Cement-based permeable nanocrystal self-repairing waterproof admixture and preparation method thereof

Abstract

The invention discloses a cement-based permeable nanocrystal self-repairing waterproof admixture and a preparation method thereof, and belongs to the technical field of building materials. The admixture is composed of quick-hardening sulphoaluminate cement, nano silicon dioxide, nano anhydrous calcium carbonate, bacillus pasteurii and the like, nanoparticles are subjected to surface modification through a silane coupling agent, microorganisms are embedded through sodium alginate to form microcapsules, the mineral activity is improved in combination with ball milling treatment, and a chemical expansion and microorganism mineralization double-repair system is constructed. After the nano-powder is modified, the dispersity is improved by 60%, pores of 10-50 nm can be filled, the survival rate of spores can reach 85% or above through microbial embedding, activation is conducted within 48 hours when the nano-powder meets water, the self-repairing efficiency of a double-repairing system on cracks of 0.1-0.3 mm is larger than or equal to 90%, and the anti-permeability pressure recovery rate after repairing is larger than or equal to 80%. The 7d anti-permeability pressure of the product is greater than or equal to 1.2 MPa, and the 28d anti-permeability pressure of the product is greater than or equal to 1.6 MPa, and the product has early-stage rapid repairing and long-term waterproof performance, solves the problems of insufficient durability and low self-repairing efficiency of a traditional material, and is suitable for underground engineering, bridges, tunnels and other scenes.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a cement-based penetrating nano-crystallization self-repairing waterproof admixture. Background Art

[0002] Traditional cement-based waterproofing materials face the core challenges of insufficient passive protection and durability. The impermeability pressure of ordinary concrete is typically ≤1.0 MPa, and crack permeability increases exponentially over time after 28 days, shortening the structural service life by 30%-50%. Passive repair methods rely on manual intervention. For example, the use of multiple layers of paint in a hotel corridor increased repair costs by 40% and extended the construction period by 20%. While self-repair technology holds great promise, microbial mineralization technology faces bottlenecks such as low spore survival rates and poor nanomaterial dispersion. Existing technologies often require specialized equipment such as ultrasonic dispersion and spray drying, increasing production costs by 30%-50%, and exhibiting significant quality fluctuations, with a standard deviation in impermeability pressure reaching 0.12 MPa.

[0003] The performance degradation of traditional waterproofing materials is particularly significant in complex environments. In low-temperature environments, the risk of brittle cracking of asphalt-based waterproofing membranes below -25°C increases dramatically. In a residential complex in Changchun, the roof leakage rate reached as high as 70% during the extreme winter because the waterproofing materials did not meet the cold resistance standard of -30°C. In high-temperature and high-humidity environments, the internal porosity of ordinary concrete increases due to water migration. In a chemical workshop, the concrete floor pressure decreased by 40% within three years due to chemical corrosion. In addition, the corrosion of steel bars caused by chloride ion penetration in marine engineering has shortened the service life of traditional concrete structures to less than 50% of the design value. For example, after using traditional repair solutions for the piers of a cross-sea bridge, they needed to be reinforced within five years due to secondary corrosion.

[0004] This patented technology, through a comprehensive innovation chain encompassing nanodispersion, microbial encapsulation, composite repair, and process optimization, systematically addresses industry challenges such as the limited durability of traditional waterproofing technologies, poor dispersibility of self-healing materials, and low microbial activity. Its core value lies in the creation of an intelligent response system that rapidly arrests early chemical expansion and permanently repairs with later microbial mineralization. Furthermore, through process innovation, it achieves low-cost and high-stability industrial production. Summary of the Invention

[0005] To solve the problems of insufficient durability of traditional waterproofing technology, poor dispersion of self-repairing materials and low microbial activity.

[0006] In order to solve the above problems, the present invention provides the following technical solutions: Cement-based penetrating nano-crystallization self-repairing waterproof admixture, including the following components: 20-30 parts of fast-hardening sulphoaluminate cement, 15-20 parts of quartz sand, 5-10 parts of silica fume, 3-5 parts of nano-silicon dioxide, 2-5 parts of nano-anhydrous calcium carbonate, 8-10 parts of metakaolin, 1-3 parts of potassium aluminum sulfate, 3-5 parts of ettringite-type expansion agent, 0.5-1 part of Bacillus pasteurianus, 0.2-0.5 part of sodium gluconate, 0.5-1 part of polycarboxylic acid-based high-efficiency water reducer, 0.5-1 part of nano-titanium dioxide, and 0.1-0.5 part of methyl cellulose Preferably, the potassium aluminum sulfate is 1-3 parts and the ettringite-type expansive agent is 3-5 parts so that the 56d anti-seepage pressure of the concrete added with the admixture is ≥1.6MPa.

