CO2 response type anti-crack self-repairing cement and preparation method thereof

Abstract

The invention relates to the technical field of cement self-repairing, in particular to CO2 response type anti-crack self-repairing cement and a preparation method thereof. Mixing the solution 2 serving as mixing water with oil well cement, or adding the gel freeze-dried powder into water to serve as mixing water to be mixed with the oil well cement, so as to prepare the CO2 response type anti-cracking self-repairing cement. The preparation method comprises the following steps: adding a carboxyl-containing vinyl monomer and a tertiary amine-containing vinyl monomer into water, and uniformly mixing to obtain a monomer mixed solution; adding a cross-linking agent, uniformly mixing to obtain a solution 1, adding an initiator, and uniformly mixing to obtain a solution 2; and standing to obtain hydrogel, washing, centrifuging, and freeze-drying to obtain gel freeze-dried powder. After the CO2 response type anti-crack self-repairing cement is hydrated, the gel can capture carbon dioxide in a cement matrix, calcium ion mineralization is promoted, and the self-repairing performance is better. Compared with a traditional cement self-repairing system, the system has the characteristics of carbon dioxide responsiveness and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cement self-repairing, in particular to a CO2-responsive anti-cracking self-repairing cement and a preparation method thereof. BACKGROUND

[0002] Cement is the main material for infrastructure construction, but it is easy to produce microcracks under the complex action of external load and environment, which weakens the mechanical properties and durability of the material and seriously shortens the service life of the building. The high-energy consumption and high-cost repair or reconstruction caused by this are likely to become a new source of carbon emissions and increase the environmental burden. Traditional repair techniques are mostly post-intervention, which is tedious and has high economic cost. Existing self-repairing materials are mainly gels and delayed reaction minerals, which will sacrifice the mechanical properties of cement and affect normal use, especially in a CO2 environment, corrosion will exacerbate the cracking of cement microcracks and the decline of mechanical properties. In addition, existing self-repairing agents are mostly granular materials, and their self-healing efficiency is limited by the distribution range of the materials.

[0003] Therefore, in order to improve the self-repairing efficiency of infrastructure in a CO2 corrosion environment and prolong the effective service period, it is necessary to provide a CO2-responsive anti-cracking self-repairing cement which has little effect on the strength of cement and good self-repairing performance. SUMMARY

[0004] In view of the defect that the existing cement self-repairing system can greatly reduce the strength of cement, the present application provides a CO2-responsive anti-cracking self-repairing cement and a preparation method thereof.

[0005] To achieve the above-mentioned purpose, the present application provides the following solutions: One of the technical solutions of the present application is a preparation method of a gel freeze-dried powder, comprising the following steps: adding a carboxyl-containing vinyl monomer and a tertiary amine-containing vinyl monomer into water and mixing to obtain a monomer mixed solution; adding a crosslinking agent to the monomer mixed solution to obtain solution 1; adding an initiator to the solution 1 to obtain solution 2; placing the solution 2 to obtain a hydrogel, and then washing, centrifuging and freeze-drying to obtain the gel freeze-dried powder; The initiator comprises an oxidizing agent and a reducing agent.

[0006] The second technical solution of the present application is a gel freeze-dried powder prepared according to the above preparation method.

[0007] The third technical solution of the present application is the application of the above gel freeze-dried powder in the preparation of a CO2-responsive anti-cracking self-repairing cement.

[0008] The fourth technical scheme of the present application is a preparation method of the CO2-responsive anti-cracking self-repairing cement, wherein the solution 2 in the preparation method is used as mixing water to mix with oil well cement, or the gel freeze-dried powder is added into water as mixing water to mix with oil well cement, so as to obtain the CO2-responsive anti-cracking self-repairing cement.

[0009] The fifth technical scheme of the present application is the CO2-responsive anti-cracking self-repairing cement prepared by the preparation method.

