A modified organic silicon waterproofing agent and its preparation method and application

Abstract

The present invention relates to the field of building waterproofing, specifically to a modified organosilicon waterproofing agent, its preparation method, and application. The modified organosilicon waterproofing agent comprises the following raw materials, by weight: 220-280 parts of organosilane, 20-50 parts of modified nano-silica, 0.1-0.2 parts of an initiator, 0.5-1.5 parts of an emulsifier, and 200-300 parts of a solvent. The modified organosilicon waterproofing agent prepared by the present invention has high adhesion to concrete substrates, good waterproofing properties, and can improve the compressive strength of concrete substrates.

Description

Technical Field

[0001] The present invention belongs to the field of building waterproofing, and in particular relates to a modified organosilicon waterproofing agent and a preparation method and application thereof. Background Art

[0002] Most building materials are porous media with numerous capillary structures within them. When exposed to water, moisture gradually penetrates from the surface into the interior through capillary action, causing numerous problems. For example, the steel bars in reinforced concrete are prone to rust, salt precipitation may occur on masonry surfaces, and wood may crack. These problems not only affect the building's appearance but also shorten its service life. Therefore, building substrates must be waterproofed. Currently, a common method is to add waterproofing agents to building materials. Existing waterproofing agents are mainly divided into two categories based on their application method: external coating waterproofing agents and incorporated waterproofing agents. Although external coating waterproofing agents can achieve relatively good results in a short period of time, these waterproofing agents have poor compatibility with the substrate and are prone to aging, resulting in a short period of waterproofing effect on concrete. To increase the lifespan of buildings, incorporated waterproofing agents have rapidly developed.

[0003] Patent CN108516719B discloses a waterproofing agent with self-repairing effect on concrete and a preparation method thereof, comprising the following steps: 2+ A magnesium salt solution with a concentration of 0.5-1.5 mol / L is mixed with sodium bentonite and / or calcium bentonite in a mass ratio of 15:1-25:1 to obtain a bentonite slurry. The bentonite slurry is then stirred uniformly, aged, and filtered to obtain a precipitate. The precipitate is then dried and pulverized to obtain a waterproofing agent. The waterproofing agent obtained by this invention has good compatibility with concrete and can achieve permanent waterproofing. However, as this waterproofing agent is inorganic, it requires relatively strict construction and post-construction maintenance conditions.

[0004] Patent CN109516712B discloses a waterproofing agent for mortar concrete and its preparation method. This mortar concrete waterproofing agent is a compound of multiple inorganic and organic admixtures, containing the following components by weight: 5-15% moisture-proofing agent, 50-60% inorganic waterproofing agent, 1-3% inorganic water-reducing agent, 1-2.5% corrosion inhibitor, 6-9% early strength agent, 3-10% surfactant, 0.1-30% high-efficiency water-reducing agent, 1-5% dispersant, and 0.1-1% thickener. This waterproofing agent combines multiple waterproofing and anti-seepage functions, requires minimal dosage, and offers excellent waterproofing effects. Furthermore, as a powder admixture, it offers a simple production process, low cost, and ease of packaging and transportation. It also effectively addresses the problem of difficult metering during use. However, the water-reducing agent used in this invention is a naphthalene-based water-reducing agent, which may cause certain environmental pollution during production and use.

[0005] Therefore, there is an urgent need for a green and environmentally friendly waterproofing agent that is easy to use. Summary of the Invention

[0006] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a modified silicone waterproofing agent and a preparation method thereof. The waterproofing agent prepared by the present invention can effectively reduce the water absorption rate of the substrate, improve the waterproofness, increase the compressive strength, and is easy to use, does not use substances harmful to the environment, and is green and environmentally friendly.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The first aspect of the present invention provides a modified organosilicon waterproofing agent, which comprises the following raw materials, in parts by weight: 220-280 parts of organosilane, 20-50 parts of modified nano-silica, 0.1-0.2 parts of initiator, 0.5-1.5 parts of emulsifier, and 200-300 parts of solvent.

