A cement mortar repair coating and its preparation process

Abstract

This invention provides a cement mortar repair coating and its preparation process. The cement mortar repair coating comprises the following raw materials in parts by weight: 4-6 parts nano-silica composite liquid, 6-10 parts bridging agent, 2-5 parts rubber powder, 0.5-1.0 parts nano-carbon fiber, 3-6 parts modified polyacrylate, 0.8-1.2 parts water-reducing agent, and 0.3-0.7 parts plasticizer. Through the synergistic effect of the nano-silica composite liquid, bridging agent, and modified polyacrylate, a multi-level structure of "rigid skeleton - flexible network - dynamic repair" is formed, thereby making the performance of the repair agent surpass that of traditional repair materials. The cement mortar repair coating of this invention can meet the repair strength requirements with a repair surface thickness of 10-20 mm, saving both repair time and repair materials.

Description

Technical Field

[0001] This invention relates to the field of cement mortar materials technology, specifically to a cement mortar material repair coating and its preparation process. Background Technology

[0002] Cement mortar is a composite material made by mixing cement as a binder with fine aggregate and water in a certain proportion. Based on composition, it can be divided into cement mortar and cement concrete. Cement mortar consists of cement, fine aggregate, and water, while cement concrete consists of cement, fine aggregate, crushed stone, and water. Both harden through cement hydration to form a high-strength structure. Cement mortar has advantages such as high strength, good durability, strong water resistance, excellent frost resistance, and low cost. Furthermore, its raw materials are widely available, making it widely used in road engineering, bridge structures, and construction. However, the hardening process of cement mortar causes shrinkage, which can easily lead to cracks in pavements and walls. Existing repair materials for cracks in cement mortar have long setting times, making it difficult to meet the time requirements for rapid repair. Summary of the Invention

[0003] In view of this, the present invention proposes a cement mortar material repair coating and its preparation process to solve the above problems.

[0004] The technical solution of this invention is implemented as follows:

[0005] A cement mortar material repair coating comprises the following raw materials in parts by weight: 4-6 parts nano silica composite liquid, 6-10 parts bridging agent, 2-5 parts rubber powder, 0.5-1.0 parts nano carbon fiber, 3-6 parts modified polyacrylate, 0.8-1.2 parts water-reducing agent, and 0.3-0.7 parts plasticizer.

[0006] Furthermore, a cement mortar material repair coating comprises the following raw materials in parts by weight: 5 parts nano silica composite liquid, 8 parts bridging agent, 3.5 parts rubber powder, 0.8 parts carbon nanofiber, 4.5 parts modified polyacrylate, 1.0 part water-reducing agent, and 0.5 parts plasticizer.

[0007] Furthermore, the nano-silica composite solution is prepared by the following method: Nano-silica powder is added to sodium hydroxide solution at a material-to-liquid ratio of (9-11):(180-220) g / mL, and ultrasonically treated at 30-50 kHz for 25-35 min. The nano-silica powder is filtered out, and centrifuged and washed at 4000-6000 rpm for 10-15 min. The washed silica powder is added to deionized water to obtain an activated nano-silica suspension, with a silica powder to deionized water mass-to-volume ratio of (9-11):(80-120) g / mL. Sodium silicate solution and deionized water are mixed, followed by the addition of polyvinyl alcohol, and stirred at 55-65℃ until completely dissolved. Solution A was obtained, with the mass-to-volume ratio of sodium silicate solution, deionized water, and polyvinyl alcohol (g / mL) being (40-60):(250-350):(4-6). The activated nano-silica suspension was slowly poured into solution A and magnetically stirred at 400-600 rpm for 55-65 min to obtain composite suspension B. Triethanolamine was added to composite suspension B at a material-to-liquid ratio of (250-300):1 (g / mL), and stirring was continued for 25-35 min to obtain nano-silica composite sol. The nano-silica composite sol was placed in a water bath at 45-50℃ for 18-22 h to mature, and then the pH was adjusted to 8.0-9.0 with citric acid to obtain nano-silica composite solution.

[0008] Further, the bridging agent is prepared by the following method: Sodium silicate is added to deionized water at a material-to-liquid ratio of 1:(9-11) g / mL and stirred until completely dissolved to obtain solution C; acrylic acid, hydroxyethyl methacrylate, and tetrasodium ethylenediaminetetraacetate are added to deionized water and stirred until completely dissolved, and sodium hydroxide is added to adjust the pH to 9.0-10.0 to obtain solution D, wherein the mass-to-volume ratio of acrylic acid, hydroxyethyl methacrylate, tetrasodium ethylenediaminetetraacetate, and deionized water is (4-6):(2.5-3.5):(0.9-1.1):(45-55) g / mL; solution D is added dropwise to solution C, and then hydroquinone is added to obtain mixture E, wherein the volume ratio of solution D, solution C, and hydroquinone is (1.8-2.2):(0.9-1.1):(0.01-0.02); and the mixture E is added at a material-to-liquid ratio of (120-180):(0.4-0.02) g / mL. 6): Add N,N'-methylenebisacrylamide and silane coupling agent (0.6-0.9%), stir at 25-30℃ for 25-35 min to form a homogeneous hybrid sol; raise the temperature to 65-70℃, add ammonium persulfate solution at a volume ratio of (135-165):(3.0-3.5), and react under a nitrogen atmosphere for 2.0-2.5 h. The ammonium persulfate solution is prepared by adding ammonium persulfate at a feed-to-liquid ratio of g / mL at a ratio of 1:(30-30%). 5) Dissolve in deionized water to obtain the bridging agent. Then add carboxylated nano-hydroxyapatite at a material-to-liquid ratio of (110-190):(1.5-2.5) g / mL and stir for 40-60 min. After the reaction is complete, cool to 20-30℃ to obtain a gel. Place the gel in a vacuum dryer at 50-55℃ for 8-10 h, and then in a vacuum dryer at 60-65℃ for 10-12 h. Pass through a 100-200 mesh sieve to obtain the bridging agent.

