Materials for repairing freeze-thaw cracks in building exterior walls, building exterior wall materials and their preparation methods

Abstract

This invention relates to the field of building materials technology and addresses the problem of freeze-thaw cracks in building exterior walls in extremely cold regions. The repair materials include butyl acrylate, glycidyl methacrylate, ethyl p-methoxycinnamate, PEG-S-S-PEG, N-TiO2@PANI composite particles, Bacillus pasteurella microcapsules, nutrient salt microcapsules, and the photoinitiator HMPP. The building exterior wall materials also include quartz sand, shale ceramsite, P·O 42.5 cement, β-hemihydrate gypsum powder, polycarboxylate superplasticizer, hydroxypropyl methylcellulose, ethylene glycol, silicone defoamer, nano-calcium carbonate, and chopped cellulose fibers. This invention can reduce overall maintenance costs, improve structural safety, and is suitable for the needs of buildings in northern regions.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a material for repairing freeze-thaw cracks in building exterior walls, building exterior wall materials, and their preparation methods. Background Technology

[0002] In frigid northern regions such as the three northeastern provinces and eastern Inner Mongolia, winter temperatures often drop below -20°C, with significant diurnal temperature variations. Residential exterior walls, mostly constructed of concrete or aerated concrete blocks, are prone to cracking due to freeze-thaw cycles. In winter, the moisture inside the walls freezes and expands, damaging the wall structure. As the snow melts in spring, the cracks widen further, leading to water seepage from the exterior walls and a decline in indoor insulation performance.

[0003] Traditional physical filler materials are rigid and lack flexibility, and their coefficient of linear expansion is incompatible with that of concrete walls or aerated concrete blocks. In winter, the large difference in shrinkage rates between the repair material and the wall can easily create tensile stress at the interface, causing cracks to reopen. In spring, meltwater seeps into incompletely filled cracks and then freezes and expands again in winter, further exacerbating crack propagation. Statistics show that the recurrence rate of cracks in exterior walls repaired using traditional physical fillers is over 60% within one year.

[0004] Freeze-thaw cracks not only exist on the surface of walls but can also penetrate deep into the wall, forming irregular cracks that are narrow on the surface and wide inside. Traditional physical fillers have poor fluidity and can only fill cracks within 20mm on the surface, unable to penetrate into the damaged areas inside the wall. Unrepaired pores and cracks inside will continue to store moisture, which, repeated freezing and expansion in winter, causes the internal structure of the wall to loosen, its compressive strength to decrease year by year, and in severe cases, it can lead to localized peeling of the exterior wall, posing a safety hazard.

[0005] While self-healing materials targeting freeze-thaw cracks have emerged in recent years, they still cannot meet the complex needs of frigid regions. Single-trigger mechanisms are ill-suited to the variable environments of these regions, and existing photocatalytic self-healing materials rely on strong ultraviolet (UV) radiation to initiate the repair process, requiring UV intensity ≥800 μW / cm². 2 In the frigid northern regions, short hours of sunshine and weak ultraviolet radiation during winter make it difficult for the repair reaction to initiate. Even if it does initiate, the repair rate is significantly reduced, failing to prevent the infiltration of winter meltwater in time. Furthermore, single-microbial self-healing materials rely on a continuously moist environment. However, in winter, the wall surface is dry, and the microorganisms are in a dormant state, unable to activate mineralization repair. Although they can initiate repair during spring meltwater, the repair cycle is long, and the generated calcium carbonate crystals are easily brittle at low temperatures, making them unable to withstand repeated freeze-thaw cycles in winter.

[0006] In summary, there is an urgent need for new types of repair and exterior wall materials that can adapt to all-season environments in frigid regions and take into account both deep repair and long-term frost resistance. Summary of the Invention

[0007] To address the technical problem of freeze-thaw cracks easily appearing on the exterior walls of buildings in frigid northern regions, this invention proposes a material for repairing freeze-thaw cracks in building exterior walls, a building exterior wall material, and its preparation method.

[0008] The technical solution of the present invention is as follows:

[0009] A material for repairing freeze-thaw cracks in building exterior walls, comprising the following components in parts by weight:

[0010] Butyl acrylate, 28-32 parts; glycidyl methacrylate, 18-22 parts; ethyl p-methoxycinnamate, 9-11 parts; PEG-SS-PEG, 4.5-5.5 parts; N-TiO2@PANI composite particles, 3.5-4.5 parts; Bacillus pasteurellium microcapsules, 7-9 parts; nutrient salt microcapsules, 7-9 parts; photoinitiator HMPP, 0.5 parts;

[0011] The N-TiO2@PANI composite particles are obtained by first reacting N-TiO2 with a nitrogen source aqueous solution and a tetrabutyl titanate-ethanol solution, and then reacting it with aniline monomer and ammonium persulfate.

[0012] The Pasteurella microcapsules were obtained through the following steps:

[0013] The bacterial culture of Bacillus pasteurellii was mixed with sodium alginate aqueous solution and then atomized into calcium chloride solution. The resulting microcapsules were collected by filtration and then added to chitosan acetate solution and stirred to obtain inner microcapsules. The PCL-nutrient salt-Tween 80 mixed solution was sprayed to uniformly coat the surface of the inner microcapsules to obtain Bacillus pasteurellii microcapsules.