[0009] In some embodiments, the method for preparing the organosilane comprises the following steps:

[0010] 2-(3,4-dihydroxyphenyl)ethylamine is added to DMF and ultrasonically treated for 5-10 minutes to obtain a solution. The solution is added dropwise to a reaction vessel containing 3-(2,3-epoxypropoxy)propyltrimethoxysilane, phenyltri(isopropyleneoxy)silane, and a catalyst. The temperature is raised to 110-120°C and the reaction is carried out for 1.5-2.5 hours. The temperature is then lowered to 75-85°C, vacuumed, and the reaction is carried out for 30-40 minutes. Isopropanol is then added and stirred for 30-40 minutes. The pH is adjusted to 5-6, distilled, and dried to obtain the organosilane.

[0011] In order to improve the storage stability of the organosilicon waterproofing agent, a large amount of emulsifier or co-emulsifier is usually added. However, the large amount of emulsifier and co-emulsifier added will greatly increase the number of hydrophilic groups in the waterproofing agent, resulting in a corresponding decrease in waterproof performance. The present invention prepares an organosilane with a specific structure for use in preparing an organosilicon waterproofing agent, which not only has good storage stability and good waterproofing, but also can improve the compressive strength of concrete. The possible reason is that the presence of some amino groups in the organosilane increases the dispersibility of the organosilane in water, which can reduce the amount of emulsifier added without affecting the waterproofing of the waterproofing agent. In addition, the presence of an appropriate amount of polar groups increases the tightness of the bond between the waterproofing agent and the concrete, further increasing the waterproofing of the concrete. Moreover, the organosilane contains a certain amount of phenyl groups, which increases the corrosion resistance of the waterproofing agent. Under extreme conditions, the waterproofing will not be reduced. In addition, the organosilane has a double bond structure, which can react with the modified nano-silica, thereby increasing the dispersibility of the modified nano-silica and forming a certain cross-linking network, which can "firmly fix" the concrete, further enhancing the compressive performance and waterproofing of the concrete.

[0012] In some embodiments, the mass ratio of the 2-(3,4-dihydroxyphenyl)ethylamine to the 3-(2,3-epoxypropyloxy)propyltrimethoxysilane is 1:(0.9-1.5).

[0013] In some embodiments, the mass ratio of the 2-(3,4-dihydroxyphenyl)ethylamine to phenyltri(isopropyleneoxy)silane is 1:(1.4-1.7).

[0014] The present invention increases the stability of the waterproofing agent without reducing its waterproofness and corrosion resistance by limiting the ratio of 2-(3,4-dihydroxyphenyl)ethylamine and 3-(2,3-epoxypropoxy)propyltrimethoxysilane; and further limits the ratio of 2-(3,4-dihydroxyphenyl)ethylamine and phenyltri(isopropyleneoxy)silane so that it can react with modified nano-silica, thereby enhancing the waterproofness of the waterproofing agent without affecting the compressive strength of concrete.

[0015] In some embodiments, the method for preparing the modified nano-silica comprises the following steps:

[0016] (1) Soaking the nano-silica in a nitric acid solution for 23-25 ​​hours, washing, and vacuum drying at 50-60° C. to obtain active nano-silica;

[0017] (2) adding the active nano-silica obtained in step (1), lauroleic acid and sulfuric acid into dichloromethane, reacting at 70-80° C. for 5-6 hours, washing and drying to obtain modified nano-silica.

[0018] Adding nano-silica to organosilane can improve the water resistance of waterproofing agents, but the particle size of nanoparticles is too small and they are very easy to agglomerate, forming secondary particles, resulting in uneven dispersion in the organosilicone system. Local defects such as voids and cracks may appear after use, affecting the water resistance and reducing the compressive strength of concrete. The present invention modifies nano-silica to increase its dispersibility in the organosilicone system, thereby improving the water resistance of the waterproofing agent and the compressive strength of concrete. The possible reason is that the groups on the surface of the activated nano-silica have higher reactivity and can react with lauroleic acid, reducing the surface energy of the nano-silica. At the same time, the double bond of lauroleic acid reacts with the organosilane, and the two synergistically avoid the problem of uneven dispersion in the organosilicone system caused by directly adding nano-silica. In addition, the long-chain alkane structure of lauroleic acid can "cross-entangle" with concrete, further improving the density of concrete, improving compressive strength, water resistance and corrosion resistance.

[0019] In some embodiments, the particle size of the nano-silica is 50-80 nm.

[0020] In some embodiments, the mass ratio of the active nano-silica to lauroleic acid is 1:(0.3-0.6).

