxide tetrahedrons and aluminum oxide octahedrons and accelerating the hydration process; but the use of the above solid wastes is also conducive to the resource utilization of bulk solid wastes.

[0013] Furthermore, in step (1), the hydrophobic agent A includes any one of silane / siloxane, phthalate, fluorosilane, etc.

[0014] Optionally, the silane / siloxane substance includes any one of hexamethyldisilazane, hexadecyltrimethoxysilane, trichloro(octadecyl)silanecyclohexyltrimethoxysilane, polydimethylsiloxane, 3-methacryloxypropyltrimethoxysilane, etc.

[0015] Optionally, the phthalate substance includes any one of neoalkoxy tris (dioctyl pyrophosphate acyloxy) titanate, neoalkoxy tris (dioctyl phosphate acyloxy) titanate, bis (dioctyl pyrophosphate acyloxy) ethylene titanate acrylamide chelate, tetraneoalkoxy bis (didecyl phosphite acyloxy) titanate, etc.

[0016] Furthermore, in step (1), the acid solution includes any one of hydrochloric acid, phosphoric acid, sulfuric acid, etc. Optionally, the acid solution makes the initial pH of the system be in the range of 4 to 6.

[0017] Furthermore, in step (1), the hydrophobic agent B includes any one of stearic acid, silane / siloxane, phthalate, fluorosilane, etc.

[0018] Optionally, the silane / siloxane substance includes any one of hexamethyldisilazane, hexadecyltrimethoxysilane, trichloro(octadecyl)silanecyclohexyltrimethoxysilane, polydimethylsiloxane, 3-methacryloxypropyltrimethoxysilane, etc.

[0019] Optionally, the phthalate substance includes any one of neoalkoxy tris (dioctyl pyrophosphate acyloxy) titanate, neoalkoxy tris (dioctyl phosphate acyloxy) titanate, bis (dioctyl pyrophosphate acyloxy) ethylene titanate acrylamide chelate, tetraneoalkoxy bis (didecyl phosphite acyloxy) titanate, etc.

[0020] Furthermore, in step (2), the cement-based cementitious material is mixed with mixing water and stirred for 1 to 4 minutes. Optionally, the stirring rate ranges from 800 to 1000 r / min.

[0021] Furthermore, in step (2), the hydrophobic agent is added and then stirred for 1 to 3 minutes. Optionally, the stirring rate ranges from 1000 to 1200 r / min.

[0022] Furthermore, in step (3), the grinding process is carried out at a rate ranging from 100 to 200 r / min and for a time ranging from 5 to 30 min.

[0023] Furthermore, in step (4), the grinding process is carried out at a rate ranging from 200 to 300 r / min and for a time ranging from 15 to 30 min.

[0024] Secondly, the present invention discloses the application of the cement-based silica-alumina micro-nano composite hydrophobic material in the fields of construction, bridges, tunnels, marine engineering, etc.

[0025] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: As mentioned above, the current method of overall hydrophobic modification of concrete faces the problem of difficulty in achieving both long-term hydrophobicity and high mechanical properties of concrete.

[0026] For this reason, the present invention first uses silicon-aluminium material as modified substrate, and utilizes acid solution to make the surface cracking of silicon-aluminium material form O-Ca-O, silicon oxygen tetrahedron O-Si-O, aluminum oxygen octahedron O-Al-O so that the surface of silicon-aluminium material is activated, and the unbonded oxygen atom of partial exposure is further connected with the hydrogen ion in water to form hydroxyl.When this modified silicon-aluminium material and the hydrophobic agent B are ground and processed, the hydrophobic agent B can be chemically bonded to the surface of modified silicon-aluminium material by the dehydration condensation between carboxyl, Si-OH and hydroxyl etc., to form silicon-aluminium hydrophobic modified powder.These have hydrophobicity because of the partial area of ​​having loaded hydrophobic agent B, and the O-Ca-O, O-Si-O, O-Al-O and the unloaded hydrophobic agent B hydroxyl part have hydrophilicity.Thus, the surface of modified silicon-aluminium material is formed into the state of active hydrophilic region and inert hydrophobic region staggered distribution. In addition, compared with simple physical coating, the hydrophobic agent B loaded on the modified silica-alumina material in the above manner is more solid and not easy to fall off, which helps the concrete maintain a longer-lasting hydrophobic function.

