Aminosilane modified stearic acid-based concrete hydrophobic material and preparation method thereof

Abstract

The invention discloses an aminosilane-modified stearic acid-based concrete hydrophobic material and a preparation method thereof. The raw materials of the hydrophobic material include stearic acid, a condensing agent, a reaction accelerator and aminosilane; the mass percentages of the raw materials are: 25%-35% of stearic acid, 25%-35% of condensing agent, 20%-25% of reaction accelerator and 10%-25% of aminosilane. In the invention, the condensing agent activates the carboxyl group in the stearic acid, so that the stearic acid is more easily stably connected with the aminosilane, and then the stearic acid molecules obtain better dispersibility and stability through the hydrophilic group of the aminosilane, solves the problem of strength damage caused by uneven internal dispersion of the concrete caused by the addition of stearic acid to the concrete, and the aminosilane can promote the hydration of the concrete, optimize the content of various hydration products, make the microstructure of the concrete more uniform, offset the inhibition of stearic acid on the hydration of the concrete, and ensure the mechanical properties of the concrete. The invention has a simple formula, simplifies the preparation process, and reduces the production cost.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials and relates to an aminosilane-modified stearic acid-based concrete hydrophobic material and a preparation method thereof. Background Art

[0002] In marine, water conservancy and underground projects, the life of concrete structures is often greatly shortened due to the penetration of corrosive ions carried by water.

[0003] The existing technology uses fatty acids, siloxanes, fluorosilanes, etc. as hydrophobic materials, which are mixed into concrete to enhance its hydrophobicity and resist penetration damage.

[0004] However, existing hydrophobic materials generally have non-wetting properties and are prone to agglomeration during the concrete mixing process, which not only causes internal defects in the concrete, but also inhibits the hydration process of the concrete, resulting in loss of concrete strength and seriously affecting the mechanical properties of the concrete. Therefore, it is difficult for existing technologies to ensure that the mechanical properties of concrete are not damaged while ensuring the hydrophobicity of the concrete. Summary of the invention

[0005] In order to solve the above problems, the present invention discloses an aminosilane-modified stearic acid-based concrete hydrophobic material and a preparation method thereof.

[0006] The invention discloses an aminosilane-modified stearic acid-based concrete hydrophobic material, the raw materials of which include stearic acid, a condensing agent, a reaction accelerator and aminosilane;

[0007] The mass percentage of each raw material is: stearic acid 25%~35%, condensation agent 25%~35%, reaction accelerator 20%~25%, aminosilane 10%~25%.

[0008] Preferably, the aminosilane is any one of aminoethylaminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane (KH-550) or 3-aminopropyltrimethoxysilane (KH-540).

[0009] Preferably, the condensing agent is any one of dicyclohexylcarbodiimide (DCC), N,N-diisopropylcarbodiimide (DIC), carbodiimide hydrochloride (EDC) or N,N'-carbonyldiimidazole (CDI).

[0010] Preferably, the reaction accelerator is any one of 4-dimethylaminopyridine (DMAP), 4-pyrrolidinopyridine (4-PPY), N-hydroxysuccinimide (HOSu), 1-hydroxybenzotriazole (HOBt), potassium hydroxide, and potassium carbonate.

[0011] The present invention also discloses a method for preparing an aminosilane-modified stearic acid-based concrete hydrophobic material. The hydrophobic material is prepared by the following steps:

[0012] Dissolving 25% to 35% by mass of stearic acid at a first preset temperature and a first preset speed for a first preset time to obtain a first solution;

[0013] Maintaining the first preset temperature and the first preset speed, sequentially adding 25% to 35% by weight of a condensing agent and 20% to 25% by weight of a reaction accelerator to the first solution, reacting for 2 h to 4 h, to obtain a second solution;

[0014] Adding 10% to 25% by mass of aminosilane to the second solution, and reacting at a second preset temperature and a second preset speed for a second preset time to obtain a third solution;

[0015] The third solution is cooled for a third preset time to obtain a solid, which is ground into powder to obtain an aminosilane-modified stearic acid-based concrete hydrophobic material.

[0016] Preferably, the first preset temperature is 70° C. to 80° C., the first preset speed is 400 r / min to 500 r / min, and the first preset time is 20 min to 25 min.

[0017] Preferably, the second preset temperature is 80°C to 100°C, the second preset speed is 500r / min to 600r / min, the second preset time is 3.5h to 4h, and the third preset time is 48h to 72h.

