Microcapsule modified self-repairing mortar, preparation method and application thereof

Abstract

This invention discloses a microcapsule-modified self-healing mortar, its preparation method, and its application, belonging to the technical field of stone cultural relic protection and restoration materials. The microcapsule-modified self-healing mortar, by mass percentage, comprises the following dry materials: 50%-70% hydraulic lime, 12%-24% nano-kaolin, 15%-25% quartz sand, 0.05%-0.2% additives, and 0.25%-2% microcapsule powder; wherein the core material of the microcapsules in the microcapsule powder is tung oil, and the wall material is barium alginate. The microcapsule-modified self-healing mortar possesses high weather resistance, excellent compatibility, and long-term durable self-healing function. By introducing tung oil-barium alginate microcapsules, the microcapsule-modified self-healing mortar synergizes with traditional restoration mortar raw materials, enabling the mortar material to trigger active repair components in the early stages of deterioration, achieving self-healing and self-repair effects.

Description

Technical Field

[0001] This invention relates to the field of materials for the protection and restoration of stone cultural relics, and in particular to a microcapsule-modified self-healing mortar, its preparation method, and its application. Background Technology

[0002] Stone artifacts, as important material carriers of human history and civilization, possess irreplaceable and invaluable value. However, during long-term preservation, due to natural factors and human activities, stone artifacts such as grottoes and stone carvings face numerous problems such as weathering, damage, and loss, seriously jeopardizing their safety and preservation of value. Therefore, using scientific, efficient, and compatible restoration mortar materials to reinforce and repair stone artifacts is one of the core tasks in the field of cultural relic protection.

[0003] Currently, the organic modification of mortars used for the restoration of stone cultural relics, both domestically and internationally, is mainly achieved through the internal incorporation of polymers. Specifically, this involves mixing polymer emulsions or redispersible latex powders such as epoxy resin, acrylic resin, organosilicon, and vinyl acetate-ethylene copolymer into lime or cement-based mortar. The polymer film-forming effect improves the system's cohesiveness, toughness, and interfacial bonding strength. Practice has shown that this type of modification can significantly improve the mortar's waterproofing and impermeability in the initial stages, reduce brittleness, and inhibit shrinkage cracking, while also optimizing its workability to some extent. However, the internal incorporation of organic components cannot solve the salt damage problem faced by stone cultural relics. In fact, by forming a water vapor barrier layer inside the stone, it can seal the already eroded salt within the stone, blocking natural leaching and desalination channels, exacerbating salt accumulation, and leading to accelerated deterioration.

[0004] More importantly, the aging and degradation of the polymer admixtures is a core defect limiting their long-term effectiveness. Under the requirements of century-long preservation of cultural relics, organic components such as epoxy resin and acrylic resin are prone to chain segment breakage, cross-linking structure destruction, and side group oxidation under the synergistic effects of light, heat, oxygen, water, and microorganisms, leading to material embrittlement, powdering, discoloration, and weakened adhesion. Existing technologies are insufficient to meet the requirements for the long-term stable preservation of stone cultural relics, failing to consider the compatibility of the materials used with the grotto temple relics themselves, the salt resistance of the materials, and their long-term self-healing function. Furthermore, the poor compatibility of some polymers with the inorganic matrix may even cause secondary damage.

[0005] Therefore, there is an urgent need to develop a new type of mortar material that can solve the above-mentioned problems of existing technology while maintaining good compatibility. This is of great significance for the safety protection and value preservation of grotto temple cultural relics. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a microcapsule-modified self-healing mortar, its preparation method, and its application. The microcapsule-modified self-healing mortar possesses high weather resistance, excellent compatibility, and long-term durable self-healing function.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a microcapsule-modified self-healing mortar, which, by weight percentage, comprises the following components in its dry form:

[0009] Hydraulic lime 50%-70%, nano-kaolin 12%-24%, quartz sand 15%-25%, admixtures 0.05%-0.2%, microcapsule powder 0.25%-2%;

[0010] The core material of the microcapsules in the microcapsule powder is tung oil, and the wall material is barium alginate.