[0021] The present invention improves the waterproofing property of the waterproofing agent by limiting the particle size of nano-silica, avoiding the decrease in stability of the silicone emulsion caused by too large a particle size and the excessive viscosity of the waterproofing agent that may affect workability due to too small a particle size. In addition, by limiting the ratio of active nano-silica and lauroleic acid, the dispersibility of the nano-silica is increased without affecting the compressive strength of the concrete.

[0022] In some embodiments, the initiator is a peroxide initiator, a persulfate initiator, or an azo compound initiator.

[0023] Preferably, the initiator is a persulfate initiator.

[0024] More preferably, the initiator is potassium persulfate.

[0025] A second aspect of the present invention provides a method for preparing a modified organosilicon waterproofing agent, comprising the following steps:

[0026] S1, adding an emulsifier to part of the solvent and stirring for 30-60 minutes to obtain an emulsifier solution; adding an initiator to the remaining solvent to obtain an initiator solution;

[0027] S2. Add organosilane and modified nano-silica to part of the emulsifier solution, stir at a speed of 900-1000 r / min for 3-5 minutes, then add the initiator solution and react at 70-80°C for 2-3 hours, then add the remaining emulsifier solution, continue stirring at a speed of 250-300 r / min for 2-4 hours to obtain a modified organosilicon waterproofing agent.

[0028] A third aspect of the present invention provides an application of a modified organosilicon waterproofing agent in the preparation of concrete, wherein the addition amount of the waterproofing agent is 0.05-3 wt % of the cement in the concrete.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention prepares an organosilane with a specific structure and modifies nano-silica, and applies the two together in the preparation process of the waterproofing agent, thereby enhancing the adhesion between the waterproofing agent and concrete, filling harmful holes in the concrete that are prone to water seepage, making the concrete uniform and dense, and improving the waterproofness while further enhancing the compressive strength. In addition, the waterproofing agent has good corrosion resistance and the waterproofness will not be significantly reduced under extreme conditions.

[0031] 2. The present invention prepares an organosilane with a specific structure for use in preparing an organosilicon waterproofing agent, thereby solving the problem that traditional organosilicon waterproofing agents require the addition of a large amount of emulsifiers or co-emulsifiers, resulting in a corresponding decrease in waterproofing performance. In addition, the presence of an appropriate amount of polar groups increases the bonding force between the waterproofing agent and concrete, further improving the compressive strength, waterproofness and corrosion resistance of the concrete.

[0032] 3. The present invention improves the dispersibility of nano-silica in the organosilicon system by modifying the nano-silica, thereby solving the problem that the nano-silica is unevenly dispersed in the organosilicon system, which may reduce the compressive strength of concrete after use. In addition, the modified nano-silica can react with organosilane, and the two synergistically avoid the problem of uneven dispersion in the organosilicon system caused by directly adding nano-silica, while improving the density of the concrete, and improving the compressive strength and water resistance. DETAILED DESCRIPTION

[0033] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples and comparative examples are intended only to illustrate the present invention and are not intended to limit the present invention. Other combinations and various modifications within the scope of the present invention may be made without departing from the spirit or scope of the present invention.

[0034] In order to facilitate those skilled in the art to implement the present invention, some of the raw materials and manufacturers of the embodiments and comparative examples are described as follows:

[0035] The compounds and related reagents used in the following examples and comparative examples can all be purchased from the market. Nano-silica with an average particle size of 30 and 60 nm were purchased from Beijing Dekedaojin Technology Co., Ltd.; the polycarboxylate water reducer model is Sika 540P, purchased from Yushan Zehe New Material Technology Co., Ltd.

[0036] Preparation Example 1

[0037] The preparation method of organosilane-1 comprises the following steps:

[0038] 10 g of 2-(3,4-dihydroxyphenyl)ethylamine was added to 50 ml of DMF and ultrasonically treated for 8 minutes to obtain a solution. The solution was added dropwise to a reaction vessel containing 12 g of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 15 g of phenyltri(isopropyleneoxy)silane, and 0.3 g of tetramethylammonium hydroxide with stirring while adding dropwise. The temperature was then raised to 115° C. and reacted for 2 hours. The temperature was then lowered to 80° C. and vacuumed to 0.1 MPa for 35 minutes. 30 ml of isopropanol was then added and stirred for 35 minutes. The pH was adjusted to 6 with glacial acetic acid, and the mixture was distilled and dried to obtain organosilane-1.