[0010] Compared with the prior art, the present application has the following beneficial effects: (1) The CO2-responsive anti-cracking self-repairing cement can capture carbon dioxide in the cement matrix after hydration, promote calcium ion mineralization, and has better self-repairing performance. Compared with the traditional cement self-repairing system, the present application has the characteristics of carbon dioxide responsiveness.

[0011] (2) The experiment proves that the gel in the CO2-responsive anti-cracking self-repairing cement has high water absorption, and the water absorption capacity of the gel reaches 5.19g / g within 17min. The gel absorbs water and expands in volume to block the micro cracks, further enhancing the self-repairing effect of the cement.

[0012] (3) The self-repairing capacity of the CO2-responsive anti-cracking self-repairing cement is significantly improved compared with the blank cement, and the self-repairing efficiency is improved by 883.58% compared with the blank G-grade oil well cement within seven days.

[0013] (4) The preparation method of the gel freeze-dried powder is based on in-situ polymerization, which can react at room temperature, has low cost, and is easy to realize industrialization. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical schemes in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0015] Figure 1 The X-ray energy spectrum analysis diagram of the gel freeze-dried powder of the CO2-responsive anti-cracking self-repairing cement prepared in Example 1 is shown in the figure. (a) is the XPS full spectrum diagram of the gel; (b) is the O element fine spectrum diagram; (c) is the N element fine spectrum diagram; (d) is the C element fine spectrum diagram.

[0016] Figure 2 The stress-strain test diagram of the gel of the CO2-responsive anti-cracking self-repairing cement prepared in Examples 1 and 6 is shown in the figure.

[0017] Figure 3 Water absorption capacity test graph of the gel of the CO2-responsive anti-cracking self-repairing cement prepared for Example 2.

[0018] Figure 4 Compressive strength and flexural strength of the CO2-responsive anti-cracking self-repairing cement prepared for the control and Examples 1-3.

[0019] Figure 5 Composition ratio graph of the CO2-responsive anti-cracking self-repairing cement prepared for the control and Examples 1-3 obtained from the thermogravimetric test.

[0020] Figure 6 Crack volume repair ratio (a) and crack area repair ratio (b) of the CO2-responsive anti-cracking self-repairing cement prepared for the control and Examples 1-3 before and after repair. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present application will now be described in detail, without being limited to, by the following examples. The following examples are presented to more completely illustrate the embodiments of the application and should not be construed as limiting the application. It is expressly understood that the descriptions and specific examples are intended to be illustrative only and are not intended to limit the scope of the application.

[0022] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. In addition, where particular ranges of values are given, understand that each intervening value, to the upper or lower limit of the ranges is also specifically included. Each smaller range that falls within the broader ranges is also specifically included. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and each range is inclusive of its end points. Accordingly, these smaller ranges are specifically included within the scope of the present application.

[0023] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application.

[0024] Many modifications and variations of this application can be made without departing from its spirit or scope, which will be apparent to those skilled in the art. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only. It is to be understood that the application is not limited in scope by the specific embodiments described herein. Rather, the intent is to embrace all changes and modifications that are within the spirit and scope of the application.

[0025] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0026] This invention utilizes a method of constructing a crack-resistant self-healing network in a cement matrix to achieve efficient self-repair of cement microcracks through its CO2 response characteristics, thereby improving its durability in corrosive environments. This is of great significance to the field of cement self-healing technology.

[0027] The first aspect of this invention provides a method for preparing a gel lyophilized powder, comprising the following steps: A vinyl monomer containing a carboxyl group and a vinyl monomer containing a tertiary amine are added to water and mixed to obtain a monomer mixed solution. A crosslinking agent was added to the monomer mixture solution to obtain solution 1; An initiator was added to solution 1 to obtain solution 2; The solution 2 was allowed to stand to obtain a hydrogel, which was then washed, centrifuged, and freeze-dried to obtain the freeze-dried gel powder. The initiator includes an oxidizing agent and a reducing agent.

