A stress-controlled release self-repairing composite material for waterproof bonding layer of bridge deck and a preparation method thereof

Abstract

The application provides a stress-controlled release type self-repairing composite material for a waterproof bonding layer of a bridge deck and a preparation method thereof, and belongs to the technical road engineering material and bridge deck paving field.The self-repairing composite material comprises a polymer modified asphalt base and a stress-controlled release type microcapsule, the stress-controlled release type microcapsule is prepared by a pH value gradient in-situ polymerization method on the surface of a capsule core to form a capsule wall, and then is modified by using a silane coupling agent to obtain the stress-controlled release type microcapsule, and the stress-controlled release type microcapsule has a capsule wall integrity rate of greater than or equal to 90% and a core material retention rate of greater than or equal to 85% under asphalt mixing conditions at 170 DEG C.The self-repairing composite material has excellent high-temperature mixing stability, stress triggering response characteristics and self-repairing functions, the interlayer pull strength and shear strength recovery rate after repair are greater than or equal to 70%, the water permeability coefficient reduction rate is greater than or equal to 80%, the durability and service life of the bridge deck paving system are significantly improved, and the whole cycle maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of road engineering materials and bridge deck paving technology, specifically to a stress-controlled release self-healing composite material for a bridge deck waterproof bonding layer and its preparation method. Background Technology

[0002] The waterproof bonding layer on bridge decks is a critical functional layer ensuring the durability of bridges; its failure directly leads to serious damage such as pavement peeling and water damage. Currently, bridge deck engineering mainly uses modified asphalt (such as SBS modified asphalt) or reactive resins (such as water-based epoxy asphalt) as bonding materials. These traditional materials are "passive" materials; once microcracks develop inside, their performance will irreversibly deteriorate, ultimately requiring expensive and inefficient renovations.

[0003] Meanwhile, although significant progress has been made in the field of self-healing materials, with various technological approaches emerging, including microcapsules, microbial mineralization, and shape memory polymers, the most relevant existing technologies still suffer from inherent defects when directly applied to the specific and demanding scenario of waterproof bonding layers for cement concrete bridge decks. These defects are fundamentally incompatible with the core needs of bridge decks.

[0004] First, the bridge deck bonding layer needs to be constructed on an inclined base surface and directly bear the subsequent paving and compaction of hot asphalt mixtures at temperatures above 160°C. This requires the material to maintain sufficient structural viscosity (anti-flow properties) at extreme high temperatures and to form a durable and high-strength bond with both the upper and lower heterogeneous interfaces (cement concrete and asphalt mixture). For example, patent CN120647244A discloses a self-healing microcapsule composite waterproof material and its preparation method. Although this material exhibits excellent flexibility and tensile properties in the field of building waterproofing, the low viscosity of its silicone resin matrix at high temperatures makes it difficult to meet the core requirement of anti-flow in bridge deck construction. In addition, its surface chemical properties and interfacial compatibility and adhesion with hot asphalt mixtures may be insufficient, and its performance index system focuses on tensile strength and elongation at break, without specifically addressing and verifying the most critical shear and pull-out bond strength and repair rate between bridge deck layers.

[0005] Secondly, the bonding layer of the bridge deck requires materials that can adapt to rapid, large-scale on-site spraying or application to form a uniform, dense thin layer of 1-3 mm, and the repair mechanism must be able to respond to microcracks caused by vehicle dynamic loads and temperature stress. Patent CN120349551A discloses a self-healing composite waterproof board and its preparation method. Although this solution forms a high-strength skeleton through glass fiber reinforcement, its rigid prefabricated board shape and complex vacuum injection molding process are completely unsuitable for the process requirements of on-site mobile construction of bridge decks. At the same time, its repair mechanism relies on external heat triggering, which is fundamentally out of touch with the actual working conditions where microcracks are generated between bridge deck layers under normal temperature and fatigue loads and need to be repaired immediately.

[0006] In summary, existing self-healing material technologies, due to either the rheological and interfacial properties of their substrate systems (such as organosilicon) or their product forms and triggering mechanisms (such as rigid plates or external thermal triggering), have failed to provide an integrated and systematic innovative design for the essential three-in-one core requirements of "bridge deck waterproofing adhesive layer"—namely, "film-forming properties and anti-flow properties under extreme construction conditions," "ultra-high adhesion to the cement / asphalt interface," and "self-healing capability under dynamic mechanical stress." Therefore, developing a specialized material that can completely overcome the aforementioned complex technical obstacles has become a highly innovative and urgent technical challenge in this field. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, the primary objective of this invention is to provide a bridge deck waterproof adhesive layer composite material with self-healing function. This composite material uses a high-performance adhesive system verified in bridge deck engineering as the matrix. By introducing high-temperature resistant, stress-triggered self-healing microcapsules, it maintains or even improves the traditional interlayer adhesive performance while endowing it with stress-controlled release self-healing ability, thereby achieving autonomous repair of microcracks and significantly extending the service life of the bridge deck pavement system.

[0008] Another object of the present invention is to provide a method for preparing the composite material, which ensures the stable and uniform dispersion of the self-healing functional components in a viscous matrix and maintains their activity through a mild and controllable process.

[0009] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0010] In a first aspect, the present invention provides a stress-controlled release self-healing composite material for a bridge deck waterproofing adhesive layer, comprising: a polymer-modified asphalt matrix, and stress-controlled release microcapsules uniformly dispersed in the polymer-modified asphalt matrix; wherein the stress-controlled release microcapsules are obtained by first preparing a capsule wall on the surface of the capsule core through a pH gradient in-situ polymerization method, and then modifying it with a silane coupling agent; the material of the capsule core includes an asphalt rejuvenator, and the material of the capsule wall includes melamine-urea-formaldehyde (MUF) resin.

[0011] Furthermore, the median particle size d(0.5) of the stress-controlled release microcapsules is 15-45 µm, d(0.9) ≤ 70 µm, and the capsule wall thickness is 0.5-5 µm. After mixing with the polymer-modified asphalt matrix at 170 °C, the capsule wall integrity rate is ≥ 90%, and the core material retention rate is ≥ 85%.

[0012] Furthermore, the amount of the stress-controlled release microcapsules in the polymer-modified asphalt matrix is ​​4%-12% of the mass of the polymer-modified asphalt matrix.

[0013] Furthermore, the method for preparing the stress-controlled release microcapsules includes the following steps:

[0014] Mix asphalt rejuvenator, anionic emulsifier and water, keep warm at 60-80 ℃ for 10-30 min, and then treat under high shear emulsification or ultrasonic dispersion conditions for 5-20 min to form an oil-in-water rejuvenator emulsion.

[0015] Urea, melamine and formaldehyde solution (formaldehyde solution mass fraction is 37%) are mixed, diluted with water, and the pH of the system is adjusted to 8.0-9.5 with an alkaline adjuster. The mixture is stirred at 65-80 ℃ for 20-50 min to obtain a transparent melamine-urea-formaldehyde copolymer precursor solution.