[0011] This invention innovatively introduces tung oil-barium alginate microcapsules into the above-mentioned mortar. In addition to the conventional physical triggering method, it can also achieve chemical response release when the sulfate concentration increases. The sulfate is fixed by barium ions in the microcapsule wall material, and the mortar self-repair is achieved by releasing tung oil in the microcapsule core material, thus achieving the dual effects of salt resistance and self-repair.

[0012] Under sulfate attack conditions, because barium sulfate has a much lower Ksp value than barium alginate, barium ions in the capsule wall material can be released in response. These ions then fix the sulfate that has penetrated into the material being repaired through a displacement reaction, forming a precipitate in situ that fills the cracks and allows the material to resist salt damage. Simultaneously, after the microcapsule wall material ruptures, the core material tung oil is released. This oil acts as a repair agent, further solidifying and bonding the microcracks in the repaired material, thereby further enhancing its weather resistance.

[0013] The microcapsule-modified self-healing mortar of this invention utilizes the synergistic effect of traditional repair mortar raw materials and microcapsule powder to enable the mortar to slowly release tung oil with repair function during use, thereby achieving the bonding and filling of micro-cracks, preventing further damage, avoiding interference and damage to the cultural relic body caused by repeated operations, and conforming to the principle of minimal intervention in cultural relic protection.

[0014] Furthermore, the microcapsule-modified self-healing mortar can effectively resist the repeated crystallization-dissolution erosion of soluble salts in the pores, significantly reduce the propagation rate of interfacial microcracks, optimize the pore structure, and ensure that the mortar body and bonding interface remain stable in extreme climatic environments for a long time, avoiding early failure phenomena such as powdering and peeling, and achieving long-term weather resistance after the restoration of stone cultural relics.

[0015] The water-cement ratio in the microcapsule-modified self-healing mortar of the present invention is preferably 0.6-0.8; more preferably 0.7.

[0016] The water-cement ratio is the ratio of the total mass of water to the total mass of the dry material.

[0017] In the microcapsule-modified self-healing mortar, the content of hydraulic lime is preferably 58wt%-60wt%.

[0018] The preferred content of the nano-metakaolin is 18wt%-22wt%.

[0019] The preferred content of the quartz sand is 18wt%-22wt%.

[0020] The content of the additive is preferably 0.08wt%-0.15wt%.

[0021] The content of the microcapsule powder is preferably 0.25wt%-1.5wt%.

[0022] Preferably, the tung oil content in the microcapsules is 70wt%-90wt%; more preferably, it is 77wt%-83%.

[0023] The tung oil content mentioned above refers to the percentage by mass of tung oil in the total mass of the microcapsules.

[0024] Preferably, the particle size of the microcapsule powder is 60-120 μm.

[0025] Preferably, the admixture is selected from one or more of the following: early strength agent, water-reducing agent, defoamer, expanding agent, retarder, and antifreeze-thaw agent; more preferably, it is a water-reducing agent.

[0026] Preferably, the hydraulic lime grade of this invention is NHL2;

[0027] Preferably, the particle size of the nano-kaolin is 50-200 nm; more preferably 70-150 nm; and even more preferably 80-120 nm.

[0028] Preferably, the particle size of the quartz sand is 20-200 mesh; more preferably 60-160 mesh; and even more preferably 100-120 mesh.

[0029] This invention also provides a method for preparing the above-mentioned microcapsule-modified self-healing mortar, comprising the following steps:

[0030] (1) Hydraulic lime, nano-kaolin, quartz sand, additives and water are mixed to obtain a mixed system S1;

[0031] (2) The microcapsule powder and the mixing system S1 are mixed to prepare the microcapsule modified self-healing mortar.

[0032] The microcapsule powder has a certain degree of water absorption. Directly mixing it with other raw material components may reduce the fluidity of the material and affect the mixing effect, thereby causing the performance of the microcapsule-modified self-healing mortar to decline. Therefore, the above preparation method first mixes other raw materials to obtain a mixed system S1, and then mixes it with the microcapsule powder.

[0033] The microcapsule-modified self-healing mortar of the present invention avoids the direct addition of polymer admixtures during the preparation process, ensuring that the mortar material has suitable water vapor permeability and capillary absorption and discharge capacity. While enhancing and repairing, it can also maintain the "breathability" of the stone and prevent the accumulation of moisture and salt inside the stone.