[0018] Preferably, 25% to 35% by mass of stearic acid is dissolved at a first preset temperature and a first preset speed for a first preset time to obtain a first solution, specifically:

[0019] 25% to 35% by mass of stearic acid is sealed and dissolved at a first preset temperature and a first preset rotation speed for a first preset time to obtain a first solution.

[0020] Preferably, 10% to 25% by mass of aminosilane is added to the second solution, and the reaction is carried out at a second preset temperature and a second preset speed for a second preset time to obtain a third solution, specifically:

[0021] 10% to 25% by mass of aminosilane is added to the second solution, and the solution is sealed and reacted for a second preset time at a second preset temperature and a second preset rotation speed to obtain a third solution.

[0022] Preferably, after obtaining the aminosilane-modified stearic acid-based concrete hydrophobic material, the method further comprises:

[0023] The aminosilane-modified stearic acid-based concrete hydrophobic material is added to a concrete mix according to a preset ratio to obtain aminosilane-modified stearic acid-based integral hydrophobic concrete.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) In the present invention, the condensing agent activates the carboxyl group in stearic acid, making it easier for stearic acid to stably connect with aminosilane, thereby making the stearic acid molecules obtain better dispersibility and stability through the hydrophilic group of aminosilane, solving the problem of strength damage caused by uneven dispersion of concrete when stearic acid is added to concrete. At the same time, aminosilane can promote the hydration of concrete, optimize the content of various hydration products, make the microstructure of concrete more uniform, offset the inhibition of stearic acid on concrete hydration, and ensure the mechanical properties of concrete;

[0026] (2) During the concrete mixing process, the aminosilane-modified stearic acid-based integral hydrophobic material of the present invention breaks the Si-O bond when it encounters water to generate silanol compounds, which react with the hydroxyl groups on the surface of the cementitious material to undergo a dehydration condensation reaction, making it closely connected with the inner surface of the concrete, thereby improving the hydrophobicity of the concrete;

[0027] (3) The present invention melts stearic acid by heating and then reacts it with aminosilane. This is different from the prior art method of dissolving stearic acid by using chloroform (chloroform is extremely toxic). The present invention uses melting to treat stearic acid, which is more environmentally friendly and safe. In addition, the present invention is different from the prior art method of hydrolyzing siloxane in advance. During the grafting process of stearic acid and aminosilane, the present invention avoids the premature breakage of the Si-O bond of aminosilane when it encounters water, ensures the activity of the stearic acid group modified by aminosilane in the dehydration condensation reaction with the hydroxyl group on the concrete surface, and greatly improves the efficiency of the hydrophobic material grafted on the concrete surface.

[0028] (4) The present invention is added to concrete, making the concrete have strong frost resistance, strong impermeability, corrosion resistance and compactness, and the strength is improved compared with ordinary concrete, thereby improving the overall quality and service life of the concrete;

[0029] (5) The present invention not only improves the reaction rate by adding a condensing agent and a reaction accelerator, but also ensures the smooth progress of the reaction and the stability of the product. Furthermore, the present invention has a simple formula, simplifies the preparation process, and reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the preparation process of the aminosilane-modified stearic acid-based concrete hydrophobic material of the present invention. DETAILED DESCRIPTION

[0031] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0032] The invention discloses an aminosilane-modified stearic acid-based concrete hydrophobic material, the raw materials of which include stearic acid, a condensing agent, a reaction accelerator and aminosilane;

[0033] The mass percentage of each raw material is: stearic acid 25%~35%, condensation agent 25%~35%, reaction accelerator 20%~25%, aminosilane 10%~25%.

[0034] Preferably, the aminosilane is any one of aminoethylaminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane (KH-550) or 3-aminopropyltrimethoxysilane (KH-540).

[0035] Preferably, the condensing agent is any one of dicyclohexylcarbodiimide (DCC), N,N-diisopropylcarbodiimide (DIC), carbodiimide hydrochloride (EDC) or N,N'-carbonyldiimidazole (CDI).

[0036] Preferably, the reaction accelerator is any one of 4-dimethylaminopyridine (DMAP), 4-pyrrolidinylpyridine (4-PPY), N-hydroxysuccinimide (HOSu), 1-hydroxybenzotriazole (HOBt), potassium hydroxide and potassium carbonate.

[0037] The reaction principle of the present invention is: firstly, the carboxyl group in stearic acid is activated by a reaction condensing agent, and the condensing agent can usually form an active intermediate with the carboxyl group. The active intermediate is more active and is very easy to condense with the amino group, so that the stearic acid and the aminosilane are stably connected.