[0014] Preferably, the specific preparation steps of the N-TiO2@PANI composite particles include:

[0015] Hydrochloric acid was added dropwise to the urea aqueous solution to adjust the pH to 2-3, thus obtaining a nitrogen source aqueous solution;

[0016] A nitrogen source aqueous solution was added to a tetrabutyl titanate-ethanol solution and stirred continuously to form a milky white sol. The sol was then transferred to a polytetrafluoroethylene reactor and reacted at 180°C for 12 hours. The mixture was then cooled to room temperature, and the product was centrifuged to collect the precipitate. The precipitate was repeatedly washed until the pH of the supernatant was 6-7. The product was then dried to obtain N-TiO2 powder.

[0017] The N-TiO2 powder was added to anhydrous ethanol and ultrasonically dispersed for 30 min. Then, aniline monomer was added and the mixture was stirred for another 1 h to obtain an N-TiO2-aniline dispersion.

[0018] Under continuous stirring and ice bath conditions, ammonium persulfate aqueous solution was slowly added dropwise to N-TiO2-aniline dispersion. After the addition was completed, the reaction was continued in the ice bath for 6 hours. After the reaction was completed, the precipitate was collected by centrifugation, washed with anhydrous ethanol, and dried to obtain N-TiO2@PANI composite particles.

[0019] Preferably, the specific preparation steps of the Bacillus pasteurellium microcapsules include:

[0020] The live bacteria concentration was 10. 9 CFU / mL of Bacillus pasteurellium culture was slowly added to sodium alginate aqueous solution on a sterile operating table, mixed evenly, and the viscosity was adjusted to 500~600mPa•s with deionized water.

[0021] Add the contents to the feed tank of a spray dryer, setting the inlet temperature to 125℃, the outlet temperature to 55℃, and the feed rate to 5mL / min. Add a 10% (w / w) calcium chloride solution to the receiving tank. The atomized particles fall into the calcium chloride solution and are stirred for 30 minutes. Then, filter and collect the gel microspheres, wash them with deionized water, and then add them to a chitosan acetate solution. Stir to form a sodium alginate-chitosan composite inner membrane. Filter and collect the composite microcapsules, wash them with deionized water until the pH of the filtrate is 6-7, and vacuum dry them to obtain the inner microcapsules.

[0022] Polycaprolactone was added to dichloromethane at a ratio of 8g:92mL and stirred to dissolve. Then, for every 8g of polycaprolactone, 0.5g of Tween 80, 10g of calcium chloride, and 6g of dipotassium hydrogen phosphate were added and stirred to obtain a PCL-nutrient-Tween 80 mixed solution. The inner layer microcapsules were evenly spread on the receiving plate of an electrostatic sprayer, and the PCL-nutrient-Tween 80 mixed solution was evenly coated on the surface of the inner layer microcapsules at a spraying rate of 2mL / h. Subsequently, the microcapsules were vacuum dried at 40℃ for 4h to obtain Bacillus pasteurellis microcapsules.

[0023] The present invention also provides a method for preparing the above-mentioned building exterior wall freeze-thaw crack repair material, comprising the following steps:

[0024] S1. Mix butyl acrylate, glycidyl methacrylate and ethyl p-methoxycinnamate and stir until the system is uniform and transparent.

[0025] S2. While stirring, add PEG-SS-PEG, then add HMPP and continue stirring to form an organic monomer matrix premix.

[0026] S3. Add twice the amount of organic monomer matrix premix to the N-TiO2@PANI composite particles, and sonicate to obtain N-TiO2@PANI dispersion slurry;

[0027] While stirring, the N-TiO2@PANI dispersion slurry is pumped into the remaining organic monomer matrix premix to form an organic monomer-N-TiO2@PANI composite matrix;

[0028] S4. After mixing the Bacillus pasteurellium microcapsules and nutrient salt microcapsules, ethanol is added to improve the surface wettability of the microcapsules. Then, the mixed microcapsules are added to the organic monomer-N-TiO2@PANI composite matrix and stirred evenly to obtain a self-healing material for freeze-thaw cracks in building exterior walls.

[0029] Preferably, the stirring speed in step S1 is 300 r / min; the stirring speed in step S2 is 500 r / min.

[0030] Preferably, the ultrasonic treatment in step S2 uses an ultrasonic disperser with a power of 300W and a frequency of 20kHz.

[0031] The stirring speed in step S2 is 800 r / min.

[0032] Preferably, the amount of ethanol used in step S4 is 10% of the total mass of the Bacillus pasteurellium microcapsules and nutrient salt microcapsules.

[0033] The present invention also provides a building exterior wall material, comprising the components of the above-mentioned building exterior wall freeze-thaw crack repair material, and further comprising:

[0034] Quartz sand, 30-35 parts; shale ceramsite, 20-25 parts; P·O 42.5 cement, 15-18 parts; β-hemihydrate gypsum powder, 5-7 parts; polycarboxylate superplasticizer, 0.8-1.2 parts; hydroxypropyl methylcellulose, 0.5-0.8 parts; ethylene glycol, 1.5-2.0 parts; silicone defoamer, 0.2-0.3 parts; nano-calcium carbonate, 1.0-1.5 parts; chopped cellulose fiber, 1.0-1.5 parts.

[0035] The quartz sand has a particle size of 0.15~0.6mm, the nano-calcium carbonate has a particle size of 50~100nm, and the chopped cellulose fibers have a length of 3~5mm.

[0036] Preferably, the silicone-based defoamer is BYK-024 or tego Foamex 810; the polycarboxylate-based water-reducing agent is PCA-1 or JM-PCA.

