Polyurea crack injection adhesive for repairing concrete cracks and application thereof

Abstract

This invention discloses a polyurea grouting adhesive for repairing concrete cracks and its application. The method first involves sequentially adsorbing phytic acid and chitosan onto the surface of magnesium hydroxide using a layer-by-layer deposition method, followed by drying and grinding to obtain a CS-PA@M composite material. Next, a dehydrated diisocyanate is prepolymerized with polyetheramine in an anhydrous environment to obtain a polyurea prepolymer. Then, dimethylthiotoluene diamine, polyetheramine, and N,N-dimethylacetamide are mixed with CS-PA@MH powder, ultrasonicated, and slowly added dropwise to the polyurea prepolymer for a post-polymerization reaction, yielding the polyurea composite material. The polyurea composite material of this invention is applied to the grouting and repair of concrete cracks. The polyurea composite material molecular chain contains abundant urea bonds and urethane groups, which can form strong hydrogen bonds with the hydroxyl groups on the cement matrix surface, significantly improving the interfacial bonding strength. This material combines high toughness, excellent impact resistance, and good adhesion properties, effectively adapting to the opening and closing movement of cracks in concrete caused by temperature changes or dynamic loads.

Description

Technical Field

[0001] This invention relates to a polyurea grouting adhesive for repairing concrete cracks, belonging to the field of concrete crack repair technology. Background Technology

[0002] Concrete, as the most widely used building material in construction engineering, has advantages such as high compressive strength, good durability, and low cost. However, the inherent brittleness of concrete, coupled with the effects of temperature changes, loads, and foundation settlement during its service life, makes it highly susceptible to cracking. Cracks not only affect the aesthetics of the structure but also reduce its integrity, durability, and load-bearing capacity. They allow corrosive media such as moisture, chloride ions, and carbon dioxide to penetrate, leading to durability problems such as steel corrosion, concrete carbonation, and freeze-thaw damage, and in severe cases, even structural failure or collapse. Therefore, timely and effective repair of concrete cracks has significant engineering and economic value. However, epoxy resin is a thermosetting rigid material with low elongation at break, exhibiting typical brittle characteristics. Under impact or dynamic loads, it cannot effectively dissipate energy, easily leading to brittle fracture or interfacial delamination. Furthermore, due to modulus mismatch, stress concentration easily occurs during temperature changes or crack opening and closing, resulting in secondary damage, making it difficult to meet the repair needs of dynamically loaded areas.

[0003] Therefore, developing a novel polyurea composite material with high toughness, excellent impact resistance, good interfacial compatibility, and high bonding performance, and applying it to the grouting and repair of concrete cracks, is of great significance for improving the durability, adaptability, and safety of crack repair. Summary of the Invention

[0004] The purpose of this invention is to provide a polyurea crack-sealing adhesive for repairing concrete cracks and its application, thereby addressing the problems existing in the prior art.

[0005] The technical solution of the present invention: a polyurea grouting adhesive for repairing concrete cracks, the method comprising the following steps:

[0006] (1) Synthesis of phytic acid, chitosan and magnesium hydroxide:

[0007] Magnesium hydroxide (Mg) was dissolved in 80-120 parts by volume of deionized water using magnetic stirring to form a magnesium hydroxide suspension. Phytic acid aqueous solution (40-50 parts by volume) was slowly added dropwise to the magnesium hydroxide suspension, and the mixture was stirred thoroughly to induce an adsorption reaction. Chitosan aqueous solution (40-50 parts by volume) was then added, and the mixture was stirred for another 10-15 minutes to obtain a white flocculent product. The white flocculent product was centrifuged and washed twice with deionized water, then dried in an oven at 75-85°C. The dried white solid product was then ground to obtain CS-PA@MH powder.

[0008] (2) Preparation of polyurea composite materials:

[0009] 4.0–5.5 parts by volume of dehydrated diisocyanate were added to the reaction vessel; 6.0–7.5 parts by volume of dehydrated polyetheramine were slowly added dropwise to the reaction vessel, and the prepolymerization reaction was carried out in an anhydrous environment with mechanical stirring at a reaction temperature of 55–65°C to obtain the prepolymer; 2.0–3.0 parts by volume of dimethylthiotoluene diamine, 8–12 parts by volume of polyetheramine and 8–12 parts by volume of N,N-dimethylacetamide were taken, mixed evenly, and 1–5 parts by mass of the CS-PA@MH powder prepared in step (1) were added, and the mixture was subjected to ultrasonic treatment to obtain a mixed solution; the mixed solution was slowly added dropwise to the prepolymer to carry out a post-polymerization reaction for a reaction time of 5–10 min to obtain the polyurea composite material, i.e., the required polyurea grouting adhesive.