[0009] Further, the modified polyacrylate is prepared by the following method: acrylic acid, methyl methacrylate, and N,N'-methylenebisacrylamide are dissolved in deionized water to obtain solution F, wherein the mass-to-volume ratio (g / mL) of acrylic acid, methyl methacrylate, N,N'-methylenebisacrylamide, and deionized water is (28-32):(9-11):(0.5-1.0):(120-180); ammonium persulfate is dissolved in deionized water to obtain ammonium persulfate solution, wherein the mass-to-volume ratio (g / mL) of ammonium persulfate to deionized water is 1:(30-35); the pH of solution F is adjusted to 7.5-8.0 with sodium hydroxide, and nitrogen gas is introduced at 35°C. After a 45-minute cooling period, the temperature is raised to 48-52℃, and ammonium persulfate solution is added dropwise to solution F. The reaction is allowed to proceed for 0.8-1.0 h, followed by a further heating to 65-75℃ for 2.0-2.5 h to obtain a polyacrylate copolymer solution. The volume ratio of solution F to ammonium persulfate solution is (18-20):1. The polyacrylate copolymer solution is then cooled to 48-52℃, and tetrasodium ethylenediaminetetraacetate is added at a material-to-liquid ratio of (12-14):1 (g / mL). The temperature is raised to 68-72℃ for 2.5-3.5 h. After the reaction is complete, the temperature is lowered to 20-30℃, and citric acid is added to adjust the pH to 6.8-7.2 to obtain the modified polyacrylate.

[0010] Furthermore, the water-reducing agent is a polycarboxylate water-reducing agent, and the plasticizer is a lignin sulfonate solution.

[0011] Furthermore, the rubber powder has a particle size of 80-120 mesh, and the carbon nanofiber has a particle size of 100-200 nm.

[0012] Furthermore, the aforementioned cement mortar repair agent is prepared according to the following process, including the following steps:

[0013] S1. Add the bridging agent, rubber powder, and carbon nanofibers to the mixer and mix them to obtain mixture I;

[0014] S2. Add nano-silica composite liquid, water-reducing agent, and plasticizer to a stirring tank, stir and mix to obtain mixture II;

[0015] S3. Add modified polyacrylate to mixture II, stir and mix to obtain mixture III, and adjust the pH using triethanolamine to maintain the pH at 9.0-11.0;

[0016] S4. Slowly add mixture I to mixture III, stir evenly, and then degas to obtain mixture IV;

[0017] S5. Seal and mature the mixture IV to obtain a cement mortar material repair coating.

[0018] Furthermore, in S1, the stirring speed is 400-600 rpm and the stirring time is 5-10 min; in S2, the stirring speed is 300-500 rpm and the stirring time is 15-25 min; in S3, the stirring speed is 150-250 rpm and the stirring time is 10-20 min; in S4, the stirring speed is 200-400 rpm and the stirring time is 25-35 min; the degassing pressure is -0.06 to -0.10 MPa; the vacuum treatment time is 8-12 min; and in S5, the sealing and curing is carried out at 23-27℃ for 22-26 h.

[0019] Furthermore, the viscosity of the cement mortar material repair coating prepared in S5 is 500-1000 mPa·s.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] The cement mortar repair coating of this invention contains a silica composite liquid that reacts with calcium hydroxide in the old cement mortar material through a pozzolanic reaction, generating a secondary hydration product, CSH gel. This breaks down the inert structure of the old cement mortar material, activates unhydrated cement particles, and forms a dense cross-linked network. The generated CSH gel is both an activation product of the old cement mortar material and a bonding medium for the hydration of the new cement mortar material, thereby achieving chemical bonding at the interface between the new and old cement mortar materials and further integrating the old and new cement. The bridging agent contains silanol generated from the hydrolysis of sodium silicate, which reacts with calcium hydroxide at the crack interface. 2 The reaction forms a three-dimensional calcium silicate gel network, providing immediate rigid support. Simultaneously, carboxylated nano-hydroxyapatite grows directionally under the guidance of the active interface provided by the nano-silica composite liquid, forming CSH / nHA hybrid crystals. These crystals achieve mechanical interlocking through both sides of the crack via a whisker reinforcement effect, constituting an inorganic reinforcing phase. Based on this, a flexible polymer network formed by the copolymerization of acrylic acid and hydroxyethyl methacrylate is interwoven within the inorganic framework, thus forming a machine-inorganic hybrid network. The modified polyacrylate, containing EDTA grafted chains, can dissolve calcium carbonate and tricalcium silicate in the old cement mortar material, thereby converting the calcium carbonate in the cracks into soluble EDTA-Ca. The modified polyacrylate dissolves the Ca... 2 + It can be captured by bridging agents, thereby accelerating mineral deposition. Through the synergistic effect of the three, a multi-level structure of "rigid skeleton-flexible network-dynamic repair" is formed, which makes the performance of the repair coating surpass that of traditional repair materials. Detailed Implementation

[0022] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0023] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0024] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0025] Example 1

[0026] A cement mortar repair coating comprises the following raw materials in parts by weight: 4 parts nano-silica composite liquid, 6 parts bridging agent, 2 parts rubber powder, 0.5 parts nano-carbon fiber, 3 parts modified polyacrylate, 0.8 parts water-reducing agent, and 0.3 parts plasticizer. The water-reducing agent is a polycarboxylate water-reducing agent, and the plasticizer is a lignin sulfonate solution. The rubber powder has a particle size of 80 mesh, and the nano-carbon fiber has a particle size of 100 nm.