[0037] The present invention also provides a method for preparing the above-mentioned building exterior wall material, comprising the following steps:

[0038] Quartz sand, shale ceramsite, nano-calcium carbonate, and short-cut cellulose fibers are mixed and stirred evenly in a mixer at a speed of 400 r / min to obtain mixed aggregate;

[0039] Add P·O 42.5 cement and β-hemihydrate gypsum powder, and continue to stir evenly at 400 r / min to form an inorganic base material;

[0040] Polycarboxylate superplasticizer, hydroxypropyl methylcellulose, ethylene glycol, and silicone defoamer are added to deionized water, wherein the amount of deionized water is 15% to 20% of the total mass of the inorganic base material. The mixture is stirred until completely dissolved, and then added to the inorganic base material. The mixture is stirred evenly at a speed of 600 r / min to form a cement-based slurry.

[0041] The above-mentioned method for preparing freeze-thaw crack repair materials for building exterior walls was used to prepare the freeze-thaw crack repair materials for building exterior walls. The materials were then added to cement-based slurry and stirred evenly at a speed of 500 r / min to obtain self-healing building exterior wall materials.

[0042] Compared with the prior art, the specific beneficial effects of the present invention are as follows:

[0043] The repair material provided by this invention utilizes a core combination of N-TiO2@PANI composite particles, Bacillus pasteurellium microcapsules, and a PEG-SS-PEG dynamic crosslinking agent. Under weak ultraviolet light in winter, N-TiO2@PANI responds and accelerates the polymerization of organic monomers to form an elastic gel. In spring, the microcapsules release bacteria to generate calcium carbonate crystals. This dual mechanism achieves a high repair rate of 78%-90%, more than twice that of traditional materials. The dynamic crosslinking agent buffers temperature stress and ensures that the crystals are tightly bonded to the substrate, reducing the annual crack recurrence rate to 3%-5%. At the same time, the organic-inorganic composite structure repairs deep cracks, with a compressive strength recovery rate of 88%-92%, solving the technical pain points of traditional filler materials such as slow repair in winter, spring recurrence, and poor strength.

[0044] The exterior wall material provided by this invention is based on a quartz sand-shale ceramsite gradation skeleton and β-hemihydrate gypsum-cement synergistic hydration, combined with an antifreeze system composed of ethylene glycol, nano-calcium carbonate, and short-cut cellulose fibers. It achieves a high compressive strength of 25.2-27.5 MPa, and the mass / strength loss rate after 50 freeze-thaw cycles is only half that of a single material. It also integrates dual self-healing components of the repair material, achieving a full-season repair rate of 84%-88% in winter and 90%-94% in spring. This overcomes the limitations of single self-healing materials, such as low strength, weak antifreeze, and poor compatibility. Overall, it reduces maintenance costs, improves structural safety, and is suitable for the needs of buildings in northern regions. Detailed Implementation

[0045] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as limiting the present invention.

[0046] In the following examples, each "part" corresponds to a mass of 3g.

[0047] Example 1.

[0048] (1) Preparation of N-TiO2@PANI composite particles:

[0049] Preparation of nitrogen source aqueous solution: Take 50 mL of deionized water, add 15 g of urea and stir until completely dissolved, add 2 mL of 37% hydrochloric acid dropwise, adjust the pH to 2.5 to obtain nitrogen source aqueous solution;

[0050] Preparation of N-TiO2 precursor: 60g of tetrabutyl titanate was slowly added dropwise to 100mL of anhydrous ethanol (magnetically stirred at 500r / min, dropping rate 1mL / min) to form a transparent TBOT-ethanol solution; the nitrogen source aqueous solution was slowly poured into the solution and stirred for 30min until a milky white sol was formed, which was then transferred to a polytetrafluoroethylene reactor and reacted at 180℃ hydrothermal for 12h.

[0051] N-TiO2 separation and drying: After the reaction, the mixture was cooled to room temperature, centrifuged at 8000 r / min for 15 min to collect the precipitate, washed 3 times with anhydrous ethanol and 2 times with deionized water (until the pH of the supernatant was 6.5), vacuum dried at 80℃ for 6 h, and ground in a planetary ball mill (ball-to-material ratio 10:1, 300 r / min, 2 h) to obtain 15-20 nm N-TiO2 powder.

[0052] Preparation of core-shell composite particles: 3g of N-TiO2 powder was added to 100mL of anhydrous ethanol and ultrasonically dispersed at 300W and 20kHz for 30min. 8g of distilled aniline monomer was added and stirred at 400r / min for 1h. 10g of ammonium persulfate was dissolved in 50mL of deionized water (ice bath 0-5℃) and slowly added dropwise to the above dispersion (dropping rate 1mL / min). The mixture was stirred at 400r / min in an ice bath for 6h. The black precipitate was collected by centrifugation at 8000r / min for 20min, washed 3 times with anhydrous ethanol, and vacuum dried at 60℃ for 4h to obtain 11g of N-TiO2@PANI composite particles.