[0010] In the aforementioned polyurea grouting adhesive for repairing concrete cracks, in step (1), the mass concentration of the phytic acid aqueous solution is 0.5% to 2.4%, and the mass concentration of the chitosan aqueous solution is 0.5% to 2%.

[0011] In the aforementioned polyurea grouting adhesive for repairing concrete cracks, in step (1), the adsorption time is 5-10 min and the drying time is 10-15 h.

[0012] In the aforementioned polyurea grouting adhesive for repairing concrete cracks, in step (2), the waterless environment is an oxygen-free environment, which is achieved by protection with nitrogen or an inert gas, with argon being the inert gas.

[0013] In the aforementioned polyurea grouting adhesive for repairing concrete cracks, in step (1), the polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol, and the diisocyanate is isophorone diisocyanate.

[0014] In the aforementioned polyurea grouting adhesive for repairing concrete cracks, in step (2), prepolymerization is carried out for 1-2 hours under mechanical stirring.

[0015] In the aforementioned polyurea grouting adhesive for repairing concrete cracks, in step (2), the mechanical stirring speed is 200-400 RPM, the ultrasonic treatment frequency is 40-80 kHz, and the ultrasonic treatment lasts for 20-40 min.

[0016] The aforementioned polyurea crack-sealing adhesive for repairing concrete cracks can be applied by simply applying the polyurea crack-sealing adhesive to the concrete crack.

[0017] The beneficial effects of this invention are as follows: Compared with the prior art, this invention improves the dispersion of MH on the PUA substrate by depositing phytic acid and chitosan on the surface of magnesium hydroxide, enhances the thermal stability of the polyurea composite material, thereby improving the adhesion durability of polyurea, further preventing the problem of detachment and cracking of the sealant, and enhancing the tensile strength of the sealant, making it less prone to breakage. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the impact resistance of different grouting mortars in the application of this invention;

[0019] Figure 2 This is a schematic diagram illustrating the bonding strength of different grouting mortars in the application of this invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0021] Embodiment 1 of the present invention: A polyurea grouting adhesive for repairing concrete cracks, the method comprising the following steps:

[0022] (1) 1 g of magnesium hydroxide was dissolved in 80 mL of deionized water by magnetic stirring to form a magnesium hydroxide suspension; 2.4 wt% and 40 mL of phytic acid aqueous solution were slowly added dropwise to the magnesium hydroxide suspension and stirred thoroughly to carry out the adsorption reaction; 2.0 wt% and 40 mL of chitosan aqueous solution were added and stirred for 10 min to obtain a white flocculent product; the white flocculent product was centrifuged and washed twice with deionized water, and dried in an oven at 80°C for 12 h; the dried white solid product was ground to obtain CS-PA@MH powder.

[0023] (2) 4.7 mL of dehydrated diisocyanate was added to the reaction vessel; 6.8 mL of dehydrated polyetheramine was slowly added dropwise to the reaction vessel, and the prepolymerization reaction was carried out in an anhydrous environment with mechanical stirring at a reaction temperature of 60°C to obtain the prepolymer; 2.3 mL of dimethylthiotoluene diamine, 10 mL of polyetheramine and 9.5 mL of N,N-dimethylacetamide were taken separately, mixed evenly, and 2.5 g of CS-PA@MH powder prepared in step (1) was added, and ultrasonic treatment was performed to obtain a mixed solution; the mixed solution was slowly added dropwise to the prepolymer to carry out a post-polymerization reaction for a reaction time of 5 min to obtain the polyurea composite material (PUA / CS-PA@MH).

[0024] The required moisture content is achieved through a drying process, which may include vacuum drying, barium chloride drying, or 4A molecular sieve drying.

[0025] The polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol. The diisocyanate is isophorone diisocyanate.

[0026] The anhydrous environment is an oxygen-free environment, achieved through nitrogen or inert gas protection, with argon being the inert gas. Prepolymerization is carried out for 1 hour under mechanical stirring at a speed of 300 RPM. The ultrasonic treatment is performed at a frequency of 60 kHz for 30 minutes.

[0027] Embodiment 2 of the present invention: A polyurea crack-sealing adhesive for repairing concrete cracks, the method comprising the following steps:

[0028] (2) 2 g of magnesium hydroxide by volume was dissolved in 120 mL of deionized water by magnetic stirring to form a magnesium hydroxide suspension; 2.4 wt% and 50 mL of phytic acid aqueous solution were slowly added dropwise to the magnesium hydroxide suspension and stirred thoroughly to carry out the adsorption reaction; 2.0 wt% and 50 mL of chitosan aqueous solution were added and stirred for 15 min to obtain a white flocculent product; the white flocculent product was centrifuged and washed twice with deionized water, and dried in an oven at 75°C for 15 h; the dried white solid product was ground to obtain CS-PA@MH powder.