[0016] A water-in-oil type regenerator emulsion and a melamine-urea-formaldehyde copolymer precursor solution were mixed. Under conditions of 55-75 °C, with the principle of maintaining a stable pH and avoiding localized over-acidity, an acidic catalyst solution was slowly added dropwise to adjust the pH to 5.8-6.5. The reaction was allowed to proceed for 0.5-2.0 h at pH 5.8-6.5, allowing the melamine-urea-formaldehyde copolymer precursor solution to complete initial adsorption and form a primary membrane on the surface of the regenerator emulsion. The acidic catalyst solution was then continuously added at a rate of 0.05-0.25 mL / min, causing the pH to gradually decrease from 5.8-6.5 to 4.8-5.5 within 1.0-2.5 h, promoting the continuous deposition of the wall material resin on the surface of the primary membrane, molecular chain extension, and cross-linking network formation. Finally, the acidic catalyst solution was added at a rate of 0.5-2.0 mL / min to lower the pH to 3.8-4.5, and the pH was maintained at a stable level. The reaction was carried out at 3.8-4.5 for 0.5-1.0 h to achieve densification of the three-dimensional network structure of the capsule wall resin; acidic catalyst solution was added at a rate of 3.0-6.0 mL / min to lower the pH of the system to 3.0-3.2, and the reaction was carried out at pH 3.0-3.2 for 1.0-1.5 h to complete the deep curing of the capsule wall and the final morphology of the microcapsules;

[0017] The polymerization reaction system was cooled to room temperature, washed, and then wet microcapsules were obtained by filtration or centrifugation. The wet microcapsules were pre-dried to a moisture content of ≤ 10%, and then a silane coupling agent was added and mixed evenly to form a chemically bonded oleophobic graft layer on the surface of the microcapsules. After drying, stress-controlled release microcapsules were obtained.

[0018] Furthermore, the mass ratio of the asphalt rejuvenator, anionic emulsifier, and water is 100:(15-40):(1000-2000).

[0019] Furthermore, the anionic emulsifier includes, but is not limited to, at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium lignosulfonate.

[0020] Furthermore, the shear rate of the high-shear emulsification condition is 8000-15000 rpm, and the ultrasonic intensity of the ultrasonic dispersion condition is 60%-90%.

[0021] Furthermore, the particle size D90 of the oil-in-water regenerator emulsion is ≤ 2 µm.

[0022] Furthermore, the molar ratio of urea to formaldehyde is 1:(1.3-2.2), and the molar ratio of melamine to formaldehyde is 1:(2.2-3.3).

[0023] Furthermore, the alkalinity regulator includes, but is not limited to, at least one of sodium hydroxide, potassium hydroxide, and triethanolamine.

[0024] Furthermore, the water-in-oil type regenerator emulsion and the melamine-urea-formaldehyde copolymer precursor are mixed at an effective mass ratio of core to wall of 1:(0.5-1.5); the effective mass ratio of core to wall of 1 is further preferred to be 1:(0.7-1.2).

[0025] Furthermore, the acidic catalyst solution includes, but is not limited to, a solution of citric acid, acetic acid, or formic acid with a mass fraction of 5%-15%.

[0026] Furthermore, the pre-drying involves vacuum drying the wet microcapsules at 50-80 °C until the moisture content is ≤ 10%.

[0027] Furthermore, the silane coupling agent accounts for 0.2%-1.2% of the dry weight of the microcapsules.

[0028] Furthermore, the silane coupling agent includes, but is not limited to, at least one of γ-aminopropyltriethoxysilane (KH550) and γ-epoxypropoxypropyltrimethoxysilane (KH560).

[0029] Furthermore, after adding the silane coupling agent, the mixture is subjected to closed mixing in a high-speed mixer at 75-105 ℃ and 800-2000 rpm for 5-20 minutes to ensure uniform mixing.

[0030] Specifically, the method for preparing the stress-controlled release microcapsules is as follows:

[0031] S1. Core pre-emulsification: By mass, mix 100 parts asphalt rejuvenator, 15-40 parts anionic emulsifier and 1000-2000 parts deionized water, keep warm at 60-80 ℃ for 10-30 min, and then treat with a high shear emulsifier or ultrasonic dispersion equipment at a shear rate of 8000-15000 rpm or an ultrasonic intensity of 60%-90% for 5-20 min to form an oil-in-water rejuvenator emulsion with a droplet diameter D90 ≤ 2 µm.

[0032] S2. Preparation of urea-urea-formaldehyde precursor solution: Mix urea, melamine, and formaldehyde solution (mass fraction 37%) at molar ratios of urea:formaldehyde = 1:(1.3-2.2) and melamine:formaldehyde = 1:(2.2-3.3), dilute with deionized water 2-6 times, adjust the pH of the system to 8.0-9.5 with an alkaline adjuster, and stir the reaction at 65-80 ℃ for 20-50 min to obtain a transparent melamine-urea-formaldehyde copolymerization precursor solution; wherein, urea accounts for 20%-45% of the total mass of melamine and urea.

[0033] S3. Gradient in-situ polymerization to construct the capsule wall:

[0034] (a) Prepolymer adsorption and deposition stage: The water-in-oil type regenerator emulsion and melamine-urea-formaldehyde copolymer precursor solution are mixed at an effective mass ratio of core to wall of 1:(0.5-1.5) and placed in a water bath at 55-75 ℃ (maintain this temperature until the end of step S3). Under mechanical stirring at 200-500 rpm, acidic catalyst solution is slowly added dropwise to adjust the pH of the system to 5.8-6.5, and the reaction is carried out at pH 5.8-6.5 for 0.5-2.0 h, so that the wall material prepolymer completes the initial adsorption on the surface of the regenerator droplet and forms the primary membrane.

[0035] (b) Wall material thickening and crosslinking stage: Acidic catalyst solution was continuously added at a rate of 0.05-0.25 mL / min using a micro-pump, so that the pH of the system gradually decreased from 5.8-6.5 to 4.8-5.5 within 1.0-2.5 h, which promoted the continuous deposition of wall material resin on the surface of the primary capsule, the extension of molecular chains and the formation of crosslinking network.