[0034] This invention uses microencapsulation technology to encapsulate active organic components, which significantly improves the compatibility of organic components with stone artifacts and fundamentally solves the problem of aging and degradation of organic components.

[0035] This invention improves the weather resistance of mortar materials, especially their ability to resist salt damage, by releasing a capsule shell in response to sulfate, and addresses aging and cracking problems through the long-term self-healing effect of tung oil, thus significantly extending the service life of mortar materials.

[0036] Preferably, the method for preparing the microcapsule powder according to the present invention includes the following steps:

[0037] (1) Mix tung oil, emulsifier and sodium alginate aqueous solution, and emulsify to obtain an oil-in-water emulsion with sodium alginate as the external phase and tung oil as the internal phase;

[0038] (2) The oil-in-water emulsion obtained in step (1) and the barium chloride solution are mixed, and microcapsule powder with tung oil as the core material and barium alginate as the wall material is prepared by reaction and drying.

[0039] Preferably, the mass ratio of tung oil to emulsifier in this invention is (2-4):(1-3).

[0040] Preferably, the mass ratio of tung oil to sodium alginate is (2-4):(1-2);

[0041] Preferably, the mass ratio of tung oil to barium chloride is (2-4):(3-4).

[0042] The concentration of sodium alginate is preferably 1wt%-2wt%;

[0043] The concentration of the barium chloride solution is preferably 2wt%-4wt%; more preferably 3wt%.

[0044] The emulsifiers include, but are not limited to, polyvinyl alcohol or Tween 80.

[0045] In the above-mentioned method for preparing microcapsule powder, the reaction described in step (2) is mainly an ionic crosslinking reaction. The ionic crosslinking reaction forms a three-dimensional network structure of barium alginate gel through the electrostatic interaction between barium ions and alginate anions.

[0046] The present invention does not have any special limitation on the drying in step (2) above, and any drying method known to those skilled in the art, such as freeze drying or vacuum drying, is acceptable.

[0047] In some specific embodiments of the present invention, freeze drying is preferred.

[0048] After the reaction in step (2) is completed, post-processing such as washing and filtration is also included.

[0049] The present invention does not impose any special limitations on the washing solvent and the filtration method, and any washing solvent and filtration method known to those skilled in the art can be used.

[0050] The microcapsule-modified self-healing mortar of this invention combines traditional repair functions with self-healing functions. It can achieve self-repair of microcracks in stone artifacts in sulfate-eroded environments, significantly improving their weather resistance.

[0051] The present invention also provides the application of the above-mentioned microcapsule modified self-healing mortar or the microcapsule modified self-healing mortar prepared by the above-mentioned preparation method in the restoration of stone cultural relics.

[0052] The stone cultural relics include, but are not limited to, grotto temples, cliff carvings, stone carvings, and rock paintings.

[0053] The repairs include, but are not limited to, damage repair and adhesive reinforcement.

[0054] The microcapsule-modified self-healing mortar of this invention can achieve both salt resistance and self-healing effects when stone cultural relics are eroded by sulfate, demonstrating excellent resistance to salt damage. Simultaneously, the self-healing effect also gives the mortar material high water and acid resistance, excellent weather resistance under various environmental influences, and the ability to maintain its effectiveness over a long period.

[0055] Furthermore, the microcapsule-modified self-healing mortar of the present invention has good compatibility with the stone cultural relic body, avoiding the problem of reduced self-healing effect caused by the difference in physical and chemical properties between the internally added polymer and the stone cultural relic. Moreover, the microcapsule-modified self-healing mortar is environmentally friendly and will not cause pollution or secondary diseases.

[0056] Preferably, the temperature range for the application environment of the microcapsule-modified self-healing mortar is 0℃-40℃.

[0057] Preferably, the relative humidity of the application environment for the microcapsule modified self-healing mortar is 40%-80%.