[0027] Secondly, the present invention uses a cement-based cementitious material as a modified base material, mixes it with mixing water and a hydrophobic agent A. During this process, the hydrophobic agent A is loaded on the surface of cement particles through dehydration condensation of Si-OH generated by its hydrolysis and hydroxyl generated by prehydration of the cement-based cementitious material, so that the cement surface forms a low surface energy hydrophobic surface with a nanostructure. At the same time, under the action of the hydrophobic agent A, the contact degree between the cement-based cementitious material and the mixing water is limited, thereby causing the cement-based cementitious material to undergo a minimum hydration reaction to construct a hydrophobically modified cement slurry in a prehydrated state.

[0028] Finally, the present invention mixes the prehydrated hydrophobically modified cement slurry with the silico-alumina hydrophobically modified powder and then grinds it. During this process, the high alkalinity of the cement slurry is not only used to neutralize the acid solution remaining in the silico-alumina hydrophobically modified powder, but also the high alkalinity of the cement slurry is used to further stimulate the silico-alumina hydrophobically modified powder, thereby increasing the reactivity of the silico-alumina hydrophobically modified powder. At the same time, the high temperature generated by grinding evaporates and removes the moisture brought by the cement slurry, thereby terminating the continued hydration of the cement clinker and forming a cement-based silico-alumina micro-nano composite hydrophobic material.

[0029] When the above-mentioned cement-based silica-alumina micro-nano composite hydrophobic material is compounded with coarse and fine aggregates to prepare concrete. Because the prehydrated hydrophobically modified cement slurry contains a small amount of CSH and ettringite produced by prehydration, it has a seed nucleation effect and can induce the clinker in the cement to accelerate hydration. At the same time, the active hydrophilic region of the silica-alumina hydrophobically modified powder is fully in contact with water and cement and participates in hydration to build a gelling system. Compared with the mode in which silica-alumina particles are only filled in the pores of concrete as fillers, the gelling component formed after the active hydrophilic region of the silica-alumina hydrophobically modified powder obtained by the present invention is hydrated enables it to be more closely combined with the concrete matrix, thereby better improving the strength of concrete. The inert hydrophobic region of the silica-alumina hydrophobically modified powder then constructs a hydrophobic system, so that the concrete material obtained has both good mechanical properties and hydrophobic properties. It can be seen that the cement-based silica-alumina micro-nano composite hydrophobic material of the present invention not only does not hinder cement hydration, but also promotes cement hydration to a certain extent, achieving a synergistic enhancement effect of hydrophobicity, impermeability and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0031] Figure 1 The following is an SEM image of the hydrophobically modified cement slurry prepared in Example 1.

[0032] Figure 2 This is the SEM image of the hydrophobically modified silica-alumina powder prepared in the following Example 1. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0034] 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 reagents and raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents and raw materials used in the present invention are used in accordance with conventional methods in the art or in accordance with the product instructions.

[0035] In addition, any methods and materials similar or equivalent to those described herein can be applied to the method of the present invention. The technical solution of the present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material comprises the following steps:

[0038] (1) Prepare the following raw materials: 75 parts by weight of 42.5 ordinary Portland cement, 25 parts by weight of fly ash, 10 parts by weight of hydrophobic agent A (polydimethylsiloxane), 10 parts by weight of hydrophobic agent B (neoalkoxy tris(dioctyl pyrophosphate) titanate), 0.5 parts by weight of phosphoric acid, and 45 parts by weight of mixing water.

[0039] (2) The 42.5% ordinary Portland cement was mixed with mixing water and stirred at 900 r / min for 2 min, and then the hydrophobic agent A was added and stirred at 1100 r / min for 1.5 min to obtain a prehydrated hydrophobic modified cement slurry (its microstructure is as follows Figure 1 as shown), spare.