[0036] (c) Structure densification stage: Increase the acid addition rate of the micro-pump to 0.5-2.0 mL / min, further reduce the pH of the system to 3.8-4.5, and react for 0.5-1.0 h under pH 3.8-4.5 conditions to achieve densification of the three-dimensional network structure of the capsule wall resin;

[0037] (d) Interface strengthening and shaping stage: Increase the acid addition rate again to 3.0-6.0 mL / min, lower the pH of the system to 3.0-3.2, and react for 1.0-1.5 h under pH 3.0-3.2 conditions to complete the deep solidification of the capsule wall and the final morphology shaping of the microcapsules;

[0038] S4. Surface oleophobic grafting modification: After the polymerization reaction, the product is cooled to room temperature and washed repeatedly 3-5 times with a mixture of deionized water and ethanol. Wet microcapsules are obtained by filtration or centrifugation. The wet microcapsules are pre-dried under vacuum at 50-80 ℃ until the moisture content is ≤ 10%, yielding microcapsules to be modified. The dry weight of the microcapsules to be modified is weighed, and then mixed with 0.2%-1.2% of the dry weight of the microcapsules as a silane coupling agent in a high-speed mixer at 75-105 ℃ and 800-2000 rpm for 5-20 min in a closed environment, so that the silane coupling agent forms a chemically bonded oleophobic grafting layer on the surface of the microcapsules. After surface oleophobic grafting modification, the integrity rate of the capsule wall after mixing with the polymer-modified asphalt matrix at 170 ℃ is ≥ 90%, and the core retention rate is ≥ 85%.

[0039] This invention uses silane coupling agents to chemically graft and modify the surface of microcapsules, introducing oleophobic organic functional groups, which significantly improves the interfacial compatibility between the hydrophilic MUF wall material and the hydrophobic asphalt matrix. Combined with gradient shear composite process, it achieves macroscopic uniform distribution and microscopic interface stability of microcapsules in viscous asphalt, avoiding agglomeration and floating. This invention chooses to perform surface graft modification after gradient in-situ polymerization to construct the capsule wall for the following reasons: (1) If silane coupling agents are added to the melamine-urea-formaldehyde copolymerization precursor solution, the alkoxy groups (-OCH3, -OC2H5) of the silane coupling agents will hydrolyze under acidic conditions to generate silanol groups (Si-OH). These silanol groups will undergo condensation reaction with the hydroxymethyl groups (-CH2OH) in the MUF prepolymer, interfering with the originally designed pH-reaction rate correspondence, resulting in the destruction of the reaction kinetics corresponding to the acid addition rates in stages (b), (c), and (d), and the failure to form the expected gradient shell structure; (2) If Silane coupling agent is added to melamine-urea-formaldehyde copolymer precursor liquid for in-situ modification. After modification, the coupling agent is evenly distributed throughout the shell (including the interior) rather than enriched on the surface. This means that a large number of oleophobic functional groups (such as aminopropyl of KH550 and epoxypropoxypropyl of KH560) used to improve compatibility with asphalt matrix are "wasted" in the interior of the shell, the effective grafting density on the surface is reduced, and the oleophobic modification effect is discounted; (3) Existing research shows that there is a critical value for the amount of silane coupling agent added. Exceeding this value will cause the shell to be over-crosslinked and brittle. The amount of coupling agent needs to take into account both the encapsulation quality and the surface modification effect, which is difficult to optimize.

[0040] S5. Post-processing: The modified microcapsules are subjected to vacuum freeze-drying or spray drying to control the final moisture content to ≤2%, thereby obtaining dried stress-controlled release microcapsules.

[0041] Furthermore, the polymer-modified asphalt matrix is ​​obtained by modifying the base asphalt with a polymer modifier, and the amount of the polymer modifier is 3%-8% of the mass of the base asphalt.

[0042] Furthermore, the polymer modifier is selected from at least one of styrene-butadiene-styrene block copolymer (SBS), styrene-butadiene rubber (SBR), and epoxy resin.

[0043] Secondly, the present invention provides a method for preparing the stress-controlled release self-healing composite material for the bridge deck waterproof bonding layer, comprising the following steps:

[0044] P1. Modification of the asphalt matrix: Heat the base asphalt to 150-170 ℃, add a polymer modifier, and shear at a shear rate of 4000-9000 rpm for 15-50 min to obtain a polymer-modified asphalt matrix;

[0045] P2. Pre-activation of stress-controlled release microcapsules: Dry stress-controlled release microcapsules under vacuum at 60-85 ℃ for 1-3 h to remove residual moisture and low molecular weight volatiles;

[0046] P3. Gradient shearing composite: Pre-activated stress-controlled release microcapsules are added to a polymer-modified asphalt matrix. Under inert gas protection at 150-170 ℃, the matrix is ​​first sheared at a low speed of 50-150 rpm for 5-10 min to ensure full wetting and contact between the stress-controlled release microcapsules and the polymer-modified asphalt matrix. Then, it is sheared at a medium speed of 250-550 rpm for 20-40 min to achieve uniform dispersion of the stress-controlled release microcapsules in the polymer-modified asphalt matrix. Finally, it is stirred at a speed of 100-200 rpm for 5-10 min to eliminate shear bubbles, thus obtaining the self-healing composite material.

[0047] Furthermore, in step P3, the pre-activated stress-controlled release microcapsules are preheated to 80-100℃ before addition to avoid a sudden drop in local temperature caused by the addition of cold material; the material temperature fluctuation is controlled to be ≤ ± 5℃ throughout the shear dispersion process.

[0048] Thirdly, the present invention provides the application of the stress-controlled release self-healing composite material for bridge deck waterproofing bonding layers, including:

[0049] The stress-controlled release self-healing composite material used for the bridge deck waterproof bonding layer is heated to 160-185 ℃ and evenly spread on the bridge deck surface after shot blasting, sandblasting or milling using a synchronous paving equipment to form a stress-responsive waterproof bonding functional layer with a thickness of 1.5-2.0 mm.

[0050] When the waterproof adhesive functional layer develops microcracks during its service life due to vehicle load, temperature shrinkage, or reflective cracks in the base layer, the stress concentration field generated at the crack tip is transmitted radially along the microcapsule. When the local stress exceeds the ultimate strength of the capsule wall material, the microcapsule undergoes directional rupture along the stress direction.

[0051] The asphalt rejuvenator encapsulated in the core of a stress-controlled release microcapsule is rapidly released under capillary effect and negative pressure suction of cracks, and is directionally transported to the microcrack area. It heals the crack interface through wetting, swelling and component migration, while simultaneously compensating for components and regenerating the properties of the aged asphalt matrix around the crack.

[0052] Furthermore, the self-healing effect of the stress-controlled release self-healing composite material used for the bridge deck waterproof bonding layer is comprehensively evaluated by multiple indicators such as interlaminar pull-out strength, interlaminar shear strength, or water permeability coefficient before and after repair; under the standard test conditions of 25 ℃, the recovery rate of pull-out strength and shear strength after repair is ≥ 70%, and the reduction rate of water permeability coefficient is ≥ 80%.

[0053] Compared with the prior art, the advantages of the present invention are:

[0054] (1) The system has both adaptability and construction tolerance: The present invention uses polymer modified asphalt as the matrix, which is itself a recognized high-performance, high-adhesion, and high-temperature resistant flow material in the field of bridge deck waterproof bonding layer; combined with stress-controlled release microcapsules modified by pH gradient in situ polymerization and silane coupling agent, these microcapsules can still maintain ≥ 90% capsule wall integrity and ≥ 85% core material retention rate under high temperature mixing process (170 ℃), which solves the common problem that traditional self-healing materials cannot withstand the hot paving conditions of bridge decks.