[0058] Compared with existing technologies, the microcapsule-modified self-healing mortar provided by this invention, by weight percentage, comprises the following dry materials: 50%-70% hydraulic lime, 12%-24% nano-kaolin, 15%-25% quartz sand, 0.05%-0.2% additives, and 0.25%-2% microcapsule powder; wherein the core material of the microcapsules in the microcapsule powder is tung oil, and the wall material is barium alginate. The microcapsule-modified self-healing mortar of this invention possesses high weather resistance, excellent compatibility, and long-term durable self-healing function. By introducing tung oil-barium alginate microcapsules, the microcapsule-modified self-healing mortar synergizes with traditional repair mortar raw materials, enabling the mortar material to trigger active repair components in the early stages of deterioration, achieving self-healing and self-repairing effects. This meets the ethical requirement of "minimal intervention" in the field of cultural heritage preservation, provides reliable technical support for the intergenerational transmission of stone cultural relics, and offers an intelligent solution for the protection and restoration of stone cultural relics that can substantially extend their service life and reduce the overall maintenance cost. Detailed Implementation

[0059] To further illustrate the present invention, the following detailed description of the microcapsule-modified self-healing mortar, its preparation method, and its application are provided in conjunction with embodiments.

[0060] Example 1

[0061] A microcapsule-modified self-healing mortar, the dry material of which is composed of the following raw materials in the indicated weight percentages: 59.65% hydraulic lime, 20% nano-kaolin, 20% quartz sand, 0.1% water-reducing agent, and 0.25% microcapsules;

[0062] The water-cement ratio of this mortar is 0.7.

[0063] The preparation method of this microcapsule-modified self-healing mortar includes the following steps:

[0064] (1) Preparation of microcapsules

[0065] First, 3 wt% tung oil and 2 wt% emulsifier (polyvinyl alcohol) were added to a 1% sodium alginate aqueous solution. The mixture was then emulsified for 10 min at 10000 r / min using a homogenizer to form an oil-in-water emulsion with sodium alginate as the external phase and tung oil as the internal phase. The oil-in-water emulsion was then dropped into a 3% barium chloride solution using a syringe. After reacting for 1 hour, the solution was washed with deionized water, filtered, and freeze-dried for 48 hours to obtain microcapsule powder with a particle size of 80 μm. The core material of the microcapsules was tung oil, and the wall material was barium alginate, with the tung oil content being 80 wt%.

[0066] (2) Preparation of mortar

[0067] Hydraulic lime, nano-kaolin, quartz sand, additives and water are mixed and stirred evenly in a mortar mixer. Then, the microcapsule powder obtained in step (1) is added and stirred and mixed again to obtain the microcapsule modified self-healing mortar.

[0068] Example 2

[0069] A microcapsule-modified self-healing mortar, the dry material of which is composed of the following raw materials in the indicated weight percentages: 59.4% hydraulic lime, 20% nano-kaolin, 20% quartz sand, 0.1% water-reducing agent, and 0.5% microcapsules;

[0070] The water-cement ratio of this mortar is 0.7.

[0071] The preparation method of the microcapsule-modified self-healing mortar is the same as in Example 1.

[0072] Example 3

[0073] A microcapsule-modified self-healing mortar, the dry material of which is composed of the following raw materials in weight percentage: 58.9% hydraulic lime, 20% nano-kaolin, 20% quartz sand, 0.1% water-reducing agent, and 1% microcapsules;

[0074] The water-cement ratio of this mortar is 0.7.

[0075] The preparation method of the microcapsule-modified self-healing mortar is the same as in Example 1.

[0076] Example 4

[0077] A microcapsule-modified self-healing mortar, the dry material of which is composed of the following raw materials in the indicated weight percentages: 58.4% hydraulic lime, 20% nano-kaolin, 20% quartz sand, 0.1% water-reducing agent, and 1.5% microcapsules;

[0078] The water-cement ratio of this mortar is 0.7.

[0079] The preparation method of the microcapsule-modified self-healing mortar is the same as in Example 1.

[0080] Comparative Example 1

[0081] Compared to Example 3, the only difference is that no microcapsules were added.

[0082] Comparative Example 2

[0083] Compared with Example 3, the only difference is that 1 wt% tung oil was added, and no microcapsules were added.

[0084] Comparative Example 3

[0085] Compared with Example 3, the only difference is that the microcapsule core material is epoxy resin.

[0086] Comparative Example 4

[0087] The only difference from Example 3 is that the microcapsule wall material is calcium alginate.