[0040] (3) The phosphoric acid, fly ash and hydrophobic agent B are added to a ball mill and mixed, and the pH of the system is adjusted to 5, and then ball milled at a rate of 200 r / min for 15 minutes to obtain a silicon-aluminum hydrophobic modified powder (its microstructure is as follows Figure 2 Then, the prehydrated hydrophobic modified cement slurry prepared in step (2) was added and ball milled at a speed of 250 r / min for 30 min. After completion, a cement-based silicon-aluminum micro-nano composite hydrophobic material was obtained.

[0041] The 28-day compressive strength of the cement-based silica-alumina micro-nano composite hydrophobic material prepared in this example was tested according to the GB175-2007 standard. Prior to testing, the cement-based silica-alumina micro-nano composite hydrophobic material, mixing water, and polycarboxylate superplasticizer were mixed in a mass ratio of 1:0.35:0.001 and stirred evenly. The resulting slurry was poured into a mold to form a test specimen. After standard curing for 28 days, the tensile strength and water absorption rate of the specimens were tested. Additionally, the contact angle of the specimens was measured to assess their hydrophobic properties. The results are shown in Table 1 below.

[0042] Table 1

[0043] Compressive strength Water absorption contact angle Example 1 64.49MPa 5.42％ 111°

[0044] Example 2

[0045] A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material comprises the following steps:

[0046] (1) Prepare the following raw materials: 80 parts by weight of 42.5 ordinary Portland cement, 20 parts by weight of metakaolin, 15 parts by weight of hydrophobic agent A (trichloro(octadecyl)silanecyclohexyltrimethoxysilane), 15 parts by weight of hydrophobic agent B (hexamethyldisilazane), 1 part by weight of hydrochloric acid, and 50 parts by weight of mixing water.

[0047] (2) The 42.5% ordinary Portland cement was mixed with mixing water and stirred at 800 r / min for 4 minutes, and then the hydrophobic agent A was added and stirred at 1000 r / min for 3 minutes to obtain a prehydrated hydrophobically modified cement slurry for standby use.

[0048] (3) Add the hydrochloric acid, metakaolin, and hydrophobic agent B to a ball mill and mix them, and adjust the pH of the system to 6. Then, ball mill them at a speed of 180 r / min for 5 minutes to obtain a silica-alumina hydrophobic modified powder. Then, continue to add the prehydrated hydrophobic modified cement slurry prepared in step (2) and ball mill them at a speed of 300 r / min for 15 minutes to obtain a cement-based silica-alumina micro-nano composite hydrophobic material.

[0049] The 28-day compressive strength of the cement-based silica-alumina micro-nano composite hydrophobic material prepared in this example was tested according to the GB175-2007 standard. Prior to testing, the cement-based silica-alumina micro-nano composite hydrophobic material, mixing water, and polycarboxylate superplasticizer were mixed in a mass ratio of 1:0.35:0.001 and stirred evenly. The resulting slurry was poured into a mold to form a test specimen. After standard curing for 28 days, the tensile strength and water absorption rate of the specimens were tested. Additionally, the contact angle of the specimens was measured to assess their hydrophobic properties. The results are shown in Table 2 below.

[0050] Table 2

[0051] Compressive strength Water absorption contact angle Example 2 52.37MPa 4.51％ 116°

[0052] Example 3

[0053] A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material comprises the following steps:

[0054] (1) Prepare the following raw materials: 50 parts by weight of 42.5 ordinary Portland cement, 50 parts by weight of mineral powder, 5 parts by weight of hydrophobic agent A (hexamethyldisilazane), 5 parts by weight of hydrophobic agent B (stearic acid), 0.1 parts by weight of sulfuric acid, and 40 parts by weight of mixing water.

[0055] (2) The 42.5% ordinary Portland cement was mixed with mixing water and stirred at 1000 r / min for 1 min, and then the hydrophobic agent A was added and stirred at 1200 r / min for 1 min to obtain a prehydrated hydrophobically modified cement slurry for use.