[0055] (2) Precise matching of stress release mechanism with bridge deck damage mode: Unlike passive repair modes such as thermal triggering and optical triggering, this invention uses the local stress field released when microcracks initiate as a trigger signal to achieve "repair initiation upon damage occurrence"; the MUF wall material prepared by pH gradient in-situ polymerization process has moderate mechanical strength and stress sensitivity, which can ensure that the microcapsules do not break prematurely in the early stage of material service and break sensitively when damage occurs. The key difference between the pH gradient polymerization process of this invention and the conventional "one-time acidification" or "simple batch acid addition" process is that this invention achieves a staged self-assembly process of "oriented deposition → chain segment growth → dense cross-linking → deep curing" of the shell resin through precise control of pH gradient. This mechanism makes the microcapsules not only have a high-density shell that is difficult to achieve by traditional processes, but more importantly, they form a cross-linking density gradient structure from the inside to the outside. This structure endows the microcapsules with excellent heat resistance and integrity (capsule wall integrity rate ≥ 90%) under high temperature asphalt mixing conditions of 170 ℃. On the other hand, it optimizes their mechanical response behavior in the stress field, ensuring that the microcapsules can sense the stress at the crack tip and release the core material in a directional manner, realizing the transformation from "passive mixing" to "stress-controlled release".

[0056] (3) Synergistic improvement of interfacial compatibility and dispersion stability: This invention uses silane coupling agent (KH550 / KH560) to chemically graft and modify the surface of microcapsules, introduces oleophobic organic functional groups, significantly improves the interfacial compatibility between hydrophilic MUF wall material and hydrophobic asphalt matrix, and combined with gradient shear composite process, realizes macroscopic uniform distribution and microscopic interface stability of microcapsules in viscous asphalt, avoiding agglomeration and floating.

[0057] (4) High repair efficiency and excellent comprehensive performance: Experiments show that the self-healing composite material provided by the present invention can achieve a pull-out strength and shear strength recovery rate of more than 70% under standard repair conditions, and the water permeability coefficient reduction rate exceeds 80%. At the same time, the incorporation of stress-controlled release microcapsules not only does not deteriorate the bonding performance of the matrix, but also improves the interlayer crack resistance to a certain extent through the "microcapsule toughening effect", thus achieving the unity of structural reinforcement and function.

[0058] (5) The preparation process is controllable and suitable for industrial production: The stress-controlled release microcapsule preparation method provided by the present invention achieves the densification growth of the shell from the inside to the outside through fine control of pH gradient. The product has uniform particle size, controllable wall thickness and good batch stability. The preparation of self-healing composite material adopts general modified asphalt production equipment. Only the process parameters are optimized. No additional investment in special large equipment is required. It has good economic benefits and promotion value. Attached Figure Description

[0059] Figure 1 This is a scanning electron microscope (SEM) image of the stress-controlled release microcapsules prepared according to the present invention.

[0060] Figure 2 Fluorescence microscopy (FM) images of the cross-section of microcapsule bitumen after complete fracture in a pull-out test. Detailed Implementation

[0061] To enable those skilled in the art to clearly and completely understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art. Obviously, the embodiments described herein are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] This invention provides a stress-controlled release self-healing composite material for a bridge deck waterproofing adhesive layer, comprising: a polymer-modified asphalt matrix, and stress-controlled release microcapsules uniformly dispersed in the polymer-modified asphalt matrix; wherein, the stress-controlled release microcapsules are obtained by first preparing a capsule wall on the surface of the capsule core through pH gradient in-situ polymerization, and then modifying it with a silane coupling agent; the material of the capsule core includes an asphalt recycling agent, and the material of the capsule wall includes melamine-urea-formaldehyde (MUF) resin.

[0063] The method for preparing the stress-controlled release microcapsules includes the following steps:

[0064] Asphalt rejuvenator, anionic emulsifier, and water are mixed and kept at 60-80 ℃ for 10-30 min, then treated under high-shear emulsification or ultrasonic dispersion conditions for 5-20 min to form an oil-in-water rejuvenator emulsion with a particle size D90 ≤2 µm; the mass ratio of the asphalt rejuvenator, anionic emulsifier, and water is 100:(15-40):(1000-2000); the anionic emulsifier includes, but is not limited to, at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium lignin sulfonate; the shear rate under the high-shear emulsification conditions is 8000-15000 rpm, and the ultrasonic intensity under the ultrasonic dispersion conditions is 60%-90%;

[0065] Urea, melamine, and formaldehyde solution (37% by mass) are mixed, diluted with water, and the pH of the system is adjusted to 8.0-9.5 with an alkaline adjuster. The mixture is stirred at 65-80 °C for 20-50 min to obtain a transparent melamine-urea-formaldehyde copolymerization precursor solution. The molar ratio of urea to formaldehyde is 1:(1.3-2.2), the molar ratio of melamine to formaldehyde is 1:(2.2-3.3), and urea accounts for 20%-45% of the total mass of melamine and urea. The alkaline adjuster includes, but is not limited to, at least one of sodium hydroxide, potassium hydroxide, and triethanolamine.

[0066] A water-in-oil regenerator emulsion and a melamine-urea-formaldehyde copolymer precursor solution were mixed at an effective mass ratio of core to wall material of 1:(0.5-1.5). To maintain a stable pH and avoid localized over-acidity, an acidic catalyst solution was slowly added dropwise at 55-75 °C to adjust the pH to 5.8-6.5. The reaction was allowed to proceed for 0.5-2.0 h at pH 5.8-6.5, allowing the melamine-urea-formaldehyde copolymer precursor solution to initially adsorb onto the surface of the regenerator emulsion and form a primary membrane. The acidic catalyst solution was then continuously added at a rate of 0.05-0.25 mL / min, causing the pH to gradually decrease from 5.8-6.5 to 4.8-5.5 within 1.0-2.5 h. This promoted the continuous deposition of the wall material resin on the primary membrane surface, molecular chain extension, and cross-linking network formation. The addition rate of the acidic catalyst solution was then increased to 0.5-2.0. The system pH was lowered to 3.8-4.5 by increasing the feed rate of the acidic catalyst solution to 3.0-6.0 mL / min, and the system pH was lowered to 3.0-3.2. The reaction was carried out at pH 3.0-3.2 for 1.0-1.5 h to achieve deep curing of the capsule wall and final morphological shaping of the microcapsules. The acidic catalyst solution included, but was not limited to, a 5%-15% (w / w) solution of citric acid, acetic acid, or formic acid.