[0007] Preferably, the nano-silicon dioxide is 3-5 parts and the silica fume is 5-10 parts, so that the CSH gel formed after cement hydration fills the capillaries.

[0008] Preferably, the waterproof admixture has an anti-seepage pressure of ≥1.2 MPa at 7 days and ≥1.6 MPa at 28 days, a self-repairing efficiency of ≥90% for cracks with a diameter of 0.1-0.3 mm, and an anti-seepage pressure recovery rate of ≥80% after self-repair.

[0009] Preferably, the Bacillus pasteurianus is encapsulated in sodium alginate according to claim 3 to form microcapsules with a diameter of 0.5-1 mm, which are released in contact with water to repair cracks.

[0010] Preferably, the ettringite-type expansion agent and Bacillus pasteurianus form a dual repair system of chemical expansion and microbial mineralization, and the self-repair efficiency of cracks with a diameter of 0.1-0.3 mm is ≥90%.

[0011] The preparation method of cement-based penetrating nano-crystallization self-repairing waterproof admixture is characterized by comprising the following steps: S1: Mix nano-silica, nano-anhydrous calcium carbonate, nano-aluminum sulfate and nano-titanium dioxide in proportion, add silane coupling agent, and stir in a high-speed mixer to improve dispersibility through surface hydroxylation reaction and avoid agglomeration; S2: Mix Bacillus pasteurianus spores with sodium alginate solution, drop into CaCl2 solution to form sodium alginate microcapsules, filter and dry them for later use to prevent the spores from being inactivated in the dry powder; S3: Silica fume, metakaolin, and potassium aluminum sulfate are mixed in proportion and put into a ball mill for grinding to control the specific surface area and promote the formation of ettringite and CSH gel crystallization during cement hydration; S4: Mix the ettringite expansion agent, embedded microbial capsules, sodium gluconate, naphthalene-based early strength water-reducing agent and methyl cellulose, and pass through a 200-mesh sieve to ensure uniform powder; S5: First, put the basic gelling system into a double-axis zero-gravity mixer and stir to form a uniform carrier; then add the nanocrystalline active component and continue stirring to evenly disperse the nanoparticles in the gelling material; finally, add the self-repairing functional component and mix at a low speed to avoid damaging the microbial capsule structure.

[0012] Preferably, in S1, high-speed stirring is performed at 800-1200 r / min for 15-20 min, and the silane coupling agent accounts for 0.5-1.0% of the nanopowder.

[0013] Preferably, the specific surface area of the silica fume-metakaolin after ball milling in S3 is ≥400 m² / kg and the particle size D50 is ≤10 μm.

[0014] Preferably, in the nano-dispersion stage of S5, the speed is 800-1000 r / min, the microbial mixing stage is ≤200 r / min, and the temperature is controlled at ≤35°C throughout the whole process.

[0015] Effects and advantages of the cement-based penetrating nano-crystallization self-repairing waterproof admixture of the present invention: 1. This patent uses 0.5%-1% silane coupling agent propyltrimethoxysilane to perform surface hydroxylation treatment on nano-silica / calcium carbonate / titanium dioxide, so that the surface of the nanoparticles changes from hydrophilic to amphiphilic. Under high-speed stirring at 800-1200r / min, the agglomerates are broken down to a monodisperse state of 20-30nm, and the dispersion uniformity is improved by 60%.

[0016] 2. This patent uses monodisperse nanoparticles to fill 10-50nm capillaries in the early stages of cement hydration, increasing the proportion of harmless pores with a pore size of less than 50nm from 45% to 72%, directly contributing to the early densification effect of a 7d anti-seepage pressure ≥1.2MPa.

[0017] 3. This patent uses an ionic cross-linked network formed by 2%-3% sodium alginate solution and 5%-10% CaCl2 to encapsulate Bacillus pasteurianus spores in 0.5-1mm microcapsules. During the drying process, the spore survival rate is increased from 40% in the exposed state to 85%, solving the problem of microbial inactivation during dry powder storage.

[0018] 4. In this patent, the sodium alginate shell swells and ruptures within 30 minutes after coming into contact with water, releasing Bacillus. The urease secreted by Bacillus can catalyze urea in the surrounding environment to produce calcium carbonate, forming a mineralized deposition layer with a thickness of 20-50μm on the surface of 0.1-0.3mm cracks. The repair efficiency is increased by 15% compared with the non-embedded process.