[0088] The mortars prepared in Examples 1, 2, 3, and 4, and Comparative Examples 1, 2, 3, and 4 were cast into 40*40*40 mm specimens and cured for 60 days before being subjected to a salt crystallization cycle destruction experiment. The specimens were immersed in a 10% sodium sulfate solution for 16 hours, then immediately placed in a 60°C oven for 8 hours, constituting one cycle.

[0089] The results showed that the microcapsule-modified self-healing mortar prepared in Example 1 had good salt resistance, but surface cracks appeared after 20 cycles and the material disintegrated after 30 cycles.

[0090] Example 2 showed excellent salt resistance, but surface cracks appeared after 25 cycles and the material disintegrated after 35 cycles.

[0091] Example 3 showed excellent salt resistance, but surface cracks appeared after 25 cycles and the material disintegrated after 35 cycles.

[0092] Example 4 showed good salt resistance, but surface cracks appeared after 20 cycles and the material disintegrated after 30 cycles.

[0093] Comparative Example 1 showed no salt resistance, and after 5 cycles, apparent cracks appeared. After 6 cycles, the material disintegrated.

[0094] Comparative Example 2 showed some salt resistance but no self-healing effect. Surface cracks appeared after 15 cycles, and the material disintegrated after 20 cycles.

[0095] Comparative Example 3 showed a self-healing effect, but its salt resistance was weak. Surface cracks appeared after 7 cycles, and the material disintegrated after 15 cycles.

[0096] Comparative Example 4 showed self-healing properties but lacked salt resistance. Surface cracks appeared after 5 cycles, and the material disintegrated after 10 cycles.

[0097] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A microcapsule-modified self-healing mortar, characterized in that, By weight percentage, its dry matter comprises the following components: Hydraulic lime 50%-70%, nano-kaolin 12%-24%, quartz sand 15%-25%, admixtures 0.05-0.2%, microcapsule powder 0.25%-2%; The core material of the microcapsules in the microcapsule powder is tung oil, and the wall material is barium alginate.

2. The microcapsule-modified self-healing mortar according to claim 1, characterized in that, The microcapsules contain 70wt%-90wt% tung oil.

3. The microcapsule-modified self-healing mortar according to claim 1, characterized in that, The microcapsule powder has a particle size of 60-120 μm.

4. The microcapsule-modified self-healing mortar according to claim 1, characterized in that, The admixture is selected from one or more of the following: early strength agent, water reducing agent, defoamer, expanding agent, retarder, and antifreeze-thaw agent.

5. The microcapsule-modified self-healing mortar according to claim 1, characterized in that, The hydraulic lime grade is NHL2; The particle size of the nano-metakaolin is 50-200 nm; The particle size of the quartz sand is 20-200 mesh.

6. The method for preparing the microcapsule-modified self-healing mortar according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Hydraulic lime, nano-kaolin, quartz sand, additives and water are mixed to obtain a mixed system S1; (2) The microcapsule powder and the mixing system S1 are mixed to prepare the microcapsule modified self-healing mortar.

7. The preparation method according to claim 6, characterized in that, The method for preparing the microcapsule powder includes the following steps: (1) Mix tung oil, emulsifier and sodium alginate aqueous solution, and emulsify to obtain an oil-in-water emulsion with sodium alginate as the external phase and tung oil as the internal phase; (2) The water-in-oil emulsion obtained in step (1) and barium chloride solution are mixed, and microcapsule powder with tung oil as the core material and barium alginate as the wall material is prepared by reaction and drying.

8. The preparation method according to claim 7, characterized in that, The mass ratio of tung oil to emulsifier is (2-4):(1-3); The mass ratio of tung oil to sodium alginate is (2-4):(1-2); The mass ratio of tung oil to barium chloride is (2-4):(3-4).

9. The application of the microcapsule-modified self-healing mortar according to any one of claims 1-5 or the microcapsule-modified self-healing mortar prepared by the preparation method according to any one of claims 6-8 in the restoration of stone cultural relics.

10. The application according to claim 9, characterized in that, The application environment temperature of the microcapsule modified self-healing mortar is 0℃-40℃; The relative humidity of the application environment for the microcapsule modified self-healing mortar is 40%-80%.