[0039] Preparation Example 2

[0040] The preparation method of organosilane-2 is the same as that of Preparation Example 1, except that the amount of 3-(2,3-epoxypropoxy)propyltrimethoxysilane added is 17 g.

[0041] Preparation Example 3

[0042] The preparation method of organosilane-3 is the same as that of Preparation Example 1, except that the amount of phenyltri(isopropyleneoxy)silane added is 18 g.

[0043] Preparation Example 4

[0044] The preparation method of organosilane-3 is the same as that of Preparation Example 1, except that phenyltri(isopropyleneoxy)silane is not added.

[0045] Preparation Example 5

[0046] The preparation method of modified nano-silica-1 comprises the following steps:

[0047] (1) 10 g of nano-silica with an average particle size of 60 nm was soaked in 100 ml of 75 wt% nitric acid solution for 24 h, washed, and vacuum-dried at 55° C. to obtain active nano-silica;

[0048] (2) 5 g of the active nano-silica obtained in step (1), 2.5 g of lauroleic acid, and 3 ml of 90 wt% sulfuric acid were added to 100 ml of dichloromethane, reacted at 75° C. for 5.5 h, washed, and dried to obtain modified nano-silica-1.

[0049] Preparation Example 5

[0050] The preparation method of modified nano-silica-2 is the same as that of Preparation Example 5, except that the average particle size of the nano-silica is 30 nm.

[0051] Preparation Example 6

[0052] The preparation method of modified nano-silica-3 is the same as that of Preparation Example 5, except that the amount of lauroleic acid added is 3.5 g.

[0053] Preparation Example 7

[0054] The preparation method of modified nano-silica-4 is the same as that of Preparation Example 5, except that an equal amount of lauroleic acid is replaced by 2-octenic acid.

[0055] Example 1

[0056] A modified organosilicon waterproofing agent comprises the following raw materials, measured in parts by weight: 1,250 parts of organosilane, 1,35 parts of modified nano-silica, 0.15 parts of potassium persulfate, 1 part of sodium dodecylsulfonate, and 250 parts of water.

[0057] The preparation method of the modified organosilicon waterproofing agent in this embodiment comprises the following steps:

[0058] S1, adding sodium lauryl sulfate to two-thirds of water by weight and stirring for 45 minutes to obtain a sodium lauryl sulfate solution; adding potassium persulfate to the remaining water to obtain a potassium persulfate solution;

[0059] S2. Add organosilane-1 and modified nano-silica-1 to half the weight of sodium dodecyl sulfonate solution, stir at a speed of 950 r / min for 4 minutes, then add potassium persulfate solution and react at 75°C for 2.5 hours, then add the remaining sodium dodecyl sulfonate solution, and continue stirring at a speed of 280 r / min for 3 hours to obtain a modified organosilicon waterproofing agent.

[0060] Example 2

[0061] A modified organosilicon waterproofing agent comprises the following raw materials, measured in parts by weight: 1,220 parts of organosilane, 1,20 parts of modified nano-silica, 0.1 parts of potassium persulfate, 0.5 parts of sodium lauryl sulfonate, and 200 parts of water.

[0062] The preparation method of the modified organosilicon waterproofing agent in this embodiment comprises the following steps:

[0063] S1, adding sodium lauryl sulfate to two-thirds of water and stirring for 30 minutes to obtain a sodium lauryl sulfate solution; adding potassium persulfate to the remaining water to obtain a potassium persulfate solution;

[0064] S2. Add organosilane-1 and modified nano-silica-1 to half the weight of sodium dodecylsulfonate solution, stir at a speed of 900 r / min for 5 minutes, then add potassium persulfate solution and react at 70°C for 3 hours, then add the remaining sodium dodecylsulfonate solution, and continue stirring at a speed of 250 r / min for 4 hours to obtain a modified organosilicon waterproofing agent.

[0065] Example 3

[0066] A modified organosilicon waterproofing agent comprises the following raw materials, measured in parts by weight: 1,280 parts of organosilane, 1,50 parts of modified nano-silica, 0.2 parts of potassium persulfate, 1.5 parts of sodium dodecylsulfonate, and 300 parts of water.