[0019] 5. This patent uses a ball mill to grind silica fume, metakaolin, and potassium aluminum sulfate for 2-3 hours to achieve a specific surface area of 450-500m 2 / kg, the exposure of silica fume glass phase active sites increased by 3 times, the dissolution rate of Al2O3 in metakaolin increased by 40%, and the synergistic formation of ettringite crystal CSH gel was promoted during cement hydration.

[0020] 6. In this patent, ettringite fills medium-sized pores of 100-500nm, and CSH gel further fills nano-scale pores, reducing the total porosity of 28d concrete from 22% to 15%, and the connected porosity from 12% to 5%, and the anti-seepage pressure is increased by 40% compared with the unground process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart for preparing the cement-based penetrating nano-crystallization self-repairing waterproof admixture of the present invention. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention. It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus. In the absence of further restrictions, the elements defined by the sentence "include..." do not exclude the presence of other identical elements in the process, method, article or apparatus that includes the elements. Example 1

[0023] This embodiment provides a method for preparing a cement-based penetrating nano-crystalline self-repairing waterproof admixture, which is applicable to the field of building materials. The following implementation contents are provided: Purpose of the experiment: A cement-based penetrating nano-crystallization self-repairing waterproof admixture is prepared.

[0024] Experimental materials: 20 parts of fast-hardening sulphoaluminate cement, 15 parts of quartz sand, 5 parts of silica fume, 3 parts of nano-silica, 2 parts of nano-anhydrous calcium carbonate, nano-aluminum sulfate, 8 parts of metakaolin, 1 part of potassium aluminum sulfate, 3 parts of ettringite-type expansion agent, 0.5 parts of Bacillus pasteurianus, 0.2 parts of sodium gluconate, 0.5 parts of polycarboxylic acid-based high-efficiency water reducer, 0.5 parts of nano-grade titanium dioxide, 0.1 parts of methyl cellulose, and 0.8 parts of naphthalene-based early strength water reducer.

[0025] Experimental equipment: SB-CL-443 forced concrete mixer, SB-CL-714 microcomputer-controlled hybrid servo pressure testing machine, SB-CL-599 concrete impermeability tester Experimental steps: S1: Mix nano-silica, nano-anhydrous calcium carbonate, nano-aluminum sulfate and nano-titanium dioxide in appropriate proportions, add 0.5%-1% silane coupling agent, and stir in a high-speed blender at 800-1200 r / min for 15-20 minutes to improve dispersion and avoid agglomeration through surface hydroxylation reaction; S2: Mix Bacillus pasteurianus spores with sodium alginate solution and drop them into CaCl2 solution to form sodium alginate microcapsules with a diameter of 0.5-1 mm. Filter and dry them for later use to prevent the spores from being inactivated in the dry powder. S3: Mix silica fume, metakaolin and potassium aluminum sulfate in proportion, put them into a ball mill and grind them for 2-3 hours, and control the specific surface area to be ≥400m 2 / kg, promoting the formation of ettringite and CSH gel crystallization during cement hydration; S4: Mix the ettringite expansion agent, embedded microbial capsules, sodium gluconate, naphthalene-based early strength water-reducing agent and methyl cellulose, and pass through a 200-mesh sieve to ensure uniform powder; S5: First, put the basic gelling system into a double-shaft zero-gravity mixer and stir at 500-800 r / min for 10 minutes to form a uniform carrier; then add the nanocrystalline active component and continue stirring for 10-15 minutes to evenly disperse the nanoparticles in the gelling material; finally, add the self-repairing functional component and mix at a low speed of 100-200 r / min for 8-10 minutes to avoid damaging the microbial capsule structure.

[0026] Experimental results: See Table 1 for details.

[0027] Table 1: Test results of Example 1 Nanopowder particle size distribution Survival rate of Bacillus pasteurianus spores Sodium alginate microcapsule particle size Active ingredient content Crack self-healing rate Microbial activation time Example 1 D50≤50nm Dry state survival rate ≥90% 0.5-1mm particle size accounts for ≥95% Characteristic peak intensity accounts for ≥85% ≥60% in 7 days, ≥85% in 2 days ≤48h The cement-based penetrating nano-crystalline self-repairing waterproof admixture prepared in Example 1 exhibits excellent comprehensive performance. The nano-powder particle size distribution is concentrated, and after surface modification, it has good dispersibility. It can effectively penetrate the cement matrix and promote crystal growth. The survival rate of Bacillus pasteurianus spores in a dry state is ≥90%, and the particle size of sodium alginate microcapsules is controlled at 0.5-1mm and accounts for ≥95%, ensuring that the activity of microorganisms in a dry powder environment is stable and can be quickly activated after contact with water. The characteristic peak intensity of the active component accounts for ≥85%, indicating that the reaction activity of raw materials such as silica fume and kaolin is significantly improved after grinding, and the calcium aluminate expansion agent and nano-crystalline material form a multiple waterproof system. The self-healing performance of the cracks is outstanding, with a self-healing rate of ≥60% in 7 days and ≥85% in 28 days. It has both early repair and long-term waterproofing effects, and is suitable for building waterproofing scenarios that require rapid response and long-lasting self-repairing capabilities. Example 2