[0067] The polymerization reaction system is cooled to room temperature, washed, and then wet microcapsules are obtained by filtration or centrifugation. The wet microcapsules are vacuum dried at 50-80 °C until the moisture content is ≤ 10%. Then, a silane coupling agent is added and the mixture is sealed and mixed in a high-speed mixer at 75-105 °C and 800-2000 rpm for 5-20 min to ensure uniform mixing, so that the silane coupling agent forms a chemically bonded oleophobic graft layer on the surface of the microcapsules. After drying, stress-controlled release microcapsules are obtained. The silane coupling agent accounts for 0.2%-1.2% of the dry weight of the microcapsules. The silane coupling agent includes, but is not limited to, at least one of γ-aminopropyltriethoxysilane (KH550) and γ-epoxypropoxypropyltrimethoxysilane (KH560).

[0068] In some examples, the median particle size d(0.5) of the stress-controlled release microcapsules is 15-45 µm, d(0.9) ≤70 µm, and the capsule wall thickness is 0.5-5 µm.

[0069] In some examples, the stress-controlled release microcapsules are incorporated into the polymer-modified asphalt matrix at an amount of 4%-12% of the mass of the polymer-modified asphalt matrix.

[0070] In some examples, the polymer-modified asphalt matrix is ​​obtained by modifying the base asphalt with a polymer modifier, wherein the amount of the polymer modifier is 3%-8% of the mass of the base asphalt; the polymer modifier is selected from at least one of styrene-butadiene-styrene block copolymer (SBS), styrene-butadiene rubber (SBR), and epoxy resin.

[0071] In the following specific embodiments, the raw materials and testing methods used are described below:

[0072] Base asphalt: SK-70 road petroleum asphalt is used.

[0073] Polymer modifiers: SBS, grade YH-791; SBR, grade 1502; epoxy resin, grade E-51.

[0074] Asphalt recycling agent: Commercially available RA-102 type asphalt recycling agent, the main components of which are cycloalkane oil and aromatics.

[0075] Emulsifiers: Sodium dodecylbenzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS), analytical grade.

[0076] Wall material monomers: melamine (99%), urea (99%), formaldehyde solution (37%), analytical grade.

[0077] Silane coupling agents: γ-aminopropyltriethoxysilane (KH550), γ-epoxypropoxypropyltrimethoxysilane (KH560), industrial grade.

[0078] Acidic catalyst: citric acid and acetic acid, prepared as a 10% aqueous solution.

[0079] Alkalinity regulator: Triethanolamine.

[0080] Performance testing methods:

[0081] Microcapsule particle size: Laser particle size analyzer (wet method).

[0082] Capsule wall integrity rate and core material retention rate: Referring to "Thermogravimetric Analysis (TG) for Plastic Polymers - Part 1: General Rules" (GB / T33047.1-2016), the microcapsules were mixed with hot asphalt at 170 ℃ for 15 min, and then the microcapsules were extracted and separated. The results were calculated by weighing and thermogravimetric analysis.

[0083] Interlayer pull-out strength: Refer to the method of "Appendix N Evaluation of positive tensile bond between waterproof layer and concrete" in the "Highway Engineering Quality Inspection and Evaluation Standard Volume 1 Civil Engineering" (JTG F80 / 1-2017).

[0084] Interlayer shear strength: Refer to method T0773 in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG 3410-2025).

[0085] Permeability coefficient: Refer to method T 0971 in the "Specifications for Field Testing of Highway Subgrade and Pavement" (JTG 3450-2019).

[0086] Repair rate: The molded specimen is pre-damaged (to about 50% of the initial strength), and after 24 hours of self-healing, the strength is retested. Repair rate = (strength after repair / initial strength) × 100%.

[0087] Self-healing performance evaluation: After curing the molded specimens in a standard laboratory environment (temperature 25 ℃ ± 2 ℃, relative humidity 50% ± 10%) for at least 4 hours, the initial strength was tested. Subsequently, the specimens were pre-damaged, with the damage level controlled to 50% ± 5% of the initial strength. The damaged specimens were then placed back in the aforementioned standard laboratory environment and left to stand for 24 hours without any external heat source or stimulation. After repair, the interlaminar tensile strength and shear strength of the specimens were tested again, and the repair rate was calculated according to the formula.

[0088] Example 1

[0089] A stress-controlled release self-healing composite material for bridge deck waterproofing adhesive layer, the preparation steps are as follows:

[0090] 1. Preparation of stress-controlled release microcapsules

[0091] 1.1 Core pre-emulsification: Weigh 100 g asphalt recycling agent, 20 g SDBS and 1500 g deionized water and mix them. Keep the mixture at 70℃ for 20 min. Then, use a high-shear emulsifier to shear at 12000 rpm for 12 min to obtain an oil-in-water recycling agent emulsion. The emulsion droplet D90 was tested to be 1.8 µm.

[0092] 1.2 Preparation of precursor solution for capsule wall: The monomers were weighed and mixed according to the molar ratio of urea:formaldehyde = 1:1.8 and melamine:formaldehyde = 1:2.8, wherein urea accounted for 35% of the total mass of melamine and urea; deionized water was added to dilute 4 times, the pH was adjusted to 9.0 with triethanolamine, and the reaction was stirred at 75 ℃ for 30 min to obtain a transparent melamine-urea-formaldehyde copolymer precursor solution.

[0093] 1.3 Gradient in-situ polymerization to construct the capsule wall: An oil-in-water regenerant emulsion and a melamine-urea-formaldehyde copolymer precursor solution were mixed at an effective mass ratio of 1:1.0 between the capsule core and the capsule wall. The mixture was placed in a 65 ℃ water bath with stirring at 350 rpm. A 10% citric acid solution was slowly added dropwise to adjust the pH to 6.0, and the reaction was carried out at pH 6.0 for 1.0 h. Citric acid solution was then added at a rate of 0.15 mL / min, lowering the pH to 5.0 within 1.5 h. The addition rate of citric acid solution was increased to 1.0 mL / min, lowering the pH to 4.0, and the reaction was carried out at pH 4.0 for 0.5 h. The addition rate of citric acid solution was again increased to 4.0 mL / min, lowering the pH to 3.1, and the reaction was carried out at pH 3.1 for 1.0 h.

[0094] 1.4 Surface modification: After washing and filtering the polymerization product, it was pre-dried under vacuum at 60 °C to a moisture content of 8%. 100 g of dry weight of microcapsules and 0.8 g of KH550 were mixed in a high-speed mixer at 90 °C and 1200 rpm for 15 min in a sealed environment.

[0095] 1.5 Drying: The modified microcapsules were freeze-dried under vacuum until the moisture content was ≤ 2% to obtain stress-controlled release microcapsules. Tests showed: d(0.5) = 28 µm, d(0.9) = 52 µm, and wall thickness = 2.5 µm.

[0096] 2. Preparation of self-healing composite materials

[0097] 2.1 Asphalt modification: Take 1000 g of base asphalt, heat it to 165 ℃, add 60 g of SBS, and shear at 7000 rpm for 30 min to obtain SBS modified asphalt matrix.

[0098] 2.2 Microcapsule pre-activation: Stress-controlled release microcapsules were vacuum dried at 75 °C for 2 h.