[0038] Furthermore, the reaction promoter of the present invention can stabilize active intermediates, inhibit the occurrence of racemization side reactions, and allow the reaction to proceed at a faster rate, thereby improving the purity and stability of the product.

[0039] That is to say, in the present invention, the condensing agent is responsible for activating the functional groups in the reactants and providing the necessary active intermediates for the reaction; while the reaction promoter is responsible for stabilizing the active intermediates and inhibiting the occurrence of their racemization. The combination of the two can simultaneously improve the reaction rate and the purity of the product.

[0040] like Figure 1As shown, the present invention also discloses a method for preparing an aminosilane-modified stearic acid-based concrete hydrophobic material, wherein the hydrophobic material is prepared by the following steps:

[0041] Melting 25% to 35% by mass of stearic acid at a first preset temperature and a first preset speed for a first preset time to obtain a first solution;

[0042] Preferably, 25% to 35% by mass of stearic acid is melted at a first preset temperature and a first preset speed for a first preset time to obtain a first solution, specifically:

[0043] The first solution is obtained by sealing and melting 25% to 35% stearic acid at a first preset temperature and a first preset rotation speed for a first preset time.

[0044] Preferably, the first preset temperature is 70°C to 80°C, and the first preset speed is 400r / min to

[0045] 500r / min, the first preset time is 20min~25min.

[0046] Maintaining the first preset temperature and the first preset speed, sequentially adding 25% to 35% by weight of a condensing agent and 20% to 25% by weight of a reaction accelerator to the first solution, reacting for 2 h to 4 h, to obtain a second solution;

[0047] Adding 10% to 25% by mass of aminosilane to the second solution, and reacting at a second preset temperature and a second preset speed for a second preset time to obtain a third solution;

[0048] The third solution is cooled for a third preset time to obtain a solid and grind the solid into powder to obtain an aminosilane-modified stearic acid-based concrete hydrophobic material.

[0049] Preferably, 10% to 25% by mass of aminosilane is added to the second solution, and the reaction is carried out at a second preset temperature and a second preset speed for a second preset time to obtain a third solution, specifically:

[0050] 10% to 25% by mass of aminosilane is added to the second solution, and the solution is sealed and reacted for a second preset time at a second preset temperature and a second preset rotation speed to obtain a third solution.

[0051] Preferably, the second preset temperature is 80°C to 100°C, and the second preset speed is 500r / min to

[0052] 600r / min, the second preset time is 3.5h~4h, and the third preset time is 48h~72h.

[0053] Preferably, after obtaining the aminosilane-modified stearic acid-based concrete hydrophobic material, the method further comprises:

[0054] The aminosilane-modified stearic acid-based concrete hydrophobic material is added into the concrete mix according to a preset ratio to obtain the aminosilane-modified stearic acid-based integral hydrophobic concrete.

[0055] The aminosilane-modified stearic acid-based hydrophobic material of the present invention has a unique amphiphilic feature, that is, one end shows excellent hydrophobicity, while the other end shows good hydrophilicity. The hydrophobic end can significantly prevent building materials such as concrete from being eroded by moisture, salts and other corrosive media through an effective chemical barrier effect, thereby greatly extending the service life and performance stability of concrete. The hydrophilic end utilizes the characteristics of high Si-O bond activity and easy breakage when exposed to water. When the material contacts water, the Si-O bond will undergo hydrolysis reaction, thereby generating silanol compounds. These silanol compounds retain the reactivity of Si, and can quickly undergo dehydration condensation reaction with the hydroxyl group on the surface of the cementitious material of concrete to form a strong chemical bond. This dehydration condensation reaction is not only conducive to the close combination between the material and the concrete, but also significantly improves the dispersibility and compatibility of the material in the concrete. By optimizing the dispersibility of the hydrophobic material, it can be further ensured that it is evenly distributed in the concrete, thereby giving full play to its hydrophobic anticorrosion and enhanced concrete performance.

[0056] The following are several embodiments and comparative examples of the present invention:

[0057] Example 1

[0058] The mass percentages of stearic acid, condensation agent, reaction accelerator and aminosilane are 28%, 28%, 21% and 23% respectively.