[0028] In a preferred embodiment of the present invention, the carboxyl-containing vinyl monomer is methacrylic acid, itaconic acid, or maleic acid; the mass fraction of the carboxyl-containing vinyl monomer in the monomer mixture solution is 1.01%-2.93%.

[0029] In a preferred embodiment of the present invention, the vinyl monomer containing tertiary amine is vinylimidazole, dimethylaminoethyl methacrylate or 3-(dimethylamino)propyl acrylate; the mass fraction of the vinyl monomer containing tertiary amine in the monomer mixture solution is 1.11%-3.20%.

[0030] In a preferred embodiment of the present invention, the crosslinking agent is methylene bisacrylamide or ethylene glycol diglycidyl ether; the mass fraction of the crosslinking agent in solution 1 is 0.071%-0.20%.

[0031] In a preferred embodiment of the present invention, the mass ratio of the oxidant to the reducing agent is 2:1; the oxidant is ammonium persulfate or potassium persulfate, and the reducing agent is sodium bisulfite or ferrous sulfate heptahydrate; the mass fraction of the initiator in solution 2 is 0.063%-0.18%.

[0032] In a preferred embodiment of the present invention, the settling time is 48 hours; and anhydrous ethanol is used for washing.

[0033] This invention does not impose any particular limitations on the freeze-drying conditions (such as pressure, temperature, and time), and adopts freeze-drying conditions commonly used by those skilled in the art.

[0034] A second aspect of the present invention provides a gel lyophilized powder prepared according to the above-described preparation method.

[0035] The third aspect of this invention provides the application of the above-mentioned gel freeze-dried powder in the preparation of CO2-responsive crack-resistant self-healing cement.

[0036] The fourth aspect of the present invention provides a method for preparing CO2-responsive crack-resistant self-healing cement, wherein the solution 2 in the above preparation method is used as mixing water and mixed with oil well cement at a water-cement ratio of 0.4-0.5, or the above-mentioned gel freeze-dried powder is added to water as mixing water and mixed with oil well cement to obtain the CO2-responsive crack-resistant self-healing cement.

[0037] When the lyophilized gel powder is added to water as mixing water, the mass fraction of the lyophilized gel powder in the mixing water is 2.24-6.44%. The fifth aspect of the present invention provides a CO2-responsive crack-resistant self-healing cement prepared according to the above-described preparation method.

[0038] The freeze-dried gel powder of this invention can respond to environmental stimuli and synergistically enhance the self-healing ability of cement. By mixing solution 2 as mixing water with oil well cement, during the repair process, the polymer network introduced by in-situ polymerization can both absorb water and expand to block gaps, and react with carbon dioxide and calcium ions in the cement pore solution to promote calcium ion mineralization.

[0039] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0040] The G-grade oil well cement used in this invention is from Sichuan Jiahua Enterprise Co., Ltd., and oil well cement produced by other companies is also suitable for this invention.

[0041] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Comparison Example Construction of blank cement system: Tap water was added to G-grade oil well cement, prepared according to GB / T 19139-2012 and cured in a curing box at 30℃±2℃ for 1 day; the water-cement ratio was 0.44.

[0043] Example 1 The preparation method of CO2-responsive crack-resistant self-healing cement is as follows: Preparation of mixed solutions: 1) Preparation of monomer mixed solution: Methacrylic acid and vinylimidazole were added to tap water and stirred evenly to obtain a monomer mixed solution with a mass fraction of 1.02% methacrylic acid and 1.11% vinylimidazole. 2) Preparation of solution 1: Add methylenebisacrylamide to the monomer mixture solution obtained in step 1) and stir until homogeneous to obtain solution 1 with a crosslinking agent mass fraction of 0.071%; 3) Preparation of solution 2: Add ammonium persulfate and sodium bisulfite to solution 1 obtained in step 2), stir evenly, and obtain solution 2 containing 0.064% of initiator by mass, wherein the mass ratio of ammonium persulfate and sodium bisulfite in the initiator is 2:1; 4) Preparation of lyophilized gel powder: Solution 2 was allowed to stand for 48 hours to allow gel formation. The gel was washed with anhydrous ethanol, centrifuged, and freeze-dried to obtain lyophilized gel powder.