[0029] (2) 5.5 mL of dehydrated diisocyanate was added to the reaction vessel; 7.5 mL of dehydrated polyetheramine was slowly added dropwise to the reaction vessel, and the prepolymerization reaction was carried out in an anhydrous environment with mechanical stirring at a reaction temperature of 65°C to obtain the prepolymer; 3.0 mL of dimethylthiotoluene diamine, 12 mL of polyetheramine and 12 mL of N,N-dimethylacetamide were taken separately, mixed evenly, and 5 g of CS-PA@MH powder prepared in step (1) was added, and ultrasonic treatment was performed to obtain a mixed solution; the mixed solution was slowly added dropwise to the prepolymer to carry out a post-polymerization reaction for a reaction time of 10 min to obtain the polyurea composite material (PUA / CS-PA@MH).

[0030] The required moisture content is achieved through a drying process, which may include vacuum drying, barium chloride drying, or 4A molecular sieve drying.

[0031] The polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol. The diisocyanate is isophorone diisocyanate.

[0032] The anhydrous environment is an oxygen-free environment, achieved through nitrogen or inert gas protection, with argon being the inert gas used. Prepolymerization is carried out for 2 hours under mechanical stirring at a speed of 400 RPM. The ultrasonic treatment is performed at a frequency of 80 kHz for 40 minutes.

[0033] Embodiment 3 of the present invention: A polyurea grouting adhesive for repairing concrete cracks, the method comprising the following steps:

[0034] (3) 1.5 g of magnesium hydroxide by volume was dissolved in 100 mL of deionized water by magnetic stirring to form a magnesium hydroxide suspension; 2.4 wt% and 45 mL of phytic acid aqueous solution were slowly added dropwise to the magnesium hydroxide suspension and stirred thoroughly to carry out the adsorption reaction; 2.0 wt% and 45 mL of chitosan aqueous solution were added and stirred for 12 min to obtain a white flocculent product; the white flocculent product was centrifuged and washed twice with deionized water, and dried in an oven at 85°C for 10 h; the dried white solid product was ground to obtain CS-PA@MH powder.

[0035] (2) 4.0 mL of dehydrated diisocyanate was added to the reaction vessel; 6.0 mL of dehydrated polyetheramine was slowly added dropwise to the reaction vessel, and the prepolymerization reaction was carried out in an anhydrous environment with mechanical stirring at a reaction temperature of 55°C to obtain the prepolymer; 2.0 mL of dimethylthiotoluene diamine, 8 mL of polyetheramine and 8 mL of N,N-dimethylacetamide were taken separately, mixed evenly, and 1 g of CS-PA@MH powder prepared in step (1) was added, and ultrasonic treatment was performed to obtain a mixed solution; the mixed solution was slowly added dropwise to the prepolymer to carry out a post-polymerization reaction for a reaction time of 5 min to obtain the polyurea composite material (PUA / CS-PA@MH).

[0036] The required moisture content is achieved through a drying process, which may include vacuum drying, barium chloride drying, or 4A molecular sieve drying.

[0037] The polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol. The diisocyanate is isophorone diisocyanate.

[0038] The anhydrous environment is an oxygen-free environment, achieved through nitrogen or inert gas protection, with argon being the inert gas used. Prepolymerization is carried out for 1.5 hours under mechanical stirring at a speed of 200 RPM. The ultrasonic treatment is performed at a frequency of 40 kHz for 20 minutes.

[0039] To evaluate the mechanical properties of polyurea composite materials in cement mortar mixing, the polyurea grouting adhesive prepared by the method in Example 1 was used for relevant experiments.

[0040] Add 675g of cement, 1350g of sand, and 303g of water to the mixing pot of a cement mortar apparatus. Mix evenly according to the relevant methods in DL / T5126-2001 "Test Procedure for Polymer Modified Cement Mortar" to obtain the cement product.

[0041] The specific testing and detection of each indicator shall be carried out as follows:

[0042] (1) Bonding performance test: The cement mortar “8” shaped specimen to be tested for bonding is pulled apart without damaging the fracture surface. Dry bonding means that the cement mortar block is taken out of the water and placed at room temperature for 2 days; wet bonding means that the cement mortar block is taken out of the water and the free water is wiped off with a cloth before bonding. Before the test, the slurry is evenly applied to the fracture surface with a thickness of (0.5-0.7) mm. Depending on the product, it can be applied once or in several layers. After application, the specimen is quickly joined together at the fracture point as the original part, tied tightly with rubber bands, and cured in a laboratory at a temperature of (20±3)℃ and a relative humidity of 50%-70% for 28 days before tensile bonding test. The test method is carried out in accordance with DL / T5126-2001 ⟪Test Procedure for Polymer Modified Cement Mortar⟫.

[0043] (2) Impact strength test: The test method shall be carried out in accordance with the test procedure of GB / T 1843-2008.