[0059] The condensing agent is carbodiimide hydrochloride;

[0060] The reaction accelerator is N-hydroxysuccinimide;

[0061] The aminosilane is 3-aminopropyltriethoxysilane (KH-550);

[0062] Step 1: Weigh each raw material;

[0063] Step 2: Place a beaker containing stearic acid on a magnetic stirring heater, seal the beaker mouth with plastic wrap, adjust the temperature to 80°C, the speed to 500r / min, stir and heat for 20 minutes to completely melt it, and obtain solution A;

[0064] Step 3: Add the weighed carbodiimide hydrochloride to solution A, keep the temperature and speed of the magnetic stirrer the same as in the previous step during the addition, and react for 1 hour to obtain solution B;

[0065] Step 4: Add N-hydroxysuccinimide to the obtained solution B. During the addition process, keep the temperature and speed of the magnetic stirrer the same as in the previous step to inhibit the racemization of the reactants in solution B and promote the reaction. React for 1 hour to obtain solution C.

[0066] Step 5: Add KH-550 to solution C, place it in a magnetic stirring heater, close the beaker mouth, adjust the temperature to 100°C, the speed to 500r / min, stir and heat to react for 4h, and obtain solution D;

[0067] Step 6: Transfer solution D from the magnetic stirring heater to room temperature and let it stand for 48 hours. The solution cools and turns into solid E.

[0068] Step 7: Grind E into powder in a grinding pot to obtain an aminosilane-modified stearic acid-based hydrophobic material.

[0069] Step 8: First moisten the mixer, then pour in coarse aggregate, fine aggregate and hydrophobic material (the amount of hydrophobic material added is 0.5% of the weight of the cementitious material in the concrete) in turn and dry mix for 1 minute. After dry mixing, mix water and water reducer and add them to the dry mixed aggregate at the same time. After stirring for 2 minutes, put the mixed concrete into the mold and place it on the vibration table for vibration compaction, and then cure it according to the standard for 28 days.

[0070] Step 9: Conduct compressive strength, contact angle and water absorption tests on the cured hydrophobic concrete specimens.

[0071] Combining the examples and the subsequent comparative examples, it can be seen that the present application can adjust the hydrophilic and hydrophobic balance of the hydrophobic material by carefully selecting and optimizing the raw material ratio, so that it has excellent hydrophobic properties and can form good adhesion with the concrete substrate. This amphiphilic feature not only improves the hydrophobic effect, but also enhances the overall performance of the concrete.

[0072] The test results of the hydrophobic concrete performance of this embodiment are shown in Table 1.

[0073] Example 2

[0074] The mass percentages of stearic acid, condensation agent, reaction accelerator and aminosilane are 32%, 32%, 23% and 13% respectively;

[0075] The condensing agent is carbodiimide hydrochloride;

[0076] The reaction accelerator is N-hydroxysuccinimide;

[0077] The aminosilane is aminoethylaminopropyltrimethoxysilane;

[0078] Step 1: Weigh each raw material;

[0079] Step 2: Place a beaker containing stearic acid on a magnetic stirring heater, seal the beaker mouth with plastic wrap, adjust the temperature to 80°C, the speed to 500r / min, stir and heat for 20 minutes to completely melt it, and obtain solution A;

[0080] Step 3: Add the weighed carbodiimide hydrochloride to solution A, keep the temperature and speed of the magnetic stirrer the same as in the previous step during the addition, and react for 1 hour to obtain solution B;

[0081] Step 4: Add N-hydroxysuccinimide to the obtained solution B. During the addition process, keep the temperature and speed of the magnetic stirrer the same as in the previous step to inhibit the racemization of the reactants in solution B and promote the reaction. React for 3 hours to obtain solution C.

[0082] Step 5: Add aminoethylaminopropyltrimethoxysilane to solution C, place it in a magnetic stirring heater, seal the beaker mouth, adjust the temperature to 100°C, the rotation speed to 500r / min, stir and heat to react for 4h, and obtain solution D.

[0083] Step 6: Transfer solution D from the magnetic stirring heater to room temperature. After 48 hours, the solution cools and turns into solid E.

[0084] Step 7: Grind E into powder in a grinding pot to obtain an aminosilane-modified stearic acid-based hydrophobic material;

[0085] Step 8: First, wet the mixer, then pour in the coarse aggregate, fine aggregate and hydrophobic material (the amount of hydrophobic material added is 0.5% of the weight of the cementitious material) and dry mix for 1 minute. After dry mixing, mix the water and water reducer and add them to the dry mixed aggregate at the same time. After stirring for 2 minutes, put the mixed concrete into the mold and put it on the vibration table for vibration compaction, and then cure it according to the standard for 28 days;

[0086] Step 9: Conduct compressive strength, contact angle and water absorption tests on the cured hydrophobic concrete specimens.