[0044] The above solution 2 was added to G-grade oil well cement as mixing water, prepared according to GB / T 19139-2012, and cured for 1 day in a curing box at 30℃±2℃; the water-cement ratio was 0.44.

[0045] Example 2 The preparation method of CO2-responsive crack-resistant self-healing cement is as follows: (1) Preparation of mixed solution: 1) Preparation of monomer mixed solution: Methacrylic acid and vinylimidazole were added to tap water and stirred evenly to obtain a monomer mixed solution with a mass fraction of 1.99% methacrylic acid and 2.18% vinylimidazole. 2) Preparation of solution 1: Add the crosslinking agent—methylenebisacrylamide—to the monomer mixture solution obtained in step 1), stir evenly, and obtain solution 1 with a crosslinking agent mass fraction of 0.14%; 3) Preparation of solution 2: Add initiator ammonium persulfate and sodium bisulfite to solution 1 obtained in step 2), stir evenly, and obtain solution 2 containing 0.12% initiator by mass, wherein the mass ratio of ammonium persulfate and sodium bisulfite in the initiator is 2:1; 4) Preparation of lyophilized gel powder: Solution 2 was allowed to stand for 48 hours to allow gel formation. The gel was washed with anhydrous ethanol, centrifuged, and freeze-dried to obtain lyophilized gel powder.

[0046] The above solution 2 was added to G-grade oil well cement as mixing water, prepared according to GB / T 19139-2012, and cured for 1 day in a curing box at 30℃±2℃; the water-cement ratio was 0.44.

[0047] Example 3 The preparation method of CO2-responsive crack-resistant self-healing cement is as follows: (1) Preparation of mixed solution: 1) Preparation of monomer mixed solution: Methacrylic acid and vinylimidazole were added to tap water and stirred evenly to obtain a monomer mixed solution with a mass fraction of 2.93% methacrylic acid and 3.20% vinylimidazole. 2) Preparation of solution 1: Add methylenebisacrylamide to the monomer mixture solution obtained in step 1) and stir until homogeneous to obtain solution 1 with a crosslinking agent mass fraction of 0.20%; 3) Preparation of solution 2: Add ammonium persulfate and sodium bisulfite to solution 1 obtained in step 2), stir evenly, and obtain solution 2 containing 0.18% of initiator by mass, wherein the mass ratio of ammonium persulfate and sodium bisulfite in the initiator is 2:1; 4) Preparation of lyophilized gel powder: Solution 2 was allowed to stand for 48 hours to allow gel formation. The gel was washed with anhydrous ethanol, centrifuged, and freeze-dried to obtain lyophilized gel powder.

[0048] The above solution 2 was added to G-grade oil well cement as mixing water, prepared according to GB / T 19139-2012, and cured for 1 day in a curing box at 30℃±2℃; the water-cement ratio was 0.44.

[0049] Example 4 The preparation method of CO2-responsive crack-resistant self-healing cement is as follows: (1) Preparation of mixed solution: 1) Preparation of monomer mixed solution: Itaconic acid and dimethylaminoethyl methacrylate were added to tap water and stirred evenly to obtain a monomer mixed solution with a mass fraction of 1.02% for itaconic acid and a mass fraction of 1.11% for dimethylaminoethyl methacrylate. 2) Preparation of solution 1: Add methylenebisacrylamide to the monomer mixture solution obtained in step 1) and stir until homogeneous to obtain solution 1 with a crosslinking agent mass fraction of 0.071%; 3) Preparation of solution 2: Add the initiator potassium persulfate and ferrous sulfate heptahydrate to solution 1 obtained in step 2), stir evenly, and obtain solution 2 containing 0.064% initiator by mass, wherein the mass ratio of potassium persulfate and ferrous sulfate heptahydrate in the initiator is 2:1; 4) Preparation of lyophilized gel powder: Solution 2 was allowed to stand for 48 hours to allow gel formation. The gel was washed with anhydrous ethanol, centrifuged, and freeze-dried to obtain lyophilized gel powder.