[0053] (2) Preparation of Bacillus pasteurellium microcapsules:

[0054] Inner layer microcapsule preparation: Take a live bacteria concentration of 10 930 mL of CFU / mL Bacillus pasteurellium culture was aseptically added to a 5% sodium alginate aqueous solution (5 g sodium alginate + 95 mL deionized water, dissolved at 60 °C). After mixing thoroughly, the viscosity was adjusted to 550 mPa•s. The mixture was then added to a spray dryer (inlet 125 °C, outlet 55 °C, feed 5 mL / min). A 10% calcium chloride solution was added to the receiving tank. After the atomized particles fell in, the mixture was stirred at 200 r / min for 30 min. The gel microspheres were collected by filtration, washed three times with deionized water, and then a 3% chitosan acetate solution (3 g chitosan + 5 mL glacial acetic acid + 95 mL water) was added. The mixture was stirred at 150 r / min for 60 min, filtered, washed until pH=6.5, and vacuum dried at 40 °C for 2 h to obtain the inner layer microcapsules.

[0055] Outer coating: 8g of polycaprolactone was added to 92mL of dichloromethane and stirred at 30℃ for 2h to dissolve. 0.5g of Tween 80, 10g of calcium chloride, and 6g of dipotassium hydrogen phosphate were added and stirred for 30min. The inner microcapsules were spread on the receiving plate of an electrostatic sprayer (voltage 18kV, nozzle 0.2mm, distance 15cm) and coated with the above solution at a spray rate of 2mL / h. The microcapsules were vacuum dried at 40℃ for 4h to obtain Bacillus pasteurellis microcapsules.

[0056] (3) Preparation of materials for repairing freeze-thaw cracks in building exterior walls:

[0057] Organic monomer premix: Take 28 parts butyl acrylate, 18 parts glycidyl methacrylate, and 9 parts ethyl p-methoxycinnamate, and stir at 300 r / min for 15 min until uniform and transparent; add 4.5 parts PEG-SS-PEG (in 3 portions, 5 min apart), stir at 500 r / min for 20 min, add 0.5 parts HMPP, and continue stirring for 10 min;

[0058] N-TiO2@PANI dispersion: Take 3.5 parts of N-TiO2@PANI composite particles, add 7 parts of organic monomer premix, sonicate at 300W and 20kHz for 20min, and pump in the remaining premix under stirring at 800r / min to form a composite matrix;

[0059] Microcapsule incorporation: Mix 7 parts of Pasteurella multocida microcapsules and 7 parts of nutrient salt microcapsules, add 1.4 parts of ethanol (10% of total mass), stir at 200 r / min for 3 min, add the composite matrix, stir at 200 r / min for 25 min to obtain the repair material.

[0060] Example 2.

[0061] (1) Preparation of N-TiO2@PANI composite particles (same as Example 1);

[0062] (2) Preparation of Bacillus pasteurellium microcapsules (same as in Example 1);

[0063] (3) Preparation of materials for repairing freeze-thaw cracks in building exterior walls:

[0064] Organic monomer premix: Take 30 parts butyl acrylate, 20 parts glycidyl methacrylate, and 10 parts ethyl p-methoxycinnamate, stir at 300 r / min for 15 min; add 5 parts PEG-SS-PEG, stir at 500 r / min for 20 min, and add 0.5 parts HMPP;

[0065] N-TiO2@PANI dispersion: Take 3.8 parts of composite particles, add 7.6 parts of premixed solution and sonicate, then pump in the remaining premixed solution;

[0066] Microcapsule incorporation: Take 8 parts of Bacillus pasteurellii microcapsules and 8 parts of nutrient salt microcapsules, add 1.6 parts of ethanol, and mix them into the composite matrix to obtain the repair material.

[0067] Example 3.

[0068] (1) Preparation of N-TiO2@PANI composite particles (same as Example 1);

[0069] (2) Preparation of Bacillus pasteurellium microcapsules (same as in Example 1);

[0070] (3) Preparation of materials for repairing freeze-thaw cracks in building exterior walls:

[0071] Organic monomer premix: Take 32 parts butyl acrylate, 22 parts glycidyl methacrylate, and 11 parts ethyl p-methoxycinnamate, stir at 300 r / min for 15 min; add 5.5 parts PEG-SS-PEG, stir at 500 r / min for 20 min, and add 0.5 parts HMPP;

[0072] N-TiO2@PANI dispersion: Take 4.5 parts of composite particles, add 9 parts of premixed solution and sonicate, then pump in the remaining premixed solution;

[0073] Microcapsule incorporation: Take 9 parts of Bacillus pasteurellii microcapsules and 9 parts of nutrient salt microcapsules, add 1.8 parts of ethanol, and mix them into the composite matrix to obtain the repair material.

[0074] Example 4.

[0075] Preparation of mixed aggregate: 30 parts of quartz sand, 20 parts of shale ceramsite, 1.0 part of nano calcium carbonate and 1.0 part of chopped cellulose fiber are added to a twin-shaft mixer and dry-mixed at 400 r / min for 2 min until there is no obvious particle agglomeration of the material to obtain mixed aggregate;

[0076] Inorganic matrix preparation: Add 15 parts of P•O42.5 cement and 5 parts of β-hemihydrate gypsum powder to the mixed aggregate, and stir at 400 r / min for 3 min until the cement and aggregate are evenly mixed and there are no white cement lumps, thus forming an inorganic matrix.