[0099] 2.3 Gradient Shear Composite: 80 g of pre-activated stress-controlled release microcapsules (8% admixture) were preheated to 90 ℃. Under nitrogen protection at 160 ℃, the preheated stress-controlled release microcapsules were added to the SBS-modified asphalt matrix. The matrix was first sheared at a low speed of 100 rpm for 8 min; then sheared at a medium speed of 400 rpm for 30 min; finally, it was kept warm and stirred at 150 rpm for 8 min to obtain a stress-controlled release self-healing composite material for the bridge deck waterproofing bonding layer.

[0100] Examples 2-5

[0101] The stress-controlled release self-healing composite materials for bridge deck waterproofing adhesive layers in Examples 2-5 were developed based on Example 1, with adjustments made to the microcapsule preparation and composite process parameters, as detailed in Table 1. The remaining steps were the same as in Example 1.

[0102] Table 1: Main process parameters of Examples 2-5

[0103]

[0104] Comparative Example 1 (without microcapsules)

[0105] The same SBS modified bitumen matrix as in Example 1 was used as the self-healing material, without the addition of any microcapsules, serving as a blank control group.

[0106] Comparative Example 2 (without modification of the microcapsules)

[0107] The self-healing composite material of this comparative example is prepared using the same process as in Example 1. The difference between Example 1 and Example 1 is that the surface oleophobic grafting modification treatment in step 1.4 is omitted in the preparation of the microcapsules. After washing and filtering the polymerization product, it is directly freeze-dried under vacuum until the water content is ≤2% to obtain the microcapsules.

[0108] Comparative Example 3 (Non-gradient polymerized microcapsules)

[0109] The self-healing composite material of this comparative example is prepared using the same process as in Example 1. The difference between Example 1 and Example 1 is that non-gradient in-situ polymerization is used to construct the capsule wall in the preparation of the microcapsules. Specifically, step 1.3 is as follows: the water-in-oil type regenerator emulsion and the melamine-urea-formaldehyde copolymer precursor solution are mixed at an effective mass ratio of 1:1.0 between the capsule core and the capsule wall. The mixture is placed in a 65 ℃ water bath and stirred at 350 rpm. A 10% citric acid solution is added dropwise to adjust the pH to 4.5, and the mixture is reacted at a constant temperature of pH 4.5 for 3.0 h.

[0110] The microcapsules were then used to prepare corresponding self-healing composite materials.

[0111] Comparative Example 4 (Conventional Shear Compound)

[0112] This comparative example uses the stress-controlled release microcapsules of Example 1 to prepare a self-healing composite material. Compared to Example 1, this comparative example omits the gradient shearing process in the preparation steps of the self-healing composite material, i.e., step 2.3 is as follows: Take 80 g of pre-activated stress-controlled release microcapsules (dosage 8%) and preheat to 90 ℃. Under nitrogen protection at 160 ℃, add the preheated stress-controlled release microcapsules to the SBS modified bitumen matrix, and shear at a constant rate of 400 rpm for 40 min to obtain the self-healing composite material.

[0113] Comparative Example 5 (Constant Rate Acid Addition)

[0114] The self-healing composite material in this comparative example follows the preparation process of Example 1, except that the acid addition rate is not adjusted in stages during the microcapsule preparation process. Instead, a constant rate of acid addition is used, as shown in step 1.3: The oil-in-water regenerator emulsion and the melamine-urea-formaldehyde copolymer precursor solution are mixed at an effective mass ratio of 1:1.0 between the capsule core and the capsule wall. A 10% citric acid solution is slowly added dropwise under a 65°C water bath and 350 rpm stirring condition to adjust the pH to 6.0. The reaction is allowed to proceed for 1.0 h. Citric acid solution is then added at a rate of 0.8 mL / min to uniformly reduce the pH of the reaction system from 6.0 to 3.1 within 3 h.

[0115] Comparative Example 6 (Changing the acid addition rate)

[0116] The self-healing composite material of this comparative example follows the preparation process of Example 1, except that the acid addition rate is changed during the microcapsule preparation process. Specifically, step 1.3 is as follows: A water-in-oil regenerator emulsion and a melamine-urea-formaldehyde copolymer precursor solution are mixed at an effective mass ratio of core to wall of 1:1.0. The mixture is placed in a 65°C water bath with stirring at 350 rpm, and a 10% citric acid solution is slowly added dropwise to adjust the pH to 6.0. The reaction is carried out at pH 6.0 for 1.0 h. Citric acid solution is then added at a rate of 3.0 mL / min to lower the pH to 4.8. The addition rate of citric acid solution is reduced to 0.8 mL / min to lower the pH to 4.0, and the reaction is carried out at pH 4.0 for 0.5 h. The addition rate of citric acid solution is further reduced to 0.1 mL / min to lower the pH to 3.1, and the reaction is carried out at pH 3.1 for 1.0 h.

[0117] Comparative Example 7 (pH adjustment only, no rate control)

[0118] The self-healing composite material in this comparative example follows the preparation process of Example 1, but differs from Example 1 in that, during the microcapsule preparation process, only the pH is adjusted in stages, but the acid addition rate is not controlled. pH adjustment is achieved by adding acid all at once, as follows: Step 1.3: The oil-in-water regenerator emulsion and the melamine-urea-formaldehyde copolymer precursor solution are mixed at an effective mass ratio of 1:1.0 between the capsule core and the capsule wall. A 10% citric acid solution is slowly added dropwise under a 65°C water bath and 350 rpm stirring condition to adjust the pH to 6.0, and the reaction is carried out at pH 6.0 for 1.0 h. Citric acid solution is added all at once within 1.5 h to lower the system pH to 5.0. Citric acid solution is added again all at once to further lower the system pH to 4.0, and the reaction is carried out at pH 4.0 for 0.5 h. Citric acid solution is added again all at once to further lower the system pH to 3.1, and the reaction is carried out at pH 3.1 for 1.0 h.

[0119] Comparative Example 8 (Modification during in-situ polymerization)

[0120] The self-healing composite material in this comparative example follows the preparation process of Example 1, except that in the preparation of the microcapsules, a silane coupling agent is added to the melamine-urea-formaldehyde copolymer precursor solution for modification. Specifically, step 1.2 is as follows: Monomers are weighed and mixed according to a molar ratio of urea:formaldehyde = 1:1.8 and melamine:formaldehyde = 1:2.8, with urea accounting for 35% of the total mass of melamine and urea. Alkane coupling agent KH550 (0.8% of the dry weight of the microcapsules) is added, and the mixture is diluted 4 times with deionized water. The pH is adjusted to 9.0 with triethanolamine, and the reaction is stirred at 75 °C for 30 min to obtain the copolymer precursor solution. Furthermore, the surface oleophobic grafting modification treatment in step 1.4 is omitted. After washing and filtering the polymerization product, it is directly freeze-dried under vacuum until the moisture content is ≤ 2%, yielding the microcapsules.