[0028] This embodiment provides a method for preparing a cement-based penetrating nano-crystallized self-repairing waterproof admixture, which is characterized by different raw material ratios, and the following implementation content: Purpose of the experiment: Preparation of a cement-based penetrating nanocrystalline self-repairing waterproof admixture Experimental materials: 25 parts of fast-hardening sulphoaluminate cement, 18 parts of quartz sand, 7 parts of silica fume, 4 parts of nano-silica, 3 parts of nano-anhydrous calcium carbonate, nano-aluminum sulfate, 9 parts of metakaolin, 2 parts of potassium aluminum sulfate, 4 parts of ettringite-type expansion agent, 0.7 parts of Bacillus pasteurianus, 0.3 parts of sodium gluconate, 0.7 parts of polycarboxylic acid-based high-efficiency water reducer, 0.8 parts of nano-grade titanium dioxide, 0.3 parts of methyl cellulose, and 0.8 parts of naphthalene-based early strength water reducer.

[0029] Experimental steps: S1: Mix nano-silica, nano-anhydrous calcium carbonate, nano-aluminum sulfate and nano-titanium dioxide in appropriate proportions, add 0.5%-1% silane coupling agent, and stir in a high-speed blender at 800-1200 r / min for 15-20 minutes to improve dispersion and avoid agglomeration through surface hydroxylation reaction; S2: Mix Bacillus pasteurianus spores with sodium alginate solution and drop them into CaCl2 solution to form sodium alginate microcapsules with a diameter of 0.5-1 mm. Filter and dry them for later use to prevent the spores from being inactivated in the dry powder. S3: Mix silica fume, metakaolin and potassium aluminum sulfate in proportion, put them into a ball mill and grind them for 2-3 hours, and control the specific surface area to be ≥400m 2 / kg, promoting the formation of ettringite and CSH gel crystallization during cement hydration; S4: Mix the ettringite expansion agent, embedded microbial capsules, sodium gluconate, naphthalene-based early strength water-reducing agent and methyl cellulose, and pass through a 200-mesh sieve to ensure uniform powder; S5: First, put the basic gelling system into a double-shaft zero-gravity mixer and stir at 500-800 r / min for 10 minutes to form a uniform carrier; then add the nanocrystalline active component and continue stirring for 10-15 minutes to evenly disperse the nanoparticles in the gelling material; finally, add the self-repairing functional component and mix at a low speed of 100-200 r / min for 8-10 minutes to avoid damaging the microbial capsule structure.

[0030] Experimental results: See Table 2 for details.

[0031] Table 2: Test results of Example 2 Nanopowder particle size distribution Survival rate of Bacillus pasteurianus spores Sodium alginate microcapsule particle size Active ingredient content Crack self-healing rate Microbial activation time Example 2 80-150nm Dry state survival rate ≥85% 0.7-0.9mm 35-40% ≥80% in 28 days 3-5 days The cement-based penetrating nano-crystalline self-repairing waterproof admixture prepared in Example 2 exhibits good functionality and stability. After the nanopowder is surface-modified with a silane coupling agent, the particle size distribution is concentrated in the range of 80-150 nm, with excellent dispersibility, and can penetrate into the pores of the cement matrix to form a dense crystalline network. The survival rate of Bacillus pasteurianus spores in a dry state is ≥85%, and the particle size of sodium alginate microcapsules is controlled at 0.7-0.9 mm, which effectively protects the activity of microorganisms and can be activated 3-5 days after contact with water, ensuring the sustainability of the self-repair function. The active component content reaches 35%-40%, and the specific surface area meets the standard after ball milling treatment, significantly promoting the formation of calcium sulfonate and CSH gel, and enhancing the density of cement hydration products. The crack self-healing performance is outstanding, with a self-healing rate of ≥80% in 28 days. Through the dual mechanism of chemical expansion of calcium sulfonate expansion agent and microbial-induced calcium carbonate crystallization, self-repair of cracks below 0.3 mm is achieved. This admixture combines the penetration and crystallization ability of nanomaterials with the self-repair properties of microorganisms. It is suitable for building bases that are subject to long-term moisture or are prone to cracking. It can effectively improve the waterproof durability and self-maintenance ability of concrete structures, and has good application potential in underground engineering, bridges and tunnels. Example 3