[0077] Preparation of modified additive solution: Take 10.8 parts of deionized water, add 0.8 parts of PCA-1 water reducing agent, 0.5 parts of hydroxypropyl methylcellulose, 1.5 parts of ethylene glycol, and 0.2 parts of BYK-024 defoamer in sequence, stir magnetically (500 r / min) for 15 min until the solution is transparent and free of precipitate, and obtain the modified additive solution;

[0078] Cement-based slurry preparation: Slowly pour the modified additive solution into the inorganic base material, adjust the twin-shaft mixer to 600 r / min and stir for 5 min until the slurry is a uniform paste (no dry lumps, can be picked up with a scraper and flow naturally without obvious stratification), thus forming cement-based slurry;

[0079] Preparation of building exterior wall material: The building exterior wall freeze-thaw crack repair material prepared in Example 1 was slowly added to the cement-based slurry and stirred at 500 r / min for 8 min. During this period, the machine was stopped every 2 min to observe and ensure that the repair material and the cement-based slurry were completely integrated, and finally the self-healing building exterior wall material was obtained.

[0080] Example 5.

[0081] Preparation of mixed aggregate: 32 parts quartz sand, 22 parts shale ceramsite, 1.2 parts nano calcium carbonate, 1.2 parts short chopped cellulose fiber, dry mixed at 400 r / min for 2 min;

[0082] Inorganic base material preparation: Add 16 parts of P•O42.5 cement and 6 parts of β-hemihydrate gypsum powder, and stir at 400 r / min for 3 min;

[0083] Preparation of modified additive solution: 14.11 parts deionized water + 1.0 parts JM-PCA + 0.6 parts hydroxypropyl methylcellulose + 1.8 parts ethylene glycol + 0.25 parts tegoFoamex810, stir at 500 r / min for 15 min;

[0084] Cement-based slurry preparation: Add the modified additive solution to the inorganic base material and stir at 600 r / min for 5 min;

[0085] Preparation of building exterior wall materials: Example 2: The repair material was added to cement-based slurry and stirred at 500 r / min for 8 min.

[0086] Example 6.

[0087] Preparation of mixed aggregate: 35 parts quartz sand, 25 parts shale ceramsite, 1.5 parts nano calcium carbonate, 1.5 parts short chopped cellulose fiber, dry mixed at 400 r / min for 2 min;

[0088] Inorganic base material preparation: Add 18 parts of P•O42.5 cement and 7 parts of β-hemihydrate gypsum powder, and stir at 400 r / min for 3 min;

[0089] Preparation of modified additive solution: 17.6 parts deionized water + 1.2 parts PCA-1 + 0.8 parts hydroxypropyl methylcellulose + 2.0 parts ethylene glycol + 0.3 parts BYK-024, stir at 500 r / min for 15 min;

[0090] Cement-based slurry preparation: Add the modified additive solution to the inorganic base material and stir at 600 r / min for 5 min;

[0091] Preparation of building exterior wall materials: Example 3: The repair material was added to cement-based slurry and stirred at 500 r / min for 8 min.

[0092] Comparative Example 1.

[0093] Mix 30 parts of 42.5 grade ordinary silicate cement, 50 parts of quartz sand, 15 parts of building gypsum, 4 parts of redispersible latex powder, and 1 part of hydroxypropyl methylcellulose evenly. Add 18 parts of deionized water and stir at 500 r / min for 10 min to form cement mortar repair material.

[0094] Comparative Example 2.

[0095] Raw materials: 20 parts of 42.5 grade ordinary Portland cement, 35 parts of quartz sand, 25 parts of ceramsite, 3 parts of nano TiO2, 10 parts of acrylic emulsion, 0.8 parts of polycarboxylate superplasticizer, 0.2 parts of defoamer, and 18 parts of deionized water;

[0096] Preparation method: First, dry mix cement, quartz sand, and ceramsite for 2 minutes, then add nano-TiO2, water-reducing agent, defoamer, and deionized water, and stir at 600 r / min for 5 minutes. Finally, add acrylic emulsion and stir at 500 r / min for 3 minutes to form a single photocatalytic self-healing exterior wall material.

[0097] Example of an effect 1.

[0098] The repair performance of the repair materials of Examples 1-3 and Comparative Example 1 was tested.

[0099] First, several C30 concrete test blocks (200mm×200mm×100mm) commonly used in frigid northern regions were prepared. These blocks were then subjected to a -20℃ freezing / 20℃ thawing cycle to create simulated freeze-thaw cracks 1mm wide and 1mm deep. The cracks were then physically filled and repaired using the repair materials from Examples 1-3 and Comparative Example 1, respectively.

[0100] 1. After repair, the temperature was -20℃ and the maximum heat output was 300 μW / cm. 2 Curing was performed for 7 days under ultraviolet light (simulating winter) and at 15℃ and 75% relative humidity (simulating spring). The remaining crack width was measured using a crack width meter. The crack repair rate was calculated as (initial crack width - remaining crack width) / initial crack width × 100%.

[0101] 2. The repaired test block was subjected to an artificial accelerated aging test, which involved 50 freeze-thaw cycles of -20℃ to 20℃ and 100 temperature fluctuations (-30℃ to 25℃) to simulate the rate of crack re-cracking after one year.

[0102] 3. After 28 days of repair, the compressive strength of the test block was measured, and the compressive strength recovery rate was calculated as: (Repaired strength / Original substrate strength) × 100%.

[0103] The test results are shown in Table 1.

[0104] Table 1

[0105]

[0106] The experimental data shows that the building exterior wall freeze-thaw crack repair material of this invention solves the technical pain points of traditional physical filling repair materials, such as slow repair in winter, easy recurrence in spring, and poor strength recovery.