[0087] The test results of the hydrophobic concrete performance of this embodiment are shown in Table 1.

[0088] The entire preparation process of the present invention is carried out under relatively mild conditions and the reaction time is moderate, which helps to simplify the production process and reduce the production cost; the prepared hydrophobic material has stable performance, is easy to store and transport, and is convenient for application in practical engineering; and the raw materials used are all environmentally friendly materials, less waste is generated during the reaction process, and energy consumption and waste are reduced.

[0089] Example 3

[0090] The mass percentages of stearic acid, condensation agent, reaction accelerator and aminosilane are 30%, 30%, 22% and 18% respectively;

[0091] The condensing agent is carbodiimide hydrochloride;

[0092] The reaction accelerator is N-hydroxysuccinimide;

[0093] The aminosilane is 3-aminopropyltrimethoxysilane (KH-540);

[0094] Step 1: Weigh each raw material;

[0095] Step 2: Place a beaker containing stearic acid on a magnetic stirring heater, seal the beaker mouth with plastic wrap, adjust the temperature to 80°C, the speed to 500r / min, stir and heat for 20 minutes to completely melt it, and obtain solution A;

[0096] Step 3: Add the weighed carbodiimide hydrochloride to solution A, keep the temperature and speed of the magnetic stirrer the same as in the previous step during the addition, and react for 30 minutes to obtain solution B;

[0097] Step 4: Add N-hydroxysuccinimide to the obtained solution B. During the addition process, keep the temperature and speed of the magnetic stirrer the same as in the previous step to inhibit the racemization of the reactants in solution B and promote the reaction. The reaction is carried out for 2 hours to obtain solution C.

[0098] Step 5: Add KH-540 to solution C, place in a magnetic stirring heater, close the beaker mouth, adjust the temperature to 100°C, the speed to 500r / min, stir and heat to react for 4h, and obtain solution D;

[0099] Step 6: Transfer solution D from the magnetic stirring heater to room temperature. After 48 hours, the solution cools and turns into solid E.

[0100] Step 7: Grind E into powder in a grinding pot to obtain an aminosilane-modified stearic acid-based hydrophobic material;

[0101] Step 8: First, wet the mixer, then pour in the coarse aggregate, fine aggregate and hydrophobic material (the amount of hydrophobic material added is 0.5% of the weight of the cementitious material) and dry mix for 1 minute. After dry mixing, mix the water and water reducer and add them to the dry mixed aggregate at the same time. After stirring for 2 minutes, put the mixed concrete into the mold and put it on the vibration table for vibration compaction, and then cure it according to the standard for 28 days;

[0102] Step 9: Conduct compressive strength, contact angle and water absorption tests on the cured hydrophobic concrete specimens.

[0103] The test results of the hydrophobic concrete performance of this embodiment are shown in Table 1.

[0104] The present invention promotes contact and mixing between the raw materials by adding the raw materials in sequence and stirring (by speed control), making the reaction more uniform and thorough, which not only improves the reaction efficiency but also makes the generated hydrophobic layer more dense and uniform. The dense hydrophobic layer can more effectively prevent the penetration of water molecules, thereby improving the hydrophobic properties of the material.

[0105] Example 4

[0106] The mass percentages of stearic acid, condensation agent, reaction accelerator and aminosilane are 28%, 28%, 21% and 23% respectively;

[0107] The condensation agent is dicyclohexylcarbodiimide;

[0108] The reaction accelerator is 4-dimethylaminopyridine;

[0109] The aminosilane is 3-aminopropyltriethoxysilane (KH-550);

[0110] Step 1: Weigh each raw material;

[0111] Step 2: Place a beaker containing stearic acid on a magnetic stirring heater, seal the beaker mouth with plastic wrap, adjust the temperature to 80°C, the speed to 500r / min, stir and heat for 20 minutes to completely melt it, and obtain solution A;

[0112] Step 3: Add the weighed dicyclohexylcarbodiimide to solution A, keep the temperature and speed of the magnetic stirrer the same as in the previous step during the addition, and react for 1 hour to obtain solution B;

[0113] Step 4: Add 4-dimethylaminopyridine to the obtained solution B. During the addition process, keep the temperature and speed of the magnetic stirrer the same as in the previous step to inhibit the racemization of the reactants in solution B and promote the reaction. The reaction is carried out for 2 hours to obtain solution C.