[0056] (3) Add the sulfuric acid, mineral powder, and hydrophobic agent B to a ball mill and mix them, and adjust the pH of the system to 4. Then, ball mill them at a speed of 100 r / min for 30 minutes to obtain a silica-alumina hydrophobic modified powder. Then, continue to add the prehydrated hydrophobic modified cement slurry prepared in step (2) and ball mill them at a speed of 200 r / min for 25 minutes to obtain a cement-based silica-alumina micro-nano composite hydrophobic material.

[0057] The 28-day compressive strength of the cement-based silica-alumina micro-nano composite hydrophobic material prepared in this example was tested according to the GB175-2007 standard. Prior to testing, the cement-based silica-alumina micro-nano composite hydrophobic material, mixing water, and polycarboxylate superplasticizer were mixed in a mass ratio of 1:0.35:0.001 and stirred evenly. The resulting slurry was poured into a mold to form a test specimen. After standard curing for 28 days, the tensile strength and water absorption rate of the specimens were tested. Additionally, the contact angle of the specimens was measured to assess their hydrophobic properties. The results are shown in Table 3 below.

[0058] Table 3

[0059] Compressive strength Water absorption contact angle Example 3 57.91MPa 6.02％ 103°

[0060] Example 4

[0061] A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material comprises the following steps:

[0062] (1) Prepare the following raw materials: 75 parts by weight of 42.5 ordinary Portland cement, 25 parts by weight of fly ash, 10 parts by weight of hydrophobic agent B (neoalkoxy tris(dioctyl pyrophosphate) titanate), 0.5 parts by weight of phosphoric acid, and 45 parts by weight of mixing water.

[0063] (2) The 42.5% ordinary Portland cement was mixed with mixing water and stirred at 900 r / min for 2 min to obtain a prehydrated hydrophobically modified cement slurry for later use.

[0064] (3) Add the phosphoric acid, fly ash, and hydrophobic agent B to a ball mill and mix them, and adjust the system pH to 5. Then, ball mill them at a speed of 200 r / min for 15 minutes to obtain a silica-alumina hydrophobic modified powder. Then, continue to add the prehydrated hydrophobic modified cement slurry prepared in step (2) and ball mill them at a speed of 250 r / min for 30 minutes to obtain a cement-based silica-alumina micro-nano composite hydrophobic material.

[0065] The 28-day compressive strength of the cement-based silica-alumina micro-nano composite hydrophobic material prepared in this example was tested according to the GB175-2007 standard. Prior to testing, the cement-based silica-alumina micro-nano composite hydrophobic material, mixing water, and polycarboxylate superplasticizer were mixed in a mass ratio of 1:0.35:0.001 and stirred evenly. The resulting slurry was poured into a mold to form a test specimen. After standard curing for 28 days, the tensile strength and water absorption rate of the specimens were tested. Additionally, the contact angle of the specimens was measured to assess their hydrophobic properties. The results are shown in Table 4 below.

[0066] Table 4

[0067] Compressive strength Water absorption contact angle Example 4 55.64MPa 11.52％ 104°

[0068] Example 5

[0069] A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material comprises the following steps:

[0070] (1) Prepare the following raw materials: 75 parts by weight of 42.5 ordinary Portland cement, 25 parts by weight of fly ash, 10 parts by weight of hydrophobic agent A (polydimethylsiloxane), 0.5 parts by weight of phosphoric acid, and 45 parts by weight of mixing water.

[0071] (2) The 42.5% ordinary Portland cement was mixed with mixing water and stirred at 900 r / min for 2 minutes, and then the hydrophobic agent A was added and stirred at 1100 r / min for 1.5 minutes to obtain a prehydrated hydrophobically modified cement slurry for use.

[0072] (3) Add the phosphoric acid and fly ash to a ball mill and mix them, adjust the system's pH to 5, and then ball mill them at a rate of 200 r / min for 15 minutes to obtain a silica-alumina hydrophobic modified powder. Then, continue to add the prehydrated hydrophobic modified cement slurry prepared in step (2) and ball mill them at a speed of 250 r / min for 30 minutes to obtain a cement-based silica-alumina micro-nano composite hydrophobic material.