[0050] The above solution 2 was added to G-grade oil well cement as mixing water, prepared according to GB / T 19139-2012, and cured for 1 day in a curing box at 30℃±2℃; the water-cement ratio was 0.44.

[0051] Example 5 The preparation method of CO2-responsive crack-resistant self-healing cement is as follows: (1) Preparation of monomer mixed solution: maleic acid and 3-(dimethylamino)propyl acrylate were added to tap water and stirred evenly to obtain a monomer mixed solution with a mass fraction of 1.02% maleic acid and a mass fraction of 1.11% 3-(dimethylamino)propyl acrylate. 2) Preparation of solution 1: Add methylenebisacrylamide to the monomer mixture solution obtained in step 1) and stir until homogeneous to obtain solution 1 with a crosslinking agent mass fraction of 0.071%; 3) Preparation of solution 2: Add ammonium persulfate and sodium bisulfite to solution 1 obtained in step 2), stir evenly, and obtain solution 2 containing 0.064% of initiator by mass, wherein the mass ratio of ammonium persulfate and sodium bisulfite in the initiator is 2:1; 4) Preparation of lyophilized gel powder: Solution 2 was allowed to stand for 48 hours to allow gel formation. The gel was washed with anhydrous ethanol, centrifuged, and freeze-dried to obtain lyophilized gel powder.

[0052] The above solution 2 was added to G-grade oil well cement as mixing water, prepared according to GB / T 19139-2012, and cured for 1 day in a curing box at 30℃±2℃; the water-cement ratio was 0.44.

[0053] Example 6 The preparation method of CO2-responsive crack-resistant self-healing cement is as follows: (1) Preparation of mixed solution: 1) Preparation of monomer mixed solution: Methacrylic acid and vinylimidazole were added to tap water and stirred evenly to obtain a monomer mixed solution with a mass fraction of 1.99% methacrylic acid and 2.18% vinylimidazole. 2) Preparation of solution 1: Add the crosslinking agent - ethylene glycol diglycidyl ether to the monomer mixture solution obtained in step 1), stir evenly to obtain solution 1 with a crosslinking agent mass fraction of 0.14%; 3) Preparation of solution 2: Add ammonium persulfate and sodium bisulfite to solution 1 obtained in step 2), stir evenly, and obtain solution 2 containing 0.12% of initiator by mass, wherein the mass ratio of ammonium persulfate and sodium bisulfite in the initiator is 2:1; 4) Preparation of lyophilized gel powder: Solution 2 was allowed to stand for 48 hours to allow gel formation. The gel was washed with anhydrous ethanol, centrifuged, and freeze-dried to obtain lyophilized gel powder.

[0054] The above solution 2 was added to G-grade oil well cement as mixing water, prepared according to GB / T 19139-2012, and cured for 1 day in a curing box at 30℃±2℃; the water-cement ratio was 0.44.

[0055] Figure 1 X-ray energy dispersive spectroscopy (EDS) analysis of the freeze-dried gel powder of CO2-responsive crack-resistant self-healing cement prepared in Example 1. From (a)-(d), it can be seen that the freeze-dried gel powder of CO2-responsive crack-resistant self-healing cement contains O, N, and C elements, where O comes from the carboxyl group in methacrylic acid and N comes from the imidazole ring in vinylimidazolium, confirming that the freeze-dried gel powder was successfully copolymerized from these two elements. In (b), functional group peaks corresponding to C=O and CO appear, confirming the carboxyl structure in the freeze-dried gel powder. In (c), functional group peaks of NR3 and C=N appear, confirming the tertiary nitrogen group structure in the gel. In (d), functional group peaks of CC and O=CO appear, consistent with the structure of the monomer.