[0121] Comparative Example 9 (changing the pH during the compaction stage)

[0122] The self-healing composite material of this comparative example follows the preparation process of Example 1, except that the pH during the microcapsule preparation stage is changed, specifically step 1.3, as follows: An oil-in-water regenerator emulsion and a melamine-urea-formaldehyde copolymer precursor solution are mixed at an effective mass ratio of 1:1.0 between the capsule core and the capsule wall. A 10% citric acid solution is slowly added dropwise under a 65°C water bath and 350 rpm stirring condition to adjust the pH to 6.0, and the reaction is carried out at pH 6.0 for 1.0 h. Citric acid solution is then added at a rate of 0.15 mL / min, lowering the pH to 5.0 within 1.5 h. The reaction is maintained at pH 5.0 for 0.5 h. The rate of citric acid solution addition is increased to 4.0 mL / min, lowering the pH from 5.0 to 3.1, and the reaction is carried out at pH 3.1 for 1.5 h.

[0123] Comparative Example 10 (changing the pH during the interface strengthening and shaping stage)

[0124] The self-healing composite material of this comparative example follows the preparation process of Example 1, except that the reaction pH is changed during the microcapsule preparation process. Specifically, step 1.3 is as follows: An oil-in-water regenerator emulsion and a melamine-urea-formaldehyde copolymer precursor solution are mixed at an effective mass ratio of core to wall of 1:1.0. The mixture is placed in a 65°C water bath with stirring at 350 rpm, and a 10% citric acid solution is slowly added dropwise to adjust the pH to 6.0. The reaction is carried out at pH 6.0 for 1.0 h. Citric acid solution is then added at a rate of 0.15 mL / min, reducing the pH to 5.0 within 1.5 h. The addition rate of citric acid solution is increased to 1.0 mL / min, reducing the pH to 4.0, and the reaction is carried out at pH 4.0 for 0.5 h. The addition rate of citric acid solution is then increased again to 5.0 mL / min, reducing the pH to 2.5, and the reaction is carried out at pH 2.5 for 1.0 h.

[0125] The composite materials prepared in Examples 1-5 and Comparative Examples 1-10 were used to simulate the molding of a bridge deck waterproof adhesive layer, and the relevant properties were tested. The results are summarized in Tables 2 and 3.

[0126] Table 2: Comparison of Key Performance Indicators of Microcapsules

[0127]

[0128] Table 2 shows that the surface oleophobic modification (Examples 1-3) significantly improved the dispersion stability and core material retention of microcapsules in high-temperature asphalt. The microcapsule wall structure prepared by the gradient polymerization process (Examples 1-3) is dense and its temperature resistance is far superior to that of the conventional one-step polymerization process (Comparative Example 3). Further comparison of Comparative Examples 5-7 shows that the control of the acid addition rate is crucial: Comparative Example 5 suffered from defects in the base layer due to the excessively rapid initial rate, and the integrity rate of the capsule wall and the core material retention rate were significantly lower than those of the Examples. Comparative Example 6 suffered from reaction runaway due to a sudden drop in pH in the initial stage, and the microcapsules were basically ineffective. Although Comparative Example 7 was slightly better than Comparative Example 3, it still suffered from structural defects due to local over-acidification, and its performance was far inferior to the pH gradient polymerization process of the present invention. The data of Comparative Example 8 shows that adding the silane coupling agent to the copolymerization precursor solution for in-situ polymerization modification interfered with the formation of the crosslinking network of MUF resin during the gradient polymerization process, resulting in a decrease in shell density. The data from Comparative Example 9 demonstrates that the structural densification stage forms a highly dense shell under specific pH conditions. This step is a necessary process to ensure the temperature resistance of the microcapsules and the encapsulation performance of the core material. Specifically, the data from Comparative Example 10 show that when the pH during the interface strengthening and shaping stage is outside the range (3.0~3.2) defined in this invention, the microcapsule shell becomes brittle due to excessive cross-linking. The capsule wall integrity rate (68.2%) and core material retention rate (61.5%) are significantly lower than those in Example 1 of this invention (94.5%, 91.2%), and flocculent precipitates appear in the system, indicating a side reaction. This result proves that strictly controlling the pH during the interface strengthening and shaping stage within the range of 3.0~3.2 is a key parameter for balancing shell densification and avoiding excessive embrittlement.

[0129] Table 3: Performance and Self-Healing Effect of Waterproof Adhesive Layers of Composite Materials

[0130]

[0131] The self-healing composite materials prepared in Examples 1-5 of this invention all exhibited excellent self-healing capabilities after the formation of microcracks, with tensile and shear strength recovery rates ≥ 70% and water permeability coefficient reduction rates ≥ 80%, significantly superior to the blank control group (Comparative Example 1 without microcapsules). The scanning electron microscope (SEM) image of the stress-controlled release microcapsules prepared in Example 1 is shown below. Figure 1 As shown, it has a regular spherical structure and a complete shell. Fluorescence microscopy (FM) images of the microcapsule bitumen cross-section after complete fracture in a pull-out test are shown below. Figure 2 As shown.

[0132] Comparative Example 2, lacking surface modification of the microcapsules, exhibited poor dispersibility and localized agglomeration, leading to a decrease in initial bond strength and a significantly lower repair rate compared to Example 1. This demonstrates that surface oleophobic modification is crucial for maintaining matrix properties and achieving repair functionality. Comparative Example 3, using microcapsules produced by non-gradient polymerization, exhibited poor temperature resistance, resulting in partial breakage and premature core material leakage during the preparation of the self-healing composite material. This led to a decrease in initial strength and poor subsequent repair performance. Comparative Example 4, employing single-speed shearing, showed inferior microcapsule dispersion uniformity compared to the gradient shearing process, with macroscopic performance slightly inferior to Example 1. This proves the necessity of gradient shearing for dispersing high-dosage, high-viscosity systems. The data from Comparative Examples 5-7 fully demonstrate that precise control of the acid addition rate and pH value in the three stages of gradient in-situ polymerization for capsule wall construction (wall thickening and crosslinking stage, structural densification stage, and interface strengthening and shaping stage) is essential for forming high-performance microcapsules and achieving excellent self-healing effects. The data from Comparative Example 8 show that adding the silane coupling agent to the copolymerization precursor solution for in-situ polymerization modification significantly interferes with the precise control of the gradient polymerization process, resulting in the microcapsules having significantly inferior temperature resistance and self-healing properties compared to Example 1 of the present invention.