[0073] The 28-day compressive strength of the cement-based silica-alumina micro-nano composite hydrophobic material prepared in this example was tested according to the GB175-2007 standard. Prior to testing, the cement-based silica-alumina micro-nano composite hydrophobic material, mixing water, and polycarboxylate superplasticizer were mixed in a mass ratio of 1:0.35:0.001 and stirred evenly. The resulting slurry was poured into a mold to form a test specimen. After standard curing for 28 days, the tensile strength and water absorption rate of the specimens were tested. Additionally, the contact angle of the specimens was measured to assess their hydrophobic properties. The results are shown in Table 5 below.

[0074] Table 5

[0075] Compressive strength Water absorption contact angle Example 5 51.23MPa 7.62％ 107°

[0076] Example 6

[0077] A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material comprises the following steps:

[0078] (1) Prepare the following raw materials: 80 parts by weight of 42.5 ordinary Portland cement, 20 parts by weight of metakaolin, 15 parts by weight of hydrophobic agent A (trichloro(octadecyl)silanecyclohexyltrimethoxysilane), 15 parts by weight of hydrophobic agent B (hexamethyldisilazane), 1 part by weight of hydrochloric acid, and 50 parts by weight of mixing water.

[0079] (2) The 42.5% ordinary Portland cement was mixed with mixing water and stirred at 800 r / min for 4 minutes, and then the hydrophobic agent A was added and stirred at 1000 r / min for 3 minutes to obtain a prehydrated hydrophobically modified cement slurry for standby use.

[0080] (3) Add the hydrochloric acid, metakaolin, and hydrophobic agent B to a ball mill and mix them, and adjust the system pH to 6. Then, ball mill them at a rate of 180 r / min for 5 minutes to obtain a silica-alumina hydrophobic modified powder. Then, continue to add the prehydrated hydrophobic modified cement slurry prepared in step (2), stir evenly, and let it stand for 15 minutes. After completion, a cement-based silica-alumina micro-nano composite hydrophobic material is obtained.

[0081] The 28-day compressive strength of the cement-based silica-alumina micro-nano composite hydrophobic material prepared in this example was tested according to the GB175-2007 standard. Prior to testing, the cement-based silica-alumina micro-nano composite hydrophobic material, mixing water, and polycarboxylate superplasticizer were mixed in a mass ratio of 1:0.35:0.001 and stirred evenly. The resulting slurry was poured into a mold to form a test specimen. After standard curing for 28 days, the tensile strength and water absorption rate of the specimens were tested. Additionally, the contact angle of the specimens was measured to assess their hydrophobic properties. The results are shown in Table 6 below.

[0082] Table 6

[0083] Compressive strength Water absorption contact angle Example 6 42.87MPa 8.47％ 98°

[0084] Example 7

[0085] A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material comprises the following steps:

[0086] (1) Prepare the following raw materials: 50 parts by weight of 42.5 ordinary Portland cement, 50 parts by weight of mineral powder, 5 parts by weight of hydrophobic agent A (hexadecyltrimethoxysilane), 5 parts by weight of hydrophobic agent B (stearic acid), and 40 parts by weight of mixing water.

[0087] (2) The 42.5% ordinary Portland cement was mixed with mixing water and stirred at 1000 r / min for 1 min, and then the hydrophobic agent A was added and stirred at 1200 r / min for 1 min to obtain a prehydrated hydrophobically modified cement slurry for use.

[0088] (3) Add the mineral powder and hydrophobic agent B into a ball mill and mix them, then ball mill them at a speed of 100 r / min for 30 minutes to obtain a silicon-aluminum hydrophobic modified powder. Then, continue to add the prehydrated hydrophobic modified cement slurry prepared in step (2) and ball mill them at a speed of 200 r / min for 25 minutes to obtain a cement-based silicon-aluminum micro-nano composite hydrophobic material.