[0044] Regarding the influence of polyurea composites on the impact resistance of concrete, such as... Figure 1 As shown, polyurea composite materials significantly improve the impact strength of cement mortar specimens. The impact strength of cement mortar specimens bonded with epoxy resin adhesive in cantilever beam impact tests was 0.97 KJ / m. 2 The impact strength of the cement specimen bonded with polyurea composite material was 4.29 KJ / m. 2 Compared to epoxy resin adhesives, the impact strength is increased by 77%. The main reason is that polyurea has high elasticity and flexibility compared to epoxy resin, which is hard and brittle. The impact strength of polyurea is 4-5 times higher than that of epoxy resin.

[0045] Regarding the influence of polyurea composite materials on the bonding performance of concrete, such as... Figure 2 As shown, polyurea composite materials improve the bonding performance of cement mortar test blocks. The maximum force of cement test blocks bonded with epoxy resin adhesive is 1810.9 N, while the maximum force of cement test blocks bonded with polyurea composite materials is 2009.3 N, showing a certain improvement compared to epoxy resin adhesive.

[0046] Polyurea composite materials possess excellent impact resistance and adhesive properties. The polyurea crack-sealing adhesive of this invention for repairing concrete cracks has the following properties:

[0047] (1) Polyurea has a certain improvement on the bonding performance of concrete compared with epoxy resin.

[0048] (2) Polyurea significantly improves the impact resistance of concrete, which is 4-5 times that of epoxy resin.

Claims

1. A polyurea crack-sealing adhesive for repairing concrete cracks, characterized in that: The method includes the following steps: (1) Synthesis of phytic acid, chitosan and magnesium hydroxide: Magnesium hydroxide (Mg) was dissolved in 80-120 parts by volume of deionized water using magnetic stirring to form a magnesium hydroxide suspension. Phytic acid aqueous solution (40-50 parts by volume) was slowly added dropwise to the magnesium hydroxide suspension, and the mixture was stirred thoroughly to induce an adsorption reaction. Chitosan aqueous solution (40-50 parts by volume) was then added, and the mixture was stirred for another 10-15 minutes to obtain a white flocculent product. The white flocculent product was centrifuged and washed twice with deionized water, then dried in an oven at 75-85°C. The dried white solid product was then ground to obtain CS-PA@MH powder. (2) Preparation of polyurea composite materials: 4.0–5.5 parts by volume of dehydrated diisocyanate were added to the reaction vessel; 6.0–7.5 parts by volume of dehydrated polyetheramine were slowly added dropwise to the reaction vessel, and the prepolymerization reaction was carried out in an anhydrous environment with mechanical stirring at a reaction temperature of 55–65°C to obtain the prepolymer; 2.0–3.0 parts by volume of dimethylthiotoluene diamine, 8–12 parts by volume of polyetheramine and 8–12 parts by volume of N,N-dimethylacetamide were taken, mixed evenly, and 1–5 parts by mass of the CS-PA@MH powder prepared in step (1) were added, and the mixture was subjected to ultrasonic treatment to obtain a mixed solution; the mixed solution was slowly added dropwise to the prepolymer to carry out a post-polymerization reaction for a reaction time of 5–10 min to obtain the polyurea composite material, i.e., the required polyurea grouting adhesive.

2. The polyurea grouting adhesive for repairing concrete cracks according to claim 1, characterized in that: In step (1), the mass concentration of the phytic acid aqueous solution is 0.5% to 2.4%, and the mass concentration of the chitosan aqueous solution is 0.5% to 2%.

3. The polyurea grouting adhesive for repairing concrete cracks according to claim 1, characterized in that: In step (1), the adsorption time is 5 to 10 minutes and the drying time is 10 to 15 hours.

4. The polyurea grouting adhesive for repairing concrete cracks according to claim 1, characterized in that: In step (2), the waterless environment is an oxygen-free environment, which is achieved by protection with nitrogen or an inert gas, with argon being used as the inert gas.

5. The polyurea grouting adhesive for repairing concrete cracks according to claim 1, characterized in that: In step (1), the polyetheramine is polyoxypropylene ether diamine with a number average molecular weight of 2000 g / mol, and the diisocyanate is isophorone diisocyanate.

6. The polyurea grouting adhesive for repairing concrete cracks according to claim 1, characterized in that: In step (2), prepolymerize for 1-2 hours under mechanical stirring.

7. The polyurea grouting adhesive for repairing concrete cracks according to claim 1, characterized in that: In step (2), the mechanical stirring speed is 200-400 RPM, the ultrasonic treatment frequency is 40-80 kHz, and the ultrasonic treatment lasts for 20-40 min.

8. The application of a polyurea grouting adhesive for repairing concrete cracks as described in any one of claims 1-7, characterized in that: Simply apply the polyurea grouting adhesive to the concrete crack.

Images