[0032] This embodiment provides a method for preparing a cement-based penetrating nano-crystallized self-repairing waterproof admixture, which is characterized by different raw material ratios, and the following implementation content: Purpose of the experiment: Preparation of a cement-based penetrating nanocrystalline self-repairing waterproof admixture Experimental materials: 30 parts of fast-hardening sulphoaluminate cement, 20 parts of quartz sand, 10 parts of silica fume, 5 parts of nano-silicon dioxide, 5 parts of nano-anhydrous calcium carbonate, nano-aluminum sulfate, 10 parts of metakaolin, 3 parts of potassium aluminum sulfate, 5 parts of ettringite-type expansion agent, 1 part of Bacillus pasteurianus, 0.5 parts of sodium gluconate, 1 part of polycarboxylic acid-based high-efficiency water reducer, 1 part of nano-grade titanium dioxide, 0.5 parts of methyl cellulose, and 0.8 parts of naphthalene-based early strength water reducer.

[0033] Experimental steps: S1: Mix nano-silica, nano-anhydrous calcium carbonate, nano-aluminum sulfate and nano-titanium dioxide in appropriate proportions, add 0.5%-1% silane coupling agent, and stir in a high-speed blender at 800-1200 r / min for 15-20 minutes to improve dispersion and avoid agglomeration through surface hydroxylation reaction; S2: Mix Bacillus pasteurianus spores with sodium alginate solution and drop them into CaCl2 solution to form sodium alginate microcapsules with a diameter of 0.5-1 mm. Filter and dry them for later use to prevent the spores from being inactivated in the dry powder. S3: Mix silica fume, metakaolin, and potassium aluminum sulfate in proportion, put them into a ball mill and grind them for 2-3 hours to control the specific surface area to be ≥400m2 / kg, so as to promote the formation of ettringite and CSH gel crystallization during cement hydration; S4: Mix the ettringite expansion agent, embedded microbial capsules, sodium gluconate, naphthalene-based early strength water-reducing agent and methyl cellulose, and pass through a 200-mesh sieve to ensure uniform powder; S5: First, put the basic gelling system into a double-shaft zero-gravity mixer and stir at 500-800 r / min for 10 minutes to form a uniform carrier; then add the nanocrystalline active component and continue stirring for 10-15 minutes to evenly disperse the nanoparticles in the gelling material; finally, add the self-repairing functional component and mix at a low speed of 100-200 r / min for 8-10 minutes to avoid damaging the microbial capsule structure.

[0034] Experimental results: See Table 3 for details.

[0035] Table 3: Test results of Example 3 Nanopowder particle size distribution Survival rate of Bacillus pasteurianus spores Sodium alginate microcapsule particle size Active ingredient content Crack self-healing rate Microbial activation time Example 3 70-140nm Dry state survival rate ≥88% 0.7-0.9mm 40-45% ≥85% in 28 days 2-4 days The cement-based penetrating nano-crystallization self-repairing waterproof admixture prepared in Example 3 exhibits excellent comprehensive performance and optimized characteristics. After the nanopowder is modified with a silane coupling agent, the particle size distribution is concentrated in the range of 70-140 nm, with excellent dispersibility. It can efficiently penetrate the cement matrix and promote the formation of nano-scale crystalline products, significantly improving the matrix density. The survival rate of Bacillus pasteurianus spores in a dry state is ≥88%, and the particle size of sodium alginate microcapsules is stable at 0.7-0.9 mm. Combined with the increase in the amount of sodium gluconate, the activation time of microorganisms after contact with water is shortened to 2-4 days, greatly improving the self-repair response speed. The active component content reaches 40%-45%, and the specific surface area meets the standard after ball milling treatment. It synergizes the calcium sulfonate expansion agent and nanoparticles to enhance the generation efficiency of calcium sulfonate and CSH gel, and construct a multiple waterproof barrier. The self-healing performance of the cracks is significantly enhanced, with a self-healing rate of ≥85% in 28 days. Through the dual mechanism of chemical expansion filling and microbial-induced calcium carbonate crystallization, efficient self-repair of cracks below 0.3 mm is achieved.

[0036] Comparative Example 1

[0037] Provided is a preparation method for a traditional cement-based self-repairing waterproof admixture, which is suitable for traditional infrastructure construction, and the following implementation contents: Purpose of the experiment: A traditional cement-based self-repairing waterproof admixture is prepared.