[0089] The 28-day compressive strength of the cement-based silica-alumina micro-nano composite hydrophobic material prepared in this example was tested according to the GB175-2007 standard. Prior to testing, the cement-based silica-alumina micro-nano composite hydrophobic material, mixing water, and polycarboxylate superplasticizer were mixed in a mass ratio of 1:0.35:0.001 and stirred evenly. The resulting slurry was poured into a mold to form a test specimen. After standard curing for 28 days, the tensile strength and water absorption rate of the specimens were tested. Additionally, the contact angle of the specimens was measured to assess their hydrophobic properties. The results are shown in Table 7 below.

[0090] Table 7

[0091] Compressive strength Water absorption contact angle Example 7 50.86MPa 14.8％ 91°

[0092] Example 8

[0093] A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material comprises the following steps:

[0094] (1) Prepare the following raw materials: 80 parts by weight of 42.5 ordinary Portland cement, 20 parts by weight of metakaolin, 15 parts by weight of hydrophobic agent A (trichloro(octadecyl)silanecyclohexyltrimethoxysilane), 15 parts by weight of hydrophobic agent B (hexamethyldisilazane), 1 part by weight of hydrochloric acid, and 50 parts by weight of mixing water.

[0095] (2) The 42.5% ordinary Portland cement was mixed with mixing water and stirred at 800 r / min for 4 minutes, and then the hydrophobic agent A was added and stirred at 1000 r / min for 3 minutes to obtain a prehydrated hydrophobically modified cement slurry for standby use.

[0096] (3) The hydrochloric acid, metakaolin, hydrophobic agent B, and the prehydrated hydrophobically modified cement slurry prepared in step (2) are mixed and ball-milled at a speed of 300 r / min for 15 minutes to obtain a cement-based silica-alumina micro-nano composite hydrophobic material.

[0097] The 28-day compressive strength of the cement-based silica-alumina micro-nano composite hydrophobic material prepared in this example was tested according to the GB175-2007 standard. Prior to testing, the cement-based silica-alumina micro-nano composite hydrophobic material, mixing water, and polycarboxylate superplasticizer were mixed in a mass ratio of 1:0.35:0.001 and stirred evenly. The resulting slurry was poured into a mold to form a test specimen. After standard curing for 28 days, the tensile strength and water absorption rate of the specimens were tested. Additionally, the contact angle of the specimens was measured to assess their hydrophobic properties. The results are shown in Table 8 below.

[0098] Table 8

[0099] Compressive strength Water absorption contact angle Example 8 48.46MPa 7.51％ 109°

[0100] Example 9

[0101] A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material comprises the following steps:

[0102] (1) Prepare the following raw materials: 50 parts by weight of 42.5 ordinary Portland cement, 50 parts by weight of mineral powder, 5 parts by weight of hydrophobic agent A (hexamethyldisilazane), 5 parts by weight of hydrophobic agent B (stearic acid), 0.1 parts by weight of sulfuric acid, and 40 parts by weight of mixing water.

[0103] (2) The sulfuric acid, mineral powder, and hydrophobic agent B are added to a ball mill and mixed, and the pH of the system is adjusted to 4. The mixture is then ball-milled at a speed of 100 r / min for 30 min to obtain a silica-alumina hydrophobic modified powder. The 42.5% ordinary Portland cement, mixing water, and hydrophobic agent A are then added and ball-milled at a speed of 200 r / min for 25 min to obtain a cement-based silica-alumina micro-nano composite hydrophobic material.

[0104] The 28-day compressive strength of the cement-based silica-alumina micro-nano composite hydrophobic material prepared in this example was tested according to the GB175-2007 standard. Prior to testing, the cement-based silica-alumina micro-nano composite hydrophobic material, mixing water, and polycarboxylate superplasticizer were mixed in a mass ratio of 1:0.35:0.001 and stirred evenly. The resulting slurry was poured into a mold to form a test specimen. After standard curing for 28 days, the tensile strength and water absorption rate of the specimens were tested. Additionally, the contact angle of the specimens was measured to assess their hydrophobic properties. The results are shown in Table 9 below.