[0114] Step 5: Add KH-550 to solution C, place it in a magnetic stirring heater, close the beaker mouth, adjust the temperature to 100°C, the speed to 500r / min, stir and heat to react for 4h, and obtain solution D;

[0115] Step 6: Transfer solution D from the magnetic stirring heater to room temperature. After 48 hours, the solution cools and turns into solid E.

[0116] Step 7: Grind E into powder in a grinding pot to obtain an aminosilane-modified stearic acid-based hydrophobic material;

[0117] Step 8: First moisten the mixer, then pour in coarse aggregate, fine aggregate and hydrophobic material (the amount of hydrophobic material added is 0.5% of the weight of the cementitious material) in turn and dry mix for 1 minute. After dry mixing, mix water and water reducer and add them to the dry mixed aggregate at the same time. After stirring for 2 minutes, put the mixed concrete into the mold and place it on the vibration table for vibration compaction, and then cure it according to the standard for 28 days.

[0118] Step 9: Conduct compressive strength, contact angle and water absorption tests on the cured test blocks.

[0119] The test results of the hydrophobic concrete performance of this embodiment are shown in Table 1.

[0120] Example 5

[0121] Compared with Example 1, the only difference is:

[0122] The amount of the hydrophobic material added in step eight is 1.0% of the weight of the cementitious material; the test results of the hydrophobic concrete performance of this embodiment are shown in Table 1.

[0123] Example 6

[0124] Compared with Example 2, the only difference is:

[0125] The amount of the hydrophobic material added in step eight is 1.0% of the weight of the cementitious material; the test results of the hydrophobic concrete performance of this embodiment are shown in Table 1.

[0126] Example 7

[0127] Compared with Example 3, the only difference is:

[0128] The amount of the hydrophobic material added in step eight is 1.0% of the weight of the cementitious material; the test results of the hydrophobic concrete performance of this embodiment are shown in Table 1.

[0129] Comparative Example 1

[0130] Compared with Example 1, the only difference is:

[0131] This comparative example provides ordinary concrete without adding hydrophobic material and with the same proportion as Example 1; the performance test results of the hydrophobic concrete of this comparative example are shown in Table 1.

[0132] Comparative Example 2

[0133] Compared with Example 1, steps 1 to 4 are the same, and the remaining steps are as follows:

[0134] Step 5: Put ethanol into a container and keep the container dry and dust-free, then add deionized water to obtain an ethanol aqueous solution; dropwise add formic acid with a concentration of 6 mol / L into the ethanol aqueous solution, adjust the pH value of the ethanol aqueous solution to 5, and obtain an acidic solution D;

[0135] Step 6: Add KH-550 to solution D to obtain a hydrolysis mixed solution E;

[0136] Step 7: Add solution E to solution C, place in a magnetic stirring heater, close the beaker mouth, adjust the temperature to 100°C, the speed to 500r / min, stir and heat to react for 4h, and obtain solution F;

[0137] Step 8: removing methanol and ethanol from solution F by distillation under reduced pressure to obtain solution G;

[0138] Step 9: Move solution G to room temperature and place it for 24 hours, then cool the solution to become solid H;

[0139] Step 10: Grind H into powder in a grinding pot to obtain an aminosilane-modified stearic acid-based hydrophobic material;

[0140] Step 11: First moisten the mixer, then pour in coarse aggregate, fine aggregate and hydrophobic material (the amount of hydrophobic material added is 0.5% of the weight of the cementitious material) in turn and dry mix for 1 minute. After dry mixing, mix water and water reducer and add them to the dry mixed aggregate at the same time. After stirring for 2 minutes, put the mixed concrete into the mold and place it on the vibration table for vibration compaction, and then cure it according to the standard for 28 days.

[0141] Step 12: Conduct compressive strength, contact angle and water absorption tests on the cured test blocks.

[0142] The test results of the hydrophobic concrete performance of this comparative example are shown in Table 1.

[0143] Comparative Example 3

[0144] In this comparative example, stearic acid is directly used as a concrete hydrophobic material, and the amount of stearic acid added is 0.5% of the weight of the cementitious material; the test results of the hydrophobic concrete performance of this comparative example are shown in Table 1.