[0038] Experimental materials: 40 parts of fast-hardening sulphoaluminate cement, 20 parts of quartz sand, 5 parts of silica fume, 8 parts of metakaolin, 3 parts of ettringite-type expansion agent, 2 parts of calcium sulphoaluminate micro-expansion agent, 0.1 part of sodium gluconate, 0.5 parts of polycarboxylic acid series, and 0.1 part of cellulose ether.

[0039] Experimental steps: S1: Pass silica fume and metakaolin through a 200-mesh sieve to remove impurities and ensure uniform particles. Crush the ettringite-type expansion agent and calcium sulfoaluminate micro-expansion agent and pass them through a 150-mesh sieve to control the particle size to ≤100μm to avoid agglomeration. S2: Add silica fume, metakaolin and calcium sulfoaluminate micro-expansion agent into the ball mill in proportion, grind at 300-500r / min for 2-3 hours, and control the specific surface area to be ≥450m 2 / kg, stimulates mineral activity and promotes uniform dispersion of expander; S3: Add retarder, water reducer and cellulose ether into a high-speed mixer and stir at 800-1000 r / min for 5-10 minutes to form a uniform admixture premix; S4: First, put the fast-hardening sulphoaluminate cement and quartz sand into a double-shaft zero-gravity mixer and stir at 200-300 r / min for 5 minutes to form a basic cementitious carrier. Then add the pre-ground active mineral-expansion agent composite component and continue stirring for 10-15 minutes until the color is uniform. Finally, add the admixture premix and mix at a low speed of 100-200 r / min for 8-10 minutes to avoid shear force damaging the expansion agent crystal structure. S5: The mixed admixture is passed through a 150-mesh sieve to remove agglomerated particles, sealed in a moisture-proof packaging bag, and stored in a dry environment to prevent the expander from absorbing moisture and becoming ineffective.

[0040] Experimental results: See Table 4 for details.

[0041] Table 4: Comparative Example 1 test results Nanopowder particle size distribution Survival rate of Bacillus pasteurianus spores Sodium alginate microcapsule particle size Active ingredient content Crack self-healing rate Microbial activation time Comparative Example 1 70-140nm Dry state survival rate ≥88% 0.7-0.9mm 40-45% ≥85% in 28 days 2-4 days The traditional cement-based self-healing waterproofing admixture prepared in Comparative Example 1 exhibits remarkable crack repair ability and structural density. Through the co-grinding of silica fume, metakaolin, and calcium sulfoaluminate micro-expansive, the active ingredient content reaches 40%-45%, and the specific surface area meets the standard. This effectively promotes cement hydration to form ettringite crystals and CSH gel, creating a dual waterproofing mechanism of chemical expansion and mineral filling. The 28-day crack self-healing rate is ≥85%, and it can effectively and independently repair shrinkage cracks smaller than 0.2 mm. This is primarily due to the volume compensation effect of the ettringite-type expansive agent and the secondary hydration reaction of the mineral admixture, which significantly reduces the matrix porosity and blocks the water penetration path. After screening, grinding, and multi-stage mixing of the raw materials, the particles are well dispersed and uniform. Although no nanomaterials or microbial components are introduced, the synergistic effect of traditional expansive agents and mineral admixtures still achieves excellent anti-seepage performance and self-healing effects. The admixture has stable workability, and the combination of water reducer and cellulose ether ensures the fluidity and water retention of the mixture, making it suitable for traditional concrete mixing processes. This solution relies on commonly used industrial raw materials and simple preparation processes, with controllable costs and strong compatibility. It is suitable for traditional infrastructure projects such as bridges, tunnels, and basements. Especially in cast-in-place concrete structures that are prone to shrinkage cracking, it can effectively improve waterproof durability and structural self-maintenance capabilities, and is both economical and practical.

[0042] The cement-based penetrating nanocrystalline self-repairing waterproof admixture prepared in Example 1 has the core advantages of nano-scale material dispersibility and microbial activity protection. After the nanopowder is modified with a silane coupling agent, the particle size distribution is concentrated, which can penetrate into the nano-scale pores of the cement matrix and promote the crystal growth of CSH gel and ettringite through surface hydroxylation reaction to form a dense waterproof network. After the Bacillus pasteurianus spores are embedded in sodium alginate microcapsules, the survival rate in the dry state is ≥90%, and the 0.5-1mm particle size accounts for ≥95%, ensuring rapid activation within 48 hours after contact with water. Sodium gluconate is used as a carbon source to trigger the self-repair mechanism of microbial-induced calcium carbonate crystallization. The characteristic peak intensity of the active component accounts for ≥85%, indicating that the reaction activity of mineral admixtures such as silica fume and metakaolin is fully stimulated. Combined with the chemical expansion effect of the ettringite expansion agent, a crack self-healing rate of ≥60% in 7 days and ≥85% in 28 days is achieved, combining early repair speed with long-term waterproof durability, and is suitable for precision building structures with high requirements for self-repair response speed.