[0027] The nano-silica composite solution was prepared by the following method: Nano-silica powder was added to sodium hydroxide solution at a material-to-liquid ratio of 9:180 (g / mL), and ultrasonically treated at 30 kHz for 35 min. The nano-silica powder was filtered out, centrifuged and washed at 4000 rpm for 15 min, and the washed silica powder was added to deionized water to obtain an activated nano-silica suspension. The mass-to-volume ratio of silica powder to deionized water was 9:80 (g / mL). Sodium silicate solution and deionized water were mixed, and then polyvinyl alcohol was added. The mixture was stirred at 55 °C until completely dissolved. Solution A was obtained, with a mass-to-volume ratio of sodium silicate solution, deionized water, and polyvinyl alcohol of 40:250:4 (g / mL). The activated nano-silica suspension was slowly poured into solution A and magnetically stirred at 400 rpm for 65 min to obtain composite suspension B. Triethanolamine was added to composite suspension B at a material-to-liquid ratio of 250:1 (g / mL), and stirring was continued for 35 min to obtain nano-silica composite sol. The nano-silica composite sol was aged in a 45℃ water bath for 22 h, and then the pH was adjusted to 8.0 with citric acid to obtain nano-silica composite solution.

[0028] The bridging agent is prepared by the following method: Sodium silicate is added to deionized water at a ratio of 1:9 (g / mL) and stirred until completely dissolved to obtain solution C; acrylic acid, hydroxyethyl methacrylate, and tetrasodium ethylenediaminetetraacetate are added to deionized water and stirred until completely dissolved; sodium hydroxide is added to adjust the pH to 9.0 to obtain solution D, wherein the mass-to-volume ratio (g / mL) of acrylic acid, hydroxyethyl methacrylate, tetrasodium ethylenediaminetetraacetate, and deionized water is 4:2.5:0.9:45; solution D is added dropwise to solution C, and then hydroquinone is added to obtain mixture E, wherein the volume ratio of solution D, solution C, and hydroquinone is 1.8:0.9:0.01; the bridging agent is added to mixture E at a ratio of 120 g / mL... N,N'-methylenebisacrylamide and silane coupling agent were added in a ratio of 0.4:0.6, and the mixture was stirred at 25°C for 35 min to form a homogeneous hybrid sol. The temperature was raised to 65°C, and ammonium persulfate solution was added at a volume ratio of 135:3.0. The mixture was reacted under a nitrogen atmosphere for 2.5 h. The ammonium persulfate solution was prepared by dissolving ammonium persulfate in deionized water at a ratio of g / mL of 1:30. Then, carboxylated nano-hydroxyapatite was added at a ratio of g / mL of 110:1.5, and the mixture was stirred for 60 min. After the reaction was completed, the mixture was cooled to 20°C to obtain a gel. The gel was then vacuum dried at 50°C for 10 h, followed by vacuum drying at 60°C for 12 h. The gel was then passed through a 100-mesh sieve to obtain the bridging agent.

[0029] The modified polyacrylate is prepared by the following method: acrylic acid, methyl methacrylate, and N,N'-methylenebisacrylamide are dissolved in deionized water to obtain solution F, wherein the mass-to-volume ratio (g / mL) of acrylic acid, methyl methacrylate, N,N'-methylenebisacrylamide, and deionized water is 28:9:0.5:120; ammonium persulfate is dissolved in deionized water to obtain ammonium persulfate solution, wherein the mass-to-volume ratio (g / mL) of ammonium persulfate to deionized water is 1:30; the pH of solution F is adjusted to 7.5 using sodium hydroxide. Nitrogen gas was introduced for 45 minutes, and then the temperature was raised to 48°C. Ammonium persulfate solution was added dropwise to solution F, and the reaction was carried out for 1.0 h. The temperature was then raised to 65°C and the reaction was carried out for 2.5 h to obtain a polyacrylate copolymer solution. The volume ratio of solution F to ammonium persulfate solution was 18:1. The polyacrylate copolymer solution was cooled to 48°C, and then tetrasodium ethylenediaminetetraacetate was added at a material-to-liquid ratio of g / mL at a ratio of 12:1. The temperature was raised to 68°C and the reaction was carried out for 3.5 h. After the reaction was completed, the temperature was cooled to 20°C, and citric acid was added to adjust the pH to 6.8 to obtain the modified polyacrylate.

[0030] Example 2

[0031] A cement mortar repair coating comprises the following raw materials in parts by weight: 6 parts nano-silica composite liquid, 10 parts bridging agent, 5 parts rubber powder, 1.0 part nano-carbon fiber, 6 parts modified polyacrylate, 1.2 parts water-reducing agent, and 0.7 parts plasticizer. The water-reducing agent is a polycarboxylate water-reducing agent, and the plasticizer is a lignin sulfonate solution. The rubber powder has a particle size of 120 mesh, and the nano-carbon fiber has a particle size of 200 nm.