[0107] Under simulated winter conditions, the 7-day crack repair rate of Examples 1-3 reached 78%-85%, which is 2.2-2.4 times that of Comparative Example 1. Under simulated spring conditions, the repair rate of Examples 1-3 further increased to 83%-90%, which is 2.1-2.3 times that of Comparative Example 1. This is because the repair material of this invention contains dual repair components: N-TiO2@PANI composite particles and Bacillus pasteurellii microcapsules. In the weak ultraviolet environment of winter, N-TiO2@PANI can respond to 300 μW / cm². 2 Under weak ultraviolet light, the photoinitiator HMPP accelerates the polymerization of organic monomers, forming an elastic gel that quickly fills cracks. In the humid spring environment, microcapsules release Bacillus pasteurellii, which utilizes nutrients to generate calcium carbonate crystals, achieving deep crack healing. In contrast, the traditional cement mortar in Comparative Example 1 relies solely on physical filling. In winter, the mortar hardens slowly and is prone to shrinkage and cracking at low temperatures. In spring, the filler is easily washed away by rain, resulting in a repair efficiency far lower than that of this invention.

[0108] The PEG-SS-PEG dynamic crosslinking agent added in this invention can form a stretchable elastic network after crack healing, buffering the stress from temperature fluctuations from -30℃ in winter to 25℃ in spring in northern regions, thus preventing secondary cracking at the interface. Simultaneously, the calcium carbonate crystals generated by microorganisms are tightly bonded to the substrate and are not easily detached due to freeze-thaw cycles. Therefore, the crack recurrence rate is extremely low, and durability is significantly improved. In contrast, the cement mortar in Comparative Example 1 is rigid and inelastic, and is prone to shrinkage differences with the substrate during temperature fluctuations, leading to rapid crack recurrence.

[0109] The organic gel and inorganic crystals of the repair material of this invention form an elastic rigid composite structure, which not only fills the surface cracks, but also penetrates into the deep cracks to repair the internal damage of the substrate; while the cement mortar of Comparative Example 1 only fills the surface, and the deep cracks still exist, resulting in insufficient strength recovery.

[0110] Comparative Example 2.

[0111] The performance of the building exterior wall materials in Examples 4-6 and Comparative Example 2 was tested.

[0112] The building exterior wall materials from Examples 4-6 and Comparative Example 2 were loaded into the mold in two stages: First, the material was filled to half the mold height and vibrated for 10 seconds to remove air bubbles; second, the mold was filled completely and vibrated for another 15 seconds until no obvious air bubbles overflowed from the surface. Excess slurry on the mold surface was smoothed with a scraper, and the mold was placed on a pressure molding machine, applying a pressure of 15 MPa and holding for 3 minutes. After demolding, the samples were placed in a standard curing chamber for 28 days. The sample dimensions were 100mm × 100mm × 100mm.

[0113] 1. Start the compression testing machine, place the specimen stably in the center of the lower platen of the testing machine, and apply a uniform loading rate of 0.5 MPa / s. Observe the surface condition of the specimen and record the maximum pressure value (F, unit kN) at the moment of specimen failure; calculate the compressive strength f = F / A × 10 -3 (Unit: MPa) The average of three valid data points for each group is taken as the 28-day compressive strength of the material in that group.

[0114] 2. Dry the sample in an oven, cool it to room temperature, and weigh the initial mass m0 using an electronic balance;

[0115] The initial length L0 of the sample was measured with vernier calipers, and the initial compressive strength f0 was measured. The two ends of the sample were sealed with waterproof sealant (only four sides were left to contact the freeze-thaw environment to simulate the freezing of the exterior wall facade). The sample was placed at room temperature for 24 hours to allow the sealant to cure.

[0116] Start the rapid freezing test chamber and set the cycle parameters: -20℃±2℃ freezing for 4h → 20℃±2℃ warm water (distilled water) thawing for 4h, one cycle for a total of 8h; completely immerse the sealed sample in the water of the test chamber, start the cycle, and perform 50 freeze-thaw cycles; after the cycle is completed, take out the sample, wipe the surface moisture with a dry cloth, cool to room temperature, remove the sealant at both ends of the sample, weigh the mass m1 after freeze-thaw, measure the length L1 after freeze-thaw, and test the compressive strength f1 after freeze-thaw.

[0117] Calculate the mass loss rate Δm = (m0 - m1) / m0 × 100% and the strength loss rate Δf = (f0 - f1) / f0 × 100%; take the average value of 3 samples in each group and record the results.

[0118] 3. Self-healing performance test of freeze-thaw cracks:

[0119] Start the rapid freezing test chamber and perform 100 freeze-thaw cycles. Use a crack width meter to select samples with a maximum crack width of 0.5mm ± 0.02mm and a crack depth of 30~50mm as the samples for this test, and record the initial crack width w0 of each sample.

[0120] At -20℃, 300μW / cm 2 The sample with cracks was placed in a box and cured for 7 days under ultraviolet light for 6 hours a day without additional humidification (simulating winter). The surface of the cracks was observed at a fixed time every day during the curing period, and the repair process was not interfered with.

[0121] In an environment of 15℃ and 75% relative humidity, without ultraviolet radiation (simulating spring), the sample containing cracks was placed in a box and continuously cured for 7 days. During this period, the surface of the cracks was observed daily, and the repair process was not interfered with.

[0122] Take out the sample and place it in an environment of 25℃±2℃ for 2 hours. Use a handheld laser crack width meter to repeatedly measure the width at 8 points along the crack length direction, and take the maximum value as the remaining crack width w1.