[0043] Example 2 shows stable waterproof and crack repair performance through the optimization of raw material ratio and the coordination of dual self-repair mechanism. The particle size distribution of nanopowder is adjusted to 80-150nm, which expands the filling capacity of micron-sized pores while ensuring dispersibility. The survival rate of Bacillus pasteurianus spores is ≥85%, the particle size of sodium alginate microcapsules is controlled at 0.7-0.9mm, and the dosage of sodium gluconate is increased. The microbial activation time is stabilized at 3-5 days, ensuring the continuous release of the self-repair function. The active component content is 35%-40%, and the specific surface area of silica fume and metakaolin meets the standard after ball milling treatment, which promotes the formation of calcium aluminate and CSH gel. Combined with the osmotic crystallization effect of nanoparticles, the crack self-healing rate is ≥80% in 28 days, and cracks below 0.3mm can be repaired. This admixture balances the penetration ability of nanomaterials and the delayed response characteristics of microbial self-repair, and is suitable for building bases with long-term moisture and long crack development cycles, such as underground pipe corridors, water conservancy dams, etc.

[0044] Example 3 is characterized by a combination of highly active components and a rapid self-repair response. The dosage of nano-silica and calcium carbonate is increased, with a particle size distribution of 70-140nm. After modification with a silane coupling agent, it has excellent dispersibility, can effectively promote the formation of nano-scale crystalline products, and improve the density of the matrix. The survival rate of Bacillus pasteurianus spores is ≥88%. The dosage of sodium gluconate is increased to 0.5 parts, and the microbial activation time is shortened to 2-4 days, achieving rapid activation of the self-repair function. The active component content reaches 40%-45%, and the ettringite-type expansion agent and nanoparticles work synergistically to strengthen the dual mechanisms of chemical expansion and crystal filling. The 28-day crack self-healing rate is ≥85%, and the repair efficiency is close to that of Comparative Example 1. However, the secondary repair ability induced by microorganisms is stronger. It is particularly suitable for harsh environments with complex loads and sudden cracks, and performs outstandingly in rapid repair and long-lasting waterproofing.

[0045] Comparative Example 1 is a traditional cement-based self-repairing waterproof admixture. It relies on the synergistic effect of the expansion agent and the mineral admixture to achieve crack repair. No nanomaterials or microorganisms are introduced. The active component content is 40%-45% and the specific surface area is ≥450m 2 / kg, promoting cement hydration to form ettringite crystals and CSH gel, chemically expanding to fill shrinkage cracks smaller than 0.2mm, with a 28-day self-healing rate of ≥85%. The raw materials are screened and mixed in multiple stages to achieve uniform particle size. The combination of a water reducer and cellulose ether ensures ease of construction and workability. The process is simple, cost-effective, and compatible with conventional concrete mixing equipment, making it suitable for conventional infrastructure projects such as bridges and basements. However, due to the lack of the deep penetration of nanomaterials and the sustained repair effect of microorganisms, its early response to microcracks and long-term repair capabilities in complex environments are slightly inferior to those of the Example series.

[0046] Examples 1-3 all introduce nanomaterial modification and microbial self-repair systems, and construct multiple repair mechanisms through nanoparticle penetration crystallization and microbial induced mineralization reactions. Comparative Example 1 relies on the chemical expansion-pore filling effect of traditional expansion agents and mineral admixtures, and the technical route is more inclined to material densification. Examples 1-3 are significantly better than Comparative Example 1 in early crack self-healing rate, microbial activation speed, and nano-scale pore repair ability. Comparative Example 1 has advantages in cost, process simplicity and compatibility with traditional construction. The ultrafineness of nanopowders gives it stronger matrix penetration ability, which can repair nano-scale defects and improve the original density of concrete. The high-activity protection of microorganisms realizes the self-repair property of responding to water, which is especially suitable for areas with frequent rainy seasons or occasional leakage scenarios. The early repair efficiency is outstanding, with a 7-day self-healing rate of ≥60%, which meets the needs of modern buildings for early detection and early repair of cracks, and prevents small cracks from expanding into structural diseases. Those skilled in the art will appreciate that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented with electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0047] In addition, each functional module in each embodiment of the present application may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0048] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited to this. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0049] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection of the present invention.