[0032] The nano-silica composite solution was prepared by the following method: Nano-silica powder was added to sodium hydroxide solution at a material-to-liquid ratio of 11:220 (g / mL), ultrasonicated at 50 kHz for 25 min, the nano-silica powder was filtered out, and washed by centrifugation at 6000 rpm for 10 min. The washed silica powder was then added to deionized water to obtain an activated nano-silica suspension, with a silica powder to deionized water mass-to-volume ratio of 11:120 (g / mL). Sodium silicate solution and deionized water were mixed, followed by the addition of polyvinyl alcohol, and stirred at 65 °C until complete. Solution A was obtained by complete dissolution, with a mass-to-volume ratio of sodium silicate solution, deionized water, and polyvinyl alcohol of 60:350:6 (g / mL). The activated nano-silica suspension was slowly poured into solution A and magnetically stirred at 600 rpm for 55 min to obtain composite suspension B. Triethanolamine was added to composite suspension B at a material-to-liquid ratio of 300:1 (g / mL), and stirring was continued for 25 min to obtain nano-silica composite sol. The nano-silica composite sol was aged in a 50℃ water bath for 18 h, and then the pH was adjusted to 9.0 with citric acid to obtain nano-silica composite solution.

[0033] The bridging agent is prepared by the following method: Sodium silicate is added to deionized water at a ratio of 1:11 (g / mL) and stirred until completely dissolved to obtain solution C; acrylic acid, hydroxyethyl methacrylate, and tetrasodium ethylenediaminetetraacetate are added to deionized water and stirred until completely dissolved; sodium hydroxide is added to adjust the pH to 10.0 to obtain solution D, wherein the mass-to-volume ratio (g / mL) of acrylic acid, hydroxyethyl methacrylate, tetrasodium ethylenediaminetetraacetate, and deionized water is 6:3.5:1.1:55; solution D is added dropwise to solution C, and then hydroquinone is added to obtain mixture E, wherein the volume ratio of solution D, solution C, and hydroquinone is 2.2:1.1:0.02; the bridging agent is added to mixture E at a ratio of 1:11 (g / mL)... N,N'-methylenebisacrylamide and silane coupling agent were added in a ratio of 80:0.6:0.9, and the mixture was stirred at 30°C for 25 min to form a homogeneous hybrid sol. The temperature was raised to 70°C, and ammonium persulfate solution was added at a volume ratio of 165:3.5. The mixture was reacted under a nitrogen atmosphere for 2.0 h. The ammonium persulfate solution was prepared by dissolving ammonium persulfate in deionized water at a ratio of 1:35 g / mL. Then, carboxylated nano-hydroxyapatite was added at a ratio of 190:2.5 g / mL, and the mixture was stirred for 40 min. After the reaction was completed, the mixture was cooled to 30°C to obtain a gel. The gel was then vacuum dried at 55°C for 8 h, followed by vacuum drying at 65°C for 10 h. The gel was then passed through a 200-mesh sieve to obtain the bridging agent.

[0034] The modified polyacrylate is prepared by the following method: acrylic acid, methyl methacrylate, and N,N'-methylenebisacrylamide are dissolved in deionized water to obtain solution F, wherein the mass-to-volume ratio (g / mL) of acrylic acid, methyl methacrylate, N,N'-methylenebisacrylamide, and deionized water is 32:11:1.0:180; ammonium persulfate is dissolved in deionized water to obtain ammonium persulfate solution, wherein the mass-to-volume ratio (g / mL) of ammonium persulfate to deionized water is 1:35; the pH of solution F is adjusted to 8.0 with sodium hydroxide. Nitrogen gas was introduced for 35 minutes, and then the temperature was raised to 52°C. Ammonium persulfate solution was added dropwise to solution F, and the reaction was allowed to proceed for 0.8 hours. The temperature was then raised to 75°C and the reaction was allowed to proceed for 2.0 hours to obtain a polyacrylate copolymer solution. The volume ratio of solution F to ammonium persulfate solution was 20:1. The polyacrylate copolymer solution was cooled to 52°C, and then tetrasodium ethylenediaminetetraacetate was added at a ratio of 14:1 (g / mL). The temperature was raised to 72°C and the reaction was allowed to proceed for 2.5 hours. After the reaction was completed, the temperature was lowered to 30°C, and citric acid was added to adjust the pH to 7.2 to obtain the modified polyacrylate.

[0035] Example 3

[0036] A cement mortar repair coating comprises the following raw materials in parts by weight: 5 parts nano-silica composite liquid, 8 parts bridging agent, 3.5 parts rubber powder, 0.8 parts carbon nanofibers, 4.5 parts modified polyacrylate, 1.0 part water-reducing agent, and 0.5 parts plasticizer. The water-reducing agent is a polycarboxylate water-reducing agent, and the plasticizer is a lignin sulfonate solution. The rubber powder has a particle size of 100 mesh, and the carbon nanofibers have a particle size of 150 nm.