[0133] Data from Comparative Example 9 shows that changing the conditions of the structural densification stage and directly lowering the pH from 5.0 to 3.1 prevented the formation of a dense three-dimensional network structure in the microcapsule shell. The result was a capsule wall integrity rate of only 70.5% (94.5% in Example 1), a core material retention rate of only 65.2% (91.2% in Example 1), and a corresponding composite material pull-out strength recovery rate of only 46.3% (82.1% in Example 1), far lower than the levels of the embodiments of this invention. This fully demonstrates that the structural densification stage is a necessary process step for forming a highly dense shell and ensuring the mechanical strength of the microcapsule and the encapsulation performance of the core material; changing the conditions of this stage or omitting this stage will not achieve the technical effects of this invention. Data from Comparative Example 10 shows that lowering the final pH of the interface strengthening and shaping stage to below the range (3.0~3.2) defined in this invention caused excessive cross-linking and embrittlement of the microcapsule shell. This indicates that the pH during the interface strengthening and shaping stage is not necessarily better the lower it is. Excessive acidification will lead to increased brittleness of the wall material, and microcapsules will be damaged in large numbers during preparation and mixing, thus failing to effectively exert their self-healing function.

[0134] In summary, this invention employs a gradient pH-controlled shell polymerization method to prepare microcapsules. Acid catalysis enables precise construction of the capsule wall prepolymer, including adsorption, thickening, cross-linking, structural compaction, and interface strengthening, followed by surface oleophobic grafting modification. Furthermore, a gradient shear composite process is used to uniformly disperse stress-controlled release microcapsules within a modified asphalt matrix, such as a styrene-butadiene-styrene block copolymer. During construction, the composite material is heated and laid on the bridge deck surface to form a stress-responsive waterproof adhesive layer. During service life, stress concentration at the microcrack tips triggers directional rupture of the microcapsules, instantly releasing and directionally migrating the core material asphalt regenerator to the crack area, achieving self-healing of cracks and asphalt regeneration. The composite material of this invention has excellent high-temperature mixing stability, stress-triggered response characteristics, and self-healing function. After repair, the interlayer pull-out strength and shear strength recovery rate is ≥ 70%, and the water permeability coefficient reduction rate is ≥ 80%. It perfectly meets the multi-dimensional and demanding requirements of bridge deck waterproofing adhesive layer for high-temperature construction, strong adhesion, and self-healing, significantly improving the durability and service life of bridge deck pavement system, reducing the full-cycle maintenance cost, and has significant engineering value and innovation.

[0135] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A stress-controlled self-healing composite material for bridge deck waterproofing adhesive layer, characterized in that, include: A polymer-modified asphalt matrix, and stress-controlled release microcapsules uniformly dispersed in the polymer-modified asphalt matrix; wherein the method for preparing the stress-controlled release microcapsules includes the following steps: The regenerator emulsion and melamine-urea-formaldehyde copolymer precursor solution were mixed, and an acidic catalyst solution was added dropwise at 55-75 °C to adjust the pH of the system to 5.8-6.5, and the reaction was allowed to proceed for 0.5-2.0 h. Then, another acidic catalyst solution was added to lower the pH of the system to 4.8-5.5 within 1.0-2.5 h. The acidic catalyst solution was then added again to lower the pH of the system to 3.8-4.5, and the reaction was allowed to proceed for 0.5-1.0 h. Finally, another acidic catalyst solution was added to lower the pH of the system to 3.0-3.2, and the reaction was allowed to proceed for 1.0-1.5 h. The reaction system was cooled to room temperature, washed, and then the wet microcapsules were obtained by filtration or centrifugation. The wet microcapsules were pre-dried, then a silane coupling agent was added and mixed thoroughly. After drying, stress-controlled release microcapsules were obtained.

2. The stress-controlled release self-healing composite material for bridge deck waterproofing bonding layer according to claim 1, characterized in that, The dosage of the stress-controlled release microcapsules is 4%-12% of the mass of the polymer-modified asphalt matrix.

3. The stress-controlled release self-healing composite material for bridge deck waterproofing bonding layer according to claim 1, characterized in that, The oil-in-water regenerant emulsion and the melamine-urea-formaldehyde copolymer precursor solution were mixed at an effective mass ratio of 1:(0.5-1.5) between the core and the wall.

4. The stress-controlled release self-healing composite material for bridge deck waterproofing bonding layer according to claim 3, characterized in that, The preparation method of the regenerator emulsion is as follows: mix asphalt regenerator, anionic emulsifier and water at a mass ratio of 100:(15-40):(1000-2000), keep warm at 60-80 ℃ for 10-30 min, and then treat under high shear emulsification or ultrasonic dispersion conditions for 5-20 min to obtain the regenerator emulsion.

5. The stress-controlled release self-healing composite material for bridge deck waterproofing bonding layer according to claim 3, characterized in that, The preparation method of melamine-urea-formaldehyde copolymerization precursor solution is as follows: urea, melamine and formaldehyde solution are mixed, diluted with water, and the pH of the system is adjusted to 8.0-9.5 with an alkaline regulator. The reaction is carried out by stirring at 65-80 ℃ to obtain melamine-urea-formaldehyde copolymerization precursor solution.

6. The stress-controlled release self-healing composite material for bridge deck waterproofing bonding layer according to claim 5, characterized in that, The molar ratio of urea to formaldehyde is 1:(1.3-2.2), and the molar ratio of melamine to formaldehyde is 1:(2.2-3.3).

7. The stress-controlled release self-healing composite material for bridge deck waterproofing bonding layer according to claim 1, characterized in that, The polymer-modified asphalt matrix is ​​obtained by modifying the base asphalt with a polymer modifier, wherein the polymer modifier is selected from at least one of styrene-butadiene-styrene block copolymer, styrene-butadiene rubber, and epoxy resin.

8. The method for preparing the stress-controlled release self-healing composite material for bridge deck waterproofing bonding layer according to any one of claims 1-7, characterized in that, Includes the following steps: The base asphalt is heated to 150-170 ℃, a polymer modifier is added, and shearing is performed at a shear rate of 4000-9000 rpm for 15-50 min to obtain a polymer-modified asphalt matrix. The stress-controlled release microcapsules were dried under vacuum at 60-85 ℃ for 1-3 h. The dried stress-controlled release microcapsules were added to the polymer-modified asphalt matrix. Under inert gas protection at 150-170 ℃, the matrix was first sheared at a low speed of 50-150 rpm for 5-10 min, then sheared at a medium speed of 250-550 rpm for 20-40 min, and finally stirred at a temperature of 100-200 rpm for 5-10 min to obtain a stress-controlled release self-healing composite material for bridge deck waterproof bonding layer.

9. The preparation method according to claim 8, characterized in that, Before adding the dried stress-controlled release microcapsules to the polymer-modified bitumen matrix, the dried stress-controlled release microcapsules are preheated to 80-100 ℃.

10. The application of the stress-controlled release self-healing composite material for the waterproof bonding layer of bridge decks according to any one of claims 1-7, characterized in that, include: The stress-controlled release self-healing composite material used for the bridge deck waterproof bonding layer is heated to 160-185 ℃ and evenly spread on the surface of the bridge deck after shot blasting, sandblasting or milling to form a stress-responsive waterproof bonding functional layer with a thickness of 1.5-2.0 mm.

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