Claims

1. Cement-based penetrating nano-crystallization self-repairing waterproof admixture, characterized in that: Includes the following components: 20-30 parts of fast-hardening sulphoaluminate cement, 15-20 parts of quartz sand, 5-10 parts of silica fume, 3-5 parts of nano-silicon dioxide, 2-5 parts of nano-anhydrous calcium carbonate, 8-10 parts of metakaolin, 1-3 parts of potassium aluminum sulfate, 3-5 parts of ettringite-type expansive agent, 0.5-1 part of Bacillus pasteurianus, 0.2-0.5 part of sodium gluconate, 0.5-1 part of polycarboxylic acid-based high-efficiency water reducer, 0.5-1 part of nano-grade titanium dioxide, 0.1-0.5 part of methyl cellulose, and 0.5-1 part of naphthalene-based early strength water reducer.

2. The cement-based penetrating nano-crystallization self-repairing waterproof admixture according to claim 1, characterized in that: The amount of the potassium aluminum sulfate is 1-3 parts and the amount of the ettringite-type expansive agent is 3-5 parts, so that the 56-day anti-seepage pressure of the concrete added with the admixture is ≥1.6 MPa.

3. The cement-based penetrating nano-crystallization self-repairing waterproof admixture according to claim 1, characterized in that: The nano-silicon dioxide is 3-5 parts and the silica fume is 5-10 parts, so that the CSH gel formed after the cement is hydrated can fill the capillaries.

4. The cement-based penetrating nano-crystallization self-repairing waterproof admixture according to claim 1, characterized in that: The waterproof admixture has an anti-seepage pressure of ≥1.2MPa at 7 days and ≥1.6MPa at 28 days, a self-repairing efficiency of ≥90% for cracks with a diameter of 0.1-0.3mm, and an anti-seepage pressure recovery rate of ≥80% after self-repair.

5. The cement-based penetrating nano-crystallization self-repairing waterproof admixture according to claim 1, characterized in that: The Bacillus pasteurianus is encapsulated in sodium alginate according to claim 3 to form microcapsules with a diameter of 0.5-1 mm, which are released when exposed to water to repair cracks.

6. The cement-based penetrating nano-crystallization self-repairing waterproof admixture according to claim 1, characterized in that: The ettringite-type expansion agent and Bacillus pasteurianus form a dual repair system of chemical expansion and microbial mineralization, and the self-repair efficiency of cracks with a diameter of 0.1-0.3 mm is ≥90%.

7. The method for preparing the cement-based penetrating nano-crystallization self-repairing waterproof admixture according to claims 1-6, characterized in that: The following steps are involved: S1: Mix nano-silica, nano-anhydrous calcium carbonate, nano-aluminum sulfate and nano-titanium dioxide in proportion, add silane coupling agent, and stir in a high-speed mixer to improve dispersibility through surface hydroxylation reaction and avoid agglomeration; S2: Mix Bacillus pasteurianus spores with sodium alginate solution, drop into CaCl2 solution to form sodium alginate microcapsules, filter and dry them for later use to prevent the spores from being inactivated in the dry powder; S3: Silica fume, metakaolin, and potassium aluminum sulfate are mixed in proportion and put into a ball mill for grinding to control the specific surface area and promote the formation of ettringite and CSH gel crystallization during cement hydration; S4: Mix the ettringite expansion agent, embedded microbial capsules, sodium gluconate, naphthalene-based early strength water-reducing agent and methyl cellulose, and pass through a 200-mesh sieve to ensure uniform powder; S5: First, put the basic gelling system into a double-shaft zero-gravity mixer and stir to form a uniform carrier; Then add the nanocrystalline active component and continue stirring to evenly disperse the nanoparticles in the gelling material. Finally, add the self-repairing functional component and mix at a low speed to avoid destroying the microbial capsule structure.

8. The method for preparing the cement-based penetrating nano-crystallization self-repairing waterproof admixture according to claim 7, characterized in that: In the S1, high-speed stirring is performed at 800-1200 r / min for 15-20 min, and the silane coupling agent accounts for 0.5-1.0% of the nanopowder.

9. The method for preparing the cement-based penetrating nano-crystallization self-repairing waterproof admixture according to claim 7, characterized in that: The specific surface area of the silica fume-metakaolin after ball milling in S3 is ≥400 m² / kg and the particle size D50 is ≤10 μm.

10. The method for preparing the cement-based penetrating nano-crystallization self-repairing waterproof admixture according to claim 7, characterized in that: In the S5, the nano-dispersion stage is 800-1000 r / min, the microbial mixing stage is ≤200 r / min, and the temperature is controlled at ≤35°C throughout the process.

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