[0145] Table 1 Test results of hydrophobic concrete performance

[0146]

[0147] From the comparison of Examples 1 to 7 with Comparative Example 1 in Table 1, it can be seen that the addition of aminosilane-modified stearic acid-based hydrophobic material reduces the water absorption rate of concrete, significantly increases the contact angle of concrete, and the compressive strength of aminosilane-modified stearic acid-based overall hydrophobic concrete is not reduced compared with ordinary concrete.

[0148] Comparative Examples 1 to 3 show that the compressive strength, water absorption and contact angle of the aminosilane-modified stearic acid-based integral hydrophobic concrete are related to the type of aminosilane, among which the hydrophobic concrete incorporating KH550 has the highest strength, and the hydrophobic concrete incorporating aminoethylaminopropyltrimethoxysilane has the lowest water absorption and the largest contact angle.

[0149] From the comparison of Examples 1, 5, 2, 6, 3, and 7, it can be seen that as the amount of aminosilane-modified stearic acid-based hydrophobic material increases, the strength of the concrete decreases slightly, the water absorption rate gradually decreases, and the contact angle gradually increases, indicating that increasing the amount of aminosilane-modified stearic acid-based hydrophobic material will improve the hydrophobic performance of the concrete.

[0150] It can be seen from Example 1 and Comparative Example 2 that after the aminosilane is hydrolyzed in advance and then reacted with stearic acid, the hydrophobicity and compressive strength of the aminosilane-modified stearic acid-based hydrophobic material prepared are reduced after being added to concrete. This is because the Si-O bond of the aminosilane breaks prematurely when it encounters water, resulting in a reduction in activity.

[0151] By comparing Example 1 with Comparative Example 3, it can be seen that the effect of directly using stearic acid as a concrete hydrophobic material is far inferior to that of aminosilane-modified stearic acid-based hydrophobic material. Although stearic acid has excellent hydrophobicity, its dispersibility in concrete is poor, and it has an inhibitory effect on cement hydration, which seriously affects the mechanical properties of concrete; and from the data in Table 1, it can be seen that stearic acid as a concrete hydrophobic material is affected by its own agglomeration characteristics, and the hydrophobic effect is limited.

[0152] In summary, the present invention ensures the strength of concrete while significantly improving the hydrophobicity of concrete. Compared with the comparative concrete, the 28d strength of aminosilane-modified stearic acid-based overall hydrophobic concrete can be increased by up to 7.1%, which effectively solves the problem of reduced concrete strength caused by the addition of hydrophobic materials; the water absorption rate of aminosilane-modified stearic acid-based overall hydrophobic concrete is reduced by up to 48%, and the contact angle is up to 129°, far exceeding 90°. Therefore, the present invention is suitable for antifreeze concrete engineering and anti-seepage concrete engineering in cold regions.

[0153] Compared with the prior art, the present invention has the following beneficial effects:

[0154] (1) In the present invention, the condensing agent activates the carboxyl group in stearic acid, making it easier for stearic acid to stably connect with aminosilane, thereby making the stearic acid molecules obtain better dispersibility and stability through the hydrophilic group of aminosilane, solving the problem of strength damage caused by uneven dispersion inside the concrete caused by the addition of stearic acid to concrete. At the same time, aminosilane can promote the hydration of concrete, optimize the content of various hydration products, and make the microstructure of concrete more uniform. This characteristic is used to offset the inhibition of stearic acid on concrete hydration, thereby ensuring the mechanical properties of concrete.

[0155] (2) During the mixing process of concrete, the aminosilane-modified stearic acid-based integral hydrophobic material of the present invention breaks the Si-O bond of the aminosilane when it comes into contact with water to generate silanol compounds, which react with the hydroxyl groups on the surface of the cementitious material to undergo a dehydration condensation reaction, thereby making it closely connected with the inner surface of the concrete, thereby improving the hydrophobicity of the concrete;

[0156] (3) The present invention melts stearic acid by heating and then reacts it with aminosilane. This is different from the method of dissolving stearic acid by chloroform (chloroform is extremely toxic) in the prior art. The present invention uses melting to treat stearic acid, which is more environmentally friendly and safe. In addition, the present invention is different from the method of hydrolyzing siloxane in advance in the prior art. During the grafting process of stearic acid and aminosilane, the present invention avoids the premature breakage of the Si-O bond of aminosilane when it encounters water, ensures the activity of the stearic acid group modified by aminosilane in the dehydration condensation reaction with the hydroxyl group on the concrete surface, and greatly improves the efficiency of the hydrophobic material grafted on the concrete surface.