[0123] Calculate the self-repair rate η = (initial crack width w0 - remaining crack width w1) / initial crack width w0 × 100% (if w1 = 0, it means the crack is completely closed, η = 100%; if w1 > w0, it means the repair has failed, η = 0).

[0124] The test results are shown in Table 2.

[0125] Table 2

[0126]

[0127] Based on the experimental results, it can be determined that the exterior wall material of the present invention has comprehensive performance advantages in terms of strength, frost resistance, and self-healing compared with the prior art.

[0128] This invention utilizes a high-density inorganic framework formed by the compounding of quartz sand and shale ceramics. The synergistic hydration of β-hemihydrate gypsum and P•O42.5 cement further enhances the material's density. Simultaneously, the self-healing component contributes to the strength of the undiluted inorganic matrix. The 28-day compressive strength of Examples 4-6 reached 25.2-27.5 MPa, representing a 13%-23% increase compared to Comparative Example 2.

[0129] The ethylene glycol added in this invention can lower the freezing point of the substrate, preventing moisture expansion from damaging the pores during freeze-thaw cycles; nano-calcium carbonate fills the micropores, reducing the channels for moisture penetration; and short-cut cellulose fibers can inhibit the propagation of microcracks caused by freeze-thaw cycles. After 50 freeze-thaw cycles, the mass loss rate of Examples 4-6 was only 3.9%-4.8%, and the strength loss rate was only 11.2%-14.5%, both significantly lower than Comparative Example 2.

[0130] The exterior wall material of this invention contains a dual self-healing system of N-TiO2@PANI and Bacillus pasteurellium microcapsules. In winter, weak ultraviolet light triggers photocatalytic polymerization, while in spring, temperature and humidity activate microbial mineralization, making it suitable for all-season environments in northern regions. Under simulated winter conditions, the self-healing rate of Examples 4-6 reaches 84%-88%, which is 1.9-2.0 times that of Comparative Example 2. Under simulated spring conditions, the repair rate of the Examples reaches 90%-94%, which is 2.5-2.6 times that of Comparative Example 2. In contrast, Comparative Example 2 relies solely on nano-TiO2, resulting in low repair efficiency under weak ultraviolet light in winter and a significantly reduced repair rate in spring due to the absence of a microbial system.

[0131] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A freeze-thaw crack repair material for architectural exterior walls, characterized by, The components include the following mass fractions: Butyl acrylate, 28-32 parts; glycidyl methacrylate, 18-22 parts; ethyl p-methoxycinnamate, 9-11 parts; PEG-S-S-PEG, 4.5-5.5 parts; N-TiO2@PANI composite particles, 3.5-4.5 parts; Bacillus pasteurii microcapsules, 7-9 parts; nutrient salt microcapsules, 7-9 parts; photoinitiator HMPP, 0.5 parts; The N-TiO2@PANI composite particles are obtained by first reacting a nitrogen source aqueous solution and a tetrabutyl titanate-ethanol solution to obtain N-TiO2, and then reacting the N-TiO2 with aniline monomers and ammonium persulfate; The Bacillus pasteurii microcapsules are obtained by the following steps: The Bacillus pasteurii bacterial solution is mixed with a sodium alginate aqueous solution, and then atomized and dropped into a calcium chloride solution to form microcapsules, which are collected by filtration. Then, a chitosan acetic acid solution is added and stirred to obtain an inner layer microcapsule. A PCL-nutrient salt-tween 80 mixed solution is uniformly coated on the surface of the inner layer microcapsule in a spraying manner to obtain the Bacillus pasteurii microcapsule.

2. The building exterior wall freeze-thaw crack repair material according to claim 1, characterized by, The specific preparation steps of the N-TiO2@PANI composite particles include: A hydrochloric acid solution is added dropwise to the urea aqueous solution to adjust the pH to 2-3 to obtain a nitrogen source aqueous solution; The nitrogen source aqueous solution is added to the tetrabutyl titanate-ethanol solution, and continuous stirring is performed to form a milky sol, which is transferred to a polytetrafluoroethylene reaction kettle. The reaction is carried out at 180°C for 12 hours, and then cooled to room temperature. The product is centrifuged to collect the precipitate, which is repeatedly washed until the pH of the supernatant is 6-7, and then dried to obtain N-TiO2 powder; The N-TiO2 powder is added to anhydrous ethanol and ultrasonically dispersed for 30 minutes, and then aniline monomers are added. The stirring is continued for 1 hour to obtain an N-TiO2-aniline dispersion liquid; Under the conditions of continuous stirring and ice bath, an ammonium persulfate aqueous solution is slowly added dropwise into the N-TiO2-aniline dispersion liquid. After the addition is completed, the reaction is continued in the ice bath for 6 hours. After the reaction is completed, the precipitate is collected by centrifugal separation, washed with anhydrous ethanol, and dried to obtain N-TiO2@PANI composite particles.