[0067] The preparation method of the modified organosilicon waterproofing agent in this embodiment comprises the following steps:

[0068] S1, adding sodium lauryl sulfate to two-thirds of water by weight and stirring for 60 minutes to obtain a sodium lauryl sulfate solution; adding potassium persulfate to the remaining water to obtain a potassium persulfate solution;

[0069] S2. Add organosilane-1 and modified nano-silica-1 to half the weight of sodium dodecyl sulfonate solution, stir at a speed of 1000 r / min for 3 minutes, then add potassium persulfate solution and react at 80°C for 2 hours, then add the remaining sodium dodecyl sulfonate solution, and continue stirring at a speed of 300 r / min for 2 hours to obtain a modified organosilicon waterproofing agent.

[0070] Example 4

[0071] A modified organosilicon waterproofing agent and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of organosilane-1 is replaced by organosilane-2.

[0072] Example 5

[0073] A modified organosilicon waterproofing agent and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of organosilane-1 is replaced by organosilane-3.

[0074] Example 6

[0075] A modified organosilicon waterproofing agent and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of organosilane-1 is replaced by organosilane-4.

[0076] Example 7

[0077] A modified organosilicon waterproofing agent and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that an equal amount of modified nano-silica-1 is replaced by modified nano-silica-2.

[0078] Example 8

[0079] A modified organosilicon waterproofing agent and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that an equal amount of modified nano-silica-1 is replaced by modified nano-silica-3.

[0080] Example 9

[0081] A modified organosilicon waterproofing agent and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that an equal amount of modified nano-silica-1 is replaced by modified nano-silica-4.

[0082] Comparative Example 1

[0083] A modified organic silicon waterproofing agent and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that an equal amount of modified nano-silica-1 is replaced by nano-silica with an average particle size of 60 nm.

[0084] Performance Testing

[0085] The waterproofing agent obtained in each embodiment and comparative example was added to concrete at 1.5wt% of the cement in the concrete, and then added to a cube mold with a side length of 100 mm and vibrated and compacted using an electric vibration table. The mold was removed after 24 hours, and the concrete was cured for 28 days at a temperature of 25°C and a relative humidity of 95% to obtain a test sample, wherein the concrete contained the following raw materials, in parts by weight: 100 parts of 42.5 ordinary Portland cement, 25 parts of fly ash, 20 parts of quartz sand, 0.5 parts of polycarboxylate water reducer, and 80 parts of water.

[0086] 1. Compressive strength

[0087] Refer to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" to test compressive strength.

[0088] 2. Water absorption

[0089] Take the test sample, dry it to constant weight, and weigh its dry weight, recorded as G0; then immerse the test sample in clean water, take it out after 48 hours, wipe the surface of the sample with a wrung-out wet towel, and weigh its wet weight when no visible water is left on the surface, recorded as G1. Calculate the water absorption rate of the test sample as follows;

[0090] Water absorption rate A = (G1-G0) / G0×100%;

[0091] For each embodiment and comparative example, 10 groups were tested in parallel and the average value was taken.

[0092] 3. Corrosion resistance

[0093] According to the alkali resistance determination method in the national standard "JCT902-2002 Organic Silicone Waterproofing Agent for Building Surfaces", a saturated Ca(OH)2 solution was prepared; the dried building substrate was immersed in the saturated Ca(OH)2 solution and corroded for 48 hours; then the corroded test sample was removed, dried to a constant weight, and its mass was weighed, recorded as G2; the corroded test sample was taken out after soaking in water for 48 hours, and the sample surface was wiped dry with a wrung-out wet towel. When there was no visible water on the surface, it was weighed, recorded as G3. The water absorption rate of the corroded test sample was calculated as follows:

[0094] B = (G3 - G2) / G2 × 100%;

[0095] For each embodiment and comparative example, 10 groups were tested in parallel and the average value was taken.

[0096] The test results are shown in Table 1.

[0097] Table 1

[0098]