[0105] Table 9

[0106] Compressive strength Water absorption contact angle Example 9 51.72MPa 7.62％ 96°

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a cement-based silicon-aluminum micro-nano composite hydrophobic material, characterized in that: The method comprises the following steps: (1) Prepare the following raw materials: 50-80 parts by weight of cement-based cementitious material, 20-50 parts by weight of silica-alumina material, 5-15 parts by weight of hydrophobic agent A, 5-15 parts by weight of hydrophobic agent B, 0.1-1 parts by weight of acid solution, and 40-50 parts by weight of mixing water; the hydrophobic agent A includes any one of silane / siloxane, titanate, and fluorosilane; the hydrophobic agent B includes any one of stearic acid, silane / siloxane, titanate, and fluorosilane; (2) Mixing the cement-based cementitious material with mixing water and stirring evenly, then adding the hydrophobic agent A and stirring evenly to obtain a prehydrated hydrophobically modified cement slurry for later use; (3) The acid solution, the silicon-aluminum material and the hydrophobic agent B are mixed and then ground to obtain a silicon-aluminum hydrophobic modified powder for standby use; (4) The prehydrated hydrophobically modified cement slurry is mixed with the silica-alumina hydrophobically modified powder and then ground to obtain the cement-based silica-alumina micro-nano composite hydrophobic material.

2. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (1), the cement-based cementitious material includes any one of ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, and fly ash Portland cement.

3. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 2, characterized in that: In step (1), the cement-based gelling material is a semi-finished product obtained in the cement clinker production stage without being ground.

4. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (1), the alumina-silica material includes at least one of mineral powder, fly ash, silica fume, metakaolin, and waste glass.

5. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (1), the silane / siloxane substance in the hydrophobic agent A includes any one of hexamethyldisilazane, hexadecyltrimethoxysilane, trichloro(octadecyl)silanecyclohexyltrimethoxysilane, polydimethylsiloxane, and 3-methacryloxypropyltrimethoxysilane.

6. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (1), the titanate substance in the hydrophobic agent A includes any one of neoalkoxy tris (dioctyl pyrophosphate acyloxy) titanate, neoalkoxy tris (dioctyl phosphate acyloxy) titanate, bis (dioctyl pyrophosphate acyloxy) ethylene titanate acrylamide chelate, and tetraneoalkoxy bis (didecyl phosphite acyloxy) titanate.

7. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (1), the acid solution includes any one of hydrochloric acid, phosphoric acid, and sulfuric acid.

8. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (1), the acid solution makes the initial pH of the system be in the range of 4 to 6.

9. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (1), the silane / siloxane substance in the hydrophobic agent B includes any one of hexamethyldisilazane, hexadecyltrimethoxysilane, trichloro(octadecyl)silanecyclohexyltrimethoxysilane, polydimethylsiloxane, and 3-methacryloxypropyltrimethoxysilane.

10. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (1), the titanate substance in the hydrophobic agent B includes any one of neoalkoxy tris (dioctyl pyrophosphate acyloxy) titanate, neoalkoxy tris (dioctyl pyrophosphate acyloxy) titanate, bis (dioctyl pyrophosphate acyloxy) ethylene titanate acrylamide chelate, and tetraneoalkoxy bis (didecyl phosphite acyloxy) titanate.

11. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (2), the cement-based gelling material is mixed with mixing water and stirred for 1 to 4 minutes.

12. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 11, characterized in that: The stirring rate of the cement-based binder after mixing with mixing water is in the range of 800~1000r / min.

13. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (2), the hydrophobic agent is added and stirred for 1 to 3 minutes.

14. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 13, characterized in that: The stirring rate range after adding the hydrophobic agent is 1000~1200r / min.

15. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to claim 1, characterized in that: In step (3), the grinding process is carried out at a rate ranging from 100 to 200 r / min and for a time ranging from 5 to 30 min.

16. The method for preparing the cement-based silicon-aluminum micro-nano composite hydrophobic material according to any one of claims 1 to 15, characterized in that: In step (4), the grinding process is carried out at a rate ranging from 200 to 300 r / min and for a time ranging from 15 to 30 min.

17. Application of the cement-based silica-alumina micro-nano composite hydrophobic material obtained by the preparation method according to any one of claims 1 to 16 in the fields of construction, bridges, tunnels, and marine engineering.

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