[0037] The nano-silica composite solution was prepared by the following method: Nano-silica powder was added to sodium hydroxide solution at a material-to-liquid ratio of 10:200 (g / mL), and ultrasonically treated at 40 kHz for 30 min. The nano-silica powder was filtered out, and washed by centrifugation at 5000 rpm for 12.5 min. The washed silica powder was added to deionized water to obtain an activated nano-silica suspension, with a silica powder to deionized water mass-to-volume ratio of 10:100 (g / mL). Sodium silicate solution and deionized water were mixed, followed by the addition of polyvinyl alcohol, and stirred at 60 °C until complete. Solution A was obtained by complete dissolution, with a mass-to-volume ratio of sodium silicate solution, deionized water, and polyvinyl alcohol of 50:300:5 (g / mL). The activated nano-silica suspension was slowly poured into solution A and magnetically stirred at 500 rpm for 60 min to obtain composite suspension B. Triethanolamine was added to composite suspension B at a material-to-liquid ratio of 275:1 (g / mL), and stirring was continued for 30 min to obtain nano-silica composite sol. The nano-silica composite sol was aged in a water bath at 47.5℃ for 20 h, and then the pH was adjusted to 8.5 with citric acid to obtain nano-silica composite solution.

[0038] The bridging agent is prepared by the following method: Sodium silicate is added to deionized water at a material-to-liquid ratio of 1:10 (g / mL) and stirred until completely dissolved to obtain solution C; acrylic acid, hydroxyethyl methacrylate, and tetrasodium ethylenediaminetetraacetate are added to deionized water and stirred until completely dissolved; sodium hydroxide is added to adjust the pH to 9.5 to obtain solution D, wherein the mass-to-volume ratio (g / mL) of acrylic acid, hydroxyethyl methacrylate, tetrasodium ethylenediaminetetraacetate, and deionized water is 5:3.0:1.0:50; solution D is added dropwise to solution C, and then hydroquinone is added to obtain mixture E, wherein the volume ratio of solution D, solution C, and hydroquinone is 2.0:1.0:0.015; the bridging agent is added to mixture E at a material-to-liquid ratio of 150:0.5: 0.75 N,N'-methylenebisacrylamide and silane coupling agent were added, and the mixture was stirred at 27.5℃ for 30 min to form a homogeneous hybrid sol. The temperature was raised to 67.5℃, and ammonium persulfate solution was added at a volume ratio of 150:3.3. The mixture was reacted under a nitrogen atmosphere for 2.0-2.5 h. The ammonium persulfate solution was prepared by dissolving ammonium persulfate in deionized water at a ratio of g / mL of 1:33. Then, carboxylated nano-hydroxyapatite was added at a ratio of g / mL of 150:2.0, and the mixture was stirred for 50 min. After the reaction was completed, the mixture was cooled to 25℃ to obtain a gel. The gel was vacuum dried at 52.5℃ for 9 h, and then vacuum dried at 62.5℃ for 11 h. The gel was then passed through a 150-mesh sieve to obtain the bridging agent.

[0039] The modified polyacrylate is prepared by the following method: acrylic acid, methyl methacrylate, and N,N'-methylenebisacrylamide are dissolved in deionized water to obtain solution F, wherein the mass-to-volume ratio (g / mL) of acrylic acid, methyl methacrylate, N,N'-methylenebisacrylamide, and deionized water is 30:10:0.7:150; ammonium persulfate is dissolved in deionized water to obtain ammonium persulfate solution, wherein the mass-to-volume ratio (g / mL) of ammonium persulfate to deionized water is 1:32.5; the pH of solution F is adjusted to 7.8 with sodium hydroxide. Nitrogen gas was introduced for 30 minutes, and then the temperature was raised to 50°C. Ammonium persulfate solution was added dropwise to solution F, and the reaction was allowed to proceed for 0.9 hours. The temperature was then raised to 70°C and the reaction was allowed to proceed for 2.2 hours to obtain a polyacrylate copolymer solution. The volume ratio of solution F to ammonium persulfate solution was 19:1. The polyacrylate copolymer solution was cooled to 50°C, and then tetrasodium ethylenediaminetetraacetate was added at a material-to-liquid ratio of g / mL at a ratio of 13:1. The temperature was raised to 70°C and the reaction was allowed to proceed for 3.0 hours. After the reaction was completed, the temperature was lowered to 25°C, and citric acid was added to adjust the pH to 7.0 to obtain the modified polyacrylate.

[0040] The cement mortar material repair coating described in Examples 1-3 is prepared according to the following process, including the following steps:

[0041] S1. Add the bridging agent, rubber powder, and carbon nanofibers to the mixer and stir at 500 rpm for 7.5 min to obtain mixture I;

[0042] S2. Add nano-silica composite liquid, water-reducing agent and plasticizer to the mixing tank, and stir at 400 rpm for 20 min to obtain mixture II;

[0043] S3. Add modified polyacrylate to mixture II and stir at 200 rpm for 15 min to obtain mixture III. Adjust the pH using triethanolamine to maintain the pH at 10.0.

[0044] S4. Slowly add mixture I to mixture III, stir at 300 rpm for 30 min, then degas under a treatment pressure of -0.080 MPa and vacuum treat for 10 min to obtain mixture IV.

[0045] S5. The mixture IV is sealed and matured at 25°C for 24 hours to obtain a cement mortar material repair coating with a viscosity of 750 mPa·s.

[0046] Example 4

[0047] Compared with Example 3, the difference in this embodiment is that the cement mortar material repair coating is prepared according to the following process, including the following steps:

[0048] S1. Add the bridging agent, rubber powder, and carbon nanofibers into a mixer and stir at 400 rpm for 10 minutes to obtain mixture I.