[0099] By comparing the experimental data of Examples 1-3 in Table 1, it can be seen that the waterproofing agent has good waterproofing and makes the concrete substrate have good compressive strength; by comparing Example 4 with Example 1, it can be seen that the change in the ratio of 2-(3,4-dihydroxyphenyl)ethylamine and 3-(2,3-epoxypropoxy)propyltrimethoxysilane may lead to a decrease in the stability of the waterproofing agent and the adhesion to the concrete, the sample is easily penetrated, and the waterproofing, corrosion resistance and compressive strength of the sample are all reduced; by comparing Example 5 with Example 1, it can be seen that the change in the ratio of 2-(3,4-dihydroxyphenyl)ethylamine and phenyltri(isopropyleneoxy)silane may lead to an increase in the brittleness of the waterproofing agent and a decrease in the compressive strength of the sample; by comparing Example 6 with Example 1, it can be seen that without adding phenyltri(isopropyleneoxy)silane, the reaction with modified nano-silica is affected, the cross-linking degree of the waterproofing agent is reduced, and the waterproofing effect of the sample is reduced. The results, corrosion resistance and compressive strength are all decreased; compared with Example 1, Example 7 shows that the particle size of nano-silica is changed, which may cause the viscosity of the waterproofing agent to be too large, making it difficult to mix evenly with the concrete, and the water resistance, corrosion resistance and compressive strength of the sample are all decreased; compared with Example 1, Example 8 shows that the ratio of active nano-silica and lauroleic acid is changed, which may cause the reaction polymerization degree with the organosilane to be too large, affecting its uniformity and making it difficult to disperse in the concrete, resulting in a decrease in the compressive strength, water resistance and corrosion resistance of the sample; compared with Example 1, Example 9 shows that an equal amount of lauroleic acid is replaced by 2-octenoic acid, which may result in insufficient compaction with the concrete, and the compressive strength, water resistance and corrosion resistance of the sample are all decreased; compared with Example 1, Comparative Example 1 shows that the direct use of nano-silica has poor dispersibility in organosilicon, and the water resistance, corrosion resistance and compressive strength of the sample are all decreased.

[0100] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A modified silicone waterproofing agent, characterized in that: The composition comprises the following raw materials in parts by weight: 220-280 parts of organosilane, 20-50 parts of modified nano-silica, 0.1-0.2 parts of initiator, 0.5-1.5 parts of emulsifier, and 200-300 parts of solvent; The preparation method of the organosilane comprises the following steps: 2-(3,4-dihydroxyphenyl)ethylamine was added to DMF and ultrasonicated for 5-10 minutes to obtain a solution. The solution was added dropwise to a reaction vessel containing 3-(2,3-epoxypropyloxy)propyltrimethoxysilane, phenyltri(isopropyleneoxy)silane, and a catalyst. The temperature was raised to 110-120°C and the reaction was carried out for 1.5-2.5 hours. The temperature was then lowered to 75-85°C, vacuumed, and the reaction was carried out for 30-40 minutes. Isopropyl alcohol was then added and stirred for 30-40 minutes. The pH was adjusted to 5-6, and the reaction was carried out by distillation and drying to obtain the organosilane. The mass ratio of the 2-(3,4-dihydroxyphenyl)ethylamine and 3-(2,3-epoxypropyloxy)propyltrimethoxysilane is 1:(0.9-1.5); The mass ratio of the 2-(3,4-dihydroxyphenyl)ethylamine to phenyltri(isopropyleneoxy)silane is 1:(1.4-1.7); The preparation method of the modified nano-silica comprises the following steps: (1) Soaking the nano-silica in a nitric acid solution for 23-25 ​​hours, washing, and vacuum drying at 50-60°C to obtain active nano-silica; (2) adding the active nano-silica obtained in step (1), lauroleic acid and sulfuric acid into dichloromethane, reacting at 70-80° C. for 5-6 hours, washing and drying to obtain modified nano-silica; The particle size of the nano-silicon dioxide is 50-80 nm; The mass ratio of the active nano-silicon dioxide to lauroleic acid is 1:(0.3-0.6).

2. The modified organic silicon waterproofing agent according to claim 1, characterized in that The initiator is a peroxide initiator or an azo compound initiator.

3. A method for preparing the modified organic silicon waterproofing agent according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1, adding an emulsifier to part of the solvent and stirring for 30-60 minutes to obtain an emulsifier solution; adding an initiator to the remaining solvent to obtain an initiator solution; S2. Add organosilane and modified nano-silica to part of the emulsifier solution, stir at a speed of 900-1000 r / min for 3-5 minutes, then add the initiator solution and react at 70-80°C for 2-3 hours, then add the remaining emulsifier solution, continue stirring at a speed of 250-300 r / min for 2-4 hours to obtain a modified organosilicon waterproofing agent.

4. Use of the modified organic silicon waterproofing agent according to any one of claims 1 to 2 or the modified organic silicon waterproofing agent obtained by the preparation method according to claim 3 in concrete preparation, characterized in that: The addition amount of the waterproofing agent is 0.05-3wt% of the cement in the concrete.

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