[0157] (4) The present invention is added to concrete, making the concrete have strong frost resistance, strong impermeability, corrosion resistance and compactness, and the strength is improved compared with ordinary concrete, thereby improving the overall quality and service life of the concrete;

[0158] (5) The present invention not only improves the reaction rate by adding a condensing agent and a reaction accelerator, but also ensures the smooth progress of the reaction and the stability of the product. Furthermore, the present invention has a simple formula, simplifies the preparation process, and reduces the production cost.

[0159] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing an aminosilane-modified stearic acid-based concrete hydrophobic material, characterized in that: The hydrophobic material is prepared by the following steps: Dissolving 25% to 35% by mass of stearic acid at a first preset temperature and a first preset speed for a first preset time to obtain a first solution; Maintaining the first preset temperature and the first preset speed, sequentially adding 25% to 35% by weight of a condensing agent and 20% to 25% by weight of a reaction accelerator to the first solution, reacting for 2 h to 4 h, to obtain a second solution; Adding 10% to 25% by mass of aminosilane to the second solution, and reacting at a second preset temperature and a second preset speed for a second preset time to obtain a third solution; The third solution is cooled for a third preset time to obtain a solid, which is ground into powder to obtain an aminosilane-modified stearic acid-based concrete hydrophobic material.

2. The method for preparing an aminosilane-modified stearic acid-based concrete hydrophobic material according to claim 1, characterized in that: The first preset temperature is 70° C. to 80° C., the first preset speed is 400 r / min to 500 r / min, and the first preset time is 20 min to 25 min.

3. The method for preparing an aminosilane-modified stearic acid-based concrete hydrophobic material according to claim 1, characterized in that: The second preset temperature is 80°C to 100°C, the second preset speed is 500r / min to 600r / min, the second preset time is 3.5h to 4h, and the third preset time is 48h to 72h.

4. The method for preparing an aminosilane-modified stearic acid-based concrete hydrophobic material according to claim 1, characterized in that: Dissolve 25% to 35% stearic acid by mass at a first preset temperature and a first preset speed for a first preset time to obtain a first solution, specifically: 25% to 35% by mass of stearic acid is sealed and dissolved at a first preset temperature and a first preset rotation speed for a first preset time to obtain a first solution.

5. The method for preparing an aminosilane-modified stearic acid-based concrete hydrophobic material according to claim 1, characterized in that: 10% to 25% by mass of aminosilane is added to the second solution, and reacted at a second preset temperature and a second preset speed for a second preset time to obtain a third solution, specifically: 10% to 25% by mass of aminosilane is added to the second solution, and the solution is sealed and reacted for a second preset time at a second preset temperature and a second preset rotation speed to obtain a third solution.

6. The method for preparing an aminosilane-modified stearic acid-based concrete hydrophobic material according to claim 1, characterized in that: After obtaining the aminosilane-modified stearic acid-based concrete hydrophobic material, the method further comprises: The aminosilane-modified stearic acid-based concrete hydrophobic material is added to a concrete mix according to a preset ratio to obtain aminosilane-modified stearic acid-based integral hydrophobic concrete.

7. An aminosilane-modified stearic acid-based concrete hydrophobic material, characterized in that: The aminosilane-modified stearic acid-based concrete hydrophobic material is prepared by the preparation method of the aminosilane-modified stearic acid-based concrete hydrophobic material according to claim 1, wherein the raw materials of the aminosilane-modified stearic acid-based concrete hydrophobic material include stearic acid, a condensing agent, a reaction accelerator and aminosilane; The mass percentage of each raw material is: stearic acid 25%~35%, condensation agent 25%~35%, reaction accelerator 20%~25%, aminosilane 10%~25%.

8. The aminosilane-modified stearic acid-based concrete hydrophobic material according to claim 7, characterized in that: The aminosilane is any one of aminoethylaminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane or 3-aminopropyltrimethoxysilane.

9. The aminosilane-modified stearic acid-based concrete hydrophobic material according to claim 7, characterized in that: The condensing agent is any one of dicyclohexylcarbodiimide, N,N-diisopropylcarbodiimide, carbodiimide hydrochloride or N,N'-carbonyldiimidazole.

10. The aminosilane-modified stearic acid-based concrete hydrophobic material according to claim 7, characterized in that: The reaction accelerator is any one of 4-dimethylaminopyridine, 4-pyrrolidinopyridine, N-hydroxysuccinimide, 1-hydroxybenzotriazole, potassium hydroxide and potassium carbonate.

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