[0049] S2. Add nano-silica composite liquid, water-reducing agent and plasticizer to the mixing tank, and stir at 300 rpm for 25 min to obtain mixture II;

[0050] S3. Add modified polyacrylate to mixture II and stir at 150 rpm for 20 min to obtain mixture III. Adjust the pH using triethanolamine to maintain the pH at 9.0.

[0051] S4. Slowly add mixture I to mixture III, stir at 200 rpm for 35 min, then degas under a treatment pressure of -0.06 MPa and vacuum treat for 12 min to obtain mixture IV;

[0052] S5. The mixture IV is sealed and matured at 23°C for 26 hours to obtain a cement mortar material repair coating with a viscosity of 500 mPa·s.

[0053] Example 5

[0054] Compared with Example 3, the difference in this embodiment is that the cement mortar material repair coating is prepared according to the following process, including the following steps:

[0055] S1. Add the bridging agent, rubber powder, and carbon nanofibers to the mixer and stir at 600 rpm for 5 minutes to obtain mixture I;

[0056] S2. Add nano-silica composite liquid, water-reducing agent and plasticizer to the mixing tank, and stir at 500 rpm for 15 min to obtain mixture II;

[0057] S3. Add modified polyacrylate to mixture II and stir at 250 rpm for 10 min to obtain mixture III. Adjust the pH using triethanolamine to maintain the pH at 11.0.

[0058] S4. Slowly add mixture I to mixture III, stir at 400 rpm for 25 min, then degas under a treatment pressure of -0.10 MPa and vacuum treat for 8 min to obtain mixture IV;

[0059] S5. The mixture IV is sealed and matured at 27°C for 22 hours to obtain a cement mortar material repair coating. The viscosity of the cement mortar material repair agent is 1000 mPa·s.

[0060] Comparative Example 1

[0061] Compared with Example 3, the difference in this comparative example is that the raw material for repairing the cement mortar coating does not include nano-silica composite liquid.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 3 is that the cement mortar material used for repairing the coating does not include a bridging agent.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 3 is that the modified polyacrylate is not included in the raw material for the cement mortar repair coating.

[0066] Comparative Example 4

[0067] Compared with Example 3, this comparative example differs in that an equal volume polyacrylate copolymer solution is used instead of modified polyacrylate. The polyacrylate copolymer solution is prepared by the following method: acrylic acid, methyl methacrylate, and N,N'-methylenebisacrylamide are dissolved in deionized water to obtain solution F, wherein the mass-to-volume ratio of acrylic acid, methyl methacrylate, N,N'-methylenebisacrylamide, and deionized water is 30:10:0.7:150 (g / mL); ammonium persulfate is dissolved in deionized water to obtain ammonium persulfate solution, wherein the mass-to-volume ratio of ammonium persulfate to deionized water is 1:32.5 (g / mL); the pH of solution F is adjusted to 7.8 with sodium hydroxide, nitrogen gas is introduced for 30 min, and then the temperature is raised to 50°C. Ammonium persulfate solution is added dropwise to solution F, the reaction is carried out for 0.9 h, and then the temperature is raised to 70°C and the reaction is carried out for 2.2 h to obtain the polyacrylate copolymer solution.

[0068] Comparative Example 5

[0069] The difference between this comparative example and Example 3 is that the cement mortar material repair coating is a commercially available cement mortar material repair agent.

[0070] Repair effect measurement

[0071] Prepare 200×200×100mm cement concrete substrate specimens with a 100mm through-crack and a 0.5mm wide crack. Add the repair agents from Examples 1-5 and Comparative Examples 1-5 at a ratio of 5% to cement concrete (cement + fine aggregate + crushed stone + water), mix thoroughly, and apply to the specimen surface to a thickness of 15mm. Cure at 25℃ and 95% humidity for 48 hours. Then test the bond strength between the repair layer and the substrate and determine the cracking strain threshold of the repair layer. Test 5 specimens for each group, and record the average results in Table 1.

[0072] Determination of setting time

[0073] Under conditions of 20℃ and 50% humidity, the repair agents of Examples 1-5 and Comparative Examples 1-5 were added at a ratio of 5% to cement mortar composed of cement, fine aggregate and water, respectively, and stirred evenly. The initial setting time and final setting time were measured. Three specimens were tested in each group, and the average results were recorded in Table 1.

[0074] Table 1

[0075]

[0076] As can be seen from Table 1, the cement mortar repair coatings prepared in Examples 1-5 can better bond with cement mortar materials, thereby giving the repaired cement mortar materials stronger bonding strength and higher resistance to strain cracking. Furthermore, the cement mortar repair additive coatings prepared in Examples 1-5 can save on the initial setting time and final setting time of cement mortar materials, thus better meeting the time requirements for rapid repair in road repair.