[0056] Figure 2 Stress-strain test graphs of CO2-responsive crack-resistant self-healing cement gels prepared with different crosslinking agents (Examples 2 and 6). As shown in the graphs, the maximum elongation at break of the CO2-responsive crack-resistant self-healing cement gel prepared in Example 1 under tensile stress is 45.6%, and the tensile fracture stress is 0.0357 MPa; the maximum elongation at break of the CO2-responsive crack-resistant self-healing cement gel prepared in Example 6 under tensile stress is 121.8%, and the tensile fracture stress is 0.0061 MPa. The former has higher strength but lower toughness; the latter has higher toughness but lower strength.

[0057] Figure 3 The image shows a test result of the water absorption capacity of the gel in the CO2-responsive crack-resistant self-healing cement prepared in Example 2. The formula for calculating the water absorption capacity is: Q = (m2 - m1) / m1; where m1 is the initial mass of the freeze-dried gel powder, and m2 is the mass of the freeze-dried gel powder after absorbing water for a period of time.

[0058] As shown in the figure, the water absorption of the CO2-responsive crack-resistant self-healing cement prepared in Example 2 reached its maximum value at 17 min, with a water absorption capacity of 5.19 g / g. This is because the polymer network contains a large number of hydrophilic groups, which make it water-absorbing.

[0059] Figure 4The figures show the compressive and flexural strengths of CO2-responsive crack-resistant self-healing cements prepared in the control example and Examples 1, 2, and 3 (with different monomer addition amounts). As can be seen from the figures, the compressive strength of the CO2-responsive crack-resistant self-healing cements in Examples 1, 2, and 3 is lower than that in the control group. This is because the introduction of the polymer network increases internal defects in the cement. The compressive strength of the CO2-responsive crack-resistant self-healing cement increases with decreasing addition amount, because lower addition amounts result in fewer internal defects caused by the polymer in the cement-based material. The flexural strength of the CO2-responsive crack-resistant self-healing cements with different addition amounts is similar to that of the control group. This is because although the hydrogel network causes internal defects in the cement matrix, the gel also enhances the toughness of the brittle cement; the two effects cancel each other out, resulting in no significant change in the flexural strength of the cement.

[0060] Figure 5 The figures show the composition ratios of the CO2-responsive crack-resistant self-healing cements (comparative example and Examples 1, 2, and 3) obtained by thermogravimetric analysis. As shown in the figures, the calcium carbonate content in the CO2-responsive crack-resistant self-healing cements of Examples 1, 2, and 3 is higher than that in the control group. This is because the introduction of the polymer network enhances the cement's ability to capture carbon dioxide, leading to the conversion of more calcium hydroxide into calcium carbonate. The calcium carbonate content in the CO2-responsive crack-resistant self-healing cement increases with the increase of monomer (corresponding to the lyophilized gel powder) addition, because a higher monomer addition amount results in more tertiary amine groups in the cementitious material that can capture carbon dioxide. This confirms the ability of the CO2-responsive crack-resistant self-healing cement to capture carbon dioxide.

[0061] Figure 6 The crack volume repair rate and crack area repair rate before and after repair of CO2-responsive crack-resistant self-healing cement are compared with those of the control example and Examples 1, 2 and 3.

[0062] The formula for calculating the crack volume repair rate is: η V =(1-V2 / V1)×100%; where: η V V1 represents the crack volume repair rate; V2 represents the crack volume after different curing days of damaged cement; V1 represents the crack volume before repair of damaged cement.

[0063] Formula for calculating crack area repair rate: η A =(1-A2 / A1)×100%; where: η A A1 represents the crack area repair rate; A2 represents the crack area after different curing days of damaged cement; A1 represents the crack area before repair of damaged cement.