3. The building exterior wall freeze-thaw crack repair material according to claim 1, characterized by, The specific preparation steps of the Bacillus pasteurii microcapsule include: A bacterial liquid of 10 9 CFU / mL of Paenibacillus popilliae was slowly added to a sodium alginate aqueous solution on a sterile operating table, mixed uniformly, and the viscosity was adjusted to 500-600 mPa•s with deionized water; The spray dryer feed tank is added, the inlet temperature is set to 125°C, the outlet temperature is set to 55°C, the feeding rate is set to 5mL / min, a 10% calcium chloride solution is added to the receiving tank, the atomized particles fall into the calcium chloride solution, and stirring is performed for 30 minutes. Subsequently, the gel microspheres are collected by filtration, washed with deionized water, and then added to a chitosan acetic acid solution to form a sodium alginate-chitosan composite inner layer film by stirring. The composite microcapsules are collected by filtration, washed with deionized water until the pH of the filtrate is 6-7, and then vacuum dried to obtain the inner layer microcapsule. The polycaprolactone is added into dichloromethane in a ratio of 8g:92mL, stirred and dissolved, and then 0.5g Tween 80, 10g calcium chloride, and 6g dipotassium hydrogen phosphate are added in a ratio of 8g polycaprolactone:0.5g Tween 80:10g calcium chloride:6g dipotassium hydrogen phosphate, and stirring is continued to obtain a PCL-nutrient salt-Tween 80 mixed solution; the inner layer microcapsules are uniformly spread on the receiving plate of an electrostatic spraying instrument, and the PCL-nutrient salt-Tween 80 mixed solution is uniformly coated on the surface of the inner layer microcapsules at a spraying rate of 2mL / h; then vacuum drying treatment is performed at 40℃ for 4h to obtain bacillus pasteurii microcapsules.

4. A method for preparing the freeze-thaw crack repair material for building exterior walls according to any one of claims 1 to 3, characterized by, The method comprises the following steps: S1, the butyl acrylate, glycidyl methacrylate, ethyl p-methoxycinnamate are mixed and stirred until the system is uniform and transparent; S2, PEG-S-S-PEG is added while stirring, followed by the addition of HMPP, and stirring is continued to form an organic monomer matrix pre-mixture; S3, twice the amount of the organic monomer matrix pre-mixture is added to the N-TiO2@PANI composite particles, and ultrasonic treatment is performed to obtain an N-TiO2@PANI dispersion slurry; The N-TiO2@PANI dispersion slurry is pumped into the remaining organic monomer matrix pre-mixture while stirring to form an organic monomer-N-TiO2@PANI composite matrix; S4, after the bacillus pasteurii microcapsules and the nutrient salt microcapsules are mixed, ethanol is added to improve the wettability of the microcapsule surface, and then the mixed microcapsules are added to the organic monomer-N-TiO2@PANI composite matrix and stirred uniformly to obtain a freeze-thaw crack self-repairing material for building exterior walls.

5. The method of claim 4, wherein the freeze-thaw crack repair material for an exterior wall of a building is prepared by mixing the water-soluble polymer and the water-soluble inorganic salt in water, and then drying the mixture. The stirring speed in step S1 is 300r / min; and the stirring speed in step S2 is 500r / min.

6. The method for preparing the self-healing material for freeze-thaw cracks in building exterior walls according to claim 4, characterized in that, The ultrasonic treatment in step S2 uses an ultrasonic disperser with a power of 300W and a frequency of 20kHz; The stirring speed in step S2 is 800r / min.

7. The method of claim 4, wherein the freeze-thaw crack repair material for an exterior wall of a building is prepared by mixing the water-soluble polymer, the water-soluble inorganic salt, and the water. The amount of ethanol used in step S4 is 10% of the total mass of the bacillus pasteurii microcapsules and the nutrient salt microcapsules.

8. A building exterior material, characterized by, The components in the freeze-thaw crack repairing material for building exterior walls in any one of claims 1-3 further comprise components: Quartz sand, 30-35 parts; shale ceramsite, 20-25 parts; P·O 42.5 cement, 15-18 parts; β-semihydrated gypsum powder, 5-7 parts; polycarboxylic acid type water reducing agent, 0.8-1.2 parts; hydroxypropyl methylcellulose, 0.5-0.8 parts; ethylene glycol, 1.5-2.0 parts; silicone type defoamer, 0.2-0.3 parts; Nano calcium carbonate, 1.0-1.5 parts; short-cut cellulose fiber, 1.0-1.5 parts; The particle size of the quartz sand is 0.15-0.6mm, the particle size of the nano calcium carbonate is 50-100nm, and the length of the short-cut cellulose fiber is 3-5mm.

9. The building exterior wall material according to claim 8, wherein The silicone type defoamer is specifically BYK-024 or teg Foamex 810; and the polycarboxylic acid type water reducing agent is specifically PCA-1 or JM-PCA.

10. A method of producing a building exterior wall material as claimed in claim 8 or 9, characterized in that, The method comprises the following steps: Mixing quartz sand, shale ceramsite, nano calcium carbonate, and short-cut cellulose fiber, and stirring uniformly in a blender at a speed of 400 r / min to obtain a mixed aggregate; Adding P·O 42.5 cement and β-hemihydrate gypsum powder, and continuously stirring uniformly at a speed of 400 r / min to form an inorganic base; Adding polycarboxylate superplasticizer, hydroxypropyl methylcellulose, ethylene glycol, and silicone defoamer into deionized water, wherein the amount of the deionized water is 15% to 20% of the total mass of the inorganic base, and stirring until completely dissolved, and then adding the inorganic base, and stirring uniformly at a speed of 600 r / min to form a cement-based slurry; Applying the preparation method of any one of claims 4 to 7 to prepare a freeze-thaw crack repairing material for building exterior walls, and adding the cement-based slurry, and stirring uniformly at a speed of 500 r / min to obtain a self-repairing building exterior wall material.

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