[0077] The cement mortar repair coating of this invention, when used, not only undergoes a chemical reaction with the underlying cement to achieve deep repair, but also forms a dense protective layer on the surface, thus providing a dual protective effect. Its core mechanism is as follows: 1. Activation and penetration of the nano-silica composite liquid: The hydroxyl groups on the surface of the nano-silica in the nano-silica composite liquid can react with calcium hydroxide in the old cement mortar material to produce a secondary hydration product, CSH gel. This breaks the inert structure in the old cement mortar material, activates unhydrated cement particles, and forms a dense cross-linked network. The generated CSH gel is both an activation product of the old cement mortar material and a bonding medium for the hydration of the new cement mortar material, thereby achieving chemical bonding at the interface of the new and old cement mortar materials, allowing for further deep integration of the new and old cement. Unhydrated cement particles in the old cement mortar material are eroded by nano-silica, causing the surface silicon-oxygen bonds to break and releasing Ca2+. 2 + Participates in secondary hydration. Furthermore, the nano-silica composite liquid can penetrate cracks through capillary action, filling micropores and forming a nanoscale protective layer on the surface, improving impermeability and durability. 2. Dynamic crack bridging and reinforcement effects of the bridging agent: The bridging agent achieves dynamic crack repair through an organic-inorganic hybrid network: Inorganic reinforcement: Tetrasodium ethylenediaminetetraacetate in the bridging agent can chelate Ca... 2 The bridging agent locally increases calcium ion concentration, accelerating CSH nucleation and thus shortening setting time. Ammonium persulfate in the bridging agent can initiate polymerization, forming a pre-crosslinked network and reducing curing time. Furthermore, the active interface provided by the nano-silica composite liquid promotes the directional growth of carboxylated nano-hydroxyapatite in the bridging agent, guiding the formation of CSH / nHA hybrid crystals at the crack interface, forming mechanical interlocking across both sides of the crack, thereby enhancing bond strength. The silane coupling agent in the bridging agent forms Si-O-Si covalent bonds at the interface, thus improving the water resistance of the cement mortar material. Organic toughening: Hydroxyethyl methacrylate in the bridging agent provides flexible segments, and tetrasodium ethylenediaminetetraacetate interacts with Ca through carboxyl groups. 2+ After absorbing strain energy through the formation of dynamic coordination bonds, the EDTA-Ca dynamic bond recombination inhibits crack propagation, thereby improving resistance to strain cracking. 3. Synergistic strengthening and self-healing of modified polyacrylates: The carboxyl groups in modified polyacrylates can capture free calcium ions at the crack interface, forming an ionic cross-linking network, accelerating mineral deposition and slurry structuring, thus shortening the setting time. By grafting tetrasodium ethylenediaminetetraacetate, Ca is continuously released... 2 + Chelating sites react with unhydrated cement particles at the crack interface to generate secondary CSH, further enhancing bond strength. When microcracks appear, the EDTA-Ca complex dynamically dissociates and recombines, achieving self-repair and thus providing resistance to strain cracking. Furthermore, the hydroxyl groups on the surface of the nano-silica in the nano-silica composite liquid form hydrogen bonds with the carboxyl groups in the modified polyacrylate, increasing the material's elastic modulus and further improving its resistance to strain cracking. 4. Synergistic effect and protective layer formation: When used, the cement mortar repair coating of this invention not only reacts chemically with the underlying cement for deep repair but also forms a dense nano-composite protective layer on the surface, effectively blocking the erosion of harmful media such as moisture and chloride ions. Through the synergistic effect of these three elements, a multi-level structure of "rigid skeleton - flexible network - dynamic repair" is formed, thereby making the performance of the repair agent surpass that of traditional repair materials.