[0064] Depend on Figure 5It can be seen that after 7 days of wet curing in a carbon dioxide atmosphere at 30℃, the repair rate of CO2-responsive crack-resistant self-healing cements with different monomer addition amounts in Examples 1, 2, and 3 was much higher than that of the control group. The crack volume repair rate of Examples 2 and 3 reached over 60% after 7 days, while that of the control group was less than 7%. Compared with the control group, the self-healing rate of the experimental group with added self-healing agent increased by 883.58%. This is because the addition of the self-healing system significantly improved the self-healing performance. After the cement stone cracks, the polymer network in the cement matrix absorbs carbon dioxide to promote calcium ion mineralization to fill the gaps.

[0065] This invention also experimented with adding the freeze-dried gel powder prepared in Example 2, along with the monomer, crosslinking agent, and initiator concentrations in Solution 2 used in the preparation of the freeze-dried gel powder in Example 2, to tap water as cement mixing water. This mixing water was then added to Grade G oil well cement, prepared according to GB / T 19139-2012, and cured for 1 day in a curing chamber at 30℃±2℃; the water-cement ratio was 0.44. The results showed that the mixing water prepared by adding the freeze-dried gel powder to tap water had performance comparable to that of the CO2-responsive crack-resistant self-healing cement prepared using Solution 2 as mixing water in Example 2.

[0066] The CO2-responsive crack-resistant self-healing cement of the present invention has significant self-healing ability, effectively filling the gap in the application of polymer networks in promoting self-healing in carbon dioxide environments.

[0067] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a gel lyophilized powder, characterized in that, Includes the following steps: A vinyl monomer containing a carboxyl group and a vinyl monomer containing a tertiary amine are added to water and mixed to obtain a monomer mixed solution. A crosslinking agent was added to the monomer mixture solution to obtain solution 1; An initiator was added to solution 1 to obtain solution 2; The solution 2 was allowed to stand to obtain a hydrogel, which was then washed, centrifuged, and freeze-dried to obtain the freeze-dried gel powder. The initiator includes an oxidizing agent and a reducing agent.

2. The method for preparing the lyophilized gel powder according to claim 1, characterized in that, The carboxyl-containing vinyl monomer is methacrylic acid, itaconic acid, or maleic acid; the mass fraction of the carboxyl-containing vinyl monomer in the monomer mixture solution is 1.01%-2.93%.

3. The method for preparing the lyophilized gel powder according to claim 1, characterized in that, The vinyl monomer containing tertiary amine is vinylimidazole, dimethylaminoethyl methacrylate, or 3-(dimethylamino)propyl acrylate; the mass fraction of the vinyl monomer containing tertiary amine in the monomer mixture solution is 1.11%-3.20%.

4. The method for preparing the lyophilized gel powder according to claim 1, characterized in that, The crosslinking agent is methylene bisacrylamide or ethylene glycol diglycidyl ether; the mass fraction of the crosslinking agent in solution 1 is 0.071%-0.20%.

5. The method for preparing the lyophilized gel powder according to claim 1, characterized in that, The mass ratio of the oxidant to the reducing agent is 2:1; the oxidant is ammonium persulfate or potassium persulfate, and the reducing agent is sodium bisulfite or ferrous sulfate heptahydrate; the mass fraction of the initiator in solution 2 is 0.063%-0.18%.

6. The method for preparing the lyophilized gel powder according to claim 1, characterized in that, The settling time was 48 hours; washing was performed using anhydrous ethanol.

7. The gel lyophilized powder prepared by the preparation method according to any one of claims 1-6.

8. The application of the gel freeze-dried powder as described in claim 7 in the preparation of CO2-responsive crack-resistant self-healing cement.

9. A method for preparing CO2-responsive crack-resistant self-healing cement, characterized in that, The CO2-responsive crack-resistant self-healing cement is prepared by mixing solution 2 from the preparation method according to any one of claims 1-6 with oil well cement at a water-cement ratio of 0.4-0.5, or by adding the freeze-dried gel powder according to claim 7 to water as mixing water with oil well cement.

10. The CO2-responsive crack-resistant self-healing cement prepared by the preparation method according to claim 9.

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