[0078] Comparing Examples 1-5 with Comparative Example 5, the cement mortar repair coatings prepared in Examples 1-5 not only have a shorter setting time, better meeting the time requirements for rapid repair, but also exhibit higher bond strength and strain cracking resistance than commercially available cement mortar repair agents. A surface repair thickness of 10-20 mm using the cement mortar repair coatings from Examples 1-5 is sufficient to meet the required repair strength, saving both time and materials.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cement mortar material repair coating, characterized in that, The raw materials include the following parts by weight: 4-6 parts nano silica composite liquid, 6-10 parts bridging agent, 2-5 parts rubber powder, 0.5-1.0 parts nano carbon fiber, 3-6 parts modified polyacrylate, 0.8-1.2 parts water-reducing agent, and 0.3-0.7 parts plasticizer; The nano-silica composite solution is prepared by the following method: nano-silica powder is added to sodium hydroxide solution at a material-to-liquid ratio of (9-11):(180-220) g / mL, and ultrasonically treated at 30-50 kHz for 25-35 min. The nano-silica powder is filtered out and centrifuged and washed at 4000-6000 rpm for 10-15 min. The washed nano-silica powder is added to deionized water to obtain an activated nano-silica suspension, wherein the mass-to-volume ratio of nano-silica powder to deionized water is (9-11):(80-120) g / mL. Sodium silicate solution and deionized water are mixed, followed by the addition of polyvinyl alcohol, and stirred at 55-65℃ until completely dissolved. Solution A is obtained by dissolving sodium silicate solution, deionized water, and polyvinyl alcohol in a mass-to-volume ratio of (40-60):(250-350):(4-6) g / mL. The activated nano-silica suspension is slowly poured into solution A and magnetically stirred at 400-600 rpm for 55-65 min to obtain composite suspension B. Triethanolamine is added to composite suspension B at a material-to-liquid ratio of (250-300):1 g / mL, and stirring is continued for 25-35 min to obtain nano-silica composite sol. The nano-silica composite sol is aged in a 45-50℃ water bath for 18-22 h, and then the pH is adjusted to 8.0-9.0 with citric acid to obtain the nano-silica composite solution. The bridging agent is prepared by the following method: Sodium silicate is added to deionized water at a material-to-liquid ratio of 1:(9-11) g / mL and stirred until completely dissolved to obtain solution C; acrylic acid, hydroxyethyl methacrylate, and tetrasodium ethylenediaminetetraacetate are added to deionized water and stirred until completely dissolved; sodium hydroxide is added to adjust the pH to 9.0-10.0 to obtain solution D, wherein the mass-to-volume ratio of acrylic acid, hydroxyethyl methacrylate, tetrasodium ethylenediaminetetraacetate, and deionized water is (4-6):(2.5-3.5):(0.9-1.1):(45-55) g / mL; solution D is added dropwise to solution C, and then hydroquinone is added to obtain mixture E, wherein the volume ratio of solution D, solution C, and hydroquinone is (1.8-2.2):(0.9-1.1):(0.01-0.02); and mixture E is added at a material-to-liquid ratio of (120-180):(0.4-0.6) g / mL. Add N,N'-methylenebisacrylamide and silane coupling agent (0.6-0.9 g / mL), stir at 25-30°C for 25-35 min to form a homogeneous hybrid sol; raise the temperature to 65-70°C, add ammonium persulfate solution at a volume ratio of (135-165):(3.0-3.5), and react under a nitrogen atmosphere for 2.0-2.5 h. The ammonium persulfate solution is prepared by adding ammonium persulfate at a feed-to-liquid ratio of g / mL at a ratio of 1:(30-35 g / mL). The bridging agent was prepared by dissolving it in deionized water. Then, carboxylated nano-hydroxyapatite was added at a material-to-liquid ratio of (110-190):(1.5-2.5 g / mL). The mixture was stirred for 40-60 min. After the reaction was completed, the mixture was cooled to 20-30℃ to obtain a gel. The gel was then vacuum dried at 50-55℃ for 8-10 h, followed by vacuum drying at 60-65℃ for 10-12 h. The gel was then passed through a 100-200 mesh sieve to obtain the bridging agent. The modified polyacrylate is prepared by the following method: acrylic acid, methyl methacrylate, and N,N'-methylenebisacrylamide are dissolved in deionized water to obtain solution F, wherein the mass-to-volume ratio (g / mL) of acrylic acid, methyl methacrylate, N,N'-methylenebisacrylamide, and deionized water is (28-32):(9-11):(0.5-1.0):(120-180); ammonium persulfate is dissolved in deionized water to obtain ammonium persulfate solution, wherein the mass-to-volume ratio (g / mL) of ammonium persulfate to deionized water is 1:(30-35); the pH of solution F is adjusted to 7.5-8.0 with sodium hydroxide, and nitrogen gas is introduced at 35- After 45 minutes, the temperature is raised to 48-52℃, and ammonium persulfate solution is added dropwise to solution F. The reaction is allowed to proceed for 0.8-1.0 h, and then the temperature is raised to 65-75℃ for 2.0-2.5 h to obtain a polyacrylate copolymer solution. The volume ratio of solution F to ammonium persulfate solution is (18-20):

1. The polyacrylate copolymer solution is then cooled to 48-52℃, and then tetrasodium ethylenediaminetetraacetate is added at a material-to-liquid ratio of (12-14):1 (g / mL). The temperature is raised to 68-72℃ for 2.5-3.5 h. After the reaction is complete, the temperature is lowered to 20-30℃, and citric acid is added to adjust the pH to 6.8-7.2 to obtain the modified polyacrylate.

2. The cement mortar material repair coating as described in claim 1, characterized in that, The raw materials include the following parts by weight: 5 parts nano silica composite liquid, 8 parts bridging agent, 3.5 parts rubber powder, 0.8 parts nano carbon fiber, 4.5 parts modified polyacrylate, 1.0 part water-reducing agent, and 0.5 parts plasticizer.

3. The cement mortar material repair coating as described in claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent, and the plasticizer is a lignin sulfonate solution.

4. The cement mortar material repair coating as described in claim 1, characterized in that, The rubber powder has a particle size of 80-120 mesh, and the carbon nanofiber has a particle size of 100-200 nm.

5. The preparation process of a cement mortar material repair coating as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Add the bridging agent, rubber powder, and carbon nanofibers to the mixer and mix them to obtain mixture I; S2. Add nano-silica composite liquid, water-reducing agent, and plasticizer to a stirring tank, stir and mix to obtain mixture II; S3. Add modified polyacrylate to mixture II, stir and mix to obtain mixture III, and adjust the pH using triethanolamine to maintain the pH at 9.0-11.0; S4. Slowly add mixture I to mixture III, stir evenly, and then degas to obtain mixture IV; S5. Seal and mature the mixture IV to obtain a cement mortar material repair coating.

6. The preparation process of a cement mortar material repair coating as described in claim 5, characterized in that, In step S1, the stirring speed is 400-600 rpm and the stirring time is 5-10 min; in step S2, the stirring speed is 300-500 rpm and the stirring time is 15-25 min; in step S3, the stirring speed is 150-250 rpm and the stirring time is 10-20 min; in step S4, the stirring speed is 200-400 rpm and the stirring time is 25-35 min; the degassing pressure is -0.06 to -0.10 MPa and the vacuum treatment time is 8-12 min; and in step S5, the sealing and curing is carried out at 23-27℃ for 22-26 h.

7. The preparation process of a cement mortar material repair coating as described in claim 5, characterized in that, The viscosity of the cement mortar material repair coating prepared in S5 is 500-1000 mPa·s.

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